1,721,087 research outputs found
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
Adsοrptiοn of isοbutanοl on zeοlites : the potential of multivariate analysis
No full textLes méthodes analytiques classiques pour la caractérisation des propriétés d’adsorption de catalyseurs ou d’adsorbants, telles que l'analyse gravimétrique ou la calorimétrie, donnent des valeurs d’enthalpies moyennées sur différents sites d'adsorption. Dans cette étude, la spectroscopie IR in situ combinée aux analyses multivariées a été utilisée pour identifier et caractériser quantitativement l'adsorption d'alcools sur des zéolithes. La méthode de résolution multivariée de courbes par moindres carrés alternés – (MCR-ALS), utilisée pour la première fois dans le domaine de l'adsorption, nous a permis de récupérer des profils de réponse purs : profils spectraux, permettant l'identification d'espèces distinctes, et isothermes d'adsorption correspondants, permettant d'évaluer les paramètres d’adsorption par ajustement de courbe d'une isotherme locale telle que l'isotherme de Langmuir ou l'implémentation de l'isotherme en tant que contrainte rigide. L’adsorption d’isobutanol dans des zéolithes acides (MFI et FER), la silice et la silicalite a été étudiée par spectroscopie infrarouge couplée ou non à des mesures gravimétriques puis analysée par des méthodes d’analyses multivariées pour distinguer l’adsorption sur les différents sites de la zéolithe, et en obtenir les paramètres thermodynamiques.Une première étude quantitative a permis de déterminer les coefficients d’absorption molaires de la pyridine, de l’isobutanol et des hydroxyles d’une zéolithe MFI afin de déterminer les quantités adsorbées sur cette zéolithe et de montrer l’apport des analyses multivariées dans ce domaine. La méthodologie MCR-ALS est ensuite développée puis appliquée pour l‘adsorption d’isobutanol sur une zéolithe MFI calcinée dans le but de déterminer les enthalpies et entropies d’adsorption propre à chaque espèce adsorbée. Trois modes d’adsorption ont été distingués pour ce système : l’adsorption de l’isobutanol sur la surface externe (Silanols), sur les aluminiums extra réseau dénommés EF-AlOH, et sur les micropores (hydroxyles pontés) de la zéolithe.L’étude a été étendue à la précédente MFI ayant été vapotraitée à température modérée (773 K) et deux ferrierites avec des tailles de cristaux différentes. En ce qui concerne la MFI vapotraitée, la méthodologie a permis de mettre en évidence la présence d’une quatrième espèce correspondant à un autre type de Silanols (dénommé Silanols fort dans cette étude), apparaissant avec le vapotraitement. Il a aussi été constaté que le vapotraitement a augmenté les valeurs des enthalpies de chaque site acide.L’application de la méthodologie FTIR-MCRALS sur les systèmes iBuOH/FER montre que l’adsorption a essentiellement lieu sur la surface externe et a mis en évidence la contribution de deux types de silanols.Classical quantitative analytical methods for the characterization of adsorbents such as gravimetric analysis or calorimetry yield enthalpy values averaged over the various adsorption sites. In this study, in situ IR spectroscopy combined with multivariate analysis has been used to identify and quantitatively characterize alcohol adsorption on zeolites. The method of multivariate curve resolution by alternating least squares – (MCR-ALS), used for the first time in the field of adsorption, enabled us to recover pure response profiles: spectral profiles, allowing the identification of distinct species, and their corresponding adsorption isotherms, allowing the evaluation of adsorption parameters by curve fitting a local isotherm such as the Langmuir isotherm or implementing the isotherm as a hard constraint.Isobutanol adsorption on acid zeolites (MFI and FER), silica and silicalite was studied by infrared spectroscopy, coupled or not to gravimetric measurements, then analyzed by multivariate analysis methods to distinguish adsorption on the different zeolite sites, and obtain their thermodynamic parameters.We began with a quantitative study to determine the molar absorption coefficients of pyridine, isobutanol and hydroxyls on an MFI zeolite, in order to quantify the quantities adsorbed on this zeolite, and to demonstrate the usefulness of multivariate analysis in refining this type of study.The MCR-ALS methodology was then developed and applied to the adsorption of isobutanol on a calcined MFI zeolite, with the aim of determining the adsorption enthalpies and entropies specific to each adsorbed species. Three adsorption modes were distinguished for this system: adsorption of isobutanol on the external surface (Silanols), on the extra-lattice aluminums known as EF-AlOH, and on the micropores (bridged hydroxyls) of the zeolite.The study was extended to the previous MFI steam-treated at moderate temperature (773 K) and two ferrierites with different crystal sizes. For the steamed MFI, the methodology revealed the presence of a fourth species corresponding to a different type of Silanols (referred to as strong Silanols in this study), appearing with steaming. It was also found that steam treatment increased the enthalpy values the acid sites of the MFI.The application of FTIR-MCRALS methodology to iBuOH/FER systems shows that adsorption takes place mainly on the external surface and has identified the contribution of two types of silanols
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
Caractérisatiοn de la diffusiοn dans les zéοlithes hiérarchisées par spectrοscοpie infrarοuge
No full textCe travail visait à développer et à évaluer une nouvelle méthode d'investigation du transport de matière dans les catalyseurs à base de zéolithes. Elle consiste en la combinaison de l'analyse gravimétrique et de la spectroscopie infrarouge. La première permet d'évaluer la diffusion de la phase gazeuse vers toute la porosité, tandis que la spectroscopie IR permet d'évaluer sélectivement la diffusion vers les sites actifs des zéolithes situés dans les micropores, en suivant l'évolution de leur taux couverture par la sonde moléculaire. Une méthode originale de traitement des données, basée sur l'inversion des équations intégrales décrivant les courbes cinétiques d'absorption ou les spectres infrarouges enregistrés au cours de l’adsorption, a également été développée. Ces méthodes ont été appliquées à la caractérisation (i) de mélanges mécaniques modèles de zéolites H-MFI et H-FAU, (ii) de zéolites H-MFI hiérarchisées obtenues par traitement dans un milieu fluorure et (iii) d'un catalyseur composite modèle constitué de Al-MCM-41 et de H-MFI hiérarchisée. Nos résultats montrent que les valeurs relatives des vitesses de diffusion mesurées par analyse gravimétrique et spectroscopie IR sont indicatives de la qualité de la connectivité entre les réseaux méso- et microporeux, et pourraient donc être utilisées pour qualifier les matériaux hiérarchisés à base de zéolithes.This work aimed at developing and benchmarking a new method of investigation of molecular diffusion in zeolite-based materials. It consists in the hyphenation of gravimetric analysis and infrared spectroscopy. The former allows assessing the diffusion from the gas phase to all the porosity, while IR spectroscopy allows for selective assessment of the diffusion to the zeolite active sites located in the micropores by monitoring the evolution of their coverage by the molecular probe. An original method of data processing, based on the inversion of the integral equations describing the uptake curves or infrared spectra has also been developed. These methods were applied to the characterization of (i) model mechanical mixtures of H-MFI and H-FAU zeolites, (ii) hierarchical H-MFI zeolites obtained by treatment in a fluoride medium, and (iii) model composite catalyst made of Al-MCM-41 and hierarchical H-MFI. Our results show that the relative values of diffusion rates as measured by gravimetry and IR spectroscopy are indicative of the quality of connectivity between meso- and microporous networks, and could thus be used to qualify zeolite-based hierarchical materials
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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