Electronic detection of dielectrophoretic forces exerted on particles flowing over interdigitated electrodes

Dielectric particles flowing through a microfluidic channel over a set of coplanar electrodes can be simultaneously capacitively detected and dielectrophoretically (DEP) actuated when the high (1.45 GHz) and low (100 kHz–20 MHz) frequency electromagnetic fields are concurrently applied through the same set of electrodes. Assuming a simple model in which the only forces acting upon the particles are apparent gravity, hydrodynamic lift, DEP force, and fluid drag, actuated particle trajectories can be obtained as numerical solutions of the equations of motion. Numerically calculated changes of particle elevations resulting from the actuation simulated in this way agree with the corresponding elevation changes estimated from the electronic signatures generated by the experimentally actuated particles. This verifies the model and confirms the correlation between the DEP force and the electronic signature profile. It follows that the electronic signatures can be used to quantify the actuation that the dielectric particle experiences as it traverses the electrode region. Using this principle, particles with different dielectric properties can be effectively identified based exclusively on their signature profile. This approach was used to differentiate viable from non-viable yeast cells (Saccharomyces cerevisiae).     

Research quality assessment in education: Impossible science,possible art?

For better or for worse, the assessment of research quality is one of the primary drivers of the behaviour of the academic community with all sorts of potential for distorting that behaviour. So, if you are going to assess research quality, how do you do it? This article explores some of the problems and possibilities, with particular reference to the UK Research Assessment Exercise and discussion around the proposed new Research Excellence Framework and the ongoing work of the Framework 7 European Education Research Quality Indicators project (EERQI). It begins by asking whether there are any meaningful generic criteria of quality which can be applied to research, and tension between such criteria and the diverse and sometimes contradictory requirements of educational research. It then looks at attempts to identify measurable indicators of quality, including consideration of the location of the publication, citation and download counts, and approaches based semantic analysis of machine readable text—but finds all these quasi ‘scientific’ attempts at quality assessment wanting (hence the ‘impossible science’). This is all the more the case because of their attachment to extrinsic correlates of quality rather than intrinsic characteristics of quality and hence the probability that the measures will induce behaviours not conducive to quality enhancement. Instead the article turns to a different approach. This is better expressed perhaps as quality ‘appreciation’, ‘discernment’ or even ‘connoisseurship’ and is rooted in the arts and humanities rather than in (quasi) science. It considers whether this might offer a better approximation to the kind of judgement involved in quality assessment of a piece of research writing than the sort of metrics approaches favoured in current discussion.     

Self-reported impacts of volunteering in UK zoos and aquariums

ABSTRACT

Zoos and aquariums are popular visitor destinations, with around 30 million visits made to them annually throughout the UK and Ireland. The role and mission of modern zoos have evolved, with the conservation of world’s remaining biodiversity now being their major purpose. They seek to aid biodiversity through a combination of public education, in situ and ex situ conservation programmes, and applied scientific research. Directly relevant to this paper, they are also institutions that actively recruit, attract and utilise volunteers. However, the impacts of volunteering in zoos and aquariums, on the volunteers themselves, are under-researched. Here we show that, in a survey of more than 500 volunteers at 19 different zoological collections in the UK, zoo volunteers report positive impacts, specifically in relation to increases in their human and social capital. We also found that these benefits were more pronounced in younger volunteers, and with those volunteers who received more initial training. We conclude that while volunteering in UK zoos correlates with significant personal benefits to individuals, zoos could aim higher and should seek to do more to maximise the positive effects of connecting volunteers with the wildlife and nature found in zoo settings, as well as tailoring their volunteer training programmes for different age groups.     

Enhancing Equity in Gifted Education: a framework for examining assessments drawing on the theory of multiple intelligences

In the United States, poor and minority students are disproportionately excluded from programs for the gifted. Current identification practices for gifted education programs are a primary barrier for these youngsters. This study investigated three alternative assessments for identifying students. Each was said to draw on the theory of multiple intelligences (Gardner, 1983) and to increase the identification of traditionally under‐served youngsters. This investigation asked: (1) Is it reasonable to associate increases in the identification of under‐served youngsters with these assessments? (2) Is it reasonable to associate each assessment with the theory of multiple intelligences? To answer these questions, qualitative data were analyzed against a framework of eight criteria. This revealed that no assessment met all eight criteria; each met a different subset of the eight.     

Scholarly reviews of U.S. history books

This study of reviews in six scholarly journals of books on U.S. history examines the sources of books reviewed; their prices, length, and other characteristics; the affiliations of the reviewers; and the timeliness and coverage of reviews. The findings indicate that, although historians rely on reviews in scholarly journals for information on current publications, these reviews are in some ways inadequate for their purposes.     

Microfluidic electromanipulation with capacitive detection for the mechanical analysis of cells

The mechanical behavior of cells offers insight into many aspects of their properties. We propose an approach to the mechanical analysis of cells that uses a combination of electromanipulation for stimulus and capacitance for sensing. To demonstrate this approach, polystyrene spheres and yeast cells flowing in a 25 μm×100 μm microfluidic channel were detected by a perpendicular pair of gold thin film electrodes in the channel, spaced 25 μm apart. The presence of cells was detected by capacitance changes between the gold electrodes. The capacitance sensor was a resonant coaxial radio frequency cavity (2.3 GHz) coupled to the electrodes. The presence of yeast cells (Saccharomyces cerevisiae) and polystyrene spheres resulted in capacitance changes of approximately 10 and 100 attoFarad (aF), respectively, with an achieved capacitance resolution of less than 2 aF in a 30 Hz bandwidth. The resolution is better than previously reported in the literature, and the capacitance changes are in agreement with values estimated by finite element simulations. Yeast cells were trapped using dielectrophoretic forces by applying a 3 V signal at 1 MHz between the electrodes. After trapping, the cells were displaced using amplitude and frequency modulated voltages to produce modulated dielectrophoretic forces. Repetitive displacement and relaxation of these cells was observed using both capacitance and video microscopy.     

Monitoring the dielectric response of single cells following mitochondrial adenosine triphosphate synthase inhibition by oligomycin using a dielectrophoretic cytometer

One of the main uses of adenosine triphosphate (ATP) within mammalian cells is powering the Na⁺/K⁺ ATPase pumps used to maintain ion concentrations within the cell. Since ion concentrations determine the cytoplasm conductivity, ATP concentration is expected to play a key role in controlling the cytoplasm conductivity. The two major ATP production pathways within cells are via glycolysis within the cytoplasm and via the electron transport chain within the mitochondria. In this work, a differential detector combined with dielectrophoretic (DEP) translation in a microfluidic channel was employed to observe single cell changes in the cytoplasm conductivity. The DEP response was made sensitive to changes in cytoplasm conductivity by measuring DEP response versus media conductivity and using double shell models to choose appropriate frequencies and media conductivity. Dielectric response of Chinese hamster ovary (CHO) cells was monitored following inhibition of the mitochondria ATP production by treatment with oligomycin. We show that in CHO cells following exposure to oligomycin (8 μg/ml) the cytoplasm conductivity drops, with the majority of the change occurring within 50 min. This work demonstrates that dielectric effects due to changes in ATP production can be observed at the single cell level.