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SUMMARY:Bacteria near Surfaces: swimming\, diffusion and stochastic resona
 nce - Rodrigo Soto\,  Universidad de Chile
DTSTART:20121107T130000Z
DTEND:20121107T140000Z
UID:TALK41473@talks.cam.ac.uk
CONTACT:Aurelia Honerkamp-Smith
DESCRIPTION:Bacteria\, like E. coli\, when placed in confined environments
  are known to be attracted to solid surfaces and swim in contact with them
  for long times. In this talk\, several aspects related to the motion of b
 acteria near surfaces are considered. First\, a simple swimmer model will 
 be introduced. It reproduces some features of bacteria-surface interaction
  including the observed circular motion. It will be shown that a purely hy
 drodynamic model is sufficient to take account of the attraction and align
 ment parallel to the walls but and extra\, non-hydrodynamic interaction\, 
 is needed to obtain the persistent motion. Second\, the induced diffusion 
 of tracers in presence of a bacterial bath is studied. A kinetic theory co
 mbined with a hydrodynamic approach allow us to compute the resulting diff
 usivity. It is shown that close to surfaces\, the induced diffusivity is e
 nhanced as a result of the smaller swimming efficiency of bacteria. Finall
 y\, the case of swimmers placed in an oscillatory shear flow is analyzed. 
 As a result of flow fluctuations\, the coarse grained displacement  of a s
 wimmer in the vorticity direction is maximized for a finite fluctuation in
 tensity. This phenomenon corresponds to an example of stochastic resonance
 .
LOCATION:MR11\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
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