1,720,978 research outputs found
Effect of boron on the water speciation in (alumino)silicate melts and glasses
No full textThe investigation of hydrous boro(alumino)silicate melts and glasses with near infrared (NIR) spectroscopy revealed an important effect of boron on the water speciation. In the NIR Spectra of B-bearing glasses new hydroxy-related bands develop at the high frequency side of the 4500 cm(-1) peak. In NaAlSi3O8 + B2O3 glasses this new peak is present as a shoulder at 4650 cm(-1), and in NaAlSi3Os-NaBSi3Os (Ab-Rd) glasses it appears as a resolved peak at 4710 cm(-1). These bands increase with increasing boron concentration, suggesting that they are due to B-OH complexes. Furthermore. the variations in the. NIR spectra indicate that with increasing B-content, but constant total water concentration. the amount of structurally bonded hydroxyl groups increases at the expense of molecular H2O. For example at a total water concentration of 4 wt.%, pure Rd-glass contains similar to50% more water as hydroxyl groups than pure Ab-glass. In-situ NIR spectroscopy at high P and T using a hydrothermal diamond-anvil cell was used to gain information about the temperature dependence of the water speciation in NaBSi3OS melts. The data demonstrate the conversion of molecular H2O to hydroxyl groups with increasing temperature. However, a fully quantitative evaluation of the high T spectra was hampered by problems with defining the correct baseline in the spectra. As an alternative approach annealing experiments on a Rd-glass containing 2.8 wt.% water were performed. The results confirm the conversion of H2O to OH groups with increasing T. but also suggest that the OH groups represented by the 4710 cm(-1) peak (B-OH) participate much less in the Conversion reaction compared to X-OH, represented by the 4500 cm(-1) peak. Copyright (C) 2004 Elsevier Ltd
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
The effect of chlorine, fluorine and water on the viscosity of aluminosilicate melts
No full textThe influence of 1.6 to 14.5 mol% water, 1.1 to 18.3 mol% fluorine (F) and 0.5 to 1.4 mol% chlorine (Cl) on the viscosity of peralkaline and peraluminous Na2O-CaO-Al2O3-SiO2 melts as a model system for phonolites was studied with the micropenetration method within the range of 10(9) to 10(13) Pa s. Water and F alone and combined decrease viscosity non-linearly. With increasing F and water concentration the further addition of F and water becomes less effective in decreasing viscosity. Water decreases the viscosity of peraluminous melts more strongly than that of peralkaline melts. In the halogen-free peraluminous sample 5 mol% water decreases T-g(12) (the temperature where the viscosity = 10(12) Pa s) by 259 +/- 5 K, while in the halogen-free peralkaline sample 5 mol% water decreases T-g(12) by 189 +/- 5 K. Fluorine (on a mol% basis) decreases the viscosity of Na2O-CaO-Al2O3-SiO2 melts less than water. In the peraluminous melts the addition of 5 mol% F decreases T-g(12) by similar to 95 K. In the peralkaline melt 5 mol% F decreases T-g(12) by similar to 30 K. However, a significant decrease in T-g(12) was only observed up to a F, concentration of 1.9 mol% F, another sample with 6.2 mol% F, showed no further decrease of T-g(12). In all hydrous peraluminous and peralkaline samples that contain F alone or combined with Cl, the decrease of viscosity due to the addition of water is smaller than in the halogen-free samples. In a peraluminous melt with 18.3 mol% F the addition of 5 mol% water decreases T-g(12) by about 152 +/- 5 K compared to the dry melt. In a peralkaline melt with 1.9 mol% F the addition of 5 mol% water decreases T-g(12) by about 146 +/- 5 K compared to the dry melt. In both cases this is significantly less than for the halogen-free samples. In peralkaline melts Cl has no influence on the decrease in viscosity upon the addition of water. The effects of water and Cl on viscosity are independent of each other and add together. The effects of water and F on viscosity are not independent, which could be, in the case of the peralkaline samples related to changes in F speciation due to the presence of water. (C) 2013 Elsevier B.V. All rights reserved.DFG [WE 1810/9-1
Compositional dependence of the rheology of halogen (F, Cl) bearing aluminosilicate melts
No full textThe rheology of three melt compositions containing different amounts of fluorine (F) and chlorine (Cl) or both was investigated with micropenetration and parallel-plate techniques. The heat capacity and configurational entropy of the melts were also determined. The observed viscosity range is between 10(5.5) and 10(13) Pa s. The melts were produced in a 1 atm furnace at temperatures between 1523 and 1923 K using oxide and carbonate compounds. The halogens were incorporated using halides and halogen-bearing ammonium compounds. The first composition is a peraluminous Na2O-CaO-Al2O3-SiO2 melt (ANCS) with an apparent NBO/T of similar to-0.08, the second composition is a peralkaline Na2O-CaO-Al2O3-SiO2 melt (NACS) (NBO/T = similar to 0.24), which is an analogue for phonolites, and the third is an aluminium-free Na2O-CaO-SiO2 melt (NCS) (NBO/T of similar to 0.68). Five halogen-bearing ANCS melts with up to 1.10 mol% Cl and 1825 mol% F, 6 halogen-bearing NACS melts with up to 138 mol% Cl and 2.58 mol% F and 3 halogen-bearing NCS melts with up to 2.15 mol% Cl and 2.04 mol% F were investigated in this study. Fluorine was found to decrease the viscosity for all compositions, but not with equal strength. Interpolated to 1 mol%, F decreases the viscosity by 0.31 +/- 0.08 log units in the peraluminous melt (ANCS), 0.57 +/- 0.11 log units in the peralkaline melt (NACS) and 0.47 +/- 0.14 log units in the NCS melt. The effect of Cl on rheology depends on the melt composition. Interpolated to 1 mol%, Cl decreases the viscosity by 0.57 +/- 0.13 log units in the peraluminous melt, but increases viscosity by 0.87 +/- 0.10 log units in the peralkaline melt. There is no measurable effect on viscosity due to the addition of chlorine to the aluminium-free melt. In the peraluminous melts the effects of F and Cl add almost linearly to decrease viscosity. In the peralkaline melts, Cl increases the viscosity while F decreases it, if both are present, the effects appear to balance each other; resulting in no change in viscosity for the addition of equal amounts (in mol%) of fluorine and chlorine. The results were obtained from samples with higher and more varied halogen contents than in the most previous studies, therefore they hold true for a wide range of concentrations of both elements and should be taken into account for modelling magmatic processes. (C) 2012 Elsevier B.V. All rights reserved.DFG [WE 1810/9-1
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
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