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  • DSC  (2)
  • Cell & Developmental Biology
  • Polymer and Materials Science
  • 1995-1999  (3)
  • 1
    ISSN: 1572-8943
    Keywords: dielectric spectroscopy (DETA) ; DSC ; dynamic mechanical (DMA) spectroscopy ; glass transition ; PET ; polymers ; relaxation ; rigid amorphous ; temperature modulated DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The relaxation strength at the glass transition for semi-crystalline polymers observed by different experimental methods shows significant deviations from a simple two-phase model. Introduction of a rigid amorphous fraction, which is non-crystalline but does not participate in the glass transition, allows a description of the relaxation behavior of such systems. The question arises when does this amorphous material vitrify. Our measurements on PET identify no separate glass transition and no devitrification over a broad temperature range. Measurements on a low molecular weight compound which partly crystallizes supports the idea that vitrification of the rigid amorphous material occurs during formation of crystallites. The reason for vitrification is the immobilization of co-operative motions due to the fixation of parts of the molecules in the crystallites. Local movements (Β-relaxation) are only slightly influenced by the crystallites and occur in the whole non-crystalline fraction.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 1155-1161 
    ISSN: 1572-8943
    Keywords: crystallisation ; DMA ; DSC ; PCL ; polymer ; temperature modulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Temperature modulated dynamic mechanical analysis (TMDMA) was performed in the same way as temperature modulated DSC (TMDSC) measurements. As in TMDSC TMDMA allows the investigation of reversible and non-reversible phenomena during crystallisation of polymers. The advantage of TMDMA compared to TMDSC is the high sensitivity for small and slow changes in crystallinity, e.g. during re-crystallisation. The combination of TMDMA and TMDSC yields new information about local processes at the surface of polymer crystallites. It is shown that during and after isothermal crystallisation the surface of the individual crystallites is in equilibrium with the surrounding melt.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 165 (1995), S. 96-106 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This study has characterized the proteoglycans from the megakaryocytic tumor cell line CHRF 288-11 and the effect of the differentiation-inducing agents phorbol-12-myristate-13-acetate (PMA) and dimethylsulfoxide (DMSO) on proteoglycan synthesis in these cells. There appeared to be two classes of proteoglycans. One, serglycin, was recognized to have a core protein of 31 kDa, an overall molecular mass of 200-300 kDa, and glycosaminoglycan chains of mean size 〈25 kDa. The size of this proteoglycan was increased by both PMA and DMSO. Synthesis was increased by PMA and reduced by DMSO. mRNA for serglycin was increased at 24 to 72 hr following PMA treatment. In addition, the cells contained a core protein triplet at 96, 110, and 120 kDa, and the medium only the bands at 96 and 110 kDa, suggesting the presence of betaglycan. Synthesis of this proteoglycan was enhanced by PMA. This proteoglycan had an overall size of 130-150 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in control cells, but in the presence of PMA, a component 〉250 kDa was present. Probes for Northern blot analysis were prepared by polymerase chain reaction (PCR) based on the sequences of human serglycin and betaglycan. The serglycin probe recognized a 1.4 kb band, and the betaglycan probe recognized a 4.1 kb band, on blots prepared from RNA from CHRF cells and cultured normal human megakaryocytes. Both proteoglycans in their intact form adhered to peptides derived from fibronectin and collagen, but the free GAGs released by alkaline borohydride digestion did not adhere. Synthesis of two proteoglycans appears to be a part of the differentiation process of megakaryocytic tumor cells and normal megakaryocytes. © 1995 Wiley-Liss Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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