Al-Cu-Mn alloys are widely used to produce automobile components like cylinder heads and engine blocks because of their capability to retain excellent thermal and mechanical characteristics at high temperatures.Howeve...Al-Cu-Mn alloys are widely used to produce automobile components like cylinder heads and engine blocks because of their capability to retain excellent thermal and mechanical characteristics at high temperatures.However,the Al-Cu-Mn-based alloys demonstrate restricted fluidity,leading to casting defects such as shrinkage and incomplete filling.This research investigated the microstructure and fluidity of Al-4.7Cu-1.0Mn-0.5Mg(wt%)alloy with minor cerium(Ce)addition.The as-cast alloys predominantly compriseα-Al matrix,accompanied by the presence of Al_(2)Cu,Al_(6)Mn,and Al_(8)Cu_(4)Ce phases.The influence of adding Ce on the fluidity of the Al-4.7Cu-1.0Mn-0.5Mg alloy was investigated using a trispiral fluidity test mold in this research.The findings suggest that the addition of Ce within the range of 0.1 wt%to 0.5 wt%in the Al-4.7Cu-1.0Mn-0.5Mg alloy results in an enhancement in fluidity.Specifically,the alloy containing 0.4 wt%Ce exhibits a significant increase in fluidity distance,from 349.7 to 485.7 mm.This improvement can be attributed to the reduction in viscosity,the refinement of secondary dendrite arm spacing,and the modification of secondary phase particles.However,a higher concentration of Ce leads to a decrease in fluidity length,potentially due to the formation of Al_(8)Cu_(4)Ce.展开更多
The effect of Cr addition on nickel aluminium bronze(NAB)alloy microstructure,mechanical properties,and erosion-corrosion behaviour has been studied.The results show that Cr addition does not change the composition of...The effect of Cr addition on nickel aluminium bronze(NAB)alloy microstructure,mechanical properties,and erosion-corrosion behaviour has been studied.The results show that Cr addition does not change the composition of the precipitated phases,more Cr entered theκphase and a small amount of Cr solubilized in the matrix,which increase the hardness of theκand matrix and decrease the potential difference between theκand matrix.NAB alloy with Cr shows high erosion-corrosion resistance at high flow rate conditions,due to its lower phase potential difference and higher surface hardness.At the flow rate of 3 m·s^(-1),the corrosion rate is 0.076 mm·year^(-1),which is~20%lower than that of the unadded Cr sample.Moreover,the corrosion product film contains Cr_(2)O_(3)and Cr^(3+),which improves the densification of the film and raises alloy’s corrosion resistance with Cr addition.The combination of mechanical and corrosion resistant properties may qualify this alloy as a potential candidate material for sustainable and safe equipment.展开更多
In this paper,the property degradation micromechanism of Al-5.10Cu-0.65 Mg-0.8Mn(wt%)alloy induced by 0.5 wt%Fe minor addition was revealed by atomic-scale scanning transmission electron microscopy and energy-dispersi...In this paper,the property degradation micromechanism of Al-5.10Cu-0.65 Mg-0.8Mn(wt%)alloy induced by 0.5 wt%Fe minor addition was revealed by atomic-scale scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy coupled with first-principles calculations.The results show that the Fe minor addition to the Al-Cu-Mg-Mn alloy leads to a slight reduction of grain size and the formation of coarse Al7Cu2Fe constituent particles.Fe tends to segregate into the T-phase dispersoids,θ'-,and S-phase precipitates by preferentially occupying Cu or Mn sites in these phase structures.The apparent Fe segregation contributes to an increase in stiffness of the T-phase and S-phase but decreased stiffness of theθ'phase.Formation of the coarse Al7Cu2Fe constituent particles and decreased stiffness of main precipitatesθ'containing Fe result in the degraded strength of the Al-Cu-Mg-Mn-Fe alloy.Further study reveals that corrosion resistance degradation of the Al-Cu-Mg-Mn-Fe alloy is associated with the increased width of precipitation free zones and consecutive grain boundary precipitates.The obtained results have significant implications for the usage of recycled Al alloys and the potential design strategies of high-performance alloys containing Fe.展开更多
Rolling contact fatigue performance is among the most important issues for applications of bearing steels.In this work,a recently developed surface modification technique,surface mechanical rolling treatment,was appli...Rolling contact fatigue performance is among the most important issues for applications of bearing steels.In this work,a recently developed surface modification technique,surface mechanical rolling treatment,was applied on a rare-earth addition bearing steel.And rolling contact fatigue behavior of treated samples was compared with that of as-received counterparts at different contacting stresses.The results demonstrated that a 700μm-thick gradient nanostructured surface layer is produced on samples by surface mechanical rolling treatment.The grain size decreases while the microhardness increases gradually with decreasing depth,reaching~23 nm and~10.2 GPa,respectively,at the top surface.Consequently,the rolling contact fatigue property is significantly enhanced.The characteristic life of treated samples is~3.2 times that of untreated counterparts according to Weibull curves at 5.6 GPa.Analyses of fatigue mechanisms demonstrated that the gradient nanostructured surface layer might not only retard material degradation and microcrack formation,but also prolong the steady-state elastic response stage under rolling contact fatigue.展开更多
Fertilization or atmospheric deposition of nitrogen(N)and phosphorus(P)to terrestrial ecosystems can alter soil N(P)availability and the nature of nutrient limitation for plant growth.Changing the allocation of leaf P...Fertilization or atmospheric deposition of nitrogen(N)and phosphorus(P)to terrestrial ecosystems can alter soil N(P)availability and the nature of nutrient limitation for plant growth.Changing the allocation of leaf P fractions is potentially an adaptive strategy for plants to cope with soil N(P)availability and nutrient-limiting conditions.However,the impact of the interactions between imbalanced anthropogenic N and P inputs on the concentrations and allocation proportions of leaf P fractions in forest woody plants remains elusive.We conducted a metaanalysis of data about the concentrations and allocation proportions of leaf P fractions,specifically associated with individual and combined additions of N and P in evergreen forests,the dominant vegetation type in southern China where the primary productivity is usually considered limited by P.This assessment allowed us to quantitatively evaluate the effects of N and P additions alone and interactively on leaf P allocation and use strategies.Nitrogen addition(exacerbating P limitation)reduced the concentrations of leaf total P and different leaf P fractions.Nitrogen addition reduced the allocation to leaf metabolic P but increased the allocation to other fractions,while P addition showed opposite trends.The simultaneous additions of N and P showed an antagonistic(mutual suppression)effect on the concentrations of leaf P fractions,but an additive(summary)effect on the allocation proportions of leaf P fractions.These results highlight the importance of strategies of leaf P fraction allocation in forest plants under changes in environmental nutrient availability.Importantly,our study identified critical interactions associated with combined N and P inputs that affect leaf P fractions,thus aiding in predicting plant acclimation strategies in the context of intensifying and imbalanced anthropogenic nutrient inputs.展开更多
A direct Michael addition reaction between imidazo[1,2-a]pyridines andα,β-unsaturated ketones using acidic alumina as a C(sp3)—H acid catalyst has been developed.The abundant C(sp3)—H acid sites(Al^(3+))on the aci...A direct Michael addition reaction between imidazo[1,2-a]pyridines andα,β-unsaturated ketones using acidic alumina as a C(sp3)—H acid catalyst has been developed.The abundant C(sp3)—H acid sites(Al^(3+))on the acidic alumina surface effectively activate the carbonyl group ofα,β-unsaturated ketones,significantly enhancing the electrophilicity of theβ-carbon and thereby facilitating selective alkylation at the C3 position of imidazo[1,2-a]pyridines.This method demonstrates excellent functional group compatibility,mild reaction conditions,low reagent costs,and operational simplicity,providing a novel strategy for the efficient synthesis of alkylated imidazo[1,2-a]pyridine derivatives.展开更多
