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The ability of purified multi-walled carbon nanotubes (MWCNTs) to adsorb diclofenac and triclosan in aqueous solutions was examined by equilibrium, kinetic, and thermodynamic parameters. The results of SEM image, BET specific surface area, XRD, TGA, and FTIR spectra indicated that the characteristics of MWCNTs were improved after purification with nitric acid. Batch experiments illustrated that the removal efficiency of diclofenac and triclosan depended mostly on the MWCNTs dosage, temperature, ion concentration, pH, and initial concentration. The maximum adsorption capacity for diclofenac and triclosan under optimum conditions was 19.9 mg g⁻¹ and 19.7 mg g⁻¹, respectively. The equilibrium data showed that adsorption behavior of diclofenac and triclosan could be described more reasonably by the pseudosecond-order model. Thermodynamic simulation showed that the adsorption was fitted with Langmuir and Freundlich adsorption isotherm, and the thermodynamic parameters revealed the process to be exothermic and spontaneous. In addition, the adsorption behavior of MWCNTs in the binary solution was successfully predicted using the ideal adsorbed solution theory. Finally, the adsorption mechanism was discussed.
In large lakes, serious sedimentation and pollution of bottom sediments has occurred in China owing to the neglect of effective protection and management. Thus, sediment management, acting as an important aspect of lake management, should be performed in lake systems. The goal of this study was to determine sediment management framework, and take a physicochemical and socioeconomic approach for sediment management. Sediment quantity and quality analysis was developed, sources of sediment and associated contaminants were analyzed, and management methods such as the ecological water network, source control, and local dredging and sediment treatment were researched respectively. Cost-benefit analysis of chemical-mechanical dewatering and subsequent sediment treatment has been performed as an example. The work in the study was aimed at providing reference for sustainable sediment management of urban lake systems in China.
In this paper, a numerical code for predicting the hydrodynamic performance of vertical-axis tidal turbine array is developed. The effect of the tip speed ratio, solidity, and preset angle on the hydrodynamic performance are discussed using a series of calculations. The load principle of the rotor and the variation principle of the turbine power coefficient are studied. All these results can be considered as a reference for the design of vertical-axis tidal turbines
Key message This study focuses on the impact of carbohydrate metabolism and endogenous polyamines levels in leaves of cucumber seedlings under salt stress by exogenous BRs.
Brassica napus is a polyploid of certain research and economical value. Resynthesizing B. napus with diploid B. rapa and B. oleracea is essential for Brassica research because of the limited genetic background of B. napus. Considering that polyploids possess better agronomic traits and resistance compared with the corresponding diploids, we investigated drought tolerance after polyploidization of B. napus and revealed the epigenetic differences between polyploids and diploids. After drought stress, B. rapa and first-generation of synthesized hybrids (F1) were more wilted than B. oleracea and F2–F4 generations. However, the relative water content and water retention in F1 were better than others after drought stress. The increased number of partially opened and closed stomata in F1 was not as significant as that in F2 and F3, but stomata density in F1 was lower than F2, and the stomatal size in F1 was significantly reduced than F3. Physiological parameters varied among different generations of B. napus and diploid parents, and most of these parameters in hybrids were higher than B. rapa and lower than B. oleracea. However, the peroxidase activity in F3 and F4 was significantly higher than both parents, and the malondialdehyde content in F3 and F4 was lower than both parents, indicating that F3 and F4 might be more adaptive to oxidative stresses than other generations. DNA methylation level was decreased in F2 and F3 compared with F1, and then increased in F4. Methylation-sensitive amplified polymorphism analysis revealed that DNA methylation and demethylation broadly happened after drought stress. The methylation and demethylation level was F1 > F4 > B. oleracea > F2 > F3 > B. rapa and B. rapa > F4 > F3 > F2 > B. oleracea > F1, respectively. The epigenetic changes under drought stress might be related to the different stress tolerances during B. napus polyploidization.
The polymorphic markers of nuclear SSR (simple sequence repeat), SNP (single nucleotide polymorphism)/ InDel (insertion–deletion length polymorphism), and cpSSR (chloroplast SSR) were used to evaluate the genetic diversity of 52 trifoliate oranges and their relatives. The two genomic DNA-based markers produced high values of PIC (polymorphic information content) at 0.45 for SNP/InDel and 0.32 for nuclear SSR, indicating that there is a large diversity of genetic variationvwithin the trifoliate oranges. Three UPGMA (unweighted pair-group method with arithmetic means) dendrograms were generated based on the results of three marker systems. At 0.76 of coefficient, all of Poncirus accessions were clustered into one group, except the 74-1 Early Poncirus, one of the three precocious trifoliate oranges, which was placed separately into another group by nuclear SSR. At a higher coefficient, the trifoliate oranges were discriminated into 4, 6 and 6 groups by nuclear SSR (0.86), SNP/InDel (0.95), and cpSSR (0.95), respectively. The results revealed that three precocious trifoliate oranges were originated from different sources. Hubei Early Poncirus and Beibei Early Poncirus were the asexual mutants of different trifoliate oranges, and 74-1 was probably a sexual hybrid. The present study also indicated that ‘Zhiwenzhou,’ a diploid chimera of trifoliate orange and Satsuma is more closely related to Satsuma rather than to trifoliate orange, which is in concordance with the results of morphological observation.
Heat stress is a major environmental stress that limits plant growth and yield worldwide. The present study was carried out to explore the physiological mechanism of heat tolerant to provide the theoretical basis for heat-tolerant breeding. The changes of leaf morphology, anatomy, nitrogen assimilation, and carbohydrate metabolism in two wucai genotypes (WS-1, heat tolerant; WS-6, heat sensitive) grown under heat stress (40°C/30°C) for 7 days were investigated. Our results showed that heat stress hampered the plant growth and biomass accumulation in certain extent in WS-1 and WS-6. However, the inhibition extent of WS-1 was significantly smaller than WS-6. Thickness of leaf lamina, upper epidermis, and palisade mesophyll were increased by heat in WS-1, which might be contributed to the higher assimilation of photosynthates. During nitrogen assimilation, WS-1 possessed the higher nitrogen-related metabolic enzyme activities, including nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase (GOGAT), and glutamate dehydrogenase (GDH), which were reflected by higher photosynthetic nitrogen-use efficiency (PNUE) with respect to WS-6. The total amino acids level had no influence in WS-1, whereas it was reduced in WS-6 by heat. And the proline contents of both wucai genotypes were all increased to respond the heat stress. Additionally, among all treatments, the total soluble sugar content of WS-1 by heat got the highest level, including higher contents of sucrose, fructose, and starch than those of WS-6. Moreover, the metabolism efficiency of sucrose to starch in WS-1 was greater than WS-6 under heat stress, proved by higher activities of sucrose phosphate synthase (SPS), sucrose synthase (SuSy), acid invertase (AI), and amylase. These results demonstrated that leaf anatomical alterations resulted in higher nitrogen and carbon assimilation in heat-tolerant genotype WS-1, which exhibited a greater performance to resist heat stress.
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