Funding for this research was provided by:
National Natural Science Foundation of China (11462011, 11732014)
Natural Science Foundation of Gansu Province (17JR5RA098)
Article History
Received: 8 May 2018
Accepted: 7 May 2019
First Online: 18 May 2019
Compliance with ethical standards
:
: We declare that we have no conflict of interest concerning the publication of this manuscript and the paper is in compliance with ethical standards.