1,721,006 research outputs found
Gabbroic dikelets in serpentinized peridotites from the Mid-Atlantic Ridge at 23°20′N
No full textMantle-derived peridotites sampled on the seafloor at 23° N along the MidAtlantic Ridge during the Hydrosnake and R.V. Akademic Mstislav Keldysh cruises show evidence of minor magmatic intrusion that produced millimetre to centimetre thick gabbroic dikelets. The nature of the intruding magma and the time relationships between intrusion events and tectonic evolution of the host peridotites is inferred from the mineralogy and textural features of veins cutting the peridotites. The occurrence of Fe-Ti-rich minerals and of zircon in the veins suggests an evolved, basaltic composition of the fluid. Pyroxene-rich, plagioclase-free veins probably represent pyroxenite dikelets inside the peridotites. In all cases, melt intrusion followed ductile deformation affecting the mantle-derived ultramafics. These observations fit with a model in which gabbroic intrusions are emplaced in mantle rocks at shallow depths beneath the ridge axis
Multistage asthenospheric melt/rock reaction in the ultraslow eastern SWIR mantle
No full textVery small amounts of melt are produced during mantle upwelling beneath the ultraslow spreading South West
Indian Ridge. Sectors of this Oceanic Ridge are characterized by nearly amagmatic spreading with rare limited
eruptions of basalts spotting a mantle-derived serpentinitic crust. A large peridotite dataset was recovered during the
Smoothseafloor French expedition leaded by D. Sauter and M. Cannat in 2005 (Sauter et al., 2013). Mantle-derived
rocks show a significant modal variability from the sample to the dredge scale with frequent occurrences of millimetric
to centimetric spinel-bearing pyroxenitic veins. Mantle residua record a multistage reactional history between small
amount of transient melts and variably depleted mantle parcels. Incomplete mineral replacements are widespread
showing that both pyroxenes are repeatedly dissolved and recrystallized leaving poekilitic pyroxene and spinel textures.
Reacting conditions are modelled assuming an incremental open-system melting model under variable critical
porosity/F ratios (Seyler et al., 2011; Brunelli et al., 2014). Incoming melts result to be generated by low degrees of
melting in the garnet field then reacting with the rock under near-batch conditions, i.e. at low rates of melt extraction
with respect to the actual rock porosity. As a consequence Na (and LREE) countertrends with melting indicators as
mineral Cr# and concentration of the moderately incompatible elements (HREE, HFSE). This results in rotation of the
REE patterns around a pivot element instead of showing progressive depletion as expected after suboceanic mantle
decompression.
Brunelli D., Paganelli E. & Seyler, M. 2014. Percolation of enriched melts during incremental open-system melting in
the spinel field: A REE approach to abyssal peridotites from the Southwest Indian Ridge. Geoch. et Cosmoch. Acta,
127, 190–203. doi:10.1016/j.gca.2013.11.040.
Sauter D., Cannat M., Searle R. 2013. Continuous exhumation of mantle-derived rocks at the Southwest Indian Ridge
for 11 million years. Nature Geosci., 6(4), 1–7. doi:10.1038/ngeo1771.
Seyler M., Brunelli D., Toplis M. J. & Mével C. (2011). Multiscale chemical heterogeneities beneath the eastern
Southwest Indian Ridge (52°E-68°E): Trace element compositions of along-axis dredged peridotites. Geochem.
Geophys. Geosyst., 12, Q0AC15. doi:10.1029/2011gc003585
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
Asthenospheric processes beneath the ultraslow Smoothseafloor region in the eastern South West Indian Ridge
No full textMantle melting at ultraslow spreading ridges is constrained by the low potential temperature and thicker-thannormal
LID that limits the extent of the melting column. As a result very small amounts of melts are produced
inhibiting the formation of a “normal” oceanic lithosphere and leading to a purely tectonic seafloor extension dominated
by serpentinization: the recently investigated Smoothseafloor type spreading (Sauter et al., 2013). At depth the reaction
of very small amounts of percolating melts and host asthenospheric mantle leaves traces of the melt/rock reactions as
incomplete mineral replacement and strongly variable modal distribution at short scale (dm). Enstatitic, and to a less
extent diopsidic, pyroxenes appear to be repeatedly dissolved and recrystallized leaving poekilitic pyroxene and spinel
leftovers. Melts enriched in incompatible elements are possibly generated in the garnet field then reacting with the rock
under near-batch conditions, i.e. at low rates of melt extraction with respect to the actual rock porosity (Brunelli et al.,
2014). Prolonged pyroxenes’ dissolution-recrystallization results in enhanced enrichment of the most incompatible
elements in the percolating melts that only occasionally are extracted from the system. As a consequence Na (and
LREE) countertrends with the melting indicators as mineral Cr# and concentration of the moderately incompatible
elements (HREE, HFSE). Accordingly the associated basalts are characterized by a strong Na enrichment and
compositional trends separated from those generated in the surrounding regions.
Brunelli D., Paganelli E. & Seyler M. 2014. Percolation of enriched melts during incremental open-system melting in
the spinel field: A REE approach to abyssal peridotites from the Southwest Indian Ridge. Geochimica et Cosmochimica
Acta, 127, 190–203. doi:10.1016/j.gca.2013.11.040
Sauter D., Cannat M., Rouméjon S., Andreani M., Birot D., Bronner A., Searle R. 2013. Continuous exhumation of
mantle-derived rocks at the Southwest Indian Ridge for 11 million years. Nature Geoscience, 6(4), 1–7.
doi:10.1038/ngeo1771
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