Internal Seminar: Bandi Unit and Rokhsar Unit

Join us for October's third Internal Seminar Series on October 30, from 17:00 to 18:00 in C700 (Lab3). This month's third seminar features the Collective Interactions Unit (Mahesh Bandi) and the Molecular Genetics Unit (Daniel Rokhsar).

Collective Interactions Unit (Mahesh Bandi)

Speaker : Venkata Sathish Akella

Title : Hydrodynamics of a self-propelled c-boat

Abstract : In the present work, we attempt to understand the hydrodynamics associated with a c-boat placed at the air-water interface. A c-boat is a disc-shaped agarose gel tablet with the water in the gel matrix replaced by camphoric acid. Camphoric acid spreads across the air-water interface due to the interfacial tension between camphoric acid and water. When the c-boat is held fixed at the air-water interface, the spread radius grows as power law in time with a scaling exponent of 1/2, in agreement with observed scaling for the time-dependent spread radius for volatile substances at the air-water interface. As the camphoric acid spreads, shear stresses caused by the Marangoni forces lead to the development of boundary layer at the air-water interface. Scaling analysis using boundary layer approximation suggests that the fluid velocity in the boundary layer scales as a power law in distance with a scaling exponent of -3/5 . When the c-boat is let go at the air-water interface, it is spontaneously set in motion by the solutal Marangoni forces. Moreover, we observe three different modes of motion, namely continuous, harmonic and periodic, due to the dissolution of camphoric acid. We explain these modes in terms of ratio of two velocity scales, U_B and U_M , where U_B is the c-boat's velocity scale and U_M is the Marangoni velocity scale. The continuous, harmonic and periodic motions are observed when U_B/U_M > 1, U_B/U_M ~ 1 and U_B/U_M < 1 respectively. Experimentally, the ratio of the velocity scales is varied by changing the interfacial tension of the air-water interface using Sodium Dodecyl Sulfate (SDS).

Molecular Genetics Unit (Daniel Rokhsar)

Speaker : Oleg Simakov

Title : Metazoan genomics and the origins of animal complexity

Abstract : Recently, many animal genomes have been sequenced and analyzed providing an unprecedented insight into how animal life evolved. The analyses shed light onto the genomic correlates of morphological transitions in animal evolution. In the presentation, I will generally discuss those findings and their implications for our understanding of origin of novelty. I will focus on the findings from the octopus genome as well as on our most recent work on the genomes of two acorn worms, shedding light on our wormy ancestors and the slimy origins of the mouth.