1,721,047 research outputs found
Structural, transport, and electronic properties of a layered dichalcogenide AuVS2 with semimetallic properties
No full textWe report on preparation, crystal structure, transport properties, and ab initio band-structure calculations of the layered compound AuVS2. Single crystals of submillimeter size are obtained by reacting powders of BaVS3 with metallic gold at 700 degreesC under an hydrostatic pressure of 3 GPa. According to single-crystal x-ray-diffraction data, the crystal structure is hexagonal with unit-cell parameters a=b=3.224+/-0.001 Angstrom, c=15.039+/-0.002 Angstrom, and space-group symmetry P6(3)/mmc. Temperature-dependent ac resistivity measurements yield a value of room-temperature in-plane resistivity rho(ab)approximate to400 muOmega cm and show a slightly metallic temperature dependence above 250 K. Below this temperature the dependence becomes weakly insulating but the resistivity remains less than or similar to800 muOmega cm at 4.2 K. This behavior is in agreement with the above band-structure calculations which indicate that AuVS2 is a semimetal with an almost vanishing density of states at the Fermi level. Both electron and hole doping would strongly enhance the metallic properties and change the very small Fermi surfaces of the undoped compound into larger pockets with mostly V 3d character
Structural, transport and electronic properties of AuVS2, a new layered dichalcogenide with semimetallic properties
No full textGoing 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
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
Crystal and electronic structures of superconducting YSr2Cu3O6+x
No full textIn order to unveil the mechanism responsible for the large decrease of T-c (DeltaT(c) approximate to -30 K) found in YSr2Cu3O6+x with respect to YBa2Cu3O6+x, we compare structural and electronic properties of these two cuprates. We report X-ray, neutron diffraction, resistivity and ac susceptibility data and results of ab initio electronic structure calculations carried out within the local density approximation. Main structural differences between the two phases are: I) the absence of long CuO chains in YSr2Cu3O6+x possibly due to a large orthorhombic distortion predicted by calculations; 2) the strong compression of the CuO5 pyramids along the z-direction, which reduces the metallic character of the bond between the chain copper and the apical oxygen. This is expected to hinder the hole transfer from the CuO chains to the superconducting CuO2 planes, thus reducing the effective doping of the planes with respect to the optimum doping level. Both the disorder associated with short CuO chains and the reduced hole transfer would qualitatively account for the observed reduction of T-c
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