Background,aim,and scope Soil microbes are important drivers of nutrient transformation and energy f low.Reclaiming forest land for agricultural use may have profound effects on soil properties and microbial communiti...Background,aim,and scope Soil microbes are important drivers of nutrient transformation and energy f low.Reclaiming forest land for agricultural use may have profound effects on soil properties and microbial communities.However,the response of soil microbial communities to soil reclamation in the dryland agroecosystem is less understood.Therefore,it is necessary to investigate the changes of soil microbial communities driven by land use conversion to promote nutrient cycling in reclaimed farmland.Materials and methods Based on the metagenomic technique,we evaluated the microbial composition and function of the newly created farmland(NF)after reclamation with two types of traditional farmland(slope farmland(SF),checkdam farmland(CF))on the Loess Plateau,and explored the response of nutrient cycling function to dominant genera and soil properties.Results The results showed that Proteobacteria,Actinobacteria,and Acidobacteria were prevalent in the three types of farmlands.Compared with SF and CF,NF increased the relative abundance of Actinobacteria and Nocardioides,as well as genes related to amino acid metabolism and carbohydrate metabolism.The relative abundance of functional genes related to carbon and nitrogen cycling in the NF was higher than that in the traditional farmland(SF and CF).The relative abundance of nutrient cycling functional genes was positively correlated with dominant genera in the three types of farmlands.Except for pH,soil physicochemical factors were negatively correlated with genes related to amino acid metabolism and carbon cycle.Discussion Previous studies have shown that the nutrient conditions of the soil may intensify the competition between the eutrophic and oligotrophic microbial populations.After long-term cultivation and fertilization,the soil properties of traditional farmland were significantly different from those of NF,leading to the differentiation of dominant microbial groups.Microbes usually have functional redundancy to cope with changing environments.Soil microbes in traditional farmland may contain more genes related to replication and repair,cell growth and death,and environmental adaptation in response to disturbances caused by agricultural practices.On the contrary,the NF was less disturbed by agricultural activities,and the soil properties were more similar to forest land,so the carbon and nitrogen cycle function genes were more abundant.The nutrient cycling function was affected by the abundance of microbial dominant groups and soil properties,which may be related to the availability of soil nutrients and agricultural disturbance in different farmlands.Aspects of soil microbial-driven nutrient cycling in agriculture could be regulated in sustainable method.Conclusions The change from forest land to farmland kept more carbon and nitrogen cycling function in the newly created farmland,while long-term agricultural activities have drastically changed the functional structure of traditional farmland,resulting in the nutrient cycling function more concentrated to meet the needs of crop growth.Recommendations and perspectives Hence,it is necessary to apply sustainable agricultural method to regulate microbial-driven nutrient cycling.The insights are meaningful for sustainable agricultural development and land management in arid areas.展开更多
Molecular dynamics(MD)simulations are employed to delve into the multifaceted effects of TiB2 nanoparticles on the intricate grain refinement mechanism,microstructural evolution,and tensile performance of Inconel 718 ...Molecular dynamics(MD)simulations are employed to delve into the multifaceted effects of TiB2 nanoparticles on the intricate grain refinement mechanism,microstructural evolution,and tensile performance of Inconel 718 superalloys during the rapid directional solidification.Specifically,the study focuses on elucidating the role of TiB2 nanoparticles in augmenting the nucleation rate during the rapid directional solidification process of Ni60Cr21Fe19 alloy system.Furthermore,subsequent tensile simulations are conducted to comprehensively evaluate the anisotropic behavior of tensile properties within the solidified microstructures.The MD results reveal that the incorporation of TiB₂nanoparticles during the rapid directional solidification of the Ni_(60)Cr_(21)Fe_(19)significantly enhances the average nucleation rate,escalating it from 1.27×10^(34)m^(-3)·s^(-1)to 2.55×10^(34)m^(-3)·s^(-1).Notably,within the face centered cube(FCC)structure,Ni atoms exhibit pronounced compositional segregation,and the solidified alloy maintains an exceptionally high dislocation density reaching up to 10^(16)m^(-2).Crucially,the rapid directional solidification process imparts a distinct microstructural anisotropy,leading to a notable disparity in tensile strength.Specifically,the tensile strength along the solidification direction is markedly superior to that perpendicular to it.This disparity arises from different deformation mechanisms under varying loading orientations.Tensile stress perpendicular to the solidification direction encourages the formation of smooth and organized mechanical twins.These twins act as slip planes,enhancing dislocation mobility and thereby improving stress relaxation and dispersion.Moreover,the results underscore the profound strengthening effect of TiB2 nanoparticles,particularly in enhancing the tensile strength along the rapid directional solidification direction.展开更多
