Soziale Ungleichheiten in der Kompetenzentwicklung in der Grundschule und der Sekundarstufe I

Im Zentrum des vorliegenden Beitrags steht die Frage, wie sich die Kompetenzen von Schülerinnen und Schülern unterschiedlicher sozialer Herkunft während der Grundschule und der Sekundarstufe I entwickeln. Dabei ist vor allem von Interesse, inwieweit bereits zu Beginn der Schullaufbahn bestehende Leistungsunterschiede zwischen Schülerinnen und Schülern mit unterschiedlichem sozialem Hintergrund im Laufe der Schulzeit weiter zunehmen, stabil bleiben oder eventuell sogar konvergierende Entwicklungsverläufe zu beobachten sind. Vor diesem Hintergrund werden vorhandene nationale und internationale Längsschnittstudien herangezogen, um ein Bild über empirisch vorzufindende Entwicklungsverläufe zeichnen zu können. Eine Reihe der vorliegenden Befunde deutet auf eine Öffnung der Leistungsschere zwischen Schülerinnen und Schülern unterschiedlicher sozialer Herkunft während der Schulzeit hin, wobei die diesbezügliche Befundlage für die Grundschule konsistenter ausfällt als für die weiterführenden Schulen. Darüber hinaus finden sich auch Hinweise dafür, dass die Schule und die institutionelle Ausgestaltung des Bildungssystems mit zur Öffnung der Leistungsschere beitragen.The article focuses on the question how competencies of students with different social backgrounds develop during elementary and secondary school. In particular, it addresses if achievement disparities which exist before school entrance increase, remain stable, or even diminish during schooling. The article draws on both national and international studies with longitudinal designs examining the achievement development of students of different social backgrounds during primary or secondary school. Although the results are mixed to some extent, a large part indicates that differences in achievement increase during the time of schooling. The evidence seems more consistent for achievement development during elementary school. Additionally, there is some indication that schools and features of the educational system contribute to increasing achievement disparities between students of different social backgrounds

Comparação de modelos matemáticos para descrição das curvas de dessorção de sementes de milho-doce Comparison of mathematical models for description of desorption curves of sweet corn seeds

Este trabalho teve como objetivo determinar as curvas de dessorção das sementes de milho-doce (Zea mays L.), cultivares Superdoce e Doce Cristal, e ajustar diferentes modelos matemáticos aos dados obtidos. As sementes das duas cultivares foram submetidas à dessorção em diversos níveis de temperatura (30, 40, 50 e 60°C), combinados com diferentes umidades relativas do ar (30, 40, 50 e 60%), até atingirem a umidade de equilíbrio. Os seguintes modelos matemáticos foram ajustados por análise de regressão: Henderson-Thompson, Chung-Pfost, Copace, Sigma-Copace, Sabbah e Smith. As sementes das duas cultivares apresentaram umidades de equilíbrio higroscópico semelhantes. Os valores da variância explicada e do desvio-padrão, bem como a distribuição dos resíduos, das duas cultivares, indicam que as equações de Chung-Pfost, Sabbah e Smith foram as que melhor se ajustaram aos dados experimentais, com pequena superioridade da primeira.<br>This work had the goal to determine the desorption curves of seeds of sweet corn cultivars Superdoce and Doce Cristal, and to adjust mathematical models to obtained data. Corn seeds were submitted to desorption under different temperature conditions (30, 40, 50 and 60°C), associated with different relative humidity (30, 40, 50 and 60%) until reaching the equilibrium humidity. The following models of regression analysis were adjusted to the experimental data: Henderson-Thompson, Chung-Pfost, Copace, Sigma-Copace, Sabbah and Smith. Seeds of both cultivars showed similar hygroscopic equilibrium. For both cultivars, the equations of Chung-Pfost, Sabbah and Smith, showed the best adjustments to the experimental data, with slight superiority of the first one