83 research outputs found
The effect of temperature changes on to quasi-static tensile and flexural performance of glass fibre reinforced PA66 composites
A significant method of reducing CO2 emissions in road vehicles is to reduce the vehicle mass. One means in which this can be achieved is to adopt lightweight materials such as thermoplastic composites. Thermoplastics offer advantages in term of weight when compared to conventional steel and aluminium casting. In this study thermal mechanical testing has been conducted on two types of commercial polyamide 66 (PA66) with 35 wt.% short glass fibre reinforcement. One of the materials was impact modified with an elastomer to increase material toughness. Experimental results showed both the reinforced PA66 materials to be temperature dependent. All test results demonstrated the trade-off in the mechanical properties of the two materials especially the impact modified. PA66 with 35 wt.% short glass fibre exhibits the best tensile strength, flexural strength and modulus for each temperature tested. Whereas the impact modified PA66 with 35 wt.% short glass fibre exhibits the higher strain and toughness for each temperature tested
An experimental investigation into localised low-velocity impact loading on glass fibre-reinforced polyamide automotive product.
In the automotive industry, more and more engineered parts are shifting from metals to engineering plastics. However localised impact loading and long term ageing effects of under-the-hood plastic components is not well understood. In this paper, localised low velocity impact experiments and simulations were conducted on glass fibre-reinforced polyamide sump to investigate typical flying stones impact scenarios. Complete components were manufactured by injection moulding techniques for the experimental samples. The samples were then subjected to a range of low velocity impact using drop weight tower and flying projectiles from an air gun. Damage assessments were then performed following the experiments. In parallel, finite element analysis using LS DYNA was carried out to virtually benchmark and to predict the strength and fracture behaviour of stressed plastic parts. This has permitted to perform numerous impact tests in different situations with varying parameters. The study results show the significant contribution of the design in terms of shock absorption. The specific sump design with a protective ribbing combined with a superior material increases considerably the impact resistance. The paper will provided detailed discussions and results from both the experiments and finite element analysis investigations
Self-reported interoceptive deficits in eating disorders: A meta-analysis of studies using the eating disorder inventory
This document is the Accepted Manuscript version of the following article: Paul M. Jenkinson, Lauren Taylor, Keith R. Laws, ‘Self-reported interoceptive deficits in eating disorders: A meta-analysis of studies using the eating disorder inventory’, Journal of Psychosomatic Research, Vol. 110: 38-45, July 2018, under embargo until 19 April 2019. The Version of Record is available online at DOI: https://doi.org/10.1016/j.jpsychores.2018.04.005Objective: An impairment of the ability to sense the physiological condition of the body – interoception – has long been proposed as central to the onset and maintenance of eating disorders. More recent attention to this topic has generally indicated the presence of interoceptive deficits in individuals with an eating disorder diagnosis; however, possible links with specific diagnosis, BMI, age, illness duration, depression, and alexithymia remain unclear from individual studies. This meta-analysis aimed to provide a necessary quantitative overview of self-reported interoceptive deficits in eating disorder populations, and the relationship between these deficits and the previously mentioned factors. Methods: Using a random effects model, our meta-analysis assessed the magnitude of differences in interoceptive abilities as measured using the Eating Disorder Inventory in 41 samples comparing people with eating disorders (n=4308) and healthy controls (n=3459). Follow-up and moderator analysis was conducted, using group comparisons and meta-regressions. Results: We report a large pooled effect size of 1.62 for eating disorders with some variation between diagnostic groups. Further moderator analysis showed that BMI, age and alexithymia were significant predictors of overall effect size. Conclusion: This meta-analysis is the first to confirm that large interoceptive deficits occur in a variety of eating disorders and crucially, in those who have recovered. These deficits may be useful in identifying and distinguishing eating disorders. Future research needs to consider both objective and subjective measures of interoception across different types of eating disorders and may fruitfully examine interoception as a possible endophenotype and target for treatment.Peer reviewe
Bivariate random-effects meta-analysis and the estimation of between-study correlation
BACKGROUND: When multiple endpoints are of interest in evidence synthesis, a multivariate meta-analysis can jointly synthesise those endpoints and utilise their correlation. A multivariate random-effects meta-analysis must incorporate and estimate the between-study correlation (ρ(B)). METHODS: In this paper we assess maximum likelihood estimation of a general normal model and a generalised model for bivariate random-effects meta-analysis (BRMA). We consider two applied examples, one involving a diagnostic marker and the other a surrogate outcome. These motivate a simulation study where estimation properties from BRMA are compared with those from two separate univariate random-effects meta-analyses (URMAs), the traditional approach. RESULTS: The normal BRMA model estimates ρ(B )as -1 in both applied examples. Analytically we show this is due to the maximum likelihood estimator sensibly truncating the between-study covariance matrix on the boundary of its parameter space. Our simulations reveal this commonly occurs when the number of studies is small or the