Refining the Factors Affecting N_(2)O Emissions from Upland Soils with and without Nitrogen Fertilizer Application at a Global Scale

Nitrous oxide(N_(2)O)is a long-lived greenhouse gas that mainly originates from agricultural soils.More and more studies have explored the sources,influencing factors and effective mitigation measures of N_(2)O in recent decades.However,the hierarchy of factors influencing N_(2)O emissions from agricultural soils at the global scale remains unclear.In this study,we carry out correlation and structural equation modeling analysis on a global N_(2)O emission dataset to explore the hierarchy of influencing factors affecting N_(2)O emissions from the nitrogen(N)and non-N fertilized upland farming systems,in terms of climatic factors,soil properties,and agricultural practices.Our results show that the average N_(2)O emission intensity in the N fertilized soils(17.83 g N ha^(-1)d^(-1))was significantly greater than that in the non-N fertilized soils(5.34 g N ha^(−1) d^(−1))(p<0.001).Climate factors and agricultural practices are the most important influencing factors on N_(2)O emission in non-N and N fertilized upland soils,respectively.For different climatic zones,without fertilizer,the primary influence factors on soil N_(2)O emissions are soil physical properties in subtropical monsoon zone,whereas climatic factors are key in the temperate zones.With fertilizer,the primary influence factors for subtropical monsoon and temperate continental zones are soil physical properties,while agricultural measures are the main factors in the temperate monsoon zone.Deploying enhanced agricultural practices,such as reduced N fertilizer rate combined with the addition of nitrification and urease inhibitors can potentially mitigate N_(2)O emissions by more than 60%in upland farming systems.

High-pressure study on calcium azide(Ca(N_(3))_(2)):Bending of azide ions stabilizes the structure

The high-pressure structure and elastic properties of calcium azide(Ca(N_(3))_(2))were investigated using in-situ highpressure x-ray diffraction and Raman scattering up to 54 GPa and 19 GPa,respectively.The compressibility of Ca(N_(3))_(2)changed as the pressure increased,and no phase transition occurred within the pressure from ambient pressure up to 54 GPa.The measured zero-pressure bulk modulus of Ca(N_(3))_(2)is higher than that of other alkali metal azides,due to differences in the ionic character of their metal-azide bonds.Using CASTEP,all vibration modes of Ca(N_(3))_(2)were accurately identified in the vibrational spectrum at ambient pressure.In the high-pressure vibration study,several external modes(ext.)and internal bending modes(ν_(2))of azide anions(N_(3)^(-))softened up to~7 GPa and then hardened beyond that pressure.This evidence is consistent with the variation observed in the F_(E)–f_(E)data analyzed from the XRD result,where the slope of the curve changes at 7.1 GPa.The main behaviors under pressure are the alternating compression,rotation,and bending of N_(3)^(-)ions.The bending behavior makes the structure of Ca(N_(3))_(2)more stable under pressure.

Single-atom photo-catalysts:Synthesis,characterization,and applications

Single-atom catalysts(SACs)are gaining popularity in catalytic reactions due to their nearly 100%atomic utilization and defined active sites,which provide great convenience for studying the catalytic mechanism of catalysts.However,SACs still present challenges such as complex formation processes,low loading and easy agglomeration of catalysts.Herein,we systematically discuss the synthesis methods for SACs,including coprecipitation,impregnation,atomic layer deposition,pyrolysis and Anti-Ostwald ripening etc.Various techniques for characterizing single-atom catalysts(SACs)are described in detail.The utilization of individual atoms in various photocatalytic reactions and their mechanisms of action in different reactions are explained.The purpose of this review is to introduce single-atom synthesis methods,characterization techniques,specific catalytic action and their applications in the direction of photocatalysis,and to provide a reference for the industrialization of photocatalytic single-atoms,which is currently impossible,in the hope of promoting further development of photocatalytic single-atoms.

