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Department of Physics
University of Arizona
Abstract-
Swimming bacteria ( Bacillus subtilis ) exhibit remarkably varied
dynamics; new features arise as the concentration and total number
of interacting individuals increases. Topics covered will include 1) the
observed distribution of swimming velocities of individual cells,
2) binary interactions, 3) influence of bounding geometry on the velocity
probability densities for speed and direction of swimming,
4) consumption/supply - driven bioconvection patterns, and 5) chaotic
dynamics of populations at high volume fraction, where the
trajectories of inert tracers include intermittent "trapping", long
flights, and transport exponents reminiscent of the superdiffusion found
in "2-d turbulence". Approaches to modeling will be introduced, for:
pair interactions, bioconvection, the origin of coherent domains leading
to "2-d turbulence", high collective velocities when volume fractions
approach close-packed, and the anomaly of a semblance of turbulence at
nominally low Reynolds number.
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