1,721,003 research outputs found
Constraining slab recycling under Vesuvius volcano from combined U-series and non-traditional stable isotope (Mo, 238U/235U) data
No full textThe fate of deeply subducted oceanic crust and overlying
sediments is of great importance for its role in the generation
of magmas in subduction-relatedgeodynamic settings. Italian
volcanoes, and Vesuvius in particular, are good laboratories to
investigate these processes due to their strong enrichment in K
and incompatible trace element that requires a significant
amount of sediment material recycled into the mantle.
Volcanic rocks from Vesuvius display ubiquitous 238U excesses
(up to 27%), a feature that is unusual in such enriched
subduction-related magmas. In addition they have among the
highest (231Pa/235U) and (226Ra/230Th) reported for arc rocks.
These characteristics require a recent addition of a high-U
component to the mantle beneath the Italy. In order to
constrain the origin and nature of this slab-related component
we present new data on non-traditional stable isotopes (Mo,
238U/235U) on both volcanic rocks and possible sedimentary
end-members. Non-traditional isotope systems such as Mo and
238U/235U are sensitive to redox-related isotopic fractionation
on the Earth’s surface, hence they may provide key
information on the type of material recycled from the
subducting slab to the mantle wedge.
The combined use of these different isotope systematics
will provide a wider picture of the mechanism and timescales
of the processes occurring from slab subduction to magmas
generation and ascent above subduction zones
Potassic and ultrapotassic magmatism in the circum-Tyrrhenian region: Significance of carbonated pelitic vs. pelitic sediment recycling at destructive plate margins
No full textThe central-western Mediterranean is one of the most important areas on Earth for studying subduction-related potassic and ultrapotassic magmatism. In the circum-Tyrrhenian area leucite-free (i.e., lamproite) and leucite-bearing (i.e., kamafugite, leucitite, and plagioleucitite) ultrapotassic rocks have been emplaced and are associated with shoshonites and high-K calc-alkaline volcanic rocks. Four different magmatic provinces are recognised from this area. Eastward and then south-eastward migration of magmatism with time occurred following roll-back of the subducting plate. Leucite-free silica-rich lamproites are restricted to the early stages of magmatism, associated with shoshonites and high-K calc-alkaline volcanic rocks. Present day volcanic activity is restricted to the Neapolitan district where ultrapotassic rocks with variable geochemical and isotopic characteristics occur. Ultrapotassic rocks are strongly enriched in incompatible trace elements with variable fractionation of Ta, Nb, and Ti with respect to Th and large ion lithophile elements. Mafic ultrapotassic rocks are also variably enriched in radiogenic Sr and Pb and unradiogenic Nd. The main geochemical and isotopic signatures result from sediment recycling within the upper mantle via subduction. Selected trace element ratios suggest that high temperatures are required to generate sediment-derived melts. Recycling of carbonated pelites play an important role in the Roman province controlling the genesis of leucite-bearing magmas. Large volumes of metasomatic components are predicted to be accommodated within a vein network in the sub-continental lithospheric mantle. Partial melting of the pure vein mineralogy is likely to generate ultrapotassic magmas of either lamproitic or kamafugitic nature. Over time, increased interaction between the metasomatic vein lithology and the surrounding mantle dilutes the alkaline component producing shoshonites and high-K calc-alkaline rocks. The addition of a further subduction-related component shortly before magma generation is required to explain the isotopic composition of rocks from the Neapolitan district. In the last phases of circum-Tyrrhenian evolution, a within-plate component appears within south-eastern Italy. This component is evident at Vulture volcano, in the Lucanian Magmatic province (SE Italy). © 2009 Elsevier B.V. All rights reserved
A comparative 87Sr/86Sr study in Red and White wines to validate its use as geochemical tracer for the geographical origin of wine
No full textRecently high precision 87Sr/86Sr analyses have shown that Red wines keep the isotopic values of the vineyard
substratum. Indeed, neither biological nor winemaking and aging processes are able to change the 87Sr/86Sr values
through the oenological food chain from grapes to Red wine. In addition, 87Sr/86Sr of Red wines and those of rocks
from the geological substratum of their vineyards correlate directly. The same holds not true for White wines,
apparently. To investigate this discrepancy, 87Sr/86Sr has been determined for the entire production chain, from
terroir to final product, of Red and White wines from the same vineyard. Sr-isotope data have been also determined
for the young pyroclastic rocks of the geological substratum, and the soil of the vineyard to disambiguate the
original contribution to the 87Sr/86Sr values of wines. Further Sr-isotope data have been determined on additives used
for fining the White wine. The analytical results do not show significant differences between oenological food
chains of Red and White wines. Preliminary data indicate that 87Sr/86Sr does not change passing from grape juices to
wine in all cases under consideration. As a corollary neither yeast nor bentonite added during vinification of both
Red and White wines do affect their Sr-isotopic values. On the other hand, 87Sr/86Sr of Red and White wines appears
to be significantly lower than values observed in rocks of their substrata. Further experiments performed on this
pilot winery would be useful to shed some lights on this issue
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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