04 Fakultät Energie-, Verfahrens- und Biotechnik

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/5

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Open Access
β-galactosidase production in two- and threedimensionally cultivated cell cultures
(1991) Klünder, Irene; Hülser, Dieter F.
In these studies, we demonstrate that the threedimensional arrangement of the cells in spheroids influences the β-galactosidase activity of transfected ltk--cells. In contrast to cells grown in monolayer culture cells growing as spheroids lost their β-galactosidase activity within few days. The reduction of β-galactosidase activity in cells grown as spheroids was not caused by a lost of the lacZ-gene as can be seen from the recovery of the β-galactosidase production when cells were retransferred in monolayer culture. As we showed in cells cultivated as monolayer, β-galactosidase activity seems to be not impaired by gradients of nutrient supply or cell cycle. These measurements are confirmed by histological sections, where the highest β-galactosidase activity was found in the viable center of the spheroids.
Open Access
Der Abbau von Modellstrukturen der Kohle: Stoffwechselweg des Dibenzofuran- und Fluorenabbaus
(1991) Engesser, Karl-Heinrich; Strubel, Volker; Trenz, Stefan Peter; Rothe, Bernd; Schmid, Andreas; Knackmuss, Hans-Joachim
Several microorganisms have been isolated degrading structural elements of coal like dibenzofuran. fluorene and biphenyl. Extensive investigation of the degradation pathways revealed a common mechanism of initial attack. Although catalyzed by different enzymes, all three substrates are converted to 3-phenyl-substituted catechols, which, after meta-cleavage are transformed to simple aromatic structures like salicylate, phthalate and benzoate. This ring cleaving enzymes have been cloned and are further analyzed after subcloning. Two different initial dioxygenases seem to be present in some strains cataIyzing ether cleavage of dibenzofuran and oxygenation of biphenyl respectively. Attempts are presently made to clone the first enzyme in order to produce higher yields of its optically active products. Some of these compounds have been characterized and may be of commercial value as fine chemicals.
Open Access
Abschaltung von dezentralen Erzeugungsanlagen infolge von Unterspannungen im Kontext von LFSM-O
(2022) Schöll, Christian; Lehner, Joachim; Weidner, Johannes; Lens, Hendrik
Bei einer Überfrequenz jenseits von 50,2 Hz müssen sämtliche Erzeugungsanlagen ihre in das Netz eingespeiste Wirkleistung reduzieren. In den zumeist resistiv geprägten Verteilungsnetzen der Mittel- und Niederspannung führt diese überfrequenzbedingte Leistungsreduktion zu einer lokalen Absenkung des Spannungsprofils. Unterschreiten die Spannungen die Vorgaben aus den Netzanschlussbedingungen, unter denen dezentrale Erzeugungsanlagen die Verbindung zum Netz aufrechterhalten müssen, kann es zu unterspannungsbedingten Schutzabschaltungen kommen. Theoretisch könnten diese bei großflächigem Auftreten zu einer Umkehr des ursprünglichen Überfrequenzereignisses in ein Unterfrequenzereignis führen. Anhand von simulationsbasierten Untersuchungen wird in diesem Beitrag jedoch aufgezeigt, dass unter realitätsnahen Annahmen und unter Berücksichtigung der nationalen Richtlinien sowie der zugehörigen netzplanerischen Leitplanken kein besonderes Risiko hinsichtlich der Anregung der beschriebenen Wirkungskette vorliegt.
