Fuel cells operated with a reformate fuel such as methanol are promising power systems for portable electronic devices due to their high safety,high energy density and low pollutant emissions.However,several critical ...Fuel cells operated with a reformate fuel such as methanol are promising power systems for portable electronic devices due to their high safety,high energy density and low pollutant emissions.However,several critical issues including methanol crossover effect,CO-tolerance electrode and efficient oxygen reduction electrocatalyst with low or non-platinum usage have to be addressed before the direct methanol fuel cells(DMFCs)become commercially available for industrial application.Here,we report a highly active and selective Mg-Co dualsite oxygen reduction reaction(ORR)single atom catalyst(SAC)with porous N-doped carbon as the substrate.The catalyst exhibits a commercial Pt/C-comparable half-wave potential of 0.806 V(versus the reversible hydrogen electrode)in acid media with good stability.Furthermore,practical DMFCs test achieves a peak power density of over 200 m W cm^(-2)that far exceeds that of commercial Pt/C counterpart(82 m W cm^(-2)).Particularly,the Mg-Co DMFC system runs over 10 h with negligible current loss under 10 M concentration methanol work condition.Experimental results and theoretical calculations reveal that the N atom coordinated by Mg and Co atom exhibits an unconventional d-band-ditto localized p-band and can promote the dissociation of the key intermediate*OOH into*O and*OH,which accounts for the near unity selective 4e-ORR reaction pathway and enhanced ORR activity.In contrast,the N atom in SAC–Co remains inert in the absorption and desorption of*OOH and*OH.This local coordination environment regulation strategy around active sites may promote rational design of high-performance and durable fuel cell cathode electrocatalysts.展开更多
Water pollution of the Yangtze River in China became one of challenges that the government is facing today. Increasing numbers of petrochemical plants were built along the river in past decades, and numbers of organic...Water pollution of the Yangtze River in China became one of challenges that the government is facing today. Increasing numbers of petrochemical plants were built along the river in past decades, and numbers of organic chemicals were discharged into the river. Our goal was to establish in vitro system on rat sertoli cells, spermatogenic cells and leydig cells to investigate the reproductive toxicity potential induced by organic extracts from petrochemical effluents. Our results showed that the organic extract depressed the viability （p 〈 0.01） and destroyed the plasma membrane integrity of sertoli cells and spermatogenic cells to a certain degree. Accordingly, proportion of early apoptotic sertoli cells and late apoptotic spermatogenic cells increased significantly. Although significant morphological changes were not detected for leydig cells, the extract was observed to inhibit their testosterone production （p 〈 0.01）. Sertoli cells and sperrnatogenic cells appeared to be more sensitive and maybe the main targets of the key toxins. These results suggested that the in vitro system on rat testicular cells may be useful to predicate reproductive toxicity potential of organic extracts from petrochemical effluents. More attention should be paid to the petrochemical effluents, because long-term accumulation of these organic compounds in organisms may cause spermatogenesis malfunction and testosterone reduction.展开更多
Photocatalytic conversion of CO_(2) to high-value products plays a crucial role in the global pursuit of carbon–neutral economy.Junction photocatalysts,such as the isotype heterojunctions,offer an ideal paradigm to n...Photocatalytic conversion of CO_(2) to high-value products plays a crucial role in the global pursuit of carbon–neutral economy.Junction photocatalysts,such as the isotype heterojunctions,offer an ideal paradigm to navigate the photocatalytic CO_(2) reduction reaction(CRR).Herein,we elucidate the behaviors of isotype heterojunctions toward photocatalytic CRR over a representative photocatalyst,g-C_(3)N_(4).Impressively,the isotype heterojunctions possess a significantly higher efficiency for the spatial separation and transfer of photogenerated carriers than the single components.Along with the intrinsically outstanding stability,the isotype heterojunctions exhibit an exceptional and stable activity toward the CO_(2) photoreduction to CO.More importantly,by combining quantitative in situ technique with the first-principles modeling,we elucidate that the enhanced photoinduced charge dynamics promotes the production of key intermediates and thus the whole reaction kinetics.展开更多
In collaboration with 12 other institutions, the Meteorological Observation Center of the China Meteorological Administration undertook a comprehensive marine observation experiment in the South China Sea using the Yi...In collaboration with 12 other institutions, the Meteorological Observation Center of the China Meteorological Administration undertook a comprehensive marine observation experiment in the South China Sea using the Yilong-10 high-altitude large unmanned aerial vehicle(UAV). The Yilong-10 UAV carried a self-developed dropsonde system and a millimeter-wave cloud radar system. In addition, a solar-powered unmanned surface vessel and two drifting buoys were used. The experiment was further supported by an intelligent, reciprocating horizontal drifting radiosonde system that was deployed from the Sansha Meteorological Observing Station, with the intent of producing a stereoscopic observation over the South China Sea. Comprehensive three-dimensional observations were collected using the system from 31 July to2 August, 2020. This information was used to investigate the formation and development processes of Typhoon Sinlaku(2020). The data contain measurements of 21 oceanic and meteorological parameters acquired by the five devices, along with video footage from the UAV. The data proved very helpful in determining the actual location and intensity of Typhoon Sinlaku(2020). The experiment demonstrates the feasibility of using a high-altitude, large UAV to fill in the gaps between operational meteorological observations of marine areas and typhoons near China, and marks a milestone for the use of such data for analyzing the structure and impact of a typhoon in the South China Sea. It also demonstrates the potential for establishing operational UAV meteorological observing systems in the future, and the assimilation of such data into numerical weather prediction models.展开更多
This paper is concerned with the robust stabilization problem of networked control systems with stochastic packet dropouts and uncertain parameters. Considering the stochastic packet dropout occuring in two channels b...This paper is concerned with the robust stabilization problem of networked control systems with stochastic packet dropouts and uncertain parameters. Considering the stochastic packet dropout occuring in two channels between the sensor and the controller, and between the controller and the actuator, networked control systems are modeled as the Markovian jump linear system with four operation modes. Based on this model, the necessary and sufficient conditions for the mean square stability of the deterministic networked control systems and uncertain networked control systems are given by using the theory of the Markovian jump linear system, and corresponding controller design procedures are proposed via the cone complementarity linearization method. Finally, the numerical example and simulations are given to illustrate the effectiveness of the proposed results.展开更多
