The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious materials.Consequently,the true triaxial compressio...The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious materials.Consequently,the true triaxial compression tests,CT scanning,SEM,and EDS tests were conducted on cemented gangue backfill samples(CGBSs)with various carbon nanotube concentrations(P_(CNT))that satisfied fractal theory for the PSD of aggregates.The mechanical properties,energy dissipations,and failure mechanisms of the CGBSs under true triaxial compression were systematically analyzed.The results indicate that appropriate carbon nanotubes(CNTs)effectively enhance the mechanical properties and energy dissipations of CGBSs through micropore filling and microcrack bridging,and the optimal effect appears at P_(CNT)of 0.08wt%.Taking PSD fractal dimension(D)of 2.500 as an example,compared to that of CGBS without CNT,the peak strength(σ_(p)),axial peak strain(ε_(1,p)),elastic strain energy(Ue),and dissipated energy(U_(d))increased by 12.76%,29.60%,19.05%,and90.39%,respectively.However,excessive CNTs can reduce the mechanical properties of CGBSs due to CNT agglomeration,manifesting a decrease inρ_(p),ε_(1,p),and the volumetric strain increment(Δε_(v))when P_(CNT)increases from 0.08wt%to 0.12wt%.Moreover,the addition of CNTs improved the integrity of CGBS after macroscopic failure,and crack extension in CGBSs appeared in two modes:detour and pass through the aggregates.Theσ_(p)and U_(d)firstly increase and then decrease with increasing D,and porosity shows the opposite trend.Theε_(1,p)andΔε_(v)are negatively correlated with D,and CGBS with D=2.150 has the maximum deformation parameters(ε_(1,p)=0.05079,Δε_(v)=0.01990)due to the frictional slip effect caused by coarse aggregates.With increasing D,the failure modes of CGBSs are sequentially manifested as oblique shear failure,"Y-shaped"shear failure,and conjugate shear failure.展开更多
A unique oscillating wind-driven triboelectric nanogenerator(OWTENG)based on the sphere's vortex-induced vibration(VIV)behavior is proposed in this study,which can harvest wind energy across a multitude of horizon...A unique oscillating wind-driven triboelectric nanogenerator(OWTENG)based on the sphere's vortex-induced vibration(VIV)behavior is proposed in this study,which can harvest wind energy across a multitude of horizontal directions.With the Euler-Lagrange method,the coupled governing equations of the OWTENG are established and subsequently validated by experimental tests.The vibrational properties and output performance of the OWTENG for varying wind speeds are analyzed,demonstrating its effectiveness in capturing wind energy across a broad range of wind speeds(from 2.20 m/s to 8.84 m/s),and the OWTENG achieves its peak output power of 106.3μW at a wind speed of 5.72 m/s.Furthermore,the OWTENG maintains a steady output power across various wind directions within the speed range of 2.20 m/s to 7.63 m/s.Nevertheless,when the wind speed exceeds 7.63 m/s,the vibrational characteristics of the sphere shift based on the wind direction,leading to fluctuations in the OWTENG's output power.This research presents an innovative approach for designing vibrational triboelectric nanogenerators,offering valuable insights into harvesting wind energy from diverse directions and speeds.展开更多
Understanding the shear mechanical behaviors and instability mechanisms of rock joints under dynamic loading remains a complex challenge.This research conducts a series of direct shear tests on real rock joints subjec...Understanding the shear mechanical behaviors and instability mechanisms of rock joints under dynamic loading remains a complex challenge.This research conducts a series of direct shear tests on real rock joints subjected to cyclic normal loads to assess the influence of dynamic normal loading amplitude(F_(d)),dynamic normal loading frequency(f_(v)),initial normal loading(F_(s)),and the joint roughness coefficient(JRC)on the mechanical properties and instability responses of these joints.The results show that unstable sliding is often accompanied by friction weakening due to dynamic normal loads.A significant negative correlation exists between cyclic normal loads and the normal displacement during the shearing process.Dynamic normal load paths vary the contact states of asperities on the rough joint surfaces,impacting the stick-slip instability mechanism of the joints,which in turn affects both the magnitude and location of the stress drop during the stick-slip events,particularly during the unloading phases.An increasing F_(d) results in a more stable shearing behavior and a reduction in the amplitude of stick-slip stress drops.The variation in f_(v) influences the amplitude of stress drop for the joints during shear,characterized by an initial decrease(f_(v)=0.25-2 Hz)before exhibiting an increment(f_(v)=2-4 Hz).As F_(s) increases,sudden failures of the interlocked rough surfaces are more prone to occur,thus producing enhanced instability and a more substantial stress drop.Additionally,a larger JRC intensifies the instability of the joints,which would induce a more pronounced decline in the stick-slip stress.The Rate and state friction(RSF)law can provide an effective explanation for the unstable sliding phenomena of joints during the oscillations of normal loads.The findings may provide certain useful references for a deeper comprehension of the sliding behaviors exhibited by rock joints when subjected to cyclic dynamic disturbances.展开更多
