The number of operational satellites and debris objects in the valuable geosynchronous ring has increased steadily over time such that active debris removal missions are necessary to ensure long-term stability. These ...The number of operational satellites and debris objects in the valuable geosynchronous ring has increased steadily over time such that active debris removal missions are necessary to ensure long-term stability. These objects are very large and tumbling, making any mission scenarios requiring physical contact very challenging. In the last 10 years, the concept of using an electrostatic tractor has been investigated extensively. With the electrostatic tractor concept, active charge emission is employed to simultaneously charge the tug or services vehicle, while aiming the charge exhaust onto the passive space debris object to charge it as well. The resulting electrostatic force has been explored to actuate this debris object to a disposal orbit or to detumble the object, all without physical contact. This paper provides a survey of the related research and reviews the charging concepts, the associated electrostatic force and torque modeling, and the feedback control developments, as well as the charge sensing research.展开更多
Purpose It is well recognised that injury prevention training can reduce injury incidence,however current coach education pathways do not provide grass-root coaches with the knowledge and confidence to deliver such tr...Purpose It is well recognised that injury prevention training can reduce injury incidence,however current coach education pathways do not provide grass-root coaches with the knowledge and confidence to deliver such training to youth players.The aim of this study was to explore differences in knowledge,understanding,attitude and confidence to deliver such injury prevention training in three European countries.Methods A total of 269 grass-root soccer coaches from 3 European countries(Czech Republic,UK,Spain)were recruited for this study.A validated questionnaire exploring knowledge,understanding,attitude towards and confidence to deliver youth injury prevention training was completed prior to a 2 h workshop on injury prevention training.Differences between countries was examined using Bayesian factors to quantify the evidence for and against the hypothesis of independence(H0)by assuming a Poisson sampling scheme(as there was no a priori restriction on any cell count,nor on the grand total)(BF10 Poisson).Results Current knowledge,attitude and confidence to deliver injury prevention training to youth players was poor across all three European countries.Relatively few coaches were currently using injury prevention training in their coaching sessions(23%).There were some country specific differences for attitude towards injury prevention training and confidence to deliver injury training,with Spanish coaches reporting a more positive attitude and confidence to deliver such training.Significantly fewer coaches in the UK were using injury prevention training compared to coaches in Spain and the Czech Republic.Conclusion As coaches identified a need for coach education and few were delivering injury prevention training,there is a clear need to embed and implement this programme into the grassroots coaching framework of sports governing bodies to improve adoption,implementation and maintenance.展开更多
The Japanese quail(Coturnix japonica) are popular both as an alternative protein source and as a model of choice for scientific research in several disciplines. There is limited published information on the histologic...The Japanese quail(Coturnix japonica) are popular both as an alternative protein source and as a model of choice for scientific research in several disciplines. There is limited published information on the histological features of the intestinal tract of Japanese quail. The only comprehensive reference is a book published in 1969. This study aims to fill that niche by providing a reference of general histological features of the Japanese quail, covering all the main sections of the intestinal tract. Both light and scanning electron microscope(SEM) images are presented. Results showed that the Japanese quail intestinal tract is very similar to that of the chicken with the exception of the luminal koilin membrane of the gizzard. Scanning electron microscopic photomicrographs show that in the Japanese quail koilin vertical rods are tightly packed together in a uniform manner making a carpet-like appearance. This differs in chicken where the conformations of vertical rods are arranged in clusters.展开更多
