5083 Al alloy sheets with different grain sizes(8.7-79.2 μm) were obtained by cold rolling and annealing. Their microstructures, intergranular corrosion(IGC), stress corrosion cracking(SCC), and crack propagation beh...5083 Al alloy sheets with different grain sizes(8.7-79.2 μm) were obtained by cold rolling and annealing. Their microstructures, intergranular corrosion(IGC), stress corrosion cracking(SCC), and crack propagation behaviors were investigated. The results showed that samples with coarse grains exhibit better IGC resistance with a corrosion depth of 15 μm. The slow strain rate test results revealed that fine-grained samples exhibit better SCC resistance with a susceptibility index(ISSRT) of 11.2%. Furthermore, based on the crack propagation mechanism, grain refinement can improve the SCC resistance by increasing the number of grain boundaries to induce the corrosion crack propagation along a tortuous path. The grains with {011} orientation could hinder crack propagation by orientating it toward the low-angle grain boundary region. The crack in the fine-grained material slowly propagates due to the tortuous path, and low H;and Cl;concentrations.展开更多
Objective: To investigate the effects of body mass index(BMI) on the outcomes of in vitro fertilization(IVF) in Chinese patients with polycystic ovary syndrome(PCOS). Methods: In the retrospective cohort study, a tota...Objective: To investigate the effects of body mass index(BMI) on the outcomes of in vitro fertilization(IVF) in Chinese patients with polycystic ovary syndrome(PCOS). Methods: In the retrospective cohort study, a total of 1074 patients with PCOS undergoing IVF between April 2010 and May 2017 in two reproductive medicine centers, respectively in eastern China(Women's Hospital, School of Medicine, Zhejiang University, Zhejiang Province) and in southern China(Maternal and Child Health Care Hospital of Liuzhou, Guangxi Province), were included. The patients were divided into four groups according to the recommended Chinese BMI cut-off points: underweight(BMI<18.5kg/m^2), normal weight(18.5kg/m^2≤BMI<24.0kg/m^2), overweight(24.0kg/m^2≤BMI<28.0kg/m^2), and obese(BMI≥28.0kg/m2). The basic characteristics of the PCOS patients, the details of IVF treatment, and the pregnancy outcomes were collected. Main results: There were no significant differences among the normal weight, overweight, and obese PCOS patients undergoing IVF on the biochemical pregnancy rate, clinical pregnancy rate, miscarriage rate, live birth rate, or term delivery rate(P>0.05), although the overweight and obese PCOS patients required more gonadotropin(Gn)(P<0.001) as well as longer stimulation period(P<0.001), and got less retrieved oocytes(P<0.05) and fertilized oocytes(P<0.05). The underweight PCOS patients required less Gn(P<0.05) and achieved higher live birth rate and term delivery rate(P<0.05), compared with the normal weight PCOS patients. Conclusions: High BMI had no negative effects on the outcomes of IVF in Chinese patients with PCOS; however, the conclusion may seem a little limited due to the retrospective design and the potential bias.展开更多
We presented a density functional theory study on doping effects of transition metals(Cr and Ti)on the Cu/graphene interface adhesion.Various undoped Cu/graphene interface structures were constructed using both the sa...We presented a density functional theory study on doping effects of transition metals(Cr and Ti)on the Cu/graphene interface adhesion.Various undoped Cu/graphene interface structures were constructed using both the sandwich and the surface models.Energetics calculations showed that the interface binding strength only weakly depends on interface coordination.Both interface models predicted the top-fcc coordination type as the most energy-favored,with a low binding energy value.Segregated Cr prefers to substituting for Cu, while Ti occupies a hollow site at the interface.Although the segregation tendencies are both very weak,once present on the interface,both dopants can greatly increase the interface binding energy and improve the adhesion.展开更多
Examining the pollination biology of plant species is not only crucial for enhancing our understanding of their reproductive biology,but also essential for elucidating their adaptation and evolutionary history.Here,we...Examining the pollination biology of plant species is not only crucial for enhancing our understanding of their reproductive biology,but also essential for elucidating their adaptation and evolutionary history.Here,we investigated the breeding system and pollination biology of two closely related species in Actaea.The flower of A.purpurea is unique in the genus with purple and chartaceous(paper-like)sepals,fewer stamens with yellow anthers and purple filaments.Through three seasons of field observation and exclusion experiments,we determined that A.purpurea was primarily pollinated by a hornet species,Vespa bicolor,which also served as the most efficient pollinator.In contrast,A.japonica was primarily pollinated by large flies.Actaea purpurea exhibited a significantly higher cumulative nectar volume than A.japonica,which could be a crucial factor in attracting V.bicolor.A control experiment further demonstrated that removing the nectar leaf(petal)significantly decreased the visiting frequency of V.bicolor.Breeding system studies revealed that both species were self-compatible,yet they primarily underwent outcrossing in natural habitats.Our study presents a compelling case of possible pollinator shift in A.purpurea accompanied by morphological divergence.A more in-depth investigation of this system would offer crucial insights into the extent to which pollinators are involved in the plant speciation process and whether they contribute to reproductive isolation between closely related species.展开更多
