Influence de traitements thermo-mécaniques sur les performances en fluage et en fatigue d'aciers martensitiques à 9% Cr

National audienceLe développement des réacteurs nucléaires de génération IV et des réacteurs à fusion nucléaire requiert l'utilisation de matériaux possédant de bonnes propriétés mécaniques au-delà de 550 °C. En service, ces matériaux seront soumis à du fluage à haute température couplé à des sollicitations cycliques de fatigue. Les aciers martensitiques à 9-12 % Cr sont pressentis pour ces applications; cependant leur comportement en fatigue et fatigue-fluage à haute température est encore insuffisant : la microstructure martensitique grossit et l'acier s'adoucit rapidement. Afin de stabiliser sa microstructure, l'acier commercial P91 a subi un traitement thermo-mécanique incluant du laminage à 600 °C suivi d'un revenu d'une heure à 700 °C. Les observations microstructurales confirment que le traitement thermo-mécanique a conduit à une martensite plus fine, émaillée de nombreux et fins précipités de type MX. Les divers essais mécaniques réalisés prouvent que ces changements ont un effet positif sur les propriétés de l'acier : sa dureté est plus élevée de 100 Hv par rapport à l'acier P91 à réception, et sa limite d'élasticité conventionnelle est supérieure de 430 MPa à 20 °C et de 220 MPa à 550 °C. La durée de vie du P91 optimisé en fluage à 650 °C sous 120 MPa est plus de 14 fois supérieure à celle du P91; et l'essai de fatigue à 650 °C et 0,7 % de déformation totale montre un adoucissement légèrement moins rapide

Overview of ¹⁴C release from irradiated zircaloys in geological disposal conditions

Carbon-14 (radiocarbon, 14C) is a long-lived radionuclide (5730 yr) of interest regarding the safety for the management of intermediate level wastes (ILW). The present study gives an overview of the release of 14C from irradiated Zircaloy cladding in alkaline media. 14C is found either in the alloy part of Zircaloy cladding due to the neutron activation of 14N impurities by 14N(n,p)14C reaction, or in the oxide layer (ZrO2) formed at the metal surface by the neutron activation of 17O from UO2 or (U-Pu)O2 fuel and water from the primary circuit in the reactor by 17O(n,α)14C reaction. Various irradiated and unirradiated Zircaloys have been studied. The total 14C inventory has been determined both experimentally and by calculations. The results seem to be in good agreement. Leaching experiments were conducted in alkaline media for several time durations. 14C was mainly released as carboxylic acids. Further, corrosion measurements were performed by using both hydrogen measurements and electrochemical measurements. The corrosion rate (CR) ranges from a few nm/yr to 100 nm/yr depending on the surface conditions and the method used for measurement. From a safety assessment point of view, the instant release fraction (IRF) was determined on irradiated Zircaloy-2. The results showed that the 14C inventory in the oxide was significantly below the 20% commonly used in safety case assessments

The relationship of parental pain catastrophizing with parents reports of children�s anxiety, depression, and headache severity

Objective Parental pain catastrophizing is a construct recognized to have a significant impact on experience of pain in both children and parents. This research aimed to investigate the probable relationship of parental pain catastrophizing with the parent�s reports of children�s anxiety, depression and headache severity amongst Iranian parents of children with chronic or recurrent headache. Materials & Methods This study was conducted in 2015-16, in two pediatric neurological centers located in Tehran, Iran; with a convenience sampling method and 212 parents (120 mothers and 92 fathers) of 132 children with a chronic or recurrent headache (migraine and tension-type). They completed the Pain Catastrophizing Scale; Numeric Pain Rating Scale, asking for the average of pain severity in last three months before the research, and the Anxiety and Depression subscales of the Children Behavioral Check List. Results The mean age of parents was 35.41 yr (SD=5.58) and the mean age of children was 9.83 yr (SD=2.77). A total of 72 girls and 60 boys participated in this study with a mean pain severity for headache in last three months before the research of 4.99 (SD=2.63). Probable sex differences according to parental pain catastrophizing, pain severity, anxiety, and depression were assessed amongst parents. In the next step, the predictability of pain severity from parental pain catastrophizing was evaluated. Results indicated a significant relationship in maternal pain catastrophizing and estimates of pain intensity by mothers. Conclusion These findings represent the importance of parent�s especially mother�s cognitive factors affecting their reports of their children�s pain and related emotional disturbances. © 2018, Iranian Child Neurology Society. All rights reserved

