1,720,993 research outputs found
Optimization and validation of a confirmatory method for determination of ten sulfonamides in feeds by LC and UV-diode array detection
No full textA simple, rapid, and reliable multiresidue method, based on liquid chromatography (LC) and ultraviolet (UV)-diode array detection (DAD), is described for assaying ten sulfonamides (sulfadiazine, sulfathiazole, sulfamerazine, sulfamethazine, sulfamethoxypyridazine, sulfamonomethoxine, sulfachloropyridazine, sulfamethoxazole, sulfaquinoxaline, and sulfadimethoxine) in feeds.
The chromatographic separation is accomplished using a C18 column, eluted with a mobile phase consisting of acetate buffer, acetonitrile, and methanol. The sample preparation requires a simple extraction with chloroform/acetone and a purification step by solid-phase extraction. The analytical parameters of precision, detection and quantification limits, recovery, and ruggedness have been evaluated by a validation procedure following the European guidelines of Regulation 882/2004/EC and Decision 657/2002/EC
Determination of deoxynivalenol and nivalenol by liquid chromatography and fluorimetric detection with on-line chemical post-column derivatization
No full textA rapid, sensitive and selective analytical method was developed for the quantitative determination of deoxynivalenol (DON) and nivalenol (NIV) in cereals intended for human and animal consumption. The method, based on liquid chromatography and fluorescence detection, involves an automated 2 channel post-column derivatization, performed with sodium hydroxide, methyl acetoacetate and ammonium acetate. The chromatographic separation was accomplished using a C18 column eluted in isocratic mode with a mixture of 0.01% acetic acid and acetonitrile. Optimal fluorescence detection was obtained by an excitation and emission wavelength of 360 nm and 470 nm, respectively. The sample preparation required a rapid extraction of mycotoxins with water and a purification step by hydrophilic-lipophilic balance column clean-up. Under the optimized experimental conditions, a complete separation of DON and NIV was obtained in less than 20 min. The on-line post-column derivatization ensures excellent results in terms of simplicity and sensitivity, with limits of detection down to 0.014 mg/kg. The proposed method was extensively validated and the analytical performances of linearity (correlation coefficient of 0.9998), selectivity, precision (intra-day precision lower than 8 %) and recovery (ranging from 89 to 101%) were evaluated, demonstrating the method feasibility in accurate confirmation analyses
HPLC, CE ed ELISA: tre tecniche a confronto per la determinazione di istamina nei prodotti ittici
No full textPolyphosphates in products of animal origin: validation of an analytical method based on ion chromatography with electrochemical conductivity detection
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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
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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