Is what you see what you get? representations, metaphors and tools in mathematics didactics

This paper is exploratory in character. The aim is to investigate ways in which it is possible to use the theoretical concepts of representations, tools and metaphors to try to understand what learners of mathematics ‘see’ during classroom interactions (in their widest sense) and what they might get from such interactions. Through an analysis of a brief classroom episode, the suggestion is made that what learners see may not be the same as what they get. From each of several theoretical perspectives utilised in this paper, what learners ‘get’ appears to be something extra. According to our analysis, this something ‘extra’ is likely to depend on the form of technology being used and the representations and metaphors that are available to both teacher and learner

Risk Intuitions and Perceptions: A Case Study of Four Year 13 (Grade 12) Students

In the New Zealand school statistics curriculum, year 12 students (aged 16-17) are required to solve problems that involve interpreting risk and relative risk within a range of meaningful contexts. In a small exploratory study we investigate the risk conceptions of four year 13 students who performed at the excellence level in their year 12 externally-assessed examination on this topic. Through questionnaires and interviews we investigate the ways in which these students perceive and express risks associated with a variety of everyday activities and also how they compare the risks of several adverse outcomes. We also explore the strategies they use when confronted with varied representations of risk such as visual, verbal and numerical. We will report on insights gained about these students’ reasoning with different risk representations, on how they interpret, evaluate and communicate risk

Einflussfaktoren auf Morbidität und Mortalität bei Patienten mit einer perkutanen endoskopischen Gastrostomie oder einer jejunalen tube through PEG

In dieser retrospektiven Arbeit wurden 245 Patienten eingeschlossen, die im Zeitraum von 2010-2012 im Schleiklinikum Schleswig eine PEG oder eine Jet-PEG erhielten. Es wurde geschaut, ob es einen Zusammenhang zwischen dem Anlagezeitpunkt, der Indikationsstellung und der einwilligenden Person mit dem Überleben der Patienten gab. Des Weiteren wurde geprüft, ob es ein bestimmtes Patientenkollektiv gab, das besonders von Aspirationspneumonien gefährdet war und ob eine Aufrüstung einer PEG auf eine Jet-PEG Aspirationspneumonien vermeiden konnte

Taylor dispersion with absorbing boundaries: A Stochastic Approach

We describe how to solve the problem of Taylor dispersion in the presence of absorbing boundaries using an exact stochastic formulation. In addition to providing a clear stochastic picture of Taylor dispersion, our method leads to closed-form expressions for all the moments of the convective displacement of the dispersing particles in terms of the transverse diffusion eigenmodes. We also find that the cumulants grow asymptotically linearly with time, ensuring a Gaussian distribution in the long-time limit. As a demonstration of the technique, the first two longitudinal cumulants (yielding respectively the effective velocity and the Taylor diffusion constant) as well as the skewness (a measure of the deviation from normality) are calculated for fluid flow in the parallel plate geometry. We find that the effective velocity and the skewness (which is negative in this case) are enhanced while Taylor dispersion is suppressed due to absorption at the boundary.Comment: 4 pages, 1 figur

Near-Field Mass Transfer in Geologic Disposal Systems: a Review

A primary purpose of performance assessment of geologic repositories for radioactive waste is to predict the extent to which radioactive species are released from the waste solids and are transported through geologic media to the environment. Reliable quantitative predictions must be made of rates of release of radionuclides from the waste into the rock, transport through the geologic media, cumulative release to the accessible environment, and maximum concentrations in ground water and surface water. Here we review theoretical approaches to making the predictions of near-field release from buried waste solids, which provide the source terms for far-field release. The extent to which approaches and issues depend on the rock media and on regulatory criteria is discussed. 53 refs., 2 figs

Imaging heterogeneities with electrical impedance tomography: laboratory results

Electrical impedance tomography (EIT) is commonly used on site as a characterisation and monitoring tool. In the present work this technique has been applied at laboratory scale in order to investigate its capabilities in controlled conditions, with particular reference to the detection of anomalies in sandy samples. Various configurations have been studied, investigating heterogeneities due to variation of porosity, grain size distribution and clay content. The results show the great potential of EIT as an imaging tool in laboratory equipment to check sample homogeneity and to monitor processes during tests