66 research outputs found
Low-temperature reactions: Tunnelling in space.
International audienceChemical reactions with activation barriers generally slow to a halt in the extreme cold of dense interstellar clouds. Low-temperature experiments on the reaction of OH with methanol have now shown that below 200 K there is a major acceleration in the rate that can only be explained by enhanced quantum mechanical tunnelling through the barrier
Cognitive engagement in the problem-based learning classroom
The objective of the present study was to examine to what extent autonomy in problem-based learning (PBL) results in cognitive engagement with the topic at hand. To that end, a short self-report instrument was devised and validated. Moreover, it was examined how cognitive engagement develops as a function of the learning process and the extent to which cognitive engagement determines subsequent levels of cognitive engagement during a one-day PBL event. Data were analyzed by means of confirmatory factor analysis, repeated measures ANOVA, and path analysis. The results showed that the new measure of situational cognitive engagement is valid and reliable. Furthermore, the results revealed that studentsâ cognitive engagement significantly increased as a function of the learning event. Implications of these findings for PBL are discussed
The pivotal role of effort beliefs in mediating implicit theories of intelligence and achievement goals & academic motivations
Empirical studies into meaning systems surrounding implicit theories of intelligence typically entail two stringent assumptions: that different implicit theories and different effort beliefs represent opposite poles on a single scale, and that implicit theories directly impact the constructs as achievement goals and academic motivations. Through an empirical study based on a large sample of university students, we aim to demonstrate that relaxing these stringent assumptions, and thereby using the meaning system framework to its full potential, will provide strong benefits: effort beliefs are crucial mediators of relationships between implicit theories and achievement goals and academic motivations, and the different poles of implicit theories and effort beliefs do expose different relationships with goal setting behaviour and academic motivations. A structural equation model, cross-validated by demonstrating gender-invariance of path coefficients, demonstrates that incremental and entity theory views have less predictive power than positive and negative effort beliefs in explaining achievement goals and motivations
Alternative PV-module structure with increased optical performances for PV-thermal applications
Photovoltaic-thermal (PV-T) collectors are hybrid collectors converting solar energy into electricity and usable heat at the same time. In this concept, PV modules are integrated as an absorber of a thermal collector. In most of the cases, the hybrid collectors are made by the superposition of a PV module on the thermal absorber of a solar collector. In this paper, another technique is presented. This technique combines the properties of each PV module and solar thermal in order to adapt them to each other. An alternative PV cell lamination was developed with increased optical and thermal performances. An increase of 2 mA/cm2 in terms of current density with our new encapsulation method was obtained compared to a reference glass/EVA module encapsulation
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