Splitting water under large current density is essential for efficient large-scale production and commercial utilization of hydrogen.However,the performance of the available electrocatalysts for hydrogen evolution rea...Splitting water under large current density is essential for efficient large-scale production and commercial utilization of hydrogen.However,the performance of the available electrocatalysts for hydrogen evolution reaction(HER)is far from satisfactory under large current density in alkaline electrolyte.Here we report a remarkably active and durable electrocatalyst,long and dense MoS2/Ni3S2 co-axial heterostructure nanowires on nickel foam(NF).Notably,it requires only 182 and 200 mV overpotential to achieve large current density of 500 and 1000 mA cm^-2,respectively,in alkaline solution,which are far superior to those of Pt/C-NF(281 and 444 mV)and the reported best non-noble metal catalysts(191 and 220 mV).The physical origin for this extraordinary HER performance is analyzed,which provides a useful guide for structure design of electrocatalysts to further improve their performance.展开更多
Injuries to the nervous system account for the widespread morbidity,mortality,and discomfort worldwide.Artificial nerve guidance conduits(NGCs)offer a promising platform for nerve reconstruction,however,they require e...Injuries to the nervous system account for the widespread morbidity,mortality,and discomfort worldwide.Artificial nerve guidance conduits(NGCs)offer a promising platform for nerve reconstruction,however,they require extracellular matrix(ECM)-like features to better mimic the in vivo microenvironment.Consequently,this research was aimed to fabricate heparin/growth factors(GFs)-immobilized artificial NGCs.Heparin was covalently immobilized onto aligned electrospun polycapro-lactone/gelatin(PCL/Gel)nanofibers.Thereafter,basic fibroblast growth factor(bFGF)and nerve growth factor(NGF)were preferentially immobilized on heparinized nanofibers;the immobilization efficiency of GFs was found to be 50%with respect to(w.r.t.)their initial loaded amounts.The in vivo implantation of NGCs in a sciatic nerve defect model revealed the successful retention(~10%w.r.t the initial loaded amount)and bioactivity of NGF for up to 5 days.The permeability of bovine serum albumin(BSA)from nanofibrous membranes was further assessed and found to be comparable with the commercialized cel-lulose acetate membranes.The bioactivity of NGCs was assessed in a sciatic nerve defect model in rats for short-term(1 week)and long-term(1-month).The NGCs displayed good structural stability and biocompatibility in vivo.The in vivo evaluation revealed the accumulation of host cells into the transplanted NGCs.Taken together;these heparin/GFs-immobilized artificial NGCs may have broad implications for nerve regeneration and related tissue engineering disciplines.展开更多
Rapid progress in tissue engineering research in past decades has opened up vast possibilities to tackle the challenges of generating tissues or organs that mimic native structures. The success of tissue engineered co...Rapid progress in tissue engineering research in past decades has opened up vast possibilities to tackle the challenges of generating tissues or organs that mimic native structures. The success of tissue engineered constructs largely depends on the incorporation of a stable vascular network that eventually anastomoses with the host vasculature to support the various biological functions of embedded cells. In recent years, significant progress has been achieved with respect to extrusion, laser, micro-molding, and electrospinning-based techniques that allow the fabrication of any geometry in a layer-by-layer fashion. Moreover, decellularized matrix, self-assembled structures, and cell sheets have been explored to replace the biopolymers needed for scaffold fabrication. While the techniques have evolved to create specific tissues or organs with outstanding geometric precision, formation of interconnected, functional, and perfused vascular networks remains a challenge. This article briefly reviews recent progress in 3D fabrication approaches used to fabricate vascular networks with incorporated cells, angiogenic factors, proteins, and/or peptides. The influence of the fabricated network on blood vessel formation, and the various features, merits, and shortcomings of the various fabrication techniques are discussed and summarized.展开更多
