asa gray

Gray   (grā)    American botanist who greatly enlarged and improved the description of North American flora and was the chief American advocate of Charles Darwin's theories.

Main Entry: ²gray
Pronunciation: 'grA
Function: noun
: the mks unit of absorbed dose of ionizing radiation equal to an energy of one joule perkilogram of irradiated material —abbreviation Gy
Gray, Louis Harold (1905–1965), British radiobiologist. In 1933 Gray established a physics laboratory tomeasure radiation in the treatment of cancer at Mount Vernon Hospital, Middlesex, England. Earlier he and Sir W. H. Bragg had formulated a theory for deducing the energy absorbed by a material exposedto gamma rays from the ionization within a small gas-filled cavity in the material. At Mount Vernon he was to apply his theory to X rays and later, in modified form, to neutrons. Gray expressed theneutron dose values in energy units, anticipating the International Commission on Radiological Units, which in 1953 adopted the rad as the unit for measuring all types of ionizing radiation. In 1975the Commission adopted the gray as the physical unit of dose.

Gray (grā), Henry. 1825?-1861.

British anatomist whose work Anatomy, Descriptive and Surgical (1858), known as Gray's Anatomy, remains a standard text.

gray   (grā)  Pronunciation Key  The SI derived unit used to measure the energy absorbed by a substance per unit weight of the substance when exposed to radiation. One gray is equal to one joule per kilogram, or 100 rads. The gray is named after British physicist Louis Harold Gray (1905-1965).