1,720,985 research outputs found
Ammoxidation of 2-Methylpyrazine
No full textThe effect of changing the relative ratios of the active components in Sb-V-Mn mixed oxides, their concentration on the support and the nature of the latter has been analysed by employing several techniques, such as X-ray diffraction, scanning electron microscopy, electron probe microanalysis and electron spin resonance spectroscopy, together with chemical analysis, a titration of the surface acidity, and determinations of both the B.E.T. surface area and the porosity. A close dependence of activity and selectivity on the nature of the support was observed, connected with the ability of the latter to suppress the formation of microporosity. The catalytic activity is due to Sb4+ species. V and Mn both act as a structural promoter, conferring electrical conductivity on the solid and so improving the rapid electron transfer from the bulk to the surface, and vice versa
Effect of primer on honeycomb-supported La0.9Ce0.1CoO3+/-delta perovskite for methane catalytic flameless combustion
No full textA set of La0.9Ce0.1CoO3 combustion catalysts, supported onto commercial cordierite monoliths, through either La2O3 or Al2O3 as primer, was prepared with different active phase/primer combinations. Two different salts were tested as precursors of the La-based primer. The behaviour of the catalysts for the methane flameless combustion was compared with that of samples prepared in the absence of any primer. The primers and the active phase were deposited by means of the dip-coating technique. The preparation conditions of the suspension and/or solution for the dip coating were studied, aiming at obtaining a uniform and resistant deposition. The catalysts were characterised, before and after the activity tests, by BET, X-ray diffraction analysis (XRD) and scanning electron microscope (SEM). The comparison between the catalysts showed that with Al2O3 as primer the catalyst possesses a higher surface area (SA) and hence a higher initial activity, while with La2O3 as primer a very high thermal stability can be obtained
O- Spin Bags Formation in (CeO2)(0.75) (La2CuO4)0.25 Catalyst after Extended Use for Reduction of NO by CO
No full text(CeO2)1-y(La2CuO4) y with y = 0.25 and 0.43 have been analyzed by EPR after an extended-time-on-stream run at 450°C, employing them as catalysts for the title reaction. Some unusual EPR low-field features have been observed, attributed to the formation of O- spin bags at low temperature
Electron Paramagnetic Resonance Study of La Cuprate-based Catalysts for Phenol Oxidation
No full textA set of six La2-xEuxCuO4+δ samples, with x ranging from 0 to 1.33 have been analysed by EPR spectroscopy and X-ray diffractometry, to obtain information on their structure and on the change brought about by their use as catalysts for phenol oxidation with hydrogen peroxide. With increasing Eu content, a transformation of the orthorhombic structure of the La cuprate (x = 0) parent compound into two different TLa and T′Eu tetragonal structures takes place, accompanied by a change of electrical conductivity and the appearance of particular features in the EPR spectrum. The latter was a most sensitive probe for monitoring the structural modification arising during the catalytic reaction, even during the very early stages when the XRD pattern does not yet show any significant change
Anisotropic quantum spin fluid and quantum spin glass in La Cuprate-based catalysts
No full textEvidence of quantum spin fluid and of quantum spin glass behaviour has been detected by extended EPR analysis in some La-cuprate catalysts of general formula La2-xEuxCuO4 + δ. Some features of the EPR spectrum, appearing in a few cases, are also discussed and attributed to a pseudo Jahn-Teller effect due to a particular coordination of up to five oxygen ions around surface copper ions at low temperature
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Effect of preparation parameters on the properties of La0.9Ce0.1CoO3 catalysts: an EMR investigation
No full textA few La1−xCexCoO3 (x = 0; 0.1) catalysts, prepared by the traditional sol–gel (SG) or by flame pyrolysis (FP) procedures have been analysed
by EPR spectroscopy at 120≤T≤300 K. No EPR line was noticed with all of the x = 0 samples. The x = 0.1 SG catalysts gave a single EPR feature
at g∼=
2, both when fresh and after catalytic reaction. This line was Lorentzian shaped at 120 K, broadening with increasing temperature, and also
becoming a bit asymmetric after catalytic use. The x = 0.1 FP samples gave an EPR spectrum only after catalytic reaction. This pattern was rather
similar to that obtained with the fresh SG sample with the same composition, but shifted towards lower magnetic field values. Furthermore, all
the FP samples showed an intense ferromagnetic signal (FMR) after degassing treatment, while they remained EPR silent after oxygenation. An
interpretation of most of these observations is here proposed on the base of polaron propagation and of formation of ferromagnetic spin bags.
A correlation between catalytic performance, XRD patterns and electron magnetic resonance (EMR) (i.e. EPR or FMR) spectra, has been also
highlighted
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