Dynamics of fronts in
chemical and bacterial media:
If youÕve seen one
front, youÕve seen them all
Abstract
Self-propagating reaction
fronts occur in many chemical and physical systems possessing two key
ingredients: a reactive medium (for example a fuel-air mixture in the case of
flames) and an autocatalyst that is a product of the reaction that also
accelerates the reaction (for example thermal energy in the case of
flames). Self-propagation occurs
when the autocatalyst diffuses into the reactive medium, initiating reaction
and creating more autocatalyst.
This enables reaction-diffusion fronts to propagate at steady rates far
from any initiation site. In
addition to flames, propagating fronts have been observed in aqueous reactions,
free-radical initiated polymerization processes and even propagating fronts of
motile bacteria such as E. coli.
This talk will focus on a comparison of the dynamics of these four
different types of fronts including propagation rates, extinction conditions
and instability mechanisms. Our
research has shown that despite the disparate nature of the reactants and
autocatalysts in these four systems, remarkably similar dynamical behavior is
observed since the underlying driving mechanisms for propagation are
similar. The key role of loss
mechanisms (heat, chemical species or cell death) and differential diffusion of
reactant and autocatalyst ("Lewis number") is demonstrated.