High resolution methods for the aerodynamic design of helicopter rotors

The research reported here was driven by a desire to obtain a prediction method for helicopter rotor performance that would have sufficient resolution to evaluate changes to the design of the blade tip. This thesis examines the effectiveness of Computational Fluid Dynamics (CFD) methods to solve this problem. An accurate, high-fidelity prediction is essential to quantify the performance of a new rotor tip shape which hitherto could not be properly assessed by a traditional approach. The CFD method lends itself to the resolution of the compressible, viscous flow around the helicopter blade tip. Starting from the surface shape required to generate a grid, together with the flow conditions, the flowfield naturally evolves from the numerical solution of the Navier-Stokes equations, based on the principles of conservation of mass, momentum and energy. Thus both the flow physics and the geometry of the tip are fully modelled by this technique. In order to demonstrate the process, the Helicopter Multi-block solver (HMB) is used to predict the performance of a series of example tail rotor configurations. The various tip shapes are evaluated and compared, initially using an Euler approach to economically cover a wide range of designs, before going on to apply the Navier-Stokes method. The concepts behind each of the tail rotor blade (TRB) tip designs are explained in the thesis. As further computational resources became available, the datum blade, and the down-selected Kuchemann-like and anhedral-Kuchemann tip blades were the subject of Navier-Stokes predictions. Early in this work, the numerical method was validated against published data, and was also compared to existing model tail rotor test data for blades having different twist. In the central part of this thesis, the computational results are further analysed to reveal the influence of blade design changes on the time-averaged induced flow, and to extract more familiar aerodynamic parameters such as the angle of attack from the 3D rotor computations. Steady Navier-Stokes predictions were obtained over a range of pitch angles such that the induced power factor could be reliably determined and the trends on profile power could also be established for the selected tip shapes. The research reported in this thesis has established that this numerical approach provides a good prediction of rotor performance, adequately resolving the flow-field and tip aerodynamics. Since the assessment of helicopter rotors may involve additional interactional effects, or a degree of unsteady flow due to operating at high pitch angles near the onset of stall, an unsteady case was also demonstrated for a tail rotor blade adjacent to a fin. It is concluded that only by using a CFD approach can a sufficiently high-fidelity prediction be obtained for helicopter rotor aerodynamics to allow progressive enhancements of future helicopter blade designs

Health visiting - the end of a UK wide service?

In 1997 Health Visiting was deemed by New Labour to be an important player in reducing health inequalities. It was acknowledged that if Health Visiting was to fulfill this vision it would have to work out with its traditional child health role and also engage with groups, communities and populations to tackle the determinants of ill health. Twelve years on, external factors such as, NHS cut backs, recent changes to how Health Visitors are regulated throughout the UK and devolved Health Visiting policy making structures have led to the rapid demise in status and legitimacy of Health Visiting and its wider public health role. This article argues that the unintended consequences of devolved Health Visiting policy has resulted in 3 recent community nursing and health-visiting reviews in Scotland and England which have made divergent policy recommendations about the role of the Health Visitor in tackling health inequalities. The recommendations outlined in the Scottish review in particular threatened to jeopardise the very future provision of a UK wide Health Visiting service. If Health Visiting is to survive as a UK wide entity, a radical independent rethink as to its future direction and its public health role is urgently required

Doing trials within trials: a qualitative study of stakeholder views on barriers and facilitators to the routine adoption of methodology research in clinical trials

Abstract Background Randomised controlled trials are the cornerstone of evidence-based health care, yet many trials struggle with recruitment and retention. All too often the methodologies employed to address these problems are not evidence-based, as rigorous methodological research on these issues is rare. The current research sought to identify barriers to the routine implementation of methodology research around recruitment and retention. Methods All registered UK clinical trials unit directors were sent a short questionnaire and invited to interview. Representatives of funding bodies and other stakeholders were also approached. Interviews were recorded and the content analysed. Results Data were grouped into four themes: acceptance of the need for methodological research; trial funding and development; trial processes; and organisational factors. The need to improve the evidence base for trials methodology is well established, but numerous barriers to implementation were perceived. Conclusions The knowledge and expertise required to routinely implement methodology research exists within the current research structures, and there are clear opportunities to develop the evidence base. However, for this to be achieved there is also a need for clear strategic coordination within the sector and promotion of the necessary resources

