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1: Surzhikov VD, et al. [III All-Russia Symposium on ...[PMID:12428624]Related Articles, Links

UI - 22314398PMID- 12428624DA - 20021112DCOM- 20021113IS - 0131-1646VI - 28IP - 4DP - 2002 Jul-AugTI - [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 - 134-7FAU - Surzhikov, V DAU - Surzhikov VDFAU - Fleishman, A NAU - Fleishman ANLA - rusPT - CongressesTT - 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 - RussiaTA - Fiziol ChelovekaJID - 7603567SB - IMMH - AnimalMH - HumanMH - *MedicineMH - Nonlinear DynamicsMH - *PhysiologyEDAT- 2002/11/14 04:00MHDA- 2002/11/26 04:00PST - ppublishSO - Fiziol Cheloveka 2002 Jul-Aug;28(4):134-7.

2: Davis PJ, et al. In vitro remifentanil metabol...[PMID:12401616]Related Articles, Links

UI - 22288635PMID- 12401616DA - 20021028DCOM- 20021119IS - 0003-2999VI - 95IP - 5DP - 2002 NovTI - In vitro remifentanil metabolism: the effects of whole blood constituents and plasma butyrylcholinesterase.PG - 1305-7, table of contentsAB - 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.eduFAU - Davis, Peter JAU - Davis PJFAU - Stiller, Richard LAU - Stiller RLFAU - Wilson, Annette SAU - Wilson ASFAU - McGowan, Francis XAU - McGowan FXFAU - Egan, Talmage DAU - Egan TDFAU - Muir, Keith TAU - Muir KTLA - engPT - Clinical TrialPT - Journal ArticleCY - United StatesTA - Anesth AnalgJID - 1310650RN - 0 (Anesthetics, Intravenous)RN - 0 (Piperidines)RN - 132875-61-7 (remifentanil)RN - EC 3.1.1.- (Butyrylcholinesterase)SB - AIMSB - IMMH - AdultMH - Anesthetics, Intravenous/blood/*metabolismMH - Butyrylcholinesterase/blood/deficiency/*metabolismMH - Erythrocytes/metabolismMH - Half-LifeMH - HumanMH - Nonlinear DynamicsMH - Piperidines/blood/*metabolismMH - Plasma/metabolismMH - Support, Non-U.S. Gov'tEDAT- 2002/10/29 04:00MHDA- 2002/11/26 04:00PST - ppublishSO - 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 - 22285369PMID- 12398473DA - 20021025DCOM- 20021107IS - 0001-4966VI - 112IP - 4DP - 2002 OctTI - Acoustical analysis and model-based sound synthesis of the kantele.PG - 1681-91AB - 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.fiFAU - Erkut, CumhurAU - Erkut CFAU - Karjalainen, MattiAU - Karjalainen MFAU - Huang, PattyAU - Huang PFAU - Valimaki, VesaAU - Valimaki VLA - engPT - Journal ArticleCY - United StatesTA - J Acoust Soc AmJID - 7503051SB - IMMH - Acoustic Stimulation/*instrumentationMH - *AcousticsMH - Equipment DesignMH - HumanMH - *MusicMH - *Nonlinear DynamicsMH - Support, Non-U.S. Gov'tEDAT- 2002/10/26 04:00MHDA- 2002/11/26 04:00PST - ppublishSO - 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 - 22285358PMID- 12398462DA - 20021025DCOM- 20021107IS - 0001-4966VI - 112IP - 4DP - 2002 OctTI - Modifications of a single saturating non-linearity account for post-onset changes in 2f1-f2 distortion product otoacoustic emission.PG - 1561-8AB - 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.ukFAU - Lukashkin, Andrei NAU - Lukashkin ANFAU - Russell, Ian JAU - Russell IJLA - engPT - Journal ArticleCY - United StatesTA - J Acoust Soc AmJID - 7503051SB - IMMH - AnimalMH - Cochlea/*physiologyMH - Guinea PigsMH - *Nonlinear DynamicsMH - Otoacoustic Emissions, Spontaneous/*physiologyMH - Support, Non-U.S. Gov'tEDAT- 2002/10/26 04:00MHDA- 2002/11/26 04:00PST - ppublishSO - 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 - 22285347PMID- 12398451DA - 20021025DCOM- 20021107IS - 0001-4966VI - 112IP - 4DP - 2002 OctTI - A nonlinear model of thermoacoustic devices.PG - 1431-44AB - 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, SergeyAU - Karpov SFAU - Prosperetti, AndreaAU - Prosperetti ALA - engPT - Journal ArticleCY - United StatesTA - J Acoust Soc AmJID - 7503051SB - IMMH - Acoustics/*instrumentationMH - *Nonlinear DynamicsMH - Support, U.S. Gov't, Non-P.H.S.MH - *Thermal ConductivityEDAT- 2002/10/26 04:00MHDA- 2002/11/26 04:00PST - ppublishSO - 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 - 22284485PMID- 12396567DA - 20021024DCOM- 20021126IS - 0899-7667VI - 14IP - 10DP - 2002 OctTI - Hebbian imprinting and retrieval in oscillatory neural networks.PG - 2371-96AB - 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.itFAU - Scarpetta, SilviaAU - Scarpetta SFAU - Zhaoping, LAU - Zhaoping LFAU - Hertz, JohnAU - Hertz JLA - engPT - Journal ArticleCY - United StatesTA - Neural ComputJID - 9426182SB - IMMH - Hippocampus/physiologyMH - *Imprinting (Psychology)MH - Mental Recall/physiologyMH - *Models, NeurologicalMH - *Neural Networks (Computer)MH - Neuronal Plasticity/physiologyMH - Nonlinear DynamicsMH - Olfactory Pathways/physiologyMH - *PeriodicityMH - Pyramidal Cells/physiologyMH - Synapses/physiologyEDAT- 2002/10/25 04:00MHDA- 2002/11/28 04:00AID - 10.1162/08997660260293265 [doi]PST - ppublishSO - Neural Comput 2002 Oct;14(10):2371-96.

