Caractérisation des sédiments des retenues pour la prévision des risques écotoxicologiques liés aux vidanges

L'acumulation de sédiments dans les retenues de barrages hydro-électriques nécessite de procéder à des opérations régulières de désenvasement indispensables à leur bon fonctionnement.Ces opérations de vidange ont le plus souvent un effet destructeur sur la faune et la flore aquatique.Cet effet destructeur est principalement lié à une diminution de la concentration en oxygène dissous et une augmentation de la teneur en matières en suspension.La méthodologie présentée a pour but d'estimer préalablement à toute vidange les risques écotoxicologlques correspondant à une telle opération. Elle implique d'une part la description et l'analyse physico-chimique des sédiments en place, d'autre part la mesure en laboratoire de la consommation en oxygène dissous des matériaux remis en suspension au cours du temps.La fiabilité d'une telle procédure a été montrée en particulier à l'occasion de vidanges de retenues situées sur le cours de l'Isère.Le protocole est décrit précisément de façon à pouvoir guider les exploitants de retenues à l'occasion des opérations de vidange qu'ils dirigent.Sediment silting up in hydroelectric dams Implies regular draining operations in order to prevent disfunction of the dams.These operations often lead to drastic lethal affects on aquatic fauna and flora.A toxicological study has clearly shown two main factors responsible for acute toxicological effects : dissolved oxygen deficit and suspended solids increase.These effects have been quantified by experimental tests on Brown trout fry (Salmo trutta fario) the results of which are summarized.The second step consisted in the prediction of water quality evolution downstream during dam draining operation, regarding both factors suspected, in order to assess ecotoxicological hazard.The proposed methodology based on a sedimentological study made in Grangent dam, located on river Loire and immediately downstream of St. Etienne urban area, and in St. Hilaire dam situated on the river Isère downstream partIt consists in sampling cored sediments and in measuring dissolved oxygen kinetic by mixing sediments with water In a reactor.The sample conservation as carried out in jar glasses kept at 4 °C.Results are reproducible as long as residual dissolved oxygen concentration is higher than 3 mg/l. If this condition is respected, oxygen consumption is strictly dependent on suspended sediment concentration.An increase in test water temperature makes the oxygen consumption rise.In accordance with these results, recommendations for dissolved oxygen measures are about 5 g/l suspended sediment concentration, with an experimental temperature reaching the temperature observed during dam draining.The variability of the results for different samples depends on the dam studied. Surface tore samples collected in St. Hilaire dam consume dissolved oxygen faster than the same bottom tore samples.However, in Grangent dam, only one surface core sample collected near the dam construction has clearly shown reducing properties. The difference between two dam sediments is very important : Grangent dam sediment have, on average, dissolved oxygen consumption three more times higher than St. Hilaire in the same duration.Taking into account dissolved oxygen kinetics by mixed sediments, and a simple aeration model using water and sediment deposits from downstream dam, may expert both suspended sediment and oxygen consumption evolution.Hazardous mortality of trout fario fry in downstream dam are quickly graphically visualized.Dam draining operator may so assess, for different suspended sediment land the harmful exposition to fish at any distance from it.This knowledge allows him to plan more strictly floodgate working : pointly dissolved oxygen continuous measurement on downstream dam is sufficient to give a mark related to model hazard assessment.The model reliability has been demonstrated by the examination of data collected during St. Hilaire dam draining operation

