A vast number of materials properties and phenomena are regulated by diffusion. However, diffusion coefficients from experiments and calculations are far from complete. Here, we report a compilation ...of vacancy formation energies (HVaF), vacancy migration energies (HVaM), vacancy activation energies (HVaQ), vacancy concentrations (CVa), and vacancy-mediated self-diffusion coefficients (DVa) as a function of temperature for 82 pure elements in bcc, fcc, and hcp structures by means of a comprehensive first-principles study. We assess the accuracy of four exchange-correlation (X–C) functionals for first-principles calculations, including the local density approximation (LDA), two generalized gradient approximations (PW91 and PBE), and PBEsol – the focus of the present work. To gain temperature-dependent diffusion properties, transition state structure searches are performed by the climbing image nudged elastic band method; and the needed equilibrium properties of energy (E0), volume (V0), bulk modulus (B0) and its pressure derivative (B′) for each structure of each element are estimated via an energy versus volume equation of state. Examination of the predicted quantities and available experimental data indicates that (i) PBEsol is a better selection in terms of getting accurate equilibrium and diffusion properties; (ii) the facility of vacancy migration can be understood from the redistribution of differential charge density, and anomalous energy pathways for vacancy migration are found for hcp Ce, La, Pr, Ti, and Zr within the basal plane; (iii) HVaQ can be predicted well from the melting point of a pure element and in particular a new relationship (HVaQ=B0V0/6), suggesting diffusivity is governed by interatomic bonding strength; and (iv) the computed quantities such as CVa, DVa, HVaF, HVaM, and HVaQ are in favorable accord with available experiments for most elements, but fall short for entropy-related properties. The present study of pure elements provides not only diffusion-related properties and a new understanding of diffusivity, but also a benchmark of first-principles calculations and a foundational dataset for the Materials Genome Initiative.
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Nickel (Ni)‐based superalloys for high‐temperature applications are often designed to form a continuous and slow‐growing oxide scale by adding Al and Cr and other beneficial elements. In the present ...work, the critical Al concentration in Ni–Al alloys needed to establish an α‐Al2O3 scale in contrast to internal oxide formation is predicted as a function of temperature by means of the CALPHAD approach coupled with models in the literature, which account for the thermodynamics and kinetics of oxidation. The present thermodynamic remodeling of the Ni–O system results in a better agreement with experimental data of oxygen solubility in Ni at high temperatures. The oxygen solubility is combined with kinetic parameters to determine oxygen permeability in Ni, and the critical Al concentration needed to establish an α‐Al2O3 scale at a given exposure temperature. Good agreement is found with available experimental data for both oxygen permeability and critical Al concentration, indicating the capacity of the CALPHAD approach to tailor oxidation resistance for materials of interest using thermodynamic and kinetic knowledge.
Graphical : Schematic representation of oxidation and critical Al concentration to form external Al2O3 scale in the Ni–Al alloy system.
The phase relations and thermodynamic properties of the Al–Co–Cr, Al–Co–Ni, Co–Cr–Ni ternary alloys are investigated using first principles calculations based on DFT (density functional theory). ...Their thermodynamic descriptions are developed by means of the CALPHAD (calculations of phase diagrams) method using experimental and computational data from the present work and the literature. Emphasis is placed on modeling the A2, B2, fcc-γ, L12-γ′ and tetragonal-σ phases in the temperature range of 1173–1623K. Liquid, A2 and fcc-γ phases are modeled using substitutional solution descriptions. A partitioning model is then used for the γ/γ′ and A2/B2 phases to effectively describe the order–disorder transitions. The critically assessed thermodynamic descriptions describe all experimentally determined phase equilibria data well. A2/B2 transitions are also shown to agree well with previous experimental findings in the Al–Co–Cr ternary system.
•A modified Al–Co–Cr thermodynamic assessment is presented.•A new Al–Co–Ni thermodynamic assessment is presented.•A new Co–Cr–Ni thermodynamic assessment is presented.•DFT calculations are used to supplement the dataset.•Important ternaries for the Al–Co–Cr–Ni quaternary presented.
