The N=8 Supergravity Hamiltonian as a Quadratic Form

We conjecture that the light-cone Hamiltonian of N=8 Supergravity can be expressed as a quadratic form. We explain why this rewriting is unique to maximally supersymmetric theories. The N=8 quartic interaction vertex is constructed and used to verify that this conjecture holds to second order in the coupling constant

Beyond the local approximation to exchange and correlation: the role of the Laplacian of the density in the energy density of Si

We model the exchange-correlation (XC) energy density of the Si crystal and atom as calculated by variational Monte Carlo (VMC) methods with a gradient analysis beyond the local density approximation (LDA). We find the Laplacian of the density to be an excellent predictor of the discrepancy between VMC and LDA energy densities in each system. A simple Laplacian-based correction to the LDA energy density is developed by means of a least square fit to the VMC XC energy density for the crystal, which fits the homogeneous electron gas and Si atom without further effort.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let

“It will not be easy to accept”: Parents conflicting attitudes towards pre-exposure prophylaxis for HIV prevention amongst adolescent girls and young women in Zimbabwe

Background: Pre-exposure prophylaxis, or PrEP, is a pill that has been hailed as a ‘game changer’ for HIV prevention, based on the belief it provides adolescent girls and young women (AGYW) with a level of user-control. However, engagement with PrEP is often dependent on societal factors, such as social attitudes towards gender, sexuality, and PrEP. As parents' communication on sexual and reproductive health issues with AGYW are central to HIV prevention, it is critical to explore how parents talk and think about PrEP. Objective: To examine parental attitudes towards PrEP for HIV prevention amongst adolescent girls and young women in eastern Zimbabwe. Method: A qualitative interview study with 14 parents from two districts in Manicaland, eastern Zimbabwe. Interviews were transcribed, translated, and subjected to thematic network analysis. The concept of ‘attitudes’ steered the analytical work. Results: Parents' attitudes towards PrEP are conflictual, multi-layered, and contingent on the context in which they reflect and talk about PrEP. While parents aspired to be supportive of innovative HIV prevention methods and wanted to see girl-children protected from HIV, they struggled to reconcile this positive and accepting attitude towards PrEP with traditional ‘good girl’ notions, which stigmatize pre-marital sex. Although a few parents articulated an acceptance of PrEP use amongst their daughters, for many this was simply not possible. Many parents thus co-produce public gender orders that prevent adolescent girls and young women from engaging with PrEP. Conclusions: While parents’ conflicting attitudes towards PrEP may provide spaces and opportunities for change, harmful gender norms and negative attitudes towards PrEP must be addressed at a community and cultural level. Only then can parents and their children have productive conversations about sexual health

Permafrost degradation risk zone assessment using simulation models

In this proof-of-concept study we focus on linking large scale climate and permafrost simulations to small scale engineering projects by bridging the gap between climate and permafrost sciences on the one hand and on the other technical recommendation for adaptation of planned infrastructures to climate change in a region generally underlain by permafrost. We present the current and future state of permafrost in Greenland as modelled numerically with the GIPL model driven by HIRHAM climate projections up to 2080. We develop a concept called Permafrost Thaw Potential (PTP), defined as the potential active layer increase due to climate warming and surface alterations. PTP is then used in a simple risk assessment procedure useful for engineering applications. The modelling shows that climate warming will result in continuing wide-spread permafrost warming and degradation in Greenland, in agreement with present observations. We provide examples of application of the risk zone assessment approach for the two towns of Sisimiut and Ilulissat, both classified with high PTP

Ion Temperatures in the Low Solar Corona: Polar Coronal Holes at Solar Minimum

In the present work we use a deep-exposure spectrum taken by the SUMER spectrometer in a polar coronal hole in 1996 to measure the ion temperatures of a large number of ions at many different heights above the limb between 0.03 and 0.17 solar radii. We find that the measured ion temperatures are almost always larger than the electron temperatures and exhibit a non-monotonic dependence on the charge-to-mass ratio. We use these measurements to provide empirical constraints to a theoretical model of ion heating and acceleration based on gradually replenished ion-cyclotron waves. We compare the wave power required to heat the ions to the observed levels to a prediction based on a model of anisotropic magnetohydrodynamic turbulence. We find that the empirical heating model and the turbulent cascade model agree with one another, and explain the measured ion temperatures, for charge-to-mass ratios smaller than about 0.25. However, ions with charge-to-mass ratios exceeding 0.25 disagree with the model; the wave power they require to be heated to the measured ion temperatures shows an increase with charge-to-mass ratio (i.e., with increasing frequency) that cannot be explained by a traditional cascade model. We discuss possible additional processes that might be responsible for the inferred surplus of wave power.Comment: 11 pages (emulateapj style), 10 figures, ApJ, in press (v. 691, January 20, 2009

Mobility deficit – Rehabilitate, an opportunity for functionality

There are many pathological conditions that cause mobility deficits and that ultimately influence someone’s autonomy.Aims: to evaluate patients with mobility deficits functional status; to implement a Rehabilitation Nursing intervention plan; to monitor health gains through mobility deficits rehabilitation.Conclusion: Early intervention and the implementation of a nursing rehabilitation intervention plan results in health gains (direct or indirect), decreases the risk of developing Pressure Ulcers (PU) and the risk of developing a situation of immobility that affects patients’ autonomy and quality of life

Synthesis, structural and physical properties of δ′\delta'-FeSe1−x_{1-x}

We report on synthesis, structural characterization, resistivity, magnetic and thermal expansion measurements on the as yet unexplored $\delta'$-phase of FeSe$_{1-x}$, here synthesized under ambient- (AP) and high-pressure (HP) conditions. We show that in contrast to $\beta$-FeSe$_{1-x}$, monophasic superconducting $\delta'$-FeSe$_{1-x}$ can be obtained in off-stoichiometric samples with excess Fe atoms preferentially residing in the van der Waals gap between the FeSe layers. The AP $\delta'$-FeSe$_{1-x}$ sample studied here ($T_c$ $\simeq$ 8.5\,K) possesses an unprecedented residual resistivity ratio RRR $\simeq$ 16. Thermal expansion data reveal a small feature around $\sim$90\,K, which resembles the anomaly observed at the structural and magnetic transitions for other Fe-based superconductors, suggesting that some kind of "magnetic state" is formed also in FeSe. %indicative of a fluctuating magnetic ordering. For HP samples (RRR $\simeq$ 3), the disorder within the FeSe layers is enhanced through the introduction of vacancies, the saturated magnetic moment of Fe is reduced and only spurious superconductivity is observed.Comment: 7 pages, 8 figures, published versio