Thermoelectric materials can be used to convert waste heat into electrical energy, which is considered to be a cleaner form of energy that reduces carbon dioxide and greenhouse gas emissions.

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BackgroundIn China, children under 18 years old who are left at rural residences for at least 6 months by either one or both of their parents migrating to work in cities are called “left-behind children (LBC)”. Due to restricted family support, they are at a greater risk of developing depressive symptoms than non-left-behind children (NLBC). The objective of this study is to explore how depressive symptoms and stress induced by negative life events such as interpersonal conflicts, punishment and loss, as well as their relationships vary for LBC with different left-behind-related characteristics.MethodsUsing data from a large school-based survey conducted in Chongqing between December 2012 and June 2013, we first identified the differences in depressive symptoms and negative-event-induced stress between LBC and NLBC, and then analyzed the variances among LBC with different left-behind-related characteristics. The data was analyzed with Chi-square test, MANCOVA, ANCOVA, ANOVA, T-test and hierarchical multiple regression analyses.ResultsWe found that LBC were more stressed when experiencing negative events and had more depressive symptoms than NLBC. Children left behind by both parents were most depressed. Negative-event-induced stress and communication on life difficulties with migrant parents were risk factors for depressive symptoms, whereas adequate communication on academic performance or children’s feelings was a protective factor against depressive symptoms. Communication duration and frequency, communication by visiting, communication on academic performance, life difficulties and children’s feelings moderated the relationship between stress and depressive symptoms, respectively. Duration of separation, communication duration and frequency, communication on academic performance, learning difficulties and children’s feelings moderated the relation between the type of parental migration and depressive symptoms, respectively.ConclusionsOur findings suggest that children left behind by both parents should be the focus of public attention for their higher susceptibility to stress-related depression. To help LBC stay mentally healthy, governments need to formulate regulations contributing to LBC’s family reunion, communities need to involve more residents to attend LBC as “surrogate parents” and teach migrant parents to communicate with LBC properly, and schools need to teach LBC how to deal with stress and communicate with migrant parents.

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