1,720,992 research outputs found
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
Qualitative characterization of a transesterification product of coconut oil by FIA-APCI-MS.
Full text linkSynopsis
Objectives The purpose of this work was the qualitative characterization of a recently transesterification product obtained from the coconut oil in the presence of polyglycerol-6 to produce a new PEG-free secondary surfactant. The purpose of a secondary surfactant is to reduce the harshness of a skin cleanser.
Methods The transesterification product was qualitatively characterized in our laboratory by flow injection analysis-atmospheric pressure chemical ionization-mass spectrometry (FIA-APCI-MS). The mass spectrum of the transesterification product was compared to those of the starting materials (polyglycerol and coconut oil).
Results The analyses highlighted the disappearance of the starting oil peaks and the appearance of new peaks assignable to the reaction products, mainly corresponding to diesters of polyglycerol. Additionally, peaks of unreacted polyglycerol are present as well as peaks of cyclization products derived from the polyglycerol starting material.
Conclusions The development of this fast and easy analytical method, requesting only few minutes to be performed, represents a very useful tool for the characterization of transesterification products during the quality control of batches under production.Resume
ObjectifsLe but de ce travail etait la caracterisation qualitative d'un produit de transesterification recemment obtenu a partir de l'huile de noix de coco en presence de polyglycerol-6 pour produire un nouveau tensioactif secondaire sans PEG, ce dernier generalement ajoute pour reduire l'agressivite d'un nettoyant pour la peau.
MethodesLe produit de transesterification a ete qualitativement caracterise dans notre laboratoire par Analyse du Debit d'injection - par Ionisation chimique a Pression atmospherique - par Spectrometrie de masse (FIA-APCI-MS). Le spectre de masse du produit de transesterification a ete compare a ceux des materiaux de depart (de polyglycerol et d'huile de noix de coco).
ResultatsLes analyses ont mis en evidence la disparition des pics d'huile de depart et l'apparition de nouveaux pics attribuables a des produits de reaction, correspondant principalement a des diesters de polyglycerol. De plus, les pics de polyglycerol non reagi sont presents ainsi que des pics de produits de cyclisation provenant de la matiere de depart de polyglycerol.
ConclusionsLe developpement de cette methode d'analyse rapide et facile represente un outil tres utile pour la caracterisation des produits de transesterification pendant le controle de la qualite des lots en production
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
Quantification of isoflavones in coffee by using solid phase extraction (SPE) and highperformance liquid chromatography–tandem mass spectrometry (HPLC-MS/MS)
No full textA new method for extracting isoflavones from espresso coffee (EC) was coupled with high-performance liquid chromatography–
tandemmass spectrometry (MS/MS) for the first time to analyse five isoflavones, which included both a glycosilated form, genistin
and the aglycons daidzein, genistein, formononetin and biochanin A. Isoflavones were extracted fromcoffee samples usingmethanol,
stored in a freezer overnight to precipitate proteic or lipidic residues and purified on SPE C18 cartridges before highperformance
liquid chromatography–MS/MS analysis. The recovery percentages obtained by spiking the matrix at concentrations
of 10 and 100 μg l1 with a standard mixture of isoflavones were in the range of 70 to 104%. The limits of detection and limits of
quantification were in the range of 0.015–0.3 μg l1 and 0.05–1 μg l1, respectively. Once validated, the method was used to analyze
the concentrations of isoflavones in six ECs and ten ground coffee samples. Only formononetin and biochanin A were found,
and their respective concentrations ranged from 0.36 to 0.41 μg l1 and from 0.58 to 3.26 μg l1 in ECs and from 0.36 to
4.27 μgkg1 and from 0.71 to 3.95 μgkg1 in ground coffees. This method confirms the high specificity and selectivity of
MS/MS systems for detecting bioactives in complex matrices such as coffee
Development of a LC-MS-MS method for the simultaneous determination of natural steroidal hormones and synthetic anabolic steroids in equine and bovine blood matrix
No full textMonitoring the hormones in equine matrix is crucial to understanding the health status of horses , and also to monitoring the abuse of these substances before a race or a horse transaction. Few analytical procedures exist which are “self made methods”, generally based on immunoassay analysis, often impossible to replicate in other laboratories or too complex for the staff. On that, it is necessary to develop new sensitive analytical methods, that can be diffused to external vets and give correct and comparable results. Furthermore, the few analytical procedures involving an HPLC-MS-MS system reported in literature allow for simultaneous quantification of no more than three or four hormones [1][2]. The proposed method makes it possible to detect and quantify seventeen hormones and metabolites in a single assay, in just ten minutes. Quantifiable hormones with the proposed method are: Pregnenolon, 17-OH-Pregnenolon, Progesteron, 17-OH-Progesteron, Androsteron, Androstenedion, DHEA, DHEAS, Testosteron, Cortisol, Corticosteron, Aldosteron, 11-Deossicortisol, 11-Deossicorticosteron, Diidrotestosteron, Estron, Estradiol. A deuterated hormone ( Testosteron-D3) has been used as internal standards in order to set a more accurate and precise procedure. The method was developed using the Agilent UHPLC chromatographic system (1290) using a Zorbax RRHD C18 – 1,8 μm column and a 6420 Agilent Mass Spectrometer . The procedure is fast and intuitive; the sample preparation is very easy, with the serum deproteinized in vials using a deproteinizing solution, centifuged and injected into the system. The mobile phases are made of water and acetonitrile, both containing formic acid.
