1. Department of Mathematics, Southeast University, Nanjing 210096, China
2. Department of Medicine, School of Medicine, Emory University, Atlanta, GA 30307;
3. The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332
4. Department of Medicine, School of Medicine, Emory University, Atlanta, GA 30307
5. Mathematical Sciences Department, Worcester Polytechnic Institute, Worcester, MA 01609
6. Mallinckrodt Institute of Radiology, Washington University, St. Louis, MO 63110
7. The Cardiovascular Research Foundation, Columbia University, New York, NY 10022
8. Department of Mathematics, Southeast University, Nanjing 210096, China;