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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 464 (1986), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 29 (1985), S. 637-642 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Exclusive semileptonic decays of heavy mesons provide interesting information on systems consisting of quarks of unequal mass. We express the formfactors of the hadronic current in terms of relativistic bound state wave functions for which we take the solutions of a relativistic harmonic oscillator potential. The wave function overlap is determined by the quark mass dependent longitudinal momentum distribution and differs from results based on non relativistic wave functions. The semileptonic widths and lepton spectra are calculated using in addition nearest pole dominance for the momentum transfer dependence of the formfactors. We compare our results with recent experimental data. The formfactor calculation also allows an estimate of special nonleptonic transitions. From the CLEO results on $$\bar B^0 \to \pi ^ + \pi ^ -$$ and $$\bar B^0 \to D^{* + } + \pi ^ -$$ we find for the corresponding Kobayashi-Maskawa matrix element ratio the limit |V ub /V cb |≲0.3.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Archive of applied mechanics 57 (1987), S. 39-50 
    ISSN: 1432-0681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Summary The plane torsion test serves for determining stress-strain curves of thin sheet metal. When a torque is applied simple shear takes place in the free zone of the specimen and causes principal tensile and compressive stresses. Under certain material and geometrical conditions these compressive stresses may cause buckling of the sheet, so that the assumed state of plane stress and plane strain which enables test evaluation is no longer fulfilled. This limits the applicability of the test. By using the strain energy method the critical conditions for elastic and plastic buckling have been analysed and discussed in comparison with experimentally obtained data. A variation of parameters showed how geometry could be varied in order to decrease the tendency towards buckling.
    Notes: Übersicht Der ebene Torsionsversuch dient zur Aufnahme der Fließkurven dünner Bleche. Durch die Torsionsbelastung im ringförmigen nicht abgestützten Teil der Platine ergibt sich ein Zug-Druck-Hauptspannungszustand, der bei bestimmten Werkstoff- und Geometriegegebenheiten ein Ausknicken des Bleches aus der Ebene bewirkt. Hierdurch wird von den für die Auswertung des Versuches vorausgesetzten ebenen Formänderungs- und Spannungszuständen abgewichen und somit seine Anwendbarkeit begrenzt. Mit Hilfe der Formänderungs-Energie-Methode wurden die kritischen Bedingungen für elastische und plastische Faltenbildung berechnet und experimentellen Ergebnissen gegenübergestellt. Die durchgeführte Variation der Geometrieparameter gibt darüber Aufschluß, durch welche Veränderungen die Faltenbildung unterdrückt werden kann.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 113 (1989), S. 279-282 
    ISSN: 1573-5036
    Keywords: forest decline ; nitrogen immission ; nutrient status ; Pinus sylvestris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Near a hen house (50–600 m), vitality ofPinus sylvestris, N-, P-, K-, Ca-, Mg-contents of the needles, N-, Mg-, K-, Ca- and Al-contents in soil extracts and NH3/NH 4 + -contents of the air were determined. Damage symptoms occurred when N-immissions hit the canopy directly. In contrast no visible decline of the above ground plant could be observed if N was mainly deposited on the soil.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 34 (1987), S. 103-115 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Recent experimental results onD-,D s - andB-decays are interpreted on the basis of the valence quark model. For nonleptonic decays generally good results are obtained using factorization with little direct annihilation. Final state interaction causes corrections, however: small bare amplitudes can be fed by stronger amplitudes through channel mixing. This effect can simulate or enhance weak annihilation processes in particular if high lying resonances contribute. A comparison of $$D^0 \to \bar K^0 \phi $$ withD s →ϱπ decays will clarify this issue. The effective QCD coefficients obtained in the analysis are discussed and used to estimate the contribution of two-body decays to the total widths. The result reflects already the lifetime differences betweenD 0 andD + mesons. Predictions for numerousB-decay branching rations allow for further tests and for a determination of so far unknown decay constants. A first bound on |V ub | from nonleptonic decays is found from the experimental limit on $$\bar B^0 \to \pi ^ + \pi ^ - $$ .
