1,720,964 research outputs found
Petrology and Sr–Nd Isotopes of High–Grade Amphibolites From Bankim Area (Central Cameroon Shear Zone), Cameroon: Constraints on Petrogenesis and Geodynamic Implications
No full textABSTRACT The Bankim area is located in the Tikar Plain, on the N50E branch of the Central Cameroon Shear Zone (CCSZ) where amphibolites occur, but their relationship with the general Pan–African metamorphism history is poorly known. The petrography, mineral chemistry, geochemistry and Sr–Nd isotope systematics of amphibolites from the Bankim area are presented in this paper in order to constrain their petrogenesis and geodynamic setting during the Pan–African orogeny. They are garnet amphibolites (GA), pyroxene amphibolites (PA) and biotite amphibolites (BA) occurring as metric flagstones showing relic of S 1 foliation, lense–like, or as sheared sinistral and dextral and/or boudinaged enclaves. In GA, garnet occurs as lobate porphyroblasts (Alm 54‐58 Gr 25‐27 Pyr 10‐12 ∙ Sp 3‐5 ). It is usually surrounded by a corona made up of hornblende, plagioclase [andesite (Ab 67‐59 An 32‐46 Or 0.5 ) to oligoclase (Ab 72 An 27 Or 0.6 )], quartz and ilmenite; the whole defining a kelyphitic microstructure (characterised by garnet + amphibole + plagioclase + opaques mineral (ilmenite) parageneses). In PA, clinopyroxene (diopside; Ca 49‐50 Mg 29‐30 Fe 19‐22 ) is mostly relic–like and displays hornblende or plagioclase (andesine (Ab 65‐67 An 32‐34 Or 0.6‐0.8 ) to oligoclase (Ab 69‐70 An 29‐30 Or 1‐1.2 )) corona showing hornblende + clinopyroxene + plagioclase + opaque minerals paragenesis. Field and microstructural data indicate that these rocks recorded a polyphase prograde–peak followed by retrograde metamorphism. The metamorphic prograde phase and peak P–T conditions exceeding 5.2 kbar/789°C occurring during the D 1 deformation phase (613–600 Ma) correspond to the collisional stage of the Pan–African orogeny within the granulite facies. Retrograde metamorphism occurred from the granulite facies to the amphibolite facies under P–T conditions of 1.4–5.2 kbar/789°C–513°C. These changes were synchronous with the early sinistral syn–D 2 (590–580 Ma) and the late dextral syn–D 3 (580–545 Ma) ductile shear deformation phases. These deformation phases, which occurred as a result of exhumation during the crustal re–equilibration related to relaxation and erosion during the post‐collisional evolution of Western Gondwana. The geochemical data indicate that the above amphibolites derived from the metamorphism of mafic protolith which represents an ancient Proterozoic crust with model ages of T DM = 1.9–1.6 Ga and initial 87 Sr/ 86 Sr 600 ratios of 0.70626–0.70894. At the end of the prograde and retrograde metamorphism of this ancient crust, it was stretched, sheared, dismembered and scattered along the Pan–African mobile zone during the CCSZ reactivations
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
Comment on “The Adamawa–Yade, a piece of Archaean crust in the Neoproterozoic Central African orogenic belt (Bafia area, Cameroon)“, by Jacqueline Tchakounté et al. [Precambrian Research 299 (2017) 210–229]
No full textkoamabayili/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
The mineralogy and geochemistry of a subvolcanic alkaline complex from the Cameroon Line: The Nda Ali massif, southwest Cameroon
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