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When humans consume seafood contaminated by lipophilic polyether phycotoxins, such as azaspiracids (AZAs), the toxins are mainly leached and absorbed in the small intestine, potentially causing intestinal damage. In this study, human intestinal epithelial Caco-2 cells were used to investigate the adverse effects of azaspiracid-2 (AZA-2) on human intestinal epithelial cells. Cell viability, apoptosis, oxidative damage and mitochondrial ultrastructure were investigated, and ribonucleic acid sequence (RNA-seq) analysis was applied to explore the potential mechanisms of AZA-2 toxicity to Caco-2 cells. Results showed that AZA-2 significantly reduced the proliferation of Caco-2 cells in a concentration-dependent response, and the 48 h EC50 of AZA-2 was 12.65 nmol L−1. AZA-2 can induce apoptosis in Caco-2 cells in a dose-dependent manner. Visible mitochondrial swelling, cristae disintegration, membrane rupture and autophagy were observed in Caco-2 cells exposed to AZA-2. Reactive oxygen species (ROS) and malondialdehyde (MDA) content were significantly increased in Caco-2 cells after 48 h of exposure to 1 and 10 nmol L−1 of AZA-2. Transcriptome analysis showed that KEGG pathways related to cellular oxidative damage and lipid metabolism were affected, mainly including mitophagy, oxidative phosphorylation, cholesterol metabolism, vitamin digestion and absorption, bile secretion and the peroxisome proliferator-activated receptor signaling pathway. The cytotoxic effects of AZA-2 on Caco-2 cells may be associated with ROS-mediated autophagy and apoptosis in mitochondrial cells. Results of this study improve understanding of the cytotoxicity and molecular mechanisms of AZA-2 on Caco-2 cells, which is significant for protecting human health. [ABSTRACT FROM AUTHOR]

A 350MW power plant main steam and reheat hot steam pipe subsidence occurred in part of the pipe section, through field inspection, calculation and checking analysis, combined with pipeline support and hanger adjustment, load testing and elevation measurement and other means, the settlement of the pipe system to optimize the overall stress state of the pipe system. Through the thermal displacement of the pipe system support lifting point, the selection and calculation of the pipe system support hanger and the overall design state stress check of the pipe system, the design state is basically consistent with the check state. Through to the key node load tests have shown that small spring hanger selection is the primary cause of section settling, combined with the spring adjustment space and calculation results are part of the hanger. Finally, the settlement of pipeline is realized, main steam pipe at the same time a stress and secondary stress were achieved about 15% of the decline, piping stress has been further optimized.

Carbon nanotubes (CNTs) show significant advantages in the development of cold cathode X-ray tubes due to their excellent field emission performance; however, there are still some problems, such as short lifetime and the low emission current of large-area CNTs. In this paper, a front-grid carbon nanotube array model was established, and the electric field intensity near the tip of the CNTs' electric field enhancement factor was analytically calculated. A simulation model of a CNT three-dimensional field emission electron gun was established by using computer simulation technology (CST). The effects of grid wire diameter, grid aperture shape, and the distribution of grid projection on the cathode surface on the cathode current, anode current, and electron transmission efficiency were analyzed. The aperture ratio was used to evaluate the grid performance, and the simulation results show that the ideal aperture ratio should be between 65 % and 85 % . A grid structure combining a coarse grid and a fine grid was designed, which can make the electric field intensity around the grid evenly distributed, and effectively increased the cathode emission current by 24.2 % compared with the structure without the fine grid. The effect of grid aperture ratio on the electron transmission efficiency was tested. The simulation results and optimized structure can provide a reference for the grid design of cold cathode emission X-ray tubes. [ABSTRACT FROM AUTHOR]