Staff training to improve participant recruitment into surgical randomised controlled trials : a feasibility Study Within A Trial (SWAT) across four host randomised controlled trials simultaneously

Objective To test the feasibility of undertaking a simultaneous Study Within A Trial (SWAT) to train staff who recruit participants into surgical randomised controlled trials (RCTs), by assessing key uncertainties around recruitment, randomisation, intervention delivery and data collection. Study design and setting Twelve surgical RCTs were eligible. Interested sites (clusters) were randomised 1:1, with recruiting staff (surgeons and nurses) offered training or no training. The primary outcome was the feasibility of recruiting sites across multiple surgical trials simultaneously. Secondary outcomes included numbers/types of staff enrolled, attendance at training, training acceptability, confidence in recruiting and participant recruitment rates six months later. Results Four RCTs (33%) comprising 91 sites participated. Of these, 29 sites agreed to participate (32%) and were randomised to intervention (15 sites, 29 staff) or control (14 sites, 29 staff). Research nurses attended and found the training to be acceptable; no surgeons attended. In the intervention group, there was evidence of increased confidence when pre and post training scores were compared (mean difference in change 1.42; 95% CI 0.56, 2.27; p = 0.002) – there was no effect on recruitment rate. Conclusion It was feasible to randomise sites across four surgical RCTs in a simultaneous SWAT design. However, as small numbers of trials and sites participated, and no surgeons attended training, strategies to improve these aspects are needed for future evaluations. Trial registration ISRCTN registry: DISC (ISRCTN18254597), registered on 4th April 2017; PROFHER 2 (ISRCTN76296703), registered on 5th April 2018; IntAct (ISRCTN13334746), registered on 10th April 2017; and START:REACTS (ISRCTN17825590), registered on 5th March 2018. The training SWAT has been submitted to the MRC SWAT repository (SWAT111) Keywords: Randomised controlled trial (RCT), Study Within A Trial (SWAT), recruitment, staff training, professional education, feasibility study, surgical trial

Effect of alirocumab on mortality after acute coronary syndromes. An analysis of the ODYSSEY OUTCOMES randomized clinical trial

Background: Previous trials of PCSK9 (proprotein convertase subtilisin-kexin type 9) inhibitors demonstrated reductions in major adverse cardiovascular events, but not death. We assessed the effects of alirocumab on death after index acute coronary syndrome. Methods: ODYSSEY OUTCOMES (Evaluation of Cardiovascular Outcomes After an Acute Coronary Syndrome During Treatment With Alirocumab) was a double-blind, randomized comparison of alirocumab or placebo in 18 924 patients who had an ACS 1 to 12 months previously and elevated atherogenic lipoproteins despite intensive statin therapy. Alirocumab dose was blindly titrated to target achieved low-density lipoprotein cholesterol (LDL-C) between 25 and 50 mg/dL. We examined the effects of treatment on all-cause death and its components, cardiovascular and noncardiovascular death, with log-rank testing. Joint semiparametric models tested associations between nonfatal cardiovascular events and cardiovascular or noncardiovascular death. Results: Median follow-up was 2.8 years. Death occurred in 334 (3.5%) and 392 (4.1%) patients, respectively, in the alirocumab and placebo groups (hazard ratio [HR], 0.85; 95% CI, 0.73 to 0.98; P=0.03, nominal P value). This resulted from nonsignificantly fewer cardiovascular (240 [2.5%] vs 271 [2.9%]; HR, 0.88; 95% CI, 0.74 to 1.05; P=0.15) and noncardiovascular (94 [1.0%] vs 121 [1.3%]; HR, 0.77; 95% CI, 0.59 to 1.01; P=0.06) deaths with alirocumab. In a prespecified analysis of 8242 patients eligible for ≥3 years follow-up, alirocumab reduced death (HR, 0.78; 95% CI, 0.65 to 0.94; P=0.01). Patients with nonfatal cardiovascular events were at increased risk for cardiovascular and noncardiovascular deaths (P<0.0001 for the associations). Alirocumab reduced total nonfatal cardiovascular events (P<0.001) and thereby may have attenuated the number of cardiovascular and noncardiovascular deaths. A post hoc analysis found that, compared to patients with lower LDL-C, patients with baseline LDL-C ≥100 mg/dL (2.59 mmol/L) had a greater absolute risk of death and a larger mortality benefit from alirocumab (HR, 0.71; 95% CI, 0.56 to 0.90; Pinteraction=0.007). In the alirocumab group, all-cause death declined wit h achieved LDL-C at 4 months of treatment, to a level of approximately 30 mg/dL (adjusted P=0.017 for linear trend). Conclusions: Alirocumab added to intensive statin therapy has the potential to reduce death after acute coronary syndrome, particularly if treatment is maintained for ≥3 years, if baseline LDL-C is ≥100 mg/dL, or if achieved LDL-C is low. Clinical Trial Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT01663402

