1,721,064 research outputs found
Improved 2D 1H-13C NMR permits in vivo analysis of Daphnia magna metabolism without isotopic enrichment
No full textThis dataset contains data from a study that assessed the feasibility of using nuclear magnetic resonance (NMR) to measure the real-time in vivo metabolic responses of the small freshwater crustacean, *Daphnia magna*, in samples derived from the wild (rather than raised in a laboratory) to investigate aquatic contaminant toxicity.
To date, nearly all previous studies have used 13C isotopically enriched D.magna, but this limits studies to lab-raised organisms. These data were taken from an experimental approach that did not require isotopic enrichment, allowing samples to be taken directly from the environment.
Due to overlap caused by the magnetic susceptibility distortions in 1D 1H NMR, 2D is required for metabolic fingerprinting in vivo. In particular, 2D 1H-13C NMR offers excellent spectral dispersion but is time-consuming and has intrinsic low sensitivity. To study D. magna in natural abundance, symmetric ASAP HSQC in combination with time-resolved non-uniform sampling (TR-NUS) was used.
This combined approach (TR-NUS ASAP HSQC) improved sensitivity up to 3 times versus standard HSQC, while reconstruction of TR-NUS data provided information on a 4 minute time scale. In turn, this allowed anoxia (and recovery from anoxia) to be studied for the first time on unlabelled Daphnia using HSQC. This method could, therefore, become key for investigating environmental adaptability and exposure in living organisms in conditions that are closer to real-time
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
Analyse RMN multi-échelle du métabolisme des micro-algues
No full textLes bio-procédés à base de microalgues sont reconnus pour des applications majeures comme la production de lipides précurseurs de biocarburant. Aujourd'hui la plupart de ces technologies vertes ne sont pas suffisamment matures en raison de coûts de production importants et sont pour cela activement développées par une importante communauté de bio-procédés. A l'interface entre la biologie et les procédés, cette communauté n'est pas familière avec la spectroscopie RMN, outil puissant d'analyse structurale et quantitative. L'objectif de cette thèse est d’évaluer le potentiel d’approches RMN multiéchelles pour le développement des bio-procédés à base de microalgues. Deux axes de recherche distincts mais complémentaires ont été développés : 1) la RMN à haut champ magnétique pour la quantification d'extraits lipidiques a montré une excellente faculté à identifier les classes lipidiques sans séparation physique de celles ci. Des séquences d'impulsions originales pour la quantification ont été évaluées, et des pistes ont qui devront être explorées ont été dégagées pour rendre l'analyse compatible en conditions de routine. Ces approches offrent une alternative pertinente aux méthodes analytiques existantes pour l'étude du métabolisme lipidique. 2) l'utilisation de la RMN de paillasse pour le suivi en ligne, non invasif et en temps réel des lipides intracellulaires dans des cultures de micro-algues, difficilement réalisable avec une autre technique d'analyse. Cette approche ouvre de nouvelles perspectives pour le contrôle et l'optimisation des bio-procédés à base de micro-algues.Microalgae-based bioprocesses are well-known for several major applications such as production of lipids as precursors of biofuel. Nowadays, most of these green technologies are not mature enough leading to high production costs. This is the reason why they are actively developed by a substantial bioprocess community. At the interface between biology and processes, this community is not necessarily familiar with NMR spectroscopy which is a powerful structural and quantitative analytical tool. The goal of this thesis is to evaluate the potential of multi-scale NMR approaches for the development of microalgaebased bioprocesses. Two distinct but complementary research axes were developed: i) high-field NMR spectroscopy for the quantification of lipid extracts showed a great aptitude for lipid class identification without physical separation. Original pulse sequences for quantification were evaluated, opening new routes that should be further explored to become applicable in routine. These approaches offer an alternative to existing analytical methods for the study of lipid metabolism. ii) the use of benchtop NMR for the online, noninvasive and real-time monitoring of intracellular lipids in microalgae cultures which is almost impossible with other analytical techniques. This approach opens new perspectives for the optimization of microalgaebased bioprocesses
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
Effect of the Solvent on the Conformation of a Depsipeptide: NMR-Derived Solution Structure of Hormaomycin in DMSO from Residual Dipolar Couplings in a Novel DMSO-Compatible Alignment Medium.
No full textThe macrocyclic compound hormaomycin has been investigated by NMR spectroscopy and by restrained molecular-dynamics simulations. Measurement of residual dipolar couplings induced by dissolving the depsipeptide in a polyacrylamide gel compatible with DMSO and their incorporation into the structure calculation of the title compound improved the precision of the family of structures. In DMSO the macrocyclic ring shows two beta-turns, whose positions in the sequence differ from those found in the CDCl3 solution structure and in the crystal structure obtained from hexylene glycol/H2O (50:50). The bulky side chain consisting of a 3-(2-nitrocyclopropyl)alanine and a chlorinated N-hydroxy-pyrrole moiety is flexible in DMSO
- …
