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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
Modeling the interplay of fO2 of fS2 along the FeS-silicate melt equilibrium
No full textIn this conribution we will discuss a simplified thermodynamic description for the saturation
of pure and stoichiometric FeS, either liquid or solid, in magmatic systems.
The Conjugated-Toop-Samis-Flood-Grjotheim model (Moretti and Ottonello, 2005)
has furnished the reference theoretical frame, since already accounting for the solubility
of gaseous sulfur and the speciation and oxidation state of sulfur in silicate
melts. Therefore, we provide here internal consistency with these previous modeling
efforts. If perhaps this does not guarantee the highest possible precision in reproducing
the features of the available reference datasets, it however limits the biases that
inevitably arise when merging different sets of experiments that are incomplete at different
degrees. Our choice encompasses the many sources of uncertainties that originate
by considering all possibly useful data from the geoscientific literature. The derived
model provides an effective sulfogeobarometer, which is superior with respect to
previous model performances. For magmas rising from depth to surface, our appraisal
of molar volumes of melt sulfur-bearing species allows us to model how iron-sulfur
multiple interactions affect oxidation-reduction processes at the different pressures,
approaching or not the FeS saturation threshold, either for liquid or solid phases. In
this respect, the nature of the operating oxygen fugacity buffer is critical. On the basis
of model results on some typical compositions of volcanological interest, Sulfur
Contents at Sulfide Saturation (SCSS) have been calculated, to be applied in all those
cases the redox constraint is lacking
Fluorine partitioning between quadrilateral clinopyroxenes and melt
Full text linkConcentrations of fluorine and chlorine were measured in glasses (quenched melts) and coexisting clinopyroxene, orthopyroxene, olivine, and plagioclase in run products of experiments previously used to measure sulfur partitioning between these phases. The partitioning of F between clinopyroxene and silicate melt was determined in 13 experiments at a variety of pressures, temperatures, and melt compositions ranging from basaltic to dacitic (49 to 66 wt.% SiO2) at 0.8 to 1.2 GPa and 1000 to 1240 26°C, at hydrous and anhydrous conditions. Additionally, we determined the crystal-melt partitioning of F for 4 experiments with plagioclase, 2 with orthopyroxene, and 1 with olivine. Although Cl was also measured in the experiments, the concentrations in the crystals are close to background concentration levels. The partition coefficients of fluorine between clinopyroxene and melt varied from ~0.09 to 0.29 and were linearly dependent upon the concentration of aluminum in the octahedral M1 site of clinopyroxene. Similar relationships are seen when our results are combined with previous measurements of the fluorine partition coefficient between clinopyroxene and melt, but each study shows its unique correlation between the F partition coefficient and AlM1. These dissimilarities in correlations with AlM1 are attributed to differing analytical protocols used in the various studies. However, the combined dataset demonstrates a linear correlation with AlM1, the inverse of the NBO/T 36ratio of the melt (T/NBO), pressure and temperature, which can be described as: ln(DFcpx/L) = (0.2298 ± 0.04847)(T/NBO) – (1.029 ± 0.8045)(AlM1) - (3889 ± 1803)(1/T) - (0.5472 ± 380.1084)(P) + 0.5871 ± 1.304 , where each uncertainty is 1 standard error in the fit (as calculated by the R-project software), T is in K 40and P is in GPa. Although this relationship reproduces 81% of the partitioning data to within 25% 41(relative), the different linear trends of the partition coefficient, DFcpx/L, versus AlM1from different laboratories suggest the need for additional investigations and development of clinopyroxene standards with certified fluorine compositions. Nevertheless, we conclude that the self-consistency of each study 44indicates that F partition coefficients determined using one protocol can be applied to minerals or glasses analyzed using the same protocol and ion microprobe to better understand the storage and transport of fluorine in magmatic systems
