1,720,961 research outputs found
An ITRAX Geochemical Study of Ferromanganiferous Sediments from the Penrhyn Basin, South Pacific Ocean
No full textManganese nodules reach abundances in excess of 30 kg per square meter in the Penrhyn Basin, central equatorial South Pacific. In the south of the Basin, they rest on dark brown ferromanganiferous clays, whereas in its northern part, the substrate becomes more calcareous and siliceous. Nine box cores representing this variability, each up to about one half meter in length, have been subjected to ITRAX XRF measurement, calibrated by laboratory WD-XRF analysis. ITRAX is an automated core scanning instrument that records optical, radiographic and elemental variations in sediment cores at a resolution as fine as 200 microns using photography, x-radiography and XRF analysis. Additional piston and gravity cores have been studied lithostratigraphically. As the sediments in the Penrhyn Basin will be badly disturbed during any future manganese nodule mining there, a detailed knowledge of their nature is a prerequisite to environmentally found nodule recovery.The cores studied were mainly collected along a transect at about 158.5° W between 12° S and the equator. South of about 4° S the sediments are uniform brown to dark brown, and ferromanganiferous pelagic clays averaging about 5–7.5% Al, 17–21% Si, 4–7.5% Fe, and 1–2% Mn. North of about 4° S the sediments become progressively more calcareous, initially in the upper parts of the cores as biological productivity increases towards the equator, but by 2.20° S they are calcareous throughout. Finally, north of 2.20° S, the cores have increased Si and decreased Ca in their upper parts, as biogenic silica co-exists with calcium carbonate as an important sediment builder under highest productivity waters at the equator. Most trace elements are higher in the clays than in the biogenic sediments and show little variation downcore.The sediments studied from the Penrhyn Basin exhibit important differences from those in other projected Pacific manganese nodule mining areas, such as the Clarion-Clipperton Zone and the Peru Basin. In the former, siliceous sediment is the main substrate in areas of high nodule abundance, whereas pelagic clay fills this role in the Penrhyn Basin. In the latter, 5–15 cm of oxic brown mud overlies sub-oxic siliceous/calcareous ooze down to below 50 cm, the expected minimum depth of sediment disturbance during manganese nodule mining. Elevated concentrations of divalent Mn occur in the pore waters of the latter. Sediments in the Penrhyn Basin do not exhibit this and are overall more oxic than those in the Peru Basin
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
Anthropogenic contaminants in Venice Lagoon sediments and their pore fluids: Results from the SIOSED Project
No full textInvestigations of sediment geochemistry and interstitial water chemistry during SIOSED (Scripps Institution of Oceanography Sediment Research Project) revealed information about the characteristics and depth range of contamination in sediments associated with dredging operations in the Venice Lagoon, Italy. Results from gravity cores indicate that contamination ranges larger and deeper in sediments associated with Porto Marghera and the Venice Industrial Zone compared with sediments at greater distances from dredged shipping canals or pollution sources. The effects of sediment re-deposition were evaluated from a pore water chemistry study of artificial banks constructed by placing dredged canal sediments on top of background sediments. Rapid decreases in dissolved sulfate associated with increases in alkalinity, sulfide, and nutrients, such as ammonium and phosphate, indicate that sediment dredging led to enhanced bio-chemical diagenesis of organic matter near the surface of the re-deposited sediments. Continued diagenesis of organic matter in re-deposited sediments maintained extrema in alkalinity, dissolved sulfate, sulfide, and ammonium. The artificial banks retained their pore water signatures over the duration of the project. Sediment redistribution can thus cause important changes in pore water profiles, as observed from the chemistry in long cores studied in this program
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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