Chorin, whose colleagues consider him one of the great applied mathematicians of the 20th century, already travels widely to speak and to teach. He expects to continue to do so among UC's 10 campuses - with the added distinction of being one of only 22 faculty members so honored in the system. Nine of them are at UC Berkeley.

"You're supposed to go around and talk to people on other campuses, but I do that anyway," said Chorin, who also is a senior scientist at the U.S. Department of Energy's Lawrence Berkeley National Laboratory.

The title of University Professor is reserved for scholars of international distinction who also are recognized and respected as exceptional teachers. It is a way to spread their talents around the UC system for a period of at least five years and no more than 10.

"He is an outstanding scholar in applied mathematics who has made important contributions in many fields," said Calvin Moore, professor and chair of mathematics in the College of Letters & Science at UC Berkeley. "His impact has been enormous in both mathematics and teaching - he has trained a whole generation of applied mathematicians."

Chorin and UC San Diego Professor Shu Chien of the departments of bioengineering and medicine were appointed the newest University Professors by the UC Board of Regents at its January meeting.

Chorin, 63, is a native of Poland who grew up in Israel and Switzerland, making his way to New York in 1962 and eventually to UC Berkeley in 1971. He specializes in scientific computing, numerical analysis and computational methods of statistical mechanics, though his true love is turbulence - the chaotic eddies and currents in any fluid that are hard to study experimentally and harder still to calculate mathematically.

"I'm very interested in turbulence, but turbulence is a very hard field - if you work 10 years and get something small, it's big progress," Chorin said. "You really have to have knowledge in lots of other fields, and you have to do other things also if you ever are going to get satisfaction."

A recent result he is proud of involved collaboration with UC Berkeley colleague Grigory Barenblatt, professor of mathematics. They discovered that a long-used rule of thumb that lets engineers predict the forces generated by turbulent flow over a wing or other surface breaks down at high velocity. They have proposed better methods to approximate the force exerted on a wall or surface by turbulent flow, and continue to explore the implications and to understand the mathematics of fluid flow.

A second area of research today involves computations that are incomplete.

"There are lots of problems where you have no hope of doing a complete calculation," he said. "There is too much complexity or too many unknowns, or you are not certain of what the equations are, or the problems have intrinsic uncertainty - turbulence is one of them. The project I am working on is, suppose the calculations you can do are limited, what's the best you can say? What conclusions can you legitimately draw from it?"

In his early years, he developed computational methods and computer software that were used widely in the aircraft industry to mathematically model air flow over airplane wings. The general techniques are still employed, though Chorin moved on to apply his methods to a large variety of other fields - water flow in oceans and lakes, flow in turbines and engines, combustion, flow in the heart and veins. These are just a few of the applications he has explored in more than 90 papers.

Two years ago, the Society for Industrial and Applied Mathematics and the American Mathematical Society honored Chorin with the 2000 Norbert Wiener Prize, one of the highest distinctions in applied mathematics. The prize citation states that Chorin's "work has stimulated important developments across the entire spectrum, from practical engineering applications to convergence proofs for numerical methods ...."

Chorin obtained his PhD from New York University in 1966 and conducted research at that institution's Courant Institute. After a year as a Visiting Miller Professor at UC Berkeley in 1971-72, he decided to stay. He is a member of the National Academy of Sciences and a fellow of the American Academy of Arts and Sciences. Among his honors is the National Academy of Sciences' Award in applied mathematics and numerical analysis.