7: Kurata Y, et al. Dynamical description of sino...[PMID:12384487]Related Articles, Links

UI - 22270903PMID- 12384487DA - 20021017DCOM- 20021122IS - 0363-6135VI - 283IP - 5DP - 2002 NovTI - Dynamical description of sinoatrial node pacemaking: improved mathematical model for primary pacemaker cell.PG - H2074-101AB - 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.jpFAU - Kurata, YasutakaAU - Kurata YFAU - Hisatome, IchiroAU - Hisatome IFAU - Imanishi, SunaoAU - Imanishi SFAU - Shibamoto, ToshishigeAU - Shibamoto TLA - engPT - Journal ArticleCY - United StatesTA - Am J Physiol Heart Circ PhysiolJID - 100901228RN - 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 - IMMH - 4-Aminopyridine/pharmacologyMH - AnimalMH - Biological Clocks/drug effects/*physiologyMH - Calcium/metabolismMH - Chelating Agents/pharmacologyMH - Computer SimulationMH - Egtazic Acid/*analogs & derivatives/pharmacologyMH - *Models, CardiovascularMH - Nonlinear DynamicsMH - Potassium/metabolismMH - Potassium Channel Blockers/pharmacologyMH - RabbitsMH - Sarcolemma/physiologyMH - Sinoatrial Node/drug effects/*physiologyMH - Support, Non-U.S. Gov'tEDAT- 2002/10/18 04:00MHDA- 2002/11/26 04:00AID - 10.1152/ajpheart.00900.2001 [doi]PST - ppublishSO - 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 - 22265940PMID- 12378128DA - 20021014DCOM- 20021125IS - 0302-282XVI - 46IP - 2DP - 2002TI - Effect of ethanol on human sleep EEG using correlation dimension analysis.PG - 104-10AB - 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, BaselAD - Center of Psychiatry and Neurology, Fukui Prefecture Hospital, Fukui, Japan. t-ko@mx1.fctv.ne.jpFAU - Kobayashi, ToshioAU - Kobayashi TFAU - Madokoro, ShigekiAU - Madokoro SFAU - Wada, YujiAU - Wada YFAU - Misaki, KiwamuAU - Misaki KFAU - Nakagawa, HirokiAU - Nakagawa HLA - engPT - Clinical TrialPT - Journal ArticleCY - SwitzerlandTA - NeuropsychobiologyJID - 7512895RN - 0 (Central Nervous System Depressants)RN - 64-17-5 (Ethanol)SB - IMMH - AdultMH - AlgorithmsMH - Central Nervous System Depressants/*pharmacologyMH - Data Interpretation, StatisticalMH - Electroencephalography/*drug effectsMH - Ethanol/*pharmacologyMH - HumanMH - MaleMH - Nonlinear DynamicsMH - Polysomnography/drug effectsMH - Sleep/*drug effectsMH - Sleep Stages/drug effectsMH - Sleep, REM/drug effectsEDAT- 2002/10/16 04:00MHDA- 2002/11/26 04:00AID - nps46104 [pii]PST - ppublishSO - Neuropsychobiology 2002;46(2):104-10.

9: Burton EJ, et al. Patterns of cerebral atrophy ...[PMID:12377138]Related Articles, Links

UI - 22265889PMID- 12377138DA - 20021014DCOM- 20021125IS - 1053-8119VI - 17IP - 2DP - 2002 OctTI - Patterns of cerebral atrophy in dementia with Lewy bodies using voxel-based morphometry.PG - 618-30AB - 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.ukFAU - Burton, E JAU - Burton EJFAU - Karas, GAU - Karas GFAU - Paling, S MAU - Paling SMFAU - Barber, RAU - Barber RFAU - Williams, E DAU - Williams EDFAU - Ballard, C GAU - Ballard CGFAU - McKeith, I GAU - McKeith IGFAU - Scheltens, PAU - Scheltens PFAU - Barkhof, FAU - Barkhof FFAU - O'Brien, J TAU - O'Brien JTLA - engPT - Clinical TrialPT - Journal ArticleCY - United StatesTA - NeuroimageJID - 9215515SB - IMMH - AgedMH - Alzheimer Disease/pathologyMH - AtrophyMH - Brain/*pathologyMH - Brain MappingMH - Cluster AnalysisMH - Comparative StudyMH - FemaleMH - Hippocampus/pathologyMH - HumanMH - Image Interpretation, Computer-Assisted/*methodsMH - Lewy Body Disease/*pathologyMH - Magnetic Resonance Imaging/*methodsMH - MaleMH - Middle AgeMH - Models, NeurologicalMH - Nonlinear DynamicsMH - Parahippocampal Gyrus/pathologyMH - Support, Non-U.S. Gov'tMH - Temporal Lobe/pathologyEDAT- 2002/10/16 04:00MHDA- 2002/11/26 04:00AID - S1053811902911973 [pii]PST - ppublishSO - Neuroimage 2002 Oct;17(2):618-30.

