Systematic characterization of degas-driven flow for poly(dimethylsiloxane) microfluidic devices

Degas-driven flow is a novel phenomenon used to propel fluids in poly(dimethylsiloxane) (PDMS)-based microfluidic devices without requiring any external power. This method takes advantage of the inherently high porosity and air solubility of PDMS by removing air molecules from the bulk PDMS before initiating the flow. The dynamics of degas-driven flow are dependent on the channel and device geometries and are highly sensitive to temporal parameters. These dependencies have not been fully characterized, hindering broad use of degas-driven flow as a microfluidic pumping mechanism. Here, we characterize, for the first time, the effect of various parameters on the dynamics of degas-driven flow, including channel geometry, PDMS thickness, PDMS exposure area, vacuum degassing time, and idle time at atmospheric pressure before loading. We investigate the effect of these parameters on flow velocity as well as channel fill time for the degas-driven flow process. Using our devices, we achieved reproducible flow with a standard deviation of less than 8% for flow velocity, as well as maximum flow rates of up to 3 nL∕s and mean flow rates of approximately 1-1.5 nL∕s. Parameters such as channel surface area and PDMS chip exposure area were found to have negligible impact on degas-driven flow dynamics, whereas channel cross-sectional area, degas time, PDMS thickness, and idle time were found to have a larger impact. In addition, we develop a physical model that can predict mean flow velocities within 6% of experimental values and can be used as a tool for future design of PDMS-based microfluidic devices that utilize degas-driven flow.     

Comparison of Knowledge and Attitudes Using Computer-based and Face-to-Face Personal Hygiene Training Methods in Food Processing Facilities

ABSTRACT:  Computer-based training is increasingly favored by food companies for training workers due to convenience, self-pacing ability, and ease of use. The objectives of this study were to determine if personal hygiene training, offered through a computer-based method, is as effective as a face-to-face method in knowledge acquisition and improved attitude toward food safety. Employees from four food processing facilities ( n = 94) were randomly assigned to a control group, a face-to-face training group, or a computer-based training group. Evaluation instruments consisted of a pretest and a posttest to measure knowledge gain, a step scale to measure attitude after training and retrospectively before training, and a brief set of interview questions. Results for both treatments and the control group indicated increases in knowledge. Analysis of the posttest scores, when controlling for the pretest scores, indicated the difference was significant ( P ≤ 0.05); however, post hoc analysis did not indicate which treatment was superior. There was a significant increase in attitude scores for both groups using paired t -tests, although the difference between groups was not significant when controlling for attitude scores before training. Issues that may limit application of the technology used in this study include low literacy and language barriers among employees, and time constraints within companies. These and other variables should be taken into account in future research studies addressing comparisons of training methods. This study is the first to demonstrate the effectiveness of computer-based training aimed at food handlers who work in food processing establishments.     

Capital and Knowledge Flows: Global higher education markets

Accelerating global flows of people and information have formed new communities and networks across social and political borders. Higher education is one such globalised knowledge community in which new patterns of knowledge, accreditation, research alliances, and social and professional relationships are emerging. In this paper I outline the push–pull dynamics of globalisation in higher education: the co-constitutive nature of local and global interests and educational formations; disjunctive flows of capital, information, people, and knowledge; and the new politics of knowledge capital as they affect academic research and the public archive of scholarly publishing and university libraries. I close with reflections on the differential consequences of globalisation on: the role of the nation state in higher education provision and reform; the role of education in nation building and national identity politics; and the governability of a global eduscape.     

Faculty roles and role preferences in ten fields of professional study

Teaching faculty in ten entry-level professional fields reported varying amounts of time devoted to teaching, research, consulting, and professional practice but did not differ in time devoted to administration. The faculty member's own role view was most closely related to time use, but for time spent in teaching and research, faculty age and institutional type (but not gender) were also significant predictors. Even after several general demographic characteristics and environmental variables that potentially differentiate professional from discipline-based faculty are taken into account, different professional fields may be characterized by group climates which influence or reinforce certain faculty roles.     

Perfectionism in Academically Gifted Students: A Systematic Review

Educational Psychology Review - Perfectionism has long been recognised as a psychological factor that can enhance or interfere with the healthy adjustment of young students who are academically...     

Incorporating Comprehensive Counselling and Guidance Models into School Curricula in Sub-Saharan Africa

There is an increasing body of evidence demonstrating the psychological and social challenges that afflict school-age children in sub-Saharan Africa. In spite of widespread calls to provide counselling and guidance services in schools, efforts at expanding these services remain fragmented and under-resourced. Grounded in both empirical and theoretical literature, this article calls for integration of counselling and guidance through a whole-school approach. Utilizing critical aspects of child and adolescent developmental theory, we summarize the current state of counselling and guidance in the region, evaluate attempts at integration, and propose adoption of a comprehensive guidance and counselling model into school curricula.