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Carl M. Tausig 《Educational theory》1969,19(3):223-235
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Matthew J. Kennedy Harold D. Ladouceur Tiffany Moeller Dickson Kirui Carl A. Batt 《Biomicrofluidics》2012,6(4)
The present work describes the operation and simulation of a microfluidic laminar-flow mixer. Diffusive mixing takes place between a core solution containing lipids in ethanol and a sheath solution containing aqueous buffer, leading to self assembly of liposomes. Present device architecture hydrodynamically focuses the lipid solution into a cylindrical core positioned at the center of a microfluidic channel of 125 × 125-μm2 cross-section. Use of the device produces liposomes in the size range of 100–300 nm, with larger liposomes forming at greater ionic strength in the sheath solution and at lower lipid concentration in the core solution. Finite element simulations compute the concentration distributions of solutes at axial distances of greater than 100 channel widths. These simulations reduce computation time and enable computation at long axial distances by utilizing long hexahedral elements in the axial flow region and fine tetrahedral elements in the hydrodynamic focusing region. Present meshing technique is generally useful for simulation of long microfluidic channels and is fully implementable using comsol Multiphysics. Confocal microscopy provides experimental validation of the simulations using fluorescent solutions containing fluorescein or enhanced green fluorescent protein. 相似文献
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Thai Thi Minh Carl Erik Schou Larsen Andreas Neef 《The Journal of Agricultural Education and Extension》2013,19(2):179-194
Abstract Purpose: The objective of this article is to analyze the introduction of participatory extension approaches (PEA) in the predominantly supply-driven, hierarchical Vietnamese extension system. Drawing on the case of the so-called Farmer Livestock School (FLS) concept, the authors investigate the potential and challenges of scaling up and out the FLS/PEA principles of participatory training methods, encompassing intensive and interactive training sessions, group-based sharing of experience, practical learning, and learning-by-doing processes. Design/Methodology/Approach: The article is based on data collected and synthesized from 36 pilot communes from 2000 to 2007 and draws on the extensive insider experience of two of its authors during their work for a DANIDA-funded livestock project. Findings: At the micro-scale and with external support, FLS has been a successful experiment of using participatory extension approaches in farmer training and extension in the livestock sector. Yet, possibilities of scaling up and institutionalizing FLS remain a challenge given the capacity and resource limitations and the resistance at various levels within the Vietnamese extension system. Practical Implications: The starting point for successfully institutionalizing participatory extension approaches should be to assess the existing system's root problems and capacities and then gradually and systematically introduce institutional innovations rather than aiming at a complete overhaul of a system that may result in the creation of a parallel universe. Originality/Value: The FLS project provided a unique opportunity to study the enabling and constraining factors of institutionalizing participatory extension approaches in a traditionally top-down oriented extension system beyond the immediate duration of an externally orchestrated project. 相似文献