10: Modre R, et al. Noninvasive myocardial activa...[PMID:12374339]Related Articles, Links

UI - 22261211PMID- 12374339DA - 20021010DCOM- 20021113IS - 0018-9294VI - 49IP - 10DP - 2002 OctTI - Noninvasive myocardial activation time imaging: a novel inverse algorithm applied to clinical ECG mapping data.PG - 1153-61AB - 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.atFAU - Modre, RobertAU - Modre RFAU - Tilg, BernhardAU - Tilg BFAU - Fischer, GeraldAU - Fischer GFAU - Wach, PaulAU - Wach PLA - engPT - Journal ArticleCY - United StatesTA - IEEE Trans Biomed EngJID - 0012737SB - IMMH - Action PotentialsMH - AdultMH - *AlgorithmsMH - Atrial Fibrillation/diagnosis/physiopathologyMH - Body Surface Potential Mapping/*methodsMH - Comparative StudyMH - *Computer SimulationMH - FemaleMH - Heart/*physiopathologyMH - HumanMH - MaleMH - Membrane Potentials/*physiologyMH - Middle AgeMH - Models, CardiovascularMH - *Myocardial ContractionMH - Nonlinear DynamicsMH - Sensitivity and SpecificityMH - Tachycardia, Atrioventricular Nodal Reentry/diagnosis/physiopathologyMH - Time FactorsEDAT- 2002/10/11 04:00MHDA- 2002/11/26 04:00PST - ppublishSO - 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 - 22251843PMID- 12365788DA - 20021007DCOM- 20021113IS - 0954-4119VI - 216IP - 5DP - 2002TI - Patient-specific spine models. Part 1: Finite element analysis of the lumbar intervertebral disc--a material sensitivity study.PG - 299-314AB - 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 JAU - Fagan MJFAU - Julian, SAU - Julian SFAU - Siddall, D JAU - Siddall DJFAU - Mohsen, A MAU - Mohsen AMLA - engPT - Journal ArticleCY - EnglandTA - Proc Inst Mech Eng [H]JID - 8908934SB - IMMH - Compressive StrengthMH - *Computer SimulationMH - ElasticityMH - Finite Element AnalysisMH - HumanMH - Intervertebral Disk/*physiologyMH - Lumbar Vertebrae/*physiologyMH - *Models, BiologicalMH - *Nonlinear DynamicsMH - Reproducibility of ResultsMH - Sensitivity and SpecificityMH - Stress, MechanicalMH - TorsionMH - Weight-Bearing/physiologyEDAT- 2002/10/09 04:00MHDA- 2002/11/26 04:00PST - ppublishSO - 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 - 22245969PMID- 12359652DA - 20021002DCOM- 20021118IS - 1073-449XVI - 166IP - 7DP - 2002 Oct 1TI - Optimal high-frequency oscillatory ventilation settings by nonlinear lung mechanics analysis.PG - 950-3AB - 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.orgFAU - Habib, Robert HAU - Habib RHFAU - Pyon, Kee HAU - Pyon KHFAU - Courtney, Sherry EAU - Courtney SELA - engPT - Journal ArticleCY - United StatesTA - Am J Respir Crit Care MedJID - 9421642SB - AIMSB - IMMH - AnimalMH - Biological Clocks/*physiologyMH - Comparative StudyMH - *High-Frequency VentilationMH - Lung ComplianceMH - Lung Volume MeasurementsMH - Models, AnimalMH - Nonlinear DynamicsMH - Pulmonary Wedge Pressure/physiologyMH - Respiratory Mechanics/*physiologyMH - Support, Non-U.S. Gov'tMH - SwineMH - Time FactorsEDAT- 2002/10/03 04:00MHDA- 2002/11/26 04:00PST - ppublishSO - 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 - 22240240PMID- 12351754DA - 20020927DCOM- 20021028IS - 1095-9203VI - 297IP - 5590DP - 2002 Sep 27TI - Random perturbations and lattice effects in chaotic population dynamics.PG - 2163; discussion 2163AD - Cornell University, Department of Theoretical and Applied Mechanics, Ithaca, NY 14853-1503, USA.FAU - Domokos, GaborAU - Domokos GFAU - Scheuring, IstvanAU - Scheuring ILA - engPT - CommentPT - Journal ArticleCY - United StatesTA - ScienceJID - 0404511SB - IMCON - Science. 2001 Oct 19;294(5542):602-5. PMID: 11641500MH - AnimalMH - *EcosystemMH - EnvironmentMH - MathematicsMH - Models, TheoreticalMH - Nonlinear DynamicsMH - Population DensityMH - *Population DynamicsMH - Stochastic ProcessesEDAT- 2002/09/28 04:00MHDA- 2002/10/29 04:00AID - 10.1126/science.297.5590.2163a [doi]AID - 297/5590/2163a [pii]PST - ppublishSO - Science 2002 Sep 27;297(5590):2163; discussion 2163.

14: Carotenuto R, et al. A new extrapolation technique...[PMID:12322888]Related Articles, Links

