Funding for this research was provided by:
National Natural Science Foundation of China (61763002)
Guangxi Natural Science Foundation (2015GXNSFBA139249)
the Joint special of Shandong Natural Science Foundation of the China Republic (ZR2017LF020)
Received: 16 February 2018
Accepted: 18 April 2018
First Online: 8 May 2018
: The authors declare that they have no competing interests.
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