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In the present study, (NH₄)₂S₂O₃ extraction methods were applied to assess bioaccumulation of methylmercury (MeHg) in rice grains, and inorganic mercury (IHg) concentrations in rice leaves were analyzed during the rice growing time to access the bioaccumulation of IHg in rice leaves. The results show that the IHg concentrations in leaves increased in the rice harvest stage, indicating that the limit or no IHg was migrated to the rice grain. Also, the Hg-contaminated leaves may potentially cause the input of ‘new Hg’ into soil, leading to a vicious Hg pollution cycle in a rice paddy system. Our results indicated that MeHg concentrations in leaves could not be used to predict the MeHg bioaccumulation in rice grain. Meanwhile, MeHg transferred capability from soil to leaves decreased with time, which could be the common effect of the decreased soil MeHg bioavailability and translocation of MeHg from leaves to rice grains.
In underwater unmanned vehicles, complex acoustic transducer arrays are always used to transmitting sound waves to detect and position underwater targets. Two methods of obtaining low-sidelobe transmitting beampatterns for acoustic transmitting arrays of underwater vehicles are investigated. The first method is the boundary element model optimization method which used the boundary element theory together with the optimization method to calculate the driving voltage weighting vector of the array. The second method is the measured receiving array manifold vector optimization method which used the measured receiving array manifold vectors and optimization method to calculate the weighting vector. Both methods can take into account the baffle effect and mutual interactions among elements of complex acoustic arrays. Computer simulation together with experiments are carried out for typical complex arrays. The results agree well and show that the two methods are both able to obtain a lower sidelobe transmitting beampattern than the conventional beamforming method, and the source level for each transmitting beam is maximized in constraint of the maximum driving voltage of array elements being constant. The effect of the second method performs even better than that of the first method, which is more suitable for practical application. The methods are very useful for the improvement of detecting and positioning capability of underwater unmanned vehicles
Sawdust is the most popular matrix used in bio-toilets, but the wood resource is scarce in many countries. The aim of our research is to explore the possibility to select cornstalks as alternative matrix in bio-toilets. The experiments were conducted to compare the biodegradation effects of feces mixed with sawdust and cornstalk by monitoring the main physical and chemical parameters. In both tests, temperature, moisture content, and pH were all maintained within a feasible range during biodegradation. The weight reduction was very remarkable, and TN, TP, and TK all significantly increased (although the loss of NH3-N occurred). These results indicated the feasibility to use cornstalks as a bio-toilet matrix, which provides an effective way to reutilize agricultural waste and helps to popularize the application of bio-toilets.
Abstract: Currently, one of the challenging tasks for Chinese engineering community is to construct a water-way crossing of Qiongzhou Strait in the south of China. This project has also gained significant attention from researchers in academia. The study presented herein is centered on providing a feasible solution for ac-complishing the above mentioned task. Initially, different alternatives as the best location, judged on the basis of the environmental constraints, are studied. Then the comparison between various structural solutions such as suspension bridge, submarine tunnel and SFT is presented. Among these solutions, SFT appears to be a very suitable alternative for Qiongzhou Strait waterway crossing due to distinctive advantages, like shorter distance, lower cost, less impact on environment and navigation, etc. Based on the appropriate conception for cross sections, support systems, materials, joints and connection schemes, a numerical model is developed by means of the FEM software ANSYS/Fluent. It is then analyzed under the influence of different environmental loading conditions, varying the wave heights and lengths, current velocities and water depths, which are typical in Qiongzhou Strait. The numerical results reveal that the proposed SFT solution performs safely even under extreme weather conditions
Discovering how to best protect one of the most endangered animals in the world, giant pandas, has always been an important project in ecological studies. Moreover, researching the living environments of giant pandas and how to recover them is one of the most important elements to these studies. In order to more effectively protect the giant pandas and their habitats, we studied the changing of Xiaohegou nature reserve landscape for 20 years, from 1994 to 2014, based on the landscape ecology theory and “3S” techniques (geographic information systems, GIS; remote sensing, RS; global navigation satellite system, GNSS). Specifically, this paper analyzes factors such as landscape fragmentation, connectivity, disturbance degree, landscape diversity, etc. Accordingly, the research presented divides giant panda habitat into nine landscape types that include: evergreen deciduous broad-leaved mixed forest, secondary broadleaved forest, mixed coniferous and deciduous broad-leaved forests, and coniferous forest, et al. The results show that: 1) before establishing the Xiaohegou Nature Reserve in 1993, deforestation was a serious problem, as the results from the 1994 landscape fragmentation suggest. 2) Logging was rampant before the implementation of the national natural forest protection project that began in 1998. Severe damage was observed on the coniferous forest in giant panda habitat. Yet, from the high level of fragmentation that was observed in the connectivity of giant panda habitat, the results suggest 1994 was the worst. After more than ten years of recovery, from 2001 to 2014, the situation of regarding the habitat’s connectivity appears better than previous years. 3) The habitat has been impacted heavily by human disturbance from 1994 to 2001, although it has shown a slight decrease in this tendency from 2001 to 2014. 4) In the past 20 years, both the diversity and evenness indexes are showing a slow drop tendency. 5) This paper analyzes the changing situation regarding the land category evolution of giant panda habitats. Coniferous forests, the main habitat of giant pandas, decreased 6.37 hm² during these 5 years, with a rate of decrease at 1.27 hm² per annum from 1994 to 1998. In the years that followed, however, the coniferous forest recovered 4.21 hm² over the course of 15 years at the rate of 0.28 hm² per annum from 1999 to 2014, providing a reference for further nature reserve policy development.
