922017 research outputs found
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Impact of occupational pesticide exposure assessment method on rist estimates for prostate cancer, non-Hodgkin's lymphoma and Parkinson's disease - results of three meta-analyses
No full textObjective: Assessment of occupational pesticide exposure in epidemiological studies of chronic diseases is challenging. Biomonitoring of current pesticide levels might not correlate with past exposure relevant to disease etiology, and indirect methods often rely on workers’ imperfect recall of exposures, or job titles. We investigated how applied exposure assessment method (EAM) influenced risk estimates for some chronic diseases. Methods: In three meta-analyses the influence of EAM type on the summary risk ratio (sRR) of prostate cancer (25 articles), Non-Hodgkin’s lymphoma (NHL) (30 articles), and Parkinson’s disease (PD) (32 articles) was investigated. EAM types analysed were: group-level assessments (e.g. job titles), self-reported exposures, expert-level assessments (e.g. job-exposure matrices), and biomonitoring (e.g. blood, urine). Additionally, sRRs were estimated by study design, publication year period, and geographic location where the study was conducted.Results: EAM types were not associated with statistically significant different sRRs across any of the health outcomes. Heterogeneity in results varied from high in cancer studies to moderate and low in PD studies. Overall, case-control designs showed significantly higher sRR estimates than prospective cohort designs. Later NHL publications showed significantly higher sRR estimates than earlier. For prostate cancer, studies from North America showed significantly higher sRR estimates than studies from Europe. Conclusion: Exposure assessment method applied in studies of occupational pesticides appears not to have a significant effect on risk estimates for prostate cancer, NHL, and PD. In systematic reviews of chronic health effects of occupational exposure to pesticides, epidemiological study design, publication year, and geographic location, should primarily be considered. <br/
A discontinuous model of duopoly with isoelastic demand and innovation costs
No full textThe paper studies the dynamic properties of a duopoly game in which firms strategically compete in quality-enhancing innovation investments and quantities. Market demands are assumed to be isolastic (reciprocal to the price) functions. The non-linearity of the demand functions, as already highlighted by T. Puu in [11], suggests the existence of complicated dynamics (cyclical or chaotic) in a standard dynamic Cournot duopoly. In addition to this, competition in innovation introduces the presence of discontinuities in the best response functions, expanding the set of possible equilibria (including asymmetric and multiple ones) of the standard Cournot duopoly and further enriching the dynamic features of the model.<br/
Bias-Variance Decompositions for Margin Losses
No full textWe introduce a novel bias-variance decomposition for a range of strictly convex margin losses, including the logistic loss (minimized by the classic LogitBoost algorithm), as well as the squared margin loss and canonical boosting loss. Furthermore, we show that, for all strictly convex margin losses, the expected risk decomposes into the risk of a “central” model and a term quantifying variation in the functional margin with respect to variations in the training data. These decompositions provide a diagnostic tool for practitioners to understand model overfitting/underfitting, and have implications for additive ensemble models—for example, when our bias-variance decomposition holds, there is a corresponding “ambiguity” decomposition, which can be used to quantify model diversity.<br/
The TRANSCEND University Consortium: Integrated Waste Management
No full textTRANSCEND (Transformative Science and Engineering for Nuclear Decommissioning) is a collaborative research consortium comprising 11 universities and 8 industry partners. The £9.4 million research program, funded primarily by the Engineering and Physical Sciences (EPSRC) Research Council of the UK, incorporates >40 projects in total, which will address some of the key challenges within the areas of nuclear decommissioning and waste management; including mobilization, processing, packaging, storage, transport and final disposal. This paper will outline a summary of the current progress and impact of Theme 1 - Integrated Waste Management. This theme focuses on underpinning science and engineering in areas of relevance to hazard reduction and decommissioning, where the three key work package objectives are: (1) New materials and methods for effluent decontamination; (2) Modelling and experiments for understanding pond and silo sludge/slurry behavior; (3) Innovative wasteform materials. In total, this theme has 15 different projects, delivered through both postdoctoral and PhD researchers, all with specific industry supervision from our partners, led by the NNL. The following provides a review of the project summaries to date, and their critical impact
