The organization of biological neuronal networks into functional modules has intrigued scientists and inspired engineers to develop artificial systems.These networks are characterized by two key properties.First,they ...The organization of biological neuronal networks into functional modules has intrigued scientists and inspired engineers to develop artificial systems.These networks are characterized by two key properties.First,they exhibit dense interconnectivity(Braitenburg and Schüz,1998;Campagnola et al.,2022).The strength and probability of connectivity depend on cell type,inter-neuronal distance,and species.Still,every cortical neuron receives input from thousands of other neurons while transmitting output to a similar number of neurons.Second,communication between neurons occurs primarily via chemical or electrical synapses.展开更多
Endometrial injury caused by repeated uterine procedures,infections,inflammation,or uterine artery dysfunction can deplete endometrial stem/progenitor cells and impair regeneration,thereby diminishing endometrial rece...Endometrial injury caused by repeated uterine procedures,infections,inflammation,or uterine artery dysfunction can deplete endometrial stem/progenitor cells and impair regeneration,thereby diminishing endometrial receptivity and evidently lowering the live birth,clinical pregnancy,and embryo implantation rates.Currently,safe and effective clinical treatment methods or gene-targeted therapies are unavailable,especially for severe endometrial injury.Umbilical cord mesenchymal stem cells and their extracellular vesicles are characterized by their simple collection,rapid proliferation,low immunogenicity,and tumorigenicity,along with their involvement in regulating angiogenesis,immune response,cell apoptosis and proliferation,inflammatory response,and fibrosis,Therefore,these cells and vesicles hold broad potential for application in endometrial repair.This article reviewed recent research on human umbilical cord mesenchymal stem cells as well as their extracellular vesicles in repairing endometrial injury.展开更多
The rapid and precise fabrication of multiscale supramolecular assemblies using micro/nanofluidic techniques has emerged as a dynamic area of research in supramolecular chemistry, materials chemistry, and organic chem...The rapid and precise fabrication of multiscale supramolecular assemblies using micro/nanofluidic techniques has emerged as a dynamic area of research in supramolecular chemistry, materials chemistry, and organic chemistry. This review summarizes the application of micro/nanofluidic techniques in constructing supramolecular assemblies, including nanoscale supramolecular assemblies such as macrocycles and cages, microscale supramolecular assemblies such as metal organic frameworks (MOFs) and covalent organic frameworks (COFs), and macroscale supramolecular assemblies such as supramolecular hydrogels. Compared to conventional synthesis methods, micro/nanofluidic techniques for the production of supramolecular assemblies have significant advantages, including enhanced safety, high reaction rates, improved selectivity/yield, and scalability. Additionally, micro/nanofluidic systems facilitate the creation of precisely controllable micro/nanoconfined environments, allowing for a unique flow behavior that improves our understanding of the supramolecular self-assembly process. Such systems may also lead to the development of novel supramolecular assemblies that differ from those generated via traditional methods.展开更多
This work is devoted to the aeronautical application of topology optimization for modular structures with multiple assemblies that consist of repeated standard modules and optional reinforcements.These kinds of struct...This work is devoted to the aeronautical application of topology optimization for modular structures with multiple assemblies that consist of repeated standard modules and optional reinforcements.These kinds of structures are widely used owing to their transportability,reconfigurability,low manufacturing and service costs.In this work,the design of airborne shelves with modular structures characterized by the standard module configuration is formulated for the first time as a topology optimization problem of multiple assemblies and multiple load cases subjected to the volume constraint.It is shown that the weighted compliance design of multiple assemblies is a compromising solution compared to the optimization result of each individual assembly of standard modules.Meanwhile,the performance of optimized airborne shelves with the modular structures can effectively be ameliorated with the help of reinforcements.展开更多
Proton exchange membrane fuel cells(PEMFCs)have been identified as a highly promising means of achieving sustainable energy conversion.A crucial factor in enhancing the performance of PEMFCs for further potential ener...Proton exchange membrane fuel cells(PEMFCs)have been identified as a highly promising means of achieving sustainable energy conversion.A crucial factor in enhancing the performance of PEMFCs for further potential energy applications is the advancement in the field of catalyst engineering that has led to remarkable performance enhancement in facilitating the oxygen reduction reaction(ORR).Subsequently,it is important to acknowledge that the techniques used in preparation of membrane electrode assemblies(MEAs),the vital constituents of PEMFCs,also possess direct and critical influence on exhibiting the full catalytic activity of meticulously crafted catalysts.Here,a succinct summary of the most recent advancements in Pt catalysts for ORR was offered and their underly catalytic mechanism were discussed.Then,both laboratory-scale and industrial-scale MEA fabrication techniques of Pt catalysts were summarized.Furthermore,a detailed analysis of the connections between materials,process,and performance in MEA fabrication was presented in order to facilitate the development of optimal catalyst layers.展开更多
