Design and optimization of a double-enzyme glucose assay in microfluidic lab-on-a-chip

An electrokinetic driven microfluidic lab-on-a-chip was developed for glucose quantification using double-enzyme assay. The enzymatic glucose assay involves the two-step oxidation of glucose, which was catalyzed by hexokinase and glucose-6-phosphate dehydrogenase, with the concomitant reduction of NADP⁺ to NADPH. A fluorescence microscopy setup was used to monitor the different processes (fluid flow and enzymatic reaction) in the microfluidic chip. A two-dimensional finite element model was applied to understand the different aspects of design and to improve the performance of the device without extensive prototyping. To our knowledge this is the first work to exploit numerical simulation for understanding a multisubstrate double-enzyme on-chip assay. The assay is very complex to implement in electrokinetically driven continuous system due to the involvement of many species, which has different transport velocity. With the help of numerical simulation, the design parameters, flow rate, enzyme concentration, and reactor length, were optimized. The results from the simulation were in close agreement with the experimental results. A linear relation exists for glucose concentrations from 0.01 to 0.10 g l⁻¹. The reaction time and the amount of enzymes required were drastically reduced compared to off-chip microplate analysis.     

Are teachers’ subjective feelings linked with need-supportive and need-thwarting motivating styles? A cross-lagged pilot study in physical education

This article examines the relations between the teachers’ subjective feeling and their motivating teaching style during physical education lessons. Doing so, it aimed at better understanding the emotional antecedents of the teaching behaviors. Twelve volunteer physical education teachers were filmed with their respective classes to assess the motivating style they used during their intervention. Immediately after, the subjective feelings they felt during the lesson were assessed using the affective slider in a video-based session. Cross-lagged multilevel modeling was then performed, controlling for emotional exhaustion level and demographic factors. Results showed that, at the within level, subjective pleasant feelings predicted positively the relatedness-supportive dimension of the motivating style, and negatively the controlling dimension. At the between level, the controlling dimension of the motivating style was positively related to the pleasant subjective feelings while the relatedness-thwarting dimension was negatively related to them. While literature has mainly examined the cognitive antecedents of teachers’ motivating styles, this study emphasizes the emotional processes occurring during the lesson. Based on the conceptual framework of teachers’ emotions model proposed by Frenzel (2014), results indicate that teachers react to their subjective feelings, modifying the way they interact with students accordingly. In parallel with cognitive determinants of teaching, the emotional dimension thus deserves to be more deeply considered in future teaching training programs.

     

Implementing Eratosthenes’ Discovery in the Classroom: Educational Difficulties Needing Attention

This paper presents a critical analysis of the accepted educational use of the method performed by Eratosthenes to measure the circumference of Earth which is often considered as a relevant means of dealing with issues related to the nature of science and its history. This method relies on a number of assumptions among which the parallelism of sun rays. The assumption of sun rays parallelism (if it is accurate) does not appear spontaneous for students who consider sun rays to be divergent. Here, we propose an educational reconstruction of Eratosthenes?? discovery based on the exploitation of a narrative written by Cleomedes during the first century AD. This implies that the students are involved in an elaboration of parallelism by an approach where the notion of ??approximation?? remains central.     

Children’s Visual Scanning of Textual Documents: Effects of Document Organization,Search Goals,and Metatextual Knowledge

This study examines children’s strategies when scanning a document to answer a specific question. More specifically, we wanted to know whether they make use of organizers (i.e., headings) when searching and whether strategic search is related to their knowledge of reading strategies. Twenty-six French fifth graders were asked to search single-page documents presented on the screen of an eye tracker in order to respond to questions requiring the location of information in either a single paragraph (Location questions) or multiple paragraphs (Comparison questions). Location questions were easier and faster to answer than Comparison questions. The presence of headers led to more selective reading strategies but did not significantly speed up the search. Strong individual differences were observed in children’s scanning strategies: Some systematically fixated headers, whereas others did not. These differences were not significantly related to the participants’ decoding or comprehension skills but rather to their knowledge of reading strategies.     

How can students’ academic performance in statistics be improved? Testing the influence of social and temporal-self comparison feedback in a web-based training environment

The aim of this study was to examine how social or temporal-self comparison feedback, delivered in real-time in a web-based training environment, could influence the academic performance of students in a statistics examination. First-year psychology students were given the opportunity to train for a statistics examination during a semester by doing online exercises in a web-based training environment. Once connected, students received in real-time either social comparison feedback (their score was compared to the mean score of all first-year students) or temporal-self comparison feedback (their score was compared, week by week, with their own previous score). The fact that students were free to connect to the web-based training environment heightened self-regulation differences such as academic procrastination, which was considered as a moderating variable in this study. Because academic performance was measured, the students’ background in mathematics and statistics was also controlled. Irrespective of the students’ background, the results reveal a positive influence of social comparison feedback on statistics exam performance, but only among students who did not delay doing exercises in the web-based training environment. By contrast, temporal-self comparison feedback did not have any effect on performance. Some recommendations for optimizing the efficacy of web-based training environments can be proposed, taking into account both social comparison feedback and academic procrastination.     

DEVELOPMENT, VALIDATION, AND USE OF A GREEK-LANGUAGE QUESTIONNAIRE FOR ASSESSING LEARNING ENVIRONMENTS IN GRADE 10 CHEMISTRY CLASSES

This study describes the development and validation of a Greek-language instrument that can be used to assess grade 10 students' perceptions of their chemistry classroom environment as a means of showing differences between chemistry learning environments in Greece (Attica) and Cyprus. The development of the instrument was based on available learning environment questionnaires. The questionnaire was administered to 1,394 students from 49 chemistry classes in Attica, and the resulting data were analyzed to explore the reliability and the validity of the new instrument. The validated questionnaire was administered to 225 students from 15 classes in urban areas of Cyprus. The data analyses supported the questionnaire's internal consistency, discriminant validity, and ability to differentiate between classrooms. Effect sizes and independent samples t test analyses revealed differences between the two samples. Cypriot students viewed their chemistry classroom environment more favorably than did the Attica students. A possible cause for this difference could be the knowledge-centered aspect of the grade 10 chemistry curriculum in Greece compared to the corresponding tool-instrumental knowledge curriculum in Cyprus.