1,721,068 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
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
Synthesis of terpene-based amphiphilic copolymers as stabilizers of film-forming waterborne latex prepared from biobased 1,3-diene terpene monomers.
No full textCe projet de thèse vise à réduire l'empreinte carbone en valorisant des produits issus de la biomasse pour synthétiser différentes classes de matériaux polymère, plus particulièrement des copolymères amphiphiles comme stabilisants pour l’élaboration de latex. Développer une nouvelle génération de matériaux biosourcés est au cœur du projet pour soutenir une économie circulaire. En valorisant les principes de la chimie verte, l'objectif final est de substituer les produits issus de ressources fossiles dont la production participe aux émissions de gaz à effet de serre, par des produits provenant de la biomasse renouvelable.La première partie de ce travail de thèse vise à synthétiser des copolymères amphiphiles à base de terpènes, produits issus de la biomasse forestière, par une stratégie de couplage de ces molécules hydrophobes sur un squelette polymère hydrophile de type poly(acide acrylique). Ce dernier a été synthétisé par polymérisation par transfert réversible par addition fragmentation (RAFT) de l’acide acrylique, monomère dont la synthèse à partir de bioressources a été décrite et connait des développements industriels récents. Le couplage avec les molécules hydrophobes terpéniques a été effectué par estérification. Dans l’optique d’une chimie plus verte limitant l’utilisation de catalyseurs présentant une certaine toxicité mais également d’atteindre un meilleur contrôle de la composition du copolymère en groupements hydrophobes, une nouvelle génération de copolymères amphiphiles biosourcés a été synthétisée par copolymérisation radicalaire contrôlée par les nitroxydes (NMP) de l’acide acrylique avec un comonomère terpénique.Afin de comprendre le comportementde ces copolymères amphiphiles pH-sensibles en phase aqueuse, ces derniers ont été caractérisés par différentes méthodes (titration potentiométrique, mesure de tension de surface...).Ces copolymères amphiphiles biosourcés ont été utilisés comme stabilisants pour la synthèse de latex terpénique par polymérisation en émulsion ou en miniémulsion. Différents paramètres de synthèse ont été étudiés dans le but d’optimiser les conversions en monomère et les caractéristiques colloïdales des latex. La stabilisation des latex par des copolymères pH-sensibles confère cette propriété aux latex pour lesquels la floculation peut être déclenchée par une modification de pH.This thesis project aims to reduce the carbon footprint by using biomass products to synthesize different classes of biobased polymer materials, more precisely amphiphilic polymers as stabilizers for the synthesis of waterborne latex. Developing a new generation of biobased materials is at the heart of the project to support a circular economy. By valorizing the principles of green chemistry, the ultimate aim is to replace products derived fromfossil resources, whose production contributes to greenhouse gas emissions, with products derived from renewable biomass.The first part of this thesis aims to synthesize amphiphilic copolymers based on terpenes, a class of products derived from forest biomass, by coupling these hydrophobic molecules onto a hydrophilic polymer backbone of poly(acrylic acid). The latter was synthesized by reversible addition fragmentation transfer (RAFT) polymerization of acrylic acid, a monomer whose synthesis from bioresources was described and is undergoing recent industrial development. The coupling with hydrophobic terpene molecules was achieved by esterification. With a view to achieve greener chemistry by limiting the use of toxic catalysts but also to target a better control over copolymer composition in hydrophobic groups, a new generation of biobased amphiphilic copolymers was synthesized by nitroxide mediated radical copolymerization (NMP) of acrylic acid with a terpene comonomer. To understand the behavior of these pH-sensitive amphiphilic copolymers in aqueous media, they were characterized by various methods (potentiometric titration, surface tension measurement, etc.).These biobased amphiphilic copolymers were used as stabilizers for the synthesis of terpene-based waterborne latex via emulsion and miniemulsion polymerization. Various synthesis parameters were studied to optimize monomer conversions and latex colloidal features. The stabilization of latex particles by pH-sensitive copolymers conferred pH-responsiveness to latex for which flocculation can be triggered through a pH change
Elaboration of transparent composite materials based on hybrid core@shell nanoparticles
