55 results match your criteria Nonlinear Biomedical Physics [Journal]


Influence of the distensibility of large arteries on the longitudinal impedance: application for the development of non-invasive techniques to the diagnosis of arterial diseases.

Nonlinear Biomed Phys 2012 Apr 16;6(1). Epub 2012 Apr 16.

Unit of research of Biophysics, Faculty of Medicine of Sousse, Sousse, Tunisie.

Background: This study shows that the arterial longitudinal impedance constitutes a hemodynamic parameter of interest for performance characterization of large arteries in normal condition as well as in pathological situations. For this purpose, we solved the Navier-Stokes equations for an incompressible flow using the finite element analysis method and the Arbitrary Lagrangian Eulerian (ALE) formulation. The mathematical model assumes a two-dimensional flow and takes into account the nonlinear terms in the equations of fluid motion that express the convective acceleration, as well as the nonlinear deformation of the arterial wall. Read More

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http://dx.doi.org/10.1186/1753-4631-6-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3442960PMC
April 2012
5 Reads

Fractional modeling dynamics of HIV and CD4+ T-cells during primary infection.

Nonlinear Biomed Phys 2012 Jan 3;6(1). Epub 2012 Jan 3.

Department of mathematics, Faculty of Science, South Valley University, Qena, Egypt.

In this paper, we introduce fractional-order into a model of HIV-1 infection of CD4+ T cells. We study the effect of the changing the average number of viral particles N with different sets of initial conditions on the dynamics of the presented model. Generalized Euler method (GEM) will be used to find a numerical solution of the HIV-1 infection fractional order model. Read More

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http://dx.doi.org/10.1186/1753-4631-6-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3275462PMC
January 2012
7 Reads

Nonlinear changes in the activity of the oxygen-dependent demethylase system in Rhodococcus erythropolis cells in the presence of low and very low doses of formaldehyde.

Nonlinear Biomed Phys 2011 Nov 21;5(1). Epub 2011 Nov 21.

Biochemistry Department, UMCS, Lublin, Poland.

The effect of exogenous, highly diluted formaldehyde on the rate of demethylation/re-methylation of veratric acid by the bacteria Rhodococcus erythropolis was studied using electrophoretic and microscopic techniques. The activity of 4-O-demethylase, responsible for accumulation of vanillic acid, and the levels of veratric and vanillic acids were determined using capillary electrophoresis. Formaldehyde was serially diluted at 1:100 ratios, and the total number of iterations was 20. Read More

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http://dx.doi.org/10.1186/1753-4631-5-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3229444PMC
November 2011
12 Reads

Entrainment of marginally stable excitation waves by spatially extended sub-threshold periodic forcing.

Nonlinear Biomed Phys 2011 Sep 25;5(1). Epub 2011 Sep 25.

University of North Carolina at Greensboro, North Carolina, 27402, USA.

We introduce a novel approach of stabilizing the dynamics of excitation waves by spatially extended sub-threshold periodic forcing. Entrainment of unstable primary waves has been studied numerically for different amplitudes and frequencies of additional sub-threshold stimuli. We determined entrainment regimes under which excitation blocks were transformed into consistent 1:1 responses. Read More

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http://dx.doi.org/10.1186/1753-4631-5-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3195090PMC
September 2011
3 Reads

Econobiophysics - game of choosing. Model of selection or election process with diverse accessible information.

Nonlinear Biomed Phys 2011 Sep 5;5(1). Epub 2011 Sep 5.

Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, 4 Trojdena St,, 02-109 Warsaw, Poland.

We propose several models applicable to both selection and election processes when each selecting or electing subject has access to different information about the objects to choose from. We wrote special software to simulate these processes. We consider both the cases when the environment is neutral (natural process) as well as when the environment is involved (controlled process). Read More

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http://dx.doi.org/10.1186/1753-4631-5-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3193801PMC
September 2011
9 Reads

On multi-strain model for Hepatitis C.

Authors:
E Ahmed Ha El-Saka

Nonlinear Biomed Phys 2011 Aug 3;5. Epub 2011 Aug 3.

Mathematics Department, Faculty of Science, Mansoura University, 35516, Mansoura, Egypt.

In this paper we present a multi-strain model for hepatitis C virus (HCV) including an immune response term. The model is presented and discussed. Also we argue that the added multi-strain term represents some basic properties of the immune system and that it should be included to study longer term behavior of the disease. Read More

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http://dx.doi.org/10.1186/1753-4631-5-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3726404PMC
August 2011
3 Reads

Discriminating between ADHD adults and controls using independent ERP components and a support vector machine: a validation study.

Nonlinear Biomed Phys 2011 Jul 19;5. Epub 2011 Jul 19.

Department of Computer Science, ETH Zurich, Switzerland.

