Paul Hewson

The influence of air and scale on wave impact pressures

Both laboratory and field tests that are described provide new information on the characteristics of wave impacts. Laboratory drop tests conducted using seawater and freshwater demonstrate that maximum impact pressures and rise times are influenced by both the level of aeration and the violence of the impact. A relationship is derived which enables the reduction in impact pressure caused by aeration to be estimated. This relationship is shown to provide a better means of predicting impact pressures in laboratory seawater wave tests from freshwater tests than either the Froude or Cauchy laws. Measurements are presented which show that, due to the different properties of seawater and freshwater, aeration levels are higher in seawater breakers than in freshwater breakers, even at a 1:25 model scale. The ways in which this affects the temporal variation in pressure and the scale relationships are discussed in some detail. Aeration and pressure measurements are also presented for full-scale wave impacts on a breakwater exposed to Atlantic waves. Attention is drawn to the likely role of expelled air and data included which indicate that the equivalent of up to 55% of entrained air does not necessarily prevent the occurrence of high impact pressures with short rise times.

Usefulness of 64-Detector Row Computed Tomography for Evaluation of Intracoronary Stents in Symptomatic Patients With Suspected In-Stent Restenosis

To determine whether 64-slice multidetector computed tomographic coronary angiography (MDCTA) can accurately assess the coronary artery lumen in symptomatic patients with previous coronary artery stents and potential in-stent restenosis (ISR). The primary aim was to determine the accuracy of binary ISR exclusion using MDCTA compared with invasive catheter angiography (ICA). Secondary aims were comparisons of stent dimensions measured using MDCTA and variables that affect accuracy. Forty patients with previous stent placement underwent both ICA and 64-slice MDCTA after elective presentation with chest pain, and ICA quantitative coronary angiographic data were used as the reference standard. Thirty-six men and 4 women (age 64 +/- 10 years; range 44 to 83) with 103 stents (2.8 +/- 1.6 stents/patient) were comparatively evaluated (stent exclusion rate 9.6%). There were 45 bare-metal and 58 drug-eluting stents (20 +/- 18 months after implantation) with an average diameter of 3.23 +/- 0.7 mm. Overall accuracy for the detection of significant ISR showed sensitivity, specificity, and positive and negative predictive values of 85%, 86%, 61%, and 96% for proximal stents > or =3 mm, which improved to 100%, 94%, 81%, and 100%; if the visible luminal diameter on MDCTA was <1.5 mm, accuracy decreased to 40%, 84%, 29%, and 90%, respectively. In conclusion, 64-slice MDCTA assessment of symptomatic patients with suspected clinically significant ISR is a realistic alternative to ICA if reference stent diameter is > or =2.5 mm and visible lumen cross-sectional diameter is > or =1.5 mm, for which a negative MDCTA result virtually excludes the presence of significant ISR.

Recruitment to Online Therapies for Depression: Pilot Cluster Randomized Controlled Trial

Background Raising awareness of online cognitive behavioral therapy (CBT) could benefit many people with depression, but we do not know how purchasing online advertising compares to placing free links from relevant local websites in increasing uptake. Objective To pilot a cluster randomized controlled trial (RCT) comparing purchase of Google AdWords with placing free website links in raising awareness of online CBT resources for depression in order to better understand research design issues. Methods We compared two online interventions with a control without intervention. The pilot RCT had 4 arms, each with 4 British postcode areas: (A) geographically targeted AdWords, (B) adverts placed on local websites by contacting website owners and requesting links be added, (C) both interventions, (D) control. Participants were directed to our research project website linking to two freely available online CBT resource sites (Moodgym and Living Life To The Full (LLTTF)) and two other depression support sites. We used data from (1) AdWords, (2) Google Analytics for our project website and for LLTTF, and (3) research project website. We compared two outcomes: (1) numbers with depression accessing the research project website, and then chose an onward link to one of the two CBT websites, and (2) numbers registering with LLTTF. We documented costs, and explored intervention and assessment methods to make general recommendations to inform researchers aiming to use similar methodologies in future studies. Results Trying to place local website links appeared much less cost effective than AdWords and although may prove useful for service delivery, was not worth pursuing in the context of the current study design. Our AdWords intervention was effective in recruiting people to the project website but our location targeting “leaked” and was not as geographically specific as claimed. The impact on online CBT was also diluted by offering participants other choices of destinations. Measuring the impact on LLTTF use was difficult as the total number using LLTTF was less than 5% of all users and record linkage across websites was impossible. Confounding activity may have resulted in some increase in registrations in the control arm. Conclusions Practitioners should consider online advertising to increase uptake of online therapy but need to check its additional value. A cluster RCT using location targeted adverts is feasible and this research design provides the best evidence of cost-effectiveness. Although our British pilot study is limited to online CBT for depression, a cluster RCT with similar design would be appropriate for other online treatments and countries and our recommendations may apply. They include ways of dealing with possible contamination (buffer zones and AdWords techniques), confounding factors (large number of clusters), advertising dose (in proportion to total number of users), record linkage (landing within target website), and length of study (4-6 months). Trial Registration clinicaltrials.gov (Registration No. NCT01469689); http://clinicaltrials.gov/ct2/show/NCT01469689 (Archived by WebCite at http://www.webcitation.org/6EtTthDOp)