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
An experimental study of the effect of Fe-Ti oxide crystallization on basaltic liquids
No full textOne-atmosphere melting experiments have been performed on two shoshonitic basalts; SO-1 and SO-20; (14 and 9 wt.% MgO, respectively) and an olivine nephelinite HF-13 (11 wt.% MgO), at different oxygen fugacities (NNO+1, NNO, and FMQ), with temperature varying from super-liquidus (1300C) to near-solidus (1075C) conditions. The experimental results reveal that iron-oxide crystallization depends strongly on oxygen fugacity, and that their precipitation drives residual liquids towards silica enrichment. Residual liquids obtained from SO-1 and SO-20 reached a maximum of 64 wt.% SiO for olivine, clinopyroxene, plagioclase and iron-oxide saturated melts at NNO+1, and 59 wt.% SiO for olivine, clinopyroxene and plagioclase saturated melts at FMQ. The experimental liquids produced from HF-13 reached a maximum of 48 wt.% SiO at NNO and NNO+1 for iron-oxide, olivine and clinopyroxene saturated melts, however no variation in SiO concentration was observed for olivine and clinopyroxene-saturated melts at FMQ
The study of melts in the ternary CaO-MgO-SiO2 at high pressure and the nature of immiscibility in binary systems /
No full textA review of immiscibility data in 62 silicate, borate and germanate binaries permits identification of four groups of cations displaying different immiscibility behaviour. The first group consists of network-modifier cations which have ionic radii ≳ 87.2 pm and coordination numbers equal to, or higher than, 5 (e.g. Ca2+, La3+, U4+). The second group involves cations with ionic radii ≲ 87.2 pm. They have at least two coordination numbers: the first one is always 4 and the second is ≥5; for this reason they are called amphoterics (e.g. Li1+, Mg2+, Al3+). The third group contains cations with variable crystal field stabilization energies (e.g. Fe2+, Ni2+, Cr3+), and the fourth group includes cations with a lone pair of electrons (e.g. Pb 2+, Bi3+, Te4+).Immiscibility data suggest that the origin of phase separation is associated with coulombic repulsions between poorly screened cations. The larger the ionic potential of a cation, the greater the repulsions with its neighbours, and the larger the size of its immiscibility field. However, amphoterics do not obey this rule because network-formers like SiO2 exert a structural control upon immiscibility which creates a selective solution mechanism that affects cations with radii ≲ 87.2 pm. Such small cations appear to be capable of fitting in pentagonal-like cages where they adopt a 4-fold coordination. In tetrahedral coordination, the bonds have a greater covalent character and the oxygens are more polarized towards the amphoterics which efficiently shield their positive charges, reducing coulombic repulsions and thus immiscibility.Experiments performed in the system CaO-MgO-SiO2 at 1.0 GPa show that pressure has little effect on miscibility gaps associated to network-modifiers such as Ca2+ and "weak" amphoterics like Mg 2+. However, it is shown that amphoterics with substantial fractions of cations in 4-fold coordination and cations with variable crystal field stabilization energies capable of high spin to low spin transitions are expected to enlarge their immiscibility fields at high pressure. Magmas rich in these cations are potential candidates to develop phase separation at depth.Experiments were also performed in the systems CaO-SiO2 and MgO-SiO2 at 1.0 GPa and results were combined with all the currently available phase equilibria and thermodynamic data at 1 bar in the same systems to critically optimize the thermodynamic properties of the liquid phase at low and high pressures. Assessments were made with the modified quasi-chemical model of Blander & Pelton using a computer program that simultaneously optimized all reliable data to give a small set of excess Gibbs free energy parameters. Pressure was found to have little effect on the topology of the CaO-SiO2 system but a pronounced one on the MgO-SiO2 binary. These contrasting behaviours from two homovalent and isochemical cations are linked to the polymorphic transition of the magnesium metasilicate. The amphoteric nature of the Mg2+ cation in the liquid phase makes MgO-SiO2 melts compressible but this effect appears to be small
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