The effects of trace cerium(Ce)addition on the microstructural and textural evolution and the dynamic recrystallization(DRX)of the ultrahigh-purity copper(Cu)containing small amounts of sulfur(S)were investigated usin...The effects of trace cerium(Ce)addition on the microstructural and textural evolution and the dynamic recrystallization(DRX)of the ultrahigh-purity copper(Cu)containing small amounts of sulfur(S)were investigated using a Gleeble-1500 thermal simulation tester at 600℃.The results show that with increasing Ce content,the grain size of the Cu-S(S2)alloy gradually decreases and the grain boundary embrittlement induced by S impurities is considerably inhibited.The addition of Ce promotes the DRX process of the S2 alloy and changes its DRX mechanism from discontinuous to continuous and twinning-induced DRX mechanisms.The texture component and intensity of the S2 alloy vary with the increase of Ce content.The addition of 120×10^(-6) Ce(mass fraction)is favorable for the grain orientation randomization,which is attributed to the promoted DRX.展开更多
AIM:To investigate the response of the anterior and posterior corneal surface in femtosecond laser-assisted convex stromal lenticule addition keratoplasty(SLAK)combined with cross-linking(CXL)for treating keratoconus ...AIM:To investigate the response of the anterior and posterior corneal surface in femtosecond laser-assisted convex stromal lenticule addition keratoplasty(SLAK)combined with cross-linking(CXL)for treating keratoconus at the first 3mo of follow-up.METHODS:In this prospective observational study,20 eyes of 20 keratoconus patients who underwent SLAK combined with CXL were included.The morphological indices in keratometry and elevation data were recorded from the Sirius at baseline and 1 and 3mo postoperatively.The mean values of maximum keratometry(K_(max)),flat keratometry(K_(1)),and steep keratometry(K_(2))at the central,3-mm,5-mm,and 7-mm areas were measured from the curvature map.The changes in anterior and posterior corneal elevation under the best-fit sphere(BFS)radius at seven points horizontally of the center,3-mm,5-mm,and 7-mm area from the center at both nasal(N)and temporal(T)side were measured from elevation map.RESULTS:For the front corneal curvature,K_(1),and K_(2) at 3-mm,5-mm,and 7-mm of the anterior corneal surface increased significantly 1mo postoperatively(all P<0.05)and remained unchanged until 3mo(P>0.05).For the back corneal curvature,K_(1) and K_(2) along the 3-mm back meridian significantly decreased after month 1(P=0.002,0.077,respectively).Posterior K_(2)-readings along the 5-mm and 7-mm did not change after surgery(P>0.05).Anterior BFS decreased 1mo(P<0.001)postoperatively but remained unchanged until 3mo after SLAK(P>0.05).There was no change in posterior BFS before and after the surgery(P>0.05).Anterior elevation at N5,N3,central,and T5 points and posterior elevation at central and T7 points shifted backward 1mo postoperatively(all P<0.05)and remained stable until 3mo(P>0.05).CONCLUSION:The myopic SLAK combined with CXL is an economical alternative for stabilizing the corneal surface in severe keraoconus.“Pseudoprogression”occurs in the early phase postoperatively,but it is not an indicator of keratoconus progression.展开更多
The effects of Zr addition on the mechanical properties and in vitro degradation behavior of Mg-1.0Yb-xZr(x=0,0.2,1.0,and 1.53,wt.%)cast alloys were investigated.The results indicated that with increasing Zr addition,...The effects of Zr addition on the mechanical properties and in vitro degradation behavior of Mg-1.0Yb-xZr(x=0,0.2,1.0,and 1.53,wt.%)cast alloys were investigated.The results indicated that with increasing Zr addition,a much refined and homogeneous equiaxed grain structure was achieved from a typical columnar grain structure,in companion with the appearance and coarsening of Zr-rich particles.Subsequent electrochemical and immersion tests demonstrated that the corrosion of the alloy was Zr-addition dependent.A trace or excessive Zr addition caused severe localized corrosion attacks,whereas Zr-free and 1.0 Zr alloyed counterparts were generally corroded uniformly.The good combination of mechanical properties and corrosion resistance of the Mg-1.0Yb-1.0Zr alloy was resulted from the refined and homogeneous equiaxed grain structure and fine dispersed Zr-rich particles,thus improving the comprehensive mechanical properties by grain refinement and reducing corrosion rate by generating a more stable and compact passivation layer during long-term immersion.展开更多
Strontium has similar chemical properties to calcium and has recently been recognized as a non-essential beneficial element for plants.In order to compare the effects of strontium and calcium on improving salt toleran...Strontium has similar chemical properties to calcium and has recently been recognized as a non-essential beneficial element for plants.In order to compare the effects of strontium and calcium on improving salt tolerance of Chinese cabbage during the germination stage,2,4,and 8 mmol/L of SrCl_(2),CaCl_(2) or an equimolar mixture of both were added separately to a 150 mmol/L NaCl solution.The results showed that Ca-Sr addition significantly increased seed viability,seed vigor,seed germination rate and seed germination uniformity of Chinese cabbage compared with the salt-control group.The differences in germination percentage(GP)and germination energy(GE)among the Ca-addition and Sr-addition groups were not significant,and the differences in coefficient of rate of germination(CRG),index of rate of germination(IRG)and coefficient of variation of the germination time(CVT)were relatively small,but clear differences were observed in germination index(GI),vigor index(VI)and coefficient of uniformity of germination(CUG).The results of GI and VI indicated that the higher the concentration of Ca-addition or Sr-addition,the more significant the enhancement of seed vigor.Under saline stress(150 mmol/L NaCl),the Ca-Sr co-addition outperformed Sr-treatment alone,and Ca-addition achieved the highest seed vigor at equivalent concentrations.Furthermore,all Ca-Sr treatments significantly enhanced the uniformity of Chinese cabbage sprouts exposed to 150 mM NaCl,with the best uniformity improved by the addition of 2 and 4 mmol/L SrCl_(2).Ca-Sr treatments increased the salt tolerance of Chinese cabbage sprouts during the germination stage mainly because the Ca2+and Sr2+significantly enhanced plasma membrane stability and reduced oxidative stress(as indicated by decreased contents of malondialdehyde and O2⋅-contents)in sprouts.The decrease of soluble sugar and proline content caused by Ca-Sr addition implies that elevated levels of these osmolytes were not the primary contributors to improved seed germinability in Chinese cabbage.These findings demonstrate that Sr is a beneficial element for enhancing salt tolerance in plants,laying a theoretical foundation for the development and application of strontium in agriculture.展开更多
Increasing anthropogenic nitrogen(N)inputs has profoundly altered soil microbial necromass carbon(MNC),which serves as a key source of soil organic carbon(SOC).Yet,the response pattern of MNC and its contribution to S...Increasing anthropogenic nitrogen(N)inputs has profoundly altered soil microbial necromass carbon(MNC),which serves as a key source of soil organic carbon(SOC).Yet,the response pattern of MNC and its contribution to SOC across a wide range of N addition rates,remain elusive.In a temperate grassland with six years'consecutive N addition spanning seven rates(0-50 g N/(m^(2)·year))in Inner Mongolia,China,we explored the responses of soil MNC and its contribution to SOC.The soil MNC showed a hump-shaped pattern to increasing N addition rates,with the N saturation threshold at 18.07 g N/(m^(2)·year).The soil MNC was driven by nematode abundance and the ratio of bacterial to fungal biomass below the N threshold,and by plant biomass allocation pattern and diversity above the N threshold.The contribution of soil MNC to SOC declined with increasing N addition rates,and was mainly regulated by the ratio of MNC to mineral-associated organic carbon and plant diversity and the ratio of bacterial to fungal biomass.In addition,the soil MNC and SOC differentially responded to N addition and were mediated by disparate biological and geochemical mechanisms,leading to the decoupled MNC production from SOC formation.Together,in this N-enriched temperate grassland,the soilmicrobial necro-mass production tends to be insufficient as a general explanation linking SOC formation.This study expands the mechanistic comprehension of the connections between external N input and soil carbon sequestration.展开更多
