The rise of antibiotic resistance as one of the most serious global public health threats has necessitated the timely clinical diagnosis and precise treatment of deadly bacterial infections.To identify which types and...The rise of antibiotic resistance as one of the most serious global public health threats has necessitated the timely clinical diagnosis and precise treatment of deadly bacterial infections.To identify which types and doses of antibiotics remain effective for fighting against multi-drug-resistant pathogens,the development of rapid and accurate antibiotic-susceptibility testing(AST)is of primary importance.Conventional methods for AST in well-plate formats with disk diffusion or broth dilution are both labor-intensive and operationally tedious.The microfluidic chip provides a versatile tool for evaluating bacterial AST and resistant behaviors.In this paper,we develop an operationally simple,3D-printed microfluidic chip for AST which automatically deploys antibiotic concentration gradients and fluorescence intensity-based reporting to ideally reduce the report time for AST to within 5 h.By harnessing a commercially available,digital light processing(DLP)3D printing method that offers a rapid,high-precision microfluidic chip-manufacturing capability,we design and realize the accurate generation of on-chip antibiotic concentration gradients based on flow resistance and diffusion mechanisms.We further demonstrate the employment of the microfluidic chip for the AST of E.coli to representative clinical antibiotics of three classes:ampicillin,chloramphenicol,and kanamycin.The determined minimum inhibitory concentration values are comparable to those reported by conventional well-plate methods.Our proposed method demonstrates a promising approach for realizing robust,convenient,and automatable AST of clinical bacterial pathogens.展开更多
According to the second law of thermodynamics,spontaneous chemical processes will ultimately reach the equilibrium state with the lowest energy.However,in biological systems,there are numerous highenergy states far fr...According to the second law of thermodynamics,spontaneous chemical processes will ultimately reach the equilibrium state with the lowest energy.However,in biological systems,there are numerous highenergy states far from equilibrium.One typical example is the transmembrane ion-concentration gradient,which plays crucial roles in maintaining homeostasis,regulating cell volume,and enabling cell signaling.Transmembrane ion-concentration gradient is achieved by an active transport process that requires the input of energy and the action of pump proteins.Replicating this process with synthetic supramolecular systems is particularly challenging,requiring both the input of energy and very specific,spatiotemporal control over ion uptake and release.In nature,pump proteins,such as protein-based ion channels,have evolved highly intricate architectures to perform this function.In contrast,Aprahamian and coworkers recently developed a much simpler smallmolecule system that functions as a molecular ion pump,utilizing light energy to pump chloride ions across a hydrophobic barrier against the concentration gradient[1].展开更多
The inherent hysteresis of NiTi alloy samples is one of the key factors limiting their elastocaloric cooling performance.However,reducing hysteresis often leads to a decrease in adiabatic temperature change(ΔT_(ad)),...The inherent hysteresis of NiTi alloy samples is one of the key factors limiting their elastocaloric cooling performance.However,reducing hysteresis often leads to a decrease in adiabatic temperature change(ΔT_(ad)),thereby hindering the application of NiTi alloys in the refrigeration field.Here,NiTi alloys with alternating high-Ni and low-Ni content were fabricated by tailoring heat input during the wire-arc directed energy deposition(DED)process,which modifies the Ni concentration gradient and enables the modulation of the elastocaloric cooling performance of NiTi alloys.The coefficient of performance of material(COP_(mat))of the high-Ni NiTi alloy samples is relatively high,but theirΔT_(ad) during deformation is lower.On the other hand,the low-Ni NiTi alloy samples,while exhibiting higherΔT_(ad),show poorer stability during cycling.Due to the synergistic effect of the microstructures in the high-Ni and low-Ni region,a favorable combination of low cyclic hysteresis and highΔT_(ad) were achieved in the composite NiTi samples.Additionally,the composite NiTi samples also demonstrate excellent cyclic stability,with a degradation rate of only 4%during the cycling process under a 2%strain condition.This study proposes a feasible approach for regulating the elastocaloric effect of NiTi alloys,paving the way for additive manufacturing to prepare elastocaloric cooling materials.展开更多
The large and small sized Cu（solid）/Al（liquid） couples were prepared to investigate the directional growth behavior of primary a（Al） phase during a concentration-gradient-controlled solidification process under ...The large and small sized Cu（solid）/Al（liquid） couples were prepared to investigate the directional growth behavior of primary a（Al） phase during a concentration-gradient-controlled solidification process under various static magnetic fields（SMFs）.The results show that in the large couples,the α（Al） dendrites reveal a directional growth character whether without or with the SMF.However,the 12 T magnetic field induces regular growth,consistent deflection and the decrease of secondary arm spacing of the dendrites.In the small couples,the α（Al） dendrites still reveal a directional growth character to some extent with a SMF of ≤5 T.However,an 8.8 T SMF destroys the directional growth and induces severe random deflections of the dendrites.When the SMF increases to 12 T,the a（Al） dendrites become quite regular despite of the consistent deflection.The directional growth arises from the continuous long-range concentration gradient field built in the melt.The morphological modification is mainly related to the suppression of natural convections and the induction of thermoelectric magnetic convection by the SMF.展开更多
Nickel(Ni)-rich layered materials have attracted considerable interests as promising cathode materials for lithium ion batteries(LIBs)owing to their higher capacities and lower cost.Nevertheless,Mn-rich cathode materi...Nickel(Ni)-rich layered materials have attracted considerable interests as promising cathode materials for lithium ion batteries(LIBs)owing to their higher capacities and lower cost.Nevertheless,Mn-rich cathode materials usually suffer from poor cyclability caused by the unavoidable side-reactions between Ni^4+ions on the surface a nd electrolytes.The design of gradient concentration(GC)particles with Ni-rich inside and Mn-rich outside is proved to be an efficient way to address the issue.Herein,a series of LiNi0.6Co0.2Mn0.2O2(LNCM 622)materials with different GCs(the atomic ratio of Ni/Mn decreasing from the core to the outer layer)have been successfully synthesized via rationally designed co-precipitation process.Experimental results demonstrate that the GC of LNCM 622 materials plays an important role in their microstructure and electrochemical properties.The as-prepared GC3.5 cathode material with optimal GC can provide a shorter pathway for lithium-ion diffusion and stabilize the near-surface region,and finally achieve excellent electrochemical performances,delivering a discharge capacity over 176 mAh·g^-1 at 0.2 C rate and exhibiting capacity retention up to 94%after 100 cycles at 1 C.T h e rationally-designed co-precipitation process for fabricating the Ni-rich layered cathode materials with gradient composition lays a solid foundation for the preparation of high-performance cathode materials for LIBs.展开更多
