Grain orientation effects on dynamic strength of FCC multicrystals at low shock pressures: a hydrodynamic instability study

Variability in local dynamic plasticity due to material anisotropy in polycrystalline metals is likely to be important on damage nucleation and growth at low pressures. Hydrodynamic instabilities could be used to study these plasticity effects by correlating measured changes in perturbation amplitudes at free surfaces to local plastic behaviour and grain orientation, but amplitude changes are typically too small to be measured reliably at low pressures using conventional diagnostics. Correlations between strength at low shock pressures and grain orientation were studied in copper (grain size?≈?800 μm) using the Richtmyer–Meshkov instability with a square-wave surface perturbation (wavelength = 150 μm, amplitude = 5 μm), shocked at 2.7 GPa using symmetric plate impacts. A Plexiglas window was pressed against the peaks of the perturbation, keeping valleys as free surfaces. This produced perturbation amplitude changes much larger than those predicted without the window. Amplitude reductions from 64 to 88% were measured in recovered samples and grains oriented close to 〈0 0 1〉 parallel to the shock had the largest final amplitude, whereas grains with shocks directions close to 〈1 0 1〉 had the lowest. Finite element simulations were performed with elastic-perfectly plastic models to estimate yield strengths leading lead to those final amplitudes. Anisotropic elasticity and these yield strengths were used to calculate the resolved shear stresses at yielding for the two orientations. Results are compared with reports on orientation dependence of dynamic yielding in Cu single crystals and the higher values obtained suggest that strength estimations via hydrodynamic instabilities are sensitive to strain hardening and strain rate effects.     

Failure of further learning: Activities,structure, and meaning

Previous research has shown that little benefit is achieved through spaced study and recall of text passages after the first recall attempt, an effect that we term the failure‐of‐further‐learning. We hypothesized that the effect occurs because a situation model of the text's gist is formed when the text is first comprehended and is consolidated when recalled; it dominates later recall after verbatim memories of more recent study episodes have been lost. Experiments 1 and 2 attempted to circumvent the effect by varying the activities of participants and requiring interactive exploration. In both experiments, recall after four, weekly sessions showed little benefit beyond performance on the first recall. Experiment 3 interfered with the formation of an immediate situation model by introducing passages that were hard to comprehend without a title. Performance improved substantially across four sessions when titles were not supplied, but the standard effect was replicated when titles were given. Experiment 4 made verbatim memories available by incorporating all re‐presentations and tests into one session; as predicted, recall improved over successive tests.     

Higher-Order Contingentism,Part 1: Closure and Generation

This paper is a study of higher-order contingentism – the view, roughly, that it is contingent what properties and propositions there are. We explore the motivations for this view and various ways in which it might be developed, synthesizing and expanding on work by Kit Fine, Robert Stalnaker, and Timothy Williamson. Special attention is paid to the question of whether the view makes sense by its own lights, or whether articulating the view requires drawing distinctions among possibilities that, according to the view itself, do not exist to be drawn. The paper begins with a non-technical exposition of the main ideas and technical results, which can be read on its own. This exposition is followed by a formal investigation of higher-order contingentism, in which the tools of variable-domain intensional model theory are used to articulate various versions of the view, understood as theories formulated in a higher-order modal language. Our overall assessment is mixed: higher-order contingentism can be fleshed out into an elegant systematic theory, but perhaps only at the cost of abandoning some of its original motivations.     

The comparative effectiveness of distributed and colocated team after-action reviews

Despite their frequent use in the military and private sectors, the comparative effectiveness of colocated and distributed after-action reviews (AARs) is relatively unknown. Consequently, this study examined the comparative effectiveness of colocated and distributed AARs across taskwork and teamwork outcomes. Data were obtained from 492 participants randomly assigned to 123 four-person teams who participated in one of six AAR conditions. The results indicated that teams in the AAR conditions had significantly higher performance and team efficacy scores than the teams in the non-AAR conditions. In summary, the findings highlight that regardless of the training environment or type of AAR, the AAR remains an effective method at increasing performance and other outcomes. Therefore, the use of distributed AARs does not engender the posited process losses that were hypothesized.     

Minimal Risk of Internalizing Problems in Typically-Developing Siblings of Children with High-Functioning Autism Spectrum Disorder

We examined anxiety and depression clinical symptom levels in 42 typically-developing (TD) siblings of children with high-functioning autism spectrum disorder (HFASD), compared to 42 TD siblings of TD children, matched on age, ethnicity, and gender. Participants were between the ages of 6 and 16. Groups were compared using the parent-report and child self-report versions of the Behavior Assessment System for Children, Second Edition, anxiety and depression clinical scales. Within-group differences were examined for parent versus child ratings. Multivariate procedures did not support clinically elevated levels of internalizing problems in siblings of children with HFASD. Results from both sources were consistent with the overall finding. The findings do not support an increased need for targeted intervention, though clinical and school-based practitioners should attend to clinical warning signs if presented.     

Neurocognitive outcomes in children with unilateral basal ganglia arterial ischemic stroke and secondary hemidystonia

Dystonia is a movement disorder that involves excessive, involuntary muscle contractions resulting in repetitive movements and/or abnormal posturing. One common cause of unilateral dystonia in childhood is ischemic stroke involving the basal ganglia and/or thalamus. Virtually nothing is known about neuropsychological outcomes in children who have dystonia following basal ganglia stroke. The present study explored whether or not children with secondary dystonia experience additional cognitive challenges when compared to children with similar patterns of brain injury, but no dystonia. We examined intellectual function, academics, and several aspects of executive function in children with unilateral basal ganglia stroke during childhood, comparing those with dystonia and those without. Although groups did not differ in terms of lesion size, we found significantly lower performance on measures of verbal and nonverbal reasoning, inhibitory control, and academic ability in children with secondary dystonia compared to those without. In contrast, there were no significant group differences on parent ratings of their child’s executive function in daily life. These findings suggest that maladaptive reorganization following basal ganglia stroke may contribute to the development of secondary dystonia and also to poor intellectual and academic outcomes in this group.     

Teacher beliefs,teacher characteristics,and school contextual factors: What are the relationships?

Background. There is a plethora of research around student beliefs and their contribution to student outcomes. However, there is less research in relation to teacher beliefs. Teacher factors are important to consider since beliefs mould thoughts and resultant instructional behaviours that, in turn, can contribute to student outcomes. Aims. The purpose of this research was to explore relationships between the teacher characteristics of gender and teaching experience, school contextual variables (socio‐economic level of school and class level), and three teacher socio‐psychological variables: class level teacher expectations, teacher efficacy, and teacher goal orientation. Sample. The participants were 68 male and female teachers with varying experience, from schools in a variety of socio‐economic areas and from rural and urban locations within New Zealand. Method. Teachers completed a questionnaire containing items related to teacher efficacy and goal orientation in reading. They also completed a teacher expectation survey. Reading achievement data were collected on students. Interrelationships were explored between teacher socio‐psychological beliefs and the teacher and school factors included in the study. Results. Mastery‐oriented beliefs predicted teacher efficacy for student engagement and classroom management. The socio‐economic level of the school and teacher gender predicted teacher efficacy for engagement, classroom management, instructional strategies, and a mastery goal orientation. Being male predicted a performance goal orientation. Conclusions. Teacher beliefs, teacher characteristics, and school contextual variables can result in differences in teacher instructional practices and differing classroom climates. Further investigation of these variables is important since differences in teachers contribute to differences in student outcomes.