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  • ASTRONOMY  (56)
  • Physics  (56)
  • 2015-2019
  • 1975-1979  (112)
  • 1950-1954
  • 1940-1944
  • 1930-1934
  • 1925-1929
  • 1978  (112)
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  • 2015-2019
  • 1975-1979  (112)
  • 1950-1954
  • 1940-1944
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  • 1
    Publikationsdatum: 2019-06-27
    Beschreibung: Continuum observations of 23 extragalactic objects have been made at a wavelength of 1 mm; nine of the 23 have been definitely detected at this wavelength. The sources detected include seven from which the 1-mm emission appears to be nonthermal, and two from which the emission appears to be thermal radiation from dust. Repeated observations of the brightest nonthermal sources permitted a search for 1-mm variations on time scales of one month to three years. BL Lac was observed to vary by more than a factor of 2 in flux, and 3C 84, 3C 120, and 3C 273 showed possible variations; 3C 279 showed no variations greater than + or - 30%. The 1-mm variations of BL Lac appear to be correlated with variations at radio wavelengths. The other sources with nonthermal spectra detected were 3C 111 and M87; the two thermal sources detected were NGC 253 and M82. Comparison of the latter two 1-mm measurements with 2.6-mm CO measurements suggests that the CO line in these galaxies is not heavily saturated.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal; vol. 220
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 599-612 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Morphological changes accompanying the deformation of polypropylene filaments with varying degrees of melt-induced orientation are examined using wide-angle x-ray scattering (WAXS), small-angle x-ray scattering (SAXS), and electron microscopy, and their behavior is compared both to completely unoriented film samples and to very highly oriented, hard elastic filaments. Melt-oriented filaments are shown to deform predominantly by a voiding mechanism at low temperatures (〈100°C), and destruction of the lamellas to produce fibrils occurs only after extensive drawing. The bimodal crystal texture of the filaments does not appear to greatly affect the low temperature deformation mechanism. High temperature (〉100°C) drawing produces a fibrillar structure containing elongated voids.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1499-1505 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: An apparatus is described which enables the rapid recording of time-resolved emission spectra on a nanosecond time scale. The instrument permits detailed study of the time-dependent photo-physical processes occurring in many polymer systems. The technique has been used to investigate the kinetics of excimer formation in methylene chloride solutions of polystyrene and poly(1-vinyl-naphthalene). Unambiguous evidence for excimer dissociation is observed in poly(1-vinylnaphthalene) but the process appears unimportant in solutions of polystyrene.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 2215-2236 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A quasi-one-dimensional model for the dynamics of a polymer in dilute solution is described. The diffusion equation in the presence of energy barriers to conformational change is solved approximately for the case of high barriers, by a method closely analogous to the method of configuration interaction in molecular quantum mechanics. The dynamic shear viscosity is calculated in terms of the model and the ultrasonic absorption is discussed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 16 (1978), S. 511-521 
    ISSN: 0360-6376
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Anionic polymerization has been used as a technique for the synthesis of five-block copolymers of polystyrene (PS), polyisoprene (PI), and poly(ethylene oxide) (PEO). Two types of such polymers, PEO-PI-PS-PI-PEO and PEO-PS-PI-PS-PEO with varying PEO block length, have been prepared, using potassium naphthalene as the initiator and tetrahydrofuran as the solvent. The polymers were purified by extraction with ethyl acetate, diethyl ether, and water. After the addition of each monomer, a sample from the living polymer solution was taken and analyzed by spectroscopy (infared (IR) and proton magnetic resonance (PMR)), osmometry, and gel-permeation chromatography (GPC) to obtain information about composition, molecular weight and molecular weight distribution of the intermediate polymers. The five-block copolymers have also been characterized by the same techniques and by elemental analysis.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 16 (1978), S. 1093-1105 
    ISSN: 0360-6376
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Films of known thickness have been prepared in situ by radio frequency (RF) glow discharge techniques with the use of vinylidene fluoride as the monomer. A description of the structure as revealed by ESCA is presented and comparison drawn with related work. Electron mean free paths have been measured as a function of kinetic energy corresponding to photoemission from the C1s (967 eV), F1s (563 eV), and F2s (1220 eV) levels of the plasma-polymerized material. The results confirm that for a given class of materials such as polymers, escape depths are not strongly dependent on fine details of structure and bonding and moreover that mean free paths are comparable with those measured for typical metals and semiconductors.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 16 (1978), S. 2353-2363 
    ISSN: 0360-6376
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The photolysis reactions of a series of isomeric fully aromatic polyamides (aramids) have been investigated in the absence of oxygen by ultraviolet and luminescence spectroscopy. Several of the aramids were found to undergo photo-Fries rearrangements to give 2-aminobenzophenone backbone units when irradiated either as films, fibers, or dissolved in liquids. Quantum yields for this rearrangement were low, 〈 1 × 10-6 mole/einstein, and increased with decreasing aramid glass transition temperature and increasing backbone mobility. The formation of gel, carbon monoxide, and a strong ESR signal were consistent with a free-radical mechanism for the rearrangement.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 16 (1978), S. 33-40 
    ISSN: 0360-6376
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The γ-initiated oxidation and presensitized photooxidation of polypropylene films and fibers are shown to be insensitive to sample thickness (if 〈150 μm) and a range of morphological parameters such as molecular orientation (in drawn samples) and fibrillar and void content. The relevance of these observations is discussed in the light of the many previous assertions as to the influence of morphological effects on oxidation rates. The γ-initiated oxidation was studied in preference to conventional thermal or photoinitiated oxidation because of the greater control over the rate of radical production available by this method.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 16 (1978), S. 523-529 
    ISSN: 0360-6376
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The concepts of limiting conversion in one-phase polymer reactions have been extended to two-phase reaction systems. The analysis of the two-phase reaction requires the consideration of the glass transition temperature of each phase and the distribution of the reacting monomer between the phases. Predicted limiting conversions are compared with experimental data for simple polystyrene and polystyrene-polybutadiene reactions in latex form. Strong agreement is found for these comparisons.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 16 (1978), S. 2365-2376 
    ISSN: 0360-6376
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A series of isomeric fully aromatic polyamides (aramids) were photodegraded in the presence of oxygen. Films and fibers of these aramids gave carboxylic acids as the major products when measured by infrared spectroscopy and potentiometric titration. These acids probably resulted from the oxygen interception of the radicals generated by photocleavage of the amide bonds. In contrast to results found upon irradiation in the absence of oxygen, carboxylic acid formation was accompanied by a rapid loss in molecular weight, and a decrease in useful mechanical properties. Quantum yields for carboxylic acid formation were ≤5.5 × 10-5 mole/einstein and decreased along the aramid series roughly in agreement with increases in Tg. The photo-Fries rearrangement product was observed in aramid fibers irradiated in air, whereas no rearrangement product was seen in films irradiated in air.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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