1. Institute of Biomedical Engineering, Tokyo Women's Medical College, 8-1 Kawadacho, Shinjuku, Tokyo 162, Japan, Department of Applied Electronic Engineering, Faculty of Science and Engineering, Tokyo Denki University, Ishizaka, Hatoyamacho, Hikigun, Saitama 350-03, Japan, and Department of Materials Science, and Research Institute for Biosciences, Science University of Tokyo, 2641 Yamazaki, Noda, Chiba 278, Japan