68 research outputs found

    LMATE: An Innovative Bachelor Degree Connecting Mathematics And Industry

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    The bachelor degree in Mathematics Applied to Technology and Enterprise (LMATE) has an innovative structure, working in partnership with industry, involving a transdisciplinarity curriculum plan, with a solid mathematical base including extensive knowledge in statistics, optimization, modeling and programming (Python, R, etc.), along with training in engineering, physics and management. LMATE presents three differences in relation to other applied mathematics portuguese bachelors degrees: it was constructed upside down towards the usual, once partner entities (enterprises, public entities and research centers) were consulted on relevant mathematical contents to solve their problems, instead of being created exclusively by the academy; in its curricular plan has optional curricular units from several engineering areas; and is the only bachelor degree in applied mathematics that has an internship integrated. As LMATE performance evaluation measures the following can be listed: the number of partner entities has increased to 37 currently; demand has been far greater than the offer of vacancies, reaching around 800%; average entry grades have been increasing (from 12.6 to 15.2); and more than 70 of the 176 students who entered in the six years of LMATE have graduated, having done internships in partner entities. Based on a follow-up study of students who have already finished LMATE to assess the quality of the knowledge acquired and its employability, it is concluded that many of finalists enroll in master\u27s degrees, the majority just after LMATE; others enter the labor market straight away, but all feel that LMATE provided them with adequate preparation

    An Extension of Gompertzian Growth Dynamics Weibull and Frechet Models

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    In this work a new probabilistic and dynamical approach to an extension of the Gompertz law is proposed. A generalized family of probability density functions, designated by Beta* (p, q), which is proportional to the right hand side of the Tsoularis-Wallace model, is studied. In particular, for p = 2, the investigation is extended to the extreme value models of Weibull and Frechet type. These models, described by differential equations, are proportional to the hyper-Gompertz growth model. It is proved that the Beta* (2, q) densities are a power of betas mixture, and that its dynamics are determined by a non-linear coupling of probabilities. The dynamical analysis is performed using techniques of symbolic dynamics and the system complexity is measured using topological entropy. Generally, the natural history of a malignant tumour is reflected through bifurcation diagrams, in which are identified regions of regression, stability, bifurcation, chaos and terminus

    Dynamical analysis in growth models: Blumberg’s equation

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    We present a new dynamical approach to the Blumberg's equation, a family of unimodal maps. These maps are proportional to Beta(p, q) probability densities functions. Using the symmetry of the Beta(p, q) distribution and symbolic dynamics techniques, a new concept of mirror symmetry is defined for this family of maps. The kneading theory is used to analyze the effect of such symmetry in the presented models. The main result proves that two mirror symmetric unimodal maps have the same topological entropy. Different population dynamics regimes are identified, when the intrinsic growth rate is modified: extinctions, stabilities, bifurcations, chaos and Allee effect. To illustrate our results, we present a numerical analysis, where are demonstrated: monotonicity of the topological entropy with the variation of the intrinsic growth rate, existence of isentropic sets in the parameters space and mirror symmetry

    Modeling Allee Effect from Beta(p, 2) Densities

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    In this work we develop and investigate generalized populational growth models, adjusted from Beta(p, 2) densities, with Allee effect. The use of a positive parameter leads the presented generalization, which yields some more flexible models with variable extinction rates. An Allee limit is incorporated so that the models under study have strong Allee effect

    Synchronization in Von Bertalanffy’s models

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    Many data have been useful to describe the growth of marine mammals, invertebrates and reptiles, seabirds, sea turtles and fishes, using the logistic, the Gom-pertz and von Bertalanffy's growth models. A generalized family of von Bertalanffy's maps, which is proportional to the right hand side of von Bertalanffy's growth equation, is studied and its dynamical approach is proposed. The system complexity is measured using Lyapunov exponents, which depend on two biological parameters: von Bertalanffy's growth rate constant and the asymptotic weight. Applications of synchronization in real world is of current interest. The behavior of birds ocks, schools of fish and other animals is an important phenomenon characterized by synchronized motion of individuals. In this work, we consider networks having in each node a von Bertalanffy's model and we study the synchronization interval of these networks, as a function of those two biological parameters. Numerical simulation are also presented to support our approaches

