| 1. |
- Cheng, Q., et al.
(författare)
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Unveiling anneal hardening in dilute Al-doped AlxCoCrFeMnNi (x=0, 0.1) high-entropy alloys
- 2021
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Ingår i: Journal of Materials Science & Technology. - : Elsevier BV. - 1005-0302. ; 91, s. 270-277
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Tidskriftsartikel (refereegranskat)abstract
- Anneal hardening has been one of the approaches to improve mechanical properties of solid solution alloys with the face-centered cubic (FCC) structure, whereby a considerable strengthening can be attained by annealing of cold-worked alloys below the recrystallization temperature (T-rx). Microscopically, this hardening effect has been ascribed to several mechanisms, i.e. solute segregation to defects (dislocation and stacking fault) and short-range chemical ordering, etc. However, none of these mechanisms can well explain the anneal hardening recently observed in phase-pure and coarse-grained FCC-structured high-entropy alloys (HEAs). Here we report the observations, using high-resolution electron channeling contrast imaging and transmission electron microscopy, of profuse and stable dislocation substructures in a cold-rolled CoCrFeMnNi HEA subject to an annealing below T-rx. The dislocation substructures are observed to be thermally stable up to T-rx, which could arise from the chemical complexity of the high-entropy system where certain elemental diffusion retardation occurs. The microstructure feature is markedly different from that of conventional dilute solid solution alloys, in which dislocation substructures gradually vanish by recovery during annealing, leading to a strength drop. Furthermore, dilute addition of 2 at.% Al leads to a reduction in both microhardness and yield strength of the cold-rolled and subsequently annealed (<= 500 degrees C) HEA. This Al induced softening effect, could be associated with the anisotropic formation of dislocation substructure, resulting from enhanced dislocation planar slip due to glide plane softening effect. These findings suggest that the strength of HEAs can be tailored through the anneal hardening effect from dislocation substructure strengthening.
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| 2. |
- Yoshiji, Satoshi, et al.
(författare)
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Proteome-wide Mendelian randomization implicates nephronectin as an actionable mediator of the effect of obesity on COVID-19 severity
- 2023
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Ingår i: Nature Metabolism. - : Springer Nature. - 2522-5812. ; 5, s. 248-264
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Tidskriftsartikel (refereegranskat)abstract
- How obesity contributes to COVID-19 severity is not fully understood. In this study, Yoshiji et al. found that the plasma protein nephronectin partially mediates the effect of obesity on the risk of COVID-19 severity using a two-step Mendelian randomization approach and omics analyses. Obesity is a major risk factor for Coronavirus disease (COVID-19) severity; however, the mechanisms underlying this relationship are not fully understood. As obesity influences the plasma proteome, we sought to identify circulating proteins mediating the effects of obesity on COVID-19 severity in humans. Here, we screened 4,907 plasma proteins to identify proteins influenced by body mass index using Mendelian randomization. This yielded 1,216 proteins, whose effect on COVID-19 severity was assessed, again using Mendelian randomization. We found that an s.d. increase in nephronectin (NPNT) was associated with increased odds of critically ill COVID-19 (OR = 1.71, P = 1.63 x 10(-10)). The effect was driven by an NPNT splice isoform. Mediation analyses supported NPNT as a mediator. In single-cell RNA-sequencing, NPNT was expressed in alveolar cells and fibroblasts of the lung in individuals who died of COVID-19. Finally, decreasing body fat mass and increasing fat-free mass were found to lower NPNT levels. These findings provide actionable insights into how obesity influences COVID-19 severity.
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| 3. |
- Cheng, Q., et al.
(författare)
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Solid solution softening in a Aloi CoCrFeMnNi high-entropy alloy
- 2020
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Ingår i: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 186, s. 63-68
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Tidskriftsartikel (refereegranskat)abstract
- Solute effects on high-entropy alloys of equiatomic proportions are scientifically intriguing because there is no such well-defined "solute" and "solvent" atoms compared to those of conventional single principal element alloys. To date, most of the face-centered cubic alloys exhibit solid solution strengthening rather than softening due to the interactions between dislocations and solute atoms. Here, we present the careful experimental measurements and demonstrate solid solution softening, albeit weak, in a single phase CoCrFeMnNi through the minor addition of 2. at.% Al. This softening effect is mostly related to the decreased Peierl's stress by Al addition.
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| 4. |
- Jiang, Xiangang, et al.