Open Access
Aktuelle Situation und Trends im Europäischen und Deutschen Kraftwerksmarkt
(2002) Voß, Alfred
Mit der Liberalisierung der Strommärkte in Europa im Jahr 1998 wurde ein Prozess des Wandels und der strukturellen Veränderungen eingeleitet, der in seiner Dynamik und Reichweite nur von wenigen vorausgesehen worden ist. Der mit der Aufhebung der rechtlich geschützten Versorgungsgebiete einsetzende Preis- und Veränderungswettbewerb hat zu Strompreiseinbrüchen sowohl bei den Großhandelspreisen wie auch bei den Endkundenpreisen geführt. Nachdem der Wholesale-Strompreis mit unter 18 Euro/MWh im Jahr 1999 sein tiefstes Niveau erreicht hatte, kam es in der Folgezeit zu einem Preisanstieg, der jedoch im Wesentlichen durch das Anziehen der Preise für Steinkohle, Erdgas und Öl bedingt war. Dem auch durch neue Marktteilnehmer härter gewordenen Wettbewerb sowie dem drohenden Margenverfall und Umsatzeinbußen begegnen die traditionellen Stromanbieter durch radikale Kostensenkungsprogramme, Umorganisationen, neue Produkte und Dienstleistungen, eine neue Kundenorientierung aber auch durch Fusionen, Übernahmen und Allianzen. Mit dem angestrebten europäischen Binnenmarkt für Energie verlieren die Grenzen zu unseren Nachbarn an Bedeutung. Dies erfordert EU-weite Kategorien und Handlungsstrategien. Diese werden derzeit noch dadurch erschwert, dass die Bedingungen für die Stromerzeugung in den einzelnen Mitgliedsstaaten der EU durchaus noch unterschiedlich sind. Angefangen von den Umweltanforderungen, der steuerlichen Belastung der Unternehmen, über direkte und indirekte staatliche Interventionen zugunsten einzelner Stromerzeugungstechnologien bis hin zu der Tatsache, dass es staatliche Unternehmen gibt, die von der ungleichgewichtigen Marktöffnung profitieren. Es ist offenkundig, dass der größte Druck der Liberalisierung und Deregulierung auf der Stromerzeugung lastet, denn die Wettbewerber kommen nicht nur aus Deutschland, sondern aus ganz Europa, d.h. die eigenen Erzeugungsanlagen stehen aus Unternehmenssicht in Konkurrenz mit denen der Wettbewerber. Kostensenkungsprogramme, Kapazitätsanpassungen aber auch neue operative Prozesse wie bilateraler und börslicher Stromhandel, Risikomanagement und Beschaffungsoptimierung sollen die Wirtschaftlichkeit und Wettbewerbsfähigkeit der bestehenden Kraftwerke sicherstellen. Nach der Konzentration auf die mehr kurzfristigen operativen Herausforderungen in den letzten Jahren, müssen sich die verbleibenden Akteure nun mit den längerfristigen Perspektiven, d.h. auch mit dem Zubau von Kraftwerksleistung beschäftigen, um den dauerhaften gewinnbringenden Fortbestand ihrer Unternehmen zu sichern. Auch aus dem Bereich der Elektrizitätswirtschaft häufen sich die Stimmen, die vor einem Mangel an Kraftwerksleistung und Versorgungsengpässen in Deutschland und Europa nach 2010 warnen, wenn nicht rechtzeitig ein Neubauprogramm in Angriff genommen wird.
Open Access
Altered lipid matrix changes energy distribution in thylakoids
(1987) Graf, Josef A.; Strasser, Reto J.; Kull, Ulrich
Photosynthetic membranes differ from other cellular rnembranes in that they have a thylakoid specific lipid composition and a high degree of polyunsaturated fatty acids. The typical acyl lipid complement of thylakoids seems to have two functions: the organization of the membrane matrix in which the pigment protein complexes are embedded and the indirect structure-function relationships between lipid matrix and pigment protein complexes which influence energy distribution behaviour. The role of high amounts of polyunsaturated fatty acids and indirect structure-function rclationships can be studied by inhibiting fatty acid desaturation sequence with pyridazinone herbicides.
