Cooperation, Punishment, Emergence of Government, and the Tragedy of Authorities

Under the conditions prevalent in the late Pleistocene epoch (small hunter-gatherer groups and frequent inter-group conflicts), coevolution of gene-related behavior and culturally transmitted group-level institutions provides a plausible explanation for the parochial altruistic and reciprocator traits of most modern humans. When, with the agricultural revolution, societies became larger and more complex, the collective nature of the monitoring and punishment of norm violators was no longer effective. This led to the emergence of new institutions of governance and social hierarchies. The transition from an egalitarian society and the acceptance of the new institutions may have been possible only if, in the majority of the population, the reciprocator trait had become an internalized norm. However, the new ruling class has its own dynamics, which in turn may lead to a new social crisis. Using a simple model inspired by previous work by Bowles and Gintis, these effects are studied here

The fractional volatility model : no-arbitrage, leverage and completeness

When the volatility process is driven by fractional noise one obtains a model which is consistent with the empirical market data. Depending on whether the stochasticity generators of log-price and volatility are independent or are the same, two versions of the model are obtained with different leverage behaviors. Here, the no-arbitrage and completeness properties of the models are rigorously studied

Elogio histórico do professor António da Silveira

info:eu-repo/semantics/publishedVersio

The impact of acetate metabolism on yeast fermentative performance and wine quality: reduction of volatile acidity of grape musts and wines

Acetic acid is the main component of the volatile acidity of grape musts and wines. It can be formed as a byproduct of alcoholic fermentation or as a product of the metabolism of acetic and lactic acid bacteria, which can metabolize residual sugars to increase volatile acidity. Acetic acid has a negative impact on yeast fermentative performance and affects the quality of certain types of wine when present above a given concentration. In this minireview, we present an overview of fermentation conditions and grape-must composition favoring acetic acid formation, as well the metabolic pathways leading to its formation and degradation by yeast. The negative effect of acetic acid on the fermentative performance of Saccharomyces cerevisiae will also be covered, including its role as a physiological inducer of apoptosis. Finally, currently available wine deacidification processes and new proposed solutions based on zymological deacidification by select S. cerevisiae strains will be discussed.Fundação para a Ciência e Tecnologi

Tomographic analysis of reflectometry data II: the phase derivative

A tomographic technique has been used in the past to decompose complex signals in its components. The technique is based on spectral decomposition and projection on the eigenvectors of a family of unitary operators. Here this technique is also shown to be appropriate to obtain the instantaneous phase derivative of the signal components. The method is illustrated on simulated data and on data obtained from plasma reflectometry experiments in the Tore Supra.Comment: 25 pages, Latex, 17 figure

Signal-adapted tomography as a tool for dust devil detection

Dust devils are important phenomena to take into account to understand the global dust circulation of a planet. On Earth, their contribution to the injection of dust into the atmosphere seems to be secondary. Elsewhere, there are many indications that the dust devil’s role on other planets, in particular on Mars, could be fundamental, impacting the global climate. The ability to identify and study these vortices from the acquired meteorological measurements assumes a great importance for planetary science. Here we present a new methodology to identify dust devils from the pressure time series testing the method on the data acquired during a 2013 field campaign performed in the Tafilalt region (Morocco) of the North- Western Sahara Desert. Although the analysis of pressure is usually studied in the time domain, we prefer here to follow a different approach and perform the analysis in a time signal-adapted domain, the relation between the two being a bilinear transformation, i.e. a tomogram. The tomographic technique has already been successfully applied in other research fields like those of plasma reflectometry or the neuronal signatures. Here we show its effectiveness also in the dust devils detection. To test our results, we compare the tomography with a phase picker time domain analysis. We show the level of agreement between the two methodologies and the advantages and disadvantages of the tomographic approach