Entrez-PubMed PubMedNucleotideProteinGenomeStructurePopSetTaxonomyOMIMBooks Search PubMed Protein Nucleotide Structure Genome PopSet OMIM Taxonomy Books ProbeSet 3D Domains UniSTS Domains SNP Journals UniGene for LimitsPreview/IndexHistoryClipboardDetails Summary Brief Abstract Citation ASN.1 MEDLINE XML UI List LinkOut Related Articles Domain Links Genome Links ProbeSet Links Nucleotide Links OMIM Links PopSet Links Protein Links SNP Links Structure Links Show: 5 10 20 50 100 200 500 Sort Author Journal Pub DateFile Text Clipboard Order Items 1-500 of 2657 of 6Next 1: Surzhikov VD, et al. [III All-Russia Symposium on ...[PMID:12428624]Related Articles, Links UI - 22314398 PMID- 12428624 DA - 20021112 DCOM- 20021113 IS - 0131-1646 VI - 28 IP - 4 DP - 2002 Jul-Aug TI - [III All-Russia Symposium on Slow Oscillatory Processes in the Human Body and Seminar on Nonlinear Dynamics in Physiology and Medicine. Novokuznestsk, May 21-25, 2001] PG - 134-7 FAU - Surzhikov, V D AU - Surzhikov VD FAU - Fleishman, A N AU - Fleishman AN LA - rus PT - Congresses TT - III Vserossiiskii simpozium"Medlennye kolebatel'nye protsessy v organizme cheloveka" i shkola-seminar po nelineinoi dinamike v fiziologii i meditsine" (Novokuznetsk, 21-25 maia 2001 g.) CY - Russia TA - Fiziol Cheloveka JID - 7603567 SB - IM MH - Animal MH - Human MH - *Medicine MH - Nonlinear Dynamics MH - *Physiology EDAT- 2002/11/14 04:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - Fiziol Cheloveka 2002 Jul-Aug;28(4):134-7. 2: Davis PJ, et al. In vitro remifentanil metabol...[PMID:12401616]Related Articles, Links UI - 22288635 PMID- 12401616 DA - 20021028 DCOM- 20021119 IS - 0003-2999 VI - 95 IP - 5 DP - 2002 Nov TI - In vitro remifentanil metabolism: the effects of whole blood constituents and plasma butyrylcholinesterase. PG - 1305-7, table of contents AB - We designed this in vitro study to determine whether the half-life of remifentanil was altered in butyrylcholinesterase-deficient patients. Test tubes containing Krebs buffered solution, whole blood, plasma, or red cells from both normal and butyrylcholinesterase-deficient patients were incubated with remifentanil. Remifentanil concentrations were determined by using gas chromatography and mean half-lives were calculated by using a nonlinear regression analysis. There were no differences in whole blood, red cells, or plasma half-life between normal and butyrylcholinesterase-deficient volunteers. In both normal and butyrylcholinesterase-deficient volunteers, whole blood and plasma had a significantly longer half-life than the red cell component. Extrapolation to the in vivo setting would suggest that a butyrylcholinesterase-deficient patient should not have altered remifentanil kinetics. IMPLICATIONS: This was a test-tube-designed study to determine whether an enzyme deficiency (butyrylcholinesterase deficiency) changes the way remifentanil is metabolized. It seems that remifentanil dosage does not need to be changed in patients with butyrylcholinesterase deficiency. AD - Department of Anesthesiology, School of Medicine, University of Pittsburgh, 3705 5th Avenue, Pittsburgh, PA 15213-2583, USA. davispj@anes.upmc.edu FAU - Davis, Peter J AU - Davis PJ FAU - Stiller, Richard L AU - Stiller RL FAU - Wilson, Annette S AU - Wilson AS FAU - McGowan, Francis X AU - McGowan FX FAU - Egan, Talmage D AU - Egan TD FAU - Muir, Keith T AU - Muir KT LA - eng PT - Clinical Trial PT - Journal Article CY - United States TA - Anesth Analg JID - 1310650 RN - 0 (Anesthetics, Intravenous) RN - 0 (Piperidines) RN - 132875-61-7 (remifentanil) RN - EC 3.1.1.- (Butyrylcholinesterase) SB - AIM SB - IM MH - Adult MH - Anesthetics, Intravenous/blood/*metabolism MH - Butyrylcholinesterase/blood/deficiency/*metabolism MH - Erythrocytes/metabolism MH - Half-Life MH - Human MH - Nonlinear Dynamics MH - Piperidines/blood/*metabolism MH - Plasma/metabolism MH - Support, Non-U.S. Gov't EDAT- 2002/10/29 04:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - Anesth Analg 2002 Nov;95(5):1305-7, table of contents. 3: Erkut C, et al. Acoustical analysis and model...[PMID:12398473]Related Articles, Links UI - 22285369 PMID- 12398473 DA - 20021025 DCOM- 20021107 IS - 0001-4966 VI - 112 IP - 4 DP - 2002 Oct TI - Acoustical analysis and model-based sound synthesis of the kantele. PG - 1681-91 AB - The five-string Finnish kantele is a traditional folk music instrument that has unique structural features, resulting in a sound of bright and reverberant timbre. This article presents an analysis of the sound generation principles in the kantele, based on measurements and analytical formulation. The most characteristic features of the unique timbre are caused by the bridgeless string termination around a tuning pin at one end and the knotted termination around a supporting bar at the other end. These result in prominent second-order nonlinearity and strong beating of harmonics, respectively. A computational model of the instrument is also formulated and the algorithm is made efficient for real-time synthesis to simulate these features of the instrument timbre. AD - Laboratory of Acoustics and Audio Signal Processing, Helsinki University of Technology, Espoo, Finland. cumhur.erkut@hut.fi FAU - Erkut, Cumhur AU - Erkut C FAU - Karjalainen, Matti AU - Karjalainen M FAU - Huang, Patty AU - Huang P FAU - Valimaki, Vesa AU - Valimaki V LA - eng PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 SB - IM MH - Acoustic Stimulation/*instrumentation MH - *Acoustics MH - Equipment Design MH - Human MH - *Music MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2002/10/26 04:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - J Acoust Soc Am 2002 Oct;112(4):1681-91. 4: Lukashkin AN, et al. Modifications of a single sat...[PMID:12398462]Related Articles, Links UI - 22285358 PMID- 12398462 DA - 20021025 DCOM- 20021107 IS - 0001-4966 VI - 112 IP - 4 DP - 2002 Oct TI - Modifications of a single saturating non-linearity account for post-onset changes in 2f1-f2 distortion product otoacoustic emission. PG - 1561-8 AB - 2f1-f2 distortion product otoacoustic emissions (DPOAEs) were recorded from guinea pigs. DPOAEs showed complex time dependence at the onset of stimulation. The DPOAE, measured during the first 500 ms, can either decrease or increase at the onset depending on both the frequencies and levels of the primary tones. These changes are closely associated with amplitude minima (notches) of the DPOAE I/O functions. These notches are characteristic of DPOAE growth functions measured from guinea pigs for primary tones of 50-60-dB sound-pressure level (SPL). Apparent changes in the DPOAE amplitude occur because the notch shifts to higher levels of the primaries during the onset of stimulation. This shift of the notch to higher levels increases for lower f2/f1 ratios but does not exceed about 2 dB. DPOAE amplitude increases for a constant level of the primaries if the onset emission is situated at the low-level, falling slope of the notch. If the onset DPOAE is located on the high-level, rising slope of the notch, then the upward shift of the notch causes the emission either to decrease monotonically, or to decrease initially and then increase. By establishing that the 2f1-f2 onset changes reflect a shift in the growth-function notch, it is possible to predict the temporal behavior of DPOAEs in the two-dimensional space of the amplitude of the primaries and for their different frequency ratios. AD - School of Biological Sciences, University of Sussex, Falmer, Brighton, United Kingdom. a.lukashkin@sussex.ac.uk FAU - Lukashkin, Andrei N AU - Lukashkin AN FAU - Russell, Ian J AU - Russell IJ LA - eng PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 SB - IM MH - Animal MH - Cochlea/*physiology MH - Guinea Pigs MH - *Nonlinear Dynamics MH - Otoacoustic Emissions, Spontaneous/*physiology MH - Support, Non-U.S. Gov't EDAT- 2002/10/26 04:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - J Acoust Soc Am 2002 Oct;112(4):1561-8. 5: Karpov S, et al. A nonlinear model of thermoac...[PMID:12398451]Related Articles, Links UI - 22285347 PMID- 12398451 DA - 20021025 DCOM- 20021107 IS - 0001-4966 VI - 112 IP - 4 DP - 2002 Oct TI - A nonlinear model of thermoacoustic devices. PG - 1431-44 AB - This paper presents a nonlinear, time-domain model of thermoacoustic devices based on cross-sectional averaged equations. Heat transfer perpendicular to the device axis--which lies at the core of thermoacoustic effects--is modeled in a novel and more realistic way. Heat conduction in the solid surfaces surrounding the fluid medium is included. Contrary to the previous versions of this model [Watanabe et al., J. Acoust. Soc. Am. 102, 3484-3496 (1997)], the present version does not require artificial damping and is numerically robust. The model performance is illustrated on several examples: a prime mover, an externally driven thermoacoustic refrigerator, and a combined prime mover/refrigerator system. AD - Department of Mechanical Engineering, The Johns Hopkins University Baltimore, Maryland 21218, USA. FAU - Karpov, Sergey AU - Karpov S FAU - Prosperetti, Andrea AU - Prosperetti A LA - eng PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 SB - IM MH - Acoustics/*instrumentation MH - *Nonlinear Dynamics MH - Support, U.S. Gov't, Non-P.H.S. MH - *Thermal Conductivity EDAT- 2002/10/26 04:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - J Acoust Soc Am 2002 Oct;112(4):1431-44. 6: Scarpetta S, et al. Hebbian imprinting and retrie...[PMID:12396567]Related Articles, Links UI - 22284485 PMID- 12396567 DA - 20021024 DCOM- 20021126 IS - 0899-7667 VI - 14 IP - 10 DP - 2002 Oct TI - Hebbian imprinting and retrieval in oscillatory neural networks. PG - 2371-96 AB - We introduce a model of generalized Hebbian learning and retrieval in oscillatory neural networks modeling cortical areas such as hippocampus and olfactory cortex. Recent experiments have shown that synaptic plasticity depends on spike timing, especially on synapses from excitatory pyramidal cells, in hippocampus, and in sensory and cerebellar cortex. Here we study how such plasticity can be used to form memories and input representations when the neural dynamics are oscillatory, as is common in the brain (particularly in the hippocampus and olfactory cortex). Learning is assumed to occur in a phase of neural plasticity, in which the network is clamped to external teaching signals. By suitable manipulation of the nonlinearity of the neurons or the oscillation frequencies during learning, the model can be made, in a retrieval phase, either to categorize new inputs or to map them, in a continuous fashion, onto the space spanned by the imprinted patterns. We identify the first of these possibilities with the function of olfactory cortex and the second with the observed response characteristics of place cells in hippocampus. We investigate both kinds of networks analytically and by computer simulations, and we link the models with experimental findings, exploring, in particular, how the spike timing dependence of the synaptic plasticity constrains the computational function of the network and vice versa. AD - Department of Physics E. R. Caianiello, Salerno University, Baronissi, Italy. silvia@sa.infn.it FAU - Scarpetta, Silvia AU - Scarpetta S FAU - Zhaoping, L AU - Zhaoping L FAU - Hertz, John AU - Hertz J LA - eng PT - Journal Article CY - United States TA - Neural Comput JID - 9426182 SB - IM MH - Hippocampus/physiology MH - *Imprinting (Psychology) MH - Mental Recall/physiology MH - *Models, Neurological MH - *Neural Networks (Computer) MH - Neuronal Plasticity/physiology MH - Nonlinear Dynamics MH - Olfactory Pathways/physiology MH - *Periodicity MH - Pyramidal Cells/physiology MH - Synapses/physiology EDAT- 2002/10/25 04:00 MHDA- 2002/11/28 04:00 AID - 10.1162/08997660260293265 [doi] PST - ppublish SO - Neural Comput 2002 Oct;14(10):2371-96. 7: Kurata Y, et al. Dynamical description of sino...[PMID:12384487]Related Articles, Links UI - 22270903 PMID- 12384487 DA - 20021017 DCOM- 20021122 IS - 0363-6135 VI - 283 IP - 5 DP - 2002 Nov TI - Dynamical description of sinoatrial node pacemaking: improved mathematical model for primary pacemaker cell. PG - H2074-101 AB - We developed an improved mathematical model for a single primary pacemaker cell of the rabbit sinoatrial node. Original features of our model include 1) incorporation of the sustained inward current (I(st)) recently identified in primary pacemaker cells, 2) reformulation of voltage- and Ca(2+)-dependent inactivation of the L-type Ca(2+) channel current (I(Ca,L)), 3) new expressions for activation kinetics of the rapidly activating delayed rectifier K(+) channel current (I(Kr)), and 4) incorporation of the subsarcolemmal space as a diffusion barrier for Ca(2+). We compared the simulated dynamics of our model with those of previous models, as well as with experimental data, and examined whether the models could accurately simulate the effects of modulating sarcolemmal ionic currents or intracellular Ca(2+) dynamics on pacemaker activity. Our model represents significant improvements over the previous models, because it can 1) simulate whole cell voltage-clamp data for I(Ca,L), I(Kr), and I(st); 2) reproduce the waveshapes of spontaneous action potentials and ionic currents during action potential clamp recordings; and 3) mimic the effects of channel blockers or Ca(2+) buffers on pacemaker activity more accurately than the previous models. AD - Department of Physiology, Kanazawa Medical University, 1-1 Daigaku, Uchinada-machi, Kahoku-gun, Ishikawa 920-0293, Japan. yasu@kanazawa-med.ac.jp FAU - Kurata, Yasutaka AU - Kurata Y FAU - Hisatome, Ichiro AU - Hisatome I FAU - Imanishi, Sunao AU - Imanishi S FAU - Shibamoto, Toshishige AU - Shibamoto T LA - eng PT - Journal Article CY - United States TA - Am J Physiol Heart Circ Physiol JID - 100901228 RN - 0 (Chelating Agents) RN - 0 (Potassium Channel Blockers) RN - 504-24-5 (4-Aminopyridine) RN - 67-42-5 (Egtazic Acid) RN - 7440-09-7 (Potassium) RN - 7440-70-2 (Calcium) RN - 85233-19-8 (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid) SB - IM MH - 4-Aminopyridine/pharmacology MH - Animal MH - Biological Clocks/drug effects/*physiology MH - Calcium/metabolism MH - Chelating Agents/pharmacology MH - Computer Simulation MH - Egtazic Acid/*analogs & derivatives/pharmacology MH - *Models, Cardiovascular MH - Nonlinear Dynamics MH - Potassium/metabolism MH - Potassium Channel Blockers/pharmacology MH - Rabbits MH - Sarcolemma/physiology MH - Sinoatrial Node/drug effects/*physiology MH - Support, Non-U.S. Gov't EDAT- 2002/10/18 04:00 MHDA- 2002/11/26 04:00 AID - 10.1152/ajpheart.00900.2001 [doi] PST - ppublish SO - Am J Physiol Heart Circ Physiol 2002 Nov;283(5):H2074-101. 8: Kobayashi T, et al. Effect of ethanol on human sl...[PMID:12378128]Related Articles, Links UI - 22265940 PMID- 12378128 DA - 20021014 DCOM- 20021125 IS - 0302-282X VI - 46 IP - 2 DP - 2002 TI - Effect of ethanol on human sleep EEG using correlation dimension analysis. PG - 104-10 AB - Our study was designed to investigate the influence of alcohol on sleep using the correlation dimension (D2) analysis. Polysomnography (PSG) was performed in 10 adult human males during a baseline night (BL-N) and an ethanol (0.8 g/kg body weight) night (Et-N). The mean D2 values during the Et-N and BL-N decreased significantly from wakefulness to stages 1, 2, and 3+4 of nonrapid eye movement (non-REM) sleep, and increased during REM sleep. The mean D2 of the sleep electroencephalogram (EEG) during stage 2 during the Et-N was significantly higher than during BL-N. In addition, the mean D2 values of the sleep EEG for the second, third and fourth sleep cycles during the Et-N were significantly higher than during the BL-N. These significant differences between BL-N and Et-N were not recognized by spectral and visual analyses. Our results suggest that D2 is a potentially useful parameter for quantitative analysis of the effect of ethanol on sleep EEGs throughout the entire night. CI - Copyright 2002 S. Karger AG, Basel AD - Center of Psychiatry and Neurology, Fukui Prefecture Hospital, Fukui, Japan. t-ko@mx1.fctv.ne.jp FAU - Kobayashi, Toshio AU - Kobayashi T FAU - Madokoro, Shigeki AU - Madokoro S FAU - Wada, Yuji AU - Wada Y FAU - Misaki, Kiwamu AU - Misaki K FAU - Nakagawa, Hiroki AU - Nakagawa H LA - eng PT - Clinical Trial PT - Journal Article CY - Switzerland TA - Neuropsychobiology JID - 7512895 RN - 0 (Central Nervous System Depressants) RN - 64-17-5 (Ethanol) SB - IM MH - Adult MH - Algorithms MH - Central Nervous System Depressants/*pharmacology MH - Data Interpretation, Statistical MH - Electroencephalography/*drug effects MH - Ethanol/*pharmacology MH - Human MH - Male MH - Nonlinear Dynamics MH - Polysomnography/drug effects MH - Sleep/*drug effects MH - Sleep Stages/drug effects MH - Sleep, REM/drug effects EDAT- 2002/10/16 04:00 MHDA- 2002/11/26 04:00 AID - nps46104 [pii] PST - ppublish SO - Neuropsychobiology 2002;46(2):104-10. 9: Burton EJ, et al. Patterns of cerebral atrophy ...[PMID:12377138]Related Articles, Links UI - 22265889 PMID- 12377138 DA - 20021014 DCOM- 20021125 IS - 1053-8119 VI - 17 IP - 2 DP - 2002 Oct TI - Patterns of cerebral atrophy in dementia with Lewy bodies using voxel-based morphometry. PG - 618-30 AB - Previous cross-sectional MRI studies based on region-of-interest analyses have shown that increased cerebral atrophy is a feature of both Dementia with Lewy bodies (DLB) and Alzheimer's disease (AD). Relative preservation of the hippocampus and temporal lobe structures in DLB compared to AD has been reported in region-of-interest-based studies. Recently, image processing techniques such as voxel-based morphometry (VBM) have been developed to provide an unbiased, visually informative, and comprehensive means of studying patterns of cerebral atrophy. We report the first study to use the voxel-based approach to assess patterns of cerebral atrophy in DLB compared to control subjects and AD. Regional gray matter volume loss was observed bilaterally in the temporal and frontal lobes and insular cortex of patients with DLB compared to control subjects. Comparison of dementia groups showed preservation of the medial temporal lobe, hippocampus, and amygdala in DLB relative to AD. Significant gray matter loss was also observed in the thalamus of AD patients compared to DLB. AD - Institute for Ageing and Health, University of Newcastle upon Tyne, United Kingdom. e.j.burton@ncl.ac.uk FAU - Burton, E J AU - Burton EJ FAU - Karas, G AU - Karas G FAU - Paling, S M AU - Paling SM FAU - Barber, R AU - Barber R FAU - Williams, E D AU - Williams ED FAU - Ballard, C G AU - Ballard CG FAU - McKeith, I G AU - McKeith IG FAU - Scheltens, P AU - Scheltens P FAU - Barkhof, F AU - Barkhof F FAU - O'Brien, J T AU - O'Brien JT LA - eng PT - Clinical Trial PT - Journal Article CY - United States TA - Neuroimage JID - 9215515 SB - IM MH - Aged MH - Alzheimer Disease/pathology MH - Atrophy MH - Brain/*pathology MH - Brain Mapping MH - Cluster Analysis MH - Comparative Study MH - Female MH - Hippocampus/pathology MH - Human MH - Image Interpretation, Computer-Assisted/*methods MH - Lewy Body Disease/*pathology MH - Magnetic Resonance Imaging/*methods MH - Male MH - Middle Age MH - Models, Neurological MH - Nonlinear Dynamics MH - Parahippocampal Gyrus/pathology MH - Support, Non-U.S. Gov't MH - Temporal Lobe/pathology EDAT- 2002/10/16 04:00 MHDA- 2002/11/26 04:00 AID - S1053811902911973 [pii] PST - ppublish SO - Neuroimage 2002 Oct;17(2):618-30. 10: Modre R, et al. Noninvasive myocardial activa...[PMID:12374339]Related Articles, Links UI - 22261211 PMID- 12374339 DA - 20021010 DCOM- 20021113 IS - 0018-9294 VI - 49 IP - 10 DP - 2002 Oct TI - Noninvasive myocardial activation time imaging: a novel inverse algorithm applied to clinical ECG mapping data. PG - 1153-61 AB - Linear approaches like the minimum-norm least-square algorithm show insufficient performance when it comes to estimating the activation time map on the surface of the heart from electrocardiographic (ECG) mapping data. Additional regularization has to be considered leading to a nonlinear problem formulation. The Gauss-Newton approach is one of the standard mathematical tools capable of solving this kind of problem. To our experience, this algorithm has specific drawbacks which are caused by the applied regularization procedure. In particular, under clinical conditions the amount of regularization cannot be determined clearly. For this reason, we have developed an iterative algorithm solving this nonlinear problem by a sequence of regularized linear problems. At each step of iteration, an individual L-curve is computed. Subsequent iteration steps are performed with the individual optimal regularization parameter. This novel approach is compared with the standard Gauss-Newton approach. Both methods are applied to simulated ECG mapping data as well as to single beat sinus rhythm data from two patients recorded in the catheter laboratory. The proposed approach shows excellent numerical and computational performance, even under clinical conditions at which the Gauss-Newton approach begins to break down. AD - Institute of Biomedical Engineering, Graz University of Technology, Austria. modre-osprain@tugraz.at FAU - Modre, Robert AU - Modre R FAU - Tilg, Bernhard AU - Tilg B FAU - Fischer, Gerald AU - Fischer G FAU - Wach, Paul AU - Wach P LA - eng PT - Journal Article CY - United States TA - IEEE Trans Biomed Eng JID - 0012737 SB - IM MH - Action Potentials MH - Adult MH - *Algorithms MH - Atrial Fibrillation/diagnosis/physiopathology MH - Body Surface Potential Mapping/*methods MH - Comparative Study MH - *Computer Simulation MH - Female MH - Heart/*physiopathology MH - Human MH - Male MH - Membrane Potentials/*physiology MH - Middle Age MH - Models, Cardiovascular MH - *Myocardial Contraction MH - Nonlinear Dynamics MH - Sensitivity and Specificity MH - Tachycardia, Atrioventricular Nodal Reentry/diagnosis/physiopathology MH - Time Factors EDAT- 2002/10/11 04:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - IEEE Trans Biomed Eng 2002 Oct;49(10):1153-61. 11: Fagan MJ, et al. Patient-specific spine models...[PMID:12365788]Related Articles, Links UI - 22251843 PMID- 12365788 DA - 20021007 DCOM- 20021113 IS - 0954-4119 VI - 216 IP - 5 DP - 2002 TI - Patient-specific spine models. Part 1: Finite element analysis of the lumbar intervertebral disc--a material sensitivity study. PG - 299-314 AB - If patient-specific finite element models of the spine could be developed, they would offer enormous opportunities in the diagnosis and management of back problems. Several generic models have been developed in the past, but there has been very little detailed examination of the sensitivity of these models' characteristics to the input parameters. This relationship must be thoroughly understood if representative patient-specific models are to be realized and used with confidence. In particular, the performance of the intervertebral discs are central to any spine model and need detailed investigation first. A generic non-linear model of an intervertebral disc was developed and subjected to compressive, flexion and torsional loading regimes. The effects of both material and geometric non-linearities were investigated for the three loading schemes and the results compared with experimental data. The basic material properties of the fibres, annulus and nucleus were then varied and the effects on the stiffness, annulus bulge and annulus stresses analysed. The results showed that the non-linear geometry assumption had a significant effect on the compression characteristics, whereas the non-linear material option did not. In contrast, the material non-linearity was more important for the flexural and torsional loading schemes. Thus, the inclusion of non-linear material and geometry analysis options in finite element models of intervertebral discs is necessary to predict in vivo load-deflection characteristics accurately. When the influence of the material properties was examined in detail, it was found that the fibre properties did not have a significant effect on the compressive stiffness of the disc but did affect the flexural and torsional stiffnesses by up to +/-20 per cent. All loading modes were sensitive to the annulus properties with stiffnesses varying by up to +/-16 per cent. The model also revealed that for a particular compressive deformation or flexural or torsional rotation, the disc bulge was not sensitive to any of the material properties over the range of properties considered. The annulus stresses did differ significantly as the material properties were varied (up to 70 per cent under a compressive load and 60 per cent during disc flexion). AD - Department of Engineering, University of Hull, UK. FAU - Fagan, M J AU - Fagan MJ FAU - Julian, S AU - Julian S FAU - Siddall, D J AU - Siddall DJ FAU - Mohsen, A M AU - Mohsen AM LA - eng PT - Journal Article CY - England TA - Proc Inst Mech Eng [H] JID - 8908934 SB - IM MH - Compressive Strength MH - *Computer Simulation MH - Elasticity MH - Finite Element Analysis MH - Human MH - Intervertebral Disk/*physiology MH - Lumbar Vertebrae/*physiology MH - *Models, Biological MH - *Nonlinear Dynamics MH - Reproducibility of Results MH - Sensitivity and Specificity MH - Stress, Mechanical MH - Torsion MH - Weight-Bearing/physiology EDAT- 2002/10/09 04:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - Proc Inst Mech Eng [H] 2002;216(5):299-314. 12: Habib RH, et al. Optimal high-frequency oscill...[PMID:12359652]Related Articles, Links UI - 22245969 PMID- 12359652 DA - 20021002 DCOM- 20021118 IS - 1073-449X VI - 166 IP - 7 DP - 2002 Oct 1 TI - Optimal high-frequency oscillatory ventilation settings by nonlinear lung mechanics analysis. PG - 950-3 AB - Use of nontidal high-frequency oscillatory ventilation (HFOV) while the lungs are expanded by an imposed airway pressure (P(aw)) in neonates is increasingly based on evidence of decreased risk of lung injury. However, an objective method to optimize P(aw) is lacking. We measured lung volume changes (deltaV(L)[t]) via respiratory inductance plethysmography over a range of P(aw) settings in five piglets before and after lung lavage. These multiple deltaV(L)(t) were then simultaneously fit by an exponential rise to maximum model, deltaV(L)(t, P(aw)) = deltaV(L,max). (1 - e(-(t/tau))), where deltaV(L,max) was a sigmoidal function of P(aw) and tau varied with lung volume. Postlavage, the effective compliance (C(EFF) = deltaV(L,max)/P(aw)) was generally decreased, whereas tau increased, indicating a slower paced volume recruitment. Model-derived C(EFF)-deltaV(L,max) relationships were altered substantially after lavage and were sigmoidal with a bell-shaped derivative function. The maximum of its derivative corresponded to a favorable (or optimal) deltaV(L)/P(aw) where the maximal increase in compliance is achieved. In conclusion, C(EFF)-deltaV(L,max) data available from respiratory inductance plethysmography provided important insight to changes in lung mechanics. These also provided a basis of an objective method (1) to optimize P(aw) during HFOV and (2) to assess the efficacy of treatments and progression/regression of underlying disease in neonates managed with HFOV. AD - Cardiopulmonary Research, Mercy Children's Hospital at St. Vincent Mercy Medical Center, Toledo, OH 43608, USA. robert_habib@mhsnr.org FAU - Habib, Robert H AU - Habib RH FAU - Pyon, Kee H AU - Pyon KH FAU - Courtney, Sherry E AU - Courtney SE LA - eng PT - Journal Article CY - United States TA - Am J Respir Crit Care Med JID - 9421642 SB - AIM SB - IM MH - Animal MH - Biological Clocks/*physiology MH - Comparative Study MH - *High-Frequency Ventilation MH - Lung Compliance MH - Lung Volume Measurements MH - Models, Animal MH - Nonlinear Dynamics MH - Pulmonary Wedge Pressure/physiology MH - Respiratory Mechanics/*physiology MH - Support, Non-U.S. Gov't MH - Swine MH - Time Factors EDAT- 2002/10/03 04:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - Am J Respir Crit Care Med 2002 Oct 1;166(7):950-3. 13: Domokos G, et al. Random perturbations and latt...[PMID:12351754]Related Articles, Links UI - 22240240 PMID- 12351754 DA - 20020927 DCOM- 20021028 IS - 1095-9203 VI - 297 IP - 5590 DP - 2002 Sep 27 TI - Random perturbations and lattice effects in chaotic population dynamics. PG - 2163; discussion 2163 AD - Cornell University, Department of Theoretical and Applied Mechanics, Ithaca, NY 14853-1503, USA. FAU - Domokos, Gabor AU - Domokos G FAU - Scheuring, Istvan AU - Scheuring I LA - eng PT - Comment PT - Journal Article CY - United States TA - Science JID - 0404511 SB - IM CON - Science. 2001 Oct 19;294(5542):602-5. PMID: 11641500 MH - Animal MH - *Ecosystem MH - Environment MH - Mathematics MH - Models, Theoretical MH - Nonlinear Dynamics MH - Population Density MH - *Population Dynamics MH - Stochastic Processes EDAT- 2002/09/28 04:00 MHDA- 2002/10/29 04:00 AID - 10.1126/science.297.5590.2163a [doi] AID - 297/5590/2163a [pii] PST - ppublish SO - Science 2002 Sep 27;297(5590):2163; discussion 2163. 14: Carotenuto R, et al. A new extrapolation technique...[PMID:12322888]Related Articles, Links UI - 22234695 PMID- 12322888 DA - 20020926 DCOM- 20021106 IS - 0885-3010 VI - 49 IP - 3 DP - 2002 Mar TI - A new extrapolation technique for resolution enhancement of pulse-echo imaging systems. PG - 374-82 AB - A new, simple extrapolation technique to enhance the lateral resolution of pulse-echo imaging systems is presented. The method attempts to build an image that could be obtained with a transducer aperture larger than that physically available, extrapolating the information contained in the image to be enhanced. The extrapolation process requires small hardware modifications of the standard echographic systems. The computational cost is very low compared with Fourier-based deconvolution approaches. The obtained computer simulations give very interesting and promising r AD - Dipartimento di Ingegneria Elettronica, Universita degli Studi Roma Tre, Italy. r.carotenuto@uniroma3.it FAU - Carotenuto, Riccardo AU - Carotenuto R FAU - Loi, Giovanna AU - Loi G FAU - Pappalardo, Massimo AU - Pappalardo M LA - eng PT - Journal Article CY - United States TA - IEEE Trans Ultrason Ferroelectr Freq Control JID - 9882735 SB - IM MH - *Algorithms MH - Comparative Study MH - *Computer Simulation MH - Cysts/ultrasonography MH - Image Enhancement/instrumentation/*methods MH - *Models, Statistical MH - Nonlinear Dynamics MH - Sensitivity and Specificity MH - Support, Non-U.S. Gov't MH - Ultrasonography/instrumentation/*methods EDAT- 2002/09/27 06:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - IEEE Trans Ultrason Ferroelectr Freq Control 2002 Mar;49(3):374-82. 15: Deserno M, et al. Osmotic pressure of charged c...[PMID:12241358]Related Articles, Links UI - 22227374 PMID- 12241358 DA - 20020920 DCOM- 20021113 IS - 1539-3755 VI - 66 IP - 1 Pt 1 DP - 2002 Jul TI - Osmotic pressure of charged colloidal suspensions: a unified approach to linearized Poisson-Boltzmann theory. PG - 011401 AB - We study theoretically the equation of state of a fluid suspension of charged objects (e.g., colloids, polyelectrolytes, clay platelets, etc.) dialyzed against an electrolyte solution using the cell model and linear Poisson-Boltzmann (PB) theory. From the volume derivative of the grand potential functional of linear theory we obtain two expressions for the osmotic pressure in terms of the potential or ion profiles, neither of which coincides with the expression known from nonlinear PB theory, namely, the density of microions at the cell boundary. We show that the range of validity of linearization depends strongly on the linearization point and prove that expansion about the self-consistently determined average potential is optimal in several respects. For instance, screening inside the suspension is automatically described by the actual ionic strength, resulting in the correct asymptotics at high colloid concentration. Together with the analytical solution of the linear PB equation for cell models of arbitrary dimension and electrolyte composition, explicit and very general formulas for the osmotic pressure ensue. A comparison with nonlinear PB theory is provided. Our analysis also shows that whether or not linear theory predicts a phase separation depends crucially on the precise definition of the pressure, showing that depending on the choice, an artificial phase separation in systems as important as DNA in physiological salt solution may result. AD - Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA. FAU - Deserno, Markus AU - Deserno M FAU - von Grunberg, Hans-Hennig AU - von Grunberg HH LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 RN - 0 (Colloids) RN - 0 (Electrolytes) RN - 0 (Macromolecular Systems) RN - 0 (Solutions) RN - 0 (Suspensions) RN - 9007-49-2 (DNA) SB - IM MH - Biophysics MH - *Colloids MH - Comparative Study MH - DNA/chemistry MH - Electrolytes MH - Linear Models MH - Macromolecular Systems MH - *Models, Chemical MH - Nonlinear Dynamics MH - Osmotic Pressure MH - Solutions MH - Suspensions MH - Thermodynamics EDAT- 2002/09/21 10:00 MHDA- 2002/11/26 04:00 PHST- 2002/Feb/01 [received] PHST- 2002/Jul/12 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Jul;66(1 Pt 1):011401. 16: Tsuda I. Toward an interpretation of d...[PMID:12239890]Related Articles, Links UI - 22225576 PMID- 12239890 DA - 20020920 DCOM- 20021001 IS - 0140-525X VI - 24 IP - 5 DP - 2001 Oct TI - Toward an interpretation of dynamic neural activity in terms of chaotic dynamical systems. PG - 793-810; discussion 810-48 AB - Using the concepts of chaotic dynamical systems, we present an interpretation of dynamic neural activity found in cortical and subcortical areas. The discovery of chaotic itinerancy in high-dimensional dynamical systems with and without a noise term has motivated a new interpretation of this dynamic neural activity, cast in terms of the high-dimensional transitory dynamics among "exotic" attractors. This interpretation is quite different from the conventional one, cast in terms of simple behavior on low-dimensional attractors. Skarda and Freeman (1987) presented evidence in support of the conclusion that animals cannot memorize odor without chaotic activity of neuron populations. Following their work, we study the role of chaotic dynamics in biological information processing, perception, and memory. We propose a new coding scheme of information in chaos-driven contracting systems we refer to as Cantor coding. Since these systems are found in the hippocampal formation and also in the olfactory system, the proposed coding scheme should be of biological significance. Based on these intensive studies, a hypothesis regarding the formation of episodic memory is given. AD - Applied Mathematics and Complex Systems Research Group, Department of Mathematics, Graduate School of Science, Hokkaido University, Sapporo, 060-0810, Japan. tsuda@math.hokudai.ac.jp FAU - Tsuda, I AU - Tsuda I LA - eng PT - Journal Article PT - Review PT - Review, Academic CY - England TA - Behav Brain Sci JID - 7808666 SB - IM MH - Brain/*physiology MH - Human MH - Memory/*physiology MH - *Mental Processes MH - *Models, Theoretical MH - Neurons/physiology MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't RF - 402 EDAT- 2002/09/21 10:00 MHDA- 2002/10/03 04:00 PST - ppublish SO - Behav Brain Sci 2001 Oct;24(5):793-810; discussion 810-48. 17: Kuo TB, et al. Sexual dimorphism in the comp...[PMID:12234825]Related Articles, Links UI - 22219679 PMID- 12234825 DA - 20020917 DCOM- 20021017 IS - 0363-6135 VI - 283 IP - 4 DP - 2002 Oct TI - Sexual dimorphism in the complexity of cardiac pacemaker activity. PG - H1695-702 AB - This study explored the effects of gender and aging on the complexity of cardiac pacemaker activity. Electrocardiogram signals were studied in normal women (n = 240) and men (n = 240) ranging in age from 40 to 79 yr. Nonlinear analysis of short-term resting R-R intervals was performed using the correlation dimension (CD), approximate entropy (ApEn), and largest Lyapunov exponent (LLE). Evidence of nonlinear structure was obtained by the surrogate data test. CD, ApEn, and LLE were negatively correlated with age. Despite similar means and SDs of the R-R intervals, women had a significantly higher CD, ApEn, and LLE compared with men in the age strata of 40-44 and 45-49 yr. CD and ApEn were strongly (r > 0.71) correlated with low- and high-frequency components. We conclude that the resting cardiac pacemaker activity of women is more complex than that of men in middle age, and the gender-related difference diminishes after the age of 50 yr. The higher complexity implies a more comprehensive neural modulation. AD - Institute of Neuroscience, Hualien, Taiwan. tbjkuo@mail.tcu.edu.tw FAU - Kuo, Terry B J AU - Kuo TB FAU - Yang, Cheryl C H AU - Yang CC LA - eng PT - Journal Article CY - United States TA - Am J Physiol Heart Circ Physiol JID - 100901228 SB - IM MH - Adult MH - Aged MH - Biological Clocks/*physiology MH - Comparative Study MH - Female MH - Heart/innervation/*physiology MH - Heart Rate/*physiology MH - Human MH - Linear Models MH - Male MH - Middle Age MH - Nonlinear Dynamics MH - Parasympathetic Nervous System/physiology MH - *Sex Characteristics MH - Support, Non-U.S. Gov't MH - Sympathetic Nervous System/physiology EDAT- 2002/09/18 10:00 MHDA- 2002/10/18 04:00 PHST- 2002/Jun/21 [aheadofprint] AID - 10.1152/ajpheart.00169.2002 [doi] AID - 00169.2002 [pii] PST - ppublish SO - Am J Physiol Heart Circ Physiol 2002 Oct;283(4):H1695-702. 18: McSharry PE, et al. Linear and non-linear methods...[PMID:12227632]Related Articles, Links UI - 22214743 PMID- 12227632 DA - 20020913 DCOM- 20020930 IS - 0140-0118 VI - 40 IP - 4 DP - 2002 Jul TI - Linear and non-linear methods for automatic seizure detection in scalp electro-encephalogram recordings. PG - 447-61 AB - The electro-encephalogram is a time-varying signal that measures electrical activity in the brain. A conceptually intuitive non-linear technique, multi-dimensional probability evolution (MDPE), is introduced. It is based on the time evolution of the probability density function within a multi-dimensional state space. A synthetic recording is employed to illustrate why MDPE is capable of detecting changes in the underlying dynamics that are invisible to linear statistics. If a non-linear statistic cannot outperform a simple linear statistic such as variance, then there is no reason to advocate its use. Both variance and MDPE were able to detect the seizure in each of the ten scalp EEG recordings investigated. Although MDPE produced fewer false positives, there is no firm evidence to suggest that MDPE, or any other non-linear statistic considered, outperforms variance-based methods at identifying seizures. AD - Department of Engineering Science, University of Oxford, UK. mcsharry@maths.ox.ac.uk FAU - McSharry, P E AU - McSharry PE FAU - He, T AU - He T FAU - Smith, L A AU - Smith LA FAU - Tarassenko, L AU - Tarassenko L LA - eng PT - Journal Article CY - England TA - Med Biol Eng Comput JID - 7704869 SB - IM MH - *Electroencephalography MH - Epilepsy/*diagnosis MH - Human MH - Linear Models MH - Nonlinear Dynamics MH - Scalp MH - *Signal Processing, Computer-Assisted MH - Support, Non-U.S. Gov't EDAT- 2002/09/14 10:00 MHDA- 2002/10/02 04:00 PST - ppublish SO - Med Biol Eng Comput 2002 Jul;40(4):447-61. 19: Schifalacqua M. The power of fractals....[PMID:12226873]Related Articles, Links UI - 22214853 PMID- 12226873 DA - 20020913 DCOM- 20021009 IS - 1532-8880 VI - 17 IP - 11 DP - 2002 Aug TI - The power of fractals. PG - 6 AD - Aurora Health Care, Milwaukee, Wis., USA. marita.schifalacqua@aurora.org FAU - Schifalacqua, Marita AU - Schifalacqua M LA - eng PT - Journal Article CY - United States TA - Patient Care Manag JID - 101083317 SB - N MH - *Attitude of Health Personnel MH - *Decision Making, Organizational MH - Fractals MH - Human MH - Leadership MH - Nonlinear Dynamics MH - Nurse Administrators/*organization & administration/*psychology EDAT- 2002/09/14 10:00 MHDA- 2002/10/10 04:00 PST - ppublish SO - Patient Care Manag 2002 Aug;17(11):6. 20: [No authors listed] Quantum age: new rules for le...[PMID:12226871]Related Articles, Links UI - 22214851 PMID- 12226871 DA - 20020913 DCOM- 20021009 IS - 1532-8880 VI - 17 IP - 11 DP - 2002 Aug TI - Quantum age: new rules for leaders. PG - 2-4 LA - eng PT - Journal Article CY - United States TA - Patient Care Manag JID - 101083317 SB - N CIN - Patient Care Manag. 2002 Aug;17(11):5-6. PMID: 12226872 MH - Attitude of Health Personnel MH - Health Facility Administrators/*organization & administration/psychology MH - Human MH - *Leadership MH - Nonlinear Dynamics MH - Outcome and Process Assessment (Health Care)/organization & administration MH - Quantum Theory MH - *Systems Analysis MH - Work EDAT- 2002/09/14 10:00 MHDA- 2002/10/10 04:00 PST - ppublish SO - Patient Care Manag 2002 Aug;17(11):2-4. 21: Kalagher J. How to turn change into oppor...[PMID:12226869]Related Articles, Links UI - 22214850 PMID- 12226869 DA - 20020913 DCOM- 20021009 IS - 1532-8880 VI - 17 IP - 11 DP - 2002 Aug TI - How to turn change into opportunity for leadership. PG - 1, 7-8 AD - jane@coachingresources.com FAU - Kalagher, Jane AU - Kalagher J LA - eng PT - Journal Article CY - United States TA - Patient Care Manag JID - 101083317 SB - N MH - Attitude of Health Personnel MH - Human MH - *Leadership MH - Nonlinear Dynamics MH - Nurse Administrators/*organization & administration/psychology MH - Nursing, Supervisory/*organization & administration MH - Organizational Innovation EDAT- 2002/09/14 10:00 MHDA- 2002/10/10 04:00 PST - ppublish SO - Patient Care Manag 2002 Aug;17(11):1, 7-8. 22: Griffiths CW, et al. What to do at low doses: a bo...[PMID:12224742]Related Articles, Links UI - 22212217 PMID- 12224742 DA - 20020912 DCOM- 20021104 IS - 0272-4332 VI - 22 IP - 4 DP - 2002 Aug TI - What to do at low doses: a bounding approach for economic analysis. PG - 679-88 AB - To quantify the health benefits of environmental policies, economists generally require estimates of the reduced probability of illness or death. For policies that reduce exposure to carcinogenic substances, these estimates traditionally have been obtained through the linear extrapolation of experimental dose-response data to low-exposure scenarios as described in the U.S. Environmental Protection Agency's Guidelines for Carcinogen Risk Assessment (1986). In response to evolving scientific knowledge, EPA proposed revisions to the guidelines in 1996. Under the proposed revisions, dose-response relationships would not be estimated for carcinogens thought to exhibit nonlinear modes of action. Such a change in cancer-risk assessment methods and outputs will likely have serious consequences for how benefit-cost analyses of policies aimed at reducing cancer risks are conducted. Any tendency for reduced quantification of effects in environmental risk assessments, such as those contemplated in the revisions to EPA's cancer-risk assessment guidelines, impedes the ability of economic analysts to respond to increasing calls for benefit-cost analysis. This article examines the implications for benefit-cost analysis of carcinogenic exposures of the proposed changes to the 1986 Guidelines and proposes an approach for bounding dose-response relationships when no biologically based models are available. In spite of the more limited quantitative information provided in a carcinogen risk assessment under the proposed revisions to the guidelines, we argue that reasonable bounds on dose-response relationships can be estimated for low-level exposures to nonlinear carcinogens. This approach yields estimates of reduced illness for use in a benefit-cost analysis while incorporating evidence of nonlinearities in the dose-response relationship. As an illustration, the bounding approach is applied to the case of chloroform exposure. AD - U.S. EPA, National Center for Environmental Economics, Washington, DC 20460, USA. griffiths.charles@epamail.epa.gov FAU - Griffiths, Charles W AU - Griffiths CW FAU - Dockins, Chris AU - Dockins C FAU - Owens, Nicole AU - Owens N FAU - Simon, Nathalie B AU - Simon NB FAU - Axelrad, Daniel A AU - Axelrad DA LA - eng PT - Journal Article CY - United States TA - Risk Anal JID - 8109978 RN - 0 (Carcinogens) RN - 67-66-3 (Chloroform) SB - IM MH - Carcinogens/administration & dosage/toxicity MH - Chloroform/administration & dosage/toxicity MH - Cost-Benefit Analysis MH - Dose-Response Relationship, Drug MH - *Environment MH - Guidelines MH - Human MH - Linear Models MH - Nonlinear Dynamics MH - Risk Assessment/*economics MH - United States MH - United States Environmental Protection Agency EDAT- 2002/09/13 10:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - Risk Anal 2002 Aug;22(4):679-88. 23: Rifkin SA, et al. Geometry of gene expression d...[PMID:12217909]Related Articles, Links UI - 22205939 PMID- 12217909 DA - 20020909 DCOM- 20021106 IS - 1367-4803 VI - 18 IP - 9 DP - 2002 Sep TI - Geometry of gene expression dynamics. PG - 1176-83 AB - MOTIVATION: A gene expression trajectory moves through a high dimensional space where each axis represents the mRNA abundance of a different gene. Genome wide gene expression has a dynamic structure, especially in studies of development and temporal response. Both visualization and analyses of such data require an explicit attention to the temporal structure. RESULTS: Using three cell cycle trajectories from Saccharomyces cerevisiae to illustrate, we present several techniques which reveal the geometry of the data. We import phase-delay time plots from chaotic systems theory as a dynamic data visualization device and show how these plots capture important aspects of the trajectories. We construct an objective function to find an optimal two-dimensional projection of the cell cycle, demonstrate that the system returns to this plane after three different initial perturbations, and explore the conditions under which this geometric approach outperforms standard approaches such as singular value decomposition and Fourier analysis. Finally, we show how a geometric analysis can isolate distinct parts of the trajectories, in this case the initial perturbation versus the cell cycle. CONTACT: junhyong.kim@yale.edu AD - Department of Ecology and Evolutionary Biology, PO Box 208106, Yale University, New Haven, CT 06520, USA. FAU - Rifkin, S A AU - Rifkin SA FAU - Kim, J AU - Kim J LA - eng PT - Journal Article CY - England TA - Bioinformatics JID - 9808944 RN - 9007-49-2 (DNA) SB - IM MH - Algorithms MH - Cell Cycle/*genetics MH - Comparative Study MH - Computer Graphics MH - DNA/chemistry/genetics MH - Fourier Analysis MH - Gene Expression/genetics MH - Gene Expression Regulation/*genetics MH - *Genome, Bacterial MH - *Models, Genetic MH - Models, Statistical MH - Nonlinear Dynamics MH - Oligonucleotide Array Sequence Analysis/methods MH - *Periodicity MH - Saccharomyces cerevisiae/chemistry/cytology/*genetics MH - Sensitivity and Specificity MH - Sequence Analysis, DNA/methods MH - Stochastic Processes MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/09/10 10:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - Bioinformatics 2002 Sep;18(9):1176-83. 24: Abd-Elmoniem KZ, et al. Real-time speckle reduction a...[PMID:12214889]Related Articles, Links UI - 22203225 PMID- 12214889 DA - 20020906 DCOM- 20021009 IS - 0018-9294 VI - 49 IP - 9 DP - 2002 Sep TI - Real-time speckle reduction and coherence enhancement in ultrasound imaging via nonlinear anisotropic diffusion. PG - 997-1014 AB - This paper presents a novel approach for speckle reduction and coherence enhancement of ultrasound images based on nonlinear coherent diffusion (NCD) model. The proposed NCD model combines three different models. According to speckle extent and image anisotropy, the NCD model changes progressively from isotropic diffusion through anisotropic coherent diffusion to, finally, mean curvature motion. This structure maximally low-pass filters those parts of the image that correspond to fully developed speckle, while substantially preserving information associated with resolved-object structures. The proposed implementation algorithm utilizes an efficient discretization scheme that allows for real-time implementation on commercial systems. The theory and implementation of the new technique are presented and verified using phantom and clinical ultrasound images. In addition, the results from previous techniques are compared with the new method to demonstrate its performance. AD - Biomedical Engineering Department, Cairo University, Giza, Egypt. FAU - Abd-Elmoniem, Khaled Z AU - Abd-Elmoniem KZ FAU - Youssef, Abou-Bakr M AU - Youssef AB FAU - Kadah, Yasser M AU - Kadah YM LA - eng PT - Journal Article CY - United States TA - IEEE Trans Biomed Eng JID - 0012737 SB - IM MH - *Algorithms MH - Anisotropy MH - Comparative Study MH - Computer Simulation MH - Echocardiography/methods MH - Evaluation Studies MH - Heart MH - Human MH - Image Processing, Computer-Assisted/*methods MH - Kidney/ultrasonography MH - Liver/ultrasonography MH - Models, Statistical MH - Nonlinear Dynamics MH - Phantoms, Imaging MH - Reproducibility of Results MH - Sensitivity and Specificity MH - *Signal Processing, Computer-Assisted MH - Support, Non-U.S. Gov't MH - Time Factors MH - Ultrasonography, Doppler, Pulsed/*instrumentation/*methods EDAT- 2002/09/07 10:00 MHDA- 2002/10/10 04:00 PST - ppublish SO - IEEE Trans Biomed Eng 2002 Sep;49(9):997-1014. 25: Xu Y, et al. Absorption and scattering ima...[PMID:12211574]Related Articles, Links UI - 22196366 PMID- 12211574 DA - 20020904 DCOM- 20020918 IS - 0003-6935 VI - 41 IP - 25 DP - 2002 Sep 1 TI - Absorption and scattering images of heterogeneous scattering media can be simultaneously reconstructed by use of dc data. PG - 5427-37 AB - We present a carefully designed phantom experimental study aimed to provide solid evidence that both absorption and scattering images of heterogeneous scattering media can be reconstructed independently from dc data. We also study the important absorption-scattering cross-talk issue. In this regard, we develop a simple normalizing scheme that is incorporated into our nonlinear finite-element-based reconstruction algorithm. Our results from the controlled phantom experiments show that the cross talk of an absorption object appearing in scattering images can be eliminated and that the cross talk of a scattering object appearing in absorption images can be reduced considerably. In addition, these carefully designed phantom experiments clearly suggest that both absorption and scattering images can be simultaneously recovered and quantitatively separated in highly scattering media by use of dc measurements. Finally, we discuss our results in light of recent theoretical findings on nonuniqueness for dc image reconstruction. AD - Department of Physics and Astronomy, Clemson University, South Carolina 29634, USA. FAU - Xu, Yong AU - Xu Y FAU - Gu, Xuejun AU - Gu X FAU - Khan, Taufiquar AU - Khan T FAU - Jiang, Huabei AU - Jiang H LA - eng ID - R01 CA 90533/CA/NCI PT - Journal Article CY - United States TA - Appl Opt JID - 0247660 SB - IM MH - Absorption MH - Algorithms MH - Finite Element Analysis MH - *Image Processing, Computer-Assisted MH - Nonlinear Dynamics MH - Phantoms, Imaging MH - Scattering, Radiation MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/09/05 10:00 MHDA- 2002/09/19 10:01 PST - ppublish SO - Appl Opt 2002 Sep 1;41(25):5427-37. 26: Pouget A, et al. A computational perspective o...[PMID:12209122]Related Articles, Links UI - 22199622 PMID- 12209122 DA - 20020904 DCOM- 20020927 IS - 1471-003X VI - 3 IP - 9 DP - 2002 Sep TI - A computational perspective on the neural basis of multisensory spatial representations. PG - 741-7 AB - We argue that current theories of multisensory representations are inconsistent with the existence of a large proportion of multimodal neurons with gain fields and partially shifting receptive fields. Moreover, these theories do not fully resolve the recoding and statistical issues involved in multisensory integration. An alternative theory, which we have recently developed and review here, has important implications for the idea of 'frame of reference' in neural spatial representations. This theory is based on a neural architecture that combines basis functions and attractor dynamics. Basis function units are used to solve the recoding problem, whereas attractor dynamics are used for optimal statistical inferences. This architecture accounts for gain fields and partially shifting receptive fields, which emerge naturally as a result of the network connectivity and dynamics. AD - Department of Brain and Cognitive Sciences, University of Rochester, Rochester, New York 14627, USA. alex@bcs.rochester.edu FAU - Pouget, Alexandre AU - Pouget A FAU - Deneve, Sophie AU - Deneve S FAU - Duhamel, Jean-Rene AU - Duhamel JR LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - England TA - Nat Rev Neurosci JID - 100962781 SB - IM MH - Animal MH - Brain/*physiology MH - Eye Movements/physiology MH - Human MH - Models, Neurological MH - Nerve Net/*physiology MH - Neural Pathways/*physiology MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Orientation/*physiology MH - Psychomotor Performance/physiology MH - Sensation/*physiology MH - Space Perception/*physiology RF - 43 EDAT- 2002/09/05 10:00 MHDA- 2002/09/28 04:00 AID - 10.1038/nrn914 [doi] AID - nrn914 [pii] PST - ppublish SO - Nat Rev Neurosci 2002 Sep;3(9):741-7. 27: Gismondi RC, et al. Artificial neural networks fo...[PMID:12204451]Related Articles, Links UI - 22193843 PMID- 12204451 DA - 20020902 DCOM- 20021118 IS - 0169-2607 VI - 69 IP - 3 DP - 2002 Nov TI - Artificial neural networks for infant mortality modelling. PG - 237-47 AB - This work aims to investigate a simple to use and easy to interpret methodology for assessing the relative importance of input variables in artificial neural networks (ANNs) applied to epidemiological modelling. The independent variables were 43 variables of the social, economic, environmental and health sector of 59 Brazilian municipalities, and the outcomes were infant mortality rates from these municipalities. Two assays were developed for the ANN modelling. On the first, all 43 variables were taken as input; and on the second, input variables were chosen with the help of factor analysis (FA). The relative importance of the input variables was investigated by means of bootstrap replications of the ANN model on the second assay. Further, multiple linear regression models (LRMs) were developed with the same data set and compared to the ANN models. The FA analysis allowed the selection of eight variables for the second assay. The percent of explained variance R(2) on the ANNs was in the range 0.74-0.80, while linear models had R(2)=0.4-0.5. These findings were validated by the bootstrap replications, in which the ANN models remained with higher R(2) and lower mean square error than the LRMs. The analysis of the best (second) ANN model indicated the highest ranking of importance for the variables literacy, agricultural and livestock sector jobs, number of commercial establishments and telephones. The approach presented here successfully integrated a data-oriented model with expert knowledge, indicating the potentiality of ANN modelling in the prediction, planning and assessment of public health actions. AD - Medical Sciences College/State University of Rio de Janeiro, Rio de Janeiro, Brazil. renan@peb.ufrj.br FAU - Gismondi, Ronaldo C AU - Gismondi RC FAU - Almeida, Renan Moritz Varnier R AU - Almeida RM FAU - Infantosi, Antonio Fernando C AU - Infantosi AF LA - eng PT - Journal Article CY - Ireland TA - Comput Methods Programs Biomed JID - 8506513 SB - IM MH - Brazil/epidemiology MH - Epidemiologic Methods MH - Human MH - Infant MH - *Infant Mortality MH - Linear Models MH - Models, Statistical MH - Multivariate Analysis MH - *Neural Networks (Computer) MH - Nonlinear Dynamics EDAT- 2002/09/03 10:00 MHDA- 2002/11/26 04:00 AID - S0169260702000068 [pii] PST - ppublish SO - Comput Methods Programs Biomed 2002 Nov;69(3):237-47. 28: Slutzky MW, et al. Identification of determinism...[PMID:12204306]Related Articles, Links UI - 22194550 PMID- 12204306 DA - 20020902 DCOM- 20021016 IS - 0165-0270 VI - 118 IP - 2 DP - 2002 Aug 30 TI - Identification of determinism in noisy neuronal systems. PG - 153-61 AB - Most neuronal ensembles are nonlinear excitable systems. Thus it is becoming common to apply principles derived from nonlinear dynamics to characterize neuronal systems. One important characterization is whether such systems contain deterministic behavior or are purely stochastic. Unfortunately, many methods used to make this distinction do not perform well when both determinism and high-amplitude noise are present which is often the case in physiological systems. Therefore, we propose two novel techniques for identifying determinism in experimental systems. The first, called short-time expansion analysis, examines the expansion rate of small groups of points in state space. The second, called state point forcing, derives from the technique of chaos control. The system state is forced onto a fixed point, and the subsequent behavior is analyzed. This technique can be used to verify the presence of fixed points (or unstable periodic orbits) and to assess stationarity. If these are present, it implies that the system contains determinism. We demonstrate the use and possible limitations of these two techniques in two systems: the Henon map, a classic example of a chaotic system, and spontaneous epileptiform bursting in the rat hippocampal slice. Identifying the presence of determinism in a physiological system assists in the understanding of the system's dynamics and provides a mechanism for manipulating this behavior. CI - Copyright 2002 Elsevier Science B.V. AD - Department of Biomedical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA. mslutzky@md.northwestern.edu FAU - Slutzky, Marc W AU - Slutzky MW FAU - Cvitanovic, Predrag AU - Cvitanovic P FAU - Mogul, David J AU - Mogul DJ LA - eng PT - Journal Article CY - Netherlands TA - J Neurosci Methods JID - 7905558 SB - IM MH - Action Potentials/physiology MH - Animal MH - Electrophysiology/*methods/statistics & numerical data MH - Hippocampus/*physiology MH - Male MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Principal Component Analysis MH - Rats MH - Rats, Sprague-Dawley MH - Stochastic Processes EDAT- 2002/09/03 10:00 MHDA- 2002/10/17 04:00 AID - S0165027002000298 [pii] PST - ppublish SO - J Neurosci Methods 2002 Aug 30;118(2):153-61. 29: Wilke M, et al. Assessment of spatial normali...[PMID:12203688]Related Articles, Links UI - 22191094 PMID- 12203688 DA - 20020830 DCOM- 20021017 LR - 20021101 IS - 1065-9471 VI - 17 IP - 1 DP - 2002 Sep TI - Assessment of spatial normalization of whole-brain magnetic resonance images in children. PG - 48-60 AB - Commonly used frameworks for spatial normalization of brain imaging data (e.g., Talairach-space) are based on one or more adult brains. As pediatric brains are different in size and shape from adult brains and continue to develop through childhood, we aimed to assess the influence of age on various spatial normalization parameters. One hundred forty-eight healthy children aged 5-18 years were included in this study. The linear scaling parameters and the deformations from the non-linear spatial normalization to both a standard adult and a custom pediatric template were analyzed within SPM99. The effect of using a brain mask on the linear and of using different levels of constraint on the non-linear spatial normalization was assessed. Of the linear scaling factors, only the X-dimension (left-right) showed a significant age-correlation when based on brain tissue, whereas the overall scaling was not correlated with age. When based on the whole head, a very strong age-effect can be found in all dimensions. Non-linear deformations also show localized correlations with age, most pronounced in parietal and frontal areas. The total amount of volume change is significantly lower when using a pediatric template. It is also substantially influenced by the degree of regularization that is exerted on the spatial normalization parameters. Our results suggest that in the cortical areas showing a strong correlation of deformation with age, caution should be used in assigning imaging results in children to a specific morphological structure. Also, to minimize the amount of deformation during non-linear spatial normalization, a pediatric template should be used. Further implications of our findings on developmental neuroimaging studies are discussed. CI - Copyright 2002 Wiley-Liss, Inc. AD - Imaging Research Center, Children's Hospital Research Foundation at Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA. wilke@athena.chmcc.org FAU - Wilke, Marko AU - Wilke M FAU - Schmithorst, Vincent J AU - Schmithorst VJ FAU - Holland, Scott K AU - Holland SK LA - eng ID - R01-HD38578-01/HD/NICHD PT - Clinical Trial PT - Journal Article CY - United States TA - Hum Brain Mapp JID - 9419065 SB - IM MH - Adolescent MH - Age Distribution MH - Age Factors MH - Brain/*anatomy & histology/*growth & development MH - Child MH - Child, Preschool MH - Female MH - Human MH - Image Processing, Computer-Assisted/*methods MH - Magnetic Resonance Imaging/*methods/*standards MH - Male MH - Nonlinear Dynamics MH - Reference Values MH - Sex Distribution MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/08/31 10:00 MHDA- 2002/10/18 04:00 AID - 10.1002/hbm.10053 [doi] PST - ppublish SO - Hum Brain Mapp 2002 Sep;17(1):48-60. 30: Davis KH, et al. Validation of the Patient Per...[PMID:12201859]Related Articles, Links UI - 22192444 PMID- 12201859 DA - 20020830 DCOM- 20021022 IS - 1098-3015 VI - 5 IP - 5 DP - 2002 Sep-Oct TI - Validation of the Patient Perception of Migraine Questionnaire. PG - 421-9 AB - OBJECTIVE: The purpose of this study was to assess the psychometric properties of the Patient Perception of Migraine Questionnaire (PPMQ), which measures patient satisfaction with migraine therapy. METHODS AND DATA: The PPMQ was administered to 940 patients as part of a 3-month, multinational, open-label, clinical trial comparing the effects of oral naratriptan 2.5 mg with the patient's customary therapy for the treatment of migraine. Psychometric properties of the PPMQ were evaluated in terms of its latent factor structure, validity, reliability, sensitivity, and development of a scoring method. Classical Test theory and Item Response theory (IRT) modeling were both used to measure reliability. RESULTS: The PPMQ was able to detect treatment differences (P >.001), and all items significantly correlated with diary ratings of headache pain (r =.18-.51, p >.0001) and the Medical Outcomes Short Form-36 pain scale (r =.27, p >.0001). A principal components factor analysis revealed that the items on the PPMQ were psychometrically distinct and unidimensional (loadings, 0.74-0.91), with the exclusion of two items. The reliability (i.e., internal item consistency) of the PPMQ post-trial was high in both treatment groups (Cronbach's alpha = 0.96). An IRT analysis also ensured the formation of homogenous items, which were stable on repeat administration. Items did not require weighting and can be simply summed to yield a total score. CONCLUSION: Based on the data from this one clinical trial, the 15-item PPMQ was shown to be a valid and reliable instrument that seems to efficiently and comprehensively measure patient perception of drug attributes in relation to the treatment of symptoms associated with migraine headaches. AD - Global Health Outcomes, GlaxoSmithKline, PO Box 13398, Research Triangle Park, NC 27709-3398, USA. khd64468@gsk.com FAU - Davis, Kimberly Hunt AU - Davis KH FAU - Black, Libby AU - Black L FAU - Sleath, Betsy AU - Sleath B LA - eng PT - Journal Article PT - Validation Studies CY - United States TA - Value Health JID - 100883818 RN - 0 (Indoles) RN - 0 (Piperidines) RN - 0 (Serotonin Agonists) RN - 121679-13-8 (naratriptan) SB - IM MH - Adult MH - Analysis of Variance MH - Factor Analysis, Statistical MH - Female MH - Human MH - Indoles/*administration & dosage MH - Male MH - Migraine/*drug therapy MH - Nonlinear Dynamics MH - Pain Measurement/classification MH - Patient Satisfaction/*statistics & numerical data MH - Piperidines/*administration & dosage MH - Psychometrics MH - Questionnaires/*standards MH - Reproducibility of Results MH - Self Efficacy MH - Sensitivity and Specificity MH - Serotonin Agonists/*administration & dosage MH - Support, Non-U.S. Gov't EDAT- 2002/08/31 10:00 MHDA- 2002/10/31 04:00 AID - 55120 [pii] PST - ppublish SO - Value Health 2002 Sep-Oct;5(5):421-9. 31: Krstin N, et al. [Experiments to determine the...[PMID:12201015]Related Articles, Links UI - 22189854 PMID- 12201015 DA - 20020830 DCOM- 20021112 IS - 0013-5585 VI - 47 IP - 7-8 DP - 2002 Jul-Aug TI - [Experiments to determine the time dependent material properties of the periodontal ligament] PG - 202-8 AB - The periodontal ligament is a tissue that attaches the tooth (root) to its alveolar socket, and thus plays an important role in the regulation of tooth movements. Detailed knowledge of the material properties of the periodontal ligament is therefore essential to an understanding of tooth reaction to forces applied during orthodontic treatment. A knowledge of material parameters can also be used in simulations of long-term tooth movements with the aim of improving orthodontic treatment. To this end, this study investigated time-dependent material properties, namely the hysteresis behaviour of the periodontal ligament under constant-velocity loading, the influence of loading velocity on the hysteresis, and its failure under constant loading. Specimens obtained from pigs were used for testing purposes, and the experiments were conducted in a special test setup using a material testing device. The material behaviour of the periodontal ligament was shown to be viscoelastic, and the elastic parameters of material behaviour were also determined. Under constant-velocity loading, material behaviour showed a nonlinear course of the stress-strain curve, also known as hysteresis. When loading was repeated several times, the maximum stress of the hysteresis decreased with each cycle. Determination of the deflection of the specimen at different velocities showed maximum stress to be dependent on the loading rate. The measured stress-strain curves were approximated by bilinear behaviour, permitting the use of finite element calculations. Also investigated was the failure behaviour of the periodontal ligament, which revealed tissue rupture to be inconstant. AD - Zentralinstitut fur Biomedizinische Technik Ulm. FAU - Krstin, N AU - Krstin N FAU - Dorow, Ch AU - Dorow Ch FAU - Franke, R P AU - Franke RP FAU - Sander, F G AU - Sander FG LA - ger PT - Journal Article TT - Experimente zur Bestimmung der zeitabhangigen Materialeigenschaften des Parodontalligaments. CY - Germany TA - Biomed Tech (Berl) JID - 1262533 SB - IM MH - Animal MH - Biomechanics MH - Elasticity MH - English Abstract MH - Human MH - Nonlinear Dynamics MH - *Orthodontics, Corrective MH - Periodontal Ligament/injuries/*physiology MH - Rupture, Spontaneous MH - Swine MH - *Tooth Movement MH - Weight-Bearing/physiology EDAT- 2002/08/31 10:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - Biomed Tech (Berl) 2002 Jul-Aug;47(7-8):202-8. 32: Paulin MG, et al. Modelling the firing pattern ...[PMID:12194187]Related Articles, Links UI - 22181877 PMID- 12194187 DA - 20020823 DCOM- 20021030 LR - 20021120 IS - 0925-2312 VI - 26-27 IP - 1-3 DP - 1999 Jun TI - Modelling the firing pattern of bullfrog vestibular neurons responding to naturalistic stimuli. PG - 223-8 AB - We have developed a neural system identification method for fitting models to stimulus-response data, where the response is a spike train. The method involves using a general nonlinear optimisation procedure to fit models in the time domain. We have applied the method to model bullfrog semicircular canal afferent neuron responses during naturalistic, broad-band head rotations. These neurons respond in diverse ways, but a simple four parameter class of models elegantly accounts for the various types of responses observed. CI - c1999 Elsevier Science B.V. All rights reserved. AD - Department of Zoology and Centre for Neuroscience, University of Otago, Dunedin, New Zealand. mpaulin@otago.ac.nz FAU - Paulin, M G AU - Paulin MG FAU - Hoffman, L F AU - Hoffman LF LA - eng PT - Journal Article CY - Netherlands TA - Neurocomputing JID - 9884927 SB - S MH - Action Potentials/*physiology MH - Animal MH - *Models, Neurological MH - *Nervous System Physiology MH - Neurons, Afferent/*physiology MH - Nonlinear Dynamics MH - Rana catesbeiana/anatomy & histology/*physiology MH - Semicircular Canals/*innervation MH - Signal Transduction/physiology MH - Vestibular Nerve/physiology MH - Vestibule/physiology EDAT- 2002/08/27 10:00 MHDA- 2002/11/01 04:00 PST - ppublish SO - Neurocomputing 1999 Jun;26-27(1-3):223-8. 33: Dhanasekharan M, et al. Viscoelastic flow modeling in...[PMID:12194181]Related Articles, Links UI - 22181866 PMID- 12194181 DA - 20020823 DCOM- 20021030 IS - 0145-8876 VI - 23 IP - 3 DP - 2000 Aug TI - Viscoelastic flow modeling in the extrusion of a dough-like fluid. PG - 237-47 AB - This work attempts to investigate the effect of viscoelasticity and three-dimensional geometry in screw channels. The Phan-Thien Tanner (PTT) constitutive equation with simplified model parameters was solved in conjunction with the flow equations. Polyflow, a commercially available finite element code was used to solve the resulting nonlinear partial differential equations. The PTT model predicted one log scale lower pressure buildup compared to the equivalent Newtonian results. However, the velocity profile did not show significant changes for the chosen PTT model parameters. Past Researchers neglected viscoelastic effects and also the three dimensional nature of the flow in extruder channels. The results of this paper provide a starting point for further simulations using more realistic model parameters, which may enable the food engineer to more accurately scale-up and design extrusion processes. AD - Department of Food Science, Rutgers University, Center for Advanced Food Technology, New Brunswick, NJ 08901, USA. FAU - Dhanasekharan, M AU - Dhanasekharan M FAU - Kokini, J L AU - Kokini JL LA - eng PT - Journal Article CY - United States TA - J Food Process Eng JID - 101148874 SB - S MH - *Elasticity MH - Flour MH - *Food Technology MH - Models, Theoretical MH - Nonlinear Dynamics MH - *Rheology MH - Stress, Mechanical MH - Support, U.S. Gov't, Non-P.H.S. MH - Viscosity EDAT- 2002/08/27 10:00 MHDA- 2002/11/01 04:00 PST - ppublish SO - J Food Process Eng 2000 Aug;23(3):237-47. 34: Kar S, et al. Class of self-limiting growth...[PMID:12188761]Related Articles, Links UI - 22176991 PMID- 12188761 DA - 20020821 DCOM- 20021021 IS - 1539-3755 VI - 65 IP - 6 Pt 1 DP - 2002 Jun TI - Class of self-limiting growth models in the presence of nonlinear diffusion. PG - 061909 AB - The source term in a reaction-diffusion system, in general, does not involve explicit time dependence. A class of self-limiting growth models dealing with animal and tumor growth and bacterial population in a culture, on the other hand, are described by kinetics with explicit functions of time. We analyze a reaction-diffusion system to study the propagation of spatial front for these models. AD - Indian Association for the Cultivation of Science, Jadavpur, Calcutta 700 032, India. FAU - Kar, Sandip AU - Kar S FAU - Banik, Suman Kumar AU - Banik SK FAU - Ray, Deb Shankar AU - Ray DS LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 SB - IM MH - Animal MH - Bacteria/growth & development MH - Diffusion MH - *Growth MH - Human MH - *Models, Biological MH - Neoplasms/pathology MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2002/08/22 10:00 MHDA- 2002/10/22 04:00 PHST- 2002/Feb/08 [received] PHST- 2002/Jun/21 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Jun;65(6 Pt 1):061909. 35: Muller J, et al. Morphological instability and...[PMID:12188707]Related Articles, Links UI - 22176937 PMID- 12188707 DA - 20020821 DCOM- 20021021 IS - 1539-3755 VI - 65 IP - 6 Pt 1 DP - 2002 Jun TI - Morphological instability and dynamics of fronts in bacterial growth models with nonlinear diffusion. PG - 061111 AB - Depending on the growth condition, bacterial colonies can exhibit different morphologies. As argued by Ben-Jacob et al. there is biological and modeling evidence that a nonlinear diffusion coefficient of the type D(b)=D(0)b(k) is a basic mechanism that underlies almost all of the patterns and generates a long-wavelength instability. We study a reaction-diffusion system with a nonlinear diffusion coefficient and find that a unique planar traveling front solution exists whose velocity is uniquely determined by k and D=D(0)/D(n), where D(n) is the diffusion coefficient of the nutrient. Due to the fact that the bacterial diffusion coefficient vanishes when b-->0, in the front solution b vanishes in a singular way. As a result the standard linear stability analysis for fronts cannot be used. We introduce an extension of the stability analysis that can be applied to singular fronts, and use the method to perform a linear stability analysis of the planar bacteriological growth front. We show that a nonlinear diffusion coefficient generates a long-wavelength instability for k>0 and D0 and k--> infinity the dynamics of the growth zone essentially reduces to that of a sharp interface problem that is reminiscent of a so-called one-sided growth problem where the growth velocity is proportional to the gradient of a diffusion field ahead of the interface. The moving boundary approximation that we derive in these limits is quite accurate but surprisingly does not become a proper asymptotic theory in the strict mathematical sense in the limit D-->0, due to lack of full separation of scales on all dynamically relevant length scales. Our linear stability analysis and sharp interface formulation will also be applicable to other examples of interface formation due to nonlinear diffusion, like in porous media or in the problem of vortex motion in superconductors. AD - Instituut-Lorentz, Universiteit Leiden, Postbus 9506, 2300 RA Leiden, The Netherlands. FAU - Muller, Judith AU - Muller J FAU - Van Saarloos, Wim AU - Van Saarloos W LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 SB - IM MH - Bacteria/*growth & development MH - Biophysics MH - Comparative Study MH - Diffusion MH - *Models, Biological MH - Nonlinear Dynamics EDAT- 2002/08/22 10:00 MHDA- 2002/10/22 04:00 PHST- 2001/Nov/26 [received] PHST- 2002/Jun/28 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Jun;65(6 Pt 1):061111. 36: Vlad MO, et al. Neutrality condition and resp...[PMID:12188706]Related Articles, Links UI - 22176936 PMID- 12188706 DA - 20020821 DCOM- 20021021 IS - 1539-3755 VI - 65 IP - 6 Pt 1 DP - 2002 Jun TI - Neutrality condition and response law for nonlinear reaction-diffusion equations, with application to population genetics. PG - 061110 AB - We study a general class of nonlinear macroscopic evolution equations with "transport" and "reaction" terms which describe the dynamics of a species of moving individuals (atoms, molecules, quasiparticles, organisms, etc.). We consider that two types of individuals exist, "not marked" and "marked," respectively. We assume that the concentrations of both types of individuals are measurable and that they obey a neutrality condition, that is, the kinetic and transport properties of the "not marked" and "marked" individuals are identical. We suggest a response experiment, which consists in varying the fraction of "marked" individuals with the preservation of total fluxes, and show that the response of the system can be represented by a linear superposition law even though the underlying dynamics of the system is in general highly nonlinear. The linear response law is valid even for large perturbations and is not the result of a linearization procedure but rather a necessary consequence of the neutrality condition. First, we apply the response theorem to chemical kinetics, where the "marked species" is a molecule labeled with a radioactive isotope and there is no kinetic isotope effect. The susceptibility function of the response law can be related to the reaction mechanism of the process. Secondly we study the geographical distribution of the nonrecurrent, nonreversible neutral mutations of the nonrecombining portion of the Y chromosome from human populations and show that the fraction of mutants at a given point in space and time obeys a linear response law of the type introduced in this paper. The theory may be used for evaluating the geographic position and the moment in time where and when a mutation originated. AD - Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA. FAU - Vlad, Marcel Ovidiu AU - Vlad MO FAU - Moran, Federico AU - Moran F FAU - Tsuchiya, Masa AU - Tsuchiya M FAU - Cavalli-Sforza, L Luca AU - Cavalli-Sforza LL FAU - Oefner, Peter J AU - Oefner PJ FAU - Ross, John AU - Ross J LA - eng ID - GM28428/GM/NIGMS PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 SB - IM MH - Biochemistry MH - Chemical Engineering MH - Chemistry, Physical MH - Diffusion MH - Evolution MH - *Genetics, Population MH - Models, Genetic MH - Mutation MH - *Nonlinear Dynamics MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/08/22 10:00 MHDA- 2002/10/22 04:00 PHST- 2001/Dec/10 [received] PHST- 2002/Jun/25 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Jun;65(6 Pt 1):061110. 37: Jacobson Z, et al. The cell assembly, Mark III: ...[PMID:12187779]Related Articles, Links UI - 22176105 PMID- 12187779 DA - 20020821 DCOM- 20020909 IS - 0020-7454 VI - 112 IP - 3 DP - 2002 Mar TI - The cell assembly, Mark III: transitions between brain states and the localization and generalization of function. PG - 277-90 AB - A connectionist model of the cerebral cortex as a Markov chain is presented. The model reconciles localization of cortical functions, apparent in neuropsychological data, with the equipotentiality and diffusion of function that was noted in classical studies of learning. In addition, the model suggests that the specificity of some cortical activity can develop quickly from initial connections that are predominantly chaotic. It is not necessary to assume a high degree of "prewired" connections in the cortex of newborns. While the model does not require initial settings to be chaotic, neither does it require initial ordering stronger than chaos. Specifically, a large and initially randomly connected network of neurons rapidly develops several ergodically distinct subnetworks that operate independently. While the ergodic units operate independently and distinctly, they exhibit the property of equipotentially in that the specific events caused by an initial event are equally likely to be at any point in the ergodic set after very few synaptic events. AD - Health Canada, Carleton University, Psychology Department, Cognitive Science Program, Ottawa, Ontario, Canada. zack_jacobson@hc.gc.ca FAU - Jacobson, Zachary AU - Jacobson Z FAU - Pullman, Norman J AU - Pullman NJ FAU - Treurniet, William AU - Treurniet W LA - eng PT - Journal Article CY - United States TA - Int J Neurosci JID - 0270707 SB - IM MH - Animal MH - Cerebral Cortex/*physiology MH - Human MH - *Markov Chains MH - Memory MH - *Models, Biological MH - *Neural Networks (Computer) MH - *Nonlinear Dynamics EDAT- 2002/08/22 10:00 MHDA- 2002/09/11 10:01 PST - ppublish SO - Int J Neurosci 2002 Mar;112(3):277-90. 38: Jaffer TS, et al. A model cochlear partition in...[PMID:12186039]Related Articles, Links UI - 22173387 PMID- 12186039 DA - 20020820 DCOM- 20021017 IS - 0001-4966 VI - 112 IP - 2 DP - 2002 Aug TI - A model cochlear partition involving longitudinal elasticity. PG - 576-89 AB - This paper addresses the issue of longitudinal stiffness within the cochlea. A one-dimensional model of the cochlear partition is presented in which the resonant sections are coupled by longitudinal elastic elements. These elements functionally represent the aggregate mechanical effect of the connective tissue that spans the length of the organ of Corti. With the plate-like morphology of the cochlear partition in mind, the contribution of longitudinal elasticity to partition dynamics is appreciable, though weak and nonlinear. If the elasticity is considered Hookian then the nonlinearity takes a cubic form. Numerical solutions are presented that demonstrate the compressive nature of the partial differential nonlinear equations and their ability to produce realistic cubic distortion product otoacoustic emissions. Within the framework of this model, some speculations can be made regarding the dynamical function of the phalangeal processes, the sharpness of active cochlear mechanics, and the propogation of pathology along the partition. AD - Institute of Biomaterial and Biomedical Engineering, Toronto, Ontario, Canada. jaffer@ecf.utoronto.ca FAU - Jaffer, Taha S A AU - Jaffer TS FAU - Kunov, Hans AU - Kunov H FAU - Wong, Willy AU - Wong W LA - eng PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 RN - 0 (Reticulin) SB - IM MH - Basilar Membrane/physiology MH - Biomechanics MH - Cochlea/*physiology MH - Elasticity MH - Human MH - Nonlinear Dynamics MH - Organ of Corti/physiology MH - Otoacoustic Emissions, Spontaneous/physiology MH - Reference Values MH - Reticulin/physiology MH - Sound Spectrography MH - Support, Non-U.S. Gov't EDAT- 2002/08/21 10:00 MHDA- 2002/10/18 04:00 PST - ppublish SO - J Acoust Soc Am 2002 Aug;112(2):576-89. 39: Temprado JJ, et al. A dynamic pattern analysis of...[PMID:12183039]Related Articles, Links UI - 22171135 PMID- 12183039 DA - 20020816 DCOM- 20021028 IS - 0304-3940 VI - 329 IP - 3 DP - 2002 Sep 6 TI - A dynamic pattern analysis of coordination between breathing and rhythmic arm movements in humans. PG - 314-8 AB - We investigated the behavioral dynamics of human breathing-wrist movement coordination in a 1:1 frequency locking task. A pronation-supination wrist movement and a short trial duration were chosen to limit both mechanical and metabolic constraints on the respiratory system. Subjects voluntarily controlled their breathing rhythm to follow the metronome. We found that pronation-expiration and pronation-inspiration patterns coexisted as the (sole) stable fixed-point attractors of the coordination system. The pronation-expiration pattern was more stable than the pronation-inspiration pattern. Depending on the oscillation frequency, this differential stability gave rise to both absolute and relative coordination. These results show that simple behavioral laws of coordination encapsulate neural coupling dynamics evidenced from experimental research in human beings and animals. They challenge the classical view that such a coupling is not present for all imposed movement frequencies. Rather, relative coordination emerges as a result of the modification of coupling strength with frequency. These results can be accommodated by the asymmetric version of the HKB model of coordination dynamics. Thus, our data suggest that the principles and models of coordination dynamics may be taken as a reference to study the coupling of the motor and physiological subsystems involved in breathing-movement coordination. AD - UMR Mouvement et Perception, CNRS et Universite de la Mediterranee, Faculte des Sciences du Sport, Marseille, France. temprado@laps.univ-mrs.fr FAU - Temprado, J J AU - Temprado JJ FAU - Milliex, L AU - Milliex L FAU - Grelot, L AU - Grelot L FAU - Coyle, T AU - Coyle T FAU - Calvin, S AU - Calvin S FAU - Laurent, M AU - Laurent M LA - eng PT - Journal Article CY - Ireland TA - Neurosci Lett JID - 7600130 SB - IM MH - Arm/*physiology MH - Human MH - Models, Neurological MH - Movement/*physiology MH - Nonlinear Dynamics MH - Periodicity MH - Respiratory Mechanics/*physiology EDAT- 2002/08/17 10:00 MHDA- 2002/10/29 04:00 AID - S030439400200455X [pii] PST - ppublish SO - Neurosci Lett 2002 Sep 6;329(3):314-8. 40: Wennekers T. Dynamic approximation of spat...[PMID:12180403]Related Articles, Links UI - 22167780 PMID- 12180403 DA - 20020815 DCOM- 20020906 IS - 0899-7667 VI - 14 IP - 8 DP - 2002 Aug TI - Dynamic approximation of spatiotemporal receptive fields in nonlinear neural field models. PG - 1801-25 AB - This article presents an approximation method to reduce the spatiotemporal behavior of localized activation peaks (also called "bumps") in non-linear neural field equations to a set of coupled ordinary differential equations (ODEs) for only the amplitudes and tuning widths of these peaks. This enables a simplified analysis of steady-state receptive fields and their stability, as well as spatiotemporal point spread functions and dynamic tuning properties. A lowest-order approximation for peak amplitudes alone shows that much of the well-studied behavior of small neural systems (e.g., the Wilson-Cowan oscillator) should carry over to localized solutions in neural fields. Full spatiotemporal response profiles can further be reconstructed from this low-dimensional approximation. The method is applied to two standard neural field models: a one-layer model with difference-of-gaussians connectivity kernel and a two-layer excitatory-inhibitory network. Similar models have been previously employed in numerical studies addressing orientation tuning of cortical simple cells. Explicit formulas for tuning properties, instabilities, and oscillation frequencies are given, and exemplary spatiotemporal response functions, reconstructed from the low-dimensional approximation, are compared with full network simulations. AD - Max-Planck-Institute for Mathematics in the Sciences, Leipzig, Germany. Thomas.Wennekers@mis.mpg.de FAU - Wennekers, Thomas AU - Wennekers T LA - eng PT - Journal Article CY - United States TA - Neural Comput JID - 9426182 SB - IM MH - Animal MH - Cerebral Cortex/*physiology MH - *Models, Neurological MH - *Nonlinear Dynamics MH - Synaptic Transmission MH - Time Factors EDAT- 2002/08/16 10:00 MHDA- 2002/09/07 10:01 AID - 10.1162/089976602760128027 [doi] PST - ppublish SO - Neural Comput 2002 Aug;14(8):1801-25. 41: Hammel M, et al. Partition of local anesthetic...[PMID:12168538]Related Articles, Links UI - 22159070 PMID- 12168538 DA - 20020809 DCOM- 20020904 IS - 0031-7144 VI - 57 IP - 7 DP - 2002 Jul TI - Partition of local anesthetic heptacaine homologs between phosphatidylcholine bilayers in unilamellar liposomes and aqueous phase: UV-VIS spectrophotometry study. PG - 499 AD - Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University, Bratislava, Slovakia. FAU - Hammel, M AU - Hammel M FAU - Uhrikova, D AU - Uhrikova D FAU - Balgavy, P AU - Balgavy P LA - eng PT - Journal Article CY - Germany TA - Pharmazie JID - 9800766 RN - 0 (Anesthetics, Local) RN - 0 (Lipid Bilayers) RN - 0 (Liposomes) RN - 0 (Phosphatidylcholines) RN - 0 (Piperidines) RN - 55792-21-7 (heptacaine) SB - IM MH - Algorithms MH - Anesthetics, Local/*chemistry MH - Chemistry, Physical MH - Light MH - *Lipid Bilayers MH - Liposomes MH - Nonlinear Dynamics MH - Phosphatidylcholines/*chemistry MH - Piperidines/*chemistry MH - Scattering, Radiation MH - Spectrophotometry, Ultraviolet MH - Structure-Activity Relationship MH - Support, Non-U.S. Gov't EDAT- 2002/08/10 10:00 MHDA- 2002/09/06 10:01 PST - ppublish SO - Pharmazie 2002 Jul;57(7):499. 42: Newman TJ, et al. Population dynamics with a re...[PMID:12167352]Related Articles, Links UI - 22158207 PMID- 12167352 DA - 20020808 DCOM- 20021115 IS - 0040-5809 VI - 62 IP - 2 DP - 2002 Sep TI - Population dynamics with a refuge: fractal basins and the suppression of chaos. PG - 121-8 AB - We consider the effect of coupling an otherwise chaotic population to a refuge. A rich set of dynamical phenomena is uncovered. We consider two forms of density dependence in the active population: logistic and exponential. In the former case, the basin of attraction for stable population growth becomes fractal, and the bifurcation diagrams for the active and refuge populations are chaotic over a wide range of parameter space. In the case of exponential density dependence, the dynamics are unconditionally stable (in that the population size is always positive and finite), and chaotic behavior is completely eradicated for modest amounts of dispersal. We argue that the use of exponential density dependence is more appropriate, theoretically as well as empirically, in a model of refuge dynamics. AD - Department of Physics, University of Virginia, Charlottesville, Virginia 22903, USA. FAU - Newman, T J AU - Newman TJ FAU - Antonovics, J AU - Antonovics J FAU - Wilbur, H M AU - Wilbur HM LA - eng PT - Journal Article CY - United States TA - Theor Popul Biol JID - 0256422 SB - IM MH - Ecology MH - *Fractals MH - Models, Biological MH - *Nonlinear Dynamics MH - Plants MH - Population Density MH - *Population Dynamics MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/08/09 10:00 MHDA- 2002/11/26 04:00 AID - S0040580902915844 [pii] PST - ppublish SO - Theor Popul Biol 2002 Sep;62(2):121-8. 43: Albrecht DG, et al. Visual cortex neurons of monk...[PMID:12163540]Related Articles, Links UI - 22153559 PMID- 12163540 DA - 20020806 DCOM- 20020923 IS - 0022-3077 VI - 88 IP - 2 DP - 2002 Aug TI - Visual cortex neurons of monkeys and cats: temporal dynamics of the contrast response function. PG - 888-913 AB - Cortical neurons display two fundamental nonlinear response characteristics: contrast-set gain control (also termed contrast normalization) and response expansion (also termed half-squaring). These nonlinearities could play an important role in forming and maintaining stimulus selectivity during natural viewing, but only if they operate well within the time frame of a single fixation. To analyze the temporal dynamics of these nonlinearities, we measured the responses of individual neurons, recorded from the primary visual cortex of monkeys and cats, as a function of the contrast of transient stationary gratings that were presented for a brief interval (200 ms). We then examined 1) the temporal response profile (i.e., the post stimulus time histogram) as a function of contrast and 2) the contrast response function throughout the course of the temporal response. We found that the shape and complexity of the temporal response profile varies considerably from cell to cell. However, within a given cell, the shape remains relatively invariant as a function of contrast and appears to be simply scaled and shifted. Stated quantitatively, approximately 95% of the variation in the temporal responses as a function of contrast could be accounted for by scaling and shifting the average poststimulus time histogram. Equivalently, we found that the overall shape of the contrast response function (measured every 2 ms) remains relatively invariant from the onset through the entire temporal response. Further, the contrast-set gain control and the response expansion are fully expressed within the first 10 ms after the onset of the response. Stated quantitatively, the same, scaled Naka-Rushton equation (with the same half-saturation contrast and expansive response exponent) provides a good fit to the contrast response function from the first 10 ms through the last 10 ms of the temporal response. Based upon these measurements, it appears as though the two nonlinear properties, contrast-set gain control and response expansion, are present in full strength, virtually instantaneously, at the onset of the response. This observation suggests that response expansion and contrast-set gain control can influence the performance of visual cortex neurons very early in a single fixation, based on the contrast within that fixation. In the DISCUSSION, we consider the implications of the results within the context of 1) slower types of contrast gain control, 2) discrimination performance, 3) drifting steady-state measurements, 4) functional models that incorporate response expansion and contrast normalization, and 5) structural models of the biochemical and biophysical neural mechanisms. AD - Department of Psychology, University of Texas, Austin 78712, USA. Albrecht@psy.psyvax.utexas.edu FAU - Albrecht, Duane G AU - Albrecht DG FAU - Geisler, Wilson S AU - Geisler WS FAU - Frazor, Robert A AU - Frazor RA FAU - Crane, Alison M AU - Crane AM LA - eng ID - EY-02688/EY/NEI PT - Journal Article CY - United States TA - J Neurophysiol JID - 0375404 SB - IM MH - Animal MH - Cats MH - Contrast Sensitivity/*physiology MH - Electrophysiology MH - Macaca MH - Models, Theoretical MH - Neurons/physiology MH - Nonlinear Dynamics MH - Support, U.S. Gov't, P.H.S. MH - Time Factors MH - Visual Cortex/cytology/*physiology MH - Visual Perception/*physiology EDAT- 2002/08/07 10:00 MHDA- 2002/09/24 06:00 PST - ppublish SO - J Neurophysiol 2002 Aug;88(2):888-913. 44: Bourriez JL, et al. [Characterization of the func...[PMID:12162181]Related Articles, Links UI - 22152700 PMID- 12162181 DA - 20020806 DCOM- 20021008 IS - 0987-7053 VI - 32 IP - 3 DP - 2002 Jun TI - [Characterization of the functional relations between cerebral structures: the linear and non-linear] PG - 147-55 AB - Two kinds of methods are available in order to assess the functional relationships between different cerebral structures from the analysis of EEG signals: linear and non-linear methods. In this paper, we describe didactically the methodological bases of signal processing. After recalling the significance of the fundamental parameters of a sine wave: frequency, amplitude and phase, we show, from a first example about an epileptic seizure propagation, how a linear variation between phase and frequency can be interpreted as a small time difference between two EEG channels. This linear method hypothesises that these two signals are respectively the input and the output of a linear system. Then, we point out the limits of this method and we introduce non-linear methods. Among the latter, a recent approach introduces a realistic model of EEG which try to relate signal measured quantities to relations between underlying structures which produce them. AD - Service de Neurophysiologie Clinique, Hopital Roger Salengro, CHRU de Lille, 59037 Lille, France. jlbourriez@chru-lille.fr FAU - Bourriez, J L AU - Bourriez JL FAU - Jacquesson, J M AU - Jacquesson JM FAU - Derambure, P AU - Derambure P FAU - Guieu, J D AU - Guieu JD LA - fre PT - Journal Article PT - Review PT - Review, Tutorial TT - Caracterisation des relations fonctionnelles entre structures cerebrales: du lineaire au non lineaire. CY - Netherlands TA - Neurophysiol Clin JID - 8804532 SB - IM MH - Algorithms MH - Brain/*physiology MH - Electroencephalography/*statistics & numerical data MH - English Abstract MH - Epilepsy/physiopathology MH - Human MH - Linear Models MH - *Nonlinear Dynamics MH - *Signal Processing, Computer-Assisted RF - 7 EDAT- 2002/08/07 10:00 MHDA- 2002/10/09 04:00 PST - ppublish SO - Neurophysiol Clin 2002 Jun;32(3):147-55. 45: Dragoi V, et al. Dynamics of neuronal sensitiv...[PMID:12161755]Related Articles, Links UI - 22184393 PMID- 12161755 DA - 20020828 DCOM- 20020927 IS - 1097-6256 VI - 5 IP - 9 DP - 2002 Sep TI - Dynamics of neuronal sensitivity in visual cortex and local feature discrimination. PG - 883-91 AB - A striking aspect of natural scenes is that image features such as line orientation are strongly correlated at neighboring spatial locations but not at distant locations. Thus, during the viewing of a scene, eye movements are often accompanied by a change in the orientation structure of the image. How does this behavior influence the discrimination of local features and their encoding by visual cortical neurons? Here we examined the perceived changes in orientation induced by brief exposure to oriented image patterns in monkeys and humans, and then used reverse correlation to investigate dynamic changes in neuronal sensitivity in the primary visual cortex (V1) of behaving monkeys. Whereas brief adaptation to an oriented grating impaired identification of nearby orientations by broadening orientation selectivity and changing the preferred orientation of individual V1 neurons, it actually enhanced the identification of orthogonal orientations by sharpening neuronal selectivity. Hence, successive exposure to image patches of dissimilar spatial structure enhances both the ability to discriminate local features and the encoding of these features by V1 neurons. AD - Department of Brain and Cognitive Sciences, Picower Center for Learning and Memory, 45 Carleton Street, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. vdragoi@ai.mit.edu FAU - Dragoi, Valentin AU - Dragoi V FAU - Sharma, Jitendra AU - Sharma J FAU - Miller, Earl K AU - Miller EK FAU - Sur, Mriganka AU - Sur M LA - eng PT - Journal Article CY - United States TA - Nat Neurosci JID - 9809671 SB - IM MH - Action Potentials/physiology MH - Adaptation, Physiological/physiology MH - Animal MH - Contrast Sensitivity/*physiology MH - Eye Movements/physiology MH - Human MH - Macaca MH - Nerve Net/*physiology MH - Neural Pathways/*physiology MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Orientation/*physiology MH - Pattern Recognition, Visual/*physiology MH - Photic Stimulation MH - Psychomotor Performance/physiology MH - Reaction Time/physiology MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. MH - Visual Cortex/*physiology EDAT- 2002/08/06 10:00 MHDA- 2002/09/28 04:00 AID - 10.1038/nn900 [doi] AID - nn900 [pii] PST - ppublish SO - Nat Neurosci 2002 Sep;5(9):883-91. 46: Theilliol D, et al. Fault diagnosis and accommoda...[PMID:12160349]Related Articles, Links UI - 22149992 PMID- 12160349 DA - 20020805 DCOM- 20020913 IS - 0019-0578 VI - 41 IP - 3 DP - 2002 Jul TI - Fault diagnosis and accommodation of a three-tank system based on analytical redundancy. PG - 365-82 AB - This paper investigates the application of a fault diagnosis and accommodation method to a real system composed of three tanks. The performance of a closed-loop system can be altered by the occurrence of faults which can, in some circumstances, cause serious damage on the system. The research goal is to prevent the system deterioration by developing a controller that has some capabilities to compensate for faults, that is, the fault accommodation or fault-tolerant control. In this paper, a two-step scheme composed of a fault detection, isolation and estimation module, and a control compensation module is presented. The main contribution is to develop a unique structured residual generator able to isolate and estimate both sensor and actuator faults. This estimation is of paramount importance to compensate for these faults and to preserve the system performances. The application of this method to the three-tank system gives encouraging results which are presented and commented on in case of various kinds of faults. AD - Centre de Recherche en Automatique de Nancy-CNRS UPRESA 7039, Universite Henri Poincare, Vandoeuvre-les-Nancy, France. didier.theilliol@cran.uhp-nancy.fr FAU - Theilliol, Didier AU - Theilliol D FAU - Noura, Hassan AU - Noura H FAU - Ponsart, Jean-Christophe AU - Ponsart JC LA - eng PT - Journal Article CY - United States TA - ISA Trans JID - 0374750 SB - IM MH - Equipment Design MH - Equipment Failure Analysis/*methods MH - *Feedback MH - *Models, Theoretical MH - *Nonlinear Dynamics MH - Quality Control MH - Sensitivity and Specificity MH - Transducers EDAT- 2002/08/06 10:00 MHDA- 2002/09/14 10:01 PST - ppublish SO - ISA Trans 2002 Jul;41(3):365-82. 47: Wang M, et al. Design and implementation of ...[PMID:12160346]Related Articles, Links UI - 22149989 PMID- 12160346 DA - 20020805 DCOM- 20020913 IS - 0019-0578 VI - 41 IP - 3 DP - 2002 Jul TI - Design and implementation of a gain scheduling controller for a water level control system. PG - 323-31 AB - The design of a gain-scheduled proportional plus integral (PI) controller for a nonlinear water-tank level control system is presented. A novel approach of determining operating points in terms of interpolation error is also given. The controller is implemented in LABVIEW in the laboratory. The field test results of the system response at different operating conditions clearly illustrate the controller's improved performance over a fixed PI controller. AD - Automation, Information College, Taiyuan University of Technology, China. FAU - Wang, Miao AU - Wang M FAU - Crusca, Francesco AU - Crusca F LA - eng PT - Journal Article CY - United States TA - ISA Trans JID - 0374750 RN - 7732-18-5 (Water) SB - IM MH - Comparative Study MH - *Computer Simulation MH - Equipment Design MH - *Feedback MH - *Nonlinear Dynamics MH - Sensitivity and Specificity MH - Water EDAT- 2002/08/06 10:00 MHDA- 2002/09/14 10:01 PST - ppublish SO - ISA Trans 2002 Jul;41(3):323-31. 48: Zheng JH, et al. Detection of deterministic be...[PMID:12154333]Related Articles, Links UI - 22148897 PMID- 12154333 DA - 20020802 DCOM- 20021023 IS - 0929-5313 VI - 13 IP - 1 DP - 2002 Jul-Aug TI - Detection of deterministic behavior within the tissue injury-induced persistent firing of nociceptive neurons in the dorsal horn of the rat spinal cord. PG - 23-34 AB - To unravel the temporal features of the peripheral tissue injury induced persistent nociceptive discharge, single wide dynamic range (WDR) unit activity was recorded extracellularly in lumbar dorsal horn of anesthetized rats and interspike interval (ISI) series were obtained. Subcutaneous (s.c.) bee venom (BV) injection induced persistent discharge of spinal WDR neurons and has been well established to be a good model in evaluation of tissue injury induced pain. By applying a more novel approach, i.e., the unstable periodic orbit (UPO) identification method, we detected a family of significant separate UPOs (period-1, 2 and 3 orbits) within the ISI series of BV-induced nociceptive discharge, but not spontaneous background activity of spinal WDR neuron. Furthermore, temporally dynamic changes of UPOs at lower period-1, 2 and 3 for 4 successive time segments within 1 h time course of WDR unit firing showed temporally dynamic changes, i.e., new orbits with longer ISIs emerged and those with shorter ISIs vanished with time change. By using this method we suggest that BV-induced nociceptive discharge of spinal WDR neuron be a kind of deterministic activity and various UPOs may play some role in temporal coding of sensory information. AD - Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an 710032, People's Republic of China. FAU - Zheng, Ji-Hong AU - Zheng JH FAU - Jian, Zhong AU - Jian Z FAU - Chen, Jun AU - Chen J LA - eng PT - Journal Article CY - United States TA - J Comput Neurosci JID - 9439510 RN - 0 (Bee Venoms) SB - IM MH - Action Potentials/physiology MH - Animal MH - Bee Venoms/pharmacology MH - Neurons/drug effects/*physiology MH - Nociceptors/*physiopathology MH - Nonlinear Dynamics MH - Rats MH - Rats, Sprague-Dawley MH - Reaction Time/physiology MH - Spinal Cord/drug effects/*physiopathology MH - Spinal Cord Injuries/*physiopathology MH - Support, Non-U.S. Gov't EDAT- 2002/08/03 10:00 MHDA- 2002/10/31 04:00 PST - ppublish SO - J Comput Neurosci 2002 Jul-Aug;13(1):23-34. 49: Heintzmann R, et al. Saturated patterned excitatio...[PMID:12152701]Related Articles, Links UI - 22147204 PMID- 12152701 DA - 20020802 DCOM- 20020830 IS - 1084-7529 VI - 19 IP - 8 DP - 2002 Aug TI - Saturated patterned excitation microscopy--a concept for optical resolution improvement. PG - 1599-609 AB - The resolution of optical microscopy is limited by the numerical aperture and the wavelength of light. Many strategies for improving resolution such as 4Pi and I5M have focused on an increase of the numerical aperture. Other approaches have based resolution improvement in fluorescence microscopy on the establishment of a nonlinear relationship between local excitation light intensity in the sample and in the emitted light. However, despite their innovative character, current techniques such as stimulated emission depletion (STED) and ground-state depletion (GSD) microscopy require complex optical configurations and instrumentation to narrow the point-spread function. We develop the theory of nonlinear patterned excitation microscopy for achieving a substantial improvement in resolution by deliberate saturation of the fluorophore excited state. The postacquisition manipulation of the acquired data is computationally more complex than in STED or GSD, but the experimental requirements are simple. Simulations comparing saturated patterned excitation microscopy with linear patterned excitation microscopy (also referred to in the literature as structured illumination or harmonic excitation light microscopy) and ordinary widefield microscopy are presented and discussed. The effects of photon noise are included in the simulations. AD - Max-Planck Institute for Biophysical Chemistry, Gottingen, Germany. rheintz@gwdg.de FAU - Heintzmann, Rainer AU - Heintzmann R FAU - Jovin, Thomas M AU - Jovin TM FAU - Cremer, Christoph AU - Cremer C LA - eng PT - Journal Article CY - United States TA - J Opt Soc Am A Opt Image Sci Vis JID - 9800943 SB - IM MH - Computer Simulation MH - *Microscopy MH - Models, Theoretical MH - Nonlinear Dynamics MH - *Optics MH - Support, Non-U.S. Gov't MH - User-Computer Interface EDAT- 2002/08/03 10:00 MHDA- 2002/08/31 10:01 PST - ppublish SO - J Opt Soc Am A Opt Image Sci Vis 2002 Aug;19(8):1599-609. 50: Dominici F, et al. On the use of generalized add...[PMID:12142253]Related Articles, Links UI - 22137383 PMID- 12142253 DA - 20020726 DCOM- 20020829 IS - 0002-9262 VI - 156 IP - 3 DP - 2002 Aug 1 TI - On the use of generalized additive models in time-series studies of air pollution and health. PG - 193-203 AB - The widely used generalized additive models (GAM) method is a flexible and effective technique for conducting nonlinear regression analysis in time-series studies of the health effects of air pollution. When the data to which the GAM are being applied have two characteristics--1) the estimated regression coefficients are small and 2) there exist confounding factors that are modeled using at least two nonparametric smooth functions--the default settings in the gam function of the S-Plus software package (version 3.4) do not assure convergence of its iterative estimation procedure and can provide biased estimates of regression coefficients and standard errors. This phenomenon has occurred in time-series analyses of contemporary data on air pollution and mortality. To evaluate the impact of default implementation of the gam software on published analyses, the authors reanalyzed data from the National Morbidity, Mortality, and Air Pollution Study (NMMAPS) using three different methods: 1) Poisson regression with parametric nonlinear adjustments for confounding factors; 2) GAM with default convergence parameters; and 3) GAM with more stringent convergence parameters than the default settings. The authors found that pooled NMMAPS estimates were very similar under the first and third methods but were biased upward under the second method. AD - Department of Biostatistics, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205-3179, USA. fdominic@jhsph.edu FAU - Dominici, Francesca AU - Dominici F FAU - McDermott, Aidan AU - McDermott A FAU - Zeger, Scott L AU - Zeger SL FAU - Samet, Jonathan M AU - Samet JM LA - eng ID - 5P30ES03819-12/ES/NIEHS PT - Journal Article CY - United States TA - Am J Epidemiol JID - 7910653 SB - IM MH - Air Pollution/*adverse effects/*statistics & numerical data MH - Algorithms MH - Epidemiologic Factors MH - Health Status MH - Human MH - *Models, Statistical MH - Morbidity MH - Mortality MH - Nonlinear Dynamics MH - Regression Analysis MH - Statistics, Nonparametric MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. MH - United States EDAT- 2002/07/27 10:00 MHDA- 2002/08/30 10:01 PST - ppublish SO - Am J Epidemiol 2002 Aug 1;156(3):193-203. 51: Gotmar G, et al. Investigation of the heteroge...[PMID:12141652]Related Articles, Books, LinkOut UI - 22136746 PMID- 12141652 DA - 20020726 DCOM- 20020906 IS - 0003-2700 VI - 74 IP - 13 DP - 2002 Jul 1 TI - Investigation of the heterogeneous adsorption behavior of selected enantiomers on immobilized alpha1-acid glycoprotein. PG - 2950-9 AB - A complete census was made of the interactions between enantiomeric solutes and the chiral protein column CHIRAL-AGP with the theory of nonlinear LC as tool. The surface is heterogeneous, having a small number of strong enantioselective adsorption sites and a large number of weak nonselective ones. When the eluent pH was increased, the "linear" retention of (i) the amines increased strongly as a result of a strong increase in the enantioselective binding strength, whereas (ii) the retention of the aprot increased slightly as a result of an increase in both the enantioselective binding strength and its capacity. The retention of (iii) the acid has a maximum originating solely from the enantioselective binding energy, whereas the nonselective equilibria decreased steadily. For all compounds, the enantioselective equilibrium constants increase relatively more than the nonselective ones with increasing pH. AD - Center for Surface Biotechnology, Uppsala, Sweden. FAU - Gotmar, Gustaf AU - Gotmar G FAU - Albareda, Nuria Robinat AU - Albareda NR FAU - Fomstedt, Torgny AU - Fomstedt T LA - eng PT - Journal Article CY - United States TA - Anal Chem JID - 0370536 RN - 0 (Orosomucoid) SB - IM MH - Adsorption MH - Algorithms MH - Chromatography, Liquid MH - Hydrogen-Ion Concentration MH - Nonlinear Dynamics MH - Orosomucoid/*chemistry MH - Stereoisomerism MH - Support, Non-U.S. Gov't MH - Thermodynamics EDAT- 2002/07/27 10:00 MHDA- 2002/09/07 10:01 PST - ppublish SO - Anal Chem 2002 Jul 1;74(13):2950-9. 52: Jing H, et al. Relationship of nonlinear ana...[PMID:12138304]Related Articles, Books, LinkOut UI - 22133221 PMID- 12138304 DA - 20020724 DCOM- 20020904 LR - 20021101 IS - 0014-3022 VI - 48 IP - 1 DP - 2002 TI - Relationship of nonlinear analysis, MRI and SPECT in the lateralization of temporal lobe epilepsy. PG - 11-9 AB - OBJECTIVES: The purpose of this study was to investigate the correlation of lateralization by nonlinear analysis, magnetic resonance imaging (MRI) and interictal single-photon emission computed tomography (SPECT) in patients with temporal lobe epilepsy. METHODS: Twenty-three patients (7 males, 16 females) were examined by MRI, interictal SPECT and EEG. Nonlinear dynamic properties of neuronal networks were estimated by calculating correlation dimensions on interictal EEG signals and corresponding surrogate data. Lateralization was detected based on the criteria introduced in this study. Concordance rates of the results among the three methods were compared. RESULTS: Epileptogenic foci were shown in the temporal areas in 21 patients using the nonlinear method (8 left, 2 right, 11 both), while 20 patients showed abnormalities in temporal lobes on MR images (13 left, 5 right, 2 both). Low cerebral blood flows of the temporal lobes were detected in all patients (11 left, 8 right, 4 both). Completely concordant lateralization was observed in 8 patients (35%) for the nonlinear method and MRI, in 9 patients (39%) for the nonlinear method and SPECT, and in 10 patients (43%) for MRI and SPECT. There were no significant differences among the concordance rates for these different methods. CONCLUSIONS: Our results revealed that correlation dimension is useful for differentiating dynamic properties of neuronal networks in the interictal state, and can provide informative data for localizing epileptogenic foci in epileptic patients. Therefore, the present nonlinear method is recommended for use with patients during presurgical evaluation. CI - Copyright 2002 S. Karger AG, Basel AD - Department of Neuropsychiatry, Faculty of Medicine, Kagoshima University, Kagoshima City, Japan. hjing@axon.rutgers.edu FAU - Jing, Hongkui AU - Jing H FAU - Takigawa, Morikuni AU - Takigawa M FAU - Benasich, April Ann AU - Benasich AA LA - eng PT - Journal Article CY - Switzerland TA - Eur Neurol JID - 0150760 SB - IM MH - Adolescent MH - Adult MH - Child MH - *Electroencephalography MH - Epilepsy, Temporal Lobe/*diagnosis/metabolism/physiopathology/radionuclide imaging MH - Female MH - Human MH - *Magnetic Resonance Imaging MH - Male MH - Nonlinear Dynamics MH - *Tomography, Emission-Computed, Single-Photon EDAT- 2002/07/26 10:00 MHDA- 2002/09/06 10:01 AID - ene48011 [pii] PST - ppublish SO - Eur Neurol 2002;48(1):11-9. 53: Kennedy JS, et al. Serial cerebrospinal fluid tr...[PMID:12137916]Related Articles, Books, LinkOut UI - 22133560 PMID- 12137916 DA - 20020724 DCOM- 20020924 IS - 0024-3205 VI - 71 IP - 14 DP - 2002 Aug 23 TI - Serial cerebrospinal fluid tryptophan and 5-hydroxy indoleacetic acid concentrations in healthy human subjects. PG - 1703-15 AB - The role of the serotonergic system in the pathogenesis of behavioral disorders such as depression, alcoholism, obsessive-compulsive disorder, and violence is not completely understood. Measurement of the concentration of neurotransmitters and their metabolites in cerebrospinal fluid (CSF) is considered among the most valid, albeit indirect, methods of assessing central nervous system function in man. However, most studies in humans have measured lumbar CSF concentrations only at single time points, thus not taking into account rhythmic or episodic variations in levels of neurotransmitters, precursors, or metabolites. We have continuously sampled lumbar CSF via subarachnoid catheter in 12 healthy volunteers, aged 20-65 years. One ml (every 10 min) CSF samples were collected at a rate of 0.1ml/min for 24-hour (h), and the levels of tryptophan (TRP) and 5-hydroxy indoleacetic acid (5-HIAA) were measured. Variability across all 12 subjects was significantly greater (P < 0.0001) than the variability seen in repeated analysis of a reference CSF sample for both 5-HIAA (32.0% vs 7.9%) and TRP (25.4% vs 7.0%), confirming the presence of significant biological variability during the 24-hr period examined. This variability could not be explained solely by meal related effects. Cosinor analysis of the 24-hr TRP concentrations from all subjects revealed a significant diurnal pattern in CSF TRP levels, whereas the 5-HIAA data were less consistent. These studies indicate that long-term serial CSF sampling reveals diurnal and biological variability not evident in studies based on single CSF samples. AD - The Eli Lilly Corporation, Indianapolis, IN, USA. FAU - Kennedy, John S AU - Kennedy JS FAU - Gwirtsman, Harry E AU - Gwirtsman HE FAU - Schmidt, Dennis E AU - Schmidt DE FAU - Johnson, Benjamin W AU - Johnson BW FAU - Fielstein, Elliot AU - Fielstein E FAU - Salomon, Ronald M AU - Salomon RM FAU - Shiavi, Richard G AU - Shiavi RG FAU - Ebert, Michael H AU - Ebert MH FAU - Parris, Winston C V AU - Parris WC FAU - Loosen, Peter T AU - Loosen PT LA - eng ID - RR-00095/RR/NCRR PT - Clinical Trial PT - Journal Article CY - England TA - Life Sci JID - 0375521 RN - 54-16-0 (Hydroxyindoleacetic Acid) RN - 73-22-3 (Tryptophan) SB - IM MH - Adult MH - Aged MH - Algorithms MH - Circadian Rhythm MH - Cluster Analysis MH - Eating/physiology MH - Female MH - Human MH - Hydroxyindoleacetic Acid/*cerebrospinal fluid MH - Male MH - Middle Age MH - Nonlinear Dynamics MH - Reference Values MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. MH - Tryptophan/*cerebrospinal fluid EDAT- 2002/07/26 10:00 MHDA- 2002/09/25 06:00 AID - S0024320502018994 [pii] PST - ppublish SO - Life Sci 2002 Aug 23;71(14):1703-15. 54: Makeig S. Response: event-related brain...[PMID:12127749]Related Articles, Books, LinkOut UI - 22127336 PMID- 12127749 DA - 20020719 DCOM- 20020910 IS - 0166-2236 VI - 25 IP - 8 DP - 2002 Aug TI - Response: event-related brain dynamics -- unifying brain electrophysiology. PG - 390 AD - Swartz Center for Computational Neuroscience, Institute for Neural Computation, University of California San Diego, La Jolla, CA 92093-0961, USA. smakeig@ucsd.edu FAU - Makeig, Scott AU - Makeig S LA - eng PT - Comment PT - Journal Article PT - Review PT - Review, Tutorial CY - England TA - Trends Neurosci JID - 7808616 SB - IM CON - Trends Neurosci. 2002 Aug;25(8):387-9. PMID: 12127748 MH - Action Potentials/*physiology MH - Brain/cytology/*physiology MH - Cognition/*physiology MH - Electroencephalography MH - Evoked Potentials/*physiology MH - Models, Neurological MH - Neurons/cytology/*physiology MH - *Nonlinear Dynamics RF - 8 EDAT- 2002/07/20 10:00 MHDA- 2002/09/11 10:01 AID - S0166223602021987 [pii] PST - ppublish SO - Trends Neurosci 2002 Aug;25(8):390. 55: Penny WD, et al. Event-related brain dynamics....[PMID:12127748]Related Articles, Books, LinkOut UI - 22127335 PMID- 12127748 DA - 20020719 DCOM- 20020910 IS - 0166-2236 VI - 25 IP - 8 DP - 2002 Aug TI - Event-related brain dynamics. PG - 387-9 AB - Event-related potentials (ERPs) provide evidence of a direct link between cognitive events and brain electrical activity in a wide range of cognitive paradigms. It has generally been held that an ERP is the result of a set of discrete stimulus-evoked brain events. A recent study, however, provides new evidence to suggest that some ERP components might be generated by stimulus-induced changes in ongoing brain dynamics. This is consistent with views emerging from several neuroscientific fields, suggesting that phase synchronization of ongoing rhythms across different spatio-temporal scales mediates the functional integration necessary to perform higher cognitive tasks. AD - Wellcome Department of Imaging Neuroscience, University College London, 12 Queen Square, London WC1N 3BG, UK. wpenny@fil.ion.ucl.ac.uk FAU - Penny, Will D AU - Penny WD FAU - Kiebel, Stephan J AU - Kiebel SJ FAU - Kilner, James M AU - Kilner JM FAU - Rugg, Mick D AU - Rugg MD LA - eng PT - Comment PT - Journal Article PT - Review PT - Review, Tutorial CY - England TA - Trends Neurosci JID - 7808616 SB - IM CON - Science. 2002 Jan 25;295(5555):690-4. PMID: 11809976 CIN - Trends Neurosci. 2002 Aug;25(8):390. PMID: 12127749 MH - Animal MH - Biological Clocks/physiology MH - Brain/cytology/*physiology MH - Cognition/*physiology MH - Evoked Potentials/*physiology MH - Human MH - Nerve Net/cytology/*physiology MH - Neural Pathways/cytology/*physiology MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Perception/*physiology MH - Support, Non-U.S. Gov't RF - 16 EDAT- 2002/07/20 10:00 MHDA- 2002/09/11 10:01 AID - S0166223602022026 [pii] PST - ppublish SO - Trends Neurosci 2002 Aug;25(8):387-9. 56: Efremova TM, et al. [Chaotic component of human h...[PMID:12125394]Related Articles, Books, LinkOut UI - 22121683 PMID- 12125394 DA - 20020719 DCOM- 20021024 IS - 0044-4677 VI - 52 IP - 3 DP - 2002 May-Jun TI - [Chaotic component of human high-frequency EEG in the state of quiet wakefulness] PG - 283-91 AB - Chaotic component of human EEG oscillations in the high-frequency band (14.7-100 Hz) was investigated. EEG was recorded from four points in symmetrical frontal and occipital scalp areas. The results of the non-linear analysis of the high-frequency EEG indicate the existence of the deterministic chaotic component with a high attractor correlation dimension. It was significantly different from the respective values of the Gaussian noise filtered in the same frequency band. In the state of quiet wakefulness (eyes closed), the dimensions of chaotic components of the EEG in all derivations did not differ from each other. Analysis of correlation pairs between the ensembles of correlation dimensions of the high-frequency EEG revealed reliable patterns of significant connections between the neocortical areas with individual features in different subjects. When the functional state of the brain was changed by hyperventilation, both the values of the correlation dimensions and the structure of inter-area connection patterns changed. We believe that the nonlinear component of high-frequency EEG is a sensitive and local characteristic of the functional state of the human brain. AD - Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow. FAU - Efremova, T M AU - Efremova TM FAU - Kulikov, M A AU - Kulikov MA LA - rus PT - Journal Article TT - Khaoticheskaia sostavliaiushchiaia vysokochastotnoi EEG cheloveka v sostoianii spokoinogo bodrstvovaniia. CY - Russia TA - Zh Vyssh Nerv Deiat Im I P Pavlova JID - 9421551 SB - IM MH - Brain/*physiology/physiopathology MH - *Electroencephalography MH - English Abstract MH - Human MH - Hyperventilation/physiopathology MH - Meditation MH - Nonlinear Dynamics MH - Normal Distribution MH - Rest MH - Wakefulness/*physiology EDAT- 2002/07/20 10:00 MHDA- 2002/10/31 04:00 PST - ppublish SO - Zh Vyssh Nerv Deiat Im I P Pavlova 2002 May-Jun;52(3):283-91. 57: Konner M. Weaving life's pattern....[PMID:12124603]Related Articles, Books, LinkOut UI - 22120343 PMID- 12124603 DA - 20020718 DCOM- 20020809 IS - 0028-0836 VI - 418 IP - 6895 DP - 2002 Jul 18 TI - Weaving life's pattern. PG - 279 AD - Emory University, Atlanta, Georgia, USA. FAU - Konner, Melvin AU - Konner M LA - eng PT - Journal Article CY - England TA - Nature JID - 0410462 SB - IM MH - Apoptosis MH - Brain/*cytology/*growth & development/physiology MH - *Cell Differentiation MH - Developmental Biology/*trends MH - Embryo/*cytology/embryology MH - Environment MH - Human MH - Human Genome Project MH - Learning/physiology MH - Nonlinear Dynamics MH - Psychology EDAT- 2002/07/19 10:00 MHDA- 2002/08/10 10:01 AID - 10.1038/418279a [doi] AID - 418279a [pii] PST - ppublish SO - Nature 2002 Jul 18;418(6895):279. 58: Diambra L. Detecting epileptic spikes....[PMID:12121320]Related Articles, Books, LinkOut UI - 22117277 PMID- 12121320 DA - 20020717 DCOM- 20020906 IS - 0013-9580 VI - 43 Suppl 5 DP - 2002 TI - Detecting epileptic spikes. PG - 194-5 AB - We present a technique for automatic detection of epileptic spikes in electroencephalogram (EEG) recordings. We used a nonlinear modeling method that enables us to detect rapidly and accurately epileptic behavior in the EEG signal. Our approach is illustrated by an application to interictal activity from a patient with focal epilepsy. AD - Departamento de Fisiologia e Biofisica ICB, Universidade de Sao Paulo, Av. Lineu Prestes 1524, cep 05508-900 Sao Paulo, SP, Brazil. FAU - Diambra, L AU - Diambra L LA - eng PT - Journal Article CY - United States TA - Epilepsia JID - 2983306R SB - IM MH - Action Potentials MH - Automation MH - Electroencephalography/*methods MH - Epilepsies, Partial/physiopathology MH - Epilepsy/*physiopathology MH - Human MH - Models, Neurological MH - Nonlinear Dynamics MH - Time Factors EDAT- 2002/07/18 10:00 MHDA- 2002/09/07 10:01 AID - epis6005 [pii] PST - ppublish SO - Epilepsia 2002;43 Suppl 5:194-5. 59: Naylor D. Changes in nonlinear signal p...[PMID:12121319]Related Articles, Books, LinkOut UI - 22117276 PMID- 12121319 DA - 20020717 DCOM- 20020906 IS - 0013-9580 VI - 43 Suppl 5 DP - 2002 TI - Changes in nonlinear signal processing in rat hippocampus associated with loss of paired-pulse inhibition or epileptogenesis. PG - 188-93 AB - PURPOSE: To study acute and chronic physiological effects of perforant path stimulation using paired-pulse and nonlinear signal analysis techniques (Wiener kernel analysis). METHODS: Two to 3-month-old Wistar rats were implanted with stimulating electrodes in the perforant path and recording electrodes in the granule cell layer. Loss of paired-pulse inhibition was produced with 2 Hz continuous and 20 Hz (10 s/min) intermittent stimulation for periods of 1-15 min (0.1 ms, 20 v pulses). Some animals received 30-60 min of stimulation, a model for status epilepticus/epileptogenesis. Responses to paired-pulse or white noise inputs were recorded sequentially. RESULTS: Loss of inhibition with brief 1-3 min of stimulation, measured by increase paired-pulse ratio (P2/P1 ISI 40 ms) from 0.25 (+/-0.27) pre- to 1.02 (+/-0.18) post-stimulation (p < 0.001), lasted 43 (+/-15) min. For 30-60 min of stimulation, the paired-pulse ratios were 0.088 (+/-0.11), 1.59 (+/-0.036), 0.06 (+/-0.11), 0.82 (+/-0.22) for pre-, immediate post-, 1 week post-, and 1 month poststimulation, respectively (p < 0.025). Compared to prestimulation values, Wiener kernel amplitudes for immediate, 1 week, and 1 month poststimulation were 24% (+/-13%), 72% (+/-17%), and 31% (+/-21%), respectively (p < 0.05). Wiener kernels 1 month poststimulation showed response prolongation with increased opportunity for excitatory interactions of inputs (particularly those separated by 4 ms). CONCLUSIONS: Brief perforant path stimulation causes sustained loss of inhibition in the dentate, possibly an early event in the transition to status epilepticus. Stimulation for 30-60 min causes chronic changes in paired-pulse and white noise (Wiener kernel) responses. Transient recovery occurs by 1 week, but later new features appear (including delayed/late inhibition and potential excitatory cross-talk) that might favor epileptic seizures. AD - VA Greater Los Angeles Healthcare System/UCLA School of Medicine, 11301 Wilshire Boulevard, Bldg 500, Rm 3256, Los Angeles, CA 90073, USA. dnaylor@ucla.edu FAU - Naylor, David AU - Naylor D LA - eng PT - Journal Article CY - United States TA - Epilepsia JID - 2983306R SB - IM MH - Animal MH - Electric Stimulation/methods MH - Epilepsy/etiology/*physiopathology MH - Hippocampus/*physiopathology MH - *Neural Inhibition MH - *Nonlinear Dynamics MH - Rats MH - Rats, Wistar MH - Signal Transduction/*physiology MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/07/18 10:00 MHDA- 2002/09/07 10:01 AID - epis6036 [pii] PST - ppublish SO - Epilepsia 2002;43 Suppl 5:188-93. 60: Tsuda A, et al. Chaotic mixing deep in the lu...[PMID:12119385]Related Articles, Books, LinkOut UI - 22133771 PMID- 12119385 DA - 20020724 DCOM- 20020904 IS - 0027-8424 VI - 99 IP - 15 DP - 2002 Jul 23 TI - Chaotic mixing deep in the lung. PG - 10173-8 AB - Our current understanding of the transport and deposition of aerosols (viruses, bacteria, air pollutants, aerosolized drugs) deep in the lung has been grounded in dispersive theories based on untested assumptions about the nature of acinar airflow fields. Traditionally, these have been taken to be simple and kinematically reversible. In this article, we apply the recently discovered fluid mechanical phenomenon of irreversible low-Reynolds number flow to the lung. We demonstrate, through flow visualization studies in rhythmically ventilated rat lungs, that such a foundation is false, and that chaotic mixing may be key to aerosol transport. We found substantial alveolar flow irreversibility with stretched and folded fractal patterns, which lead to a sudden increase in mixing. These findings support our theory that chaotic alveolar flow--characterized by stagnation saddle points associated with alveolar vortices--governs gas kinematics in the lung periphery, and hence the transport, mixing, and ultimately the deposition of fine aerosols. This mechanism calls for a rethinking of the relationship of exposure and deposition of fine inhaled particles. AD - Physiology Program, Harvard University, Boston, MA 02115, USA. atsuda@hsph.harvard.edu FAU - Tsuda, Akira AU - Tsuda A FAU - Rogers, Rick A AU - Rogers RA FAU - Hydon, Peter E AU - Hydon PE FAU - Butler, James P AU - Butler JP LA - eng ID - HL-54885/HL/NHLBI PT - Journal Article CY - United States TA - Proc Natl Acad Sci U S A JID - 7505876 SB - IM MH - Animal MH - In Vitro MH - Kinetics MH - Lung/cytology/*physiology MH - Models, Biological MH - Nonlinear Dynamics MH - Pulmonary Alveoli/physiology MH - Rats MH - Rats, Sprague-Dawley MH - Respiration, Artificial MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. MH - Time Factors EDAT- 2002/07/18 10:00 MHDA- 2002/09/06 10:01 PHST- 2002/Jul/15 [aheadofprint] AID - 10.1073/pnas.102318299 [doi] AID - 102318299 [pii] PST - ppublish SO - Proc Natl Acad Sci U S A 2002 Jul 23;99(15):10173-8. 61: [No authors listed] Nonlinear Dynamics and Chaos ...[PMID:12113258]Related Articles, Books, LinkOut UI - 22104769 PMID- 12113258 DA - 20020711 DCOM- 20020712 IS - 0077-8923 VI - 867 DP - 1998 Dec 30 TI - Nonlinear Dynamics and Chaos in Astrophysics: A Festschrift in Honor of George Contopoulos. Proceedings of the thirteenth conference of the series Florida Workshops in Nonlinear Astronomy. February 12-14, 1998. Gainesville, Florida, USA. PG - 1-335 LA - eng PT - Bibliography PT - Biography PT - Congresses PT - Festschrift PT - Historical Article CY - United States TA - Ann N Y Acad Sci JID - 7506858 SB - IM MH - Astronomy/*history MH - History of Medicine, 20th Cent. MH - History of Medicine, 21st Cent. MH - *Nonlinear Dynamics MH - Portraits PS - Contopoulos G EDAT- 2002/07/13 10:00 MHDA- 2002/07/13 10:01 PST - ppublish SO - Ann N Y Acad Sci 1998 Dec 30;867:1-335. 62: Walters GD. Developmental trajectories, t...[PMID:12112987]Related Articles, Books, LinkOut UI - 22108389 PMID- 12112987 DA - 20020712 DCOM- 20020820 LR - 20021101 IS - 0306-624X VI - 46 IP - 1 DP - 2002 Feb TI - Developmental trajectories, transitions, and nonlinear dynamical systems: a model of crime deceleration and desistance. PG - 30-44 AB - Research on crime-related developmental trajectories is reviewed with outcomes revealing the existence of several trajectories rather than a single general pattern. Each trajectory is marked by transitions that define the pattern's path and direction over time. These anticipated transitions differ from the unanticipated transitions known to precipitate crime deceleration and desistance. Borrowing principles from nonlinear dynamical systems theory--sensitive dependence on initial conditions, chaotic attractors, and self-organization in particular--this article offers a model of crime deceleration and desistance in which belief systems congruent with crime are altered in phases--initiation, transition, maintenance--to create belief systems incongruent with crime. The practical implications of this model are discussed and suggestions for future research are outlined. AD - Psychology Services, Federal Correctional Institution-Schuylkill, P.O. Box 700, Minersville, PA 17954-0700, USA. gwalters@bop.gov FAU - Walters, Glenn D AU - Walters GD LA - eng PT - Journal Article CY - United States TA - Int J Offender Ther Comp Criminol JID - 0333601 SB - IM MH - Adolescent MH - Aggression/psychology MH - Child MH - *Crime/statistics & numerical data MH - Human MH - Male MH - *Nonlinear Dynamics EDAT- 2002/07/13 10:00 MHDA- 2002/08/21 10:01 PST - ppublish SO - Int J Offender Ther Comp Criminol 2002 Feb;46(1):30-44. 63: Calhoun VD, et al. Different activation dynamics...[PMID:12112769]Related Articles, Books, LinkOut UI - 22106086 PMID- 12112769 DA - 20020711 DCOM- 20020821 LR - 20021108 IS - 1065-9471 VI - 16 IP - 3 DP - 2002 Jul TI - Different activation dynamics in multiple neural systems during simulated driving. PG - 158-67 AB - Driving is a complex behavior that recruits multiple cognitive elements. We report on an imaging study of simulated driving that reveals multiple neural systems, each of which have different activation dynamics. The neural correlates of driving behavior are identified with fMRI and their modulation with speed is investigated. We decompose the activation into interpretable pieces using a novel, generally applicable approach, based upon independent component analysis. Some regions turn on or off, others exhibit a gradual decay, and yet others turn on transiently when starting or stopping driving. Signal in the anterior cingulate cortex, an area often associated with error monitoring and inhibition, decreases exponentially with a rate proportional to driving speed, whereas decreases in frontoparietal regions, implicated in vigilance, correlate with speed. Increases in cerebellar and occipital areas, presumably related to complex visuomotor integration, are activated during driving but not associated with driving speed. CI - Copyright 2002 Wiley-Liss, Inc. AD - Division of Psychiatric Neuro-Imaging, Department of Psychiatry, Johns Hopkins University, Baltimore, Maryland 21205, USA. vcalhoun@jhu.edu FAU - Calhoun, Vince D AU - Calhoun VD FAU - Pekar, James J AU - Pekar JJ FAU - McGinty, Vince B AU - McGinty VB FAU - Adali, Tulay AU - Adali T FAU - Watson, Todd D AU - Watson TD FAU - Pearlson, Godfrey D AU - Pearlson GD LA - eng ID - 1P41RR15241-01/RR/NCRR ID - M01-RR00052/RR/NCRR PT - Journal Article CY - United States TA - Hum Brain Mapp JID - 9419065 SB - IM EIN - Hum Brain Mapp 2002 Oct;17(2):141-2 MH - Adult MH - Attention/physiology MH - Automobile Driving/*psychology MH - Brain/*anatomy & histology/*physiology MH - Brain Mapping MH - Cognition/physiology MH - Eye Movements/physiology MH - Female MH - Human MH - Laterality/physiology MH - Magnetic Resonance Imaging MH - Male MH - Motion Perception/physiology MH - Motor Skills/*physiology MH - Movement/*physiology MH - Nerve Net/*anatomy & histology/*physiology MH - Nonlinear Dynamics MH - Orientation/physiology MH - Space Perception/physiology MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/07/12 10:00 MHDA- 2002/08/22 10:01 AID - 10.1002/hbm.10032 [doi] PST - ppublish SO - Hum Brain Mapp 2002 Jul;16(3):158-67. 64: Fitzgerald AP, et al. Modelling HIV viral rebound u...[PMID:12111889]Related Articles, Books, LinkOut UI - 22107558 PMID- 12111889 DA - 20020711 DCOM- 20020910 LR - 20021101 IS - 0277-6715 VI - 21 IP - 14 DP - 2002 Jul 30 TI - Modelling HIV viral rebound using non-linear mixed effects models. PG - 2093-108 AB - Individuals infected with the human immunodeficiency virus type 1 (HIV-1) who initiate antiretroviral therapy typically experience a marked decline in concentrations of HIV-1 RNA in plasma. Often, however, viral rebound occurs within the first year of treatment and this rebound may be associated with resistance to antiretroviral therapy. For this reason, it is important to study the patterns of virological response of HIV-1 RNA to treatment. In particular, there is interest in the relationship between the lowest level of plasma HIV-1 RNA attained after initiation of therapy (nadir value) and the time until rebound. To investigate this question, we implement a simple and flexible non-linear mixed effects model for the trajectory of the HIV-1 RNA until rebound. This model is also consistent with biological insights into the effects of treatment. We also show how the problem of censoring of HIV-1 RNA values at the lower limit of assay quantification can be addressed using a multiple imputation scheme. The algorithm is simple to implement and is based on accessible software. Our application makes use of data from clinical trial 315 conducted by the AIDS Clinical Trials Group (ACTG 315). We find a strong relationship between HIV-1 RNA nadir and time to rebound, with potentially important consequences for the management of HIV-infected individuals. CI - Copyright 2002 John Wiley & Sons, Ltd. AD - Royal College of Surgeons in Ireland, Department of Epidemiology and Public Health Medicine, Mercer Street Lower, Dublin 2, Ireland. FAU - Fitzgerald, Anthony P AU - Fitzgerald AP FAU - DeGruttola, Victor G AU - DeGruttola VG FAU - Vaida, Florin AU - Vaida F LA - eng ID - AI-28076-09/AI/NIAID ID - AI-38855/AI/NIAID PT - Journal Article CY - England TA - Stat Med JID - 8215016 RN - 0 (Anti-HIV Agents) RN - 0 (RNA, Viral) SB - IM MH - Adolescent MH - Adult MH - Anti-HIV Agents/*therapeutic use MH - Child MH - Clinical Trials MH - Female MH - HIV Infections/blood/*drug therapy/virology MH - HIV-1/genetics/*growth & development MH - Human MH - Male MH - Middle Age MH - *Models, Immunological MH - *Nonlinear Dynamics MH - RNA, Viral/blood MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/07/12 10:00 MHDA- 2002/09/11 10:01 AID - 10.1002/sim.1155 [doi] PST - ppublish SO - Stat Med 2002 Jul 30;21(14):2093-108. 