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  • Articles  (1,741)
  • Chemistry  (1,724)
  • Analytical Chemistry and Spectroscopy  (80)
  • Cartilage  (12)
  • Diphosphonates  (5)
  • Atomic, Molecular and Optical Physics
  • Industrial Chemistry
  • 1970-1974  (729)
  • 1965-1969  (605)
  • 1955-1959  (407)
  • Physics  (1,741)
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  • Articles  (1,741)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 269-282 
    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: The development of gel permeation chromatography (GPC) has provided a convenient tool for the rapid determination of molecular weight distribution. The question has arisen as to the suitability of the method for specification purposes. The present work, suggested by the Naval Air Systems Command, represents an attempt to assess the precision of the method through a series of tests carried out by a number of laboratories using identical procedures on the same samples. Ten laboratories agreed to take part. Naval Ordnance Station, Indian Head, worked out standard conditions for operation of the chromatograph, for calibration of the columns, and for analysis of the GPC curves. Two samples of polystyrene were used by the various organizations for calibration of their instruments. Number-average molecular weight, heterogeneity index, and cumulative molecular weight distribution curves were determined on four samples of carboxyl-terminated polybutadiene (CTPB) and two samples of hydroxyl-terminated polybutadiene (HTPB), all unidentified except by letter code. All laboratories used identical directions for setting up CTPB and HTPB calibration curves which were based on curves determined from vapor-pressure osmometer molecular weights and GPC count numbers of fractionated material. Variation among the different laboratories was 0.15 in heterogeneity index, and a maximum of 1200 in molecular weight provided one aberrant set of values was eliminated. The six samples had heterogeneity indices from 1.15 to 1.54, while molecular weight varied from approximately 3000 to 6000. The average coefficient of variation of the molecular weight values was 6.2 ± 0.7%, which is quite acceptable. Variation in heterogeneity index was too great for specification purposes when considered among the different laboratories, but may be sufficiently good when measured by any one laboratory.
    Additional Material: 7 Ill.
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  • 2
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The acrylic esters of carnuba wax alcohols and the vinyl esters of nonhydroxy carnuba wax acids have been synthesized. The acrylic and vinyl esters have been homopolymerized and copolymerized with vinyl chloride. Acrylonitrile-acrylic ester copolymers also have been prepared. The copolymers were quite brittle when molding was attempted.
    Additional Material: 4 Tab.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 5 (1970), S. 91-99 
    ISSN: 1432-0827
    Keywords: Rickets ; Cartilage ; Vitamin D ; Calcium ; Phosphate ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Abstract Des métaphyses de rats rachitiques, alimentés par paires avec des rats témoins, normaux et traités à la vitamine D2 et des phosphates, ont été étudiées au microscope électronique. La répartition des granules mitochondriales est modifiée dans le tissu rachitique: des granules ne sont visibles que dans quelques cellules voisines de la région en voie de calcification. Les rats témoins présentent une répartition, en gradient, à travers toute la métaphyse. L'adjonction à ce régime cariogène de phosphate ou vitamine D2 ou les deux à la fois, permet de rétablir la répartition normale des granules, visible chez les témoins. Il semble qu'une des modifications spécifiques, induites dans les mitochondries des chondrocytes, par un régime pauvre en phosphate et déficient en vitamine D2, est la diminution de la formation de granules mitochondriales, contenant des produits inorganiques.
    Abstract: Zusammenfassung Wachstumszonen von rachitischen Ratten werden unter dem Elektronenmikroskop verglichen mit denjenigen von 3 Kontrollgruppen (normale Diät rachitogene Diät mit Vitamin D2 und Phosphatzusätzen und eingeschränkte Menge normaler Diät). Die Verteilung der Granula in den Mitochondrien war im rachitischen Gewebe verändert; Granula wurden nur in einigen Zellen festgestellt, welche an die Zone der provisorischen Kalzifikation angrenzten. Kontrollratten zeigten einen Gradienten von Granula auf der ganzen Wachstumsplatte. Ergänzung der rachitogenen Diät durch Phosphat, Vitamin D2 oder beide bewirkte die Wiederherstellung der Granula-Dichte und-Verteilung, welche die Kontrolltiere aufwiesen. Es wird vorgeschlagen, daß die verminderte Fähigkeit, mineralhaltige Mitochondrien-Granula zu bilden, eine spezifische Veränderung ist, welche in den Mitochondrien von Chondrocyten durch eine phosphatarme, Vitamin D2-defizitäre Diät herbeigeführt wird.
    Notes: Abstract Growth plates of rachitic, pair-fed control, normal and Vitamin D2- and phosphate-treated rachitic rats were studied with the electron microscope. Mitochondrial granule distribution was modified in the rachitic tissue; granules were noted only in a few cells adjacent to the zone of provisional calcification. Control rats demonstrated a gradient of granules throughout the growth plate. Supplementation of the rachitogenic diet with either phosphate, Vitamin D2, or both was able to re-establish the granule density and distribution found in control animals. It is suggested that one specific modification induced in mitochondria of chondrocytes by a low phosphate, Vitamin D2-deficient diet is the reduced ability to form mineral-containing mitochondrial granules.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 9 (1965), S. 1579-1584 
    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: In a previous paper it was shown that the vulcanization obtained with ethylene-propylene-diene terpolymer is equivalent or superior to that obtained with ethylene-propylene copolymer when a peroxide-dimethacrylate coagent cure system was used. In order to determine the effect of the unsaturation on the physical properties in the terpolymer, the terpolymer had been hydrogenated to remove the double bonds. Infrared spectra and bromination were used to check the extent of hydrogenation. Tensile strength, Shore A hardness, per cent elongation, and modulus indicated no decrease in vulcanization efficiency after hydrogenation. The data show that the unsaturation in the terpolymer does not contribute to the vulcanization cure with the peroxide-dimethacrylate coagent curing system.