Offspring of parents with chronic pain: A systematic review and meta-analysis of pain, health, psychological, and family outcomes

Offspring of parents with chronic pain may be at risk for poorer outcomes than offspring of healthy parents. The objective of this research was to provide a comprehensive mixed-methods systematic synthesis of all available research on outcomes in offspring of parents with chronic pain. A systematic search was conducted for published articles in English examining pain, health, psychological, or family outcomes in offspring of parents with chronic pain. Fifty-nine eligible articles were identified (31 population-based, 25 clinical, 3 qualitative), including offspring from birth to adulthood and parents with varying chronic pain diagnoses (eg, mixed pain samples, arthritis). Meta-analysis was used to synthesize the results from population-based and clinical studies, while meta-ethnography was used to synthesize the results of qualitative studies. Increased pain complaints were found in offspring of mothers and of fathers with chronic pain and when both parents had chronic pain. Newborns of mothers with chronic pain were more likely to have adverse birth outcomes, including low birthweight, preterm delivery, caesarian section, intensive care admission, and mortality. Offspring of parents with chronic pain had greater externalizing and internalizing problems and poorer social competence and family outcomes. No significant differences were found on teacher-reported externalizing problems. The meta-ethnography identified 6 key concepts (developing independence, developing compassion, learning about health and coping, missing out, emotional health, and struggles communicating with parents). Across study designs, offspring of parents with chronic pain had poorer outcomes than other offspring, although the meta-ethnography noted some constructive impact of having a parent with chronic pain. © 2015 International Association for the Study of Pain

Randomized clinical trial comparing percutaneous closure of patent foramen ovale (PFO) using the Amplatzer PFO Occluder with medical treatment in patients with cryptogenic embolism (PC-Trial): rationale and design

<p>Abstract</p> <p>Background</p> <p>Several studies have shown an association of cryptogenic stroke and embolism with patent foramen ovale (PFO), but the question how to prevent further events in such patients is unresolved. Options include antithrombotic treatment with warfarin or antiplatelet agents or surgical or endovascular closure of the PFO. The PC-Trial was set up to compare endovascular closure and best medical treatment for prevention of recurrent events.</p> <p>Methods</p> <p>The PC-Trial is a randomized clinical trial comparing the efficacy of percutaneous closure of the PFO using the Amplatzer PFO occluder with best medical treatment in patients with cryptogenic embolism, i.e. mostly cryptogenic stroke. Warfarin for 6 months followed by antiplatelet agents is recommended as medical treatment. Randomization is stratified according to patients age (<45 versus ≥45 years), presence of atrial septal aneurysm (ASA yes or no) and number of embolic events before randomization (one versus more than one event). Primary endpoints are death, nonfatal stroke and peripheral embolism.</p> <p>Discussion</p> <p>patients were randomized in 29 centers of Europe, Canada, and Australia. Randomization started February 2000. Enrollment of 414 patients was completed in February 2009. All patients will be followed-up longitudinally. Follow-up is maintained until the last enrolled patient is beyond 2.5 years of follow-up (expected in 2011).</p> <p>Trial Registration</p> <p>Trial listed in ClinicalTrials.gov as <a href="http://www.clinicaltrials.gov/ct2/show/NCT00166257">NCT00166257</a> and sponsored by AGA Medical, Plymouth, MN, USA</p

Valve replacement with the ATS open pivot bileaflet prostesis

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