Background: There are numerous event-related potential (ERP) studies in relation to attention-deficit hyperactivity disorder (ADHD), and a substantial number of ERP correlates of the disorder have been identified. However, most of the studies are limited to group differences in children. Independent component analysis (ICA) separates a set of mixed event-related potentials into a corresponding set of statistically independent source signals, which are likely to represent different functional processes. Read More

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http://dx.doi.org/10.1186/1753-4631-5-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3149569PMC
July 2011
15 Reads

Evidence of a pharmacodynamic EEG profile in rats following clonidine administration using a nonlinear analysis.

Nonlinear Biomed Phys 2011 Jun 26;5(1). Epub 2011 Jun 26.

Pfizer Global Research and Development, Ramsgate Road, Sandwich, CT13 9NJ, UK.

Background: Changes caused by clonidine in rodent electroencephalograms (EEG) have been reported with some inconsistency. For this reason, a pre-clinical study was conducted in order to confirm previous findings with both a standard spectral analysis and a sleep stage scoring procedure. In addition, a nonlinear technique for analysing the time-varying signals was implemented to compare its performance against conventional approaches. Read More

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http://dx.doi.org/10.1186/1753-4631-5-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3141322PMC
June 2011
5 Reads

New method for analysis of nonstationary signals.

Authors:
Robert A Stepien

Nonlinear Biomed Phys 2011 Jun 22;5. Epub 2011 Jun 22.

Laboratory of Biosignal Analysis Fundamentals, Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Ks, Trojdena 4 st,, Warsaw, 02-109, Poland.

Background: Analysis of signals by means of symbolic methods consists in calculating a measure of signal complexity, for example informational entropy or Lempel-Ziv algorithmic complexity. For construction of these entropic measures one uses distributions of symbols representing the analyzed signal.

Results: We introduce a new signal characteristic named sequential spectrum that is suitable for analysis of the wide group of signals, including biosignals. Read More

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http://dx.doi.org/10.1186/1753-4631-5-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3145554PMC
June 2011
5 Reads

Characterizing Deep Brain Stimulation effects in computationally efficient neural network models.

Nonlinear Biomed Phys 2011 Apr 15;5(1). Epub 2011 Apr 15.

DIEEI - Università di Catania, v,le A, Doria 6, Catania, Italy.

Background: Recent studies on the medical treatment of Parkinson's disease (PD) led to the introduction of the so called Deep Brain Stimulation (DBS) technique. This particular therapy allows to contrast actively the pathological activity of various Deep Brain structures, responsible for the well known PD symptoms. This technique, frequently joined to dopaminergic drugs administration, replaces the surgical interventions implemented to contrast the activity of specific brain nuclei, called Basal Ganglia (BG). Read More

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http://dx.doi.org/10.1186/1753-4631-5-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3104360PMC
April 2011
4 Reads

Pulse Decomposition Analysis of the digital arterial pulse during hemorrhage simulation.

Nonlinear Biomed Phys 2011 Jan 12;5(1). Epub 2011 Jan 12.

Empirical Technologies Corporation, PO Box 8175, 3046A Berkmar Drive, Charlottesville, Virginia, 22906, USA.

Background: Markers of temporal changes in central blood volume are required to non-invasively detect hemorrhage and the onset of hemorrhagic shock. Recent work suggests that pulse pressure may be such a marker. A new approach to tracking blood pressure, and pulse pressure specifically is presented that is based on a new form of pulse pressure wave analysis called Pulse Decomposition Analysis (PDA). Read More

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http://dx.doi.org/10.1186/1753-4631-5-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3025935PMC
January 2011
6 Reads

Simple fractal method of assessment of histological images for application in medical diagnostics.

Nonlinear Biomed Phys 2010 Dec 6;4(1). Epub 2010 Dec 6.

Lab, of Biosignal Analysis Fundamentals, Nalecz Institute of Biocybernetics and Biomedical Engineering Polish Academy of Sciences, Warsaw, Poland.

We propose new method of assessment of histological images for medical diagnostics. 2-D image is preprocessed to form 1-D landscapes or 1-D signature of the image contour and then their complexity is analyzed using Higuchi's fractal dimension method. The method may have broad medical application, from choosing implant materials to differentiation between benign masses and malignant breast tumors. Read More

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http://dx.doi.org/10.1186/1753-4631-4-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3017044PMC
December 2010
6 Reads

On modeling two immune effectors two strain antigen interaction.

Nonlinear Biomed Phys 2010 Nov 25;4. Epub 2010 Nov 25.

Mathematics Department, Damietta Faculty of Science, Mansoura University, 34517, New Damietta, Egypt.

In this paper we consider the fractional order model with two immune effectors interacting with two strain antigen. The systems may explain the recurrence of some diseases e.g. Read More

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http://dx.doi.org/10.1186/1753-4631-4-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3012021PMC
November 2010
4 Reads

Characterization of chaotic dynamics in the human menstrual cycle.

