1,720,973 research outputs found
Two generations of Variscan garnet: Implications from a petrochronological study of a high-grade Avalonia-derived paragneiss from the Drosendorf unit, Bohemian Massif
No full textNew evidence for the prograde and retrograde PT-path of high-pressure granulites, Moldanubian Zone, Lower Austria, by Zr-in-rutile thermometry and garnet diffusion modelling
Full text linkCompositional zoning in garnet, mineral inclusions and the application of the Zr-in-rutile thermometry on rutile inclusions in garnet in combination with conventional geothermobarometry and thermodynamic modelling allows a reconstruction of the prograde pressure-temperature evolution in felsic and mafic high-pressure granulites from the Moldanubian Zone, Bohemian Massif, Lower Austria. Most garnets in these rocks show homogeneous core compositions with high grossular contents (~30 mol%), while their rim zones have a markedly reduced grossular content. Rutile inclusions in the grossular rich garnet cores have low Zr concentrations (400 to 1300 ppm) indicating a formation temperature of ~810–820 °C which implies that the garnet host grew at these temperature conditions as well. Based on numerous polycrystalline melt inclusions, high Ti-biotite relics and a generally high Ti concentration in garnet cores, the peritectic biotite breakdown reaction is considered to be responsible for a first garnet growth, now observed as high-grossular garnet cores. The corresponding pressure is estimated to be in the range of 1.6 to 2.5 GPa, based on experimentally determined biotite breakdown reactions, thermodynamic modelling and the occurrence of high-Ti biotite in garnet cores. Rutile inclusions in low-Ca garnet rims contain significantly higher Zr concentrations (1700 to 5800 ppm) resulting in ultrahigh temperatures of ~1030 °C. Similar temperature as well as corresponding pressure estimates of 1000 ± 50 °C and 1.60 ± 0.10 GPa were obtained by geothermobarometry and thermodynamic modelling using garnet rim and re-integrated ternary feldspar compositions. These high pressure and ultrahigh temperature conditions are well known from literature for these granulites. The proposed two-phase garnet growth is not only seen in different temperatures obtained from rutile inclusions in garnet core and rim areas, but also in discontinuous trace (Cr, Ga, P, Ti, V, Zr) and heavy rare earth element profiles across garnet porphyroblasts, implying a different reaction mechanism for garnet rim growth. This second phase of garnet growth must have occurred during near isobaric heating to the ultrahigh temperature peak, most likely even at slightly lower pressures compared to the garnet core growth.
By applying a binary Fe-Mg diffusion model to strongly zoned garnet grains a maximum timescale of 5–6 million years was estimated for the exhumation and cooling process, assuming a linear cooling path from 1000 °C at 1.6 GPa to 760 °C at 0.8 GPa. This short-lived ultrahigh temperature event corresponds to cooling and exhumation rates of 40–50 °C Ma−1 and 5.3–6.6 mm y−1, respectively
Formation of low‐pressure reaction textures during near‐isothermal exhumation of hot orogenic crust (Bohemian Massif, Austria)
No full textCarboniferous Polymetamorphism Recorded in Paragneiss-Migmatites from the Bavarian Unit (Moldanubian Superunit, Upper Austria): Implications for the Tectonothermal Evolution at the End of the Variscan Orogeny
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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
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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