The association between posttraumatic stress disorder (PTSD) symptoms and suicide ideation was examined in a sample of 2,298 child survivors of the Wenchuan earthquake. Results indicated that intrusion, avoidance, hyperarousal symptom clusters, and PTSD total score were significantly associated with suicide ideation. Except for intrusion, other measures of PTSD remained as statistically significant correlates of suicide ideation even after controlling for age, gender, direct exposure, indirect exposure, and depression. Furthermore, results showed that PTSD symptoms had an indirect influence on suicide ideation that was mediated by depression. The findings suggest that avoidance and hyperarousal symptom clusters of PTSD may be two important indicators of suicide ideation among child survivors of the Wenchuan earthquake. Implications of the results for intervention and prevention of suicide behavior are discussed.

The previously developed bistable amphoteric native defect (BAND) model is used for a comprehensive explanation of the unique photophysical properties and for understanding the remarkable performance of perovskites as photovoltaic materials. It is shown that the amphoteric defects in the donor (acceptor) configuration capture a fraction of photoexcited electrons (holes) dividing them into two groups: higher-energy bright and lower-energy dark electrons (holes). The spatial separation of the dark electrons and dark holes and the k-space separation of the bright and dark charge carriers reduce electron-hole recombination rates, emulating the properties of an ideal photovoltaic material with a balanced, spatially separated transport of electrons and holes. The BAND model also offers a straightforward explanation for the exceptional insensitivity of the photovoltaic performance of polycrystalline perovskite films to structural and optical inhomogeneities. The blue-shifted radiative recombination of bright electrons and holes results in a large anti-Stokes effect that provides a quantitative explanation for the spectral dependence of the laser cooling effect measured in perovskite platelets.