1. Contribution from the Neutron Science Research Center, Japan Atomic Energy Research Institute, 8-1 Umemidai, Kizu-cho, Souraku-gun, Kyoto 619-0215, Japan, Institute of Molecular and Cellular Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan, and Graduate School of Information Science, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma, Nara 630-0101, Japan