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Rapid shallow granular flows over inclined planes are often seen in nature in the form of avalanches, landslides and pyroclastic flows. In these situations the flow develops an inversely graded (large at the top) particle-size distribution perpendicular to the plane. As the surface velocity of such flows is larger than the mean velocity, the larger material is transported to the flow front. This causes size segregation in the downstream direction, resulting in a flow front composed of large particles. Since the large particles are often more frictional than the small, the mobility of the flow front is reduced, resulting in a so-called bulbous head. This study focuses on the formation and evolution of this bulbous head, which we show to emerge in both a depth-averaged continuum framework and discrete particle simulations. Furthermore, our numerical solutions of the continuum model converge to a travelling wave solution, which allows for a very efficient computation of the long-time behaviour of the flow. We use small-scale periodic discrete particle simulations to calibrate (close) our continuum framework, and validate the simple one-dimensional (1-D) model with full-scale 3-D discrete particle simulations. The comparison shows that there are conditions under which the model works surprisingly well given the strong approximations made; for example, instantaneous vertical segregation.
The Association of Polar Early Career Scientists (APECS) is an important legacy of the International Polar Year (IPY). APECS continues to foster engagement in education, outreach and communication (EOC) activities relating to the polar regions and provide training for early career researchers (ECRs). We highlight opportunities for training, leadership and skills development, such as the annual Polar Weeks and Antarctica Day celebrations. Participation and engagement in EOC activities actively contributes to career development by enabling ECRs to develop valuable soft skills such as networking, communication and interdisciplinary knowledge. A pilot survey on EOC engagement highlighted that those who organise events also gain leadership skills such as team management. We discuss several factors contributing to the success of APECS in training the next generation of polar leaders. These include the geographical rather than discipline-specific focus of the organisation, utilisation of online resources, including social media, and the strong links with partner organisations. These examples demonstrate how the EOC legacy of IPY has continued due to APECS’ targeted efforts to create EOC opportunities and provide skills and leadership training for ECRs.
Prior research demonstrated that attention-deficit hyperactivity disorder (ADHD) is associated with binge-eating behavior, binge-eating disorder (BED), and bulimia nervosa (BN). The aim of this study was to investigate these associations in an adult twin population, and to determine the extent to which ADHD symptoms and binge-eating behavior share genetic and environmental factors.
We used self-reports of current ADHD symptoms and lifetime binge-eating behavior and associated characteristics from a sample of over 18 000 adult twins aged 20–46 years, from the population-based Swedish Twin Registry. Mixed-effects logistic regression was used to examine the association between ADHD and lifetime binge-eating behavior, BED, and BN. Structural equation modeling was used in 13 773 female twins to determine the relative contribution of genetic and environmental factors to the association between ADHD symptoms and binge-eating behavior in female adult twins.
ADHD symptoms were significantly associated with lifetime binge-eating behavior, BED, and BN. The heritability estimate for current ADHD symptoms was 0.42 [95% confidence interval (CI) 0.41–0.44], and for lifetime binge-eating behavior 0.65 (95% CI 0.54–0.74). The genetic correlation was estimated as 0.35 (95% CI 0.25–0.46) and the covariance between ADHD and binge-eating behavior was primarily explained by genetic factors (91%). Non-shared environmental factors explained the remaining part of the covariance.
The association between adult ADHD symptoms and binge-eating behavior in females is largely explained by shared genetic risk factors.
With the changing distribution of infectious diseases, and an increase in the burden of non-communicable diseases, low- and middle-income countries, including those in Africa, will need to expand their health care capacities to effectively respond to these epidemiological transitions. The interrelated risk factors for chronic infectious and non-communicable diseases and the need for long-term disease management, argue for combined strategies to understand their underlying causes and to design strategies for effective prevention and long-term care. Through multidisciplinary research and implementation partnerships, we advocate an integrated approach for research and healthcare for chronic diseases in Africa.
Relapse is distressingly common after the first episode of psychosis, yet it is poorly understood and difficult to predict. Investigating changes in cognitive function preceding relapse may provide new insights into the underlying mechanism of relapse in psychosis. We hypothesized that relapse in fully remitted first-episode psychosis patients was preceded by working memory deterioration.
Visual memory and verbal working memory were monitored prospectively in a 1-year randomized controlled trial of remitted first-episode psychosis patients assigned to medication continuation (quetiapine 400 mg/day) or discontinuation (placebo). Relapse (recurrence of positive symptoms of psychosis), visual (Visual Patterns Test) and verbal (Letter–Number span test) working memory and stressful life events were assessed monthly.
