1. a Institute of Biomedical Engineering, Tokyo Women's Medical College, 8-1, Kawada-cho, Shinjuku-ku, Tokyo 162, Japan
2. b Department of Chemical Engineering, Waseda University, 3-4-1, Ohkubo, Shinjuku-ku, Tokyo 169, Japan
3. c Institute of Biomedical Engineering, Tokyo Women's Medical College, 8-1, Kawada-cho, Shinjuku-ku, Tokyo 162, Japan
4. d Institute of Biomedical Engineering, Tokyo Women's Medical College, 8-1, Kawada-cho, Shinjuku-ku, Tokyo 162, Japan