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  • Chemistry  (12)
  • Coherent states  (1)
  • Computer Systems
  • 1975-1979  (5)
  • 1970-1974  (5)
  • 1955-1959  (1)
  • 1950-1954  (2)
Collection
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 5 (1972), S. 173-183 
    ISSN: 1572-9613
    Keywords: Coherent states ; number conservation ; action-angle variables ; conjugate property
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Utilizing the facts (i) that the number of particles in the many-boson system is conserved and (ii) that the Hamiltonian is Hermitian, a new set of variables comprising “action” and “angle” variables has been introduced. These variables are conjugate in the “mean” and provide a rigorous approach to introducing phase variables for “total-number-conserving many-boson systems.”
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 179 (1978), S. 1209-1217 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Studies on the relative efficiencies of 3d-transition metal oxides as catalysts for the polymerization of vinyl ethers revealed that V2O5 is the most efficient catalyst. Some kinetic studies with the system isobutyl vinyl ether/V2O5/benzene were carried out at ambient temperature. It was found that the rate is second order in isobutyl vinyl ether (IBVE) concentration (0,25 to 2,0mol.1-1) and the inhibition of the polymerization by pyridine suggests a cationic mechanism. Rp increases by the use of benzaldehyde along with V2O5, whereas water (3.10-3mol.1-1) seems to have no effect on Rp. Over the temperature range of 15 to 60°C, Rp as well as [η] attain a maximum value at about 32°C. [η] is unaffected by varying the amounts of oxides, whereas it increases with increasing IBVE concentration. No stereoregularity in the product polymer was observed by using V2O5 alone or in combination with modifiers such as benzaldehyde or carbon disulfide. The kinetics are interpreted in terms of the Hinshelwood-Langmuire mechanism assuming a single point adsorption.
    Additional Material: 6 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 163 (1973), S. 37-43 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Substanzpolymerisation von N-Vinylcarbazol (NVC) wurde mit 3d-Metalloxid-Katalysatoren durchgeführt, und die folgende Reaktivitätsreihe für die untersuchten Oxide wurde vorgeschlagen: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm V}_{\rm 2} {\rm O}_{\rm 5} {\rm 〉 MnO}_{\rm 2} {\rm 〉 TiO}_{\rm 2} {\rm 〉 Cr}_{\rm 2} {\rm O}_{\rm 3} {\rm 〉 NiO 〉 ZnO 〉 Cu}_{\rm 2} {\rm O 〉 CuO 〉 Co}_{\rm 3} {\rm O}_{\rm 4} {\rm andCoO} $$\end{document} wobei die Oxide des Kupfers und Kobalts nicht wirksam sind. Einige kinetische Untersuchungen wurden mit dem System NVC/MnO2 ausgeführt. Auf Grund der Verzögerung der Polymerisationsgeschwindigkeit bei Gegenwart von Wasser oder Thiophen wurde ein kationischer Mechanismus für die Polymerisation vorgeschlagen. Die Wirkungslosigkeit der Kupfer- und Kobaltoxide als Katalysatoren wurde vorläufig mit der Annahme gedeutet, daß sie eher oxydierend wirken als durch π-Komplex-Bindung. Rühren übt keinen Einfluß auf die Polymerisationsgeschwindigkeit aus.
    Notes: The bulk polymerization of N-Vinylcarbazole (NVC) is carried out using some 3 d-metal oxides as catalysts and the following order of reactivity is suggested for the various metal oxides studied: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm V}_{\rm 2} {\rm O}_{\rm 5} {\rm 〉 MnO}_{\rm 2} {\rm 〉 TiO}_{\rm 2} {\rm 〉 Cr}_{\rm 2} {\rm O}_{\rm 3} {\rm 〉 NiO 〉 ZnO 〉 Cu}_{\rm 2} {\rm O 〉 CuO 〉 Co}_{\rm 3} {\rm O}_{\rm 4} {\rm andCoO} $$\end{document} the oxides of copper and cobalt being ineffective. Some kinetic studies are carried out with the NVC/MnO2 system. Endorsed by the observed retardation of the rate in the presence of water and thiophene a cationic mechanism is suggested for the polymerization. The incapability of the oxides of Cu and Co to act as good catalysts is tentatively explained by supposing that they act as oxidizing rather than π-complexing polymerization catalysts. Stirring does not show any influence on the rate of polymerization.
    Additional Material: 3 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 151 (1972), S. 121-125 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Störung der Metachromasie eines an einem Polyanion gebundenen Farbstoffs durch Cetylpyridiniumchlorid (CPCl) wurde quantitative abgeschätzt, indem die in der wässerigen Schicht verbliebenen Farbstoffmengen nach Schütteln der metachromatischen Lösung mit Tetrachlorkohlenstoff in An- und Abwesenheit von CPCl ermittelt wurden. Die Aufhebung der Metachromasie wurde außerdem aus der konduktometrischen Titration der Farbstoff/Polyanion-Lösung mit CPCl ermittelt. CPCl verdrängt die Farbstoffionen von den Polyanionen beinahe stöchiometrisch, was bei Natriumchlorid nicht der Fall ist. Dieses besondere Verhalten von CPCl wird seiner Neigung zur Bildung hydrophober Bindungen zugeschrieben. Es wurden Methylenblau und Kristallviolett als Farbstoffe sowie Chondroitinschwefelsäure und Heparin als Polyanionen verwendet
    Notes: The disturbance of metachromasia of a dye/polyanion system by cetyl pyridinium chloride (CPCl) has been estimated quantitatively from the difference of the amounts of dye left in the aqueous layer after carbon tetrachloride extraction of the metachromatic solution in the presence and absence of CPCl, as well as from conductometric titration of the dye/polyanion solution with CPCl. Results show that CPCl, unlike sodium chloride, displaces the dye ions from the polyanions almost stoichiometrically. This special behaviour of CPCl has been assigned to its tendency to form hydrophobic bonds. As dyes methylene blue and crystal violet, as polyanions chondroitin sulfate and heparin have been used.
