Universität Stuttgart
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Item Open Access Ein Energiemodellsystem zur Analyse der Entwicklungsmöglichkeiten der Energieversorgung(1977) Voß, AlfredDas generelle Ziel der Modellentwicklungsarbeiten ist es, ein Instrumentarium für die Analyse der Entwicklungsmöglichkeiten des Energiesystems der BRD zu schaffen. Dabei sollen insbesondere die Wechselwirkungen des Systems mit seiner Umgebung, wie z. B. der gesamten Wirtschaft, der Gesellschaft und der Umwelt, berücksichtigt werden.Item Open Access Erfahrungsbericht über eine praxisbezogene Lehrveranstaltung "Warentestergebnisse und Absatzpolitik von Unternehmen", SS 1977 und WS 1977/78(1979) Arnold, UlliDie Lehrveranstaltung, über die hier berichtet werden soll, wurde vom Seminar für betriebswirtschaftliche Marktlehre der Universität Göttingen getragen. Das Seminar ist (mit-)verantwortlich für die Ausbildung von Volks- und Betriebswirten und Handelslehrern und betreut zwei Prüfungsfächer für das Diplom-Examen, nämlich "Betriebswirtschaftliche Marktlehre" (Absatz- und Beschaffungslehre) und "Handelsbetriebslehre". Für diese Fächer ist ein Pflichtveranstaltungsprogramm fixiert, das durch praxisorientierte bzw. praxissimulierende Lehrveranstaltungen wie z. B. Fallstudien-Seminare, Planspiele, Exkursionen, Fachvorträge von Praktikern, Marktforschungspraktika usw. ergänzt wird.Item Open Access On the modelling of artificial reoxygenation(1977) Markofsky, Mark; Kobus, HelmutThe results of laboratory studies on the efficiency of oxygen transfer from two dimensional bubble curtains produced by passing compressed air through a porous filter (mean diameter 180μ) and a perforated diffusor pipe (1 mm diameter ports) are presented. Comparisons with other laboratory and field data as well as with on approximate theory for oxygen transfer are made. Surface effects are found to play an important role in the present experiments tending to increase the overall apparent oxygen transfer efficiency.Item Open Access Nervous-system-specific carcinogenesis by ethylnitrosourea in the rat: molecular and cellular aspects(1977) Rajewsky, Manfred F.; Augenlicht, Leonard H.; Biessmann, Harald; Goth, Regine; Hülser, Dieter F.; Laerum, Ole D.; Lomakina, L. Ya.A lead in the search for cellular determinants favoring neoplastic transformation may be provided by the pronounced tissue specificity of the oncogenic effect of certain carcinogens which do not require enzymatic metabolic activation, i.e., in cases where this specificity cannot be due to tissue differences in the activity of enzymes involved in the formation of the ultimate reactants. A carcinogen that fulfills this condition is the ethylating agent N-ethyl-N-nitrosourea (EtNU). Alkylation of nucleic acid constituents by N-nitroso compounds in relation to mutagenesis and carcinogenesis has received considerable attention recently.Item Open Access Molecular and cellular mechanisms in nervous system-specific carcinogenesis by N-ethyl-N-nitrosourea(1976) Rajewsky, Manfred F.; Goth, Regine; Laerum, Ole D.; Biessmann, Harald; Hülser, Dieter F.A single pulse of N-ethyl-N-nitrosourea (ENU), applied to BDIX rats during the perinatal age, specifically results in a high incidence of neuroectodermal neoplasms in the central and peripheral nervous system (NS). The pronounced sensitivity of the developing NS suggests a dependence of the carcinogenic effect on the proliferative and/or differentiative state of the target cells at the time of the ENU pulse. The specificity of ENU for the NS cannot be due to tissue variations in the degree of carcinogen-cell interactions, since the reactive, electrophilic ethyl cation is produced by rapid, nonenzymatic decomposition of ENU indiscriminately in all tissues. Correspondingly, the initial molar fractions of ethylated purine bases are similar in the DNA of "high-risk" (perinatal brain) and "low-risk" tissues (e.g., liver; adult brain). However, while the respective half lives in DNA of N7-ethylguanine and N3-ethyladenine show only minor differences for both types of tissues, the mutagenic ethylation product 06-ethylguanine is removed from brain DNA very much more slowly than