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See detailDie bakterielle Signalverarbeitung am Beispiel des Sucrose Phosphotransferasesystems in Escherichia coli : Modellierung und experimentelle Überprüfung
Sauter, Thomas UL

Doctoral thesis (2003)

Bacterial signal processing was investigated concerning the sucrose phosphotransferase system (sucrose PTS) in the bacterium Escherichia coli as an example. The about 20 different phosphotransferase ... [more ▼]

Bacterial signal processing was investigated concerning the sucrose phosphotransferase system (sucrose PTS) in the bacterium Escherichia coli as an example. The about 20 different phosphotransferase systems (PTSs) of the cell fulfil besides the transport of various carbohydrates, also the function of one signal processing system. Extra- and intracellular signals are converted within the PTS protein chain to important regulatory signals affecting e.g. carbon metabolism and chemotaxis. A detailed dynamical model of the sucrose PTS was developed describing transport and signal processing function. It was formulated using a detailed description of complex formation and phosphate transfer between the chain proteins. Model parameters were taken from literature or were identified with own experiments. Using a formal algorithm including cluster analysis, PTS and glycolysis could be identified as biological functional units with limited autonomy. Simulation studies together with experimental hints showed that the dynamic behaviour of phosphate transfer in the PTS runs within one second. Therefore a description of steady state characteristics is sufficient for describing the signaling properties of the sucrose PTS. A steady state characteristic field describes the degree of phosphorylation of the PTS protein EIIACrr as a function of the input variables extracellular sucrose concentration and intracellular PEP:pyruvate ratio. The model has been validated with different experiments performed in a CSTR using an sucrose positive Escherichia coli W3110 derivative. A method for determining intracellular metabolite concentrations has been developed. A sample preparation technique using a boiling ethanol buffer solution was successfully applied. The PTS output signal degree of phosphorylation of EIIACrr was also measured. Steady state conditions with varying dilution rate and dissolved oxygen concentration and dynamical variations applying different stimuli to the culture were considered. Pulse, and stop feeding experiments with limiting sucrose concentrations were performed. Simulation and experimental results matched well. The same holds for the expanded sucrose PTS and glycolysis model. [less ▲]

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See detailGlobal analysis of piecewise linear systems using impact maps and quadratic surface Lyapunov functions
Goncalves, Jorge UL; Megretski, A.; Dahleh, M.

in IEEE Transactions on Automatic Control (2003), 48(12), 2089-2106

This paper presents an entirely new constructive global analysis methodology for a class of hybrid systems known as piecewise linear systems (PLS). This methodology infers global properties of PLS solely ... [more ▼]

This paper presents an entirely new constructive global analysis methodology for a class of hybrid systems known as piecewise linear systems (PLS). This methodology infers global properties of PLS solely by studying the behavior at switching surfaces associated with PLS. The main idea is to analyze impact maps, i.e., maps from one switching surface to the next switching surface. Such maps are known to be “unfriendly” maps in the sense that they are highly nonlinear, multivalued, and not continuous. We found, however, that an impact map induced by an linear time-invariant flow between two switching surfaces can be represented as a linear transformation analytically parametrized by a scalar function of the state. This representation of impact maps allows the search for surface Lyapunov functions (SuLF) to be done by simply solving a semidefinite program, allowing global asymptotic stability, robustness, and performance of limit cycles and equilibrium points of PLS to be efficiently checked. This new analysis methodology has been applied to relay feedback, on/off and saturation systems, where it has shown to be very successful in globally analyzing a large number of examples. In fact, it is still an open problem whether there exists an example with a globally stable limit cycle or equilibrium point that cannot be successfully analyzed with this new methodology. Examples analyzed include systems of relative degree larger than one and of high dimension, for which no other analysis methodology could be applied. This success in globally analyzing certain classes of PLS has shown the power of this new methodology, and suggests its potential toward the analysis of larger and more complex PLS. [less ▲]

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See detailZerstörungsfrei lösbares Schlusselement für axial und radial gefügte mechanische Verbindungen
Klett, Jan; Großmann, Christoph; Kammerer, Uwe et al

Patent (2003)

The connecting element comprises a bolt (1) and geometrically defined balls (2) which by a housing (4) and a tube (3) are brought into a defined position and held there. The bolt is introduced into the ... [more ▼]

The connecting element comprises a bolt (1) and geometrically defined balls (2) which by a housing (4) and a tube (3) are brought into a defined position and held there. The bolt is introduced into the mechanism consisting of the balls, housing and tube by its contour which conforms to the geometrically defined balls, with a form fit being created between the bolt and the aforesaid mechanism. As the diameter of the mechanism is greater than that of the bore in the connecting halves (6,7) a form fit is created between the connecting element and connecting partners like a screw head. [less ▲]

