Acknowledgments

Veiga, my thesis advisors, for the total support, motivation and orien-tation throughout the elaboration of this work. Their orientation and advice contributed greatly for the quality of this thesis. To all my MSc and BSc colleagues with whom i worked, I want to express my gratitude for all the support, motivation and help provided. I would like to thank my parents for all the support and help. I owe them my success. I would like to thank my girlfriend for all the support, motivation and patience during the completion of this thesis. I would like dedicate this thesis to my late uncle, who passed away during the making of this work, due to pancreatic cancer