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SUPEROXIDE SPECIES FORMED ON MgO THROUGH THE AGENGY OF PRESORBED MOLECULES
No full textJOURNAL OF CHEMICAL SOCIETY, FARADAY TRANSACTION
Surface structure and reactivity of VTiO catalysts prepared by solid-state reaction 1. Formation of a VIV interacting layer
No full textThe solid-state interaction between V2O5 and TiO2 in the 700-800 K range of temperatures gives rise to the formation of VIV sites even in the absence of reducing agents. A VIV interacting layer covering the entire surface of TiO2 anatase may be created in the absence of any indication of partial transformation to the rutile phase. The nature, amount, and distribution of these VIV sites are characterized by means of titration combined with selective extraction, reactivity measurements in o-xylene oxidation, evaluation of redox properties, and by XRD, XPS, and ESR analyses. The amount of VIV depends on the crystallographic nature (anatase or rutile) and surface area of the TiO2 and on the conditions (temperature, time, and type of atmosphere) of the heat treatment. In the anatase sample the VIV sites can be reduced to VIII, but not oxidized to VV due to the strong interaction with the titania surface. In rutile samples part of the VIV may be reduced to VIII, but also oxidized to VV. The remaining VIV sites are present in solid solution in the rutile matrix and are not accessible to redox reagents. The model of a VIV-modified TiO2 (anatase) surface is discussed with reference to the problem of surface diffusion of vanadium species on the anatase surface. In TiO2 (rutile)-based samples, due to the competition of the migration of vanadium ions toward the bulk of the rutile with respect to surface diffusion, V2O4-like islands form that are coherently intergrown into the main rutile TiO2 matrix. © 1991
EVIDENCE OF STABLE HYDROXYL RADICALS AND OTHER OXYGEN RADICAL SPECIES GENERATED BY INTERACTION OF HYDROGEN-PEROXIDE WITH MAGNESIUM-OXIDE
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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