[1] Brown Univ, Sch Engn, Providence, RI 02912 USA
[2] US Army AMRDEC, Redstone Arsenal, Huntsville, AL USA
[3] Los Alamos Natl Lab, Ctr Integrated Nanotechnol, Los Alamos, NM USA
[4] Sandia Natl Labs, Ctr Integrated Nanotechnol, POB 5800, Albuquerque, NM 87185 USA