Molecular diffusion analysis of dynamic blood flow and plasma separation driven by self-powered microfluidic devices     

Sung Oh Woo  Myungkeun Oh  Kyle Nietfeld  Bailey Boehler  Yongki Choi 《Biomicrofluidics》2021,15(3)

Integration of microfluidic devices with pressure-driven, self-powered fluid flow propulsion methods has provided a very effective solution for on-chip, droplet blood testing applications. However, precise understanding of the physical process governing fluid dynamics in polydimethylsiloxane (PDMS)-based microfluidic devices remains unclear. Here, we propose a pressure-driven diffusion model using Fick''s law and the ideal gas law, the results of which agree well with the experimental fluid dynamics observed in our vacuum pocket-assisted, self-powered microfluidic devices. Notably, this model enables us to precisely tune the flow rate by adjusting two geometrical parameters of the vacuum pocket. By linking the self-powered fluid flow propulsion method to the sedimentation, we also show that direct plasma separation from a drop of whole blood can be achieved using only a simple construction without the need for external power sources, connectors, or a complex operational procedure. Finally, the potential of the vacuum pocket, along with a removable vacuum battery to be integrated with non-PDMS microfluidic devices to drive and control the fluid flow, is demonstrated.  相似文献   

Effect of sport education on students’ perceived physical literacy,motivation, and physical activity levels in university required physical education: a cluster-randomized trial     

Choi  Siu Ming  Sum  Kim Wai Raymond  Leung  Fung Lin Elean  Wallhead  Tristan  Morgan  Kevin  Milton  Daniel  Ha  Sau Ching Amy  Sit  Hui Ping Cindy 《Higher Education》2021,81(6):1137-1155

Higher Education - Originating from the field of physical education, physical literacy is an individual disposition that accentuates the importance of lifelong physical activity. Sport education is...  相似文献   

Data‐driven refinements of a genetics learning progression     

Moraima Castro‐Faix  Ravit Golan Duncan  Jinnie Choi 《科学教学研究杂志》2021,58(1):3-39

Learning progressions are theoretical models that describe learning of scientific ideas and practices over time. These hypothetical progressions need to be tested and refined in order to productively inform instruction and assessment. In this paper, we report our attempts to revise a learning progression in genetics. In particular, we focused on two constructs that embody core ideas in classical genetics and one molecular construct. The revisions are based on analysis of pre‐ and postinterview data obtained from sixty 11th grade students before and after they engaged in a 10‐week unit that addressed these concepts. We found that while many of the students held ideas that aligned with the progression, there were several distinct dimensions of student reasoning that were not captured and led to substantial revisions of the constructs including: (a) the splitting of the construct dealing with meiosis (E) into two subconstructs (E1‐physical passage of genetic information and E2 – the role of sex cells), (b) the addition of new levels to constructs dealing with the universal nature and organization of the genetic code (A) and construct (F). For Construct A, the lower levels were expanded to include ideas about the localization of DNA in cells and to include ideas about the composition of DNA that were not captured in the progression. Revisions to Construct F included the expansion of existing levels and the addition of modes of inheritance such as codominance and incomplete dominance. The research we present offers insights about a methodological approach that can be used to test and refine progressions, as well as insights about student learning in genetics as we further describe and expand the stepping‐stone ideas in the progression and discuss further the multidimensional nature of learning progressions.  相似文献   

Integrating failure in case-based learning: a conceptual framework for failure classification and its instructional implications     

Rong  Hui  Choi  Ikseon 《Educational technology research and development : ETR & D》2019,67(3):617-637

Employing authentic cases experienced by practitioners in educational contexts is critical to expanding students’ experience and engaging students in authentic problems to promote their real-world problem-solving skills. Although in real life, practitioners experience both success and failure and learn from both, little research has been done so far to conceptualize why and how failure should be employed in case-based learning (CBL) as a way to develop students’ abilities to solve ill-structured problems. The goal of this paper is to theoretically justify the need for integrating failure cases in CBL to help students become better problem solvers. To achieve this, this paper attempted to approach failure from the perspective of human error and proposed a classification of failure based on the degree of explicitness of human error involved in problem solving. Based on discussions of potential benefits and challenges of integrating different types of failure cases in education, this paper also proposed instructional design strategies that can help facilitate better use of failure cases.

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Collagen-based brain microvasculature model in vitro using three-dimensional printed template     

Jeong Ah Kim  Hong Nam Kim  Sun-Kyoung Im  Seok Chung  Ji Yoon Kang  Nakwon Choi 《Biomicrofluidics》2015,9(2)

We present an engineered three-dimensional (3D) in vitro brain microvasculature system embedded within the bulk of a collagen matrix. To create a hydrogel template for the functional brain microvascular structure, we fabricated an array of microchannels made of collagen I using microneedles and a 3D printed frame. By culturing mouse brain endothelial cells (bEnd.3) on the luminal surface of cylindrical collagen microchannels, we reconstructed an array of brain microvasculature in vitro with circular cross-sections. We characterized the barrier function of our brain microvasculature by measuring transendothelial permeability of 40 kDa fluorescein isothiocyanate-dextran (Stoke''s radius of ∼4.5 nm), based on an analytical model. The transendothelial permeability decreased significantly over 3 weeks of culture. We also present the disruption of the barrier function with a hyperosmotic mannitol as well as a subsequent recovery over 4 days. Our brain microvasculature model in vitro, consisting of system-in-hydrogel combined with the widely emerging 3D printing technique, can serve as a useful tool not only for fundamental studies associated with blood-brain barrier in physiological and pathological settings but also for pharmaceutical applications.  相似文献   

