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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 61 (1999), S. 179-186 
    ISSN: 1572-879X
    Keywords: CO oxidation ; Cu‐ZSM‐5 ; zeolites ; DFT
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The catalytic oxidation of CO by Cu‐exchanged high‐silica zeolites (e.g., ZSM‐5) has been investigated theoretically using density functional theory. Calculations reveal two distinct, parallel pathways for oxidation of CO: (i) adsorption of O2= on a reduced Cu site followed by O atom abstraction by CO, and (ii) adsorption of CO followed by its reaction with O2= to form a cyclic compound which decomposes to form CO2=. The reduced site is regenerated via two different pathways, both of which involve oxidation of one or more CO molecules: (i) abstraction of atomic oxygen by CO from the oxidized active site, and (ii) formation of a carbonate species followed by its reaction with a molecule of CO. The relevance of these reactions to the reduction of NO is discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0932
    Keywords: Key words Cervical disc disease ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of this study is to assess the accuracy of MRI alone in the differentiation of soft cervical disc protrusion from osteophytic compression in cervical disc disease. In a retrospective study, the MRI scans of 41 patients with cervical disc disease, who had previously undergone surgery, were presented to three independent observers, randomly on two different occasions, to identify the accuracy of the diagnosis of the presence of hard or soft disc or both as a cause of compression. The observers (two neurosurgeons and one neuroradiologist) were not involved with the treatment of the cases at any stage and were unaware of the surgical findings. Their observations were compared with those of the surgeon recorded at operation. The intra-observer agreement was poor for diagnosis into three categories as hard or soft disc or both. In distinguishing between the presence or absence of hard disc, there was moderate to good (Kappa = 0.6) intra observer and fair to moderate (Kappa = 0.4) interobserver agreement. The sensitivity of diagnosis of a hard disc was high (87%) but specificity was low (44%), due to the overestimation of the presence of hard disc. There was a significantly higher incidence of hard disc in the elderly age group (76% over the fifth decade, P = 0.0073). It is concluded that MRI alone is not a very efficient diagnostic tool in distinguishing between hard and soft disc in the cervical disc disease.
    Type of Medium: Electronic Resource
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