The pathogenic cascade of Alzheimer’s disease(AD)characterized by amyloid-β protein accumulation is still poorly understood,partially owing to the limitations of relevant models without in vivo neural tissue microen...The pathogenic cascade of Alzheimer’s disease(AD)characterized by amyloid-β protein accumulation is still poorly understood,partially owing to the limitations of relevant models without in vivo neural tissue microenvironment to recapitulate cell-cell interactions.To better mimic neural tissue microenvironment,three-dimensional(3D)core-shell AD model constructs containing human neural progenitor cells(NSCs)with 2% matrigel as core bioink and 2% alginate as shell bioink have been bioprinted by a co-axial bioprinter,with a suitable shell thickness for nutrient exchange and barrier-free cell interaction cores.These constructs exhibit cell self-clustering and-assembling properties and engineered reproducibility with long-term cell viability and self-renewal,and a higher differentiation level compared to 2D and 3D MIX models.The different effects of 3D bioprinted,2D,and MIX microenvironments on the growth of NSCs are mainly related to biosynthesis of amino acids and glyoxylate and dicarboxylate metabolism on day 2 and ribosome,biosynthesis of amino acids and proteasome on day 14.Particularly,the model constructs demonstrated Aβ aggregation and higher expression of Aβ and tau isoform genes compared to 2D and MIX controls.AD model constructs will provide a promising strategy to facilitate the development of a 3D in vitro AD model for neurodegeneration research.展开更多
A conventional technique for microfluidic droplet generation is Co-axial Flow Focusing(CFF)in which a contraction zone is placed downstream of the dispersed phase nozzle.In this contraction zone,the dispersed-phase(dp...A conventional technique for microfluidic droplet generation is Co-axial Flow Focusing(CFF)in which a contraction zone is placed downstream of the dispersed phase nozzle.In this contraction zone,the dispersed-phase(dphase)fluid is pinched off by continuous-phase(c-phase)fluid to generate micro-droplets.Studying the influence of multiple parameters such as the fluids velocities and viscosities,the interfacial tension,and nozzle and orifice diameters on the droplet size is of great importance for the design and application of CFF devices.Thus,development of more complete numerical models is required.In this paper,we show our model is compatible with experimental data and then numerically investigate the effects of aforementioned parameters on the droplet generation in a CFF microfluidic device.Simulation results showed that the c-phase flow rate,viscosity and the interfacial tension had great impacts on the droplet size.The effect of the nozzle diameter on the generated droplet size was small compared to that of the orifice in a CFF device.Using the simulation results,a correlation was also developed and suggested which predicts the droplet size with less than 15%error in a wide range of the introduced dimensionless parameters.展开更多
A three-dimensional(3D)bioprinting is a new strategy for fabricating 3D cell-laden constructs that mimic the structural and functional characteristics of various tissues and provides a similar architecture and microen...A three-dimensional(3D)bioprinting is a new strategy for fabricating 3D cell-laden constructs that mimic the structural and functional characteristics of various tissues and provides a similar architecture and microenvironment of the native tissue.However,there are few reported studies on the neural function properties of bioengineered bone autografts.Thus,this study was aimed at investigating the effects of neural cell integration into 3D bioprinted bone constructs.The bioprinted hydrogel constructs could maintain long-term cell survival,support cell growth for human bone marrow-derived mesenchymal stem cells(BMMSCs),reduce cell surface biomarkers of stemness,and enhance orthopedic differentiation with higher expression of osteogenesis-related genes,including osteopontin(OPN)and bone morphogenetic protein-2.More importantly,the bioprinted constructs with neural cell integration indicated higher OPN gene and secretory alkaline phosphatase levels.These results suggested that the innervation in bioprinted bone constructs can accelerate the differentiation and maturation of bone development and provide patients with an option for accelerated bone function restoration.展开更多