Using Functional Magnetic Resonance Imaging for Liver Sparing Stereotactic Ablative Body Radiotherapy

Background and PurposeHepatocellular carcinoma (HCC) often develops on a background of liver cirrhosis and impaired liver function. As a result, radiotherapy treatments are limited by radiation-induced liver disease, parameterised by the liver mean dose (LMD). Liver function is highly heterogeneous, especially in HCC, but the use of LMD does not take this into account. One possible way to improve HCC treatments is to use functional imaging to prioritise the sparing of healthy liver tissue.Materials and MethodsAnatomical T2 and functional Hepatica iron-corrected T1 images were provided for 10 patients by Perspectum. Functional liver volumes were segmented on the functional images using a threshold. HCC stereotactic ablative body radiotherapy (SABR) plans were made using a departmental protocol. Liver-sparing plans were then made by reducing the dose to the functional sub-volume.ResultsSparing volumes varied greatly between patients, covering between 16 and 85% of the liver within the functional image. The sparing plans achieved a statistically significant (p=0.002) reduction in the functional liver mean dose, with a mean reduction of 1.4 Gy. The LMD was also significantly different (p=0.002) but had a smaller magnitude with a mean reduction of 0.7 Gy. There were some differences in the planning target volume D99% (p=0.04) but the sparing plans remained within the optimal tolerance and the D95% was not significantly different (p=0.2).ConclusionsThis study has, for the first time, demonstrated the use of Hepatic sequences in radiotherapy showing significant reductions in dose to the healthy liver. Further work is needed to validate this work in HCC SABR patients.<br/

The blind-test activity of the GOAHEAD project

This paper describes the blind-test CFD activity of the EU 6th Framework project GOAHEAD. This blind-test activity has been used to evaluate and assess the helicopter CFD codes which are today in use in Europe and to scrutinize the wind-tunnel test conditions with respect to the expected flow phenomena prior to the wind-tunnel test campaign. Results are presented for an isolated fuselage test case, a low-speed (pitch-up) test case, a cruise test case, a high-speed tail-shake test case and a highly-load rotor (dynamic-stall) test case

Impact of motion management strategies on abdominal organ at risk delineation for magnetic resonance-guided radiotherapy

Background and purposeThe impact of respiratory motion management strategies for abdominal radiotherapy, such as abdominal compression (AC) and breath hold (BH), on abdominal organ at risk (OAR) delineation on magnetic resonance imaging (MRI) is unknown. This feasibility study compared the inter- and intra- observer delineation variation on MRI acquired with AC, BH for three critical abdominal OAR.Materials and methodsT2-weighted (W) 3D MRI in free-breathing (FB) and with AC, and T1W 3D mDixon exhale BH were acquired. Four observers blinded to motion management strategy used, delineated stomach, liver, and duodenum on all MRI. One case per strategy was repeated over 6 weeks later to quantify intra-observer variation. Simultaneous truth and performance level estimation (STAPLE) contours for each OAR were generated, median and IQR mean distance to agreement (mDTA) and maximum Hausdorff distance (HD) between observer and STAPLE contours were calculated. Observers scored organ visibility on each MRI using a four-point Likert scale.ResultsA total of 27 scans including repeats were delineated. Pooled mDTA for all OARs was 1.3 mm (0.5 mm) with AC, 1.4 mm (1.0 mm) with BH, and 1.3 mm (0.5 mm) in FB. Intra-observer mDTA was highest for all organs in FB with 10.8 mm for duodenum, 1.8 mm for liver, and 2.7 mm for stomach. The pooled mean perceptual quality score value was highest for AC across organs.ConclusionsNo motion management strategy demonstrated superior similarity across OAR, emphasizing the need for personalised approaches based on individual clinical and patient factors