1,720,959 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
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
Efficient biocatalyst for large-scale synthesisof cephalosporins, obtained by combining immobilizationand site-directed mutagenesis of penicillin acylase
No full textMicrobial nucleoside phosphorylases as efficient biocatalysts for the synthesis of antiviral and antitumoral nucleosides
No full textModified nucleosides, such as 5-fluoro-2'-deoxyuridine (Floxuridine),2',3'-dideoxyinosine (Didanosine), arabinosyladenine (Vidarabine), arabinosyl-2-fluoroadenine (Fludarabine), are important antiviral and antitumor agents. These nucleosides are routinely prepared by multi-step syntheses which negatively affect the outcome of the process in terms of yield, purity and costs and with an high environmental impact. Alternatively, nucleosides can be prepared via a one-pot enzymatic process catalyzed by nucleoside phosphorylases (NPs) in fully aqueous medium. NPs catalyze the phosphorolysis of a nucleoside leading to the formation of a sugar-1-phosphate; in presence of a second nucleobase, the enzyme can catalyze the synthesis of a new nucleoside (transglycosylation). However, due to the narrow substrate specificity of NPs, the number of compounds that can be prepared by this approach is limited.
Aim of this study was to set up a collection of immobilized NPs characterized by different specificity towards variously modified nucleosides. The performance of known enzymes like thymidine phosphorylase (TP) from Escherichia coli and uridine
phosphorylase (UP) from Bacillus subtilis were investigated; in addition, new NPs, selected by using a bioinformatic approach (phylogenetic and comparative analysis) or by microbiological screening, were considered. The most promising enzymes were immobilized by ionic or covalent binding and post-immobilization cross-linking was considered to achieve the multimeric structure
stabilization. TP from E. coli and UP from B. subtilis efficiently synthesized 2'-deoxyribonucleosides; NPs from Clostridium perfringens, Aeromonas hydrophila and Citrobacter koseri were used for the synthesis of 2',3'-dideoxy- and arabino- nucleosides (Didanosine and Vidarabine). All the immobilized biocatalysts were stable at pH 10; in this condition, both substrates and products could be solubilized in high concentration, necessary to develop a preparative synthesis
Evaluating the potential of Hydrophilic Interaction Liquid Chromatography for collagen peptide mapping analysis
No full textThis study presents a systematic approach for developing an innovative hydrophilic interaction liquid chromatography (HILIC) method for collagen peptide mapping analysis. The predominant post-translational modification (PTM) of collagen, proline hydroxylation, introduces polar hydroxyl groups throughout the collagen sequence, making HILIC a promising alternative to classical reversed-phase liquid chromatography (RPLC) approaches. This study employs sixteen model peptides, selected from in silico predicted tryptic peptides with zero missed cleavages and representing diverse physicochemical properties and structural motifs of collagen. The peptides were used as standards to conduct detailed chromatographic evaluation. Various HILIC stationary phases and mobile phases were systematically examined to identify optimal separation conditions for collagen peptides, contributing to a better understanding of peptide behavior in HILIC. The study also explores the effects of sample diluent and injection mode, comparing classical injection with the Performance Optimizing Injection Sequence (POISe), to determine their impact on HILIC performance. Introducing a plug of weak solvent (acetonitrile) prior to sample injection, effectively mitigates the mismatch in eluent strength between the fully aqueous sample diluent (resulting from tryptic digestion) and the mobile phase, addressing issues of peak distortion. Different injection volumes (from 0.5 to 8 μL) and acetonitrile ratios (1:1, 1:2, 1:5 and 1:10) were tested to optimize sample injection and increase sensitivity of collagen tryptic peptides. Following method optimization, HILIC was coupled with mass spectrometry (MS) to evaluate its effectiveness in analyzing collagen-digested samples. This evaluation included the assessment of peptide sequence coverage and the method ability to identify hydroxylation patterns, thereby demonstrating its potential for detailed peptide 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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