基金The authors gratefully acknowledge the financial support of the project from the National Natural Science Foundation of China (Grant No. 50021202, 59889203, 60271026 and 50329201); Science and Technology Ministry of China ( Grant No. 2003CB314701, 2003CB314706);Education Ministry of China, the Science and Technology Department of Guangdong Province; the Education Department of Guangdong Province;the Science and Technology Department of Guangzhou City.