In order to manifest the influence of specific microstructural component on the development of severe localized corrosion in an AA2099 aluminum-lithium alloy, the corrosion behavior of the alloy subjected to solution ...In order to manifest the influence of specific microstructural component on the development of severe localized corrosion in an AA2099 aluminum-lithium alloy, the corrosion behavior of the alloy subjected to solution heat treatment, cold working and artificial ageing was investigated. Immersion testing and potentiodynamic polarization were employed to introduce localized corrosion; scanning electron microscopy and transmission electron microscopy were used to characterize the alloy microstructure and corrosion morphology. It was found that the susceptibility of the alloy to severe localized corrosion was sensitive to thermomechanical treatments. Additionally, the state of alloying elements influenced the mechanism of localized corrosion propagation. Specifically, the alloy in T8 conditions showed higher susceptibility to severe localized corrosion than that in other conditions. During potentiodynamic polarization, the alloy in solution heat-treated and T3 conditions displayed crystallographic corrosion morphology while the alloy in T6 and T8 conditions exhibited selective attack of grain interiors and grain boundaries in local regions.展开更多
AIM: To evaluate preventative effects of ischemic preconditioning(IP) in a rat model of intestinal injury induced by ischemia-reperfusion(IR).METHODS: Male Sprague-Dawley rats(250-300 g) were fasted for 24 h with free...AIM: To evaluate preventative effects of ischemic preconditioning(IP) in a rat model of intestinal injury induced by ischemia-reperfusion(IR).METHODS: Male Sprague-Dawley rats(250-300 g) were fasted for 24 h with free access to water prior to the operation.Eighteen rats were randomly divided into three experimental groups: S group(n = 6),rats were subjected to isolation of the superior mesenteric artery(SMA) for 40 min,then the abdomen was closed; IRgroup(n = 6),rats were subjected to clamping the SMA 40 min,and the abdomen was closed followed by a 4-h reperfusion; IP group(n = 6) rats underwent three cycles of 5 min ischemia and 5 min reperfusion,then clamping of the SMA for 40 min,then the abdomen was closed and a 4-h reperfusion followed.All animals were euthanized by barbiturate overdose(150 mg/kg pentobarbital sodium,i.v.) for tissue collection,and the SMA was isolated via median abdominal incision.Intestinal histologic injury was observed.Malondialdehyde(MDA),myeloperoxidase(MPO) and tumor necrosis factor(TNF)-a concentrations in intestinal tissue were measured.Intercellular adhesion molecule(ICAM)-1 and vascular cell adhesion molecule(VCAM)-1 expression,as well as nuclear factor(NF)-κB activity and expression in intestinal tissue were also determined.RESULTS: Compared with the IR group,IP reduced IR-induced histologic injury of the intestine in rats(2.00 ± 0.71 vs 3.60 ± 0.84,P < 0.05).IP significantly inhibited the increase in MDA content(5.6 ± 0.15 μmol/L vs 6.84 ± 0.18 μmol/L,P < 0.01),MPO activity(0.13 ± 0.01 U/L vs 0.24 ± 0.01 U/L,P < 0.01),and TNF-a levels(7.79 ± 2.35 pg/m L vs 10.87 ± 2.48 pg/m L,P < 0.05) in the intestinal tissue of rats.IP also markedly ameliorated the increase in ICAM-1(204.67 ± 53.27 vs 353.33 ± 45.19,P < 0.05) and VCAM-1(256.67 ± 58.59 vs 377.33 ± 41.42,P < 0.05) protein expression in the intestinal tissues.Additionally,IP remarkably decreased NF-κB activity(0.48 ± 0.16 vs 0.76 ± 0.22,P < 0.05) and protein expression(320.23 ± 38.16 vs 520.76 ± 40.53,P < 0.01) in rat intestinal tissue.CONCLUSION: IP may protect against IR-induced intestinal injury by attenuation of the neutrophilendothelial adhesion cascade via reducing ICAM-1 and VCAM-1 expression and TNF-a-induced NF-κB signaling pathway activity.展开更多