Authors:
Gn Derry Ps Derry

Nonlinear Biomed Phys 2010 Oct 5;4(1). Epub 2010 Oct 5.

Department of Physics, Loyola University Maryland, Baltimore, MD 21210, USA.

Background: The human menstrual cycle is known to exhibit a significant amount of unexplained variability. This variation is typically dismissed as random fluctuations in an otherwise periodic and predictable system. Given the many delayed nonlinear feedbacks in the multiple levels of the reproductive endocrine system, however, the menstrual cycle can properly be construed as the output of a nonlinear dynamical system, and such a system has the possibility of being in a chaotic trajectory. Read More

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https://nonlinearbiomedphys.biomedcentral.com/articles/10.11
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http://dx.doi.org/10.1186/1753-4631-4-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2959058PMC
October 2010
4 Reads

QEEG characteristics and spectrum weighted frequency for children diagnosed as autistic spectrum disorder.

Nonlinear Biomed Phys 2010 Sep 30;4(1). Epub 2010 Sep 30.

Pediatric Clinic, Faculty of Medicine, University of Skopje, Macedonia.

Background: Autistic spectrum disorders are a group of neurological and developmental disorders associated with social, communication, sensory, behavioral and cognitive impairments, as well as restricted, repetitive patterns of behavior, activities, or interests.The aim of this study was a) to analyze QEEG findings of autistic patients and to compare the results with data base; and b) to introduce the calculation of spectrum weighted frequency (brain rate) as an indicator of general mental arousal in these patients.

Results: Results for Q-EEG shows generally increased delta-theta activity in frontal region of the brain. Read More

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http://dx.doi.org/10.1186/1753-4631-4-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2959057PMC
September 2010
6 Reads

On consciousness, resting state fMRI, and neurodynamics.

Authors:
Arvid Lundervold

Nonlinear Biomed Phys 2010 Jun 3;4 Suppl 1:S9. Epub 2010 Jun 3.

Department of Biomedicine, Neuroinformatics and Image Analysis Laboratory, University of Bergen Jonas Lies vei 91, N-5009 Bergen, Norway.

Background: During the last years, functional magnetic resonance imaging (fMRI) of the brain has been introduced as a new tool to measure consciousness, both in a clinical setting and in a basic neurocognitive research. Moreover, advanced mathematical methods and theories have arrived the field of fMRI (e.g. Read More

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http://dx.doi.org/10.1186/1753-4631-4-S1-S9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2880806PMC
June 2010
4 Reads

A graph-theoretical approach in brain functional networks. Possible implications in EEG studies.

Nonlinear Biomed Phys 2010 Jun 3;4 Suppl 1:S8. Epub 2010 Jun 3.

IRCCS "Fondazione Santa Lucia", Rome, Italy .

Background: Recently, it was realized that the functional connectivity networks estimated from actual brain-imaging technologies (MEG, fMRI and EEG) can be analyzed by means of the graph theory, that is a mathematical representation of a network, which is essentially reduced to nodes and connections between them.

Methods: We used high-resolution EEG technology to enhance the poor spatial information of the EEG activity on the scalp and it gives a measure of the electrical activity on the cortical surface. Afterwards, we used the Directed Transfer Function (DTF) that is a multivariate spectral measure for the estimation of the directional influences between any given pair of channels in a multivariate dataset. Read More

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http://dx.doi.org/10.1186/1753-4631-4-S1-S8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2880805PMC
June 2010
8 Reads

Transient process of cortical activity during Necker cube perception: from local clusters to global synchrony.

Nonlinear Biomed Phys 2010 Jun 3;4 Suppl 1:S7. Epub 2010 Jun 3.

Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan.

Background: It has been discussed that neural phase-synchrony across distant cortical areas (or global phase-synchrony) was correlated with various aspects of consciousness. The generating process of the synchrony, however, remains largely unknown. As a first step, we investigate transient process of global phase-synchrony, focusing on phase-synchronized clusters. Read More

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http://dx.doi.org/10.1186/1753-4631-4-S1-S7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2880804PMC
June 2010
6 Reads

Brain function assessment in different conscious states.

Nonlinear Biomed Phys 2010 Jun 3;4 Suppl 1:S6. Epub 2010 Jun 3.

Department of Biophysics, Faculty of Medicine, Dokuz Eylul University, Izmir, 35340, Turkey.

Background: The study of brain functioning is a major challenge in neuroscience fields as human brain has a dynamic and ever changing information processing. Case is worsened with conditions where brain undergoes major changes in so-called different conscious states. Even though the exact definition of consciousness is a hard one, there are certain conditions where the descriptions have reached a consensus. Read More

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http://dx.doi.org/10.1186/1753-4631-4-S1-S6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2880803PMC
June 2010
4 Reads

Effect of noise in processing of visual information.

