GRASP Heuristics for the stochastic weighted graph fragmentation problem

Critical nodes play a major role in network connectivity. Identifying them is important to design efficient strategies to prevent malware or epidemics spread through a network. In this context, the Stochastic Weighted Graph Fragmentation Problem (SWGFP) is a combinatorial optimization problem that belongs to the N P − Complete class. Its objective consists in minimizing the impact of a random attack on a singleton, choosing appropiately a set of nodes to immunize given a restricted budget. In the SWGFP, it is assumed that the attack follows a known probability law and that it affects the whole connected component of the attacked node. In this thesis, a GRASP enriched with Path Relinking algorithm is developed to solve the SWGFP. Its performance is studied under three attack scenarios and compared with a GRASP variant that was previously developed in literature and with a Random heuristic for the problem that picks a set of nodes uniformly at random. Computational experiments show that the algorithm based on Independent Sets which is developed in this thesis, outperforms the other two, with lower expected loss scores and higher robustness.Los nodos críticos juegan un rol fundamental en la conectividad de las redes. Su identificación es importante para el diseño de estrategias eficientes para prevenir que tanto un software malicioso como una epidemia se propaguen por la red. En este contexto, el Stochastic Weighted Graph Fragmentation Problem (SWGFP) es un problema de optimización combinatoria perteneciente a la clase de problemas NP−Completos. El objetivo consiste en miniminizar el impacto de un ataque aleatorio en un nodo de la red, seleccionando adecuadamente nodos a inmunizar con un presupuesto acotado. En el SWGFP se asume que el ataque sigue una ley de probabilidad conocida en los nodos, y que afecta a toda la componente conexa del nodo seleccionado. En esta tesis se desarrolla una solución GRASP enriquecida con Path-Relinking para abordar el SWGFP. Se estudia el rendimiento de la propuesta ante tres escenarios de ataque, en comparación con una variante de GRASP anteriormente desarrollada de la literatura y una heurística aleatoria o Random para el problema en la cual los nodos son elegidos al azar. Los experimentos computacionales muestran que el algoritmo basado en Conjuntos Independientes que se desarrolla en esta tesis, presenta un mejor desempeño que los dos restantes, con valores inferiores del número esperado de pérdidas y mayor robustez

A dynamic model for rumors spread with communication costs

In this article we start by reviewing some mathematical models for the spreadof rumors. We mention some studies carried out using graphs, stochastic andprobabilistic models and also some epidemic like and evolutionary models.We analyze a repeated game with the replicator dynamics for the spread ofa rumor in a society conformed by an informed population about a rumorthat communicates the rumor to another population. The rumor can becommunicated in its original form or with the opposite content. We comparethe results obtained when only social costs are involved with the case whenalso communication costs are present.Fil: Accinelli , Elvio. Universidad Autónoma de San Luis Potosí; MéxicoFil: Quintas, Luis Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; ArgentinaFil: Muñiz, Humberto. Universidad Autónoma de San Luis Potosí; MéxicoFil: Rosenstock, Nicole. Universidad Autónoma de San Luis Potosí; Méxic

El índice de actividad individual de los estudiantes en EVA y sus rendimientos académicos: el caso de Bioestadística Veterinaria

