Charge reversal and surface charge amplification in asymmetric valence restricted primitive model planar electric double layers in the modified Poisson-Boltzmann theory

The modified Poisson-Boltzmann theory of the restricted primitive model double layer is revisited and recast in a fresh, slightly broader perspective. Derivation of relevant equations follow the techniques utilized in the earlier MPB4 and MPB5 formulations and clarifies the relationship between these. The MPB4, MPB5, and a new formulation of the theory are employed in an analysis of the structure and charge reversal phenomenon in asymmetric 2:1/1:2 valence electrolytes. Furthermore, polarization induced surface charge amplification is studied in 3:1/1:3 systems. The results are compared to the corresponding Monte Carlo simulations. The theories are seen to predict the "exact" simulation data to varying degrees of accuracy ranging from qualitative to almost quantitative. The results from a new version of the theory are found to be of comparable accuracy as the MPB5 results in many situations. However, in some cases involving low electrolyte concentrations, theoretical artifacts in the form of un-physical "shoulders" in the singlet ionic distribution functions are observed.Comment: 15 pages, 13 figure

App-based Support for Parental Self-Efficacy in the First 1000 Days: A Randomised Control Trial

This study reports a feasibility randomised control trial (RCT) of the Oliiki parenting app with 79 parents of children aged 0-6 months in the UK. Results showed, while controlling for pre-test scores, parents who were randomly allocated to the Treatment Group and used the Oliiki parenting app had significantly higher parental self-efficacy, after the 4-week intervention period, compared to the Active Control Group. Partial correlation analyses indicated that higher frequency of self-reported use of the Oliiki parenting app was associated with greater parental self-efficacy outcomes. This evidence establishes proof of concept that the Oliiki parenting app can have significant benefits on parental self-efficacy in the first 1000 days of child development

Inequalities in resources in the home learning environment

Since 23rd March 2020, UK schools have been closed for most children due to the COVID-19 pandemic. Consequently, there is a greater emphasis on the implementation of children's education by parents at home, as well as perhaps a greater reliance on access to educational technologies. There are concerns that the impact of school closures will disproportionally impact children from lower socio-economic backgrounds and widen the attainment gap between them and their peers from more affluent backgrounds (Montacute, 2020). This briefing note summarises the empirical evidence on inequalities in 1) the home learning environment and 2) resources, including educational technologies, which may affect access to education during these challenging times

Academic and social and emotional interventions in response to COVID-19 school closures

Since 23rd March 2020, UK schools have been closed for most children, due to the COVID-19 pandemic. Schools are unlikely to re-open to the majority of pupils before September, meaning some will be out of school for more than six months. As school relationships serve as a buffer against psycho-social risks and against the risk of low academic attainment, particularly for children of low-income families (Masten and Barnes, 2018), the vulnerabilities of many children may have significantly increased as a consequence of the school closures. Research suggests that long absences from school are likely to have a negative effect on academic achievement and increase achievement gaps (see Sims, 2020). Inequalities in resources and time available to families to spend on home schooling is likely to exacerbate existing achievement gaps (see Dickson & Macmillan, 2020; Outhwaite, 2020). There may also be significant challenges to mental health and wellbeing in schools after lockdown (Lee, 2020). Children and young people have been away from the community and structure that school provides. Some may carry personal losses, and some may have experienced significant stressors in the family. Mental health and wellbeing are fundamental to learning and development (Panayiotou et al., 2019), and therefore must be prioritised in the post-lockdown transition and beyond. This briefing note summarises the empirical evidence on approaches to closing achievement gaps and supporting the most vulnerable children in academic, and social and emotional learning as schools can safely re-open

A new methodological approach for evaluating the impact of educational intervention implementation on learning outcomes

Randomized control trials (RCTs) are commonly regarded as the ‘gold standard’ for evaluating educational interventions. While this experimental design is valuable in establishing causal relationships between the tested intervention and outcomes, reliance on statistical aggregation typically underplays the situated context in which interventions are implemented. Developing innovative, systematic methods for evaluating implementation and understanding its impact on outcomes is vital to moving educational evaluation research beyond questions of ‘what works’, towards better understanding the mechanisms underpinning an intervention’s effects. The current study presents a pragmatic, two-phased approach that combines qualitative data with quantitative analyses to examine the causal relationships between intervention implementation and outcomes. This new methodological approach is illustrated in the context of a maths app intervention recently evaluated in a RCT across 11 schools. In phase I, four implementation themes were identified; ‘teacher support’, ‘teacher supervision’, ‘implementation quality’, and ‘established routine’. In phase II, ‘established routine’ was found to predict 41% of the variance in children’s learning outcomes with the apps. This has significant implications for future scaling. Overall, this new methodological approach offers an innovative method for combining process and impact evaluations when seeking to gain a more nuanced understanding of what works in education and why

