POD preprocessing of IR thermal data to assess heat source distributions

International audienceInfrared thermography is a useful imaging technique for analyzing the thermomechanical behaviour of materials. It allows, under certain conditions, surface temperature monitoring and, via a diffusion model, estimation of heat sources induced by dissipative and/or thermally coupled deformation mechanisms. However, the noisy and discrete character of thermal data, the regularizing effect of heat diffusion and heat exchanges with the surroundings complicate the passage from temperature to heat source. The aim of this paper is to show that the prior use of reduced-basis projection of thermal data improves the signal-to-noise ratio before estimating the heat source distributions. The reduced basis is generated by proper orthogonal decomposition (POD) of physically-admissible thermal fields. These fields are solutions of ideal diffusion problems related to a set of putative heat sources. preprocessing is applied to different direct methods (finite differences, spectral solution, local least-squares fitting) already used in the past. The gain of this preprocessing is determined using a numerical penalizing benchmark test. The methods are finally compared using data extracted from a dynamic cyclic test on a pure copper specimen

The breadth of maternal HIV-1 specific neutralizing antibodies is not associated with a lower risk of mother-to-infant transmission

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214 Gene-specific effect of beta-adrenergic blockade on QT duration in the Long QT syndrome

BackgroundIn the long QT syndrome (LQTS) the clinical efficacy of beta-blocker treatment differs according to the genotype. We aimed to asses the effect of beta-blocker treatment in LQT1 and LQT2 patients.Patients and methods24-hour Holter ECG were recorded before and after beta-blocking therapy initiation in genotyped LQT1 (n=30, 8 males, mean age 21±17) and LQT2 patients (n=16, 8 males, mean age 19±15). QT duration was measured on consecutive 1-minute averaged QRS-T complexes leading to up to 1440 QT-RR pairs for each recording. Then, we computed subject- and condition-specific log/log QT/RR relationships which were used to calculate QT interval duration at RR=1000ms (QT1000=1000*).ResultsBefore treatment, coefficients were higher in LQT2 than in LQT1 patients (0.53±0.10 vs. 0.40±0.11, p<0.001) and QT1000 was longer in LQT2 than in LQT1 patients (521±38 vs. 481±39ms, p<0.01).Beta-blockers significantly prolonged the mean RR interval (RR = 827 ± 161 ms before treatment and 939±197ms on beta-blocker, p<0.0001). The coefficients were not significantly modified by beta-blockers (0.41±0.9 in LQT1 patients and 0.52±0.12 LQT2 patients). Beta-blocker treatment was associated with a prolongation of the QT1000 interval (from 481±39 to 498±43ms, p<0.01) in LQT1 patients but with a shortening in LQT2 patients (from 521±38 to 503±32ms, p<0.01).ConclusionsOur results confirm the elevated coefficient of the QT/RR relationship in LQTS patients. LQT2 patients showed higher coefficient and longer QT1000 when compared to LQT1 patients. The effect of beta-adrenergic blockade on QT1000 duration was gene-specific. Given the demonstrated efficacy of beta-blockers in LQT1 and 2 patients, our data suggest that QT1000 might be a poor predictor of outcome under anti-adrenergic therapy

206 The time course of new T-wave ECG descriptors following single and double dose administration of Sotalol in healthy subjects

