Sensitivity models for missing covariates in the analysis of survival data from multiple surveys

Using individual patient data from five independent surveys, we evaluate regional variations in survival in cerebral palsy. The influence of four important variables measuring disability, which are only partially observed for many cases, are analysed. Results are compared between a naive complete case analysis; a full likelihood model in which the covariates are assumed to be missing at random and in which each of the binary predictor variables are modelled as independent Bernoulli random variables; a model in which the covariates are modelled by a conditionalwise sequence, accommodating dependencies between the likelihoods of having various mixtures of disabilities; and a model in which the likelihood of a predictor variable being observed is allowed to depend on the value of the covariate itself (NMAR). Fully parametric survival regression models are used and analysis carried out in BUGS. Results suggest that proportions recorded as having severe visual or cognitive impairments are substantially lower than the actual proportions severely impaired. Associations between the likelihood of a particular covariate being recorded and the likelihood of a more severe disability imply that life expectancies for those who are very severely impaired may be up to 20% less than inferences based on complete case analyses

An Independent Evaluation of the Strategic Legal Fund for Vulnerable Young Migrants

The Strategic Legal Fund for Vulnerable Young Migrants1 (SLF) was set up by the Diana Princess of Wales Memorial Fund (DPOWMF) in 2011. When the Diana Fund closed down in late 2012, Trust for London agreed to take over the hosting of the SLF and provided additional funding with Esmée Fairbairn Foundation for a second phase (December 2012 to March 2014 initially, though this has now been extended).In 2012 an interim evaluation of the SLF concluded that it was achieving results, and suggested some changes of focus and operation for the future. One year on, the purpose of this further evaluation is: a. to identify the full range of outcomes, benefits and changes to which the SLF project has contributed in order to understand the value of what has been funded to date. b. to help Trust for London, Esmée Fairbairn Foundation and other potential funders discuss and decide if and how they want to take forward the funding of strategic legal work on migration issues in the current climate. c. to take stock of the model being used to identify, assess, support and review SLF grants and learn lessons about this which can: i) help improve current ways of working; ii) enable decisions about how such a fund should be administered in the future. d. to stimulate discussions about the potential use of such a model in funding strategic legal work in other areas of law

Competing risks, left truncation and late entry effect in A-bomb survivors cohort

The cohort under study comprises A-bomb survivors residing in Hiroshima Prefecture since 1968. After this year, thousands of survivors were newly recognized every year. The aim of this study is to determine whether the survival experience of the late entrants to the cohort is significantly different from the registered population in 1968. Parametric models that account for left truncation and competing risks were developed by using sub-hazard functions. A Weibull distribution was used to determine the possible existence of a late entry effect in Hiroshima A-bomb survivors. The competing risks framework shows that there might be a late entry effect in the male and female groups. Our findings are congruent with previous studies analysing similar populations

SED & Variability Studies of AGN

This thesis contains the results of studies into the causes of variability seen in the optical and X-ray emission from matter accreting onto supermassive black holes (SMBHs) in active galactic nuclei (AGN). The first chapter provides a brief overview of the history of optical and X-ray astronomy along with a summary of the principle properties of AGN. The second chapter investigates the dust-to-gas relationship for a sample of 1,201 X-ray detected quasars. We carry out an in-depth optical and X-ray spectral analysis and produce composite spectra for gas absorbed and dust reddened quasars. We find that the objects with the largest gas column densities are not the objects with the largest amounts of dust reddening. This study also highlights problems in constraining absorption levels in objects with low-quality X-ray spectra. We then present optical-to-X-ray spectral energy distributions (SEDs) for 170 Type 1 AGN. We use a new broadband SED model, which combines the standard disc emission with low- and high- temperature Comptonisation components through the introduction of a coronal radius. We find that objects that have an Eddington ratio greater than unity have larger disc luminosities, lower black hole mass, higher mass accretion rate and smaller coronal radii, than the rest of the sample. We conduct a detailed optical and X-ray variability study on a subset of 41 of these objects in the fourth chapter. We combined optical light curves from the Catalina Sky Survey (CSS) with long duration X-ray observations from the XMM-Newton satellite. We found that the objects with the lowest black hole masses were the least variable. However, we did not find the expected relationship between luminosity and variability, probably due to the wavelength range observed by CSS and selection biases in our sample. The final two chapters report results from pilot studies based on data from the Pan-STARRS telescope. In the fifth chapter we present an in-depth study of a highly variable object discovered as part of the Pan-STARRS supernovae search, and in the sixth chapter we investigate a subset of the light curves produced in the Medium Deep Survey (MDS) by analysing the light curves of 39 quasars including 12 broad absorption line quasars (BALQSOs). Finally, we also examine the potential for future studies, by cross-matching a large sample of spectroscopically identified Seyfert 2 AGN to the large area 3π catalogue