UI - 22234695PMID- 12322888DA - 20020926DCOM- 20021106IS - 0885-3010VI - 49IP - 3DP - 2002 MarTI - A new extrapolation technique for resolution enhancement of pulse-echo imaging systems.PG - 374-82AB - 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 rAD - Dipartimento di Ingegneria Elettronica, Universita degli Studi Roma Tre, Italy. r.carotenuto@uniroma3.itFAU - Carotenuto, RiccardoAU - Carotenuto RFAU - Loi, GiovannaAU - Loi GFAU - Pappalardo, MassimoAU - Pappalardo MLA - engPT - Journal ArticleCY - United StatesTA - IEEE Trans Ultrason Ferroelectr Freq ControlJID - 9882735SB - IMMH - *AlgorithmsMH - Comparative StudyMH - *Computer SimulationMH - Cysts/ultrasonographyMH - Image Enhancement/instrumentation/*methodsMH - *Models, StatisticalMH - Nonlinear DynamicsMH - Sensitivity and SpecificityMH - Support, Non-U.S. Gov'tMH - Ultrasonography/instrumentation/*methodsEDAT- 2002/09/27 06:00MHDA- 2002/11/26 04:00PST - ppublishSO - 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 - 22227374PMID- 12241358DA - 20020920DCOM- 20021113IS - 1539-3755VI - 66IP - 1 Pt 1DP - 2002 JulTI - Osmotic pressure of charged colloidal suspensions: a unified approach to linearized Poisson-Boltzmann theory.PG - 011401AB - 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, MarkusAU - Deserno MFAU - von Grunberg, Hans-HennigAU - von Grunberg HHLA - engPT - Journal ArticleCY - United StatesTA - Phys Rev E Stat Nonlin Soft Matter PhysJID - 101136452RN - 0 (Colloids)RN - 0 (Electrolytes)RN - 0 (Macromolecular Systems)RN - 0 (Solutions)RN - 0 (Suspensions)RN - 9007-49-2 (DNA)SB - IMMH - BiophysicsMH - *ColloidsMH - Comparative StudyMH - DNA/chemistryMH - ElectrolytesMH - Linear ModelsMH - Macromolecular SystemsMH - *Models, ChemicalMH - Nonlinear DynamicsMH - Osmotic PressureMH - SolutionsMH - SuspensionsMH - ThermodynamicsEDAT- 2002/09/21 10:00MHDA- 2002/11/26 04:00PHST- 2002/Feb/01 [received]PHST- 2002/Jul/12 [aheadofprint]PST - ppublishSO - 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 - 22225576PMID- 12239890DA - 20020920DCOM- 20021001IS - 0140-525XVI - 24IP - 5DP - 2001 OctTI - Toward an interpretation of dynamic neural activity in terms of chaotic dynamical systems.PG - 793-810; discussion 810-48AB - 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.jpFAU - Tsuda, IAU - Tsuda ILA - engPT - Journal ArticlePT - ReviewPT - Review, AcademicCY - EnglandTA - Behav Brain SciJID - 7808666SB - IMMH - Brain/*physiologyMH - HumanMH - Memory/*physiologyMH - *Mental ProcessesMH - *Models, TheoreticalMH - Neurons/physiologyMH - *Nonlinear DynamicsMH - Support, Non-U.S. Gov'tRF - 402EDAT- 2002/09/21 10:00MHDA- 2002/10/03 04:00PST - ppublishSO - 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 - 22219679PMID- 12234825DA - 20020917DCOM- 20021017IS - 0363-6135VI - 283IP - 4DP - 2002 OctTI - Sexual dimorphism in the complexity of cardiac pacemaker activity.PG - H1695-702AB - 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.twFAU - Kuo, Terry B JAU - Kuo TBFAU - Yang, Cheryl C HAU - Yang CCLA - engPT - Journal ArticleCY - United StatesTA - Am J Physiol Heart Circ PhysiolJID - 100901228SB - IMMH - AdultMH - AgedMH - Biological Clocks/*physiologyMH - Comparative StudyMH - FemaleMH - Heart/innervation/*physiologyMH - Heart Rate/*physiologyMH - HumanMH - Linear ModelsMH - MaleMH - Middle AgeMH - Nonlinear DynamicsMH - Parasympathetic Nervous System/physiologyMH - *Sex CharacteristicsMH - Support, Non-U.S. Gov'tMH - Sympathetic Nervous System/physiologyEDAT- 2002/09/18 10:00MHDA- 2002/10/18 04:00PHST- 2002/Jun/21 [aheadofprint]AID - 10.1152/ajpheart.00169.2002 [doi]AID - 00169.2002 [pii]PST - ppublishSO - 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 - 22214743PMID- 12227632DA - 20020913DCOM- 20020930IS - 0140-0118VI - 40IP - 4DP - 2002 JulTI - Linear and non-linear methods for automatic seizure detection in scalp electro-encephalogram recordings.PG - 447-61AB - 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.ukFAU - McSharry, P EAU - McSharry PEFAU - He, TAU - He TFAU - Smith, L AAU - Smith LAFAU - Tarassenko, LAU - Tarassenko LLA - engPT - Journal ArticleCY - EnglandTA - Med Biol Eng ComputJID - 7704869SB - IMMH - *ElectroencephalographyMH - Epilepsy/*diagnosisMH - HumanMH - Linear ModelsMH - Nonlinear DynamicsMH - ScalpMH - *Signal Processing, Computer-AssistedMH - Support, Non-U.S. Gov'tEDAT- 2002/09/14 10:00MHDA- 2002/10/02 04:00PST - ppublishSO - Med Biol Eng Comput 2002 Jul;40(4):447-61.

19: Schifalacqua M. The power of fractals....[PMID:12226873]Related Articles, Links

UI - 22214853PMID- 12226873DA - 20020913DCOM- 20021009IS - 1532-8880VI - 17IP - 11DP - 2002 AugTI - The power of fractals.PG - 6AD - Aurora Health Care, Milwaukee, Wis., USA. marita.schifalacqua@aurora.orgFAU - Schifalacqua, MaritaAU - Schifalacqua MLA - engPT - Journal ArticleCY - United StatesTA - Patient Care ManagJID - 101083317SB - NMH - *Attitude of Health PersonnelMH - *Decision Making, OrganizationalMH - FractalsMH - HumanMH - LeadershipMH - Nonlinear DynamicsMH - Nurse Administrators/*organization & administration/*psychologyEDAT- 2002/09/14 10:00MHDA- 2002/10/10 04:00PST - ppublishSO - Patient Care Manag 2002 Aug;17(11):6.

20: [No authors listed] Quantum age: new rules for le...[PMID:12226871]Related Articles, Links

UI - 22214851PMID- 12226871DA - 20020913DCOM- 20021009IS - 1532-8880VI - 17IP - 11DP - 2002 AugTI - Quantum age: new rules for leaders.PG - 2-4LA - engPT - Journal ArticleCY - United StatesTA - Patient Care ManagJID - 101083317SB - NCIN - Patient Care Manag. 2002 Aug;17(11):5-6. PMID: 12226872MH - Attitude of Health PersonnelMH - Health Facility Administrators/*organization & administration/psychologyMH - HumanMH - *LeadershipMH - Nonlinear DynamicsMH - Outcome and Process Assessment (Health Care)/organization & administrationMH - Quantum TheoryMH - *Systems AnalysisMH - WorkEDAT- 2002/09/14 10:00MHDA- 2002/10/10 04:00PST - ppublishSO - Patient Care Manag 2002 Aug;17(11):2-4.