The problem of robust H∞ guaranteed cost satisfactory fault-tolerant control with quadratic D stabilizability against actuator failures is investigated for a class of discrete-time systems with value-bounded uncertai...The problem of robust H∞ guaranteed cost satisfactory fault-tolerant control with quadratic D stabilizability against actuator failures is investigated for a class of discrete-time systems with value-bounded uncertainties existing in both the state and control input matrices.Based on a more practical and general model of actuator continuous gain failures,taking the transient property,robust behaviour on H∞ performance and quadratic cost performance requirements into consideration,sufficient conditions for the existence of satisfactory fault-tolerant controller are given and the effective design steps with constraints of multiple performance indices are provided.Meanwhile,the consistency of the regional pole index,H∞ norm-bound constraint and cost performance indices is set up for fault-tolerant control.A simulation example shows the effectiveness of the proposed method.展开更多
A total of 80 patients with refractory epilepsy were recruited from the Inner Mongolia Medical College Affiliated Hospital. The loci of 60% of the patients could be positioned using a combined positron emission tomogr...A total of 80 patients with refractory epilepsy were recruited from the Inner Mongolia Medical College Affiliated Hospital. The loci of 60% of the patients could be positioned using a combined positron emission tomography/CT imaging modality. Hyper- and hypometabolism foci were examined as part of this study. Patients who had abnormal metabolism in positron emission tomography/CT imaging were divided into intermittent-phase group and the seizure-phase group. The intermittent-phase group was further divided into a single-focus group and a multiple-foci group according to the number of seizure foci detected by imaging. Following gamma knife treatment, seizure frequency was significantly lower in the intermittent-phase group and the seizure-phase group. Wieser＇s classification reached Grade I or II in nearly 40% of patients. Seizure frequency was significantly lower following treatment, but Wieser＇s classification score was significantly higher in the seizure-phase group compared with the intermittent-phase group. Seizure frequency was significantly lower following treatment in the single-focus group, but Wieser＇s classification score was significantly higher in the single-focus group as compared with the multiple-foci group.展开更多
Previous studies have suggested that the transforming growth factor-β receptor ALK5 is crucial for articular chondrogenesis by bone marrow mesenchymal stem cells. Here, the wild-type ALK5 plasmids were mutated by ove...Previous studies have suggested that the transforming growth factor-β receptor ALK5 is crucial for articular chondrogenesis by bone marrow mesenchymal stem cells. Here, the wild-type ALK5 plasmids were mutated by overlapping extended PCR and transfected into bone marrow mesenchymal stem cells. The knee joint osteoarthritis mouse model was constructed by cutting oft＂ the anterior cruciate ligament and divided into three groups： saline group, bone marrow mesenchymal stem cells and ALK5-transfected bone marrow mesenchymal stem cells group. HE staining showed that the articular cartilage lesions were more serious of saline group compared with that of mesenchymal stem cell group, and this trend was more pronounced as time goes on. Immunohistochemical staining showed that although the expression level of type II collagen in all three groups down-regulated gradually upon time, its expression in ALK5-transfected bone marrow mesenchymal stem cells group was significantly enhanced compared with the other two groups. Micro-CT also suggested that ALK5 transfection of mouse bone marrow mesenchymal stem cells would promote repairing the knee cartilage lesions with arthritis of the mice. Although the osteoarthritis mechanism underlying a variety of factors work together, and the appropriate proportion of ALKS/ALK1 was also emphasized for the treatment of osteoarthritis. This work therefore demonstrated that ALK5 transfection of bone marrow mesenchymal stem cells could be a promising stem cell therapy for repair of cartilage lesions.展开更多
In this work, the homomorphism of the classic linear block code in linear network coding for the case of binary field and its extensions is studied. It is proved that the classic linear error-control block code is hom...In this work, the homomorphism of the classic linear block code in linear network coding for the case of binary field and its extensions is studied. It is proved that the classic linear error-control block code is homomorphic network error-control code in network coding. That is, if the source packets at the source node for a linear network coding are precoded using a linear block code, then every packet flowing in the network regarding to the source satisfies the same constraints as the source. As a consequence, error detection and correction can be performed at every intermediate nodes of multicast flow, rather than only at the destination node in the conventional way, which can help to identify and correct errors timely at the error-corrupted link and save the cost of forwarding error-corrupted data to the destination node when the intermediate nodes are ignorant of the errors. In addition, three examples are demonstrated which show that homomorphic linear code can be combined with homomorphic signature, McEliece public-key cryptosystem and unequal error protection respectively and thus have a great potential of practical utility.展开更多
Pulse excitation or vibration stimulation was imposed on the low permeable formation with cracks to enhance the production or injection capacity.During that process,a coupling of wave-induced flow and initial flow in ...Pulse excitation or vibration stimulation was imposed on the low permeable formation with cracks to enhance the production or injection capacity.During that process,a coupling of wave-induced flow and initial flow in dual-porous media was involved.Researchers had done much work on the rule of wave propagation in fractured porous media,whereas attentions on the variation law of flow in developing low permeable formation with cracks under vibration stimulation were not paid.In this study,the effect of low-frequency vibration on the seepage in dual-porous media was examined for the application of wave stimulation technology in developing reservoirs with natural cracks.A model for seepage of single-phase liquid in porous media with cracks under low-frequency vibration excitation was built by combining wave propagating theory for porous media with cracks and dual-porous media seepage mechanics.A governing equation group for the model,which was expressed by dimensionless fluid and solid displacements,was derived and solved with a numerical method.Variable physical properties were simulated to check the applicability of external low-frequency vibration load on dual-porous media and a parametric study for various vibration parameters.Stimulation of low-frequency vibration affected flow velocities of crack and rock matrix fluids.Compared with that in single-porous media,the stimulation effect on the fluid inner matrix of dual-porous media was relatively weakened.Different optimal vibration parameters were needed to increase the channeling flow between the crack and rock matrix or to only promote the flow velocity in the rock matrix.The theoretical study examines wave-coupled seepage field in fractured porous media with results that are applicable for low-frequency stimulation technology.展开更多
