Influence of spatial-intensity contrast in ultraintense laser-plasma interactions.

Increasing the intensity to which high power laser pulses are focused has opened up new research possibilities, including promising new approaches to particle acceleration and phenomena such as high field quantum electrodynamics. Whilst the intensity achievable with a laser pulse of a given power can be increased via tighter focusing, the focal spot profile also plays an important role in the interaction physics. Here we show that the spatial-intensity distribution, and specifically the ratio of the intensity in the peak of the laser focal spot to the halo surrounding it, is important in the interaction of ultraintense laser pulses with solid targets. By comparing proton acceleration measurements from foil targets irradiated with by a near-diffraction-limited wavelength scale focal spot and larger F-number focusing, we find that this spatial-intensity contrast parameter strongly influences laser energy coupling to fast electrons. We find that for multi-petawatt pulses, spatial-intensity contrast is potentially as important as temporal-intensity contrast.

Development of clinical practice guidelines for allied health and nursing assessment and management of Duchenne muscular dystrophy.

PURPOSE: To provide evidence-based guidance specific to allied health and nursing practice for the assessment and management of individuals with Duchenne muscular dystrophy (DMD). MATERIALS AND METHODS: Thirteen key focus areas were identified in consultation with health professionals and consumer advocacy groups. A series of systematic literature reviews were conducted to identify assessment and management strategies for each key focus area. A consensus process using modified Delphi methodology, including an Australia-New Zealand expert consensus meeting, was conducted. Recommendations underwent consultative review with key groups before being finalised and prepared for dissemination. RESULTS: This clinical practice guideline (CPG) generated 19 evidence-based recommendations, 117 consensus-based recommendations and five research recommendations across the 13 focus areas to inform allied health assessment and management of individuals with DMD. CONCLUSIONS: The resulting recommendations can be used in conjunction with existing medical CPGs to improve, standardise and advocate for allied health and rehabilitation care in DMD. The process used here may be useful for the development of CPGs in other rare diseases.Implications for rehabilitationImplementation-ready evidence-based statements to guide clinical care of individuals with DMD are provided with the potential to improve participation, function in the community and quality of life.A model for developing best practice statements for other rare neurological diseases is described.Allied health and nursing health professionals should focus research efforts to generate quality evidence to support rehabilitation practice.

High order mode structure of intense light fields generated via a laser-driven relativistic plasma aperture.

The spatio-temporal and polarisation properties of intense light is important in wide-ranging topics at the forefront of extreme light-matter interactions, including ultrafast laser-driven particle acceleration, attosecond pulse generation, plasma photonics, high-field physics and laboratory astrophysics. Here, we experimentally demonstrate modifications to the polarisation and temporal properties of intense light measured at the rear of an ultrathin target foil irradiated by a relativistically intense laser pulse. The changes are shown to result from a superposition of coherent radiation, generated by a directly accelerated bipolar electron distribution, and the light transmitted due to the onset of relativistic self-induced transparency. Simulations show that the generated light has a high-order transverse electromagnetic mode structure in both the first and second laser harmonics that can evolve on intra-pulse time-scales. The mode structure and polarisation state vary with the interaction parameters, opening up the possibility of developing this approach to achieve dynamic control of structured light fields at ultrahigh intensities.

An optically multiplexed single-shot time-resolved probe of laser-plasma dynamics.

We introduce a new approach to temporally resolve ultrafast micron-scale processes via the use of a multi-channel optical probe. We demonstrate that this technique enables highly precise time-resolved, two-dimensional spatial imaging of intense laser pulse propagation dynamics, plasma formation and laser beam filamentation within a single pulse over four distinct time frames. The design, development and optimization of the optical probe system is presented, as are representative experimental results from the first implementation of the multi-channel probe with a high-power laser pulse interaction with a helium gas jet target.

A cross-sectional study exploring the different roles of individual and group assessment methods in assessing public health nutrition competence.

BACKGROUND: Competency in the practice of public health is essential for dietitians, yet little is known about credible and dependable assessment in this field. The present study aimed to investigate the role of individual and group assessment tasks as elements of a public health nutrition competency-based assessment system. METHODS: Assessment performance data from 158 dietetics students (three group tasks and one individual task) who had completed a practical placement learning experience in a public health nutrition setting were examined using nonparametric techniques. All 158 students were deemed individually 'competent' on completion of the placement. RESULTS: The median mark was significantly lower for the individual compared to the group task, with a greater range of marks achieved in the individual assessment. There was a weak relationship between individual and group marks for the whole cohort (n = 158) (Spearman's rho correlation coefficient = 0.193, P = 0.015). Bland-Altman analysis showed that the mean (SD) agreement between the two assessment tasks was -5.9 (17.7) marks. Systematic bias between the two tasks was also demonstrated, indicating that students with the lowest average mark of the two assessments scored lower on the individual assessment task compared to their group task and those who had a higher average mark scored higher on the individual group assessment compared to their group task. CONCLUSIONS: Student performance in public health differs between individual and group assessment. Individual assessment appears to differentiate between students, yet group work is essential for the development of teamwork skills. Both should be considered in the judgement of public health nutrition competency.

