The American Association of Universities, an elite organization of institutions that excel in research, has taken the rare step of kicking out one of its members.

The group, of which Duke and UNC-Chapel Hill are members, has expelled the University of Nebraska, the first time the group has kicked out one of its own, according to this coverage in Inside Higher Ed.

The move has drawn a great deal of attention within the higher education elite. Membership in AAU is coveted, and the group rarely adds or removes members. It expelled Nebraska a year after revising its membership criteria and focuses largely on the level of biomedical research and research funding.

Members voted on Nebraska's fate last week, and the university would have remained in the group had two fewer universities voted to expel it, according to the Chronicle of Higher Education.

Vote details are not public, but presumably, UNC-CH Chancellor Holden Thorp and Duke President Richard Brodhead cast votes representing their respective institutions.

A spokesman for Thorp declined to comment Monday, deferring to AAU itself. I haven't heard definitively yet today from Duke, though it will likely decline to comment as well, I'm guessing.

A second university is leaving AAU under pressure. Syracuse University, whose credentials are also receiving scrutiny now from AAU, has announced plans to voluntarily withdraw.

The AAU's newest member is Georgia Tech, added in 2010. It has 62 members in all; Duke joined in 1938, while UNC has been a member since 1922.

N.C. State is not a member, though some feel it carries the necessary credentials. When Georgia Tech joined last year, NCSU Chancellor Randy Woodson told the Chronicle of Higher Education he'd like his institution considered.

"The AAU is the pre-eminent research-intensive membership group," Woodson told that publication. "To be part of that organization is something N.C. State aspires to."

Annual dues are $80,500, according to that same Chronicle story.