Funding for this research was provided by:
National Natural Science Foundation of China (71425002, 71874180)
Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (QYZDB-SSW-SYS036)
Text and Data Mining valid from 2019-02-14
First Online: 14 February 2019
Compliance with ethical standards
: Neither the entire manuscript nor any part of its content has been published or has been accepted elsewhere. It has not been submitted to any other journal. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.