Funding for this research was provided by:
National Natural Science Foundation of China (81502453)
Natural Science Foundation of Beijing Municipality (7162057)
Article History
Received: 16 August 2018
Accepted: 14 December 2018
First Online: 2 January 2019
Compliance with ethical standards
:
: The authors declare no potential conflicts of interest.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: Informed consent was obtained from all individual participants included in the study.