1. Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
2. Institut Pprime, Université de Poitiers—CNRS—ENSMA, SP2MI, 86962 Futuroscope, France
3. Department of Mechanical Engineering, University of California, Santa Barbara, California 93106-5070, USA
4. Materials Department, University of California, Santa Barbara, California 93106-5050, USA