The Si Tian project,designed to utilize 60 telescopes distributed across multiple sites in China,is a next-generation timedomain survey initiative.As a pathfinder for the Si Tian project,the Mini-Si Tian(MST)has been ...The Si Tian project,designed to utilize 60 telescopes distributed across multiple sites in China,is a next-generation timedomain survey initiative.As a pathfinder for the Si Tian project,the Mini-Si Tian(MST)has been proposed and implemented to test the Si Tian’s brain and data pipeline,and to evaluate the feasibility of its technology and science cases.Mounted at the Xinglong Observatory,the MST project comprises three 30 cm telescopes and has been operated since 2022 November.Each telescope of the MST possesses a large field of view,covering 2°.29×1°.53 FOV,and is equipped withg',r'andi'filters,respectively.Acting as the pioneer of the forthcoming Si Tian project,the MST is dedicated to the discovery of variable stars,transients,and outburst events,and has already obtained some interesting scientific results.In this paper,we will summarize the first-two-year operation of the MST project.展开更多
Degrading ciprofloxacin(CIP)-polluted water has recently emerged as an urgent environmental issue.This study introduced mechanochemical treatment(MCT)as an innovative and underexplored approach for the degradation of ...Degrading ciprofloxacin(CIP)-polluted water has recently emerged as an urgent environmental issue.This study introduced mechanochemical treatment(MCT)as an innovative and underexplored approach for the degradation of CIP in water.The influence of various additives(CaO,Fe_(2)O_(3),SiO_(2),Al,and Fe)on CIP degradation efficiency was investigated.Additionally,six types of composite additives(Fe-CaO,Fe-Fe_(2)O_(3),Fe-SiO_(2),Fe-Al,Al-SiO_(2),and Al-CaO)were explored,with the composite of 20%Fe and 80%SiO_(2) exhibiting notable performance.The impacts of additive content,pH value,and co-existing ions on CIP degradation efficiency were investigated.Furthermore,the effectiveness of MCT in degrading other medical pollutants(norfloxacin,ofloxacin,and enrofloxacin)was verified.The transformations and changes in the crystal structure,oxidation state,microstructure,and morphology of the Fe-SiO_(2) composite additive were characterized using X-ray diffraction,X-ray photoelectron spectroscopy,and scanning electron microscopy techniques.This study proposed a sigmoid trend kinetic model(the Delogu model)that better elucidates the MCT process.Three plausible degradation pathways were discussed based on intermediate substance identification and pertinent literature.This study not only establishes a pathway for the facile degradation of CIP pollutants through MCT but also contributes to advancements in wastewater treatment methodologies.展开更多
Moles exhibit highly effective capabilities due to their unique body structures and digging techniques,making them ideal models for biomimetic research.However,a major challenge for mole-inspired robots lies in overco...Moles exhibit highly effective capabilities due to their unique body structures and digging techniques,making them ideal models for biomimetic research.However,a major challenge for mole-inspired robots lies in overcoming resistance in granular media when burrowing with forelimbs.In the absence of effective forepaw design strategies,most robotic designs rely on increased power to enhance performance.To address this issue,this paper employs Resistive Force Theory to optimize mole-inspired forepaws,aiming to enhance burrowing efficiency.By analyzing the relationship between geometric parameters and burrowing forces,we propose several forepaw design variations.Through granular resistance assessments,an effective forepaw configuration is identified and further refined using parameters such as longitudinal and transverse curvature.Subsequently,the Particle Swarm Optimization algorithm is applied to determine the optimal forepaw design.In force-loading tests,the optimized forepaw demonstrated a 79.44%reduction in granular lift force and a 22.55%increase in propulsive force compared with the control group.In robotic burrowing experiments,the optimized forepaw achieved the longest burrow displacement(179.528 mm)and the lowest burrowing lift force(0.9355 mm/s),verifying its effectiveness in reducing the lift force and enhancing the propulsive force.展开更多
2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) is a stoichiometric oxidant that is frequently used in traditional organic synthesis. Recently, the rapid development of organic electrochemistry has led to new advancem...2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) is a stoichiometric oxidant that is frequently used in traditional organic synthesis. Recently, the rapid development of organic electrochemistry has led to new advancements in DDQ-catalyzed C—H bonds functionalization. Moreover, the challenging C—H functionalization of electron-deficient arenes has been achieved through the merger of electrochemical DDQ catalysis and photoirradiation. In addition, the synthetic utility of electrophotochemical DDQ catalysis was further demonstrated by the nucleophilic aromatic substitution (SNAr) reaction of unactivated aryl fluorides. The recent developments in electro- and electrophotochemical DDQ-catalyzed C—H/C—F func- tionalizations with attention to their strategies and mechanistic insights are summarized. It is hoped that this not only deepens the understanding of this field, but also helps relevant researchers expand the application scope of DDQ catalysis.展开更多
1.Introduction The ocean,a vital realm for human existence,encompasses distinct spatial zones,such as the free surface,airspace above the sea,and seabed.It also holds an immense wealth of resources,including oil and g...1.Introduction The ocean,a vital realm for human existence,encompasses distinct spatial zones,such as the free surface,airspace above the sea,and seabed.It also holds an immense wealth of resources,including oil and gas,renewable energy,minerals,and marine biodiversity,forming a crucial component of global life-support systems and representing a valuable asset for human survival and development[1].Moreover,as shown in Fig.1[2],the ocean sectors offer a critical avenue for contributing to many of the 17 United Nations Sustainable Development Goals for global development[3].展开更多
Rice grain size and chalkiness are important traits that influence grain yield and quality,respectively.Mining of genes for grain yield and appearance quality and clarification of their action modes are of great impor...Rice grain size and chalkiness are important traits that influence grain yield and quality,respectively.Mining of genes for grain yield and appearance quality and clarification of their action modes are of great importance in rice breeding.In this study,a rice protein disulfide isomerase-like enzyme PDIL2-3 was characterized.Expression analysis revealed that PDIL2-3 was highly expressed in endosperm and spikelet hulls.The PDIL2-3-cri lines generated by CRISPR/Cas9 technology exhibited a chalky grain phenotype with altered storage substance accumulation and increased grain size and weight,whereas exactly opposite results were obtained for PDIL2-3 overexpression lines.Cytological experiments revealed that PDIL2-3-cri increased rice seed length mainly by increasing the cell number and rice seed width mainly by increasing the cell size in grains,implying that PDIL2-3 regulates the grain size by influencing both cell division and expansion of spikelet hulls.Further flow cytometric analysis validated that PDIL2-3 has a negative effect on cell proliferation,preventing DNA duplication and cell division in spikelet hulls.Moreover,q RT-PCR results showed that the expression levels of genes related to cell cycle and storage substance synthesis were significantly changed in PDIL2-3-cri transgenic lines.Thus,our results indicated that PDIL2-3 plays a pivotal role in influencing grain size and quality of rice by affecting cell division/expansion and storage substance accumulation,providing new insights into the function of PDIL family members in rice and enriching the genetic resources for rice breeding.展开更多
Fucoxanthin,a kind of exclusively algae-derived carotenoids,could reduce lipid content and regulate gut microbiota composition in obese mice,showing potential in preventing hyperlipidemia.This study aimed to illustrat...Fucoxanthin,a kind of exclusively algae-derived carotenoids,could reduce lipid content and regulate gut microbiota composition in obese mice,showing potential in preventing hyperlipidemia.This study aimed to illustrate fucoxanthin efficacy in modulating lipid metabolism in serum and liver of high-fat-induced hyperlipidemia mice,as well as investigate the underlying association with gut microbiota changes.Results showed that fucoxanthin significantly reduced body weight gain and body white fat of the mice.In the serum,total triglycerides(TG),total cholesterol(TC)contents were significantly decreased and high-densitylipoprotein cholesterol levels was significantly upregulated.Moreover,fucoxanthin remarkedly prevented lipid accumulation in the liver.Especially,metabolomics results showed that lipids and lipid-like molecules were significantly downregulated compared with the control,indicating the advance of hepatic lipid metabolism.Bile acids profile in the liver was also greatly changed by fucoxanthin.Meanwhile,fucoxanthin remodeled gut microbiota composition and promoted the relative abundance of Desulfovibrio,Blautia and Clostridia genera.Finally,correlation analysis revealed that these gut microbiota changes were closely related with hepatic metabolites/metabolism and serum lipids.Altogether,this study showed great potential of fucoxanthin in improving serum lipids profile,hepatic lipids and bile acids metabolism of hyperlipidemia mice,which was associated with gut microbiota alteration.展开更多
In recent years,there has been a surge of interest in air-ground collaborative robotics technologies.Our research group designs a novel combination-separation air-ground robot(CSAGR),which exhibits rapid automatic com...In recent years,there has been a surge of interest in air-ground collaborative robotics technologies.Our research group designs a novel combination-separation air-ground robot(CSAGR),which exhibits rapid automatic combination and separation capabilities.During the combination process,contact effects between robots,as well as between robots and the environment,are unavoidable.Therefore,it is essential to conduct detailed and accurate modeling and analysis of the collision impact intensity and transmission pathways within the robotic system to ensure the successful execution of the combination procedure.This paper addresses the intricate surface geometries and multi-point contact challenges present in the contact regions of dual robots by making appropriate modifications to the traditional continuous contact force model and applying equivalent processing techniques.The validity of the developed model is confirmed through comparisons with results obtained from finite element analysis(FEA),which demonstrates its high fidelity.Additionally,the impact of this model on control performance is analyzed within the flight control system,thereby further ensuring the successful completion of the combination process.This research represents a pioneering application and validation of continuous contact theory in the dynamics of collisions within dual robot systems.展开更多