21: Kalagher J. How to turn change into oppor...[PMID:12226869]Related Articles, Links

UI - 22214850PMID- 12226869DA - 20020913DCOM- 20021009IS - 1532-8880VI - 17IP - 11DP - 2002 AugTI - How to turn change into opportunity for leadership.PG - 1, 7-8AD - jane@coachingresources.comFAU - Kalagher, JaneAU - Kalagher JLA - engPT - Journal ArticleCY - United StatesTA - Patient Care ManagJID - 101083317SB - NMH - Attitude of Health PersonnelMH - HumanMH - *LeadershipMH - Nonlinear DynamicsMH - Nurse Administrators/*organization & administration/psychologyMH - Nursing, Supervisory/*organization & administrationMH - Organizational InnovationEDAT- 2002/09/14 10:00MHDA- 2002/10/10 04:00PST - ppublishSO - 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 - 22212217PMID- 12224742DA - 20020912DCOM- 20021104IS - 0272-4332VI - 22IP - 4DP - 2002 AugTI - What to do at low doses: a bounding approach for economic analysis.PG - 679-88AB - 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.govFAU - Griffiths, Charles WAU - Griffiths CWFAU - Dockins, ChrisAU - Dockins CFAU - Owens, NicoleAU - Owens NFAU - Simon, Nathalie BAU - Simon NBFAU - Axelrad, Daniel AAU - Axelrad DALA - engPT - Journal ArticleCY - United StatesTA - Risk AnalJID - 8109978RN - 0 (Carcinogens)RN - 67-66-3 (Chloroform)SB - IMMH - Carcinogens/administration & dosage/toxicityMH - Chloroform/administration & dosage/toxicityMH - Cost-Benefit AnalysisMH - Dose-Response Relationship, DrugMH - *EnvironmentMH - GuidelinesMH - HumanMH - Linear ModelsMH - Nonlinear DynamicsMH - Risk Assessment/*economicsMH - United StatesMH - United States Environmental Protection AgencyEDAT- 2002/09/13 10:00MHDA- 2002/11/26 04:00PST - ppublishSO - Risk Anal 2002 Aug;22(4):679-88.

23: Rifkin SA, et al. Geometry of gene expression d...[PMID:12217909]Related Articles, Links

UI - 22205939PMID- 12217909DA - 20020909DCOM- 20021106IS - 1367-4803VI - 18IP - 9DP - 2002 SepTI - Geometry of gene expression dynamics.PG - 1176-83AB - 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.eduAD - Department of Ecology and Evolutionary Biology, PO Box 208106, Yale University, New Haven, CT 06520, USA.FAU - Rifkin, S AAU - Rifkin SAFAU - Kim, JAU - Kim JLA - engPT - Journal ArticleCY - EnglandTA - BioinformaticsJID - 9808944RN - 9007-49-2 (DNA)SB - IMMH - AlgorithmsMH - Cell Cycle/*geneticsMH - Comparative StudyMH - Computer GraphicsMH - DNA/chemistry/geneticsMH - Fourier AnalysisMH - Gene Expression/geneticsMH - Gene Expression Regulation/*geneticsMH - *Genome, BacterialMH - *Models, GeneticMH - Models, StatisticalMH - Nonlinear DynamicsMH - Oligonucleotide Array Sequence Analysis/methodsMH - *PeriodicityMH - Saccharomyces cerevisiae/chemistry/cytology/*geneticsMH - Sensitivity and SpecificityMH - Sequence Analysis, DNA/methodsMH - Stochastic ProcessesMH - Support, Non-U.S. Gov'tMH - Support, U.S. Gov't, Non-P.H.S.MH - Support, U.S. Gov't, P.H.S.EDAT- 2002/09/10 10:00MHDA- 2002/11/26 04:00PST - ppublishSO - Bioinformatics 2002 Sep;18(9):1176-83.

24: Abd-Elmoniem KZ, et al. Real-time speckle reduction a...[PMID:12214889]Related Articles, Links

UI - 22203225PMID- 12214889DA - 20020906DCOM- 20021009IS - 0018-9294VI - 49IP - 9DP - 2002 SepTI - Real-time speckle reduction and coherence enhancement in ultrasound imaging via nonlinear anisotropic diffusion.PG - 997-1014AB - 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 ZAU - Abd-Elmoniem KZFAU - Youssef, Abou-Bakr MAU - Youssef ABFAU - Kadah, Yasser MAU - Kadah YMLA - engPT - Journal ArticleCY - United StatesTA - IEEE Trans Biomed EngJID - 0012737SB - IMMH - *AlgorithmsMH - AnisotropyMH - Comparative StudyMH - Computer SimulationMH - Echocardiography/methodsMH - Evaluation StudiesMH - HeartMH - HumanMH - Image Processing, Computer-Assisted/*methodsMH - Kidney/ultrasonographyMH - Liver/ultrasonographyMH - Models, StatisticalMH - Nonlinear DynamicsMH - Phantoms, ImagingMH - Reproducibility of ResultsMH - Sensitivity and SpecificityMH - *Signal Processing, Computer-AssistedMH - Support, Non-U.S. Gov'tMH - Time FactorsMH - Ultrasonography, Doppler, Pulsed/*instrumentation/*methodsEDAT- 2002/09/07 10:00MHDA- 2002/10/10 04:00PST - ppublishSO - 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 - 22196366PMID- 12211574DA - 20020904DCOM- 20020918IS - 0003-6935VI - 41IP - 25DP - 2002 Sep 1TI - Absorption and scattering images of heterogeneous scattering media can be simultaneously reconstructed by use of dc data.PG - 5427-37AB - 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, YongAU - Xu YFAU - Gu, XuejunAU - Gu XFAU - Khan, TaufiquarAU - Khan TFAU - Jiang, HuabeiAU - Jiang HLA - engID - R01 CA 90533/CA/NCIPT - Journal ArticleCY - United StatesTA - Appl OptJID - 0247660SB - IMMH - AbsorptionMH - AlgorithmsMH - Finite Element AnalysisMH - *Image Processing, Computer-AssistedMH - Nonlinear DynamicsMH - Phantoms, ImagingMH - Scattering, RadiationMH - Support, U.S. Gov't, Non-P.H.S.MH - Support, U.S. Gov't, P.H.S.EDAT- 2002/09/05 10:00MHDA- 2002/09/19 10:01PST - ppublishSO - Appl Opt 2002 Sep 1;41(25):5427-37.

