Efficient manipulation of microparticles in bubble streaming flows     

Wang C  Jalikop SV  Hilgenfeldt S 《Biomicrofluidics》2012,6(1):12801-1280111

Oscillating microbubbles of radius 20–100 μm driven by ultrasound initiate a steady streaming flow around the bubbles. In such flows, microparticles of even smaller sizes (radius 1–5 μm) exhibit size-dependent behaviors: particles of different sizes follow different characteristic trajectories despite density-matching. Adjusting the relative strengths of the streaming flow and a superimposed Poiseuille flow allows for a simple tuning of particle behavior, separating the trajectories of particles with a size resolution on the order of 1 μm. Selective trapping, accumulation, and release of particles can be achieved. We show here how to design bubble microfluidic devices that use these concepts to filter, enrich, and preconcentrate particles of selected sizes, either by concentrating them in discrete clusters (localized both stream- and spanwise) or by forcing them into narrow, continuous trajectory bundles of strong spanwise localization.  相似文献   

A Model for Using Triadic Supervision in Counselor Preparation Programs     

Gerard Lawson  Serge F. Hein  Hildy Getz 《Counselor Education & Supervision》2009,48(4):257-270

The Council for Accreditation of Counseling and Related Educational Programs (2001) has approved the use of triadic supervision as an alternative to individual supervision in clinical instruction. However, literature describing this mode of supervision is very limited. A model for triadic supervision is described, including presession planning, in‐session strategies, and administrative considerations and supervisee evaluation. An evaluation of the model from 2 recent studies is also discussed, and recommendations are provided for using triadic supervision in counselor preparation.  相似文献   

The Effect of Three-Dimensional Simulations on the Understanding of Chemical Structures and Their Properties     

Detlef Urhahne  Sabine Nick  Sascha Schanze 《Research in Science Education》2009,39(4):495-513

In a series of three experimental studies, the effectiveness of three-dimensional computer simulations to aid the understanding of chemical structures and their properties was investigated. Arguments for the usefulness of three-dimensional simulations were derived from Mayer’s generative theory of multimedia learning. Simulations might lead to a decrease in cognitive load and thus support active learning. In our studies, the learning effectiveness of three-dimensional simulations was compared to two-dimensional illustrations by use of different versions of a computer programme concerning the modifications of carbon. The first and third study with freshman students of chemistry and biochemistry show that no more knowledge was acquired when participants learnt with three-dimensional simulations than with two-dimensional figures. In the second study with 16-year old secondary school students, use of simulations facilitated the acquisition of conceptual knowledge. It was concluded that three-dimensional simulations are more effective for younger students who lack the experience of learning with different visual representation formats in chemistry. In all three studies, a significant relationship between spatial ability and conceptual knowledge about the modifications of carbon was detected.  相似文献   

The Negotiated Project Approach: Project-Based Learning without Leaving the Standards Behind   总被引：1，自引：0，他引：1  

Sascha Mitchell  Teresa S. Foulger  Keith Wetzel  Chris Rathkey 《Early Childhood Education Journal》2009,36(4):339-346

The purpose this study was to explore how a veteran first-grade teacher collaboratively negotiated the implementation of a project with her students while, at the same time, addressed grade-level standards. Researchers investigated the teacher’s strategies for integrating the district’s standards into project topics, investigative activities, and final presentations. They also examined the teacher’s strategies for promoting students’ participation in project planning and independent problem-solving. Data sources included field notes, teacher interviews, videotaped observations, and transcribed teacher, and student interviews. As an extension to teacher-directed approaches to implementing the project approach, the results of this study revealed a collaborative approach to implementing projects that allowed the teacher and the students to work together for project planning and learning. The teacher felt successful with meeting grade level learning needs, and the students were given the opportunity to fuel their learning by expressing their natural interests and curiosities, and become problem solvers.  相似文献   

Print exposure across the reading life span     

Grolig  Lorenz  Tiffin-Richards  Simon P.  Schroeder  Sascha 《Reading and writing》2020,33(6):1423-1441

Reading and Writing - Leisure reading is a main contributor to print exposure, which is in turn related to individual differences in reading and language skills. The Author Recognition Test (ART)...  相似文献   

You cannot do this alone! Increasing task interdependence in cooperative educational videogames to encourage collaboration     

Steve Nebel  Sascha Schneider  Maik Beege  Franziska Kolda  Valerie Mackiewicz  Günter Daniel Rey 《Educational technology research and development : ETR & D》2017,65(4):993-1014

Complex, multimedia software such as educational videogames offer a wide range of elements to modify learner behavior. The adjustment of such software might support learning, especially in complex settings like collaborative or cooperative scenarios. Coming from a theoretical background of educational psychology, our experiment seeks to implement the “jigsaw strategy” within educational videogames. We conducted an experiment with sixty participants to compare conditions with or without increased task interdependence through the jigsaw strategy (i.e., the distribution of game elements and essential information). The participants had to rebuild a house from the 1894 novel Effi Briest within an adjusted version of the “sandbox” game Minecraft. The results show increased play performance, and learning outcomes with increased task interdependence. We conducted mediator and moderator analysis, which revealed a strong impact of play performance on learning outcomes. Additional analyses of mental effort, cognitive load, and efficiency allowed for deep insights into the playing and learning process. These insights enrich current theories about collaboration, mental strain, and the working memory effect and highlight the applicability of collaborative mechanics within educational videogames.  相似文献   

