Hall acceleration in a partially ionised plasma

Imperial Users onl

Autonomous rendezvous targeting techniques for national launch system application

The rendezvous targeting techniques that can be utilized to achieve autonomous guidance for delivering a cargo to Space Station Freedom (SSF) using the National Launch System's (NLS) Heavy Lift Launch Vehicle (HLLV) and the on-orbit Cargo Transfer Vehicle (CTV) are described. This capability is made possible by advancements in autonomous navigation (Global Positioning System - GPS) on-board the CTV and SSF as well as the new generation flight computers. How the HLLV launch window can be decoupled from the CTV phasing window is described. The performance trades that have to be made to determine the length of the launch window and the phasing window between the CTV and SSF are identified and recommendations made that affect mission timelines

Discovery of a lipid synthesising organ in the auditory system of an insect

Weta possess typical Ensifera ears. Each ear comprises three functional parts: two equally sized tympanal membranes, an underlying system of modified tracheal chambers, and the auditory sensory organ, the crista acustica. This organ sits within an enclosed fluid-filled channel–previously presumed to be hemolymph. The role this channel plays in insect hearing is unknown. We discovered that the fluid within the channel is not actually hemolymph, but a medium composed principally of lipid from a new class. Three-dimensional imaging of this lipid channel revealed a previously undescribed tissue structure within the channel, which we refer to as the olivarius organ. Investigations into the function of the olivarius reveal de novo lipid synthesis indicating that it is producing these lipids in situ from acetate. The auditory role of this lipid channel was investigated using Laser Doppler vibrometry of the tympanal membrane, which shows that the displacement of the membrane is significantly increased when the lipid is removed from the auditory system. Neural sensitivity of the system, however, decreased upon removal of the lipid–a surprising result considering that in a typical auditory system both the mechanical and auditory sensitivity are positively correlated. These two results coupled with 3D modelling of the auditory system lead us to hypothesize a model for weta audition, relying strongly on the presence of the lipid channel. This is the first instance of lipids being associated with an auditory system outside of the Odentocete cetaceans, demonstrating convergence for the use of lipids in hearing

Is an ounce of prevention worth a pound of cure? : A cross-sectional study of the impact of English public health grant on mortality and morbidity

OBJECTIVES: The UK government is proposing to cease cutting the local authority public health grant by reallocating part of the treatment budget to preventative activity. This study examines whether this proposal is evidenced based and, in particular, whether these resources are best reallocated to prevention, or whether this expenditure would generate more health gains if used for treatment. METHODS: Instrumental variable regression methods are applied to English local authority data on mortality, healthcare and public health expenditure to estimate the responsiveness of mortality to variations in healthcare and public health expenditure in 2013/14. Using a well-established method, these mortality results are converted to a quality-adjusted life year (QALY) basis, and this facilitates the estimation of the cost per QALY for both National Health Service (NHS) healthcare and local public health expenditure. RESULTS: Saving lives and improving the quality of life requires resources. Our estimates suggest that each additional QALY costs about £3800 from the local public health budget, and that each additional QALY from the NHS budget costs about £13 500. These estimates can be used to calculate the number of QALYs generated by a budget boost. If we err on the side of caution and use the most conservative estimates that we have, then an additional £1 billion spent on public health will generate 206 398 QALYs (95% CI 36 591 to 3 76 205 QALYs), and an additional £1 billion spent on healthcare will generate 67 060 QALYs (95% CI 21 487 to 112 633 QALYs). CONCLUSIONS: Additional public health expenditure is very productive of health and is more productive than additional NHS expenditure. However, both types of expenditure are more productive of health than the norms used by National Institute for Health and Care Excellence (£20 000-£30 000 per QALY) to judge whether new therapeutic technologies are suitable for adoption by the NHS

