Cell separation and transportation between two miscible fluid streams using ultrasound

This paper presents a two-stream microfluidic system for transporting cells or micro-sized particles from one fluid stream to another by acoustophoresis. The two fluid streams, one being the original suspension and the other being the destination fluid, flow parallel to each other in a microchannel. Using a half-wave acoustic standing wave across the channel width, cells or particles with positive acoustic contrast factors are moved to the destination fluid where the pressure nodal line lies. By controlling the relative flow rate of the two fluid streams, the pressure nodal line can be maintained at a specific offset from the fluid interface within the destination fluid. Using this transportation method, particles or cells of different sizes and mechanical properties can be separated. The cells experiencing a larger acoustic radiation force are separated and transported from the original suspension to the destination fluid stream. The other particles or cells experiencing a smaller acoustic radiation force continue flowing in the original solution. Experiments were conducted to demonstrate the effective separation of polystyrene microbeads of different sizes (3 μm and 10 μm) and waterborne parasites (Giardia lamblia and Cryptosporidium parvum). Diffusion occurs between the two miscible fluids, but it was found to have little effects on the transport and separation process, even when the two fluids have different density and speed of sound.     

Manipulating liquid plugs in microchannel with controllable air vents

An air venting element on microchannel, which can be controlled externally and automatically, was demonstrated for manipulating liquid plugs in microfluidic systems. The element's open and closed statuses correspond to the positioning and movement of a liquid plug in the microchannel. Positioning of multiple liquid plugs at an air venting element enabled the merging and mixing of the plugs. Besides these basic functions, other modes of liquid plug manipulations including plug partitioning, multiple plug mixing, and spacing adjustment between liquid plugs, were realized using combination of multiple elements. The structure, operation, and some functions of the element were demonstrated with a microfluidic chip application. The performances of the element including its failure modes, threshold flow rate, and structural optimization were also discussed.     

Exploring the Usefulness of Kelly's Personal Construct Theory in Assessing Student Learning in Science Courses

We explore the utility of George Kelly's Personal Construct Theory, specifically his repertory grid technique, to the assessment of student learning in undergraduate science courses. We provide an in-depth review of the assumptions underlying Personal Construct Theory and how these were reflected in the repertory grid technique Kelly developed. We explain how an adapted version of the repertory grid, sharing some yet not all of Kelly's assumptions, was utilised as a research tool in a recent study involving science instructors and their students. We argue that as well as having applicability as an innovative research tool, an adapted version of Kelly's repertory grid is a useful heuristic for university teachers when used as a classroom assessment technique (CAT) and indicate several features it shares with the more widely-known conceptual mapping technique, which has been used in the study of science teaching and learning for many years. We conclude by highlighting several advantages the use of repertory grids has for both students and instructors.     

School‐to‐work transition services for students with disabilities in Malaysia: organisations' views on policy and practices

Transition services are required by law for students with disabilities in many developed countries. In Malaysia, however, there is still no specific legislation mandating that school‐to‐work transition planning and services be provided to students with disabilities. This study investigated the state of the transition services provided by educational organisations to students with disabilities in Malaysia. A mixed method research design, which utilises both quantitative and qualitative research techniques, was employed to obtain information from 23 government organisations and NGOs involved in the education and training of students with disabilities. This study found that the organisations surveyed were aware of the lack of transition support and call attention to the importance of instituting a national policy on school‐to‐work transition services and supported employment systems for students with disabilities. The legislative and educational implications for Malaysia are discussed.     

Making learning visible in initial teacher education: a pedagogical characterisation scheme

This paper reports the development of a scheme of characterising pedagogical practices in initial teacher education classes. The scheme is intended to provide baseline data on classroom pedagogical practices in Singapore’s sole provider of initial teacher education (ITE). This study is original in that the research team has found no reports of independent research to characterise, through video analysis of classroom practices, the pedagogical practices experienced during ITE. By characterising the pedagogical practices of a purposive sample of ITE lessons run at the National Institute of Education Singapore, this study contributes an initial scheme to produce detailed and layered representations of pedagogical practices through video recordings, which opens a new approach to research on teacher education. The implications with regard to teacher education policy and practice will be discussed.     

Formation control and collision avoidance for a class of multi-agent systems

In this paper, a control scheme is proposed for a group of elliptical agents to achieve a predefined formation. The agents are assumed to have the same dynamics, and communication among the agents are limited. The desired formation is realized based on the reference formation and the mapping decision. In the control design, searching algorithms for both cases of minimum distance and tangents are established for each agent and its neighbors. In order to avoid collision, an optimal path planning algorithm based on collision angles, and a self-center-based rotation algorithm are also proposed. Moreover, randomized method is used to provide the optimal mapping decision for the underlying system. Two examples and analyses are presented to demonstrate the effectiveness and potential of the new control scheme.