1. Department of Mathematical Sciences and Center for Applied Mathematics and Statistics, New Jersey Institute of Technology, Newark, New Jersey 07102, USA;
2. Instituto de Física Arroyo Seco (CIFICEN-CONICET-CICPBA), Universidad Nacional del Centro de la Provincia de Buenos Aires, 7000 Tandil, Argentina
3. Nanofabrication Research Laboratory, Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
4. Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA