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  • 1
    Electronic Resource
    Electronic Resource
    Kinetic characteristics of the light ageing of rubbers based on polydieneurethanes and polyetherurethanesPaper presented at the 19th Colloquium of Danubian Countries on “Atmospheric Aging and Stabilization of Polymers” in Prague (Czechoslovakia), July 24 - 29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 147-160 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The influence of light wavelength and intensity, as well as the temperature, on photooxidation has been studied for rubbers based on polydieneurethane (PDU) or polyetherurethane (PEU). Photooxidation is shown to proceed by the chain free-radical mechanism with bimolecular (for PDU) or linear (for PEU) kinetic chain termination. The PDU oxidation kinetic parameter is equal to 0.02 [mole/(kg·s)]1/2 and does not depend on temperature. In PEU photooxidation the kinetic chain length is constant in a wide range of light intensities and is equal to 7, while the activation energy is ca 18 kJ/mole. In distinction to PEU, PDU is sensitive not only to UV but also to visible light, with this sensitivity being preserved up to high oxidation levels. The dependences of photooxidation quantum yieldes on wavelength and irradiation time have been determined.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051760113
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  • 2
    Electronic Resource
    Electronic Resource
    Dispersion coalescence: Kinetic stability of creamed dispersions (1993)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 322-334 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A Model is developed to predict the coalescence behavior in liquid-liquid dispersions. Coalescence times are based on the lifetimes of the single films that are formed between adjoining drops in a creamed or sedimented dispersion. The model is developed for smaller drop sized dispersions (〈100 μm) in which the drops are not substantially deformed due to gravitational forces. The model predicts that coalescence occurs between the emulsion drops without the gross separation of the dispersed phase (that is, the dispersion does not separate into distinct oil and water phases). As a result of interdrop coalescence, the mean drop size of the dispersed phase increases along with an increase in the polydispersity of the drop size. The model's predictions are used to develop a quantitative relationship between the lifetime of the single film and the rate of increase of the mean drop size of the dispersion. The model also accounts for the effect on dispersion stability via the models of single film drainage in the presence of surfactant.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690390212
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  • 3
    Electronic Resource
    Electronic Resource
    Inhibiting action of α-pyrophthalone in copper corrosion (1993)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 44 (1993), S. 187-192 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Mechanismus der Inhibitionswirkung von α-Pyrophthalon bei der Korrosion von KupferDer Mechanismus der Inhibitionswirkung von α-(Pyridyl)-1,3-indandion (bekannt als α-Pyrophthalon) bei der Korrosion von Kupfer in neutralen wäßrigen Lösungen wurde durch XPS-Analysen der Oberfläche, Kapazitäts- und Polarisationsmessungen untersucht.Das α-Pyrophthalon verlangsamt sowohl die kathodischen als auch die anodischen Partialreaktionen. Die Kapazitätsmessungen zeigen Adsorption der Inhibitormoleküle auf der Kupferoberfläche bei Potentialen, die viel negativer als das Korrosionspotential sind.Durch XPS-Analysen der Oberfläche wurde festgestellt, daß die Inhibitionswirkung von α-Pyrophthalon auf den Korrosionsvorgang einer Cu(αPP)2-Komplexbildung an der Kupferoberfläche zu verdanken ist. Die Zusammensetzung und die Struktur des Inhibitionsfilms setzen einen komplexen Verlauf der Reaktionen der Kupferoxidbildung und der Bildung und Ablagerung des Cu(αPP)2-Komplexes an der Oberfläche voraus.
    Notes: The mechanism of the inhibiting action of α-(pyridyl)-1,3-indandione (known as α-pyrophthalone, αPP) in the corrosion of copper in nearly neutral solutions is studied by XPS analysis of the metal surface, capacitance and polarization measurements.α-Pyrophthalone decreases the rate of the cathodic as well as of the anodic partial reaction. The capacitance measurements show that the inhibitor's molecules adsorb on the copper surface at potential values more negative than that of the corrosion potential.According to the data of the XPS analysis the inhibiting action of α-pyrophthalone on the corrosion process is determined by the formation of a Cu(αPP)2-complex on the copper surface. The composition and the structure of the inhibiting film show a complex process of the formation and the precipitation of the Cu(αPP)2-complex on the surface.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19930440504
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular conformation of a D,L stereoisomeric analogue of valinomycin, cyclo[-(L-Val-L-Hyi-L-Val-D-Hyi)2-(D-Val-L-Hyi-L-Val-D-Hyi)-] (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 417-423 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of a synthetic analogue of valinomycin, cyclo[-(L-Val-L-Hyi-L-Val-D-Hyi)2-(D-Val-L-Hyi-L-Val-D-Hyi)-] ([L-Val1, L-Val5]meso-valinomycin), C60H102N6O18, has been determined. Crystals grown from petroleum ether are orthorhombic, space group P212121, with cell parameters a = 16.41(1), b = 18.76(1), c = 25.86(1) Å, and Z = 4. The atomic coordinates for nonhydrogen atoms, except those of terminal carbons on one side chain, were refined in the anisotropic thermal motion approximation. The coordinate parameters of the H atoms were incorporated into the structure factor calculations at geometrically expected positions. Values of the standard and weighted R factors after refinement are 0.074 and 0.083, respectively. The crystal structure of the molecule is asymmetric and adopts a conformation with four 4 → 1 type and one 6 → 1 type intramolecular hydrogen bonds between amide nitrogens and carbonyl oxygens. Valinomycin binds potassium more than 100 times strongly than the D,L Stereoisomeric analogue, as a result of a different spatial orientation of potentially interacting carbonyl groups.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310407
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  • 5
    Electronic Resource
    Electronic Resource
    Crystal and molecular structure of the depsipeptide ionophore Hexadecaisoleucinomycin, cyclo-[-(D-Ile-L-Lac-L-Ile-D-Hyi)4-] (C80H136N8O24) (1992)
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 819-827 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of a synthetic depsipeptide ionophore hexadecaisoleucinomycin, cyclo[-(D-Ile-L-Lac-L-Ile-D-Hyi)4-] (C80H136N8O24), has been determined by single crystal x-ray diffraction techniques. The crystals are orthorhombic, space group P212121, number of molecules per unit cell z = 4, and cell parameters a = 11.195, b = 17.853, c = 54.835 Å. The values of the standard ( R) and weighted ( Rw ) discrepancy factors after refinement are 0.122 and 0.135, respectively. The structure is characterized by an elongated bracelet form with a twofold axis of pseudosymmetry. It is stabilized by eight intramolecular 4 → 1 hydrogen bonds between the amide C=O and N—H groups. The ester carbonyls are directed toward the inside of the molecule, their oxygen atoms forming an ellipsoidal internal cavity. The side chains are located on the molecular periphery. The conformational states of hexadecaisoleucinomycin in solution are discussed in the light of the data obtained.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360320710
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular structure of cyclo[-(D-Val-L-Hyi-L-Val-D-Hyi)2-] revealed by X-ray analysis (1992)
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 757-764 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of a synthetic analogue of valinomycin, cyclo [-(D-Val-L-Hyi-L-Val-D-Hyi)2-] (octa-meso-valinomycin) (I) (C40H68N4O12 · 1.5 · C4H8O2, Mr = 937.01 + 88.10), has been determined. Crystals grown from dioxane are monoclinic, space group P21/a, with cell parameters a = 21.487(8), b = 16.836(5), c = 16.089(4) Å, β = 111.70(4), and Z = 4. The atomic coordinates for nonhydrogen atoms were refined in the anisotropic thermal motion approximation. H atom positions were included in the structure factor calculations at their geometrically expected positions. Values of the standard and weighted R factors after refinement are 0.11 and 0.13, respectively. The conformation of the depsipeptide crystallized from dioxane is different from that crystallized from chloroform (II). The molecule adopts a rectangular shape with two type IV β-turns containing a hydrogen bond and possesses pseudorotational symmetry. The side chains are located on the molecular periphery. The orientation of the carbonyl groups of the molecule is not conducive for efficient metal-ion coordination and in the observed conformation cannot behave as an ionophore.In the crystal the molecules form infinite chains parallel to the c axis, and are stabilized by two intermolecular hydrogen bonds that are shorter and have better geometry than the intramolecular hydrogen bonds.A φ/Ψ plot for dodecadepsipeptides with a (DLLD)3 sequence has well-defined areas for Val and Hyi residues only in cases when the crystals have been grown from nonpolar or medium-polar solvents. The Φ/Ψ plot for octadepsipeptides crystallized from chloroform (II) shows this behavior also. There also is a correlation between the polarity of the solvent from which crystals of octa-meso-valinomycin or valinomycin analogues with a (DLLD) sequence of configuration have been grown and the number of the intramolecular hydrogen bonds that are formed. The more polar the solvent the fewer the number of intramolecular hydrogen bonds.Empirical energy calculations on octa-meso-valinomycin indicate that for isolated molecules, the energy of the bracelet form (II) is 4.7 kcal/mole lower than that of the rectangular form (I).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360320705
