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  • 1
    Electronic Resource
    Electronic Resource
    Biased Diffusion with Correlated Noise (1999)
    Springer
    Journal of statistical physics 95 (1999), S. 569-586 
    Details
    ISSN: 1572-9613
    Keywords: nonequilibrium steady states ; driven diffusive systems ; correlated noise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The diffusion of hard-core particles subject to a global bias is described by a nonlinear, anisotropic generalization of the diffusion equation with conserved, local noise. Using renormalization group techniques, we analyze the effect of an additional noise term, with spatially long-ranged correlations, on the long-time, long-wavelength behavior of this model. Above an upper critical dimension d LR, the long-ranged noise is always relevant. In contrast, for d〈d LR, we find a “weak noise” regime dominated by short-range noise. As the range of the noise correlations increases, an intricate sequence of stability exchanges between different fixed points of the renormalization group occurs. Both smooth and discontinuous crossovers between the associated universality classes are observed, reflected in the scaling exponents. We discuss the necessary techniques in some detail since they are applicable to a much wider range of problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004562408226
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Abhängigkeit der Wärmeübergangskoeffizienten vom Wandtemperaturverlauf und die Konsequenzen für die Berechnung von Wärmedurchgangskoeffizienten bei Wärmetauschern (1996)
    Springer
    Heat and mass transfer 31 (1996), S. 153-161 
    Details
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Abstract In a recent article [2] it has been shown that the common equation in VDI Heat Atlas [1], which has been used for the calculation of overall heat transfer coefficients, satisfies the energy balance of the heat exchanger in seldom exceptional cases only. This equation has been corrected for constant wall temperature. In this article an equation for the calculation of overall heat transfer coefficients valid for any shape of the wall temperature will be developed at which it becomes obvious, that only in the case of identical shapes of wall temperature in measurement and real heat exchanger process the calculation according to VDI Heat Atlas [1] is valid. In all other cases this procedure leads to errors.
    Notes: Zusammenfassung In einem früheren Aufsatz [2] wurde dargestellt, daß die gebräuchliche Berechnungsvorschrift für Wärmedurchgangskoeffizienten gemäß VDI-Wärmeatlas [1] nur in Ausnahmefällen der Energiebilanz für den Wärmetauscher genügt. Diese Berechnungsvorschrift wurde für den Fall konstanter Wandtemperatur korrigiert. In dieser Arbeit wird eine verallgemeinerte Gleichung für die Berechnung von Wärmedurchgangskoeffizienten bei beliebigem Wandtemperaturverlauf aufgestellt. Die Berechnung nach VDI-Wärmeatlas [1] ist danach nur im Fall gleicher Wandtemperaturverläufe bei Messung und realem Betrieb im Wärmetauscher gültig. In allen anderen Fällen führt dieses Vorgehen zu Fehlern.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02333313
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Abhängigkeit der Wärmeübergangskoeffizienten vom Wandtemperaturverlaufund die Konsequenzen für die Berechnung von Wärmedurchgangskoeffizienten bei Wärmetauschern (1996)
    Springer
    Heat and mass transfer 31 (1996), S. 153-161 
    Details
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Abstract  In a recent article [2] it has been shown that the common equation in VDI Heat Atlas [1], which has been used for the calculation of overall heat transfer coefficients, satisfies the energy balance of the heat exchanger in seldom exceptional cases only. This equation has been corrected for constant wall temperature. In this article an equation for the calculation of overall heat transfer coefficients valid for any shape of the wall temperature will be developed at which it becomes obvious, that only in the case of identical shapes of wall temperature in measurement and real heat exchanger process the calculation according to VDI Heat Atlas [1] is valid. In all other cases this procedure leads to errors.
