Nuclear DNA, which is essential for the transmission of genetic information, is constantly damaged by external stresses and is subsequently repaired by the removal of the damaged region, followed by resynthesis of the...Nuclear DNA, which is essential for the transmission of genetic information, is constantly damaged by external stresses and is subsequently repaired by the removal of the damaged region, followed by resynthesis of the excised region. Accumulation of DNA damage with failure of repair processes leads to fatal diseases such as cancer. Recent studies have suggested that intra- and extra-nuclear environments play essential roles in DNA damage. However, numerous questions regarding the role of the nuclear mechanical environment in DNA damage remain unanswered. In this study, we investigated the effects of cell confluency (cell crowding) on the morphology of cell nuclei, and cytoskeletal structures, and DNA damage in NIH3T3 skin fibroblasts and HeLa cervical cancer cells. Although nuclear downsizing was observed in both NIH3T3 and HeLa cells with cell crowding, intracellular mechanical changes in the two cell types displayed opposite tendencies. Cell crowding in NIH3T3 cells induced reinforcement of actin filament structures, cell stiffening, and nuclear downsizing, resulting in a significant decrease in endogenous DNA damage, whereas cell crowding in HeLa cells caused partial depolymerization of actin filaments and cell softening, inducing endogenous DNA damage. Ultraviolet (UV) radiation significantly increased DNA damage in NIH3T3;however, this response did not change with cell crowding. In contrast, UV radiation did not cause DNA damage in HeLa cells under either sparse or confluent conditions. These results suggested that cell crowding significantly influenced endogenous DNA damage in cells and was quite different in NIH3T3 and HeLa cells. However, cell crowding did not affect the UV-induced DNA damage in either cell type.展开更多
Vascular smooth muscle cells (VSMCs) in the arterial walls play important roles in regulating vascular contraction and dilation. VSMCs actively remodel the arterial walls and dedifferentiate from the contractile to th...Vascular smooth muscle cells (VSMCs) in the arterial walls play important roles in regulating vascular contraction and dilation. VSMCs actively remodel the arterial walls and dedifferentiate from the contractile to the synthetic phenotype under pathological conditions. The mechanism underlying phenotypic transition of VSMCs is important for understanding its role in the pathophysiology of disease. Although numerous studies have reported various biochemical pathways that stimulate the phenotypic transition of VSMCs, very little is known about relation between their phenotypic transition and cellular traction force, which affects many cellular functions. In this study, we induced the differentiation of cultured VSMCs from the synthetic to the contractile phenotype by a low-serum cultivation and investigated changes in the cell traction forces using traction force microscopy technique. The expression of α-SMA, a contractile phenotype marker protein, was significantly upregulated with maturation of actin stress fibers in the low-serum culture, indicating VSMC differentiation was promoted in our experiments. The cells changed their morphology to an elongated bipolar shape, and the direction of the cell traction forces tended to align in the direction of the cell’s major axis. Despite the promotion of contractile differentiation in VSMCs, the overall cell traction forces were significantly reduced, indicating that excessive cell mechanical tension, which might induce cell proliferation and migration, was suppressed during contractile differentiation. These results suggest that suppression of cell traction force and enhanced force polarity might be key factors in VSMC differentiation induced by low serum culture.展开更多
Homogeneous films with tailored microporous structures are crucial for several applications;however,fabricating such films presents significant challenges.This is primarily because most microporous materials have crys...Homogeneous films with tailored microporous structures are crucial for several applications;however,fabricating such films presents significant challenges.This is primarily because most microporous materials have crystal sizes in the nanoand micrometer ranges,which inevitably generates intergranular spaces in the films,thereby complicating the fabrication of these thin films.In this study,functionalized metal–organic polyhedra(MOPs)are used as discrete microporous units and assembled into homogenous microporous films.The generation of intergranular spaces is avoided while controlling packing parameters and film thicknesses.Initially,the MOP units,influenced by van der Waals forces between carbon chains of functionalized adipic acids,display an affinity to form spindle-shaped blocks and islands.As the MOP concentration increases,these structures self-assembled into a hexagonally packed structure with an in-plane orientation and a maximum stacking of two layers of MOPs.By contrast,un-functionalized MOPs form a disordered film structure owing to random agglomeration.Evidently,functionalized adipic acid influences the orientation of the MOP network films with uniformly distributed micropores,effectively preventing the formation of intergranular spaces.Additionally,formaldehyde adsorption and desorption experiments revealed that the MOP network films possess superior adsorption and desorption capacities.The proposed approach signifies a breakthrough in the fabrication of homogenous microporous films.展开更多