Using 'approach goals' to increase student motivation for independent study: a randomised controlled field trial

Motivation has an important influence on the extent to which students engage in study. Reported here is a large-scale randomised controlled trial comparing the effect of Mastery-Approach (MAp) goals, which focus on development of task mastery, and Performance-Approach (PAp) goals, which focus on demonstration of competence. The achievement goals were embedded within an online learning platform for students aged 16-18 years in England. In a sample of 1,791 students, intention to treat analysis showed students randomly allocated to receive the MAp goals (treatment group 1) engaged in more effortful learning activities on the platform, compared to students assigned to receive the PAp goals (treatment group 2) or no achievement goal messages (control group). The PAp messages had no significant impact on student effort. The research addresses a need for more ecologically valid causal evidence on achievement goal theory and has direct implications for educators managing remote learning

Thermodynamics of primitive model electrolytes in the symmetric and modified Poisson-Boltzmann theories. A comparative study with Monte Carlo simulations

Osmotic coefficients, individual and mean activity coefficients of primitive model electrolyte solutions are computed at different molar concentrations using the symmetric Poisson-Boltzmann and modified Poisson-Boltzmann theories. The theoretical results are compared with an extensive series of Monte Carlo simulation data obtained by Abbas et al. [Fluid Phase Equilib., 2007, 260, 233; J. Phys. Chem. B, 2009, 113, 5905]. The agreement between modified Poisson-Boltzmann predictions with the "exact" simulation results is almost quantitative for monovalent salts, while being semi-quantitative or better for higher and multivalent salts. The symmetric Poisson-Boltzmann results, on the other hand, are very good for monovalent systems but tend to deviate at higher concentrations and/or for multi-valent systems. Some recent experimental values for activity coefficients of HCl solution (individual and mean activities) and NaCl solution (mean activity only) have also been compared with the symmetric and modified Poisson-Boltzmann theories, and with the Monte Carlo simulations.Comment: 10 pages, 9 figure

Barriers to the Effective Adhesion of High-Density Hardwood Timbers for Glue-Laminated Beams in Australia

A number of international timbers of high commercial importance are extremely difficult to glue, which is significantly hindering access to global market opportunities for engineered wood products, especially for heavily demanded structural products. Some particularly problematic timbers in Australia are the dominant commercial hardwood species, including spotted gum (Corymbia spp.) and Darwin stringybark (Eucalyptus tetrodonta). These species are renowned for their very high mechanical properties, natural durability and attractive aesthetic appeal. However, they are notoriously difficult to glue, especially for sawn laminate-based engineered wood products, such as structural glue-laminated beams. Despite considerable effort and testing of diverse internationally established best-practice approaches to improve adhesion, glue-laminated beam samples of these timbers still frequently fail to meet the requirements of the relevant standard, mainly due to excessive glue line delamination. This paper discusses the key barriers to effective adhesion of these high-density timbers and particularly emphasises the necessity of achieving greater adhesive penetration. Greater adhesive penetration is required to enhance mechanical interlocking, entanglement and molecular interactions between the adhesive and the wood to achieve stronger and more durable bonds. Potential solutions to enhance adhesive penetration, as well as to improve gluability in general, are discussed in terms of their likelihood to satisfactorily prevent delamination and the potential to be applied at an industrial scale. This new fundamental understanding will assist the development of solutions, allowing industry to commercialise newly engineered wood products made from high-density timbers

The primitive model of ionic fluids near its critical point in the Poisson–Boltzmann and modified Poisson–Boltzmann theories

The Poisson–Boltzmann (PB) and modified Poisson–Boltzmann (MPB) theories are used to investigate the primitive model of ionic fluids in the low density–large coupling regime where the liquid–vapor transition is situated. The PB and MPB spinodal curves for the restricted primitive model are calculated from the virial route and compared with those from the mean spherical approximation (energy route) and the hybrid hypernetted‐chain/mean spherical approximation (virial route). The effect of unequal ion sizes on the critical point and spinodal curves is also considered.National Sanitation Foundation (NSF) EE.UU. CHE-8907130Fondo Institucional para la Investigación (FIPI) de la Universidad de Puerto RicoComunidad Europea (beca Marie Curie)Dirección General de Investigación Científica y Técnica (DGICYT). España PBgl / 060