1. Center for Interdisciplinary Magnetic Resonance, National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310
2. Amoco Research Center, Naperville, Illinois 60566 and Research Resources Center (M/C 937), University of Illinois at Chicago, 901 South Wolcott Avenue, Room E102 MSB, Chicago, Illinois 60612-7341