(författare)
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Internal erosion of debris-flow deposits triggered by seepage
- 2023
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Ingår i: Engineering Geology. - : Elsevier BV. - 0013-7952 .- 1872-6917. ; 314, s. 107015-
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Tidskriftsartikel (refereegranskat)abstract
- Debris flows can be triggered by runoffs at considerably steep natural channels and streams. Specifically, runoffgenerated debris-flow deposits are loose mixtures, comprising coarse and fine particles. Owing to seeping water, these fine particles are eroded and transported through the skeleton formed by the coarse particles. Such erosion can modify the porosity of deposits and influence their mechanical characteristics, which can be non-negligible for geotechnical and geological engineering. In this study, seven groups of seepage tests on gravel-sand-clay mixtures with different coarse particle content proportions (48%, 52%, 60%, 70%, 80%, 90%, and 100%) were conducted to investigate the erosion characteristics of debris-flow deposits triggered by seepage flows. In particular, concentrated leak erosion, internal instability erosion, and piping were noted in the soil with a coarse particle content of 48%-80%. Further, when the coarse particle content exceeds 80%, the soil does not disintegrate. A model coupling seepage and internal erosion was also developed to characterise internal erosion. For this model, mass conservation equations were reformulated for different types of internal erosion, based on the assumptions for the pore channel erosion of suspended materials and general erosion. Moreover, an equation based on the internal erosion rate, considering the pore size distribution and hydraulic gradient, was firstly introduced for concentrated leak and internal instability erosion. This equation could efficiently evaluate the mass of particles eroded from the soil. Lastly, the model was calibrated based on experimental data; the corresponding results are discussed herein.
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| 5. |
- Lei, Xiaoqin, et al.
(författare)
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A generalized interpolation material point method for modelling coupled thermo-hydro-mechanical problems
- 2021
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Ingår i: Computer Methods in Applied Mechanics and Engineering. - : Elsevier BV. - 0045-7825. ; 386
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a Generalized Interpolation Material Point Method (GIMP) for modelling coupled thermo-hydro-mechanical (THM) processes within unsaturated porous media. The governing equations for the coupled thermo-hydro-mechanical problems are derived based on the conservation laws of mass, momentum and energy, and are discretized within the framework of the explicit three-phase single-point GIMP. The proposed THM-coupled GIMP is validated against available analytical solutions and FEM-based numerical solutions, and is used for simulating a climate-driven slope failure process involving both temperature variation and rainfall infiltration. The proposed THM-coupled GIMP is proved to be capable to capture the fully coupled thermo-hydro-mechanical process within unsaturated porous media associated with large deformations.
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| 6. |
- Li, Xiaoqing, et al.
(författare)
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Antihyperuricemic Effect of Green Alga Ulva lactuca Ulvan through Regulating Urate Transporters
- 2021
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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 69:38, s. 11225-11235
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Tidskriftsartikel (refereegranskat)abstract
- A novel polysaccharide from Ulva lactuca (ULP) was purified using a Sepharose CL-4B column. Fourier transform infrared spectroscopy, high-performance liquid chromatography, and nuclear magnetic resonance spectroscopy were employed to analyze the structure of ULP. It consisted of rhamnose (Rha), glucuronic acid (GluA), galactose (Gal), and xylose (Xyl) at a molar ratio of 32.75:22.83:1.07:6.46 with the molecular weight of 2.24 x 10(5) Da. The four major glycosidic residues found in ULP were -> 2,3)-alpha-L-Rhap-(1 ->, -> 4)-beta-D-GlcpA-(1 ->, -> 2,6)-beta-D-Galp-(1 ->, and -> 4)-beta-D-Xylp-(1 ->. The antihyperuricemic activity of ULP was exhibited by detecting related biochemical indexes, urate transporter gene expressions, renal histopathology, and intestinal microbiota shifts. ULP obviously decreased the levels of serum uric acid (UA), blood urea nitrogen, and creatinine, while inhibited serum and hepatic xanthine oxidase activities as well as improved renal injury in hyperuricemic mice. Furthermore, the upregulation of UA excretion genes ABCG2/OAT1 and downregulation of UA resorption genes URAT1 and GLUT9 were detected. In addition, ULP exerted its antihyperuricemic effect through regulating the intestinal microbiome, characterized by elevating the helpful microbial abundance, meanwhile declining the harmful bacterial abundance and restoring the gut microbiome homeostasis. This study demonstrates the antihyperuricemic activity of ULP and its potential effect for the treatment of hyperuricemia-related diseases.
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| 7. |
- Mu, Cuicui, et al.
