1. Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette,
Indiana 47907, United States
2. Imaging Department, Merck Research Laboratories, Merck & Co., Inc., 770 Sumneytown Pike, West Point, Pennsylvania 19486, United States
3. Biometrics Research Department, Merck Research Laboratories, Merck & Co., Inc., 126 East Lincoln Avenue, Rahway, New Jersey 07065, United States