Photon correlations in positron annihilation

The two-photon positron annihilation density matrix is found to separate into a diagonal center of energy factor implying maximally entangled momenta, and a relative factor describing decay. For unknown positron injection time, the distribution of the difference in photon arrival times is a double exponential at the para-Ps decay rate, consistent with experiment (V. D. Irby, Meas. Sci. Technol. 15, 1799 (2004)).Comment: Accepted for publication in Phys. Rev.

Biocompatible polymer-assisted dispersion of multi walled carbon nanotubes in water, application to the investigation of their ecotoxicity using Xenopus laevis amphibian larvae

Carbon nanotubes (CNTs) tend to readily agglomerate and settle down in water, while the adsorption of compounds present in natural aquatic media could enhance their dispersion and stabilization in the water column. We designed a new exposure protocol to compare the biological responses of Xenopus laevis larvae exposed in semi-static conditions to size-reduced agglomerates of multi-walled carbon nanotubes (MWCNTs) in suspension in the water column and/or to larger agglomerates. Suspensions were prepared using a combination of a non-covalent functionalization with a non-toxic polymer (either carboxymethylcellulose, CMC, or gum arabic, GA) and mechanical dispersion methods (mainly ultrasonication). The ingestion of agglomerates which have settled down was incriminated in the disruption of the intestinal transit and the assimilation of nutrients, leading to acute and chronic toxicities at the highest tested concentrations. Rise in mortality, decrease in the growth rate and induction of genotoxicity from low concentrations (1 mg/L in the presence of CMC) were evidenced in presence of suspended MWCNTs in the water column. The biological responses seemed to be modulated when GA, a potential antioxidant, was used. We hypothesized that MWCNTs should interfere mainly at the surface of the gills, acting as a potential respiratory toxicant and generally inducing indirect effects

Aire and Foxp3 expression in a particular microenvironment for T-cell differentiation

peer reviewe

Residual Doping in Homoepitaxial Zinc Oxide Layers Grown by Metal Organic Vapor Phase Epitaxy

International audienceFull maximum entropy mobility spectrum analysis was carried out on the basis of temperature and magneticfield- dependent Hall measurements to assess the transport properties of homoepitaxial metal organic vapor phase epitaxy zinc oxide layers. Two different conductivity channels were clearly identified and the channel with higher mobility and higher carrier concentration is associated with the epitaxial layer. Hydrogen impurity acting as residual donor and as a passivating species for acceptors is proposed to explain the higher carrier concentration and mobility in the epilayer. In contrast to heteroepitaxial layers, no conduction channel is observed from the substrate to epilayer interface

Toxicity of CeO2 nanoparticles on a freshwater experimental trophic chain: A study in environmentally relevant conditions through the use of mesocosms

The toxicity of CeO2 NPs on an experimental freshwater ecosystem was studied in mesocosm, with a focus being placed on the higher trophic level, i.e. the carnivorous amphibian species Pleurodeles waltl. The system comprised species at three trophic levels: (i) bacteria, fungi and diatoms, (ii) Chironomus riparius larvae as primary consumers and (iii) Pleurodeles larvae as secondary consumers. NP contamination consisted of repeated additions of CeO2 NPs over 4 weeks, to obtain a final concentration of 1 mg/L. NPs were found to settle and accumulate in the sediment. No effects were observed on litter decomposition or associated fungal biomass. Changes in bacterial communities were observed from the third week of NP contamination. Morphological changes in CeO2 NPs were observed at the end of the experiment. No toxicity was recorded in chironomids, despite substantial NP accumulation (265.8±14.1mg Ce/kg). Mortality (35.3±6.8%) and a mean Ce concentration of 13.5±3.9mg/kg were reported for Pleurodeles. Parallel experiments were performed on Pleurodeles to determine toxicity pathways: no toxicity was observed by direct or dietary exposures, although Ce concentrations almost reached 100 mg/kg. In view of these results, various toxicity mechanisms are proposed and discussed. The toxicity observed on Pleurodeles in mesocosm may be indirect, due to microorganism’s interaction with CeO2 NPs, or NP dissolution could have occurred in mesocosm due to the structural complexity of the biological environment, resulting in toxicity to Pleurodeles. This study strongly supports the importance of ecotoxicological assessment of NPs under environmentally relevant conditions, using complex biological systems

Cost-Effectiveness Of Treatments For Mild-To-Moderate Obstructive Sleep Apnea In France