La suspensión de actividades presenciales en la Universidad de la República por la pandemia de COVID-19 llevó a que los espacios virtuales de aprendizaje se volvieran esenciales en la enseñanza y el aprendizaje universitario. Bioestadística I, curso de primer año de la carrera de Veterinaria, se impartió enteramente de manera remota a través de la plataforma Moodle de la Facultad de Veterinaria (Entorno Virtual de Aprendizaje [EVA]). En este trabajo se analiza la información que proporciona EVA y se la relaciona con el rendimiento de los estudiantes. El curso registró un total de 825 estudiantes matriculados en EVA. Entre el 50 % y el 70 % de los estudiantes ingresaron todas las semanas al curso, con una actividad mínima durante los fines de semana. El índice de actividad individual (IAI), definido en función de los días que el estudiante accedió a la plataforma sobre el total de días del curso, permitió cuantificar la actividad de los alumnos y evaluar su relación con el desempeño académico mediante una regresión lineal. El IAI mostró una asociación directa, positiva y significativa con el resultado final obtenido por los estudiantes. También se analizan los resultados de los rendimientos académicos de esta generación en aspectos relativos a la desvinculación, ganancia y promoción del curso; se encontró que la modalidad a distancia tuvo valores de desvinculación similares a los registrados en los años anteriores con clases presenciales. La información proporcionada por EVA es clave para poder evaluar el impacto de la pandemia y para mejorar las próximas ediciones del curso.The suspension of face-to-face activities in the Universidad de la República caused by the COVID-19 pandemic, made virtual learning spaces essential for university teaching and learning. Biostatistics 1, a first-year Veterinary course, was entirely taught remotely through the Moodle platform of the Faculty of Veterinary Medicine (Entorno Virtual de Aprendizaje [EVA]). In this study, the information provided by EVA was analyzed and associated with the students’ performance. A total of 825 students were enrolled in the course on EVA. Between 50 % and 70 % of the students entered the course every week, with minimal activity on the weekends. The Individual Activity Index (IAI), defined as the days that the student accessed the platform over the total days of the course, allowed to quantify the activity of the students and correlate that value to their academic performance through a linear regression. The IAI showed a direct, positive and significant association with the final result obtained by the students. The results of the academic performance of this generation were also analyzed in aspects related to disengagement, gain and promotion of the course, finding that the on-line modality had disengagement values similar to those registered in previous years with face-to-face classes. The information provided by EVA is key to be able to assess the impact of the pandemic and to improve the next editions of the course

Ancient proteins from ceramic vessels at Çatalhöyük West reveal the hidden cuisine of early farmers

The analysis of lipids (fats, oils and waxes) absorbed within archaeological pottery has revolutionized the study of past dietary diets and culinary practices. However, this technique can lack taxonomic and tissue specificity and is often unable to disentangle signatures resulting from the mixing of different food products. Here, we extract ancient proteins from ceramic vessels from the West Mound of the key early farming site of Çatalhöyük in Anatolia, revealing that this community processed mixes of cereals, pulses, dairy and meat products, and that particular vessels may have been reserved for specialized foods (e.g., cow milk and milk whey). Moreover, we demonstrate that dietary proteins can persist on archaeological artefacts for at least 8000 years, and that this approach can reveal past culinary practices with more taxonomic and tissue-specific clarity than has been possible with previous bio-molecular techniques

Women and ARVâ based prevention: opportunities and challenges

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138349/1/jia29419.pd

Climate and land-use changes effects on the distribution of a regional endemism: Melanophryniscus sanmartini (Amphibia, Bufonidae)

ABSTRACT Amphibians are the most threatened vertebrate group according to the IUCN. Land-use and land cover change (LULCC) and climate change (CC) are two of the main factors related to declining amphibian populations. Given the vulnerability of threatened and rare species, the study of their response to these impacts is a conservation priority. The aim of this work was to analyze the combined impact of LULCC and CC on the regionally endemic species Melanophryniscus sanmartini Klappenbach, 1968. This species is currently categorized as near threatened by the IUCN, and previous studies suggest negative effects of projected changes in climate. Using maximum entropy methods we modeled the effects of CC on the current and mid-century distribution of M. sanmartini under two IPCC scenarios - A2 (severe) and B2 (moderate). The effects of LULCC were studied by superimposing the potential distribution with current land use, while future distribution models were evaluated under the scenario of maximum expansion of soybean and afforestation in Uruguay. The results suggest that M. sanmartini is distributed in eastern Uruguay and the south of Brazil, mainly related to hilly and grasslands systems. Currently more than 10% of this species' distribution is superimposed by agricultural crops and exotic forest plantations. Contrasting with a recent modelling study our models suggest an expansion of the distribution of M. sanmartini by mid-century under both climate scenarios. However, despite the rise in climatically suitable areas for the species in the future, LULCC projections indicate that the proportion of modified habitats will occupy up to 25% of the distribution of M. sanmartini. Future change in climate conditions could represent an opportunity for M. sanmartini, but management measures are needed to mitigate the effects of habitat modification in order to ensure its survival and allow the eventual expansion of its distribution