Nonlinear Biomed Phys 2010 Jun 3;4 Suppl 1:S5. Epub 2010 Jun 3.

Department of Medical Physics, School of Medicine, University of Patras, University Campus, 265 04 Rio Patras, Greece.

Background: Information transmission and processing in the nervous system has stochastic nature. Multiple factors contribute to neuronal trial-to-trial variability. Noise and variations are introduced by the processes at the molecular and cellular level (thermal noise, channel current noise, membrane potential variations, biochemical and diffusion noise at synapses etc). Read More

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https://nonlinearbiomedphys.biomedcentral.com/articles/10.11
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http://dx.doi.org/10.1186/1753-4631-4-S1-S5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2880802PMC
June 2010
4 Reads

Cortical potential imaging using L-curve and GCV method to choose the regularisation parameter.

Nonlinear Biomed Phys 2010 Jun 3;4 Suppl 1:S4. Epub 2010 Jun 3.

Department of Biomedical Engineering, Tampere University of Technology, Tampere, Finland.

Background: The electroencephalography (EEG) is an attractive and a simple technique to measure the brain activity. It is attractive due its excellent temporal resolution and simple due to its non-invasiveness and sensor design. However, the spatial resolution of EEG is reduced due to the low conducting skull. Read More

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http://dx.doi.org/10.1186/1753-4631-4-S1-S4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2880801PMC
June 2010
8 Reads

Patterns of cortical activity during the observation of Public Service Announcements and commercial advertisings.

Nonlinear Biomed Phys 2010 Jun 3;4 Suppl 1:S3. Epub 2010 Jun 3.

IRCCS "Fondazione Santa Lucia", Rome, Italy .

Background: In the present research we were interested to study the cerebral activity of a group of healthy subjects during the observation a documentary intermingled by a series of TV advertisements. In particular, we desired to examine whether Public Service Announcements (PSAs) are able to elicit a different pattern of activity, when compared with a different class of commercials, and correlate it with the memorization of the showed stimuli, as resulted from a following subject's verbal interview.

Methods: We recorded the EEG signals from a group of 15 healthy subjects and applied the High Resolution EEG techniques in order to estimate and map their Power Spectral Density (PSD) on a realistic cortical model. Read More

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http://dx.doi.org/10.1186/1753-4631-4-S1-S3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2880800PMC
June 2010
3 Reads

Gender differences in brain areas involved in silent counting by means of fMRI.

Nonlinear Biomed Phys 2010 Jun 3;4 Suppl 1:S2. Epub 2010 Jun 3.

Diagnostic Imaging Centre, Institute of Oncology, Instituski put 4, Sremska Kamenica, Serbia.

Background: Pattern of brain asymmetries varies with handedness, gender, age, and with variety of genetic and social factors. Large-scale neuroimaging analyses can optimize the detection of asymmetric features and confirm the factors that might modulate pattern of brain asymmetries. We attempted to evaluate eventual differences between genders in hemodynamic responses to a simple language task. Read More

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http://dx.doi.org/10.1186/1753-4631-4-S1-S2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2880799PMC
June 2010
9 Reads

Why bother with a COST Action? The benefits of networking in science.

Nonlinear Biomed Phys 2010 Jun 3;4 Suppl 1:S12. Epub 2010 Jun 3.

COST Office, Brussels, 149 Ave, Louise B1050-Brussels, Belgium.

A COST Action is a consortium of -mainly- European scientists (but open to international cooperation) working on a common research area, with the same subject; COST provides funding to the Actions for networking and dissemination activities, thus the participating scientists must have secured research funding from other national or European sources. COST funding is in the scale of approximately 100 kEuros per year and in this vein, it is often criticized both in that it does not fund research and the core science and in that its funding is 'limited'. However, COST with its instruments is an integral pillar of the European Research Area, and it is through its mission that a variety of aspects of the research environment, fundamental to the success of the research, are catered for; these include scientific networking, collaboration/exchange/training and dissemination activities. Read More

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http://dx.doi.org/10.1186/1753-4631-4-S1-S12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2880798PMC
June 2010
3 Reads

A step towards non-invasive characterization of the human frontal eye fields of individual subjects.

Nonlinear Biomed Phys 2010 Jun 3;4 Suppl 1:S11. Epub 2010 Jun 3.

Laboratory for Human Brain Dynamics, AAI Scientific Cultural Services Ltd, Nicosia, Cyprus.

Background: Identifying eye movement related areas in the frontal lobe has a long history, with microstimulation in monkeys producing the most clear-cut results. For humans, however, there is still no consensus about the location and the extent of the frontal eye field (FEF). There is also no simple non-invasive method for unambiguously defining the FEF in individual subjects, a prerequisite for clinical applications. Read More

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http://dx.doi.org/10.1186/1753-4631-4-S1-S11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2880797PMC
June 2010
3 Reads

Interocular yoking in human saccades examined by mutual information analysis.

