[Objectives]To explore the change rule of polyphenol content and antioxidant activity of coarse old leaves of Yingshan Yunwu Tea in the process of human digestion.[Methods]The coarse and old leaves of Yunwu tea in Yin...[Objectives]To explore the change rule of polyphenol content and antioxidant activity of coarse old leaves of Yingshan Yunwu Tea in the process of human digestion.[Methods]The coarse and old leaves of Yunwu tea in Yingshan,Huanggang,Hubei Province were selected as the research object,and their digestion in vitro was simulated.The total polyphenol content was determined by Folin-phenol reagent colorimetric method,and the DPPH radical scavenging activity and total antioxidant activity were determined.[Results]After simulated gastrointestinal digestion in vitro,the polyphenol content and antioxidant activity of coarse old leaf tea soup showed a downward trend.After gastrointestinal digestion,the polyphenol content in tea infusion separately decreased by 31.8%and 8.5%;the scavenging rate of DPPH free radical was 97%before digestion,decreased to 92%after gastric digestion and 65%after intestinal digestion,which decreased by 5%and 27%,respectively;after gastrointestinal digestion,the total antioxidant capacity of tea soup decreased by 4.7%and 3.1%,respectively.[Conclusions]This study provided a reference for the development and application of coarse old leaves of Yingshan Yunwu tea,and provided a reference for the nutritional value evaluation and comprehensive utilization of coarse old leaves,so as to make the best use of coarse tea leaves and reduce the waste of resources.展开更多
Selective synthesis of value-added xylenes and para-xylene(PX)by CO_(2)hydrogenation reduces the dependence on fossil resource and relieves the environment burden derived from the greenhouse gas CO_(2).Herein,modified...Selective synthesis of value-added xylenes and para-xylene(PX)by CO_(2)hydrogenation reduces the dependence on fossil resource and relieves the environment burden derived from the greenhouse gas CO_(2).Herein,modified MCM-22 zeolite combined with ZnCeZrOx solid solution is reported to catalyze the tandem CO_(2)hydrogenation and toluene methylation reaction at a relatively low temperature(<603 K),showing xylene selectivity of 92.4%and PX selectivity of 62%(PX/X,67%)in total aromatics at a CO_(2)conversion of 7.7%,toluene conversion of 23.6%and low CO selectivity of 11.6%,as well as giving high STY of xylene(302.0 mg·h^(–1)·gcat^(–1))and PX(201.6 mg·h^(–1)·gcat^(–1)).The outstanding catalytic performances are closely related to decreased pore sizes and eliminated external surface acid sites in modified MCM-22,which promoted zeolite shape-selectivity and suppressed secondary reactions.展开更多
The structure-performance relationship of Cu/Al_(2)O_(3) catalysts in the hydrogenation of diethyl oxalate(DEO)for the synthesis of alcohol ether esters has been investigated by various characterization techniques inc...The structure-performance relationship of Cu/Al_(2)O_(3) catalysts in the hydrogenation of diethyl oxalate(DEO)for the synthesis of alcohol ether esters has been investigated by various characterization techniques including XRD,XPS,N2O titration,and 27Al MAS-NMR.The results showed that when the crystal configurations of Al_(2)O_(3) were the same,increasing the specific surface area could effectively refine the size of copper nanoparticles(Cu NPs),and ultimately improve the conversion of DEO.Meanwhile,the smaller size ofγ-Al_(2)O_(3)(HSAl and SBAl)loaded Cu NPs promotes the reaction towards the deep hydrogenation to produce ethanol(EtOH)and ethylene glycol(EG).Besides,the larger size of Cu NPs on the surface of amorphous Al_(2)O_(3)(HTAl and SolAl)resulted in a lower conversion rate,where ethyl glycolate(Egly)is the main product.Despite there are differences in Al^(3+)ionic coordination in Al_(2)O_(3) with different crystal structures,the experimental data showed that the differences in Al^(3+)ionic coordination did not significantly affect the catalytic performance in the hydrogenation reaction.The formation of alcohol-ether ester chemicals is critically dependent on the interactions between Cu sites and acidic sites.Among them,EG and EtOH were dehydrated to form 2-ethoxyethanol via the SN2 mechanism,while Egly and EtOH were reacted to form ethyl ethoxyacetate(EEA)via the SN2 mechanism.This study provides a theoretical basis for the optimization of the coal-based glycol processes to achieve a diversified product portfolio.展开更多
In this work,the properties and microstructure of sintered Nd-Pr-Fe-Co-Zr-Ga-Cu-B magnet prepared by the single-step annealing,double-step annealing,and triple-step annealing processes were studied.The triple-step ann...In this work,the properties and microstructure of sintered Nd-Pr-Fe-Co-Zr-Ga-Cu-B magnet prepared by the single-step annealing,double-step annealing,and triple-step annealing processes were studied.The triple-step annealed magnet exhibits the highest intrinsic coercivity of 19.72 kOe,which is a 58.5%enhancement relative to the as-sintered magnet,and has the best temperature stability of coercivity.The best continuity of grain boundary(GB)phase and the highest content of RE6Fe13Ga phase can be observed in the triple-step annealed magnet,along with relatively small grain size.After triple-step annealing process,the phase separation occurs at the triple-junction(TJ)region of the magnet,which is the Fe-rich phase identified as RE6Fe13Ga and the Fe-poor phase identified as Ia-RE_(2)O_(3).The Ia-RE_(2)O_(3)phase located at the corner of the TJ region can extend between the grains of(Nd,Pr)_(2)Fe_(14)B main phase to form the GB phase with a Fe content of less than 15 at%,thereby enhancing the magnetic isolation effect.The lattice misfit between the Ia-RE_(2)O_(3)phase and the adjacent main phase is less than 5%,which is helpful to reduce defects at the edges of the main phase grains,thus reducing the nucleation of reverse domains.展开更多
