Funding for this research was provided by:
the National Natural Science Foundation of China (71273229)
the program of Zhejiang Natural Science Foundation (LQ12G03015)
Received: 11 June 2017
Accepted: 27 July 2018
First Online: 6 August 2018
Ethics approval and consent to participate
: The oral informed consent was obtained from each participant and Zhejiang University Ethical Committee confirmed this form of consent and approved this survey (NO.ZGL2016081). All subjects joined voluntarily and were told that they had right to withdraw from this study at any time. The questionnaires were filled out by participants anonymously.
: Not applicable.
: The authors declare that they have no competing interests.
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