Funding for this research was provided by:
Tianjin Municipal Health Bureau (15KG140)
Text and Data Mining valid from 2019-06-28
Received: 1 March 2019
Accepted: 7 June 2019
First Online: 28 June 2019
Ethics approval and consent to participate
: Ethical approval All procedures performed in studies involving human participants were in accordance with the ethical standerds of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendents or comparable ethical standards.
: Informed consent Informed consent was obtained from all individual participants included in the study.
: Conflict in interest All authers declare that they have no conflict of insterest. Ethical approval This article does not contain any studies with human participants performed by any of the authers.