1,720,954 research outputs found
Modélisation de macrocycles de la famille des azacalixphyrines
No full textCette thèse porte sur la modélisation des propriétés structurales, aromatiques et spectroscopiques d'une nouvelle classe de macrocycles alternatifs aux porphyrines, les azacalixphyrines (ACPs). Ces macrocycles conjugués, synthétisés et caractérisés pour la première fois en 2010 par le groupe d’Olivier Siri à Marseille, ont montré des propriétés exceptionnelles (structure, absorption, tautomérie, et complexation). Cette thèse vise à proposer de nouveaux dérivés aux propriétés améliorées, notamment en ce qui concerne leur absorption, en utilisant les outils offerts par la chimie théorique. Parmi toutes les approches ab initio permettant de modéliser les ACPs, la théorie fonctionnelle de la densité (DFT) et sa forme dépendante du temps (TDDFT) ont été principalement appliquées, bien que des calculs utilisant des méthodes alternatives aient également été effectués, notamment à l'aide du formalisme Bethe-Salpeter (BSE/evGW) dans le cadre d'une collaboration avec l'équipe du Dr. Xavier Blase à Grenoble. Trois stratégies chimiques ont été évaluées: (i) l’extension de la délocalisation des électrons en fusionnant plusieurs unités ACP; (ii) la substitution de l’ACP via l'addition de groupes électroactifs; et (iii) le couplage du macrocycle avec un fluorophore présentant une absorption complémentaire afin d'absorber la lumière sur une plus grande gamme du spectre et déclencher des processus de transfert d'énergie entre les sous-unités. Les deux premiers axes ont été réalisés en collaboration avec l'équipe d’Olivier Siri alors que le dernier est le fruit d'une collaboration avec le groupe de Benedetta Mennucci à Pise.This thesis focuses on the modeling of the structural, aromatic, and spectroscopic properties of a new class of macrocycles alternative to porphyrins, i.e., azacalixphyrins (ACPs). These conjugated macrocycles have first been synthesized and characterized in 2010 by Siri’s group in Marseille and revealed exceptional features (structure, NIR absorption, tautomerism, and complexation). This thesis aimed at using ab initio methods to propose new ACP derivatives with improved properties with a focus on their absorption. The Density Functional Theory (DFT) and Time- Dependent DFT (TD-DFT) methods have been predominantly applied, although alternative wavefunction-based theories [the second-order Coupled-Cluster, CC2, and the Algebraic Diagrammatic Construction, ADC(2)] as well as the Bethe-Salpeter formalism, BSE/evGW, have also been used. Three major directions to develop new ACP derivatives have been investigated: (i) the extension of the ACP -conjugation path by fusing several ACP moieties leading to multimers; (ii) chemical modifications of the ACP unit by addition of electroactive groups; and (iii) coupling of the ACP moiety with a fluorophore presenting a complementary absorption spectrum in order to improve the light harvesting and to trigger excitation energy transfer processes. The two former axes have been investigated in collaboration with Siri’s team whereas the latter has arisen from a collaboration with the Mennucci’s group
Modeling excitation energy transfer in multi-BODIPY architectures
No full textThe excitation energy transfer (EET) allowing the concentration of the energy has been investigated in several multi-BODIPY architectures with the help of an approach coupling time dependent density functional theory to an implicit solvation scheme, the polarizable continuum model. We have first considered several strategies to compute the electronic coupling in a dyad varying the size of the donor/acceptor units, the bridge, the geometries and conformations. We have next studied the electronic coupling in three different architectures for which the EET rate constants have been experimentally measured both from luminescence and transient absorption data and from Förster theory. A good agreement with experimental values was obtained. Finally, in an effort to further improve these systems, we have designed several series of BODIPY triads, investigating the effect of acidochromism, core modifications, the position of the linkage and chemical substitutions on the EET coupling and rate constant. We show that several architectures allow us to increase the EET rate by one order of magnitude compared to the original compound
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
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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