Seldom could metals and alloys maintain excellent properties in cryogenic condition, such as the ductility, owing to the restrained dislocation motion.However, a face-centered-cubic(FCC) CoCrFeNi highentropy alloy(HEA...Seldom could metals and alloys maintain excellent properties in cryogenic condition, such as the ductility, owing to the restrained dislocation motion.However, a face-centered-cubic(FCC) CoCrFeNi highentropy alloy(HEA) with great ductility is investigated under the cryogenic environment. The tensile strength of this alloy can reach a maximum at 1,251±10 MPa, and the strain to failure can stay at as large as 62% at the liquid helium temperature. We ascribe the high strength and ductility to the low stacking fault energy at extremely low temperatures,which facilitates the activation of deformation twinning.Moreover, the FCC→HCP(hexagonal close-packed) transition and serration lead to the sudden decline of ductility below 77 K. The dynamical modeling and analysis of serrations at 4.2 and 20 K verify the unstable state due to the FCC→HCP transition. The deformation twinning together with phase transformation at liquid helium temperature produces an adequate strain-hardening rate that sustains the stable plastic flow at high stresses, resulting in the serration feature.展开更多
High entropy alloys with the composition of FeCoNiA10.2Si0.2 were prepared by arc melting and induction melting, denoted by A1 and A2, respectively. The samples prepared by these two techniques have a face-centered cu...High entropy alloys with the composition of FeCoNiA10.2Si0.2 were prepared by arc melting and induction melting, denoted by A1 and A2, respectively. The samples prepared by these two techniques have a face-centered cubic （FCC） phase structure and a typical dendrite morphology. The tensile yield strength and maximum strength of A2 samples are about 280 and 632 MPa, respectively. Moreover~ the elongation can reach 41.7%. These two alloys prepared by the different methods possess the similar magnetic properties. The saturation magnetization and coercivity can reach 1.151 T and 1400 A/m for A1 samples and 1.015 T and 1431 A/m for A2 samples, respectively. Phases in A2 samples do not change, which are heat treated at different temperatures, then quenched in water. Only the sample, which is heat treated at 600~C for 3 h and then furnace cooled, has a new phase precipitated. Besides, the coercivity decreases obviously at this temperature. Cold rolling and the subsequent heat treatment cannot improve the magnetic properties effectively. However, cold rolling plays an important role in improving the strength.展开更多
Generation of induced pluripotent stem （iPS） cells from somatic cells has been achieved successfully by simultaneous viral transduction of defined reprogramming transcription factors （TFs）. However, the process re...Generation of induced pluripotent stem （iPS） cells from somatic cells has been achieved successfully by simultaneous viral transduction of defined reprogramming transcription factors （TFs）. However, the process requires multiple viral vectors for gene delivery. As a result, generated iPS cells harbor numerous viral integration sites in their genomes. This can increase the probability of gene mutagenesis and genomic instability, and present significant barriers to both research and clinical application studies of iPS cells. In this paper, we present a simple lentivirus reprogramming system in which defined factors are fused in-frame into a single open reading frame （ORF） via self-cleaving 2A sequences. A GFP marker is placed downstream of the transgene to enable tracking of transgene expression. We demonstrate that this polycistronic expression system efficiently generates iPS cells. The generated iPS cells have normal karyotypes and are similar to mouse embryonic stem cells in morphology and gene expression. Moreover, they can differentiate into cell types of the three embryonic germ layers in both in vitro and in vivo assays. Remarkably, most of these iPS cells only harbor a single copy of viral vector. This system provides a valuable tool for generation of iPS cells, and our data suggest that the balance of expression of transduced reprogramming TFs in each cell is essential for the reprogramming process. More importantly, when delivered by non-integrating gene-delivery systems, this re-engineered single ORF will facilitate efficient generation of human iPS cells free of genetic modifications.展开更多
AIM: To transfer human HGF gene into the liver of rats by direct electroporation as a means to prevent radiationinduced liver damage.METHODS: Rat whole liver irradiation model was accomplished by intra-operative appro...AIM: To transfer human HGF gene into the liver of rats by direct electroporation as a means to prevent radiationinduced liver damage.METHODS: Rat whole liver irradiation model was accomplished by intra-operative approach. HGF plasmid was injected into liver and transferred by electroporation using a pulse generator. Control rats (n = 8) received electrogene therapy (EGT) vehicle plasmid and another 8rats received HGF-EGT 100 μg 48 h before WLIR.Expression of HGF in liver was examined by RT-PCR and ELISA methods. Apoptosis was determined by TUNEL assay. Histopathology was evaluated 10 wk after whole liver irradiation.RESULTS: Marked decrease of apoptotic cells and downregulation of transforming growth factor-beta 1 (TGF-β1)mRNA were observed in the HGF-EGT group 2 d after liver irradiation compared to control animals. Less evidence of radiation-induced liver damage was observed morphologically in liver specimen 10 wk after liver irradiation and longer median survival time was observed from HGF-EGT group (14 wk) compared to control rats (5 wk). (P = 0.031).CONCLUSION: For the first time it has been demonstrated that HGF-EGT would prevent liver from radiation-induced liver damage by preventing apoptosis and down-regulation of TGF-β1.展开更多
