1,721,018 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Practical aspects on how to deracemize atropizomers by means of crystallization
No full textLes techniques de séparation chirale sont importantes pour permettre des études relatives de l’activité biologique des molécules chirales. Dans cette thèse, la séparation chirale des atropisomères de la naphthamide par déracémisation, une approche combinant la racémisation avec la cristallisation, a été étudiée du point de vue pratique et théorique. Dans le chapitre 2, nous avons démontré pour la première fois l'impact de la cinétique de racémisation sur la cinétique de déracémisation induite par des cycles de température (TCID) ainsi que sur la productivité du processus. La cinétique de racémisation est liée linéairement à la cinétique globale TCID, et la productivité du procédé est liée non seulement à la cinétique de racémisation mais également à la solubilité du composé dans le solvant choisi. Dans le chapitre 3, nous avons comparés les productivités des processus de TCID et de transformation asymétrique de second ordre (SOAT). Nous avons démontré que la productivité des processus de TCID est indépendante de l'échelle du système. Ensuite, nous avons montré que SOAT est un processus permettant d’obtenir la meilleure productivité, tandis que le TCID permet d’obtenir des produits hautement énantiopurs. Dans le chapitre 4, un cas problématique de déracémisation d'un composé formant plusieurs phases solides a été réalisée à l'aide d'une étude de diagramme de phases. Bien que la racémisation ajoute de la complexité au diagramme de phase, nous avons montré la construction d'un diagramme de phase pour les composés racémisables permet de trouver les conditions permettant de mener à bien le procédé de déracémisation.Chiral separation techniques are important for enabling studies relating to the biological functions and activities of chiral molecules. In this thesis, chiral separations by deracemization, an approach that combines racemization with crystallization, have been studied from the practical and theoretical viewpoints using atropisomeric naphthamide In Chapter 2, we studied the first experimental proof of the impact of racemization kinetics on global temperature cycle induced deracemization (TCID) kinetics as well as on process productivity. The racemization kinetics are linearly related to the global TCID kinetics, and the process productivity was related not only to the racemization kinetics but also to the solubility of the compound. In Chapter3, we performed a comparison study of process productivities of TCID and second-order asymmetric transformation (SOAT). We demonstrated that the process productivity of TCID is independent of the scale of the system. Then, we found that SOAT is a productive process, while TCID gives highly enantiopure products. In Chapter 4, a problematic case of the deracemization of a single compound forming multiple solid phases was demonstrated using a phase diagram study. Although racemization adds complexity to the phase diagram, we sought to show the construction of a phase diagram for racemizable compounds and how the diagram enabling deracemization
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Benefit of analytical and chemiοmetric tools on the study of asphalt oxidation during the simulation of long-term aging
No full textDe nos jours, la compréhension du vieillissement du bitume est un sujet de premier ordre dans le secteur pétrolier. Afin de développer des bitumes de plus en plus durables, il apparaît nécessaire de mieux comprendre les mécanismes d’oxydation conduisant au vieillissement du bitume. Dans le cadre de ces travaux, plusieurs bitumes ayant été préalablement caractérisés ont été soumis à différentes durées de vieillissement simulées avec la méthode PAV. Une approche originale de fractionnement a ensuite été utilisée, la séparation chromatographique SAR-AD. La création de fonctions oxygénées a été suivie en IRTF. Dans un premier temps, l’influence primordiale de la surface de l’interface air/bitume a été mise en évidence. Une modélisation cinétique a permis de montrer que l’évolution des 8 fractions SAR-AD se composait d’une réaction rapide suivie d’une réaction lente et que les fractions aromatiques 2 et 3 étaient les plus impactées au cours du vieillissement. Des analyses multivariées ont été conduites sur les données récoltées afin d’identifier les transferts de molécules oxydées d’une fraction à une autre. De manière générale, il a été montré que les mécanismes d’oxydation liés au vieillissement sont fortement dépendants de la nature du bitume.Nowadays, understanding asphalt aging is a topic of primary importance in the petroleum industry. In order to develop increasingly durable asphalts, it appears necessary to better understand the oxidation mechanisms leading to the aging of asphalts. As part of this work, several asphalts previously characterized were subjected to different aging times simulated with the PAV method. An original method was used to fractionate asphalts, the chromatographic separation SAR-AD. The creation of oxygenated functions was monitored by FTIR. Firstly, the primordial influence of the surface of the air/bitumen interface was highlighted. Kinetic modelling showed that the evolution of the 8 SAR-AD fractions consisted of a fast reaction followed by a slow reaction and that the aromatic fractions 2 and 3 were the most impacted during aging. Multivariate analyses were conducted on the collected data to identify the transfers of oxidized molecules from one fraction to another. In general, it has been shown that the oxidation mechanisms linked to aging are highly dependent on the nature of the bitumen
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
Additive effect in supercritical fluid chromatography on enantioselective stationary phase
No full textLe développement de molécules chirales est devenu un enjeu majeur pour l’industrie pharmaceutique. Lors de la mise au point d’un nouveau principe actif, la chromatographie en phase supercritique (CPS) sur phases stationnaires énantiosélectives, est devenue une méthode incontournable pour l’analyse ou la purification d’énantiomères. Il n’en demeure pas moins que certains composés tels que les composés basiques restent délicats à analyser par cette technique et que l’ajout d’un additif basique dans la phase mobile est très souvent nécessaire. La quantité d’additif ajoutée dans la phase mobile est souvent choisie de manière arbitraire en se basant sur les spécifications des fournisseurs de phases stationnaires et sur les travaux publiés dans le domaine, sans se soucier de l’effet potentiel sur la résolution d’une modification de sa concentration. Ce travail de thèse a démontré l’importance de la concentration en additif dans la phase mobile lors de l’analyse de mélanges d’énantiomères par CPS, avec notamment des effets significatifs sur l’énantiosélectivité allant jusqu’à une inversion de leur ordre d’élution selon la concentration en additif. Dans un deuxième temps cette étude a consisté en une amélioration de notre compréhension des modes d’actions de l’additif, sur la phase stationnaire et sur la phase mobile permettant de poser des hypothèses sur les effets observés lors de la séparation d’énantiomères. La dernière partie est consacrée à la présentation de différents exemples, justifiant l’intérêt de moduler la concentration en additif lors de séparations d’énantiomères.Nowadays, the development of chiral molecule is a strategic issue for the pharmaceutical industry. During the development of a new molecular entity, supercritical fluid chromatography using enantioselective stationary phases is essential for the analysis or the purification of racemates. Despite the advantages of SFC, the analysis of some compounds like basic compounds may still be a challenge. Their analysis most of the time, requires an additive in the mobile phase. In many cases additives concentration is chosen arbitrarily, based on the columns supplier guidelines and work already published, regardless of the impact of the additive concentration on the resolution. This work has shown the impact of the additives concentration for the analysis of enantiomers by SFC, in particular a significative impact on the enantioselectivity of chiral stationary phases, with for some of them a reversal elution order depending on the additive concentration. The second objective is to improve our knowledge on the mechanism of action of the additive both on the stationary phase and the mobile phase. The last part is dedicated to the presentation of a few examples highlighting the positive impact of the variation of the additives concentration for enantiomer separation
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