Conventionally,the spatially structured light beams produced by metasurfaces primarily highlight the polarization modulation of the beams propagating along the optical axis or the beams'spatial transmission trajec...Conventionally,the spatially structured light beams produced by metasurfaces primarily highlight the polarization modulation of the beams propagating along the optical axis or the beams'spatial transmission trajectory.In particular,along the optical axis,the polarization state is either constant or varies continuously in each output plane.Here,we develop innovative spatially structured light beams with continually changing polarization along any arbitrary spatial transmission trajectories.With tri-layer metallic metasurfaces,the geometric characteristics of each layer structure can be adjusted to modulate the phase and polarization state of the incident terahertz(THz)wave.The beam will converge to the predefined trajectory along several paths to generate a Bessel-like beam with longitudinal polarization changes.We demonstrate the versatility of the approach by designing two THz-band structured light beams with varying polarization states along the spatial helical transmission trajectory.Continuous linear polarization changes and linear polarization to right circular polarization(RCP)and back to linear polarization changes are realized respectively.The experimental results are basically consistent with the simulated results.Our proposal for arbitrary trajectory structured light beams with longitudinally varying polarization offers a practical method for continuously regulating the characteristics of spatial structured light beams with non-axial transmission.This technique has potential uses in optical encryption,particle manipulation,and biomedical imaging.展开更多
Structural Health Monitoring(SHM)systems have become a crucial tool for the operational management of long tunnels.For immersed tunnels exposed to both traffic loads and the effects of the marine environment,efficient...Structural Health Monitoring(SHM)systems have become a crucial tool for the operational management of long tunnels.For immersed tunnels exposed to both traffic loads and the effects of the marine environment,efficiently identifying abnormal conditions from the extensive unannotated SHM data presents a significant challenge.This study proposed amodel-based approach for anomaly detection and conducted validation and comparative analysis of two distinct temporal predictive models using SHM data from a real immersed tunnel.Firstly,a dynamic predictive model-based anomaly detectionmethod is proposed,which utilizes a rolling time window for modeling to achieve dynamic prediction.Leveraging the assumption of temporal data similarity,an interval prediction value deviation was employed to determine the abnormality of the data.Subsequently,dynamic predictive models were constructed based on the Autoregressive Integrated Moving Average(ARIMA)and Long Short-Term Memory(LSTM)models.The hyperparameters of these models were optimized and selected using monitoring data from the immersed tunnel,yielding viable static and dynamic predictive models.Finally,the models were applied within the same segment of SHM data,to validate the effectiveness of the anomaly detection approach based on dynamic predictive modeling.A detailed comparative analysis discusses the discrepancies in temporal anomaly detection between the ARIMA-and LSTM-based models.The results demonstrated that the dynamic predictive modelbased anomaly detection approach was effective for dealing with unannotated SHM data.In a comparison between ARIMA and LSTM,it was found that ARIMA demonstrated higher modeling efficiency,rendering it suitable for short-term predictions.In contrast,the LSTM model exhibited greater capacity to capture long-term performance trends and enhanced early warning capabilities,thereby resulting in superior overall performance.展开更多
