1,720,968 research outputs found
Experimental study on a primary basanite from McMurdo Volcanic Group, Antarctica: Inference on its mantle source
No full textExperiments to reconstruct the liquidus curve and establish the phase relationships of a basanite (Mg# = 72) from the McMurdo Volcanic Group, (thought to represent a nearly primary magma) used 1.0-3.0 GPa and 1175-1550 degrees C. The results suggest that this basanite could be generated by partial melting either of a spinel Iherzolite (at P = 1.5-2.0 GPa and T = 1390-1490 degrees C) or of a garnet pyroxenite (at P > 3.0 GPa and T > 1550 degrees C) source. Several lines of petrological and geochemical evidence support the latter hypothesis. Moreover, experimental results indicate the presence of mica in the source if it is assumed that the magma lost some water during its ascent to the surface. This is supported by the presence of mica and amphibole-bearing mantle xenoliths hosted in the most primitive volcanic rocks of the McMurdo Volcanic Group. These results and observations suggest that the source of magmas underwent metasomatism prior to partial melting
Experimental determination of plagioclase and clinopyroxene crystal growth rates in an anhydrous trachybasalt from Mt Etna (Italy)
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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
Metasomatism induced by alkaline magma in the upper mantle of northern Victoria Land (Antarctica): An experimental approach
No full textMagma generation in the Ross Sea system is related to partial melting of strongly metasomatized mantle sources where amphibole most probably plays a crucial role. In this context, metasomatism induced by a mela-nephelinite melt in lithospheric mantle of the Mt. Melbourne Volcanic Province (northern Victoria Land (NVL), Antarctica) was investigated experimentally studying the effects of melt interaction with lherzolite at 1.5–2.0 GPa and
T 1⁄4 975–1300 8C, and wehrlite at 1.0 GPa and T 1⁄4 1050–1250 8C. The experiments were designed to induce melt infiltration into the ultramafic rocks. The observed modifications in minerals
are compared with those found in mantle xenoliths from NVL. The effects of metasomatic modifications are evaluated on the basis of run temperature, distance from the infiltrating melt and
the diffusion rates of chemical components. Both in lherzolite and wehrlite, clinopyroxene exhibits large compositional variations ranging from primary diopside to high-Mg–Cr–(Na) augitic
and omphacitic clinopyroxenes in lherzolite, and to low-Mg and high-Ti–Al–Fe–Na augites in wehrlite. Olivine (in wehrlite) and spinel (in lherzolite) are also compositionally modified: the
former shows enrichment in Fe and the latter displays a higher Cr/(Cr þ Al) ratio. The systematic variations in mineral compositions imply modifications of the chemistry of the infiltrating melt as recorded by the glass veinlets and patches observed in some charges. In experiments involving
wehrlite paragenesis, the glass composition approaches that of melt patches associated with both amphibole-free and amphibole-bearing natural samples, and is related to olivine þ clinopyroxene crystallization coupled with primary clinopyroxene dissolution at the contact between the metasomatizing melt and the solid matrix. Even if amphibole crystallization was
not attained in the experiments, we were able to explain the occurrence of amphibole in the natural system considering that in this case a hot metasomatizing melt infiltrates a cooler matrix
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
Seismic reflection reprocessing procedures in the frame of the SIRIPRO 1 crustal profile across Sicily.
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