1. College of Mathematics, Taiyuan University of Technology, Taiyuan, Shanxi 030024, P. R. China
2. Department of Scientific computing, Florida State University, Tallahassee, FL 32306, USA
3. Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, P. R. China
4. Beijing Key Laboratory of Metabolic Disorders Related Cardiovascular Diseases, Capital Medical University, Beijing 100069, P. R. China