Formation and evolution of scroll waves in photosensitive excitable media

Experimental and computational studies of the formation and evolution of sc roll waves in three-dimensional excitable media are presented. Scroll waves are initiated in the photosensitive Belousov-Zhabotinsky reaction by pertu rbing traveling waves transverse to their direction of propagation. Scroll rings are generated by perturbing circular waves, which expand or contract depending on the strength of an imposed excitability gradient and its direc tion relative to the rotational direction of the scroll wave. (C) 1998 Amer ican Institute of Physics. [S1054-1500(98)01104-5].