RESUMEN
This study aims to improve polyurethane-based coating by modified zirconium oxide and aluminum oxide nanoparticles for preparing thin polymeric heat insulation coatings. In the first step, the nanoparticles were chemically modified with the silane coupling agent. Then, three different weight percent of modified nanoparticles (1, 3, and 5% w/w) were mixed with polyurethane, to prepare the nanocomposites, which were coated on metallic plate samples. Then, these plates are used to measure the radiation heat transfer coefficients, absorption coefficient in a region of short wavelengths (UV/VIS/NIR), the emissivity coefficient, and thermography of the samples in a region of long wavelengths (IR). Results showed that by adding the modified nanoparticles to the polyurethane matrix, absorption was decreased and the emissivity coefficient was increased. According to the thermography results, it was observed that the surface temperature of both samples with 3% w/w of nanoparticles had the minimum temperature compare to others. Minimum heat surface observed for 3% w/w of modified nano zirconium oxide.
RESUMEN
Todays, with the industrialization of human societies, pollution of aquatic ecosystems with plastics derivatives are a serious concern, affecting the life of their organisms. The present study was conducted to investigate the size effects of micro-plastic, polystyrene on some physiological lesions of the goldfish, Carassius auratus. Fish were exposed to two sizes (0.25 and 8 µm) polystyrene at different environmentally relevant concentrations. The exposure trial was done in two steps. First, fish exposed to a stable concentration of 300 mg/L polystyrene for 168 h. Gill, intestine, and liver tissues were sampled every 24 h to investigate the accumulation of polystyrene. Then, fish were exposed in three replicates to 0 (control), 0.05, 0.5, and 5 mg/L polystyrene in two sizes of 0.25 and 8 µm for 28 days. After the exposure period, gill, liver, and intestine tissues were sampled for histological study, also, serum samples were collected for biochemical assays. Fluorescent microscope observations confirmed the accumulation of polystyrene in tissue samples with time. In addition, histological lesions were found in the liver, intestine, and gill of the exposed fish. The severity of lesions showed a size and dose-dependent pattern. Polystyrene induced the antioxidant system of exposed fish through elevating the levels of SOD and CAT activity and significant difference in expression of antioxidant related genes (CAT, SOD and HSP70). In conclusion, the results of the present study confirmed the toxic effects of microplastic, polystyrene on goldfish.