No full textL’incorporation de particules inorganiques dans une matrice polymère confère de nouvelles propriétés au matériau ou améliore de manière significative les propriétés déjà existantes. Cependant, l’apparence visuelle perçue, telle que la transparence, peut être altérée par des phénomènes de diffusion de la lumière par les particules. Cette diffusion de la lumière est principalement conditionnée par la dimension des particules –ou agrégats de particules- et la différence d’indice de réfraction entre la matrice et les charges. Afin de traiter ces deux problèmes, l’objectif de nos travaux était de contrôler simultanément l’état de dispersion des nanoparticules inorganiques dans la matrice polymère et l’indice de réfraction des nanoparticules de façon à l’ajuster à celui de la matrice. Pour élaborer ce nouveau composite, nous avons synthétisé des nanoparticules hybrides cœur@écorce avec un cœur inorganique qui apporte les nouvelles propriétés et une écorce polymère d’épaisseur contrôlée, obtenue par polymérisation radicalaire contrôlée par voie nitroxyde amorcée à la surface des nanoparticules inorganiques. L’écorce polymère limite l’agrégation des particules et permet de modifier l’indice de réfraction moyen des nanoparticules cœur@écorce. En contrôlant l’épaisseur et la nature chimique de l’écorce polymère, nous cherchons à ajuster l’indice de réfraction des nanoparticules cœur@écorce à celui de la matrice. Les nanoparticules ont ensuite été dispersées dans une matrice de poly(méthacrylate de méthyle). Les propriétés optiques des composites ont été caractérisées par spectrogoniophotométrie, afin d’obtenir des informations sur l’intensité et la distribution angulaire de la lumière transmise par le composite. La transparence des nanocomposites a été fortement améliorée en ajustant l’indice de réfraction des nanoparticules cœur@écorce à celui de la matrice.The incorporation of inorganic particles into a polymer matrix confers new properties to the material or enhances significantly existing properties. However, the perceived visual appearance, such as loss of transparency, might be modified by the scattering of light by the particles. This light scattering is mainly due to the particle –or aggregates of particles- dimensions and the refractive index difference between matrix and fillers. In order to address both issues, the objective of the present work was to control simultaneously the dispersion state of the inorganic nanoparticles into the polymeric matrix and the refractive index of the nanoparticles to match the one of the matrix. To achieve this new composite, we designed hybrid core@shell nanoparticles with an inorganic core that brings new properties and a polymer shell of controlled thickness, obtained by surface-initiated nitroxide mediated controlled radical polymerization. The polymer shell limits the aggregation of the particles and enables us to tune the average refractive index of the hybrid core@shell particle. By controlling the thickness and the chemical nature of the polymeric shell, we targeted to match the refractive index of the hybrid core@shell particle to the one of the polymeric matrix. The nanoparticles were further dispersed into a poly(methyl methacrylate) matrix. Optical properties of composites were characterized by spectrogoniophotometry which gave us informations about the intensity and the angular distribution of the transmitted light by the nanocomposites. The transparency of the nanocomposites was strongly enhanced for core@shell particles fulfilling the refractive index matching conditions
Synthesis of amphiphilic copolymers based on terpenes as stabilizers of emulsions : towards encapsulation of biocontrol agents
No full textDepuis la dernière décennie, on observe un intérêt croissant pour le développement d'alternatives aux ressources fossiles afin de préparer des formulations innovantes impliquant des matières premières issues de la biomasse. Dans ce projet de thèse, les terpènes ont été choisis comme biomasse aliphatique n'entrant pas en concurrence avec la chaîne d'approvisionnement alimentaire, afin de modifier des polymères hydrophiles biosourcés pour produire des copolymères amphiphiles efficaces dans la stabilisation d'émulsions huile végétale-dans-eau.L'objectif de ces travaux est d'étudier comment les paramètres structuraux des copolymères amphiphiles biosourcés peuvent affecter les caractéristiques des émulsions en termes de diamètres et distribution de tailles de gouttes et leur stabilité à long terme. Deux familles de polymères amphiphiles ont été ciblées à partir de deux types de polymère hydrophiles (polymère acrylique synthétisé à partir de monomère biosourcé ou polysaccharide naturel) et différents terpènes fonctionnels.Les copolymères amphiphiles biosourcés présentant les structures optimales ont été utilisés comme stabilisants d'émulsions pour encapsuler dans la phase huileuse des molécules hydrophobes d'intérêt qui sont des co-produits de la viticulture. Ces dernières molécules ont été sélectionnées pour leur activité antifongique sur plantes contre des pathogènes ciblés afin de développer des formulations de biocontrôle.Since the last decade, there has been a growing interest in the development of alternatives to fossil resources for the preparation of innovative formulations involving biomass feedstocks. In this PhD project, terpenes were selected as an aliphatic biomass not competing with the food supply chain, in order to functionalize hydrophilic biobased polymers to produce amphiphilic copolymers as efficient stabilizer of vegetable oil-in-water emulsions.The objective of this work is to study how the structural parameters of biobased amphiphilic copolymers may affect the long-term stability and features of emulsions (distribution and size of droplet diameters). For that purpose, two families of biobased amphiphilic polymers were targeted from two types of hydrophilic polymers (acrylic polymer from biobased monomer or natural polysaccharide) and different functional terpenes.The biobased amphiphilic copolymers with optimal structures were involved as emulsion stabilizers to encapsulate hydrophobic molecules of interest in the oil phase as co-product of viticulture. These molecules were selected for their antifungal activity in planta against targeted pathogens, in order to develop efficient biocontrol formulations
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