1. Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi-shi, Chiba 274, Japan
2. National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba-shi, Ibaraki 305, Japan
3. Department of Civil Engineering, Tohoku University, Aoba, Aramaki, Aoba-ku, Sendai-shi, Miyagi 980, Japan
4. Department of Dentistry, Ohu University, 31-1 Sankakudo, Tomita-cho, Koriyama-shi, Fukushima 963, Japan