1,721,358 research outputs found
Viscosity of andesitic melts—new experimental data and a revised calculation model
No full textThe viscosity of a synthetic andesite-like melt was measured in the low viscosity range (101-106 Pa s) using the falling sphere(s) method and in the high viscosity range (108-1013 Pa s) using parallel-plate viscometry. Falling sphere experiments with melts containing 2.3 and 5.6 wt.% H2O were carried out in an internally heated gas pressure vessel (IHPV) at 500 MPa confining pressure. The sinking velocity of Pt and Pd spheres and in one case of a corundum sphere was used to measure the melt viscosity. In addition, a creep experiment was performed at ambient pressure using a glass containing 2.73 wt.% H2O . A more water-rich glass (5.6 wt.% H2O ) was investigated with a high pressure parallel-plate viscometer at 400 MPa confining pressure in an IPHV. By combining our new data with previous results for a similar melt composition we derived the following expression to describe the viscosity η (in Pa s) as a function of temperature T (in K) and water content w (in wt.%){A formula is presented}. This expression reproduces the experimental data (191 in total) in the viscosity range from 101 to 1013 Pa s with a root mean squared deviation of 0.15 log units. © 2005 Elsevier B.V. All rights reserved
The temperature dependence of the speciation of water in NaAlSi3O8-KAlSi3O8 melts using fictive temperature derived from synthetic fluid-inclusions
No full textThe speciation of water dissolved in glasses along the join NaAlSi3O8-KAlSi3O8 has been investigated using infrared spectroscopy. Hydrous melts have been hydrothermally synthesized by chemical equilibration of cylinders of bubble-free anhydrous start glasses with water at 1040 ° C and 2 kbar. These melts have been isobarically and rapidly (200 degrees C/s) ''drop''-quenched to room temperature and then subsequently depressurized. The speciation of water in the quenched glasses reflects the state of water speciation at a temperature (the so-called fictive temperature) where the quenched-in structure of the glasses closely corresponds to the melt structure at equilibrium. This fictive temperature is detectable as the macroscopically measureable glass transition temperature of these melt compositions. A separate set of experiments using vesicular samples of the same chemistry has precisely defined the glass transition temperature of these melts (+/-5 degrees C) on the basis of homogenization temperatures for water-filled fluid inclusions (Romano et al. 1994). The spectroscopic data on the speciation of water in these quenched glasses has been quantified using experimentally determined absorptivities for OH and H2O for each individual melt composition. The knowledge of glass transition temperatures, together with quantitative speciation data permits an analysis of the temperature dependence of the water speciation over the 113° C range of fictive temperatures obtained for these water-saturated melts.
The variation of water speciation, cast as the equilibrium constant K where
K = [H2O][O-m]/[OH](2)
is plotted versus the fictive temperature of the melt to obtain the temperature dependence of speciation. Such a plot describes a single linear trend of the logarithm of the equilibrium constant versus reciprocal temperature, implying that the exchange of K for Na has little influence on melt speciation of water. The enthalpy derived from temperature dependence is 36.5 (+/-5) kJ/mol. The results indicate a large variation in speciation with temperature and an insensitivity of the speciation to the K-Na exchange
Using Tracer Reactivity to Overcome Some Dilemmas of Single-Well Tracer Test Inversion
No full textTracer tests are indispensable for measuring fluid transport parameters that control georeservoir performance for various uses (oil/gas production, geothermal, underground gas or energy storage, waste disposal). Single-well tests are particularly attractive for obvious reasons, however tracer signal inversion from single-well tests often faces parameter ambiguity issues, because the 'push-then-pull' configuration weakens the correlation between tracer residence time and target georeservoir parameters. The article shows how dual-tracer reactivity can alleviate this problem, and restore the sensitivity of tracer signals to parameters like fluid-rock interface areas
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
The viscosity of latitic melts from Lipari (Aeolian Islands, Italy): Inference on mixing–mingling processes in magmas
No full textThe viscosity of latitic melts occurring as enclaves in the rhyolitic lava flow of Rocche Rosse (RR, Lipari, Aeolian Islands, Italy) has been measured in the high T range (1323-1473 K) for a dissolved water content varying from 1.23 to 4.39 wt.%. Measurements were performed by the falling sphere method in an internally heated gas pressure vessel. As expected, the viscosity of latite decreases with increasing water content and temperature. No pressure effect was detected between 200 and 500 MPa. Combining the new viscosity data for hydrous melts with data for dry latite of similar base composition [Giordano, D., Mangiacapra, A., Potuzak, M., Russell, J.K., Romano, C., Dingwell, D.B., Di Muro, A., 2006. An expanded non-Arrhenian model for silicate melt viscosity: a treatment for metaluminous, peraluminous and peralkaline liquids. Chemical Geology 229, 42-56.] we propose an empirical equation to estimate the viscosity of latitic melts as a function of temperature and water content over the range 101 to 1012 Pa s. The obtained relationship reproduces the experimental data with a 1σ standard deviation of 0.22 log units. However, the empirical model is not constrained by data for hydrous melts at high viscosity and, therefore, it can only be used at low temperatures for water-poor melts. The viscosity data were used to model mixing-mingling processes between latitic and rhyolitic magmas at conditions relevant for the Rocche Rosse (RR, Lipari, Aeolian Islands) and La Fossa Cone 1888-1890 (LFC, Vulcano, Aeolian Islands) eruptions. The results demonstrate that the ratio between mafic and silicic end-members is the main parameter governing mixing-mingling interactions between magmas. This study suggests a faster ascent of magma underneath Vulcano compared to Lipari, which may be taken into account in hazard forecasting. © 2008 Elsevier B.V. All rights reserved
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