1. Department of Materials Technology, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba-shi, Chiba 263-8522, Japan; Department of Physics, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka-shi, Fukuoka 812-8581, Japan; Graduate School of Science and Engineering, Kagoshima University, Korimoto, kagoshima-shi, Kagoshima 890-0065, Japan; and Institute of Biomedical Engineering, Tokyo Women's Medical University, 8-1, Kawada-cho, Shinjyuku-ku, Tokyo 162-8666, Japan