A visiting graduate student at Brown University has been charged with murder and is being held on $10 million bond after he allegedly traveled across the country and stabbed his girlfriend to death. Mark Nickel, a spokesman for Brown, said Monday that Yongfei Ci was one of 14 graduate students who began the semester-long mathematics program at the Ivy League university Sept. 9. Nickel said Ci is a doctoral student at the University of Illinois at Urbana-Champaign. The News-Gazette of Champaign reported that Ci, 29, was arrested Friday, not long after he allegedly broke into the off-campus apartment of his estranged girlfriend, Mengchen Huang, 25, and stabbed her to death. She was also a student at the University of Illinois.