Considerable levels of methylmercury(MeHg)have been found rice-based infant cereals as a result of MeHg transfer from the rice as a raw material to the products,hence consumption of rice products may pose a potential ...Considerable levels of methylmercury(MeHg)have been found rice-based infant cereals as a result of MeHg transfer from the rice as a raw material to the products,hence consumption of rice products may pose a potential health risk to infants who may receive cereals as the major diets and are susceptible to toxicity of MeHg.Determination of bioaccessibility of MeHg would provide a more accurate assessment of MeHg exposure through consumption of rice-based cereals,yet this information remains lacking.Further,the re-adsorption of methylmercury on the residual food will affect the accurate assessment of its bioaccessibility.Our goals in this work were 1)to determine the bioaccessibility of MeHg in infant rice cereals commonly available on the market by using a typical in vitro artificial gastrointestinal digestionmodel and 2)to evaluate the effects of MeHg re-adsorption on the in vitro assessment of MeHg bioaccessibility.The determined bioaccessibility of MeHg in the studied rice cereals after the standard dual-step(using gastric followed by intestinal juice)protocol ranged from 25%to 74%,a wide range comparable to that of fish samples observed here and in previous studies.The surprisingly higher bioaccessibility of MeHg in fish and rice cereals after the gastric step only,in comparison to after the complete two-step gastrointestinal digestion,suggests the re-adsorption of MeHg on the residual food.Separate experiments with spiked MeHg standards confirmed that the MeHg released by the acetic gastric juice was re-adsorbed on the residues during the intestinal step at neutral pH.This study provided first-hand data on the bioaccessibility of MeHg in infant rice cereals and methodological implications on using in vitro digestion to evaluate the bioaccessibility of MeHg and metal contaminants in general.展开更多
Posttranslational modifications of antibody products affect their stability,charge distribution,and drug activity and are thus a critical quality attribute.The comprehensive mapping of antibody modifications and diffe...Posttranslational modifications of antibody products affect their stability,charge distribution,and drug activity and are thus a critical quality attribute.The comprehensive mapping of antibody modifications and different charge isomers(CIs)is of utmost importance,but is challenging.We intended to quantitatively characterize the posttranslational modification status of CIs of antibody drugs and explore the impact of posttranslational modifications on charge heterogeneity.The CIs of antibodies were fractionated by strong cation exchange chromatography and verified by capillary isoelectric focusing-whole column imaging detection,followed by stepwise structural characterization at three levels.First,the differences between CIs were explored at the intact protein level using a top-down mass spectrometry approach;this showed differences in glycoforms and deamidation status.Second,at the peptide level,common modifications of oxidation,deamidation,and glycosylation were identified.Peptide mapping showed nonuniform deamidation and glycoform distribution among CIs.In total,10 N-glycoforms were detected by peptide mapping.Finally,an in-depth analysis of glycan variants of CIs was performed through the detection of enriched glycopeptides.Qualitative and quantitative analyses demonstrated the dynamics of 24 N-glycoforms.The results revealed that sialic acid modification is a critical factor accounting for charge heterogeneity,which is otherwise missed in peptide mapping and intact molecular weight analyses.This study demonstrated the importance of the comprehensive analyses of antibody CIs and provides a reference method for the quality control of biopharmaceutical analysis.展开更多
This study aims to investigate mechanical properties and failure mechanisms of layered rock with rough joint surfaces under direct shear loading.Cubic layered samples with dimensions of 100 mm×100 mm×100 mm ...This study aims to investigate mechanical properties and failure mechanisms of layered rock with rough joint surfaces under direct shear loading.Cubic layered samples with dimensions of 100 mm×100 mm×100 mm were casted using rock-like materials,with anisotropic angle(α)and joint roughness coefficient(JRC)ranging from 15°to 75°and 2-20,respectively.The direct shear tests were conducted under the application of initial normal stress(σ_(n)) ranging from 1-4 MPa.The test results indicate significant differences in mechanical properties,acoustic emission(AE)responses,maximum principal strain fields,and ultimate failure modes of layered samples under different test conditions.The peak stress increases with the increasingαand achieves a maximum value atα=60°or 75°.As σ_(n) increases,the peak stress shows an increasing trend,with correlation coefficients R² ranging from 0.918 to 0.995 for the linear least squares fitting.As JRC increases from 2-4 to 18-20,the cohesion increases by 86.32%whenα=15°,while the cohesion decreases by 27.93%whenα=75°.The differences in roughness characteristics of shear failure surface induced byαresult in anisotropic post-peak AE responses,which is characterized by active AE signals whenαis small and quiet AE signals for a largeα.For a given JRC=6-8 andσ_(n)=1 MPa,asαincreases,the accumulative AE counts increase by 224.31%(αincreased from 15°to 60°),and then decrease by 14.68%(αincreased from 60°to 75°).The shear failure surface is formed along the weak interlayer whenα=15°and penetrates the layered matrix whenα=60°.Whenα=15°,as σ_(n) increases,the adjacent weak interlayer induces a change in the direction of tensile cracks propagation,resulting in a stepped pattern of cracks distribution.The increase in JRC intensifies roughness characteristics of shear failure surface for a smallα,however,it is not pronounced for a largeα.The findings will contribute to a better understanding of the mechanical responses and failure mechanisms of the layered rocks subjected to shear loads.展开更多