Objective:To explore the inhibitory effect of curcumin on colon cancer in vitro.Methods:Human colon cancer cell lines HT29 and SW620 were cultured in vitro,which were divided into test group and control group.Cells in...Objective:To explore the inhibitory effect of curcumin on colon cancer in vitro.Methods:Human colon cancer cell lines HT29 and SW620 were cultured in vitro,which were divided into test group and control group.Cells in the test groups were treated with curcumin at different concentrations,while the control groups were treated with dimethylsulfoxide(DMSO).Subsequently,methyl thiazolyl tetrazolium(MTT)assay,were carried out to estimate cellular proliferative activity.Flow cytometry using annexin-V/propidium iodide(PI)staining was performed to detect cell apoptosis.Formation of autophagosomes in the cytoplasm in colon cancer cells were detected by TEM(transmission electron microscopy analysis),and Western blot to measure the expressions of proteins related to apoptosis and autophagy.Results:MTT assay showed that curcumin inhibited the proliferative activity of both HT29 and SW620 cells,significantly different from the control group(P<0.001).The halfmaximal inhibitory concentration(IC50)of curcumin at 24 hours was 20μM for both HT29 and SW620 cells.Annexin-V FITC/PI double labeling showed that,After treatment with curcumin of 20μM for 24 hours,a significant increase was observed in apoptosis rate in both HT219 cells((10.00±0.60)%vs.(4.00±0.70)%,P<0.01;(10.50±0.40)%vs.(4.30±0.26)%,P<0.01)compared with the control cells.TEM analysis showed that curcumin increased the accumulation of autophagosomes in the cytoplasm in HT29 and SW620 cells.Western blot showed an increase in the expressions of apoptosis-related proteins including cleaved caspase-3 and cleaved poly ADP-ribose polymerase(PARP)but decrease of P62 protein in both HT29 and SW620 cells after 24-hour treatment with 20μM curcumin for 24 hours compared with the control groups.Conclusion:Curcumin can inhibit the proliferation,induce apoptosis and autophagy in human colon cancer cells.展开更多
Reducing the ever-growing level of CO_(2)in the atmosphere is critical for the sustainable development of human society in the context of global warming.Integration of the capture and upgrading of CO_(2)is,therefore,h...Reducing the ever-growing level of CO_(2)in the atmosphere is critical for the sustainable development of human society in the context of global warming.Integration of the capture and upgrading of CO_(2)is,therefore,highly desirable since each process step is costly,both energetically and economically.Here,we report a CO_(2)direct air capture(DAC)and fixation process that produces methane.Low concentrations of CO_(2)(∼400 ppm)in the air are captured by an aqueous solution of sodium hydroxide to form carbonate.The carbonate is subsequently hydrogenated to methane,which is easily separated from the reaction system,catalyzed by TiO2-supported Ru in the aqueous phase with a selectivity of 99.9%among gas-phase products.The concurrent regenerated hydroxide,in turn,increases the alkalinity of the aqueous solution for further CO_(2)capture,thereby enabling this one-ofits-kind continuous CO_(2)capture and methanation process.Engineering simulations demonstrate the energy feasibility of this CO_(2)DAC and methanation process,highlighting its promise for potential largescale applications.展开更多
One of the chief works for inspecting spot weld quality by X-ray to obtain an ideal and uniform digital image. This paper introduces three methods of image background simulation algorithm, and' the effect of backg...One of the chief works for inspecting spot weld quality by X-ray to obtain an ideal and uniform digital image. This paper introduces three methods of image background simulation algorithm, and' the effect of background correction was compared. It may be safely said that Kalman filter method is simple and fast for general image; the FFT method has a good adaptability for background simulation.展开更多
This paper reports a synergistic design of high-performance BCC high-entropy alloy based on the combined consideration of the principles of intrinsic ductility of elements,maximum atomic size difference for solid solu...This paper reports a synergistic design of high-performance BCC high-entropy alloy based on the combined consideration of the principles of intrinsic ductility of elements,maximum atomic size difference for solid solution strengthening and the valence electron concentration criterion for ductility.The single-phase BCC HfNbTaTiV alloy thus designed exhibited a high compressive yield strength of 1350 MPa and a high compressive ductility of>45%at the room temperature.This represents a 50%increase in yield strength relative to a HfNbTaTiZr alloy.This is attributed to the maximized solid solution strengthening effect caused by lattice distortion,which is estimated to be 1094 MPa.The alloy was also able to retain 53%of its yield strength and 77%of its ductility at 700℃.These properties are superior to those of most refractory BCC high-entropy alloys reported in the literature.展开更多
This study explored a multi-mechanism approach to improving the mechanical properties of a Co CrFe Mn Ni high-entropy alloy through non-equiatomic alloy design and processing.The alloy design ensures a single-phase fa...This study explored a multi-mechanism approach to improving the mechanical properties of a Co CrFe Mn Ni high-entropy alloy through non-equiatomic alloy design and processing.The alloy design ensures a single-phase face-centered cubic structure while lowering the stacking fault energy to encourage the formation of deformation twins and stacking faults by altering the equiatomic composition of the alloy.The processing strategy applied helped create a hierarchical grain size gradient microstructure with a high nanotwins population.This was achieved by means of rotationally accelerated shot peening(RASP).The non-equiatomic Co Cr Fe Mn Ni high-entropy alloy achieved a yield strength of 750 MPa,a tensile strength of 1050 MPa,and tensile uniform elongation of 27.5%.The toughness of the alloy was 2.53×10^(10)k J/m^(3),which is about 2 times that of the same alloy without the RASP treatment.The strength increase is attributed to the effects of grain boundary strengthening,dislocation strengthening,twin strengthening,and hetero-deformation strengthening associated with the heterogeneous microstructure of the alloy.The concurrent occurrence of the multiple deformation mechanisms,i.e.,dislocation deformation,twining deformation and microband deformation,contributes to achieving a suitable strain hardening of the alloy that helps to prevent early necking and to assure steady plastic deformation for high toughness.展开更多
Enhanced oxidation resistance is a primary demand for the application of refractory high-entropy alloys(RHEAs)at elevated temperatures.In this study,Al was added to a Ti_(2)VZrNb RHEA to partially substitute Nb to imp...Enhanced oxidation resistance is a primary demand for the application of refractory high-entropy alloys(RHEAs)at elevated temperatures.In this study,Al was added to a Ti_(2)VZrNb RHEA to partially substitute Nb to improve its oxidation resistance and mechanical properties.The alloy was found to have an increased oxidation resistance by forming a continuous Al_(2)O_(3)+ZrO_(2)oxide protective surface.At the same time,the room-temperature yield strength was also increased by 66%to 1273 MPa via solid solution strengthening.The low atomic mass of Al also helped to reduce the density of the alloy by 8.2%to 5.44 g cm^(−3).This resulted in a high specific yield strength of 234 MPa cm3 g^(−1) for the alloy.Meanwhile,the Ti_(2)VZrNb_(0.5)-Al_(0.5)alloy also exhibited a high compressive plasticity of>50%.These values are among the best reported so far for RHEAs.展开更多