It has shown that altering crosslink density of biopolymers will regulate the morphology of Mesenchymal Stem Cells （MSCs） and the subsequent MSCs differentia- tion. These observations have been found in a wide range...It has shown that altering crosslink density of biopolymers will regulate the morphology of Mesenchymal Stem Cells （MSCs） and the subsequent MSCs differentia- tion. These observations have been found in a wide range of biopolymers. However, a recent work published in Nature Materials has revealed that MSCs morphology and differen- tiation was unaffected by crosslink density of polydimethyl- siloxane （PDMS）, which remains elusive. To understand such unusual behaviour, we use nanoindentation tests and modelling to characterize viscoelastic properties and sur- face adhesion of PDMS with different base：crosslink ratio varied from 50：1 （50D） to 10：1 （10D）. It has shown that lower crosslink density leads to lower elastic moduli. De- spite lower nanoindentation elastic moduli, PDMS with lowest crosslink density has higher local surface adhesion which would affect cell-biomaterials interactions. This work suggests that surface adhesion is likely another important physical cue to regulate cell-biomaterials interactions.展开更多
We studied precipitation patterns in a Liesegang system under microwave irradiation in order to investigate metal salt diffusion in an electrolyte gel. The salt species and microwave irradiation power were varied. Mic...We studied precipitation patterns in a Liesegang system under microwave irradiation in order to investigate metal salt diffusion in an electrolyte gel. The salt species and microwave irradiation power were varied. Microwave irradiation induced periodic patterns of precipitation because polar molecules vibrate and rotate in an electromagnetic field. For example, the number of patterns increased with the irradiation power. Accordingly, microwave irradiation nonlinearly accelerated the diffusion of ionic molecules.展开更多
Cells sense the external environment such as a surface topography and change many cellular functions. Cell nucleus has been proposed to act as a cellular mechanosensor, and the changes in nuclear shape possibly affect...Cells sense the external environment such as a surface topography and change many cellular functions. Cell nucleus has been proposed to act as a cellular mechanosensor, and the changes in nuclear shape possibly affect the functional regulation of cells. This study demonstrated a large-scale mechanical deformation of the intracellular nucleus using polydimethylsiloxane (PDMS)-based micropillar substrates and investigated the effects of nuclear deformation on migration, proliferation, and differentiation of vascular smooth muscle cells (VSMCs). VSMCs spread completely between the fibronectin-coated pillars, leading to strong deformations of their nuclei resulted in a significant inhibition of the cell migration. The proliferation and smooth muscle differentiation of VSMCs with deformed nuclei were dramatically inhibited on the micropillars. These results indicate that the inhibition of proliferation and VSMC differentiation resulted from deformation of the nucleus with high internal stress, and this type of large-scale nuclear mechanical stress might lead the cells to a “quiescent state”.展开更多
Chicken eggshell (ES) is an aviculture byproduct that has been used as the reinforcement in the present study which is recorded worldwide as one of the vilest environmental problems. The present work deals with develo...Chicken eggshell (ES) is an aviculture byproduct that has been used as the reinforcement in the present study which is recorded worldwide as one of the vilest environmental problems. The present work deals with development of ES-reinforced Al6061 matrix composites by stir-casting process with 0 to 10 wt% of reinforcement at an interval of 2 wt%. The microstructures of the fabricated composites were examined by optical and scanning electron microscopes with energy dispersive spectrometer (SEM/EDS). Optical micrographs divulge the uniform distribution of reinforcing particles in the matrix while X-ray diffraction (XRD) patterns ensure the dispersion of ES particles reinforcement in Al6061 matrix. The properties measured include density, tensile strength and hardness values. The tensile strength and hardness of composites increase with the addition of ES particles and the maximum values were achieved at 4 wt%. Further increase of ES particles in the matrix leads to decrease in hardness and strength owing to increase in porosity.展开更多
Three-Dimensional(3D)swirling flow structures,generated by a counter-rotating dualstage swirler in a confined chamber with a confinement ratio of 1.53,were experimentally investigated at Re=2.3×10^(5)using Tomogr...Three-Dimensional(3D)swirling flow structures,generated by a counter-rotating dualstage swirler in a confined chamber with a confinement ratio of 1.53,were experimentally investigated at Re=2.3×10^(5)using Tomographic Particle Image Velocimetry(Tomo-PIV)and planar Particle Image Velocimetry(PIV).Based on the analysis of the 3D time-averaged swirling flow structures and 3D Proper Orthogonal Decomposition(POD)of the Tomo-PIV data,typical coherent flow structures,including the Corner Recirculation Zone(CRZ),Central Recirculation Zone(CTRZ),and Lip Recirculation Zone(LRZ),were extracted.The counter-rotating dual-stage swirler with a Venturi flare generates the independence process of vortex breakdown from the main stage and pilot stage,leading to the formation of an LRZ and a smaller CTRZ near the nozzle outlet.The confinement squeezes the CRZ to the corner and causes a reverse rotation flow to limit the shape of the CTRZ.A large-scale flow structure caused by the main stage features an explosive breakup,flapping,and Precessing Vortex Core(PVC).The explosive breakup mode dominates the swirling flow structures owing to the expansion and construction of the main jet,whereas the flapping mode is related to the wake perturbation.Confinement limits the expansion of PVC and causes it to contract after the impacting area.展开更多
