Single- and double-scattering production of four muons in ultraperipheral PbPb collisions at the Large Hadron Collider

We discuss production of two $\mu^+\mu^-$ pairs in ultraperipheral ultrarelativistic heavy ion collisions at the LHC. We take into account electromagnetic (two-photon) double-scattering production and for a first time direct $\gamma\gamma$ production of four muons in one scattering. We study the unexplored process $\gamma \gamma \to \mu^+\mu^-\mu^+\mu^-$. We present predictions for total and differential cross sections. Measurable nuclear cross sections are obtained and corresponding differential distributions and counting rates are presented.Comment: 13 pages, 11 figures, 1 tabl

Anti-Retroviral Treatment Outcomes among Older Adults in Zomba District, Malawi

BACKGROUND: There are approximately 3 million people aged 50 and older in sub-Saharan Africa who are HIV-positive. Despite this, little is known about the characteristics of older adults who are on treatment and their treatment outcomes. METHODS: A retrospective cohort analysis was performed using routinely collected data with Malawi Ministry of Health monitoring tools from facilities providing antiretroviral therapy services in Zomba district. Patients aged 25 years and older initiated on treatment from July 2005 to June 2010 were included. Differences in survival, by age group, were determined using Kaplan-Meier survival plots and Cox proportional hazards regression models. RESULTS: There were 10,888 patients aged 25 and older. Patients aged 50 and older (N = 1419) were more likely to be male (P<0.0001) and located in rural areas (P = 0.003) than those aged 25-49. Crude survival estimates among those aged 50-59 were not statistically different from those aged 25-49 (P = 0.925). However, survival among those aged 60 and older (N = 345) was worse (P = 0.019) than among those 25-59. In the proportional hazards model, after controlling for sex and stage at initiation, survival in those aged 50-59 did not differ significantly from those aged 25-49 (hazard ratio 1.00 (95% CI: 0.79 to 1.27; P = 0.998) but the hazard ratio was 1.46 (95% CI: 1.03 to 2.06; P = 0.032) for those aged 60 and older compared to those aged 25-49. CONCLUSIONS: Treatment outcomes of those aged 50-59 are similar to those aged 25-49. A better understanding of how older adults present for and respond to treatment is critical to improving HIV services

High impact = high statistical standards? Not necessarily so.

What are the statistical practices of articles published in journals with a high impact factor? Are there differences compared with articles published in journals with a somewhat lower impact factor that have adopted editorial policies to reduce the impact of limitations of Null Hypothesis Significance Testing? To investigate these questions, the current study analyzed all articles related to psychological, neuropsychological and medical issues, published in 2011 in four journals with high impact factors: Science, Nature, The New England Journal of Medicine and The Lancet, and three journals with relatively lower impact factors: Neuropsychology, Journal of Experimental Psychology-Applied and the American Journal of Public Health. Results show that Null Hypothesis Significance Testing without any use of confidence intervals, effect size, prospective power and model estimation, is the prevalent statistical practice used in articles published in Nature, 89%, followed by articles published in Science, 42%. By contrast, in all other journals, both with high and lower impact factors, most articles report confidence intervals and/or effect size measures. We interpreted these differences as consequences of the editorial policies adopted by the journal editors, which are probably the most effective means to improve the statistical practices in journals with high or low impact factors

SN 2003du: Signatures of the Circumstellar Environment in a Normal Type Ia Supernova?

We present observations of the Type Ia supernova 2003du and report the detectionof an unusual, high-velocity component in the Ca II infrared triplet, similar tofeatures previously observed in SN 2000cx and SN 2001el. This feature exhibits a large expansion velocity (~18,000 km/s) which is nearly constant between -7 and +2 days relative to maximum light, and disappears shortly thereafter. Otherthan this feature, the spectral evolution and light curve resemble those of a normal SN Ia. We find that the Ca II feature can plausibly be caused by a dense shell formed when circumstellar material of solar abundance is overrun by the rapidly expanding outermost layers of the SN ejecta. Model calculations show that the optical and infrared spectra are remarkably unaffected by the circumstellar interaction. In particular, no hydrogen lines are detectable in either absorption or emission. The only qualitatively different features are the strong, high-velocity feature in the Ca II IR-triplet, and a somewhat weaker O I feature near 7,300 AA. The morphology and time evolution of these features provide an estimate for the amount of accumulated matter and an indication of the mixing in the dense shell. We apply these diagnostic tools to SN 2003du and infer that about 2 x 10^{-2} M_sun of solar abundance material may have accumulated in a circumstellar shell prior to the observations. Furthermore, the early light curve data imply that the circumstellar material was originally very close to the progenitor system, perhaps from an accretion disk, Roche lobe or common envelope.Comment: 35 Pages, 11 Figures, to appear in ApJ. Resubmission includes expanded discussion & new figures to match with accepted journal versio

Frailty and use of health and community services by community-dwelling older men: the Concord Health and Ageing in Men Project

