Using memes and memetic processes to explain social and conceptual influences on student understanding about complex socio‐scientific issues

This study investigated seventh grade learners' decision making about genetic engineering concepts and applications. A social network analyses supported by technology tracked changes in student understanding with a focus on social and conceptual influences. Results indicated that several social and conceptual mechanisms potentially affected how and why ideas were taken up in the learning system of the classroom. Mechanisms included copying or memetic processes such as “do as the smart students do” and friendship selection. Study outcomes are compared with the broader literature on memes and memetic processes to reveal general evolutionary ideas such as the development of prestige, identity versus problem‐solving strategies, extended phenotypes, and memeplexes. Educational implications for this research are also addressed. © 2008 Wiley Periodicals, Inc. J Res Sci Teach 45: 900–921, 2008     

Cascaded spiral microfluidic device for deterministic and high purity continuous separation of circulating tumor cells

Inertial microfluidics is an emerging class of technologies developed to separate circulating tumor cells (CTCs). However, defining design parameters and flow conditions for optimal operation remains nondeterministic due to incomplete understanding of the mechanics, which has led to challenges in designing efficient systems. Here, we perform a parametric study of the inertial focusing effects observed in low aspect ratio curvilinear microchannels and utilize the results to demonstrate the isolation of CTCs with high purity. First, we systematically vary parameters including the channel height, width, and radius of curvature over a wide range of flow velocities to analyze its effect on size dependent differential focusing and migration behaviors of binary (10 μm and 20 μm) particles. Second, we use these results to identify optimal flow regimes to achieve maximum separation in various channel configurations and establish design guidelines to readily provide information for developing spiral channels tailored to potentially arbitrary flow conditions that yield a desired equilibrium position for optimal size based CTC separation. Finally, we describe a fully integrated, sheath-less cascaded spiral microfluidic device to continuously isolate CTCs. Human breast cancer epithelial cells were successfully extracted from leukocytes, achieving 86.76% recovery, 97.91% depletion rate, and sustaining high viability upon collection to demonstrate the versatility of the device. Importantly, this device was designed without the cumbersome trail-and-error optimization process that has hindered the development of designing such inertial microfluidic systems.     

Multi-scale approach for the rheological characteristics of emulsions using molecular dynamics and lattice Boltzmann method

An emulsion system was simulated under simple shear rates to analyze its rheological characteristics using a hierarchical multi-scale approach. The molecular dynamics (MD) simulation was used to describe the interface of droplets in an emulsion. The equations derived from the MD simulation relative to interfacial tension, temperature, and surfactant concentration were applied as input parameters within lattice Boltzmann method (LBM) calculations. In the LBM simulation, we calculated the relative viscosity of an emulsion under a simple shear rate along with changes in temperature, shear rate, and surfactant concentration. The equations from the MD simulation showed that the interfacial tension of the droplets tended to decrease with an increase in temperature and surfactant concentration. The relative viscosity from the LBM simulation decreased with an increase in temperature. The shear thinning phenomena explaining the inverse proportion between shear rate and viscosity were observed. An increase in the surfactant concentration caused an increase in the relative viscosity for a decane-in-water emulsion, because the increased deformation caused by the decreased interfacial tension significantly influenced the wall shear stress.     

Two scalable algorithms for associative text classification

Associative classification methods have been recently applied to various categorization tasks due to its simplicity and high accuracy. To improve the coverage for test documents and to raise classification accuracy, some associative classifiers generate a huge number of association rules during the mining step. We present two algorithms to increase the computational efficiency of associative classification: one to store rules very efficiently, and the other to increase the speed of rule matching, using all of the generated rules. Empirical results using three large-scale text collections demonstrate that the proposed algorithms increase the feasibility of applying associative classification to large-scale problems.     

Relationships between cognitive diagnosis, CTT, and IRT indices: an empirical investigation

Cognitive diagnosis models (CDMs) continue to generate interest among researchers and practitioners because they can provide diagnostic information relevant to classroom instruction and student learning. However, its modeling component has outpaced its complementary component??test construction. Thus, most applications of cognitive diagnosis modeling involve retrofitting of CDMs to assessments constructed using classical test theory (CTT) or item response theory (IRT). This study explores the relationship between item statistics used in the CTT, IRT, and CDM frameworks using such an assessment, specifically a large-scale mathematics assessment. Furthermore, by highlighting differences between tests with varying levels of diagnosticity using a measure of item discrimination from a CDM approach, this study empirically uncovers some important CTT and IRT item characteristics. These results can be used to formulate practical guidelines in using IRT- or CTT-constructed assessments for cognitive diagnosis purposes.     

Korean Students' Perceptions of Scientific Practices and Understanding of Nature of Science

Korean students have shown relatively little interest and confidence in learning science, despite being ranked in the top percentile in international evaluations of academic achievement in science such as the Trends in International Mathematics and Science Study. Although research indicates a positive relationship between student perceptions of science and their science learning, this area has not been sufficiently explored in Korea. Particularly, even though both students' perceptions of scientific practice and their understanding of the nature of science (NOS) are influenced by their science learning experiences at schools, little research examines how this perception, understanding, and experience are related to one another. This study aimed to uncover Korean students' perceptions of school scientific practice through exploring their drawings, writings, and responses to questionnaires. Participants were 500 Korean students in 3rd, 7th, and 10th grades who were asked to complete an open-ended questionnaire. The results indicated that Korean students typically viewed school scientific practices as experimental activities or listening to lecture; and that most participants held an insufficient understanding of the NOS. Overall, no significant relationship emerged between students' perceptions of school scientific practice and their understanding of the NOS. Our findings highlight the need to help both teachers and students understand the potential breadth of school scientific practices, beyond simple ‘activity mania.’ This study also suggests that teachers must balance implicit and explicit instructional approaches to teaching about the NOS through scientific practices in school science contexts.