Funding for this research was provided by:
National Natural Science Foundation of China (No. 81501849)
Text and Data Mining valid from 2017-03-25
Received: 20 January 2017
Accepted: 22 March 2017
First Online: 25 March 2017
Compliance with ethical standards
: The authors have no conflict of interest to declare.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.