During the long term evolution of globular clusters(GCs), some member stars are lost to the field. The recently found nitrogen-rich(N-rich) metal-poor field stars are promising candidates of these GC escapees, since N...During the long term evolution of globular clusters(GCs), some member stars are lost to the field. The recently found nitrogen-rich(N-rich) metal-poor field stars are promising candidates of these GC escapees, since N enhancement is the fingerprint of chemically enhanced populations in GCs. In this work, we discuss the possibility of identifying N-rich metal-poor field stars with the upcoming Chinese Space Station Telescope(CSST). We focus on the main survey camera with NUV, u, g, r, i, z, y filters and slitless spectrograph with a resolution about 200.The combination of UV sensitive equipment and prominent N-related molecular lines in the UV band bodes well for the identification: the color–color diagram of(u-g) versus(g-r) is capable of separating N-rich field stars from normal halo stars, if metallicity can be estimated without using the information on u-band photometry.Besides, the synthetic spectra show that a signal-to-noise ratio of 10 is sufficient to identify N-rich field stars. In the near future, a large sample of N-rich field stars found by CSST, combined with state-of-the-art N-body simulations will be crucial to deciphering GC-Galaxy co-evolution.展开更多
Using 9943 OB-type stars from LAMOST DR7 in the solar neighborhood,we fit the vertical stellar density profile with the model including a single exponential distribution at different positions(R,Φ).The distributions ...Using 9943 OB-type stars from LAMOST DR7 in the solar neighborhood,we fit the vertical stellar density profile with the model including a single exponential distribution at different positions(R,Φ).The distributions of the scale heights and scale length show that the young disk traced by the OB-type stars is not axisymmetric.The scale length decreases versus the azimuthal angleΦ,i.e.,from.■kpc withΦ=-3°to■kpc withΦ=9°.Meanwhile we find signal of non-symmetry in the distribution of the scale height of the north and south of the disk plane.The scale height in the north side shows signal of flaring of the disk,while that of the south disk stays almost constant around h_(s)=130 pc.The distribution of the displaceeent of the disk plane Z_(0)also shows variance versus the azimuthal angleΦ,which displays significant differences with the warp model constrained by the Cepheid stars.We also test different values for the position of the Sun,and the distance between the Sun and the Galactic center affects the scale heights and the displacement of the disk significantly,but that does not change our conclusion that the disk is not axisymmetric.展开更多
In this study,we conducted simulations to find the geometric aberrations expected for images taken by the Main Survey Camera of the Chinese Space Station Telescope(CSST)due to its motion.As anticipated by previous wor...In this study,we conducted simulations to find the geometric aberrations expected for images taken by the Main Survey Camera of the Chinese Space Station Telescope(CSST)due to its motion.As anticipated by previous work,our findings indicate that the geometric distortion of light impacts the focal plane's apparent scale,with a more pronounced influence as the size of the focal plane increases.Our models suggest that the effect consistently influences the pixel scale in both the vertical and parallel directions.The apparent scale variation follows a sinusoidal distribution throughout one orbital period.Simulations reveal that the effect is particularly pronounced in the center of the Galaxy and gradually diminishes along the direction of ecliptic latitude.At low ecliptic latitudes,the total aberration leads to about a 0.94 pixel offset(a 20 minute exposure)and a 0.26 pixel offset(a 300 s exposure)at the edge of the field of view.Appropriate processings for the geometric effect during the CSST pre-and post-observation phases are presented.展开更多
