1,721,141 research outputs found
Polycyclic aromatic hydrocarbons in seasonal snowcover
No full textThe chemical composition of snow can under some circumstances, be used as a monitoring tool for the estimation of atmospheric contamination. Snowfall is often the most important hydrological event in many parts of the world. Polycyclic aromatic hydrocarbons are an important and wide-spread class of environmental contaminants. Many of them have been demonstrated to have toxic and/or carcinogenic properties. PAHs are prevalent in the atmosphere at trace-levels, and therefore can be expected to be incorporated in snowfall. A sampling methodology and analytical protocol was devised to measure trace-level PAHs in snow. Samples of snow were collected from three contrasting locations: i) a remote, sub-arctic, mountain catchment in the Cairngorm Mountains of Scotland, ii) a remote boreal forest site in the Laurentian Mountains of Canada, and iii) urban and rural sites in Southern England. The samples were analysed by high performance liquid chromatography and gas chromatogrpahy with mass spectrometry detection for a maximum of 18 PAH compounds in both the dissolved and the particulate phases. Total PAH concentrations found in aged snowpack in Scotland are high (max. 3500 ng/1). This is typical of the PAH content of snow in urban regions, and is consistant with results form previous studies of snow from the same location which show elevated concentrations of trace-metals, owing to the long-range transport of contaminants from source regions. Fresh snow had lower PAH values (c. 200 ng/1), more representative of snow from remote areas. A possible positive correlation between snow acidity and PAH content was observed, and there are indications that this may be a source specific relationship. Snow from an urban site in Southampton, U.K. had a very high PAH content (6800 ng/1). Dissolved phase PAHs in snow from Canada had low concentrations of PAHs (1.0 - 240 ng/1). Particulate phase PAHs were not determined, owing to analytical difficulties. The results, whilst limited in extent, represent an important contribution to the current data available in the literature regarding trace-organic contaminants in snow.</p
The contribution of atmospheric acid deposition to ocean acidification in the subtropical North Atlantic Ocean
No full textThe absorption of anthropogenic CO2 and atmospheric deposition of acidity can both contribute to the acidification of the global ocean. Rainfall pH measurements and chemical compositions monitored on the island of Bermuda since 1980, and a long-term seawater CO2 time-series (1983–2005) in the subtropical North Atlantic Ocean near Bermuda were used to evaluate the influence of acidic deposition on the acidification of oligotrophic waters of the North Atlantic Ocean and coastal waters of the coral reef ecosystem of Bermuda. Since the early 1980's, the average annual wet deposition of acidity at Bermuda was 15 ± 14 mmol m? 2 year? 1, while surface seawater pH decreased by 0.0017 ± 0.0001 pH units each year. The gradual acidification of subtropical gyre waters was primarily due to uptake of anthropogenic CO2. We estimate that direct atmospheric acid deposition contributed 2% to the acidification of surface waters in the subtropical North Atlantic Ocean, although this value likely represents an upper limit. Acidifying deposition had negligible influence on seawater CO2 chemistry of the Bermuda coral reef, with no evident impact on hard coral calcification
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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