NSC Seminar Two talks: Geometry and statistics in turbulence, Nonlinear dynamics in invertebrate phototransduction
 Date

20060324 15:00 
20060324 16:30
 Place
 RIES N502

Speaker/Organizer
 Alain Pumir (Institut Non Lineaire de Nice)

 Geometry and statistics in turbulenceVelocity fluctuations in hydrodynamic turbulent flows have a non trivial structure, characterized by the correlations of the velocity gradient tensor. I will discuss a phenomenological model, incorporating the main known features of hydrodynamic turbulence, aimed at predicting the structure of the velocity gradient tensor, M, coarsegrained at scale r. This model is formulated as a set of stochastic differential equations.I will discuss the origin of this model, and describe the solutions obtained by using a semiclassical approach.Nonlinear dynamics in invertebrate phototransductionPhototransduction is the process whereby a photon leads to the generation of an electrical current in a retina’s cell. In invertebrate (flies), one photon leads to a wellcharacterized electric pulse. I will discuss the mechanism leading to the generation of this current. Due to Calcium mediated feedbacks, the process is highly nonlinear. Fluctuations also play a key role, due to the small number of key molecular species participating in the signal transduction.
http://wwwnsc.es.hokudai.ac.jp/seminar/seminar.html