The China Space Station Telescope(CSST)is a two-meter space telescope with multiple back-end instruments.The Fine Guidance Sensor(FGS)is an essential subsystem of the CSST Precision Image Stability System to ensure th...The China Space Station Telescope(CSST)is a two-meter space telescope with multiple back-end instruments.The Fine Guidance Sensor(FGS)is an essential subsystem of the CSST Precision Image Stability System to ensure the required absolute pointing accuracy and line-of-sight stabilization.In this study,we construct the Main Guide Star Catalog for FGS.To accomplish this,we utilize the information about the FGS and object information from the Gaia Data Release 3.We provide an FGS instrument magnitude and exclude variables,binaries,and high proper motion stars from the catalog to ensure uniform FGS guidance capabilities.Subsequently,we generate a HEALPix index,which provides a hierarchical tessellation of the celestial sphere,and employ the Voronoi algorithm to achieve a homogeneous distribution of stars across the catalog.This distribution ensures adequate coverage and sampling of the sky.The performance of the CSST guide star catalog was assessed by simulating the field of view of the FGS according to the CSST mock survey strategy catalog.The analysis of the results indicates that this catalog provides adequate coverage and accuracy.The catalog's performance meets the FGS requirements,ensuring the functioning of the FGS and its guidance capabilities.展开更多
The electrochemical CO_(2)reduction reaction to produce multi-carbon(C_(2+)) hydrocarbons or oxygenate compounds is a promising route to obtain a renewable fuel of high energy density.However,producing C_(2+)at high c...The electrochemical CO_(2)reduction reaction to produce multi-carbon(C_(2+)) hydrocarbons or oxygenate compounds is a promising route to obtain a renewable fuel of high energy density.However,producing C_(2+)at high current densities is still a challenge.Herein,we develop a Cu-Zn alloy/Cu-Zn aluminate oxide composite electrocatalytic system for enhanced conversion of CO_(2)to C_(2+)products.The Cu-Zn-Al-Layered Double Hydroxide(LDH) is used as a precursor to decompose into uniform Cu-Zn oxide/Cu-Zn aluminate pre-catalyst.Under electrochemical reduction,Cu-Zn oxide generates Cu-Zn alloy while Cu-Zn aluminate oxide remains unchanged.The alloy and oxide are closely stacked and arranged alternately,and the aluminate oxide induces the strong electron interaction of Cu,Zn and Al,creating a large number of highly active reaction interfaces composed of 0 to+3 valence metal sites.With the help of the interface effect,the optimized Cu_(9)Zn_(1)/Cu_(0.8)Zn_(0.2)Al_(2)O_(4)catalyst achieves a Faradaic efficiency of 88.5% for C_(2+)products at a current density of 400 mA cm^(-2)at-1.15 V versus reversible hydrogen electrode.The in-situ Raman and attenuate total reflectance-infrared absorption spectroscopy(ATR-IRAS) spectra show that the aluminate oxide at the interface significantly enhances the adsorption and activation of CO_(2)and the dissociation of H2O and strengthens the adsorption of CO intermediates,and the alloy promotes the C-C coupling to produce C_(2+)products.This work provides an efficient strategy to construct highly active reaction interfaces for industrial-scale electrochemical CO_(2)RR.展开更多
The electrochemical oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) are fundamental processes in a range of energy conversion devices such as fuel cells and metal–air batteries. ORR and OER both hav...The electrochemical oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) are fundamental processes in a range of energy conversion devices such as fuel cells and metal–air batteries. ORR and OER both have significant activation barriers, which severely limit the overall performance of energy conversion devices that utilize ORR/OER. Meanwhile, ORR is another very important electrochemical reaction involving oxygen that has been widely investigated. ORR occurs in aqueous solutions via two pathways: the direct 4-electron reduction or 2-electron reduction pathways from O_(2) to water(H_2O) or from O_(2) to hydrogen peroxide(H_2O_(2)). Noble metal electrocatalysts are often used to catalyze OER and ORR, despite the fact that noble metal electrocatalysts have certain intrinsic limitations, such as low storage. Thus, it is urgent to develop more active and stable low-cost electrocatalysts, especially for severe environments(e.g., acidic media). Theoretically, an ideal oxygen electrocatalyst should provide adequate binding to oxygen species. Transition metals not belonging to the platinum group metal-based oxides are a low-cost substance that could give a d orbital for oxygen species binding. As a result, transition metal oxides are regarded as a substitute for typical precious metal oxygen electrocatalysts. However, the development of oxide catalysts for oxygen reduction and oxygen evolution reactions still faces significant challenges, e.g., catalytic activity, stability, cost, and reaction mechanism. We discuss the fundamental principles underlying the design of oxide catalysts, including the influence of crystal structure, and electronic structure on their performance. We also discuss the challenges associated with developing oxide catalysts and the potential strategies to overcome these challenges.展开更多
