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

Nikolic-Jaric M  Romanuik SF  Ferrier GA  Cabel T  Salimi E  Levin DB  Bridges GE  Thomson DJ 《Biomicrofluidics》2012,6(2):24117-2411715

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).  相似文献   

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

David Bridges 《British Educational Research Journal》2009,35(4):497-517

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.  相似文献   

Scholarly reviews of U.S. history books     

Anne E. Bridges 《Publishing Research Quarterly》1989,5(3):66-74

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.  相似文献   

Counseling disabled persons throughout the period of further education and training     

Karl H. Seifert 《International journal for the advancement of counseling》1989,12(2):143-151

In this paper the special problems and needs of disabled adults during vocational rehabilitation in rehabilitation centers will be analyzed. For this purpose, the goals and measures of ideal counseling in regard to vocational choice, work and training adjustment, and social adjustment are compared with the results of evaluation studies and studies with drop-outs of these facilities. Conclusions are derived by which measures counselors can contribute essentially to the disabled trainees being better enabled to handle their adjustment problems more effectively.Paper presented at the International Round Table for the Advancement of Counseling Consultation on Counseling Disabled People and their Families, July 4–8, 1987, Vienna, Austria.  相似文献   

Assessing the characteristics of high-quality programs: Lessons from the ohio board of regents fipse study     

Jonathan L. Tafel  Karl Schilling 《Assessment Update》1992,4(6):14-14

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21世纪初图书馆的十大变换化管理   总被引：1，自引：0，他引：1  

顾敏 《图书情报工作》2007,51(12):39-43,47

分析数字革命对图书馆管理的影响，指出图书馆已由自动化管理的时代迈向变换化管理的时代，并提出图书馆的十大项变换化管理范畴，作为图书馆管理2．0概念的起点。  相似文献   

What's difficult,and what isn't: two books published in the 1960s     

Karl Miller 《Changing English: An International Journal of English Teaching》2004,11(2):183-188

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The geometry relevant to modern education     

Karl Menger 《Educational Studies in Mathematics》1971,4(1):1-17

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Microfluidic electromanipulation with capacitive detection for the mechanical analysis of cells     

G. A. Ferrier  A. N. Hladio  D. J. Thomson  G. E. Bridges  M. Hedayatipoor  S. Olson    M. R. Freeman 《Biomicrofluidics》2008,2(4)

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.  相似文献   

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

B. Saboktakin Rizi  K. Braasch  E. Salimi  M. Butler  G. E. Bridges  D. J. Thomson 《Biomicrofluidics》2014,8(6)

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.  相似文献