Scalable precision wide-field imaging in radio interferometry: II. AIRI validated on ASKAP data

Accompanying Part I, this sequel delineates a validation of the recently proposed AI for Regularisation in radio-interferometric Imaging (AIRI) algorithm on observations from the Australian Square Kilometre Array Pathfinder (ASKAP). The monochromatic AIRI-ASKAP images showcased in this work are formed using the same parallelised and automated imaging framework described in Part I: ``uSARA validated on ASKAP data''. Using a Plug-and-Play approach, AIRI differs from uSARA by substituting a trained denoising deep neural network (DNN) for the proximal operator in the regularisation step of the forward-backward algorithm during deconvolution. We build a trained shelf of DNN denoisers which target the estimated image-dynamic-ranges of our selected data. Furthermore, we quantify variations of AIRI reconstructions when selecting the nearest DNN on the shelf versus using a universal DNN with the highest dynamic range, opening the door to a more complete framework that not only delivers image estimation but also quantifies epistemic model uncertainty. We continue our comparative analysis of source structure, diffuse flux measurements, and spectral index maps of selected target sources as imaged by AIRI and the algorithms in Part I -- uSARA and WSClean. Overall we see an improvement over uSARA and WSClean in the reconstruction of diffuse components in AIRI images. The scientific potential delivered by AIRI is evident in further imaging precision, more accurate spectral index maps, and a significant acceleration in deconvolution time, whereby AIRI is four times faster than its sub-iterative sparsity-based counterpart uSARA.Comment: Accepted for publication in MNRA

Lifestyle Behaviors and Self-Rated Health: The Living for Health Program

Background. Lack of adherence to dietary and physical activity guidelines has been linked to an increase in chronic diseases in the United States (US). The aim of this study was to assess the association of lifestyle behaviors with self-rated health (SRH). Methods. This cross-sectional study used self-reported data from Living for Health Program ( 1,701) which was conducted from 2008 to 2012 in 190 health fair events in South Florida, US. Results. Significantly higher percent of females as compared to males were classified as obese (35.4% versus 27.0%), reported poor/fair SRH (23.4% versus 15.0%), and were less physically active (33.9% versus 25.4%). Adjusted logistic regression models indicated that both females and males were more likely to report poor/fair SRH if they consumed 2 servings of fruits and vegetables per day (, 95% CI 1.30–3.54; , 95% CI 1.12–7.35, resp.) and consumed mostly high fat foods (, 95% CI 1.03–2.43; , 95% CI 1.67–2.43, resp.). The association of SRH with less physical activity was only significant in females (, 95% CI 1.17–2.35). Conclusion. Gender differences in health behaviors should be considered in designing and monitoring lifestyle interventions to prevent cardiovascular diseases

Electron optics with magnetic vector potential barriers in graphene

An analysis of electron transport in graphene is presented in the presence of various arrangement of delta-function like magnetic barriers. The motion through one such barrier gives an unusual non specular refraction leading to asymmetric transmission. The symmetry is restored by putting two such barriers in opposite direction side by side. Periodic arrangements of such barriers can be used as Bragg reflectors whose reflectivity has been calculated using a transfer matrix formalism. Such Bragg reflectors can be used to make resonant cavities. We also analyze the associated band structure for the case of infinite periodic structures.Comment: Significant revision and added figure

Magnetic imaging of ion-irradiation patterned Co/Pt multilayers using complementary electron and photon probes

The three-dimensional magnetic structure and reversal mechanism of patterned Co/Pt multilayers, were imaged using complementary Lorentz transmission electron microscopy (LTEM) (in-plane component) and magnetic transmission x-ray microscopy (M-TXM) (perpendicular magnetization). The Co/Pt films with perpendicular anisotropy were patterned by ion irradiation through a stencil mask to produce in-plane magnetization in the irradiated regions. The boundaries of the patterns, defined by the transition from out-of-plane to in-plane magnetization, were found to be determined by the stencil mask, whilst the scale of the magnetic reversal by the physical microstructure. The nucleation fields were substantially reduced to 50 Oe for the in-plane regions and 1 kOe for the perpendicular regions, comparing to 4.5 kOe for the as-grown film. The perpendicular reversals were found to always originate at the pattern boundaries

Informing targeted HIV self-testing: a protocol for discrete choice experiments in Malawi, Zambia and Zimbabwe

Introduction HIV self-testing (HIVST) is a new approach to HIV testing where a person collects his or her own specimen, performs an HIV test and interprets the result, either alone or with someone he or she trusts. It is becoming increasingly relevant as a complement to standard-of-care HIV testing and is now recommended by the World Health Organization. Few studies have explored user preferences around HIVST service delivery and optimal models for increasing uptake and linkage to care, particularly among hard-to-reach populations. This paper describes an ongoing study that uses discrete choice experiments (DCE) to identify key HIVST service characteristics that drive people’s willingness to self-test for HIV and link to care, measure the relative strength of user preferences, and explore preference heterogeneity in Southern Africa. Method and Analysis Two DCEs – one on HIVST delivery and one on linkage to care after a positive self-test – are being administered in Malawi, Zambia and Zimbabwe. The designs in each country were informed by a qualitative study, which identified key HIVST service characteristics that influence user decision-making and refined scenario presentations and illustrations. Following data collection, DCE data will be analysed using a multinomial logit model as well as latent class, nested logit and generalised mixed models to examine heterogeneity in preferences by sociodemographic background, HIV testing experience and sexual behaviour. Ethics and dissemination The study has been approved by the College of Medicine Research Ethics Committee in Malawi, the Biomedical Ethics Committee of the University of Zambia, the Medical Research Council of Zimbabwe and the Research Ethics Committee of the London School of Hygiene and Tropical Medicine. Findings from the study will be presented at international conferences and in peer-reviewed journals. The results will help inform the HIVST implementation strategy in Southern Africa, particularly among populations underserved by standard-of-care services, such as men and young women

Electrical Switching Dynamics in Circular and Rectangular Ge2Sb2Te5 Nanopillar Phase Change Memory Devices

We have measured the critical phase change conditions induced by electrical pulses in Ge2Sb2Te5 nanopillar phase change memory devices by constructing a comprehensive resistance map as a function of pulse parameters (width, amplitude and trailing edge). Our measurements reveal that the heating scheme and the details of the contact geometry play the dominant role in determining the final phase composition of the device such that a non-uniform heating scheme promotes partial amorphization/crystallization for a wide range of pulse parameters enabling multiple resistance levels for data storage applications. Furthermore we find that fluctuations in the snap-back voltage and set/reset resistances in repeated switching experiments are related to the details of the current distribution such that a uniform current injection geometry (i.e. circular contact) favors more reproducible switching parameters. This shows that possible geometrical defects in nanoscale phase change memory devices may play an essential role in the performance of the smallest possible devices through modification of the exact current distribution in the active chalcogenide layer. We present a three-dimensional finite element model of the electro-thermal physics to provide insights into the underlying physical mechanisms of the switching dynamics as well as to quantitatively account for the scaling behaviour of the switching currents in both circular and rectangular contact geometries. The calculated temporal evolution of the heat distribution within the pulse duration shows distinct features in rectangular contacts providing evidence for locally hot spots at the sharp corners of the current injection site due to current crowding effects leading to the observed behaviour