Funding for this research was provided by:
the National Key Research and Development Program of China (no. 2016YFB0700504)
Text and Data Mining valid from 2019-01-08
Received: 20 September 2018
Accepted: 27 December 2018
First Online: 8 January 2019
Compliance with ethical standards
: All authors declare that they do not have conflicts to interests.