Metric for seleting the number of topics in the LDA Model

The latest technological trends are driving a vast and growing amount of textual data. Topic modeling is a useful tool for extracting information from large corpora of text. A topic template is based on a corpus of documents, discovers the topics that permeate the corpus and assigns documents to those topics. The Latent Dirichlet Allocation (LDA) model is the main, or most popular, of the probabilistic topic models. The LDA model is conditioned by three parameters: two Dirichlet hyperparameters (α and β ) and the number of topics (K). Determining the parameter K is extremely important and not extensively explored in the literature, mainly due to the intensive computation and long processing time. Most topic modeling methods implicitly assume that the number of topics is known in advance, thus considering it demands an exogenous parameter. That is annoying, leaving the technique prone to subjectivities. The quality of insights offered by LDA is quite sensitive to the value of the parameter K, and perhaps an excess of subjectivity in its choice might influence the confidence managers put on the techniques results, thus undermining its usage by firms. This dissertation’s main objective is to develop a metric to identify the ideal value for the parameter K of the LDA model that allows an adequate representation of the corpus and within a tolerable elapsed time of the process. We apply the proposed metric alongside existing metrics to two datasets. Experiments show that the proposed method selects a number of topics similar to that of other metrics, but with better performance in terms of processing time. Although each metric has its own method for determining the number of topics, some results are similar for the same database, as evidenced in the study. Our metric is superior when considering the processing time. Experiments show this method is effective.As tendências tecnológicas mais recentes impulsionam uma vasta e crescente quantidade de dados textuais. Modelagem de tópicos é uma ferramenta útil para extrair informações relevantes de grandes corpora de texto. Um modelo de tópico é baseado em um corpus de documentos, descobre os tópicos que permeiam o corpus e atribui documentos a esses tópicos. O modelo de Alocação de Dirichlet Latente (LDA) é o principal, ou mais popular, dos modelos de tópicos probabilísticos. O modelo LDA é condicionado por três parâmetros: os hiperparâmetros de Dirichlet (α and β ) e o número de tópicos (K). A determinação do parâmetro K é extremamente importante e pouco explorada na literatura, principalmente devido à computação intensiva e ao longo tempo de processamento. A maioria dos métodos de modelagem de tópicos assume implicitamente que o número de tópicos é conhecido com antecedência, portanto, considerando que exige um parâmetro exógeno. Isso é um tanto complicado para o pesquisador pois acaba acrescentando à técnica uma subjetividade. A qualidade dos insights oferecidos pelo LDA é bastante sensível ao valor do parâmetro K, e pode-se argumentar que um excesso de subjetividade em sua escolha possa influenciar a confiança que os gerentes depositam nos resultados da técnica, prejudicando assim seu uso pelas empresas. O principal objetivo desta dissertação é desenvolver uma métrica para identificar o valor ideal para o parâmetro K do modelo LDA que permita uma representação adequada do corpus e dentro de um tempo de processamento tolerável. Embora cada métrica possua método próprio para determinação do número de tópicos, alguns resultados são semelhantes para a mesma base de dados, conforme evidenciado no estudo. Nossa métrica é superior ao considerar o tempo de processamento. Experimentos mostram que esse método é eficaz

The role of muscle-enriched microRNAs as markers of failed myocardial reperfusion

PhD ThesisThe advent of primary percutaneous coronary intervention (PPCI) for the treatment of ST-elevation myocardial infarction (STEMI) has significantly reduced mortality rates in this population. However, coronary artery disease remains a leading cause of morbidity and death worldwide. This may be a consequence of inadequate myocardial reperfusion despite reestablishment of coronary artery patency following PPCI. Failed myocardial reperfusion is associated with worse prognosis but usually passes undetected, as current diagnostic methods are not routinely available. The aim of my PhD was to investigate the plasmatic kinetics of muscle-enriched micro ribonucleic acids (microRNAs) following PPCI as well as their association with cardiac damage, function and the phenomenon of failed myocardial reperfusion. Firstly, I retrospectively analysed the prognostic importance of cardiac troponins, which are established markers of myocardial injury, in a large cohort (n = 4,914) of STEMI patients treated with PPCI. Troponin levels routinely measured at 12 hours post-reperfusion were not associated with mortality, highlighting the need for identification of new prognostic markers in this population. To overcome methodological issues for microRNA quantification in plasma samples from STEMI patients, I validated an endogenous microRNA (miR-425-5p) as a control for realtime polymerase chain reaction (RT-qPCR) data normalisation. Subsequent microRNA screening and kinetics analyses revealed that the muscle-enriched miR-1 and miR-133b are rapidly released into the circulation following PPCI, reaching an initial peak at 30min and a second peak at 90min post-PCI. The presence of a second peak seemed to be associated with a higher index of microvascular resistance, a surrogate marker of failed myocardial reperfusion. In addition, miR-1 and miR-133b levels at 30min and 90min post-PPCI were associated with microvascular obstruction measured by cardiac MRI, another parameter of unsuccessful myocardial reperfusion. Finally, miR-1 and miR-133b levels were significantly elevated in a subgroup of STEMI patients with larger infarcts and worse left ventricular function and remodelling 3 months after PPCI. These findings suggest a potential new role for muscle-enriched microRNAs as tools for early identification of failed myocardial reperfusion and prognostic stratification in STEMI patients.CAPES Foundation, Brazilian Ministry of Educatio