Damming effects on dissolved inorganic carbon in different kinds of reservoirs in Jialing River,Southwest China

To assess the effects of river damming on dissolved inorganic carbon in the Jialing River, a total of 40 water samples, including inflow, outflow, and stratified water in four cascade reservoirs(Tingzikou, Xinzheng,Dongxiguan, Caojie) were collected in January and July,2016. The major cations, anions, and δ^(13)C_(DIC) values were analyzed. It was found that the dissolved compositions are dominated by carbonate weathering, while sulfuric acids may play a relatively important role during carbonate weathering and increasing DIC concentration. Different reservoirs had variable characteristics of water physiochemical stratification. The DIC concentrations of reservoir water were lower in summer than those in winter due to the dilute effects and intensive aquatic photosynthesis, as well as imported tributaries. The δ^(13)C_(DIC) values in Tingzikou Reservoir were higher during summer than those in winter,which indicated that intensive photosynthesis increased the δ^(13)C_(DIC) values in residual water, but a similar trend was not obvious in other reservoirs. Except for in Xinzheng Reservoir, the δ^(13)C_(DIC) values in inflow and outflow reservoir water were lower than those in the surface water of stratified sampling in summer. For stratified sampling, it could be found that, in summer, the Tingzikou Reservoir δ^(13)C_(DIC) values significantly decreased with water depthdue to the anaerobic breakdown of organic matter. The significant correlation(p<0.01 or 0.05) between the DIC concentrations, the δ^(13)C_(DIC) values and anthropogenic species(Na^++K^+, Cl~–, SO_4^(2-) and NO_3^-) showed that the isotope composition of DIC can be a useful tracer of contaminants. In total, Tingzikou Reservoir showed lacustrine features, Xinzheng Reservoir and Dongxiguan Reservoir had "transitional'' features, and Caojie Reservoir had a total of "fluvial'' features. Generally, cascade reservoirs in the Jialing River exhibited natural river features rather than typical lake features due to characteristics of reservoir water in physiochemical stratification, spatiotemporal variations of DIC concentrations and isotopic compositions. It is evident that the dissolved inorganic carbon dynamics of natural rivers had been partly remolded by dam building.

Biodegradation of Ammonia Nitrogen Using a Novel Candida sp. Strain N6 Immobilization

Due to the high efficiency of ammonia nitrogen degradation,a novel Candida sp.strain N6 was applied for wastewater treatment by using immobilization technology.Immobilization conditions and corresponding ammonia removal capacity of immobilized N6 beads were investigated.The immobilized N6 beads were applied to degrade simulated ammonia nitrogen wastewater.Results showed that the optimum formula of immobilized materials was 9%polyvinyl alcohol,1.5%sodium alginate,and 2%calcium chloride,under which the ammonia nitrogen removal rate of the immobilized N6 beads reached 97.97%.The following immobilization conditions were observed to be optimal:the immobilization time was 24 h,the inoculum of N6 was 3%,and the pH was 8.The immobilized N6 beads exhibited excellent ammonianitrogen degradation ability in SBRs.The ammonia nitrogen removal rate was stable at 95%-99%in the SBRs.The results indicated that immobilized N6 beads possess good application prospects in the treatment of ammonia nitrogen wastewater.

Preparation and Properties of Eco-Friendly Aerated Concrete Utilizing High-Volume Fly Ash with MgO and CaO Activators

The associated MgO in limestone is believed to affect the volume stability of cementitious materials at room tem-perature,which limits the utilization of low grade limestone.In this study,MgO was used as an alkali activator instead of partial CaO to prepare the aerated concrete under hydrother mal conditions.The expansion process was studied to evaluate the influence of the raw materials on the gas forming stability of the slurry.The pore structure(porosity,pore size and its distribution)was analyzed by the image method.The physic mechanical properties(density,strength,thermal properties)of concrete with the addition of MgO were comprehensively investigated.Besides,the mineral compositions and morphology of the hydration products were analyzed to demonstrate the infuence mechanism of MgO on the mechanical properties.Experimental results show that the final expansion rate of the slurry decreases with MgO content.A reasonable MgO content,ie,MgO/(MgO+CaO)<20%,con-tributes to improve the compressive strength,attributing to an increased reaction rate to C-S-H gel and tobermor-ite.The addition of MgO causes the thermal conductivity and specific heat to increase.The pore structure is mainly related to the amount of air entraining agent.This study has a significance for the further utilization of magnesium-rich carbonates in the autoclaved building products.

