Noise sustained waves in subexcitable media: From chemical waves to brain waves.

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 media, describe recent experimental observations in chemistry and neurophysiology, and put these observation into context with computer simulations. (c) 1998 American Institute of Physics.

Transient turing structures in a gradient-free closed system.

Transient, symmetry-breaking, spatial patterns were obtained in a closed, gradient-free, aqueous medium containing chlorine dioxide, iodine, malonic acid, and starch at 4 degrees to 5 degrees C. The conditions under which these Turing-type structures appear can be accurately predicted from a simple mathematical model of the system. The patterns, which consist of spots, stripes, or both spots and stripes, require about 25 minutes to form and remain stationary for 10 to 30 minutes.