26: Pouget A, et al. A computational perspective o...[PMID:12209122]Related Articles, Links

UI - 22199622PMID- 12209122DA - 20020904DCOM- 20020927IS - 1471-003XVI - 3IP - 9DP - 2002 SepTI - A computational perspective on the neural basis of multisensory spatial representations.PG - 741-7AB - 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.eduFAU - Pouget, AlexandreAU - Pouget AFAU - Deneve, SophieAU - Deneve SFAU - Duhamel, Jean-ReneAU - Duhamel JRLA - engPT - Journal ArticlePT - ReviewPT - Review, TutorialCY - EnglandTA - Nat Rev NeurosciJID - 100962781SB - IMMH - AnimalMH - Brain/*physiologyMH - Eye Movements/physiologyMH - HumanMH - Models, NeurologicalMH - Nerve Net/*physiologyMH - Neural Pathways/*physiologyMH - Neurons/*physiologyMH - Nonlinear DynamicsMH - Orientation/*physiologyMH - Psychomotor Performance/physiologyMH - Sensation/*physiologyMH - Space Perception/*physiologyRF - 43EDAT- 2002/09/05 10:00MHDA- 2002/09/28 04:00AID - 10.1038/nrn914 [doi]AID - nrn914 [pii]PST - ppublishSO - Nat Rev Neurosci 2002 Sep;3(9):741-7.

27: Gismondi RC, et al. Artificial neural networks fo...[PMID:12204451]Related Articles, Links

UI - 22193843PMID- 12204451DA - 20020902DCOM- 20021118IS - 0169-2607VI - 69IP - 3DP - 2002 NovTI - Artificial neural networks for infant mortality modelling.PG - 237-47AB - 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.brFAU - Gismondi, Ronaldo CAU - Gismondi RCFAU - Almeida, Renan Moritz Varnier RAU - Almeida RMFAU - Infantosi, Antonio Fernando CAU - Infantosi AFLA - engPT - Journal ArticleCY - IrelandTA - Comput Methods Programs BiomedJID - 8506513SB - IMMH - Brazil/epidemiologyMH - Epidemiologic MethodsMH - HumanMH - InfantMH - *Infant MortalityMH - Linear ModelsMH - Models, StatisticalMH - Multivariate AnalysisMH - *Neural Networks (Computer)MH - Nonlinear DynamicsEDAT- 2002/09/03 10:00MHDA- 2002/11/26 04:00AID - S0169260702000068 [pii]PST - ppublishSO - Comput Methods Programs Biomed 2002 Nov;69(3):237-47.

28: Slutzky MW, et al. Identification of determinism...[PMID:12204306]Related Articles, Links

UI - 22194550PMID- 12204306DA - 20020902DCOM- 20021016IS - 0165-0270VI - 118IP - 2DP - 2002 Aug 30TI - Identification of determinism in noisy neuronal systems.PG - 153-61AB - 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.eduFAU - Slutzky, Marc WAU - Slutzky MWFAU - Cvitanovic, PredragAU - Cvitanovic PFAU - Mogul, David JAU - Mogul DJLA - engPT - Journal ArticleCY - NetherlandsTA - J Neurosci MethodsJID - 7905558SB - IMMH - Action Potentials/physiologyMH - AnimalMH - Electrophysiology/*methods/statistics & numerical dataMH - Hippocampus/*physiologyMH - MaleMH - Neurons/*physiologyMH - Nonlinear DynamicsMH - Principal Component AnalysisMH - RatsMH - Rats, Sprague-DawleyMH - Stochastic ProcessesEDAT- 2002/09/03 10:00MHDA- 2002/10/17 04:00AID - S0165027002000298 [pii]PST - ppublishSO - 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 - 22191094PMID- 12203688DA - 20020830DCOM- 20021017LR - 20021101IS - 1065-9471VI - 17IP - 1DP - 2002 SepTI - Assessment of spatial normalization of whole-brain magnetic resonance images in children.PG - 48-60AB - 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.orgFAU - Wilke, MarkoAU - Wilke MFAU - Schmithorst, Vincent JAU - Schmithorst VJFAU - Holland, Scott KAU - Holland SKLA - engID - R01-HD38578-01/HD/NICHDPT - Clinical TrialPT - Journal ArticleCY - United StatesTA - Hum Brain MappJID - 9419065SB - IMMH - AdolescentMH - Age DistributionMH - Age FactorsMH - Brain/*anatomy & histology/*growth & developmentMH - ChildMH - Child, PreschoolMH - FemaleMH - HumanMH - Image Processing, Computer-Assisted/*methodsMH - Magnetic Resonance Imaging/*methods/*standardsMH - MaleMH - Nonlinear DynamicsMH - Reference ValuesMH - Sex DistributionMH - Support, U.S. Gov't, P.H.S.EDAT- 2002/08/31 10:00MHDA- 2002/10/18 04:00AID - 10.1002/hbm.10053 [doi]PST - ppublishSO - 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 - 22192444PMID- 12201859DA - 20020830DCOM- 20021022IS - 1098-3015VI - 5IP - 5DP - 2002 Sep-OctTI - Validation of the Patient Perception of Migraine Questionnaire.PG - 421-9AB - 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.comFAU - Davis, Kimberly HuntAU - Davis KHFAU - Black, LibbyAU - Black LFAU - Sleath, BetsyAU - Sleath BLA - engPT - Journal ArticlePT - Validation StudiesCY - United StatesTA - Value HealthJID - 100883818RN - 0 (Indoles)RN - 0 (Piperidines)RN - 0 (Serotonin Agonists)RN - 121679-13-8 (naratriptan)SB - IMMH - AdultMH - Analysis of VarianceMH - Factor Analysis, StatisticalMH - FemaleMH - HumanMH - Indoles/*administration & dosageMH - MaleMH - Migraine/*drug therapyMH - Nonlinear DynamicsMH - Pain Measurement/classificationMH - Patient Satisfaction/*statistics & numerical dataMH - Piperidines/*administration & dosageMH - PsychometricsMH - Questionnaires/*standardsMH - Reproducibility of ResultsMH - Self EfficacyMH - Sensitivity and SpecificityMH - Serotonin Agonists/*administration & dosageMH - Support, Non-U.S. Gov'tEDAT- 2002/08/31 10:00MHDA- 2002/10/31 04:00AID - 55120 [pii]PST - ppublishSO - Value Health 2002 Sep-Oct;5(5):421-9.