Risk of Fatal Injury in Older Adult Drivers, Passengers, and Pedestrians

To compare risk of fatal injury in elderly road users (drivers, passengers, pedestrians) with that of younger age groups and to assess the contribution of elderly road users to the number of reported fatalities in the population.

Risks of High-Powered Motorcycles Among Younger Adults

OBJECTIVES We assessed whether policies designed to safeguard young motorcyclists would be effective given shifts in ownership toward high-powered motorcycles. METHODS We investigated population-wide motor vehicle driver and motorcyclist casualties (excluding passengers) recorded in Britain between 2002 and 2009. To adjust for exposure and measure individual risk, we used the estimated number of trips of motorcyclists and drivers, which had been collected as part of a national travel survey. RESULTS Motorcyclists were 76 times more likely to be killed than were drivers for every trip. Older motorcyclist age-strongly linked to experience, skill set, and riding behavior-did not abate the risks of high-powered motorcycles. Older motorcyclists made more trips on high-powered motorcycles. CONCLUSIONS Tighter engine size restrictions would help reduce the use of high-powered motorcycles. Policymakers should introduce health warnings on the risks of high-powered motorcycles and the benefits of safety equipment.

An instrument for field measurement of wave impact pressures and seawater aeration

Two new transducers have been developed and combined into an instrument for the simultaneous measurement of wave impact pressures on steep fronted coastal structures and the level of aeration in the seawater striking the structure. Design criteria for the new pressure and aeration unit are discussed. A description is given of the new transducers together with a purpose-designed data acquisition system that serves seven of the units, a video camera to record breaker shape, and an accelerometer to record the structures response to the applied loading. Performance of the new instrumentation is illustrated with examples of measurements obtained from an exposed breakwater at Alderney in the Channel Islands. The complete system operates automatically requiring only routine change of batteries and data tapes.

Overestimated crash risks of young and elderly drivers

BACKGROUND Young and elderly drivers are reported to have markedly greater crash rates than drivers of other ages, but they travel less frequently and represent a minority of road users. Consequently, many crashes involving young or elderly drivers also involve drivers of middle age ranges who travel more frequently. PURPOSE To examine crash rates of young and elderly drivers, controlling for ages of all drivers involved in collisions. METHODS A retrospective longitudinal study conducted on population-wide two-vehicle crashes reported in Great Britain from 2002 through 2010 for driver age ranges (17-20, 21-29, 30-39, 40-49, 50-59, 60-69, ≥70 years) and individual driver ages among those aged 17-20 years. Annual trips made, recorded as part of a National Travel Survey, were used to estimate trip-based driver crash rates. RESULTS Crash rates of drivers aged 17-20 years were not significantly different from crash rates of drivers aged 21-29 years (rate ratio=1.14; 95% CI=0.96, 1.33) when controlling for ages of both drivers involved in two-car collisions, and drivers aged 17 years had the lowest crash rate among drivers aged 17-20 years. Crash rates of drivers aged ≥70 years equaled crash rates of drivers aged 60-69 years (rate ratio=1.00; 95% CI=0.77, 1.32) and were 1.40 times (95% CI=1.10, 1.78) lower than crash rates of drivers aged 50-59 years. CONCLUSIONS The current findings are in contrast with reports of high crash risks among young and elderly drivers, and suggest that previous reports may have overestimated the crash risks of these drivers by failing to control for ages of all drivers involved in collisions.

