51.   But Henry Aaron of the Brookings Institution, a Washington research center, was not as hopeful.

52.   But Katy Delaney, a spokesperson for the research center, would not confirm whether they had received a subpoena.

53.   But Rick Anthes, the head of the nonprofit corporation that directs the atmospheric research center in Boulder, Colo., insists that the buck has not been passed.

54.   But Soviet research centers turned out to be much harder to adapt to the market than anyone thought.

55.   But the trial was limited to treatment at university research centers and did not last long enough to determine whether the treatment increased life span.

56.   But this is new territory, too, for the Media Laboratory, the Massachusetts Institute of Technology research center.

57.   But when it comes to expanding an area a university would not otherwise expand, or starting up a new research center, the questions become murkier.

58.   But while the Net may be changing the mode of collaboration at research centers and elsewhere, even Internet aficionados agree that actual meetings are not obsolete.

59.   Chaudhari, a former manager at the research center, said he had returned to scientific research because of the pleasure of the work.

60.   Cheryl Ann Butman, a senior scientist at the Falmouth, Mass. research center, will study techniques to restore habitats for overharvested shellfish.