Background: frailty is a concept used to describe older people at high risk of adverse outcomes, including falls, functional decline, hospital or nursing home admission and death. The associations between frailty and use of specific health and community services have not been investigated. Methods: the cross-sectional relationship between frailty and use of several health and community services in the last 12 months was investigated in 1,674 community-dwelling men aged 70 or older in the Concord Health and Ageing in Men study, a population-based study conducted in Sydney, Australia. Frailty was assessed using a modified version of the Cardiovascular Health Study criteria. Results: overall, 158 (9.4%) subjects were frail, 679 (40.6%) were intermediate (pre-frail) and 837 (50.0%) were robust. Frailty was associated with use of health and community services in the last 12 months, including consulting a doctor, visiting or being visited by a nurse or a physiotherapist, using help with meals or household duties and spending at least one night in a hospital or nursing home. Frail men without disability in activities of daily living were twice more likely to have seen a doctor in the previous 2 weeks than robust men (adjusted odds ratio 2.04, 95% confidence interval 1.21-3.44), independent of age, comorbidity and socio-economic status. Conclusion: frailty is strongly associated with use of health and community services in community-dwelling older men. The high level of use of medical services suggests that doctors and nurses could play a key role in implementation of preventive intervention

Exercise intervention to prevent falls and enhance mobility in community dwellers after stroke: a protocol for a randomised controlled trial

Background: Stroke is the most common disabling neurological condition in adults. Falls and poor mobility are major contributors to stroke-related disability. Falls are more frequent and more likely to result in injury among stroke survivors than among the general older population. Currently there is good evidence that exercise can enhance mobility after stroke, yet ongoing exercise programs for general community-based stroke survivors are not routinely available. This randomised controlled trial will investigate whether exercise can reduce fall rates and increase mobility and physical activity levels in stroke survivors. Methods and design: Three hundred and fifty community dwelling stroke survivors will be recruited. Participants will have no medical contradictions to exercise and be cognitively and physically able to complete the assessments and exercise program. After the completion of the pre-test assessment, participants will be randomly allocated to one of two intervention groups. Both intervention groups will participate in weekly group-based exercises and a home program for twelve months. In the lower limb intervention group, individualised programs of weight-bearing balance and strengthening exercises will be prescribed. The upper limb/cognition group will receive exercises aimed at management and improvement of function of the affected upper limb and cognition carried out in the seated position. The primary outcome measures will be falls (measured with 12 month calendars) and mobility. Secondary outcome measures will be risk of falling, physical activity levels, community participation, quality of life, health service utilisation, upper limb function and cognition. Discussion: This study aims to establish and evaluate community-based sustainable exercise programs for stroke survivors. We will determine the effects of the exercise programs in preventing falls and enhancing mobility among people following stroke. This program, if found to be effective, has the potential to be implemented within existing community services. Trial registration: The protocol for this study is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12606000479505)

Ecosystem services, well‐being benefits and urbanization associations in a Small Island Developing State

1. Urbanization is a key driver of social and environmental change world‐wide. However, our understanding of its impacts on the multidimensional well‐being benefits that people obtain from ecosystems remains limited. 2. We explored how the well‐being contributions from land‐ and seascapes varied with urbanization level in the Solomon Islands, a fast‐urbanizing Small Island Developing State. Drawing on the social well‐being framework, we compared perceived well‐being benefits derived from ecosystem services in paired urban and rural sites. 3. Our analysis of 200 semi‐structured interviews revealed complex associations between provisioning, regulating and cultural services and well‐being benefits, with all ecosystem services contributing to material, relational and subjective well‐being dimensions. 4. Although patterns of associations between ecosystem services and well‐being benefits were similar between urban and rural dwellers, urban dwellers reported significantly fewer material, relational and subjective well‐being benefits. The most important differences between urban and rural dwellers were in terms of meeting basic material needs (e.g. income and material comfort), feeling connected to nature and feeling happy and satisfied. 5. With urbanization, livelihood activities transition from being subsistence‐based to income‐generating, which is also associated with increased wealth in urban areas. Similar to the relationship between ecosystem service well‐being benefits and urbanization, material wealth was negatively associated with perceptions of well‐being benefits. People with less material wealth appeared more reliant on nature for their multidimensional well‐being. 6. Our findings demonstrate that the altered human–nature relationships in urban areas are associated with decreases in multidimensional well‐being that people derive from nature. Improving access to particular ecosystem services, which make clear contributions to multidimensional well‐being, could be a focus for urban planners and environmental management where enhanced human–nature relationships and poverty alleviation are central goals

Why every observatory needs a disco ball

Commercial disco balls provide a safe, effective and instructive way of observing the Sun. We explore the optics of solar projections with disco balls, and find that while sunspot observations are challenging, the solar disk and its changes during eclipses are easy and fun to observe. We explore the disco ball's potential for observing the moon and other bright astronomical phenomena.Comment: 6 pages, 7 figures. Submitted to Physics Education. Comments welcom