International audienceObjectives: Untreated obstructive sleep apnea-hypopnea syndrome (OSAHS) is associated with excessive daytime sleepiness, increased risk of cardiovascular (CV) disease, and road traffic accidents (RTAs), which impact survival and health-related quality of life. This study, funded by the French National Authority for Health (HAS), aimed to assess the cost-effectiveness of different treatments (i.e., continuous positive airway pressure [CPAP], dental devices, lifestyle advice, and no treatment) in patients with mild-to-moderate OSAHS in France.Methods: A Markov model was developed to simulate the progression of two cohorts, stratified by CV risk, over a lifetime horizon. Daytime sleepiness and RTAs were taken into account for all patients while CV events were only considered for patients with high CV risk.Results: For patients with low CV risk, incremental cost-effectiveness ratio (ICER) of dental devices versus no treatment varied between 32,976 EUR (moderate OSAHS) and 45,579 EUR (mild OSAHS) per quality-adjusted life-year (QALY), and CPAP versus dental devices, above 256,000 EUR/QALY. For patients with high CV risk, CPAP was associated with a gain of 0.62 QALY compared with no treatment, resulting in an ICER of 10,128 EUR/QALY.Conclusion: The analysis suggests that it is efficient to treat all OSAHS patients with high CV risk with CPAP and that dental devices are more efficient than CPAP for mild-to-moderate OSAHS with low CV risk. However, out-of-pocket costs are currently much higher for dental devices than for CPAP (i.e., 3,326 EUR versus 2,430 EUR) as orthodontic treatment is mainly non-refundable in France

Le défi de l’intégration de l’approche par compétences lors de la sélection : conception d’un test de jugement situationnel ciblant le rôle CanMEDS de collaborateur pour la sélection au niveau postdoctoral en médecine

Introduction : L’approche par compétences est maintenant bien ancrée dans l’enseignement au niveau de la formation médicale postdoctorale. Dans ce contexte, un système de sélection également axé sur les compétences pourrait être avantageux. L’objectif principal de ce projet était de concevoir un TJS ciblant le rôle CanMEDS de collaborateur pour la sélection au niveau postdoctoral en médecine interne (MI) et en médecine familiale (MF). Méthodologie : Des entrevues d’incidents critiques ont été réalisées auprès de résidents juniors en MI ou en MF afin de générer les items du TJS. Trois leaders de l’approche par compétences ont révisé le contenu du test. Les items ont été analysés pour identifier la compétence principale du rôle CanMEDS de collaborateur, le contexte ainsi que les membres de l’équipe interprofessionnelle représentés dans les vignettes. La clé de correction a été déterminée par un panel composé de 11 experts. Cinq méthodes de notation ont été comparées. Résultats : Sept entrevues ont été réalisées. Après révision, 33 items ont été conservés dans le TJS. Les compétences clés du rôle CanMEDS de collaborateur, les contextes et les divers membres de l’équipe interprofessionnelle étaient bien distribués au travers des items. La moyenne des scores des experts variait entre 43,4 et 75,6 % en fonction des différentes méthodes de notation. Le coefficient de corrélation de Pearson entre les cinq méthodes de notation variait entre 0,80 et 0,98. Conclusion : Ce projet démontre la possibilité de concevoir un TJS utilisant le cadre CanMEDS comme trame de fond pour l’élaboration de son contenu. Ce test, couplé à une approche globale de sélection basée sur les compétences, pourrait éventuellement améliorer le pouvoir prédictif du processus de sélection au niveau de la formation médicale postdoctorale.Background: Competency-based training is well integrated into postgraduate medical education. A competency-based selection system would also be desirable. Primary objective: To develop a situational judgment test (SJT) targeting the CanMEDS Collaborator Role for the admission process in internal medicine (IM) and family medicine (FM) postgraduate training programs. Methods: Interviews using the critical incident technique were conducted with IM and FM residents in order to create items for the SJT. Three experts revised the content of the items. CanMEDS Collaborator Role key competencies, context and type of team members involved were analysed for each item. Answer key was determined by a panel of experts composed of 11 IM and FM physicians using a rate response format. Five absolute and partial credit scoring methods were compared. Results: Seven interviews were completed. After revision, 33 items were kept in the SJT. CanMEDS Collaborator Role key competencies, contexts and team members involved were well distributed over the items. Mean experts’ scores ranged from 43.4% to 75.6% with the different scoring methods. Pearson’s correlation coefficients between the five scoring methods ranged between 0.80-0.98. Conclusion: SJT targeting CanMEDS Framework Roles can help integrate competency-based selection into the postgraduate medical education admission process