With great sadness we mourn the passing of our colleague Michael Pimsner on July 17, 2022.

Mihai (known as Michael in the USA) Pimsner was a Romanian born mathematician known for his work in the K-Theory of Operator Algebras. He was born in Wallachia (part of Romania) in 1953 and was educated in Romania receiving his Ph.D. from INCREST in Bucharest in 1984. After occupying a tenured position in Germany, he accepted an invitation to join the Penn Faculty arriving at Penn in 1991, and his presence further strenghtened the research group in functional analysis/operator algebras in the mathematics department. He was internationally known for his contributions to K-theory, having participated as an invited speaker at one of the quadrennial International Congresses of Mathematicians and he was an Honorary member of the Mathematics Institute of the Romanian Academy of Sciences.

A modest but gifted man who spoke at least three languages fluently, he had a warm ingratiating smile and personality--quiet but effective and he was loved by his students to whom he was exceptionally kind. All his colleagues enjoyed their interactions with him and will miss him and the steady, reasoned part he played in the department. He fought a long battle with lung cancer with a blessed lengthy remission, but the disease returned and he died on July 17, 2022. At his death he left his daughter, Ingrid, and his granddaughter, Sybill.