1. Department of Computer Science, University of Verona, Strada le Grazie 15, 37134 Verona, Italy.
2. Consiglio Nazionale delle Ricerche (CNR)–Istituto dei Sistemi Complessi, Sede Sapienza, and Department of Physics, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy.
3. CNR–Istituto per i Processi Chimico-Fisici, Sede Secondaria di Pisa, Area della Ricerca, via G. Moruzzi 1, 56124 Pisa, Italy.
4. CNR–Istituto Officina dei Materiali (IOM), Operative Group in Grenoble, c/o Institut Laue Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9, France.
5. Department of Chemical Sciences and Technologies, University of Rome Tor Vergata, Via della Ricerca Scientifica I, 00133 Rome, Italy.
6. Department of Physics and Geology, University of Perugia, Via A. Pascoli, 06123 Perugia, Italy.
7. CNR-IOM c/o Department of Physics and Geology, University of Perugia, Via A. Pascoli, 06123 Perugia, Italy.