University of Lisbon

About: University of Lisbon is a education organization based out in Lisbon, Lisboa, Portugal. It is known for research contribution in the topics: Population & Context (language use). The organization has 19122 authors who have published 48503 publications receiving 1102623 citations. The organization is also known as: Universidade de Lisboa & Lisbon University.

A finite element analysis of the effect of electrode area and inter-electrode distance on the spatial distribution of the current density in tDCS

Abstract: We investigated the effect of electrode area and inter-electrode distance on the spatial distribution of the current density in transcranial direct current stimulation (tDCS). For this purpose, we used the finite element method to compute the distribution of the current density in a four-layered spherical head model using various electrode montages, corresponding to a range of electrode sizes and inter-electrode distances. We found that smaller electrodes required slightly less current to achieve a constant value of the current density at a reference point on the brain surface located directly under the electrode center. Under these conditions, smaller electrodes also produced a more focal current density distribution in the brain, i.e. the magnitude of the current density fell more rapidly with distance from the reference point. The combination of two electrodes with different areas produced an asymmetric current distribution that could lead to more effective and localized neural modulation under the smaller electrode than under the larger one. Focality improved rapidly with decreasing electrode size when the larger electrode sizes were considered but the improvement was less marked for the smaller electrode sizes. Also, focality was not affected significantly by inter-electrode distance unless two large electrodes were placed close together. Increasing the inter-electrode distance resulted in decreased shunting of the current through the scalp and the cerebrospinal fluid, and decreasing electrode area resulted in increased current density on the scalp under the edges of the electrode. Our calculations suggest that when working with conventional electrodes (25-35 cm(2)), one of the electrodes should be placed just 'behind' the target relative to the other electrode, for maximum current density on the target. Also electrodes with areas in the range 3.5-12 cm(2) may provide a better compromise between focality and current density in the scalp than the traditional electrodes. Finally, the use of multiple small return electrodes may be more efficient than the use of a single large return electrode.

Topography-driven isolation, speciation and a global increase of endemism with elevation

Abstract: Additional co-authors: Jose Maria Fernandez-Palacios, Rosalina Gabriel, Roy E. Gereau, Rosemary G. Gillespie, Josef Greimler, David E.V. Harter, Tsurng-Juhn Huang, Severin D.H. Irl , Daniel Jeanmonod, Anke Jentsch, Christoph Kueffer, Sandra Nogue, Rudiger Otto, Jonathan Price, Maria M. Romeiras, Dominique Strasberg, Tod Stuessy, Jens-Christian Svenning, Ole R. Vetaas, Carl Beierkuhnlein

From prejudice to discrimination: The legitimizing role of perceived threat in discrimination against immigrants

Abstract: This research analyses the mediational role of threat perception in the relationship between prejudice and discrimination (opposition to immigration and opposition to naturalization ofimmigrants). In the first study, using representative samples in 21 European countries (N ¼36566) from European Social Survey (2002), we showed that the relationship between prejudice and opposition to immigration was more strongly mediated by realistic than by symbolic threat perceptions. In Study 2, using representative samples in two countries with different traditions of immigration (Switzerland, N ¼940; Portugal, N ¼1514), we showed that realistic threat more strongly mediated the relationship between prejudice and opposition to immigration, while only symbolic threat perception mediated the link between prejudice and opposition to naturalization. The theoretical implications of considering threat perceptions as factors that legitimize discrimination are discussed. Copyright # 2009 John Wiley & Sons, Ltd.