Lamellar structures and self-replicating spots in a reaction-diffusion system

Experiments on a ferrocyanide-iodate-sulfite reaction-diffusion system reveal several different planar spatial patterns: stationary lamellae arising from a transverse front instability and a front interaction; spot patterns that undergo a continuous process of growth through replication and death through overcrowding; waves with a repulsive front interaction; and conventional excitable waves that annihilate upon collision. The patterns form in a thin gel layer that is in contact with a continuously fed stirred reservoir. Lamellae are observed in both multistable and monostable regimes of the gel layer, while the self-replicating spots are found in a monostable regime. Numerical simulations on a one-dimensional, four-species model of the ferrocyanide-iodate-sulfite reaction describe the observed front interaction phenomena and some aspects of the bifurcation sequences observed in the laboratory experiments.