1,720,972 research outputs found
Fingerprinting of vegetable oil minor components by multidimensional comprehensive gas chromatography with dual detection
No full textThe potentiality of a multidimensional comprehensive gas chromatographic (GC x GC) method, employing a simultaneous dual detection (FID and mass spectrometer), to generate peculiar two-dimensional chromatograms to be used as a chemical fingerprint, was investigated to characterize minor compounds in edible oil, particularly olive oil. The best column combination for this application was investigated comparing two column sets (orthogonal or reverse-type), equivalent in terms of theoretical plate number, but differing in stationary phase combination. The apolar x mid-polar set gave a superior separation power, thus was used for further characterization. Different levels of information were extrapolated from the two-dimensional chromatogram. Using the FID, reliable quantification of the alkyl esters fatty acids and waxes was obtained, comparable to the results obtained using the official method, as required by the European legislation. However, thanks to a slight modification of the sample preparation method, the increased separation power obtained using the GC x GC method, and the support of the mass spectrometer detector, further diagnostic information was extrapolated considering the free sterol and tocopherol fractions. In particular, the profiles of extra virgin olive oil samples were compared with a hazelnut oil sample, highlighting that the latter was characterized by a larger number of compounds, completely absent in the extra virgin olive oil samples, which can be used to detect illegal admixtures
Characterisation of minor components in vegetable oil by comprehensive gas chromatography with dual detection
No full textThe profile of minor compounds, such as alcohols, sterols, free and alkyl fatty acids, waxes, etc., was investigated in different vegetable oils by a comprehensive gas chromatographic system, coupled with a simultaneous dual detection (flame ionisation detector and mass spectrometer) for quantitative and qualitative purposes. Such a system generated a unique two-dimensional chromatogram to be used as a chemical fingerprint. Multi-level information, due not only to a more "comprehensive" preparation technique, but also thanks to the exploitation of a more powerful and sensitive analytical determination allowed the extrapolation of diagnostic information from the minor components profile of different vegetable oils, along with their characteristic profile. Furthermore, an admixture of an extra virgin olive oil with a low amount of sunflower and palm oils was evaluated, attesting to the powerful diagnostic information provided by the proposed approach. (C) 2016 Elsevier Ltd. All rights reserved
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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