Constructing new Brönsted acid sites within zeolitic materials holds paramount importance for the advancement of solid-acid catalysis.Zeo-type germanosilicates,a class of metallosilicates with a neutral framework...Constructing new Brönsted acid sites within zeolitic materials holds paramount importance for the advancement of solid-acid catalysis.Zeo-type germanosilicates,a class of metallosilicates with a neutral framework composed of tetravalent Ge and Si oxygen tetrahedrons,are conventionally considered not to generate Brönsted acid sites.Herein,we disclose an abnormal phenomenon with Ge-rich IWW-type germanosilicate(IWW-A)as an example that Ge-enriched germanosilicates are featured by mild Brönsted acidity.Using the art-of-state density functional theory calculation,19F magic angle spinning nuclear magnetic resonance,microcalorimetric and ammonia infrared mass spectrometry-temperature-programmed desorption characterizations,the nature of germanosilicate's Brönsted acidity has been demonstrated to be closely related to the neighboring framework Ge-hydroxyl pairs.Besides,the contribution of Ge-OH groups to Brönsted acidity and the role of Ge-pair structure for maintaining mild acid strength have been elucidated.In catalytic cracking of n-hexane and methanol-to-olefins reaction,the IWW-A germanosilicate exhibit high light olefins selectivity,good recyclability and low carbon deposition,outperforming the benchmark zeolite catalyst,ZSM-5 aluminosilicate.展开更多
Wire-feed direct metal deposition(DMD)additive manufacturing(AM)has demonstrated strong adaptability in microgravity environments,making it a preferred solution for in-situ space fabrication.However,space-oriented met...Wire-feed direct metal deposition(DMD)additive manufacturing(AM)has demonstrated strong adaptability in microgravity environments,making it a preferred solution for in-situ space fabrication.However,space-oriented metal AM faces significant constraints due to the high cost of Earth-to-space transport and must meet demanding requirements for miniaturization and low power consumption.This study proposes a metal fusion AM technique utilizing a Joule-laser hybrid heat source and investigates its forming mechanism and processing behavior.The influence of various process parameters on formation quality is thoroughly analyzed,and optimal conditions are identified.Experimental results indicate that,using a 0.3 mm diameter stainless steel wire,the hybrid heat source enables high-quality deposition at a low laser power of 50 W—reducing total power consumption by36%compared to single-laser wire melting.This study provides both theoretical and experimental support for developing low-power metal wire AM processes,contributing to the miniaturization and lightweighting of spaceborne AM equipment.展开更多
In this work,a novel microwave absorbing material(MAM)made of a pseudo-binary of Sr_(2)TiMoO_(6)-Al_(2)O_(3)(STM)is proposed first.The MAMs labeled as STM X(X=60,70,80 and 100,respectively),in which X is the initial w...In this work,a novel microwave absorbing material(MAM)made of a pseudo-binary of Sr_(2)TiMoO_(6)-Al_(2)O_(3)(STM)is proposed first.The MAMs labeled as STM X(X=60,70,80 and 100,respectively),in which X is the initial weight percent of Sr_(2)TiMoO_(6),were synthesized using the solid-state reaction method.Compared with STM100,some equilibrium phases,including SrTiO_(3),Mo,Sr_(8)(Al1_(2)O_(24))(MoO_(4))_(2)and a few undefined ones,are presented in the composites as evidenced by X-ray diffraction results and scanning electron microscopy due to the chemical reaction between Sr_(2)TiMoO_(6)and Al_(2)O_(3)component.Besides conductance loss,heterogeneous interfaces between various equilibrium phases introduce interfacial polarization,which causes an enhancement of dissipation for the incident electromagnetic wave.Among the synthesized samples,STM80 presents the best microwave absorbing properties.It has a minimum reflection loss(RLmin)of-26 dB and an effective absorbing bandwidth up to 2.7 GHz when the thickness is only 1 mm.This indicates that STM80 is a new type of microwave absorbing material with strong absorption and ultrathin thickness.展开更多
The Baeyer-Villiger(BV)oxidation of cyclohexanone is explored using IWV-type aluminosilicates with different Al sites as heterogeneous catalysts.The IWV framework exhibits a two-dimensional 12-membered ring(MR)pore sy...The Baeyer-Villiger(BV)oxidation of cyclohexanone is explored using IWV-type aluminosilicates with different Al sites as heterogeneous catalysts.The IWV framework exhibits a two-dimensional 12-membered ring(MR)pore system intersected by 14-MR supercages,resembling typical beta zeolite.To address the constraints associated with hydrothermal synthesis,IWV aluminosilicates were synthesized via interzeolite transformation of various FAU-type zeolites.HF-assisted transformation of dealuminated FAU zeolite resulted in the formation of a high-silica IWV aluminosilicate(Si/Al=54.6),whereas the incorporation of aluminum isopropoxide enables the tuning of Si/Al ratio down to 18.7.The alkaline conversion of protonated FAU zeolites,utilizing Na^(+)ions as mineralizing agents,produces high-Al content IWV derivatives in just four days.Catalytic evaluation demonstrates that the high-silica IWV catalyst exhibits a higher turnover number than the other IWV catalysts,along with enhancedε-caprolactone(CL)selectivity relative to that of high-silica beta zeolite.Facile modifications are performed to adjust Al sites,as characterized by pyridine-adsorbed infrared spectroscopy.Experimental evidence confirms that Al Brønsted acid sites improves the selective oxidation of cyclohexanone,while concurrently enhancing CL hydrolysis.展开更多