TA2/TA15 graded structural material（GSM） was fabricated by the laser additive manufacturing（LAM） process. The chemical composition, microstructure and micro-hardness of the as-deposited GSM were investigated. The ...TA2/TA15 graded structural material（GSM） was fabricated by the laser additive manufacturing（LAM） process. The chemical composition, microstructure and micro-hardness of the as-deposited GSM were investigated. The results show that the TA2 part of exhibiting near-equiaxed grains was Widmanst？tten α-laths microstructure. The TA15 part containing large columnar grains was fine basket-weave microstructure. The graded zone was divided into four deposited layers with 3000 μm in thickness. As the distance from the TA2 part increases, the alloy element contents and the β phase volume fraction increase, the α phase volume fraction decreases and the microstructure shows the evolution from Widmanst？tten α-laths to basket-weave α-laths gradually. The micro-hardness increases from the TA2 part to the TA15 part due to the solid solution strengthening and grain boundary strengthening.展开更多
The electrical resistivity of NZ30K-Mg alloy was measured at different heating rates during continuous heating to stud the precipitation kinetics.Two kinds of metastable phases,β＂ and β＇,formed during the heating....The electrical resistivity of NZ30K-Mg alloy was measured at different heating rates during continuous heating to stud the precipitation kinetics.Two kinds of metastable phases,β＂ and β＇,formed during the heating.Kissinger method and differentia isoconversional method were employed to assess the precipitation kinetic parameters of NZ30K-Mg alloy,activation energy Eα an pre-exponential factor A＇α.The fraction of transformation（α） and the precipitation sequence in NZ30K-Mg alloy were determinec Continuous heating transformation（CHT） and isothermal heating transformation（IHT） diagrams were further obtained for guidin the aging of NZ30K-Mg alloy.The analysis shows that the precipitation kinetic parameters of NZ30K-Mg alloy can be obtaine accurately using isoconversional method.展开更多
According to the principles of simultaneous equilibrium and mass equilibrium, the thermodynamics model of the precipitation-coordination equilibrium of Ni2＋-C2H8N2- 2-2 4C O -H2O system was established, and calculati...According to the principles of simultaneous equilibrium and mass equilibrium, the thermodynamics model of the precipitation-coordination equilibrium of Ni2＋-C2H8N2- 2-2 4C O -H2O system was established, and calculation for the relationships between concentration of each substance in solution and parameters was carried out, including pH value, concentrations of ethylenediamine and oxalate by MATLAB program. The results show that Ni exists as Ni2＋and [Ni（C2O4）n]2-2n mainly at pH〈1 and pH=1-6, respectively. When pH〉6, the complex between Ni2＋and ethylenediamine is predominant. The precursor of Ni microfiber was prepared by an oxalate precipitation process using ethylenediamine as a coordination agent, and the role of ethylenediamine in the growth of the precursor fiber was discussed. The Ni microfiber can be obtained by a thermal decomposition-reduction process of the precursor in N2 and H2 mixed atmosphere. The diameters and aspect ratios of the obtained Ni microfibers are 0.2-1 μm and 20-30, respectively.展开更多
This paper presents a new method to seek the conserved quantity from a Lie symmetry without using either Lagrangians or Hamiltonians for nonholonomic systems. The differential equations of motion of the systems are es...This paper presents a new method to seek the conserved quantity from a Lie symmetry without using either Lagrangians or Hamiltonians for nonholonomic systems. The differential equations of motion of the systems are established. The definition of the Lie symmetrical transformations of the systems is given, which only depends upon the infinitesimal transformations of groups for the generalized coordinates. The conserved quantity is directly constructed in terms of the Lie symmetry of the systems. The condition under which the Lie symmetry can lead to the conserved quantity and the form of the conserved quantity are obtained. Finally, an example is given to illustrate the application of the result.展开更多
The effects of O2 and the supported Pt nano-particles on the mechanisms and kinetics of the carbon support corrosion are investigated by monitoring the CO2 production using differential electrochemical mass spectromet...The effects of O2 and the supported Pt nano-particles on the mechanisms and kinetics of the carbon support corrosion are investigated by monitoring the CO2 production using differential electrochemical mass spectrometry in a dual-thin layer flow cell. Carbon can be oxidized in different distinct potential regimes; O2 accelerates carbon oxidation, the rates of CO2 production from carbon oxidation in O2 saturated solution are two times of that in N2 saturated solution at the same potential; Pt can catalyze the carbon oxidation, with supported Pt nanoparticles, the overpotential for carbon oxidation is much smaller than that without loading in the carbon electrode. The mechanism for the enhanced carbon oxidation by Pt and O2 are discussed.展开更多
