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  • Polymer and Materials Science  (2)
  • Metals and Metallic Materials  (1)
  • 1990-1994  (3)
  • 1940-1944
  • 1
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rotational and the translational diffusion coefficients of G-actin in solution have been obtained by polarized and depolarized dynamic light scattering, respectively. Modeling the shape of the molecule by a biaxial ellipsoid of revolution, the hydrodynamic dimensions were calculated from the Perrin equations. In completion to previous hydrodynamic measurements, a combination of both light scattering experiments provides direct information about the anisotropic form of G-actin in solution. The result indicates that the form of G-actin in solution is not significantly different from the overall structure in the solid state as obtained by x-ray crystallography.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: New and used polypropylene tailstrings from the Copper 7 (Cu-7) intrauterine device were examined by a combination of analytical techniques. Optical microscopy, scanning acoustic and electron microscopy, x-ray diffraction, energy dispersive x-ray analysis, and chemical etching were employed to elucidate both the surface and interior morphology of new Cu-7 tailstrings. Tailstrings removed from women following varying periods of use were investigated with optical microscopy, scanning and transmission electron microscopy. In addition, a subset of the used tailstrings were cultured to identify the types of microorganisms associated with them. Our findings show that unused Cu-7 tailstrings are in various stages of degradation owing to a combination of factors which include the high-draw ratio employed during manufacturing, the method of packaging, and the use of a particulate colourant. Furthermore, it is evident that used Cu-7 tailstrings undergo major deterioration while in situ because of the unfavorable interactions between the highly drawn polypropylene and the physiological environment. These results indicate that the polypropylene tailstrings as manufactured for use with the Cu-7 IUD fail to meet accepted design criteria for biomedical implants.
    Additional Material: 27 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2019-07-13
    Description: A computational model is presented for the prediction of solid/liquid phase change energy transport including the influence of free convection fluid flow in the liquid phase region. The computational model considers the velocity components of all non-liquid phase change material control volumes to be zero but fully solves the coupled mass-momentum problem within the liquid region. The thermal energy model includes the entire domain and uses an enthalpy like model and a recently developed method for handling the phase change interface nonlinearity. Convergence studies are performed and comparisons made with experimental data for two different problem specifications. The convergence studies indicate that grid independence was achieved and the comparison with experimental data indicates excellent quantitative prediction of the melt fraction evolution. Qualitative data is also provided in the form of velocity vector diagrams and isotherm plots for selected times in the evolution of both problems. The computational costs incurred are quite low by comparison with previous efforts on solving these problems.
    Keywords: Metals and Metallic Materials
    Type: NASA-CR-188468 , NAS 1.26:188468
    Format: application/pdf
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