1,721,329 research outputs found
Simple Synthesis of Enantiomerically Pure C2-Symmetric Bisoxazolidines from Amino Alcohols and Formaldehyde
No full textAsymmetric Organocatalytic Friedel-Crafts Hydroxyalkylation of Indoles Using Electrophilic Pyrazole-4,5-diones
No full textThe electrophilic reactivity of a series of novel pyrazole-4,5-dione derivatives in the organocatalytic Friedel–Crafts reaction with various substituted indoles has been tested. The disclosed procedure catalyzed by a cinchona alkaloid derivative allows the conjugation of two very important aza-heterocyclic scaffolds to generate a new class of indolylpyrazolones bearing a tetrasubstituted stereocenter in excellent yields (up to 99%) and with enantioselectivities of up to 94:6 er.</jats:p
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
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
Analyse des Bindungsverhaltens in Mehrzentrenbindungssystemen auf Basis projizierter Kraftkonstanten
No full textIn this work, projected force constants were used as a quantum chemical descriptor to investigate a selection of multicenter bonding systems in solids. First, the calculation of the force constants from phononic density functional theory-based simulations is outlined. These force constants are able to detect multicenter bonding by their long-ranging interatomic forces. A special focus was placed on phase-change materials. While they are widely used as a material for data storage devices, their bonding mechanism has not been conclusively determined. Projected force constants were used in tandem with another descriptor, the crystal orbital bond index (COBI), and suggest a three-dimensional network of linear multicenter bonds (analogous to those found in xenon difluoride or triiodide) as a bonding mechanism. Using these descriptors, many of the unusual properties found in phase-change materials could be explained. The surprising prevalence of the rock-salt structural motif, for instance, could be easily explained as it facilitates linear atomic chains in all directions and the “too small” van-der-Waals gap exhibited by phase-change materials are the result of gap-bridging multicenter bonds. In another chapter, the triiodide anion and selected polyiodides were analyzed using the two descriptors. This not only confirmed the literature-known multicenter bonding models with modern methods but also highlighted interesting structural and bond-mechanical similarities with the phase-change materials. The same structural gaps found in these compounds were also detected in polyiodides, albeit in chains instead of three-dimensional networks. Finally, the descriptor data of these two groups were contextualized and unified using the old concept of the secondary bond. In the last chapter, several other materials were analyzed using projected force constants and COBI. Zintl-phases were used as an example of 2D multicenter networks (forming an intermediate group between 3D phase-changer materials and 1D polyiodides). The sulfosalt mineral class also exhibited evidence of multicenter bonding. Instead of structural gaps, they form ionic interfacial layers between their rock-salt motifs. Finally, the high-temperature superconductor yttrium-barium-cuprate was investigated with projected force constants. While strong long-range forces could be detected, COBI demonstrated that these were not the result of multicenter bonding but rather likely connected to the same unusual vibrations that have been associated with the superconductivity mechanism in literature
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