1,720,957 research outputs found
Desorption electrospray ionization mass spectrometry for food analysis
No full textDesorption electrospray ionization mass spectrometry (DESI-MS)has found applications in many fields. Unfortunately and despite many peculiarities, its use in food science is still in its infancy. This review focuses on both technical aspects and the different ways in which this interface has been exploited in food analysis. DESI signal's reliance on interface geometry, solvent composition, and analyte distribution is deeply evaluated and microscopic pictures of these phenomena are shown in order to provide a fundament to critically understand the overviewed works. Green aspects of the technique are also described, distinguishing between direct (no sample pretreatment)and indirect methods (minimal sample pretreatment). All papers published from the appearance of DESI interface on the market are examined. Authors' goal was to produce an organic and complete overview able to provide a clear critical opinion on the key issues, available methods and future developments in this field of study
Micro extraction by packed sorbent coupled to liquid chromatography tandem mass spectrometry for the rapid and sensitive determination of cannabinoids in oral fluids
No full textThe evaluation of oral fluids (OFs) levels is useful in proving drug consumption, particularly for monitoringabuse in workplaces and for the driving under the influence of drugs (DUIDs) programs. OF is acomplex matrix and a small amount of sample is available, especially after cannabis smoking. This paperreports a method for the determination of cannabinoids and metabolites in OF: THC, 11-hydroxy-THC(OH-THC) and THC-COOH. Cannabidiol (CBD) and cannabinol (CBN) were also detected by LC–MS/MS.The OF pre-treatment was based on micro-extraction by packed sorbent (MEPS), a recently developedsolid phase extraction technique which operates with small sample volumes: only 125 L of sample wasrequired, allowing the collection by simple expectoration. Analytes elution was achieved using 2×25 Lof 50 mM NH4OH in methanol. A rapid and effective clean-up has been obtained with satisfactory recoveryvalues and a negligible matrix effect. The LOQs ranged between 0.020 ng mL−1 for THC-COOH and0.40 ng mL−1 for OH-THC. The chromatographic conditions obtained with a fused-core column alloweda good separation of the analytes in 6 min only. The whole procedure has been validated according toSOFT/AAFS guidelines.[...
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
Residue analysis of thyreostats in baby foods via matrix solid phase dispersion and liquid chromatography–dual-polarity electrospray–tandem mass spectrometry
No full textThis paper describes a rapid method for confirming residues of thyreostats in meat-based baby foods by using liquid chromatography–dual polarity electrospray–tandem mass spectrometry (LC-ES(±)-MS/MS). Six thioureylenes, belonging to the group of thiouracil and imidazole, were selected for this work: thiouracil (TU), methylthiouracil (MTU), propylthiouracil (PTU), phenylthiouracil (PhTU), mercaptobenzimidazole (MBI) and tapazole (TAP). The amphoteric nature of these compounds allows their electrospray detection in both positive and negative ionisation. Nevertheless, MS detection is not favoured by their low molecular weights, while their chromatographic retention is also thwarted by their high polarity. A pentafluorophenyl (PFP) core-shell phase column was selected to avoid peak asymmetry or peak splitting, and a dual-polarity ionisation method was optimised to obtain a sensitivity as high as possible. The method was validated according to the Commission Decision 657/2002/EC. A simple and fast procedure based on matrix solid phase dispersion (MSPD) was optimised to extract analytes from baby foods with recoveries exceeding 82%. Limit of decision (CCα) and detection capability (CCβ) were lower than the permissible maximum concentration (10 ng g−1). The validated method was then applied to assess the potential occurrence of the six selected thyreostats in nine commercial products. All the samples were found free of contamination
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
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
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