University of Madeira

About: University of Madeira is a education organization based out in Funchal, Portugal. It is known for research contribution in the topics: Population & Dendrimer. The organization has 1014 authors who have published 2759 publications receiving 59457 citations.

Vaporization of a solid surface in an ambient gas

Abstract: The net flux of vapour from a solid surface in an ambient gas is analysed with the aim to estimate the effect of vaporization cooling on the energy balance of an arc cathode under conditions typical for a high-power current breaker. If the ratio of the equilibrium vapour pressure pv to the ambient pressure p∞ is smaller than unity, the removal of vapour from the surface is due to diffusion into the bulk of the gas. As a consequence, the net flux of the vapour from the surface is much smaller than the emitted flux. An estimate of the diffusion rate under conditions typical for a high-power current breaker indicates that vaporization cooling plays a minor role in the energy balance of the cathode in this case. If ratio pv/p∞ is above unity, the flow of the vapour from the surface appears and the net flux is comparable to the emitted flux. A simple analytical solution has been obtained for this case, which is in a good agreement with results of the Monte Carlo modelling of preceding authors. If pv/p∞ exceeds approximately 4.5, vaporization occurs as into vacuum and the net flux is about 0.82 of the emitted flux.

The Demand for Football in Portugal: New Insights on Outcome Uncertainty

Abstract: The aim of this study is to identify variables that influence the stadium attendance in Portugal, and how these variables may affect decision management. Deriving a demand curve for stadium attendance in the Portuguese First Division Football League for 898 matches of five seasons (2010/2011-2014/2015), the results highlight five main explicative variables: cost, habit persistence, expected quality, team performance, and outcome uncertainty. With regard to outcome uncertainty, we employ the framework proposed by Humphreys and Zhou and we conclude for the importance of alternative factors affecting consumer choice like loss aversion and home win preference.

Theoretical and experimental developments in quantum spin liquid in geometrically frustrated magnets: a review

Abstract: The exotic substances have exotic properties. One class of such substances is geometrically frustrated magnets, where correlated spins reside in the sites of triangular or kagome lattice. In some cases, such magnet would not have long-range magnetic order. Rather, its spins tend to form kind of pairs, called valence bonds. At $$T \rightarrow 0$$ these highly entangled quantum objects condense in the form of a liquid, called quantum spin liquid (QSL). The observation of a gapless QSL in actual materials is of fundamental significance both theoretically and technologically, as it could open a path to creation of topologically protected states for quantum information processing and computation. In the present review, we consider QSL formed by spinons that are chargeless fermionic quasiparticles with spin 1/2, filling the Fermi sphere up to the Fermi momentum $$p_{\rm F}$$. We expose a state of the art in the theoretical and experimental investigations of the thermodynamic, relaxation, transport, optical and scaling properties of geometrically frustrated magnets with QSL. We show how different theoretical approaches and that based on so-called fermion condensation concept among them, permit to describe the multitude of experimental results regarding the thermodynamic and transport properties of QSL in geometrically frustrated magnets like herbertsmithite $$\hbox {ZnCu}_3(\hbox {OH})_6\hbox {Cl}_2$$, the organic insulators $$\hbox {EtMe}_3\hbox {Sb}[\hbox {Pd(dmit)}_2]_2$$ and $$\kappa {\text {-}}(\hbox {BEDT-TTF})_2\hbox {Cu}_2(\hbox {CN})_3$$, quasi-one-dimensional spin liquid in the $$\hbox {Cu}(\hbox {C}_4\hbox {H}_4\hbox {N}_2)(\hbox {NO}_3)_2$$ insulator and QSL formed in two-dimensional $$^3\hbox {He}$$. Our theoretical results are in good agreement with experimental facts, while predictions, elucidating the existence of gapless QSL in magnets, still await their experimental confirmation.

Emerging Adults and Facebook Use: the Validation of the Bergen Facebook Addiction Scale (BFAS)

Abstract: Based on the six key components of addiction, the Bergen Facebook Addiction Scale (BFAS) is a widely used instrument to assess Facebook addiction. This study aimed to conduct a psychometric validation in a Portuguese sample of emerging adults (ages 18 to 29 years). The construct validity analyses confirmed the one-factor solution and a statistically significant association found between Facebook addiction and Preference for Online Social Interaction, measured by the Generalized Problematic Internet Use Scale 2, warranted the scale criterion validity. Internal consistency was scrutinized using Cronbach’s α (α = .87) and stability measured by test-retest (r = .94). Associations between BFAS scores and Brief Symptom Inventory dimensions scores (e.g., interpersonal sensitivity, depression, anxiety) and the GPIUS2 subscale, deficient self-regulation, scores were evaluated. A subsample with higher levels of addiction was analyzed. In summary, the results of the present study support the use of the Portuguese version of the BFAS in both research and clinical milieus. Further implications for research and practice were considered.