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  • Astrophysics  (47)
  • Polymer and Materials Science  (45)
  • ASTROPHYSICS  (30)
  • 1
    Publication Date: 2019-07-13
    Description: The very high energy (VHE; E great than 100 GeV) blazar Markarian 501 was observed between April 17 and May 5 (MJD 5493854956), 2009, as part of an extensive multi-wavelength campaign from radio to VHE. Strong VHE -ray activity was detected on May 1st with Whipple and VERITAS, when the flux (E greater than 400 GeV) increased to 10 times the pre-flare baseline flux (3.9 x 10(exp -11 ph cm(exp -2 S(exp -1), reaching five times the flux of the Crab Nebula. This coincided with a decrease in the optical polarization and a rotation of the polarization angle by 15deg. This VHE flare showed a fast flux variation with an increase of a factor approximately 4 in 25 min, and a falling time of approximately 50 min. We present the observations of the quiescent state previous to the flare and of the high state after the flare, focusing on the flux and spectral variability from Whipple, VERITAS, Fermi-LAT, RXTE, and Swift combined with optical and radio data.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN44061 , Astronomy & Astrophysics (ISSN 0004-6361) (e-ISSN 1432-0746); 594; A76
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 5 (1961), S. 337-348 
    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 predicted general incompatibility of mixtures of polymers has been further confirmed. Thirty-one mixtures of homopolymer pairs showed phase separation in a common solvent. These included closely related polymers such as polyacrylates with both polymethacrylates and other polyacrylates and pairs of different polymethacrylates. Typical immiscible combinations are PMA/PEA and PEMA and PEMA/PMMA. It was also found that the presence of a common monomer constituent did not result in complete compatibility of either a homopolymer with a copolymer or a mixture of two copolymers. Apparently, none of the combinations tried were sufficiently similar to result in heats of interaction small enough to be counteracted by the small entropy change involved. Since another possibility for attaining miscibility is through polar interactions, the effects of ionic and hydrogen-bonding substituents upon polymer-polymer compatibility were considered, and selected experiments were done on a series of carboxyl-containing polymers and their sodium salts. It was concluded that hydrogen bridging occurs preferentially either intramolecularly or between polymer and solvent rather than between two different types of chains each having hydrogen-bonding ability. Thus, poly(acrylic acid) and poly(methacrylic acid) show two-phase separation in water. Although poly(sodium acrylate) and poly(sodium methacrylate) are completely miscible, mixtures of the partially neutralized acids, e.g., PAA and PNaMA mixtures, show separation. In contrast to predictions for less polar polymers, compatibility of mixtures of polymers containing high mole fractions of carboxylic acid monomers showed a pronounced dependence upon solvent. Thus, the two copolymers 45/53 EA-MAA and 47/53 MMA-MAA are incompatible in methanol or ethanol but form homogeneous solutions in DMF or DMS.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 8 (1964), S. 1541-1548 
    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: Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) of poly(ethylene terephthalate) has been carried out on samples of amorphous, cold-drawn, heat-crystallized, and acetone-crystallized polymer. From DTA it appears that for amorphous material a prolonged “secondary” crystallization process follows a primary process in the region of 140°C. For cold-drawn polymer, heat treatment does not reflect differences observed in previous x-ray diffraction studies. The TGA gives evidence that a high temperature endothermic peak observed in DTA may not be directly associated with depolymerization. With acetone-crystallized material a high degree of acetone retention is detected.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 5 (1961), S. 580-588 
    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: Torsional modulus-temperature data have been obtained on heterogeneous polymer compositions prepared by several procedures. Both the state of aggregation of the component chain molecules and their degree of compatibility are significant variables. Modulus curves similar to those for crystalline polymers can be obtained from incompatible polymers having glass temperatures sufficiently far apart. Detailed interpretations are presented for modulus curves of both individual homopolymers and bicomponent heterogeneous polymer mixtures.
    Additional Material: 8 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 7 (1963), S. 59-69 
    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 isolation of two graft copolymers of styrene on polyethyl acrylate from the ungrafted homopolymers by solvent extraction procedures is discussed. For the grafts and their corresponding mixtures ηsp/c versus c plots were determined, and no anomalies were observed. Qualitative data on the solubilities and phase properties of the grafts are given. Torsional modulus-temperature curves are shown for graft copolymer and the individual homopolymers.