    Dynamical behaviour on the parameter space: new populational growth models proportional to beta densities

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    We present new populational growth models, generalized logistic models which are proportional to beta densities with shape parameters p and 2, where p > 1, with Malthusian parameter r. The complex dynamical behaviour of these models is investigated in the parameter space (r, p), in terms of topological entropy, using explicit methods, when the Malthusian parameter r increases. This parameter space is split into different regions, according to the chaotic behaviour of the models

    Métodos analíticos em probabilidade e métodos probabilísticos em análise : fractalidade associada aos modelos beta(p,q.), evolução de populações e dimensões de Hausdorff

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    Tese de doutoramento em Estatística e Investigação Operacional (Probabilidade e Estatística), apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2008Deduzimos modelos de crescimento populacional proporcionais a densidades beta com parâmetros de forma p e 2, onde p ¸ 1, cuja complexidade dinâmica está relacionada com o parâmetro malthusiano r. Usando técnicas de dinâmica simbólica, investigámos o comportamento caótico destes modelos, em termos de entropia topológica, no espaço de parâmetros (r; p), identificando diferentes comportamentos dinâmicos. Verificámos a universalidade da constante de Feigenbaum nos modelos apresentados, usando uma fórmula diferente daquela que é usualmente apresentada na literatura. O efeito de Allee foi analisado nestes modelos. Para p > 2, eles exibem uma dinâmica populacional onde o efeito de Allee surge naturalmente. No entanto, no caso onde 1 2, they exhibit a population dynamics with natural Allee effect. However, in the case where 1 < p 2, the proposed models do not include this effect. In order to invoke it, we present some alternative models and investigate their dynamics. We also analyze the negativity of the Schwarz derivative in all the models proposed. We define random middle third Cantor set, a fractal obtained by recursive elimination of the central spacing which is defined between the minimum and the maximum of two random observations uniformly distributed, from each interval of the previous iteration The designation attached to the fractal is justified, since the expected values of the extremes of the intervals of each iteration are the endpoints of the correspondent iteration in the deterministic middle third Cantor set. We calculate the Hausdorff dimension (that intuitively evaluates how dense a set is) of the random middle third Cantor set, and we verify that although the middle third Cantor set is the expectation of the random middle third Cantor set, it is more dense than the one obtained stochastically. This result lead us to define more generally random Cantor sets FX with X _ Beta(p; q), to compute their Hausdorff dimensions, and to compute the Hausdorff dimensions of the deterministic fractals which are the expected values of those random fractals, in a similiar sense to the one that the deterministic middle third Cantor set is the expected value of random middle third Cantor set. The phenomenon is general, and we hint it's probabilistic explanation

    Evaluating the impact of culture conditions on human mesenchymal stem/stromal cell-derived exosomes through FTIR spectroscopy

