Objective The increasing recognition of the role for oxidative stress in hepatic disorders has led to extensive investigation on the protection by exogenous antioxidants against hepatic injury.In this study,we choose ...Objective The increasing recognition of the role for oxidative stress in hepatic disorders has led to extensive investigation on the protection by exogenous antioxidants against hepatic injury.In this study,we choose two typical polyphenol,quercetin and rutin,to investigate the mechanism of induction of cellular antioxidants and phase 2 enzymes in human HepG2 cells.Methods The HepG2 cells were treated with various concentrations of quercetin and rutin for 6 h and 24 h.The activities of NAD(P)H:quinone oxidoreductase(NQO1)in HepG2 cells were measured by 2,6-dichloroindophenol reduction method.The content of superoxide dismutase(SOD)was determined with the method of chemical colorimetry.The protein expressions of NQO1 and NF-E2-related factor 2(Nrf2)in HepG2 cells were detected by Western blotting.Results Incubation of HepG2 cells with quercetin and rutin resulted in a marked concentration-and time-dependent induction of a number of cellular antioxidants and phase 2 enzymes,including NQO1,SOD.Quercetin and rutin treatment of HepG2 cells also caused increase in protein expressions of NQO1 and Nrf2.Conclusions This study demonstrates that a series of phase 2 enzymes in HepG2 cells can be induced by quercetin and rutin in a concentration-and time-dependent fashion by upregulation the protein expression of nrf2.展开更多
ZTE Corporation announced on May 18, 2011 that it has won the world＇s first CDMA EV-DO Rev.B Phase 2 commercial contract from Indian telecom operator,Sistema Shyam TeleServices Ltd （SSTL）. SSTL operates its telecom...ZTE Corporation announced on May 18, 2011 that it has won the world＇s first CDMA EV-DO Rev.B Phase 2 commercial contract from Indian telecom operator,Sistema Shyam TeleServices Ltd （SSTL）. SSTL operates its telecom services ac＇ross India under the brand MrS and has over 11 million wireless customers. ZTE has also won the CDMA expansion contracts and EV-DO upgrade contracts for 10 circles of SSTL. The EV-DO Rev.B Phase 2 commercial launch will commence in Raiasthan.展开更多
The grain boundary diffusion process(GBDP)has proven to be an effective method for enhancing the coercivity of sintered Nd-Fe-B magnets.However,the limited diffusion depth and thicker shell struc-ture have impeded the...The grain boundary diffusion process(GBDP)has proven to be an effective method for enhancing the coercivity of sintered Nd-Fe-B magnets.However,the limited diffusion depth and thicker shell struc-ture have impeded the further development of magnetic properties.Currently,the primary debates re-garding the mechanism of GBDP with Tb revolve around the dissolution-solidification mechanism and the atomic substitution mechanism.To clarify this mechanism,the microstructure evolution of sintered Nd-Fe-B magnets during the heating process of GBDP has been systematically studied by quenching at different tem peratures.In this study,it was found that the formation of TbFe_(2) phase is related to the dis-solution of _(2)Fe_(14)B grains during GBDP with Tb.The theory of mixing heat and phase separation further confirms that the Nd_(2)Fe_(14)B phase dissolves to form a mixed phase of Nd and TbFe_(2),which then solidifies into the(Nd,Tb)_(2)Fe_(14)B phase.Based on the discovery of the TbFe_(2) phase,the dissolution-solidification mechanism is considered the primary mechanism for GBDP.This is supported by the elemental content of the two typical core-shell structures observed.展开更多
LiNiO_(2)(LNO)is one of the most promising cathode materials for lithium-ion batteries.Tungsten element in enhancing the stability of LNO has been researched extensively.However,the understanding of the specific dopin...LiNiO_(2)(LNO)is one of the most promising cathode materials for lithium-ion batteries.Tungsten element in enhancing the stability of LNO has been researched extensively.However,the understanding of the specific doping process and existing form of W are still not perfect.This study proposes a lithium-induced grain boundary phase W doping mechanism.The results demonstrate that the introduced W atomsfirst react with the lithium source to generate a Li–W–O phase at the grain boundary of primary particles.With the increase of lithium ratio,W atoms gradually diffuse from the grain boundary phase to the interior layered structure to achieve W doping.The feasibility of grain boundary phase doping is verified byfirst principles calculation.Furthermore,it is found that the Li2WO4 grain boundary phase is an excellent lithium ion conductor,which can protect the cathode surface and improve the rate performance.The doped W can alleviate the harmful H2↔H3 phase transition,thereby inhibiting the generation of microcracks,and improving the electrochemical performance.Consequently,the 0.3 wt%W-doped sample provides a significant improved capacity retention of 88.5%compared with the pristine LNO(80.7%)after 100 cycles at 2.8–4.3 V under 1C.展开更多
