1,721,058 research outputs found
Synthesis and characterization of white micas in the join muscovite-aluminoceladonite
No full textPotassic white micas were synthesized in the K2O-MgO-Al2O3-SiO2-H2O system along the pseudobinary join muscovite-aluminoceladonite (mu-Alcel). Composition of run products as measured by electron microprobe analysis are in the range mu(89)-Alcel(11) to mu(01)-Alcel(99). Cell parameters were determined on powder samples by full-profile Rietveld refinement, using both a single-polytype and a multi-polytype model. The results of both analysis models are in full agreement, and show that the phengite cell parameters have a distinct dependence on the celadonite content: the c parameter shows a monotonic decrease over the full compositional range, whereas the a and b parameters both increase in the Alcel(0)-Alcel(60) range but decrease in the Alcel(60)-Alcel(100) range. The monoclinic b angle decreases slightly with increasing celadonite content. The overall behavior of the cell parameters indicates a decrease of the ditrigonal distortion of the tetrahedral 6-rings, and an increased trioctahedral character of the structure at high celadonite compositions. The molar volume along the solid solution join shows a maximum at about Alcel(30). Molar volume vs. composition can be fitted by a symmetric function for the excess volume yielding a molar volume for end member aluminoceladonite of 13.957 +/- 0.006 J/bar, for muscovite 14.076 +/- 0.004 J/bar, and a symmetric positive deviation from ideal volumes of mixing with W = 0.198 +/- 0.025 J/bar, and r(2) = 0.941. The use of an asymmetric excess volume function does not significantly improve the fit quality (r(2) = 0.945)
Experimental subsolidus studies on epidote minerals
No full textDespite the fact that epidote group minerals are very typical for metamorphism at very low pressure, e.g., in geothermal fields (Bird and Spieler 2004), the first successful synthesis of zoisite and epidotess was reported by Coes (1955) in a paper in the Journal of American Ceramic Society entitled “High pressure minerals.” Synthesis conditions were 1 GPa at 800°C; zoisite was obtained from a mixture of kaolin, SiO2, CaO, and CaCl2, whereas epidote was formed by adding FeCl2·H2O to the previous mixture. Once experimental facilities enabled pressures exceeding a few hundred MPa, zoisite and epidote minerals were easily obtained from a variety of starting materials, made of oxides, gels and glasses.
Historically, early experimental studies on epidote focused on the formation at low pressure conditions, and then ventured into the simple system CaO-Al2O3-SiO2-H2O at conditions attainable by piston cylinder equipment (Newton and Kennedy 1963; Boettcher 1970) in which zoisite was found to have an extremely large temperature stability. Then, the role of Fe3+ was investigated systematically at pressures typical for the middle and lower continental crust (Holdaway 1972; Liou 1973). Epidote minerals in bulk compositions directly applicable to natural rocks were not investigated experimentally until the early 70’s (Liou et al. 1974; Apted and Liou 1983). Subsequent studies in the context of the very popular hydrous phase stabilities at subduction conditions in the 90’s extended the experimentally determined stability of epidotess in natural compositions to 3.5 GPa. With the relatively easy access to multi-anvil machines, the pressure stability of zoisite was defined (Poli and Schmidt 1998).
The increasing number of experimental studies on epidote minerals reveals that the members of this group of ubiquitous rock forming minerals have huge stability fields, which extend to 7 GPa in pressure and to more than 1200°C in temperature. However, most of the experimental studies were performed at subsolidus conditions, thus melting relations are still partially unknown.
In this chapter we focus on experimental studies in the subsolidus performed both on simplified model systems and on natural (or close to natural) rock compositions where epidotess is described by the components (clino)zoisite and epidote. Experimental investigations clarifying the role of epidote in magmatic systems are discussed in Schmidt and Poli (2004). Experimental studies on Mn bearing epidote minerals are presented by Bonazzi and Menchetti (2004), those on REE bearing allanite by Gieré and Sorensen (2004).
Unless differently stated the term epidotess employed in this chapter is intended to describe epidote mineral compositions along the pseudobinary join (clino)zoisite-epidote
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
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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