Background:Hippocampal damage caused by status epilepticus(SE)can bring about cognitive decline and emotional disorders,which are common clinical comorbidities in patients with epilepsy.It is therefore imperative to d...Background:Hippocampal damage caused by status epilepticus(SE)can bring about cognitive decline and emotional disorders,which are common clinical comorbidities in patients with epilepsy.It is therefore imperative to develop a novel therapeutic strat-egy for protecting hippocampal damage after SE.Mitochondrial dysfunction is one of contributing factors in epilepsy.Given the therapeutic benefits of mitochondrial replenishment by exogenous mitochondria,we hypothesized that transplantation of mitochondria would be capable of ameliorating hippocampal damage following SE.Methods:Pilocarpine was used to induced SE in mice.SE-generated cognitive de-cline and emotional disorders were determined using novel object recognition,the tail suspension test,and the open field test.SE-induced hippocampal pathology was assessed by quantifying loss of neurons and activation of microglia and astrocytes.The metabolites underlying mitochondrial transplantation were determined using metabonomics.Results:The results showed that peripheral administration of isolated mitochon-dria could improve cognitive deficits and depressive and anxiety-like behaviors.Exogenous mitochondria blunted the production of reactive oxygen species,pro-liferation of microglia and astrocytes,and loss of neurons in the hippocampus.The metabonomic profiles showed that mitochondrial transplantation altered multiple metabolic pathways such as sphingolipid signaling pathway and carbon metabolism.Among potential affected metabolites,mitochondrial transplantation decreased levels of sphingolipid(d18:1/18:0)and methylmalonic acid,and elevated levels of D-fructose-1,6-bisphosphate.Conclusion:To the best of our knowledge,these findings provide the first direct ex-perimental evidence that artificial mitochondrial transplantation is capable of amelio-rating hippocampal damage following SE.These new findings support mitochondrial transplantation as a promising therapeutic strategy for epilepsy-associated psychiat-ric and cognitive disorders.展开更多
电催化二氧化碳还原反应(CO_(2)RR)可以将二氧化碳转化为具有高经济价值的碳氢化合物,被认为是实现碳中和并缓解能源危机的一种有潜力的技术.铜(Cu)作为一种最有应用前景的非贵金属催化剂之一,表现出较高的催化CO_(2)RR转化为多碳产物(C...电催化二氧化碳还原反应(CO_(2)RR)可以将二氧化碳转化为具有高经济价值的碳氢化合物,被认为是实现碳中和并缓解能源危机的一种有潜力的技术.铜(Cu)作为一种最有应用前景的非贵金属催化剂之一,表现出较高的催化CO_(2)RR转化为多碳产物(C_(2+))的活性.然而,电催化CO_(2)还原成C_(2+)产物涉及一个动力学过程缓慢的C-C偶联反应,这导致C_(2+)产物的选择性较低,电流密度低,阻碍了其在工业电解槽中的实际应用.同时,CO_(2)RR产物的选择性不仅取决于热力学速率决定步骤,还取决于传质控制动力学.CO_(2)RR发生在固-气-液三相反应界面,气-液的平衡扩散可以有效抑制析氢竞争反应,进而提高CO_(2)RR的反应效率.本文设计合成了一种富晶界的Cu纳米带催化剂,并构建了气-液平衡扩散的电极结构,用于高效电催化二氧化碳还原制备乙烯(C_(2)H_(4)).以一种碱式碳酸铜(Cu_(2)CO_(3)(OH)_(2))纳米带为前驱体,在原位电化学还原条件下,前驱体中的Cu2+离子获得电子被还原为金属Cu,而释放的CO_(3)2-和OH-混合阴离子调节金属Cu的生长.生成的Cu纳米带由细小的纳米颗粒堆积而成,并暴露出大量的由Cu(111),Cu(200)和Cu(220)晶面形成的富晶界结构(GBs).同时,在CO_(2)RR测试中发现催化剂层的厚度是影响CO_(2)和电解质传质的关键因素.通过调整催化层厚度,CO_(2)和电解质可以同时到达催化剂表面,参与到CO_(2)RR中,实现了气-液平衡扩散,有效抑制了氢析出副反应.在晶界效应和气-液平衡扩散的协同作用下,优化后的电极在电流密度为700 mA cm^(-2)时,对C_(2)H_(4)和C_(2+).产物的法拉第效率分别高达67.2%和82.1%.此外,C_(2)H_(4)的部分电流密度可高达505 mA cm^(-2),高于大多数文献报道的结果.原位拉曼光谱和衰减全内反射表面增强红外吸收光谱结果表明,丰富的晶;界结构增强了CO_(2)在催化剂表面的活化,显著促进了*CO中间体的形成和吸附,加速了C-C偶联过程形成*OCCO和*OCCOH中间体,提高了C_(2)H_(4)和其他C_(2+)产物的产率.综上,本文设计了一种高活性Cu催化剂和电极结构,为高效电催化CO_(2)还原为C_(2)H_(4)等C_(2+)产物提供参考.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12074094 and 121774271)the Sino-German Mobility Program of the Sino-German Center for Science Funding(Grant No.M-0225)the Capacity Building for Science&Technology Innovation-Fundamental Scientific Research Funds(Grant No.00820531120017).
