Objective: In Western countries, the prevalence of childhood trauma (CT) ranges from 15 to 25%. CT might be indirectly associated with lower parental socioeconomic status and educational attainments. The aims of this cross-sectional study were fourfold: to assess prevalence of CT in a large sample of Iranian children; to compare the Iranian prevalence rates with those of Western countries; to explore gender-specific patterns; and to explore possible socioeconomic predictors. Method: The sample comprised 608 children (mean age 11.49 years, 51.5% females). All completed the Farsi version of the Trauma Symptoms Checklist for Children. Additionally, parents reported on their current employment status and highest educational level. Results: Trauma symptoms were reported by 20 of 295 boys and 23 of 313 girls. The overall prevalence was 7.1%. Child-reported trauma symptoms were not associated with parents’ socioeconomic status or highest educational level. Compared to prevalence findings from U.S. national surveys (ranging from 15-25% of children and adolescents), the prevalence among 11- and 12-year-olds in the present study was considerably lower. Conclusions: The overall prevalence of reported trauma symptoms among a large sample of Iranian children was unrelated to parents’ socioeconomic status, and was lower than that reported in U.S. surveys.

This paper presents a study on the gap dependent bifurcation behavior of an electro statically-actuated nano-beam. The sizedependent behavior of the beam was taken into account by applying the couple stress theory. Two small and large gap distance regimes have been considered in which the intermolecular vdW and Casimir forces are dominant, respectively. It has been shown that changing the gap size can affect the fundamental frequency of the beam. The bifurcation diagrams for small gap distance revealed that by changing the gap size, the number and type of the fixed points can change. However, for large gap regime, where the Casimir force is the dominant intermolecular force, changing the gap size does not affect the quality of the bifurcation behavior.

Using scaling methods, a single solution of Richards' equation (RE) will suffice for numerous specific cases of water flow in unsaturated soils. In this study, a new method is developed to scale RE for the soil water redistribution process. Two similarity conditions are required: similarity in the shape of the soil water content profiles as well as of the water flux density curves. An advantage of this method is that it is not restricted to a specific soil hydraulic model - hence, all such models can be applied to RE. To evaluate the proposed method, various soil textures and initial conditions were considered. After the RE was solved numerically using the HYDRUS-1D model, the solutions were scaled. The scaled soil water content profiles were nearly invariant for medium- and fine-textured soils when the soil profile was not deeply wetted. The textural range of the soils in which the similarity conditions are held decreases as the initial conditions deal with a deeply wetted profile. Thus, the scaling performance was poor in such a condition. This limitation was more pronounced in the coarse-textured soils. Based on the scaling method, a procedure is suggested by which the solution of RE for a specific case can be used to approximate solutions for many other cases. Such a procedure reduces complicated numerical calculations and provides additional opportunities for solving the highly nonlinear RE as in the case of unsaturated water flow in soils.