OBJECTIVE To describe the duration of the pre-hospital delay time and identify factors associated with prolonged pre-hospital delay in patients with acute myocardial infarction(AMI)in China.METHODS Data were collected...OBJECTIVE To describe the duration of the pre-hospital delay time and identify factors associated with prolonged pre-hospital delay in patients with acute myocardial infarction(AMI)in China.METHODS Data were collected from November 2014 to December 2019 as part of the Improving Care for Cardiovascular Dis-ease in China-Acute Coronary Syndrome(CCC-ACS)project.A total of 33,386 patients with AMI admitted to the index hospitals were included in this study.Two-level logistic regression was conducted to explore the factors associated with the pre-hospital delay and the associations between different pre-hospital delay and in-hospital outcomes.RESULTS Of the 33,386 patients with AMI,70.7%of patients arrived at hospital≥2 h after symptom onset.Old age,female,ru-ral medical insurance,symptom onset at early dawn,and non-use of an ambulance predicted a prolonged pre-hospital delay(all P<0.05).Hypertension and heart failure at admission were only significant in predicting a longer delay in patients with ST-seg-ment elevation myocardial infarction(STEMI)(all P<0.05).A pre-hospital delay of≥2 h was associated with an increased risk of mortality[odds ratio(OR)=1.36,95%CI:1.09-1.69,P=0.006]and major adverse cardiovascular events(OR=1.22,95%CI:1.02-1.47,P=0.033)in patients with STEMI compared with a pre-hospital delay of<2 h.CONCLUSIONS Prolonged pre-hospital delay is associated with adverse in-hospital outcomes in patients with STEMI in China.Our study identifies that patient characteristics,symptom onset time,and type of transportation are associated with pre-hospital delay time,and provides focuses for quality improvement.展开更多
Fatigue crack growth as a function ofαphase volume fraction in Ti-6Al-2Sn-4Zr-2Mo（Ti-6242）alloy was investigated using fatigue testing,optical microscopy,scanning electron microscopy,and transmission electron micro...Fatigue crack growth as a function ofαphase volume fraction in Ti-6Al-2Sn-4Zr-2Mo（Ti-6242）alloy was investigated using fatigue testing,optical microscopy,scanning electron microscopy,and transmission electron microscopy.Theα＋βannealing treatments with different solid solution temperatures and cooling rates were conducted in order to tailor microstructure with differentαphase features in the Ti-6242 alloy,and fatigue crack growth mechanism was discussed after detailed microstructure characterization.The results showed that fatigue crack growth rate of Ti-6242 alloy decreased with the decrease in volume fraction of the primaryαphase（αp）.Samples with a large-sizedαgrain microstructure treated at high solid solution temperature and slow cooling rate have lower fatigue crack growth rate.The appearance of secondaryαphase（αs）with the increase of solid solution temperature led to crack deflection.Moreover,a fatigue crack growth transition phenomenon was observed in the Paris regime of Ti-6242 alloy with 29.8% αp（typical bi-modal microstructure）and large-sizedαgrain microstructure,owing to the change of fatigue crack growth mechanism.展开更多
Extracellular vesicles(EVs)from mesenchymal stromal cells(MSCs)have previously been shown to protect against brain injury caused by hypoxia-ischemia(HI).The neuroprotective effects have been found to relate to the ant...Extracellular vesicles(EVs)from mesenchymal stromal cells(MSCs)have previously been shown to protect against brain injury caused by hypoxia-ischemia(HI).The neuroprotective effects have been found to relate to the anti-inflammatory effects of EVs.However,the underlying mechanisms have not previously been determined.In this study,we induced oxygen-glucose deprivation in BV-2 cells(a microglia cell line),which mimics HI in vitro,and found that treatment with MSCs-EVs increased the cell viability.The treatment was also found to reduce the expression of pro-inflammatory cytokines,induce the polarization of microglia towards the M2 phenotype,and suppress the phosphorylation of selective signal transducer and activator of transcription 3(STAT3)in the microglia.These results were also obtained in vivo using neonatal mice with induced HI.We investigated the potential role of miR-21a-5p in mediating these effects,as it is the most highly expressed miRNA in MSCs-EVs and interacts with the STAT3 pathway.We found that treatment with MSCs-EVs increased the levels of miR-21a-5p in BV-2 cells,which had been lowered following oxygen-glucose deprivation.When the level of miR-21a-5p in the MSCs-EVs was reduced,the effects on microglial polarization and STAT3 phosphorylation were reduced,for both the in vitro and in vivo HI models.These results indicate that MSCs-EVs attenuate HI brain injury in neonatal mice by shuttling miR-21a-5p,which induces microglial M2 polarization by targeting STAT3.展开更多
The effects of cold-rolling reduction,annealing temperature,and time on recrystallization behavior and kinetics of cold-rolled Zr-1Sn-0.3Nb-0.3Fe-0.1Cr alloy were investigated using the Vickers hardness test,scanning ...The effects of cold-rolling reduction,annealing temperature,and time on recrystallization behavior and kinetics of cold-rolled Zr-1Sn-0.3Nb-0.3Fe-0.1Cr alloy were investigated using the Vickers hardness test,scanning electronic microscopy(SEM),transmission electron microscopy(TEM)and electron backscatter diffractometry(EBSD).The results show that the rate of the recrystallization increased with increasing annealing temperature and rolling reduction.Recrystallized grains nucleated preferentially at sites with high density dislocation and deformation stored energy and then grew into integral grains.Recrystallization texture changed from-1010-//RD to-1120-//RD.The grain orientation changed from random orientation to the orientation with the maximum misorientation around 30°.Recrystallization kinetics and maps were constructed based on the Johnson-Mehl-Avrami-Kolmogorov(JMAK)equation to derive parameters sensitive to the microstructure.The activation energies for recrystallization of 30%,50%and 70%cold-rolling reductions were determined to be 240,249 and 180 kJ/mol,respectively.展开更多
