Correcting the Bias in the Concentration Index when Income is Grouped

The problem introduced by grouping income data when measuring socioeconomic inequalities in health (and health care) has been highlighted in a recent study. We reexamine this issue and show there is a tendency to underestimate the concentration index at an increasing rate when lowering the number of income categories. This bias results from a form of measurement error and we propose two correction methods. Firstly, the use of instrumental variables (IV) can reduce the error within income categories. Secondly, through a simple formula for correction that is based only on the number of groups. We compare the performance of these methods using data from 15 European countries and the United States. We find that the simple correction formula reduces the impact of grouping and always outperforms the IV approach. Use of this correction can substantially improve comparisons of the concentration index both across countries and across time.concentration index; errors-in-variables; instrumental variables; categorical data; first-order correction

Non-invasive assessment of lower limb alignment is accurate for pre-operative planning and post-operative follow up

Knee alignment is a fundamental measurement in the assessment, monitoring and surgical management of patients with OA. In spite of extensive research into the consequences of malalignment, there is a lack of data regarding the potential variation between supine and standing (functional) conditions. The purpose of this study was to explore this relationship in asymptomatic, osteoarthritic and prosthetic knees. Our hypothesis was that the change in alignment of these three groups would be different. Infrared position capture was used to assess knee alignment for 30 asymptomatic controls and 31 patients with OA, before and after TKA. Coronal and sagittal mechanical femorotibial (MFT) angles in extension (negative values varus/hyperextension) were measured supine and in bi-pedal stance and changes analysed using a paired t-test. To quantify this change in 3D, vector plots of ankle centre displacement relative to the knee centre were produced. Alignment in both planes changed significantly from supine to standing for all three groups, most frequently towards relative varus and extension. In the coronal plane, the mean±SD(°) of the supine/standing MFT angles was 0.1±2.5/−1.1±3.7 for asymptomatic (p=0.001), −2.5±5.7/−3.6±6.0 for osteoarthritic (p=0.009) and −0.7±1.4/ −2.5±2.0 for prosthetic knees (p<0.001). In the sagittal plane, the mean±SD(°) of the supine/standing MFT angles was −1.7±3.3/−5.5±4.9 for asymptomatic (p<0.001), 7.7±7.1/1.8±7.7 for osteoarthritic (p<0.001) and 6.8±5.1/1.4±7.6 for prosthetic knees (p<0.001). The vector plots showed that the trend of relative varus and extension in stance was similar in overall magnitude and direction between the groups. The similarities between each group did not support our hypothesis. The consistent kinematic pattern for different knee types suggests that soft tissue restraints rather than underlying joint deformity may be more influential in dynamic control of alignment from lying to standing. This potential change should be considered when positioning TKA components on supine limbs as post-operative functional alignment may be different

A statistical approach for fracture property realization and macroscopic failure analysis of brittle materials

Lacking the energy dissipative mechanics such as plastic deformation to rebalance localized stresses, similar to their ductile counterparts, brittle material fracture mechanics is associated with catastrophic failure of purely brittle and quasi-brittle materials at immeasurable and measurable deformation scales respectively. This failure, in the form macroscale sharp cracks, is highly dependent on the composition of the material microstructure. Further, the complexity of this relationship and the resulting crack patterns is exacerbated under highly dynamic loading conditions. A robust brittle material model must account for the multiscale inhomogeneity as well as the probabilistic distribution of the constituents which cause material heterogeneity and influence the complex mechanisms of dynamic fracture responses of the material. Continuum-based homogenization is carried out via finite element-based micromechanical analysis of a material neighbor which gives is geometrically described as a sampling windows (i.e., statistical volume elements). These volume elements are well-defined such that they are representative of the material while propagating material randomness from the inherent microscale defects. Homogenization yields spatially defined elastic and fracture related effective properties, utilized to statistically characterize the material in terms of these properties. This spatial characterization is made possible by performing homogenization at prescribed spatial locations which collectively comprise a non-uniform spatial grid which allows the mapping of each effective material properties to an associated spatial location. Through stochastic decomposition of the derived empirical covariance of the sampled effective material property, the Karhunen-Loeve method is used to generate realizations of a continuous and spatially-correlated random field approximation that preserve the statistics of the material from which it is derived. Aspects of modeling both isotropic and anisotropic brittle materials, from a statistical viewpoint, are investigated to determine how each influences the macroscale fracture response of these materials under highly dynamic conditions. The effects of modeling a material both explicitly by representations of discrete multiscale constituents and/or implicitly by continuum representation of material properties is studies to determine how each model influences the resulting material fracture response. For the implicit material representations, both a statistical white noise (i.e., Weibull-based spatially-uncorrelated) and colored noise (i.e., Karhunen-Loeve spatially-correlated model) random fields are employed herein

Paradoxical performance: Predictors and mechanisms associated with the yips and choking

