1. Key Laboratory of Environmental Factors and Chronic Disease Control, College of Public Health and Management, School of Basic Medicine, Ningxia Medical University, Yinchuan 750004, P. R. China
2. Urology Surgery, General Hospital of Ningxia Medical University, Yinchuan 750004, P. R. China
3. State Key Laboratory of High-efficiency Coal Utilization and Green Chemical Engineering, Ningxia University, Yinchuan 750021, P. R. China