Funding for this research was provided by:
National Natural Science Foundation of China (61703416)
Natural Science Foundation of Hunan Province, China (2018JJ3614)
Article History
First Online: 29 November 2019
Compliance with ethical standards
:
: Qing Cheng, Yanghe Feng and Zhong Liu declare that they have no conflict of interest. Yun Zhou has received research grants from NSFC and NSF-Hunan.
: This article does not contain any studies with human participants or animals performed by any of the authors.