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Purpose Recent research has identified a relationship between perceived stress and problematic smartphone usage. However, little is known about the underlying mediating and moderating mechanisms. The present study aimed to test the relationship between perceived stress and problematic smartphone usage as well as the mediating role of online social support and the moderating role of perceived social support among Chinese undergraduates. Patients and Methods A sample of 1123 college students participated in the study. The Perceived Stress Scale, Mobile Phone Addiction Index Scale, Online Social Support Questionnaire, and Perceived Social Support Scale were used. Results Perceived stress was significantly and positively associated with problematic smartphone usage, and online social support partially mediated the relationship between perceived stress and problematic smartphone usage. Moderated mediation analysis suggested that perceived social support moderated the association between perceived stress and online social support. This relationship became stronger for college students with lower levels of perceived social support. Conclusion The results of this study can contribute to a better understanding of how perceived stress increases the risk of problematic smartphone usage. The importance of reducing online social support and enhancing perceived social support in preventing undergraduates’ problematic smartphone usage is highlighted. The findings should be taken with caution given the convenience sampling and cross-sectional study design.

Background and Aims: This three-wave longitudinal study investigated the effects of stressful life events on problematic smartphone use and the mediating roles of mental health problems (i.e., depressive symptoms, poor sleep quality, and suicidal ideation) in Chinese undergraduate students.Methods: A total of 197 undergraduate students completed the three-wave surveys. Their severity of stressful life events, mental health problems, and problematic smartphone use were assessed.Results: Regression analyses revealed that stressful life events at T1 was significantly associated with problematic smartphone use at T3. Mediation analyses showed that mental health problems (i.e., depressive symptoms, poor sleep quality, and suicidal ideation) at T2 fully mediated the association between stressful life events at T1 and problematic smartphone use at T3 (B = 0.042, 0.034, and 0.022, respectively).Conclusions: The present study revealed that stressful life events and mental health problems (i.e., depressive symptoms, poor sleep quality, and suicidal ideation) are predictors of problematic smartphone use in Chinese college students.

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-Herein, we report on the joint toxicity of four fluoroquinolones and two tetracyclines (β-diketone antibiotics-DKAs) to zebrafish based on a series of toxicological endpoints and histopathological observations. A positive dose-dependence was observed in DKA-exposure groups with a 72-hpf EC 50 of 130.3 mg/L for hatching rate, 120-hpf LC 50 of 149.8 mg/L, and 120-hpf EC 50 of 135.1 mg/L for malformation rate. When zebrafish at 60 dpf were exposed to a series of DKA concentrations (45, 60 and 90 mg/L) for 7, 14 and 21 days, creatine kinase and AChE activities were significantly induced, and intracellular malondialdehyde increased in all treatments except for the 45 mg/L treatment. The transcription levels of AHRRa from livers were significantly (p < 0.05) up-regulated in all treatments after two months of DKA exposure. CKma expression from skeletal muscle was significantly down-regulated in the 90 mg/L treatment. A remarkable down-regulation of CYP3A65 was observed in the 60 mg/L treatment. DKA exposure resulted in severe tissue damage including mitochondria swelling, reduction of mitochondrial cristae, deepening of mitochondrial cristae bands, and decreasing and even disappearance of the rough endoplasmic reticulum. Total sperm motility was decreased by ca. 30% due to DKA exposure. These results provide important information for toxicity and health risks due to mixed DKA exposure in aquatic environments.