1,720,954 research outputs found
Generalized Blonder-Tinkham-Klapwijk theory and conductance spectra with particle-hole mixing interface potential
Full text linkWe extend the Blonder-Tinkham-Klapwijk treatment including particle-hole mixing boundary conditions in the Bogoliubov-de Gennes scattering problem to describe anomalous conductance features often reported in normal-metal/superconductor junctions. We calculate the differential conductance spectra and show that conductance dips, not expected in the standard formulation, can be explained in terms of a phase π-shift between the bulk and the interface order parameter. A tight-binding model is also introduced to give a quantitative description of the phase-shift in terms of the transparency and polarization of the interface. We characterize the physics arising from particle-hole mixing boundary conditions at the interface and its effects on the conductance anomalies in superconductor-normal heterostructures
Spin and charge transport in ferromagnet-superconductor-ferromagnet heterostructures: Stoner versus spin mass mismatch mechanism
Full text linkWe study transport phenomena through a ballistic
ferromagnet-superconductor-ferromagnet (F/S/F) junction, comparing the case in
which the ferromagnetic order in the two F layers is of the standard Stoner
type with the case where it is driven by a spin mass mismatch (SMM). It is
shown that the two mechanisms lead to a different behavior in the charge and
the spin conductances, especially when compared to the corresponding
non-superconducting ferromagnet-normal-ferromagnet (F/N/F) junctions. In
particular, when the injected current is perpendicular to the barrier, for high
barrier transparency and large magnetization of the F layers, the large mass
mismatch gives rise to an enhancement of both low-bias charge and spin
conductances of the F/S/F junction, which is not observed in the equal-mass
case. When all the allowed injection directions are considered, the low bias
enhancement of the charge conductance for SMM leads still holds for high
barrier transparency and large magnetization of the F layers. However, in the
case of non-transparent interfaces, spin transport with SMM ferromagnets
exhibits an opposite sign response with respect to the Stoner case at high
biases for all magnetization values, also manifesting a significant
amplification induced by superconductivity at the gap edge. The above mentioned
differences can be exploited to probe the nature of the electronic mechanism
underlying the establishment of the ferromagnetic order in a given material.Comment: 18 pages, 18 figure
Interface effects in superconducting heterostructures
Full text link2014 - 2015This work debates a theoretical investigation of the interfacial effects about heterostructures with normal metals and superconductors. At the beginning we will introduce the basic physical phenomena our calculations deal with and will describe a few experimental results. Then we will provide a description of the Blonder-Tinkham and Klapwijk (BTK) model for normal metal/superconductor junctions and we will introduce the attempt to generalize it to include proximity effect. After we will describe a generalized BTK model introducing a particle-hole mixing interface potential and we will present the main results. Finally, we will extend BTK model to include a spin-dependent potential, e.g. Rashba spin-orbit coupling, at the interface and we will analyze the spin transport properties. [edited by Author]XIV n.s
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
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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