1,720,966 research outputs found
Oxygen isotope evidence for crustal assimilation and magma mixing in the Granite Harbour Intrusives, Northern Victoria Land, Antarctica
No full textThe stable isotope composition (O,H) of whole-rock and mineral separates of Cambrian-Ordovician gabbros, diorites, granodiorites and granites forming the Mt. Abbott composite intrusions (Northern Victoria Land, Antarctica) was measured to constrain the origin and evolution of the magmas postdating the Ross Orogen. The delta(18)O values of olivine gabbros plot in the field of slightly evolved mantle-derived melts (delta(18)O(WR) = 6.8-7.4parts per thousand). The O-isotope character of the mantle source inferred from the 6180 values of cumulous olivine in gabbros (5.7-6.8parts per thousand) is enriched in O-18 compared to modem arc-related magmas. Geochemical data and concurrent high 6180 values, and initial strontium (Sr-87/Sr-86=0.7060) and neodymium (Nd-143/Nd-144=0.5122) isotope ratios indicate that the olivine gabbros formed by crustal contamination of a primary calc-alkaline basaltic melt. The diorites have high 6180 values, among the highest ever measured for dioritic rocks (8.7-10.3parts per thousand), and Sr-isotope ratios that partially overlap with the adjacent and mingled felsic lithologies (0.708-0.710). The diorites have pyroxene with high, nearly constant (delta(18)O values (8.2-8.6parts per thousand) that are independent from the silica content of the rocks; thus, they did not increase in response of the chemical evolution of the rocks. The diorites originated from the same primary calc-alkaline basalt experiencing different amounts of crustal contamination, and underwent different degrees of mixing with the adjacent granites, producing granodioritic facies and quartz/feldspar xenocrystic diorites. The delta(18)O, Sr-87/Sr-86 and Nd-143/Nd-144 compositions of the granites and granodiorites overlap (10.8-12.1parts per thousand, 0.7096-0.7108, 0.5119-0.5120). They are distinct from the values of the mafic rocks and indicate that gabbros and granites were not cogenetic. The granites are a separate melt component likely derived from nonmodal partial melting of fertile meta-igneous protoliths. (C) 2002 Elsevier Science B.V. All rights reserved
Fluid-inclusion and stable-isotope evidence for fluid infiltration and veining during metamorphism in marbles and metapelites
No full textSyn-metamorphic quartz + carbonate veins within lower-amphibolite-facies marbles and greenschist-facies metapelites of the O'Kane Canyon (northern Victoria Land, Antarctica) are characterised by fluids of different composition: H2O-CO2-CH4 mixtures (34-44 H2O, 50-61 CO2, 3-6 CH4, in mole %) (Type A), or H2O-CO2-N-2 fluids (35-43 H2O 48-54 CO2, 9-11 N-2, in mole %) (Type B). In metapelites, quartz + carbonate veins contain H2O-CO2-CH4 (Type C) fluids, which have a composition 30-68 H2O, 29-64 CO2, 2-6 CH4, in mole %) similar to Type A fluids in marbles. Isochores for both Type A and Type B fluids intersect the estimated peak conditions of 500 degrees C and 3-3.5 kbar, indicating that fluids with different compositions were trapped in the marbles during metamorphic veining. In greenschist-facies metapelites, isochores for Type C fluids cross the metamorphic P-T conditions at 2 kbar and 400 degrees C. Overall isochore distribution indicates early cooling (500-400 degrees C) without significant uplift. For the N-2-bearing Type B fluid inclusions, the delta(13)C value of the CO2 is 2.5 parts per thousand PDB and the delta D of H2O is 0 parts per thousand. The delta(18)O of host vein-quartz is 20.3 parts per thousand, and delta(13)C Of calcite within the host vein and in marble are both -1.5 parts per thousand. Tn contrast, the delta(13)C values of carbonate veins containing Type A H2O-CO2-CH4 fluids are lighter (-5.3 parts per thousand) than in the host marble (-2.9 to -1.5 parts per thousand). Type A fluid inclusions have light delta(13)C CO2 values (0.1 parts per thousand) and delta D H2O values (-84 parts per thousand). Type C inclusions also have light delta(13)C CO2 values (-3.1 parts per thousand), and variable delta D H2O (-30 and 98 parts per thousand). Fluid-inclusion and stable-isotope studies indicate that the analysed quartz-calcite veins formed by local processes in a similar structural context. The veins preserved distinct fluid-inclusion and isotopic compositions, indicating diverse sources of fluids: internally derived metamorphic H2O-CO2-N-2 mixtures (Type B), and externally derived H2O-CO2 fluids (Types A and C), interpreted in terms of mixing with a magmatic component, probably derived from local granitic rocks
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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