Black phosphorus with a superior theoretical capacity(2596 mAh g^(-1))and high conductivity is regarded as one of the powerful candidates for lithium-ion battery(LIB)anode materials,whereas the severe volume expansion...Black phosphorus with a superior theoretical capacity(2596 mAh g^(-1))and high conductivity is regarded as one of the powerful candidates for lithium-ion battery(LIB)anode materials,whereas the severe volume expansion and sluggish kinetics still impede its applications in LIBs.By contrast,the exfoliated two-dimensional phosphorene owns negligible volume variation,and its intrinsic piezoelectricity is considered to be beneficial to the Li-ion transfer kinetics,while its positive influence has not been discussed yet.Herein,a phosphorene/MXene heterostructure-textured nanopiezocomposite is proposed with even phosphorene distribution and enhanced piezo-electrochemical coupling as an applicable free-standing asymmetric membrane electrode beyond the skin effect for enhanced Li-ion storage.The experimental and simulation analysis reveals that the embedded phosphorene nanosheets not only provide abundant active sites for Li-ions,but also endow the nanocomposite with favorable piezoelectricity,thus promoting the Li-ion transfer kinetics by generating the piezoelectric field serving as an extra accelerator.By waltzing with the MXene framework,the optimized electrode exhibits enhanced kinetics and stability,achieving stable cycling performances for 1,000 cycles at 2 A g^(-1),and delivering a high reversible capacity of 524 m Ah g^(-1)at-20℃,indicating the positive influence of the structural merits of self-assembled nanopiezocomposites on promoting stability and kinetics.展开更多
Multicharged supramolecular assemblies based on luminescent macrocycle play an important role in extending their optical properties and functions.Herein,we reported macrocyclic supramolecular assemblies based on lumin...Multicharged supramolecular assemblies based on luminescent macrocycle play an important role in extending their optical properties and functions.Herein,we reported macrocyclic supramolecular assemblies based on luminescent terphen[3]arene sulfate(TP[3]AS)and tetraphenylethylene pyridinium(TPE-4Py)through electrostatic interactions,host-vip encapsulation andπ-πstacking interactions.F?rster resonance energy transfer(FRET)process from TP[3]AS to TPE-4Py was achieved with the energy transfer efficiency of 99.9%,accompanied by TPE-4Py fluorescence emission bathochromic shifted of 15 nm and enhanced by 1.68 times in PBS solution.In contrast,other non-luminescent sulfato-β-cyclodextrin and sulfobutylether-β-cyclodextrin only can enhance the fluorescence intensity of TPE-4Py without bathochromic shift.Due to the strong fluorescence and good stability of TPE-4Py@TP[3]AS,it can be used for optical imaging in living cells,which provided an effective approach for the construction of assembling-confined luminescent biomaterials.展开更多
This study presents a structural analysis algorithm called the finite particle method （FPM） for kinematically indeterminate bar assemblies. Different from the traditional analysis method, FPM is based on the combina...This study presents a structural analysis algorithm called the finite particle method （FPM） for kinematically indeterminate bar assemblies. Different from the traditional analysis method, FPM is based on the combination of the vector mechanics and numerical calculations. It models the analyzed domain composed of finite particles. Newton＇s second law is adopted to describe the motions of all particles. A convected material flame and explicit time integration for the solution procedure is also adopted in this method. By using the FPM, there is no need to solve any nonlinear equations, to calculate the stiffness matrix or equilibrium matrix, which is very helpful in the analysis of kinematically indeterminate structures. The basic formulations for the space bar are derived, following its solution procedures for bar assemblies. Three numerical examples are analyzed using the FPM. Results obtained from both the straight pretension cable and the suspension cable assembly show that the FPM can produce a more accurate analysis result. The motion simulation of the four-bar space assembly demonstrates the capability of this method in the analysis ofkinematically indeterminate structures.展开更多
Rice is one of the most important staple food for over half of the world＇s population,and a substantial increase in productivity and quality of rice grain will be required to feed a growing human population.Grain siz...Rice is one of the most important staple food for over half of the world＇s population,and a substantial increase in productivity and quality of rice grain will be required to feed a growing human population.Grain size and shape are the two important components contributing to grain yield and quality,because they impact both yield potential and end-use quality.展开更多
In order to describe and control the stress distribution and total deformation of bladed disk assemblies used in the aeroengine, a highly efficient and precise method of probabilistic analysis which is called extremum...In order to describe and control the stress distribution and total deformation of bladed disk assemblies used in the aeroengine, a highly efficient and precise method of probabilistic analysis which is called extremum response surface method(ERSM) is produced based on the previous deterministic analysis results with the finite element model(FEM). In this work, many key nonlinear factors, such as the dynamic feature of the temperature load, the centrifugal force and the boundary conditions, are taken into consideration for the model. The changing patterns with time of bladed disk assemblies about stress distribution and total deformation are obtained during the deterministic analysis, and at the same time, the largest deformation and stress nodes of bladed disk assemblies are found and taken as input target of probabilistic analysis in a scientific and reasonable way. Not only their reliability, historical sample, extreme response surface(ERS) and the cumulative probability distribution function but also their sensitivity and effect probability are obtained. Main factors affecting stress distribution and total deformation of bladed disk assemblies are investigated through the sensitivity analysis of the model. Finally, compared with the response surface method(RSM) and the Monte Carlo simulation(MCS), the results show that this new approach is effective.展开更多
