To recover the valuable elements in Bayan Obo tailings,Fe-Si bath smelting reduction was adopted to separate and enrich rare earth elements(REE),niobium and titanium from the REE-Nb-Ti-containing slag.The reduction re...To recover the valuable elements in Bayan Obo tailings,Fe-Si bath smelting reduction was adopted to separate and enrich rare earth elements(REE),niobium and titanium from the REE-Nb-Ti-containing slag.The reduction reaction process of the Fe-Si bath and the migration behavior of valuable elements in the solidification and crystallization process of silicothermic reduction tailings were investigated,and a treatment method for efficiently separating and enriching REE,Nb and Ti was explored.Thermodynamic analysis indicated that at 1600℃,with a 6 wt.%addition of Si as the reducing agent,the niobium oxide in the REE-Nb-Ti-containing slag could be selectively reduced to metallic Nb.In the Fe-Si bath reduction process,the Nb mass fraction in the metal phase increased with prolonged reaction time,peaking at 2.77%,while the Ti mass fraction consistently stayed below 0.12%.Lowering the w(CaO)/w(SiO_(2))enhanced the migration of Nb from slag to metal phase and reduced the Ti impurities.During solidification and crystallization,a significant quantity of perovskite precipitated from reduction tailings,with the REE dissolving into this perovskite.By adjusting the w(CaO)/w(SiO_(2))in tailings to 1.2-1.9 and maintaining a temperature of 1100℃for 4 h,the perovskite area fraction in the final slag could exceed 37%.Finally,a method was proposed to separate and enrich valuable elements in REE-Nb-Ti-containing slags via Fe-Si bath smelting reduction and crystallization control.展开更多
Herein,a series of manganese oxide catalysts with different valences(Mn_(3)O_(4),Mn_(2)O_(3),and MnO_(2))were designed and synthesized for the synthesis of ethylene urea(EU)from ethylenediamine(EDA)and carbon dioxide(...Herein,a series of manganese oxide catalysts with different valences(Mn_(3)O_(4),Mn_(2)O_(3),and MnO_(2))were designed and synthesized for the synthesis of ethylene urea(EU)from ethylenediamine(EDA)and carbon dioxide(CO_(2)).With a maximal EDA conversion of 82%and EU selectivity of 99%at 160℃ for 2 h,Mn_(2)O_(3) catalysts had the best catalytic activity among them,which was superior to the reported catalysts.In the following order:Mn_(2)O_(3)>MnO_(2)>Mn_(3)O_(4),the catalytic activity for the synthesis of EU from CO_(2) and EDA decreased.Further characterization showed the Mn_(2)O_(3) catalyst possessed a greater Mn^(3+)/Mn4+ratio and more surface oxygen vacancies than the MnO_(2) and Mn_(3)O_(4),which improved its capacity to adsorb and activate CO_(2) and EDA.After four recycling runs,the EDA conversion slightly declined from 82%to 56%on Mn_(2)O_(3) catalyst,while no obvious change in EU selectivity was observed.The loss of surface Ov contents and Mn^(3+)proportion were concluded as main reasons for the decrease in catalytic activity over Mn_(2)O_(3) catalyst.This work demonstrated a metal oxide catalyst that was efficient in producing EU from CO_(2) and EDA.展开更多
Improving the high-temperature performance of Inconel 718(IN718)alloys manufactured via laser powder bed fusion(LPBF)has been the most concerned issue in the industry.In this study,the effects of Ti_(2)AlC inoculants ...Improving the high-temperature performance of Inconel 718(IN718)alloys manufactured via laser powder bed fusion(LPBF)has been the most concerned issue in the industry.In this study,the effects of Ti_(2)AlC inoculants on microstructures and high-temperature mechanical properties of the as-built IN718 composites were investigated.According to statistical results of relative density and unmelted particle area in as-built alloys,the optimal energy of 112 J/mm^(3)was determined.It was observed that the precipitation of the MC carbide was significantly enhanced with the addition of Ti_(2)AlC,restricting the precipitation of the Laves phase.The MC particles were uniformly distributed along the subgrain boundaries,which contributed to the dispersion strengthening.Meanwhile,the MC particles served as nucleation sites for heterogeneous nucleation during the solidification process,facilitating the refinement of columnar and cellular grains.The simulated Scheil-Gulliver curves showed that the precipitation sequence of phases did not change with Ti_(2)AlC inoculants.The as-built 1%Ti_(2)AlC/IN718 sample demonstrated an ultimate tensile strength of 998.78 MPa and an elongation of 18.04%at 650℃,revealing a markedly improved mechanical performance compared with the LPBF-manufactured IN718 alloys.The high-temperature tensile strength of 1%Ti_(2)AlC/IN718 sample increased to 1197.99 MPa by heat treatment.It was suggested that dislocation strengthening and ordered strengthening were two most important reinforcement mechanisms.展开更多
Purpose:Patients undergoing maintenance hemodialysis(MHD)have a higher prevalence of cognitive impairment and inferior cognitive performance than the general population,and those with cognitive impairment are at highe...Purpose:Patients undergoing maintenance hemodialysis(MHD)have a higher prevalence of cognitive impairment and inferior cognitive performance than the general population,and those with cognitive impairment are at higher risk of death than those without cognitive impairment.Having diabetes has been associated with an increased risk of cognitive decline in end-stage kidney disease patients treated with peritoneal dialysis or kidney transplant.However,these findings may not extend to the hemodialysis population.Thus,we aim to investigate the relationship between having diabetes and cognitive function in MHD patients.Methods:This was a cross-sectional study.A total of 203 patients treated with MHD from two blood purification centers were enrolled as subjects.The Chinese version of the Montreal Cognitive Assessment(MoCA)was utilized to assess cognitive function.Results:MHD patients with diabetes had a significantly higher prevalence of global cognitive impairment and inferior performance in global cognition,visuospatial/executive function,naming,language,abstraction and orientation tasks compared with those without diabetes.According to the multiple linear analyses,having diabetes was significantly associated with lower global cognitive function,naming,and language scores,withβcoefficients and 95%CIs of-1.30[-2.59,-0.01],-0.25[-0.47,-0.02],and-0.32[-0.58,-0.07],respectively(all P<0.05).Having diabetes could not independently predict an increased risk of global cognitive impairment.Conclusions:In MHD patients,having diabetes is significantly associated with lower cognitive function scores.Medical staff should evaluate early and focus on the decline of cognitive function in MHD patients with diabetes,in order to achieve early diagnosis and earlv intervention.展开更多
