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.     

Viewing a phonological deficit within a multifactorial model of dyslexia

Participants were administered multiple measures of phonological awareness, oral language, and rapid automatized naming at the beginning of kindergarten and multiple measures of word reading at the end of second grade. A structural equation model was fit to the data and latent scores were used to identify children with a deficit in phonological awareness alone or in combination with other kindergarten deficits. Children with a deficit in phonological awareness in kindergarten were found to be five times more likely to have dyslexia in second grade than children without such a deficit. This risk ratio substantially increased with the addition of deficits in both oral language and rapid naming. Whereas children with one or more kindergarten deficits were at heighten risk for dyslexia, some of these children were found to be adequate or better readers. These results are discussed within a multifactorial model of dyslexia that includes both risk and protective factors.     

Definitional issues in emotion regulation research

Operational definitions of emotion regulation are frequently unclear, as are links between emotion regulation measures and underlying theoretical constructs. This is of concern because measurement decisions can have both intentional and unintentional implications for underlying conceptualizations of emotion regulation. This report examines the implications of some such decisions, including (a) focusing on types versus total amount of emotion regulation, (b) determining distinctiveness of measures of emotion versus emotion regulation strategies, (c) deciding whether and how to examine temporal sequencing of strategy use and emotion, d) using discrete versus global emotion measures, and (e) determining when emotion is being regulated. Finally, the need for better conceptualizations and empirical assessments of adaptive (vs. maladaptive) emotion regulation is discussed.     

Leadership Reflections: It is Not About the Perks

Abstract

Our guest columnist is Karl Bridges who has served in a variety of leadership roles in academic libraries. I have gotten to know Karl over the past few years as he was asked to serve in an interim dean role and then hired into the permanent dean positions. At the time, I was at the University of Wyoming and serving as a leader in sparsely populated state where everyone knows your name. Western leaders have to form a tight bond – there are fewer of us and the distances are great. But regardless of geographical situations, leaders need and depend on peer networks that provide a safe space for frank conversations and sharing ideas that help all libraries achieve their goals. Karl has dealt with changing university leadership, library transformations, and dire budget situations. Well, pretty much what every library leader must face. Despite these challenges, library leaders have an opportunity to make a real difference. Karl draws upon his years of experience to provide a thought piece about library leadership noting the complexity, the importance of leadership, and the real joy of making a difference in someone’s life. I hope you enjoy this raw look at leadership and that it reminds you of the purpose of leadership.     

A Review of “Everything You Ever Wanted to Know about Social Media But Were Afraid to Ask; Building Your Business Using Consumer Generated Media”

Curriculum materials center (CMC) collections in academic libraries play a vital role in supporting teacher education programs. The collection items consist of print and non-print materials including nontraditional items such as kits, games, models, and toys. Following a comprehensive literature review of research on CMC collections, this study seeks to raise awareness of the role played by curriculum materials centers in the history of teacher education and the challenges faced by the CMC librarians. The article provides a general overview of the CMC at Long Island University (LIU) Post library and describes local collection development strategies and issues in collection access and maintenance.     

Moving a Hospital Library

Many hospital libraries suffer from being poorly housed. This article describes a successful effort to find better space for a hospital library. Issues of planning, staff participation, and implementation are discussed, including constraints, what worked well, and what could have worked better.     

Who says you need to teach reading to 11–13-year-olds?

Research indicates that as students move through the school system, many begin to experience difficulties with reading. With this mind, this study explored current practices and perceptions about reading programmes for 11–13-year-old students in New Zealand schools. The study employed an online survey designed to investigate current reading literacy practices in a sample of New Zealand primary in years 7 and 8. Observations of practice and interviews with literacy leaders, teachers, principals and students were also carried out at five case study schools. The survey indicated that teachers may underestimate the importance of learner engagement and direct teaching strategies. The case studies exemplify the need for good professional development, supportive leadership, effective class management strategies, a positive and engaging learning environment, teachers with a passion for literacy and exemplary and sustained guided reading.     

Discipline‐related Marking Behaviour Using Percentages: a potential cause of inequity in assessment

This study set out to ascertain whether percentage mark distributions show evidence of discipline‐related marking behaviour and, if so, to consider the implications of this for equity in assessment outcomes. Performance data were obtained for 10 subjects at seven English universities for 1993–94, 1994–95 and 1995–96. The data showed that mark distributions at universities using percentages may be categorised into three Types (A,B and C). Type A distributions (English and History) are characterised by a steep‐sided negatively skewed distribution with a narrow spread. Pronounced microscale variation in the frequency is evident only in the vicinity of the mode between 55‐65%. Type B distributions (Biology, Business Studies, Fine Art, French, Law and Sociology) have a slightly broader spread and display microscale variation in frequency across a wider range of percentiles [40‐70%]. Type C distributions (Computer Studies and Mathematics) are characterised by a subdued, slightly negatively skewed distribution with a considerably wider spread. Type C distributions show conspicuous microscale variation in frequency across most of the percentile range. The types of distributions appear to reflect the relative confidence of assessors in different disciplines in awarding marks. The extremities of the percentage scale are perceived as insecure territory for the assessors of qualitative subject matter. Type A distributions are characteristic of disciplines in which the assessment is qualitative. Type B distributions may reflect the assessment of combined qualitative‐quantitative subject matter. Type C distributions are typical of disciplines in which more quantitative matter is assessed. The existence of discipline‐related patterns of distribution is a potential cause of inequity of outcomes for students on joint or multidisciplinary programmes. Data derived from institutions using grading scales show that discipline‐related patterns are less evident.