The billiard inside an ellipse deformed by the curvature flow

The billiard dynamics inside an ellipse is integrable. It has zero topological entropy, four separatrices in the phase space, and a continuous family of convex caustics: the confocal ellipses. We prove that the curvature flow destroys the integrability, increases the topological entropy, splits the separatrices in a transverse way, and breaks all resonant convex caustics.Comment: 13 pages, 1 figur

El gobierno corporativo en la cooperativa de Trabajo Asociado Recuperar

En consonancia con lo definido por la Organización Internacional de las Cooperativas de Producción Industrial, Artesanal y de Servicios, o CICOPA, las cooperativas de trabajo asociado CTA, funcionan bajo los postulados definidos en los principios y valores cooperativos y los modelos de gestión, en donde se vincula el trabajo personal de los asociados y sus aportes económicos, con el propósito de orientarlos a la producción de bienes y servicios en forma autogestionaria. En esta investigación se pretende mostrar, por medio de un estudio de caso en profundidad, como en el país es posible implementar la figura del Gobierno Corporativo para el logro y cumplimiento de los objetivos y las metas organizacionales, en una cooperativa de trabajo asociado, denominada Recuperar (CTA). En este sentido Recuperar (CTA) se ha consolidado, logrando una sostenibilidad económica y social, producto de una administración con proyección empresarial y solidaria, que responde a las necesidades de los asociados y al cumplimiento del modelo de Gobierno Corporativo como se muestra a lo largo de esta investigación.In line with that defined by the International Organization of Industrial Production Cooperatives, Handicraft and Services, or CICOPA, the CTA worker cooperatives, operate under the principles defined in the cooperative principles and values and management models, where link the individual work of partners and their economic contributions, in order to orient them to the production of goods and services on a self-administration. This research aims to show, through a case study in depth, and in the country to deploy the figure of Corporate Governance for the attainment and achievement of the objectives and organizational goals in a worker cooperative, called Lost (CTA). In this sense Recall (CTA) has been established, achieving economic and social sustainability, the product of an administration with business projections and solidarity that meets the needs of partners and compliance with corporate governance model as shown along of this research

Los efectos de la política de prevención del crimen y la violencia en México

El presente trabajo aborda dos elementos clave de la política de prevención del crimen y la violencia en México. En la primera parte se examina la conformación de la política de prevención en los últimos 10 años. En la segunda sección, se evalúan los efectos del Programa Nacional de Prevención del Delito (PRONAPRED) por medio de la técnica Propensity Score Matching (pareamiento por puntaje de propensión). Con datos a nivel municipal y tomando como variable de resultado la tasa de homicidio y la tasa de lesiones por arma de fuego, encontramos que el PRONAPRED solo tiene efectos significativos en la tasa de homicidio; sin embargo, estos son en la dirección contraria a la esperada. Los resultados de esta investigación muestran que la política de prevención en México requiere de cambios para poder cumplir con los objetivos esperados.

Modelo Credit Scoring PYMES para la medición del riesgo de morosidad de pequeña y mediana empresa : un caso de aplicación en entidad financiera

Proyecto de graduación (Licenciatura en Administración de Empresas. Énfasis en Finanzas) Instituto Tecnológico de Costa Rica, Escuela de Administración de Empresas, 2013.El presente proyecto de graduación consiste en un estudio técnico acerca de la posible existencia de métodos y herramientas que utiliza una entidad financiera para el análisis de riesgo de una empresa PYMES interesada en optar por un crédito empresarial. Así mismo este documento propone una herramienta que concentra los elementos más relevantes en el análisis inicial de un nuevo cliente o persona jurídica potencial para optar por un financiamiento bancario. Dado lo anterior el proyecto se estructura de la siguiente manera: Capítulo I Generalidades de la investigación, Capítulo II Marco Metodológico, Capítulo III Revisión del Estudio del Arte, Capítulo IV Puesta en práctica, Capítulo V Concepción de la MATRIZ SCORING PYMES, Capítulo VI Desarrollo y Análisis Estructural, Capítulo VII Conclusiones y Capitulo VIII Recomendaciones

Mitochondrial dysfunction promoted by Porphyromonas gingivalis lipopolysaccharide as a possible link between cardiovascular disease and periodontitis

