1. Nano-Materials Research Center, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, Korea, Department of Materials Science and Engineering, Korea University, Seoul 136-713, Korea, Division of Molecular Imaging, Samsung Medical Center, Seoul 135-710, Korea, Division of Metrology for Quality of Life, Korea Research Institute of Standard and Science, P.O. Box 102, Youseong, Daejeon 305-600, Korea, and Department of Radiology and Institute for Radiological Imaging Science,...