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  • 25.70.Np  (2)
  • Electrooptic effects  (2)
  • 63.30  (1)
  • Best. von Blei in Benzin, Erdölprodukten  (1)
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Keywords
  • 1
    ISSN: 1432-0630
    Keywords: 63.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract An improved set-up is described which is universally applicable in electrooptic research work on liquid crystals. The main part of the test circuit consists of a highly stabilized and dc-free square wave generator with swept amplitude. An additional sine wave modulation with very good linearity up to high voltages allows capacity versus voltage measurements in a large frequency range. Measurements in the nematic phase of ap-disubstituted phenylcyclohexane (PCH) are reported as an example of the high performance of this set-up.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 2 (1973), S. 349-350 
    ISSN: 1432-0630
    Keywords: Liquid crystals ; Electrooptic effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The transient behavior of electrically induced deformations of parallel oriented nematic liquid crystal layers was investigated. The nematic material used was a mixture of disubstituted benzoyloxybenzoic acid esters the dielectric anisotropy of which is positive at dc and low frequencies, and changes sign in the kHz range. The decay time of a deformation induced by a low frequency field can be considerably reduced by switching the frequency to the range where the dielectric anisotropy is negative. This effect becomes even more pronounced for higher viscosities.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 6 (1975), S. 309-313 
    ISSN: 1432-0630
    Keywords: Liquid crystals ; Electrooptic effects ; Elastic deformations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The rise and decay times of a Fréedericksz deformation in a planar nematic layer have been investigated. The liquid crystal used was an ester mixture with regimes of positive as well as negative dielectric anisotropy. This property allows to control both the rise and the decay times of the deformation by switching the frequency of the electric field. The kinetics was monitored with a fluorescent dye-probe.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1434-601X
    Keywords: 25.70.−z ; 25.70.Np ; 95.30.J
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The sequential break-up of 156 MeV6Li projectiles colliding with208Pb has been investigated in the very forward angular hemisphere in order to explore the role of the Coulomb and nuclear interaction in inducing projectile break-up processes. The experiments use the Karlsruhe spectrograph “Little John” with a newly developed technique to detect efficiently break-up pairs ofα-particles and deuterons emitted with small relative energies and within a small opening angle. The observed differential cross section for the projectile excitation6Li→6Li* (I=3i +) has been analysed (together with forward elastic scattering) by a coupled channel approach, and various sensitivities to the nuclear potential and other ingredients have been studied. We conclude, that in the angular region below half the grazing angle the excitation is completely due to the Coulomb force. This feature is a basis for an application of the disintegration approach for studies of radiative capture cross section of astrophysical interest.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 330 (1988), S. 77-81 
    ISSN: 1434-601X
    Keywords: 12.20.-m ; 11.80.-m ; 25.70.Np
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The high flux of equivalent photons present in relativistic heavy ion collisions of two chargesZ 1 andZ 2 gives rise to the collision of two equivalent photons. The cross-sections for various processes are directly related to the correspondingγ- γ cross-sections. As compared toγ- γ physics being studied at e+ e− colliders, we find that high energy states will not be so easily accessible at the existing facilities, however, the enhancement factor (Z 1 Z 2)2 in the expression for the cross section will provide very large photon fluxes for lower energies.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1618-2650
    Keywords: Best. von Blei in Benzin, Erdölprodukten ; Röntgenfluorescenz-Spektrometrie ; Streustrahlmethode
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Am Beispiel der Bleibestimmung in Ottokraftstoffen wird gezeigt, daß es möglich ist, die Compton-Streustrahlung einer Röhrenlinie für die Elementbestimmung mittels Röntgenfluorescenzspektrometrie als internen Standard zu benutzen. Anstelle der Compton-Streuung kann ggf. auch die gestreute Röhrenlinie selbst verwendet werden. Die Beziehung zur Konzentration des zu bestimmenden Elementes wird durch eine Vergleichsprobe mit bekannter Elementkonzentration hergestellt. Die Ergebnisse von Bleibestimmungen in Ottokraftstoffen, die nach diesem Verfahren erhalten wurden, stimmen mit den nach anderen Methoden erhaltenen Ergebnissen gut überein, sie liegen weit innerhalb der Vergleichbarkeit nach DIN 51769, Teil 1. Das beschriebene Verfahren ergibt gegenüber dem Verfahren mittels Zumischung eines internen Bezugselementes zur Probe eine Verringerung des Arbeitsaufwandes, eine Erniedrigung der unteren Bestimmbarkeitsgrenze und ggf. eine Vermeidung von Komplikationen durch Interelementeffekte.
    Notes: Summary Taking the determination of the lead content in gasoline as an example, it is shown that the Compton scattering of an X-ray tube emission line may be used as internal standard for determining elements by means of X-ray fluorescence spectroscopy. Also, the scattered tube line itself may be used instead of the Compton scattering. The relationship with the concentration of the element to be determined is established by comparison with a reference sample of known element concentration as an external standard. The results of the determination of lead in gasoline obtained by this method correlate well with those obtained by other methods and are well within the reproducibility limits specified by DIN 51769, Part 1. The method described brings about a reduction in work as compared with the method requiring the addition of an internal reference element to the sample, it brings down the bottom traceability limit and may eliminate complications caused by interelemental effects.
    Type of Medium: Electronic Resource
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