In general,acid aggregates are not used in combination with asphalt concrete because of their poor compatibility with the asphalt binder,which typically results in a scarce water stability of the concrete.In the prese...In general,acid aggregates are not used in combination with asphalt concrete because of their poor compatibility with the asphalt binder,which typically results in a scarce water stability of the concrete.In the present study,the feasibility of a new approach based on the combination of acid granite fine aggregate with alkaline limestone coarse aggregate and Portland cement filler has been assessed.The mineral and chemical compositions of these three materials have first been analyzed and compared.Then,the effect of different amounts of Portland cement(0%,25%,50%,75%and 100%of the total filler by weight)on the mechanical performance and water stability of the asphalt concrete has been considered.Asphalt concrete has been designed by using the Marshall method,and the mechanical performance indexes of this material,including the Marshall stability and indirect tensile strength(ITS),have been measured together with the related water stability indexes(namely the Marshall stability(RMS)and tensile strength ratio(TSR)).The results indicate that the alkaline limestone coarse aggregate and Portland cement filler can balance the drawback caused by the acid granite fine aggregate.The asphalt concrete has good mechanical performances and water stability when the amount of common limestone powder filler replaced by cement is not less than 75%.展开更多
The purpose of this study was to establish a high-performance liquid chromatography (HPLC) method for the simultaneous determination of sodium danshensu, protocatechuic aldehyde, rosmarinic acid, salvianolic acid B, a...The purpose of this study was to establish a high-performance liquid chromatography (HPLC) method for the simultaneous determination of sodium danshensu, protocatechuic aldehyde, rosmarinic acid, salvianolic acid B, and 4-coumaric acid in Danhong injection. The chromatographic method employed was as follows: the column was a Welch Ultimate XB-C18 column (250 mm × 4.6 mm, 10 μm), the mobile phase was a gradient elution of 0.4% formic acid aqueous solution (A) and acetonitrile (B), the detection wavelengths were 280 nm for sodium danshensu, protocatechuic aldehyde, and salvianolic acid B and 326 nm for 4-coumaric acid and rosmarinic acid, the sample volume was 10 μL, the flow rate was 1.0 mL/min, and the column temperature was 35°C. This method can realize the separation and determination of sodium danshensu, protocatechuic aldehyde, rosmarinic acid, salvianolic acid B, and 4-coumaric acid within 50 minutes. The linear relationships of the five peak areas and their concentrations are good (R<sup>2</sup>> 0.9997). The precision RSD values are all less than 1.0%. The reproducibility RSD values are all less than 1.3%. The stability RSD values are all less than 2.2%. The recovery values ranged from 92.4% to 99.4%. This method is simple, accurate, and reproducible. It can be used for the determination of sodium danshensu, protocatechuic aldehyde, rosmarinic acid, salvianolic acid B, and 4-coumaric acid in Danhong injection.展开更多
In China and East Asia,the long-term continuous observational data at daily resolution are insufficient,and thus there is a lack of good understanding of the extreme climate variation over the last 100 years plus.In t...In China and East Asia,the long-term continuous observational data at daily resolution are insufficient,and thus there is a lack of good understanding of the extreme climate variation over the last 100 years plus.In this study,the extreme temperature indices defined by ETCCDI(Expert Team on Climate Change Detection and Indices)and local meteorological administrations were analyzed for Changchun City,Northeast China,by using the daily maximum temperature(Tmax)and daily minimum temperature(Tmin)over 1909?2018.The results showed that extreme cold events,such as cold days,cold nights,frost days,icing days,and low temperature days,decreased significantly at rates of?0.41 d(10 yr)^?1,?1.45 d(10 yr)^?1,?2.28 d(10 yr)^?1,?1.16 d(10 yr)?1 and?1.90 d(10 yr)^?1,respectively.Warm nights increased significantly at a rate of 1.71 d(10 yr)^?1,but warm days decreased slightly and the number of high temperature days decreased at a rate of?0.20 d(10 yr)?1.The frequency of cold surge events increased significantly at a rate of 0.25 d(10 yr)^?1,occurring mainly from the mid-1950s to late-1980s.The average Tmax,average Tmin and extreme Tmin increased at rates of 0.09℃(10 yr)^?1,0.36℃(10 yr)^?1 and 0.54℃(10 yr)^?1,respectively;and extreme Tmax decreased significantly at a rate of?0.17℃(10 yr)^?1.In 1909?2018,1951?2018 and 1979?2018,the indices related to cold events decreased,while the trends of the indices related to warm events were different for different periods.展开更多
The conventional p-n heterojunction photocatalysts suffer from the incompatibility between the interfacial charge transfer efficiency and the redox ability of charge carriers.To optimize the interfacial charge transfe...The conventional p-n heterojunction photocatalysts suffer from the incompatibility between the interfacial charge transfer efficiency and the redox ability of charge carriers.To optimize the interfacial charge transfer of the conventional BiOI/TiO_(2) p-n photocatalyst,we synthesized the BiOI/Bi/TiO_(2) ternary photocatalyst with sandwiched metallic bismuth(Bi~0)by the oxygen-vacancy assisted method.The DFT calculation and structural characterizations confirmed the reaction of the electron-rich oxygen vacancies in the 2D-TiO_(2) nanosheets(TiO_(2)-NS)with the adsorbed BiO~+species.This reaction broke the Bi-O bonds to form Bi^(0) nanoparticles in-situ at the interface but still maintained the p-n heterojunction well.The NO-TPD and XRD analyses for samples correlated the Bi~0 formation with the oxygen vacancy concentrations well.The sandwiched Bi~0 functioned as an electronic transfer mediator like that in the Z-scheme heterostructure.Comparing with 0.20 BiOI/TiO_(2)-NP(NP,Nanoparticles),0.20 BiOI/Bi/TiO_(2)-NS-a(NS,Nanosheet)showed a much improved catalytic performance,i.e.,duplicated apparent quantum yield(AQY)and triplicated reaction rate constant(k).Also,the formation mechanism and the reaction mechanism were investigated in detail.This work provides a new strategy for the improving of the conventional p-n photocatalysts and new insights into the nature of the photocatalysis.展开更多
