which provided full support as to ideas, expertise, equipment and personnel.Therefore, there are a number of persons from both fields and both universities that have contributed to the conceptualisation, setting up and making of the several experiments, collecting and processing of data. Their contribution has been essential and without them the results presented here could not have been pursued. To all of them I am deeply indebted, but here I would like to thank especially those who, since the very beginning, escorted me through the whole PhD course. Firstly I thank Prof