The microstructure and the filiform corrosion behaviour of machined AA7150 aluminium alloy were investigated using scanning and transmission electron microscopies combined with potentiodynamic polarization and filifor...The microstructure and the filiform corrosion behaviour of machined AA7150 aluminium alloy were investigated using scanning and transmission electron microscopies combined with potentiodynamic polarization and filiform corrosion testing,respectively.It is found that the grain refinement,redistribution of alloying elements,and elements segregation at grain boundaries are evident within the near-surface region on the machined AA7150 aluminium alloy.The corrosion susceptibility of machining introduced near-surface deformed layer is significantly improved caused by the modified microstructure associated with severe deformation.Filiform corrosion resistance on the machined surface is obviously decreased,due to the surface roughness associated with machining tracks and the presence of the electrochemically more active near-surface deformed layer introduced by machining.展开更多
Al-Mg-Zn-Er-Zr alloy was compressed in temperature range from 300 to 500℃to investigate the microstructure evolution.Molecular dynamics simulations were used to study the mechanical behavior and dislocation evolution...Al-Mg-Zn-Er-Zr alloy was compressed in temperature range from 300 to 500℃to investigate the microstructure evolution.Molecular dynamics simulations were used to study the mechanical behavior and dislocation evolution.The results showed that mobile dislocations are widely distributed in alloys and make important contributions to coordinate compressive deformation.The sessile dislocations hinder the deformation,and the content is about 1/20 of that of mobile dislocations.Continuous dynamic recrystallization(CDRX)is considered to be the main recrystallization mechanism.The accumulation of dislocations can provide element diffusion channels and driving force forτ(Mg_(32)[Al,Zn]_(49))phase precipitation,resulting in the forced precipitation of discontinuousτphase to replace the continuousβphase(Al_(3)Mg_(2)),which reduces the corrosion potential,resulting in increased corrosion resistance.展开更多
Based on 1.89×10^(8) J/ψ→ΛΛ Monte Carlo(MC)events produced from a longitudinally-polarized electron beam,the sensitivity of the CP violation of A decay is studied using fast simulation software.In addition,th...Based on 1.89×10^(8) J/ψ→ΛΛ Monte Carlo(MC)events produced from a longitudinally-polarized electron beam,the sensitivity of the CP violation of A decay is studied using fast simulation software.In addition,the J/ψ→ΛΛ decay can be used to optimize the detector response using the interface provided by the fast simulation software.In the future,the STCF is expected to obtain 3.4 trillion J/ψevents,and the statistical sensitivity of the CP violation of A decay via the J/ψ→ΛΛ process is expected to reach O(10^(-5))when the electron beam polarization is 80%.展开更多
Our world is composed of various materials with different structures,where spin structures have been playing a pivotal role in spintronic devices of the contemporary information technology.Apart from conventional coll...Our world is composed of various materials with different structures,where spin structures have been playing a pivotal role in spintronic devices of the contemporary information technology.Apart from conventional collinear spin materials such as collinear ferromagnets and collinear antiferromagnetic ally coupled materials,noncollinear spintronic materials have emerged as hot spots of research attention due to exotic physical phenomena.In this review,we first introduce two types of noncollinear spin structures,i.e.,the chiral spin structure that yields real-space Berry phases and the coplanar noncollinear spin structure that could generate momentum-space Berry phases,and then move to relevant novel physical phenomena including topological Hall effect,anomalous Hall effect,multiferroic,Weyl fermions,spin-polarized current and spin Hall effect without spin-orbit coupling in these noncollinear spin systems.Afterward,we summarize and elaborate the electric-field control of the noncollinear spin structure and related physical effects,which could enable ultralow power spintronic devices in future.In the final outlook part,we emphasize the importance and possible routes for experimentally detecting the intriguing theoretically predicted spin-polarized current,verifying the spin Hall effect in the absence of spin-orbit coupling and exploring the anisotropic magnetoresistance and domain-wall-related magnetoresistance effects for noncollinear antiferromagnetic materials.展开更多
