1,720,973 research outputs found
Mercury Emissions Associated with Volcanoes and Geothermal Sources
No full textThere is some debate at present regarding the quantity of mercury naturally released by
volcanoes and its relative significance to the natural Hg budget. In order to better understand
the role of volcanoes in the global mercury budget a number of field campaigns were carried
out to evaluate the Hg/S ratios in volcanic gases around the world. Measurements have been
made of emissions of Masaya (Nicaragua), Etna and Vulcano (Italy), Tatun (Taiwan), Taal
and Makiling (Philippines) and Kilauea (Hawaii, USA). Emissions from open vents,
fumaroles, hot springs, bubbling mud pools and altered ground were investigated at these sites
and concentrations of mercury elevated above background levels were observed on most
occasions. A Lumex 915+ portable mercury vapour spectrometer was employed to record
real-time gaseous elemental mercury (GEM) concentrations alongside a Multi-GAS sensor
, H S, CO , humidity, temperature and pressure. These
box developed to monitor SO
2 2 2
measurements were carried out in parallel with the collection of GEM on gold coated sand
traps, particulate Hg (Hg(p)) on quartz mini-traps, reactive gaseous Hg (RGM) on glass
denuders and sulphur on filter packs. As observed in studies of background air Hg, most of
the GEM was the dominant form in the volcanic gases. While RGM and Hg(p) represent only
a few % of the Hg present, concentrations of these species in volcanic air was several orders
of magnitude higher than levels observed in background and industrial air studies. Hg/S ratios
volcanic flux to estimate Hg fluxes.
were determined and used in conjunction with the SO
2
-6 -5
and 10 . If
Hg/S ratios in open vent emissions at Masaya and Etna were between 10
representative of other volcanoes, these results suggest degassing of basaltic magma plays an
important part of the global atmospheric Hg budget.
With these new measurements, we shall
critically revisit the status of the global volcanic mercury emissions budget, and its
uncertainties
Plume chemistry and potential impacts of the plume from the recent activity at Halema’uma’u, Kilauea, USA.
No full textSince the 19 March 2008 explosion within Halema‘uma‘u that formed the new vent at Kilauea’s summit,
degassing rates have been greatly elevated above the levels typical of previous years. The location and
subsequent dispersion of this new degassing presents its own specific problems compared to that in the
east rift zone. For example, throughout 2008 the Halema’uma’u plume was generally blown through the
Kau desert, directly affecting downwind communities. In this study we present measurements made in July
and halogens (HF, HCl, HBr and HI) in the new
2008. We characterize the gas chemistry in terms of SO
2
plume from Halema’uma’u in order to compare them with other plumes worldwide, including those from
subduction zone settings and other emissions from Kilauea itself. Further to this we characterize the
plume’s chemistry in terms of emissions of environmentally important metallic species both in the size-
segregated aerosol (important for determining atmospheric lifetime and potential speciation) and in the
case of Hg in the gas phase (both in the elemental form and reactive forms). To complement this plume
characterization we also looked at preliminary environmental samples of grasses, rainwater and fog in
order to investigate potential future avenues for research into the environmental consequences of Kilauea’s
volcanic emissions
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
Application and evaluation of biomagnetic and biochemical monitoring of the dispersion and deposition of volcanically-derived particles at Mt. Etna, Italy
No full textBiomagnetic monitoring, using tree leaves as passive surfaces for particle collection, has been shown to be a promising technique for assessing the dispersion and deposition of particles in the context of anthropogenic pollution. By comparing leaves' magnetic properties with trace metal levels measured in the leaves, we here assess the utility of the biomagnetic technique as a sensitive, fast and inexpensive method for assessment of volcanic plume deposition. Samples of sweet chestnut leaves (Castanea sativa) were collected from the area surrounding Mt. Etna volcano in Sicily during the 2008 growing season when the volcano was displaying mild eruptive activity. Previous work has shown that the trace metal concentrations of these leaves show promise as a bio-indicator of volcanic gas, aerosol and ash deposition on the flanks of Mt. Etna. For 2008, ICPMS analysis of the elemental abundances within the leaves showed that As, Cd, Cu, Mo, Tl, K, B, Al and Co displayed elevated concentrations downwind of the volcanic source, to the E–ESE, but with overall reduced concentrations relative to 2007. Less explosive activity than 2007 and a broader, more easterly wind field may have distributed the volcanic plume over a wider area, both of which would account for reduced trace element concentrations in 2008. Correspondence of elevated concentrations in both years (2007 and 2008) with their respective wind fields suggests that plume deposition is the controlling factor rather than variability in the soils and that these leaves do indeed have potential as bio-indicators of the plume's dispersion. Magnetic analysis of the leaves shows that the spatial distribution of saturation isothermal remanent magnetisation (SIRM) and magnetic susceptibility (χlf) values display a strong correlation with the wind-influenced plume transport direction for 2008, with elevated concentrations of magnetic minerals on the eastern flanks, in broad agreement with the ICP-MS data. This spatial distribution provides further evidence of plume variability as the main control on the concentrations of magnetic particles on the leaf surfaces and on elemental uptake by the tree and suggests that biomagnetic monitoring may also hold promise as a method of assessing the dispersion and impacts of volcanic plumes. The dominant magnetic mineral on the leaf surfaces is a magnetite-like mineral (contributing >90% of the SIRM), of coarse, multidomain (MD) grain size (∼5 to 15μm). A volcanogenic source is most likely, as magnetites from anthropogenic sources are typically an order of magnitude smaller in grain size (∼0.1–1 μm). These new results from the use of environmental magnetism on leaves, in a volcanically-affected region, suggest that biomagnetic monitoring offers a new, sensitive and rapid means for the assessment of volcanic plume deposition over wide areas
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
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