Funding for this research was provided by:
NSF of China (11471196+20142RB01849)
NSF of Shandong Province, China (ZR2016JL004)
Text and Data Mining valid from 2018-01-23
Received: 16 October 2017
Accepted: 7 January 2018
First Online: 23 January 2018
: The authors declare that they have no competing interests.