Self-perceptions as mechanisms of achievement inequality: evidence across 70 countries.

Children from lower socioeconomic status (SES) backgrounds tend to have more negative self-perceptions. More negative self-perceptions are often related to lower academic achievement. Linking these findings, we asked: Do children's self-perceptions help explain socioeconomic disparities in academic achievement around the world? We addressed this question using data from the 2018 Programme for International Student Assessment (PISA) survey, including n = 520,729 records of 15-year-old students from 70 countries. We studied five self-perceptions (self-perceived competency, self-efficacy, growth mindset, sense of belonging, and fear of failure) and assessed academic achievement in terms of reading achievement. As predicted, across countries, children's self-perceptions jointly and separately partially mediated the association between socioeconomic status and reading achievement, explaining additional 11% (ΔR2 = 0.105) of the variance in reading achievement. The positive mediation effect of self-perceived competency was more pronounced in countries with higher social mobility, indicating the importance of environments that "afford" the use of beneficial self-perceptions. While the results tentatively suggest self-perceptions, in general, to be an important lever to address inequality, interventions targeting self-perceived competency might be particularly effective in counteracting educational inequalities in countries with higher social mobility.

Structure and dynamics of soft repulsive colloidal suspensions in the vicinity of the glass transition.

We use a combination of different scattering techniques and rheology to highlight the link between structure and dynamics of dense aqueous suspensions of soft repulsive colloids in the vicinity of a glass transition. Three different latex formulations with an increasing amount of the hydrophilic component resulting in either purely electrostatically or electrosterically stabilized suspensions are investigated. From the analysis of the static structure factor measured by small-angle X-ray scattering, we derive an effective volume fraction that includes contributions from interparticle interactions. We further investigate the dynamics of the suspensions using 3D cross-correlation dynamic light scattering (3DDLS) and rheology. We analyze the data using an effective hard sphere model and in particular compare the linear viscoelasticity and flow behavior to the predictions of mode coupling theory, which accounts for a purely kinetic glass transition determined by the equilibrium structure factor. We demonstrate that seemingly very different colloidal systems exhibit the same generic behavior when the effects from interparticle interactions are incorporated using an effective volume fraction description.

Developing a Simulation to Foster Prospective Mathematics Teachers' Diagnostic Competencies: the Effects of Scaffolding.

To assess individual students' abilities and misconceptions in mathematics, teachers need diagnostic competencies. Although research has addressed the quality of teachers' diagnostic competencies in recent years, it is not very clear how to foster these competencies effectively in the course of prospective teachers' university education. Research suggests that simulations with instructional support are promising tools for fostering complex competencies. We have developed a simulation that aims at measuring and fostering prospective primary school teachers' competencies to assess students' mathematical abilities and misconceptions based on their written task solutions. In this study, we analysed data from prospective primary school mathematics teachers who used one of three different versions of the simulation. Two versions contained a specific type of scaffolding, while the third version did not contain scaffolding. Specifically, the two scaffolding types were content-related scaffolding that emphasized the use of specific pedagogical content knowledge, and strategic scaffolding that emphasized diagnostic activities. The results suggest that integrating scaffolding into the simulation did not substantially influence participants' overall perception of the simulation regarding presence, authenticity, or perceived cognitive load. Compared to participants in a control group without intervention, participants who used the simulation with scaffolding had higher diagnostic accuracy regarding overall assessment of students' competence level. However, only content-related scaffolding but not strategic scaffolding or no scaffolding tended to improve participants' competence in identifying students' specific misconceptions. The results provide a first empirical basis for further development of the simulation.

Structural reorganization of a polymeric latex film during dry sintering at elevated temperatures.

Structural rearrangement in a latex powder during dry sintering at temperatures higher than the minimum film formation temperature was investigated by means of synchrotron small-angle X-ray scattering. Two major effects were identified: (1) Deformation of latex particles leads to a closure of voids between them and an extensive perfectioning of the face centered cubic colloidal crystalline ordering. Such an improvement of the colloidal crystalline structure involves preferential crystal growth along certain crystallographic directions as was evidenced by the measured unmatched relative diffraction intensity distribution of the crystallographic (111) and (220) planes. (2) Interdiffusion of polymeric chains between adjacent particles promotes a nanometer sized aggregation of nonpolymeric materials previously located in the interstices between particles. Size and size distribution of the aggregates at different dry sintering conditions were evaluated by using a model considering spheres dispersed in the system.

Digital support principles for sustained mathematics learning in disadvantaged students.

This study addresses the pressing issue of how to raise the performance of disadvantaged students in mathematics. We combined established findings on effective instruction with emerging research addressing the specific needs of disadvantaged students. A sample of N = 260 disadvantaged 6th-graders received 4 weeks (15 lessons) of fraction instruction either as usual or evidence-based instruction, with and without digital learning support (i.e., interactivity, adaptivity, and immediate explanatory feedback). To examine the sustainability of effects, we assessed students' fraction knowledge immediately after the 4 weeks and once again after a period of additional 8 weeks. Generalized linear mixed models revealed that students only benefitted from evidence-based instruction if digital support was available in addition. Digital support principles implemented in evidence-based instruction helped disadvantaged students to acquire mathematics knowledge-and to maintain this knowledge.

Assemblies of double hydrophilic block copolymers and oppositely charged dendrimers.

The association of poly(ethylene oxide-b-methacrylic acid) and poly(amidoamine) dendrimers was examined by dynamic light scattering and small angle neutron scattering. With increasing amounts of the G4 dendrimer as the counterion, the size of the assemblies increases until it reaches a hydrodynamic radius of about 70 nm. The structure is consistent with poly(methyl methacrylate) (PMAA) chains closely aggregating with the dendrimers at low dendrimer amounts and volume-filling PMAA blocks at higher dendrimer contents. Similar behavior was observed for G4 and G2 dendrimers, while smaller G0 molecules showed an opposite dependence. The results represent an example of finite size assemblies formed by "electrostatic self-assembly" that are stable in aqueous solution and represent equilibrium structures, the structure and size of which can be tuned through the building units, loading ratio, and pH.

Ion pair driven self-assembly of a flexible bis-zwitterion in polar solution: formation of discrete nanometer-sized cyclic dimers.

The self-complementary flexible bis-zwitterion 1 forms discrete nanometer-sized cyclic dimers via ion pair driven self-assembly even in polar solvents. The existence of such dimers was confirmed by DOSY NMR, FAB-MS, and scattering experiments (DLS, SANS) which all indicate the concentration-dependent formation of cyclic dimers with a hydrodynamic radius of rH approximately 2.5 nm in solution.