1,721,023 research outputs found
Development of innovative acquisition protocols for more robust and informative mass spectrometry-based metabolomics : application to the phenotyping of medical cohorts
No full textL'annotation fiable des variables constitue un enjeu majeur pour toute étude métabolomique ou lipidomique non-ciblée. Ces deux approches permettent d'étudier le phénotype, et donc, de mettre en évidence des perturbations de l'homéostasie à un temps donné et ainsi d'identifier de potentiels biomarqueurs de maladies ou de mieux appréhender les mécanismes biochimiques régissant leur développement. Dans ce contexte, l'objectif principal de ma thèse a été de développer de nouvelles méthodes d'acquisition pour les analyses métabolomiques et lipidomiques non ciblées par chromatographie liquide couplée à la spectrométrie de masse haute résolution (LC-HRMS/MS) en utilisant un Orbitrap Fusion. Ces développements ont été conduits sur des échantillons de plasma humain afin d'obtenir des spectres MS/MS plus informatifs pour les lipidome/métabolome plasmatique, de façon automatisée et sans a priori permettant d'annoter de façon fiable à un grand nombre de variables métaboliques. Pour cela, deux approches ont été utilisées, les analyses de type « Data Dependent Acquisition » (DDA) et celles de type « Data Independent Acquisition » (DIA). Dans un premier cas, les ions détectés en mode MS sont notamment sélectionnés selon un seuil d'intensité prédéfini tandis que le mode DIA permet de fragmenter tous les ions détectés, par partition de la gamme de masses. L'évaluation de ces deux méthodes d'acquisition, au travers de cette thèse, a permis de mettre en lumière les avantages et limites de chacune d'elle pour les analyses lipidomiques et métabolomiques non ciblées. De nombreuses optimisations des paramètres méthodologiques et conditions de production des données ainsi que des paramètres bioinformatiques du logiciel MS-DIAL utilisé pour leur traitement ont été réalisées. Certaines des méthodes implémentées sont d'ores et déjà utilisées pour les projets conduits au sein du laboratoire.Confident annotation of metabolic features still represents a major challenge for both non-targeted metabolomic or lipidomic approaches. These two approaches make it possible to study the phenotype of an individual, to highlight homeostasis disturbances at a given time and thus to identify potential biomarkers of diseases or get deeper insight into the biochemical mechanisms governing their development. In this context, the main objectives of my PhD thesis were to develop new acquisition methods for non-targeted metabolomic and lipidomic analyses by liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS/MS) as implemented on an Orbitrap Fusion mass spectrometer. These developments were conduced on human plasma samples in order to obtain more informative MS/MS spectra for plasma lipidome/metabolome. And this in a fully automated and without any a priori but robust manner enabling confident annotation of as many as possible metabolic features. Two approaches were used: Data Dependent Acquisition (DDA) and Data Independent Acquisition (DIA) analyses. In the first case, the ions detected in MS mode are selected according to a predefined intensity threshold, while in DIA mode all the ions are fragmented by partitioning the whole mass range. The comparative evaluation of these two acquisition methods highlighted the advantages and limitations of both approaches for non-targeted lipidomic and metabolomic analyses. Method parameters and data production conditions as well as bioinformatics parameters of the MS-DIAL software have been thoroughly optimized. Some of the developed methods are already being used in projects conducted within the laboratory
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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