And, a major difficulty has been immigration. The USA PATRIOT Act of 2001 imposed stringent new visa requirements that restricted scientists and science students from all over the world from entering the U.S. Albert Teich, who has tracked the issue for the American Association for the Advancement of Science where he is director of science and policy programs, says that problem peaked in 2003, but has since improved, especially following lobbying of Congress by scientific societies and advice from the National Academy of Sciences, whose 2009 report "Beyond 'Fortress America'" and 2007 report "Rising above the Gathering Storm" were among those to suggest the rules be eased. But the policies had a lasting impact on the ability of U.S. researchers to collaborate and recruit students, he says.
Teich adds that security concerns have cast a shadow over U.S. science in a number of ways, and points to the erection of a steel security barrier around the perimeter of the previously open campus of the National Institutes of Health in Bethesda, Md. "To me," he says, "that fence is a very dramatic visual impact of 9/11 on science."