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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Archives of dermatological research 285 (1993), S. 415-417 
    ISSN: 1432-069X
    Schlagwort(e): Sphingolipids ; Ceramides ; Aging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We measured six stratum corneum sphingolipid species (ceramides 1–6) in 26 males and 27 females, and found a significant change in their percentage composition only among female subjects of different age groups. There was a significant increase in ceramide 1 and 2 with a corresponding decrease in ceramide 3 and 6 from prepubertal age to adulthood. Thereafter the ratio of ceramide 2 to total sphingolipids decreased with age in contrast to ceramide 3 which showed an increase. Such a pattern of change in the aging population is different from that observed in scaly skin experimentally induced by tape stripping. The present results suggest a significant influence of female hormones on the composition of stratum corneum sphingolipids. Moreover, the different patterns of change in sphingolipid composition of stratum corneum lipids between scales from inflammatory skin and those from aged skin also suggest that epidermal biosynthesis of sphingolipids is influenced by epidermal proliferative activity.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 270 (1992), S. 652-658 
    ISSN: 1435-1536
    Schlagwort(e): Deformation ; fracturebehavior ; polystyreneionomers ; ionomerblends ; microstructure of theionomer ; ioncontent
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The deformation and fracture behavior of sulphonated polystyrene ionomers, and of blends of these with polystyrene have been investigated. The microstructure of the ionomer, which varies with ion content, appears to have a significant effect on mechanical properties. Both tensile strength and toughness increase appreciably at ion contents near 5 mol%, where clusters become dominant over ion pairs and multiplets. In blends of the ionomers and polystyrene, phase separation occurs and the ionomer component appears in the form of fine particles dispersed in the polystyrene matrix. These particles possess a greater effective entanglement density than the matrix, as a result of ionic crosslinking, and they provide reinforcement against early craze breakdown and fracture. Tensile strength and fracture energy increase rapidly as the ionomer concentration in the blend is increased and they become essentially independent of blend ratio above about 10 wt% of the ionomer. Tests carried out on thin film specimens of the blends show that the dispersed ionomer particles adhere well to the matrix and contribute to the fracture energy both by inducing matrix crazing and by internal fibrillation within the particles.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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