1,720,998 research outputs found
Tracking the dispersal of river water, atmospheric deposition, and shallow sedimentary trace metal inputs from the Congo region into the South Atlantic
No full textRecent work has revealed the presence of an offshore near-surface plume of dissolved trace elements in the South Atlantic Ocean (SAO). Dissolved Fe (dFe) supply from the Congo plume is equivalent to ∼40% of the annual atmospheric dFe supply to the SAO. However this plume is not captured by biogeochemical models, raising questions about its exact sources. To help understand the potential source mechanisms, we use particle tracking experiments to investigate elemental distributions. Results suggest that elevated concentrations of some elements in the Congo plume are primarily sourced from river discharge and wet atmospheric deposition with minimal influence from shelf sediments. River discharge is the main source in shelf regions and some off-shelf regions, whereas atmospheric deposition dominates the area to the southwest of the Congo River outflow. A quantitative analysis along 3 (Formula presented.) S specifically for dFe suggests a decrease in the contribution of river discharge from 90% to 30% moving off-shelf, with a corresponding increase in the contribution of atmospheric deposition. Within the shelf zone, atmospheric deposition accounts for roughly 20%–40% and could be a major source of dFe around the river mouth. Integration of data from cruise GA08 reinforces the finding that wet deposition augments the concentrations of dFe, manganese (dMn), and cobalt (dCo) at distances over 1,000 km from the river mouth. Given present-day patterns of nitrate, Fe, and Co limitation for primary producers in the SAO, changing rainfall patterns may have long-term implications for both regional elemental budgets and ecologically dependent processes sensitive to trace element ratios.</p
Trace metal fluxes from the Congo River into the South Atlantic Ocean are supplemented by atmospheric inputs from gas flaring
No full textThe Congo River in Africa has the second largest freshwater discharge volume globally and creates a near-equatorial river plume of up to 1000 km into the Atlantic Ocean[1]. The Congo constitutes a significant source of trace metals (TMs) to the ocean, and can stimulate primary productivity in the (sub)tropical ocean and impact marine ecosystems and ocean carbon uptake. The large and distal transport of TMs by Congo plume into the Atlantic is unique but also puzzling as TMs like iron (Fe) are considered to be largely removed (90-99%) during estuary mixing[2]. A recent study of 228Ra indicated a discrepancy in the TM budget in the Congo plume, which pointed towards an unknown source other than the Congo River or preservation of TMs by organic matter complexation which buffers TM against scavenging[3]. To address this puzzle, we present here a dataset of TM concentrations in river, rain and seawater from the Congo shelf (near Congo River mouth, 12.6°E, -6°S) to open South Atlantic (to 0°E, -3°S) from GEOTRACES cruise GA08. We show that wet deposition (rainfall) was the “missing” source of TMs to the Congo plume, supplying some TMs to the South Atlantic Ocean at a similar order of magnitude to the river. Concentrations of TMs including zinc (Zn), lead (Pb), cadmium (Cd) and copper (Cu) in rainwater showed an anthropogenic source, which can be linked to the numerous gas flaring platforms along the coast. Our results demonstrate that TM fluxes in the Congo plume are augmented by rainfall, which results in an apparently small removal rate of Fe (~50%), likely because Fe from rainfall is more efficiently dispersed upon deposition in the ocean and less prone to flocculation then Fe delivered by the Congo River[4]. We anticipate our study to be a starting point for more studies into TM emissions from gas flaring and impacts on surface oceans carried by rainfall
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
Trace metal fluxes of Cd, Cu, Pb and Zn from the Congo River into the South Atlantic Ocean are supplemented by atmospheric inputs
No full textThe Congo River supplies vast quantities of trace metals (TMs) to the South Atlantic Ocean, but TM budgets for the Congo plume derived using radium isotopes for GEOTRACES cruise GA08 suggest additional input other than the river outflow. Considering the tight correlations between most dissolved TMs and salinity in the plume and the high rainfall during the wet season over the Congo shelf, we hypothesized that wet atmospheric deposition is a TM source to the Congo plume. Observed TM concentrations in rainwaters across the Congo shelf were mostly comparable to values from previous work in the North Atlantic and Mediterranean Sea. Wet deposition contributed the equivalent of 43% dCd, 21% dCu, 20% dPb and 68% dZn of the Congo River fluxes. Our findings show an important role of wet deposition in supplying TMs to the South Atlantic overlapping with the region that receives substantial TM fluxes from the Congo River.
Key Points
The Congo River is an important source of trace metals (TMs) to the South Atlantic Ocean revealed by data from GEOTRACES cruise GA08
Wet deposition (rainfall) is identified as an additional TM source to the Congo plume by concurrently considering river and rain data
Rainfall supplies anthropogenic dTMs (Cd, Cu, Pb and Zn) with fluxes equivalent to 20%–68% of those from the Congo River on the Congo shelf
Plain Language Summary
The Congo River has the second largest freshwater discharge volume globally and creates an extensive near-equatorial plume into the Atlantic Ocean. The Congo plume constitutes an important source of trace metals (TMs) to the ocean, which impacts biogeochemical cycles in the tropical and subtropical ocean. However, existing work suggests a discrepancy within the TM budgets in the Congo plume and points to unknown source other than the Congo River or shelf sediments. Most TM concentrations across the Congo plume remain tightly correlated with salinity, suggesting that any additional sources are likely also freshwater-derived or enter the ocean at the river mouth coincidently with direct riverine TM inputs. Here, TM concentrations in ocean, river and rainwater collected during the GEOTRACES GA08 cruise are combined to suggest that wet deposition augmented some Congo TM fluxes to the ocean. Fluxes of anthropogenic Cd, Cu, Pb and Zn to the Congo shelf from wet deposition are of the same order of magnitude as the Congo River. Concentrations of these elements in rainwater are similar to prior observations reported for the North Atlantic and Mediterranean Sea, suggesting that a large fraction of the global range of rainwater concentrations over the ocean has been captured in our observations
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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