1. Department of Physics, Graduate School of Science and Engineering Yokohama National University 79-5 Tokiwadai, Hodogaya, Yokohama Kanagawa 240-8501 Japan
2. Graduate School of Medicine Tohoku University 2-1 Seoryo-cho, Aoba-ku, Sendai Miyagi 980-8575 Japan
3. Department of Radiological Sciences International University of Health and Welfare 2006-1 Kitakanemaru, Otawara Tochigi 324–8501 Japan
4. Graduate School of Science, Research Center for Thermal and Entropic Science Osaka University Osaka 560-0043 Japan