Biomedical subjects

T Passot

Publications and source records attributed to T Passot.

9 recordsLinked to original sources

PubMed2004

Hydrodynamics of bacterial colonies: phase diagrams.

We present numerical simulations of a recent hydrodynamic model describing the growth of bacterial colonies on agar plates. We show that this model is able to qualitatively reproduce experimentally observed phase diagrams, which relate a colony shape to the initial quantity of nutrients on the plate and the initial wetness of the agar. We also discuss the principal features resulting from the interplay between hydrodynamic motions and colony growth, as described by our model.

Algorithms↗

PubMed2003

Hydrodynamics of bacterial colonies: a model.

We propose a hydrodynamic model for the evolution of bacterial colonies growing on soft agar plates. This model consists of reaction-diffusion equations for the concentrations of nutrients, water, and bacteria, coupled to a single hydrodynamic equation for the velocity field of the bacteria-water mixture. It captures the dynamics inside the colony as well as on its boundary and allows us to identify a mechanism for collective motion towards fresh nutrients, which, in its modeling aspects, is similar to classical chemotaxis. As shown in numerical simulations, our model reproduces both usual colony shapes and typical hydrodynamic motions, such as the whirls and jets recently observed in wet colonies of Bacillus subtilis. The approach presented here could be extended to different experimental situations and provides a general framework for the use of advection-reaction-diffusion equations in modeling bacterial colonies.

Agar↗

PubMed2000

Phase dynamics of nearly stationary patterns in activator-inhibitor systems

The slow dynamics of nearly stationary patterns in a FitzHugh-Nagumo model are studied using a phase dynamics approach. A Cross-Newell phase equation describing slow and weak modulations of periodic stationary solutions is derived. The derivation applies to the bistable, excitable, and Turing unstable regimes. In the bistable case stability thresholds are obtained for the Eckhaus and zigzag instabilities and for the transition to traveling waves. Neutral stability curves demonstrate the destabilization of stationary planar patterns at low wave numbers to zigzag and traveling modes. Numerical solutions of the model system support the theoretical findings.

Journal Article↗

PubMed1999

Effect of a random noise on scaling laws of finite Prandtl number rotating convection near threshold.

A generalized Swift-Hohenberg model including a weak random forcing, viewed as mimicking the intrinsic source of noise due to boundary defects, is used to reproduce the experimentally observed power-law variation of the correlation length of rotating convection patterns as a function of the stress parameter near threshold, and to demonstrate the sensitivity of the exponent to the amplitude of the superimposed random noise. The scaling properties of rotating convection near threshold are thus conjectured to be nonuniversal.

Journal Article↗

PubMed1994