The mechanical properties of Mg–Al–Ca alloys are significantly affected by their Laves phases,including the Al_(2)Ca phase.Laves phases are generally considered to be brittle and have a detrimental effect on the duc...The mechanical properties of Mg–Al–Ca alloys are significantly affected by their Laves phases,including the Al_(2)Ca phase.Laves phases are generally considered to be brittle and have a detrimental effect on the ductility of Mg.Recently,the Al_(2)Ca phase was shown to undergo plastic deformation in a dilute Mg-Al-Ca alloy to increase the ductility and work hardening of the alloy.In the present study,we investigated the extent to which the deformation of Al_(2)Ca is driven by dislocations in the Mg matrix by simulating the interactions between the basal edge dislocations and Al_(2)Ca particles.In particular,the effects of the interparticle spacing,particle orientation,and particle size were considered.Shearing of small particles and dislocation cross-slips near large particles were observed.Both events contribute to strengthening,and accommodate to plasticity.The shear resistance of the dislocation to bypass the particles increased as the particle size increased.The critical resolved shear stress(CRSS)for activating dislocations and stacking faults was easier to reach for small Al_(2)Ca particles owing to the higher local shear stress,which is consistent with the experimental observations.Overall,this work elucidates the driving force for Al_(2)Ca particles in Mg–Al–Ca alloys to undergo plastic deformation.展开更多
Ternary layered MAX phase materials have excellent corrosion and oxidation resistance.However,their applications are limited by low hardness yet poor crack resistance,due to weak M–A metallic bonding and poor crack r...Ternary layered MAX phase materials have excellent corrosion and oxidation resistance.However,their applications are limited by low hardness yet poor crack resistance,due to weak M–A metallic bonding and poor crack resistance stemming from their extremely high plastic anisotropy with ultrahigh c/a ratio(>4).In this work,we demonstrate significant improvements in both hardness and crack resistance when the grain size of MAX phases is reduced to nanoscale.Nanocrystalline Cr_(2)AlC MAX coatings with grain size ranging from 0 to 100 nm were successfully fabricated using a controllable PVD-based twostep bottom-up strategy.Remarkable improvements are achieved in both hardness and toughness,with hardness(15.5 GPa)/record-high strength(8.53 GPa)and toughness/plasticity peaking at a grain size of 15.8 nm near the critical value.Such unusual hardening-toughening effect at nanoscale stems from homogeneous deformation mode transitions with synchronous Hall–Petch hardening.Transmission electron microscopic observations proved that both pyramidal and prismatic slip,which are unlikely to operate at microcrystalline regime at room temperature,are completely active at nanocrystalline regime,unlocking the key c-axial plasticity.As grain size further decreases approaching the critical value,a dynamic grain refinement-induced secondary sub-shear banding mechanism is triggered,which further extends the homogeneous deformation stage.These findings provide a simple route to fabricate advanced MAX phase corrosion-protection coatings with superior mechanical properties for extreme condition applications.展开更多
Layered oxides have attracted significant attention as cathodes for sodium-ion batteries(SIBs)due to their compositional versatility and tuneable electrochemical performance.However,these materials still face challeng...Layered oxides have attracted significant attention as cathodes for sodium-ion batteries(SIBs)due to their compositional versatility and tuneable electrochemical performance.However,these materials still face challenges such as structural phase transitions,Na^(+)/vacancy ordering,and Jahn–Teller distortion effect,resulting in severe capacity decay and sluggish ion kinetics.We develop a novel Cu/Y dual-doping strategy that leads to the formation of"Na–Y"interlayer aggregates,which act as structural pillars within alkali metal layers,enhancing structural stability and disrupting the ordered arrangement of Na^(+)/vacancies.This disruption leads to a unique coexistence of ordered and disordered Na^(+)/vacancy states with near-zero strain,which significantly improves Na^(+)diffusion kinetics.This structural innovation not only mitigates the unfavorable P2–O2 phase transition but also facilitates rapid ion transport.As a result,the doped material demonstrates exceptional electrochemical performance,including an ultra-long cycle life of 3000 cycles at 10 C and an outstanding high-rate capability of~70 mAh g^(−1)at 50 C.The discovery of this novel interlayer pillar,along with its role in modulating Na^(+)/vacancy arrangements,provides a fresh perspective on engineering layered oxides.It opens up promising new pathways for the structural design of advanced cathode materials toward efficient,stable,and high-rate SIBs.展开更多