Construction of a destabilizing nonlinearity for discrete-time uncertain Lurye systems
No full textThis paper considers the instability of a Lurye system consisting of an uncertain, discrete-time, linear time-invariant plant in feedback with a slope-restricted nonlinearity. There is a large literature on analyzing the stability of such systems. This includes various conditions for proving stability of the Lurye system, including the Circle criterion and the use of O’Shea-Zames-Falb multipliers. In many cases, these conditions are sufficient but not necessary to prove stability. In contrast, there is also some work to construct specific nonlinearities that demonstrate the instability of the Lurye system (with the nominal plant dynamics). This paper considers a more general case where the plant has dynamic uncertainty. The goal is to construct both an instance of the uncertain model and a corresponding nonlinearity that combined make the Lurye system unstable. A limit cycle oscillation is also computed to verify the instability. A simple example is provided to demonstrate the results
Depression and anxiety in a real-world psoriatic arthritis longitudinal study. Should we focus more on patients’ perception?
No full textObjectives: Longitudinal studies using validated tools to evaluate depression and anxiety in psoriatic arthritis (PsA) are lacking. We aimed to estimate their course in PsA and to examine possible associations with disease-related parameters and patient-reported outcomes (PROs).Methods: PsA patients attending two outpatient rheumatology clinics were consecutively enrolled (January 2019-June 2021, n=128). The hospital anxiety and depression scale (HADS) was used at two sequential visits (mean±SD: 10±6 months) to prospectively assess depression (HADS-Depression) and anxiety (HADS-Anxiety) (cut-off scores≥11). Associations with demographic, clinical, laboratory features and PROs for quality of life (QoL) (EQ-5D), functional status (HAQ-DI) and nocebo-behaviour (Q-No) were examined. ‘Change’ was the difference between values at the first and second visit.Results: Prevalence of depression and anxiety at the first visit was 19.5% and 21.1%, respectively. Depression was associated with EQ-5D [OR (95% CI): 1.70 (1.02-2.59), p=0.019] and anxiety with EQ-5D [1.81 (1.20 to 2.72), p=0.005], nocebo-behaviour [1.19 (1.01-1.40), p=0.04] and current corticosteroid use [6.95 (1.75-27.59), p=0.006]. At the second visit, HADS-Depression and HADS-Anxiety scores were improved in 40.9% and 41.9% of patients, respectively. While no associations were found for HADS-Anxiety score change, changes in HADS-Depression score correlated with changes in subjective (tender joint count, r= 0.204, p=0.049; PtG, r= 0.236, p=0.023; patient pain assessment, r= 0.266, p=0.01) but not objective (swollen joint count, ESR, CRP) parameters of disease activity.Conclusion: In PsA, depression and anxiety are associated with worse PROs, including QoL. Subjective parameters of disease activity parallel course of depression.<br/
Dynamics of electrostatic interaction and electrodiffusion in a charged thin film with nanoscale physicochemical heterogeneity: implications for low-salinity waterflooding
No full textThe slow kinetics of wettability alteration toward a more water-wetting state by low-salinity waterflooding (LSWF) in oil-brine-rock (OBR) systems is conjectured to be pertinent to the electrokinetic phenomena in the thin brine film. We hypothesize that the nanoscale physicochemical heterogeneities such as surface roughness and surface charge heterogeneity at the rock/brine interface control further the dynamics of electrodiffusion and electrostatic disjoining pressure (Πel), thus the time-scale and the magnitude of the low salinity effect (LSE). Film-scale computational fluid dynamics (CFD) simulations were performed to demonstrate this. The coupled Poisson-Nernst-Planck (PNP) equations were solved numerically in a thin water film confined between a solid surface and oil, both negatively charged. The solid surface is representative of quartz/kaolinite with patchwise physicochemical heterogeneity. The electrical properties of the oil are representative of