The manufacturing of spiral groove structure of two-dimensional valve(2D valve)feedback mechanism has shortcomings of both high cost and time-consuming.This paper presents a novel configuration of rotary electro-mecha...The manufacturing of spiral groove structure of two-dimensional valve(2D valve)feedback mechanism has shortcomings of both high cost and time-consuming.This paper presents a novel configuration of rotary electro-mechanical converter with negative feedback mechanism(REMC-NFM)in order to replace the feedback mechanism of spiral groove and thus reduce cost of valve manufacturing.In order to rapidly and quantitative evaluate the driving and feedback performance of the REMC-NFM,an analytical model taking leakage flux,edge effect and permeability nonlinearity into account is formulated based on the equivalent magnetic circuit approach.Then the model is properly simplified in order to obtain the optimal pitch angle.FEM simulation is used to study the influence of crucial parameters on the performance of REMC-NFM.A prototype of REMC-NFM is designed and machined,and an exclusive experimental platform is built.The torque-angle characteristics,torque-displacement characteristics,and magnetic flux density in the working air gap with different excitation currents are measured.The experimental results are in good agreement with the analytical and FEM simulated results,which verifies the correctness of the analytical model.For torque-angle characteristics,the overall torque increases with both current and rotation angle,which reaches about 0.48 N·m with 1.5 A and 1.5°.While for torque-displacement characteristics,the overall torque increases with current yet decrease with armature displacement due to the negative feedback mechanism,which is about 0.16 N·m with 1.5 A and 0.8 mm.Besides,experimental results of conventional torque motor are compared with counterparts of REMC-NFM in order to validate the simplified model.The research indicates that the REMC-NFM can be potentially used as the electro-mechanical converter for 2D valves in civil servo areas.展开更多
CCCH is a subfamily of zinc finger proteins involved in plant growth,development,and stresses response.The function of CCCH in regulating leaf senescence,especially its roles in abscisic acid(ABA)-mediated leaf senesc...CCCH is a subfamily of zinc finger proteins involved in plant growth,development,and stresses response.The function of CCCH in regulating leaf senescence,especially its roles in abscisic acid(ABA)-mediated leaf senescence is largely unknown.The objective of this study was to determine functions and mechanisms of CCCH gene in regulating leaf senescence in switchgrass(Panicum virgatum).A CCCH gene,PvCCCH69(PvC3H69),was cloned from switchgrass.Overexpressing PvC3H69 in rice suppressed both natural senescence with leaf aging and dark-induced leaf senescence.Endogenous ABA content,ABA biosynthesis genes(NCED3,NCED5,and AAO3),and ABA signaling-related genes(SnRKs,ABI5,and ABF2/3/4)exhibited significantly lower levels in senescencing leaves of PvC3H69-OE plants than those in WT plants.PvC3H69-suppression of leaf senescence was associated with transcriptional upregulation of genes mainly involved in the light-dependent process of photosynthesis,including light-harvesting complex proteins,PSI proteins,and PSII proteins and downregulation of ABA biosynthesis and signaling genes and senescence-associated genes.PvC3H69 could act as a repressor for leaf senescence via upregulating photosynthetic proteins and repressing ABA synthesis and ABA signaling pathways.展开更多
With the increasing requirements of electro-hydrostatic actuators(EHAs)for power,volume,and pressure,there is a growing tendency in the industry to combine the motor and pump to form a so-called'motor pump'to ...With the increasing requirements of electro-hydrostatic actuators(EHAs)for power,volume,and pressure,there is a growing tendency in the industry to combine the motor and pump to form a so-called'motor pump'to improve the integration.In this paper,a novel structure for a wet three-phase high-speed reluctance motor pump is proposed,which can further improve integration by removing the dynamic seal on the pump shaft,thereby avoiding the problems of dynamic seal wear and oil leakage and improving heat dissipation under high-speed working conditions.However,after the motor is wetted,the churning loss caused by immersion of the rotor in the oil causes additional fluid resistance torque.Based on fundamental fluid mechanics,an analytical model of the churning torque of a wet motor was established.To verify the accuracy of the analytical model,a simulation model of churning loss was established based on computational fluid dynamics(CFD),and the churning torque and flow field state were analyzed.Finally,an experimental prototype was designed and manufactured,and a test bench for churning loss was built.The oil churning torque was measured at different speeds and temperatures.The results from the analytical,simulation,and experimental models agreed well.The experimental results validated the analytical model and CFD simulation.This research provides a practical method for calculating the churning loss and serves as guidance for future optimization of churning loss reduction.展开更多
