1,720,975 research outputs found
Geological constraints on the eruption of the Jwaneng Centre kimberlite pipe, Botswana
No full textGeological mapping has allowed constraints to be placed on the eruption mechanisms involved in the formation of the Late Permian–Early Triassic Jwaneng Centre kimberlite pipe, Botswana. Twelve lithofacies and three lithofacies associations (LFA 1–3) are recognised. LFA 1 comprises massive to bedded volcaniclastic kimberlite and marginal shale breccias and outcrops over 65% of the surface area of the pipe. It is characterised by a lithic population dominated by Transvaal shale clasts. LFA 1 grades into LFA 2, which comprises massive and bedded volcaniclastic kimberlite and volcaniclastic breccias and outcrops over 19% of the surface area of the pipe. The lithic population of LFA 2 is dominated by contorted and fluidal-outlined Karoo-age mudstones and siltstones. LFA 3 comprises a wedge-shaped unit in the north of the pipe and consists of a series of allochthonous megablocks of sedimentary and volcaniclastic strata. The juvenile clast type and matrix mineral assemblages of the volcaniclastic deposits in the Centre Pipe differ from those in many other southern African kimberlite pipes. Various emplacement models for kimberlite pipes are discussed and evaluated in the light of the new geological data. Both a maar–diatreme model and an explosive volatile-driven eruption model could account for much of the geology of the Centre Pipe and distinguishing between the two models based on deposits alone is difficult. There is strong circumstantial evidence for ambient conditions favourable to phreatomagmatism at the time of the eruption, and the influence of external water may explain the differences between the Jwaneng Centre Pipe and the Class 1 kimberlites common across Southern Africa in terms of both the juvenile clasts and of the inter-clast cement. However, low abundances of some types of lithic inclusions derived from major country rock units pose an unresolved problem for a classic maar–diatreme model of pipe formation.Geological mapping has allowed constraints to be placed on the eruption mechanisms involved in the formation of the Late Permian–Early Triassic Jwaneng Centre kimberlite pipe, Botswana. Twelve lithofacies and three lithofacies associations (LFA 1–3) are recognised. LFA 1 comprises massive to bedded volcaniclastic kimberlite and marginal shale breccias and outcrops over 65% of the surface area of the pipe. It is characterised by a lithic population dominated by Transvaal shale clasts. LFA 1 grades into LFA 2, which comprises massive and bedded volcaniclastic kimberlite and volcaniclastic breccias and outcrops over 19% of the surface area of the pipe. The lithic population of LFA 2 is dominated by contorted and fluidal-outlined Karoo-age mudstones and siltstones. LFA 3 comprises a wedge-shaped unit in the north of the pipe and consists of a series of allochthonous megablocks of sedimentary and volcaniclastic strata. The juvenile clast type and matrix mineral assemblages of the volcaniclastic deposits in the Centre Pipe differ from those in many other southern African kimberlite pipes. Various emplacement models for kimberlite pipes are discussed and evaluated in the light of the new geological data. Both a maar–diatreme model and an explosive volatile-driven eruption model could account for much of the geology of the Centre Pipe and distinguishing between the two models based on deposits alone is difficult. There is strong circumstantial evidence for ambient conditions favourable to phreatomagmatism at the time of the eruption, and the influence of external water may explain the differences between the Jwaneng Centre Pipe and the Class 1 kimberlites common across Southern Africa in terms of both the juvenile clasts and of the inter-clast cement. However, low abundances of some types of lithic inclusions derived from major country rock units pose an unresolved problem for a classic maar–diatreme model of pipe formation
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
Environmental controls on the thermal performance of submarine high voltage cables
No full textThe generation of power offshore has recently seen a large amount of interest and investment. Submarine power cables are essential tools in transferring power from these offshore generation sites, to where it is consumed back on land. In addition, initiatives like the European Supergrid use submarine HV interconnectors to link electrical infrastructure on a national level. This helps to improve efficiency, and reduce total power generation and its associated costs.HV cables have been studied extensively in terrestrial soils. How their behaviour alters when buried under the seafloor is essentially unknown, despite key differences between the two respective environments. In order to make full use of these assets, accurate current ratings must be obtained
The role of fluidisation in the formation of volcaniclastic kimberlite: Grain size observations and experimental investigation
No full textVariations 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
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