Nonlinear Biomed Phys 2010 Jun 3;4 Suppl 1:S10. Epub 2010 Jun 3.

Laboratory for Human Brain Dynamics, RIKEN Brain Science Institute, 2-1 Hirosawa, Wakoshi, Saitama 351-0198, Japan .

Background: Saccadic eye movements align the two eyes precisely to foveate a target. Trial-by-trial variance of eye movement is always observed within an identical experimental condition. This has often been treated as experimental error without addressing its significance. Read More

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http://dx.doi.org/10.1186/1753-4631-4-S1-S10DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2880796PMC
June 2010
3 Reads

Classification of ADHD patients on the basis of independent ERP components using a machine learning system.

Nonlinear Biomed Phys 2010 Jun 3;4 Suppl 1:S1. Epub 2010 Jun 3.

Brain and Trauma Foundation Grisons, Poststrasse 22, 7000 Chur, Switzerland.

Background: In the context of sensory and cognitive-processing deficits in ADHD patients, there is considerable evidence of altered event related potentials (ERP). Most of the studies, however, were done on ADHD children. Using the independent component analysis (ICA) method, ERPs can be decomposed into functionally different components. Read More

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http://dx.doi.org/10.1186/1753-4631-4-S1-S1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2880795PMC
June 2010
14 Reads

Fractional-calculus diffusion equation.

Nonlinear Biomed Phys 2010 May 21;4. Epub 2010 May 21.

Applied Physics Department, Tafila Technical University, P,O, Box: 179 66110 Tafila- Jordan.

Background: Sequel to the work on the quantization of nonconservative systems using fractional calculus and quantization of a system with Brownian motion, which aims to consider the dissipation effects in quantum-mechanical description of microscale systems.

Results: The canonical quantization of a system represented classically by one-dimensional Fick's law, and the diffusion equation is carried out according to the Dirac method. A suitable Lagrangian, and Hamiltonian, describing the diffusive system, are constructed and the Hamiltonian is transformed to Schrodinger's equation which is solved. Read More

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http://dx.doi.org/10.1186/1753-4631-4-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2890680PMC
May 2010
2 Reads

Research on the relation of EEG signal chaos characteristics with high-level intelligence activity of human brain.

Nonlinear Biomed Phys 2010 Apr 27;4(1). Epub 2010 Apr 27.

Faculty of Electronic Information and Electrical Engineering, Dalian University of Technology, Dalian 116024, China.

Using phase space reconstruct technique from one-dimensional and multi-dimensional time series and the quantitative criterion rule of system chaos, and combining the neural network; analyses, computations and sort are conducted on electroencephalogram (EEG) signals of five kinds of human consciousness activities (relaxation, mental arithmetic of multiplication, mental composition of a letter, visualizing a 3-dimensional object being revolved about an axis, and visualizing numbers being written or erased on a blackboard). Through comparative studies on the determinacy, the phase graph, the power spectra, the approximate entropy, the correlation dimension and the Lyapunov exponent of EEG signals of 5 kinds of consciousness activities, the following conclusions are shown: (1) The statistic results of the deterministic computation indicate that chaos characteristic may lie in human consciousness activities, and central tendency measure (CTM) is consistent with phase graph, so it can be used as a division way of EEG attractor. (2) The analyses of power spectra show that ideology of single subject is almost identical but the frequency channels of different consciousness activities have slight difference. Read More

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http://nonlinearbiomedphys.biomedcentral.com/articles/10.118
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http://dx.doi.org/10.1186/1753-4631-4-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2867991PMC
April 2010
5 Reads

On fractional order models for Hepatitis C.

Authors:
E Ahmed H A El-Saka

Nonlinear Biomed Phys 2010 Mar 18;4(1). Epub 2010 Mar 18.

Mathematics Department, Faculty of Science, Mansoura University, 35516, Mansoura, Egypt.

In this paper we present a fractional order generalization of Perelson et al. basic hepatitis C virus (HCV) model including an immune response term. We argue that fractional order equations are more suitable than integer order ones in modeling complex systems which include biological systems. Read More

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http://dx.doi.org/10.1186/1753-4631-4-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2848051PMC
March 2010
3 Reads

On managing complex adaptive systems motivated by biosystems application to infections.

Nonlinear Biomed Phys 2009 Oct 12;3(1):11. Epub 2009 Oct 12.

Mathematics department, Faculty of Science, Mansoura 35516, Egypt.

Many attempts to control Complex adaptive systems (CAS) have failed. Here we try to learn from biosystems to derive some principles for CAS management. An application to managing infections is given. Read More

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http://dx.doi.org/10.1186/1753-4631-3-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2765945PMC
October 2009
1 Read

Influence of very low doses of mediators on fungal laccase activity - nonlinearity beyond imagination.

