Funding for this research was provided by:
National Natural Science Foundation of China (51479018)
Support Program for Longyuan Youth and Fundamental Research Funds for the Universities of Gansu Province (3132016335)
Article History
Received: 21 March 2019
Accepted: 25 September 2019
First Online: 10 October 2019
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.