1. National Institute for Research in Inorganic Materials, 1-1, Namiki, Tsukuba, Ibaraki 305-0044, Japan
2. Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku Tokyo 113-003, Japan
3. Nitta Gelatin Inc., 2-22 Futamata, Yao, Osaka 581-0024, Japan