Coordination of aproximations in secondary school students’ understanding of limit concept

The aim of this research is to characterize the coordination of the processes of approximation related to the understanding of the limit of a function. We analyze the answers of 64 post-secondary school students to 7 problems considering the dynamic and metric conception of limit of a function. Results indicate that the metric understanding of the limit in terms of inequality supports that the student is capable of coordinating the approximations in the domain and in the range when lateral approximations coincide. However, the student is not capable of this coordination when lateral approximations do not coincide. This indicates that the metric understanding of the limit begins with the previous construction of the dynamic conception in case of coincidence of the lateral approximations in the range.

Características de la tematización del esquema de límite de una función

Esta investigación estudia las diferentes estructuras subyacentes en el esquema de límite de una función observadas en 23 estudiantes de Bachillerato situados en el nivel Trans del desarrollo del esquema de límite de una función. El esquema de límite de una función se caracterizó en términos de la habilidad que los estudiantes manifestaron en la construcción de la concepción dinámica del límite mediante la coordinación de los procesos de aproximación en el dominio y en el rango, diferenciando aquellas en las que las aproximaciones laterales coinciden de las que no coinciden. Nuestros resultados sugieren que los estudiantes construyen diferentes estructuras subyacentes al esquema debido a las relaciones que establecen entre el límite de una función en un punto y su representación gráfica que permiten identificar características del esquema tematizado del límite de una función.

Amphibian Hotspots and Conservation Priorities in Eastern Cuba Identified by Species Distribution Modeling

The high rate of amphibian endemism and the severe habitat modification in the Caribbean islands make them an ideal place to test if the current protected areas network might protect this group. In this study, we model distribution and map species richness of the 40 amphibian species from eastern Cuba with the objectives of identify hotspots, detect gaps in species representation in protected areas, and select additional areas to fill these gaps. We used two modeling methods, Maxent and Habitat Suitability Models, to reach a consensus distribution map for each species, then calculate species richness by combining specific models and finally performed gap analyses for species and hotspots. Our results showed that the models were robust enough to predict species distributions and that most of the amphibian hotspots were represented in reserves, but 50 percent of the species were incompletely covered and Eleutherodactylus rivularis was totally uncovered by the protected areas. We identified 1441 additional km2 (9.9% of the study area) that could be added to the current protected areas, allowing the representation of every species and all hotspots. Our results are relevant for the conservation planning in other Caribbean islands, since studies like this could contribute to fill the gaps in the existing protected areas and to design a future network. Both cases would benefit from modeling amphibian species distribution using available data, even if they are incomplete, rather than relying only in the protection of known or suspected hotspots.

Les débats parlementaires autour du suffrage universel dans la construction de la représentation politique en Espagne et en Argentine: vers une analyse comparée (1860-1870)

This article aims to undertake a preliminary comparative review of the concepts of political representation developed by the Spanish and Argentinean liberalism during the construction of the parliamentary and constitutional regimes in the nineteenth century. The idea of the representative government, as a regulatory mechanism of political participation, is considered in terms of an analysis of the right to vote, of the processes to develop citizenship, and of political modernization. Legislation on the right to vote, born as the political right par excellence during the nineteenth century, gives an excellent guide to these political processes of major scope and depth that characterize the contemporary world. The comparison between the Spanish and Argentinean cases shows that exchanges, transfers of legislative models and cultural movements took place in the birth of the concept of political representation in both countries. This enables us to identify the differences of in each case.

Il valore del voto: Italia e Spagna nel dibattito sulla rappresentanza politica liberale (1860-1870)

During the 1860's and 1870's, Spain and Italy experienced a convergence of debates on the significance of political representation in the framework of Liberal State. Spain suffered a political and social crisis, ending with the Revolution of 1868 and the adoption of male universal suffrage in 1878. Its coeval Italy began to build its new Kingdom, anxious about state building, as well as the relevance of electoral processes in the Constitutional scheme. Although members of parliament and essayists of both countries well knew their neighbour's political reality, a dialogue on representation didn't occur. Nonetheless, we believe it is useful to analyse the survey drawn by the Italian publicist in the light of current knowledge of the opinions that prevailed in Spain. What sense did they give to the general election? How did they understand the value of the vote? Who were considered eligible voters? These questions comprise the main subjects of the essay.