Culturally Responsive Counseling for Asian Americans: Clinician Perspectives     

Mikyong?Kim-GohEmail author  Hyunmi?Choi  Myeong?Sook?Yoon 《International journal for the advancement of counseling》2015,37(1):63-76

Research has consistently found acute mental health treatment disparities among Asian Americans. One proposed reason for the underutilization of mental health services by Asian Americans is that available services are not culturally competent. This exploratory study presents qualitative data gathered from interviews with professional counselors who serve Asian American clients. Findings revealed significant barriers to counseling due to cultural stigma and shame, suppression of emotions, and communication gaps between clients and counselors. In response, clinicians frequently made adjustments to therapeutic approaches to accommodate the cultural beliefs and practices of clients and families. Implications for practice and research are discussed.  相似文献   

Influence of Cultural Orientations on Electronic Word-of-Mouth (eWOM) in Social Media     

Youngtae Choi 《Journal of Intercultural Communication Research》2019,48(3):292-313

This study explores how horizontal/vertical individualism and collectivism (HVIC) orientations influence electronic word-of-mouth (eWOM) (i.e., opinion leadership and opinion seeking) in social media. Online survey panel data through Amazon MTurk were collected from American social media users to address the research purpose. The results, using the structural equation modeling, show that the paths from horizontal individualism to opinion leadership, vertical individualism to opinion leadership and opinion seeking, horizontal collectivism to opinion leadership, and vertical collectivism to opinion leadership and opinion seeking were significant. This study provides theoretical and managerial implications regarding the influence of HVIC orientations on eWOM in social media.  相似文献   

Meritocratic Epistemic Communities: An Alternative Policy Paradigm for Higher Education          下载免费PDF全文

Seungchan Choi 《Higher Education Quarterly》2015,69(1):58-78

This paper attempts to propose an alternative policy frame for higher education policy by demonstrating the inadequacy of the market approach adopted by the 2011 English higher education policy in addressing the economic and social agenda, and by reframing higher education as a mechanism that selects and distributes talents to vocational sectors in a way that achieves socially optimal outcomes. The paper shows why government control is more appropriate than market mechanism in managing higher education cost, how effective screening and distribution of talents can be achieved through deliberation among epistemic community members and how the alternative policy frame supports a social justice agenda. The idea of a meritocratic epistemic community for screening and educating talents is central to this new frame as it facilitates the creation of a common space where competing stakeholders of one vocational sector gather together to deliberate on the merits of the future workforce.  相似文献   

Relationship between foot strike pattern,running speed,and footwear condition in recreational distance runners     

Roy T. H. Cheung  Rodney Y. L. Wong  Tim K. W. Chung  R. T. Choi  Wendy W. Y. Leung  Diana H. Y. Shek 《Sports biomechanics / International Society of Biomechanics in Sports》2017,16(2):238-247

Compared to competitive runners, recreational runners appear to be more prone to injuries, which have been associated with foot strike patterns. Surprisingly, only few studies had examined the foot strike patterns outside laboratories. Therefore, this study compared the foot strike patterns in recreational runners at outdoor tracks with previously reported data. We also investigated the relationship between foot strike pattern, speed, and footwear in this cohort. Among 434 recreational runners analysed, 89.6% of them landed with rearfoot strike (RFS). Only 6.9 and 3.5% landed with midfoot and forefoot, respectively. A significant shift towards non-RFS was observed in our cohort, when compared with previously reported data. When speed increased by 1 m/s, the odds of having forefoot strike and midfoot strike relative to RFS increased by 2.3 times and 2.6 times, respectively. Runners were 9.2 times more likely to run with a forefoot strike in minimalists compared to regular running shoes, although 70% of runners in minimalists continued to use a RFS. These findings suggest that foot strike pattern may differ across running conditions and runners should consider these factors in order to mitigate potential injury.  相似文献   

U.S. and Israeli young women’s future perceptions     

Rinat Michael  TaeSun Kim  Ashley Hutchison  Rachel Gali Cinamon  Lawrence H. Gerstein  Juno Park  Yuri Choi  Yamini Bellare  Rachael Collins 《International Journal for Educational and Vocational Guidance》2017,17(2):121-141

The current study investigated the content of future perceptions among 47 U.S. women and 48 Israeli women. Thematic analysis was used to explore participants’ qualitative responses. Women’s responses covered a wide range of topics, and were categorized into ten key themes: (a) work, (b) family/relationships, (c) property, (d) residence, (e) education, (f) general quality of life, (g) leisure, (h) pro-social activities, (i) multiple role management, and (j) religion. Results demonstrated the role of nationality in the process of exploration and future perceptions. Implications for research and practice are discussed.  相似文献