Coplanar electrowetting-induced stirring as a tool to manipulate biological samples in lubricated digital microfluidics. Impact of ambient phase on drop internal flow pattern     

Laurent Davoust  Yves Fouillet  Rachid Malk  Johannes Theisen 《Biomicrofluidics》2013,7(4)

Oscillating electrowetting on dielectrics (EWOD) with coplanar electrodes is investigated in this paper as a way to provide efficient stirring within a drop with biological content. A supporting model inspired from Ko et al. [Appl. Phys. Lett. 94, 194102 (2009)] is proposed allowing to interpret oscillating EWOD-induced drop internal flow as the result of a current streaming along the drop surface deformed by capillary waves. Current streaming behaves essentially as a surface flow generator and the momentum it sustains within the (viscous) drop is even more significant as the surface to volume ratio is small. With the circular electrode pair considered in this paper, oscillating EWOD sustains toroidal vortical flows when the experiments are conducted with aqueous drops in air as ambient phase. But when oil is used as ambient phase, it is demonstrated that the presence of an electrode gap is responsible for a change in drop shape: a pinch-off at the electrode gap yields a peanut-shaped drop and a symmetry break-up of the EWOD-induced flow pattern. Viscosity of oil is also responsible for promoting an efficient damping of the capillary waves which populate the surface of the actuated drop. As a result, the capillary network switches from one standing wave to two superimposed traveling waves of different mechanical energy, provided that actuation frequency is large enough, for instance, as large as the one commonly used in electrowetting applications (f ∼ 500 Hz and beyond). Special emphasis is put on stirring of biological samples. As a typical application, it is demonstrated how beads or cell clusters can be focused under flow either at mid-height of the drop or near the wetting plane, depending on how the nature of the capillary waves is (standing or traveling), and therefore, depending on the actuation frequency (150 Hz–1 KHz).  相似文献   

Creatine kinase,myosin heavy chains and magnetic resonance imaging after eccentric exercise     

Stephan Sorichter  Johannes Mair  Arnold Koller  Erich Muller  Christian Kremser  Werner Judmaier 《Journal of sports sciences》2013,31(9):687-691

The aim of this study was to examine the relationship between myosin heavy chain (MHC) release as a specific marker of slow-twitch muscle fibre breakdown and magnetic resonance imaging (MRI) of skeletal muscle injury after eccentric exercise. The effects of a single series of 70 high-intensity eccentric contractions of the quadriceps femoris muscle group (single leg) on plasma concentrations of creatine kinase and MHC fragments were assessed in 10 young male sport education trainees before and 1 and 4 days after exercise. To visualize muscle injury, MRI of the loaded thigh was performed before and 4 days after the eccentric exercise. All participants recorded an increase ( P ? 0.05) in creatine kinase after exercise. In five participants, T2 signal intensity was unchanged post-exercise compared with pre-exercise and MHC plasma concentration was normal; however, they showed an increase ( P ? 0.05) in creatine kinase after exercise. For the remaining five participants, there was an increase in T2 signal intensity of the loaded vastus intermedius and vastus lateralis. These changes in MRI were accompanied by an increase in MHC plasma concentration ( P ? 0.01) as well as an increase in creatine kinase ( P ? 0.01). We suggest that changes in MRI T2 signal intensity after muscle damage induced by eccentric exercise are closely related to damage to structurally bound contractile filaments of some muscle fibres. Additionally, MHC plasma release indicates that this damage affects not only fast-twitch fibres but also some slow-twitch fibres.  相似文献   

Responsiveness of the anterior cruciate ligament – Return to Sports after Injury (ACL-RSI) and Injury – Psychological Readiness to Return to Sport (I-PRRS) scales     

Anton J. Slagers  Inge van den Akker-Scheek  Jan H. B. Geertzen  Johannes Zwerver  Inge H. F. Reininga 《Journal of sports sciences》2013,31(21):2499-2505

