Dinâmica de sistemas dissipativos e não-autónomos com uma coordenada angular

Estudamos a dinâmica de sistemas não-autónomos periódicos que têm como espaço de fases o cilindro. Sempre que o sistema for dissipativo a aplicação de Poincaré tem um atractor. Procuramos condições para que este atractor seja ou não homeomorfo ao círculo. Motivados pelos resultados obtidos por M. Levi e independentemente por Q. Min, S. Xian e Z. Jinyan estudamos aplicações à equação do pêndulo forçado com atrito. Encontramos relações com a trabalho de R. A. Smith que utilizamos no estudo de sistemas de osciladores acoplados e equações ordinárias de ordem n.

Surface morphology and phase transformations of femtosecond laser-processed saphire

The morphological and structural modifications induced in sapphire by surface treatment with femtosecond laser radiation were studied. Single-crystal sapphire wafers cut parallel to the (0 1 2) planes were treated with 560 fs, 1030 nm wavelength laser radiation using wide ranges of pulse energy and repetition rate. Self-ordered periodic structures with an average spatial periodicity of similar to 300 nm were observed for fluences slightly higher than the ablation threshold. For higher fluences the interaction was more disruptive and extensive fracture, exfoliation, and ejection of ablation debris occurred. Four types of particles were found in the ablation debris: (a) spherical nanoparticles about 50 nm in diameter; (b) composite particles between 150 and 400 nm in size; (c) rounded resolidified particles about 100-500 nm in size; and (d) angular particles presenting a lamellar structure and deformation twins. The study of those particles by selected area electron diffraction showed that the spherical nanoparticles and the composite particles are amorphous, while the resolidified droplets and the angular particles, present a crystalline a-alumina structure, the same of the original material. Taking into consideration the existing ablation theories, it is proposed that the spherical nanoparticles are directly emitted from the surface in the ablation plume, while resolidified droplets are emitted as a result of the ablation process, in the liquid phase, in the low intensity regime, and by exfoliation, in the high intensity regime. Nanoparticle clusters are formed by nanoparticle coalescence in the cooling ablation plume. (C) 2013 Elsevier B.V. All rights reserved.

The K-Th derivatives of the immanant and the X-symmetric power of an operator

In recent papers, formulas are obtained for directional derivatives, of all orders, of the determinant, the permanent, the m-th compound map and the m-th induced power map. This paper generalizes these results for immanants and for other symmetric powers of a matrix.

The norm of the K- Th derivative of the X-symmetric power of an operator

In this paper, the exact value for the norm of directional derivatives, of all orders, for symmetric tensor powers of operators on finite dimensional vector spaces is presented. Using this result, an upper bound for the norm of all directional derivatives of immanants is obtained.

Dioszegia antarctica sp. nov. and Dioszegia cryoxerica sp. nov., psychrophilic basidiomycetous yeasts from polar desert soils in Antarctica

International Journal of Systematic and Evolutionary Microbiology, 60

Angular distributions in t(t)over-barH(H -> b(b)over-bar) reconstructed events at the LHC

The associated production of a Higgs boson and a top-quark pair, t (t) over barH, in proton-proton collisions is addressed in this paper for a center of mass energy of 13 TeV at the LHC. Dileptonic final states of t (t) over barH events with two oppositely charged leptons and four jets from the decays t -> bW(+) -> bl(+)v(l), (t) over bar -> (b) over barW(-) -> (b) over barl(-)(v) over bar (l) and h -> b (b) over bar are used. Signal events, generated with MadGraph5_aMC@NLO, are fully reconstructed by applying a kinematic fit. New angular distributions of the decay products as well as angular asymmetries are explored in order to improve discrimination of t (t) over barH signal events over the dominant irreducible background contribution, t (t) over barb (b) over bar. Even after the full kinematic fit reconstruction of the events, the proposed angular distributions and asymmetries are still quite different in the t (t) over barH signal and the dominant background (t (t) over barb (b) over bar).

Controlo de posição angular de uma máquina eléctrica de relutância comutada 8/6

Dissertação para obtenção do grau de Doutor em Engenharia Electrotécnica - Energia pela Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa

Acute Chagas' cardiopathy in a polar bear (Ursus maritimus) in Guadalajara, Mexico

We report a 24 year old female polar bear (Ursus maritimus) who contracted Chagas' infection at the Guadalajara Zoo, in Jalisco, México, and died of acute Chagas' carditis 15 days later. The histopathological findings are described, as well as the presence of triatomines (Triatoma longipennis Usinger) infected with Trypanosoma cruzi collected within 5 meters from the place where the animal lived in the city of Guadalajara.

Momentum risk: An approach following the correlations between active stocks

The momentum anomaly has been widely documented in the literature. However, there are still many issues where there is no consensus and puzzles left unexplained. One is that strategies based on momentum present a level of risk that is inconsistent with the diversification that it offers. Moreover, recent studies indicate that this risk is variable over time and mostly strategy-specific. This work project hypothesises and proves that this evidence is explained by the portfolio constitution of the momentum strategy over time, namely the covariance and correlation between companies in the top and down deciles and across them.

