Analysis of a Nuclear Reactor Boilure Closure Unit Through Development of a 3D Parallel Finite Element Code

Three dimensional (3D) finite element analysis (FEA) allows the mechanical integrity of complex structures to be estimated with some confidence. This research is concerned with extending an existing parallel FEA code. This code has been run on up to 16 processors on Durham University’s high performance computing (HPC) cluster and two different parallel linear solvers have been compared. A key feature of the work has been to develop tools for structural analyses. An automatic mesh refinement program has been written, the Zienkiewicz and Zhu error estimator has been coded for 3D hexahedral meshes and post processing techniques have been used to calculate and visualise principal stress data and peak stress criteria. This project also reports on three peak stress envelopes used to assess the condition of a concrete sub-structure. The development of this parallel code has enabled the deformation behaviour of a key component of a nuclear rector vessel to be determined. The BCU is a prestressed cylindrical concrete vessel (depth of 1.73m and diameter of 3.37m) sealing the top of a boilers housed within the walls of the reactor. In recent years possible problems have been identified at the Hartlepool and Heysham I Advance Gas-Cooled nuclear reactors (AGR) with respect to the structural condition of the BCU (in particular the condition of the prestressed circumferential wires designed to maintain the BCU in a state of compression). This problem provides an interesting case study for this project. Four different BCU meshes have been used containing either 40201 or 321608 elements (the elements are either 8 or 20-noded hexahedral elements). Three different load cases have been used to model the BCU. The results of the analyses confirm that the circumferential pre-stressing is vital in order to keep the BCU is a state of compression and operating under safe working conditions. These results have been confirmed using principal stress plots and three different peak stress envelopes. The results show that when the pre-stressing is released approximately one quarter of the elements contain stresses at Gauss points which exceed the peak strength of the concrete. This suggests that under these extreme conditions the BCU’s structural integrity has been severely compromised, concrete rupture is possible and the nuclear reactor is no-longer safe to operate

Evaluation contingente, qualité de l'air et santé : une étude en milieu urbain

L'évaluation monétaire des atteintes à la santé constitue une étape essentielle de la mise en place de politiques publiques ayant des retombées environnementales. L'analyse coûts-bénéfices des décisions politiques est principalement concernée. Du fait qu'aucun prix n'est disponible pour attribuer une valeur à ce type d'impacts, différentes méthodes économiques ont été conçues. Après avoir dressé un panorama des principales méthodes d'évaluation disponibles, ce cahier présente une étude détaillée de la méthode de l'évaluation contingente. La réalisation d'une évaluation contingente dans le cas d'un projet d'incinérateur en Ville de Lausanne constitue une application concrète des possibilités de cette méthode d'évaluation. Lors de la mise au point et de la réalisation de cette étude empirique, des innovations méthodologiques ont été testées. Ces innovations permettent une analyse approfondie des résultats obtenus. Ces résultats permettent de mieux chiffrer les coûts et les bénéfices du projet concerné. Ils constituent une information essentielle aussi bien pour les décideurs politiques que pour la population, confortant le rôle de l'évaluation contingente comme outil économique d'aide à la décision

Rationalité économique et logique de précaution : quelle compatibilité ?

Introduction Dans notre article précédent, nous avons proposé de considérer les situations de précaution comme résultant d’interactions homme-nature particulières, caractéristiques de la civilisation industrielle avancée, où le développement technologique contemporain brouille toujours davantage les pistes tracées par l’évolution naturelle, entraînant l’homme toujours plus loin dans l’inédit, l’incertain et l’inconnu. En réponse à cette évolution technologique préoccupante, nous avons préconi..

