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  • forest clearing  (1)
  • lipid organization  (1)
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  • 1
    ISSN: 1573-904X
    Schlagwort(e): stratum corneum ; lipid organization ; permeability ; sodium lauryl sulfate ; preheating
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The role of the structural organization of intercorneocyte lipids in the barrier function of human stratum corneum was evaluated by treatment with heat and sodium lauryl sulfate. Measurement of transepidermal water loss in treated samples was used to quantify variations in stratum corneum permeability. Thermodynamic transition of lamellar lipids and their degree of organization were evaluated by differential scanning calorimetry and small-angle X-ray diffraction, respectively. Progressively preheating stratum corneum samples from 75°C to 90°C increased stratum corneum permeability to water vapor, while the fusion temperature of lamellar lipids and the intensity of the X-ray diffraction peaks of the polar lipids decreased. Sodium lauryl sulfate induced similar variations of these three parameters. These results support the hypothesis that, in addition to the chemical nature of intercorneocyte lipids, their structural arrangement and thermodynamic properties play an important role in the barrier function of the stratum corneum to water vapor.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1573-5036
    Schlagwort(e): 13C isotope ; changes in soil ; forest clearing ; maize crop ; soil organic carbon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In southwest France, sandy spodosols have developed from Quaternary sandy eolian deposits. On these soils, numerous forest lands have been converted to continuous intensive maize cropping. A chronosequence study is realized by comparing organic C pools and 13C natural abundance of one forested and 6 agricultural sites, whose ages of cultivation range from 4 to 32 yr. δ13C ratio is found to increase with time of cultivation. After 3 decades of intensive maize cropping, about half of the initial organic C content in the forest topsoil layer has disappeared. The fraction of C derived from maize crop increases during the first decades of cultivation, but its level is significantly lower than those observed in other soils, which indicates a high mineralization rate of organic C. In this context, soil characteristics associated to intensive agricultural practices lead to a rapid and large loss of C, whereas inputs from maize seem to have only a very small long-term contribution.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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