[1] Univ Calif Berkeley, Appl Sci & Technol Grad Grp, Berkeley, CA 94720 USA
[2] Lawrence Berkeley Natl Lab, Natl Ctr Electron Microscopy, Berkeley, CA 94720 USA
[3] Los Alamos Natl Lab, Los Alamos, NM 87545 USA
[4] Univ Calif Berkeley, Dept Mech Engn, Berkeley, CA 94720 USA