Nonlinear Biomed Phys 2009 Sep 4;3(1):10. Epub 2009 Sep 4.

Biochemistry Department, Maria Curie-Skłodowska University, Lublin, Poland.

Laccase, an enzyme responsible for aerobic transformations of natural phenolics, in industrial applications requires the presence of low-molecular substances known as mediators, which accelerate oxidation processes. However, the use of mediators is limited by their toxicity and the high costs of exploitation. The activation of extracellular laccase in growing fungal culture with highly diluted mediators, ABTS and HBT is described. Read More

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http://dx.doi.org/10.1186/1753-4631-3-10DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2749849PMC
September 2009
7 Reads

Disturbed functional brain networks and neurocognitive function in low-grade glioma patients: a graph theoretical analysis of resting-state MEG.

Nonlinear Biomed Phys 2009 Aug 23;3(1). Epub 2009 Aug 23.

Department of Neurology, VU University Medical Center, Amsterdam, the Netherlands.

Background: To understand neurophysiological mechanisms underlying cognitive dysfunction in low-grade glioma (LGG) patients by evaluating the spatial structure of 'resting-state' brain networks with graph theory.

Methods: Standardized tests measuring 6 neurocognitive domains were administered in 17 LGG patients and 17 healthy controls. Magnetoencephalography (MEG) recordings were conducted during eyes-closed 'resting state'. Read More

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http://nonlinearbiomedphys.biomedcentral.com/articles/10.118
Publisher Site
http://dx.doi.org/10.1186/1753-4631-3-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2745411PMC
August 2009
9 Reads

Extracting complexity waveforms from one-dimensional signals.

Nonlinear Biomed Phys 2009 Aug 14;3(1). Epub 2009 Aug 14.

Department for Life Sciences, Institute for Multidisciplinary Research, University of Belgrade Kneza Viseslava 1, 11000 Belgrade Serbia.

Background: Nonlinear methods provide a direct way of estimating complexity of one-dimensional sampled signals through calculation of Higuchi's fractal dimension (1Read More

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http://dx.doi.org/10.1186/1753-4631-3-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2739215PMC
August 2009
12 Reads

Simulation study of autoregulation responses of peripheral circulation to systemic pulsatility.

Nonlinear Biomed Phys 2009 Jul 24;3(1). Epub 2009 Jul 24.

Dipartimento di Bioingegneria, Politecnico di Milano, P,za Leonardo da Vinci, 32, 20133, Milan, Italy.

Background: This simulation study investigated potential modulations of total peripheral resistance (TPR), due to distributed peripheral vascular activity, by means of a lumped model of the arterial tree and a non linear model of microcirculation, inclusive of local controls of blood flow and tissue-capillary fluid exchange.

Results: Numerical simulations of circulation were carried out to compute TPR under different conditions of blood flow pulsatility, and to extract the pressure-flow characteristics of the cardiovascular system. Simulations showed that TPR seen by the large arteries was increased in absence of pulsatility, while it decreased with an augmented harmonic content. Read More

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http://dx.doi.org/10.1186/1753-4631-3-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2722629PMC
July 2009
4 Reads

Comparative study of nonlinear properties of EEG signals of normal persons and epileptic patients.

Nonlinear Biomed Phys 2009 Jul 20;3(1). Epub 2009 Jul 20.

Plasma Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata - 700064, India.

Background: Investigation of the functioning of the brain in living systems has been a major effort amongst scientists and medical practitioners. Amongst the various disorder of the brain, epilepsy has drawn the most attention because this disorder can affect the quality of life of a person. In this paper we have reinvestigated the EEGs for normal and epileptic patients using surrogate analysis, probability distribution function and Hurst exponent. Read More

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http://dx.doi.org/10.1186/1753-4631-3-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2722628PMC
July 2009
3 Reads

Using the nonlinear control of anaesthesia-induced hypersensitivity of EEG at burst suppression level to test the effects of radiofrequency radiation on brain function.

Nonlinear Biomed Phys 2009 Jul 18;3(1). Epub 2009 Jul 18.

Tampere University of Technology, Pori, Finland.

Background: In this study, investigating the effects of mobile phone radiation on test animals, eleven pigs were anaesthetised to the level where burst-suppression pattern appears in the electroencephalogram (EEG). At this level of anaesthesia both human subjects and animals show high sensitivity to external stimuli which produce EEG bursts during suppression. The burst-suppression phenomenon represents a nonlinear control system, where low-amplitude EEG abruptly switches to very high amplitude bursts. Read More

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http://dx.doi.org/10.1186/1753-4631-3-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2723106PMC
July 2009
11 Reads

Critical scale of propagation influences dynamics of waves in a model of excitable medium.