X-ray microanalysis was used to study the elemental composition of the shell of the freshwater testate amoeba Difflugia tuberspinifera Hu et al.,1997 collected from Mulan Lake,Hubei province,China in July 2003.The res...X-ray microanalysis was used to study the elemental composition of the shell of the freshwater testate amoeba Difflugia tuberspinifera Hu et al.,1997 collected from Mulan Lake,Hubei province,China in July 2003.The results show that the shell is composed of ten elements:Si in greater quantity;then Ca and Al;and traces of K,Na,Cl,Fe,Mg,S and P.The analysis of results suggests that D.tuberspinifera in elemental composition appears to occupy a middle position between marine and soil testate amoebae.展开更多
The CuZrAl bulk metallic glass with minor-addition of Fe was prepared by rapid quenching method. The structures were examined by X-ray diffraction （XRD）. The effect of Fe on the glass-forming ability was studied by ...The CuZrAl bulk metallic glass with minor-addition of Fe was prepared by rapid quenching method. The structures were examined by X-ray diffraction （XRD）. The effect of Fe on the glass-forming ability was studied by differential scanning calorimetry （DSC）. The minor-addition of Fe obviously extends the supercooled liquid region ΔTx. The plastic strain of the Cu44Zr48Al7Fe bulk metallic glass is about 1.5%. The microstructures were examined by transmission electron microscopy （TEM）. It is found that when 1%-2% Fe （mole fraction） were introduced into the CuZrAl alloy matrix, nanoscale phase separation occurs in the as-prepared Cu44Zr48Al7Fe bulk metallic glass.展开更多
文摘Background,aim,and scope Soil microbes are important drivers of nutrient transformation and energy f low.Reclaiming forest land for agricultural use may have profound effects on soil properties and microbial communities.However,the response of soil microbial communities to soil reclamation in the dryland agroecosystem is less understood.Therefore,it is necessary to investigate the changes of soil microbial communities driven by land use conversion to promote nutrient cycling in reclaimed farmland.Materials and methods Based on the metagenomic technique,we evaluated the microbial composition and function of the newly created farmland(NF)after reclamation with two types of traditional farmland(slope farmland(SF),checkdam farmland(CF))on the Loess Plateau,and explored the response of nutrient cycling function to dominant genera and soil properties.Results The results showed that Proteobacteria,Actinobacteria,and Acidobacteria were prevalent in the three types of farmlands.Compared with SF and CF,NF increased the relative abundance of Actinobacteria and Nocardioides,as well as genes related to amino acid metabolism and carbohydrate metabolism.The relative abundance of functional genes related to carbon and nitrogen cycling in the NF was higher than that in the traditional farmland(SF and CF).The relative abundance of nutrient cycling functional genes was positively correlated with dominant genera in the three types of farmlands.Except for pH,soil physicochemical factors were negatively correlated with genes related to amino acid metabolism and carbon cycle.Discussion Previous studies have shown that the nutrient conditions of the soil may intensify the competition between the eutrophic and oligotrophic microbial populations.After long-term cultivation and fertilization,the soil properties of traditional farmland were significantly different from those of NF,leading to the differentiation of dominant microbial groups.Microbes usually have functional redundancy to cope with changing environments.Soil microbes in traditional farmland may contain more genes related to replication and repair,cell growth and death,and environmental adaptation in response to disturbances caused by agricultural practices.On the contrary,the NF was less disturbed by agricultural activities,and the soil properties were more similar to forest land,so the carbon and nitrogen cycle function genes were more abundant.The nutrient cycling function was affected by the abundance of microbial dominant groups and soil properties,which may be related to the availability of soil nutrients and agricultural disturbance in different farmlands.Aspects of soil microbial-driven nutrient cycling in agriculture could be regulated in sustainable method.Conclusions The change from forest land to farmland kept more carbon and nitrogen cycling function in the newly created farmland,while long-term agricultural activities have drastically changed the functional structure of traditional farmland,resulting in the nutrient cycling function more concentrated to meet the needs of crop growth.Recommendations and perspectives Hence,it is necessary to apply sustainable agricultural method to regulate microbial-driven nutrient cycling.The insights are meaningful for sustainable agricultural development and land management in arid areas.
