Rotor wake interactions with an obstacle on the ground

An investigation of the flow around an obstacle positioned within the wake of a rotor is described. A flow visualisation survey was performed using a smoke wand and particle image velocimetry, and surface pressure measurements on the obstacle were taken. The flow patterns were strongly dependent upon the rotor height above the ground and obstacle, and the relative position of the obstacle and rotor axis. High positive and suction pressures were measured on the obstacle surfaces, and these were unsteady in response to the passage of the vortex driven rotor wake over the surfaces. Integrated surface forces are of the order of the rotor thrust, and unsteady pressure information shows local unsteady loading of the same order as the mean loading. Rotor blade-tip vortex trajectories are responsible for the generation of these forces

Prostate cancer screening in primary care: Doctors’ perspectives on prostate-specific antigen (PSA) screening of asymptomatic men in Australia and the United Kingdom

Screening for prostate cancer is a highly debated public health issue. The evidence base is contested, the prostate-specific antigen (PSA) test as a screening technology is limited, no medical body recommends a population screening program for prostate cancer screening, local authorities differ in the advice they offer on the value of PSA screening in clinical care, and the substantial harms associated with PSA screening are well documented. Decisions about PSA screening most commonly occur in consultation with a general practitioner (GP). This qualitative study was designed to explain how GPs understand, reason about, and use the PSA test to screen men for prostate cancer risk in primary care. Australia and the United Kingdom draw on the same evidence base for prostate cancer screening yet have notably different rates of PSA screening; they are the two locations of this research study. In this thesis I report on GP perspectives on PSA screening. Methods: This is an empirical study using grounded theory methodology. Data were generated from in-depth interviews with GPs in Australia and the United Kingdom, who make decisions about using or not using the PSA test as a screening tool. Analysis was developed through transcript coding and detailed memo writing, using constant comparison to develop insight and connections between concepts. The overall aim of the study was to gain an in-depth understanding of how and why clinicians use the PSA test to screen for prostate cancer in primary care. Main findings: This grounded theory study found that for Australian GPs on the frontline, decision making about PSA screening is extremely difficult and complex. There was extensive variation in the clinicians’ accounts of their screening behaviour. Different motivations (values and goals) of GPs, context of the clinic and specific clinical interactions, opportunity to trust, and responses to uncertainty, were central explanations for varied practice. GPs intuitively and/or explicitly drew from multiple, potentially 3 conflicting, types of knowledge (including that from the research evidence) - developed over time – to guide their screening decisions. The study included UK GPs as a comparison case to examine the place of past and present screening policy, and healthcare system structure and organisation in influencing and incentivising particular ways of practicing. The UK experience demonstrates that Australian screening practices are not inevitable – things can be done differently. Some Australian clinicians in this study experienced significant emotional and cognitive burden, as a result of making screening decisions under challenging conditions. The empirical chapters of the thesis focus on four key issues: managing the potential for overdiagnosis, responding to uncertainty, practice and policy context, and communicating about PSA screening. The Discussion chapter draws these findings together into a new explanatory model of GPs’ decision making about PSA screening. Conclusion: This research provides an in-depth comparative analysis of important drivers of prostate cancer screening reported from the perspective of GPs in two locations with diverse screening rates. The model produced provides an explanation of the complex and varied process of PSA screening in the two jurisdictions. Policy continues to evolve and attract substantial debate in this field in Australia. Given that past attempts to intervene in PSA screening practice in Australia seem to have had limited effect, a new approach that better reflects the complexity of this issue, including the range of drivers of current practice, seems warranted. These findings offer useful empirical guidance for future policy and practice, grounded in the experiences of clinicians

Algorithms in Lattice QCD

The enormous computing resources that large-scale simulations in Lattice QCD require will continue to test the limits of even the largest supercomputers into the foreseeable future. The efficiency of such simulations will therefore concern practitioners of lattice QCD for some time to come. I begin with an introduction to those aspects of lattice QCD essential to the remainder of the thesis, and follow with a description of the Wilson fermion matrix M, an object which is central to my theme. The principal bottleneck in Lattice QCD simulations is the solution of linear systems involving M, and this topic is treated in depth. I compare some of the more popular iterative methods, including Minimal Residual, Corij ugate Gradient on the Normal Equation, BI-Conjugate Gradient, QMR., BiCGSTAB and BiCGSTAB2, and then turn to a study of block algorithms, a special class of iterative solvers for systems with multiple right-hand sides. Included in this study are two block algorithms which had not previously been applied to lattice QCD. The next chapters are concerned with a generalised Hybrid Monte Carlo algorithm (OHM C) for QCD simulations involving dynamical quarks. I focus squarely on the efficient and robust implementation of GHMC, and describe some tricks to improve its performance. A limited set of results from HMC simulations at various parameter values is presented. A treatment of the non-hermitian Lanczos method and its application to the eigenvalue problem for M rounds off the theme of large-scale matrix computations

Troubling Vulnerability: Designing with LGBT Young People's Ambivalence Towards Hate Crime Reporting

