Perfect anomalous reflections have been demonstrated in optical phase gradient metasurfaces(PGMs),but they suffer from single-frequency(narrow-band)response due to the intrinsic limitation of natural geometric periodi...Perfect anomalous reflections have been demonstrated in optical phase gradient metasurfaces(PGMs),but they suffer from single-frequency(narrow-band)response due to the intrinsic limitation of natural geometric periodicity.Here,we provide both numerical and analytical evidence that a depth gradient metasurface can achieve discrete ultra-broadband perfect anomalous reflection in the microwave range in the absence of geometric periodicity.Remarkably,by adjusting the operating frequency of the incident wave,the same effect can be steadily obtained via a physically equivalent phase periodicity in the PGM.Based on this mechanism,a perfect retroreflector with a broadband response ranging from 1 GHz to 40 GHz is realized.Our work has promising applications in communication,source tracking,and military satellites.展开更多
Species richness in any area results from the interplay of the processes of speciation,extinction,and dispersal.The relationships between species richness and climate should be considered as an outcome of the effects ...Species richness in any area results from the interplay of the processes of speciation,extinction,and dispersal.The relationships between species richness and climate should be considered as an outcome of the effects of climate on speciation,extinction,and dispersal.Diversificationrate represents the balance of speciation and extinction rates over time.Here,I explore diversificationrates in mosses across geographic and climatic gradients worldwide.Specifically,I investigate latitudinal patterns and climatic associations of the mean diversificationrate of mosses at global,hemispheric,and smaller scales.I findthat the mean diversificationrate of mosses is positively correlated with species richness of mosses,increases with decreasing latitude and increasing mean annual temperature and annual precipitation,and is more strongly associated with mean annual temperature than with annual precipitation.These findingsshed light on variation of species richness in mosses across the world.The negative relationship between species richness and latitude and the positive relationship between species richness and mean diversificationrate in mosses suggest that higher moss species richness at lower latitudes might have resulted,at least to some degree,from higher moss diversificationrates at lower latitudes.展开更多
Liver-directed therapies such as resection,ablation,and embolization offer potentially curative options for patients with primary and metastatic liver tumors as part of multidisciplinary oncology care.However,these tr...Liver-directed therapies such as resection,ablation,and embolization offer potentially curative options for patients with primary and metastatic liver tumors as part of multidisciplinary oncology care.However,these treatments pose significant hepatic decompensation risks,particularly with underlying liver disease and chemotherapy-associated steatohepatitis.Accurate assessment of liver function and portal hypertension(PH)is critical for candidate selection.While Child-Pugh score and model for end-stage liver disease are commonly used,they have substantial limitations.Hepatic venous pressure gradient(HVPG)measurement remains the gold standard for assessing PH but is invasive and not widely available.Endoscopic ultrasound(EUS)guided portal pressure gradient(PPG)measurement has emerged as a promising minimally invasive alternative.EUSPPG demonstrates excellent technical success rates,safety profile,and correlation with HVPG in early studies.By providing direct portal pressure measurement,EUS-PPG offers several advantages over existing methods for prognostication and risk stratification prior to liver-directed therapies,particularly in detecting presinusoidal hypertension.Furthermore,it has potential applications in assessing response to neoadjuvant treatments and guiding adjuvant therapies.However,research is needed to validate its predictive performance and cost-effectiveness in larger prospective cohorts and to establish its accuracy compared to non-invasive assessment of liver function.展开更多
The GH141 superalloy ring-rolled parts often face microstructural inhomogeneity during production.This work investigated the effect of post-dynamic recrystallization on the microstructural evolution of GH141 superallo...The GH141 superalloy ring-rolled parts often face microstructural inhomogeneity during production.This work investigated the effect of post-dynamic recrystallization on the microstructural evolution of GH141 superalloy after gradient thermal deformation to solve the problem of microstructural inhomogeneity.Compression tests involving double cone(DC)samples were conducted at various temperatures to assess the effect of gradient strain on internal grain microstructure variation,which ranged from the rim to the center of the samples.The results demonstrate considerable microstructural inhomogeneity induced by gradient strain in the DC samples.The delay in heat preservation facilitated post-dynamic recrystallization(PDRX)and promoted extensive recrystallization in the DC samples experiencing large gradient strain,which resulted in a homogeneous grain microstructure throughout the samples.During compression at a relatively low temperature,dynamic recrystallization(DRX)was predominantly driven by continuous dynamic recrystallization(CDRX).As the deformation temperature increased,the DRX mechanism changed from CDRX-dominated to being dominated by discontinuous dynamic recrystallization(DDRX).During the delay of the heat preservation process,PDRX was dominated by a static recrystallization mechanism,along with the occurrence of meta-dynamic recrystallization(MDRX)mechanisms.In addition,the PDRX mechanism of twin-induced recrystallization nucleation was observed.展开更多
A widely employed energy technology,known as reverse electrodialysis(RED),holds the promise of delivering clean and renewable electricity from water.This technology involves the interaction of two or more bodies of wa...A widely employed energy technology,known as reverse electrodialysis(RED),holds the promise of delivering clean and renewable electricity from water.This technology involves the interaction of two or more bodies of water with varying concentrations of salt ions.The movement of these ions across a membrane generates electricity.However,the efficiency of these systems faces a challenge due to membrane performance degradation over time,often caused by channel blockages.One potential solution to enhance system efficiency is the use of nanofluidic membranes.These specialized membranes offer high ion exchange capacity,abundant ion sources,and customizable channels with varying sizes and properties.Graphene oxide(GO)-based membranes have emerged as particularly promising candidates in this regard,garnering significant attention in recent literature.This work provides a comprehensive overview of the literature surrounding GO membranes and their applications in RED systems.It also highlights recent advancements in the utilization of GO membranes within these systems.Finally,it explores the potential of these membranes to play a pivotal role in electricity generation within RED systems.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
