The Casimir force on a surface with shallow nanoscale corrugations: Geometry and finite conductivity effects

We measure the Casimir force between a gold sphere and a silicon plate with nanoscale, rectangular corrugations with depth comparable to the separation between the surfaces. In the proximity force approximation (PFA), both the top and bottom surfaces of the corrugations contribute to the force, leading to a distance dependence that is distinct from a flat surface. The measured Casimir force is found to deviate from the PFA by up to 15%, in good agreement with calculations based on scattering theory that includes both geometry effects and the optical properties of the material

Curvature condensation and bifurcation in an elastic shell

We study the formation and evolution of localized geometrical defects in an indented cylindrical elastic shell using a combination of experiment and numerical simulation. We find that as a symmetric localized indentation on a semi-cylindrical shell increases, there is a transition from a global mode of deformation to a localized one which leads to the condensation of curvature along a symmetric parabolic crease. This process introduces a soft mode in the system, converting a load-bearing structure into a hinged, kinematic mechanism. Further indentation leads to twinning wherein the parabolic crease bifurcates into two creases that move apart on either side of the line of symmetry. A qualitative theory captures the main features of the phenomena and leads to sharper questions about the nucleation of these defects.Comment: 4 pages, 5 figures, submitted to Physical Review Letter

What Are the Public Health Effects of Direct-to-Consumer Drug Advertising?

Background to the debate: Only two industrialized countries, the United States and New Zealand, allow direct-to-consumer advertising (DTCA) of prescription medicines, although New Zealand is planning a ban [ 1]. The challenge for these governments is ensuring that DTCA is more beneficial than harmful. Proponents of DTCA argue that it helps to inform the public about available treatments and stimulates appropriate use of drugs for high-priority illnesses (such as statin use in people with ischemic heart disease). Critics argue that the information in the adverts is often biased and misleading, and that DTCA raises prescribing costs without net evidence of health benefits

Mitigating impacts of the COVID-19 pandemic on primary and lower secondary children during school closures: a rapid evidence review

BACKGROUND: To control the spread of the SARS-CoV-2 virus during the COVID-19 pandemic, UK schools were closed and education activity was undertaken at home resulting in considerable disruption to children’s education. AIMS: To identify and assess evidence of harms caused to primary and lower secondary pupils during this time and identify mitigation strategies relevant to those harms. METHODS: A rapid evidence review tailored to delivery at pace, drawing on UK evidence for harms and relevant mitigation strategies. FINDINGS ON HARM: There is evidence that the patterns of disruption to education during the pandemic have impacted on children’s learning and attainment, mental health and wellbeing, physical health and nutrition and increased exposure to risk especially for those children living in potentially dangerous domestic settings. Although the quality of the evidence is uneven, it is clear that children living in poverty have been most affected, in particular through food insecurity and conditions triggering stress and anxiety in the home, alongside their more limited opportunities to access digital resources for learning, or indeed outside space for physical activity. Attempts to distinguish harms that impact in the short term from longer lasting harms may take time. It also requires schools to have access to contextually relevant diagnostic tools they can use to assess the range of harms in need of redress in their local context. FINDINGS ON MITIGATION STRATEGIES: We found no evidence for mitigation strategies directly relevant to the harms experienced by children due to school closures under COVID-19. Mitigation strategies suggested in the UK often derived their evidence of efficacy from circumstances quite unlike the prolonged patterns of disruption to education that COVID has caused. Most were designed to address the needs of a few pupils struggling under normal circumstances and were not able to demonstrate their relevance at scale. We therefore examined the primary literature on recovery from unplanned school closures in other countries focused on school-based strategies that had been evaluated as effective under similar conditions. CONCLUSION: We found some evidence of a range of harms but little research evidence on relevant mitigation strategies and an absence of evidence on those strategies that schools themselves have adopted since re-opening, tailored to local needs. Such mitigation strategies may be highly relevant for system learning, and it is important to document and evaluate their efficacy, and indeed learn from them. Closing schools during the pandemic has revealed the importance of schools in safeguarding children. School staff should be given the training and resources to be able to identify children at risk and refer pupils to appropriate services if necessary

