Contactless microfluidic pumping using microchannel-integrated carbon black composite membranes

The ability to pump and manipulate fluid at the micron-scale is a basic requirement for microfluidic platforms. Many current manipulation methods, however, require expensive and bulky external supporting equipment, which are not typically compatible for portable applications. We have developed a contactless metal electro-osmotic micropump capable of pumping conductive buffers. The pump operates using two pairs of gallium metal electrodes, which are activated using an external voltage source and separated from a main flow channel by a thin micron-scale polydimethylsiloxane (PDMS) membrane. The thin contactless membrane allows for field penetration and electro-osmotic flow within the microchannel, but eliminates electrode damage and sample contamination commonly associated with traditional DC electro-osmotic pumps that utilize electrodes in direct contact with the working fluid. Our previous work has demonstrated the effectiveness of this method in pumping deionized water. However, due to the high resistivity of PDMS, this method proved difficult to apply towards manipulating conductive buffers. To overcome this limitation, we fabricated conductive carbon black (CB) powder directly into the contactless PDMS membranes. The increased electrical conductivity of the contactless PDMS membrane significantly increased micropump performance. Using a microfluidic T-channel device and an electro-osmotic flow model, we determined the influence that CB has on pump pressure for CB weight percents varying between 0 and 20. The results demonstrate that the CB increases pump pressure by two orders of magnitude and enables effective operations with conductive buffers.     

Preschool Temperament Assessment: A Quantitative Assessment of the Validity of Behavioral Style Questionnaire Data

Research Findings: Child temperament is an important construct, but its measurement has been marked by a number of weaknesses that have diminished the frequency with which it is assessed in practice. We address this problem by presenting the results of a quantitative construct validation study. We calculated validity indices by hypothesizing the magnitude of relationships between Behavioral Style Questionnaire (BSQ) subscales and criterion measures assessing student–teacher relationships, student characteristics related to teaching stress, and peer play interactions. We tested these hypotheses against the actual correlations observed in a sample of 44 children 40 to 68 months of age. These analyses indicated strong support for 4 of the BSQ subscales (Activity, Rhythmicity, Approach, and Adaptability) and moderate support for 1 subscale (Mood). However, new item generation and testing is recommended for 3 subscales (Intensity, Persistence, and Threshold), along with further construct definition work for the final subscale (Distractibility). Practice or Policy: These findings are particularly relevant for early childhood educators who wish to assess temperament yet are uncertain of the issues involved in its measurement. Results derived from the BSQ, viewed in context, can increase practitioners’ understandings of children's individual characteristics and guide the development of interventions to promote optimal early educational experiences for children.     

Analyse d'un programme d'electromecanique en ses concepts et principes physiques: Methode et application

Résumé L'intérêt va grandissant, dans de nombreux pays occidentaux, quant à l'utilité des connaissances scientifiques en formation professionnelle et technique. Par ailleurs, on y tend aussi, de plus en plus, à une formulation par objectifs des programmes scolaires en vue d'un rapprochement avec les tâches réelles du monde du travail. Afin de déterminer les connaissances nécessaires, une méthode générale d'analyse de programmes de formation professionnelle formulés par objectifs a été développée. Elle permet l'identification des concepts et principes scientifiques et mathématiques minimalement exigés par l'atteinte des objectifs d'apprentissage, d'en établir l'importance et d'en préciser le degré d'approfondissement requis. Elle fut utilisée pour déterminer les concepts physiques essentiels à la section Mécanique industrielle (625 heures) d'un programme d'Electromécanique de systèmes automatisés. Les résultats révèlent la présence de 41 concepts requis pendant un total de 2.452,5 heures. Un groupe restreint d'entre eux est particulièrement important.

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In many Western countries there is growing interest in the usefulness of scientific knowledge in vocational and technical training. Moreover, there is an increasing tendency in these countries to formulate objectives within teaching programmes, in order to come closer to the real tasks of the world of work. To determine what knowledge is required, a general method of analysing objective-based vocational training programmes was developed. This allows the identification of the minimum scientific and mathematical concepts and principles which are necessary to reach the learning objectives, and the establishment of their relative significance and the requisite level of detail. It has been used to determine the essential physical concepts of the industrial mechanics section (625 hours) of a programme on the electromechanics of automated systems. The results reveal the existence of 41 concepts needed for a total of 2,452.5 hours. A limited group of these is of particular importance.

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Zusammenfassung In vielen Ländern der westlichen Welt wächst das Interesse an der Verwendbarkeit wissenschaftlicher Kenntnisse in der beruflichen und technischen Ausbildung. Darüberhinaus gibt es eine zunehmende Tendenz in diesen Ländern, innerhalb der Lehrprogramme solche Ziele zu formulieren, die den tatsächlichen Erfordernissen der Arbeitswelt eher gerecht werden. Um festzustellen, welche Kenntnisse dazu notwendig sind, wurde eine allgemeine Methode zur Analyse zielgerichteter Berufsausbildungsprogramme entwickelt. Sie ermöglicht es, das Minimum an wissenschaftlichen und mathematischen Begriffen und Prinzipien zu erkennen und ihre relative Bedeutung und das erforderliche Maß an Genauigkeit festzustellen. Sie wurde angewandt, um die wichtigsten physikalischen Begriffe für die Abteilung Industriemechanik (625 Stunden) zu ermitteln in Bezug auf ein Programm zur Elektromechanik automatisierter Systeme. Die Ergebnisse zeigen, daß es 41 Begriffe sind, die für eine Gesamtanzahl von 2.452,5 Stunden gebraucht werden. Eine begrenzte Anzahl von ihnen ist von besonderer Bedeutung.