Three-dimensional(3 D)frameworks have received much attention as an effective modification strategy for next-generation high-energy-density lithium metal batteries.However,the top-growth mode of lithium(Li)on the 3 D ...Three-dimensional(3 D)frameworks have received much attention as an effective modification strategy for next-generation high-energy-density lithium metal batteries.However,the top-growth mode of lithium(Li)on the 3 D framework remains a tough challenge.To achieve a uniform bottom-up Li growth,a scheme involving Ag concentration gradient in 3 D PVDF framework(C-Ag/PVDF)is proposed.Ag nanoparticles with a concentration gradient induce an interface activity gradient in the 3 D framework,and this gradient feature is still maintained during the cycle.As a result,the C-Ag/PVDF framework delivers a long lifespan over 1800 h at a current density of 1 mA cm^(-2) with a capacity of 1 mAh cm^(-2),and shows an ultra-long life(>1300 h)even at a high current density of 4 mA cm^(-2) with a capacity of 4 mAh cm^(-2).The advantage of concentration gradient provides further insights into the optimal design of the 3 D framework for stable Li metal anode.展开更多
Lithium nickel oxide(LiNiO_(2)) cathode materials are featured with high capacity and low cost for rechargeable lithium-ion batteries but suffer from severe interface and structure instability.Here we report that rati...Lithium nickel oxide(LiNiO_(2)) cathode materials are featured with high capacity and low cost for rechargeable lithium-ion batteries but suffer from severe interface and structure instability.Here we report that rationally designed LiNiO_(2) via concentration-gradient yttrium modification exhibits alleviative side reactions and improved electrochemical performance.The LiNiO_(2) cathode with LiYO_(2)-Y_(2) O_(3) coating layer delivers a discharge capacity of 225 mAh g^(-1) with a high initial Coulombic efficiency of 93.4%.These improvements can be attributed to the formation of in-situ modified hybrid LiYO_(2)-Y_(2 O3) coating layer,which suppresses phase transformation,electrolyte oxidation and salt dissociation due to the formation of protective cathode electrolyte interface.The results indicate promising application of concentration-gradient yttrium coating as a facile approach to stabilize nickel-rich cathode materials.展开更多
Full concentration gradient lithium-rich layered oxides are catching lots of interest as the next generation cathode for lithium-ion batteries due to their high discharge voltage,reduced voltage decay and enhanced rat...Full concentration gradient lithium-rich layered oxides are catching lots of interest as the next generation cathode for lithium-ion batteries due to their high discharge voltage,reduced voltage decay and enhanced rate performance,whereas the high lithium residues on its surface impairs the structure stability and long-term cycle performance.Herein,a facile multifunctional surface modification method is implemented to eliminate surface lithium residues of full concentration gradient lithium-rich layered oxides by a wet chemistry reaction with tetrabutyl titanate and the post-annealing process.It realizes not only a stable Li_(2)TiO_(3)coating layer with 3D diffusion channels for fast Li^(+)ions transfer,but also dopes partial Ti^(4+)ions into the sub-surface region of full concentration gradient lithium-rich layered oxides to further strengthen its crystal structure.Consequently,the modified full concentration gradient lithium-rich layered oxides exhibit improved structure stability,elevated thermal stability with decomposition temperature from 289.57℃to 321.72℃,and enhanced cycle performance(205.1 mAh g^(-1)after 150 cycles)with slowed voltage drop(1.67 mV per cycle).This work proposes a facile and integrated modification method to enhance the comprehensive performance of full concentration gradient lithium-rich layered oxides,which can facilitate its practical application for developing higher energy density lithium-ion batteries.展开更多
Concentration gradient and fluid shear stress(FSS)for cell microenvironment were investigated through microfluidic technology.The Darcy–Weisbach equation combined with computational fluid dynamics modeling was exploi...Concentration gradient and fluid shear stress(FSS)for cell microenvironment were investigated through microfluidic technology.The Darcy–Weisbach equation combined with computational fluid dynamics modeling was exploited to design the microfluidic chip,and the FSS distribution on the cell model with varying micro-channels(triangular,conical,and elliptical).The diffusion with the incompressible laminar flow model by solving the time-dependent diffusion–convection equation was applied to simulate the gradient profiles of concentration in the micro-channels.For the study of single cell in-depth,the FSS was investigated by the usage of polystyrene particles and the concentration diffusion distribution was studied by the usage of different colors of dyes.A successful agreement between model simulations and experimental data was obtained.Finally,based on the established method,the communication between individual cells was envisaged and modeled.The developed method provides valuable insights and allows to continuously improve the design of microfluidic devices for the study of single cell,the occurrence and development of tumors,and therapeutic applications.展开更多
This paper describes a simple method of generating concentration gradients with linear and parabolic profiles by using a Christmas tree-shaped microfluidic network.The microfluidic gradient generator consists of two p...This paper describes a simple method of generating concentration gradients with linear and parabolic profiles by using a Christmas tree-shaped microfluidic network.The microfluidic gradient generator consists of two parts：a Christmas tree-shaped network for gradient generation and a broad microchannel for detection.A two-dimensional model was built to analyze the flow field and the mass transfer in the microfluidic network.The simulating results show that a series of linear and parabolic gradient profiles were generated via adjusting relative flow rate ratios of the two source solutions（R_L^2≥0.995 and _PR^2≥0.999）,which could match well with the experimental results（R_L^2≥0.987 and _PR^2≥0.996）.The proposed method is promising for the generation of linear and parabolic concentration gradient profiles,with the potential in chemical and biological applications such as combinatorial chemistry synthesis,stem cell differentiation or cytotoxicity assays.展开更多
