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  • American Institute of Physics (AIP)  (4)
  • Society of Exploration Geophysicists (SEG)
  • 1995-1999  (4)
  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 2016-2024 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we present and discuss experimental results on molecular mobility in propylene glycol and its three oligomers confined to the ∼100 A(ring) pores of a controlled porous glass. The objective is to elucidate the finite size effects on the dynamics of hydrogen-bonded liquids of different molecular weights but identical chemical composition. The methods of dielectric and neutron spectroscopy have been employed to investigate both the low- and high-frequency features as a function of temperature. We find that all fluids in pores separate into two distinct liquid phases. (i) molecules physisorbed at the surface which exhibit a dramatic frustration of their mobility related to a substantial positive shift of the glass transition temperature Tg by up to ΔTg≈+47 K; and (ii) relatively "free'' molecules in the inner pore space subject to only moderate retardation of the α and normal mode relaxation and substantial broadening of the distribution of relaxation times. The shift in Tg for the α process with ΔTg≈+5 K is maximal for the monomer liquid and gradually diminishes with increasing molecular weight or decreasing intermolecular hydrogen bonding. The inelastic neutron spectrum of confined propylene glycol shows the boson peak as expected in bulk strong and intermediate glass formers in the vicinity of Tg. This effect can be attributed to the finite-size induced crossover from long wave vibrations characteristic of a continuous medium to localized vibrations in a confined geometry. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 4439-4447 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new 20-channel electron cyclotron absorption diagnostic has been developed at the Rijnhuizen tokamak project. It is the first time the electron pressure profile in a tokamak plasma can be measured directly with a time resolution of 1 ms. The diagnostic measures simultaneously the emission and absorption of the second harmonic electron cyclotron frequencies. Microwaves are injected from the high field side and detected at the low field side in the equatorial midplane. The transmitted power is measured after a single pass through the plasma column. The absorption measurements are complicated by nonresonant losses: refraction of the injected microwaves (losses up to 100%), and scattering of microwaves by density fluctuations (losses 2%–3%). A fast algorithm has been developed to obtain a quantitative measure for these nonresonant losses. This calculation method is based on a parametrization of the experimental data. Combining the electron cyclotron absorption (ECA) measurements and the parametrization provides a reliable tool for determining the optical depth, the electron temperature, and the electron pressure. A good agreement was found between pressure and temperature profiles, measured with ECA and other diagnostics. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3310-3319 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article describes the fabrication and operating principles of a device suitable for measuring displacements, stresses, strains, accelerations, and forces. The device consists of an elastomeric material with a surface relief diffraction grating embossed on its surface. Mechanical compression of this element changes the way that it diffracts light. This article also describes designs and performance characteristics of simple accelerometers and pressure sensors based on these devices. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Rutherford scattering diagnostic at TEXTOR has been used to investigate the time evolution of the ion velocity distribution during sawtooth activity. Coherent averaging techniques have been employed to obtain better statistics. The time evolutions of central ion and electron density were found to be strongly correlated in four out of five cases. In one case, where saturation of the sawteeth occurred, a discrepancy between the two has been found, which could be attributed to an influx of impurities towards the end of the sawtooth. Changes of about 20% in the central toroidal rotation of the bulk ions have been found during sawtooth crashes of neutral beam injected discharges, whereas no changes were found in the ohmic case. No statistically reliable statements can be made about changes in the ion temperature. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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