258 research outputs found

    A flexible multivariate conditional autoregression with application to road safety performance indicators.

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    There is a dearth of models for multivariate spatially correlated data recorded on a lattice. Existing models incorporate some combination of three correlation terms: (i) the correlation between the multiple variables within each site, (ii) the spatial autocorrelation for each variable across the lattice, and (iii) the correlation between each variable at one site and a different variable at a neighbouring site. These may be thought of as correlation, spatial autocorrelation and spatial cross-correlation parameters respectively. This thesis develops a exible multivariate conditional autoregression model where the spatial cross-correlation is asymmetric. A comparison of the performance of the FMCAR with existing MCARs is performed through a simulation exercise. The FMCAR compares well with the other models, in terms of model fit and shrinkage, when applied to a range of simulated data. However, the FMCAR out performs all of the existing MCAR models when applied to data with asymmetric spatial crosscorrelations. To demonstrate the model, the FMCAR model is applied to road safety performance indicators. Namely, casualty counts by mode and severity for vulnerable road users in London, taken from the STATS19 dataset for 2006. However, by exploiting correlation between multiple performance indicators within local authorities and spatial auto and cross-correlation for the variables across local authorities, the FMCAR results in considerable shrinkage of the estimates of local authority performance. Whilst this does not enable local authorities to be differentiated based upon their road safety performance it produces a considerable reduction in the uncertainty surrounding their rankings. This is consistent with previous attempts to improve performance rankings. Further, although the findings of this thesis indicate that there is only mild evidence of asymmetry in the spatial cross-correlations for road casualty counts, the thesis provides a demonstration of the applicability of this model to real world social and economic problems

    Efficiency and Pooling in Western Cape Wine Grape Production

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    This paper uses a stochastic frontier and inefficiency model to test the efficiency of grape production in the Western Cape. The data covers two panels of wine grape farms (34 in Robertson and 36 in Worcester) for 2003 and 2004 and 37 table grape farms in De Doorns for 2004 only. Tests show that Cobb Douglas stochastic production frontiers, with variables to explain the inefficiencies are an appropriate representation of the five individual samples. The stochastic frontier results indicate that output can be explained by land, labour and machinery and that efficiency cab be affected by labour quality, age and education of the farmer, location, the percentage of non-bearing vines and expenditures on electricity for irrigation. These data is sufficiently good to produce reasonable results without pooling, but most applied economists would consider the possibility of improving the estimates by pooling the samples. However, pooling tests show that in this situation with small samples, when pooling is permissible it may not be helpful. More effort on determining the true distributions is needed to improve the way such samples are handled and Bayesian methods may be helpful in this respect.Crop Production/Industries, O13, Q12,

    Economic Values for Perennial Ryegrass Traits in New Zealand Dairy Farm Systems

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    Perennial ryegrass (Lolium perenne L.) is the main species used in dairy pastures throughout New Zealand. There are approximately 30 perennial ryegrass cultivars sold commercially in New Zealand, but currently there is no evaluation system which allows farmers to compare the potential impact of different cultivars on the profitability of their farm business. Such an economic evaluation system requires information on performance values (PV) for cultivars which quantifies their performance with respect to the major productivity traits (herbage accumulation (HA, kg DM/ha), nutritive value and persistence) relative to a genetic base, and economic values (EV, Doyle and Elliott 1983) which estimate the additional profit resulting from each unit change in the trait of interest (Equation 1). Economic value = Δ operating profit/Δ trait of interest (1) This paper describes a system modelling approach developed to estimate EV for seasonal HA of pasture in the major dairying regions of New Zealand. This information is used in the DairyNZ Forage Value Index system (www.dairynzfvi.co.nz) which is being developed to include information on all three productivity traits for commercially available ryegrass cultivars

    Development of a Forage Evaluation System for Perennial Ryegrass Cultivar and Endophyte Combinations in New Zealand Dairy Systems

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    An economic index for perennial ryegrass (Lolium perenne L.) cultivars is a relatively new concept, although recently introduced in Ireland (McEvoy et al. 2011). By contrast, in dairy cattle breeding, the concept of an economic index rating animals and economic values underlying that index is well entrenched (Philipson et al. 1994; Veerkamp, 1998). Historically, forage evaluation data for individual cultivars were either displayed using absolute numbers for seasonal dry matter production within a season or across all seasons with a notation to indicate statistical differences, or percentage values where a reference cultivar is 100. The adoption of an economic index and routine evaluation approach for perennial ryegrass provides a method to identify traits of economic importance to focus plant breeding efforts better and to provide clarity for farmers around predicting cultivars that will maximise farm profit. It also allows for routine tracking of genetic gain of individual traits and the economic index. In this paper, the economic based forage evaluation techniques now used in New Zealand for perennial ryegrass cultivar/endophyte combinations are presented

    The efficient use of the maternity workforce and the implications for safety and quality in maternity care : a population-based, cross-sectional study