Degradation of a metallic film under harsh thermal-mechanical-electrical coupling field conditions determines its service temperature and lifetime.In this work,the self-heating degradation behaviors of Pt thin films a...Degradation of a metallic film under harsh thermal-mechanical-electrical coupling field conditions determines its service temperature and lifetime.In this work,the self-heating degradation behaviors of Pt thin films above 1000℃were studied in situ by TEM at the nanoscale.The Pt films degraded mainly through void nucleation and growth on the Pt-SiN_(x)interface.Voids preferentially formed at the grain boundary and triple junction intersections with the interface.At temperatures above 1040℃,the voids nucleated at both the grain boundaries and inside the Pt grains.A stress simulation of the suspended membrane suggests the existence of local tensile stress in the Pt film,which promotes the nucleation of voids at the Pt-Si Nxinterface.The grain-boundary-dominated mass transportation renders the voids grow preferentially at GBs and triple junctions in a Pt film.Additionally,under the influence of an applied current,the voids that nucleated inside Pt grains grew to a large size and accelerated the degradation of the Pt film.展开更多
Harvesting the promising high energy density of advanced electrode materials in lithium-ion batteries is critically dependent on a mechanistic understanding on how the materials function and degrade along with the bat...Harvesting the promising high energy density of advanced electrode materials in lithium-ion batteries is critically dependent on a mechanistic understanding on how the materials function and degrade along with the battery cycling.Here,we tracked phase transformations during(de)lithiation of Sb_(2)Se_(3) single crystals using in situ high-resolution transmission electron microscopy(HRTEM)technique,and revealed electro-chemo-mechanical evolution at the reaction interface.The effect of this electro-chemo-mechanical coupling has a complicated interplay on the lithiation kinetics and causes various types of defects at the reaction front,including dislocation dipoles,antiphase boundaries,and cracks.In return,the formed cracks and related defects build a path for fast diffusion of lithium ions and trigger a highly anisotropic lithiation at the twisted reaction front,giving rise to the formation of presumably "dead" Sb_(2)Se_(3) nanodomains in amorphous Li_(x)Sb_(2)Se_(3).The detailed mechanistic understanding may facilitate the rational design of high-capacity electrode materials for battery applications.展开更多
Detwinning is an important plastic deformation mechanism that can significantly affect the mechanical properties of twin-structured metals.Although many detwinning mechanisms have been proposed for pure metals,it is u...Detwinning is an important plastic deformation mechanism that can significantly affect the mechanical properties of twin-structured metals.Although many detwinning mechanisms have been proposed for pure metals,it is unclear whether such a deformation model is valid for nanocrystalline alloys because of the lack of direct evidence.Here,the atomicscale detwinning deformation process of a nanocrystalline AuAg alloy with an average grain size of~15 nm was investigated in situ.The results show that there are three types of detwinning mechanisms in nanocrystalline AuAg alloys.The first type of detwinning results from grain boundary migration.The second type of detwinning occurs through combined layer-by-layer thinning and incoherent twin boundary migration.The last one occurs through incoherent twin boundary migration,which results from the collective motion of partial dislocations in an array.展开更多
The extremely high structural tolerance of ceria to oxygen vacancies(Ov)has made it a desirable catalytic material for the hydrocarbon oxidation to chemicals and pharmaceuticals and the reduction of gaseous pollutants...The extremely high structural tolerance of ceria to oxygen vacancies(Ov)has made it a desirable catalytic material for the hydrocarbon oxidation to chemicals and pharmaceuticals and the reduction of gaseous pollutants.It is proposed that the formation and diffusion of Ov originate from its outstanding reduction property.However,the formation and diffusion process of Ov over the surface of ceria at the atomic level is still unknown.Herein,the structural and valence evolution of CeO_(2)(111)surfaces in reductive,oxidative and vacuum environments from room temperature up to 700℃was studied with in situ aberration-corrected environmental transmission electron microscopy(ETEM)experiments.Ov is found to form under a high vacuum at elevated temperatures;however,the surface can recover to the initial state through the adsorption of oxygen atoms in an oxygen-contained environment.Furthermore,in hydrogen environment,the step-CeO_(2)(111)surface is not stable at elevated temperatures;thus,the steps tend to be eliminated with increasing temperature.Combined with first-principles density function calculations(DFT),it is proposed that O-terminated surfaces would develop in a hypoxic environment due to the dynamic diffusion of Ov from the outer surface to the subsurface.Furthermore,in a reductive environment,H2 facilitates the formation and diffusion of Ov while Ce-terminated surfaces develope.These results reveal dynamic atomic-scale interplay between the nanoceria surface and gas,thereby providing fundamental insights into the Ov-dependent reaction of nano-CeO_(2) during catalytic processes.展开更多
基金the funding support from the National Natural Science Fund for Distinguished Young Scholars(52125103)the National Natural Science Foundation of China(52071041,12074048 and 12147102)+2 种基金Chongqing Natural Science Foundation(cstc2020jcyj-msxm X0777 and cstc2020jcyj-msxm X0796)Science Foundation of Donghai Laboratory(DH-2022KF0307)the Fundamental Research Funds for the Central Universities(106112016CDJZR308808)。
文摘Fuel cells operated with a reformate fuel such as methanol are promising power systems for portable electronic devices due to their high safety,high energy density and low pollutant emissions.However,several critical issues including methanol crossover effect,CO-tolerance electrode and efficient oxygen reduction electrocatalyst with low or non-platinum usage have to be addressed before the direct methanol fuel cells(DMFCs)become commercially available for industrial application.Here,we report a highly active and selective Mg-Co dualsite oxygen reduction reaction(ORR)single atom catalyst(SAC)with porous N-doped carbon as the substrate.The catalyst exhibits a commercial Pt/C-comparable half-wave potential of 0.806 V(versus the reversible hydrogen electrode)in acid media with good stability.Furthermore,practical DMFCs test achieves a peak power density of over 200 m W cm^(-2)that far exceeds that of commercial Pt/C counterpart(82 m W cm^(-2)).Particularly,the Mg-Co DMFC system runs over 10 h with negligible current loss under 10 M concentration methanol work condition.Experimental results and theoretical calculations reveal that the N atom coordinated by Mg and Co atom exhibits an unconventional d-band-ditto localized p-band and can promote the dissociation of the key intermediate*OOH into*O and*OH,which accounts for the near unity selective 4e-ORR reaction pathway and enhanced ORR activity.In contrast,the N atom in SAC–Co remains inert in the absorption and desorption of*OOH and*OH.This local coordination environment regulation strategy around active sites may promote rational design of high-performance and durable fuel cell cathode electrocatalysts.
