Chen, Senlin https://orcid.org/0000-0003-0945-4271
Gu, Xiangli
Article History
Received: 21 August 2017
Accepted: 16 February 2018
First Online: 20 February 2018
Ethics approval and consent to participate
: The Iowa State University Institutional Review Board (IRB) granted approval of this study. Informed consent was waived as per the IRB approval.
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.