1. Graduate School of Information Science and Technology, The University of Hokkaido, N-14 W-9, Kita-ku, Sapporo 060-0814, Furuuchi Chemical Corporation, 6-17-17 Minami-oi, Shinagawa-ku, Tokyo 140-0013, and Biomaterials Center, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan