Working memory is a core cognitive function that supports goal-directed behavior and complex thought.We developed a spatial working memory and attention test on paired symbols(SWAPS)which has been proved to be a usefu...Working memory is a core cognitive function that supports goal-directed behavior and complex thought.We developed a spatial working memory and attention test on paired symbols(SWAPS)which has been proved to be a useful and valid tool for spatial working memory and attention studies in the fields of cognitive psychology,education,and psychiatry.The repeated administration of working memory capacity tests is common in clinical and research settings.Studies suggest that repeated cognitive tests may improve the performance scores also known as retest effects.The systematic investigation of retest effects in SWAPS is critical for interpreting scientific results,but it is still not fully developed.To address this,we recruited 77 college students aged 18–21 years and used SWAPS comprising 72 trials with different memory loads,learning time,and delay span.We repeated the test once a week for five weeks to investigate the retest effects of SWAPS.There were significant retest effects in the first two tests:the accuracy of the SWAPS tests significantly increased,and then stabilized.These findings provide useful information for researchers to appropriately use or interpret the repeated working memory tests.Further experiments are still needed to clarify the factors that mediate the retest effects,and find out the cognitive mechanism that influences the retest effects.展开更多
Clinical reports have demonstrated that the Kongsheng Zhenzhong pill （KSZZP）, a classical prescription deriving from Valuable Prescription for Emergencies, has good therapeutic effects on vascular dementia. However,...Clinical reports have demonstrated that the Kongsheng Zhenzhong pill （KSZZP）, a classical prescription deriving from Valuable Prescription for Emergencies, has good therapeutic effects on vascular dementia. However, the mechanisms that mediate its effects remain unclear. In this study, the expression of N-methyI-D-aspartate receptor 1 mRNA, the content of nitric oxide, and the concentration of calcium in neurons was determined with in situ hybridization, spectrophotometry and flow cytometry, respectively. In addition, the expressions of N-methyI-D-aspartate receptor 1, nerve growth factor protein, and glial cell line-derived neurotrophic factor protein were detected with immunohistochemistry. We found that KSZZP could significantly decrease the expression of N-methyI-D-aspartate receptor 1 mRNA and protein, the content of nitric oxide, and the concentration of calcium in neurons. KSZZP also increased the expression of nerve growth factor and glial cell line-derived neurotrophic factor protein in the hippocampus CA1 region and in the cerebral cortex. Morris water maze and passive avoidance tests verified that KSZZP ameliorated the cognitive impairments of vascular dementia rats. Moreover, the KSZZP-induced improvements in the cognitive functions of vascular dementia rats were correlated with both inhibition of N-methyl-D-aspartate-induced excitable neurotoxicity and elevation of neurotrophic factor expression.展开更多
The influence of aging on the microstructure and mechanical properties of Cu-11.6wt%Al-3.9wt%Ni-2.5wt%Mn shape memory alloy（SMA） was studied by means of scanning electron microscopy（SEM）,transmission electron micr...The influence of aging on the microstructure and mechanical properties of Cu-11.6wt%Al-3.9wt%Ni-2.5wt%Mn shape memory alloy（SMA） was studied by means of scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray diffractometer,and differential scanning calorimeter（DSC）.Experimental results show that bainite,γ2,and α phase precipitates occur with the aging effect in the alloy.After aging at 300°C,the bainitic precipitates appear at the early stages of aging,while the precipitates of γ2 phase are observed for a longer aging time.When the aging temperature increases,the bainite gradually evolves into γ2 phase and equilibrium α phase（bcc） precipitates from the remaining parent phase.Thus,the bainite,γ2,and α phases appear,while the martensite phase disappears progressively in the alloy.The bainitic precipitates decrease the reverse transformation temperature while the γ2 phase precipitates increase these temperatures with a decrease of solute content in the retained parent phase.On the other hand,these precipitations cause an increasing in hardness of the alloy.展开更多
DSC was used to study the effects of predeformation on the reverse martensitic transformation of near-equiatomic TiNi alloy. Both the start temperature As and the finish temperature Af of the reverse transformation in...DSC was used to study the effects of predeformation on the reverse martensitic transformation of near-equiatomic TiNi alloy. Both the start temperature As and the finish temperature Af of the reverse transformation increased with increasing degree of predeformation, but the algebraic difference between As and Af decreased with increasing predeformation until it reached a minimum value, then remained unchanged with further deformation. Transformation heat also increased with increasing predeformation until it reached a maximum value, then decreased with further predeformation. All the phenomena above were considered to be closely related with the release of elastic strain energy during predeformation.展开更多
Ti–51at%Ni shape memory alloys(SMAs) were successfully produced via a powder metallurgy and microwave sintering technique.The influence of sintering parameters on porosity reduction,microstructure,phase transformatio...Ti–51at%Ni shape memory alloys(SMAs) were successfully produced via a powder metallurgy and microwave sintering technique.The influence of sintering parameters on porosity reduction,microstructure,phase transformation temperatures,and mechanical properties were investigated by optical microscopy,field-emission scanning electron microscopy(FE-SEM),X-ray diffraction(XRD),differential scanning calorimetry(DSC),compression tests,and microhardness tests.Varying the microwave temperature and holding time was found to strongly affect the density of porosity,presence of precipitates,transformation temperatures,and mechanical properties.The lowest density and smallest pore size were observed in the Ti–51at%Ni samples sintered at 900°C for 5 min or at 900°C for 30 min.The predominant martensite phases of β2 and β19′ were observed in the microstructure of Ti–51at%Ni,and their existence varied in accordance with the sintering temperature and the holding time.In the DSC thermograms,multi-transformation peaks were observed during heating,whereas a single peak was observed during cooling;these peaks correspond to the presence of the β2,R,and β19′ phases.The maximum strength and strain among the Ti–51at%Ni SMAs were 1376 MPa and 29%,respectively,for the sample sintered at 900°C for 30 min because of this sample's minimal porosity.展开更多
The effect of Ta addition on the martensitic transformation characteristics and the X-ray visibility on NiTi shape memory alloy have been studied in (Ni51Ti49)1-xTax system. It was found that the transformation temper...The effect of Ta addition on the martensitic transformation characteristics and the X-ray visibility on NiTi shape memory alloy have been studied in (Ni51Ti49)1-xTax system. It was found that the transformation temperatures of the Ni51Ti49 binary alloy increased drastically by an addition of 0～4 at. pet Ta, but only slightly when the concentration exceeded 4 at. pct; the addition of Ta greatly decreases the sensitivity of the martensitic transformations to the variation in the Ni-Ti ratio. The addition of Ta to the NiTi binary alloy can improve its X-ray visibility.展开更多
