On the geometry of Abel maps for nodal curves

In this paper we give local conditions to the existence of Abel maps for nodal curves that are limits of Abel maps for smooth curves. We use this result to construct Abel maps for any degree for nodal curves with two components.Comment: 30 pages, 1 figur

Assessing the transportation of liquid fuels in South Africa using multi-criteria decision analysis: a conceptual framework and case study

With the recent unprecedented growth of many African economies, infrastructure investment has been flooding into the continent. Two key areas experiencing large growth in infrastructure development are the transport and energy sectors. This trend also continues to hold true in the South African development framework. The theme of this thesis encompasses both subjects of energy and transportation infrastructure which feature prominently in the countries development plans. When energy is discussed in South Africa, it is usually in the context of power generation and electricity distribution. This study focuses on another key component of the energy sector in the form of liquid fuel. Most of this energy is consumed for transportation purposes. The energy consumption of the transport sector in South Africa is large, totalling around 28% of Total Final Consumption (TFC) in the national energy balances. The bulk of this energy demand (97%) is in the form of liquid fuels, accounting for 84% of the national liquid fuel demand. This thesis focusses on the investigation of a Multi Criteria Decision Analysis (MCDA) model, which can be used to aid decision makers in the planning and assessment of liquid fuel transportation projects. A key feature of this thesis is the incorporation of a stochastic analysis in the MCDA model. There are two key motivations for assimilating a stochastic analysis in this investigation. The first one is the evaluation of incorporating such an analysis in an MCDA, as opposed to a more traditional sensitivity analysis. The second motivation is to assess the value of employing stochastic analysis as an input method for analysing a decision problem, where comprehensive field data can be substituted for a relevant range of simulated data. This thesis proposes a model which integrates the MCDA and stochastic analysis in the hope that it would provide a faster and more cost effective alternative for assessing certain liquid fuel transportation problems

Identifying Unmaintained Projects in GitHub

Background: Open source software has an increasing importance in modern software development. However, there is also a growing concern on the sustainability of such projects, which are usually managed by a small number of developers, frequently working as volunteers. Aims: In this paper, we propose an approach to identify GitHub projects that are not actively maintained. Our goal is to alert users about the risks of using these projects and possibly motivate other developers to assume the maintenance of the projects. Method: We train machine learning models to identify unmaintained or sparsely maintained projects, based on a set of features about project activity (commits, forks, issues, etc). We empirically validate the model with the best performance with the principal developers of 129 GitHub projects. Results: The proposed machine learning approach has a precision of 80%, based on the feedback of real open source developers; and a recall of 96%. We also show that our approach can be used to assess the risks of projects becoming unmaintained. Conclusions: The model proposed in this paper can be used by open source users and developers to identify GitHub projects that are not actively maintained anymore.Comment: Accepted at 12th International Symposium on Empirical Software Engineering and Measurement (ESEM), 10 pages, 201

Molecular mechanisms of sexual development in basidiomycetes: exploring connections with lifestyles

Dissertação para obtenção do Grau de Doutor em BiologiaThis work concerns the investigation of the molecular mechanisms of sexual reproduction in fungi and their possible implication for fungal lifestyles (parasitic vs. saprobic) and for the emergence of asexual fungal lineages. The association between pathogenicity and sexuality is well-known in the basidiomycete plant parasite Ustilago maydis (subphylum Ustilaginomycotina), an economically important smut fungus. However, Ustilago species are phylogenetically interspersed with species of the genus Pseudozyma, which are considered saprobic and asexual. In this work, a study focused on genes involved in determining sexual identity (mating type or MAT genes), showed that Pseudozyma prolifica retains full sexual competence and pathogenicity, being therefore indistinguishable from U. maydis. For other Pseudozyma species, molecular analyses of PRF1, a gene that encodes a master regulator of sexual reproduction in U. maydis, showed no substantial evidence of loss of sexual reproduction. However, some clues were also found suggesting that some Pseudozyma species may be evolving towards a saprobic lifestyle. The earliest derived lineage of Basidiomycota (subphylum Pucciniomycotina) includes also important plant pathogens (rust and anther smut fungi) as well as lineages composed solely of saprobic organisms. Among the latter, the red yeasts of the order Sporidiobolales have the advantage of completing their life cycle in culture media, but have remained very little explored concerning the characterization of mating systems, the identification of MAT genes and the evolutionary relationships between sexual and asexual species. A comprehensive analysis of more than 200 strains belonging to 32 species of the Sporidiobolales indicated that asexuality seems to originate frequently from sexual lineages, but does not seem to persist long enough to form truly asexual species devoid of MAT genes. A more in-depth investigation of the red yeasts Rhodosporidium toruloides and Sporidiobolus salmonicolor allowed the identification for the first time in the Pucciniomycotina of the complete set of MAT genes. A detailed and multidisciplinary characterization of the mating system in the latter species yielded surprising results. A novel mating system that differs substantially from the two mating paradigms in basidiomycetes, the bipolar and tetrapolar systems, was brought to light. Given the basal phylogenetic position of the Pucciniomycotina within the Basidiomycota, this new system designated pseudo-bipolar, constitutes a significant contribution to the study of the evolution of MAT systems in fungi.Fundação para a Ciência e a Tecnologia - PhD grant(SFRH/BD/29580/2006

Men’s artistic gymnastics: is the use of elastic surfaces systematic in the training process?

Em alguns esportes, o espaço de jogo representa o componente sistêmico de maior relevância: esse é o caso da Ginástica Artística (GA). Desse modo, quando nos empenhamos em compreender a lógica interna dessa modalidade precisamos dedicar especial atenção à relação ginasta-aparelho. Observamos uma mudança no paradigma de treinamento em que o uso das Superfícies Elásticas constitui um componente essencial, visando atender às características contemporâneas desse esporte, como a hipervalorização das acrobacias e a maior presença dos elementos ginásticos com “fase aérea”. Nessa oportunidade, analisamos, a partir de estudo de caso de um ginásio de treinamento de alto rendimento de Ginástica Artística Masculina, o emprego de diferentes Superfícies Elásticas (SpE) na preparação dos ginastas. Embora os treinadores reconheçam o papel fundamental das SpE para o desenvolvimento dos ginastas, seu uso cotidiano ainda é restrito a poucos equipamentos e realizado de modo assistemático. Essas dificuldades se devem principalmente à ausência de programas formativos que desenvolvam metodologias específicas e à inexistência de fornecedores de equipamentos nacionais com qualidade certificada pela Federação Internacional de Ginástica.In Artistic Gymnastics, the area (the apparatus) represents the most relevant systemic component. Thus, when one strives to comprehend the internal logic of this sport, the gymnast-apparatus relationship warrants special attention. A change in the training paradigm was observed, showing that the use of Elastic Surfaces (ES) is an essential resource, due to the contemporary features of this sport, such as the hyper-valorisation of acrobatics and a greater presence of flight elements. Through a case study developed in a men’s artistic gymnastics high-performance gymnasium, this study analysed the use of different ES in the training process. Although coaches recognize the importance of ES in training programs, the record of daily activities showed that this use is still limited to select equipment and is not systematic. Such difficulties are due mainly to the lack of educational programs to the development of certain specific methodologies and the non-existence of national equipment suppliers certified by International Gymnastics Federation