Mesure dans le 19^{19}Ne des résonances d’intérêt pour l’´étude des novæ par une nouvelle méthode de diffusion inélastique

Expérience GANILA nova is a thermonuclear runaway occurring in binary system of stars. The observation of the gamma rays emitted after anova is a way to better understand this phenomenon. According to the models, the line at 511 keV, produced in the annihilationbetween positrons and electrons, would be the most intense line several hours after the explosion. One of the main positron emitterswould be the $^{18}$F radioactive isotope. In order to improve the predictive power of the models, it is crucial to better determine theamount of $^{18}$F produced in the nova. Yet, the $^{18}$F destruction rate $^{18}$F(p,$\alpha$)$^{15}$O is given with large uncertainties. Measuring thespectroscopic properties (energy, width, spin) of states in the compound nucleus 19Ne should allow us to constrain the reaction rate.In this context, an experiment based on a new inelastic scattering method ($^{19}$Ne(p,p’)$^{19}$Ne∗) was performed at GANIL with theVAMOS spectrometer. The detection system has been adapted to detect for the first time high energy protons (p’). A good energyresolution in inverse kinematic has been reached ($\sigma$=33 keV). The angular distribution measurement of decaying particles shouldprovide the spin assignment of the states in a model independent way. Unfortunately, an unforeseen contamination has preventedus to complete this measurement. New spectroscopic information have been extracted and contributed to reduce the uncertaintyof the $^{18}$F(p,$\alpha$)$^{15}$O reaction rate in a significant way. The data are compatible with a new broad state below the proton threshold(6.41 MeV). This state seems to be sufficiently broad to contribute to the destruction reaction rate of $^{18}$F and reduces the chancesfor satellite detection.Une des clefs de la compréhension des novæ, (explosions thermonucleéaires intervenant dans les systèmes binaires d’étoiles) estl’observation des rayonnements gamma émis après l’explosion. Selon les modèles, la raie $\gamma$ à 511 keV, produite par l’annihilationdes positrons et des électrons, serait la plus intense plusieurs heures après l’explosion. Un des émetteurs principaux de positronsserait l’isotope radioactif $\beta$+ de $^{18}$F. L’amélioration du pouvoir prédictif des modèles passe par une meilleure connaissance de laquantité de $^{18}$F produite dans la nova. Or, le taux de destruction du $^{18}$F par la réaction $^{18}$F(p,$\alpha$)$^{15}$O est entaché d’incertitudes. Il est possible de contraindre ce dernier via l’étude des propriétés spectroscopiques (énergie, largeurs, spin) des états du noyaucomposé : le $^{19}$Ne. Dans ce contexte une expérience basée sur une nouvelle méthode de diffusion inélastique ($^{19}$Ne(p,p’)$^{19}$Ne∗) aété entreprise à GANIL auprès du spectromètre VAMOS. Un travail de reconfiguration a du être réalisé pour assurer une détectioninédite des protons (p’) issus de la diffusion inélastique avec ce spectromètre. Une très bonne résolution en énergie d’excitationpour une expérience en cinématique inverse (jusqu’à $\sigma$=33 keV) est atteinte. La mesure des distributions angulaires des particulesde décroissance devait fournir d’une manière indépendante des modèles le spin des états. Une contamination non attendue empêchecette mesure. De nouvelles informations spectroscopiques ont été collectées et tendent à améliorer les incertitudes associées au tauxde la réaction $^{18}$F(p,$\alpha$)$^{15}$O. Les données sont compatibles avec la présence d’un nouvel état large en dessous du seuil d’émissionproton (6.41 MeV). Cet état semble avoir une largeur suffisante (230 keV) pour contribuer significativement au taux de réaction dedestruction du $^{18}$F, amoindrissant les perspectives de détection par les satellites

Up and down the number line: modelling collaboration in contrasting school and home environments

This paper is concerned with user modelling issues such as adaptive educational environments, adaptive information retrieval, and support for collaboration. The HomeWork project is examining the use of learner modelling strategies within both school and home environments for young children aged 5 – 7 years. The learning experience within the home context can vary considerably from school especially for very young learners, and this project focuses on the use of modelling which can take into account the informality and potentially contrasting learning styles experienced within the home and school