The effects of 1 Me V electron irradiation in air at a fixed accumulated dose and dose rates of 393.8,196.9,78.8,and 39.4 Gy s^(-1)on a shape memory epoxy(SMEP)resin were studied.Under low-dose-rate irradiation,accele...The effects of 1 Me V electron irradiation in air at a fixed accumulated dose and dose rates of 393.8,196.9,78.8,and 39.4 Gy s^(-1)on a shape memory epoxy(SMEP)resin were studied.Under low-dose-rate irradiation,accelerated degradation of the shape memory performance was observed;specifically,the shape recovery ratio decreased exponentially with increasing irradiation time(that is,with decreasing dose rate).In addition,the glass transition temperature of the SMEP,as measured by dynamic mechanical analysis,decreased overall with decreasing dose rate.The dose rate effects of 1 Me V electron irradiation on the SMEP were confirmed by structural analysis using electron paramagnetic resonance(EPR)spectroscopy and Fourier transform infrared(FTIR)spectroscopy.The EPR spectra showed that the concentration of free radicals increased exponentially with increasing irradiation time.Moreover,the FTIR spectra showed higher intensities of the peaks at 1660 and 1720 cm^(-1),which are attributed to stretching vibrations of amide C=O and ketone/acid C=O,at lower dose rates.The intensities of the IR peaks at 1660 and 1720 cm^(-1) increased exponentially with increasing irradiation time,and the relative intensity of the IR peak at 2926 cm^(-1)decreased exponentially with increasing irradiation time.The solid-state13 C nuclear magnetic resonance(NMR)spectra of the SMEP before and after 1 Me V electron irradiation at a dose of 1970 k Gy and a dose rate of 78.8 Gy s^(-1) indicated damage to the CH_(2)–N groups and aliphatic isopropanol segment.This result is consistent with the detection of nitrogenous free radicals,a phenoxy-type free radical,and several types of pyrolytic carbon radicals by EPR.During the subsequent propagation process,the free radicals produced at lower dose rates were more likely to react with oxygen,which was present at higher concentrations,and form the more destructive peroxy free radicals and oxidation products such as acids,amides,and ketones.The increase in peroxy free radicals at lower dose rates was thought to accelerate the degradation of the macroscopic performance of the SMEP.展开更多
Impaired insulin signaling in Alzheimer’s disease（AD）brains：The insulin signaling pathway is a fundamental physiological mechanism that presents in nearly all vertebrate cells.However,sometimes cells stop respondi...Impaired insulin signaling in Alzheimer’s disease（AD）brains：The insulin signaling pathway is a fundamental physiological mechanism that presents in nearly all vertebrate cells.However,sometimes cells stop responding properly to insulin stimulation.This condition is known as insulin resistance,which is a hallmark of two very common conditions,metabolic syndrome and type 2 diabetes（T2D）.展开更多
The effect of aging treatment on the superelasticity and martensitic transformation critical stress in columnar-grained Cu_（71）Al_（18）Mn_（11） shape memory alloy（SMA） at the temperature ranging from 250°C ...The effect of aging treatment on the superelasticity and martensitic transformation critical stress in columnar-grained Cu_（71）Al_（18）Mn_（11） shape memory alloy（SMA） at the temperature ranging from 250°C to 400°C was investigated. The microstructure evolution during the aging treatment was characterized by optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results show that the plate-like bainite precipitates distribute homogeneously within austenitic grains and at grain boundaries. The volume fraction of bainite increases with the increase in aging temperature and aging time, which substantially improves the martensitic transformation critical stress of the alloy, whereas the bainite only slightly affects the superelasticity. This behavior is attributed to a coherent relationship between the bainite and the austenite, as well as to the bainite and the martensite exhibiting the same crystal structure. The variations of the martensitic transformation critical stress and the superelasticity of columnar-grained Cu_（71）Al_（18）Mn_（11） SMA with aging-temperature and aging time are described by the Austin-Rickett equation, where the activation energy of bainite precipitation is 77.2 kJ ·mol1. Finally, a columnar-grained Cu_（71）Al_（18）Mn_（11） SMA with both excellent superelasticity（5%-9%） and high martensitic transformation critical stress（443-677 MPa） is obtained through the application of the appropriate aging treatments.展开更多
Background:Triple-negative breast cancer(TNBC)is the most aggressive subtype and occurs in approximately 15%–20%of diagnosed breast cancers.TNBC is characterized by its highly metastatic and recurrent features,as wel...Background:Triple-negative breast cancer(TNBC)is the most aggressive subtype and occurs in approximately 15%–20%of diagnosed breast cancers.TNBC is characterized by its highly metastatic and recurrent features,as well as a lack of specific targets and targeted therapeutics.Epidermal growth factor receptor(EGFR)is highly expressed in a variety of tumors,especially in TNBC.LR004-VC-MMAE is a new EGFR-targeting antibody–drug conjugate produced by our laboratory.This study aimed to evaluate its antitumor activities against EGFR-positive TNBC and further studied its possible mechanism of antitumor action.Methods:LR004-VC-MMAE was prepared by coupling a cytotoxic payload(MMAE)to an anti-EGFR antibody(LR004)via a linker,and the drug-to-antibody ratio(DAR)was analyzed by HIC-HPLC.The gene expression of EGFR in a series of breast cancer cell lines was assessed using a publicly available microarray dataset(GSE41313)and Western blotting.MDA-MB-468 and MDA-MB-231 cells were treated with LR004-VC-MMAE(0,0.0066,0.066,0.66,6.6 nmol/L),and the inhibitory effects of LR004-VC-MMAE on cell proliferation were examined by CCK-8 and colony formation.The migration and invasion capacity of MDA-MB-468 and MDA-MB-231 cells were tested at different LR004-VCMMAE concentrations(2.5 and 5 nmol/L)with wound healing and Transwell invasion assays.Flow cytometric analysis and tumorsphere-forming assays were used to detect the killing effects of LR004-VC-MMAE on cancer stem cells(MDA-MB-468 and MDA-MB-231 cells).The mouse xenograft models were also used to evaluate the antitumor efficacy of LR004-VC-MMAE in vivo.Briefly,BALB/c nude mice were subcutaneously inoculated with MDA-MB-468 or MDAMB-231 cells.Then they were randomly divided into 4 groups(n=6 per group)and treated with PBS,naked LR004(10 mg/kg),LR004-VC-MMAE(10 mg/kg),or doxorubicin,respectively.Tumor sizes and the body weights of mice were measured every 4 d.The effects of LR004-VC-MMAE on apoptosis and cell cycle distribution were analyzed by flow cytometry.Western blotting was used to detect the effects of LR004-VC-MMAE on EGFR,ERK,MEK phosphorylation and tumor stemness marker gene expression.Results:LR004-VC-MMAE with a DAR of 4.02 were obtained.The expression of EGFR was found to be significantly higher in TNBC cells compared with non-TNBC cells(P<0.01).LR004-VC-MMAE inhibited the proliferation of EGFRpositive TNBC cells,and the ICvalues of MDA-MB-468 and MDA-MB-231 cells treated with LR004-VC-MMAE for 72 h were(0.13±0.02)nmol/L and(0.66±0.06)nmol/L,respectively,which were significantly lower than that of cells treated with MMAE[(3.20±0.60)nmol/L,P<0.01,and(6.60±0.50)nmol/L,P<0.001].LR004-VC-MMAE effectively inhibited migration and invasion of MDA-MB-468 and MDA-MB-231 cells.Moreover,LR004-VC-MMAE also killed tumor stem cells in EGFR-positive TNBC cells and impaired their tumorsphere-forming ability.In TNBC xenograft models,LR004-VC-MMAE at 10 mg/kg significantly suppressed tumor growth and achieved complete tumor regression on day 36.Surprisingly,tumor recurrence was not observed until the end of the experiment on day 52.In a mechanistic study,we found that LR004-VC-MMAE significantly induced cell apoptosis and cell cycle arrest at G/M phase in MDAMB-468[(34±5)%vs.(12±2)%,P<0.001]and MDA-MB-231[(27±4)%vs.(18±3)%,P<0.01]cells.LR004-VC-MMAE also inhibited the activation of EGFR signaling and the expression of cancer stemness marker genes such as Oct4,Sox2,KLF4 and EpCAM.Conclusions:LR004-VC-MMAE showed effective antitumor activity by inhibiting the activation of EGFR signaling and the expression of cancer stemness marker genes.It might be a promising therapeutic candidate and provides a potential therapeutic avenue for the treatment of EGFR-positive TNBC.展开更多
