Metal debris release from metal-on-metal hip arthroplasty : mechanism, quantification and clinical effects

PhD ThesisMetal on metal (MoM) hip replacements consist of a cobalt-chromium-molybdenum alloy femoral head which articulates against an acetabular cup manufactured from similar material. MoM hip replacements were introduced in the 1980s. It was thought that the overall reduction in volumetric wear as well as the avoidance of polyethylene would lead to greater longevity of these prostheses. There had been isolated reports of adverse tissue reactions with previous generations of MoM devices but it was thought that improved manufacturing technology would eliminate these problems. In the 1990s, the Birmingham Hip Resurfacing (BHR) was developed. The positive mid-term results of this device led to a rapid increase in the use of the BHR throughout the world. For obvious reasons, the enhanced stability large diameter bearings provided proved extremely attractive to surgeons and patients. Manufacturers therefore began to develop total hip replacement systems for patients unsuitable for the resurfacing procedure. These systems used bearings of size 36mm and greater, in Contrast to the existing 28mm Metasul device. From 2005 onwards there began to emerge increasing numbers of reports of local complications in the tissues adjacent to MoM prostheses. These reactions included sterile masses, tissue destruction and osteolysis. The incidence of these tissue reactions was unknown, as were the risk factors for their development. This piece of work sought to quantity the volumetric and linear wear rates of failed MoM hips and to investigate the relationship these wear rates and a number of clinical parameters. These parameters included blood, serum and hip fluid chromium and cobalt concentrations, and the macro and microscopic appearance of periprosthetic tissue at revision surgery. In this way it was hoped that component design, host and surgical factors leading to adverse tissue reactions could be identified and potentially eliminated

Bronchial thermoplasty versus mepolizumab : comparison of outcomes in a severe asthma clinic

Background and objective: BT and interleukin-blocking monoclonal antibodies are both effective therapies for severe asthma, but there have been no direct comparisons between the two treatments. The aim of this study was to compare the efficacy and safety of BT and mepolizumab, in a real-world setting. Methods: Patients with severe asthma despite optimized inhaler therapy were drawn from a severe asthma clinic in a tertiary hospital. Every patient commencing therapy with BT or mepolizumab was prospectively included in a national registry. At predetermined assessment points over a 12-month period, assessments were made of ACQ, spirometry, oral corticosteroid requiring exacerbations, reliever medication and maintenance oral corticosteroid use. Results: A total of 91 patients with severe asthma participated: mean ACQ score 3.5 ± 1.0, FEV1 51.4 ± 17.7%, maintenance oral steroids 48.3% and 11.5 ± 10.0 inhalations/day reliever therapy. Forty-seven patients received mepolizumab and 44 received BT. Baseline characteristics were similar except significantly higher blood eosinophil count in the mepolizumab group. At 12 months, there were no differences between treatment outcomes for ACQ (1.9 ± 1.3 mepolizumab vs 1.7 ± 1.3 BT), exacerbation rate (0.9 ± 1.1 vs 0.9 ± 1.5), reduction in reliever use (−6.3 ± 10.5 vs −5.0 ± 8.8 puffs/day) or reduction in oral corticosteroids (−3.3 ± 7.5 vs − 5.8 ± 6.7 mg/day). The FEV1 improved equally (160 ± 290 vs 150 ± 460 mL). Readmission or prolonged admission was observed in 18.2% of BT patients, whilst 25.5% of mepolizumab patients had discontinued treatment at 12 months, 14.9% due to an adverse event or non-compliance. Conclusion: The results suggest that BT is as efficacious as mepolizumab for the treatment of severe asthma. © 2020 Asian Pacific Society of Respirology. *Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Virginia Plummer” is provided in this record*

Boundary line models for soil nutrient concentrations and wheat yield in national-scale datasets

In boundary line analysis a biological response (e.g., crop yield) is assumed to be a function of a variable (e.g., soil nutrient concentration), which limits the response in only some subset of observations because other limiting factors also apply. The response function is therefore expressed by an upper boundary of the plot of the response against the variable. This model has been used in various branches of soil science. In this paper we apply it to the analysis of some large datasets, originating from commercial farms in England and Wales, on the recorded yield of wheat and measured concentrations of soil nutrients in within‐field soil management zones. We considered boundary line models for the effects of potassium (K), phosphorus (P) and magnesium (Mg) on yield, comparing the model with a simple bivariate normal distribution or a bivariate normal censored at a constant maximum yield. We were able to show, using likelihood‐based methods, that the boundary line model was preferable in most cases. The boundary line model suggested that the standard RB209 soil nutrient index values (Agriculture and Horticulture Development Board, nutrient management guide (RB209), 2017) are robust and apply at the within‐field scale. However, there was evidence that wheat yield could respond to additional Mg at concentrations above index 0, contrary to RB209 guidelines. Furthermore, there was evidence that the boundary line model for yield and P differs between soils at different pH and depth intervals, suggesting that shallow soils with larger pH require a larger target P index than others

Does a micro-grooved trunnion stem surface finish improve fixation and reduce fretting wear at the taper junction of total hip replacements? A finite element evaluation.