(författare)
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Ecosystem CO2 Exchange and Its Economic Implications in Northern Permafrost Regions in the 21st Century
- 2023
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Ingår i: Global Biogeochemical Cycles. - 0886-6236. ; 37:11
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Tidskriftsartikel (refereegranskat)abstract
- Climate warming increases carbon assimilation by plant growth and also accelerates permafrost CO2 emissions; however, the overall ecosystem CO2 balance in permafrost regions and its economic impacts remain largely unknown. Here we synthesize in situ measurements of net ecosystem CO2 exchange to assess current and future carbon budgets across the northern permafrost regions using the random forest model and calculate their economic implications under the Shared Socio-economic Pathways (SSPs) based on the PAGE-ICE model. We estimate a contemporary CO2 emission of 1,539 Tg C during the nongrowing season and CO2 uptake of 2,330 Tg C during the growing season, respectively. Air temperature and precipitation exert the most control over the net ecosystem exchange in the nongrowing season, while leaf area index plays a more important role in the growing season. This region will probably shift to a carbon source after 2,057 under SSP5-8.5, with a net emission of 17 Pg C during 2057–2100. The net economic benefits of CO2 budget will be $4.5, $5.0, and $2.9 trillion under SSP1-2.6, SSP2-4.5, and SSP5-8.5, respectively. Our results imply that a high-emission pathway will greatly reduce the economic benefit of carbon assimilation in northern permafrost regions.
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| 8. |
- Qin, Gang, et al.
(författare)
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An as-cast high-entropy alloy with remarkable mechanical properties strengthened by nanometer precipitates
- 2020
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Ingår i: Nanoscale. - : ROYAL SOC CHEMISTRY. - 2040-3364 .- 2040-3372. ; 12:6, s. 3965-3976
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Tidskriftsartikel (refereegranskat)abstract
- High-entropy alloys (HEAs) with good ductility and high strength are usually prepared by a combination of forging and heat-treatment processes. In comparison, the as-cast HEAs typically do not reach strengths similar to those of HEAs produced by the forging and heat-treatment processes. Here we report a novel equiatomic-ratio CoCrCuMnNi HEA prepared by vacuum arc melting. We observe that this HEA has excellent mechanical properties, i.e., a yield strength of 458 MPa, and an ultimate tensile strength of 742 MPa with an elongation of 40%. Many nanometer precipitates (5-50 nm in size) and domains (5-10 nm in size) are found in the inter-dendrite and dendrite zones of the produced HEA, which is the key factor for its excellent mechanical properties. The enthalpy of mixing between Cu and Mn, Cr, Co, or Ni is higher than those of mixing between any two of Cr, Co, Ni and Mn, which leads to the separation of Cu from the CoCrCuMnNi HEA. Furthermore, we reveal the nanoscale-precipitate-phase-forming mechanism in the proposed HEA.
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| 9. |
- Qin, Gang, et al.
(författare)
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Experimental and theoretical investigations on the phase stability and mechanical properties of Cr7Mn25Co9Ni23Cu36 high-entropy alloy
- 2021
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Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454 .- 1873-2453. ; 208
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the mechanisms of phase formation and their influence on the mechanical behavior is crucial for materials used in structural applications. Here, the phase decomposition under heat treatment in the Cr7Mn25Co9Ni23Cu36 (atomic percentage) high-entropy alloy and how secondary phases formed affect its tensile mechanical response are reported. The microstructural analysis shows that heat treatment at 800 degrees C /2 h and 600 degrees C /8 h led to the formation of sigma phase, but the sigma phase was not observed for 2 h heat treatment at 600 degrees C and below. The experimentally observed thermal stability and phases are compared to the calculated phase diagram and rationalized by recourse to thermodynamics and kinetics. The mechanism of phase decomposition is discussed based on ab initio calculations, indicating that decomposition into two solid solution phases is energetically preferred over a single solid solution phase with nominal composition.
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| 10. |
- Qu, Muchao, et al.
(författare)
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Mechanical and electrical properties of carbon nanotube/epoxy/glass-fiber composites intended for nondestructive testing
- 2023
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Ingår i: Polymers for Advanced Technologies. - : Wiley. - 1042-7147 .- 1099-1581. ; 34:8, s. 2554-2563
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Tidskriftsartikel (refereegranskat)abstract
- In this study, ternary polymer composites sheets comprising glass fiber (GF) reinforced epoxy with various fractions of carbon nanotubes (CNT) were manufactured using hot-pressing technology. A multiscale morphology analysis was presented using scanning electron microscopy. The thermal behavior of the glass fiber reinforced polymer (GFRP) was investigated using thermogravimetric analysis, DSC, and DMA, which indicated an application temperature up to 71°C for the composites. Mechanical uniaxial stretching and three-points bending tests showed that the addition of 0.1–0.2 wt% CNT decreased the dissipated energy of the specimen by 50% and increased the Young's modulus by more than 100%. During all stretching and bending measurements, the relative change in electrical resistance (RCR) was recorded as function of strain, revealing a relationship between the electrical signal and the applied deformation of the GFRP. Finally, the standard equation for fitting RCR versus strain was optimized, reducing the number of fitting parameters from five to three. The electrical and mechanical properties of the CNT/GF/epoxy composites show that they are suitable sensoring materials for wind-turbine blades and other glass-fiber reinforced epoxy constructions, especially for nondestructive testing.
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