Suppression of vortex channeling in meandered YBa2Cu3O7-d grain boundaries

We report on the in-plane magnetic field (H) dependence of the critical current density (Jc) in meandered and planar single grain boundaries (GBs) isolated in YBa2Cu3O7-d (YBCO) coated conductors. The Jc(H)properties of the planar GB are consistent with those previously seen in single GBs of YBCO films grown on SrTiO3 bi-crystals. In the straight boundary a characteristic flux channeling regime when H is oriented near the GB plane, associated with a reduced Jc, is seen. The meandered GB does not show vortex channeling since it is not possible for a sufficient length of vortex line to lie within it.Comment: Submitted to AP

Evolution of Directed Triangle Motifs in the Google+ OSN

Motifs are a fundamental building block and distinguishing feature of networks. While characteristic motif distribution have been found in many networks, very little is known today about the evolution of network motifs. This paper studies the most important motifs in social networks, triangles, and how directed triangle motifs change over time. Our chosen subject is one of the largest Online Social Networks, Google+. Google+ has two distinguishing features that make it particularly interesting: (1) it is a directed network, which yields a rich set of triangle motifs, and (2) it is a young and fast evolving network, whose role in the OSN space is still not fully understood. For the purpose of this study, we crawled the network over a time period of six weeks, collecting several snapshots. We find that some triangle types display significant dynamics, e.g., for some specific initial types, up to 20% of the instances evolve to other types. Due to the fast growth of the OSN in the observed time period, many new triangles emerge. We also observe that many triangles evolve into less-connected motifs (with less edges), suggesting that growth also comes with pruning. We complement the topological study by also considering publicly available user profile data (mostly geographic locations). The corresponding results shed some light on the semantics of the triangle motifs. Indeed, we find that users in more symmetric triangle motifs live closer together, indicating more personal relationships. In contrast, asymmetric links in motifs often point to faraway users with a high in-degree (celebrities)

The Fed as a moral enterprise - a framework for decision-making

Central bankers are currently rethinking the frameworks of monetary policy in light of the extreme disruptions and unprecedented policies of the Global Financial Crisis. The paper examines whether a rule based approach that incorporates moral considerations beyond economic utilitarianism could provide a more fair, effective and stable monetary system. It demonstrates that criticisms of Fed policies raise moral questions that reflect a widely held normative framework in the monetary arena. The paper abstracts from the criticisms and elaborates a pluralistic framework based in the work of moral philosopher W.D. Ross consisting of the basic duties of non-harm, beneficence, fidelity, justice, and reparation. It outlines a decision system that relies on moral intuition and strict attention to the facts to balance competing considerations and derive the duty to be followed in the particular circumstance.Les banquiers centraux repensent actuellement les cadres de la politique monétaire à la lumière des perturbations extrêmes et des politiques sans précédent de la crise financière mondiale. L’article examine si une approche fondée sur des règles qui intègre des considérations morales au-delà de l'utilitarisme économique pourrait fournir un système monétaire plus juste, efficace et stable. Il démontre que les critiques des politiques de la Fed soulèvent des questions morales qui reflètent un cadre normatif largement répandu dans le domaine monétaire. L'article résume les critiques et élabore un cadre pluraliste basé sur le travail du philosophe moral W.D.Ross, composé des devoirs fondamentaux de non-préjudice, de bienfaisance, de fidélité, de justice et de réparation. Il décrit un système de décision qui repose sur l'intuition morale et une attention stricte aux faits pour équilibrer les considérations alternatives et dériver le devoir à suivre dans les circonstances particulières

Bloch oscillations of Bose-Einstein condensates: Breakdown and revival

We investigate the dynamics of Bose-Einstein condensates (BEC) in a tilted one-dimensional periodic lattice within the mean-field (Gross-Pitaevskii) description. Unlike in the linear case the Bloch oscillations decay because of nonlinear dephasing. Pronounced revival phenomena are observed. These are analyzed in detail in terms of a simple integrable model constructed by an expansion in Wannier-Stark resonance states. We also briefly discuss the pulsed output of such systems for stronger static fields.Comment: RevTeX4, 9 pages, 14 figure

Hyperatlas: A New Framework for Image Federation

Hyperatlas is an open standard intended to facilitate the large-scale federation of image-based data. The subject of hyperatlas is the space of sphere-to-plane projection mappings (the FITS-WCS information), and the standard consists of coherent collections of these on which data can be resampled and thereby federated with other image data. We hope for a distributed effort that will produce a multi-faceted image atlas of the sky, made by federating many different surveys at different wavelengths and different times. We expect that hyperatlas-compliant imagery will be published and discovered through an International Virtual Observatory Alliance (IVOA) registry, and that grid-based services will emerge for the required resampling and mosaicking.Comment: Published in ADASS XIII proceeding