1,720,959 research outputs found
Real space and Q space analysis of local disorder induced by Al doping in the SmBa2Cu3O6+d superconductor
No full textThe cation substitutions for copper in RBa2Cu3O6+d (R = Y, Ln; 0 < d < 1) high Tc superconductors are widely studied in order to understand their physical properties [1]. In particular Al seems to be a suitable dopant because: i) it is a non-magnetic ion; ii) it substitutes for copper only on Cu1 (0,0,0) site, far from the superconducting planes; iii) its valence state is fixed, making simple the calculation of the total hole concentration; iiii) it is possible to vary the medium range structure of the superconductor throughout an aluminium-clustering process [2]. However, Aluminium doping introduces local disorder in the structure because of its different valence (+3 instead of +1/+2) and local environment (tetrahedric instead of square planar) in respect to copper. In order to fully understand the effect of Al doping on the physical properties of RBa2Cu3O6+d superconductors the nature of this disorder has to be defined. To do so we have investigated some SmBa2Cu3-xAlxO6+d samples with different Al concentration (x=0, 0.15, 0.33), annealed either in oxidising or in reducing conditions. The long and short range structure of the samples have been determined through the parallel real pace (PDF) and Q space (Rietveld) analysis of XRPD patterns obtained at the ID31 beamline of ESRF facility. References
[1] See, for instance, M.S. Skakle, Mater. Sci. Eng., R23, 1 (1998) and references therein
[2] M. Scavini, M. Daldosso, S. Cappelli, C. Oliva, M. Brunelli, C. Ferrero, A. Lascialfari, Europhys. Lett., 76(3), (2006) 443-44
Modulation of Cu-O chain length in SmBa2Cu3O6+d, by Al doping and clustering
No full textInhomogeneity and disorder are crucial in determining the physical properties of
nanostructured systems in which several physical interactions are active among strongly
correlated components. The specific role of short range Cu-O chain ordering on the raising of
superconductivity in SmBa2Cu3O6+δ superconductors is discussed in this work. We have
examined two Al-doped SmBa2Cu3O6+δ samples having equal aluminium and oxygen concentration
but different mean Cu-O chain lengths. The long and short range structures of the
two samples have been determined through the parallel real space and Q space analysis
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
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
Reciprocal and real space analysis of local disorder in Al doped SmBa2Cu3O6+d superconductor
No full textRelations between structure and physical properties in REBa2Cu3O6+d (RE-123) High Temperature Superconductors (RE = Y, Ln; 0 < d < 1) are not fully understood. As an example, the effect of long range or local Cu-O chain ordering on the superconducting properties has still to be unambiguously probed by experiment [1].
A suitable way to handle this problem is to perform cation substitutions for copper in RE-123 and study the physical and structural properties of the doped materials.
Aluminium seems to be an optimal substituent as it is a non-magnetic ion and it substitutes for copper only on one of the two crystallographic non-equivalent positions, Cu1 (0,0,0) [2].
As a part of a wider study on the relation between the short/long range structure and the physical properties of Al doped REBa2Cu3O6+d, the attention in the present work is focused on the structural disorder induced by Al-doping in SmBa2Cu3-xAlxO6+d
For this purpose samples of SmBa2Cu3-xAlxO6+d0< d < 1, x = 0, 0.15, 0.33) have been investigated by means of X-ray Powder Diffraction (XRPD) at the ID31 beamline of the European Synchrotron Radiation Facility, as a function of aluminium concentration, oxygen non-stoichiometry d and temperature. The XRPD data have been refined also in real space through the analysis of the pair distribution function (PDF) thanks to the high counting statistics and to the wide Q range (Qmax ~ 18 Å-1).
In highly doped samples the tetragonal-to-orthorhombic phase transition is inhibited because the local tetrahedral environment for Aluminium inhibits the formation of long Cu-O chains while oxidising. The actual length of Cu-O chains (at d ~ 1) is a function of both aluminium concentration and clustering.
The aluminium insertion induces local disorder due to heavy ion displacements as it can be evaluated comparing the atomic thermal factors (Uiso) of doped and undoped samples and by the PDF analysis
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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