Superelastic martensitic transformation(MT)confers a considerable elastocaloric response to shape memory alloys,but the significant hysteretic loss cripples the energy conversion efficiency.In the present work,large e...Superelastic martensitic transformation(MT)confers a considerable elastocaloric response to shape memory alloys,but the significant hysteretic loss cripples the energy conversion efficiency.In the present work,large elastocaloric effect with high refrigeration efficiency is realized in a polycrystalline Co_(50)V_(35)Ga_(15)Heusler alloy.Experimental results show that the studied alloy undergoes a paramagnetic type MT from L2_(1)cubic austenite to D0_(22)tetragonal martensite with a small thermal hysteresis(ΔT_(hys))of~3 K.By carefully examining the strain rate dependence of superelastic response,it is also found that the stress hysteresis(Δσ_(hys))consists of two components including intrinsic stress hysteresis(Δσ_(hys)^(int.))caused by inherent attribute of MT and extrinsic stress hysteresis(Δσ_(hys)^(ext.))aroused by applied strain rate.Accordingly,we put forward a strain relaxation equation to separate the relative contributions betweenΔσ_(hys)^(int.)andΔσ_(hys)^(ext.)quantitatively,which demonstrates that a smallΔT_(hys)is conducive to substantial decrease inΔσ_(hys)^(int.).Moreover,associated with stress-induced superelastic MT,large reversible adiabatic temperature changes(ΔT_(ad))higher than 11 K are achieved under an applied strain of 6.5%over a temperature range of at least 60 K.With the combination of a large elastocaloric cooling capacity and a low energy dissipation,significant improvements in refrigeration efficiency can be obtained in a wide strain range,being superior to those reported in most of typical elastocaloric materials near room temperature.展开更多
Small-scale rotorcraft unmanned robotic systems(SRURSs) are a kind of unmanned rotorcraft with manipulating devices. This review aims to provide an overview on aerial manipulation of SRURSs nowadays and promote relati...Small-scale rotorcraft unmanned robotic systems(SRURSs) are a kind of unmanned rotorcraft with manipulating devices. This review aims to provide an overview on aerial manipulation of SRURSs nowadays and promote relative research in the future. In the past decade, aerial manipulation of SRURSs has attracted the interest of researchers globally. This paper provides a literature review of the last 10 years(2008–2017) on SRURSs, and details achievements and challenges. Firstly, the definition, current state, development, classification, and challenges of SRURSs are introduced. Then, related papers are organized into two topical categories: mechanical structure design, and modeling and control. Following this, research groups involved in SRURS research and their major achievements are summarized and classified in the form of tables. The research groups are introduced in detail from seven parts. Finally, trends and challenges are compiled and presented to serve as a resource for researchers interested in aerial manipulation of SRURSs. The problem,trends, and challenges are described from three aspects. Conclusions of the paper are presented,and the future of SRURSs is discussed to enable further research interests.展开更多
OBJECTIVE： Few studies have investigated the ef- fects produced by combinations of polysaccharides and chemotherapeutic drugs in cancer treatment. We hypothesized that a combination of polysaccha- rides （COP） from ...OBJECTIVE： Few studies have investigated the ef- fects produced by combinations of polysaccharides and chemotherapeutic drugs in cancer treatment. We hypothesized that a combination of polysaccha- rides （COP） from Lentinus edodes and Tricholoma matsutake would improve the efficacy of 5-fluoro- uracil （5-FU）-mediated inhibition of H22 cell growth. METHODS： Mice were injected H22 cells and then treated with either 5-FU, polysaccharides from Tri- choloma matsutake （PTM）, polysaccharides from Lentinus edodes （PL）, PTM ＋ PL, 5-FU ＋ PTM, 5-FU ＋ PL, or 5-FU ＋ COR The tumor weight and volume, and splenic CD4 ＋ and CD8 ＋ T cell frequencies, were determined. Additionally, splenic natural killer （NK） cell and cytotoxic T lymphocyte （CTL） activities were assessed and the serum levels of tumor necro- sis factor-a （TNF-a）, Interleukin-2 （IL-2）, and Interfer- on-y （IFN-y） were measured. RESULTS： Compared with mice from the control,5-FU, PL, PTM, PTM ＋ PL, 5-FU ＋ PL, and 5-FU ＋ PTM groups, mice treated with 5-FU ＋ COP showed： （a） significantly reduced tumor weight and volume （P〈 0.05）, （b） significantly higher serum levels of TNF-α, IL-2, and IFN-y （P〈0.05）, （c） significantly increased CD4＋ and CD8＋ 1 cell frequencies in the spleen （P〈 0.05）, and （d） significantly increased splenic NK cell and CTL activities （P〈0.05）. The tumor weight and volume in mice treated with 5-FU＋PL or 5-FU＋PTM were significantly reduced compared with mice treated with 5-FU alone （P〈0.05）. Serum levels of TNF-α, 11.-2, and IFN-y, frequencies of CD4 ＋ and CD8＋ T cells in the spleen, and splenic NK and CTL activities were also significantly increased in mice treated with 5-FU＋PL or 5-FU＋PTM compared with mice treated with 5-FU alone （P〈0.05）. CONCLUSION： Polysaccharides from Lentinus edodes and Tricholoma matsutake could enhance the efficacy of 5-FU-mediated H22 cell growth inhi- bition.展开更多
In recent years,formation control of multi-agent has been a significant research subject in the field of cooperative control.However,previous works have mainly concentrated on formation control for simple point-mass m...In recent years,formation control of multi-agent has been a significant research subject in the field of cooperative control.However,previous works have mainly concentrated on formation control for simple point-mass model and linear model.In contrast,this paper presents a novel cooperative algorithm for multiple air vehicles formation control,which aims to devise a control strategy based on guidance route to achieve precisely coordinated formation control for a group of fixed-wing aircraft in a complex task environment.The proposed method introduces the leader-follower structure for effective organization of the multi-agent coordination.Moreover,the Partial Integrated Formation and Control(PIFC)is adopted to design the control law for Guidance-Route based Formation Control(GRFC).Additionally,the proposed approach designs two guidance-route generation strategies for two special situations to demonstrate the effectiveness of GRFC in complex task environments.Theoretical analysis reveals that the proposed control protocol for guidance command can ensure the overall stability and tracking accuracy of the system.Numerical simulations are performed to illustrate the theoretical results,and verify that the proposed approach can achieve coordinated formation control precisely in a complex task environment.展开更多
