Determination of the neutron star mass-radii relation using narrow-band gravitational wave detector

The direct detection of gravitational waves will provide valuable astrophysical information about many celestial objects. The most promising sources of gravitational waves are neutron stars and black holes. These objects emit waves in a very wide spectrum of frequencies determined by their quasi-normal modes oscillations. In this work we are concerned with the information we can extract from f and p$_I$-modes when a candidate leaves its signature in the resonant mass detectors ALLEGRO, EXPLORER, NAUTILUS, MiniGrail and SCHENBERG. Using the empirical equations, that relate the gravitational wave frequency and damping time with the mass and radii of the source, we have calculated the radii of the stars for a given interval of masses $M$ in the range of frequencies that include the bandwidth of all resonant mass detectors. With these values we obtain diagrams of mass-radii for different frequencies that allowed to determine the better candidates to future detection taking in account the compactness of the source. Finally, to determine which are the models of compact stars that emit gravitational waves in the frequency band of the mass resonant detectors, we compare the mass-radii diagrams obtained by different neutron stars sequences from several relativistic hadronic equations of state (GM1, GM3, TM1, NL3) and quark matter equations of state (NJL, MTI bag model). We verify that quark stars obtained from MIT bag model with bag constant equal to 170 MeV and quark of matter in color-superconductivity phase are the best candidates for mass resonant detectors.Comment: 10 pages and 3 figure

Electrically Charged Strange Quark Stars

The possible existence of compact stars made of absolutely stable strange quark matter--referred to as strange stars--was pointed out by E. Witten almost a quarter of a century ago. One of the most amazing features of such objects concerns the possible existence of ultra-strong electric fields on their surfaces, which, for ordinary strange matter, is around $10^{18}$ V/cm. If strange matter forms a color superconductor, as expected for such matter, the strength of the electric field may increase to values that exceed $10^{19}$ V/cm. The energy density associated with such huge electric fields is on the same order of magnitude as the energy density of strange matter itself, which, as shown in this paper, alters the masses and radii of strange quark stars at the 15% and 5% level, respectively. Such mass increases facilitate the interpretation of massive compact stars, with masses of around $2 M_\odot$, as strange quark stars.Comment: Revised version, references added, 6 pages, 4 figures, accepted for publication in Physical Review

Design, Modeling, and Simulation of a Wing Sail Land Yacht

Autonomous land yachts can play a major role in the context of environmental monitoring, namely, in open, flat, windy regions, such as iced planes or sandy shorelines. This work addresses the design, modeling, and simulation of a land yacht probe equipped with a rigid free-rotating wing sail and tail flap. The wing was designed with a symmetrical airfoil and dimensions to provide the necessary thrust to displace the vehicle. Specifically, it proposes a novel design and simulation method for free rotating wing sail autonomous land yachts. The simulation relies on the Gazebo simulator together with the Robotic Operating System (ROS) middleware. It uses a modified Gazebo aerodynamics plugin to generate the lift and drag forces and the yawing moment, two newly created plugins, one to act as a wind sensor and the other to set the wing flap angular position, and the 3D model of the land yacht created with Fusion 360. The wing sail aligns automatically to the wind direction and can be set to any given angle of attack, stabilizing after a few seconds. Finally, the obtained polar diagram characterizes the expected sailing performance of the land yacht. The described method can be adopted to evaluate different wing sail configurations, as well as control techniques, for autonomous land yachts.This work was partially financed by National Funds through the FCT – Fundação para a Ciência e a 337 Tecnologia (Portuguese Foundation for Science and Technology) as part of project UIDB/50014/2020.info:eu-repo/semantics/publishedVersio

Charge Influence On Mini Black Hole's Cross Section

In this work we study the electric charge effect on the cross section production of charged mini black holes (MBH) in accelerators. We analyze the charged MBH solution using the {\it fat brane} approximation in the context of the ADD model. The maximum charge-mass ratio condition for the existence of a horizon radius is discussed. We show that the electric charge causes a decrease in this radius and, consequently, in the cross section. This reduction is negligible for protons and light ions but can be important for heavy ions.Comment: 4 pages, 0 figure. To be published in Int. J. Mod. Phys. D

Migração e (in)segurança: conhecer para agir

Numa época em que o clima de crispação em torno dos milhares de migrantes que elegeram a Europa como destino para se fixarem é potenciado pelo cometimento de eventos de terror que assolaram várias cidades europeias, é plausível que, de forma leviana e fácil e indo de encontro ao vox populi, se construam discursos demagógicos em torno deste fluxo humano. Com o pretexto de se aquilatar da existência de eventuais pensamentos enviesados e quiçá perceções que poderão ser consideradas desajustadas da realidade como é classificado o fenómeno migratório, recorreu-se à realização do presente estudo com o qual se pretende encontrar uma resposta para à seguinte pergunta: quais as principais características dos migrantes que têm desembarcado nas costas marítimas da União Europeia? A análise dos dados obtidos permite afirmar que os migrantes na maioria são famílias, constituídas ou elementos em trânsito que procuram o reencontro com as suas famílias imigradas em Estados europeus; que existe uma relação aparente entre o número de homens, mulheres e crianças e que se está perante migrantes cada vez mais qualificados em busca de melhores condições de vida que os seus países de origem lhes negam.info:eu-repo/semantics/publishedVersio

