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In his April 2009 speech in Prague, President Barack Obama outlined a vision of a world free of nuclear weapons and pledged to "immediately and aggressively" pursue approval of the Comprehensive Nuclear Test Ban Treaty (CTBT), which prohibits any nuclear test explosions that produce a self-sustaining, supercritical chain reaction and creates a robust international verification regime. Now, within days of the second Obama-initiated global Nuclear Security Summit, the National Research Council of the National Academy of Sciences (NAS) has released its much-anticipated report on the technical and security issues related to the CTBT. It provides ample evidence that the case for the test ban has never been better.