المؤلفون: Brown, Bryan A., Ribay, Kathryn, Pérez, Greses, Boda, Phillip A., Wilsey, Matthew

المصدر: International Journal of Technology in Education and Science. Spr 2020 4(2):86-97.

تمت مراجعته من قبل الزملاء: Y

Page Count: 13

الواصفات: Teaching Methods, Culturally Relevant Education, Elementary School Students, Science Instruction, Cultural Relevance, Computer Simulation, Student Attitudes, Lesson Plans, Energy, Course Content, Social Justice, Computer Assisted Instruction, Environment, Video Technology, Computer Software, Health, Economic Factors, Food

مستخلص: This mixed-methods study examines the implications of using the tenets of culturally relevant pedagogy (CRP) to design an elementary science lesson grounded in four virtual reality (VR) videos. Given the need for additional understandings of how elementary science educators can infuse cultural relevance alongside content development, this study illuminates how designing for CRP can utilize VR as a pedagogical platform to bridge science instruction and students' lived experiences. Using pre- and post-attitudinal surveys (n=145) and post interviews (n=48), we examined students' perceptions of a single virtual reality lesson about energy and food chains. The data suggest that learning through a CRP-based VR design (CRP-VR) enhanced students? perception of the connection between the science content and its socio-political application to social justice issues. Implications highlight the potential of leveraging VR technology as a means to provide science instruction that explicitly affords students the opportunity to connect content learning and social action.

Abstractor: As Provided

المؤلفون: Jansen, Malte (ORCID 0000-0001-7081-6505), Boda, Zsófia, Lorenz, Georg (ORCID 0000-0001-6814-6901)

المصدر: Developmental Psychology. Aug 2022 58(8):1541-1556.

تمت مراجعته من قبل الزملاء: Y

Page Count: 16

الواصفات: Self Concept, Peer Relationship, Academic Achievement, Social Networks, Network Analysis, Foreign Countries, Secondary School Students, Grade 9, Grade 10, Comparative Analysis

مصطلحات جغرافية: Germany

مستخلص: Social comparisons with peers are important sources of self-development during adolescence. Many previous studies showed that students' academic self-concepts (ASC) form by contrasting one's own achievement with the average of one's class or school (the Big-Fish-Little-Pond Effect [BFLPE]). Based on social comparison theory, however, we would expect some peers to be more likely social comparison targets than other peers, for example, because they are more visible or students perceive them as similar to themselves. In this study, we used sociometric data to analyze which peers play the most important role for social comparison effects on ASC. We examined how the average achievement of friends, study partners, peers perceived as popular by the student, as well as same-gender and same-ethnic peers affect the general ASC and how these effects compare to the effect of the classroom's average achievement. The study was based on a German longitudinal sample of 2,438 students (44% no recent immigrant background, 19% Turkish immigrant background, 10% Eastern European immigrant background, 27% other immigrant background) from 117 school classes that were followed from grade 9 to 10. Results from longitudinal social network analysis do not confirm substantial incremental effects of specific types of peers, while class average achievement showed a stable negative effect (confirming the BFLPE). In addition, we could provide evidence for social selection effects based on ASC. We conclude that classrooms provide a specific setting that imposes social comparisons with the "generalized peer" rather than with specific subgroups of peers.

Abstractor: As Provided

المؤلفون: Fertig, Dávid, Sarkadi, Zsófia, Valiskó, Mónika, Boda, Dezső

مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Statistical Mechanics, Physics - Chemical Physics

الوصف: The scaling behavior for the rectification of bipolar nanopores is studied using the Nernst-Planck equation coupled to the Local Equilibrium Monte Carlo method. The bipolar nanopore's wall carries $\sigma$ and $-\sigma$ surface charge densities in its two half regions axially. Scaling means that the device function (rectification) depends on the system parameters (pore length, $H$, pore radius, $R$, concentration, $c$, voltage, $U$, and surface charge density, $\sigma$) via a single scaling parameter that is a smooth analytical function of the system parameters. Here, we suggest using a modified Dukhin number, $\mathrm{mDu}=|\sigma|l_{\mathrm{B}}^{*}\lambda_{\mathrm{D}}HU/(RU_{0})$, where $l_{\mathrm{B}}^{*}=8\pi l_{\mathrm{B}}$, $l_{\mathrm{B}}$ is the Bjerrum length, $\lambda_{\mathrm{D}}$ is the Debye length, and $U_{0}$ is a reference voltage. We show how scaling depends on $H$, $U$, and $\sigma$ and through what mechanisms these parameters influence the pore's behavior.

