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Indiana University Bloomington

Sima Setayeshgar

Sima Setayeshgar Associate Professor
Biophysics

B.S., Massachusetts Institute of Technology (1990)
Ph.D., California Institute of Technology (1998)

Phone: Swain West 155 (812)855-9127
Email: simas at indiana.edu

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I am a physicist with interests at the interface between physics and biology on scales ranging from the molecular and cellular to the macroscopic. Powerful experimental methods, such as genetic tools, two-photon and fluorescence microscopy have made biological systems an exciting area for quantitative research. In approaching such problems, a physicist must contend with the sheer complexity of biological systems and the limitations arising from the difficulties in carrying out reproducible experiments. The fact that problems and their methods of solution are common across different biological systems - for example, phototransduction in the retina and chemotactic signal transduction in E. coli - points to the existence of organizing principles, making this quest especially rewarding.

Cellular biophysics: The cell's biological functions - growth, differentiation and the generation of specialized properties - are carried out by "networks" of biochemical reactions. I am interested in better understanding the limits set by basic physical principles, such as the role of thermal and diffusive noise, on the accuracy of biochemical signaling. Comparison of theoretical limits with recent experiments on gene expression and chemotactic response in E. coli suggests that for these crucial tasks the cell's performance approaches limits set by physical laws.

Sustained nonequilibrium systems: Nonlinear processes leading to instabilities in systems far from equilibrium are responsible for the spatiotemporal phenomena that occur all around us, from fluids to chemical and biological systems, with striking similarities between macroscopic patterns in systems with different microscopic descriptions. Most of the observed patterns in nature are nonequilibrium, dissipative structures which cannot be understood in terms of minimizing a free energy, unlike their equilibrium counterparts, such as crystals. Nonetheless, common mechanisms underlying the formation of such patterns can be identified -- linear instability, slaving to marginal modes near onset, and nonlinear saturation. Theoretical approaches are focused on understanding generic properties of pattern-forming systems by building simple mathematical models of controlled and reproducible experimental systems, such as Rayleigh-Benard convection or spiral waves in chemical systems, with the hope of extending these findings to more complicated systems, such as the climate or the heart. There is growing experimental evidence that the formation and subsequent breakdown of spiral waves of electric potential in the heart, leading to a spatiotemporally disorganized state of electrical excitation, is related to fatal arrhythmias. I am interested in applying analytical and numerical tools to better understanding scroll wave instabilities in physiologically realistic domains.


Selected Publications

  • S. Setayeshgar and M. C. Cross, "Turing instability in a boundary-fed system," Physical Review E 58, 4485 (1998).
  • S. Setayeshgar and M. C. Cross, "Numerical bifurcation diagram for the two dimensional boundary-fed chlorine-dioxide-iodine-malonic acid system," Physical Review E 59, 4258 (1998).
  • S. Setayeshgar and A. J. Bernoff, "Scroll wave dynamics in the presence of slowly varying anisotropy," Physical Review Letters 88, 028101 (2002).
  • S. Setayeshgar, C. W. Gear, H. G. Othmer, and I. G. Kevrekidis,"Application of coarse integration to bacterial chemotaxis," to appear in Multiscale Modeling and Simulation: Special Issue on Material and Life Sciences, physics/0308040.
  • W. Bialek and S. Setayeshgar, "Physical limits to biochemical signaling," submitted to Proceedings of the National Academy of Sciences, USA, physics/0301001.