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International audience; We report on a liquid xenon gravity assisted recovery method for nuclear medical imaging applications. The experimental setup consists of an elevated detector enclosed in a cryostat connected to a storage tank called ReStoX. Both elements are part of XEMIS2 (XEnon Medical Imaging System): an innovative medical imaging facility for pre-clinical research that uses pure liquid xenon as detection medium. Tests based on liquid xenon transfer from the detector to ReStoX have been successfully performed showing that an unprecedented mass flow rate close to 1 ton per hour can be reached. This promising achievement as well as future areas of improvement will be discussed in this paper.

Electrochemical studies on plutonium have been supporting the development of pyrochemical processes involving plutonium at CEA. The electrochemical properties of plutonium have been studied in molten salts – ternary eutectic mixture NaCl–KCl–BaCl 2 , equimolar mixture NaCl–KCl and pure CaCl 2 – and in liquid gallium at 1073 K. The formal, or apparent, standard potential of Pu(III)/Pu redox couple in eutectic mixture of NaCl–KCl–BaCl 2 at 1073 K determined by potentiometry is equal to −2.56 V (versus Cl 2 , 1 atm/Cl − reference electrode). In NaCl–KCl eutectic mixture and in pure CaCl 2 the formal standard potentials deduced from cyclic voltammetry are respectively −2.54 V and −2.51 V. These potentials led to the calculation of the activity coefficients of Pu(III) in the molten salts. Chronoamperometry on plutonium in liquid gallium using molten chlorides – CaCl 2 and equimolar NaCl/KCl – led to the determination of the activity coefficient of Pu in liquid Ga, log γ = −7.3. This new data is a key parameter to assess the thermodynamic feasibility of a process using gallium as solvent metal. By comparing gallium with other solvent metals – cadmium, bismuth, aluminum – gallium appears to be, with aluminum, more favorable for the selectivity of the separation at 1073 K of plutonium from cerium. In fact, compared with a solid tungsten electrode, none of these solvent liquid metals is a real asset for the selectivity of the separation. The role of a solvent liquid metal is mainly to trap the elements.

This paper presents an innovative device for monolayer preparation that takes full advantage of the dynamic thin laminar flow method (DTLF). The small cylinder system provided the opportunity to prepare monolayers continuously and transfer them onto a solid substrate while moving. Hydrophilic and hydrophobic surfaces were coated with fine polystyrene particles. Multilayers were also made by simply moving the mobile DTLF device back and forth over the same surface. Technically, this was achieved by controlling the cylinder rotation and translation speeds above the substrate with a set of electrical motors. The injection of various suspensions into the thin liquid film was performed with syringes to make the fluids emerge near the rotating glass surface. The whole assembly was mounted on a mobile platform. Three fine latex particles were selected to make the primary tests of the new DTLF device. In all cases mono- and multilayers were obtained. This device opens a new avenue for the deposition of monolayer ...

The use of listeriaphages as a means of disinfecting contaminated stainless-steel and polypropylene surfaces was investigated. Surfaces artificially contaminated with L. monocytogenes 10401 and 8427 were sanitized with suspensions of listeriaphages (H387, H387-A, and 2671), all belonging to the Siphoviridae family. Phage suspensions at concentrations of up to 3.5 x 10(8) PFU/ml were at least as efficient as a 20 ppm solution of a quaternary ammonium compound (QUATAL) in reducing L. monocytogenes populations. A synergistic activity was observed when two or more phages were used in combination and when phages were suspended in QUATAL. The biological activity of the three phages was not affected by QUATAL concentrations of 50 ppm and a contact time of 4 h.

The molten salt reactor is one of the six concepts retained by the Generation IV forum in 2001. Based on the MSRE and MSBR concepts developed by ORNL in the 60s which involve a liquid fuel constituted of fluorine molten salt at a temperature close to 600 8C, new developments with innovative approach and technology have been realized which contribute to strongly improve the concept. The thorium breeder potentiality is closely related to the use of a liquid fuel which is able to be periodically treated. A reprocessing scheme has been established to treat used fuel by extraction of fission products. According to the Gen IV philosophy for closed cycle nuclear reactor, the actinides are sent back in the reactor core. In this way, the wastes radiotoxicity is strongly decreased and the use of natural resource is optimized. This paper describes an innovative reactor concept, the TMSR-NM (non-moderated thorium molten salt reactor), from the nuclear physic point of view and the different steps involving in the reprocessing scheme from the chemical point of view.

Resume Les proprietes redox du magnesium (II) ont ete etudiees par potentiometrie et voltammetrie cyclique. Le potentiel normal du systeme electrochimique Mg(s)/Mg(II) et le coefficient de diffusion du magnesium (II) ont ete determines (leurs valeurs respectives sont: E 0 (Mg(s)/Mg(II)) = −2,84± 0,01 V/(Cl 2 (1 atm)/Cl − ), D Mg(II) = (1,0±0,2) 10 −5 cm 2 s −1 ). Le produit de solubilite p K s de MgO a ete determine par simulation de la courbe de titrage des ions Mg 2+ par less ions O 2− (p K s = 6,2±0,1 dans l'echelle des molalities). Le coefficient d'activite de MgCl 2 , la solubilite de CaO et les pouvoirs chlorurants des melanges gazeux HCl/H 2 O et Cl 2 /O 2 ont ete egalement determines. Un diagramme d'equilibre E - p O 2t- est donne.