A two-dimensional detonation in H2–O2 system is simulated by a high-resolution code based on the fifth-order weighted essentially non-oscillatory(WENO)scheme in the spatial discretization and the 3th-order additive R...A two-dimensional detonation in H2–O2 system is simulated by a high-resolution code based on the fifth-order weighted essentially non-oscillatory(WENO)scheme in the spatial discretization and the 3th-order additive Runge–Kutta schemes in the time discretization,by using a detailed chemical model.The effect of a concentration gradient on cellular detonation is investigated.The results show that with the increase of the concentration gradient,the cell instability of detonation increases and gives rise to the oscillation of average detonation velocity.After a long time,for the case of the lower gradient the detonation can be sustained,with the multi-head mode and single-head mode alternating,while for the higher gradient it propagates with a single-head mode.展开更多
Inspired by biological systems that have the inherent skill to generate considerable bioelectricity from the salt content in fluids with highly selective ion channels and pumps on cell membranes, herein, a fully abiot...Inspired by biological systems that have the inherent skill to generate considerable bioelectricity from the salt content in fluids with highly selective ion channels and pumps on cell membranes, herein, a fully abiotic, single glass conical nanopores energy-harvesting is demonstrated. Ion current rectification （ICR） in negatively charged glass conical nanopores is shown to be controlled by the electrolyte concentration gradient depending on the direction of ion diffusion. The degree of ICR is enhanced with the increasing forward concentration difference. An unusual rectification inversion is observed when the concentration gradient is reversely applied. The maximum power output with the individual nanopore approaches 10^4pW. This facile and cost-efficient energy-harvesting system has the potential to power tiny biomedical devices or construct future clean-energy recovery plants.展开更多
The electron concentration horizontal gradient vector of the ionosphere and its south-north and east-west components over Chongqing station are analyzed and calculated, using the first approximation, time correlation ...The electron concentration horizontal gradient vector of the ionosphere and its south-north and east-west components over Chongqing station are analyzed and calculated, using the first approximation, time correlation and space correlation and another approach introduced. And then, the validity of the two methods is analyzed and compared.展开更多
There is limited information available on CO2 concentration and flux over marsh. The objective of this work was to characterize CO2 concentration and flux within and above marsh plant (Cares lasiocarpa Ehrh. and C. ps...There is limited information available on CO2 concentration and flux over marsh. The objective of this work was to characterize CO2 concentration and flux within and above marsh plant (Cares lasiocarpa Ehrh. and C. pseudoucuaica F. Schm) canopy at heights 0. 5, 1. 0 and 1. 5 m.CO2 concentration was measured sequentially every 3 bars by using an infrared gas analyzer. Soil and air temperature, wind speed, net radiation and soil heat flux were also measured simultaneously. Extremely drily minimum and maximum CO2 concentration rangal from 250 to 754 μmd/mol for the 4-year work. The typical minimum and maximum values ranged from 314 to 464 μmol/mol at the height of marsh plant (about 0. 5 m) during the fruiting perioed and mature date. The seasonal changes in CO2 concentration show that the minimum CO2 concentration occurred in the fruiting period and mature date, and both of their minimum values were 314 μmol/mol. This illustrates that CO2 consumed by photosynthesis was stable during the period. The flux of CO2 can be thought as a turbulent diffusion phenomenon. By micrometeorological methods, the diurnal CO2 fluxes were measured in the flowering peried, fruiting period, early mature date, late mature date and yellow-ripe stage. Their values were -0. 18, 38. 15,24. 13, 10. 9 and 4. 91 μmol/mol respectively.展开更多
Based on the commonly-used definition of the semi-permeable material(SPM),in which the solvent(such as water)can pass through but the solute cannot move freely,a novel constitutive equation is presented,in this paper,...Based on the commonly-used definition of the semi-permeable material(SPM),in which the solvent(such as water)can pass through but the solute cannot move freely,a novel constitutive equation is presented,in this paper,to theoretically express the intrinsic constitutive relationship between the porosity variation rate with time and the solute concentration variation rate with time.From this theoretical finding,a mathematical model is established to describe the solute concentrationgradient driven water flow and solute concentration variation problem in solution-saturated semi-permeable materials(SSSPMs).In particular,the solute concentration variation in the considered problem can be mathematically described as a linear homogeneous second-order partial differential equation with a variable coefficient in the front of the time term.A special mathematical transform is presented and used to solve this equation,so that the analytical solution for the solute concentration variation in the considered problem has been derived in a purely mathematical manner.The derived analytical solution is then used to provide some theoretical understanding of solute concentration variations in the SSSPM layer.展开更多
Semi-quantitative electron probe microanalysis （EPMA） mapping, scanning electron microscopy （SEM） and transmission electron microscopy （TEM） were employed to study the effect of one-step and two-step treatments ...Semi-quantitative electron probe microanalysis （EPMA） mapping, scanning electron microscopy （SEM） and transmission electron microscopy （TEM） were employed to study the effect of one-step and two-step treatments on the Zr distribution and Al3Zr dispersoid characteristics in as-cast commercial AA7150 aluminum alloy. It is shown that the Zr concentration in the dendrite centre regions is higher than that near the dendrite edges in the as-cast condition, and that homogenization at 460 °C for 20 h is insufficient to remove these concentration gradients. After homogenizing at 460-480 °C, a high number density of larger dispersoids can be observed in dendrite centre regions but not near dendrite edges. Furthermore, the dispersoid size increases with increasing the temperature during both one-step and two-step homogenization treatments.展开更多
CO2 concentrations at different heights in a broadleaved/Korean forest (with a mean height of 26 m) were measured with infrared gas analyzer IRGA (model 2250D, LI-COR Inc. and LI-COR, 820) from Aug. to Oct. of 1999, A...CO2 concentrations at different heights in a broadleaved/Korean forest (with a mean height of 26 m) were measured with infrared gas analyzer IRGA (model 2250D, LI-COR Inc. and LI-COR, 820) from Aug. to Oct. of 1999, Apr. to Jul. of 2000, and from Aug. 2002 to Sept. 2003. Based on the collected dada, the diurnal and seasonal dynamics of profiles and storage of carbon dioxide in the forest were analyzed. The diurnal CO2 profiles showed that the vertical distribution of CO2 concentration were different for daytime and nighttime, and the CO2 concentration was highest close to forest floor, no matter at daytime and nighttime. The seasonal profiles of CO2 showed that stratification in the canopy was evident during growth season. CO2 concentrations at different heights (60 m to 2.5 m) had a little change in March, with a difference of 10 mmolmol-1, but had a significant change in July, with a difference of 60 mmolmol-1. In July, there also existed a greater gradient of CO2 concentrations at canopy (22, 26 and 32 m), with a difference of 8 mmolmol-1. The calculated total storage (ΔC/Δt ) of CO2 in the air column with height of 40 m beneath eddy covariance instrument was negative, and made a little contribution to NEE.展开更多
