Web usage mining for click fraud detection

Estágio realizado na AuditMark e orientado pelo Eng.º Pedro FortunaTese de mestrado integrado. Engenharia Informática e Computação. Faculdade de Engenharia. Universidade do Porto. 201

Meta-análise de metilação de DNA em invertebrados: tendências evolutivas e indicações para avaliação ambiental

The anthropogenic impact in a variety of ecosystems has been increasing significantly in recent decades. This anthropogenic pressure translates into globally spreading phenomena like habitat fragmentation, mass extinction or biodiversity decline, that threaten ecosystem services. The mitigation of such detrimental ecological impacts is largely dependent on our ability to properly assess effects of the pressures on biological systems, i.e., with sufficient resolution levels that allows establishing reliable cause-effect relationships. High-resolution tools to assess these effects have recently been emerging, e.g., tools based in gene expression and the epigenome. The latter is strongly influenced by environmental conditions, with consequences in gene expression. Thus, the epigenome constitutes a new opportunity for the mechanistic understanding of toxic effects of environmental contaminants and for the development of biomarkers of exposure and effect. In this context, the specific objectives of the present dissertation were as follows: (i) to collect reliable genomic data of various invertebrate species representing different environmental compartments; (ii) quantify the distribution of the potential for gene body methylation based on the prevalence of CpG dinucleotides in the genome of each species; (iii) elaborate on the differential ability of invertebrate species to respond or potentially adapt to challenging and/or highly fluctuating environments based on phenotypic plasticity mediated by DNA methylation and/or related mutations; (iv) conclude on the most favourable models to address gene body methylation within an ecotoxicological context. Among the set of 27 species with reliable genomic data publicly available selected for meta-analysis, 11 recorded an observed-to-expected CpG ratio distribution (CpG O/E) that suggest the existence of gene groups with high susceptibility to methylation, and 16 have distributions suggesting that the entire genome is little or very little susceptible to methylation. Patterns of reduced susceptibility to DNA methylation have been identified among phylogenetically closely related species, which supports the theory that DNA methylation may have played a relevant role in species adaptation to new ecological niches, e.g., during the colonization of terrestrial or freshwater environments from primitive marine environments. The concentration of CG dinucleotides in the analysed genomes also allowed to discuss the suitability of different model organisms used in ecotoxicology for the development of biomarkers of exposure or effect based on DNA methylation. In this context, the following species are noteworthy as those presenting higher relative levels of CG dinucleotides in their genome: N. vectensis and T. californicus in the marine environment; D. magna and D. polymorpha in freshwater ecosystems; I. scapularis and H. saltator in the soil compartment; A. albimanus, A. albopictus and N. vitripennis representing aerial species.O impacto humano no ambiente e nos ecossistemas tem aumentado, especialmente nas décadas mais recentes. Esta pressão antropogénica é traduzida em fenómenos que são globais, como fragmentação de habitat, extinção em massa ou declínio da biodiversidade, que ameaçam os serviços dos ecossistemas. A mitigação destes impactos negativos em diferentes ecossistemas é largamente dependente da nossa capacidade para avaliar os efeitos das pressões nos sistemas biológicos com resolução suficiente, permitindo estabelecer relações fidedignas de causa-efeito. Ferramentas de elevada resolução para avaliar estes efeitos têm emergido recentemente, por exemplo, as baseadas na expressão génica e no epigenoma. Este é fortemente influenciado pelas condições ambientais, com consequências na expressão génica. Assim, o epigenoma constitui uma nova oportunidade para a compreensão mecanicista dos efeitos tóxicos dos contaminantes ambientais e para o desenvolvimento de biomarcadores de exposição e efeito. Neste contexto, os objetivos específicos da presente Dissertação foram: (i) recolher dados genómicos relativos a várias espécies de invertebrados representantes de diferentes compartimentos ambientais; (ii) quantificar a distribuição do potencial para metilação de regiões genéticas codificantes nos genomas destes organismos, com base na prevalência de dinucleótidos citosina-guanina (CpG); (iii) elaborar sobre a capacidade diferencial das espécies de invertebrados para responderem ou potencialmente se adaptarem a pressões ou flutuações ambientais, com base na plasticidade fenotípica mediada pela metilação do DNA e/ou mutações relacionadas; (iv) concluir sobre as espécies-modelo mais favoráveis para abordar a metilação de regiões genéticas codificantes num contexto ecotoxicológico. De entre o conjunto de 27 espécies selecionadas para meta-análise com dados genómicos suficientes disponíveis, 11 apresentaram distribuições do rácio entre frequência de CpG observada e esperada (CpG O/E) que sugerem a existência de grupos de genes muito suscetíveis a metilação, e 16 apresentaram distribuições que sugerem que todo o genoma é pouco ou muito pouco suscetível a metilação. Padrões de redução de suscetibilidade à metilação do ADN foram identificados entre espécies filogeneticamente próximas, que apoiam a teoria de que a metilação do DNA poderá ter tido um papel relevante na adaptação das espécies a novos nichos ecológicos, p.ex. durante a colonização de ambientes terrestres ou dulçaquícolas a partir de ambientes primitivos marinhos. A concentração de dinucleótidos CG nos genomas analisados permitiu ainda discutir sobre a adequação de diferentes organismos-modelo usados em ecotoxicologia para o desenvolvimento de biomarcadores baseados na metilação do ADN. Neste contexto, destacam-se as seguintes espécies, como modelos com uma maior quantidade relativa de dinucleótidos CG: N. vectensis e T. californicus no ambiente marinho; D. magna e D. polymorpha em ecossistemas dulçaquícolas; I. scapularis e H. saltator no compartimento solo; A. albimanus, A. albopictus e N. vitripennis para representar espécies aéreas. Complementarmente a esta evidência, a escolha de organismos-modelo neste contexto deve ser guiada pela informação existente sobre as suas respostas ecotoxicológicas ao nível fenotípico.Mestrado em Biologia Aplicad

