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We studied the feasibility of two advanced oxidation processes (AOPs), including the Fenton and ozonation processes, and a conventional sequence batch reactor (SBR) for treating wastewater from polyurethane manufacturing. The results showed that the SBR achieved a COD removal rate of 93.3% when the influent COD concentration was 1,600 mg·L-1, which was 22.1 and 522.1% higher than the best results by the Fenton (H2O2/COD = 0.0623 mM·g-1 and Fe2+/COD = 0.0102 mM·g-1) and ozonation (1 g·L-1, 45 min) processes. A COD removal rate of 90.6% for SBR was achieved after an aeration time of 12 h, and the COD degradation rate was similar to that of a zero-order reaction. A study of the SBR drivers suggested that air stripping and self-volatilization contributed to the higher COD removal rates obtained in this process. This study shows that a single SBR is practical for treating small amounts of polyurethane manufacturing wastewater, and that it had a higher ability to remove COD and resist feeding load shock than the other methods tested. But the potential risks of volatile organic compounds (VOCs) stripping out during the aeration process should be of concern.
Cucumber (Cucumis sativus L.), a biologically, agriculturally, and economically important vegetable crop consumed worldwide. Catechins (Cs) are the main astringent substances that affect the oral sensory quality of cucumber fruit, and they exhibit potential human health benefits in the amelioration of chronic diseases. However, little is known about the primary components of Cs or their regulatory mechanisms in cucumber. In this study, dynamic changes in C levels and the expression patterns of C-related genes in the peel and flesh of cucumber inbred line ‘YB’, which is strongly astringent during the early fruit development period, were examined. Only three types of Cs, gallocatechin, C and epigallocatechin gallate, were detectable in cucumber fruit, and their contents decreased with fruit development. Gallocatechin was the major C and was present in significantly greater concentrations in peel than in flesh. The expression profiles of 38 genes related to C biosynthesis were investigated by qRT-PCR. We hypothesized that CsPAL3, CsPAL5, CsC4H1, Cs4CL2, CsCHS2, CsCHI2, CsDFR2, CsF3H3, and CsANS are the important C biosynthesis regulators in cucumber fruit. The isolation of genes encoding biosynthetic enzymes provides important molecular resources for further genetic manipulations of C biosynthesis in cucumber.
The present study showed the toxicity caused by heavy metal and its detoxification responses in two desert plants: perennial Peganum harmala and annual Halogeton glomeratus. In pot experiments, 1-month-old seedlings were grown under control and three levels of combined heavy metal stress. Seedling growth as well as heavy metal accumulation, antioxidative enzymes [superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX)] activities and the contents of malondialdehyde (MDA), and hydrogen peroxide (H₂O₂) in leaves was examined after 2 months of heavy metal exposure. Compared with H. glomeratus, growth of P. harmala was more severely inhibited. In leaves, the heavy metal accumulation pattern in both the plants was dose-dependent, being more in H. glomeratus. H. glomeratus exhibited a typical antioxidative defense mechanism, as evidenced by the elevated activities of all the three enzymes tested. P. harmala exhibited a different enzyme response pattern, with a significant reduction in CAT activity, and elevated SOD and APX activities, but significantly elevated APX activity was only at the lowest heavy metal concentration. MDA and H₂O₂ contents were significantly enhanced in leaves of heavy metal-treated P. harmala, but in H. glomeratus were elevated only at the highest heavy metal treatment. These results indicated that H. glomeratus had a greater capacity than P. harmala to adapt to oxidative stress caused by heavy metal stress, and antioxidative defense in H. glomeratus might play an important role in heavy metal tolerance.
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