1. Graduate Program in Biomedical Engineering, The University of Western Ontario, London, Ontario N6A 5B9, Canada; Canadian Neutron Beam Center, Steacie Institute for Molecular Sciences, National Research Council, Chalk River, Ontario K0J 1J0, Canada; and Department of Physics and Astronomy and Department of Chemical and Biochemical Engineering, The University of Western Ontario, London, Ontario N6A 5B9, Canada