基金supported by the Na⁃tional Natural Science Foundation of China(Nos.12462006,12062016)the high-performance computing services of⁃fered by the Information Center of Nanchang Hangkong Uni⁃versity.
文摘Molecular dynamics(MD)simulations are employed to delve into the multifaceted effects of TiB2 nanoparticles on the intricate grain refinement mechanism,microstructural evolution,and tensile performance of Inconel 718 superalloys during the rapid directional solidification.Specifically,the study focuses on elucidating the role of TiB2 nanoparticles in augmenting the nucleation rate during the rapid directional solidification process of Ni60Cr21Fe19 alloy system.Furthermore,subsequent tensile simulations are conducted to comprehensively evaluate the anisotropic behavior of tensile properties within the solidified microstructures.The MD results reveal that the incorporation of TiB₂nanoparticles during the rapid directional solidification of the Ni_(60)Cr_(21)Fe_(19)significantly enhances the average nucleation rate,escalating it from 1.27×10^(34)m^(-3)·s^(-1)to 2.55×10^(34)m^(-3)·s^(-1).Notably,within the face centered cube(FCC)structure,Ni atoms exhibit pronounced compositional segregation,and the solidified alloy maintains an exceptionally high dislocation density reaching up to 10^(16)m^(-2).Crucially,the rapid directional solidification process imparts a distinct microstructural anisotropy,leading to a notable disparity in tensile strength.Specifically,the tensile strength along the solidification direction is markedly superior to that perpendicular to it.This disparity arises from different deformation mechanisms under varying loading orientations.Tensile stress perpendicular to the solidification direction encourages the formation of smooth and organized mechanical twins.These twins act as slip planes,enhancing dislocation mobility and thereby improving stress relaxation and dispersion.Moreover,the results underscore the profound strengthening effect of TiB2 nanoparticles,particularly in enhancing the tensile strength along the rapid directional solidification direction.
基金Project(2010CB731705)supported by the National Basic Research Program of China
文摘TA2/TA15 graded structural material（GSM） was fabricated by the laser additive manufacturing（LAM） process. The chemical composition, microstructure and micro-hardness of the as-deposited GSM were investigated. The results show that the TA2 part of exhibiting near-equiaxed grains was Widmanst？tten α-laths microstructure. The TA15 part containing large columnar grains was fine basket-weave microstructure. The graded zone was divided into four deposited layers with 3000 μm in thickness. As the distance from the TA2 part increases, the alloy element contents and the β phase volume fraction increase, the α phase volume fraction decreases and the microstructure shows the evolution from Widmanst？tten α-laths to basket-weave α-laths gradually. The micro-hardness increases from the TA2 part to the TA15 part due to the solid solution strengthening and grain boundary strengthening.
基金Project (2011ZX04014-052,2012ZX04012011) supported by CNC Machine Tools and Basic Manufacturing Equipment Technology Comments
文摘The electrical resistivity of NZ30K-Mg alloy was measured at different heating rates during continuous heating to stud the precipitation kinetics.Two kinds of metastable phases,β＂ and β＇,formed during the heating.Kissinger method and differentia isoconversional method were employed to assess the precipitation kinetic parameters of NZ30K-Mg alloy,activation energy Eα an pre-exponential factor A＇α.The fraction of transformation（α） and the precipitation sequence in NZ30K-Mg alloy were determinec Continuous heating transformation（CHT） and isothermal heating transformation（IHT） diagrams were further obtained for guidin the aging of NZ30K-Mg alloy.The analysis shows that the precipitation kinetic parameters of NZ30K-Mg alloy can be obtaine accurately using isoconversional method.
