[1] Columbia Univ, Dept Mech Engn, New York, NY 10027 USA
[2] Univ Calif Berkeley, Dept Mech Engn, Berkeley, CA 94720 USA
[3] Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA
[4] Naval Res Lab, Mat Sci & Technol Div, Washington, DC 20375 USA
[5] Lab Phys Sci, College Pk, MD 20740 USA
[6] Natl Inst Mat Sci, Tsukuba, Ibaraki, Japan
[7] Columbia Univ, Dept Chem, New York, NY 10027 USA
[8] Columbia Univ, Dept Phys, 538 W 120th St, New York, NY 10027 USA