基金supported by the Major State Basic Research Development Program (No.2008CB418102)the Environmental Monitoring Research Foundation of Jiangsu Province (No.0710)+1 种基金the Innovation Foundation for Youth Scholars of the State Key Laboratory of Pollution Control and Resource Reuse (No.PCRREF07002)the Specialized Research Fund for the Doctoral Program of Higher Education, SRFDP (No.200802841030)
文摘Water pollution of the Yangtze River in China became one of challenges that the government is facing today. Increasing numbers of petrochemical plants were built along the river in past decades, and numbers of organic chemicals were discharged into the river. Our goal was to establish in vitro system on rat sertoli cells, spermatogenic cells and leydig cells to investigate the reproductive toxicity potential induced by organic extracts from petrochemical effluents. Our results showed that the organic extract depressed the viability （p 〈 0.01） and destroyed the plasma membrane integrity of sertoli cells and spermatogenic cells to a certain degree. Accordingly, proportion of early apoptotic sertoli cells and late apoptotic spermatogenic cells increased significantly. Although significant morphological changes were not detected for leydig cells, the extract was observed to inhibit their testosterone production （p 〈 0.01）. Sertoli cells and sperrnatogenic cells appeared to be more sensitive and maybe the main targets of the key toxins. These results suggested that the in vitro system on rat testicular cells may be useful to predicate reproductive toxicity potential of organic extracts from petrochemical effluents. More attention should be paid to the petrochemical effluents, because long-term accumulation of these organic compounds in organisms may cause spermatogenesis malfunction and testosterone reduction.
基金This work was financially supported in part by the National Natural Science Foundation of China(Grant Nos.12047564,52071041,12074048)the Project for Fundamental and Frontier Research in Chongqing(cstc2020jcyj-msxmX0777 and cstc2020jcyj-msxmX0796)+1 种基金the Fundamental Research Funds for the Central Universities(cqu2018CDHB1A09,106112016CDJZR308808)Open access funding provided by Shanghai Jiao Tong University
文摘Photocatalytic conversion of CO_(2) to high-value products plays a crucial role in the global pursuit of carbon–neutral economy.Junction photocatalysts,such as the isotype heterojunctions,offer an ideal paradigm to navigate the photocatalytic CO_(2) reduction reaction(CRR).Herein,we elucidate the behaviors of isotype heterojunctions toward photocatalytic CRR over a representative photocatalyst,g-C_(3)N_(4).Impressively,the isotype heterojunctions possess a significantly higher efficiency for the spatial separation and transfer of photogenerated carriers than the single components.Along with the intrinsically outstanding stability,the isotype heterojunctions exhibit an exceptional and stable activity toward the CO_(2) photoreduction to CO.More importantly,by combining quantitative in situ technique with the first-principles modeling,we elucidate that the enhanced photoinduced charge dynamics promotes the production of key intermediates and thus the whole reaction kinetics.
基金supported by the Petrel Meteorological Observation Experiment Project of the China Meteorological Administration and the “Adaptive Improvement of New Observation Platform for Typhoon Observation (2018YFC1506401)” of the Ministry of Science and Technology。
文摘In collaboration with 12 other institutions, the Meteorological Observation Center of the China Meteorological Administration undertook a comprehensive marine observation experiment in the South China Sea using the Yilong-10 high-altitude large unmanned aerial vehicle(UAV). The Yilong-10 UAV carried a self-developed dropsonde system and a millimeter-wave cloud radar system. In addition, a solar-powered unmanned surface vessel and two drifting buoys were used. The experiment was further supported by an intelligent, reciprocating horizontal drifting radiosonde system that was deployed from the Sansha Meteorological Observing Station, with the intent of producing a stereoscopic observation over the South China Sea. Comprehensive three-dimensional observations were collected using the system from 31 July to2 August, 2020. This information was used to investigate the formation and development processes of Typhoon Sinlaku(2020). The data contain measurements of 21 oceanic and meteorological parameters acquired by the five devices, along with video footage from the UAV. The data proved very helpful in determining the actual location and intensity of Typhoon Sinlaku(2020). The experiment demonstrates the feasibility of using a high-altitude, large UAV to fill in the gaps between operational meteorological observations of marine areas and typhoons near China, and marks a milestone for the use of such data for analyzing the structure and impact of a typhoon in the South China Sea. It also demonstrates the potential for establishing operational UAV meteorological observing systems in the future, and the assimilation of such data into numerical weather prediction models.
基金supported by the National Natural Science Foundation of China (60574082,60804027)
文摘This paper is concerned with the robust stabilization problem of networked control systems with stochastic packet dropouts and uncertain parameters. Considering the stochastic packet dropout occuring in two channels between the sensor and the controller, and between the controller and the actuator, networked control systems are modeled as the Markovian jump linear system with four operation modes. Based on this model, the necessary and sufficient conditions for the mean square stability of the deterministic networked control systems and uncertain networked control systems are given by using the theory of the Markovian jump linear system, and corresponding controller design procedures are proposed via the cone complementarity linearization method. Finally, the numerical example and simulations are given to illustrate the effectiveness of the proposed results.
基金supported by the National Natural Science Foundation of China (6057408260804027)
文摘The problem of robust H∞ guaranteed cost satisfactory fault-tolerant control with quadratic D stabilizability against actuator failures is investigated for a class of discrete-time systems with value-bounded uncertainties existing in both the state and control input matrices.Based on a more practical and general model of actuator continuous gain failures,taking the transient property,robust behaviour on H∞ performance and quadratic cost performance requirements into consideration,sufficient conditions for the existence of satisfactory fault-tolerant controller are given and the effective design steps with constraints of multiple performance indices are provided.Meanwhile,the consistency of the regional pole index,H∞ norm-bound constraint and cost performance indices is set up for fault-tolerant control.A simulation example shows the effectiveness of the proposed method.
