Biomedical subjects

P Parmananda

Publications and source records attributed to P Parmananda.

At least 19 recordsLinked to original sources

PubMed2006

Resonance pacemakers in excitable media.

Chemical waves are initiated in an excitable medium by resonance with local periodic forcing of the excitability. Experiments are carried out with a photosensitive Belousov-Zhabotinsky medium, in which the excitability is varied according to the intensity of the imposed illumination. Complex resonance patterns are exhibited as a function of the amplitude and frequency of the forcing. Local resonance-induced wave initiation transforms the medium globally from a quiescent excitable steady state to a periodic state of successive traveling waves.

Journal Article↗

PubMed2006

Regulating noise-induced spiking using feedback.

We report successful manipulation of the noise provoked spiking behavior using delayed feedback control. Experiments were performed in a three electrode electrochemical cell under potentiostatic conditions. The uncontrolled system exhibited noise invoked oscillations whose regularity was quantified using normalized variance (NV). Superimposing delayed feedback, for appropriate values of delay (t), an enhancement in the regularity of the spike sequence was attained. Numerical simulations corroborated experimental observations.

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PubMed2006

Synchronization phenomena for a pair of locally coupled chaotic electrochemical oscillators: a survey.

Chaotic synchronization of two locally coupled electrochemical oscillators is studied numerically. Both bidirectional and unidirectional couplings are considered. For both these coupling scenarios, varying the characteristics of the coupling terms (functional form and/or strength) reveals a wide variety of synchronization phenomena. Standard diagnostic tests are performed to verify and classify the different types of synchronizations observed.

Biophysics↗

PubMed2005

Intrinsic coherence resonance in an electrochemical cell.

We study the interaction of intrinsic electrochemical noise with autonomous nonlinear dynamics of a three-electrode electrochemical cell. The amplitude of this intrinsic (internal) noise, regulated by the concentration of chloride ions, is monotonically increased and the provoked dynamics is analyzed. The experimentally constructed coherence factor beta versus the concentration of the chloride ions' curve has a unimodal shape indicating the emergence of intrinsic coherence resonance. The abscissa for the maxima of this unimodal curve corresponds to the optimum value of intrinsic noise where maximum regularity of the invoked dynamics is observed.

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PubMed2005

Stochastic resonance of electrochemical aperiodic spike trains.

Aperiodic stochastic resonance in an electrochemical system with excitable dynamics is characterized in experiments and simulations. Two different spike trains, one with stochastic and the other with chaotic interspike intervals, are imposed on the system as subthreshold aperiodic signals. Information transmission is quantified by the cross correlation between the subthreshold input signal and the noise induced system response. A maximum is exhibited in the input-output correlation as a function of the noise amplitude. Numerical simulations with an electrochemical model are in excellent agreement with the experimental observations.

Copper Sulfate↗

PubMed2004

Parameter space reduction criteria to search for synchronization domains in coupled discrete systems.

Based on analytical considerations, we introduce criteria that enable us to encapsulate the parameter domains for which chaotic synchronization in linearly coupled map systems may be attained. Our aim is to provide means to readily determine parameter regions which preclude synchronization. This results in a significant reduction of parameter space that one needs to explore. Our findings hold for both identical and quasi-identical (small parameter mismatch) maps subjected to unidirectional and bidirectional coupling. As a testing ground we present numerical calculations for the logistic and cubic maps which validate the predictive capability of our approach. Our main contribution relies on the applicability of one of our criteria to experimental situations. Since in real life it is almost impossible to construct two truly identical systems, the results for quasi-identical maps are of particular relevance.

Journal Article↗

PubMed2004

Effects of noise near a homoclinic bifurcation in an electrochemical system.

The interaction of external noise with an electrochemical oscillator (anodic dissolution of iron) has been studied experimentally on both sides of the homoclinic bifurcation. In the oscillatory regime the regularity of the limit cycle behavior was destroyed with increasing noise amplitude until no periodicity was observable any more. In contrast, the response of the excitable state (fixed point regime) became more regular at intermediate noise levels.

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PubMed2004

Noise-aided synchronization of coupled chaotic electrochemical oscillators.

We report experimental and numerical results on noise-enhanced synchronization of two coupled chaotic oscillators. Enhanced synchronization is achieved through superimposing small-amplitude Gaussian noise on a common system parameter of the two chaotic oscillators. A resonancelike behavior is found: at an optimum level of noise, maximum synchronization is attained. The simulations show that the resonance behavior occurs with both identical and nonidentical oscillators. Noncommon (asymmetric and independent) noise does not enhance synchronization; common noise seems to enhance synchronization.

Journal Article↗

PubMed2004

Experimental evidence of coexisting periodic stochastic resonance and coherence resonance phenomena.

We report evidence of coexisting period stochastic resonance (PSR) and coherence resonance (CR) phenomena in an electrochemical cell. The anodic voltage (V) in the cell is chosen such that the anodic current (I) exhibits excitable fixed point behavior. Subsequently, the anodic voltage is modulated by an external perturbation that is a composite of a subthreshold periodic pulse signal and Gaussian white noise (GWN). As the amplitude of the GWN is increased, the regularity of the invoked dynamics is analyzed using normalized variance curve. The calculated resonance curve shows a double minima, implying the existence of two optimum noise levels where enhanced regularity of the induced spike sequence is detected. Numerical simulations corroborate experimental findings.