Performance Characterization of Modified ASTM F75 Alloy for Hip Implant Application

ASTM F75 is a low-carbon CoCrMo alloy which has been used as hip implant material for decades,but the ASTM F75 implants can fail when the femoral head and the acetabular cup loosen because of limited metal-on-metal bearing.Therefore,a modified version of ASTM F75 alloy which has 90 wt.%ASTM F75 plus 10 wt.%Cr is proposed.The wear and corrosion resistance of both alloys are investigated simulating the working environment of hip implants in human body.The mechanics behavior of the femoral implant under the loading condition in human body with ASTM F75 or modified ASTM F75 material used is studied with FEA simulation.The cytotoxicity(MTT)assays of the alloys are measured and compared to that of inert ceramic and cytotoxic cobalt.The experimental and simulation results show that the proposed alloy exhibits better wear and corrosion resistance than the conventional hip implant material.Both alloys behave well with respect to stress and deformation when used for the femoral implant under the loading condition in human body.These two alloys display similar cytotoxicity performance to inert ceramic.

Bi@C nanosphere anode with Na^(+)-ether-solvent cointercalation behavior to achieve fast sodium storage under extreme low temperatures

The low ion transport is a major obstacle for low-temperature(LT)sodium-ion batteries(SIBs).Herein,a core-shell structure of bismuth(Bi)nanospheres coated with carbon(Bi@C)is constructed by utilizing a novel Bi-based complex(1,4,5,8-naphthalenetetracarboxylic dianhydride as the ligand)as the precursor,which provides an effective template to fabricate Bi-based anodes.At-40℃,the Bi@C anode achieves a high capacity,which is equivalent to 96%of that at 25℃,benefitting from the core-shell nanostructured engineering and Na^(+)-ether-solvent cointercalation process.The special Na+-diglyme cointercalation behavior may effectively reduce the activation energy and accelerate the Na+diffusion kinetics,enabling the excellent low-temperature performance of the Bi@C electrode.As expected,the fabricated Na_(3)V_(2)(PO_(4))_(3)//Bi@C full-cell delivers impressive rechargeability in the ether-based electrolyte at-40℃.Density functional theory calculations and electrochemical tests also reveal the fast reaction kinetic mechanism at LT,thanks to a much lower diffusion energy barrier(167 meV)and a lower reaction activation energy(32.2 kJ mol^(-1))of Bi@C anode in comparison with that of bulk Bi.This work provides a rational design of Bi-based electrodes for rechargeable SIBs under extreme conditions.

Repurposing Loperamide as an Anti-Infection Drug for the Treatment of Intracellular Bacterial Pathogens

Infections caused by intracellular bacterial pathogens are difficult to treat since most antibiotics have low cell permeability and undergo rapid degradation within cells.The rapid development and dissemination of antimicrobial–resistant strains have exacerbated this dilemma.With the increasing knowledge of host–pathogen interactions,especially bacterial strategies for survival and proliferation within host cells,host-directed therapy(HDT)has attracted increased interest and has emerged as a promising antiinfection method for treating intracellular infection.Herein,we applied a cell-based screening approach to a US Food and Drug Administration(FDA)-approved drug library to identify compounds that can inhibit the intracellular replication of Salmonella Typhimurium(S.Typhimurium).This screening allowed us to identify the antidiarrheal agent loperamide(LPD)as a potent inhibitor of S.Typhimurium intracellular proliferation.LPD treatment of infected cells markedly promoted the host autophagic response and lysosomal activity.A mechanistic study revealed that the increase in host autophagy and elimination of intracellular bacteria were dependent on the high expression of glycoprotein nonmetastatic melanoma protein B(GPNMB)induced by LPD.In addition,LPD treatment effectively protected against S.Typhimurium infection in Galleria mellonella and mouse models.Thus,our study suggested that LPD may be useful for the treatment of diseases caused by intracellular bacterial pathogens.Moreover,LPD may serve as a promising lead compound for the development of anti-infection drugs based on the HDT strategy.