This study presents a novel roller piston pump,in which a cam guide-roller type rolling support is adopted to replace the sliding pair support of the swash plate-slipper pair to achieve the oil suction and discharge o...This study presents a novel roller piston pump,in which a cam guide-roller type rolling support is adopted to replace the sliding pair support of the swash plate-slipper pair to achieve the oil suction and discharge of the piston cavity.In addition,the shaft distribution is used to replace the original valve plate distribution and the driving shaft is used as the distribution shaft to remove the valve plate structure,which greatly simplifies the design of the axial piston pump.Such a configuration largely reduces the number of sliding friction pairs of the pump,and avoids the influence of the sliding friction pair on it under high-speed and variable-speed conditions.Firstly,mathematical models of the mechanical and volumetric efficiencies of the roller pump are deduced respectively through force analysis and the compressibility equation.Based on the numerical simulation of MATLAB and AMESim,the effects of load pressure and rotational speed on mechanical and volumetric efficiencies are studied respectively,and it is verified that the roller pump has no structural flow pulsation.The prototype pump is then designed and built,along with a special test rig.The outlet pressure,outlet flow,and torque of the pump under different load pressures and rotational speeds are measured,and the mechanical and volumetric efficiencies of the prototype pump under various load pressures and rotational speeds are obtained.The experimental results are in good agreement with the simulated analysis.When the load pressure is 8 MPa and the speed is 5000 r/min,the mechanical and the volumetric efficiencies are 85.5% and 96.8%,respectively.When the speed is increased to 10000 r/min,the mechanical and the volumetric efficiencies are 66.7% and 95.6%,respectively.The experimental results show that the proposed roller piston pump has excellent efficiency under wide-speed and high-speed conditions and can be a potential solution as a fuel pump in aerospace fuel systems.展开更多
Photosynthesis[6CO_(2)+12H_(2)O→(CH_(2)O)+6O_(2)+6H_(2)O]in nature contains a light reaction process for oxygen evolution and a dark reaction process for carbon dioxide(CO_(2))reduction to carbohydrates,which is of g...Photosynthesis[6CO_(2)+12H_(2)O→(CH_(2)O)+6O_(2)+6H_(2)O]in nature contains a light reaction process for oxygen evolution and a dark reaction process for carbon dioxide(CO_(2))reduction to carbohydrates,which is of great significance for the survival of living matter.Therefore,for simulating photosynthesis,it is desirable to design and fabricate a bifunctional catalyst for promoting photocatalytic water oxidation and CO_(2)reduction performances.Herein,a molecular confined synthesis strategy is reasonably proposed and applied,that is the bifunctional CoO_(x)/Co/C-T(T=700,800 and 900℃)photocatalysts prepared by the pyrolysis of molecular Co-EDTA under N_(2) and air atmosphere in turn.Among the prepared photocatalysts,the CoOx/Co/C-800 shows the best photocatalytic water oxidation activity with an oxygen yield of 51.2%.In addition,for CO_(2)reduction reaction,the CO evolution rate of 12.6μmol/h and selectivity of 75%can be achieved over this catalyst.The improved photocatalytic activities are attributed to the rapid electron transfer between the photosensitizer and the catalyst,which is strongly supported by the current densityvoltage G-V,steady-state and time-resolved photoluminescence spectra(PL).Overall,this work provides a reference for the preparation and optimization of photocatalysts with the capacity for water oxidation and CO_(2)reduction reactions.展开更多
An effective strategy was proposed to control the formation of the interfacial bonding between Ru and molybdenum oxide support to stabilize the Ru atoms with the aim to enhance the hydrogen evolution reaction(HER)acti...An effective strategy was proposed to control the formation of the interfacial bonding between Ru and molybdenum oxide support to stabilize the Ru atoms with the aim to enhance the hydrogen evolution reaction(HER)activity of the resultant catalysts in alkaline medium.The different interfacial chemical bonds,including Ru–O,Ru–O–Mo,and mixed Ru–Mo/Ru–O–Mo,were prepared using an induced activation strategy by controlling the composition of reducing agents in the calcination process.And the regulation mechanism of the interfacial chemical bonds in molybdenum oxide supported Ru catalysts for optimizing HER activity was investigated by density functional theory(DFT)and experimental studies.We found that a controlled interfacial chemical Ru–O–Mo bonding in Ru-MoO_(2)/C manifests a 12-fold activity increase in catalyzing the hydrogen evolution reaction relative to the conventional metal/metal oxide catalyst(Ru-O-MoO_(2)/C).In a bifunctional effect,the interfacial chemical Ru-O-Mo sites promoted the dissociation of water and the production of hydrogen intermediates that were then adsorbed on the nearby Ru surfaces and recombined into molecular hydrogen.As compared,the nearby Ru surfaces in Ru–Mo bonding have weak adsorption capacity for the generation of these hydrogen intermediates,resulting in a 5-fold increase HER activity for Ru-Mo-MoO_(2)/C catalyst compared with Ru-O-MoO_(2)/C.展开更多
Background Since the beginning of the coronavirus disease 2019(COVID-19)pandemic,prone positioning has been widely applied for non-intubated,spontaneously breathing patients.However,the efficacy and safety of prone po...Background Since the beginning of the coronavirus disease 2019(COVID-19)pandemic,prone positioning has been widely applied for non-intubated,spontaneously breathing patients.However,the efficacy and safety of prone positioning in non-intubated patients with COVID-19-related acute hypoxemic respiratory failure remain unclear.We aimed to systematically analyze the outcomes associated with awake prone positioning(APP).Methods We conducted a systematic literature search of PubMed/MEDLINE,Cochrane Library,Embase,and Web of Science from January 1,2020,to June 3,2022.This study included adult patients with acute respiratory failure caused by COVID-19.The Preferred Reporting Items for Systematic Reviews and Meta-Analyses(PRISMA)guidelines were followed,and the study quality was assessed using the Cochrane risk-of-bias tool.The primary outcome was the reported cumulative intubation risk across randomized controlled trials(RCTs),and the effect estimates were calculated as risk ratios(RRs;95%confidence interval[CI]).Results A total of 495 studies were identified,of which 10 fulfilled the selection criteria,and 2294 patients were included.In comparison to supine positioning,APP significantly reduced the need for intubation in the overall population(RR=0.84,95%CI:0.74–0.95).The two groups showed no significant differences in the incidence of adverse events(RR=1.16,95%CI:0.48–2.76).The meta-analysis revealed no difference in mortality between the groups(RR=0.93,95%CI:0.77–1.11).Conclusions APP was safe and reduced the need for intubation in patients with respiratory failure associated with COVID-19.However,it did not significantly reduce mortality in comparison to usual care without prone positioning.展开更多