Hot deformation behaviors and microstructure evolution of Ti-3Al-5Mo-4Cr-2Zr-1Fe(Ti-35421)alloy in theβsingle field are investigated by isothermal compression tests on a Gleeble-3500 simulator at temperatures of 820-...Hot deformation behaviors and microstructure evolution of Ti-3Al-5Mo-4Cr-2Zr-1Fe(Ti-35421)alloy in theβsingle field are investigated by isothermal compression tests on a Gleeble-3500 simulator at temperatures of 820-900°C and strain rates of 0.001-1 s^(-1).The research results show that discontinuous yield phenomenon and rheological softening are affected by the strain rates and deformation temperatures.The critical conditions for dynamic recrystallization and kinetic model of Ti-35421 alloy are determined,and the Arrhenius constitutive model is constructed.The rheological behaviors of Ti-35421 alloys aboveβphase transformation temperature are predicted by the constitutive model accurately.The EBSD analysis proves that the deformation softening is controlled by dynamic recovery and dynamic recrystallization.In addition,continuous dynamic recrystallization is determined during hot deformation,and the calculation model for recrystallization grain sizes is established.Good linear dependency between the experimental and simulated values of recrystallized grain sizes indicates that the present model can be used for the prediction of recrystallized grain size with high accuracy.展开更多
BACKGROUND:The predictive scoring systems for early stent thrombosis(EST)remains blank in China.The study aims to evaluate the risk factors and conduct a prediction model of EST in the Chinese population.METHODS:EST w...BACKGROUND:The predictive scoring systems for early stent thrombosis(EST)remains blank in China.The study aims to evaluate the risk factors and conduct a prediction model of EST in the Chinese population.METHODS:EST was defined as thrombosis that occurs within the first 30 days after primary percutaneous coronary intervention(PCI).Patients from ten Chinese hospitals diagnosed as stent thrombosis(ST)from January 2010 to December 2016 were retrospectively included as the study group.A control group(1 case:2 controls)was created by including patients without ST,major adverse cardiovascular events,or cerebrovascular events during follow-up.The present study evaluated 426 patients with single-vessel lesions and ultimately included 40 patients with EST and 80 control patients,who were included to identify factors that predicted EST and to develop a prediction scoring system.The other 171 patients without integrated 1:2 pair were used for external validation.RESULTS:EST was independently associated with a low hemoglobin concentration(adjusted odds ratio[OR]0.946,95%confi dence interval[95%CI]0.901-0.993,P=0.026),a high pre-PCI Synergy between Percutaneous Coronary Intervention with Taxus and Cardiac Surgery(SYNTAX)score(OR 1.166,95%CI 1.049-1.297,P=0.004),and a DAPT(DAPT)duration of<30 days(OR 28.033,95%CI 5.302-272.834,P<0.001).The simple EST prediction score provided an area under the curve(AUC)of 0.854(95%CI 0.777-0.932,P<0.001)with 70.0%sensitivity and 90.0%specifi city,and 0.742(95%CI 0.649-0.835,P<0.001)with 54.5%sensitivity and 81.0%specifi city for external validation dataset.CONCLUSIONS:EST may be independently associated with DAPT discontinuation within 30 days,a low hemoglobin concentration,and a high SYNTAX score.The scoring system also has a good ability to predict the risk of EST and may be useful in the clinical setting.展开更多
The point defect concentrations of L12-A13X（Sc, Zr, Er） were systematically investigated using the first- principle calculations with thermodynamics approach. The results show that the constitutional point defects o...The point defect concentrations of L12-A13X（Sc, Zr, Er） were systematically investigated using the first- principle calculations with thermodynamics approach. The results show that the constitutional point defects of off- stoichiometric L12-A13X（Sc, Zr, Er） prefer to occur in X sublattice, that is X anti-site in X-rich alloy and X vacancy in Al-rich alloy, respectively. And A1 anti-site also has a high density in Al-rich Llz-A13X（Sc, Er）. It is found that the point defect concentrations of stoichiometric L12-A/3X（Sc, Zr） follow in the sequence as： A1 vacancies （VA0 〉 X vacancies （Vx） 〉 X anti-sites （XA1） 〉 A1 anti- sites （Alx）. The point defect concentration of stoichio- metric A13Er is similar to that of L12-A13X（Sc, Zr）. The result suggests that the A1 vacancy （VA1） is a dominant point defect in L12-A13X（Sc, Zr, Er）. A simple parameter Hvx-HVA1 can be used for a rough estimation of the point defect concentrations in L12-A13X structure. Some rules of point defect concentrations for L12-A13X（Sc, Zr, Er） are also revealed.展开更多
