CNN — At Columbia University, which has long borne witness to protests and dissent, the atmosphere has shifted under a new regime of policy changes ostensibly aimed at heightening security, according to CNN interviews with more than a dozen students and faculty. Students who spoke with CNN – most of whom requested to remain anonymous for fear of reprisals – described a tense mood on campus as the changes take hold. The atmosphere is far from what Maria, a master’s student at Columbia whose name has been changed to protect her identity, imagined when she enrolled last spring. “I put...