    Additional Material: 2 Ill.
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  • 6
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Equilibrium and kinetic studies of the sorption and desorption of water vapor by poly(acrylic acid), poly(sodium acrylate), sodium carboxy methyl cellulose, methyl cellulose, and a series of poly(methyl acrylate) hydrolyzates in acid and sodium salt forms were made at 30°C. It was found, as expected, that equilibrium sorption increased and was greater for polymers containing strong-electrolyte type substituents than for those containing an equivalent number of weakly ionizable units. In general, the diffusion is somewhat slower than in the case of water-insoluble polymers. It was also found that water solubility of a polymer does not per se result in anomalous water sorption. In Methocel, for example, water diffusion is both Fickian and concentration-independent. All of the results, particularly those on the poly(methyl acrylate) hydrolyzates which ranged from completely water-soluble to insoluble systems, support the following conclusion: For water-soluble polymers both anomalous diffusion and relatively high glass temperatures are associated with high concentrations along polymer chains of very polar or ionic groups, such as —OH, —COOH, and CO2-Na+. Presumably both the anomalies and high transition temperatures are associated with restricted segmental mobility resulting from strong chain-chain interactions which originate in the highly polar and ionic, water-solubilizing chain substituents.
    Additional Material: 8 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 25 (1997), S. 223-234 
    ISSN: 0142-2421
    Keywords: conversion coating ; aluminium ; alloy ; x-ray photoelectron spectroscopy ; scanning electron microscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and potentiodynamic measurements have been made on chromate conversion-coated Al 2024-T3 alloy. X-ray photoelectron spectroscopy measurements indicated that the conversion coating had a surface of CrOOH and Cr(VI), enriched in ferricyanide. The bulk of the coating was an equal mixture of CrOOH and Cr2O3 with significant levels of F- and Fe, the latter implying the presence of ferricyanide throughout the coating. Copper(II) ion was present at the interface between the conversion coating and the alloy, as well as Al3+. During ageing experiments, potentiodynamic measurements indicated that the corrosion current (icorr) decreased from ∽0.4 to ∽0.04 μA cm-2 during the first 40 h after preparation but thereafter slowly increased. No significant changes were observed in the chemistry of the coating by XPS for ageing times longer than 40 h, although morphological changes were observed with SEM. As the coating aged, a network of microcracks developed across the surface. It is believed that Cr6+ is consumed in the process in which plugs of hydrated chromium oxide form at the base of these cracks. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 11 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 23 (1995), S. 540-550 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Cerium-rich conversion coatings have been deposited onto aluminium 2024-T351 alloy by immersion into a solution containing 10 g L-1 CeCl3 and 1% H2O2 in a process described as ‘cerating’. Prior to deposition the alloy had been prepared either by using a standard chemical pretreatment used for aerospace alloys before conversion coating or by polishing. X-ray photoelectron spectroscopy and scanning electron microscopy have been used to characterize these cerium-containing conversion coatings. It was found that, during deposition, hydrated cerium oxide initially covered the intermetallics present in the alloy surface and then covered the surface generally. Deposition continued over the intermetallics throughout the conversion coating process, resulting in thick, heavily-cracked regions considerably greater than the average thickness of the film (〉0.3 μm). Elsewhere the coating was generally up to 0.2 μm thick, and appeared to comprised of deposited particles around 100 nm in size.
    Additional Material: 13 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 24 (1996), S. 634-640 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: X-ray photoelectron spectroscopy has been used to study 20, 100 and 1000 nm evaporated cerium oxide films on Si(100) single-crystal wafers. Upon exposure to the x-ray source there was loss of oxygen and generation of Ce3+. Furthermore, for the 20 nm coating, there was evidence of a shift to higher binding energies of the C 1s peak and a high binding energy O 1s component relative to the oxygen anion peak at 529.7±0.1 eV with increased exposure time to the x-ray source. No similar shift was observed in the O KLL Auger lines, suggesting that the effect was not due to differential charging of the surface with respect to the bulk of the coating. Hence the relative shift is explained in terms of electronic effects resulting from the formation of anion vacancies in the surface. These include a shift of the Fermi level due to defect states in the bandgap as well as band bending due to the positive charge set up from the anion vacancies.
    Additional Material: 8 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 11 (1973), S. 157-160 
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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