Oxidative stress is one of the factors that could explain the pathophysiological mechanism of inflammatory conditions that occur in cardiovascular disease (CVD) and periodontitis. Such inflammatory response is often evoked by specific bacteria, as the lipopolysaccharide (LPS) of Porphyromonas gingivalis is a key factor in this process. The aim of this research was to study the role of mitochondrial dysfunction in peripheral blood mononuclear cells (PBMCs) from periodontitis patients and to evaluate the influence of LPS on fibroblasts to better understand the pathophysiology of periodontitis and its relationship with CVD. PBMCs from patients showed lower CoQ10 levels and citrate synthase activity, together with high levels of ROS production. LPS-treated fibroblasts provoked increased oxidative stress and mitochondrial dysfunction by a decrease in mitochondrial protein expression, mitochondrial mass, and mitochondrial membrane potential. Our study supports the hypothesis that LPS-mediated mitochondrial dysfunction could be at the origin of oxidative stress in periodontal patients. Abnormal PBMC performance may promote oxidative stress and alter cytokine homeostasis. In conclusion, mitochondrial dysfunction could represent a possible link to understanding the interrelationships between two prominent inflammatory diseases: periodontitis and CV

Los métodos para medir la evasión de impuestos: una revisión

La presencia del déficit fiscal en Colombia hace necesario que se estudien alternativas diferentesa la de controlar el gasto. Este trabajo hace un recorrido por las principales investigacionesque se han realizado en varias regiones del mundo, pero especialmente en AméricaLatina, para identificar los métodos más precisos y accesibles, tanto para medir el nivel deevasión, como para conocer la estructura de la misma. De esta manera se pretende identificarherramientas para la construcción de propuestas alternativas, que conduzcan a disminuir y acontrolar la evasión de impuestos nacionales

Pherotypes are driving genetic differentiation within

Abstract Background The boundaries of bacterial species and the mechanisms underlying bacterial speciation are matters of intense debate. Theoretical studies have shown that recombination acts as a strong cohesive force preventing divergence in bacterial populations. Streptococcus pneumoniae populations have the telltale signs of high recombination with competence implicated as the major driving force behind gene exchange. Competence in S. pneumoniae is triggered by a quorum-sensing mechanism controlled by the competence-stimulating peptide pheromone. Results We studied the distribution of the two major pherotypes in the pneumococcal population and their association with serotype, antimicrobial resistance and genetic lineage. Using multilocus sequence data we evaluated pherotype influence on the dynamics of horizontal gene transfer. We show that pherotype is a clonal property of pneumococci. Standard population genetic analysis and multilocus infinite allele model simulations support the hypothesis that two genetically differentiated populations are defined by the major pherotypes. Conclusion Severe limitations to gene flow can therefore occur in bacterial species in the absence of geographical barriers and within highly recombinogenic populations. This departure from panmixia can have important consequences for our understanding of the response of pneumococci to human imposed selective pressures such as vaccination and antibiotic use.</p

The presence of the pilus locus is a clonal property among pneumococcal invasive isolates

Abstract Background Pili were recently recognized in Streptococcus pneumoniae and implicated in the virulence of this bacterium, which led to the proposal of using these antigens in a future pneumococcal vaccine. However, pili were found to be encoded by the rlrA islet that was not universally distributed in the species. We examined the distribution of the pilus islet, using the presence of the rlrA gene as a marker for the locus, among a collection of invasive isolates recovered in Portugal and analyzed its association with capsular serotypes, clusters defined by the pulsed-field gel electrophoretic profiles (PFGE) and multilocus sequence types. Results Only a minority of the isolates were positive for the presence of the rlrA gene (27%). There was a high correspondence between the serotype and the presence or absence of rlrA (Wallace coefficient, W = 0.778). In particular, there was an association between the presence of rlrA and the vaccine serotypes 4, 6B, 9V and 14 whereas the gene was significantly absent from other serotypes, namely 1, 7F, 8, 12B and 23F, a group that included a vaccine serotype (23F) and serotype 1 associated with enhanced invasiveness. Even within serotypes, there was variation in the presence of the pilus islet between PFGE clones and a higher Wallace coefficient (W = 0.939) indicates that carriage of the islet is a clonal property of pneumococci. Analysis of rlrA negative isolates revealed heterogeneity in the genomic region downstream of the rfl gene, the region where the islet is found in other isolates, compatible with recent loss of the islet in some lineages. Conclusion The pilus islet is present in a minority of pneumococcal isolates recovered from human invasive infections and is therefore not an essential virulence factor in these infections. Carriage of the pilus islet is a clonal property of pneumococci that may vary between isolates expressing the same serotype and loss and acquisition of the islet may be ongoing.</p