Neuronal impulses, cardiac activity, circadian rhythms, bacterial colonies, intricate patterns in nature, spiral galaxies, vortices in fluids, food chain in ecological systems, financial markets and business cycles, weather forecasting and reaction-diffusion systems, all have something in common. They belong to a wide class of nonlinear systems. Nonlinearity in the realm of dynamics has far-reaching significance in various processes occurring in the real world. Starting from the fields of chemistry, physics and biology, its roots extend into astronomy, engineering, ecology, economics and medicine.
Research Motivation :
Ventricular fibrilation and other not-completely-understood and abnormal cardiac activities has been a field of intensive research in the present century. Knowing the seriousness of these phenomenon and the unfathomableness and lack of external control of their characteristics and mechanism in the living creature, makes it imperative for us to find some other systems that show similar properties, but are far easier to handle. It has been realized that the heart is an excitable medium, that is, it has the ability to propagate signals through it without damping. Luckily for scientists, reaction diffusion systems are also another class of excitable media. It was found by researchers that these systems show similar spontaneous formation of wave-forms and vortices and response to external stimuli. We use these reaction-diffusion systems as laboratory models to generate and study the dynamics and control of various phenomena occurring in the more complex biological world. Theoretical analysis of the results and observations also reveal astonishing resemblance to problems in mathematics, physics and engineering.
Research activities at IIT Guwahati
Our current focus is the study of spiral waves and their three dimensional counterpart, scroll waves. In the heart, it is found that their occurrence leads to the rapid, unsynchronized contraction of the ventricles which thereby reduces the heartís ability to pump blood. This is expressed in the form of medical conditions such as arrhythmia and fibrillation, which may be fatal to cardiac health. So the understanding and control of these wave forms is of utmost importance. We use the Belousov Zhabotinsky reaction, to study the spiral and scroll waves and try to control them using external field gradients. Some of our recent experimental findings are listed below.
Unpinning of Scroll Waves Under the Influence of Thermal Gradient
Scroll waves can attach themselves to unexcitable obstacles and this sometimes highly elongates their life span. Hence the unpinning and annihilation of these vortices has attracted much attention over the past decades. In this work we study the influence of a thermal gradient on scroll waves pinned to inert obstacles, in the Belousov-Zhabotinsky reaction. Under a temperature gradient, scroll rings were seen to unpin from these obstacles, thus strikingly reducing their lifetimes. These results were also reproduced by numerical simulations using the Barkley model.
N. P. Das, D. Mahanta and S. Dutta, Phys. Rev. E, 90, 022916 (2014
Understanding excitable media: Experiment and theory
Physico-chemical instabilities in spatially extended systems : Effect of external fields