65: Mayes LC. The twin poles of order and c...[PMID:12102010]Related Articles, Books, LinkOut UI - 22097434 PMID- 12102010 DA - 20020709 DCOM- 20020731 LR - 20021101 IS - 0079-7308 VI - 56 DP - 2001 TI - The twin poles of order and chaos. Development as a dynamic, self-ordering system. PG - 137-70 AB - The diversity of theories regarding children's development is commensurate with the enormity of the task of seeking ordering designs for explaining behavioral and psychic ontogeny in infants, children, and adults. The purpose of this paper is to look at these developmental theories as epigenetic stages themselves. I shall suggest that the next stage in the epigenesis of theories of development is to see variability and disorder on a continuum with order and stability, as a constant dialectic that moves development along, whether at the level of the cell or at the level of fantasy. I shall explore four questions that are implicitly about development as an ordering process and about theories of development as methods for bringing order to what is an inherently messy, even chaotic. The first two questions--what does it mean to take a developmental perspective, and what does any theory of development need to explain--set the stage for the consideration of some different perspectives for thinking about development. These other perspectives, borrowed from general systems theory, focus on the interplay of order-stability and variability-instability in psychological development. The third question, asks what does a more detailed consideration of the variability or noise in development add to our current developmental perspectives? Exploring dynamic systems and self-ordering processes will lead to several fields not explicitly clinical, psychological, or even psychoanalytic, but I shall circle back to apply these ideas to psychoanalytic perspectives on development, change, and adaptation in the fourth and concluding question. What can these cross-disciplinary attitudes offer to the psychoanalytic developmental perspective, whether in the form of our theories or our work with patients? FAU - Mayes, L C AU - Mayes LC LA - eng PT - Journal Article CY - United States TA - Psychoanal Study Child JID - 0376472 SB - IM MH - Adolescent MH - Adult MH - Child MH - *Child Development MH - Child, Preschool MH - Human MH - Infant MH - *Nonlinear Dynamics MH - *Personality Development MH - Psychoanalytic Interpretation MH - *Psychoanalytic Theory MH - Psychoanalytic Therapy EDAT- 2002/07/10 10:00 MHDA- 2002/08/01 10:01 PST - ppublish SO - Psychoanal Study Child 2001;56:137-70. 66: Gamarra JG, et al. Complex discrete dynamics fro...[PMID:12094411]Related Articles, Books, LinkOut UI - 22089678 PMID- 12094411 DA - 20020703 DCOM- 20020731 IS - 0092-8240 VI - 64 IP - 3 DP - 2002 May TI - Complex discrete dynamics from simple continuous population models. PG - 611-20 AB - Nonoverlapping generations have been classically modelled as difference equations in order to account for the discrete nature of reproductive events. However, other events such as resource consumption or mortality are continuous and take place in the within-generation time. We have realistically assumed a hybrid ODE bidimensional model of resources and consumers with discrete events for reproduction. Numerical and analytical approaches showed that the resulting dynamics resembles a Ricker map, including the doubling route to chaos. Stochastic simulations with a handling-time parameter for indirect competition of juveniles may affect the qualitative behaviour of the model. AD - Complex Systems Research Group, Department of Physics FEN, Universitat Politecnica de Catalunya, Campus Nord, Modul B4-B5, 08034 Barcelona, Spain. javier@complex.upc.es FAU - Gamarra, Javier G P AU - Gamarra JG FAU - Sole, Ricard V AU - Sole RV LA - eng PT - Journal Article CY - United States TA - Bull Math Biol JID - 0401404 SB - IM MH - Animal MH - Computer Simulation MH - Ecology MH - Human MH - *Models, Biological MH - Nonlinear Dynamics MH - *Population Dynamics MH - Stochastic Processes MH - Support, Non-U.S. Gov't EDAT- 2002/07/04 10:00 MHDA- 2002/08/01 10:01 PST - ppublish SO - Bull Math Biol 2002 May;64(3):611-20. 67: Rohlmann A, et al. [Effect of a double intervert...[PMID:12090140]Related Articles, Books, LinkOut UI - 22085493 PMID- 12090140 DA - 20020701 DCOM- 20021016 IS - 0013-5585 VI - 47 IP - 5 DP - 2002 May TI - [Effect of a double intervertebral cage on the mechanical behavior of the lumbar spine] PG - 124-9 AB - A three-dimensional nonlinear finite element model of the lumbar spine was developed. Paired threaded cages and a monosegmental internal spinal fixation device were integrated into the computer model. The model was loaded with such forces as apply during standing, as well as with pure moments in the three main anatomical planes, plus an additional preload. The latter was generated by shortening the distance between the pedicle screws on the longitudinal rod of the fixator. With the exception of torsional loading, an implant appreciably reduces the mobility in the segment concerned. At the loads studied, cages had only a minor impact on the movements and stresses in the adjacent regions, but a strong influence on the stresses in the endplates in contact with them. A preload increases these stresses dramatically. Contact conditions between vertebral body and cages also have a marked effect on the stress distribution in the corresponding vertebral endplate, especially in the case of extension loading. Owing to the preload, maximum stresses were higher for the rigid bond than when contact elements were used. AD - Universitatsklinikum Benjamin Franklin, Freie Universitat Berlin. rohlmann@biomechanik.de FAU - Rohlmann, A AU - Rohlmann A FAU - Zander, Th AU - Zander T FAU - Fehrmann, M AU - Fehrmann M FAU - Klockner, C AU - Klockner C FAU - Bergmann, G AU - Bergmann G LA - ger PT - Journal Article TT - Einfluss eines doppelten Zwischenwirbelkafigs auf das mechanische Verhalten der Lendenwirbelsaule. CY - Germany TA - Biomed Tech (Berl) JID - 1262533 SB - IM MH - Biomechanics MH - *Computer Simulation MH - English Abstract MH - *Finite Element Analysis MH - Human MH - Intervertebral Disk/physiopathology/*surgery MH - Lumbar Vertebrae/*physiopathology MH - Nonlinear Dynamics MH - *Prosthesis Implantation MH - Spinal Fusion/*instrumentation MH - Support, Non-U.S. Gov't MH - Weight-Bearing/physiology EDAT- 2002/07/02 10:00 MHDA- 2002/10/17 04:00 PST - ppublish SO - Biomed Tech (Berl) 2002 May;47(5):124-9. 68: Rohlmann A, et al. [Effect of implants for repla...[PMID:12089801]Related Articles, Books, LinkOut UI - 22085153 PMID- 12089801 DA - 20020701 DCOM- 20021016 IS - 0085-4530 VI - 31 IP - 5 DP - 2002 May TI - [Effect of implants for replacement of a vertebral body on the mechanical function of the lumbar spine] PG - 503-7 AB - A three-dimensional, nonlinear finite element model of the lumbar spine was created. A bisegmental internal spinal fixation device and successively two kinds of vertebral body replacements were integrated into the computer model. The model was loaded with pure moments in the three anatomical main planes as well as with forces that are expected during standing. A vertebral body replacement drastically reduces the mobility in the implant region. An implant has only a minor influence on the mobility and stresses in the adjacent regions for the loading cases chosen. A preload, for example, caused by additional distraction from the precisely fitted ventral implant, exerts a very strong effect on the stresses in the end plates that are in contact with the implant. Different sizes of the contact area between implant and vertebral body have only a local effect on stress distribution. AD - Biomechanik-Labor, Universitatsklinikum Benjamin Franklin, Freie Universitat Berlin. rohlmann@biomechanik.de FAU - Rohlmann, A AU - Rohlmann A FAU - Zander, T AU - Zander T FAU - Fehrmann, M AU - Fehrmann M FAU - Klockner, C AU - Klockner C FAU - Bergmann, G AU - Bergmann G LA - ger PT - Evaluation Studies PT - Journal Article TT - Einfluss von Implantaten zum Ersatz eines Wirbelkorpers auf das mechanische Verhalten der Lendenwirbelsaule. CY - Germany TA - Orthopade JID - 0331266 SB - IM MH - Comparative Study MH - *Computer Simulation MH - English Abstract MH - *Finite Element Analysis MH - Human MH - Imaging, Three-Dimensional MH - Lumbar Vertebrae/physiopathology/*surgery MH - *Materials Testing MH - Nonlinear Dynamics MH - *Prostheses and Implants MH - Range of Motion, Articular/*physiology MH - Spinal Fusion/*instrumentation MH - Support, Non-U.S. Gov't MH - Weight-Bearing/*physiology EDAT- 2002/07/02 10:00 MHDA- 2002/10/17 04:00 PST - ppublish SO - Orthopade 2002 May;31(5):503-7. 69: Erlhagen W, et al. Dynamic field theory of movem...[PMID:12088245]Related Articles, Books, LinkOut UI - 22082776 PMID- 12088245 DA - 20020628 DCOM- 20020723 IS - 0033-295X VI - 109 IP - 3 DP - 2002 Jul TI - Dynamic field theory of movement preparation. PG - 545-72 AB - A theoretical framework for understanding movement preparation is proposed. Movement parameters are represented by activation fields, distributions of activation defined over metric spaces. The fields evolve under the influence of various sources of localized input, representing information about upcoming movements. Localized patterns of activation self-stabilize through cooperative and competitive interactions within the fields. The task environment is represented by a 2nd class of fields, which preshape the movement parameter representation. The model accounts for a sizable body of empirical findings on movement initiation (continuous and graded nature of movement preparation, dependence on the metrics of the task, stimulus uncertainty effect, stimulus-response compatibility effects, Simon effect, precuing paradigm, and others) and suggests new ways of exploring the structure of motor representations. AD - Institut fur Neuroinformatik, Ruhr-Universitat Bochum, Germany. FAU - Erlhagen, Wolfram AU - Erlhagen W FAU - Schoner, Gregor AU - Schoner G LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - United States TA - Psychol Rev JID - 0376476 SB - IM MH - Human MH - Models, Psychological MH - Movement/*physiology MH - Neurophysiology MH - Nonlinear Dynamics MH - Psychomotor Performance/*physiology MH - Reaction Time/physiology MH - Support, Non-U.S. Gov't RF - 99 EDAT- 2002/06/29 10:00 MHDA- 2002/07/24 10:01 PST - ppublish SO - Psychol Rev 2002 Jul;109(3):545-72. 70: Park HK, et al. Three layer impact simulation...[PMID:12085645]Related Articles, Books, LinkOut UI - 22081225 PMID- 12085645 DA - 20020627 DCOM- 20021106 IS - 0067-8856 VI - 38 DP - 2002 TI - Three layer impact simulation for large cranioplasty using non-linear finite element model. PG - 429-34 AB - In this study, we conducted biomechanical study about implant material and behavior of large cranioplasty upon post-operative impact injury. Previous studies utilized a surface model of the skull and large cranium patch (defect area is 46.7 cm2)[1,2,3,4]. It had single layer with thickness of adult skull as 7 cm in the parietal bone. After construction of the finite element model, the mesh and node data were analyzed for the static behavior of the patch. Four-node and three-node quadrilateral shell elements were mainly used in this model to adapt easily to complex shapes. The overall model consists of 4,740 nodes, 2,168 solid elements, and 4,736 shell elements. Even though, the elements could demonstrate the displacement, stress, and strain by longitudinal along the force direction, subsequent result could not reveal the dynamic behavior of the model. Normal adult skull is consisting of three layers (inner, outer and diploe layer). This structure resembles composite materials that behave differently upon impact. In order to overcome limitation of previous model, we designed physiological model and analyzed dynamic behavior with new implant materials. The composite implant with two popular materials and middle polymer layer was evaluated and compared with bony material. AD - Biomechanics Lab, Neurosurgery Department, Wayne State University, Detroit, Michigan 48201, USA. FAU - Park, Hun K AU - Park HK FAU - Dujovny, Manuel AU - Dujovny M FAU - Lee, Jong B AU - Lee JB FAU - Diaz, Fernando G AU - Diaz FG LA - eng PT - Journal Article CY - United States TA - Biomed Sci Instrum JID - 0140524 SB - IM MH - Biomechanics MH - *Computer Simulation MH - Craniocerebral Trauma/*surgery MH - Human MH - Male MH - *Models, Biological MH - *Nonlinear Dynamics MH - Skull/*radiography/*surgery MH - Stress, Mechanical MH - Tomography, X-Ray Computed EDAT- 2002/06/28 10:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - Biomed Sci Instrum 2002;38:429-34. 71: Jahangir A, et al. Dynamic thermomechanical stud...[PMID:12085594]Related Articles, Books, LinkOut UI - 22081178 PMID- 12085594 DA - 20020627 DCOM- 20021106 IS - 0067-8856 VI - 38 DP - 2002 TI - Dynamic thermomechanical studies on collagen denaturation: a comparative study of bovine pericardium and chordae tendinae. PG - 151-6 AB - Denaturation of the collagen molecule is a kinetic process, and hence a function of both temperature and duration of heating. Simple isothermal tests have traditionally provided the easiest way to isolate the role of heating in denaturation. In the present experiments, a Dynamic Hydrothermal Isometric Tension (DHIT) system has been custom-built and used to impose near-step changes temperature as a means to studying the dynamics of denaturation in fresh and crosslinked bovine Pericardium (PC) and Chordac Tendinae (CT). Irrespective of their treatment, both PC and CT followed the same pattern of force rise following a step in temperature. The force-time data were well-fitted using the Levenberg-Marquardt nonlinear least-squares method and 3 exponential functions with unique time constants (tau 1, tau 2, tau 3). This suggests the presence of three discrete mechanisms in the denaturation process. The tau 1 values for PC and CT were significantly shorter than either tau 2, or tau 3. Also, the tau 1 values of the untreated groups (either PC or CT) were similar and significantly different than those for the crosslinked tissues. This indicates that crosslinking dramatically slows the dynamic denaturation in both tissues (identified with tau 1) to the same extent. This is of considerable interest since each tissue has unique and distinct collagen architecture; therefore the dynamics of denaturation depend more on the collagen molecule than on fibrous architecture. This is the first study to identify discrete mechanisms leading to isometric denaturation changes in two collagenous tissues. While it is believed that the mechanisms identified represent (i) progressive hydration and (ii) denaturation of collagen structure, more precise identification of the processes remain to be done. AD - School of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada, B3H 3J5. jahangir@is.dal.ca FAU - Jahangir, Alireza AU - Jahangir A FAU - Lee, J Michael AU - Lee JM LA - eng PT - Journal Article CY - United States TA - Biomed Sci Instrum JID - 0140524 RN - 0 (Cross-Linking Reagents) RN - 111-30-8 (Glutaral) RN - 9007-34-5 (Collagen) SB - IM MH - Animal MH - Biomechanics MH - Cattle MH - Chordae Tendineae/*physiology MH - Collagen/*physiology MH - Comparative Study MH - Cross-Linking Reagents/pharmacology MH - Elasticity MH - Glutaral/pharmacology MH - Heat MH - In Vitro MH - Least-Squares Analysis MH - Models, Biological MH - Nonlinear Dynamics MH - Protein Denaturation MH - Support, Non-U.S. Gov't EDAT- 2002/06/28 10:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - Biomed Sci Instrum 2002;38:151-6. 72: Owis MI, et al. Study of features based on no...[PMID:12083309]Related Articles, Books, LinkOut UI - 22078003 PMID- 12083309 DA - 20020626 DCOM- 20020802 IS - 0018-9294 VI - 49 IP - 7 DP - 2002 Jul TI - Study of features based on nonlinear dynamical modeling in ECG arrhythmia detection and classification. PG - 733-6 AB - We present a study of the nonlinear dynamics of electrocardiogram (ECG) signals for arrhythmia characterization. The correlation dimension and largest Lyapunov exponent are used to model the chaotic nature of five different classes of ECG signals. The model parameters are evaluated for a large number of real ECG signals within each class and the results are reported. The presented algorithms allow automatic calculation of the features. The statistical analysis of the calculated features indicates that they differ significantly between normal heart rhythm and the different arrhythmia types and, hence, can be rather useful in ECG arrhythmia detection. On the other hand, the results indicate that the discrimination between different arrhythmia types is difficult using such features. The results of this work are supported by statistical analysis that provides a clear outline for the potential uses and limitations of these features. AD - Biomedical Engineering Department, Cairo University, Giza, Egypt. FAU - Owis, Mohamed I AU - Owis MI FAU - Abou-Zied, Ahmed H AU - Abou-Zied AH FAU - Youssef, Abou-Bakr M AU - Youssef AB FAU - Kadah, Yasser M AU - Kadah YM LA - eng PT - Journal Article CY - United States TA - IEEE Trans Biomed Eng JID - 0012737 SB - IM MH - *Algorithms MH - Arrhythmia/classification/*diagnosis MH - Databases, Factual MH - Electrocardiography/classification/*methods/statistics & numerical data MH - Human MH - *Models, Cardiovascular MH - *Nonlinear Dynamics MH - Sensitivity and Specificity MH - Signal Processing, Computer-Assisted MH - Support, Non-U.S. Gov't EDAT- 2002/06/27 10:00 MHDA- 2002/08/03 10:01 PST - ppublish SO - IEEE Trans Biomed Eng 2002 Jul;49(7):733-6. 73: Wiklund U, et al. Wavelet decomposition of card...[PMID:12083299]Related Articles, Books, LinkOut UI - 22077993 PMID- 12083299 DA - 20020626 DCOM- 20020802 IS - 0018-9294 VI - 49 IP - 7 DP - 2002 Jul TI - Wavelet decomposition of cardiovascular signals for baroreceptor function tests in pigs. PG - 651-61 AB - In this paper, the discrete wavelet transform (DWT) was applied to analyze the fluctuations in RR interval and systolic arterial pressure (SAP) recorded from eight alpha-chloralose anesthetized pigs. Our aim was to characterize the autonomic modulation before and after cardiac autonomic blockade and during baroreflex function tests. The instantaneous power of decomposed low-frequency (LF) and high-frequency (HF) components was used for a time-variant spectral analysis. Our results suggested that transient events and changes in autonomic modulation were detected with high temporal resolution. A nonlinear relationship between RR interval and SAP during pharmacologically induced changes in blood pressure was found, when the superimposed effect of respiratory sinus arrhythmia was removed. In addition, the baroslopes were nearly linear when both the LF and HF components were removed using DWT decomposition. AD - Department of Biomedical Engineering and Informatics, University Hospital, Umea, Sweden. Urban.Wiklund@vll.se FAU - Wiklund, Urban AU - Wiklund U FAU - Akay, Metin AU - Akay M FAU - Morrison, Stuart AU - Morrison S FAU - Niklasson, Urban AU - Niklasson U LA - eng PT - Journal Article CY - United States TA - IEEE Trans Biomed Eng JID - 0012737 RN - 15078-28-1 (Nitroprusside) RN - 15879-93-3 (Chloralose) RN - 59-42-7 (Phenylephrine) SB - IM MH - *Algorithms MH - Anesthesia, General MH - Animal MH - Autonomic Nervous System/physiology MH - Baroreflex/*physiology MH - Blood Pressure/physiology MH - Chloralose/pharmacology MH - Comparative Study MH - Electrocardiography/*methods/statistics & numerical data MH - Female MH - Heart Rate/drug effects MH - *Models, Cardiovascular MH - Nitroprusside/pharmacology MH - Nonlinear Dynamics MH - Phenylephrine/pharmacology MH - Sensitivity and Specificity MH - *Signal Processing, Computer-Assisted MH - Swine EDAT- 2002/06/27 10:00 MHDA- 2002/08/03 10:01 PST - ppublish SO - IEEE Trans Biomed Eng 2002 Jul;49(7):651-61. 74: Arora D, et al. Model-predictive control of h...[PMID:12083297]Related Articles, Books, LinkOut UI - 22077991 PMID- 12083297 DA - 20020626 DCOM- 20020802 IS - 0018-9294 VI - 49 IP - 7 DP - 2002 Jul TI - Model-predictive control of hyperthermia treatments. PG - 629-39 AB - A model-predictive controller (MPC) of the thermal dose in hyperthermia cancer treatments has been developed and evaluated using simulations with one-point and one-dimensional models of a tumor. The developed controller is the first effort in: 1) the application of feedback control to pulsed, high-temperature hyperthermia treatments; 2) the direct control of the treatment thermal dose rather than the treatment temperatures; and 3) the application of MPC to hyperthermia treatments. Simulations were performed with different blood flow rates in the tumor and constraints on temperatures in normal tissues. The results demonstrate that 1) thermal dose can be controlled in the presence of plant-model mismatch and 2) constraints on the maximum allowable temperatures in normal tissue and/or the pulsed power magnitude can be directly incorporated into MPC and met while delivering the desired thermal dose to the tumor. For relatively high blood flow rates and low transducer surface intensities--factors that limit the range of temperature variations in the tumor, the linear MPC, obtained by piece-wise linearization of the dose-temperature relationship, provides an adequate performance. For large temperature variations, the development of nonlinear MPC is necessary. AD - Department of Mechanical Engineering, University of Utah, Salt Lake City 84112, USA. FAU - Arora, Dhiraj AU - Arora D FAU - Skliar, Mikhail AU - Skliar M FAU - Roemer, Robert B AU - Roemer RB LA - eng ID - R01 CA 33922/CA/NCI PT - Journal Article PT - Validation Studies CY - United States TA - IEEE Trans Biomed Eng JID - 0012737 SB - IM MH - Comparative Study MH - Computer Simulation MH - Feedback MH - Human MH - Hyperthermia, Induced/instrumentation/*methods MH - *Models, Biological MH - Muscle, Skeletal/blood supply/*physiopathology MH - Neoplasms/blood supply/*physiopathology/*therapy MH - Nonlinear Dynamics MH - Sensitivity and Specificity MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. MH - Transducers MH - Ultrasonic Therapy/methods EDAT- 2002/06/27 10:00 MHDA- 2002/08/03 10:01 PST - ppublish SO - IEEE Trans Biomed Eng 2002 Jul;49(7):629-39. 75: Tokuda I, et al. Nonlinear analysis of irregul...[PMID:12083224]Related Articles, Books, LinkOut UI - 22077918 PMID- 12083224 DA - 20020626 DCOM- 20020806 IS - 0001-4966 VI - 111 IP - 6 DP - 2002 Jun TI - Nonlinear analysis of irregular animal vocalizations. PG - 2908-19 AB - Animal vocalizations range from almost periodic vocal-fold vibration to completely atonal turbulent noise. Between these two extremes, a variety of nonlinear dynamics such as limit cycles, subharmonics, biphonation, and chaotic episodes have been recently observed. These observations imply possible functional roles of nonlinear dynamics in animal acoustic communication. Nonlinear dynamics may also provide insight into the degree to which detailed features of vocalizations are under close neural control, as opposed to more directly reflecting biomechanical properties of the vibrating vocal folds themselves. So far, nonlinear dynamical structures of animal voices have been mainly studied with spectrograms. In this study, the deterministic versus stochastic (DVS) prediction technique was used to quantify the amount of nonlinearity in three animal vocalizations: macaque screams, piglet screams, and dog barks. Results showed that in vocalizations with pronounced harmonic components (adult macaque screams, certain piglet screams, and dog barks), deterministic nonlinear prediction was clearly more powerful than stochastic linear prediction. The difference, termed low-dimensional nonlinearity measure (LNM), indicates the presence of a low-dimensional attractor. In highly irregular signals such as juvenile macaque screams, piglet screams, and some dog barks, the detectable amount of nonlinearity was comparatively small. Analyzing 120 samples of dog barks, it was further shown that the harmonic-to-noise ratio (HNR) was positively correlated with LNM. It is concluded that nonlinear analysis is primarily useful in animal vocalizations with strong harmonic components (including subharmonics and biphonation) or low-dimensional chaos. AD - Department of Computer Science and Systems Engineering, Muroran Institute of Technology, Hokkaido, Japan. tokuda@csse.muroran-it.ac.jp FAU - Tokuda, Isao AU - Tokuda I FAU - Riede, Tobias AU - Riede T FAU - Neubauer, Jurgen AU - Neubauer J FAU - Owren, Michael J AU - Owren MJ FAU - Herzel, Hanspeter AU - Herzel H LA - eng PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 SB - IM MH - Animal MH - Comparative Study MH - Dogs MH - Macaca MH - *Nonlinear Dynamics MH - *Sound Spectrography MH - Species Specificity MH - Stochastic Processes MH - Swine MH - *Vocalization, Animal EDAT- 2002/06/27 10:00 MHDA- 2002/08/07 10:01 PST - ppublish SO - J Acoust Soc Am 2002 Jun;111(6):2908-19. 76: Kirk DL. Interaction between adenosine...[PMID:12083210]Related Articles, Books, LinkOut UI - 22077904 PMID- 12083210 DA - 20020626 DCOM- 20020806 IS - 0001-4966 VI - 111 IP - 6 DP - 2002 Jun TI - Interaction between adenosine triphosphate and mechanically induced modulation of electrically evoked otoacoustic emissions. PG - 2749-58 AB - It was shown previously that electrically evoked otoacoustic emissions (EEOAEs) can be amplitude modulated by low-frequency bias tones and enhanced by application of adenosine triphosphate (ATP) to scala media. These effects were attributed, respectively, to the mechano-electrical transduction (MET) channels and ATP-gated ion channels on outer hair cell (OHC) stereocilia, two conductance pathways that appear to be functionally independent and additive in their effects on ionic current through the OHC. In the experiments described here, the separate influences of ATP and MET channel bias on EEOAEs did not combine linearly. Modulated EEOAEs increased in amplitude, but lost modulation at the phase and frequency of the bias tone (except at very high sound levels) after application of ATP to scala media, even though spectral components at the modulation sideband frequencies were still present. Some sidebands underwent phase shifts after ATP. In EEOAEs modulated by tones at lower sound levels, substitution of the original phase values restored modulation to the waveform, which then resembled a linear summation of the separate effects of ATP and low-frequency bias. While the physiological meaning of this procedure is not clear, the result raises the possibility that a secondary effect of ATP on one or more nonlinear stages in the transduction process, which may have caused the phase shifts, obscured linear summation at lower sound levels. In addition, "acoustic enhancement" of the EEOAE may have introduced nonlinear interaction at higher levels of the bias tones. AD - Department of Physiology, The University of Western Australia, Crawley, Australia. FAU - Kirk, Desmond L AU - Kirk DL LA - eng PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 RN - 56-65-5 (Adenosine Triphosphate) SB - IM MH - Adenosine Triphosphate/*pharmacology MH - Animal MH - Cochlear Microphonic Potentials/drug effects MH - Hair Cells, Outer/*drug effects MH - Loudness Perception/*drug effects MH - Nonlinear Dynamics MH - Otoacoustic Emissions, Spontaneous/*drug effects MH - Pitch Discrimination/*drug effects MH - Psychoacoustics MH - Sound Spectrography MH - Support, Non-U.S. Gov't EDAT- 2002/06/27 10:00 MHDA- 2002/08/07 10:01 PST - ppublish SO - J Acoust Soc Am 2002 Jun;111(6):2749-58. 77: Ephanov A, et al. Generating pathological gait ...[PMID:12082217]Related Articles, Books, LinkOut UI - 22077837 PMID- 12082217 DA - 20020625 DCOM- 20020715 IS - 0928-7329 VI - 10 IP - 2 DP - 2002 TI - Generating pathological gait patterns via the use of robotic locomotion models. PG - 135-46 AB - In this article we explore the feasibility of modeling normal and pathological human gait using a relatively simple five-element model. We use a robust, nonlinear control scheme to regulate the gait patterns of the model. Simulated gait patterns are generated through the use of five constraint relationships that depend on four gait parameters. Two pathological conditions due to muscle weaknesses were simulated by modifying the control torques at the joints. We demonstrate that the model successfully approximates the qualitative and quantitative dynamic trends that were observed in normal and pathological human locomotion. AD - Mechanical Engineering Department, Southern Methodist University, Dallas, TX 75275, USA. FAU - Ephanov, Anton AU - Ephanov A FAU - Hurmuzlu, Yildirim AU - Hurmuzlu Y LA - eng PT - Journal Article CY - Netherlands TA - Technol Health Care JID - 9314590 SB - IM MH - Algorithms MH - Computer Simulation MH - Foot/physiopathology MH - Gait/*physiology MH - Hip/physiopathology MH - Human MH - Knee/physiopathology MH - Locomotion/*physiology MH - Motion MH - Muscle Rigidity/physiopathology MH - Muscle, Skeletal/physiopathology MH - Neural Tube Defects/physiopathology MH - Nonlinear Dynamics MH - Pain/physiopathology MH - Poliomyelitis/physiopathology MH - Posture/physiology MH - Robotics/*methods/trends EDAT- 2002/06/26 10:00 MHDA- 2002/07/16 10:01 PST - ppublish SO - Technol Health Care 2002;10(2):135-46. 78: Parham FM, et al. A physiologically based pharm...[PMID:12079424]Related Articles, Books, LinkOut UI - 22075695 PMID- 12079424 DA - 20020624 DCOM- 20020724 IS - 0041-008X VI - 181 IP - 3 DP - 2002 Jun 15 TI - A physiologically based pharmacokinetic model of p,p'-dichlorodiphenylsulfone. PG - 153-63 AB - A physiologically based pharmacokinetic model of the absorption, distribution, metabolism, and elimination of p,p'-dichlorodiphenylsulfone (DDS) in male and female rats and mice is presented. Data used in constructing the model come from single-dose intravenous administration of DDS to male Fischer 344 rats (10 mg/kg, with data taken up to 504 h after administration), from single-dose gavage administration to male rats (10, 100, or 1000 mg/kg, with data up to 72 h after administration), and from chronic feed studies in male and female rats and male and female B6C3F(1) mice (studies of duration from 2 weeks up to 18 months, with feed concentrations of DDS up to 300 ppm). The model uses diffusion-limited kinetic for the distribution of the parent compound. Because fewer data are available for the metabolites of DDS (at least five of which are known to exist in the data), the model groups the metabolites into one metabolic pathway and uses simpler flow-limited kinetics for the metabolites. The data show that the kinetics of DDS are nonlinear. Possible sources of nonlinearity considered in the model were nonlinear (Michaelis-Menten) metabolism, nonlinear absorption of DDS from the gut, and induction by DDS of its own metabolism. A model using Michaelis-Menten metabolism was not found to give a significantly better fit than one using first-order linear metabolism, but omitting either of the other nonlinear effects was found to give a significantly poorer fit to the data. Because the data from mice are limited compared to those from rats, there is more confidence in the model's description of DDS kinetics in rats than in its description of kinetics in mice. AD - National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA. parham@niehs.nih.gov FAU - Parham, Fred M AU - Parham FM FAU - Matthews, H B AU - Matthews HB FAU - Portier, C J AU - Portier CJ LA - eng PT - Journal Article CY - United States TA - Toxicol Appl Pharmacol JID - 0416575 RN - 0 (Sulfones) RN - 80-07-9 (4,4'-dichlorodiphenyl sulfone) SB - IM MH - Algorithms MH - Animal MH - Comparative Study MH - Injections, Intravenous MH - Male MH - Mice MH - Mice, Inbred Strains MH - Models, Biological MH - Nonlinear Dynamics MH - Rats MH - Rats, Inbred F344 MH - Species Specificity MH - Sulfones/*pharmacokinetics MH - Tissue Distribution EDAT- 2002/06/25 10:00 MHDA- 2002/07/26 10:01 AID - S0041008X0299410X [pii] PST - ppublish SO - Toxicol Appl Pharmacol 2002 Jun 15;181(3):153-63. 79: Fee MS, et al. The role of nonlinear dynamic...[PMID:12071206]Related Articles, Books, LinkOut UI - 22064705 PMID- 12071206 DA - 20020618 DCOM- 20020619 IS - 0028-0836 VI - 395 IP - 6697 DP - 1998 Sep 3 TI - The role of nonlinear dynamics of the syrinx in the vocalizations of a songbird. PG - 67-71 AB - Birdsong is characterized by the modulation of sound properties over a wide image of timescales. Understanding the mechanisms by which the brain organizes this complex temporal behaviour is a central motivation in the study of the song control and learning system. Here we present evidence that, in addition to central neural control, a further level of temporal organization is provided by nonlinear oscillatory dynamics that are intrinsic to the avian vocal organ. A detailed temporal and spectral examination of song of the zebra finch (Taeniopygia guttata) reveals a class of rapid song modulations that are consistent with transitions in the dynamical state of the syrinx. Furthermore, in vitro experiments show that the syrinx can produce a sequence of oscillatory states that are both spectrally and temporally complex in response to the slow variation of respiratory or syringeal parameters. As a consequence, simple variations in a small number of neural signals can result in a complex acoustic sequence. AD - Bell Laboratories, Lucent Technologies, 600 Mountain Avenue, Murray Hill, New Jersey 07974, USA. FAU - Fee, M S AU - Fee MS FAU - Shraiman, B AU - Shraiman B FAU - Pesaran, B AU - Pesaran B FAU - Mitra, P P AU - Mitra PP LA - eng PT - Journal Article CY - England TA - Nature JID - 0410462 SB - IM MH - Animal MH - Bronchi/anatomy & histology/physiology MH - In Vitro MH - Male MH - Models, Biological MH - Nonlinear Dynamics MH - Oscillometry MH - Songbirds/anatomy & histology/*physiology MH - Trachea/anatomy & histology/*physiology MH - Video Recording MH - Vocalization, Animal/*physiology EDAT- 2002/06/20 10:00 MHDA- 2002/06/20 10:01 AID - 10.1038/25725 [doi] PST - ppublish SO - Nature 1998 Sep 3;395(6697):67-71. 80: Aso R, et al. Population pharmacokinetics, ...[PMID:12067143]Related Articles, Books, LinkOut UI - 22061892 PMID- 12067143 DA - 20020617 DCOM- 20020701 LR - 20021101 IS - 0251-1649 VI - 21 IP - 3-4 DP - 2001 TI - Population pharmacokinetics, protein binding and antiarrhythmic effects of disopyramide enantiomers in arrhythmic patients. PG - 137-46 AB - Disopyramide (DP) is widely used as an antiarrhythmic agent. The antiarrhythmic effects of its enantiomers differ from each other and its metabolism and protein binding are also stereoselective. Population pharmacokinetic parameters of DP racemate, enantiomers (S(+)-DP, R(-)-DP), and their unbound concentrations (uDP, S(+)-uDP and R(-)-uDP) were analyzed using the nonlinear mixed effect model (NONMEM) program. Data were available from 108 points of 33 arrhythmic patients on maintenance therapy with DP racemate. We evaluated the factors to which pharmacokinetic parameters are attributed and the relationships between each serum concentration and the antiarrhythmic effect. A one-compartment model was fitted to the data using NONMEM. For DP, S(+)-DP and R(-)-DP, elimination rate constants (kes) were estimated as 0.0648, 0.0663 and 0.0691/h, respectively and the mean apparent volume of distribution (Vd/F) were estimated as 63.2, 54.1 and 71.6 l, respectively. Using the ke and Vd/F values estimated by NONMEM, time-concentration curves were well fitted to the observed data. Unbound fractions of both DP enantiomers showed nonlinearity and the binding ratio of S(+)-DP was 0.84 +/- 0.07, which was higher than that of R(-)-DP [0.70 +/- 0.11 (p < 0.01)]. Unbound fractions of both DP enantiomers correlated with alpha1-acid glycoprotein (AGP) (p < 0.01). On the other hand, using NONMEM, a significant proportion of the variability of Vd/F could be attributed only to AGP (p < 0.001). NONMEM was able to clarify the pharmacokinetic features in the protein binding of DP. Individual steady state concentrations were estimated by NONMEM using the Bayesian method. The average unbound concentrations of all nine responders were higher than those of the four non-responders, even though this difference was not significant. Unbound concentrations may reflect drug concentrations in the tissue, which suggests that these concentrations may indicate an antiarrhythmic effect rather than the total concentration. AD - Clinical Pharmacology Center, Nippon Medical School, Tokyo, Japan. aso@nms.ac.jp FAU - Aso, R AU - Aso R FAU - Ohashi, K AU - Ohashi K FAU - Katoh, T AU - Katoh T FAU - Ogata, H AU - Ogata H LA - eng PT - Clinical Trial PT - Journal Article PT - Randomized Controlled Trial CY - Switzerland TA - Int J Clin Pharmacol Res JID - 8110183 RN - 0 (Anti-Arrhythmia Agents) RN - 3737-09-5 (Disopyramide) SB - IM MH - Adolescent MH - Adult MH - Aged MH - Aged, 80 and over MH - Anti-Arrhythmia Agents/*pharmacokinetics/*therapeutic use MH - Arrhythmia/blood/*drug therapy/*metabolism MH - Bayes Theorem MH - Child MH - Disopyramide/*pharmacokinetics/*therapeutic use MH - Female MH - Human MH - Male MH - Middle Age MH - Nonlinear Dynamics MH - Protein Binding/drug effects/physiology MH - Stereoisomerism EDAT- 2002/06/18 10:00 MHDA- 2002/07/02 10:01 PST - ppublish SO - Int J Clin Pharmacol Res 2001;21(3-4):137-46. 81: Tarvainen MP, et al. An advanced detrending method...[PMID:12066885]Related Articles, Books, LinkOut UI - 22061636 PMID- 12066885 DA - 20020617 DCOM- 20020719 IS - 0018-9294 VI - 49 IP - 2 DP - 2002 Feb TI - An advanced detrending method with application to HRV analysis. PG - 172-5 AB - An advanced, simple to use, detrending method to be used before heart rate variability analysis (HRV) is presented. The method is based on smoothness priors approach and operates like a time-varying finite-impulse response high-pass filter. The effect of the detrending on time- and frequency-domain analysis of HRV is studied. AD - University of Kuopio, Department of Applied Physics, Finland. Mika.Tarvainen@uku.fi FAU - Tarvainen, Mika P AU - Tarvainen MP FAU - Ranta-Aho, Perttu O AU - Ranta-Aho PO FAU - Karjalainen, Pasi A AU - Karjalainen PA LA - eng PT - Journal Article CY - United States TA - IEEE Trans Biomed Eng JID - 0012737 SB - IM MH - Algorithms MH - Electrocardiography MH - Fourier Analysis MH - Heart Rate/*physiology MH - Human MH - *Models, Cardiovascular MH - Nonlinear Dynamics MH - *Signal Processing, Computer-Assisted MH - Stochastic Processes EDAT- 2002/06/18 10:00 MHDA- 2002/07/20 10:01 PST - ppublish SO - IEEE Trans Biomed Eng 2002 Feb;49(2):172-5. 82: Arambasic MB, et al. Applicational possibilities o...[PMID:12064056]Related Articles, Books, LinkOut UI - 22059884 PMID- 12064056 DA - 20020614 DCOM- 20020716 IS - 0006-6648 VI - 141 IP - 1 DP - 2002 Jan-Feb TI - Applicational possibilities of linear and non-linear (polynomial) regressions and analysis of variance: kinetics of chloramphenicol. PG - 33-44 AB - The dependance of the content and microbiological activity of Chloramphenicol (active substance) at dissolution on time and on pH, as well as that of the content and microbiological activity of Chloramphenicol (250 mg capsules) at release, on time, in in-vitro conditions, was determined using linear and non-linear (polynomial and generalized dilution) regressions. Based on the square error value, the dependance of the content and microbiological activity of Chloramphenicol (active substance) at dissolution on time and different pH values, as well as the dependance of the content and microbiological activity of Chloramphenicol (capsules) at release on time were best described by polynomial function. The comparison of the content and microbiological activity of Chloramphenicol (active substance) at dissolution at different pH values, as well as of Chloramphenicol (capsules) at release showed the significant correlation between these parameters (r = 0.999, P << 0.001). The comparision of the content, on one hand, and microbiological activity of Chloramphenicol (active substance), on the other, at dissolution at different pH values, as a function of time, was done using a modified method of one-way analysis of variance for linear regression comparisons. Based on the value of Fischer's coefficient (F), there is a statistically very significant difference between the contents and between the microbiological activities of chloramphenicol (active substance) at dissolution and different pH as a function of time (P << 0.005). AD - Pharmaceutical Factory GALENIKA a.d., Quality Control Center: Dept. Biological Control, Beograd-Zemun, Yugoslavia. FAU - Arambasic, M B AU - Arambasic MB FAU - Ristanovic, D AU - Ristanovic D FAU - Djordjevic, A AU - Djordjevic A LA - eng PT - Journal Article CY - Italy TA - Boll Chim Farm JID - 0372534 RN - 0 (Antibiotics) RN - 0 (Capsules) RN - 56-75-7 (Chloramphenicol) SB - IM MH - Algorithms MH - Analysis of Variance MH - Antibiotics/*pharmacokinetics/pharmacology MH - Capsules MH - Chloramphenicol/*pharmacokinetics/pharmacology MH - Hydrogen-Ion Concentration MH - Linear Models MH - Nonlinear Dynamics MH - Regression Analysis MH - Software EDAT- 2002/06/18 10:00 MHDA- 2002/07/18 10:01 PST - ppublish SO - Boll Chim Farm 2002 Jan-Feb;141(1):33-44. 83: Schade G. [Use of Ensemble tissue harmo...[PMID:12063627]Related Articles, Books, LinkOut UI - 22058503 PMID- 12063627 DA - 20020613 DCOM- 20021021 IS - 0935-8943 VI - 81 IP - 6 DP - 2002 Jun TI - [Use of Ensemble tissue harmonic imaging to improve the resolution in ultrasound investigations of the head and neck area] PG - 413-7 AB - BACKGROUND: Using ultrasound diagnostic, deeper areas of tissue cannot be examined as easily as superficial areas. Therefore it was necessary to develop a new image processing technique for ultrasound platforms to improve the quality of sonographical resolution in deeper areas. Tissue Harmonic Imaging is a modern technique that uses the non-linear, "harmonic" parts of ultrasound waves. Ensemble Tissue Harmonic Imaging is a new technique that uses a "Wide Band Harmonic Imaging", based on a patented phase-inversion-technique, and improves imaging quality. AIM: Aim of the study is to show if Ensemble Harmonic Imaging can improve imaging quality even in superficial areas of tissue in comparison to fundamental B-Mode-technique. METHODS: A Sonoline Elegra(R) high-end-scanner with 7.5 MHz linear array was used for this study. Differences of techniques ("fundamental"-sonographic-mode versus Ensemble Tissue Harmonic Imaging(R)-mode) are shown by investigation of six patients with various lesions of the head and neck area. CONCLUSION: In all cases there was a gain of resolution by using Ensemble Tissue Harmonic Imaging even in superficial areas. Ensemble Tissue Harmonic Imaging improves the sonographical resolution and reduces the artifacts. AD - Abteilung fur Hor-, Stimm- und Sprachheilkunde Universitatsklinikum Hamburg-Eppendorf, Germany. gschade@uke.uni-hamburg.de FAU - Schade, G AU - Schade G LA - ger PT - Journal Article TT - Einsatzmoglichkeiten von Ensembletrade mark Tissue Harmonic Imaging in der Kopf-Hals-Sonographie. CY - Germany TA - Laryngorhinootologie JID - 8912371 SB - IM MH - Artifacts MH - Comparative Study MH - Diagnosis, Differential MH - English Abstract MH - Equipment Design MH - Human MH - Image Enhancement/*instrumentation MH - Image Processing, Computer-Assisted/*instrumentation MH - Lymph Nodes/ultrasonography MH - Nonlinear Dynamics MH - Otorhinolaryngologic Diseases/*ultrasonography MH - Otorhinolaryngologic Neoplasms/*ultrasonography MH - Parotid Gland/ultrasonography MH - Parotid Neoplasms/ultrasonography MH - Sensitivity and Specificity MH - Ultrasonography/*instrumentation MH - Ultrasonography, Doppler, Color/instrumentation EDAT- 2002/06/14 10:00 MHDA- 2002/10/22 04:00 AID - 10.1055/s-2002-32209 [doi] PST - ppublish SO - Laryngorhinootologie 2002 Jun;81(6):413-7. 84: Garcia Gomez J, et al. Some kinetic aspects in the i...[PMID:12062691]Related Articles, Books, LinkOut UI - 22058315 PMID- 12062691 DA - 20020613 DCOM- 20020723 IS - 0731-7085 VI - 29 IP - 1-2 DP - 2002 Jun 20 TI - Some kinetic aspects in the immunoradiometric assay of insulin-like growth factor binding protein-3. PG - 307-15 AB - In this article the kinetics of the insulin-like growth factor binding protein-3 (IGFBP-3) reaction with its specific antibody immobilised on the inner wall of the reaction tube, and the subsequent binding of the immunocomplex formed with a second (125)I-labelled antibody are described. These reactions are used in the immunoradiometric determination of IGFBP-3. Independent variables were analyte and labelled antibody, temperature, viscosity, and the ionic strength of the medium. For the global process mono-exponential kinetics were found to be dependent on the concentrations, such dependence fitting with the models discussed in this paper. Viscosity results clearly indicate its negative influence on the direct reaction rate. Ionic strength shows noticeable but not too relevant effects, which suggests that the variation caused by the glycerol addition is not due to the influence of the dielectric constant of the solutions used. The effect of temperature shows activation parameters similar to the viscous flow energy of water, which suggests diffusion control for the global process. AD - Department of Physical Chemistry, Faculty of Pharmacy, Radioisotope Service, Valencia University Hospital, Avenida Vicent Andres Estelles s/n, 46110 Burjassot, Valencia, Spain. FAU - Garcia Gomez, J AU - Garcia Gomez J FAU - Porcar Pons, M AU - Porcar Pons M FAU - Moreno Frigols, Jose L AU - Moreno Frigols JL LA - eng PT - Journal Article CY - England TA - J Pharm Biomed Anal JID - 8309336 RN - 0 (Insulin-Like Growth Factor Binding Protein 3) SB - IM MH - Immunoradiometric Assay/*methods MH - Insulin-Like Growth Factor Binding Protein 3/*pharmacokinetics MH - Nonlinear Dynamics MH - Osmolar Concentration MH - Viscosity EDAT- 2002/06/14 10:00 MHDA- 2002/07/24 10:01 AID - S0731708502000900 [pii] PST - ppublish SO - J Pharm Biomed Anal 2002 Jun 20;29(1-2):307-15. 85: Field GD, et al. Nonlinear signal transfer fro...[PMID:12062023]Related Articles, Books, LinkOut UI - 22058634 PMID- 12062023 DA - 20020613 DCOM- 20020712 IS - 0896-6273 VI - 34 IP - 5 DP - 2002 May 30 TI - Nonlinear signal transfer from mouse rods to bipolar cells and implications for visual sensitivity. PG - 773-85 AB - We investigated the impact of rod-bipolar signal transfer on visual sensitivity. Two observations indicate that rod-rod bipolar signal transfer is nonlinear. First, responses of rods increased linearly with flash strength, while those of rod bipolars increased supralinearly. Second, fluctuations in the responses of rod bipolars were larger than expected from linear summation of the rod inputs. Rod-OFF bipolar signal transfer did not share this strong nonlinearity. Surprisingly, nonlinear rod-rod bipolar signal transfer eliminated many of the rod's single-photon responses. The impact on sensitivity, however, was more than compensated for by rejection of noise from rods that did not absorb photons. As a consequence, rod bipolars provide a near-optimal readout of rod signals at light levels near visual threshold. AD - Department of Physiology and Biophysics, University of Washington, Box 357290, Seattle 98195, USA. FAU - Field, Greg D AU - Field GD FAU - Rieke, Fred AU - Rieke F LA - eng ID - EY-11850/EY/NEI PT - Journal Article CY - United States TA - Neuron JID - 8809320 SB - IM CIN - Neuron. 2002 May 30;34(5):670-2. PMID: 12062013 MH - Animal MH - *Artifacts MH - Contrast Sensitivity/physiology MH - Dark Adaptation/physiology MH - Interneurons/cytology/*physiology MH - Mice MH - Mice, Inbred C57BL MH - Neural Inhibition/physiology MH - Neural Pathways/cytology/*physiology MH - Nonlinear Dynamics MH - Photic Stimulation MH - Phototransduction/*physiology MH - Rods (Retina)/cytology/*physiology MH - Sensory Thresholds/*physiology MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. MH - Synapses/physiology MH - Synaptic Transmission/*physiology MH - Visual Perception/*physiology EDAT- 2002/06/14 10:00 MHDA- 2002/07/13 10:01 AID - S0896627302007006 [pii] PST - ppublish SO - Neuron 2002 May 30;34(5):773-85. 86: Sterling P. Needle from a haystack. Optim...[PMID:12062013]Related Articles, Books, LinkOut UI - 22058624 PMID- 12062013 DA - 20020613 DCOM- 20020712 IS - 0896-6273 VI - 34 IP - 5 DP - 2002 May 30 TI - Needle from a haystack. Optimal signaling by a nonlinear synapse. PG - 670-2 AB - Commonly, a neuron must separate a small, rare event carried by one of its inputs from the noise carried by many others. In this issue of Neuron, demonstrate that to solve this problem, the rod bipolar neuron in mouse retina selectively amplifies a rod's single-photon signal only when it is larger than average. This nonlinearity rejects nearly three-fourths of the single-photon signals. Yet, by also rejecting noise, it provides nearly optimal filtering near absolute visual threshold. AD - Department of Neuroscience, School of Medicine, University of Pennsylvania, 123 Anatomy/Chemistry Building, Philadelphia 19104, USA. FAU - Sterling, Peter AU - Sterling P LA - eng PT - Comment PT - Journal Article PT - Review PT - Review, Tutorial CY - United States TA - Neuron JID - 8809320 SB - IM CON - Neuron. 2002 May 30;34(5):773-85. PMID: 12062023 MH - Animal MH - Artifacts MH - Dark Adaptation/physiology MH - Mice MH - Neural Pathways/cytology/*physiology MH - Nonlinear Dynamics MH - Phototransduction/physiology MH - Rods (Retina)/cytology/*physiology MH - Sensory Thresholds/physiology MH - Synapses/*physiology MH - Visual Perception/physiology RF - 10 EDAT- 2002/06/14 10:00 MHDA- 2002/07/13 10:01 AID - S0896627302007274 [pii] PST - ppublish SO - Neuron 2002 May 30;34(5):670-2. 87: Bastos de Figueiredo JC, et al. Chaos in two-loop negative fe...[PMID:12059591]Related Articles, Books UI - 22055606 PMID- 12059591 DA - 20020612 DCOM- 20020827 LR - 20021029 IS - 1539-3755 VI - 65 IP - 5 Pt 1 DP - 2002 May TI - Chaos in two-loop negative feedback systems. PG - 051905 AB - Multiloop delayed negative feedback systems, with each feedback loop having its own characteristic time lag (delay), are used to describe a great variety of systems: optical systems, neural networks, physiological control systems, etc. Previous investigations have shown that if the number of delayed feedback loops is greater than two, the system can exhibit complex dynamics and chaos, but in the case of two delayed loops only periodic solutions were found. Here we show that a period-doubling cascade and chaotic dynamics are also found in systems with two coupled delayed negative feedback loops. AD - Instituto do Coracao, Universidade de Sao Paulo, Avenida Dr. Eneas de Carvalho Aguiar, 44, 05403-000 Sao Paulo, Sao Paulo, Brazil. FAU - Bastos de Figueiredo, J C AU - Bastos de Figueiredo JC FAU - Diambra, L AU - Diambra L FAU - Glass, Leon AU - Glass L FAU - Malta, C P AU - Malta CP LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 SB - IM MH - Biophysics/*methods MH - Models, Statistical MH - Models, Theoretical MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2002/06/13 10:00 MHDA- 2002/08/28 10:01 PHST- 2001/Aug/24 [received] PHST- 2001/Dec/20 [revised] PHST- 2002/May/06 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 May;65(5 Pt 1):051905. 88: Freking A, et al. Learning and predicting time ...[PMID:12059522]Related Articles, Books UI - 22055537 PMID- 12059522 DA - 20020612 DCOM- 20020827 LR - 20021029 IS - 1539-3755 VI - 65 IP - 5 Pt 1 DP - 2002 May TI - Learning and predicting time series by neural networks. PG - 050903 AB - Artificial neural networks which are trained on a time series are supposed to achieve two abilities: first, to predict the series many time steps ahead and second, to learn the rule which has produced the series. It is shown that prediction and learning are not necessarily related to each other. Chaotic sequences can be learned but not predicted while quasiperiodic sequences can be well predicted but not learned. AD - Institut fur Theoretische Physik und Astrophysik, Universitat Wurzburg, Am Hubland, 97074 Wurzburg, Germany. FAU - Freking, Ansgar AU - Freking A FAU - Kinzel, Wolfgang AU - Kinzel W FAU - Kanter, Ido AU - Kanter I LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 SB - IM MH - Algorithms MH - Artificial Intelligence MH - Learning MH - Models, Statistical MH - Models, Theoretical MH - *Neural Networks (Computer) MH - Nonlinear Dynamics MH - Reproducibility of Results MH - Support, Non-U.S. Gov't MH - Time Factors EDAT- 2002/06/13 10:00 MHDA- 2002/08/28 10:01 PHST- 2001/Dec/06 [received] PHST- 2002/Feb/27 [revised] PHST- 2002/May/21 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 May;65(5 Pt 1):050903. 89: Kiss IZ, et al. Collective dynamics of chaoti...[PMID:12059402]Related Articles, Books, LinkOut UI - 22055948 PMID- 12059402 DA - 20020612 DCOM- 20020802 IS - 0031-9007 VI - 88 IP - 23 DP - 2002 Jun 10 TI - Collective dynamics of chaotic chemical oscillators and the law of large numbers. PG - 238301 AB - Experiments on the nontrivial collective dynamics and phase synchronization of populations of nonidentical chaotic electrochemical oscillators are presented. Without added coupling no deviation from the law of large numbers is observed. Deviations do arise with weak global or short-range coupling; large, irregular, and periodic mean field oscillations occur along with (partial) phase synchronization. AD - Department of Chemical Engineering, 102 Engineers' Way, University of Virginia, Charlottesville, Virginia 22904-4741, USA. FAU - Kiss, Istvan Z AU - Kiss IZ FAU - Zhai, Yumei AU - Zhai Y FAU - Hudson, John L AU - Hudson JL LA - eng PT - Journal Article CY - United States TA - Phys Rev Lett JID - 0401141 RN - 7440-02-0 (Nickel) SB - IM MH - Electrochemistry MH - Electrodes MH - *Models, Theoretical MH - Nickel/chemistry MH - *Nonlinear Dynamics MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/06/13 10:00 MHDA- 2002/08/03 10:01 PHST- 2001/Dec/01 [received] PHST- 2002/May/22 [aheadofprint] PST - ppublish SO - Phys Rev Lett 2002 Jun 10;88(23):238301. 90: Billings L, et al. Phase-space transport of stoc...[PMID:12059364]Related Articles, Books, LinkOut UI - 22055910 PMID- 12059364 DA - 20020612 DCOM- 20020802 IS - 0031-9007 VI - 88 IP - 23 DP - 2002 Jun 10 TI - Phase-space transport of stochastic chaos in population dynamics of virus spread. PG - 234101 AB - A general way to classify stochastic chaos is presented and applied to population dynamics models. A stochastic dynamical theory is used to develop an algorithmic tool to measure the transport across basin boundaries and predict the most probable regions of transport created by noise. The results of this tool are illustrated on a model of virus spread in a large population, where transport regions reveal how noise completes the necessary manifold intersections for the creation of emerging stochastic chaos. AD - Department of Mathematical Sciences, Montclair State University, Upper Montclair, New Jersey 07043, USA. FAU - Billings, Lora AU - Billings L FAU - Bollt, Erik M AU - Bollt EM FAU - Schwartz, Ira B AU - Schwartz IB LA - eng PT - Journal Article CY - United States TA - Phys Rev Lett JID - 0401141 SB - IM MH - Algorithms MH - *Models, Theoretical MH - *Nonlinear Dynamics MH - Population Dynamics MH - Support, U.S. Gov't, Non-P.H.S. MH - Virus Diseases/*transmission EDAT- 2002/06/13 10:00 MHDA- 2002/08/03 10:01 PHST- 2001/Sep/13 [received] PHST- 2002/May/23 [aheadofprint] PST - ppublish SO - Phys Rev Lett 2002 Jun 10;88(23):234101. 91: Riley MA, et al. Variability of determinism in...[PMID:12057885]Related Articles, Books, LinkOut UI - 22053315 PMID- 12057885 DA - 20020611 DCOM- 20020819 IS - 0022-2895 VI - 34 IP - 2 DP - 2002 Jun TI - Variability of determinism in motor behavior. PG - 99-125 AB - In investigations into perception-action systems, variability of observable behavior may be considered to (a) interfere with inquiry, (b) be neither detrimental nor particularly useful to inquiry, or (c) play a crucial role in inquiry. The authors underscore recent suggestions that alternative (c) is a preferred strategy for the study of many motor behaviors. In tutorial fashion, the authors review the concepts of variability and determinism with respect to postural and rhythmic movements. Study of the variability of those behaviors has revealed crucial features suggestive of underlying mechanisms and control, such as particular blends of noise and determinism (piecewise determinism). It has also revealed general lessons (for example, more variable does not mean more random and more controllable does not mean more deterministic) that may extend to other classes of perceptual behavior. AD - Department of Psychology, University of Cincinnati, Mail Location 0376,Cincinnati, OH 45221-0376, USA. rileym@uc.edu FAU - Riley, Michael A AU - Riley MA FAU - Turvey, M T AU - Turvey MT LA - eng PT - Journal Article CY - United States TA - J Mot Behav JID - 0236512 SB - IM MH - *Genetics, Behavioral MH - Human MH - *Models, Biological MH - Nonlinear Dynamics MH - Posture/physiology MH - Psychomotor Performance/*physiology MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/06/12 10:00 MHDA- 2002/08/20 10:01 PST - ppublish SO - J Mot Behav 2002 Jun;34(2):99-125. 92: Wagner C, et al. Construction of an associativ...[PMID:12054844]Related Articles, Books, LinkOut UI - 22050980 PMID- 12054844 DA - 20020610 DCOM- 20020806 IS - 0022-5193 VI - 215 IP - 3 DP - 2002 Apr 7 TI - Construction of an associative memory using unstable periodic orbits of a chaotic attractor. PG - 375-84 AB - Unstable periodic orbits are the skeleton of a chaotic attractor. We constructed an associative memory based on the chaotic attractor of an artificial neural network, which associates input patterns to unstable periodic orbits. By processing an input, the system is driven out of the ground state to one of the pre-defined disjunctive areas of the attractor. Each of these areas is associated with a different unstable periodic orbit. We call an input pattern learned if the control mechanism keeps the system on the unstable periodic orbit during the response. Otherwise, the system relaxes back to the ground state on a chaotic trajectory. The major benefits of this memory device are its high capacity and low-energy consumption. In addition, new information can be simply added by linking a new input to a new unstable periodic orbit. CI - Copyright 2002 Elsevier Science Ltd. All rights reserved. AD - Institute of Pharmacology, University of Bern, Friedbuehlstr. 49, CH-3010 Bern, Switzerland. clemens.wagner@pki.unibe.ch FAU - Wagner, Clemens AU - Wagner C FAU - Stucki, Jorg W AU - Stucki JW LA - eng PT - Journal Article CY - England TA - J Theor Biol JID - 0376342 SB - IM MH - *Algorithms MH - Memory MH - *Neural Networks (Computer) MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2002/06/11 10:00 MHDA- 2002/08/07 10:01 AID - 10.1006/jtbi.2001.2503 [doi] AID - S0022519301925032 [pii] PST - ppublish SO - J Theor Biol 2002 Apr 7;215(3):375-84. 93: Javorka M. [Analysis of variability of p...[PMID:12053491]Related Articles, Books UI - 22049357 PMID- 12053491 DA - 20020610 DCOM- 20020712 IS - 1210-6313 VI - 51 IP - 2 DP - 2002 May TI - [Analysis of variability of physiologic parameters using the Poincare plot] PG - 75-81 AB - The noninvasive assessment of spontaneous temporal physiological parameters variations can provide valuable information about control systems involved in their complex regulations. Recently, in addition to conventional measures describing variability in time and frequency domains, methods based on nonlinear dynamics are increasingly used in physiology. The graphical analysis using Poincare plot analysis with subsequent qualitative and quantitative analysis is one of them. The aim of this paper is to provide basic information about this method and its application in physiological research and clinical praxis. AD - Ustav fyziologie, Jesseniova lekarska fakulta UK, Martin. Mjavorka@jfmed.uniba.sk FAU - Javorka, M AU - Javorka M LA - slo PT - Journal Article TT - Analyza variability fyziologickych parametrov pomocou Poincare plotu. CY - Czech Republic TA - Cesk Fysiol JID - 2984710R SB - IM MH - Electrocardiography, Ambulatory MH - English Abstract MH - *Heart Rate MH - Human MH - *Models, Statistical MH - *Nonlinear Dynamics EDAT- 2002/06/11 10:00 MHDA- 2002/07/13 10:01 PST - ppublish SO - Cesk Fysiol 2002 May;51(2):75-81. 94: Xinghua Z, et al. A study of the effect of non-...[PMID:12052397]Related Articles, Books, LinkOut UI - 22047795 PMID- 12052397 DA - 20020607 DCOM- 20020918 IS - 0021-9290 VI - 35 IP - 7 DP - 2002 Jul TI - A study of the effect of non-linearities in the equation of bone remodeling. PG - 951-60 AB - In this paper, we introduced a high-order non-linear equation of bone remodeling to combine with FEM by introducing two non-linearities, i.e. the remodeling coefficient B(t) and the order of non-linear remodeling equation. The influence of each non-linearity was tested based on its mechanical and physiological implications discussed. We use two finite element models to investigate the influences of non-linearities in this equation: a plate subjected to a ramp load, and a 2D model of the cross-section of a vertebra. By importing the idea of topology optimization in engineering, their external shapes and internal density distributions were simulated from unfixed configurations. To a certain extent, the high-order non-linear equation of bone remodeling we suggested here can control the remodeling processes of bones in different stages of growth or at different anatomic sites more effectively, and make it more consistent with physiological reality, i.e. express the remodeling characteristic that bone's best morphology is adapted to its mechanical environment. Furthermore, it is likely to describe the process of bone growth and evolution. AD - Department of Mechanics, Jilin University, Changchun, China. FAU - Xinghua, Zhu AU - Xinghua Z FAU - He, Gong AU - He G FAU - Dong, Zhu AU - Dong Z FAU - Bingzhao, Gao AU - Bingzhao G LA - eng PT - Journal Article CY - United States TA - J Biomech JID - 0157375 SB - IM MH - Biomechanics MH - Bone Remodeling/*physiology MH - Finite Element Analysis MH - Human MH - Models, Biological MH - Nonlinear Dynamics MH - Spine/anatomy & histology/physiology MH - Support, Non-U.S. Gov't EDAT- 2002/06/08 10:00 MHDA- 2002/09/19 10:01 AID - S0021929002000283 [pii] PST - ppublish SO - J Biomech 2002 Jul;35(7):951-60. 95: Weiss JA, et al. Ligament material behavior is...[PMID:12052396]Related Articles, Books, LinkOut UI - 22047794 PMID- 12052396 DA - 20020607 DCOM- 20020918 IS - 0021-9290 VI - 35 IP - 7 DP - 2002 Jul TI - Ligament material behavior is nonlinear, viscoelastic and rate-independent under shear loading. PG - 943-50 AB - The material behavior of ligament is determined by its constituents, their organization and their interaction with each other. To elucidate the origins of the multiaxial material behavior of ligaments, we investigated ligament response to shear loading under both quasi-static and rate-dependent loading conditions. Stress relaxation tests demonstrated that the tissue was highly viscoelastic in shear, with peak loads dropping over 40% during 30 min of stress relaxation. The stress relaxation response was unaffected by three decades of change in shear strain rate (1.3, 13 and 130%/s). A novel parameter estimation technique was developed to determine material coefficients that best described the experimental response of each test specimen to shear. The experimentally measured clamp displacements and reaction forces from the simple shear tests were used with a nonlinear optimization strategy based around function evaluations from a finite element program. A transversely isotropic material with an exponential matrix strain energy provided an excellent fit to experimental load-displacement curves. The shear modulus of human MCL showed a significant increase with increasing shear strain (p<0.001), reaching a maximum of 1.72+/-0.4871 MPa. The results obtained from this study suggest that viscoelasticity in shear does not likely result from fluid flow. Gradual loading of transversely oriented microstructural features such as intermolecular collagen crosslinks or collagen-proteoglycan crosslinking may be responsible for the stiffening response under shear loading. AD - Department of Bioengineering, The University of Utah, 50 S Central Campus Drive, Rm #2480, Salt Lake City, UT 84112, USA. jeff.weiss@utah.edu FAU - Weiss, Jeffrey A AU - Weiss JA FAU - Gardiner, John C AU - Gardiner JC FAU - Bonifasi-Lista, Carlos AU - Bonifasi-Lista C LA - eng ID - AR47369/AR/NIAMS PT - Journal Article CY - United States TA - J Biomech JID - 0157375 SB - IM MH - Adult MH - Aged MH - Biomechanics MH - Elasticity MH - Female MH - Human MH - In Vitro MH - Ligaments/*physiology MH - Male MH - Middle Age MH - Models, Biological MH - Nonlinear Dynamics MH - Stress, Mechanical MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. MH - Viscosity EDAT- 2002/06/08 10:00 MHDA- 2002/09/19 10:01 AID - S0021929002000416 [pii] PST - ppublish SO - J Biomech 2002 Jul;35(7):943-50. 96: Orel VE, et al. The device and algorithm for ...[PMID:12052364]Related Articles, Books, LinkOut UI - 22048021 PMID- 12052364 DA - 20020607 DCOM- 20020822 IS - 1350-4533 VI - 24 IP - 5 DP - 2002 Jun TI - The device and algorithm for estimation of the mechanoemisson chaos in blood of patients with gastric cancer. PG - 365-71 AB - The mechanoemission (ME) of blood is developed as a result of mechanochemical activation of a sample which is layered onto chromatographic paper. This paper describes computer-controlled device, aimed for generation, detection and analysis of ME data in the blood of the persons investigated. The original algorithm for estimation of ME chaos in blood is developed. For gastric cancer patients an increase of ME chaos is observed in comparison with healthy individuals and patients with inflammation of gastric mucosa. The concept of deterministic chaos is biohierarchical for the host of a cancer patient. In the light of this we have calculated that spatial chaos for gastric cancer patients is also increased in the geometrical structure of tumor cells and magnetic resonance imaging of the stomach. The concept of deterministic chaos may find an application in the development of new multi-computer organizations for medical diagnostic equipment. AD - Physics-Technical Laboratory, Institute of Oncology, Lomonosov Str. 33/43, 252022 Kiev-22, Ukraine. orel@ucr.kiev.ua FAU - Orel, V E AU - Orel VE FAU - Romanov, A V AU - Romanov AV FAU - Dzyatkovskaya, N N AU - Dzyatkovskaya NN FAU - Mel'nik, Yu I AU - Mel'nik YI LA - eng PT - Clinical Trial PT - Controlled Clinical Trial PT - Journal Article CY - England TA - Med Eng Phys JID - 9422753 SB - IM MH - *Algorithms MH - Comparative Study MH - Diagnosis, Computer-Assisted/instrumentation/*methods MH - Gastritis/physiopathology MH - Human MH - Magnetic Resonance Imaging MH - Male MH - Middle Age MH - *Models, Cardiovascular MH - Neoplasm Staging MH - Nonlinear Dynamics MH - Radio Waves MH - Rheology MH - Stomach Neoplasms/*blood supply/diagnosis/radionuclide imaging MH - Stress, Mechanical MH - Transducers EDAT- 2002/06/08 10:00 MHDA- 2002/08/23 10:01 AID - S135045330200022X [pii] PST - ppublish SO - Med Eng Phys 2002 Jun;24(5):365-71. 97: Hamilton MF, et al. Nonlinear two-dimensional mod...[PMID:12051428]Related Articles, Books, LinkOut UI - 22046416 PMID- 12051428 DA - 20020607 DCOM- 20020703 IS - 0001-4966 VI - 111 IP - 5 Pt 1 DP - 2002 May TI - Nonlinear two-dimensional model for thermoacoustic engines. PG - 2076-86 AB - A two-dimensional model and efficient solution algorithm are developed for studying nonlinear effects in thermoacoustic engines. There is no restriction on the length or location of the stack, and the cross-sectional area of the resonator may vary with position along its axis. Reduced model equations are obtained by ordering spatial derivatives in terms of rapid variations across the pores in the stack, versus slow variations along the resonator axis. High efficiency is achieved with the solution algorithm because the stability condition for numerical integration of the model equations is connected with resonator length rather than pore diameter. Computation time is reduced accordingly, by several orders of magnitude, without sacrificing spatial resolution. The solution algorithm is described in detail, and the results are verified by comparison with established linear theory. Two examples of nonlinear effects are investigated briefly, the onset of instability through to saturation and steady state, and nonlinear waveform distortion as a function of resonator shape. AD - Department of Mechanical Engineering, The University of Texas at Austin, 78712-1063, USA. FAU - Hamilton, Mark F AU - Hamilton MF FAU - Ilinskii, Yurii A AU - Ilinskii YA FAU - Zabolotskaya, Evgenia A AU - Zabolotskaya EA LA - eng PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 SB - IM MH - *Acoustics MH - *Algorithms MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - *Temperature EDAT- 2002/06/08 10:00 MHDA- 2002/07/04 10:01 PST - ppublish SO - J Acoust Soc Am 2002 May;111(5 Pt 1):2076-86. 98: Kumon RE, et al. Directional dependence of non...[PMID:12051426]Related Articles, Books, LinkOut UI - 22046414 PMID- 12051426 DA - 20020607 DCOM- 20020703 IS - 0001-4966 VI - 111 IP - 5 Pt 1 DP - 2002 May TI - Directional dependence of nonlinear surface acoustic waves in the (001) plane of cubic crystals. PG - 2060-9 AB - Spectral evolution equations are used to perform analytical and numerical studies of nonlinear surface acoustic waves in the (001) plane of a variety of nonpiezoelectric cubic crystals. The basic theory underlying the model equations is outlined, and quasilinear solutions of the equations are presented. Expressions are also developed for a characteristic length scale for nonlinear distortion and a nonlinearity coefficient. A time-domain equation corresponding to the spectral equations is derived. Numerical calculations based on measured second- and third-order elastic constants taken from the literature are performed to predict the evolution of initially monofrequency surface waves. Nonlinearity matrix elements that indicate the coupling strength of harmonic interactions are shown to provide a useful tool for characterizing waveform distortion. The formation of compression or rarefaction shocks can be strongly dependent on the direction of propagation, and harmonic generation is suppressed or increased in certain directions. AD - Department of Mechanical Engineering, The University of Texas at Austin, 78712-1063, USA. kumon@mailaps.org FAU - Kumon, R E AU - Kumon RE FAU - Hamilton, M F AU - Hamilton MF LA - eng PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 SB - IM MH - *Acoustics MH - *Nonlinear Dynamics MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/06/08 10:00 MHDA- 2002/07/04 10:01 PST - ppublish SO - J Acoust Soc Am 2002 May;111(5 Pt 1):2060-9. 99: Munteanu L, et al. Nonlinear dynamics of the lef...[PMID:12051312]Related Articles, Books, LinkOut UI - 22046302 PMID- 12051312 DA - 20020607 DCOM- 20021127 IS - 0967-3334 VI - 23 IP - 2 DP - 2002 May TI - Nonlinear dynamics of the left ventricle. PG - 417-35 AB - The cnoidal method is applied to solve the set of nonlinear dynamic equations of the left ventricle. By using the theta-function representation of the solutions and a genetic algorithm, the ventricular motion can be described as a linear superposition of cnoidal pulses and additional terms, which include nonlinear interactions among them. AD - Institute of Solid Mechanics of the Romanian Academy, Bucharest. ligia_munteanu@hotmail.com FAU - Munteanu, Ligia AU - Munteanu L FAU - Chiroiu, Calin AU - Chiroiu C FAU - Chiroiu, Veturia AU - Chiroiu V LA - eng PT - Journal Article CY - England TA - Physiol Meas JID - 9306921 SB - IM MH - Algorithms MH - Heart/*physiology MH - Heart Ventricle/physiology MH - Human MH - *Models, Cardiovascular MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Ventricular Function, Left/*physiology EDAT- 2002/06/08 10:00 MHDA- 2002/11/28 04:00 PST - ppublish SO - Physiol Meas 2002 May;23(2):417-35. 100: Jekova I, et al. Method for ventricular fibril...[PMID:12051305]Related Articles, Books, LinkOut UI - 22046295 PMID- 12051305 DA - 20020607 DCOM- 20021127 IS - 0967-3334 VI - 23 IP - 2 DP - 2002 May TI - Method for ventricular fibrillation detection in the external electrocardiogram using nonlinear prediction. PG - 337-45 AB - The automatic external defibrillator is a lifesaving device which processes and analyses the electrocardiogram (ECG) and delivers defibrillation shock when necessary. The accuracy of the built-in algorithm for ECG analysis must be very high, with sensitivity and specificity aimed to approach the maximum values of 100%. An algorithm based on nonlinear prediction of the external ECG signal is proposed. It extracts seven parameters characterizing the prediction possibility of the assessed ECG signal. By means of the K-nearest neighbours rule the diagnostic accuracy of different combinations of these parameters was evaluated. Thus the accuracy obtained was higher than 95% with sensitivity and specificity values depending on the combination of parameters. The method was tested with ECG records from the widely recognized databases of the American Heart Association (AHA) and Massachusetts Institute of Technology (MIT). AD - Centre of Biomedical Engineering, Bulgarian Academy of Sciences, Sofia. ikdas@argo.bas.bg FAU - Jekova, Irena AU - Jekova I FAU - Dushanova, Juliana AU - Dushanova J FAU - Popivanov, David AU - Popivanov D LA - eng PT - Journal Article CY - England TA - Physiol Meas JID - 9306921 SB - IM MH - Electrocardiography/*methods MH - Human MH - *Models, Cardiovascular MH - Nonlinear Dynamics MH - Predictive Value of Tests MH - Ventricular Fibrillation/*diagnosis EDAT- 2002/06/08 10:00 MHDA- 2002/11/28 04:00 PST - ppublish SO - Physiol Meas 2002 May;23(2):337-45. 101: El-Brawany MA, et al. New approach for modelling ul...[PMID:12049966]Related Articles, Books, LinkOut UI - 22046148 PMID- 12049966 DA - 20020606 DCOM- 20020815 IS - 0301-5629 VI - 28 IP - 4 DP - 2002 Apr TI - New approach for modelling ultrasound blood backscatter signal. PG - 527-34 AB - The ultrasound (US) scattered signal from blood has been treated as a random signal by many investigators. However, the degree of randomness of a medium is a relative term that can change considerably with the resolution of the sensor. In this study, the backscattered signal from blood has been looked at as a chaotic signal. By this treatment, according to Taken's theorem, a single variable (e.g., amplitude of the blood-backscattered signal) can be used to reconstruct the nonlinear dynamics of the blood-scattered signal. Multilayer perceptron neural network architecture, with error back-propagation, has been formulated and used as a basis for building and testing the chaotic model of the backscattered signal. This chaotic model is used successfully as a short-term predictor of the backscattered signal from blood-mimicking fluid (BMF) flowing in a vascular flow phantom under pulsatile flow. This modelling approach can be useful, for example, in detecting blood-borne emboli. AD - Department of Medical Physics and Bioengineering, St. George's Hospital, Blackshaw Road, London SW17 0QT, UK. mbrawany@sghms.ac.uk FAU - El-Brawany, Mohamed A AU - El-Brawany MA FAU - Nassiri, Dariush K AU - Nassiri DK LA - eng PT - Journal Article CY - England TA - Ultrasound Med Biol JID - 0410553 SB - IM MH - Blood/*ultrasonography MH - Models, Biological MH - Nonlinear Dynamics MH - Phantoms, Imaging MH - Pulsatile Flow MH - Signal Processing, Computer-Assisted/*instrumentation MH - Support, Non-U.S. Gov't EDAT- 2002/06/07 10:00 MHDA- 2002/08/16 10:01 AID - S0301562902004763 [pii] PST - ppublish SO - Ultrasound Med Biol 2002 Apr;28(4):527-34. 102: Lucia A, et al. Curvilinear VO(2):power outpu...[PMID:12047807]Related Articles, Books, LinkOut UI - 22043529 PMID- 12047807 DA - 20020605 DCOM- 20021023 IS - 0021-521X VI - 52 IP - 1 DP - 2002 Feb TI - Curvilinear VO(2):power output relationship in a ramp test in professional cyclists: possible association with blood hemoglobin concentration. PG - 95-103 AB - The purpose of this study was to determine (1) if there exists an additional, nonlinear increase (DeltaVO(2)) in the oxygen uptake observed (VO2 (obs)) at the maximal power output reached during a ramp cycle ergometer test and that expected (VO2 (exp)) from the linear relationship between VO(2) and power output below the lactate threshold (LT) in professional riders, and (2) the relationship between DeltaVO(2) and possible explanatory mechanisms. Each of 12 professional cyclists (25 +/- 1 years; VO(2 max): 71.3 +/- 1.2 ml x kg(-1) x min(-1)) performed a ramp test until exhaustion (power output increases of 25 W x min(-1)) during which several gas-exchange and blood variables were measured (including lactate, HCO(3)(-) and K(+)). VO(2) was linearly related to power output until the LT in all subjects. Afterward, a nonlinear deflection was observed in the VO(2):power output relationship (DeltaVO(2) = 2492 +/- 55 ml x min(-1) and p < 0.05 for VO2 (obs) vs. VO2 (exp)). A significant negative correlation was encountered between DeltaVO(2) and resting hemoglobin levels before the tests (r = 20.61; p < 0.05). In conclusion, professional cyclists exhibit an attenuation of the VO(2) rise above the LT. AD - Departamento de Ciencias Morfologicas y Fisiologia, Universidad Europea de Madrid, Spain. alejandro.lucia@mrfs.cisa.uem.es FAU - Lucia, Alejandro AU - Lucia A FAU - Hoyos, Jesus AU - Hoyos J FAU - Santalla, Alfredo AU - Santalla A FAU - Perez, Margarita AU - Perez M FAU - Chicharro, Jose L AU - Chicharro JL LA - eng PT - Journal Article CY - Japan TA - Jpn J Physiol JID - 2985184R RN - 0 (Hemoglobins) RN - 50-21-5 (Lactic Acid) SB - IM MH - Adult MH - Bicycling/*physiology MH - Differential Threshold MH - Exercise Test MH - Hemoglobins/analysis MH - Human MH - Lactic Acid/blood MH - Linear Models MH - Nonlinear Dynamics MH - Osmolar Concentration MH - *Oxygen Consumption MH - Pulmonary Gas Exchange MH - *Sports EDAT- 2002/06/06 10:00 MHDA- 2002/10/31 04:00 PST - ppublish SO - Jpn J Physiol 2002 Feb;52(1):95-103. 103: Celka P, et al. Nonlinear nonstationary Wiene...[PMID:12046701]Related Articles, Books, LinkOut UI - 22041628 PMID- 12046701 DA - 20020605 DCOM- 20020719 IS - 0018-9294 VI - 49 IP - 6 DP - 2002 Jun TI - Nonlinear nonstationary Wiener model of infant EEG seizures. PG - 556-64 AB - This paper presents the estimation of a nonstationary nonlinear model of seizures in infants based on parallel Wiener structures. The model comprises two parts and is partly derived from the Roessgen et al. seizure model. The first part consists of a nonlinear Wiener model of the pure background activity, and the second part in a nonlinear Wiener model of the pure seizure activity with a time-varying deterministic input signal. The two parts are then combined in a parallel structure. The Wiener model consists of an autoregressive moving average filter followed by a nonlinear shaping function to take into account the non-Gaussian statistical behavior of the data. Model estimation was performed on 64 infants of whom four showed signs of clinical and electrical seizures. Model validation is performed using time-frequency-based entropy distance and shows an averaged improvement of 50% in modeling performance compared with the Roessgen model. AD - Signal Processing Research Centre, Queensland University of Technology, Brisbane, Australia. patrick.celka@csem.ch FAU - Celka, P AU - Celka P FAU - Colditz, P AU - Colditz P LA - eng PT - Clinical Trial PT - Controlled Clinical Trial PT - Journal Article CY - United States TA - IEEE Trans Biomed Eng JID - 0012737 SB - IM MH - Comparative Study MH - Electroencephalography/*methods/*statistics & numerical data MH - Human MH - Infant MH - *Models, Neurological MH - Nonlinear Dynamics MH - Reproducibility of Results MH - Seizures/diagnosis/*physiopathology MH - Sensitivity and Specificity MH - Signal Processing, Computer-Assisted MH - Stochastic Processes MH - Support, Non-U.S. Gov't EDAT- 2002/06/06 10:00 MHDA- 2002/07/20 10:01 PST - ppublish SO - IEEE Trans Biomed Eng 2002 Jun;49(6):556-64. 104: Pereda E, et al. Evidence of state-dependent i...[PMID:12046700]Related Articles, Books, LinkOut UI - 22041627 PMID- 12046700 DA - 20020605 DCOM- 20020719 IS - 0018-9294 VI - 49 IP - 6 DP - 2002 Jun TI - Evidence of state-dependent interhemispheric relationships in lizard EEG during the awake state. PG - 548-55 AB - The electroencephalogram (EEG) from both hemispheres of eight Canary lizards Gallotia galloti was registered at 25 degrees C and 35 degrees C during awake state with open eyes (OE) and closed eyes. The possible interdependence between the recorded EEGs was assessed by means of newly developed methods of multivariate nonlinear time-series analysis. The interdependence turned out to be significant and greater for the OE state at both temperatures, although it was of linear type in most of the cases. We conclude that the methods can be successfully applied to study the interdependence between noisy, low-amplitude EEGs. AD - Departamento de Fisica Basica, Universidad de la Laguna, Tenerife, Spain. eperdepa@ull.es FAU - Pereda, Ernesto AU - Pereda E FAU - Gamundi, Antoni AU - Gamundi A FAU - Nicolau, Maria C AU - Nicolau MC FAU - De Vera, Luis AU - De Vera L FAU - Gonzalez, Julian J AU - Gonzalez JJ LA - eng PT - Journal Article CY - United States TA - IEEE Trans Biomed Eng JID - 0012737 SB - IM MH - Animal MH - Comparative Study MH - Electroencephalography/*methods/*statistics & numerical data MH - Eye Movements/physiology MH - Lizards/*physiology MH - *Models, Neurological MH - Nonlinear Dynamics MH - Reproducibility of Results MH - Sensitivity and Specificity MH - Signal Processing, Computer-Assisted MH - Support, Non-U.S. Gov't MH - Wakefulness/*physiology EDAT- 2002/06/06 10:00 MHDA- 2002/07/20 10:01 PST - ppublish SO - IEEE Trans Biomed Eng 2002 Jun;49(6):548-55. 105: Ziarani AK, et al. A nonlinear adaptive method o...[PMID:12046699]Related Articles, Books, LinkOut UI - 22041626 PMID- 12046699 DA - 20020605 DCOM- 20020719 IS - 0018-9294 VI - 49 IP - 6 DP - 2002 Jun TI - A nonlinear adaptive method of elimination of power line interference in ECG signals. PG - 540-7 AB - A new method of elimination of power line noise in electrocardiogram signals is presented. The proposed method employs, as its main building block, a recently developed signal processing algorithm capable of extracting a specified component of a signal and tracking its variations over time. Design considerations and performance of the proposed method are presented with the aid of computer simulations. Superior performance is observed in terms of effective elimination of noise under conditions of varying powerline interference frequency. The proposed method presents a simple and robust structure which complies with practical constraints involved in the problem such as low computational resource availability and low sampling frequency. AD - Edward S. Rogers Sr. Department of Electrical and Computer Engineering, University of Toronto, ON, Canada. FAU - Ziarani, Alireza K AU - Ziarani AK FAU - Konrad, Adalbert AU - Konrad A LA - eng PT - Journal Article CY - United States TA - IEEE Trans Biomed Eng JID - 0012737 SB - IM MH - Algorithms MH - Electrocardiography/*methods MH - *Electromagnetic Fields MH - Feedback MH - Human MH - *Nonlinear Dynamics MH - Power Sources MH - Reproducibility of Results MH - *Signal Processing, Computer-Assisted MH - Support, Non-U.S. Gov't MH - Time Factors EDAT- 2002/06/06 10:00 MHDA- 2002/07/20 10:01 PST - ppublish SO - IEEE Trans Biomed Eng 2002 Jun;49(6):540-7. 106: Mino H, et al. Effects of stochastic sodium ...[PMID:12046697]Related Articles, Books, LinkOut UI - 22041624 PMID- 12046697 DA - 20020605 DCOM- 20020719 IS - 0018-9294 VI - 49 IP - 6 DP - 2002 Jun TI - Effects of stochastic sodium channels on extracellular excitation of myelinated nerve fibers. PG - 527-32 AB - The effects of the stochastic gating properties of sodium channels on the extracellular excitation properties of mammalian nerve fibers was determined by computer simulation. To reduce computation time, a hybrid multicompartment cable model including five central nodes of Ranvier containing stochastic sodium channels and 16 flanking nodes containing detenninistic membrane dynamics was developed. The excitation properties of the hybrid cable model were comparable with those of a full stochastic cable model including 21 nodes of Ranvier containing stochastic sodium channels, indicating the validity of the hybrid cable model. The hybrid cable model was used to investigate whether or not the excitation properties of extracellularly activated fibers were influenced by the stochastic gating of sodium channels, including spike latencies, strength-duration (SD), current-distance (IX), and recruitment properties. The stochastic properties of the sodium channels in the hybrid cable model had the greatest impact when considering the temporal dynamics of nerve fibers, i.e., a large variability in latencies, while they did not influence the SD, IX, or recruitment properties as compared with those of the conventional deterministic cable model. These findings suggest that inclusion of stochastic nodes is not important for model-based design of stimulus waveforms for activation of motor nerve fibers. However, in cases where temporal fine structure is important, for example in sensory neural prostheses in the auditory and visual systems, the stochastic properties of the sodium channels may play a key role in the design of stimulus waveforms. AD - Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA. hiromino@earpower.oto.uiowa.edu FAU - Mino, Hiroyuki AU - Mino H FAU - Grill, Warren M Jr AU - Grill WM Jr LA - eng ID - R01 NS40894/NS/NINDS PT - Journal Article CY - United States TA - IEEE Trans Biomed Eng JID - 0012737 RN - 0 (Sodium Channels) SB - IM MH - Action Potentials/*physiology MH - Animal MH - Comparative Study MH - Computer Simulation MH - Electric Impedance MH - Mammals MH - Markov Chains MH - *Models, Neurological MH - Nerve Fibers, Myelinated/*physiology MH - Nonlinear Dynamics MH - Ranvier's Nodes/*physiology MH - Sodium Channels/*physiology MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/06/06 10:00 MHDA- 2002/07/20 10:01 PST - ppublish SO - IEEE Trans Biomed Eng 2002 Jun;49(6):527-32. 107: Suder K, et al. Spatial dynamics of receptive...[PMID:12037629]Related Articles, Books, LinkOut UI - 22032896 PMID- 12037629 DA - 20020530 DCOM- 20020904 IS - 0014-4819 VI - 144 IP - 4 DP - 2002 Jun TI - Spatial dynamics of receptive fields in cat primary visual cortex related to the temporal structure of thalamocortical feedforward activity. Experiments and models. PG - 430-44 AB - We investigated how changes in the temporal firing rate of thalamocortical activity affect the spatiotemporal structure of receptive field (RF) subunits in cat primary visual cortex. Spike activity of 67 neurons (48 simple, 19 complex cells) was extracellulary recorded from area 17/18 of anesthetized and paralyzed cats. A total of 107 subfields (on/off) were mapped by applying a reverse correlation technique to the activity elicited by bright and dark rectangles flashed for 300 ms in a 20x10 grid. We found that the width of the (suprathreshold) discharge fields shrank on average by 22% during this 300-ms-long stimulus presentation time. Fifty-eight subfields (54%) shrank by more than 20% of peak width and only ten (less than 10%) showed a slight increase over time. The main size reduction took place 40-60 ms after response onset, which corresponded to the transition from transient peak firing to tonic visual activity in thalamocortical relay cells (TC). The experimentally obtained RFs were then fitted with the aid of a neural field model of the primary visual pathway. Assuming a Gaussian-shaped spatial sensitivity profile across the RF subfield width, the model allowed us to estimate the subthreshold RF (depolarization field, D-field) from the minimal discharge field (MDF). The model allowed us to test to what degree the temporal dynamics of thalamocortical activity contributes to the spatiotemporal changes of cortical RFs. To this end, we performed the fitting procedure either with a pure feedforward model or with a field model that also included intracortical feedback. Spatial and temporal parameters obtained from fits of the experimental RFs matched closely to those achieved by simulating a pure feedforward system with the field model but were not compatible with additional intracortical feedback. Thus, our results show that dot stimulation, which optimally excites thalamocortical cells, leads to a shrinkage with respect to the size of the RF subfield at the first transient response of visual cortical RFs which seems mainly due to a change in the thalamic firing pattern. In these experiments little or no influence from intracortical sources was observed, which, however, may play a role when using more complex visual stimuli. AD - Institute of Physiology, Department of Neurophysiology, Ruhr University, Bochum, Germany. FAU - Suder, Katrin AU - Suder K FAU - Funke, Klaus AU - Funke K FAU - Zhao, Yongqiang AU - Zhao Y FAU - Kerscher, Nicolas AU - Kerscher N FAU - Wennekers, Thomas AU - Wennekers T FAU - Worgotter, Florentin AU - Worgotter F LA - eng PT - Journal Article CY - Germany TA - Exp Brain Res JID - 0043312 SB - IM MH - Action Potentials/*physiology MH - Animal MH - Cats MH - Feedback/*physiology MH - Geniculate Bodies/cytology/physiology MH - Models, Neurological MH - Neuronal Plasticity/physiology MH - Nonlinear Dynamics MH - Photic Stimulation MH - Reaction Time/physiology MH - Support, Non-U.S. Gov't MH - Synaptic Transmission/physiology MH - Thalamus/cytology/*physiology MH - Time Factors MH - Visual Cortex/cytology/*physiology MH - Visual Fields/*physiology MH - Visual Pathways/cytology/*physiology MH - Visual Perception/*physiology EDAT- 2002/05/31 10:00 MHDA- 2002/09/06 10:01 PHST- 2001/Jun/21 [received] PHST- 2002/Feb/06 [accepted] PHST- 2002/Apr/13 [aheadofprint] AID - 10.1007/s00221-002-1061-5 [doi] PST - ppublish SO - Exp Brain Res 2002 Jun;144(4):430-44. 108: Barker P. From chaos to complex order: ...[PMID:12035679]Related Articles, Books, LinkOut UI - 22032324 PMID- 12035679 DA - 20020530 DCOM- 20020702 IS - 0031-5990 VI - 36 IP - 2 DP - 2000 Apr-Jun TI - From chaos to complex order: personal values and resources in the process of psychotherapy. PG - 51-7 AB - TOPIC: Chaos as a scientific metaphor for the therapeutic relationship. PURPOSE: To provide an approach to psychotherapy of a psychotic experience through aspects of a single case. SOURCES: Selective literature review and author's clinical work. CONCLUSIONS: Appreciation of the water metaphor, and its deployment within Eastern philosophy and psychology, may help Western therapists develop further traditional interpersonal relations today. AD - Department of Psychiatry, University of Newcastle, Royal Victoria Infirmary, Newcastle Upon Tyne, England. p.j.barker@nc/.ac.uk FAU - Barker, P AU - Barker P LA - eng PT - Journal Article CY - United States TA - Perspect Psychiatr Care JID - 0401133 SB - N MH - Adult MH - Case Report MH - Human MH - Male MH - *Nonlinear Dynamics MH - *Nurse-Patient Relations MH - Nursing Assessment MH - *Psychotherapy MH - Psychotic Disorders/*nursing/psychology MH - *Social Values EDAT- 2002/05/31 10:00 MHDA- 2002/07/03 10:01 PST - ppublish SO - Perspect Psychiatr Care 2000 Apr-Jun;36(2):51-7. 109: Hausdorff JM, et al. When human walking becomes ra...[PMID:12033228]Related Articles, Books, LinkOut UI - 22026901 PMID- 12033228 DA - 20020528 DCOM- 20020814 LR - 20021101 IS - 0378-4371 VI - 302 IP - 1-4 DP - 2001 Dec 15 TI - When human walking becomes random walking: fractal analysis and modeling of gait rhythm fluctuations. PG - 138-47 AB - We present a random walk, fractal analysis of the stride-to-stride fluctuations in the human gait rhythm. The gait of healthy young adults is scale-free with long-range correlations extending over hundreds of strides. This fractal scaling changes characteristically with maturation in children and older adults and becomes almost completely uncorrelated with certain neurologic diseases. Stochastic modeling of the gait rhythm dynamics, based on transitions between different "neural centers", reproduces distinctive statistical properties of the gait pattern. By tuning one model parameter, the hopping (transition) range, the model can describe alterations in gait dynamics from childhood to adulthood including a decrease in the correlation and volatility exponents with maturation. CI - c2001 Published by Elsevier Science B.V. AD - Beth Israel Deaconness Medical Center, Harvard Medical School, Boston, MA 02215, USA. FAU - Hausdorff, J M AU - Hausdorff JM FAU - Ashkenazy, Y AU - Ashkenazy Y FAU - Peng, C K AU - Peng CK FAU - Ivanov, P C AU - Ivanov PC FAU - Stanley, H E AU - Stanley HE FAU - Goldberger, A L AU - Goldberger AL LA - eng ID - AG14100/AG/NIA ID - HD39838/HD/NICHD ID - P41 RR13622/RR/NCRR PT - Journal Article CY - Netherlands TA - Physica A JID - 9890571 SB - S MH - Adolescent MH - Adult MH - Aged MH - Aging/*physiology MH - Child MH - Comparative Study MH - *Fractals MH - *Gait MH - Human MH - Huntington Disease MH - Male MH - *Models, Statistical MH - Nonlinear Dynamics MH - *Stochastic Processes MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/05/30 10:00 MHDA- 2002/08/15 10:01 PST - ppublish SO - Physica A 2001 Dec 15;302(1-4):138-47. 110: Hine JE, et al. Temporal nonlinearity reveale...[PMID:12031522]Related Articles, Books, LinkOut UI - 22027919 PMID- 12031522 DA - 20020528 DCOM- 20021030 IS - 0378-5955 VI - 165 IP - 1-2 DP - 2002 Mar TI - Temporal nonlinearity revealed by transient evoked otoacoustic emissions recorded to trains of multiple clicks. PG - 128-41 AB - A series of detailed experiments is described that investigates how a transient evoked otoacoustic emission (TEOAE) recorded to one-click stimulus is affected by the presence of a variable number of preceding clicks presented over a range of interclick intervals (ICIs). Part of the rationale was to determine if the resulting nonlinear temporal interactions could help explain the amplitude reduction seen when TEOAEs are recorded at very high click rates, as when using maximum length sequence stimulation. Amongst the findings was that the presence of a preceding train of clicks could either suppress or enhance emission amplitude, depending on the number of clicks in the train and the ICI. Results also indicated that the duration of the click trains, rather than the ICI, was the important factor in yielding the most suppressed response and that this seemed to depend on stimulus level. The results recorded at two levels also suggested that the cochlear temporal nonlinearity being monitored was in part related to the nonlinear process that determines the compressive input/output function for stimulus level. It is hypothesised that nonlinear temporal overlap of vibration patterns on the basilar membrane may underlie much of the pattern of results. AD - MRC Institute of Hearing Research, Royal South Hants Hospital, Southampton, Hampshire SO14 0YG, UK. j.kwint@soton.ac.uk FAU - Hine, Jemma E AU - Hine JE FAU - Thornton, A Roger D AU - Thornton AR LA - eng PT - Journal Article CY - Netherlands TA - Hear Res JID - 7900445 SB - IM MH - Acoustic Stimulation/*methods MH - Adult MH - Female MH - Human MH - Male MH - *Nonlinear Dynamics MH - Otoacoustic Emissions, Spontaneous/*physiology MH - Reaction Time EDAT- 2002/05/29 10:00 MHDA- 2002/11/01 04:00 AID - S0378595502002952 [pii] PST - ppublish SO - Hear Res 2002 Mar;165(1-2):128-41. 111: Micheloyannis S, et al. Ongoing electroencephalograph...[PMID:12031297]Related Articles, Books, LinkOut UI - 22028019 PMID- 12031297 DA - 20020528 DCOM- 20020716 IS - 0167-8760 VI - 44 IP - 3 DP - 2002 Jun TI - Ongoing electroencephalographic signal study of simple arithmetic using linear and non-linear measures. PG - 231-8 AB - This study examined patterns of variation in the ongoing electroencephalogram during performance of three visual tasks. One task required exact arithmetic calculations on Arabic numerals. A second task involved pseudoword processing as a control for the verbal (phonological) component that is, by definition, part of arithmetic tasks. A third task primarily required visual/graphemic processing, which is also involved in the other two tasks. Spectral power in the alpha range was lowest during the pseudoword task, followed by power during the arithmetic task, and finally by power in the visual task, indicating more prominent desynchronization during engagement in the analysis of word-like printed material. Finally, linear (power in the gamma range) and non-linear measures (correlation dimension) provided evidence of predominant right hemisphere engagement during the arithmetic task. AD - Clinical Neurophysiology Laboratory (L. Widen), Faculty of Medicine, University of Crete, 71409, Crete, Iraklion, Greece. mixelogj@med.uoc.gr FAU - Micheloyannis, Sifis AU - Micheloyannis S FAU - Papanikolaou, Elias AU - Papanikolaou E FAU - Bizas, Emmanuel AU - Bizas E FAU - Stam, Cornelis J AU - Stam CJ FAU - Simos, Panagiotis G AU - Simos PG LA - eng PT - Journal Article CY - Netherlands TA - Int J Psychophysiol JID - 8406214 SB - IM MH - Adult MH - Alpha Rhythm MH - Brain/*physiology MH - *Electroencephalography MH - Female MH - Human MH - Language MH - Linear Models MH - Male MH - *Mathematics MH - Mental Processes/physiology MH - Nonlinear Dynamics MH - Phonetics MH - Reading EDAT- 2002/05/29 10:00 MHDA- 2002/07/18 10:01 AID - S0167876002000077 [pii] PST - ppublish SO - Int J Psychophysiol 2002 Jun;44(3):231-8. 112: Friston KJ. Bayesian estimation of dynami...[PMID:12030834]Related Articles, Books, LinkOut UI - 22028648 PMID- 12030834 DA - 20020528 DCOM- 20020724 IS - 1053-8119 VI - 16 IP - 2 DP - 2002 Jun TI - Bayesian estimation of dynamical systems: an application to fMRI. PG - 513-30 AB - This paper presents a method for estimating the conditional or posterior distribution of the parameters of deterministic dynamical systems. The procedure conforms to an EM implementation of a Gauss-Newton search for the maximum of the conditional or posterior density. The inclusion of priors in the estimation procedure ensures robust and rapid convergence and the resulting conditional densities enable Bayesian inference about the model parameters. The method is demonstrated using an input-state-output model of the hemodynamic coupling between experimentally designed causes or factors in fMRI studies and the ensuing BOLD response. This example represents a generalization of current fMRI analysis models that accommodates nonlinearities and in which the parameters have an explicit physical interpretation. Second, the approach extends classical inference, based on the likelihood of the data given a null hypothesis about the parameters, to more plausible inferences about the parameters of the model given the data. This inference provides for confidence intervals based on the conditional density. CI - 2002 Elsevier Science (USA) AD - The Wellcome Department of Cognitive Neurology, Institute of Neurology, Queen Square, London, United Kingdom WC1N 3BG. FAU - Friston, K J AU - Friston KJ LA - eng PT - Journal Article CY - United States TA - Neuroimage JID - 9215515 RN - 7782-44-7 (Oxygen) SB - IM MH - *Bayes Theorem MH - Brain/*physiology MH - Cerebrovascular Circulation MH - Hemodynamics MH - Human MH - Likelihood Functions MH - *Magnetic Resonance Imaging MH - Models, Cardiovascular MH - Models, Neurological MH - Nonlinear Dynamics MH - Oxygen/blood MH - Probability MH - Statistics/methods MH - Support, Non-U.S. Gov't EDAT- 2002/05/29 10:00 MHDA- 2002/07/26 10:01 AID - 10.1006/nimg.2001.1044 [doi] AID - S1053811901910444 [pii] PST - ppublish SO - Neuroimage 2002 Jun;16(2):513-30. 113: de Jong N, et al. Basic acoustic properties of ...[PMID:12022933]Related Articles, Books, LinkOut UI - 22017841 PMID- 12022933 DA - 20020522 DCOM- 20021010 IS - 0742-2822 VI - 19 IP - 3 DP - 2002 Apr TI - Basic acoustic properties of microbubbles. PG - 229-40 AB - Small (encapsulated) gas bubbles in a contrast medium react to an external oscillating pressure field with volume pulsations. Depending on the magnitude of the ultrasound wave, the vibrations will be related either linearly or nonlinearly to the applied acoustic pressure. For low acoustic pressures, the instantaneous radius oscillates linearly in relation to the amplitude of the applied external pressure field. The oscillation of the bubble is governed by parameters such as resonance frequency, damping coefficients, and shell properties. For higher amplitudes of the external field, the pulsation of the bubbles becomes nonlinear. The spectrum of the scattered ultrasound wave also contains higher harmonics of the emitted frequency in addition to the fundamental frequency. The emitted frequency, bubble size, and nonlinear propagation effects have significant influence on the harmonic generation. For encapsulated bubbles exposed to even higher acoustic amplitudes, their scattering effectiveness increases dramatically and becomes transient. The scattered frequency spectrum broadens, containing higher harmonics. This consequence is due to rupture, disappearance, change of gas content, etc. Using these specific characteristics of the contrast bubbles will open new perspectives in imaging and analysis for medical diagnosis. AD - Deparment of Cardiology and Experimental Echocardiography, Throraxcenter, Erasmus University Rotterdam and the Interuniversity Cardiologic Institute Netherlands (ICIN), Utrecht, The Netherlands. dejong@tch.fgg.eur.nl FAU - de Jong, Nico AU - de Jong N FAU - Bouakaz, Ayache AU - Bouakaz A FAU - Frinking, Peter AU - Frinking P LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - United States TA - Echocardiography JID - 8511187 RN - 0 (Contrast Media) RN - 0 (Gases) SB - IM MH - *Acoustics MH - *Contrast Media MH - *Echocardiography MH - Gases MH - Linear Models MH - Microspheres MH - Nonlinear Dynamics MH - Pressure RF - 28 EDAT- 2002/05/23 10:00 MHDA- 2002/10/11 04:00 PST - ppublish SO - Echocardiography 2002 Apr;19(3):229-40. 114: Xiao G, et al. Nonrigid registration of 3-D ...[PMID:12022628]Related Articles, Books, LinkOut UI - 22017322 PMID- 12022628 DA - 20020522 DCOM- 20021122 IS - 0278-0062 VI - 21 IP - 4 DP - 2002 Apr TI - Nonrigid registration of 3-D free-hand ultrasound images of the breast. PG - 405-12 AB - Three-dimensional (3-D) ultrasound imaging of the breast enables better assessment of diseases than conventional two-dimensional (2-D) imaging. Free-hand techniques are often used for generating 3-D data from a sequence of 2-D slice images. However, the breast deforms substantially during scanning because it is composed primarily of soft tissue. This often causes tissue mis-registration in spatial compounding of multiple scan sweeps. To overcome this problem, in this paper, instead of introducing additional constraints on scanning conditions, we use image processing techniques. We present a fully automatic algorithm for 3-D nonlinear registration of free-hand ultrasound data. It uses a block matching scheme and local statistics to estimate local tissue deformation. A Bayesian regularization method is applied to the sample displacement field. The final deformation field is obtained by fitting a B-spline approximating mesh to the sample displacement field. Registration accuracy is evaluated using phantom data and similar registration errors are achieved with (0.19 mm) and without (0.16 mm) gaps in the data. Experimental results show that registration is crucial in spatial compounding of different sweeps. The execution time of the method on moderate hardware is sufficiently fast for fairly large research studies. AD - Department of Engineering Science, University of Oxford, UK. FAU - Xiao, Guofang AU - Xiao G FAU - Brady, J Michael AU - Brady JM FAU - Noble, J Alison AU - Noble JA FAU - Burcher, Michael AU - Burcher M FAU - English, Ruth AU - English R LA - eng PT - Journal Article CY - United States TA - IEEE Trans Med Imaging JID - 8310780 SB - IM MH - *Algorithms MH - Anisotropy MH - Bayes Theorem MH - Breast Neoplasms/ultrasonography MH - Fibroadenoma/ultrasonography MH - Human MH - Image Enhancement/*methods MH - Imaging, Three-Dimensional/*methods MH - Models, Statistical MH - Nonlinear Dynamics MH - Phantom Limb MH - Reproducibility of Results MH - Sensitivity and Specificity MH - Ultrasonography, Mammary/instrumentation/*methods EDAT- 2002/05/23 10:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - IEEE Trans Med Imaging 2002 Apr;21(4):405-12. 115: Hasegawa M, et al. Solving large scale traveling...[PMID:12022514]Related Articles, Books, LinkOut UI - 22017205 PMID- 12022514 DA - 20020522 DCOM- 20021202 IS - 0893-6080 VI - 15 IP - 2 DP - 2002 Mar TI - Solving large scale traveling salesman problems by chaotic neurodynamics. PG - 271-83 AB - We propose a novel approach for solving large scale traveling salesman problems (TSPs) by chaotic dynamics. First, we realize the tabu search on a neural network, by utilizing the refractory effects as the tabu effects. Then, we extend it to a chaotic neural network version. We propose two types of chaotic searching methods, which are based on two different tabu searches. While the first one requires neurons of the order of n2 for an n-city TSP, the second one requires only n neurons. Moreover, an automatic parameter tuning method of our chaotic neural network is presented for easy application to various problems. Last, we show that our method with n neurons is applicable to large TSPs such as an 85,900-city problem and exhibits better performance than the conventional stochastic searches and the tabu searches. AD - Wireless Communications Division, Independent Administrative Institution, Yokosuka-shi, Kanagawa, Japan. mikio@crl.go.jp FAU - Hasegawa, Mikio AU - Hasegawa M FAU - Ikeguch, Tohru AU - Ikeguch T FAU - Aihara, Kazuyuki AU - Aihara K LA - eng PT - Journal Article CY - United States TA - Neural Netw JID - 8805018 SB - IM MH - *Commerce/statistics & numerical data MH - Comparative Study MH - *Neural Networks (Computer) MH - *Nonlinear Dynamics MH - *Problem Solving MH - Support, Non-U.S. Gov't EDAT- 2002/05/23 10:00 MHDA- 2002/12/03 04:00 PST - ppublish SO - Neural Netw 2002 Mar;15(2):271-83. 116: Billings SA, et al. Nonlinear fisher discriminant...[PMID:12022513]Related Articles, Books, LinkOut UI - 22017204 PMID- 12022513 DA - 20020522 DCOM- 20021202 IS - 0893-6080 VI - 15 IP - 2 DP - 2002 Mar TI - Nonlinear fisher discriminant analysis using a minimum squared error cost function and the orthogonal least squares algorithm. PG - 263-70 AB - The nonlinear discriminant function obtained using a minimum squared error cost function can be shown to be directly related to the nonlinear Fisher discriminant (NFD). With the squared error cost function, the orthogonal least squares (OLS) algorithm can be used to find a parsimonious description of the nonlinear discriminant function. Two simple classification techniques will be introduced and tested on a number of real and artificial data sets. The results show that the new classification technique can often perform favourably compared with other state of the art classification techniques. AD - Department of Automatic Control and Systems Engineering, University of Sheffield, UK. s.billings@sheffield.ac.uk FAU - Billings, Steve A AU - Billings SA FAU - Lee, Kian L AU - Lee KL LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - United States TA - Neural Netw JID - 8805018 SB - IM MH - *Algorithms MH - Comparative Study MH - Costs and Cost Analysis/methods MH - *Discriminant Analysis MH - *Least-Squares Analysis MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't RF - 20 EDAT- 2002/05/23 10:00 MHDA- 2002/12/03 04:00 PST - ppublish SO - Neural Netw 2002 Mar;15(2):263-70. 117: Escabi MA, et al. Nonlinear spectrotemporal sou...[PMID:12019330]Related Articles, Books, LinkOut UI - 22014137 PMID- 12019330 DA - 20020520 DCOM- 20020529 IS - 1529-2401 VI - 22 IP - 10 DP - 2002 May 15 TI - Nonlinear spectrotemporal sound analysis by neurons in the auditory midbrain. PG - 4114-31 AB - The auditory system of humans and animals must process information from sounds that dynamically vary along multiple stimulus dimensions, including time, frequency, and intensity. Therefore, to understand neuronal mechanisms underlying acoustic processing in the central auditory pathway, it is essential to characterize how spectral and temporal acoustic dimensions are jointly processed by the brain. We use acoustic signals with a structurally rich time-varying spectrum to study linear and nonlinear spectrotemporal interactions in the central nucleus of the inferior colliculus (ICC). Our stimuli, the dynamic moving ripple (DMR) and ripple noise (RN), allow us to systematically characterize response attributes with the spectrotemporal receptive field (STRF) methods to a rich and dynamic stimulus ensemble. Theoretically, we expect that STRFs derived with DMR and RN would be identical for a linear integrating neuron, and we find that approximately 60% of ICC neurons meet this basic requirement. We find that the remaining neurons are distinctly nonlinear; these could either respond selectively to DMR or produce no STRFs despite selective activation to spectrotemporal acoustic attributes. Our findings delineate rules for spectrotemporal integration in the ICC that cannot be accounted for by conventional linear-energy integration models. AD - W. M. Keck Center for Integrative Neuroscience and University of California San Francisco/University of California Berkeley Joint Bioengineering Graduate Group, University of California, San Francisco, California 94143, USA. escabi@engr.uconn.edu FAU - Escabi, Monty A AU - Escabi MA FAU - Schreiner, Christoph E AU - Schreiner CE LA - eng ID - DC02260/DC/NIDCD ID - NS34835/NS/NINDS PT - Journal Article CY - United States TA - J Neurosci JID - 8102140 SB - IM MH - Acoustic Stimulation/instrumentation/*methods MH - Action Potentials/physiology MH - Animal MH - Auditory Perception/*physiology MH - Cats MH - Electrodes, Implanted MH - Electrophysiology MH - Inferior Colliculus/physiology MH - Mesencephalon/*physiology MH - Models, Neurological MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Reaction Time/physiology MH - Sound Spectrography MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. MH - Time Factors EDAT- 2002/05/23 10:00 MHDA- 2002/05/30 10:01 AID - 20026325 [doi] AID - 22/10/4114 [pii] PST - ppublish SO - J Neurosci 2002 May 15;22(10):4114-31. 118: Pavec D, et al. Kinematic modeling for the as...[PMID:12018649]Related Articles, Books, LinkOut UI - 22012711 PMID- 12018649 DA - 20020520 DCOM- 20020604 IS - 1534-4320 VI - 9 IP - 4 DP - 2001 Dec TI - Kinematic modeling for the assessment of wheelchair user's stability. PG - 362-8 AB - A computer kinematic model was developed to simulate the lateral and transverse stabilities of wheelchair users in order to compare the effect of different backrests. This model is composed of ellipsoids and parallelepipeds representing the main components of the human body, the seating devices and the wheelchair. A fifteen-segment three-dimensional (3-D) model linked by spherical and revolute joints was created using the ADAMS software (Mechanical Dynamics, Inc.). Torsional springs and dampers are used at the joints to represent four sets of articulation stiffness. Seating devices are represented with 45 rectangular surface patches. The interface between human body and seating devices is modeled by contact elements, which included the specification of stiffness, damping, and deformation of cushions and buttocks. Simulations of a user and his wheelchair moving at 1.4 m/s on a tilted pathway were performed. Different indexes [trunk lateral tilt (TLT) and trunk transverse rotation (TTR)] were measured and compared to those of a similar experimental study on four subjects. The effect of joint stiffness was quantified and a sensitivity study showed the importance of the hip, neck, lumbar, and thoracic joint stiffness on model response (between 16% and 68%). Two backrests (standard and highly contoured) were tested with the kinematic model and their stability compared. Overall, the coherence between the simulations and the experiments shows that this approach is appropriate to compare various seating devices (maximal difference of 1.3 degrees between the simulated and experimental curves for the intermediate joint stiffness sets). The smallest rotations of the highly contoured backrest (6.3 degrees versus 8.9 degrees for TLT and 3.9 degrees versus 6.7 degrees for TTR) suggest that the contouring of the mid torso is more efficient than the lower torso to provide stability to the wheelchair user. This model is an adequate tool to test and improve the design of seating aids. AD - Department of Mechanical Engineering, Ecole Polytechnique de Montreal, QC, Canada. FAU - Pavec, D AU - Pavec D FAU - Aubin, C E AU - Aubin CE FAU - Aissaoui, R AU - Aissaoui R FAU - Parent, F AU - Parent F FAU - Dansereau, J AU - Dansereau J LA - eng PT - Journal Article CY - United States TA - IEEE Trans Neural Syst Rehabil Eng JID - 101097023 SB - IM MH - Biomechanics MH - Comparative Study MH - Computer Simulation MH - Elasticity MH - Equilibrium/*physiology MH - Evaluation Studies MH - Human MH - Joints/*physiology MH - *Models, Biological MH - Nonlinear Dynamics MH - Posture/*physiology MH - Support, Non-U.S. Gov't MH - *Wheelchairs EDAT- 2002/05/23 10:00 MHDA- 2002/06/05 10:01 PST - ppublish SO - IEEE Trans Neural Syst Rehabil Eng 2001 Dec;9(4):362-8. 119: Bell IR, et al. Translating a nonlinear syste...[PMID:12017501]Related Articles, Books, LinkOut UI - 22010984 PMID- 12017501 DA - 20020517 DCOM- 20020625 IS - 1078-6791 VI - 8 IP - 3 DP - 2002 May-Jun TI - Translating a nonlinear systems theory model for homeopathy into empirical tests. PG - 58-66 AB - Various investigators have proposed that nonlinear systems theory, notably chaos and complexity theory, provides a heuristically useful modelfor conceptualizing the way in which complementary and alternative medicine therapies, which purport to modify subtle energies, effect change throughout the individual as a whole. In this paper we apply this theory to classical homeopathy and outline an empirical approach for testing the resultant hypotheses. Such research may advance understanding of the mechanisms of homeopathic remedy effects and provide a direction for homeopathic research that expands the previous emphasis on clinical trials and the remedies themselves. In refocusing attention on the dynamics of the patient as a nonlinear complex system, the proposed research program is consistent with the homeopathic emphasis on the individual rather than the disease. This approach may have additional applications that can elucidate similar effects of other energy medicine modalities (eg, acupuncture) on the healing process of the person as a unified whole. AD - Department of Psychiatry, University of Arizona, Tucson, USA. FAU - Bell, Iris R AU - Bell IR FAU - Baldwin, Carol M AU - Baldwin CM FAU - Schwartz, Gary E AU - Schwartz GE LA - eng ID - K24 AT00057-01/AT/NCCAM ID - P50 AT00008-02/AT/NCCAM ID - R21 AT00315-01/AT/NCCAM ID - U01HL53938-0851/HL/NHLBI PT - Journal Article PT - Review PT - Review, Tutorial CY - United States TA - Altern Ther Health Med JID - 9502013 RN - 0 (Materia Medica) SB - IM MH - Homeopathy/*standards MH - Human MH - Materia Medica/*standards MH - Models, Theoretical MH - *Nonlinear Dynamics MH - Research Design MH - Sick Role MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. MH - Systems Theory RF - 103 EDAT- 2002/05/23 10:00 MHDA- 2002/06/26 10:01 PST - ppublish SO - Altern Ther Health Med 2002 May-Jun;8(3):58-66. 120: Novak KE, et al. The use of overlapping submov...[PMID:12021817]Related Articles, Books, LinkOut UI - 22015634 PMID- 12021817 DA - 20020521 DCOM- 20020904 IS - 0014-4819 VI - 144 IP - 3 DP - 2002 Jun TI - The use of overlapping submovements in the control of rapid hand movements. PG - 351-64 AB - Rapid targeted movements are subject to special control considerations, since there may be inadequate time available for either visual or somatosensory feedback to be effective. In our experiments, subjects rapidly rotated a knob to align a pointer to one of several targets. We recognized three different types of movement segments: the primary movement, and two types of submovement, which frequently followed. The submovements were initiated either before or after the end of the primary movement. The former, or "overlapping" type of submovement altered the kinematics of the overall movement and was consequently difficult to detect. We used a direct, objective test of movement regularity to detect overlapping submovements, namely, examining the number of jerk and snap zero crossings during the second half of a movement. Any overlapping submovements were parsed from the overall movement by subtracting the velocity profile of the primary movement. The velocity profiles of the extracted submovements had near-symmetric bell shapes, similar to the shapes of both pure primary movements and nonoverlapping submovements. This suggests that the same neural control mechanisms may be responsible for producing all three types of movement segments. Overlapping submovements corrected for errors in the amplitude of the primary movement. Furthermore, they may account for the previously observed, speed-dependent asymmetry of the velocity profile. We used a nonlinear model of the musculoskeletal system to explain most of the kinematic features of these rapid hand movements, including how discrete submovements are superimposed on a primary movement. Finally, we present a plausible scheme for how the central nervous system may generate the commands to control these rapid hand movements. AD - Northwestern University, Department of Physiology, Chicago, IL 60611, USA. k-novak@northwestern.edu FAU - Novak, K E AU - Novak KE FAU - Miller, L E AU - Miller LE FAU - Houk, J C AU - Houk JC LA - eng PT - Journal Article CY - Germany TA - Exp Brain Res JID - 0043312 SB - IM MH - Adult MH - Biomechanics MH - Central Nervous System/physiology MH - Female MH - Hand/*innervation/physiology MH - Human MH - Male MH - Middle Age MH - Movement/*physiology MH - Muscle Contraction/*physiology MH - Muscle, Skeletal/*innervation/physiology MH - Nonlinear Dynamics MH - Psychomotor Performance/*physiology MH - Variation (Genetics)/physiology EDAT- 2002/05/22 10:00 MHDA- 2002/09/06 10:01 PHST- 2001/Jan/29 [received] PHST- 2002/Feb/04 [accepted] PHST- 2002/Apr/13 [aheadofprint] AID - 10.1007/s00221-002-1060-6 [doi] PST - ppublish SO - Exp Brain Res 2002 Jun;144(3):351-64. 121: Elliott T, et al. Multiplicative synaptic norma...[PMID:12020448]Related Articles, Books, LinkOut UI - 22016486 PMID- 12020448 DA - 20020521 DCOM- 20020606 IS - 0899-7667 VI - 14 IP - 6 DP - 2002 Jun TI - Multiplicative synaptic normalization and a nonlinear Hebb rule underlie a neurotrophic model of competitive synaptic plasticity. PG - 1311-22 AB - Synaptic normalization is used to enforce competitive dynamics in many models of developmental synaptic plasticity. In linear and semilinear Hebbian models, multiplicative synaptic normalization fails to segregate afferents whose activity patterns are positively correlated. To achieve this, the biologically problematic device of subtractive synaptic normalization must be used instead. Our own model of competition for neurotrophic support, which can segregate positively correlated afferents, was developed in part in an attempt to overcome these problems by removing the need for synaptic normalization altogether. However, we now show that the dynamics of our model decompose into two decoupled subspaces, with competitive dynamics being implemented in one of them through a nonlinear Hebb rule and multiplicative synaptic normalization. This normalization is "emergent" rather than imposed. We argue that these observations permit biologically plausible forms of synaptic normalization to be viewed as abstract and general descriptions of the underlying biology in certain scaleless models of synaptic plasticity. AD - Department of Electronics and Computer Science, University of Southampton, Highfield, Southampton, SO17 1BJ, UK. te@ecs.soton.ac.uk FAU - Elliott, T AU - Elliott T FAU - Shadbolt, N R AU - Shadbolt NR LA - eng PT - Journal Article CY - United States TA - Neural Comput JID - 9426182 SB - IM MH - Animal MH - Human MH - *Models, Neurological MH - Neuronal Plasticity/*physiology MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Synapses/*physiology EDAT- 2002/05/22 10:00 MHDA- 2002/06/12 10:01 AID - 10.1162/089976602753712954 [doi] PST - ppublish SO - Neural Comput 2002 Jun;14(6):1311-22. 122: Russier M, et al. GABA and glycine co-release o...[PMID:12015425]Related Articles, Books, LinkOut UI - 22010330 PMID- 12015425 DA - 20020516 DCOM- 20021021 IS - 0022-3751 VI - 541 IP - Pt 1 DP - 2002 May 15 TI - GABA and glycine co-release optimizes functional inhibition in rat brainstem motoneurons in vitro. PG - 123-37 AB - Whole-cell patch clamp recordings of miniature inhibitory postsynaptic currents (mIPSCs) were obtained in identified abducens motoneurons (aMns) from young rats (P5-P13). Three types of mIPSC were distinguished according to their kinetics and their sensitivity to receptor antagonists: faster decaying events mediated by glycine receptors (glyRs), slower decaying events mediated by GABA(A) receptors (GABA(A)Rs), and mIPSCs displaying two components corresponding to GABA and glycine co-release. Dual component events accounted for approximately 30 % of mIPSCs, independently of the rat's age and were also identified during evoked transmitter release. In contrast, the kinetics of glyR- and GABA(A)R-mediated mIPSCs became faster during development. Monosynaptic inhibitory postsynaptic potentials (IPSPs) were able to fully inhibit motoneuron discharge elicited by current pulses. When the GABA(A)R-mediated component or the glyR-mediated component of the IPSP was blocked, the inhibition of motoneuron firing was reduced. The 20-80 % rise time and duration of GABA(A)R-mediated IPSPs were significantly longer than those mediated by glyRs. The time window of inhibition for each component was determined using single postsynaptic action potentials elicited with various delays from the onset of the IPSP. GlyR-mediated IPSPs induced fast transient inhibition whereas GABA(A)R-mediated IPSPs induced slow sustained suppression of firing. Using a modelling approach, we found that the two components summated non-linearly. We conclude that in developing aMns, co-release of GABA and glycine determines the strength and timing of inhibition through non-linear interactions between the two components, thus optimizing inhibition of motoneuron function. AD - Neurobiologie des Canaux Ioniques, INSERM U464, IFR Jean Roche, Faculte de Medecine Nord, Universite de la Mediterranee, Boulevard Pierre Dramard, 13916 Marseille Cedex 20, France. russier@jean-roche.univ-mrs.fr FAU - Russier, Michael AU - Russier M FAU - Kopysova, Irina L AU - Kopysova IL FAU - Ankri, Norbert AU - Ankri N FAU - Ferrand, Nadine AU - Ferrand N FAU - Debanne, Dominique AU - Debanne D LA - eng PT - Journal Article CY - England TA - J Physiol JID - 0266262 RN - 0 (Excitatory Amino Acid Antagonists) RN - 0 (Potassium Channels) RN - 0 (Receptors, GABA-A) RN - 56-12-2 (gamma-Aminobutyric Acid) RN - 56-40-6 (Glycine) SB - IM MH - Animal MH - Brain Stem/cytology/*metabolism MH - Electrophysiology MH - Excitatory Amino Acid Antagonists/pharmacology MH - Excitatory Postsynaptic Potentials/physiology MH - Glycine/antagonists & inhibitors/*metabolism MH - In Vitro MH - Kinetics MH - Membrane Potentials/physiology MH - Microscopy, Video MH - Models, Neurological MH - Motor Neurons/*metabolism MH - Neural Pathways/physiology MH - Nonlinear Dynamics MH - Patch-Clamp Techniques MH - Potassium Channels/metabolism MH - Rats MH - Rats, Wistar MH - Receptors, GABA-A/antagonists & inhibitors MH - Reflex, Vestibulo-Ocular/physiology MH - Support, Non-U.S. Gov't MH - Synapses/drug effects/metabolism MH - gamma-Aminobutyric Acid/*metabolism EDAT- 2002/05/17 10:00 MHDA- 2002/10/22 04:00 AID - PHY_16063 [pii] PST - ppublish SO - J Physiol 2002 May 15;541(Pt 1):123-37. 123: Perez de la Parte M, et al. Development of a GPC-based sl...[PMID:12014799]Related Articles, Books, LinkOut UI - 22008957 PMID- 12014799 DA - 20020516 DCOM- 20020604 IS - 0019-0578 VI - 41 IP - 1 DP - 2002 Jan TI - Development of a GPC-based sliding mode controller. PG - 19-30 AB - This article presents a sliding mode controller that uses a generalized predictive controller in the reaching mode. The proposed predictive sliding mode controller is developed from a first-order-plus-deadtime model that represents a good approximation to many chemical processes. The predictive sliding mode controller has six tuning parameters and the tuning rules are given in the paper. Four simulation examples show the features of the proposed controller, which overcomes some of the disadvantages of sliding mode control and generalized predictive control strategies. AD - Departamento de Ingenieria de Sistemas y Automatica, Universidad de Sevilla, Spain. FAU - Perez de la Parte, Mercedes AU - Perez de la Parte M FAU - Camacho, Oscar AU - Camacho O FAU - Camacho, Eduardo F AU - Camacho EF LA - eng PT - Journal Article CY - United States TA - ISA Trans JID - 0374750 SB - IM MH - Algorithms MH - *Computer Simulation MH - *Feedback MH - *Models, Theoretical MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2002/05/17 10:00 MHDA- 2002/06/05 10:01 PST - ppublish SO - ISA Trans 2002 Jan;41(1):19-30. 124: Manjarrez E, et al. Stochastic resonance in human...[PMID:12009526]Related Articles, Books, LinkOut UI - 22007879 PMID- 12009526 DA - 20020515 DCOM- 20020807 LR - 20021101 IS - 0304-3940 VI - 324 IP - 3 DP - 2002 May 24 TI - Stochastic resonance in human electroencephalographic activity elicited by mechanical tactile stimuli. PG - 213-6 AB - Stochastic resonance (SR) is a phenomenon in which the response of a non-linear system to a weak input signal is optimized by the presence of noise. The aim of this study was to demonstrate the experimental occurrence of SR in electroencephalographic (EEG) activity elicited by mechanical tactile stimuli. Our experiments show that EEG responses evoked by mechanical tactile stimuli in the region overlying the somatosensory cortical area were optimized by the addition of certain noise amplitudes. All subjects showed distinct SR behavior. The signal-to-noise ratio (SNR) of the response evoked by mechanical indentations of the skin was an inverted U-like function of the input noise. As the noise amplitude increased, SNR values became larger. A maximum value was reached with a particular noise amplitude value. Beyond such peak, with higher noise amplitudes, the curve subsided gradually. To our knowledge, this is the first documented evidence that such remarkable phenomenon embodies electrical processes of the human brain. Such behavior might explain related findings described in psychophysical studies. AD - Instituto de Fisiologia, Benemerita Universidad Autonoma de Puebla, 14 Sur 6301, Col. San Manuel. Apartado Postal 406, Puebla, Pue. CP 72570, Mexico. emanjar@siu.buap.mx FAU - Manjarrez, E AU - Manjarrez E FAU - Diez-Martinez, O AU - Diez-Martinez O FAU - Mendez, I AU - Mendez I FAU - Flores, A AU - Flores A LA - eng PT - Journal Article CY - Ireland TA - Neurosci Lett JID - 7600130 SB - IM MH - Adolescent MH - Adult MH - Afferent Pathways/*physiology MH - *Artifacts MH - Biological Clocks/physiology MH - Electroencephalography MH - Evoked Potentials, Somatosensory/*physiology MH - Female MH - Human MH - Male MH - Mechanoreceptors/*physiology MH - Neural Conduction/physiology MH - *Nonlinear Dynamics MH - Physical Stimulation MH - Signal Transduction/physiology MH - Somatosensory Cortex/*physiology MH - Stochastic Processes MH - Support, Non-U.S. Gov't MH - Synaptic Transmission/physiology MH - Touch/*physiology EDAT- 2002/05/16 10:00 MHDA- 2002/08/08 10:01 AID - S0304394002002124 [pii] PST - ppublish SO - Neurosci Lett 2002 May 24;324(3):213-6. 125: Tham SY, et al. Application of the artificial...[PMID:12008137]Related Articles, Books, LinkOut UI - 22004039 PMID- 12008137 DA - 20020514 DCOM- 20020722 IS - 0731-7085 VI - 28 IP - 3-4 DP - 2002 May 15 TI - Application of the artificial neural network in quantitative structure-gradient elution retention relationship of phenylthiocarbamyl amino acids derivatives. PG - 581-90 AB - Quantitative structure-retention relationship(QSRR) method was used to model reversed-phase high-performance liquid chromatography (RP-HPLC) separation of 18 selected amino acids. Retention data for phenylthiocarbamyl (PTC) amino acids derivatives were obtained using gradient elution on ODS column with mobile phase of varying acetonitrile, acetate buffer and containing 0.5 ml/l of triethylamine (TEA). Molecular structure of each amino acid was encoded with 36 calculated molecular descriptors. The correlation between the molecular descriptors and the retention time of the compounds in the calibration set was established using the genetic neural network method. A genetic algorithm (GA) was used to select important molecular descriptors and supervised artificial neural network (ANN) was used to correlate mobile phase composition and selected descriptors with the experimentally derived retention times. Retention time values were used as the network's output and calculated molecular descriptors and mobile phase composition as the inputs. The best model with five input descriptors was chosen, and the significance of the selected descriptors for amino acid separation was examined. Results confirmed the dominant role of the organic modifier in such chromatographic systems in addition to lipophilicity (log P) and molecular size and shape (topological indices) of investigated solutes. AD - School of Pharmaceutical Science, USM, Penang 11800, Malaysia. FAU - Tham, S Y AU - Tham SY FAU - Agatonovic-Kustrin, S AU - Agatonovic-Kustrin S LA - eng PT - Journal Article CY - England TA - J Pharm Biomed Anal JID - 8309336 RN - 0 (Amino Acids) RN - 0 (Indicators and Reagents) RN - 0 (Thiocarbamates) SB - IM MH - Amino Acids/*analysis MH - Artificial Intelligence MH - Chromatography, High Pressure Liquid MH - Indicators and Reagents MH - Neural Networks (Computer) MH - Nonlinear Dynamics MH - Reference Standards MH - Solubility MH - Structure-Activity Relationship MH - Thiocarbamates/*analysis EDAT- 2002/05/15 10:00 MHDA- 2002/07/23 10:01 AID - S0731708501006902 [pii] PST - ppublish SO - J Pharm Biomed Anal 2002 May 15;28(3-4):581-90. 126: Roche O, et al. A virtual screening method fo...[PMID:12007180]Related Articles, Books, LinkOut UI - 22020928 PMID- 12007180 DA - 20020523 DCOM- 20021104 IS - 1439-4227 VI - 3 IP - 5 DP - 2002 May 3 TI - A virtual screening method for prediction of the HERG potassium channel liability of compound libraries. PG - 455-9 AB - A computer-based method has been developed for prediction of the hERG (human ether-a-go-go related gene) K(+)-channel affinity of low molecular weight compounds. hERG channel blockage is a major concern in drug design, as such blocking agents can cause sudden cardiac death. Various techniques were applied to finding appropriate molecular descriptors for modeling structure-activity relationships: substructure analysis, self-organizing maps (SOM), principal component analysis (PCA), partial least squares fitting (PLS), and supervised neural networks. The most accurate prediction system was based on an artificial neural network. In a validation study, 93 % of the nonblocking agents and 71 % of the hERG channel blockers were correctly classified. This virtual screening method can be used for general compound-library shaping and combinatorial library design. AD - F. Hoffmann-La Roche AG, Pharmaceuticals Division, 4070 Basel, Switzerland. FAU - Roche, Olivier AU - Roche O FAU - Trube, Gerhard AU - Trube G FAU - Zuegge, Jochen AU - Zuegge J FAU - Pflimlin, Pascal AU - Pflimlin P FAU - Alanine, Alexander AU - Alanine A FAU - Schneider, Gisbert AU - Schneider G LA - eng PT - Journal Article CY - Germany TA - Chembiochem JID - 100937360 RN - 0 (HERG protein) RN - 0 (Potassium Channels) SB - IM MH - Combinatorial Chemistry Techniques MH - Databases, Factual MH - Drug Design MH - Human MH - Linear Models MH - Molecular Structure MH - Neural Networks (Computer) MH - Nonlinear Dynamics MH - Potassium Channels/*chemistry MH - Structure-Activity Relationship EDAT- 2002/05/15 10:00 MHDA- 2002/11/26 04:00 AID - 10.1002/1439-7633(20020503)3:5<455::AID-CBIC455>3.0.CO;2-L [doi] PST - ppublish SO - Chembiochem 2002 May 3;3(5):455-9. 127: Henry H, et al. Scroll waves in isotropic exc...[PMID:12006004]Related Articles, Books UI - 22001866 PMID- 12006004 DA - 20020513 DCOM- 20020911 LR - 20021029 IS - 1539-3755 VI - 65 IP - 4 Pt 2A DP - 2002 Apr TI - Scroll waves in isotropic excitable media: linear instabilities, bifurcations, and restabilized states. PG - 046235 AB - Scroll waves are three-dimensional analogs of spiral waves. The linear stability spectrum of untwisted and twisted scroll waves is computed for a two-variable reaction-diffusion model of an excitable medium. Different bands of modes are seen to be unstable in different regions of parameter space. The corresponding bifurcations and bifurcated states are characterized by performing direct numerical simulations. In addition, computations of the adjoint linear stability operator eigenmodes are also performed and serve to obtain a number of matrix elements characterizing the long-wavelength deformations of scroll waves. AD - Laboratoire de Physique Statistique, Associe au CNRS et aux Universites Paris VI et VII, Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris Cedex 05, France. FAU - Henry, Herve AU - Henry H FAU - Hakim, Vincent AU - Hakim V LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 SB - IM MH - Animal MH - Arrhythmia/physiopathology MH - Computer Simulation MH - Heart/physiology MH - Human MH - *Nonlinear Dynamics EDAT- 2002/05/15 10:00 MHDA- 2002/09/12 10:01 PHST- 2001/Nov/20 [received] PHST- 2002/Apr/11 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Apr;65(4 Pt 2A):046235. 128: Volkov EI, et al. Multirhythmicity generated by...