1,720,955 research outputs found
Development of a method to analyze reaction mixtures by APPI mass spectrometry
No full textL'objectif du projet est de mettre au point et d’évaluer le champ d’application d’une méthode apportant une information rapide et précise sur la composition du milieu réactionnel (identification et quantification des composés issus d'un substrat d'intérêt), la plus universelle possible et facile à mettre en œuvre.
Le principe de cette méthode, [TMOA-APPI-MS], repose sur le marquage d'un composé d'intérêt par une molécule organique chimiquement inerte et possédant des caractéristiques d'ionisation sélective par spectrométrie de masse APPI. Dans cette approche, le marqueur (triméthoxybenzène) est sélectivement ionisé et seules les molécules marquées sont détectées.
Dans un premier temps, la méthode a été comparée avec des méthodes classiques (RMN, GC, HPLC) dans un couplage carbonylant de Sonogashira. Puis, l’étude de milieux plus complexes comportant des amines a été entreprise. Celle-ci a permis l’optimisation de conditions réactionnelles pour la synthèse d’hétérocycles à partir d’une ynone marquée. Suite à cette étude, une réaction de déséthylation de la triéthylamine catalysée par du platine a été découverte de manière fortuite grâce à la méthode.
Une étude de validation de découverte de «nouvelles réactions» a ensuite été effectuée. Des conditions réactionnelles décrites et non décrites dans la littérature ont été appliquées à des substrats modèles marqués portant des fonctions alcynes ou diynes; les réactions ont été analysées par [TMOA-APPI-MS] afin de vérifier que la méthode est en mesure de détecter toutes nouvelles transformations. Ce criblage systématique de conditions réactionnelles a révélé que l’argent catalyse sélectivement l’hydratation des alcynes terminaux.The aim of the project is to set up a universal method, easy to implement, that gives a rapid and precise information on the composition of the reaction mixture (identification and quantification of compounds of interest) and to evaluate the scope of the method.
The principle of this method, [TMOA-APPI-MS], relies on the labeling of a compound of interest by an organic molecule that is chemically inert and owns selective ionization by APPI. In this method, the label (trimethoxybenzene) is selectively ionized and only the labeled molecules are detected. The label decreases the influence of the other functions on the molecule or in the reaction mixture and allows a standardization of the analysis conditions.
The method was first compared with classical techniques (NMR, GC, HPLC) in a carbonylative Sonogashira coupling. The study of more complex reaction mixture with amines was then undertaken. This study enabled the optimization of reaction conditions for the synthesis of heterocycles starting from a labeled ynone. A reaction of deethylation of triethylamine catalyzed by platinum was discovered by the method [TMOA-APPI-MS].
A study to validate the discovery of "new reactions" was then undertaken. Known and new reaction conditions were applied to labeled model substrates with alkyne or diyne functions. The reactions were analyzed by the method [TMOA-APPI-MS], in order to ensure its ability to detect new transformations. This systematic screening showed that silver selectively catalyzes the hydration of terminal alkynes
Développement d'une méthode d'analyse des milieux réactionnels par spectrométrie de masse APPI
No full textL'objectif du projet est de mettre au point et d évaluer le champ d application d une méthode apportant une information rapide et précise sur la composition du milieu réactionnel (identification et quantification des composés issus d'un substrat d'intérêt), la plus universelle possible et facile à mettre en œuvre. Le principe de cette méthode, [TMOA-APPI-MS], repose sur le marquage d'un composé d'intérêt par une molécule organique chimiquement inerte et possédant des caractéristiques d'ionisation sélective par spectrométrie de masse APPI. Dans cette approche, le marqueur (triméthoxybenzène) est sélectivement ionisé et seules les molécules marquées sont détectées. Dans un premier temps, la méthode a été comparée avec des méthodes classiques (RMN, GC, HPLC) dans un couplage carbonylant de Sonogashira. Puis, l étude de milieux plus complexes comportant des amines a été entreprise. Celle-ci a permis l optimisation de conditions réactionnelles pour la synthèse d hétérocycles à partir d une ynone marquée. Suite à cette étude, une réaction de déséthylation de la triéthylamine catalysée par du platine a été découverte de manière fortuite grâce à la méthode. Une étude de validation de découverte de nouvelles réactions a ensuite été effectuée. Des conditions réactionnelles décrites et non décrites dans la littérature ont été appliquées à des substrats modèles marqués portant des fonctions alcynes ou diynes; les réactions ont été analysées par [TMOA-APPI-MS] afin de vérifier que la méthode est en mesure de détecter toutes nouvelles transformations. Ce criblage systématique de conditions réactionnelles a révélé que l argent catalyse sélectivement l hydratation des alcynes terminaux.The aim of the project is to set up a universal method, easy to implement, that gives a rapid and precise information on the composition of the reaction mixture (identification and quantification of compounds of interest) and to evaluate the scope of the method. The principle of this method, [TMOA-APPI-MS], relies on the labeling of a compound of interest by an organic molecule that is chemically inert and owns selective ionization by APPI. In this method, the label (trimethoxybenzene) is selectively ionized and only the labeled molecules are detected. The label decreases the influence of the other functions on the molecule or in the reaction mixture and allows a standardization of the analysis conditions. The method was first compared with classical techniques (NMR, GC, HPLC) in a carbonylative Sonogashira coupling. The study of more complex reaction mixture with amines was then undertaken. This study enabled the optimization of reaction conditions for the synthesis of heterocycles starting from a labeled ynone. A reaction of deethylation of triethylamine catalyzed by platinum was discovered by the method [TMOA-APPI-MS]. A study to validate the discovery of "new reactions" was then undertaken. Known and new reaction conditions were applied to labeled model substrates with alkyne or diyne functions. The reactions were analyzed by the method [TMOA-APPI-MS], in order to ensure its ability to detect new transformations. This systematic screening showed that silver selectively catalyzes the hydration of terminal alkynes.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF
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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