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See detailEl aprendizaje y la ensenanza de los movimientos: Contradicciones entre la teoría y la práctica del deporte?
Bund, Andreas UL; Hopf, Herbert

in Educación física Chile (2003), 262

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See detailA framework for designing transgenic crops - science, safety, and citizen’s concerns.
König, Ariane UL

in Nature Biotechnology (2003), 21

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See detailDerivative relationships between volume and surface area of compact regions in Rd
Marichal, Jean-Luc UL

Presentation (2003, October 21)

We explore the idea that the derivative of the volume, V , of a region in Rp with respect to r equals its surface area, A, where r = p V/A. We show that the families of regions for which this formula for ... [more ▼]

We explore the idea that the derivative of the volume, V , of a region in Rp with respect to r equals its surface area, A, where r = p V/A. We show that the families of regions for which this formula for r is valid, which we call homogeneous families, include all the families of similar regions. We determine equivalent conditions for a family to be homogeneous, provide examples of homogeneous families made up of non-similar regions, and offer a geometric interpretation of r in a few cases. [less ▲]

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See detailZur Wirkung externaler versus internaler Aufmerksamkeitsfoki beim Erlernen einer Bewegungsfertigkeit mit proximalem Effekt
Bund, Andreas UL; Gass, Svenja; Weidenauer, Jörg

in Krug, Jürgen; Müller, Thomas (Eds.) Messplätze - Messplatztraining - Motorisches Lernen (2003, October)

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See detailGibt es Präferenzen beim selbstgesteuerten Bewegungslernen?
Bund, Andreas UL

in Krug, Jürgen; Müller, Thomas (Eds.) Messplätze - Messplatztraining - Motorisches Lernen (2003, October)

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See detailRapid stimulation of free glucuronate formation by non-glucuronidable xenobiotics in isolated rat hepatocytes
Linster, Carole UL; Van Schaftingen, Emile

in Journal of Biological Chemistry (2003), 278(38), 36328-33

Vitamin C synthesis in rat liver is enhanced by several xenobiotics, including aminopyrine and chloretone. The effect of these agents has been linked to induction of enzymes potentially involved in the ... [more ▼]

Vitamin C synthesis in rat liver is enhanced by several xenobiotics, including aminopyrine and chloretone. The effect of these agents has been linked to induction of enzymes potentially involved in the formation of glucuronate, a precursor of vitamin C. Using isolated rat hepatocytes as a model, we show that a series of agents (aminopyrine, antipyrine, chloretone, clotrimazole, metyrapone, proadifen, and barbital) induced in a few minutes an up to 15-fold increase in the formation of glucuronate, which was best observed in the presence of sorbinil, an inhibitor of glucuronate reductase. They also caused an approximately 2-fold decrease in the concentration of UDP-glucuronate but little if any change in the concentration of UDP-glucose. Depletion of UDP-glucuronate with resorcinol or d-galactosamine markedly decreased the formation of glucuronate both in the presence and in the absence of aminopyrine, confirming the precursor-product relationship between UDP-glucuronate and free glucuronate. Most of the agents did not induce the formation of detectable amounts of glucuronides, indicating that the formation of glucuronate is not due to a glucuronidation-deglucuronidation cycle. With the exception of barbital (which inhibits glucuronate reductase), all of the above mentioned agents also caused an increase in the concentration of ascorbic acid. They had little effect on glutathione concentration, and their effect on glucuronate and vitamin C formation was not mimicked by glutathione-depleting agents such as diamide and buthionine sulfoximine. It is concluded that the stimulation of vitamin C synthesis exerted by some xenobiotics is mediated through a rapid increase in the conversion of UDP-glucuronate to glucuronate, which does not apparently involve a glucuronidation-deglucuronidation cycle. [less ▲]

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See detailUn système plurilingue peut-il être efficace?
Martin, Romain UL; Houssemand, Claude UL

in Cahiers du Service de Pédagogie Expérimentale (SPE) (2003, September), 15(16), 157-164

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See detail"Kinder stark machen!" Selbstvertrauen fördern
Bund, Andreas UL; Biemann, Anja; Sudermann, Arthur

in Sportpraxis (2003), 44(4), 20-24

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See detailStrategien beim selbstgesteuerten Bewegungslernen
Bund, Andreas UL

Scientific Conference (2003, September)

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See detail„Kleider machen Leute“. Die äußere Erscheinung als Attribut von Personkategorien
Kneer, Julia; Krolak-Schwerdt, Sabine UL

Scientific Conference (2003, September)

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