The authors thank Drs. Chikahiro Miyake and Masahiro Tamoi for their help in preparing the
manuscript. We also thank Miss Naoko Hamamoto for her assistance. Research in our laboratories
has been supported by the ‘‘Research for the Future’’ programs (JSPS-RFTF97R16001 and JSPS-
00L01604) of the Japan Society for the Promotion of Science.