1,720,960 research outputs found
Crystallographic texture analysis: applications in mineralogy and archaeometry
No full textTexture analysis by diffraction
methods has greatly advanced in the last few years
because of instrumental and computational
developments, and it is now to be considered a
routine tool for the analysis of crystallite orientation
in a wide variety of materials, including rocks,
industrial products, and archaeological samples. The
advances in the experimental measurements are
mainly linked to the use of flexible experimental
setups at large radiation sources, such as
synchrotrons and neutron sources, which allow
faster data collection, the use of samples of any size,
and complete coverage of texture and reciprocal
space. The developments in the data analysis are
mainly related to the use of the full diffraction
profiles in place of the single-peak methods. This
produces pole figures and orientation distribution
functions (ODF) that are statistically more
significant and less prone to biases in the data
analysis. Furthermore it opens the possibility of
analysis of complex polyphasic materials, which are
hard to characterize by other experimental
techniques. Applications are discussed concerning
the texture analysis of metamorphic rocks and
archaeological samples
Synthesis and characterization of white micas in the join muscovite-aluminoceladonite
No full textPotassic white micas were synthesized in the K2O-MgO-Al2O3-SiO2-H2O system along the pseudobinary join muscovite-aluminoceladonite (mu-Alcel). Composition of run products as measured by electron microprobe analysis are in the range mu(89)-Alcel(11) to mu(01)-Alcel(99). Cell parameters were determined on powder samples by full-profile Rietveld refinement, using both a single-polytype and a multi-polytype model. The results of both analysis models are in full agreement, and show that the phengite cell parameters have a distinct dependence on the celadonite content: the c parameter shows a monotonic decrease over the full compositional range, whereas the a and b parameters both increase in the Alcel(0)-Alcel(60) range but decrease in the Alcel(60)-Alcel(100) range. The monoclinic b angle decreases slightly with increasing celadonite content. The overall behavior of the cell parameters indicates a decrease of the ditrigonal distortion of the tetrahedral 6-rings, and an increased trioctahedral character of the structure at high celadonite compositions. The molar volume along the solid solution join shows a maximum at about Alcel(30). Molar volume vs. composition can be fitted by a symmetric function for the excess volume yielding a molar volume for end member aluminoceladonite of 13.957 +/- 0.006 J/bar, for muscovite 14.076 +/- 0.004 J/bar, and a symmetric positive deviation from ideal volumes of mixing with W = 0.198 +/- 0.025 J/bar, and r(2) = 0.941. The use of an asymmetric excess volume function does not significantly improve the fit quality (r(2) = 0.945)
In the elderly subiects with Hypertension the postprandial hypotension is a reproducible event and resposible for severe clinical consequences
No full text
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
Early copper Alpine metallurgy
No full textA few of the oldest Alpine copper objects, dating from the Late Neolithic and the Early Copper Age of the Italian Eastern Alps (Alto Adige and Trentino), have been analyzed in order to interpret the manufacturing processes. Conventional metallographic analysis using optical microscopy with reflected light was employed to investigate two copper fragments from Isera La Torretta, Trento. State-of-the-art techniques of crystallographic texture analysis using neutron powder diffraction were used to study three copper axes from Alto Adige: The copper axe of the Iceman, and those from Castelrotto and Colma, Bolzano. The results of the experiments allowed full interpretation of the metallurgical techniques. The copper objects from Isera were rolled from sheets of native copper that had previously been slightly thinned at room temperature. The Iceman and the Colma copper axes were cast into bivalve molds and never underwent significant hot or cold working. The copper axe from Castelrotto shows a marked cube texture deriving from extensive recrystallization due to cold working followed by high
temperature annealing. All three axes are presently in the softened state. Neutron diffraction texture analysis proved to be an excellent innovative technique for the totally non-invasive metallographic analysis and interpretation of thick metal objects
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
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