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The characteristics of landfilled municipal solid waste have great influence on the design, operation, and management of landfills, affecting settlement, slope stability, and leachate/gas well integrity. Through analysis and study we observed that the landfill method is widely used to dispose of municipal solid waste (MSW), especially in developing countries. The research results of MSW landfill properties are different due to waste inhomogeneity. In this paper, MSW physical composition, unit weight, and permeability coefficient of landfills in several countries were reviewed and discussed. Landfilled MSW has strong regional and temporal characteristics. Landfilled MSW of developing countries has high organic content ranges from 75.00% to 97.15%. The organic contents in landfills of most developed regions are relatively small. The unit weight ranged from 4.9-17.8 kN/m³ and the permeability coefficient ranged from 3.5×10⁻² cm/sec to 5.0×10⁻⁸ cm/sec within 60 m. In the process of waste degradation, MSW physical composition, unit weight, and permeability coefficient are changed. Waste classification improves the recovery and utilization of landfill and reduces the amount of waste, which affects the characteristics of landfilled MSW. Thus, strengthening waste classification, recycling, and recovery of MSW is significant and meaningful for construction, operation, and management of landfills.
A number of imprinted genes have been observed in plants, animals and humans. They not only control growth and developmental traits, but may also be responsible for survival traits. Based on the Cox proportional hazards (PH) model, we constructed a general parametric model for dissecting genomic imprinting, in which a baseline hazard function is selectable for fitting the effects of imprinted quantitative trait loci (iQTL) genotypes on the survival curve. The expectation–maximisation (EM) algorithm is derived for solving the maximum likelihood estimates of iQTL parameters. The imprinting patterns of the detected iQTL are statistically tested under a series of null hypotheses. The Bayesian information criterion (BIC) model selection criterion is employed to choose an optimal baseline hazard function with maximum likelihood and parsimonious parameterisation. We applied the proposed approach to analyse the published data in an F2 population of mice and concluded that, among five commonly used survival distributions, the log-logistic distribution is the optimal baseline hazard function for the survival time of hyperoxic acute lung injury (HALI). Under this optimal model, five QTL were detected, among which four are imprinted in different imprinting patterns.
Using a CIRAS-2 portable photosynthesis system, the photosynthesis, transpiration, and light responses of Aralia elata were studied under different soil moisture values with the aim of understanding the adaptability of this species to different light and soil water conditions. The results showed that the net photosynthetic rate (Pn), transpiration rate (Tr), and water use efficiency (WUE) of A. elata varied in response to different levels of photon flux density (PFD). When PFD was between 800 and 1,800 μmol m⁻² s⁻¹, Pn changed little in response to the increasing light intensity, whereas Tr decreased gradually and WUE increased significantly. Light saturation point (LSP) and light compensation point (LCP) were approximately 800 and 30 μmol m⁻² s⁻¹, respectively. The soil water content had little effect on LSP and LCP, but significantly affected photosynthetic quantum efficiency (Φ) and dark respiratory rate (Rd). By defining the Pn and WUE as the indexes of plant productivity and soil water efficiency, respectively, the soil moisture availability and productivity of A. elata were graded and evaluated, and six types of soil water grading were established. Thus, at RWC values between 44.5% and 79.2% in which both Pn and WUE were maintained at a high level, the results can provide theoretical support for highly productive and efficienct water management in A. elata.
The karst habitats of southwestern China are characterized by a highly heterogeneous distribution of water resources. We hypothesized that the clonal integration between connected ramets of the clonal vine Ficus tikoua was an important adaptive strategy to the patchy distribution of water resources in these habitats. We grew ramet pairs (each consisting of a parent and an offspring ramet) in both homogeneously and heterogeneously watered conditions. The offspring ramets were wellwatered, whereas their connected parent ramets were randomly assigned to four water treatments: well-watered, mild water stress, moderate water stress, and severe water stress. Increasing water stress decreased leaf water potential, relative water content, net assimilation rate, maximum quantum yield of PSII (Fv/Fm), and biomass of the parent ramets. Subjecting the parents to water stress significantly increased root biomass and root mass ratio (RMR) of their offspring ramets. Exploitation of plentiful water resources through the increased adventitious roots connected to another soil patch permitted the complete restoration of water relations and photosynthetic capacity of offspring ramets after an initial depression. Water relations and gas exchange of the parents were not affected by the water supply to their connected offspring ramets, suggesting that offspring ramets hardly exported water to the stressed parents. However, net assimilation rate and proline content of the offspring ramets increased when they were connected to water-stressed parents. The compensatory photosynthetic responses of offspring ramets connected to stressed parents revealed an increasing trend as the experiment progressed. Morphological and physiological plasticity of F. tikoua in response to heterogeneous water resources allow them to adapt to karst habitats and be suitable candidates for vegetation restoration projects.
In this study, we used poplar as a model plant and investigated the effects of gaseous nitrogen dioxide (NO2, 4 ll 1-1) on stomatal conductance, photosynthesis, dark- and photorespiration of Populus alba 9 Populus berolinensis hybrid leaves using the photosynthesis system and scanning electron microscope technique. The results showed that net photosynthetic rates were significantly reduced in leaves exposed to 4 ll 1-1 NO2 for 48 h as compared with leaves exposed to ambient carbon dioxide 380 ll 1-1 and ambient NO2\0.1 ll 1-1 (the control) and the leaves exposed for 14 h. The decline of net photosynthetic rate was caused mainly by NO2 treatment. Dark respiration rates were dependent on co-action of the two factors (leaf temperature and NO2 treatment time). Postillumination carbon dioxide burst in the exposed leaves occurred at 13–15 s after turning the light off, whereas this phenomenon was absent in the control leaves.
There is significant genetic diversity within a species in terms of nitrogen utilization efficiency (NUtE), and genotypes with higher NUtE can help reduce nitrogen (N) fertilization rates and therefore mitigate ecological problems. Determining various characteristic differences in the NUtE of crops is helpful for dissecting the mechanisms of N use efficiency within crop species. In this study, a pot experiment, as well as a hydroponic experiment, was conducted to investigate the differences in oilseed rape biomass, N nutrition traits, N metabolism enzyme activity, root exudates and root RNA expression levels at the vegetative stage between the high and low NUtE genotypes. NUtE was negatively correlated with leaf SPAD values (− 0.341**), N accumulation (− 0.362*) and total biomass (− 0.395**), while there was no significant correlation between NUtE and N content (− 0.150 ns). The root biomass; primary root length and root activity; root N content and accumulation; transpiration rate, and stomatal conductance; root nitrate reductase, glutamine synthetase, and glutamate synthetase activity; the number of alkanes; expression levels of BnNRT1.1 and BnNRT2.1 of the low NUtE genotypes were higher than those of the high NUtE ones. It was concluded that during the vegetative growth stage, compared with the high NUtE oilseed genotypes, low NUtE oilseed genotypes demonstrate higher physiological activity or stronger growth potency at the vegetative growth stage.
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