Gradient coil is an essential component of a magnetic resonance imaging(MRI)scanner.To achieve high spatial resolution and imaging speed,a high-efficiency gradient coil with high slew rate is required.In consideration...Gradient coil is an essential component of a magnetic resonance imaging(MRI)scanner.To achieve high spatial resolution and imaging speed,a high-efficiency gradient coil with high slew rate is required.In consideration of the safety and comfort of the patient,the mechanical stability,acoustic noise and peripheral nerve stimulation(PNS)are also need to be concerned for practical use.In our previous work,a high-efficiency whole-body gradient coil set with a hybrid cylindrical-planar structure has been presented,which offers significantly improved coil performances.In this work,we propose to design this transverse gradient coil system with transformed magnetic gradient fields.By shifting up the zero point of gradient fields,the designed new Y-gradient coil could provide enhanced electromagnetic performances.With more uniform coil winding arrangement,the net torque of the new coil is significantly reduced and the generated sound pressure level(SPL)is lower at most tested frequency bands.On the other hand,the new transverse gradient coil designed with rotated magnetic gradient fields produces considerably reduced electric field in the human body,which is important for the use of rapid MR sequences.It's demonstrated that a safer and patient-friendly design could be obtained by using transformed magnetic gradient fields,which is critical for practical use.展开更多
The changes in strain gradient induced by grain boundaries are crucial for enhancing the plasticity of gradient magnesium(Mg)alloys.The change of strain distribution influence by grain boundaries during plastic deform...The changes in strain gradient induced by grain boundaries are crucial for enhancing the plasticity of gradient magnesium(Mg)alloys.The change of strain distribution influence by grain boundaries during plastic deformation of the gradient structure was examined.In this paper,the gradient structure AZ31 Mg-alloy plate with the surface fine grain(FG)to the center coarse grain(CG)was fabricated using hard plate rolling(HPR).The microstructure and strain distribution of Mg-alloy with a gradient structure were analyzed by electron backscatter diffraction(EBSD)and Digital image correlation(DIC)during uniaxial tensile.The findings indicate that the gradient structure sample(GS sample)displays a uniform strain distribution during the tensile process.Coarse-grain sample(CG sample)have obvious strain concentration,which leads to premature fracture.Based on EBSD characterization,low-angle grain boundaries(LAGBs)accumulates in the CG during plastic deformation.Orientation of CG tends to the(0001)basal.At the same time,the density of geometrically necessary dislocations(GNDs)inside CG has changed,which improves the Heterogeneous deformation induced(HDI)stress of gradient structure.During the uniaxial tensile,LAGBs accumulates in CG and changes the strain distribution of the gradient structure,which induces the accumulation of GNDs,and hence improving the properties of the GS Mg-alloy.These findings unveil the mechanism of strength-plasticity synergism of GS alloys from a new perspective and offer insights into the application of GS in Mg-alloys.展开更多
The morphological distribution of absorbent in composites is equally important with absorbents for the overall electromagnetic properties,but it is often ignored.Herein,a comprehensive consideration including electrom...The morphological distribution of absorbent in composites is equally important with absorbents for the overall electromagnetic properties,but it is often ignored.Herein,a comprehensive consideration including electromagnetic component regulation,layered arrangement structure,and gradient concentration distribution was used to optimize impedance matching and enhance electromagnetic loss.On the microscale,the incorporation of magnetic Ni nanoparticles into MXene nanosheets(Ni@MXene)endows suitable intrinsic permittivity and permeability.On the macroscale,the layered arrangement of Ni@MXene increases the effective interaction area with electromagnetic waves,inducing multiple reflection/scattering effects.On this basis,according to the analysis of absorption,reflection,and transmission(A-R-T)power coefficients of layered composites,the gradient concentration distribution was constructed to realize the impedance matching at low-concentration surface layer,electromagnetic loss at middle concentration interlayer and microwave reflection at high-concentration bottom layer.Consequently,the layered gradient composite(LG5-10-15)achieves complete absorption coverage of X-band at thickness of 2.00-2.20 mm with RL_(min) of-68.67 dB at 9.85 GHz in 2.05 mm,which is 199.0%,12.6%,and 50.6%higher than non-layered,layered and layered descending gradient composites,respectively.Therefore,this work confirms the importance of layered gradient structure in improving absorption performance and broadens the design of high-performance microwave absorption materials.展开更多
The cobalt-free Mn-based Li-rich layered oxide material has the advantages of low cost,high energy density,and good performance at low temperatures,and is the promising choice for energy storage batteries.However,the ...The cobalt-free Mn-based Li-rich layered oxide material has the advantages of low cost,high energy density,and good performance at low temperatures,and is the promising choice for energy storage batteries.However,the long-cycling stability of batteries needs to be improved.Herein,the Mn-based Li-rich cathode materials with small amounts of Li2 MnO3 crystal domains and gradient doping of Al and Ti elements from the surface to the bulk have been developed to improve the structure and interface stability.Then the batteries with a high energy density of 600 Wh kg^(-1),excellent capacity retention of 99.7%with low voltage decay of 0.03 mV cycle^(-1) after 800 cycles,and good rates performances can be achieved.Therefore,the structure and cycling stability of low voltage Mn-based Li-rich cathode materials can be significantly improved by the bulk structure design and interface regulation,and this work has paved the way for developing low-cost and high-energy Mn-based energy storage batteries with long lifetime.展开更多
We combine gradient data from the Macao Science Satellite-1(MSS-1),CHAllenging Minisatellite Payload(CHAMP),Swarm-A,and Swarm-C satellites to develop a 110-degree lithospheric magnetic field model.We then comprehensiv...We combine gradient data from the Macao Science Satellite-1(MSS-1),CHAllenging Minisatellite Payload(CHAMP),Swarm-A,and Swarm-C satellites to develop a 110-degree lithospheric magnetic field model.We then comprehensively evaluate the performance of the model by power spectral comparisons,correlation analyses,sensitivity matrix assessments,and comparisons with existing lithospheric field models.Results showed that using near east–west gradient data from MSS-1 significantly enhances the model correlation in the spherical harmonic degree(N) range of 45–60 while also mitigating the decline in correlation at higher degrees(N > 60).Furthermore,the unique orbital characteristics of MSS-1 enable its gradient data to provide substantial contributions to modeling in the mid-to low-latitude regions.With continued data acquisition from MSS-1 and further optimization of data processing methods,the performance of the model is expected to improve.展开更多
