[1] Cornell Univ, Dept Math, Ithaca, NY 14853 USA
[2] Univ Calif Berkeley, Dept Math, Berkeley, CA 94720 USA
[3] Div Engn & Appl Sci, Cambridge, MA 02138 USA
[4] Prot Pathways, Woodland Hills, CA USA
[5] Univ Calif Los Angeles, Dept Math, Los Angeles, CA 90024 USA