Determinants of Profitability in the Tourism Sector in Portugal

This paper examines the impact on the profitability of firms in the Portuguese tourism sector of both internal (size, age, growth, debt) and external (real GDP growth rate, sovereign debt crisis, location) determinants. Panel data models have been employed on a large sample of small and medium sized firms, from 2009 to 2017, a period critically influenced by both the financial and the ensuing sovereign debt crisis in the southern European countries. Alternative profitability measures have been used and the results have been largely robust to the distinct models’ specifications. The results suggested that profitability is positively affected by firm’s size and age and by economic real growth rates, and negatively influenced by the firm’s indebtedness ratio and the sovereign debt crisis. Firms in the main tourism regions are generally more profitable, and relatively less affected by the sovereign debt crisis, that was particularly harmful to micro-size firms

Leveraging different meronym discovery methods for bridging resolution in French

International audienceThis paper presents a statistical system for resolving bridging descriptions in French, a language for which current lexical resources have a very low overage. The system is similar to that developed for English by Poesio but it was enriched to integrate meronymic information extracted automatically from both web queries and raw text using syntactic patterns. Through various experiments on the DEDE corpus, we show that although still mediocre the performance of our system compare favorably to those obtained by Poesio for English. In addition, our evaluation indicates that the different meronym extraction methods have a cumulative effect, but that the text pattern-based extraction method is more robust and leads to higher accuracy than the web-based approach

Standardization of an isolated pig heart preparation with parabiotic circulation: methodological considerations

In the present study we standardized an experimental model of parabiotic circulation of isolated pig heart. The isolated heart was perfused with arterial blood from a second animal as support and submitted to regional ischemia for 30 min, followed by total ischemia for 90 min and reperfusion for 90 min. Parameters for measurement of ventricular performance using different indices measured directly or indirectly from intraventricular pressure were defined as: maximum peak pressure, final diastolic pressure, pressure developed, first derivative of maximum pressure (dP/dt max), first derivative of minimum pressure (dP/dt min), systolic stress of the left ventricle (sigmas), and maximum elastance of the left ventricle. Isolated hearts subjected to regional and global ischemia presented significant worsening of all measured parameters. Less discriminative parameters were dP/dt max and dP/dt min. Elastance was the most sensitive parameter during the reperfusion period, demonstrating an early loss of ventricular function during reperfusion. The model proved to be stable and reproducible and permitted the study of several variables in the isolated heart, such as ischemia and reperfusion phenomena, the effects of different drugs, surgical interventions, etc. The model introduces an advantage over the classical models which use crystalloid solutions as perfusate, because parabiotic circulation mimics heart surgery with extracorporeal circulation.64965

Thickness-modulated tungsten-carbon superconducting nanostructures grown by focused ion beam induced deposition for vortex pinning up to high magnetic fields

We report efficient vortex pinning in thickness-modulated tungsten–carbon-based (W–C) nanostructures grown by focused ion beam induced deposition (FIBID). By using FIBID, W–C superconducting films have been created with thickness modulation properties exhibiting periodicity from 60 to 140 nm, leading to a strong pinning potential for the vortex lattice. This produces local minima in the resistivity up to high magnetic fields (2.2 T) in a broad temperature range due to commensurability effects between the pinning potential and the vortex lattice. The results show that the combination of single-step FIBID fabrication of superconducting nanostructures with built-in artificial pinning landscapes and the small intrinsic random pinning potential of this material produces strong periodic pinning potentials, maximizing the opportunities for the investigation of fundamental aspects in vortex science under changing external stimuli (e.g., temperature, magnetic field, electrical current)

Explorar e Investigar em Matemática: Uma Actividade Fundamental no Ensino e na Aprendizagem

Investigar, ensinar e aprender são actividades que podem estar presentes, de forma articulada, no ensino-aprendizagem da Matemática e na actividade profissional do professor. Para isso, é necessário conceber tarefas que possam ser o ponto de partida para investigações e explorações matemáticas dos alunos e discutir o modo como podem ser trabalhadas na sala de aula. Recorrendo a exemplos de actividades realizadas por professores de Matemática portugueses, analiso a actividade de aprendizagem suscitada por tarefas deste tipo e discuto as respectivas potencialidades. Finalmente, refiro as condições respeitantes à cultura profissional dos professores que podem favorecer uma actividade de investigação sobre a sua própria profissional, com relevo para a colaboração e a dimensão associativa.Researching, teaching and learning are activities that may be present, in coordination, teaching and learning of mathematics in the work of the teacher. Therefore, it is necessary to design tasks that may be the starting point for mathematical investigations and explorations of the students and discuss how they can be worked in the classroom. Drawing on examples of activities carried out by Portuguese teachers of mathematics by examining the activity of learning raised by such tasks and discuss their potencial. Finally, I refer to conditions relating to the professional culture of teachers who can promote the research activity on their own training, with an emphasis on collaboration and associative dimension

Tunneling spectroscopy in the magnetic superconductor TmNi2B2C

We present new measurements about the tunneling conductance in the borocarbide superconductor TmNi$_2$B$_2$C. The results show a very good agreement with weak coupling BCS theory, without any lifetime broadening parameter, over the whole sample surface. We detect no particular change of the tunneling spectroscopy below 1.5K, when both the antiferromagnetic (AF) phase and the superconducting order coexist.Comment: Submitted to Phys. Rev. B, Rapid Communication

Magnetic field-induced dissipation-free state in superconducting nanostructures

A superconductor in a magnetic field acquires a finite electrical resistance caused by vortex motion. A quest to immobilize vortices and recover zero resistance at high fields made intense studies of vortex pinning one of the mainstreams of superconducting research. Yet, the decades of efforts resulted in a realization that even promising nanostructures, utilizing vortex matching, cannot withstand high vortex density at large magnetic fields. Here, we report a giant reentrance of vortex pinning induced by increasing magnetic field in a W-based nanowire and a TiN-perforated film densely populated with vortices. We find an extended range of zero resistance with vortex motion arrested by self-induced collective traps. The latter emerge due to order parameter suppression by vortices confined in narrow constrictions by surface superconductivity. Our findings show that geometric restrictions can radically change magnetic properties of superconductors and reverse detrimental effects of magnetic field

Disordered hyperuniformity in superconducting vortex lattices

The current carrying capability of type II superconductors under magnetic fields is determined to a large extent by the interaction of superconducting vortices with pinning centers. Vortices are arranged in lattices with varying degrees of disorder depending on the balance between the intervortex interactions and the pinning strength. We analyze here vortex arrangements in disordered vortex lattices of different superconducting systems, single crystals (Co-doped NbSe2, LiFeAs, and CaKFe4As4), and amorphous W- based thin films (with critical temperatures T-c from 4 K to 35 K and critical fields from 3.4 T to more than 90 T). We calculate for each case the structure factor and number variance and compare to calculations on an interacting set of partially pinned particles. We find that random density fluctuations appear when pinning overcomes interactions and show that the suppression of density fluctuations is correlated to the presence of interactions. We discuss the results within the framework of hyperuniform distributions and find that all studied lattices follow a similar increase of the number variance with the defect density