The Bush administration is coming under criticism at the 15th International AIDS conference in Bangkok for blocking many top federal scientists from attending the conference. Two years ago the U.S. sent a delegation of about 230, but this year only 50 were sent. At the conference at least 40 sessions had to be canceled because of the absence of U.S. scientists. The Bush administration claimed the cut backs were financially not politically motivated. But some say the decision is rooted in the last conference in Spain, when AIDS activists booed Tommy Thompson, the head of Health and Human Services, so loudly his speech was nearly inaudible.