Investigating the microstructures and properties of gradient materials has been regarded as a promising way to accelerate the identification of optimal compositions for applications. Herein, a supergravity method is a...Investigating the microstructures and properties of gradient materials has been regarded as a promising way to accelerate the identification of optimal compositions for applications. Herein, a supergravity method is applied to prepare the graded entropic alloys Al-Zn-Li-Mg-Cu. Through carefully optimizing the experimental conditions, the graded microstructures and hardness values appear after the supergravity technique. The morphology of the alloy significantly changes from the bulk intermetallics to eutectic structures along the supergravity force direction, which results from the crushed and graded aluminum oxide combined with the extremelystrong force. The results show that with this supergravity method, a performance-enhanced alloy can potentially be achieved through the centrifugation in a short time span and thus it paves the way for designing and synthesizing entropic alloys with intriguing properties.展开更多
This study investigated the atomic-scale deformation mechanism of multiphase CoCrFeNi high-entropy alloys(HEAs)at liquid helium,liquid nitrogen,and room temperatures.A million-atom multiphase HEA was prepared using mo...This study investigated the atomic-scale deformation mechanism of multiphase CoCrFeNi high-entropy alloys(HEAs)at liquid helium,liquid nitrogen,and room temperatures.A million-atom multiphase HEA was prepared using molecular dynamics simulation involving melt and quench processes.The HEA exhibited high-density dislocations and some twins,consistent with experimental observations.Quantitative analysis revealed an inconsistent evolution of the microstructure under tensile deformation.In particular,the elastic and initial plastic stages exhibited an increase in the disordered structure at the expense of the face-centered cubic and hexagonal close-packed structures,followed by a subsequent transformation involving multiple structural rearrangements.Furthermore,through sparse identification,a model depicting microstructural evolution during tension was extracted for the CoCrFeNi HEA at three typical temperatures and three tensile rates.The model highlighted the importance of the body-centered cubic structure in the evolutionary process.展开更多
The multi-component composition characteristics of high-temperature near-α Ti alloys were investigated in the present work by means of a cluster formula approach. The uniform cluster formula [CN12 cluster](glue atom)...The multi-component composition characteristics of high-temperature near-α Ti alloys were investigated in the present work by means of a cluster formula approach. The uniform cluster formula [CN12 cluster](glue atom)3 for the hexagonal close-packed α solid solution was first obtained based on the Friedel oscillation theory, with a total atom number in the formula of Z = 16. Then it was analyzed that the Z values in the cluster composition formulas of typical near-α Ti alloys are within the range of Z = 16.0016.30, being perfectly consistent with the ideal Z = 16. Based on it, a series of new alloys with Z = 16 and with Nb/Ta substitution for Mo in Ti1100 alloy were designed, suction-cast into φ 6 mm rods, and then heat-treated with solid solution and aging. It was found that the alloy with co-addition of Mo, Ta and Nb has a high strength and good ductility at both room and high temperatures. More importantly, the additions of Nb and Ta can contribute to the formation of continuous and compact Al2O3 scales, resulting in an obvious improvement of oxidation resistances at both 923 K and 1073 K. The effects of Mo, Ta and Nb on the oxidation behaviors of the designed alloys at 1073 K were further discussed.展开更多
AIM： To evaluate whether the effect of Gin dipeptideenriched total parenteral nutrition （TPN） on postoperative cytokine alteration depended on the disease severity of surgical patients. METHODS： Forty-eight patien...AIM： To evaluate whether the effect of Gin dipeptideenriched total parenteral nutrition （TPN） on postoperative cytokine alteration depended on the disease severity of surgical patients. METHODS： Forty-eight patients with major abdominal surgery were allocated to two groups to receive isonitrogenous （0.228 g nitrogen/kg per d） and isocaloric （30 kcal/kg per d） TPN for 6 d. Control group （Cony） using conventional TPN solution received 1.5 g amino acids/kg per day, whereas the test group received 0.972 g amino acids/kg per day and 0.417 g L-alanyI-L-glutamine （Ala-GIn）/kg per day. Blood samples were collected on d 1 and d 6 postoperatively for plasma interleukin （IL）-2, IL-6, IL-8, and interferon （IFN）-γ analysis. RESULTS： Plasma IL-2 and IFN-γ were not detectable. IL-6 concentrations were significantly lower on the 6^th postoperative day in the Ala-GIn group than those in the Cony group in patients with APACHE Ⅱ≤6, whereas no difference was noted in patients with APACHE Ⅱ〉6. There was no difference in IL-8 levels between the two groups. No difference in cumulative nitrogen balance was observed on d 2-5 after the operation between the two groups （Ala-GIn -3.2±1.6 g vs Cony -6.5±2.7 g）. A significant inverse correlation was noted between plasma IL-6 levels and cumulative nitrogen balance postoperatively in the Ala-GIn group, whereas no such correlation was observed in the Conv group. CONCLUSION： TPN supplemented with Gin dipeptide had no effect on plasma IL-8 levels after surgery. However, Gin supplementation had a beneficial effect on decreasing systemic IL-6 production after surgery in patients with low admission illness severity, and lower plasma IL-6 may improve nitrogen balance in patients with abdominal surgery when Gin was administered.展开更多
