Funding for this research was provided by:
Guangzhou Science, Technology and Innovation Commission (201510010220)
Text and Data Mining valid from 2019-01-21
Received: 11 October 2018
Accepted: 10 January 2019
First Online: 21 January 2019
Ethics approval and consent to participate
: The study protocol was approved by the Institutional Review Board of the Sun Yat-sen University, conducted according to the principles expressed in the Declaration of Helsinki and written informed consent was obtained from all participants.
: Not applicable.
: The authors declare that they have no competing interests.
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