查看更多>>摘要：The diversification of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) communities and their potential nitrification activity (PNA) on a large scale have not been well documented. In this work, seven paddy soils from different geographic regions in Sichuan, P. R. China were selected to determine the spatial distribution of the activities,abundances and community compositions of AOB and AOA. PNA varied greatly among paddy soils, and was positively correlated with soil pH (P< 0.05). The abundance of AOA was 81.1 to 1670.0 times more than that of AOB, which indicates paddy soil environments favor the growth of AOA. Denaturing gradient gel electrophoresis fingerprints of amoA genes exhibited distinct spatial differences in AOA compositions rather than in AOB compositions. Sequencing analysis revealed that acidic soils were dominated by AOA within marine group 1.1a-associated lineage, whereas the soil group 1.1b lineage AOA predominated in neutral and alkaline soils. Both nitrosopira cluster 3-like and Nitrosomonas cluster 7-like AOB dominated the AOB communities in the paddy soils. Redundancy analysis suggested that soil NH4+-N content was the most significant driver determining the AOB community structure, while no significant correlation between AOA community structure and soil properties was found. The findings highlight that the activity and composition of ammonia oxidizers exhibit spatial variations in complex paddy fields due to the joint influence of soil variables associated with pH and N availability.
查看更多>>摘要：High-quality LDH-NO3-CO3 whiskers were synthesized via a liquid precipitation method using Mg(NO3)2·6H2O and Al(NO3)3·9H2O as raw materials and Na2CO3-NaHCO3 buffer solutions as precipitant. The whiskers were characterized by X-ray diffraction, transmission electron microscope, and Brunauer-Emmett-Teller N2 surface area measurement. The influence of buffer solution concentration on the characteristics of the sample was investigated. The results show that the buffer solution concentration has significant impact on whiskers with intercalated structure. Overall, LDH-NO3-CO3 whiskers with well-defined geometry, distinct intercalated structure, high quality, and good dispersion capability can be obtained under the following conditions: buffer solution volumetric ratio of 60％, reaction temperature of 55 °C, and reaction time of 269 h.
查看更多>>摘要：Fenneropenaeus penicillatus is an endangered species in China due to overfishing and damage to or loss of habitat. In this study, 41 new microsatellite markers were developed by using the FIASCO protocol with subsequent analysis on 30 wild individuals from Ningde, China. Our analysis shows that 35 loci were polymorphic and six loci were monomorphic. For the 35 polymorphic loci, the number of alleles ranged from 2 to 7, with an average of 3.6571. The polymorphism information content ranged from 0.121 to 0.794. The observed heterozygosity rate ranged from 0.0000 to 0.8889, and expected heterozygosity ranged from 0.1111 to 0.8129. However, 12 loci did not conform to Hardy-Weinberg equilibrium after Bonferroni correction. This is the first time the genetic diversity of F. penicillatus has been explored in Ningde. This group is at a low level of genetic diversity;therefore further measures should be taken to protect this species. Furthermore, these new microsatellite markers will be useful for the future conservation of F. penicillatus.
查看更多>>摘要：To investigate the effect of adding microfiber glass on the magnetic and mechanic properties of anisotropic Nd-Fe-B magnets, the Nd-Fe-B magnets with epoxy resin lubricant were prepared by calendering and magnetic alignment steps with heating. The effect of heating during magnetic alignment process on magnetic and mechanic properties of the prepared Nd-Fe-B magnets was investigated and optimized. As a result, heating unaligned flexible bonded magnets to 100 °C for 30 min during magnetic alignment resulted in the largest (BH) max , which increased to over 61.5％ with DOA increasing and to over 38％ compared with unaligned Nd-Fe-B magnets prepared by one step method.
查看更多>>摘要：Five-axis ball-end milling is commonly used to machine the complex surfaces. Local tool interference phenomenon which often occurs in five-axis milling should be urgently solved. In this paper, a simplified method to detect the occurrence of local tool interference and modify tool position is proposed. First, the detection matrix is established to detect local tool interference at all the cutter location points on tool path simultaneously in five-axis ball-end milling of complex surfaces. The algorithm of detection matrix based on point arithmetic is simple. Secondly, the new coordinates of the modified interfering-free points are obtained precisely by using the genetic algorithm. The feasibility of the method is validated by simulation in Matlab.This research is benefit to simplify the calculation of local tool interference detection and tool position modification.
查看更多>>摘要：The field seismic data is disturbed by the interferential information, which has low signal to noise ratio (SNR). That is disadvantage for seismic data interpretation. So it is important to remove the noise of seismic data. Independent component analysis (ICA) can remove most of the noise interference. However, ICA has some defects in noise reduction, because it needs some conditions that seismic data is independent reciprocally for denoising. To solve these defects, this paper proposes an improved ICA algorithm to noise reduction. Through simulation experiments, it can be obtained that the best decomposition levels of the new algorithm is 3. At last, the proposed improved ICA is applied to deal with the actual seismic data. The results show that it can effectively eliminate most of seismic noise such as random noise, linear interference, surface waves, and so on.The improved ICA is not only easy to denoising, but also has excellent mathematical theoretical properties.
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