Agriculturización, inequidad distributiva y fractura del tejido social

Los cambios operados en la actividad agrícola en nuestro país a lo largo de las últimas dos décadas, identificados genéricamente bajo la denominación de agriculturización, han generado múltiples impactos, muchos de ellos de carácter contradictorio. Así, el crecimiento de la actividad económica, el incremento en los saldos exportables y en los recursos fiscales conviven, entre otras manifestaciones, con la agudización de las tensiones derivadas de la concentración económica, con nuevos impactos e incertidumbres de carácter ambiental, con desequilibrios territoriales crecientes, con la ampliación de la brecha laboral y con el incremento en la inequidad distributiva. Este trabajo presenta los resultados de un análisis exploratorio orientado a pequeñas localidades de la región pampeana, en el cual se visualiza el surgimiento de fuertes signos de fractura del tejido social, derivados del crecimiento de la inequidad distributiva de la riqueza en el interior del espacio rural. Dos tendencias fundamentales constituyen los emergentes de este proceso: 1°) los cambios en los estilos de vida de los sectores relacionados con la actividad agrícola, visibles fundamentalmente en modificaciones en las pautas de consumo (sobre todo entre los jóvenes); y 2°) la heterogeneización de las percepciones de los pobladores sobre la valorización del trabajo en la comunidad. La reconstrucción de estos procesos, escasamente abordados en la literatura académica, se realizó a través de estrategias metodológicas que combinan métodos cuanti y cualitativos, tomando como caso de estudio una pequeña localidad en la Provincia de Santa Fe

La invención de las masas : Ciudad, corporalidades y culturas. Rosario, 1910-1945

El libro reconstruye una multiplicidad de experiencias y prácticas urbanas. Sus páginas exploran tiempo-espacios, cuerpos, narraciones y esquemas culturales quebrados en una ciudad que se configura en el umbral de lo masivo. Protagonizada por Rosario y sus agentes, la narración transcurre entre el centenario de la Revolución de Mayo y las vísperas del peronismo. Las fiestas del centenario, la formación de dispositivos disciplinarios y biopolíticos para el cultivo de los cuerpos, la producción y diseminación de espacios verdes, la segregación urbana, la cuestión de la vivienda, las asociaciones y movimientos vecinales, las bibliotecas populares, las prácticas futbolísticas, las exhibiciones cinematográficas, los choques de la incultura y la organización de los carnavales dibujan un mapa y un recorrido curvo y complejo. Roldán ensaya la reunión de procesos, fuerzas y vectores dispersos que se chocan, se rompen y transforman. Es la escritura de una confluencia y sus desperfectos. Universos desconectados se ensamblan por yuxtaposición y contraste en una composición que pretende dar vida y movimiento a una multiplicidad social, corporal, cultural, histórica y urbana.

Nueva terminal de pasajeros para el aeropuerto Federico García Lorca, Granada - Jaén

El presente proyecto de construcción define las actuaciones para la ejecución de la Nueva Terminal de pasajeros para el aeropuerto Federico García Lorca, Granada – Jaén, situado entre los términos municipales de Chauchina y Santa Fe, en la provincia de Granada. Estudios realizados por AENA, en colaboración con el Ministerio de Fomento, dejan constancia de los déficits en cuanto a capacidad de las instalaciones del aeropuerto se refiere, en múltiples facetas. En el caso de la terminal de pasajeros, sus principales elementos de servicio han sido sometidos a estudio, revelando claras faltas en numerosos puntos. El más relevante son las carencias en cuanto a capacidad, respecto a la demanda existente, y especialmente la demanda prevista para un cierto horizonte de estudio. Además, las nuevas normativas de aplicación en aeropuertos internacionales publicadas por la International Air Transport Association (IATA) entran en conflicto con ciertos parámetros de diseño de las instalaciones actuales. Se requiere una remodelación del conjunto para adaptarse a estas exigencias de validez internacional.

Crack mechanical failure in lithium niobate crystal under ion irradiation; novel simulation by extended finite elements