BACKGROUND The risk factors and prediction models for diabetic foot(DF)remain incompletely understood,with several potential factors still requiring in-depth investigations.AIM To identify risk factors for new-onset D...BACKGROUND The risk factors and prediction models for diabetic foot(DF)remain incompletely understood,with several potential factors still requiring in-depth investigations.AIM To identify risk factors for new-onset DF and develop a robust prediction model for hospitalized patients with type 2 diabetes.METHODS We included 6301 hospitalized patients with type 2 diabetes from January 2016 to December 2021.A univariate Cox model and least absolute shrinkage and selection operator analyses were applied to select the appropriate predictors.Nonlinear associations between continuous variables and the risk of DF were explored using restricted cubic spline functions.The Cox model was further employed to evaluate the impact of risk factors on DF.The area under the curve(AUC)was measured to evaluate the accuracy of the prediction model.RESULTS Seventy-five diabetic inpatients experienced DF.The incidence density of DF was 4.5/1000 person-years.A long duration of diabetes,lower extremity arterial disease,lower serum albumin,fasting plasma glucose(FPG),and diabetic nephropathy were independently associated with DF.Among these risk factors,the serum albumin concentration was inversely associated with DF,with a hazard ratio(HR)and 95%confidence interval(CI)of 0.91(0.88-0.95)(P<0.001).Additionally,a U-shaped nonlinear relationship was observed between the FPG level and DF.After adjusting for other variables,the HRs and 95%CI for FPG<4.4 mmol/L and≥7.0 mmol/L were 3.99(1.55-10.25)(P=0.004)and 3.12(1.66-5.87)(P<0.001),respectively,which was greater than the mid-range level(4.4-6.9 mmol/L).The AUC for predicting DF over 3 years was 0.797.CONCLUSION FPG demonstrated a U-shaped relationship with DF.Serum albumin levels were negatively associated with DF.The prediction nomogram model of DF showed good discrimination ability using diabetes duration,lower extremity arterial disease,serum albumin,FPG,and diabetic nephropathy(Clinicaltrial.gov NCT05519163).展开更多
Objective:To systematically review the safety of different types of chikungunya vaccines in human populations.Methods:This study retrieved randomized controlled trials(RCTs)reporting on the safety of chikungunya vacci...Objective:To systematically review the safety of different types of chikungunya vaccines in human populations.Methods:This study retrieved randomized controlled trials(RCTs)reporting on the safety of chikungunya vaccines in human populations through electronic searches of the Web of Science,PubMed,EMbase,and Cochrane Library databases.Two reviewers independently performed literature screening,data extraction,and risk of bias assessment for the included studies.Meta-analysis was conducted using STATA 18.0 software.Results:A total of eight RCTs involving 9336 subjects were included in this study.Meta-analysis showed that three out of the five chikungunya vaccines(VLA1553,mRNA-1388,and PXVX0317)exhibited favorable safety profiles,with no significant increase in the incidence of serious adverse events.The vaccine group had a higher incidence of any adverse events[risk ratio(RR)=1.26,P<0.001]and any systemic adverse events(RR=1.18,P=0.010)compared to the placebo group.The incidence of local adverse events was also higher in the vaccine group(RR=2.09,P<0.001).However,there were no significant differences between the two groups in the incidences of erythema(RR=1.41,P=0.402),headache(RR=1.14,P=0.457),or arthralgia(RR=1.45,P=0.660).Conclusions:Current evidence supports that chikungunya vaccines have a favorable safety profile.However,due to limitations in the number and quality of included studies,further high-quality research is needed to validate these conclusions.展开更多
Designing Fischer-Tropsch synthesis(FTS)catalysts to selectively produce liquid hydrocarbon fuels is a crucial challenge.Herein,we selectively introduced Co nanoparticles(NPs)into the micropores and mesopores of an or...Designing Fischer-Tropsch synthesis(FTS)catalysts to selectively produce liquid hydrocarbon fuels is a crucial challenge.Herein,we selectively introduced Co nanoparticles(NPs)into the micropores and mesopores of an ordered mesoporous MFI zeolite(OMMZ)through impregnation,which controlled the carbon number distribution in the FTS products by tuning the position of catalytic active sites in differently sized pores.The Co precursors coordinated by acetate with a size of 9.4×4.2×2.5Åand by 2,2'-bipyridine with a size of 9.5×8.7×7.9Å,smaller and larger than the micropores(ca.5.5Å)of MFI,made the Co species incorporated in OMMZ's micropores and mesopores,respectively.The carbon number products synthesized with the Co NPs confined in mesopores were larger than that in micropores.The high jet and diesel selectivities of 66.5%and 65.3%were achieved with Co NPs confined in micropores and mesopores of less acidic Na-type OMMZ,respectively.Gasoline and jet selectivities of 76.7%and 70.8%were achieved with Co NPs confined in micropores and mesopores of H-type OMMZ with Brönsted acid sites,respectively.A series of characterizations revealed that the selective production of diesel and jet fuels was due to the C-C cleavage suppressing of heavier hydrocarbons by the Co NPs located in mesopores.展开更多
