Nonlinear Finite Element Analysis of Nanoindentation of Viral Capsids

Recent Atomic Force Microscope (AFM) nanoindentation experiments measuring mechanical response of the protein shells of viruses have provided a quantitative description of their strength and elasticity. To better understand and interpret these measurements, and to elucidate the underlying mechanisms, this paper adopts a course-grained modeling approach within the framework of three-dimensional nonlinear continuum elasticity. Homogeneous, isotropic, elastic, thick shell models are proposed for two capsids: the spherical Cowpea Chlorotic Mottle Virus (CCMV), and the ellipsocylindrical bacteriophage $\phi 29$. As analyzed by the finite element method, these models enable parametric characterization of the effects of AFM tip geometry, capsid dimensions, and capsid constitutive descriptions. The generally nonlinear force response of capsids to indentation is shown to be insensitive to constitutive details, and greatly influenced by geometry. Nonlinear stiffening and softening of the force response is dependent on the AFM tip dimensions and shell thickness. Fits of the models capture the roughly linear behavior observed in experimental measurements and result in estimates of Young's moduli of $\approx$280--360 MPa for CCMV and $\approx$4.5 GPa for $\phi 29$.Comment: 24 pages, 10 figures, submitted to Biophysical Journa

Efficient optimization of the integrity behavior of analog nonlinear devices using surrogate models

A novel technique to analyze and optimize the integrity behavior of nonlinear analog devices in the presence of noise is proposed. The technique leverages surrogate models, as such reducing the simulation time, avoiding time-consuming and expensive measurements after tape-out and hiding the original netlist of the circuit, while maintaining high accuracy. Easy integration of the surrogates into a circuit simulator together with pertinent subcircuits representing, e. g., board and package, allows mimicking the integrity behavior of a complete setup while still being in the design phase. In this contribution, the method is applied to a case study, being a voltage regulator designed for automotive applications

Harmonic balance surrogate-based immunity modeling of a nonlinear analog circuit

A novel harmonic balance surrogate-based technique to create fast and accurate behavioral models predicting, in the early design stage, the performance of nonlinear analog devices during immunity tests is presented. The obtained immunity model hides the real netlist, reduces the simulation time, and avoids expensive and time-consuming measurements after tape-out, while still providing high accuracy. The model can easily be integrated into a circuit simulator together with additional subcircuits, e.g., board and package models, as such allowing to efficiently reproduce complete immunity test setups during the early design stage and without disclosing any intellectual property. The novel method is validated by means of application to an industrial case study, being an automotive voltage regulator, clearly showing the technique's capabilities and practical advantages

The ‘Self-Regulated Learning Opportunities Questionnaire’: a Diagnostic Instrument for Teacher Educators’ Professional Development

Many recent studies have stressed the importance of students’ self-regulated learning (SRL) skills for successful learning. Although primary teacher educators are aware of the importance of SRL for their students, they often find it difficult to implement SRL opportunities in their teaching. To support teacher professional development, an SRL model was described in a previous theoretical study. In the present article, this SRL model is elaborated towards the ‘SRL Opportunities Questionnaire’ (SRLOQ) that can be applied by primary teacher educators as a diagnostic instrument for classroom settings. A four-phase research design is applied consisting of scale development, score validation, further validation of the SRLOQ in primary teacher education, and a confirmatory factor analysis. Finally, a single case study is described that illustrates the usefulness of the SRLOQ in classroom practice

Effects of increased self-regulated learning opportunities on student teachers’ metacognitive and motivational development.

This intervention study focused on the relationships between student teachers’ self-regulated learning (SRL) opportunities, their use of metacognitive learning strategies and their motivation for learning. Results indicate that student teachers’ use of metacognitive learning strategies increases significantly in learning environments with increased SRL opportunities. In opposite to these findings, no significant difference was shown between student teachers’ motivation for learning before and after the research period. However, student teachers’ expectancy, a component within the motivational construct, did increase significantly in the research period. Finally, minor significant positive correlations were found between the metacognitive and motivational constructs measured. In general, the level of SRL opportunities turns out to be a moderate predictor of student teachers’ use of metacognitive learning strategies and motivation for learning, both important constructs for their academic career

Kritische vragen ter bevordering van de reflectiekwaliteit van pabostudenten

Er komt steeds meer aandacht voor zelfgestuurd leren (ZGL) als manier om studenten actiever en bewuster te laten leren. Vanuit het beleidskader Opleiden in School zijn in het studiejaar 2013-2014 intervisiemomenten voor pabostudenten op de werkplek georganiseerd met de intentie de mogelijkheden tot ZGL van de studenten geleidelijk te implementeren op de werkplek. Om hierbij een verdieping in reflectiekwaliteit van pabostudenten (n=28) te bewerkstelligen, hebben twee pabodocenten, vier leerkrachten basisonderwijs en drie onderzoekers samengewerkt aan een instrument met stimulerende vragen, gericht op toenemende verdieping in reflectieniveaus. Een belangrijk principe is er dat er een geleidelijke ontwikkeling plaatsvindt van docentsturing naar studentsturing. De eerste bevindingen laten zien dat het instrument (aanstaande) leraren ondersteunt bij het stellen van betekenisgerichte vragen ter bevordering van het reflectieniveau. Tevens stijgt het percentage betekenisgerichte reflectie