文摘Conventionally,the spatially structured light beams produced by metasurfaces primarily highlight the polarization modulation of the beams propagating along the optical axis or the beams'spatial transmission trajectory.In particular,along the optical axis,the polarization state is either constant or varies continuously in each output plane.Here,we develop innovative spatially structured light beams with continually changing polarization along any arbitrary spatial transmission trajectories.With tri-layer metallic metasurfaces,the geometric characteristics of each layer structure can be adjusted to modulate the phase and polarization state of the incident terahertz(THz)wave.The beam will converge to the predefined trajectory along several paths to generate a Bessel-like beam with longitudinal polarization changes.We demonstrate the versatility of the approach by designing two THz-band structured light beams with varying polarization states along the spatial helical transmission trajectory.Continuous linear polarization changes and linear polarization to right circular polarization(RCP)and back to linear polarization changes are realized respectively.The experimental results are basically consistent with the simulated results.Our proposal for arbitrary trajectory structured light beams with longitudinally varying polarization offers a practical method for continuously regulating the characteristics of spatial structured light beams with non-axial transmission.This technique has potential uses in optical encryption,particle manipulation,and biomedical imaging.
基金supported by the Research and Development Center of Transport Industry of New Generation of Artificial Intelligence Technology(Grant No.202202H)the National Key R&D Program of China(Grant No.2019YFB1600702)the National Natural Science Foundation of China(Grant Nos.51978600&51808336).
文摘Structural Health Monitoring(SHM)systems have become a crucial tool for the operational management of long tunnels.For immersed tunnels exposed to both traffic loads and the effects of the marine environment,efficiently identifying abnormal conditions from the extensive unannotated SHM data presents a significant challenge.This study proposed amodel-based approach for anomaly detection and conducted validation and comparative analysis of two distinct temporal predictive models using SHM data from a real immersed tunnel.Firstly,a dynamic predictive model-based anomaly detectionmethod is proposed,which utilizes a rolling time window for modeling to achieve dynamic prediction.Leveraging the assumption of temporal data similarity,an interval prediction value deviation was employed to determine the abnormality of the data.Subsequently,dynamic predictive models were constructed based on the Autoregressive Integrated Moving Average(ARIMA)and Long Short-Term Memory(LSTM)models.The hyperparameters of these models were optimized and selected using monitoring data from the immersed tunnel,yielding viable static and dynamic predictive models.Finally,the models were applied within the same segment of SHM data,to validate the effectiveness of the anomaly detection approach based on dynamic predictive modeling.A detailed comparative analysis discusses the discrepancies in temporal anomaly detection between the ARIMA-and LSTM-based models.The results demonstrated that the dynamic predictive modelbased anomaly detection approach was effective for dealing with unannotated SHM data.In a comparison between ARIMA and LSTM,it was found that ARIMA demonstrated higher modeling efficiency,rendering it suitable for short-term predictions.In contrast,the LSTM model exhibited greater capacity to capture long-term performance trends and enhanced early warning capabilities,thereby resulting in superior overall performance.
基金support from the China Manned Space Project Nos. CMS-CSST-2021-B03,CMS-CSST-2021-A08, and________the National Natural Science Foundation of China under grant No. 12233013,12073090+8 种基金the Natural Science Foundation of Guangdong Province under grant No. 2022A1515010732grant support provided by Proyecto Fondecyt Iniciación No. 11220340ANID Concurso de Fomento a la Vinculación Internacional para Instituciones de Investigación Regionales (Modalidad corta duración) Proyecto No. FOVI210020Joint Committee ESO-Government of Chile 2021 (ORP 023/2021)Becas Santander Movilidad Internacional Profesores 2022, Banco Santander Chilesupport from the National Natural Science Foundation of China through grant 21BAA00619the one-hundred-talent project of Sun Yat-sen Universitythe Fundamental Research Funds for the Central UniversitiesSun Yat-sen University (22hytd09)。
文摘During the long term evolution of globular clusters(GCs), some member stars are lost to the field. The recently found nitrogen-rich(N-rich) metal-poor field stars are promising candidates of these GC escapees, since N enhancement is the fingerprint of chemically enhanced populations in GCs. In this work, we discuss the possibility of identifying N-rich metal-poor field stars with the upcoming Chinese Space Station Telescope(CSST). We focus on the main survey camera with NUV, u, g, r, i, z, y filters and slitless spectrograph with a resolution about 200.The combination of UV sensitive equipment and prominent N-related molecular lines in the UV band bodes well for the identification: the color–color diagram of(u-g) versus(g-r) is capable of separating N-rich field stars from normal halo stars, if metallicity can be estimated without using the information on u-band photometry.Besides, the synthetic spectra show that a signal-to-noise ratio of 10 is sufficient to identify N-rich field stars. In the near future, a large sample of N-rich field stars found by CSST, combined with state-of-the-art N-body simulations will be crucial to deciphering GC-Galaxy co-evolution.
