1,720,956 research outputs found
COOLING HISTORY OF A DYKE ON ALICUDI (AEOLIAN ISLANDS) FROM INTRACRYSTALLINE FE-2+-MG EXCHANGE-REACTION IN CLINOPYROXENE
No full textSeven rock samples were collected from the cross-section of a 2.8-m-thick andesitic dyke on Alicudi (Aeolian Islands, Sicily).
Thin section microprobe analysis of phenocrysts (pyroxenes, olivine and plagioclase) and whole-rock X-ray fluorescence show that samples at the chilled margins are sharply distinct, with the highest Mg, Cr and Ni contents.
Seven single crystals of clinopyroxene were analysed by microprobe techniques, while their structures were refined using the X-ray diffraction method; different Mg-Fe2+ ordering in the M2 and M1 sites of clinopyroxene were observed across the dyke section.
The equilibration temperature, evaluated by applying the geothermometer proposed by Molin & Zanazzi (1991), gives the highest values at the dyke margins (850-degrees-C) and the lowest values close to the middle (630-degrees-C).
By applying the theoretical model of Jaeger (1968) for the cooling of volcanic bodies, as well as the Kudo & Weill (1970) plagioclase-liquid geothermometer (modified by Mathez, 1973), it was possible to calculate the cooling rates across the dyke section: from 8 and 34-degrees-C/h near the boundaries to 1-degrees-C/h in the middle
CRYSTAL-CHEMISTRY OF CLINOPYROXENES FROM FILICUDI AND SALINA (AEOLIAN ISLANDS, ITALY) - GEOTHERMOMETRY AND BAROMETRY
No full textSingle clinopyroxene crystals from calc-alkaline volcanic rocks of Filicudi and Salina (Aeolian Islands, Italy) have been studied by X-ray diffraction and microprobe techniques to examine the relations between clinopyroxene crystal chemistry and the petrological features of the host rocks. The clinopyroxenes of Filicudi and Salina are chemically quite similar, but two different groups can be distinguished, diopsides and augites, often coexisting in the same rock. The Filicudi clinopyroxenes are generally characterized by a smaller cell volume and a more closely-packed structure; comparison with crystals from different environments suggests a higher pressure of crystallization for the Filicudi rocks.
A relationship between SiO2 content of magma and clinopyroxene intracrystalline equilibration temperature is discussed in terms of different cooling history due to the more pronounced explosive character of the more silicic magmas, leading to more rapid quenching of eruption products. For a given rock-type, clinopyroxene equilibration temperature is also a function of sample position in the volcanic sequence, to which different cooling rates can be assigned
Rockfall Hazard Analysis and prevention in the Middle-Eastern sector of the Cinque Terre area (Italy)
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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
Rockfall Risk Assessment and Management Along the “Via dell’Amore” (Lovers’ Lane) in the Cinque Terre National Park (Italy)
No full textThe Via dell’Amore (Lovers’ Lane) is a 1 km long coastal path linking Manarola with
Riomaggiore, the two eastern villages at the “Cinque Terre”. Realized at the start of the
nineteenth century as a service road for the modernization of the railway, it’s now considered
as one of the highlights of the Cinque Terre National Park. The trail has been historically
affected by rockfall phenomena: the bedrock is made up of heterogeneous rock masses; blocks
diameter ranges from 0.5 to 2 m, determining high speed values during their fall. The
probability of a fatal event to occur is high, as recently proved by the four Australian women
injured in September 2012: this occurrence caused the closure of the trail up to the present.
The actual risk level is not acceptable, taking in consideration also the elevated vulnerability
values. The main goal is to decrease both rockfall hazard and vulnerability: in the first place,
through passive slope protection methods such as rockfall shelters and protecting wire meshes;
in the second instance, through an early warning system connected to the civil protection corp
and an environmental education program involving tourists and inhabitants
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
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