Three types of alpine plant species,Carex montis-everestii,Quercus aquifolioidesandStipa capillacea, along an altitudinal gradient of 3005–5025 m on the Tibetan Plateau, were chosen to test the generality of the hypothesis that foliar carbon isotope composition (δ¹³C) of C3 plants increases significantly with altitude and to determine climate drivers shaping its altitudinal pattern. Temperature and relative humidity showed significantly negative correlations with altitude; however, precipitation and soil water potential remained unchanged with altitude. Foliar δ¹³C of C. montis-everestii,Q. aquifolioides,S. capillaceaalone or combined together did not significantly increase with altitude, which does not support the leading hypothesis of increased foliar δ¹³C with altitude. There was no difference in foliar δ¹³C among all three species. Multi-factor correlation analyses showed that temperature, precipitation and relative humidity alone did not affect foliar δ¹³C ofC. montis-everestiiandS. capillacea, but conferred significant effects on foliar δ¹³C of Q. aquifolioides.
The objective of this study was to determine and compare the effect of five different pretreatments including sulfite treatment (ST), osmotic dehydration (OD), steam blanching (SB), s team blanching plus osmotic dehydration (SB+OD), and ultrasound treatment (UT), on the microwave vacuum drying (MVD) kinetics, the physicochemical properties, and sensory quality of the apple slices. The results showed that the p retreatments prior to MVD could reduce the drying time of apple slices by 25–45% as compared to the non-pretreated apple slices, and the drying time in the SB+OD apple slices sample was shortest. Whether pretreated or not, MVD process was controlled by diffusion and characterized by a two-stage falling-rate drying. As calculated according to the Fick’s law of diffusion, the moisture diffusivities (Deff) ranged from 1.64×10¯⁸ to 3.46×10¯⁸ m2 /s. Different pretreatment methods had a signifi cant infl uence on the physicochemical properties and sensory qualities of the dried products (p<0.05). The SB+OD-pretreated apple slices showed the lowest shrinkage (59.5%) and the highest total sugar content (77.90 g/100 g dry matter). Besides, the OD-pretreated apple slices showed the highest density (0.953 g/cm3 ) and the lowest titratable acidity (1.67 g/100 g dry matter). In addition, the ST-pretreated samples showed the highest titratable acidity (3.21 g/100 g dry matter) and vitamin C content (12.74 mg/100 g dry matter), while the sample pretreated by SB showed the highest total phenolics content (18.37 mg/g dry matter). Non-sulfi te-pretreated samples were superior to the sulfi te treatment or the control in flavor but inferior to the sulfi te treatment in color. Results of preference sensory evaluation showed that the dried apple slices were preferred by the panelists in the following order: SB+OD>SB>UT>OD>ST>the control.
