1. Rochish Thaokar Department of Chemical Engg IIT Bombay rochish@che.iitb.ac.in www.che.iitb.ac.in/faculty.html rochish@che.iitb.ac.in Nanomachines: A DNA Miniplasmid Theoretical analysis of nanomachines and biological motors Intrinsic curvature and anisotropy for asymmetry in potential A Thermal ratchet can cause it move at around 50 nm/s A potential ratchet can make it move at 10 micros/s Switching times is Smoluchowski times and so very fast

2. Force Extension curves: DNA loops and deflections A semiflexible chain which is looped or non-straight can be expressed by a WLC model The persistence length is re-normalized The renormalisation is due to enthalpic effects The theory explains discrepancies in the force-extension curves of semiflexible polymers, looped and kinked DNAs and DNA protein complexes

3. Electrohydrodynamic instability in Microfluidics and Charged membranes and deformation of vesicles and dielectric drops Electrohydrodynamic instability in Perfect and Leaky dielectrics due to destabilising Maxwells stresses The long and short wave instability undergo supercritical bifurcation under flow due to nonlinear effects, making it useful in pumping fluids in microfluidics A charged membrane is predicted subcritical by the Debye Huckel theory while the the Poisson Boltzmann’s theory predicts supercritical bifurcation AC electrokinetics and drop deformation under electric field

4. Swimming at Low Reynolds number: Three celled animal Stability of Oscillatory flows over flexible surfaces A torus represents a force free torque free swimmer Swimming velocity proportional to rotational velocity and square of the slenderness Reversal of direction with the thickness of “Guide rails” A purely oscillatory instability found for time periodic flow of fluids over viscoelastic gels Theory and experiments show qualitative agreement The instability should be relevant in biological systems

5. Nanomachines: A DNA Miniplasmid ● Igor M Kulic, RochishThaokar, Helmut Schiessel, Europhysics Letters, 72,527-533, 200 ● I.M.Kulic, Rochish Thaokar, Helmut Schiessel, J Phys Cond Matt, 17, S3965, 2005 ● Force Extension curves: DNA loops and deflections ● Igor Kulic, H Mohrbach, V Lobaskin, Rochish Thaokar, Helmut Schiessel, Physical Review E, 72, 041905-1-5,2005 ● Igor Kulic, H Mohrbach, Rochish Thaokar, Helmut Schiessel, “Equation of state of a looped DNA”, Physical Review E (Under Review) ● Electrohydrodynamics ● Thaokar R, Kumaran V, Physics of Fluids, 17,084104, 2005 ● Thaokar, R. Kumaran V, Physical Review E,66,051913, 2003 ● Stability of Oscillatory flows over flexible surfaces ● Thaokar R, Shankar, V. and Kumaran V, EPJB, 23, 533, 2001 ● Thaokar, R. Kumaran V, Journal of Fluid Mechanics,66,051913, 2003 ● Thaokar, R., Kumaran V, EPJB, 41,135