Nonlinear Biomed Phys 2009 Jul 9;3(1). Epub 2009 Jul 9.

Department of Physics and Astronomy, University of North Carolina at Greensboro, Greensboro, NC, USA.

Background: Duration and speed of propagation of the pulse are essential factors for stability of excitation waves. We explore the propagation of excitation waves resulting from periodic stimulation of an excitable cable to determine the minimal stable pulse duration in a rate-dependent modification of a Chernyak-Starobin-Cohen reaction-diffusion model.

Results: Various pacing rate dependent features of wave propagation were studied computationally and analytically. Read More

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http://dx.doi.org/10.1186/1753-4631-3-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2720971PMC
July 2009
4 Reads

Comments on introducing the immune system.

Authors:
E Ahmed

Nonlinear Biomed Phys 2009 Jun 11;3(1). Epub 2009 Jun 11.

Mathematics department, Faculty of Science, Mansoura 35516, Egypt.

It is argued that by studying some design principles of the immune system, e.g. nonlinearity and being a complex adaptive system, one can easily find some explanations of basic properties of the system e. Read More

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http://dx.doi.org/10.1186/1753-4631-3-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2701935PMC
June 2009
1 Read

Everything you wanted to ask about EEG but were afraid to get the right answer.

Nonlinear Biomed Phys 2009 May 26;3(1). Epub 2009 May 26.

Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland.

We answer several important questions concerning EEG. We also shortly discuss importance of nonlinear methods of contemporary physics in EEG analysis. Basic definitions and explanation of fundamental concepts may be found in my previous publications in NBP. Read More

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http://dx.doi.org/10.1186/1753-4631-3-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2698918PMC
May 2009
8 Reads

Hilbert-Huang versus Morlet wavelet transformation on mismatch negativity of children in uninterrupted sound paradigm.

Nonlinear Biomed Phys 2009 Feb 2;3(1). Epub 2009 Feb 2.

Department of Mathematical Information Technology, University of Jyväskylä, Jyväskylä, Finland.

Background: Compared to the waveform or spectrum analysis of event-related potentials (ERPs), time-frequency representation (TFR) has the advantage of revealing the ERPs time and frequency domain information simultaneously. As the human brain could be modeled as a complicated nonlinear system, it is interesting from the view of psychological knowledge to study the performance of the nonlinear and linear time-frequency representation methods for ERP research. In this study Hilbert-Huang transformation (HHT) and Morlet wavelet transformation (MWT) were performed on mismatch negativity (MMN) of children. Read More

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http://dx.doi.org/10.1186/1753-4631-3-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2654895PMC
February 2009
12 Reads
5 Citations

Recognizing brain activities by functional near-infrared spectroscope signal analysis.

Nonlinear Biomed Phys 2008 Jul 1;2(1). Epub 2008 Jul 1.

Chaos and Fractals Informatics Laboratory, Nagaoka University of Technology, 1603-1 Kamitomiokamachi, Nagaoka, Niigata, 940-2188, Japan.

Background: Functional Near-Infrared Spectroscope (fNIRs) is one of the latest technologies which utilize light in the near-infrared range to determine brain activities. Near-infrared technology allows design of safe, portable, wearable, non-invasive and wireless qualities monitoring systems. This indicates that fNIRs signal monitoring of brain hemodynamics can be value in helping to understand brain tasks. Read More

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http://dx.doi.org/10.1186/1753-4631-2-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2474833PMC
July 2008
5 Reads

Global behavior of epidemic transmission on heterogeneous networks via two distinct routes.

Nonlinear Biomed Phys 2008 May 1;2(1). Epub 2008 May 1.

School of Mathematics and Computational Science, Anhui University, Hefei 230039, China.

In the study of epidemic spreading two natural questions are: whether the spreading of epidemics on heterogenous networks have multiple routes, and whether the spreading of an epidemic is a local or global behavior? In this paper, we answer the above two questions by studying the SIS model on heterogenous networks, and give the global conditions for the endemic state when two distinct routes with uniform rate of infection are considered. The analytical results are also verified by numerical simulations. Read More

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http://dx.doi.org/10.1186/1753-4631-2-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2409347PMC
May 2008
3 Reads

Force plate monitoring of human hemodynamics.

Authors:
Jan Kríz Petr Seba

Nonlinear Biomed Phys 2008 Feb 22;2(1). Epub 2008 Feb 22.

University of Hradec Králové, Rokitanského 62, CZ - 500 03 Hradec Králové, Czech Republic.

Background: Noninvasive recording of movements caused by the heartbeat and the blood circulation is known as ballistocardiography. Several studies have shown the capability of a force plate to detect cardiac activity in the human body. The aim of this paper is to present a new method based on differential geometry of curves to handle multivariate time series obtained by ballistocardiographic force plate measurements. Read More

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http://dx.doi.org/10.1186/1753-4631-2-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2315646PMC
February 2008
2 Reads

From conformons to human brains: an informal overview of nonlinear dynamics and its applications in biomedicine.