Applied field magnetoplasmadynamic thrusters(AF-MPDTs), with their high specific impulse and considerable thrust, are increasingly favored for large-scale space missions. This paper presents the composition, functiona...Applied field magnetoplasmadynamic thrusters(AF-MPDTs), with their high specific impulse and considerable thrust, are increasingly favored for large-scale space missions. This paper presents the composition, functionality, and testing methods of a high-power electric propulsion performance testing system, along with the vacuum ignition test results of a 100 kW superconducting MPD thruster. The relationships between thruster efficiency, magnetic field strength, current,and mass flow rate are analyzed. For each combination of current and flow rate in an AF-MPDT, there is an optimal magnetic field strength where the thruster efficiency reaches its peak. Under conditions of 320 A current and 60 mg/s flow rate,the optimal magnetic field strength is 0.5 T, yielding the highest thruster efficiency of 71%.展开更多
[Objectives]This study was condcuted to investigate the formula optimization and nutritional components of Brassica vegetable juice beverage.[Methods]Brassica was selected as the raw material to optimize the formula o...[Objectives]This study was condcuted to investigate the formula optimization and nutritional components of Brassica vegetable juice beverage.[Methods]Brassica was selected as the raw material to optimize the formula of the vegetable juice beverage.The vitamin C content and flavor components were analyzed in both sterilized and non-sterilized samples.[Results]Based on water,the optimal formula for the Brassica vegetable juice beverage was determined as:20%Brassica juice,5%erythritol,and 0.1%citric acid.The highest vitamin C content was observed in unsterilized samples(12.167 mg/100 g sample),followed by samples sterilized at 71℃for 15 s(9.864 mg/100 g sample).The most significant loss of vitamin C occurred under sterilization conditions of 68℃for 30 min.GC-MS analysis detected a total of seven volatile components in the Brassica vegetable juice beverage,including siloxanes,alcohols,aldehydes,and methoxyphenyl oxime.Before sterilization,siloxane compounds(D3,D4,D5)showed the highest content in the Brassica vegetable juice,accounting for 63.606%,followed by methoxyphenyl oxime at 24.802%.After sterilization,siloxane compounds(D3,D4,D5)exhibited the highest content reaching 81.963%,while methoxyphenyl oxime taking the second place decreased to 14.276%.[Conclusions]This study provides new insights and methodologies for the development and utilization of Brassica crops and other agricultural products,offering a theoretical foundation for accelerating the integrated development of Brassica processing and sales.展开更多
The magnetoplasmadynamic thruster(MPDT) is characterized by its high specific impulse and substantial thrust density, making it a promising propulsion system for deep space exploration missions. In both laboratory exp...The magnetoplasmadynamic thruster(MPDT) is characterized by its high specific impulse and substantial thrust density, making it a promising propulsion system for deep space exploration missions. In both laboratory experiments and practical applications, cathode ablation has emerged as a critical concern. An optical diagnostic approach based on monochromatic radiation temperature measurement, utilizing plume emission spectra and the selection of an appropriate test band, has been successfully employed. This method provides an accurate temperature distribution across the cathode surface, offering a novel testing technique for the optimization and evaluation of magnetic plasma thruster designs.展开更多
The integration of emerging technologies such as artificial intelligence and cloud computing is accelerating the development of intelligent and autonomous satellite systems.However,limitations in onboard sensing,compu...The integration of emerging technologies such as artificial intelligence and cloud computing is accelerating the development of intelligent and autonomous satellite systems.However,limitations in onboard sensing,computing,storage,and energy resources continue to constrain the intelligent functionalities of individual satellites.Currently,most studies focus on either satellite intelligence or satellite networking,while systematic studies on their integration remain scarce.To address this gap,this paper introduces the concept of an intelligent satellite cluster system,which leverages satellite networks to enable collaborative intelligence among satellites,thereby enhancing the overall system intelligence.After summarizing the typical use cases of the intelligent satellite cluster system,we analyze the corresponding demands on network capabilities.Based on these demands,we propose the concept of the Internet of satellites(IoS)tailored to support the intelligent satellite cluster system.Specifically,we design both the logical and physical architectures of IoS and elaborate on its key enabling technologies.Finally,we present the research progress and outcomes achieved by our team on these core technologies,and discuss the challenges that remain.This paper aims to build consensus around intelligent and connected satellite technologies,promote innovation and standardization,and enhance the intelligent service capabilities of future large-scale satellite systems.展开更多
基金Supported by High-level Training Project of Huanggang Normal University in 2021(202108504).