The microvibrations produced by momentum wheel assemblies（MWA） can degrade the performance of instruments with high pointing precision and stability on spacecraft.This paper concentrates on analyzing and testing the...The microvibrations produced by momentum wheel assemblies（MWA） can degrade the performance of instruments with high pointing precision and stability on spacecraft.This paper concentrates on analyzing and testing the microvibrations produced by MWA.We analyze the disturbance sources produced by mass imbalance,structural mode,bearing irregularity and nonlinear stiffness,and random noise;then,test a well-balanced MWA by a highly sensitive measurement system consisting of a Kistler table and an optical tabletop.The results show that the test system has a resolution of less than 0.003 N in the frequency range of 3-300 Hz.The dynamic imbalance of the MWA cannot excite the radial rocking mode,but there are dynamic amplifications when the poly-harmonic disturbances intersect with the structural modes.Especially at high rotational speed（〉3 000 rev/min）,the main disturbance sources of the MWA come from the bearing irregularity interacting with radial translation mode in the high frequency range.Thus,bearing noise deserves more attention for the well-balanced MWA,and alternative of high quality bearings are proposed to reduce the microvibrations.展开更多
Nature and technology often adopt structures that can be described as tubular helical assemblies.However,the role and mechanisms of these structures remain elusive.In this paper,we study the mechanical response under ...Nature and technology often adopt structures that can be described as tubular helical assemblies.However,the role and mechanisms of these structures remain elusive.In this paper,we study the mechanical response under compression and extension of a tubular assembly composed of 8 helical Kirchholf rods,arranged in pairs with opposite chirality and connected by pin joints,both analytically and numerically.We first focus on compression and find that,whereas a single helical rod would buckle,the rods of the assembly deform coherently as stable helical shapes wound around a common axis.Moreover,we investigate the response of the assembly under different boundary conditions,highlighting the emergence of a central region where rods remain circular helices.Secondly,we study the effects of different hypotheses on the elastic properties of rods,i.e.,stress-free rods when straight versus when circular helices,Kirchhoff’s rod model versus Sadowsky’s ribbon model.Summing up,our findings highlight the key role of mutual interactions in generating a stable ensemble response that preserves the helical shape of the individual rods,as well as some interesting features,and they shed some light on the reasons why helical shapes in tubular assemblies are so common and persistent in nature and technology.展开更多
Bubble functions are finite element modes that are zero on the boundary of the element but nonzero at the other point. The present paper adds bubble functions to the ordinary Complex Finite Strip Method(CFSM) to calcu...Bubble functions are finite element modes that are zero on the boundary of the element but nonzero at the other point. The present paper adds bubble functions to the ordinary Complex Finite Strip Method(CFSM) to calculate the elastic local buckling stress of plates and plate assemblies. The results indicate that the use of bubble functions greatly improves the convergence of the Finite Strip Method(FSM) in terms of strip subdivision, and leads to much smaller storage required for the structure stiffness and stability matrices. Numerical examples are given, including plates and plate structures subjected to a combination of longitudinal and transverse compression, bending and shear. This study illustrates the power of bubble functions in solving stability problems of plates and plate structures.展开更多
Hydrothermal reactions of uranyl nitrate and 4,4＇-oxidiphthalic acid（H4L） resulted in the formation of three new uranyl-organic framework materials,namely（NH4）2[（UO2）3（L）2]·5H2O（1）,（NEt4）[（UO2）3（...Hydrothermal reactions of uranyl nitrate and 4,4＇-oxidiphthalic acid（H4L） resulted in the formation of three new uranyl-organic framework materials,namely（NH4）2[（UO2）3（L）2]·5H2O（1）,（NEt4）[（UO2）3（H2O）（L）（HL）]（2） and（UO2）7（H2O）2（phen）4（L）2（HL）2（3）（NEt4 = tetraethylammonium,phen = 1,10-phenanthroline）.These three structures all comprise common uranyl pentagonal bipyramids.In 1,UO7polyhedra are linked by hexadentate ligands to form a 3D framework with 1D channels,in which are located NH4^＋ ions and water molecules.While in 2,the organic ligands adopt pentadentate and hexadentate coordination modes,ligating UO7 units to create a layered structure with channels filled by NEt4^＋ ions.For 3,uranyl square bipyramids are also accommodated together with pentagonal bipyramids,which are linked by tetradentate carboxylate ligands to produce the layered assembly.Phen molecules also coordinate to the uranyl centers to build up the structure.Luminescent studies indicate that 2 and 3 exhibit the characteristic uranyl emission.展开更多
Mixing of freshwater and seawater creates the well-known salinity gradients along the estuaries. In order to investigate how phytoplankton respond to the acute salinity changes, we exposed natural phytoplankton assemb...Mixing of freshwater and seawater creates the well-known salinity gradients along the estuaries. In order to investigate how phytoplankton respond to the acute salinity changes, we exposed natural phytoplankton assemblies from the Jiulong River Estuary to differential saline field water while continuously monitoring their photosynthetic performances under both indoor-and outdoor-growth conditions. When the natural cell assemblies from salinity 30 field water were exposed to series low saline field water(salinity 25, 17, 13 and 7.5), the effective Photosystem II quantum yield(ΔF/Fm′) decreased sharply, e.g., to one-fifth of its initials after 5 min exposure to salinity 7.5 field water, and then increased fast during the following 40 min and almost completely recovered after 320 min. During such an exposure process, non-photochemical quenching(NPQ) sharply increased from 0 to 0.85 within 5 min, and then decreased to nearly 0 within the following 70 min. When these cells re-acclimated to salinity 7.5 field water were exposed to series high saline field water(salinity 13, 17, 25 and 30), a similar response pattern was observed, with the decreased ΔF/Fm′ accompanied with increased NPQ, and followed by the recovery-induced increase in ΔF/Fm′ and decrease in NPQ. A similar response pattern as ΔF/Fm′to the acute osmotic stress was also observed in the photosynthetic carbon fixation capacity according to radiocarbon(14C) incorporation. Our results indicate that estuarine phytoplankton assemblies could rapidly recover from the acute osmotic stress, implying a potential cause for their frequent blooms in coastal-estuarine waters where despite drastically varying salinity, available nutrients are abundant due to the land-derived runoffs or mixing-caused relaxations from sediments.展开更多
