1,721,142 research outputs found
Flow injection determination of choline in milk hydrolysates by an immobilized enzyme reactor coupled to a selective hydrogen peroxide amperometric sensor
No full textA choline oxidase (ChO) immobilized enzyme reactor (IMER) prepared by glutaraldehyde coupling of the enzyme on aminopropyl modified
controlled pore glass beads is described. The ChO–IMER was coupled, in a flow injection configuration system, to an interference free hydrogen
peroxide amperometric sensor based on a Pt surface modified by an overoxidized polypyrrole film. The resulting analytical device responds
selectively to choline and displays a sensitivity of 46.9±0.2CmM-1 and a limit of detection, calculated at a signal-to-noise ratio equal to 3, of
7M. Sensitivity remains constant for about 20 days and then starts to slowly deteriorate and after 2 months a 70% of the initial sensitivity was
still retained. The application to choline determination in milk hydrolysates is demonstrated. Short- and long-term drift observed in the analytical
response can be corrected by a bracketing technique
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
Quantitation of major choline fractions in milk and dietary supplements using a phospolipase-D bioreactor coupled to a choline amperometric biosensor
No full textCurrent analytical methods lack the capacity of simultaneous determination of the content of free
choline and phosphatidyl-bound choline, mainly phosphatidyl choline, in raw milk. Quantitative
determination of total, free, and phosphatidyl-bound choline in milk and a dietary supplement is
described using a phospholipase D packed bioreactor coupled to a choline oxidase-based amperometric
biosensor. The response for choline and phosphatidyl choline was linear up to 0.5 mM and 1
mM, respectively, and the detection limits were 0.02 and 0.03 mM, respectively. The conversion
efficiency of phosphatidyl choline to choline was 50% at 0.2 mL min-1. The within days coefficient of
variation for choline and phosphatidyl choline determination in milk samples was 2.8% and 3.2%,
respectively. With the addition of an acid hydrolysis step, the method can quantify the concentrations
of total, free, phosphatidyl-bound, and non-phosphatidyl-bound choline esters, thus permitting
determination of major choline fractions in a complex matrix
Determination of choline in milk, milk powder and soy lecithin hydrolysates by flow injection analysis and amperometric detection with choline oxidase based biosensor
No full textA fast-response and interference-free amperometric biosensor based on choline oxidase immobilized
onto an electropolymerized polypyrrole film for flow injection determination of choline in milk, milk
powder, and soy lecithin hydrolysates is described. The sensor displayed an Imax value of 1.9 ( 0.2
íA and an apparent Michaelis - Menten constant, k¢M, equal to 1.75 ( 0.07 mM. Detection limits of
0.12 íM could be obtained. Because even a slight deterioration of the anti-interference membrane
can adversely affect measurement accuracy, a real time monitoring of the biosensor selectivity has
been achieved by a dual Pt electrode flow-through cell where the enzyme modified electrode is coupled
to an enzyme-free electrode in a parallel configuration. Finally, bracketing technique (alternate
injections of sample and standards) allows a two-point calibration to be performed in real-time,
correcting for any drift in sensor response
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
Identification of anthocyanins and anthocyanin-derived pigments in Primitivo red wine by HPLC-ESI-MS/MS
No full textDispelling 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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