Estudo comparativo para gestão das atividades de manutenção e reabilitação de pavimentos em SIG

Num contexto de sustentabilidade urbana, as ruas pavimentadas representam um valioso patrimônio, cuja conservação é essencial para garantir diversos objetivos econômicos, sociais e ambientais. Quando os custos de conservação são maiores que os recursos disponíveis, as prioridades podem ser definidas com base em um conjunto de critérios técnicos, mensuráveis ou aspectos relativos a condições subjetivas e dependentes do contexto de cada cidade. O objetivo geral deste trabalho é comparar cenários gerados com base em diferentes mapas de prioridades, desenvolvidos através de um modelo que recorre à Análise Multicriterial e ao Sistema de Informação Geográfica. No estudo de caso foi adotada uma base de dados georreferenciados da cidade de São Carlos-SP, com as características associadas às ruas pavimentadas. Pode-se destacar a flexibilidade quando se insere ou se retira algum critério da estrutura de decisão, aliada à facilidade de trabalhar com mapas representativos de alternativas que condicionam a análise

O papel da violência escolar no abandono da carreira docente: proposta de uma matriz analítica

A violência escolar é tema de pesquisa no Brasil desde os anos 1980 e está entre os principais desafios enfrentados pela educação no país. O objetivo central deste artigo é discutir o papel das experiências de violência escolar no abandono da carreira docente. Para isso, entrevistamos uma ex-professora que, assim como muitas outras, abandonou a docência após sofrer exaustão emocional em decorrência das violências sofridas na escola. A partir da literatura e da investigação narrativa dos relatos da ex-docente, consideramos importante reconhecer que a violência escolar é uma experiência objetivamente regulada e subjetivamente vivida. Enquanto realidade objetivamente regulada, a violência pode ser classificada como crime, incivilidade e violência simbólica. Como experiência subjetivamente vivida, podemos distinguir diferentes graus de banalização que, no sentido empregado por Arendt, designa a superfluidade e a superficialidade das relações humanas em sistemas totalitários. Juntas, as duas dimensões, objetiva e subjetiva, formam o que denominamos matriz da violência escolar, uma ferramenta analítica potencialmente útil para investigar como a violência influencia os percursos profissionais docentes. Os resultados ainda permitiram entender como os diversos agentes escolares (alunos, diretor e a própria professora) participam da produção da violência escolar e como as partes envolvidas têm percepções conflitantes. Por fim, implicações na formação de professores são discutidas.School violence has been a research topic in Brazil since the 1980’s and it is one of the main challenges the national education system faces. The central objective of this article is to discuss the role of the experiences of school violence in the abandonment of the teaching career. To this end, we interviewed a former teacher who – as many others - had given up teaching after suffering emotional exhaustion due to the violence experienced at school. Based on literature and on the narrative inquiry of the former teacher’s reports, we considered it important to realize that school violence is an experience which is objectively regulated and subjectively experienced. While an objectively regulated reality, violence can be classified as a crime, incivility and symbolic violence. As a subjectively lived experience, we can distinguish various levels of trivialization that – in Arendt’s sense – designate the superfluity and the superficiality of the social relationships in totalitarian systems. Together, both dimensions – objective and subjective – constitute what we term as the school violence matrix, which is an analytical tool that is potentially useful for investigating how the violence can influence the paths of teaching professionals. Also, the results enabled us to understand how the several school agents (students, the principal and even the teacher) participate in the production of school violence and how the parties involved have conflicting perceptions. At last, implications for the teachers’ education are discussed