The Weibullian behavior of single grain crushing strength was investigated experimentally and numerically with the aim of enhancing the understanding of rock grain breakage.The morphologies of pebble grains were obtai...The Weibullian behavior of single grain crushing strength was investigated experimentally and numerically with the aim of enhancing the understanding of rock grain breakage.The morphologies of pebble grains were obtained using white light 3D laser scanning and image processing.A grain shape library was constructed for grain shape analysis with different shape descriptors.The use of the shape library and grain stability analysis is discussed for a suggested procedure to rotate a grain to its most stable configuration.Single grain crushing tests were performed for 30 pebbles to obtain force-displacement curves and fracture patterns.Each grain was compressed diametrically between flat platens.As expected,the values of the stress at bulk fracture follow a Weibull distribution.A procedure for generating crushable agglomerates with realistic particle shapes was demonstrated,which was accomplished in the discrete element modeling(DEM)of the single grain crushing test.The work presented here is novel in that both the heterogeneous micro-structures and randomly distributed flaws are considered.The DEM results demonstrate that the proposed modeling approach and calibrated parameters are reliable and can reflect the crushing behavior of rock pebbles.Finally,three parametric studies were presented evaluating the effects of micro-crack density,micro-crack disorder,and grain morphology on the Weibullian behavior of the crushing strength,none of which has previously been thoroughly considered.These three studies provide a deeper insight into the origin of the Weibullian behavior of single grain crushing strength.展开更多
Climate change significantly impacts forest ecosystems in arid and semi-arid regions.However,spatiotemporal patterns of climate-sensitive changes in individual tree growth under increased climate warming and precipita...Climate change significantly impacts forest ecosystems in arid and semi-arid regions.However,spatiotemporal patterns of climate-sensitive changes in individual tree growth under increased climate warming and precipitation in north-west China is unclear.The dendrochronological method was used to study climate response sensitivity of radial growth of Picea schrenkiana from 158 trees at six sites during 1990-2020.The results show that climate warming and increased precipitation significantly promoted the growth of trees.The response to temperature first increased,then decreased.However,the response to increased precipitation and the self-calibrating Palmer Drought Severity Index(scPDSI)increased significantly.In most areas of the Tianshan Mountains,the proportion of trees under increased precipitation and scPDSI positive response was relatively high.Over time,small-diameter trees were strongly affected by drought stress.It is predicted that under continuous warming and increased precipitation,trees in most areas of the Tianshan Mountains,especially those with small diameters,will be more affected by precipitation.展开更多
The previous research regarding the gait planning of quadruped robot focuses on the sequence for lifting o and placing the feet, but neglects the influence of body height. However, body height a ects gait performance ...The previous research regarding the gait planning of quadruped robot focuses on the sequence for lifting o and placing the feet, but neglects the influence of body height. However, body height a ects gait performance significantly, such as in terms of the stride length and stability margin. We herein study the performance of a quadruped robot using the equivalent mechanism concept based on metamorphosis. Assuming the constraints between standing feet and the ground with hinges, the ground, standing legs and robot body are considered as a parallel mechanism, and each swing leg is regarded as a typical serial manipulator. The equivalent mechanism varies while the robot moves on the ground. One gait cycle is divided into several periods, including step forward stages and switching stages. There exists a specific equivalent mechanism corresponding to each gait period. The robot's locomotion can be regarded as the motion of these series of equivalent mechanisms. The kinematics model and simplified model of the equivalent mechanism is established. A new definition of the multilegged robot stability margin, based on friction coe cient, is presented to evaluate the robot stability. The stable workspaces of the equivalent mechanism in the step forward stage of trotting gait under di erent friction coe cients are analyzed. The stride length of the robots is presented by analyzing the relationship between the stable workspaces of the equivalent mechanisms of two adjacent step forward stages in one gait cycle. The simulation results show that the stride length is larger with increasing friction coe cient. We herein propose a new method based on metamorphosis, and an equivalent mechanism to analyze the stability margin and stable workspace of the multilegged robot.展开更多
基金supported by the National Key R&D Program of China(grant No.2023YFA1608304 and No.2023YFA1608300)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0550100 and XDB0550000)the National Natural Science Foundation of China(NSFC,grant Nos.12090041,12090040,11903054,12422303,and 12261141690)。
文摘The Si Tian project,designed to utilize 60 telescopes distributed across multiple sites in China,is a next-generation timedomain survey initiative.As a pathfinder for the Si Tian project,the Mini-Si Tian(MST)has been proposed and implemented to test the Si Tian’s brain and data pipeline,and to evaluate the feasibility of its technology and science cases.Mounted at the Xinglong Observatory,the MST project comprises three 30 cm telescopes and has been operated since 2022 November.Each telescope of the MST possesses a large field of view,covering 2°.29×1°.53 FOV,and is equipped withg',r'andi'filters,respectively.Acting as the pioneer of the forthcoming Si Tian project,the MST is dedicated to the discovery of variable stars,transients,and outburst events,and has already obtained some interesting scientific results.In this paper,we will summarize the first-two-year operation of the MST project.