Rolling contact fatigue performance is among the most important issues for applications of bearing steels.In this work,a recently developed surface modification technique,surface mechanical rolling treatment,was appli...Rolling contact fatigue performance is among the most important issues for applications of bearing steels.In this work,a recently developed surface modification technique,surface mechanical rolling treatment,was applied on a rare-earth addition bearing steel.And rolling contact fatigue behavior of treated samples was compared with that of as-received counterparts at different contacting stresses.The results demonstrated that a 700μm-thick gradient nanostructured surface layer is produced on samples by surface mechanical rolling treatment.The grain size decreases while the microhardness increases gradually with decreasing depth,reaching~23 nm and~10.2 GPa,respectively,at the top surface.Consequently,the rolling contact fatigue property is significantly enhanced.The characteristic life of treated samples is~3.2 times that of untreated counterparts according to Weibull curves at 5.6 GPa.Analyses of fatigue mechanisms demonstrated that the gradient nanostructured surface layer might not only retard material degradation and microcrack formation,but also prolong the steady-state elastic response stage under rolling contact fatigue.展开更多
The intricate hierarchical structure of musculoskeletal tissues,including bone and interface tissues,necessitates the use of complex scaffold designs and material structures to serve as tissue-engineered substitutes.T...The intricate hierarchical structure of musculoskeletal tissues,including bone and interface tissues,necessitates the use of complex scaffold designs and material structures to serve as tissue-engineered substitutes.This has led to growing interest in the development of gradient bone scaffolds with hierarchical structures mimicking the extracellular matrix of native tissues to achieve improved therapeutic outcomes.Building on the anatomical characteristics of bone and interfacial tissues,this review provides a summary of current strategies used to design and fabricate biomimetic gradient scaffolds for repairing musculoskeletal tissues,specifically focusing on methods used to construct compositional and structural gradients within the scaffolds.The latest applications of gradient scaffolds for the regeneration of bone,osteochondral,and tendon-to-bone interfaces are presented.Furthermore,the current progress of testing gradient scaffolds in physiologically relevant animal models of skeletal repair is discussed,as well as the challenges and prospects of moving these scaffolds into clinical application for treating musculoskeletal injuries.展开更多
The Michelson Interferometer for Global High-resolution Thermospheric Imaging(MIGHTI)onboard the Ionospheric Connection Explorer(ICON)satellite offers the opportunity to investigate the altitude profile of thermospher...The Michelson Interferometer for Global High-resolution Thermospheric Imaging(MIGHTI)onboard the Ionospheric Connection Explorer(ICON)satellite offers the opportunity to investigate the altitude profile of thermospheric winds.In this study,we used the red-line measurements of MIGHTI to compare with the results estimated by Horizontal Wind Model 14(HWM14).The data selected included both the geomagnetic quiet period(December 2019 to August 2022)and the geomagnetic storm on August 26-28,2021.During the geomagnetic quiet period,the estimations of neutral winds from HWM14 showed relatively good agreement with the observations from ICON.According to the ICON observations,near the equator,zonal winds reverse from westward to eastward at around 06:00 local time(LT)at higher altitudes,and the stronger westward winds appear at later LTs at lower altitudes.At around 16:00 LT,eastward winds at 300 km reverse to westward,and vertical gradients of zonal winds similar to those at sunrise hours can be observed.In the middle latitudes,zonal winds reverse about 2-4 h earlier.Meridional winds vary more significantly than zonal winds with seasonal and latitudinal variations.According to the ICON observations,in the northern low latitudes,vertical reversals of meridional winds are found at 08:00-13:00 LT from 300 to 160 km and at around 18:00 LT from 300 to 200 km during the June solstice.Similar reversals of meridional winds are found at 04:00-07:00 LT from 300 to 160 km and at 22:00-02:00 LT from 270 to 200 km during the December solstice.In the southern low latitudes,meridional wind reversals occur at 08:00-11:00 LT from 200 to 160 km and at 21:00-02:00 LT from 300 to 200 km during the June solstice.During the December solstice,reversals of the meridional wind appear at 20:00-01:00 LT below 200 km and at 06:00-11:00 LT from 300 to 160 km.In the northern middle latitudes,the northward winds are dominant at 08:00-14:00 LT at 230 km during the June solstice.Northward winds persist until 16:00 LT at 160 and 300 km.During the December solstice,the northward winds are dominant from 06:00 to 21:00 LT.The vertical variations in neutral winds during the geomagnetic storm on August 26-28 were analyzed in detail.Both meridional and zonal winds during the active geomagnetic period observed by ICON show distinguishable vertical shear structures at different stages of the storm.On the dayside,during the main phase,the peak velocities of westward winds extend from a higher altitude to a lower altitude,whereas during the recovery phase,the peak velocities of the westward winds extend from lower altitudes to higher altitudes.The velocities of the southward winds are stronger at lower altitudes during the storm.These vertical structures of horizontal winds during the storm could not be reproduced by the HWM14 wind estimations,and the overall response to the storm of the horizontal winds in the low and middle latitudes is underestimated by HWM14.The ICON observations provide a good dataset for improving the HWM wind estimations in the middle and upper atmosphere,especially the vertical variations.展开更多
In this paper,we propose a three-term conjugate gradient method for solving unconstrained optimization problems based on the Hestenes-Stiefel(HS)conjugate gradient method and Polak-Ribiere-Polyak(PRP)conjugate gradien...In this paper,we propose a three-term conjugate gradient method for solving unconstrained optimization problems based on the Hestenes-Stiefel(HS)conjugate gradient method and Polak-Ribiere-Polyak(PRP)conjugate gradient method.Under the condition of standard Wolfe line search,the proposed search direction is the descent direction.For general nonlinear functions,the method is globally convergent.Finally,numerical results show that the proposed method is efficient.展开更多
In this paper,we study and characterize the volume estimates of geodesic balls on Finsler gradient Ricci solitons.We get the upper bounds on the volumes of geodesic balls of all three kinds of Finsler gradient Ricci s...In this paper,we study and characterize the volume estimates of geodesic balls on Finsler gradient Ricci solitons.We get the upper bounds on the volumes of geodesic balls of all three kinds of Finsler gradient Ricci solitons under certain condition about the Laplacian of thedistance function.展开更多