In this study,the microstructures and mechanical properties of 9%Cr reduced activation ferritic/martensitic（RAFM） steel friction stir welded joints were investigated.When a W-Re tool is used,the recommended welding ...In this study,the microstructures and mechanical properties of 9%Cr reduced activation ferritic/martensitic（RAFM） steel friction stir welded joints were investigated.When a W-Re tool is used,the recommended welding parameters are 300 rpm rotational speed,60 mm/min welding speed and10 kn axial force.In stir zone（SZ）,austenite dynamic recrystallization induced by plastic deformation and the high cooling rates lead to an obvious refinement of prior austenite grains and martensite laths.The microstructure in SZ contains lath martensite with high dislocation density,a lot of nano-sized MX and M3C phase particles,but almost no M23C6 precipitates.In thermal mechanically affect zone（TMAZ）and heat affect zone（HAZ）,refinement of prior austenite and martensitic laths and partial dissolution of M（23）C6 precipitates are obtained at relatively low rotational speed.However,with the increase of heat input,coarsening of martensitic laths,prior austenite grains,and complete dissolution of M23C6 precipitates are achieved.Impact toughness of SZ at-20℃ is slightly lower than that of base material（BM）,and exhibits a decreasing trend with the increase of rotational speed.展开更多
The friction pull plug welding(FPPW)of the 2219-T87 tungsten inert gas(TIG)welded joint was investigated,and the microstructures,precipitate evolution,mechanical properties,and fracture morphologies of this joint were...The friction pull plug welding(FPPW)of the 2219-T87 tungsten inert gas(TIG)welded joint was investigated,and the microstructures,precipitate evolution,mechanical properties,and fracture morphologies of this joint were analyzed and discussed.In this study,defectfree joints were obtained using a rotational speed of 7000 r/min,an axial feeding displacement of 12 mm,and an axial force of 20-22 kN.The results indicated that within these welding parameters,metallurgical bonding between the plug and plate is achieved by the formation of recrystallized grains.The microstructural features of the FPPW joint can be divided into different regions,including the heat-affected zone(HAZ),thermomechanically affected zone(TMAZ),recrystallization zone(RZ),heat-affected zone in the TIG weld(TIG-HAZ),and the thermomechanically affected zone in the TIG weld(TIG-TMAZ).In the TIG-TMAZ,the grains were highly deformed and elongated due to the shear and the extrusion that produces the plug during the FPPW process.The main reason for the softening in the TMAZ is determined to be the dissolution ofθ’and coarsening ofθprecipitate particles.In a tensile test,the FPPW joint welded with an axial force of 22 kN showed the highest ultimate tensile strength of 237 MPa.The locations of cracks and factures in the TIG-TMAZ were identified.The fracture morphology of the tensile sample showed good plasticity and toughness of the joints.展开更多
In the present study, the weld formation and mechanical properties of the AA-5A06 friction pull plug welded(FPPW) joints were improved by controlling the axial force history. Several defect-free FPPW joints were made ...In the present study, the weld formation and mechanical properties of the AA-5A06 friction pull plug welded(FPPW) joints were improved by controlling the axial force history. Several defect-free FPPW joints were made successfully by using the welding parameters of 15–20 k N/s axial loading rate, 20–30 k N axial welding force and 6–7 mm axial feeding displacement. The results indicated that using higher axial loading rate and axial welding force produced more stable heat generation and shorter frictional heating time between the frictional interface. In this case, the plastic flow of the materials around the hole could be further improved since the axial feeding displacement of the plug was increased. The maximum ultimate tensile strength(UTS) and elongation of the FPPW 5A06 joints were 314 MPa and 4.8%, respectively. The thermal mechanically affect zone(TMAZ) had the lowest hardness value throughout the joint and was found as the fracture location to all the tensile samples. The softening of TMAZ was mainly caused by the weakening of the cold work hardening and the coarsening of grains.展开更多
A binder-free Ni3S2 electrode was prepared directly on a graphene-coated Ni foam （G/Ni） substrate through surface sulfiding of substrate using thiourea as the sulfur source in this work. The Ni3S2 showed a flower-li...A binder-free Ni3S2 electrode was prepared directly on a graphene-coated Ni foam （G/Ni） substrate through surface sulfiding of substrate using thiourea as the sulfur source in this work. The Ni3S2 showed a flower-like morphology and was uniformly distributed on the G/Ni surface. The flower-like Ni3S2 was composed of cross-arrayed nanoflakes with a diameter and a thickness of 1-2 μm and -50 nm, re- spectively. The free space in the flowers and the thin feature of Ni3S2 buffered the volume changes and relieved mechanical strain during re- peated cycling. The intimate contact with the Ni substrate and the fixing effect of graphene maintained the structural stability of the Ni3S2 electrode during cycling. The G/Ni-supported Ni3S2 maintained a reversible capacity of 250 mAh·g^-1 after 100 cycles at 50 mA·g^-1, demon- strating the good cycling stability as a result of the unique microstructure of this electrode material.展开更多
Size-based partitioning of phytoplankton is a useful tool for monitoring key phytoplankton traits, and it provides a better understanding of phytoplankton dynamics. Our aim is to determine the variation in the differe...Size-based partitioning of phytoplankton is a useful tool for monitoring key phytoplankton traits, and it provides a better understanding of phytoplankton dynamics. Our aim is to determine the variation in the different size classes of phytoplankton to the total phytoplankton biomass during the spring and autumn of 2010 and examine the relationship between phytoplankton size structure and environmental variables and zooplankton community structure near the Changjiang Estuary. In the spring, phytoplankton populations were predominantly consisted of nanophytoplankton throughout the study region. In the autumn, picophytoplankton and nanophytoplankton collectively dominated the phytoplankton community. A Pearson correlation analysis highlighted the role of temperature and trophic conditions on the contributions of nanophytoplankton and picophytoplankton. The grazing pressure exerted by mesozooplankton could have played an important role in determining the microphytoplankton community structure.展开更多