Journal Article↗

PubMed2003

Fingerprints of determinism in an apparently stochastic corrosion process.

We detect hints of determinism in an apparently stochastic corrosion problem. This experimental system has industrial relevance as it mimics the corrosion processes of pipelines transporting water, hydrocarbons, or other fuels to remote destinations. We subject this autonomous system to external periodic perturbations. Keeping the amplitude of the superimposed perturbations constant and varying the frequency, the system's response is analyzed. It reveals the presence of an optimal forcing frequency for which maximal response is achieved. These results are consistent with those for a deterministic system and indicate a classical resonance between the forcing signal and the autonomous dynamics. Numerical studies using a generic corrosion model are carried out to complement the experimental findings.

Journal Article↗

PubMed2003

Tracking fixed-point dynamics in an electrochemical system using delayed-feedback control.

We report numerical and experimental results indicating successful tracking of stabilized fixed points solutions in an electrochemical system. By applying a continuous delayed-feedback technique, periodic oscillations are suppressed via stabilization of a steady-state fixed point. Subsequently, using a simple continuation method involving an update term, this stabilized fixed point is tracked through the bifurcation diagram as a system parameter is slowly varied. Under the influence of this tracking protocol, inception of oscillatory dynamics is precluded over large parameter domains and through bifurcations.

Journal Article↗

PubMed2003

Experiments on coherence resonance: noisy precursors to Hopf bifurcations.

Experimental and numerical evidence of coherence resonance in an electrochemical system is reported. External noise with a Gaussian distribution is superimposed on the system when the anodic current is exhibiting stationary (fixed point) dynamics below a supercritical Hopf bifurcation. The amplitude of the added stochastic perturbations is increased monotonically and the induced oscillatory behavior is analyzed. It is observed, both in experiments and in simulations, that the regularity of the noise induced current oscillations reaches a maximum value for an optimum noise level. This is indicative of coherence resonance and can be explained with a mechanism based on noisy precursors to a Hopf bifurcation.

Journal Article↗

PubMed2002

Resonant forcing of a silent Hodgkin-Huxley neuron.

Dynamical behavior of a silent Hodgkin-Huxley neuron subjected to external periodic perturbations is investigated. Induced dynamics for this forced system, exhibit nonlinear resonance with respect to the forcing frequency. Within the U-shaped resonance curve, both regular (phase locked) and irregular spike sequences are invoked. For appropriate tuning frequencies, this simple system generates spike trains recordings similar to ones observed in actual experiments.

Journal Article↗

PubMed2002

Resonances via deterministic and stochastic perturbations: a comparative study.

We study periodic and coherence resonances invoked by aperiodic yet deterministic perturbations. Chaotic perturbations with varying levels of intrinsic correlations are superimposed parametrically on an excitable chemical model. This enables us to analyze the system response and characterize the induced resonances as a function of correlation in the perturbing signal. Using standard measures such as normalized variance and normalized number of peaks, dynamics for different deterministic signals are quantified and eventually compared to resonances invoked via stochastic perturbations.

Journal Article↗

PubMed2002

Suppressing spatiotemporal disorder via local perturbations in an electrochemical cell.

We report experimental results depicting suppression of complex spatiotemporal dynamics under the influence of local periodic stimulations. In an experimental electrochemical system, applying a continuous forcing signal to one of the sites in an array of eight coupled oscillators, the naturally complex behavior of the remaining seven electrodes can be converted to periodic responses. The oscillations remain periodic as long as the forcing is active and revert back to exhibiting chaotic dynamics after the control is switched off. These results can also be interpreted as experimental realization of "phase-synchronization" induced via local driving in an extended system. A possible relevance to the experimentally observed calcium wave patterns is pointed out.

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PubMed2002

Birhythmicity induced by perturbing an oscillating electrochemical system.

We describe the generation of new limit cycles in electrochemical systems under the influence of external periodic perturbations. For certain specific parameters of a nonharmonic forcing function, two coexisting periodic orbits can be generated from a single limit cycle observed in the unperturbed dynamics. This inception of birhythmicity (bistability) is observed in both simulations and actual experiments involving potentiostatic electrodissolution of copper in an acetate buffer.

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PubMed2001

Maintenance of transient chaos using a neural-network-assisted feedback control.

A stable period-3 orbit in the parametric vicinity of a chaotic attractor is destabilized using two distinct feedback strategies. This results in the inception and subsequent maintenance of the otherwise short-lived chaotic transients. Both the techniques employed are based on the exclusion of trajectories from the near vicinity of the open loop stable period-3 attractor; the first relies on the traditional proportional feedback method while the second one includes a predictive term enabling delimitation of exclusion zones for the system dynamics. The implementation of these strategies involves construction of appropriate reference models in the form of an artificial-neural-network approximator.

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PubMed2001

Resonance induced pacemakers: a new class of organizing centers for wave propagation in excitable media.

Propagation of waves in an extended excitable system is considered. It is shown that traveling wave fronts can be triggered and maintained via local periodic modulations of an appropriate system parameter. For a finite range of perturbation frequencies, this new class of pacemakers introduces spatiotemporal self-organization in an otherwise quiescent medium. Excitation waves of activity similar to those observed in heart tissue cultures and other biological preparations can emerge in the presence of these pacemakers.

Biological Clocks↗