High entropy compounds were proven to exhibit excellent catalytic activity.Here,a series of amorphous CrMnFeCoNi Oxy-carbide films were successfully synthesized by one-step electrodeposition.As demonstrated,the film p...High entropy compounds were proven to exhibit excellent catalytic activity.Here,a series of amorphous CrMnFeCoNi Oxy-carbide films were successfully synthesized by one-step electrodeposition.As demonstrated,the film presented superior electrocatalytic activity for oxygen evolution reaction(OER)with an overpotential of 295 mV at a current density of 10 mA/cm^(2).Uniquely,selective dissolution of Chromium(Cr)was observed,which increased the catalytic activity and showed high stability under a large current density of up to 400 mA/cm^(2).Cr dissolution not only increased the surface area but also improved the conductivity due to newly formed metal-metal bonding,promoting electron transfer and improving OER performance.As revealed by density functional theory(DFT)calculations,Cr-dissolution mediates the bonding of OER intermediates over surface active sites and ultimately reduces OER overpotential.The one-step electrodeposition method and the micro-dissolution mechanism provided a potential way to design and prepare high entropy compound electrodes,aiming to achieve efficient water electrolysis.展开更多
This study presents a numerical analysis of three-dimensional steady laminar flow in a rectangular channel with a 180-degree sharp turn. The Navier-Stokes equations are solved by using finite difference method for Re ...This study presents a numerical analysis of three-dimensional steady laminar flow in a rectangular channel with a 180-degree sharp turn. The Navier-Stokes equations are solved by using finite difference method for Re = 900. Three-dimensional streamlines and limiting streamlines on wall surface are used to analyze the three-dimensional flow characteristics. Topological theory is applied to limiting streamlines on inner walls of the channel and two-dimensional streamlines at several cross sections. It is also shown that the flow impinges on the end wall of turn and the secondary flow is induced by the curvature in the sharp turn.展开更多
The development of advanced magnetoelectric(ME)composites necessitates high-performance materials that arecapable of achieving high levels of ME coupling,minimal magnetic loss,and absence or limited reliance on extern...The development of advanced magnetoelectric(ME)composites necessitates high-performance materials that arecapable of achieving high levels of ME coupling,minimal magnetic loss,and absence or limited reliance on externalexcitation sources.In this paper,a(2-2)connectivity ME laminate integrates multiple layers of FeSiB alloy(Metglas)andPb(Mg,Nb)O_(3)-PbTiO_(3)(PMN-PT)single crystal,achieving a remarkable ME coupling coefficient of 2033.4 V/Oe·cm(sevenfold rise)by laser thermal annealing treatment.Here,the laser-induced nanostructures on Metglas,with anoxidized insulation layer and soft and hard magnetic dipole layer improve the Magneto-electric-mechanical couplingwith a mechanical quality factor(Q_(m))exceeding 350.More importantly,the interaction between amorphous andnanocrystalline dipoles triggers an Exchange Bias(EB)effect,leading to a self-biasing performance of 67.45 V/Oe·cm.Furthermore,the composite exhibits an excellent passive DC magnetic detection limit of 22 nT,and an improved weakAC magnetic detection limit down to 383 fT.These explorations offer the potential to enhance passive currentmeasurement,and underwater communication,extend weak magnetic positioning and brain magnetic detection.展开更多
Bisphenol-A polycarbonate/dioctyl phthalate blend samples crystallized at a hydrostatic pressure were investigated by WAXD,DSC and SEM measurements.Some novel stereo-open spherulitic structures,i.e.,peony-,cabbage-,se...Bisphenol-A polycarbonate/dioctyl phthalate blend samples crystallized at a hydrostatic pressure were investigated by WAXD,DSC and SEM measurements.Some novel stereo-open spherulitic structures,i.e.,peony-,cabbage-,seaweed-,and lotus-like spherulites,were observed which belong to a three-dimensional structure and were only composed of crystalline region.The foleded-chain lamellar crystal was proved to be the sub-structure of these spherulites.This study also suggests a new route to grow such crystals so as to promote the understanding of the formation process and mechanism of polymer spherulites.展开更多
Tailored surface textures at the micro- or nanoscale dimensions are widely used to get required functional performances. Rotary ultrasonic texturing （RUT） technique has been proved to be capable of fabricating perio...Tailored surface textures at the micro- or nanoscale dimensions are widely used to get required functional performances. Rotary ultrasonic texturing （RUT） technique has been proved to be capable of fabricating periodic micro- and nanostructures. In the present study, diamond tools with geometrically defined cutting edges were designed for fabricating different types of tailored surface textures using the RUT method. Surface generation mechanisms and machinable structures of the RUT process are analyzed and simulated with a 3D-CAD program. Textured surfaces generated by using a triangular pyramid cutting tip are constructed. Different textural patterns from several micrometers to several tens of micrometers with few burrs were successfully fabricated, which proved that tools with a proper two-rake-face design are capable of removing cutting chips efficiently along a sinusoidal cutting locus in the RUT process. Technical applications of the textured surfaces are also discussed. Wetting properties of textured aluminum surfaces were evaluated by combining the test of surface roughness features. The results show that the real surface area of the textured aluminum surfaces almost doubled by comparing with that of a flat surface, and anisotropic wetting properties were obtained due to the obvious directional textural features.展开更多
