1. Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996
2. The Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
3. Instituto de Física Arroyo Seco, Universidad Nacional del Centro de la Provincia de Buenos Aires (UNCPBA), Pinto 399, Tandil, Argentina
4. Department of Mathematical Sciences, Center for Applied Mathematics and Statistics, New Jersey Institute of Technology, Newark, New Jersey