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In this paper, a detailed numerical and experimental investigation into the optimisation of hydrodynamic micro-trapping arrays for high-throughput capture of single polystyrene (PS) microparticles and three different types of live cells at trapping times of 30 min or less is described. Four different trap geometries (triangular, square, conical, and elliptical) were investigated within three different device generations, in which device architecture, channel geometry, inter-trap spacing, trap size, and trap density were varied. Numerical simulation confirmed that (1) the calculated device dimensions permitted partitioned flow between the main channel and the trap channel, and further, preferential flow through the trap channel in the absence of any obstruction; (2) different trap shapes, all having the same dimensional parameters in terms of depth, trapping channel lengths and widths, main channel lengths and widths, produce contrasting streamline plots and that the interaction of the fluid with the different geometries can produce areas of stagnated flow or distorted field lines; and (3) that once trapped, any motion of the trapped particle or cell or a shift in its configuration within the trap can result in significant increases in pressures on the cell surface and variations in the shear stress distribution across the cell’s surface. Numerical outcomes were then validated experimentally in terms of the impact of these variations in device design elements on the percent occupancy of the trapping array (with one or more particles or cells) within these targeted short timeframes. Limitations on obtaining high trap occupancies in the devices were shown to be primarily a result of particle aggregation, channel clogging and the trap aperture size. These limitations could be overcome somewhat by optimisation of these device design elements and other operational variables, such as the average carrier fluid velocity. For example, for the 20 μm polystyrene microparticles, the number of filled traps increased from 32% to 42% during 5–10 min experiments in devices with smaller apertures. Similarly, a 40%–60% reduction in trapping channel size resulted in an increase in the amount of filled traps, from 0% to almost 90% in 10 min, for the human bone marrow derived mesenchymal stem cells, and 15%–85% in 15 min for the human embryonic stem cells. Last, a reduction of the average carrier fluid velocity by 50% resulted in an increase from 80% to 92% occupancy of single algae cells in traps. Interestingly, changes in the physical properties of the species being trapped also had a substantial impact, as regardless of the trap shape, higher percent occupancies were observed with cells compared to single PS microparticles in the same device, even though they are of approximately the same size. This investigation showed that in microfluidic single cell capture arrays, the trap shape that maximizes cell viability is not necessarily the most efficient for high-speed single cell capture. However, high-speed trapping configurations for delicate mammalian cells are possible but must be optimised for each cell type and designed principally in accordance with the trap size to cell size ratio. 相似文献
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The founding of the Korean Women Taekwondo Federation means the fetal movement of women taekwondo in Korea and it can be said to have been quite significant in that it increased women's confidence in their statuses and activities in the environments of the times when women's social activities were increasing. The development of women taekwondo competitions began in earnest when the first women taekwondo hall in the world was opened as a result of passionate activities of early female taekwondo practitioners and the first taekwondo club was established in Ehwa Woman's University. Women's aspiration towards the challenge to the Olympic Games as well as international competitions is gradually increasing through the expansion of the base of women taekwondo. The status of women taekwondo in Korea that has been enhanced through challenges to various international competitions thus far beginning with the single taekwondo championship of foreigners in Korea in 1968 can be said to have contributed to the enhancement of the status of Korea as the birthplace of taekwondo and it is considered that women taekwondo could have continuously developed through diverse taekwondo championships by age held with women's steady effort and the expansion of the base of women taekwondo instructors. 相似文献
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Jane Morgan-Daniel Xan Y. Goodman Sandra G. Franklin Kelsa Bartley Matthew Nicholas Noe JJ Pionke 《Journal of the Medical Library Association》2021,109(1):141
The Medical Library Association (MLA) appointed a Diversity and Inclusion Task Force (DITF) in 2017. Sandra G. Franklin, AHIP, FMLA, chaired the task force and guided initiatives. From 2017 to 2020, the task force completed a review of MLA defining documents—including the mission, vision, values, and code of ethics—resulting in language updates to these documents. As MLA transitioned through the communities process, the DITF contributed to the transition. Other recommended essential changes to MLA profiles to promote awareness included updating pronouns to promote gender inclusivity and suggestions for the Annual Meeting Innovation Task Force. DITF members actively brought diversity and inclusion programming and engagement to MLA members at annual meetings. The task force held a fish bowl conversation, an open forum, and a Diversity Dialogues roundtable discussion; provided interactive discussion boards; and designed an MLA diversity button. Beyond MLA annual meetings, the task force hosted two critical librarianship meetings and a Twitter chat to engage MLA members with diversity and inclusion topics. Task force members promoted diversity and inclusion beyond their task force appointments with presentations at chapter meetings and other non-DITF MLA annual meeting programming. A notable task force accomplishment included completing a survey of MLA members to gather baseline demographic characteristics, including never before collected data about disability, socioeconomics, and caregiver status. This report provides an overview of DITF activities from 2017 to 2020. 相似文献
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This paper reports the development of a scalable continuous microfluidic-based method for the preparation of multilayered biopolymer microcapsules and microparticles, with a size range of 1 to 100 μm, in a single-layered polydimethylsiloxane-based device. This new approach has been utilised to produce polyethylene oxide (PEO)-based microparticles, layered with subsequent stage wise coatings of polylactide-based block copolymers and polyvinylpyrrolidone. The production process was shown to allow for on-chip encapsulation of protein and vitamin molecules in the biopolymer micro particles, without any further handling after collection from the device. We have studied the release profiles in the case of model molecules of distinctive molecular weights, namely, vitronectin, horse radish peroxidase, and vitamin B(12). We compared the release properties of the microparticles to those from macro-gels of the same materials prepared off-chip. The results indicated that the microparticles have definitively different molecular weight cut-off characteristics, likely due to a denser microstructure within the microparticles compared to the bulk hydrogels. This difference suggests that significant benefits may exist in the use of this method to produce layered biopolymer microparticles in achieving improved controlled release and encapsulation. 相似文献
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Microvascular network formation is a significant and challenging goal in the engineering of large three-dimensional artificial tissue structures. We show here the development of a fully patent, 3D endothelial cell (microvascular) microfluidic network that has a single inlet and outlet, created in only 28 h in a microdevice involving fluid flow equivalent to natural vasculature. Our microdevice features a tailored "multi-rung ladder" network, a stylized mimic of an arterial-to-venous pedicle, designed to also allow for systematic and reproducible cell seeding. Immunofluorescence staining revealed a highly contiguous endothelial monolayer (human umbilical vein endothelial cells) throughout the whole network after 24 h of continuous perfusion. This network persisted for up to 72 h of culture, providing a useful template from which the effects of surface chemistry, fluid flow, and environmental conditions on the development of artificial vascular networks ex vivo may be rapidly and robustly evaluated. 相似文献
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