Al80Ni6 Y8 Co4 Cu2 amorphous ribbons were isothermally annealed and a mixed structure consisting of α-Al particle with a size of less than 15nm and Al3Ni compound with a size of about 30nm was obtained. The crystall...Al80Ni6 Y8 Co4 Cu2 amorphous ribbons were isothermally annealed and a mixed structure consisting of α-Al particle with a size of less than 15nm and Al3Ni compound with a size of about 30nm was obtained. The crystallization kinetics of Al80Ni6 Y8 Co4 Cu2 amorphous alloy shows that the precipitation of α-Al particles is the growth process controlled by diffusion of the solute elements rejected from the growing crystals. By quenching at different cooling rates, a mixed structure consisting of nanoscale α-Al particles and the remaining glass matrix or structure consisting of nanoscale particle (Al phase or Al3Ni compound) with a size of about 100nm was formed. The addition of Co elements and Cu elements to Al-Ni-Y alloy systems increases the glass formation ability of the alloy and the thermal stability of the supercooled liquid region against crystallization, which results from significant difference of atomic size, strong bonding nature among constituent elements and the low diffisivity of the solute elements due to the concentration gradient in the growing front of crystals.展开更多
The size of bubbles created in the flotation process is of great importance to the efficiency of the mineral separation achieved.Meanwhile,it is believed that frother transport between phases is perhaps the most impor...The size of bubbles created in the flotation process is of great importance to the efficiency of the mineral separation achieved.Meanwhile,it is believed that frother transport between phases is perhaps the most important reason for the interactive nature of the phenomena occurring in the bulk and froth phases in flotation,as frother adsorbed in the surface of rising bubbles is removed from the bulk phase and then released into the froth as a fraction of the bubbles burst.This causes the increased concentration in the froth compared to the bulk concentration,named as frother partitioning.Partitioning reflects the adsorption of frother on bubbles and how to influence bubble size is not known.There currently exists no such a topic aiming to link these two key parameters.To fill this vacancy,the correspondence between bubble size and frother partitioning was examined.Bubble size was measured by sampling-for-imaging(SFI)technique.Using total organic carbon(TOC)analysis to measure the frother partitioning between froth and bulk phases was determined.Measurements have shown,with no exceptions including four different frothers,higher frother concentration is in the bulk than in the froth.The results also show strong partitioning giving an increase in bubble size which implies there is a compelling relationship between these two,represented by CFroth/CBulk and D32.The CFroth/CBulkand D32 curves show similar exponential decay relationships as a function of added frother in the system,strongly suggesting that the frother concentration gradient between the bulk solution and the bubble interface is the driving force contributing to bubble size reduction.展开更多
In this paper,one-and two-dimensional numerical simulations are carried out to study the effects of fuel concentration gradients(such as steep,intermediate and shallow)on the detonation wave behavior.The equivalent ra...In this paper,one-and two-dimensional numerical simulations are carried out to study the effects of fuel concentration gradients(such as steep,intermediate and shallow)on the detonation wave behavior.The equivalent ratio range of detonation propagation,the quenching mechanism and the change of cell size are discussed in detail.The simulation results show,as the fuel concentration gradient increases,the detonation wavefront decays faster and decouples into a leading shock and a following flame at equivalence ratios of 0.68,0.64 and 0.62,respectively.Moreover,there are two modes of the quenching mechanism.One occurs in the steep gradient that the detonation wave fails rapidly.The O_(2)in front of the detonation wave passes through the detonation wave and forms some unburned O_(2)pockets.The unburned pockets are affected by the marginal walls and reduce the heat release.The other occurs in the intermediate and shallow gradients that more triple points will survive in the flow field,which leads to a difference in the propagation speed of the detonation wavefront.This makes the detonation wavefront bent and deformed.The unburned O_(2)pockets are affected by the strong instability near the triple points and show different distribution characteristics compared with the steep gradient,which may be helpful to the detonation propagation.In addition,as the fuel concentration gradient increases,the triple points moving toward the wall gradually disappear while the triple points that move toward the center can continue to survive,which leads to the gradual increase in cell size and irregularity of the cell structure.展开更多
基金the National Natural Science Foundation of China(No.51908467)and by institutional funds from the Westlake University。
文摘The rise of antibiotic resistance as one of the most serious global public health threats has necessitated the timely clinical diagnosis and precise treatment of deadly bacterial infections.To identify which types and doses of antibiotics remain effective for fighting against multi-drug-resistant pathogens,the development of rapid and accurate antibiotic-susceptibility testing(AST)is of primary importance.Conventional methods for AST in well-plate formats with disk diffusion or broth dilution are both labor-intensive and operationally tedious.The microfluidic chip provides a versatile tool for evaluating bacterial AST and resistant behaviors.In this paper,we develop an operationally simple,3D-printed microfluidic chip for AST which automatically deploys antibiotic concentration gradients and fluorescence intensity-based reporting to ideally reduce the report time for AST to within 5 h.By harnessing a commercially available,digital light processing(DLP)3D printing method that offers a rapid,high-precision microfluidic chip-manufacturing capability,we design and realize the accurate generation of on-chip antibiotic concentration gradients based on flow resistance and diffusion mechanisms.We further demonstrate the employment of the microfluidic chip for the AST of E.coli to representative clinical antibiotics of three classes:ampicillin,chloramphenicol,and kanamycin.The determined minimum inhibitory concentration values are comparable to those reported by conventional well-plate methods.Our proposed method demonstrates a promising approach for realizing robust,convenient,and automatable AST of clinical bacterial pathogens.