The phase relations and thermodynamic properties of the condensed Al-Co-Cr ternary alloy system are investigated using first-principles calculations based on density functional theory (DFT) and ...phase-equilibria experiments that led to X-ray diffraction (XRD) and electron probe micro-analysis (EPMA) measurements. A thermodynamic description is developed by means of the calculations of phase diagrams (CALPHAD) method using experimental and computational data from the present work and the literature. Emphasis is placed on modeling the bcc-A2, B2, fcc-γ, and tetragonal-σ phases in the temperature range of 1173 to 1623 K. Liquid, bcc-A2 and fcc-γ phases are modeled using substitutional solution descriptions. First-principles special quasirandom structures (SQS) calculations predict a large bcc-A2 (disordered)/B2 (ordered) miscibility gap, in agreement with experiments. A partitioning model is then used for the A2/B2 phase to effectively describe the order-disorder transitions. The critically assessed thermodynamic description describes all phase equilibria data well. A2/B2 transitions are also shown to agree well with previous experimental findings.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Titanium alloys are highly sought after due to their excellent mechanical properties. One of the most commonly used Ti alloys is Ti–6Al–4V, which contains 6%Al and 4%V by weight. Despite the ...popularity of this alloy, no thermodynamic description of the ternary Al–Ti–V system has been published in the open literature. In this work an assessment procedure of the ternary Al–Ti–V system was initiated based on the binary descriptions by Witusiewitcz et al. (J. Alloys Compds. 465 (2008) 64–77 1) for (Al-Ti), Gong et al. (Int. J. Mater. Res. 95 (2004) 978–986 2) for (Al–V) and Saunders (COST 507, 2 (1998) 297–298 3) for (Ti–V). When combining the three binary systems and looking at the extrapolated ternary isothermal sections, it was found that there was a very large miscibility gap in the bcc phase. The origin of this miscibility gap was mainly the Al-V system and therefore it was decided to reassess this system. The Al–V system was reassessed according to available experimental data along with the enthalpies of formation of all compounds as well as the enthalpies of mixing for all terminal phases obtained by first-principles calculations based on the density functional theory. For the Al8V5 phase there are two different sets of data for the enthalpies of formation. These two sets are investigated in this work and it is found that the set not used by Gong et al. in their assessment of the Al–V binary system gives better extrapolations. The final description produced improved extrapolated ternary isothermal sections.
A thermodynamic database for the Al-Co-Cr-Ni system is built via the Calphad method by extrapolating re-assessed ternary subsystems. A minimum number of quaternary parameters are included, which are ...optimized using experimental phase equilibrium data obtained by electron probe micro-analysis and x-ray diffraction analysis of NiCoCrAlY alloys spanning a wide compositional range, after annealing at 900 °C, 1100 °C and 1200 °C, and water quenching. These temperatures are relevant to oxidation and corrosion resistant MCrAlY coatings, where M corresponds to some combination of nickel and cobalt. Comparisons of calculated and measured phase compositions show excellent agreement for the β-γ equilibrium, and good agreement for three-phase β-γ-σ and β-γ-α equilibria. An extensive comparison with existing Ni-base databases (TCNI6, TTNI8, NIST) is presented in terms of phase compositions.
We introduce and demonstrate a switchable novel linear polarization grating (LPG) consisting of a circular polarization grating (CPG) and a special cycloidal diffractive quarter waveplate (CQWP). The ...CQWP is developed that marvelously matches the polarization-state of beams passing through the CPG. Such an LPG is so polarization-sensitive that it can split an incident linear polarized beam into two proportionally controllable left- or right-handed circularly polarized lights. We establish rigorous simulation model based on finite element method to investigate near-field polarization-state distribution of CPGs. Furthermore, LPGs are demonstrated and the diffraction properties are obtained with simulation and Jones Matrix analysis. The combination of CPGs and CQWPs is achieved with polymerizable liquid crystal. The experimental results of deflection angle and polarization selectivity of LPGs are consistent with those of simulation.