Zinc, as one of the essential microelements in crop plant, plays a crucial role in resistance to drought stress. To acquire a comprehensive of the physiological mechanism of resistance to drought stress enhanced by supplemental Zn in cotton, a hydroponic trial was conducted to investigate the changes in antioxidants and osmoregulation substances under zinc deficient and zinc sufficient conditions after 0, 3, 6 and 48 h of polyethylene glycol 6000-simulated drought stress. The present research showed that supplemental Zn significantly enhanced photosynthetic rate, chlorophyll a, chlorophyll b and dry matter of cotton under polyethylene glycol 6000 simulated drought stress, indicating that supplemental zinc improved the cotton growth. The antioxidant enzymes activities such as catalase, ascorbate peroxidase and superoxide dismutase, and non-enzymatic antioxidants such as carotenoid, reduced glutathione and ascorbic acid were all significantly enhanced and malonaldehyde content was remarkably reduced by supplemental zinc under polyethylene glycol 6000 simulated drought stress, indicating that the capacity of scavenging active oxygen species was improved by supplemental zinc in cotton. The osmoregulation substances such as soluble sugar, proline and soluble protein were all enhanced by supplemental zinc under Polyethylene glycol 6000 simulated drought stress, suggesting that zinc enhanced the osmotic adjustment capacity of cotton. It is implied that supplemental zinc could enhance the resistance to drought stress by inducing the buildup of antioxidative defences and osmotic adjustment ability in cotton.
Calycosin and calycosin-7-O-β-D-glucoside (CG) are major isoflavonoids in Astragalus membranaceus and have multiple beneficial activities. Adventitious roots (ARs) are becoming attractive resources to obtain biologically active compounds. Salicylic acid (SA) is an important endogenous phytohormone, which is involved in the regulation of biotic and abiotic stresses. However, little is known about the potential role of SA on isoflavonoid accumulations under chilling stress. In the present study, calycosin was found to accumulate mostly in its glucosyl conjugate (CG) form in A. membranaceus ARs (AMARs). Compared to control conditions (25 °C), chilling (5 °C) induced the accumulation of CG, which was confirmed by increased expression levels of gene-encoding enzymes in the CG biosynthetic pathway. Furthermore, chilling triggered the accumulation of SA prior to CG accumulation. In addition, the inhibition of SA biosynthesis with paclobutrazol (PAC) in chilling-exposed AMARs suppressed the accumulation of CG and gene expressions, while exogenous addition of SA to PAC-treated AMARs restored CG content and gene expressions. These results indicated that in AMARs, SA involved in chilling-induced CG accumulation by regulating the expression levels of genes in the CG biosynthetic pathway.
Heterotrophic nitrifying bacteria are attracting increasing interest due to their advantages in treatment of wastewater with high nitrogen concentration. In this work, four bacterial isolates (WS-1, WS-4, WS-6, and WS-7) with the capability of simultaneous heterotrophic nitrification and aerobic denitrification from soil, sludge, and water by a fast isolation procedure were studied. Isolates WS-1, WS-6, and WS-7 were identified as Pseudomonas sp. and WS-4 as Agrobacterium sp. based on 16S rRNA gene sequence analysis. All four isolates could utilize ammonia, nitrate, and nitrite as sole nitrogen source and the metabolic characteristics were shown to be related with the genus. In addition, Agrobacterium sp. WS-4 accumulated less nitrate than the three Pseudomonas sp. strains with ammonia as the sole nitrogen source. When nitrate or nitrite was the sole nitrogen source, Agrobacterium sp. did not produce ammonia, and it consumed the least nitrogen compared with the three Pseudomonas sp. isolates. Our studies implied that Pseudomonas sp. strains had great potential in treating high nitrogen in wastewater.
Paeonia sect. Moutan is a wide known ornamental plant in the world. The objective of this study was to provide the theoretical basis for scientific preservation and utilization of tree peony resources of Hunan province of China. Simple sequence repeat (SSR) markers were applied to reveal the genetic diversity and relationship of 21 tree peony resources and 45 domestic and foreign tree peony cultivars. Clear bands, the size of which ranged from 115 bp to 379 bp, were detected with 14 primers. In total, 90 alleles were detected and the number of alleles detected with one primer varied between 5 and 13; the number of effective alleles ranged from 1.183 to 2.070; the polymorphism ratio of each locus was 100%. The observed heterozygosity, which ranged from 0.120 to 0.851 with an average of 0.532, was larger than the expected one, which ranged from 0.090 to 0.470 with an average of 0.300. Shannon index ranged from 0.137 to 0.695 and fixation index ranged from −0.332 to −0.869. The results show abundant genetic diversity in tree peony of Hunan province and SSR markers distinguishing homonymous tree peony resources successfully.
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