基金supported by the Natural ScienceFoundation of Inner Mongolia, No. 20080404Zd29
文摘A total of 80 patients with refractory epilepsy were recruited from the Inner Mongolia Medical College Affiliated Hospital. The loci of 60% of the patients could be positioned using a combined positron emission tomography/CT imaging modality. Hyper- and hypometabolism foci were examined as part of this study. Patients who had abnormal metabolism in positron emission tomography/CT imaging were divided into intermittent-phase group and the seizure-phase group. The intermittent-phase group was further divided into a single-focus group and a multiple-foci group according to the number of seizure foci detected by imaging. Following gamma knife treatment, seizure frequency was significantly lower in the intermittent-phase group and the seizure-phase group. Wieser＇s classification reached Grade I or II in nearly 40% of patients. Seizure frequency was significantly lower following treatment, but Wieser＇s classification score was significantly higher in the seizure-phase group compared with the intermittent-phase group. Seizure frequency was significantly lower following treatment in the single-focus group, but Wieser＇s classification score was significantly higher in the single-focus group as compared with the multiple-foci group.
基金This work was financially supported by National Natural Science Foundation of China （81600838, 51502262）, Key Research and Development Program of Zhejiang, China （2017C01054）, Medical Technology and Education of Zhejiang Province of China （2016KYB178）, Research Science and Technology Department of Zhejiang Province social welfare development projects under Grant 2013C33161, Natural Science Foundation of Zhejiang Provence of China under Grant LY 15H 160019, and Ningbo Natural Science Foundation 2016A610166.
文摘Previous studies have suggested that the transforming growth factor-β receptor ALK5 is crucial for articular chondrogenesis by bone marrow mesenchymal stem cells. Here, the wild-type ALK5 plasmids were mutated by overlapping extended PCR and transfected into bone marrow mesenchymal stem cells. The knee joint osteoarthritis mouse model was constructed by cutting oft＂ the anterior cruciate ligament and divided into three groups： saline group, bone marrow mesenchymal stem cells and ALK5-transfected bone marrow mesenchymal stem cells group. HE staining showed that the articular cartilage lesions were more serious of saline group compared with that of mesenchymal stem cell group, and this trend was more pronounced as time goes on. Immunohistochemical staining showed that although the expression level of type II collagen in all three groups down-regulated gradually upon time, its expression in ALK5-transfected bone marrow mesenchymal stem cells group was significantly enhanced compared with the other two groups. Micro-CT also suggested that ALK5 transfection of mouse bone marrow mesenchymal stem cells would promote repairing the knee cartilage lesions with arthritis of the mice. Although the osteoarthritis mechanism underlying a variety of factors work together, and the appropriate proportion of ALKS/ALK1 was also emphasized for the treatment of osteoarthritis. This work therefore demonstrated that ALK5 transfection of bone marrow mesenchymal stem cells could be a promising stem cell therapy for repair of cartilage lesions.
基金supported by Natural Science Foundation of China (No.61271258)
文摘In this work, the homomorphism of the classic linear block code in linear network coding for the case of binary field and its extensions is studied. It is proved that the classic linear error-control block code is homomorphic network error-control code in network coding. That is, if the source packets at the source node for a linear network coding are precoded using a linear block code, then every packet flowing in the network regarding to the source satisfies the same constraints as the source. As a consequence, error detection and correction can be performed at every intermediate nodes of multicast flow, rather than only at the destination node in the conventional way, which can help to identify and correct errors timely at the error-corrupted link and save the cost of forwarding error-corrupted data to the destination node when the intermediate nodes are ignorant of the errors. In addition, three examples are demonstrated which show that homomorphic linear code can be combined with homomorphic signature, McEliece public-key cryptosystem and unequal error protection respectively and thus have a great potential of practical utility.
基金the Scientific and Technological Research Project of Higher Education Institutions in Hebei Province(QN2019163)China Postdoctoral Science Foundation(2018M631765)+1 种基金the Doctoral Funds of Yanshan University(BL17024)a grant from Hebei Province Postdoctoral Advanced Programs(B2018003011).
文摘Pulse excitation or vibration stimulation was imposed on the low permeable formation with cracks to enhance the production or injection capacity.During that process,a coupling of wave-induced flow and initial flow in dual-porous media was involved.Researchers had done much work on the rule of wave propagation in fractured porous media,whereas attentions on the variation law of flow in developing low permeable formation with cracks under vibration stimulation were not paid.In this study,the effect of low-frequency vibration on the seepage in dual-porous media was examined for the application of wave stimulation technology in developing reservoirs with natural cracks.A model for seepage of single-phase liquid in porous media with cracks under low-frequency vibration excitation was built by combining wave propagating theory for porous media with cracks and dual-porous media seepage mechanics.A governing equation group for the model,which was expressed by dimensionless fluid and solid displacements,was derived and solved with a numerical method.Variable physical properties were simulated to check the applicability of external low-frequency vibration load on dual-porous media and a parametric study for various vibration parameters.Stimulation of low-frequency vibration affected flow velocities of crack and rock matrix fluids.Compared with that in single-porous media,the stimulation effect on the fluid inner matrix of dual-porous media was relatively weakened.Different optimal vibration parameters were needed to increase the channeling flow between the crack and rock matrix or to only promote the flow velocity in the rock matrix.The theoretical study examines wave-coupled seepage field in fractured porous media with results that are applicable for low-frequency stimulation technology.
基金Youth Science and Technology Project of Hebei Provincial Health Department,Approval number:20181535.
