1,720,973 research outputs found
Characteristic Performance of Guard Electrode in LA–SF–ICP– MS for Multi-Element Quantification
No full textImproved in situ zircon U–Pb dating at high spatial resolution (5–16 μm) by laser ablation–single collector–sector field–ICP–MS using Jet sample and X skimmer cones
No full textGeochemical Characteristics of Selenium and Its Correlation to Other Elements and Minerals in Selenium-Enriched Rocks in Ziyang County, Shaanxi Province, China
No full textZiyang County, Shaanxi Province, China is a world known selenium (Se)-enriched area, and a severe selenosis incident was reported in Naore Village during the 1990s. This study investigated the geochemical characteristics of Se and its fractions in Se-enriched rocks from Ziyang. Se distribution is uneven, ranging from 0.23 to 57.00 mu g/g (17.29 +/- 15.52 mu g/g). Se content is higher in slate than chert, and even lower in carbonate rocks. Cd, As and V are enriched but Pb is depleted in Se-enriched strata. Se has different correlations both with TS (total sulfur) (R-2=0.59 for chert) and TC (total carbon) (R-2=0.77 for slate, R-2=0.87 for carbonate). Se has significant positive correlations with V (r=0.65), As (r=0.485), Cd (r=0.459) and Pb (r=0.405). The Se level correlates with mineral content, positively with pyrite, chlorite and illite, negatively with albite. Se associated with sulfide/selenide and elemental Se are the predominant fractions of total recovered Se, suggesting that a reducing environment and the formation of sulfides were significant to Se deposition during its geochemical cycle. Although low concentration of bio-available Se (average 5.62%+/- 3.69%) may reduce the risk of Se poisoning in the target area, utilization of Se-rich rock as natural fertilizer should be restricted
Improved selenium bioavailability of selenium-enriched slate via calcination with a Ca-based sorbent
No full textFertilizing soil with selenium (Se)-enriched slate could increase Se levels in crops; however, this process is limited by the low Se bioavailability of Se-enriched slate. In this work, a calcination procedure for Se -enriched slate using CaO as a sorbent was developed, and the process significantly improved the bioavailability of Se. The calcination experiments were conducted with the calcium (Ca)-based sorbents CaO or CaCO3 at 300-800 degrees C. Most of the Se in the organic matter and sulfides were emitted between 400 and 650 degrees C, and CaO exhibited a higher adsorption efficiency of Se compared with CaCO3. The optimum temperature was 600 degrees C as determined by the high contents of bioavailable Se (10 times that of the original slate) and Se(VI) in the calcinated samples with the sorbent CaO. Both the physical adsorption of CaO and the formation of CaSeO3 contributed to the conversion of Se associated with organic matter and sulfide minerals to bioavailable Se species. The transformation of Se(IV) to Se(VI) might have been caused by the co-oxidation of O-2 and the generation of HCl during the calcination process. The Se concentrations in potatoes amended with activated slate reached 650 +/- 23 mu g/kg, which verified the high Se bioavailability of the calcinated product. The proposed calcination procedure could support the exploitation of Se -enriched slate and the preparation of Se soil amendments. (C) 2016 Elsevier B.V. All rights reserved
Comparison of Ultrafine Powder Pellet and Flux-free Fusion Glass for Bulk Analysis of Granitoids by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry
No full textTwo sample preparation techniques (ultrafine powder pellet and flux‐free fusion glass) for LA‐ICP‐MS bulk analysis of granitoids were compared. Ultrafine powder particles produced by wet milling were characterised as d50: ~ 1.0 μm, d90: ~ 5.0 μm. Agate abrasion (balls and vial) during wet milling affects only SiO2 measurements and is negligible for other elements. For the flux‐free fusion glass, a second grinding of the initial fused glass and re‐melting were necessary to produce compositionally homogeneous glasses. Nickel and Cu can be contaminated during the fusion procedure, and Sn and Pb were depleted after the melting process. The homogeneity of fusion glasses was comparable to that of MPI‐DING glasses, while the powder pellets were less homogeneous. This heterogeneity is ascribed to large (up to 10 μm) crystal fragments (e.g., biotite) persisting in powders even after 45 min of milling. For most elements of interest, both preparation techniques give reliable LA‐ICP‐MS results of granitoid reference materials within 10% of the reference values. Thus, we can recommend both techniques to avoid common problems associated with acid dissolution ICP‐MS. For high‐precision measurements (especially Zr, Hf, Th and U), the flux‐free fusion glass technique is a better choice than ultrafine powder pellets
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
The Preparation and Preliminary Characterisation of Three Synthetic Andesite Reference Glass Materials (ARM-1, ARM-2, ARM-3) for In Situ Microanalysis
No full textThree synthetic reference glasses were prepared by directly fusing and stirring 3.8 kg of high-purity oxide powders to provide reference materials for microanalytical work. These glasses have andesitic major compositions and are doped with fifty-four trace elements in nearly identical abundance (500, 50, 5 mu µg g−1) using oxide powders or element solutions, and are named ARM-1, 2 and 3, respectively. We further document that sector-field (SF) ICP-MS (Element 2 or Element XR) is capable of sweeping seventy-seven isotopes (from 7Li to 238U, a total of sixty-eight elements) in 1 s and, thus, is able to quantify up to sixty-eight elements by laser sampling. Micro- and bulk analyses indicate that the glasses are homogeneous with respect to major and trace elements. This paper provides preliminary data for the ARM glasses using a variety of analytical techniques (EPMA, XRF, ICP-OES, ICP-MS, LA-Q-ICP-MS and LA-SF-ICP-MS) performed in ten laboratories. Discrepancies in the data of V, Cr, Ni and Tl exist, mainly caused by analytical limitations. Preliminary reference and information values for fifty-six elements were calculated with uncertainties [2 relative standard error (RSE)] estimated in the range of 1-20%
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
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