NEWARK, N.J. (Associated Press) - Israel Gelfand, who was considered one of the world's top mathematicians and did work that was important in the development of medical imaging devices, has died at age 96.

Gelfand's son Sergei, Gelfand, said his father died Monday of natural causes at a hospital in New Brunswick, N.J.

Gelfand, from Ukraine, was a distinguished professor of mathematics at Rutgers University. He conducted pioneering research, mentored mathematicians and established correspondence schools in Russia and the United States for budding mathematicians in remote areas. He remained active until 2008, running seminars that placed the pursuit of math knowledge ahead of academic titles.

He taught at Moscow State University before moving to the U.S. in 1989. He joined the Rutgers faculty in 1990.

Rutgers University Professor Valdimir Retakh, who worked with Gelfand in Russia and the U.S., said his work in representation theory is part of the foundation of modern physics and his research in integral geometry was vital to the advent of medical imaging devices.

Gelfand won numerous awards, including the Wolf Prize in Mathematics in 1978 and the 1989 Kyoto Prize, a Japanese award for significant contributions to humanity. He wrote more than 800 articles and 30 books in many areas of mathematics.

Gelfand's weekly seminars were legendary among mathematicians, as was his sense of humor. The seminars almost always ran long, typically ending when a custodian came to clean the lecture hall.