Gradient nano-grained structure is frequently engineered into metallic materials,including Mg alloys,to achieve superior combination of strength and ductility.Nevertheless,the influence of this microstructural feature...Gradient nano-grained structure is frequently engineered into metallic materials,including Mg alloys,to achieve superior combination of strength and ductility.Nevertheless,the influence of this microstructural feature on aging precipitation behavior remains inadequately understood.In this study,the age-precipitation behavior of a gradient nano-grained Mg-Gd-Ag-Zr alloy prepared via ultrasonic severe surface rolling was investigated.The result indicates that the aging precipitation behavior exhibits a depth-dependent variation within this alloy.In the nano-grained surface layer,hierarchicalβnano-precipitates are predominant,while at greater depths,the precipitates consist ofβnanoparticles located at grain boundaries,along with intragranularβ′andγ″nano-plates.The formation ofβnano-precipitates deviates from the conventional precipitation behavior observed in Mg-Gd-Ag alloys,and is attributed to the high density of defects induced by the surface nano-grained structure.This finding advances our understanding of the precipitation behavior in the alloys with heterogeneous microstructure.展开更多
Traditional symmetrical rolling often induces through-thickness gradient microstructures and textures.In this study,ultra-high purity(99.999 wt.%)tantalum(Ta)served as a model material to address the texture gradient ...Traditional symmetrical rolling often induces through-thickness gradient microstructures and textures.In this study,ultra-high purity(99.999 wt.%)tantalum(Ta)served as a model material to address the texture gradient issue by employing dynamic offsets and shear force adjustment rolling(DS rolling)as an advanced rolling technique.The strain and stress distributions in Ta plates for DS rolling and symmetrical rolling processes were analyzed using Deform 3D software.Through-thickness textures and microstructures were characterized via electron backscatter diffraction.The results revealed that DS rolling effectively solved the problem of texture gradient by increasing the average shear strain from 0.05 to 0.56.In turn,the shear stress reduced the energy storage orientation dependence of{100}and{111}grains.Furthermore,DS rolling refined the recrystallized grains on an average of 30.9%.展开更多
There is a pressing need for high-performance,high-strength low-alloy structural(HSLA)steels in various engineering fields,such as hydraulic components,engineering machinery,bridges,ships,and pressure vessels.In this ...There is a pressing need for high-performance,high-strength low-alloy structural(HSLA)steels in various engineering fields,such as hydraulic components,engineering machinery,bridges,ships,and pressure vessels.In this study,a gradient dislocation-cell structure is introduced into an HSLA steel through ultrasonic severe surface rolling.The cell size is approximately 614 nm at the topmost surface layer,and increases with increasing the depth.Most of the cell walls have a misorientation ranging from 2°to 15°,indicating they belong to low angle grain boundaries(LAGBs),while some cell walls have a misorientation of less than 2°,corresponding to dense dislocation walls(DDWs).This unique gradient structure offers an exceptional combination of strength and ductility,with a high yield strength of 522.3±1.4 MPa and an accepted elongation of 25.5±1.7%.The morphology and size of the dislocation cells remain remarkably stable after uniaxial tension,demonstrating their efficacy as effective barriers hindering dislocation movement and thus enhancing strength and hardness.This gradient dislocation-cell structure facilitates inhomogeneous plastic deformation during uniaxial tensile loading,resulting in a pronounced accumulation of geometrically necessary dislocations(GNDs).These GNDs play a significant role in conferring favorable mechanical properties by inducing hetero-deformation-induced(HDI)strengthening effects and forest hardening effects.This study presents a promising avenue for achieving the desired mechanical properties in HSLA steel.展开更多
Understanding the underlying mechanisms driving species assembly along elevational gradients is of great interest in ecology and biogeography.The Himalaya is one of the world’s hotspots of biodiversity,and the elevat...Understanding the underlying mechanisms driving species assembly along elevational gradients is of great interest in ecology and biogeography.The Himalaya is one of the world’s hotspots of biodiversity,and the elevational gradient of the central Himalaya in Nepal is one of the longest elevational gradients in the world.Mosses are important constituents of vegetation in the Himalaya,and knowledge of geographic patterns and ecological causes of phylogenetic structure of mosses along elevational gradients in the Himalaya is critical to understanding the assembly of plant diversity in general,and moss diversity in particular,in the Himalaya.Here,we investigate the relationships of phylogenetic structure metrics reflecting different evolutionary depths with elevation and climatic variables representing mean temperature and precipitation conditions,climate extremes,and climate seasonality for mosses distributed along an elevational gradient spanning about 5000 m in the central Himalaya,Nepal.For a given climatic variable,different metrics of phylogenetic structure show different spatial and climatic patterns,but all phylogenetic metrics standardized for species richness show that phylogenetic dispersion in moss assemblages tend to increase with increasing elevation and decreasing temperature.The standardized effect size of mean pairwise distance of moss assemblages shows a triphasic(zig-zag)pattern,which is generally consistent with the triphasic patterns previously found in angiosperms and ferns along the same elevational gradient.Our study shows that temperature-related variables and climate seasonality variables are more important drivers of phylogenetic dispersion in mosses in Nepal,compared with precipitation-related variables and climate extreme variables,respectively.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12274313,62275184,and 62411540033)Collaborative Innovation Center of Suzhou Nano Science and Technology,Suzhou Basic Research Project(Grant No.SJC2023003)+1 种基金the Gusu Leading Talent Plan for Scientific and Technological Innovation and Entrepreneurship(Grant No.ZXL2024400)the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Perfect anomalous reflections have been demonstrated in optical phase gradient metasurfaces(PGMs),but they suffer from single-frequency(narrow-band)response due to the intrinsic limitation of natural geometric periodicity.Here,we provide both numerical and analytical evidence that a depth gradient metasurface can achieve discrete ultra-broadband perfect anomalous reflection in the microwave range in the absence of geometric periodicity.Remarkably,by adjusting the operating frequency of the incident wave,the same effect can be steadily obtained via a physically equivalent phase periodicity in the PGM.Based on this mechanism,a perfect retroreflector with a broadband response ranging from 1 GHz to 40 GHz is realized.Our work has promising applications in communication,source tracking,and military satellites.