A methodology for the capture and analysis of hybrid data: a case study of program debugging

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Inclined plate settling for emergency water treatment: towards optimisation

Previous work revealed the potential of an inclined plate settler (IPS) for water treatment in emergency relief applications. Whilst preliminary data demonstrated the tested IPS prototype’s capacity to achieve stable turbidity reductions, further optimisation was warranted. This paper reports on the optimisation and preliminary field testing of an IPS prototype. Trials revealed that after system modification, treatment objectives with regards to turbidity reductions (i.e. < 5 NTU) could be achieved. Such positive results were largely due to the addition of a hydraulic flocculation (conditioning) stage

Comparison of established and emerging biodosimetry assays

Rapid biodosimetry tools are required to assist with triage in the case of a large-scale radiation incident. Here, we aimed to determine the dose-assessment accuracy of the well-established dicentric chromosome assay (DCA) and cytokinesis-block micronucleus assay (CBMN) in comparison to the emerging &gamma;-H2AX foci and gene expression assays for triage mode biodosimetry and radiation injury assessment. Coded blood samples exposed to 10 X-ray doses (240 kVp, 1 Gy/min) of up to 6.4 Gy were sent to participants for dose estimation. Report times were documented for each laboratory and assay. The mean absolute difference (MAD) of estimated doses relative to the true doses was calculated. We also merged doses into binary dose categories of clinical relevance and examined accuracy, sensitivity and specificity of the assays. Dose estimates were reported by the first laboratories within 0.3-0.4 days of receipt of samples for the &gamma;-H2AX and gene expression assays compared to 2.4 and 4 days for the DCA and CBMN assays, respectively. Irrespective of the assay we found a 2.5-4-fold variation of interlaboratory accuracy per assay and lowest MAD values for the DCA assay (0.16 Gy) followed by CBMN (0.34 Gy), gene expression (0.34 Gy) and &gamma;-H2AX (0.45 Gy) foci assay. Binary categories of dose estimates could be discriminated with equal efficiency for all assays, but at doses &ge;1.5 Gy a 10% decrease in efficiency was observed for the foci assay, which was still comparable to the CBMN assay. In conclusion, the DCA has been confirmed as the gold standard biodosimetry method, but in situations where speed and throughput are more important than ultimate accuracy, the emerging rapid molecular assays have the potential to become useful triage tools

Measurement of the scintillation time spectra and pulse-shape discrimination of low-energy beta and nuclear recoils in liquid argon with DEAP-1

The DEAP-1 low-background liquid argon detector was used to measure scintillation pulse shapes of electron and nuclear recoil events and to demonstrate the feasibility of pulse-shape discrimination (PSD) down to an electron-equivalent energy of 20 keV. In the surface dataset using a triple-coincidence tag we found the fraction of beta events that are misidentified as nuclear recoils to be $<1.4\times 10^{-7}$ (90% C.L.) for energies between 43-86 keVee and for a nuclear recoil acceptance of at least 90%, with 4% systematic uncertainty on the absolute energy scale. The discrimination measurement on surface was limited by nuclear recoils induced by cosmic-ray generated neutrons. This was improved by moving the detector to the SNOLAB underground laboratory, where the reduced background rate allowed the same measurement with only a double-coincidence tag. The combined data set contains $1.23\times10^8$ events. One of those, in the underground data set, is in the nuclear-recoil region of interest. Taking into account the expected background of 0.48 events coming from random pileup, the resulting upper limit on the electronic recoil contamination is $<2.7\times10^{-8}$ (90% C.L.) between 44-89 keVee and for a nuclear recoil acceptance of at least 90%, with 6% systematic uncertainty on the absolute energy scale. We developed a general mathematical framework to describe PSD parameter distributions and used it to build an analytical model of the distributions observed in DEAP-1. Using this model, we project a misidentification fraction of approx. $10^{-10}$ for an electron-equivalent energy threshold of 15 keV for a detector with 8 PE/keVee light yield. This reduction enables a search for spin-independent scattering of WIMPs from 1000 kg of liquid argon with a WIMP-nucleon cross-section sensitivity of $10^{-46}$ cm$^2$, assuming negligible contribution from nuclear recoil backgrounds.Comment: Accepted for publication in Astroparticle Physic