The generation of particulate debris at the taper junction of total hip replacements (THRs), can cause failure of the artificial hip. The taper surfaces of femoral heads and trunnions of femoral stems are generally machined to a certain roughness to enhance fixation. However, the effect of the surface roughness of these surfaces on the fixation, wear and consequently clinical outcomes of the design is largely unknown. In this study, we asked whether a micro-grooved trunnion surface finish (1) improves the fixation and (2) reduces the wear rate at the taper junction of THRs. We used 3D finite element (FE) models of THRs to, firstly, investigate the effect of initial fixation of a Cobalt-Chromium femoral head with a smooth taper surface mated with a Titanium (1) micro-grooved and (2) smooth, trunnion surface finishes. Secondly, we used a computational FE wear model to compare the wear evolution between the models, which was then validated against wear measurements of the taper surface of explanted femoral heads. The fixation at the taper junction was found to be better for the smooth couplings. Over a 7 million load cycle analysis in-silico, the linear wear depth and the total material loss was around 3.2 and 1.4 times higher for the femoral heads mated with micro-grooved trunnions. It was therefore concluded that smooth taper and trunnion surfaces will provide better fixation at the taper junction and reduce the volumetric wear rates

The effect of bronchial thermoplasty on airway volume measured 12 months post-procedure

Bronchial thermoplasty induces atrophy of the airway smooth muscle layer, but the mechanism whereby this improves patient health is unclear. In this study, we use computed tomography (CT) to evaluate the effects of bronchial thermoplasty on airway volume 12 months post-procedure. 10 consecutive patients with severe asthma were evaluated at baseline by the Asthma Control Questionnaire (ACQ), and high-resolution CT at total lung capacity (TLC) and functional residual capacity (FRC). The CT protocol was repeated 4 weeks after the left lung had been treated by bronchial thermoplasty, but prior to right lung treatment, and then again 12 months after both lungs were treated. The CT data were also used to model the implications of including the right middle lobe (RML) in the treatment field. The mean patient age was 62.7 +/- 7.7 years and forced expiratory volume in 1 s (FEV1) 42.9 +/- 11.5% predicted. 12 months post-bronchial-thermoplasty, the ACQ improved, from 3.4 +/- 1.0 to 1.5 +/- 0.9 (p=0.001), as did the frequency of oral steroid-requiring exacerbations (p=0.008). The total airway volume increased 12 months after bronchial thermoplasty in both the TLC (p=0.03) and the FRC scans (p=0.02). No change in airway volume was observed in the untreated central airways. In the bronchial thermoplasty-treated distal airways, increases in airway volume of 38.4 +/- 31.8% at TLC (p=0.03) and 30.0 +/- 24.8% at FRC (p=0.01) were observed. The change in distal airway volume was correlated with the improvement in ACQ (r=-0.71, p=0.02). Modelling outputs demonstrated that treating the RML conferred no additional benefit. Bronchial thermoplasty induces long-term increases in airway volume, which correlate with symptomatic improvement

3.6 and 4.5 μm Phase Curves and Evidence for Non-equilibrium Chemistry in the Atmosphere of Extrasolar Planet HD 189733b

