Refractory high-entropy alloys hold the potential for high-temperature applications beyond the capability of the state-of-the-art Ni-based superalloys, and thus, it is important to study their solid ...solution formation characteristics and mechanical properties. In this study, designed by CALPHAD method, formation of as-cast arc-melted body-centered cubic MoNbTaTiV was experimentally verified using X-ray diffraction and scanning electron microscopy. The measured density and lattice parameter for MoNbTaTiV are 9.29g/cm3 and 3.224 Å, which obey the rule of mixtures (ROM). The alloy exhibits high hardness at 443 Hv, high yield strength at 1.4 GPa, and good compressive fracture strength at 2.45 GPa with a fracture strain of ∼30% at room temperature. The yield strength and hardness values of this alloy, and other single-phase refractory high-entropy alloys, are estimated using a simple model of solid solution strengthening. Reasonable agreement between modeling prediction and experiments is obtained. In addition, first-principles density functional theory calculations predict an enthalpy of formation of −0.865 kJ/mol for the MoNbTaTiV alloy, with calculated atomic volume and elastic properties (e.g., bulk and elastic moduli) obeying the ROM.
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•MoNbTaTiV exhibits the BCC structure, agreeing with CALPHAD calculations.•Predicted solid solution strengthening agrees well with experiments.•Hardness of BCC high entropy alloys is about three times the yield strength.•Calculated atomic volume and bulk and shear moduli obey the rule of mixtures.
This study reports the design and development of ductile and strong refractory single-phase high-entropy alloys (HEAs) for high temperature applications, based on NbTaV with addition of Ti and W. ...Assisted by CALPHAD modeling, a single body-centered cubic solid solution phase was experimentally confirmed in the as-cast ingots using X-ray diffraction and scanning electron microscopy. The observed elemental segregation in each alloy qualitatively agrees with CALPHAD prediction. The Vickers microhardnesses (and yield strengths) of the alloys are about 3 (and 3.5–4.4) times that those estimated from the rule of mixture. While NbTaTiVW shows an impressive yield strength of 1420MPa with fracture strain of 20%, NbTaTiV exhibits exceptional compressive ductility at room temperature.
Mg-based materials are promising candidates for high capacity hydrogen storage. However, their poor hydrogenation/dehydrogenation kinetics and high desorption temperature are the main obstacles to ...their applications. This paper reports a method for in situ formation of cycle stable CeH2.73-MgH2-Ni nanocomposites, from the hydrogenation of as-melt Mg80Ce18Ni2 alloy, with excellent hydrogen storage performance. The nanocomposites demonstrate reversible hydrogen storage capacity of more than 4.0 wt %, at a low desorption temperature with fast kinetics and long cycle life. The temperature for the full hydrogenation/dehydrogenation cycle of the composites is significantly decreased to 505 K, which is about 100 K lower than that for pure Mg. The hydrogen desorption activation energy is 63 ± 3 kJ/mol H2 for the composites, which is significantly lower than those of Mg3Ce alloy and pure Mg (104 ± 7 and 158 ± 2 kJ/mol H2, respectively). X-ray diffraction and transmission electron microscopy have been used to reveal the mechanism that delivers this excellent cycle stability and fast hydriding/dehydriding kinetics. It is found that the hydriding/dehydriding process is catalyzed by the combination of in situ formed extremely fine CeH2/CeH2.73 and Ni to Mg/MgH2. In addition, this nanocomposite structure can effectively suppress Mg/MgH2 grain growth and enable the material to maintain its high performance for more than 500 hydrogenation dehydrogenation cycles.
The fire characteristics under natural ventilation in the cable compartment of the utility tunnel are studied. A series of small-scale fire experimental tests are conducted to obtain the maximum ...temperature below the ceiling of different ignition vertical heights and cable types. In this paper, the ceiling temperature decay and heat release rate (HRR) are studied in the cable compartment of utility tunnel. Through experimental tests, the fire characteristics of placing the fire source on the near wall side 3.0 m away from the shaft of the utility tunnel cable compartment are studied. The results showed that under the action of natural ventilation, with the decrease of fuel quantity, the mass loss of cable decreases, and the maximum temperature below the ceiling of the cable compartment in the utility tunnel decreases. ZRYJV cables burn more sufficient combustion than RVVR cables. A new empirical association for total HRR is proposed. Those experimental test results are used as validation data for the newly proposed empirical correlation of total HRR. This paper hopes to provide some basic fire safety references for the utility tunnel planning of the urban underground cable compartment.