Recently,various topics on high-entropy alloys have been reported and great amounts of excellent properties have been investigated,including high strength,great corrosion resistance,great thermal stability,good fatigu...Recently,various topics on high-entropy alloys have been reported and great amounts of excellent properties have been investigated,including high strength,great corrosion resistance,great thermal stability,good fatigue and fracture properties,etc.Among all these research activities,high-entropy alloys tend to form face-centered-cubic(FCC)or body-centeredcubic(BCC)solid solutions due to their high-entropy stabilization effect,while the hexagonal structures are rarely reported.Up to now,the reported hexagonal high-entropy alloys are mainly composed of rare-earth elements and transitional elements.Their phase transformation and magnetic properties have also aroused wide concern.This study summarizes the above results and provides the forecast to the future.展开更多
Fatigue failures cost approximately 4% of the United States' gross domestic product(GDP). The design of highly fatigue-resistant materials is always in demand. Different from conventional strategies of alloy desig...Fatigue failures cost approximately 4% of the United States' gross domestic product(GDP). The design of highly fatigue-resistant materials is always in demand. Different from conventional strategies of alloy design, high-entropy alloys(HEAs) are defined as materials with five or more principal elements, which could be solid solutions. This locally-disordered structure is expected to lead to unique fatigue-resistant properties. In this review, the studies of the fatigue behavior of HEAs during the last five years are summarized. The four-point-bending high-cycle fatigue coupled with statistical modelling, and the fatigue-crack-growth behavior of HEAs, are reviewed. The effects of sample defects and nanotwins-deformation mechanisms on four-point-bending high-cycle fatigue of HEAs are discussed in detail. The influence of stress ratio and temperature on fatigue-crack-growth characteristics of HEAs is also discussed. HEAs could exhibit comparable or greater fatigue properties, relative to conventional materials. Finally,the possible future work regarding the fatigue behavior of HEAs is suggested.展开更多
BACKGROUND The Coronavirus Disease 2019(COVID-19)caused by the severe acute respiratory syndrome coronavirus 2 virus is an international health concern with substantial morbidity and mortality.COVID-associated cystiti...BACKGROUND The Coronavirus Disease 2019(COVID-19)caused by the severe acute respiratory syndrome coronavirus 2 virus is an international health concern with substantial morbidity and mortality.COVID-associated cystitis(CAC),presents as new onset or exacerbated urinary symptoms,resembling overactive bladder(OAB)symptoms.AIM To examines the long-term outcomes of patients with CAC in the context of Long COVID.METHODS A cohort of 350 patients admitted to Detroit Hospitals with COVID-19 between May and December 2020,displaying CAC symptoms following discharge,was prospectively followed.Initial urologic evaluations occurred at 10-14 wk and were repeated at 21-28 mo postdischarge.Symptoms were managed conservatively,employing behavioral modifications and standard OAB medications.Participants completed surveys assessing urinary symptoms and quality of life(QoL)at both time points.The primary outcome was the Urology Care Foundation Overactive Bladder Assessment Tool.RESULTS 87%of the final cohort(n=310)reported symptom improvement at 21-28 mo post-discharge.Patients with new onset CAC symptoms showed a median decrease of 9-10 points in OAB and QoL scores,while those with existing symptoms experienced a decrease of 6 points.Overall,95.4%of patients with new onset symptoms reported symptom improvement at follow-up,contrasting with 60.7%among those with existing symptoms.CONCLUSION This study presents the first long-term follow-up of adult patients with CAC,revealing a promising prognosis with conservative management measures in the context of Long COVID.These findings provide reassurance to patients regarding symptom resolution and underscore the need for further research into this evolving aspect of COVID-19's impact on urological health.展开更多
Background/Aims: Longitudinal studies on the relationship between hepatitis B virus (HBV) genotypes and reactivation of hepatitis B and progression to cirrhosis were very rare. Methods: Liver biochemistry, virological...Background/Aims: Longitudinal studies on the relationship between hepatitis B virus (HBV) genotypes and reactivation of hepatitis B and progression to cirrhosis were very rare. Methods: Liver biochemistry, virological markers and ultrasound were monitored in 202 hepatitis B e antigen (HBeAg)positive patients with normal alanine aminotransferase (ALT) at baseline for 3- 20 (average 10.8) years, and the outcome was correlated with HBV genotypes. Results: There were 150 genotype B and 52 genotype C patients. Hepatitis activity during the HBeAg- positive phase showed no significant difference. However, genotype B was associated with a significantly earlier and higher rate of HBeAg seroconversion. HBeAg seroconversion correlated with age at entry for genotype B and with ALT levels for genotype C. Reactivation of hepatitis B was significantly more common in genotype C patients. Five genotype B and 10 genotype C patients progressed to cirrhosis. Multivariate analysis revealed that genotype C (P=0.03) and reactivation of hepatitis B (P=0.0004) were independent factor predictive of cirrhosis. Conclusions: Rate and factors of HBeAg seroconversion, and rate of reactivation of hepatitis B differed between genotype B and genotype C patients. Genotype C and reactivation of hepatitis B were associated with increased risk of cirrhosis.展开更多
We investigate two configurations of Raman fiber amplifier in the 1530-1570 nm region. The gain spectrum variation is decreased from 8.31 dB to 2.48 dB when appropriately adjust the individual two pumps and optical fi...We investigate two configurations of Raman fiber amplifier in the 1530-1570 nm region. The gain spectrum variation is decreased from 8.31 dB to 2.48 dB when appropriately adjust the individual two pumps and optical fiber.展开更多
