Nonlinear effects of multifrequency hydrodynamic instabilities on ablatively accelerated thin shells

Two-dimensional numerical simulations of ablatively accelerated thin-shell fusion targets, susceptible to rupture and failure by Rayleigh–Taylor instability, are presented. The results show that nonlinear effects of Rayleigh–Taylor instability are manifested in the dynamics of the "bubble" (head of the nonlinear fluid perturbation) rather than in the dynamics of the spike (tail of the perturbation). The role of multiwavelength perturbations on the shell is clarified, and rules are presented to predict the dominant nonlinear mode-mode interactions which limit shell performance. It is also shown that the essential dynamics of strongly driven flows are governed by the classical Rayleigh–Taylor instability of an ideal, incompressible, thin fluid layer

Childhood maltreatment and attention deficit hyperactivity disorder symptoms in adults: a large twin study

BACKGROUND: Childhood maltreatment (CM) has been associated with increased risk of attention deficit hyperactivity disorder (ADHD) in children and adults. It is, however, unclear whether this association is causal or due to familial confounding. Method Data from 18 168 adult twins, aged 20-46 years, were drawn from the population-based Swedish twin registry. Retrospective self-ratings of CM (emotional and physical neglect, physical and sexual abuse and witnessing family violence), and self-ratings for DSM-IV ADHD symptoms in adulthood were analysed. Possible familial confounding was investigated using a within twin-pair design based on monozygotic (MZ) and dizygotic (DZ) twins. RESULTS: CM was significantly associated with increased levels of ADHD symptom scores in adults [regression coefficient: 0.40 standard deviations, 95% confidence interval (CI) 0.37-0.43]. Within twin-pair analyses showed attenuated but significant estimates within DZ (0.29, 95% CI 0.21-0.36) and MZ (0.18, 95% CI 0.10-0.25) twin pairs. Similar results emerged for hyperactive/impulsive and inattentive ADHD symptom scores separately in association with CM. We conducted sensitivity analyses for early maltreatment, before age 7, and for abuse and neglect separately, and found similarly reduced estimates in DZ and MZ pairs. Re-traumatization after age 7 did not significantly influence results. CONCLUSIONS: CM was significantly associated with increased ADHD symptoms in adults. Associations were partly due to familial confounding, but also consistent with a causal interpretation. Our findings support cognitive neuroscience studies investigating neural pathways through which exposure to CM may influence ADHD. Clinicians treating adults with ADHD should be aware of the association with maltreatment

The impact of two workplace-based health risk appraisal interventions on employee lifestyle parameters, mental health and work ability: results of a randomized controlled trial

Health risk appraisals (HRA) are a common type of workplace health promotion programme offered by American employers. In the United Kingdom, evidence of their effectiveness for promoting health behaviour change remains inconclusive. This randomized controlled trial examined the effects of two HRA interventions on lifestyle parameters, mental health and work ability in a UK context. A total of 180 employees were randomized into one of three groups: Group A (HRA augmented with health promotion and education activities), Group B (HRA only) and Group C (control, no intervention). After 12 months, changes in mean scoring in 10 lifestyle, mental health and work ability indices were compared, Groups A and B demonstrated non-significant improvements in 70% and 80%, respectively, compared with controls (40%). Odds ratios revealed that, compared with the control group, Group A was 29.2 (95% CI: 9.22–92.27) times more likely to report a perceived change in lifestyle behaviour; Group B 4.4 times (95% CI: 1.65–11.44). In conclusion, participation in the HRA was associated with a higher likelihood of perceived lifestyle behaviour change which was further increased in the augmented HRA group, thereby providing preliminary evidence that HRA and augmented HRA in particular may help UK employees make positive healthy lifestyle changes

Mechanical Forces Due to Lightning Strikes to Aircraft A Pseudo-Stereo DIC Technique for Measuring Full-Field Displacement