Genomic imprinting can lead to allele-specific expression(ASE),where one allele is preferentially expressed more than the other.Perturbations in genomic imprinting or ASE genes have been widely observed across various...Genomic imprinting can lead to allele-specific expression(ASE),where one allele is preferentially expressed more than the other.Perturbations in genomic imprinting or ASE genes have been widely observed across various neurological disorders,notably autism spectrum disorder(ASD).In this study,we crossed rhesus cynomolgus monkeys to produce hybrid monkeys and established a framework to evaluate their allele-specific gene expression patterns using the parental genomes as a reference.Our proof-of-concept analysis of the hybrid monkeys identified 353 genes with allele-biased expression in the brain,enabling us to determine the chromosomal locations of ASE clusters.Importantly,we confirmed a significant enrichment of ASE genes associated with neuropsychiatric disorders,including ASD,highlighting the potential of hybrid monkey models in advancing our understanding of genomic imprinting.展开更多
Microenvironments of the catalytic center,which play a vital role in adjusting electrocatalytic CO_(2) reduction reaction(ECO_(2) RR)activity,have received increasing attention during the past few years.However,contro...Microenvironments of the catalytic center,which play a vital role in adjusting electrocatalytic CO_(2) reduction reaction(ECO_(2) RR)activity,have received increasing attention during the past few years.However,controllable microenvironment construction and the effects of multi-microenvironment variations for improving ECO_(2) RR performance remain unclear.Herein,we summarize the representative strategies for tuning the catalyst and local microenvironments to enhance ECO_(2) RR selectivity and activity.The multifactor synergetic effects of microen-vironment regulation for enhancing CO_(2) accessibility,stabilizing key intermediates,and improving the performance of ECO_(2) RR catalysts are discussed in detail,as well as perspectives on the challenges when investigating ECO_(2) RR microenvironments.We anticipate that the discussions in this review will inspire further research in microenvironment engineering to accelerate the development of the ECO 2 RR for practical application.展开更多
Mg基制氢材料具有来源广泛、反应温和、工艺简单、安全可控、理论产氢量高等优势,是当今的研究热点.本文提出采用高能球磨方法制备Mg-Bi系含氧酸盐Bi_(x)M_(y)O_(z)(M=Ti,V,Cr,Mo,W)复合材料以改善Mg水解制氢性能.本工作研究发现,掺杂Bi...Mg基制氢材料具有来源广泛、反应温和、工艺简单、安全可控、理论产氢量高等优势,是当今的研究热点.本文提出采用高能球磨方法制备Mg-Bi系含氧酸盐Bi_(x)M_(y)O_(z)(M=Ti,V,Cr,Mo,W)复合材料以改善Mg水解制氢性能.本工作研究发现,掺杂Bi_(2)Mo O_(6)的Mg基复合制氢材料具有较好的性能,Mg-7 wt%Bi_(2)Mo O_(6)在298.15 K的最大产氢速率为756.1 m L g^(-1)min(-1).通过引入多壁碳纳米管(CNTs)可以进一步改善Mg-Bi_(2)Mo O_(6)的产氢性能,Mg-7 wt%Bi_(2)Mo O_(6)/CNTs的最大产氢速率达2172.4 m L g^(-1)min(-1),产氢活化能下降至23.6 k J mol^(-1).X光电子能谱(XPS)分析表明Bi_(2)Mo O_(6)/CNTs与Mg在球磨过程中发生固相反应生成Bi单质.密度泛函理论(DFT)计算揭示Bi原子掺杂可改变Mg的局域电荷分布,增强Mg对H_(2)O的吸附能,并降低H_(2)O解离后H原子的吸附能,促进水解反应进行.展开更多
The combined effect from sulfate and chloride is one of the important reasons to cause the damage of lining concrete in highway tunnels. To investigate the effect of chloride ions on the corrosion of lining concretes ...The combined effect from sulfate and chloride is one of the important reasons to cause the damage of lining concrete in highway tunnels. To investigate the effect of chloride ions on the corrosion of lining concretes under sulfate attack, ultrasonic detecting, compression test and X-ray Diffraction （XRD） were performed on the concretes to obtain the ultrasonic velocity, corrosion thickness, compression strength and corrosion products. The ultrasonic results, compression strength and XRD patterns confirmed that the existence of chloride certainly depressed the corrosion damage on the lining concretes under sulfate attack, and the depressing effect increased with the content of chloride in the composite solution. The corrosion damage on the concretes experienced three stages independent of the composition of corrosive solution： initial slower enhancement on the strength, stabilization period and linear degradation period. The existence of chloride mainly affected the final degradation stage and obviously decreased the corrosion thickness.展开更多
Two new 3 D metal-organic frameworks（MOFs） named [Pr2（PDA）3-3 H2 O]-H2 O（1） and[Nd2（PDA）3-3 H2 O] H2 O（2） [2,6-Pyridinedicarboxylic acid（H2 PDA）] were synthesized by solvothermal method. They were characte...Two new 3 D metal-organic frameworks（MOFs） named [Pr2（PDA）3-3 H2 O]-H2 O（1） and[Nd2（PDA）3-3 H2 O] H2 O（2） [2,6-Pyridinedicarboxylic acid（H2 PDA）] were synthesized by solvothermal method. They were characterized by elemental analyses（EA）, infrared spectroscopy（FT-IR）, thermogravimetric analysis（TG）, photocatalysis performance and single crystal X-ray diffraction studies（XRD）.The XRD analysis indicated that MOFs（1） and（2） both belong to the monoclinic system with space group P2（1）/C. The structural model were drawn by the diamond software, and the structure revel that MOFs（1） and（2） adopt three-dimensional（3 D） frameworks constructed by cross-linking of one-dimensional（1 D） infinite chain secondary building unit（SBU） by 2,6-Pyridinedicarboxylic acid and hydrogen bond as linker. These frameworks feature channels inside which coordinated H20 solvent molecules are located. Thermogravimetric analysis showed that both MOFs are thermally stable, the photocatalytic evaluation showed the materials have a good prospect in degration methylene blue. As for complex1, the decomposition efficiency of Methylene blue was about 91.08% after 130 min and the complex 2 reach 90.45% after 160 min under the sun light.展开更多
基金supported by the Science and Technology Planning Project of Zhejiang Provincial Department of Transportation(2021012)Zhejiang Provincial Natural Science Foundation of China under Grant(No.LGG21E080002).
