1. Institute
for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
2. Frontier
Fiber Technology and Science, Graduate School of Engineering, University of Fukui, 3-9-1 Bukyo, Fukui, Fukui, 910-8507, Japan
3. Korea Atomic Energy Research Institute, Daejeon, 1045 Daedeok-daero, Yuseong-gu, 305-353, Korea
4. Department
of Bioengineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan