Investigation on selection crystal behavior of a Ni3Al-based single crystal superalloy IC6SX

AbstractThe grain selection occurring during the solidification of a Ni3Al-base single crystal superalloy IC6SX prepared by spiral grain selection method was studied systematically. Results showed that the equiaxed grains were transformed into columnar grains within starter block and most of columnar grains then will be eliminated. The crystal were formed after the remained columnar grains were eliminated through preferred growth and coupling of spiral structure in Spiral grain selection. The results can explain the competitive growth mechanism of the spiral grain selection and can be used to optimize process design to lay an important foundation for improving preparation processes of single crystal superalloy

miR-338-5p Regulates the Viability, Proliferation, Apoptosis and Migration of Rheumatoid Arthritis Fibroblast-Like Synoviocytes by Targeting NFAT5

Background/Aims: MicroRNAs (miRNAs) have been reported to be involved in Rheumatoid arthritis (RA) pathogenesis and prognosis. However, little is known about the disease mechanism in RA. Here, we aim to investigate the potential association between miR-338-5p and NFAT5 in RA. Methods: Aberrant expression of miR-338-5p in RA tissues and rheumatoid arthritis fibroblast-like synoviocytes (RAFLSs) compared to the normal were determined by RT-qPCR. Cell viability was determined using the CCK-8 assay, and cell apoptosis was analyzed via Annexin V-FITC/PI double staining and was detected using flow cytometry. The targeted relationship was determined by TargetScan database and dual luciferase reporter gene assay. Results: Upregulation of miR-338-5p facilitated the proliferation, migration, invasion and induced G0/G1 arrest of RAFLSs while miR-338-5p inhibitor functioned oppositely. Nuclear factor of activated T-cells 5 (NFAT5) was confirmed as a downstream target of miR-338-5p which expression was directly suppressed by miR-338-5p. Overexpression of NFAT5 attenuated the proliferation and metastasis of RAFLSs and those changes could be rescued by co-transfection of miR-338-5p. Conclusion: miR-338-5p promotes RAFLS’s viability and proliferation, migration by targeting NFAT5, suggesting a novel therapeutic strategy for RA

5-Fluorouracil targets thymidylate synthase in the selective suppression of TH17 cell differentiation

While it is well established that treatment of cancer patients with 5-Fluorouracil (5-FU) can result in immune suppression, the exact function of 5-FU in the modulation of immune cells has not been fully established. We found that low dose 5-FU selectively suppresses TH17 and TH1 cell differentiation without apparent effect on Treg, TH2, and significantly suppresses thymidylate synthase (TS) expression in TH17 and TH1 cells but has a lesser effect in tumor cells and macrophages. Interestingly, the basal expression of TS varies significantly between T helper phenotypes and knockdown of TS significantly impairs TH17 and TH1 cell differentiation without affecting the differentiation of either Treg or TH2 cells. Finally, low dose 5-FU is effective in ameliorating colitis development by suppressing TH17 and TH1 cell development in a T cell transfer colitis model. Taken together, the results highlight the importance of the anti-inflammatory functions of low dose 5-FU by selectively suppressing TH17 and TH1 immune responses

Effects of Normal Force on the Tribocorrosion Behavior of a Nickel-Based Superalloy in Alkaline Solution: An Electrochemical Study

The tribocorrosion behavior of Inconel 690TT in NaOH (pH = 9.8) solution at different normal forces was investigated by an electrochemical method. The results indicated that normal force had a great effect on the tribocorrosion behavior and mechanism. When normal force increased from 15 to 30 N, fretting regime was in gross slip regime (GSR), and wear volume gradually increased. When normal force further increased to 45 N, wear volume significantly decreased due to the fretting regime changing from GSR to partial slip regime (PSR). When fretting ran in GSR, the corrosion resistance decreased with the negative shift of open circuit potential (OCP). However, when the fretting regime changed to PSR, the corrosion reaction significantly decreased due to the adhesive wear. Fretting wear broke the passive film at the contacting surface, which caused the worn surface to be more active and prone to corrosion. However, the broken passive film was quickly repaired in subsequent oxidation. The break and repair of passive film strongly depended on normal force. In GSR, the increase in normal force aggravated the break of passive film. In PSR, the passive film was not easy to break with a further increase of normal force