within-study variation is relatively large; it also causes upwardly biased between-study variance estimates, which are inflated to compensate for the restriction on [Formula: see text] (B). Importantly, this does not induce any systematic bias in the pooled estimates and produces conservative standard errors and mean-square errors. Furthermore, the normal BRMA is preferable to two normal URMAs; the mean-square error and standard error of pooled estimates is generally smaller in the BRMA, especially given data missing at random. For meta-analysis of proportions we then show that a generalised BRMA model is better still. This correctly uses a binomial rather than normal distribution, and produces better estimates than the normal BRMA and also two generalised URMAs; however the model may sometimes not converge due to difficulties estimating ρ(B). CONCLUSION: A BRMA model offers numerous advantages over separate univariate synthesises; this paper highlights some of these benefits in both a normal and generalised modelling framework, and examines the estimation of between-study correlation to aid practitioners
North American montane red foxes: expansion, fragmentation, and the origin of the Sacramento Valley red fox
GWAS meta-analysis of intrahepatic cholestasis of pregnancy implicates multiple hepatic genes and regulatory elements
Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific liver disorder affecting 0.5–2% of pregnancies. The majority of cases present in the third trimester with pruritus, elevated serum bile acids and abnormal serum liver tests. ICP is associated with an increased risk of adverse outcomes, including spontaneous preterm birth and stillbirth. Whilst rare mutations affecting hepatobiliary transporters contribute to the aetiology of ICP, the role of common genetic variation in ICP has not been systematically characterised to date. Here, we perform genome-wide association studies (GWAS) and meta-analyses for ICP across three studies including 1138 cases and 153,642 controls. Eleven loci achieve genome-wide significance and have been further investigated and fine-mapped using functional genomics approaches. Our results pinpoint common sequence variation in liver-enriched genes and liver-specific cis-regulatory elements as contributing mechanisms to ICP susceptibility
Genomic reconstruction of the SARS-CoV-2 epidemic in England.
The evolution of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus leads to new variants that warrant timely epidemiological characterization. Here we use the dense genomic surveillance data generated by the COVID-19 Genomics UK Consortium to reconstruct the dynamics of 71 different lineages in each of 315 English local authorities between September 2020 and June 2021. This analysis reveals a series of subepidemics that peaked in early autumn 2020, followed by a jump in transmissibility of the B.1.1.7/Alpha lineage. The Alpha variant grew when other lineages declined during the second national lockdown and regionally tiered restrictions between November and December 2020. A third more stringent national lockdown suppressed the Alpha variant and eliminated nearly all other lineages in early 2021. Yet a series of variants (most of which contained the spike E484K mutation) defied these trends and persisted at moderately increasing proportions. However, by accounting for sustained introductions, we found that the transmissibility of these variants is unlikely to have exceeded the transmissibility of the Alpha variant. Finally, B.1.617.2/Delta was repeatedly introduced in England and grew rapidly in early summer 2021, constituting approximately 98% of sampled SARS-CoV-2 genomes on 26 June 2021
Finite element analysis of localised impact loading on short glass fibrereinforced polyamide engine oil pan subjected to low velocity impact from flying projectiles
This paper investigates low velocity impact involving a glass fibre-reinforced
polyamide engine oil pan as part of a complete new development of thermoplastic
components. The assessment of the impact resistance has driven the need to
employ LS DYNA for finite element modelling in order to virtually benchmark and
predict the strength and fracture behaviour of stressed plastic parts. In order
to develop a reliable predictive capability and to validate simulations,
complete components were manufactured by injection moulding techniques for the
experimental samples. Low velocity impact investigations were carried out using
a gas gun and a falling weight tester in order to simulate impact events to
which the oil pan is subjected whilst in operational service. This was intended
to point out damage tolerance and failure mechanisms likely to occur in the
structure. The study results show the significant contribution of the design in
terms of shock absorption. Specific oil pan design with protective ribbing
combined with a superior material considerably improves the impact resistance.
The paper provides results and discussions on experimental and finite element
analysis investigations before concluding with some remarks
Low Velocity Impact Behavior of Glass Filled Fiber-Reinforced Thermoplastic Engine Components
This paper concerns automotive parts located underneath the engine and in
particular the engine oil pan. Classically made of stamped steel or cast
aluminum, new developments have allowed the manufacture oil pans with polyamide
66 reinforced by 35% weight of short glass fiber. However, polyamides have some
limitations and the most significant is their response to localized impact
loading. The nature of the impact considered here is of a typical stone
collected from the road and projected into the oil pan. Low velocity impact
investigations were carried out using a gas gun and drop weight tower. The study
shows that the design of the oil pan has a significant contribution in the shock
absorption. In addition to the material properties, the geometry and the ribbing
both cleverly combined, increase the impact resistance of the component
significantly. Areas of oil pan design improvement have been identified and
conclusions drawn
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