Funding for this research was provided by:
Jyväskylän Yliopisto (PhD grant)
Beijing Municipal Science and Technology Commission (Z161100002616001)
Beijing Science and Technology Commission in Tongzhou District (KJ2015CX004)
Text and Data Mining valid from 2019-01-25
Received: 24 August 2018
Revised: 20 December 2018
Accepted: 18 January 2019
First Online: 25 January 2019
Compliance with ethical standards
: On behalf of all authors, the corresponding author states that there is no conflict of interest.
: This research has been approved by the Ethics Committees of Xuanwu Hospital, Capital Medical University and Luhe Hospital, Capital Medical University, and it has been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.