1,720,962 research outputs found
Selenium and tellurium concentrations of British coals
No full textStandard mode and collision/reaction cell mass spectroscopy methods have been utilised in order to overcome spectral interferences and provide ultra-low quantification of selenium (Se) and tellurium (Te) in British coals for the first time. The accurate detection of Se and Te in coals is becoming increasingly important, as coals and pyrite have been identified as potentially significant trace element sources. The mean Se concentration of British coals bear comparison to that of world coals, with anomalous Se content (concentrations above 4 mg/kg) across westerly exposures, often coinciding with high sulphur (S) content and visible pyrite. New Te data for British coals gives a mean concentration of 0.02 mg/kg, with anomalous Te in Ayrshire. There is a positive correlation in the Te/Se ratio across the sample set. The close relationship between Se and Te, as well as Se-Te with both early syngenetic and later cleat filling pyrite, confirms an important role for sulphides in Se and Te sequestration in British coals. The high Se-Bowland Shale and/or Ordovician volcanics may have provided the trace element source British coals of similar or younger age. Regional intrusive activity (shallow Se and Te concentrations of British coals LB draft manuscript tabular intrusions or more extensive plutons) and episodes of intense deformation can alter the thermal maturity of coals, and may have driven the movement of trace element-rich fluids through strata, locally enriching coals in Se and Te
Determination of Se and Te in coal at ultra-trace levels by ICP-MS after microwave-induced combustion
No full textA method for ultra-trace determination of Se and Te in coal by inductively coupled plasma mass spectrometry (ICP-MS) was developed. Samples (up to 500 mg) were prepared by microwave-induced combustion (MIC) in a closed system pressurized with 20 bar of oxygen. Inorganic acids or their mixtures
were evaluated as absorbing solution. Using HNO3 + HCl (1 + 1), results obtained for Se and Te after sample preparation by MIC agreed with those obtained by reference methods, microwave-assisted wet digestion (MAWD) using concentrated HNO3 and HF, and solid sampling electrothermal vaporization
inductively coupled plasma mass spectrometry (SS-ETV-ICP-MS), and also with a certified reference material of coal (NIST 1632c) for Se. Very low limits of quantification (LOQ) were obtained: 0.002 and 0.007 mg kg1 for Se and Te, respectively. Major elements were determined in final solutions obtained
by MAWD and MIC, and their concentration in solutions of MIC was negligible (<10 mg L1), minimizing the risk of interference in ICP-MS analysis. The proposed method was applied to samples of coal from the United Kingdom, with a wide range of inorganic composition (from 3 to 41% ash content), showing
its robustness and feasibility for routine analysis. Se concentration ranged from 0.291 to 11.5 mg kg1, and Te was mainly found at ultra-trace levels (<0.007 to 0.11 mg kg1). The proposed method presents several advantages over the reference methods, such as the use of a higher sample mass, low LOQs and,
an important aspect, no need of using HF
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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