1,720,961 research outputs found
Analisi dello Stanozololo e suoi metaboliti in urine bovine mediante LC-MS-MS
No full textC.N.R.-AREA DELLA RICERCA DI ROMA
Identification of hydroxycinnamic acid-tartaric acid esters in wine by HPLC-tandem mass spectrometry
No full textIn this work hydroxycinnamic acid esters of tartaric acid (mono-p-coumaroyl tartaric acid, monocaffeoyl tartaric acid, monoferuloyl tartaric acid esters) were separated, identified and quantified in several red wines by high performance liquid chromatography coupled with tandem mass spectrometry. The method features direct analysis of wines with no preparation and analysis of grape juice with minimum sample manipulation. For the identification was used both a triple quadrupole and a quadrupole-Tof, while for the quantification a triple quadrupole. At the same time two impurities, due to interfering substances coming from methanol (stored in bottles with polypropylene tops without Teflon protection), were characterised. These impurities had the same molecular weight as the investigated compounds. (C) 2010 Elsevier Ltd. All rights reserved
Chromatographic analysis of trans resveratrol in Italian wines: Comparisons between FL, UV and MS detection
No full textResveratrol (3,5,4'-trihydroxystilbene) is a phytoalexin that belongs to the group of stilbenes, known to occur in gropes and consequently in grape products. Its presence in wine is an important qualitative parameter because of the several beneficial effects on human health. The aim of this work is the development of a high-performance liquid chromatographic (HPLC) method for the determination of trans resveratrol in wines, and comparisons between the results obtained by different detection techniques: UV-vis spectroscopy, fluorescence spectroscopy and mass spectrometry. Resveratrol is analysed on a C-18 column using gradient elution. The method permits direct injection of sample, revealing to be time-saving, overcoming the need of sample pre-treatment steps. Detection limits were 154.8 ng mL(-1) by HPLC-UV, 118.0 ng mL(-1) by HPLC-FL and 48.0 ng mL(-1) by HPLC-MS. Trans resveratrol has been then quantified in a group of 52 wines derived from different Italian regions, cultivars and winemaking technologies by HPLC-UV
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
Detection of boldenone and its major metabolites by liquid chromatography-tandem mass spectrometry in urine samples
No full textBoldenone is an androgenic anabolic steroid (AAS) intensively used for growth promoting purposes in animals destined for meat prodn. and as a performance enhancer in athletics. Therefore its use is officially banned either in animals intended for consumption or in humans. Because most anabolic steroids are completely metabolized and usually no parent steroid is excreted, metabolite identification is crucial to detect the illegal use of anabolic steroids either in humans or in livestock. The aim of this work is the investigation of 17.beta.-boldenone and its main metabolites, 17.beta.-sulfate, 17.beta.-glucuronide, 5.beta.-androst-1-en-17.beta.-ol-3-one and 17.alpha.-boldenone, in human and bovine urine developing a multiresidue anal. After solid phase extn. of urine samples, detection is carried out by high performance liq. chromatog.-tandem mass spectrometry in multiple reaction monitoring. The av. recovery for all the investigated compds. is above 70%. The developed method is very easy, quick and highly specific. Linearity, precision, decision limit and detection capability were also evaluated
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
Excretion study of stanozolol in bovine by HPLC-tandem mass spectrometry
No full textStanozolol is an anabolic steroid illicitly used for growth promoting purposes in animal prodn. For reasons of public health the use of anabolic steroids as growth promoters is officially banned in Europe in animals intended for consumption. The aim of this work is the investigation of stanozolol metabolites, 3'-hydroxystanozolol, 4.beta.-hydroxystanozolol and 16.beta.-hydroxystanozolol in urine samples after stanozolol administration to a young calf. After solid phase extn. of urine samples, detection is carried out by HPLC-MS-MS multiple reaction monitoring. Av. recovery for the three metabolites is 80%. The method is highly specific and has been validated in terms of linearity, inter and intra day precision. In addn. the decision limit CC.alpha. and the detection capability CC.beta. have been detecte
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