Background： The broiler industry has undergone intense genetic selection over the past 50 yr. resulting in improvements for growth and feed efficiency, however, significant variation remains for performance and growt...Background： The broiler industry has undergone intense genetic selection over the past 50 yr. resulting in improvements for growth and feed efficiency, however, significant variation remains for performance and growth traits. Production improvements have been coupled with unfavourable metabolic consequences, including immunological trade-offs for growth, and excess fat deposition. To determine whether interactions between fatty acid（FA） metabolism and innate immunity may be associated with performance variations commonly seen within commercial broiler flocks, total carcass lipid %, carcass and blood FA composition, as wel as genes involved with FA metabolism, immunity and cel ular stress were investigated in male birds of a broiler strain, layer strain and F1 layer × broiler cross at d 14 post hatch. Heterophil：lymphocyte ratios, relative organ weights and bodyweight data were also compared.Results： Broiler bodyweight（n = 12） was four times that of layers（n = 12） by d 14 and had significantly higher carcass fat percentage compared to the cross（n = 6; P = 0.002） and layers（P = 0.017） which were not significantly different from each other（P = 0.523）. The carcass and whole blood FA analysis revealed differences in the FA composition between the three groups indicating altered FA metabolism, despite al being raised on the same diet. Genes associated with FA synthesis andβ-oxidation were upregulated in the broilers compared to the layers indicating a net overal increase in FA metabolism,which may be driven by the larger relative liver size as a percentage of bodyweight in the broilers. Genes involved in innate immunity such as TLR2 and TLR4, as wel as organel e stress indicators ERN1 and XBP1 were found to be nonsignificant, with the exception of high expression levels of XBP1 in layers compared to the cross and broilers. Additional y there was no difference in heterophil： lymphocytes between any of the birds.Conclusions： The results provide evidence that genetic selection may be as展开更多
Chemoselective hydrodeoxygenation of vanillin is of great importance in converting biomass into high value-added chemicals.Herein,we describe a facile photochemical route to access palladium single atoms and clusters ...Chemoselective hydrodeoxygenation of vanillin is of great importance in converting biomass into high value-added chemicals.Herein,we describe a facile photochemical route to access palladium single atoms and clusters supported on silicoaluminophosphate-31(SAPO-31)as a highly active,chemoselective,and reusable catalyst for hydrodeoxygenation of vanillin.Characterizations by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy,extended X-ray absorption fine structure measurement,and CO-absorbed diffuse reflectance infrared Fourier transform spectroscopy reveal the atomically dispersed palladium single atoms and clusters are loosely bonded and randomly dispersed,without forming strong palladium-palladium metallic bonding,over the SAPO-31 support.This catalyst,with a full metal availability to the reactants,exhibits exceptional catalytic activity(TOF:3,000 h^(−1),Yield:>99%)in the hydrodeoxygenation of vanillin toward 2-methoxy-4-methylphenol(MMP)under mild conditions(1 atm,80°C,30 min),along with excellent stability,scalability(up to 100-fold),and wide substrate scope.The superior catalytic performance can be attributed to the synergistic effect of the positively charged palladium single atoms and fully exposed clusters,as well as the strong metal-support interactions.This work may offer a new avenue for the design and synthesis of fully exposed metal catalysts with targeted functionalities.展开更多
Catalytic C−H bond activation is one of the backbones of the chemical industry.Supported metal subnanoclusters consisting of a few atoms have shown attractive properties for heterogeneous catalysis.However,the creatio...Catalytic C−H bond activation is one of the backbones of the chemical industry.Supported metal subnanoclusters consisting of a few atoms have shown attractive properties for heterogeneous catalysis.However,the creation of such catalyst systems with high activity and excellent anti-sintering ability remains a grand challenge.Here,we report on alkali ion-promoted Pd subnanoclusters supported over defectiveγ-Al_(2)O_(3) nanosheets,which display exceptional catalytic activity for C−H bond activation in the benzene oxidation reaction.The presence of Pd subnanoclusters is verified by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy,X-ray absorption spectroscopy,and X-ray photoelectron spectroscopy.This catalyst shows excellent catalytic activity,with a turnover frequency of 280 h^(−1) and yield of 98%,in benzene oxidation reaction to give phenol under mild conditions.Moreover,the introduction of alkali ion greatly retards the diffusion and migration of metal atoms when tested under high-temperature sintering conditions.Density functional theory(DFT)calculations reveal that the addition of alkali ion to Pd nanoclusters can significantly impact the catalyst’s structure and electronic properties,and eventually promote its activity and stability.This work sheds light on the facile and scalable synthesis of highly active and stable catalyst systems with alkali additives for industrially important reactions.展开更多