Analysing the influence mechanism of the riblet protrusion height on turbulent drag components is more beneficial in organising the vortical structure over the riblet surface.Therefore, the Large Eddy Simulation(LES) ...Analysing the influence mechanism of the riblet protrusion height on turbulent drag components is more beneficial in organising the vortical structure over the riblet surface.Therefore, the Large Eddy Simulation(LES) is used to investigate the vortex structure over the riblet surface with different protrusion heights. Then, the variations of Reynolds stress and viscous shear stress in a turbulent channel are analysed. As a result, the drag reduction rate increases from3.4% when the riblets are completely submerged in the turbulent boundary layer to 7.9% when the protrusion height is 11.2. Further analysis shows that the protrusion height affects the streamwise vortices and the normal diffusivity of spanwise and normal vortices, thus driving the variation of Reynolds stress. Compared with the smooth surface, the vorticity strength and the number of streamwise vortices are weakened near the wall but increase in the logarithmic layer with increased protrusion height. Meanwhile, the normal diffusivity of spanwise vorticity decreases with the increase of protrusion height, and the normal diffusivity of normal vorticity is the smallest when the protrusion height is 11.2. Moreover, the protrusion height affects the velocity gradient of the riblet tip and riblet valley, thus driving the variation of viscous shear stress. With the increase of protrusion height, the velocity gradient of the riblet tip increases dramatically but decreases in the riblet valley.展开更多
The presence of excess Ta in high-temperature protective coatings can compromise the integrity of the Al_(2)O_(3)scale on the surface,which has a negative impact on the oxidation behavior and reduces the service life....The presence of excess Ta in high-temperature protective coatings can compromise the integrity of the Al_(2)O_(3)scale on the surface,which has a negative impact on the oxidation behavior and reduces the service life.The effects of oxygen doping on the isothermal oxidation of three sputtered nanocrystalline coatings were investigated at 1100°C.The results indicated that oxygen doping inhibited the diffusion of Ta from the coating to the oxide scale,which was primarily attributed to the preferential oxidation of the Al in the coating.However,excess oxygen doping decreased the amount of Al available for the formation of the Al_(2)O_(3)scale on the coating,thus reducing the inhibitory effect on Ta oxidation.Moreover,doping with excess O caused spalling of the oxide scale.Therefore,the right balance in O doping is crucial for suppressing Ta oxidation while maintaining the integrity of the oxide scale.展开更多
The damping properties were improved by preparing Al matrix composites reinforced with glass cenospheres through the pressure infiltration method.Transmission electron microscopy and scanning electron microscopy were ...The damping properties were improved by preparing Al matrix composites reinforced with glass cenospheres through the pressure infiltration method.Transmission electron microscopy and scanning electron microscopy were employed to characterize the microstructure of the composites.The low-frequency damping properties were examined by using a dynamic mechanical thermal analyzer,aiming at exploring the changing trend of damping capacity with strain,temperature,and frequency.The findings demonstrated that the damping value rose as temperature and strain increased,with a maximum value of 0.15.Additionally,the damping value decreased when the frequency increased.Dislocation damping under strain and interfacial damping under temperature served as the two primary damping mechanisms.The increase in the density of dislocation strong pinning points following heat treatment reduced the damping value,which was attributed to the heat treatment enhancement of the interfacial bonding force of the composites.展开更多
To date, the Xunyang mercury(Hg) mining district is the only ongoing large-scale Hg mining district in China. To understand the influence of Hg contamination mode from the Hg mining and smelting activities, 27 samplin...To date, the Xunyang mercury(Hg) mining district is the only ongoing large-scale Hg mining district in China. To understand the influence of Hg contamination mode from the Hg mining and smelting activities, 27 sampling sites in the Xunyang Hg mining district were chosen in this study. Total gaseous mercury(TGM) in ambient air was measured using a Lumex-RA915 automatic Hg analyzer in2011. Rice samples and soil samples from rhizosphere were collected systematically and simultaneously. Total Hg(THg) and methylmercury(Me Hg) concentrations in rice grain and soil samples and Hg speciation with modified sequential selective extractions were measured. The local environment was seriously polluted with Hg. The TGM(302 ± 376 ng·m-3, ranging from 24 to 2220 ng·m^(-3)) in the local ambient air, THg(28 ± 30 mg·kg^(-1), ranging from 0.31 to 121 mg·kg^(-1)) and Me Hg(2.3 ± 1.9 lg·kg^(-1),ranging from 0.24 to 8.9 lg·kg^(-1)) in soil samples were at the sample level with Hg contaminated area. The THg concentration(26 ± 16 lg·kg^(-1)ranging from 4.5 to 71 lg·kg^(-1)) in most of the rice grain samples clearly exceeds the threshold level(20 lg·kg^(-1)) in the Chinese national guidelines for cereals(NY 861-2004). The inorganic mercury(IHg)(9.1 ± 5.6 lg·kg^(-1), ranging from 1.2 to 24 lg·kg^(-1)) and Me Hg(14 ± 9.8 lg·kg^(-1), ranging from 2.1 to 59 lg·kg^(-1))concentration in rice grain samples were at the same level with Hg contaminated area. The main species of Hg in paddy soils reveal strong complex Hg and residue Hg. According to the correlation analysis, a Hg pollution mode from local Hg mining and smelting was hypothesized, including Hg emission, transportation, methylation, and uptake process.展开更多