ESSAYS ON ASSESSING METHODS FOR MODELLING THE DISTRIBUTION OF HEALTHCARE COSTS

This thesis comprises three essays on assessing methods for modelling the distribution of healthcare costs. Chapter 2 extends the literature on modelling healthcare cost data by applying the generalised beta of the second kind (GB2) distribution to English hospital inpatient cost data. A quasi-experimental design, estimating models on a sub-population of the data and evaluating performance on another sub-population, is used to compare this distribution with its nested and limiting cases. While, for these data, the beta of the second kind (B2) distribution and generalised gamma (GG) distribution outperform the GB2, our results illustrate that the GB2 can be used as a device for choosing among competing parametric distributions for healthcare cost data. In Chapter 3, we conduct a quasi-Monte Carlo comparison of the recent developments in parametric and semi-parametric regression methods for healthcare costs, both against each other and against standard practice. The population of English NHS hospital inpatient episodes for the financial year 2007-2008 (summed for each patient: 6,164,114 observations in total) is randomly divided into two equally sized sub-populations to form an estimation set and a validation set. Evaluating out-of-sample using the validation set, a conditional density approximation estimator shows considerable promise in forecasting conditional means, performing best for accuracy of forecasting and amongst the best four (of sixteen compared) for bias and goodness-of-fit. The best performing model for bias is linear regression with square root transformed dependent variable, while a generalised linear model with square root link function and Poisson distribution performs best in terms of goodness-of-fit. Commonly used models utilising a log link are shown to perform badly relative to other models considered in our comparison. Chapter 4 examines methods for estimating the full conditional distribution of healthcare costs. Understanding the data generating process behind healthcare costs remains a key empirical issue. Although much research to date has focused on the prediction of the conditional mean cost, this can potentially miss important features of the full conditional distribution such as tail probabilities. We conduct a quasi-Monte Carlo experiment using English NHS inpatient data to compare 14 approaches to modelling the distribution of healthcare costs: nine of which are parametric, and have commonly been used to fit healthcare costs, and five others designed specifically to construct a counterfactual distribution. Our results indicate that no one method is clearly dominant and that there is a tradeoff between bias and precision of tail probability forecasts. We find that distributional methods demonstrate significant potential, particularly with larger sample sizes where the variability of predictions is reduced. Parametric distributions such as log-normal, generalised gamma and generalised beta of the second kind are found to estimate tail probabilities with high precision, but with varying bias depending upon the cost threshold being considered

Does public long-term care expenditure improve care-related quality of life in England?

Public long-term care (LTC) systems are common across Organisation for Economic Co-operation and Development countries and they provide services to support people experiencing difficulties with their activities of daily living. This study investigates the marginal effect of changes in public LTC expenditure on care-related quality of life (CRQoL) in England. The public LTC programme for people aged 18 or older in England is called Adult Social Care (ASC) and it is provided and managed by local authorities. We collect data on outcomes and characteristics of public ASC users, and on public ASC expenditure and characteristics of local authorities across England in 2017/18. We employ an instrumental variable approach using conditionally exogenous elements of the public funding system to estimate the effect of public ASC expenditure on users’ CRQoL. Our findings show that increasing public ASC expenditure by £1,000 per user generates 0.0031 additional CRQoL. These results suggest that public ASC is effective in increasing users’ quality of life but only to a relatively small extent. Combined with other findings on the effect of LTC expenditure on mortality, this study can inform policy makers in the UK and around the world about whether social care provides good value for money

Cured today, ill tomorrow: a method for including future unrelated medical costs in economic evaluation in England and Wales

Objectives: In many countries, future unrelated medical costs occurring during life-years gained are excluded from economic evaluation, and benefits of unrelated medical care are implicitly included, leading to life-extending interventions being disproportionately favored over quality of life-improving interventions. This article provides a standardized framework for the inclusion of future unrelated medical costs and demonstrates how this framework can be applied in England and Wales. Methods: Data sources are combined to construct estimates of per-capita National Health Service spending by age, sex, and time to death, and a framework is developed for adjusting these estimates for costs of related diseases. Using survival curves from 3 empirical examples illustrates how our estimates for unrelated National Health Service spending can be used to include unrelated medical costs in cost-effectiveness analysis and the impact depending on age, life-years gained, and baseline costs of the target group. Results: Our results show that including future unrelated medical costs is feasible and standardizable. Empirical examples show that this inclusion leads to an increase in the ICER of between 7% and 13%. Conclusions: This article contributes to the methodology debate over unrelated costs and how to systematically include them in economic evaluation. Results show that it is both important and possible to include future unrelated medical costs