1,720,980 research outputs found
Trace metal chemistry of hydrothermal plumes
No full textThis thesis examines the nature of trace metal cycling in hydrothermal plumes, which have only recently been recognized as a significant source of Fe to the oceans. To study the influence of hydrothermal vents and their plumes on global trace metal cycles, two “black smoker” type vents and a previously unrecognized type of off-axis venting are examined. The trace metal chemistry of previously uncharacterized vents from the Von Damm vent field (VDVF) and the Beebe vent field (BVF) on the Mid-Cayman Rise (MCR) are described along with the processes of colloid formation in plumes over the Mid-Cayman Rise. Also Fe isotope analyses of a hydrothermal plume in the Southern Ocean reveals distinct isotope signatures to deep-waters dependent on plume chemistry. The role of soluble, colloidal and particulate partitioning of trace metals is understood to mediate the entire inventory of hydrothermal trace metals entering the ocean. In plumes over the MCR colloids are found to dominate dissolved iron (dFe) (48 to 87 % at Beebe and 14 to 81 % at Von Damm) in hydrothermal plumes. At Beebe soluble Fe (sFe) remains stable throughout plume dispersion, while particulate Fe is enriched (~25 %) by aggregating colloids. In the Von Damm plume colloidal Fe (cFe) and sFe maxima appear in the most dispersed regions of the plume where particulate Fe (pFe) is low. Plume processing of cFe and pFe will control the flux of dFe to the deep ocean from hydrothermal systems. This study shows that in order to accurately model the flux of dFe from vents, the behaviour of cFe needs to be incorporated into models of hydrothermal vent dFe fluxes, which at present do not consider these processes. Iron isotopes provide a means to measure the impact of hydrothermal venting on the oceanic Fe inventory, but no studies have examined the mechanism producing hydrothermal dFe isotope compositions. This study demonstrates that ?56Fe values of dFe (?56dFe) within the hydrothermal plume change dramatically during plume dispersal, ranging from -2.39 ± 0.05 ‰ to -0.13 ± 0.06 ‰ (2 SD). The isotopic composition of total dissolvable Fe (?56TDFe) was consistently heavier than dFe consistent with Fe oxyhydroxide precipitation as the plume ages. It is estimated that stable dFe exported from the plume will have a ?56dFe of -0.28 ‰, and this provides the first highly resolved constraint on hydrothermal plumes as a source of dFe isotopes to the ocean interior. This suggests that this distinctive isotope signature can be used to trace plume dFe inputs to the deep ocean. This will help constrain the impact of hydrothermal Fe on ocean biogeochemistry.<br/
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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