The project was supported by the National Nature Science Foundation of China (71271042, 11361019), the Program to Sponsor Teams for Innovation in the Construction of Talent Highlands in Guangxi Institutions of Higher Learning ((2011)47), the Fundamental Research Funds for the Central Universities of China (ZYGX2012J119), the Guangxi Provincial Natural Science Foundation of China (2014GXNSFBA118006, 2013GXNSFDA019001), the Scientific Research Fund of Guangxi Provincial Education Department (2013YB104, YB2014150) and the Science Foundation of Hengyang Normal University (14B30).