1. Institut für Physik, Universität Augsburg, Universitätsstrasse 1, 86159 Augsburg, Germany
2. Department of Physics, Simon Fraser University, 8888 University Drive, V5A 1S6 Burnaby, BC, Canada
3. Department of Mechanical Engineering, Boston University, 110 Cummington Street, Boston, Massachusetts 02215
4. Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, V5A 1S6 Burnaby, BC, Canada