Deformation of red blood cells using acoustic radiation forces

Acoustic radiation forces have been used to manipulate cells and bacteria in a number of recent microfluidic applications. The net force on a cell has been subject to careful investigation over a number of decades. We demonstrate that the radiation forces also act to deform cells. An ultrasonic standing wave field is created in a 0.1 mm glass capillary at a frequency of 7.9 MHz. Using osmotically swollen red-blood cells, we show observable deformations up to an aspect ratio of 1.35, comparable to deformations created by optical tweezing. In contrast to optical technologies, ultrasonic devices are potentially capable of deforming thousands of cells simultaneously. We create a finite element model that includes both the acoustic environment of the cell, and a model of the cell membrane subject to forces resulting from the non-linear aspects of the acoustic field. The model is found to give reasonable agreement with the experimental results, and shows that the deformation is the result of variation in an acoustic force that is directed outwards at all points on the cell membrane. We foresee applications in diagnostic devices, and in the possibility of mechanically stimulating cells to promote differentiation and physiological effects.     

Contrast agent-free sonoporation: The use of an ultrasonic standing wave microfluidic system for the delivery of pharmaceutical agents

Sonoporation is a useful biophysical mechanism for facilitating the transmembrane delivery of therapeutic agents from the extracellular to the intracellular milieu. Conventionally, sonoporation is carried out in the presence of ultrasound contrast agents, which are known to greatly enhance transient poration of biological cell membranes. However, in vivo contrast agents have been observed to induce capillary rupture and haemorrhage due to endothelial cell damage and to greatly increase the potential for cell lysis in vitro. Here, we demonstrate sonoporation of cardiac myoblasts in the absence of contrast agent (CA-free sonoporation) using a low-cost ultrasound-microfluidic device. Within this device an ultrasonic standing wave was generated, allowing control over the position of the cells and the strength of the acoustic radiation forces. Real-time single-cell analysis and retrospective post-sonication analysis of insonated cardiac myoblasts showed that CA-free sonoporation induced transmembrane transfer of fluorescent probes (CMFDA and FITC-dextran) and that different mechanisms potentially contribute to membrane poration in the presence of an ultrasonic wave. Additionally, to the best of our knowledge, we have shown for the first time that sonoporation induces increased cell cytotoxicity as a consequence of CA-free ultrasound-facilitated uptake of pharmaceutical agents (doxorubicin, luteolin, and apigenin). The US-microfluidic device designed here provides an in vitro alternative to expensive and controversial in vivo models used for early stage drug discovery, and drug delivery programs and toxicity measurements.     

Who's Afraid of Positivism? A comment on Shilling and Abraham

This paper is a response to articles by Shilling and Abraham, which were concerned with the relationship between Giddens’ structuration meta‐theory, differentiation‐polarisation theory, and positivism. Despite their conflicting conclusions, both authors criticise my reconstruction of differentiation‐polarisation theory, and I try to clarify the nature of that reconstruction and the theory it represents. It seems to me that these articles display misunderstandings of, and unwarranted prejudice against, positivism; though they are of course by no means alone in this. I suggest that while the sort of debate in which these authors engage is welcome, there needs to be a more open‐minded approach towards the theoretical and methodological resources available to sociologists of education, including those frequently dismissed as positivist.     

The Work Context of Teaching: an analytic framework for the study of teachers in classrooms

Teachers do not work under ideal circumstances. The resources allocated through the school organisation confront them with particular imperatives, dilemmas and possibilities which they feel obliged to take into account in their routine activity.

Using the notion of ‘competent membership’ this paper develops an analytic framework derived from the sociology of organisations which focuses attention on the work context of teaching. Specifically, it is argued: (1) that routine teacher activity constitutes a practical response to perceived exigencies of the situation, and (2) that these exigencies can be attributed to particular organisational arrangements.     

Reviewing the role of teachers in achieving Education for All in Cambodia

Over the last 20 years education policies in Cambodia have been driven by the global Education for All (EFA) campaign and have resulted in a rapid increase in the rates of primary education enrolment. However, the increasing number of children enrolling in schools has not always translated into high rates of primary education completion. Against this background the authors argue that while teachers play a significant role in keeping children in school and helping them to progress further in the education system, that role has been somewhat sidelined in the main debates about achieving EFA. They suggest that, while genuine problems exist with the qualifications and motivation of many Cambodian teachers, positive results could come from emphasizing their roles in achieving the wider goals of the education system and society, and thus promoting their active participation in furthering EFA.     

The effects of different drawing materials on children’s drawings of positive and negative human figures

Children tend to use certain drawing strategies differentially when asked to draw topics with positive and negative emotional characterisations. These effects have however only been established when children are asked to use standard drawing materials. The present study was designed to investigate whether the above pattern of children’s response when drawing characterised figures would alter when children are asked to use different drawing materials. One hundred and thirty‐two children (69 boys and 63 girls) aged between four and 11 years were divided into two conditions and completed two counterbalanced test sessions, rating colour preferences and drawing characterised figures using either stick or block crayons. It was found that some drawing strategies varied in relation to drawing materials and in relation to the precise characterisation employed. The results are discussed in terms of the need for interpretations of emotional information in children’s drawings to take account of the exact materials used.     

‘Rule of thumb methods no longer suffice’: development of British coal industry education and training 1900–circa 1970 and lessons for present-day education policy-makers

This paper traces the origins and development of coal mining education and training in Britain from 1900 to the 1970s, by which time the coal industry had substantially declined. It looks at the progress from working-class self-help to national policy in support of education and training. The research makes use of college prospectuses and principals' reports to identify the kind of courses offered at several former mining and technical colleges located on the Lancashire and Yorkshire coalfields. The research also identifies funding available to those who worked in the industry, from new employees to those aspiring to be colliery and area managers. The paper also briefly summarises what policy-makers can learn from studying the former mining industry's education and training framework.     

Implications of educational theory for the design of instructional multimedia

Interactive multimedia provides a useful vehicle to reconsider the place of educational theories in the design of interactive learning environments. This paper serves to address a number of such theories, especially those centred on student learning, and in particular, attempts to draw out the implications they present for designing effective instructional multimedia. It is argued that we need to develop coherency rather than divergency, in our theoretical perspectives so that we might optimise the development of new technologies in teaching and learning. This rationale is then used to advance one such perspective, based on the role of dynamic modelling tools.