Roentgen (unit) this derivative quantity the roentgen equivalent physical (rep) to distinguish it from the ICR roentgen. The introduction of the roentgen measurement unit, which relied upon measuring the ionisation of air, replaced earlier less accurate practices that relied on timed exposure, film exposure, or fluorescence. This led the way to setting exposure limits,and the National Council on Radiation Protection and Measurements of the United States established the first formal dose limit in 1931 as 0.1 roentgen per day. The International X-ray and Radium Protection Committee, now known as the International Commission on Radiological Protection (ICRP) soon followed with a limit of
Sanford Burnham Prebys Medical Discovery Institute In 2007, T. Denny Sanford gave the Institute $20 million through Sanford Health, a hospital which received significant donations from T. Denny Sanford previously, allowing it to create the Sanford Children's Health Research Center, which has sites in Sioux Falls, South Dakota and La Jolla, CA, the latter within the campus of SBP. In 2010, the Institute adopted the name Sanford-Burnham Medical Research Institute following a $50 million pledge of support from Sanford. An anonymous gift of $275 million was made in 2014. In 2015, the Institute changed its name again to Sanford Burnham Prebys Medical Discovery Institute following a