Wave propagation in a photosensitive, subexcitable Belousov-Zhabotinsky medium is made possible by periodic modulation of a homogeneous illumination field. The propagation can be understood in terms of an interplay between the radial expansion of the wave and the motion of its free ends as the excitability varies periodically. This description leads to a simple kinematic analysis that provides ...

Chemical waves are initiated in an excitable medium by resonance with local periodic forcing of the excitability. Experiments are carried out with a photosensitive Belousov-Zhabotinsky medium, in which the excitability is varied according to the intensity of the imposed illumination. Complex resonance patterns are exhibited as a function of the amplitude and frequency of the forcing. Local reso...

We discuss a novel type of spatiotemporal pattern that can be observed in subexcitable media when coupled to a thermal environment. These patterns have been recently observed in several different types of systems: a subexcitable photosensitive Belousov-Zhabotinsky reaction, hippocampal slices of rat brains, and astrocyte syncytium. In this paper, we introduce the basic concepts of subexcitable ...

We describe a novel nucleation mechanism of scroll rings in three-dimensional reaction-diffusion systems with anomalous dispersion. The vortices form after the collision of two spherical wave fronts from a third, trailing wave that only partially annihilates in the wake of its predecessor. Depending on the relative positions of the three relevant wave sources, one obtains untwisted or twisted s...