ERRATA P. 7 Many of the acknowledgements of a thesis are done at the last minute. My acknowledgements were no exception. It is during this time that one often forgets to mention some of their biggest inspiration encouragement and support. I want to thank Hannes Högni Vilhjálmsson — for his friendship, comments, our weekly lunches, and his encouragement. He does excellent work, and I am grateful to know him. Social Catalysts 1 2 Social Catalysts