Smoothing group-based trajectory models through B-splines

Purpose This paper investigates the use of B-spline smoothers as an alternative to polynomials in time when estimating trajectory shape in group-based trajectory models. The use of polynomials in these models can cause undesirable curve shapes, such as uplifts at the end of the trajectory, which may not be present in the data. Moreover, polynomial curves are global, meaning that a data point at one end of the trajectory can affect the shape of the curve at the end. Methods We use the UK Offenders Index 1963 birth cohort to investigate the use of B-splines. The models are fitted using Latent Gold, and two information criteria (BIC and ICL-BIC are used to estimate the number of knots of the B-spline, as well as the number of groups. A small simulation study is also presented. Results A three-group solution was chosen. It is shown that B-splines can provide a better fit to the observed data than cubic polynomials. The offending trajectory groups correspond to the classic groups of adolescent-limited, low-rate chronic and high-rate chronic which were proposed by Moffitt. However ,the shapes of the two chronic trajectory curves are more consistent with the life-course persistent nature of chronic offending than the traditional cubic polynomial curves. The simulation shows improved performance of the B-spline over cubic polynomials. Conclusions The use of B-splines is recommended when fitting group-based trajectory models. Some software products need further development to include such facilities, and we encourage this development

School choice, competition and ethnic segregation in Lancashire:evidence from structural models of two-sided matching

This thesis uses administrative data from the National Pupil Database (NPD) to examine the phenomenon of ethnic sorting into English secondary schools. The thesis investigates the contribution of parental decision-making to observed patterns of school segregation, and also argues that sorting influences the efficacy of competition-based policies for ed- ucational improvement. Focusing upon three towns with ethnically-mixed populations in the North West of Eng- land – Blackburn, Oldham and Preston – the thesis investigates the hypothesis that segregation can be explained by the aggregate effect of individual choices. It is proposed that parents’ preferences for the ethnic characteristics of school peer groups, and socio- economic differences in parental regard for school test score performance, are important factors in contributing to uneven sorting in schools. The impact of sorting on market structure is also examined, both in relation to the amount of choice that parents en- joy in segregated school markets, and the amount of competition that schools face from neighbouring schools. In order to study school choice in the three markets, the thesis develops a random utility model for parental preferences, incorporating proximity, test scores, and preferences for ethnic peer groups. However, data on individuals’ choice of school are lacking in England, and data on pupil allocations from the NPD do not relate straightforwardly to preferences, since popular schools have limited capacity. To deal with this limitation of the data, the thesis adopts a structural game-theoretic model of two-sided matchings, and develops an innovative method to estimate the parameters of the random utility model. In developing the method the thesis considers the inferential properties – notably identification and large-sample bias – of two-sided empirical models, and provides simulation evidence to support the use of such models for estimation of preferences in large many-to-one markets. The thesis contributes to the, hitherto primarily US-based, evidence on ethnic self- segregation in schools. It concludes that there is robust evidence that preferences for ethnic peer groups contribute to sorting in the markets studied. The thesis also presents evidence that different socio-economic groups place different weight upon academic per- formance when choosing a school. In relation to the effects of sorting on competition, the thesis shows that peer preferences and sorting reduce the potential for schools to compete on quality. Finally, the thesis concludes that preference-induced sorting not only hinders the establishment of self-improving school markets, but also inhibits the inter-group contact necessary for socially-cohesive, diverse communities to flourish

The Role of Serine Proteases and Antiproteases in the Cystic Fibrosis Lung

Cystic fibrosis (CF) lung disease is an inherited condition with an incidence rate of approximately 1 in 2500 new born babies. CF is characterized as chronic infection of the lung which leads to inflammation of the airway. Sputum from CF patients contains elevated levels of neutrophils and subsequently elevated levels of neutrophil serine proteases. In a healthy individual these proteases aid in the phagocytic process by degrading microbial peptides and are kept in homeostatic balance by cognate antiproteases. Due to the heavy neutrophil burden associated with CF the high concentration of neutrophil derived proteases overwhelms cognate antiproteases. The general effects of this protease/antiprotease imbalance are impaired mucus clearance, increased and self-perpetuating inflammation, and impaired immune responses and tissue. To restore this balance antiproteases have been suggested as potential therapeutics or therapeutic targets. As such a number of both endogenous and synthetic antiproteases have been trialed with mixed success as therapeutics for CF lung disease

The effect of the Winter Fuel Payment on household temperature and health: a regression discontinuity design study