IntroductionThe aim of the study was to assess the time course effect of IKr blockade on ECG biomarkers of ventricular repolarization and to evaluate the accuracy of a fully automatic approach for QT duration evaluation.Methods12-lead digital ECG Holter were recorded in 38 healthy subjects (27 males, mean age=27.4±8.0 years) on baseline conditions (day 0) and after administration of 160 mg (day 1) and 320 mg (day 2) of d-l Sotalol. For each 24-hour period and each subject, ECGs were extracted every 10 minutes during the 4-hour period following drug dosage. Ventricular repolarization was characterized using 3 biomarker categories: conventional ECG time intervals, Principal Component Analysis (PCA) analysis on the T-wave, and fully automatic biomarkers computed from a mathematical model of the T-wave.ResultsQT interval was significantly prolonged starting 1h20 minutes after drug dosing with 160 mg and 1h 10 minutes after drug dosing with 320 mg. PCA ventricular repolarization parameters sotalol-induced changes were delayed (>3 hours). After sotalol dosing, the early phase of the T-wave changed earlier than the late phase prolongation. Globally, the modeled surrogate QT paralleled manual QT changes.The duration of manual QT and automatic surrogate QT were strongly correlated (R2=0.92, p<0.001). The Bland & Altman plot revealed a non-stationary systematic bias (bias =26.5ms ±1.96*SD = 16ms).ConclusionsChanges in different ECG biomarkers of ventricular repolarization display different kinetics after administration of a potent potassium channel blocker. These differences need to be taken into account when designing ventricular repolarization ECG studies

Dissipation des métaux en fatigue gigacyclique

Ce travail vise à mesurer des distributions de dissipation induites par la fatigue gigacyclique de matériaux métalliques. L'exposé présentera le dispositif thermographique utilisé ainsi que des résultats récents obtenus sur un cuivre pur sollicité à 20kHz à différents niveaux de contrainte tous très inférieurs à la limite d'endurance. Ces distributions hétérogènes de dissipation seront ensuite reliées aux mécanismes progressifs d'endommagement de la matière et seront confrontés à des images micrographiques réalisées sur ces mêmes échantillons

Effets dissipatifs en fatigue : étude de l'influence de la fréquence de sollicitation

Ce travail vise à caractériser la nature des effets dissipatifs produits lors d’essais de fatigue dans les matériaux métalliques pour des niveaux de contrainte inférieurs à la limite macroscopique d’élasticité. L’exposé présente deux dispositifs de sollicitation en fatigue. Le matériau étudié est un cuivre pur. Le premier dispositif comprend une machine hydraulique traditionnelle fonctionnant à des fréquences de quelques dizaines de Hertz. Le second système exploite le phénomène de résonance et permet d’effectuer des essais dynamiques à une fréquence de 20 kHz. Dans les 2 cas, un dispositif thermographique est utilisé pour mesurer des champs de température à la surface de l’échantillon. L’exploitation des champs permet alors d’accéder aux sources de chaleur et plus particulièrement, à la dissipation intrinsèque. Une méthode de traitement d’image ainsi qu’une forme d’équation de diffusion de la chaleur, adaptée à chacune des situations, sont présentées. Les énergies dissipées par cycle, issues des deux types d’essais, sont finalement montrées. Ces premiers résultats mettent en évidence une quasi-indépendance de cette énergie en fonction de la fréquence, illustrant un comportement indépendant de la vitesse de déformation

Very high cycle fatigue for single phase ductile materials: Comparison between α-iron, copper and α-brass polycrystals

In this paper, the main results obtained in the framework of a National French Agency project called DISFAT, standing for “Dissipation in Fatigue”, are presented. The project was dedicated to the microplastic mechanisms leading to crack initiation in the case of ductile metals loaded in very high cycle fatigue. Fatigue tests were carried out at 20 kHz using an ultrasonic facility. In order to investigate the microplastic mechanisms, slip markings at the surface of the specimens were observed and the self-heating of the specimen during the tests was measured by thermography to deduce the dissipated energy. Polycrystalline copper, α-brass and α-iron were investigated. A good correlation was found between persistent slip bands and dissipated energy. The dissipated energy for the three materials was of the same order of magnitude but while α-iron reached a stable dissipative state, the dissipated energy in the case of copper and α-brass was found to continue to increase gradually with increasing numbers of cycles. That change in dissipated energy during cycling was consistent with the development of persistent slip bands. Both were discussed with regard to the materials

Gain-of-function human STAT1 mutations impair IL-17 immunity and underlie chronic mucocutaneous candidiasis