Flexible temperature sensors have been extensively investigated due to their prospect of wide application in various flexible electronic products.However,most of the current flexible temperature sensors only work well...Flexible temperature sensors have been extensively investigated due to their prospect of wide application in various flexible electronic products.However,most of the current flexible temperature sensors only work well in a narrow temperature range,with their application at high or low temperatures still being a big challenge.This work proposes a flexible thermocouple temperature sensor based on aerogel blanket substrate,the temperature-sensitive layer of which uses the screen-printing technology to prepare indium oxide and indium tin oxide.It has good temperature sensitivity,with the test sensitivity reaching 226.7μV℃^(−1).Most importantly,it can work in a wide temperature range,from extremely low temperatures down to liquid nitrogen temperature to high temperatures up to 1200℃,which is difficult to be achieved by other existing flexible temperature sensors.This temperature sensor has huge application potential in biomedicine,aerospace and other fields.展开更多
The flow visualization technique using shear-sensitive liquid crystal is applied to the investigation of a Mach 2 internal supersonic flow with pseudo-shock wave （PSW） in a pressure-vacuum supersonic wind tunnel. It...The flow visualization technique using shear-sensitive liquid crystal is applied to the investigation of a Mach 2 internal supersonic flow with pseudo-shock wave （PSW） in a pressure-vacuum supersonic wind tunnel. It provides qualitative information mainly concerning the overall flow structure, such as the turbulent boundary layer separation, reattachment locations and the dimensionalities of the flow. Besides, it can also give understanding of the surface streamlines, vortices in separation region and the corner effect of duct flow. Two kinds of crystals with different viscosities are used in experiments to analyze the viscosity effect. Results are compared with schlieren picture, confirming the effectiveness of liquid crystal in flow-visualization.展开更多
This paper first reviews the application research works of wavelet transform on the fluid mechanics. Then the theories of continuous wavelet transform and multi-dimensional orthogonal(discrete) wavelet transform, incl...This paper first reviews the application research works of wavelet transform on the fluid mechanics. Then the theories of continuous wavelet transform and multi-dimensional orthogonal(discrete) wavelet transform, including wavelet multiresolution analysis, are introduced. At last the applications of wavelet transform on 2 D and 3 D turbulent wakes and turbulent boundary layer flows are described based on the hot-wire, 2 D particle image velocimetry(PIV) and 3 D tomographic PIV.展开更多
The interaction between the machining process and the machine tool （IMPMT） plays an important role on high precision components manufacturing. However, most researches are focused on the machining process or the mac...The interaction between the machining process and the machine tool （IMPMT） plays an important role on high precision components manufacturing. However, most researches are focused on the machining process or the machine tool separately, and the interaction between them has been always overlooked. In this paper, a novel simplified method is proposed to realize the simulation of IMPMT by combining use the finite element method and state space method. In this method, the transfer function of the machine tool is built as a small state space. The small state space is obtained from the complicated finite element model of the whole machine tool. Furthermore, the control system of the machine tool is integrated with the transfer function of the machine tool to generate the cutting trajectory. Then, the tool tip response under the cutting force is used to predict the machined surface. Finally, a case study is carried out for a fly-cutting machining process, the dynamic response analysis of an ultra-precision fly-cutting machine tool and the machined surface verifies the effectiveness of this method. This research proposes a simplified method to study the IMPMT, the relationships between the machining process and the machine tool are established and the surface generation is obtained.展开更多
The instability of one single low-speed streak in a zero-pressure-gradient laminar boundary layer is investigated experimentally via both hydrogen bubble visualization and planar particle image velocimetry(PIV) measur...The instability of one single low-speed streak in a zero-pressure-gradient laminar boundary layer is investigated experimentally via both hydrogen bubble visualization and planar particle image velocimetry(PIV) measurement. A single low-speed streak is generated and destabilized by the wake of an interference wire positioned normal to the wall and in the upstream. The downstream development of the streak includes secondary instability and self-reproduction process, which leads to the generation of two additional streaks appearing on either side of the primary one. A proper orthogonal decomposition(POD) analysis of PIV measured velocity field is used to identify the components of the streak instability in the POD mode space: for a sinuous/varicose type of POD mode, its basis functions present anti-symmetric/symmetric distributions about the streak centerline in the streamwise component, and the symmetry condition reverses in the spanwise component. It is further shown that sinuous mode dominates the turbulent kinematic energy(TKE) through the whole streak evolution process, the TKE content first increases along the streamwise direction to a saturation value and then decays slowly. In contrast, varicose mode exhibits a sustained growth of the TKE content,suggesting an increasing competition of varicose instability against sinuous instability.展开更多
