Funding for this research was provided by:
National Natural Science Foundation of China (21675131)
Natural Science Foundation of Chongqing (CSTC-2015jcyjB50001)
Fundamental Research Funds for the Central Universities (XDJK2018D012)
Article History
Received: 23 October 2018
Accepted: 23 January 2019
First Online: 2 February 2019
Compliance with ethical standards
: The author(s) declare that they have no competing interests.