Purpose
To investigate the potential candidate microRNA (miRNA) biomarkers for the clinical diagnosis, classification, and prognosis of gastric cancer (GC).
Methods
We use bioinformatics overlapping ...subclasses analysis to find the tumor grade and lymphatic metastasis-related GC specific miRNAs from the Cancer Genome Atlas (TCGA) database. Then, we further investigated these GC specific miRNAs distributions in different GC clinical features and their correlations overall survival on the basis of GC patients’ information and their related RNA sequencing profile from TCGA. Finally, we randomly selected some of key miRNAs use qRT-PCR to confirm the reliability and validity.
Results
22 GC specific key miRNAs were identified (Fold-change >2,
P
< 0.05), 11 of them were discriminatively expressed with tumor size, grade, TNM stage and lymphatic metastasis (
P
< 0.05). In addition, nine miRNAs (miR-196b-5p, miR-135b-5p, miR-183-5p, miR-182-5p, miR-133a-3p, miR-486-5p, miR-144-5p, miR-129-5p and miR-145-5p) were found to be significantly associated with overall survival (log-rank
P
< 0.05). Finally, four key miRNAs (miR-183-5p, miR-486-5p, miR-30c-2-3p and miR-133a-3p) were randomly selected to validation and their expression levels in 53 newly diagnosed GC patients by qRT-PCR. Results showed that the fold-changes between TCGA and qRT-PCR were 100 % in agreement. We also found miR-183-5p and miR-486-5p were significantly correlated with tumor TNM stage (
P
< 0.05), and miR-30c-2-3p and miR-133a-3p were associated with tumor differentiation degree and lymph-node metastasis (
P
< 0.05). These verified miRNAs clinically relevant, and the bioinformatics analysis results were almost the same.
Conclusion
These key miRNAs may functions as potential candidate biomarkers for the clinical diagnosis, classification and prognosis for GC.
Abstract
Constrained by the Nielsen-Ninomiya no-go theorem, in all so-far experimentally determined Weyl semimetals (WSMs) the Weyl points (WPs) always appear in pairs in the momentum space with no ...exception. As a consequence, Fermi arcs occur on surfaces which connect the projections of the WPs with opposite chiral charges. However, this situation can be circumvented in the case of unpaired WP, without relevant surface Fermi arc connecting its surface projection, appearing singularly, while its Berry curvature field is absorbed by nontrivial charged nodal walls. Here, combining angle-resolved photoemission spectroscopy with density functional theory calculations, we show experimentally that a singular Weyl point emerges in PtGa at the center of the Brillouin zone (BZ), which is surrounded by closed Weyl nodal walls located at the BZ boundaries and there is no Fermi arc connecting its surface projection. Our results reveal that nontrivial band crossings of different dimensionalities can emerge concomitantly in condensed matter, while their coexistence ensures the net topological charge of different dimensional topological objects to be zero. Our observation extends the applicable range of the original Nielsen-Ninomiya no-go theorem which was derived from zero dimensional paired WPs with opposite chirality.
Refractory high-entropy alloys (RHEAs) are newly developed candidate materials for high-temperature applications. Among the existing RHEAs, NbMoTaW RHEA possesses the best mechanical properties with ...combined high strength, excellent thermal stability and softening resistance at elevated temperatures. However, the NbMoTaW RHEA is quite brittle at room temperature, which would restrict its application as structural material. Here, TixNbMoTaW RHEAs were developed by alloying Ti in the NbMoTaW RHEA. It shows that the room temperature ductility of the RHEAs increases from 1.9% of the NbMoTaW RHEA to 11.5% of the TiNbMoTaW RHEA, and the yield strength increases from 996MPa of the NbMoTaW RHEA to 1455MPa of the TiNbMoTaW RHEA. In addition, the TixNbMoTaW RHEAs keep stable single BCC structure up to their melt points. The present result indicates that Ti addition could effectively enhance both the ductility and strength of the NbMoTaW RHEA. The combined performance of superior mechanical properties and high thermal stability of the TixNbMoTaW RHEAs promises them an important role in engineering applications.