Remitted first-episode patients (n = 102) participated in the study. Relapsers (n = 53) and non-relapsers (n = 49) had similar baseline demographic and clinical profiles. Logistic regression analyses indicated relapse was associated with visual working memory deterioration 2 months before relapse [odds ratio (OR) 3.07, 95% confidence interval (CI) 1.19–7.92, P = 0.02], more stressful life events 1 month before relapse (OR 2.11, 95% CI 1.20–3.72, P = 0.01) and medication discontinuation (OR 5.52, 95% CI 2.08–14.62, P = 0.001).
Visual working memory deterioration beginning 2 months before relapse in remitted first-episode psychosis patients (not baseline predictor) may reflect early brain dysfunction that heralds a psychotic relapse. The deterioration was found to be unrelated to a worsening of psychotic symptoms preceding relapse. Testable predictors offer insight into the brain processes underlying relapse in psychosis.
In this paper the Very High Energy (VHE) gamma-ray astronomy program at the University of Adelaide is described. VHE gamma rays with energies above ~5 × 1011eV are observed using the atmospheric Cerenkov technique. Results from the first three years observations at Woomera and the current upgrading of the telecope are described. The CANGAROO project, a collaboration between the University of Adelaide and a number of Japanese institutions, is also introduced.
The CANGAROO project incorporates two Čerenkov imaging telescopes at Woomera to obtain stereo images of very high-energy gamma-ray (and cosmic-ray) showers. The first stereo observations, with one imaging system, were made in March 1992, and preliminary stereo imaging observations began in July 1992. This paper describes the stereo imaging technique, the sources under investigation, and the indications from the first data sets.
The Collaboration of Australia and Nippon for a GAmma Ray Observatory in the Outback operates two large telescopes at Woomera (South Australia), which detect the Čerenkov light images produced in the atmosphere by electronpositron cascades initiated by very high energy (~1 TeV or 1012 eV) gamma rays. These gamma rays arise from a different mechanism than at EGRET energies: inverse Compton (IC) emission from relativistic electrons.
The spoke-like images are recorded by a multi-pixel camera which facilitates the rejection of the large numbers of oblique and ragged cosmic ray images. A field of view ~3.5° is required. The Australian team operates a triple 4 m diameter mirror telescope, BIGRAT, with a 37 photomultiplier tube camera and energy threshold 600 GeV. The Japanese operate a single, highly accurate 3.8 m diameter f/1 telescope and high resolution 256 photomultipler tube camera. In 1998 a new 7 m telescope is planned for Woomera with a design threshold ~;200GeV.
Preterm birth may be spontaneous or medically indicated for maternal or fetal reasons. Around 20–25% of preterm births (PTB) follow preterm premature rupture of the membranes (PPROM), however the cause of preterm labour is often unknown. It may represent early maturation and activation of the normal labour process or it may be precipitated by pathological causes. The normal process of labour has a diurnal variation with more deliveries occurring at night. Evidence demonstrating that the diurnal variation persists in preterm deliveries suggest that at least a proportion are due to early maturation of the normal process and the logical assumption is that these may be amenable to prevention or effective treatment. Whatever the cause of preterm delivery, there appears to be a common pathway resulting in activation of inflammatory processes. It is important to distinguish the physiological and pathological causes of preterm labour and not to assume that all inflammation is pathological. The distinction is clinically important since pathological causes may be associated with an adverse intrauterine environment, which would be a contraindication to delaying delivery.
Engineered remediation technologies such as denitrifying bioreactors target single contaminants along a nutrient transfer continuum. However, mixed contaminant discharges to a water body are more common from agricultural systems. Indeed, evidence presented herein indicates that pollution swapping within denitrifying bioreactor systems adds to such deleterious discharges. The present paper proposes a more holistic approach to contaminant remediation on farms, moving from the use of ‘denitrifying bioreactors’ to the concept of a ‘permeable reactive interceptor’ (PRI). Besides management changes, a PRI should contain additional remediation cells for specific contaminants in the form of solutes, particles or gases. Balance equations and case studies representing different geographic areas are presented and used to create weighting factors. Results showed that national legislation with respect to water and gaseous emissions will inform the eventual PRI design. As it will be expensive to monitor a system continuously in a holistic manner, it is suggested that developments in the field of molecular microbial ecology are essential to provide further insight in terms of element dynamics and the environmental controls on biotransformation and retention processes within PRIs. In turn, microbial and molecular fingerprinting could be used as an in-situ cost-effective tool to assess nutrient and gas balances during the operational phases of a PRI.
Information on the burden of hepatitis C virus (HCV) disease is needed to inform policy decisions on primary and secondary prevention. Specimen-based laboratory data (1989–2004) were converted to person-based data and combined with notification data (2004–2009) to describe the burden of HCV infection in Ireland. More than 10 000 people were confirmed as HCV infected in 1989–2004, with the numbers peaking in 2000. The predominant genotypes were 1 (55%) and 3 (39%). Drug use was the most likely risk factor in 80%, with receipt of blood or blood products in 16%. It is estimated that 20 000–50 000 people in Ireland are chronically infected with HCV, a population prevalence of 0·5–1·2%, which is similar to other countries in Northern Europe. This is the first published estimate of the number of chronic HCV infections in Ireland. These data will be of value in health service planning and will contribute to the understanding of HCV infection in Europe.