Open Access
Analysis of transient stability of generator groups in the future power system
(2022) Scheifele, Daniel; Lens, Hendrik
Transient stability is an essential property of electrical power systems. It describes the ability of the system to maintain synchronous operation of all generators. Classically, transient stability of individual generators is analyzed based on possible loss of synchronism after near short-circuit faults. In contrast, this paper considers transient stability of generator groups as a potential instability phenomenon in future grid scenarios. We investigate and analyze relevant factors of influence and countermeasures and modeling aspects to consider when studying the phenomenon. Based thereon we discuss the effectiveness of possible countermeasures. The main focus of this paper is to provide a better understanding of the underlying dependencies within the power system and their impact on the stability itself.
Open Access
The application of throughflow optimisation to the design of radial and mixed flow turbines
(2010) Cox, Graham D.; Fischer, Christian; Casey, Michael V.
Radial and mixed flow turbines are important components of turbochargers in automotive engines. Their aerodynamic design is generally compromised by severe mechanical constraints, to deal with high temperature and unsteady operation, but also by the requirement of low inertia for rapid turbocharger response from low engine speed. Conventionally, the designer deals with these constraints in the preliminary design, using a high degree of empiricism, followed by extensive CFD analysis and geometry optimisation. This paper describes a new approach to the preliminary design using a quasi-3D throughflow method coupled to an optimiser, which allows a more rapid consideration of the design issues before moving on to 3D CFD analysis. The throughflow-based optimisation system was able to increase efficiency by over 3% at the same inertia or to reduce inertia by 20-30% at the same efficiency, compared to a baseline design.
Open Access
Are biological effects of shock waves caused by free radicals?
(1991) Suhr, Dierk; Brümmer, Franz; Hülser, Dieter F.
Stone fragmentation in extracorporeal shock wave lithotripsy as well as accompanying tissue damage are attributed to cavitation. We attempted to demonstrate and localize the occurrence of cavitation in cell-free solutions and MGH-U1 cells using sensitive dyes for the detection of cavitation-generated free radicals.
Open Access
Assessing, comparing and managing risks from energy supply strategies on a regional basis : a case study for Baden-Württemberg
(1988) Kallenbach, Ulrich; Friedrich, Rainer; Unger, Hermann; Voß, Alfred
In this paper a regional case study within the envisaged joint inter-agency project on "Assessing and Managing Health and Environmental Risks from Energy and Other Complex Industrial Systems" is proposed for Baden-Württemberg. The Institut für Kernenergetik und Energiesysteme (IKE) has performed a number of studies dealing with the evaluation and reduction of emissions and risks of energy systems. So, a very detailed data base is available which can serve as a suitable basis for further investigations related to risk management. Consequently this paper consists of three main sections with emphasis on: - description of research projects carried out by IKE in the field of energy systems and risk evaluations, - description of aims and procedures of an ongoing study on restructuring measures for the energy system in Baden-Württemberg and, - the proposal for a regional case study on risk management in the energy field for Baden-Württemberg.
Open Access
Auswirkungen eines Ausstiegs aus der Nutzung der Kernenergie
(1988) Voß, Alfred
Der Ruf nach einem Ausstieg aus der Atomenergie ist lauter geworden und verschiedene gesellschaftliche Gruppen und politische Parteien fordern die sofortige oder mittelfristige Stillegung der Kernkraftwerke in unserem Land. In diesem Zusammenhang sind in jüngster Zeit eine Reihe von Untersuchungen in Auftrag gegeben bzw. Ergebnisse von Untersuchungen und Studien veröffentlicht worden, die sich mehr oder weniger umfassend mit Fragen, Aspekten und den Auswirkungen eines Kernenergieverzichts auf die Energieversorgung, die Gesamtwirtschaft und Umwelt befassen. Das Spektrum der Befunde über die ökonomischen und ökologischen Folgen eines Kernenergieverzichts, das von diesen Studien aufgespannt wird, ist breit und die Aussagen sind für einen Außenstehenden durchaus nicht ohne Widersprüche. So werden einmal die Auswirkungen eines Kernenergieverzichts auf die Stromerzeugungskosten als vernachlässigbar klein und in anderen Fällen mit mehr als 8 Pfg/kWh beziffert. Die Spannweite der Beschäftigungseffekte reicht, um ein weiteres Beispiel anzuführem, von eInem Beschäftigungsverlust von 170 000 Arbeitsplätzen bis zu einer Erhöhung der Zahl von Arbeitsplätzen um etwa 130 000.
