1. Department of Mechanical Engineering, Vanderbilt University, Nashville, TN 37235
2. Department of Mechanical Engineering, Santa Clara University, Santa Clara, CA 95053
3. Department of Biomedical Engineering, University of Arizona, Tucson, AZ 85724; Department of Medicine, University of Arizona, Tucson, AZ 85724; Sarver Heart Center, University of Arizona, Tucson, AZ 85724