Aportes de Los Ejes DOC en la construcción del Conocimiento Profesional del Profesor en formación

El Conocimiento Profesional del Profesor (CPP) de ciencias, se ha constituido en una línea de investigación de la didáctica de las ciencias, en razón de la necesidad de comprender cómo los profesores en formación y en ejercicio construyen un conocimiento singular de la profesión docente. Así, los Ejes DOC (Dinamizador, Obstáculo y Cuestionamiento), se abordan como un dispositivo conceptual de orden reflexivo sobre los aspectos que se articulan en la construcción del Conocimiento Profesional del profesor. En este sentido, presentamos los resultados de un proceso de I-A, realizado en el marco de una tesis doctoral (Fonseca, 2016), en donde el profesor en formación comprende que la evaluación y la estrategia de enseñanza (investigación escolar), se constituyen en Ejes DOC que aportan en su proceso de formación como profesor de biología

A generic template for FSSIM

Agricultural and Food Policy, Environmental Economics and Policy, Land Economics/Use,

Fabrication and Testing of Doped Uranium Nitride as an Accident Tolerant Fuel Alternative

Nuclear energy is a carbon-free energy source often considered less harmful to the environment than fossil fuels. However, accidents have shown that there are some safety concerns regarding nuclear energy that need to be continuously assessed and further improved. Research into new types of improved fuels, also known as Accident Tolerant Fuels, has therefore become of great importance. Different alternative claddings and fuel materials have been explored in recent years. Amongst these fuels, uranium nitride (UN) has very attractive thermomechanical properties. Nonetheless, UN is easily oxidized in thepresence of air or water, making it undesirable for water-cooled reactors.In this thesis, UN microspheres were manufactured through a sol-gel method, followed by carbothermic reduction and nitridation. The as-produced microspheres were pressed and sintered into pellets using spark plasma sintering. Thorium, chromium, and aluminum were studied as additives to improve the oxidation resistance of UN. It was observed that Th produced a homogeneous solid solution with UN between 0 % and 20 mol-% thorium metal content. Chromium showed that there was a solubility limit in the UN. Depending on the synthesis conditions, the resulting material can be manufactured to either contain a ternary phase (U2CrN3) or metallic chromium. No solubility of aluminum nitride was detected in the UN matrix.Doping with Th and Cr proved to be efficient in improving the oxidation in air, by increasing the onset oxidation temperatures and decreasing the reaction rates of the pellets. In most cases, the high porosity of the microspheres counterbalanced any protective effect caused by the dopant. Aluminum-containing samples showed the worst oxidation resistance in air due to poor solubility of AlN in the UN. Steam interaction of Cr-doped pellets also showed a delay in the hydrolysis of the UN when Cr is present. The last exposure environment was water, and it was shown that undoped UN pellets can survive at 100 \ub0C and 1 bar pressure with zero mass change. However, at higher temperatures and pressures, 200 \ub0C and 15 bar or 300 \ub0C and 85 bar, pellet disintegration into a UO2 powder was observed. An incomplete reaction was also observed for the Th-doped pellet in the exposure test at 200 \ub0C, indicating that no improvement in the corrosion resistance of UN in water was achieved by doping with thorium. On the other hand, Cr-doped pellets exposed to water at 200 and 300 \ub0C showed partial crumbling. The resulting material was unreacted UN with some UO2 byproduct

Advances in Accident Tolerant Fuel Research by Doping of Uranium Nitride

Nuclear energy is a carbon-free energy source alternative often considered less harmful to the environment than fossil fuels. However, accidents have shown that there are some safety concerns regarding nuclear energy that need to be assessed before it can be considered completely safe. The loss of cooling systems during the nuclear accident at Fukushima nuclear accident exposed the flaws of the fuel used today, UO2 encapsulated in a Zr alloy. Research into new types of improved fuels, also known as Accident Tolerant Fuels (ATF), has therefore became of great importance. Different alternative claddings and fuel materials have been explored in recent years. Amongst these, uranium nitride (UN) has shown to have very attractive thermomechanical properties. Nonetheless, UN reacts readily in oxidizing environments, making it undesirable for water-cooled reactors.In this study, UN microspheres were manufactured through a sol-gel method, followed by carbothermic reduction and nitridation. The as-produced microspheres were pressed and sintered into pellets using spark plasma sintering (SPS). It was seen that the spherical shape was lost during sintering and densities between 77 and 98% of theoretical density were obtained, depending on the sintering parameters. For example, sintering at 1650 \ub0C and 75 MPa for at least 5 minutes proved to produce pellets with densities close to 95% of theoretical densities, which are similar to densities used today in nuclear reactors.Thorium and chromium were introduced as additives to form a protective oxide scale and improve the oxidation resistance of UN. It was seen that Th produced a homogeneous solid solution with uranium nitride between 0 and 20 % thorium molar metal ratio. Chromium, on the other hand, showed that there was a solubility limit in UN, and precipitation of a Cr-rich phase was observed. During exposure in air, the doped materials seem to reduce the oxidation kinetics, increasing onset temperatures and decreasing the reaction rates. Pellet exposure to water at high temperatures showed that pellets can survive at 100 \ub0C and 1 bar pressure with zero mass change. However, at higher temperatures and pressures, 200 \ub0C and 15 bar or 300 \ub0C and 85 bar, pellet disintegration into a UO2 powder was observed. An incomplete reaction was also observed for the Th-doped pellet in the exposure test at 200 \ub0C, indicating that no improvement in the corrosion resistance of UN in water was achieved by doping with thorium