Desenvolvimento e implementação de técnicas avançadas usando desvios com aplicação a calibrações no domínio de metrologia angular

O trabalho desenvolvido no decurso da elaboração da dissertação aqui apresentada decorreu no departamento de Metrologia do Instituto Português da Qualidade no âmbito de estágio. O tema que foi abordado está inserido na área de Metrologia Angular, onde a grandeza que se mede é o ângulo plano. Por esse facto os dois equipamentos de medição principais que foram utilizados foram o autocolimador e a mesa rotativa. O objectivo principal do trabalho visou a utilização de novas técnicas de avaliação de dados, que consistiu na separação dos erros do autocolimador e da mesa rotativa, quando a calibrar o autocolimador e trabalhá-los separadamente com o propósito de verificar se as incertezas são mais baixas relativamente aos métodos clássicos de calibração e assim garantir uma maior exactidão nos resultados. Este trabalho implicou a implementação de uma nova técnica de medição, assim como a implementação de um novo processo de obtenção dos dados. Estas técnicas baseiam-se em aplicar certos desvios aos dois sistemas que vão permitir a construção dos erros separadamente, tanto do autocolimador como da mesa rotativa, e que vai permitir, deste modo, que não seja necessário recorrer a padrões externos. A obtenção desses erros foi construída utilizando as Transformadas de Fourier Discretas, pois através destas é possível recuperar/gerar valores que entretanto se perderam, ou não foram possíveis de adquirir. Com o trabalho realizado, o laboratório implementou um novo método de calibração do sistema composto pelos instrumentos de medição, autocolimador e mesa rotativa, garantindo que os erros estão em conformidade

Alpha generation with Twitter’s daily momentum

This thesis does not set out to focus on the dynamics relationship between Twitter and stock prices, but instead tries to understand if using relevant information extracted from tweets has the power to increase investors’ stock picking ability, and generate alpha in portfolio’s choice relative to a benchmark. Despite the short period analyzed, it gives promising results that the sentiment analysis performed by Social Market Analytics Inc. applied to an equity portfolio, is able to generate positive abnormal returns, statistically significant in and out of sample.

Introducing risk parity on momentum and carry portfolios

The momentum and carry anomalies have been extensively documented in the literature. However, there are still many issues relating to the risks associated to them that are left unexplained. One is the fact that an investor holds for too long the most volatile assets, both under momentum and carry strategies. Therefore, they present a level of risk and a probability of extreme events to happen inconsistent. This work project hypothesizes and proves the introduction of risk parity rules on the weights of the portfolios do increase risk rewarding of carry strategies. However, it fails under momentum strategies.

A sixth-order finite volume method for the 1D biharmonic operator: application to intramedullary nail simulation

A new very high-order finite volume method to solve problems with harmonic and biharmonic operators for one- dimensional geometries is proposed. The main ingredient is polynomial reconstruction based on local interpolations of mean values providing accurate approximations of the solution up to the sixth-order accuracy. First developed with the harmonic operator, an extension for the biharmonic operator is obtained, which allows designing a very high-order finite volume scheme where the solution is obtained by solving a matrix-free problem. An application in elasticity coupling the two operators is presented. We consider a beam subject to a combination of tensile and bending loads, where the main goal is the stress critical point determination for an intramedullary nail.

Search for new phenomena in events with a photon and missing transverse momentum in pp collisions at s√=8 TeV with the ATLAS detector

Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum with the ATLAS experiment at the LHC are reported. Data were collected in proton--proton collisions at a center-of-mass energy of 8 TeV and correspond to an integrated luminosity of 20.3 fb−1. The observed data are well described by the expected Standard Model backgrounds. The expected (observed) upper limit on the fiducial cross section for the production of such events is 6.1 (5.3) fb at 95% confidence level. Exclusion limits are presented on models of new phenomena with large extra spatial dimensions, supersymmetric quarks, and direct pair production of dark-matter candidates.

Search for vector-like B quarks in events with one isolated lepton, missing transverse momentum and jets at s√= 8 TeV with the ATLAS detector

A search has been performed for pair production of heavy vector-like down-type (B) quarks. The analysis explores the lepton-plus-jets final state, characterized by events with one isolated charged lepton (electron or muon), significant missing transverse momentum and multiple jets. One or more jets are required to be tagged as arising from b-quarks, and at least one pair of jets must be tagged as arising from the hadronic decay of an electroweak boson. The analysis uses the full data sample of pp collisions recorded in 2012 by the ATLAS detector at the LHC, operating at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb−1. No significant excess of events is observed above the expected background. Limits are set on vector-like B production, as a function of the B branching ratios, assuming the allowable decay modes are B→Wt/Zb/Hb. In the chiral limit with a branching ratio of 100% for the decay B→Wt, the observed (expected) 95% CL lower limit on the vector-like B mass is 810 GeV (760 GeV). In the case where the vector-like B quark has branching ratio values corresponding to those of an SU(2) singlet state, the observed (expected) 95% CL lower limit on the vector-like B mass is 640 GeV (505 GeV). The same analysis, when used to investigate pair production of a colored, charge 5/3 exotic fermion T5/3, with subsequent decay T5/3→Wt, sets an observed (expected) 95% CL lower limit on the T5/3 mass of 840 GeV (780 GeV).