We present new, full-orbit observations of the infrared phase variations of the canonical hot Jupiter HD 189733b obtained in the 3.6 and 4.5 μm bands using the Spitzer Space Telescope. When combined with previous phase curve observations at 8.0 and 24 μm, these data allow us to characterize the exoplanet's emission spectrum as a function of planetary longitude and to search for local variations in its vertical thermal profile and atmospheric composition. We utilize an improved method for removing the effects of intrapixel sensitivity variations and robustly extracting phase curve signals from these data, and we calculate our best-fit parameters and uncertainties using a wavelet-based Markov Chain Monte Carlo analysis that accounts for the presence of time-correlated noise in our data. We measure a phase curve amplitude of 0.1242% ± 0.0061% in the 3.6 μm band and 0.0982% ± 0.0089% in the 4.5 μm band, corresponding to brightness temperature contrasts of 503 ± 21 K and 264 ± 24 K, respectively. We find that the times of minimum and maximum flux occur several hours earlier than predicted for an atmosphere in radiative equilibrium, consistent with the eastward advection of gas by an equatorial super-rotating jet. The locations of the flux minima in our new data differ from our previous observations at 8 μm, and we present new evidence indicating that the flux minimum observed in the 8 μm is likely caused by an overshooting effect in the 8 μm array. We obtain improved estimates for HD 189733b's dayside planet-star flux ratio of 0.1466% ± 0.0040% in the 3.6 μm band and 0.1787% ± 0.0038% in the 4.5 μm band, corresponding to brightness temperatures of 1328 ± 11 K and 1192 ± 9 K, respectively; these are the most accurate secondary eclipse depths obtained to date for an extrasolar planet. We compare our new dayside and nightside spectra for HD 189733b to the predictions of one-dimensional radiative transfer models from Burrows et al. and conclude that fits to this planet's dayside spectrum provide a reasonably accurate estimate of the amount of energy transported to the night side. Our 3.6 and 4.5 μm phase curves are generally in good agreement with the predictions of general circulation models for this planet from Showman et al., although we require either excess drag or slower rotation rates in order to match the locations of the measured maxima and minima in the 4.5, 8.0, and 24 μm bands. We find that HD 189733b's 4.5 μm nightside flux is 3.3σ smaller than predicted by these models, which assume that the chemistry is in local thermal equilibrium. We conclude that this discrepancy is best explained by vertical mixing, which should lead to an excess of CO and correspondingly enhanced 4.5 μm absorption in this region. This result is consistent with our constraints on the planet's transmission spectrum, which also suggest excess absorption in the 4.5 μm band at the day-night terminator

The accuracy of crime statistics: Assessing the impact of police data bias on geographic crime analysis

Objectives: Police-recorded crimes are used by police forces to document community differences in crime and design spatially-targeted strategies. Nevertheless, crimes known to police are affected by selection biases driven by underreporting. This paper presents a simulation study to analyze if crime statistics aggregated at small spatial scales are affected by larger bias than maps produced for larger geographies. Methods: Based on parameters obtained from the UK Census, we simulate a synthetic population consistent with the characteristics of Manchester. Then, based on parameters derived from the Crime Survey for England and Wales, we simulate crimes suffered by individuals, and their likelihood to be known to police. This allows comparing the difference between all crimes and police-recorded incidents at different scales. Results: Measures of dispersion of the relative difference between all crimes and police-recorded crimes are larger when incidents are aggregated to small geographies. The percentage of crimes unknown to police varies widely across small areas, underestimating crime in certain places while overestimating it in others. Conclusions: Micro-level crime analysis is affected by a larger risk of bias than crimes aggregated at larger scales. These results raise awareness about an important shortcoming of micro-level mapping, and further efforts are needed to improve crime estimates

Atmospheric circulation of hot Jupiters: Coupled radiative-dynamical general circulation model simulations of HD 189733b and HD 209458b

We present global, three-dimensional numerical simulations of HD 189733b and HD 209458b that couple the atmospheric dynamics to a realistic representation of non-gray cloud-free radiative transfer. The model, which we call the Substellar and Planetary Atmospheric Radiation and Circulation (SPARC) model, adopts the MITgcm for the dynamics and uses the radiative model of McKay, Marley, Fortney, and collaborators for the radiation. Like earlier work with simplified forcing, our simulations develop a broad eastward equatorial jet, mean westward flow at higher latitudes, and substantial flow over the poles at low pressure. For HD 189733b, our simulations without TiO and VO opacity can explain the broad features of the observed 8 and 24-micron light curves, including the modest day-night flux variation and the fact that the planet/star flux ratio peaks before the secondary eclipse. Our simulations also provide reasonable matches to the Spitzer secondary-eclipse depths at 4.5, 5.8, 8, 16, and 24 microns and the groundbased upper limit at 2.2 microns. However, we substantially underpredict the 3.6-micron secondary-eclipse depth, suggesting that our simulations are too cold in the 0.1-1 bar region. Predicted temporal variability in secondary-eclipse depths is ~1% at Spitzer bandpasses, consistent with recent observational upper limits at 8 microns. We also show that nonsynchronous rotation can significantly alter the jet structure. For HD 209458b, we include TiO and VO opacity; these simulations develop a hot (>2000 K) dayside stratosphere. Despite this stratosphere, we do not reproduce current Spitzer photometry of this planet. Light curves in Spitzer bandpasses show modest phase variation and satisfy the observational upper limit on day-night phase variation at 8 microns. (abridged)Comment: 20 pages (emulate-apj format), 21 figures, final version now published in ApJ. Includes expanded discussion of radiative-transfer methods and two new figure