Diesel soot aggregates emitted from a model dynamometer and 11 on-road vehicles were segregated by a micro-orifice uniform deposit impactor （MOUDI）. The elemental contents and morphological parameters of the aggrega...Diesel soot aggregates emitted from a model dynamometer and 11 on-road vehicles were segregated by a micro-orifice uniform deposit impactor （MOUDI）. The elemental contents and morphological parameters of the aggregates were then examined by scanning electron microscopy coupled with an energy dispersive spectrometer （SEM-EDS）, and combined with a fractional Brownian motion （fBm） processor. Two mode-size distributions of aggregates collected from diesel vehicles were confirmed. Mean mass concentration of 339 mg/m3 （dC/dlogdp） existed in the dominant mode （180-320 nm）. A relatively high proportion of these aggregates appeared in PM 1, accentuating the relevance regarding adverse health effects. Furthermore, the fBm processor directly parameterized the SEM images of fractal like aggregates and successfully quantified surface texture to extract Hurst coefficients （H） of the aggregates. For aggregates from vehicles equipped with a universal cylinder number, the H value was independent of engine operational conditions. A small H value existed in emitted aggregates from vehicles with a large number of cylinders. This study found that aggregate fractal dimension related to H was in the range of 1.641-1.775, which is in agreement with values reported by previous TEM-based experiments. According to EDS analysis, carbon content ranged in a high level of 30%-50% by weight for diesel soot aggregates. The presence of Na and Mg elements in these sampled aggregates indicated the likelihood that some engine enhancers composed of biofuel or surfactants were commonly used in on-road vehicles in Taiwan. In particular, the morphological H combined with carbon content detection can be useful for characterizing chain-like or cluster diesel soot aggregates in the atmosphere.展开更多
High-entropy amorphous alloys present high hardness,but low tensile ductility.Here,deformation behavior of the amorphous/crystalline Fe Co Cr Ni high-entropy alloy(HEA)composite prepared by the previous experiment is ...High-entropy amorphous alloys present high hardness,but low tensile ductility.Here,deformation behavior of the amorphous/crystalline Fe Co Cr Ni high-entropy alloy(HEA)composite prepared by the previous experiment is investigated using atomic simulations.The result shows the partial dislocations in the crystal HEA layer,and the formation of shear bands in the amorphous HEA layer occurs after yielding.The strength of the amorphous/crystalline HEA composite reduces with increasing the thickness of the amorphous layer,agreeing with the previous experiments.The coupled interaction between the crystal plasticity and amorphous plasticity in amorphous/crystalline HEA composites results in a more homogeneous redistribution of plastic deformation to cause interface hardening,due to the complex stress field in the amorphous layer.The current findings provide the insight into the deformation behavior of the amorphous/crystalline HEA composite at the nanoscale,which are useful for optimizing the structure of the HEA composite with high strength and good plasticity.展开更多
Dynamic strain aging （DSA） effect on SA508-III reactor pressure vessel （RPV） steel was investigated. The SA508-III RPV steel was subjected to tension tests at different strain rates （1.1× 10-5 s-1 and 6.6...Dynamic strain aging （DSA） effect on SA508-III reactor pressure vessel （RPV） steel was investigated. The SA508-III RPV steel was subjected to tension tests at different strain rates （1.1× 10-5 s-1 and 6.6× 10-5 s-1） and different temperatures （500 and 550 ℃） to evaluate the influence of strain rate and temperature on the serrated flow behavior, which is the repetitive and discontinuous yielding phenomenon on the stress-strain curves. The higher temperature leads to the higher density of precipitates, M23C6 carbides and needle-like Mo2C carbides. It was found that the samples under tension test of 6.6 × 10-5 s-1 and 500 ℃ possess superior mechanical properties and mainly show A-type serrations on the tension test curves. Then, the local regress method was used to filter the DSA curves, thus to show the real trend of the curves. It has been found that the less time of interaction between dislocations and precipitates under higher strain rates leads to a higher strength of the sample. The more tiny-stress drops on the 550 ℃ serration curve can be attributed to the hardening phase, M23C6 carbides and needle-like Mo2C carbides. The higher percentage of the small stress drops on the serration curves represents the higher mechanical strength.展开更多
基金supported in part by the Nationa Natural Science Foundation of China (51471025, 51671020, 51471024 and 11771407)the Department of Energy (DOE), Office of Fossil Energy, National Energy Technology Laboratory (DE-FE-0011194)+1 种基金the support from the US Army Research Office project (W911NF-13-1-0438)the support from the National Science Foundation (DMR-1611180 and 1809640)
文摘Seldom could metals and alloys maintain excellent properties in cryogenic condition, such as the ductility, owing to the restrained dislocation motion.However, a face-centered-cubic(FCC) CoCrFeNi highentropy alloy(HEA) with great ductility is investigated under the cryogenic environment. The tensile strength of this alloy can reach a maximum at 1,251±10 MPa, and the strain to failure can stay at as large as 62% at the liquid helium temperature. We ascribe the high strength and ductility to the low stacking fault energy at extremely low temperatures,which facilitates the activation of deformation twinning.Moreover, the FCC→HCP(hexagonal close-packed) transition and serration lead to the sudden decline of ductility below 77 K. The dynamical modeling and analysis of serrations at 4.2 and 20 K verify the unstable state due to the FCC→HCP transition. The deformation twinning together with phase transformation at liquid helium temperature produces an adequate strain-hardening rate that sustains the stable plastic flow at high stresses, resulting in the serration feature.