Consumption of energy drinks by children and young people: a systematic review examining evidence of physical effects and consumer attitudes

ObjectiveTo update an earlier review, published in 2016, on the health and other outcomes associated with children and young people's consumption of energy drinks (EDs).Study designReview article.Systematic reviewSystematic searches of nine databases (ASSIA, CINAHL, Cochrane Library, DARE, Embase, ERIC, MEDLINE, PsycINFO and Web of Science) retrieved original articles reporting the effects of EDs experienced by children and young people up to the age of 21 years. Searches were restricted by publication dates (January 2016 to July 2022) and language (English). Studies assessed as being weak were excluded from the review. Included studies underwent narrative synthesis.ResultsA total of 57 studies were included. Boys consumed EDs more than girls. Many studies reported a strong positive association between ED consumption and smoking, alcohol use, binge drinking, other substance use and the intentions to initiate these behaviours. Sensation-seeking and delinquent behaviours were positively associated with ED consumption, as were short sleep duration, poor sleep quality and low academic performance. Additional health effects noted in the updated review included increased risk of suicide, psychological distress, attention-deficit hyperactivity disorder symptoms, depressive and panic behaviours, allergic diseases, insulin resistance, dental caries and erosive tooth wear.ConclusionsThis review adds to the growing evidence that ED consumption by children and young people is associated with numerous adverse physical and mental health outcomes. Where feasible and ethical, additional longitudinal studies are required to ascertain causality. The precautionary principle should be considered in regulatory policy and restriction of ED sales to this population

Pour une approche évolutive de la précaution

« Tout coule, l’homme ne se baignejamais deux fois dans le même fleuve »(Héraclite, VIe - Ve siècle, AD) Introduction Cet article propose d’adopter une perspective sur la précaution issue d’un paradigme en pleine expansion, le paradigme évolutif. Ce paradigme présente une approche reposant sur une vision du monde à la fois ancienne (remontant à la dialectique d’Héraclite) et très récente (issue des développements les plus récents des sciences traditionnelles, comme la physique des processus i..

Plant–virus–vector interactions: Tobacco rattle virus infection alters root volatile emissions to attract nematode vectors

Plant–virus–vector interactions mediate important ecological processes and can significantly reduce crop production. Almost all plant viruses require vectors for transmission and use sophisticated mechanisms to achieve this: they manipulate host plants to release volatile chemical that attract their vectors. This chemoattraction has been demonstrated in above-ground interactions but has never been studied in viruses transmitted by soil-dwelling nematodes. Tobacco rattle virus (TRV) is an important pest of potato, transmitted by trichodorid nematodes. This work uses a model plant system to investigate the effects of TRV infection on host root architecture, root volatile release and chemoattraction of its nematode vectors. TRV infection alters root structure, producing a smaller and more compact root system. It modifies root volatile profiles compared to uninfected plants, which leads to trichodorids preferentially moving towards infected plants. The TRV genome contains genes known as 2b and 2c; implicated for nematode transmission. Mutations in these genes reduce the severity of root architecture symptoms, remove differences in the profile of volatiles released from infected roots compared with uninfected ones and, in the case of 2b, make plants less attractive to nematodes than plants infected with viruses without mutations. The release of the volatile 2-ethyl-1-hexanol significantly increased in roots infected by TRV. When added to uninfected plants, it made them more attractive to nematodes than untreated counterparts. This work demonstrates TRV manipulates the production of host root volatiles, leading to increased attraction of trichodorid vectors. 2b and 2c are important in this interaction and 2-ethyl-1-hexanol is a strong component of the attractant signal. This new knowledge shows nematode transmitted viruses use similar mechanisms to attract their vectors as their better-studied aboveground counterparts and contributes to the study of volatile- mediated rhizosphere interactions with implications for agricultural pest control

Molecular gene markers for nitrification and denitrification and comparison with agricultural soil nitrous oxide emissions

Nitrous oxide (N2O) is an important greenhouse gas that accounts for 6% of total global forcing. Soils produce 70% of yearly global emissions and arable agriculture contributes significantly to this. Most N2O production is from microbial activity and soil microbes produce N2O from two main pathways, nitrification and denitrification. It is important to understand the relationship between N2O production and its microbial origins under different crop regimes for better mitigation of N2O emissions in arable agriculture. Due to the phylogenetic spread of nitrifiers and denitrifiers, a functional gene approach is preferable for studying the microbial origins of these processes. Open gas chamber sampling was carried out on open-bottomed soil cores filled with agricultural soils. Cores were either unplanted or filled planted with either Triticum aestivum or Brassica napus. Nitrogen was added as urea solution to some of the cores to simulate fertilizer addition. Soil-atmosphere fluxes of N2O were quantified and soil samples were taken for DNA extractions and analysis of the functional genes. Flux data suggested evidence for differences in N2O emissions between T. aestivum and B. napus. N2O fluxes were significantly lower in cores planted with T. aesitivum compared to unplanted and B. napus cores when treated with nitrogen. There was no significant difference in presence of functional genes with nitrogen addition or between different planting regimes. This study found that different crops respond differently to N addition, causing significant changes in N2O emissions. It offers an additional tool to make decisions about soil and agricultural management, such as N addition and will enable more sustainable use of soils