Swift heavy ion irradiation (ions with mass heavier than 15 and energy exceeding MeV/amu) transfer their energy mainly to the electronic system with small momentum transfer per collision. Therefore, they produce linear regions (columnar nano-tracks) around the straight ion trajectory, with marked modifications with respect to the virgin material, e.g., phase transition, amorphization, compaction, changes in physical or chemical properties. In the case of crystalline materials the most distinctive feature of swift heavy ion irradiation is the production of amorphous tracks embedded in the crystal. Lithium niobate is a relevant optical material that presents birefringence due to its anysotropic trigonal structure. The amorphous phase is certainly isotropic. In addition, its refractive index exhibits high contrast with those of the crystalline phase. This allows one to fabricate waveguides by swift ion irradiation with important technological relevance. From the mechanical point of view, the inclusion of an amorphous nano-track (with a density 15% lower than that of the crystal) leads to the generation of important stress/strain fields around the track. Eventually these fields are the origin of crack formation with fatal consequences for the integrity of the samples and the viability of the method for nano-track formation. For certain crystal cuts (X and Y), these fields are clearly anisotropic due to the crystal anisotropy. We have used finite element methods to calculate the stress/strain fields that appear around the ion-generated amorphous nano-tracks for a variety of ion energies and doses. A very remarkable feature for X cut-samples is that the maximum shear stress appears on preferential planes that form +/-45º with respect to the crystallographic planes. This leads to the generation of oriented surface cracks when the dose increases. The growth of the cracks along the anisotropic crystal has been studied by means of novel extended finite element methods, which include cracks as discontinuities. In this way we can study how the length and depth of a crack evolves as function of the ion dose. In this work we will show how the simulations compare with experiments and their application in materials modification by ion irradiation.

Ionoluminescence on α-quartz: mechanisms and modeling

Ionoluminescence of α - quartz exhibits two dominant emission bands peaking at 1.9 eV. (NBOHCs) and 2.7 eV (STEs. The evolution of the red emission yield does not show a correlation with the concentrations of neither the NBOHC nor with that of other color centers. The blue emission yield closely follows the amorphization kinetics independently measured by RBS/C spectrometry. A simple theoretical model has been proposed; it assumes that the formation and recombination of STEs are the primary event and both, the light emissions and the lattice structural damage are a consequence this phenomenon. The model leads to several simple mathematical equations that can be used to simulate the IL yields and provide a reasonable fit to experimental kinetic data.

A molecular dynamics study of swift heavy ion irradiation of amorphous silica: the role of thermal effects

Irradiation with swift heavy ions (SHI), roughly defined as those having atomic masses larger than 15 and energies exceeding 1 MeV/amu, may lead to significant modification of the irradiated material in a nanometric region around the (straight) ion trajectory (latent tracks). In the case of amorphous silica, SHI irradiation originates nano-tracks of higher density than the virgin material (densification). As a result, the refractive index is increased with respect to that of the surroundings. Moreover, track overlapping leads to continuous amorphous layers that present a significant contrast with respect to the pristine substrate. We have recently demonstrated that SHI irradiation produces a large number of point defects, easily detectable by a number of experimental techniques (work presented in the parallel conference ICDIM). The mechanisms of energy transfer from SHI to the target material have their origin in the high electronic excitation induced in the solid. A number of phenomenological approaches have been employed to describe these mechanisms: coulomb explosion, thermal spike, non-radiative exciton decay, bond weakening. However, a detailed microscopic description is missing due to the difficulty of modeling the time evolution of the electronic excitation. In this work we have employed molecular dynamics (MD) calculations to determine whether the irradiation effects are related to the thermal phenomena described by MD (in the ps domain) or to electronic phenomena (sub-ps domain), e.g., exciton localization. We have carried out simulations of up to 100 ps with large boxes (30x30x8 nm3) using a home-modified version of MDCASK that allows us to define a central hot cylinder (ion track) from which heat flows to the surrounding cold bath (unirradiated sample). We observed that once the cylinder has cooled down, the Si and O coordination numbers are 4 and 2, respectively, as in virgin silica. On the other hand, the density of the (cold) cylinder increases with respect to that of silica and, furthermore, the silica network ring size decreases. Both effects are in agreement with the observed densification. In conclusion, purely thermal effects do not explain the generation of point defects upon irradiation, but they do account for the silica densification.

Physical characterization of laser interaction and shock generation in laser processing: coupled theoretical-experimental analysis

Outline: • Introduction • Fundamental Physics of the Laser-Plasma Interaction in Laser Shock Processing • Theoretical/Computational Model Description • Some Results. Analysis of Interaction Parameters • Experimental Validation. Diagnosis Setup • Discussion and Outlook