Surface rumpling is detrimental to high temperature protective coatings as it shortens their lifetime and leads to adhesion losses and unexpected corrosion degradation.The driving force and mass transport mechanism be...Surface rumpling is detrimental to high temperature protective coatings as it shortens their lifetime and leads to adhesion losses and unexpected corrosion degradation.The driving force and mass transport mechanism behind of rumpling remains to be clarified.In the present investigation,we subjected two types of nanocrystalline coating systems to avoid the influence of interdiffusion on rumpling study.One group was an ordinary nanocrystalline coating,and the other group was designed and prepared with trace oxygen by reactive magnetron sputtering.Systematic cyclic oxidation test at 1100°C was also car-ried out.Results show the ordinary nanocrystalline coating oxidized rapidly,which leads to the fast consumption of Al and the acceleration of phase transition in the coating.Meanwhile,severe surface rumpling is observed due to the stress release of nanocrystals through plastic deformation.Besides,the reactive doping of oxygen can significantly reduce the consumption process of Al in nanocrystalline coat-ing.The rumpling is controlled due to the improvement of coefficient of thermal expansion and Young’s modulus of the coating.Thereafter,the cyclic oxidation resistance is improved.展开更多
Ordered macroporous titania photonic crystals （PCs） and photonic balls were fabricated by functional modified polymer colloidal crystals. The TiO2 PCs and balls formed through this method exhibit no cracks and lacun...Ordered macroporous titania photonic crystals （PCs） and photonic balls were fabricated by functional modified polymer colloidal crystals. The TiO2 PCs and balls formed through this method exhibit no cracks and lacunae in large areas on their surface and their inner structures.展开更多
Sixty sediment samples were collected from the main Songhua River in three years. Twelve polybrominated diphenyl ether( PBDE) congeners( BDE17,28,47,66,99,100,153,154,138,183,and BDE-209) were detected to state the po...Sixty sediment samples were collected from the main Songhua River in three years. Twelve polybrominated diphenyl ether( PBDE) congeners( BDE17,28,47,66,99,100,153,154,138,183,and BDE-209) were detected to state the pollution situation. The results showed that the total concentration of total PBDEs ranges from 0. 424 to 23. 0 ng / g dry weight,with the mean of 3. 02 ng / g,and the total PBDEs concentration is at relative low level compared with those worldwide. The congener profile showed that BDE-209 is the dominant congener that accounts for more than 80. 1% of total PBDEs in sediments,followed by BDE-47 and BDE-99. These profiles are consistent with a high consumption of Deca-BDEs for the brominated flame retardant market in China. The results of spatial and seasonal observations indicated that local sources,temperature variation, and hydrologic conditions are significant factors on PBDEs concentrations. Hazard quotients suggested that PBDEs pose no potential risk to benthic organisms in detected area at present.展开更多
Along with the development of economy and society, type 2 diabetic mellitus(T2DM) has become one of the most common diseases at the global level. As one of the complications of T2 DM, diabetic neuropathic pain(DNP) st...Along with the development of economy and society, type 2 diabetic mellitus(T2DM) has become one of the most common diseases at the global level. As one of the complications of T2 DM, diabetic neuropathic pain(DNP) stubbornly and chronically affects the health and life of human beings. In the pain field, dorsal root ganglion(DRG) is generally considered as the first stage of the sensory pathway where the hyperexcitability of injured neurons is associated with different kinds of peripheral neuropathic pains. The abnormal electrophysiology is mainly due to the changed properties of voltage-gated sodium channels(VGSCs) and the increased sodium currents(INa). Curcumin is an active ingredient extracted from turmeric and has been demonstrated to ameliorate T2 DM and its various complications including DNP effectively. The present study demonstrates that the INa of small-sized DRG neurons are significantly increased with the abnormal electrophysiological characteristics of VGSCs in type 2 diabetic neuropathic pain rats. And these abnormalities can be ameliorated efficaciously by a period of treatment with curcumin.展开更多
The catalytic oxidative cou pling of methane(OCM)to C_(2) hydrocarbons(C_(2)H_(6) and C_(2)H_(4))represents one of the most effective ways to convert natural gas to more useful products,which can be performed effectiv...The catalytic oxidative cou pling of methane(OCM)to C_(2) hydrocarbons(C_(2)H_(6) and C_(2)H_(4))represents one of the most effective ways to convert natural gas to more useful products,which can be performed effectively using La_(0.6)Sr0.4Co_(0.2)Fe_(0.8)O_(3-δ)(LSCF)perovskite hollow fiber membrane microreactor.In this work,the effects of adding a thin BaCe_(0.8)Gd_(0.2)O_(3-δ)(BCG)catalyst film onto the inner LSCF fiber surface as the OCM catalyst and a porous Ba0.5Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)(BSCF)perovskite layer onto the outer LSCF surface to improve the oxygen permeation were evaluated.Between 700℃and 1000℃,methane conversion increased in the order of uncoated,BCG and BSCF-coated,and BCG-coated LSCF hollow fiber while Coselectivity and C_(2)-yield increased in the order of BCG and BSCF-coated,uncoated,and BCG-coated LSCF hollow fiber.Oxygen permeation flux at the same temperature range,on the other hand,was enhanced in the order of uncoated,BCG-coated,and BCG and BSCF-coated LSCF hollow fiber.This finding demonstrates the complex interplay between oxygen permeation and OCM performance.The BCG and BSCFcoated hollow fiber was also subjected to thermal cycles between 850℃and 900℃for up to 175 hours during which the fiber showed minor degradation in oxygen permeation fluxes and relatively stable OCM performance.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.52174092,51904290,and 52374147)the Natural Science Foundation of Jiangsu Province,China(No.BK20220157)+2 种基金the Fundamental Research Funds for the Central Universities,China(No.2022YCPY0202)the National Key Research and Development Program of China(No.2023YFC3804204)the Major Program of Xinjiang Uygur Autonomous Region S cience and Technology(No.2023A01002)。
