Funding for this research was provided by:
The National Natural Science Foundation of China (61773004)
The Natural Science Foundation of Chongqing Municipal Education Commission (KJ1705138, KJ1705118)
The Natural Science Foundation of Chongqing (cstc2017jcyjAX0082)
Article History
Received: 14 December 2017
Accepted: 3 April 2018
First Online: 12 April 2018
Competing interests
: The authors declare that they have no competing interests.