First broadcast March 2004
Recent legislation brought in to fight terrorism has resulted in tighter border controls for scientists and information.
As a result, American science is concentrating on defence technologies and there is less money available for fundamental research.
Part 1: Visas
After the 11 September 2001 attacks on the United States, border controls were tightened and it became much more difficult for scientists to enter the US.
Scientists argue that science requires the free flow of ideas, and that if scientists cannot move freely across international borders, science will suffer.
Some science students wishing to study in the US have had to wait months for a visa.
But the State Department, which oversees visa policy accepts that scientists have had to wait too long for visas, but says that the situation is now improving.
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