文摘Species richness in any area results from the interplay of the processes of speciation,extinction,and dispersal.The relationships between species richness and climate should be considered as an outcome of the effects of climate on speciation,extinction,and dispersal.Diversificationrate represents the balance of speciation and extinction rates over time.Here,I explore diversificationrates in mosses across geographic and climatic gradients worldwide.Specifically,I investigate latitudinal patterns and climatic associations of the mean diversificationrate of mosses at global,hemispheric,and smaller scales.I findthat the mean diversificationrate of mosses is positively correlated with species richness of mosses,increases with decreasing latitude and increasing mean annual temperature and annual precipitation,and is more strongly associated with mean annual temperature than with annual precipitation.These findingsshed light on variation of species richness in mosses across the world.The negative relationship between species richness and latitude and the positive relationship between species richness and mean diversificationrate in mosses suggest that higher moss species richness at lower latitudes might have resulted,at least to some degree,from higher moss diversificationrates at lower latitudes.
文摘Liver-directed therapies such as resection,ablation,and embolization offer potentially curative options for patients with primary and metastatic liver tumors as part of multidisciplinary oncology care.However,these treatments pose significant hepatic decompensation risks,particularly with underlying liver disease and chemotherapy-associated steatohepatitis.Accurate assessment of liver function and portal hypertension(PH)is critical for candidate selection.While Child-Pugh score and model for end-stage liver disease are commonly used,they have substantial limitations.Hepatic venous pressure gradient(HVPG)measurement remains the gold standard for assessing PH but is invasive and not widely available.Endoscopic ultrasound(EUS)guided portal pressure gradient(PPG)measurement has emerged as a promising minimally invasive alternative.EUSPPG demonstrates excellent technical success rates,safety profile,and correlation with HVPG in early studies.By providing direct portal pressure measurement,EUS-PPG offers several advantages over existing methods for prognostication and risk stratification prior to liver-directed therapies,particularly in detecting presinusoidal hypertension.Furthermore,it has potential applications in assessing response to neoadjuvant treatments and guiding adjuvant therapies.However,research is needed to validate its predictive performance and cost-effectiveness in larger prospective cohorts and to establish its accuracy compared to non-invasive assessment of liver function.
基金supported by Shandong Provincial Natural Science Foundation of China(Nos.ZR2024JQ020 and ZR2021QE102)the Taishan Scholars Program of Shandong Province,China(Nos.tsqn202211115,tsqn201909081,and tsqn202306162)+2 种基金the National Natural Science Foundation of China(No.52274397)Yantai high-end talent introduction“Double Hundred Plan”,China(2021)the Graduate Innovation Foundation of Yantai University,China(No.KGIFYTU2520).
文摘The GH141 superalloy ring-rolled parts often face microstructural inhomogeneity during production.This work investigated the effect of post-dynamic recrystallization on the microstructural evolution of GH141 superalloy after gradient thermal deformation to solve the problem of microstructural inhomogeneity.Compression tests involving double cone(DC)samples were conducted at various temperatures to assess the effect of gradient strain on internal grain microstructure variation,which ranged from the rim to the center of the samples.The results demonstrate considerable microstructural inhomogeneity induced by gradient strain in the DC samples.The delay in heat preservation facilitated post-dynamic recrystallization(PDRX)and promoted extensive recrystallization in the DC samples experiencing large gradient strain,which resulted in a homogeneous grain microstructure throughout the samples.During compression at a relatively low temperature,dynamic recrystallization(DRX)was predominantly driven by continuous dynamic recrystallization(CDRX).As the deformation temperature increased,the DRX mechanism changed from CDRX-dominated to being dominated by discontinuous dynamic recrystallization(DDRX).During the delay of the heat preservation process,PDRX was dominated by a static recrystallization mechanism,along with the occurrence of meta-dynamic recrystallization(MDRX)mechanisms.In addition,the PDRX mechanism of twin-induced recrystallization nucleation was observed.
基金Key Research and Development Program of Zhejiang Province,Grant/Award Number:2021C04019National Natural Science Foundation of China,Grant/Award Number:U20A20338Natural Science Foundation of Zhejiang Province,Grant/Award Number:LQ21H180012.
文摘A widely employed energy technology,known as reverse electrodialysis(RED),holds the promise of delivering clean and renewable electricity from water.This technology involves the interaction of two or more bodies of water with varying concentrations of salt ions.The movement of these ions across a membrane generates electricity.However,the efficiency of these systems faces a challenge due to membrane performance degradation over time,often caused by channel blockages.One potential solution to enhance system efficiency is the use of nanofluidic membranes.These specialized membranes offer high ion exchange capacity,abundant ion sources,and customizable channels with varying sizes and properties.Graphene oxide(GO)-based membranes have emerged as particularly promising candidates in this regard,garnering significant attention in recent literature.This work provides a comprehensive overview of the literature surrounding GO membranes and their applications in RED systems.It also highlights recent advancements in the utilization of GO membranes within these systems.Finally,it explores the potential of these membranes to play a pivotal role in electricity generation within RED systems.
