Polytechnic Institute of Lisbon

About: Polytechnic Institute of Lisbon is a education organization based out in Lisbon, Portugal. It is known for research contribution in the topics: Monetary policy & New Keynesian economics. The organization has 261 authors who have published 368 publications receiving 3569 citations. The organization is also known as: Polytechnical Institute of Lisbon.

Globalization, Regime-Switching, and EU Stock Markets: the Impact of the Sovereign Debt Crises

Abstract: The electoral cycle literature has developed in two clearly distinct phases. The first one considered the existence of non-rational (naive) voters whereas the second one considered fully rational voters. It is our view that an intermediate approach is more appropriate, i.e. one that considers learning voters, which are boundedly rational. In this sense, one may consider perceptrons as learning mechanisms used by voters to perform a classification of the incumbent in order to distinguish opportunistic (electorally motivated) from benevolent (non-electorally motivated) behaviour of the government. The paper explores precisely the problem of how to classify a government showing in which, if so, circumstances a perceptron can resolve that problem. This is done by considering a model recently considered in the literature, i.e. one allowing for output persistence, which is a feature of aggregate supply that, indeed, may turn impossible to correctly classify the government.

SUFFIX ARRAYS - A Competitive Choice for Fast Lempel-Ziv Compressions

Abstract: Keywords: Lempel-Ziv, Lossless Data Compression, Suffix Arrays, Suffix Tre es, String Matching.Abstract: Lossless compression algorithms of the Lempel-Ziv (LZ) family are widely used in a variety of applications.The LZ encoder and decoder exhibit a high asymmetry, regarding time and memory requirements, with theformer being much more demanding. Several techniques have been used to speed up the encoding process;among them is the use of suffix trees. In this paper, we explore the use of a simple data structure, namedsuffix array , to hold the dictionary of the LZ encoder, and propose an algorithm to search the dictionary.A comparison with the suffix tree based LZ encoder is carried out, showin g that the compression ratios areroughly the same. The ammount of memory required by the suffix arra y is fixed, being much lower than thevariable memory requirements of the suffix tree encoder, which depen ds on the text to encode. We concludethat suffix arrays are a very interesting option regarding the tradeoff b etween time, memory, and compressionratio, when compared with suffix trees, that make them preferable in som e compression scenarios.

Populational Growth Model Proportional to Beta Densities

Abstract: We consider populations growth models with Allee effect, proportional to beta densities with shape parameters p and 2, where the dynamical complexity is related with the Malthusian parameter r. For p > 2, these models exhibit a population dynamics with natural Allee effect. However, in the case of 1< p• 2, the proposed models do not include this effect. In order to inforce it, we present some alternative models and investigate their dynamics, presenting some important results.

Fungal Contamination of Sandpits from Recreational Parks and Schools: A Potential Risk for Human Health

Abstract: Sandpits used by children are frequently visited by wild life which constitutes a source of fungal pathogens and allergenic fungi. This study aimed to take an unannounced snapshot of the urban levels of fungal contaminants in sands, using for this purpose two public recreational parks, three elementary schools and two kindergartens. All samples were from Lisbon and neighboring municipalities and were tested for fungi of clinical interest. Potentially pathogenic fungi were isolated from all samples besides one. Fusarium dimerum (32.4%) was found to be the dominant species in one park and Chrysonilia spp. in the other (46.6%). Fourteen different species and genera were detected and no dermatophytes were found. Of a total of 14 species and genera, the fungi most isolated from the samples of the elementary schools were Penicillium spp. (74%), Cladophialophora spp. (38%) and Cladosporium spp. (90%). Five dominant species and genera were isolated from the kindergartens. Penicillium spp. was the only genus isolated in one, though with remarkably high counts (32500 colony forming units per gram). In the other kindergarten Penicillium spp. were also the most abundant species, occupying 69% of all the fungi found. All of the samples exceeded the Maximum Recommended Value (MRV) for beach sand defined by Brandao et al. 2011, which are currently the only quantitative guidelines available for the same matrix. The fungi found confirm the potential risk of exposure of children to keratinophilic fungi and demonstrates that regular cleaning or replacing of sand needs to be implemented in order to minimize contamination.