Acknowledgements

Special thanks to the colleagues and friends of the Non-linear Physics Group (former Statistical Mechanics and Non-linear Physics Group) of the Instituto de Física de la Facultad de Ciencias (IFFC), Universidad de la República (UdelaR), Uruguay. Many have come and gone, but all remain in my dearest memories.

Specially, I thank my dear friends, Arturo C. Martí and Cecilia Cabeza (please, mind that the picture was taken after my M.Sc. viva in July, 2010). They have always been a constant source for support and inspiration.

I want to express my most sincere gratitude to Cristina Masoller, a dear friend from the DONLL group, Departament de Física i Enginyería Nuclear, at the Universidad Politecnica de Catalunya (UPC), Barcelona, Spain.

Many thanks to the ICSMB group at the University of Aberdeen (UoA), Aberdeen, Scotland. Thanks to them, my Ph.D. and life in Scotland was a complete joy.

And specially, to my dear friends Murilo S. Baptista and Lucas Fernandes, who have a special place in my heart.

Many thanks to the many friends at the Departamento de Física, at both, the Universidade Estadual de Ponta Grossa and the Universidade Federal do Parana, Brazil.