Chemical pattern formation in three dimensions

Chemical pattern formation in three dimensions. Irving Epstein and his coworkers at Brandeis University in Waltham, Massachusetts, have shown that a chemical mechanism for producing patterns in two dimensions also works in three. Proposed in 1952 by Alan Turing, the mechanism relies on the competition between a slow-diffusing chemical that activates a reaction and a fast-diffusing chemical that inhibits the reaction. Nudging the reaction–diffusion system into a metastable state yields stable stripes, spots, and other periodic patterns. Turing's analysis and its subsequent experimental confirmation was for two-dimensional systems. Although computer simulations suggest the mechanism also operates in 3D, proving it in the lab is challenging: The extra spatial dimension makes it difficult to see patterns inside the medium. To meet that challenge, the Brandeis team used optical tomography to view a medium made up of aqueous droplets embedded in oil. Turing's model doesn't ordinarily apply to such an inhomogeneous medium....