文摘High entropy alloys with the composition of FeCoNiA10.2Si0.2 were prepared by arc melting and induction melting, denoted by A1 and A2, respectively. The samples prepared by these two techniques have a face-centered cubic （FCC） phase structure and a typical dendrite morphology. The tensile yield strength and maximum strength of A2 samples are about 280 and 632 MPa, respectively. Moreover~ the elongation can reach 41.7%. These two alloys prepared by the different methods possess the similar magnetic properties. The saturation magnetization and coercivity can reach 1.151 T and 1400 A/m for A1 samples and 1.015 T and 1431 A/m for A2 samples, respectively. Phases in A2 samples do not change, which are heat treated at different temperatures, then quenched in water. Only the sample, which is heat treated at 600~C for 3 h and then furnace cooled, has a new phase precipitated. Besides, the coercivity decreases obviously at this temperature. Cold rolling and the subsequent heat treatment cannot improve the magnetic properties effectively. However, cold rolling plays an important role in improving the strength.
文摘Generation of induced pluripotent stem （iPS） cells from somatic cells has been achieved successfully by simultaneous viral transduction of defined reprogramming transcription factors （TFs）. However, the process requires multiple viral vectors for gene delivery. As a result, generated iPS cells harbor numerous viral integration sites in their genomes. This can increase the probability of gene mutagenesis and genomic instability, and present significant barriers to both research and clinical application studies of iPS cells. In this paper, we present a simple lentivirus reprogramming system in which defined factors are fused in-frame into a single open reading frame （ORF） via self-cleaving 2A sequences. A GFP marker is placed downstream of the transgene to enable tracking of transgene expression. We demonstrate that this polycistronic expression system efficiently generates iPS cells. The generated iPS cells have normal karyotypes and are similar to mouse embryonic stem cells in morphology and gene expression. Moreover, they can differentiate into cell types of the three embryonic germ layers in both in vitro and in vivo assays. Remarkably, most of these iPS cells only harbor a single copy of viral vector. This system provides a valuable tool for generation of iPS cells, and our data suggest that the balance of expression of transduced reprogramming TFs in each cell is essential for the reprogramming process. More importantly, when delivered by non-integrating gene-delivery systems, this re-engineered single ORF will facilitate efficient generation of human iPS cells free of genetic modifications.
基金Zhejiang Provincial Natural Science Foundation(LY23E010002)National Natural Science Foundation of China(52061027)+2 种基金Science and Technology Program Project of Gansu Province(22YF7GA155,22CX8GA109)Lanzhou Youth Science and Technology Talent Innovation Project(2023-QN-91)Higher Education Research Project of Lanzhou University of Technology(GJ2021A-4)。
基金Supported by National Science Council grant NSC-91-275-9075-001 for the development of Boron Neutron Capture Therapy for Hepatoma Treatment
文摘AIM: To transfer human HGF gene into the liver of rats by direct electroporation as a means to prevent radiationinduced liver damage.METHODS: Rat whole liver irradiation model was accomplished by intra-operative approach. HGF plasmid was injected into liver and transferred by electroporation using a pulse generator. Control rats (n = 8) received electrogene therapy (EGT) vehicle plasmid and another 8rats received HGF-EGT 100 μg 48 h before WLIR.Expression of HGF in liver was examined by RT-PCR and ELISA methods. Apoptosis was determined by TUNEL assay. Histopathology was evaluated 10 wk after whole liver irradiation.RESULTS: Marked decrease of apoptotic cells and downregulation of transforming growth factor-beta 1 (TGF-β1)mRNA were observed in the HGF-EGT group 2 d after liver irradiation compared to control animals. Less evidence of radiation-induced liver damage was observed morphologically in liver specimen 10 wk after liver irradiation and longer median survival time was observed from HGF-EGT group (14 wk) compared to control rats (5 wk). (P = 0.031).CONCLUSION: For the first time it has been demonstrated that HGF-EGT would prevent liver from radiation-induced liver damage by preventing apoptosis and down-regulation of TGF-β1.