This paper is the first part of a global study on the oxidation process of a Fe–9Cr–1Mo martensitic steel (T91) in static liquid Pb–Bi. It focuses on the oxygen transport mode across the oxide scale. The oxide layer has a duplex structure composed of an internal Fe–Cr spinel layer and an external magnetite layer. Oxygen 18 tracer experiments are performed: they show that the magnetite layer grows at the Pb–Bi/ oxide interface whereas the Fe–Cr spinel layer grows at the metal/oxide interface. Oxygen seems to diffuse across the oxide scale dissolved inside nanometric lead penetrations called nano-channels. Specific experiments are performed to characterize the nano-channels.

During two-phase electrolysis for aluminium, fluorine or hydrogen production there are bubbles which are created at the electrode which imply a great hydrodynamic acceleration but also a quite important electrical field and electrochemical processes disturbance. This disturbance can lead to the modification of the local current density and to anode effects for example. There are also few local experimental measurements in term of chemical composition, temperature or current density because considered media are often very aggressive (high temperature, very strong reactivity). Then, the modelling and numerical simulation appears to be one important tool to understand and optimize associated processes, though the rigorous validation of numerical calculations is difficult. The goal of the present work is the modelling and the numerical simulation of the local gas production at an industrial scale vertical electrode. Because bubbles modify species, heat and electricity transport and are motion sources, there is a strong coupling between all these phenomena and between the bubble scale and the macroscopic one. Because bubbles are at the origin of all macroscopic disturbances, it appears necessary to investigate phenomenological laws at the bubble scale. The finite volume of the Fluidyn® and Fluent® software has been used.

During two-phase electrolysis for hydrogen, aluminium or fluor production, there are bubbles which are created at electrodes which imply a great hydrodynamic acceleration but also quite important electrical properties and electrochemical processes disturbance. There are few works concerning the local modelling of electrochemical processes during a two-phase electrolysis process. Nevertheless, effects like the anode effect, particularly expensive on the point of the process efficiency, should need a better understanding. The goal of the present work is to present the modelling and the numerical simulation of the gas production, from the single bubble scale to the macroscopic electrochemical cell, during the two-phase electrolysis process. Bubbles are motion sources for the electrolysis cell flow, and then hydrodynamic properties are strongly coupled with species transport and electrical performances. The presence of bubbles modifies these global and local properties: the electrolysis cell and the current density distribution are modified. The present work shows theoretical modelling on both scales and also performance changes during the two-phase electrolysis processes.

Recombinant horse L apoferritin was labeled with a fluorescent dye, 7-fluoro-4-sulfamoyl-2, 1, 3-benzoxadiazole (ABD-F) to monitor “intact” inter-molecular interactions in ferritin 2D assembly on a mercury surface by using protein engineering and chemical modifications.

X-ray diffraction, transmission electron microscopy examinations and selected area electron diffraction patterns were used to investigate the crystallographic parameters and morphologies of the starting Goethite and of the iron resulting from its electrochemical reduction, in a 50 % NaOH-H2 O mixture, at 363 K.It was shown that the iron crystallites exhibit essentially the same morphology and particle size as α-FeOOH. Furthermore, the metal crystals stay in a definite orientation in relation to the Goethite ones. This electrochemical process leads to a metal powder presenting a well-defined and reproducible texture.

Metallic magnesium is chemically corroded by the 2HF-KF mixture at 80{degrees}C, with the formation of a passivating microporous magnesium fluoride layer as revealed by electron scanning micrograph and cyclic voltammetry. A more compact layer can be obtained electrochemically. This paper reports on the corrosion mechanism studied by ac impedance measurements. The reaction pathway involves oxidation, desorption, diffusion, and presipitation steps. Kinetic parameters (charge and mass transfer) have been determined by a computerized simulation method.

The storage-life of bulk-stored cod under CO2 atmosphere and air were compared. Gutted fish or fillets were distributed in bulk, among coolers containing 100% air or 25% CO2-75% N2, which were then stored at 0 ± 1°C for 20 days. Sensory assessments and chemical tests (pH, total volatile nitrogen) were carried out to estimate the raw-state quality and the bacterial spoilage. An important difference was observed between the storage life of cod under carbon dioxide atmosphere and air; microbiological and sensory assessments suggested a storage life exceeding 20 days and total volatile nitrogen results about 6–7 days under gas atmosphere, which was nearly twice as long as in air. Storage in CO2 atmosphere was effective in inhibiting the growth of some bacteria on the fish, thereby contributing to the significant extension of the shelf life of the product.