In this letter, a novel model is proposed for modeling the nonlinearity and memory effects of power amplifiers. The classical Volterra model is modified through a function of the sum of nonlinearity order with sum of ...In this letter, a novel model is proposed for modeling the nonlinearity and memory effects of power amplifiers. The classical Volterra model is modified through a function of the sum of nonlinearity order with sum of memory length. The parameters of this model can be extracted in digital domain since the model is analyzed based on the envelope signals. The model we proposed enables a substantial reduction in the number of coefficients involved, and with excellent accuracy.展开更多
A new finite strain elatoplastic J2-flow model with coupling effects of both isotropic and anisotropic hardening is proposed with the co-rotational logarithmic rate.In terms of certain single-variable shape functions ...A new finite strain elatoplastic J2-flow model with coupling effects of both isotropic and anisotropic hardening is proposed with the co-rotational logarithmic rate.In terms of certain single-variable shape functions representing uniaxial loading and unloading curves,explicit multi-axial expressions for the three hardening quantities incorporated in the new model proposed are derived in unified forms for the purpose of automatically and accurately simulating complex pseudoelastic-to-plastic transition effects of shape memory alloys(SMAs)under multiple loading-unloading cycles.Numerical examples show that with only a single parameter of direct physical meaning for each cycle,accurate and explicit simulations may be achieved for extensive data from multiple cycle tests.展开更多
Ciprofloxacin (CFX) was loaded on Bana clay (Cameroon) and CFX loaded-clays have been evaluated as drug delivery system. Raw clays and CFX loaded compounds have been characterized by some physico-chemicals methods. &l...Ciprofloxacin (CFX) was loaded on Bana clay (Cameroon) and CFX loaded-clays have been evaluated as drug delivery system. Raw clays and CFX loaded compounds have been characterized by some physico-chemicals methods. <i>In vitro</i> release studies have been done in gastric and phosphate buffer experimental mediums;bacteriological studies have been made up on <i>Escherichia coli</i> and <i>Staphylococcus aureus</i>. X-ray diffractometry patterns of loaded compounds show a basal spacing increasing due to CFX intercalation. On Fourier-Transformed Infrared spectrometry spectra, appearance of CFX characteristic bands and shifting of certain bands already presents on clay confirmed CFX intercalation. After 96 h of CFX released from release mediums, prolonged and continue profiles have been observed. Diffusion tests displayed an inhibition radius of ~2 cm on gelose seeded with <i>Escherichia coli</i> and <i>Staphylococcus aureus</i> due to CFX. The overall results show a modified release of ciprofloxacin with an effective antibacterial activity, giving the way for a new ciprofloxacin drug delivery system using Bana clay as carrier.展开更多
RF power amplifiers (PAs) are usually considered as memoryless devices in most existing predistortion techniques. Nevertheless, in wideband communication systems, PA memory effects can no longer be ignored and memoryl...RF power amplifiers (PAs) are usually considered as memoryless devices in most existing predistortion techniques. Nevertheless, in wideband communication systems, PA memory effects can no longer be ignored and memoryless predistortion cannot linearize PAs effectively. After analyzing PA memory effects, a novel predistortion method based on wavelet networks (WNs) is proposed to linearize wideband RF power amplifiers. A complex wavelet network with tapped delay lines is applied to construct the predistorter and then a complex backpropagation algorithm is developed to train the predistorter parameters. The simulation results show that compared with the previously published feed-forward neural network predistortion method, the proposed method provides faster convergence rate and better performance in reducing out-of-band spectral regrowth.展开更多
BACKGROUND： Central adrenergic nerve and 5-serotonergic nerve can influence central cholinergic nerve on learning and memory and make easy for study; however, ginsenoside of stem and leaf （GSL） can improve function...BACKGROUND： Central adrenergic nerve and 5-serotonergic nerve can influence central cholinergic nerve on learning and memory and make easy for study; however, ginsenoside of stem and leaf （GSL） can improve functions of central adrenergic nerve; moreover, 5-serotonergic nerve and the combination with choline can produce synergistic effect and enhance learning and memory ability so as to improve learning and memory disorder of patients with Alzheimer disease （AD）. OBJECTIVE ： To observe the effects of GSL combining with choline on learning and memory of AD model rats DESIGN ： Randomized grouping design and controlled animal study SETIING ： Department of Pharmacology, Taishan Medical College MATERIALS ： The experiment was carried out in the Pharmacological Department of Medical College of Jilin University from October 1996 to January 1997. Forty healthy male Wistar rats of clean grade were randomly divided into 5 groups, including sham-injury group, model group, GSL group, choline group and combination group, with 8 rats in each group. Main medications： GSL with the volume more than 92.8% was provided by Department of Chemistry, Norman Bethune Medical College of Jilin University. Panaxatriol, the main component, was detected with thin layer scanning technique and regarded as the index of GSL quality [（55±1）%, CV= 2%, n = 5]. Choline was provided by the Third Shanghai Laboratory Factory. METHODS ： 150 nmol quinolinic acid was used to damage bilateral Meynert basal nuclei of adult rats so as to establish AD models. Rats in GSL, choline and combination groups were intragastric administrated with 400 mg/kg GSL, 200 mg/kg choline （20 mL/kg）, and both respectively last for 17 days starting from two days before operation. Rats in sham-injury group and model group were perfused with the same volume of distilled water once in each morning for the same days. （1） Passive avoidance step-down test： Five minutes later, rats jumped up safe platform when they were shocked with 36 V alternating current. If rats jumped down from the platform and the feet touched railings, the response was wrong. Numbers of wrong response were recorded within 3 minutes, and then the test was redone after 24 hours. （2） Morris water-maze spatial localization task： Swimming from jumping-off to platform directly was regarded as right response. Additionally, 4 successively right responses were regarded as the standard. Each rat was trained 10 times a day with 120 s per time for 3 successive days. The interval was 30 s. Three days later, numbers of right response were recorded. The training times were increased to 30 for unlearned rats. （3） Measurement of activity of choline acetylase in cerebral cortex： Rats were sacrificed at 17 days after operation to obtain cerebral cortex to measure activity of choline acetylase with radiochemistry technique. （4） Synergistic effect： It was expressed as Q value： Q value = factual incorporative effect/anticipant incorporative effect; Q ≥ 1 was regarded as synergistic effect. Anticipant incorporative effect = （EA＋EB-EA·EB）, EA and EB were single timing effect, respectively in GSL group and choline group. E（step-down test and Morris water maze test） = （x in model group - factual value in medicine groups）/x in model group; E （activity of choline acetylase） = （factual value in medicine groups -xin model group）/xin model group. MAIN OUTCOME MEASURES ： （1） Passive avoidance step-down test and Morris water-maze spatial localization task in the study of learning and memory; （2） activity of choline acetylase. RESULTS ： All 40 rats were involved in the final analysis. （1） Passive avoidance response： At learning phase on first day and retesting phase on the next day, numbers of wrong responses within 3 minutes were more in model group than sham operation group, and there was significant difference [（5.88±1.46）, （2.25±0.87） times; （2.63±1.06）, （0.50±0.53） times; P 〈 0.01]; numbers of wrong responses within 3 minutes were less in combination group than model