Ferrimagnets, which contain the advantages of both ferromagnets(detectable moments) and antiferromagnets(ultrafast spin dynamics), have recently attracted great attention. Here, we report the optimization of epitaxial...Ferrimagnets, which contain the advantages of both ferromagnets(detectable moments) and antiferromagnets(ultrafast spin dynamics), have recently attracted great attention. Here, we report the optimization of epitaxial growth of a tetragonal perpendicularly magnetized ferrimagnet Mn_(2)Ga on MgO. Electrical transport, magnetic properties and the anomalous Hall effect(AHE) were systematically studied. Furthermore, we successfully integrated high-quality epitaxial ferrimagnetic Mn_(2)Ga thin films onto ferroelectric 0.7PbMg_(1/3)Nb_(2/3)O_(3)–0.3PbTiO_(3) single crystals with a MgO buffer layer. It was found that the AHE of such a ferrimagnet can be effectively modulated by a small electric field over a large temperature range in a nonvolatile manner. This work thus demonstrates the great potential of ferrimagnets for developing high-density and low-power spintronic devices.展开更多
The emerging Ni-based superconducting oxide thin films are rather intriguing to the entire condensed matter physics. Here, we report some brief experimental results on transport measurements for a 14-nm-thick supercon...The emerging Ni-based superconducting oxide thin films are rather intriguing to the entire condensed matter physics. Here, we report some brief experimental results on transport measurements for a 14-nm-thick superconducting Nd_(0.8)Sr_(0.2)NiO_(2)/SrTiO_(3) thin-film heterostructure with an onset transition temperature of~9.5 K. Photoluminescence measurements reveal that there is negligible oxygen vacancy creation in the SrTiO_(3) substrate during thin-film deposition and post chemical reduction for the Nd_(0.8)Sr_(0.2)NiO_(2)/SrTiO_(3) heterostructure. It was found that the critical current density of the Nd_(0.8)Sr_(0.2)NiO_(2)/SrTiO_(3) thin-film heterostructure is relatively small, ~4×10^(3) A·cm^(-2). Although the surface steps of SrTiO_(3) substrates lead to an anisotropy for in-plane resistivity, the superconducting transition temperatures are almost the same. The out-of-plane magnetotransport measurements yield an upper critical field of~11.4 T and an estimated in-plane Ginzburg–Landau coherence length of~5.4 nm. High-field magnetotransport measurements up to 50 T reveal anisotropic critical fields at 1.8 K for three different measurement geometries and a complicated Hall effect. An electric field applied via the SrTiO_(3) substrate slightly varies the superconducting transition temperature. These experimental results could be useful for this rapidly developing field.展开更多
The recently reported 9-15 K superconductivity in Nd0.8Sr0.2NiO2/SrTi03 heterostructures that were fabricated by a soft-chemical topotactic reduction approach based on precursor Nd0.8Sr0.2NiO3 thin films deposited on ...The recently reported 9-15 K superconductivity in Nd0.8Sr0.2NiO2/SrTi03 heterostructures that were fabricated by a soft-chemical topotactic reduction approach based on precursor Nd0.8Sr0.2NiO3 thin films deposited on SrTiO3 substrates,has excited an immediate surge of research interest.To explore an alternative physical path instead of chemical reduction to realizing superconductivity in this compound,using pulsed laser deposition,we systematically fabricated 63 Nd0.8Sr0.2NiOx(NSNO)thin films at a wide range of oxygen partial pressures on various oxide substrates.Transport measurements did not find any signature of superconductivity in all the 63 thin-film samples.With the oxygen content reducing in the NSNO films by lowering the deposition oxygen pressure,the NSNO films are getting more resistive and finally become insulating.Furthermore,we tried to cap a 20-nm-thick amorphous LaAlO3 layer on a Nd0.8Sr0.2NiO3 thin film deposited at a high oxygen pressure of 20 Pa to create oxygen vacancies on its surface and did not succeed in obtaining higher conductivity either.Our experimental results together with the recent report on the absence of superconductivity in synthesized bulk Nd0.8Sr0.2NiO2 crystals suggest that the chemical reduction approach could be unique for yielding superconductivity in NSNO/SrTiO3 heterostructures.However,SrTiO3 substrates could be reduced to generate oxygen vacancies during the chemical reduction process as well,which may thus partially contribute to conductivity.展开更多
