1,720,969 research outputs found
LC-MS/MS Method for the Detection of Hormones: Development, Validation, and Application in Various Bovine Matrices
Get PDFA liquid chromatography-tandem mass spectrometry method was developed for the simultaneous determination of fourteen hormones belonging to different families in various bovine matrices (muscle, liver, kidney, bile, and hair). The modified QuEChERS method was applied to ensure the extraction of the analytes. The additives of the mobile phase, the parameters of the mass spectrometer, as well as those of the ionization source were optimized to enhance detection sensitivity. On the other hand, the parameters influencing sample extraction including the choice of the extraction solvent and its acidification, the solvent water ratio, the use of buffer salts, and the purification of the extract were also optimized. The method was validated according to the Commission Decision 2002/657/EC. Good recoveries were obtained (from 60 to 116.8 %) with coefficients of variation in terms of repeatability and reproducibility lower than 23%. The values of the decision limit CCα and the detection capability CCβ were lower than 1 and 2 μg/kg respectively in muscle and liver for most of the analyte. The matrix effect was also evaluated. Finally, this method was applied to detect hormones in two hundred and thirty-four (234) real samples. A preliminary long-term exposure assessment was evaluated based on the obtained data
VALIDATION OF CONFIRMATORY MULTI-RESIDUE METHOD FOR THE DETERMINATION OF THIRTEEN HORMONES RESIDUES IN SEVERAL BOVINES MATRICES USING HPLC-MS/MS
Get PDFSynthetic and natural hormones are used in the production and intensive breeding of animals as growth factors and reproductive regulators.
However, the illegal and inappropriate use of these substances increases the risk of introducing residues into the food chain. Also because of their
carcinogenic and teratogenic effects, the European Union has banned the use of these substances since 1985. For this reason, the development of sensitive and reliable analytical methods for the monitoring of their residues in food has become a necessity. A liquid chromatography analysis method coupled to mass spectrometry and based on Quechers extraction has been developed to analyse thirteen synthetic and natural hormones in muscles. In order to study the reliability of this method, its validation has been carried out in different bovine matrices (liver, kidney, bile, and hair) according to European Decision 2002/657 / EC. The method demonstrates good linearity (R2> 0.99) as well as accuracy with coefficients of variation for repeatability and reproducibility less than 23%. The values of CCα and CCβ were determined for each analyte indicating values ranging from 0.13 to 0.86 μg.kg-1 and 0.25 to 1.72 μg.kg-1 respectively for most of the analytes. Higher values were obtained for 17β-estradiol, estriol, 17α-ethinyl-estradiol ranging from 1.73 to 13.95 μg.kg-1 for CCα and from 3.47 to 23.87 μg.kg-1 for CCβ. The recovery rate in the different matrices (liver, kidney, bile, and hair) varies from 51.5 to 107 %. The matrix effect of the method was evaluated, indicating significant suppression values for the liver and the kidney, which varied respectively from -45 to -15.5 % and -35 to - 2.5%. In the same way, the other two matrices hair and bile show smaller matrix effects than the others. Finally, this method has been successfully applied to detect anabolic hormones in nighty one samples (muscle, liver, kidney, bile) available from different local butchers. Progesterone was found in 41 samples at 0.11 to 11.7 μg.kg−1 otherwise testosterone was observed in 43 samples ranging from 0.5 to 9.72 μg.kg−1
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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