1,720,968 research outputs found
A Geochemical Study of Hydrothermal Signals in Marine Sediments: The Rainbow Hydro thermal Area, 36 degrees on the Mid-Atlantic Ridge
No full textThe geochemistry of a suite of cores accumulating at increasing distance down-stream of a major hydrothermal vent site has been characterized for the first time, in order to examine the changing chemistry of particles being deposited from the plume with distance from the vent, to try to establish the different processes operating in the plume, particularly with regard to scavenging of elements from seawater, and to quantify the fluxes from seawater to the sediments as a result of venting, for a wide range of major and trace elements (Mg, Fe, V, Mn, Co, Cu, Zn, REE, PGE, Os isotopes).Sediment cores were collected at 2-25km downplume of the Rainbow hydrothermal vent site at 36o14'N on the Mid-Atlantic Ridge, a known site of vigorous high-temperature venting. Samples from long-term sediment traps located 0.5-2 km from this vent were also studied. All samples showed similar bulk chemistry, with an overprint of hydrothermally derived material. Sedimentation rates of 40-60 mg.m2d-1 for the cores were established using bulk radiocarbon dating of the carbonate material, and were found to be of the same order as the sediment traps 11-25 mg.m2.d-1. The maximum age of the core samples ranged from 8-26 x 103 radiocarbon years.For many elements, particularly the PGEs, the element to iron ratios in plume derived material were found to be up to an order of magnitude higher than those found globally in metalliferous sediments of hydrogenous origin. Burial fluxes to the Rainbow sediments have been calculated for hydrothermally derived elements - Mn (16-37 μmol.cm-2.kyr-1), Fe (368-718μmol.cm-2.kyr-1), Co(0.3-0.5μmol.cm-2.kyr-1), Cu(3.5-12μmol.cm-2.kyr-1), Zn(0.2-0.6μmol.cm-2.kyr-1), - and elements scavenged from seawater by hydrothermal Fe-oxyhydroxides - P (36-64μmol.cm-2.kyr-1), V (3-5μmol.cm-2.kyr-1), As (0.6-1.4μmol.cm-2.kyr-1), Pd(20-53pmol.cm-2.kyr-1), Os (0.1-2.3pmol.cm-2.kyr-1), Ir(0.2-0.6pmol.cm-2.kyr-1), Pt(6.5 - 18.5pmol.cm-2.kyr-1). Magnesium from seawater appears to co-precipitate with Fe in the vent plume at this site, and Mg burial fluxes are calculated to be 73-146μmol.cm-2.kyr-1 . Burial fluxes of the hydrothermally derived elements represent only a fraction of the estimated vent output, implying that vent products are dispersed over long distances. Element/Fe ratios for scavenged elements are high compared to other metalliferous sediments, indicating enhanced scavenging efficiency at this site.</p
The inorganic carbon chemistry in coastal and shelf waters around Ireland
No full textThe wintertime spatial distribution of carbonate parameters in outer estuarine and coastal waters around Ireland is described from total alkalinity (TA) and dissolved inorganic carbon (DIC) data collected between 2010 and 2013. Due to predominantly limestone bedrock of their river catchments, the River Shannon and Barrow, Nore and Suir River system export high concentrations (>3800 ?mol kg?1) of TA to their estuarine and inshore coastal waters where estuarine alkalinity decreases with increasing salinity. TA is lower in rivers with a non-calcareous bedrock, with positively correlated alkalinity-salinity relationships in both the Lee and Foyle outer estuaries. Winter pCO2 in the Shannon, Barrow/Nore/Suir and Lee estuaries is supersaturated relative to atmospheric CO2, while pCO2 in the outer Liffey estuary is slightly lower than atmospheric CO2 in three consecutive winters, indicative of a CO2 sink. Winter pCO2 is close to atmospheric equilibrium along the western shelf and through the centre of the Irish Sea, while it is a CO2 sink across the North Channel. While aragonite was supersaturated in most Irish waters, it was close to undersaturation in both the Lee estuary, attributed to its low alkalinity freshwater source, and Barrow/Nore/Suir estuary related to the flux of high concentrations of DIC from this river system. The seasonal impacts on inorganic carbon chemistry was also investigated by comparing winter and summer data collected between 2009 and 2013 along two transects in western coastal waters and along the western shelf edge. DIC was ~60 ?mol kg?1 lower in summer relative to winter in the coastal transects and 39 ?mol kg?1 lower along the shelf edge, accompanied by depleted nutrients and supersaturation of dissolved oxygen during summer, indicative of primary production. TA was generally higher in summer relative to winter corresponding with a decrease in nitrate, indicating that primary production dominated the TA distribution over calcification. An exception to this was at two stations along the shelf edge where TA was lower in summer relative to winter (51 ?mol kg?1) and coincides with high reflectance in satellite images from a coccolithophore bloom at the time of sampling. While pCO2 was close to atmospheric equilibrium along the shelf edge during winter, this area was a CO2 sink during summer, apart from the stations where calcification was likely occurring resulting in elevated CO2 relative to atmospheric concentrations
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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