Consumption of energy drinks by children and young people: a systematic review examining evidence of physical effects and consumer attitudes

ObjectiveTo update an earlier review, published in 2016, on the health and other outcomes associated with children and young people\u27s consumption of energy drinks (EDs).Study designReview article.Systematic reviewSystematic searches of nine databases (ASSIA, CINAHL, Cochrane Library, DARE, Embase, ERIC, MEDLINE, PsycINFO and Web of Science) retrieved original articles reporting the effects of EDs experienced by children and young people up to the age of 21 years. Searches were restricted by publication dates (January 2016 to July 2022) and language (English). Studies assessed as being weak were excluded from the review. Included studies underwent narrative synthesis.ResultsA total of 57 studies were included. Boys consumed EDs more than girls. Many studies reported a strong positive association between ED consumption and smoking, alcohol use, binge drinking, other substance use and the intentions to initiate these behaviours. Sensation-seeking and delinquent behaviours were positively associated with ED consumption, as were short sleep duration, poor sleep quality and low academic performance. Additional health effects noted in the updated review included increased risk of suicide, psychological distress, attention-deficit hyperactivity disorder symptoms, depressive and panic behaviours, allergic diseases, insulin resistance, dental caries and erosive tooth wear.ConclusionsThis review adds to the growing evidence that ED consumption by children and young people is associated with numerous adverse physical and mental health outcomes. Where feasible and ethical, additional longitudinal studies are required to ascertain causality. The precautionary principle should be considered in regulatory policy and restriction of ED sales to this population.PROSPERO registrationCRD42021255484

Yield and risk associated with prolonged presurgical video-EEG monitoring: a systematic review

OBJECTIVE: Presurgical long-term video-EEG monitoring (LT-VEEG) is an important part of the presurgical evaluation in patients with focal epilepsy. Multiple seizures need to be recorded, often in limited time and with the need to taper anti-seizure medication (ASM). The aim of this study was to systematically study the yield – in terms of success – and risks associated with presurgical LT-VEEG, and to identify all previously reported contributing variables. METHODS: A systematic review of the databases of PubMed Medline, Embase, Cochrane Central, and the Cochrane Database of Systematic Reviews were searched following the Preferred Reporting Items for Systematic Reviews (PRISMA) guideline. Publications about presurgical LT-VEEG reporting on variables contributing to yield and risk were included. Study characteristics of all included studies were extracted following a standardized template. Within these articles, studies presenting multivariable analyses of factors contributing to the risk of adverse events or the success of LT-VEEG were identified. RESULTS: We found 36 articles reporting on LT-VEEG, including 4,703 presurgical patients, both children and adults. Presurgical LT-VEEG monitoring led to an average yield of 85%. Adverse events occurred with an averaged total event rate of 17%, but the type of included events was variable among studies. Factors reported to independently contribute to successful LT-VEEG were: baseline seizure frequency, a shorter interval from the most recent seizure, extratemporal lobe epilepsy, and no requirement for ASM reduction. Factors independently contributing to the occurrence of adverse events were: ASM tapering, a history of status epilepticus, a history of focal to bilateral tonic-clonic seizures, psychiatric comorbidity, and ASM taper rate. SIGNIFICANCE: This study reveals that the data on factors contributing to yield and risk of adverse events is significant and variable, and often reported with inadequate statistics. Future research is warranted to develop guidelines for ASM withdrawal during presurgical video-EEG monitoring, taking predefined factors for success and risks of adverse events into account