Parametrization and penalties in spline models with an application to survival analysis

In this paper we show how a simple parametrization, built from the definition of cubic splines, can aid in the implementation and interpretation of penalized spline models, whatever configuration of knots we choose to use. We call this parametrization value-first derivative parametrization. We perform Bayesian inference by exploring the natural link between quadratic penalties and Gaussian priors. However, a full Bayesian analysis seems feasible only for some penalty functionals. Alternatives include empirical Bayes methods involving model selection type criteria. The proposed methodology is illustrated by an application to survival analysis where the usual Cox model is extended to allow for time-varying regression coefficients

THE USE of CONSORTIA for the INTERNATIONALIZATION of FIRMS – MOTA-ENGIL CASE STUDY

Internationalization has been widely studied throughout the years. Broadly, it has been predicted as irrevocable and having increasing impact on firm-related strategy. Within entry modes, consortium, has not received as much attention as others. Hence, it seems important to understand how this specific entry mode allows the entrance of firms in the international markets. This study intends to answer the question of “how” to internationalize, anticipating the consortium as the most feasible way for construction firms to enter certain markets. The reasons that determine its choice concern the specificness of the projects, markets and of the firm. In the first part of the study, we review the existent literature on consortia as an entry mode and as a tool of internationalization used by construction firms. Through this review we build a framework that reveals the motivations that lead to this choice. In the second part, we present the case study of Mota-Engil, as a potential source of valuable information which may contribute to the understanding of the phenomenon under study. This case study corroborates the motivations found to create consortia. The paper closes with its contributions, limitations and suggestions for future researches.consortia, internationalization, cooperation, construction

Comparison of cloud height and depth from atmospheric modelling and ceilometer measurements

In the current study, the cloud base height obtained from the ceilometer measurements, in Evora (south of Portugal), are compared with the results obtained from atmospheric modelling. The atmospheric model adopted is the nonhydrostatic MesoNH model, initiated and forced by ECMWF (European Centre for Medium-Range weather Forecasts) analyses. Also the simulated cloud depth results are presented. The availability of mesoscale modelling for the region, as well as the cloud local vertical distributions obtained from the ceilometer, provide a good opportunity to compare cloud base height and estimate the errors associated. From the obtained results it is possible to observe that the simulated cloud base height values are in good agreement with the correspondent values obtained from the ceilometer measurements

Hormona estrogénio (B- Estradiol) e de testosterona, como fatores responsáveis por alterações no perfil lipídico e composição corporal, em jovens do sexo masculino que realizam atividade física vigorosa