ABSTRACT

The ACL-Return to Sport after Injury (ACL-RSI) and Injury-Psychological Readiness to Return to Sport (I-PRRS) scales were developed to assess psychological factors associated with return to sports. Validity and reliability have been determined. The aim of this study was to investigate the responsiveness of the Dutch ACL-RSI and I-PRRS. Seventy patients with ACL reconstruction completed both scales twice 2 months apart, plus a Global Rating of Change (GRC) questionnaire. Distribution and logistic regression-based methods were used to study responsiveness. The Standardized Response Mean (SRM) for the ACL-RSI was 0.3 and for the I-PRRS 0.1, indicating low responsiveness. The minimally important change (MIC) for ACL-RSI was 2.6 and for the I-PRRS 0.9. Since the standard error of measurement (SEM) and smallest detectable change (SDC) were larger than MIC in individual patients, it does not seem possible to distinguish minimally important changes from measurement error in individual patients with either scale. At the group level responsiveness seemed sufficient; hence, both scales can be used to investigate the effectiveness of an intervention at the group level. Both scales can also be used in cross-sectional research and in clinical practice as screening instruments to identify patients at risk of not returning to sports.  相似文献   

Kinematic differences of elite and high-performance tennis players in the cross court and down the line forehand     

Johannes Landlinger  Stefan Josef Lindinger  Thomas Stöggl  Herbert Wagner  Erich Müller 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(4):280-295

This study identified and compared the full body kinematics of different skill levels in the forehand groundstroke when balls were hit cross court and down the line. Forty-three three-dimensional retro-reflective marker trajectories of six elite and seven high-performance players were recorded using an eight-camera 400 Hz, Vicon motion analysis system. The six highest horizontal velocity forehands with reliable kinematics of all participants were analysed for each specific situation (a total of 156 analysed shots). Significant differences (p < 0.01) and large effect sizes were observed between elite and high-performance players in linear velocity of the shoulder (2.0 vs. 1.2 m/s), angular velocity of the pelvis (295 vs. 168 °/s), and angular velocity of the upper trunk (453 vs. 292 °/s) at impact. The elite group showed a tendency towards higher racquet velocities at impact (p < 0.05). No significant differences were found in angular displacement of the racquet, hip alignment, or shoulder alignment at the completion of the backswing; nor did angular displacement vary significantly at impact. Irrespective of the group, different shoulder, hip, and racquet angles were found at impact, depending on the situation. The results should assist coaches when striving to improve their players' forehand.  相似文献   

Teaching multiplication to low math performers: Guided versus structured instruction     

Kroesbergen  Evelyn H.  van Luit  Johannes E.H. 《Instructional Science》2002,30(5):361-378

The results of an intervention program forstudents with difficulties learning mathematicsare reported. Two kinds of math intervention,guided versus structured instruction, werecompared to regular math instruction. A totalof 75 students from regular and specialeducation, aged seven to thirteen,participated. Ability and automaticitymultiplication tests were administered beforeand after the four-month training period. Theresults show that the students in both of theexperimental conditions improved more than thestudents in the control condition. Someadditional differences were found between thetwo experimental interventions. Guidedinstruction appeared to be more effective forlow performing students than structuredinstruction and especially for those studentsin regular education. Special educationstudents appear to benefit most from structuredinstruction for the automaticity ofmultiplication problems. A three monthfollow-up test showed the acquired knowledge tobe well-established in both groups.  相似文献   

How did teachers make a living? The teacher occupation,livelihood diversification and the rise of mass schooling in nineteenth-century Sweden     

Johannes Westberg 《History of education》2019,48(1):19-40

Drawing inspiration from the new social history of livelihood, this article examines how rural nineteenth-century teachers made a living by engaging in livelihood diversification. By using a wide variety of source materials from nineteenth-century Sweden, this article shows that, far from specialising exclusively in teaching, teachers were often engaged in multiple occupations as late as the year 1900, and that teachers’ work ranged from activities that were encouraged to those that were frowned upon or even illegal. As a result, this article sheds new light on teaching as an occupation in the nineteenth century and contributes to the discussion of the social and economic positions of teachers. By investigating how teachers earned their livelihoods, this article also addresses the role of teachers’ multiple occupations in the expansion of mass schooling during the nineteenth century.  相似文献   

