1,720,956 research outputs found
Impact of volcanic plume emissions on rain water chemistry during the January 2010 Nyamuragira eruptive event: Implications for essential potable water resources
No full textOn January 2, 2010 the Nyamuragira volcano erupted lava fountains extending up to 300m vertically along an ∼1.5km segment of its southern flank cascading ash and gas on nearby villages and cities along the western side of the rift valley. Because rain water is the only available potable water resource within this region, volcanic impacts on drinking water constitutes a major potential hazard to public health within the region. During the 2010 eruption, concerns were expressed by local inhabitants about water quality and feelings of physical discomfort (e.g. nausea, bloating, indigestion, etc.) after consuming rain water collected after the eruption began. We present the elemental and ionic chemistry of drinking water samples collected within the region on the third day of the eruption (January 5, 2010). We identify a significant impact on water quality associated with the eruption including lower pH (i.e. acidification) and increases in acidic halogens (e.g. F- and Cl-), major ions (e.g. SO42-, NH4+, Na+, Ca2+), potentially toxic metals (e.g. Al3+, Mn2+, Cd2+, Pb2+, Hf4+), and particulate load. In many cases, the water's composition significantly exceeds World Health Organization (WHO) drinking water standards. The degree of pollution depends upon: (1) ash plume direction and (2) ash plume density. The potential negative health impacts are a function of the water's pH, which regulates the elements and their chemical form that are released into drinking water. © 2012 Elsevier B.V
Gas chemistry of the Dallol region of the Danakil Depression in the Afar region of the northern-most East African Rift
No full textA combination of noble and major gas composition and isotope geochemistry provides a window into the source of volatiles and the mechanisms of transport associated with a series of hot springs located near the Dallol volcano within the Danakil Depression along the Red Sea arm of the Afar triple junction. The helium isotopic composition of these gases range up to 11.9 times the atmospheric ratio (11.9R/Ra), which suggests that the Afar plume interacts with the Afar depression across at least the 300km transect from Tendaho-Gabo basin to Dallol within the Danakil Depression. The 4He/40Ar* of ~14 in the mantle-rich end-member at Dallol indicates significant degassing prior to emplacement at Dallol either during basaltic dyke intrusions beneath the Danakil Depression or during the release and transport of fluids from a degassed subsolidus source in the upper mantle along high permeability fracture zones. The CO2/3He of the magmatic end-member is ~2× higher (7.7×109) and more positive δ13C (CO2) (-2.1%;) than other archetypal plumes (e.g. Hawaii, Iceland, etc.). The Dallol composition is consistent with a hypothetical model that assumes a plume-type starting composition and experiences ~92% degassing (where helium is preferentially degassed with respect to CO2) and the addition of CO2 from the thermal degradation of carbonate. Non-atmospheric excess N2 with a δ15N (N2) of +3.5 to +4%; dominates the Dallol volatiles and suggests interaction between mantle fluids and Proterozoic meta-sediments. By comparing and modeling the range in atmospherically (e.g. 20Ne, 36Ar, 84Kr) and mantle-derived (e.g. 4He/40Ar*and CO2/3He) components in Dallol volatiles, we propose that the coherent variations in these gases result from mixing of magmatic volatiles with extremely degassed remnant fluids present within the hydrothermal reservoir. © 2012 Elsevier B.V
Fumarolic gases at Mombacho Volcano (Nicaragua): presence of magmatic gas species and implications for volcanic surveillance
No full textMombacho is a deeply dissected volcano belonging to the Quaternary volcanic chain of Nicaragua. The southern, historic collapse crater (El Crater) currently hosts a fumarolic field with a maximum temperature of 121°C. Chemical and isotopic data from five gas-sampling field campaigns carried out in 2002, 2003 and 2005 highlight the presence of high-temperature gas components (e.g. SO2, HCl and HF), which indicate a significant contribution of juvenile magmatic fluids to the hydrothermal system feeding the gas discharges. This is strongly supported by the mantle-derived helium and carbon isotopic signatures, although the latter is partly masked by either a sedimentary subduction-related or a shallow carbonate component. The observed chemical and isotopic composition of the Mombacho fluids seems to indicate that this volcanic system, although it has not experienced eruptive events during the last centuries, can be considered active and possibly dangerous, in agreement with the geophysical data recorded in the region. Systematic geochemical monitoring of the fumarolic gas discharges, coupled with a seismic and ground deformation network, is highly recommended in order to monitor a possible new eruptive phase
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
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