1,721,022 research outputs found
The biogeochemical control of arsenic in certain estuaries
No full textSemi-continuous hydride generation atomic absorption spectrometry for the analysis of dissolved arsenic speciation in water, was optimised and used to detect sub-nonagram quantities of inorganic arsenic(III) and arsenic(V), monomethylarsenic and dimethylarsenic species in saline waters. High performance liquid chromatography-hydride generation AAS was also developed for the analysis of organoarsenicals in marine macro-algae. The biogeochemical control of arsenic was then studied in two estuarine ecosystems. The temporal speciation of arsenic in Southampton Water (Hampshire U.K.) was monitored and related to planktonic and bacterial activity. The spring and summer depletion of arsenic(V) was associated with the production of methylated and reduced arsenic(III) by marine diatoms and flagellates, but not bacteria. At times up to 50% of the total dissolved arsenic was present in these forms. A UV photodecomposition technique was developed that broke down organoarsenicals that do not form hydrides, such as arsenobetaine, arsenocholine and arsenosugars, to hydride reducible derivatives. This allowed their detection in algal extracts and sea water. Photodecomposition of arsenicals present in Solent water revealed increases of up to 30% in total dissolved arsenic, above that measured by conventional hydride generation; mainly as dimethyl- and inorganic arsenic. The `extra' arsenic showed seasonality and was associated with an abundance of phytoplankton. The other system studied was that of the Tamar, an estuary dominated by non-riverine inputs of arsenic from past mining activity. Surveys revealed two maxima in inorganic arsenic. One derived from mine leachates in the upper reaches, and a second from the release of arsenic-rich porewaters by tidal scouring, in the mudflat dominated mid-estuary. Estuarine particulate material was shown to partially regulate the dissolved level of inorganic arsenic. Methylated arsenic showed no affinity for the suspended sediments.</p
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
Spatial and temporal (annual and decadal) trends of metal(loid) concentrations and loads in an acid mine drainage-affected river
Get PDFAcid mine drainage (AMD) is a worldwide problem that degrades river systems and is difficult and expensive to remediate. To protect affected catchments, it is vital to understand the behaviour of AMD-related metal(loid) contaminants as a function of space and time. To address this, the sources, loads and transport mechanisms of arsenic (As), copper (Cu), zinc (Zn), iron (Fe) and sulfur (S) in a representative AMD-affected catchment (the Carnon River in Cornwall, UK) were determined over a 12-month sampling period and with 22 years of monitoring data collected by the Environment Agency (England) (EA). The main source of metal(loid)s to the Carnon River was the County Adit which drains AMD from approximately 60 km of underground historical mine workings. Maximum aqueous concentrations of Fe, Cu and Zn occurred immediately downstream of the County Adit confluence with the Carnon River, whereas maximum As and S concentrations occurred further downstream, suggesting the presence of diffuse sources. Discharge and concentration relationships suggested that discharge drove Cu and Zn release, whereas pH and Eh influenced Fe, S, and As mobility. Total loads (represented by unfiltered sample contaminant concentrations) to the coastal zone were high, ranging from 183 to 354 kg/month As, 307–742 kg/month Cu, 189–1960 kg/month Fe, 53,400–125,000 kg/month S and 1280–3320 kg/month Zn. The longevity and increasing amounts of contaminant discharge were confirmed with 22 years of EA monitoring data. This study highlights the complex and multifaceted behaviour of contaminant metal(loid)s within AMD-affected riverine systems and the fact that point and diffuse sources can constitute significant long-term liabilities for such environments
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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