[1] Los Alamos National Laboratory, Theoretical Division, Center for Nonlinear Studies, Los Alamos, NM 87545
[2] Dept. of Mathematics and Statistics, University of Massachusetts, Lederle Graduate Research Tower, Amherst, MA 01003-4515
[3] Department of Chemical Engineering, Princeton University, 6 Olden Street, Princeton, NJ 08544
[4] Deparment of Mathematics, University of California, Irvine, CA 92697-3875