The grain growth retardation mechanism and the effect of cooling rate on VC-doped WC–Co cemented carbides were investigated in this work.WC–30Co and WC–30Co–VC were prepared by powder metallurgy,liquid-phase sinte...The grain growth retardation mechanism and the effect of cooling rate on VC-doped WC–Co cemented carbides were investigated in this work.WC–30Co and WC–30Co–VC were prepared by powder metallurgy,liquid-phase sintering at 1400 ℃ and followed by water quenching（[150 ℃/s） or furnace cooling（＊0.083 ℃/s）.Based on the results of electron probe microanalysis（EPMA）,we found that WC concentration in the Co binder was independent of VC doping during liquid-phase sintering,hence barely contributing to the retardation of WC grain growth.In contrast,the（W,V）Cx phase formed at the WC/Co interfaces played a major role in retarding WC grain growth during liquid-phase sintering.The effect of cooling rate on the morphology of（W,V）Cxwas revealed by high-resolution transmission electron microscopy（HRTEM） and energy-dispersive spectroscopy（EDS）.In the water-quenched WC–30Co–VC,（W,V）Cxprecipitates were found as thin layers at the WC/Co interfaces.In contrast,both thin layers of similar thickness and nanoparticles of（W,V）Cx were observed in the furnace-cooled counterpart.These observations listed above suggested that thin（W,V）Cxlayers were stable structures effectively suppressing the growth of WC grains and their thickness remained independent of the cooling rate.The（W,V）Cxnanoparticles,however,may be inhibited through rapid cooling,ensuring the VC-doped WC–Co cemented carbides desired toughness.展开更多
The efect of cold rolling and annealing on the microstructure and properties of an Fe-13Cr-4.5Al-2.2Mo-1.1Nb alloy was investigated.The results showed that the recrystallization rate increased with increasing annealin...The efect of cold rolling and annealing on the microstructure and properties of an Fe-13Cr-4.5Al-2.2Mo-1.1Nb alloy was investigated.The results showed that the recrystallization rate increased with increasing annealing temperature and rolling reduction.Recrystallization kinetics was constructed based on Johnson-Mehl-Avrami-Kolmogorov equation.The apparent activation energies of recrystallization were 161.385,144.770,and 95.362 kJ/mol for the samples with 30%,50%,and 70%cold-rolling reduction,respectively.With the cold-rolling reduction increasing,the textureγfber partly changed to<100>//ND.After annealing,γfber of the alloy with 30%thickness reduction retained,the subgrains disappeared through merging,and the proportion of coincident site lattice grain boundaries increased and became more continuous.30%cold-rolling reduction alloy annealed at 730°C for 120 min not only possessed relatively high yield strength(YS)of^730 MPa and ultimate tensile strength(UTS)of^880 MPa,but also exhibited elongation of^16%at room temperature.After annealing at 730°C for 120 min,70%cold-rolled alloy has fner and more uniform grain,with higher elongation of^22%,YS of^615 MPa and UTS of^774 MPa.The mechanism of mechanical properties diference was explained according to Schmid factor analysis.These results provided an efective way for tuning strength and ductility of FeCrAl alloy.展开更多
Two dimensional asynchronous spectra were used to characterize coordination between carbonyl group of butanone and metal ions by using an approach proposed in our recent paper.Spectral variation of n-π^＊transition b...Two dimensional asynchronous spectra were used to characterize coordination between carbonyl group of butanone and metal ions by using an approach proposed in our recent paper.Spectral variation of n-π^＊transition band of carbonyl group is used to probe the coordination even if metal ions does not possess any characteristic peak in spectra.Experimental results indicate that Ca^2＋ and Al^3＋ show considerable ability to coordinate with the carbonyl group of butanone and bring about spectral variation of the n-π-＊transition band,which is manifested by cross peaks in 2D asynchronous spectra.展开更多
Ni-based self-lubricating composites containing a fixed amount of hexagonal boron nitride (h-BN)(5 wt%) and different amounts of graphene (0-1.5 wt%) were prepared by ultrasonic dispersion, high-energy ball milling, a...Ni-based self-lubricating composites containing a fixed amount of hexagonal boron nitride (h-BN)(5 wt%) and different amounts of graphene (0-1.5 wt%) were prepared by ultrasonic dispersion, high-energy ball milling, and spark plasma sintering. The effects of the graphene content on the physical, mechanical, and wear properties of the Ni/h-BN composites were evaluated. These properties were first enhanced with increasing graphene content, reaching optimal behavior for a graphene content of 1 wt%, and then degraded with further graphene addition. Compared to the pure Ni/h-BN composite, the relative density, hardness, and bending strength of the composite with 1 wt% graphene increased by 2.7%, 7.4%, and 6.3%, respectively, while the friction coefficient decreased by 56% to 0.31, and a reduction in wear rate by a factor of 5-15 was observed. The mechanism for improving the wear properties of the composite with added graphene was due to the formation of a graphene lubricating film on the worn surface, which increased the load bearing capacity of the surface and enhanced lubrication during wear.展开更多
基金financial support and Program of the Ministry of Education in China (2011)。
文摘5083 Al alloy sheets with different grain sizes(8.7-79.2 μm) were obtained by cold rolling and annealing. Their microstructures, intergranular corrosion(IGC), stress corrosion cracking(SCC), and crack propagation behaviors were investigated. The results showed that samples with coarse grains exhibit better IGC resistance with a corrosion depth of 15 μm. The slow strain rate test results revealed that fine-grained samples exhibit better SCC resistance with a susceptibility index(ISSRT) of 11.2%. Furthermore, based on the crack propagation mechanism, grain refinement can improve the SCC resistance by increasing the number of grain boundaries to induce the corrosion crack propagation along a tortuous path. The grains with {011} orientation could hinder crack propagation by orientating it toward the low-angle grain boundary region. The crack in the fine-grained material slowly propagates due to the tortuous path, and low H;and Cl;concentrations.
