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  • 1975-1979  (4)
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Publisher
Year
  • 1
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A two-component (core-halo) emission model has been applied reconciling hard and soft X-ray burst emissions with the microwave burst radiation. The core region is represented by a nonthermal energy distribution (Maxwellian+power law tail) and assumed to be surrounded by a thermal halo. Parameters characterizing the energy distribution and emission measures have been derived numerically from soft and hard X-ray measurements. Using an artificial magnetic field model the microwave flux spectrum has been calculated on the basis of gyro-synchrotron emission and absorption by solving the equation of radiation transfer along the ray trajectories. Open parameters were used to adapt the spectrum to the radio measurements. Thus probable informations about the most appropriate magnetic field parameters as well as about the time- and frequency- dependent source diameters (yielding growth velocities of the core region during the impulsive phase) are deduced for the burst of 1972 May 18 as an example. A fit of the observed spectrum at the burst maximum is consistent with a magnetic field of 150O G at the core centre decreasing up to about 40 G at the top of the halo at a height of 50 000 km above the centre, a core density of 1010 cm−3 decreasing to 109 cm−3 at the outer halo boundary, and a core diameter of 15 000 km (∼]20″). Due to the simple geometry and emission process adopted,- the model refers primarily to special impulsive bursts. For the representation of broad band microwave bursts, e.g. type IV μ, events, a more complex source geometry and/or other variants of the emission mechanism must be invoked.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Electron spin resonance (ESR) observations of the solid-state thermal polymerization of bis(p-toluene sulphonate) of 2,4-hexadiyne-1, 6-diol at 60°C, 70°C, and 80°C are reported. The weak paramagnetism observed in polycrystalline samples is interpreted in terms of departures of the polymer chain from an equilibrium conformation. Decomposition occurs at 70°C and 80°C during the final phase of polymerization producing additional paramagnetic centers. Lineshape parameters measured during polymerization show changes which we attribute to changes in the delocalization and mobility of the paramagnetic center. We conclude that the nature of paramagnetism in crystalline conjugated diacetylene polymers is a chain defect property characteristic of interband electronic states close to the valence band.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The solid-state thermal polymerization of 2,4-hexadiyne-1, 6-diol has been studied by a variety of methods. Pure monomer heated under vacuum or in an inert gas atmosphere is found to polymerize readily, unlike material heated in air. X-ray diffraction reveals that samples anneal during polymerization. Initially, a long chain polymer is formed, but above 20% conversion a less perfect product is obtained. Measurements suggest a complex molecular rearrangement during the nonideal phase of polymerization. Possible models for this process are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal degradation of the monomer and polymer of bis(p-toluenesulfonate) of 2,4-hexadiyne-1,6-diol has been investigated. Decomposition during the latter stages of solid-state thermal polymerization at 80°C and of 100% polymer at 112°C was observed by mass spectrometry and the decomposition fragments identified. Mechanisms for this low-temperature degradation are suggested. Pyrolysis of the monomer and polymer between 400 and 1000°C was studied by gas chromatography and mass spectrometry. The principal pyrolysis products are triacetylene and p-toluenesulfonic acid. The fragmentation routes leading to and derived from these products are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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