[en] Some of the common methods used in process analysis technology are demonstrated taking the example of gas analysis (e.g. emission measurements): Analyses with non-dispersive infrared photometers, the conductivity measurements still frequently used in hydrogen analyses amongst others, electrochemical methods (e.g. to measure oxygen - making use of the paramagnetic properties of O₂) and finally chemoluminescence measurements. (RB)

[en] Space projects have given new impetus to cosmochemistry which so far had dealt only with meteorite research. The space missions of the last few years have yielded important information on the chemical composition of planet surfaces (Mars, Mercury, Venus) and atmospheres and on the 'solar composition' (primeval nebula) of the planets Jupiter, Saturn, Uranus, and Neptune. Some problems of the chemical processes have been solved while others have arisen. (RB)

[en] Zircon, ZrSiO₄, whose mineralogy (structure, varieties, locations) is firstly presented, is often used as gem due to its brillicance, high dispersion (refractive index over 1,9); it appears either colourless or in vivid colours. It is also an important material for high temperature ceramics as well as starting material for zirconium metal which is also used as cladding material for fuel elements in nuclear reactors. Organic zirconium compounds are also technically significant. (orig.)

[en] Rare earths and rare earth compounds are used in many technical processes, e.g. in steel metallurgy, as magnetic materials, as hydrogen storage materials, catalysts, phosphoruses, ceramics additives and laser materials. (GG)

[en] The causes of stratospheric ozone depletion are exclusively man-made. Chlorofluorocarbons and, to a smaller extent, halones interfere with the chain mechanisms of photochemical ozone depletion. They thereby lower the concentration of stationary ozone. Contrary to expectations, compensatory effects consisting in enhanced ozone formation in lower layers do not occur. Heterogeneous processes at ice particles during the cold polar night contribute particularly to ozone loss. Reactions at these particles activate chlorine-containing storage compounds in such a way that the light of the rising sun in spring leads to enhanced release of compounds containing radicals which deplete ozone. This phenomenon is well documented for the events during the formation of the ozone hole over the Antarctic, but the winterly north polar region, too, shows similar instances of coupling between meteorological conditioning and chlorine-induced ozone depletion. (orig./EF)

[en] Shales, granites and rock salt are currently under investigation as host rocks for radioactive waste. With respect to heat-producing waste (spent fuel, high-active waste) these rock types comprise contrasting mechanical and chemical behavior. The differences are due to the respective geological formations: Shales form by slow accumulation of fine-grained minerals from seawater with subsequent compaction and diagenesis; crystallization of deep-seated magmas at 700 to 850 C is the process that generates granitic rocks in the upper 20 km of the earth's continental crust; rock salt is a chemical sediment which forms by precipitation of chloride and sulfate minerals from seawater evaporation in shallow marine basins under arid conditions. The extent of chemical reactions between granitic rocks and migrating saline fluids upon canister-induced heating is quite small. However, thermally induced reactions between sheet silicate minerals in shales may result in a gradual loss of adsorption capacities for released radionuclides. Canister-induced temperature gain in rock salt results in increasing creep rates which lead to an enhanced enclosure process. Great care has to be taken in the selection of salt formations as host rocks with respect to brines; depending on their composition and temperature brines might react with e.g. potash-seams.

[en] The article briefly reviews the early history of radiation therapy, the progress achieved up to the present, and the limits set. The main subject of the article is the effects of ionizing radiation on cells, and the radiation-induced damage to the DNA, which is explained discussing the chemical mechanisms leading to strand breaks in the DNA, inducing damage, and eventually cell death. The damage is induced either directly by ionization of the DNA, or indirectly through OH-radicals. The chemical effect of oxygen enhancing the radiation-induced damage is also explained. (MG)

[en] The spectroscopic measurement of X-ray absorption by surfaces is a procedure used in the determination of local geometric factors relating to adsorbed atoms and molecules and thus constitutes a method of 'surface crystallography'. It was only with the advent of high-performance synchrotons, which as a source of radiation ensure a continuous spectrum of intensive rays over a broad range of wave lengths, that this technique has been made available. In the past, the structure of surfaces covered with adsorbate was chiefly determined on the basis of Low-Energy Electron Diffraction (LEED). X-ray diffraction, which is the classic method in the analysis of crystalline structures and certainly has merit in the research on atomic structures, only is of limited usefulness in surface examinations. (orig.)

No abstract available

[en] As described in the preceding article, all elements with atomic masses above that of iron and also the radioactive elements thorium and uranium have been formed by a supernova star explosion. Their long-lived isotopes of thorium and uranium are now distributed in the earth crust. The chemistry of uranium and thorium is of less importance, but these elements can be used to produce enormous amounts of energy in nuclear power stations. It will be described how it works. Surprisingly, small natural nuclear reactors were producing heat during hundreds of thousand years. Subsequently, we are dealing with this phenomenon, the principle of nuclear fission, the different types of nuclear reactors, security aspects and new developments.