1. Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, Department of Mechanical Engineering, Clemson University, Clemson, South Carolina 29634, Department of Physics, University of Missouri-Kansas City, Kansas City, Missouri 64110, U.S. Naval Research Laboratory, Washington, D.C. 20375, and Department of Chemical Engineering, West Virginia University, Morgantown, West Virginia 26506