1. Department of Metallurgical & Materials Engineering, Colorado School of Mines, 1500 Illinois St., Golden, Colorado 80401
2. Mechanical Engineering Department, Stanford University, 440 Escondido Mall, Stanford, California 94305
3. National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, Colorado 80401
4. and Department of Physics, Colorado School of Mines, 1523 Illinois Street, Golden, Colorado 80401