Acknowledgements
I would like to express my sincere gratitude to Dr Tanja Poppelreteur that, even if she was not my supervisor, has always found the time for a meeting in her busy schedule and to my supervisor, Dr Emeka Efe Osaji for his guidance and his suggestions. I wish to thank my colleagues, who have always been available for me, my family for their continuous and unparalleled love, help and support, and my friends that even when I am not present for them, they are there for me. Particular consideration deserves my friend Andrea, for his help and his sincere advice when I moved to Manchester. Finally, but most importantly, I thank my partner Nadine for her patience, unconditional love and full support.
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