1,193 research outputs found
Teaching science and technology at primary school level: theoretical and practical considerations for primary school teachers' professional training.
This paper focuses on the importance of starting science and technology education at a young age and at the consequential importance of providing primary school teachers with enough professional background to be able to effectively incorporate science and technology into their teaching. We will discuss a large-scale program in The Netherlands that is aimed at the professionalization of elementary school teachers in the field of science and technology. Theoretical and practical considerations will be provided for the three pillars that ideally should be included in teacher training programs in this domain: (1) Primary school teachers’ knowledge of and competency in scientific concepts and scientific reasoning; (2) Primary school teachers’ attitude towards science (in terms of cognitive, affective, and behavioural dimensions of attitude); and (3) Primary school teachers’ pedagogical competency to enhance inquiry-based learning
Effects of company visits on Dutch primary school children's attitudes toward technical professions
Technology-oriented company visits could potentially provide children with a stimulating ‘real-world’ setting to develop more broad and positive images of and attitudes toward technology and technical professions. The present study was the first to explore whether children’s images of and attitudes toward technology, technical competencies and technical professions could be affected by technology-oriented company visits, as they are presently carried out in the Netherlands. A previously validated measurement instrument was used to measure children’s images and attitudes prior to and after the visits and results were compared to similar measurements among children who did not take part in the visits. In addition, based on recent review studies about school visits to science centers, we derived several key theoretical guidelines for organizing effective school visits. Based on these guidelines, structured interviews were carried out with all teachers prior to the company visits. Results indicated that children’s images and attitudes remained mostly unaffected by the company visits, a finding that could be explained by the fact that the level of in-school preparation, follow-up activities and teachers’ level of involvement during the visits was generally low. In addition, observations during the visits showed that the activities at the technical companies were mostly ‘hands-on’ and stereotypical (e.g., working with machines). Based on these findings, we formulate a set of new guidelines for technology-oriented company visits that could improve the desired attitudinal effects
Bistable hysteresis and resistance switching in hydrogen gold junctions
Current-voltage characteristics of H2-Au molecular junctions exhibit
intriguing steps around a characteristic voltage of 40 mV. Surprisingly, we
find that a hysteresis is connected to these steps with a typical time scale >
10 ms. This time constant scales linearly with the power dissipated in the
junction beyond an ofset power P_s = IV_s. We propose that the hysteresis is
related to vibrational heating of both the molecule in the junction and a set
of surrounding hydrogen molecules. Remarkably, we can engineer our junctions
such that the hysteresis' characteristic time becomes >days. We demonstrate
that reliable switchable devices can be built from such junctions.Comment: Submitted to Phys. Rev. Let
Numerical modelling of physical processes governing larval transport in the southern North Sea
A three-dimensional hydrodynamic model (GETM) was coupled with a particle
tracking routine (GITM) to study the inter-annual variability in transport
paths of particles in the North Sea and English Channel. For validation, a
comparison with observed drifter trajectories is also presented here. This
research investigated to what extent variability in the hydrodynamic
conditions alone (reflecting passive particle transport) contributed to
inter-annual variability in the transport of eggs and larvae. In this
idealised study, no a priori selection of specific spawning grounds or
periods was made and no active behaviour (vertical migration) or mortality
was included. In this study, egg and larval development towards coastal
nursery areas was based solely on sea water temperature, while settlement
areas were defined by a threshold water depth. Results showed strong
inter-annual variability in drift direction and distance, caused by a
combination of wind speed and direction. Strong inter-annual variability was
observed both in absolute amount of settlement in several coastal areas, and
in the relative importance of the different areas. The effects of wind and
temperature variability are minor for settlement along the western shores of
the North Sea and in the English Channel, but have a very significant impact
on settlement along the eastern shores of the North Sea. Years with strong
south-westerly winds across the Dover Straight resulted in higher settlement
figures along its eastern shores of the North Sea (standard deviation
37% of the mean annual settlement value). Settlement in the western
Dutch Wadden Sea did not only show inter-annual variability, but patterns
were also variable within each year and revealed seasonal changes in the
origin of particles: during winter, stronger currents along with colder
temperatures generally result in particles originating from further away
Bulk and Surface Nucleation Processes in Ag2S Conductance Switches
We studied metallic Ag formation inside and on the surface of Ag2S thin
films, induced by the electric field created with a STM tip. Two clear regimes
were observed: cluster formation on the surface at low bias voltages, and full
conductance switching at higher bias voltages (V > 70mV). The bias voltage at
which this transition is observed is in agreement with the known threshold
voltage for conductance switching at room temperature. We propose a model for
the cluster formation at low bias voltage. Scaling of the measured data with
the proposed model indicates that the process takes place near steady state,
but depends on the STM tip geometry. The growth of the clusters is confirmed by
tip retraction measurements and topography scans. This study provides improved
understanding of the physical mechanisms that drive conductance switching in
solid electrolyte memristive devices.Comment: In press for PR
Modelling survival and connectivity of Mnemiopsis leidyi in the south-western North Sea and Scheldt estuaries
Three different models were applied to study the reproduction, survival and dispersal of Mnemiopsis leidyi in the Scheldt estuaries and the southern North Sea: a high-resolution particle tracking model with passive particles, a low-resolution particle tracking model with a reproduction model coupled to a biogeochemical model, and a dynamic energy budget (DEB) model. The results of the models, each with its strengths and weaknesses, suggest the following conceptual situation: (i) the estuaries possess enough retention capability to keep an overwintering population, and enough exchange with coastal waters of the North Sea to seed offshore populations; (ii) M. leidyi can survive in the North Sea, and be transported over considerable distances, thus facilitating connectivity between coastal embayments; (iii) under current climatic conditions, M. leidyi may not be able to reproduce in large numbers in coastal and offshore waters of the North Sea, but this may change with global warming; however, this result is subject to substantial uncertainty. Further quantitative observational work is needed on the effects of temperature, salinity and food availability on reproduction and on mortality at different life stages to improve models such as used here
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