Multicentric Approach Mechanisms as a Strategy for the Implementation of Public Policies - Reflections in the Context of the Creative Economy

This essay aimed to identify central elements in the field of public policies to allow the proposals of guidelines for the improvement and effectiveness of their designs in the context of Creative Economy aiming at the contribution to the theoretical discussions of the theme From the literary review it was possible to list feasible strategies for sustaining such policies based on the multicentric approach which can strengthen governance processes by making them more participatory and democrati

On phantom thermodynamics with negative temperature

We discuss the thermodynamic properties of the Friedmann-Robertson-Walker universe with dark energy fluids labelled by $\omega=p/\rho<-1/3$. Using the integrability condition, we show that the phantom phase of $w<-1$ can still be thermodynamically allowed even when the temperature takes on negative values because in that case, there exists at least a condition of keeping physical values for $p$ and $\rho$Comment: 8 pages, 1figure, title changed, version to appear in PL

The use of the recognition heuristicas an investment strategy in European stock markets

Purpose – People often face constraints such as a lack of time or information in taking decisions, which leads them to use heuristics. In these situations, fast and frugal rules may be useful for making adaptive decisions with fewer resources, even if it leads to suboptimal choices. When applied to financial markets, the recognition heuristic predicts that investors acquire the stocks that they are aware of, thereby inflating the price of the most recognized stocks. This paper aims to study the profitability against the market of the most recognized stocks in Europe. Design/methodology/approach – In this paper, the authors perform a survey and use Google Trends to study the profitability against the market of the most recognized stocks in Europe. Findings – The authors conclude that a recognition heuristic portfolio yields poorer returns than a market portfolio. In contrast, from the data collected on Google Trends, weak evidence was found that strong increases in companies monthly search volumes may lead to abnormal returns in the following month. Research limitations/implications – The applied investment strategy does not account for transaction costs, which may jeopardize its profitability given the fact that it is necessary to revise the portfolio on a monthly basis. Despite the results obtained, they are useful to understanding the performance of recognition heuristic strategies over a comprehensive time horizon, and it would be interesting to depict its viability during different market conditions. This analysis could provide additional information about a preferable scenario for employing our strategies and, ultimately, enhance the profitability of recognition heuristic strategies. Practical implications – Through the exhaustive analysis performed here on the recognition heuristic in the European stock market, it is possible to conclude that no evidence was found for the viability of exploring this type of strategy. In fact, the investors would always gain better returns when adopting a passive investment strategy. Therefore, it would be wise to assume that the European market presents at least a degree of efficiency where no investment would yield abnormal returns following the recognition heuristic. Originality/value – The main objective of this paper is to study the performance of the recognition heuristic in the financial markets and to contribute to the knowledge in this field. Although many authors have already studied this heuristic when applied to financial markets, there is a lack of consensus in the literature.Propósito – Las personas a menudo enfrentan limitaciones como la falta de tiempo o de información para tomar