Exchange-coupling in thermal annealed bimagnetic core/shell nanoparticles

In this study we demonstrate that the effective coupling of the magnetic phases in core/shell nanoparticles can be promoted by an appropriate thermal annealing. In this way, the magnetization thermal stability of the hard ferrimagnetic CoFe2O4 oxide can be increased up to room temperature when coupled to a CoO antiferromagnetic core in an inverse core/shell structure. In addition, the results show that, being encapsulated in a ∼2 nm thick CoFe2O4 shell, the CoO core is successfully protected against oxidation which is crucial for the effectiveness of the magnetic coupling at the interface.Fil: Lavorato, Gabriel Carlos. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lima, Enio Junior. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zysler, Roberto Daniel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Winkler, Elin Lilian. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Bourdieu en la educación científica: consecuencias para la enseñanza y la investigación

 A lo largo de las últimas décadas, el desarrollo y la consolidación de un abordaje sociocultural a la educación científica han dado lugar a un creciente interés por referencias de ámbitos como la sociología de la ciencia y la sociología de la educación del sociólogo francés Pierre Bourdieu (1930 - 2002). Con el propósito general de contribuir al avance de la apropiación de la obra de Bourdieu por parte de la investigación en educación científica, el presente artículo presenta algunas de las ideas más importantes de este autor y discute sus consecuencias para la enseñanza de ciencias y su investigación.

Aplicação web para monitoramento e emissão de boletins de alerta da ferrugem do cafeeiro utilizando árvores de decisão.

A ferrugem, causada pelo fungo Hemileia vastatrix Berk. et Br., é a principal doença do cafeeiro em todo o mundo, causando prejuízos de 35% em média e podendo chegar a mais de 50% de perda na produção (ZAMBOLIN, et al., 2002). Para esse tipo de doença, existem diversos modelos de alerta, porém poucos foram validados e não se tem registro de uso continuado. A partir disso, este trabalho descreve uma aplicação desenvolvida para analisar e informar o risco de epidemias da ferrugem do cafeeiro, no âmbito de estações de avisos fitossanitários da Fundação PROCAFÉ, localizadas nos municípios de Boa Esperança, Carmo de Minas e Varginha, no Estado de Minas Gerais

Temperature increase impairs recognition among nestmates in the social wasp Polybia paulista H. von Ihering, 1896 (Vespidae: Polistinae: Epiponini)

Cuticular hydrocarbons (CHCs) of most terrestrial arthropods primarily serve as a protective barrier against desiccation and infection. Throughout evolution, these compounds have acquired another fundamental function: the exchange of signals during interactions between nestmates. However, even though cuticular hydrocarbons perform a dual function in social insects, little is known about the effect(s) of one function on the other in social insects, and no study has evaluated this relationship in social wasps. Therefore, the present study tests the hypothesis that the level of aggressiveness presented during induced encounters between nestmates of Polybia paulista who were subjected to different conditions temperature is different than between nestmates who remained under the same temperature conditions. If the hypothesis is confirmed, it is likely because the cuticle of the wasps that had been exposed to temperature variation adjusted to these conditions leading them not to recognize the cuticular chemical signature of their colony. To test this hypothesis, workers were exposed to temperature variation in a BOD chamber and then subjected to encounters with workers who were maintained at a constant temperature of 24℃. We also used control groups to evaluate the effect of isolation alone among the groups. According to our results, our hypothesis was confirmed, the level of aggressiveness presented between nestmates who were exposed to temperature variation and those who remained at 24℃ was significantly higher than the levels of aggressiveness presented between nestmates who remained isolated but under constant temperature during the same period, in some cases, it was similar to the aggressiveness presented in encounters between wasps from different colonies. During these encounters, wasps performed alarm behavior, bites, and stings not seen during encounters between wasps that remained under the same temperature, but in isolated groups. The lack of aggressive behavior under isolated conditions indicates that isolation had no effect on chemical recognition signature. These results suggest that temperature variation may have caused some change in the cues that allow recognition between nestmates. On the other hand, these results were not caused by isolation or stress generated by the study design and difference in the CHC profile of workers, as described in the literature, is consistent with our results

Probing the two-scale-factor universality hypothesis by exact rotation symmetry-breaking mechanism

We probe the two-scale factor universality hypothesis by evaluating, firstly explicitly and analytically at the one-loop order, the loop quantum corrections to the amplitude ratios for O($N$) $\lambda\phi^{4}$ scalar field theories with rotation symmetry-breaking in three distinct and independent methods in which the rotation symmetry-breaking mechanism is treated exactly. We show that the rotation symmetry-breaking amplitude ratios turn out to be identical in the three methods and equal to their respective rotation symmetry-breaking ones, although the amplitudes themselves, in general, depend on the method employed and on the rotation symmetry-breaking parameter. At the end, we show that all these results can be generalized, through an inductive process based on a general theorem emerging from the exact calculation, to any loop level and physically interpreted based on symmetry ideas.Comment: 17 pages, 3 figure