Isolated horizons in numerical relativity: constructing the excised Kerr spacetime in Dirac gauge

Using a constrained formalism for Einstein equations in Dirac gauge, we propose to compute excised quasistationary initial data for black hole spacetimes in full general relativity. Vacuum spacetime settings are numerically constructed by using the isolated horizon formalism; we especially tackle the conformal metric part of our equations, assuming global stationarity. We show that a no-boundary treatment can be used on the horizon for the equation related to the conformal metric. We relate this finding to previous suggestions in the literature, and use our results to assess the widely used conformally flat approximation for computing black hole initial data.Comment: 3 pages, 1 figure; to appear in the proceedings of the 12th Marcel Grossmann meeting on general relativit

An excision scheme for black holes in constrained evolution formulations: spherically symmetric case

Excision techniques are used in order to deal with black holes in numerical simulations of Einstein equations and consist in removing a topological sphere containing the physical singularity from the numerical domain, applying instead appropriate boundary conditions at the excised surface. In this work we present recent developments of this technique in the case of constrained formulations of Einstein equations and for spherically symmetric spacetimes. We present a new set of boundary conditions to apply to the elliptic system in the fully-constrained formalism of Bonazzola et al. (2004), at an arbitrary coordinate sphere inside the apparent horizon. Analytical properties of this system of boundary conditions are studied and, under some assumptions, an exponential convergence toward the stationary solution is exhibited for the vacuum spacetime. This is verified in numerical examples, together with the applicability in the case of the accretion of a scalar field onto a Schwarzschild black hole. We also present the successful use of the excision technique in the collapse of a neutron star to a black hole, when excision is switched on during the simulation, after the formation of the apparent horizon. This allows the accretion of matter remaining outside the excision surface and for the stable long-term evolution of the newly formed black hole.Comment: 14 pages, 9 figures. New section added and changes included according to published articl

Planificación estratégica orientada a mejorar la calidad educativa: Colegio Polivalente Ena Bellemans Montti

Tesis (Magíster en Liderazgo para la Gestión Educacional)La necesidad de acercar la brecha de desigualdad que existe entre los Colegios Particulares Pagados, los Municipales y Subvencionados, es cada día más necesaria y urgente, por esa razón surge la necesidad de revisar la forma en que se gestionan todos los aspectos de los establecimientos. La Gestión Educativa en todas sus áreas: pedagógica, administrativa, financiera y en especial en el área de las personas es la gran diferencia que incide en los resultados del proceso educativo. El objetivo de la investigación es demostrar que mediante la aplicación de técnicas modernas de gestión integradas, es posible mejorar la gestión educativa en los ámbitos de: liderazgo, currículum y resultados, y por ende los niveles de logro académico de los alumnos que se educan en un colegio particular subvencionado gratuito con alto índice de vulnerabilidad social. Para investigar al respecto, observamos la realidad educativa en el ámbito de la Gestión Integral, del colegio Ena Bellemans Montti de Rancagua, en los cursos de 1° a 4° medio de la modalidad Científico Humanista durante el año 2010 y analizamos lo siguiente: Liderazgo, Niveles de Logro alcanzados por los alumnos en los subsectores de Lenguaje y Comunicación, y Matemáticas, antes y después de la aplicación de una Planificación Estratégica Integral basada en el diagnóstico inicial. Los resultados obtenidos en relación a Liderazgo fueron la modificación de las actitudes observadas en el diagnóstico inicial, lo que se tradujo en una mayor integración de los docentes en el aspecto curricular, de convivencia y de trabajo en equipo, mejoraron las comunicaciones con el sostenedor, permitiendo la dotación de nuevos recursos materiales y de personal, la articulación con redes de apoyo externo, se instaló la reflexión pedagógica, y la comprensión que el resultado de la gestión de un colegio es un trabajo colaborativo y participativo de todos los estamentos que conforman la Comunidad Educativa. En relación a los resultados cuantitativos se aprecia una notable mejoría en los niveles de logro alcanzados en los subsectores de Lenguaje y Comunicación, y Matemáticas. Al realizar un seguimiento de la evolución de los niveles de logro en el tiempo se parecía una curva ascendente, la que se comprueba con los resultados de mediciones externas como la Prueba de Selección Universitaria, donde se alcanzó el año 2010 una mejoría cercana a los 30 puntos con respecto al año anterior

