Funding for this research was provided by:
National Natural Science Foundation of China (11471235; 11601052)
Chongqing Research Program of Basic Research and Frontier Technology (cstc2017jcyjBX0037)
Article History
Received: 19 December 2017
Accepted: 2 April 2018
First Online: 11 April 2018
Competing interests
: The authors declare that they have no competing interests.