1. a Fuji Xerox Co. Ltd., Corporate Research Group, Corporate Research Laboratory , 430 Sakai, Nakai-machi, Ashigarakami-gun, Kanagawa, 259-0157, Japan
2. b Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Department of Bioengineering , 4259-B-40 Nagatsuta-cho, Midori-ku, Yokohama, 226-8501, Japan