Mixing characterisation for a serpentine microchannel equipped with embedded barriers

This paper describes the design, simulation, fabrication and experimental analysis of a passive micromixer for the mixing of biological solvents. The mixer consists of a T-junction, followed by a serpentine microchannel. the serpentine has three arcs, each equipped with circular barriers that are patterned as two opposing triangles. >The barriers are engineered to induce periodic perturbations in the flow field and enhance the mixing. CFD (Computational Fluid Dynamics) method is applied to optimise the geometric variables of the mixer before fabrication. The mixer is made from PDMS (Polydimethylsiloxane) using photo- and soft-lithography techniques. Experimental measurements are performed using yellow and blue food dyes as the mixing fluids. The mixing is measured by analysing the composition of the flow's colour across the outlet channel. The performance of the mixer is examined in a wide range of flow rates from 0.5 to 10 µl/min. Mixing efficiencies of higher than 99.4% are obtained in the experiments confirming the results of numerical simulations. The proposed mixer can be employed as a part of lab-on-a-chip for biomedical applications.

An embedded two-layer feature selection approach for microarray data analysis

Feature selection is an important technique in dealing with application problems with large number of variables and limited training samples, such as image processing, combinatorial chemistry, and microarray analysis. Commonly employed feature selection strategies can be divided into filter and wrapper. In this study, we propose an embedded two-layer feature selection approach to combining the advantages of filter and wrapper algorithms while avoiding their drawbacks. The hybrid algorithm, called GAEF (Genetic Algorithm with embedded filter), divides the feature selection process into two stages. In the first stage, Genetic Algorithm (GA) is employed to pre-select features while in the second stage a filter selector is used to further identify a small feature subset for accurate sample classification. Three benchmark microarray datasets are used to evaluate the proposed algorithm. The experimental results suggest that this embedded two-layer feature selection strategy is able to improve the stability of the selection results as well as the sample classification accuracy.

A framework for re-thinking learning in science from recent cognitive science perspectives

Recent accounts by cognitive scientists of factors affecting cognition imply the need to reconsider current dominant conceptual theories about science learning. These new accounts emphasize the role of context, embodied practices and narrative-based representation rather than learners’ cognitive constructs. In this paper we analyze data from a longitudinal study of primary school children’s learning to outline a framework based on these contemporary accounts, and to delineate key points of difference from conceptual change perspectives. The findings suggest this framework provides strong theoretical and practical insights into how children learn and the key role of representational negotiation in this learning. We argue that the nature and process of conceptual change can be re-interpreted in terms of the development of students’ representational resources.

Affect : initiating heuristic life

This paper re-examines the relationship between affect and effect, discussing them as research values that have emerged from the life sciences, the arts and philosophy and, more importantly, considering them as systems of relations underpinning experiential orientation by which to initiate change and hold the world in place. The notion of æffect may be defined as the continuous measure performed upon the systems of affect/effect and reapplied to events and things. Æffect is a coordinated system of cognition where concurrent measures impact on each other. In doing so, they specify perception and action on multiple registers and scales of events. It is important to recognise that the functioning of affective and effective systems in the body allows, and even requires, paradoxical logics to coexist and be deployed as processes that shape the organism-person-environment. Discussion of selected works from Arakawa and Gins will supply examples of tactics that combine built environments with discursive constraints to guide embodied attention. The practice of embodied cognition dilates the thresholds separating the organism from person and the person from environment, and moves towards an atmospheric intricateness (Arakawa and Gins 2003a:25) that may become the blocs of a new materialism for heuristic life.