1. Department of Precision Engineering, Faculty of Engineering, Kyoto University, Yoshida-honmachi, Sakyoku, Kyoto, 606–01, Japan
2. Faculty of Medicine, Kyoto University, Yoshida-Konoecho, Sakyoku, Kyoto, 606–01, Japan
3. Electronic Research Laboratory, Kobe Steel, Ltd., Nishiku, Kobe, 651–22, Japan
4. Deptartment of Biomaterials/Handicap Research, Institute for Surgical Sciences, Goteborg University, Medicinaregatan 8, S-413 90 Gothenburg, Sweden