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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 421-424 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The existence of long-range potential fluctuations (PF) in compensated semiconductors results from the nonuniform distribution of ionized impurities, and it was observed that PF can be erased when the material is submitted to a critical field, the value of which depends on the sample. Data on the temperature and time dependence of the discharge current of a semi-insulating GaAs crystal, which has been submitted to a critical field, are reported. The discharge current decreases with a time constant equal to the reverse of the electron emission coefficient of deep centers brought out of equilibrium by the external field. Not only the activation energy of the emission coefficient, but also the density of the deep center species responsible for the discharge current, can be determined from the data. In the case of the GaAs sample studied in this paper, the observed discharge current results from the return to equilibrium of the Cr acceptor center HL1.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 1059-1064 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Data on ac and dc field dependence of the conductivity of semi-insulating GaAs crystals are reported. The existence of long-range potential fluctuations in these samples has been previously reported. Field-enhanced conductivity results from the decrease of the maximum depth of the wells due to barrier lowering, up to a critical field at which the effect of potential fluctuations disappears. The transient behavior is also discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 2646-2650 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Complex conductivity measurements of unannealed and annealed semi-insulating GaAs crystals are reported. A model of fluctuations of well-defined magnitude superimposed to a Gaussian distribution accounts for the σac ∝ ω2 dependence observed above 106 Hz in some unannealed samples. The effect of annealing on the magnitude of long-range potential fluctuations and on the average carrier density is analyzed.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0021-9673
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of environmental contamination and toxicology 60 (1998), S. 944-948 
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of radioanalytical and nuclear chemistry 106 (1986), S. 55-63 
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Extraction of WO 4 2− and ReO 4 − by Adogen-381, tricaprylmethylammonium chloride, Hyamine 10-X, trioctylphosphine oxide or dibenzylsulphoxide in xylene from HNO3, HCl or H2SO4 acid medium was investigated. Based on the separation factors obtained, the separation of ReO 4 − from WO 4 2− was elucidated. ReO 4 − was separated from WO 4 2− in high radiochemical purity: 〉99.9% by three successive extractions and strippings using Adogen-381 from HCl or HNO3 acid medium.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 23 (1987), S. 83-85 
    ISSN: 1612-1112
    Keywords: Capillary gas chromatography ; Amino acid enantiomers ; Fluoroesters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An optimum gas chromatographic separation of all protein amino acids in one run on capillaries coated with Chirasil-Val is difficult to achieve. Overlap of enantiomers of different amino acids may occur because the relative retention times depend upon the overall polarity of the stationary phase, the film thickness and the actual temperature programm. Employment of different derivatives formed by esterification with isopropanol, n-propanol, isobutanol and n-butanol and by acylation with trifluoroacetic, pentafluoropropionic and heptafluorobutyric anhydrides yields patterns of relative elution of all amino acid enantiomers. Thus, even critical pairs of amino acid enantiomers can be separated or shifted in their relative retention times. All amino acid enantiomers can be separated and quantitatively estimated.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 31 (1991), S. 31-40 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Resolution of enantiomers ; Thermodynamic analysis ; Enthalpy of interaction ; Extrapolation of net retention time
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The calculation of capacity factors, k′, from net retention times, t′R, and the corresponding dead times, tM, at different temperatures suffers from the limited accuracy of the tM values. If the temperature coefficient racy of the tM values. If the temperature coefficient d ln k′/d (1/T) only is required, it is sufficient to determine net retention times (t′R)p at constant inlet pressure pi for different temperatures, since the temperature dependence of (tM)p can be assumed as (tM)p=A·eB/T, with B being approximately independent of the column inlet pressure and of the nature of the carrier gas. The extrapolation and interpolation of (t′R)p may be either performed by linear regression or graphically with a nomogram for ln (t′R)p versus 1/T. The resolution factor, α, of two components, e.g. enantiomers which are resolved on a chiral stationary phase, can be treated in a similar way. Examples are given for the resolution of enantiomers of two non-proteinogenic amino acids on the new polysiloxane phase L-Chirasil-CPG.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 328 (1987), S. 255-258 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Three different detectors for gas chromatography are compared in respect to sensitivity and selectivity: the flame-ionization detector, the nitrogen-selective alkali-flame ionization detector and the electron-capture detector. Their suitability for amino acid analysis is discussed, especially concerning sensitivity and linearity of detection. The nitrogen-selective detector proved to be most suitable both in respect to sensitivity and selectivity. The detection limit is in the range of less than 1 pg using the nitrogen-selective detector, about 1 – 2 pg with the electron-capture detector and about 5 –15 pg using the flame-ionization detector.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 1 (1977), S. 299-318 
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: This paper presents a rational approach to the finite strain analysis of elastic-plastic materials. An updated incremental finite element technique was applied to problems of shallow foundations of homogeneous as well as multilayer soils. This was based on a variational principle which is suitable for such problems.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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