Funding for this research was provided by:
National Natural Science Foundation of China (31470885, 31300752, 31270971, 81502615)
Article History
Received: 10 December 2016
Accepted: 14 February 2017
First Online: 28 February 2017
Compliance with ethical standards
:
: All authors declared no conflict of interest.
: This study was approved by hospital medical ethics committee of the Tai’an City Central Hospital and Qilu Hospital of Shandong University.