999 resultados para Primary cementing
Resumo:
In constant, search for micro/mesoporous materials, gallium phosphates, have attracted continued interest due to the large pore size reported for some of these solids in comparison with analogous aluminum phosphates. However up to now, the porosity of gallium phosphates collapsed upon template removal or exposure to the ambient moisture. In the present work, we describe high-surface thermally stable mesoporous gallium phosphates synthesized from gallium propoxide and PCl3 and different templating agents such as amines (dipropylamine, piperidine and aminopiperidine) and quaternary ammonium salts (C16H33(CH3)3NBr and C16PyCl). These highly reactive precursors have so far not been used as gallium and phosphate sources for the synthesis of gallophosphates. Conceptually, our present synthetic procedure is based on the fast formation of gallium phosphate nanoparticles via the reaction of gallium propoxide with PCl3 and subsequent construction of the porous material with nanoparticles as building blocks. The organization of the gallophosphate nanoparticles in stable porous structures is effected by the templates. Different experimental procedures varying the molar composition of the sol-gel, pH and the pretreatment of gallium precursor were assayed, most of them leading to satisfactory materials in terms of thermal stability and porosity. In this way, a series of gallium phosphates with surface are above 200 m(2) g(-1), and narrow pore size from 3 to 6 nm and remarkable thermal stability (up to 550 degrees C) have been prepared. In some cases, the structure tends to show some periodicity and regularity as determined by XRD. The remarkable stability has allowed us to test the catalytic activity of gallophosphates for the aerobic oxidation of alkylaromatics with notable good results. Our report reopens the interest for gallophosphates in heterogeneous catalysis. (C) 2010 Elsevier Inc. All rights reserved.
Resumo:
Background: Previous research has produced conflicting results regarding the effects of season of birth and age-position on cognitive attainments. In Northern Ireland the school year divides the summer season into two providing an opportunity to evaluate the relative contribution of season of birth and age-position effects. Aims: To investigate the relationship between attainment in literacy skills and month of birth for primary and secondary school pupils and to determine the relationship between motor skills and month of birth in primary school pupils. Sample: One thousand one hundred and twenty four primary school pupils participated, and results for key stage 3 (KS3) English and GCSE English Language, for 3,493 Year 10 and 3,697 Year 12 secondary school pupils, respectively, were obtained. Method: Primary school pupils were individually assessed using standardised reading and spelling tests, as well as tests of motor skill. They were also assessed using a standardised group reading test in their class groups. For the secondary school pupils, the results for two year cohorts, in KS3 English and GCSE English language, respectively, were analysed. Results: For the primary school pupils there was evidence of both a season of birth and an age-position effect on all of the cognitive measures, particularly in the early years of schooling. There was, also, evidence of a significant age-position effect at both KS3 and GCSE in favour of the older pupils. For the younger primary school pupils there was evidence of significant age-position effects on both motor measures. Conclusions: The findings from the present study suggest that month of birth may be related to both season of birth and age-position effects. These effects may be compounded, particularly in the early years of primary school, when summer born children are youngest in their year, as in England. In Northern Ireland, age-position effects are also evident in secondary school public examination results, which may have implications for long-term life choices. © 2009 The British Psychological Society.
Resumo:
The relationship between components of emotional intelligence (EI) (interpersonal
ability, intrapersonal ability, adaptability and stress management) and academic
performance in English, maths and science was examined in a sample of 86 children
(49 males and 37 females) aged 11–12 years during the primary–secondary school
transition period. Results indicated that for both males and females, intrapersonal
ability had little relationship with academic achievement, while adaptability had the
strongest relationship with achievement in all subjects. Gender differences were particularly
pronounced for science, for which stronger relationships were observed with all
EI components for males. In addition, apparent only for males was a negative
relationship between stress management and science. These findings offer support for
the current inclusion of a personal and emotional element in the primary school curriculum,
and indicate that such training is likely to help males more than females to make
a successful transition from primary to secondary school.
