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The flow of λ-DNA solutions in a gradual micro-contraction was investigated using direct measurement techniques. The effects on DNA transport in microscale flows are significant because the flow behavior is influenced by macromolecular conformations, both viscous and elastic forces dominate inertial forces at this length scale, and the fully extended length of the molecule approaches the characteristic channel length wc (L/wc ∼ 0.13). This study examines the flow of semi-dilute and entangled DNA solutions in a gradual planar micro-contraction for low Reynolds numbers (3.7 × 10−6 < Re < 3.1 × 10−1) and high Weissenberg numbers (0.4 < Wi < 446). The semi-dilute DNA solutions have modest elasticity number, El = Wi/Re = 55, and do not exhibit viscoelastic behavior. For the entangled DNA solutions, we access high elasticity numbers (7.9 × 103 < El < 6.0 × 105). Video microscopy and streak images of entangled DNA solution flow reveal highly elastic behavior evidenced by the presence of large, stable vortices symmetric about the centerline and upstream of the channel entrance. Micro-particle image velocimetry measurements are used to obtain high resolution, quantitative velocity measurements of the vortex growth in this micro-contraction flow. These direct measurements provide a deeper understanding of the underlying physics of macromolecular transport in microfluidic flow, which will enable the realization of enhanced designs of lab-on-a-chip systems. 相似文献
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Nancy C. Dorian 《Educational Media International》2013,50(3):134-137
Abstract The broadcast media challenge the survival of small languages as never before. To date the result largely has been negative, since broadcast media can penetrate to the remote areas that often shelter small languages and can invade even the strongest small‐language sanctuary ‐‐ the home. Where modern media have been enlisted to serve small languages, the uses to which the small languages have been put have been mostly serious and usually educational. This emphasis on the serious overlooks the strongest attributes of most small languages: their rich individuality as repositories of local flavour and folk tradition. These could be mustered for use in broadcasting to great effect and benefit in the support of beleaguered small languages. 相似文献
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In this article we discuss verbal strategies used by children to express and construct a sense of togetherness. In a case study the language of one child was audiotaped over 2 years (at the start he was 3 years old) in his interactions with other children and teachers. Brown and Levinson's theoretical model for analysing the politeness strategies of adults is used to analyse the verbal strategies of these children. Three general mechanisms for expressing togetherness are distinguished: expression of common ground, of cooperation and of care. The expression of common ground seems a specific domain for 2- and 3-year-olds at the day care centre. Young children use imitation and repetition of (nonsense) words and the explicit reference to sameness as a favourite mode of expressing common ground. Dans cet article, nous examinons les stratégies verbales utilisées par les enfants pour exprimer et construire un sens de e togetherness f . Dans une étude de cas, le langage d'un enfant a été enregistrésur deux ans (à partir de l'âge de trois ans) dans ses interactions avec d'autres enfants et ses enseignants. Le modèle théorique d'analyse des stratégies de politesse des adultes de Brown et Levinson est utilisé pour analyser les stratégies verbales de ces enfants. On distingue trois mécanismes généraux d'expression de la e togetherness f : expression de points communs, de coopération et d'affection. L'expression de points communs semble être un domaine spécifique pour les enfants de deux et trois ans de l'école maternelle. Les jeunes enfants emploient l'imitation et la répétition de mots (dépourvus de sens) et la référence explicite à la similitude comme mode préféré d'expression de points communs. En este artículo hablamos de las estrategias verbales usadas por los niños para expresar y elaborar un sentido de unión. En un estudio de caso, se grabó el lenguaje de un niño durante dos años (al inicio tenía tres años) en sus interacciones con otros niños y professores. Su usa el modelo teórico de Brown and Levinson para analizar las estrategias de buena educación de adultos a fin de analizar las estrategias verbales de estos niños. Se distinguen tres mecanismos generales para expresar unión: expresión de puntos en común, de cooperación y de atención. La expresión de puntos en común parece un dominio específico para los niños de dos y tres años en la guardería. Los menores usan imitaciones y repeticiones de palabras (sin sentido) y la referencia explícita a identidad como un modo favorito de expresión del punto común. 相似文献
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ABSTRACTMost Massive Open Online Courses (MOOC) research studies have focused on students’ demographics, surveys, and retention data, while little attention has been paid to the authentic voices of the learners: the expressions of experiences, perceptions, and emotions in the MOOC students’ own words. In this paper, we conducted and analyzed in-depth interviews with learners from two MOOCs on the same subject. Findings confirm that learners enrolled in MOOCs for career and/or personal purposes. Learners’ expressions of feeling a human connection to the instructor in videos had important implications for video editing decisions. Many of the reasons given for dropping out of active participation in MOOCs were related to the learners’ lack of time because of other commitments. We expect the results from this study to provide a new understanding of MOOC learners and their perceptions of the courses; key insights should guide video editing considerations and encourage the use of instructor communication pathways such as regular emails to students in future MOOC offerings. 相似文献
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Dorian Stoilescu 《Health information and libraries journal》2009,26(2):143-150
Objective: This paper presents the design of the Virtual Olympic Games Framework (VOGF), a computer application designated for athletics, health care, general well‐being, nutrition and fitness, which offers multiple benefits for its participants. Background: A special interest in starting the design of the framework was in exploring how people can connect and participate together using existing computer technologies (i.e. gaming consoles, exercise equipment with computer interfaces, devices of measuring health, speed, force and distance and Web 2.0 applications). Method: A stationary bike set‐up offering information to users about their individual health and athletic performances has been considered as a starting model. Conclusions: While this model is in the design stage, some preliminary findings are encouraging, suggesting the potential for various fields: sports, medicine, theories of learning, technologies and cybercultural studies. First, this framework would allow participants to perform a variety of sports and improve their health. Second, this would involve creating an online environment able to store health information and sport performances correlated with accessing multi‐media data and research about performing sports. Third, participants could share experiences with other athletes, coaches and researchers. Fourth, this framework also provides support for the research community in their future investigations. 相似文献
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Dorian A. Barrow Samuel N. Lochan 《International Review of Education/Internationale Zeitschrift für Erziehungswissenschaft/Revue internationale l'éducation》2012,11(1):405-422
Globally, private supplementary tutoring is a huge business and the practice is expanding rapidly in many regions of the world where it never existed before. In some of these regions it is posing a novel set of challenges for education planners and policy makers. The aim of this study was to examine the extent to which supplementary tutoring is impacting on the goals of the formal education system in Trinidad and Tobago (T&T). The participation rate in supplementary tutoring at primary school level in T&T was found to be high (88.2 per cent at Standard Five level), with the majority of the students being privately tutored by their regular school teachers. Their main motivation for taking private tutoring lessons was to try to secure a place in one of the few elite secondary schools in the country. The authors of this paper admit that there is no quick solution to the problem, especially if it is understood as a part of the process of cultural change. They contend that the key to breaking the elitist tradition lies in modifying public understanding about education and convincing parents and citizens at large that a wide range of options and opportunities exists outside the narrow confines of the old colonial economy and the old colonial schools. 相似文献