The stabilization of non-precious metals as isolated active sites with high loading density over nitrogendoped carbon materials is essential for realizing the industrial application of single atom catalysts.However,ac...The stabilization of non-precious metals as isolated active sites with high loading density over nitrogendoped carbon materials is essential for realizing the industrial application of single atom catalysts.However,achieving high loading of single cobalt active sites with greatly enhanced oxygen reduction reaction(ORR)activity and stability remains challenging.Here,an efficient approach was described to create a single atom cobalt electrocatalyst(Co SAs/NC)which possesses enhanced mesoporosity and specific surface area that greatly favor the mass transportation and exposure of accessible active sites.The electronic structure of the catalyst by the strong metal-support interaction has been elucidated through experimental characterizations and theoretical calculations.Due to dramatically enhanced mass transport and electron transfer endowed by morphology and electronic structure engineering,Co SAs/NC exhibits remarkable ORR performance with excellent activity(onset and half-wave potentials of 1.04 V(RHE)and 0.90 V(RHE),Tafel slope of 69.8 mV dec^(-1)and J_(k) of 18.8 mA cm^(-2)at 0.85 V)and stability(7 mV activity decay after 10,000 cycles).In additio n,the catalyst demonstrates great promise as an alternative to traditional Pt/C catalyst in zinc-air batteries while maintaining high performance in terms of high specific capacity of(796.1 mAh/g_(Zn)),power density(175.4 mW/cm^(2)),and long-term cycling stability(140 h).This study presents a facile approach to design SACs with highly accessible active sites for electrochemical transformations.展开更多
Atomically dispersed single atom catalysts represent an ideal means of converting less valuable organics into value-added chemicals of interest with high efficiency.Herein,we describe a facile synthetic approach to cr...Atomically dispersed single atom catalysts represent an ideal means of converting less valuable organics into value-added chemicals of interest with high efficiency.Herein,we describe a facile synthetic approach to create defect-containingβ-FeOOH doped with isolated palladium atoms that bond covalently to the nearby oxygen and iron atoms.The presence of singly dispersed palladium atoms is confirmed by spherical aberration correction electron microscopy and extended X-ray absorption fine structure measurements.This single palladium atom catalyst manifests outstanding catalytic efficiency(conversion:99%;selectivity 99%;turnover frequency:2,440 h^(-1))in the selective hydrogenation of cinnamaldehyde to afford hydrocinnamaldehyde.Experimental measurements and density functional theory(DFT)calculations elucidate the high catalytic activity and the strong metal-support interaction stem from the unique coordination environment of the isolated palladium atoms.These findings may pave the way for the facile construction of single atom catalysts in a defect-mediated strategy for efficient organic transformations in heterogeneous catalysis.展开更多
We investigate primal and mixed u−p isogeometric collocation methods for application to nearly-incompressible isotropic elasticity.The primal method employs Navier’s equations in terms of the displacement unknowns,an...We investigate primal and mixed u−p isogeometric collocation methods for application to nearly-incompressible isotropic elasticity.The primal method employs Navier’s equations in terms of the displacement unknowns,and the mixed method employs both displacement and pressure unknowns.As benchmarks for what might be considered acceptable accuracy,we employ constant-pressure Abaqus finite elements that are widely used in engineering applications.As a basis of comparisons,we present results for compressible elasticity.All the methods were completely satisfactory for the compressible case.However,results for low-degree primal methods exhibited displacement locking and in general deteriorated in the nearly-incompressible case.The results for the mixed methods behaved very well for two of the problems we studied,achieving levels of accuracy very similar to those for the compressible case.The third problem,which we consider a“torture test”presented a more complex story for the mixed methods in the nearly-incompressible case.展开更多
文摘The number of operational satellites and debris objects in the valuable geosynchronous ring has increased steadily over time such that active debris removal missions are necessary to ensure long-term stability. These objects are very large and tumbling, making any mission scenarios requiring physical contact very challenging. In the last 10 years, the concept of using an electrostatic tractor has been investigated extensively. With the electrostatic tractor concept, active charge emission is employed to simultaneously charge the tug or services vehicle, while aiming the charge exhaust onto the passive space debris object to charge it as well. The resulting electrostatic force has been explored to actuate this debris object to a disposal orbit or to detumble the object, all without physical contact. This paper provides a survey of the related research and reviews the charging concepts, the associated electrostatic force and torque modeling, and the feedback control developments, as well as the charge sensing research.
