Institute for Applied Computing, National Research Council of Italy, Via dei Taurini 19, Rome, 00185, Italy. f.castiglione@iac.cnr.it.|Institute for Applied Computing, National Research Council of Italy, Via dei Taurini 19, Rome, 00185, Italy.|Department of Biology, University of Tor Vergata, Via della ricerca scientifica 1, Rome, 00133, Italy.|Department of Mathematics and Statistics, American University of Sharjah, P.O.Box 26666, Sharjah, UAE.