Funding for this research was provided by:
National Natural Science Foundation of China (61671472)
Natural Science Foundation of Jiangsu Province (BK20160079)
National Natural Science Foundation of China (61371123)
National Natural Science Foundation of China (91438115)
Article History
Received: 20 April 2018
Accepted: 30 July 2018
First Online: 16 August 2018
Competing interests
: The authors declare that they have no competing interests.
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