    Additional Material: 2 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 72 (1978), S. 57-66 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Poly(N-vinylcarbazol) wurde mit verschiedenen Reagenzien sulfoniert und die Ionenaustauschkapazität der erhaltenen Harze bestimmt. Eine maximale Kapazität von 4,5 meq · g-1 des trockenen Harzes wurde durch 10stündige Reaktion mit 98,8proz. H2SO4 bei 30°C erhalten. Die pH-Titrationskurven lassen einen starken monofunktionellen Kationenaustauscher mit einem pK-Wert von 2,2 erkennen. Das Harz zeigt eine mäßige Austauschgeschwindigkeit mit NaCl und ist bis zu 250°C thermisch stabil.
    Notes: Poly(N-vinyl carbazole) was sulfonated with different sulfonating agents and ion exchange capacities of the resins produced were evaluated. A maximum capacity of 4.5 meq · g-1 of dry resin was realized when sulfonation was done with 98.8% H2SO4 at 30°C for 10 h. The pH titration curves reveal the nature of a strong monofunctional cation exchanger with a pK value of 2.2. The resin exhibits a moderate rate of exchange with NaCl and is thermally stable up to ca. 250°C.
    Additional Material: 4 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 73 (1978), S. 53-61 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Ein Kationenaustauscher wurde durch Kondensation von Polyisobutylvinyläther und Furfural hergestellt. Als Katalysator diente konzentrierte Schwefelsäure. Der Austauscher wurde durch Messen der Austauschkapazität, durch Untersuchen seiner thermischen Belastbarkeit und durch Bestimmen seines Verhaltens bei der pH-Titration charakterisiert. Es scheint sich um einen Austauscher mit schwachen Säregruppen zu handlen, die wohl als —COOH-Gruppen vorliegen und durch Oxidation aus den Furfuralgruppen entstanden sein dürften.
    Notes: A cation exchange resin was synthesized from the condensation product of poly(iso-butyl vinyl ether) and furfural by treating it with concentration sulphuric acid. The resin produced was characterized by measuring its total and salt splitting capacities, and by studying its thermal characteristics and behaviour to pH metric titration. The latter suggests the resin to be a weak one possibly containing —COOH groups, which result from the oxidation of the furfural aldehyde group by sulphuric acid.
    Additional Material: 2 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 23 (1979), S. 2327-2334 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Cation-exchange resins have been synthesized through the condensation of N-vinylcarbazole and poly(N-vinylcarbazole) with furfural in presence of anhydrous AlCl3 and subsequent sulfonation of the condensates. The resins have been characterized in respect to their polyfunctionality, exchange capacity, and thermal stability.
    Additional Material: 3 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 24 (1979), S. 683-692 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Influence of hydrofuramide and ethanolamines on efficient vulcanization (EV), semi-EV, and conventional sulfur vulcanization accelerated by tetramethyl thiuram disulfide is reported. In the case of thiuram vulcanization, the amines increase the cure rate but reduce the crosslink density. The interaction of tetramethyl thiuram disulfide with amines has been studied. The amines interact with thiuram disulfide (TMTD) giving rise to the formation of gaseous products. Thermogravimetric analysis shows weight loss of about 50% in case of TMTD-ethanolamine system and 25% in case of TMTD-hydrofuramide system. Gas chromatographic studies of the gaseous products indicate that it consists mainly of H2S. The other constituents in the gaseous product are CO2 and a thiol. A possible reaction based on these observations to account for decrease in crosslink density in thiuram vulcanization caused by amines is reported.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 34 (1951), S. 652-677 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die vorliegende Arbeit befasst sich mit der Konstitutionsaufklärung des Andrographolids, eines Bitterstoffes der indischen Medizinalpflanze Andrographis paniculata Nees. Verschiedene, in der früheren Literatur vorkommende Widersprüche und Unstimmigkeiten konnten dabei abgeklärt werden.
    Additional Material: 3 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 13 (1954), S. 461-469 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The scattering of light by solutions of a well-fractionated sample of polymethyl methacrylate in acetone, methyl ethyl ketone, and benzene, have been measured using 4358 and 5461 A. wave lengths as incident radiations. The average molecular weights of the polymer from turbidity measurements and lengths determined from angular dissymmetries of scattered light are 571,000 and 760 A. in acetone, 38,400,000 and 715 A. in methyl ethyl ketone, and 408,000 and 375 A. in benzene. The abnormal molecular weight observed in methyl ethyl ketone solution may be ascribed to low μ - μ0 value of the medium. The greater molecular extension in ketone than in benzene solutions is explained in terms of the relative magnitudes of solute-solvent interaction. The depolarization ratios ρu, ρv and ρh have been measured and the decrease of ρv and ρh with increase in concentration of the polymer in ketonic solvents and little change under similar conditions in benzene, are discussed in the light of the “molecular field effect” of Gans.
    Additional Material: 3 Ill.
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