基金Project supported by the Zhejiang Provincial Natural Science Foundation for Distinguished Young Scholars(No.LR16H040001)the Key Project of Science and Technology Department of Zhejiang Province(No.2018C03010)+2 种基金the Zhejiang Provincial&Ministry of Health Research Fund for Medical Sciences(Nos.WKJ-ZJ-1522 and WKJ-ZJ-1722)the National Key Technology R&D Program of China(No.2014BAI05B04)the Guangxi Natural Science Foundation(Nos.2015GXNSFBA139177,2017GXNSFAA198199,and 2017GXNSFAA198193),China
文摘Objective: To investigate the effects of body mass index(BMI) on the outcomes of in vitro fertilization(IVF) in Chinese patients with polycystic ovary syndrome(PCOS). Methods: In the retrospective cohort study, a total of 1074 patients with PCOS undergoing IVF between April 2010 and May 2017 in two reproductive medicine centers, respectively in eastern China(Women's Hospital, School of Medicine, Zhejiang University, Zhejiang Province) and in southern China(Maternal and Child Health Care Hospital of Liuzhou, Guangxi Province), were included. The patients were divided into four groups according to the recommended Chinese BMI cut-off points: underweight(BMI<18.5kg/m^2), normal weight(18.5kg/m^2≤BMI<24.0kg/m^2), overweight(24.0kg/m^2≤BMI<28.0kg/m^2), and obese(BMI≥28.0kg/m2). The basic characteristics of the PCOS patients, the details of IVF treatment, and the pregnancy outcomes were collected. Main results: There were no significant differences among the normal weight, overweight, and obese PCOS patients undergoing IVF on the biochemical pregnancy rate, clinical pregnancy rate, miscarriage rate, live birth rate, or term delivery rate(P>0.05), although the overweight and obese PCOS patients required more gonadotropin(Gn)(P<0.001) as well as longer stimulation period(P<0.001), and got less retrieved oocytes(P<0.05) and fertilized oocytes(P<0.05). The underweight PCOS patients required less Gn(P<0.05) and achieved higher live birth rate and term delivery rate(P<0.05), compared with the normal weight PCOS patients. Conclusions: High BMI had no negative effects on the outcomes of IVF in Chinese patients with PCOS; however, the conclusion may seem a little limited due to the retrospective design and the potential bias.
基金Project(2018YFE0306100) supported by the National MCF Energy R&D Program of China
文摘We presented a density functional theory study on doping effects of transition metals(Cr and Ti)on the Cu/graphene interface adhesion.Various undoped Cu/graphene interface structures were constructed using both the sandwich and the surface models.Energetics calculations showed that the interface binding strength only weakly depends on interface coordination.Both interface models predicted the top-fcc coordination type as the most energy-favored,with a low binding energy value.Segregated Cr prefers to substituting for Cu, while Ti occupies a hollow site at the interface.Although the segregation tendencies are both very weak,once present on the interface,both dopants can greatly increase the interface binding energy and improve the adhesion.
基金supported by the National Natural Science Foundation of China(31870194)the Innovation Capability Support Program of Shaanxi(Program No.2023KJXX-019)the Fundamental Research Funds for the Central Universities(GK202301008 to J.Q.Zhang).
文摘Examining the pollination biology of plant species is not only crucial for enhancing our understanding of their reproductive biology,but also essential for elucidating their adaptation and evolutionary history.Here,we investigated the breeding system and pollination biology of two closely related species in Actaea.The flower of A.purpurea is unique in the genus with purple and chartaceous(paper-like)sepals,fewer stamens with yellow anthers and purple filaments.Through three seasons of field observation and exclusion experiments,we determined that A.purpurea was primarily pollinated by a hornet species,Vespa bicolor,which also served as the most efficient pollinator.In contrast,A.japonica was primarily pollinated by large flies.Actaea purpurea exhibited a significantly higher cumulative nectar volume than A.japonica,which could be a crucial factor in attracting V.bicolor.A control experiment further demonstrated that removing the nectar leaf(petal)significantly decreased the visiting frequency of V.bicolor.Breeding system studies revealed that both species were self-compatible,yet they primarily underwent outcrossing in natural habitats.Our study presents a compelling case of possible pollinator shift in A.purpurea accompanied by morphological divergence.A more in-depth investigation of this system would offer crucial insights into the extent to which pollinators are involved in the plant speciation process and whether they contribute to reproductive isolation between closely related species.
