1,721,199 research outputs found
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
BETA-AMINO ACIDS AS TOOL FOR THE PREPARATION OF FOLDAMERS AND NANOMATERIALS
No full textbeta-Amino acids are analogues of alpha-amino acids (AAs) in which the amino group is linked to the beta-carbon instead of the alpha-carbon. In this thesis are reported different approces to beta amino acids both from the synthetic and applicative points of view.
Beta-2,3-diaryl-beta amino acids: Development of diastero- and enantioselective synthesis of variously substituted 2,3-Diaryl amino esters using a TiCl4 catalyzed Mannich-like reation. Preparation of -Hybrid peptides containing 2,3-Diaryl amino acids and Alanine. Structural characterization of -hybrid using NMR analysis and X-Ray diffraction to understand if their strong aromatic component affect the secondary structure of these peptide. Studies on the self assembly of these derivatives in order to obtain sopramolecular architectures.
Tetrahydroisoquinoline-4-carboxylic acid (TIC): Development of a simple and scalable synthesis of tetrahydroisoquinoline 4-carboxylic acid, solving the problems encountered using the literature synthetic protocol. Bio-enzymatic resolution of TIC. Preparation of model peptides in in order to study TIC conformational behavior.
Rhodium catalyzed transformation of diazobarbonyl-piperidine derived from beta amino acids n efficient preparation of three different classes of -diazocarbonylpiperidine compounds derived from -AAs, including the simple Nipecotic acid, its benzocondensate, i.e. TIC, and TIC derivatives in which a further aryl moiety is present at position 3. Generation of rhodium carbenes starting from diazocarbonyl derivatives and rhodium-(II) dimer catalysts to give intramolecular carbene insertion.Search of the best catalyst and the optimal reaction conditions to drive the chemoselectivity of the insertion reaction. NMR characterization of the polycyclic compounds obtained by intramolecular carbene insertions
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
Alpha-diazocarbonyl-piperidine derivatives : chemoselective rhodium catalysed transformation
No full textSeveral natural compounds or compounds of biological interest contain the piperidine nucleus that, in many cases, is inserted in complex structures or simply condensed with other rings.
Our interest is address to the preparation of different piperidine systems using a very interesting chemistry that combines the use of α-diazocarbonyl compounds and rhodium (II) dimer catalysts.
Our studies were focused on the synthesis of piperidine derivatives, or their benzocondensed analogues as well as of more complex structures such as hexahidrobenzophenanthidine alkaloids or crinine derivatives.
Several piperidine, all functionalized with diazo-keto function, characterized by a different substitution pattern and stereochemistry, were used as starting materials. These key intermediates when treated with a rhodium catalyst afford electrophilic carbenes that could give a chemoselective C-H or N-H insertion, or reactions with an aromatic ring depending on the nature of the catalyst.
Simple diazoketo-piperidine afforded CH insertion giving tropone derivatives. More complex compounds could be obtained from tetrahydroisoquinoline derivative
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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