Funding for this research was provided by:
National Natural Science Foundation of China (61472414)
National Natural Science Foundation of China (61772514)
National Natural Science Foundation of China (61602061)
Article History
Received: 20 April 2018
Accepted: 7 September 2018
First Online: 25 September 2018
Competing interests
: The authors declare that they have no competing interests.
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