1,720,973 research outputs found
Identification of TAGs in archaeological amorphous organic residues by core shell RP stationary phase HPLC and ESI-MS-QTOF detection
No full textA method based on the use of a Poroshell 120 EC-C18 column (3.0. mm. ×. 50. mm, 2.7. μm) with a high resolution electrospray ionization-quadrupole-time of flight (ESI-Q-ToF) tandem mass spectrometer as detection system was optimized for the identification of triacylglycerols (TAGs) in complex archaeological residues.The best performances in chromatographic separation and Q-ToF detection sensitivity were reached by using a mixture of iPrOH/MeOH at a 0.6. mL/min flow rate. Triolein (OOO) was eluted in 12.30. min and the chromatographic resolution against tripalmitin (PPP) was 1.4. Very good limits of detection and quantification limits were also achieved (LOD. <. 0.03. μg/g LOQ. <. 0.10. μg/g).These achievements were compared with the results provided by traditional particle columns and with the results reported in the recent literature regarding TAGs analysis in archaeological residues. Thanks to the unprecedented chromatographic separation and detection sensitivity attained, it was possible for the first time to perform TAGs researches in archaeological residues and reference materials with a dataset containing more than 500 molecular formula
HPLC-APCI-MS analysis of triacylglycerols (TAGs) in historical pharmaceutical ointments from the eighteenth century
No full textThe lipid fractions of residues from historical pharmaceutical ointments were analysed by reversed-phase liquid chromatography coupled with atmospheric pressure chemical ionization and mass spectrometer detection. The residues were contained in a series of historical apothecary jars, dating from the eighteenth century and conserved at the "Aboca Museum" in Sansepolcro (Arezzo, Italy) and at the pharmacy of the "Real Cartuja de Valldemossa" in Palma de Majorca (Spain). The analytical protocol was set up using a comparative study based on the evaluation of triacylglycerol (TAG) compositions in raw natural lipid materials and in laboratory-reproduced ointments. These ointments were prepared following pharmaceutical recipes reported in historical treatises and used as reference materials. The reference materials were also subjected to stress treatments in order to evaluate the modification occurring in the TAG profiles as an effect of ageing. TAGs were successfully detected in the reproduced formulations even in mixtures of up to ten ingredients and after harsh degradative treatments, and also in real historical samples. No particular interferences were detected from other non-lipid ingredients of the formulations. The TAG compositions detected in the historical ointments indicated a predominant use of olive oil and pig adipose material as lipid ingredients. The detection of a high level of tristearine and myristyl-palmitoyl-stearyl glycerol in two of the samples suggested the presence of a fatty material of a different origin (maybe a ruminant). On the basis of the positional isomer ratio, sn-PPO/sn-POP, it was possible to hypothesize an exclusive use of pig fat in one sample. We also evaluated the application of principal component analysis of TAG profiles as an approach for the multivariate statistical comparison of the reference and historical ointments
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Multi analytical study on Khol residues from the ancient Egyptian city of Assiut
No full textMulti-analytical chemical approaches are nowadays considered an important source of complementary information in archaeological functional studies. Here we report the results of an investigation carried out by means of liquid chromatography-mass-spectrometry (LC-MS), pyrolysis-gas chromatography-mass spectrometry (py-GC-MS) and Raman micro-spectroscopy (μRaman) applied onto residues sampled from ceramic vessels, found in the ancient cities of Assiut (Egypt, Middle Kingdom). These items, characterized by the typical conical shape of Kohl containers, represented an extraordinary opportunity to study, at the same time, well preserved archaeological records and the related contents. Thanks to the combined analysis, it was possible to hypothesize the original recipes adopted to prepare the ancient cosmetic. The profile of the fatty ingredients resulted congruent with the information collected by the archaeologist from the excavation site, regarding the culture and the ancient Egyptian practice of eye-painting. The analysis of the sedimentary material confirmed the provenance of the archaeological recor
Omega-3 rich oils from microalgae: A chitosan mediated in situ transesterification method
No full textMicroalgae are a precious source of polyunsaturated fatty acids (PUFA), however extraction is difficult due to the peculiar microalgae cell structure. Here we describe a new method based on the application of chitosan nanoaggregates as CO2 responsive emulsifier, used to promote the swelling of algae cell wall and the formation of a large oil – ethanol interphase area during the ethanolysis. Tests were carried out with Pseudokirchneriella subcapitata and Nannochloropsis sp. at different biomass/ethanol/chitosan ratios. CO2 was added to trigger demulsification to promote an easy recovery of the lipid fraction. The highest yields in PUFA were obtained with Nannochloropsis sp. (207.9 mg/g of oil) using 0.4% wt of chitosan and 1:10 biomass:ethanol ratio; 43.6 mg/g of linolenic acid were obtained from Pseudokirchneriella subcapitata. Overall, because the method employs ethanol, a generally recognized as safe (GRAS) solvent, and food grade additives, it is suited for the preparation of PUFA supplements
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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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