In this communication,a new supramolecualr amphiphile was successfully constructed based on water soluble pillar[5]arene and a unique vip which contain a CO_(2) responsive tertiary amine unit and a UV responsive cou...In this communication,a new supramolecualr amphiphile was successfully constructed based on water soluble pillar[5]arene and a unique vip which contain a CO_(2) responsive tertiary amine unit and a UV responsive coumarin group.When vip molecule 1 dispersed in water,it self-assembled into sheet-like structures.Upon bubbling CO_(2),1 transformed into 1 H due to the tertiary amine unit was protonated,accompany the nano-sheets transformed into vesicles.Further irradiation of 1 H with 365 nm light for 3 h,the coumarin group reacted with each other to form bola-type amphiphie 2 H.In this case,vesicles collapsed and re-assembled into nano-tubes.However,when addition of WPS into the solution of 1 H,the vesicles transformed into micelles,this is due to the formation of supramolecular amphiphile WP5&1 H.Upon irradiation of WP5&1 H with 365 nm light for 3 h,nano-ribbons observed instead of micelles in the solution.Notably,nanotubes from 2 H could also transform into nano-ribbons after adding WPS.The selfassembly process and the resultant assemblies were characterized by TEM,SEM,DLS,SAXS and NMR technologies.Due to both CO_(2) and light are "green" for living organisms,we anticipated our system can offer the possibilities in "on demand" drug absorption and release.展开更多
By introducing a host molecule cucurbit[8]uril(CB[8]) into a charge transfer system containing an amphiphile 1-[11-(naphthalene-2-ylmethoxy)-11-oxoundecyl]pyridinium(NP) and an electron-deficient molecule methyl violo...By introducing a host molecule cucurbit[8]uril(CB[8]) into a charge transfer system containing an amphiphile 1-[11-(naphthalene-2-ylmethoxy)-11-oxoundecyl]pyridinium(NP) and an electron-deficient molecule methyl viologen(MV), a novel and anisotropic ternary building block was constructed by hostvip interactions, thereby leading to the morphology transformation of the final assemblies from thinfilms(NP/MV complexes) into diamond-like structures(NP/MV/CB[8] complexes). These intriguing assemblies were firstly discovered and were similar with the shape of well-known metal organic frameworks(MOFs), but just comprised three small organic molecules without metal ions. This finding can enrich the shape of current supramolecular assemblies and thus contributing to more potential applications in material science.展开更多
A nontoxic and biocompatible thermoseed is developed for the magnetic hyperthermia.Two kinds of thermoseed materials:hierarchical hollow and solid lichee-like Fe_(3)O_(4) assemblies,are synthesized by a facile hydroth...A nontoxic and biocompatible thermoseed is developed for the magnetic hyperthermia.Two kinds of thermoseed materials:hierarchical hollow and solid lichee-like Fe_(3)O_(4) assemblies,are synthesized by a facile hydrothermal method.The crystal structure of Fe_(3)O_(4) assemblies are characterized by x-ray diffraction,scanning electron microscopy,and transmission electron microscopy.Moreover,the prepared Fe_(3)O_(4) assemblies are used as a magnetic heat treatment agent,and their heating efficiency is investigated.Compared to solid assembly,hollow lichee-like Fe_(3)O_(4) assembly exhibits a higher specific absorption rate of 116.53 W/g and a shorter heating time,which is ascribed to its higher saturation magnetization,larger initial particle size,and the unique hierarchical hollow structure.Furthermore,the magnetothermal effect is primarily attributed to Neel relaxation.Overall,we propose a facile and convenient approach to enhance the heating efficiency of magnetic nanoparticles by forming hollow hierarchical assemblies.展开更多
Decentralisation of infrastructure delivery to sub-national governments has become commonplace in governments worldwide especially in developing countries such as Ghana. This is due to the benefits of decentralisation...Decentralisation of infrastructure delivery to sub-national governments has become commonplace in governments worldwide especially in developing countries such as Ghana. This is due to the benefits of decentralisation in improving public service delivery. However, decentralised infrastructure delivery is marred with numerous challenges that render most local governments incapable of providing infrastructure within their localities. This paper explored the bureaucratic factors that impede infrastructure delivery at the MMDAs in Ghana. A questionnaire survey with 121 construction professionals in the Departments of Works (DoWs) of the MMDAs within the Ashanti and Greater Accra Regions of Ghana was conducted. The results indicated six (6) major components of the bureaucratic factors that impede the delivery of infrastructure at the MMDAs: Central government bureaucracy;Minimal control of MMDAs;Political influence;MMDA project funding;Lack of capacity of MMDAs;and Political interference. This paper calls for a more committed central government to the establishment of adequate decentralised structures and implementation of major reforms that would remove the bureaucratic obstacles in the delivery of infrastructure at the MMDAs, to ensure effective infrastructure delivery at the MMDAs.展开更多
基金supported in part by the Rosetrees Trust(#CF-2023-I-2_113)by the Israel Ministry of Innovation,Science,and Technology(#7393)(to ES).
文摘The organization of biological neuronal networks into functional modules has intrigued scientists and inspired engineers to develop artificial systems.These networks are characterized by two key properties.First,they exhibit dense interconnectivity(Braitenburg and Schüz,1998;Campagnola et al.,2022).The strength and probability of connectivity depend on cell type,inter-neuronal distance,and species.Still,every cortical neuron receives input from thousands of other neurons while transmitting output to a similar number of neurons.Second,communication between neurons occurs primarily via chemical or electrical synapses.