This paper describes the design and development of the timer based on liquid level measurement system in which timer 555 is used in astable mode. The capacitor charging time i. e. the ON time pulse width of the ti...This paper describes the design and development of the timer based on liquid level measurement system in which timer 555 is used in astable mode. The capacitor charging time i. e. the ON time pulse width of the timer output waveform which is measured using a digital storage oscillator （DSO）,is linearly proportional to the capacitance of a co-axial cylindrical capacitive transducer, and this capacitance once again linearly varies with the change in liquid level. Hence, we obtain a linear relationship between the liquid level and the capacitor charging time. The main advantages of this developed system are linear input-output relationship, small in size, easily portable, cost effective, and independent on the ambient temperature effect. The system can also be exploited to measure dielectric constant of liquid or solid in various process industries.展开更多
In this paper,key dimensions of a co-axial dual-mechanical-port flux-switching permanent magnet(CADMP-FSPM)machine for fuel-based extended range electric vehicles(ER-EVs),including split ratio,stator/rotor pole arcs,r...In this paper,key dimensions of a co-axial dual-mechanical-port flux-switching permanent magnet(CADMP-FSPM)machine for fuel-based extended range electric vehicles(ER-EVs),including split ratio,stator/rotor pole arcs,rotor yoke thickness,etc.,are analyzed and optimized.Firstly,the topologies and operation principles of an exampled 3-phase CADMP-FSPM are introduced briefly,in which an inner-rotor FSPM machine with 12-stator-slots/10-rotor-poles for high-speed generation and an outer-rotor FSPM machine with 12-stator-slots/22-rotor-poles for low-speed motoring are assembled co-axially.Then,the relationship between the key dimensions and electromagnetic performance,particularly for electromagnetic torque(power),of the CADMP-FSPM machine is studied by 2D-finite element analysis(FEA).Further,the reasonable matches of split ratio,rotor/stator pole arcs and rotor yoke are determined and the original CADMP-FSPM machine is optimized correspondingly.Finally,the static characteristics,including no-load PM flux-linkage,electro-motive-force(EMF),winding inductances,cogging torques and electromagnetic torques,of the original and optimized machines are compared by 2D-FEA.The results verify that the optimized CADMP-FSPM machine can exhibit improved torque characteristics than the original one,i.e.,the torque ripples of the inner and outer machines can be reduced by 22.7%and 4.7%,respectively,and the average torque of the inner and outer machines can be increased by 0.43Nm and 2Nm,respectively.展开更多
基金supported by the National Natural Science Foundation of China(51325205,51290273,51521091,and 51861135201)the Chinese Academy of Sciences(XDB30000000,and ZDBS-LY-JSC027)+2 种基金Liaoning Revitalization Talents Program(XLYC1808013)the Program for Guangdong Introducing Innovative and Enterpreneurial Teams(2017ZT07C341)the Development and Reform Commission of Shenzhen Municipality for the development of the“Low-Dimensional Materials and Devices”discipline,and the Economic,Trade and Information Commission of Shenzhen Municipality for the“2017 Graphene Manufacturing Innovation Center Project”(201901171523).
文摘Splitting water under large current density is essential for efficient large-scale production and commercial utilization of hydrogen.However,the performance of the available electrocatalysts for hydrogen evolution reaction(HER)is far from satisfactory under large current density in alkaline electrolyte.Here we report a remarkably active and durable electrocatalyst,long and dense MoS2/Ni3S2 co-axial heterostructure nanowires on nickel foam(NF).Notably,it requires only 182 and 200 mV overpotential to achieve large current density of 500 and 1000 mA cm^-2,respectively,in alkaline solution,which are far superior to those of Pt/C-NF(281 and 444 mV)and the reported best non-noble metal catalysts(191 and 220 mV).The physical origin for this extraordinary HER performance is analyzed,which provides a useful guide for structure design of electrocatalysts to further improve their performance.
基金The part of this research was also funded by Grant-in-Aid for JSPS Fellows(Grant#JP21F21353)JSPS KAKENHI funding(JP18J20984 and JP21H01732).