基金financial supports of National Natural Science Foundation of China(22171226)Natural Science Basic Research Program of Shaanxi(2022JC-06).
文摘According to the second law of thermodynamics,spontaneous chemical processes will ultimately reach the equilibrium state with the lowest energy.However,in biological systems,there are numerous highenergy states far from equilibrium.One typical example is the transmembrane ion-concentration gradient,which plays crucial roles in maintaining homeostasis,regulating cell volume,and enabling cell signaling.Transmembrane ion-concentration gradient is achieved by an active transport process that requires the input of energy and the action of pump proteins.Replicating this process with synthetic supramolecular systems is particularly challenging,requiring both the input of energy and very specific,spatiotemporal control over ion uptake and release.In nature,pump proteins,such as protein-based ion channels,have evolved highly intricate architectures to perform this function.In contrast,Aprahamian and coworkers recently developed a much simpler smallmolecule system that functions as a molecular ion pump,utilizing light energy to pump chloride ions across a hydrophobic barrier against the concentration gradient[1].
基金financially supported by the National Natural Science Foundation of China(Nos.52275374 and 52205414)the Key Research and Development Projects of Shaanxi Province(No.2023-YBGY-361)+1 种基金the Xi’an Jiaotong University Basic Research Funds for Freedom of Exploration and Innovation-Student Programs(No.xzy022024099)the Taihu Lake Innovation Fund for the School of Future Technology of Xi’an Jiaotong University.
文摘The inherent hysteresis of NiTi alloy samples is one of the key factors limiting their elastocaloric cooling performance.However,reducing hysteresis often leads to a decrease in adiabatic temperature change(ΔT_(ad)),thereby hindering the application of NiTi alloys in the refrigeration field.Here,NiTi alloys with alternating high-Ni and low-Ni content were fabricated by tailoring heat input during the wire-arc directed energy deposition(DED)process,which modifies the Ni concentration gradient and enables the modulation of the elastocaloric cooling performance of NiTi alloys.The coefficient of performance of material(COP_(mat))of the high-Ni NiTi alloy samples is relatively high,but theirΔT_(ad) during deformation is lower.On the other hand,the low-Ni NiTi alloy samples,while exhibiting higherΔT_(ad),show poorer stability during cycling.Due to the synergistic effect of the microstructures in the high-Ni and low-Ni region,a favorable combination of low cyclic hysteresis and highΔT_(ad) were achieved in the composite NiTi samples.Additionally,the composite NiTi samples also demonstrate excellent cyclic stability,with a degradation rate of only 4%during the cycling process under a 2%strain condition.This study proposes a feasible approach for regulating the elastocaloric effect of NiTi alloys,paving the way for additive manufacturing to prepare elastocaloric cooling materials.
基金Projects(51201029,51071042,51374067)supported by the National Natural Science Foundation of ChinaProjects(N130409002,N130209001)supported by the Research Funds for the Central UniversitiesProject(2012M520637)supported by the China Postdoctoral Science Foundation
文摘The large and small sized Cu（solid）/Al（liquid） couples were prepared to investigate the directional growth behavior of primary a（Al） phase during a concentration-gradient-controlled solidification process under various static magnetic fields（SMFs）.The results show that in the large couples,the α（Al） dendrites reveal a directional growth character whether without or with the SMF.However,the 12 T magnetic field induces regular growth,consistent deflection and the decrease of secondary arm spacing of the dendrites.In the small couples,the α（Al） dendrites still reveal a directional growth character to some extent with a SMF of ≤5 T.However,an 8.8 T SMF destroys the directional growth and induces severe random deflections of the dendrites.When the SMF increases to 12 T,the a（Al） dendrites become quite regular despite of the consistent deflection.The directional growth arises from the continuous long-range concentration gradient field built in the melt.The morphological modification is mainly related to the suppression of natural convections and the induction of thermoelectric magnetic convection by the SMF.
基金the financial support of the National Natural Science Foundation of China(Grant Nos.91834301,91534102 and 21271058)Science and Technology Project of Anhui Province(Nos.201903a05020021 and 17030901067).