Journalists’ Coverage of Online Firestorms in German-Language News Media     

Sabine Einwiller  Benno Viererbl  Sascha Himmelreich 《Journalism Practice》2017,11(9):1178-1197

When people perceive events that conflict with their expectations they can easily express their agitation and concerns online and likely find others who share their opinion. When large quantities of messages containing negative word-of-mouth suddenly spread in social media we speak of an online firestorm. By covering the outcry, journalists elevate it onto a mainstream communication platform and support the process of scandalization. Content analysis was used to explore how journalists, working for German-language media, cover this phenomenon. Over a period of 16 months, 130 online firestorms were identified and analyzed. Based on a typology of online firestorms, we have found that the majority of cases address events of perceived discrimination and moral misconduct aiming at societal change. Vilification of the organization or person occurred to a much lesser extent. Thus, journalistic coverage of the phenomenon focuses on the rectification attempts of an aroused public. Image-repair responses of the firestorm objects are quoted by journalists in about half of the articles, thereby providing some balanced reporting about the online criticism. This study provides an initial insight into how online firestorms are used as a topic of news coverage by journalists and explores journalists’ contribution to attempts of online scandalization.  相似文献   

Game Outcome Uncertainty and the Demand for International Football Games: Evidence From the German TV Market     

Dominik Schreyer  Sascha L. Schmidt  Benno Torgler 《Journal of Media Economics》2017,30(1):31-45

This article adopts a comprehensive 2-step approach to dissolve recent confusion regarding the role of game outcome uncertainty in the TV demand for international team sports. Analyzing the German TV demand for 457 international football games broadcasted during 6 Fédération Internationale de Football Association World Cups and 5 Union des Associations Européennes de Football European Championships and 287 international games played by the Germany national football team, this study reveals that solely the demand for friendly games is affected by increasing uncertainty regarding the expected game outcomes.  相似文献   

Longitudinal couplings between interest and conceptual understanding in secondary school chemistry: an activity-based perspective     

Lars Höft  Sascha Bernholt 《International Journal of Science Education》2019,41(5):607-627

This paper presents the findings of a three-year longitudinal study (Grades 9–11; N?=?756 students in German secondary schools; mean starting age?=?14.7 years) that explores the development of and the interplay between upper-secondary students’ individual interest and conceptual understanding in chemistry. Students’ individual interest was assessed in seven dimensions of school science activities (realistic, investigative, artistic, social, conventional, and networking) according to Dierks et al.'s RIASEC+N model. The data was collected annually using paper-and-pencil questionnaires. In order to analyse the longitudinal relation between students’ academic interest and conceptual understanding, Eccles et al.'s Expectancy-Value Theoretical Model of Achievement Choices (EEVT) was utilised and seven bivariate cross-lagged models were performed to investigate the assumed reciprocal relations between both constructs. Regarding the developmental progression of individual interest and conceptual knowledge, latent growth curve models indicate a small decrease in all of the seven dimensions of students’ interest in school science activities and concomitant a moderate growth of students’ conceptual understanding. Moreover, structural equation modelling suggests weak reciprocal relations between students’ conceptual understanding and their interest in investigative, social and networking school science activities, respectively. Furthermore, students’ interest in enterprising activities predicted their subsequent conceptual understanding. No systematic pattern of cross-lagged effects between the three remaining interest dimensions and conceptual understanding were found. The results indicate that school science activities, which provide the potential for cognitively activating learning opportunities, could enhance the relation between students’ interest and conceptual understanding. Implications for teaching practice and further research are discussed.  相似文献   

Student Teachers’ Knowledge About Chemical Representations     

Vahide Taskin  Sascha Bernholt  Ilka Parchmann 《International Journal of Science and Mathematics Education》2017,15(1):39-55

Chemical representations serve as a communication tool not only in exchanges between scientists but also in chemistry lessons. The goals of the present study were to measure the extent of student teachers’ knowledge about chemical representations, focusing on chemical formulae and structures in particular, and to explore which factors related to the education in school and university contribute to inter-individual differences. Using a quantitative cross-sectional design, 322 students from 12 German universities in different stages of their university education were tested with the Chemical Representations Inventory (CRI, Taskin, Bernholt, & Parchmann, 2015). In addition, a short questionnaire was administered containing demographic data and possible factors that could have an effect on students’ success in solving the items of the inventory. The data was analyzed by using Rasch modeling. The results show that student teachers’ knowledge about chemical representations is quite low, with an average of students’ total achievement of 50 % in the corresponding inventory on chemical representations. A multivariate linear model revealed that passing exam(s) in organic chemistry at university, the grade of school leaving certificate, gender as well as studying chemistry in upper secondary school on basic and advanced levels are significant predictors of student teachers’ knowledge. In total, these predictors are able to explain 30.3 % of the variance in the test results. The dominance of school-related variables in the regression analysis indicates that school education seems to be still important after several years of studying and is not equalized by education at university.  相似文献