Gray (unit) Gray (unit) The gray (symbol: Gy) is a derived unit of ionizing radiation dose in the International System of Units (SI). It is defined as the absorption of one joule of radiation energy per kilogram of matter. It is used as a unit of the radiation quantity absorbed dose which measures the energy deposited in a unit mass at a certain position, and of the radiation quantity kerma, which is the amount of energy that is transferred from photons to electrons per unit mass at a certain position. The corresponding cgs unit to the gray is the rad (equivalent to
National Energy Research Scientific Computing Center hours) with University of Arizona, Massachusetts Institute of Technology, University of California Berkeley, Princeton, University of California Los Angeles, University of Kentucky, University of California Irvine, George Washington University and the University of Chicago rounding out the top 10. Geographically, 5,853 of NERSC's users are in North America, 30 in South America, seven in Africa, 335 in the Middle East/Asia Pacific region and 662 in Europe. National Energy Research Scientific Computing Center The National Energy Research Scientific Computing Center, or NERSC, is a high performance computing (supercomputer) user facility operated by Lawrence Berkeley National Laboratory for the United States Department