Self-assembly route for photonic crystals with a bandgap in the visible region

Three-dimensional photonic crystals, or periodic materials, that do not allow the propagation of photons in all directions with a wavelength in the visible region have not been experimentally fabricated, despite there being several potential structures and the interesting applications and physics that this would lead to. We show using computer simulations that two structures that would enable a bandgap in the visible region, diamond and pyrochlore, can be self-assembled in one crystal structure from a binary colloidal dispersion. In our approach, these two structures are obtained as the large (Mg) and small (Cu) sphere components of the colloidal analogue of the MgCu(2) Laves phase, whose growth can be selected and directed using appropriate wall patterning. The method requires that the particles consist of different materials, so that one of them can be removed selectively after drying (for example, by burning or dissolution). Photonic calculations show that gaps appear at relatively low frequencies indicating that they are robust and open for modest contrast, enabling fabrication from more materials.     

A randomized controlled evaluation study of the effects of a one-day advanced rider training course

Motorcyclists have a relative high risk of crash involvement. As a consequence there is an on-going search for safety measures to improve road safety for motorcyclists. One popular measure is motorcycle training. Although intuitively sound, there are only few thorough studies on rider training courses and they do not always show a positive safety effect.     

Gender differences in computer attitudes: Does the school matter?

In most western countries, the participation of females in ICT professional careers is not only low but is also still falling [Anderson, N., Lankhear, C., Timms, C., & Courtney, L. (in press). Because it’s boring, irrelevant and I don’t like computers’: Why high school girls avoid professionally-oriented ICT subjects. Computers & Education.]. Policy makers as well as researchers often assume that the interest of girls in computing and ICT-professions could be increased at school. For example, female teachers who are confident ICT-users, are expected to act as positive role models for girls. However, because most of the research on gender and computing has been focussing on the influence of none-school related factors, there is little empirical evidence that schools or teachers are able to influence girls’ attitude toward ICT. Using the data of a Dutch large-scale survey on ICT use in primary education (almost 4000 grade 5 students), this study explores the influence of both none-school related factors and school related factors on students’ computer attitude. Although the between-school variance of girls’ computer attitude is higher than that of boys’ computer attitude, multilevel analyses show that most of the variance in computer attitude is explained by none-school related student factors. Two school related factors turned out to have a small positive effect on the computer attitude of girls: a teacher-centred pedagogical approach and the computer experience of female teachers.     

Tracing tools to resolve neural circuits

In this paper we summarize neuroanatomical tracing methods, in particular combinations of methods designed to achieve the combined goals of tracing connectivity and extracting extra information from the projection or the target neurons. These combinations include techniques that identify projection fibres together with the neurons from which they originate, methods which establish the morphological or chemical identity of the target neurons and techniques to verify the presence of contacts between the terminal boutons on fibres and prospective target neurons. In the second part of this paper we describe a method recently developed in our laboratory, which consists of fluorescence tracing (introducing marker #1) combined with immunofluorescence with different fluorochromes (markers #2 and #3). This method enables us to observe the distribution of terminals of a particular set of projection fibres in contact with neurons belonging to two chemically different populations of interneuron. Multifluorescence confocal laser scanning is used for image acquisition of fibres and processes of presumed target neurons, and follow-up is by three-dimensional computer reconstruction. These reconstructions are used to determine that the contacts between the differentially labelled structures are real, i.e. with no optically empty space in between regardless of the angle of inspection. The specific experiments reported in this paper comprise the tracing with biotinylated dextran amine of fibres in the rat brain running from the presubiculum to layer III of the medial division of the entorhinal cortex. We studied the possibility of contacts in the latter area between the terminal boutons of these projecting fibres in association with presumed target neurons, i.e. parvalbumin and calretinin expressing interneurons.     

Organizing Creativity: Creativity and Innovation under Constraints

The best way of organizing creativity within organizations remains somewhat enigmatic to scholars, particularly when it comes to the role of constraints. On the one hand, creative organizations are often associated with freedom, autonomy, weak rules and few boundaries. On the other hand, several studies suggest that constraints, particularly design constraints, often stimulate creativity rather than suppress it. All in all, findings are mixed and inconclusive, and further research that explores this area of tension is required. The goal of this paper is twofold. Firstly, we introduce the topic of constraints and creativity, and raise some of the open questions in this field. By way of illustration, we report on a preliminary study about the role of constraints. Secondly, we set the stage for the contributions in this special issue on creativity and innovation under constraints, by identifying four central themes for further research. We subsequently outline the articles in this issue, and show how each of them contributes to one or more of these themes.     

Dealing with Uncertainties in Fresh Water Supply: Experiences in the Netherlands

Developing fresh water supply strategies for the long term needs to take into account the fact that the future is deeply uncertain. Not only the extent of climate change and the extent and nature of its impacts are unknown, also socio-economic conditions may change in unpredictable ways, as well as social preferences. Often, it is not possible to find solid ground for estimating probabilities for the relevant range of imaginable possible future developments. Yet, some of these may have profound impacts and consequences for society which could be reduced by timely proactive adaptation. In response to these and similar challenges, various approaches, methods and techniques have been proposed and are being developed to specifically address long-term strategy development under so-called deep uncertainty. This paper, first, offers a brief overview of developments in the field of planning under (deep) uncertainty. Next, we illustrate application of three different approaches to fresh water provision planning under uncertainty in case studies in the Netherlands: a resilience approach, oriented to (re) designing fresh water systems in such a way that they will be less vulnerable, resp. will be able to recover easily from future disturbances; a robustness approach, oriented to quantitative assessment of system performance for various system configurations (adaptation options) under a range of external disturbances, and an exploratory modeling approach, developed to explore policy effectiveness and system operation under a very wide set of assumptions about future conditions.     

At Odds: Laughing and Thinking? The Appreciation,Processing, and Persuasiveness of Political Satire

This study constructs and tests a conceptual model of how and for whom political satire affects political attitudes. With an experiment, we show that young adults compared to older people are more absorbed in satirical items than in regular news. Subsequently, absorption decreased counterarguing such that the attitude toward the satirized object was affected negatively. By contrast, we show that political satire positively affects the attitude toward the satirized subject via perceived funniness; this was particularly strong among those who held views congruent with the satire or lacked background knowledge, which follows disposition theory. Investigating the underlying and conditional processes gave insight into mechanisms through which satire influences attitudes and pinpointed possible reasons for mixed effects of this infotainment genre.     

The effect of hyperosmotic treatment on the functioning of ampullary electroreceptor organs

The condition of the microvilli of the apical membrane in ampullary electroreceptor organs of the freshwater catfish, Ictalurus nebulosus, was manipulated by administration of hyperosmotic solutions (500 mM) in order to investigate to what extent the apical surface area determines the sensitivity and the shape of the frequency curves. Electrophysiological recordings demonstrated that hyperosmotic sucrose and glucose solutions reduce the sensitivity by 80%, and alter the shape of the frequency curves. The synaptic delay and the average spontaneous activity remained almost unchanged. Calculations with an equivalent electric circuit of an electroreceptor cell indicate that a reduction in apical surface area can account for these effects. Apparently, the sensitivity and the frequency curves in ampullary organs in freshwater catfish depend on the apical surface area. A hyperosmotic urea solution proved to be less suitable to investigate the effect of manipulations of the apical surface area. The almost total loss in sensitivity caused by administration of urea is caused by both shunting of the stimulus by leaky tight junctions and a reduced synaptic efficacy. The repetitive activity observed after exposure to glucose or sucrose must be attributed to malfunctioning of postsynaptic parts of the receptor organ.