Funding for this research was provided by:
the National Natural Science Foundation of China (11771383, 11601095)
the Natural Science Foundation of Guangxi Province (2016GXNSFDA380019, 2014GXNSFFA118001)
Natural Science Foundation of Guangxi Province (2016GXNSFBA380185)
Article History
Received: 11 December 2018
Accepted: 1 July 2019
First Online: 12 July 2019
Competing interests
: The authors declare that they have no competing interests.