Tetrads in SU(3) X SU(2) X U(1) Yang-Mills geometrodynamics

The relationship between gauge and gravity amounts to understanding underlying new geometrical local structures. These structures are new tetrads specially devised for Yang-Mills theories, Abelian and Non-Abelian in four-dimensional Lorentzian spacetimes. In the present manuscript a new tetrad is introduced for the Yang-Mills SU(3) X SU(2) X U(1) formulation. These new tetrads establish a link between local groups of gauge transformations and local groups of spacetime transformations. New theorems are proved regarding isomorphisms between local internal SU(3) X SU(2) X U(1) groups and local tensor products of spacetime LB1 and LB2 groups of transformations. The new tetrads and the stress-energy tensor allow for the introduction of three new local gauge invariant objects. Using these new gauge invariant objects and in addition a new general local duality transformation, a new algorithm for the gauge invariant diagonalization of the Yang-Mills stress-energy tensor is developed.Comment: There is a new appendix. The unitary transformations by local SU(2) subgroup elements of a local group coset representative is proved to be a new local group coset representative. This proof is relevant to the study of the memory of the local tetrad SU(3) generated gauge transformations. Therefore, it is also relevant to the group theorems proved in the paper. arXiv admin note: substantial text overlap with arXiv:gr-qc/060204

Time asymmetric spacetimes near null and spatial infinity. I. Expansions of developments of conformally flat data

The Conformal Einstein equations and the representation of spatial infinity as a cylinder introduced by Friedrich are used to analyse the behaviour of the gravitational field near null and spatial infinity for the development of data which are asymptotically Euclidean, conformally flat and time asymmetric. Our analysis allows for initial data whose second fundamental form is more general than the one given by the standard Bowen-York Ansatz. The Conformal Einstein equations imply upon evaluation on the cylinder at spatial infinity a hierarchy of transport equations which can be used to calculate in a recursive way asymptotic expansions for the gravitational field. It is found that the the solutions to these transport equations develop logarithmic divergences at certain critical sets where null infinity meets spatial infinity. Associated to these, there is a series of quantities expressible in terms of the initial data (obstructions), which if zero, preclude the appearance of some of the logarithmic divergences. The obstructions are, in general, time asymmetric. That is, the obstructions at the intersection of future null infinity with spatial infinity are different, and do not generically imply those obtained at the intersection of past null infinity with spatial infinity. The latter allows for the possibility of having spacetimes where future and past null infinity have different degrees of smoothness. Finally, it is shown that if both sets of obstructions vanish up to a certain order, then the initial data has to be asymptotically Schwarzschildean to some degree.Comment: 32 pages. First part of a series of 2 papers. Typos correcte

Can Schwarzschildean gravitational fields suppress gravitational waves?

Gravitational waves in the linear approximation propagate in the Schwarzschild spacetime similarly as electromagnetic waves. A fraction of the radiation scatters off the curvature of the geometry. The energy of the backscattered part of an initially outgoing pulse of the quadrupole gravitational radiation is estimated by compact formulas depending on the initial energy, the Schwarzschild radius, and the location and width of the pulse. The backscatter becomes negligible in the short wavelength regime.Comment: 18 pages, Revtex. Added three references; a new comment in Sec. 7; several misprints corrected. To appear in the Phys. Rev.

Computational modelling of full interaction between crystal plasticity and oxygen diffusion at a crack tip

Oxidation-promoted crack growth, one of the major concerns for nickel-based superalloys, is closely linked to the diffusion of oxygen into the crack tip. The phenomenon is still not well understood yet, especially the full interaction between oxygen diffusion and severe near-tip mechanical deformation. This work aimed at the development of a robust numerical strategy to model the full coupling of crystal plasticity and oxygen diffusion in a single crystal nickel-based superalloy. In order to accomplish this, finite element package ABAQUS is used as a platform to develop a series of user-defined subroutines to model the fully coupled process of deformation and diffusion. The formulation allowed easy incorporation of nonlinear material behaviour, various loading conditions and arbitrary model geometries. Using this method, finite element analyses of oxygen diffusion, coupled with crystal plastic deformation, were carried out to simulate oxygen penetration at a crack tip and associated change of near-tip stress field, which has significance in understanding crack growth acceleration in oxidation environment. Based on fully coupled diffusion-deformation analyses, a case study was carried out to predict crack growth rate in oxidation environment and under dwell-fatigue loading conditions, for which a two-parameter failure criterion, in terms of accumulated inelastic strain and oxygen concentration at the crack tip, has been utilized

