Disponibilidad de boro en un suelo de Justiniano Posse y respuesta a la aplicación foliar en soja

Trabajo final integrador. (Area de Consolidación Sistemas Agrícolas de Producción Extensivos)--UNC-Facultad de Ciencias Agropecuarias, 2014.En un suelo Hapludol Típico en Justiniano Posse, se realizó una aplicación foliar con Boro (BO3H3) con cinco tratamientos (0, 30, 60, 120, 240 B mg kg-1) y cuatro repeticiones. No se encontraron diferencias significativas entre tratamientos para las variables rendimiento, peso de mil granos, peso hectolítrico y contenido de B en grano. El contenido de B en planta y grano se halló en el límite inferior del rango normal para todos los tratamientos lo que indicaría que podría haber una respuesta a futuro. Se analizó la disponibilidad (n=3), a través de 5 métodos diferentes de extracción, dando diferencias entre ellos. Se realizó un nuevo muestreo para determinar variabilidad (n=30) de B en superficie mediante el método CaCl2 dando valores altos a muy altos superando el umbral crítico (0,5 mg kg-1 B) justificando la poca respuesta en rendimiento. Se obtuvo una correlación positiva entre B (0-10 cm) y el contenido de materia orgánica

Non-equilibrium Lifshitz theory as a steady state of a full dynamical quantum system

In this work we analyze the validity of Lifshitz's theory for the case of non-equilibrium scenarios from a full quantum dynamical approach. We show that Lifshitz's framework for the study of the Casimir pressure is the result of considering the long-time regime (or steady state) of a well-defined fully quantized problem, subjected to initial conditions for the electromagnetic field interacting with real materials. For this, we implement the closed time path formalism developed in previous works to study the case of two half spaces (modeled as composite environments, consisting in quantum degrees of freedom plus thermal baths) interacting with the electromagnetic field. Starting from initial uncorrelated free subsystems, we solve the full time evolution, obtaining general expressions for the different contributions to the pressure that take part on the transient stage. Using the analytic properties of the retarded Green functions, we obtain the long-time limit of these contributions to the total Casimir pressure. We show that, in the steady state, only the baths' contribute, in agreement with the results of previous works, where this was assumed without justification. We also study in detail the physics of the initial conditions' contribution and the concept of modified vacuum modes, giving insights about in which situations one would expect a non vanishing contribution at the steady state of a non-equilibrium scenario. This would be the case when considering finite width slabs instead of half-spaces

Non-relativistic gravity theories in four spacetime dimensions

In this work we present a non-relativistic gravity theory defined in four spacetime dimensions using the MacDowell-Mansouri geometrical formulation. We obtain a Newtonian gravity action which is constructed from the curvature of a Newton-Hooke version of the so-called Newtonian algebra. We show that the non-relativistic gravity theory presented here contains the Poisson equation in presence of a cosmological constant. Moreover we make contact with the Modified Newtonian Dynamics (MOND) approach for gravity by considering a particular ansatz for a given gauge field. We extend our results to a generalized non-relativistic MacDowell-Mansouri gravity theory by considering a generalized Newton-Hooke algebra.Comment: 20 page

Optimal Control of a PEM Fuel Cell for the Inputs Minimization

The trajectory tracking problem of a proton exchange membrane (PEM) fuel cell is considered. To solve this problem, an optimal controller is proposed. The optimal technique has the objective that the system states should reach the desired trajectories while the inputs are minimized. The proposed controller uses the Hamilton-Jacobi-Bellman method where its Riccati equation is considered as an adaptive function. The effectiveness of the proposed technique is verified by two simulations

Analysis of the Fracture of Reinforced Concrete Flat Elements Subjected to Explosions. Experimental Procedure and Numerical Validation

Many of the material models most frequently used for the numerical simulation of the behavior of concrete when subjected to high strain rates have been originally developed for the simulation of ballistic impact. Therefore, they are plasticity-based models in which the compressive behavior is modeled in a complex way, while their tensile failure criterion is of a rather simpler nature. As concrete elements usually fail in tensión when subjected to blast loading, available concrete material models for high strain rates may not represent accurately their real behavior. In this research work an experimental program of reinforced concrete fíat elements subjected to blast load is presented. Altogether four detonation tests are conducted, in which 12 slabs of two different concrete types are subjected to the same blast load. The results of the experimental program are then used for the development and adjustment of numerical tools needed in the modeling of concrete elements subjected to blast

Kinetic Modeling of the UV/H2O2 Process: Determining the Effective Hydroxyl Radical Concentration

A kinetic model for pollutant degradation by the UV/H2O2 system was developed. The model includes the background matrix effect, the reaction intermediate action, and the pH change during time. It was validated for water containing phenol and three different ways of calculating HO° level time-evolution were assumed (non-pseudo-steady, pseudo-steady and simplified pseudo-steady state; denoted as kinetic models A, B and C, respectively). It was found that the kind of assumption considered was not significant for phenol degradation. On the other hand, taking into account the high levels of HO2° formed in the reaction solution compared to HO° concentration (~10–7 M >>>> ~10–14 M), HO2° action in transforming phenol was considered. For this purpose, phenol-HO2° reaction rate constant was calculated and estimated to be 1.6x103 M-1 s-1, resulting in the range of data reported from literature. It was observed that, although including HO2° action allowed slightly improving the kinetic model degree of fit, HO° developed the major role in phenol conversion, due to their high oxidation potential. In this sense, an effective level of HO° can be determined in order to be maintained throughout the UV/H2O2 system reaction time for achieving an efficient pollutant degradation

Peces marinos de los ordenes Gadiformes, Ophidiiformes y Lophiiformes en aguas colombianas del Pacífico oriental tropical

This document compiles information and records from different reference museum holdings, from around the world, of species of Gadiforms, Ophidiiforms and Lophiiforms from Colombian waters of the Pacific. Also included are records of species of these groups from adjacent waters. The latter records could indicate biogeographic connectivity – i.e. that the same species also occur in Colombian waters, but due to inadequate sampling efforts, they have not yet been collected.En el presente documento se recopila información y registros de colecciones de referencia de diferentes museos del mundo de las especies de Ophidiiformes, Gadiformes, and Lophiiformes de aguas colombianas del Pacífico. También se incluyen registros de colección de especies de estos grupos en aguas adyacentes. Estos últimos podrían indicar conectividad biogeográfica – i.e., que la misma especie ocurra también en aguas colombianas, pero que debido a un insuficiente esfuerzo de muestreo no ha sido colectada a la fecha

RECURSIVIDAD ORGANIZACIONAL: OBSERVACIÓN A UN SISTEMA (EDUCATIVO) AUTORREFERENTEU

Una organización social educativa (para el caso una estancia infantil), tiene como objetivo implementar estrategias educativas, las cuales se configuran a partir del PEIN buscando introducir al niño a un entorno educativo formal, con el fin de plantear su rol como ser social en espacios de interacció