文摘Endometrial injury caused by repeated uterine procedures,infections,inflammation,or uterine artery dysfunction can deplete endometrial stem/progenitor cells and impair regeneration,thereby diminishing endometrial receptivity and evidently lowering the live birth,clinical pregnancy,and embryo implantation rates.Currently,safe and effective clinical treatment methods or gene-targeted therapies are unavailable,especially for severe endometrial injury.Umbilical cord mesenchymal stem cells and their extracellular vesicles are characterized by their simple collection,rapid proliferation,low immunogenicity,and tumorigenicity,along with their involvement in regulating angiogenesis,immune response,cell apoptosis and proliferation,inflammatory response,and fibrosis,Therefore,these cells and vesicles hold broad potential for application in endometrial repair.This article reviewed recent research on human umbilical cord mesenchymal stem cells as well as their extracellular vesicles in repairing endometrial injury.
基金the National Nature Science Foundation of China (Nos. 22107028 and 22103062)Program of Shanghai Outstanding Academic Leaders (No. 21XD1421200)Science and Technology Commission of Shanghai Municipality (No. 22JC1403900).
文摘The rapid and precise fabrication of multiscale supramolecular assemblies using micro/nanofluidic techniques has emerged as a dynamic area of research in supramolecular chemistry, materials chemistry, and organic chemistry. This review summarizes the application of micro/nanofluidic techniques in constructing supramolecular assemblies, including nanoscale supramolecular assemblies such as macrocycles and cages, microscale supramolecular assemblies such as metal organic frameworks (MOFs) and covalent organic frameworks (COFs), and macroscale supramolecular assemblies such as supramolecular hydrogels. Compared to conventional synthesis methods, micro/nanofluidic techniques for the production of supramolecular assemblies have significant advantages, including enhanced safety, high reaction rates, improved selectivity/yield, and scalability. Additionally, micro/nanofluidic systems facilitate the creation of precisely controllable micro/nanoconfined environments, allowing for a unique flow behavior that improves our understanding of the supramolecular self-assembly process. Such systems may also lead to the development of novel supramolecular assemblies that differ from those generated via traditional methods.
基金supported by the National Natural Science Foundation of China (Nos. 12032018 and 12172294)。
文摘This work is devoted to the aeronautical application of topology optimization for modular structures with multiple assemblies that consist of repeated standard modules and optional reinforcements.These kinds of structures are widely used owing to their transportability,reconfigurability,low manufacturing and service costs.In this work,the design of airborne shelves with modular structures characterized by the standard module configuration is formulated for the first time as a topology optimization problem of multiple assemblies and multiple load cases subjected to the volume constraint.It is shown that the weighted compliance design of multiple assemblies is a compromising solution compared to the optimization result of each individual assembly of standard modules.Meanwhile,the performance of optimized airborne shelves with the modular structures can effectively be ameliorated with the help of reinforcements.
基金financially supported by the National Natural Science Foundation of China(Nos.51802059,21905070 and 22075062)Shenzhen Science and Technology Program(Nos.JCYJ20210324120400002 and SGDX20210823103803017)+4 种基金the Key Research and Development Program of Shandong Province(No.2022CXGC010305)Heilongjiang Postdoctoral Fund(No.LBHZ18066),Heilongjiang Touyan Team(No.HITTY-20190033)the Fundamental Research Funds for the Central Universities(No.FRFCU5710051922)the High-Level Professional Team in Shenzhen(No.KQTD20210811090045006)Guangdong Basic and Applied Basic Research Foundation(No.2022B1515120001)。
文摘Proton exchange membrane fuel cells(PEMFCs)have been identified as a highly promising means of achieving sustainable energy conversion.A crucial factor in enhancing the performance of PEMFCs for further potential energy applications is the advancement in the field of catalyst engineering that has led to remarkable performance enhancement in facilitating the oxygen reduction reaction(ORR).Subsequently,it is important to acknowledge that the techniques used in preparation of membrane electrode assemblies(MEAs),the vital constituents of PEMFCs,also possess direct and critical influence on exhibiting the full catalytic activity of meticulously crafted catalysts.Here,a succinct summary of the most recent advancements in Pt catalysts for ORR was offered and their underly catalytic mechanism were discussed.Then,both laboratory-scale and industrial-scale MEA fabrication techniques of Pt catalysts were summarized.Furthermore,a detailed analysis of the connections between materials,process,and performance in MEA fabrication was presented in order to facilitate the development of optimal catalyst layers.
