Biomedical subjects

P Parmananda

Publications and source records attributed to P Parmananda.

27 records · Page 2Linked to original sources

PubMed2001

Controlling spatiotemporal chemical chaos using delayed feedback.

Control of chemical chaos in a spatially extended system mimicking CO oxidation on a Pt(110) single-crystal surface is achieved using delayed feedback techniques. For appropriate parameter values the uncontrolled model system exhibits both amplitude and phase turbulence. Superimposing a delayed feedback on the natural dynamics, suppression of spatiotemporal complexity is attained via stabilization of ordered states consisting of stable patterns.

Journal Article↗

PubMed2000

Human electroencephalogram induces transient coherence in excitable spatiotemporal chaos.

A time series from a human electroencephalogram (EEG) is used as a local perturbation to a reaction-diffusion model with spatiotemporal chaos. For certain finite ranges of amplitude and frequency it is observed that the strongly irregular perturbations can induce transient coherence in the chaotic system. This could be interpreted as "on-line" detection of an inherently correlated pattern embedded in the EEG.

Brain↗

PubMed2000

Noise-aided control of chaotic dynamics in a logistic map

Controlling chaos involves employing small perturbations to a control parameter, resulting in the stabilization of the system (naturally chaotic) on one of the infinite unstable periodic orbits embedded in the chaotic attractor. In this Brief Report we study the constructive role of external noise in increasing the efficiency of controlling chaos. Using a logistic map as an example, control of chaotic dynamics is achieved using a linear delayed-feedback strategy. Working in the subthreshold regime of control (where the value of control constant is less than the minimum value required to stabilize the period-1 target state), system dynamics in the presence of superimposed noise (system plus control plus noise) exhibit a resonance effect. Furthermore it is observed that the time required to reach the target state decreases appreciably in the presence of an optimum level of noise.

Journal Article↗

PubMed2000

Self-exciting chaos as a dynamic model for irregular neural spiking

We introduce a nonlinear dynamical system with self-exciting chaotic dynamics. Its interspike interval return map shows a noisy Poisson-like distribution. Spike sequences from different initial conditions are unrelated but possess the same mean frequency. In the presence of noisy perturbations, sequences started from different initial conditions synchronize. The features of the model are compared with experimental results for irregular spike sequences in neurons. Self-exciting chaos offers a mechanism for temporal coding of complex input signals.

Journal Article↗

PubMed1999

Stabilization of unstable steady states and periodic orbits in an electrochemical system using delayed-feedback control.

We report numerical and experimental results indicating successful stabilization of unstable steady states and periodic orbits in an electrochemical system. Applying a continuous delayed-feedback technique not only periodic and chaotic oscillations are suppressed via stabilization of steady-state solutions but also the chaotic dynamics can be converted to periodic behavior. In all cases the feedback perturbation vanishes as a target state is attained.

Journal Article↗

PubMed1996