文摘In general,acid aggregates are not used in combination with asphalt concrete because of their poor compatibility with the asphalt binder,which typically results in a scarce water stability of the concrete.In the present study,the feasibility of a new approach based on the combination of acid granite fine aggregate with alkaline limestone coarse aggregate and Portland cement filler has been assessed.The mineral and chemical compositions of these three materials have first been analyzed and compared.Then,the effect of different amounts of Portland cement(0%,25%,50%,75%and 100%of the total filler by weight)on the mechanical performance and water stability of the asphalt concrete has been considered.Asphalt concrete has been designed by using the Marshall method,and the mechanical performance indexes of this material,including the Marshall stability and indirect tensile strength(ITS),have been measured together with the related water stability indexes(namely the Marshall stability(RMS)and tensile strength ratio(TSR)).The results indicate that the alkaline limestone coarse aggregate and Portland cement filler can balance the drawback caused by the acid granite fine aggregate.The asphalt concrete has good mechanical performances and water stability when the amount of common limestone powder filler replaced by cement is not less than 75%.
文摘The purpose of this study was to establish a high-performance liquid chromatography (HPLC) method for the simultaneous determination of sodium danshensu, protocatechuic aldehyde, rosmarinic acid, salvianolic acid B, and 4-coumaric acid in Danhong injection. The chromatographic method employed was as follows: the column was a Welch Ultimate XB-C18 column (250 mm × 4.6 mm, 10 μm), the mobile phase was a gradient elution of 0.4% formic acid aqueous solution (A) and acetonitrile (B), the detection wavelengths were 280 nm for sodium danshensu, protocatechuic aldehyde, and salvianolic acid B and 326 nm for 4-coumaric acid and rosmarinic acid, the sample volume was 10 μL, the flow rate was 1.0 mL/min, and the column temperature was 35°C. This method can realize the separation and determination of sodium danshensu, protocatechuic aldehyde, rosmarinic acid, salvianolic acid B, and 4-coumaric acid within 50 minutes. The linear relationships of the five peak areas and their concentrations are good (R<sup>2</sup>> 0.9997). The precision RSD values are all less than 1.0%. The reproducibility RSD values are all less than 1.3%. The stability RSD values are all less than 2.2%. The recovery values ranged from 92.4% to 99.4%. This method is simple, accurate, and reproducible. It can be used for the determination of sodium danshensu, protocatechuic aldehyde, rosmarinic acid, salvianolic acid B, and 4-coumaric acid in Danhong injection.
基金the National Key R&D Program of China(Grant No.2018YFA0605603).
文摘In China and East Asia,the long-term continuous observational data at daily resolution are insufficient,and thus there is a lack of good understanding of the extreme climate variation over the last 100 years plus.In this study,the extreme temperature indices defined by ETCCDI(Expert Team on Climate Change Detection and Indices)and local meteorological administrations were analyzed for Changchun City,Northeast China,by using the daily maximum temperature(Tmax)and daily minimum temperature(Tmin)over 1909?2018.The results showed that extreme cold events,such as cold days,cold nights,frost days,icing days,and low temperature days,decreased significantly at rates of?0.41 d(10 yr)^?1,?1.45 d(10 yr)^?1,?2.28 d(10 yr)^?1,?1.16 d(10 yr)?1 and?1.90 d(10 yr)^?1,respectively.Warm nights increased significantly at a rate of 1.71 d(10 yr)^?1,but warm days decreased slightly and the number of high temperature days decreased at a rate of?0.20 d(10 yr)?1.The frequency of cold surge events increased significantly at a rate of 0.25 d(10 yr)^?1,occurring mainly from the mid-1950s to late-1980s.The average Tmax,average Tmin and extreme Tmin increased at rates of 0.09℃(10 yr)^?1,0.36℃(10 yr)^?1 and 0.54℃(10 yr)^?1,respectively;and extreme Tmax decreased significantly at a rate of?0.17℃(10 yr)^?1.In 1909?2018,1951?2018 and 1979?2018,the indices related to cold events decreased,while the trends of the indices related to warm events were different for different periods.
基金financially supported by the National Natural Science Foundation of China(No.21043006 and 51702205)the Education Department of Guangdong Province(No.2018KTSCX063 and 2013KJCX0081)+2 种基金the Science and Technology Planning Project of Guangdong Province(No.2014A020216045)the 2020 Li Ka Shing Foundation Cross-Disciplinary Research Grant(2020LKSFG09A)the Guangdong Key Discipline Fund at GTIIT。
文摘The conventional p-n heterojunction photocatalysts suffer from the incompatibility between the interfacial charge transfer efficiency and the redox ability of charge carriers.To optimize the interfacial charge transfer of the conventional BiOI/TiO_(2) p-n photocatalyst,we synthesized the BiOI/Bi/TiO_(2) ternary photocatalyst with sandwiched metallic bismuth(Bi~0)by the oxygen-vacancy assisted method.The DFT calculation and structural characterizations confirmed the reaction of the electron-rich oxygen vacancies in the 2D-TiO_(2) nanosheets(TiO_(2)-NS)with the adsorbed BiO~+species.This reaction broke the Bi-O bonds to form Bi^(0) nanoparticles in-situ at the interface but still maintained the p-n heterojunction well.The NO-TPD and XRD analyses for samples correlated the Bi~0 formation with the oxygen vacancy concentrations well.The sandwiched Bi~0 functioned as an electronic transfer mediator like that in the Z-scheme heterostructure.Comparing with 0.20 BiOI/TiO_(2)-NP(NP,Nanoparticles),0.20 BiOI/Bi/TiO_(2)-NS-a(NS,Nanosheet)showed a much improved catalytic performance,i.e.,duplicated apparent quantum yield(AQY)and triplicated reaction rate constant(k).Also,the formation mechanism and the reaction mechanism were investigated in detail.This work provides a new strategy for the improving of the conventional p-n photocatalysts and new insights into the nature of the photocatalysis.
