1,720,959 research outputs found
Vancomycin as chiral selector for enantioselective separation of selected profen nonsteroidal anti-inflammatory drugs in capillary liquid chromatography
No full textThe chiral selector vancomycin was used either as mobile phase additive or bound as a chiral stationary phase (CSP) for the stereoselective separation of seven racemic nonsteroidal anti-inflammatory drugs (NSAIDs), fenoprofen, carprofen, flurbiprofen, indoprofen, flobufen, ketoprofen, and suprofen, by capillary liquid chromatography. The effect of the type of stationary phase, the chiral column Chirobiotic V or the achiral stationary phases Nucleosil 100 C8 HD and Nucleosil 100 C18 HD, and the concentration of vancomycin in the mobile phase on separation of the drug enantiomers were evaluated. All the drugs, except flobufen, were successfully enantioseparated on Nucleosil 100 C8 HD with 4 mM vancomycin present in the mobile phase (composed of methanol and buffer) in the reversed phase mode. On the vancomycin-bonded chiral stationary phase, it was difficult to get enantioseparations of the profen NSAIDs. However, flobufen gave better enantioseparation on the vancomycin CSP. The better enantioresolution of the majority of profen derivatives on the achiral columns with vancomycin added to the mobile phase can be attributed in particular to the higher separation efficiency of this capillary chromatographic system. In addition, vancomycin dimers, formed in the mobile phase, seem to offer a better steric arrangement for stereoselective interaction to these analytes than the vancomycin bonded on the CSP. These substantial differences in the CS structure significantly influence the chiral discrimination mechanism
"New organic monosized microspheres for use in enantiomer separations by high-performance liquid chromatography"
No full textMonosized nonporous resin particles were prepared in aqueous medium by polymerisation of urea with formaldehyde in the presence of soluble Fe(III) hydrolysis polymers. Measurements of the geometrical parameters showed that the material particle size distribution was in the range 2.5–3.5 μm (average particle diameter 2.99 μm with standard deviation 0.49), and had a sphericity index of 0.851. Particle pore-size was determined by gel permeation chromatography. The microspheres exhibited exceptional mechanical strength, chemical stability in the pH range between 1–13, and low tendency toward swelling in the solvents commonly used in liquid chromatography. The synthesis of a chiral urea-formaldehyde based resin for the enantiomer separation of underivatized phenylalanine by ligand exchange chromatography is reported
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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