On the turning away

AMERICA is, both proverbially and in reality, a nation of immigrants. That is particularly true of its scientific community which has, since the second world war, attracted and relied on foreign talent to help create the world's most formidable research machine. Since the country's economic and military might depend in large measure on the success of that machine, anything which diminishes this flow of talent is likely to be bad for America. And a study released on May 4th by the National Science Foundation (NSF) suggests that delays in the processing of visas since September 11th 2001 are having just that effect.