文摘The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious materials.Consequently,the true triaxial compression tests,CT scanning,SEM,and EDS tests were conducted on cemented gangue backfill samples(CGBSs)with various carbon nanotube concentrations(P_(CNT))that satisfied fractal theory for the PSD of aggregates.The mechanical properties,energy dissipations,and failure mechanisms of the CGBSs under true triaxial compression were systematically analyzed.The results indicate that appropriate carbon nanotubes(CNTs)effectively enhance the mechanical properties and energy dissipations of CGBSs through micropore filling and microcrack bridging,and the optimal effect appears at P_(CNT)of 0.08wt%.Taking PSD fractal dimension(D)of 2.500 as an example,compared to that of CGBS without CNT,the peak strength(σ_(p)),axial peak strain(ε_(1,p)),elastic strain energy(Ue),and dissipated energy(U_(d))increased by 12.76%,29.60%,19.05%,and90.39%,respectively.However,excessive CNTs can reduce the mechanical properties of CGBSs due to CNT agglomeration,manifesting a decrease inρ_(p),ε_(1,p),and the volumetric strain increment(Δε_(v))when P_(CNT)increases from 0.08wt%to 0.12wt%.Moreover,the addition of CNTs improved the integrity of CGBS after macroscopic failure,and crack extension in CGBSs appeared in two modes:detour and pass through the aggregates.Theσ_(p)and U_(d)firstly increase and then decrease with increasing D,and porosity shows the opposite trend.Theε_(1,p)andΔε_(v)are negatively correlated with D,and CGBS with D=2.150 has the maximum deformation parameters(ε_(1,p)=0.05079,Δε_(v)=0.01990)due to the frictional slip effect caused by coarse aggregates.With increasing D,the failure modes of CGBSs are sequentially manifested as oblique shear failure,"Y-shaped"shear failure,and conjugate shear failure.
基金Project supported by the National Natural Science Foundation of China(Nos.12202151 and 12272140)。
文摘A unique oscillating wind-driven triboelectric nanogenerator(OWTENG)based on the sphere's vortex-induced vibration(VIV)behavior is proposed in this study,which can harvest wind energy across a multitude of horizontal directions.With the Euler-Lagrange method,the coupled governing equations of the OWTENG are established and subsequently validated by experimental tests.The vibrational properties and output performance of the OWTENG for varying wind speeds are analyzed,demonstrating its effectiveness in capturing wind energy across a broad range of wind speeds(from 2.20 m/s to 8.84 m/s),and the OWTENG achieves its peak output power of 106.3μW at a wind speed of 5.72 m/s.Furthermore,the OWTENG maintains a steady output power across various wind directions within the speed range of 2.20 m/s to 7.63 m/s.Nevertheless,when the wind speed exceeds 7.63 m/s,the vibrational characteristics of the sphere shift based on the wind direction,leading to fluctuations in the OWTENG's output power.This research presents an innovative approach for designing vibrational triboelectric nanogenerators,offering valuable insights into harvesting wind energy from diverse directions and speeds.
基金funding support from the National Natural Science Foundation of China(Grant Nos.52174092,and 51904290)open fund of Key Laboratory of Safety and High-efficiency Coal Mining,Ministry of Education(Anhui University of Science and Technology)(Grant No.JYBSYS202311).
文摘Understanding the shear mechanical behaviors and instability mechanisms of rock joints under dynamic loading remains a complex challenge.This research conducts a series of direct shear tests on real rock joints subjected to cyclic normal loads to assess the influence of dynamic normal loading amplitude(F_(d)),dynamic normal loading frequency(f_(v)),initial normal loading(F_(s)),and the joint roughness coefficient(JRC)on the mechanical properties and instability responses of these joints.The results show that unstable sliding is often accompanied by friction weakening due to dynamic normal loads.A significant negative correlation exists between cyclic normal loads and the normal displacement during the shearing process.Dynamic normal load paths vary the contact states of asperities on the rough joint surfaces,impacting the stick-slip instability mechanism of the joints,which in turn affects both the magnitude and location of the stress drop during the stick-slip events,particularly during the unloading phases.An increasing F_(d) results in a more stable shearing behavior and a reduction in the amplitude of stick-slip stress drops.The variation in f_(v) influences the amplitude of stress drop for the joints during shear,characterized by an initial decrease(f_(v)=0.25-2 Hz)before exhibiting an increment(f_(v)=2-4 Hz).As F_(s) increases,sudden failures of the interlocked rough surfaces are more prone to occur,thus producing enhanced instability and a more substantial stress drop.Additionally,a larger JRC intensifies the instability of the joints,which would induce a more pronounced decline in the stick-slip stress.The Rate and state friction(RSF)law can provide an effective explanation for the unstable sliding phenomena of joints during the oscillations of normal loads.The findings may provide certain useful references for a deeper comprehension of the sliding behaviors exhibited by rock joints when subjected to cyclic dynamic disturbances.
基金supported by the National Natural Science Foundation of China(No.22306111)Shandong Provincial Natural Science Foundation of China(Nos.ZR2022QB242 and ZR2020ZD20).