基金supported by the National Key Research and Development Program of China(Grants No.2021YFC2902701,2021YFC2902100,2019YFC1805600,2018YFC1801800)the Fundamental Research Funds for the Central Universities(Grant No.2022QN1051)+1 种基金the Shandong Provincial Major Science and Technology Innovation Project(Grant No.2021CXGC011206)the Key Project of the National Natural Science Foundation of China(Grant No.52130402).
文摘Degrading ciprofloxacin(CIP)-polluted water has recently emerged as an urgent environmental issue.This study introduced mechanochemical treatment(MCT)as an innovative and underexplored approach for the degradation of CIP in water.The influence of various additives(CaO,Fe_(2)O_(3),SiO_(2),Al,and Fe)on CIP degradation efficiency was investigated.Additionally,six types of composite additives(Fe-CaO,Fe-Fe_(2)O_(3),Fe-SiO_(2),Fe-Al,Al-SiO_(2),and Al-CaO)were explored,with the composite of 20%Fe and 80%SiO_(2) exhibiting notable performance.The impacts of additive content,pH value,and co-existing ions on CIP degradation efficiency were investigated.Furthermore,the effectiveness of MCT in degrading other medical pollutants(norfloxacin,ofloxacin,and enrofloxacin)was verified.The transformations and changes in the crystal structure,oxidation state,microstructure,and morphology of the Fe-SiO_(2) composite additive were characterized using X-ray diffraction,X-ray photoelectron spectroscopy,and scanning electron microscopy techniques.This study proposed a sigmoid trend kinetic model(the Delogu model)that better elucidates the MCT process.Three plausible degradation pathways were discussed based on intermediate substance identification and pertinent literature.This study not only establishes a pathway for the facile degradation of CIP pollutants through MCT but also contributes to advancements in wastewater treatment methodologies.
基金financially supported in-part by the National Natural Science Foundation of China(52275011)the Natural Science Foundation of Guangdong Province(2023B1515020080)+3 种基金the Natural Science Foundation of Guangzhou(2024A04J2552)the Fundamental Research Funds for the Central Universities,the Young Elite Scientists Sponsorship Program by the China Association for Science and Technology(CAST)(2021QNRC001)the Guangdong Basic and Applied Basic Research Foundation(Grant No.2023A1515011253)the Higher Education Institution Featured Innovation Project of Department of Education of Guangdong Province(GrantNo.2023KTSCX138).
文摘Moles exhibit highly effective capabilities due to their unique body structures and digging techniques,making them ideal models for biomimetic research.However,a major challenge for mole-inspired robots lies in overcoming resistance in granular media when burrowing with forelimbs.In the absence of effective forepaw design strategies,most robotic designs rely on increased power to enhance performance.To address this issue,this paper employs Resistive Force Theory to optimize mole-inspired forepaws,aiming to enhance burrowing efficiency.By analyzing the relationship between geometric parameters and burrowing forces,we propose several forepaw design variations.Through granular resistance assessments,an effective forepaw configuration is identified and further refined using parameters such as longitudinal and transverse curvature.Subsequently,the Particle Swarm Optimization algorithm is applied to determine the optimal forepaw design.In force-loading tests,the optimized forepaw demonstrated a 79.44%reduction in granular lift force and a 22.55%increase in propulsive force compared with the control group.In robotic burrowing experiments,the optimized forepaw achieved the longest burrow displacement(179.528 mm)and the lowest burrowing lift force(0.9355 mm/s),verifying its effectiveness in reducing the lift force and enhancing the propulsive force.
文摘2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) is a stoichiometric oxidant that is frequently used in traditional organic synthesis. Recently, the rapid development of organic electrochemistry has led to new advancements in DDQ-catalyzed C—H bonds functionalization. Moreover, the challenging C—H functionalization of electron-deficient arenes has been achieved through the merger of electrochemical DDQ catalysis and photoirradiation. In addition, the synthetic utility of electrophotochemical DDQ catalysis was further demonstrated by the nucleophilic aromatic substitution (SNAr) reaction of unactivated aryl fluorides. The recent developments in electro- and electrophotochemical DDQ-catalyzed C—H/C—F func- tionalizations with attention to their strategies and mechanistic insights are summarized. It is hoped that this not only deepens the understanding of this field, but also helps relevant researchers expand the application scope of DDQ catalysis.
