Affiliation: | a Department of Mathematics, West Virginia University, Morgantown, WV 26506, USA;b School of Mathematics Science, Peking University, Beijing, 100871, PR China;c Department of Mathematics, University of Houston, Houston, TX 77204, USA;d Department of Computer Science, University of Houston, Houston, TX 77204, USA;e Department of Physics, University of Houston, Houston, TX 77204, USA;f Department of Chemistry and Ames Laboratory, Iowa State University, Ames, IS 50011, USA |