Plant roots and microorganisms are integral to the phosphorus(P)transformation process in forest soils.However,the specific mechanisms by which they affect soil P availability under long-term nitrogen(N)addition remai...Plant roots and microorganisms are integral to the phosphorus(P)transformation process in forest soils.However,the specific mechanisms by which they affect soil P availability under long-term nitrogen(N)addition remain elusive.Therefore,a long-term N addition experiment was conducted in a temperate forest in China.After 11-year N addition,measurements focused on P fractions,soil microbial biomass(SMB),microbial community(PLFAs),phosphatase activity,fine root biomass(FRB),and fine root biomass P(FRBP).The results demonstrated that N addition significantly decreased Resin-P and total extractable organic P(Po),while having no significant effect on total extractable inorganic P(Pi).Moreover,a strong positive correlation was observed between Resin-P and total extractable Po,suggesting that under N addition,organic P serves as the primary source of soluble P.This implies that continuous N deposition may exhaust the potential P source stored as organic P in forest soils.N addition also led to a reduction in SMB and FRB.Notably,microbial biomass P and FRBP were positively correlated with Resin-P and total extractable Po,indicating that the decrease in SMB and FRB is the main contributor to the decline in soluble P and organic P.Additionally,N addition significantly reduced phosphatase activity,suggesting an inhibition of the organic P hydrolysis process.In conclusion,N addition decreases P input into the soil by reducing SMB and FRB,and inhibits the transformation of different P forms by lowering enzyme activity.Consequently,soil organic P and soluble P decline,further intensifying P limitation.展开更多
In this study,the effects of Eu addition on the microstructures and mechanical properties of A390 alloy were investigated,along with the spheroidization mechanism of primary silicon with Eu.The results showed that whe...In this study,the effects of Eu addition on the microstructures and mechanical properties of A390 alloy were investigated,along with the spheroidization mechanism of primary silicon with Eu.The results showed that when the Eu addition reached 0.6 wt%,both refinement and spheroidization of primary silicon,alongside fibrous eutectic silicon can be obtained.Owing to such a microstructural modification,the ultimate tensile strength and elongation were increased by 24.9%and 101.2%,respectively.While in the unmodified alloy,the octahedral,plate-like,and five-star primary silicon particles exhibited fewΣ3 twin boundaries,whereas in the Eu-modified alloy,spheroidal primary silicon displayed curvedΣ3 twin boundaries,sub-grain boundaries,and specialΣ9 twin boundaries.Atom probe tomography analysis indicated that Al and Eu atoms were present in the spheroidal primary silicon as spheroidal,T-shaped,straight rod-like,and curved rod-like clusters,with the Al:Eu ratio of 2.92±0.46.The spheroidization mechanism of primary silicon was proposed through five aspects:(ⅰ)spheroidal clusters inducing parallel and intersectingΣ3 twins,(ⅱ)straight rod-like clusters causing poisoning of twin plane re-entrant edge,(ⅲ)T-shaped clusters leading to multithickness intersectingΣ3 twins,(ⅳ)curved rod-like clusters resulting in curvedΣ3 twins,and(ⅴ)curved rod-like clusters induce specialΣ9 twins.These mechanisms facilitate a transition from initially anisotropic to isotropic growth of primary silicon with Eu addition.The present work provides an important insight for the development of a novel way to achieve the primary Si spheroidization and the improvement of mechanical properties of hypereutectic Al-Si alloys.展开更多
Powdery mildew is a serious disease caused by Blumeria graminis f.sp.tritici(Bgt)that critically threatens the yield and quality of wheat(Triticum aestivum L.).Using effective powdery mildew resistance genes is the op...Powdery mildew is a serious disease caused by Blumeria graminis f.sp.tritici(Bgt)that critically threatens the yield and quality of wheat(Triticum aestivum L.).Using effective powdery mildew resistance genes is the optimal method for controlling this disease.Against the background of high genetic homogeneity among the modern commercial cultivars that are mainly derived from conventional interbreeding,the resistance genes from wheat relatives have especially prominent advantages.Octoploid triticale,produced from common wheat and rye(Secale cereale L.)through distant hybridization,is a new synthetic species and valuable gene donor for wheat improvement.In this study,we developed the wheat-rye line YT5 through the hybridization of octaploid triticale and two wheat lines.YT5 was confirmed to be a 6RL ditelosomic addition and 1R(1B)substitution line using genomic in situ hybridization(GISH),multicolor fluorescence in situ hybridization(mc-FISH),multicolor GISH(mc-GISH)and molecular marker analysis.Genetic analysis showed that the powdery mildew resistance in YT5 was derived from the rye chromosome arm 6RL.After inoculation with different Bgt isolates at the seedling stage,YT5 had compound reaction patterns with both obvious spores and hypersensitivity,and it gradually became highly resistant until the adult-plant stage,thus showing a resistance response significantly different from the reported Pm genes from rye chromosome 6RL.YT5 also showed promising agronomic performance,so it is expected to be an elite resistance donor for wheat improvement.To promote the transfer of the chromosome arm 6RL of YT5 in marker-assisted selection(MAS)breeding,we selected and verified two 6RL-specific kompetitive allelespecific PCR(KASP)markers that can be applied to efficiently detect this chromosome arm in different wheat backgrounds.展开更多
Nitrogen(N)enrichment is expected to induce a greater phosphorus(P)limitation,despite the acceleration of soil P cycling.However,the changing patterns in plant P and soil available P after N enrichment,and their regul...Nitrogen(N)enrichment is expected to induce a greater phosphorus(P)limitation,despite the acceleration of soil P cycling.However,the changing patterns in plant P and soil available P after N enrichment,and their regulatory mechanisms,remain poorly understood in alpine meadows.Here,we conducted a field experiment with four N addition rates(0,5,10,and 15 g N m^(-2)yr^(-1))in an alpine meadow,and investigated the P in plants,microorganisms,and soil to determine their patterns of change after short-term N addition.Our results showed that N addition significantly increased plant biomass,and the plant P pool showed a non-linear response to the N addition gradient.Soil available P initially increased and then declined with increasing N addition,whereas the occluded inorganic P decreased markedly.The critical factors for soil available P varied with different N addition rates.At lower N addition levels(0 and 5 g N m^(-2)yr^(-1)),soil acidification facilitated the mobilization of occluded inorganic P to increase soil available P.Conversely,at higher N addition levels(10 and 15 g N m^(-2)yr^(-1)),the elevated soil microbial biomass P intensified the competition with plants for soil P,leading to a decline in soil available P.This study highlights the nonlinear responses of the plant P pool and soil available P concentration to N addition rates.These responses suggest the need for developing ecosystem models to assess different effects of increasing N rates,which would enable more accurate predictions of the plant P supply and soil P cycling under N enrichment.展开更多