文摘Objective:To explore the inhibitory effect of curcumin on colon cancer in vitro.Methods:Human colon cancer cell lines HT29 and SW620 were cultured in vitro,which were divided into test group and control group.Cells in the test groups were treated with curcumin at different concentrations,while the control groups were treated with dimethylsulfoxide(DMSO).Subsequently,methyl thiazolyl tetrazolium(MTT)assay,were carried out to estimate cellular proliferative activity.Flow cytometry using annexin-V/propidium iodide(PI)staining was performed to detect cell apoptosis.Formation of autophagosomes in the cytoplasm in colon cancer cells were detected by TEM(transmission electron microscopy analysis),and Western blot to measure the expressions of proteins related to apoptosis and autophagy.Results:MTT assay showed that curcumin inhibited the proliferative activity of both HT29 and SW620 cells,significantly different from the control group(P<0.001).The halfmaximal inhibitory concentration(IC50)of curcumin at 24 hours was 20μM for both HT29 and SW620 cells.Annexin-V FITC/PI double labeling showed that,After treatment with curcumin of 20μM for 24 hours,a significant increase was observed in apoptosis rate in both HT219 cells((10.00±0.60)%vs.(4.00±0.70)%,P<0.01;(10.50±0.40)%vs.(4.30±0.26)%,P<0.01)compared with the control cells.TEM analysis showed that curcumin increased the accumulation of autophagosomes in the cytoplasm in HT29 and SW620 cells.Western blot showed an increase in the expressions of apoptosis-related proteins including cleaved caspase-3 and cleaved poly ADP-ribose polymerase(PARP)but decrease of P62 protein in both HT29 and SW620 cells after 24-hour treatment with 20μM curcumin for 24 hours compared with the control groups.Conclusion:Curcumin can inhibit the proliferation,induce apoptosis and autophagy in human colon cancer cells.
基金the Natural Science Foundation of China(grant nos.21725301,21932002,21821004,91645115,51872008,22172183,22172150,and 22222306)the National Key R&D Program of China(grant nos.2017YFB060220 and 2021YFA-1502804)+3 种基金the Beijing Outstanding Young Scientists Projects(grant nos.BJJWZYJH01201910005018 and BJJWZYJH01201914430039)the Strategic Priority Research Program of the Chinese Academy of Science(grant no.XDB0450102)the K.C.Wong Education Foundation(grant no.GJTD-2020-15)the Innovation Program for Quantum Science and Technology(grant no.2021ZD0303302).
文摘Reducing the ever-growing level of CO_(2)in the atmosphere is critical for the sustainable development of human society in the context of global warming.Integration of the capture and upgrading of CO_(2)is,therefore,highly desirable since each process step is costly,both energetically and economically.Here,we report a CO_(2)direct air capture(DAC)and fixation process that produces methane.Low concentrations of CO_(2)(∼400 ppm)in the air are captured by an aqueous solution of sodium hydroxide to form carbonate.The carbonate is subsequently hydrogenated to methane,which is easily separated from the reaction system,catalyzed by TiO2-supported Ru in the aqueous phase with a selectivity of 99.9%among gas-phase products.The concurrent regenerated hydroxide,in turn,increases the alkalinity of the aqueous solution for further CO_(2)capture,thereby enabling this one-ofits-kind continuous CO_(2)capture and methanation process.Engineering simulations demonstrate the energy feasibility of this CO_(2)DAC and methanation process,highlighting its promise for potential largescale applications.
基金support of National Key Lab.of Metal Precision Hot Processing
文摘One of the chief works for inspecting spot weld quality by X-ray to obtain an ideal and uniform digital image. This paper introduces three methods of image background simulation algorithm, and' the effect of background correction was compared. It may be safely said that Kalman filter method is simple and fast for general image; the FFT method has a good adaptability for background simulation.
基金This work was financially supported by the Basic Science Center Program for Multiphase Evolution in Hyper-gravity of the National Natural Science Foundation of China(No.51988101)the National Natural Science Foundation of China(Nos.52071003,91860202,11604006)+4 种基金the Beijing Municipal Education Commission Project(Nos.PXM2020-014204-000021and PXM2019-014204-500032)the Beijing Outstanding Young Scientists Projects(No.BJJWZYJH01201910005018)the Beijing Natural Science Foundation(No.Z180014)the“111”project(No.DB18015)supported by the Australian Research Council(No.DP190102990)。
文摘This paper reports a synergistic design of high-performance BCC high-entropy alloy based on the combined consideration of the principles of intrinsic ductility of elements,maximum atomic size difference for solid solution strengthening and the valence electron concentration criterion for ductility.The single-phase BCC HfNbTaTiV alloy thus designed exhibited a high compressive yield strength of 1350 MPa and a high compressive ductility of>45%at the room temperature.This represents a 50%increase in yield strength relative to a HfNbTaTiZr alloy.This is attributed to the maximized solid solution strengthening effect caused by lattice distortion,which is estimated to be 1094 MPa.The alloy was also able to retain 53%of its yield strength and 77%of its ductility at 700℃.These properties are superior to those of most refractory BCC high-entropy alloys reported in the literature.
基金the support of Basic Science Center Program for Multiphase Evolution in Hyper-gravity of the National Natural Science Foundation of China(51988101)NSFC programs(52071003,91860202,11604006)+4 种基金Beijing Municipal Education Commission Project(PXM2020014204000021 and PXM2019014204500032)Beijing Outstanding Young Scientists Projects(BJJWZYJH01201910005018)Beijing Natural Science Foundation(Z180014)“111”project(DB18015)the support by the Australian Research Council(DP190102990)to his work in this study。
文摘This study explored a multi-mechanism approach to improving the mechanical properties of a Co CrFe Mn Ni high-entropy alloy through non-equiatomic alloy design and processing.The alloy design ensures a single-phase face-centered cubic structure while lowering the stacking fault energy to encourage the formation of deformation twins and stacking faults by altering the equiatomic composition of the alloy.The processing strategy applied helped create a hierarchical grain size gradient microstructure with a high nanotwins population.This was achieved by means of rotationally accelerated shot peening(RASP).The non-equiatomic Co Cr Fe Mn Ni high-entropy alloy achieved a yield strength of 750 MPa,a tensile strength of 1050 MPa,and tensile uniform elongation of 27.5%.The toughness of the alloy was 2.53×10^(10)k J/m^(3),which is about 2 times that of the same alloy without the RASP treatment.The strength increase is attributed to the effects of grain boundary strengthening,dislocation strengthening,twin strengthening,and hetero-deformation strengthening associated with the heterogeneous microstructure of the alloy.The concurrent occurrence of the multiple deformation mechanisms,i.e.,dislocation deformation,twining deformation and microband deformation,contributes to achieving a suitable strain hardening of the alloy that helps to prevent early necking and to assure steady plastic deformation for high toughness.