In sport, the ability to perform under heightened levels of pressure is one of the largest differences between those who are successful and those who are not. There are a number of phenomena associated with breakdowns in an athlete’s performance in high pressure environments, collectively known as paradoxical performances (Baumeister & Showers, 1986). The two most prevalent and researched forms of paradoxical performance are the yips and choking. Although choking has been identified as playing a key role in understanding the yips, to date, no literature has explored these phenomena simultaneously. The current literature highlights potential mechanisms which may explain the yips and choking, such as the Attentional Control Theory (Eysenck & Derekshan, 2011) and the Conscious Processing Hypothesis (Masters, 1992). However, there is limited literature on the potential predictors that may increase the susceptibility of both these paradoxical performances and those which do, focus on golf. There are three aims of this thesis. The first aim was to develop a definition that best encompasses all aspects of the yips. This was achieved by conducting a systematic review of the yips literature which supported the development of a new two dimensional yips model including individuals with both focal dystonia and choking (type-III). The second aim was to investigate potential predictors associated with both the yips and choking that was achieved by completing two studies. The first explored the lived experiences of elite level archers who have experienced both choking and the yips and revealed a number of potential predictors associated with both the yips and choking. The second study tested these predictors using online questionnaires with elite level archers and golfers, and confirmed two discrete predictive models for yips and choking. The final aim of the thesis was to investigate the potential mechanisms associated with performance under pressure. A lab-based study where golfers and archers performed under both high and low pressure found that pressure elicited a range of psychological, physiological and kinematic changes in performance. The proposed two dimensional model from the systematic review received initial support for its application. A number of participants met the criteria for each of the different classifications: type-I, those who experience focal dystonia like symptoms; type-II, those who experience choking like symptoms and; type-III, those who experience both focal dystonia and choking like symptoms. This thesis also highlights the role of social predictors of the yips and choking with perfectionistic self-presentation being the most influential for those susceptible for the yips. These findings will enable practitioners to have a better understanding to effectively classify those who experience choking and the yips. This will allow practitioners to more effectively intervene with those who experience different classifications of the yips. The thesis also highlights the issues in the current literature that surround the measurement and conceptualisation of the yips type-I, type-II and type-III behaviour and provides future directions

Accretion Disc Evolution in Single and Binary T Tauri Stars

We present theoretical models for the evolution of T Tauri stars surrounded by circumstellar discs. The models include the effects of pre-main-sequence stellar and time dependent disc evolution, and incorporate the effects of stellar magnetic fields acting on the inner disc. For single stars, consistency with observations in Taurus-Auriga demands that disc dispersal occurs rapidly, on much less than the viscous timescale of the disc, at roughly the epoch when heating by stellar radiation first dominates over internal viscous dissipation. Applying the models to close binaries, we find that because the initial conditions for discs in binaries are uncertain, studies of extreme mass ratio systems are required to provide a stringent test of theoretical disc evolution models. We also note that no correlation of the infra-red colours of T Tauri stars with their rotation rate is observed, in apparent contradiction to the predictions of simple magnetospheric accretion models.Comment: 11 pages, MNRAS in pres

A petrographic and chemical study of the Bevier coal seam

Samples of coal were taken at three inch intervals vertically down the Bevier seam at three localities in Macon and Randolph Counties. Channel samples were collected at the three localities. All samples were analyzed for ash content, total sulphur content, crucible swelling number, and volatile content. The channel samples were analyzed for pyritic sulphur, “sulphate sulphur, and organic sulphur. Thin sections of the samples were used in an estimation of anthraxylon and attritus contents. In all the samples studied, volatile content of the coal seemed to be related to the ash content and the sulphur content. Crucible swelling number also seemed to be related to the volatile content. No correlation was found between the petrographic properties (as seen in thin section) and the analysis figures for ash, sulphur, crucible swelling number, and volatile matter. No apparent stratigraphic correlation could be made from one locality to another on the basis of detailed analysis. However, the rank of the coal is the same, and the shale bench is present in each locality. The lowest sulphur content found in any of the detailed samples was just over 2.0 per cent, a value which is referred to as the background sulphur. Of 64 analyses for sulphur, 31 samples contained between 2.0 and 2.5 per cent sulphur. The coal ash contained a maximum of 0.01 per cent of germanium --Abstract, page 1

Short-run subsidies, take-up, and long-run demand for off-grid solar for the poor: Evidence from large-scale randomized trials in Rwanda

More than a billion people lack access to modern electricity and instead rely on kerosene and other dirty lighting sources, grid expansion is not expected to keep pace with population growth, and both contribute to climate change. Moreover, pneumonia is the leading cause of death for under-fives in the world and kerosene smoke is a significant risk factor. For-profit distribution of low-cost solar LEDs has been touted as an answer, but adoption remains low, especially by the poorest. This study estimates demand curves for both the initial price of low-cost solar LEDs as well as the subsequent user fee for repeated purchases, while also estimating the impact of shortrun subsidies, or a free trial period, on long-run demand. We find uptake is highly sensitive to price with most households purchasing at zero price and none at full cost. Furthermore, using unique objective big data on long-term usage we show that households that received lights for free use their lights as much as those that paid a positive price, disproving the notion, in this context, that consumers will not use goods they received for free. Finally, we find short-term subsidies for user fees actually increases long-term demand in the context of repeated purchases