In this work we consider a structured population with groups and subgroups of individuals. The intra-group dynamics is assumed to be fast in comparison with the inter-group dynamics. We study linear discrete models where the slow dynamics is represented by a single matrix and the fast dynamics is described by means of the first k terms of a converging sequence of different matrices. The number k can be interpreted as the ratio between the two time scales. The aim of this (...) work is to extend aggregation techniques to the case of fast changing environments. The main idea of aggregation is to build up a new system, with lower dimension, that summarizes the information concerning the fast process. This "aggregated" system provides essential information on the original one. It is shown that the asymptotic behavior of the original system can be approximated by the asymptotic behavior of the aggregated system when the ratio between the two time scales is large enough. We present an example of an age structured population in a patchy environment. The migration process is assumed to be fast in comparison with the demographic process. Numerical simulations illustrate that the asymptotic growth rate and the stable age distribution of the population in the original and the aggregated systems are getting closer as the ratio k increases. (shrink)

As the result of the complexity inherent in nature, mathematical models employed in ecology are often governed by a large number of variables. For instance, in the study of population dynamics we often deal with models for structured populations in which individuals are classified regarding their age, size, activity or location, and this structuring of the population leads to high dimensional systems. In many instances, the dynamics of the system is controlled by processes whose time scales are very different from (...) each other. Aggregation techniques take advantage of this situation to build a low dimensional reduced system from which behavior we can approximate the dynamics of the complex original system.In this work we extend aggregation techniques to the case of time dependent discrete population models with two time scales where both the fast and the slow processes are allowed to change at their own characteristic time scale, generalizing the results of previous studies. We propose a non-autonomous model with two time scales, construct an aggregated model and give relationship between the variables governing the original and the reduced systems. We also explore how the properties of strong and weak ergodicity, regarding the capacity of the system to forget initial conditions, of the original system can be studied in terms of the reduced system. (shrink)

Este trabajo estudia el concepto de “lo sublime” en la cultura barroca, con el objetivo de demostrar que, aunque no fue teorizado sistemáticamente hasta el siglo XVIII, este cobró durante el siglo XVII una centralidad y, sobre todo, un significado filosófico semejantes a los que se impondrían posteriormente y que, según veremos, está estrechamente ligado con el concepto de “nihilismo”.

"El XI Encuentro Internacional de Escritores de Monterrey organizado por el Consejo para la Cultura y las Artes de Nuevo León, tuvo como invitados a autores de México, Ecuador, Cuba, Estados Unidos, Perú, Uruguay, Costa Rica, Venezuela, Argentina y Nueva Zelanda. La sede del encuentro fue el Area Tierra del Museo de Historia Mexicana durante el 5, 6, y 7 de octubre de 2006"--Page 4 of cover.

Pretende-se investigar a estética e a religião na filosofia de Max Horkheimer, enquanto instâncias de crítica à ordem estabelecida e à imagem de uma sociedade possível ainda não realizada. Mesmo não tendo desenvolvido um pensamento estético de grande envergadura, como foram os casos de Adorno e Marcuse, suas esparsas considerações sobre a relação entre arte e sociedade coincidiram, durante longo período, com as de seus dois colegas do Instituto de Pesquisa Social. Ou seja, a arte autêntica é conhecimento e crítica (...) à sociedade estabelecida. Por sua vez, a religião, embora seja um sentimento verdadeiro, é posta em um nível inferior e concebida como refúgio para os miseráveis, dentro da tradição marxista na qual o filósofo se inserira inicialmente. Ao final da vida, porém, Horkheimer pareceu mais inclinado a considerar que, no mundo administrado, apenas o sentimento religioso cumpria a condição de imagem de um mundo inteiramente outro. As razões para essa mudança de perspectiva podem ser buscadas na sua avaliação tardia sobre a relação entre arte e sociedade. (shrink)

A collection of essays on the human genome, European patent law, cloning, and genetic malpractice suits.