An observational study investigating the impact of simulated patients in teaching communication skills in preclinical dietetic students.

BACKGROUND: Simulated patients (SPs) are often used in dietetics for the teaching and assessment of communication skills. The present study aimed to determine the impact of a SP encounter on communication skills in undergraduate preclinical dietetic students in the context of the resources required for delivering this educational strategy. METHODS: This observational study collected assessment data from four cohorts of third-year dietetic students to examine the effect of participation in SP-embedded Objective Structured Clinical Exams. Students completed two SP interviews, 2 weeks apart, and communication skills were measured on both occasions. A subgroup of students received a video of their SP encounter. Differences between the two SP interview scores were compared to assess the impact of the SP encounter on communication skills. The required staff and resources were described. RESULTS: Data were collected involving 215 students. Out of 30 marks, there was a modest mean (SD) improvement in communication skills from the first to the second SP interview of 2.5 (4.2) (P < 0.01). There was an association between student ability and improvement in communication skills, with failing students demonstrating the greatest improvement between SP encounters. There were no observed benefits for the subset of students who received videos. CONCLUSIONS: Providing repeat SP interview opportunities results in only modest improvement in communication skills for most students. The use of SPs needs to be considered in context of the substantial costs and resources involved and tailored to student ability.

Observations of body mass index in Duchenne muscular dystrophy: a longitudinal study.

BACKGROUND/OBJECTIVES: Nutritional issues that are associated with Duchenne muscular dystrophy (DMD) remain poorly understood. The aim of this analysis was to describe and explore longitudinal observations of body mass index (BMI) in a cohort of children with DMD. SUBJECTS/METHODS: Anthropometric and clinical characteristics were collected retrospectively and longitudinally for boys with DMD seen in two large neuromuscular clinics. BMI Z-scores were determined using the Centers for Disease Control and Prevention reference values for children (2000). RESULTS: Medical records (n=193) were examined from which 75% were included for analysis. The mean age of the cohort at the time of data collection was 11.9 years, with 72% of patients currently or previously using steroids. The highest prevalence of obesity based on the BMI Z-score was 50% at the age of 10 years. Longitudinally, BMI Z-scores from the age of 2 to 12 years plot approximately one s.d. above the mean, after which there is a marked and progressive decline. BMI gainers were identified for whom BMI Z-score increased by 1.65 units compared with the 0.09 units in non-gainers. BMI gainers were younger when they had their first BMI measurement (5.9 vs 7.2 years), and this measure was significantly lower compared with the non-gainers (BMI Z-score: 0.04 vs 1.17). In this cohort, BMI was associated with age, ambulatory status and lung function. CONCLUSIONS: This study demonstrates that boys with DMD using steroid therapy experience shifts in BMI. A declining BMI appears to be associated with increasing age. Interpretation of growth patterns is limited here by a lack of normative growth references in DMD.

A review of nutrition in Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is a recessive X linked genetic disorder characterised by progressive muscle weakness and reduced muscle tone. Affecting only boys, it limits life expectancy to approximately 20 years. A literature review was conducted using MEDLINE and the Cochrane Library, employing the term 'Duchenne muscular dystrophy'. A total of 1491 articles in English were recovered. These papers were searched thematically under the headings: body composition (n = 10), energy expenditure (n = 10), nutrition (n = 6), corticosteroid therapy (n = 55) and gene therapy (n = 199). Key dietetic practice points were identified relevant to nutritional management. Papers supporting these key themes were assigned a level of evidence and grade of recommendation. There is limited high-quality evidence to guide the nutritional management of boys with DMD. Currently, the majority of evidence is based on expert opinion and clinical expertise. Delayed growth, short stature, muscle wasting and increased fat mass are characteristics of DMD and impact on nutritional status and energy requirements. The early introduction of steroids has altered the natural history of the disease, but can exacerbate weight gain in a population already susceptible to obesity. Prior to commencing steroids, anticipatory guidance for weight management should be provided. Malnutrition is a feature of end stage disease requiring a multidisciplinary approach, such as texture modification and supplemental feeding. Micronutrient requirements are yet to be determined but, as a result of corticosteroid treatment, vitamin D and calcium should be supplemented. Some evidence exists supporting supplementation with creatine monohydrate to improve muscle strength. More research is needed to provide a higher quality of evidence for dietitians working within this area.