1. Bioengineering Institute; Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, NY 10027
2. Department of Physiology, Columbia University, New York, NY 10027
3. Laboratoire de Biophysique, UER Sante Medecine Biologie Humaine, Universite Paris Nord, 74, rue Marcel Cachin, 93000 Bobigny, France