Activity autocorrelation in financial markets. A comparative study between several models

We study the activity, i.e., the number of transactions per unit time, of financial markets. Using the diffusion entropy technique we show that the autocorrelation of the activity is caused by the presence of peaks whose time distances are distributed following an asymptotic power law which ultimately recovers the Poissonian behavior. We discuss these results in comparison with ARCH models, stochastic volatility models and multi-agent models showing that ARCH and stochastic volatility models better describe the observed experimental evidences.Comment: 15 pages, 4 figure

Las exequias de Carlos III en Palma de Mallorca

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La "festa barroca" a la Mallorca del segle XVII

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Les mineralitzacions de Manganès de Natjà (Llitera) i d'Estopanyà (Baixa Ribagorça) Països Catalans

En este trabajo se estudian las mineralizaciones de manganeso, constituidas principalmente por Psilomelana y Pirolusita, que se han desarrollado a expensas de la meteorización de las calizas cretácicas sitas en las inmediaciones de Estopanyà y de Natjà.Para ello, se inicia el trabajo con una breve síntesis de los condicionantes geológicos, sobre los que se han desarrollado tales normalizaciones, para pasar a estudiar, luego, cada uno los yacimientos.Tras los estudios, se llega a la conclusión de que posiblemente los citados yacimientos tienen su origen en la meteorización de las calizas cretácicas, ligada al desarrollo de fenómenos kársticos en las mismas

The Role of Ghrelin in Reward-Based Eating

The peptide hormone ghrelin acts in the central nervous system as a potent orexigenic signal. Not only is ghrelin recognized as playing an important role in feeding circuits traditionally thought of as affecting body weight homeostasis, but also an accumulating number of scientific studies have identified ghrelin as being a key regulator of reward-based, hedonic eating behaviors. In the current article, we review ghrelin's orexigenic actions, the evidence linking ghrelin to food reward behavior, potential mechanisms by which ghrelin mediates reward-based eating behavior, and those studies suggesting an obligatory role for ghrelin in the changed eating behaviors induced by stress.Instituto Multidisciplinario de Biología Celula

The Role of Ghrelin in Reward-Based Eating

The peptide hormone ghrelin acts in the central nervous system as a potent orexigenic signal. Not only is ghrelin recognized as playing an important role in feeding circuits traditionally thought of as affecting body weight homeostasis, but also an accumulating number of scientific studies have identified ghrelin as being a key regulator of reward-based, hedonic eating behaviors. In the current article, we review ghrelin's orexigenic actions, the evidence linking ghrelin to food reward behavior, potential mechanisms by which ghrelin mediates reward-based eating behavior, and those studies suggesting an obligatory role for ghrelin in the changed eating behaviors induced by stress.Instituto Multidisciplinario de Biología Celula