group, and there was significant difference [learning phase： （1.12±0.83）, （5.88±1.46） times; retesting phase： （0.38±0.74）, （2.63±1.06）times, P 〈 0.01]; moreover, effect was stronger than that in GSL group and choline group. The Q value was 1.07 and 1.59, respectively and it showed synergistic effect. Spatial localization task： Training times were more in model group than sham operation group, and there was significant difference [（2.9±2.5）, （12.6±3.5） times; P 〈 0.01]. Training times were less in combination group than model group, and there was significant difference [（11.8±2.4）, （27.9±2.5） times, P 〈 0.01]; moreover, effect was stronger than that in GSL group and choline group. The Q value was 1.07 and it showed synergistic effect. （3） Activity of choline acetylase： Activity was lower in model group than sham operation group, and there was significant difference [（30.56±8.33）, （61.11 ±8.33） nkat/g; P 〈 0.01]. Activity was higher in combination group than model group and there was significant difference [（50.00±8.33）, （30.56±8.33） nkat/g, P 〈 0.01];moreover, effect was stronger than that in GSL group and choline group. The Q value was 1.5 and it showed synergistic effect. CONCLUSZON： GSL in combination with choline can synergically improve the disorder of learning and memory of AD model rats. Its mechanism may be involved in enhancing the function of central cholinergic system.展开更多
The emergence of additive manufacturing technology,particularly laser powder bed fusion,has revitalized NiTi alloy production.However,challenges arise regarding its mechanical properties and diminishing shape memory e...The emergence of additive manufacturing technology,particularly laser powder bed fusion,has revitalized NiTi alloy production.However,challenges arise regarding its mechanical properties and diminishing shape memory effect,which hinder its widespread application.Heat treatment has been identified as a method to enhance the performance of metallic materials in the realm of additive manufacturing.This process eliminates residual stress and enhances performance through precipitation strengthening.This study conducted a comprehensive annealing investigation on NiTi alloys to explore the impact of annealing time and temperature on the phase transformation behavior and shape memory performance.The mechanism underlying the performance enhancement was analyzed using scanning electron microscopy,energy-dispersive X-ray spectroscopy,electron backscatter diffraction,and transmission electron microscopy.The findings revealed that different annealing conditions resulted in multistep phase transformation behavior,with the 500℃-5 h sample exhibiting the best mechanical properties owing to the formation of nanoscale dispersed precipitates like Ni_(4)Ti_(3).However,higher temperatures led to larger precipitates,significantly weakening the properties of the NiTi alloy.Additionally,the annealing treatment did not have a notable impact on the grain size,texture strength,or direction.This study provides valuable insights for optimizing the heat treatment process of LPBF-NiTi alloys.展开更多
Annealing has been a popular method to improve the soft magnetism of metallic glasses (MGs), which however usually makes MGs brittle and difficult to process. Here, it is demonstrated that the embrittled Fe-based MG c...Annealing has been a popular method to improve the soft magnetism of metallic glasses (MGs), which however usually makes MGs brittle and difficult to process. Here, it is demonstrated that the embrittled Fe-based MG can be reductilized and the coercivity can be further lowered through the rejuvenation of memory effect. The synchronous improvement in the plasticity and soft magnetic properties is attributed to the combination effects of releasing much residual stress, decreasing the magnetic anisotropy, and homogenizing the glasses during the rejuvenation process. The current work opens a new perspective to improve the properties of MGs by utilizing the memory effect and holds promising commercial application potential.展开更多
Because of the discrete charge storage mechanism, charge trapping memory（CTM） technique is a good candidate for aerospace and military missions. The total ionization dose（TID） effects on CTM cells with Al2O3/HfO2/...Because of the discrete charge storage mechanism, charge trapping memory（CTM） technique is a good candidate for aerospace and military missions. The total ionization dose（TID） effects on CTM cells with Al2O3/HfO2/Al2O3（AHA） high-k gate stack structure under in-situ 10 keV x-rays are studied. The C-V characteristics at different radiation doses demonstrate that charge stored in the device continues to be leaked away during the irradiation,thereby inducing the shift of flat band voltage（V（fb））. The dc memory window shows insignificant changes, suggesting the existence of good P/E ability. Furthermore, the physical mechanisms of TID induced radiation damages in AHA-based CTM are analyzed.展开更多
Functional fatigue in the superelastic NiTi shape memory alloys occurs due to the accumulation of dislocations and retention of martensite with the cyclic loading.These mechanisms reduce the amount of the material ava...Functional fatigue in the superelastic NiTi shape memory alloys occurs due to the accumulation of dislocations and retention of martensite with the cyclic loading.These mechanisms reduce the amount of the material available for the stress-induced transformation and,thus,lower the elastocaloric effect that originates from the stress-induced latent heat variations.In this study,the individual contributions of the micromechanisms responsible for the functional fatigue in superelastic NiTi at different maximum tensile stress(σ_(max))are critically examined.Results show that the elastocaloric effect degrades significantly with cycling,and the saturated degraded value increases with σ_(max);the steady-state adiabatic temperature change is unexpectedly non-proportional to σ_(max).An overheating treatment(‘healing’)after mechanical fatigue reverts the retained martensite into austenite,making it available for subsequent transformation and restoring the elastocaloric effect significantly.Such a restoration increases exponentially with σ_(max).Consequently,the steady-state elastocaloric effect of the healed NiTi is proportional to σ_(max) and can reach more than twice that of NiTi without healing.The work sheds light on the physical origins of elastocaloric degradation of superelastic NiTi and also provides a feasible method for ameliorating functional fatigue.展开更多
基金the National Natural Science Foundation of China(No.91632103)the Shanghai Education Commission Research and Innovation Program(No.2019-01-07-00-02-E00037)+2 种基金the Program of Shanghai Subject Chief Scientist(No.17XD1401700)the Higher Education Disciplinary Innovation Programthe“Eastern Scholar”Project。
文摘Working memory is a core cognitive function that supports goal-directed behavior and complex thought.We developed a spatial working memory and attention test on paired symbols(SWAPS)which has been proved to be a useful and valid tool for spatial working memory and attention studies in the fields of cognitive psychology,education,and psychiatry.The repeated administration of working memory capacity tests is common in clinical and research settings.Studies suggest that repeated cognitive tests may improve the performance scores also known as retest effects.The systematic investigation of retest effects in SWAPS is critical for interpreting scientific results,but it is still not fully developed.To address this,we recruited 77 college students aged 18–21 years and used SWAPS comprising 72 trials with different memory loads,learning time,and delay span.We repeated the test once a week for five weeks to investigate the retest effects of SWAPS.There were significant retest effects in the first two tests:the accuracy of the SWAPS tests significantly increased,and then stabilized.These findings provide useful information for researchers to appropriately use or interpret the repeated working memory tests.Further experiments are still needed to clarify the factors that mediate the retest effects,and find out the cognitive mechanism that influences the retest effects.
