1. Department of Physics, Michigan Technological University, Houghton, MI, 49931, USA
2. Department of Mechanical Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106-5070, USA
3. DEVCOM Army Research Laboratory, Weapons, and Materials Research Directorate, ATTN: FCDD-RLW, Aberdeen Proving Ground, Aberdeen, Maryland 21005-5069, USA