AIM:To investigate the protective effect of clodronatecontaining liposomes against severe acute pancreatitis(SAP)-triggered acute gastric mucosal injury(AGMI) in rats.METHODS:Clodronate- and phosphate-buffered saline(...AIM:To investigate the protective effect of clodronatecontaining liposomes against severe acute pancreatitis(SAP)-triggered acute gastric mucosal injury(AGMI) in rats.METHODS:Clodronate- and phosphate-buffered saline(PBS)-containing liposomes were prepared by reverse-phase evaporation.The SAP rat model was established by injecting sodium taurocholate into the pancreatic subcapsular space.Sprague-Dawley rats were randomly divided into three groups:control(C),SAP plus PBS-containing liposome(P) and SAP plus clodronate-containing liposome(T).Serum tumor necrosis factor(TNF)-α levels were estimated by ELISA.Pathological changes in the gastric mucosa and pancreas were observed by hematoxylin and eosin(HE) staining.Apoptotic cells were detected by terminal deoxynucleotidyl transferase d UTP nick end labeling staining.The numbers of macrophages in the gastric mucosa were analyzed by CD68 immunohistochemical staining.RESULTS:The liposomes had a mean diameter of 150 ± 30 nm.The TNF-α levels were significantly higher in the P group than that in the C group(2 h,145.13 ± 11.50 vs 23.2 ± 2.03; 6 h,245.06 ± 12.11 vs 30.28 ± 6.07,P < 0.05),and they were significantly lower in the T group than that in the P group(2 h,93.24 ± 23.11 vs 145.13 ± 11.50; 6 h,135.18 ± 13.10 vs 245.06 ± 12.11,P < 0.05).The pathological scores of the pancreas were lower in the T group than in the P group(2 h,1.88 ± 0.83 vs 4.13 ± 0.83; 6 h,2.87 ± 0.64 vs 6.25 ± 0.88,P < 0.01).The pathological scores of the gastric mucosa were also lower in the T group than in the P group(2 h,1.12 ± 0.64 vs 2 ± 0.75; 6 h,1.58 ± 0.53 vs 3 ± 1.31,P < 0.05).In addition,increased CD68 levels were observed in the gastric mucosa of the P group compared with the C group.Clodronate-containing liposomes decreased the CD68 levels in the mucosa of the T group.The apoptotic indexes of the gastric mucosa were higher in the T group than in the P group(2 h,15.7 ± 0.92 vs 11.5 ± 1.64; 6 h,21.12 ± 1.06 vs 12.6 ± 2.44,P < 0.01).CONCLUSION:Gastric macrophages contribute to the pathogenesis of gastric injury in SAP.Clodronatecontaining liposomes have protective effects against AGMI in rats with SAP.展开更多
The deciduous linden tree （Tilia amurensis Rupr.） is protected at National Level II in China as a species of ecological and economic importance. The objective of this study was to assess and compare the ectomycorrhi...The deciduous linden tree （Tilia amurensis Rupr.） is protected at National Level II in China as a species of ecological and economic importance. The objective of this study was to assess and compare the ectomycorrhizal communities associated with T. amurensis in natural versus urban forests of central Heilongjiang Province. The percentage of T. amurensis colonisation by ectomycorrhiza was more than 60 % in urban forests, compared to 34-49 % in natural forests. Use of a combi- nation of morphological and molecular methods docu- mented 18 ECM （ectomycorrhizal） types among three sites; 12-13 ECM species were identified in the natural sites versus 9 species in the urban site. Four ECM species （Boletus sp., Tuber sp., Inocybe sp.2, Leccinum sp.1） were the dominant mycorrhizal symbionts, and Cenococcum geophilum and Russula sp. were found only in the natural forests.展开更多
In this research,2205/Q235 B clad plates were prepared by a vacuum hot rolling composite process.The effects of adding Fe,Ni,and Nb interlayers on the bonding interface structures and the shear strengths of the clad s...In this research,2205/Q235 B clad plates were prepared by a vacuum hot rolling composite process.The effects of adding Fe,Ni,and Nb interlayers on the bonding interface structures and the shear strengths of the clad steel plates were studied.The results showed that 2205 duplex stainless steel and the three interlayers produced a large amount of plastic deformation and low-angle boundaries,and the main structures were the recrystallized and deformed grains.There were many recrystallized grains in the microstructure of the Q235 B low-carbon steel due to the low deformation in the rolling process.The Fe interlayer had better wettability with the two kinds of steel,but the lower strength led to the reduction of shear strength by about14 MPa compared with the original clad steel plate.The C element in the Q235 B low-carbon steel easily diffused into the Fe interlayer,and the clad steel plate attained a poor corrosion resistance because a large decarburization area was formed.The Nb interlayer reacted with the Mo element in the 2205 duplex stainless steel to form an Nb-Mo binary alloy,which generated long-banded ferrite.The decarburization area was also produced because the Nb reacted with the C element in the Q235 B to form hard and brittle NbCx.As a result,the shear strength was significantly reduced by about 282 MPa,and the corrosion resistance of the bonding surface was deteriorated.The Ni interlayer did not react with the alloy elements in both sides,and therefore effectively prevented element diffusion and improved the corrosion resistance of the bonding surface.Due to the low strength of the Ni interlayer and the increased number of bonding surfaces of the clad steel plates,the shear strength was reduced to some extent(about 40 MPa),but it still met the engineering application standards.展开更多
AIM：To investigate the impact of adipose-derived mesenchymal stem cells（ADSCs） on cell viability and extracellular matrix（ECM） synthesis of corneal stromal cells（CSCs）. METHODS：ADSCs and CSCs were obtained fro...AIM：To investigate the impact of adipose-derived mesenchymal stem cells（ADSCs） on cell viability and extracellular matrix（ECM） synthesis of corneal stromal cells（CSCs）. METHODS：ADSCs and CSCs were obtained from the corneas of New Zealand white rabbits and indirectly cocultured in vitro. The proliferative capacity of CSCs in the different groups was assessed by CCK-8 assays. Annexin V-fluorescein isothiocyanate（FITC）/proliferation indices（PI） assays were used to detect the apoptosis of CSCs. The expression levels of matrix metalloproteinase（MMP）, such as MMP1, MMP2, MMP9, and collagens were also evaluated by Western blot. RESULTS：ADSCs significantly promoted proliferation and invasion of CSCs in the indirect co-culture assays. The co-cultural group displayed much higher ability of proliferation, especially under the co-culture conditions of ADSCs for 3d, compared with that CSCs cultured alone. The PI of CSCs in the co-culture system were increased approximately 3-8-fold compared with the control group. A significant change was observed in the proportions of cells at apoptosis（early and late） between the negative control group（6.34% and 2.06%） and the ADCSs-treated group（4.69% and 1.59%）. The expression levels of MMPs were down regulated in the co-culture models. Compared with the control group, the decrease intensities of MMP-1, MMP-2 and MMP-9 in CSCs/ADSCs group were observed, 3.90-fold, 1.09-fold and 3.03-fold, respectively. However, the increase intensities of collagen type（I, II, III, IV, and V） in CSCs were observed in CSCs/ADSCs group, 3.47-fold,4.30-fold, 2.35-fold, 2.55-fold and 2.43-fold, respectively, compared to that in the control group. The expressions of aldehyde dehydrogenase and fibronectin in CSCs were upregulated in the co-culture models.CONCLUSION：ADSCs play a promotive role in CSCs＇ growth and invasion, which may be partially associated with MMPs decrease and collagens increase, resulting in a positive participation in the plasticity and ECM synthesis of CSCs. This provided a new insight into the extensive role of ADSCs in CSCs and a potential molecular target for corneal therapy.展开更多
