Extruding the vortex lattice: two reacting populations of dislocations

A controllable soft solid is realised in vortex matter in a type II superconductor. The two-dimensional unit cell area can be varied by a factor of $10^4$ in the solid phase, without a change of crystal symmetry offering easy exploration of extreme regimes compared to ordinary materials. The capacity to confine two-dimensional vortex matter to mesoscopic regions provides an arena for the largely unexplored metallurgy of plastic deformation at large density gradients. Our simulations reveal a novel plastic flow mechanism in this driven non-equilibrium system, utilising two distinct, but strongly interacting, populations of dislocations. One population facilitates the relaxation of density; a second aids the relaxation of shear stresses concentrated at the boundaries. The disparity of the bulk and shear moduli in vortex matter ensures the dislocation motion follows the overall continuum flow reflecting density variation

Achieving Ethical Trade through Social Tariffs: The SITS Regime

In the 1990s many heterodox economists joined labor, human rights and environmental advocates in calling for the inclusion of binding labor and environmental standards in trade agreements, along with other measures to ensure that deepening economic integration would serve the goals of promoting human development. Neoclassical trade theorists universally opposed these measures, arguing that countries’ choices over standards represented an entirely legitimate source of comparative advantage. In the end, the free traders prevailed. Over the past five years several mainstream trade theorists have reversed course, and begun to call for fair trade. In this context, fair trade is back on the policy agenda. This paper explores the fair trade proposals that emerged in the 1990s, and counterpoises the multilateral Social Index Tariff Structure (SITS) as an alternative fair trade regime. A SITS regime seeks to protect high standards in those countries where they prevail, while providing both the incentives and means for countries that perform poorly in this regard to improve their standards over time. This working paper explores the construction of a hypothetical SITS regime; estimates the effects of the regime on bilateral trade flows; and generates estimates of the development funds that SITS would make available to promote human development in low-income countries. The authors find that a global system of social tariffs that are very small in magnitude would generate new, substantial and stable flows of development funds while incentivizing a race to the top in labor and environmental standards.

Exploring the knowledge of algebra for teaching.

For the past few decades, researchers in mathematics education have been exploring the concept of pedagogical content knowledge (PCK)—or knowledge related to teaching content—and applying it to various areas of mathematics, such as algebra. Research related to teacher knowledge of algebra is critical because researchers (e.g., Hill, Rowan, & Ball, 2005) have found correlations between some types of teacher knowledge and student achievement in mathematics; students from around the world are outperforming U.S. students on international assessments of mathematics, including algebra (Organization for Economic Cooperation and Development, 2014, 2016); and algebra plays an integral role in the K-12 mathematics curriculum in the U.S. (National Council of Teachers of Mathematics, 2000). Given this background, the purpose of this study was to explore the knowledge of algebra for teaching (KAT) by investigating the following research questions: What is the factor structure underlying mathematics teachers’ KAT, as measured by an established instrument? Are KAT constructs measured similarly in preservice and inservice teachers? And if so, are there latent mean differences in the KAT of these two groups? These research questions were addressed using multiple-group confirmatory factor analysis—a form of structural equation modeling—to analyze survey data (n = 1,248) gathered by KAT researchers at Michigan State University. These researchers designed an instrument to measure three types of algebra knowledge, based on their conceptual framework of KAT: knowledge of school algebra; knowledge of advanced mathematics; and mathematics-for-teaching knowledge, which is similar to PCK (Reckase, McCrory, Floden, Ferrini-Mundy, & Senk, 2015). The analyses suggested that KAT may be a unidimensional construct because a one-factor KAT model fit the data better than a two- or three-factor model. Additionally, the analyses suggested that KAT was measured similarly in preservice and inservice teachers, and that preservice teachers had slightly higher KAT than inservice teachers. Following the results, there is a discussion of connections between the findings and the research literature and implications of the findings, such as providing more CK- and PCK-focused professional development opportunities for algebra teachers. The researcher concludes with some recommendations for future research and closing remarks

Extruding the vortex lattice:two reacting populations of dislocations

A controllable soft solid is realised in vortex matter (Eskildse

CCD QE in the Soft X-ray Range

e2v has previously provided back-illuminated CCDs for several solar observation projects, resulting in a number of key articles on CCD QE in the soft X-ray region. To update these, e2v has arranged for tests on X-ray optimised EMCCDs at a synchrotron. These have shown QE of at least 45% from 40 eV to 2000 eV, with Enhanced process devices having significantly higher QE than Basic process. The measured values were similar to data published from the SDO SXI mission, showing that the e2v process has been stable over many years. The soft X-ray QE measurements show a reasonable fit to the simple layer model for energies > 600 eV. For energies < 100 eV, measurements show slightly lower QE than the model prediction for both Basic and Enhanced processes. For energies 100 eV to 600 eV, measurements show a reasonable fit to the model for the Basic process, but less improvement from the Enhanced process than the model predicts. Comparing the ~80% typical QE for UV-optimised CCDs at 385 nm with the 45% QE measured at 120 eV in this study, there is a discrepancy in QE for two photon energies with the same absorption length measured on CCDs from the same back-thinning process (one type with AR coating, one type without)

LaJuana Terrell and Debra Watkins in a Joint Senior Recital

This is the program for the joint senior recital of mezzo-soprano LaJuana Terrell and pianist Debra Watkins. Pianist Jonathan Besancon accompanied Terrell. The recital took place in the Mabee Fine Arts Center Recital Hall on November 13, 1980

The development of art for art's sake in Australia : 1880-1915

Before leaving for Europe in 1886 Emmanuel Phillips— Fox was a student of George Folingsby at the National Gallery School of Victoria

Density driven vortex motion in narrow channel superconductors

We present simulations and continuum calculations of the rheology and structure of vortex matter confined to flow in narrow channels. First, through the use of Langevin dynamics we perform two-dimensional Couette flow simulations of the vortex liquid in a homogeneous magnetic field. In this sheared geometry we report wall slip at the channel boundary for high shear rates. A result that contrasts with the Newtonian constitutive relation suggested by Marchetti and Nelson(Marchetti, M. C. & Nelson, D. R. Phys. Rev. B 42 , 9938 (1990)). We also find structural ordering near the solid channel boundaries above the bulk melting temperature, Tm bulk We also present simulations and analysis of a novel field gradient applied to a narrow channel superconductor. Here the “solid” vortex lattice flows plastically by enlisting two distinct populations of dislocations. One that relaxes density along the channel and the other that relaxes shear stresses at the boundary. In spite of the lack of a commensurate field over the majority of the channel, the vortex glass remains commensurate with the width of the channel along its entire length by stretching parallel to the flow direction. This non-equilibrium system reaches a steady-state marked by a stable density profile and localised repeatable non-linear dislocation motion. We are further able to show the source of this non-linearity is due to image forces in the channel edges. For wider channels we discuss and implement a novel vortex reservoir geometry de- signed to generate a continuous source of circular grain boundary scars - bubbles. The presence of the bubbles in the channel does not alter the density of the channel but does disturb the steady-state structure and motion of the other populations of dislocations. Finally we discuss the details of a new versatile simulation software that was created for this research, VLSim. This software utilises object-orientation techniques to allow fast future prototyping of varied geometry and magnetic fields