1,720,970 research outputs found
Magma dynamics as inferred by plagioclase textural and compositional zoning at Mount Etna volcano
No full textA new perspective on the geochemical signature of Mt. Etna alkaline magmas
No full textThe occurrence of LREE enrichment and HREE
fractionation (LaN/YbN = 18) led many authors to hypothesize
the presence of residual phases in the source of Etnean
alkaline magmas that preferentially retain HREE, such as
garnet. The occurrence of garnet was commonly bounded to
lherzolites, thus implying the onset of partial melting at depth
greater than 80 km. This would indicate the occurrence of a
thermal regime related to an astenospheric plume-like
structure, whose evidence is still matter of debate. On the
other hand, if such a structure does not occur, the melting
process should be mainly under the control of slight pressure
changes induced by regional lithospheric stretching at more
shallow depth. Recent work has shown that partial melting of
a source composed of both spinel lherzolite and garnet
pyroxenite can produce sub-alkaline magmas, which can
preserve a garnet signature at more shallow depth. Here, we
investigate the role that partial melting of a heterogeneous
metasomatized source, constituted of spinel lherzolite and
garnet pyroxenite, can have in producing a trace element
signature consistent with that observed for Etnean alkaline
magmas. Xenoliths of deep provenance found in the Hyblean
area indicate that silicate melts, and related metasomatic
fluids, may have intruded a spinel lherzolite mantle to give
origin to a garnet-bearing pyroxenite. As a result, the spinel
lherzolite mantle is veined by garnet pyroxenite where phases
related to metasomatizing agents, such as amphibole and
phlogopite, have been stabilized. Mass balance calculations
have been performed for simulating partial melting of such a
source. Results have been compared with three representative
mantle-equilibrated magmas, calculated by adding an
ultramafic assemblage to compositions of the prehistoric lavas
of Mt. Maletto, and of the 1763 and 2005 eruptions. Different
proportions of spinel lherzolite and garnet pyroxenite, along
with variable modal contents of metasomatic phases, can
account for the trace element signature of the large spectrum
of Etnean alkaline magmas and for their geochemical
variability through time
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
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