1. Division of Physiology, Department of Experimental and Clinical Medicine, University of Florence, 50134 Florence, Italy
2. National Institute of Optics, National Research Council, 50125 Florence, Italy
3. Institute for Experimental Cardiovascular Medicine, University of Freiburg, Freiburg,Germany
4. Department of Mathematics, UBC, Vancouver British Columbia V6T 1Z2, Canada
5. Department of Cardiology, Leiden University Medical Center, Albinusdreef 2 2333 ZA Leiden, The Netherlands
6. Department of Physiology, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec H3G 1Y6, Canada