Accelerating Electrocatalytic Nitrate Reduction to Ammonia via Weakening of Intermediate Adsorption on Cu-Based

Cu-based materials are commonly used in electrocatalytic nitrate reduction reactions(NO 3 RR).NO 3 RR is a“two birds,one stone”approach,simultaneously removing NO 3−pollutants and producing valuable ammonia(NH 3).However,the strong coordination between the NO 3−intermediate and the catalytic active sites seriously hinders the conversion effi ciency.Here,we determined that,through encapsulation strategies,the carbon layer could weaken the NO 3−intermediate binding to active sites,resulting in higher NH 3 yields.We experimentally fabricated electrocatalysts,i.e.,Cu nanoparticles encapsulating(or loaded on)N-doped carbon nanofi bers(NCNFs)called Cu@NCNFs(Cu-NCNFs),using electrostatic spinning.As a result,Cu@NCNFs can achieve NH 3 yields of 17.08 mg/(h·mg cat)at a voltage of−0.84 V and a Faraday effi ciency of 98.15%.Meanwhile,the electrochemical properties of the Cu nanoparticles on the surface of carbon fi bers(Cu-NCNFs)are lower than those of the Cu@NCNFs.The in situ Raman spectra of Cu@NCNFs and Cu-NCNFs under various reduction potentials during the NO 3 RR process show that catalyst encapsulation within carbon layers can eff ectively reduce the adsorption of N species by the catalyst,thus improving the catalytic performance in the nitrate-to-ammonia catalytic conversion process.

基于渗流网络的聚合物基柔性应变传感复合材料研究进展

基于渗流网络的柔性导电高分子复合材料具有制备简便、加工性良好、成本低、电学与应变传感性能可调等优点,是构筑柔性应变传感材料的重要方式,也是目前研究的热点。文中首先介绍柔性力敏材料的渗流网络、导电机理、性能参数及相关数值模拟,并详细介绍了逾渗曲线,然后总结了导电填料含量、形貌与维数、导电填料协同作用、填料与基体间的相互作用以及网络形态结构等因素对力敏性能的影响规律,最后展望了基于渗流网络的聚合物基柔性力敏材料的发展趋势。

聚合物/MXene柔性力敏材料制备及应用研究进展

MXene作为一种新型的二维纳米材料,拥有优良的导电性,在柔性力敏材料领域有广泛的应用前景。为了构筑柔性力敏材料,通常将MXene与柔性聚合物或多孔聚合物相结合,从而实现柔性及大形变。柔性力敏材料中,MXene的分布、导电网络结构与形态由制备方法决定,进而决定传感器的类型和应用类型及场合。文中从MXene柔性力敏材料的制备策略角度出发,总结了浸渍法、喷涂法、真空过滤法、冰模板法及其它方法对MXene柔性力敏材料性能的影响,同时归纳了MXene柔性力敏材料在生理信号、细微人体动作、关节运动信号监测以及对信号进行示踪等方面的应用进展。

基于考古情境的化学综合实践活动设计——“考古”陶片中残留油脂的检测

针对实际考古问题进行分析,提炼实践活动主题,围绕“考古陶片中残留油脂的分析检测”这一主题设计化学综合实践活动。通过陶片中残留油脂的分析检测,引导学生了解化学技术手段在考古中的跨学科应用。学生通过实验操作提取“考古”陶片中的脂肪酸残留,并将其交换为脂肪酸甲酯,通过气相色谱进行表征,最后结合陶片及其考古背景分析陶片的使用情况。该实验可向化学、生物化学、人类学以及考古等专业学生开放,可帮助学生了解并掌握样品分离和制备、衍生化、气相色谱和多组分样品分析等方面的基本概念和实践操作。

