Analysis of the rod-drop experiments performed during the CABRI commissioning tests

International audienceCABRI is an experimental pulse reactor operated by the CEA at the Cadarache research center. After its refurbishment, it is now able to provide experiments in prototypical PWR conditions (155 bar, 300DC). Before operating, commissioning tests were performed, including control rod worth measurements. These experi-ments are done thanks to the rod-drop technique, which gathers static and dynamic effects. This paper reminds the theoretical background of the rod drop analysis. Then it gives a rigorous definition for the MSM factors (i.e. spatial correction factors to take into account the modification of the detector efficiency). An uncertainty analysis is performed and results prove the validity of the proposed model. Finally, the conclusion focuses on some possible improvements, like a rigorous importance calculation using the stochastic code TRIPOLI-4 and the use of different nuclear data libraries

Characterisation of adipocyte-derived extracellular vesicle subtypes identifies distinct protein and lipid signatures for large and small extracellular vesicles

Extracellular vesicles (EVs) are biological vectors that can modulate the metabolism of target cells by conveying signalling proteins and genomic material. The level of EVs in plasma is significantly increased in cardiometabolic diseases associated with obesity, suggesting their possible participation in the development of metabolic dysfunction. With regard to the poor definition of adipocyte-derived EVs, the purpose of this study was to characterise both qualitatively and quantitatively EVs subpopulations secreted by fat cells. Adipocyte-derived EVs were isolated by differential centrifugation of conditioned media collected from 3T3-L1 adipocytes cultured for 24 h in serum-free conditions. Based on morphological and biochemical properties, as well as quantification of secreted EVs, we distinguished two subpopulations of adipocyte-derived EVs, namely small extracellular vesicles (sEVs) and large extracellular vesicles (lEVs). Proteomic analyses revealed that lEVs and sEVs exhibit specific protein signatures, allowing us not only to define novel markers of each population, but also to predict their biological functions. Despite similar phospholipid patterns, the comparative lipidomic analysis performed on these EV subclasses revealed a specific cholesterol enrichment of the sEV population, whereas lEVs were characterised by high amounts of externalised phosphatidylserine. Enhanced secretion of lEVs and sEVs is achievable following exposure to different biological stimuli related to the chronic low-grade inflammation state associated with obesity. Finally, we demonstrate the ability of primary murine adipocytes to secrete sEVs and lEVs, which display physical and biological characteristics similar to those described for 3T3-L1. Our study provides additional information and elements to define EV subtypes based on the characterisation of adipocyte-derived EV populations. It also underscores the need to distinguish EV subpopulations, through a combination of multiple approaches and markers, since their specific composition may cause distinct metabolic responses in recipient cells and tissues

Experimental Evolution of a Plant Pathogen into a Legume Symbiont

Following acquisition of a rhizobial symbiotic plasmid, adaptive mutations in the virulence pathway allowed pathogenic Ralstonia solanacearum to evolve into a legume symbiont under plant selection

Small sample reactivity worths calculation exact perturbation theory and Monte Carlo transport

International audienceThe goal of this work is to calculate with a decent precision and accuracy the effect induced by the oscillation-or the substitution-of a pure sample of material at the center of a critical nuclear reactor core. The difference between the calculated and measured reactivity worth might hopefully be used to feedback nuclear data. Frequently, Monte Carlo transport codes fail in that task due to their inefficiency to reach convergence on such small reactivity differences (e.g. measured effects are sometimes lower than 1 pcm). Various deterministic and stochastic approaches have been used in the past, but they failed to provide unquestionable results for all isotopes. In this paper, we present a new methodology that allows exact calculation (i.e. not limited to first order) of these effects using Monte Carlo Neutron Transport codes. This method has several advantages: (1) It does not require significant code developments and it can be applied with almost any standard Monte Carlo codes. (2) It does not relied on any assumptions other than standard assumptions made by these codes: thus, it can be used to calculate any kinds of perturbation (e.g. concentration, geometry, medium, cross-sections) with a variable degree of effectiveness; still, it converges to the true value obtained from the difference of two independent runs. (3) In contrary of direct Monte Carlo perturbation technics, the more perturbations are small and locally contained, the more it performs. Validation cases confirm the numerical good behavior of the method named Black Body Exact Perturbation

Symbioses bacteries-legumineuses: un dialogue moleculaire

National audienc

Development and validation of sensitivity and uncertainty calculations using the 3D neutron transport code CRONOS2 at an industrial scale

International audienceEvaluating uncertainties on reactivity is a major issue for conception of nuclear reactors. These uncertainties mainly come from the lack of knowledge on nuclear and technological data. The common method for the propagation of the nuclear data uncertainties consists in using the Standard Perturbation Theory to calculate reactivity sensitivity to the desire nuclear data. In such a method, sensitivities are combined with a priori nuclear data covariance matrices, such as the COMAC set developed by CEA. In this study, COMAC nuclear data uncertainties have been propagated on the BEAVRS benchmark using a classical two-step APOLLO2/CRONOS2 scheme. A procedure implementing Standard Perturbation Theory has been created using the 3D neutron transport code CRONOS2 in order to allow a full-core uncertainty propagation with 4 groups industrial scheme. CRONOS2 sensitivities are compared to sensitivities calculated by the IFP method in Monte Carlo codes. For the purpose of the tests, dedicated covariance matrices have been created by condensation from 49 to 4 groups of the COMAC matrix. In conclusion, RONOS2 sensitivities are greed with the sensitivities calculated by the IFP method, which validates the calculation procedure. In addition, reactivity uncertainty calculated by this method is close to values found for this type of reactor. Finally, the calculation method allows computing ensitivities quickly with a good accurate

Etude de l’endoparasitisme expérimental de

Les auteurs étudient, à l’aide de techniques histochimiques, les modifications engendrées par le parasitisme au niveau des constituants glucidiques, protidiques et lipidiques des cellules hépatiques et pancréatiques.On note, au niveau du foie et du pancréas, une réaction inflammatoire typique : infiltration histiocytaire ou leucocytaire et présence de substance fibrinoïde de nature glycoprotéique complexe.On constate dans le foie parasité une déplétion importante du glycogène, même au niveau de territoires non immédiatement au contact des parasites. Ceux-ci se comportent comme une véritable « pompe » à glycogène dont l’effet se fait sentir à distance.A noter également la richesse du parasite en lipides complexes