1. School of Basic Medicine, Medical College, Qingdao University, Qingdao, Shandong 266071, P.R. China
2. Department of Gynaecology and Obstetrics, Qingdao Municipal Hospital, Qingdao, Shandong 266071, P.R. China
3. College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao, Shandong 266071, P.R. China