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  • 1
    Electronic Resource
    Electronic Resource
    Estimation of nitrogen-15 levels in derivatized amino acids using gas chromatography quadrupole mass spectrometry with chemical ionization and selected ion monitoringAbbreviation: HFBA = heptafluorobutyric anhydride. (1978)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 5 (1978), S. 648-653 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The data indicate that a commercial, low resolution mass spectrometer can be used with chemical ionization and selected ion monitoring, without a data system, to estimate nitrogen-15 isotopic enrichment with a sensitivity and precision adequate for many biological studies. This was demonstrated using derivatized amino acid mixtures with separation and direct introduction into the mass spectrometer via a gas chromatograph. The method can discriminate between mean levels separated by 0.1 atom % 15N with 68% confidence at the 0.1 nmol level. Labeled dansylamide samples, inserted by probe, were also measured for 15N content.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200051203
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Electric fields and secondary emission near a dielectric-metal interface (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Dielectric surface-charge distributions near a metal-dielectric interface in vacuum depend upon secondary emission processes in the presence of normal and tangential components of electric field. From measured charge distributions created by exposing a specimen of fluorinated ethylene-propylene to monoenergetic electron fluxes, it has been possible to calculate potentials and fields on and near the dielectric surface. The effect of the normal electric field upon secondary emission is measured directly, and the effect of the tangential field is inferred from the charge-distribution data. The critical point (unity crossover) for secondary emission is shifted by the application of fields, so that it occurs at much higher primary energies than normally. Primary beams having energies up to 20 keV are used, and surface fields are as high as 20 kV/mm.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: IEEE Transactions on Electrical Insulation; EI-14; Feb. 197
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Stable dielectric charge distributions from field enhancement of secondary mission (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The emission of secondary electrons from dielectrics subject to numerous effects of electric field which are experimentally difficult to control is discussed. Measurements are reported using pulse techniques such that local fields do not build to significant levels, but measurements with fields present are also of interest. A specific series of measurements under controlled conditions are described and their implications in terms of fields, magnitude and angle, near the dielectric surface were examined. The measurements were made for a charged fluorinated-ethylene-propylene surface near a grounded aluminum half-round resting on the surface. The geometry produced a stable surface-charge gradient being controlled by a strongly enhanced secondary emission for which a model is constructed. Observations of surface flashovers under various conditions confirm the predictions of some scaling exercises.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA. Lewis Res. Center Spacecraft Charging Technol., 1978; p 734-746
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Potential mapping with charged-particle beams (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Experimental methods of mapping the equipotential surfaces near some structure of interest rely on the detection of charged particles which have traversed the regions of interest and are detected remotely. One method is the measurement of ion energies for ions created at a point of interest and expelled from the region by the fields. The ion energy at the detector in eV corresponds to the potential where the ion was created. An ionizing beam forms the ions from background neutrals. The other method is to inject charged particles into the region of interest and to locate their exit points. A set of several trajectories becomes a data base for a systematic mapping technique. An iterative solution of a boundary value problem establishes concepts and limitations pertaining to the mapping problem.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA. Lewis Res. Center Spacecraft Charging Technol., 1978; p 606-620
    Format: text
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    NASA TECHNICAL REPORTS
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