1,721,175 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
Molecular simulation of aqueous electrolytes in nanoporous carbons : blue energy and water desalination
No full textLors du mélange de l'eau douce des rivières avec l'eau salée de la mer, une quantité considérable d'énergie est dissipée. Plusieurs procédés sont actuellement à l'étude pour parvenir à exploiter cette énergie bleue (Blue Energy). Inversement, la désalinisation de l'eau de mer pour la production d'eau potable nécessite de très grandes quantités d'énergie. Depuis la proposition en 2009 d'une nouvelle approche pour parvenir à ces objectifs, grâce à des cycles thermodynamiques reposant sur la charge/décharge d'électrodes à forte/faible concentration en sel, expérimentateurs et ingénieurs ont essayé d'améliorer le procédé. Dans ce contexte, l'utilisation d'électrodes nanoporeuses de carbone semble une piste très prometteuse. Un défi de taille reste à relever pour déterminer les quantités pertinentes (capacité électrique et quantité de sel adsorbé en fonction de la composition de l'électrolyte et de sa concentration). En effet, les modèles traditionnels (Poisson-Boltzmann, etc) ne peuvent pas être utilisés dans ce cas où les interactions au niveau moléculaire jouent un rôle essentiel. Nous surmontons cette difficulté grâce aux simulations de dynamique moléculaire, qui permettent également de comprendre les mécanismes microscopiques à l'origine des propriétés observées. Nous étudions également l'influence de la structure microporeuse de l'électrode de carbone ainsi que l'effet de la nature du sel chimique.When fresh river water mixes with salty sea water, a large amount of energy is lost. Conversely, the desalination of seawater for the production of drinking water requires very large amounts of energy. A new approach has been proposed in 2009 to harvest this "blue energy", thanks to the charge/discharge of electrodes in electrolytes with high/low salt concentration. The use of nanoporous carbon electrodes seems promising, but the traditional models (such as Poisson-Boltzmann) used to determine the relevant quantities do not apply in this case where molecular interactions play an essential role. We overcome this difficulty by performing molecular dynamics simulations of nanoporous carbon electrodes in the presence of an aqueous electrolyte. We evaluate the electrical capacity and the amount of ions adsorbed inside the electrodes as a function of the electrolyte composition and its concentration. In addition, these simulations allow us to understand the microscopic mechanisms leading to the storage of the charge, the effect of the structure of the carbon electrode, the salt concentration in the electrolyte and the chemical nature of the salt
Modeling of NMR relaxometry for monoatomic and quadrupolar ions in condensed matter
No full textL'interprétation des expériences de relaxométrie RMN nécessite une modélisation précise des interactions entre le noyau étudié et son environnement. Pour un noyau quadrupolaire, l'interaction entre le gradient du champ électrique (EFG) émis par l'environnement avec le quadruple électrostatique du noyau est prépondérante. Notre travail a porté sur le développement du calcul des temps de relaxation RMN pour ces noyaux par simulation moléculaire. Nous nous sommes intéressés à la relaxation d'ions mono-atomiques en phase condensée à travers deux systèmes simples et réalistes : des solutions aqueuses d'électrolytes et des verres de silicate de sodium. L'EFG dé aux électrons de l'ion est obtenu en calculant la réponse du nuage électronique grâce à des calculs quantiques combinés à une récente méthode pour reconstruire la contribution des électrons de cœur. L'EFG dû à l'environnement est obtenu à partir d'une simulation moléculaire où les interactions sont décrites par un champ de force polarisable nouvellement développé. Les temps de relaxation obtenus en combinant ces deux contributions reproduisent correctement les résultats expérimentaux. Les simulations moléculaires nous permettent aussi d'extraire les mécanismes microscopiques. Pour les ions dans l'eau à dilution infinie, nous avons étudié les propriétés statistiques et dynamiques des fluctuations de l'EFG. Nous avons montré en particulier le rôle fondamental des fluctuations de densité de l'eau dans la première sphère de solvatation de l'ion. Cette thèse ouvre la voie à une meilleur compréhension des processus de relaxation RMN des ions mono-atomiques quadrupolaires dans des systèmes simples ou complexes.Interpreting NMR relaxometry experiments requires an accurate modeling of interactions between the nucleus under study and its environment. For a quadrupolar nucleus, the interaction between the electric field gradient (EFG) arising from the environment and the electrostatic