In this paper, an experimental study on the sulphate attack resistance of high-performance concrete (HPC) with two different water-to-binder ratios (w/b) under compressive loading is presented. The sulphate concentrat...In this paper, an experimental study on the sulphate attack resistance of high-performance concrete (HPC) with two different water-to-binder ratios (w/b) under compressive loading is presented. The sulphate concentration, compressive strength, and the mass change in the HPC specimens were determined for immersion in a Na2SO4 solution over different durations under external compressive loading by self-regulating loading equipment. The effects of the compressive stress, the w/b ratio, and the Na2SO4 solution concentration on the HPC sulphate attack resistance under compressive loading were analysed. The results showed that the HPC sulphate attack resistance under compressive loading was closely related to the stress level, the w/b ratio, and the Na2SO4 solution concentration. Applying a 0.3 stress ratio for the compressive loading or reducing the w/b ratio clearly improved the HPC sulphate attack resistance, whereas applying a 0.6 stress ratio for the compressive loading or exposing the HPC to a more concentrated Na2SO4 solution accelerated the sulphate attack and HPC deterioration.展开更多
Commercial hydrogen production involves the development of efficient hydrogen evolution reaction catalysts.Herein,we adopted a friction stir processing(FSP)technique to mix immiscible metals homogenously and obtain a ...Commercial hydrogen production involves the development of efficient hydrogen evolution reaction catalysts.Herein,we adopted a friction stir processing(FSP)technique to mix immiscible metals homogenously and obtain a self-supporting copper-silver(CuAg)catalyst.The gust of Ag atoms with larger atomic sizes caused a tensile strain in the Cu matrix.Meanwhile,the chemical-potential difference induced electron transfer from Cu to Ag,and the two factors jointly led to the upshift of Cu d-band and improved the catalytic activity.Consequently,the CuAg electrode exhibited a high turnover frequency(12 times that of pure Cu),a low overpotential at high current density(superior to platinum foil),and high durability(1.57%decay over 180 h).Our work demonstrates that FSP is a powerful method for preparing self-supporting catalysts of immiscible alloys with high catalytic performance.展开更多
To address the issue of hemilabile catalyst in olefin polymerization catalysis, a cyclizing strategy was used to construct novel N-bridged phosphine-carbonyl palladium and nickel catalysts, resulting in improvements o...To address the issue of hemilabile catalyst in olefin polymerization catalysis, a cyclizing strategy was used to construct novel N-bridged phosphine-carbonyl palladium and nickel catalysts, resulting in improvements on ethylene(co)polymerizations. The N-bridged phosphinecarbonyl Pd catalysts(Pd1-Pd5) and Ni catalysts(Ni1-Ni5) bearing five-to eight-membered-ring structures were designed and synthesized.Catalytic performance for ethylene(co)polymerization became better as the size of N-containing bridge increased. The seven-membered-ring bridged catalysts Pd4 and Ni4 exhibited the best performance in terms of catalytic activity, polymer molecular weight and incorporation of acrylates and acrylic acid. The better performance of these catalysts bearing larger-size bridges was tentatively attributed to the methyleneinduced higher electron density around nitrogen, which strenghtens the coordination of carbonyl group to metal center, and also to the steric effect offered by this cyclization. This work provides a new strategy to enhance hemilabile polymerization catalysts.展开更多
Temperature and pressure play key roles in Global Navigation Satellite System(GNSS)precipitable water vapor(PWV)retrieval.The National Aeronautics and Space Administration(NASA)and European Center for Medium-Range Wea...Temperature and pressure play key roles in Global Navigation Satellite System(GNSS)precipitable water vapor(PWV)retrieval.The National Aeronautics and Space Administration(NASA)and European Center for Medium-Range Weather Forecasts(ECMWF)have released their latest reanalysis product:the modern-era retrospective analysis for research and applications,version 2(MERRA-2)and the fifthgeneration ECMWF reanalysis(ERA5),respectively.Based on the reanalysis data,we evaluate and analyze the accuracy of the surface temperature and pressure products in China using the the measured temperature and pressure data from 609 ground meteorological stations in 2017 as reference values.Then the accuracy of the two datasets and their performances in estimating GNSS PWV are analyzed.The PWV derived from the pressure and temperature products of ERA5 and MERRA-2 has high accuracy.The annual average biases of pressure and temperature for ERA5 are-0.07 hPa and 0.45 K,with the root mean square error(RMSE)of 0.95 hPa and 2.04 K,respectively.The annual average biases of pressure and temperature for MERRA-2 are-0.01 hPa and 0.38 K,with the RMSE of 1.08 h Pa and 2.66 K,respectively.The accuracy of ERA5 is slightly higher than that of MERRA-2.The two reanalysis data show negative biases in most regions of China,with the highest to lowest accuracy in the following order:the south,north,northwest,and Tibet Plateau.Comparing the GNSS PWV calculated using MERRA-2(GNSS MERRA-2 PWV)and ERA5(GNSS ERA5 PWV)with the radiosonde-derived PWV from 48 co-located GNSS stations and the measured PWV of the co-location radiosonde stations,it is found that the accuracy of GNSS ERA5 PWV is better than that of GNSS MERRA-2 PWV.These results show the different applicability of surface temperature and pressure products from MERRA-2 and ERA5 data,indicating that both have important applications in meteorological research and GNSS water vapor monitoring in China.展开更多
基金supported by the National Key R&D Program of China(No.2021YFC2901200)National Natural Science Foundation of China(Nos.52174383 and 52374412)Liaoning Provincial Natural Science Foundation of China(No.2022-YQ-09).