[PMID:12006001]Related Articles, Books, LinkOut UI - 22001863 PMID- 12006001 DA - 20020513 DCOM- 20020911 LR - 20021029 IS - 1539-3755 VI - 65 IP - 4 Pt 2A DP - 2002 Apr TI - Multirhythmicity generated by slow variable diffusion in a ring of relaxation oscillators and noise-induced abnormal interspike variability. PG - 046232 AB - The deterministic and noise-dependent dynamics of a ring of three Ohmically coupled electronic relaxation oscillators are considered by means of numerical simulations. Each isolated oscillator is described by a set of two ordinary differential equations with very different characteristic times. The emergence of the limit cycle via the Hopf bifurcation results from the N-shaped current-versus-voltage characteristic of the nonlinear resistor. The phase diagram is calculated for a ring of three such oscillators in the presence of small detuning. Special attention is focused on two parameter areas, one near a transition to the homogeneous and the other near the inhomogeneous stable steady state. Along with other nontrivial limit cycles, essentially asymmetrical limit cycles termed dynamic traps may arise in these two areas. A dynamic trap is a regime in which one or two oscillators do not perform full-amplitude oscillations and, correspondingly, do not generate spikes. The interspike interval (ISI) distribution in the presence of noise is calculated as a function of the coupling strength in both areas of the parameter plane. The distributions are extremely polymodal near the homogeneous steady state even if the in-phase limit cycle is dominating. The origins of this abnormal enhancement of ISI variability are discussed in detail. A similar analysis shows that nontrivial periodic attractors are observable in the vicinity of the inhomogeneous stable steady states only if the level of noise is relatively low. In this case, the dominance of the in-phase limit cycle basin results in an almost unimodal distribution of interspike intervals. AD - Department of Theoretical Physics, Lebedev Physical Institute, Leninskii 53, Moscow, Russia. FAU - Volkov, E I AU - Volkov EI FAU - Volkov, D V AU - Volkov DV LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 RN - 0 (Solutions) SB - IM MH - Action Potentials/*physiology MH - Biological Clocks MH - Electrophysiology/instrumentation/methods MH - *Models, Biological MH - *Models, Chemical MH - *Noise MH - Nonlinear Dynamics MH - Oscillometry/instrumentation/methods MH - Relaxation/*physiology MH - Solutions/chemistry MH - Support, Non-U.S. Gov't EDAT- 2002/05/15 10:00 MHDA- 2002/09/12 10:01 PHST- 2001/Apr/09 [received] PHST- 2002/Jan/22 [revised] PHST- 2002/Apr/10 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Apr;65(4 Pt 2A):046232. 129: So P, et al. Limits to the experimental de...[PMID:12005994]Related Articles, Books UI - 22001856 PMID- 12005994 DA - 20020513 DCOM- 20020911 LR - 20021029 IS - 1539-3755 VI - 65 IP - 4 Pt 2A DP - 2002 Apr TI - Limits to the experimental detection of nonlinear synchrony. PG - 046225 AB - Chaos synchronization is often characterized by the existence of a continuous function between the states of the components. However, in coupled systems without inherent symmetries, the synchronization set can be extremely complicated. We describe and illustrate three typical complications that can arise, and we discuss how existing methods for detecting synchronization will be hampered by the presence of these features. AD - Department of Physics and Astronomy and the Krasnow Institute for Advanced Study, George Mason University, Fairfax, Virginia 22030, USA. FAU - So, Paul AU - So P FAU - Barreto, Ernest AU - Barreto E FAU - Josic, Kresimir AU - Josic K FAU - Sander, Evelyn AU - Sander E FAU - Schiff, Steven J AU - Schiff SJ LA - eng ID - 1K25MH01963/MH/NIMH ID - 2R01MH50006/MH/NIMH ID - 7K0ZMH01493/MH/NIMH PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 SB - IM MH - *Models, Biological MH - *Nonlinear Dynamics MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/05/15 10:00 MHDA- 2002/09/12 10:01 PHST- 2001/Aug/06 [received] PHST- 2002/Jan/16 [revised] PHST- 2002/Apr/09 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Apr;65(4 Pt 2A):046225. 130: Andreyev YV, et al. Dynamic separation of chaotic...[PMID:12005989]Related Articles, Books UI - 22001851 PMID- 12005989 DA - 20020513 DCOM- 20020911 LR - 20021029 IS - 1539-3755 VI - 65 IP - 4 Pt 2A DP - 2002 Apr TI - Dynamic separation of chaotic signals in the presence of noise. PG - 046220 AB - The problem of separation of a noise-contaminated observed sum of chaotic signals into the individual components is considered. A noise threshold is found above which high-quality separation is impossible. Below the threshold, each signal is recovered with any prescribed accuracy with a separation method. The threshold effect is shown to be associated with the information content of chaotic signals and a theoretical estimate is given for the threshold. AD - Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Mokhovaya Street 11, GSP-3, Moscow 103907, Russia. chaos@mail.cplire.ru FAU - Andreyev, Yuri V AU - Andreyev YV FAU - Dmitriev, Alexander S AU - Dmitriev AS FAU - Efremova, Elena V AU - Efremova EV LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 SB - IM MH - *Models, Biological MH - *Models, Theoretical MH - *Nonlinear Dynamics MH - Oscillometry/methods MH - Signal Transduction/*physiology EDAT- 2002/05/15 10:00 MHDA- 2002/09/12 10:01 PHST- 2001/Oct/04 [received] PHST- 2002/Apr/05 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Apr;65(4 Pt 2A):046220. 131: Yulmetyev R, et al. Quantification of heart rate ...[PMID:12005926]Related Articles, Books UI - 22001788 PMID- 12005926 DA - 20020513 DCOM- 20020911 LR - 20021101 IS - 1539-3755 VI - 65 IP - 4 Pt 2A DP - 2002 Apr TI - Quantification of heart rate variability by discrete nonstationary non-Markov stochastic processes. PG - 046107 AB - We develop the statistical theory of discrete nonstationary non-Markov random processes in complex systems. The objective of this paper is to find the chain of finite-difference non-Markov kinetic equations for time correlation functions (TCF) in terms of nonstationary effects. The developed theory starts from careful analysis of time correlation through nonstationary dynamics of vectors of initial and final states and nonstationary normalized TCF. Using the projection operators technique we find the chain of finite-difference non-Markov kinetic equations for discrete nonstationary TCF and for the set of nonstationary discrete memory functions (MF's). The last one contains supplementary information about nonstationary properties of the complex system on the whole. Another relevant result of our theory is the construction of the set of dynamic parameters of nonstationarity, which contains some information of the nonstationarity effects. The full set of dynamic, spectral and kinetic parameters, and kinetic functions (TCF, short MF's statistical spectra of non-Markovity parameter, and statistical spectra of nonstationarity parameter) has made it possible to acquire the in-depth information about discreteness, non-Markov effects, long-range memory, and nonstationarity of the underlying processes. The developed theory is applied to analyze the long-time (Holter) series of RR intervals of human ECG's. We had two groups of patients: the healthy ones and the patients after myocardial infarction. In both groups we observed effects of fractality, standard and restricted self-organized criticality, and also a certain specific arrangement of spectral lines. The received results demonstrate that the power spectra of all orders (n=1,2, ...) MF m(n)(t) exhibit the neatly expressed fractal features. We have found out that the full sets of non-Markov, discrete and nonstationary parameters can serve as reliable and powerful means of diagnosis of the cardiovascular system states and can be used to distinguish healthy data from pathologic data. AD - Department of Theoretical Physics, Kazan State Pedagogical University, Mezhlauk Street, 1, 420021 Kazan, Russia. rmy@dtp.ksu.ras.ru FAU - Yulmetyev, Renat AU - Yulmetyev R FAU - Hanggi, Peter AU - Hanggi P FAU - Gafarov, Fail AU - Gafarov F LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 SB - IM MH - Adolescent MH - Adult MH - Aged MH - Cardiovascular System/pathology/physiopathology MH - Databases MH - Diagnosis, Computer-Assisted MH - Electrocardiography/statistics & numerical data MH - Fractals MH - Heart Failure, Congestive/diagnosis MH - Heart Rate/*physiology MH - Human MH - Kinetics MH - *Markov Chains MH - Memory MH - Middle Age MH - Myocardial Infarction/diagnosis MH - *Nonlinear Dynamics MH - Software/statistics & numerical data MH - Time Factors EDAT- 2002/05/15 10:00 MHDA- 2002/09/12 10:01 PHST- 2001/Mar/30 [received] PHST- 2001/Sep/26 [revised] PHST- 2002/Mar/25 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Apr;65(4 Pt 2A):046107. 132: Robinson PA, et al. Dynamics of large-scale brain...[PMID:12005890]Related Articles, Books, LinkOut UI - 22001752 PMID- 12005890 DA - 20020513 DCOM- 20021108 IS - 1539-3755 VI - 65 IP - 4 Pt 1 DP - 2002 Apr TI - Dynamics of large-scale brain activity in normal arousal states and epileptic seizures. PG - 041924 AB - Links between electroencephalograms (EEGs) and underlying aspects of neurophysiology and anatomy are poorly understood. Here a nonlinear continuum model of large-scale brain electrical activity is used to analyze arousal states and their stability and nonlinear dynamics for physiologically realistic parameters. A simple ordered arousal sequence in a reduced parameter space is inferred and found to be consistent with experimentally determined parameters of waking states. Instabilities arise at spectral peaks of the major clinically observed EEG rhythms-mainly slow wave, delta, theta, alpha, and sleep spindle-with each instability zone lying near its most common experimental precursor arousal states in the reduced space. Theta, alpha, and spindle instabilities evolve toward low-dimensional nonlinear limit cycles that correspond closely to EEGs of petit mal seizures for theta instability, and grand mal seizures for the other types. Nonlinear stimulus-induced entrainment and seizures are also seen, EEG spectra and potentials evoked by stimuli are reproduced, and numerous other points of experimental agreement are found. Inverse modeling enables physiological parameters underlying observed EEGs to be determined by a new, noninvasive route. This model thus provides a single, powerful framework for quantitative understanding of a wide variety of brain phenomena. AD - Theoretical Physics Group and Center for Wave Physics, School of Physics, University of Sydney, New South Wales 2006, Australia. FAU - Robinson, P A AU - Robinson PA FAU - Rennie, C J AU - Rennie CJ FAU - Rowe, D L AU - Rowe DL LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 SB - IM MH - Adult MH - Arousal/*physiology MH - Brain/metabolism/*physiology/*physiopathology MH - Cerebral Cortex/physiology/physiopathology MH - Electroencephalography MH - Epilepsy/*physiopathology MH - Epilepsy, Absence/physiopathology MH - Epilepsy, Tonic-Clonic/physiopathology MH - Evoked Potentials/physiology MH - Human MH - Models, Neurological MH - Nonlinear Dynamics MH - Thalamus/physiology/physiopathology EDAT- 2002/05/15 10:00 MHDA- 2002/11/26 04:00 PHST- 2001/Oct/03 [received] PHST- 2002/Apr/11 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Apr;65(4 Pt 1):041924. 133: Rulkov NF. Modeling of spiking-bursting ...[PMID:12005888]Related Articles, Books UI - 22001750 PMID- 12005888 DA - 20020513 DCOM- 20021108 IS - 1539-3755 VI - 65 IP - 4 Pt 1 DP - 2002 Apr TI - Modeling of spiking-bursting neural behavior using two-dimensional map. PG - 041922 AB - A simple model that replicates the dynamics of spiking and spiking-bursting activity of real biological neurons is proposed. The model is a two-dimensional map that contains one fast and one slow variable. The mechanisms behind generation of spikes, bursts of spikes, and restructuring of the map behavior are explained using phase portrait analysis. The dynamics of two coupled maps that model the behavior of two electrically coupled neurons is discussed. Synchronization regimes for spiking and bursting activities of these maps are studied as a function of coupling strength. It is demonstrated that the results of this model are in agreement with the synchronization of chaotic spiking-bursting behavior experimentally found in real biological neurons. AD - Institute for Nonlinear Science, University of California, San Diego, La Jolla, California 92093-0402, USA. FAU - Rulkov, Nikolai F AU - Rulkov NF LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 SB - IM MH - Action Potentials/*physiology MH - Electric Stimulation/methods MH - *Models, Neurological MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Oscillometry MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Synaptic Transmission/physiology EDAT- 2002/05/15 10:00 MHDA- 2002/11/26 04:00 PHST- 2001/Oct/05 [received] PHST- 2002/Apr/10 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Apr;65(4 Pt 1):041922. 134: Del Prete V, et al. Replica symmetric evaluation ...[PMID:12005884]Related Articles, Books UI - 22001746 PMID- 12005884 DA - 20020513 DCOM- 20021108 IS - 1539-3755 VI - 65 IP - 4 Pt 1 DP - 2002 Apr TI - Replica symmetric evaluation of the information transfer in a two-layer network in the presence of continuous and discrete stimuli. PG - 041918 AB - In a previous paper we have evaluated analytically the mutual information between the firing rates of N independent units and a set of multidimensional continuous and discrete stimuli, for a finite population size and in the limit of large noise. Here, we extend the analysis to the case of two interconnected populations, where input units activate output ones via Gaussian weights and a threshold linear transfer function. We evaluate the information carried by a population of M output units, again about continuous and discrete correlates. The mutual information is evaluated solving saddle-point equations under the assumption of replica symmetry, a method that, by taking into account only the term linear in N of the input information, is equivalent to assuming the noise to be large. Within this limitation, we analyze the dependence of the information on the ratio M/N, on the selectivity of the input units and on the level of the output noise. We show analytically, and confirm numerically, that in the limit of a linear transfer function and of a small ratio between output and input noise, the output information approaches asymptotically the information carried in input. Finally, we show that the information loss in output does not depend much on the structure of the stimulus, whether purely continuous, purely discrete or mixed, but only on the position of the threshold nonlinearity, and on the ratio between input and output noise. AD - SISSA, Programme in Neuroscience, via Beirut 4, 34014 Trieste, Italy. FAU - Del Prete, Valeria AU - Del Prete V FAU - Treves, Alessandro AU - Treves A LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 SB - IM MH - Action Potentials/*physiology MH - Computer Simulation MH - Information Theory MH - Models, Neurological MH - Nerve Net/*physiology MH - Neural Pathways/physiology MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2002/05/15 10:00 MHDA- 2002/11/26 04:00 PHST- 2001/Jul/29 [received] PHST- 2001/Dec/14 [revised] PHST- 2002/Apr/04 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Apr;65(4 Pt 1):041918. 135: Hassan SA, et al. Morphological ordering in bio...[PMID:12005880]Related Articles, Books UI - 22001742 PMID- 12005880 DA - 20020513 DCOM- 20021108 IS - 1539-3755 VI - 65 IP - 4 Pt 1 DP - 2002 Apr TI - Morphological ordering in biopolymers: informational statistical thermodynamic approach. PG - 041914 AB - We consider the question of the emergence of morphological ordering in an open far-from-equilibrium model of a biopolymer. We apply informational statistical thermodynamics, which was shown to be appropriate to deal with dissipative systems displaying complex behavior. The formation of nonlinear spatial ordering consisting in the emergence of static charge-density waves, producing a bioelectret-type state, is evidenced. This kind of behavior may arise in biopolymers under the influence of biochemical processes. AD - Department of Physiology and Biophysics, Mount Sinai School of Medicine, New York, New York 10029-6574, USA. FAU - Hassan, Sergio A AU - Hassan SA FAU - Mesquita, Marcus V AU - Mesquita MV FAU - Vasconcellos, Aurea R AU - Vasconcellos AR FAU - Luzzi, Roberto AU - Luzzi R LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 RN - 0 (Biopolymers) SB - IM MH - Biopolymers/*chemistry MH - Computational Biology/*statistics & numerical data MH - Information Theory MH - Models, Statistical MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - *Thermodynamics EDAT- 2002/05/15 10:00 MHDA- 2002/11/26 04:00 PHST- 1999/Dec/15 [received] PHST- 2001/Oct/29 [revised] PHST- 2002/Apr/03 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Apr;65(4 Pt 1):041914. 136: Quian Quiroga R, et al. Performance of different sync...[PMID:12005869]Related Articles, Books UI - 22001731 PMID- 12005869 DA - 20020513 DCOM- 20021108 IS - 1539-3755 VI - 65 IP - 4 Pt 1 DP - 2002 Apr TI - Performance of different synchronization measures in real data: a case study on electroencephalographic signals. PG - 041903 AB - We study the synchronization between left and right hemisphere rat electroencephalographic (EEG) channels by using various synchronization measures, namely nonlinear interdependences, phase synchronizations, mutual information, cross correlation, and the coherence function. In passing we show a close relation between two recently proposed phase synchronization measures and we extend the definition of one of them. In three typical examples we observe that except mutual information, all these measures give a useful quantification that is hard to be guessed beforehand from the raw data. Despite their differences, results are qualitatively the same. Therefore, we claim that the applied measures are valuable for the study of synchronization in real data. Moreover, in the particular case of EEG signals their use as complementary variables could be of clinical relevance. AD - John von Neumann Institute for Computing, Forschungszentrum Julich GmbH, D-52425 Julich, Germany. rodri@vis.caltech.edu FAU - Quian Quiroga, R AU - Quian Quiroga R FAU - Kraskov, A AU - Kraskov A FAU - Kreuz, T AU - Kreuz T FAU - Grassberger, P AU - Grassberger P LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 RN - 2552-55-8 (Ibotenic Acid) SB - IM MH - Animal MH - Brain Injuries/chemically induced/physiopathology MH - Comparative Study MH - Cortical Synchronization/drug effects/*methods/statistics & numerical data MH - Disease Models, Animal MH - Epilepsy, Absence/genetics MH - Human MH - Ibotenic Acid/toxicity MH - Male MH - Nonlinear Dynamics MH - Rats MH - Rats, Inbred Strains MH - Support, U.S. Gov't, Non-P.H.S. MH - Thalamic Nuclei/drug effects/injuries MH - Time Factors EDAT- 2002/05/15 10:00 MHDA- 2002/11/26 04:00 PHST- 2001/Sep/18 [received] PHST- 2002/Mar/15 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Apr;65(4 Pt 1):041903. 137: Frisch T, et al. Unwinding globules under tens...[PMID:12005860]Related Articles, Books UI - 22001722 PMID- 12005860 DA - 20020513 DCOM- 20021108 IS - 1539-3755 VI - 65 IP - 4 Pt 1 DP - 2002 Apr TI - Unwinding globules under tension and polymer collapse. PG - 041801 AB - Polymer collapse is known to be mediated by the formation of pearls. These intermediate structures behave as small globules under tension. The globule size is studied by molecular dynamic simulations as a function of the strength of an external stretching force applied to its ends, for different values of the chain length. A very strong first-order-like transition from a compact globule state to a stretched one is observed. A model of this transition in terms of a globule-chain system is presented. The critical force, above which the globule unwinds, is shown to satisfy a power law scaling like N(1/3) in the number of monomers. AD - Institut de Recherche sur les Phenomenes Hors Equilibre, 49, rue F. Joliot-Curie, Boite Postale 146, 13384 Marseille, France. frisch@irphe.univ-mrs.fr FAU - Frisch, Thomas AU - Frisch T FAU - Verga, Alberto AU - Verga A LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 RN - 0 (Polymers) RN - 0 (Proteins) SB - IM MH - Models, Chemical MH - Nonlinear Dynamics MH - Polymers/*chemistry MH - Protein Conformation MH - Protein Folding MH - Proteins/chemistry EDAT- 2002/05/15 10:00 MHDA- 2002/11/26 04:00 PHST- 2001/Jul/16 [received] PHST- 2002/Apr/02 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Apr;65(4 Pt 1):041801. 138: Chen Z, et al. Effect of nonstationarities o...[PMID:12005806]Related Articles, Books UI - 22001668 PMID- 12005806 DA - 20020513 DCOM- 20021108 IS - 1539-3755 VI - 65 IP - 4 Pt 1 DP - 2002 Apr TI - Effect of nonstationarities on detrended fluctuation analysis. PG - 041107 AB - Detrended fluctuation analysis (DFA) is a scaling analysis method used to quantify long-range power-law correlations in signals. Many physical and biological signals are "noisy," heterogeneous, and exhibit different types of nonstationarities, which can affect the correlation properties of these signals. We systematically study the effects of three types of nonstationarities often encountered in real data. Specifically, we consider nonstationary sequences formed in three ways: (i) stitching together segments of data obtained from discontinuous experimental recordings, or removing some noisy and unreliable parts from continuous recordings and stitching together the remaining parts-a "cutting" procedure commonly used in preparing data prior to signal analysis; (ii) adding to a signal with known correlations a tunable concentration of random outliers or spikes with different amplitudes; and (iii) generating a signal comprised of segments with different properties-e.g., different standard deviations or different correlation exponents. We compare the difference between the scaling results obtained for stationary correlated signals and correlated signals with these three types of nonstationarities. We find that introducing nonstationarities to stationary correlated signals leads to the appearance of crossovers in the scaling behavior and we study how the characteristics of these crossovers depend on (a) the fraction and size of the parts cut out from the signal, (b) the concentration of spikes and their amplitudes (c) the proportion between segments with different standard deviations or different correlations and (d) the correlation properties of the stationary signal. We show how to develop strategies for preprocessing "raw" data prior to analysis, which will minimize the effects of nonstationarities on the scaling properties of the data, and how to interpret the results of DFA for complex signals with different local characteristics. AD - Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215, USA. FAU - Chen, Zhi AU - Chen Z FAU - Ivanov, Plamen Ch AU - Ivanov PCh FAU - Hu, Kun AU - Hu K FAU - Stanley, H Eugene AU - Stanley HE LA - eng ID - P41RR13622/RR/NCRR PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 SB - IM MH - Comparative Study MH - Computer Simulation MH - *Fourier Analysis MH - Noise MH - *Nonlinear Dynamics MH - Physics/methods MH - *Signal Processing, Computer-Assisted MH - Signal Transduction MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/05/15 10:00 MHDA- 2002/11/26 04:00 PHST- 2001/Nov/12 [received] PHST- 2002/Apr/08 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Apr;65(4 Pt 1):041107. 139: Trombettoni A, et al. Superfluidity versus disorder...[PMID:12005755]Related Articles, Books, LinkOut UI - 22001971 PMID- 12005755 DA - 20020513 DCOM- 20020709 IS - 0031-9007 VI - 88 IP - 17 DP - 2002 Apr 29 TI - Superfluidity versus disorder in the discrete nonlinear Schrodinger equation. PG - 173902 AB - We study the discrete nonlinear Schrodinger equation (DNLS) in an annular geometry with on-site defects. The dynamics of a traveling plane-wave maps onto an effective nonrigid pendulum Hamiltonian. The different regimes include the complete reflection and refocusing of the initial wave, solitonic structures, and a superfluid state. In the superfluid regime, which occurs above a critical value of nonlinearity, a plane wave travels coherently through the randomly distributed defects. This superfluidity criterion for the DNLS is analogous to (yet very different from) the Landau superfluidity criteria in translationally invariant systems. Experimental implications for the physics of Bose-Einstein condensate gases trapped in optical potentials and of arrays of optical fibers are discussed. AD - Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA. FAU - Trombettoni, A AU - Trombettoni A FAU - Smerzi, A AU - Smerzi A FAU - Bishop, A R AU - Bishop AR LA - eng PT - Journal Article CY - United States TA - Phys Rev Lett JID - 0401141 SB - IM MH - Mathematical Computing MH - Models, Biological MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/05/15 10:00 MHDA- 2002/07/10 10:01 PHST- 2001/Sep/04 [received] PHST- 2002/Apr/15 [aheadofprint] PST - ppublish SO - Phys Rev Lett 2002 Apr 29;88(17):173902. 140: Cohen S, et al. Technology for dental educati...[PMID:12004719]Related Articles, Books, LinkOut UI - 22000620 PMID- 12004719 DA - 20020513 DCOM- 20020612 IS - 0363-6771 VI - 49 IP - 3 DP - 2001 May-Jun TI - Technology for dental education: new models, new paradigms, and new opportunities. PG - 236-7 FAU - Cohen, S AU - Cohen S FAU - Abbey, L M AU - Abbey LM LA - eng PT - Editorial CY - United States TA - Gen Dent JID - 7610466 SB - D MH - Clinical Competence MH - Cognition MH - Computer Communication Networks MH - Computer-Assisted Instruction MH - *Education, Dental MH - *Educational Technology MH - Human MH - Learning MH - Models, Educational MH - Multimedia MH - Nonlinear Dynamics MH - Problem Solving MH - Science/education MH - Teaching/methods MH - Thinking EDAT- 2002/05/15 10:00 MHDA- 2002/06/13 10:01 PST - ppublish SO - Gen Dent 2001 May-Jun;49(3):236-7. 141: Melnick M, et al. Mouse submandibular gland mor...[PMID:12002815]Related Articles, Cited in PMC, Books, LinkOut UI - 21997492 PMID- 12002815 DA - 20020510 DCOM- 20020530 LR - 20021101 IS - 1045-4411 VI - 11 IP - 2 DP - 2000 TI - Mouse submandibular gland morphogenesis: a paradigm for embryonic signal processing. PG - 199-215 AB - Signal processing is the sine qua non of embryogenesis. At its core, any single signal transduction pathway may be understood as classic Information Theory, adapted as an open system such that, because of networking, the "receiver" is presented with more information than was initially signaled by the "source". Over 40 years ago, Waddington presented his "Epigenetic Landscape" as a metaphor for the hierarchical nature of embryogenesis. Mathematically, Waddington's landscape may be modeled as a neural net. The "black box" of the neural net is an interacting network of signal transduction pathways (using hormones, growth factors, cytokines, neurotransmitters, and others) which inform the Boolean logic gates. An emerging theme in developmental biology is that defined sets of epigenetic circuits are used in multiple places, at multiple times, for similar and sometimes different purposes during organogenesis. As we show here, submandibular gland embryonic and fetal development is a splendid paradigm of these epigenetic circuits and their phenotypic outcomes, such as branching and lumen formation. AD - Laboratory for Developmental Genetics, University of Southern California, Los Angeles 90089-0641, USA. mmelnick@hsc.usc.edu FAU - Melnick, M AU - Melnick M FAU - Jaskoll, T AU - Jaskoll T LA - eng ID - DE 11942/DE/NIDCR PT - Journal Article PT - Review PT - Review, Tutorial CY - United States TA - Crit Rev Oral Biol Med JID - 9009999 RN - 0 (Cytokines) RN - 0 (Glucocorticoids) RN - 0 (Growth Substances) RN - 0 (Mucins) SB - D SB - IM MH - Animal MH - Apoptosis MH - Cell Division MH - Computer Simulation MH - Cybernetics MH - Cytokines/physiology MH - Embryo and Fetal Development/physiology MH - Epithelium/embryology MH - Gene Expression Regulation, Developmental MH - Glucocorticoids/physiology MH - Growth Substances/physiology MH - Mesoderm/cytology MH - Mice MH - Models, Biological MH - Morphogenesis/physiology MH - Mucins/genetics MH - Neural Networks (Computer) MH - Nonlinear Dynamics MH - Signal Transduction/*physiology MH - Software MH - Submandibular Gland/*embryology MH - Support, U.S. Gov't, P.H.S. RF - 79 EDAT- 2002/05/11 10:00 MHDA- 2002/05/31 10:01 PST - ppublish SO - Crit Rev Oral Biol Med 2000;11(2):199-215. 142: Doze P, et al. Quantification of beta-adreno...[PMID:12002702]Related Articles, Books, LinkOut UI - 21997378 PMID- 12002702 DA - 20020510 DCOM- 20021113 IS - 1619-7070 VI - 29 IP - 3 DP - 2002 Mar TI - Quantification of beta-adrenoceptor density in the human heart with (S)-[11C]CGP 12388 and a tracer kinetic model. PG - 295-304 AB - The aim of this study was to determine whether the beta-adrenoceptor receptor density (Bmax) and the ligand affinity (KD) of (S)-[11C]CGP 12388 for the beta-adrenoceptor receptor could be determined using full tracer kinetic modelling of the transport of the ligand and its interaction with the receptor. This approach minimises the a priori assumptions and may thus serve as a gold standard to validate other simplified methods. Dynamic positron emission tomography (PET) data were acquired in six healthy subjects during 60 min. Three different injection protocols were applied, each consisting of three injections with varying SAs: high specific activity (SA), low SA or unlabelled ligand only. Arterial blood samples were collected via a cannula in the radial artery. Time-activity data in myocardial tissue were obtained using regions of interest (ROIs) on short-axis planes. All data were analysed with a two-tissue compartment, six-parameter (K1, k2, k(on), k(off), Bmax, F(bv)) model that relies on explicit compartments for describing the kinetics of both labelled and unlabelled radioligand. Time-activity curves showed that unlabelled ligand could displace the radioligand from the receptor. This resulted in increased radioactivity levels in plasma. Modelling results yielded Bmax values of 9.74+/-1.80 nM and a KD of 0.58+/-0.22 nM, assuming a reaction volume of 0.15. In addition, parametric polar images of Bmax could be calculated. The protocol with injections of high SA, low SA, and unlabelled ligand, respectively, was found to be the most sensitive to parameter changes. We conclude that with tracer kinetic modelling of (S)-[11C]CGP 12388, the beta-adrenoceptor density in the human heart can accurately be obtained in vivo. This approach may thus serve as a gold standard. AD - PET Center, Groningen University Hospital, The Netherlands. FAU - Doze, Petra AU - Doze P FAU - Elsinga, Philip H AU - Elsinga PH FAU - van Waarde, Aren AU - van Waarde A FAU - Pieterman, Remge M AU - Pieterman RM FAU - Pruim, Jan AU - Pruim J FAU - Vaalburg, Willem AU - Vaalburg W FAU - Willemsen, Antoon T M AU - Willemsen AT LA - eng PT - Clinical Trial PT - Journal Article CY - Germany TA - Eur J Nucl Med Mol Imaging JID - 101140988 RN - 0 (Benzimidazoles) RN - 0 (Carbon Radioisotopes) RN - 0 (Receptors, Adrenergic, beta) RN - 108929-47-1 (CGP 12388) SB - IM MH - Adult MH - Benzimidazoles/*blood/diagnostic use MH - Carbon Radioisotopes/*blood/diagnostic use MH - Comparative Study MH - Computer Simulation MH - Female MH - Heart Ventricle/*radionuclide imaging MH - Human MH - Male MH - Middle Age MH - *Models, Cardiovascular MH - Myocardium/*metabolism MH - Nonlinear Dynamics MH - Receptors, Adrenergic, beta/*analysis/metabolism MH - Reference Values MH - Reproducibility of Results MH - Sensitivity and Specificity MH - Support, Non-U.S. Gov't MH - Tomography, Emission-Computed EDAT- 2002/05/11 10:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - Eur J Nucl Med Mol Imaging 2002 Mar;29(3):295-304. 143: Werner J, et al. Simulation and prediction of ...[PMID:12002174]Related Articles, Books, LinkOut UI - 21996843 PMID- 12002174 DA - 20020510 DCOM- 20020604 IS - 0018-9294 VI - 49 IP - 5 DP - 2002 May TI - Simulation and prediction of cardiotherapeutical phenomena from a pulsatile model coupled to the Guyton circulatory model. PG - 430-9 AB - In order to use simulation prediction for cardiotherapeutical purposes, the well-documented and physiologically validated circulatory Guyton model was coupled to a cardiac pulsatile model which comprises the hemodynamics of the four chambers including valvular effects, as well as the Hill, Frank-Starling, Laplace, and autonomic nervous system (ANS) effects. The program is written in the "C" language and available for everybody. The program system was submitted to validation and plausibility tests both as to the steady-state and the dynamic properties. Pressures, volumes and flows and other variables turned out to be compatible with published experimental and clinical recordings both under physiological and pathophysiological conditions. The results from the application to cardiac electrotherapy emphasize the importance of atrial contraction to ventricular filling, the adequate atrio-ventricular delay, the effect of impaired ventricular relaxation, and the significance of the choice of the adequate cardiac pacemaker, both with respect to the stimulation site and the adequate sensor controlling pacing rate. The simulation will be further developed, tested and applied for cardiological purposes. AD - Department of Biomedical Engineering of the Medical Faculty, Ruhr-University, Bochum, Germany. werner@biomed.ruhr-uni-bochum.de FAU - Werner, Jurgen AU - Werner J FAU - Bohringer, Daniel AU - Bohringer D FAU - Hexamer, Martin AU - Hexamer M LA - eng PT - Journal Article CY - United States TA - IEEE Trans Biomed Eng JID - 0012737 SB - IM MH - Blood Circulation/*physiology MH - Comparative Study MH - *Computer Simulation MH - Electric Stimulation Therapy MH - Human MH - *Models, Cardiovascular MH - Nonlinear Dynamics MH - Pulsatile Flow/*physiology MH - Reproducibility of Results MH - Support, Non-U.S. Gov't EDAT- 2002/05/11 10:00 MHDA- 2002/06/05 10:01 PST - ppublish SO - IEEE Trans Biomed Eng 2002 May;49(5):430-9. 144: Dalla Man C, et al. The oral glucose minimal mode...[PMID:12002173]Related Articles, Books, LinkOut UI - 21996842 PMID- 12002173 DA - 20020510 DCOM- 20020604 IS - 0018-9294 VI - 49 IP - 5 DP - 2002 May TI - The oral glucose minimal model: estimation of insulin sensitivity from a meal test. PG - 419-29 AB - Recently, a new approach has been proposed to estimate insulin sensitivity (S(I)) from an oral glucose tolerance test or a meal using an "integral equation". Here, we improve on the "integral equation" by resorting to a "differential equation" approach. The classic glucose kinetics minimal model was used with the addition of a parametric model for the rate of appearance into plasma of oral glucose (Ra). Three behavioral models of Ra were proposed: piecewise-linear (P), spline (S) and dynamic (D). All three models performed satisfactorily allowing a precise estimation of S(I) and a plausible reconstruction of Ra. Mean S(I) estimates were virtually identical: S(I)P = 6.81 +/- 0.87 (SE); S(I)S = 6.53 +/- 0.80; and S(I)D = 6.62 +/- 0.79. S(I) strongly correlated with the integral-equation index (I) S(I)I: r = 0.99, p < 0.01 for models D and S, and r 0.97, p < 0.01 for P. Also, SI compared well with insulin sensitivity estimated from intravenous glucose tolerance test in the same subjects (r = 0.75, p < 0.01; r = 0.71, p < 0.01; r = 0.73, p < 0.01, respectively, for P, S, and D models versus s(I)IVGTT). Finally, the novel approach allows estimation of SI from a shorter test (120 min): model P yielded S(I)R = 7.16 +/- 1.0 (R for reduced) which correlated very well with S(I)P and S(I)I (respectively, r = 0.94, p < 0.01; r = 0.95, p < 0.01) and still satisfactorily with S(I)IVGTT (r = 0.77, p < 0.01). AD - Department of Electronics and Informatics, University of Padova, Italy. FAU - Dalla Man, Chiara AU - Dalla Man C FAU - Caumo, Andrea AU - Caumo A FAU - Cobelli, Claudio AU - Cobelli C LA - eng ID - RR-00585/RR/NCRR ID - RR-12609/RR/NCRR PT - Journal Article CY - United States TA - IEEE Trans Biomed Eng JID - 0012737 RN - 0 (Blood Glucose) RN - 11061-68-0 (Insulin) SB - IM MH - Blood Glucose/drug effects/*metabolism MH - Comparative Study MH - Computer Simulation MH - Female MH - Glucose Tolerance Test/*methods MH - Human MH - Insulin/metabolism/*pharmacology MH - Male MH - Middle Age MH - *Models, Biological MH - Nonlinear Dynamics MH - Reproducibility of Results MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/05/11 10:00 MHDA- 2002/06/05 10:01 PST - ppublish SO - IEEE Trans Biomed Eng 2002 May;49(5):419-29. 145: Prange MT, et al. Regional, directional, and ag...[PMID:12002135]Related Articles, Books, LinkOut UI - 21996804 PMID- 12002135 DA - 20020510 DCOM- 20021115 IS - 0148-0731 VI - 124 IP - 2 DP - 2002 Apr TI - Regional, directional, and age-dependent properties of the brain undergoing large deformation. PG - 244-52 AB - The large strain mechanical properties of adult porcine gray and white matter brain tissues were measured in shear and confirmed in compression. Consistent with local neuroarchitecture, gray matter showed the least amount of anisotropy, and corpus callosum exhibited the greatest degree of anisotropy. Mean regional properties were significantly distinct, demonstrating that brain tissue is inhomogeneous. Fresh adult human brain tissue properties were slightly stiffer than adult porcine properties but considerably less stiff than the human autopsy data in the literature. Mixed porcine gray/white matter samples were obtained from animals at "infant" and "toddler" stages of neurological development, and shear properties compared to those in the adult. Only the infant properties were significantly different (stiffer) from the adult. AD - Department of Bioengineering, University of Pennsylvania, Philadelphia 19104-6392, USA. mprange@exponent.com FAU - Prange, Michael T AU - Prange MT FAU - Margulies, Susan S AU - Margulies SS LA - eng ID - R49/CCR-312712/CC/CDC PT - Journal Article PT - Validation Studies CY - United States TA - J Biomech Eng JID - 7909584 SB - IM MH - Aging/*physiology MH - Animal MH - Anisotropy MH - Comparative Study MH - Compressive Strength MH - *Computer Simulation MH - Corpus Callosum/anatomy & histology/physiology MH - Elasticity MH - In Vitro MH - Internal Capsule/anatomy & histology/physiology MH - *Models, Neurological MH - Nonlinear Dynamics MH - Prosencephalon/anatomy & histology/*physiology MH - Reference Values MH - Regression Analysis MH - Reproducibility of Results MH - Sensitivity and Specificity MH - Stress, Mechanical MH - Support, U.S. Gov't, P.H.S. MH - Swine MH - Thalamus/anatomy & histology/physiology EDAT- 2002/05/11 10:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - J Biomech Eng 2002 Apr;124(2):244-52. 146: Travis BR, et al. An analysis of turbulent shea...[PMID:12002124]Related Articles, Books, LinkOut UI - 21996793 PMID- 12002124 DA - 20020510 DCOM- 20021115 IS - 0148-0731 VI - 124 IP - 2 DP - 2002 Apr TI - An analysis of turbulent shear stresses in leakage flow through a bileaflet mechanical prostheses. PG - 155-65 AB - In this work, estimates of turbulence were made from pulsatile flow laser Doppler velocimetry measurements using traditional phase averaging and averaging after the removal of cyclic variation. These estimates were compared with estimates obtained from steady leakage flow LDV measurements and an analytical method. The results of these studies indicate that leakage jets which are free and planar in shape may be more unstable than other leakage jets, and that cyclic variation does not cause a gross overestimation of the Reynolds stresses at large distances from the leakage jet orifice. AD - School of Chemical Engineering, Georgia Institute of Technology and Emory University, Atlanta 30332, USA. FAU - Travis, Brandon R AU - Travis BR FAU - Leo, Hwa L AU - Leo HL FAU - Shah, Parina A AU - Shah PA FAU - Frakes, David H AU - Frakes DH FAU - Yoganathan, Ajit P AU - Yoganathan AP LA - eng PT - Journal Article CY - United States TA - J Biomech Eng JID - 7909584 SB - IM MH - Blood Flow Velocity MH - Elasticity MH - Equipment Failure Analysis/*methods MH - *Heart Valve Prosthesis MH - *Hemodynamics MH - Laser-Doppler Flowmetry MH - *Models, Cardiovascular MH - Nonlinear Dynamics MH - Periodicity MH - Pulsatile Flow MH - Stress, Mechanical MH - Support, Non-U.S. Gov't MH - Vascular Capacitance MH - Vascular Resistance EDAT- 2002/05/11 10:00 MHDA- 2002/11/26 04:00 PST - ppublish SO - J Biomech Eng 2002 Apr;124(2):155-65. 147: Mager DE, et al. General pharmacokinetic model...[PMID:11999290]Related Articles, Books, LinkOut UI - 21993933 PMID- 11999290 DA - 20020509 DCOM- 20020528 IS - 1567-567X VI - 28 IP - 6 DP - 2001 Dec TI - General pharmacokinetic model for drugs exhibiting target-mediated drug disposition. PG - 507-32 AB - Drugs that bind with high affinity and to a significant extent (relative to dose) to a pharmacologic target such as an enzyme, receptor, or transporter may exhibit nonlinear pharmacokinetic (PK) behavior. Processes such as receptor-mediated endocytosis may result in drug elimination. A general PK model for characterizing such behavior is described and explored through computer simulations and applications to several therapeutic agents. Simulations show that model predicted plasma concentration vs. time profiles are expected to be polyexponential with steeper distribution phases for lower doses and similar terminal disposition phases. Noncompartmental parameters always show apparent Vss and CL(D) decreasing with dose, but apparent clearance decreases only when the binding process produces drug elimination. The proposed model well captured the time-course of drug concentrations for the aldose reductase inhibitor imirestat, the endothelin receptor antagonist bosentan, and recombinant human interferon-beta 1a. This type of model has a mechanistic basis and considerable utility for fully describing the kinetics for various doses of relevant drugs. AD - Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, State University of New York, 14260, USA. FAU - Mager, D E AU - Mager DE FAU - Jusko, W J AU - Jusko WJ LA - eng ID - GM57980/GM/NIGMS PT - Journal Article CY - England TA - J Pharmacokinet Pharmacodyn JID - 101096520 RN - 0 (Fluorenes) RN - 0 (Hydantoins) RN - 0 (Sulfonamides) RN - 147536-97-8 (bosentan) RN - 77238-31-4 (Interferon-beta) RN - 89391-50-4 (imirestat) SB - IM MH - Dose-Response Relationship, Drug MH - Drug Delivery Systems/methods/*statistics & numerical data MH - Drug Evaluation, Preclinical/methods/statistics & numerical data MH - Fluorenes/blood/pharmacokinetics MH - Human MH - Hydantoins/blood/pharmacokinetics MH - Interferon-beta/blood/pharmacokinetics MH - Male MH - *Models, Chemical MH - Nonlinear Dynamics MH - *Pharmacokinetics MH - Sulfonamides/blood/pharmacokinetics MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/05/10 10:00 MHDA- 2002/05/29 10:01 PST - ppublish SO - J Pharmacokinet Pharmacodyn 2001 Dec;28(6):507-32. 148: Wu JZ, et al. Simulation of mechanical resp...[PMID:11996844]Related Articles, Books, LinkOut UI - 21993107 PMID- 11996844 DA - 20020508 DCOM- 20021106 IS - 1350-4533 VI - 24 IP - 4 DP - 2002 May TI - Simulation of mechanical responses of fingertip to dynamic loading. PG - 253-64 AB - Extended exposure to mechanical vibration has been related to many vascular, sensorineural and musculoskeletal disorders of the hand-arm system, frequently termed 'hand-arm vibration syndrome' (HAVS). A two-dimensional, nonlinear finite element model of a fingertip is developed to study the stress and strain fields of the soft tissue under dynamic loading, that may be encountered while grasping and operating a hand-held power tool. The model incorporates the most essential anatomical elements of a fingertip, such as soft tissue, bone, and nail. The finger is assumed to be in contact with a steel plate, simulating the interaction between the fingertip and a vibrating machine tool or handle. The soft tissue is assumed to be nonlinearly visco-elastic, while the nail, bone, and steel plate are considered to be linearly elastic. In order to study the time-dependent deformation behavior of the fingertip, the numerical simulations were performed under ramp-like loading with different ramping periods and sinusoidal vibrations of the contacting plate at three different frequencies (1, 10, and 31.5 Hz). Owing to relatively large deformations of the soft tissue under specified static and dynamic loading, Lagrangian large deformation theory was applied in the present analysis. The effects of the loading rate and the frequency of the sinusoidal vibration on the time-dependent strain/stress distributions in the different depth within the soft tissue of the fingertip are investigated numerically. Our simulations suggest that the soft tissue of the fingertip experiences high local stress and strain under dynamic loading and the fingertip may separate from the vibrating contact surface due to the viscous deformation behaviour of the soft tissue. For a given deformation, the high frequency loading produces a higher stress in the tissues compared to that obtained at a low frequency loading. The present model may serve as a useful tool to study the mechanism of tissue degeneration under vibratory loading encountered during operation of hand-held power tools. AD - National Institute for Occupational Safety and Health, Morgantown, West Virginia 2650, USA. jwu@cdc.gov FAU - Wu, J Z AU - Wu JZ FAU - Dong, R G AU - Dong RG FAU - Rakheja, S AU - Rakheja S FAU - Schopper, A W AU - Schopper AW LA - eng PT - Journal Article CY - England TA - Med Eng Phys JID - 9422753 SB - IM MH - Comparative Study MH - *Computer Simulation MH - Elasticity MH - Fingers/*anatomy & histology/*physiology MH - Finite Element Analysis MH - Human MH - *Models, Biological MH - Motion MH - Nails/anatomy & histology/physiology MH - *Nonlinear Dynamics MH - Pressure MH - Reproducibility of Results MH - Sensitivity and Specificity MH - Skin Physiology MH - Stress, Mechanical MH - Vibration MH - Viscosity MH - Weight-Bearing EDAT- 2002/05/09 10:00 MHDA- 2002/11/26 04:00 AID - S1350453302000188 [pii] PST - ppublish SO - Med Eng Phys 2002 May;24(4):253-64. 149: Allmer G. [Organization versus chaos in...[PMID:11995089]Related Articles, Books, LinkOut UI - 21991667 PMID- 11995089 DA - 20020508 DCOM- 20020718 IS - 0303-4461 VI - 53 IP - 8-9 DP - 2000 Aug-Sep TI - [Organization versus chaos in the hospital] PG - 30-1 FAU - Allmer, G AU - Allmer G LA - ger PT - Journal Article TT - Organisation versus Chaos im Krankenhaus. CY - Austria TA - Osterr Krankenpflegez JID - 0423177 SB - N MH - Germany MH - Human MH - *Nonlinear Dynamics MH - *Nurse's Role MH - Nursing Service, Hospital/*organization & administration MH - Nursing Staff, Hospital/*organization & administration MH - Quality Assurance, Health Care/*organization & administration EDAT- 2002/05/09 10:00 MHDA- 2002/07/19 10:01 PST - ppublish SO - Osterr Krankenpflegez 2000 Aug-Sep;53(8-9):30-1. 150: Yeragani VK, et al. Diminished chaos of heart rat...[PMID:11983187]Related Articles, Books, LinkOut UI - 21978838 PMID- 11983187 DA - 20020501 DCOM- 20020821 IS - 0006-3223 VI - 51 IP - 9 DP - 2002 May 1 TI - Diminished chaos of heart rate time series in patients with major depression. PG - 733-44 AB - BACKGROUND: Depression and anxiety have been linked to serious cardiovascular events in patients with preexisting cardiac illness. A decrease in cardiac vagal function as suggested by a decrease in heart rate (HR) variability has been linked to sudden death. METHODS: We compared LLE and nonlinearity scores of the unfiltered (UF) and filtered time series (very low, low, and high frequency; VLF, LF and HF) of HR between patients with depression (n = 14) and healthy control subjects (n = 18). RESULTS: We found significantly lower LLE of the unfiltered series in either posture, and HF series in patients with major depression in supine posture (p <.002). LLE (LF/UF), which may indicate relative sympathetic activity was also significantly higher in supine and standing postures in patients (p <.05); LF/HF (LLE) was also higher in patients (p <.05) in either posture. CONCLUSIONS: These findings suggest that major depression is associated with decreased cardiac vagal function and a relative increase in sympathetic function, which may be related to the higher risk of cardiovascular mortality in this group and illustrates the usefulness of nonlinear measures of chaos such as LLE in addition to the commonly used spectral measures. AD - Department of Psychiatry, Wayne State University School of Medicine, Detroit, Michigan, USA. FAU - Yeragani, Vikram Kumar AU - Yeragani VK FAU - Rao, K A Radha Krishna AU - Rao KA FAU - Smitha, M Ramesh AU - Smitha MR FAU - Pohl, Robert B AU - Pohl RB FAU - Balon, Richard AU - Balon R FAU - Srinivasan, K AU - Srinivasan K LA - eng PT - Journal Article CY - United States TA - Biol Psychiatry JID - 0213264 SB - IM MH - Adult MH - Depressive Disorder/*physiopathology/*psychology MH - Electrocardiography MH - Female MH - Heart Rate/*physiology MH - Human MH - Male MH - *Nonlinear Dynamics MH - Psychiatric Status Rating Scales EDAT- 2002/05/02 10:00 MHDA- 2002/08/22 10:01 AID - S0006322301013476 [pii] PST - ppublish SO - Biol Psychiatry 2002 May 1;51(9):733-44. 151: Bellazzi R, et al. A hybrid input-output approac...[PMID:11977806]Related Articles, Books, LinkOut UI - 21974147 PMID- 11977806 DA - 20020429 DCOM- 20020610 IS - 1532-0464 VI - 34 IP - 4 DP - 2001 Aug TI - A hybrid input-output approach to model metabolic systems: an application to intracellular thiamine kinetics. PG - 221-48 AB - Models of the dynamics of complex metabolic systems offer potential benefits to the deep comprehension of the system under study as well as for the performance of certain tasks. Unfortunately, dynamic modeling of a great deal of metabolic systems may be problematic due to the incompleteness of the available knowledge about the underlying mechanisms and to the lack of an adequate observational data set. In theory, a valid alternative to classical structural modeling through ordinary differential equations could be represented by input-output approaches. But, in practice, such methods, which learn the nonlinear dynamics of the system from input-output data, fail when the experimental data set is poor either in size or in quality. Such a situation is not rare in the case of metabolic systems. This paper deals with a hybrid approach which aims at overcoming the problems addressed above. More specifically, it allows us to solve the identification problems of the intracellular thiamine kinetics in the intestine tissue. The method, which is half way between the structural and input-output approach, uses the outcomes of the simulation of a qualitative structural model to build a good initialization of a fuzzy system identifier. Such an initialization allows us to efficiently cope with both the incompleteness of knowledge and the inadequacy of the available data set, and to derive an input-output model of the intracellular thiamine kinetics in the intestine tissue. The comparison of the predictions of the intracellular thiamine kinetics obtained by the application of such a model with those obtained by traditional approaches, namely compartmental models, neural networks, and fuzzy systems, highlighted a better performance of our model. As the structural assumptions are relaxed, we obtained a model slightly less informative than a purely structural one but robust enough to be used as a simulator. The paper also discusses the interpretative potential offered by such a model, as tested on diabetic subjects. AD - Dipartimento di Informatica e Sistemistica, Universita di Pavia, via Ferrata 1, 27100 Pavia, Italy. FAU - Bellazzi, R AU - Bellazzi R FAU - Guglielmann, R AU - Guglielmann R FAU - Ironi, L AU - Ironi L FAU - Patrini, C AU - Patrini C LA - eng PT - Journal Article CY - United States TA - J Biomed Inform JID - 100970413 RN - 59-43-8 (Thiamine) SB - IM MH - Animal MH - Computational Biology MH - Diabetes Mellitus/metabolism MH - Fuzzy Logic MH - Human MH - Intestinal Absorption MH - Intracellular Fluid/metabolism MH - Kinetics MH - *Models, Biological MH - Neural Networks (Computer) MH - Nonlinear Dynamics MH - Thiamine/*metabolism EDAT- 2002/04/30 10:00 MHDA- 2002/06/11 10:01 PST - ppublish SO - J Biomed Inform 2001 Aug;34(4):221-48. 152: Breakspear M, et al. Detection and description of ...[PMID:11976053]Related Articles, Books, LinkOut UI - 21972429 PMID- 11976053 DA - 20020426 DCOM- 20020718 IS - 1388-2457 VI - 113 IP - 5 DP - 2002 May TI - Detection and description of non-linear interdependence in normal multichannel human EEG data. PG - 735-53 AB - OBJECTIVES: This study examines human scalp electroencephalographic (EEG) data for evidence of non-linear interdependence between posterior channels. The spectral and phase properties of those epochs of EEG exhibiting non-linear interdependence are studied. METHODS: Scalp EEG data was collected from 40 healthy subjects. A technique for the detection of non-linear interdependence was applied to 2.048 s segments of posterior bipolar electrode data. Amplitude-adjusted phase-randomized surrogate data was used to statistically determine which EEG epochs exhibited non-linear interdependence. RESULTS: Statistically significant evidence of non-linear interactions were evident in 2.9% (eyes open) to 4.8% (eyes closed) of the epochs. In the eyes-open recordings, these epochs exhibited a peak in the spectral and cross-spectral density functions at about 10 Hz. Two types of EEG epochs are evident in the eyes-closed recordings; one type exhibits a peak in the spectral density and cross-spectrum at 8 Hz. The other type has increased spectral and cross-spectral power across faster frequencies. Epochs identified as exhibiting non-linear interdependence display a tendency towards phase interdependencies across and between a broad range of frequencies. CONCLUSIONS: Non-linear interdependence is detectable in a small number of multichannel EEG epochs, and makes a contribution to the alpha rhythm. Non-linear interdependence produces spatially distributed activity that exhibits phase synchronization between oscillations present at different frequencies. The possible physiological significance of these findings are discussed with reference to the dynamical properties of neural systems and the role of synchronous activity in the neocortex. AD - Brain Dynamics Centre, Westmead Hospital, NSW, 2145, Australia. mbreak@physics.usyd.edu.au FAU - Breakspear, M AU - Breakspear M FAU - Terry, J R AU - Terry JR LA - eng PT - Journal Article CY - Netherlands TA - Clin Neurophysiol JID - 100883319 SB - IM MH - Adult MH - Artifacts MH - Brain/cytology/*physiology MH - *Electroencephalography MH - Human MH - Middle Age MH - *Models, Neurological MH - Muscle, Skeletal/innervation MH - Neurons/*physiology MH - *Nonlinear Dynamics MH - Periodicity MH - Reference Values MH - Scalp MH - Support, Non-U.S. Gov't EDAT- 2002/04/27 10:00 MHDA- 2002/07/19 10:01 AID - S1388245702000512 [pii] PST - ppublish SO - Clin Neurophysiol 2002 May;113(5):735-53. 153: Walsh M. Chaos, complexity and nursing...[PMID:11975303]Related Articles, Books, LinkOut UI - 21971874 PMID- 11975303 DA - 20020426 DCOM- 20020610 IS - 0029-6570 VI - 14 IP - 32 DP - 2000 Apr 26-May 2 TI - Chaos, complexity and nursing. PG - 39-42 AB - Chaos and complexity theories have implications for nursing practice. Chaotic systems, potentially including health, the NHS and nursing, are governed by rules which should be understood in order to try to predict future behaviour. Complexity relates to the interconnectedness of things and fits neatly with the concept of holistic care. It can also make important contributions towards restructuring and reorganising nursing. AD - St Martin's College, Carlisle. FAU - Walsh, M AU - Walsh M LA - eng PT - Journal Article CY - England TA - Nurs Stand JID - 9012906 SB - N MH - Feedback MH - Fractals MH - Fuzzy Logic MH - Great Britain MH - Human MH - *Models, Nursing MH - *Nonlinear Dynamics MH - Nursing/*organization & administration MH - Philosophy, Nursing MH - State Medicine/organization & administration MH - Stochastic Processes MH - *Systems Theory EDAT- 2002/04/27 10:00 MHDA- 2002/06/11 10:01 PST - ppublish SO - Nurs Stand 2000 Apr 26-May 2;14(32):39-42. 154: Moseley L, et al. Graphs: looking at relationsh...[PMID:11971390]Related Articles, Books, LinkOut UI - 21968038 PMID- 11971390 DA - 20020424 DCOM- 20020604 IS - 0029-6570 VI - 15 IP - 1 DP - 2000 Sep 20-26 TI - Graphs: looking at relationships. PG - 48-53; quiz 54-5 AB - Research articles often incorporate data in the form of graphs. This article acts as a study guide to enable readers to understand and interpret the data produced in this way. AD - School of Care Sciences, University of Glamorgan. FAU - Moseley, L AU - Moseley L FAU - Mead, D AU - Mead D LA - eng PT - Journal Article CY - England TA - Nurs Stand JID - 9012906 SB - N MH - *Audiovisual Aids MH - Bias (Epidemiology) MH - Causality MH - *Data Interpretation, Statistical MH - Human MH - Linear Models MH - Nonlinear Dynamics MH - Nursing Research/education/methods MH - Reproducibility of Results EDAT- 2002/04/25 10:00 MHDA- 2002/06/05 10:01 PST - ppublish SO - Nurs Stand 2000 Sep 20-26;15(1):48-53; quiz 54-5. 155: Comte JC, et al. Dissipative lattice model wit...[PMID:11970697]Related Articles, Books, LinkOut UI - 21967736 PMID- 11970697 DA - 20020423 DCOM- 20020809 IS - 1063-651X VI - 60 IP - 6 Pt B DP - 1999 Dec TI - Dissipative lattice model with exact traveling discrete kink-soliton solutions: discrete breather generation and reaction diffusion regime. PG - 7484-9 AB - We introduce a nonlinear Klein-Gordon lattice model with specific double-well on-site potential, additional constant external force and dissipation terms, which admits exact discrete kink or traveling wave fronts solutions. In the non-dissipative or conservative regime, our numerical simulations show that narrow kinks can propagate freely, and reveal that static or moving discrete breathers, with a finite but long lifetime, can emerge from kink-antikink collisions. In the general dissipative regime, the lifetime of these breathers depends on the importance of the dissipative effects. In the overdamped or diffusive regime, the general equation of motion reduces to a discrete reaction diffusion equation; our simulations show that, for a given potential shape, discrete wave fronts can travel without experiencing any propagation failure but their collisions are inelastic. AD - Laboratoire d'Electronique, Informatique et Image (LE21) Universite de Bourgogne, Aile des Sciences de l'Ingenieur, BP 47870, 21078 Dijon Cedex, France. FAU - Comte, J C AU - Comte JC FAU - Marquie, P AU - Marquie P FAU - Remoissenet, M AU - Remoissenet M LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics JID - 9887340 RN - 9007-49-2 (DNA) SB - IM MH - Base Pairing MH - Biophysics MH - Calcium Signaling MH - DNA/chemistry MH - Hydrogen Bonding MH - Models, Biological MH - *Models, Theoretical MH - Nonlinear Dynamics EDAT- 2002/04/24 10:00 MHDA- 2002/08/10 10:01 PHST- 1999/Jun/07 [received] PST - ppublish SO - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999 Dec;60(6 Pt B):7484-9. 156: Lipniacki T. Chemically driven traveling w...[PMID:11970669]Related Articles, Books, LinkOut UI - 21967708 PMID- 11970669 DA - 20020423 DCOM- 20020809 LR - 20021101 IS - 1063-651X VI - 60 IP - 6 Pt B DP - 1999 Dec TI - Chemically driven traveling waves in DNA. PG - 7253-61 AB - The nonlinear mechanical model constructed in a previous paper [Nuovo Cimento D 20, 833 (1998)] is developed in order to study the dynamics of the DNA double helix. It is assumed that the hydrophobic interaction between subsequent base pairs may be influenced by a RNA polymerase. The Lagrangian, constructed on the basis of "geometrical" properties of the DNA molecule, depends on time and contains first and second derivatives of the twist angle. The energy dissipation term is added to the dynamical equations resulting from the Lagrange formalism. It is proved that the system has pulse-like solitary wave solutions for which the dissipated energy is balanced by the energy pumped by the advancing RNA polymerase. The physical interpretation of our solution is the local untwisting of the DNA molecule during transcription of messenger RNA. AD - Institute of Fundamental Technological Research, Polish Academy of Science, Swietokrzyska Street 21, 00-049 Warsaw, Poland. FAU - Lipniacki, T AU - Lipniacki T LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics JID - 9887340 RN - 63231-63-0 (RNA) RN - 9007-49-2 (DNA) RN - EC 2.7.7.6 (DNA-Directed RNA Polymerases) SB - IM MH - Base Pairing/genetics MH - DNA/*chemistry/genetics MH - DNA-Directed RNA Polymerases/chemistry/genetics MH - Models, Chemical MH - Models, Genetic MH - Nonlinear Dynamics MH - *Nucleic Acid Conformation MH - RNA/chemistry/genetics MH - Support, Non-U.S. Gov't MH - Thermodynamics MH - Transcription, Genetic EDAT- 2002/04/24 10:00 MHDA- 2002/08/10 10:01 PHST- 1999/Feb/17 [received] PHST- 1999/May/11 [revised] PST - ppublish SO - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999 Dec;60(6 Pt B):7253-61. 157: Suguna C, et al. Minimal model for complex dyn...[PMID:11970497]Related Articles, Books, LinkOut UI - 21967535 PMID- 11970497 DA - 20020423 DCOM- 20020826 IS - 1063-651X VI - 60 IP - 5 Pt B DP - 1999 Nov TI - Minimal model for complex dynamics in cellular processes. PG - 5943-9 AB - Cellular functions are controlled and coordinated by the complex circuitry of biochemical pathways regulated by genetic and metabolic feedback processes. This paper aims to show, with the help of a minimal model of a regulated biochemical pathway, that the common nonlinearities and control structures present in biomolecular interactions are capable of eliciting a variety of functional dynamics, such as homeostasis, periodic, complex, and chaotic oscillations, including transients, that are observed in various cellular processes. AD - Centre for Cellular and Molecular Biology, Hyderabad 500 007, India. FAU - Suguna, C AU - Suguna C FAU - Chowdhury, K K AU - Chowdhury KK FAU - Sinha, S AU - Sinha S LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics JID - 9887340 SB - IM MH - Biochemistry MH - Biophysics MH - Feedback MH - *Models, Biological MH - Nonlinear Dynamics MH - Thermodynamics EDAT- 2002/04/24 10:00 MHDA- 2002/08/27 10:01 PHST- 1999/Jun/11 [received] PST - ppublish SO - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999 Nov;60(5 Pt B):5943-9. 158: Chen CN, et al. Monte Carlo dynamics in globa...[PMID:11970036]Related Articles, Books, LinkOut UI - 21967072 PMID- 11970036 DA - 20020423 DCOM- 20021023 IS - 1063-651X VI - 60 IP - 2 Pt B DP - 1999 Aug TI - Monte Carlo dynamics in global optimization. PG - 2388-93 AB - Several very different optimization problems are studied by using the fixed-temperature Monte Carlo dynamics and found to share many common features. The most surprising result is that the cost function of these optimization problems itself is a very good stochastic variable to describe the complicated Monte Carlo processes. A multidimensional problem can therefore be mapped into a one-dimensional diffusion problem. This problem is either solved by direct numerical simulation or by using the Fokker-Planck equations. Above certain temperatures, the first passage time distribution functions of the original Monte Carlo processes are reproduced. At low temperatures, the first passage time has a path dependence and the single-stochastic-variable description is no longer valid. This analysis also provides a simple method to characterize the energy landscapes. AD - Institute of Physics, Academia Sinica, Taipei, Taiwan. FAU - Chen, C N AU - Chen CN FAU - Chou, C I AU - Chou CI FAU - Hwang, C R AU - Hwang CR FAU - Kang, J AU - Kang J FAU - Lee, T K AU - Lee TK FAU - Li, S P AU - Li SP LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics JID - 9887340 SB - IM MH - Crystallography, X-Ray MH - *Monte Carlo Method MH - Nonlinear Dynamics MH - Normal Distribution MH - Protein Folding MH - Thermodynamics EDAT- 2002/04/24 10:00 MHDA- 2002/10/31 04:00 PHST- 1999/Jan/26 [received] PST - ppublish SO - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999 Aug;60(2 Pt B):2388-93. 159: Caroppo D, et al. Chaos in neural networks with...[PMID:11970013]Related Articles, Books, LinkOut UI - 21967049 PMID- 11970013 DA - 20020423 DCOM- 20021023 IS - 1063-651X VI - 60 IP - 2 Pt B DP - 1999 Aug TI - Chaos in neural networks with a nonmonotonic transfer function. PG - 2186-92 AB - Time evolution of diluted neural networks with a nonmonotonic transfer function is analytically described by flow equations for macroscopic variables. The macroscopic dynamics shows a rich variety of behaviors: fixed-point, periodicity, and chaos. We examine in detail the structure of the strange attractor and in particular we study the main features of the stable and unstable manifolds, the hyperbolicity of the attractor, and the existence of homoclinic intersections. We also discuss the problem of the robustness of the chaos and we prove that in the present model chaotic behavior is fragile (chaotic regions are densely intercalated with periodicity windows), according to a recently discussed conjecture. Finally we perform an analysis of the microscopic behavior and in particular we examine the occurrence of damage spreading by studying the time evolution of two almost identical initial configurations. We show that for any choice of the parameters the two initial states remain microscopically distinct. AD - Dipartimento Interateneo di Fisica and Istituto Nazionale di Fisica Nucleare, Sezione di Bari, via Amendola 173, 70126 Bari, Italy. FAU - Caroppo, D AU - Caroppo D FAU - Mannarelli, M AU - Mannarelli M FAU - Nardulli, G AU - Nardulli G FAU - Stramaglia, S AU - Stramaglia S LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics JID - 9887340 SB - IM MH - Models, Theoretical MH - *Neural Networks (Computer) MH - *Nonlinear Dynamics MH - Synapses MH - Time Factors EDAT- 2002/04/24 10:00 MHDA- 2002/10/31 04:00 PHST- 1999/Mar/23 [received] PST - ppublish SO - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999 Aug;60(2 Pt B):2186-92. 160: Tanabe S, et al. Response of coupled noisy exc...[PMID:11970012]Related Articles, Books, LinkOut UI - 21967048 PMID- 11970012 DA - 20020423 DCOM- 20021023 IS - 1063-651X VI - 60 IP - 2 Pt B DP - 1999 Aug TI - Response of coupled noisy excitable systems to weak stimulation. PG - 2182-5 AB - It is known that coupling can enhance the response of noisy bistable devices to weak periodic modulation. This work examines whether a similar phenomenon occurs in the active rotator model for excitable systems. We study the dynamics of assemblies of weakly periodically modulated active rotators. The addition of noise to these brings about a number of behaviors that have no counterpart in networks of bistable systems. The analysis of the dynamics of the solution of the Fokker-Planck equation of active rotator networks shows that these new behaviors are similar to generic responses of periodically forced autonomous oscillators. This is because noise alone, in the absence of other inputs, can regularize the dynamics of single active rotators through coherence resonance, and lead to regular synchronous activity at the level of networks. We argue that similar phenomena take place in a broad class of excitable systems. AD - Department of System and Human Science, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531 Osaka, Japan. FAU - Tanabe, S AU - Tanabe S FAU - Shimokawa, T AU - Shimokawa T FAU - Sato, S AU - Sato S FAU - Pakdaman, K AU - Pakdaman K LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics JID - 9887340 SB - IM MH - Acoustic Stimulation MH - *Excitatory Postsynaptic Potentials MH - Models, Biological MH - *Nervous System MH - *Noise MH - Nonlinear Dynamics MH - Oscillometry MH - Synaptic Transmission/*physiology EDAT- 2002/04/24 10:00 MHDA- 2002/10/31 04:00 PHST- 1999/Feb/16 [received] PST - ppublish SO - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999 Aug;60(2 Pt B):2182-5. 161: Bressloff PC. Mean-field theory of globally...[PMID:11970009]Related Articles, Books, LinkOut UI - 21967045 PMID- 11970009 DA - 20020423 DCOM- 20021023 IS - 1063-651X VI - 60 IP - 2 Pt B DP - 1999 Aug TI - Mean-field theory of globally coupled integrate-and-fire neural oscillators with dynamic synapses. PG - 2160-70 AB - We analyze the effects of synaptic depression or facilitation on the existence and stability of the splay or asynchronous state in a population of all-to-all, pulse-coupled neural oscillators. We use mean-field techniques to derive conditions for the local stability of the splay state and determine how stability depends on the degree of synaptic depression or facilitation. We also consider the effects of noise. Extensions of the mean-field results to finite networks are developed in terms of the nonlinear firing time map. AD - Nonlinear and Complex Systems Group, Department of Mathematical Sciences, Loughborough University, Loughborough, Leicestershire LE11 3TU, United Kingdom. FAU - Bressloff, P C AU - Bressloff PC LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics JID - 9887340 SB - IM MH - Models, Neurological MH - Nerve Net/physiology MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Oscillometry MH - Support, Non-U.S. Gov't MH - Synapses/*physiology MH - Synaptic Transmission/physiology EDAT- 2002/04/24 10:00 MHDA- 2002/10/31 04:00 PHST- 1999/Feb/02 [received] PST - ppublish SO - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999 Aug;60(2 Pt B):2160-70. 162: Coombes S, et al. Mode locking and Arnold tongu...[PMID:11970001]Related Articles, Books, LinkOut UI - 21967037 PMID- 11970001 DA - 20020423 DCOM- 20021023 IS - 1063-651X VI - 60 IP - 2 Pt B DP - 1999 Aug TI - Mode locking and Arnold tongues in integrate-and-fire neural oscillators. PG - 2086-96 AB - An analysis of mode-locked solutions that may arise in periodically forced integrate-and-fire (IF) neural oscillators is introduced based upon a firing map formulation of the dynamics. A q:p mode-locked solution is identified with a spike train in which p firing events occur in a period qDelta, where Delta is the forcing period. A linear stability analysis of the map of firing times around such solutions allows the determination of the Arnold tongue structure for regions in parameter space where stable solutions exist. The analysis is verified against direct numerical simulations for both a sinusoidally forced IF system and one in which a periodic sequence of spikes is used to induce a biologically realistic synaptic input current. This approach is extended to the case of two synaptically coupled IF oscillators, showing that mode-locked states can exist for some self-consistently determined common period of repetitive firing. Numerical simulations show that such solutions have a bursting structure where regions of spiking activity are interspersed with quiescent periods before repeating. The influence of the synaptic current upon the Arnold tongue structure is explored in the regime of weak coupling. AD - Nonlinear and Complex Systems Group, Department of Mathematical Sciences, Loughborough University, Leicestershire LE11 3TU, United Kingdom. FAU - Coombes, S AU - Coombes S FAU - Bressloff, P C AU - Bressloff PC LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics JID - 9887340 SB - IM MH - Action Potentials/physiology MH - Comparative Study MH - Membrane Potentials/physiology MH - Models, Biological MH - Models, Statistical MH - Neurons/physiology MH - Nonlinear Dynamics MH - Oscillometry/*methods/statistics & numerical data MH - Support, Non-U.S. Gov't MH - Synapses/*physiology MH - Synaptic Transmission/*physiology EDAT- 2002/04/24 10:00 MHDA- 2002/10/31 04:00 PHST- 1999/Feb/05 [received] PST - ppublish SO - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999 Aug;60(2 Pt B):2086-96. 163: So P, et al. Box-counting dimension withou...[PMID:11969771]Related Articles, Books, LinkOut UI - 21966806 PMID- 11969771 DA - 20020423 DCOM- 20020827 IS - 1063-651X VI - 60 IP - 1 DP - 1999 Jul TI - Box-counting dimension without boxes: computing D0 from average expansion rates. PG - 378-85 AB - We propose an efficient iterative scheme for calculating the box-counting (capacity) dimension of a chaotic attractor in terms of its average expansion rates. Similar to the Kaplan-Yorke conjecture for the information dimension, this scheme provides a connection between a geometric property of a strange set and its underlying dynamical properties. Our conjecture is demonstrated analytically with an exactly solvable two-dimensional hyperbolic map, and numerically with a more complicated higher-dimensional nonhyperbolic map. AD - Department of Physics and Astronomy and the Krasnow Institute for Advanced Study, George Mason University, Fairfax, Virginia 22030, USA. FAU - So, P AU - So P FAU - Barreto, E AU - Barreto E FAU - Hunt, B R AU - Hunt BR LA - eng ID - 5-21215/PHS PT - Journal Article CY - United States TA - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics JID - 9887340 SB - IM MH - *Biophysics MH - Models, Statistical MH - Models, Theoretical MH - Nonlinear Dynamics MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/04/24 10:00 MHDA- 2002/08/28 10:01 PHST- 1998/Oct/20 [received] PHST- 1999/Feb/16 [revised] PST - ppublish SO - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999 Jul;60(1):378-85. 164: Cao J. Global stability analysis in ...[PMID:11969575]Related Articles, Books, LinkOut UI - 21966610 PMID- 11969575 DA - 20020423 DCOM- 20020827 IS - 1063-651X VI - 59 IP - 5 Pt B DP - 1999 May TI - Global stability analysis in delayed cellular neural networks. PG - 5940-4 AB - In this paper, the author analyzes further problems of global stability for a class of cellular neural networks with delays by means of the Lyapunov functional method, inequalities a(2)+b(2)> or =2ab and a(3)+b(3)+c(3)> or =3abc (a,b,c > or =0) analysis technique, some stability criteria are obtained under more general conditions. These criteria can be applied to design globally stable networks and thus have important significance in both theory and applications. AD - Adult Education College, Yunnan University, Kunming 650091, People's Republic of China. FAU - Cao, J AU - Cao J LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics JID - 9887340 SB - IM MH - Biophysics MH - *Models, Neurological MH - Nerve Net/*physiology MH - Neural Networks (Computer) MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2002/04/24 10:00 MHDA- 2002/08/28 10:01 PHST- 1998/Oct/12 [received] PHST- 1998/Dec/17 [revised] PST - ppublish SO - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999 May;59(5 Pt B):5940-4. 165: Vilar JM, et al. Noise and periodic modulation...[PMID:11969573]Related Articles, Books, LinkOut UI - 21966608 PMID- 11969573 DA - 20020423 DCOM- 20020827 IS - 1063-651X VI - 59 IP - 5 Pt B DP - 1999 May TI - Noise and periodic modulations in neural excitable media. PG - 5920-7 AB - We have analyzed the interplay between noise and periodic modulations in a mean field model of a neural excitable medium. For this purpose, we have considered two types of modulations, namely, variations of the resistance and oscillations of the threshold. In both cases, stochastic resonance is present, irrespective of whether the system is monostable or bistable. AD - Departament de Fisica Fonamental, Facultat de Fisica, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona, Spain. FAU - Vilar, J M AU - Vilar JM FAU - Sole, R V AU - Sole RV FAU - Rubi, J M AU - Rubi JM LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics JID - 9887340 SB - IM MH - Biophysics MH - *Models, Neurological MH - Nerve Net/physiology MH - Neurons/physiology MH - Nonlinear Dynamics MH - Stochastic Processes MH - Support, Non-U.S. Gov't EDAT- 2002/04/24 10:00 MHDA- 2002/08/28 10:01 PHST- 1997/Jun/23 [received] PHST- 1997/Dec/29 [revised] PST - ppublish SO - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999 May;59(5 Pt B):5920-7. 166: Mezentseva LV, et al. [Analysis of ECG in ventricul...[PMID:11969179]Related Articles, Books, LinkOut UI - 21965832 PMID- 11969179 DA - 20020423 DCOM- 20020520 IS - 0006-3029 VI - 47 IP - 2 DP - 2002 Mar-Apr TI - [Analysis of ECG in ventricular fibrillation in man and animals based on chaos theory] PG - 369-75 AB - The methods of the chaos theory were used to estimate the degree of irregularity of ventricular fibrillation in human and experimental animals. To verify the hypothesis that the degree of chaos depends on the species of the living organisms, the parameters characterizing the degrees of irregularity of ventricular fibrillation were estimated and compared. The comparative analysis was performed using 32 fragments of electrocardiographic records from five patients with sudden ventricular fibrillation bouts and 215 episodes of induced fibrillation in 17 animals. It was shown that fibrillation in human and animals has a different degree of regularity and different values of the chaotic component. The highest values of chaos were recorded in dogs, the lowest degree of chaos was observed in human. Rabbits and rats are intermediate, between dogs and humans. The fractuality of the structure-function organization of myocardium is discussed. AD - Anokhin Research Institute of Normal Physiology, Russian Academy of Medical Sciences, ul. Bol'shaya Nikitskaya 6, korp. 4, Moscow, 103009 Russia. FAU - Mezentseva, L V AU - Mezentseva LV FAU - Kashtanov, S I AU - Kashtanov SI FAU - Vostrikov, V A AU - Vostrikov VA FAU - Zviagintseva, M A AU - Zviagintseva MA FAU - Kosharskaia, I L AU - Kosharskaia IL LA - rus PT - Journal Article TT - Analiz EKG pri fibrilliatsii zheludochkov u cheloveka i zhivotnykh na osnove teorii khaosa. CY - Russia TA - Biofizika JID - 0372666 SB - IM MH - Animal MH - Dogs MH - *Electrocardiography MH - English Abstract MH - Human MH - Nonlinear Dynamics MH - Rabbits MH - Rats MH - Rats, Wistar MH - Ventricular Fibrillation/*physiopathology EDAT- 2002/04/24 10:00 MHDA- 2002/05/22 10:01 PST - ppublish SO - Biofizika 2002 Mar-Apr;47(2):369-75. 167: Pliusnina TIu, et al. [New spatial-temporal dynamic...[PMID:11969164]Related Articles, Books, LinkOut UI - 21965817 PMID- 11969164 DA - 20020423 DCOM- 20020520 IS - 0006-3029 VI - 47 IP - 2 DP - 2002 Mar-Apr TI - [New spatial-temporal dynamics in a reaction-electrodiffusion system] PG - 277-82 AB - The properties of a system reaction-electrodiffusion were studied using two-component model of interaction and diffusion of charged particles near membrane in solutions of low ionic strength to which traditional assumptions about local electroneutrality of medium are not applicable. It is shown that the effect of self-consistent electric field leads to bistability, the appearance of localized structures with contrast charge distribution and regimes aperiodical in time and in space. AD - Biological Department, Lomonosov Moscow State University, Vorob'evy Gory, Moscow, 119899 Russia. FAU - Pliusnina, T Iu AU - Pliusnina TIu FAU - Lobanov, A I AU - Lobanov AI FAU - Lavrova, A I AU - Lavrova AI FAU - Starozhilova, T K AU - Starozhilova TK FAU - Riznichenko, G Iu AU - Riznichenko GIu FAU - Rubin, A B AU - Rubin AB LA - rus PT - Journal Article TT - Novye prostranstvenno-vremennye rezhimy v sisteme reaktsiia-elektrodiffuziia. CY - Russia TA - Biofizika JID - 0372666 SB - IM MH - Algorithms MH - *Cell Membrane MH - Diffusion MH - Electricity MH - English Abstract MH - Kinetics MH - Models, Biological MH - Nonlinear Dynamics MH - Osmolar Concentration EDAT- 2002/04/24 10:00 MHDA- 2002/05/22 10:01 PST - ppublish SO - Biofizika 2002 Mar-Apr;47(2):277-82. 168: Medvinsky AB, et al. Chaos and order in plankton d...[PMID:11966216]Related Articles, Books, LinkOut UI - 21963146 PMID- 11966216 DA - 20020422 DCOM- 20020618 IS - 0044-4596 VI - 63 IP - 2 DP - 2002 Mar-Apr TI - Chaos and order in plankton dynamics. Complex behavior of a simple model. PG - 149-58 AB - The role of the diffusive interaction between fish-populated and fish-free habitats in a patchy environment in plankton pattern formation is studied by means of a minimal reaction-diffusion model of the nutrient-plankton-fish food chain. It is shown that such interaction can give rise to spatio-temporal plankton patterns. The fractal dimension of the patterns is shown dependent on the fish predation rate. The spatially averaged plankton dynamics depending on both fish predation rate and distance between fish-populated habitats can exhibit chaotic and regular behavior. The chaotic plankton dynamics is characteristic of a wide parameter range. AD - Institute for Theoretical & Experimental Biophysics, Pushchino, Moscow Region, 142290 Russia. medvinsky@venus.iteb.serpukhov.su FAU - Medvinsky, Alexander B AU - Medvinsky AB FAU - Tikhonova, Irene A AU - Tikhonova IA FAU - Petrovskii, Sergey V AU - Petrovskii SV FAU - Malchow, Horst AU - Malchow H FAU - Venturino, Ezio AU - Venturino E LA - eng PT - Journal Article CY - Russia TA - Zh Obshch Biol JID - 0424252 SB - IM MH - Animal MH - Comparative Study MH - Ecosystem MH - Fishes MH - *Food Chain MH - Marine Biology MH - *Models, Biological MH - Nonlinear Dynamics MH - Plankton/*growth & development MH - Population Dynamics MH - Support, Non-U.S. Gov't EDAT- 2002/04/23 10:00 MHDA- 2002/06/19 10:01 PST - ppublish SO - Zh Obshch Biol 2002 Mar-Apr;63(2):149-58. 169: Mitsis GD, et al. Modeling of nonlinear physiol...[PMID:11962778]Related Articles, Books, LinkOut UI - 21957870 PMID- 11962778 DA - 20020418 DCOM- 20021018 IS - 0090-6964 VI - 30 IP - 2 DP - 2002 Feb TI - Modeling of nonlinear physiological systems with fast and slow dynamics. I. Methodology. PG - 272-81 AB - Effective modeling of nonlinear dynamic systems can be achieved by employing Laguerre expansions and feedforward artificial neural networks in the form of the Laguerre-Volterra network (LVN). This paper presents a different formulation of the LVN that can be employed to model nonlinear systems displaying complex dynamics effectively. This is achieved by using two different filter banks, instead of one as in the original definition of the LVN, in the input stage and selecting their structural parameters in an appropriate way. Results from simulated systems show that this method can yield accurate nonlinear models of Volterra systems, even when considerable noise is present, separating at the same time the fast from the slow components of these systems effectively. AD - Department of Biomedical Engineering, University of Southern California, University Park, Los Angeles 90089-1451, USA. FAU - Mitsis, G D AU - Mitsis GD FAU - Marmarelis, V Z AU - Marmarelis VZ LA - eng ID - RR-01861/RR/NCRR PT - Journal Article CY - United States TA - Ann Biomed Eng JID - 0361512 SB - IM MH - Algorithms MH - Computer Simulation MH - *Models, Biological MH - *Neural Networks (Computer) MH - *Nonlinear Dynamics MH - Sensitivity and Specificity MH - Stochastic Processes MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/04/19 10:00 MHDA- 2002/10/19 04:00 PST - ppublish SO - Ann Biomed Eng 2002 Feb;30(2):272-81. 170: Armoundas AA, et al. A stochastic nonlinear autore...[PMID:11962771]Related Articles, Books, LinkOut UI - 21957863 PMID- 11962771 DA - 20020418 DCOM- 20021018 LR - 20021120 IS - 0090-6964 VI - 30 IP - 2 DP - 2002 Feb TI - A stochastic nonlinear autoregressive algorithm reflects nonlinear dynamics of heart-rate fluctuations. PG - 192-201 AB - Current methods for detecting nonlinear determinism in a time series require long and stationary data records, as most of them assume that the observed dynamics arise only from the internal, deterministic workings of the system, and the stochastic portion of the signal (the noise component) is assumed to be negligible. To explicitly account for the stochastic portion of the data we recently developed a method based on a stochastic nonlinear autoregressive (SNAR) algorithm. The method iteratively estimates nonlinear autoregressive models for both the deterministic and stochastic portions of the signal. Subsequently, the Lyapunov exponents (LE) are calculated for the estimated models in order to examine if nonlinear determinism is present in the deterministic portion of the fitted model. To determine if nonlinear dynamic analysis of heart-rate fluctuations can be used to assess arrhythmia susceptibility by predicting the outcome of invasive cardiac electrophysiologic study (EPS), we applied the SNAR algorithm to noninvasively measured resting sinus-rhythm heart-rate signals obtained from 16 patients. Our analysis revealed that a positive LE was highly correlated to a patient with a positive outcome of EPS. We found that the statistical accuracy of the SNAR algorithm in predicting the outcome of EPS was 88% (sensitivity=100%, specificity=75%, positive predictive value=80%, negative predictive value=100%, p=0.0019). Our results suggest that the SNAR algorithm may serve as a noninvasive probe for screening high-risk populations for malignant cardiac arrhythmias. AD - Division of Health Sciences and Technology, Harvard University-Massachusetts Institute of Technology, Cambridge, USA. FAU - Armoundas, Antonis A AU - Armoundas AA FAU - Ju, Kihwan AU - Ju K FAU - Iyengar, Nikhil AU - Iyengar N FAU - Kanters, Jorgen K AU - Kanters JK FAU - Saul, Philip J AU - Saul PJ FAU - Cohen, Richard J AU - Cohen RJ FAU - Chon, Ki H AU - Chon KH LA - eng PT - Evaluation Studies PT - Journal Article CY - United States TA - Ann Biomed Eng JID - 0361512 SB - IM SB - S MH - Adult MH - Aged MH - *Algorithms MH - Computer Simulation MH - Electrocardiography/*methods MH - Female MH - Heart Rate/*physiology MH - Human MH - Male MH - Middle Age MH - *Models, Cardiovascular MH - *Models, Statistical MH - Nonlinear Dynamics MH - Predictive Value of Tests MH - Reproducibility of Results MH - Sensitivity and Specificity MH - Stochastic Processes MH - Support, Non-U.S. Gov't MH - Ventricular Fibrillation/*diagnosis EDAT- 2002/04/19 10:00 MHDA- 2002/10/19 04:00 PST - ppublish SO - Ann Biomed Eng 2002 Feb;30(2):192-201. 171: Wagers S, et al. Nonlinearity of respiratory m...[PMID:11960927]Related Articles, Books, LinkOut UI - 21958988 PMID- 11960927 DA - 20020418 DCOM- 20020621 IS - 8750-7587 VI - 92 IP - 5 DP - 2002 May TI - Nonlinearity of respiratory mechanics during bronchoconstriction in mice with airway inflammation. PG - 1802-7 AB - Respiratory system resistance (R) and elastance (E) are commonly estimated by fitting the linear equation of motion P = EV + RV + P0 (Eq. 1) to measurements of respiratory pressure (P), lung volume (V), and flow (V). However, the respiratory system is unlikely to behave linearly under many circumstances. We determined the importance of respiratory system nonlinearities in two groups of mechanically ventilated Balb/c mice [controls and mice with allergically inflamed airways (ova/ova)], by assessing the impact of the addition of nonlinear terms (E2V2 and R2V(V)) on the goodness of model fit seen with Eq. 1. Significant improvement in fit (51.85 +/- 4.19%) was only seen in the ova/ova mice during bronchoconstriction when the E2V2 alone was added. An improvement was also observed with addition of the E2V2 term in mice with both low and high lung volumes ventilated at baseline, suggesting a volume-dependent nonlinearity of E. We speculate that airway closure in the constricted ova/ova mice accentuated the volume-dependent nonlinearity by decreasing lung volume and overdistending the remaining lung. AD - Vermont Lung Center, Department of Medicine, University of Vermont, Burlington 05405, USA. ssw6609739@cs.com FAU - Wagers, Scott AU - Wagers S FAU - Lundblad, Lennart AU - Lundblad L FAU - Moriya, Henrique T AU - Moriya HT FAU - Bates, Jason H T AU - Bates JH FAU - Irvin, Charles G AU - Irvin CG LA - eng ID - 1 P20 RR-15557-01/RR/NCRR ID - HL-56638/HL/NHLBI ID - HL-60793/HL/NHLBI PT - Journal Article CY - United States TA - J Appl Physiol JID - 8502536 RN - 62-51-1 (Methacholine Chloride) RN - 9006-59-1 (Ovalbumin) SB - IM MH - Administration, Inhalation MH - Animal MH - Asthma/*physiopathology MH - Bronchoalveolar Lavage Fluid/cytology/immunology MH - *Bronchoconstriction/drug effects/physiology MH - Cell Count MH - Disease Models, Animal MH - Female MH - Lung Volume Measurements MH - Methacholine Chloride/administration & dosage MH - Mice MH - Mice, Inbred BALB C MH - *Nonlinear Dynamics MH - Ovalbumin/immunology MH - Pneumonia/*physiopathology MH - Positive-Pressure Respiration MH - Respiration, Artificial MH - *Respiratory Mechanics/drug effects/physiology MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/04/19 10:00 MHDA- 2002/06/22 10:01 AID - 10.1152/japplphysiol.00883.2001 [doi] PST - ppublish SO - J Appl Physiol 2002 May;92(5):1802-7. 172: Mahon NG, et al. Fractal correlation propertie...[PMID:11959043]Related Articles, Books, LinkOut UI - 21956372 PMID- 11959043 DA - 20020417 DCOM- 20020522 LR - 20021101 IS - 1388-9842 VI - 4 IP - 2 DP - 2002 Mar TI - Fractal correlation properties of R-R interval dynamics in asymptomatic relatives of patients with dilated cardiomyopathy. PG - 151-8 AB - BACKGROUND AND AIM: asymptomatic relatives of patients with familial dilated cardiomyopathy who have left ventricular enlargement [LVE] are at risk for progression to dilated cardiomyopathy. A novel index of the fractal correlation properties of heart rate variability (HRV), the short-term scaling component (proportional, variant(1)) in detrended fluctuation analysis, is a promising prognostic tool in left ventricular dysfunction. The aim of this study was to compare values of proportional, variant(1) and conventional HRV indices in LVE relatives with dilated cardiomyopathy patients and normal controls. METHODS: time-domain and spectral HRV measures, and the short-term scaling component ( proportional, variant(1)) were assessed from 24-h Holter recordings from 22 LVE relatives (left ventricular end-diastolic dimension >112% predicted, normal fractional shortening), 24 dilated cardiomyopathy patients and 14 controls. RESULTS: the time domain index SDNN was lower in dilated cardiomyopathy patients [101.8(+/-44.0)] than in LVE relatives [161.7(+/-53.9)] or controls [152.9(+/-51.4)], P=0.01. Similarly, triangular index and spectral measures were reduced in dilated cardiomyopathy patients but not in LVE relatives or controls. In contrast, the short term scaling component ( proportional, variant(1)) in detrended fluctuation analysis was reduced in both dilated cardiomyopathy patients [1.06(+/-0.33)] and in LVE relatives [1.15 (+/-0.20)], compared with controls [1.32(+/-0.16)], P=0.01. Among DCM patients the short-term scaling component ( proportional, variant(1)) was significantly associated with echocardiographic deterioration during follow-up (3.7+/-2.1 year) (P=0.004). CONCLUSION: the short-term scaling component ( proportional, variant(1)) is reduced in asymptomatic relatives of dilated cardiomyopathy patients who have LVE. AD - Department of Cardiological Sciences, St George's Hospital Medical School, London, UK. mahonn@ccf.org FAU - Mahon, Niall G AU - Mahon NG FAU - Hedman, Antti E AU - Hedman AE FAU - Padula, Mina AU - Padula M FAU - Gang, Yi AU - Gang Y FAU - Savelieva, Irina AU - Savelieva I FAU - Waktare, Johan E P AU - Waktare JE FAU - Malik, Marek M AU - Malik MM FAU - Huikuri, Heikki V AU - Huikuri HV FAU - McKenna, William J AU - McKenna WJ LA - eng PT - Evaluation Studies PT - Journal Article CY - Netherlands TA - Eur J Heart Fail JID - 100887595 SB - IM MH - Adolescent MH - Adult MH - Aged MH - Cardiomyopathy, Congestive/diagnosis/*etiology/mortality MH - Case-Control Studies MH - Comparative Study MH - Disease Progression MH - Echocardiography MH - Electrocardiography, Ambulatory MH - Family Health MH - Female MH - Follow-Up Studies MH - *Fractals MH - Heart Rate/physiology MH - Human MH - London/epidemiology MH - Male MH - Middle Age MH - *Nonlinear Dynamics MH - Pilot Projects MH - Predictive Value of Tests MH - Prognosis MH - Prospective Studies MH - Risk Factors MH - Statistics MH - Support, Non-U.S. Gov't MH - Survival Analysis MH - Time Factors MH - Ventricular Dysfunction, Left/complications/diagnosis/mortality EDAT- 2002/04/18 10:00 MHDA- 2002/05/25 10:01 AID - S1388984201002276 [pii] PST - ppublish SO - Eur J Heart Fail 2002 Mar;4(2):151-8. 173: Peng J, et al. A new approach to stability o...[PMID:11958493]Related Articles, Books, LinkOut UI - 21954664 PMID- 11958493 DA - 20020417 DCOM- 20021008 IS - 0893-6080 VI - 15 IP - 1 DP - 2002 Jan TI - A new approach to stability of neural networks with time-varying delays. PG - 95-103 AB - The stability of neural networks is a prerequisite for successful applications of the networks as either associative memories or optimization solvers. Because the integration and communication delays are ubiquitous, the stability of neural networks with delays has received extensive attention. However, the approach used in the previous investigation is mainly based on Liapunov's direct method. Since the construction of Liapunov function is very skilful, there is little compatibility among the existing results. In this paper, we develop a new approach to stability analysis of Hopfield-type neural networks with time-varying delays by defining two novel quantities of nonlinear function similar to the matrix norm and the matrix measure, respectively. With the new approach, we present sufficient conditions of the stability, which are either the generalization of those existing or new. The developed approach may be also applied for any general system with time delays rather than Hopfield-type neural networks. AD - Institute for Information and System Science, Faculty of Science, Xi'an Jiaotong University, PR China. jgpeng@xjtu.edu.cn FAU - Peng, Jigen AU - Peng J FAU - Qiao, Hong AU - Qiao H FAU - Xu, Zong-ben AU - Xu ZB LA - eng PT - Journal Article CY - United States TA - Neural Netw JID - 8805018 SB - IM MH - *Neural Networks (Computer) MH - Nonlinear Dynamics MH - Time Factors EDAT- 2002/04/18 10:00 MHDA- 2002/10/09 04:00 PST - ppublish SO - Neural Netw 2002 Jan;15(1):95-103. 174: Laird AR, et al. Characterizing instantaneous ...[PMID:11954057]Related Articles, Books, LinkOut UI - 21950531 PMID- 11954057 DA - 20020415 DCOM- 20020726 IS - 1065-9471 VI - 16 IP - 2 DP - 2002 Jun TI - Characterizing instantaneous phase relationships in whole-brain fMRI activation data. PG - 71-80 AB - Typically, fMRI data is processed in the time domain with linear methods such as regression and correlation analysis. We propose that the theory of phase synchronization may be used to more completely understand the dynamics of interacting systems, and can be applied to fMRI data as a novel method of detecting activation. Generalized synchronization is a phenomenon that occurs when there is a nonlinear functional relationship present between two or more coupled, oscillatory systems, whereas phase synchronization is defined as the locking of the phases while the amplitudes may vary. In this study, we developed an application of phase synchronization analysis that is appropriate for fMRI data, in which the phase locking condition is investigated between a voxel time series and the reference function of the task performed. A synchronization index is calculated to quantify the level of phase locking, and a nonparametric permutation test is used to determine the statistical significance of the results. We performed the phase synchronization analysis on the data from five volunteers for an event-related finger-tapping task. Functional maps were created that provide information on the interrelations between the instantaneous phases of the reference function and the voxel time series in a whole-brain fMRI activation data set. We conclude that this method of analysis is useful for revealing additional information on the complex nature of the fMRI time series. CI - Copyright 2002 Wiley-Liss, Inc. AD - Department of Physics, University of Wisconsin, Madison, Wisconsin, USA. laird@mr.radiology.wisc.edu FAU - Laird, Angela R AU - Laird AR FAU - Rogers, Baxter P AU - Rogers BP FAU - Carew, John D AU - Carew JD FAU - Arfanakis, Konstantinos AU - Arfanakis K FAU - Moritz, Chad H AU - Moritz CH FAU - Meyerand, M Elizabeth AU - Meyerand ME LA - eng PT - Journal Article CY - United States TA - Hum Brain Mapp JID - 9419065 SB - IM MH - Adult MH - *Algorithms MH - Biological Clocks/*physiology MH - Brain/*physiology MH - Brain Mapping/*methods MH - Data Interpretation, Statistical MH - Evoked Potentials/*physiology MH - Evoked Potentials, Motor/physiology MH - Fingers/innervation MH - Human MH - Laterality/physiology MH - Magnetic Resonance Imaging/*methods MH - Motor Cortex/anatomy & histology/physiology MH - Movement/physiology MH - *Nonlinear Dynamics MH - Psychomotor Performance/physiology MH - Reaction Time/physiology MH - Statistics MH - Time Factors EDAT- 2002/04/16 10:00 MHDA- 2002/07/27 10:01 AID - 10.1002/hbm.10027 [pii] PST - ppublish SO - Hum Brain Mapp 2002 Jun;16(2):71-80. 175: Baranowski R, et al. Assessment of the RR versus Q...[PMID:11953908]Related Articles, Books, LinkOut UI - 21950812 PMID- 11953908 DA - 20020415 DCOM- 20020522 IS - 0022-0736 VI - 35 IP - 2 DP - 2002 Apr TI - Assessment of the RR versus QT relation by a new symbolic dynamics method. Gender differences in repolarization dynamics. PG - 95-103 AB - A new method based on symbolic dynamics was applied to assess RR-QT dynamics and to compare gender differences. Segments of 10,000 RR and QT from the night were selected. The values of RR and QT were coded as follows. Each RR and QT interval was compared with their means in the last 50 beats [xRR, xQT]; when the interval was larger than x + delta then it was coded as a "2", where delta is the tolerance parameter; when it was less than x - delta-the code was a "0"; when it was larger than x-delta and and the less than x+delta-then it was coded as a "1." The tolerance parameter "delta" was equal to 10 ms for RR and 4 ms for QT. We obtained pairs of symbols representing the values of RR and QT-symbolic words. The results were presented in form of the probability density of the symbolic words. Mean RR, mean QT, SDRR, SDQT, QTc (Bazett formula) were also calculated. Electrocardiogram data of healthy individuals: 20 women and 20 men (mean age 39 +/- 12) were analyzed. There were significant gender differences in RR-QT dynamics. During heart rate acceleration the probability of QT shortening (the probability of the word "00") was higher in men than in women (P =.003). During heart rate deceleration QT lengthening (the word "22") was more frequently observed in men than in women (P =.003) as well. The QT reaction to RR interval changes is less complex in women than in men. In discriminant analysis, when QTc was ignored in the model, the RR-QT dynamics separated genders with 67% accuracy (chi(2) = 9.1, P <.003). RR-QT dynamics can be analyzed with symbolic dynamics methods. The gender differences in repolarization are not only due to QTc duration alone but also result from the dependence of the duration of QT on the RR duration. AD - National Institute of Cardiology Warsaw, Poland. rbaranowskI@ikard.waw.pl FAU - Baranowski, Rafal AU - Baranowski R FAU - Zebrowski, Jan J AU - Zebrowski JJ LA - eng PT - Evaluation Studies PT - Journal Article CY - United States TA - J Electrocardiol JID - 0153605 SB - IM MH - Adult MH - Age Factors MH - Aged MH - Comparative Study MH - *Electrocardiography MH - Female MH - Heart Rate/*physiology MH - Human MH - Male MH - *Nonlinear Dynamics MH - Observer Variation MH - Reference Values MH - *Sex MH - Statistics MH - Support, Non-U.S. Gov't MH - *Symbolism EDAT- 2002/04/16 10:00 MHDA- 2002/05/25 10:01 AID - ajelc0350095 [pii] PST - ppublish SO - J Electrocardiol 2002 Apr;35(2):95-103. 176: Natarajan V, et al. Comparison of linear gradient...[PMID:11948443]Related Articles, Books, LinkOut UI - 21942185 PMID- 11948443 DA - 20020411 DCOM- 20020905 LR - 20021101 IS - 0006-3592 VI - 78 IP - 4 DP - 2002 May 20 TI - Comparison of linear gradient and displacement separations in ion-exchange systems. PG - 365-75 AB - The linear gradient mode of chromatography is the most widely employed mode of operation in ion-exchange chromatographic separations. However, in recent years, the displacement mode has received considerable attention because of its promise of high throughput and high resolution. To enable a comparison of these two modes of chromatography, it is essential to identify the optimum operating conditions for each. We employed an iterative algorithm to carry out the necessary optimization. The Steric Mass Action model of ion-exchange chromatography is used in concert with the solid-film linear-driving force model to describe the chromatographic behavior of the solutes in these systems. The performances of displacement and gradient modes of chromatography are compared for different types of separation problems. It turns out that for "easy" separations, both the modes are equally effective. However, for challenging separations, the displacement mode is superior to the gradient mode. Our results shed significant light on the performance of gradient and displacement modes in protein ion-exchange systems. CI - Copyright 2002 Wiley Periodicals, Inc. AD - Department of Chemical Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA. FAU - Natarajan, V AU - Natarajan V FAU - Ghose, S AU - Ghose S FAU - Cramer, S M AU - Cramer SM LA - eng PT - Journal Article CY - United States TA - Biotechnol Bioeng JID - 7502021 RN - 0 (Proteins) RN - 0 (Resins, Plant) RN - 9007-43-6 (Cytochrome c) RN - 9012-36-6 (Sepharose) RN - 9035-75-0 (Chymotrypsinogen) RN - EC 3.1.27.5 (Ribonuclease, Pancreatic) SB - IM MH - Adsorption MH - *Algorithms MH - Animal MH - Cattle MH - Chromatography, Ion Exchange/*instrumentation/*methods MH - Chymotrypsinogen/isolation & purification MH - Comparative Study MH - Computer Simulation MH - Cytochrome c/isolation & purification MH - Equipment Design MH - Horses MH - *Models, Chemical MH - Nonlinear Dynamics MH - Proteins/*isolation & purification MH - Quality Control MH - Resins, Plant/chemistry MH - Ribonuclease, Pancreatic/isolation & purification MH - Sensitivity and Specificity MH - Sepharose/chemistry/isolation & purification MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/04/12 10:00 MHDA- 2002/09/06 10:01 AID - 10.1002/bit.10231 [pii] PST - ppublish SO - Biotechnol Bioeng 2002 May 20;78(4):365-75. 177: Umur A, et al. Monochorionic twins and twin-...[PMID:11945087]Related Articles, Books, LinkOut UI - 21946011 PMID- 11945087 DA - 20020411 DCOM- 20020807 LR - 20021029 IS - 0143-4004 VI - 23 IP - 2-3 DP - 2002 Feb-Mar TI - Monochorionic twins and twin-twin transfusion syndrome: the protective role of arterio-arterial anastomoses. PG - 201-9 AB - Unidirectional arterio-venous (AV) anastomoses often result in twin-twin transfusion syndrome (TTTS). Additional oppositely directed anastomoses may compensate for the circulatory imbalance and either prevent, delay the onset, or moderate the severity of TTTS. Intuitively, higher pressure gradient, oppositely-directed AV anastomoses (indicated as VA) would be expected to compensate better for TTTS than lower pressure gradient arterio-arterial (AA) anastomoses. However, clinical evidence suggests AA anastomoses compensate more efficaciously, because virtually all non-TTTS monochorionic twin placentas have AAs (84 per cent), contrary to TTTS placentas, where only 30 per cent have an AA. We sought to explain this observation by comparing the capabilities of various size VA and AA anastomoses to compensate for the effects of the primary AV. As study design we used a previously developed mathematical computer model of TTTS to determine ranges of anastomotic vascular resistances which cause varying fetal and amniotic fluid discordances. Anastomotic resistances were related with the radii of their feeding vessels, using fractal geometry modelling to mimic the placental vascular tree, and various assumptions regarding arterial blood flow. The results were as follows. An AA anastomosis of equal size as the feeding artery of an AV or VA has a significantly smaller resistance. The primary AV anastomosis may be compensated by both VA as well as AA anastomoses. However, VA transfusion adequately compensates AV flow only for a small range of VA to AV vascular radius ratios. In contrast, AA transfusion compensates the AV flow for a much wider range of AA to AV vascular radius ratios. In conclusion, the wider range of AA than VA radii for adequate compensation of the AV explains the finding that an AA protects more frequently than a VA of similar size against the manifestations of TTTS. These results may possibly allow future risk stratification of monochorionic twins by non-invasive sonographic assessment of the size and type of anastomoses. CI - Copyright 2002 Elsevier Science Ltd. AD - Laser Center and Department of Obstetrics and Gynecology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands. FAU - Umur, A AU - Umur A FAU - van Gemert, M J C AU - van Gemert MJ FAU - Nikkels, P G J AU - Nikkels PG FAU - Ross, M G AU - Ross MG LA - eng ID - HL 40899/HL/NHLBI PT - Journal Article CY - England TA - Placenta JID - 8006349 SB - IM MH - Adult MH - Amniotic Fluid/physiology MH - Arterio-Arterial Fistula/*physiopathology MH - Female MH - Fetal Blood/physiology MH - Fetofetal Transfusion/*physiopathology/prevention & control MH - Fractals MH - Hemodynamics/physiology MH - Human MH - Microcirculation/*physiology MH - Models, Biological MH - Nonlinear Dynamics MH - Placenta/blood supply MH - Pregnancy MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. MH - *Twins, Monozygotic EDAT- 2002/04/12 10:00 MHDA- 2002/08/08 10:01 AID - 10.1053/plac.2001.0758 [doi] AID - S0143400401907581 [pii] PST - ppublish SO - Placenta 2002 Feb-Mar;23(2-3):201-9. 178: Holt TA. A chaotic model for tight dia...[PMID:11942997]Related Articles, Books, LinkOut UI - 21940417 PMID- 11942997 DA - 20020410 DCOM- 20020924 IS - 0742-3071 VI - 19 IP - 4 DP - 2002 Apr TI - A chaotic model for tight diabetes control. PG - 274-8 AB - The principles of non-linear dynamics ('chaos') theory may improve our understanding of the difficulties of blood glucose control in diabetes, may lead to alternative control strategies in selected individuals, and might even enlighten the issues involved in automated glucose control for the future. Possible experimental and mathematical methods of identifying chaotic behaviour in glucose profiles are briefly discussed. Advice based on this model is suggested for those aiming at tight blood glucose control. AD - The Danby Practice, Dale End Surgery, Danby, Whitby, UK. FAU - Holt, T A AU - Holt TA LA - eng PT - Journal Article CY - England TA - Diabet Med JID - 8500858 RN - 0 (Blood Glucose) SB - IM MH - Automation MH - Blood Glucose/*metabolism MH - Diabetes Mellitus/*blood MH - Diabetes Mellitus, Non-Insulin-Dependent/blood MH - Human MH - Islets of Langerhans/physiopathology MH - Models, Biological MH - Nonlinear Dynamics EDAT- 2002/04/12 10:00 MHDA- 2002/09/25 06:00 AID - 662 [pii] PST - ppublish SO - Diabet Med 2002 Apr;19(4):274-8. 179: Pali T, et al. Structural studies on membran...[PMID:11944054]Related Articles, Books, LinkOut UI - 21940358 PMID- 11944054 DA - 20020410 DCOM- 20020703 IS - 1425-8153 VI - 7 IP - 1 DP - 2002 TI - Structural studies on membrane proteins using non-linear spin label EPR spectroscopy. PG - 87-91 AB - Non-linear electron spin resonance (EPR) techniques suitable for measuring proximity relationships in membranes are reviewed. These were developed during the past decade in order to measure changes sensitively in the spin-lattice relaxation time (T1) of nitroxyl spin labels covalently attached to membrane lipids or proteins. In combination with paramagnetic quenching agents and double spin-labelling, the methods were further developed for distance measurements. Selected examples are given to illustrate different methods, and types of data obtained for both integral and peripheral membrane proteins. AD - Institute of Biophysics, Biological Research Centre, P.O.Box 521, 6701 Szeged, Hungary. tpali@nucleus.szbk.u-szeged.hu FAU - Pali, Tibor AU - Pali T FAU - Marsh, Derek AU - Marsh D LA - eng PT - Journal Article CY - Poland TA - Cell Mol Biol Lett JID - 9607427 RN - 0 (Membrane Lipids) RN - 0 (Membrane Proteins) RN - 0 (Spin Labels) SB - IM MH - Electron Spin Resonance Spectroscopy/*methods MH - Membrane Lipids/chemistry MH - Membrane Proteins/*chemistry MH - Nonlinear Dynamics MH - Protein Conformation MH - Spin Labels MH - Support, Non-U.S. Gov't EDAT- 2002/04/11 10:00 MHDA- 2002/07/04 10:01 PST - ppublish SO - Cell Mol Biol Lett 2002;7(1):87-91. 180: Billings L, et al. Exciting chaos with noise: un...[PMID:11942524]Related Articles, Books, LinkOut UI - 21939036 PMID- 11942524 DA - 20020410 DCOM- 20020920 IS - 0303-6812 VI - 44 IP - 1 DP - 2002 Jan TI - Exciting chaos with noise: unexpected dynamics in epidemic outbreaks. PG - 31-48 AB - In this paper, we identify a mechanism for chaos in the presence of noise. In a study of the SEIR model, which predicts epidemic outbreaks in childhood diseases, we show how chaotic dynamics can be attained by adding stochastic perturbations at parameters where chaos does not exist apriori. Data recordings of epidemics in childhood diseases are still argued as deterministic chaos. There also exists noise due to uncertainties in the contact parameters between those who are susceptible and those who are infected, as well as random fluctuations in the population. Although chaos has been found in deterministic models, it only occurs in parameter regions that require a very large population base or other large seasonal forcing. Our work identifies the mechanism whereby chaos can be induced by noise for realistic parameter regions of the deterministic model where it does not naturally occur. AD - Department of Mathematical Sciences, Montclair State University, Upper Montclair, NJ 07043, USA. billingsl@mail.montclair.edu FAU - Billings, L AU - Billings L FAU - Schwartz, I B AU - Schwartz IB LA - eng PT - Journal Article CY - Germany TA - J Math Biol JID - 7502105 SB - IM MH - Child MH - Child, Preschool MH - *Disease Outbreaks MH - Human MH - Measles/*epidemiology MH - *Models, Biological MH - *Nonlinear Dynamics MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/04/11 10:00 MHDA- 2002/09/21 10:01 PST - ppublish SO - J Math Biol 2002 Jan;44(1):31-48. 181: Pascale R. Surfing the edge of chaos. In...[PMID:11942092]Related Articles, Books, LinkOut UI - 21939792 PMID- 11942092 DA - 20020410 DCOM- 20020503 IS - 1527-3547 VI - 45 IP - 2 DP - 2002 Mar-Apr TI - Surfing the edge of chaos. Interview by Joe Flower and Patrice Guillaume. PG - 16-20 FAU - Pascale, Richard AU - Pascale R LA - eng PT - Interview CY - United States TA - Health Forum J JID - 100884164 SB - H MH - Efficiency, Organizational MH - Guidelines MH - Health Services Administration/*trends MH - *Leadership MH - *Nonlinear Dynamics MH - *Organizational Innovation MH - Probability MH - Social Change MH - United States EDAT- 2002/04/11 10:00 MHDA- 2002/05/04 10:01 PST - ppublish SO - Health Forum J 2002 Mar-Apr;45(2):16-20. 182: Petermann M, et al. [A road between order and dis...[PMID:11941833]Related Articles, Books, LinkOut UI - 21939530 PMID- 11941833 DA - 20020410 DCOM- 20020718 IS - 0253-0465 VI - 92 IP - 10 DP - 1999 Oct TI - [A road between order and disorder] PG - 76-80 FAU - Petermann, M AU - Petermann M FAU - Waeny, P AU - Waeny P LA - fre PT - Journal Article TT - Un chemin entre l'ordre et le desordre. CY - Switzerland TA - Krankenpfl Soins Infirm JID - 8000153 SB - N MH - Clinical Competence MH - Curriculum MH - *Education, Nursing, Diploma Programs MH - Faculty, Nursing MH - Human MH - Nonlinear Dynamics MH - Switzerland EDAT- 2002/04/11 10:00 MHDA- 2002/07/19 10:01 PST - ppublish SO - Krankenpfl Soins Infirm 1999 Oct;92(10):76-80. 183: Baraduc P, et al. Population computation of vec...[PMID:11936964]Related Articles, Books, LinkOut UI - 21935756 PMID- 11936964 DA - 20020408 DCOM- 20020429 IS - 0899-7667 VI - 14 IP - 4 DP - 2002 Apr TI - Population computation of vectorial transformations. PG - 845-71 AB - Many neurons of the central nervous system are broadly tuned to some sensory or motor variables. This property allows one to assign to each neuron a preferred attribute (PA). The width of tuning curves and the distribution of PAs in a population of neurons tuned to a given variable define the collective behavior of the population. In this article, we study the relationship of the nature of the tuning curves, the distribution of PAs, and computational properties of linear neuronal populations. We show that noise-resistant distributed linear algebraic processing and learning can be implemented by a population of cosine tuned neurons assuming a nonuniform but regular distribution of PAs. We extend these results analytically to the noncosine tuning and uniform distribution case and show with a numerical simulation that the results remain valid for a nonuniform regular distribution of PAs for broad noncosine tuning curves. These observations provide a theoretical basis for modeling general nonlinear sensorimotor transformations as sets of local linearized representations. AD - INSERM U483, Universite Pierre et Marie Curie 75005 Paris, France. Pierre.Baraduc@snv.jussieu.fr FAU - Baraduc, Pierre AU - Baraduc P FAU - Guigon, Emmanuel AU - Guigon E LA - eng PT - Journal Article CY - United States TA - Neural Comput JID - 9426182 SB - IM MH - Algorithms MH - Linear Models MH - Movement/physiology MH - Neural Networks (Computer) MH - Neural Pathways/physiology MH - Neurons/*physiology MH - Neurons, Afferent/physiology MH - Nonlinear Dynamics MH - Population EDAT- 2002/04/09 10:00 MHDA- 2002/05/01 10:01 AID - 10.1162/089976602317318983 [doi] PST - ppublish SO - Neural Comput 2002 Apr;14(4):845-71. 184: Wiskott L, et al. Slow feature analysis: unsupe...[PMID:11936959]Related Articles, Books, LinkOut UI - 21935751 PMID- 11936959 DA - 20020408 DCOM- 20020429 IS - 0899-7667 VI - 14 IP - 4 DP - 2002 Apr TI - Slow feature analysis: unsupervised learning of invariances. PG - 715-70 AB - Invariant features of temporally varying signals are useful for analysis and classification. Slow feature analysis (SFA) is a new method for learning invariant or slowly varying features from a vectorial input signal. It is based on a nonlinear expansion of the input signal and application of principal component analysis to this expanded signal and its time derivative. It is guaranteed to find the optimal solution within a family of functions directly and can learn to extract a large number of decorrelated features, which are ordered by their degree of invariance. SFA can be applied hierarchically to process high-dimensional input signals and extract complex features. SFA is applied first to complex cell tuning properties based on simple cell output, including disparity and motion. Then more complicated input-output functions are learned by repeated application of SFA. Finally, a hierarchical network of SFA modules is presented as a simple model of the visual system. The same unstructured network can learn translation, size, rotation, contrast, or, to a lesser degree, illumination invariance for one-dimensional objects, depending on only the training stimulus. Surprisingly, only a few training objects suffice to achieve good generalization to new objects. The generated representation is suitable for object recognition. Performance degrades if the network is trained to learn multiple invariances simultaneously. AD - Computational Neurobiology Laboratory, Salk Institute for Biological Studies, San Diego, CA 92168, USA. l.wiskott@biologie.hu-berlin.de FAU - Wiskott, Laurenz AU - Wiskott L FAU - Sejnowski, Terrence J AU - Sejnowski TJ LA - eng PT - Journal Article CY - United States TA - Neural Comput JID - 9426182 SB - IM MH - Algorithms MH - *Artificial Intelligence MH - Computer Simulation MH - *Neural Networks (Computer) MH - Nonlinear Dynamics MH - *Pattern Recognition MH - Photoreceptors MH - Support, Non-U.S. Gov't MH - Visual Perception EDAT- 2002/04/09 10:00 MHDA- 2002/05/01 10:01 AID - 10.1162/089976602317318938 [doi] PST - ppublish SO - Neural Comput 2002 Apr;14(4):715-70. 185: Doiron B, et al. Ghostbursting: a novel neuron...[PMID:11932557]Related Articles, Books, LinkOut UI - 21929946 PMID- 11932557 DA - 20020404 DCOM- 20020625 IS - 0929-5313 VI - 12 IP - 1 DP - 2002 Jan-Feb TI - Ghostbursting: a novel neuronal burst mechanism. PG - 5-25 AB - Pyramidal cells in the electrosensory lateral line lobe (ELL) of weakly electric fish have been observed to produce high-frequency burst discharge with constant depolarizing current (Turner et al., 1994). We present a two-compartment model of an ELL pyramidal cell that produces burst discharges similar to those seen in experiments. The burst mechanism involves a slowly changing interaction between the somatic and dendritic action potentials. Burst termination occurs when the trajectory of the system is reinjected in phase space near the "ghost" of a saddle-node bifurcation of fixed points. The burst trajectory reinjection is studied using quasi-static bifurcation theory, that shows a period doubling transition in the fast subsystem as the cause of burst termination. As the applied depolarization is increased, the model exhibits first resting, then tonic firing, and finally chaotic bursting behavior, in contrast with many other burst models. The transition between tonic firing and burst firing is due to a saddle-node bifurcation of limit cycles. Analysis of this bifurcation shows that the route to chaos in these neurons is type I intermittency, and we present experimental analysis of ELL pyramidal cell burst trains that support this model prediction. By varying parameters in a way that changes the positions of both saddle-node bifurcations in parameter space, we produce a wide gallery of burst patterns, which span a significant range of burst time scales. AD - Physics Department, University of Ottawa, 150 Louis Pasteur, Ontario, Canada K1N 6N5. bdoiron@physics.uottawa.ca FAU - Doiron, Brent AU - Doiron B FAU - Laing, Carlo AU - Laing C FAU - Longtin, Andre AU - Longtin A FAU - Maler, Leonard AU - Maler L LA - eng PT - Journal Article CY - United States TA - J Comput Neurosci JID - 9439510 RN - 0 (Sodium Channels) RN - 7440-23-5 (Sodium) RN - 7440-70-2 (Calcium) SB - IM MH - Action Potentials/*physiology MH - Animal MH - Biological Clocks/physiology MH - Brain Stem/cytology/*physiology MH - Calcium/metabolism MH - Cell Compartmentation/physiology MH - Dendrites/physiology/ultrastructure MH - Electric Fish/anatomy & histology/*physiology MH - *Electricity MH - *Models, Neurological MH - Nonlinear Dynamics MH - Pyramidal Cells/*physiology MH - Sensation/*physiology MH - Sodium/metabolism MH - Sodium Channels/physiology MH - Support, Non-U.S. Gov't MH - Time Factors EDAT- 2002/04/05 10:00 MHDA- 2002/06/26 10:01 PST - ppublish SO - J Comput Neurosci 2002 Jan-Feb;12(1):5-25. 186: Matassini L, et al. Software corrections of vocal...[PMID:11932030]Related Articles, Books, LinkOut UI - 21929599 PMID- 11932030 DA - 20020404 DCOM- 20020709 IS - 0169-2607 VI - 68 IP - 2 DP - 2002 May TI - Software corrections of vocal disorders. PG - 135-45 AB - We discuss how vocal disorders can be post-corrected via a simple nonlinear noise reduction scheme. This work is motivated by the need of a better understanding of voice dysfunctions. This would entail a 2-fold advantage for affected patients: Physicians can perform better surgical interventions and on the other hand researchers can try to build up devices that can help to improve voice quality, i.e. in a phone conversation, avoiding any surgical treatment. As a first step, a proper signal classification is performed, through the idea of geometric signal separation in a feature space. Then through the analysis of the different regions populated by the samples coming from healthy people and from patients affected by T1A glottis cancer, one is able to understand which kind of interventions are necessary in order to correct the illness, i.e. to move the corresponding feature vector from the sick region to the healthy one. We discuss such a filter and show its performance. AD - Max-Planck-Institut fur Physik komplexer Systeme, Nothnitzer Strasse 38, D 01187 Dresden, Germany. lorenzo@mpipks-dresden.mpg.de FAU - Matassini, Lorenzo AU - Matassini L FAU - Manfredi, Claudia AU - Manfredi C LA - eng PT - Journal Article CY - Ireland TA - Comput Methods Programs Biomed JID - 8506513 SB - IM MH - Human MH - Nonlinear Dynamics MH - *Software MH - Voice Disorders/physiopathology/*rehabilitation EDAT- 2002/04/05 10:00 MHDA- 2002/07/10 10:01 AID - S0169260701001614 [pii] PST - ppublish SO - Comput Methods Programs Biomed 2002 May;68(2):135-45. 187: Baker RJ, et al. Auditory filter nonlinearity ...[PMID:11931310]Related Articles, Books, LinkOut UI - 21928280 PMID- 11931310 DA - 20020404 DCOM- 20020430 IS - 0001-4966 VI - 111 IP - 3 DP - 2002 Mar TI - Auditory filter nonlinearity in mild/moderate hearing impairment. PG - 1330-9 AB - Sensorineural hearing loss has frequently been shown to result in a loss of frequency selectivity. Less is known about its effects on the level dependence of selectivity that is so prominent a feature of normal hearing. The aim of the present study is to characterize such changes in nonlinearity as manifested in the auditory filter shapes of listeners with mild/moderate hearing impairment. Notched-noise masked thresholds at 2 kHz were measured over a range of stimulus levels in hearing-impaired listeners with losses of 20-50 dB. Growth-of-masking functions for different notch widths are more parallel for hearing-impaired than for normal-hearing listeners, indicating a more linear filter. Level-dependent filter shapes estimated from the data show relatively little change in shape across level. The loss of nonlinearity is also evident in the input/output functions derived from the fitted filter shapes. Reductions in nonlinearity are clearly evident even in a listener with only 20-dB hearing loss. AD - Human Communication and Deafness, School of Education, University Of Manchester, United Kingdom. richard.baker@man.ac.uk FAU - Baker, Richard J AU - Baker RJ FAU - Rosen, Stuart AU - Rosen S LA - eng PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 SB - IM MH - Acoustic Stimulation MH - Adult MH - Auditory Threshold/*physiology MH - Basilar Membrane/physiopathology MH - Female MH - Hair Cells, Outer/physiopathology MH - Hearing Loss, High-Frequency/diagnosis/physiopathology MH - Hearing Loss, Noise-Induced/diagnosis/physiopathology MH - Hearing Loss, Sensorineural/diagnosis/*physiopathology MH - Human MH - Loudness Perception/physiology MH - Male MH - Middle Age MH - Nonlinear Dynamics MH - Perceptual Masking/physiology MH - Pitch Discrimination/physiology MH - Sound Spectrography MH - Support, Non-U.S. Gov't EDAT- 2002/04/05 10:00 MHDA- 2002/05/01 10:01 PST - ppublish SO - J Acoust Soc Am 2002 Mar;111(3):1330-9. 188: Dahaba AA, et al. End-stage renal failure reduc...[PMID:11927475]Related Articles, Books, LinkOut UI - 21924571 PMID- 11927475 DA - 20020402 DCOM- 20020819 IS - 0832-610X VI - 49 IP - 4 DP - 2002 Apr TI - End-stage renal failure reduces central clearance and prolongs the elimination half life of remifentanil. PG - 369-74 AB - PURPOSE: To evaluate the pharmacokinetics of remifentanil in 13 end-stage renal failure patients compared to matched control patients with normal renal function. METHODS: Remifentanil was infused for 20 min at a rate of 0.1 microg x kg(-1) x min(-1). Serial arterial blood samples (3 mL) were drawn at the start of infusion (zero), five, ten, 15, 20, 22.5, 25, 27.5, 30, 35, 40, 45, 50, 55 and 60 min. Blood samples were immediately preserved with citric acid and chilled on ice. High performance liquid chromatography-tandem mass spectrometry concentration assay was performed using GI 95779B internal standard. RESULTS: A two-compartment pharmacokinetic model provided an adequate fit for individual patient data. There was no difference in the mean +/- SD distribution half life (t1/2) between the renal failure group (1.65 +/- 0.7 min) and the control group (1.58 +/- 0.54 min). There was a significant difference in the central clearance (Cl(c)) and elimination half life (t1/2) ss) between the renal failure group (28 +/- 7 mL x kg(-1) x min(-1) and 18.86 +/- 2.06 min, respectively) and the control group (46.3 +/- 13.8 mL x kg(-1) x min(-1) and 16.35 +/- 2.99 min, respectively). Remifentanil blood concentrations were significantly higher in the renal failure group than in the control group. CONCLUSION: We have demonstrated a significant reduction in the Cl(c) and a prolongation of t1/2 ss of remifentanil in end-stage renal failure patients. While statistically significant, these variations in the pharmacokinetics of remifentanil were clinically modest and may be explained by a reduced volume of distribution in the period following hemodialysis. AD - Departments of Anaesthesiology and Intensive Care Medicine, and Medical Chemistry and Pregl Laboratory, Karl-Franzens University, Graz, Austria. Ashraf.Dahaba@kfunigraz.ac.at FAU - Dahaba, Ashraf A AU - Dahaba AA FAU - Oettl, Karl AU - Oettl K FAU - von Klobucar, Fedor AU - von Klobucar F FAU - Reibnegger, Gilbert AU - Reibnegger G FAU - List, Werner F AU - List WF LA - eng PT - Clinical Trial PT - Journal Article PT - Randomized Controlled Trial CY - Canada TA - Can J Anaesth JID - 8701709 RN - 0 (Analgesics, Opioid) RN - 0 (Piperidines) RN - 132875-61-7 (remifentanil) SB - IM MH - Analgesics, Opioid/*pharmacokinetics MH - Area Under Curve MH - Chromatography, High Pressure Liquid MH - Comparative Study MH - Female MH - Half-Life MH - Human MH - Kidney Failure, Chronic/*metabolism MH - Male MH - Middle Age MH - Nonlinear Dynamics MH - Piperidines/*pharmacokinetics MH - Prospective Studies MH - Spectrum Analysis, Mass EDAT- 2002/04/03 10:00 MHDA- 2002/08/20 10:01 PST - ppublish SO - Can J Anaesth 2002 Apr;49(4):369-74. 189: Dorow C, et al. [Experimental model of tooth ...[PMID:11921633]Related Articles, Books, LinkOut UI - 21919787 PMID- 11921633 DA - 20020329 DCOM- 20020528 IS - 0013-5585 VI - 47 IP - 1-2 DP - 2002 Jan-Feb TI - [Experimental model of tooth mobility in the human "in vivo"] PG - 20-5 AB - The aim of the present study was to investigate experimentally the mechanical properties of tooth deflection under external loading. These properties have a significant impact on tooth movement during orthodontic treatment. The stresses and strains caused by tooth movement influence bone remodelling, which is the basis of orthodontic treatment. The movement of a tooth as a direct reaction to the forces acting on it is termed "initial" movement. It is nonlinear and has a clearly time-dependent component. While the initial tooth movement represents the totality of the reaction mechanisms of all the tissues of the tooth unit, it is determined primarily by the mechanical properties of the periodontal ligament (PDL). The PDL is the softest tissue of the tooth unit and is therefore subject to the largest deformations when forces act on the crown of the tooth. The objective of orthodontic treatment is to achieve as precise and rapid tooth movement as possible, without provoking such undesired effects as bone and root resorption. To enable the implementation of an optimal orthodontic force system that meets these requirements, a thorough knowledge of the biomechanics of tooth movement is a must. AD - Universitatsklinik Ulm, Poliklinik fur Kieferorthopadie, Ulm, Germany. christina.dorow@medizin.uni-ulm.de FAU - Dorow, C AU - Dorow C FAU - Krstin, N AU - Krstin N FAU - Sander, F G AU - Sander FG LA - ger PT - Journal Article TT - Experimentelle Untersuchung der Zahnbeweglichkeit am Menschen "in vivo". CY - Germany TA - Biomed Tech (Berl) JID - 1262533 SB - IM MH - Biomechanics MH - English Abstract MH - Human MH - Nonlinear Dynamics MH - Orthodontics, Corrective MH - Periodontal Ligament/physiology MH - Signal Processing, Computer-Assisted MH - Support, Non-U.S. Gov't MH - *Tooth Movement/instrumentation EDAT- 2002/03/30 10:00 MHDA- 2002/05/29 10:01 PST - ppublish SO - Biomed Tech (Berl) 2002 Jan-Feb;47(1-2):20-5. 190: Stoop R, et al. Collective bursting in layer ...[PMID:11918995]Related Articles, Books, LinkOut UI - 21916529 PMID- 11918995 DA - 20020328 DCOM- 20020619 IS - 0926-6410 VI - 13 IP - 3 DP - 2002 May TI - Collective bursting in layer IV. Synchronization by small thalamic inputs and recurrent connections. PG - 293-304 AB - Layer IV is believed to be the cortical signal amplifier, for example, of thalamic signals. A previous spiny stellate recurrent network model of this layer is made more realistic by the addition of inhibitory basket neurons. We study the persistence and characteristics of previously observed collective firing behavior, and investigate what additional features would need to be implemented to generate in vivo type neuronal firing. It is shown that neuronal activity is only coarsely synchronized within the network. By applying methods of noise-cleaning, it emerges that the firing of individual neurons is of low-dimensional hyperchaotic nature, as found in the analysis of measured cat in vivo spike trains. In order to reproduce in vivo firing patterns, it is sufficient to have time-varying thalamic input. Conclusions from low-dimensional hyperchaotic behavior of network-embedded neurons are drawn. We interpret observed in vivo pattern-sharpening features of stimuli and outline possible connections to epilepsy. From our results, it follows that emergent global behavior is likely to be the result of the interaction between comparably simple neuronal components, driven by input specificity. AD - Institut fur Neuroinformatik der Universitat Zurich UNIZH und der Eidgenossischen Technischen Hochschule Zurich ETHZ, Winterthurerstr. 190, CH-8057, Zurich, Switzerland. ruedi@ini.phys.ethz.ch FAU - Stoop, Ruedi AU - Stoop R FAU - Blank, Daniel AU - Blank D FAU - Kern, Albert AU - Kern A FAU - v d Vyver, Jan Jan AU - v d Vyver JJ FAU - Christen, Markus AU - Christen M FAU - Lecchini, Stefano AU - Lecchini S FAU - Wagner, Clemens AU - Wagner C LA - eng PT - Journal Article CY - Netherlands TA - Brain Res Cogn Brain Res JID - 9214304 SB - IM MH - Action Potentials/physiology MH - Afferent Pathways/physiology MH - Animal MH - Cats MH - Cerebral Cortex/*physiology MH - Female MH - Fractals MH - Neural Inhibition/physiology MH - *Neural Networks (Computer) MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Thalamus/*physiology MH - Visual Cortex/physiology EDAT- 2002/03/29 10:00 MHDA- 2002/06/20 10:01 AID - S0926641001001239 [pii] PST - ppublish SO - Brain Res Cogn Brain Res 2002 May;13(3):293-304. 191: Todder D, et al. Dynamic analysis of inter-wor...[PMID:11918446]Related Articles, Books, LinkOut UI - 21915382 PMID- 11918446 DA - 20020328 DCOM- 20020722 IS - 0306-9877 VI - 57 IP - 6 DP - 2001 Dec TI - Dynamic analysis of inter-words time intervals: a method to analyze the structure of communicative signals. PG - 772-9 AB - Speech analyses are usually focused on words as signifiers ignoring inter-words time intervals (IWIs), which are related to the 'form' of speech, rather than to its 'content'. Applying the method of power spectrum analysis to inter-vocalizations time intervals of bird singing, underlying periodic processes were detected. In contrast, human IWIs revealed non-periodicity, which may be random or chaotic. To differentiate between these two possibilities, the non-linear dynamic methods of unstable periodic orbits and correlation dimension were applied to show that IWIs are characterized by a low dimensional chaotic attractor. Its correlation dimension of 3.2 +/- 1.1 suggests a minimum number of four variables underlying the system. The methods developed in the present communication can be further applied: (a) for the measurement of specific alterations in the processes underlying the form of speech in human disorders, i.e., schizophrenia, (b) for the assessment of normal and pathological developmental aspects of speech processes in children; (c) for comparing communicative signals between humans and other species. AD - Department of Psychiatry, Faculty for Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel. FAU - Todder, D AU - Todder D FAU - Avissar, S AU - Avissar S FAU - Schreiber, G AU - Schreiber G LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - Scotland TA - Med Hypotheses JID - 7505668 SB - IM MH - Adult MH - Animal MH - Birds/physiology MH - Female MH - Human MH - Male MH - Middle Age MH - Nonlinear Dynamics MH - Signal Processing, Computer-Assisted MH - *Speech MH - Time Factors MH - Vocalization, Animal RF - 47 EDAT- 2002/03/29 10:00 MHDA- 2002/07/23 10:01 AID - S0306987701914926 [pii] PST - ppublish SO - Med Hypotheses 2001 Dec;57(6):772-9. 192: Verotta D, et al. Non-linear dynamics models ch...[PMID:11916507]Related Articles, Books, LinkOut UI - 21914604 PMID- 11916507 DA - 20020327 DCOM- 20020514 IS - 0025-5564 VI - 176 IP - 2 DP - 2002 Apr TI - Non-linear dynamics models characterizing long-term virological data from AIDS clinical trials. PG - 163-83 AB - Human immunodeficiency virus (HIV) dynamics represent a complicated variant of the text-book case of non-linear dynamics: predator-prey interaction. The interaction can be described as naturally reproducing T-cells (prey) hunted and killed by virus (predator). Virus reproduce and increase in number as a consequence of successful predation; this is countered by the production of T-cells and the reaction of the immune system. Multi-drug anti-HIV therapy attempts to alter the natural dynamics of the predator-prey interaction by decreasing the reproductive capability of the virus and hence predation. These dynamics are further complicated by varying compliance to treatment and insurgence of resistance to treatment. When following the temporal progression of viral load in plasma during therapy one observes a short-term (1-12 weeks) decrease in viral load. In the long-term (more than 12 weeks from the beginning of therapy) the reduction in viral load is either sustained, or it is followed by a rebound, oscillations and a new (generally lower than at the beginning of therapy) viral load level. Biomathematicians have investigated these dynamics by means of simulations. However the estimation of the parameters associated with the dynamics from real data has been mostly limited to the case of simplified, in particular linearized, models. Linearized model can only describe the short-term changes of viral load during therapy and can only predict (apparent) suppression. In this paper we put forward relatively simple models to characterize long-term virus dynamics which can incorporate different factors associated with resurgence: (Fl) the intrinsic non-linear HIV-1 dynamics, (F2) drug exposure and in particular compliance to treatment, and (F3) insurgence of resistant HIV-1 strains. The main goal is to obtain models which are mathematically identifiable given only measurements of viral load, while retaining the most crucial features of HIV dynamics. For the purpose of illustration we demonstrate an application of the models using real AIDS clinical trial data involving patients treated with a combination of anti-retroviral agents using a model which incorporates compliance data. AD - Department of Biopharmaceutical Sciences, School of Pharmacy, University of California, Box 0446, San Francisco, CA 94143-0446, USA. davide@ariel1.ucsf.edu FAU - Verotta, Davide AU - Verotta D FAU - Schaedeli, Franziska AU - Schaedeli F LA - eng ID - GM51197/GM/NIGMS PT - Journal Article CY - United States TA - Math Biosci JID - 0103146 RN - 0 (Anti-HIV Agents) SB - IM MH - Acquired Immunodeficiency Syndrome/*drug therapy/*virology MH - Anti-HIV Agents/*pharmacology/therapeutic use MH - HIV-1/*growth & development MH - Human MH - Longitudinal Studies MH - *Models, Biological MH - Nonlinear Dynamics MH - Patient Compliance MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. MH - Viral Load EDAT- 2002/03/28 10:00 MHDA- 2002/05/15 10:01 AID - S0025556402000901 [pii] PST - ppublish SO - Math Biosci 2002 Apr;176(2):163-83. 