基金the National Basic Research Program of China(973Program),No.2007CB512601Science and Technology Development Plan of TCM in Shandong Province,No.2009-006Science and Technology Plan in Colleges and Universities of Shandong Province,No.J11LF60,J11LF08
文摘Clinical reports have demonstrated that the Kongsheng Zhenzhong pill （KSZZP）, a classical prescription deriving from Valuable Prescription for Emergencies, has good therapeutic effects on vascular dementia. However, the mechanisms that mediate its effects remain unclear. In this study, the expression of N-methyI-D-aspartate receptor 1 mRNA, the content of nitric oxide, and the concentration of calcium in neurons was determined with in situ hybridization, spectrophotometry and flow cytometry, respectively. In addition, the expressions of N-methyI-D-aspartate receptor 1, nerve growth factor protein, and glial cell line-derived neurotrophic factor protein were detected with immunohistochemistry. We found that KSZZP could significantly decrease the expression of N-methyI-D-aspartate receptor 1 mRNA and protein, the content of nitric oxide, and the concentration of calcium in neurons. KSZZP also increased the expression of nerve growth factor and glial cell line-derived neurotrophic factor protein in the hippocampus CA1 region and in the cerebral cortex. Morris water maze and passive avoidance tests verified that KSZZP ameliorated the cognitive impairments of vascular dementia rats. Moreover, the KSZZP-induced improvements in the cognitive functions of vascular dementia rats were correlated with both inhibition of N-methyl-D-aspartate-induced excitable neurotoxicity and elevation of neurotrophic factor expression.
文摘The influence of aging on the microstructure and mechanical properties of Cu-11.6wt%Al-3.9wt%Ni-2.5wt%Mn shape memory alloy（SMA） was studied by means of scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray diffractometer,and differential scanning calorimeter（DSC）.Experimental results show that bainite,γ2,and α phase precipitates occur with the aging effect in the alloy.After aging at 300°C,the bainitic precipitates appear at the early stages of aging,while the precipitates of γ2 phase are observed for a longer aging time.When the aging temperature increases,the bainite gradually evolves into γ2 phase and equilibrium α phase（bcc） precipitates from the remaining parent phase.Thus,the bainite,γ2,and α phases appear,while the martensite phase disappears progressively in the alloy.The bainitic precipitates decrease the reverse transformation temperature while the γ2 phase precipitates increase these temperatures with a decrease of solute content in the retained parent phase.On the other hand,these precipitations cause an increasing in hardness of the alloy.
基金the National Natural Science Foundation of China under grant No. 59601004,59731030.
文摘DSC was used to study the effects of predeformation on the reverse martensitic transformation of near-equiatomic TiNi alloy. Both the start temperature As and the finish temperature Af of the reverse transformation increased with increasing degree of predeformation, but the algebraic difference between As and Af decreased with increasing predeformation until it reached a minimum value, then remained unchanged with further deformation. Transformation heat also increased with increasing predeformation until it reached a maximum value, then decreased with further predeformation. All the phenomena above were considered to be closely related with the release of elastic strain energy during predeformation.
基金financial support under the University Research Grant No.Q.J130000.3024.00M57
文摘Ti–51at%Ni shape memory alloys(SMAs) were successfully produced via a powder metallurgy and microwave sintering technique.The influence of sintering parameters on porosity reduction,microstructure,phase transformation temperatures,and mechanical properties were investigated by optical microscopy,field-emission scanning electron microscopy(FE-SEM),X-ray diffraction(XRD),differential scanning calorimetry(DSC),compression tests,and microhardness tests.Varying the microwave temperature and holding time was found to strongly affect the density of porosity,presence of precipitates,transformation temperatures,and mechanical properties.The lowest density and smallest pore size were observed in the Ti–51at%Ni samples sintered at 900°C for 5 min or at 900°C for 30 min.The predominant martensite phases of β2 and β19′ were observed in the microstructure of Ti–51at%Ni,and their existence varied in accordance with the sintering temperature and the holding time.In the DSC thermograms,multi-transformation peaks were observed during heating,whereas a single peak was observed during cooling;these peaks correspond to the presence of the β2,R,and β19′ phases.The maximum strength and strain among the Ti–51at%Ni SMAs were 1376 MPa and 29%,respectively,for the sample sintered at 900°C for 30 min because of this sample's minimal porosity.
基金Shanxi Province Natural Science FOundation State Key Laboratory of Solidilication Processing.
文摘The effect of Ta addition on the martensitic transformation characteristics and the X-ray visibility on NiTi shape memory alloy have been studied in (Ni51Ti49)1-xTax system. It was found that the transformation temperatures of the Ni51Ti49 binary alloy increased drastically by an addition of 0～4 at. pet Ta, but only slightly when the concentration exceeded 4 at. pct; the addition of Ta greatly decreases the sensitivity of the martensitic transformations to the variation in the Ni-Ti ratio. The addition of Ta to the NiTi binary alloy can improve its X-ray visibility.