文摘Nickel(Ni)-rich layered materials have attracted considerable interests as promising cathode materials for lithium ion batteries(LIBs)owing to their higher capacities and lower cost.Nevertheless,Mn-rich cathode materials usually suffer from poor cyclability caused by the unavoidable side-reactions between Ni^4+ions on the surface a nd electrolytes.The design of gradient concentration(GC)particles with Ni-rich inside and Mn-rich outside is proved to be an efficient way to address the issue.Herein,a series of LiNi0.6Co0.2Mn0.2O2(LNCM 622)materials with different GCs(the atomic ratio of Ni/Mn decreasing from the core to the outer layer)have been successfully synthesized via rationally designed co-precipitation process.Experimental results demonstrate that the GC of LNCM 622 materials plays an important role in their microstructure and electrochemical properties.The as-prepared GC3.5 cathode material with optimal GC can provide a shorter pathway for lithium-ion diffusion and stabilize the near-surface region,and finally achieve excellent electrochemical performances,delivering a discharge capacity over 176 mAh·g^-1 at 0.2 C rate and exhibiting capacity retention up to 94%after 100 cycles at 1 C.T h e rationally-designed co-precipitation process for fabricating the Ni-rich layered cathode materials with gradient composition lays a solid foundation for the preparation of high-performance cathode materials for LIBs.
基金supported by the Fundamental Research Funds for the Central Universities,China(ZYGX2019Z008)the National Natural Science Foundation of China(52072061)the Open Fund of the Key Laboratory for Renewable Energy,Chinese Academy of Sciences,Beijing Key Laboratory for New Energy Materials and Devices。
文摘Three-dimensional(3 D)frameworks have received much attention as an effective modification strategy for next-generation high-energy-density lithium metal batteries.However,the top-growth mode of lithium(Li)on the 3 D framework remains a tough challenge.To achieve a uniform bottom-up Li growth,a scheme involving Ag concentration gradient in 3 D PVDF framework(C-Ag/PVDF)is proposed.Ag nanoparticles with a concentration gradient induce an interface activity gradient in the 3 D framework,and this gradient feature is still maintained during the cycle.As a result,the C-Ag/PVDF framework delivers a long lifespan over 1800 h at a current density of 1 mA cm^(-2) with a capacity of 1 mAh cm^(-2),and shows an ultra-long life(>1300 h)even at a high current density of 4 mA cm^(-2) with a capacity of 4 mAh cm^(-2).The advantage of concentration gradient provides further insights into the optimal design of the 3 D framework for stable Li metal anode.
基金supported by the National Key R&D Program of China (2016YFA0202503)the SINOPEC Project (129015-1)+2 种基金the National Natural Science Foundation of China (21835004 and21925503)the 111 Project from the Ministry of Education of China(B12015)the Fundamental Research Funds for the Central Universities。
文摘Lithium nickel oxide(LiNiO_(2)) cathode materials are featured with high capacity and low cost for rechargeable lithium-ion batteries but suffer from severe interface and structure instability.Here we report that rationally designed LiNiO_(2) via concentration-gradient yttrium modification exhibits alleviative side reactions and improved electrochemical performance.The LiNiO_(2) cathode with LiYO_(2)-Y_(2) O_(3) coating layer delivers a discharge capacity of 225 mAh g^(-1) with a high initial Coulombic efficiency of 93.4%.These improvements can be attributed to the formation of in-situ modified hybrid LiYO_(2)-Y_(2 O3) coating layer,which suppresses phase transformation,electrolyte oxidation and salt dissociation due to the formation of protective cathode electrolyte interface.The results indicate promising application of concentration-gradient yttrium coating as a facile approach to stabilize nickel-rich cathode materials.
基金financially supported by the Natural Science Foundation of Shandong Province(ZR2022QB166,ZR2020KE032)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA22010600)+3 种基金the Youth Innovation Promotion Association of CAS(2021210)the Foundation of Qingdao Postdoctoral Application Program(Y63302190F)the Natural Science Foundation of Qingdao Institute ofBioenergy and Bioprocess Technology(QIBEBT SZ202101)support from the Max Planck-POSTECH-Hsinchu Center for Complex Phase Materials
文摘Full concentration gradient lithium-rich layered oxides are catching lots of interest as the next generation cathode for lithium-ion batteries due to their high discharge voltage,reduced voltage decay and enhanced rate performance,whereas the high lithium residues on its surface impairs the structure stability and long-term cycle performance.Herein,a facile multifunctional surface modification method is implemented to eliminate surface lithium residues of full concentration gradient lithium-rich layered oxides by a wet chemistry reaction with tetrabutyl titanate and the post-annealing process.It realizes not only a stable Li_(2)TiO_(3)coating layer with 3D diffusion channels for fast Li^(+)ions transfer,but also dopes partial Ti^(4+)ions into the sub-surface region of full concentration gradient lithium-rich layered oxides to further strengthen its crystal structure.Consequently,the modified full concentration gradient lithium-rich layered oxides exhibit improved structure stability,elevated thermal stability with decomposition temperature from 289.57℃to 321.72℃,and enhanced cycle performance(205.1 mAh g^(-1)after 150 cycles)with slowed voltage drop(1.67 mV per cycle).This work proposes a facile and integrated modification method to enhance the comprehensive performance of full concentration gradient lithium-rich layered oxides,which can facilitate its practical application for developing higher energy density lithium-ion batteries.
基金National Natural Science Foundation of China(No.21804045)Fujian Provincial Department of Science and Technology(No.2019I0014)Promotion Program for Young and Middle-aged Teachers in Science and Technology Research of Huaqiao University(No.ZQN-PY612)。
文摘Concentration gradient and fluid shear stress(FSS)for cell microenvironment were investigated through microfluidic technology.The Darcy–Weisbach equation combined with computational fluid dynamics modeling was exploited to design the microfluidic chip,and the FSS distribution on the cell model with varying micro-channels(triangular,conical,and elliptical).The diffusion with the incompressible laminar flow model by solving the time-dependent diffusion–convection equation was applied to simulate the gradient profiles of concentration in the micro-channels.For the study of single cell in-depth,the FSS was investigated by the usage of polystyrene particles and the concentration diffusion distribution was studied by the usage of different colors of dyes.A successful agreement between model simulations and experimental data was obtained.Finally,based on the established method,the communication between individual cells was envisaged and modeled.The developed method provides valuable insights and allows to continuously improve the design of microfluidic devices for the study of single cell,the occurrence and development of tumors,and therapeutic applications.
