krogh george (6 Ergebnisse)

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Skand. Arch. Physiol., 72/3-4. - Berlin & Leipzig, Walter de Gruyter, 1935, 8°, pp.73-214, 44 Abbildungen, 3 Taf., orig. Broschur. First Print! "The availability of "heavy" water D20 together with the accurate methods for its determination in weak solution in H20 have opened up possibilities for the study of permeability problems. D20 and especially DHO which is predominantly present in weak solutions of heavy water behave in diffusion very nearly as normal water. The rate of diffusion of molecules in liquids depends namely in first approximation on the radius of the molecules alone. This was shown by Einstein to be the case for the movement of colloidal particles, and from the fact that numerous endeavours to separate radioactive isotopes through diffusion in liquids have failed entirely we conclude that Einsteins considerations are also applicable to the diffusion of small molecules. The radius of D20 is only 0-1 per cent larger than that of H2O molecules and the difference for DHO is still less, and we must assume that the diffusion coefficients of ordinary and heavy water will differ less than 0-1 per cent. The permeability of frogs skin has been studied before in a large number of experiments by Wertheimer, Pohle, Jurisic, Adolph and others. Without going into details we can state that on the basis of these experiments it is generally assumed that the skin allows water and certain dissolved substances to pass in, but resists in the living state the outward passage. It is claimed further (Adolph 1934) that in the living animal the nervous system influences definitely the rates of passage through the skin. ." G.v. Hevesy, et al. Georg von Hevesy (1885-1966), Hungarian physicist and chemist. He received the 1943 Nobel Prize in Chemistry for his work on the use of isotopes as tracers in studying chemical processes. Hevesy was the first to apply the radioactive tracer technique to biology, and he later used it in medical research. He also discovered X-ray fluorescence analysis. He was codiscoverer of hafnium, element 72 in the periodic table. Hevesy became an associate of the Institute of Theoretical Physics, Copenhagen, in 1920 and also of the Institute for Research in Organic Chemistry, Stockholm, in 1943.