1. Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8521, Japan
2. Department of Basic Science, Kyushu Institute of Technology, Kitakyushu, Fukuoka 804-8550, Japan
3. Institute of Physics, National Academy of Sciences of Ukraine, 46 Nauka Ave., Kyiv 03028, Ukraine