HCI is increasingly working with ?vulnerable? people yet there is a danger that the label of vulnerability can alienate and stigmatize the people such work aims to support. We report our study investigating the application of interaction design to increase rates of hate crime reporting amongst Lesbian, Gay, Bisexual and Transgender young people. During design-led workshops participants expressed ambivalence towards reporting. While recognizing their exposure to hate crime they simultaneously rejected ascription as victim as implied in the act of reporting. We used visual communication design to depict the young people?s ambivalent identities and contribute insights on how these fail and succeed to account for the intersectional, fluid and emergent nature of LGBT identities through the design research process. We argue that by producing ambiguous designed texts, alongside conventional qualitative data, we ?trouble? our design research narratives as a tactic to disrupt static and reductive understandings of vulnerability within HCI

Impact and Cost-Effectiveness of Point-Of-Care CD4 Testing on the HIV Epidemic in South Africa.

Rapid diagnostic tools have been shown to improve linkage of patients to care. In the context of infectious diseases, assessing the impact and cost-effectiveness of such tools at the population level, accounting for both direct and indirect effects, is key to informing adoption of these tools. Point-of-care (POC) CD4 testing has been shown to be highly effective in increasing the proportion of HIV positive patients who initiate ART. We assess the impact and cost-effectiveness of introducing POC CD4 testing at the population level in South Africa in a range of care contexts, using a dynamic compartmental model of HIV transmission, calibrated to the South African HIV epidemic. We performed a meta-analysis to quantify the differences between POC and laboratory CD4 testing on the proportion linking to care following CD4 testing. Cumulative infections averted and incremental cost-effectiveness ratios (ICERs) were estimated over one and three years. We estimated that POC CD4 testing introduced in the current South African care context can prevent 1.7% (95% CI: 0.4% - 4.3%) of new HIV infections over 1 year. In that context, POC CD4 testing was cost-effective 99.8% of the time after 1 year with a median estimated ICER of US$4,468/DALY averted. In healthcare contexts with expanded HIV testing and improved retention in care, POC CD4 testing only became cost-effective after 3 years. The results were similar when, in addition, ART was offered irrespective of CD4 count, and CD4 testing was used for clinical assessment. Our findings suggest that even if ART is expanded to all HIV positive individuals and HIV testing efforts are increased in the near future, POC CD4 testing is a cost-effective tool, even within a short time horizon. Our study also illustrates the importance of evaluating the potential impact of such diagnostic technologies at the population level, so that indirect benefits and costs can be incorporated into estimations of cost-effectiveness

Primary goals, information-giving and men\u27s understanding: A qualitative study of Australian and UK doctors\u27 varied communication about PSA screening

Objectives: (1) To characterise variation in general practitioners’ (GPs’) accounts of communicating with men about prostate cancer screening using the prostate-specific antigen (PSA) test, (2) to characterise GPs’ reasons for communicating as they do and (3) to explain why and under what conditions GP communication approaches vary. Study design and setting: A grounded theory study. We interviewed 69 GPs consulting in primary care practices in Australia (n=40) and the UK (n=29). Results: GPs explained their communication practices in relation to their primary goals. In Australia, three different communication goals were reported: to encourage asymptomatic men to either have a PSA test, or not test, or alternatively, to support men to make their own decision. As well as having different primary goals, GPs aimed to provide different information (from comprehensive to strongly filtered) and to support men to develop different kinds of understanding, from population-level to ‘gist’ understanding. Taking into account these three dimensions (goals, information, understanding) and building on Entwistle et al’s Consider an Offer framework, we derived four overarching approaches to communication: Be screened, Do not be screened, Analyse and choose, and As you wish. We also describe ways in which situational and relational factors influenced GPs’ preferred communication approach. Conclusion: GPs’ reported approach to communicating about prostate cancer screening varies according to three dimensions—their primary goal, information provision preference and understanding sought—and in response to specific practice situations. If GP communication about PSA screening is to become more standardized in Australia, it is likely that each of these dimensions will require attention in policy and practice support interventions

Spatial modeling of individual-level infectious disease transmission: Tuberculosis data in Manitoba, Canada

Geographically dependent individual level models (GD-ILMs) are a class of statistical models that can be used to study the spread of infectious disease through a population in discrete-time in which covariates can be measured both at individual and area levels. The typical ILMs to illustrate spatial data are based on the distance between susceptible and infectious individuals. A key feature of GD-ILMs is that they take into account the spatial location of the individuals in addition to the distance between susceptible and infectious individuals. As a motivation of this article, we consider tuberculosis (TB) data which is an infectious disease which can be transmitted through individuals. It is also known that certain areas/demographics/communities have higher prevalent of TB (see Section 4 for more details). It is also of interest of policy makers to identify those areas with higher infectivity rate of TB for possible preventions. Therefore, we need to analyze this data properly to address those concerns. In this article, the expectation conditional maximization algorithm is proposed for estimating the parameters of GD-ILMs to be able to predict the areas with the highest average infectivity rates of TB. We also evaluate the performance of our proposed approach through some simulations. Our simulation results indicate that the proposed method provides reliable estimates of parameters which confirms accuracy of the infectivity rates