基金financially supported by the National Key Research and Development Program of China(No.2017YFB1002900)the National Natural Science Foundation of China(No.51661145021)+5 种基金the Key Natural Science Program of Jiangsu Province(Nos.BE2022118,BE2021643 and BE2016772)the Traction Project of Key Laboratory of Advanced Carbon Materials and Wearable Energy Technologies of Jiangsu Province(No.Q816000217)the Scholarship from Key Laboratory of Modern Optical Technologies of Ministry of Education of Chinathe Priority Academic Program Development(PAPD)of Jiangsu Higher Education InstitutionsChina Prosperity Green Industry Foundation of Ministry of Industry and Information Technologysupported by the open project of synchrotron radiation characterization of chain oriented/stacked polar topology and energy modulation of supramolecules(No.2100982)。
文摘Black phosphorus with a superior theoretical capacity(2596 mAh g^(-1))and high conductivity is regarded as one of the powerful candidates for lithium-ion battery(LIB)anode materials,whereas the severe volume expansion and sluggish kinetics still impede its applications in LIBs.By contrast,the exfoliated two-dimensional phosphorene owns negligible volume variation,and its intrinsic piezoelectricity is considered to be beneficial to the Li-ion transfer kinetics,while its positive influence has not been discussed yet.Herein,a phosphorene/MXene heterostructure-textured nanopiezocomposite is proposed with even phosphorene distribution and enhanced piezo-electrochemical coupling as an applicable free-standing asymmetric membrane electrode beyond the skin effect for enhanced Li-ion storage.The experimental and simulation analysis reveals that the embedded phosphorene nanosheets not only provide abundant active sites for Li-ions,but also endow the nanocomposite with favorable piezoelectricity,thus promoting the Li-ion transfer kinetics by generating the piezoelectric field serving as an extra accelerator.By waltzing with the MXene framework,the optimized electrode exhibits enhanced kinetics and stability,achieving stable cycling performances for 1,000 cycles at 2 A g^(-1),and delivering a high reversible capacity of 524 m Ah g^(-1)at-20℃,indicating the positive influence of the structural merits of self-assembled nanopiezocomposites on promoting stability and kinetics.
基金the National Natural Science Foundation of China(Nos.21971192,21807038)the Tianjin Municipal Education Commission(No.2021KJ188)the China Postdoctoral Science Foundation(No.2021T140343)。
文摘Multicharged supramolecular assemblies based on luminescent macrocycle play an important role in extending their optical properties and functions.Herein,we reported macrocyclic supramolecular assemblies based on luminescent terphen[3]arene sulfate(TP[3]AS)and tetraphenylethylene pyridinium(TPE-4Py)through electrostatic interactions,host-vip encapsulation andπ-πstacking interactions.F?rster resonance energy transfer(FRET)process from TP[3]AS to TPE-4Py was achieved with the energy transfer efficiency of 99.9%,accompanied by TPE-4Py fluorescence emission bathochromic shifted of 15 nm and enhanced by 1.68 times in PBS solution.In contrast,other non-luminescent sulfato-β-cyclodextrin and sulfobutylether-β-cyclodextrin only can enhance the fluorescence intensity of TPE-4Py without bathochromic shift.Due to the strong fluorescence and good stability of TPE-4Py@TP[3]AS,it can be used for optical imaging in living cells,which provided an effective approach for the construction of assembling-confined luminescent biomaterials.
基金supported by the National Natural Science Foundation of China (No. 50638050)the National High-Tech R&D (863) Program (No. 2007AA04Z441), China
文摘This study presents a structural analysis algorithm called the finite particle method （FPM） for kinematically indeterminate bar assemblies. Different from the traditional analysis method, FPM is based on the combination of the vector mechanics and numerical calculations. It models the analyzed domain composed of finite particles. Newton＇s second law is adopted to describe the motions of all particles. A convected material flame and explicit time integration for the solution procedure is also adopted in this method. By using the FPM, there is no need to solve any nonlinear equations, to calculate the stiffness matrix or equilibrium matrix, which is very helpful in the analysis of kinematically indeterminate structures. The basic formulations for the space bar are derived, following its solution procedures for bar assemblies. Three numerical examples are analyzed using the FPM. Results obtained from both the straight pretension cable and the suspension cable assembly show that the FPM can produce a more accurate analysis result. The motion simulation of the four-bar space assembly demonstrates the capability of this method in the analysis ofkinematically indeterminate structures.
基金supported by grants from the National Natural Science Foundation of China (No.91635302)the National Key Research and Development Program of China (2016YFD0100401)+1 种基金the Chinese Academy of Sciences (XDA08010101)the State Key Laboratory of Plant Cell and Chromosome Engineering (PCCEKF-2017-04)
文摘Rice is one of the most important staple food for over half of the world＇s population,and a substantial increase in productivity and quality of rice grain will be required to feed a growing human population.Grain size and shape are the two important components contributing to grain yield and quality,because they impact both yield potential and end-use quality.
基金Projects(51375032,51175017,51245027)supported by the National Natural Science Foundation of China
文摘In order to describe and control the stress distribution and total deformation of bladed disk assemblies used in the aeroengine, a highly efficient and precise method of probabilistic analysis which is called extremum response surface method(ERSM) is produced based on the previous deterministic analysis results with the finite element model(FEM). In this work, many key nonlinear factors, such as the dynamic feature of the temperature load, the centrifugal force and the boundary conditions, are taken into consideration for the model. The changing patterns with time of bladed disk assemblies about stress distribution and total deformation are obtained during the deterministic analysis, and at the same time, the largest deformation and stress nodes of bladed disk assemblies are found and taken as input target of probabilistic analysis in a scientific and reasonable way. Not only their reliability, historical sample, extreme response surface(ERS) and the cumulative probability distribution function but also their sensitivity and effect probability are obtained. Main factors affecting stress distribution and total deformation of bladed disk assemblies are investigated through the sensitivity analysis of the model. Finally, compared with the response surface method(RSM) and the Monte Carlo simulation(MCS), the results show that this new approach is effective.