a crude-oil sample. The OBR system is initially under chemical equilibrium with high salinity (HS) brine, then is exposed to low salinity (LS) brine. The time-scale of reaching chemical equilibrium under LS, and the evolution of electric potential were investigated. We find that surface roughness increases the diffusion time up to 3-fold due to increased tortuosity. Also, the effect of surface roughness and surface charge heterogeneity on the effective diffusioncoefficient (Deff) is minor. While surface roughness and surface charge 1 heterogeneity affect the disjoining pressure (Πel) significantly, the influence of surface roughness on Πel is more pronounced under HS than LS conditions. In contrast, the effect of surface charge heterogeneity (introduced by kaolinite patches on quartz) is more appreciable under LS than HS. Our findings imply that the LS effect can be enhanced in rough, heterogeneously charged systems like clayey sandstone, although its magnitude depends on the charge density of the roughness. We introduce two scaling factors, namely the effective diffusion coefficient (Deff) and the retardation coefficient (ω), to upscale the nanoscale results to pore-scale and beyond
Pore-scale Large Eddy Simulation of Turbulent Flow and Heat Transfer over Porous Media
No full textThis paper investigates turbulent fluid flow and heat transfer over a porous medium in a channel using pore-scale large eddy simulation. Special attention is placed on the exchange of heat and flow between the porous and non-porous regions through the interface between the two regions. For this purpose, two different porous systems made of a packed bed of spheres and rectangular rods are analysed and the results are compared against a solid block case of the same size. Flow visualization shows that a significant portion of the fluid entering the porous blocks leaks from the porous region to the non-porous region through the porous-fluid interface. To discuss the effects of this flow leakage on the flow features and heat transfer, discussions are made regarding velocity, pressure, and temperature fields, as well as coherent structures, and turbulence production. The flow pattern inside the porous region indicates that the flow leakage clogs the pore channels inside the porous medium which induces a significant reduction in the streamwise momentum of the pore flow. In addition, coherent structures show that flow leakage leads to the creation of counter-rotating vortex pairs of fluid flow within and above the porous block that results in the formation of organized hairpin structures. Finally, the comparison of turbulence production for the porous and solid cases together with the onset growth of the Kelvin-Helmholtz instability on the porous-fluid interface show a reduction in turbulent kinetic energy above the leading edge of porous blocks. This observation implies that for the porous cases the transition to turbulence is postponed to the downstream of the porous block and it is not achieved as fast as the solid block
Bridging disconnected networks of first and second lines of biologic therapies in rheumatoid arthritis with registry data: Bayesian evidence synthesis with target trial emulation
No full textObjective: We aim to utilise real world data in evidence synthesis to optimise an evidence base for the effectiveness of biologic therapies in rheumatoid arthritis in order to allow for evidence on first-line therapies to inform second-line effectiveness estimates.Study design and setting: We use data from the British Society for Rheumatology Biologics Register for Rheumatoid Arthritis (BSRBR-RA) to supplement RCT evidence obtained from the literature, by emulating target trials of treatment sequences to estimate treatment effects in each line of therapy. Treatment effects estimates from the target trials inform a bivariate network meta-analysis (NMA) of first and second-line treatments.Results: Summary data were obtained from 21 trials of biologic therapies including 2 for second-line treatment and results from six emulated target trials of both treatment lines. Bivariate NMA resulted in a decrease in uncertainty around the effectiveness estimates of the second-line therapies, when compared to the results of univariate NMA, and allowed for predictions of treatment effects not evaluated in second-line RCTs.Conclusion: Bivariate NMA provides effectiveness estimates for all treatments in first- and second-line, including predicted effects in second-line where these estimates did not exist in the data. This novel methodology may have further applications, for example for bridging networks of trials in children and adults