193: De Leenheer EM, et al. Longitudinal and cross-sectio...[PMID:11915881]Related Articles, Books, LinkOut UI - 21910338 PMID- 11915881 DA - 20020326 DCOM- 20020409 LR - 20021203 IS - 0003-4894 VI - 111 IP - 3 Pt 1 DP - 2002 Mar TI - Longitudinal and cross-sectional phenotype analysis in a new, large Dutch DFNA2/KCNQ4 family. PG - 267-74 AB - We analyzed hearing thresholds, speech recognition scores, and vestibular responses in 32 affected persons in a large family with DFNA2/KCNQ4-related hearing impairment caused by a W276S missense mutation. Linear regression analysis of individual longitudinal data revealed significant threshold progression (1 dB/y) and offset (at age zero). The mean offset thresholds were 5, 21, 40, 39, 31, and 51 dB hearing level (HL) at 0.25, 0.5, 1, 2, 4, and 8 kHz, respectively. Cross-sectional analysis of last-visit thresholds against age produced less-steep slopes and higher offset thresholds. Nonlinear regression analysis of last-visit phoneme recognition scores against age in 25 cases showed that speech recognition did not deteriorate before the third decade. A hyperactive vestibuloocular reflex was found in 3 of 11 cases: 2 persons were especially susceptible to motion sickness. Persons with this KCNQ4 mutation showed congenital, progressive high-frequency impairment without substantial loss of speech recognition during the first decades of life. AD - Department of Otorhinolaryngology, University Medical Center St Radboud Nijmegen, The Netherlands. FAU - De Leenheer, Els M R AU - De Leenheer EM FAU - Huygen, Patrick L M AU - Huygen PL FAU - Coucke, Paul J AU - Coucke PJ FAU - Admiraal, Ronald J C AU - Admiraal RJ FAU - van Camp, G AU - van Camp G FAU - Cremers, Cor W AU - Cremers CW LA - eng PT - Journal Article CY - United States TA - Ann Otol Rhinol Laryngol JID - 0407300 RN - 0 (KCNQ4 protein) RN - 0 (Potassium Channels) SB - AIM SB - IM MH - Adolescent MH - Adult MH - Age Distribution MH - Aged MH - Audiometry MH - Auditory Threshold MH - Child MH - Chromosome Mapping MH - Cross-Sectional Studies MH - *DNA Mutational Analysis MH - Disease Progression MH - Female MH - Hearing Loss, Sensorineural/diagnosis/*epidemiology/*genetics/physiopathology MH - Human MH - Linear Models MH - Linkage (Genetics) MH - Longitudinal Studies MH - Male MH - Middle Age MH - Mutation, Missense/genetics MH - Netherlands/epidemiology MH - Nonlinear Dynamics MH - Pedigree MH - Phenotype MH - Potassium Channels/*genetics MH - Support, Non-U.S. Gov't MH - Vestibular Function Tests EDAT- 2002/03/28 10:00 MHDA- 2002/04/10 10:01 PST - ppublish SO - Ann Otol Rhinol Laryngol 2002 Mar;111(3 Pt 1):267-74. 194: Patuzzi R. Non-linear aspects of outer h...[PMID:11914520]Related Articles, Books, LinkOut UI - 21911642 PMID- 11914520 DA - 20020326 DCOM- 20020607 IS - 1420-3030 VI - 7 IP - 1 DP - 2002 Jan-Feb TI - Non-linear aspects of outer hair cell transduction and the temporary threshold shifts after acoustic trauma. PG - 17-20 AB - The 200-Hz cochlear microphonic potential (CM) and the compound action potential (CAP) of the auditory nerve evoked by tone-bursts were recorded in the basal turn of the cochlea of anaesthetised guinea pigs, before and after exposure to traumatic high-frequency tones that produce a temporary threshold shift (TTS) in this cochlear region. The drop in CM and the TTS were highly correlated, suggesting that it is the disruption of the outer hair cells generating the CM that causes the TTS. The previously measured rise in endocochlear potential and drop in organ of Corti K+ levels suggest that the TTS is due to a temporary closure of outer hair cell mechanoelectrical transduction (MET) channels, which produces a drop in the mechanical sensitivity of the organ of Corti, due to disruption of the active process provided by outer hair cells. The time course of the onset and recovery of TTS is consistent with a kinetic folding and refolding of MET channels over a time course of hours and days. Mathematical modelling of this putative channel folding suggests that TTS recovery may be accelerated by the presentation of additional sounds during the recovery period. We present electrophysiological data (CM and CAP measurements) showing that this accelerated recovery occurs. Using two-tone complexes (phase-locked 5- and 10-kHz traumatic tones, and 10-kHz traumatic tones with 25-Hz bias tones), we also show that the mechanisms producing TTS are non-linear and asymmetric, and that the greatest 'trauma' occurs when the hair bundles of outer hair cells are deflected away from the basal body of these cells (i.e. in the direction normally causing hyperpolarisation of the cell membrane potential). CI - Copyright 2002 S. Karger AG, Basel AD - Auditory Laboratory, Physiology, University of Western Australia, Nedlands, W.A., Australia. rpatuzzi@cyllene.uwa.edu.au FAU - Patuzzi, Robert AU - Patuzzi R LA - eng PT - Journal Article CY - Switzerland TA - Audiol Neurootol JID - 9606930 SB - IM MH - Animal MH - Auditory Fatigue/*physiology MH - Auditory Threshold/physiology MH - Cochlear Microphonic Potentials MH - Cochlear Nerve/physiopathology MH - Evoked Potentials, Auditory/physiology MH - Guinea Pigs MH - Hair Cells, Outer/*physiopathology MH - Hearing Loss, Noise-Induced/*physiopathology MH - *Nonlinear Dynamics MH - Signal Transduction/*physiology MH - Synaptic Transmission/physiology EDAT- 2002/03/27 10:00 MHDA- 2002/06/12 10:01 AID - aud07017 [pii] PST - ppublish SO - Audiol Neurootol 2002 Jan-Feb;7(1):17-20. 195: Rasmussen S, et al. Defense of the ansatz for dyn...[PMID:11911787]Related Articles, Books, LinkOut UI - 21909199 PMID- 11911787 DA - 20020325 DCOM- 20020430 IS - 1064-5462 VI - 7 IP - 4 DP - 2001 TI - Defense of the ansatz for dynamical hierarchies. PG - 367-73 AB - Gross and McMullin [Artificial Life, 7, 355-365] criticize the conclusions of our article on dynamical hierarchies [Artificial Life, 7, 329-353]. In this note we respond to their criticisms. After clarifying our ansatz, we argue that the simulations presented by Gross and McMullin present no evidence against the ansatz, in part because their simulations use a different simulation framework, and in part because their simulations are no less complex than ours. We also clarify why the micelles in our simulations are third-order emergent structures, and why we emphasize realism in our simulation. AD - EES-6 MS-T003, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. FAU - Rasmussen, S AU - Rasmussen S FAU - Baas, N A AU - Baas NA FAU - Mayer, B AU - Mayer B FAU - Nilsson, M AU - Nilsson M LA - eng PT - Journal Article CY - United States TA - Artif Life JID - 9433814 SB - IM MH - *Models, Theoretical MH - *Nonlinear Dynamics MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/03/26 10:00 MHDA- 2002/05/01 10:01 AID - 10.1162/106454601317297004 [doi] PST - ppublish SO - Artif Life 2001;7(4):367-73. 196: Gross D, et al. Is it the right ansatz?...[PMID:11911786]Related Articles, Books, LinkOut UI - 21909198 PMID- 11911786 DA - 20020325 DCOM- 20020430 IS - 1064-5462 VI - 7 IP - 4 DP - 2001 TI - Is it the right ansatz? PG - 355-65 AB - This article is a response to Rasmussen et al. [Artificial Life, 7, 329-350], in which the authors suggest that, within a particular simulation "framework," there is a tight correspondence between the complexity of the primitive objects and the emergence of dynamical hierarchies. As an example they report a two-dimensional artificial chemistry that supports the spontaneous emergence of micellar structures, which they classify as third-order structures. We report in this article that essentially comparable phenomena can be produced with relatively simpler primitive objects. We also question the order classification of the micellar structures. AD - RINCE, Dublin City University, Dublin 9, Ireland. FAU - Gross, D AU - Gross D FAU - McMullin, B AU - McMullin B LA - eng PT - Comment PT - Journal Article CY - United States TA - Artif Life JID - 9433814 SB - IM CON - Artif Life. 2001;7(4):329-53. PMID: 11911785 MH - Micelles MH - *Models, Theoretical MH - Nonlinear Dynamics EDAT- 2002/03/26 10:00 MHDA- 2002/05/01 10:01 AID - 10.1162/106454601317296997 [doi] PST - ppublish SO - Artif Life 2001;7(4):355-65. 197: Rasmussen S, et al. Ansatz for dynamical hierarch...[PMID:11911785]Related Articles, Books, LinkOut UI - 21909197 PMID- 11911785 DA - 20020325 DCOM- 20020430 IS - 1064-5462 VI - 7 IP - 4 DP - 2001 TI - Ansatz for dynamical hierarchies. PG - 329-53 AB - Complex, robust functionalities can be generated naturally in at least two ways: by the assembly of structures and by the evolution of structures. This work is concerned with spontaneous formation of structures. We define the notion of dynamical hierarchies in natural systems and show the importance of this particular kind of organization for living systems. We then define a framework that enables us to formulate, investigate, and manipulate such dynamical hierarchies. This framework allows us to simultaneously investigate different levels of description together with their interrelationship, which is necessary to understand the nature of dynamical hierarchies. Our framework is then applied to a concrete and very simple formal, physicochemical, dynamical hierarchy involving water and monomers at level one, polymers and water at level two, and micelles (polymer aggregates) and water at level three. Formulating this system as a simple two-dimensional molecular dynamics (MD) lattice gas allows us within one dynamical system to demonstrate the successive emergence of two higher levels (three levels all together) of robust structures with associated properties. Second, we demonstrate how the framework for dynamical hierarchies can be used for realistic (predictive) physicochemical simulation of molecular self-assembly and self-organization processes. We discuss the detailed process of micellation using the three-dimensional MD lattice gas. Finally, from these examples we can infer principles about formal dynamical hierarchies. We present an ansatz for how to generate robust, higher-order emergent properties in formal dynamical systems that is based on a conjecture of a necessary minimal complexity within the fundamental interacting structures once a particular simulation framework is chosen. AD - EES-6 and T-CNLS, MS-T003, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. steen@lanl.gov FAU - Rasmussen, S AU - Rasmussen S FAU - Baas, N A AU - Baas NA FAU - Mayer, B AU - Mayer B FAU - Nilsson, M AU - Nilsson M FAU - Olesen, M W AU - Olesen MW LA - eng PT - Journal Article CY - United States TA - Artif Life JID - 9433814 RN - 0 (Gases) RN - 0 (Polymers) SB - IM CIN - Artif Life. 2001;7(4):355-65. PMID: 11911786 MH - Chemistry, Physical MH - Gases/chemistry MH - Micelles MH - *Models, Theoretical MH - *Nonlinear Dynamics MH - Polymers/chemistry MH - Support, Non-U.S. Gov't EDAT- 2002/03/26 10:00 MHDA- 2002/05/01 10:01 AID - 10.1162/106454601317296988 [doi] PST - ppublish SO - Artif Life 2001;7(4):329-53. 198: Ochsenbein F, et al. Dynamical characterization of...[PMID:11910038]Related Articles, Books, LinkOut UI - 21907880 PMID- 11910038 DA - 20020322 DCOM- 20020703 IS - 0961-8368 VI - 11 IP - 4 DP - 2002 Apr TI - Dynamical characterization of residual and non-native structures in a partially folded protein by (15)N NMR relaxation using a model based on a distribution of correlation times. PG - 957-64 AB - A spectral density model based on a truncated lorentzian distribution of correlation times is used to analyze the nanosecond time-scale dynamics of the partially unfolded domain 2 of annexin I from its (15)N NMR relaxation parameters measured at three magnetic field strengths. The use of a distribution of correlation times enables the characterization of the dynamical features of the NH bonds of the protein in terms of heterogeneity of dynamical states in the nanosecond range. The variation along the sequence of the two dynamical parameters introduced, namely the center and the width of the distribution, points out the different types of residual secondary structures present in the D2 domain. Moreover, it allows a physically sensible interpretation of the dynamical behavior of the different residual helices and of the non-native structures. Also, a striking correspondence is found between the parameters obtained using an extended Lipari and Szabo model and the parameters obtained using the distribution of correlation times. This result led us to propose a specific interpretation of the model-free order parameter for internal motions in the nanosecond range in the case of unfolded states. AD - CNRS, Institut de Chimie des Substances Naturelles, F-91190 Gif sur Yvette, France. carine@icsn.cnrs-gif.fr FAU - Ochsenbein, Francoise AU - Ochsenbein F FAU - Neumann, Jean-Michel AU - Neumann JM FAU - Guittet, Eric AU - Guittet E FAU - van Heijenoort, Carine AU - van Heijenoort C LA - eng PT - Journal Article CY - United States TA - Protein Sci JID - 9211750 RN - 0 (Annexin I) RN - 0 (Nitrogen Isotopes) RN - 0 (Peptide Fragments) SB - IM MH - Annexin I/*chemistry MH - Magnetics MH - Models, Molecular MH - Nitrogen Isotopes/diagnostic use MH - Nonlinear Dynamics MH - Nuclear Magnetic Resonance, Biomolecular/*methods MH - Peptide Fragments/chemistry MH - Protein Conformation MH - *Protein Folding MH - Support, Non-U.S. Gov't EDAT- 2002/03/23 10:00 MHDA- 2002/07/04 10:01 PST - ppublish SO - Protein Sci 2002 Apr;11(4):957-64. 199: Martin HG, et al. Linearity and scaling of a st...[PMID:11909131]Related Articles, Books, LinkOut UI - 21907451 PMID- 11909131 DA - 20020322 DCOM- 20020610 LR - 20021029 IS - 1539-3755 VI - 65 IP - 3 Pt 1 DP - 2002 Mar TI - Linearity and scaling of a statistical model for the species abundance distribution. PG - 032901 AB - We derive a linear recursion relation for the species abundance distribution in a statistical model of ecology and demonstrate the existence of a scaling solution. AD - Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801, USA. FAU - Martin, Hector Garcia AU - Martin HG FAU - Goldenfeld, Nigel AU - Goldenfeld N LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 SB - IM MH - Algorithms MH - *Ecology MH - Linear Models MH - Models, Statistical MH - Nonlinear Dynamics EDAT- 2002/03/23 10:00 MHDA- 2002/06/11 10:01 PHST- 2001/Jul/05 [received] PHST- 2002/Feb/13 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Mar;65(3 Pt 1):032901. 200: Sener MK, et al. General random matrix approac...[PMID:11909118]Related Articles, Books, LinkOut UI - 21907438 PMID- 11909118 DA - 20020322 DCOM- 20020610 LR - 20021029 IS - 1539-3755 VI - 65 IP - 3 Pt 1 DP - 2002 Mar TI - General random matrix approach to account for the effect of static disorder on the spectral properties of light harvesting systems. PG - 031916 AB - We develop a random matrix model approach to study static disorder in pigment-protein complexes in photosynthetic organisms. As a case study, we examine the ring of B850 bacteriochlorophylls in the peripheral light-harvesting complex of Rhodospirillum molischianum, formulated in terms of an effective Hamiltonian describing the collective electronic excitations of the system. We numerically examine and compare various models of disorder and observe that both the density of states and the absorption spectrum of the model show remarkable spectral universality. For the case of unitary disorder, we develop a method to analytically evaluate the density of states of the ensemble using the supersymmetric formulation of random matrix theory. Succinct formulas that can be readily applied in future studies are provided in an appendix. AD - Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA. FAU - Sener, Melih K AU - Sener MK FAU - Schulten, Klaus AU - Schulten K LA - eng ID - 1R01 GM60946/GM/NIGMS ID - 5P41 RR05969/RR/NCRR PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 RN - 0 (Photosynthetic Reaction Center, Bacterial) SB - IM MH - Models, Molecular MH - Models, Theoretical MH - Nonlinear Dynamics MH - *Photosynthesis MH - *Photosynthetic Reaction Center, Bacterial MH - Rhodospirillum/physiology MH - Spectrophotometry/methods MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/03/23 10:00 MHDA- 2002/06/11 10:01 PHST- 2001/Jun/06 [received] PHST- 2001/Aug/29 [revised] PHST- 2002/Mar/06 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Mar;65(3 Pt 1):031916. 201: Patnaik PR. Can imperfections help to imp...[PMID:11906738]Related Articles, Books, LinkOut UI - 21905066 PMID- 11906738 DA - 20020321 DCOM- 20020530 IS - 0167-7799 VI - 20 IP - 4 DP - 2002 Apr TI - Can imperfections help to improve bioreactor performance? PG - 135-7 AB - Pilot-scale and larger bioreactors differ from small laboratory-scale reactors in terms of a greater occurrence of noise and incomplete mixing of the broth. Conventional control tries to induce good mixing and to filter out the noise as completely as possible. As such an 'ideal' operation is difficult to achieve, recent work has tried to exploit the non-ideal features to improve the performance. Using artificial neural networks, the degree of mixing, the extent of filtering of noise and the distribution of plasmid copy number (in a recombinant fermentation) can be controlled effectively on-line. This strategy generates better productivities than well-mixed noise-free operations, which suggests that deviations from ideal behaviour should be gainfully harnessed and not suppressed. AD - Institute of Microbial Technology, Chandigarh, India. pratap@imtech.res.in FAU - Patnaik, Pratap R AU - Patnaik PR LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - England TA - Trends Biotechnol JID - 8310903 RN - 0 (Recombinant Proteins) SB - IM MH - *Bioreactors MH - Equipment Design/methods MH - Feedback MH - Fermentation/*physiology MH - *Models, Biological MH - *Neural Networks (Computer) MH - Nonlinear Dynamics MH - Recombinant Proteins/biosynthesis MH - Reproducibility of Results MH - *Stochastic Processes RF - 22 EDAT- 2002/03/22 10:00 MHDA- 2002/05/31 10:01 AID - S0167779901019229 [pii] PST - ppublish SO - Trends Biotechnol 2002 Apr;20(4):135-7. 202: Zhang YL, et al. The vibration of an artery-li...[PMID:11905556]Related Articles, Books, LinkOut UI - 21902309 PMID- 11905556 DA - 20020321 DCOM- 20020918 IS - 0954-4119 VI - 216 IP - 1 DP - 2002 TI - The vibration of an artery-like tube conveying pulsatile fluid flow. PG - 1-11 AB - A hybrid method for investigating pulsatile fluid flow in a long, thin, artery-like tube subjected to external excitations is presented. The non-linear partial differential equations governing the motion of the system, which incorporate the influence of circumferential strains, are solved by a combination of a finite element method, a finite difference method and a method of characteristics with interpolation. An initially axially stretched elastic tube conveying pulsating fluid, simply supported at both ends, is modelled to assess the effect of external harmonic excitation on the dynamic responses of the tube and the fluid flow. The results agree well with new experimental data. Comparison of the predicted results with those of a decoupled model demonstrates that it is necessary to consider the mechanism of fluid-structure interaction fully in the study of initially stretched cylindrical tubes conveying pulsatile fluid flow. An analysis of these coupling effects is presented for Womersley numbers alpha = 2.81 and 3.97 and a mean flow Reynolds number Re = 875. AD - Department of Chemical Engineering and Chemical Technology, Imperial College of Science, Technology and Medicine, London, UK. FAU - Zhang, Y L AU - Zhang YL FAU - Reese, J M AU - Reese JM FAU - Gorman, D G AU - Gorman DG FAU - Madhok, R AU - Madhok R LA - eng PT - Journal Article CY - England TA - Proc Inst Mech Eng [H] JID - 8908934 SB - IM MH - Aorta/*physiology MH - Biomedical Engineering MH - Blood Flow Velocity MH - Great Britain MH - *Hemodynamics MH - Human MH - Materials Testing MH - Models, Cardiovascular MH - Models, Statistical MH - Nonlinear Dynamics MH - *Prostheses and Implants MH - Pulse MH - *Vibration EDAT- 2002/03/22 10:00 MHDA- 2002/09/19 10:01 PST - ppublish SO - Proc Inst Mech Eng [H] 2002;216(1):1-11. 203: Mayama H, et al. Self-oscillating polymer chai...[PMID:11901691]Related Articles, Books, LinkOut UI - 21899706 PMID- 11901691 DA - 20020320 DCOM- 20020409 IS - 1359-6640 IP - 120 DP - 2001 TI - Self-oscillating polymer chain in a laser field. PG - 67-84; discussion 85-104 AB - We have investigated the dynamical behaviour of the rhythmic conformational change between the folded compact state and the unfolded state in a single polymer chain under thermodynamically open conditions. It is shown that the spontaneous rhythmic change in the conformation of a single polymer chain (T4DNA, 166 kbp, contour length: 56 microns) is generated using a focused continuous wave (CW) Nd:YAG laser beam (wavelength lambda = 1064 nm), where the focused laser beam plays a dual role, both trapping a polymer chain at the focus and creating a temperature gradient around the focus. Furthermore, the whole process of the rhythmic conformational change: the course of melting, nucleation and growth between the folded and unfolded states has been clarified. The rhythmic change in the conformation is discussed in terms of the limit-cycle oscillation driven by the dissipation of the photon energy. AD - Department of Physics, Graduate School of Science, Kyoto University, CREST (Core Research for Evolutional and Scientific Technology) of JST (Japan Science and Technology Corporation), Kyoto 606-8502, Japan. mayama@chem.scphys.kyoto-u.ac.jp FAU - Mayama, H AU - Mayama H FAU - Yoshikawa, K AU - Yoshikawa K LA - eng PT - Journal Article CY - England TA - Faraday Discuss JID - 9212301 RN - 9007-49-2 (DNA) SB - IM MH - Bacteriophage T4/chemistry MH - DNA/*chemistry MH - Lasers MH - Nonlinear Dynamics MH - Nucleic Acid Conformation MH - Spectrometry, Fluorescence MH - Support, Non-U.S. Gov't MH - Thermodynamics EDAT- 2002/03/21 10:00 MHDA- 2002/04/10 10:01 PST - ppublish SO - Faraday Discuss 2001;(120):67-84; discussion 85-104. 204: Zagora J, et al. Excitability in chemical and ...[PMID:11901683]Related Articles, Books, LinkOut UI - 21899719 PMID- 11901683 DA - 20020320 DCOM- 20020409 IS - 1359-6640 IP - 120 DP - 2001 TI - Excitability in chemical and biochemical pH-autocatalytic systems. PG - 313-24; discussion 325-51 AB - Using two different kinds of pH systems--the papain catalyzed hydrolysis of N-benzoyl-L-arginine ethyl ester in a membrane reactor and the bromate-sulfite-ferrocyanide (BSF) reaction in the CSTR--we study the relation among excitability, oscillations and bistability, and the ability of the system to respond to external periodic perturbations. Excitable properties of dynamical systems are examined in terms of a threshold set which is used to characterise dynamics in the reactor subject to external periodic stimuli. A precise definition and a method of calculating the threshold set are formulated. Two kinds of excitability distinguished by either direct or indirect initiation of the activatory process are found in both pH systems. Periodic pulsed perturbations of the BSF system display a nontrivial dependence of an excitation number on the forcing period. We examined this system also in oscillatory mode by looking at the phase shifts caused by single-pulse perturbations and constructing the phase transition curves (PTCs). AD - Department of Chemical Engineering & Center for Nonlinear Dynamics of Chemical and Biological Systems, Prague Institute of Chemical Technology, Technicka 5, 166 28 Prague 6, Czech Republic. FAU - Zagora, J AU - Zagora J FAU - Voslar, M AU - Voslar M FAU - Schreiberova, L AU - Schreiberova L FAU - Schreiber, I AU - Schreiber I LA - eng PT - Journal Article CY - England TA - Faraday Discuss JID - 9212301 RN - 0 (Bromates) RN - 0 (Ferrocyanides) RN - 0 (Sulfites) RN - 13408-63-4 (hexacyanoferrate II) RN - EC 3.4.22.2 (Papain) SB - IM MH - Algorithms MH - Bromates/chemistry MH - *Catalysis MH - Ferrocyanides/chemistry MH - Hydrogen-Ion Concentration MH - Kinetics MH - Membranes, Artificial MH - Nonlinear Dynamics MH - Papain/chemistry MH - Sulfites/chemistry MH - Support, Non-U.S. Gov't EDAT- 2002/03/21 10:00 MHDA- 2002/04/10 10:01 PST - ppublish SO - Faraday Discuss 2001;(120):313-24; discussion 325-51. 205: Mair T, et al. Spatio-temporal dynamics in g...[PMID:11901679]Related Articles, Books, LinkOut UI - 21899715 PMID- 11901679 DA - 20020320 DCOM- 20020409 IS - 1359-6640 IP - 120 DP - 2001 TI - Spatio-temporal dynamics in glycolysis. PG - 249-59; discussion 325-51 AB - During the glycolytic degradation of sugar in a thin layer of yeast extract, travelling waves of NADH and protons can be generated that carry a state of high enzymatic activity through the system. The controlled initiation of such waves with an activator of the enzyme phosphofructokinase (PFK) and the influence of various salts and co-factors on the propagation dynamics are investigated. Furthermore a first study of the dispersion of waves is presented. The experimental characterisation of this in vitro system contributes to unravelling the possible role of glycolysis for biological information processing. In this context, the provision of chemically available energy in the absence of compartmentation by glycolysis is of primary importance. AD - Otto-von-Guericke-Universitat Magdeburg, Institute of Experimental Physics, Group of Biophysics, Universitatsplatz 2, 39106 Magdeburg, Germany. FAU - Mair, T AU - Mair T FAU - Warnke, C AU - Warnke C FAU - Muller, S C AU - Muller SC LA - eng PT - Journal Article CY - England TA - Faraday Discuss JID - 9212301 RN - 0 (Protons) RN - 53-84-9 (NAD) RN - EC 2.7.1 - (Phosphofructokinases) SB - IM MH - Glycolysis/*physiology MH - Kinetics MH - NAD/chemistry MH - Nonlinear Dynamics MH - Phosphofructokinases/chemistry MH - Protons MH - Saccharomyces cerevisiae/chemistry/enzymology EDAT- 2002/03/21 10:00 MHDA- 2002/04/10 10:01 PST - ppublish SO - Faraday Discuss 2001;(120):249-59; discussion 325-51. 206: Hanke W, et al. Control of the excitability o...[PMID:11901678]Related Articles, Books, LinkOut UI - 21899714 PMID- 11901678 DA - 20020320 DCOM- 20020409 IS - 1359-6640 IP - 120 DP - 2001 TI - Control of the excitability of neuronal tissue by weak external forces. PG - 237-48; discussion 325-51 AB - The spreading depression (SD) is a pronounced example of excitation-depression waves in excitable media, to which neuronal tissue according to its structure and functions belongs. SD waves can especially easily be observed in the vertebrate retina which is neuronal tissue and a true part of the central nervous system (CNS). According to the high intrinsic optical signal (IOS) concomitant with the retinal spreading depression (rSD), it can be monitored with standard video imaging techniques, thus the retina has been used in our studies as a suitable model system for neuronal tissue in general. In particular, the control of wave set-up and propagation in excitable media by weak external forces is of high interest. Accordingly, the interaction of rSD waves with DC and AC electromagnetic fields of low amplitude and frequency and with gravity has been investigated in this study. The dependence of rSD-wave propagation velocity on the given parameters as one important indication of excitability control has been investigated in detail. Our results with rSD waves are partially compared to another well known excitable medium, the Belousov-Zhabotinsky reaction, where some data about the effects of electrical fields and gravity have already been published. AD - University of Hohenheim, Institute of Physiology, Garbenstrasse 30, 70599 Stuttgart, Germany. hanke@uni-hohenheim.de FAU - Hanke, W AU - Hanke W FAU - Wiedemann, M AU - Wiedemann M FAU - de Lima, V M AU - de Lima VM LA - eng PT - Journal Article CY - England TA - Faraday Discuss JID - 9212301 SB - IM MH - Animal MH - Chickens/*physiology MH - Electromagnetic Fields MH - Gravitation MH - In Vitro MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Retina/*cytology MH - Support, Non-U.S. Gov't EDAT- 2002/03/21 10:00 MHDA- 2002/04/10 10:01 PST - ppublish SO - Faraday Discuss 2001;(120):237-48; discussion 325-51. 207: Hauser MJ, et al. pH oscillations in the hemin-...[PMID:11901677]Related Articles, Books, LinkOut UI - 21899713 PMID- 11901677 DA - 20020320 DCOM- 20020409 IS - 1359-6640 IP - 120 DP - 2001 TI - pH oscillations in the hemin-hydrogen peroxide-sulfite reaction. PG - 229-36; discussion 325-51 AB - Oscillatory behaviour in the pH value has been observed during the oxidation of sulfite by hydrogen peroxide mediated by hemin, a well known enzyme model compound, in a continuous-flow stirred tank reactor. The dynamics of this reaction has been studied for a variety of flow rates of the reactants. As the flow rates increase, the oscillations evolve from relaxation oscillations to more complex shapes, displaying, among others, bursting behaviour. A reaction mechanism is proposed that involves the autocatalytic oxidation of HSO3- by H2O2, while slow equilibria between different pH-dependent forms of hemin account for the feedback loop which gives rise to oscillatory dynamics. It is shown in experiments that no participation of CO2 is required for oscillations to occur. AD - Abteilung Biophysik, Institut fur Experimentelle Physik, Otto-von-Guericke-Universitat, Universitatsplatz 2, 39106 Magdeburg, Germany. marcus.hauser@physik.uni-magdeburg.de FAU - Hauser, M J AU - Hauser MJ FAU - Strich, A AU - Strich A FAU - Bakos, R AU - Bakos R FAU - Nagy-Ungvarai, Z AU - Nagy-Ungvarai Z FAU - Muller, S C AU - Muller SC LA - eng PT - Journal Article CY - England TA - Faraday Discuss JID - 9212301 RN - 0 (Oxidants) RN - 0 (Sulfites) RN - 16009-13-5 (Hemin) RN - 7722-84-1 (Hydrogen Peroxide) SB - IM MH - Catalysis MH - Hemin/*chemistry MH - Hydrogen Peroxide/*chemistry MH - Hydrogen-Ion Concentration MH - Models, Chemical MH - Nonlinear Dynamics MH - Oxidants/*chemistry MH - Oxidation-Reduction MH - Sulfites/*chemistry MH - Support, Non-U.S. Gov't EDAT- 2002/03/21 10:00 MHDA- 2002/04/10 10:01 PST - ppublish SO - Faraday Discuss 2001;(120):229-36; discussion 325-51. 208: Hauser MJ, et al. Oscillatory dynamics protect ...[PMID:11901676]Related Articles, Books, LinkOut UI - 21899712 PMID- 11901676 DA - 20020320 DCOM- 20020409 IS - 1359-6640 IP - 120 DP - 2001 TI - Oscillatory dynamics protect enzymes and possibly cells against toxic substances. PG - 215-27; discussion 325-51 AB - We have used the oscillating peroxidase-oxidase (PO) reaction as a model system to study how oscillatory dynamics may affect the influence of toxic reaction intermediates on enzyme stability. In the peroxidase-oxidase reaction reactive intermediates, such as hydrogen peroxide, superoxide, and hydroxyl radical are formed. Such intermediates inactivate many cellular macromolecules such as proteins and nucleic acids. These reaction intermediates also react with peroxidase itself to form an inactive enzyme. The fact that the PO reaction shows bistability between an oscillatory and a steady state gives us a unique possibility to compare such inactivation when the system is in one of these two states. We show that inactivation of peroxidase is slower when the system is in an oscillatory state, and using numerical simulations we provide evidence that oscillatory dynamics lower the average concentration of the reactive intermediates. AD - Institut fur Experimentelle Physik, Abteilung Biophysik, Otto-von-Guericke Universitat, Postfach 4120, D-39016 Magdeburg, Germany. FAU - Hauser, M J AU - Hauser MJ FAU - Kummer, U AU - Kummer U FAU - Larsen, A Z AU - Larsen AZ FAU - Olsen, L F AU - Olsen LF LA - eng PT - Journal Article CY - England TA - Faraday Discuss JID - 9212301 RN - 0 (Enzymes) RN - 0 (Free Radicals) RN - 0 (Poisons) RN - EC 1. (Oxidoreductases) RN - EC 1.11.1. (Peroxidases) RN - EC 1.11.1.- (Horseradish Peroxidase) SB - IM MH - Cells/*drug effects MH - Enzymes/*drug effects MH - Free Radicals MH - Horseradish Peroxidase/chemistry MH - Nonlinear Dynamics MH - Oxidoreductases/chemistry MH - Peroxidases/chemistry MH - Poisons/*toxicity MH - Support, Non-U.S. Gov't EDAT- 2002/03/21 10:00 MHDA- 2002/04/10 10:01 PST - ppublish SO - Faraday Discuss 2001;(120):215-27; discussion 325-51. 209: Nicolis G. Nonlinear kinetics: at the cr...[PMID:11901668]Related Articles, Books, LinkOut UI - 21899701 PMID- 11901668 DA - 20020320 DCOM- 20020409 IS - 1359-6640 IP - 120 DP - 2001 TI - Nonlinear kinetics: at the crossroads of chemistry, physics and life sciences. PG - 1-10; discussion 85-104 AD - Center for Nonlinear Phenomena and Complex Systems, Universite Libre de Bruxelles, C.P. 231, Bd. du Triomphe, 1050 Brussels, Belgium. FAU - Nicolis, G AU - Nicolis G LA - eng PT - Journal Article CY - England TA - Faraday Discuss JID - 9212301 SB - IM MH - Biology/*trends MH - Chemistry/*trends MH - Kinetics MH - *Nonlinear Dynamics MH - Physics/*trends MH - Support, Non-U.S. Gov't EDAT- 2002/03/21 10:00 MHDA- 2002/04/10 10:01 PST - ppublish SO - Faraday Discuss 2001;(120):1-10; discussion 85-104. 210: Amemiya K, et al. Relationship between the flow...[PMID:11896841]Related Articles, Books, LinkOut UI - 21896068 PMID- 11896841 DA - 20020318 DCOM- 20020809 IS - 0305-182X VI - 29 IP - 3 DP - 2002 Mar TI - Relationship between the flow of bolus and occlusal condition during mastication--computer simulation based on the measurement of characteristics of the bolus. PG - 245-56 AB - The purpose of the present study was to clarify the relationship between the flow of a bolus and occlusal condition during mastication. First, the characteristics of a bolus under mastication was measured in subjects having different occlusal conditions. Secondly, the flow of a bolus between the upper and lower first molars under mastication was simulated using finite element non-linear dynamic analysis. Measurement of the elasticity of the bolus clarified the phenomenon of its communition. The measurement of the viscosity of the bolus clarified the phenomenon of its mixing with saliva. In addition, a relationship between the elasticity and the viscosity of the bolus at the point of just before swallowing was investigated. The flow of the bolus under mastication was revealed to vary according to the occlusal condition. These results suggest a close relationship between the occlusal condition, the flow of the bolus and its characteristics. AD - First Department of Orthodontics, Faculty of Dentistry, Tokyo Medical and Dental University, Tokyo, Japan. FAU - Amemiya, K AU - Amemiya K FAU - Hisano, M AU - Hisano M FAU - Ishida, T AU - Ishida T FAU - Soma, K AU - Soma K LA - eng PT - Journal Article CY - England TA - J Oral Rehabil JID - 0433604 SB - D SB - IM MH - Adult MH - *Computer Simulation MH - Deglutition/physiology MH - *Dental Occlusion MH - Elasticity MH - Female MH - Finite Element Analysis MH - Food MH - Human MH - Male MH - Malocclusion, Angle Class I/physiopathology MH - Malocclusion, Angle Class II/physiopathology MH - Malocclusion, Angle Class III/physiopathology MH - Mandible/physiology MH - Mastication/*physiology MH - Maxilla MH - *Models, Biological MH - Molar/physiology MH - Movement MH - Nonlinear Dynamics MH - Poisson Distribution MH - Rheology MH - Saliva/physiology MH - Support, Non-U.S. Gov't MH - Viscosity EDAT- 2002/03/19 10:00 MHDA- 2002/08/10 10:01 AID - 910 [pii] PST - ppublish SO - J Oral Rehabil 2002 Mar;29(3):245-56. 211: Jing H, et al. Nonlinear analysis of EEG aft...[PMID:11896348]Related Articles, Books, LinkOut UI - 21893291 PMID- 11896348 DA - 20020315 DCOM- 20020528 IS - 0736-0258 VI - 19 IP - 1 DP - 2002 Jan TI - Nonlinear analysis of EEG after repetitive transcranial magnetic stimulation. PG - 16-23 AB - The purpose of this study was to investigate whether repetitive transcranial magnetic stimulation (rTMS) can change nonlinear dynamic properties of the cerebral cortex. Two rTMS trains (10 Hz, 3 seconds, 100% of motor threshold) were administered to the left frontal area in healthy subjects. EEG signals were collected at 14 electrode sites before and after stimulation, and were filtered digitally into delta, theta, alpha, beta, and gamma bands. Basing on an improved algorithm introduced in the authors' recent study, dimension estimates were calculated on these signals as well as on the corresponding surrogate data. Sham treatment was designed into this study. The data showed that EEG signals obviously exhibited lower dimension estimates than the surrogate data, whereas the theta and alpha rhythms presented the lowest values among the frequency components. rTMS increased the dimension estimates of EEG signals during the first 2 minutes. Similar findings were also obtained on the delta and beta components. This study revealed that EEG signals in the normal state can be described by a nonlinear dynamic process. This process can be affected temporarily by rTMS. Neuronal networks revealed by EEG signals show more complicated properties after stimulation. AD - Department of Neuropsychiatry, Faculty of Medicine, Kagoshima University, Japan. hjing@axon.rutgers.edu FAU - Jing, Hongkui AU - Jing H FAU - Takigawa, Morikuni AU - Takigawa M LA - eng PT - Journal Article CY - United States TA - J Clin Neurophysiol JID - 8506708 SB - IM MH - Adult MH - Algorithms MH - Cerebral Cortex/*physiology MH - Electroencephalography/*statistics & numerical data MH - *Electromagnetic Fields MH - Evoked Potentials/physiology MH - Frontal Lobe/physiology MH - Human MH - Male MH - Nerve Net/physiology MH - *Nonlinear Dynamics MH - Reference Values MH - Signal Processing, Computer-Assisted EDAT- 2002/03/16 10:00 MHDA- 2002/05/29 10:01 PST - ppublish SO - J Clin Neurophysiol 2002 Jan;19(1):16-23. 212: Slob W. Dose-response modeling of con...[PMID:11896297]Related Articles, Books, LinkOut UI - 21893814 PMID- 11896297 DA - 20020315 DCOM- 20020621 IS - 1096-6080 VI - 66 IP - 2 DP - 2002 Apr TI - Dose-response modeling of continuous endpoints. PG - 298-312 AB - A family of (nested) dose-response models is introduced herein that can be used for describing the change in any continuous endpoint as a function of dose. A member from this family of models may be selected using the likelihood ratio test as a criterion, to prevent overparameterization. The proposed methodology provides for a formal approach of model selection, and a transparent way of assessing the benchmark dose. Apart from a number of natural constraints, the model expressions follow from an obvious way of quantifying differences in sensitivity between populations. As a consequence, dose-response data that relate to both sexes can be efficiently analyzed by incorporating the data from both sexes in the same analysis, even if the sexes are not equally sensitive to the compound studied. The idea of differences in sensitivity is closely related to the assessment factors used in risk assessment. Thus, the models are directly applicable to estimating such factors, if data concerning populations to be compared are available. Such information is valuable for further validation or adjustment of default assessment factors, as well as for informing distributional assessment factors in a probabilistic risk assessment. The various applications of the proposed methodology are illustrated by real data sets. AD - National Institute of Public Health and the Environment (RIVM), P.O. Box 1, 3720 BA Bilthoven, The Netherlands. wout.slob@rivm.nl FAU - Slob, Wout AU - Slob W LA - eng PT - Journal Article CY - United States TA - Toxicol Sci JID - 9805461 SB - IM MH - Animal MH - Data Interpretation, Statistical MH - Dose-Response Relationship, Drug MH - Endpoint Determination MH - Female MH - Male MH - *Models, Statistical MH - Nonlinear Dynamics MH - Toxicology/methods EDAT- 2002/03/16 10:00 MHDA- 2002/06/22 10:01 PST - ppublish SO - Toxicol Sci 2002 Apr;66(2):298-312. 213: Saether BE, et al. Demographic characteristics a...[PMID:11896278]Related Articles, Books, LinkOut UI - 21893789 PMID- 11896278 DA - 20020315 DCOM- 20020422 IS - 1095-9203 VI - 295 IP - 5562 DP - 2002 Mar 15 TI - Demographic characteristics and population dynamical patterns of solitary birds. PG - 2070-3 AB - In birds and many other animals, there are large interspecific differences in the magnitude of annual variation in population size. Using time-series data on populations of solitary bird species, we found that fluctuations in population size of solitary birds were affected by the deterministic characteristics of the population dynamics as well as the stochastic factors. In species with highly variable populations, annual variation in recruitment was positively related to the return rate of adults between successive breeding seasons. In stable populations, more recruits were found in years with low return rates of breeding adults. This identifies a gradient, associated with the position of the species along a "slow-fast" continuum of life history variation, from highly variable populations with a recruitment-driven demography to stable, strongly density-regulated populations with a survival-restricted demography. These results suggest that patterns in avian population fluctuations can be predicted from a knowledge of life-history characteristics and/or temporal variation in certain demographic traits. AD - Department of Zoology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway. bernt-erik.sather@chembio.ntnu.no FAU - Saether, Bernt-Erik AU - Saether BE FAU - Engen, Steinar AU - Engen S FAU - Matthysen, Erik AU - Matthysen E LA - eng PT - Journal Article CY - United States TA - Science JID - 0404511 SB - IM CIN - Science. 2002 Mar 15;295(5562):2023-4. PMID: 11896258 MH - Animal MH - Behavior, Animal MH - Birds/*physiology MH - Breeding MH - Ecosystem MH - Female MH - Homing Behavior MH - Likelihood Functions MH - Logistic Models MH - Male MH - Nonlinear Dynamics MH - Population Density MH - Population Dynamics MH - Seasons MH - Species Specificity MH - Stochastic Processes MH - Support, Non-U.S. Gov't MH - Territoriality EDAT- 2002/03/16 10:00 MHDA- 2002/04/23 10:01 AID - 10.1126/science.1068766 [doi] AID - 295/5562/2070 [pii] PST - ppublish SO - Science 2002 Mar 15;295(5562):2070-3. 214: Kim JM, et al. Changes in brain complexity d...[PMID:11893868]Related Articles, Books, LinkOut UI - 21891121 PMID- 11893868 DA - 20020314 DCOM- 20020503 LR - 20021101 IS - 0302-282X VI - 45 IP - 2 DP - 2002 TI - Changes in brain complexity during valproate treatment in patients with partial epilepsy. PG - 106-12 AB - OBJECTIVE: The effect of valproate (VPA) on human electroencephalography (EEG) was studied using nonlinear dynamics analysis to investigate changes in brain complexity. METHODS: We propose a spatial linear mode complexity (SLMC) measure to quantify the complexity of spatial linear modes in multichannel EEGs. Nine patients with complex partial seizures who had not previously been exposed to antiepileptic drugs (AEDs) were included in this study. Eighteen-channel EEG data were collected before and after VPA therapy. Changes in brain complexity were examined using the proposed SLMC measure, which reflects brain complexity. Fifteen normal, healthy subjects were included as a control group. To compare SLMC with spectral analysis, we performed spectral analysis within the conventional frequency bands. RESULTS: Spectral analysis showed that the patient group had decreased relative power of the alpha2 band in the T7, P3, O1 and C4 leads before VPA treatment and an increased relative theta power in the O1 lead relative to the control group. However, no significant changes occurred in any lead at any frequency band after VPA treatment. The mean SLMC value was significantly lower in the patient group before treatment than in the control group (p = 0.026). The average SLMC value for all patients increased after treatment and neared that of the control group, although statistical significance was not attained (p = 0.074). CONCLUSIONS: These results suggest that epilepsy patients have interictal abnormalities that are demonstrated by reduced brain complexity, and that VPA partially reverses this trend. Nonlinear analysis of EEG data may be useful in evaluating the effect of AEDs. CI - Copyright 2002 S. Karger AG, Basel AD - Department of Neurology, College of Medicine, Chungnam National University, Taejon, Korea. FAU - Kim, Jae-Moon AU - Kim JM FAU - Jung, Ki-Young AU - Jung KY FAU - Choi, Chung-Mi AU - Choi CM LA - eng PT - Journal Article CY - Switzerland TA - Neuropsychobiology JID - 7512895 RN - 0 (Anticonvulsants) RN - 99-66-1 (Valproic Acid) SB - IM MH - Adolescent MH - Adult MH - Anticonvulsants/*therapeutic use MH - Brain/*physiopathology MH - Electroencephalography MH - Epilepsies, Partial/*drug therapy/*physiopathology MH - Female MH - Human MH - Male MH - Middle Age MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Valproic Acid/*therapeutic use EDAT- 2002/03/15 10:00 MHDA- 2002/05/04 10:01 AID - nps45106 [pii] PST - ppublish SO - Neuropsychobiology 2002;45(2):106-12. 215: Sun JX, et al. [Research progress of methods...[PMID:11892741]Related Articles, Books UI - 21888038 PMID- 11892741 DA - 20020313 DCOM- 20020509 IS - 1002-0837 VI - 14 IP - 3 DP - 2001 Jun TI - [Research progress of methods of heart rate variability analysis] PG - 230-4 AB - One of the hotspots in the analysis of ECG is heart rate variability (HRV). In the present, the method mostly used for the analysis of HRV signal is linear analysis, and nonlinear analysis seldom used. Research progress of several methods of HRV analysis is presented. Principles and characteristics of using nonlinear analysis for the study of HRV are analyzed in detail. Fractal dimension, complexity and approximate entropy are discussed. AD - Institute of Space Medico-Engineering, Beijing, China. FAU - Sun, J X AU - Sun JX FAU - Bai, Y Q AU - Bai YQ LA - chi PT - Journal Article CY - China TA - Space Med Med Eng (Beijing) JID - 9425305 SB - S MH - Electrocardiography MH - English Abstract MH - Entropy MH - *Fractals MH - Heart Rate/*physiology MH - Human MH - Linear Models MH - Models, Cardiovascular MH - *Nonlinear Dynamics EDAT- 2002/03/15 10:00 MHDA- 2002/05/10 10:01 PST - ppublish SO - Space Med Med Eng (Beijing) 2001 Jun;14(3):230-4. 216: Thomas DD, et al. Changes in actin and myosin s...[PMID:11892285]Related Articles, Books, LinkOut UI - 21890109 PMID- 11892285 DA - 20020314 DCOM- 20020904 IS - 0080-1844 VI - 36 DP - 2002 TI - Changes in actin and myosin structural dynamics due to their weak and strong interactions. PG - 7-19 AB - Figure 3 summarizes the effects of actomyosin binding on the internal and global dynamics of either protein, as discussed in this chapter. These effects depend primarily on the strength of the interaction; which in turn depends on the state of the nucleotide at the myosin active site. When either no nucleotide or ADP is bound, the interaction is strong and the effect on each protein is maximal. When the nucleotide is ATP or ADP.Pi, or the equivalent nonhydrolyzable analogs, the interaction is weak and the effect on molecular dynamics of each protein is minimal. The weaker effects in weak-binding states are not simply the reflection of lower occupancy of binding sites--the molecular models in Fig. 3 illustrate the effects of the formation of the ternary complex, after correction for the free actin and myosin in the system. Thus EPR on myosin (Berger and Thomas 1991; Thomas et al. 1995) and pyrene fluorescence studies on actin (Geeves 1991) have shown that the formation of a ternary complex has a negligible effect on the internal dynamics of both [figure: see text] proteins (left side of Fig. 3, white arrows). As shown by both EPR (Baker et al. 1998; Roopnarine et al. 1998) and phosphorescence (Ramachandran and Thomas 1999), both domains of myosin are dynamically disordered in weak-binding states, and this is essentially unaffected by the formation of the ternary complex (left side of Fig. 3, indicated by disordered myosin domains). The only substantial effect of the formation of the weak interaction that has been reported is the EPR-detected (Ostap and Thomas 1991) restriction of the global dynamics of actin upon weak myosin binding (left column of Fig. 3, gray arrow). The effects of strong actomyosin formation are much more dramatic. While substantial rotational dynamics, both internal and global, exist in both myosin and actin in the presence of ADP or the absence of nucleotides, spin label EPR, pyrene fluorescence, and phosphorescence all show dramatic restrictions in these motions upon formation of the strong ternary complex (right column of Fig. 3). One implication of this is that the weak-to-strong transition is accompanied by a disorder-to-order transition in both actin and myosin, and this is itself an excellent candidate for the structural change that produces force (Thomas et al. 1995). Another clear implication is that the crystal structures obtained for isolated myosin and actin are not likely to be reliable representations of structures that exist in ternary complexes of these proteins (Rayment et al. 1993a and 1993b; Dominguez et al. 1998; Houdusse et al. 1999). This is clearly true of the strong-binding states, since the spectroscopic studies indicate consistently that substantial changes occur in both proteins upon strong complex formation. For the weak complexes, the problem is not that complex formation induces large structural changes, but that the structures themselves are dynamically disordered. This is probably why so many different structures have been obtained for myosin S1 with nucleotides bound--each crystal is selecting one of the many different substates represented by the dynamic ensemble. Finally, there is the problem that the structures of actomyosin complexes are probably influenced strongly by their mechanical coupling to muscle protein lattice (Baker at al. 2000). Thus, even if co-crystals of actin and myosin are obtained in the future, an accurate description of the structural changes involved in force generation will require further experiments using site-directed spectroscopic probes of both actin and myosin, in order to detect the structural dynamics of these ternary complexes under physiological conditions. AD - Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA. FAU - Thomas, David D AU - Thomas DD FAU - Prochniewicz, Ewa AU - Prochniewicz E FAU - Roopnarine, Osha AU - Roopnarine O LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - Germany TA - Results Probl Cell Differ JID - 0173555 RN - 0 (Actins) RN - 56-65-5 (Adenosine Triphosphate) RN - EC 3.6.1.4 (Myosins) SB - IM MH - Actins/*chemistry/ultrastructure MH - Adenosine Triphosphate/metabolism MH - Animal MH - Catalytic Domain/physiology MH - Human MH - Muscle Contraction/*physiology MH - Muscle, Skeletal/*metabolism/ultrastructure MH - Myosins/*chemistry/ultrastructure MH - Nonlinear Dynamics MH - Protein Binding/physiology MH - Protein Structure, Tertiary/physiology RF - 55 EDAT- 2002/03/15 10:00 MHDA- 2002/09/06 10:01 PST - ppublish SO - Results Probl Cell Differ 2002;36:7-19. 217: Lebedev SV, et al. Use of linearity of the Sokol...[PMID:11891474]Related Articles, Books, LinkOut UI - 21889152 PMID- 11891474 DA - 20020313 DCOM- 20020731 IS - 0143-3636 VI - 23 IP - 2 DP - 2002 Feb TI - Use of linearity of the Sokoloff model to improve performance of non-linear search. PG - 181-5 AB - The three-parameter Sokoloff equation is used to measure the rates of glucose consumption in the brain in vivo. This equation depends linearly on one of its parameters, k1, which is responsible for the glucose transport from plasma to tissue. By equating to zero the first derivative of the minimization function with respect to k1, it is possible to express this parameter as a function of the other two and reduce the non-linear search from three to two dimensions. This approach was examined by the Nelder-Mead simplex method and the Levenberg-Marquardt algorithm. In both cases the process of convergence was more robust and required fewer iterations to achieve a given accuracy than the direct three-parameter non-linear search. AD - Department of Psychiatry, New York University School of Medicine, New York, USA. FAU - Lebedev, S V AU - Lebedev SV FAU - Van Gelder, P W AU - Van Gelder PW FAU - Tsui, W H AU - Tsui WH LA - eng ID - AG13616/AG/NIA PT - Journal Article CY - England TA - Nucl Med Commun JID - 8201017 RN - 50-99-7 (Glucose) SB - IM MH - *Algorithms MH - Brain/*metabolism/radionuclide imaging MH - Comparative Study MH - Glucose/*metabolism MH - Human MH - *Models, Neurological MH - *Nonlinear Dynamics MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/03/14 10:00 MHDA- 2002/08/01 10:01 PST - ppublish SO - Nucl Med Commun 2002 Feb;23(2):181-5. 218: Mohr E, et al. Heart rate variability: a non...[PMID:11890975]Related Articles, Books, LinkOut UI - 21889209 PMID- 11890975 DA - 20020313 DCOM- 20020617 IS - 0031-9384 VI - 75 IP - 1-2 DP - 2002 Feb 1-15 TI - Heart rate variability: a noninvasive approach to measure stress in calves and cows. PG - 251-9 AB - The aim of this study was to evaluate the usefulness of heart rate variability (HRV) and its specific parameters as a new approach to assess stress load in cattle. We recorded HRV in 52 calves in three groups and in 31 cows in two groups. In calves we divided Group 1 with no obvious stress load (n=18), Group 2 with external stress load (n=17), and Group 3 with internal stress load from sickness (n=17). In cattle we divided lactating cows (n=21) and nonlactating cows (n=10). HRV parameters were analyzed in the time domain and in the frequency domain. Moreover, we applied Recurrence Quantification Analysis (RQA) to quantify nonlinear components of HRV. In calves, linear HRV parameter decreased from Group 1 to Group 3 (P<.05). However, not a single parameter showed significant differences regarding all three groups. The value of all nonlinear measurements increased at the same time (P<.05). The only parameter that exhibited significant differences between all three groups was the longest diagonal line segment in the recurrence plot (L(MAX)) which is inversely related to the Lyapunov exponent. We did not find differences concerning the linear HRV parameters between the two groups in the cows. The nonlinear parameter Determinism showed significant higher values in lactating cows compared to nonlactating cows. The importance of particular HRV-parameters was tested by applying a discriminant analysis approach. In calves and cattle nonlinear parameters were most important to indicate the level of stress load on the animals. Based on the results we assume HRV to be a valuable physiological indicator for stress load in animals. Whereas linear parameters of HRV are supposed to be useful to separate qualitative different level of stress, nonlinear components of HRV distinguish quantitative different challenges for the animals. AD - Agrar- und Umweltwissenschaftliche Fakultat, FB Agrarokologie, Universitat Rostock, Justus-von Liebig-Weg 8, 18051 Rostock, Germany. elmar.mohr@agrarfak.uni-rostock.de FAU - Mohr, Elmar AU - Mohr E FAU - Langbein, Jan AU - Langbein J FAU - Nurnberg, Gerd AU - Nurnberg G LA - eng PT - Journal Article CY - United States TA - Physiol Behav JID - 0151504 SB - IM MH - Animal MH - Data Interpretation, Statistical MH - Dogs MH - Electrocardiography MH - Entropy MH - Exertion/physiology MH - Female MH - Heart Rate/*physiology MH - Lactation/physiology MH - Linear Models MH - Nonlinear Dynamics MH - Pregnancy MH - Stress, Psychological/*physiopathology MH - Telemetry MH - Temperature EDAT- 2002/03/14 10:00 MHDA- 2002/06/18 10:01 AID - S0031938401006515 [pii] PST - ppublish SO - Physiol Behav 2002 Feb 1-15;75(1-2):251-9. 219: Fuhry L, et al. Non-linear interaction of ang...[PMID:11889508]Related Articles, Books, LinkOut UI - 21886312 PMID- 11889508 DA - 20020312 DCOM- 20020530 IS - 0014-4819 VI - 143 IP - 3 DP - 2002 Apr TI - Non-linear interaction of angular and translational vestibulo-ocular reflex during eccentric rotation in the monkey. PG - 303-17 AB - Eccentric sinusoidal rotation with the nose facing out or in leads to gain modulation of the vestibulo-ocular reflex (VOR), which is a result of an interaction between angular and translational VOR. There are conflicting reports with regard to the type of interaction. Combined angular and translational VOR during eccentric sinusoidal rotations over a wide range of target distances (12-180 cm), eccentricities (centric, 30 and 50 cm nose-out and nose-in eccentric) and frequencies (0.1-4 Hz) were studied in macaque monkeys trained to fixate earth-stationary light-emitting diode (LED) targets while binocular eye positions were measured using magnetic search coils. The monkeys were also exposed to sudden unpredictable position steps with peak accelerations of 500 degrees/s(2) using similar eccentricities and target distances. VOR gain enhancement during nose-out eccentric sinusoidal rotation was almost compensatory when the target was visible and was independent of stimulus frequency. Mean responses were still close to ideal when the target was extinguished; however, individual data showed increased variability. Sensitivities of the translational portion of the combined VOR were compensatory. These sensitivities were clearly reduced during nose-in eccentric sinusoidal rotation. Thus, especially for close targets at 4 Hz combined VOR was not compensatory, independent of target visibility. VOR elicited by sudden position steps showed a sequential response: (1) purely angular VOR (up to 40-45 ms); (2) additional translational VOR that was not modulated by target distance (45-65 ms); and (3) translational VOR weighted for target location (>65 ms). We conclude that angular and translational VOR have different latencies during transient accelerations and interact differently during agonistic (nose-out) and antagonistic stimulation (nose-in). AD - Institute of Physiology, Academy of Sciences of the Czech Republic, Praha. fuhry@lrz.uni-muenchen.de FAU - Fuhry, L AU - Fuhry L FAU - Nedvidek, J AU - Nedvidek J FAU - Haburcakova, C AU - Haburcakova C FAU - Buttner, U AU - Buttner U LA - eng PT - Journal Article CY - Germany TA - Exp Brain Res JID - 0043312 SB - IM MH - Acceleration MH - Afferent Pathways/*physiology MH - Animal MH - Brain/*physiology MH - Equilibrium/*physiology MH - Eye Movements/physiology MH - Macaca mulatta/*physiology MH - Nonlinear Dynamics MH - Physical Stimulation MH - Psychomotor Performance/physiology MH - Reaction Time/physiology MH - Reflex, Vestibulo-Ocular/*physiology MH - Rotation MH - Support, Non-U.S. Gov't MH - Vestibule/*physiology EDAT- 2002/03/13 10:00 MHDA- 2002/05/31 10:01 PHST- 2001/May/22 [received] PHST- 2001/Nov/26 [accepted] PHST- 2002/Feb/05 [aheadofprint] AID - 10.1007/s00221-001-0986-4 [doi] PST - ppublish SO - Exp Brain Res 2002 Apr;143(3):303-17. 220: Zhou X, et al. A dynamic model for simulatin...[PMID:11886831]Related Articles, Books, LinkOut UI - 21884321 PMID- 11886831 DA - 20020311 DCOM- 20020529 IS - 1350-4533 VI - 24 IP - 2 DP - 2002 Mar TI - A dynamic model for simulating a trip and fall during gait. PG - 121-7 AB - The purpose of this study was to develop an analytical model to simulate a trip and fall during gait. The human body was modeled as a 12 degree-of-freedom linkage system. The kinematics of the lower extremity for one cycle of gait were obtained for a healthy subject using an optoelectronic three-dimensional data acquisition system. Inverse dynamics was used to compute the moments about the hip, knee and ankle joints of the lower extremity. These moments were then used as input actuators to the joints in to a forward dynamics model to simulate the swing phase of gait from toe-off to heel-strike. An optimization procedure to minimize errors associated with the computed experimental torque was applied to correct for mathematical instability. An experiment was performed to measure the three-dimensional foot--obstacle contact force for a healthy subject tripping on an obstacle during gait. The contact force was applied to the swing limb of the forward dynamics model for 0.09 s beginning at 0.04 s after toe-off. Tripping on an obstacle followed by a muscle-relaxed fall was simulated. The simulation results were visualized with animation software. AD - The University of Chicago, Department of Surgery, Section of Orthopaedic Surgery and Rehabilitation Medicine, Chicago, IL, USA. FAU - Zhou, Xiaodong AU - Zhou X FAU - Draganich, Louis F AU - Draganich LF FAU - Amirouche, Farid AU - Amirouche F LA - eng PT - Journal Article CY - England TA - Med Eng Phys JID - 9422753 SB - IM MH - *Accidental Falls MH - *Activities of Daily Living MH - *Computer Simulation MH - Equilibrium/physiology MH - Feedback MH - Gait/*physiology MH - Human MH - Male MH - Middle Age MH - *Models, Biological MH - Movement MH - Nonlinear Dynamics MH - Rotation MH - Stress, Mechanical MH - Torque MH - Weight-Bearing EDAT- 2002/03/12 10:00 MHDA- 2002/05/30 10:01 AID - S1350453301001254 [pii] PST - ppublish SO - Med Eng Phys 2002 Mar;24(2):121-7. 221: Yang N, et al. Motion quality evaluation of ...[PMID:11886830]Related Articles, Books, LinkOut UI - 21884320 PMID- 11886830 DA - 20020311 DCOM- 20020529 IS - 1350-4533 VI - 24 IP - 2 DP - 2002 Mar TI - Motion quality evaluation of upper limb target-reaching movements. PG - 115-20 AB - Fitts' Law was extended in the polar coordinate system, and a set of indices for human motion evaluation is proposed. In this paper, the index of difficulty and the index of performance are introduced as the general indices for the quality measure of plane target-to-target movement. As an example, the target-reaching movement of the upper limb, which is a basic functional action of upper limbs in the activities of daily living, was experimentally investigated. Five healthy subjects were asked to perform six target-reaching tasks with different indices of difficulty. All movements were recorded using a Vicon motion analysis system. The movement quality was measured using these evaluation indices. AD - Rehabilitation Engineering Research Centre, Department of Precision Instruments, Tsinghua University, Beijing 100084, China. FAU - Yang, Nianfeng AU - Yang N FAU - Zhang, Ming AU - Zhang M FAU - Huang, Changhua AU - Huang C FAU - Jin, Dewen AU - Jin D LA - eng PT - Journal Article CY - England TA - Med Eng Phys JID - 9422753 SB - IM MH - Activities of Daily Living MH - Adult MH - Arm/*physiology MH - Human MH - Male MH - *Models, Biological MH - Movement/*physiology MH - Nonlinear Dynamics MH - Psychomotor Performance/*physiology MH - Range of Motion, Articular/physiology MH - Reproducibility of Results MH - Time Factors EDAT- 2002/03/12 10:00 MHDA- 2002/05/30 10:01 AID - S1350453301001217 [pii] PST - ppublish SO - Med Eng Phys 2002 Mar;24(2):115-20. 222: Gharagozloo P, et al. Substituted pentacyclic carba...[PMID:11881995]Related Articles, Books, LinkOut UI - 21877152 PMID- 11881995 DA - 20020307 DCOM- 20020426 IS - 0022-2623 VI - 45 IP - 6 DP - 2002 Mar 14 TI - Substituted pentacyclic carbazolones as novel muscarinic allosteric agents: synthesis and structure-affinity and cooperativity relationships. PG - 1259-74 AB - Two series of pentacyclic carbazolones, 22 and 23, have been synthesized utilizing a facile intramolecular Dielsminus signAlder reaction and are allosteric modulators at muscarinic acetylcholine receptors. Their affinities and cooperativities with acetylcholine and the antagonist N-methylscopolamine (NMS) at M(1)minus signM(4) receptors have been analyzed and compared. All of the synthesized compounds are negatively cooperative with acetylcholine. In contrast, the majority of the compounds exhibit positive cooperativity with NMS, particularly at M(2) and M(4) receptors. The subtype selectivity, in terms of affinity, was in general M(2) > M(1) > M(4) > M(3). The largest increases in affinity produced by a single substitution of the core structure were given by the 1-OMe (22b) and 1-Cl (22d) derivatives. The position of the N in the ring did not appear to be important for binding affinity or cooperativity. Two compounds 22y and 23i, both trisubstituted analogues, were the most potent compounds synthesized, with dissociation constants of 30minus sign100 nM for the M(2) NMS-liganded and unliganded receptor, respectively. The results indicate that the allosteric site, like the primary binding site, is capable of high-affinity interactions with molecules of relatively low molecular weight. AD - MRC Technology Research Division, 1-3 Burtonhole Lane, Mill Hill, London, NW7 1AD, UK. parviz.gharagozloo@pharma.com FAU - Gharagozloo, Parviz AU - Gharagozloo P FAU - Lazareno, Sebastian AU - Lazareno S FAU - Miyauchi, Masao AU - Miyauchi M FAU - Popham, Angela AU - Popham A FAU - Birdsall, Nigel J M AU - Birdsall NJ LA - eng PT - Journal Article CY - United States TA - J Med Chem JID - 9716531 RN - 0 (Carbazoles) RN - 0 (Ketones) RN - 0 (Muscarinic Antagonists) RN - 0 (Polycyclic Hydrocarbons) RN - 13265-10-6 (N-Methylscopolamine) RN - 51-84-3 (Acetylcholine) SB - IM MH - Acetylcholine/metabolism MH - Allosteric Regulation MH - Animal MH - Binding, Competitive MH - CHO Cells MH - Carbazoles/*chemical synthesis/pharmacology MH - Hamsters MH - Human MH - Ketones/*chemical synthesis/pharmacology MH - Least-Squares Analysis MH - Muscarinic Antagonists/*chemical synthesis/pharmacology MH - N-Methylscopolamine/agonists MH - Nonlinear Dynamics MH - Polycyclic Hydrocarbons/*chemical synthesis/pharmacology MH - Structure-Activity Relationship MH - Support, Non-U.S. Gov't EDAT- 2002/03/08 10:00 MHDA- 2002/04/27 10:01 AID - jm010946z [pii] PST - ppublish SO - J Med Chem 2002 Mar 14;45(6):1259-74. 223: Lagane B, et al. Lateral distribution of chole...[PMID:11880170]Related Articles, Books, LinkOut UI - 21868893 PMID- 11880170 DA - 20020306 DCOM- 20020509 IS - 0301-4622 VI - 95 IP - 1 DP - 2002 Jan 23 TI - Lateral distribution of cholesterol in membranes probed by means of a pyrene-labelled cholesterol: effects of acyl chain unsaturation. PG - 7-22 AB - The lateral distribution of cholesterol in membranes in the fluid state was investigated by studying the variation of the molar absorption coefficient of pyrene-labelled cholesterol (Py-chol) vs. its concentration in vesicles made of phosphatidylcholine, with variable acyl chain unsaturations. Absorption measurements indicated non-ideal mixing of Py-chol in unsaturated lipids, a process mainly controlled by the cholesterol moiety of the probe. Similar abilities of cholesterol and Py-chol in perturbing the phase properties of pure saturated phosphatidylcholine were observed by DSC experiments. Immiscibility of sterols was corroborated by fluorescence polarization measurements, which indicated a weaker ordering effect of cholesterol in unsaturated membranes. The sizes and the quantities of sterol oligomers formed were calculated. A model for the lateral distribution of cholesterol in membranes is proposed and is applied to known cholesterol/phosphatidylcholine phase diagrams. Finally, the results are discussed with regard to recent models of biological membrane organization, (i.e. rafts). AD - Institut de Pharmacologie et de Biologie Structurale du CNRS, 205 route de Narbonne, 31077 cedex 4, Toulouse, France. FAU - Lagane, B AU - Lagane B FAU - Mazeres, S AU - Mazeres S FAU - Le Grimellec, C AU - Le Grimellec C FAU - Cezanne, L AU - Cezanne L FAU - Lopez, A AU - Lopez A LA - eng PT - Journal Article CY - Netherlands TA - Biophys Chem JID - 0403171 RN - 0 (Indicators and Reagents) RN - 0 (Lipids) RN - 57-88-5 (Cholesterol) SB - IM MH - Calorimetry, Differential Scanning MH - Cholesterol/*chemistry MH - Fluorescence Polarization Immunoassay MH - Indicators and Reagents MH - Lipids/chemistry MH - *Membranes, Artificial MH - Models, Chemical MH - Nonlinear Dynamics MH - Spectrophotometry, Ultraviolet MH - Support, Non-U.S. Gov't EDAT- 2002/03/07 10:00 MHDA- 2002/05/10 10:01 AID - S0301462201002356 [pii] PST - ppublish SO - Biophys Chem 2002 Jan 23;95(1):7-22. 224: Duck FA. Nonlinear acoustics in diagno...[PMID:11879947]Related Articles, Books, LinkOut UI - 21874666 PMID- 11879947 DA - 20020307 DCOM- 20020530 IS - 0301-5629 VI - 28 IP - 1 DP - 2002 Jan TI - Nonlinear acoustics in diagnostic ultrasound. PG - 1-18 AB - The propagation of ultrasonic waves is nonlinear. Phenomena associated with the propagation of diagnostic ultrasound pulses cannot be predicted using linear assumptions alone. These include a progressive distortion in waveform, the generation of frequency harmonics and acoustic shocks, excess deposition of energy and acoustic saturation. These effects occur most strongly when ultrasound propagates within liquids with comparatively low acoustic attenuation, such as water, amniotic fluid or urine. Within soft tissues, similar effects occur, although they are limited by absorption and scattering. Nonlinear effects are of considerable importance during acoustic measurements, especially when these are used to predict in situ exposure. Harmonic generation may be used to create images. These offer improvements over conventional B-mode images in spatial resolution and, more significantly, in the suppression of acoustic clutter and side-lobe artifacts. B/A has promise as a parameter for tissue characterisation, but methods for imaging B/A have shown limited success. AD - Medical Physics Department, Royal United Hospital, Bath, UK. f.duck@bath.ac.uk FAU - Duck, Francis A AU - Duck FA LA - eng PT - Journal Article PT - Review PT - Review, Academic CY - England TA - Ultrasound Med Biol JID - 0410553 SB - IM MH - *Acoustics MH - Human MH - *Nonlinear Dynamics MH - *Ultrasonography, Doppler, Pulsed RF - 143 EDAT- 2002/03/07 10:00 MHDA- 2002/05/31 10:01 AID - S030156290100463X [pii] PST - ppublish SO - Ultrasound Med Biol 2002 Jan;28(1):1-18. 225: Lett M. A case for chaos theory in nu...[PMID:11878502]Related Articles, Books, LinkOut UI - 21867280 PMID- 11878502 DA - 20020306 DCOM- 20020404 IS - 0813-0531 VI - 18 IP - 3 DP - 2001 Mar-May TI - A case for chaos theory in nursing. PG - 14-9 AB - This paper addresses the question of why nurses should understand chaos theory. A critique of the literature is used to demonstrate how chaos theory has been utilised in a number of disciplines, including nursing. Possible applications of chaos theory in nursing are proposed in order to demonstrate where it might assist nurses, in particular researchers, educators and policy makers. The appropriateness of the application of chaos theory as a framework for knowledge generation is also discussed. AD - Australian Catholic University, Fitzroy, Victoria. FAU - Lett, M AU - Lett M LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - Australia TA - Aust J Adv Nurs JID - 8409358 SB - N MH - Human MH - Information Science MH - Knowledge MH - Mathematics MH - Models, Educational MH - Models, Nursing MH - *Nonlinear Dynamics MH - Nursing Research MH - *Nursing Theory MH - Nursing, Supervisory MH - Science MH - Systems Theory RF - 25 EDAT- 2002/03/07 10:00 MHDA- 2002/04/09 10:01 PST - ppublish SO - Aust J Adv Nurs 2001 Mar-May;18(3):14-9. 226: Liley DT, et al. A spatially continuous mean f...[PMID:11878285]Related Articles, Books, LinkOut UI - 21862525 PMID- 11878285 DA - 20020304 DCOM- 20020806 IS - 0954-898X VI - 13 IP - 1 DP - 2002 Feb TI - A spatially continuous mean field theory of electrocortical activity. PG - 67-113 AB - A set of nonlinear continuum field equations is presented which describes the dynamics of neural activity in cortex. These take into account the most pertinent anatomical and physiological features found in cortex with all parameter values obtainable from independent experiment. Derivation of a white noise fluctuation spectrum from a linearized set of equations shows the presence of strong resonances that correspond to electroencephalographically observed 0.3-4 Hz (mammalian delta), 4-8 Hz (mammalian theta), 8-13 Hz (mammalian alpha) and >13 Hz (mammalian beta) activity. Numerical solutions of a full set of one-dimensional nonlinear equations include properties analogous to cortical evoked potentials, travelling waves at experimentally observed velocities, threshold type spike activity and limit cycle, chaotic and noise driven oscillations at the frequency of the mammalian alpha rhythm. All these types of behaviour are generated with parameters that are within ranges reported experimentally. The strong dependence of the phenomena observed on inhibitory-inhibitory interactions is demonstrated. These results suggest that the classically described alpha may be instantiated in a number of qualitatively distinct dynamical regimes, all of which depend on the integrity of inhibitory-inhibitory population interactions. AD - School of Biophysical Sciences and Electrical Engineering, Swinburne University of Technology, Hawthorn, Victoria, Australia. dliley@swin.edu.au FAU - Liley, David T J AU - Liley DT FAU - Cadusch, Peter J AU - Cadusch PJ FAU - Dafilis, Mathew P AU - Dafilis MP LA - eng PT - Journal Article CY - England TA - Network JID - 9431867 RN - 0 (Neurotransmitters) SB - IM MH - Algorithms MH - Cerebral Cortex/*physiology MH - *Electroencephalography MH - Electrophysiology MH - Kinetics MH - Linear Models MH - Membrane Potentials/physiology MH - Models, Neurological MH - Neural Conduction/physiology MH - Neurotransmitters/physiology MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Synaptic Transmission/physiology EDAT- 2002/03/07 10:00 MHDA- 2002/08/07 10:01 PST - ppublish SO - Network 2002 Feb;13(1):67-113. 227: Molinari M, et al. Comparison of algorithms for ...[PMID:11876245]Related Articles, Books, LinkOut UI - 21865092 PMID- 11876245 DA - 20020305 DCOM- 20020819 IS - 0967-3334 VI - 23 IP - 1 DP - 2002 Feb TI - Comparison of algorithms for non-linear inverse 3D electrical tomography reconstruction. PG - 95-104 AB - Non-linear electrical impedance tomography reconstruction algorithms usually employ the Newton-Raphson iteration scheme to image the conductivity distribution inside the body. For complex 3D problems, the application of this method is not feasible any more due to the large matrices involved and their high storage requirements. In this paper we demonstrate the suitability of an alternative conjugate gradient reconstruction algorithm for 3D tomographic imaging incorporating adaptive mesh refinement and requiring less storage space than the Newton-Raphson scheme. We compare the reconstruction efficiency of both algorithms for a simple 3D head model. The results show that an increase in speed of about 30% is achievable with the conjugate gradient-based method without loss of accuracy. AD - Department of Electronics and Computer Science, University of Southampton, UK. FAU - Molinari, Marc AU - Molinari M FAU - Cox, Simon J AU - Cox SJ FAU - Blott, Barry H AU - Blott BH FAU - Daniell, Geoffrey J AU - Daniell GJ LA - eng PT - Journal Article CY - England TA - Physiol Meas JID - 9306921 SB - IM MH - *Algorithms MH - Comparative Study MH - Electric Impedance MH - Electrodes MH - Image Processing, Computer-Assisted/*statistics & numerical data MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Tomography/*statistics & numerical data EDAT- 2002/03/06 10:00 MHDA- 2002/08/20 10:01 PST - ppublish SO - Physiol Meas 2002 Feb;23(1):95-104. 228: Molinari M, et al. Optimal imaging with adaptive...[PMID:11876225]Related Articles, Books, LinkOut UI - 21865094 PMID- 11876225 DA - 20020305 DCOM- 20020819 IS - 0967-3334 VI - 23 IP - 1 DP - 2002 Feb TI - Optimal imaging with adaptive mesh refinement in electrical impedance tomography. PG - 121-8 AB - In non-linear electrical impedance tomography the goodness of fit of the trial images is assessed by the well-established statistical chi2 criterion applied to the measured and predicted datasets. Further selection from the range of images that fit the data is effected by imposing an explicit constraint on the form of the image, such as the minimization of the image gradients. In particular, the logarithm of the image gradients is chosen so that conductive and resistive deviations are treated in the same way. In this paper we introduce the idea of adaptive mesh refinement to the 2D problem so that the local scale of the mesh is always matched to the scale of the image structures. This improves the reconstruction resolution so that the image constraint adopted dominates and is not perturbed by the mesh discretization. The avoidance of unnecessary mesh elements optimizes the speed of reconstruction without degrading the resulting images. Starting with a mesh scale length of the order of the electrode separation it is shown that, for data obtained at presently achievable signal-to-noise ratios of 60 to 80 dB, one or two refinement stages are sufficient to generate high quality images. AD - Department of Electronics and Computer Science, University of Southampton, UK. FAU - Molinari, Marc AU - Molinari M FAU - Blott, Barry H AU - Blott BH FAU - Cox, Simon J AU - Cox SJ FAU - Daniell, Geoffrey J AU - Daniell GJ LA - eng PT - Journal Article CY - England TA - Physiol Meas JID - 9306921 SB - IM MH - Algorithms MH - Computer Simulation MH - Data Interpretation, Statistical MH - *Electric Impedance MH - Electrodes MH - Image Processing, Computer-Assisted/*methods MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Tomography/*statistics & numerical data EDAT- 2002/03/06 10:00 MHDA- 2002/08/20 10:01 PST - ppublish SO - Physiol Meas 2002 Feb;23(1):121-8. 229: Lin CC, et al. Neural and mechanical contrib...[PMID:11874142]Related Articles, Books, LinkOut UI - 21862839 PMID- 11874142 DA - 20020304 DCOM- 20020816 IS - 0090-6964 VI - 30 IP - 1 DP - 2002 Jan TI - Neural and mechanical contributions to the stretch reflex: a model synthesis. PG - 54-67 AB - A model for the soleus stretch reflex in the decerebrate cat was synthesized from models of the neural and muscular components, including the two proprioceptors (the muscle spindle and Golgi tendon organ) and their associated afferents (Ia, II, and Ib), the alpha motoneuron pool with its reflex pathways, the branches of the alpha motoneurons to the intrafusal muscles (beta innervation), and the extrafusal muscle. Parameters for the muscle and receptor models were chosen independently to match their responses in isolation. Reflex gains and gamma inputs were estimated to fit the response to stretch measured by Nichols and Houk. The chosen reflex gains and gamma inputs are not unique; many different combinations reproduced the characteristic stretch response. With a single set of fixed parameters, the model predicted many mechanical properties of the stretch reflex, including linearization effects (when the stretch magnitude and direction are varied), as well as the dependence on operating force and initial muscle length. The model did not accurately predict the responses at higher stretch velocities, due to failure of the extrafusal muscle model. AD - Cleveland FES Center, L.B. Stokes VA Medical Center and Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA. FAU - Lin, Chou-Ching K AU - Lin CC FAU - Crago, Patrick E AU - Crago PE LA - eng PT - Journal Article CY - United States TA - Ann Biomed Eng JID - 0361512 SB - IM MH - Animal MH - Biomechanics MH - Cats MH - Computer Simulation MH - Decerebrate State/physiopathology MH - Feedback MH - Mechanoreceptors/*physiology MH - *Models, Biological MH - Muscle Spindles/*physiology MH - Muscle, Skeletal/*physiology MH - Nonlinear Dynamics MH - *Reflex, Stretch/physiology MH - Reproducibility of Results MH - Sensitivity and Specificity MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/03/05 10:00 MHDA- 2002/08/17 10:01 PST - ppublish SO - Ann Biomed Eng 2002 Jan;30(1):54-67. 230: Hoffman AH, et al. Using uniaxial pseudorandom s...[PMID:11874141]Related Articles, Books, LinkOut UI - 21862838 PMID- 11874141 DA - 20020304 DCOM- 20020816 IS - 0090-6964 VI - 30 IP - 1 DP - 2002 Jan TI - Using uniaxial pseudorandom stress stimuli to develop soft tissue constitutive equations. PG - 44-53 AB - A nonlinear systems identification method was used to develop constitutive equations for soft tissue specimens under uniaxial tension. The constitutive equations are developed from a single test by applying a pseudorandom Gaussian (PGN) stress input to the specimen, measuring the resulting strain, and calculating the Volterra-Wiener kernels. First and second order kernels were developed for two tissues with widely different properties, rat medial collateral knee ligaments, and rat skin. These kernels were used to predict the strain response to a variety of sinusoidal stress inputs. These predicted strains were compared with the measured strain response using the normalized mean squared error (NMSE). Results showed NMSEs in the range of 0.01-0.08 provided that the magnitudes of the applied stresses were present in the original PGN stress input. Overall, the method provides a means to develop soft tissue constitutive equations that can predict both nonlinear and viscoelastic behavior over a wide range of stress inputs. AD - Department of Mechanical Engineering, Worcester Polytechnic Institute, MA 01609-2280, USA. ahoffman@wpi.edu FAU - Hoffman, Allen H AU - Hoffman AH FAU - Grigg, Peter AU - Grigg P LA - eng ID - NS-10783/NS/NINDS ID - NS-26222/NS/NINDS PT - Evaluation Studies PT - Journal Article CY - United States TA - Ann Biomed Eng JID - 0361512 SB - IM MH - Animal MH - Comparative Study MH - Connective Tissue/*physiology MH - Elasticity MH - Medial Collateral Ligament, Knee/*physiology MH - *Models, Statistical MH - *Nonlinear Dynamics MH - Normal Distribution MH - Rats MH - Rats, Sprague-Dawley MH - *Skin Physiology MH - Stochastic Processes MH - Stress, Mechanical MH - Support, U.S. Gov't, P.H.S. MH - Viscosity EDAT- 2002/03/05 10:00 MHDA- 2002/08/17 10:01 PST - ppublish SO - Ann Biomed Eng 2002 Jan;30(1):44-53. 231: Korenberg MJ, et al. Parallel cascade recognition ...[PMID:11874136]Related Articles, Books, LinkOut UI - 21862845 PMID- 11874136 DA - 20020304 DCOM- 20020816 IS - 0090-6964 VI - 30 IP - 1 DP - 2002 Jan TI - Parallel cascade recognition of exon and intron DNA sequences. PG - 129-40 AB - Many of the current procedures for detecting coding regions on human DNA sequences combine a number of individual techniques such as discriminant analysis and neural net methods. Recent papers have used techniques from nonlinear systems identification, in particular, parallel cascade identification (PCI), as one means for classifying protein sequences into their structure/function groups. In the present paper, PCI is used in a pilot study to distinguish exon (coding) from intron (noncoding; interspersed within genes) human DNA sequences. Only the first exon and first intron sequences with known boundaries in genomic DNA from the beta T-cell receptor locus were used for training. Then, the parallel cascade classifiers were able to achieve classification rates of about 89% on novel sequences in a test set, and averaged about 82% when results of a blind test were included. In testing over a much wider range of human nucleotide sequences, PCI classifiers averaged 83.6% correct classifications. These results indicate that parallel cascade classifiers may be useful components in future coding region detection programs. AD - Department of Electrical and Computer Engineering, Queen's University, Kingston, Ontario, Canada. korenber@post.queensu.ca FAU - Korenberg, Michael J AU - Korenberg MJ FAU - Lipson, Edward D AU - Lipson ED FAU - Green, James R AU - Green JR FAU - Solomon, Jerry E AU - Solomon JE LA - eng PT - Journal Article CY - United States TA - Ann Biomed Eng JID - 0361512 RN - 9007-49-2 (DNA) SB - IM MH - *Algorithms MH - Artificial Intelligence MH - DNA/classification/genetics MH - Exons/*genetics MH - Feasibility Studies MH - Genes, T-Cell Receptor beta/genetics MH - Human MH - Introns/*genetics MH - Nonlinear Dynamics MH - *Pattern Recognition MH - Sensitivity and Specificity MH - Sequence Analysis, DNA/*methods EDAT- 2002/03/05 10:00 MHDA- 2002/08/17 10:01 PST - ppublish SO - Ann Biomed Eng 2002 Jan;30(1):129-40. 232: Munday D. Edge of chaos....[PMID:11872783]Related Articles, Books, LinkOut UI - 21862103 PMID- 11872783 DA - 20020301 DCOM- 20020405 LR - 20021008 IS - 0141-0768 VI - 95 IP - 3 DP - 2002 Mar TI - Edge of chaos. PG - 165 FAU - Munday, Daniel AU - Munday D LA - eng PT - Comment PT - Letter CY - England TA - J R Soc Med JID - 7802879 SB - IM CON - J R Soc Med. 2001 Dec;94(12):613-6. PMID: 11733585 MH - Great Britain MH - Human MH - *Nonlinear Dynamics MH - State Medicine/*organization & administration/statistics & numerical data MH - Waiting Lists EDAT- 2002/03/02 10:00 MHDA- 2002/04/06 10:01 PST - ppublish SO - J R Soc Med 2002 Mar;95(3):165. 233: Bratman RL. Edge of chaos....[PMID:11872780]Related Articles, Books, LinkOut UI - 21862100 PMID- 11872780 DA - 20020301 DCOM- 20020405 LR - 20021008 IS - 0141-0768 VI - 95 IP - 3 DP - 2002 Mar TI - Edge of chaos. PG - 165 FAU - Bratman, R L AU - Bratman RL LA - eng PT - Comment PT - Letter CY - England TA - J R Soc Med JID - 7802879 SB - IM CON - J R Soc Med. 2001 Dec;94(12):613-6. PMID: 11733585 MH - Great Britain MH - Human MH - Nonlinear Dynamics MH - State Medicine/*organization & administration EDAT- 2002/03/02 10:00 MHDA- 2002/04/06 10:01 PST - ppublish SO - J R Soc Med 2002 Mar;95(3):165. 234: Navarro V, et al. Seizure anticipation in human...[PMID:11872619]Related Articles, Books, LinkOut UI - 21861513 PMID- 11872619 DA - 20020301 DCOM- 20020503 LR - 20021101 IS - 0006-8950 VI - 125 IP - Pt 3 DP - 2002 Mar TI - Seizure anticipation in human neocortical partial epilepsy. PG - 640-55 AB - The transition of brain activity towards an epileptic seizure is still a poorly understood phenomenon. Dynamic changes in brain activity have been detected several minutes before seizure emergence in populations of patients with mesial temporal lobe epilepsy (MTLE), using non-linear analysis of intracranial EEG recordings. Similar detection of a pre-ictal state has been obtained with standard scalp EEG recordings using a modified non-linear method. Here we applied this strategy to the seizures of patients with neocortical partial epilepsy. Results obtained by non-linear similarity analysis of 41 seizures from 11 patients with refractory partial epilepsy originating from various sites of the neocortex showed that (i) a pre-ictal state was detected in 90% of the patients and in 83% of the seizures whatever their location, with a mean anticipation time of 7.5 min; (ii) similar pre-ictal dynamic changes were detected when non-linear analysis methods were applied to either intracranial or scalp EEG recordings; (iii) the recording sites exhibiting these pre-ictal changes were distributed both within the epileptogenic focus and at remote locations; (iv) most pre-ictal dynamic changes were not correlated with linear changes in the frequency spectrum or with changes in the visually inspected EEG and the patients' behaviour. Hypotheses on the neuronal mechanisms underlying the pre-ictal period are discussed. The present results, together with those recently obtained in an MTLE population, suggest that changes in pre-ictal dynamics are a general phenomenon associated with seizure emergence in a wide population of patients with partial epilepsy, wherever the epileptogenic focus is located. The possibility of anticipating the onset of seizures has considerable therapeutic implications. AD - Laboratoire de Neurosciences Cognitives et Imagerie Cerebrale (LENA), CNRS UPR 640, Paris, France. FAU - Navarro, Vincent AU - Navarro V FAU - Martinerie, Jacques AU - Martinerie J FAU - Le Van Quyen, Michel AU - Le Van Quyen M FAU - Clemenceau, Stephane AU - Clemenceau S FAU - Adam, Claude AU - Adam C FAU - Baulac, Michel AU - Baulac M FAU - Varela, Francisco AU - Varela F LA - eng PT - Journal Article CY - England TA - Brain JID - 0372537 SB - AIM SB - IM MH - Adolescent MH - Adult MH - Causality MH - Diagnosis, Differential MH - Electroencephalography MH - Epilepsies, Partial/*diagnosis/pathology/*physiopathology MH - Female MH - Human MH - Laterality/physiology MH - Male MH - Middle Age MH - Neocortex/pathology/*physiopathology MH - Nonlinear Dynamics MH - Predictive Value of Tests MH - Reproducibility of Results MH - Support, Non-U.S. Gov't MH - Time Factors EDAT- 2002/03/02 10:00 MHDA- 2002/05/04 10:01 PST - ppublish SO - Brain 2002 Mar;125(Pt 3):640-55. 235: Stroud JS, et al. Numerical analysis of flow th...[PMID:11871610]Related Articles, Books, LinkOut UI - 21860289 PMID- 11871610 DA - 20020301 DCOM- 20020905 IS - 0148-0731 VI - 124 IP - 1 DP - 2002 Feb TI - Numerical analysis of flow through a severely stenotic carotid artery bifurcation. PG - 9-20 AB - The results of computational simulations may supplement MR and other in vivo diagnostic techniques to provide an accurate picture of the hemodynamics in particular vessels, which may help demonstrate the risks of embolism or plaque rupture posed by particular plaque deposits. In this study, a model based on an endarterectomy specimen of the plaque in a carotid bifurcation was examined. The flow conditions include steady flow at Reynolds numbers of 300, 600, and 900 as well as unsteady pulsatile flow. Both dynamic pressure and wall shear stress are very high, with shear values up to 70 N/m2, proximal to the stenosis throat in the internal carotid artery, and both vary significantly through the flow cycle. The wall shear stress gradient is also strong along the throat. Vortex shedding is observed downstream of the most severe occlusion. Two turbulence models, the Chien and Goldberg varieties of k-epsilon, are tested and evaluated for their relevance in this geometry. The Chien model better captures phenomena such as vortex shedding. The flow distal to stenosis is likely transitional, so a model that captures both laminar and turbulent behavior is needed. AD - Department of Mechanical Engineering, University of California, Berkeley, 94720, USA. FAU - Stroud, J S AU - Stroud JS FAU - Berger, S A AU - Berger SA FAU - Saloner, D AU - Saloner D LA - eng ID - HL61806/HL/NHLBI ID - HL61823/HL/NHLBI PT - Journal Article CY - United States TA - J Biomech Eng JID - 7909584 SB - IM MH - Arteriosclerosis/*physiopathology MH - Blood Flow Velocity MH - Carotid Arteries/*pathology/*physiopathology MH - Carotid Stenosis/*physiopathology MH - Comparative Study MH - Computer Simulation MH - Constriction, Pathologic MH - Endarterectomy, Carotid MH - Finite Element Analysis MH - Human MH - *Models, Cardiovascular MH - Nonlinear Dynamics MH - Pressure MH - Pulsatile Flow MH - Regional Blood Flow/physiology MH - Rheology MH - Sensitivity and Specificity MH - Stress, Mechanical MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/03/02 10:00 MHDA- 2002/09/06 10:01 PST - ppublish SO - J Biomech Eng 2002 Feb;124(1):9-20. 236: Sverdlik A, et al. Time-dependent mechanical beh...[PMID:11871608]Related Articles, Books, LinkOut UI - 21860298 PMID- 11871608 DA - 20020301 DCOM- 20020905 IS - 0148-0731 VI - 124 IP - 1 DP - 2002 Feb TI - Time-dependent mechanical behavior of sheep digital tendons, including the effects of preconditioning. PG - 78-84 AB - The time-dependent mechanical properties of sheep digital extensor tendons were studied by sequences of stress-relaxation tests. The results exhibited irreversible preconditioning and reversible viscoelasticity. Preconditioning effects were manifested by stress decay during consecutive stretch cycles to the same strain level, accompanied by elongation of the tendon's reference length. They intensified with increased strain level, and were reduced or became negligible as the strain decreased. The significance of intrinsic response mechanisms was studied via a structural model that includes viscoelasticity, preconditioning, and morphology of the tendon's collagen fibers. Model/data comparisons showed good agreement and good predictive power, suggesting that preconditioning can be integrated into comprehensive material characterization of tendons. AD - Department of Biomedical Engineering, Technion-Israel Institute of Technology, Haifa. bmesver@tx.technion.ac.il FAU - Sverdlik, A AU - Sverdlik A FAU - Lanir, Y AU - Lanir Y LA - eng PT - Journal Article CY - United States TA - J Biomech Eng JID - 7909584 SB - IM MH - Algorithms MH - Animal MH - Comparative Study MH - Computer Simulation MH - Elasticity MH - Female MH - Forelimb MH - Hoof and Claw/physiology MH - In Vitro MH - *Models, Biological MH - Nonlinear Dynamics MH - Reproducibility of Results MH - Sensitivity and Specificity MH - Sheep MH - Stress, Mechanical MH - Support, Non-U.S. Gov't MH - Tendons/*physiology MH - Tensile Strength MH - Time Factors MH - Viscosity EDAT- 2002/03/02 10:00 MHDA- 2002/09/06 10:01 PST - ppublish SO - J Biomech Eng 2002 Feb;124(1):78-84. 237: Kleen M, et al. Chaos -- no randomness in car...[PMID:11867920]Related Articles, Books, LinkOut UI - 21856409 PMID- 11867920 DA - 20020227 DCOM- 20020828 IS - 0014-312X VI - 34 IP - 1-2 DP - 2002 Jan-Apr TI - Chaos -- no randomness in cardiac physiology. PG - 176-80 AD - Department of Anesthesiology, Klinikum Grosshadern, University of Munich, Germany. martin.kleen@gmx.de FAU - Kleen, Martin AU - Kleen M FAU - Habler, Oliver AU - Habler O FAU - Zwissler, Bernhard AU - Zwissler B FAU - Kemming, Gregor AU - Kemming G FAU - Kisch-Wedel, Hille AU - Kisch-Wedel H LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - Switzerland TA - Eur Surg Res JID - 0174752 SB - IM MH - Coronary Circulation/*physiology MH - Heart/*physiology MH - Human MH - *Models, Cardiovascular MH - *Nonlinear Dynamics RF - 6 EDAT- 2002/02/28 10:00 MHDA- 2002/08/29 10:01 AID - esr34176 [pii] PST - ppublish SO - Eur Surg Res 2002 Jan-Apr;34(1-2):176-80. 238: Lipsitz LA. Dynamics of stability: the ph...[PMID:11867648]Related Articles, Books, LinkOut UI - 21856681 PMID- 11867648 DA - 20020227 DCOM- 20020321 IS - 1079-5006 VI - 57 IP - 3 DP - 2002 Mar TI - Dynamics of stability: the physiologic basis of functional health and frailty. PG - B115-25 AB - Under basal resting conditions most healthy physiologic systems demonstrate highly irregular, complex dynamics that represent interacting regulatory processes operating over multiple time scales. These processes prime the organism for an adaptive response, making it ready and able to react to sudden physiologic stresses. When the organism is perturbed or deviates from a given set of boundary conditions, most physiologic systems evoke closed-loop responses that operate over relatively short periods of time to restore the organism to equilibrium. This transiently alters the dynamics to a less complex, dominant response mode, which is denoted "reactive tuning." Aging and disease are associated with a loss of complexity in resting dynamics and maladaptive responses to perturbations. These alterations in the dynamics of physiologic systems lead to functional decline and frailty. Nonlinear mathematical techniques that quantify physiologic dynamics may predict the onset of frailty, and interventions aimed toward restoring healthy dynamics may prevent functional decline. AD - Hebrew Rehabilitation Center for Aged, Beth Israel Deaconess Medical Center, and Harvard Medical School Division on Aging, Boston, Massachusetts 02131, USA. Lipsitz@mail.hrca.harvard.edu FAU - Lipsitz, Lewis A AU - Lipsitz LA LA - eng ID - AG04390/AG/NIA ID - AG05134/AG/NIA ID - AG08812/AG/NIA PT - Journal Article CY - United States TA - J Gerontol A Biol Sci Med Sci JID - 9502837 SB - AIM SB - IM MH - Aged MH - Aged, 80 and over MH - Aging/*physiology MH - *Frail Elderly MH - *Health MH - Human MH - Nonlinear Dynamics MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/02/28 10:00 MHDA- 2002/03/22 10:01 PST - ppublish SO - J Gerontol A Biol Sci Med Sci 2002 Mar;57(3):B115-25. 239: Biswal B, et al. Neural network model for appa...[PMID:11863975]Related Articles, Books, LinkOut UI - 21854382 PMID- 11863975 DA - 20020226 DCOM- 20020311 IS - 0031-9007 VI - 88 IP - 8 DP - 2002 Feb 25 TI - Neural network model for apparent deterministic chaos in spontaneously bursting hippocampal slices. PG - 088102 AB - A neural network model that exhibits stochastic population bursting is studied by simulation. First return maps of interburst intervals exhibit recurrent unstable-periodic-orbit(UPO)-like trajectories similar to those found in experiments on hippocampal slices. Applications of various control methods and surrogate analysis for UPO detection also yield results similar to those of experiments. Our results question the interpretation of the experimental data as evidence for deterministic chaos and suggest caution in the use of UPO-based methods for detecting determinism in time-series data. AD - ICA1, University of Stuttgart, Pfaffenwaldring 27, D-70569 Stuttgart, Germany. FAU - Biswal, B AU - Biswal B FAU - Dasgupta, C AU - Dasgupta C LA - eng PT - Journal Article CY - United States TA - Phys Rev Lett JID - 0401141 SB - IM MH - Hippocampus/*physiology MH - *Models, Neurological MH - *Neural Networks (Computer) MH - *Nonlinear Dynamics EDAT- 2002/02/28 10:00 MHDA- 2002/03/12 10:01 PHST- 2001/Jun/07 [received] PHST- 2002/Feb/07 [aheadofprint] PST - ppublish SO - Phys Rev Lett 2002 Feb 25;88(8):088102. 240: McCaffery G, et al. Wavelet and receiver operatin...[PMID:11863575]Related Articles, Books UI - 21853980 PMID- 11863575 DA - 20020226 DCOM- 20020422 LR - 20021029 IS - 1539-3755 VI - 65 IP - 2 Pt 1 DP - 2002 Feb TI - Wavelet and receiver operating characteristic analysis of heart rate variability. PG - 022901 AB - Multiresolution wavelet analysis has been used to study the heart rate variability in two classes of patients with different pathological conditions. The scale dependent measure of Thurner et al. was found to be statistically significant in discriminating patients suffering from hypercardiomyopathy from a control set of normal subjects. We have performed Receiver Operating Characteristc (ROC) analysis and found the ROC area to be a useful measure by which to label the significance of the discrimination, as well as to describe the severity of heart dysfunction. AD - Department of Physics and Astronomy, University of Wales, Cardiff, United Kingdom. FAU - McCaffery, G AU - McCaffery G FAU - Griffith, T M AU - Griffith TM FAU - Naka, K AU - Naka K FAU - Frennaux, M P AU - Frennaux MP FAU - Matthai, C C AU - Matthai CC LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 SB - IM MH - Analysis of Variance MH - Biophysics MH - Cardiomyopathy, Hypertrophic/physiopathology MH - Heart Rate/*physiology MH - Human MH - Models, Cardiovascular MH - Nonlinear Dynamics MH - ROC Curve MH - Support, Non-U.S. Gov't MH - Syncope, Vasovagal/physiopathology EDAT- 2002/02/28 10:00 MHDA- 2002/04/23 10:01 PHST- 2001/Sep/17 [received] PHST- 2002/Jan/15 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2002 Feb;65(2 Pt 1):022901. 241: Heinz MG, et al. Quantifying the implications ...[PMID:11863202]Related Articles, Books, LinkOut UI - 21851968 PMID- 11863202 DA - 20020226 DCOM- 20020329 IS - 0001-4966 VI - 111 IP - 2 DP - 2002 Feb TI - Quantifying the implications of nonlinear cochlear tuning for auditory-filter estimates. PG - 996-1011 AB - The relation between auditory filters estimated from psychophysical methods and peripheral tuning was evaluated using a computational auditory-nerve (AN) model that included many of the response properties associated with nonlinear cochlear tuning. The phenomenological AN model included the effects of dynamic level-dependent tuning, compression, and suppression on the responses of high-, medium-, and low-spontaneous-rate AN fibers. Signal detection theory was used to evaluate psychophysical performance limits imposed by the random nature of AN discharges and by random-noise stimuli. The power-spectrum model of masking was used to estimate psychophysical auditory filters from predicted AN-model detection thresholds for a tone signal in fixed-level notched-noise maskers. Results demonstrate that the role of suppression in broadening peripheral tuning in response to the noise masker has implications for the interpretation of psychophysical auditory-filter estimates. Specifically, the estimated psychophysical auditory-filter equivalent-rectangular bandwidths (ERBs) that were derived from the nonlinear AN model with suppression always overestimated the ERBs of the low-level peripheral model filters. Further, this effect was larger for an 8-kHz signal than for a 2-kHz signal, suggesting a potential characteristic-frequency (CF) dependent bias in psychophysical estimates of auditory filters due to the increase in strength of cochlear nonlinearity with increases in CF. AD - Speech and Hearing Sciences Program, Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge 02139, USA. mgheinz@bme.jhu.edu FAU - Heinz, Michael G AU - Heinz MG FAU - Colburn, H Steven AU - Colburn HS FAU - Carney, Laurel H AU - Carney LH LA - eng ID - R01DC00100/DC/NIDCD ID - R01DC01641/DC/NIDCD ID - T32DC00038/DC/NIDCD PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 SB - IM MH - Auditory Perception/*physiology MH - Cochlea/*innervation MH - Cochlear Nerve/physiology MH - Human MH - *Nonlinear Dynamics MH - Psychophysics MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/02/28 10:00 MHDA- 2002/03/30 10:01 PST - ppublish SO - J Acoust Soc Am 2002 Feb;111(2):996-1011. 242: de BE, et al. The mechanical waveform of th...[PMID:11863200]Related Articles, Books, LinkOut UI - 21851966 PMID- 11863200 DA - 20020226 DCOM- 20020329 IS - 0001-4966 VI - 111 IP - 2 DP - 2002 Feb TI - The mechanical waveform of the basilar membrane. IV. Tone and noise stimuli. PG - 979-89 AB - Analysis of mechanical cochlear responses to wide bands of random noise clarifies many effects of cochlear nonlinearity. The previous paper [de Boer and Nuttall, J. Acoust. Soc. Am. 107, 1497-1507 (2000)] illustrates how closely results of computations in a nonlinear cochlear model agree with responses from physiological experiments. In the present paper results for tone stimuli are reported. It was found that the measured frequency response for pure tones differs little from the frequency response associated with a noise signal. For strong stimuli, well into the nonlinear region, tones have to be presented at a specific level with respect to the noise for this to be true. In this report the nonlinear cochlear model originally developed for noise analysis was modified to accommodate pure tones. For this purpose the efficiency with which outer hair cells modify the basilar-membrane response was made into a function of cochlear location based on local excitation. For each experiment, the modified model is able to account for the experimental findings, within 1 or 2 dB. Therefore, the model explains why the type of filtering that tones undergo in the cochlea is essentially the same as that for noise signals (provided the tones are presented at the appropriate level). AD - Academic Medical Center, University of Amsterdam, The Netherlands. e.d.boer@hccnet.nl FAU - de, Boer Egbert AU - de BE FAU - Nuttall, Alfred L AU - Nuttall AL LA - eng ID - NIDCD-DC-00141/DC/NIDCD PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 SB - IM MH - Acoustic Stimulation MH - Basilar Membrane/*physiology MH - Biomechanics MH - Cochlea/physiology MH - Human MH - *Noise MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/02/28 10:00 MHDA- 2002/03/30 10:01 PST - ppublish SO - J Acoust Soc Am 2002 Feb;111(2):979-89. 243: Murphy KD, et al. Grazing instabilities and pos...[PMID:11863190]Related Articles, Books, LinkOut UI - 21851956 PMID- 11863190 DA - 20020226 DCOM- 20020329 IS - 0001-4966 VI - 111 IP - 2 DP - 2002 Feb TI - Grazing instabilities and post-bifurcation behavior in an impacting string. PG - 884-92 AB - A theoretical and experimental investigation of the nonlinear dynamic response of a periodically excited string subject to a knife-edge amplitude restraint is presented. The amplitude restraint creates an impact condition as the amplitude of the response grows. The focus of this work is on the influence of a grazing instability; this zero-velocity impact event leads to complicated, post-bifurcation behavior ranging from multifrequency, periodic motion to chaos. In addition to looking at the response numerically, parameter combinations leading to an incidence of grazing are clearly identified in the excitation force excitation frequency parameter space using a multiple scales perturbation analysis. Modeling issues, numerical difficulties, and experimental limitations are also discussed. AD - Department of Mechanical Engineering, University of Connecticut, Storrs 06269-3139, USA. FAU - Murphy, K D AU - Murphy KD FAU - Morrison, T M AU - Morrison TM LA - eng PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 SB - IM MH - *Motion MH - *Nonlinear Dynamics MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/02/28 10:00 MHDA- 2002/03/30 10:01 PST - ppublish SO - J Acoust Soc Am 2002 Feb;111(2):884-92. 244: Tappert FD, et al. Study of a novel range-depend...[PMID:11863177]Related Articles, Books, LinkOut UI - 21851942 PMID- 11863177 DA - 20020226 DCOM- 20020329 IS - 0001-4966 VI - 111 IP - 2 DP - 2002 Feb TI - Study of a novel range-dependent propagation effect with application to the axial injection of signals from the Kaneohe source. PG - 757-62 AB - A novel range-dependent propagation effect occurs when a source is placed on the seafloor in shallow water with a downward refracting sound speed profile, and sound waves propagate down a slope into deep water. Under these conditions, small grazing-angle sound waves slide along the bottom downward and outward from the source until they reach the depth of the sound channel axis in deep water, where they are detached from the sloping bottom and continue to propagate outward near the sound channel axis. This "mudslide" effect is one of a few robust and predictable acoustic propagation effects that occur in range-dependent ocean environments. As a consequence of this effect, a bottom mounted source in shallow water can inject a significant amount of acoustic energy into the axis of the deep ocean sound channel that can then propagate to very long ranges. Numerical simulations with a full-wave range-dependent acoustic model show that the Kaneohe experiment had the appropriate source, bathymetry, and sound speed profiles that allows this effect to operate efficiently. This supports the interpretation that some of the near-axial acoustic signals, received near the coast of California from the bottom mounted source located in shallow water in Kaneohe Bay, Oahu, Hawaii, were injected into the sound channel of the deep Pacific Ocean by this mechanism. Numerical simulations suggest that the mudslide effect is robust. AD - Division of Applied Marine Physics, University of Miami, RSMAS, Florida 33149, USA. FAU - Tappert, Frederick D AU - Tappert FD FAU - Spiesberger, John L AU - Spiesberger JL FAU - Wolfson, Michael A AU - Wolfson MA LA - eng PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 RN - 7732-18-5 (Water) SB - IM MH - Nonlinear Dynamics MH - Oceans and Seas MH - *Sound MH - Support, U.S. Gov't, Non-P.H.S. MH - Water EDAT- 2002/02/28 10:00 MHDA- 2002/03/30 10:01 PST - ppublish SO - J Acoust Soc Am 2002 Feb;111(2):757-62. 245: Plantier F, et al. Measurement of the B/A nonlin...[PMID:11863173]Related Articles, Books, LinkOut UI - 21851937 PMID- 11863173 DA - 20020226 DCOM- 20020329 IS - 0001-4966 VI - 111 IP - 2 DP - 2002 Feb TI - Measurement of the B/A nonlinearity parameter under high pressure: application to water. PG - 707-15 AB - An experimental apparatus was developed to measure, over a wide range of pressure, the acoustical nonlinear parameter B/A with an uncertainty of 2.2% in order to study the influence of pressure on the value of this parameter in liquids. The experimental technique rests on an improved thermodynamic method which uses a highly sensitive phase comparison technique to measure the change in speed of sound with pressure. The apparatus was then used to measure B/A in water within the pressure range from 0.1 to 50 MPa and at temperatures of between 303.15 and 373.15 K. The data obtained were compared with those in the literature which come from numerical derivation of speed of sound measurements. AD - Laboratoire des Fluides Complexes, Faculte des Sciences et Techniques, Pau, France. FAU - Plantier, F AU - Plantier F FAU - Daridon, J L AU - Daridon JL FAU - Lagourette, B AU - Lagourette B LA - eng PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 RN - 7732-18-5 (Water) SB - IM MH - Acoustics MH - *Nonlinear Dynamics MH - *Pressure MH - Temperature MH - Ultrasonics MH - *Water EDAT- 2002/02/28 10:00 MHDA- 2002/03/30 10:01 PST - ppublish SO - J Acoust Soc Am 2002 Feb;111(2):707-15. 246: Richards VM. Effects of a limited class of...[PMID:11863157]Related Articles, Books, LinkOut UI - 21851969 PMID- 11863157 DA - 20020226 DCOM- 20020329 IS - 0001-4966 VI - 111 IP - 2 DP - 2002 Feb TI - Effects of a limited class of nonlinearities on estimates of relative weights. PG - 1012-7 AB - Perturbation analyses have been applied in recent years to determine the relative contribution of individual stimulus components in detection and discrimination tasks. Responses to stimulus samples are compared to stimulus parameters to determine the details of the decision rule. Often, a linear model is assumed and it is of interest to determine the relative contribution of different stimulus elements to the decision. Here, biases in estimated relative weights are considered for the case where the decision variable is given by D = (sigma(alphaiXn(i))k)m and the stimulus components, the Xi, are normally distributed, of equal variance, and mutually independent. The alphai are the "true" combination weights, and n, k, and m are positive reals. The method used to estimate relative weights is the correlation coefficient between the Xi and the observer's responses. Estimates of relative alphai do not depend on m but may depend on the mean values of the Xi and the values of n and k (a dependence on the variance, sigmai2, holds even for linear transformations). AD - Department of Psychology, University of Pennsylvania, Philadelphia 19104, USA. FAU - Richards, Virginia M AU - Richards VM LA - eng ID - R01 DC 02012/DC/NIDCD PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 SB - IM MH - *Computer Simulation MH - *Decision Making MH - Human MH - *Nonlinear Dynamics MH - Support, U.S. Gov't, P.H.S. MH - *Weight Perception EDAT- 2002/02/28 10:00 MHDA- 2002/03/30 10:01 PST - ppublish SO - J Acoust Soc Am 2002 Feb;111(2):1012-7. 247: Gottschalk A. Derivation of the visual cont...[PMID:11860681]Related Articles, Books, LinkOut UI - 21851256 PMID- 11860681 DA - 20020225 DCOM- 20020313 IS - 0899-7667 VI - 14 IP - 3 DP - 2002 Mar TI - Derivation of the visual contrast response function by maximizing information rate. PG - 527-42 AB - A graph of neural output as a function of the logarithm of stimulus intensity often produces an S-shaped function, which is frequently modeled by the hyperbolic ratio equation. The response of neurons in early vision to stimuli of varying contrast is an important example of this. Here, the hyperbolic ratio equation with a response exponent of two is derived exactly by considering the balance between information rate and the neural costs of making that information available, where neural costs are a function of synaptic strength and spike rate. The maximal response and semisaturation constant of the neuron can be related to the stimulus ensemble and therefore shift accordingly to exhibit contrast gain control and normalization. FAU - Gottschalk, Allan AU - Gottschalk A LA - eng ID - EY10915/EY/NEI PT - Journal Article CY - United States TA - Neural Comput JID - 9426182 SB - IM MH - Contrast Sensitivity/*physiology MH - Human MH - *Models, Neurological MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/02/28 10:00 MHDA- 2002/03/14 10:01 AID - 10.1162/089976602317250889 [doi] PST - ppublish SO - Neural Comput 2002 Mar;14(3):527-42. 248: Bressloff PC, et al. An amplitude equation approac...[PMID:11860680]Related Articles, Books, LinkOut UI - 21851255 PMID- 11860680 DA - 20020225 DCOM- 20020313 IS - 0899-7667 VI - 14 IP - 3 DP - 2002 Mar TI - An amplitude equation approach to contextual effects in visual cortex. PG - 493-525 AB - A mathematical theory of interacting hypercolumns in primary visual cortex (V1) is presented that incorporates details concerning the anisotropic nature of long-range lateral connections. Each hypercolumn is modeled as a ring of interacting excitatory and inhibitory neural populations with orientation preferences over the range 0 to 180 degrees. Analytical methods from bifurcation theory are used to derive nonlinear equations for the amplitude and phase of the population tuning curves in which the effective lateral interactions are linear in the amplitudes. These amplitude equations describe how mutual interactions between hypercolumns via lateral connections modify the response of each hypercolumn to modulated inputs from the lateral geniculate nucleus; such interactions form the basis of contextual effects. The coupled ring model is shown to reproduce a number of orientation-dependent and contrast-dependent features observed in center-surround experiments. A major prediction of the model is that the anisotropy in lateral connections results in a nonuniform modulatory effect of the surround that is correlated with the orientation of the center. FAU - Bressloff, Paul C AU - Bressloff PC FAU - Cowan, Jack D AU - Cowan JD LA - eng PT - Journal Article CY - United States TA - Neural Comput JID - 9426182 SB - IM MH - Animal MH - Anisotropy MH - Human MH - *Models, Neurological MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Visual Cortex/*physiology MH - Visual Pathways/physiology EDAT- 2002/02/28 10:00 MHDA- 2002/03/14 10:01 AID - 10.1162/089976602317250870 [doi] PST - ppublish SO - Neural Comput 2002 Mar;14(3):493-525. 249: Ellison GT. Letting the Gini out of the b...[PMID:11858212]Related Articles, Books, LinkOut UI - 21836791 PMID- 11858212 DA - 20020218 DCOM- 20020225 IS - 0277-9536 VI - 54 IP - 4 DP - 2002 Feb TI - Letting the Gini out of the bottle? Challenges facing the relative income hypothesis. PG - 561-76 AB - The relative income hypothesis interprets statistical associations between income inequality and average health status at the population level, as evidence that income inequality has a deleterious psychosocial effect on individual health. An alternative explanation is that these, population-level associations, are statistical artefacts of curvilinear, individual-level relationships between income and health. Indeed, provided the cost-benefit ratio of health-enhancing goods and services vary, the law of diminishing returns should produce curvilinear, asymptotic relationships between income and health at the individual level, which create ('artefactual') associations between income inequality and health at the population level. However, proponents of the relative income hypothesis have argued that these relationships are unlikely to be responsible for the associations observed between income inequality and average health status amongst high-income populations. In these populations, the individual-level relationships between income and health would be nearer their asymptotes, where a shallower slope should ensure that income inequality has little (if any) 'artefactual' effect on average health status. Yet this argument was based on analyses of population-level data which underestimated the slope and curvilinearity of underlying, individual-level relationships between income and health. It is therefore likely that (at least some part of) the population-level associations between income inequality and average health status (amongst low-, middle- and high-income populations) are 'artefacts' of curvilinear, individual-level relationships between income and health. Nevertheless, it is also possible that income inequality is somehow (partly or wholly) responsible for the curvilinear nature of individual-level relationships between income and health. Likewise, it is possible that income inequality alters the height, slope and/or curvilinearity of these relationships in such a way that income inequality has an independent effect on individual health. In either instance, the 'artefactual' effect of curvilinear relationships between income and health at the individual level would simply reflect the mechanism underlying the relative income hypothesis. AD - Faculty of Healthcare Sciences, St George's Hospital Medical School, London, UK. g.ellison@ioe.ac.uk FAU - Ellison, George T H AU - Ellison GT LA - eng PT - Journal Article CY - England TA - Soc Sci Med JID - 8303205 SB - IM MH - Comparative Study MH - Female MH - *Health Status MH - Human MH - Income/*statistics & numerical data/trends MH - *Life Expectancy MH - Male MH - Models, Econometric MH - Nonlinear Dynamics MH - Poverty/*statistics & numerical data/trends MH - Reproducibility of Results MH - Research Design MH - Risk Factors MH - Socioeconomic Factors MH - Survival Analysis EDAT- 2002/02/23 10:00 MHDA- 2002/02/28 10:01 PST - ppublish SO - Soc Sci Med 2002 Feb;54(4):561-76. 250: Hastings CA, et al. New algorithms for processing...[PMID:11857732]Related Articles, Books, LinkOut UI - 21846951 PMID- 11857732 DA - 20020221 DCOM- 20020415 IS - 0951-4198 VI - 16 IP - 5 DP - 2002 TI - New algorithms for processing and peak detection in liquid chromatography/mass spectrometry data. PG - 462-7 AB - Two new algorithms for automated processing of liquid chromatography/mass spectrometry (LC/MS) data are presented. These algorithms were developed from an analysis of the noise and artifact distribution in such data. The noise distribution was analyzed by preparing histograms of the signal intensity in LC/MS data. These histograms are well fit by a sum of two normal distributions in the log scale. One new algorithm, median filtering, provides increased performance compared to averaging adjacent scans in removing noise that is not normally distributed in the linear scale. Another new algorithm, vectorized peak detection, provides increased robustness with respect to variation in the noise and artifact distribution compared to methods based on determining an intensity threshold for the entire dataset. Vectorized peak detection also permits the incorporation of existing algorithms for peak detection in ion chromatograms and/or mass spectra. The application of these methods to LC/MS spectra of complex biological samples is described. CI - Copyright 2002 John Wiley & Sons, Ltd. AD - SurroMed, Inc., 2375 Garcia Ave., Mountain View, CA 94043, USA. chastings@surromed.com FAU - Hastings, Curtis A AU - Hastings CA FAU - Norton, Scott M AU - Norton SM FAU - Roy, Sushmita AU - Roy S LA - eng PT - Journal Article CY - England TA - Rapid Commun Mass Spectrom JID - 8802365 SB - IM MH - *Algorithms MH - Chromatography, Liquid/*statistics & numerical data MH - Data Interpretation, Statistical MH - Nonlinear Dynamics MH - Spectrum Analysis, Mass/*statistics & numerical data EDAT- 2002/02/22 10:00 MHDA- 2002/04/16 10:01 AID - 10.1002/rcm.600 [pii] PST - ppublish SO - Rapid Commun Mass Spectrom 2002;16(5):462-7. 251: Noykova N, et al. Quantitative analyses of anae...[PMID:11857285]Related Articles, Books, LinkOut UI - 21845506 PMID- 11857285 DA - 20020221 DCOM- 20020906 IS - 0006-3592 VI - 78 IP - 1 DP - 2002 Apr 5 TI - Quantitative analyses of anaerobic wastewater treatment processes: identifiability and parameter estimation. PG - 89-103 AB - We investigated the problem of identifying the parameters of a nonlinear fifth order model describing the population dynamics of two main bacterial groups in an anaerobic wastewater treatment process. In addition to addressing problems concerning structural and practical identifiability, we also analyzed how mathematical descriptions of bacterial population dynamics can model real data. Using three data sets recorded under different experimental conditions, we estimated important biochemical parameters and demonstrated that our model could describe the data successfully. Parameters, which are simultaneously determined using information from all three experiments, have more reliable estimates. We conclude that, after appropriate estimation, this model can be used for optimization and the control of continuous processes. CI - Copyright 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 78: 89-103, 2002; DOI 10.1002/bit.10179 AD - Department of Mathematical Sciences, University of Turku, FIN-20014 Turku, Finland. FAU - Noykova, Nelly AU - Noykova N FAU - Muller, Thorsten G AU - Muller TG FAU - Gyllenberg, Mats AU - Gyllenberg M FAU - Timmer, Jens AU - Timmer J LA - eng PT - Journal Article CY - United States TA - Biotechnol Bioeng JID - 7502021 SB - IM MH - Anaerobiosis/physiology MH - Bacteria, Anaerobic/*metabolism/physiology MH - Biodegradation MH - Comparative Study MH - Computer Simulation MH - Ecosystem MH - *Models, Biological MH - Monte Carlo Method MH - Nonlinear Dynamics MH - Sensitivity and Specificity MH - Stochastic Processes MH - Support, Non-U.S. Gov't MH - Waste Disposal, Fluid/methods MH - Water Purification/*methods EDAT- 2002/02/22 10:00 MHDA- 2002/09/07 10:01 AID - 10.1002/bit.10179 [pii] PST - ppublish SO - Biotechnol Bioeng 2002 Apr 5;78(1):89-103. 252: Mattioni BE, et al. Development of quantitative s...[PMID:11855972]Related Articles, Books, LinkOut UI - 21846364 PMID- 11855972 DA - 20020221 DCOM- 20020408 IS - 0095-2338 VI - 42 IP - 1 DP - 2002 Jan-Feb TI - Development of quantitative structure-activity relationship and classification models for a set of carbonic anhydrase inhibitors. PG - 94-102 AB - Mathematical models are developed to find quantitative structure-activity relationships that correlate chemical structure and inhibition toward three carbonic anhydrase (CA) isozymes: CA I, II, and IV. Numerical descriptors are generated to encode important topological, geometric, and electronic features of molecular structure. After descriptor generation, multiple linear regression, and computational neural network (CNN) analyses are performed on various descriptor subsets to find superior models for prediction. Committees of five CNNs were utilized to average final predicted values for the 142-compound data set. For inhibitors of CA I, an 8-5-1 CNN committee produced a training set rms error of 0.105 log K(i) (r(2) = 0.994) and prediction set rms error of 0.208 log K(i) (r(2) = 0.980). Training and prediction set rms errors of 0.140 log K(i) (r(2) = 0.992) and 0.231 log K(i) (r(2) = 0.971), respectively, were produced by a 9-5-1 CNN committee for inhibitors of CA II. For prediction of CA IV inhibitors, an 8-5-1 CNN committee produced training and prediction set rms errors of 0.147 log K(i) (r(2) = 0.992) and 0.211 log K(i) (r(2) = 0.991), respectively. In addition, classification models were built using k-nearest neighbor (kNN) analysis to solve two- and three-class problems for inhibitors of CA IV. A three-descriptor classification model proved superior in labeling compounds as active or inactive inhibitors for the two-class problem. Training and prediction set percent classification rates of 100% and 87.1%, respectively, were obtained. For the three-class (active/moderate/inactive) problem, a five-descriptor model was deemed optimal producing a training set percent classification rate of 98.8% and prediction set rate of 79.0%. AD - Department of Chemistry, The Pennsylvania State University, 152 Davey Laboratory, University Park, Pennsylvania 16802, USA. FAU - Mattioni, Brian E AU - Mattioni BE FAU - Jurs, Peter C AU - Jurs PC LA - eng PT - Journal Article CY - United States TA - J Chem Inf Comput Sci JID - 7505012 RN - 0 (Carbonic Anhydrase Inhibitors) SB - IM MH - Carbonic Anhydrase Inhibitors/*chemistry/classification/*pharmacology MH - Databases, Factual MH - Human MH - Linear Models MH - Mathematics MH - Models, Chemical MH - Neural Networks (Computer) MH - Nonlinear Dynamics MH - Quantitative Structure-Activity Relationship EDAT- 2002/02/22 10:00 MHDA- 2002/04/09 10:01 AID - ci0100696 [pii] PST - ppublish SO - J Chem Inf Comput Sci 2002 Jan-Feb;42(1):94-102. 253: Repucci MA, et al. General strategy for hierarch...[PMID:11853266]Related Articles, Books, LinkOut UI - 21842088 PMID- 11853266 DA - 20020220 DCOM- 20020815 IS - 0090-6964 VI - 29 IP - 12 DP - 2001 Dec TI - General strategy for hierarchical decomposition of multivariate time series: implications for temporal lobe seizures. PG - 1135-49 AB - We describe a novel method for the analysis of multivariate time series that exploits the dynamic relationships among the multiple signals. The approach resolves the multivariate time series into hierarchically dependent underlying sources, each driven by noise input and influencing subordinate sources in the hierarchy. Implementation of this hierarchical decomposition (HD) combines principal components analysis (PCA), autoregressive modeling, and a novel search strategy among orthogonal rotations. For model systems conforming to this hierarchical structure, HD accurately extracts the underlying sources, whereas PCA or independent components analysis does not. The interdependencies of cortical, subcortical, and brainstem networks suggest application of HD to multivariate measures of brain activity. We show first that HD indeed resolves temporal lobe ictal electrocorticographic data into nearly hierarchical form. A previous analysis of these data identified characteristic nonlinearities in the PCA-derived temporal components that resembled those seen in absence (petit mal) seizure electroencephalographic traces. However, the components containing these characteristic nonlinearities accounted for only a small fraction of the power. Analysis of these data with HD reveals furthermore that components containing characteristic nonlinearities, though small, can be at the origin of the hierarchy. This finding supports the link between temporal lobe and absence epilepsy. AD - Department of Neurology and Neuroscience, Weill Graduate School of Medical Sciences of Cornell University, New York, NY 10021, USA. FAU - Repucci, M A AU - Repucci MA FAU - Schiff, N D AU - Schiff ND FAU - Victor, J D AU - Victor JD LA - eng ID - EY7138/EY/NEI ID - EY7977/EY/NEI ID - EY9314/EY/NEI ID - NS02172/NS/NINDS PT - Journal Article PT - Validation Studies CY - United States TA - Ann Biomed Eng JID - 0361512 SB - IM MH - *Algorithms MH - Computer Simulation MH - Electroencephalography/*methods MH - Epilepsy, Absence/*diagnosis/physiopathology MH - Epilepsy, Temporal Lobe/*diagnosis/physiopathology MH - Human MH - Models, Neurological MH - *Nonlinear Dynamics MH - Reproducibility of Results MH - Sensitivity and Specificity MH - *Signal Processing, Computer-Assisted MH - Stochastic Processes MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/02/21 10:00 MHDA- 2002/08/16 10:01 PST - ppublish SO - Ann Biomed Eng 2001 Dec;29(12):1135-49. 254: Meeren HK, et al. Cortical focus drives widespr...[PMID:11850474]Related Articles, Books, LinkOut UI - 21839237 PMID- 11850474 DA - 20020218 DCOM- 20020226 IS - 1529-2401 VI - 22 IP - 4 DP - 2002 Feb 15 TI - Cortical focus drives widespread corticothalamic networks during spontaneous absence seizures in rats. PG - 1480-95 AB - Absence seizures are the most pure form of generalized epilepsy. They are characterized in the electroencephalogram by widespread bilaterally synchronous spike-wave discharges (SWDs), which are the reflections of highly synchronized oscillations in thalamocortical networks. To reveal network mechanisms responsible for the initiation and generalization of the discharges, we studied the interrelationships between multisite cortical and thalamic field potentials recorded during spontaneous SWDs in the freely moving WAG/Rij rat, a genetic model of absence epilepsy. Nonlinear association analysis revealed a consistent cortical "focus" within the peri-oral region of the somatosensory cortex. The SWDs recorded at other cortical sites consistently lagged this focal site, with time delays that increased with electrode distance (corresponding to a mean propagation velocity of 1.4 m/sec). Intra-thalamic relationships were more complex and could not account for the observed cortical propagation pattern. Cortical and thalamic sites interacted bi-directionally, whereas the direction of this coupling could vary throughout one seizure. However, during the first 500 msec, the cortical focus was consistently found to lead the thalamus. These findings argue against the existence of one common subcortical pacemaker for the generation of generalized spike-wave discharges characteristic for absence seizures in the rat. Instead, the results suggest that a cortical focus is the dominant factor in initiating the paroxysmal oscillation within the corticothalamic loops, and that the large-scale synchronization is mediated by ways of an extremely fast intracortical spread of seizure activity. Analogous mechanisms may underlie the pathophysiology of human absence epilepsy. AD - Department of Comparative and Physiological Psychology, Nijmegen Institute of Cognition and Information, University of Nijmegen, 6500 HE Nijmegen, The Netherlands. h.meeren@vumc.nl. FAU - Meeren, Hanneke K M AU - Meeren HK FAU - Pijn, Jan Pieter M AU - Pijn JP FAU - Van Luijtelaar, Egidius L J M AU - Van Luijtelaar EL FAU - Coenen, Anton M L AU - Coenen AM FAU - Lopes da Silva, Fernando H AU - Lopes da Silva FH LA - eng PT - Journal Article CY - United States TA - J Neurosci JID - 8102140 SB - IM MH - Action Potentials MH - Animal MH - Biological Clocks MH - Brain Mapping MH - Cerebral Cortex/*physiopathology MH - Disease Models, Animal MH - Electric Stimulation MH - Electrodes, Implanted MH - Electroencephalography MH - Epilepsies, Partial/complications/*physiopathology MH - Epilepsy, Absence/complications/*physiopathology MH - Evoked Potentials MH - Evoked Potentials, Somatosensory MH - Nerve Net/*physiopathology MH - Nonlinear Dynamics MH - Rats MH - Rats, Inbred Strains MH - Signal Processing, Computer-Assisted MH - Support, Non-U.S. Gov't MH - Thalamus/*physiopathology MH - Time Factors MH - Wakefulness EDAT- 2002/02/19 10:00 MHDA- 2002/02/28 10:01 AID - 22/4/1480 [pii] PST - ppublish SO - J Neurosci 2002 Feb 15;22(4):1480-95. 255: Ferri R, et al. Non-linear EEG measures durin...[PMID:11850092]Related Articles, Books, LinkOut UI - 21838860 PMID- 11850092 DA - 20020218 DCOM- 20020408 LR - 20021101 IS - 0167-8760 VI - 43 IP - 3 DP - 2002 Mar TI - Non-linear EEG measures during sleep: effects of the different sleep stages and cyclic alternating pattern. PG - 273-86 AB - The objective of this work was to study the non-linear aspects of sleep EEG, taking into account the different sleep stages and the peculiar organization of its phasic events in ordered sequences (CAP) by applying a series of new non-linear measures (non-linear cross prediction or NLCP), which appear more reliable for the detection and characterization of non-linear structures in experimental data than the commonly used correlation dimension. Eight healthy subjects aged 18-20 years participated in this study. Polysomnography was performed in all subjects; signals were sampled at 128 Hz and stored on hard disk. The C3 or C4 derivation was used for all the subsequent computational steps, which were performed on EEG epochs (4096 data points) selected from sleep stage 2 (S2) and slow-wave sleep (SWS), in both CAP and non-CAP (NCAP) conditions. Also, epochs from sleep stage 1 (S1), REM and wakefulness preceding sleep were recorded. The dynamic properties of the EEG were assessed by means of the non-linear cross-prediction test, which uses three different 'model' time series in order to predict non-linearly the original data set (Pred, Ama, and Tir). Pred is a measure of the predictability of the time series, and Ama and Tir are measures of asymmetry, indicating non-linear structure. The non-linear measures applied in this study indicate that sleep EEG tends to show non-linear structure only during CAP periods, both during S2 and SWS. Moreover, during CAP periods, non-linearity can only be detected during the phase A1 subtypes (and partially A2) of CAP. The A3 phases show characteristics of non-stationarity and bear some resemblance to wakefulness. Based on the results of this study, sleep might be considered as a dynamically evolving sequence of different states of the EEG, which we could track by detecting non-linearity, mostly in association with CAP. Our results clearly show that detectable non-linearity in the EEG is closely related to the occurrence of the phase A of CAP. AD - Sleep Research Center, Oasi Institute for Research on Mental Retardation and Brain Aging (IRCCS), Via Conte Ruggero 73, 94018, Troina, Italy. rferri@oasi.en.it FAU - Ferri, Raffaele AU - Ferri R FAU - Parrino, Liborio AU - Parrino L FAU - Smerieri, Arianna AU - Smerieri A FAU - Terzano, Mario G AU - Terzano MG FAU - Elia, Maurizio AU - Elia M FAU - Musumeci, Sebastiano A AU - Musumeci SA FAU - Pettinato, Salvatore AU - Pettinato S FAU - Stam, Cornelis J AU - Stam CJ LA - eng PT - Clinical Trial PT - Journal Article CY - Netherlands TA - Int J Psychophysiol JID - 8406214 SB - IM MH - Adolescent MH - Adult MH - Data Interpretation, Statistical MH - Electroencephalography/*statistics & numerical data MH - Female MH - Human MH - Male MH - Nonlinear Dynamics MH - Polysomnography MH - Sleep/*physiology MH - Sleep Stages/*physiology MH - Statistics, Nonparametric EDAT- 2002/02/19 10:00 MHDA- 2002/04/09 10:01 AID - S0167876002000065 [pii] PST - ppublish SO - Int J Psychophysiol 2002 Mar;43(3):273-86. 256: Yeragani VK, et al. Heart rate time series: decre...[PMID:11850054]Related Articles, Books, LinkOut UI - 21839922 PMID- 11850054 DA - 20020218 DCOM- 20020605 IS - 0165-1781 VI - 109 IP - 1 DP - 2002 Jan 31 TI - Heart rate time series: decreased chaos after intravenous lactate and increased non-linearity after isoproterenol in normal subjects. PG - 81-92 AB - In this study, we reanalyzed our previous heart rate time series data on the effects of intravenous sodium lactate (n=9) and intravenous isoproterenol (n=11) using non-linear techniques. Our prior findings of significantly higher baseline non-linear scores (NL: S(netGS)) and significantly lower largest Lyapunov exponents in supine posture in patients with panic disorder compared to control subjects prompted this study. We obtained the largest Lyapunov exponent (LLE), and a measure of non-linearity (NL: S(netGS)) of heart rate time series. LLE quantifies predictability and NL quantifies the deviation from linear processes. There was a significant increase in NL score, (S(netGS)) after isoproterenol infusions and a significant decrease in LLE (an increase in predictability indicating decreased chaos), after intravenous lactate in supine posture in normal control subjects. Increased NL scores in supine posture after intravenous isoproterenol may be due to a relative increase in cardiac sympathetic activity or a decrease in vagal activity at least in certain circumstances, and an overall decrease in LLE may indicate an impaired cardiac autonomic flexibility after intravenous sodium lactate, as LLE is diminished by autonomic blockade by atropine. Band analysis of LLE (LF/HF) (LF: 0.04-0.15 Hz and HF: 0.15-0.5 Hz) showed an increase of these ratios during either condition with a higher sympathovagal interaction after the drug administration. These findings may throw new light on the association of anxiety and significant cardiovascular events. AD - Department of Psychiatry, Wayne State University School of Medicine, Detroit, MI, USA. vikramyershr@yahoo.com FAU - Yeragani, Vikram Kumar AU - Yeragani VK FAU - Rao, Radhakrishna AU - Rao R FAU - Jayaraman, Anusha AU - Jayaraman A FAU - Pohl, Robert AU - Pohl R FAU - Balon, Richard AU - Balon R FAU - Glitz, Debra AU - Glitz D LA - eng PT - Journal Article CY - Ireland TA - Psychiatry Res JID - 7911385 RN - 0 (Adrenergic beta-Agonists) RN - 50-21-5 (Lactic Acid) RN - 7683-59-2 (Isoproterenol) SB - IM MH - Adrenergic beta-Agonists/administration & dosage/*adverse effects MH - Adult MH - Anxiety Disorders/*chemically induced/*physiopathology MH - Drug Administration Schedule MH - Female MH - Heart Rate/*drug effects/*physiology MH - Human MH - Injections, Intravenous MH - Isoproterenol/administration & dosage/*adverse effects MH - Lactic Acid/administration & dosage/*adverse effects MH - Male MH - *Nonlinear Dynamics MH - Sampling Studies MH - Supine Position MH - Time Factors EDAT- 2002/02/19 10:00 MHDA- 2002/06/06 10:01 AID - S0165178101003559 [pii] PST - ppublish SO - Psychiatry Res 2002 Jan 31;109(1):81-92. 