1,721,032 research outputs found
Global variations in abyssal peridotite compositions
No full textPublisher's PDFAbyssal peridotites are ultramafic rocks collected frommid-ocean ridges that are the residues of adiabatic decompression
melting. Their compositions provide information on the degree of melting and melt–rock interaction
involved in the formation of oceanic lithosphere, as well as providing constraints on pre-existing mantle heterogeneities.
This review presents a compilation of abyssal peridotite geochemical data (modes, mineral major
elements, and clinopyroxene trace elements) for N1200 samples from 53 localities on 6 major ridge systems.
On the basis of composition and petrography, peridotites are classified into one of five lithological groups: (1) residual
peridotite, (2) dunite, (3) gabbro-veined and/or plagioclase-bearing peridotite, (4) pyroxenite-veined
peridotite, and (5) other types of melt-added peridotite. Almost a third of abyssal peridotites are veined, indicating
that the oceanic lithospheric mantle is more fertile, on average, than estimates based on residual peridotites
alone imply. All veins appear to have formed recently during melt transport beneath the ridge, though some pyroxenites
may be derived from melting of recycled oceanic crust.
A limited number of samples are available at intermediate and fast spreading rates, with samples from the East
Pacific Rise indicating high degrees of melting. At slow and ultra-slow spreading rates, residual abyssal peridotites
define a large (0–15% modal clinopyroxene and spinel Cr#=0.1–0.6) compositional range. These variations
do not match the prediction for how degree of melting should vary as a function of spreading rate. Instead, the
compositional ranges of residual peridotites are derived from a combination of melting, melt–rock interaction
and pre-existing compositional variability, where melt–rock interaction is used here as a general term to refer
to the wide range of processes that can occur during melt transport in the mantle. Globally, ~10% of abyssal peridotites
are refractory (0% clinopyroxene, spinel Cr# N 0.5, bulk Al2O3 b 1wt.%) and someridge sections are dominated
by harzburgiteswhile lacking a significant basaltic crust. Abyssal ultramafic samples thus indicate that the
mantle ismulti-component, probably consisting of at least three components (lherzolite, harzburgite, and pyroxenite).
Overall, the large compositional rangeamong residual andmelt-added peridotites implies that the oceanic
lithospheric mantle is heterogeneous, which will lead to the generation of further heterogeneities upon subduction
back into the mantle.University of Delaware. Department of Geological Sciences
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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