Effect of Stress on Creep Behavior of Single Crystal Alloy IC6SX at 980°C

Ni3Al-based single crystal alloy IC6SX was prepared by seed crystal method. The effect of different stress conditions on creep behavior of this alloy at 980°C was investigated. The results showed that the creep life of this alloy at 980°C decreased significantly with the increase of stress. When the stress increased from 180 MPa to 230 MPa, the creep life dropped from 245.5 h to 69.3 h, and the steady-state creep rate increased slightly but not significantly. Meanwhile, the morphology of γ′ phase and dislocation after creep were studied. The results showed that with the increase of stress, the density of dislocations in the γ′ phase increased gradually, the strength of this alloy decreased gradually, so the creep life decreased significantly. The Y-NiMo phase resolved from the γ phase decreased gradually as the creep life decreased. The creep experiment of the alloy was carried out at 980°C. Due to the higher temperature, the diffusion of atoms in this alloy became faster. Deformation was not only caused by the slippage of dislocations in the crystal but also by the diffusion of atoms. Therefore, the creep mechanism of single crystal alloy IC6SX at this temperature is a mixed mechanism of dislocation glide and diffusion

Fast Algorithm of Numerical Solutions for Strong Nonlinear Partial Differential Equations

Because of a high mobility ratio in the chemical and gas flooding for oil reservoirs, the problems of numerical dispersion and low calculation efficiency also exist in the common methods, such as IMPES and adaptive implicit methods. Therefore, the original calculation process, “one-step calculation for pressure and multistep calculation for saturation,” was improved by introducing a velocity item and using the fractional flow in a direction to calculate the saturation. Based on these developments, a new algorithm of numerical solution for “one-step calculation for pressure, one-step calculation for velocity, and multi-step calculation for fractional flow and saturation” was obtained, and the convergence condition for the calculation of saturation was also proposed. The simulation result of a typical theoretical model shows that the nonconvergence occurred for about 6,000 times in the conventional algorithm of IMPES, and a high fluctuation was observed in the calculation steps. However, the calculation step of the fast algorithm was stabilized for 0.5 d, indicating that the fast algorithm can avoid the nonconvergence caused by the saturation that was directly calculated by pressure. This has an important reference value in the numerical simulations of chemical and gas flooding for oil reservoirs

Theoretical Simulation Study on Controlling Factors in Horizontal Well CO Stimulation of Heavy Oil

Since CO 2 Stimulation in Horizontal Wells can avoid the problem of steam flooding, clay swelling, and sand production, it has been carried out in many fields. To improve the research on the controlling factors and their influence and establish a specific reservoir selecting method, this paper founded the components and geology model according to typical heavy oil reservoirs firstly. Comparing with pilot test, the theoretical model result could give expression to the characteristic of large water ratio descend rang, long period of validity, and high rounds effectiveness. Secondly, this study designed simulation scheme including factors of geology, development, and stimulation technology, to filter the controlling factors of the oil incremental and well reopened water cut and describe their influence. Based on it, we proposed a quick filter criterion to choose heavy oil reservoirs for CO 2 stimulation

The effect of Al and Cr elements on the oxidation resistance of MoSi2 via first-principles calculation

The properties of structure, energy and oxidation resistance of interstitial and substitutable MoSi2 systems have been investigated using the density functional theory. The calculated lattice constants for pristine MoSi2 confirm the early experimental results. In the interstitial MoSi2, the impurity energy of O atom was computed for the stable interstitial site in the systems. The results reveal that the O atom prefers to occupy the Oct2 site with the lowest impurity energy. In the substitution MoSi2, the Si sites tend to be substituted with Al and Cr atoms, whereas, Mo sites do not behave like the Si sites. The co-substitution of Al/Cr atoms and the direction of the O diffusion in MoSi2 have been analyzed as well. The results from electronic structural analysis indicate that the Si-O bond is the main factor to inhibit the diffusion of O, and the alloying elements of Al and Cr contribute to the oxidation resistance of MoSi2. Keywords: MoSi2, Alloying element, Impurity, Substitution, Oxidation resistanc

Effects of MgO Expansive Agent and Steel Fiber on Crack Resistance of a Bridge Deck

To prevent cracks caused by shrinkage of the deck of the Xiaoqing River Bridge, MgO concrete (MC) and steel fiber reinforced MgO concrete (SMC) were used. The deformation and strength of the deck were measured in the field, the resistance to chloride penetration of the concrete was measured in the laboratory, and the pore structure of the concrete was analyzed by a mercury intrusion porosimeter (MIP). The results showed that the expansion caused by the hydration of MgO could suppress the shrinkage of the bridge deck, and the deformation of the deck changed from −88.3 × 10−6 to 24.9 × 10−6, effectively preventing shrinkage cracks. At the same time, due to the restriction of the expansion of MgO by the steel bars, the expansion of the bridge deck in the later stage gradually stabilized, and no harmful expansion was produced. When steel fiber and MgO were used at the same time, the three-dimensional distribution of steel fiber further limited the expansion of MgO. The hydration expansion of MgO in confined space reduced the porosity of concrete, optimized the pore structure, and improved the strength and durability of concrete. The research on the performance of concrete in the in-situ test section showed that MgO and steel fiber were safe for the bridge deck, which not only solved the problem of shrinkage cracking of the bridge deck but also further improved the mechanical properties of the bridge deck