1. Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
2. NTT Device Technology Laboratories, NTT Corporation, Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-0198, Japan
3. Science and Core Technology Laboratories, NTT Corporation, Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-0198, Japan