Quantitative optical tomography of chemical waves and their organizing centers.

Interference from topological, chemical and biological analogies led to the guess that a wide variety of homogeneous three-dimensional materials characterized by "excitability" might support persistent particle-like "organizing centers." These are vortex filaments, typically rings, around which excitation fronts circulate in the uniform medium. Robust organizing centers were recently discovered numerically in several cases, motivating a search for them in nature. But if a candidate were observed there would still be no way to examine it for the expected topological intricacies. To solve this problem we designed and constructed a hybrid chemical/optical/computational instrument using the familiar principles of tomography by filtered backprojection. We demonstrate here that it can quantitatively resolve chemical vortex filaments in a new excitable medium fashioned for the purpose. The next step, not described here, is to use the light sensitivity of this medium to contrive initial conditions from which topologically exotic organizing centers would arise and possibly persist. (c) 1996 American Institute of Physics.