基金the financial support from the National Natural Science Foundation of China (NSFC, 51471025 and 51671020)
文摘Investigating the microstructures and properties of gradient materials has been regarded as a promising way to accelerate the identification of optimal compositions for applications. Herein, a supergravity method is applied to prepare the graded entropic alloys Al-Zn-Li-Mg-Cu. Through carefully optimizing the experimental conditions, the graded microstructures and hardness values appear after the supergravity technique. The morphology of the alloy significantly changes from the bulk intermetallics to eutectic structures along the supergravity force direction, which results from the crushed and graded aluminum oxide combined with the extremelystrong force. The results show that with this supergravity method, a performance-enhanced alloy can potentially be achieved through the centrifugation in a short time span and thus it paves the way for designing and synthesizing entropic alloys with intriguing properties.
基金supported by the National Natural Science Foundation of China(Grant Nos.U23A2065,52071298,and 51971123)the National Science Foundation(Grant Nos.DMR-1611180 and 1809640)。
文摘This study investigated the atomic-scale deformation mechanism of multiphase CoCrFeNi high-entropy alloys(HEAs)at liquid helium,liquid nitrogen,and room temperatures.A million-atom multiphase HEA was prepared using molecular dynamics simulation involving melt and quench processes.The HEA exhibited high-density dislocations and some twins,consistent with experimental observations.Quantitative analysis revealed an inconsistent evolution of the microstructure under tensile deformation.In particular,the elastic and initial plastic stages exhibited an increase in the disordered structure at the expense of the face-centered cubic and hexagonal close-packed structures,followed by a subsequent transformation involving multiple structural rearrangements.Furthermore,through sparse identification,a model depicting microstructural evolution during tension was extracted for the CoCrFeNi HEA at three typical temperatures and three tensile rates.The model highlighted the importance of the body-centered cubic structure in the evolutionary process.
基金financially supported by the National Key Research and Development Plan(No.2017YFB0702400)the Science Challenge Project(No.TZ2016004)+1 种基金the National Magnetic Confinement Fusion Energy Research Project(No.2015GB121004)the Foundation of Guangxi Key Laboratory of Information Materials(No.161002-K)
文摘The multi-component composition characteristics of high-temperature near-α Ti alloys were investigated in the present work by means of a cluster formula approach. The uniform cluster formula [CN12 cluster](glue atom)3 for the hexagonal close-packed α solid solution was first obtained based on the Friedel oscillation theory, with a total atom number in the formula of Z = 16. Then it was analyzed that the Z values in the cluster composition formulas of typical near-α Ti alloys are within the range of Z = 16.0016.30, being perfectly consistent with the ideal Z = 16. Based on it, a series of new alloys with Z = 16 and with Nb/Ta substitution for Mo in Ti1100 alloy were designed, suction-cast into φ 6 mm rods, and then heat-treated with solid solution and aging. It was found that the alloy with co-addition of Mo, Ta and Nb has a high strength and good ductility at both room and high temperatures. More importantly, the additions of Nb and Ta can contribute to the formation of continuous and compact Al2O3 scales, resulting in an obvious improvement of oxidation resistances at both 923 K and 1073 K. The effects of Mo, Ta and Nb on the oxidation behaviors of the designed alloys at 1073 K were further discussed.
基金Supported by a Research Grant from the National Science Council,Taipei, Taiwan, No. NSC91-2314-B002-245
文摘AIM： To evaluate whether the effect of Gin dipeptideenriched total parenteral nutrition （TPN） on postoperative cytokine alteration depended on the disease severity of surgical patients. METHODS： Forty-eight patients with major abdominal surgery were allocated to two groups to receive isonitrogenous （0.228 g nitrogen/kg per d） and isocaloric （30 kcal/kg per d） TPN for 6 d. Control group （Cony） using conventional TPN solution received 1.5 g amino acids/kg per day, whereas the test group received 0.972 g amino acids/kg per day and 0.417 g L-alanyI-L-glutamine （Ala-GIn）/kg per day. Blood samples were collected on d 1 and d 6 postoperatively for plasma interleukin （IL）-2, IL-6, IL-8, and interferon （IFN）-γ analysis. RESULTS： Plasma IL-2 and IFN-γ were not detectable. IL-6 concentrations were significantly lower on the 6^th postoperative day in the Ala-GIn group than those in the Cony group in patients with APACHE Ⅱ≤6, whereas no difference was noted in patients with APACHE Ⅱ〉6. There was no difference in IL-8 levels between the two groups. No difference in cumulative nitrogen balance was observed on d 2-5 after the operation between the two groups （Ala-GIn -3.2±1.6 g vs Cony -6.5±2.7 g）. A significant inverse correlation was noted between plasma IL-6 levels and cumulative nitrogen balance postoperatively in the Ala-GIn group, whereas no such correlation was observed in the Conv group. CONCLUSION： TPN supplemented with Gin dipeptide had no effect on plasma IL-8 levels after surgery. However, Gin supplementation had a beneficial effect on decreasing systemic IL-6 production after surgery in patients with low admission illness severity, and lower plasma IL-6 may improve nitrogen balance in patients with abdominal surgery when Gin was administered.
