ABSTRACT
Long-range ordered phases in most high-entropy and medium-entropy alloys (HEAs/MEAs) exhibit poor ductility, stemming from their brittle nature of complex crystal structure with specific bonding state. Here, we propose a design strategy to severalfold strengthen a single-phase face-centered cubic (fcc) Ni2CoFeV MEA by introducing trigonal κ and cubic L12 intermetallic phases via hierarchical ordering. The tri-phase MEA has an ultrahigh tensile strength exceeding 1.6 GPa and an outstanding ductility of 30% at room temperature, which surpasses the strength-ductility synergy of most reported HEAs/MEAs. The simultaneous activation of unusual dislocation multiple slip and stacking faults (SFs) in the κ phase, along with nano-SF networks, Lomer-Cottrell locks, and high-density dislocations in the coupled L12 and fcc phases, contributes to enhanced strain hardening and excellent ductility. This work offers a promising prototype to design super-strong and ductile structural materials by harnessing the hierarchical ordered phases.
ABSTRACT
Body-centered cubic refractory metallic materials exhibit excellent high-temperature strength, but often suffer from brittle intergranular fracture due to the recrystallization-induced enrichment of trace elements at grain boundaries (GBs). Here, we report a fully-recrystallized pure molybdenum (Mo) material with room temperature (RT) superplasticity, fabricated by a facile method of powder metallurgy, Y-type hot rolling and annealing. By engineering the ultralow concentration of O at GBs, the inherent GB brittleness of Mo can be largely eliminated, which, in conjunction with high fractions of soft texture and low angle GBs, enables a significant development of ordered dislocation networks and the effective dislocation transmission across low angle GBs. Synergy of these factors greatly suppress the brittle intergranular fracture of Mo, contributing to an enhanced deformability of 108.7% at RT. These findings should have general implication for fabricating a broad class of refractory metals and alloys toward harsh applications.
ABSTRACT
Netrin-1 is typically known as a neuronal guidance factor. Studies have reported the proangiogenic, antiapoptotic, and antiinflammatory properties of Netrin-1. A critical role for Netrin-1 in ischemic organ damage, myocardial infarction (MI) in particular, has also been demonstrated, making Netrin-1 a potential therapeutic target for the treatment of cardiovascular diseases (CVDs). Mesenchymal stem cells (MSCs) have shown promising therapeutic efficacy in preclinical studies. However, limited clinical success was observed, mainly due to poor MSC survival. Given the reported beneficial impact of Netrin-1 in tissue repair and cell survival, we examined the effects of Netrin-1 in MSC therapy against MI-induced ischemic cardiac injury in rats and type 2 diabetic (T2D) mice. MSCs were isolated and Netrin-1-expressing MSCs were obtained by transduction with a Netrin-1-encoding retroviral vector. The Netrin-1-MSCs were then delivered intramyocardially to the infarct sites of rats and T2D mice with MI. Thirty days after MSC implantation, changes at the infarct area, level of collagen deposition, and cardiac hypertrophy were assessed. Molecular mechanisms underlying the effects of Netrin-1 were also investigated. Attenuated MI-induced myocardial dysfunction was observed after Netrin-1-MSC treatment. Protective effects of the Netrin-1-MSCs were attributable primarily to better MSC survival and migration, which is mediated by Netrin-1-induced phosphorylation of p44/42 mitogen-activated protein kinase. Netrin-1-stimulated nitric oxide production was also responsible, which could promote neovessel formation and progenitor cell mobilization in vivo. We report a protective role for Netrin-1 against MI-induced ischemic injuries, reinstating its promising potential as a therapeutic target for CVDs and, more importantly, for patients with CVD with coexisting diabetes.
Subject(s)
Mesenchymal Stem Cell Transplantation/methods , Mesenchymal Stem Cells/metabolism , Myocardial Infarction/pathology , Myocardial Infarction/therapy , Nerve Growth Factors/metabolism , Tumor Suppressor Proteins/metabolism , Analysis of Variance , Animals , Blotting, Western , DNA Primers/genetics , Genetic Vectors/genetics , Humans , Male , Mice , Mice, Inbred C57BL , Nerve Growth Factors/genetics , Netrin-1 , Nitric Oxide/metabolism , Peptide Fragments/metabolism , Phosphorylation , Rats , Rats, Sprague-Dawley , Retroviridae , Reverse Transcriptase Polymerase Chain Reaction , Tetrazolium Salts , Thiazoles , Transcription Factors , Transduction, Genetic , Tumor Suppressor Protein p53/metabolism , Tumor Suppressor Proteins/geneticsABSTRACT
A rapid, reliable and sensitive reverse-phase high-performance liquid chromatography method with fluorescence detection (RP-FLD-HPLC) was developed and validated for simultaneous analysis of the abamectin (ABA), emamectin (EMA) benzoate and ivermectin (IVM) residues in rice. After extraction with acetonitrile/water (2 : 1) with sonication, the avermectin (AVMs) residues were directly derivatised by N-methylimidazole (N-NMIM) and trifluoroacetic anhydride (TFAA) and then analysed on RP-FLD-HPLC. A good linear relationship (r(2 )> 0.99) was obtained for three AVMs ranging from 0.01 to 5 microg ml(-1), i.e. 0.01-5.0 microg g(-1) in rice matrix. The limit of detection (LOD) and the limit of quantification (LOQ) were between 0.001 and 0.002 microg g(-1) and between 0.004 and 0.006 microg g(-1), respectively. Recoveries were from 81.9% to 105.4% and precision less than 12.4%. The proposed method was successfully applied to routine analysis of the AVMs residues in rice.
