1,721,006 research outputs found
A direct screening procedure for diuretics in human urine by liquid chromatography- tandem mass spectrometry with Information Dependent Acquisition
No full textBACKGROUND: Diuretics are a class of compounds largely used for either therapeutic (edemas, hypertension, etc.) or illegal (doping) purposes. Probably owing to the substantial variety of their chemical structures, which makes them hardly extractable from a biological matrix in a single procedure, a quite short list of screening methods can be retrieved in the literature.
METHODS: This work presents a screening procedure for 24 diuretics based on the direct injection of urine (after 50 folds dilution) in a LC-ESI-MS/MS system (Applied Biosytems 4000 QTrap). Two information dependent acquisitions (IDA), one in positive, one in negative ionization, allowed the acquisition of one selected reaction monitoring transition for each compound, which, when a significant peak was found, triggered the acquisition of the enhanced product ion (EPI) spectrum.
RESULTS AND CONCLUSIONS: EPI spectra were stored in a library and the procedure was able to recognize by library matching various diuretics in real positive samples. The limits of detection were comprised between 0.002 and 0.25 mg/l and ion suppression was not found to significantly influence the analysis
Possibilità terapeutiche nei carcinomi polmonari localmente resecabili e con M1 encefaliche sincrone di piccole dimensioni. Risultati su 53 pazienti trattati in modo combinato mediante radiochirurgia stereotassica con Gamma Knife ed exeresi polmonare
No full textLC-MS-MS Analysis of 2,4-dinitrophenol and its phase I and II metabolites in a ase of fatal poisoning
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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
Ehtyl glucuronide and ethyl sulfate determination in serum by liquid chromatography-electrospray tandem mass spectrometry
No full textBACKGROUND: Ethyl glucuronide (EtG) and ethyl sulphate (EtS) are two ethanol metabolites that can be detected in serum up to 8 h after ethanol elimination. Their presence is therefore indicative of recent ethanol consumption in case of delayed sampling after an event (e.g. car crash).
METHODS: A LC-ESI-MS-MS method for the determination of EtG and EtS in serum was developed and validated. Two product ions together with the parent ions were monitored for identification. Pentadeuterated-EtG was used as internal standard.
RESULTS: Excellent linearity for EtG (from 0.22 to 45 micromol/l) and EtS (from 0.40 to 80 micromol/l) was observed (r(2)>or=0.9998). LOD and LLOQ were 0.04 and 0.20 micromol/l for EtG and 0.08 and 0.40 micromol/l for EtS, respectively. Accuracy (bias) and precision (relative standard deviation), studied at four different quality control levels, were always better than 7%. Matrix effects were found to be negligible. The method was applied to several samples obtained from known alcoholics and social drinkers.
CONCLUSIONS: A sensitive and specific determination of EtG and EtS in serum samples was achieved despite a simple and fast sample preparation. To our knowledge, this is the first fully validated method for the simultaneous determination of the two alcohol metabolites in serum
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