基金Supported by the National Natural Science Foundation of China(81372358,81527801,51303140,and 81602489)the Natural Science Foundation of Hubei Province(2014CFA029)+1 种基金the Colleges of Hubei Province Outstanding Youth Science and Technology Innovation Team(T201305)the Applied Foundational Research Program of Wuhan Municipal Science and Technology Bureau(2015060101010056)
文摘This paper describes a simple method of generating concentration gradients with linear and parabolic profiles by using a Christmas tree-shaped microfluidic network.The microfluidic gradient generator consists of two parts：a Christmas tree-shaped network for gradient generation and a broad microchannel for detection.A two-dimensional model was built to analyze the flow field and the mass transfer in the microfluidic network.The simulating results show that a series of linear and parabolic gradient profiles were generated via adjusting relative flow rate ratios of the two source solutions（R_L^2≥0.995 and _PR^2≥0.999）,which could match well with the experimental results（R_L^2≥0.987 and _PR^2≥0.996）.The proposed method is promising for the generation of linear and parabolic concentration gradient profiles,with the potential in chemical and biological applications such as combinatorial chemistry synthesis,stem cell differentiation or cytotoxicity assays.
基金Natural National Science Foundation of China(Grant Nos.11972090,11732003,and U1830139)the Beijing Natural Science Foundation,China(Grant No.8182050)the National Key Research and Development Program of China(Grant No.2017YFC0804700).
文摘A two-dimensional detonation in H2–O2 system is simulated by a high-resolution code based on the fifth-order weighted essentially non-oscillatory(WENO)scheme in the spatial discretization and the 3th-order additive Runge–Kutta schemes in the time discretization,by using a detailed chemical model.The effect of a concentration gradient on cellular detonation is investigated.The results show that with the increase of the concentration gradient,the cell instability of detonation increases and gives rise to the oscillation of average detonation velocity.After a long time,for the case of the lower gradient the detonation can be sustained,with the multi-head mode and single-head mode alternating,while for the higher gradient it propagates with a single-head mode.
基金financial support from the National Natural Science Foundation of China(Nos.21375111,21127005,20975084)the Ph.D.Programs Foundation of the Ministry of Education of China(No.20110121110011)
文摘Inspired by biological systems that have the inherent skill to generate considerable bioelectricity from the salt content in fluids with highly selective ion channels and pumps on cell membranes, herein, a fully abiotic, single glass conical nanopores energy-harvesting is demonstrated. Ion current rectification （ICR） in negatively charged glass conical nanopores is shown to be controlled by the electrolyte concentration gradient depending on the direction of ion diffusion. The degree of ICR is enhanced with the increasing forward concentration difference. An unusual rectification inversion is observed when the concentration gradient is reversely applied. The maximum power output with the individual nanopore approaches 10^4pW. This facile and cost-efficient energy-harvesting system has the potential to power tiny biomedical devices or construct future clean-energy recovery plants.
基金Supported by the National Natural Science Foundation of China(6 95 710 2 0 ) and the Research Fund for the Doctoral Program of H
文摘The electron concentration horizontal gradient vector of the ionosphere and its south-north and east-west components over Chongqing station are analyzed and calculated, using the first approximation, time correlation and space correlation and another approach introduced. And then, the validity of the two methods is analyzed and compared.
文摘There is limited information available on CO2 concentration and flux over marsh. The objective of this work was to characterize CO2 concentration and flux within and above marsh plant (Cares lasiocarpa Ehrh. and C. pseudoucuaica F. Schm) canopy at heights 0. 5, 1. 0 and 1. 5 m.CO2 concentration was measured sequentially every 3 bars by using an infrared gas analyzer. Soil and air temperature, wind speed, net radiation and soil heat flux were also measured simultaneously. Extremely drily minimum and maximum CO2 concentration rangal from 250 to 754 μmd/mol for the 4-year work. The typical minimum and maximum values ranged from 314 to 464 μmol/mol at the height of marsh plant (about 0. 5 m) during the fruiting perioed and mature date. The seasonal changes in CO2 concentration show that the minimum CO2 concentration occurred in the fruiting period and mature date, and both of their minimum values were 314 μmol/mol. This illustrates that CO2 consumed by photosynthesis was stable during the period. The flux of CO2 can be thought as a turbulent diffusion phenomenon. By micrometeorological methods, the diurnal CO2 fluxes were measured in the flowering peried, fruiting period, early mature date, late mature date and yellow-ripe stage. Their values were -0. 18, 38. 15,24. 13, 10. 9 and 4. 91 μmol/mol respectively.
基金supported by the National Natural Science Foundation of China(Grant No.42162028).
文摘Based on the commonly-used definition of the semi-permeable material(SPM),in which the solvent(such as water)can pass through but the solute cannot move freely,a novel constitutive equation is presented,in this paper,to theoretically express the intrinsic constitutive relationship between the porosity variation rate with time and the solute concentration variation rate with time.From this theoretical finding,a mathematical model is established to describe the solute concentrationgradient driven water flow and solute concentration variation problem in solution-saturated semi-permeable materials(SSSPMs).In particular,the solute concentration variation in the considered problem can be mathematically described as a linear homogeneous second-order partial differential equation with a variable coefficient in the front of the time term.A special mathematical transform is presented and used to solve this equation,so that the analytical solution for the solute concentration variation in the considered problem has been derived in a purely mathematical manner.The derived analytical solution is then used to provide some theoretical understanding of solute concentration variations in the SSSPM layer.