quadrupole of the nucleus is preponderant. The present work deals with a new method to compute NMR relaxation times for such nuclei with molecular simulations. We consider the relaxation of monoatomic ions in condensed matter through two simple and realistic systems: aqueous electrolytes and sodosilicate glasses. The EFG due to electrons around the ion is obtained by computing the electronic response with quantum calculation combined with a new method to obtain the contribution of core electrons. The EFG due to the environment is obtained from a molecular simulation where interactions are described using a recently developed polarisable force field. NMR relaxation times obtained by combining both these contributions compare well with experimental data. Molecular simulations allow us to highlight the microscopic mechanisms. For ions in water at infinite dilution, we studied the statistical and dynamical properties of EFG fluctuations. We notably demonstrated the primary role of water density fluctuations in the first solvation shell around the ion. This thesis opens the way for a better understanding of the mechanism behind the NMR relaxation of monoatomic and quadrupolar ions in simple and complex systems
Fluctuations du courant ionique dans les nanopores
No full textLe transport ionique à l'échelle nanométrique joue un rôle clé dans des domaines aussi divers que les systèmes biologiques, la détection de l'ADN à travers les nanopores, le stockage de l'électricité ou la récupération d'énergie bleue et le dessalement de l’eau. Dans les nanopores, le petit nombre de porteurs de charge et leur mouvement thermique entraînent la prédominance des fluctuations du courant électrique par rapport aux électrolytes bulk. Ces fluctuations encodent des informations sur les processus microscopiques qui conduisent au transport ionique. L'interprétation de ces fluctuations reste cependant un grand défi pour la modélisation, en raison de la variété des phénomènes couplés à considérer et des échelles de longueur et de temps correspondantes, telles que le mouvement Brownien, les interactions électrostatiques et hydrodynamiques, et les interactions avec les parois solides. Dans ce travail, nous utilisons des simulations de dynamique brownienne et la théorie de la fonctionnelle de la densité stochastique pour modéliser les fluctuations électriques dans les électrolytes. Nous analysons les effets combinés de la concentration en sel, de la distance de confinement, du champ électrique appliqué et de l'adsorption aux surfaces des parois sur la conductivité dépendante du champ et de la fréquence. Pour atteindre cet objectif, nous développons et utilisons des approches théoriques dédiées pour calculer les coefficients de transport et les facteurs de structure dynamiques. La comparaison entre les simulations de solvants implicites et explicites confirme généralement les prédictions des descriptions les plus simples, mais met également en évidence leurs limites, et fournit des informations sur la manière d’améliorer ces descriptions. Dans l'ensemble, cette thèse contribue à une compréhension globale des fluctuations électriques et du transport ionique à l'échelle nanométrique.Ionic transport at the nanoscale plays a key role in fields as diverse as biological systems, DNA sensing through nanopore, electricity storage or blue energy harvesting and desalination. In nanopores, the small number of charge carriers and their thermal motion result in the predominance of electrical current fluctuations compared to bulk electrolytes. These fluctuations encode information on the microscopic processes resulting in ionic transport. Interpreting these fluctuations remains however a great challenge for modelling, due to the variety of coupled phenomena to be considered and their corresponding length and time scales, such as thermal motion, electrostatic and hydrodynamic interactions, and interactions with the solid walls. In this work, we use Brownian dynamics simulations and stochastic density functional theory to model electrical fluctuations in electrolytes. We analyze the combined effects of salt concentration, confining distance, applied electric field and adsorption at the wall surfaces on the field- and frequency-dependent conductivity. To achieve this goal, we develop and use dedicated theoretical approaches to compute transport coefficients and the dynamical structure factors. The comparison between implicit and explicit solvent simulations generally supports the predictions of the simpler descriptions, but also highlights their limitations and provides insights on how to improve them. Overall, this thesis contributes to a comprehensive understanding of electrical fluctuations and ionic transport at the nanoscale
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