Nonlinear Biomed Phys 2007 Jul 5;1(1). Epub 2007 Jul 5.

Institute of Biocybernetics and Biomedical Engineering Polish Academy of Sciences, Warsaw, Poland.

Methods of contemporary physics are increasingly important for biomedical research but, for a multitude of diverse reasons, most practitioners of biomedicine lack access to a comprehensive knowledge of these modern methodologies. This paper is an attempt to describe nonlinear dynamics and its methods in a way that could be read and understood by biomedical professionals who usually are not trained in advanced mathematics. After an overview of basic concepts and vocabulary of nonlinear dynamics, deterministic chaos, and fractals, application of nonlinear methods of biosignal analysis is discussed. Read More

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http://nonlinearbiomedphys.biomedcentral.com/articles/10.118
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http://dx.doi.org/10.1186/1753-4631-1-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1997128PMC
July 2007
7 Reads

Stochastic nonlinear dynamics pattern formation and growth models.

Nonlinear Biomed Phys 2007 Jul 5;1(1). Epub 2007 Jul 5.

Department of Interdisciplinary Studies, Faculty of Engineering, University of Tel Aviv, Tel Aviv 69978, Israel.

Stochastic evolutionary growth and pattern formation models are treated in a unified way in terms of algorithmic models of nonlinear dynamic systems with feedback built of a standard set of signal processing units. A number of concrete models is described and illustrated by numerous examples of artificially generated patterns that closely imitate wide variety of patterns found in the nature. Read More

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http://dx.doi.org/10.1186/1753-4631-1-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1997127PMC
July 2007
3 Reads

Estimating the distribution of dynamic invariants: illustrated with an application to human photo-plethysmographic time series.

Authors:
Michael Small

Nonlinear Biomed Phys 2007 Jul 23;1(1). Epub 2007 Jul 23.

Department of Electronic and Information Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.

Dynamic invariants are often estimated from experimental time series with the aim of differentiating between different physical states in the underlying system. The most popular schemes for estimating dynamic invariants are capable of estimating confidence intervals, however, such confidence intervals do not reflect variability in the underlying dynamics. We propose a surrogate based method to estimate the expected distribution of values under the null hypothesis that the underlying deterministic dynamics are stationary. Read More

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http://dx.doi.org/10.1186/1753-4631-1-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1997126PMC
July 2007
3 Reads

Virtual respiratory system in investigation of CPAP influence on optimal breathing frequency in obstructive lungs disease.

Nonlinear Biomed Phys 2007 Jul 16;1(1). Epub 2007 Jul 16.

Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland.

Background: Continuous Positive Airway Pressure (CPAP) is a commonly accepted method of spontaneous breathing support in obstructive lung disease. Previous work suggested that the cause of the CPAP efficacy in the obstructive lung disease localized in bronchi of middle order (OLDMO) is not as obvious as, for example, in the obstructive sleep apnea. Since CPAP reduces obstruction and the optimal breathing frequency (BF) depends on the obstruction level, it seems to be important to analyze the dependence of the optimal BF on CPAP. Read More

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http://dx.doi.org/10.1186/1753-4631-1-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1997125PMC
July 2007
2 Reads

Graph theoretical analysis of complex networks in the brain.

Nonlinear Biomed Phys 2007 Jul 5;1(1). Epub 2007 Jul 5.

Department of Clinical Neurophysiology, VU University Medical Center, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands.

Since the discovery of small-world and scale-free networks the study of complex systems from a network perspective has taken an enormous flight. In recent years many important properties of complex networks have been delineated. In particular, significant progress has been made in understanding the relationship between the structural properties of networks and the nature of dynamics taking place on these networks. Read More

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http://dx.doi.org/10.1186/1753-4631-1-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1976403PMC
July 2007
4 Reads

Synchronized dynamics of cortical neurons with time-delay feedback.

Nonlinear Biomed Phys 2007 Jul 5;1(1). Epub 2007 Jul 5.

US Naval Research Laboratory, Code 6792, Nonlinear Systems Dynamics Section, Plasma Physics Division, Washington, DC 20375, USA.

The dynamics of three mutually coupled cortical neurons with time delays in the coupling are explored numerically and analytically. The neurons are coupled in a line, with the middle neuron sending a somewhat stronger projection to the outer neurons than the feedback it receives, to model for instance the relay of a signal from primary to higher cortical areas. For a given coupling architecture, the delays introduce correlations in the time series at the time-scale of the delay. Read More

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http://dx.doi.org/10.1186/1753-4631-1-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1976404PMC
July 2007
5 Reads