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  • 1
    ISSN: 1432-0630
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The increase in brain iron associated with several neurodegenerative diseases may lead to an increased production of free radicals via the Fenton reaction. Intracellular iron is usually tightly regulated, being bound by ferritin in an insoluble ferrihydrite core. The neurotoxin 6-hydroxydopamine (6-OHDA) releases iron from the ferritin core by reducing it to the ferrous form. Iron release induced by 6-OHDA and structurally related compounds and two other dopaminergic neurotoxins, 1-methyl-4-phenylpyridinium iodide (MPP+) and 1-trichloromethyl-1,2,3,4-tetrahydro-β-carboline (TaClo), were compared, to identify the structural characteristics important for such release. 1,2,4-Trihydroxybenzene (THB) was most effective in releasing ferritin-bound iron, followed by 6-OHDA, dopamine, catechol, and hydroquinone. Resorcinol, MPP+, and TaClo were ineffective. The ability to release iron was associated with a low oxidation potential. It is proposed that a low oxidation potential and an ortho-dihydroxyphenyl structure are important in the mechanism by which ferritin iron is mobilized. In the presence of ferritin, both 6-OHDA and THB strongly stimulated lipid peroxidation, an effect abolished by the addition of the iron chelator deferoxamine. These results suggest that ferritin iron release contributes to free radical-induced cell damage in vivo.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Recent developments in scannning transmission electron microscopy (STEM) instrumentation have pushed the limits of the achievable spatial resolution for analytical measurements into the subnanometer regime, which is necessary for the characterization of semiconducting heterostructures and interfaces. Z-Contrast (or high-angle annular dark field) imaging combines atomic resolution with chemical contrast. Such images are not affected by contrast reversals due to objective lens defocus or changes in specimen thickness, such as phase contrast images (bright field images). Parallel detection of electron energy-loss spectra allows spatially resolved quantitative chemical information to be obtained even for high energy losses and when using a very fine electron probe diameter (down to 〈 0.3 nm). Examples demonstrating the performance of these techniques are given for AlGaAs/GaAs heterostructures used for very high speed and very high frequency devices. While high-resolution Z-contrast imaging is superior with respect to the spatial resolution achieved and the acquisition time needed, electron energy-loss spectroscopy (EELS) can be used to record chemical line profiles with slightly decreased spatial resolution. In particular it can be used to quantify the Z-contrast images by means of point analysis. Thus, the combination of Z-contrast imaging and EELS can give information beyond the scope of either individual characterization technique.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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