基金Supported by the National t)asic Research Program of China (2009CB623403), the National High Technology Research and De velopment Program of China (2009AA034802), the National Natural Science Foundation of China (20706030, U0834004), the Science & Technology Support Program (Industry) of Jiangsu Province of China (BE2008141), the Natural Science Foundation of the Jiangsu Higher Education Institutions (09KJA530002) and 333 High-Level Personnel Training Project in Jiangsu Province. ** To whom correspondence should be addressed. E-mail: Xuehonggu@yahoo.com