基金financial support from the National Natural Science Foundation of China (No 51671020)Fundamental Research Funds for the Central Universities (No. FRF-MP-19-013)。
文摘Recently,various topics on high-entropy alloys have been reported and great amounts of excellent properties have been investigated,including high strength,great corrosion resistance,great thermal stability,good fatigue and fracture properties,etc.Among all these research activities,high-entropy alloys tend to form face-centered-cubic(FCC)or body-centeredcubic(BCC)solid solutions due to their high-entropy stabilization effect,while the hexagonal structures are rarely reported.Up to now,the reported hexagonal high-entropy alloys are mainly composed of rare-earth elements and transitional elements.Their phase transformation and magnetic properties have also aroused wide concern.This study summarizes the above results and provides the forecast to the future.
基金supported by the Department of Energy(DOE),Office of Fossil Energy,National Energy Technology Laboratory(Grant No.DE-FE-0024054,DE-FE-0011194)the U.S.Army Research Office Project(Grant No.W911NF-13-1-0438)+4 种基金the National Science Foundation(DMR-1611180)the QuesTek Innovation LLC(limited liability company)the Ministry of Science and Technology of Taiwan(Grant No.MOST105-2221-E-007-017-MY3)the Department of Materials Science and Engineering at the National Tsing Hua University(Taiwan)the School of Materials Science and Engineering of the Dalian University of Technology,China
文摘Fatigue failures cost approximately 4% of the United States' gross domestic product(GDP). The design of highly fatigue-resistant materials is always in demand. Different from conventional strategies of alloy design, high-entropy alloys(HEAs) are defined as materials with five or more principal elements, which could be solid solutions. This locally-disordered structure is expected to lead to unique fatigue-resistant properties. In this review, the studies of the fatigue behavior of HEAs during the last five years are summarized. The four-point-bending high-cycle fatigue coupled with statistical modelling, and the fatigue-crack-growth behavior of HEAs, are reviewed. The effects of sample defects and nanotwins-deformation mechanisms on four-point-bending high-cycle fatigue of HEAs are discussed in detail. The influence of stress ratio and temperature on fatigue-crack-growth characteristics of HEAs is also discussed. HEAs could exhibit comparable or greater fatigue properties, relative to conventional materials. Finally,the possible future work regarding the fatigue behavior of HEAs is suggested.
基金The study was reviewed and approved by the Wayne State University Institutional Review Board(Protocol Number:IRB-20-04-2126).
文摘BACKGROUND The Coronavirus Disease 2019(COVID-19)caused by the severe acute respiratory syndrome coronavirus 2 virus is an international health concern with substantial morbidity and mortality.COVID-associated cystitis(CAC),presents as new onset or exacerbated urinary symptoms,resembling overactive bladder(OAB)symptoms.AIM To examines the long-term outcomes of patients with CAC in the context of Long COVID.METHODS A cohort of 350 patients admitted to Detroit Hospitals with COVID-19 between May and December 2020,displaying CAC symptoms following discharge,was prospectively followed.Initial urologic evaluations occurred at 10-14 wk and were repeated at 21-28 mo postdischarge.Symptoms were managed conservatively,employing behavioral modifications and standard OAB medications.Participants completed surveys assessing urinary symptoms and quality of life(QoL)at both time points.The primary outcome was the Urology Care Foundation Overactive Bladder Assessment Tool.RESULTS 87%of the final cohort(n=310)reported symptom improvement at 21-28 mo post-discharge.Patients with new onset CAC symptoms showed a median decrease of 9-10 points in OAB and QoL scores,while those with existing symptoms experienced a decrease of 6 points.Overall,95.4%of patients with new onset symptoms reported symptom improvement at follow-up,contrasting with 60.7%among those with existing symptoms.CONCLUSION This study presents the first long-term follow-up of adult patients with CAC,revealing a promising prognosis with conservative management measures in the context of Long COVID.These findings provide reassurance to patients regarding symptom resolution and underscore the need for further research into this evolving aspect of COVID-19's impact on urological health.
文摘Background/Aims: Longitudinal studies on the relationship between hepatitis B virus (HBV) genotypes and reactivation of hepatitis B and progression to cirrhosis were very rare. Methods: Liver biochemistry, virological markers and ultrasound were monitored in 202 hepatitis B e antigen (HBeAg)positive patients with normal alanine aminotransferase (ALT) at baseline for 3- 20 (average 10.8) years, and the outcome was correlated with HBV genotypes. Results: There were 150 genotype B and 52 genotype C patients. Hepatitis activity during the HBeAg- positive phase showed no significant difference. However, genotype B was associated with a significantly earlier and higher rate of HBeAg seroconversion. HBeAg seroconversion correlated with age at entry for genotype B and with ALT levels for genotype C. Reactivation of hepatitis B was significantly more common in genotype C patients. Five genotype B and 10 genotype C patients progressed to cirrhosis. Multivariate analysis revealed that genotype C (P=0.03) and reactivation of hepatitis B (P=0.0004) were independent factor predictive of cirrhosis. Conclusions: Rate and factors of HBeAg seroconversion, and rate of reactivation of hepatitis B differed between genotype B and genotype C patients. Genotype C and reactivation of hepatitis B were associated with increased risk of cirrhosis.
