1,720,954 research outputs found
Composition and mineralogy of PGE-rich chromitites in the Nurali Lherzolite-Gabbro complex, southern urals, Russia
No full textWe have investigated two subeconomic bodies of chromitite in the Nurali Iherzolite-gabbro complex, in the southern Urals, Russia, with regard to the composition of the chromian spinel and the distribution and mineralogy of the platinum-group elements (PGE). The bodies of chromitite, referred to as CHR-I and CHR-II, occur as small concordant lenses located at two stratigraphic levels within layered wehrlite and clinopyroxenite, overlying the Iherzolitie mantle tectonite. The chromian spinel is Al-rich, showing an increase of Cr/(Cr + Al), Fe2+/(Fe2+ + Mg) and TiO2 from CHR-I to CHR-II. The total PGE contents vary from 1.26 to 11.61 ppm, and show increase in (Pt + Pd)/(Os + Ir + Ru) from 0.1 to 52.2 as a result of the appearance of magmatic sulfides in the upper chromitite. The PGM assemblage shows a drastic change from laurite-erlichmanite-dominated to enriched in Pt Pd sulfides and alloys. Laurite is the first PGM to crystallize, and its composition typically reflects the Ru/Os ratio of the primitive mantle, indicating that the parent melt of the chromitite did not undergo fractionation during ascent. The Nurali chromitites are rather unusual as they have characteristics in common with chromitites associated with ophiolitic cumulates, layered intrusions, Alaskan-type complexes, and the subcontinental orogenic mantle
Chromite composition and platinum-group mineral assemblage in the Uktus Uralian-Alaskan-type complex (Central Urals, Russia)
No full textChromitite segregations in dunites of the Uktus Uralian-Alaskan-type complex (Central Urals, Russia) display large variation of the chromite composition: Cr/(Cr + Al) - 0.46-0.77, Fe2+/(Fe2+ + Mg) = 0.28-0.66, and Fe3+ /(Fe3+ + Fe2+) =0.23-0.59. Three types of PGM assemblages have been recognized, varying in accordance with chromite composition: type I, dominated by Ru-Os-Ir (sulfides), is associated with magnesiochromite having Fe3+ /(Fe3+ + Fe2+) < 0.30, in the southern dunite body. Type 11, containing abundant Pt-Ir (alloys, minor sulfides), is found in magnesiochromite with Fe3+ /(Fe3+ + Fe2+) = 0.40-0.44; type III, consisting of Ir-Rh-Pt-Pd (alloys, sulfarsenides, antimonides) in Fe-rich chromite having Fe2+ /(Fe2+ + Mg) = 0.66 and Fe3+ /(Fe3+ + Fe2+) = 0.59. Positive anomalies of Ir and Pt, and a negative peak of Ru characterize the PGE patterns of chromitites with type II and III PGM assemblages, whereas a positive Pt anomaly is observed in their dunite host. Intensive fractionation of Pt-Fe alloys in the Uktus chromitites reflects the anomalous behavior of Pt which is decoupled from Rh and Pd. Among other factors, the high iron activity and oxygen fugacity in the parent melt appear to exert a major control on precipitation of Pt-Fe alloys, below sulfur saturation. The strong Pt anomaly in chromitites from Uktus may indicate that Uralian-Alaskan-type magmas were derived from a Pt-rich mantle source
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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