257: Almeida JS. Predictive non-linear modelin...[PMID:11849962]Related Articles, Books, LinkOut UI - 21838561 PMID- 11849962 DA - 20020218 DCOM- 20020429 IS - 0958-1669 VI - 13 IP - 1 DP - 2002 Feb TI - Predictive non-linear modeling of complex data by artificial neural networks. PG - 72-6 AB - An artificial neural network (ANN) is an artificial intelligence tool that identifies arbitrary nonlinear multiparametric discriminant functions directly from experimental data. The use of ANNs has gained increasing popularity for applications where a mechanistic description of the dependency between dependent and independent variables is either unknown or very complex. This machine learning technique can be roughly described as a universal algebraic function that will distinguish signal from noise directly from experimental data. The application of ANNs to complex relationships makes them highly attractive for the study of biological systems. Recent applications include the analysis of expression profiles and genomic and proteomic sequences. AD - Department of Biometry and Epidemiology, Medical University South Carolina, 135 Rutledge Avenue, PO Box 250551, Charleston SC 29425, USA. almeidaj@musc.edu FAU - Almeida, Jonas S AU - Almeida JS LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - England TA - Curr Opin Biotechnol JID - 9100492 SB - IM MH - Biochemistry MH - Biotechnology MH - *Neural Networks (Computer) MH - *Nonlinear Dynamics RF - 35 EDAT- 2002/02/19 10:00 MHDA- 2002/05/01 10:01 AID - S0958166902002884 [pii] PST - ppublish SO - Curr Opin Biotechnol 2002 Feb;13(1):72-6. 258: Zhou Y, et al. Improved parametric image gen...[PMID:11848713]Related Articles, Books, LinkOut UI - 21839710 PMID- 11848713 DA - 20020218 DCOM- 20020422 IS - 1053-8119 VI - 15 IP - 3 DP - 2002 Mar TI - Improved parametric image generation using spatial-temporal analysis of dynamic PET studies. PG - 697-707 AB - The value of parametric images that represent both spatial distribution and quantification of the physiological parameters of tracer kinetics has long been recognized. However, the inherent high noise level of pixel kinetics of dynamic PET makes it unsuitable to generate parametric images of the microparameters of tracer kinetic model by conventional weighted nonlinear least squares (WNLS) fitting. Based on the concept that both spatial and temporal information should be integrated to improve parametric image quality, a nonlinear ridge regression with spatial constraint (NLRRSC) parametric imaging algorithm was proposed in this study. For NLRRSC, a term that penalizes local spatial variation of parameters was added to the cost function of WNLS fitting. The initial estimates and spatial constraint were estimated by component representation model (CRM) with cluster analysis. A hierarchical cluster with average linkage method was used to extract components. The ridge parameter was determined by linear ridge regression theory at each iteration, and a modified Gauss-Newton algorithm was used for minimizing the cost function. Results from a computer simulation showed that the percent mean square error of estimates obtained by NLRRSC can be decreased by 60-80% compared to that of WNLS. The parametric images estimated by NLRRSC are significantly better than the ones generated by WNLS. A highly correlated linear relationship was found between the ROI values calculated from the microparametric images generated by NLRRSC and estimates from ROI kinetic fitting. NLRRSC provided a reliable estimate of glucose metabolite uptake rate with a comparable image quality compared to Patlak analysis. In conclusion, NLRRSC is a reliable and robust parametric imaging algorithm for dynamic PET studies. CI - (c)2002 Elsevier Science (USA). AD - The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Medical Institutions, Baltimore, MD 21287, USA. FAU - Zhou, Yun AU - Zhou Y FAU - Huang, Sung-Cheng AU - Huang SC FAU - Bergsneider, Marvin AU - Bergsneider M FAU - Wong, Dean F AU - Wong DF LA - eng ID - NS 30308/NS/NINDS PT - Journal Article CY - United States TA - Neuroimage JID - 9215515 RN - 0 (Blood Glucose) RN - 63503-12-8 (Fludeoxyglucose F 18) SB - IM MH - Algorithms MH - Blood Glucose/*metabolism MH - Brain/physiology/*radionuclide imaging MH - Cluster Analysis MH - Computer Simulation MH - Fludeoxyglucose F 18/diagnostic use MH - Human MH - *Image Processing, Computer-Assisted/statistics & numerical data MH - Mathematical Computing MH - Nonlinear Dynamics MH - Statistics, Nonparametric MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. MH - *Tomography, Emission-Computed/statistics & numerical data EDAT- 2002/02/19 10:00 MHDA- 2002/04/23 10:01 AID - 10.1006/nimg.2001.1021 [doi] AID - S1053811901910213 [pii] PST - ppublish SO - Neuroimage 2002 Mar;15(3):697-707. 259: Ueda T, et al. Correlation of Lorenz scatter...[PMID:11848164]Related Articles, Books, LinkOut UI - 21836677 PMID- 11848164 DA - 20020218 DCOM- 20020731 LR - 20021101 IS - 1064-1963 VI - 24 IP - 1-2 DP - 2002 Jan-Feb TI - Correlation of Lorenz scatterplots with frequency-domain heart rate variability. PG - 11-21 AB - Heart rate (HR) variability is important with respect to disease prognosis and the effects of drugs. Lorenz scatterplots provide a simple way to evaluate HR variability visually. The relation of Lorenz scatterplots to frequency-domain HR variability was examined in 75 Holter recordings and in simulated HR trends. The length of Lorenz scatterplots was double-exponentially correlated with total frequency and very-low frequency powers, with correlation coefficients (r) of 0.88. The width of Lorenz scatterplots was highly correlated with the high frequency power (r=0.98). The sum of the width and length of Lorenz scatterplots was highly correlated with the total frequency power (r=0.92). Identical results were obtained when simulated HR trends were used. In conclusion, Lorenz scatterplots provide a simple way to estimate the frequency-domain HR variability. AD - Department of Internal Medicine, Okayama University Medical School, Okayama, Japan. FAU - Ueda, Toshiyuki AU - Ueda T FAU - Nakatsu, Takaaki AU - Nakatsu T FAU - Yamane, Shinichi AU - Yamane S FAU - Kurazono, Sekiko AU - Kurazono S FAU - Murakami, Takashi AU - Murakami T FAU - Mashima, Keiichi AU - Mashima K FAU - Tominaga, Y AU - Tominaga Y FAU - Mukouhara, Naoki AU - Mukouhara N FAU - Kusachi, Shozo AU - Kusachi S FAU - Tsuji, Takao AU - Tsuji T LA - eng PT - Journal Article CY - United States TA - Clin Exp Hypertens JID - 9305929 SB - IM MH - Adolescent MH - Adult MH - Aged MH - Aged, 80 and over MH - Artifacts MH - Cardiac Output, Low/physiopathology MH - Computer Simulation MH - Electrocardiography, Ambulatory MH - Female MH - Heart Rate/*physiology MH - Human MH - Hypertension/physiopathology MH - Male MH - Middle Age MH - Models, Cardiovascular MH - Myocardial Ischemia/physiopathology MH - Nonlinear Dynamics MH - Reference Values MH - Statistics/*methods EDAT- 2002/02/19 10:00 MHDA- 2002/08/01 10:01 PST - ppublish SO - Clin Exp Hypertens 2002 Jan-Feb;24(1-2):11-21. 260: Turkel MC, et al. Relational complexity: a theo...[PMID:11847753]Related Articles, Books, LinkOut UI - 21837395 PMID- 11847753 DA - 20020218 DCOM- 20020315 IS - 0894-3184 VI - 13 IP - 4 DP - 2000 Oct TI - Relational complexity: a theory of the nurse-patient relationship within an economic context. PG - 307-13 AD - Florida Atlantic University, Boca Raton, USA. FAU - Turkel, M C AU - Turkel MC FAU - Ray, M A AU - Ray MA LA - eng PT - Journal Article CY - United States TA - Nurs Sci Q JID - 8805022 SB - N MH - Attitude of Health Personnel MH - Attitude to Health MH - Cost Control MH - Cost-Benefit Analysis MH - Health Care Costs/*statistics & numerical data MH - Health Care Reform/organization & administration MH - Health Facility Administrators/psychology MH - Human MH - Humanism MH - *Models, Economic MH - *Models, Nursing MH - Nonlinear Dynamics MH - *Nurse-Patient Relations MH - Nurses/psychology MH - Nursing Administration Research MH - Nursing Care/*psychology MH - Nursing Methodology Research MH - *Nursing Theory MH - Organizational Innovation MH - Science MH - Support, Non-U.S. Gov't MH - Time Factors MH - United States MH - Workload EDAT- 2002/02/19 10:00 MHDA- 2002/03/16 10:01 PST - ppublish SO - Nurs Sci Q 2000 Oct;13(4):307-13. 261: Wall LM. Exercise: a unitary concept....[PMID:11847655]Related Articles, Books, LinkOut UI - 21837235 PMID- 11847655 DA - 20020218 DCOM- 20020315 IS - 0894-3184 VI - 12 IP - 1 DP - 1999 Jan TI - Exercise: a unitary concept. PG - 68-72 AB - Nursing science provides the opportunity to frame one's vision of humans and health and create interventions that facilitate wellness. This article contributes to nursing science by reconceptualizing exercise as a unitary concept using Parse's process of concept inventing. Concept inventing is a way to uncover the uniqueness of particular concepts and articulate their essence within the simultaneity paradigm. It differs from traditional, linear processes that are derived from the totality paradigm. Through the process of concept inventing, exercise is described within Rogers's science of unitary human beings and conceptualized as the purposeful, rhythmic flow of human movement. AD - Memorial Sloan-Kettering Cancer Center, New York, USA. FAU - Wall, L M AU - Wall LM LA - eng ID - 1 F31 NR07234-01/NR/NINR PT - Journal Article PT - Review PT - Review, Tutorial CY - United States TA - Nurs Sci Q JID - 8805022 SB - N MH - Exercise/*psychology MH - Health Promotion/methods MH - *Holistic Health MH - Human MH - Knowledge MH - *Models, Nursing MH - *Models, Psychological MH - Nonlinear Dynamics MH - *Nursing Theory MH - Self Care/methods/psychology MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. MH - Systems Theory RF - 30 EDAT- 2002/02/19 10:00 MHDA- 2002/03/16 10:01 PST - ppublish SO - Nurs Sci Q 1999 Jan;12(1):68-72. 262: Mitchell GJ. Evidence-based practice: crit...[PMID:11847648]Related Articles, Books, LinkOut UI - 21837230 PMID- 11847648 DA - 20020218 DCOM- 20020315 IS - 0894-3184 VI - 12 IP - 1 DP - 1999 Jan TI - Evidence-based practice: critique and alternative view. PG - 30-5 AD - Sunnybrook & Women's College Health Science Centre, Toronto, Canada. gail.mitchell@sunnybrook.on.ca FAU - Mitchell, G J AU - Mitchell GJ LA - eng PT - Journal Article CY - United States TA - Nurs Sci Q JID - 8805022 SB - N MH - *Evidence-Based Medicine MH - Human MH - Humanism MH - *Knowledge MH - Leadership MH - Nonlinear Dynamics MH - Nurse's Role MH - Nurse-Patient Relations MH - *Nursing Process MH - *Nursing Research MH - *Nursing Theory MH - Patient Participation MH - Philosophy, Nursing MH - Systems Theory MH - Thinking EDAT- 2002/02/19 10:00 MHDA- 2002/03/16 10:01 PST - ppublish SO - Nurs Sci Q 1999 Jan;12(1):30-5. 263: Haigh C. Using chaos theory: the impli...[PMID:11843985]Related Articles, Books, LinkOut UI - 21833447 PMID- 11843985 DA - 20020214 DCOM- 20020327 IS - 0309-2402 VI - 37 IP - 5 DP - 2002 Mar TI - Using chaos theory: the implications for nursing. PG - 462-9 AB - AIMS OF THE PAPER: The purpose of this paper is to review chaos theory and to examine the role that it may have in the discipline of nursing. BACKGROUND: In this paper, the fundamental ingredients of chaotic thinking are outlined. The earlier days of chaos thinking were characterized by an almost exclusively physiological focus. By the 21st century, nurse theorists were applying its principles to the organization and evaluation of care delivery with varying levels of success. Whilst the biological use of chaos has focused on pragmatic approaches to knowledge enhancement, nursing has often focused on the mystical aspects of chaos as a concept. CONCLUSIONS: The contention that chaos theory has yet to find a niche within nursing theory and practice is examined. The application of chaotic thinking across nursing practice, nursing research and statistical modelling is reviewed. The use of chaos theory as a way of identifying the attractor state of specific systems is considered and the suggestion is made that it is within statistical modelling of services that chaos theory is most effective. AD - Pain Management, Faculty of Health, University of Central Lancashire, Preston, UK. loracenna@hotmail.com FAU - Haigh, Carol AU - Haigh C LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - England TA - J Adv Nurs JID - 7609811 SB - IM SB - N MH - Human MH - Knowledge MH - Models, Statistical MH - *Nonlinear Dynamics MH - Nursing/*organization & administration MH - Nursing Research/organization & administration MH - *Nursing Theory MH - Philosophy, Nursing MH - Science MH - Symbolism MH - *Systems Theory MH - Thinking RF - 31 EDAT- 2002/02/15 10:00 MHDA- 2002/03/28 10:01 AID - 2113 [pii] PST - ppublish SO - J Adv Nurs 2002 Mar;37(5):462-9. 264: Valette H, et al. Anesthesia affects the dispos...[PMID:11842447]Related Articles, Books, LinkOut UI - 21831302 PMID- 11842447 DA - 20020213 DCOM- 20020503 IS - 0887-4476 VI - 44 IP - 1 DP - 2002 Apr TI - Anesthesia affects the disposition of [18F]fluoro-A-85380: a PET study in monkeys. PG - 58-9 AD - Service Hospitalier Frederic Joliot, Department of Medical Research-French Atomic Agency, Orsay, France. valette@shfj.cea.fr FAU - Valette, Heric AU - Valette H FAU - Bottlaender, Michel AU - Bottlaender M FAU - Coulon, Christine AU - Coulon C FAU - Ottaviani, Michele AU - Ottaviani M FAU - Syrota, Andre AU - Syrota A LA - eng PT - Journal Article CY - United States TA - Synapse JID - 8806914 RN - 0 (A 85380) RN - 0 (Adrenergic alpha-Agonists) RN - 0 (Anesthetics, Dissociative) RN - 0 (Azetidines) RN - 0 (Fluorine Radioisotopes) RN - 0 (Receptors, Nicotinic) RN - 6740-88-1 (Ketamine) RN - 7361-61-7 (Xylazine) SB - IM MH - Adrenergic alpha-Agonists/*pharmacology MH - Anesthetics, Dissociative/*pharmacology MH - Animal MH - Azetidines/*metabolism MH - Brain/*drug effects/radionuclide imaging MH - Drug Interactions/physiology MH - Fluorine Radioisotopes/*metabolism MH - Ketamine/*pharmacology MH - Metabolic Clearance Rate/drug effects/physiology MH - Neurons/*drug effects/radionuclide imaging MH - Nonlinear Dynamics MH - Papio MH - Receptors, Nicotinic/*drug effects/metabolism MH - Tomography, Emission-Computed MH - Xylazine/*pharmacology EDAT- 2002/02/14 10:00 MHDA- 2002/05/04 10:01 AID - 10.1002/syn.10047 [pii] PST - ppublish SO - Synapse 2002 Apr;44(1):58-9. 265: Gobburu JV, et al. Application of resampling tec...[PMID:11841044]Related Articles, Books, LinkOut UI - 21825072 PMID- 11841044 DA - 20020211 DCOM- 20020719 LR - 20021101 IS - 0724-8741 VI - 19 IP - 1 DP - 2002 Jan TI - Application of resampling techniques to estimate exact significance levels for covariate selection during nonlinear mixed effects model building: some inferences. PG - 92-8 AB - PURPOSE: One of the main objectives of the nonlinear mixed effects modeling is to provide rational individualized dosing strategies by explaining the interindividual variability using intrinsic and/or extrinsic factors (covariates). The aim of the current study was to evaluate, using computer simulations and real data, methods for estimating the exact significance level for including or excluding a covariate during model building. METHODS: Original data were simulated using a simple one-compartment pharmacokinetic model with (full model) or without (null model) covariates (one or two). The covariate values in the original data were resampled (using either permutations or parametric bootstrap methods) to generate data under the null hypothesis that there is no covariate effect. The original and permuted data were fitted to null and full models, using first-order and first-order condition estimation (with or without interaction) methods in NONMEM, to compare the asymptotic and conditional p-value. Target log-likelihood ratio cutoffs for assessing covariate effects were derived. RESULTS: The simulations showed that for sparse as well as dense data, the first-order condition estimation methods yielded the best results while the first-order method performs somewhat better for sparse data. Depending on the modeling objective, the appropriate asymptotic p-value can be substituted for the conditional significance level. Target log-likelihood ratio cutoffs should be determined separately for each covariate when exact p-values are important. CONCLUSIONS: Resampling methods can be employed to estimate the exact significance level for including a covariate during nonlinear mixed effects model building. Some reasonable inferences can be drawn for potential application to design future population analyses. AD - Division of Pharmaceutical Evaluation, Office of Clinical Pharmacology and Biopharmaceutics, Center for Drug Evauation and Research, Food and Drug Administration, Rockville, Maryland 20852 USA. gobburuj@cder.fda.gov FAU - Gobburu, Jogarao V S AU - Gobburu JV FAU - Lawrence, John AU - Lawrence J LA - eng PT - Journal Article CY - United States TA - Pharm Res JID - 8406521 RN - 0 (Anticonvulsants) SB - IM MH - Adolescent MH - Anticonvulsants/pharmacokinetics MH - Child MH - Child, Preschool MH - Computer Simulation MH - Human MH - Likelihood Functions MH - *Nonlinear Dynamics MH - Pharmacology/*statistics & numerical data EDAT- 2002/02/14 10:00 MHDA- 2002/07/20 10:01 PST - ppublish SO - Pharm Res 2002 Jan;19(1):92-8. 266: Kashtanov SI, et al. [Effect of emotional stress o...[PMID:11840965]Related Articles, Books, LinkOut UI - 21830142 PMID- 11840965 DA - 20020213 DCOM- 20020422 IS - 0869-8139 VI - 87 IP - 12 DP - 2001 Dec TI - [Effect of emotional stress on the cardiac rhythm variability in rats] PG - 1626-33 AB - A degree of irregularities of the heart rhythm was studied by two methods: chaos-analysis and the HRV (heart rate variability) analysis. Our study shows an individual response in 3 groups of animals: 1--animals with low initial level of chaos (correlation dimension (PD2 < 2); 2--animals with high level of chaos (PD2 > 4); and animals with middle level of chaos (2 < PD2 < 4). The first two groups proved to be more sensitive to stress than the third group. Moreover we found that the electrical stability of the heart as measured by the fibrillation threshold, was higher for the chaos third group. The animals of the first two groups had low cardiac stability and high risk of stress-induced cardiac disturbances. AD - P. K. Anokhin Research Institute of Normal Physiology, Russian Acad. Med. Sci., Moscow, 103009, B. Nikitskaya, 6, Russia. FAU - Kashtanov, S I AU - Kashtanov SI FAU - Mezentseva, L V AU - Mezentseva LV FAU - Zviagintseva, M A AU - Zviagintseva MA FAU - Kosharskaia, I L AU - Kosharskaia IL LA - rus PT - Journal Article TT - Vliianie emotsional'nogo stressa na variabel'nost' serdechnogo ritma u krys. CY - Russia TA - Ross Fiziol Zh Im I M Sechenova JID - 9715665 SB - IM MH - Animal MH - English Abstract MH - *Heart Rate MH - Male MH - Nonlinear Dynamics MH - Rats MH - Rats, Wistar MH - Stress, Psychological/complications/*physiopathology MH - Ventricular Fibrillation/etiology/physiopathology EDAT- 2002/02/14 10:00 MHDA- 2002/04/23 10:01 PST - ppublish SO - Ross Fiziol Zh Im I M Sechenova 2001 Dec;87(12):1626-33. 267: Oda GA, et al. A model for "splitting" of ru...[PMID:11837951]Related Articles, Books, LinkOut UI - 21825331 PMID- 11837951 DA - 20020211 DCOM- 20020723 IS - 0748-7304 VI - 17 IP - 1 DP - 2002 Feb TI - A model for "splitting" of running-wheel activity in hamsters. PG - 76-88 AB - Splitting of locomotor activity rhythm in hamsters occurs when the animals are exposed for several weeks to constant light. The authors propose a mathematical model that explains splitting in terms of a switch in the sign of coupling of two oscillators, from positive to negative, due to long-term exposure to constant light. The model assumes that the two oscillators are not identical and that the negative coupling strengths achieved by each individual animal are variable. With these assumptions, the model provides a unified picture of all different splitting patterns presented by the hamsters, provides an explanation for why the two activity components cross each other during many patterns, and explains why the phase difference achieved by the split components is often near 180 degrees. AD - Department of Biology, NSF Center for Biological Timing, University of Virginia, Charlottesville 22903-2477, USA. FAU - Oda, Gisele A AU - Oda GA FAU - Friesen, W Otto AU - Friesen WO LA - eng PT - Journal Article CY - United States TA - J Biol Rhythms JID - 8700115 SB - IM MH - Algorithms MH - Animal MH - Behavior, Animal/physiology MH - Circadian Rhythm/*physiology MH - Hamsters MH - Models, Biological MH - Motor Activity/*physiology MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/02/12 10:00 MHDA- 2002/07/24 10:01 PST - ppublish SO - J Biol Rhythms 2002 Feb;17(1):76-88. 268: Keller F, et al. PK-PD curve-fitting problems ...[PMID:11837379]Related Articles, Books, LinkOut UI - 21824734 PMID- 11837379 DA - 20020211 DCOM- 20020813 IS - 0946-1965 VI - 40 IP - 1 DP - 2002 Jan TI - PK-PD curve-fitting problems with the Hill equation? Try one of the 1-exp functions derived from Hodgkin, Douglas or Gompertz. PG - 23-9 AB - Non-linear phenomena are observed with enzyme kinetics, protein binding, pharmacokinetics or pharmacodynamics. The Hill equation, the Michaelis-Menten equation extended by a power coefficient, is traditionally used for sigmoid curve fitting. Sigmoid saturation phenomena can also be described by exponential functions (1-exp), extended by a power coefficient such as those derived by Hodgkin, Douglas or Gompertz. Comparing the 4 equations, the sigmoid 1-exp function in the form of Hodgkin and Huxley comes closest to the principle of simplicity and succinctness with regard to definition, slope and flexibility of the inflection point. To compare the applicability, a standardized sample of 250 curves was generated by each I of the 4 equations and mutually fitted with the remaining 3. The Hill equation gives the closest fit with the data generated by the other functions. The Douglas variant exhibits the highest rate of convergence. The Gompertz function provides the basic feature of a baseline effect. CONCLUSION: The sigmoid functions investigated (Hill, Hodgkin, Douglas, Gompertz) have differing characteristics and can be used interchangeably for solving specific problems in non-linear modeling. AD - Nephrology, University Ulm, Germany. frieder.keller@medizin.uni-ulm.de FAU - Keller, F AU - Keller F FAU - Giehl, M AU - Giehl M FAU - Czock, D AU - Czock D FAU - Zellner, D AU - Zellner D LA - eng PT - Journal Article CY - Germany TA - Int J Clin Pharmacol Ther JID - 9423309 SB - IM MH - *Mathematics MH - Nonlinear Dynamics MH - *Pharmacokinetics EDAT- 2002/02/12 10:00 MHDA- 2002/08/14 10:01 PST - ppublish SO - Int J Clin Pharmacol Ther 2002 Jan;40(1):23-9. 269: Breakspear M. Nonlinear phase desynchroniza...[PMID:11835608]Related Articles, Books, LinkOut UI - 21823853 PMID- 11835608 DA - 20020307 DCOM- 20020430 IS - 1065-9471 VI - 15 IP - 3 DP - 2002 Mar TI - Nonlinear phase desynchronization in human electroencephalographic data. PG - 175-98 AB - Ensembles of coupled nonlinear systems represent natural candidates for the modeling of brain dynamics. The objective of this study is to examine the complex signal produced by coupled chaotic attractors, to discuss their potential relevance to distributed processes in the brain, and to illustrate a method of detecting their contribution to human EEG morphology. Two measures of quantifying the behavior of coupled nonlinear systems are presented: a measure of phase synchrony and a novel measure of intermittent phase desynchronization. These are used to quantify the behavior of numerical examples of coupled chaotic attractors. Experimental evidence of their contribution to the morphology of the human alpha rhythm is then illustrated in a study of EEG recordings from 40 healthy human subjects. Amplitude-adjusted phase-randomized surrogate data is used to test the null hypothesis that the observed patterns of phase coherence can be described by purely linear methods. Statistical analysis reveals that this null hypothesis can be robustly rejected in a small number (approximately 4%) of EEG epochs. These findings are discussed with reference to the adaptive function and complex dynamics of the brain. CI - Copyright 2002 Wiley-Liss, Inc. AD - Brain Dynamics Centre, Department of Psychological Medicine, Westmead Hospital, Darcy Road, Westmead, Sydney, NSW 2048, Australia. mbreak@physics.usyd.edu.au FAU - Breakspear, Michael AU - Breakspear M LA - eng PT - Journal Article CY - United States TA - Hum Brain Mapp JID - 9419065 SB - IM MH - Adult MH - Brain/physiology MH - Confidence Intervals MH - Cortical Synchronization/methods/*statistics & numerical data MH - Human MH - Middle Age MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2002/02/09 10:00 MHDA- 2002/05/01 10:01 AID - 10.1002/hbm.10011 [pii] PST - ppublish SO - Hum Brain Mapp 2002 Mar;15(3):175-98. 270: Waliszewski P, et al. Neuronal differentiation and ...[PMID:11835520]Related Articles, Books, LinkOut UI - 21824512 PMID- 11835520 DA - 20020208 DCOM- 20020423 IS - 0887-4476 VI - 43 IP - 4 DP - 2002 Mar 15 TI - Neuronal differentiation and synapse formation occur in space and time with fractal dimension. PG - 252-8 AB - The analysis of a set of experimental data obtained by an independent team of researchers confirms that neuronal differentiation or synapse formation do occur in time and space with fractal dimension. The interacting cells create first a dynamic system with its own attractor, (i.e., a fragment of time and space where the dynamic processes occur and where no further evolution of the system is possible at all owing to the action of the intrasystemic forces unless some extrasystemic forces act upon it). This attractor is then modified in the active manner by the differentiating cells until the system attains a degenerated stationary state and differentiation ends. The fractal structure of the system is also lost in the course of tumor progression. Our data indicate that the cellular system can attain the degenerated stationary state, leaving the attractor with a fractal dimension directly or undergoing diversification into many attractors and going through the areas of deterministic chaos. Since evolution of the cellular system is driven by the cooperative dynamic processes, as reflected by the changes of the mean fractal dimension between the intervals of the Gompertzian curve, it is likely that cells differentiate into neurons and create synapses with a conjugated probability and non-Gaussian distribution rather than with the classical probability and the Gaussian distribution. These findings can help to optimize features of artificial neural networks. They also define a simple in vitro biological model for biophysical and biochemical studies on natural neural networks. CI - Copyright 2002 Wiley-Liss, Inc. AD - Department of Theoretical Chemistry, Adam Mickiewicz University, Poznan, Poland. WaliszP@amu.edu.pl FAU - Waliszewski, Przemyslaw AU - Waliszewski P FAU - Konarski, Jerzy AU - Konarski J LA - eng PT - Journal Article CY - United States TA - Synapse JID - 8806914 SB - IM MH - Cell Differentiation/*physiology MH - Cell Division/physiology MH - Central Nervous System/cytology/*embryology/*growth & development MH - *Fractals MH - Gene Expression Regulation, Developmental/physiology MH - *Models, Neurological MH - Neurons/cytology/*physiology MH - *Nonlinear Dynamics MH - Stem Cells/cytology/physiology MH - Synapses/*physiology/ultrastructure MH - Time Factors MH - Tumor Cells, Cultured/cytology/physiology EDAT- 2002/02/09 10:00 MHDA- 2002/04/24 10:01 AID - 10.1002/syn.10042 [pii] PST - ppublish SO - Synapse 2002 Mar 15;43(4):252-8. 271: Glorieux C, et al. Nonlinearity of acoustic wave...[PMID:11831827]Related Articles, Books, LinkOut UI - 21820376 PMID- 11831827 DA - 20020207 DCOM- 20020329 IS - 0001-4966 VI - 111 IP - 1 Pt 1 DP - 2002 Jan TI - Nonlinearity of acoustic waves at solid-liquid interfaces. PG - 95-103 AB - The small-amplitude and finite-amplitude propagation characteristics of laser line source excited and laser detected Scholte waves are investigated. Acoustic waves with Mach numbers up to 0.054 are observed at the interface between water and glass. In our case of a hard solid-liquid interface, the Scholte wave propagates very much like a bulk wave, for which the simple-wave equation holds. The experimental results are well fitted with this model, extended with an attenuation term. An anomalously large (compared with low amplitude viscous effects) attenuation reveals possible leakage of energy from the Scholte wave to bulk waves, through a mechanism of nonlinear mixing between the different wave modes and viscosity induced turbulence. AD - Laboratorium voor Akoestiek en Thermische Fysica, Departement Natuurkunde, Katholieke Universiteit Leuven, Belgium. FAU - Glorieux, Christ AU - Glorieux C FAU - Van, deRostyneKris AU - Van D FAU - Gusev, Vitalyi AU - Gusev V FAU - Gao, Weimin AU - Gao W FAU - Lauriks, Walter AU - Lauriks W FAU - Thoen, Jan AU - Thoen J LA - eng PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 SB - IM MH - *Acoustics MH - Lasers MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Time Factors EDAT- 2002/02/08 10:00 MHDA- 2002/03/30 10:01 PST - ppublish SO - J Acoust Soc Am 2002 Jan;111(1 Pt 1):95-103. 272: Jalowiecki P, et al. [Specific nature of the softw...[PMID:11828851]Related Articles, Books, LinkOut UI - 21687406 PMID- 11828851 DA - 20020206 DCOM- 20020301 IS - 0465-5893 VI - 52 IP - 5 DP - 2001 TI - [Specific nature of the software used to construct simulations: physiologically-based toxicokinetic models] PG - 361-8 AB - Building of the physiologically-based toxicokinetic (PBTK) models is based on the application of simulation languages, such as advanced continuous simulation language (ACSL). The aim of this study was to develop the principles of constructing the fundamental model and the models dedicated to chemicals found in the work environment (e.g. trimethylbenzene (TMB) isomers present in the petrochemical, paint and lacquer and related industries). The fundamental model is based on four main compartments (fat tissues, richly perfused tissue, slowly perfused tissue and liver) and six auxiliary compartments (lungs, venous blood, arterial blood, body weight, inhaled air and exhaled air). The basic element of the PBTK model comprises blocks containing definitions of variables and constants supplemented by the following parameters: command, calculated, transferred and resulted. The models dedicated to various chemicals and organisms are built by a suitable modification of the fundamental model. All sets of command parameters values for the organism, chemical and simulation are written in the text files and loaded before or during the simulation. The empirical data obtained in experiments with volunteers are used in a similar way. The specimen dedicated model was built for 1,2,3-TMB (hemimellitene). 2,3-Dimethylbenzoic acid (2,3,-DMBA) (a hemimelitene metabolite) excretion rate data obtained from an experiment during which volunteers were exposed to hemimellitene at 25 at 100 mg/m3 were compared with the results of the computer simulation. A high convergence of the comparable values was obtained. Simulations were also made for exposure periods of one week and one month. The results confirmed the experiment-based recommendations on the assessment of the occupational exposure. The application of the new physiologically-based toxicokinetic models renders it possible to forecast toxic chemical (or it metabolite) concentrations corresponding to the concentrations of those chemicals in the workplace atmosphere. AD - Zaklad Zagrozen Chemicznych i Pylowych Instytut Medycyny Pracy, Lodz. FAU - Jalowiecki, P AU - Jalowiecki P FAU - Kostrzewski, P AU - Kostrzewski P LA - pol PT - Journal Article TT - Specyfika stosowanego oprogramowania w konstruowaniu symulacyjnych, fizjologicznych modeli toksykokinetycznych (PBTK). CY - Poland TA - Med Pr JID - 0376642 RN - 0 (Hazardous Substances) SB - IM MH - Body Fluid Compartments MH - *Computer Simulation MH - English Abstract MH - Hazardous Substances/*analysis MH - Human MH - *Models, Biological MH - Nonlinear Dynamics MH - Programming Languages MH - *Software MH - Toxicology/*methods EDAT- 2002/02/07 10:00 MHDA- 2002/03/02 10:01 PST - ppublish SO - Med Pr 2001;52(5):361-8. 273: Harrell WA, et al. Social psychological models o...[PMID:11827220]Related Articles, Books, LinkOut UI - 21684872 PMID- 11827220 DA - 20020205 DCOM- 20020325 IS - 0022-4545 VI - 141 IP - 6 DP - 2001 Dec TI - Social psychological models of choice behavior and drivers' left turns. PG - 714-22 AB - ABSTRACT. The authors reanalyzed data from a simulated left-turn experiment (P. A. Hancock, J. K. Caird, S. Shekhar, & M. Vercruyssen, 1991) to test the adequacy of the nonlinear Gray-Tallman satisfaction balance model of choice behavior (L. N. Gray & I. Tallman, 1984) in predicting left turns. Participants (Hancock et al., 1991) were 40 experienced U.S. drivers who were exposed to simulated oncoming traffic; the size of the vehicle (motorcycle, compact vehicle, full-sized vehicle, delivery truck), its speed (10-70 mph, or 16-112 kmph), and the intervehicle time gap (3-9 s) varied. Hancock et al. (1991) measured (a) the likelihood of a left turn and (b) the occurrence of a collision. The probability of a left turn was greater for larger intervehicle time gaps and for oncoming smaller vehicles traveling at higher speeds. The Gray-Tallman (1984) model explained 69% of the variation in turning versus 57% for a linear regression model. In making decisions people tend to treat the values and costs affecting choices in a multiplicative, rather than linear, fashion. The Gray-Tallman model also has the potential for incorporating, both theoretically and mathematically, an unlimited range of potential values and costs that may influence left turn decisions. AD - Centre for Experimental Sociology University of Alberta, Edmonton, Canada. aharrell@gpu.srv.ualberta.ca FAU - Harrell, W A AU - Harrell WA FAU - Spaulding, L M AU - Spaulding LM LA - eng PT - Journal Article CY - United States TA - J Soc Psychol JID - 0376372 SB - IM MH - Adult MH - Automobile Driving/*psychology MH - *Choice Behavior MH - Computer Simulation MH - Decision Making MH - Female MH - Human MH - Male MH - *Models, Psychological MH - Nonlinear Dynamics MH - *Psychology, Social MH - Risk-Taking EDAT- 2002/02/06 10:00 MHDA- 2002/03/26 10:01 PST - ppublish SO - J Soc Psychol 2001 Dec;141(6):714-22. 274: Miller KD, et al. Neural noise can explain expa...[PMID:11826034]Related Articles, Books, LinkOut UI - 21683743 PMID- 11826034 DA - 20020204 DCOM- 20020326 IS - 0022-3077 VI - 87 IP - 2 DP - 2002 Feb TI - Neural noise can explain expansive, power-law nonlinearities in neural response functions. PG - 653-9 AB - Many phenomenological models of the responses of simple cells in primary visual cortex have concluded that a cell's firing rate should be given by its input raised to a power greater than one. This is known as an expansive power-law nonlinearity. However, intracellular recordings have shown that a different nonlinearity, a linear-threshold function, appears to give a good prediction of firing rate from a cell's low-pass-filtered voltage response. Using a model based on a linear-threshold function, Anderson et al. showed that voltage noise was critical to converting voltage responses with contrast-invariant orientation tuning into spiking responses with contrast-invariant tuning. We present two separate results clarifying the connection between noise-smoothed linear-threshold functions and power-law nonlinearities. First, we prove analytically that a power-law nonlinearity is the only input-output function that converts contrast-invariant input tuning into contrast-invariant spike tuning. Second, we examine simulations of a simple model that assumes instantaneous spike rate is given by a linear-threshold function of voltage and voltage responses include significant noise. We show that the resulting average spike rate is well described by an expansive power law of the average voltage (averaged over multiple trials), provided that average voltage remains less than about 1.5 SDs of the noise above threshold. Finally, we use this model to show that the noise levels recorded by Anderson et al. are consistent with the degree to which the orientation tuning of spiking responses is more sharply tuned relative to the orientation tuning of voltage responses. Thus neuronal noise can robustly generate power-law input-output functions of the form frequently postulated for simple cells. AD - Departments of Physiology and Otolaryngology, W. M. Keck Center for Integrative Neuroscience, University of California-San Francisco, San Francisco, CA 94143-0444, USA. ken@phy.ucsf.edu FAU - Miller, Kenneth D AU - Miller KD FAU - Troyer, Todd W AU - Troyer TW LA - eng ID - EY 11001/EY/NEI PT - Journal Article CY - United States TA - J Neurophysiol JID - 0375404 SB - IM MH - Action Potentials/physiology MH - Animal MH - Computer Simulation MH - *Models, Neurological MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Support, U.S. Gov't, P.H.S. MH - Visual Cortex/cytology/physiology EDAT- 2002/02/05 10:00 MHDA- 2002/03/27 10:01 PST - ppublish SO - J Neurophysiol 2002 Feb;87(2):653-9. 275: Leger F, et al. Maximum a posteriori Bayesian...[PMID:11825098]Related Articles, Books, LinkOut UI - 21683269 PMID- 11825098 DA - 20020204 DCOM- 20020415 IS - 0312-5963 VI - 41 IP - 1 DP - 2002 TI - Maximum a posteriori Bayesian estimation of oral cyclosporin pharmacokinetics in patients with stable renal transplants. PG - 71-80 AB - OBJECTIVE: To develop a maximum a posteriori probability (MAP) Bayesian estimator for the pharmacokinetics of oral cyclosporin, based on only three timepoints, and evaluate its performance with respect to a full-profile nonlinear regression approach. PATIENTS: 20 adult patients with stable renal transplants given orally administered microemulsified cyclosporin and mycophenolate. METHODS: Cyclosporin was assayed by liquid chromatography-mass spectrometry. Nonlinear regression and MAP Bayesian estimation were performed using a home-made program and a previously designed pharmacokinetic model including an S-shaped absorption profile described by a gamma distribution. OUTCOME MEASURES AND RESULTS: MAP Bayesian estimation using the best limited sampling strategy (before administration, and 1 and 3 hours after administration) was compared with nonlinear regression (taken as the reference method) for the prediction of the different pharmacokinetic parameters and exposure indices. Median relative prediction error was -0.49 and -3.42% for area under the concentration-time curve over the administration interval of 12 hours (AUC12) and estimated peak drug concentration (Cmax), respectively (nonsignificant). Relative precision was 2.00 and 4.32%, and correlation coefficient (r) was 0.985 and 0.955, for AUC12 and Cmax, respectively. CONCLUSION: This paper reports preliminary results in a stable renal transplant patient population, showing that MAP Bayesian estimation can allow accurate prediction of AUC12 and Cmax with only three samples (0, 1 and 3 hours). Although these results require confirmation by further studies in other clinical settings, using other drug combinations, other analytical methods and commercially available pharmacokinetic software, the method seems promising as a tool for the therapeutic drug monitoring of cyclosporin in clinical practice or for exposure-controlled studies. AD - Service de Pharmacologie et Toxicologie, CHU Dupuytren, Limoges, France. marquet@unilim.fr FAU - Leger, Frederic AU - Leger F FAU - Debord, Jean AU - Debord J FAU - Le Meur, Yann AU - Le Meur Y FAU - Rousseau, Annick AU - Rousseau A FAU - Buchler, Mathias AU - Buchler M FAU - Lachatre, Gerard AU - Lachatre G FAU - Paintaud, Gilles AU - Paintaud G FAU - Marquet, Pierre AU - Marquet P LA - eng PT - Clinical Trial PT - Journal Article CY - New Zealand TA - Clin Pharmacokinet JID - 7606849 RN - 0 (Emulsions) RN - 0 (Immunosuppressive Agents) RN - 59865-13-3 (Cyclosporine) SB - IM MH - Administration, Oral MH - Adult MH - Aged MH - Area Under Curve MH - Bayes Theorem MH - Biological Availability MH - Cyclosporine/administration & dosage/blood/*pharmacokinetics MH - Emulsions MH - Female MH - Human MH - Immunosuppressive Agents/administration & dosage/blood/*pharmacokinetics MH - *Kidney Transplantation MH - Likelihood Functions MH - Male MH - Mass Fragmentography MH - Middle Age MH - Models, Statistical MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2002/02/05 10:00 MHDA- 2002/04/16 10:01 AID - 410106 [pii] PST - ppublish SO - Clin Pharmacokinet 2002;41(1):71-80. 276: Ohashi K, et al. Influence of age on the pharm...[PMID:11824652]Related Articles, Books, LinkOut UI - 21682276 PMID- 11824652 DA - 20020204 DCOM- 20020715 IS - 0251-1649 VI - 21 IP - 2 DP - 2001 TI - Influence of age on the pharmacokinetics of vapiprost, a thromboxane A2 receptor antagonist, and platelet aggregation: comparison of pharmacokinetics by routine approach and population pharmacokinetics. PG - 85-94 AB - The effects of a single-dose oral administration of a thromboxane A2 receptor antagonist, vapiprost (SN-309), on pharmacokinetic profile and inhibition of platelet aggregation were investigated in six healthy elderly volunteers (age: 65-72 years) and the influence of age on these parameters was studied by comparison with the results obtained in phase-I data involving healthy young participants. Although direct comparison of pharmacokinetic parameters was inappropriate because of different models, high Cmax and AUC values were obtained on comparison with the young. The inhibition of platelet aggregation in platelet rich plasma induced by U-46619 or collagen was rapidly established and remained suppressed for more than 8 h, although the effect was short-acting compared with the inhibition period in the young. This suggests that dose adjustment in the elderly is unnecessary In addition to a routine pharmacokinetic approach to determine the time-profile of vapiprost, population pharmacokinetics were studied using data from 51 volunteers in five clinical trials including the two above-mentioned studies. By fitting 812 plasma-monitoring points into the two-compartment model, the effects of several factors including age on parameters were investigated, based on the nonlinear mixed effect model. Clearance in the elderly attenuated 82.2% of that in the young, the distribution volume varied with platelet counts and delayed absorption was observed in volunteers with, rather than without, food intake. Closer bridging studies with other countries have resulted in the current local situation of abbreviating phase-III studies. Consequently to clarify the pharmacokinetic profile of the elderly in Japan and other countries, the population pharmacokinetics approach based on the data in the various phase I-II trials is useful. AD - Clinical Pharmacology Center, Nippon Medical School, Tokyo, Japan. kaz@nms.ac.jp FAU - Ohashi, K AU - Ohashi K FAU - Aso, R AU - Aso R LA - eng PT - Clinical Trial PT - Clinical Trial, Phase I PT - Journal Article CY - Switzerland TA - Int J Clin Pharmacol Res JID - 8110183 RN - 0 (Biphenyl Compounds) RN - 0 (Heptanoic Acids) RN - 0 (Prostaglandin Antagonists) RN - 0 (Receptors, Thromboxane) RN - 85505-64-2 (vapiprost) RN - 9007-34-5 (Collagen) SB - IM MH - Aged MH - Aging/*metabolism MH - Algorithms MH - Area Under Curve MH - Biphenyl Compounds/adverse effects/*pharmacokinetics MH - Collagen/pharmacology MH - Comparative Study MH - Half-Life MH - Heptanoic Acids/adverse effects/*pharmacokinetics MH - Human MH - Male MH - Nonlinear Dynamics MH - Platelet Aggregation/*drug effects MH - Population MH - Prostaglandin Antagonists/adverse effects/*pharmacokinetics MH - Receptors, Thromboxane/*antagonists & inhibitors EDAT- 2002/02/05 10:00 MHDA- 2002/07/16 10:01 PST - ppublish SO - Int J Clin Pharmacol Res 2001;21(2):85-94. 277: Vimal RP. Spatial-frequency-tuned mecha...[PMID:11822590]Related Articles, Books, LinkOut UI - 21680286 PMID- 11822590 DA - 20020201 DCOM- 20020212 IS - 1084-7529 VI - 19 IP - 2 DP - 2002 Feb TI - Spatial-frequency-tuned mechanisms of the red-green channel estimated by oblique masking. PG - 276-88 AB - The sustained spatial-frequency-tuned (SF-tuned) mechanisms of nonoriented units were examined by means of orthogonal masking for the Red-Green (R-G) color channel, and those of oriented units by oblique masking for the achromatic channel but not for the color channels. An oblique-masking technique minimizes the artifacts that are due to spatial phase effects, local cues, spatial beats, spatial probability summation, and changing criteria. Therefore the spatial characteristics of the R-G color channel are now investigated by an oblique-masking technique and linked with my paper on orthogonal masking [J. Opt. Soc. Am. A 15, 1 (1998)]. The R-G channel was defined by the minimum-flicker and hue-cancellation techniques. A color monitor system was used to generate spatially localized (D6) vertical color test patterns [0.063-8 cycles per degree (cpd)] and sinusoidal oblique color masks (0.031-16 cpd, 1.2-60% contrasts). Color contrast sensitivity functions (CSFs), threshold elevation (TE) versus mask SF (TvSF) curves, and TE versus mask contrast (TvC) curves were measured by the method of constant stimuli with a two-interval forced-choice technique by using Powell's achromatizing lens under sustained (Gaussian, 2-s-duration) conditions. Results show the following: (1) The color CSF is a low-pass function of SF with average half-height SF of 0.7 cpd and cutoff SF of 14 cpd with the use of a color-detection criterion. (2) TvSF curves are broadly bandpass and fall into five groups, peaking at approximately 0.13, 0.5, 2, 4, and 8 cpd. The root-mean-square cone-color CSF is 3.8-5.4 times the stimulus-color CSF. (3) A "crowding effect" similar to that of the TvSF curves of the achromatic channel was also found, but the TvSF curves of the R-G channel are not sharply peaked, similar to the result for orthogonal masking. Data analysis led to the following conclusions: (1) A simple multiple-mechanism model yields one low-pass color mechanism (with average half-height SF of 0.54 cpd) and five bandpass SF-tuned color mechanisms; these six mechanisms are necessary to explain the CSF, TvSF, and TvC data simultaneously. (2) The bandpass mechanisms peaked at approximately 0.13, 0.5, 2, 4, and 8 cpd with average full bandwidths at half-heights of 3.6, 3.2, 2.1, 1.2, and 1.3 octaves, respectively. (3) Since oblique-masking color mechanisms (unlike achromatic oriented mechanisms) have broad orientation tuning under sustained conditions and there is a significant orthogonal masking, the oblique-masking color mechanisms may have contributions from both oriented and nonoriented units. (4) The high degree of similarity between the SF-tuned filters of mechanisms derived from oblique- and orthogonal-masking data suggests that most of the chromatic SF tuning is already accomplished by nonoriented units. (5) The quality of the fit to oblique- and orthogonal-masking data combined dropped enough to reject the hypothesis that the former taps the performance of only the same nonoriented mechanisms as those by the latter. Adding gain parameters that reduce the TEs for orthogonal masking gave a better fit, suggesting that orientation gains are one of the factors involved in the transformation of information from nonoriented to oriented mechanisms. However, the fit was still worse than that for oblique-(6) Since masking-alone or orthogonal-masking-alone data, suggesting that more factors may be involved. primate parvo lateral geniculate nucleus (pLGN) units behave in a fairly linear manner, the color contrast nonlinearity (which follows the linear filter) of a mechanism may be post-pLGN. AD - Vision Research Institute, Lexington, Massachusetts 02420-2544, USA. VimalRam@hotmail.com FAU - Vimal, RamLakhan Pandey AU - Vimal RP LA - eng ID - R01-EY09511/EY/NEI PT - Journal Article CY - United States TA - J Opt Soc Am A Opt Image Sci Vis JID - 9800943 SB - IM MH - Color Perception/*physiology MH - Contrast Sensitivity/physiology MH - Human MH - *Models, Biological MH - Nonlinear Dynamics MH - *Perceptual Masking MH - Sensory Thresholds MH - Space Perception/*physiology MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. MH - Time Perception/*physiology EDAT- 2002/02/02 10:00 MHDA- 2002/02/13 10:01 PST - ppublish SO - J Opt Soc Am A Opt Image Sci Vis 2002 Feb;19(2):276-88. 278: Wikan A. From chaos to chaos. An analy...[PMID:11822543]Related Articles, Books, LinkOut UI - 21680235 PMID- 11822543 DA - 20020201 DCOM- 20020703 IS - 0303-6812 VI - 43 IP - 6 DP - 2001 Dec TI - From chaos to chaos. An analysis of a discrete age-structured prey-predator model. PG - 471-500 AB - Discrete age-structured density-dependent one-population models and discrete age-structured density-dependent prey-predator models are considered. Regarding the former, we present formal proofs of the nature of bifurcations involved as well as presenting some new results about the dynamics in unstable and chaotic parameter regions. Regarding the latter, we show that increased predation may act both as a stabilizing and a destabilizing effect. Moreover, we find that possible periodic dynamics of low period, either exact or approximate, may not be generated by the predator, but it may be generated by the prey. Finally, what is most interesting from the biological point of view, is that given that the prey, in absence of the predator, exhibits periodic or almost periodic oscillations of low period, then the introduction of the predator does not alter this periodicity in any substantial way until the stabilizing effect of increased predation becomes so strong that a stable equilibrium is achieved. AD - Harstad College, Norway. Arild.Wikan@hih.no FAU - Wikan, A AU - Wikan A LA - eng PT - Journal Article CY - Germany TA - J Math Biol JID - 7502105 SB - IM MH - Aging MH - Animal MH - *Nonlinear Dynamics MH - *Population Dynamics MH - Predatory Behavior EDAT- 2002/02/02 10:00 MHDA- 2002/07/04 10:01 PST - ppublish SO - J Math Biol 2001 Dec;43(6):471-500. 279: Short TG, et al. Efficient trial design for el...[PMID:11818774]Related Articles, Books, LinkOut UI - 21676107 PMID- 11818774 DA - 20020130 DCOM- 20020402 IS - 0003-3022 VI - 96 IP - 2 DP - 2002 Feb TI - Efficient trial design for eliciting a pharmacokinetic-pharmacodynamic model-based response surface describing the interaction between two intravenous anesthetic drugs. PG - 400-8 AB - BACKGROUND: The authors published a pharmacokinetic- pharmacodynamic model for two drugs based on response surface methodology. Because of the complexity of the model, they performed a simulation study to answer two questions about use of the model: (1) which study design would be most satisfactory; and (2) how many patients would need to be studied to adequately describe an entire response surface. METHODS: Data were simulated using realistic variability for two hypothetical intravenous anesthetic drugs that interact synergistically and that could be given by computer-controlled infusion. Three trial designs were simulated, one that made a series of parallel slices of the response surface, one that crisscrossed the response surface, and one that made a series of radial slices across the surface. Series of 5, 10, 20, and 40 "subjects" were simulated. A pooled data approach was used to assess the ability of the various trial designs and numbers of subjects to adequately identify the interaction response surface and estimate the original response surface. RESULTS: The crisscross design was shown to be the most robust in terms of its ability to both discriminate the correct order of the interaction term and to discriminate the original response surface using the least number of patients. Twenty subjects would be required to adequately define a surface using the crisscross study design, and 40 subjects would be required using the other trial designs. CONCLUSIONS: The results showed that a number of trial designs would be viable, but a design that crossed the surface in a crisscross fashion would give the most robust result with the least patients. AD - Palo Alto Veterans Administration Health Care Center, Palo Alto, California, USA. tims@adhb.govt.nz FAU - Short, Timothy G AU - Short TG FAU - Ho, Tam Yuk AU - Ho TY FAU - Minto, Charles F AU - Minto CF FAU - Schnider, Thomas W AU - Schnider TW FAU - Shafer, Steven L AU - Shafer SL LA - eng PT - Journal Article CY - United States TA - Anesthesiology JID - 1300217 RN - 0 (Anesthetics, Intravenous) SB - AIM SB - IM MH - Algorithms MH - Anesthetics, Intravenous/*pharmacokinetics/*pharmacology MH - Computer Simulation MH - Drug Synergism MH - Models, Biological MH - Nonlinear Dynamics MH - Research Design MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/01/31 10:00 MHDA- 2002/04/03 10:01 PST - ppublish SO - Anesthesiology 2002 Feb;96(2):400-8. 280: Orme BA, et al. Enhanced efficiency of feedin...[PMID:11817746]Related Articles, Books, LinkOut UI - 21675405 PMID- 11817746 DA - 20020130 DCOM- 20020715 IS - 0265-0746 VI - 18 IP - 3 DP - 2001 Sep TI - Enhanced efficiency of feeding and mixing due to chaotic flow patterns around choanoflagellates. PG - 293-325 AB - The motion of particles and feeding currents created by micro-organisms due to a flagellum are considered. The calculations are pertinent to a range of sessile organisms, but we concentrate on a particular organism, namely Salpingoeca amphoridium (SA) (a choanoflagellate), due to the availability of experimental data (Pettitt, 2000). These flow fields are characterized as having very small Reynolds numbers, which implies that viscous forces dominate over inertial ones consistent with using the Stokes flow equations. The flow generated by the flagellum is modelled via the consideration of a point force known as a stokeslet. The interaction between the boundary, to which the organism is attached, and its flagellum leads to toroidal eddies, which serve to transport particles towards the micro-organism, promoting filtering of nutrients by the microvilli which constitute the cell's collar (the filtering mechanism in SA). It is our conjecture that the interaction of multiple toroidal eddies will lead to chaotic advection and hence enhance the domain of feeding for these organisms. The degree of mixing in the region around SA is investigated using chaotic and statistical measures to study the influence the flagellum has on the surrounding fluid. The three-dimensional particle paths around such organisms are also considered with the aim of showing that the plane within which they are situated is an attractor. AD - School of Mathematics and Statistics, The University of Birmingham, Edgbaston, UK. FAU - Orme, B A AU - Orme BA FAU - Otto, S R AU - Otto SR FAU - Blake, J R AU - Blake JR LA - eng PT - Journal Article CY - England TA - IMA J Math Appl Med Biol JID - 8704892 SB - IM MH - Animal MH - Feeding Behavior MH - Flagella/*physiology MH - Mastigophora/*physiology MH - *Models, Biological MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2002/01/31 10:00 MHDA- 2002/07/16 10:01 PST - ppublish SO - IMA J Math Appl Med Biol 2001 Sep;18(3):293-325. 281: Raykov T. Estimation of congeneric scal...[PMID:11817096]Related Articles, Books, LinkOut UI - 21591590 PMID- 11817096 DA - 20011205 DCOM- 20020130 IS - 0007-1102 VI - 54 IP - Pt 2 DP - 2001 Nov TI - Estimation of congeneric scale reliability using covariance structure analysis with nonlinear constraints. PG - 315-23 AB - A method of composite reliability estimation using covariance structure analysis with nonlinear constraints is outlined. To motivate the developments, initially a short overview of research is presented, demonstrating that in many cases the widely used coefficient alpha is an unsatisfactory index of scale reliability already at the population level. As an alternative, the proposed covariance structure analysis procedure is based on the theoretical formula of the scale reliability coefficient in terms of parameters pertaining to a given set of congeneric components. The described approach is illustrated with several numerical examples and its performance compared with that of coefficient alpha. AD - Department of Psychology, Fordham University, Bronx, NY 10458, USA. FAU - Raykov, T AU - Raykov T LA - eng PT - Journal Article CY - England TA - Br J Math Stat Psychol JID - 0004047 SB - IM MH - *Analysis of Variance MH - Bias (Epidemiology) MH - Human MH - *Nonlinear Dynamics MH - Psychological Tests/*statistics & numerical data MH - *Psychometrics MH - Reproducibility of Results MH - Support, Non-U.S. Gov't EDAT- 2002/01/31 10:00 MHDA- 2002/01/31 10:01 PST - ppublish SO - Br J Math Stat Psychol 2001 Nov;54(Pt 2):315-23. 282: Ferrando PJ. A nonlinear congeneric model ...[PMID:11817095]Related Articles, Books, LinkOut UI - 21591589 PMID- 11817095 DA - 20011205 DCOM- 20020130 IS - 0007-1102 VI - 54 IP - Pt 2 DP - 2001 Nov TI - A nonlinear congeneric model for continuous item responses. PG - 293-313 AB - This paper presents a unidimensional item response model intended for personality and attitude items that use a continuous response format. The model's starting point is the linear congeneric model for item scores, but it takes into account the bounded nature of the item responses and assumes that their conditional distributions for a fixed trait level are truncated normal. This assumption leads to nonlinear item-trait regressions and considerably modifies some aspects of the linear model. The linear model is considered as an approximation to the modified version, and an interval is defined in which the approximation is satisfactory. Procedures for estimating the item and subject parameters are described. The applicability of the model is illustrated using real data. AD - Universidad Rovira i Virgili, Facultad de Psicologia, Carretera Valls s/n, 43007 Tarragona, Spain. pjfp@astor.urv.es FAU - Ferrando, P J AU - Ferrando PJ LA - eng PT - Journal Article CY - England TA - Br J Math Stat Psychol JID - 0004047 SB - IM MH - Human MH - *Models, Statistical MH - *Nonlinear Dynamics MH - Personality Inventory/*statistics & numerical data MH - *Psychometrics MH - Reference Values EDAT- 2002/01/31 10:00 MHDA- 2002/01/31 10:01 PST - ppublish SO - Br J Math Stat Psychol 2001 Nov;54(Pt 2):293-313. 283: Verbeken EK. Classifying interstitial lung...[PMID:11816816]Related Articles, Books, LinkOut UI - 21591068 PMID- 11816816 DA - 20011205 DCOM- 20020403 IS - 0904-1850 VI - 32 DP - 2001 Sep TI - Classifying interstitial lung diseases in a fractal lung: a morphologist's view "anno Domini 2000". PG - 107s-113s AB - Interstitial lung diseases (ILDs) remain a challenging problem for the pathologist. New insights in aetiology and pathogenesis, new diagnostic tools and successful research have led to a renewed interest in ILDs during the last few years, and highlighted the need for a novel classification, particularly of the chronic and/or idiopathic categories of interstitial pneumonias. The present paper compares the terminology of the latter categories in current and previous classifications and briefly discusses the pathological basis for the classifications of ILDs in general, and for the idiopathic interstitial pneumonias (IIPs) in particular. The difference between high versus low morphological specificity determines the pathological classifications. The classification of lIPs relies upon a pattern recognition taking temporal and spatial distribution into consideration. The last section of this paper discusses recent research opposing the conventional pathological approach, analogous to the mechanical two-compartment model of the lung, in which a discontinuity is considered between these two compartments, and thus, a distinction is made between interstitial lung diseases with and without bronchiolitis. In the recent "fractal" concept, the continuity of the lung architecture is emphasized: the lung is a so-called fractal tree with noninteger dimensions. In this fractal model, an interstitial lung disease effects a peripheral part of the pulmonary fractal tree and this may or may not include bronchioles. AD - Dept of Pathology, Katholieke Universiteit Leuven, Belgium. FAU - Verbeken, E K AU - Verbeken EK LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - Denmark TA - Eur Respir J Suppl JID - 8910681 SB - IM MH - Bronchiolitis/etiology MH - Diagnosis, Differential MH - *Fractals MH - Human MH - Lung/*pathology MH - Lung Diseases, Interstitial/*classification/diagnosis/etiology MH - Nonlinear Dynamics MH - Sensitivity and Specificity RF - 24 EDAT- 2002/01/31 10:00 MHDA- 2002/04/04 10:01 PST - ppublish SO - Eur Respir J Suppl 2001 Sep;32:107s-113s. 284: Bhattacharya J, et al. Interdependencies in the spon...[PMID:11812395]Related Articles, Books, LinkOut UI - 21671307 PMID- 11812395 DA - 20020128 DCOM- 20020214 IS - 0167-8760 VI - 42 IP - 3 DP - 2001 Nov TI - Interdependencies in the spontaneous EEG while listening to music. PG - 287-301 AB - We studied the patterns of interdependency between different brain regions during the performance of higher cognitive functions. Our goal was to check the existence in these patterns of both task-related differences (e.g. listening to music vs. rest) and training-related differences (musicians vs. non-musicians). For this purpose, a non-linear measure, called similarity index (S.I.), was used to detect asymmetric interdependencies between different brain regions by means of EEG signals. Relatively active and passive regions of the brain were found where the degree of activity was represented by excited degrees of freedom. The S.I. obtained during listening to different kinds of music was compared statistically with the S.I. with eyes closed, and significant changes (P< or = 0.05) were entered into schematic brain maps. A topographical representation of the S.I. yielded differences in the interdependency while performing different cognitive tasks. The results demonstrate the occurrence of task-related differences in both groups of subjects. Furthermore, subjects with musical training possessed significantly higher degrees of interdependencies than such without musical training while listening to music but not to text. We conclude that the new measure can be successfully applied for studying the dynamical co-operation between cortical areas during higher cognitive functioning. AD - Commission for Scientific Visualization, Austrian Academy of Sciences, Sonnenfelsgasse 19/2, A-1010 Vienna, Austria. joydeep.bhattacharya@oeaw.ac.at FAU - Bhattacharya, J AU - Bhattacharya J FAU - Petsche, H AU - Petsche H FAU - Pereda, E AU - Pereda E LA - eng PT - Journal Article CY - Netherlands TA - Int J Psychophysiol JID - 8406214 SB - IM MH - Adult MH - Auditory Perception/*physiology MH - Brain/physiology MH - Brain Mapping/methods MH - Comparative Study MH - *Electroencephalography/methods MH - Human MH - *Music MH - Nonlinear Dynamics MH - Statistics, Nonparametric MH - Support, Non-U.S. Gov't EDAT- 2002/01/29 10:00 MHDA- 2002/02/15 10:01 AID - S0167876001001532 [pii] PST - ppublish SO - Int J Psychophysiol 2001 Nov;42(3):287-301. 285: Engbert R, et al. Synchronizing movements with ...[PMID:11812036]Related Articles, Books, LinkOut UI - 21671001 PMID- 11812036 DA - 20020128 DCOM- 20020416 IS - 0278-2626 VI - 48 IP - 1 DP - 2002 Feb TI - Synchronizing movements with the metronome: nonlinear error correction and unstable periodic orbits. PG - 107-16 AB - The control of human hand movements is investigated in a simple synchronization task. We propose and analyze a stochastic model based on nonlinear error correction; a mechanism which implies the existence of unstable periodic orbits. This prediction is tested in an experiment with human subjects. We find that our experimental data are in good agreement with numerical simulations of our theoretical model. These results suggest that feedback control of the human motor systems shows nonlinear behavior. CI - Copyright 2001 Elsevier Science (USA). AD - Department of Physics, University of Potsdam, Germany. engbert@rz.uni-potsdam.de FAU - Engbert, Ralf AU - Engbert R FAU - Krampe, Ralf Th AU - Krampe RT FAU - Kurths, Jurgen AU - Kurths J FAU - Kliegl, Reinhold AU - Kliegl R LA - eng PT - Journal Article CY - United States TA - Brain Cogn JID - 8218014 SB - IM MH - Hand/*physiology MH - Human MH - Movement/*physiology MH - *Nonlinear Dynamics MH - *Psychomotor Performance MH - Support, Non-U.S. Gov't MH - Time Factors EDAT- 2002/01/29 10:00 MHDA- 2002/04/17 10:01 AID - 10.1006/brcg.2001.1307 [doi] AID - S0278262601913077 [pii] PST - ppublish SO - Brain Cogn 2002 Feb;48(1):107-16. 286: Vial S, et al. Volume delineation by fusion ...[PMID:11811836]Related Articles, Books, LinkOut UI - 21670167 PMID- 11811836 DA - 20020128 DCOM- 20020718 LR - 20021004 IS - 0278-0062 VI - 20 IP - 12 DP - 2001 Dec TI - Volume delineation by fusion of fuzzy sets obtained from multiplanar tomographic images. PG - 1362-72 AB - Techniques of three-dimensional (3-D) volume delineation from tomographic medical imaging are usually based on 2-D contour definition. For a given structure, several different contours can be obtained depending on the segmentation method used or the user's choice. The goal of this work is to develop a new method that reduces the inaccuracies generally observed. A minimum volume that is certain to be included in the volume concerned (membership degree mu = 1), and a maximum volume outside which no part of the volume is expected to be found (membership degree mu = 0), are defined semi-automatically. The intermediate fuzziness region (0 < mu < 1) is processed using the theory of possibility. The resulting fuzzy volume is obtained after data fusion from multiplanar slices. The influence of the contrast-to-noise ratio was tested on simulated images. The influence of slice thickness as well as the accuracy of the method were studied on phantoms. The absolute volume error was less than 2% for phantom volumes of 2-8 cm3, whereas the values obtained with conventional methods were much larger than the actual volumes. Clinical experiments were conducted, and the fuzzy logic method gave a volume lower than that obtained with the conventional method. Our fuzzy logic method allows volumes to be determined with better accuracy and reproducibility. AD - Laboratoire de Biophysique (UPRES EA 1049), ITM, Hopital Universitaire, and Universite des Sciences et Technologies, Lille, France. FAU - Vial, S AU - Vial S FAU - Gibon, D AU - Gibon D FAU - Vasseur, C AU - Vasseur C FAU - Rousseau, J AU - Rousseau J LA - eng PT - Journal Article PT - Validation Studies CY - United States TA - IEEE Trans Med Imaging JID - 8310780 SB - IM MH - Artificial Intelligence MH - Brain Neoplasms/*diagnosis/secondary MH - Comparative Study MH - Computer Simulation MH - Contrast Sensitivity MH - *Fuzzy Logic MH - Human MH - Imaging, Three-Dimensional/*methods MH - Magnetic Resonance Imaging MH - Meningeal Neoplasms/*diagnosis/secondary MH - Meningioma/*diagnosis/secondary MH - Models, Neurological MH - Nonlinear Dynamics MH - Phantoms, Imaging MH - Reproducibility of Results MH - Sensitivity and Specificity MH - Software Validation MH - Support, Non-U.S. Gov't EDAT- 2002/01/29 10:00 MHDA- 2002/07/19 10:01 PST - ppublish SO - IEEE Trans Med Imaging 2001 Dec;20(12):1362-72. 287: Oh J, et al. A multistage perceptual quali...[PMID:11811835]Related Articles, Books, LinkOut UI - 21670166 PMID- 11811835 DA - 20020128 DCOM- 20020718 IS - 0278-0062 VI - 20 IP - 12 DP - 2001 Dec TI - A multistage perceptual quality assessment for compressed digital angiogram images. PG - 1352-61 AB - This paper describes a multistage perceptual quality assessment (MPQA) model for compressed images. The motivation for the development of a perceptual quality assessment is to measure (in)visible differences between original and processed images. The MPQA produces visible distortion maps and quantitative error measures informed by considerations of the human visual system (HVS). Original and decompressed images are decomposed into different spatial frequency bands and orientations modeling the human cortex. Contrast errors are calculated for each frequency and orientation, and masked as a function of contrast sensitivity and background uncertainty. Spatially masked contrast error measurements are then made across frequency bands and orientations to produce a single perceptual distortion visibility map (PDVM). A perceptual quality rating (PQR) is calculated from the PDVM and transformed into a one to five scale, PQR(1-5), for direct comparison with the mean opinion score, generally used in subjective ratings. The proposed MPQA model is based on existing perceptual quality assessment models, while it is differentiated by the inclusion of contrast masking as a function of background uncertainty. A pilot study of clinical experiments on wavelet-compressed digital angiogram has been performed on a sample set of angiogram images to identify diagnostically acceptable reconstruction. Our results show that the PQR(1-5) of diagnostically acceptable lossy image reconstructions have better agreement with cardiologists' responses than objective error measurement methods, such as peak signal-to-noise ratio A Perceptual thresholding and CSF-based Uniform quantization (PCU) method is also proposed using the vision models presented in this paper. The vision models are implemented in the thresholding and quantization stages of a compression algorithm and shown to produce improved compression ratio performance with less visible distortion than that of the embedded zerotrees wavelet (EZWs). AD - Electronic, Electrical and Computer Engineering, The University of Birmingham, UK. FAU - Oh, J AU - Oh J FAU - Woolley, S I AU - Woolley SI FAU - Arvanitis, T N AU - Arvanitis TN FAU - Townend, J N AU - Townend JN LA - eng PT - Journal Article CY - United States TA - IEEE Trans Med Imaging JID - 8310780 SB - IM MH - Algorithms MH - Comparative Study MH - Contrast Sensitivity MH - Coronary Angiography/*methods MH - Feasibility Studies MH - Feedback MH - Fourier Analysis MH - Human MH - Image Processing, Computer-Assisted/*methods MH - Mathematics MH - Models, Biological MH - Nonlinear Dynamics MH - Pattern Recognition MH - Sensitivity and Specificity EDAT- 2002/01/29 10:00 MHDA- 2002/07/19 10:01 PST - ppublish SO - IEEE Trans Med Imaging 2001 Dec;20(12):1352-61. 288: Yukawa E, et al. Pharmacoepidemiologic investi...[PMID:11808828]Related Articles, Books, LinkOut UI - 21666942 PMID- 11808828 DA - 20020125 DCOM- 20020708 LR - 20021101 IS - 0091-2700 VI - 42 IP - 1 DP - 2002 Jan TI - Pharmacoepidemiologic investigation of clonazepam relative clearance by mixed-effect modeling using routine clinical pharmacokinetic data in Japanese patients. PG - 81-8 AB - The effects of drug-drug interactions on clonazepam clearance were examined through a retrospective analysis of serum concentration data from pediatric and adult epileptic patients. Patients received clonazepam as monotherapy or in combination with other antiepileptic drugs. A total of 259 serum clonazepam concentrations gathered from 137 patients were used in a population analysis of drug-drug interactions on clonazepam clearance. Data were analyzed using a nonlinear mixed-effects modeling (NONMEM) technique. The final model describing clonazepam clearance was CL = 152 x TBW(-0.181) x DIF, where CL is clearance (ml/kg/h), TBWis total body weight (kg), and DIF (drug interaction factor) is a scaling factor for concomitant medication with a value of 1 for patients on clonazepam monotherapy, 1.18 for those patients receiving concomitant administration of clonazepam and one antiepileptic drug (carbamazepine or valproic acid), and 2.12 x TBW(-0.119) for those patients receiving concomitant administration of clonazepam and more than two antiepileptic drugs. Clonazepam clearance decreased in a weight-related fashion in children, with minimal changes observed in adults. Concomitant administration of clonazepam and carbamazepine resulted in a 22% increase in clonazepam clearance. Concomitant administration of clonazepam and valproic acid resulted in a 12% increase in clonazepam clearance. Concomitant administration of clonazepam with two or more antiepileptic drugs resulted in a 23% to 75% increase in clonazepam clearance. AD - Laboratory of Clinical Pharmacokinetics, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan. FAU - Yukawa, Eiji AU - Yukawa E FAU - Satou, Masayasu AU - Satou M FAU - Nonaka, Toshiharu AU - Nonaka T FAU - Yukawa, Miho AU - Yukawa M FAU - Ohdo, Shigehiro AU - Ohdo S FAU - Higuchi, Shun AU - Higuchi S FAU - Kuroda, Takeshi AU - Kuroda T FAU - Goto, Yoshinobu AU - Goto Y LA - eng PT - Journal Article CY - United States TA - J Clin Pharmacol JID - 0366372 RN - 0 (Anticonvulsants) RN - 1622-61-3 (Clonazepam) SB - IM MH - Adolescent MH - Adult MH - Anticonvulsants/blood/*pharmacokinetics/pharmacology MH - Child MH - Child, Preschool MH - Clonazepam/blood/*pharmacokinetics/pharmacology MH - Confidence Intervals MH - Dose-Response Relationship, Drug MH - Drug Therapy, Combination MH - Female MH - Human MH - Infant MH - Japan/epidemiology MH - Male MH - Metabolic Clearance Rate/physiology MH - *Models, Biological MH - Nonlinear Dynamics MH - Retrospective Studies MH - Support, Non-U.S. Gov't EDAT- 2002/01/26 10:00 MHDA- 2002/07/09 10:01 PST - ppublish SO - J Clin Pharmacol 2002 Jan;42(1):81-8. 289: Giuliani A, et al. Recurrence quantification ana...[PMID:11807945]Related Articles, Books, LinkOut UI - 21666587 PMID- 11807945 DA - 20020124 DCOM- 20020403 IS - 0887-3585 VI - 46 IP - 2 DP - 2002 Feb 1 TI - Recurrence quantification analysis reveals interaction partners in paramyxoviridae envelope glycoproteins. PG - 171-6 AB - The paramyxovirus envelope fuses with the host cell membrane by cooperative interaction of two transmembrane glycoproteins: the hemagglutinin neuraminidase (HN) and the fusion (F) glycoprotein. The interaction appears to be finely regulated, as both proteins must derive from the same viral species to obtain a functional interaction. Because HN and F do not form stable complexes, this interaction is poorly characterized. This article demonstrates that a modification of a classical bioinformatic method based on the co-evolution of interacting partners can detect the specificity of the HN and F interaction. The proposed approach relies on a relatively new nonlinear signal analysis technique, recurrence quantification analysis (RQA), applied to the hydrophobicity sequences of viral proteins. This technique is able to shed light on the interaction between HN and F proteins in the virus-cell fusion and, more generally, permits the quantitative comparison of nonhomologue protein systems. On the contrary, the same co-evolution approach, based on the classical sequence alignment procedure, was unable to discriminate interacting partners from the general strict correlation existing between the evolution of viral proteins as a whole. The cooperation between HN and F in the fusion process is thus demonstrated by a bioinformatic, purely sequence-dependent, perspective. CI - Copyright 2001 Wiley-Liss, Inc. AD - Comparative Toxicology and Ecotoxicology Laboratory, Istituto Superiore di Sanita, Roma, Italy. alesandro.giuliani@iss.it FAU - Giuliani, Alessandro AU - Giuliani A FAU - Tomasi, Maurizio AU - Tomasi M LA - eng PT - Journal Article CY - United States TA - Proteins JID - 8700181 RN - 0 (Glycoproteins) RN - 0 (HN Protein) RN - 0 (Viral Fusion Proteins) SB - IM MH - Computational Biology/*methods MH - Data Interpretation, Statistical MH - Glycoproteins/physiology MH - HN Protein/*physiology MH - Nonlinear Dynamics MH - Paramyxoviridae/*physiology MH - Protein Interaction Mapping/*methods MH - Sequence Alignment MH - Viral Fusion Proteins/*physiology EDAT- 2002/01/25 10:00 MHDA- 2002/04/04 10:01 AID - 10.1002/prot.10044 [pii] PST - ppublish SO - Proteins 2002 Feb 1;46(2):171-6. 290: Buckley JG, et al. Postural sway and active bala...[PMID:11807327]Related Articles, Books, LinkOut UI - 21665578 PMID- 11807327 DA - 20020124 DCOM- 20020205 IS - 0894-9115 VI - 81 IP - 1 DP - 2002 Jan TI - Postural sway and active balance performance in highly active lower-limb amputees. PG - 13-20 AB - OBJECTIVE: To determine the balance performance of active lower-limb amputees during quiet standing and under dynamic conditions. DESIGN: Center-of-pressure excursions during quiet standing and the standing balance performance on a single axis stabilimeter was assessed in six unilateral lower-limb amputees and six able-bodied controls. Stabilimeter trials were repeated with subjects standing so that pivoting occurred either in the anteroposterior or mediolateral direction or in the mediolateral direction but with vision occluded. RESULTS: Center-of-pressure excursions were significantly greater (P < 0.05) for amputees in both the mediolateral and anteroposterior directions. During all stabilimeter tests, amputees spent significantly less time in balance than able-bodied controls (P < 0.05), and this was attributed to a nonsignificant increase in the average time the stabilimeter spent in contact with the ground. Group differences in the average time of contact in the anteroposterior test condition were meaningful (effect size, 1.19). CONCLUSIONS: Amputees had poorer static and dynamic balance than able-bodied controls. Amputees had a greater problem controlling dynamic balance in the anteroposterior direction than the mediolateral direction. Findings highlight the importance of the ankle in maintaining balance in situations that involve body movements in the sagittal plane. AD - Department of Exercise and Sport Science, Manchester Metropolitan University, Hassall Road, Alsager, Stoke-on-Trent ST7 2HL, Manchester, UK. FAU - Buckley, John G AU - Buckley JG FAU - O'Driscoll, Dan AU - O'Driscoll D FAU - Bennett, Simon J AU - Bennett SJ LA - eng PT - Journal Article CY - United States TA - Am J Phys Med Rehabil JID - 8803677 SB - AIM SB - IM MH - Adult MH - *Amputees MH - Case-Control Studies MH - *Equilibrium MH - Human MH - Leg MH - Male MH - Nonlinear Dynamics MH - Posture EDAT- 2002/01/25 10:00 MHDA- 2002/02/06 10:01 PST - ppublish SO - Am J Phys Med Rehabil 2002 Jan;81(1):13-20. 291: Weiss M, et al. P-glycoprotein inhibitors enh...[PMID:11805234]Related Articles, Books, LinkOut UI - 21667774 PMID- 11805234 DA - 20020125 DCOM- 20020225 IS - 0022-3565 VI - 300 IP - 2 DP - 2002 Feb TI - P-glycoprotein inhibitors enhance saturable uptake of idarubicin in rat heart: pharmacokinetic/pharmacodynamic modeling. PG - 688-94 AB - Little is known about cardiac uptake kinetics of idarubicin, including a possible protective role of P-glycoprotein (Pgp)-mediated transport. This study therefore investigated uptake and negative inotropic action of idarubicin in the single-pass isolated perfused rat heart by using a pharmacokinetic/pharmacodynamic modeling approach. Idarubicin was administered as a 10-min constant infusion of 0.5 mg followed by a 70-min washout period in the absence and presence of the Pgp antagonists verapamil or amiodarone. Outflow concentration and left ventricular developed pressure were measured and the model parameters were estimated by simultaneous nonlinear regression. The results indicate the existence of a saturable, Michaelis-Menten type uptake process into the heart (K(m) = 3.06 microM, V(max) = 46.0 microM/min). Verapamil and amiodarone significantly enhanced the influx rate (V(max) increased 1.8-fold), suggesting that idarubicin is transported by Pgp directly out of the membrane before it gets into the cell. Verapamil and amiodarone attenuated the negative inotropic action of idarubicin, which was linked to the intracellular concentration of idarubicin. AD - Section of Pharmacokinetics, Department of Pharmacology, Martin Luther University Halle-Wittenberg, Halle, Germany. michael.weiss@medizin.uni-halle.de FAU - Weiss, Michael AU - Weiss M FAU - Kang, Wonku AU - Kang W LA - eng PT - Journal Article CY - United States TA - J Pharmacol Exp Ther JID - 0376362 RN - 0 (Antibiotics, Anthracycline) RN - 0 (Calcium Channel Blockers) RN - 0 (Enzyme Inhibitors) RN - 0 (P-Glycoprotein) RN - 1951-25-3 (Amiodarone) RN - 52-53-9 (Verapamil) RN - 58957-92-9 (Idarubicin) SB - IM MH - Algorithms MH - Amiodarone/pharmacology MH - Animal MH - Antibiotics, Anthracycline/*metabolism/toxicity MH - Calcium Channel Blockers/pharmacology MH - Depression, Chemical MH - Enzyme Inhibitors/pharmacology MH - Heart/*drug effects MH - Heart Rate/drug effects MH - Idarubicin/*metabolism/toxicity MH - In Vitro MH - Kinetics MH - Male MH - Models, Biological MH - Myocardium/*metabolism MH - Nonlinear Dynamics MH - P-Glycoprotein/*antagonists & inhibitors MH - Rats MH - Rats, Sprague-Dawley MH - Support, Non-U.S. Gov't MH - Verapamil/pharmacology EDAT- 2002/01/24 10:00 MHDA- 2002/02/28 10:01 PST - ppublish SO - J Pharmacol Exp Ther 2002 Feb;300(2):688-94. 292: Khirani S, et al. Positive end expiratory press...[PMID:11804239]Related Articles, Books, LinkOut UI - 21662584 PMID- 11804239 DA - 20020123 DCOM- 20020718 IS - 0001-5342 VI - 49 IP - 4 DP - 2001 TI - Positive end expiratory pressure and expiratory flow limitation: a model study. PG - 277-90 AB - Patients suffering from chronic obstructive pulmonary diseases, frequently exhibit expiratory airflow limitation. We propose a mathematical model describing the mechanical behavior of the ventilated respiratory system. This model has to simulate applied positive end-expiratory pressure (PEEP) effects during expiration, a process used by clinicians to improve airflow. The proposed model consists of a nonlinear two-compartment system. One of the compartments represents the collapsible airways and mimics its dynamic compression, the other represents the lung and chest wall compartment. For all clinical conditions tested (n=16), the mathematical model simulates the removal of expiratory airflow limitation at PEEP lower than 70-80% of intrinsic end-expiratory pressure (PEEPi), i.e. the end-expiratory alveolar pressure (PAet) without PEEP. It also shows the presence of an optimal PEEP. The optimal PEEP contributes to decrease PAet from 7.4+/-0.9 (SD) to 5.4+/-0.9 hPa (p < 0.0001; mild flow limitation) and from 11.8+/-1.1 to 7.8+/-0.7 hPa (p < 0.0001; severe flow limitation). Resistance of the collapsible compartment is decreased from 53+/-7 to 8.2+/-5.9 hPa.L(-1).s (p < 0.0001; mild flow limitation) and from 80+/-11 to 6.9+/-5.4 hPa.L(-1).s (p < 0.0001; severe flow limitation). This simplistic mathematical model gives a plausible explanation of the expiratory airflow limitation removal with PEEP and a rationale to the practice of PEEP application to airflow limited patients. AD - Laboratoire Techniques en Imagerie Modelisation et Cognition (Institut IMAG), Faculte de Medecine, La Tronche, France. FAU - Khirani, S AU - Khirani S FAU - Biot, L AU - Biot L FAU - Eberhard, A AU - Eberhard A FAU - Baconnier, P AU - Baconnier P LA - eng PT - Journal Article CY - Netherlands TA - Acta Biotheor JID - 0421520 SB - IM MH - Airway Resistance/*physiology MH - Forced Expiratory Flow Rates/physiology MH - Human MH - *Models, Theoretical MH - *Nonlinear Dynamics MH - Positive-Pressure Respiration/*statistics & numerical data MH - Pulmonary Alveoli/physiopathology MH - Pulmonary Disease, Chronic Obstructive/*physiopathology EDAT- 2002/01/24 10:00 MHDA- 2002/07/19 10:01 PST - ppublish SO - Acta Biotheor 2001;49(4):277-90. 293: Ichinose N, et al. [Nonlinear analysis on geneti...[PMID:11802436]Related Articles, Books, LinkOut UI - 21661099 PMID- 11802436 DA - 20020122 DCOM- 20020226 IS - 0039-9450 VI - 46 IP - 16 Suppl DP - 2001 Dec TI - [Nonlinear analysis on genetic network systems] PG - 2598-602 AD - ichinose@ims.u-tokyo.ac.jp FAU - Ichinose, N AU - Ichinose N FAU - Kobayashi, T AU - Kobayashi T FAU - Aihara, K AU - Aihara K LA - jpn PT - Journal Article PT - Review PT - Review, Tutorial CY - Japan TA - Tanpakushitsu Kakusan Koso JID - 0413762 SB - IM MH - Gene Expression MH - Genes/*physiology MH - *Models, Genetic MH - *Nonlinear Dynamics RF - 9 EDAT- 2002/01/23 10:00 MHDA- 2002/02/28 10:01 PST - ppublish SO - Tanpakushitsu Kakusan Koso 2001 Dec;46(16 Suppl):2598-602. 294: Fujieda S, et al. Effect of gravity field on th...[PMID:11799985]Related Articles, Books, LinkOut UI - 21656842 PMID- 11799985 DA - 20020118 DCOM- 20020426 IS - 0273-1177 VI - 28 IP - 4 DP - 2001 TI - Effect of gravity field on the nonequilibrium/nonlinear chemical oscillation reactions. PG - 537-43 AB - Biological systems have evolved for a long time under the normal gravity. The Belousov-Zhabotinsky (BZ) reaction is a nonlinear chemical system far from the equilibrium that may be considered as a simplified chemical model of the biological systems so as to study the effect of gravity. The reaction solution is comprised of bromate in sulfuric acid as an oxidizing agent, 1,4-cyclohexanedione as an organic substrate, and ferroin as a metal catalyst. Chemical waves in the BZ reaction-diffusion system are visualized as blue and red patterns of ferriin and ferroin, respectively. After an improvement to the tubular reaction vessels in the experimental setup, the traveling velocity of chemical waves in aqueous solutions was measured in time series under normal gravity, microgravity, hyper-gravity, and normal gravity using the free-fall facility of JAMIC (Japan Microgravity Center), Hokkaido, Japan. Chemical patterns were collected as image data via CCD camera and analyzed by the software of NIH image after digitization. The estimated traveling velocity increased with increasing gravity as expected. It was clear experimentally that the traveling velocity of target patterns in reaction diffusion system was influenced by the effect of convection and correlated closely with the gravity field. CI - c2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved. AD - Department of Chemistry, Ochanomizu University, Tokyo, Japan. FAU - Fujieda, S AU - Fujieda S FAU - Mori, Y AU - Mori Y FAU - Nakazawa, A AU - Nakazawa A FAU - Mogami, Y AU - Mogami Y LA - eng PT - Journal Article CY - United States TA - Adv Space Res JID - 9878935 RN - 0 (Bromates) RN - 0 (Bromides) RN - 0 (Cyclohexanones) RN - 0 (Phenanthrolines) RN - 0 (Sodium Compounds) RN - 0 (Solutions) RN - 0 (Sulfuric Acids) RN - 14708-99-7 (ferroin) RN - 7647-15-6 (sodium bromide) RN - 7664-93-9 (sulfuric acid) RN - 7789-38-0 (sodium bromate) SB - S MH - Bromates/chemistry MH - Bromides/chemistry MH - Cells/chemistry MH - *Convection MH - Cyclohexanones/chemistry MH - Diffusion MH - *Gravitation MH - Image Processing, Computer-Assisted MH - Models, Chemical MH - Nonlinear Dynamics MH - Oscillometry MH - Oxidation-Reduction MH - Phenanthrolines/chemistry MH - Sodium Compounds/chemistry MH - Solutions/*chemistry MH - Sulfuric Acids/chemistry MH - Support, Non-U.S. Gov't MH - *Weightlessness EDAT- 2002/01/22 10:00 MHDA- 2002/04/27 10:01 PST - ppublish SO - Adv Space Res 2001;28(4):537-43. 295: Coltman DW, et al. Age-dependent sexual selectio...[PMID:11798432]Related Articles, Books, LinkOut UI - 21657616 PMID- 11798432 DA - 20020118 DCOM- 20020712 IS - 0962-8452 VI - 269 IP - 1487 DP - 2002 Jan 22 TI - Age-dependent sexual selection in bighorn rams. PG - 165-72 AB - Although mating systems and sexual selection have been intensively studied in ungulate model systems, very few studies have combined genetic paternity analysis with individual phenotypic data over several breeding seasons. We used microsatellite paternity analysis to determine the parentage of 83 bighorn sheep (Ovis canadensis) born between 1995 and 2000 at Ram Mountain, Alberta, Canada. We could assign the paternity of 64 lambs at a high level of statistical confidence (95%). Within each season, the most successful ram sired an average of 35.5% of the lambs with assigned paternity, and a single ram sired 26.1% of all lambs over the six mating seasons. Although a few large-horned, mature (age 8+ years) rams had very high reproductive success, younger rams sired ca. 50% of the lambs. Mixed-effects models indicated that mating success increases as a nonlinear function of age, with horn length increasingly positive in correlation with mating success in older rams. These results indicate that young or small rams possibly achieve mating success through alternative mating tactics that are less dependent on body and weapon size, such as coursing and blocking. Sexual selection is therefore likely to have age-dependent effects on traits such as agility, body and horn size. AD - Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK. d.coltman@sheffield.ac.uk FAU - Coltman, D W AU - Coltman DW FAU - Festa-Bianchet, M AU - Festa-Bianchet M FAU - Jorgenson, J T AU - Jorgenson JT FAU - Strobeck, C AU - Strobeck C LA - eng PT - Journal Article CY - England TA - Proc R Soc Lond B Biol Sci JID - 7505889 SB - IM MH - Age Factors MH - Animal MH - Female MH - Linkage Disequilibrium MH - Male MH - Nonlinear Dynamics MH - Sex Behavior, Animal/*physiology MH - Sheep/genetics/*physiology EDAT- 2002/01/19 10:00 MHDA- 2002/07/13 10:01 AID - 10.1098/rspb.2001.1851 [doi] PST - ppublish SO - Proc R Soc Lond B Biol Sci 2002 Jan 22;269(1487):165-72. 296: Griffin DR. Is the universe designed? Yes...[PMID:11797749]Related Articles, Books, LinkOut UI - 21656017 PMID- 11797749 DA - 20020118 DCOM- 20020208 IS - 0077-8923 VI - 950 DP - 2001 Dec TI - Is the universe designed? Yes and no. PG - 191-205 AB - Addressing the title's question from the perspective of Whitehead's process theology, fourteen basic notions of which are explained, I argue that the universe is not designed in six common senses of that notion: It was not created out of nothing, all at once, through punctuated creationism, from a blueprint, solely for humans, or even with humans specifically in mind. But it is designed in two looser senses of the term: It reflects a divine aim at richness of experience, and it involved a divine establishment of this cosmic epoch's fundamental contingent principles--an idea that is consistent with process theism's view of divine power as purely persuasive. AD - Center for Process Studies, Claremont School of Theology, California 91711, USA. davraygrif@aol.com FAU - Griffin, D R AU - Griffin DR LA - eng PT - Journal Article CY - United States TA - Ann N Y Acad Sci JID - 7506858 SB - IM MH - *Extraterrestrial Environment MH - Human MH - Mind-Body Relations (Metaphysics) MH - Nonlinear Dynamics MH - *Theology EDAT- 2002/01/19 10:00 MHDA- 2002/02/09 10:01 PST - ppublish SO - Ann N Y Acad Sci 2001 Dec;950:191-205. 297: Kubota Y, et al. Transient versus asymptotic d...[PMID:11796942]Related Articles, Books, LinkOut UI - 21655318 PMID- 11796942 DA - 20020117 DCOM- 20020405 IS - 0929-5313 VI - 11 IP - 3 DP - 2001 Nov-Dec TI - Transient versus asymptotic dynamics of CaM kinase II: possible roles of phosphatase. PG - 263-79 AB - Calmodulin-dependent protein kinase II (CaMKII) is known to play a key role during induction of long-term potentiation (LTP). Given the dependence of LTP on the frequency of synaptic activation, several previous modeling efforts have proposed that biochemical properties of CaMKII itself might be in part responsible for this dependence. Recently, De Koninck and Schulman (1998) have provided direct experimental evidence that the enzyme itself is sensitive to the frequency of Ca(2+) activation. Here we demonstrate the ability of a detailed biophysical model constructed solely on enzyme kinetics of purified proteins to generate the frequency sensitivity demonstrated by De Koninck and Schulman. Quantitative analysis of the model reveals that this frequency sensitivity is provided by a mechanism different from those previously postulated. This analysis leads to specific predictions concerning the effects of mutations on this process. We further employ the model to examine the asymptotic behavior of CaMKII-phosphatase system during longer simulated periods of stimulation. The analyses of the model suggest that the transient and asymptotic frequency sensitivity of this enzyme are dependent on different biochemical mechanisms. These results may be applicable to Ca(2+)/calmodulin signaling pathways in general. AD - ERATO (Exploratory Research for Advance Technology Kitano Symbiotic Systems)-Caltech Systems Biology Group and Control and Dynamical Systems, MC 107-81, California Institute of Technology, CA 91125, USA. ykubota@cmgm.stanford.edu FAU - Kubota, Y AU - Kubota Y FAU - Bower, J M AU - Bower JM LA - eng PT - Journal Article CY - United States TA - J Comput Neurosci JID - 9439510 RN - 0 (Calmodulin) RN - 0 (Protein Isoforms) RN - 7440-70-2 (Calcium) RN - EC 2.7.1.123 (Ca(2+)-Calmodulin Dependent Protein Kinase) RN - EC 2.7.10.- (calmodulin-dependent protein kinase II) RN - EC 3.1.3.16 (Phosphoprotein Phosphatase) SB - IM MH - Animal MH - Ca(2+)-Calmodulin Dependent Protein Kinase/genetics/*metabolism MH - Calcium/metabolism/pharmacology MH - Calcium Signaling/*physiology MH - Calmodulin/metabolism/pharmacology MH - Central Nervous System/*enzymology MH - Electric Stimulation MH - Human MH - Kinetics MH - Long-Term Potentiation/*physiology MH - *Models, Neurological MH - Mutation/physiology MH - Nonlinear Dynamics MH - Phosphoprotein Phosphatase/*metabolism MH - Phosphorylation MH - Protein Isoforms/genetics/metabolism MH - Signal Transduction/physiology MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Synapses/*enzymology MH - Synaptic Transmission/*physiology MH - Time Factors EDAT- 2002/01/18 10:00 MHDA- 2002/04/06 10:01 PST - ppublish SO - J Comput Neurosci 2001 Nov-Dec;11(3):263-79. 298: Henry FS, et al. Kinematically irreversible ac...[PMID:11796699]Related Articles, Books, LinkOut UI - 21655301 PMID- 11796699 DA - 20020117 DCOM- 20020408 IS - 8750-7587 VI - 92 IP - 2 DP - 2002 Feb TI - Kinematically irreversible acinar flow: a departure from classical dispersive aerosol transport theories. PG - 835-45 AB - Current theories describe aerosol transport in the lung as a dispersive (diffusion-like) process, characterized by an effective diffusion coefficient in the context of reversible alveolar flow. Our recent experimental data, however, question the validity of these basic assumptions. In this study, we describe the behavior of fluid particles (or bolus) in a realistic, numerical, alveolated duct model with rhythmically expanding walls. We found acinar flow exhibiting multiple saddle points, characteristic of chaotic flow, resulting in substantial flow irreversibility. Computations of axial variance of bolus spreading indicate that the growth of the variance with respect to time is faster than linear, a finding inconsistent with dispersion theory. Lateral behavior of the bolus shows fine-scale, stretch-and-fold striations, exhibiting fractal-like patterns with a fractal dimension of 1.2, which compares well with the fractal dimension of 1.1 observed in our experimental studies performed with rat lungs. We conclude that kinematic irreversibility of acinar flow due to chaotic flow may be the dominant mechanism of aerosol transport deep in the lungs. AD - School of Engineering, City University, London EC1V 0HB, United Kingdom. FAU - Henry, F S AU - Henry FS FAU - Butler, J P AU - Butler JP FAU - Tsuda, A AU - Tsuda A LA - eng ID - HL-47428/HL/NHLBI ID - HL-54885/HL/NHLBI PT - Journal Article CY - United States TA - J Appl Physiol JID - 8502536 RN - 0 (Aerosols) SB - IM MH - Aerosols MH - Animal MH - Biomechanics MH - Body Fluids/metabolism MH - Fractals MH - Lung/*physiology MH - *Models, Biological MH - Motion MH - Nonlinear Dynamics MH - Pulmonary Alveoli/physiology MH - *Pulmonary Ventilation MH - Rats MH - Respiratory Mechanics MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/01/18 10:00 MHDA- 2002/04/09 10:01 AID - 10.1152/japplphysiol.00385.2001 [doi] PST - ppublish SO - J Appl Physiol 2002 Feb;92(2):835-45. 299: Clarke BC, et al. Genes active in developing wh...[PMID:11793221]Related Articles, Cited in PMC, Books, LinkOut UI - 21652676 PMID- 11793221 DA - 20020116 DCOM- 20020322 LR - 20021101 IS - 1438-793X VI - 1 IP - 1 DP - 2000 May TI - Genes active in developing wheat endosperm. PG - 44-55 AB - This paper describes the construction and characterisation of a cDNA library from wheat endosperm tissue during the early stages of grain filling. Developing wheat endosperm tissue was characterised with respect to standard measures including dry weight, cytological appearance and timing of expression of major sources of mRNA such as the seed storage protein genes. In addition, the full complement of proteins present at mid-endosperm development was examined using 2D-electrophoretic techniques. Based on this characterisation, endosperm from the developing grain 8-12 days post-anthesis was chosen for isolating mRNA and preparing cDNA. At this stage in development the mRNA population is not yet dominated by the accumulation of mRNA from seed storage protein genes. A cDNA library, not normalised, containing a high percentage of full length cDNA clones was constructed and 4,319 clones sequenced ("single-pass"). Partitioning of the cDNA sequences into gene families and singletons provided the basis for quantifying the accumulation of sequence classes relative to the total number of sequences determined. The accumulation of gene families/singletons was not linear. However, mathematical modeling of the data suggested that the maximum number of different genes expressed is within the range of 4,500-8,000 (detailed in the Appendix). If an average is taken of these extremes, approximately 27% of the gene products were visible as proteins in the 2D-electrophoretic analysis. Analysis of a functional class of genes relevant to wheat grain end-use, namely the glutenin/gliadin seed storage protein class of genes, revealed a new category of gene characterised by a distinctive N-terminal domain and a reduced central repetitive domain. AD - CSIRO Plant Industry, PO Box 1600, Canberra, ACT 2601, Australia. b.clarke@pi.csiro.au FAU - Clarke, B C AU - Clarke BC FAU - Hobbs, M AU - Hobbs M FAU - Skylas, D AU - Skylas D FAU - Appels, R AU - Appels R LA - eng PT - Journal Article CY - Germany TA - Funct Integr Genomics JID - 100939343 RN - 0 (DNA, Plant) RN - 0 (Plant Proteins) SB - IM MH - Amino Acid Sequence MH - Base Sequence MH - Comparative Study MH - DNA, Plant/genetics/isolation & purification MH - Expressed Sequence Tags MH - Gene Library MH - *Genes, Plant MH - Microsatellite Repeats/genetics MH - Models, Theoretical MH - Molecular Sequence Data MH - Nonlinear Dynamics MH - Nucleic Acid Hybridization MH - Oligonucleotide Array Sequence Analysis MH - Plant Proteins/biosynthesis/chemistry/*genetics MH - Protein Structure, Tertiary MH - Seeds/*genetics/growth & development/metabolism MH - Sequence Alignment MH - Sequence Analysis, DNA MH - Support, Non-U.S. Gov't MH - Time Factors MH - Transcription, Genetic MH - Triticum/*embryology/*genetics/metabolism EDAT- 2002/01/17 10:00 MHDA- 2002/03/23 10:01 PHST- 1999/Oct/20 [received] PHST- 2000/Feb/04 [accepted] AID - 10.1007/s101420000008 [doi] PST - ppublish SO - Funct Integr Genomics 2000 May;1(1):44-55. 300: Worz R. [Multidimensional, nonlinear ...[PMID:11789124]Related Articles, Books, LinkOut UI - 21647622 PMID- 11789124 DA - 20020114 DCOM- 20020222 VI - 119 IP - 3-4 DP - 2001 Nov 29 TI - [Multidimensional, nonlinear pain concept. A broad approach for explaining and understanding complex pain syndromes] PG - 129-33 AB - The traditional mechanistic, deterministic, point-to-point-model of Descartes with its modifications of specificity, intensity, pattern and gate-control-theory turned out to be suitable for acute pain. Symptomatic pain as a result of a lesion or organic disease has to be differentiated principally from multifactorial pain syndromes. They can be regarded as open dynamic systems. The implication of consciousness of chronic pain patients with its essential intentionality opens degrees of freedom for the patients on the one hand, but uncertainty in the response to treatment measures, compliance and prognosis on the other hand. For complex regional pain, for chronifying syndromes and for the majority of chronic pain states the non-deterministic, non-linear, multidimensional pain concept is proposed. FAU - Worz, R AU - Worz R LA - ger PT - Journal Article TT - Die multidimensionale, nonlineare Schmerzkonzeption. Ein breiter Ansatz fur Erklarung und Verstandnis komplexer Schmerzsyndrome. CY - Germany TA - Fortschr Med Orig JID - 101120496 SB - IM MH - Complex Regional Pain Syndromes/*psychology MH - English Abstract MH - Fibromyalgia/psychology MH - Human MH - Low Back Pain/psychology MH - Nonlinear Dynamics MH - *Pain Measurement MH - Pain Threshold MH - *Sick Role EDAT- 2002/01/16 10:00 MHDA- 2002/02/23 10:01 PST - ppublish SO - Fortschr Med Orig 2001 Nov 29;119(3-4):129-33. 301: Kuusela TA, et al. Nonlinear methods of biosigna...[PMID:11788429]Related Articles, Books, LinkOut UI - 21648191 PMID- 11788429 DA - 20020114 DCOM- 20020214 IS - 0363-6135 VI - 282 IP - 2 DP - 2002 Feb TI - Nonlinear methods of biosignal analysis in assessing terbutaline-induced heart rate and blood pressure changes. PG - H773-83 AB - The aim of this study was to characterize how different nonlinear methods characterize heart rate and blood pressure dynamics in healthy subjects at rest. The randomized, placebo-controlled crossover study with intravenous terbutaline was designed to induce four different stationary states of cardiovascular regulation system. The R-R interval, systolic arterial blood pressure, and heart rate time series were analyzed with a set of methods including approximate entropy, sample entropy, Lempel-Ziv entropy, symbol dynamic entropy, cross-entropy, correlation dimension, fractal dimensions, and stationarity test. Results indicate that R-R interval and systolic arterial pressure subsystems are mutually connected but have different dynamic properties. In the drug-free state the subsystems share many common features. When the strength of the baroreflex feedback loop is modified with terbutaline, R-R interval and systolic blood pressure lose mutual synchrony and drift toward their inherent state of operation. In this state the R-R interval system is rather complex and irregular, but the blood pressure system is much simpler than in the drug-free state. AD - Department of Physics, University of Turku, 20014 Turku, Finland. tom.kuusela@utu.fi FAU - Kuusela, Tom A AU - Kuusela TA FAU - Jartti, Tuomas T AU - Jartti TT FAU - Tahvanainen, Kari U O AU - Tahvanainen KU FAU - Kaila, Timo J AU - Kaila TJ LA - eng PT - Clinical Trial PT - Journal Article PT - Randomized Controlled Trial CY - United States TA - Am J Physiol Heart Circ Physiol JID - 100901228 RN - 0 (Sympathomimetics) RN - 23031-25-6 (Terbutaline) SB - IM MH - Adult MH - Blood Pressure/*drug effects MH - Cross-Over Studies MH - Entropy MH - Heart Rate/*drug effects MH - Human MH - Male MH - *Models, Cardiovascular MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Sympathomimetics/*administration & dosage MH - Terbutaline/*administration & dosage EDAT- 2002/01/15 10:00 MHDA- 2002/02/15 10:01 AID - 10.1152/ajpheart.00559.2001 [doi] PST - ppublish SO - Am J Physiol Heart Circ Physiol 2002 Feb;282(2):H773-83. 302: Russ DW, et al. Metabolic costs of isometric ...[PMID:11788378]Related Articles, Books, LinkOut UI - 21648140 PMID- 11788378 DA - 20020114 DCOM- 20020214 IS - 0193-1849 VI - 282 IP - 2 DP - 2002 Feb TI - Metabolic costs of isometric force generation and maintenance of human skeletal muscle. PG - E448-57 AB - During isometric contractions, no true work is performed, so the force-time integral (FTI) is often used to approximate isometric work. However, the relationship between FTI and metabolic cost is not as linear. We tested the hypothesis that this nonlinearity was due to the cost of attaining a given force being greater than that of maintaining it. The ATP consumed per contraction in the human medial gastrocnemius muscle (n = 6) was determined by use of (31)P-NMR spectroscopy during eight different electrical stimulation protocols. Each protocol consisted of 8 trains of a single frequency (20 or 80 Hz) and duration (300, 600, 1,200, or 1,800 ms) performed under ischemic conditions. The cost of force generation was determined from the ATP turnover during the short-duration trains that did not attain a steady force level. Estimates of the cost of force maintenance at each frequency were determined by subtracting the ATP turnover during the shorter-duration trains from the turnover during the long-duration trains. The force generation phase of an isometric contraction was indeed more metabolically costly than the force maintenance phase during both 20- and 80-Hz stimulation. Thus the mean rate of ATP hydrolysis appeared to decline as contraction duration increased. Interestingly, the metabolic costs of maintaining force during 20-Hz and 80-Hz stimulation were comparable, although different levels of force were produced. AD - Department of Biomechanics and Movement Science, University of Delaware, Newark, Delaware 19716, USA. FAU - Russ, David W AU - Russ DW FAU - Elliott, Mark A AU - Elliott MA FAU - Vandenborne, Krista AU - Vandenborne K FAU - Walter, Glenn A AU - Walter GA FAU - Binder-Macleod, Stuart A AU - Binder-Macleod SA LA - eng ID - HD-33738/HD/NICHD ID - HD-42164/HD/NICHD ID - RR-2305/RR/NCRR PT - Journal Article CY - United States TA - Am J Physiol Endocrinol Metab JID - 100901226 RN - 56-65-5 (Adenosine Triphosphate) SB - IM MH - Adenosine Triphosphate/metabolism MH - Adult MH - *Energy Metabolism MH - Female MH - Human MH - Isometric Contraction/*physiology MH - Male MH - Models, Biological MH - Muscle, Skeletal/metabolism/*physiology MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/01/15 10:00 MHDA- 2002/02/15 10:01 AID - 10.1152/ajpendo.00285.2001 [doi] PST - ppublish SO - Am J Physiol Endocrinol Metab 2002 Feb;282(2):E448-57. 303: Zamuner S, et al. Estimate the time varying bra...[PMID:11786282]Related Articles, Books, LinkOut UI - 21646677 PMID- 11786282 DA - 20020111 DCOM- 20020419 IS - 0969-8051 VI - 29 IP - 1 DP - 2002 Jan TI - Estimate the time varying brain receptor occupancy in PET imaging experiments using non-linear fixed and mixed effect modeling approach. PG - 115-23 AB - Positron-Emission Tomography (PET) is an imaging technology currently used in drug development as a non-invasive measure of drug distribution and interaction with biochemical target system. The level of receptor occupancy achieved by a compound can be estimated by comparing time-activity measurements in an experiment done using tracer alone with the activity measured when the tracer is given following administration of unlabelled compound. The effective use of this surrogate marker as an enabling tool for drug development requires the definition of a model linking the brain receptor occupancy with the fluctuation of plasma concentrations. However, the predictive performance of such a model is strongly related to the precision on the estimate of receptor occupancy evaluated in PET scans collected at different times following drug treatment. Several methods have been proposed for the analysis and the quantification of the ligand-receptor interactions investigated from PET data. The aim of the present study is to evaluate alternative parameter estimation strategies based on the use of non-linear mixed effect models allowing to account for intra and inter-subject variability on the time-activity and for covariates potentially explaining this variability. A comparison of the different modeling approaches is presented using real data. The results of this comparison indicates that the mixed effect approach with a primary model partitioning the variance in term of Inter-Individual Variability (IIV) and Inter-Occasion Variability (IOV) and a second stage model relating the changes on binding potential to the dose of unlabelled drug is definitely the preferred approach. AD - GlaxoSmthKline, Via A. Fleming 4, 37135 Verona, Italy. FAU - Zamuner, Stefano AU - Zamuner S FAU - Gomeni, Roberto AU - Gomeni R FAU - Bye, Alan AU - Bye A LA - eng PT - Journal Article CY - England TA - Nucl Med Biol JID - 9304420 RN - 0 (Antiemetics) RN - 0 (Piperidines) RN - 0 (Tetrazoles) RN - 168266-90-8 (GR 205171) SB - IM MH - Animal MH - Antiemetics/pharmacokinetics MH - Brain/metabolism/*radionuclide imaging MH - Macaca mulatta MH - *Nonlinear Dynamics MH - Piperidines/pharmacokinetics MH - Tetrazoles/pharmacokinetics MH - Time Factors MH - *Tomography, Emission-Computed EDAT- 2002/01/12 10:00 MHDA- 2002/04/20 10:01 AID - S096980510100275X [pii] PST - ppublish SO - Nucl Med Biol 2002 Jan;29(1):115-23. 304: Ansakorpi H, et al. Heart rate dynamics in refrac...[PMID:11784820]Related Articles, Books, LinkOut UI - 21644157 PMID- 11784820 DA - 20020110 DCOM- 20020131 IS - 0022-3050 VI - 72 IP - 1 DP - 2002 Jan TI - Heart rate dynamics in refractory and well controlled temporal lobe epilepsy. PG - 26-30 AB - OBJECTIVES: Disorders of cardiovascular and other autonomic nervous system functions are often found in patients with temporal lobe epilepsy (TLE). Cardiovascular dysregulation in TLE has previously been quantified assessing traditional time and frequency domain measures of heart rate (HR) variability from short term ECG recordings. However, new complexity and fractal measures of HR variability based on non-linear dynamics and fractals ("chaos theory") may disclose certain patterns of HR dynamics that cannot be detected using only conventional measures. METHODS: In addition to the traditional spectral and non-spectral components of HR variability, fractal correlation properties, approximate entropy (ApEn) of RR interval dynamics, and the slope of the power law relation were measured from 24 hour ambulatory ECG recordings to evaluate interictal autonomic cardiovascular regulatory function in 19 patients with refractory TLE, 25 patients with well controlled TLE, and in 34 healthy age and sex matched control subjects. RESULTS: The traditional time and frequency domain measures were lower in patients with TLE than in controls (p<0.05). In addition, the power law slope (p<0.005) and ApEn (p<0.05) were also reduced in TLE patients. Furthermore, ApEn was smaller in patients with refractory TLE than in patients with well-controlled TLE ( p<0.01), whereas the long term fractal correlation value alpha2 was lower in patients with well controlled TLE (p<0.05). An altered HR variation was not associated with any particular AED regimen. CONCLUSIONS: In addition to reduced overall HR variability, the long term fractal organisation and complexity of HR dynamics seem to be altered in TLE. These abnormalities in HR behaviour may partly contribute to the occurrence of adverse cardiovascular events, such as life threatening arrhythmias in patients with TLE. AD - Departments of Neurology and Medicine, Division of Cardiology, University of Oulu, Oulu, Finland. htansakorpi@hotmail.com FAU - Ansakorpi, H AU - Ansakorpi H FAU - Korpelainen, J T AU - Korpelainen JT FAU - Huikuri, H V AU - Huikuri HV FAU - Tolonen, U AU - Tolonen U FAU - Myllyla, V V AU - Myllyla VV FAU - Isojarvi, J I T AU - Isojarvi JI LA - eng PT - Journal Article CY - England TA - J Neurol Neurosurg Psychiatry JID - 2985191R RN - 0 (Anticonvulsants) SB - IM MH - Adult MH - Anticonvulsants/*administration & dosage/adverse effects MH - Autonomic Nervous System/drug effects/physiopathology MH - Death, Sudden/etiology MH - Electrocardiography, Ambulatory MH - Epilepsy, Temporal Lobe/drug therapy/*physiopathology MH - Female MH - Fractals MH - Heart Rate/drug effects/*physiology MH - Human MH - Male MH - Nonlinear Dynamics MH - Risk Factors MH - Signal Processing, Computer-Assisted EDAT- 2002/01/11 10:00 MHDA- 2002/02/01 10:01 PST - ppublish SO - J Neurol Neurosurg Psychiatry 2002 Jan;72(1):26-30. 305: Vaughn J, et al. Measurement of finite-strain ...[PMID:11784547]Related Articles, Books, LinkOut UI - 21644109 PMID- 11784547 DA - 20020110 DCOM- 20020409 IS - 0021-9290 VI - 35 IP - 2 DP - 2002 Feb TI - Measurement of finite-strain dependent permeability of biomembranes. PG - 287-91 AB - A complete understanding of fluid exchanges in tissues and organs requires knowledge of the permeability of their delimiting membranes as a function of the finite strain that they experience. One reason for the current dearth of data in the literature is the need for new theoretically motivated experimental approaches. In this paper, we use a general scaling to identify non-dimensional parameters that are measured easily by combining a simple pressure-driven diffusion chamber with a method to induce equibiaxial and homogeneous finite strains that can be measured via a non-contacting video system. Illustrative results on excised bovine epicardium reveal a nonlinear relationship between a non-dimensional permeability and finite strain up to stretches of 60%. AD - Biomedical Engineering Program, 233 Zachry Engineering Center, Texas A&M University, College Station, TX 77843-3120, USA. FAU - Vaughn, J AU - Vaughn J FAU - Czipura, A AU - Czipura A FAU - Humphrey, J D AU - Humphrey JD LA - eng PT - Journal Article CY - United States TA - J Biomech JID - 0157375 SB - IM MH - Animal MH - Cattle MH - Diffusion Chambers, Culture/instrumentation MH - Equipment Design MH - *Models, Biological MH - Nonlinear Dynamics MH - Pericardium/*metabolism MH - Permeability MH - Stress, Mechanical MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/01/11 10:00 MHDA- 2002/04/18 10:01 AID - S002192900100210X [pii] PST - ppublish SO - J Biomech 2002 Feb;35(2):287-91. 306: Jaasma MJ, et al. Biomechanical effects of intr...[PMID:11784542]Related Articles, Books, LinkOut UI - 21644104 PMID- 11784542 DA - 20020110 DCOM- 20020409 IS - 0021-9290 VI - 35 IP - 2 DP - 2002 Feb TI - Biomechanical effects of intraspecimen variations in tissue modulus for trabecular bone. PG - 237-46 AB - Although recent nanoindentation studies have revealed the existence of substantial variations in tissue modulus within single specimens of trabecular bone, little is known regarding the biomechanical effects of such intraspecimen variations. In this study, high-resolution finite element modeling was used to investigate these effects. With limited literature information on the spatial distribution of intraspecimen variations in tissue modulus, two plausible spatial distributions were evaluated. In addition, three specimens (human femoral neck, human vertebral body, and bovine proximal tibia) were studied to assess the role of trabecular architecture. Results indicated that for all specimen/distribution combinations, the apparent modulus of the whole specimen decreased nonlinearly with increasing coefficient of variation (COV) of tissue modulus within the specimen. Apparent modulus decreased by <4% when tissue modulus COV was increased from 0% to 20% but decreased by 7-24%, depending on the assumed spatial distribution, for an increase in tissue modulus COV from 20% to 50%. For compressive loading to the elastic limit, increasing tissue modulus COV from 20% to 50% caused up to a 28-fold increase in the amount of failed tissue, depending on assumed spatial distribution and trabecular architecture. We conclude that intraspecimen variations in tissue modulus, if large, may have appreciable effects on trabecular apparent modulus and tissue-level failure. Since the observed effects depended on the assumed spatial distribution of the tissue modulus variations, a description of such distributions, particularly as a function of age, disease, and drug treatment, may provide new insight into trabecular bone structure-function relationships. AD - Orthopaedic Biomechanics Laboratory, Department of Mechanical Engineering, University of California, 2166 Etcheverry Hall, Berkeley, CA 94720-1740, USA. mjaasma@biomech1.me.berkeley.edu FAU - Jaasma, Michael J AU - Jaasma MJ FAU - Bayraktar, Harun H AU - Bayraktar HH FAU - Niebur, Glen L AU - Niebur GL FAU - Keaveny, Tony M AU - Keaveny TM LA - eng ID - AR-41481/AR/NIAMS ID - AR-43784/AR/NIAMS PT - Journal Article CY - United States TA - J Biomech JID - 0157375 SB - IM MH - Adult MH - Aged MH - Animal MH - Biomechanics MH - Cattle MH - Elasticity MH - Female MH - Femur/*physiology MH - Finite Element Analysis MH - Human MH - Male MH - *Models, Biological MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. MH - Tensile Strength MH - Thoracic Vertebrae/*physiology MH - Tibia/*physiology MH - Variation (Genetics) MH - Weight-Bearing/physiology EDAT- 2002/01/11 10:00 MHDA- 2002/04/18 10:01 AID - S0021929001001932 [pii] PST - ppublish SO - J Biomech 2002 Feb;35(2):237-46. 307: Garon M, et al. Streaming potentials maps are...[PMID:11784539]Related Articles, Books, LinkOut UI - 21644101 PMID- 11784539 DA - 20020110 DCOM- 20020409 IS - 0021-9290 VI - 35 IP - 2 DP - 2002 Feb TI - Streaming potentials maps are spatially resolved indicators of amplitude, frequency and ionic strength dependant responses of articular cartilage to load. PG - 207-16 AB - Streaming potential distributions were measured on the surface of articular cartilage in uniaxial unconfined compression using a linear array of microelectrodes. Potential profiles were obtained for sinusoidal and ramp/stress-relaxation displacements and exhibited dependencies on radial position, sinusoidal amplitude and frequency, time during stress relaxation, and on ionic strength. The measurements agreed with trends predicted by biphasic and related models. In particular, the absolute potential amplitude was maximal at the disk center, as was the predicted fluid pressure and the potential gradient (the electric field) was seen to be maximal at the disk periphery, as was the predicted fluid velocity. We also observed a similarity between non-linear behavior of streaming potential amplitude and load amplitude with respect to sinusoidal displacement amplitude. Taken together, these results support many of the phenomena concerning relative fluid-solid movement and fluid pressurization predicted by biphasic and related models, and they indicate the general utility of spatially resolved measurements of streaming potentials for the investigation of electromechanical phenomena in tissues. For example, these streaming potential maps could be used to non-destructively diagnose cartilage extracellular matrix composition and function, as well as to quantify spatially and temporally varying physical signals in cartilage that can induce cellular and extracellular biological responses to load. AD - Institute of Biomedical Engineering, Ecole Polytechnique of Montreal, P.O. Box 6079 Station Centre-ville, Montreal, Quebec, Canada H3C 3A7. mike@grbb.polymtl.ca FAU - Garon, M AU - Garon M FAU - Legare, A AU - Legare A FAU - Guardo, R AU - Guardo R FAU - Savard, P AU - Savard P FAU - Buschmann, M D AU - Buschmann MD LA - eng PT - Journal Article CY - United States TA - J Biomech JID - 0157375 RN - 0 (Ions) SB - IM MH - Animal MH - Biomechanics MH - Cartilage, Articular/*physiology MH - Cattle MH - Elasticity MH - Electrophysiology MH - Ions MH - Nonlinear Dynamics MH - Pressure MH - Stress, Mechanical MH - Support, Non-U.S. Gov't MH - Viscosity MH - Weight-Bearing/physiology EDAT- 2002/01/11 10:00 MHDA- 2002/04/18 10:01 AID - S002192900100197X [pii] PST - ppublish SO - J Biomech 2002 Feb;35(2):207-16. 308: Caille N, et al. Contribution of the nucleus t...[PMID:11784536]Related Articles, Books, LinkOut UI - 21644098 PMID- 11784536 DA - 20020110 DCOM- 20020409 IS - 0021-9290 VI - 35 IP - 2 DP - 2002 Feb TI - Contribution of the nucleus to the mechanical properties of endothelial cells. PG - 177-87 AB - The cell nucleus plays a central role in the response of the endothelium to mechanical forces, possibly by deforming during cellular adaptation. The goal of this work was to precisely quantify the mechanical properties of the nucleus. Individual endothelial cells were subjected to compression between glass microplates. This technique allows measurement of the uniaxial force applied to the cell and the resulting deformation. Measurements were made on round and spread cells to rule out the influence of cell morphology on the nucleus mechanical properties. Tests were also carried out with nuclei isolated from cell cultures by a chemical treatment. The non-linear force-deformation curves indicate that round cells deform at lower forces than spread cells and nuclei. Finite-element models were also built with geometries adapted to actual morphometric measurements of round cells, spread cells and isolated nuclei. The nucleus and the cytoplasm were modeled as separate homogeneous hyperelastic materials. The models simulate the compression and yield the force-deformation curve for a given set of elastic moduli. These parameters are varied to obtain a best fit between the theoretical and experimental data. The elastic modulus of the cytoplasm is found to be on the order of 500N/m(2) for spread and round cells. The elastic modulus of the endothelial nucleus is on the order of 5000N/m(2) for nuclei in the cell and on the order of 8000N/m(2) for isolated nuclei. These results represent an unambiguous measurement of the nucleus mechanical properties and will be important in understanding how cells perceive mechanical forces and respond to them. AD - Biomedical Engineering Laboratory, Swiss Federal Institute of Technology, PSE-A, 1015 Lausanne, Switzerland. FAU - Caille, Nathalie AU - Caille N FAU - Thoumine, Olivier AU - Thoumine O FAU - Tardy, Yanik AU - Tardy Y FAU - Meister, Jean-Jacques AU - Meister JJ LA - eng PT - Journal Article CY - United States TA - J Biomech JID - 0157375 SB - IM MH - Animal MH - Biomechanics MH - Cattle MH - Cell Nucleus/*physiology MH - Cells, Cultured MH - Computer Simulation MH - Cytoplasm/physiology MH - Elasticity MH - Endothelium, Vascular/cytology/*physiology MH - *Models, Biological MH - Nonlinear Dynamics MH - Pressure MH - Support, Non-U.S. Gov't EDAT- 2002/01/11 10:00 MHDA- 2002/04/18 10:01 AID - S0021929001002019 [pii] PST - ppublish SO - J Biomech 2002 Feb;35(2):177-87. 309: Piazza SJ, et al. Three-dimensional dynamic sim...[PMID:11783731]Related Articles, Books, LinkOut UI - 21641183 PMID- 11783731 DA - 20020109 DCOM- 20020528 IS - 0148-0731 VI - 123 IP - 6 DP - 2001 Dec TI - Three-dimensional dynamic simulation of total knee replacement motion during a step-up task. PG - 599-606 AB - A three-dimensional dynamic model of the tibiofemoral and patellofemoral articulations was developed to predict the motions of knee implants during a step-up activity. Patterns of muscle activity, initial joint angles and velocities, and kinematics of the hip and tinkle were measured experimentally and used as inputs to the simulation. Prosthetic knee kinematics were determined by integration of dynamic equations of motion subject to forces generated by muscles, ligaments, and contact at both the tibiofemoral and patellofemoral articulations. The modeling of contacts between implants did not rely upon explicit constraint equations; thus, changes in the number of contact points were allowed without modification to the model formulation. The simulation reproduced experimentally measured flexion-extension angle of the knee (within one standard deviation), but translations at the tibiofemoral articulations were larger during the simulated step-up task than those reported for patients with total knee replacements. AD - Center for Locomotion Studies and Department of Kinesiology, Pennsylvania State University, University Park 16802, USA. FAU - Piazza, S J AU - Piazza SJ FAU - Delp, S L AU - Delp SL LA - eng PT - Journal Article CY - United States TA - J Biomech Eng JID - 7909584 SB - IM MH - Adult MH - *Arthroplasty, Replacement, Knee MH - *Computer Simulation MH - Electromyography MH - Human MH - Knee/*physiopathology MH - Ligaments, Articular/physiology MH - *Models, Biological MH - Motion MH - Movement/*physiology MH - Muscle, Skeletal/physiology MH - Nonlinear Dynamics MH - Support, U.S. Gov't, Non-P.H.S. MH - Tendons/physiology EDAT- 2002/01/11 10:00 MHDA- 2002/05/29 10:01 PST - ppublish SO - J Biomech Eng 2001 Dec;123(6):599-606. 310: Sandler R, et al. An analysis of the effect of ...[PMID:11783730]Related Articles, Books, LinkOut UI - 21641182 PMID- 11783730 DA - 20020109 DCOM- 20020528 IS - 0148-0731 VI - 123 IP - 6 DP - 2001 Dec TI - An analysis of the effect of lower extremity strength on impact severity during a backward fall. PG - 590-8 AB - At least 280 000 hip fractures occur annually in the U.S. at an estimated cost of $9 billion. While over 90 percent of these are caused by falls, only about 2 percent of all falls result in hip fracture. Evidence suggests that the most important determinants of hip fracture risk during a fall are the body's impact velocity and configuration. Accordingly, protective responses for reducing impact velocity and the likelihood for direct impact to the hip, strongly influence fracture risk. One method for reducing the body's impact velocity and kinetic energy during a fall is to absorb energy in the lower extremity muscles during descent, as occurs during sitting and squatting. In the present study, we employed a series of in verted pendulum models to determine: (a) the theoretical effect of this mechanism on impact severity during a backward fall, and (b) the effect on impact severity of age-related declines (or exercise-induced enhancements) in lower extremity strength. Compared to the case of a fall with zero energy absorption in the lower extremity joints, best-case falls (which involved 81 percent activation of ankle and hip muscles, but only 23 percent activation of knees muscles) involved 79 percent attenuation (from 352 J to 74 J) in the body's vertical kinetic energy at impact (KEv), and 48 percent attenuation (from 3.22 to 1.68 m/s) in the downward velocity of the pelvis at impact (v(v)). Among the mechanisms responsible for this were: (1) eccentric contraction of lower extremity muscles during descent, which resulted in up to 150 J of energy absorption; (2) impact with the trunk in an upright configuration, which reduced the change in potential energy associated with the fall by 100 J; and (3) knee extension during the final stage of descent, which "transferred" up to 90 J of impact energy into horizontal (as opposed to vertical) kinetic energy. Declines in joint strength reduced the effectiveness of mechanisms (1) and (3), and thereby increased impact severity However, even with reductions of 80 percent in available torques, KEv was attenuated by 50 percent. This indicates the importance of both technique and strength in reducing impact severity. These results provide motivation for attempts to reduce elderly individuals' risk for fall-related injury through the combination of instruction in safe falling techniques and exercises that enhance lower extremity strength. AD - Department of Orthopaedic Surgery, San Francisco General Hospital, CA 94110, USA. FAU - Sandler, R AU - Sandler R FAU - Robinovitch, S AU - Robinovitch S LA - eng ID - R01AR46890/AR/NIAMS ID - R49/CCR019335/CC/CDC PT - Journal Article CY - United States TA - J Biomech Eng JID - 7909584 SB - IM MH - Accidental Falls/prevention & control MH - Aged/*physiology MH - Biomechanics MH - Comparative Study MH - Computer Simulation MH - Female MH - Human MH - Joints/*physiology MH - Leg/*physiology MH - *Models, Biological MH - Muscle Contraction/physiology MH - Muscle Weakness/physiopathology MH - Muscle, Skeletal/*physiology MH - Nonlinear Dynamics MH - Posture/*physiology MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. MH - Torque EDAT- 2002/01/11 10:00 MHDA- 2002/05/29 10:01 PST - ppublish SO - J Biomech Eng 2001 Dec;123(6):590-8. 311: Tang D, et al. Steady flow and wall compress...[PMID:11783725]Related Articles, Books, LinkOut UI - 21641177 PMID- 11783725 DA - 20020109 DCOM- 20020528 IS - 0148-0731 VI - 123 IP - 6 DP - 2001 Dec TI - Steady flow and wall compression in stenotic arteries: a three-dimensional thick-wall model with fluid-wall interactions. PG - 548-57 AB - Severe stenosis may cause critical flow and wall mechanical conditions related to artery fatigue, artery compression, and plaque rupture, which leads directly to heart attack and stroke. The exact mechanism involved is not well understood. In this paper a nonlinear three-dimensional thick-wall model with fluid-wall interactions is introduced to simulate blood flow in carotid arteries with stenosis and to quantify physiological conditions under which wall compression or even collapse may occur. The mechanical properties of the tube wall were selected to match a thick-wall stenosis model made of PVA hydrogel. The experimentally measured nonlinear stress-strain relationship is implemented in the computational model using an incremental linear elasticity approach. The Navier-Stokes equations are used for the fluid model. An incremental boundary iteration method is used to handle the fluid-wall interactions. Our results indicate that severe stenosis causes considerable compressive stress in the tube wall and critical flow conditions such as negative pressure, high shear stress, and flow separation which may be related to artery compression, plaque cap rupture, platelet activation, and thrombus formation. The stress distribution has a very localized pattern and both maximum tensile stress (five times higher than normal average stress) and maximum compressive stress occur inside the stenotic section. Wall deformation, flow rates, and true severities of the stenosis under different pressure conditions are calculated and compared with experimental measurements and reasonable agreement is found. AD - Mathematical Sciences Department, Worcester Polytechnic Institute, MA 01609, USA. FAU - Tang, D AU - Tang D FAU - Yang, C AU - Yang C FAU - Kobayashi, S AU - Kobayashi S FAU - Ku, D N AU - Ku DN LA - eng PT - Journal Article CY - United States TA - J Biomech Eng JID - 7909584 SB - IM MH - Aortic Valve Stenosis/*physiopathology MH - Carotid Arteries/*physiopathology MH - Comparative Study MH - Finite Element Analysis MH - Hemodynamics/physiology MH - Human MH - *Models, Cardiovascular MH - Nonlinear Dynamics MH - Numerical Analysis, Computer-Assisted MH - Pressure MH - Reproducibility of Results MH - Stress, Mechanical MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/01/11 10:00 MHDA- 2002/05/29 10:01 PST - ppublish SO - J Biomech Eng 2001 Dec;123(6):548-57. 312: Carrasco S, et al. Correlation among Poincare pl...[PMID:11780765]Related Articles, Books, LinkOut UI - 21639126 PMID- 11780765 DA - 20020108 DCOM- 20020528 IS - 0309-1902 VI - 25 IP - 6 DP - 2001 Nov-Dec TI - Correlation among Poincare plot indexes and time and frequency domain measures of heart rate variability. PG - 240-8 AB - PRIMARY OBJECTIVE: In order to corroborate the rported performance advantage of Poincare plot indexes as autonomic activity markers, the correlation among these indexes and those computed from the time and frequency domains were obtained. METHODS AND PROCEDURES: Starting from the RR series derived from the ECG of 21 healthy volunteers during five manoeuvres, longitudinal (L), transverse (T) axis, and autocorrelation (r) from Poincare plots, rMSSD and standard deviation (SD) in the temporal domain, and frequency domain indexes were computed. MAIN OUTCOMES AND RESULTS: Poincare plot indexes were correlated in a better way with the time indexes, rather than the spectral measures. A strong correlation (0.997) between L and SD was observed, while an underlying mathematical relationship was established for T vs rMSSD. CONCLUSIONS: Poincare plot indexes may be considered as equivalent or surrogates of the temporal ones, and they do not have a better performance as autonomic markers. AD - Departmento de Canarias de la Salud, Universidad Autonoma Metropolitana Iztapalapa, Mexico, DF. scas@xanum.uam.mx FAU - Carrasco, S AU - Carrasco S FAU - Gaitan, M J AU - Gaitan MJ FAU - Gonzalez, R AU - Gonzalez R FAU - Yanez, O AU - Yanez O LA - eng PT - Journal Article CY - England TA - J Med Eng Technol JID - 7702125 SB - IM MH - Adult MH - Cluster Analysis MH - Comparative Study MH - Electrocardiography MH - Exercise/physiology MH - Female MH - Heart Rate/*physiology MH - Human MH - Male MH - *Models, Statistical MH - Nonlinear Dynamics MH - Reference Values MH - Rest/physiology MH - Signal Processing, Computer-Assisted EDAT- 2002/01/10 10:00 MHDA- 2002/05/29 10:01 PST - ppublish SO - J Med Eng Technol 2001 Nov-Dec;25(6):240-8. 313: Gu X, et al. Testing the parsimony test of...[PMID:11779825]Related Articles, Books, LinkOut UI - 21638306 PMID- 11779825 DA - 20020107 DCOM- 20020213 LR - 20020311 IS - 1088-9051 VI - 12 IP - 1 DP - 2002 Jan TI - Testing the parsimony test of genome duplications: a counterexample. PG - 1-2 AD - Department of Zoology, Iowa State University, Ames, Iowa 50011, USA. xgu@iastate.edu FAU - Gu, Xun AU - Gu X FAU - Huang, Wei AU - Huang W LA - eng ID - R01 GM62118/GM/NIGMS PT - Comment PT - Journal Article CY - United States TA - Genome Res JID - 9518021 SB - IM CON - Genome Res. 2001 May;11(5):771-80. PMID: 11337473 MH - Arabidopsis/*genetics MH - *Gene Duplication MH - *Genome, Plant MH - Models, Genetic MH - Models, Statistical MH - Nonlinear Dynamics MH - Phylogeny MH - Stochastic Processes MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/01/10 10:00 MHDA- 2002/02/14 10:01 AID - 10.1101/gr.214402 [doi] PST - ppublish SO - Genome Res 2002 Jan;12(1):1-2. 314: Hotchkiss JR Jr, et al. Oscillations and noise: inher...