Injection of a relativistic electron beam into a high intensity optical lattice

We present a numerical study of the injection and trapping process of a bunch of relativistic free electrons into a transverse high intensity optical lattice. We unravel different injection regimes depending on the characteristic length scale of the onset of the optical lattice , and explore how the characteristics of the electron beam and of the high intensity lattice affect the trapping rate. The average transverse kinetic energy , and the induced longitudinal energy broadening are studied. The analysis of the transverse phase space exhibits a complex behavior , leading to inhomogeneities that may affect the amplification dynamics of X-ray Free Electron Laser

X-ray scattering from warm dense iron

We have carried out X-ray scattering experiments on iron foil samples that have been compressed and heated using laser-driven shocks created with the VULCAN laser system at the Rutherford-Appleton Laboratory. This is the highest Z element studied in such experiments so far and the first time scattering from warm dense iron has been reported. Because of the importance of iron in telluric planets, the work is relevant to studies of warm dense matter in planetary interiors. We report scattering results as well as shock breakout results that, in conjunction with hydrodynamic simulations, suggest the target has been compressed to a molten state at several 100 GPa pressure. Initial comparison with modelling suggests more work is needed to understand the structure factor of warm dense iron

Crit Care Sci

We hypothesized that the use of mechanical insufflation-exsufflation can reduce the incidence of acute respiratory failure within the 48-hour post-extubation period in intensive care unit-acquired weakness patients. This was a prospective randomized controlled open-label trial. Patients diagnosed with intensive care unit-acquired weakness were consecutively enrolled based on a Medical Research Council score ≤ 48/60. The patients randomly received two daily sessions; in the control group, conventional chest physiotherapy was performed, while in the intervention group, chest physiotherapy was associated with mechanical insufflation-exsufflation. The incidence of acute respiratory failure within 48 hours of extubation was evaluated. Similarly, the reintubation rate, intensive care unit length of stay, mortality at 28 days, and survival probability at 90 days were assessed. The study was stopped after futility results in the interim analysis. We included 122 consecutive patients (n = 61 per group). There was no significant difference in the incidence of acute respiratory failure between treatments (11.5% control group versus 16.4%, intervention group; p = 0.60), the need for reintubation (3.6% versus 10.7%; p = 0.27), mean length of stay (3 versus 4 days; p = 0.33), mortality at Day 28 (9.8% versus 15.0%; p = 0.42), or survival probability at Day 90 (21.3% versus 28.3%; p = 0.41). Mechanical insufflation-exsufflation combined with chest physiotherapy seems to have no impact in preventing postextubation acute respiratory failure in intensive care unit-acquired weakness patients. Similarly, mortality and survival probability were similar in both groups. Nevertheless, given the early termination of the trial, further clinical investigation is strongly recommended. NCT01931228

Electron-ion temperature relaxation in warm dense hydrogen observed with picosecond resolved X-Ray scattering

Angularly resolved X-ray scattering measurements from fs-laser heated hydrogen have been used to determine the equilibration of electron and ion temperatures in the warm dense matter regime. The relaxation of rapidly heated cryogenic hydrogen is visualized using 5.5 keV X-ray pulses from the Linac Coherent Light (LCLS) source in a 1 Hz repetition rate pump-probe setting. We demonstrate that the electron-ion energy transfer is faster than quasi-classical Landau-Spitzer models that use ad hoc cutoffs in the Coulomb logarithm

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

Contains fulltext : 172380.pdf (publisher's version ) (Open Access

La diffusion Thomson X comme diagnostic pour les plasmas denses et tièdes. : Expériences et modélisation

