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We have investigated the effects of N on the electronic properties of Si-doped GaAs1-xNx alloy films and AlGaAs/GaAsN modulation-doped heterostructures. For bulk-like alloy films, the electron mobility is independent of free carrier concentration and arsenic species, and decreases with increasing N composition. Thus, N-related defects are the main source of scattering in the dilute nitride alloys. For AlGaAs/GaAsN heterostructures, gated and illuminated magnetoresistance measurements reveal a two-dimensional electron gas mobility which increases with carrier concentration to a constant value. Thus, in contrast to the long-range ionized scattering sources which are dominant in N-free heterostructures, N-induced neutral scattering sources are the dominant source of scattering in AlGaAs/GaAsN heterostructures. Finally, a decrease in free carrier concentration with increasing N composition is apparent for bulk-like films, while the free carrier concentration is independent of N composition in modulation-doped heterostructures. Since N and Si atoms are spatially separated in the modulation-doped heterostructures, N–Si defect complexes in the bulk GaAsN layers are likely acting as trapping centers. [ABSTRACT FROM AUTHOR]

We have investigated the mechanisms of GaAs1-xNx film growth by plasma-assisted molecular-beam epitaxy. A comparison of in situ reflection high-energy electron diffraction and scanning tunneling microscopy (STM), with ex situ atomic force microscopy, reveals a temperature-dependent interplay between surface and step-edge diffusion. At low temperatures, layer-by-layer growth is observed, presumably due to limited adatom surface mobility. As the temperature increases, the interplay between surface and step-edge diffusion leads to multilayer growth. For sufficiently high temperatures, adatoms overcome the step-edge diffusion barrier, resulting in layer-by-layer growth once again. The temperature range for multilayer growth is influenced by the Ga flux and may be narrowed by using As2. Using in situ STM, we quantified the activation energies for Ga surface diffusion, Ed, and step-edge diffusion, Ee, during layer-by-layer GaAsN growth. We estimate Ed=0.75 and 0.96 eV for growth using As4 and As2, respectively. Thus, the narrowing of the multilayer growth temperature range is likely due to the decrease in Ga surface diffusion length through the use of As2 in lieu of As4. Furthermore, we estimate Ee=80 meV, larger than what has been reported for GaAs growth. [ABSTRACT FROM AUTHOR]

We have investigated stress evolution in dilute nitride GaAs1-xNx alloy films grown by plasma-assisted molecular-beam epitaxy. For coherently strained films (x<2.5%), a comparison of stresses measured via in situ wafer curvature measurements, with those determined from x-ray rocking curves using a linear interpolation of lattice parameter and elastic constants, suggests significant bowing of the elastic properties of GaAsN. The observed stress differences are used to quantify the composition-dependent elastic constant bowing parameters. For films with x>2.5%, in situ wafer curvature measurements reveal a signature for stress relaxation. Atomic force microscopy and transmission electron microscopy measurements indicate that stress relaxation occurs by a combination of elastic relaxation via island formation and plastic relaxation associated with the formation of stacking faults. [ABSTRACT FROM AUTHOR]

Objectives: Social prescription is classically thought of as an initiative for older people. This qualitative study aimed to evaluate the first socially prescribed creative play programme for families of 0-3-year-old children in the UK, examining the experience of the parents throughout the stages of the programme., Study Design: The evaluation ran longitudinally over 5 weeks using interviews, field notes, and questionnaire data., Methods: The evaluation was carried out over 5 weeks in 2022 using intervention leaders' and researcher's field notes, nine parent semi-structured interviews, and 17 parent questionnaires on their experiences. Data were analysed using inductive interpretive thematic analysis., Results: After analysis of the corpus of data, three themes that interacted with each other were identified: Support Systems that Parents Trust, Calming in Chaos, and Practical Parenting Utility. Parents said that they were more likely to sign up for the programme when they trusted the recommender and the organisation running the programme. They found the socially prescribed group more relaxed and calm than other groups, and their daily lives. The knowledge about health behaviours and modelling of play were the main take-home skills reported., Conclusion: In order for parents to be receptive to practical parenting knowledge the SP aimed to foster, parents must first establish trust in a calming atmosphere. Social links and child development were the key factors parents identified linking to well-being. This research could inform public health policy on social prescription for families., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: Occupational characteristics are associated with late-life cognition. However, little is known about the association between occupational factors and cognition in early adulthood, especially when controlling for early life socioeconomic status (SES) and cognition in childhood. Importantly, sex may shape the impact of occupational characteristics that provide cognitive stimulation given that education, occupational status, and workplace experiences differ by sex., Methods: Using data on 12,129 participants ages 24-32 from the U.S.-based National Longitudinal Study of Adolescent to Adult Health, we investigated the association between four factors of occupational cognitive stimulation (repetition, freedom, analytic skills, and social interaction) and young-adult episodic and working memory independent of childhood and young-adult SES, using linear regression. We adjusted for confounding due to sex, race/ethnicity, age, childhood cognition, and education. We further investigated effect measure modification of this association by sex in stratified regression models., Results: Overall, 1-unit increases in both occupational analytic skills and social interaction were significantly associated with 0.101 (95%CI: 0.28, 0.173) and 0.096 (95%CI: 0.032, 0.160) SD higher memory, respectively. However, when sex-stratified, among men, a 1-unit increase on the social interaction scale was associated with 0.16 (95%CI: 0.05, 0.27) SD higher memory, while there was no association among women., Conclusion: Our results indicate that even in adulthood, activities that stimulate the mind can contribute to improved cognitive function, and the most beneficial forms of occupational stimulation are those that use analytic skills and involve social interaction (particularly among young men)., (© 2022 The Authors.)

No research exists on how body mass index (BMI) changes with age over the full life span and social disparities therein. This study aims to fill the gap using an innovative life-course research design and analytic methods to model BMI trajectories from early adolescence to old age across 20th-century birth cohorts and test sociodemographic variation in such trajectories. We conducted the pooled integrative data analysis (IDA) to combine data from four national population-based NIH longitudinal cohort studies that collectively cover multiple stages of the life course (Add Health, MIDUS, ACL, and HRS) and estimate mixed-effects models of age trajectories of BMI for men and women. We examined associations of BMI trajectories with birth cohort, race/ethnicity, parental education, and adult educational attainment. We found higher mean levels of and larger increases in BMI with age across more recent birth cohorts as compared with earlier-born cohorts. Black and Hispanic excesses in BMI compared with Whites were present early in life and persisted at all ages, and, in the case of Black-White disparities, were of larger magnitude for more recent cohorts. Higher parental and adulthood educational attainment were associated with lower levels of BMI at all ages. Women with college-educated parents also experienced less cohort increase in mean BMI. Both race and education disparities in BMI trajectories were larger for women compared with men., Competing Interests: Competing interest statement: Y.C.Y. and B.L. are coauthors on a 2017 article.