基金supported by the CCC-ACS Project(NCT02306616)which is a collaborative project of the American Heart Association and the Chinese Society of Cardiology.
文摘OBJECTIVE To describe the duration of the pre-hospital delay time and identify factors associated with prolonged pre-hospital delay in patients with acute myocardial infarction(AMI)in China.METHODS Data were collected from November 2014 to December 2019 as part of the Improving Care for Cardiovascular Dis-ease in China-Acute Coronary Syndrome(CCC-ACS)project.A total of 33,386 patients with AMI admitted to the index hospitals were included in this study.Two-level logistic regression was conducted to explore the factors associated with the pre-hospital delay and the associations between different pre-hospital delay and in-hospital outcomes.RESULTS Of the 33,386 patients with AMI,70.7%of patients arrived at hospital≥2 h after symptom onset.Old age,female,ru-ral medical insurance,symptom onset at early dawn,and non-use of an ambulance predicted a prolonged pre-hospital delay(all P<0.05).Hypertension and heart failure at admission were only significant in predicting a longer delay in patients with ST-seg-ment elevation myocardial infarction(STEMI)(all P<0.05).A pre-hospital delay of≥2 h was associated with an increased risk of mortality[odds ratio(OR)=1.36,95%CI:1.09-1.69,P=0.006]and major adverse cardiovascular events(OR=1.22,95%CI:1.02-1.47,P=0.033)in patients with STEMI compared with a pre-hospital delay of<2 h.CONCLUSIONS Prolonged pre-hospital delay is associated with adverse in-hospital outcomes in patients with STEMI in China.Our study identifies that patient characteristics,symptom onset time,and type of transportation are associated with pre-hospital delay time,and provides focuses for quality improvement.
基金support of National Natural Science Foundation of China under Grant No.51401175the Research Fund for the Doctoral Program of China(No.20130162110005)
文摘Fatigue crack growth as a function ofαphase volume fraction in Ti-6Al-2Sn-4Zr-2Mo（Ti-6242）alloy was investigated using fatigue testing,optical microscopy,scanning electron microscopy,and transmission electron microscopy.Theα＋βannealing treatments with different solid solution temperatures and cooling rates were conducted in order to tailor microstructure with differentαphase features in the Ti-6242 alloy,and fatigue crack growth mechanism was discussed after detailed microstructure characterization.The results showed that fatigue crack growth rate of Ti-6242 alloy decreased with the decrease in volume fraction of the primaryαphase（αp）.Samples with a large-sizedαgrain microstructure treated at high solid solution temperature and slow cooling rate have lower fatigue crack growth rate.The appearance of secondaryαphase（αs）with the increase of solid solution temperature led to crack deflection.Moreover,a fatigue crack growth transition phenomenon was observed in the Paris regime of Ti-6242 alloy with 29.8% αp（typical bi-modal microstructure）and large-sizedαgrain microstructure,owing to the change of fatigue crack growth mechanism.
基金supported by the National Natural Science Foundation of China,Nos.81873768,82072535,81671213(to ZW),81770436(to WQC)the National Key Project of Chronic Non-Communicable Disease of China,No.2016YFC1300403(to WQC).
文摘Extracellular vesicles(EVs)from mesenchymal stromal cells(MSCs)have previously been shown to protect against brain injury caused by hypoxia-ischemia(HI).The neuroprotective effects have been found to relate to the anti-inflammatory effects of EVs.However,the underlying mechanisms have not previously been determined.In this study,we induced oxygen-glucose deprivation in BV-2 cells(a microglia cell line),which mimics HI in vitro,and found that treatment with MSCs-EVs increased the cell viability.The treatment was also found to reduce the expression of pro-inflammatory cytokines,induce the polarization of microglia towards the M2 phenotype,and suppress the phosphorylation of selective signal transducer and activator of transcription 3(STAT3)in the microglia.These results were also obtained in vivo using neonatal mice with induced HI.We investigated the potential role of miR-21a-5p in mediating these effects,as it is the most highly expressed miRNA in MSCs-EVs and interacts with the STAT3 pathway.We found that treatment with MSCs-EVs increased the levels of miR-21a-5p in BV-2 cells,which had been lowered following oxygen-glucose deprivation.When the level of miR-21a-5p in the MSCs-EVs was reduced,the effects on microglial polarization and STAT3 phosphorylation were reduced,for both the in vitro and in vivo HI models.These results indicate that MSCs-EVs attenuate HI brain injury in neonatal mice by shuttling miR-21a-5p,which induces microglial M2 polarization by targeting STAT3.