基金support of the 111 Project(No.B18017)the National Equipment Pre-Research Project of the 13th Five-Year Plan(No.30508040601)。
文摘The effects of 1 Me V electron irradiation in air at a fixed accumulated dose and dose rates of 393.8,196.9,78.8,and 39.4 Gy s^(-1)on a shape memory epoxy(SMEP)resin were studied.Under low-dose-rate irradiation,accelerated degradation of the shape memory performance was observed;specifically,the shape recovery ratio decreased exponentially with increasing irradiation time(that is,with decreasing dose rate).In addition,the glass transition temperature of the SMEP,as measured by dynamic mechanical analysis,decreased overall with decreasing dose rate.The dose rate effects of 1 Me V electron irradiation on the SMEP were confirmed by structural analysis using electron paramagnetic resonance(EPR)spectroscopy and Fourier transform infrared(FTIR)spectroscopy.The EPR spectra showed that the concentration of free radicals increased exponentially with increasing irradiation time.Moreover,the FTIR spectra showed higher intensities of the peaks at 1660 and 1720 cm^(-1),which are attributed to stretching vibrations of amide C=O and ketone/acid C=O,at lower dose rates.The intensities of the IR peaks at 1660 and 1720 cm^(-1) increased exponentially with increasing irradiation time,and the relative intensity of the IR peak at 2926 cm^(-1)decreased exponentially with increasing irradiation time.The solid-state13 C nuclear magnetic resonance(NMR)spectra of the SMEP before and after 1 Me V electron irradiation at a dose of 1970 k Gy and a dose rate of 78.8 Gy s^(-1) indicated damage to the CH_(2)–N groups and aliphatic isopropanol segment.This result is consistent with the detection of nitrogenous free radicals,a phenoxy-type free radical,and several types of pyrolytic carbon radicals by EPR.During the subsequent propagation process,the free radicals produced at lower dose rates were more likely to react with oxygen,which was present at higher concentrations,and form the more destructive peroxy free radicals and oxidation products such as acids,amides,and ketones.The increase in peroxy free radicals at lower dose rates was thought to accelerate the degradation of the macroscopic performance of the SMEP.
文摘Impaired insulin signaling in Alzheimer’s disease（AD）brains：The insulin signaling pathway is a fundamental physiological mechanism that presents in nearly all vertebrate cells.However,sometimes cells stop responding properly to insulin stimulation.This condition is known as insulin resistance,which is a hallmark of two very common conditions,metabolic syndrome and type 2 diabetes（T2D）.
基金financially supported by the National Natural Science Foundation of China (Nos. 51574027 and 51604206)the Financial Support from the State Key Laboratory for Advanced Metals and Materials (No. 2016Z-22)
文摘The effect of aging treatment on the superelasticity and martensitic transformation critical stress in columnar-grained Cu_（71）Al_（18）Mn_（11） shape memory alloy（SMA） at the temperature ranging from 250°C to 400°C was investigated. The microstructure evolution during the aging treatment was characterized by optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results show that the plate-like bainite precipitates distribute homogeneously within austenitic grains and at grain boundaries. The volume fraction of bainite increases with the increase in aging temperature and aging time, which substantially improves the martensitic transformation critical stress of the alloy, whereas the bainite only slightly affects the superelasticity. This behavior is attributed to a coherent relationship between the bainite and the austenite, as well as to the bainite and the martensite exhibiting the same crystal structure. The variations of the martensitic transformation critical stress and the superelasticity of columnar-grained Cu_（71）Al_（18）Mn_（11） SMA with aging-temperature and aging time are described by the Austin-Rickett equation, where the activation energy of bainite precipitation is 77.2 kJ ·mol1. Finally, a columnar-grained Cu_（71）Al_（18）Mn_（11） SMA with both excellent superelasticity（5%-9%） and high martensitic transformation critical stress（443-677 MPa） is obtained through the application of the appropriate aging treatments.
基金supported by the CAMS Innovation Fund for Medical Sciences(CIFMS)(2021-1-I2M-026)the Beijing Natural Science Foundation(7202133)the Non-profit Central Research Institute Fund of Chinese Academy of Medical Sciences(2021-RW350-002)。
文摘Background:Triple-negative breast cancer(TNBC)is the most aggressive subtype and occurs in approximately 15%–20%of diagnosed breast cancers.TNBC is characterized by its highly metastatic and recurrent features,as well as a lack of specific targets and targeted therapeutics.Epidermal growth factor receptor(EGFR)is highly expressed in a variety of tumors,especially in TNBC.LR004-VC-MMAE is a new EGFR-targeting antibody–drug conjugate produced by our laboratory.This study aimed to evaluate its antitumor activities against EGFR-positive TNBC and further studied its possible mechanism of antitumor action.Methods:LR004-VC-MMAE was prepared by coupling a cytotoxic payload(MMAE)to an anti-EGFR antibody(LR004)via a linker,and the drug-to-antibody ratio(DAR)was analyzed by HIC-HPLC.The gene expression of EGFR in a series of breast cancer cell lines was assessed using a publicly available microarray dataset(GSE41313)and Western blotting.MDA-MB-468 and MDA-MB-231 cells were treated with LR004-VC-MMAE(0,0.0066,0.066,0.66,6.6 nmol/L),and the inhibitory effects of LR004-VC-MMAE on cell proliferation were examined by CCK-8 and colony formation.The migration and invasion capacity of MDA-MB-468 and MDA-MB-231 cells were tested at different LR004-VCMMAE concentrations(2.5 and 5 nmol/L)with wound healing and Transwell invasion assays.Flow cytometric analysis and tumorsphere-forming assays were used to detect the killing effects of LR004-VC-MMAE on cancer stem cells(MDA-MB-468 and MDA-MB-231 cells).The mouse xenograft models were also used to evaluate the antitumor efficacy of LR004-VC-MMAE in vivo.Briefly,BALB/c nude mice were subcutaneously inoculated with MDA-MB-468 or MDAMB-231 cells.Then they were randomly divided into 4 groups(n=6 per group)and treated with PBS,naked LR004(10 mg/kg),LR004-VC-MMAE(10 mg/kg),or doxorubicin,respectively.Tumor sizes and the body weights of mice were measured every 4 d.The effects of LR004-VC-MMAE on apoptosis and cell cycle distribution were analyzed by flow cytometry.Western blotting was used to detect the effects of LR004-VC-MMAE on EGFR,ERK,MEK phosphorylation and tumor stemness marker gene expression.Results:LR004-VC-MMAE with a DAR of 4.02 were obtained.The expression of EGFR was found to be significantly higher in TNBC cells compared with non-TNBC cells(P<0.01).LR004-VC-MMAE inhibited the proliferation of EGFRpositive TNBC cells,and the ICvalues of MDA-MB-468 and MDA-MB-231 cells treated with LR004-VC-MMAE for 72 h were(0.13±0.02)nmol/L and(0.66±0.06)nmol/L,respectively,which were significantly lower than that of cells treated with MMAE[(3.20±0.60)nmol/L,P<0.01,and(6.60±0.50)nmol/L,P<0.001].LR004-VC-MMAE effectively inhibited migration and invasion of MDA-MB-468 and MDA-MB-231 cells.Moreover,LR004-VC-MMAE also killed tumor stem cells in EGFR-positive TNBC cells and impaired their tumorsphere-forming ability.In TNBC xenograft models,LR004-VC-MMAE at 10 mg/kg significantly suppressed tumor growth and achieved complete tumor regression on day 36.Surprisingly,tumor recurrence was not observed until the end of the experiment on day 52.In a mechanistic study,we found that LR004-VC-MMAE significantly induced cell apoptosis and cell cycle arrest at G/M phase in MDAMB-468[(34±5)%vs.(12±2)%,P<0.001]and MDA-MB-231[(27±4)%vs.(18±3)%,P<0.01]cells.LR004-VC-MMAE also inhibited the activation of EGFR signaling and the expression of cancer stemness marker genes such as Oct4,Sox2,KLF4 and EpCAM.Conclusions:LR004-VC-MMAE showed effective antitumor activity by inhibiting the activation of EGFR signaling and the expression of cancer stemness marker genes.It might be a promising therapeutic candidate and provides a potential therapeutic avenue for the treatment of EGFR-positive TNBC.