Bulk metallic glasses(BMGs)are typically characterized by high strength and elasticity.However,they generally demonstrate a deficiency in plastic deformation capability at room temperatures.In this work,Cu_(50-x)Zr_(4...Bulk metallic glasses(BMGs)are typically characterized by high strength and elasticity.However,they generally demonstrate a deficiency in plastic deformation capability at room temperatures.In this work,Cu_(50-x)Zr_(46)Al4Agx(x=0,1,2,3,4)alloys were prepared by arc melting and copper mold casting to investigate their structure,glass-forming ability,and mechanical properties.The results show that the addition of Ag can increase the parameter of DTx and g in Cu_(50)Zr_(46)Al_(4)alloy by 116%and 1.5%respectively,effectively enhancing its thermal stability and glass-forming ability.Compressive fracture tests reveal that the addition of Ag can significantly improve the yield strength,ultimate strength,and plasticity of the Cu_(50)Zr_(46)Al_(4)alloy.Specifically,with the Ag addition of 1 at.%,the alloy’s ultimate strength and plasticity increased by 71.8%and 21 times,respectively.Furthermore,the introduction of Ag can effectively control the free volume content in the Cu_(50)Zr_(46)Al_(4)alloy,thereby tuning the hardness of the material.This work provides valuable insights into improving the mechanical performance of BMGs through micro-alloying approaches.展开更多
Global warming and nitrogen(N)deposition have a profound impact on greenhouse gas(GHG)fluxes and consequently,they also affect climate change.However,the global combined effects of warming and N addition on GHG fluxes...Global warming and nitrogen(N)deposition have a profound impact on greenhouse gas(GHG)fluxes and consequently,they also affect climate change.However,the global combined effects of warming and N addition on GHG fluxes remain to be fully understood.To address this knowledge gap,a globalmeta-analysis of 197 datasets was performed to assess the response of GHG fluxes to warming and N addition and their interactions under various climate and experimental conditions.The results indicate that warming significantly increased CO_(2)emissions,while N addition and the combined warming and N addition treatments had no impact on CO_(2)emissions.Moreover,both warming and N addition and their interactions exhibited positive effects on N_(2)O emissions.Under the combined warming and N addition treatments,warming was observed to exert a positive main effect on CO_(2)emissions,while N addition had a positive main effect on N_(2)O emissions.The interactive effects of warming and N addition exhibited antagonistic effects on CO_(2),N_(2)O,and CH_(4)emissions,with CH_(4)uptake dominated by additive effects.Furthermore,we identified biome and climate factors as the two treatments.These findings indicate that both warming and N addition substantially impact soil GHG fluxes and highlight the urgent need to investigate the influence of the combination of warming and N addition on terrestrial carbon and N cycling under ongoing global change.展开更多
Amid global climate change, rising levels of nitrogen(N) deposition have attracted considerable attention for their potential effects on the carbon cycle of terrestrial ecosystems. The desert steppes are a crucial yet...Amid global climate change, rising levels of nitrogen(N) deposition have attracted considerable attention for their potential effects on the carbon cycle of terrestrial ecosystems. The desert steppes are a crucial yet vulnerable ecosystem in arid areas, but their response to the combination of N addition and precipitation(a crucial factor in arid areas) remains underexplored. This study systematically explored the impact of N addition and precipitation on net ecosystem exchange(NEE) in a desert steppe in northern China. Specifically, we conducted a 2-a experiment from 2022 to 2023 with eight N addition treatments in the Urat desert steppe of Inner Mongolia Autonomous Region, China, to examine changes in NEE and explore its driving factors. The structural equation model(SEM) and multiple regression model were applied to determine the relationship of NEE with plant community characteristics and soil physical-chemical properties. Statistical results showed that N addition has no significant effect on NEE.However, it has a significant impact on the functional traits of desert steppe plant communities. SEM results further revealed that N addition has no significant effect on NEE in the desert steppe, whereas annual precipitation can influence NEE variations. The multiple regression model analysis indicated that plant functional traits play an important role in explaining the changes in NEE, accounting for 62.15% of the variation in NEE. In addition, plant height, as an important plant functional trait indicator, shows stronger reliability in predicting the changes in NEE and becomes a more promising predictor. These findings provide valuable insights into the complex ecological mechanisms governing plant community responses to precipitation and nutrient availability in the arid desert steppes, contributing to the improved monitoring and prediction of desert steppe ecosystem responses to global climate change.展开更多
Friction stir lap welding(FSLW)was adopted to join successfully dissimilar AZ31B Mg alloy and TC4 Ti alloy with Sn foil addition of 30μm thickness.Interfacial microstructure,tensile shear performances and bonding mec...Friction stir lap welding(FSLW)was adopted to join successfully dissimilar AZ31B Mg alloy and TC4 Ti alloy with Sn foil addition of 30μm thickness.Interfacial microstructure,tensile shear performances and bonding mechanism of the joints obtained using three different rotation speeds were studied.High-performance FSLW Mg/Ti dissimilar joints with maximum tensile shear strength of 593.3 N/mm were produced at 1180 r/min,and which was mainly attributed to ultrastrong reaction interlayer consisting of 125.9 nm thick(Mg_(2)Sn+Mg)transition layer and discontinuous(Ti_(6)Sn_(5)+Ti_(3)Al)IMCs layer with 6.58 nm thickness at the interface.The formation of the reaction interlayer was beneficial for high interfacial strength,resulting in significantly improving the joint strength.The fracture of all FSLW joints located on AZ31B Mg stirred zone adjacent to(Mg_(2)Sn+Mg)transition layer or along the crack propagation direction of the AZ31B/TC4 interface with different fracture mechanisms,and which could be consistent with interfacial microstructure.展开更多
Catalytic asymmetric hydrophosphination of unsaturated substrates has been proven to be one of the most straightforward ways to achieve chiral phosphine compounds.Although the methodologies of transition metals and or...Catalytic asymmetric hydrophosphination of unsaturated substrates has been proven to be one of the most straightforward ways to achieve chiral phosphine compounds.Although the methodologies of transition metals and organocatalysts catalyzed enantioselective hydrophosphination reactions have been well developed during the last decade,the enantioselective construction of quinoline and isoquinoline-based phosphines remains challenging.Furthermore,the chiral quinoline-based phosphines play a significant role in the preparation of chiral P,N-ligands.Herein,we report a comprehensive investigation for the asymmetric addition of diarylphosphine oxides to a wide range ofα,β-unsaturated quinolines and isoquinolines,catalyzed by commercial chiral phosphoric acid,affording the corresponding products with up to 99%yield and 98%ee.展开更多
基金Project supported by the National Natural Science Foundation of China (52171030)the Key Basic Research Project of the Basic Strengthen Program (2021-JCJQ-ZD-043-00)the National Key Research and Development Program of China (2018YFA0702903)。
文摘Al-Cu-Mn alloys are widely used to produce automobile components like cylinder heads and engine blocks because of their capability to retain excellent thermal and mechanical characteristics at high temperatures.However,the Al-Cu-Mn-based alloys demonstrate restricted fluidity,leading to casting defects such as shrinkage and incomplete filling.This research investigated the microstructure and fluidity of Al-4.7Cu-1.0Mn-0.5Mg(wt%)alloy with minor cerium(Ce)addition.The as-cast alloys predominantly compriseα-Al matrix,accompanied by the presence of Al_(2)Cu,Al_(6)Mn,and Al_(8)Cu_(4)Ce phases.The influence of adding Ce on the fluidity of the Al-4.7Cu-1.0Mn-0.5Mg alloy was investigated using a trispiral fluidity test mold in this research.The findings suggest that the addition of Ce within the range of 0.1 wt%to 0.5 wt%in the Al-4.7Cu-1.0Mn-0.5Mg alloy results in an enhancement in fluidity.Specifically,the alloy containing 0.4 wt%Ce exhibits a significant increase in fluidity distance,from 349.7 to 485.7 mm.This improvement can be attributed to the reduction in viscosity,the refinement of secondary dendrite arm spacing,and the modification of secondary phase particles.However,a higher concentration of Ce leads to a decrease in fluidity length,potentially due to the formation of Al_(8)Cu_(4)Ce.
