Tunable pinning of a superconducting vortex a by a magnetic vortex

The interaction between a straight vortex line in a superconducting film and a soft magnetic nanodisk in the magnetic vortex state in the presence of a magnetic field applied parallel to the film surfaces is studied theoretically. The superconductor is described by London theory and the nanodisk by the Landau-Lifshitz continuum theory of magnetism, using the approximation known as the rigid vortex model. Pinning of the vortex line by the nanodisk is found to result, predominantly, from the interaction between the vortex line and the changes in the nanodisk magnetization induced by the magnetic field of the vortex line and applied field. In the context of the rigid vortex model, these changes result from the displacement of the magnetic vortex. This displacement is calculated analytically by minimizing the energy, and the pinning potential is obtained. The applied field can tune the pinning potential by controlling the displacement of the magnetic vortex. The nanodisk magnetization curve is predicted to change in the presence of the vortex lineComment: 9 pages, 8 figures. Submitted to Phys. Rev.

Michael Lipsky, 'Street-Level Bureaucracy: Dilemmas of the Individual in Public Service'

This Handbook brings together a collection of leading international authors to reflect on the influence of central contributions, or classics, that have shaped the development of the field of public policy and administration. The Handbook reflects on a wide range of key contributions to the field, selected on the basis of their international and wider disciplinary impact. Focusing on classics that contributed significantly to the field over the second half of the 20th century, it offers insights into works that have explored aspects of the policy process, of particular features of bureaucracy, and of administrative and policy reforms. Each classic is discussed by a leading international scholars. They offer unique insights into the ways in which individual classics have been received in scholarly debates and disciplines, how classics have shaped evolving research agendas, and how the individual classics continue to shape contemporary scholarly debates. In doing so, this volume offers a novel approach towards considering the various central contributions to the field. The Handbook offers students of public policy and administration state-of-the-art insights into the enduring impact of key contributions to the fiel

Building the field of health policy and systems research: framing the questions.

In the first of a series of articles addressing the current challenges and opportunities for the development of Health Policy & Systems Research (HPSR), Kabir Sheikh and colleagues lay out the main questions vexing the field

Global Structure of the Nightside Proton Precipitation during Substorms using Simulations and Observations

In regions of thin strong current sheets, the first adiabatic invariant of protons can be violated leading to pitch angle diffusion into the loss cone and ultimately auroral precipitation. The central plasma sheet typically provides a stretched enough magnetic field configuration to account for the nightside proton precipitation. During substorms, the outflow from the near earth reconnection line at approximately 20 RE brings magnetic flux from the highly stretched magnetotail into the near earth magnetosphere. Once there, the flux piles up forming an azimuthally localized region where the magnetic field is more dipolar. Current flows into and out of the ionospere at the edges of this dipolarized region forming the substorm current wedge (SCW). As the substorm continues, the SCW typically grows azimuthally and radially as the result of the continued flux pileup. Using the OpenGGCM global MHD simulation, we show that the proton precipitation can be split azimuthally due to the arrested scattering in the strongly dipolarized region at the center of the SCW. However, at the edges of the SCW where the dipolarization is not as complete (and certainly outside the SCW), the mean gyroradii increase due to the energization of the near earth magnetotail may be sufficient to facilitate continued scattering. The simulation predictions of auroral splitting are compared to a statistical study using data from the IMAGE SI-12 instrument. The IMAGE SI-12 frequently shows localized azimuthal splitting of the proton aurora similar to the simulations. Additionally, the splitting of the proton aurora is much more common for stronger substorms (lower AL and onset latitude) winch is also argued to be consistent with the simulations

Curiosities of REPINs and RAYTs

Repetitive extragenic palindromic (REP) sequences are a ubiquitous feature of bacterial genomes. Recent work shows that REPs are remnants of a larger mobile genetic element termed a REPIN. REPINs consists of two REP sequences in inverted orientation separated by a spacer region and are thought to be non-autonomous mobile genetic elements that exploit the transposase encoded by REP-Associated tYrosine Transposases (RAYTs). Complimentarity between the two ends of the REPIN suggests that the element forms hairpin structures in single stranded DNA or RNA. In addition to REPINs, other more complex arrangements of REPs have been identified in bacterial genomes, including the genome of the model organism Pseudomonas fluorescens SBW25. Here, we summarize existing knowledge and present new data concerning REPIN diversity. We also consider factors affecting the evolution of REPIN diversity, the ease with which REPINs might be co-opted by host genomes and the consequences of REPIN activity for the structure of bacterial genomes

The azimuthal component of Poynting's vector and the angular momentum of light

The usual description in basic electromagnetic theory of the linear and angular momenta of light is centred upon the identification of Poynting's vector as the linear momentum density and its cross product with position, or azimuthal component, as the angular momentum density. This seemingly reasonable approach brings with it peculiarities, however, in particular with regards to the separation of angular momentum into orbital and spin contributions, which has sometimes been regarded as contrived. In the present paper, we observe that densities are not unique, which leads us to ask whether the usual description is, in fact, the most natural choice. To answer this, we adopt a fundamental rather than heuristic approach by first identifying appropriate symmetries of Maxwell's equations and subsequently applying Noether's theorem to obtain associated conservation laws. We do not arrive at the usual description. Rather, an equally acceptable one in which the relationship between linear and angular momenta is nevertheless more subtle and in which orbital and spin contributions emerge separately and with transparent forms