文摘To recover the valuable elements in Bayan Obo tailings,Fe-Si bath smelting reduction was adopted to separate and enrich rare earth elements(REE),niobium and titanium from the REE-Nb-Ti-containing slag.The reduction reaction process of the Fe-Si bath and the migration behavior of valuable elements in the solidification and crystallization process of silicothermic reduction tailings were investigated,and a treatment method for efficiently separating and enriching REE,Nb and Ti was explored.Thermodynamic analysis indicated that at 1600℃,with a 6 wt.%addition of Si as the reducing agent,the niobium oxide in the REE-Nb-Ti-containing slag could be selectively reduced to metallic Nb.In the Fe-Si bath reduction process,the Nb mass fraction in the metal phase increased with prolonged reaction time,peaking at 2.77%,while the Ti mass fraction consistently stayed below 0.12%.Lowering the w(CaO)/w(SiO_(2))enhanced the migration of Nb from slag to metal phase and reduced the Ti impurities.During solidification and crystallization,a significant quantity of perovskite precipitated from reduction tailings,with the REE dissolving into this perovskite.By adjusting the w(CaO)/w(SiO_(2))in tailings to 1.2-1.9 and maintaining a temperature of 1100℃for 4 h,the perovskite area fraction in the final slag could exceed 37%.Finally,a method was proposed to separate and enrich valuable elements in REE-Nb-Ti-containing slags via Fe-Si bath smelting reduction and crystallization control.
基金supported by the National Natural Science Foundation of China(No.22278041)the Foundation of State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering(No.2022-K78)+1 种基金Jiangsu Province Key Laboratory of Fine Petrochemical Engineering(No.KF2107)the Advanced Catalysis and Green Manufacturing Collab-orative Innovation Center(No.ACGM2022-10-07)。
文摘Herein,a series of manganese oxide catalysts with different valences(Mn_(3)O_(4),Mn_(2)O_(3),and MnO_(2))were designed and synthesized for the synthesis of ethylene urea(EU)from ethylenediamine(EDA)and carbon dioxide(CO_(2)).With a maximal EDA conversion of 82%and EU selectivity of 99%at 160℃ for 2 h,Mn_(2)O_(3) catalysts had the best catalytic activity among them,which was superior to the reported catalysts.In the following order:Mn_(2)O_(3)>MnO_(2)>Mn_(3)O_(4),the catalytic activity for the synthesis of EU from CO_(2) and EDA decreased.Further characterization showed the Mn_(2)O_(3) catalyst possessed a greater Mn^(3+)/Mn4+ratio and more surface oxygen vacancies than the MnO_(2) and Mn_(3)O_(4),which improved its capacity to adsorb and activate CO_(2) and EDA.After four recycling runs,the EDA conversion slightly declined from 82%to 56%on Mn_(2)O_(3) catalyst,while no obvious change in EU selectivity was observed.The loss of surface Ov contents and Mn^(3+)proportion were concluded as main reasons for the decrease in catalytic activity over Mn_(2)O_(3) catalyst.This work demonstrated a metal oxide catalyst that was efficient in producing EU from CO_(2) and EDA.
基金supported by the National Natural Science Foundation of China(Nos.52374396 and 52122409).
文摘Improving the high-temperature performance of Inconel 718(IN718)alloys manufactured via laser powder bed fusion(LPBF)has been the most concerned issue in the industry.In this study,the effects of Ti_(2)AlC inoculants on microstructures and high-temperature mechanical properties of the as-built IN718 composites were investigated.According to statistical results of relative density and unmelted particle area in as-built alloys,the optimal energy of 112 J/mm^(3)was determined.It was observed that the precipitation of the MC carbide was significantly enhanced with the addition of Ti_(2)AlC,restricting the precipitation of the Laves phase.The MC particles were uniformly distributed along the subgrain boundaries,which contributed to the dispersion strengthening.Meanwhile,the MC particles served as nucleation sites for heterogeneous nucleation during the solidification process,facilitating the refinement of columnar and cellular grains.The simulated Scheil-Gulliver curves showed that the precipitation sequence of phases did not change with Ti_(2)AlC inoculants.The as-built 1%Ti_(2)AlC/IN718 sample demonstrated an ultimate tensile strength of 998.78 MPa and an elongation of 18.04%at 650℃,revealing a markedly improved mechanical performance compared with the LPBF-manufactured IN718 alloys.The high-temperature tensile strength of 1%Ti_(2)AlC/IN718 sample increased to 1197.99 MPa by heat treatment.It was suggested that dislocation strengthening and ordered strengthening were two most important reinforcement mechanisms.
基金This study was in part supported by the project of Nanjing Medical Science and Technology Development Foundation(YKK17231).
文摘Purpose:Patients undergoing maintenance hemodialysis(MHD)have a higher prevalence of cognitive impairment and inferior cognitive performance than the general population,and those with cognitive impairment are at higher risk of death than those without cognitive impairment.Having diabetes has been associated with an increased risk of cognitive decline in end-stage kidney disease patients treated with peritoneal dialysis or kidney transplant.However,these findings may not extend to the hemodialysis population.Thus,we aim to investigate the relationship between having diabetes and cognitive function in MHD patients.Methods:This was a cross-sectional study.A total of 203 patients treated with MHD from two blood purification centers were enrolled as subjects.The Chinese version of the Montreal Cognitive Assessment(MoCA)was utilized to assess cognitive function.Results:MHD patients with diabetes had a significantly higher prevalence of global cognitive impairment and inferior performance in global cognition,visuospatial/executive function,naming,language,abstraction and orientation tasks compared with those without diabetes.According to the multiple linear analyses,having diabetes was significantly associated with lower global cognitive function,naming,and language scores,withβcoefficients and 95%CIs of-1.30[-2.59,-0.01],-0.25[-0.47,-0.02],and-0.32[-0.58,-0.07],respectively(all P<0.05).Having diabetes could not independently predict an increased risk of global cognitive impairment.Conclusions:In MHD patients,having diabetes is significantly associated with lower cognitive function scores.Medical staff should evaluate early and focus on the decline of cognitive function in MHD patients with diabetes,in order to achieve early diagnosis and earlv intervention.
