Funding for this research was provided by:
the Beijing Municipal Administration of Hospitals' Ascent Plan (DFL20150701)
the Beijing Natural Science Foundation (7172106)
Text and Data Mining valid from 2019-01-04
Received: 25 October 2018
Accepted: 5 December 2018
First Online: 4 January 2019
Compliance with ethical standards
: Huijun Zhao, Xuhong Zhao, Ting Lei, Man Zhang declare that they have no conflicts of interest.
: This work was supported by the Beijing Municipal Administration of Hospitals’ Ascent Plan (DFL20150701) and the Beijing Natural Science Foundation (7172106).
: All procedures performed in studies involving human participants were conducted in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. This article does not contain any studies with animals performed by any of the authors.
: Informed consent was obtained from all individual participants included in the study.