Revista de libros

Se reseñan los siguientes libros: * Jean Doat: La Expresión Corporal del Comediante. Traducción de Osvaldo Bonet, Cuadernos Eudeba de la Editorial Universitaria de Buenos Aires; 1959, edición en rústica de 54 páginas * Hans Jantzen: La arquitectura gótica, trad, de José M. Coco Ferraris, Edit. “Nueva Visión”, Buenos Aires, 1959, vol. rúst., 199 págs. * André Berge: La libertad en la educación. Traducción de Selva E. Ucha. Editorial Kapelusz, Buenos Aires 1959. Volumen en rústica de 113 páginas * Luis Farré: Heráclito (exposición y fragmentos). Ed. Aguilar. Buenos Aires, 1959. Vol. rústica 174 págs. * Juan Collantes de Terán: Las novelas de Ricardo Güiraldes. Escuela de Estudios Hispano-Americanos de Sevilla, Sevilla, 1959; vol. rúst. 209 páginas * Luis E. Valcárcel: Etnohistoria del Perú Antiguo, Universidad Nacional Mayor de San Marcos, Patronato del Libro Universitario, Lima, Perú, 1959, 204 págs. con una bibliografía y cuadros cronológicos; liminar por Manuel Mujica Gallo; carátula por Alfredo Ruiz RosasUniversidad Nacional de La Plat

Relación dialógica emergente para la gestión y ordenamiento del territorio. Exploración de eco-proyectos en el borde oeste de la ciudad de Córdoba en su interfase urbana-metropolitana

Ponencia presentada en la 53º IFLA World Congress International Federation of Landascape Architects. Tasting the Landscape. Torino, Italia. 2016El estudio hace énfasis en los Paisajes del Borde, particularizando en el Borde Oeste de la Ciudad de Córdoba, República Argentina, en su interfase con el área metropolitana y su relación con las Infraestructuras en una escala urbano-territorial como medio de reconciliación entre la arquitectura, la ciudad y el territorio. Se reconoce la interacción dialógica Paisaje e Infraestructura y en particular a las Infraestructuras Verdes constituida por una red interconectada de paisajes de valor ambiental, cultural y visual que conforman una estructura ecológica, básica y compleja, que estructuran el territorio y traspasan las áreas de fronteras entre el campo, la ciudad, y los límites jurisdiccionales constituyendo un sistema de ordenadores en el paisaje y una herramienta posible para la gestión y el ordenamiento del territorio. El proyecto en ese marco, contempla la redefinición de las infraestructuras urbanas como una hibridación de infraestructuras verdes y la valoración de los paisajes que las contienen, a través de un estudio que permita la elaboración de catálogos de paisaje con sus variantes e invariantes y la realización de ensayos donde dialoguen el paisaje y la infraestructuras con exploraciones de hibridación redefiniendo las infraestructuras urbanas como soportes de Eco-proyectos y como medio de reconciliación entre la naturaleza y el artificio.Fil: Álvarez, Teresita. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño; ArgentinaFil: Castellán, Walter. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño; ArgentinaFil: Garat, Oscar E. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño; ArgentinaFil: Figueroa Langou, Santiago. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño; ArgentinaFil: Homola, Iván F. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño; ArgentinaFil: Fank, Lucía. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño; ArgentinaFil: Monguillot, Silvia S. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño; ArgentinaFil: Soneira, Francisco. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño; ArgentinaFil: Rodríguez, Estefanía. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño; ArgentinaIngeniería Arquitectónic

Ante el aborto como política pública

Declaración emitida conjuntamente por Facultades de Derecho de Universidades Católicas en Argentina  HAN ADHERIDO POSTERIORMENTE: Jose Luis Lopez CerviñoFacultad de Derecho y Ciencias Sociales, sede San Juan Carina FernandezFacultad de Derecho y Ciencias Sociales, sede San Luis UNIVERSIDAD CATOLICA DE CUYO Eduardo RomaniFacultad de Ciencias Jurídicas UNIVERSIDAD CATOLICA DE SALTA