文摘[Objectives]To explore the change rule of polyphenol content and antioxidant activity of coarse old leaves of Yingshan Yunwu Tea in the process of human digestion.[Methods]The coarse and old leaves of Yunwu tea in Yingshan,Huanggang,Hubei Province were selected as the research object,and their digestion in vitro was simulated.The total polyphenol content was determined by Folin-phenol reagent colorimetric method,and the DPPH radical scavenging activity and total antioxidant activity were determined.[Results]After simulated gastrointestinal digestion in vitro,the polyphenol content and antioxidant activity of coarse old leaf tea soup showed a downward trend.After gastrointestinal digestion,the polyphenol content in tea infusion separately decreased by 31.8%and 8.5%;the scavenging rate of DPPH free radical was 97%before digestion,decreased to 92%after gastric digestion and 65%after intestinal digestion,which decreased by 5%and 27%,respectively;after gastrointestinal digestion,the total antioxidant capacity of tea soup decreased by 4.7%and 3.1%,respectively.[Conclusions]This study provided a reference for the development and application of coarse old leaves of Yingshan Yunwu tea,and provided a reference for the nutritional value evaluation and comprehensive utilization of coarse old leaves,so as to make the best use of coarse tea leaves and reduce the waste of resources.
文摘Selective synthesis of value-added xylenes and para-xylene(PX)by CO_(2)hydrogenation reduces the dependence on fossil resource and relieves the environment burden derived from the greenhouse gas CO_(2).Herein,modified MCM-22 zeolite combined with ZnCeZrOx solid solution is reported to catalyze the tandem CO_(2)hydrogenation and toluene methylation reaction at a relatively low temperature(<603 K),showing xylene selectivity of 92.4%and PX selectivity of 62%(PX/X,67%)in total aromatics at a CO_(2)conversion of 7.7%,toluene conversion of 23.6%and low CO selectivity of 11.6%,as well as giving high STY of xylene(302.0 mg·h^(–1)·gcat^(–1))and PX(201.6 mg·h^(–1)·gcat^(–1)).The outstanding catalytic performances are closely related to decreased pore sizes and eliminated external surface acid sites in modified MCM-22,which promoted zeolite shape-selectivity and suppressed secondary reactions.
文摘The structure-performance relationship of Cu/Al_(2)O_(3) catalysts in the hydrogenation of diethyl oxalate(DEO)for the synthesis of alcohol ether esters has been investigated by various characterization techniques including XRD,XPS,N2O titration,and 27Al MAS-NMR.The results showed that when the crystal configurations of Al_(2)O_(3) were the same,increasing the specific surface area could effectively refine the size of copper nanoparticles(Cu NPs),and ultimately improve the conversion of DEO.Meanwhile,the smaller size ofγ-Al_(2)O_(3)(HSAl and SBAl)loaded Cu NPs promotes the reaction towards the deep hydrogenation to produce ethanol(EtOH)and ethylene glycol(EG).Besides,the larger size of Cu NPs on the surface of amorphous Al_(2)O_(3)(HTAl and SolAl)resulted in a lower conversion rate,where ethyl glycolate(Egly)is the main product.Despite there are differences in Al^(3+)ionic coordination in Al_(2)O_(3) with different crystal structures,the experimental data showed that the differences in Al^(3+)ionic coordination did not significantly affect the catalytic performance in the hydrogenation reaction.The formation of alcohol-ether ester chemicals is critically dependent on the interactions between Cu sites and acidic sites.Among them,EG and EtOH were dehydrated to form 2-ethoxyethanol via the SN2 mechanism,while Egly and EtOH were reacted to form ethyl ethoxyacetate(EEA)via the SN2 mechanism.This study provides a theoretical basis for the optimization of the coal-based glycol processes to achieve a diversified product portfolio.