文摘In this letter, a novel model is proposed for modeling the nonlinearity and memory effects of power amplifiers. The classical Volterra model is modified through a function of the sum of nonlinearity order with sum of memory length. The parameters of this model can be extracted in digital domain since the model is analyzed based on the envelope signals. The model we proposed enables a substantial reduction in the number of coefficients involved, and with excellent accuracy.
基金Project supported by the National Natural Science Foundation of China(No.11372172)and the Start-up Fund from Jinan University in Guangzhou of China。
文摘A new finite strain elatoplastic J2-flow model with coupling effects of both isotropic and anisotropic hardening is proposed with the co-rotational logarithmic rate.In terms of certain single-variable shape functions representing uniaxial loading and unloading curves,explicit multi-axial expressions for the three hardening quantities incorporated in the new model proposed are derived in unified forms for the purpose of automatically and accurately simulating complex pseudoelastic-to-plastic transition effects of shape memory alloys(SMAs)under multiple loading-unloading cycles.Numerical examples show that with only a single parameter of direct physical meaning for each cycle,accurate and explicit simulations may be achieved for extensive data from multiple cycle tests.
文摘Ciprofloxacin (CFX) was loaded on Bana clay (Cameroon) and CFX loaded-clays have been evaluated as drug delivery system. Raw clays and CFX loaded compounds have been characterized by some physico-chemicals methods. <i>In vitro</i> release studies have been done in gastric and phosphate buffer experimental mediums;bacteriological studies have been made up on <i>Escherichia coli</i> and <i>Staphylococcus aureus</i>. X-ray diffractometry patterns of loaded compounds show a basal spacing increasing due to CFX intercalation. On Fourier-Transformed Infrared spectrometry spectra, appearance of CFX characteristic bands and shifting of certain bands already presents on clay confirmed CFX intercalation. After 96 h of CFX released from release mediums, prolonged and continue profiles have been observed. Diffusion tests displayed an inhibition radius of ~2 cm on gelose seeded with <i>Escherichia coli</i> and <i>Staphylococcus aureus</i> due to CFX. The overall results show a modified release of ciprofloxacin with an effective antibacterial activity, giving the way for a new ciprofloxacin drug delivery system using Bana clay as carrier.
基金Project (No. 60372026) supported by the National Natural ScienceFoundation of China
文摘RF power amplifiers (PAs) are usually considered as memoryless devices in most existing predistortion techniques. Nevertheless, in wideband communication systems, PA memory effects can no longer be ignored and memoryless predistortion cannot linearize PAs effectively. After analyzing PA memory effects, a novel predistortion method based on wavelet networks (WNs) is proposed to linearize wideband RF power amplifiers. A complex wavelet network with tapped delay lines is applied to construct the predistorter and then a complex backpropagation algorithm is developed to train the predistorter parameters. The simulation results show that compared with the previously published feed-forward neural network predistortion method, the proposed method provides faster convergence rate and better performance in reducing out-of-band spectral regrowth.
文摘BACKGROUND： Central adrenergic nerve and 5-serotonergic nerve can influence central cholinergic nerve on learning and memory and make easy for study; however, ginsenoside of stem and leaf （GSL） can improve functions of central adrenergic nerve; moreover, 5-serotonergic nerve and the combination with choline can produce synergistic effect and enhance learning and memory ability so as to improve learning and memory disorder of patients with Alzheimer disease （AD）. OBJECTIVE ： To observe the effects of GSL combining with choline on learning and memory of AD model rats DESIGN ： Randomized grouping design and controlled animal study SETIING ： Department of Pharmacology, Taishan Medical College MATERIALS ： The experiment was carried out in the Pharmacological Department of Medical College of Jilin University from October 1996 to January 1997. Forty healthy male Wistar rats of clean grade were randomly divided into 5 groups, including sham-injury group, model group, GSL group, choline group and combination group, with 8 rats in each group. Main medications： GSL with the volume more than 92.8% was provided by Department of Chemistry, Norman Bethune Medical College of Jilin University. Panaxatriol, the main component, was detected with thin layer scanning technique and regarded as the index of GSL quality [（55±1）%, CV= 2%, n = 5]. Choline was provided by the Third Shanghai Laboratory Factory. METHODS ： 150 nmol quinolinic acid was used to damage bilateral Meynert basal nuclei of adult rats so as to establish AD models. Rats in GSL, choline and combination groups were intragastric administrated with 400 mg/kg GSL, 200 mg/kg choline （20 mL/kg）, and both respectively last for 17 days starting from two days before operation. Rats in sham-injury group and model group were perfused with the same volume of distilled water once in each morning for the same days. （1） Passive avoidance step-down test： Five minutes later, rats jumped up safe platform when they were shocked with 36 V alternating current. If rats jumped down from the platform and the feet touched railings, the response was wrong. Numbers of wrong response were recorded within 3 minutes, and then the test was redone after 24 hours. （2） Morris water-maze spatial localization task： Swimming from jumping-off to platform directly was regarded as right response. Additionally, 4 successively right responses were regarded as the standard. Each rat was trained 10 times a day with 120 s per time for 3 successive days. The interval was 30 s. Three days later, numbers of right response were recorded. The training times were increased to 30 for unlearned rats. （3） Measurement of activity of choline acetylase in cerebral cortex： Rats were sacrificed at 17 days after operation to obtain cerebral cortex to measure activity of choline acetylase with radiochemistry technique. （4） Synergistic effect： It was expressed as Q value： Q value = factual incorporative effect/anticipant incorporative effect; Q ≥ 1 was regarded as synergistic effect. Anticipant incorporative effect = （EA＋EB-EA·EB）, EA and EB were single timing effect, respectively in GSL group and choline group. E（step-down test and Morris water maze test） = （x in model group - factual value in medicine groups）/x in model group; E （activity of choline acetylase） = （factual value in medicine groups -xin model group）/xin model group. MAIN OUTCOME MEASURES ： （1） Passive avoidance step-down test and Morris water-maze spatial localization task in the study of learning and memory; （2） activity of choline acetylase. RESULTS ： All 40 rats were involved in the final analysis. （1） Passive avoidance response： At learning phase on first day and retesting phase on the next day, numbers of wrong responses within 3 minutes were more in model group than sham operation group, and there was significant difference [（5.88±1.46）, （2.25±0.87） times; （2.63±1.06）, （0.50±0.53） times; P 〈 0.01]; numbers of wrong responses within 3 minutes were less in combination group than model group, and there was significant difference [learning phase： （1.12±0.83）, （5.88±1.46） times; retesting phase： （0.38±0.74）, （2.63±1.06）times, P 〈 0.01]; moreover, effect was stronger than that in GSL group and choline group. The Q value was 1.07 and 1.59, respectively and it showed synergistic effect. Spatial localization task： Training times were more in model group than sham operation group, and there was significant difference [（2.9±2.5）, （12.6±3.5） times; P 〈 0.01]. Training times were less in combination group than model group, and there was significant difference [（11.8±2.4）, （27.9±2.5） times, P 〈 0.01]; moreover, effect was stronger than that in GSL group and choline group. The Q value was 1.07 and it showed synergistic effect. （3） Activity of choline acetylase： Activity was lower in model group than sham operation group, and there was significant difference [（30.56±8.33）, （61.11 ±8.33） nkat/g; P 〈 0.01]. Activity was higher in combination group than model group and there was significant difference [（50.00±8.33）, （30.56±8.33） nkat/g, P 〈 0.01];moreover, effect was stronger than that in GSL group and choline group. The Q value was 1.5 and it showed synergistic effect. CONCLUSZON： GSL in combination with choline can synergically improve the disorder of learning and memory of AD model rats. Its mechanism may be involved in enhancing the function of central cholinergic system.