基金Projects(51301214,51441002)supported by the National Natural Science Foundation of ChinaProject(cstc2013jcyj A50017)supported by Fundamental and Cutting-edge Research Plan of Chongqing,China+1 种基金Project supported by EPSRC LATEST2 Program,UKProject supported by Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry
文摘In order to manifest the influence of specific microstructural component on the development of severe localized corrosion in an AA2099 aluminum-lithium alloy, the corrosion behavior of the alloy subjected to solution heat treatment, cold working and artificial ageing was investigated. Immersion testing and potentiodynamic polarization were employed to introduce localized corrosion; scanning electron microscopy and transmission electron microscopy were used to characterize the alloy microstructure and corrosion morphology. It was found that the susceptibility of the alloy to severe localized corrosion was sensitive to thermomechanical treatments. Additionally, the state of alloying elements influenced the mechanism of localized corrosion propagation. Specifically, the alloy in T8 conditions showed higher susceptibility to severe localized corrosion than that in other conditions. During potentiodynamic polarization, the alloy in solution heat-treated and T3 conditions displayed crystallographic corrosion morphology while the alloy in T6 and T8 conditions exhibited selective attack of grain interiors and grain boundaries in local regions.
基金Supported by Grants from the Fundamental Research Funds for the Central Universities,No.2013JDHZ08Personnel training Specialized Research Fundation of The Second Affiliated Hospital of Xi’an Jiaotong University of China,No.RC(GG)201404
文摘AIM: To evaluate preventative effects of ischemic preconditioning(IP) in a rat model of intestinal injury induced by ischemia-reperfusion(IR).METHODS: Male Sprague-Dawley rats(250-300 g) were fasted for 24 h with free access to water prior to the operation.Eighteen rats were randomly divided into three experimental groups: S group(n = 6),rats were subjected to isolation of the superior mesenteric artery(SMA) for 40 min,then the abdomen was closed; IRgroup(n = 6),rats were subjected to clamping the SMA 40 min,and the abdomen was closed followed by a 4-h reperfusion; IP group(n = 6) rats underwent three cycles of 5 min ischemia and 5 min reperfusion,then clamping of the SMA for 40 min,then the abdomen was closed and a 4-h reperfusion followed.All animals were euthanized by barbiturate overdose(150 mg/kg pentobarbital sodium,i.v.) for tissue collection,and the SMA was isolated via median abdominal incision.Intestinal histologic injury was observed.Malondialdehyde(MDA),myeloperoxidase(MPO) and tumor necrosis factor(TNF)-a concentrations in intestinal tissue were measured.Intercellular adhesion molecule(ICAM)-1 and vascular cell adhesion molecule(VCAM)-1 expression,as well as nuclear factor(NF)-κB activity and expression in intestinal tissue were also determined.RESULTS: Compared with the IR group,IP reduced IR-induced histologic injury of the intestine in rats(2.00 ± 0.71 vs 3.60 ± 0.84,P < 0.05).IP significantly inhibited the increase in MDA content(5.6 ± 0.15 μmol/L vs 6.84 ± 0.18 μmol/L,P < 0.01),MPO activity(0.13 ± 0.01 U/L vs 0.24 ± 0.01 U/L,P < 0.01),and TNF-a levels(7.79 ± 2.35 pg/m L vs 10.87 ± 2.48 pg/m L,P < 0.05) in the intestinal tissue of rats.IP also markedly ameliorated the increase in ICAM-1(204.67 ± 53.27 vs 353.33 ± 45.19,P < 0.05) and VCAM-1(256.67 ± 58.59 vs 377.33 ± 41.42,P < 0.05) protein expression in the intestinal tissues.Additionally,IP remarkably decreased NF-κB activity(0.48 ± 0.16 vs 0.76 ± 0.22,P < 0.05) and protein expression(320.23 ± 38.16 vs 520.76 ± 40.53,P < 0.01) in rat intestinal tissue.CONCLUSION: IP may protect against IR-induced intestinal injury by attenuation of the neutrophilendothelial adhesion cascade via reducing ICAM-1 and VCAM-1 expression and TNF-a-induced NF-κB signaling pathway activity.