基金supported by the National Natural Science Foun-dation of China(52088102)the KeyR&DProgram of Shandong Province,China(2021ZLGX04).
文摘1.Introduction The ocean,a vital realm for human existence,encompasses distinct spatial zones,such as the free surface,airspace above the sea,and seabed.It also holds an immense wealth of resources,including oil and gas,renewable energy,minerals,and marine biodiversity,forming a crucial component of global life-support systems and representing a valuable asset for human survival and development[1].Moreover,as shown in Fig.1[2],the ocean sectors offer a critical avenue for contributing to many of the 17 United Nations Sustainable Development Goals for global development[3].
基金supported in part by grants from the National Natural Science Foundation of China(32472141,32101746,and 32102231)Natural Science Foundation of Hubei Province(JCZRLH202500540,2021CFB033,and 2022CFB393)。
文摘Rice grain size and chalkiness are important traits that influence grain yield and quality,respectively.Mining of genes for grain yield and appearance quality and clarification of their action modes are of great importance in rice breeding.In this study,a rice protein disulfide isomerase-like enzyme PDIL2-3 was characterized.Expression analysis revealed that PDIL2-3 was highly expressed in endosperm and spikelet hulls.The PDIL2-3-cri lines generated by CRISPR/Cas9 technology exhibited a chalky grain phenotype with altered storage substance accumulation and increased grain size and weight,whereas exactly opposite results were obtained for PDIL2-3 overexpression lines.Cytological experiments revealed that PDIL2-3-cri increased rice seed length mainly by increasing the cell number and rice seed width mainly by increasing the cell size in grains,implying that PDIL2-3 regulates the grain size by influencing both cell division and expansion of spikelet hulls.Further flow cytometric analysis validated that PDIL2-3 has a negative effect on cell proliferation,preventing DNA duplication and cell division in spikelet hulls.Moreover,q RT-PCR results showed that the expression levels of genes related to cell cycle and storage substance synthesis were significantly changed in PDIL2-3-cri transgenic lines.Thus,our results indicated that PDIL2-3 plays a pivotal role in influencing grain size and quality of rice by affecting cell division/expansion and storage substance accumulation,providing new insights into the function of PDIL family members in rice and enriching the genetic resources for rice breeding.
基金funded by the National Natural Science Foundation of China(31901624)the Key-Area Research and Development Program of Guangdong Province(2018B020206001)+2 种基金Guangdong Province Zhujiang Talent Program(2019ZT08H476)Shenzhen Science and Technology Program(KQTD20180412181334790)the Innovation Team Project of Universities in Guangdong Province(2020KCXTD023)。
文摘Fucoxanthin,a kind of exclusively algae-derived carotenoids,could reduce lipid content and regulate gut microbiota composition in obese mice,showing potential in preventing hyperlipidemia.This study aimed to illustrate fucoxanthin efficacy in modulating lipid metabolism in serum and liver of high-fat-induced hyperlipidemia mice,as well as investigate the underlying association with gut microbiota changes.Results showed that fucoxanthin significantly reduced body weight gain and body white fat of the mice.In the serum,total triglycerides(TG),total cholesterol(TC)contents were significantly decreased and high-densitylipoprotein cholesterol levels was significantly upregulated.Moreover,fucoxanthin remarkedly prevented lipid accumulation in the liver.Especially,metabolomics results showed that lipids and lipid-like molecules were significantly downregulated compared with the control,indicating the advance of hepatic lipid metabolism.Bile acids profile in the liver was also greatly changed by fucoxanthin.Meanwhile,fucoxanthin remodeled gut microbiota composition and promoted the relative abundance of Desulfovibrio,Blautia and Clostridia genera.Finally,correlation analysis revealed that these gut microbiota changes were closely related with hepatic metabolites/metabolism and serum lipids.Altogether,this study showed great potential of fucoxanthin in improving serum lipids profile,hepatic lipids and bile acids metabolism of hyperlipidemia mice,which was associated with gut microbiota alteration.
基金Supported by National Natural Science Foundation of China(Grant Nos.T2121003 and 91748201).
文摘In recent years,there has been a surge of interest in air-ground collaborative robotics technologies.Our research group designs a novel combination-separation air-ground robot(CSAGR),which exhibits rapid automatic combination and separation capabilities.During the combination process,contact effects between robots,as well as between robots and the environment,are unavoidable.Therefore,it is essential to conduct detailed and accurate modeling and analysis of the collision impact intensity and transmission pathways within the robotic system to ensure the successful execution of the combination procedure.This paper addresses the intricate surface geometries and multi-point contact challenges present in the contact regions of dual robots by making appropriate modifications to the traditional continuous contact force model and applying equivalent processing techniques.The validity of the developed model is confirmed through comparisons with results obtained from finite element analysis(FEA),which demonstrates its high fidelity.Additionally,the impact of this model on control performance is analyzed within the flight control system,thereby further ensuring the successful completion of the combination process.This research represents a pioneering application and validation of continuous contact theory in the dynamics of collisions within dual robot systems.