文摘Injuries to the nervous system account for the widespread morbidity,mortality,and discomfort worldwide.Artificial nerve guidance conduits(NGCs)offer a promising platform for nerve reconstruction,however,they require extracellular matrix(ECM)-like features to better mimic the in vivo microenvironment.Consequently,this research was aimed to fabricate heparin/growth factors(GFs)-immobilized artificial NGCs.Heparin was covalently immobilized onto aligned electrospun polycapro-lactone/gelatin(PCL/Gel)nanofibers.Thereafter,basic fibroblast growth factor(bFGF)and nerve growth factor(NGF)were preferentially immobilized on heparinized nanofibers;the immobilization efficiency of GFs was found to be 50%with respect to(w.r.t.)their initial loaded amounts.The in vivo implantation of NGCs in a sciatic nerve defect model revealed the successful retention(~10%w.r.t the initial loaded amount)and bioactivity of NGF for up to 5 days.The permeability of bovine serum albumin(BSA)from nanofibrous membranes was further assessed and found to be comparable with the commercialized cel-lulose acetate membranes.The bioactivity of NGCs was assessed in a sciatic nerve defect model in rats for short-term(1 week)and long-term(1-month).The NGCs displayed good structural stability and biocompatibility in vivo.The in vivo evaluation revealed the accumulation of host cells into the transplanted NGCs.Taken together;these heparin/GFs-immobilized artificial NGCs may have broad implications for nerve regeneration and related tissue engineering disciplines.
基金supported by the Natural Sciences and Engineering Research Council of Canada [NSERC RGPIN-2014-05648]
文摘Rapid progress in tissue engineering research in past decades has opened up vast possibilities to tackle the challenges of generating tissues or organs that mimic native structures. The success of tissue engineered constructs largely depends on the incorporation of a stable vascular network that eventually anastomoses with the host vasculature to support the various biological functions of embedded cells. In recent years, significant progress has been achieved with respect to extrusion, laser, micro-molding, and electrospinning-based techniques that allow the fabrication of any geometry in a layer-by-layer fashion. Moreover, decellularized matrix, self-assembled structures, and cell sheets have been explored to replace the biopolymers needed for scaffold fabrication. While the techniques have evolved to create specific tissues or organs with outstanding geometric precision, formation of interconnected, functional, and perfused vascular networks remains a challenge. This article briefly reviews recent progress in 3D fabrication approaches used to fabricate vascular networks with incorporated cells, angiogenic factors, proteins, and/or peptides. The influence of the fabricated network on blood vessel formation, and the various features, merits, and shortcomings of the various fabrication techniques are discussed and summarized.
基金supported from the Key Research and Development Projects of Chinese People’s Liberation Army(Grant No.BWS17J036)Natural Science Foundation of China(Grant No.32000956)China Postdoctoral Science Foundation(Grant No.2020M670294).
文摘The pathogenic cascade of Alzheimer’s disease(AD)characterized by amyloid-β protein accumulation is still poorly understood,partially owing to the limitations of relevant models without in vivo neural tissue microenvironment to recapitulate cell-cell interactions.To better mimic neural tissue microenvironment,three-dimensional(3D)core-shell AD model constructs containing human neural progenitor cells(NSCs)with 2% matrigel as core bioink and 2% alginate as shell bioink have been bioprinted by a co-axial bioprinter,with a suitable shell thickness for nutrient exchange and barrier-free cell interaction cores.These constructs exhibit cell self-clustering and-assembling properties and engineered reproducibility with long-term cell viability and self-renewal,and a higher differentiation level compared to 2D and 3D MIX models.The different effects of 3D bioprinted,2D,and MIX microenvironments on the growth of NSCs are mainly related to biosynthesis of amino acids and glyoxylate and dicarboxylate metabolism on day 2 and ribosome,biosynthesis of amino acids and proteasome on day 14.Particularly,the model constructs demonstrated Aβ aggregation and higher expression of Aβ and tau isoform genes compared to 2D and MIX controls.AD model constructs will provide a promising strategy to facilitate the development of a 3D in vitro AD model for neurodegeneration research.
