Generalized theory and application of Stokes parameter measurements made with a single photoelastic modulator

We report in this paper a generalized theory that describes the interaction between a monochromatic light beam and an optical system that includes one photoelastic modulator, one analyzer, and one photodetector. Based on the theory, a detailed four-step procedure is presented, which allows a precise measurement of the four Stokes parameters. An analysis of the systematic and random errors arising from the four-step measurements is also given as well as a calibration procedure that involves the use of a general retardation plate. As a practical application the procedure is used to analyze the magneto-optical properties of magnetic thin films grown on GaAs(001) substrates

Co-rich cobalt platinum nanowire arrays: effects of annealing

The effects of annealing on the crystal structure and magnetic properties of Co-rich cobalt platinum nanowire arrays embedded in anodic aluminium oxide membranes have been investigated. For this purpose, a rapid thermal annealing to temperatures of 300 °C to 800 °C has been used. Transmission electron microscopy and scanning electron microscopy show that the nanowires have a mean diameter of 14 nm and an estimated wire density of 7.8×1010 cm-2. From x-ray diffraction patterns, we find that the nanowires are hcp and possess a preferred texture in which the c axis of the grains tends to lie along the major axis of the wire. Vibrating sample magnetometry measurements indicate that the easy axis is along the nanowire axis direction. Hysteresis loops, saturation magnetization, squareness ratio (Mr/Ms), and coercivity (perpendicular and parallel to the nanowire axis) have all been investigated as a function of the annealing temperature (TA). Coercivity parallel to the wire axis first increases with TA, attains a maximum at 600 °C (which is 150% of the as-deposited sample), and then decreases. By contrast there is relatively little change in the coercivity measured perpendicular to the wires. The saturation magnetization for the as-deposited sample is 1360 emu/cc and remains almost constant for annealing temperatures up to 500 °C: for TA>500 °C it decreases significantly. The maximum (Mr/Ms) ratio attained in this study is 0.99, the highest value reported thus far for cobalt platinum alloy nanowires. The data suggest that these materials are potential candidates for high-density magnetic recording media

Magnetically soft, high moment grain-refined Fe films: application to magnetic tunnel junctions

The effect of N-doping on the microstructure and magnetic properties of thin Fe layers has been employed to construct all Fe-electrode magnetic tunnel junctions that displayed the tunneling magnetoresistance (TMR) effect. Using low nitrogen doses, a reduction in coercivity was achieved due to grain refinement, without a concurrent decrease in the saturation magnetization of the Fe films caused by the formation of crystalline iron nitride phases. It was demonstrated that this N-induced grain refinement can be applied beneficially to control the switching field of the "free" layer in magnetic trilayer structures. In general the ability to control magnetic softness without reducing saturation magnetization will prove important for incorporating high spin-polarized materials into spin valves and TMR devices

An investigation into the feasibility of psychological interventions for managing the symptoms of trauma and insomnia for women in prison

BackgroundFemale prison populations, when compared to a general population, appear to contain higher prevalence’s of trauma histories with the majority of women in prison having experienced sexual or physical violence in childhood or during their adult lives (Moloney and Moller, 2009). Resultantly, many women in prison exhibit psychological difficulties as a consequence of past victimization including conditions such as Post-Traumatic Stress Disorder, Borderline Personality Disorder, emotional dysregulation, depression, insomnia and also physical morbidity (Zlotnick, 1997).ObjectiveThe objective of this investigation at an HMP was to recognise the experiences and mental health of women who access psychological support in prison and to provide a preliminary understanding of the effectiveness of group psychological intervention to improve symptoms of trauma and insomnia. DesignThis HMP investigation was a cohort feasibility study, which utilized a mixed-method approach to enhance the understanding of the participant’s experiences of accessing psychological support in prison (Sandelowski, 2000). The 71 women invited to participate in the study were designated into one of four psychological group interventions through a process of purposive sequential sampling. The psychometric evaluations of the Post-Traumatic Stress Disorder Symptom Scale (PSS-SR), the General Health Questionnaire – 28 (GHQ-28) and the Insomnia Severity Index (ISI) were administered to measure symptoms of trauma and insomnia before the commencement of the respective psychological group interventions, and three weeks subsequent at the participant’s attendance in the matching intervention focus group.Results Descriptive statistics were used to interpret the clinical effectiveness of the 4 group interventions; and at the 3-week follow-up points the group mean percentage outcomes indicated the ‘exercise as therapy’ (PSS-SR, -16%; GHQ-28, -14%; ISI, -12%) and the ‘improving your sleep’ (PSS-SR, -12%; GHQ-28, -12%; ISI -36%) groups to be more effective at treating the patients symptoms of trauma and sleep than the ‘introduction to anxiety management’ (PSS-SR, -11%; GHQ-28, +8%; ISI, +4%) and the ‘introduction to mindfulness’ (PSS-SR, +1%; GHQ-28, +3%; ISI, +21%) interventions. The quantitative approach also provided information about group intervention non-participation and this illustrated that 30% of women were released or transferred prior to their clinical appointment. Whereas, the qualitative findings from undertaking thematic analysis of the focus groups discourse provided the emergence of six themes that helped to explain the women’s experiences of accessing psychological treatment in prison. These themes were, ‘a pathway to care’, ‘stigma as a therapeutic barrier’, ‘the patient or prisoner paradox’, ‘the retraumatising nature of prison’, ‘the significance of sleep’ and ‘women as stakeholders’. Conclusion The findings of the HMP investigation indicate that prison is an unhelpful environment for women who have trauma histories, as prison can be a factor for the continuation or exacerbation of trauma symptoms and insomnia, even when the women have access to group psychological support. The HMP investigation recommends a series of interim interventions to address the prison culture unhelpful to the psychological wellbeing of detained women. The study’s ultimate recommendation proposes the transformation of HMP into a specialised trauma-focused hospital to manage women detained within the criminal justice system who exhibit symptoms of trauma and insomnia