decisiones, lo que las lleva a utilizar heurísticas. En estas situaciones, reglas rápidas y frugales pueden ser útiles para tomar decisiones adaptativas con menos recursos, incluso si conducen a elecciones subóptimas. Cuando se aplica a los mercados financieros, la heurística de reconocimiento predice que los inversores adquieren las acciones que conocen, inflando así el precio de las acciones más reconocidas. Este trabajo tiene como objetivo estudiar la rentabilidad frente al mercado de las acciones más reconocidas de Europa. Diseño/metodología/enfoque: en este artículo, los autores realizan una encuesta y utilizan Google Trends para estudiar la rentabilidad frente al mercado de las acciones más reconocidas de Europa. Hallazgos – Los autores concluyen que una cartera heurística de reconocimiento produce peores rendimientos que una cartera de mercado. Por el contrario, a partir de los datos recopilados en Google Trends, se encontró evidencia débil de que los fuertes aumentos en los volúmenes de búsqueda mensuales de las empresas pueden generar retornos anormales en el mes siguiente. Limitaciones/implicaciones de la investigación – La estrategia de inversión aplicada no tiene en cuenta los costos de transacción, lo que puede poner en peligro su rentabilidad dado que es necesario revisar la cartera mensualmente. A pesar de los resultados obtenidos, son útiles para comprender el desempeño de las estrategias heurísticas de reconocimiento en un horizonte temporal integral, y sería interesante representar su viabilidad en diferentes condiciones de mercado. Este análisis podría proporcionar información adicional sobre un escenario preferible para emplear nuestras estrategias y, en última instancia, mejorar la rentabilidad de las estrategias heurísticas de reconocimiento. Implicaciones prácticas – A través del análisis exhaustivo realizado aquí sobre la heurística de reconocimiento en el mercado de valores europeo, es posible concluir que no se encontró evidencia de la viabilidad de explorar este tipo de estrategia. De hecho, los inversores siempre obtendrán mejores rendimientos al adoptar una estrategia de inversión pasiva. Por lo tanto, sería prudente suponer que el mercado europeo presenta al menos un grado de eficiencia en el que ninguna inversión produciría rendimientos anormales siguiendo la heurística de reconocimiento. Originalidad/valor – El principal objetivo de este artículo es estudiar el desempeño de la heurística de reconocimiento en los mercados financieros y contribuir al conocimiento en este campo. Aunque muchos autores ya han estudiado esta heurística aplicada a los mercados financieros, existe una falta de consenso en la literatura

Analysis of factors and drivers in graduates success among Portugal, India and Italy –defining success

Success emerges as a very wide concept. This project aims to understand the factors and drivers in graduates’ success across Portugal, India and Italy. The present research is focused on the factors that account for these graduates’ definition of success. The study analyzed the topic following an exhaustive exploratory research, which started with the collection of secondary data to support and better understand the topic, followed by a valuable qualitative research which used in-depth interviews to obtain rich insights. These first two steps retrieved the guidelines to create a questionnaire for the quantitative component. After analyzing the results and establish the most adequate relationships, it was found that this generation of business graduates identify success as being composed by career and personal achievement, albeit they highly associate overall success as a well balanced and meaningful life, in detriment to material goods. These results are of great value to the higher education institutions, who have the power to interfere in these factors and better tailor their services offer to students’ expectations and aspirations