A agenda Mulheres, Paz e Segurança: um olhar sobre as forças de segurança

No vigésimo aniversário da agenda Mulheres, Paz e Segurança (Resolução 1325 (2000) do Conselho de Segurança das Nações Unidas), apesar do progresso registado, ainda persistem barreiras à sua total implementação. Portugal não sendo exceção, é recomendável, e oportuno, que reforce o desempenho para a participação integradora das mulheres na paz e segurança internacionais, especialmente no espetro de ação das forças de segurança. O artigo, com base no conceito de política pública, recorre a um inquérito por questionário aplicado a um universo de 288 cadetes das duas forças de segurança (GNR e PSP). O artigo sugere que o resultado deste inquérito pode reforçar a noção da necessidade de implementação da agenda neste setor, fornecer recomendações para a próxima década sobre a vantagem integradora das mulheres no domínio da paz e da segurança e contribuir para o desenvolvimento de sociedades mais pacíficas, justas e inclusivas.info:eu-repo/semantics/publishedVersio

Constraining relativistic models through heavy ion collisions

Relativistic models can be successfully applied to the description of compact star properties in nuclear astrophysics as well as to nuclear matter and finite nuclei properties, these studies taking place at low and moderate temperatures. Nevertheless, all results are model dependent and so far it is unclear whether some of them should be discarded. Moreover, in the regime of hot hadronic matter very few calculations exist using these relativistic models, in particular when applied to particle yields in heavy ion collisions. In the present work we comment on the known constraints that can help the selection of adequate models in this regime and investigate the main differences that arise when the particle production during a Au+Au collision at RHIC is calculated with different models.Comment: 9 pages, 1 figure, 3 table

Structural dynamic updating using a global optimization methodology

In this article, we present the application of a global optimization technique, in particular the GlobalSearch command from MatLab®, in the updating of structural dynamic models. For comparative purposes, we evaluate the efficiency of the global method relatively to the local search method previously used in the Finite Element Model Updating program. The Finite Element Model Updating programs are designed with the primary purpose of validating and optimizing structural numerical models. The first step for structural optimization process is to idealize the desired behavior of the dynamic model to develop, or collect experimental data of a physical model considered as the reference model. The process begins with the construction, on a finite element program, of a numerical model with initial physical parameters, preferably close to the reference model parameters. The numerical model is then submitted, through a Finite Element Model Updating program, to a successive parametric updating until improving its dynamic behavior described by their natural frequencies, mode shapes and damping properties, be similar to the dynamic behavior of the reference model. The Sequential Quadratic Programming algorithm was already used in the optimization of the Finite Element Model Updating program, and the obtained solutions showed that it can’t achieve the global optimal value of the objective function. This kind of methods, used for nonlinear constrained optimization problems, have, generally, difficulties to achieve the global optimum, since they are local optimization methods.Centre for Mechanical and Materials Technologies (CT2M) and Algoritmi R&D Centreinfo:eu-repo/semantics/publishedVersio

Hipertiroidismo por Secreção Inapropriada Não Tumoral de TSH

Apresenta-se um caso clínico de hipertiroidismo por secreção inapropriada não tumoral de TSH, numa mulher de 31 anos, investigado na sequência do achado de T3 e TSH elevados após tiroidecto mia. A resposta exagerada de TSH à TRH e a supressão parcial após triiodotironina aliadas à normal expressão morfológica tomodensitométrica da região selar confirmaram o diagnóstico. As terapêuticas com bromocriptina e ocjreotido revelaram-se ineficazes na supressa da TSH. O ensaio com 3-5-3’ ácido triiodotiroacético ficou deferido pela ocorrência de gravidez e aleitamento

Seroprevalence of antibodies against SARS-CoV-2 among health care workers in a Portuguese hospital

"Background: Health care workers (HCW) are presumably exposed to a higher risk of infection by SARS-CoV-2 and could possibly represent a source of transmission to susceptible patients. Thus, characterization of SARS-CoV-2 infection among HCW is necessary to better understand the determinants of viral transmission and properly implement strategies to prevent dissemination and protect HCW and vulnerable patients. The aim of this study was to estimate the seroprevalence of antibodies against SARS-CoV-2 in a Portuguese tertiary hospital, in the period of July 2020 to March 2021, before the generalized use of the SARS-CoV-2 vaccine, characterize its evolution over time, and identify risk factors associated with seroconversion. Methods: HCW were approached to collect serum samples for qualitative SARS-CoV-2 antibody testing and completion of an online survey capturing demographics, previous symptoms, and details of health care and community exposure. Odds ratio with bivariable and multivariable logistic regression was used to assess characteristics associated with seroprevalence. Results: One thousand HCW were included for analysis. Two hundred nineteen HCW (22%) were seropositive for immunoglobulin G against SARS-CoV-2, and 166 (17%) were seropositive for immunoglobulin M, most of whom reported a previous diagnosis of SARS-CoV-2 infection. The risk factors associated with seroconversion included a previous COVID-19 diagnosis, contact with patients, occupational contact with colleagues, and outside contact. However, in a multivariate logistic regression analysis, only a previous diagnosis and outside contact were associated with seroconversion. Seropositivity decreased over time, especially 28 weeks after infection. Conclusion: HCWs have a high seroprevalence for SARS-CoV-2 infection, probably due to a combination of health care and community exposure. Seropositivity decreases over time, but further studies are needed to better understand our adaptive immune response.