1. Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611-7200, LECO Corporation, 3000 Lakeview Avenue, St. Joseph, Michigan 49085-2396, INFICON, Inc., 6878 Santa Teresa Boulevard, San Jose, California 95119, and Department of Pharmacology, Medical University of South Carolina, 173 Ashley Avenue, BSB 303, Charleston, South Carolina 29425