HARTFORD, Conn. -- More than two dozen research studies at 20 universities have been significantly affected since regulations on processing visas for foreign scientists were tightened after the Sept. 11 attacks, a newspaper reported.

The research involves diseases such as AIDS, cancer, the West Nile virus, leukemia and bioterrorism, the Hartford Courant said in a story prepared for today's editions.

Leaders of the National Academies complained in December that heightened security is "having serious, unintended consequences for American science, engineering, and medicine."

State Department officials have said they are working to clear a visa backlog, but The Courant said interviews with scientists and educators indicate the problem may be getting even worse.

"It has the potential of isolating the U.S. scientific community from the world scientific community," said Douglas Osheroff, a Nobel Prize winner who heads the physics department at Stanford University.

Hearing on Wednesday

A hearing on the issue is tentatively scheduled for Wednesday in the Science Committee of the U.S. House of Representatives.

The Courant said it found many studies that had been delayed by visa problems. Most of the stranded researchers had been working in the United States, left for brief trips abroad and could not get re-entry visas, the newspaper said.

Among them:

At Rutgers University in New Jersey, hundreds of cultures used in cancer experiments languish in researcher Guanfang Shi's lab. Shi has been stuck in China since December, when she traveled to Beijing for what she had expected to be a quick visit with her parents.

At the University of Utah, research into molecular compounds that can inhibit HIV awaits the return of a key researcher stranded in his native Egypt since May.

A West Nile vaccine project at the University of Kansas has been stymied by a series of visa delays, most recently that of a Russian epidemiologist.

Research into leukemia at the University of Alabama has been stalled since December while a researcher waits in China for approval to return.

A State Department spokesman told the newspaper that most visa applications are now being processed in less than a month, and that those involving scientific research considered sensitive to U.S. security interests are taking two to three months.

But scientists say delays have stretched as long as 11 months. They blame an understaffed, overwhelmed system and a jittery bureaucracy they say is applying policies broadly.

"I'm anticipating we're going to experience more, rather than fewer, problems," said Kevin Casey, Harvard University's director of federal and state relations.