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Magmatic crystallisation of Cr-Al diopside and Al-Fe3+ diopside from the ancient alkaline basalts (Mt. Etna, Sicily)
No full textThe Role of Chaotic Dynamics and Flow Fields in the Development of Disequilibrium Textures in Volcanic Rocks
No full textDisequilibrium textures in minerals are often observed in igneous rocks. Their occurrence is commonly related to the variation of intensive variables (e.g. pressure, temperature, etc.) that perturbed a pre-existing state of equilibrium. However, if the variation of intensive variables provides a reliable explanation for the occurrence of disequilibrium textures in minerals, it does not explain why, over very short length scales (<1–2 cm), in the same rock, crystals of the same mineral phase often appear to have reacted very differently to the disequilibrium process. A good example of this puzzling phenomenon is given by clinopyroxene phenocrysts occurring in the Santa Venera alkali basalt (Mt. Etna, Italy), in which a great variety of disequilibrium textures, coexisting on very short length scales (<1–2 cm), are observed. Clinopyroxenes exhibit heterogeneously resorbed Cr–Al diopside cores around which a rim of Al–Fe3+ diopside, having a highly variable area, has grown. The area of the Al–Fe3+ diopside rim is used as a discriminant parameter for the studied pyroxenes as it displays a tri-modal statistical distribution. In addition, the chemical zoning from the core to the rim of pyroxenes exhibits both continuous and discontinuous patterns. These continuous and discontinuous patterns are associated with crystals having low and high values of the rim area, respectively. To explain these zoning patterns, a mixing process between magmas having different geochemical and thermodynamic properties, governed by chaotic dynamics, is proposed. In particular, the occurrence in the same system, and at short length scales, of regular and chaotic regions is suggested as the basic dynamic inducing a heterogeneous distribution of the magmas involved in the mixing process; this leads to a strong control on the propagation of the disequilibrium phenomena and on the crystallization of pyroxenes, even over short length scales. The occurrence of regular and chaotic regions within the same magmatic system can explain the entire spectrum of features observed in the studied pyroxenes, from the occurrence of the tri-modal distribution of rim areas to the presence of two distinct patterns of chemical zoning, continuous and discontinuous, from the core to the rim of pyroxenes
Illegitimate Pyroxenes or Chaotic Dynamics? The Role of Flow Fields in the Petrogenesis of Igneous Rocks
No full textIllegitimate Pyroxenes or Chaotic Dynamics? The Role of Flow Fields in the Petrogenesis of Igneous Rocks
No full text
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
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