O papel mediador do medo

Este estudo analisa os comportamentos de proteção de estudantes portugueses do ensino superior no contexto de pandemia e a sua relação com a perceção de risco e o medo face à COVID-19. A amostra foi composta por 335 estudantes com idades entre os 18 e os 29 anos de idade (M=21.42; DP=2.43). Os participantes preencheram um inquérito sobre comportamentos de proteção e perceção de risco e a Fear of COVID-19 Scale. Os resultados demonstraram que os comportamentos preventivos mais adotados foram a lavagem/desinfeção das mãos ao longo do dia e o uso de máscara na via pública ou espaços públicos exteriores e os comportamentos de evitamento mais adotados foram o evitar de locais com agrupamentos de pessoas e de convívios presenciais com os colegas/amigos. Verificou-se uma associação positiva entre os comportamentos de proteção, a perceção de gravidade e o medo face à COVID-19. Também se verificou que a perceção de gravidade, quando mediada pelo medo tem influência indireta, em ambos os tipos de comportamentos de proteção (i.e., preventivos e de evitamento). Os resultados são discutidos atendendo ao papel da perceção de risco e do medo nas respostas comportamentais dos jovens, num contexto de pandemia.This study analyzes the protective behaviors of Portuguese higher education students in the context of a pandemic and their relationship with perception of risk and fear of COVID-19. The sample was consisted of 335 students, aged between 18 and 29 years old (M=21.42; SD=2.43). The participants completed a survey on protective behaviors and risk perception and the Fear of COVID-19 Scale. The results showed that the most adopted preventive behaviors were hand washing/disinfection throughout the day and the use of masks on public streets or outdoor public spaces. The most adopted avoidant behaviors were avoiding places with gatherings of people and face-to-face interactions with colleagues/friends. There was a positive association between protective behaviors, perception of severity and fear of COVID-19. It was also found that the perception of severity, when mediated by fear, had an indirect effect on both types of protective behavior (i.e., preventive and avoidant). These results are discussed, considering the role of risk perception and fear in the behavioral responses adopted by young people, in a pandemic context

A Hierarchical Flow Solver for Optimisation with PDE Constraints

Active flow control plays a central role in many industrial applications such as e.g. control of crystal growth processes, where the flow in the melt has a significant impact on the quality of the crystal. Optimal control of the flow by electro-magnetic fields and/or boundary temperatures leads to optimisation problems with PDE constraints, which are frequently governed by the time-dependent Navier-Stokes equations. The mathematical formulation is a minimisation problem with PDE constraints. By exploiting the special structure of the first order necessary optimality conditions, the so called Karush-Kuhn-Tucker (KKT)-system, this thesis develops a special hierarchical solution approach for such equations, based on the distributed control of the Stokes-- and Navier--Stokes. The numerical costs for solving the optimisation problem are only about 20-50 times higher than a pure forward simulation, independent of the refinement level. Utilising modern multigrid techniques in space, it is possible to solve a forward simulation with optimal complexity, i.e., an appropriate solver for a forward simulation needs O(N) operations, N denoting the total number of unknowns for a given computational mesh in space and time. Such solvers typically apply appropriate multigrid techniques for the linear subproblems in space. As a consequence, the developed solution approach for the optimal control problem has complexity O(N) as well. This is achieved by a combination of a space-time Newton approach for the nonlinearity and a monolithic space-time multigrid approach for 'global' linear subproblems. A second inner monolithic multigrid method is applied for subproblems in space, utilising local Pressure-Schur complement techniques to treat the saddle-point structure. The numerical complexity of this algorithm distinguishes this approach from adjoint-based steepest descent methods used to solve optimisation problems in many practical applications, which in general do not satisfy this complexity requirement

Mycobacterium tuberculosis type VII secretion system effectors differentially impact the ESCRT endomembrane damage response