MMonCa: A flexible and powerful new Kinetic Monte Carlo simulator

Kinetic Monte Carlo (KMC) is a widely used technique to simulate the evolution of radiation damage inside solids. Despite de fact that this technique was developed several decades ago, there is not an established and easy to access simulating tool for researchers interested in this field, unlike in the case of molecular dynamics or density functional theory calculations. In fact, scientists must develop their own tools or use unmaintained ones in order to perform these types of simulations. To fulfil this need, we have developed MMonCa, the Modular Monte Carlo simulator. MMonCa has been developed using professional C++ programming techniques and has been built on top of an interpreted language to allow having a powerful yet flexible, robust but customizable and easy to access modern simulator. Both non lattice and Lattice KMC modules have been developed. We will present in this conference, for the first time, the MMonCa simulator. Along with other (more detailed) contributions in this meeting, the versatility of MMonCa to study a number of problems in different materials (particularly, Fe and W) subject to a wide range of conditions will be shown. Regarding KMC simulations, we have studied neutron-generated cascade evolution in Fe (as a model material). Starting with a Frenkel pair distribution we have followed the defect evolution up to 450 K. Comparison with previous simulations and experiments shows excellent agreement. Furthermore, we have studied a more complex system (He-irradiated W:C) using a previous parametrization [1]. He-irradiation at 4 K followed by isochronal annealing steps up to 500 K has been simulated with MMonCa. The He energy was 400 eV or 3 keV. In the first case, no damage is associated to the He implantation, whereas in the second one, a significant Frenkel pair concentration (evolving into complex clusters) is associated to the He ions. We have been able to explain He desorption both in the absence and in the presence of Frenkel pairs and we have also applied MMonCa to high He doses and fluxes at elevated temperatures. He migration and trapping dominate the kinetics of He desorption. These processes will be discussed and compared to experimental results. [1] C.S. Becquart et al. J. Nucl. Mater. 403 (2010) 75

Effect of ion flux on helium retention in helium-irradiated tungsten

Helium retention in irradiated tungsten leads to swelling, pore formation, sample exfoliation and embrittlement with deleterious consequences in many applications. In particular, the use of tungsten in future nuclear fusion plants is proposed due to its good refractory properties. However, serious concerns about tungsten survivability stems from the fact that it must withstand severe irradiation conditions. In magnetic fusion as well as in inertial fusion (particularly with direct drive targets), tungsten components will be exposed to low and high energy ion (helium) irradiation, respectively. A common feature is that the most detrimental situations will take place in pulsed mode, i.e., high flux irradiation. There is increasing evidence on a correlation between a high helium flux and an enhancement of detrimental effects on tungsten. Nevertheless, the nature of these effects is not well understood due to the subtleties imposed by the exact temperature profile evolution, ion energy, pulse duration, existence of impurities and simultaneous irradiation with other species. Physically based Kinetic Monte Carlo is the technique of choice to simulate the evolution of radiation-induced damage inside solids in large temporal and space scales. We have used the recently developed code MMonCa (Modular Monte Carlo simulator), presented in this conference for the first time, to study He retention (and in general defect evolution) in tungsten samples irradiated with high intensity helium pulses. The code simulates the interactions among a large variety of defects and impurities (He and C) during the irradiation stage and the subsequent annealing steps. In addition, it allows us to vary the sample temperature to follow the severe thermo-mechanical effects of the pulses. In this work we will describe the helium kinetics for different irradiation conditions. A competition is established between fast helium cluster migration and trapping at large defects, being the temperature a determinant factor. In fact, high temperatures (induced by the pulses) are responsible for large vacancy cluster formation and subsequent additional trapping with respect to low flux irradiation.

EDROMO: An accurate propagator for elliptical orbits in the perturbed two-body problem

EDROMO is a special perturbation method for the propagation of elliptical orbits in the perturbed two-body problem. The state vector consists of a time-element and seven spatial elements, and the independent variable is a generalized eccentric anomaly introduced through a Sundman time transformation. The key role in the derivation of the method is played by an intermediate reference frame which enjoys the property of remaining fixed in space as long as perturbations are absent. Three elements of EDROMO characterize the dynamics in the orbital frame and its orientation with respect to the intermediate frame, and the Euler parameters associated to the intermediate frame represent the other four spatial elements. The performance of EDromo has been analyzed by considering some typical problems in astrodynamics. In almost all our tests the method is the best among other popular formulations based on elements.

Collision avoidance maneuver optimization

The paper presents a high accuracy fully analytical formulation to compute the miss distance and collision probability of two approaching objects following an impulsive collision avoidance maneuver. The formulation hinges on a linear relation between the applied impulse and the objects relative motion in the b-plane, which allows to formulate the maneuver optimization problem as an eigenvalue problem. The optimization criterion consists of minimizing the maneuver cost in terms of delta-V magnitude in order to either maximize collision miss distance or to minimize Gaussian collision probability. The algorithm, whose accuracy is verified in representative mission scenarios, can be employed for collision avoidance maneuver planning with reduced computational cost when compared to fully numerical algorithms.

Gravitational actions upon a tether in a non-uniform gravity field with arbitrary number of zonal harmonics

We develop general closed-form expressions for the mutual gravitational potential, resultant and torque acting upon a rigid tethered system moving in a non-uniform gravity field produced by an attracting body with revolution symmetry, such that an arbitrary number of zonal harmonics is considered. The final expressions are series expansion in two small parameters related to the reference radius of the primary and the length of the tether, respectively, each of which are scaled by the mutual distance between their centers of mass. A few numerical experiments are performed to study the convergence behavior of the final expressions, and conclude that for high precision applications it might be necessary to take into account additional perturbation terms, which come from the mutual Two-Body interaction.