1,720,957 research outputs found
Influence of metallic cations in the witting reaction: useful step for the synthesis of anticancer agents
No full textAlkenes with a well defined geometric configuration represent an essential class of key intermediates, and they are a continuous challenge in the synthesis of many natural products and drugs. Different methodologies have been developed, and the Wittig reaction and related transformations for its high level of geometrical control have become the most frequently employed.
The counter ion of the base used can be choose in order to obtain different stereoselectivity in Wittig reactions, and in recent years, our efforts are focused on the study of the presence of cerium for a better selectivity towards the formation of (Z)-alkenes.
In nature (Z)-alkenes are abundant and capital importance for their biological activity, for this we interested at the synthesis of hydroxyl-substituted alkenylbenzenes because they are effective anticancer agents. Typical component of this family is the (Z)-Climacostol, a toxin belonging to the family of resorcinolic lipids. It is present in prokaryotes as well as in single-celled and multicellular eukaryotes and has attracted great attention due its antimicrobial, cytotoxic and anticancer activities
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
An Efficient Lewis Acid Catalyzed Povarov Reaction for the One-Pot Stereocontrolled Synthesis of Polyfunctionalized Tetrahydroquinolines
Full text linkAn easy and efficient synthetic methodology for the one-pot stereocontrolled synthesis of tetrahydroquinolines through Lewis acid activated Povarov reaction is described. The protocol takes advantage of the very cheap, easy to handle, and environmentally friendly cerium trichloride as catalyst and allows to obtain either the anti- or the syn-isomer of the final tetrahydroquinoline with good selectivity, by performing the reaction in solvent or solventless conditions. The scope of the reaction is expanded to the one-pot synthesis of N-alkyltetrahydroquinolines through a very efficient iminium-Povarov approach. A deeper insight on the reaction system was provided by the study on the side reactions occurring in the reaction conditions and on the nature of the stereoselectivity
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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