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排序方式: 共有262条查询结果,搜索用时 15 毫秒
161.
Jacquelyn A. Brown Virginia Pensabene Dmitry A. Markov Vanessa Allwardt M. Diana Neely Mingjian Shi Clayton M. Britt Orlando S. Hoilett Qing Yang Bryson M. Brewer Philip C. Samson Lisa J. McCawley James M. May Donna J. Webb Deyu Li Aaron B. Bowman Ronald S. Reiserer John P. Wikswo 《Biomicrofluidics》2015,9(5)
The blood-brain barrier (BBB) is a critical structure that serves as the gatekeeper between the central nervous system and the rest of the body. It is the responsibility of the BBB to facilitate the entry of required nutrients into the brain and to exclude potentially harmful compounds; however, this complex structure has remained difficult to model faithfully in vitro. Accurate in vitro models are necessary for understanding how the BBB forms and functions, as well as for evaluating drug and toxin penetration across the barrier. Many previous models have failed to support all the cell types involved in the BBB formation and/or lacked the flow-created shear forces needed for mature tight junction formation. To address these issues and to help establish a more faithful in vitro model of the BBB, we have designed and fabricated a microfluidic device that is comprised of both a vascular chamber and a brain chamber separated by a porous membrane. This design allows for cell-to-cell communication between endothelial cells, astrocytes, and pericytes and independent perfusion of both compartments separated by the membrane. This NeuroVascular Unit (NVU) represents approximately one-millionth of the human brain, and hence, has sufficient cell mass to support a breadth of analytical measurements. The NVU has been validated with both fluorescein isothiocyanate (FITC)-dextran diffusion and transendothelial electrical resistance. The NVU has enabled in vitro modeling of the BBB using all human cell types and sampling effluent from both sides of the barrier. 相似文献
162.
Education systems around the world need to recruit highly motivated individuals to become teachers and prepare professionally competent teacher education graduates to take up these broadened and deepened roles and responsibilities with a deep and lasting engagement to the profession. This article reports on a mixed-methods study that examines types of teaching motivation in relation to various facets of professional competence and planned engagement in future teaching. One hundred and thirty-two student teachers of a postgraduate diploma in education programme participated in the quantitative survey of whom seven were interviewed. The quantitative data analysis shows the positive association between ‘intrinsic–altruistic motivation constellation’ and selected facets of professional competence, with ‘intrinsic–multifaceted and stimulating job nature’ as the most distinctive type of teaching motivation. To complement the quantitative findings, the qualitative data analysis reveals two professional orientations of the ‘intrinsic–altruistic motivation constellation’, namely (1) student-centred orientation and (2) subject-centred orientation. In addition, three types of professional development aspirations are identified: ‘classroom engaged careerists’, ‘highly engaged persisters’ and ‘pessimists’. The study provides insights into the design of appropriate ITE practices to support professional learning in the light of student teachers’ motivations. It also suggests the importance of matching career opportunities and beginning teachers’ professional development aspirations and supporting ‘pessimists’ in the face of the stringent job market. 相似文献
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Keith May 《British journal of educational technology : journal of the Council for Educational Technology》2008,39(2):237-243
This is a personal account of the work of the Manpower Services Commission (MSC) in the 1980s and early 1990s. The contribution of the MSC, The Department of Employment and the Learning Technology Unit is not widely understood and appreciated. During that period, it was one of the major agencies for encouraging and funding the use of technology-based learning—not only in the training area but also in education. 相似文献
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