Li, Ping
Feng, Meiqiang
Funding for this research was provided by:
the Beijing Natural Science Foundation of China (1163007)
Article History
Received: 8 December 2017
Accepted: 16 April 2018
First Online: 23 April 2018
Ethics approval and consent to participate
: Not applicable.
: The authors declare that there is no conflict of interest regarding the publication of this manuscript. The authors declare that they have no competing interests.
: Not applicable.