Precision is one of the most important aspects of manufacturing.High precision creates high quality,high performance,exchangeability,reliability,and added value for industrial products.Over the past decades,remarkable...Precision is one of the most important aspects of manufacturing.High precision creates high quality,high performance,exchangeability,reliability,and added value for industrial products.Over the past decades,remarkable advances have been achieved in the area of high-precision manufacturing technologies,where the form accuracy approaches the nanometer level and surface roughness the atomic level.These extremely high precision manufacturing technologies enable the development of high-performance optical elements,semiconductor substrates,biomedical parts,and so on,thereby enhancing the ability of human beings to explore the macroand microscopic mysteries and potentialities of the natural world.In this paper,state-of-the-art high-precision material removal manufacturing technologies,especially ultraprecision cutting,grinding,deterministic form correction polishing,and supersmooth polishing,are reviewed and compared with insights into their principles,methodologies,and applications.The key issues in extreme precision manufacturing that should be considered for future R&D are discussed.展开更多
文摘Nuclear DNA, which is essential for the transmission of genetic information, is constantly damaged by external stresses and is subsequently repaired by the removal of the damaged region, followed by resynthesis of the excised region. Accumulation of DNA damage with failure of repair processes leads to fatal diseases such as cancer. Recent studies have suggested that intra- and extra-nuclear environments play essential roles in DNA damage. However, numerous questions regarding the role of the nuclear mechanical environment in DNA damage remain unanswered. In this study, we investigated the effects of cell confluency (cell crowding) on the morphology of cell nuclei, and cytoskeletal structures, and DNA damage in NIH3T3 skin fibroblasts and HeLa cervical cancer cells. Although nuclear downsizing was observed in both NIH3T3 and HeLa cells with cell crowding, intracellular mechanical changes in the two cell types displayed opposite tendencies. Cell crowding in NIH3T3 cells induced reinforcement of actin filament structures, cell stiffening, and nuclear downsizing, resulting in a significant decrease in endogenous DNA damage, whereas cell crowding in HeLa cells caused partial depolymerization of actin filaments and cell softening, inducing endogenous DNA damage. Ultraviolet (UV) radiation significantly increased DNA damage in NIH3T3;however, this response did not change with cell crowding. In contrast, UV radiation did not cause DNA damage in HeLa cells under either sparse or confluent conditions. These results suggested that cell crowding significantly influenced endogenous DNA damage in cells and was quite different in NIH3T3 and HeLa cells. However, cell crowding did not affect the UV-induced DNA damage in either cell type.
文摘Vascular smooth muscle cells (VSMCs) in the arterial walls play important roles in regulating vascular contraction and dilation. VSMCs actively remodel the arterial walls and dedifferentiate from the contractile to the synthetic phenotype under pathological conditions. The mechanism underlying phenotypic transition of VSMCs is important for understanding its role in the pathophysiology of disease. Although numerous studies have reported various biochemical pathways that stimulate the phenotypic transition of VSMCs, very little is known about relation between their phenotypic transition and cellular traction force, which affects many cellular functions. In this study, we induced the differentiation of cultured VSMCs from the synthetic to the contractile phenotype by a low-serum cultivation and investigated changes in the cell traction forces using traction force microscopy technique. The expression of α-SMA, a contractile phenotype marker protein, was significantly upregulated with maturation of actin stress fibers in the low-serum culture, indicating VSMC differentiation was promoted in our experiments. The cells changed their morphology to an elongated bipolar shape, and the direction of the cell traction forces tended to align in the direction of the cell’s major axis. Despite the promotion of contractile differentiation in VSMCs, the overall cell traction forces were significantly reduced, indicating that excessive cell mechanical tension, which might induce cell proliferation and migration, was suppressed during contractile differentiation. These results suggest that suppression of cell traction force and enhanced force polarity might be key factors in VSMC differentiation induced by low serum culture.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean Government(MSIT)(Nos.NRF-2021R1C1C2012825,2022R1A2B5B01001826,2022R1A5A2021216,and No.RS-2023-00218255)。
文摘Homogeneous films with tailored microporous structures are crucial for several applications;however,fabricating such films presents significant challenges.This is primarily because most microporous materials have crystal sizes in the nanoand micrometer ranges,which inevitably generates intergranular spaces in the films,thereby complicating the fabrication of these thin films.In this study,functionalized metal–organic polyhedra(MOPs)are used as discrete microporous units and assembled into homogenous microporous films.The generation of intergranular spaces is avoided while controlling packing parameters and film thicknesses.Initially,the MOP units,influenced by van der Waals forces between carbon chains of functionalized adipic acids,display an affinity to form spindle-shaped blocks and islands.As the MOP concentration increases,these structures self-assembled into a hexagonally packed structure with an in-plane orientation and a maximum stacking of two layers of MOPs.By contrast,un-functionalized MOPs form a disordered film structure owing to random agglomeration.Evidently,functionalized adipic acid influences the orientation of the MOP network films with uniformly distributed micropores,effectively preventing the formation of intergranular spaces.Additionally,formaldehyde adsorption and desorption experiments revealed that the MOP network films possess superior adsorption and desorption capacities.The proposed approach signifies a breakthrough in the fabrication of homogenous microporous films.