[PMID:11779729]Related Articles, Books, LinkOut UI - 21637845 PMID- 11779729 DA - 20020107 DCOM- 20020213 IS - 1073-449X VI - 165 IP - 1 DP - 2002 Jan 1 TI - Oscillations and noise: inherent instability of pressure support ventilation? PG - 47-53 AB - Pressure support ventilation (PSV) is almost universally employed in the management of actively breathing ventilated patients with acute respiratory failure. In this partial support mode of ventilation, a fixed pressure is applied to the airway opening, and flow delivery is monitored by the ventilator. Inspiration is terminated when measured inspiratory flow falls below a set fraction of the peak flow rate (flow cutoff); the ventilator then cycles to a lower pressure and expiration commences. We used linear and nonlinear mathematical models to investigate the dynamic behavior of pressure support ventilation and confirmed the predicted behavior using a test lung. Our mathematical and laboratory analyses indicate that pressure support ventilation in the setting of airflow obstruction can be accompanied by marked variations in tidal volume and end-expiratory alveolar pressure, even when subject effort is unvarying. Unstable behavior was observed in the simplest plausible linear mathematical model and is an inherent consequence of the underlying dynamics of this mode of ventilation. The mechanism underlying the observed instability is "feed forward" behavior mediated by oscillatory elevation in end-expiratory pressure. In both mathematical and mechanical models, unstable behavior occurred at impedance values and ventilator settings that are clinically realistic. AD - Section of Pulmonary and Critical Care and Section of Surgery, Regions Hospital and University of Minnesota, St. Paul, Minnesota 55101, USA. John.R.Hotchkiss@HealthPartners.com FAU - Hotchkiss, John R Jr AU - Hotchkiss JR Jr FAU - Adams, Alexander B AU - Adams AB FAU - Stone, Mary K AU - Stone MK FAU - Dries, David J AU - Dries DJ FAU - Marini, John J AU - Marini JJ FAU - Crooke, Philip S AU - Crooke PS LA - eng ID - SCOR 50152/SC/NCI PT - Journal Article PT - Validation Studies CY - United States TA - Am J Respir Crit Care Med JID - 9421642 SB - AIM SB - IM MH - Adult MH - Airway Resistance/*physiology MH - *Artifacts MH - Bias (Epidemiology) MH - Comparative Study MH - Feedback MH - Human MH - *Linear Models MH - *Models, Biological MH - *Nonlinear Dynamics MH - Oscillometry MH - Peak Expiratory Flow Rate MH - *Positive-Pressure Respiration/adverse effects/instrumentation/methods/standards MH - Positive-Pressure Respiration, Intrinsic/etiology/physiopathology MH - Predictive Value of Tests MH - Respiratory Insufficiency/*physiopathology/therapy MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. MH - Systems Theory MH - Tidal Volume EDAT- 2002/01/10 10:00 MHDA- 2002/02/14 10:01 PST - ppublish SO - Am J Respir Crit Care Med 2002 Jan 1;165(1):47-53. 315: Neubert MG, et al. Transient dynamics and patter...[PMID:11779624]Related Articles, Books, LinkOut UI - 21638629 PMID- 11779624 DA - 20020107 DCOM- 20020313 IS - 0025-5564 VI - 175 IP - 1 DP - 2002 Jan TI - Transient dynamics and pattern formation: reactivity is necessary for Turing instabilities. PG - 1-11 AB - The theory of spatial pattern formation via Turing bifurcations - wherein an equilibrium of a nonlinear system is asymptotically stable in the absence of dispersal but unstable in the presence of dispersal - plays an important role in biology, chemistry and physics. It is an asymptotic theory, concerned with the long-term behavior of perturbations. In contrast, the concept of reactivity describes the short-term transient behavior of perturbations to an asymptotically stable equilibrium. In this article we show that there is a connection between these two seemingly disparate concepts. In particular, we show that reactivity is necessary for Turing instability in multispecies systems of reaction-diffusion equations, integrodifference equations, coupled map lattices, and systems of ordinary differential equations. AD - Biology Department, MS #34, Woods Hole Oceanographic Institution, Woods Hole, MA 02543-1049, USA. mneubert@whoi.edu FAU - Neubert, Michael G AU - Neubert MG FAU - Caswell, Hal AU - Caswell H FAU - Murray, J D AU - Murray JD LA - eng PT - Journal Article CY - United States TA - Math Biosci JID - 0103146 SB - IM MH - Animal MH - *Ecology MH - *Models, Biological MH - Nonlinear Dynamics MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/01/10 10:00 MHDA- 2002/03/14 10:01 AID - S0025556401000876 [pii] PST - ppublish SO - Math Biosci 2002 Jan;175(1):1-11. 316: Marino AA, et al. Nonlinear determinism in the ...[PMID:11777283]Related Articles, Books, LinkOut UI - 21633022 PMID- 11777283 DA - 20020104 DCOM- 20020701 IS - 0882-0139 VI - 30 IP - 4 DP - 2001 Nov TI - Nonlinear determinism in the immune system. In vivo influence of electromagnetic fields on different functions of murine lymphocyte subpopulations. PG - 313-34 AB - Animal studies of the effects of low-frequency electromagnetic fields (EMFs) on the immune system appear inconsistent, and recent evidence indicates that inconspicuous experimental problems are not responsible. We hypothesized that the inconsistencies resulted from use of linear methods and models to study inherently nonlinear input-output relationships. Using a novel analytical method, we found that exposure of mice to 5 G, 60 Hz, for 1-105 days in 6 independent experiments consistently affected a broad panel of immune variables when and only when the reaction of the immune system was modeled to allow the possibility of nonlinearity in the relationship between the field and the immune variables. It was possible to mimic the pattern observed in the immune data by sampling from a known chaotic system, suggesting the possibility that the observed pattern was the result of intrinsic nonlinear regulatory mechanisms in the immune system. Overall, the results suggested that lymphoid sub-populations were vulnerable to the physiological consequences of EMF transduction, that it may never be possible to predict specific changes in particular immune-system variables, and that the underlying behavior of the immune system (that which occurs in the absence of specific inputs) may be governed by laws that manifest extreme sensitivity to prior states. AD - Department of Orthopaedic Surgery, LSU Health Sciences Center, Shreveport, Louisiana 71130-3932, USA. amarino@lsuhsc.edu FAU - Marino, A A AU - Marino AA FAU - Wolcott, R M AU - Wolcott RM FAU - Chervenak, R AU - Chervenak R FAU - Jourd'heuil, F AU - Jourd'heuil F FAU - Nilsen, E AU - Nilsen E FAU - Frilot, C 2nd AU - Frilot C 2nd LA - eng PT - Journal Article CY - United States TA - Immunol Invest JID - 8504629 SB - IM MH - Animal MH - Bone Marrow Cells/*cytology MH - Electromagnetic Fields/*adverse effects MH - Female MH - Immune System MH - Lymphocyte Subsets MH - Mice MH - Mice, Inbred C57BL MH - Nonlinear Dynamics MH - Spleen/*cytology MH - Support, U.S. Gov't, P.H.S. MH - Thymus Gland/*cytology EDAT- 2002/01/05 10:00 MHDA- 2002/07/02 10:01 PST - ppublish SO - Immunol Invest 2001 Nov;30(4):313-34. 317: Parmanto B, et al. Recurrent neural networks for...[PMID:11776736]Related Articles, Books, LinkOut UI - 21633296 PMID- 11776736 DA - 20020104 DCOM- 20020128 IS - 0026-1270 VI - 40 IP - 5 DP - 2001 TI - Recurrent neural networks for predicting outcomes after liver transplantation: representing temporal sequence of clinical observations. PG - 386-91 AB - OBJECTIVES: This paper investigates a version of recurrent neural network with the backpropagation through time (BPTT) algorithm for predicting liver transplant graft failure based on a time series sequence of clinical observations. The objective is to improve upon the current approaches to liver transplant outcome prediction by developing a more complete model that takes into account not only the preoperative risk assessment, but also the early postoperative history. METHODS: A 6-fold cross-validation procedure was used to measure the performance of the networks. The data set was divided into a learning set and a test set by maintaining the same proportion of positive and negative cases in the original set. The effects of network complexity on overfitting were investigated by constructing two types of networks with different numbers of hidden units. For each type of network, 10 individual networks were trained on the learning set and used to form a committee. The performance of the networks was measured exhaustively with respect to both the entire training and test sets. RESULTS: The networks were capable of learning the time series problem and achieved good performances of 90% correct classification on the learning set and 78% on the test set. The prediction accuracy increases as more information becomes progressively available after the operation with the daily improvement of 10% on the learning set and 5% on the test set. CONCLUSIONS: Recurrent neural networks trained with BPTT algorithm are capable of learning to represent temporal behavior of the time series prediction task. This model is an improvement upon the current model that does not take into account postoperative temporal information. AD - Department of Health Information Management & Center for Biomedical Informatics, University of Pittsburgh, USA. parmanto+@pitt.edu FAU - Parmanto, B AU - Parmanto B FAU - Doyle, H R AU - Doyle HR LA - eng PT - Journal Article CY - Germany TA - Methods Inf Med JID - 0210453 SB - IM MH - Adult MH - Algorithms MH - *Decision Support Systems, Clinical MH - Female MH - Graft Survival MH - Human MH - Liver Transplantation/*adverse effects/mortality MH - Male MH - Monte Carlo Method MH - *Neural Networks (Computer) MH - Nonlinear Dynamics MH - Pennsylvania/epidemiology MH - Postoperative Complications/epidemiology MH - Sensitivity and Specificity MH - *Treatment Failure MH - Treatment Outcome EDAT- 2002/01/05 10:00 MHDA- 2002/01/29 10:01 PST - ppublish SO - Methods Inf Med 2001;40(5):386-91. 318: Tirsch WS, et al. [Nonlinear analysis of heart ...[PMID:11776214]Related Articles, Books, LinkOut UI - 21632669 PMID- 11776214 DA - 20020103 DCOM- 20020424 IS - 0013-5585 VI - 43 IP - 3 DP - 1998 TI - [Nonlinear analysis of heart rate for objective assessment of cardiac autonomic dysfunction after craniocerebral trauma] PG - 145-8 AD - GSF-Institut fur Medizinische Informatik und Systemforschung, 85764 Neuherberg. FAU - Tirsch, W S AU - Tirsch WS FAU - Keidel, M AU - Keidel M FAU - Siebert, M AU - Siebert M FAU - Perz, S AU - Perz S FAU - Doktor, L AU - Doktor L FAU - Diener, H C AU - Diener HC LA - ger PT - Journal Article TT - Nichtlineare Analyse der Herzfrequenz zur Objektivierung kardioautonomer Dysfunktion nach Schadel-Hirn-Trauma. CY - Germany TA - Biomed Tech (Berl) JID - 1262533 SB - IM MH - Adult MH - Autonomic Nervous System Diseases/*diagnosis/physiopathology MH - Brain Concussion/*diagnosis/physiopathology MH - *Electrocardiography MH - Fourier Analysis MH - Fractals MH - Heart/*innervation MH - Heart Rate/*physiology MH - Human MH - Neurasthenia/diagnosis/physiopathology MH - *Nonlinear Dynamics MH - Prospective Studies MH - *Signal Processing, Computer-Assisted MH - Support, Non-U.S. Gov't EDAT- 2002/01/05 10:00 MHDA- 2002/04/25 10:01 PST - ppublish SO - Biomed Tech (Berl) 1998;43(3):145-8. 319: Halberg FE, et al. Chronomics....[PMID:11774864]Related Articles, Books, LinkOut UI - 21630629 PMID- 11774864 DA - 20011231 DCOM- 20020612 IS - 0753-3322 VI - 55 Suppl 1 DP - 2001 TI - Chronomics. PG - 153s-190s AB - Several international meetings have revealed an accumulating body of reference values for well-established about-daily and about-yearly rhythms of photic origin and evidence also for about-7-day, -27-day, -half-yearly, -10.5- and -21-yearly, and even -50-yearly rhythmicities in us as well as around us, as invisible non-photic heliogeophysical signatures possibly built into individuals and/or populations, complementing the biological year and day. In time series (biological or other) that are dense and sufficiently long, the characteristics of rhythms, chaos (deterministic and other) and trends can all be quantified as elements of structures called chronomes. Chronobiological methodology assesses uncertainties in comparisons of endpoints in all elements of chronomes, before and after: 1) changes in lifestyle, such as meal quality, quantity, timing and salting of the food; 2) preventive non-drug interventions to limit the risk of vascular disease; or 3) drug treatments for high-risk subjects as well as for those with actual vascular disease, all on a practicable, individualized and also a general population basis. A collateral hierarchy characterizes molecular to psychosocial aspects of living beings that are exposed to their socio-ecological environs and thus are synchronizable and/or otherwise manipulable by society, meals, lighting, heating, and non-photic, non-thermic environmental variations that become predictable to the extent that they appear to constitute cycles, yet adhere only to a statistical, rather than a deterministic causality. With this qualification, chronome mapping with outcomes could eventually serve an individualized optimization of lifestyle, for chronoprevention and chronotherapy as well as for inquiries into the evolution and future of life, a budding chronoastrobiology, in keeping with the original title of the conference. AD - Halberg Chronobiology Center University of Minnesota, Minneapolis, USA. FAU - Halberg, F E AU - Halberg FE FAU - Cornelissen, G AU - Cornelissen G FAU - Otsuka, K AU - Otsuka K FAU - Schwartzkopff, O AU - Schwartzkopff O FAU - Halberg, J AU - Halberg J FAU - Bakken, E E AU - Bakken EE LA - eng PT - Journal Article PT - Review PT - Review, Academic CY - France TA - Biomed Pharmacother JID - 8213295 SB - IM MH - Animal MH - Chronobiology/*physiology MH - Earth (Planet) MH - Electromagnetic Fields MH - Human MH - Nonlinear Dynamics MH - *Periodicity MH - Risk Assessment MH - Solar System RF - 159 EDAT- 2002/01/05 10:00 MHDA- 2002/06/13 10:01 PST - ppublish SO - Biomed Pharmacother 2001;55 Suppl 1:153s-190s. 320: Yambe T, et al. Fluctuations of Emax of the l...[PMID:11774863]Related Articles, Books, LinkOut UI - 21630628 PMID- 11774863 DA - 20011231 DCOM- 20020612 IS - 0753-3322 VI - 55 Suppl 1 DP - 2001 TI - Fluctuations of Emax of the left ventricle: effect of atrial natriuretic polypeptide. PG - 147s-152s AB - Recently the circadian rhythm of fluctuations in heart rate variability (HRV) has gained increasing attention, and the use of appropriate treatment corresponding to the circadian rhythm has become an important issue. However, the question has been raised as to whether the rhythm of fluctuation is only limited to HRV, and if a rhythm is also present in the contraction of the heart. The mathematical technique of electrical circuit simulation of the cardiovascular system was used to observe the Emax rhythm. In this study, the therapeutic effect of various drugs, including atrial natriuretic polypeptide (ANP), was confirmed. The effect of inotropic drugs including ANP on Emax was observed, and the results based on an old and a new method of determining Emax . were examined. Furthermore, the chaos analysis of Emax was also made. The time series of Emax showed an increased complexity due to the administration of ANP. In conclusion, it might be important to consider not only the fluctuation of HRV, but also an analysis of the fluctuation in the contraction of the heart. AD - Department of Medical Engineering and Cardiology, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan. yambe@idac.tohoku.ac.jp FAU - Yambe, T AU - Yambe T FAU - Yoshizawa, M AU - Yoshizawa M FAU - Taira, R AU - Taira R FAU - Tanaka, A AU - Tanaka A FAU - Iguchi, A AU - Iguchi A FAU - Tabayashi, K AU - Tabayashi K FAU - Tobita, S AU - Tobita S FAU - Nitta, S AU - Nitta S LA - eng PT - Journal Article CY - France TA - Biomed Pharmacother JID - 8213295 RN - 0 (Adrenergic beta-Antagonists) RN - 525-66-6 (Propranolol) RN - 85637-73-6 (Atrial Natriuretic Factor) SB - IM MH - Adrenergic beta-Antagonists/pharmacology MH - Animal MH - Atrial Natriuretic Factor/*physiology MH - Circadian Rhythm/*physiology MH - Electrophysiology MH - Goats/physiology MH - Heart Rate/drug effects MH - Hemodynamics/physiology MH - Nonlinear Dynamics MH - Propranolol/pharmacology MH - Support, Non-U.S. Gov't MH - Ventricular Function, Left/*physiology EDAT- 2002/01/05 10:00 MHDA- 2002/06/13 10:01 PST - ppublish SO - Biomed Pharmacother 2001;55 Suppl 1:147s-152s. 321: Chen Y. A remark on 'On stability of ...[PMID:11771724]Related Articles, Books, LinkOut UI - 21627544 PMID- 11771724 DA - 20011228 DCOM- 20020528 IS - 0893-6080 VI - 14 IP - 10 DP - 2001 Dec TI - A remark on 'On stability of nonlinear continuous-time neural networks with delays'. PG - 1463 FAU - Chen, Y AU - Chen Y LA - eng PT - Letter CY - United States TA - Neural Netw JID - 8805018 SB - IM MH - *Neural Networks (Computer) MH - *Nonlinear Dynamics EDAT- 2002/01/05 10:00 MHDA- 2002/05/29 10:01 PST - ppublish SO - Neural Netw 2001 Dec;14(10):1463. 322: Krakovska A. [The chaos theory and physiol...[PMID:11770386]Related Articles, Books UI - 21627217 PMID- 11770386 DA - 20011227 DCOM- 20020122 IS - 1210-6313 VI - 50 IP - 4 DP - 2001 Nov TI - [The chaos theory and physiology of the heart] PG - 192-200 AB - Chaos theory was received with the great enthusiasm. It has provided a new, attractive approach to irregular, nonperiodic phenomena: apparently stochastic behaviour might be explained by a few nonlinear differential equations. During the last years, it became clear that chaos in the exact sense is hardly to be proved in real systems, such as the cardiac dynamics. Despite this fact, new methods, originally developed for chaotic signals, are successfully applied to fetal ECG extraction, noise filtering and heart dynamics modelling. AD - Ustav merania Slovenskej akademie vied, Bratislava. umerkrak@savba.sk FAU - Krakovska, A AU - Krakovska A LA - slo PT - Journal Article TT - Teoria chaosu a fyziologia srdca. CY - Czech Republic TA - Cesk Fysiol JID - 2984710R SB - IM MH - Electrocardiography MH - English Abstract MH - Fractals MH - Heart/*physiology MH - Heart Rate MH - Human MH - Models, Theoretical MH - *Nonlinear Dynamics EDAT- 2002/01/05 10:00 MHDA- 2002/01/23 10:01 PST - ppublish SO - Cesk Fysiol 2001 Nov;50(4):192-200. 323: Mohtashemi M, et al. Transient dynamics and early ...[PMID:11767206]Related Articles, Books, LinkOut UI - 21616177 PMID- 11767206 DA - 20011219 DCOM- 20020506 IS - 0303-6812 VI - 43 IP - 5 DP - 2001 Nov TI - Transient dynamics and early diagnostics in infectious disease. PG - 446-70 AB - To date, mathematical models of the dynamics of infectious disease have consistently focused on understanding the long-term behavior of the interacting components, where the steady state solutions are paramount. However for most acute infections, the longterm behavior of the pathogen population is of little importance to the host and population health. We introduce the notion of transient pathology, where the short-term dynamics of interaction between the immune system and pathogens is the principal focus. We identify the amplifying effect of the absence of a fully operative immune system on the pathogenesis of the initial inoculum, and its implication for the acute severity of the infection. We then formalize the underlying dynamics, and derive two measures of transient pathogenicity: the peak of infection (maximum pathogenic load) and the time to peak of infection, both crucial to understanding the early dynamics of infection and its consequences for early intervention. AD - Department of Computer Science, Massachusetts Institute of Technology, 545 Technology Square, Room 421, Cambridge, MA 02139, USA. mojdeh@medg.lcs.mit.edu FAU - Mohtashemi, M AU - Mohtashemi M FAU - Levins, R AU - Levins R LA - eng PT - Journal Article CY - Germany TA - J Math Biol JID - 7502105 SB - IM MH - Communicable Diseases/*immunology/*microbiology MH - Human MH - *Models, Immunological MH - Nonlinear Dynamics MH - Numerical Analysis, Computer-Assisted MH - Time Factors EDAT- 2002/01/05 10:00 MHDA- 2002/05/07 10:01 PST - ppublish SO - J Math Biol 2001 Nov;43(5):446-70. 324: Provenzano P, et al. Nonlinear ligament viscoelast...[PMID:11764321]Related Articles, Books, LinkOut UI - 21606894 PMID- 11764321 DA - 20011214 DCOM- 20020509 IS - 0090-6964 VI - 29 IP - 10 DP - 2001 Oct TI - Nonlinear ligament viscoelasticity. PG - 908-14 AB - Ligaments display time-dependent behavior, characteristic of a viscoelastic solid, and are nonlinear in their stress-strain response. Recent experiments (25) reveal that stress relaxation proceeds more rapidly than creep in medial collateral ligaments, a fact not explained by linear viscoelastic theory but shown by Lakes and Vanderby (17) to be consistent with nonlinear theory. This study tests the following hypothesis: nonlinear viscoelasticity of ligament requires a description more general than the separable quasilinear viscoelasticity (QLV) formulation commonly used. The experimental test for this hypothesis involves performing both creep and relaxation studies at various loads and deformations below the damage threshold. Freshly harvested, rat medial collateral ligaments (MCLs) were used as a model. Results consistently show a nonlinear behavior in which the rate of creep is dependent upon stress level and the rate of relaxation is dependent upon strain level. Furthermore, relaxation proceeds faster than creep; consistent with the experimental observations of Thornton et al. (25) The above results from rat MCLs are not consistent with a separable QLV theory. Inclusion of these nonlinearities would require a more general formulation. AD - Department of Biomedical Engineering, University of Wisconsin-Madison, 53792-3228, USA. FAU - Provenzano, P AU - Provenzano P FAU - Lakes, R AU - Lakes R FAU - Keenan, T AU - Keenan T FAU - Vanderby, R Jr AU - Vanderby R Jr LA - eng PT - Journal Article CY - United States TA - Ann Biomed Eng JID - 0361512 SB - IM MH - Animal MH - Elasticity MH - In Vitro MH - Ligaments/*physiology MH - Male MH - Medial Collateral Ligament, Knee/physiology MH - *Models, Biological MH - Nonlinear Dynamics MH - Rats MH - Rats, Sprague-Dawley MH - Stress, Mechanical MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Time Factors EDAT- 2002/01/05 10:00 MHDA- 2002/05/10 10:01 PST - ppublish SO - Ann Biomed Eng 2001 Oct;29(10):908-14. 325: Dorval AD, et al. Real-Time linux dynamic clamp...[PMID:11764320]Related Articles, Books, LinkOut UI - 21606893 PMID- 11764320 DA - 20011214 DCOM- 20020509 IS - 0090-6964 VI - 29 IP - 10 DP - 2001 Oct TI - Real-Time linux dynamic clamp: a fast and flexible way to construct virtual ion channels in living cells. PG - 897-907 AB - We describe a system for real-time control of biological and other experiments. This device, based around the Real-Time Linux operating system, was tested specifically in the context of dynamic clamping, a demanding real-time task in which a computational system mimics the effects of nonlinear membrane conductances in living cells. The system is fast enough to represent dozens of nonlinear conductances in real time at clock rates well above 10 kHz. Conductances can be represented in deterministic form, or more accurately as discrete collections of stochastically gating ion channels. Tests were performed using a variety of complex models of nonlinear membrane mechanisms in excitable cells, including simulations of spatially extended excitable structures, and multiple interacting cells. Only in extreme cases does the computational load interfere with high-speed "hard" real-time processing (i.e., real-time processing that never falters). Freely available on the worldwide web, this experimental control system combines good performance. immense flexibility, low cost, and reasonable ease of use. It is easily adapted to any task involving real-time control, and excels in particular for applications requiring complex control algorithms that must operate at speeds over 1 kHz. AD - Department of Biomedical Engineering, Center for BioDynamics, Boston University, MA 02215, USA. FAU - Dorval, A D AU - Dorval AD FAU - Christini, D J AU - Christini DJ FAU - White, J A AU - White JA LA - eng PT - Journal Article CY - United States TA - Ann Biomed Eng JID - 0361512 RN - 0 (Ion Channels) SB - IM MH - Computer Simulation MH - *Computer Systems MH - Electric Conductivity MH - Feedback MH - Ion Channels/*physiology MH - Membrane Potentials/*physiology MH - *Models, Neurological MH - Nerve Net/physiology MH - Neurons/physiology MH - Nonlinear Dynamics MH - Patch-Clamp Techniques/*instrumentation/*methods MH - Stochastic Processes MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2002/01/05 10:00 MHDA- 2002/05/10 10:01 PST - ppublish SO - Ann Biomed Eng 2001 Oct;29(10):897-907. 326: Sun M, et al. Extraction and analysis of ea...[PMID:11764318]Related Articles, Books, LinkOut UI - 21606891 PMID- 11764318 DA - 20011214 DCOM- 20020509 IS - 0090-6964 VI - 29 IP - 10 DP - 2001 Oct TI - Extraction and analysis of early ictal activity in subdural electroencephalogram. PG - 878-86 AB - Subdural electroencephalograms (SEEGs) are of great value in localizing primary epileptogenic regions in patients undergoing evaluation for focal resective epilepsy surgery. The data segments which contain a transition from interictal to ictal activity carry the most critical diagnostic information. Computer signal extraction within this transition period represents a challenging signal processing problem. In this work a two-step method is presented to extract early ictal activity. In the first step we employ a nonlinear signal decomposition technique in the wavelet domain to separate SEEG data into ictal and background components. In the second step we use time-frequency analysis and a novel integration algorithm to extract the desired information. Our experiments on clinically recorded data indicate that this method is highly effective allowing us to reveal important hidden features in the data which could not otherwise be observable. AD - Department of Neurosurgery, University of Pittsburgh, PA 15260, USA. mrsun@meuronet.pitt.edu FAU - Sun, M AU - Sun M FAU - Scheuer, M L AU - Scheuer ML FAU - Sclabassi, R J AU - Sclabassi RJ LA - eng ID - NS38494/NS/NINDS ID - NS39047/NS/NINDS PT - Journal Article CY - United States TA - Ann Biomed Eng JID - 0361512 SB - IM MH - Adult MH - Child, Preschool MH - Electroencephalography/*methods MH - Female MH - Human MH - Male MH - Nonlinear Dynamics MH - Seizures/*diagnosis MH - *Signal Processing, Computer-Assisted MH - Spectrum Analysis MH - Subdural Space/physiology MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. EDAT- 2002/01/05 10:00 MHDA- 2002/05/10 10:01 PST - ppublish SO - Ann Biomed Eng 2001 Oct;29(10):878-86. 327: Wang R. A hybrid learning network for...[PMID:11762901]Related Articles, Books, LinkOut UI - 21597901 PMID- 11762901 DA - 20011212 DCOM- 20020509 IS - 0954-898X VI - 12 IP - 4 DP - 2001 Nov TI - A hybrid learning network for shift, orientation, and scaling invariant pattern recognition. PG - 493-512 AB - A three-layer neural network is presented as a generic approach for visual pattern recognition invariant with respect to the geometric appearance such as translation, orientation and scale of the patterns. The invariant recognition is achieved by representing the geometric variations internally in the network by nodes in the input and middle layers, which are laterally connected and trained by a hybrid algorithm combining both competitive and Hebbian learning. As the result of the hybrid learning, each pattern will be represented by a particular subset of middle-layer nodes all specialized to respond to the same pattern but with different geometric appearances. The nodes in the output layer are then trained by competitive learning to recognize the different pattern internally represented by the middle-layer nodes, independent of their location, orientation and size. The proposed algorithm is generic and robust and can be applied to various practical recognition problems. Moreover, the network is relatively simple and biologically plausible and can serve as a computational model to account for the invariant object recognition in the biological visual system. AD - Engineering Department, Harvey Mudd College, Claremont, CA 91711, USA. ruye_wang@hmc.edu FAU - Wang, R AU - Wang R LA - eng PT - Journal Article CY - England TA - Network JID - 9431867 SB - IM MH - Algorithms MH - *Artificial Intelligence MH - Computer Simulation MH - Feedback/physiology MH - Learning/physiology MH - *Models, Neurological MH - *Neural Networks (Computer) MH - Nonlinear Dynamics MH - Pattern Recognition MH - Pattern Recognition, Visual/physiology EDAT- 2002/01/05 10:00 MHDA- 2002/05/10 10:01 PST - ppublish SO - Network 2001 Nov;12(4):493-512. 328: Zhang XS, et al. EEG complexity as a measure o...[PMID:11759923]Related Articles, Books, LinkOut UI - 21595368 PMID- 11759923 DA - 20011210 DCOM- 20020103 IS - 0018-9294 VI - 48 IP - 12 DP - 2001 Dec TI - EEG complexity as a measure of depth of anesthesia for patients. PG - 1424-33 AB - A new approach for quantifying the relationship between brain activity patterns and depth of anesthesia (DOA) is presented by analyzing the spatio-temporal patterns in the electroencephalogram (EEG) using Lempel-Ziv complexity analysis. Twenty-seven patients undergoing vascular surgery were studied under general anesthesia with sevoflurane, isoflurane, propofol, or desflurane. The EEG was recorded continuously during the procedure and patients' anesthesia states were assessed according to the responsiveness component of the observer's assessment of alertness/sedation (OAA/S) score. An OAA/S score of zero or one was considered asleep and two or greater was considered awake. Complexity of the EEG was quantitatively estimated by the measure C(n), whose performance in discriminating awake and asleep states was analyzed by statistics for different anesthetic techniques and different patient populations. Compared with other measures, such as approximate entropy, spectral entropy, and median frequency, C(n) not only demonstrates better performance (93% accuracy) across all of the patients, but also is an easier algorithm to implement for real-time use. The study shows that C(n) is a very useful and promising EEG-derived parameter for characterizing the (DOA) under clinical situations. AD - Siemens Medical Solutions USA, Inc., Danvers, MA 01923, USA. FAU - Zhang, X S AU - Zhang XS FAU - Roy, R J AU - Roy RJ FAU - Jensen, E W AU - Jensen EW LA - eng PT - Journal Article PT - Validation Studies CY - United States TA - IEEE Trans Biomed Eng JID - 0012737 SB - IM MH - Adult MH - Aged MH - Aged, 80 and over MH - Algorithms MH - Anesthesia/*methods MH - Brain/physiology MH - Confidence Intervals MH - Consciousness/physiology MH - *Electroencephalography MH - Female MH - Human MH - Male MH - Middle Age MH - *Models, Neurological MH - Monitoring, Physiologic/methods MH - *Nonlinear Dynamics MH - Sleep/physiology MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Vascular Surgical Procedures EDAT- 2002/01/05 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - IEEE Trans Biomed Eng 2001 Dec;48(12):1424-33. 329: Ulanowicz RE. The balance between adaptabil...[PMID:11755484]Related Articles, Books, LinkOut UI - 21628736 PMID- 11755484 DA - 20011228 DCOM- 20020319 IS - 0303-2647 VI - 64 IP - 1-3 DP - 2002 Jan TI - The balance between adaptability and adaptation. PG - 13-22 AB - In his 1983 book, Adaptability, Michael Conrad explored the quantitative relationship between adaptability and adaptation using the conditional 'entropy' of information theory as his primary tool. The conditional entropy can be used to estimate the connectivity of the network of system exchanges, a key indicator of system stability. In fact, the May-Wigner criterion for the stability of linear dynamical systems can be recast using the conditional entropy to help identify the boundary along which adaptability and adaptation are exactly in balance-the 'edge of chaos' as it is popularly known. Real data on networks of ecosystem flows indicate that in general these systems do not exist nigh upon the edge of chaos, but rather they populate a much wider 'window of vitality' that exists between the realms of chaotic and deterministic dynamics. It appears that the magnitudes of network flows within this region are distributed in power law fashion. The theory also suggests that an absolute limit to the connectivity of natural self-organizing systems exists, at approximately 3.015 effective connections per node. AD - Chesapeake Biological Laboratory, Center for Environmental Sciences, University of Maryland, PO Box 38, Solomons, MD 20688-0038, USA. ulan@cbl.umces.edu FAU - Ulanowicz, Robert E AU - Ulanowicz RE LA - eng PT - Biography PT - Historical Article PT - Journal Article CY - Ireland TA - Biosystems JID - 0430773 SB - IM MH - *Adaptation, Physiological MH - *Ecosystem MH - Entropy MH - Evolution MH - History of Medicine, 20th Cent. MH - Information Theory MH - *Models, Biological MH - Nonlinear Dynamics PS - Conrad M EDAT- 2002/01/05 10:00 MHDA- 2002/03/20 10:01 AID - S0303264701001708 [pii] PST - ppublish SO - Biosystems 2002 Jan;64(1-3):13-22. 330: Roche O, et al. Development of a virtual scre...[PMID:11754585]Related Articles, Books, LinkOut UI - 21629502 PMID- 11754585 DA - 20011228 DCOM- 20020122 IS - 0022-2623 VI - 45 IP - 1 DP - 2002 Jan 3 TI - Development of a virtual screening method for identification of "frequent hitters" in compound libraries. PG - 137-42 AB - A computer-based method was developed for rapid and automatic identification of potential "frequent hitters". These compounds show up as hits in many different biological assays covering a wide range of targets. A scoring scheme was elaborated from substructure analysis, multivariate linear and nonlinear statistical methods applied to several sets of one and two-dimensional molecular descriptors. The final model is based on a three-layered neural network, yielding a predictive Matthews correlation coefficient of 0.81. This system was able to correctly classify 90% of the test set molecules in a 10-times cross-validation study. The method was applied to database filtering, yielding between 8% (compilation of trade drugs) and 35% (Available Chemicals Directory) potential frequent hitters. This filter will be a valuable tool for the prioritization of compounds from large databases, for compound purchase and biological testing, and for building new virtual libraries. AD - F. Hoffmann-La Roche AG, CH-4070 Basel, Switzerland. FAU - Roche, Olivier AU - Roche O FAU - Schneider, Petra AU - Schneider P FAU - Zuegge, Jochen AU - Zuegge J FAU - Guba, Wolfgang AU - Guba W FAU - Kansy, Manfred AU - Kansy M FAU - Alanine, Alexander AU - Alanine A FAU - Bleicher, Konrad AU - Bleicher K FAU - Danel, Franck AU - Danel F FAU - Gutknecht, Eva-Maria AU - Gutknecht EM FAU - Rogers-Evans, Mark AU - Rogers-Evans M FAU - Neidhart, Werner AU - Neidhart W FAU - Stalder, Henri AU - Stalder H FAU - Dillon, Michael AU - Dillon M FAU - Sjogren, Eric AU - Sjogren E FAU - Fotouhi, Nader AU - Fotouhi N FAU - Gillespie, Paul AU - Gillespie P FAU - Goodnow, Robert AU - Goodnow R FAU - Harris, William AU - Harris W FAU - Jones, Phil AU - Jones P FAU - Taniguchi, Mikio AU - Taniguchi M FAU - Tsujii, Shinji AU - Tsujii S FAU - von der Saal, Wolfgang AU - von der Saal W FAU - Zimmermann, Gerd AU - Zimmermann G FAU - Schneider, Gisbert AU - Schneider G LA - eng PT - Journal Article CY - United States TA - J Med Chem JID - 9716531 RN - 0 (Organic Chemicals) RN - 0 (Pharmaceutical Preparations) SB - IM MH - *Databases, Factual MH - Linear Models MH - Molecular Structure MH - Neural Networks (Computer) MH - Nonlinear Dynamics MH - Organic Chemicals/*chemistry MH - Pharmaceutical Preparations/chemistry EDAT- 2002/01/05 10:00 MHDA- 2002/01/23 10:01 AID - jm010934d [pii] PST - ppublish SO - J Med Chem 2002 Jan 3;45(1):137-42. 331: Takeuchi T, et al. Nonlinear pharmacokinetics of...[PMID:11754038]Related Articles, Books, LinkOut UI - 21621613 PMID- 11754038 DA - 20011225 DCOM- 20020220 IS - 0142-2782 VI - 22 IP - 6 DP - 2001 Sep TI - Nonlinear pharmacokinetics of TAK-044, a new endothelin antagonist, in rats. PG - 221-30 AB - The mechanism of the nonlinear pharmacokinetics of TAK-044 in rats was shown from in vivo and in vitro studies to be due to capacity-limited hepatic uptake. In the rats, which were given intravenous injections of (14)C-labeled TAK-044 ([(14)C]TAK-044) (1, 3, 10, 30 and 100 mg/kg), the AUC(inf) per unit dose of unchanged compound increased remarkably. An analysis model indicated that the CL(tot), V(1) and k(12) values of TAK-044 decreased significantly with increasing dose, whereas the k(el) values remained constant over the doses examined. The uptake clearance of [(14)C]TAK-044 by several tissues was investigated by an integration plot at doses from 0.3 to 60 mg/kg. This study showed that the liver played the principal role in the removal of TAK-044 from the plasma, while hepatic uptake was capacity-limited at doses greater than 30 mg/kg. The hepatic uptake study using rat hepatocytes indicated that a carrier-mediated transport system contributed to the hepatic uptake of TAK-044, and this system had high affinity (K(m,in vitro); 8.4 micromol/L) with low capacity (V(max,in vitro); 86.3 pmol/mg protein/min). These results show that the saturation of hepatic uptake by the carrier-mediated transport system could explain the nonlinear pharmacokinetics of TAK-044 in rats. CI - Copyright 2001 John Wiley & Sons, Ltd. AD - Drug Analysis and Pharmacokinetics Research Laboratories, Pharmaceutical Research Division, Takeda Chemical Industries Ltd., 2-17-85, Juso-Honmachi, Yodogawaku, Osaka 532-8686, Japan. Takeuchi_Toshiyuki@takeda.co.jp FAU - Takeuchi, T AU - Takeuchi T FAU - Tagawa, Y AU - Tagawa Y FAU - Hagihara, K AU - Hagihara K FAU - Maeshiba, Y AU - Maeshiba Y FAU - Yamashita, K AU - Yamashita K FAU - Tsukuda, R AU - Tsukuda R FAU - Yoshimura, Y AU - Yoshimura Y LA - eng PT - Journal Article CY - England TA - Biopharm Drug Dispos JID - 7911226 RN - 0 (Antimetabolites) RN - 0 (Endothelins) RN - 0 (Peptides, Cyclic) RN - 157380-72-8 (TAK 044) SB - IM MH - Animal MH - Antimetabolites/pharmacology MH - Area Under Curve MH - Bile/metabolism MH - Cell Separation MH - Dose-Response Relationship, Drug MH - Endothelins/*antagonists & inhibitors MH - Hepatocytes/drug effects/metabolism MH - In Vitro MH - Infusions, Intravenous MH - Liver/drug effects/metabolism MH - Male MH - Nonlinear Dynamics MH - Peptides, Cyclic/*pharmacokinetics MH - Rats MH - Rats, Wistar EDAT- 2001/12/26 10:00 MHDA- 2002/02/21 10:01 AID - 10.1002/bdd.262 [pii] PST - ppublish SO - Biopharm Drug Dispos 2001 Sep;22(6):221-30. 332: Tod M, et al. Estimation of pharmacokinetic...[PMID:11750944]Related Articles, Books, LinkOut UI - 21622486 PMID- 11750944 DA - 20011225 DCOM- 20020225 IS - 0169-2607 VI - 67 IP - 1 DP - 2002 Jan TI - Estimation of pharmacokinetic parameters by orthogonal regression: comparison of four algorithms. PG - 13-26 AB - The contribution of non-linear orthogonal regression for estimation of individual pharmacokinetic parameters when drug concentrations and sampling times are subject to error was studied. The first objective was to introduce and compare four numerical approaches that involve different degrees of approximation for parameter estimation by orthogonal regression. The second objective was to compare orthogonal with non-orthogonal regression. These evaluations were based on simulated data sets from 300 'subjects', thereby enabling precision and accuracy of parameter estimates to be determined. The pharmacokinetic model was a one-compartment open model with first-order absorption and elimination rates. The inter-individual coefficients of variation (CV) of the pharmacokinetic parameters were in the range 33-100%. Eight measurement-error models for times and concentrations (homo- or heteroscedastic with constant CV) were considered. Accuracy of the four algorithms was very close in almost all instances (typical bias, 1-4%). Precision showed three expected trends: root mean squared error (RMSE) increased when the residual error was larger or the number of observations was smaller, and it was highest for the absorption rate constant and common error variance. Overall, RMSE ranged from 5 to 40%. It was found that the simplest algorithm for othogonal regression performed as well as the more complicated approaches. Errors in sampling time resulted in an increased bias and imprecision in individual parameter estimates (especially for k(a) in our example) and in common error variance when the estimation method did not take into account these errors. In this situation, use of orthogonal regression resulted in smaller bias and better precision. AD - Departement de Pharmacotoxicologie, Hopital Avicenne, 125 Route de Stalingrad, 93009 Cedex, Bobigny, France. michel.tod@avc.ap-hop-paris.fr FAU - Tod, Michel AU - Tod M FAU - Aouimer, Azzedine AU - Aouimer A FAU - Petitjean, Olivier AU - Petitjean O LA - eng PT - Journal Article CY - Ireland TA - Comput Methods Programs Biomed JID - 8506513 RN - 0 (Anti-Infective Agents, Fluoroquinolone) RN - 85721-33-1 (Ciprofloxacin) SB - IM MH - *Algorithms MH - Anti-Infective Agents, Fluoroquinolone/pharmacokinetics MH - Ciprofloxacin/pharmacokinetics MH - Comparative Study MH - *Computer Simulation MH - Human MH - *Models, Biological MH - *Models, Statistical MH - *Nonlinear Dynamics MH - *Pharmacokinetics MH - *Regression Analysis EDAT- 2001/12/26 10:00 MHDA- 2002/02/28 10:01 AID - S0169260700001486 [pii] PST - ppublish SO - Comput Methods Programs Biomed 2002 Jan;67(1):13-26. 333: Papadopoulos MC, et al. Is the National Health Servic...[PMID:11733585]Related Articles, Books, LinkOut UI - 21590586 PMID- 11733585 DA - 20011204 DCOM- 20020114 LR - 20021009 IS - 0141-0768 VI - 94 IP - 12 DP - 2001 Dec TI - Is the National Health Service at the edge of chaos? PG - 613-6 AB - We used chaos and complexity theory to analyse waiting-list data (1998-2001) pertaining to over 20 000 National Health Service (NHS) patients from general surgical, orthopaedic and neurosurgical units across England. Plots of frequency versus quarter-to-quarter change in waiting times revealed a power relation which seems independent of surgical specialty and hospital location. One interpretation of these findings is that, for the period in question, the NHS was a system at the edge of chaos. This hypothesis might explain why waiting times have resisted attempts at shortening. AD - Department of Neurosurgery, Hurstwood Park Neurological Centre, Hayward's Heath RH16 4EX, UK. MPapadopoulos@compuserve.com FAU - Papadopoulos, M C AU - Papadopoulos MC FAU - Hadjitheodossiou, M AU - Hadjitheodossiou M FAU - Chrysostomou, C AU - Chrysostomou C FAU - Hardwidge, C AU - Hardwidge C FAU - Bell, B A AU - Bell BA LA - eng PT - Journal Article CY - England TA - J R Soc Med JID - 7802879 SB - IM CIN - J R Soc Med. 2002 Apr;95(4):220. PMID: 11934926 CIN - J R Soc Med. 2002 Apr;95(4):220. PMID: 11934925 CIN - J R Soc Med. 2002 Mar;95(3):164. PMID: 11872779 CIN - J R Soc Med. 2002 Mar;95(3):165. PMID: 11872780 CIN - J R Soc Med. 2002 Mar;95(3):165. PMID: 11872783 MH - Ambulatory Care/organization & administration/standards MH - Great Britain MH - Human MH - Nonlinear Dynamics MH - Referral and Consultation/organization & administration/standards MH - State Medicine/organization & administration/*standards MH - *Waiting Lists EDAT- 2001/12/26 10:00 MHDA- 2002/01/15 10:01 PST - ppublish SO - J R Soc Med 2001 Dec;94(12):613-6. 334: Rudnicka AR, et al. Nonlinear behavior of certain...[PMID:11733285]Related Articles, Books, LinkOut UI - 21590848 PMID- 11733285 DA - 20011204 DCOM- 20011213 LR - 20021101 IS - 0161-6420 VI - 108 IP - 12 DP - 2001 Dec TI - Nonlinear behavior of certain optic nerve head parameters and their determinants in normal subjects. PG - 2358-68 AB - OBJECTIVE: To investigate the relationship between the absolute area of certain optic disc parameters and a number of ocular dimensional characteristics and demographic factors in young, healthy subjects. DESIGN: Cross-sectional study. PARTICIPANTS: One hundred twenty-one subjects, aged 16.5 to 35.4 years participated, encompassing a wide range of refractive error from +4 diopters (D) to -25.75 D. One eye from each subject was randomly selected for examination. MAIN OUTCOME MEASURES: Absolute size of the optic disc parameters: optic disc area (DA), neuroretinal rim area (NRA), optic cup area (CA), and peripapillary atrophy area (PA). METHODS: Absolute sizes of optic disc parameters were determined from digitized photographic color transparencies, taking into consideration the magnification of the fundus camera and human eye. Relationships between the absolute size of the optic disc features and axial length, crystalline lens thickness, anterior chamber depth, ocular refraction, front surface keratometry, age, and gender were examined. RESULTS: Axial length, lens thickness, front surface keratometry, and age demonstrated positive associations with all optic disc parameters, and anterior chamber depth and ocular refraction demonstrated negative associations in all cases. Multiple regression analysis revealed that the associations observed univariately for age, anterior chamber depth, lens thickness, front surface keratometry, and ocular refraction were confounded by axial length for all disc parameters. After taking logs, DA and NRA exhibit an exponential relationship with axial length, whereas PA and CA exhibit a linear relationship with axial length. DA and NRA increase by approximately 3% per millimeter increase in axial length at 20 mm and up to 40% for DA and 50% for NRA at an axial length of 35 mm. PA and CA are estimated to increase by 26% (10%-44%) and 10% (5%-16%), respectively, per millimeter increase in axial length. Females have approximately 5% smaller DA and 7% smaller NRA than males, but these effects are not statistically significant (P > 0.2). From the multiple regression analysis, females have 31% larger optic cup areas (1%-57%, P = 0.03) and 24% smaller PA (42% smaller to 5% larger P = 0.06) than males, but these effects are of borderline statistical significance at 5%. CONCLUSIONS: Of the ocular biometric factors considered, axial length seems to be the most important predictor of the absolute area of the optic disc parameters. No association exists between any disc parameter and age in this sample of subjects less than 40 years of age. Females exhibited smaller values for DA, NRA, and PA than did males, differences that were not statistically significant, and larger CA (P = 0.03). AD - Wolfson Institute of Preventive Medicine, St. Bartholomew's and The Royal London School of Medicine and Dentistry, Charterhouse Square, London EC1M 6BQ, England, UK. FAU - Rudnicka, A R AU - Rudnicka AR FAU - Frost, C AU - Frost C FAU - Owen, C G AU - Owen CG FAU - Edgar, D F AU - Edgar DF LA - eng PT - Journal Article CY - United States TA - Ophthalmology JID - 7802443 SB - IM MH - Adolescent MH - Adult MH - Biometry/methods MH - Cross-Sectional Studies MH - Female MH - Human MH - Male MH - Nonlinear Dynamics MH - Optic Disk/*anatomy & histology MH - Photography MH - Random Allocation MH - Reference Values MH - Sex Factors MH - Support, Non-U.S. Gov't EDAT- 2001/12/26 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - Ophthalmology 2001 Dec;108(12):2358-68. 335: Hlaing WM, et al. Body mass index growth in a s...[PMID:11748820]Related Articles, Books, LinkOut UI - 21614176 PMID- 11748820 DA - 20011218 DCOM- 20020117 LR - 20021101 IS - 1042-0533 VI - 13 IP - 6 DP - 2001 Nov-Dec TI - Body mass index growth in a sample of U.S. children: repeated measures data analysis of the Minneapolis Children's Blood Pressure Study. PG - 821-31 AB - Longitudinal assessments of the body mass index (BMI) in children and adolescents are limited. The purpose of the study was to describe the growth patterns of the BMI in children and young adults. Black and White children of Minneapolis Children's Blood Pressure Study (MCBPS) were 6 to 9 years old at entry and were followed for 12 years at 19 separate visits. Those with at least five visits (n = 1,302) were included for analysis, using non-linear mixed effects models in conjunction with the Gompertz curve. The growth patterns of four sex-ethnic groups were different at three levels: starting level (SL) (kg/m(2)), asymptote level (AL) (kg/m(2)), and peak growth age (PGA) (in years). In this context, SL is the average BMI level at age 6, AL is the average BMI level when growth diminishes, and PGA is the average age at which the rate of growth in the BMI peaks. The SL (16.3 +/- 0.1) for White males was significantly greater than SL in the other three sex-ethnic groups, among which there were no significant differences. There was a significant ethnic difference in AL between Black females (25.5 +/- 0.3) and White females (24.4 +/- 0.2) and a marginally significant difference in AL between Black females and Black males (24.4 +/- 0.3). For PGA, only sex differences were significant: Black females reached the peak at the earliest age at (11.5 +/- 0.1) years, followed by White females (11.7 +/- 0.1), Black males (12.6 +/- 0.1), and White males (12.8 +/- 0.1). CI - Copyright 2001 Wiley-Liss, Inc. AD - Department of Public Health, Florida International University, North Miami, Florida 33181, USA. hlaingw@fiu.edu FAU - Hlaing, W M AU - Hlaing WM FAU - Prineas, R J AU - Prineas RJ FAU - Zhu, Y AU - Zhu Y FAU - Leaverton, P E AU - Leaverton PE LA - eng PT - Journal Article CY - United States TA - Am J Human Biol JID - 8915029 SB - IM MH - Adolescent MH - Adult MH - *Body Mass Index MH - Caucasoid Race MH - Child MH - Female MH - *Growth MH - Human MH - Longitudinal Studies MH - Male MH - Minnesota MH - Negroid Race MH - Nonlinear Dynamics MH - Sex Factors EDAT- 2001/12/19 10:00 MHDA- 2002/01/18 10:01 AID - 10.1002/ajhb.1127 [pii] PST - ppublish SO - Am J Human Biol 2001 Nov-Dec;13(6):821-31. 336: Marino AA, et al. Nonlinear dynamical law gover...[PMID:11748671]Related Articles, Books, LinkOut UI - 21614423 PMID- 11748671 DA - 20011218 DCOM- 20020408 IS - 0197-8462 VI - 22 IP - 8 DP - 2001 Dec TI - Nonlinear dynamical law governs magnetic field induced changes in lymphoid phenotype. PG - 529-46 AB - The results of many different types of animal and human studies dealing with the biological effects of exposure to low frequency electromagnetic fields (EMFs) have consistently been both positive and negative. We addressed the question of why this pattern had occurred so commonly in biological studies involving exposure to EMFs and hypothesized that it stemmed from the prevalent use of a linear model to characterize what are inherently nonlinear input-output relationships. The hypothesis was tested by analyzing biological data using a novel statistical procedure that could be adjusted to detect either nonlinear or linear effects. The reliability of the procedure was established using positive and negative controls and by comparison with the results obtained from sampling a known nonlinear system. In four independent experiments, male and female mice were exposed continuously to 0.1 or 0.5 mT, 60 Hz, for 175 days, and the effect on 20 immune parameters was measured using flow cytometry and functional assays. In each experiment, EMF exposure resulted in statistically significant changes in lymphoid phenotype when and only when the response of the animals to the fields was analyzed as if it were governed by nonlinear laws. Our results suggest that the pattern of inconsistency in the EMF bioeffects studies is an artifact resulting from an incorrect choice of the conceptual model for the relation between the field and the biological effect it causally determines. CI - Copyright 2001 Wiley-Liss, Inc. AD - Department of Orthopaedic Surgery, LSU Health Sciences Center, Shreveport, Louisiana 71130-3932, USA. amarino@lsuhsc.edu FAU - Marino, A A AU - Marino AA FAU - Wolcott, R M AU - Wolcott RM FAU - Chervenak, R AU - Chervenak R FAU - Jourd'heuil, F AU - Jourd'heuil F FAU - Nilsen, E AU - Nilsen E FAU - Frilot, C 2nd AU - Frilot C 2nd LA - eng PT - Journal Article CY - United States TA - Bioelectromagnetics JID - 8008281 RN - 0 (Antigens, CD) RN - 0 (Immunoglobulins) SB - IM MH - Animal MH - Antigens, CD/metabolism MH - Biophysics MH - Bone Marrow Cells/immunology MH - Electromagnetic Fields/*adverse effects MH - Female MH - Human MH - Immunoglobulins/metabolism MH - Likelihood Functions MH - Lymphocytes/*immunology MH - Male MH - Mice MH - Mice, Inbred C57BL MH - Models, Biological MH - Nonlinear Dynamics MH - Spleen/cytology/immunology MH - Support, U.S. Gov't, P.H.S. MH - Thymus Gland/cytology/immunology EDAT- 2001/12/19 10:00 MHDA- 2002/04/09 10:01 AID - 10.1002/bem.82 [pii] PST - ppublish SO - Bioelectromagnetics 2001 Dec;22(8):529-46. 337: Yarosh DB. Why is DNA damage signaling s...[PMID:11746746]Related Articles, Books, LinkOut UI - 21610561 PMID- 11746746 DA - 20011217 DCOM- 20020109 IS - 0893-6692 VI - 38 IP - 2-3 DP - 2001 TI - Why is DNA damage signaling so complicated? Chaos and molecular signaling. PG - 132-4 AB - Molecular signaling in eukaryotic cells is accomplished by complex and redundant pathways converging on key molecules that are allosterically controlled by a limited number of signaling proteins. The p53-signaling pathway is an example of a complicated sequence of signals produced in response to DNA damage. This pattern of signaling may arise from chance occurrences at the origin of life and the necessities imposed on a nanomolar system. From this viewpoint, chaos theory may explain the origin, complexity, and convergence of these pathways. CI - Copyright 2001 Wiley-Liss, Inc. AD - AGI Dermatics, Freeport, New York 11520, USA. danyarosh@agiderm.com FAU - Yarosh, D B AU - Yarosh DB LA - eng PT - Journal Article CY - United States TA - Environ Mol Mutagen JID - 8800109 SB - IM MH - Animal MH - *DNA Damage MH - *DNA Repair MH - Genes, p53 MH - Human MH - Nonlinear Dynamics MH - Signal Transduction EDAT- 2001/12/18 10:00 MHDA- 2002/01/10 10:01 AID - 10.1002/em.1063 [pii] PST - ppublish SO - Environ Mol Mutagen 2001;38(2-3):132-4. 338: Some IT, et al. Stability parameter estimatio...[PMID:11745733]Related Articles, Books, LinkOut UI - 21611976 PMID- 11745733 DA - 20011217 DCOM- 20020304 IS - 0022-3549 VI - 90 IP - 11 DP - 2001 Nov TI - Stability parameter estimation at ambient temperature from studies at elevated temperatures. PG - 1759-66 AB - The determination of specific kinetic constants k(i) in pH-profile studies is often undertaken at ambient temperature. However, when dealing with a drug substance that is stable at ambient temperature, the pH-profile study is conducted at a chosen elevated temperature and the kinetic parameters are given at this particular elevated temperature. But in stability studies we generally need kinetic constants at ambient or storage temperature for practical reasons (information and storage conditions of formulation). To assess this ambient kinetic information from studies at elevated temperatures, cumulative sequential steps are usually employed with very few statistical concerns on the final estimates. The statistical problems on these final estimates in cumulative procedures are highlighted in many papers. Because these stability parameters are useful for drug formulation and storage conditions, good practical decisions have to be made on the basis of statistically unbiased identified parameters. We propose in this paper a nonlinear model that allows the direct determination of specific activation energies E(ai) that are linked to the specific kinetic constants k(i). Hence, a mathematical relationship between drug concentration C, pH, temperature T, and time t is obtained. Kinetic data from acetylsalicylic acid (ASA) hydrolysis (first-order kinetics) are used to validate the model. The results show that it is possible to obtain directly, by an extrapolation procedure, the kinetic parameters (specific kinetic constants k(i), specific activation energies E(ai), and dissociation constant pK(a)) at low temperature from data gathered at elevated temperatures using more meaningful statistics. CI - Copyright 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association AD - Laboratory of Bioanalytical Chemistry, Toxicology and Applied Physical Chemistry Pharmacy Institute, Free University of Brussels, Campus de la Plaine, CP 205/1, Boulevard du triomphe, B-1050 Bruxelles, Belgium. FAU - Some, I T AU - Some IT FAU - Bogaerts, P AU - Bogaerts P FAU - Hanus, R AU - Hanus R FAU - Hanocq, M AU - Hanocq M FAU - Dubois, J AU - Dubois J LA - eng PT - Journal Article CY - United States TA - J Pharm Sci JID - 2985195R SB - IM MH - *Data Interpretation, Statistical MH - *Drug Stability MH - Heat MH - Models, Theoretical MH - Nonlinear Dynamics MH - Pharmacokinetics MH - Support, Non-U.S. Gov't MH - *Temperature EDAT- 2001/12/18 10:00 MHDA- 2002/03/05 10:01 AID - 10.1002/jps.1125 [pii] PST - ppublish SO - J Pharm Sci 2001 Nov;90(11):1759-66. 339: Eucker SA, et al. Analysis of left ventricular ...[PMID:11744675]Related Articles, Books, LinkOut UI - 21611133 PMID- 11744675 DA - 20011217 DCOM- 20020410 IS - 8750-7587 VI - 92 IP - 1 DP - 2002 Jan TI - Analysis of left ventricular hemodynamics in physiological hyperspace. PG - 323-30 AB - Our laboratory has previously shown that it is possible to elucidate novel physiological relationships by analyzing the left ventricular pressure (P) contour in the phase [time derivative of P (dP/dt) vs. P] plane (Eucker SA, Lisauskas JB, Singh J, and Kovacs SJ, J Appl Physiol 90: 2238-2244, 2001). To further characterize cardiac physiology, we introduce a method that combines P-volume (V) and phase plane-derived information in physiological hyperspace. From four-dimensional (P, V, dP/dt, time derivative of V) hyperspace, we consider three-dimensional embedding diagrams having dP/dt, P, and V as coordinate axes. Our method facilitates analysis of physiological function independent of inotropic state and permits assessment of P-V-based relationships in the phase plane and vice versa. To test feasibility, the method was applied to murine hemodynamic data. As predicted from first principles, the area of the P-V loop (ventricular external work) correlated closely (r = 0.97) with phase plane limit cycle area (external power). The P-V plane-derived linear (r = 0.99) end-systolic P-V relationship (maximum elastance) appeared linear in the phase plane (r = 0.85). We conclude that analysis of data in physiological hyperspace is generalizable: it facilitates quantitative characterization of ventricular systolic and diastolic function and can guide discovery of novel physiological relationships. AD - Cardiovascular Biophysics Laboratory, Washington University, St. Louis, Missouri 63110, USA. FAU - Eucker, Stephanie A AU - Eucker SA FAU - Lisauskas, Jennifer AU - Lisauskas J FAU - Courtois, Michael R AU - Courtois MR FAU - Kovacs, Sandor J AU - Kovacs SJ LA - eng ID - HL-04023/HL/NHLBI ID - HL-54179/HL/NHLBI PT - Journal Article CY - United States TA - J Appl Physiol JID - 8502536 SB - IM MH - Algorithms MH - Animal MH - Blood Pressure/physiology MH - Heart Catheterization MH - Linear Models MH - Mice MH - Models, Biological MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. MH - Ventricular Function, Left/*physiology EDAT- 2001/12/18 10:00 MHDA- 2002/04/11 10:01 AID - 10.1152/japplphysiol.00560.2001 [doi] PST - ppublish SO - J Appl Physiol 2002 Jan;92(1):323-30. 340: Arieli R, et al. Modeling pulmonary and CNS O(...[PMID:11744667]Related Articles, Books, LinkOut UI - 21611125 PMID- 11744667 DA - 20011217 DCOM- 20020410 IS - 8750-7587 VI - 92 IP - 1 DP - 2002 Jan TI - Modeling pulmonary and CNS O(2) toxicity and estimation of parameters for humans. PG - 248-56 AB - The power expression for cumulative oxygen toxicity and the exponential recovery were successfully applied to various features of oxygen toxicity. From the basic equation, we derived expressions for a protocol in which PO(2) changes with time. The parameters of the power equation were solved by using nonlinear regression for the reduction in vital capacity (DeltaVC) in humans: %DeltaVC = 0.0082 x t(2)(PO(2)/101.3)(4.57), where t is the time in hours and PO(2) is expressed in kPa. The recovery of lung volume is DeltaVC(t) = DeltaVC(e) x e(-(-0.42 + 0.00379PO(2))t), where DeltaVC(t) is the value at time t of the recovery, DeltaVC(e) is the value at the end of the hyperoxic exposure, and PO(2) is the prerecovery oxygen pressure. Data from different experiments on central nervous system (CNS) oxygen toxicity in humans in the hyperbaric chamber (n = 661) were analyzed along with data from actual closed-circuit oxygen diving (n = 2,039) by using a maximum likelihood method. The parameters of the model were solved for the combined data, yielding the power equation for active diving: K = t(2) (PO(2)/101.3)(6.8), where t is in minutes. It is suggested that the risk of CNS oxygen toxicity in diving can be derived from the calculated parameter of the normal distribution: Z = [ln(t) - 9.63 +3.38 x ln(PO(2)/101.3)]/2.02. The recovery time constant for CNS oxygen toxicity was calculated from the value obtained for the rat, taking into account the effect of body mass, and yielded the recovery equation: K(t) = K(e) x e(-0.079t), where K(t) and K(e) are the values of K at time t of the recovery process and at the end of the hyperbaric oxygen exposure, respectively, and t is in minutes. AD - Israel Naval Medical Institute, Israel. rarieli@netvision.net.il FAU - Arieli, R AU - Arieli R FAU - Yalov, A AU - Yalov A FAU - Goldenshluger, A AU - Goldenshluger A LA - eng PT - Journal Article CY - United States TA - J Appl Physiol JID - 8502536 RN - 0 (Reactive Oxygen Species) RN - 7782-44-7 (Oxygen) SB - IM MH - Algorithms MH - Diving/*physiology MH - Human MH - Kinetics MH - Lung Diseases/*chemically induced MH - Models, Biological MH - Neurotoxicity Syndromes/*pathology MH - Nonlinear Dynamics MH - Oxygen/*toxicity MH - Reactive Oxygen Species/metabolism MH - Vital Capacity/physiology EDAT- 2001/12/18 10:00 MHDA- 2002/04/11 10:01 AID - 10.1152/japplphysiol.00434.2001 [doi] PST - ppublish SO - J Appl Physiol 2002 Jan;92(1):248-56. 341: Mangel M. Complex adaptive systems, agi...[PMID:11742525]Related Articles, Books, LinkOut UI - 21608073 PMID- 11742525 DA - 20011214 DCOM- 20020122 IS - 0022-5193 VI - 213 IP - 4 DP - 2001 Dec 21 TI - Complex adaptive systems, aging and longevity. PG - 559-71 AB - Mortality and reproduction are intimately entwined in the study of aging and longevity. I apply the modern theory of complex adaptive systems (nonlinear, stochastic, dynamic methods) to questions of aging and longevity. I begin by highlighting major questions that must be answered in order to obtain a deeper understanding of aging. These are: (i) What should (in an evolutionary sense) mortality trajectories look like? (ii) Why does caloric restriction slow aging? (iii) Why does reproduction cause delayed mortality? (iv) Why does compensatory growth cause delayed mortality? I show how dynamic state variable models based on stochastic dynamic programming (Clark & Mangel, 2000) can be used to embed genetic theories of senescence (either mutation accumulation or antagonistic pleiotropy) in the somatic environment, as George Williams called for in 1957, and how they make the disposable soma theory of aging operational. Such models will allow unification of genetic and phenotypic theories of aging. CI - Copyright 2001 Academic Press. AD - Department of Environmental Studies and Institute of Marine Sciences, University of California, Santa Cruz, CA 95064, USA. msmangel@casts.ucsc.edu FAU - Mangel, M AU - Mangel M LA - eng PT - Journal Article PT - Review PT - Review, Academic CY - England TA - J Theor Biol JID - 0376342 SB - IM MH - *Adaptation, Physiological MH - Aging/*physiology MH - Animal MH - Human MH - Longevity/physiology MH - *Models, Biological MH - Models, Genetic MH - Nonlinear Dynamics MH - *Systems Theory MH - Terminology RF - 115 EDAT- 2001/12/18 10:00 MHDA- 2002/01/23 10:01 AID - 10.1006/jtbi.2001.2431 [doi] AID - S0022519301924312 [pii] PST - ppublish SO - J Theor Biol 2001 Dec 21;213(4):559-71. 342: Edelstein-Keshet L, et al. Modelling perspectives on agi...[PMID:11742522]Related Articles, Books, LinkOut UI - 21608070 PMID- 11742522 DA - 20011214 DCOM- 20020122 IS - 0022-5193 VI - 213 IP - 4 DP - 2001 Dec 21 TI - Modelling perspectives on aging: can mathematics help us stay young? PG - 509-25 AB - We survey several types of mathematical models that keep track of age distributions in a population, or follow some aspects of aging, such as loss of replicative potential of stem cells. The properties of a class of linear models of this type are discussed and compared. We illustrate the applicability of such models with a simple example based on hypothetical stem cell dynamics developed to address age-related telomere loss in the human granulocyte pool. We then describe the contrasting behaviour of nonlinear systems. Examples are drawn from the class of "dynamical diseases" to illustrate some of the aspects of nonlinear systems. Applications of these, and other models to the problems of aging and replicative aging are discussed. CI - Copyright 2001 Academic Press. AD - Department of Mathematics, UBC, Vancouver, BC, Canada V6T 1Z2. FAU - Edelstein-Keshet, L AU - Edelstein-Keshet L FAU - Israel, A AU - Israel A FAU - Lansdorp, P AU - Lansdorp P LA - eng ID - R0IAI29524/AI/NIAID PT - Journal Article PT - Review PT - Review, Academic CY - England TA - J Theor Biol JID - 0376342 SB - IM MH - Age Distribution MH - Aging/*physiology MH - Animal MH - Cell Division/physiology MH - Human MH - *Models, Biological MH - Nonlinear Dynamics MH - Population Dynamics MH - Stem Cells/cytology MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. RF - 47 EDAT- 2001/12/18 10:00 MHDA- 2002/01/23 10:01 AID - 10.1006/jtbi.2001.2429 [doi] AID - S0022519301924294 [pii] PST - ppublish SO - J Theor Biol 2001 Dec 21;213(4):509-25. 343: Lyles MB, et al. Structural basis for the bind...[PMID:11741482]Related Articles, Books, LinkOut UI - 21617444 PMID- 11741482 DA - 20011219 DCOM- 20020114 IS - 0022-2623 VI - 44 IP - 26 DP - 2001 Dec 20 TI - Structural basis for the binding affinity of xanthines with the DNA intercalator acridine orange. PG - 4650-60 AB - Caffeine (CAF), a methyl-substituted xanthine, interacts with polyaromatic DNA intercalators and has been hypothesized to interfere with their intercalation into DNA. Optical absorption spectroscopy was used to determine the binding affinities (K(assoc)) and structural effects of a series of methyl-substituted xanthines and a series of methyl-substituted uric acids (8-oxoxanthine) with the known DNA intercalator acridine orange (AO). There is evidence that complexation occurred (K(assoc) > or = 150 M(-1); binding curve saturation approximately > or =50%) between AO and 1,7-dimethylxanthine (155 M(-1)), 1,3-dimethylxanthine (theophylline, 157 M(-1)), 1,3,7-trimethylxanthine (CAF, 256 M(-1)), 1,3-dimethyl-8-chloroxanthine (413 M(-1)), 1,3,7,9-tetramethyl-8-oxyxanthine (tetramethyl uric acid or TMU, 552 M(-1)), and theophylline ethylenediamine (aminophylline, 596 M(-1)). No definitive evidence of complexation occurred between AO and 16 other substituted xanthines or purines, although there was some evidence of weak complexation (K(assoc) < 150 M(-1)) between AO and eight of the sixteen. Three common structural similarities were identified among those compounds found to form significant bonding with AO: (i) the N(1) or N(3) on the xanthine structure must be substituted with a methyl group; (ii) oxygen or chlorine substitution at C(8) increases binding affinity to AO when resonate states remain unchanged; and (iii) K(assoc) increases with an increase in number of methyl group substitutions on the 1- or 3-methylxanthine core structure. These results are explained on the basis of complex stabilization due predominately to hydrophobic attraction, with a contribution from charge transfer between donor and acceptor components. This information can be used in the manipulation of the physical or chemical characteristics of biologically active polyaromatic molecules. AD - Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, Texas 78229, USA. FAU - Lyles, M B AU - Lyles MB FAU - Cameron, I L AU - Cameron IL FAU - Rawls, H R AU - Rawls HR LA - eng ID - DE00152/DE/NIDCR PT - Journal Article CY - United States TA - J Med Chem JID - 9716531 RN - 0 (Intercalating Agents) RN - 0 (Xanthines) RN - 65-61-2 (Acridine Orange) SB - IM MH - Acridine Orange/*chemistry MH - Intercalating Agents/*chemistry MH - Methylation MH - Nonlinear Dynamics MH - Spectrophotometry MH - Structure-Activity Relationship MH - Support, U.S. Gov't, P.H.S. MH - Xanthines/*chemistry EDAT- 2001/12/14 10:00 MHDA- 2002/01/15 10:01 AID - jm9904708 [pii] PST - ppublish SO - J Med Chem 2001 Dec 20;44(26):4650-60. 344: Jonsson EN, et al. Nonlinearity detection: advan...[PMID:11741248]Related Articles, Books, LinkOut UI - 21616818 PMID- 11741248 DA - 20011219 DCOM- 20020215 IS - 1522-1059 VI - 2 IP - 3 DP - 2000 TI - Nonlinearity detection: advantages of nonlinear mixed-effects modeling. PG - E32 AB - The purpose of this study was to address the question of whether the use of nonlinear mixed-effect models has an impact on the detection and characterization of nonlinear processes (pharmacokinetic and pharmacodynamic) in rich data obtained from a few subjects. Simulations were used to assess the difference between applying population analysis, ie, nonlinear mixed-effects models as implemented in NONMEM, and the standard 2-stage (STS) method as the data analysis method for detection and characterization of nonlinearities. Three situations were considered, 2 pharmacokinetic and 1 pharmacodynamic. Both the first-order (FO) and FO conditional estimation (FOCE) algorithms were used for the population analyses. Within each situation, rich data were simulated for 8 subjects at multiple dose levels. The true nonlinear model and a simpler linear model were fit to each data set using each of the STS, FO, and FOCE methods. Criteria were prespecified to determine when each data analysis method detected the true nonlinear model. For all 3 simulated situations, the application of population analysis with the FOCE algorithm enabled the detection and characterization of the true nonlinear models in at least a 4-fold lower dose level than the STS approach. For both of the pharmacokinetic settings, population analysis with the FO algorithm performed much more poorly than the STS approach. The superior detection and characterization of nonlinearities provided by population analysis with the FOCE algorithm should allow drug developers to better predict and define how a drug should be used in clinical practice in such situations. AD - Department of Pharmacy, Division of Biopharmaceutics and Pharmacokinetics, Uppsala University, Box 580, S-751 23 Uppsala, Sweden. niclas.jonsson@biof.uu.se FAU - Jonsson, E N AU - Jonsson EN FAU - Wade, J R AU - Wade JR FAU - Karlsson, M O AU - Karlsson MO LA - eng PT - Journal Article CY - United States TA - AAPS PharmSci JID - 100897065 SB - IM MH - Algorithms MH - *Nonlinear Dynamics MH - *Pharmacokinetics MH - Pharmacology/*methods EDAT- 2001/12/14 10:00 MHDA- 2002/02/16 10:01 PST - epublish SO - AAPS PharmSci 2000;2(3):E32. 345: Maurer T, et al. Comparison of methods for ana...[PMID:11741224]Related Articles, Books, LinkOut UI - 21616794 PMID- 11741224 DA - 20011219 DCOM- 20020129 IS - 1522-1059 VI - 2 IP - 1 DP - 2000 TI - Comparison of methods for analyzing kinetic data from mechanism-based enzyme inactivation: application to nitric oxide synthase. PG - E8 AB - The goals of this study were (1) to investigate the performance of 2 classical methods of kinetic analysis when applied to data from enzyme systems in which mechanism-based inactivation and enzyme degradation are present, and (2) to develop and validate a nonlinear method of kinetic data analysis that may perform better under these situations. A composite equation was derived to link various parameters that govern the kinetics of mechanism-based inactivation, viz., enzyme activity, inhibitor-binding affinity (K(I)), inactivation rate (k(inact)), and enzyme degradation (k(deg)). The relative accuracy and precision of parameter estimation by the Dixon and Kitz-Wilson methods and a new nonlinear method were evaluated by computer simulation. The behavior of these methods of analysis were validated experimentally, using the nitric oxide synthase enzyme, both in purified form and as expressed in murine macrophage cell cultures. We showed that the Dixon method, as expected, could not provide accurate estimates of K(I) in the presence of either enzyme inactivation or instability. The Kitz-Wilson method could provide accurate estimates of these parameters; however, the precisions of these estimates were poorer than those obtained using the nonlinear method of analysis. We conclude that the nonlinear approach is superior to classical methods of data analysis for enzyme inhibitor kinetics, based on better efficiency, accuracy, and precision. AD - Department of Pharmaceutics, School of Pharmacy, University at Buffalo, State University of New York, Buffalo, NY 14260, USA. FAU - Maurer, T AU - Maurer T FAU - Fung, H L AU - Fung HL LA - eng ID - HL 22273/HL/NHLBI PT - Journal Article CY - United States TA - AAPS PharmSci JID - 100897065 RN - 0 (Enzyme Inhibitors) RN - 50903-99-6 (NG-Nitroarginine Methyl Ester) RN - EC 1.14.13.39 (Nitric-Oxide Synthase) SB - IM MH - Algorithms MH - Animal MH - Cell Line MH - Comparative Study MH - Enzyme Inhibitors/pharmacology MH - Kinetics MH - Mice MH - Models, Biological MH - NG-Nitroarginine Methyl Ester/pharmacology MH - Nitric-Oxide Synthase/*antagonists & inhibitors/metabolism MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. EDAT- 2001/12/14 10:00 MHDA- 2002/01/30 10:01 PST - epublish SO - AAPS PharmSci 2000;2(1):E8. 346: Lee JM, et al. Detrended fluctuation analysi...[PMID:11738639]Related Articles, Books, LinkOut UI - 21600624 PMID- 11738639 DA - 20011212 DCOM- 20020226 IS - 0010-4825 VI - 32 IP - 1 DP - 2002 Jan TI - Detrended fluctuation analysis of EEG in sleep apnea using MIT/BIH polysomnography data. PG - 37-47 AB - A number of natural time series including electroencephalogram (EEG) show highly non-stationary characteristics in their behavior. We analyzed the EEG in sleep apnea that typically exhibits non-stationarity and long-range correlations by calculating its scaling exponents. Scaling exponents of the EEG dynamics are obtained by analyzing its fluctuation with detrended fluctuation analysis (DFA), which is suitable for non-stationary time series. We found the mean scaling exponents of EEG is discriminated according to Non-REM, REM (Rapid Eye Movement) and waken stage, and gradually increased from stage 1 to stage 2, 3 and 4. AD - Department of Biomedical Engineering, College of Medicine, Hanyang University Haengdang-dong, Seongdong-ku, 133-791, Seoul, South Korea. FAU - Lee, Jong Min AU - Lee JM FAU - Kim, Dae Jin AU - Kim DJ FAU - Kim, In Young AU - Kim IY FAU - Park, Kwang Suk AU - Park KS FAU - Kim, Sun I AU - Kim SI LA - eng PT - Journal Article CY - United States TA - Comput Biol Med JID - 1250250 SB - IM MH - Cerebral Cortex/physiopathology MH - Human MH - Mathematical Computing MH - Nonlinear Dynamics MH - *Polysomnography MH - *Signal Processing, Computer-Assisted MH - Sleep Apnea Syndromes/*diagnosis/physiopathology MH - Sleep Stages/physiology MH - Support, Non-U.S. Gov't EDAT- 2001/12/12 10:00 MHDA- 2002/02/28 10:01 AID - S0010482501000312 [pii] PST - ppublish SO - Comput Biol Med 2002 Jan;32(1):37-47. 347: Ferri R, et al. Non-linear EEG analysis in ch...[PMID:11738199]Related Articles, Books, LinkOut UI - 21600563 PMID- 11738199 DA - 20011212 DCOM- 20020212 IS - 1388-2457 VI - 112 IP - 12 DP - 2001 Dec TI - Non-linear EEG analysis in children with epilepsy and electrical status epilepticus during slow-wave sleep (ESES). PG - 2274-80 AB - OBJECTIVE: The objective of this work was to study the non-linear aspects of electroencephalography (EEG) in children with epilepsy and electrical status epilepticus during slow-wave sleep (ESES). METHODS: In this study, we recorded the sleep EEG in 5 subjects with ESES (4 males and one female, aged 6.5-10 years) who were also mentally retarded and affected by cerebral palsy (3 subjects) and hydrocephalus (two subjects). The signals were sampled at 128Hz and stored on hard disk. All the subsequent computational steps were performed on EEG epochs (4096 data points) selected from wakefulness and non-rapid eye movement (non-REM) (with ESES) or REM sleep. The dynamic properties of the EEG were assessed by means of the non-linear cross prediction (NLCP) test which uses 3 different 'model' time series in order to predict non-linearly the original data set (Pred, Ama and Tir). Pred is a measure of the predictability of the time series and Ama and Tir are measures of asymmetry, indicating non-linear structure. Moreover, the correlation dimension (D2) was estimated by means of the algorithm by for the epochs showing non-linear nature. RESULTS: The NLCP test provided evidence of significant non-linear dynamics in all epochs of non-REM sleep, when ESES was evident. Only during this stage, the possible presence of low-dimensional chaos could also be suspected (average D2=4.02; range 3.16-6.21). EEG without ESES could not be distinguished from linearly filtered noise. CONCLUSIONS: The results of the present study seem to indicate that subjects with ESES show a profound modification of their EEG dynamics with the occurrence, during sleep, of long periods characterized by non-linear dynamics and, probably, low-dimensional chaotic structure able to modify in a substantial way their brain functioning during sleep. AD - Sleep Research Center, Oasi Institute, Via Conte Ruggero 73, 94018, Troina, Italy. rferri@oasi.en.it FAU - Ferri, R AU - Ferri R FAU - Elia, M AU - Elia M FAU - Musumeci, S A AU - Musumeci SA FAU - Stam, C J AU - Stam CJ LA - eng PT - Journal Article CY - Netherlands TA - Clin Neurophysiol JID - 100883319 SB - IM MH - Child MH - *Electroencephalography MH - Epilepsy/*physiopathology MH - Female MH - Forecasting MH - Human MH - Male MH - *Nonlinear Dynamics MH - Sleep Stages/*physiology MH - Sleep, REM/physiology MH - Status Epilepticus/*physiopathology EDAT- 2001/12/12 10:00 MHDA- 2002/02/13 10:01 AID - S1388245701006769 [pii] PST - ppublish SO - Clin Neurophysiol 2001 Dec;112(12):2274-80. 348: Parthimos D, et al. Universal scaling properties ...[PMID:11736209]Related Articles, Books UI - 21604827 PMID- 11736209 DA - 20011213 DCOM- 20020329 LR - 20021029 IS - 1539-3755 VI - 64 IP - 6 Pt 1 DP - 2001 Dec TI - Universal scaling properties of type-I intermittent chaos in isolated resistance arteries are unaffected by endogenous nitric oxide synthesis. PG - 061906 AB - Spontaneous fluctuations in flow in isolated rabbit ear resistance arteries may exhibit almost-periodic behavior interrupted by chaotic bursts that can be classified as type-I Pomeau-Manneville intermittency. This conclusion was supported by the construction of parabolic return maps and identification of the characteristic probability distributions for the number of oscillations per laminar segment (n) associated with the type-I scenario. Pharmacological inhibition of nitric oxide (NO) synthesis by the vascular endothelium modulated the dynamics of the reinjection mechanism, and thus the generic shape of the probability distribution for n. Nevertheless, average laminar length was related to a derived bifurcation parameter varepsilon according to power-law scaling of the form approximately varepsilon(beta), where the estimated critical exponent beta was close to the theoretical value of -0.5 both in the presence and absence of NO synthesis. AD - Department of Diagnostic Radiology, Wales Heart Research Institute, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, Wales, United Kingdom. FAU - Parthimos, D AU - Parthimos D FAU - Edwards, D H AU - Edwards DH FAU - Griffith, T M AU - Griffith TM LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 RN - 10102-43-9 (Nitric Oxide) SB - IM MH - Animal MH - Biophysics MH - Ear/physiology MH - Models, Chemical MH - Models, Statistical MH - Nitric Oxide/*biosynthesis/*chemistry MH - Nonlinear Dynamics MH - Oscillometry MH - Rabbits MH - Support, Non-U.S. Gov't EDAT- 2001/12/12 10:00 MHDA- 2002/03/30 10:01 PHST- 2001/May/04 [received] PHST- 2001/Nov/20 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2001 Dec;64(6 Pt 1):061906. 349: de Vries G. Bursting as an emergent pheno...[PMID:11735975]Related Articles, Books UI - 21603532 PMID- 11735975 DA - 20011212 DCOM- 20020312 LR - 20021029 IS - 1539-3755 VI - 64 IP - 5 Pt 1 DP - 2001 Nov TI - Bursting as an emergent phenomenon in coupled chaotic maps. PG - 051914 AB - A two-dimensional map exhibiting chaotic bursting behavior similar to the bursting electrical activity observed in biological neurons and endocrine cells is examined. Model parameters are changed so that the bursting behavior is destroyed. We show that bursting can be recovered in a population of such nonbursting cells when they are coupled via the mean field. The phenomenon is explained with a geometric bifurcation analysis. The analysis reveals that emergent bursting in the network is due to coupling alone and is very robust to changes in the coupling strength, and that heterogeneity in the model parameters does not play a role. AD - Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2G1. devries@math.ualberta.ca FAU - de Vries, G AU - de Vries G LA - eng PT - Journal Article CY - United States TA - Phys Rev E Stat Nonlin Soft Matter Phys JID - 101136452 SB - IM MH - Biophysics MH - Electrophysiology MH - Endocrine Glands/physiology MH - Membrane Potentials MH - *Models, Biological MH - Models, Neurological MH - Neurons/physiology MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2001/12/12 10:00 MHDA- 2002/03/13 10:01 PHST- 2001/Jun/26 [received] PHST- 2001/Oct/25 [aheadofprint] PST - ppublish SO - Phys Rev E Stat Nonlin Soft Matter Phys 2001 Nov;64(5 Pt 1):051914. 350: Kvist EE, et al. Quantitative pharmacogenetics...[PMID:11735606]Related Articles, Books, LinkOut UI - 21594343 PMID- 11735606 DA - 20011207 DCOM- 20020307 LR - 20021101 IS - 0312-5963 VI - 40 IP - 11 DP - 2001 TI - Quantitative pharmacogenetics of nortriptyline: a novel approach. PG - 869-77 AB - OBJECTIVE: To quantitatively model nortriptyline clearance as a function of the cytochrome P450 (CYP) 2D6 genotype and to estimate the contribution of genotype to the interindividual variability in steady-state plasma concentration and metabolic clearance. DESIGN: Modelling study using data from two previously published studies. PARTICIPANTS: 20 healthy volunteers receiving single oral doses of nortriptyline and 20 patients with depression on steady-state oral treatment. METHODS: A total of 275 nortriptyline plasma concentrations were analysed by standard nonlinear regression and nonlinear mixed effect models. The pharmacokinetic model was a 1-compartment model with first order absorption and elimination. All participants had previously been genotyped with respect to the CYP2D6 polymorphism. RESULTS: A model in which the intrinsic clearance is a linear function of the number of functional CYP2D6 genes and hepatic blood flow is fixed to 60 L/h gave the closest fit of the pharmacokinetic model to the data. Stable estimates were obtained for population pharmacokinetic parameters and interindividual variances. Assuming 100% absorption, the model allows systemic clearance and bioavailability to be estimated. Bioavailability was found to vary between 0.17 and 0.71, depending on the genotype. Using the frequency distribution of CYP2D6 genotype with the above results we estimate that, in compliant Swedish individuals on nortriptyline monotherapy, the number of functional CYP2D6 genes could explain 21% of the total interindividual variance in oral clearance of nortriptyline and 34% of that in steady-state plasma concentrations. CONCLUSION: Nonlinear mixed-effects modelling can be used to quantify the influence of the number of functional CYP2D6 genes on the metabolic clearance and plasma concentration of drugs metabolised by this enzyme. Gene dose has a significant impact on drug pharmacokinetics and prior knowledge of it may aid in predicting plasma concentration of the drug and thus tailoring patient-specific dosage regimens. AD - Department of Medical Laboratory Sciences and Technology, Karolinska Institutet, Huddinge University Hospital, Stockholm, Sweden. FAU - Kvist, E E AU - Kvist EE FAU - Al-Shurbaji, A AU - Al-Shurbaji A FAU - Dahl, M L AU - Dahl ML FAU - Nordin, C AU - Nordin C FAU - Alvan, G AU - Alvan G FAU - Stahle, L AU - Stahle L LA - eng PT - Clinical Trial PT - Journal Article CY - New Zealand TA - Clin Pharmacokinet JID - 7606849 RN - 0 (Antidepressive Agents, Tricyclic) RN - 72-69-5 (Nortriptyline) RN - EC 1.14.14.1 (Cytochrome P-450 CYP2D6) SB - IM MH - Adolescent MH - Adult MH - Aged MH - Algorithms MH - Antidepressive Agents, Tricyclic/blood/*pharmacokinetics MH - Cytochrome P-450 CYP2D6/*genetics/metabolism MH - Genotype MH - Human MH - Male MH - Metabolic Clearance Rate MH - Middle Age MH - Models, Biological MH - Nonlinear Dynamics MH - Nortriptyline/blood/*pharmacokinetics MH - Support, Non-U.S. Gov't EDAT- 2001/12/12 10:00 MHDA- 2002/03/08 10:01 AID - 401105 [pii] PST - ppublish SO - Clin Pharmacokinet 2001;40(11):869-77. 351: Rome K, et al. Heel pad stiffness in runners...[PMID:11733128]Related Articles, Books, LinkOut UI - 21590272 PMID- 11733128 DA - 20011204 DCOM- 20020110 LR - 20021101 IS - 0268-0033 VI - 16 IP - 10 DP - 2001 Dec TI - Heel pad stiffness in runners with plantar heel pain. PG - 901-5 AB - OBJECTIVE: To evaluate significant differences in heel pad stiffness within a cohort of runners with diagnosed plantar heel pain and to explore the clinical importance of maximum heel pad stiffness values. DESIGN: A cross-sectional design was used to quantify the heel pad stiffness of 166 runners with 33 diagnosed with plantar heel pain. BACKGROUND: Palpation is still widely used to evaluate heel pad stiffness subjectively in everyday clinical practice. However, there is limited quantifiable data pertaining to heel pad stiffness measurements in runners and those with heel pain. METHODS: A portable hand-held device measured force applied by a metal probe, and its displacement into the plantar surface of the heel pad. Non-linear modelling allowed curve coefficients b0 and b1 to be evaluated and was described by an exponential function using a non-linear regression equation. Exploratory analysis was used to describe a single-point approximation for clinical use. RESULTS: An independent t-test demonstrated a statistically significant difference between the curve coefficient b1 (p<0.05). No significant difference was found for coefficient b0 between the plantar heel pain group and the non-plantar heel pain group (p>0.05). Exploratory analysis demonstrated maximum mean stiffness of 3.22 N/mm for the non-plantar heel pain group and 2.87 N/mm for the plantar heel pain-group, an 11% mean difference. CONCLUSION: The results suggested that heel pad stiffness may be associated with plantar heel pain subjects. RELEVANCE: Heel pad stiffness measurements may give a better insight into the mechanical properties of the heel pad in subjects with plantar heel pain. AD - Rehabilitation Research Unit, School of Health, University of Teesside, TS1 3BA, Middlesbrough, UK. k.rome@tees.ac.uk FAU - Rome, K AU - Rome K FAU - Webb, P AU - Webb P FAU - Unsworth, A AU - Unsworth A FAU - Haslock, I AU - Haslock I LA - eng PT - Clinical Trial PT - Controlled Clinical Trial PT - Journal Article CY - England TA - Clin Biomech (Bristol, Avon) JID - 8611877 SB - IM MH - Adolescent MH - Adult MH - Biomechanics MH - Cohort Studies MH - Comparative Study MH - Connective Tissue/pathology/*physiopathology MH - Cross-Sectional Studies MH - Female MH - Heel/anatomy & histology/*injuries/*physiopathology MH - Human MH - Male MH - Nonlinear Dynamics MH - Pain/*etiology MH - Pain Measurement MH - Probability MH - Risk Assessment MH - Running/*injuries MH - Stress, Mechanical MH - Weight-Bearing/physiology EDAT- 2001/12/06 10:00 MHDA- 2002/01/11 10:01 AID - S026800330100081X [pii] PST - ppublish SO - Clin Biomech (Bristol, Avon) 2001 Dec;16(10):901-5. 352: Miyoshi H, et al. Chaotic behavior in the locom...[PMID:11732198]Related Articles, Books, LinkOut UI - 21589651 PMID- 11732198 DA - 20011204 DCOM- 20020212 IS - 0033-183X VI - 216 IP - 1-2 DP - 2001 TI - Chaotic behavior in the locomotion of Amoeba proteus. PG - 66-70 AB - The locomotion of Amoeba proteus has been investigated by algorithms evaluating correlation dimension and Lyapunov spectrum developed in the field of nonlinear science. It is presumed by these parameters whether the random behavior of the system is stochastic or deterministic. For the analysis of the nonlinear parameters, n-dimensional time-delayed vectors have been reconstructed from a time series of periphery and area of A. proteus images captured with a charge-coupled-device camera, which characterize its random motion. The correlation dimension analyzed has shown the random motion of A. proteus is subjected only to 3-4 macrovariables, though the system is a complex system composed of many degrees of freedom. Furthermore, the analysis of the Lyapunov spectrum has shown its largest exponent takes positive values. These results indicate the random behavior of A. proteus is chaotic and deterministic motion on an attractor with low dimension. It may be important for the elucidation of the cell locomotion to take account of nonlinear interactions among a small number of dynamics such as the sol-gel transformation, the cytoplasmic streaming, and the relating chemical reaction occurring in the cell. AD - Department of Biological Sciences, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta 4259, Midoriku, Yokohama 226-8501, Japan. FAU - Miyoshi, H AU - Miyoshi H FAU - Kagawa, Y AU - Kagawa Y FAU - Tsuchiya, Y AU - Tsuchiya Y LA - eng PT - Journal Article CY - Austria TA - Protoplasma JID - 9806853 SB - IM MH - Algorithms MH - Amoeba/*physiology MH - Animal MH - Cell Movement/*physiology MH - Models, Biological MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Time Factors EDAT- 2001/12/06 10:00 MHDA- 2002/02/13 10:01 PST - ppublish SO - Protoplasma 2001;216(1-2):66-70. 353: Theraulaz G, et al. Model of droplet dynamics in ...[PMID:11732177]Related Articles, Books, LinkOut UI - 21589632 PMID- 11732177 DA - 20011204 DCOM- 20011217 IS - 0092-8240 VI - 63 IP - 6 DP - 2001 Nov TI - Model of droplet dynamics in the Argentine ant Linepithema Humile (Mayr). PG - 1079-93 AB - The formation of droplets of ants Linepithema humile (Mayr) is observed under certain experimental conditions: a fluctuating aggregate forms at the end of a rod and a droplet containing up to 40 ants eventually falls down. When the flux of incoming ants is sufficient, this process can continue for several hours, leading to the formation and fall of tens of droplets. Previous work indicates that the time series of drop-to-drop intervals may result from a nonlinear low-dimensional dynamics, and the interdrop increments exhibit long-range anticorrelations. A model of aggregation and droplet formation, based on experimental observations, is introduced and shown to reproduce these properties. AD - Laboratoire d'Ethologie et Cognition Animale, CNRS-ERS 2382, Universite Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex, France. theraula@cict.fr FAU - Theraulaz, G AU - Theraulaz G FAU - Bonabeau, E AU - Bonabeau E FAU - Sauwens, C AU - Sauwens C FAU - Deneubourg, J L AU - Deneubourg JL FAU - Lioni, A AU - Lioni A FAU - Libert, F AU - Libert F FAU - Passera, L AU - Passera L FAU - Sole, R AU - Sole R LA - eng PT - Journal Article CY - United States TA - Bull Math Biol JID - 0401404 SB - IM MH - Animal MH - Ants/*physiology MH - Computer Simulation MH - Female MH - France MH - Male MH - *Models, Biological MH - Nonlinear Dynamics MH - *Social Behavior MH - Support, Non-U.S. Gov't EDAT- 2001/12/06 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - Bull Math Biol 2001 Nov;63(6):1079-93. 354: Khoo MC. Respiratory instability and v...[PMID:11729933]Related Articles, Books, LinkOut UI - 21586405 PMID- 11729933 DA - 20011203 DCOM- 20020701 IS - 0065-2598 VI - 499 DP - 2001 TI - Respiratory instability and variability: why is respiration such a mess? A workshop summary. PG - 495-500 FAU - Khoo, M C AU - Khoo MC LA - eng PT - Journal Article CY - United States TA - Adv Exp Med Biol JID - 0121103 SB - IM MH - Biological Clocks/physiology MH - Circadian Rhythm MH - Human MH - Models, Biological MH - Models, Statistical MH - Nonlinear Dynamics MH - Pulmonary Ventilation/*physiology MH - Respiration MH - *Respiratory Physiology MH - Time Factors EDAT- 2001/12/04 10:00 MHDA- 2002/07/02 10:01 PST - ppublish SO - Adv Exp Med Biol 2001;499:495-500. 355: Martin P, et al. Compressive nonlinearity in t...[PMID:11724944]Related Articles, Free in PMC, Cited in PMC, Books, LinkOut UI - 21592994 PMID- 11724944 DA - 20011205 DCOM- 20020110 IS - 0027-8424 VI - 98 IP - 25 DP - 2001 Dec 4 TI - Compressive nonlinearity in the hair bundle's active response to mechanical stimulation. PG - 14386-91 AB - The auditory system's ability to interpret sounds over a wide range of amplitudes rests on the nonlinear responsiveness of the ear. Whether measured by basilar-membrane vibration, nerve-fiber activity, or perceived loudness, the ear is most sensitive to small signals and grows progressively less responsive as stimulation becomes stronger. Seeking a correlate of this behavior at the level of mechanoelectrical transduction, we examined the responses of hair bundles to direct mechanical stimulation. As reported by the motion of an attached glass fiber, an active hair bundle from the bullfrog's sacculus oscillates spontaneously. Sinusoidal movement of the fiber's base by as little as +/-1 nm, corresponding to the application at the bundle's top of a force of +/-0.3 pN, causes detectable phase-locking of the bundle's oscillations to the stimulus. Although entrainment increases as the stimulus grows, the amplitude of the hair-bundle movement does not rise until phase-locking is nearly complete. A bundle is most sensitive to stimulation at its frequency of spontaneous oscillation. Far from that frequency, the sensitivity of an active hair bundle resembles that of a passive bundle. Over most of its range, an active hair bundle's response grows as the one-third power of the stimulus amplitude; the bundle's sensitivity declines accordingly in proportion to the negative two-thirds power of the excitation. This scaling behavior, also found in the response of the mammalian basilar membrane to sound, signals the operation of an amplificatory process at the brink of an oscillatory instability, a Hopf bifurcation. AD - Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, 1230 York Avenue, New York, NY 10021-6399, USA. FAU - Martin, P AU - Martin P FAU - Hudspeth, A J AU - Hudspeth AJ LA - eng ID - DC00241/DC/NIDCD PT - Journal Article CY - United States TA - Proc Natl Acad Sci U S A JID - 7505876 SB - IM MH - Animal MH - Compressive Strength MH - Hair Cells/*physiology MH - Hearing/physiology MH - In Vitro MH - Models, Biological MH - Movement MH - Nonlinear Dynamics MH - Oscillometry MH - Rana catesbeiana/physiology MH - Stress, Mechanical MH - Support, U.S. Gov't, P.H.S. EDAT- 2001/11/29 10:00 MHDA- 2002/01/11 10:01 PHST- 2001/Nov/27 [aheadofprint] AID - 10.1073/pnas.251530498 [doi] AID - 251530498 [pii] PST - ppublish SO - Proc Natl Acad Sci U S A 2001 Dec 4;98(25):14386-91. 356: Frangakis AS, et al. Noise reduction in electron t...[PMID:11722164]Related Articles, Books, LinkOut UI - 21580128 PMID- 11722164 DA - 20011127 DCOM- 20020325 IS - 1047-8477 VI - 135 IP - 3 DP - 2001 Sep TI - Noise reduction in electron tomographic reconstructions using nonlinear anisotropic diffusion. PG - 239-50 AB - Electron tomography is a powerful technique capable of giving unique insights into the three-dimensional structural organization of pleomorphic biological objects. However, visualization and interpretation of the resulting volumetric data are hampered by an extremely low signal-to-noise ratio, especially when ice-embedded biological specimens are investigated. Usually, isosurface representation or volume rendering of such data is hindered without any further signal enhancement. We propose a novel technique for noise reduction based on nonlinear anisotropic diffusion. The approach combines efficient noise reduction with excellent signal preservation and is clearly superior to conventional methods (e.g., low-pass and median filtering) and invariant wavelet transform filtering. The gain in the signal-to-noise ratio is verified and demonstrated by means of Fourier shell correlation. Improved visualization performance after processing the 3D images is demonstrated with two examples, tomographic reconstructions of chromatin and of a mitochondrion. Parameter settings and discretization stencils are presented in detail. CI - (c)2001 Elsevier Science. AD - Max-Planck-Institut fur Biochemie, Am Klopferspitz 18a, Martinsried, D-82152, Germany. FAU - Frangakis, A S AU - Frangakis AS FAU - Hegerl, R AU - Hegerl R LA - eng PT - Journal Article CY - United States TA - J Struct Biol JID - 9011206 RN - 0 (Chromatin) RN - 0 (Macromolecular Systems) SB - IM MH - Anisotropy MH - Chromatin/chemistry/ultrastructure MH - Diffusion MH - Image Processing, Computer-Assisted/*methods/statistics & numerical data MH - Macromolecular Systems MH - Models, Molecular MH - Molecular Structure MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Tomography/*methods/statistics & numerical data EDAT- 2001/11/28 10:00 MHDA- 2002/03/26 10:01 AID - 10.1006/jsbi.2001.4406 [doi] AID - S1047847701944065 [pii] PST - ppublish SO - J Struct Biol 2001 Sep;135(3):239-50. 357: Grozinger M, et al. Neural net classification of ...[PMID:11721988]Related Articles, Books, LinkOut UI - 21578597 PMID- 11721988 DA - 20011127 DCOM- 20020409 IS - 0340-1200 VI - 85 IP - 5 DP - 2001 Nov TI - Neural net classification of REM sleep based on spectral measures as compared to nonlinear measures. PG - 335-41 AB - In various studies the implementation of nonlinear and nonconventional measures has significantly improved EEG (electroencephalogram) analyses as compared to using conventional parameters alone. A neural network algorithm well approved in our laboratory for the automatic recognition of rapid eye movement (REM) sleep was investigated in this regard. Originally based on a broad range of spectral power inputs, we additionally supplied the nonlinear measures of the largest Lyapunov exponent and correlation dimension as well as the nonconventional stochastic measures of spectral entropy and entropy of amplitudes. No improvement in the detection of REM sleep could be achieved by the inclusion of the new measures. The accuracy of the classification was significantly worse, however, when supplied with these variables alone. In view of results demonstrating the efficiency of nonconventional measures in EEG analysis, the benefit appears to depend on the nature of the problem. AD - Department of Psychiatry, University of Mainz, Germany. groezing@mail.uni-mainz.de FAU - Grozinger, M AU - Grozinger M FAU - Fell, J AU - Fell J FAU - Roschke, J AU - Roschke J LA - eng PT - Journal Article CY - Germany TA - Biol Cybern JID - 7502533 SB - IM MH - Adult MH - Algorithms MH - *Electroencephalography MH - Entropy MH - Human MH - Male MH - *Neural Networks (Computer) MH - Nonlinear Dynamics MH - Sleep, REM/*physiology MH - Support, Non-U.S. Gov't EDAT- 2001/11/28 10:00 MHDA- 2002/04/18 10:01 PST - ppublish SO - Biol Cybern 2001 Nov;85(5):335-41. 358: Christini DJ, et al. The role of nonlinear dynamic...[PMID:11720623]Related Articles, Cited in PMC, Books, LinkOut UI - 21577867 PMID- 11720623 DA - 20011126 DCOM- 20011214 IS - 1521-737X VI - 1 IP - 4 DP - 1999 Sep-Oct TI - The role of nonlinear dynamics in cardiac arrhythmia control. PG - 190-200 AB - The field of nonlinear dynamics has made important contributions toward a mechanistic understanding of cardiac arrhythmias. In recent years, many of these advancements have been in the area of arrhythmia control. This paper reviews the literature on analytical, modeling, and experimental nonlinear dynamical arrhythmia control with a focus on stimulation and pharmacologic techniques that have been developed, and in some cases used in experiments, to control reentrant rhythms (including spiral and scroll waves) and fibrillation. Although such approaches currently have practical limitations, they offer hope that nonlinear dynamical control techniques will be clinically useful in the coming years. AD - Division of Cardiology, Department of Medicine, Cornell University Medical College, New York, NY 10021, USA. FAU - Christini, D J AU - Christini DJ FAU - Stein, K M AU - Stein KM FAU - Markowitz, S M AU - Markowitz SM FAU - Mittal, S AU - Mittal S FAU - Slotwiner, D J AU - Slotwiner DJ FAU - Lerman, B B AU - Lerman BB LA - eng ID - R01 HL56139/HL/NHLBI PT - Journal Article CY - United States TA - Heart Dis JID - 100887299 SB - IM MH - Animal MH - Arrhythmia/*prevention & control MH - Human MH - *Nonlinear Dynamics MH - Support, U.S. Gov't, P.H.S. EDAT- 2001/11/27 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - Heart Dis 1999 Sep-Oct;1(4):190-200. 359: Hongxuan Z, et al. Qualitative chaos analysis fo...[PMID:11719075]Related Articles, Books, LinkOut UI - 21576390 PMID- 11719075 DA - 20011123 DCOM- 20020122 IS - 1350-4533 VI - 23 IP - 8 DP - 2001 Oct TI - Qualitative chaos analysis for ventricular tachycardia and fibrillation based on symbolic complexity. PG - 523-8 AB - Ventricular fibrillation (VF) is one of the most serious malignant arrhythmias, usually resulting from immediate degeneration of ventricular tachycardia (VT). The surrogate data test (SDT) has been employed in the qualitative detection and analysis of cardiac chaos. Unfortunately, the current SDT method, based on the GP (Grassberger and Procaccia) algorithm, may not be suitable for the analysis of VF rhythm, which has been shown to be a high-dimensional signal. This paper proposes a novel qualitative analysis method based on symbolic dynamics for chaotic systems: the complexity dispersity method. Compared with the GP algorithm, our qualitative complexity method demonstrates better analytical accuracy and robustness and requires less data points (5 seconds vs 20 seconds). When used in the analysis of experimental data, our method achieved 100% accuracy in the detection of cardiac pathology for VT and VF. AD - Department of Biomedical Engineering, College of Life Science and Biotechnology, Shanghai Jiao Tong University, 200030, Shanghai, PR China. zhanghx@bme.sjtu.edu.cn FAU - Hongxuan, Z AU - Hongxuan Z FAU - Yisheng, Z AU - Yisheng Z LA - eng PT - Journal Article CY - England TA - Med Eng Phys JID - 9422753 SB - IM MH - Algorithms MH - Animal MH - Defibrillators, Implantable MH - Dogs MH - Models, Statistical MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Tachycardia, Ventricular/*pathology MH - Ventricular Fibrillation/*pathology EDAT- 2001/11/24 10:00 MHDA- 2002/01/23 10:01 AID - S1350453301000807 [pii] PST - ppublish SO - Med Eng Phys 2001 Oct;23(8):523-8. 360: Torrens F. A new topological index to el...[PMID:11718476]Related Articles, Books, LinkOut UI - 21574977 PMID- 11718476 DA - 20011122 DCOM- 20020506 IS - 0920-654X VI - 15 IP - 8 DP - 2001 Aug TI - A new topological index to elucidate apolar hydrocarbons. PG - 709-19 AB - A new topological charge-transfer index is applied to elucidate the polar character of hydrocarbons. The dipole moments calculated by algebraic and vector semisums of charge-transfer indices are defined in this work. The combination of the charge-transfer indices allows the estimation of the molecular dipole moments. The ability of the indices for the description of the molecular charge distribution is established by comparing them with the dipole moment of a heterogeneous set of 57 polar and 53 apolar hydrocarbons. Linear and nonlinear correlation models are obtained. The new charge-transfer index, mu(vec), elucidates whether hydrocarbons are apolar, and improves the multivariable nonlinear regression equation for the dipole moment. When comparing with previous results, smaller superpositions of the corresponding pairs Gk, Jk are observed in our fits. This diminishes the risk of colinearity. AD - Institut Universitari de Ciencia Molecular, Universitat de Valencia, Burjassot, Spain. Francisco.Torrens@uv.es FAU - Torrens, F AU - Torrens F LA - eng PT - Journal Article CY - Netherlands TA - J Comput Aided Mol Des JID - 8710425 RN - 0 (Hydrocarbons) SB - IM MH - Drug Design MH - Electrostatics MH - Hydrocarbons/*chemistry MH - Linear Models MH - Models, Chemical MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2001/11/23 10:00 MHDA- 2002/05/07 10:01 PST - ppublish SO - J Comput Aided Mol Des 2001 Aug;15(8):709-19. 361: Murray AF. Novelty detection using produ...[PMID:11718424]Related Articles, Books, LinkOut UI - 21574925 PMID- 11718424 DA - 20011122 DCOM- 20020418 IS - 0893-6080 VI - 14 IP - 9 DP - 2001 Nov TI - Novelty detection using products of simple experts--a potential architecture for embedded systems. PG - 1257-64 AB - The 'Product of Experts' architecture (concentrating on binary-stochastic elements) is described in the context of its suitability for implementation as mixed-mode hardware, with algorithmic modifications that render the training procedure hardware-implementable. Results show that the PoE is capable of modelling non-linear, multi-dimensional data drawn from both artificial and real sources. The capability of the PoE to perform on-line novelty detection is described and demonstrated on both artificial and real data. AD - Department of Electronics and Electrical Engineering, University of Edinburgh, Scotland, UK. a.f.murray@ee.ed.ac.uk FAU - Murray, A F AU - Murray AF LA - eng PT - Journal Article CY - United States TA - Neural Netw JID - 8805018 SB - IM MH - *Algorithms MH - *Neural Networks (Computer) MH - *Nonlinear Dynamics MH - Signal Processing, Computer-Assisted MH - Statistics/methods MH - *Stochastic Processes EDAT- 2001/11/23 10:00 MHDA- 2002/04/19 10:01 PST - ppublish SO - Neural Netw 2001 Nov;14(9):1257-64. 362: Ishii S, et al. Reconstruction of chaotic dyn...[PMID:11718423]Related Articles, Books, LinkOut UI - 21574924 PMID- 11718423 DA - 20011122 DCOM- 20020418 IS - 0893-6080 VI - 14 IP - 9 DP - 2001 Nov TI - Reconstruction of chaotic dynamics by on-line EM algorithm. PG - 1239-56 AB - In this paper, we discuss the reconstruction of chaotic dynamics by using a normalized Gaussian network (NGnet), which is a network of local linear regression units. The NGnet is trained by an on-line EM algorithm in order to learn the vector field of the chaotic dynamics. We investigate the robustness of our approach to two kinds of noise processes: system noise and observation noise. System noise disturbs the system dynamics itself. Observation noise is added when the state variables are observed. It is shown that the trained NGnet is able to reproduce a chaotic attractor, which approximates the complexity and instability of the original chaotic attractor well, even under various noise conditions. The trained NGnet also shows good prediction performance. When only part of the dynamical variables are observed, the delay embedding method is used. The NGnet is then trained to learn the vector field in the delay coordinate space. Experiments show that the chaotic dynamics embedded in the delay coordinate space is able to be learned under the two types of noise. AD - Nara Institute of Science and Technology, Ikoma-shi, Japan. ishii@is.aist-nara.ac.jp FAU - Ishii, S AU - Ishii S FAU - Sato, M A AU - Sato MA LA - eng PT - Journal Article CY - United States TA - Neural Netw JID - 8805018 SB - IM MH - *Algorithms MH - Artifacts MH - *Neural Networks (Computer) MH - *Nonlinear Dynamics MH - Normal Distribution EDAT- 2001/11/23 10:00 MHDA- 2002/04/19 10:01 PST - ppublish SO - Neural Netw 2001 Nov;14(9):1239-56. 363: Talukder A, et al. A closed-form neural network ...[PMID:11718421]Related Articles, Books, LinkOut UI - 21574922 PMID- 11718421 DA - 20011122 DCOM- 20020418 IS - 0893-6080 VI - 14 IP - 9 DP - 2001 Nov TI - A closed-form neural network for discriminatory feature extraction from high-dimensional data. PG - 1201-18 AB - We consider a new neural network for data discrimination in pattern recognition applications. We refer to this as a maximum discriminating feature (MDF) neural network. Its weights are obtained in closed-form, thereby overcoming problems associated with other nonlinear neural networks. It uses neuron activation functions that are dynamically chosen based on the application. It is theoretically shown to provide nonlinear transforms of the input data that are more general than those provided by other nonlinear multilayer perceptron neural network and support-vector machine techniques for cases involving high-dimensional (image) inputs where training data are limited and the classes are not linearly separable. We experimentally verify this on synthetic examples. AD - Jet Propulsion Laboratory/California Institute of Technology, Pasadena 91109, USA. FAU - Talukder, A AU - Talukder A FAU - Casasent, D AU - Casasent D LA - eng PT - Journal Article CY - United States TA - Neural Netw JID - 8805018 SB - IM MH - Algorithms MH - Animal MH - Brain/*physiology MH - Human MH - Image Processing, Computer-Assisted/instrumentation/*methods MH - *Neural Networks (Computer) MH - Neurons/physiology MH - *Nonlinear Dynamics MH - Pattern Recognition, Visual/physiology MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2001/11/23 10:00 MHDA- 2002/04/19 10:01 PST - ppublish SO - Neural Netw 2001 Nov;14(9):1201-18. 364: Oussar Y, et al. How to be a gray box: dynamic...[PMID:11718417]Related Articles, Books, LinkOut UI - 21574918 PMID- 11718417 DA - 20011122 DCOM- 20020418 IS - 0893-6080 VI - 14 IP - 9 DP - 2001 Nov TI - How to be a gray box: dynamic semi-physical modeling. PG - 1161-72 AB - A general methodology for gray-box, or semi-physical, modeling is presented. This technique is intended to combine the best of two worlds: knowledge-based modeling, whereby mathematical equations are derived in order to describe a process, based on a physical (or chemical, biological, etc.) analysis, and black-box modeling, whereby a parameterized model is designed, whose parameters are estimated solely from measurements made on the process. The gray-box modeling technique is very valuable whenever a knowledge-based model exists, but is not fully satisfactory and cannot be improved by further analysis (or can only be improved at a very large computational cost). We describe the design methodology of a gray-box model, and illustrate it on a didactic example. We emphasize the importance of the choice of the discretization scheme used for transforming the differential equations of the knowledge-based model into a set of discrete-time recurrent equations. Finally, an application to a real, complex industrial process is presented. AD - Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris, Laboratoire d'Electronique, France. yacine.oussar@espci.fr FAU - Oussar, Y AU - Oussar Y FAU - Dreyfus, G AU - Dreyfus G LA - eng PT - Journal Article CY - United States TA - Neural Netw JID - 8805018 SB - IM MH - *Algorithms MH - *Neural Networks (Computer) MH - Nonlinear Dynamics MH - Physics EDAT- 2001/11/23 10:00 MHDA- 2002/04/19 10:01 PST - ppublish SO - Neural Netw 2001 Nov;14(9):1161-72. 365: Felici F, et al. Effect of human exposure to a...[PMID:11718277]Related Articles, Books, LinkOut UI - 21574778 PMID- 11718277 DA - 20011122 DCOM- 20020409 LR - 20020610 IS - 1439-6319 VI - 85 IP - 6 DP - 2001 Oct TI - Effect of human exposure to altitude on muscle endurance during isometric contractions. PG - 507-12 AB - The aim of this study was to evaluate the influence of exposure to altitude on muscle endurance during isometric contractions. Six sedentary subjects were studied. Surface electromyograph (sEMG) activity was recorded from the right biceps brachii (BB) during exhausting isometric exercise at 80% maximal voluntary contraction. Experiments were performed before, during and 6 months after a 12 day stay at the EV-K2 laboratory (Nepal, 5,050 m above sea level). From the sEMG signals from BB, the median frequencies (fmed) were computed for consecutive 1 s epochs. The sEMG was also analysed using a non-linear tool, the recurrence quantification analysis, and the percentage of determinism (%DET) was then calculated. The haemoglobin saturation significantly decreased at altitude. The mean (SD) BB endurance time decreased from 22.4 (4) s to 18.3 (4.7) s (P < 0.05). After exposure to altitude a significant variation in fmed and %DET slopes was observed. We concluded that during the first period of acclimatisation at altitude there was an impairment of isometric muscle endurance performance and there was also evidence of a modified myoelectric activity pattern suggesting a greater fatigability of the neuromuscular system. AD - University Institute of Motor Sciences, Faculty of Motor Sciences, Laboratory of Exercise Physiology, Rome, Italy. francesco.felici@uniromal.it FAU - Felici, F AU - Felici F FAU - Rosponi, A AU - Rosponi A FAU - Sbriccoli, P AU - Sbriccoli P FAU - Scarcia, M AU - Scarcia M FAU - Bazzucchi, I AU - Bazzucchi I FAU - Iannattone, M AU - Iannattone M LA - eng PT - Journal Article CY - Germany TA - Eur J Appl Physiol JID - 100954790 SB - IM SB - S MH - Adult MH - *Altitude MH - Electromyography MH - Human MH - Isometric Contraction/*physiology MH - Male MH - Muscle Fatigue/physiology MH - Nonlinear Dynamics MH - Physical Endurance/*physiology MH - Support, Non-U.S. Gov't EDAT- 2001/11/23 10:00 MHDA- 2002/04/18 10:01 PST - ppublish SO - Eur J Appl Physiol 2001 Oct;85(6):507-12. 366: Solodovnikov A, et al. Robustness of a neural networ...[PMID:11717532]Related Articles, Books, LinkOut UI - 21574208 PMID- 11717532 DA - 20011121 DCOM- 20020201 IS - 0929-5313 VI - 11 IP - 2 DP - 2001 Sep-Oct TI - Robustness of a neural network model for differencing. PG - 165-73 AB - A neural network, originally proposed as a model for nuclei in the auditory brainstem, uses gradients of cell thresholds to reliably compute the difference of inputs over wide input ranges. The encoding of difference is linear even though the individual components of the network are finite, saturating, nonlinear devices highly dependent on input level. Theorems are proven that explain the linear dependence of network output on difference and that show the robustness of the network to perturbations of the threshold gradients. There is some evidence that the network exists in the neural tissue of the auditory brainstem. AD - Department of Mathematics, Duke University, Durham, NC 27708, USA. FAU - Solodovnikov, A AU - Solodovnikov A FAU - Reed, M C AU - Reed MC LA - eng PT - Journal Article CY - United States TA - J Comput Neurosci JID - 9439510 SB - IM MH - Action Potentials/physiology MH - Animal MH - Auditory Pathways/*physiology MH - Brain Stem/cytology/*physiology MH - Cochlear Nucleus/physiology MH - Human MH - Laterality/physiology MH - Models, Neurological MH - Nerve Net/*physiology MH - Neural Inhibition/physiology MH - Neural Networks (Computer) MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Olivary Nucleus/physiology MH - Reproducibility of Results MH - Sound Localization/*physiology MH - Support, U.S. Gov't, Non-P.H.S. MH - Synaptic Transmission/*physiology EDAT- 2001/11/22 10:00 MHDA- 2002/02/02 10:01 PST - ppublish SO - J Comput Neurosci 2001 Sep-Oct;11(2):165-73. 367: Herrmann A, et al. Noise and the PSTH response t...[PMID:11717530]Related Articles, Books, LinkOut UI - 21574206 PMID- 11717530 DA - 20011121 DCOM- 20020201 IS - 0929-5313 VI - 11 IP - 2 DP - 2001 Sep-Oct TI - Noise and the PSTH response to current transients: I. General theory and application to the integrate-and-fire neuron. PG - 135-51 AB - An analytical model is proposed that can predict the shape of the poststimulus time histogram (PSTH) response to a current pulse of a neuron subjected to uncorrelated background input. The model is based on an explicit description of noise in the form of an escape rate and corresponding hazard function. Two forms of the model are presented. The full model is nonlinear and can be integrated numerically, while the linearized version can be solved analytically. In the linearized version, the PSTH response to a current input is proportional to a filtered version of the input pulse. The bandwidth of the filter is determined by the amount of noise. In the limit of high noise, the response is similar to the time course of the potential induced by the input pulse, while for low noise it is proportional to its derivative. For low noise, a second peak occurs after one mean interval. The full nonlinear model predicts an asymmetry between excitatory and inhibitory current inputs. We compare our results with simulations of the integrate-and-fire model with stochastic background input. We predict that changes in PSTH shape due to noise should be observable in many types of neurons in both subthreshold and suprathreshold regimes. AD - Laboratory of Computational Neuroscience, Swiss Federal Institute of Technology, EPFL-DI, CH-1015 Lausanne-EPFL, Switzerland. alix.herrmann@epfl.ch FAU - Herrmann, A AU - Herrmann A FAU - Gerstner, W AU - Gerstner W LA - eng PT - Journal Article CY - United States TA - J Comput Neurosci JID - 9439510 RN - 0 (Ion Channels) SB - IM MH - Action Potentials/*physiology MH - Algorithms MH - Animal MH - Cell Membrane/physiology MH - Central Nervous System/*physiology MH - Electricity/adverse effects MH - Excitatory Postsynaptic Potentials/*physiology MH - Human MH - Ion Channels/physiology MH - Linear Models MH - Models, Neurological MH - Neural Inhibition/*physiology MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Normal Distribution MH - Synaptic Transmission/*physiology EDAT- 2001/11/22 10:00 MHDA- 2002/02/02 10:01 PST - ppublish SO - J Comput Neurosci 2001 Sep-Oct;11(2):135-51. 368: Oie KS, et al. Human multisensory fusion of ...[PMID:11716976]Related Articles, Books, LinkOut UI - 21574480 PMID- 11716976 DA - 20011121 DCOM- 20020123 IS - 0304-3940 VI - 315 IP - 3 DP - 2001 Nov 27 TI - Human multisensory fusion of vision and touch: detecting non-linearity with small changes in the sensory environment. PG - 113-6 AB - Previous investigations using relatively large amplitude sensory stimuli or complete removal of sensory input have demonstrated non-linear processing of sensory information for postural control. In the present study, we asked whether a linear range of sensory fusion exists when smaller amplitude stimuli are used. The amplitudes of visual and somatosensory input were simultaneously co-varied within a trial. The postural responses were characterized by analyzing how the Fourier transform of postural sway at the driving frequency varied with sensory movement amplitudes. If the postural control system is linear with constant weighting of sensory inputs, then the pattern of Fourier transforms should be a linear function of movement amplitude. However, in 28 of 58 trials we observed non-linearity in this function. The results clearly show that even at very small amplitudes of sensory change, the nervous system processes multisensory information in a non-linear fashion. AD - Program in Neuroscience & Cognitive Science and the Department of Kinesiology, University of Maryland, College Park, MD, USA. FAU - Oie, K S AU - Oie KS FAU - Kiemel, T AU - Kiemel T FAU - Jeka, J J AU - Jeka JJ LA - eng PT - Journal Article CY - Ireland TA - Neurosci Lett JID - 7600130 SB - IM MH - Fourier Analysis MH - Human MH - *Nonlinear Dynamics MH - Posture/physiology MH - Touch/*physiology MH - Vision/*physiology EDAT- 2001/11/22 10:00 MHDA- 2002/01/24 10:01 AID - S0304394001023485 [pii] PST - ppublish SO - Neurosci Lett 2001 Nov 27;315(3):113-6. 369: Wu Q, et al. Determination of release and ...[PMID:11716947]Related Articles, Books, LinkOut UI - 21574356 PMID- 11716947 DA - 20011121 DCOM- 20020208 IS - 0165-0270 VI - 112 IP - 2 DP - 2001 Dec 15 TI - Determination of release and uptake parameters from electrically evoked dopamine dynamics measured by real-time voltammetry. PG - 119-33 AB - Quantifying mechanisms underlying extracellular signaling by the neurotransmitter dopamine (DA) is a difficult task, particularly in the complex extracellular microenvironment of the intact brain. In this study, two methods for evaluating release and uptake from DA dynamics monitored by real-time voltammetry are described. Both are based on a neurochemical model characterizing electrically evoked levels of DA as a balance between these opposing mechanisms. The theoretical basis of what is called here nonlinear regression and single curve analyses is given. Fitting simulated data tests the reliability of the methods. The two analyses are also compared with an experimental data set describing the effects of pharmacologically inhibiting the DA transporter in the caudate-putamen (CP) and nucleus accumbens (NAc). The results indicate that nonlinear regression and single curve analyses are suitable for quantifying release and uptake mechanisms underlying DA neurotransmission. Additionally, the most important experimental finding of this technical study was the independent confirmation of high affinity (approximately 0.2 microM) DA uptake in the intact striatum. AD - Department of Biological Sciences, Cellular and Integrative Physiology Section, Illinois State University, 244 SLB, Normal, IL 61790, USA. FAU - Wu, Q AU - Wu Q FAU - Reith, M E AU - Reith ME FAU - Wightman, R M AU - Wightman RM FAU - Kawagoe, K T AU - Kawagoe KT FAU - Garris, P A AU - Garris PA LA - eng ID - DA 08379/DA/NIDA ID - NS 15841/NS/NINDS ID - NS 35298/NS/NINDS PT - Journal Article CY - Netherlands TA - J Neurosci Methods JID - 7905558 RN - 0 (Dopamine Uptake Inhibitors) RN - 0 (Membrane Transport Proteins) RN - 0 (dopamine-binding protein) RN - 24526-64-5 (Nomifensine) RN - 50-36-2 (Cocaine) RN - 51-61-6 (Dopamine) SB - IM MH - Action Potentials/drug effects/physiology MH - Animal MH - Cocaine/pharmacology MH - Corpus Striatum/drug effects/*metabolism MH - Dopamine/*metabolism/pharmacology/secretion MH - Dopamine Uptake Inhibitors/pharmacology MH - Electric Stimulation/instrumentation/methods MH - Electrophysiology/instrumentation/*methods MH - Extracellular Space/drug effects/metabolism MH - Kinetics MH - Male MH - Membrane Transport Proteins/antagonists & inhibitors/metabolism MH - *Models, Neurological MH - Neostriatum/drug effects/metabolism MH - Nomifensine/pharmacology MH - Nonlinear Dynamics MH - Nucleus Accumbens/drug effects/metabolism MH - Presynaptic Terminals/drug effects/*metabolism MH - Rats MH - Rats, Sprague-Dawley MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. MH - Synaptic Transmission/drug effects/*physiology EDAT- 2001/11/22 10:00 MHDA- 2002/02/09 10:01 AID - S0165027001004599 [pii] PST - ppublish SO - J Neurosci Methods 2001 Dec 15;112(2):119-33. 370: Gefen A, et al. In vivo biomechanical behavio...[PMID:11716870]Related Articles, Books, LinkOut UI - 21574199 PMID- 11716870 DA - 20011121 DCOM- 20020111 IS - 0021-9290 VI - 34 IP - 12 DP - 2001 Dec TI - In vivo biomechanical behavior of the human heel pad during the stance phase of gait. PG - 1661-5 AB - A technique is introduced for simultaneous measurements of the heel pad tissue deformation and the heel-ground contact stresses developing during the stance phase of gait. Subjects walked upon a gait platform integrating the contact pressure display optical method for plantar pressure measurements and a digital radiographic fluoroscopy system for skeletal and soft tissue motion recording. Clear images of the posterior-plantar aspect of the calcaneus and enveloping soft tissues were obtained simultaneously with the pressure distribution under the heel region throughout the stance phase of gait. The heel pad was shown to undergo a rapid compression during initial contact and heel strike, reaching a strain of 0.39 +/- 0.05 in about 150 ms. The stress-strain relation of the heel pad was shown to be highly non-linear, with a compression modulus of 105 +/- 11 kPa initially and 306 +/- 16 kPa at 30% strain. The energy dissipation during heel strike was evaluated to be 17.8+/-0.8%. The present technique is useful for biomechanical as well as clinical evaluation of the stress-strain and energy absorption characteristics of the heel pad in vivo, during natural gait. AD - Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel. gefen@eng.tau.ac.il FAU - Gefen, A AU - Gefen A FAU - Megido-Ravid, M AU - Megido-Ravid M FAU - Itzchak, Y AU - Itzchak Y LA - eng PT - Journal Article CY - United States TA - J Biomech JID - 0157375 SB - IM MH - Adult MH - Biomechanics MH - Female MH - Gait/*physiology MH - Heel/*physiology MH - Human MH - Models, Biological MH - Nonlinear Dynamics MH - Pressure MH - Stress, Mechanical EDAT- 2001/11/22 10:00 MHDA- 2002/01/12 10:01 AID - S0021929001001439 [pii] PST - ppublish SO - J Biomech 2001 Dec;34(12):1661-5. 371: Soetanto D, et al. Stabilization of human standi...[PMID:11716861]Related Articles, Books, LinkOut UI - 21574190 PMID- 11716861 DA - 20011121 DCOM- 20020111 IS - 0021-9290 VI - 34 IP - 12 DP - 2001 Dec TI - Stabilization of human standing posture using functional neuromuscular stimulation. PG - 1589-97 AB - Functional neuromuscular stimulation (FNS)/functional electrical stimulation (FES) is a potential way to restore some functionality to the limbs of patients with spinal cord injury through direct/indirect stimulation of the motoneuron. One of the constraints for wider use of FNS on paraplegic patients is the lack of efficient control algorithm. Most of the published works on FNS/FES control are based on oversimplified models of human body dynamics. An innovative control strategy for stabilizing the standing posture of paraplegic patients is proposed here which is a combination of a proportional-plus-derivative controller for motions of the skeletal system and a control action prediction mechanism to produce musculotendon activation. The goal is to produce musculotendon torque which can approximate those demanded by the controller for the skeletal system. In computer simulations, using a detailed skeletal-musculotendon-muscle activation dynamics model of human body, this FNS/FES control approach can stabilize a paraplegic patient's standing posture with the minimum number of musculotendon groups. Also, it is found that this control strategy can maintain stability even in the presence of reasonable variations in the controller's musculotendon parameters. AD - Instituto de Sistemas e Robotica, Lisboa, Portugal. didik@isr.isr.ist.utl.pt FAU - Soetanto, D AU - Soetanto D FAU - Kuo, C Y AU - Kuo CY FAU - Babic, D AU - Babic D LA - eng PT - Journal Article CY - United States TA - J Biomech JID - 0157375 SB - IM MH - Computer Simulation MH - Electric Stimulation MH - Human MH - Models, Biological MH - Neuromuscular Junction/*physiopathology MH - Nonlinear Dynamics MH - Paraplegia/*physiopathology MH - Posture/*physiology EDAT- 2001/11/22 10:00 MHDA- 2002/01/12 10:01 AID - S0021929001001440 [pii] PST - ppublish SO - J Biomech 2001 Dec;34(12):1589-97. 372: Oliveira GM, et al. Definition and application of...[PMID:11712957]Related Articles, Books, LinkOut UI - 21569795 PMID- 11712957 DA - 20011119 DCOM- 20020103 IS - 1064-5462 VI - 7 IP - 3 DP - 2001 Summer TI - Definition and application of a five-parameter characterization of one-dimensional cellular automata rule space. PG - 277-301 AB - Cellular automata (CA) are important as prototypical, spatially extended, discrete dynamical systems. Because the problem of forecasting dynamic behavior of CA is undecidable, various parameter-based approximations have been developed to address the problem. Out of the analysis of the most important parameters available to this end we proposed some guidelines that should be followed when defining a parameter of that kind. Based upon the guidelines, new parameters were proposed and a set of five parameters was selected; two of them were drawn from the literature and three are new ones, defined here. This article presents all of them and makes their qualities evident. Then, two results are described, related to the use of the parameter set in the Elementary Rule Space: a phase transition diagram, and some general heuristics for forecasting the dynamics of one-dimensional CA. Finally, as an example of the application of the selected parameters in high cardinality spaces, results are presented from experiments involving the evolution of radius-3 CA in the Density Classification Task, and radius-2 CA in the Synchronization Task. AD - Universidade Presbiteriana Mackenzie, Rua da Consolacao 896, 01302-907 Sao Paulo, Brazil. gina@mackenzie.com.br FAU - Oliveira, G M AU - Oliveira GM FAU - de Oliveira, P P AU - de Oliveira PP FAU - Omar, N AU - Omar N LA - eng PT - Journal Article CY - United States TA - Artif Life JID - 9433814 SB - IM MH - *Cells MH - Mathematical Computing MH - *Models, Theoretical MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2001/11/20 10:00 MHDA- 2002/01/05 10:01 AID - 10.1162/106454601753238645 [doi] PST - ppublish SO - Artif Life 2001 Summer;7(3):277-301. 373: Isaeva VV, et al. Quasi-fractal organization of...[PMID:11712137]Related Articles, Books, LinkOut UI - 21569306 PMID- 11712137 DA - 20011119 DCOM- 20020214 LR - 20021101 IS - 1607-6729 VI - 377 DP - 2001 Mar-Apr TI - Quasi-fractal organization of the gastrovascular system of the jellyfish Aurelia aurita: order and chaos. PG - 110-2 AD - Institute of Marine Biology, Far East Division, Russian Academy of Sciences, ul. Pal'chevskogo 17, Vladivostok, 690041 Russia. FAU - Isaeva, V V AU - Isaeva VV FAU - Chernyshev, A V AU - Chernyshev AV FAU - Shkuratov, D AU - Shkuratov D LA - eng PT - Journal Article CY - Russia TA - Dokl Biochem Biophys JID - 101126895 SB - IM MH - Animal MH - *Fractals MH - Gastrointestinal System/anatomy & histology/*blood supply MH - *Nonlinear Dynamics MH - Scyphozoa/*anatomy & histology MH - Support, Non-U.S. Gov't EDAT- 2001/11/20 10:00 MHDA- 2002/02/15 10:01 PST - ppublish SO - Dokl Biochem Biophys 2001 Mar-Apr;377:110-2. 374: Rossiter HB, et al. Effects of prior exercise on ...[PMID:11711581]Related Articles, Books, LinkOut UI - 21568316 PMID- 11711581 DA - 20011116 DCOM- 20020122 IS - 0022-3751 VI - 537 IP - Pt 1 DP - 2001 Nov 15 TI - Effects of prior exercise on oxygen uptake and phosphocreatine kinetics during high-intensity knee-extension exercise in humans. PG - 291-303 AB - 1. A prior bout of high-intensity square-wave exercise can increase the temporal adaptation of pulmonary oxygen uptake (.V(O2)) to a subsequent bout of high-intensity exercise. The mechanisms controlling this adaptation, however, are poorly understood. 2. We therefore determined the dynamics of intramuscular [phosphocreatine] ([PCr]) simultaneously with those of .V(O2) in seven males who performed two consecutive bouts of high-intensity square-wave, knee-extensor exercise in the prone position for 6 min with a 6 min rest interval. A magnetic resonance spectroscopy (MRS) transmit-receive surface coil under the quadriceps muscle allowed estimation of [PCr]; .V(O2) was measured breath-by-breath using a custom-designed turbine and a mass spectrometer system. 3. The .V(O2) kinetics of the second exercise bout were altered compared with the first such that (a) not only was the instantaneous rate of .V(O2) change (at a given level of .V(O2)) greater but the phase II tau was also reduced - averaging 46.6 +/- 6.0 s (bout 1) and 40.7 +/- 8.4 s (bout 2) (mean +/- S.D.) and (b) the magnitude of the later slow component was reduced. 4. This was associated with a reduction of, on average, 16.1% in the total exercise-induced [PCr] decrement over the 6 min of the exercise, of which 4.0% was due to a reduction in the slow component of [PCr]. There was no discernable alteration in the initial rate of [PCr] change. The prior exercise, therefore, changed the multi-compartment behaviour towards that of functionally first-order dynamics. 5. These observations demonstrate that the .V(O2) responses relative to the work rate input for high-intensity exercise are non-linear, as are, it appears, the putative phosphate-linked controllers for which [PCr] serves as a surrogate. AD - Department of Physiology, St George's Hospital Medical School, Cranmer Terrace, Tooting, London SW17 0RE, UK. FAU - Rossiter, H B AU - Rossiter HB FAU - Ward, S A AU - Ward SA FAU - Kowalchuk, J M AU - Kowalchuk JM FAU - Howe, F A AU - Howe FA FAU - Griffiths, J R AU - Griffiths JR FAU - Whipp, B J AU - Whipp BJ LA - eng PT - Journal Article CY - England TA - J Physiol JID - 0266262 RN - 67-07-2 (Phosphocreatine) SB - IM MH - Adult MH - Case Report MH - Exercise/*physiology MH - Human MH - Kinetics MH - Knee/*physiology MH - Male MH - Models, Biological MH - Muscle, Skeletal/*metabolism MH - Nonlinear Dynamics MH - Oxygen Consumption/*physiology MH - Phosphocreatine/*metabolism MH - Support, Non-U.S. Gov't EDAT- 2001/11/17 10:00 MHDA- 2002/01/23 10:01 AID - PHY_12842 [pii] PST - ppublish SO - J Physiol 2001 Nov 15;537(Pt 1):291-303. 375: Harrison MA, et al. Dynamical mechanism for coexi...[PMID:11708854]Related Articles, Books, LinkOut UI - 21566370 PMID- 11708854 DA - 20011115 DCOM- 20020107 IS - 0022-5193 VI - 213 IP - 1 DP - 2001 Nov 7 TI - Dynamical mechanism for coexistence of dispersing species. PG - 53-72 AB - Dispersal of organisms may play an essential role in the coexistence of species. Recent studies of the evolution of dispersal in temporally varying environments suggest that clones differing in dispersal rates can coexist indefinitely. In this work, we explore the mechanism permitting such coexistence for a model of dispersal in a patchy environment, where temporal heterogeneity arises from endogenous chaotic dynamics. We show that coexistence arises from an extreme type of intermittent behavior, namely the phenomenon known as on-off intermittency. In effect, coexistence arises because of an alternation between synchronized and de-synchronized dynamical behaviors. Our analysis of the dynamical mechanism for on-off intermittency lends strong credence to the proposition that chaotic synchronism may be a general feature of species coexistence, where competing species differ only in dispersal rate. CI - Copyright 2001 Academic Press. AD - Department of Physics and Astronomy, The University of Kansas, Lawrence, KS 66045, USA. mafh@fhs.lawrence.ks.us FAU - Harrison, M A AU - Harrison MA FAU - Lai, Y C AU - Lai YC FAU - Holt, R D AU - Holt RD LA - eng PT - Journal Article CY - England TA - J Theor Biol JID - 0376342 SB - IM MH - Animal MH - Competitive Behavior MH - Ecosystem MH - *Models, Biological MH - Nonlinear Dynamics MH - *Population Dynamics MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2001/11/16 10:00 MHDA- 2002/01/10 10:01 AID - 10.1006/jtbi.2001.2404 [doi] AID - S002251930192404X [pii] PST - ppublish SO - J Theor Biol 2001 Nov 7;213(1):53-72. 376: Summers V. Overshoot effects using Schro...