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
The Amazing Race en Discovery Channel 2 January 2010 and filming took place between May and June 2010. The show was to be broadcast in high-definition television. Filming for the second season of "The Amazing Race en Discovery Channel" lasted for 25 days and covered nearly . The second season spanned eight countries in two continents. Among them, 4 were unvisited countries, including Bolivia, Guatemala, Ecuador and Venezuela. Previously visited countries were Mexico, Brazil and Argentina. Colombia was also a previously visited country never visited in the original American version at the time of air, it will later be visited in the twenty-eighth season in 2016. The