生成式人工智能对欧洲教育的影响及对中国的启示

近期,美国OpenAI公司推出的生成式人工智能工具(ChatGPT)在全球范围内引起了各行各业的兴趣,特别是关于大型语言模型的应用与教育的利害关系引发了格外关注。而随着生成式人工智能技术的推广,关于其影响的辩论在欧洲以及世界各地已持续了数月。在教育领域,有观点认为这种新技术的推广将引发颠覆性变革,也有观点认为技术创新可以影响教育,但却没有改变它最基本的模式和规则。因此,教育界亟需了解和掌握此次技术变革的总体趋势和发展方向,以应对未来教育的变革。通过总结欧洲及大多数西方国家在教育数字化转型中面临的挑战和应对之策,及其对生成式人工智能技术的理解,提出在教育领域引入大型语言模型的机会、风险和挑战。首先,大型语言模型提供了学习机会,可以帮助教师改善教学质量,而这些机会因学习者不同而存在差异;其次,大型语言模型有可能彻底改变教学方式,并辅助教学过程,特别是在个性化学习、教学设计、语言学习专业发展等领域;再次,需要从不同视角来探索大型语言模型在教育中的应用,如学习者视角、教师视角、行政及管理者视角、研究者视角、雇主视角等;最后,大型语言模型也为教育带来了风险和挑战,如版权问题、偏见和公平、学习者对该模型过分依赖、教师对该模型过分依赖、缺乏深度学习和专业知识、模型生成结果与学生作答难以区分等。

电化学氮还原氨反应催化剂的最新研究进展

氨是重要的化工产品之一,广泛应用于化肥和燃料生产等领域.目前我国仍采用传统的Haber-Bosch工艺合成氨,该工艺消耗大量的化石燃料并造成环境污染.因此,开发一种高效、环保的氨合成方法代替Haber-Bosch工艺,减少能源消耗和保护环境具有非常重要的意义.电化学氮还原(eNRR)工艺由于使用可再生能源,成为有前景的替代方法之一.但目前eNRR工艺面临着许多挑战:较大的过电位以及析氢反应都会导致氨合成反应性能不理想.因此,理性设计电催化剂以提高氨合成效率成为当务之急.本文总结了近年e NRR领域的最新进展,以期为开发高性能催化剂提供借鉴.本文从eNRR的反应机理入手,介绍了eNRR的检测方法和反应条件,总结了近年来电催化剂的设计策略、原位表征方法和理论计算的研究成果,并对领域未来发展进行展望.首先,从理论热力学和NH3检测等方面讨论了eNRR的关键难点.然后,从形态、结构、空位、掺杂、协同效应、异质结构和单原子等多方面总结了eNRR催化剂的设计策略.此外,介绍了原位拉曼、原位红外、原位电化学质谱和原位X射线吸收光谱等技术在电催化氮还原机理研究中的重要作用.讨论了密度泛函理论(DFT)对于研究eNRR过程中的反应能垒和催化剂电子轨道分布的重要作用.最后,介绍了当前eNRR所面临的挑战,并就如何提高NH3产率和选择性提出了建议,如采用流动电解槽中固-液-气三相界面设计可确保N_(2)与催化剂之间有更大的接触面积和更长的接触时间,从而提高N2转化率;改变电解液成分或催化反应条件等方式以延长催化剂的使用寿命;通过原位表征手段对催化反应过程进行实时监测,以进一步揭示催化机理等.综上,eNRR领域取得的进展说明了在水溶液中通过可再生的电力将N_(2)还原成NH_3具有可行性.尽管现阶段存在eNRR效率不高、工艺不成熟等问题,但随着理论研究与实验结果的更好结合,原位表征技术的进一步发展和应用,未来在高效、稳定的氨合成电催化剂设计方面将会取得更大的进展,进而实现绿色合成氨的工业化应用,为减少能源消耗和碳排放做出贡献.

