1,720,977 research outputs found
Cambrian arc evolution along the SE Gondwana active margin: A synthesis from Tasmania‐New Zealand‐Australia‐Antarctica correlations
No full textBelts of Cambrian rocks with are affinities in eastern Australia, Tasmania, New Zealand, and Antarctica are part of a single convergent margin, active over 30-40 Ma from the latest Early Cambrian to the Late Cambrian. Two Of the most complete sequences are exposed in western Tasmania and the northern South island of New Zealand (Takaka Terrane). Throughout the Middle Cambrian, magmatism in these two regions, in the Lachlan Fold Belt (SE Australia) and the Bowers Terrane (Antarctica) is represented by intra-oceanic are and back are sequences. In the mid-Middle Cambrian, collision of these are segments with the proto-Gondwana continent is recorded by obducted boninite-bearing ophiolites in Tasmania and SE Australia. Postcollisional magmatism of latest Middle to early Late Cambrian age (e.g., Mount Read Volcanics of Tasmania and Stavely Volcanic Complex of Victoria) terminates convergent tectonics in SE Australia and Tasmania. In contrast, no postcollisional volcanism is known from the Bowers Terrane in Antarctica and from New Zealand. In Antarctica, Cambrian igneous activity in the Wilson Terrane and Transantarctic Mountains formed in an active continental margin setting and lasted through the Middle and Late Cambrian. This suggests that the Wilson Terrane is the lateral continuation on continental basement of the Bowers and Takaka Terrane arcs. The differences between the Australian - Tasmanian and New Zealand - Antarctic are segments may result from a change in subduction polarity along the are chain, suggested by structural features, sedimentation patterns, and isotope systematics. In the SE Australian and Tasmanian are segments the proto-Gondwana plate subducted beneath the Pacific plate whereas subduction in the Antarctic and New Zealand segments was of opposite polarity. Common to most Cambrian fragments in SE proto Gondwana is the tectonic overprint by the Ross-Delamerian orogeny from the Middle Cambrian to Early Ordovician, thus paleogeographically linking all the fragments by the end of the Cambrian. The presence of Early Cambrian intra-oceanic rocks at the SE proto-Gondwana margin suggests separation of Laurentia from Gondwana prior to the Early Cambrian
Behaviour of high field strength elements in subduction zones: constraints from Kamchatka-Aleutian arc lavas
No full textModels explaining the characteristic depletion of High Field Strength Elements (HFSE) relative to elements of similar compatibility in subduction zone magmas invoke either (1) the presence of HFSE-rich minerals in the subduction regime or (2) a selectively lower mobility of HFSE during subduction metasomatism of the mantle. In order to investigate the properties of HTSE in subduction regimes closer, we performed high precision measurements of Nb/Ta, Zr/Hf, and Lu/Hf ratios together with Hf-176/Hf-177 analyses on arc rocks from Kamchatka and the western Aleutians. The volcanic rocks of the Kamchatka region comprise compositional end members for both fluid and slab melt controlled mantle regimes, thus enabling systematic studies on the HFSE mobility at different conditions in the subarc mantle. Hf-Nd isotope and systematic Zr/Hf and Lu/Hf covariations illustrate that Zr-Hf and Lu are immobile in fluid-dominated regimes. Hf-Nd isotope compositions furthermore indicate the presence of "Indian" type depleted mantle beneath Kamchatka, as previously shown for the Mariana and Izu-Bonin arcs. In addition to a depleted mantle component, Hf-Nd isotope compositions enable identification of a more enriched mantle wedge component in the back-arc (Sredinny Ridge) that most likely consists of mantle lithosphere. The ratios of Nb/Ta and Zr/Hf are decoupled in rocks from fluid-dominated sources, indicating that Nb and Ta can be enriched in the mantle by subduction fluids to a small extent. In contrast to the fluid-dominated regime in Central Kamchatka, the budget of HFSE and Lit in rocks from the Northern Kamchatka Depression and in adakitic rocks from the western Aleutians is significantly affected by slab melts that originate from subducted oceanic crust. Compositions of the rocks with the highest slab melt components in their source (Sr/ Y>30) provide no evidence that either Nb/Ta or Zr/Hf ratios are fractionated at a globally significant scale during melting of subducted oceanic crust. Subduction processes are therefore an unlikely candidate to explain the terrestrial Nb-Ta paradox (i.e., the subchondritic Nb/Ta ratios in all accessible terrestrial silicate reservoirs). (C) 2004 Elsevier B.V. All rights reserved
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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