US Depart ment of Energy Grants(DE-FG05-88ER40407,DE-FG02-96ER40983,DE-FG02-95ER40093);Contract(W-7405-ENG48,DE-AC03-76SF00098,DE-AC07-76ID01570);The Work at Tsinghua University was supported by National Natural Science Foundation of China(10575057,10775078);Major State Basic Research Development Program of China(2007CB815005)~~