Resumo:
Playful structure is a new pedagogic image representing a more balanced and integrated perspective on early years pedagogy, aiming to blend apparent dichotomies and contradictions and to sustain and evolve play-based practice beyond Year 1. Playful structure invites teachers and children to initiate and maintain a degree of playfulness in the child’s whole learning experience, even when the learning intentions demand a supportive structure. Thus, playfulness becomes characteristic of the interaction between adult and the child and not just characteristic of child-initiated versus adult-initiated activities, or of play-time versus task-time. The paper is based on intensive observations and interviews with teachers in Northern Ireland who participated in a play-based and informal curriculum. This paper explains how playful structure rests on complementary processes of infusion of structure into play-based activities and infusion of playfulness into more structured activities, illustrated by cameos. ‘Infusion’ suggests the subtle blending process that allows apparent dichotomies and contradictions to be resolved in practice.
Resumo:
In the United Kingdom tensions have existed for many years between the pedagogical traditions of pre-school, which tend to adopt developmentally oriented practices, and the more formal or subject-oriented curriculum framework of primary school. These tensions have been particularly acute in the context of Northern Ireland, which has the earliest school starting age throughout Europe. In response to international research evidence and practice, a play-based and developmentally appropriate curriculum, known as the Enriched Curriculum (EC), was introduced as a pilot in Year 1 and 2 classes in over 100 primary schools in Northern Ireland between 2000 and 2002 and continued until the Foundation Stage became statutory for all primary schools in 2007. This paper outlines four key lessons that have been learned from the first four years of the evaluation of this experience. These include the value and the meaning of a play-based curriculum; the importance of teachers’ confidence and knowledge; teaching reading in a play-based curriculum; and easing transitions in a play-based curriculum.
Resumo:
The lymphotropic and myelotropic nature of wild-type measles virus (wt-MV) is well recognized, with dendritic cells and lymphocytes expressing the MV receptor CD150 mediating systemic spread of the virus. Infection of respiratory epithelial cells has long been considered crucial for entry of MV into the body. However, the lack of detectable CD150 on these cells raises the issue of their importance in the pathogenesis of measles. This study utilized a combination of in vitro, ex vivo and in vivo model systems to characterize the susceptibility of epithelial cells to wt-MV of proven pathogenicity. Low numbers of MV-infected epithelial cells in close proximity to underlying infected lymphocytes or myeloid cells suggested infection via the basolateral side of the epithelium in the macaque model. In primary cultures of human bronchial epithelial cells, foci of MV-infected cells were only observed following infection via the basolateral cell surface. The extent of infection in primary cells was enhanced both in vitro and in ex vivo cornea rim tissue by disrupting the integrity of the cells prior to the application of virus. This demonstrated that, whilst epithelial cells may not be the primary target cells for wt-MV, areas of epithelium in which tight junctions are disrupted can become infected using high m.o.i. The low numbers of MV-infected epithelial cells observed in vivo in conjunction with the absence of infectious virus release from infected primary cell cultures suggest that epithelial cells have a peripheral role in MV transmission.
Resumo:
This study builds on and contributes to work on assessment of children in primary school, particularly in science. Previous research has examined primary science assessment from different standpoints, but no studies have speci?cally addressed children’s perspectives. This article provides additional insight into issues surrounding children’s assessment in primary school and how the assessment of science might develop in England after the science SATs (Standard Assessment Tests) were abolished in 2009. Some research suggests that primary science assessment via SATs is a major reason for the observed decline in children’s engagement with science in upper primary and lower secondary school. The analytic focus on engaging children as coresearchers to assist in the process of gathering informed views and interpreting ?ndings from a large sample of children’s views enables another contribution. The study, based on a survey of 1000 children in primary and secondary schools in England and Wales, reveals that despite being assessed under two different regimes (high-stakes national tests in England and moderated teacher assessment in Wales), children’s views of science assessment are remarkably consistent. Most appreciate the usefulness of science assessment and value frequent, non-SATs testing for monitoring/improving science progress. There was a largely negative impact, however, of science
assessment on children’s well-being, particularly due to stress. The paper demonstrates that children provide an important perspective on assessment and that including their views can improve policy-making in relation to primary science assessment.