基金Project supported by the Major Special Project of Fujian Province(2023HZ021005)the Guiding Project of Fujian Province(2023H0006)+2 种基金the Major Project of Science and Technology of Fuzhou(2022-ZD-010)the Young and Middle-aged Teachers Education Scientific Research Project of Fujian Province(JAT200594,JAT231008)the Natural Science Foundation of Fujian Province(2022J011151)。
文摘In this work,the properties and microstructure of sintered Nd-Pr-Fe-Co-Zr-Ga-Cu-B magnet prepared by the single-step annealing,double-step annealing,and triple-step annealing processes were studied.The triple-step annealed magnet exhibits the highest intrinsic coercivity of 19.72 kOe,which is a 58.5%enhancement relative to the as-sintered magnet,and has the best temperature stability of coercivity.The best continuity of grain boundary(GB)phase and the highest content of RE6Fe13Ga phase can be observed in the triple-step annealed magnet,along with relatively small grain size.After triple-step annealing process,the phase separation occurs at the triple-junction(TJ)region of the magnet,which is the Fe-rich phase identified as RE6Fe13Ga and the Fe-poor phase identified as Ia-RE_(2)O_(3).The Ia-RE_(2)O_(3)phase located at the corner of the TJ region can extend between the grains of(Nd,Pr)_(2)Fe_(14)B main phase to form the GB phase with a Fe content of less than 15 at%,thereby enhancing the magnetic isolation effect.The lattice misfit between the Ia-RE_(2)O_(3)phase and the adjacent main phase is less than 5%,which is helpful to reduce defects at the edges of the main phase grains,thus reducing the nucleation of reverse domains.
文摘Constructing new Brönsted acid sites within zeolitic materials holds paramount importance for the advancement of solid-acid catalysis.Zeo-type germanosilicates,a class of metallosilicates with a neutral framework composed of tetravalent Ge and Si oxygen tetrahedrons,are conventionally considered not to generate Brönsted acid sites.Herein,we disclose an abnormal phenomenon with Ge-rich IWW-type germanosilicate(IWW-A)as an example that Ge-enriched germanosilicates are featured by mild Brönsted acidity.Using the art-of-state density functional theory calculation,19F magic angle spinning nuclear magnetic resonance,microcalorimetric and ammonia infrared mass spectrometry-temperature-programmed desorption characterizations,the nature of germanosilicate's Brönsted acidity has been demonstrated to be closely related to the neighboring framework Ge-hydroxyl pairs.Besides,the contribution of Ge-OH groups to Brönsted acidity and the role of Ge-pair structure for maintaining mild acid strength have been elucidated.In catalytic cracking of n-hexane and methanol-to-olefins reaction,the IWW-A germanosilicate exhibit high light olefins selectivity,good recyclability and low carbon deposition,outperforming the benchmark zeolite catalyst,ZSM-5 aluminosilicate.
基金supported by Key Research and Development Program of Sichuan province(Grant No.2025YFHZ0051)Open Fund of State Key Laboratory for Manufacturing Systems Engineering(Grant No.sk1ms2024008)。
文摘Wire-feed direct metal deposition(DMD)additive manufacturing(AM)has demonstrated strong adaptability in microgravity environments,making it a preferred solution for in-situ space fabrication.However,space-oriented metal AM faces significant constraints due to the high cost of Earth-to-space transport and must meet demanding requirements for miniaturization and low power consumption.This study proposes a metal fusion AM technique utilizing a Joule-laser hybrid heat source and investigates its forming mechanism and processing behavior.The influence of various process parameters on formation quality is thoroughly analyzed,and optimal conditions are identified.Experimental results indicate that,using a 0.3 mm diameter stainless steel wire,the hybrid heat source enables high-quality deposition at a low laser power of 50 W—reducing total power consumption by36%compared to single-laser wire melting.This study provides both theoretical and experimental support for developing low-power metal wire AM processes,contributing to the miniaturization and lightweighting of spaceborne AM equipment.
基金supported by the National Natural Science Foundation of China(No.52402078)Yunnan Major Scientific and Technological Projects(No.202302AG050010)+1 种基金Yunnan Fundamental Research Projects(No.202201BE070001-008)the National Key Research and Development Program of China(No.2022YFB3708600)。
文摘In this work,a novel microwave absorbing material(MAM)made of a pseudo-binary of Sr_(2)TiMoO_(6)-Al_(2)O_(3)(STM)is proposed first.The MAMs labeled as STM X(X=60,70,80 and 100,respectively),in which X is the initial weight percent of Sr_(2)TiMoO_(6),were synthesized using the solid-state reaction method.Compared with STM100,some equilibrium phases,including SrTiO_(3),Mo,Sr_(8)(Al1_(2)O_(24))(MoO_(4))_(2)and a few undefined ones,are presented in the composites as evidenced by X-ray diffraction results and scanning electron microscopy due to the chemical reaction between Sr_(2)TiMoO_(6)and Al_(2)O_(3)component.Besides conductance loss,heterogeneous interfaces between various equilibrium phases introduce interfacial polarization,which causes an enhancement of dissipation for the incident electromagnetic wave.Among the synthesized samples,STM80 presents the best microwave absorbing properties.It has a minimum reflection loss(RLmin)of-26 dB and an effective absorbing bandwidth up to 2.7 GHz when the thickness is only 1 mm.This indicates that STM80 is a new type of microwave absorbing material with strong absorption and ultrathin thickness.
基金supported by the National Natural Science Foundation of China(No.22302116)the Fundamental Research Program of Shanxi Province(No.202203021212412)Qingchuang Technology Support Program of the University in Shandong Province(No.2023KJ246).