文摘Considerable levels of methylmercury(MeHg)have been found rice-based infant cereals as a result of MeHg transfer from the rice as a raw material to the products,hence consumption of rice products may pose a potential health risk to infants who may receive cereals as the major diets and are susceptible to toxicity of MeHg.Determination of bioaccessibility of MeHg would provide a more accurate assessment of MeHg exposure through consumption of rice-based cereals,yet this information remains lacking.Further,the re-adsorption of methylmercury on the residual food will affect the accurate assessment of its bioaccessibility.Our goals in this work were 1)to determine the bioaccessibility of MeHg in infant rice cereals commonly available on the market by using a typical in vitro artificial gastrointestinal digestionmodel and 2)to evaluate the effects of MeHg re-adsorption on the in vitro assessment of MeHg bioaccessibility.The determined bioaccessibility of MeHg in the studied rice cereals after the standard dual-step(using gastric followed by intestinal juice)protocol ranged from 25%to 74%,a wide range comparable to that of fish samples observed here and in previous studies.The surprisingly higher bioaccessibility of MeHg in fish and rice cereals after the gastric step only,in comparison to after the complete two-step gastrointestinal digestion,suggests the re-adsorption of MeHg on the residual food.Separate experiments with spiked MeHg standards confirmed that the MeHg released by the acetic gastric juice was re-adsorbed on the residues during the intestinal step at neutral pH.This study provided first-hand data on the bioaccessibility of MeHg in infant rice cereals and methodological implications on using in vitro digestion to evaluate the bioaccessibility of MeHg and metal contaminants in general.
基金the financial support from the National Key Program for Basic Research of China(Grant Nos.:2018YFC0910302 and 2017YFF0205400)the National Natural Science Foundation of China(Grant No.:81530021)Innovation Foundation of Medicine(Grant Nos.:BWS14J052 and 16CXZ027)
文摘Posttranslational modifications of antibody products affect their stability,charge distribution,and drug activity and are thus a critical quality attribute.The comprehensive mapping of antibody modifications and different charge isomers(CIs)is of utmost importance,but is challenging.We intended to quantitatively characterize the posttranslational modification status of CIs of antibody drugs and explore the impact of posttranslational modifications on charge heterogeneity.The CIs of antibodies were fractionated by strong cation exchange chromatography and verified by capillary isoelectric focusing-whole column imaging detection,followed by stepwise structural characterization at three levels.First,the differences between CIs were explored at the intact protein level using a top-down mass spectrometry approach;this showed differences in glycoforms and deamidation status.Second,at the peptide level,common modifications of oxidation,deamidation,and glycosylation were identified.Peptide mapping showed nonuniform deamidation and glycoform distribution among CIs.In total,10 N-glycoforms were detected by peptide mapping.Finally,an in-depth analysis of glycan variants of CIs was performed through the detection of enriched glycopeptides.Qualitative and quantitative analyses demonstrated the dynamics of 24 N-glycoforms.The results revealed that sialic acid modification is a critical factor accounting for charge heterogeneity,which is otherwise missed in peptide mapping and intact molecular weight analyses.This study demonstrated the importance of the comprehensive analyses of antibody CIs and provides a reference method for the quality control of biopharmaceutical analysis.
基金financial support from the National Natural Science Foundation of China(Nos.52174092,51904290,52004272,52104125,42372328,and U23B2091)Natural Science Foundation of Jiangsu Province,China(Nos.BK20220157 and BK20240209)+3 种基金the Fundamental Research Funds for the Central Universities,China(No.2022YCPY0202)Xuzhou Science and Technology Project,China(Nos.KC21033 and KC22005)Yunlong Lake Laboratory of Deep Underground Science and Engineering Project,China(No.104023002)the Graduate Innovation Program of China University of Mining and Technology(No.2023WLTCRCZL052)。
文摘This study aims to investigate mechanical properties and failure mechanisms of layered rock with rough joint surfaces under direct shear loading.Cubic layered samples with dimensions of 100 mm×100 mm×100 mm were casted using rock-like materials,with anisotropic angle(α)and joint roughness coefficient(JRC)ranging from 15°to 75°and 2-20,respectively.The direct shear tests were conducted under the application of initial normal stress(σ_(n)) ranging from 1-4 MPa.The test results indicate significant differences in mechanical properties,acoustic emission(AE)responses,maximum principal strain fields,and ultimate failure modes of layered samples under different test conditions.The peak stress increases with the increasingαand achieves a maximum value atα=60°or 75°.As σ_(n) increases,the peak stress shows an increasing trend,with correlation coefficients R² ranging from 0.918 to 0.995 for the linear least squares fitting.As JRC increases from 2-4 to 18-20,the cohesion increases by 86.32%whenα=15°,while the cohesion decreases by 27.93%whenα=75°.The differences in roughness characteristics of shear failure surface induced byαresult in anisotropic post-peak AE responses,which is characterized by active AE signals whenαis small and quiet AE signals for a largeα.For a given JRC=6-8 andσ_(n)=1 MPa,asαincreases,the accumulative AE counts increase by 224.31%(αincreased from 15°to 60°),and then decrease by 14.68%(αincreased from 60°to 75°).The shear failure surface is formed along the weak interlayer whenα=15°and penetrates the layered matrix whenα=60°.Whenα=15°,as σ_(n) increases,the adjacent weak interlayer induces a change in the direction of tensile cracks propagation,resulting in a stepped pattern of cracks distribution.The increase in JRC intensifies roughness characteristics of shear failure surface for a smallα,however,it is not pronounced for a largeα.The findings will contribute to a better understanding of the mechanical responses and failure mechanisms of the layered rocks subjected to shear loads.