Overall, the method is very simple and robust and it brings about a remarkable saving of time and money with respect to previously reported methods; in fact, using the UHPLC–Tandem Mass spectrometer enables simultaneous quantification of seventeen Steroidal Hormones. The method has been applied to a number of equine and bovine blood samples supplied from different breeding farms and territorial vests
Simultaneous determination of taurine, glucuronolactone and glucuronic acid in energy drinks by Ultra High Performance Liquid Chromatography-Tandem Mass Spectrometry (Triple Quadrupole)
No full textIn this work, we present for the first time a rapid and robust UHPLC–MS/MS method for analyzing taurine,
GlcLA and GlcA in energy drinks simultaneously and without derivatization. The separation of three
analytes was achieved using a Kinetex Hilic analytical column (100 mm
×
4.6 mm i.d.) and a mobile phase
formed by water (A) and acetonitrile (B) both with formic acid 0.1% at a flow rate of 0.8 ml min−1 with
isocratic elution in 3.5 min. Calibration curves were calculated using the method of standard addition
in a concentration range from 2 to 6 mg/100 ml for taurine (R2 > 0.987), from 0.4 to 1.2 mg/100 ml for
GlcLa (R2 > 0.997), and from 0.2 to 0.6 mg/100 ml for GlcA acid (R2 > 0.998). The validated method was
applied to the analysis of nine commercial energy drinks. The level of taurine found ranged from 0.01 to
0.45 g/100 ml, and it matched with that reported in the labels of the analyzed energy drink samples
Importance of Espresso Coffee Machine Parameters on the Extraction of Chlorogenic Acids in a Certified Italian Espresso by Using SPE-HPLC-DAD
No full textChlorogenic acids (CGA) are a group of phenolic acid derivatives, which are commonly found in coffee at
concentrations reaching 0.1-0.2%. A method based on high performance liquid chromatography-diode array
detector (HPLC-DAD) is proposed for the simultaneous determination of three chlorogenic acids, i.e.
3-O-caffeoylquinic acid (3-CQA), 5-O-caffeoylquinic acid (5-CQA) and 3,5-di-O-caffeoylquinic acid
(3,5-diCQA), in time portions of espresso coffee. Two different espresso coffee machines working with different
pressure and temperature curves, and two different blends (i.e. Arabica and Robusta) were used. The method
presents good linearities (correlation coefficient greater than 0.99) and recoveries (in the range 67-99%) for the 3
chlorogenic acids. The concentration of total CGAs in a cup of Certified Italian Espresso ranged from 1522.5 to
2223.4 mg kg-1 and CGA isomer contents were, in decreasing order, 5-CQA > 3-CQA > 3,5-diCQA.
The concentration of total chlorogenic acids was higher in Espresso coffee (EC) prepared with Aurelia machine
rather than with Leva; Arabica blend possessed higher level ot total chlorogenic acids than Robusta samples
Quantification of caffeine, trigonelline and nicotinic acid in espresso coffee: the influence of espresso machines and coffee cultivars
No full textCaffeine, trigonelline and nicotinic acid are important bioactive constituents of coffee. In this
work, the combination of different water temperatures and pressures in the settings of the
espresso coffee (EC) machine was evaluated, to assess how these factors influence
how effectively caffeine, trigonelline and nicotinic acid are extracted from both Arabica and
Robusta samples. The proposed analytical method, based on a high performance liquid
chromatography (HPLC) system coupled to a variable wavelength detector (VWD), showed
good linearity (R240.9985) and good recoveries (71–92%); after validation for three monitored
compounds, the method was used to analyze 20 commercial samples. The combination of a
temperature of 92 C and pressure at 7 or 9 bar seems to be the ideal setting for the most
efficient extraction of these compounds and consequently for their intake; the compound
extracted in the greatest quantity was caffeine, which was in the range of 116.87–199.68mg in
a 25ml cup of coffee
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