1,721,179 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
A new photo-induced approach to metal@polymer nanohybrid materials : from design to characterization and implementation of a multi-property coating on textile materials
No full textCe travail de thèse a pour objectif principal le développement d’une stratégie innovante de synthèse de revêtements nanohybrides métal@polymère applicable à la métallisation de substrats rigides et flexibles, et notamment les textiles. Pour cela la voie photo-induite a été employée afin d’induire simultanément la polymérisation d’une matrice et la synthèse in situ de nanoparticules métalliques, ce qui représente une alternative à la chimie thermique traditionnellement utilisée. Le contrôle des paramètres photoniques et chimiques permet d’agir sur le couplage des cinétiques de ces réactions et par là, d’induire une structuration particulière du revêtement métallique généré photo-chimiquement. Le matériau ainsi obtenu présente une architecture modulable qui conditionne ses propriétés spécifiques d’usage : optiques, plasmoniques, électriques, acoustiques, antimicrobiennes, mouillage... Ces propriétés ont été évaluées pour un revêtement nanoparticules d’argent@polymère sur support modèle en verre puis sur textile. Le contrôle de la morphologie des nanoparticules et de leur organisation conduit à des aspects brillant ou mat mais également argenté,doré ou cuivré. Des surfaces flexibles hautement réfléchissantes (réflectance supérieure à 90 %) et présentant un caractère antimicrobien ont ainsi été obtenues. L’application d’un post-traitement thermique au revêtement photo-induit sur verre entraîne une diminution des forces stabilisatrices de Van der Waals ce qui favorise une évolution de la morphologie et l’organisation des nanoparticules via des phénomènes de migration et coalescence. Cela entraîne une évolution des propriétés qui en découlent avec, en particulier, une amélioration spectaculaire de la conductivité électrique des revêtements (8 ordres de grandeur). Pour mieux appréhender la durabilité de ce revêtement, une étude de vieillissement a également été conduite. Dans la perspective d’une future industrialisation de ce procédé, techniquement et économiquement viable, la question de l’ignifugation du revêtement ainsi que les points associés au changement d’échelle ont été abordés. L’écoconception,le caractère « safe by design » et la mise en œuvre de procédés facilement transposables à l’échelle industrielle pour générer des surfaces flexibles et multipropriétés constituent des innovations majeures de ce travail.This PhD work aimed at developing a new approach for the synthesis of nanohybrid metal@polymer coatings to metallizing both rigid and flexible substrates, and in particular textile materials. To this end, an innovative process in which the photo-polymerization of a resin and the in situ synthesis of metal nanoparticles are simultaneously induced through photonic activation was proposed as an effective alternative to traditional thermal chemistry. Thus, the precise tuning of the photonic and chemical parameters has a direct influence on the kinetic coupling between photopolymerization and photo-reduction processes that control the intimate structure of the coating. The materials thus obtained have an adjustable architecture which governs its specific characteristics such as reflectivity, plasmonic, electrical conductivity, acoustic, antimicrobial properties, wettability, etc. All of them have been characterized in the case of a silver@polymer nanohybrid coating, first, on a model substrate (glass slides) and then, on a selection of textile materials. By controlling the morphology of silver nanoparticles and their spatial organization, it was possible to obtain matt or glossy aspects, as well as silver, gold or copper effects. The surfaces thus obtained are flexible, highly reflective (reflectivity exceeding 90%) and have antibacterial activity. Annealing the photo-generated coatings induces beneficial effects on the morphology and the organization of metal nanoparticles, due to the reduction of stabilizing Vander Waals forces that induce migration and coalescence phenomena. The resulting properties evolved, for example, due to percolation, electrical conductivity is improved by 7 to 8 orders of magnitude. Finally, to gain a better understanding of the durability of this coating, an ageing study was also carried out. In view of a future industrialization of this process, which is technically and economically viable, the fireproofing of the coating and the issues related to scaling up where addressed. Eco-design, safe by design aspect and the development of a process that can be easily transposed to industry to generate flexible and multi-properties surfaces are the moststricking innovations of this work
Development of mono- and bi-metallic@polymer hybrid coatings with plasmonic activities by a photoinduced approach : synthesis, characterisation and potential applications
No full textLes matériaux hybrides jouent un rôle essentiel dans la création de nouveaux matériaux avancés. De plus, la possibilité de concevoir et de fabriquer ces assemblages complexes de manière précise en vue d'applications spécifiques constitue un domaine de recherche en plein essor avec un grand potentiel d'innovation. Durant ce travail de thèse, des revêtements plasmoniques ont été développés par voie photoinduite, une approche à la fois propre, éco-efficiente et viable industriellement. Cette technique utilise la lumière UV pour déclencher des réactions telles que la photoréduction de précurseurs métalliques et la photopolymérisation de la matrice. Dans le contexte actuel de la course à la décarbonation, l'utilisation de la lumière comme outil d'activation des processus chimiques, renforce l'intérêt de l'approche photoinduite. Celle-ci a donc été utilisée pour synthétiser in situ des nanoparticules mono- et bi-métalliques (BNPs) à base d'or et/ou d'argent dans des copolymères à blocs semi-cristallins de type polyuréthanes thermoplastiques (TPU) ou des acrylates photopolymérisables. Ces nanoparticules mono- ou bi-métalliques sont alors confinées dans la matrice polymère, empêchant leur agglomération et profèrent aux nouveaux matériaux des propriétés optiques uniques selon les métaux composant les NPs ainsi que leurs