1. Department of Mathematics, University of Akron, Akron, OH 44325
2. Department of Mathematics, University of Pennsylvania, Philadelphia, PA 19104
3. Department of Biology, University of Pennsylvania, Philadelphia, PA 19104
4. Department of Mechanical Engineering, Johns Hopkins School of Medicine, Baltimore, MD 21205
5. Institute for NanoBioTechnology, Johns Hopkins School of Medicine, Baltimore, MD 21205
6. Center for Cell Dynamics, Johns Hopkins School of Medicine, Baltimore, MD 21205
7. Department of Biomedical Engineering, Binghamton University, SUNY, Binghamton, NY 13902