Supported by the National Natural Science Foundation of China under Grant Nos.60473075; 60773063 (国家自然科学基金);the Key Program National Natural Science Foundation of China under Grant No.60533110 (国家自然科学基金重点项目);the National Basic Research Program of China under Grant No.2006CB303000 (国家重点基础研究发展计划(973));the Program for New Century Excellent Talents in University (NCET) under Grant No.NCET-05-0333 (新世纪优秀人才支持计划)