基金Project(STRFML-2013)supported by the Science and Technology on Reactor Fuel and Materials Laboratory,ChinaProject(2014BAC03B05)supported by the Key Projects of the National Science and Technology of China
文摘The effects of cold-rolling reduction,annealing temperature,and time on recrystallization behavior and kinetics of cold-rolled Zr-1Sn-0.3Nb-0.3Fe-0.1Cr alloy were investigated using the Vickers hardness test,scanning electronic microscopy(SEM),transmission electron microscopy(TEM)and electron backscatter diffractometry(EBSD).The results show that the rate of the recrystallization increased with increasing annealing temperature and rolling reduction.Recrystallized grains nucleated preferentially at sites with high density dislocation and deformation stored energy and then grew into integral grains.Recrystallization texture changed from-1010-//RD to-1120-//RD.The grain orientation changed from random orientation to the orientation with the maximum misorientation around 30°.Recrystallization kinetics and maps were constructed based on the Johnson-Mehl-Avrami-Kolmogorov(JMAK)equation to derive parameters sensitive to the microstructure.The activation energies for recrystallization of 30%,50%and 70%cold-rolling reductions were determined to be 240,249 and 180 kJ/mol,respectively.
基金the financial supports from the National Natural Science Foundation of China (Nos. 52001163, 52075237)the Primary Research and Development Plan of Jiangsu Province, China (No. BE2019119)
文摘Hot deformation behaviors and microstructure evolution of Ti-3Al-5Mo-4Cr-2Zr-1Fe(Ti-35421)alloy in theβsingle field are investigated by isothermal compression tests on a Gleeble-3500 simulator at temperatures of 820-900°C and strain rates of 0.001-1 s^(-1).The research results show that discontinuous yield phenomenon and rheological softening are affected by the strain rates and deformation temperatures.The critical conditions for dynamic recrystallization and kinetic model of Ti-35421 alloy are determined,and the Arrhenius constitutive model is constructed.The rheological behaviors of Ti-35421 alloys aboveβphase transformation temperature are predicted by the constitutive model accurately.The EBSD analysis proves that the deformation softening is controlled by dynamic recovery and dynamic recrystallization.In addition,continuous dynamic recrystallization is determined during hot deformation,and the calculation model for recrystallization grain sizes is established.Good linear dependency between the experimental and simulated values of recrystallized grain sizes indicates that the present model can be used for the prediction of recrystallized grain size with high accuracy.
基金from National Key R&D Program of China(2016YFC1301300,2016YFC1301302)。
文摘BACKGROUND:The predictive scoring systems for early stent thrombosis(EST)remains blank in China.The study aims to evaluate the risk factors and conduct a prediction model of EST in the Chinese population.METHODS:EST was defined as thrombosis that occurs within the first 30 days after primary percutaneous coronary intervention(PCI).Patients from ten Chinese hospitals diagnosed as stent thrombosis(ST)from January 2010 to December 2016 were retrospectively included as the study group.A control group(1 case:2 controls)was created by including patients without ST,major adverse cardiovascular events,or cerebrovascular events during follow-up.The present study evaluated 426 patients with single-vessel lesions and ultimately included 40 patients with EST and 80 control patients,who were included to identify factors that predicted EST and to develop a prediction scoring system.The other 171 patients without integrated 1:2 pair were used for external validation.RESULTS:EST was independently associated with a low hemoglobin concentration(adjusted odds ratio[OR]0.946,95%confi dence interval[95%CI]0.901-0.993,P=0.026),a high pre-PCI Synergy between Percutaneous Coronary Intervention with Taxus and Cardiac Surgery(SYNTAX)score(OR 1.166,95%CI 1.049-1.297,P=0.004),and a DAPT(DAPT)duration of<30 days(OR 28.033,95%CI 5.302-272.834,P<0.001).The simple EST prediction score provided an area under the curve(AUC)of 0.854(95%CI 0.777-0.932,P<0.001)with 70.0%sensitivity and 90.0%specifi city,and 0.742(95%CI 0.649-0.835,P<0.001)with 54.5%sensitivity and 81.0%specifi city for external validation dataset.CONCLUSIONS:EST may be independently associated with DAPT discontinuation within 30 days,a low hemoglobin concentration,and a high SYNTAX score.The scoring system also has a good ability to predict the risk of EST and may be useful in the clinical setting.
基金financially supported by the National Natural Science Foundation of China(Nos.51401093 and 51341010)the Natural Science Foundation of Jiangsu Province (No.BK20130233)
文摘The point defect concentrations of L12-A13X（Sc, Zr, Er） were systematically investigated using the first- principle calculations with thermodynamics approach. The results show that the constitutional point defects of off- stoichiometric L12-A13X（Sc, Zr, Er） prefer to occur in X sublattice, that is X anti-site in X-rich alloy and X vacancy in Al-rich alloy, respectively. And A1 anti-site also has a high density in Al-rich Llz-A13X（Sc, Er）. It is found that the point defect concentrations of stoichiometric L12-A/3X（Sc, Zr） follow in the sequence as： A1 vacancies （VA0 〉 X vacancies （Vx） 〉 X anti-sites （XA1） 〉 A1 anti- sites （Alx）. The point defect concentration of stoichio- metric A13Er is similar to that of L12-A13X（Sc, Zr）. The result suggests that the A1 vacancy （VA1） is a dominant point defect in L12-A13X（Sc, Zr, Er）. A simple parameter Hvx-HVA1 can be used for a rough estimation of the point defect concentrations in L12-A13X structure. Some rules of point defect concentrations for L12-A13X（Sc, Zr, Er） are also revealed.