Organic peroxides (POs) are organic molecules with one or more peroxide (−O–O−) functional groups. POs are commonly regarded as chemically labile termination products from gas-phase radical chemistry ...and therefore serve as temporary reservoirs for oxidative radicals (HO x and RO x ) in the atmosphere. Owing to their ubiquity, active gas-particle partitioning behavior, and reactivity, POs are key reactive intermediates in atmospheric multiphase processes determining the life cycle (formation, growth, and aging), climate, and health impacts of aerosol. However, there remain substantial gaps in the origin, molecular diversity, and fate of POs due to their complex nature and dynamic behavior. Here, we summarize the current understanding on atmospheric POs, with a focus on their identification and quantification, state-of-the-art analytical developments, molecular-level formation mechanisms, multiphase chemical transformation pathways, as well as environmental and health impacts. We find that interactions with SO2 and transition metal ions are generally the fast PO transformation pathways in atmospheric liquid water, with lifetimes estimated to be minutes to hours, while hydrolysis is particularly important for α-substituted hydroperoxides. Meanwhile, photolysis and thermolysis are likely minor sinks for POs. These multiphase PO transformation pathways are distinctly different from their gas-phase fates, such as photolysis and reaction with OH radicals, which highlights the need to understand the multiphase partitioning of POs. By summarizing the current advances and remaining challenges for the investigation of POs, we propose future research priorities regarding their origin, fate, and impacts in the atmosphere.
Organic peroxides play a vital role in the formation, evolution, and health impacts of atmospheric aerosols, yet their molecular composition and fate in the particle phase remain poorly understood. ...Here, we identified, using iodometry-assisted liquid chromatography mass spectrometry, a large suite of isomer-resolved peroxide monomers (C8–10H12–18O5–8) and dimers (C15–20H22–34O5–14) in secondary organic aerosol formed from ozonolysis of the most abundant monoterpene (α-pinene). Combining aerosol isothermal evaporation experiments and multilayer kinetic modeling, bulk peroxides were found to undergo rapid particle-phase chemical transformation with an average lifetime of several hours under humid conditions, while the individual peroxides decompose on timescales of half an hour to a few days. Meanwhile, the majority of isomeric peroxides exhibit distinct particle-phase behaviors, highlighting the importance of the characterization of isomer-resolved peroxide reactivity. Furthermore, the reactivity of most peroxides increases with aerosol water content faster in a low relative humidity (RH) range than in a high RH range. Such non-uniform water effects imply a more important role of water as a plasticizer than as a reactant in influencing the peroxide reactivity. The high particle-phase reactivity of organic peroxides and its striking dependence on RH should be considered in atmospheric modeling of their fate and impacts on aerosol chemistry and health effects.
Metaplastic carcinoma of the breast (MCB) is a poorly understood subtype of breast cancer. It is generally characterized by the coexistence of ductal carcinomatous and transdifferentiated sarcomatous ...components, but the underlying molecular alterations, possibly related to epithelial-mesenchymal transition (EMT), remain elusive. We performed transcriptional profiling using half-a-genome oligonucleotide microarrays to elucidate genetic profiles of MCBs and their differences to those of ductal carcinoma of breasts (DCBs) using discarded specimens of four MCBs and 34 DCBs. Unsupervised clustering disclosed distinctive expression profiles between MCBs and DCBs. Supervised analysis identified gene signatures discriminating MCBs from DCBs and between MCB subclasses. Notably, many of the discriminator genes were associated with downregulation of epithelial phenotypes and with synthesis, remodeling and adhesion of extracellular matrix, with some of them have known or inferred roles related to EMT. Importantly, several of the discriminator genes were upregulated in a mutant Snail-transfected MCF7 cell known to exhibit features of EMT, thereby indicating a crucial role for EMT in the pathogenesis of MCBs. Finally, the identification of SPARC and vimentin as poor prognostic factors reinforced the role of EMT in cancer progression. These data advance our understanding of MCB and offer clues to the molecular alterations underlying EMT.
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