Background: The Winter Fuel Payment (WFP) is a non-NHS population-level policy intervention that aims to reduce cold exposure and enhance the health and well-being of older adults. Labelling this cash transfer as 'winter fuel' has been shown to lead to increased household energy expenditure, but it is not known if this expenditure produces warmer homes or health benefits. Objectives: First, the association between indoor temperature and health was established to identify the outcome measures most likely to be affected by the WFP. Then, whether or not receiving the WFP is associated with raised household temperature levels and/or improved health was assessed. Design: Random and fixed effects regression models were used to estimate the link between ambient indoor temperature and health. A regression discontinuity (RD) design analysis exploiting the sharp eligibility criteria for the WFP was employed to estimate the potential impact of the payment. Setting: The sample was drawn from the English Longitudinal Study of Ageing (ELSA), an observational study of community-dwelling individuals aged ≥ 50 years in England. Participants: Analyses examining the association between household temperature and health had a maximum sample of 12,210 adults aged 50–90 years. The RD analyses drew on a maximum of 5902 observations. Intervention: The WFP provides households with a member who is aged > 60 years (up to 2010, from which point the minimum age increased) in the qualifying week with a lump sum annual payment, typically in November or December. Main outcome measures: Differences in indoor temperature were examined, and, following an extensive literature review of relevant participant-reported health indicators and objectively recorded biomarkers likely to be affected by indoor temperature, a series of key measures were selected: blood pressure, inflammation, lung function, the presence of chest infections, subjective health and depressive symptom ratings. Data sources: The first six waves of the ELSA were drawn from, accessible through the UK Data Service (SN:5050 English Longitudinal Study of Ageing: Waves 0–7, 1998–2015). Results: Results from both random and fixed-effects multilevel regression models showed that low levels of indoor temperature were associated with raised systolic and diastolic blood pressure levels and raised fibrinogen levels. However, across the RD models, no evidence was found that the WFP was consistently associated with differences in either household temperature or the health of qualifying (vs. non-qualifying) households. Limitations: The presence of small effects cannot be ruled out, not detectable because of the sample size in the current study. Conclusions: This study capitalised on the sharp assignment rules regarding WFP eligibility to estimate the potential effect of the WFP on household temperature and health in a national sample of English adults. The RD design employed did not identify evidence linking the WFP to warmer homes or potential health and well-being effects. Future work: Further research should utilise larger samples of participants close to the WFP eligibility cut-off point examined during particularly cold weather in order to identify whether or not the WFP is linked to health benefits not detected in the current study, which may have implications for population health and the evaluation of the effectiveness of the WFP. Funding: The National Institute for Health Research Public Health Research programme

The railplug: Development of a new ignitor for internal combustion engines

The goal of the railplug project is to commercialize this miniaturized railgun as an engine technology as rapidly as possible. To improve the technology transfer process, a board of industrial advisors was established. A list of representatives is included at the end of this annual report. The Railplug External Advisory Board (REAB) met in Austin on March 17--18, 1991 to discuss the project plan. A list of comments from the REAB is included at the end of this progress report, along with our written response to those comments. An alternate first'' meeting with some representatives of the REAB was held on July 9, 1991. This meeting was attended by most of the board members who were unable to attend the first meeting. The second meeting of the REAB was held in Toronto, Canada, on October 10, 1991. A list of the board members comments from this meeting is included at the end of this report, along with our written response to those comments. These meetings have proven to be most useful in assuring that this project is conducted as efficiently as possible. The railplug project is essentially divided into three main tasks: (1) Railplug system development; (2) application of railplugs to engines; and (3) railplug durability. The status of each of these tasks is described below

The Impact of Experience with a Family Member with Alzheimer's Disease on Views about the Disease across Five Countries

The objective of this paper is to understand how the public's beliefs in five countries may change as more families have direct experience with Alzheimer's disease. The data are derived from a questionnaire survey conducted by telephone (landline and cell) with 2678 randomly selected adults in France, Germany, Poland, Spain, and the United States. The paper analyzes the beliefs and anticipated behavior of those in each country who report having had a family member with Alzheimer's disease versus those who do not. In one or more countries, differences were found between the two groups in their concern about getting Alzheimer's disease, knowledge that the disease is fatal, awareness of certain symptoms, and support for increased public spending. The results suggest that as more people have experience with a family member who has Alzheimer's disease, the public will generally become more concerned about Alzheimer's disease and more likely to recognize that Alzheimer's disease is a fatal disease. The findings suggest that other beliefs may only be affected if there are future major educational campaigns about the disease. The publics in individual countries, with differing cultures and health systems, are likely to respond in different ways as more families have experience with Alzheimer's disease