Li, Ping
Feng, Meiqiang
Qin, Peige
Funding for this research was provided by:
the Beijing Natural Science Foundation (1163007)
Article History
Received: 17 January 2018
Accepted: 16 May 2018
First Online: 22 May 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.