文摘We investigate two configurations of Raman fiber amplifier in the 1530-1570 nm region. The gain spectrum variation is decreased from 8.31 dB to 2.48 dB when appropriately adjust the individual two pumps and optical fiber.
基金supported by the "National"Science Council of Taiwan, China (No. NSC 92-2211-E-241-008,96-2221-E-241-011-MY3)
文摘Diesel soot aggregates emitted from a model dynamometer and 11 on-road vehicles were segregated by a micro-orifice uniform deposit impactor （MOUDI）. The elemental contents and morphological parameters of the aggregates were then examined by scanning electron microscopy coupled with an energy dispersive spectrometer （SEM-EDS）, and combined with a fractional Brownian motion （fBm） processor. Two mode-size distributions of aggregates collected from diesel vehicles were confirmed. Mean mass concentration of 339 mg/m3 （dC/dlogdp） existed in the dominant mode （180-320 nm）. A relatively high proportion of these aggregates appeared in PM 1, accentuating the relevance regarding adverse health effects. Furthermore, the fBm processor directly parameterized the SEM images of fractal like aggregates and successfully quantified surface texture to extract Hurst coefficients （H） of the aggregates. For aggregates from vehicles equipped with a universal cylinder number, the H value was independent of engine operational conditions. A small H value existed in emitted aggregates from vehicles with a large number of cylinders. This study found that aggregate fractal dimension related to H was in the range of 1.641-1.775, which is in agreement with values reported by previous TEM-based experiments. According to EDS analysis, carbon content ranged in a high level of 30%-50% by weight for diesel soot aggregates. The presence of Na and Mg elements in these sampled aggregates indicated the likelihood that some engine enhancers composed of biofuel or surfactants were commonly used in on-road vehicles in Taiwan. In particular, the morphological H combined with carbon content detection can be useful for characterizing chain-like or cluster diesel soot aggregates in the atmosphere.
基金the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.51621004)the National Natural Science Foundation of China(Nos.51871092,11772122,and 51771233)+4 种基金the State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body(No.71865015)the Fundamental Research Funds for the Central Universities(No.531107051151)the National Key Research and Development Program of China(Nos.2016YFB0700300 and 2016YFB1100103)support of the U.S.Army Research Office Project(Nos.W911NF-13-1-0438 and W911NF-19-2-0049)with the program managerssupport from the National Science Foundation(Nos.DMR-1611180 and 1809640)with the program directors,Drs.J.Yang,J.G.Shiflet,and D.Farkas。
文摘High-entropy amorphous alloys present high hardness,but low tensile ductility.Here,deformation behavior of the amorphous/crystalline Fe Co Cr Ni high-entropy alloy(HEA)composite prepared by the previous experiment is investigated using atomic simulations.The result shows the partial dislocations in the crystal HEA layer,and the formation of shear bands in the amorphous HEA layer occurs after yielding.The strength of the amorphous/crystalline HEA composite reduces with increasing the thickness of the amorphous layer,agreeing with the previous experiments.The coupled interaction between the crystal plasticity and amorphous plasticity in amorphous/crystalline HEA composites results in a more homogeneous redistribution of plastic deformation to cause interface hardening,due to the complex stress field in the amorphous layer.The current findings provide the insight into the deformation behavior of the amorphous/crystalline HEA composite at the nanoscale,which are useful for optimizing the structure of the HEA composite with high strength and good plasticity.
文摘Dynamic strain aging （DSA） effect on SA508-III reactor pressure vessel （RPV） steel was investigated. The SA508-III RPV steel was subjected to tension tests at different strain rates （1.1× 10-5 s-1 and 6.6× 10-5 s-1） and different temperatures （500 and 550 ℃） to evaluate the influence of strain rate and temperature on the serrated flow behavior, which is the repetitive and discontinuous yielding phenomenon on the stress-strain curves. The higher temperature leads to the higher density of precipitates, M23C6 carbides and needle-like Mo2C carbides. It was found that the samples under tension test of 6.6 × 10-5 s-1 and 500 ℃ possess superior mechanical properties and mainly show A-type serrations on the tension test curves. Then, the local regress method was used to filter the DSA curves, thus to show the real trend of the curves. It has been found that the less time of interaction between dislocations and precipitates under higher strain rates leads to a higher strength of the sample. The more tiny-stress drops on the 550 ℃ serration curve can be attributed to the hardening phase, M23C6 carbides and needle-like Mo2C carbides. The higher percentage of the small stress drops on the serration curves represents the higher mechanical strength.
