Thermal transport properties and size effects in very dilute superfluid mixtures of3He in4He

The effective thermal conductivity _eff has been measured for 1.6 K for mixtures with 10^–6–2. Both _eff and the derived impurity mass diffusion coefficient D_iso show an unexpected dependence on the height h of the fluid layer. A scaled representation of D_iso leads to a purely phenomenological model involving an effective length scale, proportional to X^–1 and temperature independent. The relations so obtained are consistent with the observations as well as with the observed transition curve Q_C(X) to non-linear behavior.     

High resolution XPS characterization of chemical functionalised MWCNTs and SWCNTs

High resolution XPS analysis of chemical functionalised multi-wall carbon nanotubes (MWCNTs) and single wall carbon nanotubes (SWCNT) was done with ESCA300 (overall instrument resolution of 0.35 eV). Information to the degree of functionalisation was ascertained by argon ion bombardment of the samples followed by XPS analysis to detect the functional groups, the percentage atomic concentration of various elements present and whether or not the detected functional groups imposed a chemical shift on the CNT atoms. The results show that true chemical functionalisation was achieved and by argon ion bombardment these functional groups can be altered relative to the C 1s carbon atoms of the CNT. The choice of chemicals used for functionalisation, the techniques employed and the types of nanotubes treated are important factors in chemical characterisation. The carbon atom on the nanotube ring to which the functional group (atom) is bonded, the chirality of the CNT, the electronegativity of the functional group, the bond type and whether the CNT is single-wall or multi-wall, or cut (short) could play a role in determining the chemical shift on the CNTs atoms. These investigations are relevant to chemical functionalisation of carbon nanotubes for various applications for example DNA sensors and other biomedical sensors.     

SeaDoc: a self-adaptive document link provision system for framework extension tasks

It has been demonstrated that object-oriented frameworks can bring all kinds of advantages to application developers. To gain the advantages, application developers have to follow the framework-based development process. One step of the process is to integrate new components for framework extension. This is defined as a framework extension task in this work. In this task, application developers have to (1) retrieve examples, (2) acquire necessary documents, which are defined as the documents containing example adaptation information, and (3) adapt examples. Currently, acquiring necessary documents requires a lot of time because it is achieved through manually searching the Internet. Although there are many approaches to correctly acquiring those documents, the focus is never on time reduction. To satisfy the new criterion, we find the following challenging issues: (1) the dynamics of the valid document version, and (2) the uncertainty of the relevant necessary documents. The first issue is that the valid document version varies according to the framework version under which the retrieved example is workable. The second one is that the relevant necessary documents cannot be decided until a specific necessary document is specified. To resolve those two issues, a Self-adaptive Document link provision system, named SeaDoc, is provided in this work. SeaDoc resolves the dynamics by dynamically constructing document links with the corresponding valid document version. SeaDoc also resolves the uncertainty by adaptively selecting highly relevant document links. The experimental results show that SeaDoc reduces the time by 73 and 83 % compared with other two approaches.     

Feature extraction of the first difference of EMG time series for EMG pattern recognition

This paper demonstrates the utility of a differencing technique to transform surface EMG signals measured during both static and dynamic contractions such that they become more stationary. The technique was evaluated by three stationarity tests consisting of the variation of two statistical properties, i.e., mean and standard deviation, and the reverse arrangements test. As a result of the proposed technique, the first difference of EMG time series became more stationary compared to the original measured signal. Based on this finding, the performance of time-domain features extracted from raw and transformed EMG was investigated via an EMG classification problem (i.e., eight dynamic motions and four EMG channels) on data from 18 subjects. The results show that the classification accuracies of all features extracted from the transformed signals were higher than features extracted from the original signals for six different classifiers including quadratic discriminant analysis. On average, the proposed differencing technique improved classification accuracies by 2–8%.     

The cholesterol-lowering effect of guar gum is not the result of a simple diversion of bile acids toward fecal excretion

The effects of partially hydrolyzed, nonviscous, guar gum (PHGG) on cholesterol metabolism and digestive balance have been compared with those of native guar gum (GUAR) in rats adapted to 0.4% cholesterol diets. Both types of guar gum elicited acidic fermentations in the large intestine, but only GUAR effectively lowered plasma cholesterol (P<0.001), chiefly in the triglyceride-rich lipoprotein fraction. The biliary bile acid excretion was significantly enhanced in rats fed GUAR (P<0.05), as well as the intestinal and cecal bile acid pool (P<0.001). In rats fed GUAR and to a lesser extent in those fed PHGG, the fecal excretion of bile acids and neutral sterol was higher than in controls (P<0.01). The digestive balance (cholesterol intake-steroid excretion) was positive in control rats (+47 μmol/d), whereas it was negative in rats fed GUAR (−20 μmol/d), which could involve a higher rate of endogenous cholesterol synthesis. In rats fed PHGG, the steroid balance remained slightly positive. Liver 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity was very low (22 pmol/min/mg protein), owing to cholesterol supplementation, in control rats or in rats fed PHGG, whereas it was markedly higher (+463%) in rats fed GUAR. In conclusion, even if PHGG does alter some parameters of the enterohepatic cycle of cholesterol and bile acids, its effects are not sufficient to elicit a significant cholesterol-lowering effect. The intestinal (ileal or cecal) reabsorption of bile acids was not reduced, but rather increased, by GUAR; nevertheless the intestinal capacities of reabsorption were overwhelmed by the enlargement of the digestive pool of bile acids. In the present model, induction of HMG-CoA reductase probably takes place in the presence of elevated portal bile acid concentrations.     