基金supported by Beijing Nova Program(No.20230484371)the National Key Research and Development Program of China(No.2021YFB3700700).
文摘The effect of Cr addition on nickel aluminium bronze(NAB)alloy microstructure,mechanical properties,and erosion-corrosion behaviour has been studied.The results show that Cr addition does not change the composition of the precipitated phases,more Cr entered theκphase and a small amount of Cr solubilized in the matrix,which increase the hardness of theκand matrix and decrease the potential difference between theκand matrix.NAB alloy with Cr shows high erosion-corrosion resistance at high flow rate conditions,due to its lower phase potential difference and higher surface hardness.At the flow rate of 3 m·s^(-1),the corrosion rate is 0.076 mm·year^(-1),which is~20%lower than that of the unadded Cr sample.Moreover,the corrosion product film contains Cr_(2)O_(3)and Cr^(3+),which improves the densification of the film and raises alloy’s corrosion resistance with Cr addition.The combination of mechanical and corrosion resistant properties may qualify this alloy as a potential candidate material for sustainable and safe equipment.
基金supported by the National Natural Science Foundation of China(Nos.U20A20274 and 52061003)the Natural Science Foundation of Yunnan Province(No.202301AT070209)the Science and Technology Major Project of Yunnan Province(No.202102AG050017).
文摘In this paper,the property degradation micromechanism of Al-5.10Cu-0.65 Mg-0.8Mn(wt%)alloy induced by 0.5 wt%Fe minor addition was revealed by atomic-scale scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy coupled with first-principles calculations.The results show that the Fe minor addition to the Al-Cu-Mg-Mn alloy leads to a slight reduction of grain size and the formation of coarse Al7Cu2Fe constituent particles.Fe tends to segregate into the T-phase dispersoids,θ'-,and S-phase precipitates by preferentially occupying Cu or Mn sites in these phase structures.The apparent Fe segregation contributes to an increase in stiffness of the T-phase and S-phase but decreased stiffness of theθ'phase.Formation of the coarse Al7Cu2Fe constituent particles and decreased stiffness of main precipitatesθ'containing Fe result in the degraded strength of the Al-Cu-Mg-Mn-Fe alloy.Further study reveals that corrosion resistance degradation of the Al-Cu-Mg-Mn-Fe alloy is associated with the increased width of precipitation free zones and consecutive grain boundary precipitates.The obtained results have significant implications for the usage of recycled Al alloys and the potential design strategies of high-performance alloys containing Fe.
基金The financial supports by the Chinese Academy of Sciences(Nos.XDC04030300 and XDB0510303)CAS-HK Joint Laboratory of Nanomaterials and MechanicsShenyang National Laboratory for Materials Science are acknowledged.
文摘Rolling contact fatigue performance is among the most important issues for applications of bearing steels.In this work,a recently developed surface modification technique,surface mechanical rolling treatment,was applied on a rare-earth addition bearing steel.And rolling contact fatigue behavior of treated samples was compared with that of as-received counterparts at different contacting stresses.The results demonstrated that a 700μm-thick gradient nanostructured surface layer is produced on samples by surface mechanical rolling treatment.The grain size decreases while the microhardness increases gradually with decreasing depth,reaching~23 nm and~10.2 GPa,respectively,at the top surface.Consequently,the rolling contact fatigue property is significantly enhanced.The characteristic life of treated samples is~3.2 times that of untreated counterparts according to Weibull curves at 5.6 GPa.Analyses of fatigue mechanisms demonstrated that the gradient nanostructured surface layer might not only retard material degradation and microcrack formation,but also prolong the steady-state elastic response stage under rolling contact fatigue.
基金supported by the National Natural Science Foundation of China(No.41473068)supported by China Postdoctoral Science Foundation(No.2022M722667)。
文摘Fertilization or atmospheric deposition of nitrogen(N)and phosphorus(P)to terrestrial ecosystems can alter soil N(P)availability and the nature of nutrient limitation for plant growth.Changing the allocation of leaf P fractions is potentially an adaptive strategy for plants to cope with soil N(P)availability and nutrient-limiting conditions.However,the impact of the interactions between imbalanced anthropogenic N and P inputs on the concentrations and allocation proportions of leaf P fractions in forest woody plants remains elusive.We conducted a metaanalysis of data about the concentrations and allocation proportions of leaf P fractions,specifically associated with individual and combined additions of N and P in evergreen forests,the dominant vegetation type in southern China where the primary productivity is usually considered limited by P.This assessment allowed us to quantitatively evaluate the effects of N and P additions alone and interactively on leaf P allocation and use strategies.Nitrogen addition(exacerbating P limitation)reduced the concentrations of leaf total P and different leaf P fractions.Nitrogen addition reduced the allocation to leaf metabolic P but increased the allocation to other fractions,while P addition showed opposite trends.The simultaneous additions of N and P showed an antagonistic(mutual suppression)effect on the concentrations of leaf P fractions,but an additive(summary)effect on the allocation proportions of leaf P fractions.These results highlight the importance of strategies of leaf P fraction allocation in forest plants under changes in environmental nutrient availability.Importantly,our study identified critical interactions associated with combined N and P inputs that affect leaf P fractions,thus aiding in predicting plant acclimation strategies in the context of intensifying and imbalanced anthropogenic nutrient inputs.
文摘A direct Michael addition reaction between imidazo[1,2-a]pyridines andα,β-unsaturated ketones using acidic alumina as a C(sp3)—H acid catalyst has been developed.The abundant C(sp3)—H acid sites(Al^(3+))on the acidic alumina surface effectively activate the carbonyl group ofα,β-unsaturated ketones,significantly enhancing the electrophilicity of theβ-carbon and thereby facilitating selective alkylation at the C3 position of imidazo[1,2-a]pyridines.This method demonstrates excellent functional group compatibility,mild reaction conditions,low reagent costs,and operational simplicity,providing a novel strategy for the efficient synthesis of alkylated imidazo[1,2-a]pyridine derivatives.
