Ten reasons for performing hemodynamic monitoring using transesophageal echocardiography.

International audienc

Interactions argilite de Tournemire/fer métal en contexte in situ (résultats à 10 ans de contact)

Dans le cadre du concept de stockage de déchets radioactifs à vie longue en couche géologique profonde développé par l'Andra, l IRSN mène une étude in situ sur la Station Expérimentale de Tournemire, en collaboration avec EDF afin de déterminer les interactions acier/argilite dans un contexte naturel. Au terme de 10 ans d interaction, deux forages ont été sur-carottés afin de caractériser les transformations de l argilite de Tournemire au contact d aciers carbone et inoxydables et de comparer les phénomènes réactifs mis en évidence et ceux induits par des simulations numériques par des codes de calcul géochimique et couplant chimie-transport.Les échantillons argilite/acier carbone montrent une importante corrosion du disque d acier. Le fer libéré sous la forme d auréoles et dans les fissures de la roche perturbe l argilite au contact entraînant des modifications minéralogiques et structurales. La précipitation d oxydes de fer ainsi qu une dissolution de la calcite et des feuillets smectitiques des interstratifiés I/S sont identifiés. Une zonation métal/métal corrodé/argilite perturbée/argilite saine est mise en évidence et des variations de porosité sont observées marquant les interfaces entre deux zones. Les simulations géochimiques montrent que l essentiel des modifications est rapidement initié lors de la mise en place du système et que l oxygène piégé à la fermeture du système est consommé par la corrosion des aciers mais surtout qu il diffuse dans le matériau encaissant par gradient de concentration.Les échantillons argilite/acier inoxydable présentent une très faible corrosion par piqûration de l acier. La minéralogie de l argilite ne semble pas perturbée au contWithin the framework of a long lived radioactive waste storage concept in deep geological layer developed by Andra, IRSN leads an in situ study on the Experimental Station of Tournemire, in association with EDF to determine the interactions steel/argillite in a natural context. After 10 years of interaction, two drillings overcoring performed to characterize the processings of the Tournemire argillite in contact with carbon and stainless steels and to compare reactive phenomena highlighted and those induced by simulations tools combining chemistry and transport.Argillite/carbon steel samples show a significant corrosion of steel disk. Iron released, in the form of rings and cracks in the rock, disrupts the argillite in contact resulting in mineralogical and structural changes. Iron oxides precipitation and a calcite and smectitic leaf of mixed-layers I/S dissolution are identified. A succession of areas: metal/metal corroded/argillite disturbed/argillite is highlighted and porosity variations are observed on the interfaces between two areas. Geochemical simulations show that major changes are initiated speedly during establishment of the system and the oxygen trapped in the closed system is consumed by the corrosion of steel but mostly it diffuses into the surrounding material through concentration gradient.Argillite/stainless steel samples have a very low pitting corrosion of steel disk. This does not seem to affect the mineralogy of the argillite in contact.POITIERS-SCD-Bib. électronique (861949901) / SudocSudocFranceF

A selection of thermodynamic properties for zeolites: application to the cement/clay interactions

Deep disposal concepts are usually based on a multibarrier concept that may involve a physical contact between clayey and cementitious materials. In such context, zeolites are a group of important phases, which group most of the transition phases between cement and the clayey barrier since zeolites have been shown to form readily after the weathering of clays in a hyperalkaline environment [1]. Thermodynamic properties can be found in the literature for some of the zeolites of interest in deep disposal contexts. However, there is still a lack of consistency among the available thermodynamics datasets. A first task realized in the present work consists in a critical selection of the thermodynamic datasets published so far. The selection could be achieved with some confidence for a rather large list of minerals. Some questions and uncertainties still remain for phases like phillipsite, chabazite or gismondine. Cases from the previous critical selection indicate the role of kinetics in the precipitation of zeolites, which can help in moderating the phase relations indicated by thermodynamics and can be related to field observations or experimental results. In addition, the concept of rock acidity can applied with success in order to investigate the phase relations between cements, zeolites and clayey materials

Theory and Implementation of Complex-Valued Neural Networks

This work explains in detail the theory behind Complex-Valued Neural Network (CVNN), including Wirtinger calculus, complex backpropagation, and basic modules such as complex layers, complex activation functions, or complex weight initialization. We also show the impact of not adapting the weight initialization correctly to the complex domain. This work presents a strong focus on the implementation of such modules on Python using cvnn toolbox. We also perform simulations on real-valued data, casting to the complex domain by means of the Hilbert Transform, and verifying the potential interest of CVNN even for non-complex data.Comment: 42 pages, 18 figure

Thermodynamics of hydration of MX80-Na: an experimental study of the hydration energies

