Roentgen (unit) One roentgen deposits of absorbed dose in dry air, or in soft tissue. One roentgen of X-rays may deposit anywhere from in bone depending on the beam energy. This tissue-dependent conversion from kerma to absorbed dose is called the F-factor in radiotherapy contexts. The conversion depends on the ionizing energy of a reference medium, which is ambiguous in the latest NIST definition. The roentgen has its roots in the Villard unit defined in 1908 by the American Roentgen Ray Society as "the quantity of radiation which liberates by ionisation one esu of electricity per cm of air under normal conditions
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