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R. Gagné et L.P. Leclerc, du département de didactique de l'Université Laval, sont également co-auteurs de cet article. Pour des raisons bibliographiques, LaRevue Internationale de Pédagogie limite à trois le nombre des auteurs nommés. Nous remercions Jasmin Côté pour sa contribution à la phase initiale des travaux et Alcide Brisson pour sa participation à certains aspects de l'analyse. Nous remercions également le Ministère de l'Enseignement supérieur et de la Science pour son aide financière dans le cadre du programme RDF.     

Relationships between peer interactive play and social competence in at‐risk preschool children

Relationships between peer interactive play and social competence in a sample of preschool children (N = 85) considered at risk for academic difficulties were examined. Ratings of peer interactive play and social emotional development were collected from parents and teachers on the Penn Interactive Peer Play Scale and Vineland Social‐Emotional Early Childhood Scale. Multivariate techniques revealed significant correlations between parent and teacher ratings on the measures. Results are discussed within the context of conducting multifaceted, ecological assessments of preschool children. Implications for school psychologists are noted with regard to the important associations between peer interactive play and social–emotional development. The psychometric integrity of the PIPPS is further validated and extended beyond the initial standardization sample to include a sample of primarily Caucasian children living in a more rural area. © 2004 Wiley Periodicals, Inc. Psychol Schs 41: 173–189, 2004.     

Efficacy of online training for improving camp staff competency

Preparing competent staff is a critical issue within the camp community. This quasi-experimental study examined the effectiveness of an online course for improving staff competency in camp healthcare practices among college-aged camp staff and a comparison group (N = 55). We hypothesized that working in camp would increase competency test scores due to opportunities for staff to experientially apply knowledge learned online. Hierarchical linear modeling was used to analyse the cross-level effects of a between-individuals factor (assignment to experimental or comparison group) and within-individual effects of time (pre-test, post-test #1, and post-test #2) on online course test scores. At post-test #2, the difference in average test scores between groups was ~30 points, with the treatment group scoring lower on average than the comparison group. Factors that may have influenced these findings are explored, including fatigue and the limited durability of online learning. Recommendations for research and practice are discussed.     

Search behavior in cats and dogs: Interspecific differences in working memory and spatial cognition

Cats’ and dogs’ search behavior was compared in different problems where an object was visibly moved behind a screen that was then visibly moved to a new position. In Experiments 1 (cats) and 2 (dogs), one group was tested with identical screens and the other group was tested with dissimilar screens. Results showed that in both species, search behavior was based on processing of spatial information rather than on recognition of the visual features of the target screen. Cats and dogs were unable to find the object by inferring its invisible movement. They reached a high level of success only if there was direct perceptual evidence that the object could not be at its initial position. When the position change was indicated by an indirect cue, cats searched more at the object’s initial than final position, whereas dogs searched equally at both positions. Interspecific similarities and differences are interpreted in terms of the requirements for resetting working memory.     

Dielectrophoretic discrimination of bovine red blood cell starvation age by buffer selection and membrane cross-linking

We report an interesting buffer electric relaxation time tuning technique, coupled with a glutaraldehyde cross-linking cell fixation reaction, which allows for sensitive dielectrophoretic analysis and discrimination of bovine red blood cell (bRBC) starvation age. The buffer composition is selected such that two easily accessible dielectrophoretic crossover frequencies (cof) exist. Low concentration glutaraldehyde fixation was observed to produce a threefold decrease in the higher cof with a comparable increase in the lower cof also witnessed. More importantly, increased glutaraldehyde fixation concentration significantly increased the higher cof by a factor found to be sensitive to the bRBC starvation age.     

Learning of Core Disciplinary Ideas: Efficacy Comparison of Two Contrasting Modes of Science Instruction

Science curricula and teaching methods vary greatly, depending in part on which facets of science are emphasized, e.g., core disciplinary ideas or science practices and process skills, and perspectives differ considerably on desirable pedagogies. Given the multi-faceted nature of science and the variety of teaching methods found in practice, it is no simple task to determine what teaching approaches might be most effective and for what purposes. Research into relative efficacy faces considerable challenges, with confounding factors, ambiguities, conflations, and lack of controls being threats to validity. We provide a conceptual framework characterizing the many teaching strategies found in practice as being variants of two fundamental contrasting epistemic modes, and we disentangle conflations of terms and confusions of constructs in both teaching practice and research. Instructional units for two science topics were developed in parallel in the alternative epistemic modes, differing in concept learning paths but otherwise equivalent. We conducted a randomized controlled study of the comparative efficacy of the two modes for learning core disciplinary ideas, using operationally defined active-direct and guided-inquiry teaching methods. Five middle school teachers taught each unit in both modes over 4 years of classroom trials in an 8-day summer program for eighth grade students. Student understanding of core ideas was assessed using pre- and post-tests, and learning gains were analyzed by mode, teacher, topic, and trial year. Although routes to concept understanding were very different in the two modes, eventual student learning gains were similar, within statistical variation. Efficacy variations between and within teachers were greater than between modes, indicating the importance of teacher effects on student achievement. Findings suggest that teachers need not be bound to one mode throughout and can flexibly decide on the pedagogical approach for each concept and situation, on several grounds other than efficacy of core content acquisition alone.