基金financially supported by the National Natural Science Foundation of China (Grant Nos.51325401 and U1660201)the National Magnetic Confinement Fusion Energy Research Project (Grant No.2015GB119001)
文摘In this study,the microstructures and mechanical properties of 9%Cr reduced activation ferritic/martensitic（RAFM） steel friction stir welded joints were investigated.When a W-Re tool is used,the recommended welding parameters are 300 rpm rotational speed,60 mm/min welding speed and10 kn axial force.In stir zone（SZ）,austenite dynamic recrystallization induced by plastic deformation and the high cooling rates lead to an obvious refinement of prior austenite grains and martensite laths.The microstructure in SZ contains lath martensite with high dislocation density,a lot of nano-sized MX and M3C phase particles,but almost no M23C6 precipitates.In thermal mechanically affect zone（TMAZ）and heat affect zone（HAZ）,refinement of prior austenite and martensitic laths and partial dissolution of M（23）C6 precipitates are obtained at relatively low rotational speed.However,with the increase of heat input,coarsening of martensitic laths,prior austenite grains,and complete dissolution of M23C6 precipitates are achieved.Impact toughness of SZ at-20℃ is slightly lower than that of base material（BM）,and exhibits a decreasing trend with the increase of rotational speed.
基金financially supported by the National Natural Science Foundation of China(Nos.51875401 and 52075376).
文摘The friction pull plug welding(FPPW)of the 2219-T87 tungsten inert gas(TIG)welded joint was investigated,and the microstructures,precipitate evolution,mechanical properties,and fracture morphologies of this joint were analyzed and discussed.In this study,defectfree joints were obtained using a rotational speed of 7000 r/min,an axial feeding displacement of 12 mm,and an axial force of 20-22 kN.The results indicated that within these welding parameters,metallurgical bonding between the plug and plate is achieved by the formation of recrystallized grains.The microstructural features of the FPPW joint can be divided into different regions,including the heat-affected zone(HAZ),thermomechanically affected zone(TMAZ),recrystallization zone(RZ),heat-affected zone in the TIG weld(TIG-HAZ),and the thermomechanically affected zone in the TIG weld(TIG-TMAZ).In the TIG-TMAZ,the grains were highly deformed and elongated due to the shear and the extrusion that produces the plug during the FPPW process.The main reason for the softening in the TMAZ is determined to be the dissolution ofθ’and coarsening ofθprecipitate particles.In a tensile test,the FPPW joint welded with an axial force of 22 kN showed the highest ultimate tensile strength of 237 MPa.The locations of cracks and factures in the TIG-TMAZ were identified.The fracture morphology of the tensile sample showed good plasticity and toughness of the joints.
基金the Science and Technology Program of Tianjin(Granted No.18ZXCLGX00060)the National Natural Science Foundation of China(Granted No.51875401)。
文摘In the present study, the weld formation and mechanical properties of the AA-5A06 friction pull plug welded(FPPW) joints were improved by controlling the axial force history. Several defect-free FPPW joints were made successfully by using the welding parameters of 15–20 k N/s axial loading rate, 20–30 k N axial welding force and 6–7 mm axial feeding displacement. The results indicated that using higher axial loading rate and axial welding force produced more stable heat generation and shorter frictional heating time between the frictional interface. In this case, the plastic flow of the materials around the hole could be further improved since the axial feeding displacement of the plug was increased. The maximum ultimate tensile strength(UTS) and elongation of the FPPW 5A06 joints were 314 MPa and 4.8%, respectively. The thermal mechanically affect zone(TMAZ) had the lowest hardness value throughout the joint and was found as the fracture location to all the tensile samples. The softening of TMAZ was mainly caused by the weakening of the cold work hardening and the coarsening of grains.
基金financially supported by the Scientific and Technological Project of State Grid Corporation of China
文摘A binder-free Ni3S2 electrode was prepared directly on a graphene-coated Ni foam （G/Ni） substrate through surface sulfiding of substrate using thiourea as the sulfur source in this work. The Ni3S2 showed a flower-like morphology and was uniformly distributed on the G/Ni surface. The flower-like Ni3S2 was composed of cross-arrayed nanoflakes with a diameter and a thickness of 1-2 μm and -50 nm, re- spectively. The free space in the flowers and the thin feature of Ni3S2 buffered the volume changes and relieved mechanical strain during re- peated cycling. The intimate contact with the Ni substrate and the fixing effect of graphene maintained the structural stability of the Ni3S2 electrode during cycling. The G/Ni-supported Ni3S2 maintained a reversible capacity of 250 mAh·g^-1 after 100 cycles at 50 mA·g^-1, demon- strating the good cycling stability as a result of the unique microstructure of this electrode material.
基金The National Basic Research Program(973 Program)of China under contract No.2010CB428702the Science and Technology Planning Project of Guangdong Province of China under contract No.2016A030303012the Strategic Priority Research Program of the Chinese Academy of Sciences under contract No.XDA11020304
文摘Size-based partitioning of phytoplankton is a useful tool for monitoring key phytoplankton traits, and it provides a better understanding of phytoplankton dynamics. Our aim is to determine the variation in the different size classes of phytoplankton to the total phytoplankton biomass during the spring and autumn of 2010 and examine the relationship between phytoplankton size structure and environmental variables and zooplankton community structure near the Changjiang Estuary. In the spring, phytoplankton populations were predominantly consisted of nanophytoplankton throughout the study region. In the autumn, picophytoplankton and nanophytoplankton collectively dominated the phytoplankton community. A Pearson correlation analysis highlighted the role of temperature and trophic conditions on the contributions of nanophytoplankton and picophytoplankton. The grazing pressure exerted by mesozooplankton could have played an important role in determining the microphytoplankton community structure.