Seismic evidence for crustal underplating beneath a large igneous province: The Sierra Leone Rise, equatorial Atlantic

Wide-angle seismic profiles reveal anomalously thick crust with a high-velocity (> 7.3 km s− 1) zone under the Sierra Leone Rise, a major mid-plate elevation in the Atlantic lying between the Cape Verde platform and the Cameroon Volcanic Line. A profile recorded over the crest using an ocean-bottom seismometer and surface sonobuoys shows that beneath a 3 km water layer and 1 km of sediments, the basement extends to 16–20 km below sea level. Most velocity-depth values fall outside the expected range for Mesozoic–early Cenozoic ocean floor and stretched continental crust. The detection of 7.3–7.5 km s− 1 material beneath thick, lower-velocity volcanics suggests that magmatic underplating of the crust has occurred. A prominent change in velocity gradient 10–12 km below sea level may mark the transition to underplated material emplaced during the late Cretaceous–early Cenozoic. A pronounced change in Moho depth lies on the line of a long offset fracture zone extending from the African margin, implying underplating was influenced by a pre-existing discontinuity in the lithosphere. Other seismic lines show 7.0–7.2 km s− 1 basement above the underplated zone extending into water depths of almost 5 km. This is probably the intrusive foundation of early-formed crust over a mantle hot-spot. It is suggested that the development of the Sierra Leone Rise is distinct from other Atlantic hot-spot features to which it has been linked because of its setting in a region of intense lithospheric shear

Optimizing computational methods of modeling vertebroplasty in experimentally augmented human lumbar vertebrae

Vertebroplasty has been widely used for the treatment of osteoporotic compression fractures but the efficacy of the technique has been questioned by the outcomes of randomized clinical trials. Finite‐element (FE) models allow an investigation into the structural and geometric variation that affect the response to augmentation. However, current specimen‐specific FE models are limited due to their poor reproduction of cement augmentation behavior. The aims of this study were to develop new methods of modeling the vertebral body in both a nonaugmented and augmented state. Experimental tests were conducted using human lumbar spine vertebral specimens. These tests included micro‐computed tomography imaging, mechanical testing, augmentation with cement, reimaging, and retesting. Specimen‐specific FE models of the vertebrae were made comparing different approaches to capturing the bone material properties and to modeling the cement augmentation region. These methods significantly improved the modeling accuracy of nonaugmented vertebrae. Methods that used the registration of multiple images (pre‐ and post‐augmentation) of a vertebra achieved good agreement between augmented models and their experimental counterparts in terms of predictions of stiffness. Such models allow for further investigation into how vertebral variation influences the mechanical outcomes of vertebroplasty

Transport spectroscopy of an impurity spin in a carbon nanotube double quantum dot.

We make use of spin selection rules to investigate the electron spin system of a carbon nanotube double quantum dot. Measurements of the electron transport as a function of the magnetic field and energy detuning between the quantum dots reveal an intricate pattern of the spin state evolution. We demonstrate that the complete set of measurements can be understood by taking into account the interplay between spin-orbit interaction and a single impurity spin coupled to the double dot. The detection and tunability of this coupling are important for quantum manipulation in carbon nanotubes

Risks and benefits of oxygen therapy

Mootha and Chinnery review the risks and benefits of oxygen administration in mitochondrial disease. They highlight probable harm from hyperoxia and possible benefit from hypoxia. At first sight this is counter-intuitive. It seems improbable that reducing the availability of a substrate that enables high-energy phosphate production via oxidative phosphorylation would be of benefit. But recent clinical data beyond the field of inherited metabolic disease support this approach

Fast binary CT using Fourier null space regularization (FNSR)

X-ray CT is increasingly being adopted in manufacturing as a non destructive inspection tool. Traditionally, industrial workflows follow a two step procedure of reconstruction followed by segmentation. Such workflows suffer from two main problems: (1) the reconstruction typically requires thousands of projections leading to increased data acquisition times. (2) The application of the segmentation process a posteriori is dependent on the quality of the original reconstruction and often does not preserve data fidelity. We present a fast iterative x-ray CT method which simultaneously reconstructs and segments an image from a limited number of projections called Fourier null space regularization (FNSR). The novelty of the approach is in the explicit updating of the image null space with values derived from a regularized image from the previous iteration, thus compensating for any missing projections and effectively regularizing the reconstruction. The speed of the method is achieved by directly applying the Fourier Slice Theorem where the non-uniform fast Fourier transform (NUFFT) is used to compute the frequency spectrum of the projections at their positions in the image k-space. At each iteration a segmented image is computed which is used to populate the null values of the image k-space effectively steering the reconstruction towards a binary solution. The effectiveness of the method to generate accurate reconstructions is demonstrated and benchmarked against other iterative reconstruction techniques using a series of numerical examples. Finally, FNSR is validated using industrial x-ray CT data where accurate reconstructions were achieved with 18 or more projections, a significant reduction from the 5000 needed by filtered back projection