Microbial community diversity analysis of <i>Panax ginseng</i>rhizosphere and non-rhizosphere soil using randomly amplified polymorphic DNA method

DNA sequence diversities of soil microbial communities in rhizosphere and non-rhizosphere of 1 - 6 years Panax ginseng were evaluated by random amplified polymorphic DNA (RAPD). Total genomic DNA of soil samples were amplified by twenty-four out of two hundred random primers. The products were separated in agarose gel, and 359 and 181 reliable fragments were generated, of which, 324 and 123 were polymorphic. The gene diversity index, Shannon’s information index, and similarity coefficient were calculated, and results showed that, diversity of soil microbial community at DNA level was present. Furthermore, with the increasing of P. ginseng growing at one site, deference on soil microbial community DNA sequence between rhizosphere and non-rhizosphere tend to be more and more significant. In addition, RAPD technique was proved to be an effective tool to assess the diversity of soil microbial communities. From results we deduced that, the ecological function that performed by soil microbes may changed following the change of microbial community in rhizospheric and non-rhizospheric soils, and finally broke the balance of soil nutrition and energy cycle, soil spatial structure, microbial ecology etc.

Promoting NO_(x)reduction via in situ activation of perovskite supported Pd catalysts under alternating lean-burn/fuel-rich operating atmospheres

Herein,we report the excellent De-NO_(x)performance of La0.7Sr0.3MnO3(LSM)perovskite-supported Pd catalysts(Pd-LSM)in alternating lean-burn/fuel-rich atmospheres using C3H6 as reductant and describe the in situ activation of the Pd catalysts via metal-support interaction(MSI)tuning.The NO_(x)reduction conversion of the Pd-LSM catalyst increased significantly from 56.1%to 90.1%and the production of N2O was suppressed.Our results demonstrated that this behavior was mainly attributed to the in situ transformation of Pd2+into Pd0 during the reaction.The generated Pd0 species could readily activate the C3H6 reductant and achieve an eight-fold higher turnover frequency than Pd2+for the reduction of NO_(x).Moreover,excessive MSIs inhibited the in situ generation of Pd0,and thereby,lowered the De-NO_(x)activity of the catalyst even at high Pd dispersion.In addition,the Pd-LSM catalysts exhibited much higher S tolerance than conventional Al_(2)O_(3)-supported catalysts.Our study provides a new approach for analyzing and designing highly active metal catalysts operated under dynamic alternating oxidizing/reducing atmospheric conditions.

Effect of Initial Microstructure Prior to Extrusion on the Microstructure and Mechanical Properties of Extruded AZ80 Alloy with a Low Temperature and a Low Ratio

Magnesium(Mg)alloys are the lightest metal structural material for engineering applications and therefore have a wide market of applications.However,compared to steel and aluminum alloys,Mg alloys have lower mechanical properties,which greatly limits their application.Extrusion is one of the most important processing methods for Mg and its alloys.However,the effect of such a heterogeneous microstructure achieved at low temperatures on the mechanical properties is lacking investigation.In this work,commercial AZ80 alloys with different initial microstructures(as-cast and as-homogenized)were selected and extruded at a low extrusion temperature of 220℃and a low extrusion ratio of 4.The microstructure and mechanical properties of the two extruded AZ80 alloys were investigated.The results show that homogenized-extruded(HE)sample exhibits higher strength than the cast-extruded(CE)sample,which is mainly attributed to the high number density of fine dynamic precipitates and the high fraction of recrystallized ultrafine grains.Compared to the coarse compounds existing in CE sample,the fine dynamical precipitates of Mg17(Al,Zn)12form in the HE sample can effectively promote the dynamical recrystallization during extrusion,while they exhibit a similar effect on the size and orientation of the recrystallized grains.These results can facilitate the designing of high-strength wrought magnesium alloys by rational microstructure construction.

约4900年前东亚和东南亚枢纽地区狩猎采集向农业的转变

The southward expansion of East Asian farmers profoundly influenced the social evolution of Southeast Asia by introducing cereal agriculture.However,the timing and routes of cereal expansion in key regions are unclear due to limited empirical evidence.Here we report macrofossil,microfossil,multiple isotopic(C/N/Sr/O)and paleoproteomic data directly from radiocarbon-dated human samples,which were unearthed from a site in Xingyi in central Yunnan and which date between 7000 and 3300 a BP.Dietary isotopes reveal the earliest arrival of millet ca.4900 a BP,and greater reliance on plant and animal agriculture was indicated between 3800 and 3300 a BP.The dietary differences between hunter-gatherer and agricultural groups are also evident in the metabolic and immune system proteins analysed from their skeletal remains.The results of paleoproteomic analysis indicate that humans had divergent biological adaptations,with and without farming.The combined application of isotopes,archaeobotanical data and proteomics provides a new approach to documenting dietary and health changes across major subsistence transitions.

