1,720,993 research outputs found
Carbonate dissolution during subduction revealed by diamond-bearing rocks from the Alps
No full textSubduction zones modulate the global carbon cycle. Carbon is transported into the mantle by the subducting slab and returned to the surface by degassing at arc volcanoes above the subduction zone1,2. However, the mechanisms for the transfer of carbon from the subducting slab and sediments into the overlying mantle wedge are poorly understood. Decarbonation-a metamorphic reaction between silicate and carbonate minerals that releases CO2 -was thought to be the primary mechanism. Yet, thermodynamic models show that decarbonation occurs at much greater pressures and temperatures than those found in typical subduction zones. Carbon should therefore be retained in the slab and transported to great depths in the mantle, rather than supply the arc volcanoes. Here we identify diamonds in ultrahigh-pressure rocks from the Italian western Alps that have an oceanic origin. We assess the geochemistry of diamond-bearing fluid inclusions and find that they contain bicarbonate, carbonate and sulphate ions, silica monomers, and crystals of carbonate and silicate. This fluid geochemistry indicates that carbon was released from the slab at relatively shallow depths through dissolution, not decarbonation. We conclude that dissolution, driven by fluids released from the subducted slab, is an important mechanism for the transfer of carbon into the mantle and ultimately back into the atmosphere, helping to balance the carbon flux. © 2011 Macmillan Publishers Limited. All rights reserved
THE KAKOPETROS AND RAVDOUCHA IRON-OXIDE DEPOSITS, WESTERN CRETE, GREECE:FLUID TRANSPORT AND MINERALIZATION WITHIN A DETACHMENT ZONE
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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
A calibration of the triple oxygen isotope fractionation in the SiO2-H2O system and applications to natural samples
No full textIt is now recognized that variations in the Delta O-17 of terrestrial materials resulting from purely mass dependent fractionations, though small, have geological significance. In this study, the delta O-18 and delta O-17 values of selected low temperature quartz and silica samples were measured in order to derive the quartz-water fractionation-temperature relationship for the three oxygen isotope system. A O-18/O-16 quartz-water fractionation equation valid for all temperatures was generated from published high temperature exchange experiments and low temperature empirical estimates and is given by 1000 ln alpha(18O/16O)(qz-H2O) = 4.20(0.11)x10(6)/T-2 - 3.3(0.2)x1000/T (T in Kelvins). The equilibrium delta O-17-delta O-18 relationship is given by the equation ln alpha(17O/16O) = theta ln alpha(18O/16O). The variation of theta with temperature for the quartz-water system was determined empirically using low temperature marine diatoms, microcrystalline quartz and a modern sinter sample. A best fit to the data give the equation theta(SiO2-H2O) = - (1.85+0.04)/T + 0.5305 , indistinguishable from an earlier theoretical estimate. Application of the quartz-water triple isotope system to low temperature samples provides constraints on both temperature and composition of the water with which the silica last equilibrated. Authigenic quartz crystallization temperatures cluster around 50 degrees C, which are lower than many previous estimates. The combined delta O-18 and delta O-17 values of samples considered to be in equilibrium with ocean or meteoric waters can be used to estimate both formation temperatures and the delta O-18 value of the meteoric water. Unlike other multiple isotopes systems, such as combined H and O isotopes in cherts, the oxygen source and diagenetic potential for both O-17/O-16 and O-18/O-16 ratios are identical, simplifying interpretations from ancient samples. (C) 2016 Elsevier Ltd. All rights reserved.National Science Foundation [NSF EAR 1551226, EAR 1450802
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
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
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