1. Department of Biomedical Engineering, University of Florida, Gainesville, FL 32611, U.S.A.
2. Department of Electrical and Computer Engineering, University of Florida, Gainesville, FL 32611, U.S.A.
3. Department of Mathematics, University of Florida, Gainesville, FL 32611, U.S.A.
4. Department of Biomedical Engineering and Department of Electrical and Computer Engineering, University of Florida, Gainesville, FL 32611, U.S.A.