973 resultados para 6-51


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We investigate the gradual changes of the microstructure of two blends of high-density polyethylene (HDPE) and polyamide 6 (PA6) at opposite composition filled with increasing amounts of an organomodified clay. The filler locates preferentially inside the polyamide phase, bringing about radical alterations in the micron-scale arrangement of the polymer phases. When the host polyamide represents the major constituent, a sudden reduction of the average sizes of the polyethylene droplets was observed upon addition of even low amounts of organoclay. A morphology refinement was also noticed at low filler contents when the particles distributes inside the minor phase. In this case, however, keep increasing the organoclay content eventually results in a high degree of PA6 phase continuity. Rheological analyses reveal that the filler loading at which the polyamide assembles in a continuous network corresponds to the critical threshold for its rheological transition from a liquid- to a gel-like behaviour, which is indicative of the structuring of the filler inside the host PA6. On the basis of this finding, a schematic mechanism is proposed in which the role of the filler in driving the space arrangement of the polymer phases is discussed. Finally, we show that the synergism between the reinforcing action of the filler and its ability to affect the blend microstructure can be exploited in order to enhance relevant technological properties of the materials, such as their high temperature structural integrity.

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Este trabajo analiza los resultados de una investigación sobre hábitos lectores del alumnado asturiano de 6º de Educación Primaria en su tiempo libre. El estudio utiliza una muestra de 324 escolares de centros públicos urbanos, con edades comprendidas entre los 11 y 12 años, para analizar datos relativos a la actitud hacia la lectura, la importancia de ésta entre las actividades de ocio y la frecuencia lectora.Más de la mitad de los escolares manifiesta una actitud bastante favorable hacia la lectura, y ésta es una de sus actividades de ocio habituales, aunque dedican más tiempo a ver televisión, practicar deportes, usar el ordenador y escuchar música. La mayoría son lectores frecuentes, aunque los no lectores y lectores ocasionales ascienden hasta un 12,96%. Los escolares encuestados leen principalmente libros, seguidos de revistas y cómics, mientras que poco más de un tercio dice leer periódicos frecuentemente.Esta investigación revela también algunas variaciones en actitud hacia la lectura y frecuencia lectora según el centro educativo de procedencia que se pueden relacionar con variables de tipo socio-económico. Además, se observan diferencias entre niños y niñas, pues éstas superan a sus compañeros varones en interés y frecuencia lectora, además de manifestar también divergencias en las preferencias de materiales de lectura.

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Background: Many school-based interventions are being delivered in the absence of evidence of effectiveness (Snowling & Hulme, 2011, Br. J. Educ. Psychol., 81, 1).Aim: This study sought to address this oversight by evaluating the effectiveness of the commonly used the Lexia Reading Core5 intervention, with 4- to 6-year-old pupils in Northern Ireland.Sample: A total of 126 primary school pupils in year 1 and year 2 were screened on the Phonological Assessment Battery 2nd Edition (PhAB-2). Children were recruited from the equivalent year groups to Reception and Year 1 in England and Wales, and Pre-kindergarten and Kindergarten in North America.
Methods: A total of 98 below-average pupils were randomized (T0) to either an 8-week block (inline image = 647.51 min, SD = 158.21) of daily access to Lexia Reading Core5 (n = 49) or a waiting-list control group (n = 49). Assessment of phonological skills was completed at post-intervention (T1) and at 2-month follow-up (T2) for the intervention group only.
Results: Analysis of covariance which controlled for baseline scores found that the Lexia Reading Core5 intervention group made significantly greater gains in blending, F(1, 95) = 6.50, p = .012, partial η2 = .064 (small effect size) and non-word reading, F(1, 95) = 7.20, p = .009, partial η2 = .070 (small effect size). Analysis of the 2-month follow-up of the intervention group found that all group treatment gains were maintained. However, improvements were not uniform among the intervention group with 35% failing to make progress despite access to support. Post-hoc analysis revealed that higher T0 phonological working memory scores predicted improvements made in phonological skills.
Conclusions: An early-intervention, computer-based literacy program can be effective in boosting the phonological skills of 4- to 6-year-olds, particularly if these literacy difficulties are not linked to phonological working memory deficits.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)