1,720,960 research outputs found
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
Development of Hetero-Vinylbenziodoxolone Reagents for Applications in Synthetic Methodology and Biomolecule Functionalization
No full textAmong the numerous existing chemical motifs, alkenes, alkynes, enol ethers and enamides, with an unsaturated carbon-carbon bond, are versatile functional groups that are found in many natural products and bioactive compounds. They are widely used as valuable building blocks for the design and synthesis of complex organic molecules. Therefore, the development of new strategies to introduce those motifs into molecules is highly desirable. Traditionally, the treatment of human disease has been dominated by small-molecule drugs, but new therapeutic agents, such as peptide conjugates, have emerged as promising next generation of medications. Besides, the development of new therapeutics to cure diseases strongly relies on the study and understanding of biological processes. In this regard, the functionalization of peptides and proteins is of high interest and spite of significant achievements, the need for more efficient and diverse strategies remains present. Because of their low toxicity, high functional group tolerance, and stability in biocompatible media, hypervalent iodine reagents are valuable tools for late-stage peptide and protein functionalization. In this context, the first goal of my PhD was to develop new hypervalent iodine reagents to access valuable enamide and enol ether motifs. To this end, the synthesis of stereodefined enamide- and enol ether-based vinylbenziodoxolone reagents (N- and O-VBX) was achieved. The N- and O-VBXs were obtained by stereoselective addition of sulfonamide and phenol nucleophiles onto the alkynyl triple bond of ethynylbenziodoxolone reagents (EBX). The reaction tolerated a broad range of functional groups and stable VBXs reagents could be isolated in high yields. The second objective of this thesis was to study the reactivity of the newly developed VBX reagents. The enhanced reactivity of the hypervalent bond allowed their use as formal vinyl cations in presence of nucleophiles and in palladium catalyzed cross-coupling reactions at room temperature. In addition, a new mode of reactivity of hypervalent iodine was described. The O-VBX reagents were shown to be synthetic equivalents of oxy-allyl cation precursors. The new transformation, promoted by an excess of base, was working especially well with phenol nucleophiles, leading to aryl enol ethers bearing an allylic ether with complete E-stereoselectivity. In absence of external nucleophiles, the 2-iodobenzoate group of the reagent could be transferred, leading to aryl enol esters with still complete E-stereoselectivity. Finally, this chemistry was applied to the late-stage functionalization of peptides and proteins. Taking advantage of the ability of phenol nucleophiles to react with EBXs, we developed a selective tyrosine bioconjugation methodology. Under physiological conditions, tyrosine-containing peptides and proteins could react with EBXs to give stable O-VBX bioconjugates. The methodology tolerated a broad range of functional groups, with the exception of the cysteine side-chain. Complex peptides of different sizes and proteins were successfully labelled with high chemo- and site-selectivity. The installed hypervalent iodine bioconjugates could be further functionalized by palladium-catalyzed Suzuki-Miyaura cross-coupling reactions and strain-promoted azide-alkyne cycloadditions. The potential of the doubly-orthogonal functionalization was further demonstrated in a cellular uptake experiment.LCS
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
Access to Vinyl Ethers and Ketones with Hypervalent Iodine Reagents as Oxy-Allyl Cation Synthetic Equivalents
No full textWe report an Umpolung strategy of enol ethers to generate oxy-allyl cation equivalents based on the use of hypervalent iodine reagents. Under mild basic conditions, the addition of nucleophiles to aryloxy-substituted vinylbenziodoxolone (VBX) reagents, easily available in two steps from silyl alkynes, resulted in the stereoselective formation of substituted aryl enol ethers. The reaction was most efficient with phenols as nucleophiles, but preliminary results were also achieved for C- and N- nucleophiles. In absence of external nucleophiles, the 2-iodobenzoate group of the reagent was transferred. The obtained aryl enol ethers could then be transformed into alpha-difunctionalized ketones by oxidation. The described "allyl cation"-like reactivity contrast with the well-established "vinyl-cation" behavior of alkenyl iodonium salts.LCS
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