基金financially supported by the National Natural Science Foundation of China(Nos.52071133,U21A2051)the Henan Province Science and Technology Tackling Key Problems Project,China(No.222102230001)+2 种基金the Zhongyuan Scholar Workstation Funded Project,China(No.224400510025)the Henan Key Research and Development Project,China(No.221111230600)Luoyang Major Science and Technology Innovation Special Project,China(No.2201017A)。
文摘The effects of trace cerium(Ce)addition on the microstructural and textural evolution and the dynamic recrystallization(DRX)of the ultrahigh-purity copper(Cu)containing small amounts of sulfur(S)were investigated using a Gleeble-1500 thermal simulation tester at 600℃.The results show that with increasing Ce content,the grain size of the Cu-S(S2)alloy gradually decreases and the grain boundary embrittlement induced by S impurities is considerably inhibited.The addition of Ce promotes the DRX process of the S2 alloy and changes its DRX mechanism from discontinuous to continuous and twinning-induced DRX mechanisms.The texture component and intensity of the S2 alloy vary with the increase of Ce content.The addition of 120×10^(-6) Ce(mass fraction)is favorable for the grain orientation randomization,which is attributed to the promoted DRX.
基金Supported by the Social Development Grant of Shaanxi Province(No.2022SF-404)the Science and Technology Program of Xi’an,China(No.23YXYJ0010,No.23YXYJ0037)+1 种基金the Research Project of Xi’an Health Commission(No.2024ms05)the Technology Innovation Supporting Program of Shaanxi(No.2024RS-CXTD-11).
文摘AIM:To investigate the response of the anterior and posterior corneal surface in femtosecond laser-assisted convex stromal lenticule addition keratoplasty(SLAK)combined with cross-linking(CXL)for treating keratoconus at the first 3mo of follow-up.METHODS:In this prospective observational study,20 eyes of 20 keratoconus patients who underwent SLAK combined with CXL were included.The morphological indices in keratometry and elevation data were recorded from the Sirius at baseline and 1 and 3mo postoperatively.The mean values of maximum keratometry(K_(max)),flat keratometry(K_(1)),and steep keratometry(K_(2))at the central,3-mm,5-mm,and 7-mm areas were measured from the curvature map.The changes in anterior and posterior corneal elevation under the best-fit sphere(BFS)radius at seven points horizontally of the center,3-mm,5-mm,and 7-mm area from the center at both nasal(N)and temporal(T)side were measured from elevation map.RESULTS:For the front corneal curvature,K_(1),and K_(2) at 3-mm,5-mm,and 7-mm of the anterior corneal surface increased significantly 1mo postoperatively(all P<0.05)and remained unchanged until 3mo(P>0.05).For the back corneal curvature,K_(1) and K_(2) along the 3-mm back meridian significantly decreased after month 1(P=0.002,0.077,respectively).Posterior K_(2)-readings along the 5-mm and 7-mm did not change after surgery(P>0.05).Anterior BFS decreased 1mo(P<0.001)postoperatively but remained unchanged until 3mo after SLAK(P>0.05).There was no change in posterior BFS before and after the surgery(P>0.05).Anterior elevation at N5,N3,central,and T5 points and posterior elevation at central and T7 points shifted backward 1mo postoperatively(all P<0.05)and remained stable until 3mo(P>0.05).CONCLUSION:The myopic SLAK combined with CXL is an economical alternative for stabilizing the corneal surface in severe keraoconus.“Pseudoprogression”occurs in the early phase postoperatively,but it is not an indicator of keratoconus progression.
基金the financial supports from the China Scholarship Council(No.201808505057)。
文摘The effects of Zr addition on the mechanical properties and in vitro degradation behavior of Mg-1.0Yb-xZr(x=0,0.2,1.0,and 1.53,wt.%)cast alloys were investigated.The results indicated that with increasing Zr addition,a much refined and homogeneous equiaxed grain structure was achieved from a typical columnar grain structure,in companion with the appearance and coarsening of Zr-rich particles.Subsequent electrochemical and immersion tests demonstrated that the corrosion of the alloy was Zr-addition dependent.A trace or excessive Zr addition caused severe localized corrosion attacks,whereas Zr-free and 1.0 Zr alloyed counterparts were generally corroded uniformly.The good combination of mechanical properties and corrosion resistance of the Mg-1.0Yb-1.0Zr alloy was resulted from the refined and homogeneous equiaxed grain structure and fine dispersed Zr-rich particles,thus improving the comprehensive mechanical properties by grain refinement and reducing corrosion rate by generating a more stable and compact passivation layer during long-term immersion.
基金funded by the Natural Science Foundation of Shandong Province(ZR2020MC144)the Scientific Research Training Program for Undergraduates of Qufu Normal University(XJ2024016).
文摘Strontium has similar chemical properties to calcium and has recently been recognized as a non-essential beneficial element for plants.In order to compare the effects of strontium and calcium on improving salt tolerance of Chinese cabbage during the germination stage,2,4,and 8 mmol/L of SrCl_(2),CaCl_(2) or an equimolar mixture of both were added separately to a 150 mmol/L NaCl solution.The results showed that Ca-Sr addition significantly increased seed viability,seed vigor,seed germination rate and seed germination uniformity of Chinese cabbage compared with the salt-control group.The differences in germination percentage(GP)and germination energy(GE)among the Ca-addition and Sr-addition groups were not significant,and the differences in coefficient of rate of germination(CRG),index of rate of germination(IRG)and coefficient of variation of the germination time(CVT)were relatively small,but clear differences were observed in germination index(GI),vigor index(VI)and coefficient of uniformity of germination(CUG).The results of GI and VI indicated that the higher the concentration of Ca-addition or Sr-addition,the more significant the enhancement of seed vigor.Under saline stress(150 mmol/L NaCl),the Ca-Sr co-addition outperformed Sr-treatment alone,and Ca-addition achieved the highest seed vigor at equivalent concentrations.Furthermore,all Ca-Sr treatments significantly enhanced the uniformity of Chinese cabbage sprouts exposed to 150 mM NaCl,with the best uniformity improved by the addition of 2 and 4 mmol/L SrCl_(2).Ca-Sr treatments increased the salt tolerance of Chinese cabbage sprouts during the germination stage mainly because the Ca2+and Sr2+significantly enhanced plasma membrane stability and reduced oxidative stress(as indicated by decreased contents of malondialdehyde and O2⋅-contents)in sprouts.The decrease of soluble sugar and proline content caused by Ca-Sr addition implies that elevated levels of these osmolytes were not the primary contributors to improved seed germinability in Chinese cabbage.These findings demonstrate that Sr is a beneficial element for enhancing salt tolerance in plants,laying a theoretical foundation for the development and application of strontium in agriculture.
基金supported by the National Natural Science Foundation of China(Nos.42130515 and 32301450)the Open Foundation of State Key Laboratory of Desert and Oasis Ecology,Xinjiang Institute of Ecology and Geography,Chinese Academy of Sciences.
