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
Wilhelm Barthlott (Geodiversity), including migration and globalization. His Biodiversity Distribution Map has been published in numerous textbooks in addition to being the foundation for many postgraduate studies. In the framework of the BMBF-BIOTA-AFRICA project led by him, biodiversity patterns in Africa as a model continent are analyzed and potential impacts of climate change are investigated. Wilhelm Barthlott was the first botanist to use high resolution in scanning electron microscopy systematically in the research of biological surfaces since 1970. Most prominent among his results was the discovery of the self-cleaning effect of superhydrophobic micro- and nanostructured surfaces, which were technically realized with the