Funding for this research was provided by:
National Natural Science Foundation of China (61629101)
National Natural Science Foundation of China (61471067)
National Science and Technology major projects (2015ZX03002008)
Article History
Received: 10 November 2017
Accepted: 19 April 2018
First Online: 2 May 2018
Competing interests
: The authors declare that they have no competing interests.
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