Reversible expansion of gallium-stabilized delta-plutonium

The transient expansion of plutonium-gallium alloys observed both in the lattice parameter as well as in the dimension of a sample held at ambient temperature is explained by assuming incipient precipitation of Pu{sub 3}Ga. However, this ordered {zeta}{prime}-phase is also subject to radiation-induced disordering. As a result, the gallium-stabilized {delta}-phase, being metastable at ambient temperature, is both driven towards thermodynamic equilibrium by radiation-enhanced diffusion of gallium and at the same time pushed back to its metastable state by radiation-induced disordering. A steady state is reached in which only a modest fraction of the gallium present is tied up in the {zeta}{prime}-phase

Reversible expansion of gallium-stabilized (delta)-plutonium

It is shown that the transient expansion of plutonium-gallium alloys observed both in the lattice parameter as well as in the dimension of a sample held at ambient temperature can be explained by assuming incipient precipitation of Pu{sub 3}Ga. However, this ordered {zeta}-phase is also subject to radiation-induced disordering. As a result, the gallium-stabilized {delta}-phase, being metastable at ambient temperature, is driven towards thermodynamic equilibrium by radiation-enhanced diffusion of gallium and at the same time reverted back to its metastable state by radiation-induced disordering. A steady state is reached in which only a modest fraction of the gallium present is arranged in ordered {zeta}-phase regions

Nature of non-magnetic strongly-correlated state in delta-plutonium

Ab-initio relativistic dynamical mean-field theory is applied to resolve the long-standing controversy between theory and experiment in the "simple" face-centered cubic phase of plutonium called delta-Pu. In agreement with experiment, neither static nor dynamical magnetic moments are predicted. In addition, the quasiparticle density of states reproduces not only the peak close to the Fermi level, which explains the large coefficient of electronic specific heat, but also main 5f features observed in photoelectron spectroscopy.Comment: 9 pages, 3 figure

Évaluation de l’alimentation normale “confort” dans le pôle oncologie : application pratique

Les traitements par chimiothérapie entraînent chez les patients des modifications du goût. L’alimentation normale “confort” a pour but de pallier à ces difficultés afin de leur redonner l’envie de manger. Élaboré en étroite collaboration avec le service de restauration, le menu est adapté aux besoins des patients. Il est basé sur une structure particulière comportant des aliments froids, faciles à manger, à goût neutre, en petite quantité, avec un dîner “léger”. Un an après sa mise en place, une évaluation a été réalisée. Elle concernait : les commandes de repas, la formation des soignants et la satisfaction des patients. Bien que la formation des soignants soit satisfaisante, l’évolution des commandes de ce repas est faible (4 menus/jour). Cependant les patients évalués sont plutôt satisfaits : ils aiment les entrées, la viande froide, les produits laitiers et les fruits cuits proposés. Le dîner demeure encore un repas difficile à consommé malgré les modifications proposées. La présentation, la qualité et la variété des aliments les satisfont même si une amélioration doit être effectuée au niveau de la variété en général qui n’obtient qu’un 80 % de satisfaction. Seule la présentation de la viande froide doit être revue. En conclusion cette alimentation normale confort semble convenir dans 86 % des cas aux patients d’autant plus qu’ils ont choisi leur menu. Il faut que les services de restauration, de diététique et cliniques renforcent leur collaboration pour améliorer la qualité du soin nutritionnel et la qualité de vie de ces patients

Robust acoustic particle manipulation: a thin-reflector design for moving particles to a surface

Existing ultrasonic manipulation devices capable of pushing particles to a surface (“quarter-wave” devices) have significant potential in sensor applications. A configuration for achieving this that uses the first thickness resonance of a layered structure with both a thin reflector layer and thin-fluid layer is described here. Crucially, this mode is efficient with lossy reflector materials such as polymers, produces a more uniform acoustic radiation force at the reflector, and is less sensitive to geometric variations than previously described quarter-wave devices. This design is thus expected to be suitable for mass produced, disposable device

X ray diffraction investigation of Pu-Ce and Pu-Ce-Ga alloys stabilized in the delta-phase

International audienceIn the actinides series (progressive filling of the 5f-sub shell), Pu interlinks the light actinides withdelocalized 5f electrons, and the heavy actinides with localized Sf electrons. At this boundary, 8-Pu is a hightemperature allotrope with an intermediate Sf behaviour. It reaches stability at room temperature by alloying withdeltagen solutes like At, Ga, Am, Ce. X-Ray Diffraction showed that the Sf electrons of 5Pu tend to delocalize in thePu-Al and Pu-Ga alloys (Ga and Al atoms are smaller than 8-Pu atoms) whereas they tend to localize in the Pu-Amalloys (Am atoms are bigger than 8-Pu atoms). Ce atoms, also bigger than 8-Pu atoms, are expected to induce asimilar behaviour as Am atoms. However, in the Pu-Ce alloys, Ce atoms exhibit an aiiotropic transformation(y-Ce->a-Ce) caused by the lattice strains: a derealization of the 4f electrons of Ce involves a reduction of itsatomic volume and disturbs the investigation of the Sf electrons behaviour. In this work, some Pu-Ce and Pu-Ga-Cealloys were studied and showed a cooperative deltagen effect of Ga and Ce. This result, together with previousstudies in literature, indicates that the mechanism of the 8 phase stabilization by Ce and Am are not equivalent. Itseems mat the localization of the Sf electrons of Pu by Ce alloying is uncertain. Photoemision measurements areplanned in order to confirm this hypothesis

Mixed metal dielectric gratings for pulse compression applications

International audienc

High reflection mirrors for pulse compression gratings References and links

International audienceWe report an experimental investigation of high reflection mirrors used to fabricate gratings for pulse compression application at the wavelength of 1.053µm. Two kinds of mirrors are studied: the mixed Metal MultiLayer Dielectric (MMLD) mirrors which combine a gold metal layer with some e-beam evaporated dielectric bilayers on the top and the standard e-beam evaporated MultiLayer Dielectric (MLD) mirrors. Various samples were manufactured, damage tested at a pulse duration of 500fs. Damage sites were subsequently observed by means of Nomarski microscopy and white light interferometer microscopy. The comparison of the results evidences that if MMLD design can offer damage performances rather similar to MLD design, it also exhibits lower stresses; being thus an optimal mirror substrate for a pulse compression grating operating under vacuum

Investigations of efficient barrier layer on metal foils for flexible thin film solar cells

International audienc

Determination of single crystal elastic constants in textured polycrystalline materials: inverse approach coupling x-ray diffraction and self consistent model applied to a copper sample

La diffraction des rayons X couplée à l'utilisation d'un modèle polycristallin (modèle auto-cohérent) est utilisée pour déterminer les constantes d'élasticité monocristallines d'un matériau polycristallin texturé. En effet, la connaissance du tenseur de rigidité élastique cijkl d'un solide est fondamentale pour les études s'attachant à la compréhension des propriétés mécaniques de la matière (approches théoriques ou expérimentales). Si, d'autres techniques permettent de déterminer le tenseur d'élasticité d'un matériau (ultrasons par exemple), elles nécessitent souvent l'utilisation d'un monocristal. Ceci n'est pas toujours réalisable, en particulier pour des alliages de concentrations variables. La diffraction des rayons X se révèle alors une alternative intéressante pour l'étude de matériaux polycristallins