Given the large number of ways, one can contribute (directly and indi- rectly) to a thesis that reflects four years of work, I have to thank numerous people for their help. Therefore, it is quite obvious that this foreword can only reflect the most important contributions to my work. First of all, I would like to thank my supervisor, Prof. Martin T. Bohl for his contribution to this thesis. His ongoing support and the various insights he provided were a great help to my research. I also appreciate the freedom I had and his confidence in my work. I would also like to thank my second supervisor, Prof