基金supported by the National Natural Science Foundation of China(Nos.52261035,52201223,52371006,52371194)Applied Basic Projects of Yunnan province(No.202101BA070001-233).
文摘Superelastic martensitic transformation(MT)confers a considerable elastocaloric response to shape memory alloys,but the significant hysteretic loss cripples the energy conversion efficiency.In the present work,large elastocaloric effect with high refrigeration efficiency is realized in a polycrystalline Co_(50)V_(35)Ga_(15)Heusler alloy.Experimental results show that the studied alloy undergoes a paramagnetic type MT from L2_(1)cubic austenite to D0_(22)tetragonal martensite with a small thermal hysteresis(ΔT_(hys))of~3 K.By carefully examining the strain rate dependence of superelastic response,it is also found that the stress hysteresis(Δσ_(hys))consists of two components including intrinsic stress hysteresis(Δσ_(hys)^(int.))caused by inherent attribute of MT and extrinsic stress hysteresis(Δσ_(hys)^(ext.))aroused by applied strain rate.Accordingly,we put forward a strain relaxation equation to separate the relative contributions betweenΔσ_(hys)^(int.)andΔσ_(hys)^(ext.)quantitatively,which demonstrates that a smallΔT_(hys)is conducive to substantial decrease inΔσ_(hys)^(int.).Moreover,associated with stress-induced superelastic MT,large reversible adiabatic temperature changes(ΔT_(ad))higher than 11 K are achieved under an applied strain of 6.5%over a temperature range of at least 60 K.With the combination of a large elastocaloric cooling capacity and a low energy dissipation,significant improvements in refrigeration efficiency can be obtained in a wide strain range,being superior to those reported in most of typical elastocaloric materials near room temperature.
基金supported by the National Natural Science Foundation of China (Nos. 91748201 and 51505014)
文摘Small-scale rotorcraft unmanned robotic systems(SRURSs) are a kind of unmanned rotorcraft with manipulating devices. This review aims to provide an overview on aerial manipulation of SRURSs nowadays and promote relative research in the future. In the past decade, aerial manipulation of SRURSs has attracted the interest of researchers globally. This paper provides a literature review of the last 10 years(2008–2017) on SRURSs, and details achievements and challenges. Firstly, the definition, current state, development, classification, and challenges of SRURSs are introduced. Then, related papers are organized into two topical categories: mechanical structure design, and modeling and control. Following this, research groups involved in SRURS research and their major achievements are summarized and classified in the form of tables. The research groups are introduced in detail from seven parts. Finally, trends and challenges are compiled and presented to serve as a resource for researchers interested in aerial manipulation of SRURSs. The problem,trends, and challenges are described from three aspects. Conclusions of the paper are presented,and the future of SRURSs is discussed to enable further research interests.
基金Supported by Department of Science and Technology of Jilin Province(No.yyzx201123-2No.20130522056JH)
文摘OBJECTIVE： Few studies have investigated the ef- fects produced by combinations of polysaccharides and chemotherapeutic drugs in cancer treatment. We hypothesized that a combination of polysaccha- rides （COP） from Lentinus edodes and Tricholoma matsutake would improve the efficacy of 5-fluoro- uracil （5-FU）-mediated inhibition of H22 cell growth. METHODS： Mice were injected H22 cells and then treated with either 5-FU, polysaccharides from Tri- choloma matsutake （PTM）, polysaccharides from Lentinus edodes （PL）, PTM ＋ PL, 5-FU ＋ PTM, 5-FU ＋ PL, or 5-FU ＋ COR The tumor weight and volume, and splenic CD4 ＋ and CD8 ＋ T cell frequencies, were determined. Additionally, splenic natural killer （NK） cell and cytotoxic T lymphocyte （CTL） activities were assessed and the serum levels of tumor necro- sis factor-a （TNF-a）, Interleukin-2 （IL-2）, and Interfer- on-y （IFN-y） were measured. RESULTS： Compared with mice from the control,5-FU, PL, PTM, PTM ＋ PL, 5-FU ＋ PL, and 5-FU ＋ PTM groups, mice treated with 5-FU ＋ COP showed： （a） significantly reduced tumor weight and volume （P〈 0.05）, （b） significantly higher serum levels of TNF-α, IL-2, and IFN-y （P〈0.05）, （c） significantly increased CD4＋ and CD8＋ 1 cell frequencies in the spleen （P〈 0.05）, and （d） significantly increased splenic NK cell and CTL activities （P〈0.05）. The tumor weight and volume in mice treated with 5-FU＋PL or 5-FU＋PTM were significantly reduced compared with mice treated with 5-FU alone （P〈0.05）. Serum levels of TNF-α, 11.-2, and IFN-y, frequencies of CD4 ＋ and CD8＋ T cells in the spleen, and splenic NK and CTL activities were also significantly increased in mice treated with 5-FU＋PL or 5-FU＋PTM compared with mice treated with 5-FU alone （P〈0.05）. CONCLUSION： Polysaccharides from Lentinus edodes and Tricholoma matsutake could enhance the efficacy of 5-FU-mediated H22 cell growth inhi- bition.