基金funded by EPSRC–Newcastle University Sandpit Workshop Award
文摘It has shown that altering crosslink density of biopolymers will regulate the morphology of Mesenchymal Stem Cells （MSCs） and the subsequent MSCs differentia- tion. These observations have been found in a wide range of biopolymers. However, a recent work published in Nature Materials has revealed that MSCs morphology and differen- tiation was unaffected by crosslink density of polydimethyl- siloxane （PDMS）, which remains elusive. To understand such unusual behaviour, we use nanoindentation tests and modelling to characterize viscoelastic properties and sur- face adhesion of PDMS with different base：crosslink ratio varied from 50：1 （50D） to 10：1 （10D）. It has shown that lower crosslink density leads to lower elastic moduli. De- spite lower nanoindentation elastic moduli, PDMS with lowest crosslink density has higher local surface adhesion which would affect cell-biomaterials interactions. This work suggests that surface adhesion is likely another important physical cue to regulate cell-biomaterials interactions.
文摘We studied precipitation patterns in a Liesegang system under microwave irradiation in order to investigate metal salt diffusion in an electrolyte gel. The salt species and microwave irradiation power were varied. Microwave irradiation induced periodic patterns of precipitation because polar molecules vibrate and rotate in an electromagnetic field. For example, the number of patterns increased with the irradiation power. Accordingly, microwave irradiation nonlinearly accelerated the diffusion of ionic molecules.
文摘Cells sense the external environment such as a surface topography and change many cellular functions. Cell nucleus has been proposed to act as a cellular mechanosensor, and the changes in nuclear shape possibly affect the functional regulation of cells. This study demonstrated a large-scale mechanical deformation of the intracellular nucleus using polydimethylsiloxane (PDMS)-based micropillar substrates and investigated the effects of nuclear deformation on migration, proliferation, and differentiation of vascular smooth muscle cells (VSMCs). VSMCs spread completely between the fibronectin-coated pillars, leading to strong deformations of their nuclei resulted in a significant inhibition of the cell migration. The proliferation and smooth muscle differentiation of VSMCs with deformed nuclei were dramatically inhibited on the micropillars. These results indicate that the inhibition of proliferation and VSMC differentiation resulted from deformation of the nucleus with high internal stress, and this type of large-scale nuclear mechanical stress might lead the cells to a “quiescent state”.
文摘Chicken eggshell (ES) is an aviculture byproduct that has been used as the reinforcement in the present study which is recorded worldwide as one of the vilest environmental problems. The present work deals with development of ES-reinforced Al6061 matrix composites by stir-casting process with 0 to 10 wt% of reinforcement at an interval of 2 wt%. The microstructures of the fabricated composites were examined by optical and scanning electron microscopes with energy dispersive spectrometer (SEM/EDS). Optical micrographs divulge the uniform distribution of reinforcing particles in the matrix while X-ray diffraction (XRD) patterns ensure the dispersion of ES particles reinforcement in Al6061 matrix. The properties measured include density, tensile strength and hardness values. The tensile strength and hardness of composites increase with the addition of ES particles and the maximum values were achieved at 4 wt%. Further increase of ES particles in the matrix leads to decrease in hardness and strength owing to increase in porosity.
基金supported by the National Natural Science Foundation of China(Nos.12232002,12072017,12002199,and 11721202)。
文摘Three-Dimensional(3D)swirling flow structures,generated by a counter-rotating dualstage swirler in a confined chamber with a confinement ratio of 1.53,were experimentally investigated at Re=2.3×10^(5)using Tomographic Particle Image Velocimetry(Tomo-PIV)and planar Particle Image Velocimetry(PIV).Based on the analysis of the 3D time-averaged swirling flow structures and 3D Proper Orthogonal Decomposition(POD)of the Tomo-PIV data,typical coherent flow structures,including the Corner Recirculation Zone(CRZ),Central Recirculation Zone(CTRZ),and Lip Recirculation Zone(LRZ),were extracted.The counter-rotating dual-stage swirler with a Venturi flare generates the independence process of vortex breakdown from the main stage and pilot stage,leading to the formation of an LRZ and a smaller CTRZ near the nozzle outlet.The confinement squeezes the CRZ to the corner and causes a reverse rotation flow to limit the shape of the CTRZ.A large-scale flow structure caused by the main stage features an explosive breakup,flapping,and Precessing Vortex Core(PVC).The explosive breakup mode dominates the swirling flow structures owing to the expansion and construction of the main jet,whereas the flapping mode is related to the wake perturbation.Confinement limits the expansion of PVC and causes it to contract after the impacting area.
基金supported by the JSPS KAKENHI(Grant No.JP21K04724)the Iketani Science and Technology Foundation(No.0331126-A).
