Funding for this research was provided by:
National Natural Science Foundation of China (81671248)
Beijing Municipal Science & Technology Commission (Z161100000216151)
Text and Data Mining valid from 2019-07-13
Received: 25 February 2019
Accepted: 9 July 2019
First Online: 13 July 2019
Compliance with Ethical Standards
: 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.
: The authors declare that they have no conflict of interest.