基金Project(CX2012B046)supported by Hunan Provincial Innovation Foundation for Postgraduate,ChinaProject(20090162120080)supported by the Doctorate Fund of Education Minister of China
文摘According to the principles of simultaneous equilibrium and mass equilibrium, the thermodynamics model of the precipitation-coordination equilibrium of Ni2＋-C2H8N2- 2-2 4C O -H2O system was established, and calculation for the relationships between concentration of each substance in solution and parameters was carried out, including pH value, concentrations of ethylenediamine and oxalate by MATLAB program. The results show that Ni exists as Ni2＋and [Ni（C2O4）n]2-2n mainly at pH〈1 and pH=1-6, respectively. When pH〉6, the complex between Ni2＋and ethylenediamine is predominant. The precursor of Ni microfiber was prepared by an oxalate precipitation process using ethylenediamine as a coordination agent, and the role of ethylenediamine in the growth of the precursor fiber was discussed. The Ni microfiber can be obtained by a thermal decomposition-reduction process of the precursor in N2 and H2 mixed atmosphere. The diameters and aspect ratios of the obtained Ni microfibers are 0.2-1 μm and 20-30, respectively.
文摘This paper presents a new method to seek the conserved quantity from a Lie symmetry without using either Lagrangians or Hamiltonians for nonholonomic systems. The differential equations of motion of the systems are established. The definition of the Lie symmetrical transformations of the systems is given, which only depends upon the infinitesimal transformations of groups for the generalized coordinates. The conserved quantity is directly constructed in terms of the Lie symmetry of the systems. The condition under which the Lie symmetry can lead to the conserved quantity and the form of the conserved quantity are obtained. Finally, an example is given to illustrate the application of the result.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.20773116）, the one hundred Talents＇ Program Sciences, and the National China （No.2010CB923302） of the Chinese Academy of Basic Research Program of
文摘The effects of O2 and the supported Pt nano-particles on the mechanisms and kinetics of the carbon support corrosion are investigated by monitoring the CO2 production using differential electrochemical mass spectrometry in a dual-thin layer flow cell. Carbon can be oxidized in different distinct potential regimes; O2 accelerates carbon oxidation, the rates of CO2 production from carbon oxidation in O2 saturated solution are two times of that in N2 saturated solution at the same potential; Pt can catalyze the carbon oxidation, with supported Pt nanoparticles, the overpotential for carbon oxidation is much smaller than that without loading in the carbon electrode. The mechanism for the enhanced carbon oxidation by Pt and O2 are discussed.
文摘X-ray microanalysis was used to study the elemental composition of the shell of the freshwater testate amoeba Difflugia tuberspinifera Hu et al.,1997 collected from Mulan Lake,Hubei province,China in July 2003.The results show that the shell is composed of ten elements:Si in greater quantity;then Ca and Al;and traces of K,Na,Cl,Fe,Mg,S and P.The analysis of results suggests that D.tuberspinifera in elemental composition appears to occupy a middle position between marine and soil testate amoebae.
基金Project (2010ZDJH10) supported by the Nanjing University of Science and Technology Research Funding, ChinaProject (BK2007213) supported by the Natural Science Foundation of Jiangsu Province, China
文摘The CuZrAl bulk metallic glass with minor-addition of Fe was prepared by rapid quenching method. The structures were examined by X-ray diffraction （XRD）. The effect of Fe on the glass-forming ability was studied by differential scanning calorimetry （DSC）. The minor-addition of Fe obviously extends the supercooled liquid region ΔTx. The plastic strain of the Cu44Zr48Al7Fe bulk metallic glass is about 1.5%. The microstructures were examined by transmission electron microscopy （TEM）. It is found that when 1%-2% Fe （mole fraction） were introduced into the CuZrAl alloy matrix, nanoscale phase separation occurs in the as-prepared Cu44Zr48Al7Fe bulk metallic glass.