文摘The microvibrations produced by momentum wheel assemblies（MWA） can degrade the performance of instruments with high pointing precision and stability on spacecraft.This paper concentrates on analyzing and testing the microvibrations produced by MWA.We analyze the disturbance sources produced by mass imbalance,structural mode,bearing irregularity and nonlinear stiffness,and random noise;then,test a well-balanced MWA by a highly sensitive measurement system consisting of a Kistler table and an optical tabletop.The results show that the test system has a resolution of less than 0.003 N in the frequency range of 3-300 Hz.The dynamic imbalance of the MWA cannot excite the radial rocking mode,but there are dynamic amplifications when the poly-harmonic disturbances intersect with the structural modes.Especially at high rotational speed（〉3 000 rev/min）,the main disturbance sources of the MWA come from the bearing irregularity interacting with radial translation mode in the high frequency range.Thus,bearing noise deserves more attention for the well-balanced MWA,and alternative of high quality bearings are proposed to reduce the microvibrations.
基金Open access funding provided by Scuola Superiore Sant’Anna within the CRUI-CARE Agreement.
文摘Nature and technology often adopt structures that can be described as tubular helical assemblies.However,the role and mechanisms of these structures remain elusive.In this paper,we study the mechanical response under compression and extension of a tubular assembly composed of 8 helical Kirchholf rods,arranged in pairs with opposite chirality and connected by pin joints,both analytically and numerically.We first focus on compression and find that,whereas a single helical rod would buckle,the rods of the assembly deform coherently as stable helical shapes wound around a common axis.Moreover,we investigate the response of the assembly under different boundary conditions,highlighting the emergence of a central region where rods remain circular helices.Secondly,we study the effects of different hypotheses on the elastic properties of rods,i.e.,stress-free rods when straight versus when circular helices,Kirchhoff’s rod model versus Sadowsky’s ribbon model.Summing up,our findings highlight the key role of mutual interactions in generating a stable ensemble response that preserves the helical shape of the individual rods,as well as some interesting features,and they shed some light on the reasons why helical shapes in tubular assemblies are so common and persistent in nature and technology.
基金the Natural Science Foundation of Jiangxi Province of Chinathe Basic Theory Research Foundation of Nanchang University
文摘Bubble functions are finite element modes that are zero on the boundary of the element but nonzero at the other point. The present paper adds bubble functions to the ordinary Complex Finite Strip Method(CFSM) to calculate the elastic local buckling stress of plates and plate assemblies. The results indicate that the use of bubble functions greatly improves the convergence of the Finite Strip Method(FSM) in terms of strip subdivision, and leads to much smaller storage required for the structure stiffness and stability matrices. Numerical examples are given, including plates and plate structures subjected to a combination of longitudinal and transverse compression, bending and shear. This study illustrates the power of bubble functions in solving stability problems of plates and plate structures.
基金the support of this work by National Natural Science Foundation of China(Nos.21571171,21301168,U1407101)Jilin Province Youth Foundation(No.20130522123JH)
文摘Hydrothermal reactions of uranyl nitrate and 4,4＇-oxidiphthalic acid（H4L） resulted in the formation of three new uranyl-organic framework materials,namely（NH4）2[（UO2）3（L）2]·5H2O（1）,（NEt4）[（UO2）3（H2O）（L）（HL）]（2） and（UO2）7（H2O）2（phen）4（L）2（HL）2（3）（NEt4 = tetraethylammonium,phen = 1,10-phenanthroline）.These three structures all comprise common uranyl pentagonal bipyramids.In 1,UO7polyhedra are linked by hexadentate ligands to form a 3D framework with 1D channels,in which are located NH4^＋ ions and water molecules.While in 2,the organic ligands adopt pentadentate and hexadentate coordination modes,ligating UO7 units to create a layered structure with channels filled by NEt4^＋ ions.For 3,uranyl square bipyramids are also accommodated together with pentagonal bipyramids,which are linked by tetradentate carboxylate ligands to produce the layered assembly.Phen molecules also coordinate to the uranyl centers to build up the structure.Luminescent studies indicate that 2 and 3 exhibit the characteristic uranyl emission.
基金The National Natural Science Foundation of China under contract Nos 41890853 and 41676156the National Basic Research Program of China(973 Program)under contract No.2015CB452903+3 种基金the Strategic Priority Research Program of Chinese Academy of Sciences under contract Nos XDA13020103 and XDA11020305the Natural Science Foundation of Guangdong Province under contract Nos 2015A030313826 and 2017A030313216the Special Fund for Agro-scientific Research in the Public Interest under contract No.201403008the Science and Technology Planning Project of Guangdong Province under contract No.2017B030314052
文摘Mixing of freshwater and seawater creates the well-known salinity gradients along the estuaries. In order to investigate how phytoplankton respond to the acute salinity changes, we exposed natural phytoplankton assemblies from the Jiulong River Estuary to differential saline field water while continuously monitoring their photosynthetic performances under both indoor-and outdoor-growth conditions. When the natural cell assemblies from salinity 30 field water were exposed to series low saline field water(salinity 25, 17, 13 and 7.5), the effective Photosystem II quantum yield(ΔF/Fm′) decreased sharply, e.g., to one-fifth of its initials after 5 min exposure to salinity 7.5 field water, and then increased fast during the following 40 min and almost completely recovered after 320 min. During such an exposure process, non-photochemical quenching(NPQ) sharply increased from 0 to 0.85 within 5 min, and then decreased to nearly 0 within the following 70 min. When these cells re-acclimated to salinity 7.5 field water were exposed to series high saline field water(salinity 13, 17, 25 and 30), a similar response pattern was observed, with the decreased ΔF/Fm′ accompanied with increased NPQ, and followed by the recovery-induced increase in ΔF/Fm′ and decrease in NPQ. A similar response pattern as ΔF/Fm′to the acute osmotic stress was also observed in the photosynthetic carbon fixation capacity according to radiocarbon(14C) incorporation. Our results indicate that estuarine phytoplankton assemblies could rapidly recover from the acute osmotic stress, implying a potential cause for their frequent blooms in coastal-estuarine waters where despite drastically varying salinity, available nutrients are abundant due to the land-derived runoffs or mixing-caused relaxations from sediments.
