1. Institute of Physics, Faculty of Mathematics and Physics, Charles University, Prague 2 121 16, Czech Republic
2. Department of Macromolecular Physics, Faculty of Mathematics and Physics, Charles University, Prague 8 180 00, Czech Republic
3. College of Chemistry, Chemical Engineering and Resource Utilization, Northeast Forestry University, Harbin 145040, China
4. School of Biological and Environmental Sciences, Kwansei Gakuin University, 1 Gakuen-Uegahara, Sanda, Hyogo 669-1330, Japan