Funding for this research was provided by:
National Natural Science Foundation of China (81670662)
Received: 19 April 2018
Accepted: 6 May 2019
First Online: 16 May 2019
Ethics approval and consent to participate
: Ethics approval: Not applicableThe study protocol was based on the principles of the Declaration of Helsinki. Written informed consent was obtained from all participants.
: Written informed consent to publish was obtained from all participants.
: The authors declare that they have no competing interests.
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