INTRODUÇÃO: As doenças cardiovasculares, são um problema à escala mundial tornando-se imperativo adotar medidas preventivas. A prática da atividade física e uma alimentação equilibrada têm sido apontadas como estratégias para adquirir benefícios cardiovasculares OBJETIVO: Verificar a influência da Hormona Estrogénio (E2) e de Testosterona (T), no perfil lipídico e composição corporal, em atletas de alta competição do sexo masculino, por ser o género com maior prevalência de doença cardiovascular. METODOLOGIA: Foram selecionados 42 indivíduos do sexo masculino, dos quais 20 são jogadores de futebol profissionais (15-18 anos) e pertencem ao grupo de desportistas (GD) e como grupo controlo (GC), 22 alunos da universidade (18-28 anos), onde 59.09% dos alunos tinha um estilo de vida sedentário e 40.9% eram suficientemente ativos. O GD treina 2 vezes por dia, 4 vezes por semana (duração entre os 60 e 90 minutos cada), e disputam um jogo de futebol ao fim de semana. Estes atletas são igualmente sujeitos a um controlo dietético. Foram avaliadas medidas antropométricas e realizadas analises clinicas. No GC foi aplicado o IPAQ.RESULTADOS: Encontraram-se diferenças significativas entre os grupos, principalmente nas pregas cutâneas, abdominal e subescapular (GD <GC), no perímetro da cintura (GD<GC) no perfil lipídico (GD< GC) nos triglicéridos e HDL-C e nos níveis de T e E2 (GD>GC). Verificamos uma forte correlação entre nível de atividade física e de T e significativa entre o aumento do E2 e o exercício. Forte correlação entre o aumento dos níveis de T e a redução das pregas subescapular e abdominal e perímetro da cintura. CONCLUSÕES: Os resultados obtidos no presente estudo sugerem que a prática regular da atividade física vigorosa melhora os níveis de composição corporal, particularmente na redução da gordural abdominal e perfil lipidico, como verificado no GC, através do aumento dos níveis de T. Resultados que vão de encontro as evidencias cientificas de indivíduos que pratiquem, regularmente, atividade física vigorosa numa relação de dose-efeito adquirem benefícios cardiovasculares reduzindo o risco de mortalidade. (Teramoto et al 2009; Tompson et al 2007); Abstract: Estrogen (β-estradiol) and Testosterone hormones as responsible factors for, changes in lipid profile and body composition in young male who practice vigorous physical exercise. Background: Cardiovascular diseases are a worldwide problem, making it imperative to adopt preventive measures. The practice of physical activity and a balanced diet have been identified as strategies to acquire cardiovascular benefits. OBJECTIVE: Determine the changes in hormone, testosterone (T) and estrogen (E2) levels, resulting from the regular practice of vigorous physical activity and its influence on body composition and lipid profiles in male athletes, for being the kind with a higher prevalence of cardiovascular disease, to be the genre with a higher prevalence of cardiovascular disease. METHODS: In this study where recruited 42 male participants 20 of them professional soccer players (SG) (age 15-28 years) and as control group (CG) 22 students (aged 18-28 years), where 59.09% of the students had a sedentary lifestyle, and 40.9% were sufficiently active.The SG workout two times a day, 4 times a week (duration between 60 and 90 minutes each), and competing in football match`s at the weekend. The SG is also subject to a medical diet control. Anthropometric evaluation body composition and clinical analysis where used to determinate the lipid profile and the hormone levels. IPAQ in CG. RESULTS: There were significant differences between groups mainly in abdominal and subscapular skinfolds (SG<CG), waist circumference (SG<CG), in the lipid profile the triglycerides (SG<CG) and HDL- C levels (CG>SG) and in the levels of T and E2 (SG>CG). We noticed a strong correlation between increase physical activity and the levels of T and significant increase among the E2 levels with exercise. There`s a strong correlation between the increase of T levels and the reduction of subscapular, abdominal skinfolds and waist circumference. CONCLUSIONS: The results of the present study suggest that vigorous physical activity have improved the body composition, particularly in the reduction of central fat, in SG and here lipid profile by the increased levels of T. The findings support the evidence that individuals who practice vigorous physical activity in a relationship of "dose-effect" acquire additional benefits in reducing the risk of mortality (Teramoto et al 2009; Tompson et al 2007)

Penalized spline models and applications

Penalized spline regression models are a popular statistical tool for curve fitting problems due to their flexibility and computational efficiency. In particular, penalized cubic spline functions have received a great deal of attention. Cubic splines have good numerical properties and have proven extremely useful in a variety of applications. Typically, splines are represented as linear combinations of basis functions. However, such representations can lack numerical stability or be difficult to manipulate analytically. The current thesis proposes a different parametrization for cubic spline functions that is intuitive and simple to implement. Moreover, integral based penalty functionals have simple interpretable expressions in terms of the components of the parametrization. Also, the curvature of the function is not constrained to be continuous everywhere on its domain, which adds flexibility to the fitting process. We consider not only models where smoothness is imposed by means of a single penalty functional, but also a generalization where a combination of different measures of roughness is built in order to specify the adequate limit of shrinkage for the problem at hand. The proposed methodology is illustrated in two distinct regression settings

Workshop em Ciências da Terra e do Espaço - Livro de Atas

O presente livro foi produzido no âmbito da unidade curricular Seminário do programa de Doutoramento em Ciências da Terra e do Espaço (DCTE) e do Mestrado em Ciências da Terra, da Atmosfera e do Espaço (MCTAE), que incluiu a organização da edição de 2018 do Workshop em Ciências da Terra e do Espaço da Universidade de Évora (WCTE2018). Neste volume estão reunidos os artigos de investigação produzidos pelos estudantes que frequentam a referida unidade curricular. O WCTE assume-se, desde a sua primeira edição em 2013, como um espaço de partilha de conhecimento e treino de comunicação em ciência. Nesse sentido, procura proporcionar aos estudantes que frequentam a Unidade de Seminário uma experiência efetiva não apenas na preparação e apresentação de comunicações orais e artigos de investigação, mas também na organização do próprio evento. Na edição do WCTE2018, que ocorreu no dia 10 de janeiro, foram submetidos e apresentados 9 trabalhos, que abrangem as várias temáticas que dos cursos MCTAE e DCTE