First Author:   Francesco Reito University of Catania reito@unict.it   Corso Italia 55 Catania, 95100, Italy   00393288242694(Phone) 00393288242694(Fax) Second Author: Maurizio Caserta University of Catania caserta@unict.it   Corso Italia 55 Catania, 95100, Italy   00393472351834(Phone)