Modelling treatment, age- and gender-specific recovery in acute injury studies

Background: Acute injury studies often measure physical ability repeatedly over time through scores that have a finite range. This can result in a faster score change at the beginning of the study than towards the end, motivating the investigation of the rate of change. Additionally, the bounds of the score and their dependence on covariates are often of interest. Methods: We argue that transforming bounded data is not satisfactory in some settings. Motivated by the Collaborative Ankle Support Trial (CAST), which investigated different methods of immobilisation for severe ankle sprains, we developed a model under the assumption that the recovery rate at a specific time is proportional to the current score and the remaining score. This model enables a direct interpretation of the covariate effects. We have re-analyzed the CAST data using these improved methods, and explored novel relationships between age, gender and recovery rate. Results: We confirm that using below knee cast is advantageous compared with a tubular bandage in relation with the recovery rate. An age and gender effect on the recovery rate and the maximum achievable score is demonstrated, with older female patients recovering less fast (age-effect: -0.21, 95% confidence interval (CI) [-0.28,- 0.14]; gender effect: -0.06, CI [-0.12,-0.004]) and achieving a lower maximum score (age-effect: -8.07, CI [-11.68,-4.01]; gender-effect: -5.34, CI [-8.18, -2.50]) than younger male patients. Conclusions: Our model is able to accurately model repeated measurements on the original scale, while accounting for the bounded nature of a score. We demonstrate that recovery in acute injury trials can differ substantially by age and gender. Older female patients are less likely to recover well from a sprain

Creating a Poverty Map for Azerbaijan

"Poverty maps"-that is, graphic representations of spatially disaggregated estimates of welfare-are being increasingly used to geographically target scarce resources. But the development of detailed poverty maps in many low resource settings is hampered because of data constraints. Data on income or consumption are often unavailable and, where they are, direct survey estimates for small areas are likely to yield unacceptably large standard errors due to limited sample sizes. Census data offer the required level of coverage but do not generally contain the appropriate information. This has led to the development of a range of alternative methods aimed either at combining survey data with unit record data from the census to produce estimates of income or expenditure for small areas or at developing alternative welfare rankings, such as asset indices, using existing census data. This paper develops a set of poverty maps for Azerbaijan that can be used by different users. Two alternative approaches to the measurement and mapping of welfare are adopted. First, a map is derived using imputed household consumption. This involves combining information from the 2002 Household Budget Survey (HBS) with 1999 census data. Second, an alternative map is constructed using an asset index based on data from the 1999 census to produce estimates of welfare at the rayon level. This provides a unique opportunity to compare the welfare rankings obtained at the regional level under the two alternative approaches. In order to visually present the spatially disgaggregated estimates of welfare in Azerbaijan, this paper has also produced a digital census map of Azerbaijan. This involved matching the census enumeration areas to a digital settlement map of Azerbaijan. Therefore, it is now possible for the State Statistical Committee of Azerbaijan to display graphically the results of the 1999 census of Azerbaijan along with other data.Rural Poverty Reduction,Economic Theory&Research,Poverty Lines,Poverty Diagnostics,Technology Industry

Nausea and vomiting in pregnancy (NVP) is not just 'Morning Sickness' : data from a prospective cohort study

Background: Nausea and vomiting in pregnancy is usually called ‘morning sickness’. This is felt by sufferers to trivialise the condition. Symptoms have been described as occurring both before and after noon, but daily symptom patterns have not been clearly described and statistically modelled to enable the term ‘morning sickness’ to be accurately analysed. Aim: To describe the daily variation in nausea and vomiting symptoms during early pregnancy in a group of sufferers. Design and setting: A prospective cohort study of females recruited from 15 May 2014 to 17 February 2017 by Swiss Precision Diagnostics (SPD) Development Company Limited, which was researching hormone levels in early pregnancy and extended its study to include the description of pregnancy symptoms. Method: Daily symptom diaries of nausea and vomiting were kept by females who were trying to conceive. They also provided daily urine samples, which when analysed enabled the date of ovulation to be determined. Data from 256 females who conceived during the first month of the study are included in this article. Daily symptom patterns and changes in daily patterns by week of pregnancy were modelled. Functional data analysis was used to produce estimated symptom probability functions. Results: There was a peak probability of nausea in the morning, a lower but sustained probability of nausea throughout the day, and a slight peak in the evening. Vomiting had a defined peak incidence in the morning. Conclusion: Referring to nausea and vomiting in pregnancy as simply ‘morning sickness’ is inaccurate, simplistic, and therefore unhelpful

Long-term survival for a cohort of adults with cerebral palsy

The aim of this study was to investigate long-term survival and examine causes of death in adult patients with cerebral palsy (CP). A 1940–1950 birth cohort based on paediatric case referral allows for long-term survival follow-up. Survival is analyzed by birth characteristics and severity of disability from age 20 years (and age 2y for a subset of the data). Survival outcome compared with that expected in the general population based on English life tables. The main cohort consisted of 341 individuals, with 193 males and 148 females. Conditional on surviving to age 20 years, almost 85% of the cohort survived to age 50 years (a comparable estimate for the general population is 96%). Very few deaths were attributed to CP for those people dying over 20 years of age. Females survived better than males. However, females faced a greater increase in risk relative to the general population than did males. We conclude that survival outlook is good though lower than in the general population. The relative risk of death compared with the UK population decreases with age, although it shows some indication of rising again after age 50 years. Many more deaths were caused by diseases of the respiratory system among those dying in their 20s and 30s than would be expected in the general population. Many fewer deaths than expected in this age group are caused by injuries and accidents. For those people who die in their 40s and 50s, an increase in deaths due to diseases of the circulatory system and neoplasms is observed. More deaths than expected in this age group are due to diseases of the nervous system