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    Background: The performance of maternity services is seen as a touchstone of whether or not we are delivering high-quality NHS care. Staffing has been identified in numerous reports as being a critical component of safe, effective, user-centred care. There is little evidence regarding the impact of maternity workforce staffing and skill mix on the safety, quality and cost of maternity care in the UK. Objectives: To understand the relationship between organisational factors, maternity workforce staffing and skill mix, cost and indicators of safe and high-quality care. Design and methods: Data included Hospital Episode Statistics (HES) from 143 NHS trusts in England in 2010–11 (656,969 delivery records), NHS Workforce Statistics, England, 2010–11, Care Quality Commission Maternity Survey of women’s experiences 2010 and NHS reference costs 2010/11. Ten indicators were derived from HES data. They included healthy mother and healthy baby outcomes and mode of birth. Adjustments were made for background characteristics and clinical risk. Data were analysed to examine the influence of organisational factors, staffing and costs using multilevel logistic regression models. A production function analysis examined the relationship between staffing, skill mix and output. Results: Outcomes were largely determined by women’s level of clinical risk [based on National Institute for Health and Care Excellence (NICE) guidance], parity and age. The effects of trust size and trust university status were small. Larger trust size reduced the chance of a healthy mother outcome and also reduced the likelihood of a healthy mother/healthy baby dyad outcome, and increased the chances of other childbirth interventions. Increased investment in staff did not necessarily have an effect on the outcome and experience measures chosen, although there was a higher rate of intact perineum and also of delivery with bodily integrity in trusts with greater levels of midwifery staffing. An analysis of the multiplicative effects of parity and clinical risk with the staffing variables was more revealing. Increasing the number of doctors had the greatest impact on outcomes in higher-risk women and increasing the number of midwives had the greatest impact on outcomes in lower-risk women. Although increased numbers of support workers impacted on reducing childbirth interventions in lower-risk women, they also had a negative impact on the healthy mother/healthy baby dyad outcomes in all women. In terms of maximising the capacity of a trust to deliver babies, midwives and support workers were found to be substitutes for each other, as were consultants and other doctors. However, any substitution between staff groups could impact on the quality of care given. Economically speaking, midwives are best used in combination with consultants and other doctors. Conclusions: Staffing levels have positive and negative effects on some outcomes, and deployment of doctors and midwives where they have most beneficial impact is important. Managers may wish to exercise caution in increasing the number of support workers who care for higher-risk women. There also appear to be limited opportunities for role substitution. Future work: Wide variations in outcomes remain after adjustment for sociodemographic and clinical risk, and organisational factors. Further research is required on what may be influencing unexplained variation such as organisational climate and culture, use of NICE guidelines in practice, variation of models of care within trusts and women’s choices. Funding: The National Institute for Health Research Health Services and Delivery Research programme

    Do people favour policies that protect future generations? Evidence from a British survey of adults

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    Long-range temporal choices are built into contemporary policy-making, with policy decisions having consequences that play out across generations. Decisions are made on behalf of the public who are assumed to give much greater weight to their welfare than to the welfare of future generations. The paper investigates this assumption. It briefly discusses evidence from sociological and economic studies before reporting the findings of a British survey of people's intergenerational time preferences based on a representative sample of nearly 10,000 respondents. Questions focused on two sets of policies: (i) health policies to save lives and (ii) environmental policies to protect against floods that would severely damage homes, businesses and other infrastructure. For both sets of policies, participants were offered a choice of three policy options, each bringing greater or lesser benefits to their, their children's and their grandchildren's generations. For both saving lives and protecting against floods, only a minority selected the policy that most benefited their generation; the majority selected policies bringing equal or greater benefits to future generations. Our study raises questions about a core assumption of standard economic evaluation, pointing instead to concern for future generations as a value that many people hold in common

    Anthroposophic perspectives in primary care

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    A core challenge of contemporary medicine is to integrate the technological successes of biomedical science with a comprehensive under-standing of the physical, psychosocial, ecological, and spiritual dimensions of health and illness. Toward this end, bridges are being created between conventional medicine and alternative systems of healing which reflect a holistic model of the human being. Even when both conventional and complementary approaches are used side-by-side in the same patient, they remain separate in their basic assumptions and goals. Today\u27s mechanistic disease model is cut off from such notions as life-energy, consciousness, and spirituality, so integral to many alternative paradigms. Anthroposophically Extended Medicine (AEM) is a comprehensive healing system that successfully integrates biomedicine with a more complete understanding of human reality. Originating in Europe at the beginning of the 20th century, AEM has its roots in the Western, scientific worldview. By expanding this worldview, anthroposophy offers the clinician new possibilities for scientific investigation; it also creates bridges to the wisdom of older healing traditions of both East and West

    The Heritability of Amyotrophic Lateral Sclerosis in a Clinically Ascertained United States Research Registry

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    The genetic basis of amyotrophic lateral sclerosis (ALS) is not entirely clear. While there are families with rare highly penetrant mutations in Cu/Zn superoxide dismutase 1 and several other genes that cause apparent Mendelian inheritance of the disease, most ALS occurs in families without another affected individual. However, twin studies suggest that all ALS has a substantial genetic basis. Herein, we estimate the genetic contribution to ALS in a clinically ascertained case series from the United States.We used the database of the Emory ALS Center to ascertain individuals with ALS along with their family histories to determine the concordance among parents and offspring for the disease. We found that concordance for all parent-offspring pairs was low (<2%). With this concordance we found that ALS heritability, or the proportion of the disease explained by genetic factors, is between 40 and 45% for all likely estimates of ALS lifetime prevalence.We found the lifetime risk of ALS is 1.1% in first-degree relatives of those with ALS. Environmental and genetic factors appear nearly equally important for the development of ALS
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