文摘Objective The increasing recognition of the role for oxidative stress in hepatic disorders has led to extensive investigation on the protection by exogenous antioxidants against hepatic injury.In this study,we choose two typical polyphenol,quercetin and rutin,to investigate the mechanism of induction of cellular antioxidants and phase 2 enzymes in human HepG2 cells.Methods The HepG2 cells were treated with various concentrations of quercetin and rutin for 6 h and 24 h.The activities of NAD(P)H:quinone oxidoreductase(NQO1)in HepG2 cells were measured by 2,6-dichloroindophenol reduction method.The content of superoxide dismutase(SOD)was determined with the method of chemical colorimetry.The protein expressions of NQO1 and NF-E2-related factor 2(Nrf2)in HepG2 cells were detected by Western blotting.Results Incubation of HepG2 cells with quercetin and rutin resulted in a marked concentration-and time-dependent induction of a number of cellular antioxidants and phase 2 enzymes,including NQO1,SOD.Quercetin and rutin treatment of HepG2 cells also caused increase in protein expressions of NQO1 and Nrf2.Conclusions This study demonstrates that a series of phase 2 enzymes in HepG2 cells can be induced by quercetin and rutin in a concentration-and time-dependent fashion by upregulation the protein expression of nrf2.
文摘ZTE Corporation announced on May 18, 2011 that it has won the world＇s first CDMA EV-DO Rev.B Phase 2 commercial contract from Indian telecom operator,Sistema Shyam TeleServices Ltd （SSTL）. SSTL operates its telecom services ac＇ross India under the brand MrS and has over 11 million wireless customers. ZTE has also won the CDMA expansion contracts and EV-DO upgrade contracts for 10 circles of SSTL. The EV-DO Rev.B Phase 2 commercial launch will commence in Raiasthan.
基金supported by the National Key Research and Development Program of China(2022YFB3505503)the National Natural Science Foundation of China(52201230)+2 种基金the Key R&D Program of Shandong Province(2022CXGC020307)the China Postdoctoral Science Foundation(2022M71204)the Beijing NOVA Program(Z211100002121092).
文摘The grain boundary diffusion process(GBDP)has proven to be an effective method for enhancing the coercivity of sintered Nd-Fe-B magnets.However,the limited diffusion depth and thicker shell struc-ture have impeded the further development of magnetic properties.Currently,the primary debates re-garding the mechanism of GBDP with Tb revolve around the dissolution-solidification mechanism and the atomic substitution mechanism.To clarify this mechanism,the microstructure evolution of sintered Nd-Fe-B magnets during the heating process of GBDP has been systematically studied by quenching at different tem peratures.In this study,it was found that the formation of TbFe_(2) phase is related to the dis-solution of _(2)Fe_(14)B grains during GBDP with Tb.The theory of mixing heat and phase separation further confirms that the Nd_(2)Fe_(14)B phase dissolves to form a mixed phase of Nd and TbFe_(2),which then solidifies into the(Nd,Tb)_(2)Fe_(14)B phase.Based on the discovery of the TbFe_(2) phase,the dissolution-solidification mechanism is considered the primary mechanism for GBDP.This is supported by the elemental content of the two typical core-shell structures observed.
基金supported by the National Natural Science Foundation of China(No.52122407,No.52174285,52404317)the Science and Technology Innovation Program of Hunan Province(No.2022RC3048).
文摘LiNiO_(2)(LNO)is one of the most promising cathode materials for lithium-ion batteries.Tungsten element in enhancing the stability of LNO has been researched extensively.However,the understanding of the specific doping process and existing form of W are still not perfect.This study proposes a lithium-induced grain boundary phase W doping mechanism.The results demonstrate that the introduced W atomsfirst react with the lithium source to generate a Li–W–O phase at the grain boundary of primary particles.With the increase of lithium ratio,W atoms gradually diffuse from the grain boundary phase to the interior layered structure to achieve W doping.The feasibility of grain boundary phase doping is verified byfirst principles calculation.Furthermore,it is found that the Li2WO4 grain boundary phase is an excellent lithium ion conductor,which can protect the cathode surface and improve the rate performance.The doped W can alleviate the harmful H2↔H3 phase transition,thereby inhibiting the generation of microcracks,and improving the electrochemical performance.Consequently,the 0.3 wt%W-doped sample provides a significant improved capacity retention of 88.5%compared with the pristine LNO(80.7%)after 100 cycles at 2.8–4.3 V under 1C.