Arousing News Characteristics in Dutch Television News 1990–2004: An Exploration of Competitive Strategies     

Paul Hendriks Vettehen  Johannes Beentjes  Koos Nuijten  Allerd Peeters 《Mass Communication and Society》2013,16(1):93-112

This study investigates the processes by which competition in the television news market might promote the presence of arousing characteristics in television news. A total of 3,024 news stories from six Dutch television news programs over the period 1990 to 2004 were investigated through content analysis. The findings of the study show overall increases in all 6 arousing characteristics. The findings also show that commercial newcomers included more arousing characteristics in their news stories than the public service broadcasters, that commercial newcomers developed a news format that featured more arousing characteristics, and that existing programs reacted to newcomers by increasing the amount of arousing characteristics in their news stories.  相似文献   

Mathematical thinking intervention programmes for preschool children with normal and low number sense     

Pirjo Aunio  Jarkko Hautam?ki  Johannes E. H. Van Luit 《欧洲特需教育杂志》2013,28(2):131-146

This study investigated the possibility of enhancing the level of preschoolers’ number sense by introducing two intervention programmes, Let’s think! and Young children with special educational needs count, too! .Forty‐five preschoolers, mean age 66.4 months, were randomly assigned to the experimental and control groups. The experimental group received instruction twice a week, for half an hour, and for a period of nine months. Pretest–postest comparison revealed that the experimental group showed enhanced number‐sense performance immediately after the instruction ended, but the between‐group difference faded after six months. There were no statistically significant differences between the groups in general mathematical thinking abilities (transfer tasks) after the intervention.  相似文献   

CONSTRUCTIVISM AND EDUCATION: MISUNDERSTANDINGS AND PEDAGOGICAL IMPLICATIONS     

Emery J. Hyslop-Margison  Johannes Strobel 《The Teacher Educator》2013,48(1):72-86

Constructivism is a popular concept in contemporary teacher education programs. However, a genuine concern arises with the concept's application because many teachers and teacher educators claim that knowledge is constructed, without appreciating the epistemological and pedagogical implications such a claim entails. This article employs Phillips' (1995) Phillips, D. C. 1995. The good, the bad, and the ugly: The many faces of constructivism. Educational Researcher, 24(7): 5–12. [Crossref] , [Google Scholar] analytic framework that divides the pedagogical applications of constructivism into three distinct categories: the good, the bad, and the ugly. Reviewing the constructivist epistemologies of Dewey and Vygotsky also enables the exploration of how constructivism might inform both our understanding of the impediments students confront when learning new knowledge and our understanding of general constructivist pedagogical practices. The primary objective in this article is to provide teacher educators and teachers with a richer understanding of constructivism—its limitations and its strengths—while offering concrete pedagogical strategies for its classroom application.  相似文献   

Learning and Collective Knowledge Construction With Social Media: A Process-Oriented Perspective     

Joachim Kimmerle  Johannes Moskaliuk  Aileen Oeberst  Ulrike Cress 《教育心理学家》2013,48(2):120-137

Social media are increasingly being used for educational purposes. The first part of this article briefly reviews literature that reports on educational applications of social media tools. The second part discusses theories that may provide a basis for analyzing the processes that are relevant for individual learning and collective knowledge construction. We argue that a systems-theoretical constructivist approach is appropriate to examine the processes of educational social media use, namely, self-organization, the internalization of information, the externalization of knowledge, and the interplay of externalization and internalization providing the basis of a co-evolution of cognitive and social systems. In the third part we present research findings that illustrate and support this systems-theoretical framework. Concluding, we discuss the implications for educational design and for future research on learning and collective knowledge construction with social media.  相似文献