1,720,981 research outputs found
High-pressure single-crystal synchrotron X-ray diffraction study of lillianite
No full textIn this paper, high-pressure data from a synchrotron X-ray diffraction study on a lillianite (Pb3Bi2S6) single crystal up to similar to 21 GPa are presented. A phase transition from lillianite (space group Bbmm, LP lillianite) to the high-pressure form beta-Pb3Bi2S6 (space group Pbnm, HP lillianite) was confirmed and bracketed between 4.90 and 4.92 GPa. The transition is reversible but of first-order with a hysteresis of similar to 2.8 GPa. It showed weak effects of pseudo-merohedral twinning that disappeared upon decompression, testifying to a full recovery of the single crystal of lillianite This makes lillianite an interesting shape-memory material.With a bulk modulus K-4.9 = 78(3) GPa and K' = 5.1(4), beta-Pb3Bi2S6 is markedly less compressible than lillianite [K-0 = 44(2) GPa, K' = 7(1)]. Compressional anisotropy increases markedly in beta-Pb3Bi2S6 with compressibility along the b axis [M-0b = 130(6) GPa and M-b' = 19(3) in lillianite, M-4.9b = 145(4) GPa and M-b' = 16.0(7) in beta-Pb3Bi2S6] significantly larger than that along the other two axes [M-0a = 118(5) GPa, M-a' = 21(3), M-0c = 139(12) GPa, and M-c' = 31(10) in lillianite, M-4.9a = 242(12) GPa, M-a' = 8(1), M-4.9c = 242(5) GPa, and M-c' = 29(1) in beta-Pb3Bi2S6].The behavior of lillianite at high pressure is an interesting case study in relation to non-quenchable ultrahigh-pressure phases likely occurring in the inner Earth, like post-perovskite MgSiO3, the oxide homologue N = 1 of the lillianite series. The beta-Pb3Bi2S6 structure, on the other hand, is the N = 3 homologue of the meneghinite series to which the higher-pressure modification of the post-perovskite structure also belongs (homologue N = 1). This makes the two forms of Pb3Bi2S6 potential equivalents of high- and ultrahigh-pressure Mg silicates that could occur both in the deep earth and in other rocky extrasolar planetary bodies.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Understanding multiscale structure-property correlations in PVDF-HFP electrospun fiber membranes by SAXS and WAXS.
No full textElectrospinning is a versatile technique to produce nanofibrous membranes with applications in filtration, biosensing, biomedical and tissue engineering. The structural and therefore physical properties of electrospun fibers can be finely tuned by changing the electrospinning parameters. The large parameter window makes it challenging to optimize the properties of fibers for a specific application. Therefore, a fundamental understanding of the multiscale structure of fibers and its correlation with their macroscopic behaviors is required for the design and production of systems with dedicated applications. In this study, we demonstrate that the properties of poly(vinylidene fluoride-co-hexafluoro propylene) (PVDF-HFP) electrospun fibers can be tuned by changing the rotating drum speed used as a collector during electrospinning. Indeed, with the help of multiscale characterization techniques such as scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), and wide-angle X-ray scattering (WAXS), we observe that increasing the rotating drum speed not only aligns the fibers but also induces polymeric chain rearrangements at the molecular scale. Such changes result in enhanced mechanical properties and an increase of the piezoelectric β-phase of the PVDF-HFP fiber membranes. We detect nanostructural deformation behaviors when the aligned fibrous membrane is uniaxially stretched along the fiber alignment direction, while an increase in the alignment of the fibers is observed for randomly aligned samples. This was analyzed by performing in situ SAXS measurements coupled with uniaxial tensile loading of the fibrous membranes along the fiber alignment direction. The present study shows that fibrous membranes can be produced with varying degrees of fiber orientation, piezoelectric β-phase content, and mechanical properties by controlling the speed of the rotating drum collector during the fiber production. Such aligned fiber membranes have potential applications for neural or musculoskeletal tissue engineering
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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