文摘High entropy compounds were proven to exhibit excellent catalytic activity.Here,a series of amorphous CrMnFeCoNi Oxy-carbide films were successfully synthesized by one-step electrodeposition.As demonstrated,the film presented superior electrocatalytic activity for oxygen evolution reaction(OER)with an overpotential of 295 mV at a current density of 10 mA/cm^(2).Uniquely,selective dissolution of Chromium(Cr)was observed,which increased the catalytic activity and showed high stability under a large current density of up to 400 mA/cm^(2).Cr dissolution not only increased the surface area but also improved the conductivity due to newly formed metal-metal bonding,promoting electron transfer and improving OER performance.As revealed by density functional theory(DFT)calculations,Cr-dissolution mediates the bonding of OER intermediates over surface active sites and ultimately reduces OER overpotential.The one-step electrodeposition method and the micro-dissolution mechanism provided a potential way to design and prepare high entropy compound electrodes,aiming to achieve efficient water electrolysis.
文摘This study presents a numerical analysis of three-dimensional steady laminar flow in a rectangular channel with a 180-degree sharp turn. The Navier-Stokes equations are solved by using finite difference method for Re = 900. Three-dimensional streamlines and limiting streamlines on wall surface are used to analyze the three-dimensional flow characteristics. Topological theory is applied to limiting streamlines on inner walls of the channel and two-dimensional streamlines at several cross sections. It is also shown that the flow impinges on the end wall of turn and the secondary flow is induced by the curvature in the sharp turn.
基金supported by the National Key Research and Development Program(Grant No.2021YFB3201800)the Natural Science Foundation of China(Grants 62131017,U22A2019)the Key R&D Project of Shaanxi Province-University Joint Project(2023GXLH-020).
文摘The development of advanced magnetoelectric(ME)composites necessitates high-performance materials that arecapable of achieving high levels of ME coupling,minimal magnetic loss,and absence or limited reliance on externalexcitation sources.In this paper,a(2-2)connectivity ME laminate integrates multiple layers of FeSiB alloy(Metglas)andPb(Mg,Nb)O_(3)-PbTiO_(3)(PMN-PT)single crystal,achieving a remarkable ME coupling coefficient of 2033.4 V/Oe·cm(sevenfold rise)by laser thermal annealing treatment.Here,the laser-induced nanostructures on Metglas,with anoxidized insulation layer and soft and hard magnetic dipole layer improve the Magneto-electric-mechanical couplingwith a mechanical quality factor(Q_(m))exceeding 350.More importantly,the interaction between amorphous andnanocrystalline dipoles triggers an Exchange Bias(EB)effect,leading to a self-biasing performance of 67.45 V/Oe·cm.Furthermore,the composite exhibits an excellent passive DC magnetic detection limit of 22 nT,and an improved weakAC magnetic detection limit down to 383 fT.These explorations offer the potential to enhance passive currentmeasurement,and underwater communication,extend weak magnetic positioning and brain magnetic detection.
文摘Bisphenol-A polycarbonate/dioctyl phthalate blend samples crystallized at a hydrostatic pressure were investigated by WAXD,DSC and SEM measurements.Some novel stereo-open spherulitic structures,i.e.,peony-,cabbage-,seaweed-,and lotus-like spherulites,were observed which belong to a three-dimensional structure and were only composed of crystalline region.The foleded-chain lamellar crystal was proved to be the sub-structure of these spherulites.This study also suggests a new route to grow such crystals so as to promote the understanding of the formation process and mechanism of polymer spherulites.
基金Supported by Japan Society for the Promotion of Science(Grant Nos.14J04115,16K17990)
文摘Tailored surface textures at the micro- or nanoscale dimensions are widely used to get required functional performances. Rotary ultrasonic texturing （RUT） technique has been proved to be capable of fabricating periodic micro- and nanostructures. In the present study, diamond tools with geometrically defined cutting edges were designed for fabricating different types of tailored surface textures using the RUT method. Surface generation mechanisms and machinable structures of the RUT process are analyzed and simulated with a 3D-CAD program. Textured surfaces generated by using a triangular pyramid cutting tip are constructed. Different textural patterns from several micrometers to several tens of micrometers with few burrs were successfully fabricated, which proved that tools with a proper two-rake-face design are capable of removing cutting chips efficiently along a sinusoidal cutting locus in the RUT process. Technical applications of the textured surfaces are also discussed. Wetting properties of textured aluminum surfaces were evaluated by combining the test of surface roughness features. The results show that the real surface area of the textured aluminum surfaces almost doubled by comparing with that of a flat surface, and anisotropic wetting properties were obtained due to the obvious directional textural features.
基金supported by The National Key Research and Development Program of China(2020YFB2009100)Natural Science Basic Research Program of Shaanxi(Program No.2022JQ-508)National Science and Technology Major Project(Grant No.J2019-V-0006-0100),Open research fund of SKLMS(Grant No.sklms2021009).