    Additional Material: 1 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 10 (1966), S. 429-435 
    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: Polyacrylonitrile sheet cast by a novel method described in Part I is clear, colorless, chemically resistant, brittle, and rather weak. It undergoes irreversible thermal changes above about 80°C., but if heated quickly, it can be oriented to give greater strength parallel to the direction of orientation. Some improvement in strength can be achieved by the use of fibrous fillers. Certain copolymers are stronger than the homopolymer but have lower softening temperatures.
    Additional Material: 1 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 1175-1189 
    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: Studies have been made of the γ-induced emulsion polymerization of styrene and comparisons made with chemically initiated emulsion polymerization. The polymerization proceeded smoothly to high conversions at 0 and 60°C, the reaction showing a high G (monomer) value. Complete conversions were obtained with total doses of less than 0.05 Mrad. In accordance with the behavior expected of systems having a constant rate of initiation, the molecular weight was found to decrease with decreasing temperature. The molecular weight and particle size distributions were narrower than those obtained in chemically initiated emulsion polymerizations at the same temperature. The radiation-induced emulsion polymerization of vinyl acetate proceeded smoothly at temperatures in the range 0-50°C to give polymers of much higher molecular weight than these obtained from chemically initiated polymerizations at the same temperature. Complete conversion was attained after a dose of 0.02 Mrad for latices approaching 50% solids. The elimination of ionic endgroups in the poly(vinyl acetate) radicals tends to drive the polymerization from the aqueous phase, resulting in faster rates and higher molecular weights than are obtained from chemically initiated systems. Rates of polymerization were found to be independent of temperature and the molecular weight of the polymer to be independent of dose rate. Latices of poly(vinyl acetate) of high solids content were evaluated for latex and film properties and found to have improvements over commercially available samples in both areas, especially in clarity of film and scrub resistance. A number of acrylate and maleate esters were copolymerized with vinyl acetate in a radiation-initiated emulsion system. High molecular weight copolymers were produced after low dose.
    Additional Material: 7 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 15 (1971), S. 1479-1492 
    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: A rapid iteration method has been developed to correct the molecular weight averages calculated from raw GPC data for dispersion. Though simple in its performance, it covers the general case that the instrumental spreading characteristics (Tung's resolution factor h) depend on the elution volume. Moreover, it is irrelevant whether the calibration curve, being the logarithmic plot of the molecular weight versus the elution volume, is linear or not. The method has been applied to a number of well-characterized polystyrene mixtures and yields molecular weight averages which agree with those predicted theoretically. The effect of asymmetry exerted by the dispersion on both molecular weight averages M̄n and M̄w is also discussed.
    Additional Material: 6 Ill.
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  • 8
    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: The separation of various liquid mixtures including systems of chloroform-hydrocarbons or ethyl ether, water-alcohols and water-nucleophilic organic solvents have been investigated by the pervaporation technique. Membranes were obtained by grafting Lewis base onto poly(tetrafluoroethylene) (PTFE) films. The PTFE backbone has been chosen for its mechanical and chemical resistance. N-Vinylpyrrolidone and 4-vinylpyridine were selected because of their great affinity for the electrophilic compounds. In all cases, the compound which has the greatest affinity for the membrane pervaporates selectively through modified PTFE films. Selectivity and rates were studied. It is concluded that because selectivity is very important, total separation of different mixtures is possible at a good yield, with a faster rate when the temperature is increased or the thickness of the membrane is decreased.
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  • 9
    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: The effect of some factors including temperature, pressure, film thickness, and grafting ratio on the fractionation of binary liquid mixtures has been investigated by pervaporation through poly(tetrafluoroethylene) films grafted with N-vinylpyrrolidone or 4-vinylpyridine. The purpose was to estimate the best conditions in which the pervaporation process must be carried out. It was concluded that the pervaporation rate is increased at roughly constant selectivity when the temperature of the liquid charge is higher or when the downstream vapor pressure or the film thickness are decreased. A pressure higher than 1 atmosphere above the liquid does not increase the rate. When the grafting ratio is increased, the rate shows a maximum, and for particular conditions, the selectivity becomes much higher.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 18 (1974), S. 857-865 
    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: Polystyrene has been fractured in tension at two temperatures in n-heptane and n-propanol and the fracture surfaces studied by optical and scanning electron microscopy. The test temperatures were selected such as to be approximately 20°C above and below the temperatures at which it was expected1 that a glass-to-rubber transition would occur in the solvent-penetrated craze material. It was found that features of the fracture process and also structure of the fracture surfaces were different at the two temperatures. These changes have been interpreted in terms of a Tg occurring in the craze material.
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