基金the National Natural Science Foundation of China(No. 52176032)the Natural Science Foundation of Tianjin Municipal Science and Technology Commission, China(No. 22JCQNJC00050)the National Science and Technology Major Project, China(No.2017-Ⅱ-0005-0016)
文摘Analysing the influence mechanism of the riblet protrusion height on turbulent drag components is more beneficial in organising the vortical structure over the riblet surface.Therefore, the Large Eddy Simulation(LES) is used to investigate the vortex structure over the riblet surface with different protrusion heights. Then, the variations of Reynolds stress and viscous shear stress in a turbulent channel are analysed. As a result, the drag reduction rate increases from3.4% when the riblets are completely submerged in the turbulent boundary layer to 7.9% when the protrusion height is 11.2. Further analysis shows that the protrusion height affects the streamwise vortices and the normal diffusivity of spanwise and normal vortices, thus driving the variation of Reynolds stress. Compared with the smooth surface, the vorticity strength and the number of streamwise vortices are weakened near the wall but increase in the logarithmic layer with increased protrusion height. Meanwhile, the normal diffusivity of spanwise vorticity decreases with the increase of protrusion height, and the normal diffusivity of normal vorticity is the smallest when the protrusion height is 11.2. Moreover, the protrusion height affects the velocity gradient of the riblet tip and riblet valley, thus driving the variation of viscous shear stress. With the increase of protrusion height, the velocity gradient of the riblet tip increases dramatically but decreases in the riblet valley.
基金supported by the National Natural Science Foundation of China under Grant Nos.51671053 and 51801021the Fundamental Research Funds for the Central Universities(No.N2302007)the Ministry of Industry and Information Technology Project(No.MJ-2017-J-99).
文摘The presence of excess Ta in high-temperature protective coatings can compromise the integrity of the Al_(2)O_(3)scale on the surface,which has a negative impact on the oxidation behavior and reduces the service life.The effects of oxygen doping on the isothermal oxidation of three sputtered nanocrystalline coatings were investigated at 1100°C.The results indicated that oxygen doping inhibited the diffusion of Ta from the coating to the oxide scale,which was primarily attributed to the preferential oxidation of the Al in the coating.However,excess oxygen doping decreased the amount of Al available for the formation of the Al_(2)O_(3)scale on the coating,thus reducing the inhibitory effect on Ta oxidation.Moreover,doping with excess O caused spalling of the oxide scale.Therefore,the right balance in O doping is crucial for suppressing Ta oxidation while maintaining the integrity of the oxide scale.
基金financially supported by the National Key Research and Development Program of China(No.2022YFE0121400)the National Natural Science Foundation of China(Nos.52071117,52111530297,51601047)+1 种基金the Heilongjiang Provincial Science Fund for Distinguished Young Scholars,China(No.JQ2021E002)the Guangdong Basic and Applied Basic Research Foundation,China(No.2022B1515120016)。
文摘The damping properties were improved by preparing Al matrix composites reinforced with glass cenospheres through the pressure infiltration method.Transmission electron microscopy and scanning electron microscopy were employed to characterize the microstructure of the composites.The low-frequency damping properties were examined by using a dynamic mechanical thermal analyzer,aiming at exploring the changing trend of damping capacity with strain,temperature,and frequency.The findings demonstrated that the damping value rose as temperature and strain increased,with a maximum value of 0.15.Additionally,the damping value decreased when the frequency increased.Dislocation damping under strain and interfacial damping under temperature served as the two primary damping mechanisms.The increase in the density of dislocation strong pinning points following heat treatment reduced the damping value,which was attributed to the heat treatment enhancement of the interfacial bonding force of the composites.
基金financially supported by National Key Basic Research Program of China (973 Program,No.2013CB430004)the National Natural Science Foundation of China (No.41273152+1 种基金41473123)CAS Youth Innovation Promotion Association,Chinese Academy of Sciences (No.2011280)
文摘To date, the Xunyang mercury(Hg) mining district is the only ongoing large-scale Hg mining district in China. To understand the influence of Hg contamination mode from the Hg mining and smelting activities, 27 sampling sites in the Xunyang Hg mining district were chosen in this study. Total gaseous mercury(TGM) in ambient air was measured using a Lumex-RA915 automatic Hg analyzer in2011. Rice samples and soil samples from rhizosphere were collected systematically and simultaneously. Total Hg(THg) and methylmercury(Me Hg) concentrations in rice grain and soil samples and Hg speciation with modified sequential selective extractions were measured. The local environment was seriously polluted with Hg. The TGM(302 ± 376 ng·m-3, ranging from 24 to 2220 ng·m^(-3)) in the local ambient air, THg(28 ± 30 mg·kg^(-1), ranging from 0.31 to 121 mg·kg^(-1)) and Me Hg(2.3 ± 1.9 lg·kg^(-1),ranging from 0.24 to 8.9 lg·kg^(-1)) in soil samples were at the sample level with Hg contaminated area. The THg concentration(26 ± 16 lg·kg^(-1)ranging from 4.5 to 71 lg·kg^(-1)) in most of the rice grain samples clearly exceeds the threshold level(20 lg·kg^(-1)) in the Chinese national guidelines for cereals(NY 861-2004). The inorganic mercury(IHg)(9.1 ± 5.6 lg·kg^(-1), ranging from 1.2 to 24 lg·kg^(-1)) and Me Hg(14 ± 9.8 lg·kg^(-1), ranging from 2.1 to 59 lg·kg^(-1))concentration in rice grain samples were at the same level with Hg contaminated area. The main species of Hg in paddy soils reveal strong complex Hg and residue Hg. According to the correlation analysis, a Hg pollution mode from local Hg mining and smelting was hypothesized, including Hg emission, transportation, methylation, and uptake process.