基金funded by the National Natural Science Foundation of China(nos.51631006 and 51825101)。
文摘The mechanical properties of Mg–Al–Ca alloys are significantly affected by their Laves phases,including the Al_(2)Ca phase.Laves phases are generally considered to be brittle and have a detrimental effect on the ductility of Mg.Recently,the Al_(2)Ca phase was shown to undergo plastic deformation in a dilute Mg-Al-Ca alloy to increase the ductility and work hardening of the alloy.In the present study,we investigated the extent to which the deformation of Al_(2)Ca is driven by dislocations in the Mg matrix by simulating the interactions between the basal edge dislocations and Al_(2)Ca particles.In particular,the effects of the interparticle spacing,particle orientation,and particle size were considered.Shearing of small particles and dislocation cross-slips near large particles were observed.Both events contribute to strengthening,and accommodate to plasticity.The shear resistance of the dislocation to bypass the particles increased as the particle size increased.The critical resolved shear stress(CRSS)for activating dislocations and stacking faults was easier to reach for small Al_(2)Ca particles owing to the higher local shear stress,which is consistent with the experimental observations.Overall,this work elucidates the driving force for Al_(2)Ca particles in Mg–Al–Ca alloys to undergo plastic deformation.
基金supported by the National Sci-ence Fund for Distinguished Young Scholars of China(No.52025014)the National Natural Science Foundation of China(Nos.U22A20111 and 52171090)the Natural Science Foundation of Zhe-jiang Province(No.LD24E010003).
文摘Ternary layered MAX phase materials have excellent corrosion and oxidation resistance.However,their applications are limited by low hardness yet poor crack resistance,due to weak M–A metallic bonding and poor crack resistance stemming from their extremely high plastic anisotropy with ultrahigh c/a ratio(>4).In this work,we demonstrate significant improvements in both hardness and crack resistance when the grain size of MAX phases is reduced to nanoscale.Nanocrystalline Cr_(2)AlC MAX coatings with grain size ranging from 0 to 100 nm were successfully fabricated using a controllable PVD-based twostep bottom-up strategy.Remarkable improvements are achieved in both hardness and toughness,with hardness(15.5 GPa)/record-high strength(8.53 GPa)and toughness/plasticity peaking at a grain size of 15.8 nm near the critical value.Such unusual hardening-toughening effect at nanoscale stems from homogeneous deformation mode transitions with synchronous Hall–Petch hardening.Transmission electron microscopic observations proved that both pyramidal and prismatic slip,which are unlikely to operate at microcrystalline regime at room temperature,are completely active at nanocrystalline regime,unlocking the key c-axial plasticity.As grain size further decreases approaching the critical value,a dynamic grain refinement-induced secondary sub-shear banding mechanism is triggered,which further extends the homogeneous deformation stage.These findings provide a simple route to fabricate advanced MAX phase corrosion-protection coatings with superior mechanical properties for extreme condition applications.
基金supported by the “Pioneer” and “Leading Goose” R&D Program of Zhejiang Province of China (No. 2024C01056)the support from London South Bank University
文摘Layered oxides have attracted significant attention as cathodes for sodium-ion batteries(SIBs)due to their compositional versatility and tuneable electrochemical performance.However,these materials still face challenges such as structural phase transitions,Na^(+)/vacancy ordering,and Jahn–Teller distortion effect,resulting in severe capacity decay and sluggish ion kinetics.We develop a novel Cu/Y dual-doping strategy that leads to the formation of"Na–Y"interlayer aggregates,which act as structural pillars within alkali metal layers,enhancing structural stability and disrupting the ordered arrangement of Na^(+)/vacancies.This disruption leads to a unique coexistence of ordered and disordered Na^(+)/vacancy states with near-zero strain,which significantly improves Na^(+)diffusion kinetics.This structural innovation not only mitigates the unfavorable P2–O2 phase transition but also facilitates rapid ion transport.As a result,the doped material demonstrates exceptional electrochemical performance,including an ultra-long cycle life of 3000 cycles at 10 C and an outstanding high-rate capability of~70 mAh g^(−1)at 50 C.The discovery of this novel interlayer pillar,along with its role in modulating Na^(+)/vacancy arrangements,provides a fresh perspective on engineering layered oxides.It opens up promising new pathways for the structural design of advanced cathode materials toward efficient,stable,and high-rate SIBs.
