Sommaire:

In this talk, I will illustrate how simple growth dynamics, when coupled with environmental properties, can lead to a diversity of self-organization phenomena in two experimental model systems: reaction waves propagating in disordered flows, and living microorganisms growing on viscous substrates. Resulting from the balance between molecular diffusion and nonlinear chemical kinetics, autocatalytic reactions can generate self-sustained fronts which propagate like progressive waves. I will show that in the presence of a disordered flow, the front fluctuations display scaling laws consistent with the universal behavior predicted by the Kardar-Parisi-Zhang stochastic growth model. Controlled by the mean flow amplitude, the system encompasses three distinct universality classes associated with different front morphologies and dynamical behaviors. In a second system, I will focus on mutual interactions between microbial growth and fluid flows. I will show that the metabolic activity of an expanding population of microorganisms can produce strong hydrodynamical flows when grown on top of a viscous medium. These flows in turn affect the growth dynamics, and can drive positive feedback phenomena such as accelerated propagation, fragmentation of the initial colony and the formation of growing microbial jets.

Pour plus d'informations, merci de contacter Merindol R.