Superinflation, quintessence, and the avoidance of the initial singularity

We consider the dynamics of a spatially flat universe dominated by a self-interacting nonminimally coupled scalar field. The structure of the phase space and complete phase portraits for the conformal coupling case are given. It is shown that the non-minimal coupling modifies drastically the dynamics of the universe. New cosmological behaviors are identified, including superinflation ($\dot{H}>0$), avoidance of big bang singularities through classical birth of the universe from empty Minkowski space, and spontaneous entry into and exit from inflation. The relevance of this model to the description of quintessence is discussed.Comment: RevTex, 10 pages, 4 figures, To appear in the proceedings of the 5th Peyresq meetin

Online-learning at ISCTE-IUL: towards a sustainable education paradigm

Online-learning platforms have long been praised for their great benefits, such as the way they contribute to long-distance students being able to overcome geographical barriers to their education, and the way they allow students to self-manage, by autonomously deciding when they enroll and complete courses. This empowers people from all over the world to engage in lifelong-learning that may have an important impact in their daily lives, especially in developing countries. Besides these benefits, there’s also an important dimension that is often overlooked: the contribution that the use of online-learning platforms has in providing a sustainable environment by reducing environmentally-damaging effects and the use of scarce resources. In this paper, we present the economical and environmental impact that the use of an online-learning platform has had in a public University in Lisbon, Portugal. We first present the online-learning platform that was developed in-house and follow up by describing the positive impact that this education paradigm has had in the lives of students, in reducing costs at the University, and in contributing to a more sustainable future.info:eu-repo/semantics/acceptedVersio

Foraminifers from the Lower-Middle Jurassic boundary of the Lusitanian Basin: Murtinheira section (North Sector) and Zambujal de Alcaria section (Central Sector)

Comunicação apresentada ao VIII Congresso Nacional de Geologia, em Braga (9-16 de Julho 2010)análise da diversidade taxonómica e das abundâncias relativas nas associações de foraminíferos da passagem Jurássico Inferior-Médio em dois sectores da Bacia Lusitânica indica que tais associações apresentam diferenças nas suas composições, aparentemente homogéneas. Assim, as associações de zonas proximais (perfil de Zambujal de Alcaria) são mais abundantes e com maior diversidade que as registadas em zonas distais (perfil da Murtinheira). Além disso, a maioria dos taxa comuns em ambas as zonas apresentam diferenças nas suas abundâncias relativas, que parecem resultar de preferências paleo-ambientais distintas.The analysis of diversity and relative abundances of foraminiferal assemblages from two sections located in the Lusitanian Basin, and corresponding to the Lower-Middle Jurassic boundary, shows that these apparently homogeneous assemblages present differences in their composition. Assemblages from shallow zones (Zambujal de Alcaria section) show higher diversity and abundance than assemblages from deeper zones (Murtinheira section). Species recorded in both areas show distinct values on their relative abundances, as a possible relationship with their palaeo-environmental preferences

Tracking e-learning through published papers: a systematic review

Electronic learning (e-learning) is a broader approach to learning that brings new opportunities for learning and teaching in many fields of education far from the traditional classroom environment. Over the past decades, research in the field indicates a proliferation of e-learning contents and discrepancies that affect interoperability patterns in education for students and teachers; however, little has been done to assess the usability of e-learning systems. From a different perspective, this study aims to provide information on the numerous findings relating to the cumulative results of e-learning in education. This systematic review uses a full protocol with the aim of standardizing and specifying all the procedures adopted to collect and code 99 academic articles from 2010 to 2018 with keywords: education and e-learning. The text analysis as conducted using the qualitative software Leximancer to extract meaning from the large number of articles retrieved. The results highlight four dominant themes, namely education systems and learning issues that in turn promote student behaviours and the use of online learning tools. This research contributes towards providing research propositions that can be used in a cogent theoretical framework and, based on the analysis, we also propose a new definition of e-learning.info:eu-repo/semantics/acceptedVersio

Modeling and simulation of wetted porous thermal barriers operating under high temperature or high heat flux

Porous media with high water content can be successfully used as thermal barriers to operate under high exposure temperatures and/or high heat fluxes. Modeling and simulation of such systems presents difficulties and challenges, which are pointed and worked out in this work. Liquid water and water vapor transfers are considered, including the capillary effects for the liquid phase, as well as the air transfer inside the porous medium. Heat transfer model includes conduction, radiation, enthalpy convection, sensible heating and phase change. A realistic model is considered at the exposed boundary in what concerns mass transfer: the outflow mass transfer is dictated by the water effusion and not by the convection transfer mechanism between the exposed surface and the environment. A set of numerical aspects is detailed, concerning both the numerical modeling and the solution of the discretization equations, which are crucial to obtain successful simulations. Some illustrative results are presented, showing the potential of the wetted porous media when used as thermal barriers, as well as the capabilities of the presented physical and numerical models to deal with such systems.http://www.sciencedirect.com/science/article/B6V3H-4RKDHVC-2/1/633ef2cefc7a7e2178f1d59743e3d24

Indirect Impact Assessment of Pluvial Flooding in Urban Areas Using a Graph-Based Approach: The Mexico City Case Study

This paper presents the application of a graph-based methodology for the assessment of flood impacts in an urban context. In this methodology, exposed elements are organized as nodes on a graph, which is used to propagate impacts from directly affected nodes to other nodes across graph links. Compared to traditional approaches, the main advantage of the adopted methodology lies in the possibility of identifying and understanding indirect impacts and cascading effects. The application case concerns floods numerically reconstructed in Mexico City in response to rainfall events of increasing return periods. The hazard reconstruction was carried out by using a simplified hydrological/hydraulic model of the urban drainage system, implemented in EPASWMM, the Storm Water Management Model developed by the United States Environmental Protection Agency. The paper shows how the impacts are propagated along different orders of the impact chain for each return period and compares the risk curves between direct and indirect impact. It also highlights the extent to which the reduction in demand of services from consumers and the loss of services from suppliers are respectively contributing to the final indirect impacts. Finally, it illustrates how different impact mitigation measures can be formulated based on systemic information provided by the analysis of graph properties and taking into account indirect impacts