1,720,958 research outputs found
Superconducting anti-dot arrays from self-assembly template methods
No full textWe present results of electrochemical deposition of superconducting Pb in the pores of templates prepared by self-assembly from colloidal suspensions of polystyrene latex spheres. This technique enables us to create highly ordered superconducting nanostructures with 3D architectures on length scales ranging from 50 to 1000 nm. The prepared samples show pronounced Little-Parks oscillations in T-c and matching effects in magnetization and magnetic susceptibility. Real and imaginary parts of susceptibility follow a universal Cole-Cole curve. Self-field effects play an important role in commensurability behaviour of magnetic moment at low temperatures
Commensurability effects induced by a periodic array of nanoscale anti-dots in Nb superconductor
No full textWe study the interactions of the vortex lattice with a periodic square array of holes in a superconducting Nb film using magnetic and resistive measurements. Three different temperature regions have been observed. They are governed by interplay between vortex–vortex interactions and pinning by holes. At low temperatures flux jumps suppress the commensurability anomalies. In all measurements a peak has been observed close to commensurate states 5–7. The Cole–Cole plot reveals significant changes in the flux penetration mechanism at this point
Vortex phases in YBa2Cu3Oy for B vertical bar vertical bar CuO: impact of regular and random pinning
No full textUsing high angular resolution magnetic measurements we studied YBa2Cu3Oy single crystals with different oxygen contents (6.76y<7.00), for the magnetic field direction closely parallel to the crystal CuO planes. Our data show that the intrinsic pinning resulting in a smectic phase is a dominant factor at low temperatures. Near Tc the point defect pinning prevails and induces a transition from the smectic into a vortex glass phase.<br/
Vortex phases in YBa2Cu3Oy (y=6.5) for B parallel to CuO: impact of regular and random pinning arrays
No full textUsing high angular resolution (up to 10-4 degree) resistive measurements we studied a YBa2Cu3O6.5 single crystal for the magnetic field (B<28 T) direction closely parallel (within the lock-in angle of 0.3°) to the crystal CuO-planes. Our data show that the vortices become confined between the CuO-planes below a well-defined temperature Tcf. Using a pseudo-flux transformer geometry for electrical transport measurements we demonstrate directly a smectic-like vortex movement for temperatures below TS. Our measurements reveal a rich phase diagram for magnetic field orientation BCuO, originating from the inter-play between pinning by the CuO-planes, point-like disorder from oxygen vacancies and temperature fluctuations. Commensurability between the inter-vortex distance and the CuO-layer period causes a pronounced oscillatory behaviour dominated by in-plane vortex movement.<br/
Shape induced anomalies in vortex pinning and dynamics of superconducting antidot arrays with spherical cavities
No full textUsing electrochemical deposition of Pb in the pores of templates prepared by self-assembly from colloidal suspensions of polystyrene latex spheres, well ordered superconducting antidot arrays with spherically shaped holes are fabricated. In contrast to conventional lithographic arrays the samples with spherical cavities demonstrate significantly reduced pinning strength favoring the formation of commensurate states. The ac-flux penetration acquires a hybrid intra- and intervalley regime. For high ac drives an unusual inversion to paramagnetic ac shielding is found at commensurate states
Self-assembly routes towards creating superconducting and magnetic arrays
No full textUsing self-assembly from colloidal suspensions of polystyrene latex spheres we prepared well-ordered templates. By electrochemical deposition of magnetic and superconducting metals in the pores of such templates highly ordered magnetic and superconducting anti-dot nano-structures with 3D architectures were created. Further developments of this template preparation method allow us to obtain dot arrays and even more complicated structures. In magnetic anti-dot arrays we observe a large increase in coercive field produced by nanoscale (50–1000nm) holes. We also find the coercive field to demonstrate an oscillatory dependence on film thickness. In magnetic dot arrays we have explored the genesis of 3D magnetic vortices and determined the critical dot size. Superconducting Pb anti-dot arrays show pronounced Little-Parks oscillations in Tc and matching effects in magnetization and magnetic susceptibility. The spherical shape of the holes results in significantly reduced pinning strength as compared to standard lithographic samples. Our results demonstrate that self-assembly template methods are emerging as a viable, low cost route to prepare sub-micron structures
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
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