Analysis of a model for the dynamics of prions II

A new mathematical model for the dynamics of prion proliferation involving an ordinary differential equation coupled with a partial integro-differential equation is analyzed, continuing earlier work. We show the well-posedness of this problem in a natural phase space, i.e. there is a unique global semiflow in the phase space associated to the problem. A theorem of threshold type is derived for this model which is typical for mathematical epidemics. If a certain combination of kinetic parameters is below or at the threshold, there is a unique steady state, the disease-free equilibrium, which is globally asymptotically stable; above the threshold it is unstable, and there is another unique steady state, the disease equilibrium, which inherits that property

Helping behaviour during cooperative learning and learning gains

Is helping behaviour (i.e., solicited help and peer tutoring) during cooperative learning (CL) related to subsequent learning gains? And can teachers influence pupils’ helping behaviour? One hundred one 5th grade pupils from multiethnic schools, 10-12 years old, participated in the study. Forty two pupils (31 immigrant) worked in an experimental condition, characterized by the stimulation of solicited high quality help and 59 (24 immigrant) worked in a control condition. It was found that learning gains were predicted positively by pupils’ unsolicited helping behaviour (i.e., peer tutoring) and negatively by solicited help. Furthermore, teachers were able to affect pupils’ low quality solicited help only. Lastly, immigrant pupils used less helping behaviour than local pupils, irrespective of CL setting

The first research agenda for the chiropractic profession in Europe

Research involving chiropractors is evolving and expanding in Europe while resources are limited. Therefore, we considered it timely to initiate a research agenda for the chiropractic profession in Europe. The aim was to identify and suggest priorities for future research in order to best channel the available resources and facilitate advancement of the professio

Health Care for the Poor in Omaha-Douglas County: Problems and Policy Options

The health-care system in Omaha-Douglas County is on the verge of dramatic changes because of federal cutbacks, expanding cost-containment efforts, and an increasingly competitive medical market. As a result, problems are now arising because of increasing difficulties in providing health care to the poor

A neural model of cross-modal association in insects

Abstract. We developed a computational model of learning in the Mushroom Body, a region of multimodal integration in the insect brain. Using realistic neural dynamics and a biologically-based learning rule (spike timing dependent plasticity), the model is tested as part of an insect brain inspired architecture within a closed loop behavioural task. Replicating in simulation an experiment carried out on bushcrickets, we show the system can successfully associate visual to auditory cues, so as to maintain a steady heading towards an intermittent sound source.

Celestial compass sensor mimics the insect eye for navigation under cloudy and occluded skies

Insects use the sun’s position (even when concealed) as a compass for navigation by filtering celestial light intensity and polarisation through their compound eyes. To replicate this functionality, we present a sensor that imitates essential aspects of insect eyes, particularly the fan-like arrangement of polarised light receptors in their dorsal rim area. Our sensor comprises a ring of eight pairs of photodiodes (evaluating two orthogonal orientations of polarised light) to analyse the skylight coming from different directions. Because the layout of our sensor aligns with the polarised light pattern in the sky, a circular-mean model that integrates information spatially across the analysers can estimate the solar azimuth. When using the same sensor design, our model achieves lower compass errors than alternative (and computationally more complex) algorithms, especially under cloudy and occluded skies. Thus, the morphology and processing of the insect celestial compass provide an efficient and robust directional input for navigation

Methodological challenges for collaborative learning research

Research on collaborative learning, both face-to-face and computer-supported, has thrived in the past 10 years. The studies range from outcome-oriented (individual and group learning) to process-oriented (impact of interaction on learning processes, motivation and organisation of collaboration) to mixed studies. Collaborative learning research is multi-disciplinary. This introduces a multitude of theoretical accounts for collaborative learning, accompanied by a broad spectrum of methods to study processes and outcomes of collaboration. This special issue will provide an overview of methods that are at the core of current research effort, but also identifies opportunities and problems to sensibly combine methods into mixed method approaches

Ocean acidification promotes otolith growth and calcite deposition in gilthead sea bream (Sparus aurata) larvae

This work received funding from the Marine Alliance for Science and Technology for Scotland (MASTS) Small Grant initiative (SG330 and SG407). MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. PBW would like to thank the Royal Society for the award of an Industry Fellowship. Financial support to CRB and JG were through the BIOACID (Biological Impacts of Ocean Acidification; Phase II) research programme.The effects of ocean acidification on otolith crystallization and growth rates were investigated in gilthead sea bream (Sparus aurata) larvae. Larvae were exposed to three different pH levels: pH8.2, pH7.7 and pH7.3 for a period of 18 days post-fertilization. For the first time, we demonstrate that pH has a significant impact on the carbonate polymorph composition, showing calcite in a significant percentage of individuals at low pH. Around 21% of the larvae exposed to pH7.3 showed irregular calcitic otoliths rather than commonly found round aragonitic otoliths. Calcitic otoliths showed a moderate level of heritability suggesting an important role of genetic factors. We also observed significantly larger otoliths in larvae reared at pH7.7 and pH7.3 compared to pH8.2 in both sagittae and lapilli. Our results demonstrate that otolith growth rates in gilthead sea bream larvae increase at low pH while a significant proportion of larvae are prone to the formation of calcitic otoliths at pH7.3.Publisher PDFPeer reviewe