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, his alma mater, announced his death.

“Osamu was a quiet and brilliant researcher,” Martin L. Chalfie, a professor of biological sciences at Columbia University who with Dr. Shimomura and Roger Y. Tsien of the University of California, San Diego, said by email. “What always struck me about Osamu was his intense dedication and masterful work on a fundamental problem in biology — how can different organisms generate light? — that was, ironically, far from the limelight before the Nobel.”