文摘Flexible temperature sensors have been extensively investigated due to their prospect of wide application in various flexible electronic products.However,most of the current flexible temperature sensors only work well in a narrow temperature range,with their application at high or low temperatures still being a big challenge.This work proposes a flexible thermocouple temperature sensor based on aerogel blanket substrate,the temperature-sensitive layer of which uses the screen-printing technology to prepare indium oxide and indium tin oxide.It has good temperature sensitivity,with the test sensitivity reaching 226.7μV℃^(−1).Most importantly,it can work in a wide temperature range,from extremely low temperatures down to liquid nitrogen temperature to high temperatures up to 1200℃,which is difficult to be achieved by other existing flexible temperature sensors.This temperature sensor has huge application potential in biomedicine,aerospace and other fields.
文摘The flow visualization technique using shear-sensitive liquid crystal is applied to the investigation of a Mach 2 internal supersonic flow with pseudo-shock wave （PSW） in a pressure-vacuum supersonic wind tunnel. It provides qualitative information mainly concerning the overall flow structure, such as the turbulent boundary layer separation, reattachment locations and the dimensionalities of the flow. Besides, it can also give understanding of the surface streamlines, vortices in separation region and the corner effect of duct flow. Two kinds of crystals with different viscosities are used in experiments to analyze the viscosity effect. Results are compared with schlieren picture, confirming the effectiveness of liquid crystal in flow-visualization.
基金the National Natural Science Foundation of China(Nos.11721202 and 11772035)support from JSPS Research Fellowships for Young Scientists(2019~2022)。
文摘This paper first reviews the application research works of wavelet transform on the fluid mechanics. Then the theories of continuous wavelet transform and multi-dimensional orthogonal(discrete) wavelet transform, including wavelet multiresolution analysis, are introduced. At last the applications of wavelet transform on 2 D and 3 D turbulent wakes and turbulent boundary layer flows are described based on the hot-wire, 2 D particle image velocimetry(PIV) and 3 D tomographic PIV.
基金Supported by National Natural Science Foundation of China(Grant No.51505107)Natural Scientific Research Innovation Foundation in Harbin Institute of Technology of China(Grant No.HIT.NSRIF.2017029)
文摘The interaction between the machining process and the machine tool （IMPMT） plays an important role on high precision components manufacturing. However, most researches are focused on the machining process or the machine tool separately, and the interaction between them has been always overlooked. In this paper, a novel simplified method is proposed to realize the simulation of IMPMT by combining use the finite element method and state space method. In this method, the transfer function of the machine tool is built as a small state space. The small state space is obtained from the complicated finite element model of the whole machine tool. Furthermore, the control system of the machine tool is integrated with the transfer function of the machine tool to generate the cutting trajectory. Then, the tool tip response under the cutting force is used to predict the machined surface. Finally, a case study is carried out for a fly-cutting machining process, the dynamic response analysis of an ultra-precision fly-cutting machine tool and the machined surface verifies the effectiveness of this method. This research proposes a simplified method to study the IMPMT, the relationships between the machining process and the machine tool are established and the surface generation is obtained.
基金supported by the National Natural Science Foundation of China (Grants 11372001,11672020,and 11490552)the Fundamental Research Funds for the Central Universities of China (Grant YWF-16-JCTD-A-05)
文摘The instability of one single low-speed streak in a zero-pressure-gradient laminar boundary layer is investigated experimentally via both hydrogen bubble visualization and planar particle image velocimetry(PIV) measurement. A single low-speed streak is generated and destabilized by the wake of an interference wire positioned normal to the wall and in the upstream. The downstream development of the streak includes secondary instability and self-reproduction process, which leads to the generation of two additional streaks appearing on either side of the primary one. A proper orthogonal decomposition(POD) analysis of PIV measured velocity field is used to identify the components of the streak instability in the POD mode space: for a sinuous/varicose type of POD mode, its basis functions present anti-symmetric/symmetric distributions about the streak centerline in the streamwise component, and the symmetry condition reverses in the spanwise component. It is further shown that sinuous mode dominates the turbulent kinematic energy(TKE) through the whole streak evolution process, the TKE content first increases along the streamwise direction to a saturation value and then decays slowly. In contrast, varicose mode exhibits a sustained growth of the TKE content,suggesting an increasing competition of varicose instability against sinuous instability.
文摘Precision is one of the most important aspects of manufacturing.High precision creates high quality,high performance,exchangeability,reliability,and added value for industrial products.Over the past decades,remarkable advances have been achieved in the area of high-precision manufacturing technologies,where the form accuracy approaches the nanometer level and surface roughness the atomic level.These extremely high precision manufacturing technologies enable the development of high-performance optical elements,semiconductor substrates,biomedical parts,and so on,thereby enhancing the ability of human beings to explore the macroand microscopic mysteries and potentialities of the natural world.In this paper,state-of-the-art high-precision material removal manufacturing technologies,especially ultraprecision cutting,grinding,deterministic form correction polishing,and supersmooth polishing,are reviewed and compared with insights into their principles,methodologies,and applications.The key issues in extreme precision manufacturing that should be considered for future R&D are discussed.