文摘Increasing anthropogenic nitrogen(N)inputs has profoundly altered soil microbial necromass carbon(MNC),which serves as a key source of soil organic carbon(SOC).Yet,the response pattern of MNC and its contribution to SOC across a wide range of N addition rates,remain elusive.In a temperate grassland with six years'consecutive N addition spanning seven rates(0-50 g N/(m^(2)·year))in Inner Mongolia,China,we explored the responses of soil MNC and its contribution to SOC.The soil MNC showed a hump-shaped pattern to increasing N addition rates,with the N saturation threshold at 18.07 g N/(m^(2)·year).The soil MNC was driven by nematode abundance and the ratio of bacterial to fungal biomass below the N threshold,and by plant biomass allocation pattern and diversity above the N threshold.The contribution of soil MNC to SOC declined with increasing N addition rates,and was mainly regulated by the ratio of MNC to mineral-associated organic carbon and plant diversity and the ratio of bacterial to fungal biomass.In addition,the soil MNC and SOC differentially responded to N addition and were mediated by disparate biological and geochemical mechanisms,leading to the decoupled MNC production from SOC formation.Together,in this N-enriched temperate grassland,the soilmicrobial necro-mass production tends to be insufficient as a general explanation linking SOC formation.This study expands the mechanistic comprehension of the connections between external N input and soil carbon sequestration.
基金supported by the Key Research Program Foundation of Higher Education in Henan Province(Grant No.24A180027)the China Postdoctoral Science Foundation(Grant No.2023M741727)+2 种基金the Xinyang Academy of Ecological Research Open Foundation(Grant No.2023XYQN14)the Postdoctoral Science Foundation of Henan Province(Grant No.202103058)the Major Applied Research Program in Humanities and Social Sciences of Henan Provincial Education Department(Grant No.2022-YYZD-22).
文摘Plant roots and microorganisms are integral to the phosphorus(P)transformation process in forest soils.However,the specific mechanisms by which they affect soil P availability under long-term nitrogen(N)addition remain elusive.Therefore,a long-term N addition experiment was conducted in a temperate forest in China.After 11-year N addition,measurements focused on P fractions,soil microbial biomass(SMB),microbial community(PLFAs),phosphatase activity,fine root biomass(FRB),and fine root biomass P(FRBP).The results demonstrated that N addition significantly decreased Resin-P and total extractable organic P(Po),while having no significant effect on total extractable inorganic P(Pi).Moreover,a strong positive correlation was observed between Resin-P and total extractable Po,suggesting that under N addition,organic P serves as the primary source of soluble P.This implies that continuous N deposition may exhaust the potential P source stored as organic P in forest soils.N addition also led to a reduction in SMB and FRB.Notably,microbial biomass P and FRBP were positively correlated with Resin-P and total extractable Po,indicating that the decrease in SMB and FRB is the main contributor to the decline in soluble P and organic P.Additionally,N addition significantly reduced phosphatase activity,suggesting an inhibition of the organic P hydrolysis process.In conclusion,N addition decreases P input into the soil by reducing SMB and FRB,and inhibits the transformation of different P forms by lowering enzyme activity.Consequently,soil organic P and soluble P decline,further intensifying P limitation.
基金financially supported by the National Natural Science Foundation of China(Nos.52301046,U24A2028 and U22A20174)the Program for Science&Technology Innovation Talents in Universities of Henan Province(25HASTIT007)+2 种基金the Frontier Exploration Projects of Longmen Laboratory(No.LMQYT-SKT005)the Central Plains Talents Planthe support of Provincial and Ministerial Co-construction of Collaborative Innovation Center for Non-ferrous Metal New Materials and Advanced Processing Technology
文摘In this study,the effects of Eu addition on the microstructures and mechanical properties of A390 alloy were investigated,along with the spheroidization mechanism of primary silicon with Eu.The results showed that when the Eu addition reached 0.6 wt%,both refinement and spheroidization of primary silicon,alongside fibrous eutectic silicon can be obtained.Owing to such a microstructural modification,the ultimate tensile strength and elongation were increased by 24.9%and 101.2%,respectively.While in the unmodified alloy,the octahedral,plate-like,and five-star primary silicon particles exhibited fewΣ3 twin boundaries,whereas in the Eu-modified alloy,spheroidal primary silicon displayed curvedΣ3 twin boundaries,sub-grain boundaries,and specialΣ9 twin boundaries.Atom probe tomography analysis indicated that Al and Eu atoms were present in the spheroidal primary silicon as spheroidal,T-shaped,straight rod-like,and curved rod-like clusters,with the Al:Eu ratio of 2.92±0.46.The spheroidization mechanism of primary silicon was proposed through five aspects:(ⅰ)spheroidal clusters inducing parallel and intersectingΣ3 twins,(ⅱ)straight rod-like clusters causing poisoning of twin plane re-entrant edge,(ⅲ)T-shaped clusters leading to multithickness intersectingΣ3 twins,(ⅳ)curved rod-like clusters resulting in curvedΣ3 twins,and(ⅴ)curved rod-like clusters induce specialΣ9 twins.These mechanisms facilitate a transition from initially anisotropic to isotropic growth of primary silicon with Eu addition.The present work provides an important insight for the development of a novel way to achieve the primary Si spheroidization and the improvement of mechanical properties of hypereutectic Al-Si alloys.
基金supported by the National Key Research and Development Program of China(2021YFD1200600)the National Natural Science Foundation of China(32272105).
文摘Powdery mildew is a serious disease caused by Blumeria graminis f.sp.tritici(Bgt)that critically threatens the yield and quality of wheat(Triticum aestivum L.).Using effective powdery mildew resistance genes is the optimal method for controlling this disease.Against the background of high genetic homogeneity among the modern commercial cultivars that are mainly derived from conventional interbreeding,the resistance genes from wheat relatives have especially prominent advantages.Octoploid triticale,produced from common wheat and rye(Secale cereale L.)through distant hybridization,is a new synthetic species and valuable gene donor for wheat improvement.In this study,we developed the wheat-rye line YT5 through the hybridization of octaploid triticale and two wheat lines.YT5 was confirmed to be a 6RL ditelosomic addition and 1R(1B)substitution line using genomic in situ hybridization(GISH),multicolor fluorescence in situ hybridization(mc-FISH),multicolor GISH(mc-GISH)and molecular marker analysis.Genetic analysis showed that the powdery mildew resistance in YT5 was derived from the rye chromosome arm 6RL.After inoculation with different Bgt isolates at the seedling stage,YT5 had compound reaction patterns with both obvious spores and hypersensitivity,and it gradually became highly resistant until the adult-plant stage,thus showing a resistance response significantly different from the reported Pm genes from rye chromosome 6RL.YT5 also showed promising agronomic performance,so it is expected to be an elite resistance donor for wheat improvement.To promote the transfer of the chromosome arm 6RL of YT5 in marker-assisted selection(MAS)breeding,we selected and verified two 6RL-specific kompetitive allelespecific PCR(KASP)markers that can be applied to efficiently detect this chromosome arm in different wheat backgrounds.
基金funded by the National Natural Science Foundation of China(31971746 and 32171685)。
文摘Nitrogen(N)enrichment is expected to induce a greater phosphorus(P)limitation,despite the acceleration of soil P cycling.However,the changing patterns in plant P and soil available P after N enrichment,and their regulatory mechanisms,remain poorly understood in alpine meadows.Here,we conducted a field experiment with four N addition rates(0,5,10,and 15 g N m^(-2)yr^(-1))in an alpine meadow,and investigated the P in plants,microorganisms,and soil to determine their patterns of change after short-term N addition.Our results showed that N addition significantly increased plant biomass,and the plant P pool showed a non-linear response to the N addition gradient.Soil available P initially increased and then declined with increasing N addition,whereas the occluded inorganic P decreased markedly.The critical factors for soil available P varied with different N addition rates.At lower N addition levels(0 and 5 g N m^(-2)yr^(-1)),soil acidification facilitated the mobilization of occluded inorganic P to increase soil available P.Conversely,at higher N addition levels(10 and 15 g N m^(-2)yr^(-1)),the elevated soil microbial biomass P intensified the competition with plants for soil P,leading to a decline in soil available P.This study highlights the nonlinear responses of the plant P pool and soil available P concentration to N addition rates.These responses suggest the need for developing ecosystem models to assess different effects of increasing N rates,which would enable more accurate predictions of the plant P supply and soil P cycling under N enrichment.