Open Access
Die Bedeutung der Kerntechnik für die Bewältigung der Energie-, Umwelt- und Klimaprobleme
(1991) Voß, Alfred
Eine klimaverträgliche Begrenzung der Treibhausgasemissionen wird wohl nur erreicht werden können, wenn die dafür verfügbaren, begrenzten Aufwendungen streng nach dem ökonomischen Prinzip verwendet werden, mit jeder aufgewendeten Mark eine möglichst hohe Treibhausgasminderung zu realisieren. Dies ist ein zentrales Kriterium für die Erarbeitung von Strategien und Konzepten zur Abwendung der Klimagefahren. Die Kernenergie könnte insgesamt bis zum Jahr 2005 etwa 150 Mio. t CO2 vermeiden, dies sind 20% der gegenwärtigen gesamten CO2-Emissionen in Westdeutschland, ohne daß auf die Volkswirtschaft zusätzliche Kostenbelastungen zukommen würden. Jedoch kann auch der Ausbau der Kernenergie bis zum Jahr 2005 nur einen begrenzten Beitrag zur Minderung der CO2-Emissionen leisten, der allein die Minderungsziele nicht erreichen läßt.
Open Access
Biophysical investigations of the in vitro effects of shock waves and ultrasound
(1993) Brümmer, Franz; Suhr, Dierk; Irmer, Ulrich; Bachleitner, Christoph; Hülser, Dieter F.
To investigate the interactions of ultrasonic waves with biological tissues, we developed and standardized several in vitro models. Using these systems - artificial stones, human erythrocytes, L1210 mouse leukemia cells, multicellular spheroids, cavitation assay - we are able to elucidate the mechanisms of interaction as well as the cause of clinically observed side effects.
Open Access
Challenges and state of the art in industrial FSW - pushing the limits by high speed welding of complex 3D contours
(2018) Hoßfeld, Max; Hofferbert, Dave
Over the last 25 years, Friction Stir Welding (FSW) has been gradually moving from research over first applications into mass production. Today, requirements for consistently high-quality welds occur in parallel with a demand for high throughput as well as production flexibility. This paper gives an insight to the state of the art of industrial FSW mass production, current trends, challenges and market demands as well as the potential of high speed complex contour welding on modern multi-axis FSW machinery with respect to process parameters, material properties, machinery requirements and control algorithms, and methods. The design strategy of complex 3D contours as a chance to maximize efficiency is introduced; challenges of its implementation with respect to the state of the art in FSW are described. This includes the importance of advanced force control methods, fixture design, clamping forces and methodology for sustaining high-quality welds as well as the management of distortions and residual stresses by thermal management and optimization of process parameters. Examples of successful weld performance are described. Steps to be taken that result in high-quality welds, as well as situations to be avoided, are discussed. The publication was written based on results of the DFG project RO 651/16-1 that was carried out at the University of Stuttgart.
Open Access
Changes of the membrane matrix rearrange pigment complexes : abstract only
(1984) Graf, Josef A.; Strasser, Reto J.; Kull, Ulrich
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Open Access
Characterization of gap junctions by electrophysiological and electronmicroscopical methods
(1990) Hülser, Dieter F.; Paschke, Dietmar; Brümmer, Franz; Eckert, Reiner
Gap junctions are ubiquitous in the animal kingdom from mesozoa to vertebrates. They must be discriminated from desmosomes which anchor cells together to form structural or functional units as well as from tight junctions which seal membranes of epithelial cells to each other so that the paracellular path becomes impermeable to molecules and a polarity of apical and basolateral surface is maintained.