Polarized absorption, photoacoustic, fluorescence excitation and fluorescence emission spectra of phycobilisomes were measured when embedded in polyvinyl alcohol films. The phycobilisomes were isolated from the following organisms: Anabaena cylindrica, Nostoc punctiforma and Synechococcus elongatus. The ratio of photoacoustic spectra to absorption was taken as a measure of thermal dissipation of excitation energy. The isotropic samples and those oriented by the film stretching were investigated. The stretching of the sample strongly influences the efficiency of excitation energy transfer occurring among biliproteins in phycobilisomes, as is seen from the dramatic changes in the fluorescence and thermal dissipation spectra. The effect of stretching the film depends on the shape of phycobilisomes and on the strength of interactions between biliproteins in phycobilisomes.

The study of the different oxides of iron (II) and iron (III) was carried out potentiometrically in LiCl-KCl eutectic at 470/sup 0/C by means of an yttria-stabilized zirconia electrode indicator of the oxide ion activity and an iron electrode indicator of the ferrous ion activity. These measurements were complemented by the determination of cyclic voltammograms and by x-ray diffraction and infrared spectrophotometrY analysis of certain compounds formed. The main results obtained are the following: strong oxidizing power (oxidation of Cl-/sup 1/ ions into Cl/sub 2/) and high oxoacidity (great stability of ferric oxide) of Fe/sup 3/ ions; possible redissolution of Fe/sub 2/O/sup 3/ in the oxide ion rich media by the formation of ferrate (III) ion; FeO/sub 2/-*Fe/sup 2 +/ ions react with O/sup 2/- ions to to form ferrous oxide, which is probably stabilized in the form of a solid solution FeO-LiFeO/sub 2/ of composition Fe/sub 1-y/Li/sub y/O. Magnetic oxide, Fe/sub 3/O/sub 4/, is stable and can be obtained by the action of oxide ions on a mixture of iron (II) and iron (III). This work is pertinent to the construction of rechargeable and high performance batteries. 34 refs.

The effect of the lipidic environment on the emission properties of chlorophyll a in mixed Langmuir-Blodgett films was studied. For a pigment:lipid molar ratio of 1:100, the fluorescence excitation and emission spectra have maxima at 438 nm and 678 nm respectively. Two lifetimes were necessary to fit the time-resolved fluorescence decay curves: 4.6 ns and 2.2 ns with respective contributions of 74% and 26%. The long component is attributed to the monomeric pigment and the short component to hydrated dimers or oligomers. Lecithins and galactolipids have identical effects on the emission properties of chlorophyll a, indicating that there is no specificity in the pigment-lipid interactions. However, some lipids are found to have the same effect as acids on the chlorophyll monoayers and, among them, some require careful purification in order to eliminate this acidic reaction. Those data suggest that the lipids of thylakoid membranes are good diluents and are not destructive to chlorophyll a.

A study was made of thin films of aluminum, cadmium, copper, gold, magnesium, and zinc using an RCA electron microscope capable of 30A resolving power. The films were formed by evaporation and condensation on collodion substrates in vacuum. An evaporating chamber was devised that permitted control of the temperature of the condensing surface. Photographs of the surfaces show that all the films are made of agglomerates of the metals separated by interstices of various widths. All evidence leads to the conclusion that the surface structure is explainable by assuming migration of the atoms over the surface. The observed structure can be used to explain the electrical conductivity, the optical reflectivity, and adsorptivity of thin films. Electron microscopic studies also provide a ready means of classifying surfaces according to the mobility of the atoms comprising them, and thus enable a rough estimate of the potential distribution over the surface to be made.

The RCA diffraction adapter for its electron microscopes uses a weak magnetic lens to focus the diffraction patterns. The accuracy of the results obtained in electron diffraction analysis with such a system is discussed, and it is shown that lattice spacings may be determined with an accuracy of one percent if reasonable precautions are observed in calibration and operation of the instrument. A method is also described for measuring the accelerating voltage of the electrons from data obtained from the diffraction pattern. Electron diffraction patterns are shown of a number of thin film materials which are commonly used as specimen supports in electron diffraction analyses and electron microscopy. The effects of aging and beam exposure on the patterns produced by these films are determined.

X-ray diffraction, transmission electron microscopy examinations and selected area electron diffraction patterns were used to investigate the crystallographic parameters and morphologies of the starting Goethite and of the iron resulting from its electrochemical reduction, in a 50 % NaOH-H2 O mixture, at 363 K.It was shown that the iron crystallites exhibit essentially the same morphology and particle size as α-FeOOH. Furthermore, the metal crystals stay in a definite orientation in relation to the Goethite ones. This electrochemical process leads to a metal powder presenting a well-defined and reproducible texture.

Copper nuclear quadrupole resonance (NQR) and zero field nuclear magnetic resonance (ZFNMR) studies of YBa$_2$Cu$_3$O$_{6.5}$ show that a magnetic phase appears in underdoped 123 superconductors treated in ambient wet air. The studies give convincing evidence that the ``empty'' CuO chains play the role of easy water insertion channels. The reaction occurs first in ordered regions of the crystallites. The final product of the reaction is a non-superconducting antiferromagnetic compound characterized by at least two types of magnetically ordered copper ions with ZFNMR spectra respectively in the frequency ranges of 46-96 and 96-135 MHz respectively. Even for powder samples fixed in an epoxy resin, the reaction is found to occur partly after a few years., 3 pages, 3 figures