Bragg- and Moving-glasses: a theory of disordered vortex lattices

We study periodic lattices, such as vortex lattices in type II superconductors in a random pinning potential. For the static case we review the prediction that the phase diagram of such systems consists of a topologically ordered Bragg glass phase, with quasi long range translational order, at low fields. This Bragg glass phase undergoes a transition at higher fields into another glassy phase, with dislocations, or a liquid. This proposition is compatible with a large number of experimental results on BSCCO or Thalium compounds. Further experimental consequences of our results and relevance to other systems will be discussed. When such vortex systems are driven by an external force, we show that, due to periodicity in the direction transverse to motion, the effects of static disorder persist even at large velocity. In $d=3$, at weak disorder, or large velocity the lattice forms a topologically ordered glass state, the ``moving Bragg glass'', an anisotropic version of the static Bragg glass. The lattice flows through well-defined, elastically coupled, static channels. We determine the roughness of the manifold of channels and the positional correlation functions. The channel structure also provides a natural starting point to study the influence of topological defects such as dislocations. In $d=2$ or at strong disorder the channels can decouple along the direction of motion leading to a ``smectic'' like flow. We also show that such a structure exhibits an effective transverse critical pinning force due to barriers to transverse motion, and discuss the experimental consequences of this effect.Comment: Proceedings of M2S-HTSC-V conference (Beijing, Feb 97) to be published in Physica C; 4 pages, 3 figures, uses espcrc2.st

Irreversibility, Mechanical Entanglement and Thermal Melting in Superconducting Vortex Crystals with Point Impurities

We discuss the onset of irreversibility and entanglement of vortex lines in high Tc superconductors due to point disorder and thermal fluctuations using a simplified cage model. A combination of Flory arguments, known results from directed polymers in random media, and a Lindemann criterion are used to estimate the field and temperature dependence of irreversibility, mechanical entanglement and thermal melting. The qualitative features of this dependence, including its nonmonotonicity when disorder is sufficiently strong, are in good agreement with recent experiments.Comment: 7 pages, uses RevTeX, multicol.sty and epsf.sty, 5 EPS figures include

Phase diagrams of flux lattices with disorder

We review the prediction, made in a previous work [Phys. Rev. B 52 (1995)], that the phase diagram of type II superconductors consists of a topologically ordered Bragg glass phase at low fields undergoing a transition at higher fields into a vortex glass or a liquid. We estimate the position of the phase boundary using a Lindemann criterion. We find that the proposed phenomenology is compatible with recent experiments on superconductors.Comment: 7 pages 2 figures, uses epsfi

Structure of vortex liquid phase in irradiated BSCCO(2212) crystals

The c-axis resistivity in irradiated and in pristine BSCCO(2212) crystals is measured as a function of the in-plane magnetic field component at fixed out-of-plane component B_\perp in the vortex liquid phase at T=67 K. From this data we extract the dependence of the phase difference correlation length inside layers on B_\perp and estimate the average length of pieces of vortex lines confined inside columnar defects as a function of the filling factor f=B_\perp / B_\phi. The maximum length, about 15 interlayer distances, is reached near f=0.35.Comment: 4 pages, 4 figure

London 2012 (Re)calling: Youth memories and Olympic ‘legacy’ ether in the hinterland

Engendering interest and support among young people was a key strategy for the organisers of the London 2012 Olympic Games. Part of the approach entailed promoting the event as a context and inspirational catalyst to propel young people's proclivities toward, and enduring participation in, sport and physical activity. Although a variety of participatory platforms were entertained, the discipline of physical education remained a favoured space in which enduring Olympic imperatives could be amalgamated with government policy objectives. In this paper data are presented taken from the initial three years of a longitudinal study on young people's engagement with the London 2012 Olympic Games, sport, physical activity and physical education within the UK's West Midlands region. Memory scholarship is brought together with Olympic critiques, legacy debates, youth work and discussions about physical education to conceptualise participants' anticipations and recollections of the London 2012 Olympic Games as a triptych of narrative fragments: each provides insights regarding youth experiences and the remnants of Olympic ether in the country's hinterland. The paper offers a means subsequently to think differently about how we might play with the qualitative sociological/historiographical moments (experiences, voices, accounts, stories, etc.) that we capture in and through our work

Malnutrition in cleft lip and palate children in Uganda

The objective of this study is to investigate the nutritional status of patients with cleft lip and/or palate when compared to non-cleft lip or palate patients. A retrospective analysis was carried out of all patients aged less than 1 year who were operated on in the Comprehensive Rehabilitation Services in Uganda hospital since opening in April 2009 to November 2010. The data was divided into three groups: cleft lip patients; cleft lip and palate patients and non-cleft patients. The WHO anthropometric calculator was used to calculate weight-for-age Z scores on each patient for the initial outpatient appointment and the operation. The demographic data and Z scores were compared using independent T tests. Three hundred and twenty-one patients were identified, 131 patients had cleft lip alone, 112 patients had cleft lip and palate and 78 patients had no cleft. The cleft lip and palate group had significantly lower Z scores for both the outpatient appointment and operation (i.e. were more malnourished) than either the cleft lip group or the non-cleft group. Malnutrition is a well-documented problem associated with cleft lip and palate. Our research confirms this malnutrition but also highlights the severity of the malnutrition. The patients with cleft lip and palate are unable to feed adequately and therefore need intervention. We operate on these patients once they reach a target weight of 3 kg and repair both lip and palate in one operation to enable patients to feed and improve their nutritional status

Threading dislocation lines in two-sided flux-array decorations

Two-sided flux decoration experiments indicate that threading dislocation lines (TDLs), which cross the entire film, are sometimes trapped in metastable states. We calculate the elastic energy associated with the meanderings of a TDL. The TDL behaves as an anisotropic and dispersive string with thermal fluctuations largely along its Burgers vector. These fluctuations also modify the structure factor of the vortex solid. Both effects can, in principle, be used to estimate the elastic moduli of the material