Showing papers by "Michael E. Fisher published in 2006"

Static and dynamic critical behavior of a symmetrical binary fluid: a computer simulation.

Abstract: A symmetrical binary, A+B Lennard-Jones mixture is studied by a combination of semi-grand-canonical Monte Carlo (SGMC) and molecular dynamics (MD) methods near a liquid-liquid critical temperature Tc. Choosing equal chemical potentials for the two species, the SGMC switches identities (A→B→A) to generate well-equilibrated configurations of the system on the coexistence curve for T Tc. A finite-size scaling analysis of the concentration susceptibility above Tc and of the order parameter below Tc is performed, varying the number of particles from N=400 to 12 800. The data are fully compatible with the expected critical exponents of the three-dimensional Ising universality class. The equilibrium configurations from the SGMC runs are used as initial states for microcanonical MD runs, from which transport coefficients are extracted. Self-diffusion coefficients are obtained from the Einstein relation, while the interdiffusion coefficient and the shear viscosit...

Critical dynamics in a binary fluid: simulations and finite-size scaling.

Abstract: We report comprehensive simulations of the critical dynamics of a symmetric binary LennardJones mixture near its consolute point. The self-diffusion coefficient exhibits no detectable anomaly. The data for the shear viscosity and the mutual-diffusion coefficient are fully consistent with the asymptotic power laws and amplitudes predicted by renormalization-group and mode-coupling theories provided finite-size effects and the background contribution to the relevant Onsager coefficient are suitably accounted for. This resolves a controversy raised by recent molecular simulations.

Vectorial Loading of Processive Motor Proteins: Microtubule buckling experiment revisited

Abstract: Submitted for the MAR06 Meeting of The American Physical Society Vectorial Loading of Processive Motor Proteins: Microtubule buckling experiment revisited MICHAEL E. FISHER, Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742, YOUNG C. KIM, Laboratory of Chemical Physics, NIDDK, NIH, Bethesda, MD 20892 — Experiments on the motor protein kinesin by Howard and coworkers (1996) observed the buckling of partially clamped microtubules caused by bound motors responding to the induced parallel, Fx, and perpendicular, Fz, load components. To analyze such results, we have applied simple mechanochemical models for vectorial loads F = (Fx, Fy, Fz) by implementing a three-dimensional free-energy landscape formulation. An expression for the velocity, V (Fx, Fz; [ATP]), is obtained by fitting to the velocity and randomness data of Block and coworkers (2003) who imposed both resisting (Fx < 0) and assisting (Fx > 0) loads. While our results agree qualitatively with the buckling experiments, the analysis predicts that the velocity decreases under perpendicular loading (Fz > 0) contrary to the conclusion of Howard and coworkers. This suggests the possibility that the geometry of stressed microtubules might influence the motility of kinesin motors. [1] Y. C. Kim and M. E. Fisher, J. Phys.: Condens. Matter 17, S3821 (2005). Michael E. Fisher Institute for Physical Science and Technology, University of Maryland College Park, MD 20742 Date submitted: 09 Jan 2006 Electronic form version 1.4