The dynamics and stability of lubricating oil films during droplet transport by electrowetting in microfluidic devices

The operation of digital microfluidic devices with water droplets manipulated by electrowetting is critically dependent on the static and dynamic stability and lubrication properties of the oil films that separate the droplets from the solid surfaces. The factors determining the stability of the films and preventing surface fouling in such systems are not yet thoroughly understood and were experimentally investigated in this study. The experiments were performed using a standard digital microfluidic cartridge in which water droplets enclosed in a thin, oil-filled gap were transported over an array of electrodes. Stable, continuous oil films separated the droplets from the surfaces when the droplets were stationary. During droplet transport, capillary waves formed in the films on the electrode surfaces as the oil menisci receded. The waves evolved into dome-shaped oil lenses. Droplet deformation and oil displacement caused the films at the surface opposite the electrode array to transform into dimples of oil trapped over the centers of the droplets. Lower actuation voltages were associated with slower film thinning and formation of fewer, but larger, oil lenses. Lower ac frequencies induced oscillations in the droplets that caused the films to rupture. Films were also destabilized by addition of surfactants to the oil or droplet phases. Such a comprehensive understanding of the oil film behavior will enable more robust electrowetting-actuated lab-on-a-chip devices through prevention of loss of species from droplets and contamination of surfaces at points where films may break.     

The myths about e‐learning in higher education

Proponents have marketed e‐learning by focusing on its adoption as the right thing to do while disregarding, among other things, the concerns of the potential users, the adverse effects on users and the existing research on the use of e‐learning or related innovations. In this paper, the e‐learning‐adoption proponents are referred to as the technopositivists. It is argued that most of the technopositivists in the higher education context are driven by a personal agenda, with the aim of propagating a technopositivist ideology to stakeholders. The technopositivist ideology is defined as a ‘compulsive enthusiasm’ about e‐learning in higher education that is being created, propagated and channelled repeatedly by the people who are set to gain without giving the educators the time and opportunity to explore the dangers and rewards of e‐learning on teaching and learning. Ten myths on e‐learning that the technopositivists have used are presented with the aim of initiating effective and constructive dialogue, rather than merely criticising the efforts being made.     

Using data for decision-making: perspectives from 16 principals in Michigan, USA

In response to the vast amounts of data associated with the accountability movement and the rhetoric of data-informed decision-making, we interviewed 16 principals to find out what streams of data they used and what decisions they made by using the data. We found that: (a) student achievement data are predominantly used to the extent of neglecting other streams of data such as student and community background data and school process data; (b) student achievement data are used more for accountability purposes—for assessing “of” rather than “for” the learning; (c) different streams of data are rarely used together to derive rich meaning for decision-making; and (d) school districts differ in the extent to which their principals use data to improve curriculum and instruction. The study pointed both to the challenges and to the opportunities of making data-informed decisions to improve our schools.     

Expression of self-concept and adjustment against repeated aggressions: the case of a longitudinal study on school bullying

Bullying between students in the school setting is an increasing problem. Bullying can be defined as any form of repeated mental or physical violence carried out by one or several individuals on a person who is not capable of defending himself (Roland and Idsoe, Aggress Behav 27:446–462, 2001). The aim of this paper is to observe the expression of self-concept and adjustment strategies developed by children subject to this kind of violence. Five hundred twenty-four students between the ages of 8 and 12 (m = 9.44) participated in the longitudinal study. Two measurements were made during the same school year at an interval of 6 months. The results show that the student victims of bullying present weaker self-conceptions than the control group. Recourse to avoidance strategies would be dominant among student victims of bullying. Moreover, recourse to “avoidance” type strategies would lead to an increase in the frequency of bullying while recourse to “approach”-type strategies would lead to a reduction in it. Furthermore, it would seem that recourse to avoidance strategies at T1 lowers the student’s self-concepts at T2. The opposite effect is observed with the approach strategies. These different results emphasize the necessity to establish prevention programs which allow an intervention simultaneously on the level of the school, the family, and the student.     

Neuromuscular, biochemical and perceptual post-match fatigue in professional rugby league forwards and backs

In this study, we investigated changes in creatine kinase, perceptual and neuromuscular fatigue of professional rugby league players after match-play. Twenty-three male rugby league players (10 backs, 13 forwards) had their creatine kinase, perceptual ratings of fatigue, attitude to training, muscle soreness, and flight time in a countermovement jump measured before and 1 and 2 days after (day 1 and day 2 respectively) league matches. Total playing time, offensive and defensive contacts were also recorded for each player. Creatine kinase was higher both 1 and 2 days after than before matches (P < 0.05) in forwards and backs. Similarly, perceived fatigue and muscle soreness were higher than pre-match on both days 1 and 2 (P < 0.05), but did not differ between groups (P > 0.05). Jump performance was lower on day 1 but not day 2 for both groups (P < 0.05). While total playing time was longer in backs (P < 0.05), relative frequencies for all contacts were greater in forwards (P < 0.05). Contacts for forwards were correlated with all markers of fatigue (P < 0.05), but only flight time was correlated with offensive contacts in backs (P < 0.05). Despite the mechanisms of fatigue being different between forwards and backs, our results highlight the multidimensional nature of fatigue after a rugby league match and that these markers do not differ between positions.     

LibStatCAT: a library statistical collection assessment tool for individual libraries & cooperative collection development

The following presentation to the Acquisitions Institute at Timberline Lodge focuses on LibStatCAT, a prototype collection assessment tool under development at Portland State University. Our presentation explores the current uses of LibStatCAT, as well as future developments of LibStatCAT as a regional library data farm for comprehensive assessment of library collections and services for individual libraries and cooperative collection development. We share a variety of other collection assessment tools in use at Portland State University Library.