March 22, 2000 UPTON, NY - Painting a bridge can be a costly and
time-consuming undertaking, especially if the paint job doesn't
last. So scientists have been working on ways to test paint
durability before the brushes even get wet. At a March 22
session at the American Physical Society meeting in Minneapolis,
scientists from the University of Missouri at Kansas City, who
worked in collaboration with physicist Bent Nielsen of the U.S.
Department of Energy's Brookhaven National Laboratory, will
present findings that could lead to the development of an
extremely sensitive and quick durability test. The technique is
called positron annihilation. Essentially, the scientists
bombard small painted samples of metal with a beam of positrons,
or positively charged electrons. When these "antielectrons"
interact with the electrons in the molecules of the paint, they
annihilate one another and send out gamma rays that give the
scientists information about the molecules in the paint. The
technique can detect nanometer-sca