[PMID:11707346]Related Articles, Books, LinkOut UI - 21564209 PMID- 11707346 DA - 20011114 DCOM- 20020123 IS - 0378-5955 VI - 162 IP - 1-2 DP - 2001 Dec TI - Overshoot effects using Schroeder-phase harmonic maskers in listeners with normal hearing and with hearing impairment. PG - 1-9 AB - Overshoot was examined in normal-hearing listeners and in listeners with sensorineural hearing loss using positive (m(+)) and negative (m(-)) Schroeder-phase harmonic maskers and brief (5-ms) 1000-Hz and 4000-Hz signals. Maskers were 460 ms in duration and contained equal-amplitude harmonics of a 100-Hz fundamental frequency. For each masker, probes were presented at temporal locations near the start of the masker (probe onsets 3, 5.5, 8, 10.5, and 13 ms following masker onset) and at the same positions (relative to masker fine structure) 150 ms later, near the temporal center of each masker. Probes were held constant at either 60 or 80 dB sound-pressure level (SPL) and masker levels were varied adaptively to determine masked thresholds at each position within the 10-ms masker period. Overshoot effects were greatest for conditions where cochlear processing was likely to be highly nonlinear, i.e., for normal-hearing listeners tested at moderate presentation levels (60 dB SPL probes). In addition, greater overshoot was observed for m(+) than for m(-) maskers. These findings are consistent with earlier suggestions that masking effectiveness of m(+) complexes is particularly influenced by cochlear nonlinearity (Summers, V. and Leek, M.R., 1998. Hear. Res. 188, 139-150) and with evidence linking overshoot to nonlinearity in peripheral auditory processing. AD - Army Audiology and Speech Center, Walter Reed Army Medical Center, Washington, DC 20307-5001, USA. walter.summers@na.amedd.army.mil FAU - Summers, V AU - Summers V LA - eng ID - CD 03553/PHS PT - Journal Article CY - Netherlands TA - Hear Res JID - 7900445 SB - IM MH - Acoustic Stimulation/methods MH - Adult MH - Aged MH - *Auditory Threshold MH - Cochlea/physiopathology MH - Hearing Disorders/*physiopathology MH - Human MH - Middle Age MH - Nonlinear Dynamics MH - *Perceptual Masking MH - Reference Values MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. MH - Time Factors EDAT- 2001/11/15 10:00 MHDA- 2002/01/24 10:01 AID - S0378595501003422 [pii] PST - ppublish SO - Hear Res 2001 Dec;162(1-2):1-9. 377: Araki O, et al. Dual information representati...[PMID:11705411]Related Articles, Books, LinkOut UI - 21562958 PMID- 11705411 DA - 20011113 DCOM- 20020114 IS - 0899-7667 VI - 13 IP - 12 DP - 2001 Dec TI - Dual information representation with stable firing rates and chaotic spatiotemporal spike patterns in a neural network model. PG - 2799-822 AB - Although various means of information representation in the cortex have been considered, the fundamental mechanism for such representation is not well understood. The relation between neural network dynamics and properties of information representation needs to be examined. We examined spatial pattern properties of mean firing rates and spatiotemporal spikes in an interconnected spiking neural network model. We found that whereas the spatiotemporal spike patterns are chaotic and unstable, the spatial patterns of mean firing rates (SPMFR) are steady and stable, reflecting the internal structure of synaptic weights. Interestingly, the chaotic instability contributes to fast stabilization of the SPMFR. Findings suggest that there are two types of network dynamics behind neuronal spiking: internally-driven dynamics and externally driven dynamics. When the internally driven dynamics dominate, spikes are relatively more chaotic and independent of external inputs; the SPMFR are steady and stable. When the externally driven dynamics dominate, the spiking patterns are relatively more dependent on the spatiotemporal structure of external inputs. These emergent properties of information representation imply that the brain may adopt a dual coding system. Recent experimental data suggest that internally driven and externally driven dynamics coexist and work together in the cortex. AD - School of Knowledge Science, Japan Advanced Institute of Science and Technology, Tatsunokuchi, Ishikawa 923-1292, Japan. FAU - Araki, O AU - Araki O FAU - Aihara, K AU - Aihara K LA - eng PT - Journal Article CY - United States TA - Neural Comput JID - 9426182 SB - IM MH - Action Potentials/*physiology MH - Animal MH - *Computer Simulation MH - *Models, Neurological MH - Neural Conduction/physiology MH - *Neural Networks (Computer) MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Time Factors EDAT- 2001/11/14 10:00 MHDA- 2002/01/15 10:01 AID - 10.1162/089976601317098538 [doi] PST - ppublish SO - Neural Comput 2001 Dec;13(12):2799-822. 378: Schliekelman P, et al. Egg size evolution and energe...[PMID:11703099]Related Articles, Books, LinkOut UI - 21561651 PMID- 11703099 DA - 20011112 DCOM- 20011207 IS - 0040-5809 VI - 60 IP - 2 DP - 2001 Sep TI - Egg size evolution and energetic constraints on population dynamics. PG - 73-92 AB - We use population models that are based on dynamic energy budget models for individuals in order to study the evolution of offspring size and its relationship to the evolution of population dynamics. We show the existence of alternative evolutionarily stable strategies for offspring investment strategy resulting from a trade off between offspring number and time-to-maturity. The model predicts egg energy in Daphnia magna well, and suggests that the observed egg energy in D. magna is the result of selection for minimal egg investment constrained by minimum viable egg energy, combined with selection for a juvenile energy reserve. The selection for minimal egg size pushes populations toward chaotic dynamics. However, the minimum viable egg size combined with low efficiency of conversion of energy to new biomass is sufficient to keep population dynamics out of chaos. CI - Copyright 2001 Academic Press. AD - Biomathematics Graduate Program, Department of Statistics, North Carolina State University, Raleigh, North Carolina 27695-8203, USA. pdschlie2@stat.uga.edu FAU - Schliekelman, P AU - Schliekelman P FAU - Ellner, S P AU - Ellner SP LA - eng PT - Journal Article CY - United States TA - Theor Popul Biol JID - 0256422 SB - IM MH - Animal MH - Daphnia/genetics/*physiology MH - *Energy Metabolism MH - *Evolution MH - Models, Statistical MH - Nonlinear Dynamics MH - *Ovum MH - Population Dynamics MH - Support, Non-U.S. Gov't EDAT- 2001/11/13 10:00 MHDA- 2002/01/05 10:01 AID - 10.1006/tpbi.2001.1524 [doi] AID - S0040580901915242 [pii] PST - ppublish SO - Theor Popul Biol 2001 Sep;60(2):73-92. 379: Beloussov LV. Morphogenetic fields: outlini...[PMID:11702649]Related Articles, Books, LinkOut UI - 21559674 PMID- 11702649 DA - 20011112 DCOM- 20011220 IS - 0035-6050 VI - 94 IP - 2 DP - 2001 May-Aug TI - Morphogenetic fields: outlining the alternatives and enlarging the context. PG - 219-35 AB - Several alternative properties which we define as deterministic or field ones are formulated and analyzed in their relations to the realms of morphogenesis and biophoton emission. In spite of all the differences between these two groups of events both of them share the properties of non-additivity, delocalization, self-focusing and several others which we relate to the field phenomena. To a large extent, the field properties of the biological systems are associated with a set of oscillations of different time periods. We suggest that even such deterministic events as, for example, a ligand-receptor coupling are acting, within an activated cell, as the switches and/or modulators of its field properties. AD - Department of Embryology, Faculty of Biology, Moscow State University, Moscow. FAU - Beloussov, L V AU - Beloussov LV LA - eng PT - Journal Article CY - Italy TA - Riv Biol JID - 0416643 SB - IM MH - Animal MH - Comparative Study MH - *Embryology MH - Fishes/embryology MH - Fourier Analysis MH - *Morphogenesis MH - Nonlinear Dynamics MH - Photons MH - Research MH - Stress, Mechanical MH - Support, Non-U.S. Gov't MH - Thermodynamics MH - Time Factors EDAT- 2001/11/13 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - Riv Biol 2001 May-Aug;94(2):219-35. 380: Binder MD, et al. Relationship between simulate...[PMID:11698517]Related Articles, Books, LinkOut UI - 21555293 PMID- 11698517 DA - 20011107 DCOM- 20020206 IS - 0022-3077 VI - 86 IP - 5 DP - 2001 Nov TI - Relationship between simulated common synaptic input and discharge synchrony in cat spinal motoneurons. PG - 2266-75 AB - Synchronized discharge of individual motor units is commonly observed in the muscles of human subjects performing voluntary contractions. The amount of this synchronization is thought to reflect the extent to which motoneurons in the same and related pools share common synaptic input. However, the relationship between the proportion of shared synaptic input and the strength of synchronization has never been measured directly. In this study, we simulated common shared synaptic input to cat spinal motoneurons by driving their discharge with noisy, injected current waveforms. Each motoneuron was stimulated with a number of different injected current waveforms, and a given pair of waveforms were either completely different or else shared a variable percentage of common elements. Cross-correlation histograms were then compiled between the discharge of motoneurons stimulated with noise waveforms with variable degrees of similarity. The strength of synchronization increased with the amount of simulated "common" input in a nonlinear fashion. Moreover, even when motoneurons had >90% of their simulated synaptic inputs in common, only approximately 25-45% of their spikes were synchronized. We used a simple neuron model to explore how variations in neuron properties during repetitive discharge may lead to the low levels of synchronization we observed experimentally. We found that small variations in spike threshold and firing rate during repetitive discharge lead to large decreases in synchrony, particularly when neurons have a high degree of common input. Our results may aid in the interpretation of studies of motor unit synchrony in human hand muscles during voluntary contractions. AD - Department of Physiology and Biophysics, School of Medicine, University of Washington, Seattle, Washington 98195, USA. mdbinder@u.washington.edu FAU - Binder, M D AU - Binder MD FAU - Powers, R K AU - Powers RK LA - eng ID - NS-26840/NS/NINDS ID - NS-31925/NS/NINDS PT - Journal Article CY - United States TA - J Neurophysiol JID - 0375404 SB - IM MH - Action Potentials/physiology MH - Animal MH - Cats MH - Computer Simulation MH - Electric Stimulation MH - *Models, Neurological MH - Motor Neurons/*physiology MH - Nonlinear Dynamics MH - Reaction Time MH - Spinal Cord/*physiology MH - Support, U.S. Gov't, P.H.S. MH - Synapses/*physiology EDAT- 2001/11/08 10:00 MHDA- 2002/02/07 10:01 PST - ppublish SO - J Neurophysiol 2001 Nov;86(5):2266-75. 381: Day SJ, et al. Experimental simulation of ca...[PMID:11698507]Related Articles, Books, LinkOut UI - 21555283 PMID- 11698507 DA - 20011107 DCOM- 20020206 IS - 0022-3077 VI - 86 IP - 5 DP - 2001 Nov TI - Experimental simulation of cat electromyogram: evidence for algebraic summation of motor-unit action-potential trains. PG - 2144-58 AB - Prompted by the observation that the slope of the relationship between average rectified electromyography (EMG) and the ensemble activation rate of a pool of motor units progressively decreased (showing a downward nonlinearity), an experimental study was carried out to test the widely held notion that the EMG is the simple algebraic sum of motor-unit action-potential trains. The experiments were performed on the cat soleus muscle under isometric conditions, using electrical stimulation of alpha-motor axons isolated in ventral root filaments. The EMG signals were simulated experimentally under conditions where the activation of nearly the entire pool of motor units or of subsets of motor units was completely controlled by the experimenter. Sets of individual motor units or of small groups of motor units were stimulated independently, using stimulation profiles that were strictly repeatable between trials. This permitted a rigorous quantitative comparison of EMGs that were recorded during combined activation of multiple motor filaments with EMGs that were synthesized from the algebraic summation of motor unit action potential trains generated by individual nerve filaments. These were recorded separately by individually stimulating the same filaments with the same activation profiles that were employed during combined stimulation. During combined activation of up to 10 motor filaments, experimentally recorded and computationally synthesized EMGs were virtually identical. This indicates that EMG signals indeed are the outcome of the simple algebraic summation of motor-unit action-potential trains generated by concurrently active motor units. For both recorded and synthesized EMGs, it was confirmed that EMG magnitude increased nonlinearly with the ensemble activation rate of a pool of motor units. The nonlinearity was largely abolished when EMG magnitude was estimated as the sum of rectified, instead of raw, motor-unit action-potential trains. This suggests that the downward nonlinearity in the EMG-ensemble activation rate relation is due to signal cancellation arising from the perfectly linear summation of positive and negative components of action-potential waveforms. The findings provide a much needed post hoc validation of the concept of EMG generation by strict algebraic summation of motor unit action potentials that is generally relied on in theoretical modeling studies of EMG and in EMG decomposition algorithms. AD - Department of Clinical Neurosciences, Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada. FAU - Day, S J AU - Day SJ FAU - Hulliger, M AU - Hulliger M LA - eng PT - Journal Article CY - United States TA - J Neurophysiol JID - 0375404 SB - IM MH - Action Potentials/physiology MH - Animal MH - Cats MH - Comparative Study MH - Computer Simulation MH - *Electromyography MH - *Models, Neurological MH - Motor Neurons/*physiology MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2001/11/08 10:00 MHDA- 2002/02/07 10:01 PST - ppublish SO - J Neurophysiol 2001 Nov;86(5):2144-58. 382: Broufas GD, et al. Development, survival and rep...[PMID:11697783]Related Articles, Books, LinkOut UI - 21554137 PMID- 11697783 DA - 20011107 DCOM- 20020430 IS - 0168-8162 VI - 25 IP - 6 DP - 2001 TI - Development, survival and reproduction of Euseius finlandicus (Acari: Phytoseiidae) at different constant temperatures. PG - 441-60 AB - Development, survival and reproduction of Euseius finlandicus Oudemans were studied at seven constant temperatures (15, 20, 25, 27, 30, 32 and 34 degrees C) in the laboratory. Within the temperature range tested, developmental period from egg to adult varied from 148 to 360.5 h and 133.7 to 336.5 h for females and males, respectively. The lower thermal threshold for immature development for females and males was 8.9 and 6.4 degrees C, respectively. Survival during immature development exceeded 90% at all the temperatures from 15 to 32 degrees C, but at 34 degrees C an abrupt decline was recorded. Female longevity decreased gradually from 82.7 d at 15 degrees C to 12.2 d at 34 degrees C. The mean generation time ranged from 44.3 d at 15 degrees C to 15.9 d at 32 degrees C. The highest rm value (0.2817) was obtained at 30 degrees C and the lowest at 15 degrees C (0.0976). Temperatures above 30 degrees C had an adverse effect on population increase. AD - Laboratory of Applied Zoology and Parasitology, Aristotle University of Thessaloniki, Greece. FAU - Broufas, G D AU - Broufas GD FAU - Koveos, D S AU - Koveos DS LA - eng PT - Journal Article CY - Netherlands TA - Exp Appl Acarol JID - 8507436 SB - IM MH - Animal MH - Female MH - Fertility MH - Linear Models MH - Longevity MH - Male MH - Mites/growth & development/*physiology MH - Models, Biological MH - Nonlinear Dynamics MH - Reproduction MH - Sex Ratio MH - Support, Non-U.S. Gov't MH - Temperature MH - Time Factors EDAT- 2001/11/08 10:00 MHDA- 2002/05/01 10:01 PST - ppublish SO - Exp Appl Acarol 2001;25(6):441-60. 383: Stambolieva K, et al. Nonlinear dynamics of human p...[PMID:11695530]Related Articles, Books, LinkOut UI - 21551946 PMID- 11695530 DA - 20011106 DCOM- 20020306 IS - 0323-9950 VI - 26 IP - 3 DP - 2001 TI - Nonlinear dynamics of human postural sway during upright stance. PG - 159-63 AB - We present a procedure for characterizing the postural sway during quiet upright stance using methods of nonlinear dynamics. The displacements of the centre of foot pressure in anterior-posterior and lateral directions were measured using a force platform. We examined the changes of the postural control mechanisms when visual or proprioceptive information are reduced. We applied four analytic procedures to test the nature of posturographic time series: Kolmogorov-Smirnov test for amplitude distribution; shapes of autocorelation functions; structure functions and log-log plots of power spectra. Nongaussian distribution and nonlinear dynamics were established by all tests. The power spectra (PS) exhibited an exponential decreasing shape, which is commonly referred to as "1/f noise". The fractal structure of the process was characterised by fractal dimension (Df) and shape of structure functions. Our results show that the maintenance of postural stability in upright stance and reduced sensory inputs is nonlinear dynamic process with fractal structure. AD - Motor Control Laboratory, Institute of Physiology, Bulgarian Academy of Sciences, Sofia. katia@bio.bas.bg FAU - Stambolieva, K AU - Stambolieva K FAU - Popivanov, D AU - Popivanov D FAU - Grigorova, V AU - Grigorova V LA - eng PT - Journal Article CY - Bulgaria TA - Acta Physiol Pharmacol Bulg JID - 7512568 SB - IM MH - Adult MH - Human MH - Nonlinear Dynamics MH - Posture/*physiology MH - Proprioception/*physiology MH - Support, Non-U.S. Gov't EDAT- 2001/11/07 10:00 MHDA- 2002/03/07 10:01 PST - ppublish SO - Acta Physiol Pharmacol Bulg 2001;26(3):159-63. 384: Xie D, et al. Multipulse feed strategy for ...[PMID:11694060]Related Articles, Books, LinkOut UI - 21545425 PMID- 11694060 DA - 20011105 DCOM- 20020412 LR - 20021101 IS - 0273-2289 VI - 95 IP - 2 DP - 2001 Aug TI - Multipulse feed strategy for glycerol fed-batch fermentation: a steady-state nonlinear optimization approach. PG - 103-12 AB - During glycerol fed-batch fermentation, the process could be divided into multiple equal subintervals, and the feed operation was performed in pulse form at the start of each subinterval. Based on the macrokinetic models, the multipulse feed strategy for both glucose and corn steep slurry was determined by a general nonlinear optimization approach to maximize the final glycerol productivity and still control the residual glucose at a low concentration. The experimental results in a 600-mL Airlift Loop Reactor showed that the tested data with this strategy agreed well with the corresponding model prediction, and that the feed mode with nonlinear optimization could improve the glycerol productivity significantly compared with those determined just by limited experimental optimization in previous studies. AD - Institute of Applied Chemistry, Department of Chemical Engineering, Tsinghua University, Beijing, China. xiedm@tsinghua.edu.cn FAU - Xie, D AU - Xie D FAU - Liu, D AU - Liu D FAU - Zhu, H AU - Zhu H FAU - Liu, T AU - Liu T LA - eng PT - Journal Article CY - United States TA - Appl Biochem Biotechnol JID - 8208561 RN - 0 (Culture Media) RN - 50-99-7 (Glucose) RN - 56-81-5 (Glycerol) SB - IM MH - *Bioreactors MH - Biotechnology MH - Candida/metabolism MH - Culture Media MH - Fermentation MH - Glucose/metabolism MH - Glycerol/*metabolism MH - Kinetics MH - Models, Biological MH - Nonlinear Dynamics MH - Zea mays EDAT- 2001/11/06 10:00 MHDA- 2002/04/16 10:01 PST - ppublish SO - Appl Biochem Biotechnol 2001 Aug;95(2):103-12. 385: Dushanova J. Does the Kolmogorov entropy g...[PMID:11693411]Related Articles, Books, LinkOut UI - 21544764 PMID- 11693411 DA - 20011105 DCOM- 20020305 IS - 0323-9950 VI - 26 IP - 1-2 DP - 2001 TI - Does the Kolmogorov entropy give more information about the organization of the voluntary movement? PG - 93-6 AB - Nonlinear temporal and spatial dynamic changes of human EEG signals during voluntary finger movements were investigated with tracking Kolmogorov entropy (K2). Segments with higher values of K2 defined dynamic transients, distinguishing consecutive phases of the movement organization. The maximum of K2, determined immediately before the movement onset, was specific only for the contralateral sensorimotor area. This nonlinear characteristic, computed over time for EEG single records, indicates the local dynamic properties and detect those EEG patterns, where the underlying process changes the dynamics prior to the task performance. In addition to the present mechanisms, found by the linear methods, qualitatively new mechanisms of neuronal activity were discovered in brain functioning during the organization of voluntary movements. AD - Institute of Physiology, Bulgarian Academy of Sciences, Sofia. juliana@iph.bio.bas.bg FAU - Dushanova, J AU - Dushanova J LA - eng PT - Journal Article CY - Bulgaria TA - Acta Physiol Pharmacol Bulg JID - 7512568 SB - IM MH - Brain/*physiology MH - Electroencephalography MH - Entropy MH - Human MH - Movement/*physiology MH - Nonlinear Dynamics MH - Psychomotor Performance MH - Support, Non-U.S. Gov't EDAT- 2001/11/06 10:00 MHDA- 2002/03/07 10:01 PST - ppublish SO - Acta Physiol Pharmacol Bulg 2001;26(1-2):93-6. 386: Popivanov D, et al. Nonlinear EEG dynamics during...[PMID:11693391]Related Articles, Books, LinkOut UI - 21544770 PMID- 11693391 DA - 20011105 DCOM- 20020305 IS - 0323-9950 VI - 26 IP - 1-2 DP - 2001 TI - Nonlinear EEG dynamics during imagined self-paced movements. PG - 119-22 AB - The majority of studies devoted to reveal electrophysiological correlates of words and sentences comprehension, imageability and remembering are based on the event-related potentials and frequency synchronization in different narrow frequency bands. These linear methods reveal some patterns of EEG activity in time and frequency domain. Having in mind that the activation of many cortical structures is a result of mass of nonlinearly interconnected neurons, the linear methods seem to be insufficient to discover the complexity of the information transfer. We revealed recently nonlinear dynamic transients in EEG, long before real performance of goal-directed voluntary movements with different temporal and spatial distributions over frontal, sensorimotor and parietal cortical areas (Popivanov and Dushanova, 1999). The aim of this study was to establish whether similar behavior of the nonlinear characteristics exists when the subject imagines movements of a given type. The Kolmogorov entropy computed over time after the sentence end proved to be an useful characteristic that complement the linear methods. AD - Motor Control Laboratory, Institute of Physiology, BAS, Sofia, Bulgaria. dapo@bio.bas.bg FAU - Popivanov, D AU - Popivanov D FAU - Dushanova, J AU - Dushanova J FAU - Sauleva, Z AU - Sauleva Z LA - eng PT - Journal Article CY - Bulgaria TA - Acta Physiol Pharmacol Bulg JID - 7512568 SB - IM MH - *Eidetic Imagery MH - Electroencephalography MH - Entropy MH - Human MH - Nonlinear Dynamics MH - *Psychomotor Performance/*physiology MH - Support, Non-U.S. Gov't EDAT- 2001/11/06 10:00 MHDA- 2002/03/07 10:01 PST - ppublish SO - Acta Physiol Pharmacol Bulg 2001;26(1-2):119-22. 387: Popivanov D, et al. EEG frequency dynamics during...[PMID:11693390]Related Articles, Books, LinkOut UI - 21544769 PMID- 11693390 DA - 20011105 DCOM- 20020305 IS - 0323-9950 VI - 26 IP - 1-2 DP - 2001 TI - EEG frequency dynamics during movements imagery. PG - 115-8 AB - The study is an attempt to reveal the EEG frequency dynamic changes over sites covering areas reflecting the cognitive processes during movement imagery. Subjects were instructed to imagine a self-paced movement after listening to randomized sentences differing in lack of object or instrument of action. EEG was recorded over frontal, sensorimotor and temporo-parietal areas in both hemispheres. Frequency dynamics was estimated using power spectra (PS), band-pass filtering and bispectra. Two types of frequency dynamics were established: (A) a linear one, up to 24 Hz, with most pronounced oscillations in 12-14 Hz and in 16-22 Hz, synchronized first in frontal and precentral areas; (B) a nonlinear one between 24 and 63 Hz, with fractal structure and self-similarity, characterized by fractal dimension of 1.7-1.9. The narrow band of 23-26 Hz in the boundary between linear and nonlinear regimes expressed obvious synchronization and time re-distribution of oscillations among sites and sentence-types. AD - Motor Control Laboratory, Institute of Physiology, BAS, Sofia, Bulgaria. dapo@bio.bas.bg FAU - Popivanov, D AU - Popivanov D FAU - Likova, L AU - Likova L FAU - Sauleva, Z AU - Sauleva Z LA - eng PT - Journal Article CY - Bulgaria TA - Acta Physiol Pharmacol Bulg JID - 7512568 SB - IM MH - *Eidetic Imagery MH - Electrodes MH - Electroencephalography MH - Human MH - Nonlinear Dynamics MH - Psychomotor Performance/*physiology MH - Support, Non-U.S. Gov't EDAT- 2001/11/06 10:00 MHDA- 2002/03/07 10:01 PST - ppublish SO - Acta Physiol Pharmacol Bulg 2001;26(1-2):115-8. 388: Brennan M, et al. Do existing measures of Poinc...[PMID:11686633]Related Articles, Books, LinkOut UI - 21542841 PMID- 11686633 DA - 20011031 DCOM- 20011217 IS - 0018-9294 VI - 48 IP - 11 DP - 2001 Nov TI - Do existing measures of Poincare plot geometry reflect nonlinear features of heart rate variability? PG - 1342-7 AB - Heart rate variability (HRV) is concerned with the analysis of the intervals between heartbeats. An emerging analysis technique is the Poincare plot, which takes a sequence of intervals and plots each interval against the following interval. The geometry of this plot has been shown to distinguish between healthy and unhealthy subjects in clinical settings. The Poincare plot is a valuable HRV analysis technique due to its ability to display nonlinear aspects of the interval sequence. The problem is, how do we quantitatively characterize the plot to capture useful summary descriptors that are independent of existing HRV measures? Researchers have investigated a number of techniques: converting the two-dimensional plot into various one-dimensional views; the fitting of an ellipse to the plot shape; and measuring the correlation coefficient of the plot. We investigate each of these methods in detail and show that they are all measuring linear aspects of the intervals which existing HRV indexes already specify. The fact that these methods appear insensitive to the nonlinear characteristics of the intervals is an important finding because the Poincare plot is primarily a nonlinear technique. Therefore, further work is needed to determine if better methods of characterizing Poincare plot geometry can be found. AD - Department of Electrical and Electronic Engineering, The University of Melboume, Parkville, Victoria, Australia. mbrennan@ee.mu.oz.au FAU - Brennan, M AU - Brennan M FAU - Palaniswami, M AU - Palaniswami M FAU - Kamen, P AU - Kamen P LA - eng PT - Journal Article CY - United States TA - IEEE Trans Biomed Eng JID - 0012737 SB - IM MH - Analysis of Variance MH - Biomedical Engineering MH - Heart Rate/*physiology MH - Human MH - *Models, Cardiovascular MH - Models, Statistical MH - *Nonlinear Dynamics EDAT- 2001/11/01 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - IEEE Trans Biomed Eng 2001 Nov;48(11):1342-7. 389: Brennan M, et al. Distortion properties of the ...[PMID:11686624]Related Articles, Books, LinkOut UI - 21542832 PMID- 11686624 DA - 20011031 DCOM- 20011217 IS - 0018-9294 VI - 48 IP - 11 DP - 2001 Nov TI - Distortion properties of the interval spectrum of IPFM generated heartbeats for heart rate variability analysis. PG - 1251-64 AB - The integral pulse frequency modulation (IPFM) model converts a continuous-time signal into a modulated series of event times, often represented as a pulse train. The IPFM process is important to the field of heart rate variability (HRV) as a simple model of the sinus modulation of heart rate. In this paper, we discuss the distortion properties associated with employing the interval spectrum for the recovery of the input signal from an IPFM process's output pulse train. The results state, in particular for HRV, how precisely the interval spectrum can be used to infer the modulation signal responsible for a series of heartbeats. We have developed a detailed analytical approximation of the interval spectrum of an IPFM process with multiple sinusoids as the input signal. Employing this result, we describe the structure and the distortion of the interval spectrum. The distortion properties of the interval spectrum are investigated systematically for a pair of frequency components. The effects of linear and nonlinear distortion of the fundamentals, the overall contribution of harmonic components to the total power, the relative contribution of "folded back" power due to aliasing and the total distortion of the input spectrum are investigated. We also provide detailed comparisons between the interval spectrum and the spectrum of counts (SOC). The spectral distortion is significant enough that caution should be taken when interpreting the interval spectrum, especially for high frequencies or large modulation amplitudes. Nevertheless, the distortion levels are not significantly larger than those of the SOC. Therefore, the spectrum of intervals may be considered a viable technique that suffers more distortion than the SOC. AD - Department of Electrical and Electronic Engineering, University of Melbourne, Parkville, Victoria, Australia. mbrennan@ee.mu.oz.au FAU - Brennan, M AU - Brennan M FAU - Palaniswami, M AU - Palaniswami M FAU - Kamen, P AU - Kamen P LA - eng PT - Journal Article CY - United States TA - IEEE Trans Biomed Eng JID - 0012737 SB - IM MH - Analysis of Variance MH - Biomedical Engineering MH - Comparative Study MH - *Computer Simulation MH - *Heart Rate MH - Human MH - *Models, Cardiovascular MH - Nonlinear Dynamics EDAT- 2001/11/01 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - IEEE Trans Biomed Eng 2001 Nov;48(11):1251-64. 390: Ghazanfar AA, et al. Role of cortical feedback in ...[PMID:11685413]Related Articles, Books, LinkOut UI - 21541246 PMID- 11685413 DA - 20011030 DCOM- 20011211 IS - 0014-4819 VI - 141 IP - 1 DP - 2001 Nov TI - Role of cortical feedback in the receptive field structure and nonlinear response properties of somatosensory thalamic neurons. PG - 88-100 AB - Previous studies have suggested that the descending pathway from the primary somatosensory (SI) cortex to the ventral posterior nucleus of the thalamus has only a mild facilitative influence over thalamic neurons. Given the large numbers of corticothalamic terminations within the rat somatosensory thalamus and their complex topography, we sought to examine the role of corticothalamic feedback in the genesis of spatiotemporal receptive fields and the integration of complex tactile stimuli in the thalamus. By combining focal cortical inactivation (produced by microinjection of the GABA(A) agonist muscimol), with chronic multielectrode recordings, we observed that feedback from the rat SI cortex has multiple influences on its primary thalamic relay, the ventral posterior medial (VPM) nucleus. Our data demonstrate that, when single-whisker stimuli were used, the elimination of cortical feedback caused significant changes in the spatiotemporal structure of the receptive fields of VPM neurons. Cortical feedback also accounted for the nonlinear summation of VPM neural responses to simultaneously stimulated whiskers, in effect "linearizing" the responses. These results argue that the integration and transmission of tactile information through VPM are strongly influenced by the state of SI cortex. AD - Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA. asifg@tuebingen.mpg.de FAU - Ghazanfar, A A AU - Ghazanfar AA FAU - Krupa, D J AU - Krupa DJ FAU - Nicolelis, M A AU - Nicolelis MA LA - eng ID - DE-11121-01/DE/NIDCR PT - Journal Article CY - Germany TA - Exp Brain Res JID - 0043312 SB - IM MH - Animal MH - Feedback/*physiology MH - Female MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Rats MH - Rats, Long-Evans MH - Reaction Time/physiology MH - Somatosensory Cortex/*physiology MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. MH - Thalamus/*physiology MH - Ventral Thalamic Nuclei/physiology MH - Vibrissae/physiology EDAT- 2001/10/31 10:00 MHDA- 2002/01/05 10:01 PHST- 2001/Feb/05 [received] PHST- 2001/Jul/06 [accepted] AID - 10.1007/s002210100849 [doi] PST - ppublish SO - Exp Brain Res 2001 Nov;141(1):88-100. 391: Kirshenbaum N, et al. Non-linear development of pos...[PMID:11685395]Related Articles, Books, LinkOut UI - 21541228 PMID- 11685395 DA - 20011030 DCOM- 20011218 IS - 0014-4819 VI - 140 IP - 4 DP - 2001 Oct TI - Non-linear development of postural control and strategy use in young children: a longitudinal study. PG - 420-31 AB - This longitudinal analysis confirmed a non-monotonic pattern of postural control development in children from age 5 to 8 years suggested by previous cross-sectional studies. Postural control was considered in terms of control strategy and its variability operationalized by mean and standard deviation of center of pressure (COP) velocity; and of effectiveness and its variability operationalized by mean and standard deviation of COP anteroposterior (a-p) excursion. Periods of significant variability were used to indicate behavioral transitions. Seventeen healthy children (nine males, eight females) aged 5-6 years (61.5-75 months) were tested at 3- to 4-month intervals up to age 8 years (83-97 months) in eyes-open quiet stance on a force platform for 30 s in each of ten trials. Data were reorganized into six developmental categories based on adjacent test dates prior to (-1) and after (+1, +2, +3, +4) a subject's trial with the lowest COP velocity (0). Developmental category is proposed to represent level of sensorimotor integrative skill. Within-subject ANCOVAs revealed a significant effect (P<0.0001) for developmental category with covariance due to height, weight and actual age removed. Post hoc tests showed a significant effect (P<0.0001) on measures of strategy. However, differences in COP velocity (type of strategy used) and differences in its variability (denoting a transition between strategies) were not always coincident. Performance outcome (COP a-p excursion) changed near linearly across categories. It was concluded that a non-monotonic change in control strategy as indicated by COP velocity describes the development of quiet stance equilibrium. A transition occurs from a primarily open-loop to incorporation of open- and closed-loop components of control. Honing of strategy used precedes and follows transitions. Constriction of velocity and excursion may typify the early stages of bimodal strategy. Developmental categories describe affiliation with the strategy employed and may represent differentiable levels of sensorimotor integrative skill. They may be more useful in assessing progression of equilibrium control than consecutive age in years. AD - 4000 Young St., Suite 833, North York, ON M4N 2N9, Canada. FAU - Kirshenbaum, N AU - Kirshenbaum N FAU - Riach, C L AU - Riach CL FAU - Starkes, J L AU - Starkes JL LA - eng PT - Journal Article CY - Germany TA - Exp Brain Res JID - 0043312 SB - IM MH - Adaptation, Physiological/physiology MH - Aging/*physiology MH - Central Nervous System/*growth & development/*physiology MH - Child MH - Child, Preschool MH - Equilibrium/*physiology MH - Feedback/physiology MH - Female MH - Human MH - Longitudinal Studies MH - Male MH - Movement/physiology MH - *Nonlinear Dynamics MH - Observer Variation MH - Posture/*physiology MH - Psychomotor Performance/*physiology MH - Support, Non-U.S. Gov't EDAT- 2001/10/31 10:00 MHDA- 2002/01/05 10:01 PHST- 2000/Sep/18 [received] PHST- 2001/Jun/14 [accepted] AID - 10.1007/s002210100835 [doi] PST - ppublish SO - Exp Brain Res 2001 Oct;140(4):420-31. 392: Abelo A, et al. Pharmacodynamic modelling of ...[PMID:11684409]Related Articles, Books, LinkOut UI - 21541190 PMID- 11684409 DA - 20011030 DCOM- 20020205 IS - 0928-0987 VI - 14 IP - 4 DP - 2001 Dec TI - Pharmacodynamic modelling of reversible gastric acid pump inhibition in dog and man. PG - 339-46 AB - H 335/25, a 4-amino quinoline, belongs to a new class of reversible gastric acid pump inhibitors. A potential advantage of such drugs over the irreversible proton pump inhibitors (PPIs) is better control over the effect-time profile. Dose escalation studies were performed to characterize the effect on acid secretion in dogs (n=24) and healthy male subjects (n=12). The effect-time profile was delayed compared to the concentration-time profile. A model-based approach, using non-linear mixed effects modelling, was applied to quantify and elucidate the mechanism for the delayed effect. Three different models were investigated: (1) a slow equilibration preceding the formation of drug-enzyme complex, modelled by an effect-compartment, (2) a slow equilibration between free drug, free enzyme and drug-enzyme complex, described by a kinetic binding model, and (3) a delay between enzyme inhibition and the measured response, described by an indirect response model. Model 2 was shown to be superior to models 1 and 3, for both dog and human data. The dissociation rate constant, k(off), was estimated to be 0.85 and 0.88 h and the calculated equilibration constant, K(d), was 160 and 250 nM in dog and man, respectively. Simulations of the predicted time-course of the effect beyond the 4-5-h observation period was similar for the three models. AD - AstraZeneca AB, R&D Department, S-431 83 Molndal/Sodertalje, Sweden. angela.abelo@astrazeneca.com FAU - Abelo, A AU - Abelo A FAU - Gabrielsson, J AU - Gabrielsson J FAU - Holstein, B AU - Holstein B FAU - Eriksson, U G AU - Eriksson UG FAU - Holmberg, J AU - Holmberg J FAU - Karlsson, M O AU - Karlsson MO LA - eng PT - Journal Article CY - Netherlands TA - Eur J Pharm Sci JID - 9317982 RN - 0 (Aminoquinolines) RN - 0 (Antimalarials) RN - 0 (Proton Pumps) RN - 578-68-7 (4-aminoquinoline) SB - IM MH - Administration, Oral MH - Adult MH - Aminoquinolines/administration & dosage/blood/pharmacokinetics MH - Animal MH - Antimalarials/administration & dosage/blood/pharmacokinetics MH - Comparative Study MH - Dogs MH - Dose-Response Relationship, Drug MH - Gastric Acid/*secretion MH - Human MH - Male MH - *Models, Biological MH - Models, Chemical MH - Nonlinear Dynamics MH - Proton Pumps/*antagonists & inhibitors/*secretion EDAT- 2001/10/31 10:00 MHDA- 2002/02/06 10:01 AID - S0928098701001877 [pii] PST - ppublish SO - Eur J Pharm Sci 2001 Dec;14(4):339-46. 393: Blum JD. Overcoming managed care regul...[PMID:11683046]Related Articles, Books, LinkOut UI - 21540118 PMID- 11683046 DA - 20011030 DCOM- 20011204 IS - 0748-383X VI - 11 IP - 2 DP - 2001 Summer TI - Overcoming managed care regulatory chaos through a restructured federalism. PG - 327-50 AD - Loyola University Chicago, School of Law Institute for Health Law, USA. FAU - Blum, J D AU - Blum JD LA - eng PT - Journal Article PT - Legal Cases CY - United States TA - Health Matrix Clevel JID - 9311154 SB - H MH - Facility Regulation and Control/*legislation & jurisprudence MH - *Government MH - Health Policy/*legislation & jurisprudence MH - Human MH - Managed Care Programs/*legislation & jurisprudence MH - Medicaid MH - Medicare MH - Nonlinear Dynamics MH - State Government MH - United States EDAT- 2001/10/31 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - Health Matrix Clevel 2001 Summer;11(2):327-50. 394: Chen T. Global exponential stability ...[PMID:11681757]Related Articles, Books, LinkOut UI - 21537836 PMID- 11681757 DA - 20011029 DCOM- 20020320 IS - 0893-6080 VI - 14 IP - 8 DP - 2001 Oct TI - Global exponential stability of delayed Hopfield neural networks. PG - 977-80 AB - In this paper, we discuss delayed Hopfield neural networks, investigating their global exponential stability. Sufficient conditions ensuring global exponential stability of delayed Hopfield neural networks are given. AD - Lab of Nonlinear Mathematics Science, Institute of Mathematics, Fudan University, Shanghai, PR China. tchen@fudan.edu.cn FAU - Chen, T AU - Chen T LA - eng PT - Journal Article CY - United States TA - Neural Netw JID - 8805018 SB - IM MH - *Algorithms MH - *Neural Networks (Computer) MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2001/10/30 10:00 MHDA- 2002/03/21 10:01 PST - ppublish SO - Neural Netw 2001 Oct;14(8):977-80. 395: Hrycej T. Estimates of average complexi...[PMID:11681753]Related Articles, Books, LinkOut UI - 21537845 PMID- 11681753 DA - 20011029 DCOM- 20020320 IS - 0893-6080 VI - 14 IP - 8 DP - 2001 Oct TI - Estimates of average complexity of neurocontrol algorithms. PG - 1089-98 AB - Neurocontrol algorithms can be operated in a batch mode or an incremental mode. Furthermore, some of them have variants with and without an explicit plant model. These variants exhibit fundamentally different behavior with regard to the volume of data necessary for convergence. To assess this difference, simplified algorithms in a discrete state space using the dynamic programming framework are analyzed: a batch algorithm, and two incremental algorithms with and without a plant model. Analysis shows that the batch algorithm is the fastest, while the two incremental algorithms (in particular the model-free variant) are considerably slower, measured in expected number of samples to convergence. AD - DaimlerChrysler AG, Research Center Ulm, Germany. tomas.hrycej@daimlerchrysler.com FAU - Hrycej, T AU - Hrycej T LA - eng PT - Journal Article CY - United States TA - Neural Netw JID - 8805018 SB - IM MH - *Algorithms MH - *Neural Networks (Computer) MH - *Nonlinear Dynamics EDAT- 2001/10/30 10:00 MHDA- 2002/03/21 10:01 PST - ppublish SO - Neural Netw 2001 Oct;14(8):1089-98. 396: Ampazis N, et al. A dynamical model for the ana...[PMID:11681752]Related Articles, Books, LinkOut UI - 21537844 PMID- 11681752 DA - 20011029 DCOM- 20020320 IS - 0893-6080 VI - 14 IP - 8 DP - 2001 Oct TI - A dynamical model for the analysis and acceleration of learning in feedforward networks. PG - 1075-88 AB - A dynamical system model is derived for feedforward neural networks with one layer of hidden nodes. The model is valid in the vicinity of flat minima of the cost function that rise due to the formation of clusters of redundant hidden nodes with nearly identical outputs. The derivation is carried out for networks with an arbitrary number of hidden and output nodes and is, therefore, a generalization of previous work valid for networks with only two hidden nodes and one output node. The Jacobian matrix of the system is obtained, whose eigenvalues characterize the evolution of learning. Flat minima correspond to critical points of the phase plane trajectories and the bifurcation of the eigenvalues signifies their abandonment. Following the derivation of the dynamical model, we show that identification of the hidden nodes clusters using unsupervised learning techniques enables the application of a constrained application (Dynamically Constrained Back Propagation-DCBP) whose purpose is to facilitate prompt bifurcation of the eigenvalues of the Jacobian matrix and, thus, accelerate learning. DCBP is applied to standard benchmark tasks either autonomously or as an aid to other standard learning algorithms in the vicinity of flat minima. Its application leads to significant reduction in the number of required epochs for convergence. AD - Institute of Informatics and Telecommunications, National Center for Scientific Research Demokritos, Athens, Greece. FAU - Ampazis, N AU - Ampazis N FAU - Perantonis, S J AU - Perantonis SJ FAU - Taylor, J G AU - Taylor JG LA - eng PT - Journal Article CY - United States TA - Neural Netw JID - 8805018 SB - IM MH - *Acceleration MH - *Algorithms MH - *Artificial Intelligence MH - *Neural Networks (Computer) MH - *Nonlinear Dynamics EDAT- 2001/10/30 10:00 MHDA- 2002/03/21 10:01 PST - ppublish SO - Neural Netw 2001 Oct;14(8):1075-88. 397: Wang R. A hybrid learning network for...[PMID:11681751]Related Articles, Books, LinkOut UI - 21537843 PMID- 11681751 DA - 20011029 DCOM- 20020320 IS - 0893-6080 VI - 14 IP - 8 DP - 2001 Oct TI - A hybrid learning network for shift-invariant recognition. PG - 1061-73 AB - A neural network and the associated learning algorithm are presented as a generic approach for invariant recognition of visual patterns independent of their geometric attributes, such as spatial location, orientation and scale. The network is a multi-layer hierarchy with each layer composed of a set of groups of nodes. The groups of the input layer represent local areas spatially arranged in the visual field according to the geometric variations. Each node in the subsequent higher layers receives input laterally from other groups of the same layer as well as vertically from the layer below. The learning that takes place in the vertical feed forward paths between layers is based on an unsupervised hybrid algorithm combining both competitive learning and Hebbian learning. As the result of the architecture and the hybrid learning, the desired invariant recognition emerges at the output layer of the network. The network can serve as a simple and biologically plausible computational model to account for the invariant object recognition in the biological visual system. Also, as the algorithm is generic and robust, it can be applied to solve various practical recognition problems. AD - Engineering Department, Harvey Mudd College, Claremont, CA 91711, USA. ruye_wang@hmc.edu FAU - Wang, R AU - Wang R LA - eng PT - Journal Article CY - United States TA - Neural Netw JID - 8805018 SB - IM MH - *Algorithms MH - Animal MH - *Artificial Intelligence MH - Human MH - *Image Processing, Computer-Assisted MH - Linear Models MH - Nerve Net/physiology MH - *Neural Networks (Computer) MH - Neural Pathways/physiology MH - Neurons/physiology MH - Nonlinear Dynamics MH - Pattern Recognition, Visual/*physiology MH - Synaptic Transmission/physiology MH - Visual Cortex/physiology EDAT- 2001/10/30 10:00 MHDA- 2002/03/21 10:01 PST - ppublish SO - Neural Netw 2001 Oct;14(8):1061-73. 398: Riede T, et al. The harmonic-to-noise ratio a...[PMID:11681395]Related Articles, Books, LinkOut UI - 21537484 PMID- 11681395 DA - 20011029 DCOM- 20020102 IS - 0001-4966 VI - 110 IP - 4 DP - 2001 Oct TI - The harmonic-to-noise ratio applied to dog barks. PG - 2191-7 AB - Dog barks are typically a mixture of regular components and irregular (noisy) components. The regular part of the signal is given by a series of harmonics and is most probably due to regular vibrations of the vocal folds, whereas noise refers to any nonharmonic (irregular) energy in the spectrum of the bark signal. The noise components might be due to chaotic vibrations of the vocal-fold tissue or due to turbulence of the air. The ratio of harmonic to nonharmonic energy in dog barks is quantified by applying the harmonics-to-noise ratio (HNR). Barks of a single dog breed were recorded in the same behavioral context. Two groups of dogs were considered: a group of ten healthy dogs (the normal sample), and a group of ten unhealthy dogs, i.e., dogs treated in a veterinary clinic (the clinic sample). Although the unhealthy dogs had no voice disease, differences in emotion or pain or impacts of surgery might have influenced their barks. The barks of the dogs were recorded for a period of 6 months. The HNR computation is based on the Fourier spectrum of a 50-ms section from the middle of the bark. A 10-point moving average curve of the spectrum on a logarithmic scale is considered as estimator of the noise level in the bark, and the maximum difference of the original spectrum and the moving average is defined as the HNR measure. It is shown that a reasonable ranking of the voices is achievable based on the measurement of the HNR. The HNR-based classification is found to be consistent with perceptual evaluation of the barks. In addition, a multiparametric approach confirms the classification based on the HNR. Hence, it may be concluded that the HNR might be useful as a novel parameter in bioacoustics for quantifying the noise within a signal. AD - Institut fur Biologie, Humboldt-Universitat zu Berlin, Germany. tobiasriede@web.de FAU - Riede, T AU - Riede T FAU - Herzel, H AU - Herzel H FAU - Hammerschmidt, K AU - Hammerschmidt K FAU - Brunnberg, L AU - Brunnberg L FAU - Tembrock, G AU - Tembrock G LA - eng PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 SB - IM MH - Animal MH - Animal Communication MH - Dog Diseases/physiopathology MH - Dogs/*physiology MH - Emotions/physiology MH - Female MH - Male MH - Noise MH - Nonlinear Dynamics MH - Reference Values MH - Sound Spectrography/*veterinary MH - Vocal Cords/physiology MH - Vocalization, Animal/*physiology MH - Voice Disorders/physiopathology/veterinary EDAT- 2001/10/30 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Acoust Soc Am 2001 Oct;110(4):2191-7. 399: Jiang JJ, et al. Modeling of chaotic vibration...[PMID:11681389]Related Articles, Books, LinkOut UI - 21537478 PMID- 11681389 DA - 20011029 DCOM- 20020102 IS - 0001-4966 VI - 110 IP - 4 DP - 2001 Oct TI - Modeling of chaotic vibrations in symmetric vocal folds. PG - 2120-8 AB - The chaos mechanism of above-range phonation was examined in symmetrically modeled vocal folds by using the traditional two-mass model assumption. The Poincare map technique was used to display chaotic attractors. This method provided an effective description of irregular vocal-fold movements. The power spectrum, Lyapunov exponent, and Kaplan-Yorke dimension were employed to describe chaotic vibrations in the vocal-fold model. These nonlinear dynamic analyses suggested that, for the positive Lyapunov exponent, chaotic attractors contribute to irregular vocal-fold vibrations. Descriptions of complicated irregular vibrations of the vocal fold yielded evidence of chaos. To investigate the effects of independent parameters such as subglottal pressure, coupling stiffness, and phonation neutral area, bifurcation diagrams based on the Poincare map were discussed. The results confirmed that the dynamics of the two-mass model was strongly influenced by independent parameters. Nonlinear dynamic methods were expected to provide useful information for better understanding of irregular vocal-fold vibrations as well as of the dynamic mechanism of above-range phonation in excised larynx experimentation. AD - Department of Surgery, University of Wisconsin Medical School, Madison 53792-7375, USA. jiang@surgery.wisc.edu FAU - Jiang, J J AU - Jiang JJ FAU - Zhang, Y AU - Zhang Y FAU - Stern, J AU - Stern J LA - eng ID - R29 DC2977/DC/NIDCD PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 SB - IM MH - Human MH - *Nonlinear Dynamics MH - Phonation/*physiology MH - Pulmonary Ventilation/physiology MH - Support, U.S. Gov't, P.H.S. MH - Vibration MH - Vocal Cords/*physiology EDAT- 2001/10/30 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Acoust Soc Am 2001 Oct;110(4):2120-8. 400: Heinz MG, et al. Rate and timing cues associat...[PMID:11681385]Related Articles, Books, LinkOut UI - 21537474 PMID- 11681385 DA - 20011029 DCOM- 20020102 IS - 0001-4966 VI - 110 IP - 4 DP - 2001 Oct TI - Rate and timing cues associated with the cochlear amplifier: level discrimination based on monaural cross-frequency coincidence detection. PG - 2065-84 AB - The perceptual significance of the cochlear amplifier was evaluated by predicting level-discrimination performance based on stochastic auditory-nerve (AN) activity. Performance was calculated for three models of processing: the optimal all-information processor (based on discharge times), the optimal rate-place processor (based on discharge counts), and a monaural coincidence-based processor that uses a non-optimal combination of rate and temporal information. An analytical AN model included compressive magnitude and level-dependent-phase responses associated with the cochlear amplifier, and high-, medium-, and low-spontaneous-rate (SR) fibers with characteristic frequencies (CFs) spanning the AN population. The relative contributions of nonlinear magnitude and nonlinear phase responses to level encoding were compared by using four versions of the model, which included and excluded the nonlinear gain and phase responses in all possible combinations. Nonlinear basilar-membrane (BM) phase responses are robustly encoded in near-CF AN fibers at low frequencies. Strongly compressive BM responses at high frequencies near CF interact with the high thresholds of low-SR AN fibers to produce large dynamic ranges. Coincidence performance based on a narrow range of AN CFs was robust across a wide dynamic range at both low and high frequencies, and matched human performance levels. Coincidence performance based on all CFs demonstrated the "near-miss" to Weber's law at low frequencies and the high-frequency "mid-level bump." Monaural coincidence detection is a physiologically realistic mechanism that is extremely general in that it can utilize AN information (average-rate, synchrony, and nonlinear-phase cues) from all SR groups. AD - Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge 02139, USA. mgheinz@bme.jhu.edu FAU - Heinz, M G AU - Heinz MG FAU - Colburn, H S AU - Colburn HS FAU - Carney, L H AU - Carney LH LA - eng ID - T32DC00038/DC/NIDCD PT - Journal Article CY - United States TA - J Acoust Soc Am JID - 7503051 SB - IM MH - Audiometry, Pure-Tone MH - Basilar Membrane/*physiology MH - Cochlea/*physiology MH - Cochlear Nerve/*physiology MH - Dominance, Cerebral/physiology MH - Evoked Potentials, Auditory/physiology MH - Human MH - Loudness Perception/*physiology MH - Nerve Fibers/*physiology MH - Nonlinear Dynamics MH - Pitch Discrimination/*physiology MH - Psychoacoustics MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. EDAT- 2001/10/30 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Acoust Soc Am 2001 Oct;110(4):2065-84. 401: Rusov V, et al. About some physical mechanism...[PMID:11678150]Related Articles, Books, LinkOut UI - 21533080 PMID- 11678150 DA - 20011024 DCOM- 20011207 LR - 20020522 IS - 1350-4487 VI - 34 IP - 1-6 DP - 2001 Jun TI - About some physical mechanisms of statistics of radiation-induced effects formation and non-linear cell response in low dose area. PG - 105-8 AB - A new cascade-stochastic approach to solve the direct and inverse problems of radiation-induced effect statistics in track biodetectors is presented in this paper. The analysis of the experimental data has made it possible to establish a non-linear nature of the "dose-effect" dependence in low dose area. For the first time, a new determination of the relative biological efficiency and quality coefficient of ionizing radiation in area of low doses are proposed. CI - c2001 Published by Elsevier Science Ltd. AD - Department of Theoretical and Experimental Nuclear Physics, Odessa Polytechnic University, Shevchenko av I, Odessa 65044, Ukraine. siiis@e.net.ua FAU - Rusov, V AU - Rusov V FAU - Zelentsova, T AU - Zelentsova T FAU - Melentchuk, I AU - Melentchuk I FAU - Beglaryan, M AU - Beglaryan M LA - eng PT - Journal Article CY - England TA - Radiat Meas JID - 9890953 RN - 0 (Chromatin) SB - S MH - Cell Nucleus/*radiation effects MH - Chromatin/radiation effects MH - Dose-Response Relationship, Radiation MH - Human MH - Linear Energy Transfer MH - Lymphocytes/*radiation effects MH - Micronuclei MH - *Models, Statistical MH - *Nonlinear Dynamics MH - Radiation Dosage MH - Relative Biological Effectiveness MH - *Stochastic Processes EDAT- 2001/10/27 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - Radiat Meas 2001 Jun;34(1-6):105-8. 402: Tossavainen T, et al. Postural control as assessed ...[PMID:11677742]Related Articles, Books, LinkOut UI - 21533637 PMID- 11677742 DA - 20011025 DCOM- 20020220 LR - 20020319 IS - 0365-5237 VI - 545 DP - 2001 TI - Postural control as assessed with virtual reality. PG - 53-6 AB - We studied the use of virtual reality technology as a stimulus in balance examinations. A pilot study was made using a small group of healthy subjects to investigate the effect of alcohol and virtual reality stimulus on the subjects' balance. The tests showed that blood alcohol concentration accounted for almost 50% of the increased lateral body sway velocity. The new stimulus technique based on virtual reality technology seems to be effective and flexible for postural investigations. AD - Department of Computer and Information Sciences, University of Tampere, Tampere. tt@cs.uta.fi FAU - Tossavainen, T AU - Tossavainen T FAU - Juhola, M AU - Juhola M FAU - Aalto, H AU - Aalto H FAU - Toppila, E AU - Toppila E FAU - Pyykko, I AU - Pyykko I FAU - Honkavaara, P AU - Honkavaara P FAU - Laurikkala, J AU - Laurikkala J FAU - Laakso, J AU - Laakso J LA - eng PT - Clinical Trial PT - Journal Article PT - Randomized Controlled Trial CY - Norway TA - Acta Otolaryngol Suppl JID - 0370355 RN - 64-17-5 (Ethanol) SB - IM SB - S MH - Adult MH - Double-Blind Method MH - Ethanol/blood/pharmacology MH - Feedback MH - Head/physiology MH - Human MH - Male MH - Movement/drug effects/physiology MH - Nonlinear Dynamics MH - Pilot Projects MH - *Posture MH - *User-Computer Interface MH - Visual Perception/drug effects EDAT- 2001/10/27 10:00 MHDA- 2002/02/21 10:01 PST - ppublish SO - Acta Otolaryngol Suppl 2001;545:53-6. 403: Chang YH, et al. A model of ventilation distri...[PMID:11676446]Related Articles, Books, LinkOut UI - 21526234 PMID- 11676446 DA - 20011023 DCOM- 20011207 IS - 0278-6826 VI - 30 IP - 3 DP - 1999 Mar TI - A model of ventilation distribution in the human lung. PG - 309-19 AB - A thorough analysis of aerosol particle deposition in the human lung requires the knowledge of the distribution of inspired air at respiration. In this paper, a mathematical model of ventilation distribution has been developed using a five-lobe airway model. The model accounts for the nonlinear effects of compliance and resistance on airway dynamics. Ventilation distributions were determined under different gravitational force conditions. A larger gravity leads to a greater nonuniformity of ventilation between the upper and lower lobes of the lung. Ventilation distributions in different lobes of the lung at various inspiratory flow rates were also calculated. At slow inspiratory flow rates, ventilation was found to be nonuniform with more air entering the lower lobes. As the flow rate increases, this nonuniformity became smaller. The calculated results compare favorably with existing experimental data. When a different gas is inspired instead of air, a preferential distribution of ventilation to the upper lobes was found if the density of the inspired gas is greater than that of the air. AD - Department of Mechanical and Aerospace Engineering, State University of New York at Buffalo, Amherst, NY 14260, USA. FAU - Chang, Y H AU - Chang YH FAU - Yu, C P AU - Yu CP LA - eng PT - Journal Article CY - England TA - Aerosol Sci Technol JID - 9886760 RN - 0 (Aerosols) RN - 2551-62-4 (Sulfur Hexafluoride) RN - 7782-44-7 (Oxygen) SB - S MH - *Aerosols MH - Airway Resistance MH - Comparative Study MH - *Gravitation MH - Human MH - Lung/metabolism/*physiology MH - Lung Compliance MH - Lung Volume Measurements MH - Mathematics MH - Models, Anatomic MH - *Models, Biological MH - Nonlinear Dynamics MH - Oxygen/pharmacokinetics MH - Pulmonary Ventilation/*physiology MH - Sulfur Hexafluoride/pharmacokinetics EDAT- 2001/10/26 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - Aerosol Sci Technol 1999 Mar;30(3):309-19. 404: de Zee M, et al. Moment dependency of the seri...[PMID:11672714]Related Articles, Books, LinkOut UI - 21528863 PMID- 11672714 DA - 20011023 DCOM- 20020220 IS - 0021-9290 VI - 34 IP - 11 DP - 2001 Nov TI - Moment dependency of the series elastic stiffness in the human plantar flexors measured in vivo. PG - 1399-406 AB - The moment dependency of the series elastic stiffness (SES) in the human plantar flexors was investigated in vivo with the quick release method. At an ankle moment of 100 N m produced with either voluntary or electrical stimulation we found non-significantly different SES of 506+/-72 and 529+/-125 N m rad(-1), respectively. It has recently been proposed that the amount of series elastic tissue involved in plantar flexion changes with the moment level produced by the plantar flexors (Hof, J. Biomech 31 (1998) 793). However, our results indicate that the amount of series elastic tissue involved in plantar flexions remained constant with changing moment levels. We therefore propose that the series elastic component (SEC) in human plantar flexors act as one structure or rather one combination of anatomical structures which is engaged at all muscle activation levels, and that the mechanical properties (i.e. the stress-strain function) are determined by the combined tissue mechanical properties. Additionally, our results demonstrated that the SES in the human plantar flexors at moments levels up to about isometric maximum did not reach an asymptote where the stiffness is independent of moment, i.e. SEC of the plantar flexors is, during many daily activities, loaded for the greatest part in the non-linear part of the stress-strain function. AD - Center for Sensory-Motor Interaction, Aalborg University, Fredrik Bajers Vej 7-D3, 9220 Aalborg, Denmark. mdz@ime.auc.dk FAU - de Zee, M AU - de Zee M FAU - Voigt, M AU - Voigt M LA - eng PT - Journal Article CY - United States TA - J Biomech JID - 0157375 SB - IM MH - Adult MH - Ankle Joint/*physiology MH - Biomechanics MH - Elasticity MH - Electric Stimulation MH - Female MH - Human MH - Isometric Contraction/physiology MH - Male MH - Muscle, Skeletal/*physiology MH - Nonlinear Dynamics MH - Stress, Mechanical MH - Support, Non-U.S. Gov't EDAT- 2001/10/24 10:00 MHDA- 2002/02/21 10:01 AID - S0021929001001336 [pii] PST - ppublish SO - J Biomech 2001 Nov;34(11):1399-406. 405: van Putten MJ, et al. Is the EEG really "chaotic" i...[PMID:11668899]Related Articles, Books, LinkOut UI - 21525966 PMID- 11668899 DA - 20011023 DCOM- 20020325 IS - 0739-5175 VI - 20 IP - 5 DP - 2001 Sep-Oct TI - Is the EEG really "chaotic" in hypsarrhythmia? PG - 72-9 AD - Dept. of Neurology and Clinical Neurophysiology, Leyenburg Hospital, The Hague. M.van_Putten@lumc.nl FAU - van Putten, M J AU - van Putten MJ FAU - Stam, C J AU - Stam CJ LA - eng PT - Journal Article CY - United States TA - IEEE Eng Med Biol Mag JID - 8305985 SB - IM MH - Biomedical Engineering MH - Child, Preschool MH - Data Interpretation, Statistical MH - Electroencephalography/*statistics & numerical data MH - Female MH - Human MH - Infant MH - Male MH - Nonlinear Dynamics MH - Spasms, Infantile/*physiopathology EDAT- 2001/10/24 10:00 MHDA- 2002/03/26 10:01 PST - ppublish SO - IEEE Eng Med Biol Mag 2001 Sep-Oct;20(5):72-9. 406: Palus M, et al. Synchronization and informati...[PMID:11668898]Related Articles, Books, LinkOut UI - 21525965 PMID- 11668898 DA - 20011023 DCOM- 20020325 IS - 0739-5175 VI - 20 IP - 5 DP - 2001 Sep-Oct TI - Synchronization and information flow in EEGs of epileptic patients. PG - 65-71 AD - Clinic of Paediatric Neurology, 2nd Medical Faculty, Charles University. mp@cs.cas.cz FAU - Palus, M AU - Palus M FAU - Komarek, V AU - Komarek V FAU - Prochazka, T AU - Prochazka T FAU - Hrncir, Z AU - Hrncir Z FAU - Sterbova, K AU - Sterbova K LA - eng PT - Journal Article CY - United States TA - IEEE Eng Med Biol Mag JID - 8305985 SB - IM MH - Adult MH - Biomedical Engineering MH - Data Interpretation, Statistical MH - Electroencephalography/*statistics & numerical data MH - Epilepsy/*diagnosis/*physiopathology MH - Human MH - Infant MH - Information Theory MH - Male MH - Monitoring, Physiologic/statistics & numerical data MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2001/10/24 10:00 MHDA- 2002/03/26 10:01 PST - ppublish SO - IEEE Eng Med Biol Mag 2001 Sep-Oct;20(5):65-71. 407: Iannella N, et al. A spiking neural network arch...[PMID:11665783]Related Articles, Books, LinkOut UI - 21521880 PMID- 11665783 DA - 20011022 DCOM- 20020426 IS - 0893-6080 VI - 14 IP - 6-7 DP - 2001 Jul-Sep TI - A spiking neural network architecture for nonlinear function approximation. PG - 933-9 AB - Multilayer perceptrons have received much attention in recent years due to their universal approximation capabilities. Normally, such models use real valued continuous signals, although they are loosely based on biological neuronal networks that encode signals using spike trains. Spiking neural networks are of interest both from a biological point of view and in terms of a method of robust signaling in particularly noisy or difficult environments. It is important to consider networks based on spike trains. A basic question that needs to be considered however, is what type of architecture can be used to provide universal function approximation capabilities in spiking networks? In this paper, we propose a spiking neural network architecture using both integrate-and-fire units as well as delays, that is capable of approximating a real valued function mapping to within a specified degree of accuracy. AD - Brain Science Institute, RIKEN, Saitama, Japan. angelo@postman.riken.go.jp FAU - Iannella, N AU - Iannella N FAU - Back, A D AU - Back AD LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - United States TA - Neural Netw JID - 8805018 SB - IM MH - Action Potentials/*physiology MH - Animal MH - Central Nervous System/*physiology MH - Human MH - Nerve Net/*physiology MH - *Neural Networks (Computer) MH - Neurons/*physiology MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Synaptic Transmission/*physiology RF - 10 EDAT- 2001/10/23 10:00 MHDA- 2002/04/27 10:01 PST - ppublish SO - Neural Netw 2001 Jul-Sep;14(6-7):933-9. 408: Levy N, et al. Distributed synchrony in a ce...[PMID:11665773]Related Articles, Books, LinkOut UI - 21521870 PMID- 11665773 DA - 20011022 DCOM- 20020426 IS - 0893-6080 VI - 14 IP - 6-7 DP - 2001 Jul-Sep TI - Distributed synchrony in a cell assembly of spiking neurons. PG - 815-24 AB - We investigate the formation of a Hebbian cell assembly of spiking neurons, using a temporal synaptic learning curve that is based on recent experimental findings. It includes potentiation for short time delays between pre- and post-synaptic neuronal spiking, and depression for spiking events occurring in the reverse order. The coupling between the dynamics of synaptic learning and that of neuronal activation leads to interesting results. One possible mode of activity is distributed synchrony, implying spontaneous division of the Hebbian cell assembly into groups, or subassemblies, of cells that fire in a cyclic manner. The behavior of distributed synchrony is investigated both by simulations and by analytic calculations of the resulting synaptic distributions. AD - School of Physics and Astronomy, Tel Aviv University, Israel. FAU - Levy, N AU - Levy N FAU - Horn, D AU - Horn D FAU - Meilijson, I AU - Meilijson I FAU - Ruppin, E AU - Ruppin E LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - United States TA - Neural Netw JID - 8805018 SB - IM MH - Action Potentials/*physiology MH - Animal MH - Cortical Synchronization MH - Human MH - Learning/*physiology MH - *Models, Neurological MH - Nerve Net/*physiology MH - Neuronal Plasticity/*physiology MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Synaptic Transmission/*physiology RF - 19 EDAT- 2001/10/23 10:00 MHDA- 2002/04/27 10:01 PST - ppublish SO - Neural Netw 2001 Jul-Sep;14(6-7):815-24. 409: Siegel RM, et al. Deterministic dynamics emergi...[PMID:11665764]Related Articles, Books, LinkOut UI - 21521861 PMID- 11665764 DA - 20011022 DCOM- 20020426 IS - 0893-6080 VI - 14 IP - 6-7 DP - 2001 Jul-Sep TI - Deterministic dynamics emerging from a cortical functional architecture. PG - 697-713 AB - Cerebral cortex has a range of interconnected functional architectures. Some appear random and without structure, while others are geometrical. Although the biological details certainly constrain spatial temporal patterns in neural networks, the influence that the laws of deterministic dynamics bring to bear on even isolated simple geometries are unknown. Layer II/III of primary visual cortex has long range horizontal connections with projections to and from other layers. The long range excitatory connections were modeled in isolation as an isolated laterally connected functional architecture. The Hodgkin-Huxley or Pinsky-Rinzel equations were used to simulate the neuronal elements. Waves of activity could propagate through the functional architecture; depending on the synaptic kinetics, the system could settle down into quiescence, oscillations, or seemingly random behavior. Order could be found in random-looking behavior by the application of techniques from chaos theory. Furthermore, the range and transitions of the temporal patterns in the modeled collection of neurons are similar to those found in other non-linear systems. The possibility that the temporal patterns of neurons in situ are also constrained by these mathematical laws is discussed. AD - Center for Molecular and Behavioral Neuroscience, Rutgers University, Newark, NJ 07102, USA. axon@cortex.rutgers.edu FAU - Siegel, R M AU - Siegel RM FAU - Read, H L AU - Read HL LA - eng ID - EY-9223/EY/NEI ID - RR-12873/RR/NCRR PT - Journal Article CY - United States TA - Neural Netw JID - 8805018 RN - 0 (Ion Channels) SB - IM MH - Action Potentials/*physiology MH - Animal MH - Biological Clocks/physiology MH - Ion Channels/physiology MH - *Models, Neurological MH - Nerve Net/*physiology MH - Neural Pathways/physiology MH - Neurons/*physiology MH - *Nonlinear Dynamics MH - Rats MH - Reaction Time/physiology MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. MH - Synapses/physiology MH - Synaptic Transmission/*physiology MH - Vision/physiology MH - Visual Cortex/physiology EDAT- 2001/10/23 10:00 MHDA- 2002/04/27 10:01 PST - ppublish SO - Neural Netw 2001 Jul-Sep;14(6-7):697-713. 410: Sternad D, et al. Bouncing a ball: tuning into ...[PMID:11642701]Related Articles, Books, LinkOut UI - 21520373 PMID- 11642701 DA - 20011019 DCOM- 20020315 IS - 0096-1523 VI - 27 IP - 5 DP - 2001 Oct TI - Bouncing a ball: tuning into dynamic stability. PG - 1163-84 AB - Rhythmically bouncing a ball with a racket was investigated and modeled with a nonlinear map. Model analyses provided a variable defining a dynamically stable solution that obviates computationally expensive corrections. Three experiments evaluated whether dynamic stability is optimized and what perceptual support is necessary for stable behavior. Two hypotheses were tested: (a) Performance is stable if racket acceleration is negative at impact, and (b) variability is lowest at an impact acceleration between -4 and -1 m/s2. In Experiment 1 participants performed the task, eyes open or closed, bouncing a ball confined to a 1-dimensional trajectory. Experiment 2 eliminated constraints on racket and ball trajectory. Experiment 3 excluded visual or haptic information. Movements were performed with negative racket accelerations in the range of highest stability. Performance with eyes closed was more variable, leaving acceleration unaffected. With haptic information, performance was more stable than with visual information alone. AD - Department of Kinesiology, The Pennsylvania State University, University Park 16802, USA. dxs48@psu.edu FAU - Sternad, D AU - Sternad D FAU - Duarte, M AU - Duarte M FAU - Katsumata, H AU - Katsumata H FAU - Schaal, S AU - Schaal S LA - eng PT - Journal Article CY - United States TA - J Exp Psychol Hum Percept Perform JID - 7502589 SB - IM MH - Adult MH - Biomechanics MH - Female MH - Human MH - Male MH - Models, Psychological MH - *Motion Perception MH - Nonlinear Dynamics MH - Periodicity MH - Random Allocation MH - Support, U.S. Gov't, Non-P.H.S. MH - Tennis MH - Visual Perception EDAT- 2001/10/20 10:00 MHDA- 2002/03/16 10:01 PST - ppublish SO - J Exp Psychol Hum Percept Perform 2001 Oct;27(5):1163-84. 411: Henson SM, et al. Lattice effects observed in c...[PMID:11641500]Related Articles, Books, LinkOut UI - 21521692 PMID- 11641500 DA - 20011019 DCOM- 20011204 LR - 20021028 IS - 0036-8075 VI - 294 IP - 5542 DP - 2001 Oct 19 TI - Lattice effects observed in chaotic dynamics of experimental populations. PG - 602-5 AB - Animals and many plants are counted in discrete units. The collection of possible values (state space) of population numbers is thus a nonnegative integer lattice. Despite this fact, many mathematical population models assume a continuum of system states. The complex dynamics, such as chaos, often displayed by such continuous-state models have stimulated much ecological research; yet discrete-state models with bounded population size can display only cyclic behavior. Motivated by data from a population experiment, we compared the predictions of discrete-state and continuous-state population models. Neither the discrete- nor continuous-state models completely account for the data. Rather, the observed dynamics are explained by a stochastic blending of the chaotic dynamics predicted by the continuous-state model and the cyclic dynamics predicted by the discrete-state models. We suggest that such lattice effects could be an important component of natural population fluctuations. AD - Department of Mathematics, Andrews University, Berrien Springs, MI 49104, USA. henson@andrews.edu FAU - Henson, S M AU - Henson SM FAU - Costantino, R F AU - Costantino RF FAU - Cushing, J M AU - Cushing JM FAU - Desharnais, R A AU - Desharnais RA FAU - Dennis, B AU - Dennis B FAU - King, A A AU - King AA LA - eng PT - Journal Article CY - United States TA - Science JID - 0404511 SB - IM CIN - Science. 2002 Sep 27;297(5590):2163; discussion 2163. PMID: 12351754 MH - Animal MH - *Ecosystem MH - Environment MH - Mathematics MH - Models, Statistical MH - *Models, Theoretical MH - *Nonlinear Dynamics MH - *Population Density MH - *Population Dynamics MH - Stochastic Processes MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Tribolium/*physiology EDAT- 2001/10/20 10:00 MHDA- 2002/01/05 10:01 AID - 10.1126/science.1063358 [doi] AID - 294/5542/602 [pii] PST - ppublish SO - Science 2001 Oct 19;294(5542):602-5. 412: Namiot VA. [A theoretical approach to "m...[PMID:11605385]Related Articles, Books, LinkOut UI - 21517910 PMID- 11605385 DA - 20011018 DCOM- 20011101 IS - 0006-3029 VI - 46 IP - 5 DP - 2001 Sep-Oct TI - [A theoretical approach to "macroscopic fluctuations" effect] PG - 856-8 AB - At present there is no generally accepted theory of the effect of macroscopic fluctuations. It the article, an attempt is made to relate this effect to some basic properties of quantum systems, in particular, to the formal absence of dynamic chaos in these systems. Based on this approach, it was shown why the level of the effect must be of the same order of magnitude as the level of noise and cannot exceed this level as the number of experiments increases. It was shown qualitatively what is the cause of the similarity of histograms observed in different experiments. AD - Research Institute of Nuclear Physics, Lomonosov Moscow State University, Vorob'evy Gory, Moscow, 117234 Russia. FAU - Namiot, V A AU - Namiot VA LA - rus PT - Journal Article TT - K teorii effekta"makroskopicheskikh fluktuatsii". CY - Russia TA - Biofizika JID - 0372666 SB - IM MH - English Abstract MH - *Extraterrestrial Environment MH - Nonlinear Dynamics MH - *Quantum Theory MH - Statistical Distributions EDAT- 2001/10/19 10:00 MHDA- 2001/11/03 10:01 PST - ppublish SO - Biofizika 2001 Sep-Oct;46(5):856-8. 413: Strelkov VV. [The "near zone" effect in dy...[PMID:11605374]Related Articles, Books, LinkOut UI - 21517899 PMID- 11605374 DA - 20011018 DCOM- 20011101 IS - 0006-3029 VI - 46 IP - 5 DP - 2001 Sep-Oct TI - [The "near zone" effect in dynamic chaos] PG - 807-10 AB - The dynamics of the system with a determined chaotic behavior (Lorentz system) was studied by comparing the histograms. It was shown that the dynamics of the system exhibits phenomena similar to those observed in studies of fluctuations in physical systems. In particular, upon comparison of histograms constructed from different time intervals, the "near zone" effect makes itself evident. It was shown that a very slight modulation of only one parameter of the system leads to a change in behavior. AD - International Laser Center, Lomonosov Moscow State University, Vorob'evy Gory, Moscow, 119899 Russia. FAU - Strelkov, V V AU - Strelkov VV LA - rus PT - Journal Article TT - Effect "blizhnei zony" v dinamicheskom khaose. CY - Russia TA - Biofizika JID - 0372666 SB - IM MH - English Abstract MH - *Models, Theoretical MH - *Nonlinear Dynamics MH - Physics MH - Statistical Distributions EDAT- 2001/10/19 10:00 MHDA- 2001/11/03 10:01 PST - ppublish SO - Biofizika 2001 Sep-Oct;46(5):807-10. 414: Li LP, et al. The asymmetry of transient re...[PMID:11601739]Related Articles, Books, LinkOut UI - 21487349 PMID- 11601739 DA - 20011016 DCOM- 20020506 IS - 0148-0731 VI - 123 IP - 5 DP - 2001 Oct TI - The asymmetry of transient response in compression versus release for cartilage in unconfined compression. PG - 519-22 AB - Observations in compression tests of articular cartilage have revealed unequal load increments for compression and release of the same amplitude applied to a disk with an identical previously imposed compression (in equilibrium). The mechanism of this asymmetric transient response is investigated here using a nonlinear fibril-reinforced model. It is found that the asymmetry is predominantly produced by the fibril stiffening with its tensile strain. In addition, allowing the hydraulic permeability to decrease significantly with compressive dilatation of cartilage increases the transient fibril strain, resulting in a stronger asymmetry. Large deformation also enhances the asymmetry as a consequence of stronger fibril stiffening. AD - Biosyntech Inc., Park of Science and High Technology, Laval, Canada. leping@grbb.polymtl.ca FAU - Li, L P AU - Li LP FAU - Buschmann, M D AU - Buschmann MD FAU - Shirazi-Adl, A AU - Shirazi-Adl A LA - eng PT - Journal Article CY - United States TA - J Biomech Eng JID - 7909584 SB - IM MH - Biomechanics MH - Biomedical Engineering MH - Cartilage, Articular/*physiology MH - Compressive Strength MH - Elasticity MH - Human MH - In Vitro MH - Models, Biological MH - Nonlinear Dynamics MH - Stress, Mechanical MH - Support, Non-U.S. Gov't EDAT- 2001/10/17 10:00 MHDA- 2002/05/07 10:01 PST - ppublish SO - J Biomech Eng 2001 Oct;123(5):519-22. 415: Oram MW, et al. Excess synchrony in motor cor...[PMID:11600633]Related Articles, Books, LinkOut UI - 21486674 PMID- 11600633 DA - 20011015 DCOM- 20011204 IS - 0022-3077 VI - 86 IP - 4 DP - 2001 Oct TI - Excess synchrony in motor cortical neurons provides redundant direction information with that from coarse temporal measures. PG - 1700-16 AB - Previous studies have shown that measures of fine temporal correlation, such as synchronous spikes, across responses of motor cortical neurons carries more directional information than that predicted from statistically independent neurons. It is also known, however, that the coarse temporal measures of responses, such as spike count, are not independent. We therefore examined whether the information carried by coincident firing was related to that of coarsely defined spike counts and their correlation. Synchronous spikes were counted in the responses from 94 pairs of simultaneously recorded neurons in primary motor cortex (MI) while monkeys performed arm movement tasks. Direct measurement of the movement-related information indicated that the coincident spikes (1- to 5-ms precision) carry approximately 10% of the information carried by a code of the two spike counts. Inclusion of the numbers of synchronous spikes did not add information to that available from the spike counts and their coarse temporal correlation. To assess the significance of the numbers of coincident spikes, we extended the stochastic spike count matched (SCM) model to include correlations between spike counts of the individual neural responses and slow temporal dependencies within neural responses (approximately 30 Hz bandwidth). The extended SCM model underestimated the numbers of synchronous spikes. Therefore as with previous studies, we found that there were more synchronous spikes in the neural data than could be accounted for by this stochastic model. However, the SCM model accounts for most (R(2) = 0.93 +/- 0.05, mean +/- SE) of the differences in the observed number of synchronous spikes to different directions of arm movement, indicating that synchronous spiking is directly related to spike counts and their broad correlation. Further, this model supports the information theoretic analysis that the synchronous spikes do not provide directional information beyond that available from the firing rates of the same pool of directionally tuned MI neurons. These results show that detection of precisely timed spike patterns above chance levels does not imply that those spike patterns carry information unavailable from coarser population codes but leaves open the possibility that excess synchrony carries other forms of information or serves other roles in cortical information processing not studied here. AD - School of Psychology, University of St. Andrews, Fife KY16 9JU, United Kingdom. FAU - Oram, M W AU - Oram MW FAU - Hatsopoulos, N G AU - Hatsopoulos NG FAU - Richmond, B J AU - Richmond BJ FAU - Donoghue, J P AU - Donoghue JP LA - eng PT - Journal Article CY - United States TA - J Neurophysiol JID - 0375404 SB - IM MH - Action Potentials/*physiology MH - Animal MH - Electrophysiology MH - Macaca fascicularis MH - Motor Cortex/cytology/*physiology MH - Movement/physiology MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Regression Analysis MH - Time Factors EDAT- 2001/10/16 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Neurophysiol 2001 Oct;86(4):1700-16. 416: Radhakrishna RK, et al. Nonlinear measures of heart r...[PMID:11593766]Related Articles, Books, LinkOut UI - 21478179 PMID- 11593766 DA - 20011011 DCOM- 20011204 IS - 1566-0702 VI - 83 IP - 3 DP - 2000 Oct 2 TI - Nonlinear measures of heart rate time series: influence of posture and controlled breathing. PG - 148-58 AB - In this study, we investigated measures of nonlinear dynamics and chaos theory in regards to heart rate variability in 27 normal control subjects in supine and standing postures, and 14 subjects in spontaneous and controlled breathing conditions. We examined minimum embedding dimension (MED), largest Lyapunov exponent (LLE) and measures of nonlinearity (NL) of heart rate time series. MED quantifies the system's complexity, LLE predictability and NL, a measure of deviation from linear processes. There was a significant decrease in complexity (P < 0.00001), a decrease in predictability (P < 0.00001) and an increase in nonlinearity (P = 0.00001) during the change from supine to standing posture. Decrease in MED, and increases in NL score and LLE in standing posture appear to be partly due to an increase in sympathetic activity of the autonomous nervous system in standing posture. An improvement in predictability during controlled breathing appears to be due to the introduction of a periodic component. AD - Department of ECE, Indian Institute of Science, Bangalore, India. FAU - Radhakrishna, R K AU - Radhakrishna RK FAU - Dutt, D N AU - Dutt DN FAU - Yeragani, V K AU - Yeragani VK LA - eng PT - Clinical Trial PT - Journal Article CY - Netherlands TA - Auton Neurosci JID - 100909359 SB - IM MH - Adult MH - Autonomic Nervous System/physiology MH - Female MH - Heart Rate/*physiology MH - Human MH - Male MH - *Models, Cardiovascular MH - Nonlinear Dynamics MH - Posture/*physiology MH - Predictive Value of Tests MH - Reference Values MH - Reproducibility of Results MH - *Respiration MH - Signal Processing, Computer-Assisted MH - Time Factors EDAT- 2001/10/12 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - Auton Neurosci 2000 Oct 2;83(3):148-58. 417: Sasaki O, et al. Nonlinear analysis of orthost...[PMID:11591445]Related Articles, Books, LinkOut UI - 21476039 PMID- 11591445 DA - 20011009 DCOM- 20011207 LR - 20020222 IS - 0168-0102 VI - 41 IP - 2 DP - 2001 Oct TI - Nonlinear analysis of orthostatic posture in patients with vertigo or balance disorders. PG - 185-92 AB - The stabilometry signals involve irregular and unpredictable components. In order to identify the hidden dynamics that underlie the multi-link networks consisted of the multiple sensory systems, motor components and central integration, we applied a nonlinear analysis to these signals. We evaluated the postural control differences between eyes open and closed by means of the dynamical closeness between two states, known as similarity index, for the patients with vestibular disorders. We were able to demonstrate that some patients (eight of 21) showed a difference between the conventional and nonlinear measures. Especially, the similarity index tended to reflect the clinical course of the vestibular compensation and the findings in the patients with benign paroxysmal positional vertigo (BPPV) demonstrated that its vestibular function may include various pathologies besides canalithiasis. These results suggest that nonlinear analysis can elucidate the complex postural control networks and this procedure may also be able to provide the new findings of the stabilometry examinations. AD - Department of Otolaryngology, Shinshu University School of Medicine, 3-1-1 Asahi, Postal Code 390-8621, Matsumoto, Japan. sasaki-o@hsp.md.shinshu-u.ac.jp FAU - Sasaki, O AU - Sasaki O FAU - Gagey, P M AU - Gagey PM FAU - Ouaknine, A M AU - Ouaknine AM FAU - Martinerie, J AU - Martinerie J FAU - Le Van Quyen, M AU - Le Van Quyen M FAU - Toupet, M AU - Toupet M FAU - L'Heritier, A AU - L'Heritier A LA - eng PT - Journal Article CY - Ireland TA - Neurosci Res JID - 8500749 SB - IM SB - S MH - Adult MH - Aged MH - Algorithms MH - Central Nervous System/*physiopathology MH - Cues MH - Equilibrium/*physiology MH - Feedback/physiology MH - Female MH - Human MH - Male MH - Middle Age MH - *Nonlinear Dynamics MH - Orientation/physiology MH - Posture/*physiology MH - Reference Values MH - Space Perception/physiology MH - Stochastic Processes MH - Vertigo/*diagnosis/*physiopathology MH - Vestibule/injuries/pathology/*physiopathology EDAT- 2001/10/10 10:00 MHDA- 2002/01/05 10:01 AID - S0168010201002760 [pii] PST - ppublish SO - Neurosci Res 2001 Oct;41(2):185-92. 418: Lu S, et al. A new algorithm for linear an...[PMID:11585035]Related Articles, Books, LinkOut UI - 21468762 PMID- 11585035 DA - 20011004 DCOM- 20011205 IS - 0018-9294 VI - 48 IP - 10 DP - 2001 Oct TI - A new algorithm for linear and nonlinear ARMA model parameter estimation using affine geometry. PG - 1116-24 AB - A linear and nonlinear autoregressive (AR) moving average (MA) (ARMA) identification algorithm is developed for modeling time series data. The new algorithm is based on the concepts of affine geometry in which the salient feature of the algorithm is to remove the linearly dependent ARMA vectors from the pool of candidate ARMA vectors. For noiseless time series data with a priori incorrect model-order selection, computer simulations show that accurate linear and nonlinear ARMA model parameters can be obtained with the new algorithm. Many algorithms, including the fast orthogonal search (FOS) algorithm, are not able to obtain correct parameter estimates in every case, even with noiseless time series data, because their model-order search criteria are suboptimal. For data contaminated with noise, computer simulations show that the new algorithm performs better than the FOS algorithm for MA processes, and similarly to the FOS algorithm for ARMA processes. However, the computational time to obtain the parameter estimates with the new algorithm is faster than with FOS. Application of the new algorithm to experimentally obtained renal blood flow and pressure data show that the new algorithm is reliable in obtaining physiologically understandable transfer function relations between blood pressure and flow signals. AD - Department of Electrical Engineering and Center for Biomedical Engineering, City College of the City University of New York, NY 10031, USA. FAU - Lu, S AU - Lu S FAU - Ju, K H AU - Ju KH FAU - Chon, K H AU - Chon KH LA - eng PT - Journal Article CY - United States TA - IEEE Trans Biomed Eng JID - 0012737 SB - IM MH - *Algorithms MH - Animal MH - Blood Pressure/*physiology MH - Computer Simulation MH - Least-Squares Analysis MH - Linear Models MH - Nonlinear Dynamics MH - Rats MH - Rats, Sprague-Dawley MH - Renal Circulation/*physiology MH - Signal Processing, Computer-Assisted MH - Support, Non-U.S. Gov't EDAT- 2001/10/05 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - IEEE Trans Biomed Eng 2001 Oct;48(10):1116-24. 419: Soloviev MV. [On possible role of chaotic ...[PMID:11582752]Related Articles, Books, LinkOut UI - 21467338 PMID- 11582752 DA - 20011003 DCOM- 20011204 LR - 20020619 IS - 1561-9125 VI - 8 DP - 2001 TI - [On possible role of chaotic behavior of the gene regulation system in aging] PG - 27-33 AB - 1. The facts of biology of aging say that the modification of activity of few key genes may lead to the significant increase of life span. 2. The experiments with computational models of gene regulation show that these models are characterized by metastable behavior typical for the chaotic systems. 3. The force of mortality in Gompertz equation grows exponentially in time. It allows to hypothesize that at least at the level of gene regulation aging can be a chaotic process (here implied that chaos is a kind of the complex systems dynamics controlled by strictly determined rules). This approach allows to describe aging from the view point of the information theory--as the forgetting of the right functioning of the organism (i.e. forgetting the state of health) caused by fluctuations (weak nonspecific influencies on the system). Average rate of such forgetting (described by parameter, named Lyapunov exponent) could be identified with the exponent of mortality rate in Gompertz equation. And the parameter inverse to Lyapunov's exponent (Lyapunov time), that describes the time of the initial (healthy) state forgetting, well corresponds to the time of the puberty beginning (i.e. the minimal time for the healthy state to be kept) for human beings, mice, and fruit flies (organisms whose parameters of aging are most perfectly known). AD - N.N. Petrov Research Institute of Oncology, 197758, St. Petersburg, Pesochny-2, Leningradskaya, 68. msoloviev@mail.ru FAU - Soloviev, M V AU - Soloviev MV LA - rus PT - Journal Article TT - O vozmozhnoi roli khaoticheskogo povedeniia sistemy gennoi reguliatsii v starenii organizma. CY - Russia TA - Adv Gerontol JID - 100971443 SB - IM MH - Aging/genetics/*physiology MH - English Abstract MH - Gene Expression Regulation/genetics/*physiology MH - Human MH - *Nonlinear Dynamics EDAT- 2001/10/05 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - Adv Gerontol 2001;8:27-33. 420: Martin G, et al. Nonlinear mill control....[PMID:11577824]Related Articles, Books, LinkOut UI - 21461570 PMID- 11577824 DA - 20011001 DCOM- 20011025 IS - 0019-0578 VI - 40 IP - 4 DP - 2001 TI - Nonlinear mill control. PG - 369-79 AB - A mill is a mechanical device that grinds mined or processed material into small particles. The process is known to display significant deadtime, and, more notably, severe nonlinear behavior. Over the past 25 years attempts at continuous mill control have met varying degrees of failure, mainly due to model mismatch caused by changes in the mill process gains. This paper describes an on-line control application on a closed-circuit cement mill that uses nonlinear model predictive control technology. The nonlinear gains for the control model are calculated on-line from a neural network model of the process. AD - Business Development, Pavilion Technologies, Inc, Austin, TX 78758, USA. gmartin@pav.com FAU - Martin, G AU - Martin G FAU - McGarel, S AU - McGarel S LA - eng PT - Journal Article CY - United States TA - ISA Trans JID - 0374750 SB - IM MH - Algorithms MH - Computer Simulation MH - Drug Industry/*instrumentation MH - Nonlinear Dynamics EDAT- 2001/10/02 10:00 MHDA- 2001/10/26 10:01 PST - ppublish SO - ISA Trans 2001;40(4):369-79. 421: Budygin EA, et al. Terminal effects of ethanol o...[PMID:11574942]Related Articles, Books, LinkOut UI - 21459106 PMID- 11574942 DA - 20010927 DCOM- 20011204 IS - 0887-4476 VI - 42 IP - 2 DP - 2001 Nov TI - Terminal effects of ethanol on dopamine dynamics in rat nucleus accumbens: an in vitro voltammetric study. PG - 77-9 AB - To assess the direct effects of acute ethanol on dopamine (DA) terminals, evoked DA release and uptake were measured in rat nucleus accumbens slices using fast-scan cyclic voltammetry. Low and moderate concentrations of ethanol (20, 45 and 100 mM) did not alter evoked DA release, while high concentrations (150 and 200 mM) significantly decreased DA release (18 and 36%, respectively) in a calcium-dependent manner. No significant difference was found between the rate of DA disappearance measured before and after the drug. These data indicate that uptake of DA through the dopamine transporter is unaffected by ethanol, even at high concentrations. Therefore, low to moderate concentrations of ethanol have no effect on DA dynamics at the level of the nerve terminal in the nucleus accumbens. This is consistent with the hypothesis that cell body regions of DA neurons are the primary target for the stimulating and reinforcing effects of ethanol. High concentrations of ethanol can locally depress DA release, and this may correlate with the sedative actions of the drug. CI - Copyright 2001 Wiley-Liss, Inc. AD - Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA. srjones@wfubmc.edu FAU - Budygin, E A AU - Budygin EA FAU - Phillips, P E AU - Phillips PE FAU - Wightman, R M AU - Wightman RM FAU - Jones, S R AU - Jones SR LA - eng ID - AA11997/AA/NIAAA ID - DA10900/DA/NIDA PT - Journal Article CY - United States TA - Synapse JID - 8806914 RN - 51-61-6 (Dopamine) RN - 64-17-5 (Ethanol) SB - IM MH - Alcohol-Induced Disorders, Nervous System/*metabolism/physiopathology MH - Animal MH - Dopamine/metabolism/*secretion MH - Dose-Response Relationship, Drug MH - Ethanol/*pharmacology MH - Male MH - Neural Pathways/drug effects/metabolism/secretion MH - *Nonlinear Dynamics MH - Nucleus Accumbens/*drug effects/metabolism/secretion MH - Presynaptic Terminals/*drug effects/metabolism/secretion MH - Rats MH - Rats, Sprague-Dawley MH - Substance-Related Disorders/metabolism/pathology/physiopathology MH - Support, U.S. Gov't, P.H.S. MH - Ventral Tegmental Area/drug effects/metabolism/secretion EDAT- 2001/09/28 10:00 MHDA- 2002/01/05 10:01 AID - 10.1002/syn.1101 [pii] PST - ppublish SO - Synapse 2001 Nov;42(2):77-9. 422: McCann ME, et al. The pharmacokinetics of epidu...[PMID:11574352]Related Articles, Books, LinkOut UI - 21458207 PMID- 11574352 DA - 20010927 DCOM- 20011018 IS - 0003-2999 VI - 93 IP - 4 DP - 2001 Oct TI - The pharmacokinetics of epidural ropivacaine in infants and young children. PG - 893-7 AB - The pharmacokinetic variables of ropivacaine were characterized after epidural bolus injection in pediatric patients. The subjects, 7 infants (aged 3-11 mo) and 11 young children (aged 12-48 mo), received 1.7 mg/kg of ropivacaine via a lumbar epidural catheter. Total plasma concentrations of ropivacaine measured over 24 h were assayed by high-pressure liquid chromatography, and pharmacokinetic modeling was performed by Nonlinear Mixed Effects Modeling analysis. The median peak venous plasma concentrations (C(max)) in infants and young children were 610 microg/L (interquartile range [IQR], 550-725 microg/L) and 640 microg/L (IQR, 540-750 microg/L), respectively. The median times to maximum plasma ropivacaine concentration (T(max)) were 60 min (IQR, 60-120 min) in infants and 60 min (IQR, 30-90 min) in young children. There were no statistical differences between median values of C(max) and T(max) between infants and young children. The calculated clearance (CL) in infants was 4.26 mL x min(-1) x kg(-1) (9% coefficient of variation), and in young children it was 6.15 mL x min(-1) x kg(-1) (11% coefficient of variation). The CL for infants was significantly less than the CL for young children (P < 0.01). The volume of distribution was estimated to be 2370 mL/kg (9% coefficient of variation) for both young children and infants. No systemic toxicity was observed in either group. IMPLICATIONS: This study revealed that the pharmacokinetic variables of lumbar epidural bolus ropivacaine in pediatric patients aged 3 to 48 mo are similar to those of adults, except that drug clearance was less in infants compared with older children. AD - Department of Anesthesia, Children's Hospital, Boston, Massachusetts 02115, USA. McCann_M@tch.harvard.edu FAU - McCann, M E AU - McCann ME FAU - Sethna, N F AU - Sethna NF FAU - Mazoit, J X AU - Mazoit JX FAU - Sakamoto, M AU - Sakamoto M FAU - Rifai, N AU - Rifai N FAU - Hope, T AU - Hope T FAU - Sullivan, L AU - Sullivan L FAU - Auble, S G AU - Auble SG FAU - Berde, C B AU - Berde CB LA - eng PT - Clinical Trial PT - Journal Article CY - United States TA - Anesth Analg JID - 1310650 RN - 0 (Amides) RN - 0 (Anesthetics, Local) RN - 84057-95-4 (ropivacaine) SB - AIM SB - IM MH - Algorithms MH - Amides/*pharmacokinetics MH - Anesthesia, Epidural MH - Anesthesia, General MH - Anesthetics, Local/*pharmacokinetics MH - Child, Preschool MH - Chromatography, High Pressure Liquid MH - Female MH - Human MH - Infant MH - Male MH - Models, Biological MH - Nonlinear Dynamics MH - Spectrophotometry, Ultraviolet EDAT- 2001/09/28 10:00 MHDA- 2001/10/19 10:01 PST - ppublish SO - Anesth Analg 2001 Oct;93(4):893-7. 423: Sarbadhikari SN, et al. Chaos in the brain: a short r...[PMID:11574252]Related Articles, Books, LinkOut UI - 21458898 PMID- 11574252 DA - 20010927 DCOM- 20011220 IS - 1350-4533 VI - 23 IP - 7 DP - 2001 Sep TI - Chaos in the brain: a short review alluding to epilepsy, depression, exercise and lateralization. PG - 445-55 AB - Electroencephalograms (EEGs) reflect the electrical activity of the brain. Even when they are analyzed from healthy individuals, they manifest chaos in the nervous system. EEGs are likely to be produced by a nonlinear system, since a nonlinear system with at least 3 degrees of freedom (or state variables) may exhibit chaotic behavior. Furthermore, such systems can have multiple stable states governed by "chaotic" ("strange") attractors. A key feature of chaotic systems is the presence of an infinite number of unstable periodic fixed points, which are found in spontaneously active neuronal networks (e.g., epilepsy). The brain has chemicals called neurotransmitters that convey the information through the 10(16) synapses residing there. However, each of these neurotransmitters acts through various receptors and their numerous subtypes, thereby exhibiting complex interactions. Albeit in epilepsy the role of chaos and EEG findings are well proven, in another condition, i.e., depression, the role of chaos is slowly gaining ground. The multifarious roles of exercise, neurotransmitters and (cerebral) hemispheric lateralization, in the case of depression, are also being established. The common point of reference could be nonlinear dynamics. The purpose of this review is to study those nonlinear/chaotic interactions and point towards new theoretical models incorporating the oscillation caused by the same neurotransmitter acting on its different receptor subtypes. This may lead to a better understanding of brain neurodynamics in health and disease. AD - Department of Physiology, Sikkim Manipal Institute of Medical Sciences, Sikkim 737 102, India. drsupten@yahoo.com FAU - Sarbadhikari, S N AU - Sarbadhikari SN FAU - Chakrabarty, K AU - Chakrabarty K LA - eng PT - Journal Article PT - Review PT - Review, Academic CY - England TA - Med Eng Phys JID - 9422753 RN - 0 (Neurotransmitters) SB - IM MH - Brain/*physiology/physiopathology MH - Depression/*physiopathology MH - *Electroencephalography MH - Epilepsy/*physiopathology MH - Exercise/*physiology MH - Human MH - Laterality/*physiology MH - Models, Neurological MH - Neurotransmitters/physiology MH - *Nonlinear Dynamics RF - 101 EDAT- 2001/09/28 10:00 MHDA- 2002/01/05 10:01 AID - S1350453301000753 [pii] PST - ppublish SO - Med Eng Phys 2001 Sep;23(7):445-55. 424: Diekmann O, et al. On the formulation and analys...[PMID:11570590]Related Articles, Books, LinkOut UI - 21454321 PMID- 11570590 DA - 20010925 DCOM- 20020313 IS - 0303-6812 VI - 43 IP - 2 DP - 2001 Aug TI - On the formulation and analysis of general deterministic structured population models. II. Nonlinear theory. PG - 157-89 AB - This paper is as much about a certain modelling methodology, as it is about the constructive definition of future population states from a description of individual behaviour and an initial population state. The key idea is to build a nonlinear model in two steps, by explicitly introducing the environmental condition via the requirement that individuals are independent from one another (and hence equations are linear) when this condition is prescribed as a function of time. A linear physiologically structured population model is defined by two rules, one for reproduction and one for development and survival, both depending on the initial individual state and the prevailing environmental condition. In Part I we showed how one can constructively define future population state operators from these two ingredients. A nonlinear model is a linear model together with a feedback law that describes how the environmental condition at any particular time depends on the population size and composition at that time. When applied to the solution of the linear problem, the feedback law yields a fixed point problem. This we solve constructively by means of the contraction mapping principle, for any given initial population state. Using subsequently this fixed point as input in the linear population model, we obtain a population semiflow. We then say that we solved the nonlinear problem. AD - Department of Mathematics, University of Utrecht, The Netherlands. FAU - Diekmann, O AU - Diekmann O FAU - Gyllenberg, M AU - Gyllenberg M FAU - Huang, H AU - Huang H FAU - Kirkilionis, M AU - Kirkilionis M FAU - Metz, J A AU - Metz JA FAU - Thieme, H R AU - Thieme HR LA - eng PT - Journal Article CY - Germany TA - J Math Biol JID - 7502105 SB - IM MH - Animal MH - Cannibalism MH - *Models, Biological MH - Nonlinear Dynamics MH - *Population Dynamics MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2001/09/26 10:00 MHDA- 2002/03/14 10:01 PST - ppublish SO - J Math Biol 2001 Aug;43(2):157-89. 425: Yakushevich LV. Is DNA a nonlinear dynamical ...[PMID:11568475]Related Articles, Books, LinkOut UI - 21453381 PMID- 11568475 DA - 20010924 DCOM- 20020131 IS - 0250-5991 VI - 26 IP - 3 DP - 2001 Sep TI - Is DNA a nonlinear dynamical system where solitary conformational waves are possible? PG - 305-13 AB - DNA is considered as a nonlinear dynamical system in which solitary conformational waves can be excited. The history of the approach, the main results, and arguments in favour and against are presented. Perspectives are discussed pertaining to studies of DNA's nonlinear properties. AD - Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290 Russia. yakushev@icb.psn.ru FAU - Yakushevich, L V AU - Yakushevich LV LA - eng PT - Journal Article CY - India TA - J Biosci JID - 8100809 RN - 9007-49-2 (DNA) SB - IM MH - DNA/*chemistry/metabolism MH - Mathematics MH - Models, Molecular MH - *Nonlinear Dynamics MH - *Nucleic Acid Conformation EDAT- 2001/09/25 10:00 MHDA- 2002/02/01 10:01 PST - ppublish SO - J Biosci 2001 Sep;26(3):305-13. 426: Trillenberg P, et al. Random walks, random sequence...[PMID:11568159]Related Articles, Books, LinkOut UI - 21453251 PMID- 11568159 DA - 20010924 DCOM- 20011204 LR - 20020201 IS - 8750-7587 VI - 91 IP - 4 DP - 2001 Oct TI - Random walks, random sequences, and nonlinear dynamics in human optokinetic nystagmus. PG - 1750-9 AB - Optokinetic nystagmus (OKN) is a reflexive eye movement with target-following slow phases (SP) alternating with oppositely directed fast phases (FP). We measured the following from OKN in three humans: FP beginning and ending positions, amplitudes, and intervals and SP amplitudes and velocities. We sought to predict future values of each parameter on the basis of past values, using state-space representation of the sequence (time-delay embedding) and local second-order approximation of trajectories. Predictability is an indication of determinism: this approach allows us to investigate the relative contributions of random and deterministic dynamics in OKN. FP beginning and ending positions showed good predictability, but SP velocity was less predictable. FP and SP amplitudes and FP intervals had little or no predictability. FP beginnings and endings were as predictable as randomized versions that retain linear autocorrelation; this is typical of random walks. Predictability of FP intervals did not change under random rearrangement, which is characteristic of a random process. Only linear determinism was demonstrated; nonlinear interactions may exist that would not be detected by our present approach. AD - Department of Neurology, Medical University of Lubeck, Ratzeburger Allee 160, D-23538 Lubeck, Germany. trillenberg_p@neuro.mu-luebeck.de FAU - Trillenberg, P AU - Trillenberg P FAU - Gross, C AU - Gross C FAU - Shelhamer, M AU - Shelhamer M LA - eng PT - Clinical Trial PT - Journal Article CY - United States TA - J Appl Physiol JID - 8502536 SB - IM SB - S MH - Human MH - Models, Neurological MH - Nonlinear Dynamics MH - Nystagmus, Optokinetic/*physiology MH - Software MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Walking/*physiology EDAT- 2001/09/25 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Appl Physiol 2001 Oct;91(4):1750-9. 427: Campbell KB, et al. Nonlinear myofilament regulat...[PMID:11566798]Related Articles, Books, LinkOut UI - 21450435 PMID- 11566798 DA - 20010921 DCOM- 20011207 IS - 0006-3495 VI - 81 IP - 4 DP - 2001 Oct TI - Nonlinear myofilament regulatory processes affect frequency-dependent muscle fiber stiffness. PG - 2278-96 AB - To investigate the role of nonlinear myofilament regulatory processes in sarcomeric mechanodynamics, a model of myofilament kinetic processes, including thin filament on-off kinetics and crossbridge cycling kinetics with interactions within and between kinetic processes, was built to predict sarcomeric stiffness dynamics. Linear decomposition of this highly nonlinear model resulted in the identification of distinct contributions by kinetics of recruitment and by kinetics of distortion to the complex stiffness of the sarcomere. Further, it was established that nonlinear kinetic processes, such as those associated with cooperative neighbor interactions or length-dependent crossbridge attachment, contributed unique features to the stiffness spectrum through their effect on recruitment. Myofilament model-derived sarcomeric stiffness reproduces experimentally measured sarcomeric stiffness with remarkable fidelity. Consequently, characteristic features of the experimentally determined stiffness spectrum become interpretable in terms of the underlying contractile mechanisms that are responsible for specific dynamic behaviors. AD - Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology, Washington State University, Pullman, Washington 99163, USA. cvselkbc@vetmed.wsu.edu FAU - Campbell, K B AU - Campbell KB FAU - Razumova, M V AU - Razumova MV FAU - Kirkpatrick, R D AU - Kirkpatrick RD FAU - Slinker, B K AU - Slinker BK LA - eng PT - Journal Article CY - United States TA - Biophys J JID - 0370626 RN - 0 (Tropomyosin) RN - 0 (Troponin) RN - 7440-70-2 (Calcium) SB - IM MH - Algorithms MH - Animal MH - Binding Sites/physiology MH - Biomechanics MH - Calcium/physiology MH - Elasticity MH - Kinetics MH - Microfilaments/*physiology/ultrastructure MH - *Models, Biological MH - Muscle Contraction/physiology MH - Muscle Fibers/*physiology/ultrastructure MH - Myocardium/metabolism MH - Nonlinear Dynamics MH - Sarcomeres/*physiology/ultrastructure MH - Tropomyosin/chemistry/physiology MH - Troponin/chemistry/physiology EDAT- 2001/09/22 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - Biophys J 2001 Oct;81(4):2278-96. 428: von der Twer T, et al. Optimal nonlinear codes for t...[PMID:11563536]Related Articles, Books, LinkOut UI - 21447243 PMID- 11563536 DA - 20010920 DCOM- 20020219 IS - 0954-898X VI - 12 IP - 3 DP - 2001 Aug TI - Optimal nonlinear codes for the perception of natural colours. PG - 395-407 AB - We discuss how visual nonlinearity can be optimized for the precise representation of environmental inputs. Such optimization leads to neural signals with a compressively nonlinear input-output function the gradient of which is matched to the cube root of the probability density function (PDF) of the environmental input values (and not to the PDF directly as in histogram equalization). Comparisons between theory and psychophysical and electrophysiological data are roughly consistent with the idea that parvocellular (P) cells are optimized for precision representation of colour: their contrast-response functions span a range appropriately matched to the environmental distribution of natural colours along each dimension of colour space. Thus P cell codes for colour may have been selected to minimize error in the perceptual estimation of stimulus parameters for natural colours. But magnocellular (M) cells have a much stronger than expected saturating nonlinearity; this supports the view that the function of M cells is mainly to detect boundaries rather than to specify contrast or lightness. AD - Bergische Universitat Wuppertal, Germany. twer@wppc16.physik.uni-wuppertal.de FAU - von der Twer, T AU - von der Twer T FAU - MacLeod, D I AU - MacLeod DI LA - eng ID - EY01711/EY/NEI PT - Journal Article CY - England TA - Network JID - 9431867 SB - IM MH - Algorithms MH - Color Perception/*physiology MH - Discrimination (Psychology)/physiology MH - Electrophysiology MH - Neurophysiology MH - Nonlinear Dynamics MH - Probability Theory MH - Psychophysics MH - Support, U.S. Gov't, P.H.S. EDAT- 2001/09/21 10:00 MHDA- 2002/02/20 10:01 PST - ppublish SO - Network 2001 Aug;12(3):395-407. 429: Zetzsche C, et al. Nonlinear and extra-classical...[PMID:11563533]Related Articles, Books, LinkOut UI - 21447240 PMID- 11563533 DA - 20010920 DCOM- 20020219 IS - 0954-898X VI - 12 IP - 3 DP - 2001 Aug TI - Nonlinear and extra-classical receptive field properties and the statistics of natural scenes. PG - 331-50 AB - The neural mechanisms of early vision can be explained in terms of an information-theoretic optimization of the neural processing with respect to the statistical properties of the natural environment. Recent applications of this approach have been successful in the prediction of the linear filtering properties of ganglion cells and simple cells, but the relations between the environmental statistics and cortical nonlinearities, like those of end-stopped or complex cells, are not yet fully understood. Here we present extensions of our previous investigations of the exploitation of higher-order statistics by nonlinear neurons. We use multivariate wavelet statistics to demonstrate that a strictly linear processing would inevitably leave substantial statistical dependencies between the outputs of the units. We then consider how the basic nonlinearities of cortical neurons--gain control and ON/OFF half-wave rectification--can exploit these higher-order statistical dependencies. We first show that gain control provides an adaptation to the polar separability of the multivariate probability density function (PDF), and, together with an output nonlinearity, enables an overcomplete sparse coding. We then consider how the remaining higher-order dependencies between different units can be exploited by a combination of basic ON/OFF point nonlinearities and subsequent weighted linear combinations. We consider two statistical optimization schemes for the computation of the optimal weights: principal component analysis (PCA) and independent component analysis (ICA). Since the intermediate nonlinearities transform some of the higher-order dependencies into second-order dependencies even the basic PCA approach is able to exploit part of the redundancies. ICA ignores this second-order structure, but can exploit higher-order dependencies. Both schemes yield a variety of nonlinear units which comprise the typical nonlinear processing properties, such as end-stopping, side-stopping, complex-cell properties and extra-classical receptive field properties, but the 'ideal' complex cells seem only to occur with PCA. Thus, a combination of ON/OFF nonlinearities with an integrated PCA-ICA strategy seems necessary to exploit the statistical properties of natural images. AD - Institut fur Medizinische Psychologie, Ludwig-Maximilians-Universitat Munchen, Germany. chris@imp.med.uni-muenchen.de FAU - Zetzsche, C AU - Zetzsche C FAU - Rohrbein, F AU - Rohrbein F LA - eng PT - Journal Article CY - England TA - Network JID - 9431867 SB - IM MH - Algorithms MH - Models, Neurological MH - Models, Statistical MH - Neural Networks (Computer) MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Orientation MH - Space Perception/*physiology MH - Support, Non-U.S. Gov't MH - Visual Cortex/physiology EDAT- 2001/09/21 10:00 MHDA- 2002/02/20 10:01 PST - ppublish SO - Network 2001 Aug;12(3):331-50. 430: Censi F, et al. Non-linear coupling of atrial...[PMID:11561820]Related Articles, Books, LinkOut UI - 21445724 PMID- 11561820 DA - 20010919 DCOM- 20020219 IS - 0340-1200 VI - 85 IP - 3 DP - 2001 Sep TI - Non-linear coupling of atrial activation processes during atrial fibrillation in humans. PG - 195-201 AB - The activation patterns underlying the electrical activity of the heart during atrial fibrillation (AF) are not entirely random. The aim of this study was to assess the local organization of the activation processes during AF by estimating the non-linear coupling between activation sequences (ASs) in two atrial sites. To quantitatively estimate the degree of non-linear coupling we extracted two indices based on a multivariate embedding procedure and on the estimation of the correlation dimension (CD) and correlation entropy (CE), termed independence of complexity and of independence of predictability, respectively. We analysed AS in two atrial sites in 30 informed subjects during chronic AF of type I, II and III (Wells' classification), ten 6-s-long episodes of each type. Surrogates were used to reject the hypothesis that the time series were generated by linear stochastic dynamics. We estimated CD and CE according to the coarse-grained approach, which leads to a fixed high value for the embedding dimension in all the analysed ASs, and a typical value for the distance between the two ASs in the phase space. Various degrees of organization, ranging from completely synchronized to fully de-coupled signals, were observed: significant degrees of non-linear coupling were found in segments belonging in types I and II AF, whereas type III electrograms always turned out to be weakly coupled. This finding links the morphology of single electrograms to the synchronization between pairs of closely spaced electrograms. Our bivariate approach suggests that the measurement of organization during AF should be based on the estimation of the non-linear coupling between two sites. This approach appears to be more reliable and sensitive than non-linear analysis of single electrograms or linear analysis of their coupling. AD - Department of Computer and Systems Science, La Sapienza University of Rome, Italy. censi@dis.uniroma1.it FAU - Censi, F AU - Censi F FAU - Barbaro, V AU - Barbaro V FAU - Bartolini, P AU - Bartolini P FAU - Calcagnini, G AU - Calcagnini G FAU - Michelucci, A AU - Michelucci A FAU - Cerutti, S AU - Cerutti S LA - eng PT - Journal Article CY - Germany TA - Biol Cybern JID - 7502533 SB - IM MH - Adult MH - Aged MH - Atrial Fibrillation/*physiopathology MH - Female MH - Human MH - Male MH - Middle Age MH - *Models, Biological MH - Nonlinear Dynamics MH - Stochastic Processes EDAT- 2001/09/20 10:00 MHDA- 2002/02/20 10:01 PST - ppublish SO - Biol Cybern 2001 Sep;85(3):195-201. 431: Anishchenko T, et al. Normalized entropy applied to...[PMID:11560083]Related Articles, Books, LinkOut UI - 21444544 PMID- 11560083 DA - 20010918 DCOM- 20020219 LR - 20021101 IS - 1439-6319 VI - 85 IP - 3-4 DP - 2001 Aug TI - Normalized entropy applied to the analysis of interindividual and gender-related differences in the cardiovascular effects of stress. PG - 287-98 AB - Nonlinear dynamic methods are considered to be a potential tool for studying the complex behavior of the cardiovascular system. In the present study, interindividual and gender-related differences in cardiovascular (CV) responses to various stress stimuli were studied using conventional CV variables such as heart rate (HR) and blood pressure (BP), as well as a recently introduced criterion of system complexity, normalized entropy (E/H, where E is entropy and H is system energy). A group of healthy students (n = 270) of both genders (17-20 years of age) were subjected to noise exposure, mental arithmetic, arithmetic against noise and examination stress. Results showed that CV reactivity depended upon the kind of stress imposed and the gender of the subject. HR and BP stress-induced responses did not differ between men and women. However, men had higher absolute BP levels at baseline and during exposure to stressors. Stress-induced pressor responses lasted longer in men than in women. Changes in the complexity degree of CV signals, as assessed by E/H, were more pronounced and prolonged than those of HR and BP. Unlike the latter, E/H changed significantly in all stress situations for each subject tested and could be divided into two types of stress-induced response. These results allow one to conclude that E/H can better quantitate individual differences in CV stress reactivity in comparison with HR and BP. These findings suggest that stress-induced changes in CV functioning are more varied than can be revealed by applying conventional CV measures. AD - Department of Biology, Saratov State University, Astrakhanskaya St. 83, Saratov, 410026, Russia. FAU - Anishchenko, T AU - Anishchenko T FAU - Igosheva, N AU - Igosheva N FAU - Yakusheva, T AU - Yakusheva T FAU - Glushkovskaya-Semyachkina, O AU - Glushkovskaya-Semyachkina O FAU - Khokhlova, O AU - Khokhlova O LA - eng PT - Journal Article CY - Germany TA - Eur J Appl Physiol JID - 100954790 SB - IM MH - Adolescent MH - Adult MH - Blood Pressure/*physiology MH - Comparative Study MH - Electrocardiography MH - *Entropy MH - Female MH - Human MH - Male MH - Mental Processes/physiology MH - *Models, Cardiovascular MH - Noise MH - Nonlinear Dynamics MH - *Sex Characteristics MH - Stress/*physiopathology MH - Support, Non-U.S. Gov't EDAT- 2001/09/19 10:00 MHDA- 2002/02/20 10:01 PST - ppublish SO - Eur J Appl Physiol 2001 Aug;85(3-4):287-98. 432: Bakharev BV, et al. [Rhythmical processes in the ...[PMID:11558385]Related Articles, Books, LinkOut UI - 21443020 PMID- 11558385 DA - 20010917 DCOM- 20010927 IS - 0006-3029 VI - 46 IP - 4 DP - 2001 Jul-Aug TI - [Rhythmical processes in the cerebral cortex bioelectrical activity in arousal reaction: qualitative nonlinear analysis involving refractoriness] PG - 715-23 AB - An integral equation that takes into account the absolute and relative refractory periods of cortical cells was added to the earlier obtained integral equations describing the cooperation of excitatory and inhibitory neurons of the cerebral cortex, and its substantiation was suggested. The steady states and the stable region of oscillations of the mean membrane potential of excitatory neurons were investigated depending on the mean afferent influx value on the assumption of the normal threshold distribution of cells. The existence of a parameter multitude in the region of stability was shown when a suppression of the delta-rhythm and an enhancement of the theta-rhythm up to its dominance take place increasing nonspecific afferent influx, which shows up a white noise, and decrease of the theta-rhythm during further increase in nonspecific activation. Simultaneously the frequencies of the major cerebral rhythms increase. The conformity of the theoretically calculated dependences of changes of the spectrum upon increasing nonspecific afferent influx to the experimental data obtained during the electrical stimulation of the rabbit midbrain reticular formation was demonstrated. AD - Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290 Russia. FAU - Bakharev, B V AU - Bakharev BV FAU - Zhadin, M N AU - Zhadin MN FAU - Agladze, N N AU - Agladze NN LA - rus PT - Journal Article TT - Ritmicheskie protsessy v bioelektricheskoi aktivnosti kory golovnogo mozga pri reaktsii aktivatsii: kachestvennyi nelineinyi analiz s uchetom refrakternosti. CY - Russia TA - Biofizika JID - 0372666 SB - IM MH - Afferent Pathways/physiology MH - Algorithms MH - Animal MH - Cerebral Cortex/*physiology MH - English Abstract MH - Membrane Potentials MH - Models, Neurological MH - Neurons/physiology MH - Nonlinear Dynamics MH - Rabbits MH - *Refractory Period, Neurologic EDAT- 2001/09/18 10:00 MHDA- 2001/09/28 10:01 PST - ppublish SO - Biofizika 2001 Jul-Aug;46(4):715-23. 433: Gapeev AB, et al. [Model analysis of the effect...[PMID:11558378]Related Articles, Books, LinkOut UI - 21443013 PMID- 11558378 DA - 20010917 DCOM- 20010927 IS - 0006-3029 VI - 46 IP - 4 DP - 2001 Jul-Aug TI - [Model analysis of the effect of modulated electromagnetic fields with various parameters of modulating signals in cells] PG - 661-75 AB - A theoretical analysis of the dependence of cell response to modulated electromagnetic fields on the parameters of modulating signals was performed on the basis of the model for calcium-dependent membrane-associated intracellular signaling systems. Expressed amplitude-frequency "windows" in the response of the nonlinear system to external influence were shown to depend on the effective time during which the amplitude of the influencing signal exceeded some threshold value, which is determined by the properties of the system. The presence of negative values in the influencing signal, i.e. the variations in the rate of some process around the inherent value, played an important role for the effect characteristics. The response of the nonlinear system to external influence strongly depended on the waveform of the modulating signal which is determined not only by frequency spectrum, but also by the initial phase of each frequency component. To ensure a regime for the optimal effect, the rates of increase and drop in the modulating signal amplitude should be synchronized with dynamic processes in the biological object being exposed. AD - Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290 Russia. FAU - Gapeev, A B AU - Gapeev AB FAU - Sokolov, P A AU - Sokolov PA FAU - Chemeris, N K AU - Chemeris NK LA - rus PT - Journal Article TT - Model'nyi analiz osobennostei deistviia modulirovannykh elektromagnitnykh polei na kletochnom urovne pri razlichnykh parametrakh moduliruiushchikh signalov. CY - Russia TA - Biofizika JID - 0372666 SB - IM MH - Algorithms MH - Calcium Signaling MH - Cell Membrane MH - *Electromagnetic Fields MH - English Abstract MH - Models, Biological MH - Nonlinear Dynamics MH - *Signal Transduction EDAT- 2001/09/18 10:00 MHDA- 2001/09/28 10:01 PST - ppublish SO - Biofizika 2001 Jul-Aug;46(4):661-75. 434: Faure P, et al. Is there chaos in the brain? ...[PMID:11558325]Related Articles, Books, LinkOut UI - 21442960 PMID- 11558325 DA - 20010917 DCOM- 20011011 LR - 20021029 IS - 0764-4469 VI - 324 IP - 9 DP - 2001 Sep TI - Is there chaos in the brain? I. Concepts of nonlinear dynamics and methods of investigation. PG - 773-93 AB - In the light of results obtained during the last two decades in a number of laboratories, it appears that some of the tools of nonlinear dynamics, first developed and improved for the physical sciences and engineering, are well-suited for studies of biological phenomena. In particular it has become clear that the different regimes of activities undergone by nerve cells, neural assemblies and behavioural patterns, the linkage between them, and their modifications over time, cannot be fully understood in the context of even integrative physiology, without using these new techniques. This report, which is the first of two related papers, is aimed at introducing the non expert to the fundamental aspects of nonlinear dynamics, the most spectacular aspect of which is chaos theory. After a general history and definition of chaos the principles of analysis of time series in phase space and the general properties of chaotic trajectories will be described as will be the classical measures which allow a process to be classified as chaotic in ideal systems and models. We will then proceed to show how these methods need to be adapted for handling experimental time series; the dangers and pitfalls faced when dealing with non stationary and often noisy data will be stressed, and specific criteria for suspecting determinism in neuronal cells and/or assemblies will be described. We will finally address two fundamental questions, namely i) whether and how can one distinguish, deterministic patterns from stochastic ones, and, ii) what is the advantage of chaos over randomness: we will explain why and how the former can be controlled whereas, notoriously, the latter cannot be tamed. In the second paper of the series, results obtained at the level of single cells and their membrane conductances in real neuronal networks and in the study of higher brain functions, will be critically reviewed. It will be shown that the tools of nonlinear dynamics can be irreplaceable for revealing hidden mechanisms subserving, for example, neuronal synchronization and periodic oscillations. The benefits for the brain of adopting chaotic regimes with their wide range of potential behaviours and their aptitude to quickly react to changing conditions will also be considered. AD - Biologie cellulaire et moleculaire du neurone (Inserm V261), Institut Pasteur, 25 rue Docteur Roux, 75724 Paris, 15, France. FAU - Faure, P AU - Faure P FAU - Korn, H AU - Korn H LA - eng PT - Journal Article PT - Review PT - Review, Academic CY - France TA - C R Acad Sci III JID - 8503078 SB - IM MH - Animal MH - Brain/*physiology MH - Human MH - *Models, Neurological MH - *Nonlinear Dynamics MH - Stochastic Processes MH - Support, U.S. Gov't, Non-P.H.S. RF - 86 EDAT- 2001/09/18 10:00 MHDA- 2001/10/12 10:01 AID - S0764446901013774 [pii] PST - ppublish SO - C R Acad Sci III 2001 Sep;324(9):773-93. 435: Plsek PE, et al. Complexity science: The chall...[PMID:11557716]Related Articles, Books, LinkOut UI - 21441286 PMID- 11557716 DA - 20010914 DCOM- 20011004 LR - 20020910 IS - 0959-8138 VI - 323 IP - 7313 DP - 2001 Sep 15 TI - Complexity science: The challenge of complexity in health care. PG - 625-8 AD - Paul E Plsek & Associates Inc, 1005 Allenbrook Lane, Roswell, GA 30075, USA. paulplsek@directedcreativity.com FAU - Plsek, P E AU - Plsek PE FAU - Greenhalgh, T AU - Greenhalgh T LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - England TA - BMJ JID - 8900488 SB - AIM SB - IM CIN - BMJ. 2002 Jan 19;324(7330):171. PMID: 11822341 CIN - BMJ. 2002 Jan 19;324(7330):171-2. PMID: 11822342 CIN - Scand J Prim Health Care. 2001 Dec;19(4):214-7. PMID: 11822642 MH - Adaptation, Psychological MH - Delivery of Health Care/*organization & administration MH - Family Practice/organization & administration MH - Human MH - Nonlinear Dynamics MH - *Systems Theory RF - 27 EDAT- 2001/09/15 10:00 MHDA- 2001/10/05 10:01 PST - ppublish SO - BMJ 2001 Sep 15;323(7313):625-8. 436: Westwick DT, et al. Separable least squares ident...[PMID:11556727]Related Articles, Books, LinkOut UI - 21440440 PMID- 11556727 DA - 20010914 DCOM- 20020506 IS - 0090-6964 VI - 29 IP - 8 DP - 2001 Aug TI - Separable least squares identification of nonlinear Hammerstein models: application to stretch reflex dynamics. PG - 707-18 AB - The Hammerstein cascade, consisting of a zero-memory nonlinearity followed by a linear filter, is often used to model nonlinear biological systems. This structure can represent some high-order nonlinear systems accurately with relatively few parameters. However, it is not possible, in general, to estimate the parameters of a Hammerstein cascade in closed form. The most effective method available to date uses an iterative approach, which alternates between estimating the linear element from a crosscorrelation, and then fitting a polynomial to the nonlinearity via linear regression. This paper proposes the use of separable least squares optimization methods to estimate the linear and nonlinear elements simultaneously in a least squares framework. A separable least squares algorithm for the identification of Hammerstein cascades is developed and used to analyze stretch reflex electromyogram data from two experimental subjects. The results show that in each case the proposed algorithm produced a better model, in that it predicted the system's response to novel inputs more accurately, than did models estimated using the traditional iterative algorithm. Monte-Carlo simulations demonstrated that when the input is a non-Gaussian, nonwhite signal, as is often the case experimentally, the traditional iterative identification approach produces biased models, whereas the separable least squares approach proposed in this paper does not. AD - Department of Electrical and Computer Engineering, University of Calgary, Alberta, Canada. westwick@enel.ucalgary.ca FAU - Westwick, D T AU - Westwick DT FAU - Kearney, R E AU - Kearney RE LA - eng PT - Journal Article CY - United States TA - Ann Biomed Eng JID - 0361512 SB - IM MH - Algorithms MH - Biomedical Engineering MH - Case-Control Studies MH - Computer Simulation MH - Electromyography MH - Human MH - Least-Squares Analysis MH - *Models, Neurological MH - Nonlinear Dynamics MH - Reflex, Stretch/*physiology MH - Spinal Cord Injuries/physiopathology MH - Support, Non-U.S. Gov't EDAT- 2001/09/15 10:00 MHDA- 2002/05/07 10:01 PST - ppublish SO - Ann Biomed Eng 2001 Aug;29(8):707-18. 437: Stefanovska A, et al. Modelling couplings among the...[PMID:11556674]Related Articles, Books, LinkOut UI - 21440388 PMID- 11556674 DA - 20010914 DCOM- 20020206 IS - 0967-3334 VI - 22 IP - 3 DP - 2001 Aug TI - Modelling couplings among the oscillators of the cardiovascular system. PG - 551-64 AB - A mathematical model of the cardiovascular system is simulated numerically. The basic unit in the model is an oscillator that possesses a structural stability and robustness motivated by physiological understanding and by the analysis of measured time series. Oscillators with linear couplings are found to reproduce the main characteristic features of the experimentally obtained spectra. To explain the variability of cardiac and respiratory frequencies, however, it is essential to take into account the rest of the system, i.e. to consider the effect of noise. It is found that the addition of noise also results in epochs of synchronization, as observed experimentally. Preliminary analysis suggests that there is a mixture of linear and parametric couplings, but that the linear coupling seems to dominate. AD - Group of Nonlinear Dynamics and Synergetics. Faculty of Electrical Engineering, University of Ljubljana, Slovenia. aneta@osc.fe.uni-lj.si FAU - Stefanovska, A AU - Stefanovska A FAU - Luchinsky, D G AU - Luchinsky DG FAU - McClintock, P V AU - McClintock PV LA - eng PT - Journal Article CY - England TA - Physiol Meas JID - 9306921 SB - IM MH - Artifacts MH - Blood Pressure/physiology MH - Heart Rate/physiology MH - Human MH - *Models, Cardiovascular MH - Nonlinear Dynamics MH - *Periodicity MH - Regional Blood Flow/physiology MH - Stochastic Processes MH - Support, Non-U.S. Gov't EDAT- 2001/09/15 10:00 MHDA- 2002/02/07 10:01 PST - ppublish SO - Physiol Meas 2001 Aug;22(3):551-64. 438: Mechelli A, et al. Nonlinear coupling between ev...[PMID:11554805]Related Articles, Books, LinkOut UI - 21439754 PMID- 11554805 DA - 20010913 DCOM- 20011204 IS - 1053-8119 VI - 14 IP - 4 DP - 2001 Oct TI - Nonlinear coupling between evoked rCBF and BOLD signals: a simulation study of hemodynamic responses. PG - 862-72 AB - The aim of this work was to investigate the dependence of BOLD responses on different patterns of stimulus input/neuronal changes. In an earlier report, we described an input-state-output model that combined (i) the Balloon/Windkessel model of nonlinear coupling between rCBF and BOLD signals, and (ii) a linear model of how regional flow changes with synaptic activity. In the present investigation, the input-state-output model was used to explore the dependence of simulated PET (rCBF) and fMRI (BOLD) signals on various parameters pertaining to experimental design. Biophysical simulations were used to estimate rCBF and BOLD responses as functions of (a) a prior stimulus, (b) epoch length (for a fixed SOA), (c) SOA (for a fixed number of events), and (d) stimulus amplitude. We also addressed the notion that a single neuronal response may differ, in terms of the relative contributions of early and late neural components, and investigated the effect of (e) the relative size of the late or "endogenous" neural component. We were interested in the estimated average rCBF and BOLD responses per stimulus or event, not in the statistical efficiency with which these responses are detected. The BOLD response was underestimated relative to rCBF with a preceding stimulus, increasing epoch length, and increasing SOA. Furthermore, the BOLD response showed some highly nonlinear behaviour when varying stimulus amplitude, suggesting some form of hemodynamic "rectification." Finally, the BOLD response was underestimated in the context of large late neuronal components. The difference between rCBF and BOLD is attributed to the nonlinear transduction of rCBF to BOLD signal. Our simulations support the idea that varying parameters that specify the experimental design may have differential effects in PET and fMRI. Moreover, they show that fMRI can be asymmetric in its ability to detect deactivations relative to activations when an absolute baseline is stipulated. Finally, our simulations suggest that relative insensitivity to BOLD signal in specific regions, such as the temporal lobe, may be partly explained by higher cognitive functions eliciting a relatively large late endogenous neuronal component. CI - Copyright 2001 Academic Press. AD - Wellcome Department of Cognitive Neurology, Institute of Neurology, 12 Queen Square, London, WC1N 3BG, United Kingdom. FAU - Mechelli, A AU - Mechelli A FAU - Price, C J AU - Price CJ FAU - Friston, K J AU - Friston KJ LA - eng PT - Journal Article CY - United States TA - Neuroimage JID - 9215515 RN - 7782-44-7 (Oxygen) SB - IM MH - Arousal/*physiology MH - Brain/*blood supply MH - Comparative Study MH - Hemodynamics/*physiology MH - Human MH - *Image Enhancement MH - Image Processing, Computer-Assisted MH - *Magnetic Resonance Imaging MH - Models, Neurological MH - Neurons/physiology MH - *Nonlinear Dynamics MH - Oxygen/*blood/physiology MH - Regional Blood Flow/physiology MH - Sensitivity and Specificity MH - Support, Non-U.S. Gov't MH - Tomography, Emission-Computed EDAT- 2001/09/14 10:00 MHDA- 2002/01/05 10:01 AID - 10.1006/nimg.2001.0876 [doi] AID - S1053811901908766 [pii] PST - ppublish SO - Neuroimage 2001 Oct;14(4):862-72. 439: Stamatakis EA, et al. Spatial normalization of lesi...