基金Project(EP/R001715/1)supported by the UK Engineering and Physical Sciences Research Council。
文摘The microstructure and the filiform corrosion behaviour of machined AA7150 aluminium alloy were investigated using scanning and transmission electron microscopies combined with potentiodynamic polarization and filiform corrosion testing,respectively.It is found that the grain refinement,redistribution of alloying elements,and elements segregation at grain boundaries are evident within the near-surface region on the machined AA7150 aluminium alloy.The corrosion susceptibility of machining introduced near-surface deformed layer is significantly improved caused by the modified microstructure associated with severe deformation.Filiform corrosion resistance on the machined surface is obviously decreased,due to the surface roughness associated with machining tracks and the presence of the electrochemically more active near-surface deformed layer introduced by machining.
基金financially supported by the National Key Research and Development Program of China(No.2021YFB 3704202)the General Program of Science and Technology Development Project of Beijing Municipal Education Commission(No.KM 202110005010)the Innovative Research Group Project of the National Natural Science Fund(No.51621003)。
文摘Al-Mg-Zn-Er-Zr alloy was compressed in temperature range from 300 to 500℃to investigate the microstructure evolution.Molecular dynamics simulations were used to study the mechanical behavior and dislocation evolution.The results showed that mobile dislocations are widely distributed in alloys and make important contributions to coordinate compressive deformation.The sessile dislocations hinder the deformation,and the content is about 1/20 of that of mobile dislocations.Continuous dynamic recrystallization(CDRX)is considered to be the main recrystallization mechanism.The accumulation of dislocations can provide element diffusion channels and driving force forτ(Mg_(32)[Al,Zn]_(49))phase precipitation,resulting in the forced precipitation of discontinuousτphase to replace the continuousβphase(Al_(3)Mg_(2)),which reduces the corrosion potential,resulting in increased corrosion resistance.
基金Supported by the National Key R&D Program of China(2022YFA1602200),the Science and Technology Innovation Program of Hunan Province,China(2020RC3054)the International Partnership Program of the Chinese Academy of Sciences(211134KYSB20200057)。
文摘Based on 1.89×10^(8) J/ψ→ΛΛ Monte Carlo(MC)events produced from a longitudinally-polarized electron beam,the sensitivity of the CP violation of A decay is studied using fast simulation software.In addition,the J/ψ→ΛΛ decay can be used to optimize the detector response using the interface provided by the fast simulation software.In the future,the STCF is expected to obtain 3.4 trillion J/ψevents,and the statistical sensitivity of the CP violation of A decay via the J/ψ→ΛΛ process is expected to reach O(10^(-5))when the electron beam polarization is 80%.
基金financially supported by the National Natural Science Foundation of China(Nos.51822101,51861135104,51771009 and 11704018).
文摘Our world is composed of various materials with different structures,where spin structures have been playing a pivotal role in spintronic devices of the contemporary information technology.Apart from conventional collinear spin materials such as collinear ferromagnets and collinear antiferromagnetic ally coupled materials,noncollinear spintronic materials have emerged as hot spots of research attention due to exotic physical phenomena.In this review,we first introduce two types of noncollinear spin structures,i.e.,the chiral spin structure that yields real-space Berry phases and the coplanar noncollinear spin structure that could generate momentum-space Berry phases,and then move to relevant novel physical phenomena including topological Hall effect,anomalous Hall effect,multiferroic,Weyl fermions,spin-polarized current and spin Hall effect without spin-orbit coupling in these noncollinear spin systems.Afterward,we summarize and elaborate the electric-field control of the noncollinear spin structure and related physical effects,which could enable ultralow power spintronic devices in future.In the final outlook part,we emphasize the importance and possible routes for experimentally detecting the intriguing theoretically predicted spin-polarized current,verifying the spin Hall effect in the absence of spin-orbit coupling and exploring the anisotropic magnetoresistance and domain-wall-related magnetoresistance effects for noncollinear antiferromagnetic materials.
