Adolescent Loneliness in 70 Countries Across Africa, America, and Asia: A Comparison of Prevalence and Correlates

Purpose: Emerging studies address adolescent loneliness a public health problem due to its negative associations with adverse health. However, evidence concerning adolescent loneliness and its correlation in nonwestern, low- and middle-income countries is scarce. This study examined the prevalence of loneliness and its correlates (i.e., sex, bullying victimization, and peer support) across 70 countries from five WHO regions. Methods: Data were collected from the Global School–based Student Health Survey of children aged 13–17 (2003–2018) years. Loneliness was defined as feeling lonely most of the time or always in the past 12 months based on self-reports. The prevalence of loneliness was estimated, and multivariable logistic regression ascertained prevalence ratios of correlates by country. Meta-analysis was used to examine regional and overall pooled estimates. Results: Among the 248,017 students included in the study, the overall prevalence of loneliness was 11.7% (95% confidence interval (CI): 10.6–12.7), with significant variations across countries. Girls (vs. boys prevalence ratio (PR = 1.4 95% CI: 1.3–1.4), students who experienced bullying victimization (PR = 2.2, 95% CI: 2.1–2.3), and students who reported a lack of close friends (PR = 1.8, 95% CI: 1.7–1.9) were at increased risk of experiencing loneliness. There was significant heterogeneity between countries for sex and lack of close friends but not for bullying victimization. Discussion: Adolescent loneliness is prevalent globally, especially in Africa and the Eastern Mediterranean. The considerable heterogeneity in its prevalence and correlates suggest that tailoring to the country context may benefit policy initiatives. Bullying may be a common intervention target in all countries

Bound states in d-density-wave phases

We investigate the quasiparticle spectrum near surfaces in a two-dimensional system with d-density-wave order within a mean-field theory. For Fermi surfaces with perfect nesting for the ordering wave vector of the d-density-wave, a zero energy bound state occurs at [110] surfaces, in close analogy with the known effect in d-wave superconducting states or graphite. When the shape of the Fermi surface is changed by doping, the bound state energy moves away from the Fermi level. Furthermore, away from half-filling we find inhomogeneous phases with domain walls of the d-density-wave order parameter. The domain walls also support low energy bound states. These phenomena might provide an experimental test for hidden d-density-wave order in the high-Tc cuprates.Comment: 6 pages, 5 figure

Numerical study of the lattice vacancy effects on the single-channel electron transport of graphite ribbons

Lattice vacancy effects on electrical conductance of nanographite ribbon are investigated by means of the Landauer approach using a tight binding model. In the low-energy regime ribbons with zigzag boundary provide a single conducting channel whose origin is connected with the presence of edge states. It is found that the chemical potential dependence of conductance strongly depends on the difference ($\Delta$) of the number of removed A and B sublattice sites. The large lattice vacancy with $\Delta\neq 0$ shows $2\Delta$ zero-conductance dips in the single-channel region, however, the large lattice vacancy with $\Delta=0$ has no dip structure in this region. The connection between this conductance rule and the Longuet-Higgins conjecture is also discussed