B23/NPM is a major nucleolar phosphoprotein that has a critical role in cell proliferation and cell death. Here, we show that it forms a complex with Akt on growth factor (GF) stimulation in both the ...cytoplasm and the nucleus, for which Akt activation is indispensable. The C terminus of B23 (239-294 residues) potently binds pleckstrin homology (PH) domain of Akt. Akt binding to B23 protects it from proteolytic degradation by caspase-3, leading to the up-regulation of cell survival. Interestingly, unsumoylated B23 K263R, but not wild-type B23, strongly interacts with Akt in the nucleoplasm in the absence of GFs. Furthermore, we show that Akt2, but not other isoforms, specifically regulates B23 sumoylation and protein stability. Also, nuclear Akt regulates the cell cycle progression activity of B23. Therefore, our findings support that nuclear Akt binds and stabilizes B23 in the nucleoplasm, and regulates its activities in cell survival and cell cycle.
To investigate the value of metagenomic next-generation sequencing (mNGS) in the diagnosis of Pneumocystis jirovecii pneumonia (PJP) in patients undergoing allogeneic hematopoietic stem cell ...transplantation (allo-HSCT) .
The data of 98 patients with suspected pulmonary infection after allo-HSCT who underwent pathogen detection from bronchoalveolar lavage fluid between June 2016 and August 2023 at Nanfang Hospital were analyzed. The diagnostic performance of mNGS, conventional methods, and real-time quantitative polymerase chain reaction (qPCR) for PJP were compared.
A total of 12 patients were diagnosed with PJP, including 11 with a proven diagnosis and 1 with a probable diagnosis. Among the patients with a proven diagnosis, 1 was positive by both conventional methods and qPCR, and 10 were positive by qPCR only. Pneumocystis jirovecii was detected by mNGS in all 12 patients. The diagnostic sensitivity of mNGS for PJP was 100%, which was greater than that of conventional methods (8.3%,
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Altered glucose metabolism has been described as a cause of chemoresistance in multiple tumor types. The present study aimed to identify the expression profile of glucose metabolism in drug-resistant ...acute myeloid leukemia (AML) cells and provide potential strategies for the treatment of drug-resistant AML. Bone marrow and serum samples were obtained from patients with AML that were newly diagnosed or had relapsed. The messenger RNA expression of hypoxia inducible factor (HIF)-1α, glucose transporter (GLUT)1, and hexokinase-II was measured by quantitative polymerase chain reaction. The levels of LDH and β subunit of human F1-F0 adenosine triphosphate synthase (β-F1-ATPase) were detected by enzyme-linked immunosorbent and western blot assays. The HL-60 and HL-60/ADR cell lines were used to evaluate glycolytic activity and effect of glycolysis inhibition on cellular proliferation and apoptosis. Drug-resistant HL-60/ADR cells exhibited a significantly increased level of glycolysis compared with the drug-sensitive HL-60 cell line. The expression of HIF-1α, hexokinase-II, GLUT1 and LDH were increased in AML patients with no remission (NR), compared to healthy control individuals and patients with complete remission (CR) and partial remission. The expression of β-F1-ATPase in patients with NR was decreased compared with the expression in the CR group. Treatment of HL-60/ADR cells with 2-deoxy-D-glucose or 3-bromopyruvate increased in vitro sensitivity to Adriamycin (ADR), while treatment of HL-60 cells did not affect drug cytotoxicity. Subsequent to treatment for 24 h, apoptosis in these two cell lines showed no significant difference. However, glycolytic inhibitors in combination with ADR increased cellular necrosis. These findings indicate that increased glycolysis and low efficiency of oxidative phosphorylation may contribute to drug resistance. Targeting glycolysis is a viable strategy for modulating chemoresistance in AML.
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