1,720,956 research outputs found
Convergent high stereoselective preparation of the C12-C24 fragment of Macrolactin A.
No full textThe convergent synthesis of the C12-C24 fragment (lower part) of macrolactin A is described. The
adapted strategy allowed building up the lower moiety by the assembly of three key intermediates
via organometallic addition. One hydroxylic stereogenic center was introduced by the application
of chiral sulfoxides methodology on fragment C19-C24. The preparation of the versatile 1,3-anti
diol synthon C12-C16 was achieved via opening of chiral epoxide and subsequent oxidation to a
hydroxy ketone. Finally, reductive elimination of the appropriate allylic dibenzoate with Na/Hg
introduced directly the C16-C19 (E,E)-diene unit, in a highly efficient stereoselective fashion
Approccio alla sintesi totale della Macrolattina A; potente inibitore del virus dell’HIV
No full textA General Protocol for the Regio High Yielding Opening of Different Glycidol Derivatives
No full textNew functionalised hydroxymethyl ketones from the mild and chemoselective KMnO4 oxidation of chiral terminal olefins
No full textVarious terminal olefinic compounds are directly converted
into the corresponding α-hydroxy ketones in good yields by
potassium permanganate oxidation. The reaction is also
highly chemoselective in the presence of differently protected hydroxy groups and can be utilised for the preparation
of polyfunctional compounds such as polyols
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
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