1. School of Physics University of Electronic Science and Technology of China Chengdu 611713 China
2. Department of Physics University of Alberta Edmonton AB T6G 2E1 Canada
3. Wacker Chair of Macromolecular Chemistry Technical University of Munich Lichtenbergstraße 4 85747 Garching bei München Germany
4. Department of Experimental Oncology Cross Cancer Institute 11560 Univ. Ave Edmonton AB T6G 1Z2 Canada