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
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