1,721,061 research outputs found
Chlorine solubility in peraluminous rhyolites from Soufriere Hills volcano, Monserrat: implications for magmatic degassing
No full textPre-eruptive volatile (H2O, F, Cl, and S)contents of phonolitic magmas feeding the 3600-year-old Avellino eruption from Vesuvius, southern Italy
No full textThe behaviour of H2O, F, Cl and S prior to and during the Plinian phase of the 3550-year old Avellino eruption was determined by the study of unheated primary glass inclusions and matrix glasses. The fall deposit can be divided into two sub-units on the basis of an abrupt change in colour: a phonolitic white layer at the base and a tephriphonolitic banded grey pumice layer at the top. The original tephriphonolitic magma is always found mixed with the phonolitic magma. Primary glass inclusions were only found in feldspar, amphibole and garnet associated with the white pumice. Glass inclusions in the products of the Avellino Plinian eruption contain a mean of 3.10 +/- 0.74 wt.% H2O, 0.95 +/- 0.15 wt.% F, 0.59 +/- 0.02 wt.% Cl, and 560 +/- 55 ppm S. The concentration of CO2 was below the detection Limit. Coexisting matrix glasses contain similar amounts of halogens but significantly less water (similar to 0.5 wt.%) and sulphur (similar to 100 ppm), suggesting that during the eruption the halogens did not behave as volatiles. Owing to the lack of primary glass inclusions and its hybrid nature, similar conclusions can only be hypothesised for the tephriphonolitic magma on the basis of volatile element distribution in the matrix glasses. Taking into account both our data and data from parental mafic melt inclusions by a previous study by P. Marianelli and co-workers, it has been possible to reconstruct the behaviour of volatiles in the Avellino magmatic reservoir in two stages: (1) variation of volatiles during crystal fractionation; and (2) exsolution of an "excess" gas phase when volatiles reach their solubility limit in silicate melts. The agreement between our data and the solubility limit of chlorine, sulphur and probably water in phonolitic melts at the postulated pressure and temperature (i.e., 100 MPa and 850 degrees C), suggests that such a phase exists. Compared to the other volatiles, fluorine does not exhibit a behaviour (i.e., flat distribution) consistent with the attainment of its solubility limit in phonolites. Using the petrologic method, the minimum output of volatiles during the Plinian phase of the Avellino eruption was hypothesised to be about 2 x 10 6 tons of H2SO4 and 25 x 10 6 tons of H2O. Due to both the presence of an "excess" vapour phase prior to eruption and the assumptions inherent in the petrologic method, the total calculated amounts should be considered as very conservative estimates of volatile outputs during the eruption
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
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
Volatile element zonation in Campanian Ignimbrite magmas (Phlegrean Fields, Italy): evidence from the study of glass inclusions and matrix glasses
No full textThe distribution of H2O, F, Cl and S in the Campanian Ignimbrite (CI) magma chamber was investigated through study of primary glass inclusions and matrix glasses from pumices of the Plinian fall deposit. The eruption, fed by trachytic to phono-trachytic magmas, mainly produced a trachytic non-welded to partially welded tuff, underlain by a minor cogenetic fallout deposit. The entire chemical variability of the eruptive products is well represented in the pumices of the Plinian fall deposit, which we divide into a basal Lower Fall Unit (LFU) and an overlying Upper Fall Unit (UFU). Primary glass inclusions were only found in clinopyroxenes associated with the LFU pumice and contain a mean of 1.60 +/- 0.32 wt% H2O (analysed by FTIR), 0.11 +/- 0.08 wt% F, 0.37 +/- 0.03 wt% Cl and 0.08 +/- 0.04 wt% SO3 (EMP analysis); CO2 concentrations were below the FTIR detection limit (10-20 ppm). The coexisting matrix glasses contain similar amounts of halogens and sulfur but less water (similar to0.60 wt%). Partially degassed matrix glasses from UFU pumices contain a mean of 0.30 +/- 0.02 H2O, 0.28 +/- 0.10 F, 0.04 +/- 0.02 SO3 and 0.80 +/- 0.04 wt% Cl. To reconstruct the total amount of volatiles dissolved in the most evolved trachytes we have used experimental solubility data and mass:balance calculations concerning the amount of crystal fractionation required to produce the most evolved trachyte from the least evolved trachyte; these yield an estimated pre-eruptive magma volatile content (H2O + Cl + F) of similar to5.5 wt% for the most evolved magmas. On the basis of new determinations of Cl solubility limits in hydrous trachytic melts coexisting with an aqueous fluid phase + hydrosaline melt (brine), we suggest that the upper part of the magma chamber which fed the CI eruption was fluid(s) saturated and at a minimum depth of similar to2 km. Variations in eruptive style (Plinian fallout, pyroclastic flows) do not appear to be related to significant variations in pre-eruptive volatile contents
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