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The application of artificial mussels in conjunction with transplanted bivalves to assess elemental exposure in a platinum mining area
Get PDFThere is increasing evidence that platinum group elements (PGE) are pollutants of emerging
concern worldwide. Limited information exists on levels, particularly in regions where PGEs are
mined. A passive sampling device (i.e., the artificial mussel (AM)) and transplanted indicator
organisms (i.e., the freshwater clam Corbicula fluminalis africana) were deployed along a PGE mining
gradient in the Hex River, South Africa, and concentrations of As, Cd, Co, Cr, Ni, Pb, Pt, V, and Zn
were determined after six weeks of exposure. Results showed differential uptake patterns for Pt, Cr,
and Ni between the AMs and clams indicating availability differences. For monitoring purposes,
a combination of AMs and indicator organisms provides a more holistic assessment of element
exposure in aquatic environment
Validation of artificial mussels as indicators of platinum group element exposure in the Hex River System
Get PDFMSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2019Platinum group elements (PGE) occur naturally in the environment in very low concentrations. However, these elements have increased over the last couple of decades, since they have been increasingly used in a number of applications. Mining activities in South Africa have been reported to contribute prominently to PGE emissions in the environment. The knowledge of (PGE) contamination in freshwater systems is important for the risk assessment for aquatic health and water resource management. From this study it could be seen that laboratory bioaccumulation studies alone are not sufficient since organisms in natural environments are affected by different environmental conditions that influence the bioavailability of metals to organisms. PGE concentrations in living organisms from field studies give valuable information on the metals that are associated with the mining activities and the bioavailable PGE fraction and the effective PGE concentrations inside of the organisms. The use of the artificial mussel (AM) have been successfully applied for a wide range of metals in marine, and more recently, fresh water systems, but never before used for determining PGE concentrations. The design of the AM was validated and optimised in the laboratory for uptake of PGEs. An optimum loading and elution protocol was developed for platinum (Pt). It was demonstrated that the Chelex® beads in the AMs accumulate Pt in a dose-response relationship and reflect the bioavailable environmental concentrations. The AMs were exposed to environmental PGEs alongside an established bioindicator species. This obtained information on the bioaccumulation and effects of the biota and how the bioaccumulation correlates with the measured uptake by the AMs when exposed for the same period. Both the AMs and the transplanted organisms were exposed in plastic baskets at each site. Metals that were analysed during this study include As, Cd, Co, Cr, Ni, Pb, Pd, Pt, V and Zn. When the AMs were exposed in the tailings dam and the two impoundments different PGE concentrations could be found. The AMs accumulated significantly higher Pd concentrations in Bospoort Dam during the second survey, while these concentrations were similar in the two impoundments during the first survey. For Pt it could be seen that these concentrations were similar in both impoundments during the second survey and Bospoort Dam contained slightly higher Pt concentrations during the first survey. The water concentrations reflect that there is a Pd concentration gradient along the Hex River, while the Pt concentrations were similar in the two impoundments, and the tailings dam contained significantly higher PGE concentrations. The accumulation patterns within in the AMs and the transplanted clams indicated different uptake patterns. Clams will take up metals from the water both in the dissolved form and as complexes bound to particulate matter. Thus the physical and chemical conditions at the different sites and during the different surveys influence the form of the metal available for uptake by the clams. On the other hand the AMs showed great accumulation patterns for all metals. The AMs correlated well with the concentrations found in the water column, which indicated that Bospoort Dam had higher metal concentrations, while the transplanted clams indicated that Olifantsnek Dam had higher concentrations. It was found that the clams from the reference site were exposed to high metal concentrations at the source site prior to deployment. It is therefore highly likely that the responses following deployment in the study sites were masked by the pre-exposed conditions. Mechanisms against oxidative stress were observed with increased CAT activities (non-significant increases) when exposed to conditions in Olifantsnek Dam. These responses in turn caused a depletion in energy reserves and damage to lipid and protein content of the clams. Metallothionein induction (based on total metals) were higher in Bospoort Dam, while the Pt-MT were higher in the reference clams and to a degree in Olifantsnek Dam, which correlated with Pt concentrations found in the clam tissues. This study provided some insight into PGE concentrations that can be found in PGE mining areas in South Africa, in areas that are not impacted (Olifantsnek Dam) by these activities to areas that are heavily impacted (tailings dam)National Research Foundation (NRF)Master
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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