from the DNA of other tissues. Together with their high rate of DNA replication during the perinatal age, the incapacity of rat brain cells for enzymatic elimination of 06-alkylguanine from their DNA could account for an increased probability of neoplastic conversion, and hence for the NS specificity of ENU in the rat.Item Open Access Methods for reducing thermal influences on the accuracy of machine tools(1977) Spur, Günter; Lechler, Gerhard; Heisel, UweAs the automation of manufacturing process is increasing and because higher machining accuracy is mandatory the disturbance variables influencing the performance of machine tools must be controlled. This paper attempts to give a survey of the present knowledge of the thermal behaviour of machine tools. The effects of thermal disturbances are described and compared with other disturbances. Common methods for the investigation of the thermal behaviour are presented. The methods for reducing thermal disturbances are classified under different topics. Known methods are summarized.Item Open Access Resonance and relaxation attenuation by neutral acceptors in a magnetic field(1977) Schad, Hanspeter; Lassmann, Kurt; Zeile, HeinrichFine structure, level splitting, and relaxation times of the acceptor ground state in cubic semiconductors can be deduced from ultrasonic attenuation. By the application of a magnetic field it is possible to vary the coupling strength and the number of acceptors on speaking terms with the ultrasonic wave. Making use of this possibility, we have determined directly effective coupling constants for relaxation attenuation and the temperature dependence of the critical intensity for saturation of the resonant interaction. Results obtained for p-type GaAs and Si are discussed in comparison with analogous results for glasses.Item Open Access Effect of buoyancy on the flow and temperature fields near injection wells(1979) Mehlhorn, Hans; Kobus, HelmutThe injection of heated water into a ground water stream of constant velocity is studied. The heated water is discharged through a fully penetrating injection well into a confined aquifer of constant thickness. For steady state conditions and under the assumption that heat conduction and dispersion in the aquifer and through the confining layers are negligible in comparison to the convective heat transport, it is shown that the flow and temperature field is dependent on the relative infiltration rate and on the relative buoyancy of well discharge. First results of a steady-state three-dimensional numerical model are given.Item Open Access Verbraucherschutz bei öffentlichen Gütern(1977) Arnold, UlliDie Analyse der Verbraucherschutzaspekte hinsichtlich des Austausches von Gütern und Leistungen, die öffentliche Anbieter zur Verfügung stellen, ist u.E. dazu geeignet, die Verknüpfungen produktions- und konsumorientierter Bedürfnisse aufzuzeigen, weil hier eine Interessenidentität zwischen "Produzent" und "Konsument" behauptet wird. Öffentliche Güter und Leistungen werden nicht vermittels marktlicher Transaktionen ausgetauscht, sondern von staatlichen Institutionen individuell oder kollektiv zur Verfügung gestellt. Öffentliche Güter im engsten Sinne (sogn. "reine öffentliche Güter") sind solche, die kollektiv zur Verfügung gestellt werden; alle Bürger werden gleichsam pauschal als Nachfrager angesehen. Der wesentliche Unterschied zum privaten Güteraustausch liegt darin, daß die Nachfrager gezwungenermaßen nur mit einem Anbieter zu tun haben und daß keine direkte Relation zwischen Beiträgen und Anreizen besteht. Die Beiträge werden global über die Besteuerung der Bürger erhoben; eine Rückkopplunq der Verbraucher, wie sie privaten Anbietern gegenüber möglich ist, entfällt.Item Open Access ODMR of phanes and charge transfer phanes(1979) Schweitzer, Dieter; Goldacker, Wilfried; Hausser, Karl H.; Staab, Heinz A.Triplet zero field splitted parameters |D| and |E| and decay rates ki of the triplet sublevels of two stereoisomeric tetramethoxy [2.2] paracyclophanes as well as those of two CT [2.2] paracyclophanes in low concentration in glasses and small neat single ctystals as measured by ODMR in zero fields at 1,3 K are presented.