Showing papers by "Technische Universität Darmstadt published in 1978"
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TL;DR: In this article, the elements Os, Ru and Ir have been determined in fifteen chromites from nine different Greek localities and the examined chromites show a relatively homogenous distribution of the above elements, which also exhibit a pronounced linear correlation compared to each other.
51 citations
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TL;DR: The thermodynamic parameters of five different highly purified viroid "species" were determined by applying UV-absorption melting analysis and temperature jump methods and it is shown that the following refinement of the earlier model is in complete accordance with the experimental data.
Abstract: The thermodynamic parameters of five different highly purified viroid "species" were determined by applying UV-absorption melting analysis and temperature jump methods. Their thermal denaturation proved to be a highly cooperative process with midpoint-temperatures (Tm) between 48.5 and 51 degrees C in 0.01 M sodium cacodylate, 1 mM EDTA, pH 6.8. The values of the apparent reaction enthalpies of the different viroid species range between 3,140 and 3,770 kJ/mol. Although the cooperativity is as high as found in homogeneous RNA double helices the Tm-value of viroid melting is more than 30 degrees C lower than in the homogeneous RNA. In order to explain this deviation, melting curves were simulated for different models of the secondary structure of viroids using literature values of the thermodynamic parameters of nucleic acids. Our calculations show that the following refinement of our earlier model is in complete accordance with the experimental data: In their native conformation viroids exist as an extended rodlike structure characterized by a series of double helical sections and internal loops. In the different viroid species 250-300 nucleotides out of total 350 nucleotides are needed to interprete the thermodynamic behaviour.
48 citations
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TL;DR: The URANUS code as discussed by the authors is a digital computer program for the thermal and mechanical analysis of integral fuel rods, which is built around a quasi-two-dimensional analysis of fuel and cladding.
40 citations
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TL;DR: In this paper, the authors present quantitative calculations of positron emission dynamically induced in the collision of PbPb and PbU. The results are compared with recent measurements, yielding evidence for new processes characteristic for quantum electrodynamics of strong fields.
20 citations
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01 Jun 1978TL;DR: In this article, the metastable decay of the helium-like and lithium-like Ar16+ and Ar15+ atoms has been observed in a foil-excited beam using a flat-crystal spectrometer.
Abstract: Besides the prompt x-ray emission of Ar-ions, the metastable decay of the heliumlike3
P
2- and the lithiumlike4
P
5/2-levels of highly ionized Ar16+ and Ar15+ atoms has been observed in a foil-excited beam using a flat-crystal spectrometer. Due to the highx-ray energy resolution of the spectrometer the two3
P
2 →1
S
0 and4
P
5/2 →2
S
1/2 transitions could be resolved. The experiment yielded (3128 ±2) eV for the3P2 → and (3091 ± 2)eV for the4
P
5/2 →2
S
1/2 transition energy respectively. Using a time of flight technique the lifetimes of the3
P
2- and the4
P
5/2-states were determined to be (1.44 ±0.09)ns and (0.66 ± 0.05) ns.
16 citations
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TL;DR: In this article, the charge state dependence of K and L x-ray production has been studied for 1.4 MeV/amu Cu+q (16≦q≦23) collisions with Kr and Xe gas targets.
Abstract: The charge state dependence ofK andL x-ray production has been studied for 1.4 MeV/amu Cu+q (16≦q≦23) collisions with Kr and Xe gas targets. For q≧20 an almost linear increase in theK x-ray emission of Cu and Kr, and in theL x-ray emission of Xe is observed. The experimental results are compared to existing theoretical models based on the quasimolecular picture.
13 citations
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TL;DR: In this article, a search with radiochemical methods for long-lived superheavy elements in 238U targets bombarded with intense beams of136Xe ions produced negative results, and a formation cross section of ≤ 1×10−35 cm2 was deduced at 95% confidence level for nuclides with half-lives between 1 and 200 d.
Abstract: A search with radiochemical methods for long-lived superheavy elements in 238U targets bombarded with intense beams of136Xe ions produced negative results. A formation cross section of ≤1×10−35 cm2 is deduced at 95% confidence level for nuclides with half-lives between 1 and 200 d.
11 citations
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TL;DR: In this article, the 12C induced reactions on 24Mg leading to two heavy nuclei in the exit channel were studied at several bombarding energies between 42 and 84 MeV. By means of a kinematical analysis the two-nuclei exclusive events are separated from those where the binary fragmentation is followed by light-particle evaporation.
9 citations
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TL;DR: In this paper, an algorithm to extract the multiplicity and the higher moments of a multiplicity distribution from the measured counting rates of multiple coincidences is described, which results in a well converging procedure to obtain the moments.
Abstract: An algorithm to extract the multiplicity and the higher moments of a multiplicity distribution from the measured counting rates of multiple coincidences is described. In the statistical averaging process a direct transformation to the central moments is performed which results in a well converging procedure to obtain the moments. Important aspects of error analysis and of numerics are outlined. The generality of the formalism allows applications beyond nuclear physics. Guidelines for optimizing an experimental set-up are given.
8 citations
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TL;DR: In this paper, a time-of-flight telescope using two thin plastic scintillator films as start-and stop-detectors is described, achieving separation of different ions with different energies by time measurement and by thin film light response.
5 citations
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TL;DR: In this article, the state-of-the-art in fuel rod structural analysis is discussed and possible future developments in this field are outlined, and the conclusion is drawn that the most important goal for future research is a deeper understanding of material behavior.
Abstract: The state-of-the-art in fuel rod structural analysis is discussed, and possible future developments in this field are outlined. The conclusion is drawn that the most important goal for future research is a deeper understanding of material behavior. It is suggested that a strategy of successive use of diverse models appropriate to the varying degrees of theoretical sophistication be followed in fuel rod structural analysis: preliminary work should be an analysis of the integral fuel rod with one-dimensional models, followed by local two-dimensional analyses. Finally, the deterministic analyses should be augmented by probabilistic work. All these modeling approaches are inevitably complementary in exhaustive fuel rod analysis, but they are, despite the tremendous theoretical efforts, no substitute for fuel rod performance tests. Nevertheless, analytical modeling will remain an indispensable tool for a long time to come, since with this theoretical background, the interpretation of experimental results is facilitated, and a better insight into fuel rod behavior is provided.
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01 Jan 1978TL;DR: In this article, it is shown that with increasing integration the relation between perfect integrated circuits and the total number of produced integrated circuits decreases, and that the achieved quality standard and the failure level determine the scale of integration at which the minimum cost can be achieved.
Abstract: In the production of large scale integrated semiconductor circuits, and especially of semiconductor memories with high storage capacity, the deviations from the intended ideal state, i.e. the failures, are very important, as their nature and concentration determine the number of individual devices (transistors) and individual functions (storage elements) that can be combined as an integrated circuit (IC) on a single monocristalline substrate. The special dependences are characterized by the facts that with increasing integration the relation between perfect integrated circuits (i.e. without failures) and the total number of produced integrated circuits decreases, and, furthermore, that the achieved quality standard and the failure level determine the scale of integration at which the minimum cost can be achieved. Finally, the quality standard of the factory determines the reliability in a high degree, i.e. the frequency with which the integrated circuits installed in the electronic equipment fail in operation.