基金National Natural Science Foundation of China(Grant Nos.51975524,51405443)National Key Research and Development Program of China(Grant No.2019YFB2005200).
文摘The manufacturing of spiral groove structure of two-dimensional valve(2D valve)feedback mechanism has shortcomings of both high cost and time-consuming.This paper presents a novel configuration of rotary electro-mechanical converter with negative feedback mechanism(REMC-NFM)in order to replace the feedback mechanism of spiral groove and thus reduce cost of valve manufacturing.In order to rapidly and quantitative evaluate the driving and feedback performance of the REMC-NFM,an analytical model taking leakage flux,edge effect and permeability nonlinearity into account is formulated based on the equivalent magnetic circuit approach.Then the model is properly simplified in order to obtain the optimal pitch angle.FEM simulation is used to study the influence of crucial parameters on the performance of REMC-NFM.A prototype of REMC-NFM is designed and machined,and an exclusive experimental platform is built.The torque-angle characteristics,torque-displacement characteristics,and magnetic flux density in the working air gap with different excitation currents are measured.The experimental results are in good agreement with the analytical and FEM simulated results,which verifies the correctness of the analytical model.For torque-angle characteristics,the overall torque increases with both current and rotation angle,which reaches about 0.48 N·m with 1.5 A and 1.5°.While for torque-displacement characteristics,the overall torque increases with current yet decrease with armature displacement due to the negative feedback mechanism,which is about 0.16 N·m with 1.5 A and 0.8 mm.Besides,experimental results of conventional torque motor are compared with counterparts of REMC-NFM in order to validate the simplified model.The research indicates that the REMC-NFM can be potentially used as the electro-mechanical converter for 2D valves in civil servo areas.
文摘CCCH is a subfamily of zinc finger proteins involved in plant growth,development,and stresses response.The function of CCCH in regulating leaf senescence,especially its roles in abscisic acid(ABA)-mediated leaf senescence is largely unknown.The objective of this study was to determine functions and mechanisms of CCCH gene in regulating leaf senescence in switchgrass(Panicum virgatum).A CCCH gene,PvCCCH69(PvC3H69),was cloned from switchgrass.Overexpressing PvC3H69 in rice suppressed both natural senescence with leaf aging and dark-induced leaf senescence.Endogenous ABA content,ABA biosynthesis genes(NCED3,NCED5,and AAO3),and ABA signaling-related genes(SnRKs,ABI5,and ABF2/3/4)exhibited significantly lower levels in senescencing leaves of PvC3H69-OE plants than those in WT plants.PvC3H69-suppression of leaf senescence was associated with transcriptional upregulation of genes mainly involved in the light-dependent process of photosynthesis,including light-harvesting complex proteins,PSI proteins,and PSII proteins and downregulation of ABA biosynthesis and signaling genes and senescence-associated genes.PvC3H69 could act as a repressor for leaf senescence via upregulating photosynthetic proteins and repressing ABA synthesis and ABA signaling pathways.
基金This work is supported by the National Key R&D Program of China(No.2019YFB2005202).
文摘With the increasing requirements of electro-hydrostatic actuators(EHAs)for power,volume,and pressure,there is a growing tendency in the industry to combine the motor and pump to form a so-called'motor pump'to improve the integration.In this paper,a novel structure for a wet three-phase high-speed reluctance motor pump is proposed,which can further improve integration by removing the dynamic seal on the pump shaft,thereby avoiding the problems of dynamic seal wear and oil leakage and improving heat dissipation under high-speed working conditions.However,after the motor is wetted,the churning loss caused by immersion of the rotor in the oil causes additional fluid resistance torque.Based on fundamental fluid mechanics,an analytical model of the churning torque of a wet motor was established.To verify the accuracy of the analytical model,a simulation model of churning loss was established based on computational fluid dynamics(CFD),and the churning torque and flow field state were analyzed.Finally,an experimental prototype was designed and manufactured,and a test bench for churning loss was built.The oil churning torque was measured at different speeds and temperatures.The results from the analytical,simulation,and experimental models agreed well.The experimental results validated the analytical model and CFD simulation.This research provides a practical method for calculating the churning loss and serves as guidance for future optimization of churning loss reduction.
基金supported by the National Key Research and Development Program of China(No.2019YFB2005202).
文摘This study presents a novel roller piston pump,in which a cam guide-roller type rolling support is adopted to replace the sliding pair support of the swash plate-slipper pair to achieve the oil suction and discharge of the piston cavity.In addition,the shaft distribution is used to replace the original valve plate distribution and the driving shaft is used as the distribution shaft to remove the valve plate structure,which greatly simplifies the design of the axial piston pump.Such a configuration largely reduces the number of sliding friction pairs of the pump,and avoids the influence of the sliding friction pair on it under high-speed and variable-speed conditions.Firstly,mathematical models of the mechanical and volumetric efficiencies of the roller pump are deduced respectively through force analysis and the compressibility equation.Based on the numerical simulation of MATLAB and AMESim,the effects of load pressure and rotational speed on mechanical and volumetric efficiencies are studied respectively,and it is verified that the roller pump has no structural flow pulsation.The prototype pump is then designed and built,along with a special test rig.The outlet pressure,outlet flow,and torque of the pump under different load pressures and rotational speeds are measured,and the mechanical and volumetric efficiencies of the prototype pump under various load pressures and rotational speeds are obtained.The experimental results are in good agreement with the simulated analysis.When the load pressure is 8 MPa and the speed is 5000 r/min,the mechanical and the volumetric efficiencies are 85.5% and 96.8%,respectively.When the speed is increased to 10000 r/min,the mechanical and the volumetric efficiencies are 66.7% and 95.6%,respectively.The experimental results show that the proposed roller piston pump has excellent efficiency under wide-speed and high-speed conditions and can be a potential solution as a fuel pump in aerospace fuel systems.
