Funding for this research was provided by:
National Natural Science Foundation of China (11674161)
Natural Science Foundation of Jiangsu Province (BK20181250)
Jiangsu Provincial Department of Education (2017JSJG086)
Undergraduate teaching reform project from Nanjing University (201612B5)
The program B for outstanding PhD candidate from Nanjing University (201802B022)
Received: 11 November 2018
Accepted: 12 February 2019
First Online: 21 February 2019
: The authors declare that they have no competing interests.
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