Association between sleep habits and behavioral problems in early adolescence: a descriptive study

[Background] Sleep habits are related to children's behavior, emotions, and cognitive functioning. A strong relationship exists between sleep habits and behavioral problems. However, precisely which sleep habits are associated with behavioral problems remains unclear. Therefore, the purpose of this study is to clarify the relationship between sleep habits and behavioral problems in early adolescence. [Methods] This study used data from a larger longitudinal research, specifically, data from the year 2021. First-year junior high school students (12–14 years) in Japan were surveyed; their parents (N = 1288) completed a parent-report questionnaire. The main survey items were subject attributes, the Pittsburgh Sleep Quality Index (PSQI), and the Strength and Difficulties Questionnaire (SDQ). [Results] Of the 652 valid responses received, 604 individuals who met the eligibility criteria (no developmental disability in the child and completion of all survey items) were included in the analysis. To examine the relationship between sleep habits and behavioral problems, logistic regression analysis using the inverse weighted method with propensity score was conducted with sleep habits (sleep quality, time to fall asleep, sleep duration, sleep efficiency, sleep difficulty, use of sleeping pills, difficulty waking during the day, and sleep disturbances) as explanatory variables and behavioral problems (overall difficulty in SDQ) as objective variables. The propensity score was calculated by employing the logistic regression using the inverse weighted method based on propensity scores. Propensity scores were calculated based on gender, family structure, household income, and parental educational background. The results showed that behavioral problems tended to be significantly higher in the group at risk for sleep quality, sleep difficulties, daytime arousal difficulties, and sleep disturbances than in the group with no risk. [Conclusion] The results suggest that deterioration in sleep quality, sleep difficulties, daytime arousal difficulties, and sleep disturbances may increase the risk of behavioral problems in adolescents

Epitaxial growth and magnetic properties of Fe4−xMnxN thin films grown on MgO(0 0 1) substrates by molecular beam epitaxy

Epitaxial Fe4−xMnxN (x = 0, 1, 2, 3, and 4) thin films were successfully grown on MgO(0 0 1) single-crystal substrates by molecular beam epitaxy, and their crystalline qualities and magnetic properties were investigated. It was found that the lattice constants of Fe4−xMnxN obtained from X-ray diffraction measurement increased with the Mn content. The ratio of the perpendicular lattice constant c to the in-plane lattice constant a of Fe4−xMnxN was found to be about 0.99 at x2. The magnetic properties evaluated using a vibrating sample magnetometer at room temperature revealed that all of the Fe4−xMnxN films exhibited ferromagnetic behavior regardless of the value of x. In addition, the saturation magnetization decreased non-linearly as the Mn content increased. Finally, FeMn3N and Mn4N exhibited perpendicular anisotropy and their uniaxial magnetic anisotropy energies were 2.2 × 105 and 7.5 × 105 erg/cm3, respectively

Structural characterization and magnetic properties of L10-MnAl films grown on different underlayers by molecular beam epitaxy

We grow MnAl films on different underlayers by molecular beam epitaxy (MBE), and investigate their structural and magnetic properties. L10-ordered MnAl films were successfully grown both on an MgO(0 0 1) single-crystalline substrate and on an Mn4N(0 0 1) buffer layer formed on MgO(0 0 1) and SrTiO3(0 0 1) substrates. For the MgO substrate, post rapid thermal annealing (RTA) drastically improved the crystalline quality and the degree of L10-ordering, whereas no improvement in the crystallinity was achieved by altering the substrate temperature (TS) during MBE growth. However, high-quality L10-MnAl films were formed on the Mn4N buffer layer by simply varying TS. Structural analysis using X-ray diffraction showed MnAl on an MgO substrate had a cubic structure whereas MnAl on the Mn4N buffer had a tetragonal structure. This difference in crystal structure affected the magnetic properties of the MnAl films. The uniaxial magnetic anisotropy constant (Ku) was drastically improved by inserting an Mn4N buffer layer. We achieved a perpendicular magnetic anisotropy of Ku = 5.0 ± 0.7 Merg/cm3 for MnAl/Mn4N film on MgO and 6.0 ± 0.2 Merg/cm3 on STO. These results suggest that Mn4N has potential as an underlayer for L10-MnAl

Molecular beam epitaxy growth of Mn4−xNixN thin films on MgO(0 0 1) substrates and their magnetic properties

We grew Mn4−xNixN epitaxial thin films on MgO(0 0 1) by molecular beam epitaxy, as well as studied their crystalline qualities and magnetic properties. The films were decomposed into Ni8N or Mn-Ni alloys when x ≥ 2, as confirmed by X-ray diffraction and reflection high-energy electron diffraction, but this decomposition was mitigated by reducing the substrate growth temperature. The lattice constants decreased with increased Ni substitution except when the Mn ratio was high, while the crystal orientation tended to degrade. The magnetic properties were measured via vibrating sample magnetometer, and it was found that the saturation magnetization (MS) and perpendicular magnetic anisotropy (PMA) diminished with a small amount of Ni substitution. Specifically, the MS value was remarkably decreased from 86.3 ± 1.1 emu/cm3 (Mn4N) to 19.0 ± 0.5 emu/cm3 (Mn3.85Ni0.25N), and the magnetic anisotropy constant was decreased from approximately 0.94–0.027 Merg/cm3, respectively. The PMA vanished with further Ni substitution. Ultimately, a small MS and a PMA were simultaneously achieved with a small amount of Ni substitution. These properties support spin transfer torque, which can be applied to the emerging non-volatile memory devices using domain wall motion