Spring 2020 Seminar

Talks are 12:00 noon on Thursdays in Olin Science 268, unless otherwise noted.

February 6, 2020

Julianna_Detrick Casey_Miller John_Buggeln

Active Mixing of Swimming Bacteria in Hyperbolic and Vortex Flows

John Buggeln '20, Julianna Detrick'21, Casey Miller '21, Bucknell University

Abstract:We present experiments on the effects of imposed, laminar fluid flows on the motion of active (self-propelled) tracers. The active tracers are bacillus subtilis bacteria, including a wild-type strain and two variations, one with the GFP mutation and one with a smooth-swimming mutation for which the microbe doesn't tumble. The imposed flows are simple hyperbolic flows and vortex chain flows. We test theories that predict ``swimming invariant manifolds'' (SwIMs) that act as one-way barriers that impede the motion of active tracers in the flow. For the hyperbolic flows, we investigate the structure of the barriers as a function of the imposed flow magnitude. For the vortex flow, we investigate the effects of SwIMs that encircle the vortex centers. We also test predictions of chaotic trajectories of smooth-swimming tracers for time-independent, two-dimensional flows.

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February 20, 2020

Will_Williams

How do we know what’s going on in the world of the super super super small: Testing QED in neutral beryllium-9

William Williams, Smith College

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January 23, 2020

Blake Pantoja

Discovering from Planets to Low-Mass Stars Using Radial Velocities and Direct Imaging.

Blake Pantoja, Bucknell University

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