基金financially supported by the National Natural Science Foundation of China(No.22075119)the Natural Science Foundation of Gansu Province(No.21JR7RA440).
文摘Photosynthesis[6CO_(2)+12H_(2)O→(CH_(2)O)+6O_(2)+6H_(2)O]in nature contains a light reaction process for oxygen evolution and a dark reaction process for carbon dioxide(CO_(2))reduction to carbohydrates,which is of great significance for the survival of living matter.Therefore,for simulating photosynthesis,it is desirable to design and fabricate a bifunctional catalyst for promoting photocatalytic water oxidation and CO_(2)reduction performances.Herein,a molecular confined synthesis strategy is reasonably proposed and applied,that is the bifunctional CoO_(x)/Co/C-T(T=700,800 and 900℃)photocatalysts prepared by the pyrolysis of molecular Co-EDTA under N_(2) and air atmosphere in turn.Among the prepared photocatalysts,the CoOx/Co/C-800 shows the best photocatalytic water oxidation activity with an oxygen yield of 51.2%.In addition,for CO_(2)reduction reaction,the CO evolution rate of 12.6μmol/h and selectivity of 75%can be achieved over this catalyst.The improved photocatalytic activities are attributed to the rapid electron transfer between the photosensitizer and the catalyst,which is strongly supported by the current densityvoltage G-V,steady-state and time-resolved photoluminescence spectra(PL).Overall,this work provides a reference for the preparation and optimization of photocatalysts with the capacity for water oxidation and CO_(2)reduction reactions.
基金supports by the National Natural Science Foundation of China(No.21978126).
文摘An effective strategy was proposed to control the formation of the interfacial bonding between Ru and molybdenum oxide support to stabilize the Ru atoms with the aim to enhance the hydrogen evolution reaction(HER)activity of the resultant catalysts in alkaline medium.The different interfacial chemical bonds,including Ru–O,Ru–O–Mo,and mixed Ru–Mo/Ru–O–Mo,were prepared using an induced activation strategy by controlling the composition of reducing agents in the calcination process.And the regulation mechanism of the interfacial chemical bonds in molybdenum oxide supported Ru catalysts for optimizing HER activity was investigated by density functional theory(DFT)and experimental studies.We found that a controlled interfacial chemical Ru–O–Mo bonding in Ru-MoO_(2)/C manifests a 12-fold activity increase in catalyzing the hydrogen evolution reaction relative to the conventional metal/metal oxide catalyst(Ru-O-MoO_(2)/C).In a bifunctional effect,the interfacial chemical Ru-O-Mo sites promoted the dissociation of water and the production of hydrogen intermediates that were then adsorbed on the nearby Ru surfaces and recombined into molecular hydrogen.As compared,the nearby Ru surfaces in Ru–Mo bonding have weak adsorption capacity for the generation of these hydrogen intermediates,resulting in a 5-fold increase HER activity for Ru-Mo-MoO_(2)/C catalyst compared with Ru-O-MoO_(2)/C.
基金supported by the Clinical Research Plan of SHDC (grant number:SHDC2020CR2013A)the Clinical Research Plan of SHDC (grant number:SHDC2020CR5010-003).
文摘Background Since the beginning of the coronavirus disease 2019(COVID-19)pandemic,prone positioning has been widely applied for non-intubated,spontaneously breathing patients.However,the efficacy and safety of prone positioning in non-intubated patients with COVID-19-related acute hypoxemic respiratory failure remain unclear.We aimed to systematically analyze the outcomes associated with awake prone positioning(APP).Methods We conducted a systematic literature search of PubMed/MEDLINE,Cochrane Library,Embase,and Web of Science from January 1,2020,to June 3,2022.This study included adult patients with acute respiratory failure caused by COVID-19.The Preferred Reporting Items for Systematic Reviews and Meta-Analyses(PRISMA)guidelines were followed,and the study quality was assessed using the Cochrane risk-of-bias tool.The primary outcome was the reported cumulative intubation risk across randomized controlled trials(RCTs),and the effect estimates were calculated as risk ratios(RRs;95%confidence interval[CI]).Results A total of 495 studies were identified,of which 10 fulfilled the selection criteria,and 2294 patients were included.In comparison to supine positioning,APP significantly reduced the need for intubation in the overall population(RR=0.84,95%CI:0.74–0.95).The two groups showed no significant differences in the incidence of adverse events(RR=1.16,95%CI:0.48–2.76).The meta-analysis revealed no difference in mortality between the groups(RR=0.93,95%CI:0.77–1.11).Conclusions APP was safe and reduced the need for intubation in patients with respiratory failure associated with COVID-19.However,it did not significantly reduce mortality in comparison to usual care without prone positioning.
基金supported by the National Key Research and Development Program of China(2022YFF0710901 to Q.S.)the National Natural Science Foundation of China(grants 31825018 and 82021001 toQ.S.+5 种基金81827901 and 32170567 toG.W.)the ShanghaiMunicipal Science and Technology Major Project(2018SHZDZX05 to Q.S.and Z.Liu)the Biological Resources Program of the Chinese Academy of Sciences(KFJ-BRP-005)the Strategic Priority Research Programof the Chinese Academy of Sciences(XDB32060000 to Q.S.and Z.Liu)the Basic Frontier Scientific Research Program of the Chinese Academy of Sciences From 0 to 1 original innovation project(ZDBS-LY-SM019 to Z.Liu)the China National Postdoctoral Program for Innovative Talents(BX20200350 to Z.Lu).