文摘Purpose It is well recognised that injury prevention training can reduce injury incidence,however current coach education pathways do not provide grass-root coaches with the knowledge and confidence to deliver such training to youth players.The aim of this study was to explore differences in knowledge,understanding,attitude and confidence to deliver such injury prevention training in three European countries.Methods A total of 269 grass-root soccer coaches from 3 European countries(Czech Republic,UK,Spain)were recruited for this study.A validated questionnaire exploring knowledge,understanding,attitude towards and confidence to deliver youth injury prevention training was completed prior to a 2 h workshop on injury prevention training.Differences between countries was examined using Bayesian factors to quantify the evidence for and against the hypothesis of independence(H0)by assuming a Poisson sampling scheme(as there was no a priori restriction on any cell count,nor on the grand total)(BF10 Poisson).Results Current knowledge,attitude and confidence to deliver injury prevention training to youth players was poor across all three European countries.Relatively few coaches were currently using injury prevention training in their coaching sessions(23%).There were some country specific differences for attitude towards injury prevention training and confidence to deliver injury training,with Spanish coaches reporting a more positive attitude and confidence to deliver such training.Significantly fewer coaches in the UK were using injury prevention training compared to coaches in Spain and the Czech Republic.Conclusion As coaches identified a need for coach education and few were delivering injury prevention training,there is a clear need to embed and implement this programme into the grassroots coaching framework of sports governing bodies to improve adoption,implementation and maintenance.
基金conducted within the Poultry CRC,established and supported under the Australian Government's Cooperative Research Centres Program
文摘The Japanese quail(Coturnix japonica) are popular both as an alternative protein source and as a model of choice for scientific research in several disciplines. There is limited published information on the histological features of the intestinal tract of Japanese quail. The only comprehensive reference is a book published in 1969. This study aims to fill that niche by providing a reference of general histological features of the Japanese quail, covering all the main sections of the intestinal tract. Both light and scanning electron microscope(SEM) images are presented. Results showed that the Japanese quail intestinal tract is very similar to that of the chicken with the exception of the luminal koilin membrane of the gizzard. Scanning electron microscopic photomicrographs show that in the Japanese quail koilin vertical rods are tightly packed together in a uniform manner making a carpet-like appearance. This differs in chicken where the conformations of vertical rods are arranged in clusters.
基金financially supported by the Australian Poultry Cooperative Research Centre
文摘Background： The broiler industry has undergone intense genetic selection over the past 50 yr. resulting in improvements for growth and feed efficiency, however, significant variation remains for performance and growth traits. Production improvements have been coupled with unfavourable metabolic consequences, including immunological trade-offs for growth, and excess fat deposition. To determine whether interactions between fatty acid（FA） metabolism and innate immunity may be associated with performance variations commonly seen within commercial broiler flocks, total carcass lipid %, carcass and blood FA composition, as wel as genes involved with FA metabolism, immunity and cel ular stress were investigated in male birds of a broiler strain, layer strain and F1 layer × broiler cross at d 14 post hatch. Heterophil：lymphocyte ratios, relative organ weights and bodyweight data were also compared.Results： Broiler bodyweight（n = 12） was four times that of layers（n = 12） by d 14 and had significantly higher carcass fat percentage compared to the cross（n = 6; P = 0.002） and layers（P = 0.017） which were not significantly different from each other（P = 0.523）. The carcass and whole blood FA analysis revealed differences in the FA composition between the three groups indicating altered FA metabolism, despite al being raised on the same diet. Genes associated with FA synthesis andβ-oxidation were upregulated in the broilers compared to the layers indicating a net overal increase in FA metabolism,which may be driven by the larger relative liver size as a percentage of bodyweight in the broilers. Genes involved in innate immunity such as TLR2 and TLR4, as wel as organel e stress indicators ERN1 and XBP1 were found to be nonsignificant, with the exception of high expression levels of XBP1 in layers compared to the cross and broilers. Additional y there was no difference in heterophil： lymphocytes between any of the birds.Conclusions： The results provide evidence that genetic selection may be as
基金The authors greatly acknowledge the financial support from the China Postdoctoral Science Foundation(Nos.2019M661247 and 2020T130091)Postdoctoral Science Foundation of Heilongjiang Province(LBH-Z19047)+1 种基金Scientific Research Foundation for Returned Scholars of Heilongjiang Province of China(719900091)Key Laboratory of Functional Inorganic Material Chemistry(Heilongjiang University),Ministry of Education.