Être à l’écoute des élèves : un incontournable dans la classe de mathématiques

Abstract

This article examines a unique professional development initiative in mathematics teaching that focuses on the design and field testing of pedagogical resources for primary teachers. We examine a particular aspect of the project—namely, helping teachers move from a model centred on explanation and repetitive exercises to an approach centred on listening and responding to students' thinking. In particular, the initiative emphasizes the important role played by students’ reasoning in the construction of their own computational algorithms. This analysis provides evidence that professional development that aims to deepen understanding of students’ mathematical thinking, that provides resources to support the implementation of new teaching strategies, and that strives to establish a collaborative environment enables educators to gain confidence and to develop expertise in their interactions with students in the context of problem solving.     

Developing authentic assessment: Case studies of secondary school mathematics teachers’ experiences

Abstract

Authentic assessment techniques in mathematics raise issues that merit the attention of practitioners, educators, and researchers. Teacher training in assessment, the reliability and validity of authentic assessment, the variety of methods employed in such assessment, and the ways assessment is employed are all concerns that emerge as new assessment techniques other than the expected paper‐and‐pencil tests are implemented. At the secondary school level, new assessment techniques are emerging in mathematics classrooms and little is known about these experiences. This article specifically addresses the issues associated with authentic assessment by describing and exploring mathematics teachers’ experiences as they implement these assessment techniques in their secondary school mathematics program. It summarizes the findings of a qualitative study of five secondary school mathematics teachers in Ontario, Canada, and offers suggestions as to how to support teachers through such a change project. How teachers use authentic assessment, the problems they encounter, and the theoretical and practical issues that emerge are all questions that require exploration and understanding.     

The development of a formative scenario-based computer assisted assessment tool in psychology for teachers: The PePCAA project

Formative computer assisted assessment has become increasingly attractive in Higher Education where providing useful feedback to large numbers of students can be difficult. However, the nature of such assessments has often been limited to objective questions such as multiple-choice. This paper reports on the development and initial trialling of a more innovative, formative use of computer assisted assessment in a Higher Education context. The European funded PePCAA (Pedagogical Psychology Computer Assisted Assessment) project developed a series of scenario-based computer-delivered formative assessments of pedagogical psychology for teachers and trainee teachers, using a range of software features, including the addition of confidence measurement. The project had a two-fold aim: to provide a tool to improve understanding of pedagogical psychology and to explore the potential of more innovative techniques of computer assisted assessment to motivate students and to assess deeper learning. The combination of computer-delivered formative assessment with innovative question styles and confidence ratings is believed to be unique for pedagogical psychology. Scenarios were based on realistic classroom situations and focused on problem solving or on utilising best practice. The PePCAA Learning Assessment Circle (PLAC) provided a framework for indexing the kinds of processes required of users. In the UK, small scale trialling involved a total of 23 teacher trainees such that each assessment was attempted by about seven participants. Participants completed evaluation questionnaires after each assessment. Responses from learners indicated that the UK scenarios were generally very well received and had at least partly achieved the aim of stimulating deeper learning. Transfer of assessments between countries proved more difficult than expected. The next stage of development should be to conduct a larger pilot, thus allowing full investigation of the reliability and validity of the assessments. There is also scope for further development of the PePCAA approach and for its application in other subjects.     

Effect of external index of refraction on multimode fiber couplers

The dependence of the performance of fused-taper multimode fiber couplers on the refractive index of the material surrounding the taper region has been investigated both theoretically and experimentally. It has been identified that for a 2 × 2 multimode fiber coupler there is a range of output-power-coupling ratios for which the effect of the external refractive index is negligible. When the coupler is tapered beyond this region, the performance becomes dependent on the external index of refraction and lossy. To analyze the multimode coupler-loss mechanism, we develop a two-dimensional ray-optics model that incorporates trapped cladding-mode loss and core-mode loss through frustrated total internal reflection.

Computer-simulation results support the experimental observations. Related issues such as coupler fabrication and packaging are also discussed.