Roentgen (unit) Roentgen (unit) The roentgen or röntgen () (symbol R) is a legacy unit of measurement for the exposure of X-rays and gamma rays. It is defined as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air. In 1928 it was the first international measurement quantity for ionising radiation to be defined for radiation protection, and was an easily replicated method of measuring air ionization directly by using an ion chamber. It is named after the German physicist Wilhelm Röntgen, who discovered X-rays. Although relatively easy to measure, it had
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