文摘The Baeyer-Villiger(BV)oxidation of cyclohexanone is explored using IWV-type aluminosilicates with different Al sites as heterogeneous catalysts.The IWV framework exhibits a two-dimensional 12-membered ring(MR)pore system intersected by 14-MR supercages,resembling typical beta zeolite.To address the constraints associated with hydrothermal synthesis,IWV aluminosilicates were synthesized via interzeolite transformation of various FAU-type zeolites.HF-assisted transformation of dealuminated FAU zeolite resulted in the formation of a high-silica IWV aluminosilicate(Si/Al=54.6),whereas the incorporation of aluminum isopropoxide enables the tuning of Si/Al ratio down to 18.7.The alkaline conversion of protonated FAU zeolites,utilizing Na^(+)ions as mineralizing agents,produces high-Al content IWV derivatives in just four days.Catalytic evaluation demonstrates that the high-silica IWV catalyst exhibits a higher turnover number than the other IWV catalysts,along with enhancedε-caprolactone(CL)selectivity relative to that of high-silica beta zeolite.Facile modifications are performed to adjust Al sites,as characterized by pyridine-adsorbed infrared spectroscopy.Experimental evidence confirms that Al Brønsted acid sites improves the selective oxidation of cyclohexanone,while concurrently enhancing CL hydrolysis.
基金Supported by National Natural Science Foundation of China,No.81972947Academic Promotion Programme of Shandong First Medical University,No.2019LJ005.
文摘BACKGROUND The risk factors and prediction models for diabetic foot(DF)remain incompletely understood,with several potential factors still requiring in-depth investigations.AIM To identify risk factors for new-onset DF and develop a robust prediction model for hospitalized patients with type 2 diabetes.METHODS We included 6301 hospitalized patients with type 2 diabetes from January 2016 to December 2021.A univariate Cox model and least absolute shrinkage and selection operator analyses were applied to select the appropriate predictors.Nonlinear associations between continuous variables and the risk of DF were explored using restricted cubic spline functions.The Cox model was further employed to evaluate the impact of risk factors on DF.The area under the curve(AUC)was measured to evaluate the accuracy of the prediction model.RESULTS Seventy-five diabetic inpatients experienced DF.The incidence density of DF was 4.5/1000 person-years.A long duration of diabetes,lower extremity arterial disease,lower serum albumin,fasting plasma glucose(FPG),and diabetic nephropathy were independently associated with DF.Among these risk factors,the serum albumin concentration was inversely associated with DF,with a hazard ratio(HR)and 95%confidence interval(CI)of 0.91(0.88-0.95)(P<0.001).Additionally,a U-shaped nonlinear relationship was observed between the FPG level and DF.After adjusting for other variables,the HRs and 95%CI for FPG<4.4 mmol/L and≥7.0 mmol/L were 3.99(1.55-10.25)(P=0.004)and 3.12(1.66-5.87)(P<0.001),respectively,which was greater than the mid-range level(4.4-6.9 mmol/L).The AUC for predicting DF over 3 years was 0.797.CONCLUSION FPG demonstrated a U-shaped relationship with DF.Serum albumin levels were negatively associated with DF.The prediction nomogram model of DF showed good discrimination ability using diabetes duration,lower extremity arterial disease,serum albumin,FPG,and diabetic nephropathy(Clinicaltrial.gov NCT05519163).
基金supported by Health Commission of Sichuan Province Medical Science and Technology Program(Grant No:24WSXT041).
文摘Objective:To systematically review the safety of different types of chikungunya vaccines in human populations.Methods:This study retrieved randomized controlled trials(RCTs)reporting on the safety of chikungunya vaccines in human populations through electronic searches of the Web of Science,PubMed,EMbase,and Cochrane Library databases.Two reviewers independently performed literature screening,data extraction,and risk of bias assessment for the included studies.Meta-analysis was conducted using STATA 18.0 software.Results:A total of eight RCTs involving 9336 subjects were included in this study.Meta-analysis showed that three out of the five chikungunya vaccines(VLA1553,mRNA-1388,and PXVX0317)exhibited favorable safety profiles,with no significant increase in the incidence of serious adverse events.The vaccine group had a higher incidence of any adverse events[risk ratio(RR)=1.26,P<0.001]and any systemic adverse events(RR=1.18,P=0.010)compared to the placebo group.The incidence of local adverse events was also higher in the vaccine group(RR=2.09,P<0.001).However,there were no significant differences between the two groups in the incidences of erythema(RR=1.41,P=0.402),headache(RR=1.14,P=0.457),or arthralgia(RR=1.45,P=0.660).Conclusions:Current evidence supports that chikungunya vaccines have a favorable safety profile.However,due to limitations in the number and quality of included studies,further high-quality research is needed to validate these conclusions.