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supported by the Instrument Developing Project of Magnetic Resonance Union of Chinese Academy of Sciences,Grant No.2022GZL002.
文摘Gradient coil is an essential component of a magnetic resonance imaging(MRI)scanner.To achieve high spatial resolution and imaging speed,a high-efficiency gradient coil with high slew rate is required.In consideration of the safety and comfort of the patient,the mechanical stability,acoustic noise and peripheral nerve stimulation(PNS)are also need to be concerned for practical use.In our previous work,a high-efficiency whole-body gradient coil set with a hybrid cylindrical-planar structure has been presented,which offers significantly improved coil performances.In this work,we propose to design this transverse gradient coil system with transformed magnetic gradient fields.By shifting up the zero point of gradient fields,the designed new Y-gradient coil could provide enhanced electromagnetic performances.With more uniform coil winding arrangement,the net torque of the new coil is significantly reduced and the generated sound pressure level(SPL)is lower at most tested frequency bands.On the other hand,the new transverse gradient coil designed with rotated magnetic gradient fields produces considerably reduced electric field in the human body,which is important for the use of rapid MR sequences.It's demonstrated that a safer and patient-friendly design could be obtained by using transformed magnetic gradient fields,which is critical for practical use.
基金supported by the Natural Science Foundation of Heilongjiang Province(JQ2022E004)。
文摘The changes in strain gradient induced by grain boundaries are crucial for enhancing the plasticity of gradient magnesium(Mg)alloys.The change of strain distribution influence by grain boundaries during plastic deformation of the gradient structure was examined.In this paper,the gradient structure AZ31 Mg-alloy plate with the surface fine grain(FG)to the center coarse grain(CG)was fabricated using hard plate rolling(HPR).The microstructure and strain distribution of Mg-alloy with a gradient structure were analyzed by electron backscatter diffraction(EBSD)and Digital image correlation(DIC)during uniaxial tensile.The findings indicate that the gradient structure sample(GS sample)displays a uniform strain distribution during the tensile process.Coarse-grain sample(CG sample)have obvious strain concentration,which leads to premature fracture.Based on EBSD characterization,low-angle grain boundaries(LAGBs)accumulates in the CG during plastic deformation.Orientation of CG tends to the(0001)basal.At the same time,the density of geometrically necessary dislocations(GNDs)inside CG has changed,which improves the Heterogeneous deformation induced(HDI)stress of gradient structure.During the uniaxial tensile,LAGBs accumulates in CG and changes the strain distribution of the gradient structure,which induces the accumulation of GNDs,and hence improving the properties of the GS Mg-alloy.These findings unveil the mechanism of strength-plasticity synergism of GS alloys from a new perspective and offer insights into the application of GS in Mg-alloys.
基金support for this work by Key Research and Development Project of Henan Province(Grant.No.241111232300)the National Natural Science Foundation of China(Grant.No.52273085 and 52303113)the Open Fund of Yaoshan Laboratory(Grant.No.2024003).
文摘The morphological distribution of absorbent in composites is equally important with absorbents for the overall electromagnetic properties,but it is often ignored.Herein,a comprehensive consideration including electromagnetic component regulation,layered arrangement structure,and gradient concentration distribution was used to optimize impedance matching and enhance electromagnetic loss.On the microscale,the incorporation of magnetic Ni nanoparticles into MXene nanosheets(Ni@MXene)endows suitable intrinsic permittivity and permeability.On the macroscale,the layered arrangement of Ni@MXene increases the effective interaction area with electromagnetic waves,inducing multiple reflection/scattering effects.On this basis,according to the analysis of absorption,reflection,and transmission(A-R-T)power coefficients of layered composites,the gradient concentration distribution was constructed to realize the impedance matching at low-concentration surface layer,electromagnetic loss at middle concentration interlayer and microwave reflection at high-concentration bottom layer.Consequently,the layered gradient composite(LG5-10-15)achieves complete absorption coverage of X-band at thickness of 2.00-2.20 mm with RL_(min) of-68.67 dB at 9.85 GHz in 2.05 mm,which is 199.0%,12.6%,and 50.6%higher than non-layered,layered and layered descending gradient composites,respectively.Therefore,this work confirms the importance of layered gradient structure in improving absorption performance and broadens the design of high-performance microwave absorption materials.
基金supported by the National Key R&D Program of China(No.2022YFB2404400)the National Natural Science Foundation of China(Nos.U23A20577,52372168,92263206 and 21975006)+1 种基金the“The Youth Beijing Scholars program”(No.PXM2021_014204_000023)the Beijing Natural Science Foundation(Nos.2222001 and KM202110005009).
文摘The cobalt-free Mn-based Li-rich layered oxide material has the advantages of low cost,high energy density,and good performance at low temperatures,and is the promising choice for energy storage batteries.However,the long-cycling stability of batteries needs to be improved.Herein,the Mn-based Li-rich cathode materials with small amounts of Li2 MnO3 crystal domains and gradient doping of Al and Ti elements from the surface to the bulk have been developed to improve the structure and interface stability.Then the batteries with a high energy density of 600 Wh kg^(-1),excellent capacity retention of 99.7%with low voltage decay of 0.03 mV cycle^(-1) after 800 cycles,and good rates performances can be achieved.Therefore,the structure and cycling stability of low voltage Mn-based Li-rich cathode materials can be significantly improved by the bulk structure design and interface regulation,and this work has paved the way for developing low-cost and high-energy Mn-based energy storage batteries with long lifetime.