Educating Health Professionals about Drug and Device Promotion: Advocates' Recommendations

Mansfield and colleagues outline the recommendations from four advocacy groups for improving the education of health professionals on promotion of drugs and devices

Neutron, electron and X-ray scattering investigation of Cr1-xVx near Quantum Criticality

The weakness of electron-electron correlations in the itinerant antiferromagnet Cr doped with V has long been considered the reason that neither new collective electronic states or even non Fermi liquid behaviour are observed when antiferromagnetism in Cr$_{1-x}$V$_{x}$ is suppressed to zero temperature. We present the results of neutron and electron diffraction measurements of several lightly doped single crystals of Cr$_{1-x}$V$_{x}$ in which the archtypal spin density wave instability is progressively suppressed as the V content increases, freeing the nesting-prone Fermi surface for a new striped charge instability that occurs at x$_{c}$=0.037. This novel nesting driven instability relieves the entropy accumulation associated with the suppression of the spin density wave and avoids the formation of a quantum critical point by stabilising a new type of charge order at temperatures in excess of 400 K. Restructuring of the Fermi surface near quantum critical points is a feature found in materials as diverse as heavy fermions, high temperature copper oxide superconductors and now even elemental metals such as Cr.Comment: 6 pages, 6 figures. Accepted to Physical Review

Continuous melting of compact polymers

The competition between chain entropy and bending rigidity in compact polymers can be addressed within a lattice model introduced by P.J. Flory in 1956. It exhibits a transition between an entropy dominated disordered phase and an energetically favored crystalline phase. The nature of this order-disorder transition has been debated ever since the introduction of the model. Here we present exact results for the Flory model in two dimensions relevant for polymers on surfaces, such as DNA adsorbed on a lipid bilayer. We predict a continuous melting transition, and compute exact values of critical exponents at the transition point.Comment: 5 pages, 1 figur

Isolation of digital dermatitis treponemes from hoof lesions in wild North American elk (Cervus elaphus) in Washington State, USA

Since 2008, a large increase in the numbers of cases of lameness have been seen in wild North American elk (Cervus elaphus) from Washington State, USA. The most recent cases manifested as foot lesions similar both clinically and pathologically to those seen in digital dermatitis (DD) in cattle and sheep, a disease with a bacterial etiopathogenesis. To determine whether the same bacteria considered responsible for DD are associated with elk lameness, lesion samples were subjected to bacterial isolation studies and PCR assays for three phylogroups of relevant DD treponemes. The DD treponemes were isolated from lesional tissues but not from control feet or other areas of the diseased foot (including the coronary band or interdigital space), suggesting that the bacteria are strongly associated with DD lesions and may therefore be causal. In addition, PCR analysis revealed that all three unique DD treponeme phylotypes were found in elk hoof disease, and in 23 of samples, all 3 DD-associated treponemes were present in lesions. Sequence analysis of the 16S rRNA gene showed that the elk lesion treponemes were phylogenetically almost identical to those isolated from cattle and sheep DD lesions. The isolates were particularly similar to two of the three culturable DD treponeme phylotypes: specifically, the Treponema medium/Treponema vincentii-like and Treponema phagedenis-like DD spirochetes. The third treponeme culturable phylogroup (Treponema pedis), although detected by PCR, was not isolated. This is the first report describing isolation of DD treponemes from a wildlife host, suggesting that the disease may be evolving to include a wider spectrum of cloven-hoofed animals. Copyright © 2015, American Society for Microbiology. All Rights Reserved

Symmetry Reduction by Lifting for Maps

We study diffeomorphisms that have one-parameter families of continuous symmetries. For general maps, in contrast to the symplectic case, existence of a symmetry no longer implies existence of an invariant. Conversely, a map with an invariant need not have a symmetry. We show that when a symmetry flow has a global Poincar\'{e} section there are coordinates in which the map takes a reduced, skew-product form, and hence allows for reduction of dimensionality. We show that the reduction of a volume-preserving map again is volume preserving. Finally we sharpen the Noether theorem for symplectic maps. A number of illustrative examples are discussed and the method is compared with traditional reduction techniques.Comment: laTeX, 31 pages, 5 figure