[PMID:11554803]Related Articles, Books, LinkOut UI - 21439752 PMID- 11554803 DA - 20010913 DCOM- 20011204 IS - 1053-8119 VI - 14 IP - 4 DP - 2001 Oct TI - Spatial normalization of lesioned HMPAO-SPECT images. PG - 844-52 AB - We investigated the effect of nonlinear alignment on SPECT images with lesions. Linear alignment produces reliable results but the introduction of nonlinear methods can improve matching by accounting for global brain shape. We examined the hypothesis that nonlinear alignment can introduce unwanted image distortions when lesions are present. We set out to quantify possible distortions by constructing artificial lesions in order to obtain images with controllable characteristics. We examined the use of basis functions (in SPM96 and SPM99) and other nonlinear models (in AIR3.08) designed to achieve optimum alignment between image and template. We found that the use of models with high degrees of nonlinearity will result in unwanted deformations and that the safest way to align images with lesions is to use 12-point linear affine transformations. Masking was examined as a remedy to distortions caused by nonlinear methodologies and produced significantly improved results. CI - Copyright 2001 Academic Press. AD - Department of Psychology, University of Stirling, Stirling, FK9 4LA, Scotland. e.a.stamatakis@stir.ac.uk FAU - Stamatakis, E A AU - Stamatakis EA FAU - Wilson, J T AU - Wilson JT FAU - Wyper, D J AU - Wyper DJ LA - eng PT - Journal Article CY - United States TA - Neuroimage JID - 9215515 RN - 0 (Contrast Media) RN - 100504-35-6 (Technetium Tc 99m Exametazime) SB - IM MH - Artifacts MH - Brain Injuries/*radionuclide imaging MH - Cerebrovascular Accident/*radionuclide imaging MH - *Contrast Media MH - Human MH - Image Processing, Computer-Assisted MH - *Nonlinear Dynamics MH - Reference Values MH - Support, Non-U.S. Gov't MH - Technetium Tc 99m Exametazime/*diagnostic use MH - *Tomography, Emission-Computed, Single-Photon EDAT- 2001/09/14 10:00 MHDA- 2002/01/05 10:01 AID - 10.1006/nimg.2001.0884 [doi] AID - S1053811901908845 [pii] PST - ppublish SO - Neuroimage 2001 Oct;14(4):844-52. 440: Birn RM, et al. Spatial heterogeneity of the ...[PMID:11554800]Related Articles, Books, LinkOut UI - 21439749 PMID- 11554800 DA - 20010913 DCOM- 20011204 IS - 1053-8119 VI - 14 IP - 4 DP - 2001 Oct TI - Spatial heterogeneity of the nonlinear dynamics in the FMRI BOLD response. PG - 817-26 AB - Recent studies of blood oxygenation level dependent (BOLD) signal responses averaged over a region of interest have demonstrated that the response is nonlinear with respect to stimulus duration. Specifically, shorter duration stimuli produce signal changes larger than expected from a linear system. The focus of this study is to characterize the spatial heterogeneity of this nonlinear effect. A series of MR images of the visual and motor cortexes were acquired during visual stimulation and finger tapping, respectively, at five different stimulus durations (SD). The nonlinearity was assessed by fitting ideal linear responses to the responses at each SD. This amplitude, which is constant for different SD in a linear system, was normalized by the amplitude of the response to a blocked design, thus describing the amount by which the stimulus is larger than predicted from a linear extrapolation of the response to the long duration stimulus. The amplitude of the BOLD response showed a nonlinear behavior that varied considerably and consistently over space, ranging from almost linear to 10 times larger than a linear prediction at short SD. In the motor cortex different nonlinear behavior was found in the primary and supplementary motor cortexes. AD - Laboratory of Brain and Cognition, National institute of Mental Health, NIH Bethesda, Maryland , USA. FAU - Birn, R M AU - Birn RM FAU - Saad, Z S AU - Saad ZS FAU - Bandettini, P A AU - Bandettini PA LA - eng PT - Journal Article CY - United States TA - Neuroimage JID - 9215515 RN - 7782-44-7 (Oxygen) SB - IM MH - Adult MH - Arousal/physiology MH - Brain Mapping MH - Human MH - *Image Enhancement MH - Image Processing, Computer-Assisted MH - *Magnetic Resonance Imaging MH - Motor Activity/physiology MH - Motor Cortex/*physiology MH - *Nonlinear Dynamics MH - Oxygen/*blood MH - Reference Values MH - Regional Blood Flow/physiology MH - Visual Cortex/*physiology MH - Visual Perception/physiology EDAT- 2001/09/14 10:00 MHDA- 2002/01/05 10:01 AID - 10.1006/nimg.2001.0873 [doi] AID - S1053811901908730 [pii] PST - ppublish SO - Neuroimage 2001 Oct;14(4):817-26. 441: Retel V, et al. Nonlinear model of skin mecha...[PMID:11554700]Related Articles, Books, LinkOut UI - 21438487 PMID- 11554700 DA - 20010913 DCOM- 20020214 IS - 0909-752X VI - 7 IP - 3 DP - 2001 Aug TI - Nonlinear model of skin mechanical behaviour analysis with finite element method. PG - 152-8 AB - BACKGROUND/AIMS: A problem commonly encountered in plastic and reconstructive surgery is the prediction of the stress put on the skin when various types of skin flaps are used. METHODS/RESULTS: We developed a mathematical model based on the finite element method, in order to determine the stress field, by simulating the mechanical behaviour of human skin during wound closure. We chose to take into account the low compressive strength by modifying the mechanical parameters of the model at each step of the calculation. The model has been developed and tested on a diamond-shaped incision and applied on a Limberg incision. CONCLUSION: The results presented are the Von Mises stress in the area of skin around the scar and, when possible, the resultant closure force. They show the relevance of the method. AD - Laboratoire de Mecanique Appliquee R. Chaleat, Universite de Franche-Comte, Besancon, France. FAU - Retel, V AU - Retel V FAU - Vescovo, P AU - Vescovo P FAU - Jacquet, E AU - Jacquet E FAU - Trivaudey, F AU - Trivaudey F FAU - Varchon, D AU - Varchon D FAU - Burtheret, A AU - Burtheret A LA - eng PT - Journal Article CY - Denmark TA - Skin Res Technol JID - 9504453 SB - IM MH - Biomechanics MH - Human MH - *Models, Biological MH - Nonlinear Dynamics MH - Reproducibility of Results MH - Skin/surgery MH - *Skin Physiology MH - Surgical Flaps/*physiology EDAT- 2001/09/14 10:00 MHDA- 2002/02/15 10:01 PST - ppublish SO - Skin Res Technol 2001 Aug;7(3):152-8. 442: Ganzach Y. Nonlinear models of clinical ...[PMID:11554674]Related Articles, Books, LinkOut UI - 21438461 PMID- 11554674 DA - 20010913 DCOM- 20011011 IS - 0956-7976 VI - 12 IP - 5 DP - 2001 Sep TI - Nonlinear models of clinical judgement: communal nonlinearity and nonlinear accuracy. PG - 403-7 AB - Despite our intuition that representative expert judgments are highly nonlinear, previous studies have shown only little, if any, nonlinearity in such judgments. The current study presents a method for assessing nonlinearity in judgment that is based on estimating communal nonlinearity--the systematic nonlinearity shared by the community of judges. The article also examines the predictive accuracy of communal nonlinearity, and compares it with the corresponding linear accuracy. AD - Faculty of Management, Tel Aviv University, Israel. yoavgn@post.tau.ac.il FAU - Ganzach, Y AU - Ganzach Y LA - eng PT - Journal Article CY - United States TA - Psychol Sci JID - 9007542 SB - IM MH - Adult MH - *Decision Making MH - Female MH - Human MH - Intuition MH - *Judgment MH - Male MH - Neurotic Disorders/*diagnosis/psychology MH - *Nonlinear Dynamics MH - Personality Inventory/statistics & numerical data MH - Psychometrics MH - Psychotic Disorders/*diagnosis/psychology MH - Support, Non-U.S. Gov't EDAT- 2001/09/14 10:00 MHDA- 2001/10/12 10:01 PST - ppublish SO - Psychol Sci 2001 Sep;12(5):403-7. 443: Jansen BH, et al. Evoked potential enhancement ...[PMID:11552347]Related Articles, Books, LinkOut UI - 21436645 PMID- 11552347 DA - 20010912 DCOM- 20011004 IS - 0026-1270 VI - 40 IP - 4 DP - 2001 TI - Evoked potential enhancement using a neurophysiologically-based model. PG - 338-45 AB - OBJECTIVE: Single trial evoked potentials (EP) are generally obscured by the much larger spontaneous or background electroencephalogram (EEG). A novel method was developed to enhance single trial EPs. The potential of this approach was explored using actual flash evoked visual EPs. METHOD: The basic procedure is a variant of the adaptive filtering approach. At the core of our method is a mathematical, but neurophysiologically-realistic, nonlinear model of the cortical structures involved in generating EEG and EP activity. The model parameters are adjusted by a genetic algorithm in such a way that the model output resembles the actually observed pre-stimulus EEG activity. When post-stimulus EEG is passed through the inverse model, enhancement of the single trial EP should, theoretically, occur. RESULTS: Evidence was found that, in case of visual evoked potentials obtained by flashing light through closed eyelids, alpha activity continues to around 150 ms post-stimulus, at which point a low frequency potential arises, cresting 100 ms later and disappearing after another 100 ms or so. Also, it was found that an individual's response varies considerably from trial to trial. CONCLUSION: The inverse modeling approach presented here is effective at enhancing single trial EP activity. One potential application is to distinguish trials that contain a response from those that do not, which could result in improved ensemble averages. AD - Department of Electrical and Computer Engineering, and Bioengineering Research Center, University of Houston, Houston, USA. bjansen@uh.edu FAU - Jansen, B H AU - Jansen BH FAU - Kavaipatti, A B AU - Kavaipatti AB FAU - Markusson, O AU - Markusson O LA - eng PT - Clinical Trial PT - Journal Article PT - Randomized Controlled Trial CY - Germany TA - Methods Inf Med JID - 0210453 SB - IM MH - Adult MH - Algorithms MH - Electroencephalography/*methods MH - *Evoked Potentials, Visual MH - Human MH - Male MH - Models, Neurological MH - Nerve Net MH - Nonlinear Dynamics MH - *Signal Processing, Computer-Assisted EDAT- 2001/09/13 10:00 MHDA- 2001/10/05 10:01 PST - ppublish SO - Methods Inf Med 2001;40(4):338-45. 444: Wills PR, et al. Studies of solute self-associ...[PMID:11551437]Related Articles, Books, LinkOut UI - 21435713 PMID- 11551437 DA - 20010911 DCOM- 20011011 IS - 0301-4622 VI - 91 IP - 3 DP - 2001 Jul 24 TI - Studies of solute self-association by sedimentation equilibrium: allowance for effects of thermodynamic non-ideality beyond the consequences of nearest-neighbor interactions. PG - 253-62 AB - A sedimentation equilibrium study of alpha-chymotrypsin self-association in acetate-chloride buffer, pH 4.1 I 0.05, has been used to illustrate determination of a dimerization constant under conditions where thermodynamic non-ideality is manifested beyond the consequences of nearest-neighbor interactions. Because the expressions for the experimentally determinable interaction parameters comprise a mixture of equilibrium constant and excluded volume terms, the assignment of reasonable magnitudes to the relevant virial coefficients describing non-associative cluster formation is essential for the evaluation of a reliable estimate of the dimerization constant. Determination of these excluded volume parameters by numerical integration over the potential-of-mean-force is shown to be preferable to their calculation by approximate analytical solutions of the integral for this relatively small enzyme monomer with high net charge (+10) under conditions of low ionic strength (0.05 M). AD - Department of Physics, University of Auckland, Auckland, New Zealand. FAU - Wills, P R AU - Wills PR FAU - Winzor, D J AU - Winzor DJ LA - eng PT - Journal Article CY - Netherlands TA - Biophys Chem JID - 0403171 RN - EC 3.4.21.1 (Chymotrypsin) SB - IM MH - Algorithms MH - Centrifugation MH - Chymotrypsin/*chemistry MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - *Thermodynamics EDAT- 2001/09/12 10:00 MHDA- 2001/10/12 10:01 AID - S0301462201001740 [pii] PST - ppublish SO - Biophys Chem 2001 Jul 24;91(3):253-62. 445: Graham N, et al. A note about preferred orient...[PMID:11551062]Related Articles, Books, LinkOut UI - 21434912 PMID- 11551062 DA - 20010911 DCOM- 20010927 IS - 1084-7529 VI - 18 IP - 9 DP - 2001 Sep TI - A note about preferred orientations at the first and second stages of complex (second-order) texture channels. PG - 2273-81 AB - Complex (second-order) channels have been useful in explaining many of the phenomena of perceived texture segregation. These channels contain two stages of linear filtering with an intermediate pointwise nonlinearity. One unanswered question about these hypothetical channels is that of the relationship between the preferred orientations of the two stages of filtering. Is a particular orientation at the second stage equally likely to occur with all orientations at the first stage, or is there a bias in the "mapping" between the two stages' preferred orientations? In this study we consider two possible mappings: that where the orientations at the two stages are identical (called "consistent" here) and that where the orientations at the two stages are perpendicular ("inconsistent"). We explore these mappings using a texture-segregation task with textures composed of arrangements of grating-patch elements. The results imply that, to explain perceived texture segregation, complex channels with a consistent orientation mapping must be either somewhat more prevalent or more effective than those with an inconsistent mapping. AD - Department of Psychology, Columbia University, New York, New York 10027, USA. nvg@psych.columbia.edu FAU - Graham, N AU - Graham N FAU - Wolfson, S S AU - Wolfson SS LA - eng ID - EY06933/EY/NEI ID - EY08459/EY/NEI PT - Journal Article CY - United States TA - J Opt Soc Am A Opt Image Sci Vis JID - 9800943 SB - IM MH - Contrast Sensitivity/*physiology MH - Human MH - Linear Models MH - Nonlinear Dynamics MH - Photic Stimulation/methods MH - Support, U.S. Gov't, P.H.S. MH - Visual Fields EDAT- 2001/09/12 10:00 MHDA- 2001/09/28 10:01 PST - ppublish SO - J Opt Soc Am A Opt Image Sci Vis 2001 Sep;18(9):2273-81. 446: Benton CP, et al. Computational modeling of non...[PMID:11551055]Related Articles, Books, LinkOut UI - 21434905 PMID- 11551055 DA - 20010911 DCOM- 20010927 IS - 1084-7529 VI - 18 IP - 9 DP - 2001 Sep TI - Computational modeling of non-Fourier motion: further evidence for a single luminance-based mechanism. PG - 2204-8 AB - It is generally assumed that the perception of non-Fourier motion requires the operation of some nonlinearity before motion analysis. We apply a computational model of biological motion processing to a class of non-Fourier motion stimuli designed to investigate nonlinearity in human visual processing. The model correctly detects direction of motion in these non-Fourier stimuli without recourse to any preprocessing nonlinearity. This demonstrates that the non-Fourier motion in some non-Fourier stimuli is directly available to luminance-based motion mechanisms operating on measurements of local spatial and temporal gradients. AD - Department of Psychology, University College London, UK. chris.benton@bristol.ac.uk FAU - Benton, C P AU - Benton CP FAU - Johnston, A AU - Johnston A FAU - McOwan, P W AU - McOwan PW FAU - Victor, J D AU - Victor JD LA - eng ID - EY7977/EY/NEI PT - Journal Article CY - United States TA - J Opt Soc Am A Opt Image Sci Vis JID - 9800943 SB - IM MH - Fourier Analysis MH - Human MH - *Light MH - *Models, Neurological MH - *Models, Psychological MH - Motion Perception/*physiology MH - Nonlinear Dynamics MH - Photic Stimulation/methods MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. MH - Visual Perception/physiology EDAT- 2001/09/12 10:00 MHDA- 2001/09/28 10:01 PST - ppublish SO - J Opt Soc Am A Opt Image Sci Vis 2001 Sep;18(9):2204-8. 447: Dumoulin SO, et al. Centrifugal bias for second-o...[PMID:11551052]Related Articles, Books, LinkOut UI - 21434902 PMID- 11551052 DA - 20010911 DCOM- 20010927 IS - 1084-7529 VI - 18 IP - 9 DP - 2001 Sep TI - Centrifugal bias for second-order but not first-order motion. PG - 2179-89 AB - Limited-lifetime Gabor stimuli were used to assess both first- and second-order motion in peripheral vision. Both first- and second-order motion mechanisms were present at a 20-deg eccentricity. Second-order motion, unlike first-order, exhibits a bias for centrifugal motion, suggesting a role for the second-order mechanism in optic flow processing. AD - Department of Ophthalmology, McGill University, Montreal, Quebec, Canada. serge@bic.mni.mcgill.ca FAU - Dumoulin, S O AU - Dumoulin SO FAU - Baker, C L Jr AU - Baker CL Jr FAU - Hess, R F AU - Hess RF LA - eng PT - Journal Article CY - United States TA - J Opt Soc Am A Opt Image Sci Vis JID - 9800943 SB - IM MH - Anisotropy MH - *Contrast Sensitivity/*physiology MH - Human MH - *Light MH - Linear Models MH - Motion Perception/*physiology MH - Nonlinear Dynamics MH - Photic Stimulation/methods MH - Psychometrics/methods MH - Stochastic Processes MH - Support, Non-U.S. Gov't MH - Visual Fields EDAT- 2001/09/12 10:00 MHDA- 2001/09/28 10:01 PST - ppublish SO - J Opt Soc Am A Opt Image Sci Vis 2001 Sep;18(9):2179-89. 448: Chubb C, et al. Second-order processes in vis...[PMID:11551051]Related Articles, Books, LinkOut UI - 21434901 PMID- 11551051 DA - 20010911 DCOM- 20010927 IS - 1084-7529 VI - 18 IP - 9 DP - 2001 Sep TI - Second-order processes in vision: introduction. PG - 2175-8 AD - Department of Cognitive Science, University of California, Irvine 92697, USA. FAU - Chubb, C AU - Chubb C FAU - Olzak, L AU - Olzak L FAU - Derrington, A AU - Derrington A LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - United States TA - J Opt Soc Am A Opt Image Sci Vis JID - 9800943 SB - IM MH - Animal MH - Contrast Sensitivity/*physiology MH - Human MH - Light MH - Linear Models MH - *Models, Neurological MH - *Models, Psychological MH - Motion Perception/*physiology MH - *Nonlinear Dynamics MH - Visual Pathways/physiology MH - Visual Perception/*physiology RF - 105 EDAT- 2001/09/12 10:00 MHDA- 2001/09/28 10:01 PST - ppublish SO - J Opt Soc Am A Opt Image Sci Vis 2001 Sep;18(9):2175-8. 449: Marino AA, et al. Coincident nonlinear changes ...[PMID:11549888]Related Articles, Books, LinkOut UI - 21434396 PMID- 11549888 DA - 20010910 DCOM- 20020110 IS - 1021-7401 VI - 9 IP - 2 DP - 2001 TI - Coincident nonlinear changes in the endocrine and immune systems due to low-frequency magnetic fields. PG - 65-77 AB - OBJECTIVE: The characteristic biological effects of low-frequency electromagnetic fields (EMFs) appear to be functional changes in the central nervous, endocrine and immune systems. For unapparent reasons, however, the results of similar studies have often differed markedly from one another. We recognized that it had generally been assumed, in the studies, that EMF effects would exhibit a dose-effect relationship, which is a basic property of linear systems. Prompted by recent developments in the theory on nonlinear systems, we hypothesized that there was a nonlinear relationship between EMFs and the effects they produced in the endocrine and immune systems. METHODS: We developed a novel analytical method that could be used to distinguish between linear and nonlinear effects, and we employed it to examine the effect of EMFs on the endocrine and immune systems. RESULTS: Mice exposed to 5 G, 60 Hz for 1-175 days in 7 independent experiments reliably exhibited changes in serum corticosterone and lymphoid phenotype when the data were analyzed while allowing that the field exposure and the resulting effects could be nonlinearly related. When the analysis was restricted to linear relationships, no effects due to the field were found. CONCLUSIONS: The results indicated that transduction of EMFs resulted in changes in both the endocrine and immune systems, and that the laws governing the changes in each system were not the type that govern conventional dose-effect relationships. Evidence based on mathematical modeling was found suggesting that the coincident changes could have been causally related. CI - Copyright 2001 S. Karger AG, Basel AD - Department of Orthopaedic Surgery, LSU Health Sciences Center, Shreveport, LA 71130-3932, USA. amarino@lsuhsc.edu FAU - Marino, A A AU - Marino AA FAU - Wolcott, R M AU - Wolcott RM FAU - Chervenak, R AU - Chervenak R FAU - Jourd'heuil, F AU - Jourd'heuil F FAU - Nilsen, E AU - Nilsen E FAU - Frilot, C 2nd AU - Frilot C 2nd FAU - Pruett, S B AU - Pruett SB LA - eng PT - Journal Article CY - Switzerland TA - Neuroimmunomodulation JID - 9422763 RN - 50-22-6 (Corticosterone) SB - IM MH - Animal MH - Bone Marrow Cells/immunology/radiation effects MH - Corticosterone/blood MH - Dose-Response Relationship, Radiation MH - *Electromagnetic Fields MH - Endocrine System/*radiation effects MH - Immune System/immunology/*radiation effects MH - Killer Cells, Natural/immunology/radiation effects MH - Male MH - Mice MH - Mice, Inbred C57BL MH - Models, Biological MH - Neuroimmunomodulation/radiation effects MH - Nonlinear Dynamics MH - Spleen/immunology/radiation effects MH - Support, U.S. Gov't, P.H.S. MH - Thymus Gland/immunology/radiation effects EDAT- 2001/09/11 10:00 MHDA- 2002/01/11 10:01 AID - nim09065 [pii] PST - ppublish SO - Neuroimmunomodulation 2001;9(2):65-77. 450: Patoux A, et al. Comparison of nonlinear mixed...[PMID:11549207]Related Articles, Books, LinkOut UI - 21432842 PMID- 11549207 DA - 20010910 DCOM- 20020122 LR - 20021101 IS - 0031-6970 VI - 57 IP - 4 DP - 2001 Jul TI - Comparison of nonlinear mixed-effect and non-parametric expectation maximisation modelling for Bayesian estimation of carboplatin clearance in children. PG - 297-303 AB - OBJECTIVE: The pharmacodynamic-pharmacokinetic relationships for carboplatin involve the area under the curve of ultrafiltrable plasma concentrations versus time (AUC). The objective of the study was to compare two specific population pharmacokinetic methodologies, nonlinear mixed-effect model (NONMEM) and non-parametric expectation maximisation (NPEM), when they are applied to sparse carboplatin pharmacokinetic data in order to obtain an individual value for carboplatin clearance by Bayesian estimation. METHODS: The data from 117 patients (from 1 month to 18 years old) were available. For 20 patients randomly selected, the carboplatin clearance obtained by Bayesian estimation using two plasma ultrafiltrable concentrations was compared with that obtained by individual analysis using all concentrations. RESULTS: Both methodologies were unbiased with mean relative percentage errors (95%CI) of -1.9% ( 7.8; +4.1%) and +6.4% (-2.1; +14.9%) for NONMEM and NPEM, respectively. A comparison of precision between the two methods showed that they were not significantly different (12.5% for NONMEM, and 18.9% for NPEM), but the percentage error ranged between -21% and + 19% for NONMEM, and -35% and + 42% for NPEM. A NONMEM analysis was also performed with all the data available (117 children) in order to update an equation describing the relationship between carboplatin clearance and the patients' covariates. The best relationship corresponded to the equation: clearance (ml/min) = [4.47 x body weight x (1 -0.22 x Np)/(l + 0.0156 x Scr)] +6.4, with body weight in kilograms and where Scr is serum creatinine in micromoles per litre and Np= 1 or 0 for unilateral nephrectomy or not, respectively. CONCLUSION: These methodologies may be useful for dose individualisation and drug monitoring of carboplatin in paediatric patients. Since the mode of administration of carboplatin in paediatric practice in some protocols is daily 1-h i.v. infusion repeated up to five times, dose individualisation may be performed from the clearance observed after the first administration, given an overall target AUC. AD - Institut Claudius-Regaud, and Universite Paul-Sabatier, Toulouse, France. FAU - Patoux, A AU - Patoux A FAU - Bleyzac, N AU - Bleyzac N FAU - Boddy, A V AU - Boddy AV FAU - Doz, F AU - Doz F FAU - Rubie, H AU - Rubie H FAU - Bastian, G AU - Bastian G FAU - Maire, P AU - Maire P FAU - Canal, P AU - Canal P FAU - Chatelut, E AU - Chatelut E LA - eng PT - Journal Article CY - Germany TA - Eur J Clin Pharmacol JID - 1256165 RN - 0 (Antineoplastic Agents) RN - 41575-94-4 (Carboplatin) SB - IM MH - Adolescent MH - Antineoplastic Agents/*pharmacokinetics MH - Bayes Theorem MH - Carboplatin/*pharmacokinetics MH - Child MH - Child, Preschool MH - Comparative Study MH - Female MH - Human MH - Infant MH - Male MH - *Models, Theoretical MH - Nonlinear Dynamics MH - Statistics, Nonparametric EDAT- 2001/09/11 10:00 MHDA- 2002/01/23 10:01 PST - ppublish SO - Eur J Clin Pharmacol 2001 Jul;57(4):297-303. 451: Keil CT, et al. Degradation of validity over ...[PMID:11548973]Related Articles, Books, LinkOut UI - 21432603 PMID- 11548973 DA - 20010910 DCOM- 20011011 IS - 0033-2909 VI - 127 IP - 5 DP - 2001 Sep TI - Degradation of validity over time: a test and extension of Ackerman's model. PG - 673-97 AB - The dynamic nature of the predictor-criterion relationship has long been a concern in psychology, especially with regard to the deterioration of validity over time. The authors examine P. L. Ackerman's ( 1987, 1988) hypothesized relationships between different types of predictors and criteria over time using data from previous longitudinal studies. Expert ratings categorized predictors and criteria according to P. L. Ackerman's model. Regression results support the predicted negative curvilinear relationship between cognitive ability and consistent and inconsistent task performance but do not support the predicted relationships between perceptual speed ability and psychomotor ability and consistent and inconsistent task performance. Deterioration of validity was more ubiquitous than has been suggested previously, and the pervasive form of deterioration was cubic with a negative trend. Findings are discussed in the context of catastrophe-chaos models. AD - American Institutes of Research, Washington, District of Columbia 20007, USA. ckeil@air.org FAU - Keil, C T AU - Keil CT FAU - Cortina, J M AU - Cortina JM LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - United States TA - Psychol Bull JID - 0376473 SB - IM MH - Human MH - Models, Statistical MH - Nonlinear Dynamics MH - *Psychometrics MH - *Psychomotor Performance MH - *Reaction Time MH - Reproducibility of Results RF - 75 EDAT- 2001/09/11 10:00 MHDA- 2001/10/12 10:01 PST - ppublish SO - Psychol Bull 2001 Sep;127(5):673-97. 452: Guccione JM, et al. Residual stress produced by v...[PMID:11547315]Related Articles, Books, LinkOut UI - 21431860 PMID- 11547315 DA - 20010907 DCOM- 20011011 IS - 0022-5223 VI - 122 IP - 3 DP - 2001 Sep TI - Residual stress produced by ventricular volume reduction surgery has little effect on ventricular function and mechanics: a finite element model study. PG - 592-9 AB - OBJECTIVES: Residual stress is the stress (force per unit area) that remains when all external loads (eg, left ventricular chamber and pericardial pressures) are removed. It has been suggested that ventricular volume reduction surgery can reconstitute the residual stress-strain state of the left ventricle. To determine the extent to which residual stress is involved, we used a mathematical (finite element) model to simulate the effect of volume reduction operations on left ventricular stroke volume/end-diastolic pressure (Starling) relationships, as well as on regional distributions of stress in the local muscle fiber direction (fiber stress). METHODS: The nonlinear stress-strain relationship for the diastolic myocardium was anisotropic with respect to the local muscle fiber direction. An elastance model for active fiber stress was incorporated in an axisymmetric geometric model of the dilated, poorly contractile left ventricular wall. RESULTS: When residual stress is implemented in the model simulation of volume reduction operations, the additional decrease in stroke volume at fixed left ventricular end-diastolic pressure is small (10% volume reduction: 2.0% at 1 mm Hg and 2.0% at 20 mm Hg; 20% volume reduction: 2.2% at 1 mm Hg and 3.1% at 20 mm Hg). Furthermore, there is little change in the mean fiber stress throughout the left ventricular wall (10% volume reduction: +1.0% at end-diastole and -0.3% at end-systole; 20% volume reduction: +2.1% at end-diastole and -1.0% at end-systole). CONCLUSIONS: These results suggest that residual stress produced by volume reduction operations has little effect on left ventricular function and the mean fiber stresses at end-diastole and end-systole. AD - Department of Surgery, University of California, San Francisco, Calif, USA. Julius.Guccione@med.va.gov FAU - Guccione, J M AU - Guccione JM FAU - Moonly, S M AU - Moonly SM FAU - Wallace, A W AU - Wallace AW FAU - Ratcliffe, M B AU - Ratcliffe MB LA - eng ID - R01-HL-58759/HL/NHLBI ID - R01-HL-63348/HL/NHLBI PT - Journal Article CY - United States TA - J Thorac Cardiovasc Surg JID - 0376343 SB - AIM SB - IM MH - Anisotropy MH - Cardiomyopathy, Congestive/*physiopathology/*surgery MH - Diastole MH - Elasticity MH - *Finite Element Analysis MH - Heart Failure, Congestive/*physiopathology/*surgery MH - Heart Ventricle/*surgery MH - Human MH - *Models, Cardiovascular MH - *Nonlinear Dynamics MH - Stress, Mechanical MH - *Stroke Volume MH - Support, U.S. Gov't, P.H.S. MH - Systole MH - Treatment Outcome MH - *Ventricular Function, Left MH - *Ventricular Pressure EDAT- 2001/09/08 10:00 MHDA- 2001/10/12 10:01 AID - a114939 [pii] PST - ppublish SO - J Thorac Cardiovasc Surg 2001 Sep;122(3):592-9. 453: Gholmieh G, et al. A biosensor for detecting cha...[PMID:11544043]Related Articles, Books, LinkOut UI - 21428747 PMID- 11544043 DA - 20010906 DCOM- 20020122 IS - 0956-5663 VI - 16 IP - 7-8 DP - 2001 Sep TI - A biosensor for detecting changes in cognitive processing based on nonlinear systems analysis. PG - 491-501 AB - A new type of biosensor, based on hippocampal slices cultured on multielectrode arrays, and using nonlinear systems analysis for the detection and classification of agents interfering with cognitive function is described. A new method for calculating first and second order kernel was applied for impulse input-spike output datasets and results are presented to show the reliability of the estimations of this parameter. We further decomposed second order kernels as a sum of nine exponentially decaying Laguerre base functions. The data indicate that the method also reliably estimates these nine parameters. Thus, the state of the system can now be described with a set of ten parameters (first order kernel plus nine coefficients of Laguerre base functions) that can be used for detection and classification purposes. AD - Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089-1451, USA. FAU - Gholmieh, G AU - Gholmieh G FAU - Soussou, W AU - Soussou W FAU - Courellis, S AU - Courellis S FAU - Marmarelis, V AU - Marmarelis V FAU - Berger, T AU - Berger T FAU - Baudry, M AU - Baudry M LA - eng PT - Journal Article CY - England TA - Biosens Bioelectron JID - 9001289 RN - 0 (Chemical Warfare Agents) RN - 0 (Environmental Pollutants) RN - 124-87-8 (Picrotoxin) SB - IM MH - Animal MH - Biosensing Techniques/*methods MH - Chemical Warfare Agents/toxicity MH - Cognition/*drug effects MH - Electrophysiology MH - Environmental Pollutants/toxicity MH - Hippocampus/drug effects/physiology MH - In Vitro MH - Nonlinear Dynamics MH - Picrotoxin/toxicity MH - Rats MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Systems Analysis MH - Tissue Culture EDAT- 2001/09/07 10:00 MHDA- 2002/01/23 10:01 AID - S0956566301001634 [pii] PST - ppublish SO - Biosens Bioelectron 2001 Sep;16(7-8):491-501. 454: Hu Z, et al. Linear and nonlinear analysis...[PMID:11543238]Related Articles, Books UI - 20603596 PMID- 11543238 DA - 20000820 DCOM- 20000820 LR - 20010904 IS - 1002-0837 VI - 11 IP - 4 DP - 1998 Aug TI - Linear and nonlinear analysis of heart rate variability during lower body negative pressure. PG - 235-9 AB - In order to measure the changes of heart rate variability (HRV) under lower body negative pressure (LBNP), time and frequency domain parameters as well as the relative LZ Complexity were used to analyse HRV. Fifteen healthy male subjects in supine position were subjected to sequential LBNP (-2.7 kPa 2 min, -4.0 kPa 3 min, -5.3 kPa 5 min, -6.7 kPa 10 min). They were divided into two groups: intolerant group (group A) and tolerant group (group B). There was a similar decreasing trend for R-R interval at -5.3 kPa and -6.7 kPa in both groups. Spectral analysis showed no significant alternations in both groups. At -6.7 kPa, complexity showed significant differences from the baseline values in both groups. Furthermore, there was a more significant reduction of complexity in group A than that in group B. These results showed that LBNP is associated with a decrease of HRV complexity. In addition, this study suggests that nonlinear dynamics measurement of heart rate variability may provide a sensitive index in the regulation of cardiovascular system. AD - Institute of Space Medico-Engineering, Beijing. FAU - Hu, Z AU - Hu Z FAU - Zhao, G AU - Zhao G FAU - Yang, J AU - Yang J FAU - Jiao, J AU - Jiao J FAU - Zhong, C AU - Zhong C FAU - Lu, L AU - Lu L LA - eng PT - Journal Article CY - CHINA TA - Space Med Med Eng (Beijing) JID - 9425305 SB - S MH - Adult MH - Algorithms MH - Cardiovascular Physiology MH - Comparative Study MH - Heart Rate/*physiology MH - Human MH - *Lower Body Negative Pressure MH - Male MH - *Nonlinear Dynamics MH - Spectrum Analysis MH - Supine Position EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Space Med Med Eng (Beijing) 1998 Aug;11(4):235-9. 455: Hu Z, et al. [Nonlinear dynamic analysis o...[PMID:11543226]Related Articles, Books, LinkOut UI - 20603589 PMID- 11543226 DA - 20000820 DCOM- 20000820 LR - 20010904 IS - 1002-0837 VI - 11 IP - 2 DP - 1998 Apr TI - [Nonlinear dynamic analysis of heart rate variability during exercise] PG - 111-5 AB - Nonlinear dynamic analysis was used to examine the changes of complexity of heart rate variability (HRV) under rest and exercise. Nine healthy male subjects participated in the test. Each subject had a rest in supine position for 10 min, and then exercised on a cycle ergometer (10 min at 50 W and 10 min at 100 W). The results showed that R-R interval and its standard deviation reduced, and at the same time the values of nonlinear dynamics indices (complexity, entropy, correlation dimension, capacity dimension) also decreased during exercise. Moreover, at 100W work load the decrease of these indices was greater than that of 50W. It shows that physical exercise may reduce the complexity of HRV, and nonlinear dynamic indices could be used in distinguishing the complexity of heart rate variability under different physiological conditions. AD - Institute of Space Medico-Engineering, Beijing, China. FAU - Hu, Z AU - Hu Z FAU - Liu, Y AU - Liu Y FAU - Zhong, C AU - Zhong C FAU - Zhao, G AU - Zhao G FAU - Liu, B AU - Liu B LA - chi PT - Journal Article CY - CHINA TA - Space Med Med Eng (Beijing) JID - 9425305 SB - S MH - Adult MH - English Abstract MH - Exercise/*physiology MH - Exercise Test MH - Heart Rate/*physiology MH - Human MH - Male MH - *Nonlinear Dynamics MH - Rest MH - Supine Position EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Space Med Med Eng (Beijing) 1998 Apr;11(2):111-5. 456: Stanley HE, et al. Statistical physics and physi...[PMID:11543220]Related Articles, Books, LinkOut UI - 20603577 PMID- 11543220 DA - 20000813 DCOM- 20000813 LR - 20010904 IS - 0378-4371 VI - 270 IP - 1-2 DP - 1999 Aug 1 TI - Statistical physics and physiology: monofractal and multifractal approaches. PG - 309-24 AB - Even under healthy, basal conditions, physiologic systems show erratic fluctuations resembling those found in dynamical systems driven away from a single equilibrium state. Do such "nonequilibrium" fluctuations simply reflect the fact that physiologic systems are being constantly perturbed by external and intrinsic noise? Or, do these fluctuations actually, contain useful, "hidden" information about the underlying nonequilibrium control mechanisms? We report some recent attempts to understand the dynamics of complex physiologic fluctuations by adapting and extending concepts and methods developed very recently in statistical physics. Specifically, we focus on interbeat interval variability as an important quantity to help elucidate possibly non-homeostatic physiologic variability because (i) the heart rate is under direct neuroautonomic control, (ii) interbeat interval variability is readily measured by noninvasive means, and (iii) analysis of these heart rate dynamics may provide important practical diagnostic and prognostic information not obtainable with current approaches. The analytic tools we discuss may be used on a wider range of physiologic signals. We first review recent progress using two analysis methods--detrended fluctuation analysis and wavelets--sufficient for quantifying monofractual structures. We then describe recent work that quantifies multifractal features of interbeat interval series, and the discovery that the multifractal structure of healthy subjects is different than that of diseased subjects. AD - Department of Physics, Boston University, MA 02215, USA. hes@bu.edu FAU - Stanley, H E AU - Stanley HE FAU - Amaral, L A AU - Amaral LA FAU - Goldberger, A L AU - Goldberger AL FAU - Havlin, S AU - Havlin S AU - Ivanov PCh FAU - Peng, C K AU - Peng CK LA - eng PT - Journal Article CY - NETHERLANDS TA - Physica A JID - 9890571 SB - S MH - *Biophysics MH - Death, Sudden, Cardiac MH - *Fractals MH - Heart Diseases/physiopathology MH - Heart Failure, Congestive MH - Heart Rate/*physiology MH - *Homeostasis MH - Human MH - Models, Cardiovascular MH - Models, Statistical MH - *Nonlinear Dynamics MH - Stochastic Processes EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Physica A 1999 Aug 1;270(1-2):309-24. 457: Cai LY, et al. [Complexity analysis of surfa...[PMID:11543051]Related Articles, Books UI - 20601673 PMID- 11543051 DA - 20000629 DCOM- 20000629 LR - 20010904 IS - 1002-0837 VI - 13 IP - 2 DP - 2000 Apr TI - [Complexity analysis of surface EMG signals] PG - 124-7 AB - Objective: Since the neurophysiological system is a highly nonlinear dynamic system, nonlinear dynamic information of EMG signals were extracted to describe its characteristics. Method: Two-channel surface EMG signals were extracted and analyzed to reflect the complexity degree of the dynamics of the neurophysiological system. Result: Complexity measures of four kinds of forearm motions were calculated and compared. They showed a good separability. Conclusion: Experimental results proved that this measure, having a simple algorithm, is suitable for short data sets and suitable for real time processing. It provides a new measurable index for both physiological and pathological analysis. AD - Department of Biomedical Engineering, Shanghai Jiao Tong University, China. FAU - Cai, L Y AU - Cai LY FAU - Wang, Z Z AU - Wang ZZ FAU - Zhang, H H AU - Zhang HH LA - chi PT - Journal Article CY - CHINA TA - Space Med Med Eng (Beijing) JID - 9425305 SB - S MH - Comparative Study MH - *Electromyography MH - English Abstract MH - Forearm/*physiology MH - Hand Strength/physiology MH - Movement/*physiology MH - Muscle, Skeletal/physiology MH - *Nonlinear Dynamics MH - Pronation/physiology MH - Supination/physiology EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Space Med Med Eng (Beijing) 2000 Apr;13(2):124-7. 458: Ivanov PCh, et al. Stochastic feedback and the r...[PMID:11542723]Related Articles, Books UI - 20600709 PMID- 11542723 DA - 20000402 DCOM- 20000402 LR - 20010904 IS - 0295-5075 VI - 43 IP - 4 DP - 1998 Aug 15 TI - Stochastic feedback and the regulation of biological rhythms. PG - 363-8 AB - We propose a general approach to the question of how biological rhythms spontaneously self-regulate, based on the concept of "stochastic feedback". We illustrate this approach by considering at a coarse-grained level the neuroautonomic regulation of the heart rate. The model generates complex dynamics and successfully acounts for key characteristics of cardiac variability, including the l/f power spectrum, the functional form and scaling of the distribution of variations, and correlations in the Fourier phases indicating nonlinear dynamics. AD - Department of Physics, Boston University, MA 02215, USA. AU - Ivanov PCh FAU - Nunes Amaral, L A AU - Nunes Amaral LA FAU - Goldberger, A L AU - Goldberger AL FAU - Stanley, H E AU - Stanley HE LA - eng ID - MH-54081/MH/NIMH PT - Journal Article CY - FRANCE TA - Europhys Lett JID - 9886346 SB - S MH - Circadian Rhythm/*physiology MH - Fractals MH - Heart Rate/*physiology MH - Homeostasis/*physiology MH - Human MH - Mathematics MH - *Models, Cardiovascular MH - *Nonlinear Dynamics MH - *Stochastic Processes MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Europhys Lett 1998 Aug 15;43(4):363-8. 459: Amaral LA, et al. Modeling heart rate variabili...[PMID:11542688]Related Articles, Books UI - 20600500 PMID- 11542688 DA - 20000326 DCOM- 20000326 LR - 20021029 IS - 0010-4655 VI - 121-122 DP - 1999 TI - Modeling heart rate variability by stochastic feedback. PG - 126-8 AB - We consider the question of how the cardiac rhythm spontaneously self-regulates and propose a new mechanism as a possible answer. We model the neuroautonomic regulation of the heart rate as a stochastic feedback system and find that the model successfully accounts for key characteristics of cardiac variability, including the 1/f power spectrum, the functional form and scaling of the distribution of variations of the interbeat intervals, and the correlations in the Fourier phases which indicate nonlinear dynamics. AD - Department of Physics, Massachusetts Institute of Technology, Cambridge 02139, USA. http://polymer.bu.edu/amaral FAU - Amaral, L A AU - Amaral LA FAU - Goldberger, A L AU - Goldberger AL AU - Ivanov PCh FAU - Stanley, H E AU - Stanley HE LA - eng PT - Journal Article CY - NETHERLANDS TA - Comput Phys Commun JID - 100971327 SB - S MH - Heart/innervation MH - Heart Rate/*physiology MH - Human MH - *Models, Cardiovascular MH - *Nonlinear Dynamics MH - Parasympathetic Nervous System/physiology MH - Sinoatrial Node/physiology MH - *Stochastic Processes MH - Sympathetic Nervous System/physiology EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Comput Phys Commun 1999;121-122:126-8. 460: Fulget N, et al. MELISSA: global control strat...[PMID:11542550]Related Articles, Books, LinkOut UI - 20600212 PMID- 11542550 DA - 20000220 DCOM- 20000220 LR - 20010904 IS - 0273-1177 VI - 24 IP - 3 DP - 1999 TI - MELISSA: global control strategy of the artificial ecosystem by using first principles models of the compartments. PG - 397-405 AB - MELISSA is a micro-organisms based ecosystem conceived as a tool for understanding the behaviour of artificial ecosystems, and developing the technology for a future biological life support system for long term space mission. The driving element of MELISSA is the recovering of oxygen and edible biomass from waste (faeces, urea). Due to its intrinsic instability and the safety requirements of manned missions, an important control strategy is developed to pilot this system and to optimize its recycling performance. This is a hierarchical control strategy. Each MELISSA compartment has its local control system, and taking into account the states of other compartments and a global desired functioning point, the upper level determines the setpoints for each compartment. The developed approach is based on first principles models of each compartment (physico chemical equations, stoichiometries, kinetic rates, ...). Those models are used to develop a global simulator of the system (in order to study the global functioning). They are also used in the control strategy, which is a non linear predictive model based strategy. This paper presents the general approach of the control strategy of the loop from the compartment level up to the overall loop. At the end, some simulation and experimental results are presented. AD - ADERSA-7, Verrieres-le-Buisson, France. FAU - Fulget, N AU - Fulget N FAU - Poughon, L AU - Poughon L FAU - Richalet, J AU - Richalet J FAU - Lasseur, C h AU - Lasseur C LA - eng PT - Journal Article CY - ENGLAND TA - Adv Space Res JID - 9878935 RN - 0 (Nitrates) SB - S MH - Biomass MH - *Computer Simulation MH - Cyanobacteria/growth & development/metabolism MH - *Ecological Systems, Closed MH - Equipment Design MH - Evaluation Studies MH - Food MH - Human MH - *Life Support Systems MH - Mathematics MH - *Models, Biological MH - Nitrates/chemistry/metabolism MH - Nonlinear Dynamics MH - Rhodobacter/growth & development/metabolism MH - Software MH - Space Flight/instrumentation MH - Waste Management EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Adv Space Res 1999;24(3):397-405. 461: West BJ, et al. Fractal fluctuations in cardi...[PMID:11542384]Related Articles, Books, LinkOut UI - 99605297 PMID- 11542384 DA - 19991128 DCOM- 19991128 LR - 20010904 IS - 0378-4371 VI - 270 IP - 3-4 DP - 1999 Aug 15 TI - Fractal fluctuations in cardiac time series. PG - 552-66 AB - Human heart rate, controlled by complex feedback mechanisms, is a vital index of systematic circulation. However, it has been shown that beat-to-beat values of heart rate fluctuate continually over a wide range of time scales. Herein we use the relative dispersion, the ratio of the standard deviation to the mean, to show, by systematically aggregating the data, that the correlation in the beat-to-beat cardiac time series is a modulated inverse power law. This scaling property indicates the existence of long-time memory in the underlying cardiac control process and supports the conclusion that heart rate variability is a temporal fractal. We argue that the cardiac control system has allometric properties that enable it to respond to a dynamical environment through scaling. AD - Army Research Office, Research Triangle, NC 27709-2211, USA. westb@aro-emh1.army.mil FAU - West, B J AU - West BJ FAU - Zhang, R AU - Zhang R FAU - Sanders, A W AU - Sanders AW FAU - Miniyar, S AU - Miniyar S FAU - Zuckerman, J H AU - Zuckerman JH FAU - Levine, B D AU - Levine BD LA - eng ID - HL53206-03/HL/NHLBI PT - Journal Article CY - NETHERLANDS TA - Physica A JID - 9890571 SB - S MH - Adult MH - *Cardiovascular Physiology MH - Feedback MH - Female MH - *Fractals MH - Heart Rate/*physiology MH - Human MH - Male MH - Mathematics MH - Models, Cardiovascular MH - Models, Statistical MH - *Nonlinear Dynamics MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. MH - Time Factors EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Physica A 1999 Aug 15;270(3-4):552-66. 462: Kaplan DT, et al. Application of non-linear dyn...[PMID:11541828]Related Articles, Books, LinkOut UI - 99602908 PMID- 11541828 DA - 19990710 DCOM- 19990710 LR - 20010904 IS - 0276-6574 VI - 13 DP - 1987 TI - Application of non-linear dynamics to the characterization of cardiac electrical instability. PG - 439-42 AB - Beat-to-beat alternation in the morphology of the ECG has been previously observed in hearts susceptible to fibrillation. In addition, fibrillation has been characterized by some as a chaotic state. Period doubling phenomena, such as alternation, and the onset of chaos have been connected by non-linear dynamical systems theory. In this paper, we describe the use of a technique from nonlinear dynamics theory, the construction of a first return nap, to assess the susceptibility to fibrillation threshhold in canine experiments. AD - Harvard University, Cambridge, Massachusetts, USA. FAU - Kaplan, D T AU - Kaplan DT FAU - Cohen, R J AU - Cohen RJ LA - eng ID - F33615-84-C-0601/NASA ID - N00014-80-C-0520/NASA ID - NAG-327/NA/NASA PT - Journal Article CY - UNITED STATES TA - Comput Cardiol JID - 7504430 SB - S MH - Animal MH - Dogs MH - Electrocardiography MH - Heart Conduction System/*physiopathology MH - Heart Rate/*physiology MH - Hypothermia, Induced MH - Mathematics MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Ventricular Fibrillation/*physiopathology EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Comput Cardiol 1987;13:439-42. 463: Butler GC, et al. Probing heart rate and blood ...[PMID:11541049]Related Articles, Books UI - 99601215 PMID- 11541049 DA - 19990306 DCOM- 19990306 LR - 20010904 IS - 0958-5036 VI - 2 IP - 2 DP - 1992 Apr TI - Probing heart rate and blood pressure control mechanisms during graded levels of lower body negative pressure (LBNP). PG - 133-40 AB - Following space flight or head down tilt bed rest, cardiovascular deconditioning is often observed as a failure to maintain arterial blood pressure with symptoms of presyncope or syncope. LBNP can be used as a stressor of the cardiovascular system to observe the regulatory process. We have recently developed a new method to study cardiovascular control. Coarse graining spectral analysis (CGSA), allows simultaneous extraction of the harmonic components to evaluate sympathetic and parasympathetic nervous activities, and of the underlying complexity of the physiological response as given by the slope (beta) or fractal dimension (DF). The recognition that system complexity plays a major role in maintenance of cardiovascular stability is a relatively new concept. It was the purpose of the present study to examine the underlying complexity of heart rate and systolic blood pressure (SBP) variablities as indicated by the DF and power spectral analysis. Eight healthy men completed a test protocol of 20 min supine rest followed sequentially by 10 min at -5, -15, -25, -40, and -50 mmHg LBNP, and 10 min supine recovery. At rest, DF of R-R interval was 3.57 (beta = 1.56 +/- 0.12). There was a progressive decline in DF with LBNP, until at -50 mmHg, DF decreased to 1.2 (beta = 2.66 +/- 0.09). The DF for SBP was 1.3 (beta = 2.1 +/- 0.18) at rest, and was not significantly changed during LBNP. In the mid- and high-frequency ranges of the spectra, there was a moderately high degree of coherence between the variability in R-R interval and SBP. These findings indicate that short term SBP has a relatively low and unchanged complexity compared to heart rate. The changes in DF of heart rate variability were marked with increasing levels of LBNP. The results of this, and our previous study, indicate that a decline of DF to a critical level (near 1.4) is associated with orthostatic hypotension. These data show the utility of simple, non-invasive methods of data collection in conjunction with sophisticated data analysis techniques to point to possible mechanisms of orthostatic hypotension. AD - Department of Kinesiology, University of Waterloo, Canada. FAU - Butler, G C AU - Butler GC FAU - Yamamoto, Y AU - Yamamoto Y FAU - Xing, H C AU - Xing HC FAU - Northey, D R AU - Northey DR FAU - Hughson, R L AU - Hughson RL LA - eng PT - Journal Article CY - ENGLAND TA - Microgravity Q JID - 100971563 SB - S MH - Adult MH - Aerospace Medicine MH - Blood Pressure/*physiology MH - Fractals MH - Heart Rate/*physiology MH - Human MH - Hypotension, Orthostatic/*prevention & control MH - *Lower Body Negative Pressure MH - Male MH - Monitoring, Physiologic MH - Nonlinear Dynamics MH - Spectrum Analysis MH - Supine Position MH - Support, Non-U.S. Gov't MH - Syncope/prevention & control EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Microgravity Q 1992 Apr;2(2):133-40. 464: Wagner SW, et al. Regression models for calcula...[PMID:11540953]Related Articles, Books, LinkOut UI - 98617361 PMID- 11540953 DA - 19980922 DCOM- 19980922 LR - 20021101 IS - 0002-1962 VI - 89 IP - 2 DP - 1997 Mar-Apr TI - Regression models for calculating gas fluxes measured with a closed chamber. PG - 279-84 AB - Portable closed chambers provide a valuable tool for measuring crop photosynthesis and evapotranspiration. Typically, the rates of change of CO2 and water vapor concentration are assumed to be constant in the short time required to make the closed-chamber measurement, and a linear regression model is used to estimate the CO2 and H2O fluxes. However, due to the physical and physiological effects the measurement system has on the measured process, assuming a constant rate and using a linear model may underestimate the flux. Our objective was to provide a model that estimates the CO2 and H20 exchange rates at the time of chamber closure. We compared the linear regression model with a quadratic regression model using field measurements from two studies. Generally, 60 to 100% of all chamber measurement data sets were significantly nonlinear, causing the quadratic model to yield fluxes 10 to 40% greater than those calculated with the linear regression model. The frequency and degree of nonlinearity were related to the measured rate and chamber volume. Closed-chamber data should be tested for nonlinearity and an appropriate model used to calculate flux. The quadratic model provides users of well-mixed closed chambers an alternative to a simple linear model for data sets with significant nonlinearity. AD - USDA-ARS, North Central Soil Conservation Res. Lab., Morris, MN 56267, USA. swagner@mail.mrsars.usda.gov FAU - Wagner, S W AU - Wagner SW FAU - Reicosky, D C AU - Reicosky DC FAU - Alessi, R S AU - Alessi RS LA - eng PT - Journal Article CY - UNITED STATES TA - Agron J JID - 9882885 RN - 124-38-9 (Carbon Dioxide) RN - 7732-18-5 (Water) SB - S MH - Carbon Dioxide/*metabolism MH - Comparative Study MH - *Environment, Controlled MH - Evaluation Studies MH - Life Support Systems MH - *Linear Models MH - *Nonlinear Dynamics MH - Photosynthesis MH - *Plant Transpiration MH - Soybeans MH - Water/*metabolism MH - Zea mays EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Agron J 1997 Mar-Apr;89(2):279-84. 465: Chon KH, et al. Detection of chaotic determin...[PMID:11540720]Related Articles, Books, LinkOut UI - 98616786 PMID- 11540720 DA - 19980813 DCOM- 19980813 LR - 20010904 IS - 0167-2789 VI - 99 DP - 1997 TI - Detection of chaotic determinism in time series from randomly forced maps. PG - 471-86 AB - Time series from biological system often display fluctuations in the measured variables. Much effort has been directed at determining whether this variability reflects deterministic chaos, or whether it is merely "noise". Despite this effort, it has been difficult to establish the presence of chaos in time series from biological sytems. The output from a biological system is probably the result of both its internal dynamics, and the input to the system from the surroundings. This implies that the system should be viewed as a mixed system with both stochastic and deterministic components. We present a method that appears to be useful in deciding whether determinism is present in a time series, and if this determinism has chaotic attributes, i.e., a positive characteristic exponent that leads to sensitivity to initial conditions. The method relies on fitting a nonlinear autoregressive model to the time series followed by an estimation of the characteristic exponents of the model over the observed probability distribution of states for the system. The method is tested by computer simulations, and applied to heart rate variability data. AD - Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, USA. FAU - Chon, K H AU - Chon KH FAU - Kanters, J K AU - Kanters JK FAU - Cohen, R J AU - Cohen RJ FAU - Holstein-Rathlou, N H AU - Holstein-Rathlou NH LA - eng ID - HL-45623/HL/NHLBI ID - HL09029/HL/NHLBI ID - NAGW-3927/NA/NASA ID - etc. PT - Journal Article CY - NETHERLANDS TA - Physica D JID - 9890573 SB - S MH - *Algorithms MH - *Computer Simulation MH - Heart Rate/*physiology MH - Human MH - Least-Squares Analysis MH - Linear Models MH - Models, Biological MH - *Models, Statistical MH - *Nonlinear Dynamics MH - Stochastic Processes MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. MH - Time Factors EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Physica D 1997;99:471-86. 466: Chernyak YB, et al. Correspondence between discre...[PMID:11540551]Related Articles, Books, LinkOut UI - 98612720 PMID- 11540551 DA - 19980623 DCOM- 19980623 LR - 20010904 IS - 1063-651X VI - 55 IP - 3 Pt B DP - 1997 Mar TI - Correspondence between discrete and continuous models of excitable media: trigger waves. PG - 3215-33 AB - We present a theoretical framework for relating continuous partial differential equation (PDE) models of excitable media to discrete cellular automata (CA) models on a randomized lattice. These relations establish a quantitative link between the CA model and the specific physical system under study. We derive expressions for the CA model's plane wave speed, critical curvature, and effective diffusion constant in terms of the model's internal parameters (the interaction radius, excitation threshold, and time step). We then equate these expressions to the corresponding quantities obtained from solution of the PDEs (for a fixed excitability). This yields a set of coupled equations with a unique solution for the required CA parameter values. Here we restrict our analysis to "trigger" wave solutions obtained in the limiting case of a two-dimensional excitable medium with no recovery processes. We tested the correspondence between our CA model and two PDE models (the FitzHugh-Nagumo medium and a medium with a "sawtooth" nonlinear reaction source) and found good agreement with the numerical solutions of the PDEs. Our results suggest that the behavior of trigger waves is actually controlled by a small number of parameters. AD - Division of Health Sciences and Technology, Harvard University-Massachusetts Institute of Technology, Cambridge, USA. yurich@atrium.mit.edu FAU - Chernyak, Y B AU - Chernyak YB FAU - Feldman, A B AU - Feldman AB FAU - Cohen, R J AU - Cohen RJ LA - eng ID - NAGW-3927/NA/NASA PT - Journal Article CY - UNITED STATES TA - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics JID - 9887340 SB - S MH - Animal MH - Arrhythmia/physiopathology MH - *Biophysics MH - *Cell Physiology MH - Electrophysiology MH - Heart Diseases/*physiopathology MH - Heart Ventricle/*physiology MH - Human MH - Mathematics MH - Membrane Potentials MH - *Models, Biological MH - Myocardium MH - Neuromuscular Junction/*physiology MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1997 Mar;55(3 Pt B):3215-33. 467: Zhang Z, et al. [Approximate entropy analysis...[PMID:11540387]Related Articles, Books, LinkOut UI - 98607311 PMID- 11540387 DA - 19980408 DCOM- 19980408 LR - 20010904 IS - 1002-0837 VI - 10 IP - 5 DP - 1997 Oct TI - [Approximate entropy analysis of changes in heart rate dynamics associated with aerobic training] PG - 344-8 AB - To elucidate the effects of aerobic training on heart rate dynamics, heart rate variability (HRV) of eight students before and after a six-month aerobic training and HRV of six athletes, were analyzed with conventional time and frequency domain methods as well as with the approximate entropy(ApEn). The results showed that after a six-month aerobic training, heart rate ApEn significantly decreased (P < 0.01, P < 0.05) during both supine control and -6.67 kPa/30 min lower body negative pressure (LBNP). The heart rate ApEn of the athletes during supine control and early stage of LBNP testing was significantly lower (P < 0.01, P < 0.05) than that of the students before training. It was found that the values of ApEn were negatively correlated with the duration of LBNP in the student group (P < 0.01). However, both the time and frequency domain analyses were unable to detect the aforementioned changes. The results suggest that aerobic training can decrease the complexity of heart rate dynamics, and the synchronization in heart rate control during LBNP is probably a sustained process. AD - Department of Aerospace Physiology, The Fourth Military Medical University, Xi'an, China. FAU - Zhang, Z AU - Zhang Z FAU - Zhang, L AU - Zhang L FAU - Wang, S AU - Wang S FAU - Zheng, J AU - Zheng J LA - chi PT - Journal Article CY - CHINA TA - Space Med Med Eng (Beijing) JID - 9425305 SB - S MH - Aerospace Medicine MH - English Abstract MH - *Entropy MH - Exercise/*physiology MH - Heart Rate/*physiology MH - Human MH - *Lower Body Negative Pressure MH - Nonlinear Dynamics MH - Physical Fitness/*physiology EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Space Med Med Eng (Beijing) 1997 Oct;10(5):344-8. 468: Velayudhan A, et al. Simultaneous concentration an...[PMID:11540088]Related Articles, Books, LinkOut UI - 97606591 PMID- 11540088 DA - 19970219 DCOM- 19970219 LR - 20010904 IS - 0001-1541 VI - 41 IP - 5 DP - 1995 May TI - Simultaneous concentration and purification through gradient deformation chromatography. PG - 1184-93 AB - Mobile-phase additives, commonly used to modulate absorbate retention in gradient elution chromatography, are usually assumed to be either linearly retained or unretained. Previous theoretical work from our laboratory has shown that these modulators, such as salts in ion-exchange and hydrophobic interaction chromatography and organic modifiers in reversed-phase chromatography, can absorb nonlinearly, giving rise to gradient deformation. Consequently, adsorbate peaks that elute in the vicinity of the head of the deformed gradient may exhibit unusual shapes, form shoulders, and/or be concentrated. These effects for a reversed-phase sorbent with aqueous acetonitrile (ACN) as the modulator are verified experimentally. Gradient deformation is demonstrated experimentally and agrees with simulations based on ACN isotherm parameters that are independently determined from batch equilibrium studies using the layer model. Unusual absorbate peak shapes were found experimentally for single-component injections of phenylalanine, similar to those calculated by the simulations. A binary mixture of tryptophan and phenylalanine is used to demonstrate simultaneous concentration and separation, again in agreement with simulations. The possibility of gradient deformation in ion-exchange and hydrophobic interaction chromatography is discussed. AD - Laboratory of Renewable Resources Engineering, Purdue University, West Lafayette, IN 47907, USA. FAU - Velayudhan, A AU - Velayudhan A FAU - Hendrickson, R L AU - Hendrickson RL FAU - Ladisch, M R AU - Ladisch MR LA - eng ID - BCS-8912150/BC/NCI ID - NAGW-2329/NA/NASA PT - Journal Article CY - UNITED STATES TA - AIChE J JID - 9879346 RN - 0 (Acetonitriles) RN - 63-91-2 (Phenylalanine) RN - 73-22-3 (Tryptophan) RN - 75-05-8 (acetonitrile) RN - 7732-18-5 (Water) SB - S MH - Acetonitriles/*chemistry MH - Adsorption MH - Chromatography, Liquid/*methods MH - Mathematics MH - *Models, Chemical MH - Nonlinear Dynamics MH - Phenylalanine/*chemistry MH - Support, U.S. Gov't, Non-P.H.S. MH - Time Factors MH - Tryptophan/chemistry MH - Water/chemistry EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - AIChE J 1995 May;41(5):1184-93. 469: Young GE, et al. A design methodology for nonl...[PMID:11539600]Related Articles, Books UI - 97621501 PMID- 11539600 DA - 19971010 DCOM- 19971010 LR - 20021029 IS - 0022-0434 VI - 106 DP - 1984 Mar TI - A design methodology for nonlinear systems containing parameter uncertainty. PG - 15-20 AB - A design methodology capable of dealing with nonlinear systems containing parameter uncertainty is presented. A generalized sensitivity analysis is incorporated which utilizes sampling of the parameter space and statistical inference. For a system with j adjustable and k nonadjustable parameters, this methodology (which includes an adaptive random search strategy) is used to determine the combination of j adjustable parameter values which maximizes the probability of the performance indices simultaneously satisfying design criteria given the uncertainty in the k nonadjustable parameters. AD - School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater 74078, USA. FAU - Young, G E AU - Young GE FAU - Auslander, D M AU - Auslander DM LA - eng ID - 442483-23303/NASA PT - Journal Article CY - UNITED STATES TA - J Dyn Syst Meas Control JID - 100971391 SB - S MH - Algorithms MH - *Ecological Systems, Closed MH - Facility Design and Construction/*methods MH - *Life Support Systems MH - Mathematics MH - *Models, Statistical MH - *Nonlinear Dynamics MH - Statistics, Nonparametric MH - Support, U.S. Gov't, Non-P.H.S. MH - Systems Integration EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - J Dyn Syst Meas Control 1984 Mar;106:15-20. 470: Goldberger AL. Fractal mechanisms in the ele...[PMID:11539106]Related Articles, Books, LinkOut UI - 96717594 PMID- 11539106 DA - 19961216 DCOM- 19961216 LR - 20010904 IS - 0739-5175 VI - 11 IP - 2 DP - 1992 Jun TI - Fractal mechanisms in the electrophysiology of the heart. PG - 47-52 AB - The mathematical concept of fractals provides insights into complex anatomic branching structures that lack a characteristic (single) length scale, and certain complex physiologic processes, such as heart rate regulation, that lack a single time scale. Heart rate control is perturbed by alterations in neuro-autonomic function in a number of important clinical syndromes, including sudden cardiac death, congestive failure, cocaine intoxication, fetal distress, space sickness and physiologic aging. These conditions are associated with a loss of the normal fractal complexity of interbeat interval dynamics. Such changes, which may not be detectable using conventional statistics, can be quantified using new methods derived from "chaos theory." AD - Cardiovascular Division, Harvard Medical School, USA. FAU - Goldberger, A L AU - Goldberger AL LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - UNITED STATES TA - IEEE Eng Med Biol Mag JID - 8305985 SB - S MH - Computer Simulation MH - Electrocardiography MH - Electrophysiology MH - *Fractals MH - Heart/*physiology/physiopathology MH - Heart Conduction System/physiology/physiopathology MH - Heart Rate/*physiology MH - Human MH - Models, Biological MH - Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. MH - Ventricular Function/*physiology RF - 25 EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - IEEE Eng Med Biol Mag 1992 Jun;11(2):47-52. 471: Kaplan DT, et al. Nonlinear dynamics in cardiac...[PMID:11539069]Related Articles, Books, LinkOut UI - 96717504 PMID- 11539069 DA - 19961216 DCOM- 19961216 LR - 20010904 IS - 0025-5564 VI - 90 DP - 1988 TI - Nonlinear dynamics in cardiac conduction. PG - 19-48 AB - Electrical conduction in the heart shows many phenomena familiar from nonlinear dynamics. Among these phenomena are multiple basins of attraction, phase locking, and perhaps period-doubling bifurcations and chaos. We describe a simple cellular-automation model of electrical conduction which simulates normal conduction patterns in the heart as well as a wide range of disturbances of heart rhythm. In addition, we review the application of percolation theory to the analysis of the development of complex, self-sustaining conduction patterns. AD - Harvard-MIT, Division of Health Sciences and Technology, Cambridge, Massachusetts 02139, USA. FAU - Kaplan, D T AU - Kaplan DT FAU - Smith, J M AU - Smith JM FAU - Saxberg, B E AU - Saxberg BE FAU - Cohen, R J AU - Cohen RJ LA - eng ID - NAGW-988/NA/NASA PT - Journal Article PT - Review PT - Review, Tutorial CY - UNITED STATES TA - Math Biosci JID - 0103146 SB - S MH - Animal MH - Atrial Function/physiology MH - Electrophysiology MH - Heart/*physiology MH - Heart Conduction System/*physiology MH - Human MH - *Models, Cardiovascular MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. MH - Tachycardia, Ventricular/*physiopathology MH - Ventricular Fibrillation/*physiopathology MH - Ventricular Function/physiology RF - 26 EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Math Biosci 1988;90:19-48. 472: Peng CK, et al. Quantification of scaling exp...[PMID:11538314]Related Articles, Books, LinkOut UI - 96601898 PMID- 11538314 DA - 19960221 DCOM- 19960221 LR - 20021029 IS - 1054-1500 VI - 5 IP - 1 DP - 1995 TI - Quantification of scaling exponents and crossover phenomena in nonstationary heartbeat time series. PG - 82-7 AB - The healthy heartbeat is traditionally thought to be regulated according to the classical principle of homeostasis whereby physiologic systems operate to reduce variability and achieve an equilibrium-like state [Physiol. Rev. 9, 399-431 (1929)]. However, recent studies [Phys. Rev. Lett. 70, 1343-1346 (1993); Fractals in Biology and Medicine (Birkhauser-Verlag, Basel, 1994), pp. 55-65] reveal that under normal conditions, beat-to-beat fluctuations in heart rate display the kind of long-range correlations typically exhibited by dynamical systems far from equilibrium [Phys. Rev. Lett. 59, 381-384 (1987)]. In contrast, heart rate time series from patients with severe congestive heart failure show a breakdown of this long-range correlation behavior. We describe a new method--detrended fluctuation analysis (DFA)--for quantifying this correlation property in non-stationary physiological time series. Application of this technique shows evidence for a crossover phenomenon associated with a change in short and long-range scaling exponents. This method may be of use in distinguishing healthy from pathologic data sets based on differences in these scaling properties. AD - Cardiovascular Division, Harvard Medical School, Boston, Massachusetts 02215, USA. FAU - Peng, C K AU - Peng CK FAU - Havlin, S AU - Havlin S FAU - Stanley, H E AU - Stanley HE FAU - Goldberger, A L AU - Goldberger AL LA - eng PT - Journal Article CY - UNITED STATES TA - Chaos JID - 100971574 SB - S MH - Heart Diseases/physiopathology MH - Heart Failure, Congestive/*physiopathology MH - Heart Rate/*physiology MH - Human MH - Mathematics MH - Models, Statistical MH - *Nonlinear Dynamics MH - Stochastic Processes MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. MH - Systole/*physiology MH - Time Factors EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Chaos 1995;5(1):82-7. 473: Goldberger AL. Is the normal heartbeat chaot...[PMID:11537649]Related Articles, Books, LinkOut UI - 95607824 PMID- 11537649 DA - 19950510 DCOM- 19950510 LR - 20010904 IS - 0886-1714 VI - 6 DP - 1991 Apr TI - Is the normal heartbeat chaotic or homeostatic? PG - 87-91 AB - Limits to the usefulness of homeostasis as a guiding physiological principle are revealed by new mechanisms derived from study of nonlinear systems that generate a type of variability called chaos. Loss of complex physiological variability may occur in certain pathological conditions including heart rate dynamics before sudden death and with aging. AD - Harvard Medical School, Boston, MA 02215. FAU - Goldberger, A L AU - Goldberger AL LA - eng ID - NAG2-514/NA/NASA ID - RO1 HL-42172/HL/NHLBI PT - Journal Article PT - Review PT - Review, Tutorial CY - UNITED STATES TA - News Physiol Sci JID - 8609378 SB - S MH - Death, Sudden, Cardiac MH - Fractals MH - Heart Conduction System/physiology MH - Heart Rate/*physiology MH - Homeostasis/*physiology MH - Human MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Support, U.S. Gov't, P.H.S. RF - 16 EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - News Physiol Sci 1991 Apr;6:87-91. 474: Mesland DA. Possible actions of gravity o...[PMID:11536951]Related Articles, Books, LinkOut UI - 96604341 PMID- 11536951 DA - 19960306 DCOM- 19960306 LR - 20011102 IS - 0273-1177 VI - 12 IP - 1 DP - 1992 TI - Possible actions of gravity on the cellular machinery. PG - 15-25 AB - Since the first flight of the ESA Biorack on the German Spacelab Mission D1 in 1985 evidence has been obtained that biological cells and small unicellular organisms function differently under conditions of microgravity. However, there is still lack of scientific proof that these effects are caused by a direct influence on the cells in the weightlessness condition. The question how normal gravity may play a role in cellular activity is being addressed and the results show that gravity may provide important signals during certain state transitions in the cell. These would be gravity-sensitive windows in the biological process. Also, by amplification mechanisms inside the cell, the cell may assume a state that is typical for normal gravity conditions and would change in microgravity. Experimental tools are discussed that would provide the conditions to obtain evidence for direct action of gravity and for the possible existence of gravity-sensitive windows. AD - European Space Research and Technology Centre, Noordwijk, The Netherlands. FAU - Mesland, D A AU - Mesland DA LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - ENGLAND TA - Adv Space Res JID - 9878935 SB - S MH - Animal MH - *Cell Physiology MH - Cytoskeleton/physiology/ultrastructure MH - *Gravitation MH - Gravity Perception/*physiology MH - Human MH - Models, Biological MH - Nonlinear Dynamics MH - Otolithic Membrane/cytology/physiology/ultrastructure MH - Plant Roots/cytology MH - Plastids/physiology/ultrastructure MH - Rotation MH - *Space Flight MH - *Weightlessness RF - 26 EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Adv Space Res 1992;12(1):15-25. 475: Donskoy DM, et al. Nonlinear acoustic waves in p...[PMID:11536846]Related Articles, Books, LinkOut UI - 99605103 PMID- 11536846 DA - 19990927 DCOM- 19990927 LR - 20010904 IS - 0001-4966 VI - 102 IP - 5 Pt 1 DP - 1997 Nov TI - Nonlinear acoustic waves in porous media in the context of Biot's theory. PG - 2521-8 AB - The nonlinear dynamic equations introduced by Biot to model porous media have not been implemented to describe nonlinear acoustic waves in such media. In this work the equations are revised and a mathematical model depicting the physical nonlinearity is established. A perturbation technique is then applied to find solutions to the nonlinear Biot equations. An important feature of the developed model is the introduction of the dependence of the structural parameters of the medium on its porosity. The model establishes a correlation between the measurable effective nonlinear parameter and structural parameters of the porous medium. This suggests employing nonlinear measurements as a diagnostic tool for porous media. AD - Stevens Institute of Technology, Hoboken, New Jersey 07030, USA. FAU - Donskoy, D M AU - Donskoy DM FAU - Khashanah, K AU - Khashanah K FAU - McKee, T G Jr AU - McKee TG Jr LA - eng ID - NAGW-4586/NA/NASA PT - Journal Article CY - UNITED STATES TA - J Acoust Soc Am JID - 7503051 SB - S MH - *Acoustics MH - Elasticity MH - Geologic Sediments MH - Geology MH - Mathematics MH - *Models, Theoretical MH - *Nonlinear Dynamics MH - Porosity MH - Soil MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - J Acoust Soc Am 1997 Nov;102(5 Pt 1):2521-8. 476: Hill NA, et al. A biased random walk model fo...[PMID:11536821]Related Articles, Books, LinkOut UI - 98607576 PMID- 11536821 DA - 19980428 DCOM- 19980428 LR - 20010904 IS - 0022-5193 VI - 186 IP - 4 DP - 1997 Jun 21 TI - A biased random walk model for the trajectories of swimming micro-organisms. PG - 503-26 AB - The motion of swimming micro-organisms that have a preferred direction of travel, such as single-celled algae moving upwards (gravitaxis) or towards a light source (phototaxis), is modelled as the continuous limit of a correlated and biased random walk as the time step tends to zero. This model leads to a Fokker-Planck equation for the probability distribution function of the orientation of the cells, from which macroscopic parameters such as the mean cell swimming direction and the diffusion coefficient due to cell swimming can be calculated. The model is tested on experimental data for gravitaxis and phototaxis and used to derive values for the macroscopic parameters for future use in theories of bioconvection, for example. AD - Department of Applied Mathematical Studies, University of Leeds, England. FAU - Hill, N A AU - Hill NA FAU - Hader, D P AU - Hader DP LA - eng PT - Journal Article CY - ENGLAND TA - J Theor Biol JID - 0376342 SB - S MH - Algorithms MH - Animal MH - Biophysics MH - Chlamydomonas/*cytology/physiology MH - Convection MH - Dinoflagellida/*cytology/physiology MH - *Gravitation MH - Gravity Perception/physiology MH - *Light MH - Models, Biological MH - *Models, Statistical MH - Motor Activity/*physiology MH - Nonlinear Dynamics MH - Orientation MH - Swimming EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 AID - S0022519397904215 [pii] PST - ppublish SO - J Theor Biol 1997 Jun 21;186(4):503-26. 477: Baxter DA, et al. Complex oscillations in simpl...[PMID:11536793]Related Articles, Books, LinkOut UI - 97623967 PMID- 11536793 DA - 19971101 DCOM- 19971101 LR - 20010904 IS - 0006-3185 VI - 192 IP - 1 DP - 1997 Feb TI - Complex oscillations in simple neural systems. PG - 167-9 AD - Department of Neurobiology and Anatomy, The University of Texas Medical School at Houston 77030, USA. FAU - Baxter, D A AU - Baxter DA FAU - Byrne, J H AU - Byrne JH LA - eng PT - Journal Article CY - UNITED STATES TA - Biol Bull JID - 2984727R SB - S MH - Animal MH - Aplysia/*cytology/physiology MH - *Computer Simulation MH - Electrophysiology MH - *Gravitation MH - *Models, Neurological MH - Neurons/*physiology MH - *Nonlinear Dynamics MH - Oscillometry EDAT- 2001/09/07 10:00 MHDA- 2001/09/11 10:01 PST - ppublish SO - Biol Bull 1997 Feb;192(1):167-9. 478: Sen K, et al. Feature analysis of natural s...[PMID:11535690]Related Articles, Books, LinkOut UI - 21427206 PMID- 11535690 DA - 20010905 DCOM- 20011204 IS - 0022-3077 VI - 86 IP - 3 DP - 2001 Sep TI - Feature analysis of natural sounds in the songbird auditory forebrain. PG - 1445-58 AB - Although understanding the processing of natural sounds is an important goal in auditory neuroscience, relatively little is known about the neural coding of these sounds. Recently we demonstrated that the spectral temporal receptive field (STRF), a description of the stimulus-response function of auditory neurons, could be derived from responses to arbitrary ensembles of complex sounds including vocalizations. In this study, we use this method to investigate the auditory processing of natural sounds in the birdsong system. We obtain neural responses from several regions of the songbird auditory forebrain to a large ensemble of bird songs and use these data to calculate the STRFs, which are the best linear model of the spectral-temporal features of sound to which auditory neurons respond. We find that these neurons respond to a wide variety of features in songs ranging from simple tonal components to more complex spectral-temporal structures such as frequency sweeps and multi-peaked frequency stacks. We quantify spectral and temporal characteristics of these features by extracting several parameters from the STRFs. Moreover, we assess the linearity versus nonlinearity of encoding by quantifying the quality of the predictions of the neural responses to songs obtained using the STRFs. Our results reveal successively complex functional stages of song analysis by neurons in the auditory forebrain. When we map the properties of auditory forebrain neurons, as characterized by the STRF parameters, onto conventional anatomical subdivisions of the auditory forebrain, we find that although some properties are shared across different subregions, the distribution of several parameters is suggestive of hierarchical processing. AD - Sloan Center for Theoretical Neuroscience, University of California, 513 Parnassus Ave., Berkeley, CA 94720-1650, USA. kamal@phy.ucsf.edu FAU - Sen, K AU - Sen K FAU - Theunissen, F E AU - Theunissen FE FAU - Doupe, A J AU - Doupe AJ LA - eng ID - NS-34835/NS/NINDS PT - Journal Article CY - United States TA - J Neurophysiol JID - 0375404 SB - IM MH - Animal MH - Auditory Pathways/*physiology MH - Electrophysiology MH - Linear Models MH - Male MH - Models, Neurological MH - Nonlinear Dynamics MH - Prosencephalon/*physiology MH - Songbirds/*physiology MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. MH - Vocalization, Animal/*physiology EDAT- 2001/09/06 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Neurophysiol 2001 Sep;86(3):1445-58. 479: Herzog RI, et al. Persistent TTX-resistant Na+ ...[PMID:11535682]Related Articles, Books, LinkOut UI - 21427198 PMID- 11535682 DA - 20010905 DCOM- 20011204 IS - 0022-3077 VI - 86 IP - 3 DP - 2001 Sep TI - Persistent TTX-resistant Na+ current affects resting potential and response to depolarization in simulated spinal sensory neurons. PG - 1351-64 AB - Small dorsal root ganglion (DRG) neurons, which include nociceptors, express multiple voltage-gated sodium currents. In addition to a classical fast inactivating tetrodotoxin-sensitive (TTX-S) sodium current, many of these cells express a TTX-resistant (TTX-R) sodium current that activates near -70 mV and is persistent at negative potentials. To investigate the possible contributions of this TTX-R persistent (TTX-RP) current to neuronal excitability, we carried out computer simulations using the Neuron program with TTX-S and -RP currents, fit by the Hodgkin-Huxley model, that closely matched the currents recorded from small DRG neurons. In contrast to fast TTX-S current, which was well fit using a m(3)h model, the persistent TTX-R current was not well fit by an m(3)h model and was better fit using an mh model. The persistent TTX-R current had a strong influence on resting potential, shifting it from -70 to -49.1 mV. Inclusion of an ultra-slow inactivation gate in the persistent current model reduced the potential shift only slightly, to -56.6 mV. The persistent TTX-R current also enhanced the response to depolarizing inputs that were subthreshold for spike electrogenesis. In addition, the presence of persistent TTX-R current predisposed the cell to anode break excitation. These results suggest that, while the persistent TTX-R current is not a major contributor to the rapid depolarizing phase of the action potential, it contributes to setting the electrogenic properties of small DRG neurons by modulating their resting potentials and response to subthreshold stimuli. AD - Department of Neurology, Paralyzed Veterans of America/Eastern Paralyzed Veterans Association Neuroscience Research Center, Yale School of Medicine, New Haven, CT 06510, USA. FAU - Herzog, R I AU - Herzog RI FAU - Cummins, T R AU - Cummins TR FAU - Waxman, S G AU - Waxman SG LA - eng PT - Journal Article CY - United States TA - J Neurophysiol JID - 0375404 RN - 0 (Sodium Channels) RN - 4368-28-9 (Tetrodotoxin) RN - 7440-23-5 (Sodium) SB - IM MH - Action Potentials/drug effects/physiology MH - Animal MH - Computer Simulation MH - Ganglia, Spinal/*cytology MH - Ion Channel Gating/drug effects/physiology MH - Membrane Potentials/drug effects/physiology MH - Mice MH - Mice, Mutant Strains MH - *Models, Neurological MH - Neurons, Afferent/*physiology MH - Nonlinear Dynamics MH - Patch-Clamp Techniques MH - Sodium/*metabolism MH - Sodium Channels/physiology MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. MH - Tetrodotoxin/*pharmacology EDAT- 2001/09/06 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Neurophysiol 2001 Sep;86(3):1351-64. 480: MacLean JN, et al. Voltage-sensitivity of motone...[PMID:11535663]Related Articles, Books, LinkOut UI - 21427179 PMID- 11535663 DA - 20010905 DCOM- 20011204 IS - 0022-3077 VI - 86 IP - 3 DP - 2001 Sep TI - Voltage-sensitivity of motoneuron NMDA receptor channels is modulated by serotonin in the neonatal rat spinal cord. PG - 1131-8 AB - Both N-methyl-D-aspartate (NMDA) and serotonin (5-HT) receptors contribute to the generation of rhythmic motor patterns in the rat spinal cord. Co-application of these chemicals is more effective at producing locomotor-like activity than either neurochemical alone. In addition, NMDA application to rat spinal motoneurons, synaptically isolated in tetrodotoxin, induces nonlinear membrane behavior that results in voltage oscillations which can be blocked by 5-HT antagonists. However, the mechanisms underlying NMDA and 5-HT receptor interactions pertinent to motor rhythm production remain to be determined. In the present study, an in vitro neonatal rat spinal cord preparation was used to examine whether NMDA receptor-mediated nonlinear membrane voltage is modulated by 5-HT. Whole-cell recordings of spinal motoneurons demonstrated that 5-HT shifts the region of NMDA receptor-dependent negative slope conductance (RNSC) of the current-voltage relationship to more hyperpolarized potentials and enhances whole-cell inward current. The influence of 5-HT on the RNSC was similar to the effect on the RNSC of decreasing the extracellular Mg(2+)concentration. The results suggest that 5-HT may modulate this form of membrane voltage nonlinearity by regulating Mg(2+) blockade of the NMDA ionophore. AD - Department of Physiology, University of Manitoba, 730 William Ave., Winnipeg, Manitoba R3E 3J7, Canada. FAU - MacLean, J N AU - MacLean JN FAU - Schmidt, B J AU - Schmidt BJ LA - eng PT - Journal Article CY - United States TA - J Neurophysiol JID - 0375404 RN - 0 (Excitatory Amino Acid Agonists) RN - 0 (Receptors, N-Methyl-D-Aspartate) RN - 4368-28-9 (Tetrodotoxin) RN - 50-67-9 (Serotonin) RN - 6384-92-5 (N-Methylaspartate) RN - 7439-95-4 (Magnesium) SB - IM MH - Animal MH - Animals, Newborn MH - Excitatory Amino Acid Agonists/pharmacology MH - Ion Channel Gating/drug effects/physiology MH - Magnesium/pharmacology MH - Membrane Potentials/drug effects/physiology MH - Motor Neurons/*physiology MH - N-Methylaspartate/pharmacology MH - Nonlinear Dynamics MH - Patch-Clamp Techniques MH - Rats MH - Rats, Sprague-Dawley MH - Receptors, N-Methyl-D-Aspartate/*physiology MH - Serotonin/*pharmacology MH - Spinal Cord/cytology/*physiology MH - Support, Non-U.S. Gov't MH - Tetrodotoxin/pharmacology EDAT- 2001/09/06 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Neurophysiol 2001 Sep;86(3):1131-8. 481: Stacey WC, et al. Synaptic noise improves detec...[PMID:11535661]Related Articles, Books, LinkOut UI - 21427177 PMID- 11535661 DA - 20010905 DCOM- 20011204 IS - 0022-3077 VI - 86 IP - 3 DP - 2001 Sep TI - Synaptic noise improves detection of subthreshold signals in hippocampal CA1 neurons. PG - 1104-12 AB - Stochastic resonance (SR) is a phenomenon whereby the detection of a low-level signal is enhanced in a nonlinear system by the introduction of noise. Studies of the effects of SR in neurons have suggested that noise could play a prominent role in improving detection of small signals. Most experimental SR research has focused on the role of noise in sensory neurons using physiological stimuli. Computer simulations show that signal detection in hippocampal neurons is improved by the addition of physiological levels of noise applied extracellularly to synaptic inputs. These results were confirmed experimentally. We now report that endogenous noise sources can also improve signal detection. The noise source was generated by modulating the random synaptic activity on the apical dendrites of CA1 cells in rat hippocampal slices using subthreshold cathodic current. Intracellular recordings of CA1 cells showed that even small increases of synaptic noise are able to greatly improve the detection of an independent, synaptic, subthreshold stimulus as predicted by the simulations. The noise variance in the CA1 cell was compared with the resting variance and with variance changes caused by several endogenous noise sources. In all cases, the increased noise variance was well within the physiological range. These results were supplemented and analyzed with a CA1 computer model. The improved signal detection with small amounts of endogenous noise suggests that the diverse inputs to CA1 are able to improve detection of subthreshold synaptic signals and could provide a means to modulate detection of specific inputs in the hippocampus. AD - Neural Engineering Center, Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106. FAU - Stacey, W C AU - Stacey WC FAU - Durand, D M AU - Durand DM LA - eng PT - Journal Article CY - United States TA - J Neurophysiol JID - 0375404 SB - IM MH - Action Potentials/physiology MH - Animal MH - Computer Simulation MH - Denervation MH - Electrodes MH - Excitatory Postsynaptic Potentials/physiology MH - Hippocampus/*cytology MH - *Models, Neurological MH - Neurons/*physiology MH - Nonlinear Dynamics MH - Organ Culture MH - Rats MH - Rats, Sprague-Dawley MH - Stochastic Processes MH - Support, Non-U.S. Gov't MH - Synapses/*physiology EDAT- 2001/09/06 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Neurophysiol 2001 Sep;86(3):1104-12. 482: Zhang ZG, et al. Dynamic platelet accumulation...[PMID:11532435]Related Articles, Books, LinkOut UI - 21423187 PMID- 11532435 DA - 20010904 DCOM- 20011207 IS - 0006-8993 VI - 912 IP - 2 DP - 2001 Sep 7 TI - Dynamic platelet accumulation at the site of the occluded middle cerebral artery and in downstream microvessels is associated with loss of microvascular integrity after embolic middle cerebral artery occlusion. PG - 181-94 AB - Information is lacking regarding dynamic platelet accumulation at the site of the occluded middle cerebral artery (MCA) and the relationship between platelet aggregation in downstream cerebral microvessels and loss of perfusion and vascular integrity of these microvessels. In the present study, we employed a model of embolic MCA occlusion in the rat to simultaneously measure temporal and spatial profiles of platelet accumulation at the site of the embolus occluding the MCA and within downstream cerebral microvessels. We also measured the integrity of microvessels and matrix metalloproteinase (MMP) activity in ischemic brain. Rats (n=36) were subjected to embolic MCA occlusion. Immunohistochemistry was used to detect microvascular integrity, plasminogen activator inhibitor 1 (PAI-1) and the deposition of fibrin. SDS-PAGE zymography was used to measure MMP2 and MMP9 activities. Accumulation of platelets and increases in PAI-1 immunoreactivity at the site of the embolus occluding the MCA were detected 1 h (n=7) and 4 h (n=7) after ischemia, respectively, and numbers of GPIIb/IIIa immunoreactive downstream cerebral microvessels increased significantly (209+/-59; n=7; P<0.05) 4 h after ischemia, suggesting dynamic platelet aggregation. A significant (n=7; P<0.01) diffuse loss of type IV collagen immunoreactivity in microvessels was temporally associated with platelet GPIIb/IIIa immunoreactivity within the vessels. Triple immunostaining revealed that microvessels containing platelet aggregates exhibited loss of type IV collagen immunoreactivity and both intra- and extra-vascular fibrin deposition, suggesting that intravascular platelet aggregation is associated with decreases in the integrity of the microvascular basal lamina and blood-brain barrier leakage. A significant increase (P<0.05) in MMP9 was detected at 4 h (n=3) and 24 h (n=3) after ischemia but levels of MMP2 were not significantly changed in ischemic brain. Our data suggest that dynamic platelet aggregation in ischemic brain may contribute to time-dependent resistance to fibrinolysis. In addition, platelet deposition and increased MMP9 coincided with degradation of type IV collagen and loss of vascular integrity. These data suggest an important role for post-occlusive distal platelet deposition in the pathophysiology of stroke. AD - Department of Neurology, Henry Ford Health Sciences Center, 2799 West Grand Boulevard, Detroit, MI 48202, USA. FAU - Zhang, Z G AU - Zhang ZG FAU - Zhang, L AU - Zhang L FAU - Tsang, W AU - Tsang W FAU - Goussev, A AU - Goussev A FAU - Powers, C AU - Powers C FAU - Ho, K L AU - Ho KL FAU - Morris, D AU - Morris D FAU - Smyth, S S AU - Smyth SS FAU - Coller, B S AU - Coller BS FAU - Chopp, M AU - Chopp M LA - eng ID - 19278/PHS ID - 54469/PHS ID - PO1 NS23393/NS/NINDS ID - RO1 NS33627/NS/NINDS PT - Journal Article CY - Netherlands TA - Brain Res JID - 0045503 RN - 0 (Collagen Type IV) RN - 0 (Laminin) RN - 0 (Plasminogen Activator Inhibitor 1) RN - 0 (Platelet Glycoprotein GPIIb-IIIa Complex) RN - EC 3.4.24.- (Matrix Metalloproteinases) RN - EC 3.4.24.24 (Gelatinase A) RN - EC 3.4.24.35 (Gelatinase B) SB - IM MH - Animal MH - Blood Coagulation/*physiology MH - Blood Platelets/cytology/*physiology/ultrastructure MH - Blood-Brain Barrier/physiology MH - Brain/*enzymology/pathology/ultrastructure MH - Brain Ischemia/*enzymology/pathology/physiopathology MH - Cerebrovascular Circulation/physiology MH - Collagen Type IV/metabolism MH - Disease Models, Animal MH - Gelatinase A/metabolism MH - Gelatinase B/metabolism MH - Immunohistochemistry MH - In Vitro MH - Infarction, Middle Cerebral Artery/enzymology/pathology/*physiopathology MH - Laminin/metabolism MH - Male MH - Matrix Metalloproteinases/*metabolism MH - Microcirculation/pathology/*physiopathology/ultrastructure MH - Microscopy, Electron MH - Nonlinear Dynamics MH - Plasminogen Activator Inhibitor 1/metabolism MH - Platelet Glycoprotein GPIIb-IIIa Complex/metabolism MH - Rats MH - Rats, Wistar MH - Support, U.S. Gov't, P.H.S. MH - Time Factors EDAT- 2001/09/05 10:00 MHDA- 2002/01/05 10:01 AID - S0006899301027354 [pii] PST - ppublish SO - Brain Res 2001 Sep 7;912(2):181-94. 483: Neufeld Z. Excitable media in a chaotic ...[PMID:11531505]Related Articles, Books, LinkOut UI - 21424981 PMID- 11531505 DA - 20010904 DCOM- 20011025 IS - 0031-9007 VI - 87 IP - 10 DP - 2001 Sep 3 TI - Excitable media in a chaotic flow. PG - 108301 AB - The response to a localized perturbation of an excitable medium under stirring by chaotic advection is investigated. It is found that below a critical stirring rate a localized perturbation produces a coherent global excitation of the system. For very slow stirring, however, the coherence of the global excitation is gradually lost. We propose a simple model to describe the effect of the flow on the excitable dynamics, and explain the observed behavior as a consequence of a steady excited filament state found in the reduced problem. AD - Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW, United Kingdom. FAU - Neufeld, Z AU - Neufeld Z LA - eng PT - Journal Article CY - United States TA - Phys Rev Lett JID - 0401141 SB - IM MH - Algorithms MH - Diffusion MH - Motion MH - *Nonlinear Dynamics MH - Support, Non-U.S. Gov't EDAT- 2001/09/05 10:00 MHDA- 2001/10/26 10:01 PHST- 2000/Dec/04 [received] PHST- 2001/Mar/26 [revised] PHST- 2001/Aug/15 [aheadofprint] PST - ppublish SO - Phys Rev Lett 2001 Sep 3;87(10):108301. 484: Yang N, et al. Angle-resolved second-harmoni...[PMID:11531479]Related Articles, Books, LinkOut UI - 21424955 PMID- 11531479 DA - 20010904 DCOM- 20011025 IS - 0031-9007 VI - 87 IP - 10 DP - 2001 Sep 3 TI - Angle-resolved second-harmonic light scattering from colloidal particles. PG - 103902 AB - We report angle-resolved second-harmonic generation (SHG) measurements from suspensions of centrosymmetric micron-size polystyrene spheres with surface-adsorbed dye (malachite green). The second-harmonic scattering profiles differ qualitatively from linear light scattering profiles of the same particles. We investigated these radiation patterns using several polarization configurations and particle diameters. We introduce a simple Rayleigh-Gans-Debye model to account for the SHG scattering anisotropy. The model compares favorably with our experimental data. Our measurements suggest scattering anisotropy may be used to isolate particle nonlinear optics from other bulk nonlinear optical effects in suspension. AD - Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, Pennsylvania 19104-6396, USA. FAU - Yang, N AU - Yang N FAU - Angerer, W E AU - Angerer WE FAU - Yodh, A G AU - Yodh AG LA - eng PT - Journal Article CY - United States TA - Phys Rev Lett JID - 0401141 RN - 0 (Colloids) RN - 0 (Polystyrenes) RN - 0 (Rosaniline Dyes) RN - 10309-95-2 (malachite green) SB - IM MH - Anisotropy MH - *Colloids MH - Light MH - Microspheres MH - Nonlinear Dynamics MH - Polystyrenes MH - Rosaniline Dyes MH - Scattering, Radiation MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2001/09/05 10:00 MHDA- 2001/10/26 10:01 PHST- 2001/Mar/16 [received] PHST- 2001/Aug/16 [aheadofprint] PST - ppublish SO - Phys Rev Lett 2001 Sep 3;87(10):103902. 485: Hongxuan Z, et al. Pathological analysis of myoc...[PMID:11530825]Related Articles, Books, LinkOut UI - 21421669 PMID- 11530825 DA - 20010903 DCOM- 20011220 IS - 0309-1902 VI - 25 IP - 3 DP - 2001 May-Jun TI - Pathological analysis of myocardial cell under ventricular tachycardia and fibrillation based on symbolic dynamics. PG - 112-7 AB - Ventricular fibrillation (VF) is one of the most serious malignant arrhythmias usually resulting from immediate degeneration of ventricular tachycardia (VT). In order to analyse the nonlinear dynamics of the cardiac micro-mechanism under VT and VT rhythm, at the cellular level, myocardial cell action potentials are investigated under different rhythm, normal sinus rhythm, VT and VT. On the basis of nonlinear chaotic theory and symbolic dynamics, we put forward new definitions, complexity rate, etc, and obtained some useful properties for cellular electrophysiological analysis. The results of the experiments and computation show that the myocardial cellular signals under VT and VF rhythm are different kinds of chaotic signals in that the cardiac chaos attractor under VF is higher than that under VT. The analytical complexity theory has been promising in the clinical application. AD - Department of Biomedical Engineering, College of Life Science and Biotechnology, Shanghai Jiao Tong University, PR China. zhanghx@bme.situ.edu.ch FAU - Hongxuan, Z AU - Hongxuan Z FAU - Yisheng, Z AU - Yisheng Z FAU - Yuhong, X AU - Yuhong X FAU - Thakor, N V AU - Thakor NV LA - eng PT - Journal Article CY - England TA - J Med Eng Technol JID - 7702125 SB - IM MH - Action Potentials MH - Animal MH - Cardiac Pacing, Artificial MH - Electrophysiology MH - Heart/*physiopathology MH - In Vitro MH - Myocardium/cytology MH - Nonlinear Dynamics MH - Rabbits MH - Support, Non-U.S. Gov't MH - Tachycardia, Ventricular/*physiopathology MH - Ventricular Fibrillation/*physiopathology EDAT- 2001/09/04 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Med Eng Technol 2001 May-Jun;25(3):112-7. 486: Noble D. From genes to whole organs: c...[PMID:11529307]Related Articles, Books, LinkOut UI - 21419994 PMID- 11529307 DA - 20010831 DCOM- 20020124 VI - 239 DP - 2001 TI - From genes to whole organs: connecting biochemistry to physiology. PG - 111-23; discussion 123-8, 150-9 AB - The successful analysis of physiological processes requires quantitative understanding of the functional interactions between the key components of cells, organs and systems, and how these interactions change in disease states. This information does not reside in the genome, or even in the individual proteins that genes code for. There is therefore no alternative to copying nature and computing these interactions to determine the logic of healthy and diseased states. The rapid growth in biological databases, models of cells, tissues and organs, and in computing power has made it possible to explore functionality all the way from the level of genes to whole organs and systems. Examples are given of genetic modifications of the Na+ channel protein in the heart that predispose people to ventricular fibrillation, and of multiple target therapy in drug development. Complexity in biological systems also arises from tissue and organ geometry. This is illustrated using modelling of the whole heart. AD - University Laboratory of Physiology, University of Oxford, UK. FAU - Noble, D AU - Noble D LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - England TA - Novartis Found Symp JID - 9807767 RN - 0 (Anti-Arrhythmia Agents) RN - 0 (Proteins) RN - 0 (Proteome) SB - IM MH - Animal MH - Anti-Arrhythmia Agents/pharmacology/therapeutic use MH - Biochemistry MH - *Computer Simulation MH - Gene Expression MH - Genome MH - Heart Failure, Congestive/genetics/metabolism MH - Human MH - *Models, Biological MH - Mutation MH - Nonlinear Dynamics MH - Physiology MH - Proteins/*genetics/*physiology MH - Proteome RF - 31 EDAT- 2001/09/01 10:00 MHDA- 2002/01/25 10:01 PST - ppublish SO - Novartis Found Symp 2001;239:111-23; discussion 123-8, 150-9. 487: Ebersole JS. The last word....[PMID:11528302]Related Articles, Books, LinkOut UI - 21419427 PMID- 11528302 DA - 20010830 DCOM- 20011204 IS - 0736-0258 VI - 18 IP - 3 DP - 2001 May TI - The last word. PG - 299-300 FAU - Ebersole, J S AU - Ebersole JS LA - eng PT - Editorial CY - United States TA - J Clin Neurophysiol JID - 8506708 SB - IM MH - Cerebral Cortex/physiopathology MH - Electroencephalography/*statistics & numerical data MH - Epilepsy/*diagnosis/physiopathology MH - Human MH - Linear Models MH - Monitoring, Physiologic MH - Neurons/physiology MH - Nonlinear Dynamics MH - Signal Processing, Computer-Assisted EDAT- 2001/08/31 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Clin Neurophysiol 2001 May;18(3):299-300. 488: Jerger KK, et al. Early seizure detection....[PMID:11528297]Related Articles, Books, LinkOut UI - 21419426 PMID- 11528297 DA - 20010830 DCOM- 20011204 IS - 0736-0258 VI - 18 IP - 3 DP - 2001 May TI - Early seizure detection. PG - 259-68 AB - For patients with medically intractable epilepsy, there have been few effective alternatives to resective surgery, a destructive, irreversible treatment. A strategy receiving increased attention is using interictal spike patterns and continuous EEG measurements from epileptic patients to predict and ultimately control seizure activity via chemical or electrical control systems. This work compares results of seven linear and nonlinear methods (analysis of power spectra, cross-correlation, principal components, phase, wavelets, correlation integral, and mutual prediction) in detecting the earliest dynamical changes preceding 12 intracranially-recorded seizures from 4 patients. A method of counting standard deviations was used to compare across methods, and the earliest departures from thresholds determined from non-seizure EEG were compared to a neurologist's judgement. For these data, the nonlinear methods offered no predictive advantage over the linear methods. All the methods described here were successful in detecting changes leading to a seizure between one and two minutes before the first changes noted by the neurologist, although analysis of phase correlation proved the most robust. The success of phase analysis may be due in part to its complete insensitivity to amplitude, which may provide a significant source of error. AD - Krasnow Institute for Advanced Study, George Mason University, Fairfax, Virginia 22030-4444, USA. FAU - Jerger, K K AU - Jerger KK FAU - Netoff, T I AU - Netoff TI FAU - Francis, J T AU - Francis JT FAU - Sauer, T AU - Sauer T FAU - Pecora, L AU - Pecora L FAU - Weinstein, S L AU - Weinstein SL FAU - Schiff, S J AU - Schiff SJ LA - eng PT - Journal Article CY - United States TA - J Clin Neurophysiol JID - 8506708 SB - IM MH - Brain Mapping MH - Cerebral Cortex/physiopathology/surgery MH - Child MH - Cortical Synchronization MH - *Electroencephalography MH - Epilepsy/*diagnosis/physiopathology/surgery MH - Evoked Potentials/physiology MH - Fourier Analysis MH - Human MH - *Linear Models MH - Monitoring, Physiologic MH - Neurons/physiology MH - *Nonlinear Dynamics MH - Signal Processing, Computer-Assisted EDAT- 2001/08/31 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Clin Neurophysiol 2001 May;18(3):259-68. 489: Savit R, et al. Understanding dynamic state c...[PMID:11528296]Related Articles, Books, LinkOut UI - 21419425 PMID- 11528296 DA - 20010830 DCOM- 20011204 LR - 20021101 IS - 0736-0258 VI - 18 IP - 3 DP - 2001 May TI - Understanding dynamic state changes in temporal lobe epilepsy. PG - 246-58 AB - The authors review their work in applying nonlinear dynamics to predict onset of seizures in patients with medically refractory temporal lobe epilepsy. The underlying mathematical methodology is presented in some detail. To illustrate their approach, they present an extensive discussion of the analysis of preictal data from two seizures of one patient, and from one disease-free subject. They find similar behavior in some nonlinear measures across seizures, which suggests the possibility of forming a robust method of seizure prediction. However, despite clinical and electrographic preictal and ictal similarity, they have also found marked heterogeneity in other nonlinear measures of preictal activity across seizures arising out of stage 2 nonrapid eye movement sleep. The underlying basis for this variation remains uncertain and needs to be the subject of further intense study to gain a better understanding of the dynamic basis of epilepsy. The origin of these heterogeneities may or may not be related to the much larger differences in nonlinear measures between patients and disease-free subjects. To understand these differences, the authors think it is crucial to pay close attention to potentially confounding factors such as behavioral and other state changes, and to study and report in detail the ways in which relevant nonlinear measures behave in the presence of such changes, independent of seizure onset. AD - Physics Department, Center for Theoretical Physics, Center for the Study of Complex Systems, University of Michigan, Ann Arbor 48109, USA. FAU - Savit, R AU - Savit R FAU - Li, D AU - Li D FAU - Zhou And, W AU - Zhou And W FAU - Drury, I AU - Drury I LA - eng ID - RO1 NS36803/NS/NINDS PT - Journal Article CY - United States TA - J Clin Neurophysiol JID - 8506708 SB - IM MH - Adolescent MH - Adult MH - *Electroencephalography MH - Epilepsies, Partial/diagnosis/physiopathology/surgery MH - Epilepsy, Temporal Lobe/diagnosis/*physiopathology/surgery MH - Evoked Potentials/physiology MH - Female MH - Human MH - Male MH - Middle Age MH - Models, Theoretical MH - Monitoring, Physiologic MH - Neurons/physiology MH - *Nonlinear Dynamics MH - Reference Values MH - Signal Processing, Computer-Assisted MH - Sleep Stages/physiology MH - Support, U.S. Gov't, P.H.S. MH - Temporal Lobe/physiopathology/surgery EDAT- 2001/08/31 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Clin Neurophysiol 2001 May;18(3):246-58. 490: Protopopescu VA, et al. Epileptic event forewarning f...[PMID:11528295]Related Articles, Books, LinkOut UI - 21419429 PMID- 11528295 DA - 20010830 DCOM- 20011204 LR - 20021101 IS - 0736-0258 VI - 18 IP - 3 DP - 2001 May TI - Epileptic event forewarning from scalp EEG. PG - 223-45 AB - The authors present a model-independent approach to quantify changes in the dynamics underlying nonlinear time-serial data. From time-windowed datasets, the authors construct discrete distribution functions on the phase space. Condition change between base case and test case distribution functions is assessed by dissimilarity measures via L1 distance and chi2 statistic. The discriminating power of these measures is first tested on noiseless data from the Lorenz and Bondarenko models, and is then applied to detecting dynamic change in multichannel clinical scalp EEG data. The authors compare the dissimilarity measures with the traditional nonlinear measures used in the analysis of chaotic systems. They also assess the potential usefulness of the new measures for robust, accurate, and timely forewarning of epileptic events. AD - Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6355, USA. FAU - Protopopescu, V A AU - Protopopescu VA FAU - Hively And, L M AU - Hively And LM FAU - Gailey, P C AU - Gailey PC LA - eng PT - Journal Article CY - United States TA - J Clin Neurophysiol JID - 8506708 SB - IM MH - Adolescent MH - Adult MH - Artifacts MH - Cerebral Cortex/physiopathology MH - Child MH - Child, Preschool MH - *Electroencephalography MH - Epilepsies, Partial/diagnosis/physiopathology MH - Epilepsy/*diagnosis/physiopathology MH - Epilepsy, Generalized/diagnosis/physiopathology MH - Epilepsy, Temporal Lobe/diagnosis/physiopathology MH - Evoked Potentials/physiology MH - Female MH - Human MH - Male MH - Middle Age MH - *Nonlinear Dynamics MH - Sensitivity and Specificity MH - Signal Processing, Computer-Assisted MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2001/08/31 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Clin Neurophysiol 2001 May;18(3):223-45. 491: Lehnertz K, et al. Nonlinear EEG analysis in epi...[PMID:11528294]Related Articles, Books, LinkOut UI - 21419428 PMID- 11528294 DA - 20010830 DCOM- 20011204 IS - 0736-0258 VI - 18 IP - 3 DP - 2001 May TI - Nonlinear EEG analysis in epilepsy: its possible use for interictal focus localization, seizure anticipation, and prevention. PG - 209-22 AB - Several recent studies emphasize the high value of nonlinear EEG analysis particularly for improved characterization of epileptic brain states. In this review the authors report their work to increase insight into the spatial and temporal dynamics of the epileptogenic process. Specifically, they discuss possibilities for seizure anticipation, which is one of the most challenging aspects of epileptology. Although there are numerous studies exploring basic neuronal mechanisms that are likely to be associated with seizures, to date no definite information is available regarding how, when, or why a seizure occurs. Nonlinear EEG analysis now provides strong evidence that the interictal-ictal state transition is not an abrupt phenomenon. Rather, findings indicate that it is indeed possible to detect a preseizure phase. The unequivocal definition of such a state with a sufficient length would enable investigations of basic mechanisms leading to seizure initiation in humans, and development of adequate seizure prevention strategies. AD - Department of Epileptology and Institute for Radiation and Nuclear Physics, University of Bonn, Germany. FAU - Lehnertz, K AU - Lehnertz K FAU - Andrzejak, R G AU - Andrzejak RG FAU - Arnhold, J AU - Arnhold J FAU - Kreuz, T AU - Kreuz T FAU - Mormann, F AU - Mormann F FAU - Rieke, C AU - Rieke C FAU - Widman And, G AU - Widman And G FAU - Elger, C E AU - Elger CE LA - eng PT - Journal Article CY - United States TA - J Clin Neurophysiol JID - 8506708 SB - IM MH - Animal MH - Cerebral Cortex/physiopathology MH - *Electroencephalography MH - Epilepsies, Partial/*diagnosis/physiopathology MH - Human MH - Neurons/physiology MH - *Nonlinear Dynamics MH - Sensitivity and Specificity MH - Signal Processing, Computer-Assisted MH - Support, Non-U.S. Gov't EDAT- 2001/08/31 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Clin Neurophysiol 2001 May;18(3):209-22. 492: Le Van Quyen M, et al. Characterizing neurodynamic c...[PMID:11528293]Related Articles, Books, LinkOut UI - 21419424 PMID- 11528293 DA - 20010830 DCOM- 20011204 IS - 0736-0258 VI - 18 IP - 3 DP - 2001 May TI - Characterizing neurodynamic changes before seizures. PG - 191-208 AB - The study of dynamic changes in neural activity preceding epileptic seizure allows the characterization of a preictal state several minutes before seizure onset. This opens up new perspectives for studying the mechanisms of epileptogenesis as well as for possible therapeutic interventions, which represent a major breakthrough. In this review the authors present and discuss the results from their group in this domain using nonlinear analysis of brain signals, as well as the limitations of this topic and current questions. AD - LENA (laboratoire de Neurosciences Cognitives et Imagerie Cerebrale), CNRS UPR 640, Paris, France. FAU - Le Van Quyen, M AU - Le Van Quyen M FAU - Martinerie, J AU - Martinerie J FAU - Navarro, V AU - Navarro V FAU - Baulac And, M AU - Baulac And M FAU - Varela, F J AU - Varela FJ LA - eng PT - Journal Article PT - Review PT - Review, Tutorial CY - United States TA - J Clin Neurophysiol JID - 8506708 SB - IM MH - Animal MH - Cerebral Cortex/physiopathology MH - *Cortical Synchronization MH - *Electroencephalography MH - Epilepsy/diagnosis/*physiopathology MH - Evoked Potentials/physiology MH - Human MH - Neurons/physiology MH - Nonlinear Dynamics MH - Recruitment (Neurology)/physiology MH - Synaptic Transmission/*physiology RF - 90 EDAT- 2001/08/31 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Clin Neurophysiol 2001 May;18(3):191-208. 493: Mandelblat Y, et al. Period doubling of calcium sp...[PMID:11524577]Related Articles, Books, LinkOut UI - 21415682 PMID- 11524577 DA - 20010828 DCOM- 20011204 IS - 0929-5313 VI - 11 IP - 1 DP - 2001 Jul-Aug TI - Period doubling of calcium spike firing in a model of a Purkinje cell dendrite. PG - 43-62 AB - Recordings from cerebellar Purkinje cell dendrites have revealed that in response to sustained current injection, the cell firing pattern can move from tonic firing of Ca(2+) spikes to doublet firing and even to quadruplet firing or more complex firing. These firing patterns are not modified substantially if Na(+) currents are blocked. We show that the experimental results can be viewed as a slow transition of the neuronal dynamics through a period-doubling bifurcation. To further support this conclusion and to understand the underlying mechanism that leads to doublet firing, we develop and study a simple, one-compartment model of Purkinje cell dendrite. The neuron can also exhibit quadruplet and chaotic firing patterns that are similar to the firing patterns that some of the Purkinje cells exhibit experimentally. The effects of parameters such as temperature, applied current, and potassium reversal potential in the model resemble their effects in experiments. The model dynamics involve three time scales. Ca(2+)- dependent K(+) currents, with intermediate time scales, are responsible for the appearance of doublet firing, whereas a very slow hyperpolarizing current transfers the neuron from tonic to doublet firing. We use the fast-slow analysis to separate the effects of the three time scales. Fast-slow analysis of the neuronal dynamics, with the activation variable of the very slow, hyperpolarizing current considered as a parameter, reveals that the transitions occurs via a cascade of period-doubling bifurcations of the fast and intermediate subsystem as this slow variable increases. We carry out another analysis, with the Ca(2+) concentration considered as a parameter, to investigate the conditions for the generation of doublet firing in systems with one effective variable with intermediate time scale, in which the rest state of the fast subsystem is terminated by a saddle-node bifurcation. We find that the scenario of period doubling in these systems can occur only if (1) the time scale of the intermediate variable (here, the decay rate of the calcium concentration) is slow enough in comparison with the interspike interval of the tonic firing at the transition but is not too slow and (2) there is a biostability of the fast subsystem of the spike-generating variables. AD - Department of Physiology and Zlotowski Center for Neuroscience, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel. FAU - Mandelblat, Y AU - Mandelblat Y FAU - Etzion, Y AU - Etzion Y FAU - Grossman, Y AU - Grossman Y FAU - Golomb, D AU - Golomb D LA - eng PT - Journal Article CY - United States TA - J Comput Neurosci JID - 9439510 RN - 0 (Calcium Channels) RN - 0 (Chelating Agents) RN - 4368-28-9 (Tetrodotoxin) RN - 67-42-5 (Egtazic Acid) RN - 7440-70-2 (Calcium) RN - 85233-19-8 (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid) SB - IM MH - Action Potentials/drug effects/*physiology MH - Animal MH - Biological Clocks/drug effects/physiology MH - Calcium/metabolism MH - Calcium Channels/drug effects/metabolism MH - Calcium Signaling/drug effects/*physiology MH - Cell Compartmentation/*physiology MH - Chelating Agents/pharmacology MH - Dendrites/drug effects/*metabolism/ultrastructure MH - Egtazic Acid/*analogs & derivatives/pharmacology MH - Guinea Pigs MH - Male MH - Models, Neurological MH - Nonlinear Dynamics MH - Organ Culture MH - Periodicity MH - Purkinje Cells/cytology/drug effects/*metabolism MH - Support, Non-U.S. Gov't MH - Synaptic Transmission/drug effects/physiology MH - Temperature MH - Tetrodotoxin/pharmacology EDAT- 2001/08/29 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Comput Neurosci 2001 Jul-Aug;11(1):43-62. 494: Hahn PJ, et al. Bistability dynamics in simul...[PMID:11524575]Related Articles, Books, LinkOut UI - 21415680 PMID- 11524575 DA - 20010828 DCOM- 20011204 IS - 0929-5313 VI - 11 IP - 1 DP - 2001 Jul-Aug TI - Bistability dynamics in simulations of neural activity in high-extracellular-potassium conditions. PG - 5-18 AB - Modulation of extracellular potassium concentration ([K](o)) has a profound impact on the excitability of neurons and neuronal networks. In the CA3 region of the rat hippocampus synchronized epileptiform bursts occur in conditions of increased [K](o). The dynamic nature of spontaneous neuronal firing in high [K](o) is therefore of interest. One particular interest is the potential presence of bistable behaviors such as the coexistence of stable repetitive firing and fixed rest potential states generated in individual cells by the elevation of [K](o). The dynamics of repetitive activity generated by increased [K](o) is investigated in a 19-compartment hippocampal pyramidal cell (HPC) model and a related two-compartment reduced HPC model. Results are compared with those for the Hodgkin-Huxley equations in similar conditions. For neural models, [K](o) changes are simulated as a shift in the potassium reversal potential (E(K)). Using phase resetting and bifurcation analysis techniques, all three models are shown to have specific regions of E(K) that result in bistability. For activity in bistable parameter regions, stimulus parameters are identified that switch high-potassium model behavior from repetitive firing to a quiescent state. Bistability in the HPC models is limited to a very small parameter region. Consequently, our results suggest that it is likely some HPCs in networks exposed to high [K](o) continue to burst such that a stable, quiescent network state does not exist. In [K](o) ranges where HPCs are not bistable, the population may still exhibit bistable behaviors where synchronous population events are reversibly annihilated by phase resetting pulses, suggesting the existence of a nonsynchronous network attractor. AD - Department of Neuroscience, Neural Engineering Center, Case Western Reserve University, Cleveland, OH 44106, USA. pjh4@po.cwru.edu FAU - Hahn, P J AU - Hahn PJ FAU - Durand, D M AU - Durand DM LA - eng PT - Journal Article CY - United States TA - J Comput Neurosci JID - 9439510 RN - 7440-09-7 (Potassium) SB - IM MH - Action Potentials/*physiology MH - Animal MH - Biological Clocks/physiology MH - Cell Compartmentation/physiology MH - Cell Membrane/metabolism MH - Dendrites/metabolism MH - Epilepsy/metabolism/physiopathology MH - Extracellular Space/*metabolism MH - Hippocampus/*metabolism MH - Models, Neurological MH - Nerve Net/metabolism MH - Nonlinear Dynamics MH - Potassium/*metabolism MH - Pyramidal Cells/*metabolism MH - Rats MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, Non-P.H.S. EDAT- 2001/08/29 10:00 MHDA- 2002/01/05 10:01 PST - ppublish SO - J Comput Neurosci 2001 Jul-Aug;11(1):5-18. 495: Inouye M. Predicting outcomes of patien...[PMID:11523966]Related Articles, Books, LinkOut UI - 21414818 PMID- 11523966 DA - 20010828 DCOM- 20010906 IS - 0894-9115 VI - 80 IP - 9 DP - 2001 Sep TI - Predicting outcomes of patients in Japan after first acute stroke using a simple model. PG - 645-9 AB - OBJECTIVE: Prediction of patient outcome can be useful as an aid to clinical decision making. Many studies, including my own, have constructed predictive multivariate models for outcome following stroke rehabilitation therapy, but these have often required several minutes work with a pocket calculator. The aim is to develop a simple, easy-to-use model that has strong predictive power. METHODS: Four hundred sixty-four consecutive patients with first stroke who were admitted to a rehabilitation hospital during a period of 19 mo were enrolled in the study. Sex, age, the stroke type, Functional Independence Measure total score on admission (X), onset to admission interval (number of days from stroke onset to rehabilitation admission), and length of rehabilitation hospital stay (number of days from hospital admission to discharge) were the independent variables. Functional Independence Measure total score at discharge (Y) was the dependent variable. RESULTS: Stepwise multiple regression analysis resulted in the model containing age (P < 0.0001), X (P < 0.0001), and onset to admission interval (P < 0.0001). The equation was: Y = 68.6 - 0.32 (age) + 0.80X - 0.13 (onset to admission interval), a multiple correlation coefficient (R) = 0.82, and a multiple correlation coefficient squared (R2) = 0.68. Simple regression analysis revealed the relation between Xand Y: Y = 0.85X + 37.36, and R = 0.80 R2 = 0.64. In fact, plots of X vs. Ywere nonlinear, but seemed to be able to be linearized by some form of equation. It was found that there is a linear relation between logX and Y. The equation is Y = 106.88x - 95.35, where x = logX, R = 0.84, and R2 = 0.70. The correlation is improved by a regression analysis of a natural logarithmic transformation of X (R = 0.84 vs. R = 0.82). CONCLUSION: The results in this study confirm that the simple regression model using a logarithmic transformation of X (R = 0.84) has predictive power over the simple regression model (R = 0.80). This model is well validated and clinically useful. AD - Department of Internal Medicine, Hyogo Rehabilitation Center Hospital, Kobe, Japan. FAU - Inouye, M AU - Inouye M LA - eng PT - Journal Article PT - Validation Studies CY - United States TA - Am J Phys Med Rehabil JID - 8803677 SB - AIM SB - IM MH - *Activities of Daily Living MH - Acute Disease MH - Aged MH - Analysis of Variance MH - Cerebral Hemorrhage/complications MH - Cerebral Infarction/complications MH - Cerebrovascular Accident/etiology/physiopathology/psychology/*rehabilitation MH - Female MH - Human MH - Japan MH - Length of Stay/statistics & numerical data MH - *Linear Models MH - Male MH - Middle Age MH - *Nonlinear Dynamics MH - Predictive Value of Tests MH - Prognosis MH - *Regression Analysis MH - Rehabilitation Centers MH - *Severity of Illness Index MH - Subarachnoid Hemorrhage/complications EDAT- 2001/08/29 10:00 MHDA- 2001/09/08 10:01 PST - ppublish SO - Am J Phys Med Rehabil 2001 Sep;80(9):645-9. 496: Derleth RP, et al. Modeling temporal and compres...[PMID:11520641]Related Articles, Books, LinkOut UI - 21411811 PMID- 11520641 DA - 20010824 DCOM- 20011207 IS - 0378-5955 VI - 159 IP - 1-2 DP - 2001 Sep TI - Modeling temporal and compressive properties of the normal and impaired auditory system. PG - 132-49 AB - Three modifications of a psychoacoustically and physiologically motivated processing model [Dau et al., J. Acoust. Soc. Am. 102 (1997a) 2892-2905] are presented and tested. The modifications aim at simulating sensorineural hearing loss and incorporate a level-dependent peripheral compression whose properties are affected by hearing impairment. Model 1 realizes this difference by introducing for impaired listeners an instantaneous level-dependent expansion prior to the adaptation stage of the model. Model 2 and Model 3 realize a level-dependent compression with time constants of 5 and 15 ms, respectively, for normal hearing and a reduced compression for impaired hearing. In Model 2, the compression occurs after the envelope extraction stage, while in Model 3, envelope extraction follows compression. All models account to a similar extent for the recruitment phenomenon measured with narrow-band stimuli and for forward-masking data of normal-hearing and hearing-impaired subjects using a 20-ms, 2-kHz tone signal and a 1-kHz-wide bandpass noise masker centered at 2 kHz. A clear difference between the different models occurs for the processing of temporally fluctuating stimuli. A modulation-rate-independent increase in modulation-response level for simulating impaired hearing is only predicted by Model 1 while the other two models realize a modulation-rate-dependent increase. Hence, the predictions of Model 2 and Model 3 are in conflict with the results of modulation-matching experiments reported in the literature. It is concluded that key properties of sensorineural hearing loss (altered loudness perception, reduced dynamic range, normal temporal properties but prolonged forward-masking effects) can effectively be modeled by incorporating a fast-acting expansion within the current processing model prior to the nonlinear adaptation stage. Based on these findings, a model of both normal and impaired hearing is proposed which incorporates a fast-acting compressive nonlinearity, representing the cochlear nonlinearity (which is reduced in impaired listeners), followed by an instantaneous expansion and the nonlinear adaptation stage which represent aspects of the retro-cochlear information processing in the auditory system. AD - Graduiertenkolleg Psychoakustik, Medizinische Physik, Carl von Ossietzky Universitat Oldenburg, D-26111 Oldenburg, Germany. FAU - Derleth, R P AU - Derleth RP FAU - Dau, T AU - Dau T FAU - Kollmeier, B AU - Kollmeier B LA - eng PT - Journal Article CY - Netherlands TA - Hear Res JID - 7900445 SB - IM MH - Auditory Pathways/physiology MH - Auditory Perception/*physiology MH - Auditory Threshold/physiology MH - Cochlea/physiology MH - Hearing/*physiology MH - Hearing Loss, Sensorineural/*physiopathology MH - Human MH - Loudness Perception/physiology MH - *Models, Biological MH - Nonlinear Dynamics MH - Perceptual Masking/physiology MH - Psychoacoustics MH - Support, Non-U.S. Gov't EDAT- 2001/08/25 10:00 MHDA- 2002/01/05 10:01 AID - S0378595501003227 [pii] PST - ppublish SO - Hear Res 2001 Sep;159(1-2):132-49. 497: Bresler T, et al. The dynamics of SAP90/PSD-95 ...[PMID:11520177]Related Articles, Books, LinkOut UI - 21412256 PMID- 11520177 DA - 20010824 DCOM- 20011204 IS - 1044-7431 VI - 18 IP - 2 DP - 2001 Aug TI - The dynamics of SAP90/PSD-95 recruitment to new synaptic junctions. PG - 149-67 AB - SAP90/PSD-95 is thought to be a central organizer of the glutamatergic synapse postsynaptic reception apparatus. To assess its potential role during glutamatergic synapse formation, we used GFP-tagged SAP90/PSD-95, time lapse confocal microscopy, and cultured hippocampal neurons to determine its dynamic recruitment into new synaptic junctions. We report that new SAP90/PSD-95 clusters first appeared at new axodendritic contact sites within 20-60 min of contact establishment. SAP90/PSD-95 clustering was rapid, with kinetics that fit a single exponential with a mean time constant of approximately 23 min. Most new SAP90/PSD-95 clusters were found juxtaposed to functional presynaptic boutons as determined by labeling with FM 4-64. No evidence was found for the existence of discrete transport particles similar to those previously reported to mediate presynaptic active zone cytoskeleton assembly. Instead, we found that SAP90/PSD-95 is recruited to nascent synapses from a diffuse dendritic cytoplasmic pool. Our findings show that SAP90/PSD-95 is recruited to nascent synaptic junctions early during the assembly process and indicate that its assimilation is fundamentally different from that of presynaptic active zone components. CI - Copyright 2001 Academic Press. AD - Rappaport Institute, Technion, Haifa, Israel. FAU - Bresler, T AU - Bresler T FAU - Ramati, Y AU - Ramati Y FAU - Zamorano, P L AU - Zamorano PL FAU - Zhai, R AU - Zhai R FAU - Garner, C C AU - Garner CC FAU - Ziv, N E AU - Ziv NE LA - eng ID - PO1 AG06569/AG/NIA ID - RO1 NS39471/NS/NINDS PT - Journal Article CY - United States TA - Mol Cell Neurosci JID - 9100095 RN - 0 (Indicators and Reagents) RN - 0 (Luminescent Proteins) RN - 0 (Nerve Tissue Proteins) RN - 0 (synapse-associated protein 90) RN - 147336-22-9 (green fluorescent protein) RN - 56-86-0 (Glutamic Acid) SB - IM MH - Animal MH - Animals, Newborn MH - Cell Communication/*physiology MH - Cell Differentiation/*physiology MH - Cytosol/metabolism/ultrastructure MH - Dendrites/metabolism/ultrastructure MH - Glutamic Acid/metabolism MH - Hippocampus/cytology/*growth & development/metabolism MH - Immunohistochemistry MH - Indicators and Reagents/pharmacokinetics MH - Intracellular Membranes/metabolism/ultrastructure MH - Kinetics MH - Luminescent Proteins/pharmacokinetics MH - Microscopy, Confocal MH - Nerve Tissue Proteins/*metabolism MH - Neurons/cytology/*metabolism MH - Nonlinear Dynamics MH - Presynaptic Terminals/metabolism/ultrastructure MH - Protein Transport/*physiology MH - Rats MH - Rats, Sprague-Dawley MH - Support, Non-U.S. Gov't MH - Support, U.S. Gov't, P.H.S. MH - Synapses/*metabolism/ultrastructure MH - Time Factors MH - Transport Vesicles/metabolism/ultrastructure EDAT- 2001/08/25 10:00 MHDA- 2002/01/05 10:01 AID - 10.1006/mcne.2001.1012 [doi] AID - S1044743101910127 [pii] PST - ppublish SO - Mol Cell Neurosci 2001 Aug;18(2):149-67. 498: Lee YJ, et al. Detection of non-linearity in...[PMID:11516741]Related Articles, Books, LinkOut UI - 21407702 PMID- 11516741 DA - 20010822 DCOM- 20010906 IS - 1388-2457 VI - 112 IP - 7 DP - 2001 Jul TI - Detection of non-linearity in the EEG of schizophrenic patients. PG - 1288-94 AB - OBJECTIVE: The aim of this study is to detect non-linearity in the EEG of schizophrenia with a modified method of surrogate data. We also want to identify if dimension complexity (correlation dimension using spatial embedding) could be used as a discriminating statistic to demonstrate non-linearity in the EEG. The difference between the attractor dimension of healthy subjects and schizophrenic subjects is expected to be interpreted as reflecting some mechanisms underlying brain wave by views of non-linear dynamics analysis may reflect mechanistic differences. METHODS: EEGs were recorded with 14 electrodes in 18 healthy male subjects (average age: 26.3; range: 20--35) and 18 male schizophrenic patients (average age: 30.6; range: 24--40) during a resting eye-closed state. Neither of two groups was taking medicines. All artificial epochs in the EEG records were rejected by an experienced doctor's visual inspection. RESULTS: Testing non-linearity with modified surrogate data, we showed that correlation dimension of EEG data of schizophrenia does refuse the null hypothesis that the data were resulted from a linear dynamic system. A decrease of dimension complexity was found in the EEG of schizophrenia compared with controls. We interpreted it as the result of the psychopath's dysfunction overall brain. The surrogating procedure results in a significant increase in D(s). CONCLUSIONS: Non-linearity of the EEG in schizophrenia was proven in our study. We think the correlation dimension with spatial embedding as a good discriminating statistic for testing such non-linearity. Moreover, schizophrenic patients' EEGs were compared with controls and a lower dimension complexity was found. The results of our study indicate the possibility of using the methods of non-linear time series analysis to identify the EEGs of schizophrenic patients. AD - Department of Biomedical Engineering, Shanghai Jiaotong University, Shanghai 200030, China. FAU - Lee, Y J AU - Lee YJ FAU - Zhu, Y S AU - Zhu YS FAU - Xu, Y H AU - Xu YH FAU - Shen, M F AU - Shen MF FAU - Zhang, H X AU - Zhang HX FAU - Thakor, N V AU - Thakor NV LA - eng PT - Clinical Trial PT - Journal Article CY - Netherlands TA - Clin Neurophysiol JID - 100883319 SB - IM MH - Adult MH - Algorithms MH - Analysis of Variance MH - *Electroencephalography MH - Human MH - Male MH - Nonlinear Dynamics MH - Pilot Projects MH - Schizophrenia/*physiopathology MH - Support, Non-U.S. Gov't EDAT- 2001/08/23 10:00 MHDA- 2001/09/08 10:01 AID - S1388245701005442 [pii] PST - ppublish SO - Clin Neurophysiol 2001 Jul;112(7):1288-94. 499: Wendling F, et al. Interpretation of interdepend...[PMID:11516732]Related Articles, Books, LinkOut UI - 21407693 PMID- 11516732 DA - 20010822 DCOM- 20010906 IS - 1388-2457 VI - 112 IP - 7 DP - 2001 Jul TI - Interpretation of interdependencies in epileptic signals using a macroscopic physiological model of the EEG. PG - 1201-18 AB - This paper presents a neurophysiologically relevant model in which vectorial epileptiform electroencephalographic (EEG) signals are produced from multiple coupled neural populations. This model is used to evaluate the performances of non-linear regression analysis as a method to characterize couplings between neural populations from EEG signals they produce. Two quantities, estimated on generated signals, namely the non-linear correlation coefficient and the direction index, are related to the degree and direction of coupling parameters of the model. Their statistical behavior is first studied on a set of signals simulated for relevant configurations of the model. They are then measured on real stereoelectroencephalographic (SEEG) signals. Results obtained in three patients suffering from temporal lobe epilepsy (TLE) show that abnormal functional couplings between cerebral structures, that establish during seizures, can be interpreted in terms of causality. Perspectives are oriented to the identification of epileptogenic networks in TLE. AD - Laboratoire Traitement du Signal et de L'Image - INSERM, Universite de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France. fabrice.wendling@univ-rennes1.fr FAU - Wendling, F AU - Wendling F FAU - Bartolomei, F AU - Bartolomei F FAU - Bellanger, J J AU - Bellanger JJ FAU - Chauvel, P AU - Chauvel P LA - eng PT - Clinical Trial PT - Journal Article CY - Netherlands TA - Clin Neurophysiol JID - 100883319 SB - IM MH - Algorithms MH - Brain/physiopathology MH - Computer Simulation MH - Electroencephalography/*methods/statistics & numerical data MH - Epilepsy, Temporal Lobe/*physiopathology MH - Human MH - Models, Neurological MH - Neurons/physiology MH - Nonlinear Dynamics MH - Signal Processing, Computer-Assisted EDAT- 2001/08/23 10:00 MHDA- 2001/09/08 10:01 AID - S1388245701005478 [pii] PST - ppublish SO - Clin Neurophysiol 2001 Jul;112(7):1201-18. 500: Palanchon P, et al. New technique for emboli dete...[PMID:11516540]Related Articles, Books, LinkOut UI - 21408675 PMID- 11516540 DA - 20010822 DCOM- 20010927 IS - 0301-5629 VI - 27 IP - 6 DP - 2001 Jun TI - New technique for emboli detection and discrimination based on nonlinear characteristics of gas bubbles. PG - 801-8 AB - Detection and characterization of emboli in the blood stream is of high clinical importance for making decisions after surgery. In this study, a new technique based on the nonlinear oscillations of gas bubbles was applied to gaseous emboli detection, characterization and sizing. To simulate gaseous emboli, an experimental system was developed to produce air bubbles of uniform diameters ranging from 19 microm up to 200 microm. The ultrasonic setup consisted of low-frequency transducers operating at 130 kHz and 250 kHz and using low acoustic pressures (30 kPa and 55 kPa). The experimental and theoretical results show that, depending on the transmitted frequency and the bubble sizes, higher harmonic components were produced in the frequency spectrum of the backscattered echo. Nonresonating bubbles scatter either linearly when their sizes are far away from the resonance size or nonlinearly at the second or third harmonic frequency when their sizes are getting close to the resonance size. Only resonant bubbles or bubbles very close to the resonance size are able to scatter at higher harmonic frequencies (fourth and fifth). This property is used to discriminate resonating bubbles from other bubble sizes. The appearance of harmonic component in the frequency spectrum seems to be an unambiguous tool to differentiate gaseous emboli from solid emboli that scatter linearly. AD - Department of Cardiology, Thoraxcentre, Erasmus Medical Centre Rotterdam, Rotterdam, The Netherlands. palanchon@tch.fgg.eur.nl FAU - Palanchon, P AU - Palanchon P FAU - Bouakaz, A AU - Bouakaz A FAU - van Blankenstein, J H AU - van Blankenstein JH FAU - Klein, J AU - Klein J FAU - Bom, N AU - Bom N FAU - de Jong, N AU - de Jong N LA - eng PT - Journal Article CY - England TA - Ultrasound Med Biol JID - 0410553 SB - IM MH - Acoustics MH - Embolism, Air/*ultrasonography MH - Microspheres MH - Models, Theoretical MH - Nonlinear Dynamics MH - Phantoms, Imaging MH - Transducers MH - Ultrasonics EDAT- 2001/08/23 10:00 MHDA- 2001/09/28 10:01 AID - S0301562901003842 [pii] PST - ppublish SO - Ultrasound Med Biol 2001 Jun;27(6):801-8. 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