VOCs氧化催化剂设计与结构调控

近年来我国环境空气质量显著改善,NOx与SO_(2)等传统污染物得到有效控制,挥发性有机物(Volatile Organic Compounds,VOCs)排放控制逐渐成为进一步解决区域复合型大气污染问题的关键因素。催化氧化法因其处理效率高、能耗低及适用范围广等优势,已成为最具应用前景的VOCs减排技术之一。高性能催化剂的研发是该技术的核心,结合反应机理进行催化剂设计和结构调控是目前研究的热点和重点。本文首先对VOCs催化氧化机理进行概述;其次从单一过渡金属氧化物、混合金属氧化物、复合金属氧化物以及相界面结构调控角度综述了非贵金属催化剂结构调控的相关研究进展;聚焦贵金属分散状态,总结了贵金属催化剂中贵金属纳米颗粒/团簇催化剂尺寸效应与载体效应相关研究成果,并对目前新兴的单原子催化剂基于金属-载体相互作用的调控手段进行概括;最后对VOCs氧化催化剂的研究现状与趋势进行总结与展望。我们认为深入解析构效关系,研发简约和精细化的催化剂结构调控手段并适配实际工况和工业放大是未来研究的重点发展方向。

A-site defects in LaSrMnO_(3) perovskite-based catalyst promoting NOx storage and reduction for lean-burn exhausts

Herein,we report the high De-NOx performance of the A-site defective perovskite-based Pd/La_(0.5)Sr_(0.3)MnO_(3) catalyst.The formation of the defective perovskite structure can be proved by both the increased Mn^(4+)/Mn^(3+) ratio and serious lattice contraction due to cationic nonstoichiometry.It promotes the Sr doping into perovskite lattice and reduces the formation of the SrCO_(3) phase.Our results demonstrate that below 300℃ the A-site defective perovskite can be more efficiently regenerated than the SrCO_(3) phase as NOx storage sites due to the latter’s stronger basicity,and also exhibits the higher NO oxidation ability than the A-site stoichiometric and excessive catalysts.Both factors promote the lowtemperature De-NOx activity of the Pd/La_(0.5)Sr_(0.3)MnO_(3) catalyst through improving its NOx trapping efficiency.Nevertheless,above 300℃,the NOx reduction becomes the determinant of the De-NOx activity of the perovskite-based catalysts.A-site defects can weaken the interactions between perovskite and Pd,inducing activation of Pd sites by in-situ transformation from PdO to metallic Pd in the alternative leanburn/fuel-rich atmospheric alternations,which boosts the De-NOx activity of the Pd/La_(0.5)Sr_(0.3)MnO_(3) catalyst.The Pd/L_(0.5)Sr_(0.3)MnO_(3) catalyst exhibits the high sulfur tolerance as well.These findings provide insight into optimizing the structural properties and catalytic activities of the perovskite-based catalysts via tuning formulation,and have potential to be applied for various related catalyst systems.

A comprehensive multi‐hazard risk assessment model for an urban agglomeration with multiple factors

To assist the Department of Emergency Management in understanding the overall risk characteristics and situation of an urban agglomeration for a reasonable risk prevention and control strategy,this study developed a comprehensive multi-hazard risk assessment model for an urban agglomeration with multiple factors.The proposed model includes disaster probability and disaster loss sub-models.The model evaluated four types of disaster risk in urban agglomerations:natural disasters,accidental disasters,public health incidents,and social security incidents.In addition,a variety of factors were integrated into the model,including the socioeconomic foundation of urban agglomerations,the oligopoly effect of core cities,historical disaster losses,the effect of disaster chains,the ability of disaster prevention and mitigation,and intercity coordinated rescue capabilities.Finally,the risk assessment model was applied to the Beijing-Tianjin-Hebei urban agglomeration.The assessment results were compared to the distribution of the new coronavirus pneumonia epidemic in the target urban agglomeration.The results showed that after analyzing the risk characteristics and evaluating the risk levels,the model not only showed the comprehensive risk levels and distribution of urban agglomerations but also revealed the high-risk areas and the key points of risk prevention and control.More importantly,the results obtained through the model can facilitate the strategic planning of disaster prevention and mitigation for urban agglomerations.

结核分枝杆菌Rv3194c蛋白的亚细胞定位

【目的】Rv3194c基因编码的是结核分枝杆菌的PDZ信号蛋白,本研究探讨该蛋白的亚细胞定位,为其细胞结合蛋白的筛选奠定基础。【方法】从H37Rv基因组中扩增出编码只含有PDZ结构域的tRv3194c (Rv3194c 1–234 aa)的基因片段,在3′端加T2A和EGFP序列,一并插入真核表达载体构建出pcDNA3.1-tRv3194c-T2A-EGFP。将构建好的质粒瞬时转染L929细胞,并共感染重组痘苗病毒vTF7-3,用间接免疫荧光、流式细胞分选以及Western blotting检测融合蛋白的表达以及亚细胞定位。【结果】成功构建出真核表达载体pcDNA3.1-tRv3194c-T2A-EGFP,瞬时转染L929细胞后融合蛋白tRv3194c定位于线粒体膜上,且重组痘苗病毒vTF7-3的感染有助于靶蛋白表达水平的提高。【结论】Rv3194蛋白的PDZ结构域与线粒体外膜相关蛋白结合,为了解该蛋白在细胞内的致病机制提供重要线索。