Dual-mode on-demand droplet routing in multiple microchannels using a magnetic fluid as carrier phase

We present dual-mode, on-demand droplet routing in a multiple-outlet microfluidic device using an oil-based magnetic fluid. Magnetite (Fe₃O₄) nanoparticle-contained oleic acid (MNOA) was used as a carrier phase for droplet generation and manipulation. The water-in-MNOA droplets were selectively distributed in a curved microchannel with three branches by utilizing both a hydrodynamic laminar flow pattern and an external magnetic field. Without the applied magnetic field, the droplets travelled along a hydrodynamic centerline that was displaced at each bifurcating junction. However, in the presence of a permanent magnet, they were repelled from the centerline and diverted into the desired channel when the repelled distance exceeded the minimum offset allocated to the channel. The repelled distance, which is proportional to the magnetic field gradient, was manipulated by controlling the magnet''s distance from the device. To evaluate routing performance, three different sizes of droplets with diameters of 63, 88, and 102 μm were directed into designated outlets with the magnet positioned at varying distances. The result demonstrated that the 102-μm droplets were sorted with an accuracy of ∼93%. Our technique enables on-demand droplet routing in multiple outlet channels by simply manipulating magnet positions (active mode) as well as size-based droplet separation with a fixed magnet position (passive mode).     

Computational investigations of the mixing performance inside liquid slugs generated by a microfluidic T-junction

Droplet-based microfluidics has gained extensive research interest as it overcomes several challenges confronted by conventional single-phase microfluidics. The mixing performance inside droplets/slugs is critical in many applications such as advanced material syntheses and in situ kinetic measurements. In order to understand the effects of operating conditions on the mixing performance inside liquid slugs generated by a microfluidic T-junction, we have adopted the volume of fluid method coupled with the species transport model to study and quantify the mixing efficiencies inside slugs. Our simulation results demonstrate that an efficient mixing process is achieved by the intimate collaboration of the twirling effect and the recirculating flow. Only if the reagents are distributed transversely by the twirling effect, the recirculating flow can bring in convection mechanism thus facilitating mixing. By comparing the mixing performance inside slugs at various operating conditions, we find that slug size plays the key role in influencing the mixing performance as it determines the amount of fluid to be distributed by the twirling effect. For the cases where short slugs are generated, the mixing process is governed by the fast convection mechanism because the twirling effect can distribute the fluid to the flow path of the recirculating flow effectively. For cases with long slugs, the mixing process is dominated by the slow diffusion mechanism since the twirling effect is insufficient to distribute the large amount of fluid. In addition, our results show that increasing the operating velocity has limited effects on improving the mixing performance. This study provides the insight of the mixing process and may benefit the design and operations of droplet-based microfluidics.     

The Effects of Late Arts Education on Adults with Early Visual Disabilities

In this study, non-participant observations of visually disabled adult students in extra mural arts education are analysed through Walter Doyle’s theory of ambiguity and risk in classroom tasks. This study finds these students attempted to avoid activity, or re-negotiate lecturers’ expectations, when their performance became especially threatening to their self-esteem. Additionally, it was found that lecturers were often reluctant to push their students as soon as they realised this risk to them. These results appear to show a phenomenon similar to learned helplessness.     

The industrial lot and its sampling implications

It is shown that wrong inferences are drawn from samples because of failure to understand what constitutes a lot and because of failure to verify the existence of a lot in the practically useful sense. Time-tried methods of making valid inferences from samples without increased cost are pointed out.     

Exploring the Causal Effect of Interpretation Bias on Attachment Expectations

Attachment theory implies that children's inclination to interpret attachment figures behavior as supportive and available causally influences children's trust in their attachment figure's availability. An experiment was conducted to test whether training children (8–12 years old) to interpret ambiguous interactions with their mothers in a more secure way increases their trust in their mother's availability. Participants (N = 49) were randomly assigned to either a secure condition to train children to interpret their mother's behavior as supportive or a neutral placebo condition, where interpretations were unrelated to maternal support. Results supported the hypothesis: After the secure training, children interpreted maternal behavior more securely and trusted more in her availability. This suggests that attachment‐related processing biases causally affect attachment expectations.     

Vygotsky’s sociocultural theory in the context of globalization

The article reviews the social-educational theorization of the early Soviet psychologist L. S. Vygotsky (1896–1934) in the light of the impact of communicative globalization in educational practice. Vygotsky proposed four “genetic domains” for investigating higher cognitive processes: the phylogenetic (humans undergoing natural evolution), the cultural-historical (social activity of humans), the ontogenetic (individual lifespan), and the microgenetic (immediate events). Vygotskian sociocultural theory is widely used in educational research, especially Vygotsky’s notion of mediated development via tools and signs. Since Vygotsky, communicative globalization has transformed educational potentials. Nevertheless, provided adjustments are made to Vygotsky’s genetic method to incorporate time-space compression, the mutual presence of the genetic domains, and the glonacal heuristic, Vygotskian theory continues to be useful in socially-situated investigations of educational development and transformation, and opens another way into the global, for example investigation of the role of global mediation in learning.     

Student & tutor consensus: a partnership in assessment for learning

The mistakes made when attempting tasks often prove to be some of the most invaluable learning experiences. Despite this, outcome and results driven assessment formats largely penalise student performance errors or reward students who succeed by chance. The consequences of this paradigm are visible effects on student relationships with assessment. The student–tutor consensus approach to assessment was introduced to capture student learning achieved ‘from’ assessment to complement the measurement of performance outcomes. This approach parallels student and tutor judgement in a grade negotiation, affording the student an opportunity to share with their assessor what they have learned from the assessment activity. This student self-awareness was then considered alongside the conventional outcome-based score awarded by the tutor to generate a final grade for the assessed activity. Our study evaluated the perceptions of 90 undergraduate students enrolled in the bachelor of paramedic studies, who participated in this novel assessment approach as part of a final-year capstone topic. The results comprehensively indicated value for all aspects of the assessment approach, as well as a recognition that the skills will be useful in their future professional roles.