31: Krstin N, et al. [Experiments to determine the...[PMID:12201015]Related Articles, Links

UI - 22189854PMID- 12201015DA - 20020830DCOM- 20021112IS - 0013-5585VI - 47IP - 7-8DP - 2002 Jul-AugTI - [Experiments to determine the time dependent material properties of the periodontal ligament]PG - 202-8AB - 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, NAU - Krstin NFAU - Dorow, ChAU - Dorow ChFAU - Franke, R PAU - Franke RPFAU - Sander, F GAU - Sander FGLA - gerPT - Journal ArticleTT - Experimente zur Bestimmung der zeitabhangigen Materialeigenschaften des Parodontalligaments.CY - GermanyTA - Biomed Tech (Berl)JID - 1262533SB - IMMH - AnimalMH - BiomechanicsMH - ElasticityMH - English AbstractMH - HumanMH - Nonlinear DynamicsMH - *Orthodontics, CorrectiveMH - Periodontal Ligament/injuries/*physiologyMH - Rupture, SpontaneousMH - SwineMH - *Tooth MovementMH - Weight-Bearing/physiologyEDAT- 2002/08/31 10:00MHDA- 2002/11/26 04:00PST - ppublishSO - 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 - 22181877PMID- 12194187DA - 20020823DCOM- 20021030LR - 20021120IS - 0925-2312VI - 26-27IP - 1-3DP - 1999 JunTI - Modelling the firing pattern of bullfrog vestibular neurons responding to naturalistic stimuli.PG - 223-8AB - 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.nzFAU - Paulin, M GAU - Paulin MGFAU - Hoffman, L FAU - Hoffman LFLA - engPT - Journal ArticleCY - NetherlandsTA - NeurocomputingJID - 9884927SB - SMH - Action Potentials/*physiologyMH - AnimalMH - *Models, NeurologicalMH - *Nervous System PhysiologyMH - Neurons, Afferent/*physiologyMH - Nonlinear DynamicsMH - Rana catesbeiana/anatomy & histology/*physiologyMH - Semicircular Canals/*innervationMH - Signal Transduction/physiologyMH - Vestibular Nerve/physiologyMH - Vestibule/physiologyEDAT- 2002/08/27 10:00MHDA- 2002/11/01 04:00PST - ppublishSO - Neurocomputing 1999 Jun;26-27(1-3):223-8.

33: Dhanasekharan M, et al. Viscoelastic flow modeling in...[PMID:12194181]Related Articles, Links

