H C Hemker1, S Bloemen2, P W Hemker3. 1. Cardiovascular Research Institute Maastricht (CARIM), Maastricht, the Netherlands. Electronic address: hc.hemker@thrombin.com. 2. Cardiovascular Research Institute Maastricht (CARIM), Maastricht, the Netherlands. Electronic address: s.bloemen@thrombin.com. 3. Centrum Wiskunde & Informatica (CWI), Amsterdam, the Netherlands. Electronic address: p.w.hemker@xs4all.nl.