الوصول الحر: http://arxiv.org/abs/2103.17085Test

المؤلفون: Sarkadi, Zsófia, Fertig, Dávid, Ható, Zoltán, Valiskó, Mónika, Boda, Dezső

مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Statistical Mechanics, Physics - Chemical Physics, Physics - Computational Physics

الوصف: Scaling of the behavior of a nanodevice means that the device function (selectivity) is a unique smooth and monotonic function of a scaling parameter that is an appropriate combination of the system's parameters. For the uniformly charged cylindrical nanopore studied here these parameters are the electrolyte concentration, $c$, voltage, $U$, the radius and the length of the nanopore, $R$ and $H$, and the surface charge density on the nanopore's surface, $\sigma$. Due to the non-linear dependence of selectivites on these parameters, scaling can only be applied in certain limits. We show that the Dukhin number, $\mathrm{Du}=|\sigma|/eRc\sim |\sigma|\lambda_{\mathrm{D}}^{2}/eR$ ($\lambda_{\mathrm{D}}$ is the Debye length), is an appropriate scaling parameter in the nanotube limit ($H\rightarrow\infty$). Decreasing the length of the nanopore, namely, approaching the nanohole limit ($H\rightarrow 0$), an alternative scaling parameter has been obtained that contains the pore length and is called the modified Dukhin number: $\mathrm{mDu}\sim \mathrm{Du}\, H/\lambda_{\mathrm{D}}\sim |\sigma|\lambda_{\mathrm{D}}H/eR$. We found that the reason of non-linearity is that the double layers accumulating at the pore wall in the radial dimension correlate with the double layers accumulating at the entrances of the pore near the membrane on the two sides. Our modeling study using the Local Equilibrium Monte Carlo method and the Poisson-Nernst-Planck theory provides concentration, flux, and selectivity profiles, that show whether the surface or the volume conduction dominates in a given region of the nanopore for a given combination of the variables. We propose that the inflection point of the scaling curve may be used to characterize the transition point between the surface and volume conductions.
Comment: arXiv admin note: substantial text overlap with arXiv:2012.14265

الوصول الحر: http://arxiv.org/abs/2103.00706Test

المؤلفون: Fertig, Dávid, Boda, Dezső, Szalai, István

المصدر: Phys. Rev. E 103, 062608 (2021)

مصطلحات موضوعية: Condensed Matter - Soft Condensed Matter, Condensed Matter - Mesoscale and Nanoscale Physics

الوصف: We report Brownian Dynamics simulation results for the relative permittivity of electrorheological (ER) fluids in an applied electric field. The relative permittivity of an ER fluid can be calculated from the Clausius-Mosotti (CM) equation in the small applied field limit. When a strong field is applied, however, the ER spheres are organized into chains and assemblies of chains in which case the ER spheres are polarized not only by the external field but by each other. This manifests itself in an enhanced dielectric response, e.g., in an increase in the relative permittivity. The correction to the relative permittivity and the time dependence of this correction is simulated on the basis of a model in which the ER particles are represented as polarizable spheres. In this model, the spheres are also polarized by each other in addition to the applied field. Our results are qualitatively similar to those obtained by Horv\'ath and Szalai experimentally (\textit{Phys. Rev. E}, \textbf{86}, 061403, 2012). We report characteristic time constants obtained from bi-exponential fits that can be associated with formation of pairs and short chains as well as with aggregation of chains. The electric field dependence of the induced dielectric increment reveals the same qualitative behavior that experiments did: three regions with different slopes corresponding to different aggregation processes are identified.

الوصول الحر: http://arxiv.org/abs/2101.07839Test

المؤلفون: Sarkadi, Zsófia, Fertig, D'avid, Valiskó, Mónika, Boda, Dezső

مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Chemical Physics

الوصف: We show that a modified version of the Dukhin number is an appropriate scaling parameter for the ionic selectivity of uniformly charged nanopores. The modified Dukhin number is an unambiguous function of the variables $\sigma$ (surface charge), $R$ (pore radius), and $c$ (salt concentration), and defined as $\mathrm{mDu}=|\sigma|/e(R/\lambda)$, where $\lambda$ is the screening length of the electrolyte carrying the $c$ dependence ($\lambda\sim c^{-1/2}$). Scaling means that the device function (selectivity) is a smooth and (in this case) monotonic function of mDu. The original Dukhin number defined as $\mathrm{Du}=|\sigma|/eRc$ ($c^{-1}$ dependence) was introduced to indicate whether the surface or the volume conduction is dominant in the pore. The modified version satisfies scaling and characterizes selectivity in the intermediate regime, where both surface and bulk conductions are present and the pore is neither perfectly selective, nor perfectly non-selective. Our modeling study using the Local Equilibrium Monte Carlo method and the Poisson-Nernst-Planck theory provides the radial flux profiles from which the radial selectivity profile can be computed. These profiles show in which region of the nanopore the surface or the volume conduction dominates for a given combination of the variables $\sigma$, $R$, and $c$. We show that the inflection point of the scaling curve may be used to characterize the transition point between the surface and volume conductions.

الوصول الحر: http://arxiv.org/abs/2012.14265Test

المؤلفون: Fertid, Dávid, Boda, Dezső, Szalai, István

مصطلحات موضوعية: Condensed Matter - Materials Science, Condensed Matter - Statistical Mechanics

الوصف: We report a systematic study of the dynamics of chain formation in electrorheological (ER) fluids using Brownian Dynamics simulations. The parameters of the system such as applied electric field, polarizability, dipole moment, friction coefficient, and number density are expressed in reduced units and changed in a wide range in order to map the system's behavior as a function of them. We define time constants obtained from bi-exponential fits to time dependence of various physical quantities such as dipolar energy, diffusion constant, and average chain length. The smaller time constant is associated with the formation of shorter chains (pairs, triplets, and so on), while the larger time constant is associated with the formation of longer chains in the regime of those that overarch the simulation cell. We use the approximation that the dipole moments are induced by the applied electric field only, as usual in the literature. However, we report preliminary results for the case when particle-particle polarization is also possible.

