Ling, Chen
Liu, Xiaorong
Shen, Ying
Chen, Zhi
Fan, Jianfeng
Jiang, Yeping
Meng, Qun
Article History
Received: 5 July 2017
Revised: 2 January 2018
Accepted: 4 January 2018
First Online: 22 March 2018
Compliance with ethical standards
: The study was approved by the institutional review board of the Beijing Municipal Science & Technology Commission and the Capital Medical University Institutional Review Board. All participants gave prior written informed consent.
: The authors declare that they have no conflicts of interest regarding this study.