基金supported by the National Key R&D Program of China(2021YFA1200201)the National Natural Science Foundation of China(52071003,91860202,and 11604006)+4 种基金Beijing Nova Program(Z211100002121170)Beijing Municipal Education Commission Project(PXM2020_014204_000021 and PXM2019_014204_500032)Beijing Outstanding Young Scientists Projects(BJJWZYJH01201910005018)Beijing Natural Science Foundation(Z180014)“111”project(DB18015)。
文摘Enhanced oxidation resistance is a primary demand for the application of refractory high-entropy alloys(RHEAs)at elevated temperatures.In this study,Al was added to a Ti_(2)VZrNb RHEA to partially substitute Nb to improve its oxidation resistance and mechanical properties.The alloy was found to have an increased oxidation resistance by forming a continuous Al_(2)O_(3)+ZrO_(2)oxide protective surface.At the same time,the room-temperature yield strength was also increased by 66%to 1273 MPa via solid solution strengthening.The low atomic mass of Al also helped to reduce the density of the alloy by 8.2%to 5.44 g cm^(−3).This resulted in a high specific yield strength of 234 MPa cm3 g^(−1) for the alloy.Meanwhile,the Ti_(2)VZrNb_(0.5)-Al_(0.5)alloy also exhibited a high compressive plasticity of>50%.These values are among the best reported so far for RHEAs.
基金financially supported by the Basic Science Center Program for Multiphase Evolution in Hyper-gravity of the National Natural Science Foundation of China(51988101)NSFC Programs(Nos.52071003,91860202,11604006)+3 种基金the Beijing Municipal Education Commission Project(Nos.PXM2020014204000021 and PXM201901420400032)the Beijing Outstanding Young Scientists Projects(No.BJJWZYJH01201910005018)the Beijing Natural Science Foundation(No.Z180014)the“111 Project(No.DB18015)。
文摘Degradation of a metallic film under harsh thermal-mechanical-electrical coupling field conditions determines its service temperature and lifetime.In this work,the self-heating degradation behaviors of Pt thin films above 1000℃were studied in situ by TEM at the nanoscale.The Pt films degraded mainly through void nucleation and growth on the Pt-SiN_(x)interface.Voids preferentially formed at the grain boundary and triple junction intersections with the interface.At temperatures above 1040℃,the voids nucleated at both the grain boundaries and inside the Pt grains.A stress simulation of the suspended membrane suggests the existence of local tensile stress in the Pt film,which promotes the nucleation of voids at the Pt-Si Nxinterface.The grain-boundary-dominated mass transportation renders the voids grow preferentially at GBs and triple junctions in a Pt film.Additionally,under the influence of an applied current,the voids that nucleated inside Pt grains grew to a large size and accelerated the degradation of the Pt film.
基金supported by the National Key R&D Program of China(2018YFB1304902)the National Natural Science Foundation of China(11904372,U1813211,and 12004034)+2 种基金Beijing Institute of Technology Research Fund Program for Young ScholarsBeijing Institute of Technology Laboratory Research Project(2019BITSYA03)China Postdoctoral Science Foundation Funded Project(2021M690386)。
文摘Harvesting the promising high energy density of advanced electrode materials in lithium-ion batteries is critically dependent on a mechanistic understanding on how the materials function and degrade along with the battery cycling.Here,we tracked phase transformations during(de)lithiation of Sb_(2)Se_(3) single crystals using in situ high-resolution transmission electron microscopy(HRTEM)technique,and revealed electro-chemo-mechanical evolution at the reaction interface.The effect of this electro-chemo-mechanical coupling has a complicated interplay on the lithiation kinetics and causes various types of defects at the reaction front,including dislocation dipoles,antiphase boundaries,and cracks.In return,the formed cracks and related defects build a path for fast diffusion of lithium ions and trigger a highly anisotropic lithiation at the twisted reaction front,giving rise to the formation of presumably "dead" Sb_(2)Se_(3) nanodomains in amorphous Li_(x)Sb_(2)Se_(3).The detailed mechanistic understanding may facilitate the rational design of high-capacity electrode materials for battery applications.
基金supported by Beijing Natural Science Foundation(Z180014)Beijing Outstanding Young Scientists Projects(BJJWZYJH01201910005018)the National Natural Science Foundation of China(51771104)。
文摘Detwinning is an important plastic deformation mechanism that can significantly affect the mechanical properties of twin-structured metals.Although many detwinning mechanisms have been proposed for pure metals,it is unclear whether such a deformation model is valid for nanocrystalline alloys because of the lack of direct evidence.Here,the atomicscale detwinning deformation process of a nanocrystalline AuAg alloy with an average grain size of~15 nm was investigated in situ.The results show that there are three types of detwinning mechanisms in nanocrystalline AuAg alloys.The first type of detwinning results from grain boundary migration.The second type of detwinning occurs through combined layer-by-layer thinning and incoherent twin boundary migration.The last one occurs through incoherent twin boundary migration,which results from the collective motion of partial dislocations in an array.
基金Project supported by the National Key Research and Development Plan(2021YFA1200201)the Natural Science Foundation of China(51872008)+1 种基金the"111"Project under the DB18015 grantBeijing Outstanding Young Scientists Projects(BJJWZYJH01201910005018)。
文摘The extremely high structural tolerance of ceria to oxygen vacancies(Ov)has made it a desirable catalytic material for the hydrocarbon oxidation to chemicals and pharmaceuticals and the reduction of gaseous pollutants.It is proposed that the formation and diffusion of Ov originate from its outstanding reduction property.However,the formation and diffusion process of Ov over the surface of ceria at the atomic level is still unknown.Herein,the structural and valence evolution of CeO_(2)(111)surfaces in reductive,oxidative and vacuum environments from room temperature up to 700℃was studied with in situ aberration-corrected environmental transmission electron microscopy(ETEM)experiments.Ov is found to form under a high vacuum at elevated temperatures;however,the surface can recover to the initial state through the adsorption of oxygen atoms in an oxygen-contained environment.Furthermore,in hydrogen environment,the step-CeO_(2)(111)surface is not stable at elevated temperatures;thus,the steps tend to be eliminated with increasing temperature.Combined with first-principles density function calculations(DFT),it is proposed that O-terminated surfaces would develop in a hypoxic environment due to the dynamic diffusion of Ov from the outer surface to the subsurface.Furthermore,in a reductive environment,H2 facilitates the formation and diffusion of Ov while Ce-terminated surfaces develope.These results reveal dynamic atomic-scale interplay between the nanoceria surface and gas,thereby providing fundamental insights into the Ov-dependent reaction of nano-CeO_(2) during catalytic processes.