文摘Semi-quantitative electron probe microanalysis （EPMA） mapping, scanning electron microscopy （SEM） and transmission electron microscopy （TEM） were employed to study the effect of one-step and two-step treatments on the Zr distribution and Al3Zr dispersoid characteristics in as-cast commercial AA7150 aluminum alloy. It is shown that the Zr concentration in the dendrite centre regions is higher than that near the dendrite edges in the as-cast condition, and that homogenization at 460 °C for 20 h is insufficient to remove these concentration gradients. After homogenizing at 460-480 °C, a high number density of larger dispersoids can be observed in dendrite centre regions but not near dendrite edges. Furthermore, the dispersoid size increases with increasing the temperature during both one-step and two-step homogenization treatments.
基金This study is supported by The Development Plan of State Key Fundamental Research of China (973) (contract No. 2002CB412502),by Knowledge Innovation Project of CAS (KZCX1-SW-01-03) and by Natural Science Foundation of China (30170167).
文摘CO2 concentrations at different heights in a broadleaved/Korean forest (with a mean height of 26 m) were measured with infrared gas analyzer IRGA (model 2250D, LI-COR Inc. and LI-COR, 820) from Aug. to Oct. of 1999, Apr. to Jul. of 2000, and from Aug. 2002 to Sept. 2003. Based on the collected dada, the diurnal and seasonal dynamics of profiles and storage of carbon dioxide in the forest were analyzed. The diurnal CO2 profiles showed that the vertical distribution of CO2 concentration were different for daytime and nighttime, and the CO2 concentration was highest close to forest floor, no matter at daytime and nighttime. The seasonal profiles of CO2 showed that stratification in the canopy was evident during growth season. CO2 concentrations at different heights (60 m to 2.5 m) had a little change in March, with a difference of 10 mmolmol-1, but had a significant change in July, with a difference of 60 mmolmol-1. In July, there also existed a greater gradient of CO2 concentrations at canopy (22, 26 and 32 m), with a difference of 8 mmolmol-1. The calculated total storage (ΔC/Δt ) of CO2 in the air column with height of 40 m beneath eddy covariance instrument was negative, and made a little contribution to NEE.
文摘Al80Ni6 Y8 Co4 Cu2 amorphous ribbons were isothermally annealed and a mixed structure consisting of α-Al particle with a size of less than 15nm and Al3Ni compound with a size of about 30nm was obtained. The crystallization kinetics of Al80Ni6 Y8 Co4 Cu2 amorphous alloy shows that the precipitation of α-Al particles is the growth process controlled by diffusion of the solute elements rejected from the growing crystals. By quenching at different cooling rates, a mixed structure consisting of nanoscale α-Al particles and the remaining glass matrix or structure consisting of nanoscale particle (Al phase or Al3Ni compound) with a size of about 100nm was formed. The addition of Co elements and Cu elements to Al-Ni-Y alloy systems increases the glass formation ability of the alloy and the thermal stability of the supercooled liquid region against crystallization, which results from significant difference of atomic size, strong bonding nature among constituent elements and the low diffisivity of the solute elements due to the concentration gradient in the growing front of crystals.
基金Project supported by the Collaborative Research and Development Program of Natural Sciences and Engineering Research Council of Canada
文摘The size of bubbles created in the flotation process is of great importance to the efficiency of the mineral separation achieved.Meanwhile,it is believed that frother transport between phases is perhaps the most important reason for the interactive nature of the phenomena occurring in the bulk and froth phases in flotation,as frother adsorbed in the surface of rising bubbles is removed from the bulk phase and then released into the froth as a fraction of the bubbles burst.This causes the increased concentration in the froth compared to the bulk concentration,named as frother partitioning.Partitioning reflects the adsorption of frother on bubbles and how to influence bubble size is not known.There currently exists no such a topic aiming to link these two key parameters.To fill this vacancy,the correspondence between bubble size and frother partitioning was examined.Bubble size was measured by sampling-for-imaging(SFI)technique.Using total organic carbon(TOC)analysis to measure the frother partitioning between froth and bulk phases was determined.Measurements have shown,with no exceptions including four different frothers,higher frother concentration is in the bulk than in the froth.The results also show strong partitioning giving an increase in bubble size which implies there is a compelling relationship between these two,represented by CFroth/CBulk and D32.The CFroth/CBulkand D32 curves show similar exponential decay relationships as a function of added frother in the system,strongly suggesting that the frother concentration gradient between the bulk solution and the bubble interface is the driving force contributing to bubble size reduction.
基金The authors would like to acknowledge the National Natural Science Foundation of China(Grant No.52071103)for supporting this work.
文摘In this paper,one-and two-dimensional numerical simulations are carried out to study the effects of fuel concentration gradients(such as steep,intermediate and shallow)on the detonation wave behavior.The equivalent ratio range of detonation propagation,the quenching mechanism and the change of cell size are discussed in detail.The simulation results show,as the fuel concentration gradient increases,the detonation wavefront decays faster and decouples into a leading shock and a following flame at equivalence ratios of 0.68,0.64 and 0.62,respectively.Moreover,there are two modes of the quenching mechanism.One occurs in the steep gradient that the detonation wave fails rapidly.The O_(2)in front of the detonation wave passes through the detonation wave and forms some unburned O_(2)pockets.The unburned pockets are affected by the marginal walls and reduce the heat release.The other occurs in the intermediate and shallow gradients that more triple points will survive in the flow field,which leads to a difference in the propagation speed of the detonation wavefront.This makes the detonation wavefront bent and deformed.The unburned O_(2)pockets are affected by the strong instability near the triple points and show different distribution characteristics compared with the steep gradient,which may be helpful to the detonation propagation.In addition,as the fuel concentration gradient increases,the triple points moving toward the wall gradually disappear while the triple points that move toward the center can continue to survive,which leads to the gradual increase in cell size and irregularity of the cell structure.