基金the support of the National Natural Science Foundation of China (Nos. 42250103, 41974073, and 41404053)the Macao Foundation and the preresearch project of Civil Aerospace Technologies (Nos. D020308 and D020303)funded by China’s National Space Administration, the Specialized Research Fund for State Key Laboratories。
文摘We combine gradient data from the Macao Science Satellite-1(MSS-1),CHAllenging Minisatellite Payload(CHAMP),Swarm-A,and Swarm-C satellites to develop a 110-degree lithospheric magnetic field model.We then comprehensively evaluate the performance of the model by power spectral comparisons,correlation analyses,sensitivity matrix assessments,and comparisons with existing lithospheric field models.Results showed that using near east–west gradient data from MSS-1 significantly enhances the model correlation in the spherical harmonic degree(N) range of 45–60 while also mitigating the decline in correlation at higher degrees(N > 60).Furthermore,the unique orbital characteristics of MSS-1 enable its gradient data to provide substantial contributions to modeling in the mid-to low-latitude regions.With continued data acquisition from MSS-1 and further optimization of data processing methods,the performance of the model is expected to improve.
基金The financial supports by the Chinese Academy of Sciences(Nos.XDC04030300 and XDB0510303)CAS-HK Joint Laboratory of Nanomaterials and MechanicsShenyang National Laboratory for Materials Science are acknowledged.
文摘Rolling contact fatigue performance is among the most important issues for applications of bearing steels.In this work,a recently developed surface modification technique,surface mechanical rolling treatment,was applied on a rare-earth addition bearing steel.And rolling contact fatigue behavior of treated samples was compared with that of as-received counterparts at different contacting stresses.The results demonstrated that a 700μm-thick gradient nanostructured surface layer is produced on samples by surface mechanical rolling treatment.The grain size decreases while the microhardness increases gradually with decreasing depth,reaching~23 nm and~10.2 GPa,respectively,at the top surface.Consequently,the rolling contact fatigue property is significantly enhanced.The characteristic life of treated samples is~3.2 times that of untreated counterparts according to Weibull curves at 5.6 GPa.Analyses of fatigue mechanisms demonstrated that the gradient nanostructured surface layer might not only retard material degradation and microcrack formation,but also prolong the steady-state elastic response stage under rolling contact fatigue.
基金supported by the National Natural Science Foundation of China(Grant No.52473121,52403370 and 52221006)Fundamental Research Funds for the Central Universities(buctrc202020,buctrc202312).
文摘The intricate hierarchical structure of musculoskeletal tissues,including bone and interface tissues,necessitates the use of complex scaffold designs and material structures to serve as tissue-engineered substitutes.This has led to growing interest in the development of gradient bone scaffolds with hierarchical structures mimicking the extracellular matrix of native tissues to achieve improved therapeutic outcomes.Building on the anatomical characteristics of bone and interfacial tissues,this review provides a summary of current strategies used to design and fabricate biomimetic gradient scaffolds for repairing musculoskeletal tissues,specifically focusing on methods used to construct compositional and structural gradients within the scaffolds.The latest applications of gradient scaffolds for the regeneration of bone,osteochondral,and tendon-to-bone interfaces are presented.Furthermore,the current progress of testing gradient scaffolds in physiologically relevant animal models of skeletal repair is discussed,as well as the challenges and prospects of moving these scaffolds into clinical application for treating musculoskeletal injuries.
基金supported by the National Key R&D Program of China (Grant No.2022YFF0503700)the special funds of Hubei Luojia Laboratory (Grant No.220100011)+1 种基金supported by the International Space Science Institute–Beijing(ISSI-BJ) project“The Electromagnetic Data Validation and Scientific Application Research based on CSES Satellite”and ISSI/ISSI-BJ project,“Multi-Scale Magnetosphere–Ionosphere–Thermosphere Interaction.”
文摘The Michelson Interferometer for Global High-resolution Thermospheric Imaging(MIGHTI)onboard the Ionospheric Connection Explorer(ICON)satellite offers the opportunity to investigate the altitude profile of thermospheric winds.In this study,we used the red-line measurements of MIGHTI to compare with the results estimated by Horizontal Wind Model 14(HWM14).The data selected included both the geomagnetic quiet period(December 2019 to August 2022)and the geomagnetic storm on August 26-28,2021.During the geomagnetic quiet period,the estimations of neutral winds from HWM14 showed relatively good agreement with the observations from ICON.According to the ICON observations,near the equator,zonal winds reverse from westward to eastward at around 06:00 local time(LT)at higher altitudes,and the stronger westward winds appear at later LTs at lower altitudes.At around 16:00 LT,eastward winds at 300 km reverse to westward,and vertical gradients of zonal winds similar to those at sunrise hours can be observed.In the middle latitudes,zonal winds reverse about 2-4 h earlier.Meridional winds vary more significantly than zonal winds with seasonal and latitudinal variations.According to the ICON observations,in the northern low latitudes,vertical reversals of meridional winds are found at 08:00-13:00 LT from 300 to 160 km and at around 18:00 LT from 300 to 200 km during the June solstice.Similar reversals of meridional winds are found at 04:00-07:00 LT from 300 to 160 km and at 22:00-02:00 LT from 270 to 200 km during the December solstice.In the southern low latitudes,meridional wind reversals occur at 08:00-11:00 LT from 200 to 160 km and at 21:00-02:00 LT from 300 to 200 km during the June solstice.During the December solstice,reversals of the meridional wind appear at 20:00-01:00 LT below 200 km and at 06:00-11:00 LT from 300 to 160 km.In the northern middle latitudes,the northward winds are dominant at 08:00-14:00 LT at 230 km during the June solstice.Northward winds persist until 16:00 LT at 160 and 300 km.During the December solstice,the northward winds are dominant from 06:00 to 21:00 LT.The vertical variations in neutral winds during the geomagnetic storm on August 26-28 were analyzed in detail.Both meridional and zonal winds during the active geomagnetic period observed by ICON show distinguishable vertical shear structures at different stages of the storm.On the dayside,during the main phase,the peak velocities of westward winds extend from a higher altitude to a lower altitude,whereas during the recovery phase,the peak velocities of the westward winds extend from lower altitudes to higher altitudes.The velocities of the southward winds are stronger at lower altitudes during the storm.These vertical structures of horizontal winds during the storm could not be reproduced by the HWM14 wind estimations,and the overall response to the storm of the horizontal winds in the low and middle latitudes is underestimated by HWM14.The ICON observations provide a good dataset for improving the HWM wind estimations in the middle and upper atmosphere,especially the vertical variations.