基金supported by the National Natural Science Foun-dation of China(Grant Nos.12404228 and 52371148)the Science and Technology Research Program of Chongqing Ed-ucation Commission of China(Grant No.KJQN202200510).
文摘Bulk metallic glasses(BMGs)are typically characterized by high strength and elasticity.However,they generally demonstrate a deficiency in plastic deformation capability at room temperatures.In this work,Cu_(50-x)Zr_(46)Al4Agx(x=0,1,2,3,4)alloys were prepared by arc melting and copper mold casting to investigate their structure,glass-forming ability,and mechanical properties.The results show that the addition of Ag can increase the parameter of DTx and g in Cu_(50)Zr_(46)Al_(4)alloy by 116%and 1.5%respectively,effectively enhancing its thermal stability and glass-forming ability.Compressive fracture tests reveal that the addition of Ag can significantly improve the yield strength,ultimate strength,and plasticity of the Cu_(50)Zr_(46)Al_(4)alloy.Specifically,with the Ag addition of 1 at.%,the alloy’s ultimate strength and plasticity increased by 71.8%and 21 times,respectively.Furthermore,the introduction of Ag can effectively control the free volume content in the Cu_(50)Zr_(46)Al_(4)alloy,thereby tuning the hardness of the material.This work provides valuable insights into improving the mechanical performance of BMGs through micro-alloying approaches.
基金supported by Ningxia Key Research and Development Fund Project of China(No.2023BCF01048)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2023-JC-YB-182).
文摘Global warming and nitrogen(N)deposition have a profound impact on greenhouse gas(GHG)fluxes and consequently,they also affect climate change.However,the global combined effects of warming and N addition on GHG fluxes remain to be fully understood.To address this knowledge gap,a globalmeta-analysis of 197 datasets was performed to assess the response of GHG fluxes to warming and N addition and their interactions under various climate and experimental conditions.The results indicate that warming significantly increased CO_(2)emissions,while N addition and the combined warming and N addition treatments had no impact on CO_(2)emissions.Moreover,both warming and N addition and their interactions exhibited positive effects on N_(2)O emissions.Under the combined warming and N addition treatments,warming was observed to exert a positive main effect on CO_(2)emissions,while N addition had a positive main effect on N_(2)O emissions.The interactive effects of warming and N addition exhibited antagonistic effects on CO_(2),N_(2)O,and CH_(4)emissions,with CH_(4)uptake dominated by additive effects.Furthermore,we identified biome and climate factors as the two treatments.These findings indicate that both warming and N addition substantially impact soil GHG fluxes and highlight the urgent need to investigate the influence of the combination of warming and N addition on terrestrial carbon and N cycling under ongoing global change.
基金supported by the Major Science and Technology Project of Inner Mongolia Autonomous Region (2024JBGS0011-02)Foundation for Innovative Research Groups in Basic Research of Gansu Province (25JRRA490)+1 种基金Youth Innovation Promotion Association of the Chinese Academy of Sciences (2022437)National Natural Science Foundation of China (42207538)。
文摘Amid global climate change, rising levels of nitrogen(N) deposition have attracted considerable attention for their potential effects on the carbon cycle of terrestrial ecosystems. The desert steppes are a crucial yet vulnerable ecosystem in arid areas, but their response to the combination of N addition and precipitation(a crucial factor in arid areas) remains underexplored. This study systematically explored the impact of N addition and precipitation on net ecosystem exchange(NEE) in a desert steppe in northern China. Specifically, we conducted a 2-a experiment from 2022 to 2023 with eight N addition treatments in the Urat desert steppe of Inner Mongolia Autonomous Region, China, to examine changes in NEE and explore its driving factors. The structural equation model(SEM) and multiple regression model were applied to determine the relationship of NEE with plant community characteristics and soil physical-chemical properties. Statistical results showed that N addition has no significant effect on NEE.However, it has a significant impact on the functional traits of desert steppe plant communities. SEM results further revealed that N addition has no significant effect on NEE in the desert steppe, whereas annual precipitation can influence NEE variations. The multiple regression model analysis indicated that plant functional traits play an important role in explaining the changes in NEE, accounting for 62.15% of the variation in NEE. In addition, plant height, as an important plant functional trait indicator, shows stronger reliability in predicting the changes in NEE and becomes a more promising predictor. These findings provide valuable insights into the complex ecological mechanisms governing plant community responses to precipitation and nutrient availability in the arid desert steppes, contributing to the improved monitoring and prediction of desert steppe ecosystem responses to global climate change.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.52005240,52164045)Young Talent Program of Major Disciplines of Academic and Technical Leaders in Jiangxi Province(No.20212BCJ23028)Outstanding Youth Foundation in Jiangxi Province(No.20224ACB214012).
文摘Friction stir lap welding(FSLW)was adopted to join successfully dissimilar AZ31B Mg alloy and TC4 Ti alloy with Sn foil addition of 30μm thickness.Interfacial microstructure,tensile shear performances and bonding mechanism of the joints obtained using three different rotation speeds were studied.High-performance FSLW Mg/Ti dissimilar joints with maximum tensile shear strength of 593.3 N/mm were produced at 1180 r/min,and which was mainly attributed to ultrastrong reaction interlayer consisting of 125.9 nm thick(Mg_(2)Sn+Mg)transition layer and discontinuous(Ti_(6)Sn_(5)+Ti_(3)Al)IMCs layer with 6.58 nm thickness at the interface.The formation of the reaction interlayer was beneficial for high interfacial strength,resulting in significantly improving the joint strength.The fracture of all FSLW joints located on AZ31B Mg stirred zone adjacent to(Mg_(2)Sn+Mg)transition layer or along the crack propagation direction of the AZ31B/TC4 interface with different fracture mechanisms,and which could be consistent with interfacial microstructure.
基金supported by the National Natural Science Foundation of China(22361053)Yunnan Fundamental Research Projects(202301AU070125,202401BC070018)+1 种基金Scientific Research of Department of Education for Yunnan Province(2025Y0679)Yunnan Key Laboratory of Chiral Functional Substance Research and Application(202402AN360010).
文摘Catalytic asymmetric hydrophosphination of unsaturated substrates has been proven to be one of the most straightforward ways to achieve chiral phosphine compounds.Although the methodologies of transition metals and organocatalysts catalyzed enantioselective hydrophosphination reactions have been well developed during the last decade,the enantioselective construction of quinoline and isoquinoline-based phosphines remains challenging.Furthermore,the chiral quinoline-based phosphines play a significant role in the preparation of chiral P,N-ligands.Herein,we report a comprehensive investigation for the asymmetric addition of diarylphosphine oxides to a wide range ofα,β-unsaturated quinolines and isoquinolines,catalyzed by commercial chiral phosphoric acid,affording the corresponding products with up to 99%yield and 98%ee.