基金supported by the National Natural Science Foundation of China(NSFC,grant Nos.12173013,12103062,12003045,and 11903012)the National Key Basic R&D Program of China via 2019YFA0405500+2 种基金supported by the Natural Science Foundation of Hebei Province under grant A2021205006 and A2019205166by the project of the Hebei provincial department of science and technology under grant number 226Z7604Gthe science research grants from the China Manned Space Project。
文摘Using 9943 OB-type stars from LAMOST DR7 in the solar neighborhood,we fit the vertical stellar density profile with the model including a single exponential distribution at different positions(R,Φ).The distributions of the scale heights and scale length show that the young disk traced by the OB-type stars is not axisymmetric.The scale length decreases versus the azimuthal angleΦ,i.e.,from.■kpc withΦ=-3°to■kpc withΦ=9°.Meanwhile we find signal of non-symmetry in the distribution of the scale height of the north and south of the disk plane.The scale height in the north side shows signal of flaring of the disk,while that of the south disk stays almost constant around h_(s)=130 pc.The distribution of the displaceeent of the disk plane Z_(0)also shows variance versus the azimuthal angleΦ,which displays significant differences with the warp model constrained by the Cepheid stars.We also test different values for the position of the Sun,and the distance between the Sun and the Galactic center affects the scale heights and the displacement of the disk significantly,but that does not change our conclusion that the disk is not axisymmetric.
基金generously supported by the National Natural Science Foundation of China(NSFC,Grant Nos.12073047 and 12273077)the National Key Research and Development(Grant No.2022YFF0711500)。
文摘In this study,we conducted simulations to find the geometric aberrations expected for images taken by the Main Survey Camera of the Chinese Space Station Telescope(CSST)due to its motion.As anticipated by previous work,our findings indicate that the geometric distortion of light impacts the focal plane's apparent scale,with a more pronounced influence as the size of the focal plane increases.Our models suggest that the effect consistently influences the pixel scale in both the vertical and parallel directions.The apparent scale variation follows a sinusoidal distribution throughout one orbital period.Simulations reveal that the effect is particularly pronounced in the center of the Galaxy and gradually diminishes along the direction of ecliptic latitude.At low ecliptic latitudes,the total aberration leads to about a 0.94 pixel offset(a 20 minute exposure)and a 0.26 pixel offset(a 300 s exposure)at the edge of the field of view.Appropriate processings for the geometric effect during the CSST pre-and post-observation phases are presented.
基金the support by National Key R&D Program of China(No.2022YFF0503403,2022YFF0711500)the support of National Natural Science Foundation of China(NSFC,grant Nos.11988101,12073047,12273077,12022306,12373048,12263005)+3 种基金the support from the Ministry of Science and Technology of China(Nos.2020SKA0110100)the science research grants from the China Manned Space Project(Nos.CMS-CSST-2021-B01,CMSCSST-2021-A01)CAS Project for Young Scientists in Basic Research(No.YSBR-062)the support from K.C.Wong Education Foundation。
文摘The China Space Station Telescope(CSST)is a two-meter space telescope with multiple back-end instruments.The Fine Guidance Sensor(FGS)is an essential subsystem of the CSST Precision Image Stability System to ensure the required absolute pointing accuracy and line-of-sight stabilization.In this study,we construct the Main Guide Star Catalog for FGS.To accomplish this,we utilize the information about the FGS and object information from the Gaia Data Release 3.We provide an FGS instrument magnitude and exclude variables,binaries,and high proper motion stars from the catalog to ensure uniform FGS guidance capabilities.Subsequently,we generate a HEALPix index,which provides a hierarchical tessellation of the celestial sphere,and employ the Voronoi algorithm to achieve a homogeneous distribution of stars across the catalog.This distribution ensures adequate coverage and sampling of the sky.The performance of the CSST guide star catalog was assessed by simulating the field of view of the FGS according to the CSST mock survey strategy catalog.The analysis of the results indicates that this catalog provides adequate coverage and accuracy.The catalog's performance meets the FGS requirements,ensuring the functioning of the FGS and its guidance capabilities.