General practitioner commissioning consortia and budgetary risk: evidence from the modelling of 'fair share' practice budgets for mental health.

Objectives: To contribute to current policy debates regarding the devolution of commissioning responsibilities to locally-based consortia of general practices in England by assessing the potential magnitude and significance of budgetary risk for commissioning units of different sizes. Methods: Predictive distributions of practice-level mental health care resource needs (used by the Department of Health to set ‘fair-share’ practice budgets) are aggregated to a range of hypothetical, but spatially-contiguous, consortia serving populations of up to 400,000 patients. The resulting joint distributions describe the extent to which the legitimate mental health needs of consortia populations are likely to vary. Budgetary risk is calculated as the likelihood that a consortias resource needs will, in any given year, exceed its allocation (taken as the mean of its predictive distribution) by more than 1%, 3%, 5% or 10%. The relationship between population size and budgetary risk is then explored. Results: If between 500 and 600 consortia are created in England (serving 87,000 to 104,000 patients) then, in order to meet the legitimate mental health needs of their patients, each year around 15 to 26 consortia will overspend by at least 5%, and one or two by at least 10%. The budgetary risk faced by consortia serving smaller/larger populations can be read off the graphs provided. Conclusions: Unless steps are taken to mitigate budgetary risk, the devolution of decision-making and introduction of fixed budgets is likely to result in significant financial instability. It will be difficult to reconcile the policy objectives of devolved commissioning, best met through relatively small and fully accountable consortia, with the need for financial stability, which is best met by pooling risk across larger populations.

Modelling multivariate disease rates with a latent structure mixture model

There has been considerable recent interest in multivariate modelling of the geographical distribution of morbidity or mortality rates for potentially related diseases. The motivations for this include investigation of similarities or dissimilarities in the risk distribution for the different diseases, as well as ‘borrowing strength’ across disease rates to shrink the uncertainty in geographical risk assessment for any particular disease. A number of approaches to such multivariate modelling have been suggested and this paper proposes an extension to these which may provide a richer range of dependency structures than those encompassed so far. We develop a model which incorporates a discrete mixture of latent structures and argue that this provides potential to represent an enhanced range of correlation structures between diseases at the same time as implicitly allowing for less restrictive spatial correlation structures between geographical units. We compare and contrast our approach to other commonly used multivariate disease models and demonstrate comparative results using data taken from cancer registries on four carcinomas in some 300 geographical units in England, Scotland and Wales.

Policy analytics need more than a spreadsheet: a case study in funding formulae

This article presents two case studies, concerning the allocation of £Billions by a mechanism communicated via spreadsheet models. It argues that technical analytic skills as well as policy development skills are a vital component of governance. In the UK, Central Government uses funding formulae to distribute money to local service providers. One commonly stated goal of such formulae is equity of service provision. However, given the complexity of public services, together with variations in need, delivery style and the exercise of stakeholder judgement as to which needs should be met and how, such formulae frequently obscure the process by which equity has been taken into account. One policy ‘solution’ to managing such tensions is to seek ‘transparency’. With respect to funding formulae, this commonly involves publishing the underlying data and formulae in spreadsheets. This paper extends the argument that such ‘transparency’ requires an audience that understands the policy assumptions (and related conceptualisations), data sources, methodological approaches and interpretation of results. It demonstrates how the search for policy ‘transparency’ is also met by the technical quality assurance goals that the operational research community would recognise as best practice in the development both of software generally and spreadsheet models specifically. Illustrative examples of complex formulae acting to subvert equity are drawn from the English Fire and Rescue Service and Police Service allocation formulae. In the former, an increase in the amount of deprivation, as measured by one of six indicators, has the perverse effect of decreasing the financial allocation. In the latter, metropolitan areas such as London are found to gain most from the inclusion of variables measuring sparsity. The conclusion from these scenarios is that the steps needed to for technical quality assurance and policy transparency are mutually reinforcing goals, with policy analysts urged to make greater use of technical analytic skills in software development.