Characterization of microbial communities in sediments of the South Yellow Sea

Illumina sequencing and quantitative PCR(qPCR)based on the 16 S ribosomal RNA(rRNA)gene were conducted to characterize the vertical distribution of bacterial and archaeal communities in the sediments of two sites from the South Yellow Sea.Both bacterial and archaeal communities showed a clear stratified distribution with sediment depth.The microbial communities in the upper layers were distinct from those in the deeper layers;the relative abundances of sequences of Thaumarchaeota,Gammaproteobacteria,and Actinobacteria were higher in the upper than in the deeper sediments,whereas the sequences of Bathyarchaeia,Lokiarchaeota,Euryarchaeota,Chloroflexi,and Deltaproteobacteria were relatively more abundant in the deeper sediments.Sediment depth and total organic carbon(TOC)can significantly influence both the bacterial and archaeal communities.Furthermore,bacterial and archaeal groups potentially involved in nitrogen,sulfur,and methane metabolism were detected in both sites.In our study,both ammonia-oxidizing bacteria(Nitrospira)and ammonia-oxidizing archaea(Candidatus Nitrosopumilus)were responsible for ammonia oxidization.Additionally,sulfur-reducing bacteria SEEP-SRB1 forming consortia with anaerobic methane-oxidizing archaea ANME-2 a-2 b were capable of anaerobic methane oxidation(AOM)in the 3400-02 sediment samples.

The Analysis of Wall Shear Stress Modulated by Acute Exercise in the Human Common Carotid Artery with an Elastic Tube Model

Assessment of the magnitude and pattern of wall shear stress(WSS)in vivo is the prerequisite for studying the quantitative relationship between exercise-induced WSS and arterial endothelial function.In the previous studies,the calculation of the WSS modulated by exercise training was primarily based upon the rigid tube model,which did not take non-linear effects of vessel elastic deformation into consideration.In this study,with an elastic tube model,we estimated the effect of a bout of 30-minute acute cycling exercise on the WSS and the flow rate in the common carotid artery according to the measured inner diameter,center-line blood flow velocity,heart rates and the brachial blood pressures before and after exercise training.Furthermore,the roles of exerciseinduced arterial diameter and blood flow rate in the change of WSS were also determined.The numerical results demonstrate that acute exercise significantly increases the magnitudes of blood flow rate and WSS.Moreover,the vessel elastic deformation is a non-negligible factor in the calculation of the WSS induced by exercise,which generates greater effects on the minimum WSS than the maximum WSS.Additionally,the contributions of exercise-induced variations in blood flow rate and diameter are almost identical in the change of the mean WSS.

Vision-Based Fixed-Time Uncooperative Aerial Target Tracking for UAV

Dear Editor,In this letter,a vision-based fixed-time control is proposed for an unmanned aerial vehicle(UAV)with actuator saturation to track an uncooperative target.The fixed-time control is designed in backstepping framework.The relative states between UAV and the target are not directly measured,and are estimated by an onboard monocular camera.

Elucidating the Role of Mass Transfer in Electrochemical Redox Reactions on Electrospun Fibers

Mass transfer can tune the surface concentration of reactants and products and subsequently infl uence the catalytic perfor-mance.The morphology of nanomaterials plays an important role in the mass transfer of reaction microdomains,but related studies are lacking.Herein,a facile electrospinning technique utilizing cellulose was employed to fabricate a series of carbon nanofi bers with diff erent diameters,which exhibited excellent electrochemical nitrate reduction reaction and oxygen evolu-tion reaction activities.Furthermore,the microstructure of electrocatalysts could infl uence the gas-liquid-solid interfacial mass transfer,resulting in diff erent electrochemical performances.

An Empirical Analysis on the Impact of Rural Financial Development on the Income Gap between Urban and Rural Residents in Heilongjiang Province

The high-quality development of rural finance is an important support for rural revitalization.In recent years,it continuously expands the investment in rural finance in Heilongjiang Province,and optimizes the rural financial service system and mechanism.The overall income level and living conditions of rural residents have been significantly improved,but there still exists income gap between urban and rural residents.Therefore,based on analyzing and combing current situation and problems of rural financial development and urban-rural income gap in Heilongjiang Province,multiple linear regression model is used to study the impact of rural financial development on the income gap between urban and rural residents in Heilongjiang Province.The research results show that the scale of rural financial development in Heilongjiang Province will enlarge the income gap between urban and rural residents,while rural financial development efficiency and urbanization level reduce income gap between urban and rural residents in Heilongjiang Province.Based on the above conclusions,some policy suggestions to promote the equalization of urban and rural income in Heilongjiang Province are puts forward in this paper.