文摘Chemoselective hydrodeoxygenation of vanillin is of great importance in converting biomass into high value-added chemicals.Herein,we describe a facile photochemical route to access palladium single atoms and clusters supported on silicoaluminophosphate-31(SAPO-31)as a highly active,chemoselective,and reusable catalyst for hydrodeoxygenation of vanillin.Characterizations by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy,extended X-ray absorption fine structure measurement,and CO-absorbed diffuse reflectance infrared Fourier transform spectroscopy reveal the atomically dispersed palladium single atoms and clusters are loosely bonded and randomly dispersed,without forming strong palladium-palladium metallic bonding,over the SAPO-31 support.This catalyst,with a full metal availability to the reactants,exhibits exceptional catalytic activity(TOF:3,000 h^(−1),Yield:>99%)in the hydrodeoxygenation of vanillin toward 2-methoxy-4-methylphenol(MMP)under mild conditions(1 atm,80°C,30 min),along with excellent stability,scalability(up to 100-fold),and wide substrate scope.The superior catalytic performance can be attributed to the synergistic effect of the positively charged palladium single atoms and fully exposed clusters,as well as the strong metal-support interactions.This work may offer a new avenue for the design and synthesis of fully exposed metal catalysts with targeted functionalities.
基金support of this work by the China Postdoctoral Science Foundation(Nos.2019M661247 and 2020T130091)Postdoctoral Science Foundation of Heilongjiang Province(No.LBH-Z19047)+2 种基金Scientific Research Foundation for Returned Scholars of Heilongjiang Province of China(No.719900091)Heilongjiang Touyan Innovation Team Program,the National Key Technology Research and Development Program of China(No.2017YFA0403403)the National Natural Science Foundation of China(No.21872131)。
文摘Catalytic C−H bond activation is one of the backbones of the chemical industry.Supported metal subnanoclusters consisting of a few atoms have shown attractive properties for heterogeneous catalysis.However,the creation of such catalyst systems with high activity and excellent anti-sintering ability remains a grand challenge.Here,we report on alkali ion-promoted Pd subnanoclusters supported over defectiveγ-Al_(2)O_(3) nanosheets,which display exceptional catalytic activity for C−H bond activation in the benzene oxidation reaction.The presence of Pd subnanoclusters is verified by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy,X-ray absorption spectroscopy,and X-ray photoelectron spectroscopy.This catalyst shows excellent catalytic activity,with a turnover frequency of 280 h^(−1) and yield of 98%,in benzene oxidation reaction to give phenol under mild conditions.Moreover,the introduction of alkali ion greatly retards the diffusion and migration of metal atoms when tested under high-temperature sintering conditions.Density functional theory(DFT)calculations reveal that the addition of alkali ion to Pd nanoclusters can significantly impact the catalyst’s structure and electronic properties,and eventually promote its activity and stability.This work sheds light on the facile and scalable synthesis of highly active and stable catalyst systems with alkali additives for industrially important reactions.