The Serine 814 of TRPC6 Is Phosphorylated under Unstimulated Conditions

TRPC are nonselective cation channels involved in calcium entry. Their regulation by phosphorylation has been shown to modulate their routing and activity. TRPC6 activity increases following phosphorylation by Fyn, and is inhibited by protein kinase G and protein kinase C. A previous study by our group showed that TRPC6 is phosphorylated under unstimulated conditions in a human embryonic kidney cells line (HEK293). To investigate the mechanism responsible for this phosphorylation, we used a MS/MS approach combined with metabolic labeling and showed that the serine at position 814 is phosphorylated in unstimulated cells. The mutation of Ser814 into Ala decreased basal phosphorylation but did not modify TRPC6 activity. Even though Ser814 is within a consensus site for casein kinase II (CK2), we showed that CK2 is not involved in the phosphorylation of TRPC6 and does not modify its activity. In summary, we identified a new basal phosphorylation site (Ser814) on TRPC6 and showed that CK2 is not responsible for the phosphorylation of this site

A Study of the Residual 39Ar Content in Argon from Underground Sources

The discovery of argon from underground sources with significantly less 39Ar than atmospheric argon was an important step in the development of direct-detection dark matter experiments using argon as the active target. We report on the design and operation of a low background detector with a single phase liquid argon target that was built to study the 39Ar content of the underground argon. Underground argon from the Kinder Morgan CO2 plant in Cortez, Colorado was determined to have less than 0.65% of the 39Ar activity in atmospheric argon.Comment: 21 pages, 10 figure

Differential regulation of lipopolysaccharide and Gram-positive bacteria induced cytokine and chemokine production in splenocytes by Gαi proteins

AbstractHeterotrimeric Gi proteins play a role in lipopolysaccharide (LPS) and Staphylococcus aureus (SA) activated signaling leading to inflammatory mediator production. We hypothesized that genetic deletion of Gi proteins would alter cytokine and chemokine production induced by LPS and SA. LPS- and heat killed SA-induced cytokine and chemokine production in splenocytes from wild type (WT), Gαi2 (−/−) or Gαi1/3 (−/−) mice were investigated. LPS- or SA-induced production of TNFα, IL-6, IFNγ, IL-12, IL-17, GM-CSF, MIP-1α, MCP-1, MIG and IP-10 were significantly increased (1.2 to 33 fold, p<0.05) in splenocytes harvested from Gαi2(−/−) mice compared with WT mice. The effect of Gαi protein depletion was remarkably isoform specific. In splenocytes from Gαi1/3 (−/−) mice relative to WT mice, SA-induced IL-6, IFNγ, GM-CSF, and IP-10 levels were decreased (59% to 86%, p<0.05), whereas other LPS- or SA-stimulated cytokines and chemokines were not different relative to WT mice. LPS- and SA-induced production of KC were unchanged in both groups of the genetic deficient mice. Splenocytes from both Gαi2 (−/−) and Gαi1/3 (−/−) mice did not exhibit changes in TLR2 and TLR4 expression. Also analysis of splenic cellular composition by flow cytometry demonstrated an increase in splenic macrophages and reduced CD4 T cells in both Gαi2 (−/−) and Gαi1/3 (−/−) mice relative to WT mice. The disparate response of splenocytes from the Gαi2 (−/−) relative to Gαi1/3 (−/−) mice therefore cannot be attributed to major differences in spleen cellular composition. These data demonstrate that Gi2 and Gi1/3 proteins are both involved and differentially regulate splenocyte inflammatory cytokine and chemokine production in a highly Gi isoform specific manner in response to LPS and Gram-positive microbial stimuli