基金supported by the National Natural Science Foundation of China(Nos.21801139,21871227)Natural Science Foundation of Jiangsu Province(No.BK20180942)the Natural Science Foundation of Nantong University for High-Level Talent(No.03083004)。
文摘In this communication,a new supramolecualr amphiphile was successfully constructed based on water soluble pillar[5]arene and a unique vip which contain a CO_(2) responsive tertiary amine unit and a UV responsive coumarin group.When vip molecule 1 dispersed in water,it self-assembled into sheet-like structures.Upon bubbling CO_(2),1 transformed into 1 H due to the tertiary amine unit was protonated,accompany the nano-sheets transformed into vesicles.Further irradiation of 1 H with 365 nm light for 3 h,the coumarin group reacted with each other to form bola-type amphiphie 2 H.In this case,vesicles collapsed and re-assembled into nano-tubes.However,when addition of WPS into the solution of 1 H,the vesicles transformed into micelles,this is due to the formation of supramolecular amphiphile WP5&1 H.Upon irradiation of WP5&1 H with 365 nm light for 3 h,nano-ribbons observed instead of micelles in the solution.Notably,nanotubes from 2 H could also transform into nano-ribbons after adding WPS.The selfassembly process and the resultant assemblies were characterized by TEM,SEM,DLS,SAXS and NMR technologies.Due to both CO_(2) and light are "green" for living organisms,we anticipated our system can offer the possibilities in "on demand" drug absorption and release.
基金the financial supports from the National Natural Science Foundation of China (Nos. 31860516, 21662009, 21702037)Frontiers Science Center for Asymmetric Synthesis and Medicinal Molecules, Department of Education, Guizhou Province [Qianjiaohe KY No. (2020)004]Program of Introducing Talents of Discipline to Universities of China (111 Program, No. D20023)。
文摘By introducing a host molecule cucurbit[8]uril(CB[8]) into a charge transfer system containing an amphiphile 1-[11-(naphthalene-2-ylmethoxy)-11-oxoundecyl]pyridinium(NP) and an electron-deficient molecule methyl viologen(MV), a novel and anisotropic ternary building block was constructed by hostvip interactions, thereby leading to the morphology transformation of the final assemblies from thinfilms(NP/MV complexes) into diamond-like structures(NP/MV/CB[8] complexes). These intriguing assemblies were firstly discovered and were similar with the shape of well-known metal organic frameworks(MOFs), but just comprised three small organic molecules without metal ions. This finding can enrich the shape of current supramolecular assemblies and thus contributing to more potential applications in material science.
基金supported by the National Natural Science Foundation of China(Grant No.61975162)Youth Research Foundation of Shanxi Datong University(Grant No.2019Q1)+1 种基金Important R&D Projects of Shanxi Province,China(Grant No.201803D121083)Shanxi Scholarship Council,China(Grant No.2020-135)。
文摘A nontoxic and biocompatible thermoseed is developed for the magnetic hyperthermia.Two kinds of thermoseed materials:hierarchical hollow and solid lichee-like Fe_(3)O_(4) assemblies,are synthesized by a facile hydrothermal method.The crystal structure of Fe_(3)O_(4) assemblies are characterized by x-ray diffraction,scanning electron microscopy,and transmission electron microscopy.Moreover,the prepared Fe_(3)O_(4) assemblies are used as a magnetic heat treatment agent,and their heating efficiency is investigated.Compared to solid assembly,hollow lichee-like Fe_(3)O_(4) assembly exhibits a higher specific absorption rate of 116.53 W/g and a shorter heating time,which is ascribed to its higher saturation magnetization,larger initial particle size,and the unique hierarchical hollow structure.Furthermore,the magnetothermal effect is primarily attributed to Neel relaxation.Overall,we propose a facile and convenient approach to enhance the heating efficiency of magnetic nanoparticles by forming hollow hierarchical assemblies.
文摘Decentralisation of infrastructure delivery to sub-national governments has become commonplace in governments worldwide especially in developing countries such as Ghana. This is due to the benefits of decentralisation in improving public service delivery. However, decentralised infrastructure delivery is marred with numerous challenges that render most local governments incapable of providing infrastructure within their localities. This paper explored the bureaucratic factors that impede infrastructure delivery at the MMDAs in Ghana. A questionnaire survey with 121 construction professionals in the Departments of Works (DoWs) of the MMDAs within the Ashanti and Greater Accra Regions of Ghana was conducted. The results indicated six (6) major components of the bureaucratic factors that impede the delivery of infrastructure at the MMDAs: Central government bureaucracy;Minimal control of MMDAs;Political influence;MMDA project funding;Lack of capacity of MMDAs;and Political interference. This paper calls for a more committed central government to the establishment of adequate decentralised structures and implementation of major reforms that would remove the bureaucratic obstacles in the delivery of infrastructure at the MMDAs, to ensure effective infrastructure delivery at the MMDAs.