基金Supported by the Science and Technology Project of Guangxi(Guike AD23023002)。
文摘In this paper,we propose a three-term conjugate gradient method for solving unconstrained optimization problems based on the Hestenes-Stiefel(HS)conjugate gradient method and Polak-Ribiere-Polyak(PRP)conjugate gradient method.Under the condition of standard Wolfe line search,the proposed search direction is the descent direction.For general nonlinear functions,the method is globally convergent.Finally,numerical results show that the proposed method is efficient.
基金Supported by NSFC(Nos.12371051,12141101,11871126)。
文摘In this paper,we study and characterize the volume estimates of geodesic balls on Finsler gradient Ricci solitons.We get the upper bounds on the volumes of geodesic balls of all three kinds of Finsler gradient Ricci solitons under certain condition about the Laplacian of thedistance function.
基金supported by the Changzhou Sci&Tech Program(Grant No.20240764)Key Laboratory of Advanced Structural Materials(Changchun University of Technology),Ministry of Education,China(Grant No.ASM-202207).
文摘Gradient nano-grained structure is frequently engineered into metallic materials,including Mg alloys,to achieve superior combination of strength and ductility.Nevertheless,the influence of this microstructural feature on aging precipitation behavior remains inadequately understood.In this study,the age-precipitation behavior of a gradient nano-grained Mg-Gd-Ag-Zr alloy prepared via ultrasonic severe surface rolling was investigated.The result indicates that the aging precipitation behavior exhibits a depth-dependent variation within this alloy.In the nano-grained surface layer,hierarchicalβnano-precipitates are predominant,while at greater depths,the precipitates consist ofβnanoparticles located at grain boundaries,along with intragranularβ′andγ″nano-plates.The formation ofβnano-precipitates deviates from the conventional precipitation behavior observed in Mg-Gd-Ag alloys,and is attributed to the high density of defects induced by the surface nano-grained structure.This finding advances our understanding of the precipitation behavior in the alloys with heterogeneous microstructure.
基金funded by the National Key Research and Development Program of China(No.2022YFB3705504)the Key Research and Development Program of Hebei Province,China(No.21310301D)+1 种基金the Central Government Guidance Fund for Local Science and Technology,China(No.226Z1003G)the Natural Science Foundation Innovation Group Funding Project of Hebei Province,China(No.E2021203011).
文摘Traditional symmetrical rolling often induces through-thickness gradient microstructures and textures.In this study,ultra-high purity(99.999 wt.%)tantalum(Ta)served as a model material to address the texture gradient issue by employing dynamic offsets and shear force adjustment rolling(DS rolling)as an advanced rolling technique.The strain and stress distributions in Ta plates for DS rolling and symmetrical rolling processes were analyzed using Deform 3D software.Through-thickness textures and microstructures were characterized via electron backscatter diffraction.The results revealed that DS rolling effectively solved the problem of texture gradient by increasing the average shear strain from 0.05 to 0.56.In turn,the shear stress reduced the energy storage orientation dependence of{100}and{111}grains.Furthermore,DS rolling refined the recrystallized grains on an average of 30.9%.
基金Supported by National Natural Science Foundation of China(Grant No.U1910212)the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘There is a pressing need for high-performance,high-strength low-alloy structural(HSLA)steels in various engineering fields,such as hydraulic components,engineering machinery,bridges,ships,and pressure vessels.In this study,a gradient dislocation-cell structure is introduced into an HSLA steel through ultrasonic severe surface rolling.The cell size is approximately 614 nm at the topmost surface layer,and increases with increasing the depth.Most of the cell walls have a misorientation ranging from 2°to 15°,indicating they belong to low angle grain boundaries(LAGBs),while some cell walls have a misorientation of less than 2°,corresponding to dense dislocation walls(DDWs).This unique gradient structure offers an exceptional combination of strength and ductility,with a high yield strength of 522.3±1.4 MPa and an accepted elongation of 25.5±1.7%.The morphology and size of the dislocation cells remain remarkably stable after uniaxial tension,demonstrating their efficacy as effective barriers hindering dislocation movement and thus enhancing strength and hardness.This gradient dislocation-cell structure facilitates inhomogeneous plastic deformation during uniaxial tensile loading,resulting in a pronounced accumulation of geometrically necessary dislocations(GNDs).These GNDs play a significant role in conferring favorable mechanical properties by inducing hetero-deformation-induced(HDI)strengthening effects and forest hardening effects.This study presents a promising avenue for achieving the desired mechanical properties in HSLA steel.
文摘Understanding the underlying mechanisms driving species assembly along elevational gradients is of great interest in ecology and biogeography.The Himalaya is one of the world’s hotspots of biodiversity,and the elevational gradient of the central Himalaya in Nepal is one of the longest elevational gradients in the world.Mosses are important constituents of vegetation in the Himalaya,and knowledge of geographic patterns and ecological causes of phylogenetic structure of mosses along elevational gradients in the Himalaya is critical to understanding the assembly of plant diversity in general,and moss diversity in particular,in the Himalaya.Here,we investigate the relationships of phylogenetic structure metrics reflecting different evolutionary depths with elevation and climatic variables representing mean temperature and precipitation conditions,climate extremes,and climate seasonality for mosses distributed along an elevational gradient spanning about 5000 m in the central Himalaya,Nepal.For a given climatic variable,different metrics of phylogenetic structure show different spatial and climatic patterns,but all phylogenetic metrics standardized for species richness show that phylogenetic dispersion in moss assemblages tend to increase with increasing elevation and decreasing temperature.The standardized effect size of mean pairwise distance of moss assemblages shows a triphasic(zig-zag)pattern,which is generally consistent with the triphasic patterns previously found in angiosperms and ferns along the same elevational gradient.Our study shows that temperature-related variables and climate seasonality variables are more important drivers of phylogenetic dispersion in mosses in Nepal,compared with precipitation-related variables and climate extreme variables,respectively.