基金the National Natural Science Foundation of China(Nos.52121001,51822101,51861135104 and 51771009)。
文摘Ferrimagnets, which contain the advantages of both ferromagnets(detectable moments) and antiferromagnets(ultrafast spin dynamics), have recently attracted great attention. Here, we report the optimization of epitaxial growth of a tetragonal perpendicularly magnetized ferrimagnet Mn_(2)Ga on MgO. Electrical transport, magnetic properties and the anomalous Hall effect(AHE) were systematically studied. Furthermore, we successfully integrated high-quality epitaxial ferrimagnetic Mn_(2)Ga thin films onto ferroelectric 0.7PbMg_(1/3)Nb_(2/3)O_(3)–0.3PbTiO_(3) single crystals with a MgO buffer layer. It was found that the AHE of such a ferrimagnet can be effectively modulated by a small electric field over a large temperature range in a nonvolatile manner. This work thus demonstrates the great potential of ferrimagnets for developing high-density and low-power spintronic devices.
基金financially supported by the National Natural Science Foundation of China(Nos.51822101,51861135104 and 51771009)。
文摘The emerging Ni-based superconducting oxide thin films are rather intriguing to the entire condensed matter physics. Here, we report some brief experimental results on transport measurements for a 14-nm-thick superconducting Nd_(0.8)Sr_(0.2)NiO_(2)/SrTiO_(3) thin-film heterostructure with an onset transition temperature of~9.5 K. Photoluminescence measurements reveal that there is negligible oxygen vacancy creation in the SrTiO_(3) substrate during thin-film deposition and post chemical reduction for the Nd_(0.8)Sr_(0.2)NiO_(2)/SrTiO_(3) heterostructure. It was found that the critical current density of the Nd_(0.8)Sr_(0.2)NiO_(2)/SrTiO_(3) thin-film heterostructure is relatively small, ~4×10^(3) A·cm^(-2). Although the surface steps of SrTiO_(3) substrates lead to an anisotropy for in-plane resistivity, the superconducting transition temperatures are almost the same. The out-of-plane magnetotransport measurements yield an upper critical field of~11.4 T and an estimated in-plane Ginzburg–Landau coherence length of~5.4 nm. High-field magnetotransport measurements up to 50 T reveal anisotropic critical fields at 1.8 K for three different measurement geometries and a complicated Hall effect. An electric field applied via the SrTiO_(3) substrate slightly varies the superconducting transition temperature. These experimental results could be useful for this rapidly developing field.
基金financially supported from the National Natural Science Foundation of China(Nos.51822101,51861135104,51771009 and 11704018)
文摘The recently reported 9-15 K superconductivity in Nd0.8Sr0.2NiO2/SrTi03 heterostructures that were fabricated by a soft-chemical topotactic reduction approach based on precursor Nd0.8Sr0.2NiO3 thin films deposited on SrTiO3 substrates,has excited an immediate surge of research interest.To explore an alternative physical path instead of chemical reduction to realizing superconductivity in this compound,using pulsed laser deposition,we systematically fabricated 63 Nd0.8Sr0.2NiOx(NSNO)thin films at a wide range of oxygen partial pressures on various oxide substrates.Transport measurements did not find any signature of superconductivity in all the 63 thin-film samples.With the oxygen content reducing in the NSNO films by lowering the deposition oxygen pressure,the NSNO films are getting more resistive and finally become insulating.Furthermore,we tried to cap a 20-nm-thick amorphous LaAlO3 layer on a Nd0.8Sr0.2NiO3 thin film deposited at a high oxygen pressure of 20 Pa to create oxygen vacancies on its surface and did not succeed in obtaining higher conductivity either.Our experimental results together with the recent report on the absence of superconductivity in synthesized bulk Nd0.8Sr0.2NiO2 crystals suggest that the chemical reduction approach could be unique for yielding superconductivity in NSNO/SrTiO3 heterostructures.However,SrTiO3 substrates could be reduced to generate oxygen vacancies during the chemical reduction process as well,which may thus partially contribute to conductivity.
