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  • 1
    Electronic Resource
    Electronic Resource
    Preliminary observations on nitrogen transport during summer in a small spring-fed Ontario stream (1976)
    Springer
    Hydrobiologia 49 (1976), S. 59-63 
    Details
    ISSN: 1573-5117
    Keywords: Streams ; Nitrogen ; Nutrients ; Denitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen transport in a 2 km-long, spring-fed stream was studied during the summer months by analyzing weekly water samples from four stations. The water at the spring had a consistently high level of nitrate-N ranging from about 7 mg/l in late spring to about 3 mg/l in early fall. However, over the length of the stream, 60% (about 97 kg) of the incoming nitrate-N is lost from the water during the summer period. The loss, which does not appear to be attributable to the uptake by aquatic macrophytes or to immobilization, is thought to result from denitrification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00016169
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    Paper (German National Licenses)
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  • 2
    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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  • 3
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    Mapping of electrical potential distribution with charged particle beams (1979)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Potentials were measured using a beam of soft X-rays in air at 2 x 10 to the -5 power Torr. Ions were detected by a continuous-dynode electron multiplier after they passed through a retarding field. Ultimate resolution depends upon the diameter of the X-ray beam which was 3 mm. When the fields in the region of interest were such to disperse the ions, only a small fraction were detected and the method of measurement was not very reliable. Yet reasonable data could be collected if the ions traveled in parallel paths toward the detector. Development should concentrate on increasing the aperture of the detector from the pinhole which was used to something measured in centimeters. Also increasing the strength of the source would provide a stronger signal and more reliable data. Measurements were made at an estimated ion current to 10 to the -15 power A from a 10 cm length of the X-ray beam, this current being several orders of magnitude below what would have a perturbing effect on the region to be measured. Consequently, the source strength can be increased and prospects for this method of measurement are good.
    Keywords: NUCLEAR AND HIGH-ENERGY PHYSICS
    Type: NASA-CR-158713
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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