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  • 1985-1989  (4)
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  • 1
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel method for determining the local concentration of Al in the AlxGa1−xAs layer of AlxGa1−xAs-GaAs multiple quantum well structures is reported. By scanning a 10 A(ring) electron beam across the interface, the (200) dark-field scanning transmission electron microscopy (STEM) image shows the contrast of the AlxGa1−xAs-GaAs multilayer since the intensity of the (200) diffraction is sensitive to the Al concentration. The line scan intensity profile of the (200) diffraction, along a uniform specimen region of known thickness, shows the intensity variation of the (200) diffraction and reflects the local content of Al in each region. The simulation of the nanodiffraction patterns produces a chart of the (200) diffraction intensity versus the Al concentration for the determination of the local change of the Al concentration. A molecular beam epitaxy grown AlxGa1−xAs-GaAs specimen (x=0.57 as determined from Raman spectroscopy) is tested and the dark-field STEM studies show two thin layers of x=0.46 at the 1/3 and 2/3 height level within every AlxGa1−xAs layer.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial & engineering chemistry research 26 (1987), S. 1725-1735 
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0851
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study was undertaken to study natural killer (NK) cell activity in patients with colorectal cancer at peripheral and local levels. Mononuclear cells were isolated from uninvolved colorectal mucosa, tumor tissue and peripheral blood, and tested against the colon carcinoma cell line CaCo-2 and the erythroleukemia cell line K-562. Peripheral blood NK cell activity from the patients showed similar levels compared with healthy controls, whereas, mononuclear cells of tumor tissue were found to have a significantly decreased NK cell activity compared to the normal intestinal mucosa (P〈0.01). No relation was found between the NK cell activity and the advancement of the disease according to the Duke's stage. Interferon-γ (IFN-γ) stimulated the NK cell activity of the mononuclear cells from blood, mucosa and tumor. However, the increase of NK cell activity after IFN-γ stimulation was lower in the tumor compared to the mucosa (P〈0.02). The lectin, phytohaemagglutinin, increased the cytotoxicity of mononuclear cells from blood, mucosa and tumor to a similar level. These results suggest that patients with colorectal tumors exhibit a normal NK cell activity in peripheral blood and intestinal mucosa; however, a diminished NK cell activity exists at the tumor level. Although mononuclear cells isolated from the tumor have a normal response to lectin stimulation they show hyporesponsiveness to IFN-γ stimulation with regard to their NK cell activity.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple procedure to carry out the direct analysis of calcium, magnesium, sodium and potassium in water by flow injection analysis (FIA) using flame atomic absorption spectroscopy (AAS) or flame photometry (FP) has been developed, using a well stirred dilution chamber to extend the calibration range, and both a double injector and the merging zone technique to add a lanthanum solution to samples and standards. The results obtained in the analysis of real samples agree with those found by a batch flame atomic procedure. The use of the dilution chamber makes it possible to carry out the calibration using the dilution profile of a single concentrate standard for each element, and an empirical dilution equation, which could be employed for all the elements is determined in each work session.
    Type of Medium: Electronic Resource
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