National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [51172085, 51102105, 11104088]; Key Project of Natural Science Foundation of Hubei ProvinceNatural Science Foundation of Hubei Province [2011CDA092]; Self-determined Research Funds of CCNU from the Colleges' Basic Research and Operation of MOE [CCNU12A01009]; Singapore National Research Foundation under NRFNational Research Foundation, Singapore [NRFRF2010-07]