基金supported by the National Natural Science Foundation of China (NSFC)(22075201)the National Key Research and Development Program of China (2022YFB4101800)。
文摘The electrochemical CO_(2)reduction reaction to produce multi-carbon(C_(2+)) hydrocarbons or oxygenate compounds is a promising route to obtain a renewable fuel of high energy density.However,producing C_(2+)at high current densities is still a challenge.Herein,we develop a Cu-Zn alloy/Cu-Zn aluminate oxide composite electrocatalytic system for enhanced conversion of CO_(2)to C_(2+)products.The Cu-Zn-Al-Layered Double Hydroxide(LDH) is used as a precursor to decompose into uniform Cu-Zn oxide/Cu-Zn aluminate pre-catalyst.Under electrochemical reduction,Cu-Zn oxide generates Cu-Zn alloy while Cu-Zn aluminate oxide remains unchanged.The alloy and oxide are closely stacked and arranged alternately,and the aluminate oxide induces the strong electron interaction of Cu,Zn and Al,creating a large number of highly active reaction interfaces composed of 0 to+3 valence metal sites.With the help of the interface effect,the optimized Cu_(9)Zn_(1)/Cu_(0.8)Zn_(0.2)Al_(2)O_(4)catalyst achieves a Faradaic efficiency of 88.5% for C_(2+)products at a current density of 400 mA cm^(-2)at-1.15 V versus reversible hydrogen electrode.The in-situ Raman and attenuate total reflectance-infrared absorption spectroscopy(ATR-IRAS) spectra show that the aluminate oxide at the interface significantly enhances the adsorption and activation of CO_(2)and the dissociation of H2O and strengthens the adsorption of CO intermediates,and the alloy promotes the C-C coupling to produce C_(2+)products.This work provides an efficient strategy to construct highly active reaction interfaces for industrial-scale electrochemical CO_(2)RR.
基金the Natural Science Foundation of China (22005250)National Key R D Program of China (2022YFB2502000)FWO (12ZV320N)。
文摘The electrochemical oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) are fundamental processes in a range of energy conversion devices such as fuel cells and metal–air batteries. ORR and OER both have significant activation barriers, which severely limit the overall performance of energy conversion devices that utilize ORR/OER. Meanwhile, ORR is another very important electrochemical reaction involving oxygen that has been widely investigated. ORR occurs in aqueous solutions via two pathways: the direct 4-electron reduction or 2-electron reduction pathways from O_(2) to water(H_2O) or from O_(2) to hydrogen peroxide(H_2O_(2)). Noble metal electrocatalysts are often used to catalyze OER and ORR, despite the fact that noble metal electrocatalysts have certain intrinsic limitations, such as low storage. Thus, it is urgent to develop more active and stable low-cost electrocatalysts, especially for severe environments(e.g., acidic media). Theoretically, an ideal oxygen electrocatalyst should provide adequate binding to oxygen species. Transition metals not belonging to the platinum group metal-based oxides are a low-cost substance that could give a d orbital for oxygen species binding. As a result, transition metal oxides are regarded as a substitute for typical precious metal oxygen electrocatalysts. However, the development of oxide catalysts for oxygen reduction and oxygen evolution reactions still faces significant challenges, e.g., catalytic activity, stability, cost, and reaction mechanism. We discuss the fundamental principles underlying the design of oxide catalysts, including the influence of crystal structure, and electronic structure on their performance. We also discuss the challenges associated with developing oxide catalysts and the potential strategies to overcome these challenges.
基金the National Natural Science Foundation of China(Grant No.82173803,81872847).