It´s Not My Money: An Experiment on Risk Aversion and the House-money Effect

The house-money effect -people´s tendency to be more daring with easily-gotten money- is abehavioral pattern that poses questions about the external validity of experiments in economics: to what extent do people behave in experiments like they would have in a real-life situation, given that they play with easily-gotten house money? We ran an economic experiment with 66 students to measure the house-money effect on their risk preferences. They received an amount of money with which they made risky decisions involving losses and gains; a treatment group got the money 21 days in advance and a control group got it the day of the experiment. We find that, when facing possible losses, people in the treatment group showed a lower tolerance to risk than people in the control group. If the players are assumed to have a CRRA utility function and to behave according to expected-utility theory, the risk-attitude adjustment corresponds to an average increase of 1 in their risk aversion coefficient. While the exact pattern of this house-money adjustment differs by gender, it is not possible to determine the sign of this gender effect unambiguously. In any case, it is advisable to include credible controls for the house-money effect in experimental work in economics.House-money effect, risk aversion, prospect theory, economic experiment, external validity.

Drengskapr: el camino del guerrero escandinavo

El trabajo es un texto sobre la ética de los guerreros escandinavos de la Era Vikinga (797-1100), basado en las Sagas de los Islandeses, Piedras Rúnicas y Versos de los poetas provenientes de Escandinavia. La investigación enseña la manera en que la ética escandinava fue mutando a lo largo del periodo, mostrando la influencia que sobre esta tuvieron el cristianismo, la formación de monarquías y las expediciones vikingas, entre otros factores. El texto muestra, en resumen, en primer lugar, las estructuras socio-culturales de la ética escandinava, en seguida la manera en que unos guerreros aprehendían tales estructuras y las llevaban a la práctica en diferentes periodos, y por último, la manera en que unos guerreros rechazaron la relación con sus dioses al desarrollar su ética desde los principios culturales.The dissertation it s a text about the ethics of the Scandinavian warriors of the Viking Age (797-1100), based on the Islandic Sagas, Rune stones and verses of the poets from Scandinavia. The investigation shows the way in which the Scandinavian ethics were mutating along the epoch, displaying the influence that on this had the Christianity, the formation of Monarchies and the Viking expeditions, among other factors. The study illustrate, in brief, in the first place, the socio-cultural structures of the Scandinavian ethics, then, the way in which some warriors apprehend such structures y take them to action in different times, last, it shows the means by which some warriors rejected the relation with their gods when developing theirs ethics from the cultural principles.Historiador (a)Pregrad

Application of initial data sequences to the study of Black Hole dynamical trapping horizons

Non-continuous "jumps" of Apparent Horizons occur generically in 3+1 (binary) black hole evolutions. The dynamical trapping horizon framework suggests a spacetime picture in which these "Apparent Horizon jumps" are understood as spatial cuts of a single spacetime hypersurface foliated by (compact) marginally outer trapped surfaces. We present here some work in progress which makes use of uni-parametric sequences of (axisymmetric) binary black hole initial data for exploring the plausibility of this spacetime picture. The modelling of Einstein evolutions by sequences of initial data has proved to be a successful methodological tool in other settings for the understanding of certain qualitative features of evolutions in restricted physical regimes.Comment: Contribution to the proceedings volume of the Spanish Relativity Meeting 2008: Physics and Mathematics of Gravitation, Salamanca, Spain, 15-19 Sep 200

Understanding the Role of Power during the Implementation of BRT Systems

This research is about power. It is completely immersed in modern societies, reflections on power have not settled its definition. Regardless of centuries of considerations about power, there is still much to learn about its exercise. For decades, power has been analysed by scholars all over the world; however, transport planners have avoided issues concerning power. This dissertation focuses on the use of power during planning and implementation processes of two Bus Rapid Transit Systems; one in Quito, Ecuador, and another in Cambridge, England. Using a multimethod phronetic approach, this research examines how decisions were made for the implementation of BRT in the selected case studies. Phronetic methodology aims to explain social phenomena by piecing together large and small details that shape the context of events; in this case, existing planning documentation and the narratives of key stakeholders and decision-makers —such as former Mayors, Council Members, and Heads of Transport Departments— were used to understand the reasons behind the adoption of bus systems. Despite the contextual differences of geography, population, and political and administrative terms between Quito and Cambridge, there are key themes found in both case studies. Solving congestion and improving economic growth is a key motivation for the implementation of the systems in both cases. A complex network of actors is formed during the planning processes of BRT systems that shape the way decisions are made. In both cases, an isolated group of actors that lack the opportunity to exercise power was also identified. A sophisticated mixture of power mechanisms were discovered, which contained actors that had more experience, training and opportunities to exercise power. The findings of the analysis of power in Quito and Cambridge suggest that stakeholders with opportunities to exercise power —from the beginning— are also actors with more opportunities to influence the final uptake of the systems. Planners interested in participatory processes need to focus efforts to involve different communities as early as possible in the planning processes. The inclusion of communities does not guarantee that their needs and objectives will be incorporated into the planning process. A set of power mechanisms need to be developed by all members involved in the process. An early participation of these communities can help focus planning on solving people’s needs rather than the implementation of a specific scheme