Mycobacterium tuberculosis causes tuberculosis, which kills more people than any other infection. M. tuberculosis grows in macrophages, cells that specialize in engulfing and degrading microorganisms. Like many intracellular pathogens, in order to cause disease, M. tuberculosis damages the membrane-bound compartment (phagosome) in which it is enclosed after macrophage uptake. Recent work showed that when chemicals damage this type of intracellular compartment, cells rapidly detect and repair the damage, using machinery called the endosomal sorting complex required for transport (ESCRT). Therefore, we hypothesized that ESCRT might also respond to pathogen-induced damage. At the same time, our previous work showed that the EsxG-EsxH heterodimer of M. tuberculosis can inhibit ESCRT, raising the possibility that M. tuberculosis impairs this host response. Here, we show that ESCRT is recruited to damaged M. tuberculosis phagosomes and that EsxG-EsxH undermines ESCRT-mediated endomembrane repair. Thus, our studies demonstrate a battle between host and pathogen over endomembrane integrity.Intracellular pathogens have varied strategies to breach the endolysosomal barrier so that they can deliver effectors to the host cytosol, access nutrients, replicate in the cytoplasm, and avoid degradation in the lysosome. In the case of Mycobacterium tuberculosis, the bacterium perforates the phagosomal membrane shortly after being taken up by macrophages. Phagosomal damage depends upon the mycobacterial ESX-1 type VII secretion system (T7SS). Sterile insults, such as silica crystals or membranolytic peptides, can also disrupt phagosomal and endolysosomal membranes. Recent work revealed that the host endosomal sorting complex required for transport (ESCRT) machinery rapidly responds to sterile endolysosomal damage and promotes membrane repair. We hypothesized that ESCRTs might also respond to pathogen-induced phagosomal damage and that M. tuberculosis could impair this host response. Indeed, we found that ESCRT-III proteins were recruited to M. tuberculosis phagosomes in an ESX-1-dependent manner. We previously demonstrated that the mycobacterial effectors EsxG/TB9.8 and EsxH/TB10.4, both secreted by the ESX-3 T7SS, can inhibit ESCRT-dependent trafficking of receptors to the lysosome. Here, we additionally show that ESCRT-III recruitment to sites of endolysosomal damage is antagonized by EsxG and EsxH, both within the context of M. tuberculosis infection and sterile injury. Moreover, EsxG and EsxH themselves respond within minutes to membrane damage in a manner that is independent of calcium and ESCRT-III recruitment. Thus, our study reveals that T7SS effectors and ESCRT participate in a series of measures and countermeasures for control of phagosome integrity

Why neutron guides may end up breaking down? Some results on the macroscopic behaviour of alkali-borosilicate glass support plates under neutron irradiation

In this paper we report on a first part of a study on the mechanisms leading to brittle fracture in neutron guides made of glass as structural element. Such devices are widely used to deliver thermal and cold neu tron beams to experimental lines in most large neutron research facilities. We present results on macroscopic properties of samples of guide glass substrates which are subjected to neutron irradiation at relatively large fluences. The results show a striking dependence of some of the macroscopic properties such as density, shape or surface curvature upon the specific chemical composition of a given glass. The relevance of the present findings for the installation of either replacement guides at the existing facilities or for the deployment of instruments for ongoing projects such as the European Spallation Source is briefly discussed

Low-Energy Nuclear Astrophysics - the Fascinating Region of A=7

We discuss results and future plans for low-energy reactions that play an important role in current nuclear astrophysics research and that happen to concentrate around the region of A=7. The 7Be(p,gamma)8B and the 3He(4He,gamma)7Be reactions are crucial for understanding the solar-neutrino oscillations phenomenon and the latter one plays a central role in the issue of cosmic 7Li abundance and Big-Bang Nucleosynthesis. We also present results regarding the host dependence of the half life of the electron-capture 7Be radio-nuclide.Comment: 8 pages, 6 figures. Proceedings of the Erice School on Nuclear Physics, 2006. To appear in: "Prog. Part. Nucl. Phys.