1,721,171 research outputs found
Highly dispersed vanadium-based catalysts: characterization by means of FT-IR and micro-Raman spectroscopies
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Synthesis and characterization of mesoporous and microporous carbons with potential applications as hydrogen storage media
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Propene adsorption and reaction on zeolites and pillared clays
No full textComparative IR and UV-Vis spectroscopic studies of propene adsorption and reaction on H-mordenite, dealuminated H-mordenite, dealuminated mazzite, montmorillonite and Al~3-pillared montmorillonite have been carried out. On all systems propene is first transformed into polymeric species (C.H2.+~+). On HMOR (both as such and dealuminated), allylic carbocations are successively produced by loss of H 2, the monoenic species (C.H2~., +) being formed at room temperature and the dienic (C,H2..3 § and trienic (C.Hz,_s +) species at higher temperatures. These species are not observed on the other systems, although they are presumably formed as unstable intermediates. In fact, on all the zeolites studied here two cyclic penta-atomic and hexa-atomic allylic carbocations have been observed for the first time. On all systems, the final products of reaction are polyaromatic species which, on the basis of their reaction with NH 3 still exhibit unsaturated carbocation behaviour. The activity of the various samples depends on their pore dimensions and on the nature of acidic sites involved: the larger the available pore space, the more branched is the polymer and the more difficult it is to observe allylic carbocations. Evidence is provided for a Bronsted-induced mechanism
Acidity of ITQ-2 zeolite as studied by FT-IR spectroscopy of adsorbed molecules in comparison with that of MCM-22
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Frontiera 1931. Dino Garrone e la cultura italiana degli anni '20-'30. Atti del Convegno
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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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