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  • 6
    ISSN: 1573-0867
    Keywords: 1-amidino-2-thiourea ; 3,5-diamino-1,2,4-thiadiazole ; dicyandiamide ; thiourea ; nitrification inhibitor ; urea ; ammonium sulfate ; Nitrosomonas europaea ; N-fertilizer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The degradation of guanylthiourea (GTU) via 3,5-diamino-1,2,4-thiadiazole (TDZ) to dicyandiamide (DCD) was studied in selected soils. All three compounds could be determined by HPLC. GTU decomposed rapidly (within hours-days), the reaction from TDZ to DCD continued more slowly (within days-weeks). Soil type and temperature had an essential effect on the rate of degradation; conspicuous was a more rapid breakdown of GTU in presence of ammonium sulfate (AS) than in combination with urea. Each compound is a nitrification inhibitor; inNitrosomonas cell suspensions, 0.5 ppm GTU and 10 ppm TDZ achieved an effect comparable to 200 ppm DCD. The combination of these two effects—degradation in soil and inhibition of nitrification—were studied in soil incubation experiments. The three substances had inhibitory effects also in soil, however at significantly different application rates (20 ppm GTU or TDZ and 30 ppm DCD). Using these concentrations, AS/DCD and urea/GTU showed similar effects. Urea/GTU retarded nitrification by the factor 1.7 as compared to urea/DCD. AS/GTU had no advantage over AS/DCD which can be explained by the more rapid degradation of GTU in presence of AS. Urea/GTU apparently presents a promising possibility to utilize N-fertilizers more efficiently.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 64 (1986), S. 235-268 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The range of chaotic behavior in the Josephson effect is investigated experimentally in tin tunnel junctions and indium microbridges subjected to dc and rf bias. Chaos is found to occur between frequencies of 0.1/(2πRC) and the plasma frequency at intermediate hysteresis. The low-hysteresis onset of chaos is studied systematically by varying the critical current of an Sn/ox/Sn tunnel junction as a function of temperature. The results agree with simulations and theoretical predictions.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 38 (1987), S. 655-658 
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The average bond lengths and bond angles of the structural units of polycyanurates synthesized by polycyclotrimerization of 2,2-bis(4-cyanatophenyl)propane were measured by single crystal X-ray analysis of model compounds. An off-lattice Monte Carlo model was developed for the simulation of the geometrical structure of cyanurate oligomers with polymerization degrees up to 31. Excluded volume effects were taken into account in the form of hard spheres. The calculated results show that an occurrence of intramolecular cyclizations, which was supposed in the literature, is possible.
    Notes: Die Größen der Bindungsabstände und -winkel der in Polycyanuraten auf Basis von 2,2-Bis(4-cyanatophenyl)propan auftretenden Strukturelemente wurden durch Röntgenkristallstrukturanalyse von Modellsubstanzen ermittelt. Darauf aufbauend wurde ein Monte-Carlo off-lattice Modell zur Simulation der geometrischen Struktur auftretender Oligomere bis zu einem Polymerisationsgrad 31 entwickelt, in dem Effekte des ausgeschlossenen Volumens in Form von hard-sphere Potentialen berücksichtigt sind. Die Ergebnisse belegen unter anderem die aus experimentellen Daten resultierende Vermutung des Auftretens intramolekularer Cyclisierungen.
    Additional Material: 7 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 39 (1988), S. 548-551 
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Unter Zugrundelegung der Kinetik der Hauptreaktionen bis zum Gelpunkt - Polycyclotrimerisierung der Cyanat-gruppe, Einschubreaktion des Glycidethers und Abspaltung eines Phenols - wurde mit Hilf der Kaskadentheorie ein statistisches Strukturmodell der Reaktion von Dicyanaten mit Bisglycidethern entwickelt. Es wurde gefunden, daß die Verschiebung des kritischen OCN-Umsatzes zu höheren Werten im Vergleich zu den klassischen 50% für die reine Polycyclotrimerisation in der Abspaltung eines Phenols mit dem Grundkörper des Cyanatmonomers begründet ist.
    Notes: Basing on the kinetics of the main reactions up to the gelation point - cyclotrimerization of the cyanate, insertion of the glycidylether group and abstraction of a phenol - a statistical structural model for the reaction of a dicyanate with a bisglycidylether was developed using a cascade approach. It was found that the critical OCN conversion shift to higher values compared with the classical 50% for the pure polycyclotrimerization is caused by the abstraction of the phenol with the aromatic rest of the cyanate monomer.
    Additional Material: 3 Ill.
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  • 10
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The chemical structures formed at the reaction of glycidylethers with aromatic cyanates were identified. In dependence on the molar ratio of the monomers, different parts of triazines, alkylisocyanurates, oxazolidinones, phenols, secondary hydroxyl groups, and double bonds were obtained.
    Notes: Die bei der Reaktion von Glycidethern und aromatischen Cyansäureestern gebildeten chemischen Strukturen wurden identifiziert. In Abhängigkeit vom Stoffmengenverhältnis der Monomere wurden unterschiedliche Anteile an Triazinen, Alkylisocyanuraten, Oxazolidinonen, Phenolen, sekundären Hydroxylgruppen und Doppelbindungen erhalten.
    Additional Material: 4 Ill.
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