Funding for this research was provided by:
Mega-Projects of National Science Research for the 12th Five-Year Plan (2012ZX10001-006)
Mega-Projects of National Science Research for the 13th Five-Year Plan (2017ZX110201101)
Received: 17 January 2019
Accepted: 15 May 2019
First Online: 22 May 2019
Ethics approval and consent to participate
: The study was reviewed and approved by the local ethics review committee. All participants provided written informed consent prior to research participation.
: Not applicable.
: The authors declare that they have no competing interests.