The storage and utilization of carbohydrates in response to elevation mediated by tree organs in subtropical evergreen broad-leaved forests

Global climate change can affect tree growth and carbon sink function by influencing plant carbohydrate synthesis and utilization,while elevation can be used as an ideal setting under natural conditions to simulate climate change effects.The effect of elevation on tree growth may depend on organ type.However,the allocation patterns of nonstructural and structural carbohydrates(NSCs and SCs,respectively)in different tree organs and their response to elevation remain unclear.We selected four dominant tree species,Schima superba,Castanopsis eyrei,Castanopsis fargesii and Michelia maudiae,along an elevation gradient from 609 to 1,207 m in subtropical evergreen broad-leaved forests and analyzed leaf,trunk,and fine root NSCs,carbon(C),nitrogen(N)and phosphorus(P)concentrations and the relative abundance of SCs.Leaf NSCs increased initially and then decreased,and trunk NSCs increased with increasing elevation.However,root NSCs decreased with increasing elevation.The relative abundance of SCs in leaves and trunks decreased,while the relative abundance of root SCs increased with increasing elevation.No significant correlations between SCs and NSCs in leaves were detected,while there were negative correlations between SCs and NSCs in trunks,roots,and all organs.Hierarchical partitioning analysis indicated that plant C/N and C/P were the main predictors of changes in SCs and NSCs.Our results suggest that tree organs have divergent responses to elevation and that increasing elevation will inhibit the aboveground part growth and enhance the root growth of trees.A tradeoff between the C distribution used for growth and storage was confirmed along the elevation gradient,which is mainly manifested in the"sink"organs of NSCs.Our results provide insight into tree growth in the context of global climate change scenarios in subtropical forest ecosystems.

Microstructure evolution and mechanical anisotropy of M50 steel ball bearing rings during multi-stage hot forging

This study aimed to explore the evolution of flow lines and microstructures of M50-steel bearing ring and the anisotropy of its tensile mechanical properties after Multi-Stage Hot Forging(MSHF) and subsequent spheroidizing annealing(MSHFA). To this end, the present study mainly employed stereo microscopy, Optical Metallurgical Microscopy(OMM), Scanning Electron Microscopy(SEM), and Electron Backscatter Diffraction(EBSD) to characterize and analyze the workpiece at each processing stage of MSHF while performing microhardness measurement and uniaxial tensile experiment to test and analyze the mechanical properties of the workpiece. Macro-structure observation showed that the simulation results of flow lines at each stage were consistent with the experimental results. Microscopic observation showed that, after MSHF, deformation gradually became less significant along the outward radial direction of the bearing ring. After MSHFA,the microstructures of the bearing ring became uniform, whereas primary carbides did not dissolve.The mechanical properties were better in the axial direction(AD) than in the radial(RD) and circumferential directions(CD) after MSHF due to the smaller grain width. After MSHFA, the mechanical properties in the ADs and CDs were better than those in the RDs, which was due to the large cross-sectional area of carbides along the flow-line direction.

Process design and microstructure-property evolution during shear spinning of Ti_(2)AlNb-based alloy

Rotationally symmetric workpieces of Ti_(2)AlNb-based alloys have great potential for high-temperature service condition in aviation industry,while the poor workability limits their application until now.In this study,shear spinning and heat treatment were first conducted to investigate the corresponding microstructure evolution and mechanical properties of Ti_(2)AlNb conical workpieces.The microstructure of the 1^(st) and 2^(nd) pass spun workpieces(SP1 and SP2)mainly consisted of B2+retainedα2phases.After two passes spinning,the B2 phase texture changed from<111>//ND of as-received alloy to be<001>//ND.The ultimate tensile stress(UTS)of SP1 and SP2 was increased to 1163 MPa and 932 MPa,respectively,compared with 782 MPa of as-received alloy at 650℃.Also,the yield stress anomaly(YSA)occurred in SP1 and SP2 because{110}<111>and{112}<111>cross slip systems of B2 phase were difficult to slip at or below room temperature(RT),but they became active at 650℃ and above.As an essential step for increasing the spinnability of multi-pass spinning process of the Ti_(2)AlNb alloy,the H3heat treatment scheme,i.e.960℃/2 h+850℃/12 h,was carried out between two successive passes to increase the hot workability,by which the ductility of the heat treated as-spun workpieces with the microstructure of B2+primary O+acicular secondary O+high amount spheroidizedα2phases reached 72.1%at 900℃.After being subject to the H1 heat treatment scheme,i.e.960℃-2 h,the spun workpieces with the microstructure of B2+primary O+intergranular primaryα2phases achieved an optimized comprehensive mechanical properties both at room temperature and 650℃,which should be chosen as the post-spinning heat treatment process for the service requirement.

Dose rate effects on shape memory epoxy resin during 1 Me V electron irradiation in air

The effects of 1 Me V electron irradiation in air at a fixed accumulated dose and dose rates of 393.8,196.9,78.8,and 39.4 Gy s^(-1)on a shape memory epoxy(SMEP)resin were studied.Under low-dose-rate irradiation,accelerated degradation of the shape memory performance was observed;specifically,the shape recovery ratio decreased exponentially with increasing irradiation time(that is,with decreasing dose rate).In addition,the glass transition temperature of the SMEP,as measured by dynamic mechanical analysis,decreased overall with decreasing dose rate.The dose rate effects of 1 Me V electron irradiation on the SMEP were confirmed by structural analysis using electron paramagnetic resonance(EPR)spectroscopy and Fourier transform infrared(FTIR)spectroscopy.The EPR spectra showed that the concentration of free radicals increased exponentially with increasing irradiation time.Moreover,the FTIR spectra showed higher intensities of the peaks at 1660 and 1720 cm^(-1),which are attributed to stretching vibrations of amide C=O and ketone/acid C=O,at lower dose rates.The intensities of the IR peaks at 1660 and 1720 cm^(-1) increased exponentially with increasing irradiation time,and the relative intensity of the IR peak at 2926 cm^(-1)decreased exponentially with increasing irradiation time.The solid-state13 C nuclear magnetic resonance(NMR)spectra of the SMEP before and after 1 Me V electron irradiation at a dose of 1970 k Gy and a dose rate of 78.8 Gy s^(-1) indicated damage to the CH_(2)–N groups and aliphatic isopropanol segment.This result is consistent with the detection of nitrogenous free radicals,a phenoxy-type free radical,and several types of pyrolytic carbon radicals by EPR.During the subsequent propagation process,the free radicals produced at lower dose rates were more likely to react with oxygen,which was present at higher concentrations,and form the more destructive peroxy free radicals and oxidation products such as acids,amides,and ketones.The increase in peroxy free radicals at lower dose rates was thought to accelerate the degradation of the macroscopic performance of the SMEP.