文摘Designing Fischer-Tropsch synthesis(FTS)catalysts to selectively produce liquid hydrocarbon fuels is a crucial challenge.Herein,we selectively introduced Co nanoparticles(NPs)into the micropores and mesopores of an ordered mesoporous MFI zeolite(OMMZ)through impregnation,which controlled the carbon number distribution in the FTS products by tuning the position of catalytic active sites in differently sized pores.The Co precursors coordinated by acetate with a size of 9.4×4.2×2.5Åand by 2,2'-bipyridine with a size of 9.5×8.7×7.9Å,smaller and larger than the micropores(ca.5.5Å)of MFI,made the Co species incorporated in OMMZ's micropores and mesopores,respectively.The carbon number products synthesized with the Co NPs confined in mesopores were larger than that in micropores.The high jet and diesel selectivities of 66.5%and 65.3%were achieved with Co NPs confined in micropores and mesopores of less acidic Na-type OMMZ,respectively.Gasoline and jet selectivities of 76.7%and 70.8%were achieved with Co NPs confined in micropores and mesopores of H-type OMMZ with Brönsted acid sites,respectively.A series of characterizations revealed that the selective production of diesel and jet fuels was due to the C-C cleavage suppressing of heavier hydrocarbons by the Co NPs located in mesopores.
文摘Applied field magnetoplasmadynamic thrusters(AF-MPDTs), with their high specific impulse and considerable thrust, are increasingly favored for large-scale space missions. This paper presents the composition, functionality, and testing methods of a high-power electric propulsion performance testing system, along with the vacuum ignition test results of a 100 kW superconducting MPD thruster. The relationships between thruster efficiency, magnetic field strength, current,and mass flow rate are analyzed. For each combination of current and flow rate in an AF-MPDT, there is an optimal magnetic field strength where the thruster efficiency reaches its peak. Under conditions of 320 A current and 60 mg/s flow rate,the optimal magnetic field strength is 0.5 T, yielding the highest thruster efficiency of 71%.
基金Supported by 2025 Horizontal Fund Project of Institute of Agricultural Products Processing and Nuclear Agricultural Technology,Hubei Academy of Agricultural Sciences(20120250022).
文摘[Objectives]This study was condcuted to investigate the formula optimization and nutritional components of Brassica vegetable juice beverage.[Methods]Brassica was selected as the raw material to optimize the formula of the vegetable juice beverage.The vitamin C content and flavor components were analyzed in both sterilized and non-sterilized samples.[Results]Based on water,the optimal formula for the Brassica vegetable juice beverage was determined as:20%Brassica juice,5%erythritol,and 0.1%citric acid.The highest vitamin C content was observed in unsterilized samples(12.167 mg/100 g sample),followed by samples sterilized at 71℃for 15 s(9.864 mg/100 g sample).The most significant loss of vitamin C occurred under sterilization conditions of 68℃for 30 min.GC-MS analysis detected a total of seven volatile components in the Brassica vegetable juice beverage,including siloxanes,alcohols,aldehydes,and methoxyphenyl oxime.Before sterilization,siloxane compounds(D3,D4,D5)showed the highest content in the Brassica vegetable juice,accounting for 63.606%,followed by methoxyphenyl oxime at 24.802%.After sterilization,siloxane compounds(D3,D4,D5)exhibited the highest content reaching 81.963%,while methoxyphenyl oxime taking the second place decreased to 14.276%.[Conclusions]This study provides new insights and methodologies for the development and utilization of Brassica crops and other agricultural products,offering a theoretical foundation for accelerating the integrated development of Brassica processing and sales.
文摘The magnetoplasmadynamic thruster(MPDT) is characterized by its high specific impulse and substantial thrust density, making it a promising propulsion system for deep space exploration missions. In both laboratory experiments and practical applications, cathode ablation has emerged as a critical concern. An optical diagnostic approach based on monochromatic radiation temperature measurement, utilizing plume emission spectra and the selection of an appropriate test band, has been successfully employed. This method provides an accurate temperature distribution across the cathode surface, offering a novel testing technique for the optimization and evaluation of magnetic plasma thruster designs.
基金supported in part by National Natural Science Foundation of China(62401612)in part by Beijing Nova Program of China(20230484258).
文摘The integration of emerging technologies such as artificial intelligence and cloud computing is accelerating the development of intelligent and autonomous satellite systems.However,limitations in onboard sensing,computing,storage,and energy resources continue to constrain the intelligent functionalities of individual satellites.Currently,most studies focus on either satellite intelligence or satellite networking,while systematic studies on their integration remain scarce.To address this gap,this paper introduces the concept of an intelligent satellite cluster system,which leverages satellite networks to enable collaborative intelligence among satellites,thereby enhancing the overall system intelligence.After summarizing the typical use cases of the intelligent satellite cluster system,we analyze the corresponding demands on network capabilities.Based on these demands,we propose the concept of the Internet of satellites(IoS)tailored to support the intelligent satellite cluster system.Specifically,we design both the logical and physical architectures of IoS and elaborate on its key enabling technologies.Finally,we present the research progress and outcomes achieved by our team on these core technologies,and discuss the challenges that remain.This paper aims to build consensus around intelligent and connected satellite technologies,promote innovation and standardization,and enhance the intelligent service capabilities of future large-scale satellite systems.
