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 route markers in this season were coloured blue and black, including the clue envelopes and the Pit Stop. None of the eliminated teams were present at the Finish Line. Applications were accepted from 13 December 2009 and finished on 8 February 2010. Semi-finalist interviews were held sometime in March 2010 and the final casting interviews took place around April 2010. According to Discovery's official website, the four official sponsors of the second season of "The Amazing Race en Discovery Channel" were Bridgestone, Samsung, Visa and Wii Party. The sponsors played a major role in the series by providing prizes and