A Molecular Dynamics Study on the Dislocation-Precipitate Interaction in a Nickel Based Superalloy during the Tensile Deformation.

In the present paper, the dislocation-precipitate interaction in the Inconel 718 superalloy is studied by means of molecular dynamics simulation. The atomistic model composed of the ellipsoidal Ni3Nb precipitate (γ″ phase) and the Ni matrix is constructed, and tensile tests on the composite Ni3Nb@Ni system along different loading directions are simulated. The dislocation propagation behaviors in the precipitate interior and at the surface of the precipitate are characterized. The results indicate that the dislocation shearing and bypassing simultaneously occur during plastic deformation. The contact position of the dislocation on the surface of the precipitate could affect the penetration depth of the dislocation. The maximum obstacle size, allowing for the dislocation shearing on the slip planes, is found to be close to 20 nm. The investigation of anisotropic plastic deformation behavior shows that the composite system under the loading direction along the major axis of the precipitate experiences stronger shear strain localizations than that with the loading direction along the minor axis of the precipitate. The precipitate size effect is quantified, indicating that the larger the precipitate, the lower the elastic limit of the flow stress of the composite system. The dislocation accumulations in the precipitate are also examined with the dislocation densities given on specific slip systems. These findings provide atomistic insights into the mechanical behavior of nickel-based superalloys with nano-precipitates.

Notoginsenoside R1 attenuates breast cancer progression by targeting CCND2 and YBX3.

BACKGROUND: Breast cancer (BC) is a common malignancy with highly female incidence. So far the function of notoginsenoside R1 (NGR1), the extract from Panax notoginseng, has not been clearly elucidated in BC. METHODS: Optimal culture concentration and time of NGR1 were investigated by cell counting kit-8 assay. Cell proliferation ability was measured by colony formation assays. Transwell assay was used to detect the effect of NGR1 on cell migration and invasion. The apoptosis rate of cells between each group was measured by TUNEL assay. RESULTS: NGR1 treatment has an inhibitory effect on proliferation, migration, invasion, and angiogenesis and a stimulating effect on cell cycle arrest and apoptosis of Michigan Cancer Foundation-7 (MCF-7) cells. The 50% growth inhibitory concentration for MCF-7 cells at 24 h was 148.9 mmol/L. The proportions of MCF-7 cells arrested in the G0/G1 phase were 36.94±6.78%, 45.06±5.60%, and 59.46±5.60% in the control group, 75, and 150 mmol/L groups, respectively. Furthermore, we revealed that NGR1 treatment attenuates BC progression by targeted downregulating CCND2 and YBX3 genes. Additionally, YBX3 activates phosphatidylinositol 3-phosphate kinase (PI3K)/protein kinase B (Akt) signaling pathway by activating kirsten rat sarcoma viral oncogene, which is an activator of the PI3K/Akt signaling pathway. CONCLUSION: These results suggest that NGR1 can act as an efficacious drug candidate that targets the YBX3/PI3K/Akt axis in patients with BC.

Soil C:N:P stoichiometry at different altitudes in Mao'er Mountain, Guangxi, China.

We explored vertical distribution of soil organic carbon (C), nitrogen (N) and phosphorus (P) for examining the relationship between soil C:N:P stoichiometry and both altitudes and soil depths in Mao'er Mountain in Guangxi, South China. A total of ten sites from different altitudes were selected and soil genetic horizon samples were collected along soil profiles at each site. Soil organic C, N, P, pH, bulk density and particle size composition were measured. Results showed that soil C, N, C/P ratio and N/P ratio increased with the increases of altitude. Soil P concentrations and C/N ratio increased within low altitudes then decreased or with no obvious changes. Soil C, N, P, C/P and N/P ratios significantly decreased, whereas C/N ratio did not change with the increases of soil depth. Soil C and N highly coupled within horizons (CV of C/N was 4.0%) and soil P had little spatial variability (CV were 31.0% and 22.0% within altitudes and horizons, respectively). The results from redundancy analysis showed that the first two axes explained 74.8% of the variability of C:N:P stoichiometry. Soil pH, bulk density, and altitude had significant effects on C:N:P stoichiometry, whereas clay, silt, and sand had no effect.