X ray Thomson Scattering : a diagnostic for warm dense matter.Les plasmas denses et tièdes (WMD, pour warm dense matter) sont définis par la zone qui, dans le diagramme densité-température, se situe entre les solides et les plasmas. C’est une région thermodynamique où la physique est difficile à décrire en raison des fortes interactions entre les particules et des couplages complexes qui relient entre elles les structures ioniques et électroniques. Pour ces plasmas, typiques de l’intérieur des planètes joviennes, des étoiles denses et des implosions obtenues par confinement inertiel, la validité des théories standard de la matière condensée et/ou de la physique statistique des plasmas est discutable. En l’absence de données expérimentales de référence, les différents paramètres nécessaires au calcul des propriétés de ces plasmas sont essentiellement déterminés par la théorie. La validation des modèles théoriques est donc indispensable. Elle passe par la comparaison entre les résultats des calculs théoriques et des données expérimentales de référence.La diffusion Thomson X (DTX) est une extension dans le domaine X du diagnostique plasma optique classique correspondant. Les espoirs sont grands d’utiliser les spectres DTX pour mesurer les paramètres thermodynamiques et structurels des plasmas WDM, afin de disposer d’un diagnostique puissant et polyvalent pour les études sur la fusion par confinement inertiel et l’astrophysique de laboratoire.Au cours de la thèse, différentes expériences en collaboration ont été réalisées sur de grandes installations laser (LULI, France ; RAL, UK ; Titan, US). Des spectres DTX ont étés obtenus et des diagnostics plasma permettant de mesurer les paramètres plasma de façon indépendante ont été mis en œuvre.Par ailleurs un travail numérique a été réalisé au CEA et un code permettant de simuler les spectres de diffusion Thomson X à partir des modèles classiques. Le code a été écrit afin de pouvoir être interfacé facilement avec les données provenant de modèles plus puissants développés par ailleurs au CEA : codes d’atome moyen SCAALP ou code de dynamique moléculaire quantique abinit. Ce travail à mis en évidence le fait que les barres sur les spectres résolus en angle permettent d’éliminer les modèles linéaires dans lesquels les corrélations ne sont pas prises en compte, clairement en dehors de leur domaine de validité dans le cas des plasmas WDM.Cependant l’analyse de l’influence du choix du modèle de matière choisi pour évaluer les corrélations ioniques et l’écrantage électronique sur l’analyse des spectres résolus en énergie met en avant le fait que les paramètres plasmas extraits dépendent encore largement du modèle choisi.Il reste aujourd’hui un effort expérimental à fournir. Des nouvelles avancées à la fois dans le domaine de la connaissance des plasmas WDM et du développement du diagnostique DTX ne pourront être obtenus qu’en améliorant les sources X utilisées, l’homogénéité du plasma sondé ainsi que sa caractérisation

Geant4 physics list comparison for the simulation of phase-contrast mammography (XPulse project)

International audienceBreast cancer is the most frequent cancer in women. Early and accurate detection of the disease is a major factor in patient survival. To this end, phase-contrast imaging has gained significant interest in recent years. The aim of this work was to validate the physics models of a Geant4 mammography imaging simulation (in the context of the XPulse project) by comparing to EGSnrc results

A stereotaxic atlas and technique for nuclei of the diencephalon of rainbow trout (Salmo gairdneri)

International audienceA stereotaxic apparatus and technique for electrode placement in diencephalic nuclei of sexually immature rainbow trout of 120-140 g body weight is described. An atlas of nuclei in the diencephalon is also presented

Injection of a relativistic electron beam into a high intensity optical lattice

We present a numerical study of the injection and trapping process of a bunch of relativistic free electrons into a transverse high intensity optical lattice. We unravel different injection regimes depending on the characteristic length scale of the onset of the optical lattice , and explore how the characteristics of the electron beam and of the high intensity lattice affect the trapping rate. The average transverse kinetic energy , and the induced longitudinal energy broadening are studied. The analysis of the transverse phase space exhibits a complex behavior , leading to inhomogeneities that may affect the amplification dynamics of X-ray Free Electron Laser .Vers un Laser Ultra-Compact à Electrons Libres dans le domaine