An experimental study was conducted to determine the mechanisms of transport for delivery of cardiovascular agents using a pH-sensitive hydrogel as the carrier. Copolymer gels based on hydrophilic (2-hydroxyethyl methacrylate) and polybasic (N,N-diethylaminoethyl methacrylate) monomers were formed as membranes and analyzed for their potential to control the diffusion of model solutes as well as heparin and streptokinase. The polybasic materials were selected because they would allow drug delivery to be triggered by microenvironmental pH fluctuations around the site of a blood clot. In slightly basic solutions, the polymers remained in a thermodynamic state of phase-separation, while the polymer absorbed more solution and the mesh size increased once the pH was less than the pKb of the polybasic moiety. The hydrogels' equilibrium swelling ratios were determined as a function of pH, and the mesh sizes were determined by rubber elasticity measurements. Diffusion of model solutes, as well as heparin, was studied using side-by-side diffusion cells to determine the influence of gel morphology and mesh size on the screening of the solutes. Streptokinase release from these gels was modulated by environmental pH.
We are building a biosensor based on ion channels inserted into lipid bilayers that are suspended across an aperture in silicon. The process flow only involves conventional optical lithography and deep Si reactive ion etching to create micromachined apertures in a silicon wafer. In order to provide surface properties for lipid bilayer attachment that are similar to those of the fluorocarbon films that are currently used, we coated the silicon surface with a fluoropolymer using plasma-assisted chemical vapor deposition. When compared with the surface treatment methods using self-assembled monolayers of fluorocarbon chemicals, this novel approach towards modifying the wettability of a silicon dioxide surface provides an easy and fast method for subsequent lipid bilayer formation. Current-Voltage measurements on OmpF ion channels incorporated into these membranes show the voltage dependent gating action expected from a working porin ion channel.
The amorphous to polycrystalline transformation of silicon implanted with high doses of In, Bi, Ga, and Sn is investigated. Each of these elements forms a low temperature eutectic with crystalline silicon and the details of the phase transformations in these systems are found to be very similar. A general model for the transformation based on the nature of the binary solutions is presented.
We present results on the analysis of the interdiffusion process of discrete GaAs layers into a semiinfinite InGaAIP halfspace using Si doping as an agent for enhanced interdiffusion. Very strong segregation and preferential bonding phenomena are observed, resulting in extensive defect formation and loss of lattice match at the virtual interface.
The templated syntheses of our zeolite-type frameworks of metal halides frequently result in the formation of glassy phases or viscous liquids that might be described as ambient temperature molten salts. Having discovered that certain of these materials exhibit remarkable birefringence, we have investigated the structure of both the glass and liquid forms of alkylammonium templated zinc chloride materials by neutron and X-ray diffraction, as well as DSC and polarizing microscopy techniques. Further template control using alkylammonium surfactants as directors has yielded an entire family of liquid crystalline materials with up to 90% inorganic content. The compositional dependence of the structure of these liquid crystalline phases suggests that these materials are best described as “solvent-free” lyotropic liquid crystals.
We report materials characterization on optically pumped InGaN/GaN lasers by farfield and spectral measurements. Through a comparison between measured and calculated farfield data for an In0.15Ga0.85N/In0.05Ga0.95N multi quantum well laser structure with AIGaN cladding layers, we could extract important information about the optical confinement in the transverse direction. The analysis of Fourier-transformed emission spectra of our devices allowed us to make qualitative statements about the material quality in terms of surface pits and cracks. We believe that optical pumping with these supplementary techniques is an important and powerful tool which helps to overcome critical material quality requirements in gallium-nitride.
We investigated an international outbreak of Salmonella Agona with a distinct PFGE pattern associated with an Irish Food company (company X) producing pre-cooked meat products sold in various food outlet chains in Europe. The outbreak was first detected in Ireland. We undertook national and international case-finding, food traceback and microbiological investigation of human, food and environmental samples. We undertook a matched case-control study on Irish cases. In total, 163 cases in seven European countries were laboratory-confirmed. Consumption of food from food outlet chains supplied by company X was significantly associated with being a confirmed case (mOR 18·3, 95% CI 2·2–149·2) in the case-control study. The outbreak strain was isolated from the company's pre-cooked meat products and production premises. Sufficient evidence was gathered to infer the vehicles of infection and sources of the outbreak and to justify the control measures taken, which were plant closure and food recall.