基金supported by National Key R&D Program of China(Grant No.2022YFB4601701)74th Batch of General Funding from the China Postdoctoral Science Foundation(Grant No.2023M741341)+7 种基金5th Batch of Special Grants from the China Postdoctoral Science Foundation(before the station,Grant No.2023TQ0129)Postdoctoral Fellowship Program of CPSF(Grant No.GZB20230257)National Natural Science Foundation of China(Grant Nos.52375289,52205310)Natural Science Foundation of Shandong Province(Grant No.ZR2021QE263)Science and Technology Development Program of Jilin Province(Grant No.20230508045RC)Capital Construction Fund plan within the budget of Jilin Province(Grant No.2023C041-4)Chongqing Natural Science Foundation(Grant No.CSTB2022NSCQ-MSX0225)the Shandong Postdoctoral Science Foundation(Grant No.SDCX-ZG-202400238).
文摘The emergence of additive manufacturing technology,particularly laser powder bed fusion,has revitalized NiTi alloy production.However,challenges arise regarding its mechanical properties and diminishing shape memory effect,which hinder its widespread application.Heat treatment has been identified as a method to enhance the performance of metallic materials in the realm of additive manufacturing.This process eliminates residual stress and enhances performance through precipitation strengthening.This study conducted a comprehensive annealing investigation on NiTi alloys to explore the impact of annealing time and temperature on the phase transformation behavior and shape memory performance.The mechanism underlying the performance enhancement was analyzed using scanning electron microscopy,energy-dispersive X-ray spectroscopy,electron backscatter diffraction,and transmission electron microscopy.The findings revealed that different annealing conditions resulted in multistep phase transformation behavior,with the 500℃-5 h sample exhibiting the best mechanical properties owing to the formation of nanoscale dispersed precipitates like Ni_(4)Ti_(3).However,higher temperatures led to larger precipitates,significantly weakening the properties of the NiTi alloy.Additionally,the annealing treatment did not have a notable impact on the grain size,texture strength,or direction.This study provides valuable insights for optimizing the heat treatment process of LPBF-NiTi alloys.
基金support from the National Natural Science Foundation of China(No.52231006)Junqiang Wang acknowledges financial support from the National Key R&D Program of China(No.2018YFA0703600)the National Natural Science Foundation of China(Nos.92163108 and 52222105).
文摘Annealing has been a popular method to improve the soft magnetism of metallic glasses (MGs), which however usually makes MGs brittle and difficult to process. Here, it is demonstrated that the embrittled Fe-based MG can be reductilized and the coercivity can be further lowered through the rejuvenation of memory effect. The synchronous improvement in the plasticity and soft magnetic properties is attributed to the combination effects of releasing much residual stress, decreasing the magnetic anisotropy, and homogenizing the glasses during the rejuvenation process. The current work opens a new perspective to improve the properties of MGs by utilizing the memory effect and holds promising commercial application potential.
基金Supported by the National Natural Science Foundation of China under Grant No 616340084the Youth Innovation Promotion Association of Chinese Academy of Sciences under Grant No 2014101+1 种基金the International Cooperation Project of Chinese Academy of Sciencesthe Austrian-Chinese Cooperative R&D Projects under Grant No 172511KYSB20150006
文摘Because of the discrete charge storage mechanism, charge trapping memory（CTM） technique is a good candidate for aerospace and military missions. The total ionization dose（TID） effects on CTM cells with Al2O3/HfO2/Al2O3（AHA） high-k gate stack structure under in-situ 10 keV x-rays are studied. The C-V characteristics at different radiation doses demonstrate that charge stored in the device continues to be leaked away during the irradiation,thereby inducing the shift of flat band voltage（V（fb））. The dc memory window shows insignificant changes, suggesting the existence of good P/E ability. Furthermore, the physical mechanisms of TID induced radiation damages in AHA-based CTM are analyzed.
基金financially supported by the Agency for Science,Technology and Research(A*STAR)of Singapore via the Structural Metal Alloys Programme(No.A18B1b0061).
文摘Functional fatigue in the superelastic NiTi shape memory alloys occurs due to the accumulation of dislocations and retention of martensite with the cyclic loading.These mechanisms reduce the amount of the material available for the stress-induced transformation and,thus,lower the elastocaloric effect that originates from the stress-induced latent heat variations.In this study,the individual contributions of the micromechanisms responsible for the functional fatigue in superelastic NiTi at different maximum tensile stress(σ_(max))are critically examined.Results show that the elastocaloric effect degrades significantly with cycling,and the saturated degraded value increases with σ_(max);the steady-state adiabatic temperature change is unexpectedly non-proportional to σ_(max).An overheating treatment(‘healing’)after mechanical fatigue reverts the retained martensite into austenite,making it available for subsequent transformation and restoring the elastocaloric effect significantly.Such a restoration increases exponentially with σ_(max).Consequently,the steady-state elastocaloric effect of the healed NiTi is proportional to σ_(max) and can reach more than twice that of NiTi without healing.The work sheds light on the physical origins of elastocaloric degradation of superelastic NiTi and also provides a feasible method for ameliorating functional fatigue.