基金financially supported by the National Development and Reform Commission of China(Grant No.20121743)the National Natural Science Foundation of China(Grant No.51474244)
文摘The grain growth retardation mechanism and the effect of cooling rate on VC-doped WC–Co cemented carbides were investigated in this work.WC–30Co and WC–30Co–VC were prepared by powder metallurgy,liquid-phase sintering at 1400 ℃ and followed by water quenching（[150 ℃/s） or furnace cooling（＊0.083 ℃/s）.Based on the results of electron probe microanalysis（EPMA）,we found that WC concentration in the Co binder was independent of VC doping during liquid-phase sintering,hence barely contributing to the retardation of WC grain growth.In contrast,the（W,V）Cx phase formed at the WC/Co interfaces played a major role in retarding WC grain growth during liquid-phase sintering.The effect of cooling rate on the morphology of（W,V）Cxwas revealed by high-resolution transmission electron microscopy（HRTEM） and energy-dispersive spectroscopy（EDS）.In the water-quenched WC–30Co–VC,（W,V）Cxprecipitates were found as thin layers at the WC/Co interfaces.In contrast,both thin layers of similar thickness and nanoparticles of（W,V）Cx were observed in the furnace-cooled counterpart.These observations listed above suggested that thin（W,V）Cxlayers were stable structures effectively suppressing the growth of WC grains and their thickness remained independent of the cooling rate.The（W,V）Cxnanoparticles,however,may be inhibited through rapid cooling,ensuring the VC-doped WC–Co cemented carbides desired toughness.
基金The authors express gratitude to the financial support of the Key Project of Nuclear Safety and Advanced Nuclear Technology(2019YFB1901002)the National Natural Science Foundation of China(U1867201,51801194)+1 种基金the Sichuan Applied Basic Research Project(2018JY0430)the Project supported by State Key Laboratory of Powder Metallurgy,Central South University,Changsha,China.
文摘The efect of cold rolling and annealing on the microstructure and properties of an Fe-13Cr-4.5Al-2.2Mo-1.1Nb alloy was investigated.The results showed that the recrystallization rate increased with increasing annealing temperature and rolling reduction.Recrystallization kinetics was constructed based on Johnson-Mehl-Avrami-Kolmogorov equation.The apparent activation energies of recrystallization were 161.385,144.770,and 95.362 kJ/mol for the samples with 30%,50%,and 70%cold-rolling reduction,respectively.With the cold-rolling reduction increasing,the textureγfber partly changed to<100>//ND.After annealing,γfber of the alloy with 30%thickness reduction retained,the subgrains disappeared through merging,and the proportion of coincident site lattice grain boundaries increased and became more continuous.30%cold-rolling reduction alloy annealed at 730°C for 120 min not only possessed relatively high yield strength(YS)of^730 MPa and ultimate tensile strength(UTS)of^880 MPa,but also exhibited elongation of^16%at room temperature.After annealing at 730°C for 120 min,70%cold-rolled alloy has fner and more uniform grain,with higher elongation of^22%,YS of^615 MPa and UTS of^774 MPa.The mechanism of mechanical properties diference was explained according to Schmid factor analysis.These results provided an efective way for tuning strength and ductility of FeCrAl alloy.
基金financially supported by the National Natural Science Foundation of China(No.51373003)Beijing Natural Science Foundation(No.2122059)
文摘Two dimensional asynchronous spectra were used to characterize coordination between carbonyl group of butanone and metal ions by using an approach proposed in our recent paper.Spectral variation of n-π^＊transition band of carbonyl group is used to probe the coordination even if metal ions does not possess any characteristic peak in spectra.Experimental results indicate that Ca^2＋ and Al^3＋ show considerable ability to coordinate with the carbonyl group of butanone and bring about spectral variation of the n-π-＊transition band,which is manifested by cross peaks in 2D asynchronous spectra.
基金Program of the Ministry of Education in China (2011)
文摘Ni-based self-lubricating composites containing a fixed amount of hexagonal boron nitride (h-BN)(5 wt%) and different amounts of graphene (0-1.5 wt%) were prepared by ultrasonic dispersion, high-energy ball milling, and spark plasma sintering. The effects of the graphene content on the physical, mechanical, and wear properties of the Ni/h-BN composites were evaluated. These properties were first enhanced with increasing graphene content, reaching optimal behavior for a graphene content of 1 wt%, and then degraded with further graphene addition. Compared to the pure Ni/h-BN composite, the relative density, hardness, and bending strength of the composite with 1 wt% graphene increased by 2.7%, 7.4%, and 6.3%, respectively, while the friction coefficient decreased by 56% to 0.31, and a reduction in wear rate by a factor of 5-15 was observed. The mechanism for improving the wear properties of the composite with added graphene was due to the formation of a graphene lubricating film on the worn surface, which increased the load bearing capacity of the surface and enhanced lubrication during wear.