الوصول الحر: http://arxiv.org/abs/2011.07380Test

المؤلفون: Fertig, Dávid, Valiskó, Mónika, Boda, Dezső

مصطلحات موضوعية: Condensed Matter - Soft Condensed Matter, Condensed Matter - Mesoscale and Nanoscale Physics

الوصف: Bipolar nanopores have powerful rectification properties due to the asymmetry in the charge pattern on the wall of the nanopore. In particular, bipolar nanopores have positive and negative surface charges along the pore axis. Rectification is strong if the radius of the nanopore is small compared to the screening length of the electrolyte so that both cations and anions have depletion zones in the respective regions. The depths of these depletion zones is sensitive to sign of the external voltage. In this work, we are interested in the effect of the presence of strong ionic correlations (both between ions and between ions and surface charge) due to the presence of multivalent ions and large surface charges. We show that strong ionic correlations cause leakage of the coions, a phenomenon that is absent in mean field theories. In this modeling study, we use both the mean-field Poisson-Nernst-Planck (PNP) theory and a particle simulation method, Local Equilibrium Monte Carlo (LEMC), to show that phenomena such as overcharging and charge inversion cannot be reproduced with PNP, while LEMC is able to produce nonmonotonic dependence of currents and rectification as a function of surface charge strength.

الوصول الحر: http://arxiv.org/abs/2011.07404Test

المؤلفون: Mádai, Eszter, Valiskó, Mónika, Boda, Dezső

المصدر: Phys. Chem. Chem. Phys. 117(20):2793-2801, 2019

مصطلحات موضوعية: Physics - Applied Physics, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Soft Condensed Matter

الوصف: We model and simulate a nanopore sensor that selectively binds analyte ions. This binding leads to the modulation of the local concentrations of the ions of the background electrolyte (KCl), and, thus, to the modulation of the ionic current flowing through the pore. The nanopore's wall carries a bipolar charge pattern with a larger positive buffer region determining the anions as the main charge carriers and the smaller negative binding region containing binding sites. This charge pattern proved to be an appropriate one as shown by a previous comparative study of varying charge patterns (M\'adai et al.\ \textit{J. Mol. Liq.}, 2019, \textbf{283}, 391--398.). Binding of the positive analyte ions attracts more anions in the pore thus increasing the current. The asymmetric nature of the pore results in an additional device function, rectification. Our model, therefore, is a dual response device. Using a reduced model of the nanopore studied by a hybrid computer simulation method (Local Equilibrium Monte Carlo coupled to the Nernst-Planck equation) we show that we can create a sensor whose underlying mechanisms are based on the changes of the local electric field as a response to changing thermodynamic conditions. The change of the electric field results in changes in the local ionic concentrations (depletion zones), and, thus, changes in ionic currents.

الوصول الحر: http://arxiv.org/abs/1911.02083Test

المؤلفون: Fertig, Dávid, Matejczyk, Bartłomiej, Valiskó, Mónika, Gillespie, Dirk, Boda, Dezső

مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Statistical Mechanics, Physics - Chemical Physics

الوصف: We present a scaling behavior of a rectifying bipolar nanopore as a function of the parameter $\xi=R_{\mathrm{P}}/(\lambda z_{\mathrm{if}})$, where $R_{\mathrm{P}}$ is the radius of the pore, $\lambda$ is the characteristic screening length of the electrolyte filling the pore, and $z_{\mathrm{if}}=\sqrt{z_{+}|z_{-}|}$ is a scaling factor that makes scaling work for electrolytes containing multivalent ions ($z_{+}$ and $z_{-}$ are cation and the anion valences). By scaling we mean that the rectification of the pore (defined as the ratio of currents in the forward and reversed biased states) depends on pore radius, concentration, $c$, and ion valences via the parameter $\xi$ implicitly. This feature is based on the fact that rectification depends on the voltage-sensitive appearance of depletion zones that, in turn, depend on the relation of $R_{\mathrm{P}}$ to the rescaled screening length $\lambda z_{\mathrm{if}}$. In this modeling study, we use the Poisson-Nernst-Planck (PNP) theory and a particle simulation method, the Local Equilibrium Monte Carlo (LEMC). The latter can compute ion correlations that are ignored in the mean-field treatment of PNP and that are very important for multivalent ions (we show results for 1:1, 2:1, 3:1, and 2:2 electrolytes). In addition to the $z_{\mathrm{if}}$ factor, we show that one must choose a screening length appropriate to the system, in our case the Debye length for $\lambda$ for PNP and the screening length given by the Mean Spherical Approximation for LEMC.

الوصول الحر: http://arxiv.org/abs/1911.01772Test