years with their thorough guidance and comprehensive expertise and for many in-depth discussions on the focus of this dissertation. Secondly, I would like to thank my colleague Dr. Jur ¿ gen Meyerdirks, who acted as my key scienti c sparring partner over the last two years, and who continuously demonstrated his ability to bring me back to earth. Additionally, I would like to thank my colleague Dr. Thomas Klenke, who gave me the chance to be part of a challenging European project consortium and who supported me with his expertise on the project and the dissertation. Furthermore, I would like to express my special thanks to Gerard McGovern, who thoroughly improved my English.