Hydration properties of swelling clay minerals may be very variable depending on the chemical composition of the clay, on the nature of the interlayer cations and on the interlayer charge (Berend et al., 1995; Vieillard et al., 2011). The Wyoming smectite has been largely studied, notably for assessing its hydration behavior as a function of the interlayer cations, in connection with its structural characteristics (Ferrage et al., 2005; Salles et al., 2007). In the present work, carried out as part of a collaborative Andra/BRGM/HydrASA research program for ThermoChimie project, we propose an original experimental study, based on adsorption and desorption isotherms performed on MX80 clay samples. The goal is to determine energetic contributions to the reactions of hydration, which have been revealed to be non-negligible with respect to the stability of the clay minerals (Gailhanou et al., submitted). In particular, the present work addresses the problems of the hysteresis loop between adsorption and desorption isotherms and of the irreversibility of hydration reactions. This is directly related to the application of classical thermodynamics to the hydration reactions of clay minerals. In a first stage, an experimental study is dedicated to better understand the origin of the hysteresis loop which is systematically observed for the adsorption-desorption isotherms at 25°C. The development of the hysteresis loop has been studied by considering several kinetically related parameters: stabilization periods, temperatures (from 25°C to 60°C) and hydration steps (Figure 1). No sensible change was observed in the hysteresis loop. Therefore, the amount of adsorbed water depends on the followed reaction pathway (adsorption or desorption). The variations in microstructures and in the distribution of hydration layers (0/1/2 water layers; Ferrage et al., 2005) as a function of relative humidity (RH) could provide a possible explanation for this phenomenon

Extending the prediction of the thermodynamic properties of clay minerals to the trapping of trace elements

The thermodynamic properties of clay minerals, which control the stability of these minerals in solution, are still a matter of debate in spite of recent advances (Gailhanou et al., submitted). This is especially the case for the minerals that may structurally include trace elements and potential radionuclides such like Ni, Cd, Co, Cr, Mn, Pb, ... The usual methods developed in order to predict thermodynamic properties are parameterised using a given set of minerals. For clay minerals, the latter are mainly composed by Si, Al, Fe and Mg, apart from the alkalis elements (Chermak and Rimstidt, 1989), which means that predictions are limited to minerals whose layers are composed by Si, Al, Fe and Mg. At the vicinity of H&ILW disposal cells, the possible interactions between clay rock or engineered barrier and waste degradation products can result in the appearance of clay minerals that may structurally include radionuclides within an irreversible trapping process. This work aims at proposing a method for predicting the thermodynamic properties of such minerals. Theoretical principle and selection of calibration phases Vieillard (1994) has developed a methodology of estimation based on the difference of electronegativity by considering three scales of values of the parameter HO=(Mz+clay) in the three sites of phyllosilicates. We have considered the work of Vieillard (1994) that originally applies to the estimate of H0f and extended it to the estimate of Cp(T), S0 and V. Some popular estimate methods (Chermak and Rimstidt, 1989) are based on the hypothesis that the thermodynamic property of a mineral can be obtained by combining the properties of its components. An improvement of this principle had consisted in decomposing minerals into their polyhedral components (Chermak and Rimstidt, 1989). Now, we can write the fictive solution equilibrium with a basic polyhedral component MxOy as: and assumming the entropy of this fictive reaction is zero, we can define a SO= parameter as: . The value for the oxide analog of the polyhedral unit is obtained by implementing S0 of the oxide in the S0(MxOy) term. We have also defined, from the same reasoning, similar parameters for heat capacity and volume of the basic polyhedral components: ; . Results and discussion On Figure 1, we have displayed, for entropy, the correlation obtained between calculated values of SO= for the polyhedral unit and for the oxide analog. A straight line and a second-order function are obtained, for the interlayer and octahedral cations, respectively, with a good correlation coefficient. Fig. 1 - Development of predictive capacity for entropy estimates The implementation of the derived semi-empirical, first or second order relations allows to estimate the thermodynamic properties of a clay mineral, MX80 (Na0.409K0.024Ca0.009(Si3.738Al0.262)(Al1.598Mg0.214Fe3+0.173Fe2+0.035)O10(OH)2) in the present case, loaded by 6 radionuclides and to compare the values with the results obtained by Gailhanou et al. (submitted).The results can be expressed in terms of the concentrations for the elements Ni, Cd, Co, Cr, Mn and Pb and in terms of energetic potential with respect to the measurements performed by Gailhanou et al. (submitted)

Reformar el imperio: el proceso de la toma de decisiones en la creación de las intendencias americanas (1765-1787)

The establishment of the intendencia system in the West Indies was a complex process. An analysis of the decision-making process enables us to highlight some of its major characteristics. We argue that decision-making was not only limited by royal approval, but involved strategic, tactical and operational aspects. The creation of intendencias was adapted to the local circumstances of the particular region of the West Indies. This flexibility also transformed the nature of intendencias, since those created by the Marquis of Esquilache did not have the same objectives as those created by José de Gálvez. On the whole, these new jurisdictions implied a new vision of Superior Gobierno.La implantación del sistema de intendencias en las Indias resultó ser un proceso complejo. Su análisis desde el punto de vista de la toma de decisiones nos permitió subrayar algunas de sus características. La toma de decisiones no se limitaba únicamente a la aprobación real, sino que era un proceso que tenía dimensiones estratégicas, tácticas y operativas. En cada territorio de las Indias el proceso se adaptó a las realidades locales. Esta flexibilidad también implicó transformaciones en la naturaleza de las intendencias. Las intendencias creadas por el marqués de Esquilache no tenían los mismos objetivos que las que fueron creadas por José de Gálvez. Estas nuevas jurisdicciones conllevaban una nueva visión del superior gobierno