Dedicated to my son, Eliott Jacques Gaby Rohat i Foreword by the supervisor Under normal circumstances, Guillaume would have submitted and defended this thesis in person. Sadly, the circumstances are, by no stretch of the imagination, normal. Guillaume passed away, completely unexpectedly, on October 2nd 2019. We were all shocked by this tragic news. Guillaume was busy with the final details of his thesis. The acknowledgements to the thesis were already written, the date for the defence had been chosen, and the committee had been invited. He planned to defend his thesis on November 19 at the University of Geneva in Switzerland. The place of the defence was Geneva, because Guillaume did his research at the University of Geneva and pursued a double doctoral degree from the University of Geneva and the University of Twente. Guillaume's work was very important, not only to us as his supervisors, but also to the broader scientific community. Therefore, we decided to look into the possibility to award Guillaume a posthumous doctorate degree. We asked Guillaume's partner, Elodie Charriere, and his family how they would feel about this, and they indicated that it would mean a lot to them.