1,720,973 research outputs found
A comprehensive study for the validation of a LC/MS/MS method for the determination of free and total forms of urinary cortisol and its metabolites
No full textSeveral pathological conditions can be related to the alteration of the urinary levels of cortisol (F) and itsmetabolites. The determination of each of them in the free and free plus conjugated form can provide adeeper insight into the impaired activity of the cortisol metabolism enzymes, thus improving the diag-nosis protocol currently based only on the determination of total amount of urinary cortisol metabolites.In that view, an LC–MS/MS method for the determination of the free and total amount of urinary F, cor-tisone (E), tetrahydrocortisol (THF), allo-tetrahydrocortisol (A-THF) and tetrahydrocortisone (THE) wasthus developed and validated. Deconjugation of glucocorticoids was carried out by enzymatic hydroly-sis. Analytes were extracted by solid phase extraction, separated by liquid chromatography and analyzedvia electro-spray ionization (negative ion mode) triple-quadrupole mass spectrometry in the selectedreaction monitoring mode using a stable isotope-labeled internal standard.Baseline separation for all compounds, in particular the two stereoisomers A-THF and THF, wasobtained. Matrix effects, not reported so far, were observed and minimized for the determination ofurinary free E and THE. Validated range was 0.5–1000 ng/mL for A-THF and THF, 5–800 ng/mL for E andTHE and 1–1000 ng/mL for F, with R2values greater than 0.9981. The LOD and LOQ of the describedmethod ranged from 0.1 to 3.0 ng/mL, while the extraction recoveries resulted close to 100% for all theglucocorticoids determined. Precision and accuracy were well within ±10%. As suggested by the resultsobtained in the preliminary study on polycystic ovary syndrome (PCOS) urine samples, the method canbe used to support clinical diagnosis of pathologies related to cortisol metabolism. In fact, levels of freeand total glucocorticoids in control subjects were in agreement with previously reported data, as well asfree and total A-THF/THF ratio in PCOS patients. Conversely, in the latter free F/E and A-THF + THF/THEratios were lower than in control subjects (P < 0.01), suggesting a possible alteration of 11-HSD1 and11-HSD2 activity, to be further investigated
Configuration of the vitamin E analogue garcinoic acid extracted from Garcinia Kola seeds
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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
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