PhD Abstract: 

We investigate bacterial chemotactic strategies using run-tumble and run-reverse-flick motility patterns. The former is typically observed in enteric bacteria such as Escherichia coli and Salmonella, and the latter is observed in marine bacteria Vibrio alginolyticus and possibly exhibited by other polar flagellated species. It is shown that while the 3-step motility pattern helps the bacterium to localize near hot spots, an exploitative behavior, its exploratory potential in short times can be significantly enhanced by employing a non-Poissonian regulation scheme for its flagellar motor switches.

We also explored the interaction of polymer solutions with Vibrio alginolyticus. As the polymer concentrations increase, the flick of Vibrio alginolyticus is suppressed by the surrounding media. Two theoretic models are developed to explain the interaction, which confirms non-Poissonian property of Vibrio alginolyticus swimming interval distribution and reveals that motor fluctuations can be modeled with a damped harmonic oscillator. The motor fluctuations are coupled with the viscoelastic environment so that a resonance-like effect can be observed. On the other hand, we only see the decreasing of swimming speed with increasing polymer concentration, which is different from the non-monotonic results of E. coli observed by Martinez et al. The swimming speed vs. concentration of polymer solutions shows a scaling law.

http://d-scholarship.pitt.edu/cgi/users/home?screen=EPrint::View&eprintid=34479.

Publications

LaAlO₃/SrTiO₃: a tale of two magnetisms
Yun-Yi Pai, Anthony Tylan-Tyler, Patrick Irvin, Jeremy Levy
arxiv:1610.00789 (2016)

Physics of SrTiO₃-based heterostructures and nanostructures: a review
Yun-Yi Pai, Anthony Tylan-Tyler, Patrick Irvin, Jeremy Levy
Rep. Prog. Phys. 81 036503 (2018)

One-Dimensional Nature of Pairing and Superconductivity at the LaAlO₃/SrTiO₃ Interface
Yun-Yi Pai, Hyungwoo Lee, Jung-Woo Lee, Anil Annadi, Guanglei Cheng, Shicheng Lu, Michelle Tomczyk, Mengchen Huang, Chang-Beom Eom, Patrick Irvin, Jeremy Levy
Phys. Rev. Lett. 120, 147001 (2018)