Chronic mucocutaneous candidiasis disease (CMCD) may be caused by autosomal dominant (AD) IL-17F deficiency or autosomal recessive (AR) IL-17RA deficiency. Here, using whole-exome sequencing, we identified heterozygous germline mutations in STAT1 in 47 patients from 20 kindreds with AD CMCD. Previously described heterozygous STAT1 mutant alleles are loss-of-function and cause AD predisposition to mycobacterial disease caused by impaired STAT1-dependent cellular responses to IFN-γ. Other loss-of-function STAT1 alleles cause AR predisposition to intracellular bacterial and viral diseases, caused by impaired STAT1-dependent responses to IFN-α/β, IFN-γ, IFN-λ, and IL-27. In contrast, the 12 AD CMCD-inducing STAT1 mutant alleles described here are gain-of-function and increase STAT1-dependent cellular responses to these cytokines, and to cytokines that predominantly activate STAT3, such as IL-6 and IL-21. All of these mutations affect the coiled-coil domain and impair the nuclear dephosphorylation of activated STAT1, accounting for their gain-of-function and dominance. Stronger cellular responses to the STAT1-dependent IL-17 inhibitors IFN-α/β, IFN-γ, and IL-27, and stronger STAT1 activation in response to the STAT3-dependent IL-17 inducers IL-6 and IL-21, hinder the development of T cells producing IL-17A, IL-17F, and IL-22. Gain-of-function STAT1 alleles therefore cause AD CMCD by impairing IL-17 immunity

Bone Marrow Transplant

Mucopolysaccharidosis type I-H (MPS I-H) is a rare lysosomal storage disorder caused by α-L-Iduronidase deficiency. Early haematopoietic stem cell transplantation (HSCT) is the sole available therapeutic option to preserve neurocognitive functions. We report long-term follow-up (median 9 years, interquartile range 8-16.5) for 51 MPS I-H patients who underwent HSCT between 1986 and 2018 in France. 4 patients died from complications of HSCT and one from disease progression. Complete chimerism and normal α-L-Iduronidase activity were obtained in 84% and 71% of patients respectively. No difference of outcomes was observed between bone marrow and cord blood stem cell sources. All patients acquired independent walking and 91% and 78% acquired intelligible language or reading and writing. Intelligence Quotient evaluation (n = 23) showed that 69% had IQ ≥ 70 at last follow-up. 58% of patients had normal or remedial schooling and 62% of the 13 adults had good socio-professional insertion. Skeletal dysplasia as well as vision and hearing impairments progressed despite HSCT, with significant disability. These results provide a long-term assessment of HSCT efficacy in MPS I-H and could be useful in the evaluation of novel promising treatments such as gene therapy

Dissipative effects in high and very high cycle fatigue

Cette étude présente une analyse mécanique et énergétique de la fatigue des matériaux métalliques à grand et très grand nombre de cycles. Des bilans d'énergie en fatigue sont réalisés à partir de techniques d'imagerie quantitatives. Les sources de chaleur sont déterminées à partir des champs de température mesurés par caméra infrarouge. Les champs cinématiques sont obtenus en utilisant une technique de corrélation d'image numérique et permettent d'estimer l'énergie de déformation mise en jeu. Un premier objectif est d'analyser la pertinence énergétique des concepts de limite de fatigue et d'état cyclique stabilisé. Un deuxième objectif est de comparer les champs de dissipation à l'échelle mésoscopique aux distributions de bandes de glissement. Enfin, la comparaison d'essais de fatigue conventionnelle (30-50 Hz) et ultrasonique (20 kHz) permet d'analyser les effets de la fréquence sur le comportement dissipatif du matériau.This work presents a mechanical and energy analysis of metallic materials during high and very high cycle fatigue tests. Energy balances are derived from quantitative imaging techniques. Heat sources are estimated from temperature fields measured by an infrared camera. Kinematic fields are obtained by using digital image correlation techniques and used to compute the deformation energy. A first aim is to analyse the energy relevance of the concepts of fatigue limit and stabilzed cyclic behavior. A second aim is to compare dissipation fields at mesoscale with the microstrural distribution of slip bands. Finally, conventional (30-50 Hz) and ultrasonic (20kHz) fatigue tests are used to analyse the frequency effect on the dissipative behavior of the material