基金Supported by Jiangsu Planned Projects for Postdoctoral Research Funds,No.1302096BNatural Science Foundation of Jiangsu Province,No.BK2011484 and No.2012704National Natural Science Foundation of China,No.81070287
文摘AIM:To investigate the protective effect of clodronatecontaining liposomes against severe acute pancreatitis(SAP)-triggered acute gastric mucosal injury(AGMI) in rats.METHODS:Clodronate- and phosphate-buffered saline(PBS)-containing liposomes were prepared by reverse-phase evaporation.The SAP rat model was established by injecting sodium taurocholate into the pancreatic subcapsular space.Sprague-Dawley rats were randomly divided into three groups:control(C),SAP plus PBS-containing liposome(P) and SAP plus clodronate-containing liposome(T).Serum tumor necrosis factor(TNF)-α levels were estimated by ELISA.Pathological changes in the gastric mucosa and pancreas were observed by hematoxylin and eosin(HE) staining.Apoptotic cells were detected by terminal deoxynucleotidyl transferase d UTP nick end labeling staining.The numbers of macrophages in the gastric mucosa were analyzed by CD68 immunohistochemical staining.RESULTS:The liposomes had a mean diameter of 150 ± 30 nm.The TNF-α levels were significantly higher in the P group than that in the C group(2 h,145.13 ± 11.50 vs 23.2 ± 2.03; 6 h,245.06 ± 12.11 vs 30.28 ± 6.07,P < 0.05),and they were significantly lower in the T group than that in the P group(2 h,93.24 ± 23.11 vs 145.13 ± 11.50; 6 h,135.18 ± 13.10 vs 245.06 ± 12.11,P < 0.05).The pathological scores of the pancreas were lower in the T group than in the P group(2 h,1.88 ± 0.83 vs 4.13 ± 0.83; 6 h,2.87 ± 0.64 vs 6.25 ± 0.88,P < 0.01).The pathological scores of the gastric mucosa were also lower in the T group than in the P group(2 h,1.12 ± 0.64 vs 2 ± 0.75; 6 h,1.58 ± 0.53 vs 3 ± 1.31,P < 0.05).In addition,increased CD68 levels were observed in the gastric mucosa of the P group compared with the C group.Clodronate-containing liposomes decreased the CD68 levels in the mucosa of the T group.The apoptotic indexes of the gastric mucosa were higher in the T group than in the P group(2 h,15.7 ± 0.92 vs 11.5 ± 1.64; 6 h,21.12 ± 1.06 vs 12.6 ± 2.44,P < 0.01).CONCLUSION:Gastric macrophages contribute to the pathogenesis of gastric injury in SAP.Clodronatecontaining liposomes have protective effects against AGMI in rats with SAP.
基金financially supported by Wild Plants Protection Management Program of State Forestry Administration and Start Research Grants of Postdoctoral Researcher in Heilongjiang
文摘The deciduous linden tree （Tilia amurensis Rupr.） is protected at National Level II in China as a species of ecological and economic importance. The objective of this study was to assess and compare the ectomycorrhizal communities associated with T. amurensis in natural versus urban forests of central Heilongjiang Province. The percentage of T. amurensis colonisation by ectomycorrhiza was more than 60 % in urban forests, compared to 34-49 % in natural forests. Use of a combi- nation of morphological and molecular methods docu- mented 18 ECM （ectomycorrhizal） types among three sites; 12-13 ECM species were identified in the natural sites versus 9 species in the urban site. Four ECM species （Boletus sp., Tuber sp., Inocybe sp.2, Leccinum sp.1） were the dominant mycorrhizal symbionts, and Cenococcum geophilum and Russula sp. were found only in the natural forests.
基金financially supported by the Shandong Taishan Industry Leading Talents Project(SF1503302301)
文摘In this research,2205/Q235 B clad plates were prepared by a vacuum hot rolling composite process.The effects of adding Fe,Ni,and Nb interlayers on the bonding interface structures and the shear strengths of the clad steel plates were studied.The results showed that 2205 duplex stainless steel and the three interlayers produced a large amount of plastic deformation and low-angle boundaries,and the main structures were the recrystallized and deformed grains.There were many recrystallized grains in the microstructure of the Q235 B low-carbon steel due to the low deformation in the rolling process.The Fe interlayer had better wettability with the two kinds of steel,but the lower strength led to the reduction of shear strength by about14 MPa compared with the original clad steel plate.The C element in the Q235 B low-carbon steel easily diffused into the Fe interlayer,and the clad steel plate attained a poor corrosion resistance because a large decarburization area was formed.The Nb interlayer reacted with the Mo element in the 2205 duplex stainless steel to form an Nb-Mo binary alloy,which generated long-banded ferrite.The decarburization area was also produced because the Nb reacted with the C element in the Q235 B to form hard and brittle NbCx.As a result,the shear strength was significantly reduced by about 282 MPa,and the corrosion resistance of the bonding surface was deteriorated.The Ni interlayer did not react with the alloy elements in both sides,and therefore effectively prevented element diffusion and improved the corrosion resistance of the bonding surface.Due to the low strength of the Ni interlayer and the increased number of bonding surfaces of the clad steel plates,the shear strength was reduced to some extent(about 40 MPa),but it still met the engineering application standards.
基金Supported by Important Subject Fund of Science Technology Department of Zhejiang Province(No.2013C03048-1)
文摘AIM：To investigate the impact of adipose-derived mesenchymal stem cells（ADSCs） on cell viability and extracellular matrix（ECM） synthesis of corneal stromal cells（CSCs）. METHODS：ADSCs and CSCs were obtained from the corneas of New Zealand white rabbits and indirectly cocultured in vitro. The proliferative capacity of CSCs in the different groups was assessed by CCK-8 assays. Annexin V-fluorescein isothiocyanate（FITC）/proliferation indices（PI） assays were used to detect the apoptosis of CSCs. The expression levels of matrix metalloproteinase（MMP）, such as MMP1, MMP2, MMP9, and collagens were also evaluated by Western blot. RESULTS：ADSCs significantly promoted proliferation and invasion of CSCs in the indirect co-culture assays. The co-cultural group displayed much higher ability of proliferation, especially under the co-culture conditions of ADSCs for 3d, compared with that CSCs cultured alone. The PI of CSCs in the co-culture system were increased approximately 3-8-fold compared with the control group. A significant change was observed in the proportions of cells at apoptosis（early and late） between the negative control group（6.34% and 2.06%） and the ADCSs-treated group（4.69% and 1.59%）. The expression levels of MMPs were down regulated in the co-culture models. Compared with the control group, the decrease intensities of MMP-1, MMP-2 and MMP-9 in CSCs/ADSCs group were observed, 3.90-fold, 1.09-fold and 3.03-fold, respectively. However, the increase intensities of collagen type（I, II, III, IV, and V） in CSCs were observed in CSCs/ADSCs group, 3.47-fold,4.30-fold, 2.35-fold, 2.55-fold and 2.43-fold, respectively, compared to that in the control group. The expressions of aldehyde dehydrogenase and fibronectin in CSCs were upregulated in the co-culture models.CONCLUSION：ADSCs play a promotive role in CSCs＇ growth and invasion, which may be partially associated with MMPs decrease and collagens increase, resulting in a positive participation in the plasticity and ECM synthesis of CSCs. This provided a new insight into the extensive role of ADSCs in CSCs and a potential molecular target for corneal therapy.
