Roentgen equivalent man has been defined since 1976 as equal to 0.01 sievert, which is the more commonly used SI unit outside the United States. A number of earlier definitions going back to 1945 were derived from the roentgen unit, which was named after Wilhelm Röntgen, a German scientist who discovered X-rays. The acronym is now a misleading historical artifact, since 1 roentgen actually deposits about 0.96 rem in soft biological tissue, when all weighting factors equal unity. Older units of rem following other definitions are up to 17% smaller than the modern rem. One rem carries with it a 0.05% chance of
Friedrich Wilhelm Theile Friedrich Wilhelm Theile Friedrich Wilhelm Theile (11 November 1801, in Buttstädt – 20 October 1879, in Weimar) was a German physician and anatomist. In 1825 he received his medical doctorate from the University of Jena with the dissertation-thesis "De Musculis nervisque laryngeis". From 1828, with Heinrich Wilhelm Ferdinand Wackenroder, he was in charge of the pharmaceutical institute at Jena. In 1831 he became an associate professor, and three years later relocated to the University of Bern as a full professor of anatomy. From 1853 he practiced medicine in Weimar, during which time, he largely concerned himself with literary activities. In