1,721,023 research outputs found
Immiscibilité entre liquides silicatés dans les mésostases et les inclusions vitreuses des andésites basiques de Santorin (Arc Egéen)
No full textImmiscibility textures have been observed in basic andesites from the Skaros series, Santorini (Greece). They occur both in the groundmass as Fe-rich brown glassy globules enclosed in a Si-rich clear glass, and in plagioclase phenocrysts as minute Si-rich glassy globules within a Fe-rich brown glass. The clear glass exhibits a granitic normative composition with high Si, Al, Na and K contents whereas the brown glass is characterized by high Fe, Ti, Mg, Ca and Mn contents with a pyroxenitic composition. The present study suggests that silicate liquid immiscibility is controlled in plagioclase phenocrysts by concentration gradients at the liquid-mineral interface, and in the groundmass by liquid composition (especially Ti).L'étude pétrographique des andésites basiques du centre éruptif de Skaros (Santorin) permet de mettre en évidence l'existence de textures d' immiscibilité dans le verre résiduel de la mésostase (globules de verre brun enrichi en Fe disséminés dans un verre clair enrichi en Si), ainsi que dans les inclusions vitreuses des phénocristaux de plagioclase (le verre brun enrichi en Fe englobe des globules de verre clair enrichi en Si). Le verre clair présente une composition normative typiquement granitique tandis que le verre brun se caractérise par une composition normative pyroxénitique. Cette étude suggère que le développement de liquides immiscibles dans les inclusions vitreuses de plagioclase résulterait du gradient de concentration à l'interface liquide-minéral. L' immiscibilité dans la mésostase serait principalement contrôlée par la composition chimique du liquide magmatique (essentiellement par les teneurs en Ti).Luais Béatrice. Immiscibilité entre liquides silicatés dans les mésostases et les inclusions vitreuses des andésites basiques de Santorin (Arc Egéen). In: Bulletin de Minéralogie, volume 110, 1, 1987. pp. 93-109
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
Origin of the mass-dependent germanium isotopic continuum in the early Solar System
No full textInternational audienceThe warm, reduced, volatile-poor inner Solar System and cold, oxidized, volatile-rich outer Solar System are characterized by neutron-poor and neutron-rich isotopic anomalies, respectively. Nucleosynthetic isotopic anomalies recorded in meteorites, asteroidal bodies, and planets are thus indicative of their regions of formation. However, whether these reservoirs evolved as closed systems or underwent some degree of intermixing remains uncertain. Here, we report new high-precision mass-dependent germanium isotopic compositions revealing that carbonaceous chondrites exhibit higher and more variable d74/70 Ge values than ordinary chondrites, defining a strong continuous trend in both Ge concentrations and isotopic compositions. We highlight that similar strong correlations with matrix mass fraction occur across all chondrite groups, but that the non-carbonaceous (NCC, inner Solar System)-carbonaceous (CC, outer Solar System) dichotomy observed in e 48 Ca, e 54 Cr, e 50 Ti, and e64 Ni nucleosynthetic anomalies is maintained. In the d 74/70 Ge vs. e 48 Ca, e54 Cr, e 50 Ti, and e 64 Ni spaces, two distinct mixing lines are resolved within both the NCC and CC reservoirs, between NCC and CC-type chondrules and CI-type matrix. Extending the NCC-CI chondrite correlation to primitive achondrites, main-group pallasites, and the mantles of Mars and Earth reveals that these silicate reservoirs plot away from the OC-CI mixing lines, highlighting the possible existence of a neutron-poor matrix component in the inner Solar System. Overall, the Ge isotopic systematics of the Solar System suggest that chondrules and their matrices did not form exclusively in a single reservoir, but rather formed throughout the inner and outer Solar System
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
Temporal changes in Nd isotopic composition of Piton de la Fournaise magmatism (Réunion Island, Indian Ocean)
No full textInternational audienceA Nd isotopic study of twelve historical samples and fifty-seven core samples covering the last 530 ka of volcanic activity of the Piton de la Fournaise volcano of Réunion Island was undertaken, with additional new Sr isotopic analyses of historical samples. The core samples were obtained from the cliffs of the deep (ca.1000 m) canyons of the Remparts and Langevin Rivers. Four types of rocks, namely basalts (MgO = 5-9 wt.%), high-Mg basalts (MgO = 10-20 wt.%), plagioclase-rich basalts, and differentiated samples (SiO2 = 48-53 wt.%) occur randomly throughout the lava sections. The overall variations in Nd isotopic ratios (0.512751 to 0.512902) are small, but significant. The range of Nd isotopic variations is larger than previously described in the literature, and extends toward lower values. Nd isotopic ratios increase through time and are broadly negatively correlated with the alkalinity index. The older alkaline Remparts samples (527-290 ka) (average ɛNd = +3.26) exhibit lower 143Nd/144Nd ratios than the younger tholeiitic Langevin samples (70-40 ka) (average ɛNd = +4.17) and the historical lavas (1901-1956) (average ɛNd = +4.74). Comparison of 143Nd/144Nd ratios with available 87Sr/86Sr ratios on the same set of samples (Remparts and Langevin series [Albarède et al., 1997]; historical series, this study) shows no correlation between Sr and Nd isotopes. It is suggested that the high Nd isotopic ratios of historical tholeiitic samples would be representative of the isotopic composition of the Réunion plume. The increase in Nd isotopic ratios over 530 ka reflects the effect of decreasing contribution of an enriched component to the Réunion plume through time. This enriched component would occur as isolated blobs in the mantle source
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