基金supported by the National Natural Science Foundation of China (No. 50974107)the Engineering Project of High School Subject Innovation (No. B07028), China
文摘In this paper, an experimental study on the sulphate attack resistance of high-performance concrete (HPC) with two different water-to-binder ratios (w/b) under compressive loading is presented. The sulphate concentration, compressive strength, and the mass change in the HPC specimens were determined for immersion in a Na2SO4 solution over different durations under external compressive loading by self-regulating loading equipment. The effects of the compressive stress, the w/b ratio, and the Na2SO4 solution concentration on the HPC sulphate attack resistance under compressive loading were analysed. The results showed that the HPC sulphate attack resistance under compressive loading was closely related to the stress level, the w/b ratio, and the Na2SO4 solution concentration. Applying a 0.3 stress ratio for the compressive loading or reducing the w/b ratio clearly improved the HPC sulphate attack resistance, whereas applying a 0.6 stress ratio for the compressive loading or exposing the HPC to a more concentrated Na2SO4 solution accelerated the sulphate attack and HPC deterioration.
基金supported by the National Natural Science Foundation of China (Nos.51871160 and 52101266)the Natural Science Foundation of Hefei Grant (No.2022046)。
文摘Commercial hydrogen production involves the development of efficient hydrogen evolution reaction catalysts.Herein,we adopted a friction stir processing(FSP)technique to mix immiscible metals homogenously and obtain a self-supporting copper-silver(CuAg)catalyst.The gust of Ag atoms with larger atomic sizes caused a tensile strain in the Cu matrix.Meanwhile,the chemical-potential difference induced electron transfer from Cu to Ag,and the two factors jointly led to the upshift of Cu d-band and improved the catalytic activity.Consequently,the CuAg electrode exhibited a high turnover frequency(12 times that of pure Cu),a low overpotential at high current density(superior to platinum foil),and high durability(1.57%decay over 180 h).Our work demonstrates that FSP is a powerful method for preparing self-supporting catalysts of immiscible alloys with high catalytic performance.
基金financial support from the National Natural Science Foundation of China (Nos. 22122110 ad 21871250)the Jilin Provincial Science and Technology Department Program (No. 20200801009GH)Shaanxi Provincial Natural Science Basic Research Program-Shaanxi Coal and Chemical Industry Group Co., Ltd. Joint Fund (No. 2019JLZ-02)。
文摘To address the issue of hemilabile catalyst in olefin polymerization catalysis, a cyclizing strategy was used to construct novel N-bridged phosphine-carbonyl palladium and nickel catalysts, resulting in improvements on ethylene(co)polymerizations. The N-bridged phosphinecarbonyl Pd catalysts(Pd1-Pd5) and Ni catalysts(Ni1-Ni5) bearing five-to eight-membered-ring structures were designed and synthesized.Catalytic performance for ethylene(co)polymerization became better as the size of N-containing bridge increased. The seven-membered-ring bridged catalysts Pd4 and Ni4 exhibited the best performance in terms of catalytic activity, polymer molecular weight and incorporation of acrylates and acrylic acid. The better performance of these catalysts bearing larger-size bridges was tentatively attributed to the methyleneinduced higher electron density around nitrogen, which strenghtens the coordination of carbonyl group to metal center, and also to the steric effect offered by this cyclization. This work provides a new strategy to enhance hemilabile polymerization catalysts.
基金the National Natural Science Foundation of China(Grant No.42204006)the Guangxi Natural Science Foundation of China(2020GXNSFBA297145)+1 种基金the“Ba Gui Scholars”program of the provincial government of Guangxi,and Innovation Project of GuangXi Graduate Education(Grant No.YCSW2022322)Open Research Fund Program of the Key Laboratory of Geospace Environment and Geodesy,Ministry of Education,China(GrantNo.20-01-03,21-01-04)
文摘Temperature and pressure play key roles in Global Navigation Satellite System(GNSS)precipitable water vapor(PWV)retrieval.The National Aeronautics and Space Administration(NASA)and European Center for Medium-Range Weather Forecasts(ECMWF)have released their latest reanalysis product:the modern-era retrospective analysis for research and applications,version 2(MERRA-2)and the fifthgeneration ECMWF reanalysis(ERA5),respectively.Based on the reanalysis data,we evaluate and analyze the accuracy of the surface temperature and pressure products in China using the the measured temperature and pressure data from 609 ground meteorological stations in 2017 as reference values.Then the accuracy of the two datasets and their performances in estimating GNSS PWV are analyzed.The PWV derived from the pressure and temperature products of ERA5 and MERRA-2 has high accuracy.The annual average biases of pressure and temperature for ERA5 are-0.07 hPa and 0.45 K,with the root mean square error(RMSE)of 0.95 hPa and 2.04 K,respectively.The annual average biases of pressure and temperature for MERRA-2 are-0.01 hPa and 0.38 K,with the RMSE of 1.08 h Pa and 2.66 K,respectively.The accuracy of ERA5 is slightly higher than that of MERRA-2.The two reanalysis data show negative biases in most regions of China,with the highest to lowest accuracy in the following order:the south,north,northwest,and Tibet Plateau.Comparing the GNSS PWV calculated using MERRA-2(GNSS MERRA-2 PWV)and ERA5(GNSS ERA5 PWV)with the radiosonde-derived PWV from 48 co-located GNSS stations and the measured PWV of the co-location radiosonde stations,it is found that the accuracy of GNSS ERA5 PWV is better than that of GNSS MERRA-2 PWV.These results show the different applicability of surface temperature and pressure products from MERRA-2 and ERA5 data,indicating that both have important applications in meteorological research and GNSS water vapor monitoring in China.