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  • 7
    Electronic Resource
    Electronic Resource
    Study on the synthesis of perfluorovinyl-sulfonic functional monomer and its copolymerization with tetrafluoroethylene (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 47 (1993), S. 735-741 
    Details
    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: Tetrafiuoroethylene (TFE) and hexafluoropropylene (HFP) were subjected to reactions with freshly distilled sulfur trioxide to obtain 1-fluorosulfonyldifluoro-acetylfluoride (FSDFAF, yield 65-70%) and pentafluoro-2-propenylfluorosulfate (PPFS, yield up to 50%). A subsequent reaction of FSDFAF with PPFS under anhydrous conditions led to a preparation of 2-(1-pentafluoro-2-propenyloxy)tetrafluoroethanesulfonyl fluoride (PPOTESF, yield 40-41%) whose structure was proved by both infrared (IR) spectroscopy and nuclear magnetic resonance (19F NMR). TFE was copolymerized with PPOTESF in bulk by using a free radical initiator of the hydrocarbon type at a temperature of 50°C. Various TFE/PPOTESF mole ratios were employed and the presence of sulfonyl fluoride (—SO2F) functional groups in the copolymers was proven by IR spectroscopy. The copolymers were subjected to alkaline hydrolysis and the —SO2F content was found not to exceed 0.70-0.80 mEq/g with polymer yields in the range of 11-31%. The reactivity ratios r1 and r2 related to TFE and PPOTESF, respectively, were determined by using the Fineman-Ross method. A random distribution of PPOTESF units along the polymeric chain, consisting mainly of TFE fragments, was found to exist. The copolymers had melting temperatures 40-45°C lower than polytetrafluoroethylene and were thermally stable to 305-315°C. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070470417
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis of a copolymer of tetrafluoroethylene and 1-fluorosulfonyl-difluoroacetylfluoride (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 2761-2766 
    Details
    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: Tetrafluoroethylene (TFE) was copolymerized with 1-fluorosulfonyl-difluoroacetylfluoride (FSDFAF) in both the bulk and solution by using a free radical initiator at temperature 50°C. The presence of sulfonyl fluoride (—SO2F) functional groups in the copolymers was proved by infrared (IR) spectroscopy. The copolymers were subjected to alkaline hydrolysis followed by an acid treatment and the —SO2F groups content was found not to exceed 0.40-0.50 meq/g with polymer yield ranging between 1 and 36%. Copolymerization in solution of 1,1,2-trichloro-1,2,2-trifluoroethane (Freon 113) under TFE pressure about 1.0 MPa and TFE/FSDFAF mole ratio 1.5-2.0 was proposed for further investigations. A random distribution of single FSDFAF units along the polymeric chain consisting mainly of TFE fragments was considered to exist. The copolymers had melting temperatures within 10-15°C lower than polytetrafluoroethylene and their thermal stability was 360-380°C.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070421014
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  • 9
    Electronic Resource
    Electronic Resource
    Mass spectrometric study of laser-induced pyrolytic decomposition of TMA (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 1 (1992), S. 287-292 
    Details
    ISSN: 1057-9257
    Keywords: LCVD ; TMA ; Pyrolysis ; Copper bromide vapour laser ; Mass spectrometry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: The composition of the gaseous phase during pyrolytic laser-induced chemical vapour deposition (LCVD) of aluminium from trimethylaluminium (TMA) was determined. The analysis was carried out in situ by means of a quadrupole mass spectrometer (QMS) in a closed reaction cell. The decomposition of the aluminium alkyl was induced by a copper bromide vapour laser on the surface of (111) silicon monocrystalline wafer at 0.22 GW m-2 average power density, 120 μm s-1 scanning speed and 100 Pa (1 mbar) partial pressure of TMA. The detected gaseous products of the pyrolysis of TMA were ethane, ethylene, methane and hydrogen. The presence of ethane and ethylene was probably due to the unconventional way of decomposition caused by pulsed laser irradiation. The mass peak dynamics of the created pyrolytic products at m/e = 28, 16 and 2 indicated significant production of ethane + ethylene, methane and hydrogen in the ratio 1:5:1.75.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/amo.860010605
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  • 10
    Electronic Resource
    Electronic Resource
    Polymer-supported molybdenum and vanadium catalysts for epoxidation of alkenes by alkyl hydroperoxides (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 807-812 
    Details
    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: Polymer-supported molybdenum and vanadium catalysts were synthesized using gel-type crosslinked copolymers with microheterogeneous structure. The supports were composed of inert ethylene-propylene rubber and crosslinked high molecular weight poly(ethylene oxide) matrices and polymeric ligands grafted or forming interpenetrating networks: poly(acrylic acid), poly(methacrylic acid), poly(4-vinylpyridine), and polyvinyl alcohol. Catalytic activity and selectivity of some of these complexes were tested in epoxidation of styrene by ethylbenzene hydroperoxide. Molybdenyl cations are strongly coordinated with pyridine-containing copolymers giving catalysts of high activity and selectivity. They provide conversion and selectivity above 70%. Because of the microheterogeneous mosaic-like structure of the supports, better accessibility of the active sites is achieved.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070420325
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