Funding for this research was provided by:
National Natural Science Foundation of China (NO.31470994)
National Natural Science Foundation of China (NO.31400894)
Beijing Social Science Fund (No. 15JYB016)
Article History
First Online: 7 May 2018
Compliance with Ethical Standards
:
: The authors declare that they have no conflict of interest.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of Peking University First Hospital 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.