Funding for this research was provided by:
National Natural Science Foundation of China (61272240, 61672324, 61672322)
Natural Science Foundation of Shandong Province (2016ZRE27468, ZR2012FM037)
Text and Data Mining valid from 2017-09-27
First Online: 27 September 2017
Compliance with ethical standards
: Author Qian Ma declares that she has no conflict of interest. Author Jun Ma declares that he has no conflict of interest.
: This article does not contain any studies with human participants performed by any of the authors.