Abstract. One of the major considerations currently affecting the design of composite aircraft structures is the damage resulting from lightning attachment. Full-field measurements of the displacement of materials under lightning attachment would provide a greater understanding of the forces induced by the high current waveform. Furthermore the understanding of the forces involved would allow for the validation of finite element models to simulate the effects of lightning attachment, therefore aiding in the design of solutions to reduce damage to aircraft structures. The study aimed to develop a pseudo-stereo high speed digital image correlation technique in order to obtain full-field information during lightning attachment based on a 100kA initial strike over a 500μs duration, the most severe waveform experienced. The technique that was developed gave full-field measurements for a 550x550x2mm 6082-T6 aluminium panel under a 100kA lightning attachment. Two correlation measurements were recorded at 3000 and 5000 frames per second. The displacement results are comparative with the theory of a cylindrical pressure expansion arising from the acoustic shockwave on attachment to the material. Further developments to this system could allow for more reliable results and higher frame rates which can be used to develop finite element simulations based on measured physical data

Core conditions for alpha heating attained in direct-drive inertial confinement fusion

It is shown that direct-drive implosions on the OMEGA laser have achieved core conditions that would lead to significant alpha heating at incident energies available on the National Ignition Facility (NIF) scale. The extrapolation of the experimental results from OMEGA to NIF energy assumes only that the implosion hydrodynamic efficiency is unchanged at higher energies. This approach is independent of the uncertainties in the physical mechanism that degrade implosions on OMEGA, and relies solely on a volumetric scaling of the experimentally observed core conditions. It is estimated that the current best-performing OMEGA implosion [Regan et al., Phys. Rev. Lett. 117, 025001 (2016)10.1103/PhysRevLett.117.025001] extrapolated to a 1.9 MJ laser driver with the same illumination configuration and laser-target coupling would produce 125 kJ of fusion energy with similar levels of alpha heating observed in current highest performing indirect-drive NIF implosions.United States. Department of Energy (DE-FC02-04ER54789)United States. National Nuclear Security Administration (DE-NA0001944

A Comparative Analysis of the Status Anxiety Hypothesis of Socio-economic Inequalities in Health Based on 18,349 individuals in Four Countries and Five Cohort Studies.

The status anxiety hypothesis proposes that systematic inflammation as a consequence of chronic psycho-social stress is a possible pathway linking socio-economic position (SEP) to premature ageing and is a possible explanation for cross-national variation in patterns of health and well-being. Harmonised data from the LIFEPATH consortium on 18,349 individuals aged 50 to 75 and 30,632 observations are used to measure variation in the association between inflammation measured as C-reactive protein and SEP across four countries (Britain, Ireland, Portugal and Switzerland) and five studies (ELSA, Whitehall II, TILDA, EPIPorto and SKIPOGH). Adjusting for population composition, mean concentrations of CRP are highest in Portugal, the country with the highest income inequality and lowest in Switzerland, a lower income inequality country. Across all of the studies, lower SEP groups have higher mean concentrations of CRP and, as predicted by the theory, absolute differentials between SEP groups reflect the pattern of societal income inequality. Adjustment for lifestyle indicators reduces SEP differentials by between 45% and 52% but cannot account for country variation in mean inflammation

A Comparative Analysis of the Status Anxiety Hypothesis of Socio-economic Inequalities in Health Based on 18,349 individuals in Four Countries and Five Cohort Studies

The status anxiety hypothesis proposes that systematic inflammation as a consequence of chronic psycho-social stress is a possible pathway linking socio-economic position (SEP) to premature ageing and is a possible explanation for cross-national variation in patterns of health and well-being. Harmonised data from the LIFEPATH consortium on 18,349 individuals aged 50 to 75 and 30,632 observations are used to measure variation in the association between inflammation measured as C-reactive protein and SEP across four countries (Britain, Ireland, Portugal and Switzerland) and five studies (ELSA, Whitehall II, TILDA, EPIPorto and SKIPOGH). Adjusting for population composition, mean concentrations of CRP are highest in Portugal, the country with the highest income inequality and lowest in Switzerland, a lower income inequality country. Across all of the studies, lower SEP groups have higher mean concentrations of CRP and, as predicted by the theory, absolute differentials between SEP groups reflect the pattern of societal income inequality. Adjustment for lifestyle indicators reduces SEP differentials by between 45% and 52% but cannot account for country variation in mean inflammation

Plasmas and Controlled Nuclear Fusion

Contains research objectives and reports on four research projects.U. S. Atomic Energy Commission (Contract AT(30-1)-3980