基金co-supported by the National Natural Science Foundation of China(Nos.61773031 and 61573042)Graduate Innovation Practice Fund of Beihang University,China(No.YCSJ-01-201915)funded by the State Key Laboratory of Software Development Environment,China.
文摘In recent years,formation control of multi-agent has been a significant research subject in the field of cooperative control.However,previous works have mainly concentrated on formation control for simple point-mass model and linear model.In contrast,this paper presents a novel cooperative algorithm for multiple air vehicles formation control,which aims to devise a control strategy based on guidance route to achieve precisely coordinated formation control for a group of fixed-wing aircraft in a complex task environment.The proposed method introduces the leader-follower structure for effective organization of the multi-agent coordination.Moreover,the Partial Integrated Formation and Control(PIFC)is adopted to design the control law for Guidance-Route based Formation Control(GRFC).Additionally,the proposed approach designs two guidance-route generation strategies for two special situations to demonstrate the effectiveness of GRFC in complex task environments.Theoretical analysis reveals that the proposed control protocol for guidance command can ensure the overall stability and tracking accuracy of the system.Numerical simulations are performed to illustrate the theoretical results,and verify that the proposed approach can achieve coordinated formation control precisely in a complex task environment.
基金financial support by the National Key R&D Program of China (No. 2017YFC0404801)National Natural Science Foundation of China (Grant Nos. 51579193 and 51779194)Major Special Project of Guizhou Science Cooperation (No.[2017]3005-2)
文摘The Weibullian behavior of single grain crushing strength was investigated experimentally and numerically with the aim of enhancing the understanding of rock grain breakage.The morphologies of pebble grains were obtained using white light 3D laser scanning and image processing.A grain shape library was constructed for grain shape analysis with different shape descriptors.The use of the shape library and grain stability analysis is discussed for a suggested procedure to rotate a grain to its most stable configuration.Single grain crushing tests were performed for 30 pebbles to obtain force-displacement curves and fracture patterns.Each grain was compressed diametrically between flat platens.As expected,the values of the stress at bulk fracture follow a Weibull distribution.A procedure for generating crushable agglomerates with realistic particle shapes was demonstrated,which was accomplished in the discrete element modeling(DEM)of the single grain crushing test.The work presented here is novel in that both the heterogeneous micro-structures and randomly distributed flaws are considered.The DEM results demonstrate that the proposed modeling approach and calibrated parameters are reliable and can reflect the crushing behavior of rock pebbles.Finally,three parametric studies were presented evaluating the effects of micro-crack density,micro-crack disorder,and grain morphology on the Weibullian behavior of the crushing strength,none of which has previously been thoroughly considered.These three studies provide a deeper insight into the origin of the Weibullian behavior of single grain crushing strength.
基金funded by the National Natural Science Foundation of China(No.31971460 and 32271646)the National Key Research and Development Program of China(2021YFD2200401)。
文摘Climate change significantly impacts forest ecosystems in arid and semi-arid regions.However,spatiotemporal patterns of climate-sensitive changes in individual tree growth under increased climate warming and precipitation in north-west China is unclear.The dendrochronological method was used to study climate response sensitivity of radial growth of Picea schrenkiana from 158 trees at six sites during 1990-2020.The results show that climate warming and increased precipitation significantly promoted the growth of trees.The response to temperature first increased,then decreased.However,the response to increased precipitation and the self-calibrating Palmer Drought Severity Index(scPDSI)increased significantly.In most areas of the Tianshan Mountains,the proportion of trees under increased precipitation and scPDSI positive response was relatively high.Over time,small-diameter trees were strongly affected by drought stress.It is predicted that under continuous warming and increased precipitation,trees in most areas of the Tianshan Mountains,especially those with small diameters,will be more affected by precipitation.
基金Supported by National Natural Science Foundation of China(Grant Nos.51775011,91748201)
文摘The previous research regarding the gait planning of quadruped robot focuses on the sequence for lifting o and placing the feet, but neglects the influence of body height. However, body height a ects gait performance significantly, such as in terms of the stride length and stability margin. We herein study the performance of a quadruped robot using the equivalent mechanism concept based on metamorphosis. Assuming the constraints between standing feet and the ground with hinges, the ground, standing legs and robot body are considered as a parallel mechanism, and each swing leg is regarded as a typical serial manipulator. The equivalent mechanism varies while the robot moves on the ground. One gait cycle is divided into several periods, including step forward stages and switching stages. There exists a specific equivalent mechanism corresponding to each gait period. The robot's locomotion can be regarded as the motion of these series of equivalent mechanisms. The kinematics model and simplified model of the equivalent mechanism is established. A new definition of the multilegged robot stability margin, based on friction coe cient, is presented to evaluate the robot stability. The stable workspaces of the equivalent mechanism in the step forward stage of trotting gait under di erent friction coe cients are analyzed. The stride length of the robots is presented by analyzing the relationship between the stable workspaces of the equivalent mechanisms of two adjacent step forward stages in one gait cycle. The simulation results show that the stride length is larger with increasing friction coe cient. We herein propose a new method based on metamorphosis, and an equivalent mechanism to analyze the stability margin and stable workspace of the multilegged robot.