UI - 22181866PMID- 12194181DA - 20020823DCOM- 20021030IS - 0145-8876VI - 23IP - 3DP - 2000 AugTI - Viscoelastic flow modeling in the extrusion of a dough-like fluid.PG - 237-47AB - 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, MAU - Dhanasekharan MFAU - Kokini, J LAU - Kokini JLLA - engPT - Journal ArticleCY - United StatesTA - J Food Process EngJID - 101148874SB - SMH - *ElasticityMH - FlourMH - *Food TechnologyMH - Models, TheoreticalMH - Nonlinear DynamicsMH - *RheologyMH - Stress, MechanicalMH - Support, U.S. Gov't, Non-P.H.S.MH - ViscosityEDAT- 2002/08/27 10:00MHDA- 2002/11/01 04:00PST - ppublishSO - 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 - 22176991PMID- 12188761DA - 20020821DCOM- 20021021IS - 1539-3755VI - 65IP - 6 Pt 1DP - 2002 JunTI - Class of self-limiting growth models in the presence of nonlinear diffusion.PG - 061909AB - 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, SandipAU - Kar SFAU - Banik, Suman KumarAU - Banik SKFAU - Ray, Deb ShankarAU - Ray DSLA - engPT - Journal ArticleCY - United StatesTA - Phys Rev E Stat Nonlin Soft Matter PhysJID - 101136452SB - IMMH - AnimalMH - Bacteria/growth & developmentMH - DiffusionMH - *GrowthMH - HumanMH - *Models, BiologicalMH - Neoplasms/pathologyMH - Nonlinear DynamicsMH - Support, Non-U.S. Gov'tEDAT- 2002/08/22 10:00MHDA- 2002/10/22 04:00PHST- 2002/Feb/08 [received]PHST- 2002/Jun/21 [aheadofprint]PST - ppublishSO - 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 - 22176937PMID- 12188707DA - 20020821DCOM- 20021021IS - 1539-3755VI - 65IP - 6 Pt 1DP - 2002 JunTI - Morphological instability and dynamics of fronts in bacterial growth models with nonlinear diffusion.PG - 061111AB - 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, JudithAU - Muller JFAU - Van Saarloos, WimAU - Van Saarloos WLA - engPT - Journal ArticleCY - United StatesTA - Phys Rev E Stat Nonlin Soft Matter PhysJID - 101136452SB - IMMH - Bacteria/*growth & developmentMH - BiophysicsMH - Comparative StudyMH - DiffusionMH - *Models, BiologicalMH - Nonlinear DynamicsEDAT- 2002/08/22 10:00MHDA- 2002/10/22 04:00PHST- 2001/Nov/26 [received]PHST- 2002/Jun/28 [aheadofprint]PST - ppublishSO - 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 - 22176936PMID- 12188706DA - 20020821DCOM- 20021021IS - 1539-3755VI - 65IP - 6 Pt 1DP - 2002 JunTI - Neutrality condition and response law for nonlinear reaction-diffusion equations, with application to population genetics.PG - 061110AB - 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 OvidiuAU - Vlad MOFAU - Moran, FedericoAU - Moran FFAU - Tsuchiya, MasaAU - Tsuchiya MFAU - Cavalli-Sforza, L LucaAU - Cavalli-Sforza LLFAU - Oefner, Peter JAU - Oefner PJFAU - Ross, JohnAU - Ross JLA - engID - GM28428/GM/NIGMSPT - Journal ArticleCY - United StatesTA - Phys Rev E Stat Nonlin Soft Matter PhysJID - 101136452SB - IMMH - BiochemistryMH - Chemical EngineeringMH - Chemistry, PhysicalMH - DiffusionMH - EvolutionMH - *Genetics, PopulationMH - Models, GeneticMH - MutationMH - *Nonlinear DynamicsMH - Support, U.S. Gov't, Non-P.H.S.MH - Support, U.S. Gov't, P.H.S.EDAT- 2002/08/22 10:00MHDA- 2002/10/22 04:00PHST- 2001/Dec/10 [received]PHST- 2002/Jun/25 [aheadofprint]PST - ppublishSO - 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 - 22176105PMID- 12187779DA - 20020821DCOM- 20020909IS - 0020-7454VI - 112IP - 3DP - 2002 MarTI - The cell assembly, Mark III: transitions between brain states and the localization and generalization of function.PG - 277-90AB - 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.caFAU - Jacobson, ZacharyAU - Jacobson ZFAU - Pullman, Norman JAU - Pullman NJFAU - Treurniet, WilliamAU - Treurniet WLA - engPT - Journal ArticleCY - United StatesTA - Int J NeurosciJID - 0270707SB - IMMH - AnimalMH - Cerebral Cortex/*physiologyMH - HumanMH - *Markov ChainsMH - MemoryMH - *Models, BiologicalMH - *Neural Networks (Computer)MH - *Nonlinear DynamicsEDAT- 2002/08/22 10:00MHDA- 2002/09/11 10:01PST - ppublishSO - 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 - 22173387PMID- 12186039DA - 20020820DCOM- 20021017IS - 0001-4966VI - 112IP - 2DP - 2002 AugTI - A model cochlear partition involving longitudinal elasticity.PG - 576-89AB - 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.caFAU - Jaffer, Taha S AAU - Jaffer TSFAU - Kunov, HansAU - Kunov HFAU - Wong, WillyAU - Wong WLA - engPT - Journal ArticleCY - United StatesTA - J Acoust Soc AmJID - 7503051RN - 0 (Reticulin)SB - IMMH - Basilar Membrane/physiologyMH - BiomechanicsMH - Cochlea/*physiologyMH - ElasticityMH - HumanMH - Nonlinear DynamicsMH - Organ of Corti/physiologyMH - Otoacoustic Emissions, Spontaneous/physiologyMH - Reference ValuesMH - Reticulin/physiologyMH - Sound SpectrographyMH - Support, Non-U.S. Gov'tEDAT- 2002/08/21 10:00MHDA- 2002/10/18 04:00PST - ppublishSO - 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 - 22171135PMID- 12183039DA - 20020816DCOM- 20021028IS - 0304-3940VI - 329IP - 3DP - 2002 Sep 6TI - A dynamic pattern analysis of coordination between breathing and rhythmic arm movements in humans.PG - 314-8AB - 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.frFAU - Temprado, J JAU - Temprado JJFAU - Milliex, LAU - Milliex LFAU - Grelot, LAU - Grelot LFAU - Coyle, TAU - Coyle TFAU - Calvin, SAU - Calvin SFAU - Laurent, MAU - Laurent MLA - engPT - Journal ArticleCY - IrelandTA - Neurosci LettJID - 7600130SB - IMMH - Arm/*physiologyMH - HumanMH - Models, NeurologicalMH - Movement/*physiologyMH - Nonlinear DynamicsMH - PeriodicityMH - Respiratory Mechanics/*physiologyEDAT- 2002/08/17 10:00MHDA- 2002/10/29 04:00AID - S030439400200455X [pii]PST - ppublishSO - Neurosci Lett 2002 Sep 6;329(3):314-8.

40: Wennekers T. Dynamic approximation of spat...[PMID:12180403]Related Articles, Links

UI - 22167780PMID- 12180403DA - 20020815DCOM- 20020906IS - 0899-7667VI - 14IP - 8DP - 2002 AugTI - Dynamic appr