the National Natural Science Foundation of China under Grant Nos.60403014; 60603034 (国家自然科学基金);the National High-Tech Research and Development Plan of China under Grant Nos.2006AA01Z159; 2006AA01Z177; 2007AA01Z140; 2007AA01Z178 (国家高技术研究发展计划(863));the National Basic Research Program of China under Grant No.2002CB312002 (国家重点基础研究发展计划(973));the Natural Science Foundation of Jiangsu Province of China under Grant No.BK2006712 (江苏省自然科学基金)