Funding for this research was provided by:
National Natural Science Foundation of China (51809024)
China Scholarship Council (2011605031)
Fundamental Research Funds for the Central Universities (2019CDYGYB028)
German Federal Ministry of Education and Research (FKZ02WT1141)
Received: 14 February 2020
Accepted: 30 April 2020
First Online: 12 May 2020
Ethics approval and consent to participate
: Not applicable.
: All authors agreed to publish the paper.
: The authors declare that they have no competing interests.