基金Supported by the National Basic Research Program under Grant No 2006CB921907, the National Natural Science Foundation of China under Grant Nos 10774139 and 60621064, Knowledge Innovation Project of Chinese Academy of Sciences, the Program for New Century Excellent Talents in University, International Cooperation Program of Chinese Academy of Sciences, and Ministry of Science and Technology of China, the Foundation for Author of National Excellent Doctoral Dissertation of China under Grant 200729, and China Postdoctoral Science Foundation under Grant No 20070420736.