Funding for this research was provided by:
National Natural Science Foundation of China (31770837)
Qingdao People’s Livelihood Science and technology plan (18-6-1-68-nsh)
Received: 23 December 2018
Accepted: 26 February 2019
First Online: 9 March 2019
Ethics approval and consent to participate
: The study protocol was approved by the Ethics Committee of Qingdao Municipal Hospital before participation (Approval NO.2017–20). All the subjects have signed written informed consent.
: Not applicable.
: The authors declare that they have no competing interests.
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