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    In the last decade, the therapeutic effects of mesenchymal stem/stromal cells (MSCs) have been attributed to a paracrine activity exerted by extracellular vesicles secreted by MSCs, as exosomes. Their properties as intercellular communication vehicles have led to an increase interest in their use for cell-free therapeutic applications. The present work aimed to evaluate how different culture conditions, as culture medium (xenogeneic -free (XF) vs serum-containing medium), conditioning time (1, 2 and 3 days) and different MSC donors (n=6), affect the chemical characteristics of exosomes. For that, purified MSC-derived exosomes were characterized by Fourier-Transform InfraRed (FTIR) spectroscopy, a highly sensitive, fast and high throughput technique. The principal component analysis (PCA) of pre-processed FTIR spectra of purified exosomes was conducted, enabling the evaluation of the replica variance of the exosomes chemical fingerprint in a reduced dimensionality space. For that, different pre-processing methods were studied as baseline correction, standard normal variation and first and second derivative. It was observed that the chemical fingerprint of exosomes is more dependent of the medium used for MSCs cultivation than the MSC donor and conditioning days. Exosomes secreted by MSCs cultured with serum-containing medium presented a more homogenous chemical fingerprint than exosomes obtained with XF medium. Moreover, for a given medium (XF or serum-containing medium), the exosomes chemical fingerprint depends more of the MSC donor than of the conditioning days. The regression vector of the PCA enabled to identified relevant spectral bands that enabled the separation of samples in the score-plot of the previous analysis. Ratios between these spectral bands were determined, since these attenuate artifacts due to cell quantity and baseline distortions underneath each band. Statistically inference analysis of the ratios of spectral bands were conducted, by comparing the equality of the means of the populations using appropriate hypothesis tests and considering the significance level of 5%. It was possible to define ratios of spectral bands, that can be used as biomarkers, enabling the discrimination of exosomes chemical fingerprint in function of the medium used for MSC grown and the MSC donor. This work is therefore a step forward into understanding how different culture conditions and MSC donors affect MSC exosomes characteristics

    Plantas medicinais: um estudo etnobotânico nos quintais do Sítio Cruz, São Miguel, Rio Grande do Norte, Brasil

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    The homegardens are agroforestry systems mainly composed of several species of medicinal use. The aim of this study was to perform an ethnobotanical survey of medicinal species in the homegardens of the Sítio Cruz in São Miguel, Rio Grande do Norte. We interviewed people responsible for twenty homegardens. We used the methodology of participatory research, the snowball technique, participatory mapping and semi-structured interviews. Most intervieweds were female (90%) and average age 52 years. Were found on average 24 species per homegarden. Sixty ethnospecies and 35 families were cited. The families Lamiaceae, Rutaceae and Anacardiaceae were the most frequent and major diseases were related to respiratory problems. The leaves were the plant parts most used mainly in the form of tea and “lambedor”. The homegardens have wide variety of medicinal species that are used to treat major diseases in the community. It also occurs managed diversity of spaces within the homegarden, where the number of medicinal species is kept variable. The woman has a fundamental role in the cultivation and use of plants and maintenance of the homegardens. The intervieweds have little knowledge of the possible risks in the use of medicinal plants, which is an aspect to be worked in the community in other studies.Os quintais são sistemas agroflorestais compostos por diversas espécies, principalmente de uso medicinal. O objetivo neste trabalho foi efetuar um levantamento etnobotânico das espécies medicinais dos quintais do Sítio Cruz em São Miguel, Rio Grande do Norte. Foram entrevistadas vinte pessoas responsáveis por quintais. Utilizou-se a metodologia de pesquisa participante, técnica da bola de neve, mapeamento participativo e entrevistas semi-estruturadas. A maioria dos entrevistados era do sexo feminino (90%) e a idade média, 52 anos. Nos quintais do Sítio Cruz foram encontradas, em média, 24 espécies por quintal. Sessenta etnoespécies e 35 famílias botânicas foram citadas. As famílias Lamiaceae, Anacardiaceae e Rutaceae foram as mais frequentes e as principais doenças estavam relacionadas com problemas respiratórios. As folhas foram as partes da planta mais utilizadas, principalmente na forma de chá e lambedor. Os quintais do Sítio Cruz apresentam grande diversidade de espécies medicinais que são usadas para tratar as principais doenças na comunidade. Ocorre também diversidade de espaços manejados dentro do quintal, nos quais o número de espécies medicinais mantidas é variável. A mulher tem papel fundamental no cultivo e uso das plantas e manutenção dos quintais. Os entrevistados têm pouco conhecimento dos possíveis riscos na utilização de plantas medicinais, sendo este um aspecto a ser trabalhado na comunidade em outros estudos
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