Desarrollo de un modelo financiero para la comercialización de vivienda de interés prioritario y social por medio de sistema de autofinanciamiento o consorcio

La vivienda constituye un factor determinante de desarrollo social y económico, en la medida que posibilita la disminución de la pobreza y la miseria, la reactivación de la economía y la generación de empleo. Un factor fundamental son las directrices que fomentan la vivienda para las clases menos favorecidas llamada en nuestro país como La política de vivienda de interés social, la cual ha adquirido una creciente dimensión desde que se puso en marcha. Sin embargo, no ha jugado hasta ahora un papel importante en la reducción del déficit de vivienda pues la insuficiencia de suelos para la vivienda de interés prioritario y la falta de proyectos de este tipo dada la demanda actual de éste mercado ha influido de manera importante en este resultado y el avance de ésta política no se ha perfeccionado mas allá de generar sistemas de financiación de vivienda.Housing constitutes a determining factor of social and economic development, in the measure that makes possible the reduction of poverty and misery, the reactivation of the economy and job creation. A fundamental factor is the guidelines promoting housing for the underprivileged classes called in our country as the social interest housing policy, which has acquired a growing dimension since it was launched. However, it has not so far played an important role in reducing the housing deficit because the insufficiency of land for housing of priority interest and the lack of projects of this type given the current demand of this market has influenced important way in this result and the advancement of this policy has not been perfected beyond generating housing finance systems

Tensile Hoop Behavior of Irradiated Zircaloy-4 Nuclear Fuel Cladding

A method for evaluating the room temperature ductility behavior of irradiated Zircaloy-4 nuclear fuel cladding has been developed and applied to evaluate tensile hoop strength of material irradiated to different levels. The test utilizes a polyurethane plug fitted within a tubular cladding specimen. A cylindrical punch is used to compress the plug axially, which generates a radial displacement that acts upon the inner diameter of the specimen. Position sensors track the radial displacement of the specimen outer diameter as the compression proceeds. These measurements coupled with ram force data provide a load-displacement characterization of the cladding response to internal pressurization. The development of this simple, cost-effective, highly reproducible test for evaluating tensile hoop strain as a function of internal pressure for irradiated specimens represents a significant advance in the mechanical characterization of irradiated cladding. In this project, nuclear fuel rod assemblies using Zircaloy-4 cladding and two types of mixed uranium-plutonium oxide (MOX) fuel pellets were irradiated to varying levels of burnup. Fuel pellets were manufactured with and without thermally induced gallium removal (TIGR) processing. Fuel pellets manufactured by both methods were contained in fuel rod assemblies and irradiated to burnup levels of 9, 21, 30, 40, and 50 GWd/MT. These levels of fuel burnup correspond to fast (E > 1 MeV) fluences of 0.27, 0.68, 0.98, 1.4 and 1.7 1021 neutrons/cm2, respectively. Following irradiation, fuel rod assemblies were disassembled; fuel pellets were removed from the cladding; and the inner diameter of cladding was cleaned to remove residue materials. Tensile hoop strength of this cladding material was tested using the newly developed method. Unirradiated Zircaloy-4 cladding was also tested. With the goal of determining the effect of the two fuel types and different neutron fluences on clad ductility, tensile hoop strength tests were performed on cladding for these varying conditions. Experimental data revealed negligible performance differences for cladding containing TIGR vs non-TIGR processed fuel pellets. Irradiation hardening was observed in tensile hoop data as the strength of the cladding increased with increasing neutron dose and appeared to saturate for a fast fluence of 1.7 1021 neutrons/cm2

Spatial analysis of bovine tuberculosis in the State of Mexico, Mexico

Bovine tuberculosis (bTB) is a chronic infectious disease that affects both domestic animals and wildlife. Veterinary epidemiology studies evaluate bTB using geographic information systems (GIS), which can characterise the spatial and temporal distribution of diseases and identify the geographic areas and animal populations at risk of contracting a disease. The present study used space‑time permutation scan statistic to identify the spatial and temporal distribution of bTB from 2005 to 2010 in the State of Mexico with the goal of creating a similarity model using Mahalanobis Distance to identify areas suitable for bTB occurrence. Three significant clusters were identified using space‑time permutation scan statistic and the similarity model identified several areas with suitable environmental and demographic characteristics. The results demonstrate that the occurrence of bTB in the State of Mexico is not randomly distributed