Uniqueness of the Fock quantization of scalar fields under mode preserving canonical transformations varying in time

We study the Fock quantization of scalar fields of Klein-Gordon type in nonstationary scenarios propagating in spacetimes with compact spatial sections, allowing for different field descriptions that are related by means of certain nonlocal linear canonical transformations that depend on time. More specifically, we consider transformations that do not mix eigenmodes of the Laplace-Beltrami operator, which are supposed to be dynamically decoupled. In addition, we assume that the canonical transformations admit an asymptotic expansion for large eigenvalues (in norm) of the Laplace-Beltrami operator in the form of a series of half integer powers. Canonical transformations of this kind are found in the study of scalar perturbations in inflationary cosmologies, relating for instance the physical degrees of freedom of these perturbations after gauge fixing with gauge invariant canonical pairs of Bardeen quantities. We characterize all possible transformations of this type and show that, independently of the initial field description, the combined criterion of requiring (i) invariance of the vacuum under the spatial symmetries and (ii) a unitary implementation of the dynamics, leads to a unique equivalence class of Fock quantizations, all of them related by unitary transformations. This conclusion provides even further robustness to the validity of the proposed criterion, completing the results that have already appeared in the literature about the uniqueness of the Fock quantization under changes of field description when one permits exclusively local time dependent canonical transformations that scale the field configuration.Comment: 12 pages, submitted to Phys. Rev.

A generic template for FSSIM

The aim of this report is to describe the generic template of the Farm System Simulator FSSIM) designed to be applied for any farming systems across Europe for simulating farmer behaviour and assessing policy impacts. FSSIM is a bio-economic farm model which integrates biophysical processes, farm decision making and resource endowment. It consists of an agricultural management module (FSSIM-AM) and a mathematical programming model (FSSIM-MP). FSSIM-AM aims to identify current and alternative activities and to quantify their input output coefficients (both yields and environmental effects). FSSIM-MP seeks to describe the farmer’s behaviour given a set of biophysical, socio-economic and policy constraints and to predict his/her reactions under news technologies, policy and market changes

De la empatía a la compasión : las respuestas compasivas como una alternativa a la empatía

En las últimas décadas, ha habido un gran desarrollo en las investigaciones acerca de la empatía y en menor medida acerca de la compasión. La neurociencia, la psicología social y la filosofía han dado su parecer respecto de ambas, sin embargo, no hay un acuerdo definitivo acerca del origen, la naturaleza y el alcance de la empatía. Existen diversos fenómenos intersubjetivos que suelen confundirse con las dos capacidades propuestas en el presente análisis. Por ello intento establecer con la mayor claridad posible el significado de nociones como "contagio emocional", "empatía", "súper empatía", "empatía positiva y negativa" y "compasión". Este paso es de fundamental importancia, dado que los propios investigadores no se ponen de acuerdo en sus respectivos alcances. Singer (2009) dice: A pesar de que cada uno de nosotros cree saber qué cosa es empatía, compasión o contagio emocional, si miran más de cerca las definiciones existentes, se darán cuenta que no existe actualmente una sola y claramente delimitada definición de empatía. Con una opinión que apunta en esa misma dirección, Batson (2006) afirma que: Aún cuando todos (aquéllos que estudian a la empatía) típicamente concuerdan en quela empatía es importante, a menudo no se ponen de acuerdo acerca de por qué es importante, acerca de qué efectos tiene, de dónde viene e incluso acerca de qué se trata.(Batson, D. 2006: p.235)Tanto la empatía como la compasión contribuyen a que la convivencia mejore. Es razonable preguntarse si es posible transformar la sociedad de modo que las personas sean más compasivas o empáticas. También lo es preguntarse si esto es deseable. Considero que sí, teniendo los reparos que realizan investigadores como Baron-Cohen, quien sostiene que un exceso de empatía haría que uno se focalice tanto en los demás que abandone su propio interés, provocando un daño para uno mismo. Para el autor es preferible que haya un equilibrio, y es por eso que la mayoría de las personas, como se verá más adelante, son medianamente empáticas. El objetivo general del presente trabajo es fundamentar la idea de que la compasión es una posible respuesta alternativa a la empatía frente al dolor de otro, en tanto que permite controlar la angustia que se produce en el agente. Para ello intento justificar una descripción de ambas que contemple tanto sus aspectos emocionales y cognitivos, como así también los positivos y negativos. La hipótesis principal radica en que la compasión, desprovista de los prejuicios que la colocan en el ámbito de lo religioso y aceptándola como una práctica que puede convertirse en una forma de vida, permite evitar los efectos no deseados de la empatía negativa, especialmente en los casos de quienes conviven permanentemente con el dolor ajeno. A su vez, predispone al agente de mejor manera para la acción prosocial ya que es una práctica que puede mejorarse a través del entrenamiento.Fil: Fonseca, Guillermo. Universidad Nacional de Córdoba. Facultad de Filosofía y Humanidades. Escuela de Filosofía; Argentina.Filosofía, Historia y Filosofía de la Ciencia y la Tecnologí