1. Contribution from the Department of Chemistry and Laboratory for Biochemical and Genetic Engineering, Rice University, P.O. Box 1892 MS-60, Houston, Texas 77251-1892, TDA Research, 12345 West 52nd Avenue, Wheat Ridge, Colorado 80033, NanoTechnologies of Texas, P.O. Box 2441, Bellaire, Texas 77402-2441, and Research Reactor Facility, University of MissouriColumbia, Columbia, Missouri 65211