文摘Genomic imprinting can lead to allele-specific expression(ASE),where one allele is preferentially expressed more than the other.Perturbations in genomic imprinting or ASE genes have been widely observed across various neurological disorders,notably autism spectrum disorder(ASD).In this study,we crossed rhesus cynomolgus monkeys to produce hybrid monkeys and established a framework to evaluate their allele-specific gene expression patterns using the parental genomes as a reference.Our proof-of-concept analysis of the hybrid monkeys identified 353 genes with allele-biased expression in the brain,enabling us to determine the chromosomal locations of ASE clusters.Importantly,we confirmed a significant enrichment of ASE genes associated with neuropsychiatric disorders,including ASD,highlighting the potential of hybrid monkey models in advancing our understanding of genomic imprinting.
基金This research was supported by the Special Fund Project of Jiangsu Province for Scientific and Technological Innovation in Carbon Peaking and Carbon Neutrality(BK20220023)National Natural Science Foun-dation of China(21902009)Startup Funding at Jiangnan University.
文摘Microenvironments of the catalytic center,which play a vital role in adjusting electrocatalytic CO_(2) reduction reaction(ECO_(2) RR)activity,have received increasing attention during the past few years.However,controllable microenvironment construction and the effects of multi-microenvironment variations for improving ECO_(2) RR performance remain unclear.Herein,we summarize the representative strategies for tuning the catalyst and local microenvironments to enhance ECO_(2) RR selectivity and activity.The multifactor synergetic effects of microen-vironment regulation for enhancing CO_(2) accessibility,stabilizing key intermediates,and improving the performance of ECO_(2) RR catalysts are discussed in detail,as well as perspectives on the challenges when investigating ECO_(2) RR microenvironments.We anticipate that the discussions in this review will inspire further research in microenvironment engineering to accelerate the development of the ECO 2 RR for practical application.
文摘Mg基制氢材料具有来源广泛、反应温和、工艺简单、安全可控、理论产氢量高等优势,是当今的研究热点.本文提出采用高能球磨方法制备Mg-Bi系含氧酸盐Bi_(x)M_(y)O_(z)(M=Ti,V,Cr,Mo,W)复合材料以改善Mg水解制氢性能.本工作研究发现,掺杂Bi_(2)Mo O_(6)的Mg基复合制氢材料具有较好的性能,Mg-7 wt%Bi_(2)Mo O_(6)在298.15 K的最大产氢速率为756.1 m L g^(-1)min(-1).通过引入多壁碳纳米管(CNTs)可以进一步改善Mg-Bi_(2)Mo O_(6)的产氢性能,Mg-7 wt%Bi_(2)Mo O_(6)/CNTs的最大产氢速率达2172.4 m L g^(-1)min(-1),产氢活化能下降至23.6 k J mol^(-1).X光电子能谱(XPS)分析表明Bi_(2)Mo O_(6)/CNTs与Mg在球磨过程中发生固相反应生成Bi单质.密度泛函理论(DFT)计算揭示Bi原子掺杂可改变Mg的局域电荷分布,增强Mg对H_(2)O的吸附能,并降低H_(2)O解离后H原子的吸附能,促进水解反应进行.
文摘The combined effect from sulfate and chloride is one of the important reasons to cause the damage of lining concrete in highway tunnels. To investigate the effect of chloride ions on the corrosion of lining concretes under sulfate attack, ultrasonic detecting, compression test and X-ray Diffraction （XRD） were performed on the concretes to obtain the ultrasonic velocity, corrosion thickness, compression strength and corrosion products. The ultrasonic results, compression strength and XRD patterns confirmed that the existence of chloride certainly depressed the corrosion damage on the lining concretes under sulfate attack, and the depressing effect increased with the content of chloride in the composite solution. The corrosion damage on the concretes experienced three stages independent of the composition of corrosive solution： initial slower enhancement on the strength, stabilization period and linear degradation period. The existence of chloride mainly affected the final degradation stage and obviously decreased the corrosion thickness.
基金financial supports from the NSFC (51361005, U1501242, 51371060 and 51671062)Guangxi Natural Science Foundation (2014GXNSFAA118319, 2014GXNAFDA118005)+1 种基金Guangxi Key Laboratory of Information Materials (161002-Z, 161002-K)Guangxi Scientific Technology Team (2012GXNSFGA06002)
文摘Two new 3 D metal-organic frameworks（MOFs） named [Pr2（PDA）3-3 H2 O]-H2 O（1） and[Nd2（PDA）3-3 H2 O] H2 O（2） [2,6-Pyridinedicarboxylic acid（H2 PDA）] were synthesized by solvothermal method. They were characterized by elemental analyses（EA）, infrared spectroscopy（FT-IR）, thermogravimetric analysis（TG）, photocatalysis performance and single crystal X-ray diffraction studies（XRD）.The XRD analysis indicated that MOFs（1） and（2） both belong to the monoclinic system with space group P2（1）/C. The structural model were drawn by the diamond software, and the structure revel that MOFs（1） and（2） adopt three-dimensional（3 D） frameworks constructed by cross-linking of one-dimensional（1 D） infinite chain secondary building unit（SBU） by 2,6-Pyridinedicarboxylic acid and hydrogen bond as linker. These frameworks feature channels inside which coordinated H20 solvent molecules are located. Thermogravimetric analysis showed that both MOFs are thermally stable, the photocatalytic evaluation showed the materials have a good prospect in degration methylene blue. As for complex1, the decomposition efficiency of Methylene blue was about 91.08% after 130 min and the complex 2 reach 90.45% after 160 min under the sun light.