基金supported by the Postdoctoral Research Foundation of China(2019M661247,2020T130091)Scientific Research Foundation for Returned Scholars of Heilongjiang Province of China(719900091)+1 种基金Program for Overseas Talents Introduction of Northeast Petroleum University(15041260303)Heilongjiang Touyan Innovation Team Program。
文摘The stabilization of non-precious metals as isolated active sites with high loading density over nitrogendoped carbon materials is essential for realizing the industrial application of single atom catalysts.However,achieving high loading of single cobalt active sites with greatly enhanced oxygen reduction reaction(ORR)activity and stability remains challenging.Here,an efficient approach was described to create a single atom cobalt electrocatalyst(Co SAs/NC)which possesses enhanced mesoporosity and specific surface area that greatly favor the mass transportation and exposure of accessible active sites.The electronic structure of the catalyst by the strong metal-support interaction has been elucidated through experimental characterizations and theoretical calculations.Due to dramatically enhanced mass transport and electron transfer endowed by morphology and electronic structure engineering,Co SAs/NC exhibits remarkable ORR performance with excellent activity(onset and half-wave potentials of 1.04 V(RHE)and 0.90 V(RHE),Tafel slope of 69.8 mV dec^(-1)and J_(k) of 18.8 mA cm^(-2)at 0.85 V)and stability(7 mV activity decay after 10,000 cycles).In additio n,the catalyst demonstrates great promise as an alternative to traditional Pt/C catalyst in zinc-air batteries while maintaining high performance in terms of high specific capacity of(796.1 mAh/g_(Zn)),power density(175.4 mW/cm^(2)),and long-term cycling stability(140 h).This study presents a facile approach to design SACs with highly accessible active sites for electrochemical transformations.
基金We acknowledge the financial support from the China Postdoctoral Science Foundation(Nos.2019M661247 and 2020T130091)Postdoctoral Science Foundation of Heilongjiang Province(No.LBH-Z19047)+2 种基金the Scientific Research Foundation for Returned Scholars of Heilongjiang Province of China(No.719900091)the National Key R&D Program of China(No.2017YFA0403403)the National Natural Science Foundation of China(No.21872131).
文摘Atomically dispersed single atom catalysts represent an ideal means of converting less valuable organics into value-added chemicals of interest with high efficiency.Herein,we describe a facile synthetic approach to create defect-containingβ-FeOOH doped with isolated palladium atoms that bond covalently to the nearby oxygen and iron atoms.The presence of singly dispersed palladium atoms is confirmed by spherical aberration correction electron microscopy and extended X-ray absorption fine structure measurements.This single palladium atom catalyst manifests outstanding catalytic efficiency(conversion:99%;selectivity 99%;turnover frequency:2,440 h^(-1))in the selective hydrogenation of cinnamaldehyde to afford hydrocinnamaldehyde.Experimental measurements and density functional theory(DFT)calculations elucidate the high catalytic activity and the strong metal-support interaction stem from the unique coordination environment of the isolated palladium atoms.These findings may pave the way for the facile construction of single atom catalysts in a defect-mediated strategy for efficient organic transformations in heterogeneous catalysis.
基金FF and LDL gratefully acknowledge the financial support of the German Research Foundation(DFG)within the DFG Priority Program SPP 1748“Reliable Simulation Techniques in Solid Mechanics”.AR has been partially supported by the MIUR-PRIN project XFAST-SIMS(No.20173C478 N).
文摘We investigate primal and mixed u−p isogeometric collocation methods for application to nearly-incompressible isotropic elasticity.The primal method employs Navier’s equations in terms of the displacement unknowns,and the mixed method employs both displacement and pressure unknowns.As benchmarks for what might be considered acceptable accuracy,we employ constant-pressure Abaqus finite elements that are widely used in engineering applications.As a basis of comparisons,we present results for compressible elasticity.All the methods were completely satisfactory for the compressible case.However,results for low-degree primal methods exhibited displacement locking and in general deteriorated in the nearly-incompressible case.The results for the mixed methods behaved very well for two of the problems we studied,achieving levels of accuracy very similar to those for the compressible case.The third problem,which we consider a“torture test”presented a more complex story for the mixed methods in the nearly-incompressible case.
