AIP Conference Proceedings [AIP ORGANIZED BY THE HELLENIC PHYSICAL SOCIETY WITH THE COOPERATION OF THE PHYSICS DEPARTMENTS OF GREEK UNIVERSITIES: 7th International Conference of the Balkan Physical Union - Alexandroupolis (Greece) (09–13 September 2009)] - Helio-Geomagnetic Activity and the Time Distribution of Myocardial Infractions during the Solar Cycle 23 (1997–2007). A Preliminary Study based on a Greek Hospital Data