    Notes: Zusammenfassung  In einem früheren Aufsatz [2] wurde dargestellt, daß die gebräuchliche Berechnungsvorschrift für Wärmedurchgangskoeffizienten gemäß VDI-Wärmeatlas [1] nur in Ausnahmefällen der Energiebilanz für den Wärmetauscher genügt. Diese Berechnungsvorschrift wurde für den Fall konstanter Wandtemperatur korrigiert. In dieser Arbeit wird eine verallgemeinerte Gleichung für die Berechnung von Wärmedurchgangskoeffizienten bei beliebigem Wandtemperaturverlauf aufgestellt. Die Berechnung nach VDI-Wärmeatlas [1] ist danach nur im Fall gleicher Wandtemperaturverläufe bei Messung und realem Betrieb im Wärmetauscher gültig. In allen anderen Fällen führt dieses Vorgehen zu Fehlern.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002310050039
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Diagnostic imaging using rare-earth chelates (1998)
    Springer
    Lasers in medical science 13 (1998), S. 14-21 
    Details
    ISSN: 1435-604X
    Keywords: Fluorescence ; Lanthanide chelate ; Probes ; Tissue selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract A new class of polyazamacrocyclic chelates of terbium is studied that have rich spectroscopic properties, tissue selectivity [1], millisecond fluorescence lifetimes, sharply spiked emission spectra (〈15 nm FWHM), large Stokes shifts (〉280 nm), good water solubility [1] and high fluorescence quantum yields (∼0.6 for PCTMB) [1]. We report our in vitro and ex vivo spectroscopic evaluation of these chelates. Additionally, results from cellular binding specificity studies using Sprague-Dawley rats with UMR 108 osteosarcomas are presented. Finally, endoscopic imaging of dosed tissue demonstrates the potential to use the Tb(III) chelates as contrast enhancement markers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00592956
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Field Theory of Critical Behavior in Driven Diffusive Systems with Quenched Disorder (1999)
    Springer
    Journal of statistical physics 96 (1999), S. 817-859 
    Details
    ISSN: 1572-9613
    Keywords: driven diffusive systems ; nonequilibrium steady states ; lattice gas ; phase transitions ; field-theoretic renormalization group ; quenched disorder
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present a field-theoretic renormalization-group study for the critical behavior of a uniformly driven diffusive system with quenched disorder, which is modeled by different kinds of potential barriers between sites. Due to their symmetry properties, these different realizations of the random potential barriers lead to three different models for the phase transition to transverse order and to one model for the phase transition to longitudinal order all belonging to distinct universality classes. In these four models, which have different upper critical dimensions d c, we find the critical scaling behavior of the vertex functions in spatial dimensions d〈d c. The deviation from purely diffusive behavior is characterized by the anomaly exponent η, which we calculate at first and second order, respectively, in ε=d c−d. In each model η turns out to be positive, which means superdiffusive spread of density fluctuations in the driving force direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004610726108
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  • 6
    Electronic Resource
    Electronic Resource
    Monitoring of nicotine in air using sorptive enrichment on polydimethylsiloxane and TD-CGC-NPD (1999)
    Springer
    Chromatographia 49 (1999), S. 520-524 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Sorptive preconcentration ; Air monitoring ; Nicotine ; Hospital air
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A novel method for the enrichment of nicotine from gaseous samples is presented. It is based on the sampling of 6 liters of air onto a cartridge packed with 100% polydimethylsiloxane (PDMS) particles. The analytes are dissolved (partitioned) into the PDMS phase which results in much better recoveries and reproducibilities compared to those obtained on common adsorbents. The PDMS tube is then placed in a thermal desorption (TD) unit connected to a CGC-NPD or CGC-MS system. The procedure was employed for routinely monitoring air in a hospital. Nicotine was typically found at levels ranging from 5 to 250 μg m−3 (ppb) depending on the location and number of smokers present. Additionally, the efficiency of nicotine filters was determined by sampling simultaneously at the filter in- and outlet and was found to be 46%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467752
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    The synthesis and polymerization of oxo-crown ethers (1996)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 47 (1996), S. 485-491 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A novel synthetic route to and a polymerization procedure for oxo-crown ethers 2, 11-dioxo-18-crown-6 (1), 2-oxo-12-crown-4 (2) and 2-oxo-21-crown-7 (3) are described. Cyclization of the ω-hydroxycarboxylic acid precursors of 1 - 3 has been achieved by heating these precursors in the presence of a Lewis acid catalyst (CoCl2) and a template salt (MCl). Cyclization yields up to 82% were reached, using CsCl as template salt. Oxo-crown ethers 1 - 3 have been polymerized using SnOct2 as catalyst, giving polymers with molecular weights of approximately 5 kg/mol and dispersities of ca. 1.8 (measured with polyethylene oxide standards). The polymerization of 2 was monitored with 1H-NMR and SEC giving information about (a) the influence of monomer/catalyst ratio and temperature on polymerization rate and (b) the influence of temperature on molecular weight (distribution). The possibility of introducing endgroups into poly(2-oxo-12-crown-4) using SnOct2-catalyzed polymerization was also studied.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1996.010471103
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