Open Access
Commercialisation of renewable energies issues and actions
(1988) Voß, Alfred
The technical development of renewable energy technologies has made remarkable progress during the past fifteen years. A set of technologies has reached technical maturity and economic competitiveness, at least in some markets. In accordance with general energy policy objectives, it is justified to embark on a government-supported commercialization strategy for these mature technologies. This strategy should lift the barriers to the market penetration of those mature technologies and help to establish a self-sustaining market. The most significant areas of governmental actions relate to: the improvement of information and its dissemination; the constitution of an appropriate legal, regulatory and institutional framework; as well as undistorted market conditions, and the establishment of self-sustaining markets for renewable energy technologies.
Open Access
Comparison of centralized and decentralized energy supply systems
(1991) Pfeifer, Thomas; Fahl, Ulrich; Voß, Alfred
Communal energy programs are often embedded in a conception of a decentralized energy supply system where electricity is produced by a number of smaller power plants. For a comprehensive survey the question arises whether these decentralized systems are more advantageous than centralized systems with regard to the criterions energy consumption, safety of supply, environmental compatibility and economy. In the following, after a definition of the term "decentralized", the present structure of the energy supply system in the Federal Republic of Germany is examined under the point of view whether it is more centralized or more decentralized. Then, a detailed investigation into effects of a decentralized compared to more centralized energy supply system is presented. Assuming two alternatives of supply, different energy generating plants are exemplary discussed. At last, problems concerning the organization of decentralized energy supply system which are of special interest for local and regional energy strategies are considered.
Open Access
Convection effects on stratification during charging of a hot water store
(1989) Hahne, Erich; Kübler, Rainer; Kallweit, Jörg
In domestic hot water stores the preservation of hot water layers is essential for the effective operation. Such stores are operated intermittently: when hot water is taken from the store, cold water is fed into it, so that part of the water in the store is hot and part of it is cold. These two parts should not mix, because this would deteriorate the efficiency of the store. When mixing occurs between the hot and cold parts, the hot water temperature is decreased. Thus, the store has, to be heated to a temperature above the needed temperature from the very beginning. With higher temperature, heat losses are also larger. More heat has to be fed into the mixed store than into the stratified when the same amount of heat shall be taken out with the same amount of water. Consequently, the energetic store efficiency as the ratio of heat taken from the store to heat fed into the store is less when the store temperature is higher. Thus, the store with no mixing is the best store.
Open Access
Cost-effectiveness analysis: the key for the identification of efficient response strategies to the climate issue : conceptual approach and modelling tools
(1989) Voß, Alfred; Schmid, Günter
Any reduction of greenhouse gases, particularly of carbon dioxid, to climatologically acceptable levels implies fundamental structural changes within the energy system. In the wake of drastic environment driven changes the need for effective and economically viable control strategies is evident. The paper argues that "cost-effectiveness analysis" is the appropriate point of departure for the identification of efficient response strategies. The approach and available analytical tools are outlined and the limitations are discussed. Preliminary results of a case study for the F.R.G. are presented.
Open Access
Cost-optimal emission control strategies : results of a comprehensive cost-effectiveness analysis for reducing air pollution from multiple sources
(1987) Voß, Alfred; Boysen, Barbara; Friedrich, Rainer; Mattis, Marcus
Since a cost-benefit analysis on the subject cannot be carried out because of informational difficulties, a cost-effectiveness approach for identifying the most rational cours of action seems to be the appropriate tool. Based on a careful consideration of the costs and potential emission reductions of various control measures, the "cost-effectiveness analysis" selects the most cost-effective combination from the many possibilities of environmental improvement methods aiming at the same target, e.g. the reduction of SO2- and NOx-emissions. From a methodological point of view this approach is relatively straigthforward and the rational behind it is maximizing emission reduction while minimizing related control costs.