文摘Background:Hippocampal damage caused by status epilepticus(SE)can bring about cognitive decline and emotional disorders,which are common clinical comorbidities in patients with epilepsy.It is therefore imperative to develop a novel therapeutic strat-egy for protecting hippocampal damage after SE.Mitochondrial dysfunction is one of contributing factors in epilepsy.Given the therapeutic benefits of mitochondrial replenishment by exogenous mitochondria,we hypothesized that transplantation of mitochondria would be capable of ameliorating hippocampal damage following SE.Methods:Pilocarpine was used to induced SE in mice.SE-generated cognitive de-cline and emotional disorders were determined using novel object recognition,the tail suspension test,and the open field test.SE-induced hippocampal pathology was assessed by quantifying loss of neurons and activation of microglia and astrocytes.The metabolites underlying mitochondrial transplantation were determined using metabonomics.Results:The results showed that peripheral administration of isolated mitochon-dria could improve cognitive deficits and depressive and anxiety-like behaviors.Exogenous mitochondria blunted the production of reactive oxygen species,pro-liferation of microglia and astrocytes,and loss of neurons in the hippocampus.The metabonomic profiles showed that mitochondrial transplantation altered multiple metabolic pathways such as sphingolipid signaling pathway and carbon metabolism.Among potential affected metabolites,mitochondrial transplantation decreased levels of sphingolipid(d18:1/18:0)and methylmalonic acid,and elevated levels of D-fructose-1,6-bisphosphate.Conclusion:To the best of our knowledge,these findings provide the first direct ex-perimental evidence that artificial mitochondrial transplantation is capable of amelio-rating hippocampal damage following SE.These new findings support mitochondrial transplantation as a promising therapeutic strategy for epilepsy-associated psychiat-ric and cognitive disorders.
文摘电催化二氧化碳还原反应(CO_(2)RR)可以将二氧化碳转化为具有高经济价值的碳氢化合物,被认为是实现碳中和并缓解能源危机的一种有潜力的技术.铜(Cu)作为一种最有应用前景的非贵金属催化剂之一,表现出较高的催化CO_(2)RR转化为多碳产物(C_(2+))的活性.然而,电催化CO_(2)还原成C_(2+)产物涉及一个动力学过程缓慢的C-C偶联反应,这导致C_(2+)产物的选择性较低,电流密度低,阻碍了其在工业电解槽中的实际应用.同时,CO_(2)RR产物的选择性不仅取决于热力学速率决定步骤,还取决于传质控制动力学.CO_(2)RR发生在固-气-液三相反应界面,气-液的平衡扩散可以有效抑制析氢竞争反应,进而提高CO_(2)RR的反应效率.本文设计合成了一种富晶界的Cu纳米带催化剂,并构建了气-液平衡扩散的电极结构,用于高效电催化二氧化碳还原制备乙烯(C_(2)H_(4)).以一种碱式碳酸铜(Cu_(2)CO_(3)(OH)_(2))纳米带为前驱体,在原位电化学还原条件下,前驱体中的Cu2+离子获得电子被还原为金属Cu,而释放的CO_(3)2-和OH-混合阴离子调节金属Cu的生长.生成的Cu纳米带由细小的纳米颗粒堆积而成,并暴露出大量的由Cu(111),Cu(200)和Cu(220)晶面形成的富晶界结构(GBs).同时,在CO_(2)RR测试中发现催化剂层的厚度是影响CO_(2)和电解质传质的关键因素.通过调整催化层厚度,CO_(2)和电解质可以同时到达催化剂表面,参与到CO_(2)RR中,实现了气-液平衡扩散,有效抑制了氢析出副反应.在晶界效应和气-液平衡扩散的协同作用下,优化后的电极在电流密度为700 mA cm^(-2)时,对C_(2)H_(4)和C_(2+).产物的法拉第效率分别高达67.2%和82.1%.此外,C_(2)H_(4)的部分电流密度可高达505 mA cm^(-2),高于大多数文献报道的结果.原位拉曼光谱和衰减全内反射表面增强红外吸收光谱结果表明,丰富的晶;界结构增强了CO_(2)在催化剂表面的活化,显著促进了*CO中间体的形成和吸附,加速了C-C偶联过程形成*OCCO和*OCCOH中间体,提高了C_(2)H_(4)和其他C_(2+)产物的产率.综上,本文设计了一种高活性Cu催化剂和电极结构,为高效电催化CO_(2)还原为C_(2)H_(4)等C_(2+)产物提供参考.