基金supported by the National Natu-ral Science Foundation of China under Grant(Nos.51671053 and 51801021)the National Key R&D Program of China under Grant(No.2017YFB0306100)+1 种基金the Fundamental Research Funds for the Central Universities(No.N2102015)by the Ministry of Indus-try and Information Technology Project(No.MJ-2017-J-99).
文摘Surface rumpling is detrimental to high temperature protective coatings as it shortens their lifetime and leads to adhesion losses and unexpected corrosion degradation.The driving force and mass transport mechanism behind of rumpling remains to be clarified.In the present investigation,we subjected two types of nanocrystalline coating systems to avoid the influence of interdiffusion on rumpling study.One group was an ordinary nanocrystalline coating,and the other group was designed and prepared with trace oxygen by reactive magnetron sputtering.Systematic cyclic oxidation test at 1100°C was also car-ried out.Results show the ordinary nanocrystalline coating oxidized rapidly,which leads to the fast consumption of Al and the acceleration of phase transition in the coating.Meanwhile,severe surface rumpling is observed due to the stress release of nanocrystals through plastic deformation.Besides,the reactive doping of oxygen can significantly reduce the consumption process of Al in nanocrystalline coat-ing.The rumpling is controlled due to the improvement of coefficient of thermal expansion and Young’s modulus of the coating.Thereafter,the cyclic oxidation resistance is improved.
基金This work was financially supported by the Beijing Foundation of Natural Science, China(No. Z012013).
文摘Ordered macroporous titania photonic crystals （PCs） and photonic balls were fabricated by functional modified polymer colloidal crystals. The TiO2 PCs and balls formed through this method exhibit no cracks and lacunae in large areas on their surface and their inner structures.
基金Sponsored by the National Natural Science Foundation of China(Grant No.21277038)
文摘Sixty sediment samples were collected from the main Songhua River in three years. Twelve polybrominated diphenyl ether( PBDE) congeners( BDE17,28,47,66,99,100,153,154,138,183,and BDE-209) were detected to state the pollution situation. The results showed that the total concentration of total PBDEs ranges from 0. 424 to 23. 0 ng / g dry weight,with the mean of 3. 02 ng / g,and the total PBDEs concentration is at relative low level compared with those worldwide. The congener profile showed that BDE-209 is the dominant congener that accounts for more than 80. 1% of total PBDEs in sediments,followed by BDE-47 and BDE-99. These profiles are consistent with a high consumption of Deca-BDEs for the brominated flame retardant market in China. The results of spatial and seasonal observations indicated that local sources,temperature variation, and hydrologic conditions are significant factors on PBDEs concentrations. Hazard quotients suggested that PBDEs pose no potential risk to benthic organisms in detected area at present.
基金supported by a grant from the National Natural Science Foundation of China(No.81073125)Natural Science Foundation of Zhejiang Province(Y2090252)
文摘Along with the development of economy and society, type 2 diabetic mellitus(T2DM) has become one of the most common diseases at the global level. As one of the complications of T2 DM, diabetic neuropathic pain(DNP) stubbornly and chronically affects the health and life of human beings. In the pain field, dorsal root ganglion(DRG) is generally considered as the first stage of the sensory pathway where the hyperexcitability of injured neurons is associated with different kinds of peripheral neuropathic pains. The abnormal electrophysiology is mainly due to the changed properties of voltage-gated sodium channels(VGSCs) and the increased sodium currents(INa). Curcumin is an active ingredient extracted from turmeric and has been demonstrated to ameliorate T2 DM and its various complications including DNP effectively. The present study demonstrates that the INa of small-sized DRG neurons are significantly increased with the abnormal electrophysiological characteristics of VGSCs in type 2 diabetic neuropathic pain rats. And these abnormalities can be ameliorated efficaciously by a period of treatment with curcumin.
基金the research funding provided by the National Natural Science Foundation of China(21805206,22179073).
文摘The catalytic oxidative cou pling of methane(OCM)to C_(2) hydrocarbons(C_(2)H_(6) and C_(2)H_(4))represents one of the most effective ways to convert natural gas to more useful products,which can be performed effectively using La_(0.6)Sr0.4Co_(0.2)Fe_(0.8)O_(3-δ)(LSCF)perovskite hollow fiber membrane microreactor.In this work,the effects of adding a thin BaCe_(0.8)Gd_(0.2)O_(3-δ)(BCG)catalyst film onto the inner LSCF fiber surface as the OCM catalyst and a porous Ba0.5Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)(BSCF)perovskite layer onto the outer LSCF surface to improve the oxygen permeation were evaluated.Between 700℃and 1000℃,methane conversion increased in the order of uncoated,BCG and BSCF-coated,and BCG-coated LSCF hollow fiber while Coselectivity and C_(2)-yield increased in the order of BCG and BSCF-coated,uncoated,and BCG-coated LSCF hollow fiber.Oxygen permeation flux at the same temperature range,on the other hand,was enhanced in the order of uncoated,BCG-coated,and BCG and BSCF-coated LSCF hollow fiber.This finding demonstrates the complex interplay between oxygen permeation and OCM performance.The BCG and BSCFcoated hollow fiber was also subjected to thermal cycles between 850℃and 900℃for up to 175 hours during which the fiber showed minor degradation in oxygen permeation fluxes and relatively stable OCM performance.