基金project has received funding support from the Natural Sciences and Engineering Research Council of Canada(NSERC)to PR。
文摘A conventional technique for microfluidic droplet generation is Co-axial Flow Focusing(CFF)in which a contraction zone is placed downstream of the dispersed phase nozzle.In this contraction zone,the dispersed-phase(dphase)fluid is pinched off by continuous-phase(c-phase)fluid to generate micro-droplets.Studying the influence of multiple parameters such as the fluids velocities and viscosities,the interfacial tension,and nozzle and orifice diameters on the droplet size is of great importance for the design and application of CFF devices.Thus,development of more complete numerical models is required.In this paper,we show our model is compatible with experimental data and then numerically investigate the effects of aforementioned parameters on the droplet generation in a CFF microfluidic device.Simulation results showed that the c-phase flow rate,viscosity and the interfacial tension had great impacts on the droplet size.The effect of the nozzle diameter on the generated droplet size was small compared to that of the orifice in a CFF device.Using the simulation results,a correlation was also developed and suggested which predicts the droplet size with less than 15%error in a wide range of the introduced dimensionless parameters.
基金supported from the Key Research and Development Projects of Chinese People’s Liberation Army(No.BWS17J036)Natural Science Foundation of China(Grant No.32000956)China Postdoctoral Science Foundation(Grant No.2020M670294).
文摘A three-dimensional(3D)bioprinting is a new strategy for fabricating 3D cell-laden constructs that mimic the structural and functional characteristics of various tissues and provides a similar architecture and microenvironment of the native tissue.However,there are few reported studies on the neural function properties of bioengineered bone autografts.Thus,this study was aimed at investigating the effects of neural cell integration into 3D bioprinted bone constructs.The bioprinted hydrogel constructs could maintain long-term cell survival,support cell growth for human bone marrow-derived mesenchymal stem cells(BMMSCs),reduce cell surface biomarkers of stemness,and enhance orthopedic differentiation with higher expression of osteogenesis-related genes,including osteopontin(OPN)and bone morphogenetic protein-2.More importantly,the bioprinted constructs with neural cell integration indicated higher OPN gene and secretory alkaline phosphatase levels.These results suggested that the innervation in bioprinted bone constructs can accelerate the differentiation and maturation of bone development and provide patients with an option for accelerated bone function restoration.
文摘This paper describes the design and development of the timer based on liquid level measurement system in which timer 555 is used in astable mode. The capacitor charging time i. e. the ON time pulse width of the timer output waveform which is measured using a digital storage oscillator （DSO）,is linearly proportional to the capacitance of a co-axial cylindrical capacitive transducer, and this capacitance once again linearly varies with the change in liquid level. Hence, we obtain a linear relationship between the liquid level and the capacitor charging time. The main advantages of this developed system are linear input-output relationship, small in size, easily portable, cost effective, and independent on the ambient temperature effect. The system can also be exploited to measure dielectric constant of liquid or solid in various process industries.
基金This work was supported by The National Basic Research Program(973 Program)(2013CB035603).
文摘In this paper,key dimensions of a co-axial dual-mechanical-port flux-switching permanent magnet(CADMP-FSPM)machine for fuel-based extended range electric vehicles(ER-EVs),including split ratio,stator/rotor pole arcs,rotor yoke thickness,etc.,are analyzed and optimized.Firstly,the topologies and operation principles of an exampled 3-phase CADMP-FSPM are introduced briefly,in which an inner-rotor FSPM machine with 12-stator-slots/10-rotor-poles for high-speed generation and an outer-rotor FSPM machine with 12-stator-slots/22-rotor-poles for low-speed motoring are assembled co-axially.Then,the relationship between the key dimensions and electromagnetic performance,particularly for electromagnetic torque(power),of the CADMP-FSPM machine is studied by 2D-finite element analysis(FEA).Further,the reasonable matches of split ratio,rotor/stator pole arcs and rotor yoke are determined and the original CADMP-FSPM machine is optimized correspondingly.Finally,the static characteristics,including no-load PM flux-linkage,electro-motive-force(EMF),winding inductances,cogging torques and electromagnetic torques,of the original and optimized machines are compared by 2D-FEA.The results verify that the optimized CADMP-FSPM machine can exhibit improved torque characteristics than the original one,i.e.,the torque ripples of the inner and outer machines can be reduced by 22.7%and 4.7%,respectively,and the average torque of the inner and outer machines can be increased by 0.43Nm and 2Nm,respectively.
