Department of Mathematics, Center for Mathematical and Complex Biological Systems, Center for Complex Biological Systems, University of California, Irvine, California, USA.|Department of Mathematics, Center for Mathematical and Complex Biological Systems, Center for Complex Biological Systems, University of California, Irvine, California, USA.|Department of Mathematics, Center for Mathematical and Complex Biological Systems, Center for Complex Biological Systems, University of California, Irvine, California, USA.|Department of Mathematics, Center for Mathematical and Complex Biological Systems, Center for Complex Biological Systems, University of California, Irvine, California, USA.|Department of Mathematics, Center for Mathematical and Complex Biological Systems, Center for Complex Biological Systems, University of California, Irvine, California, USA.|Department of Mathematics, Center for Mathematical and Complex Biological Systems, Center for Complex Biological Systems, University of California, Irvine, California, USA.