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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 926-932 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Capillary and short gravity water waves generated in the range of 7–45 Hz by pulsating air from a loudspeaker have been measured using an electrical surface potential probe placed a fixed distance of 0.4 mm above the mean water surface. The surface potential wave gauge (measuring wave amplitude) is compared to a wire resistance-type gauge (measuring wave amplitude) and a laser gauge (measuring wave slope). The wave gauges show good agreement for the capillary waves measured. Gravity water waves with frequencies of 1.0, 1.5, and 1.8 Hz and heights of 1–3 cm could also be successfully measured with the surface potential probe fixed 2.5 cm above the mean water surface. Measurements of waves generated by 2.5-, 4.0-, and 6.0-m/s winds showed that spectra recorded by the surface potential probe qualitatively agree with those of the wire wave gauge when the surface potential probe's height above the mean water surface is adjusted in accordance with the wind speed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Archives of environmental contamination and toxicology 29 (1995), S. 277-283 
    ISSN: 1432-0703
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik , Medizin
    Notizen: Abstract The effects of the herbicide atrazine on marine phytoplankton typical of the German Bight (North Sea) were investigated by means of four mesocosm (tank) experiments. Three tanks were spiked with atrazine (120, 560, and 5,800 ng/L, respectively). These concentrations cover the range found in the German Bight, in coastal waters, and in the estuary of the river Elbe. The lowest atrazine concentration applied was of the same order of magnitude as the background concentration of triazine herbicides in North Sea water near the island of Heligoland. A relationship between concentration of atrazine (dosis) and concentration of “excreted” dissolved organic phosphorus (DOP) as well as dissolved organic nitrogen (DON) (effect) can be inferred, where high concentrations of triazines lead to high concentrations of DON and DOP. Furthermore, the decrease in the pH-value from 9.2 to about 8.7–8.9 in the three tanks spiked with atrazine during the “stationary growth phase” in comparison with the fourth tank (control, i.e., background levels) implies that photosynthesis is reduced. This effect is accompanied by lower chlorophyll concentrations, reduced primary production, and higher concentrations of amino acids in the water.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Marine biology 36 (1976), S. 135-146 
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The physical and chemical properties of the sea surface can be altered considerably by the formation of slicks and the accumulation of particles (including plankton). Investigations of natural slicks near the island of Sylt consisted of analyses of the dissolved and particulate surface-active substances, as well as the identification of plankton and bacteria collected by a surface-film sampler. The analyzed surface material consisted primarily of phytoplankton (Prorocentrum micans in particular), bacteria, detritus and dissolved compounds of fatty acids. These fatty acid compounds alone would not account for the slick. The slick appeared to be caused by the calm weather, the active accumulation of P. micans at the surface, and the increase in bacteria associated with this accumulation. Here a decrease was observed in the dissolved surface-active substances compared with the concentration usually found in normal surface waters, of which the total fatty acid content in a sample was taken as indicator. In some cases a correlation was found between fatty acids and particulate matter in naturally occurring slicks. Particularly large variations were found in the fatty acid patterns in the filtrate and filter residue at a time when no slick was present and no particulate matter had accumulated at the surface.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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