1,720,978 research outputs found
Evolution of the sources of ttg and associated rocks during the archean from in-situ 87sr/86sr isotope analysis of apatite by la-mc-icpms
No full textRadiogenic isotopes provide an important means towards elucidating Archean crustal
evolution. The global Hf and Nd isotope record of Archean crustal fragments has been
instrumental to unveiling the history of ancient crustal growth and differentiation. The Rb-Sr
system could provide valuable complementary constraints in this regard, as this system is
particularly sensitive to the composition of magmatic rocks, and the age of their source.
Application of this system has so far been complicated, however, by its susceptibility to isotope
re-equilibration or alteration of the Rb/Sr parent-daughter ratio. In-situ Sr isotope analysis of
primary igneous minerals with very low Rb/Sr, such as apatite, provides a new means to
determine the initial 87Sr/86Sr (87Sr/86Sri) values for igneous rocks directly. In this study, we
apply in-situ Sr isotope analysis of apatite by LA-MC-ICPMS to tonalite-trondhjemitegranodiorite
(TTG) rocks and end-member sanukitoids from Archean cratons worldwide. The
87Sr/86Sri values of sanukitoids are relatively radiogenic, supporting the model in which such
rocks are formed by flux melting of a mantle strongly enriched by metasomatism, possibly by
slab-derived fluids. The 87Sr/86Sri values for TTGs formed between 3.72 and 3.45 Ga are
generally radiogenic, indicating aged amphibolite sources. The 87Sr/86Sri values of younger TTGs
are systematically lower and were derived from mafic sources that had a prehistory, on average,
of not more than 0.2 Gyr. This evolution matches with observations from Hf isotopes for TTGs
of similar age and indicates a systematic change in the nature or efficiency of TTG crust
formation during the Paleoarchean. In-situ Sr isotope analysis of apatite provides a useful
method to uncover the Sr record of the early continental crust, and enables constraints on local
source evolution and the general two-step evolutionary process of Archean crust formation.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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