structures : cœur-coquilles Au@Ag et Ag@Au ou alliages. Le contrôle de la synthèse des différentes structures en une unique étape d'exposition aux UV et la compréhension des mécanismes mis en jeu ainsi que l'indentification des BNPs synthétisés ont été réalisés. De plus, l'impact de la présence des NPs sur les chaînes polymères et leur mobilité a été étudié. Les nanomatériaux hybrides développés possèdent à la fois les propriétés dues à la matrice polymère utilisée et aux nanoparticules métalliques confinées dans le polymère, notamment grâce à l'exploitation de la résonance plasmonique des nanoparticules. Des études préliminaires ont été réalisées afin de valider leurs utilisations potentielles dans divers domaines tel que la photonique, la photocatalyse pour la dégradation des polluants organiques dans l'eau, la détection des métaux lourds, l'électronique et les arts graphiques.Hybrid materials are essential for the creation of new advanced materials. The ability to precisely design and manufacture these complex assemblies for specific applications is a fast-growing area of research with great potential for innovation. During this PhD thesis, plasmonic coatings were developed using a photoinduced process, which is a clean, eco-efficient and industrially viable approach. This process uses UV light to trigger reactions such as the photoreduction of metal precursors and the photopolymerisation of the polymer matrix. In the current global context of reducing carbon footprints, the use of light as a tool to activate chemical processes reinforces interest in the photoinduced approach.This technique was therefore used to synthesise in situ mono- and bi-metallic nanoparticles (BNPs), based on gold and/or silver, in semi-crystalline block copolymers such as thermoplastic polyurethanes (TPU) or photopolymerisable acrylates. These mono- or bi-metallic nanoparticles are confined in the polymer matrix, thereby preventing their agglomeration, and they give the new materials unique optical properties depending on the chosen metals and overall structure: core-shell Au@Ag and Ag@Au or alloys. The different structures were obtained through a single step synthesis by controlling the synthesis parameters and understanding the mechanisms involved. In addition, the NPs impact on the polymer chains and their mobility was studied.The developed hybrid nanomaterials have properties that are due to the chosen polymer matrix and the metal nanoparticles confined within the polymer, in particular thanks to the nanoparticles plasmon resonance. Preliminary studies have been carried out to validate their potential applications in various fields such as photonics, photocatalysis, heavy metal detection, electronics and graphic arts
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
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
Síntesis fotoasistida de materiales de carbono nanoporosos
No full textL'utilisation des réactions photo-assistées pour obtenir des carbones nanoporeux et des composites nanoporeux métal/carbone a été exploré. Une polycondensation photo-induite par UV (et solaire simulé), était employée pour préparer des résines phénoliques, à base de glyoxal, en présence d'un tensioactif, comme agent directeur de mésostructure. Après pyrolyse, des matériaux carbonés aux propriétés texturales et physicochimiques contrôlées ont été obtenus.Le degré de réticulation de la résine photopolymérisée, et le degré d'interaction avec l'agent de surface ont été déterminés par la structure, groupes fonctionnels, ainsi que par le nombre de positions réactives des hydroxybenzenes utilisés. Le choix approprié du précurseur organique, du type hydroxybenzène, et des paramètres de synthèse, ont permis de contrôler la morphologie, l'ordre structural et la distribution de taille des pores des matériaux de carbone obtenus dans toute la gamme micro/mésoporeuse. De plus, l'incorporation d'ions métalliques (sels Au3+, Ag+) a simultanément permis la polycondensation photoassistée de la résine phénolique et la photoréduction des ions métalliques, produisant des nanoparticules métalliques (NPs) intégrées dans la matrice polymère. Après pyrolyse, les matériaux obtenus contiennent des NPs métalliques hautement dispersées dans la matrice de carbone. Les micrographies MET ont montré que la taille et la qualité de la dispersion des nanoparticules métalliques peuvent être contrôlées en modifiant les paramètres chimiques.Cette approche photoassistée rapide, simple et rentable ouvre de grandes perspectives dans la synthèse de carbones poreux et de matériaux hybrides.The objective was to explore photoassisted reactions to prepare porous carbons and metal/carbon nanohybrids. A photoinduced polycondensation, UV and simulated solar light, was implemented for the preparation of different glyoxal-phenolic resins in the presence of a surfactant, as mesostructure director agent. After pyrolysis, these precursors render carbon materials with controlled textural and physicochemical properties.By appropriate choice of the organic precursor and synthesis parameters, it was possible to control the morphology, structural order, and pore size distribution of the final carbon materials throughout the micro/mesoporous range.The degree of crosslinking of the photopolymerized resin was determined by the structure, as well as the number of reactive positions in the organic precursors (e.g., the non-substituted positions respect the hydroxyl group moieties). E. g. bisphenol A (di-phenolic type), resulted in highly branched clusters that presented low interaction with the template, giving rise to a structure with dense porosity mainly composed of narrow micropores. In contrast, the poly hydroxy-benzene type precursors, which present a higher degree of interaction with the surfactant, promote a more open structure.The incorporation of metal ions (Au3+, Ag+ salts) during the one-pot process, allowed the simultaneous photopolycondensation of the phenolic resin and photoreduction of metal ions, yielding metal nanoparticles. After pyrolysis the resulting materials contain highly dispersed metal NPs in the carbon matrix.This fast, simple and cost-effective photoassisted approach opens up great prospects in the synthesis of porous carbons and hybrid materials
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