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
Hugo Wilhelm von Ziemssen Hugo Wilhelm von Ziemssen Hugo (Wilhelm) von Ziemssen (13 December 1829 – 21 January 1902) was a German physician, born in Greifswald. He studied medicine at the universities of Greifswald, Berlin, and Würzburg. In 1863 he was called to the University of Erlangen as a professor of pathology and therapy as well as the director of the medical clinic. In 1874 he relocated to Munich as a professor and director of the general hospital. He made advances in electrotherapeutics, conducted research on cold-water treatment for typhoid fever and lung inflammation, and became an authority on diseases of the larynx and