Creep-Fatigue Crack Initiation Simulation of a Modified 12% Cr Steel Based on Grain Boundary Cavitation and Plastic Slip Accumulation.

High-temperature components in power plants may fail due to creep and fatigue. Creep damage is usually accompanied by the nucleation, growth, and coalescence of grain boundary cavities, while fatigue damage is caused by excessive accumulated plastic deformation due to the local stress concentration. This paper proposes a multiscale numerical framework combining the crystal plastic frame with the meso-damage mechanisms. Not only can it better describe the deformation mechanism dominated by creep from a microscopic viewpoint, but also reflects the local damage of materials caused by irreversible microstructure changes in the process of creep-fatigue deformation to some extent. In this paper, the creep-fatigue crack initiation analysis of a modified 12%Cr steel (X12CrMoWvNBN10-1-1) is carried out for a given notch specimen. It is found that creep cracks usually initiate at the triple grain boundary junctions or at the grain boundaries approximately perpendicular to the loading direction, while fatigue cracks always initiate from the notch surface where stress is concentrated. In addition to this, the crack initiation life can be quantitatively described, which is affected by the average grain size, initial notch size, stress range and holding time.

LncRNA NEAT1/miR-185-5p/IGF2 axis regulates the invasion and migration of colon cancer.

BACKGROUND: Long noncoding RNAs (lncRNA) are important in the growth and metastasis of colon cancer. The objective of this study was to describe the potential role of lncRNA NEAT1 in the progression of colon cancer. METHODS: Quantitative real-time polymerase chain reaction was used for detecting NEAT1, miR-185-5p, and IGF2 in colon cancer cells and tissues. The potential diagnostic value of NEAT1 in colon cancer was analyzed with the receiver operating characteristic curve. Kaplan-Meier method was applied for evaluating the association between NEAT1 expression and the overall survival of osteosarcoma patients, whereas Transwell assay was introduced to examine the potential invasion and migration of colon cancer cells. In addition, the binding of NEAT1/IGF2 to miR-185-5p was confirmed by RNA pull-down and RNA-binding protein immunoprecipitation assays and dual-luciferase reporter gene assay. Finally, rescue experiments were conducted to confirm the role of NEAT1/miR-185-5p/IGF2 axis in colon cancer. RESULTS: Colon cancer patients with low NEAT1 expression presented with longer overall survival than those with high expression. The migration and invasion of colon cancer cells were considerably promoted by overexpressed NEAT1. Both NEAT1 and IGF2 bound to miR-185-5p. CONCLUSION: NEAT1 upregulate IGF2 expression through absorbing miR-185-5p to enhances the migration and invasion of colon cancer cells.

To flip or not to flip? Assessing the inversion barrier of the tetraphenylene framework with enantiopure 2,15-dideuteriotetraphenylene and 2,7-dimethyltetraphenylene.

Two chiral tetraphenylenes, 2,15-dideuteriotetraphenylene (7) and 2,7-dimethyltetraphenylene (15) were synthesized and resolved to address the tetraphenylene inversion barrier problem. Neutron diffraction investigation of enantiopure 7 showed that the molecule retained its chirality integrity during its synthesis from enantiopure precursors and therefore rules out the possibility of the tetraphenylene framework possessing a low-energy barrier to inversion. Thermal study on 15 and tetraphenylene 1 further revealed that their inversion barriers were not overcome up to 600 degrees C, at which temperature these compounds underwent skeletal contraction into triphenylene with activation energies of 62.8 and 58.2 kcal/mol, respectively. This result is supported by computational studies which yielded an inversion barrier of 135 kcal/mol for tetraphenylene as a consequence of the peri-hydrogen repulsions at its planar conformation.

Synthesis, resolution, and applications of 1,16-dihydroxytetraphenylene as a novel building block in molecular recognition and assembly.

This paper concerns the synthesis of 1,16-dihydroxytetraphenylene (DHTP) (2) by employing a novel NBS bromination route. (+/-)-DHTP 2 was successfully resolved into its optical antipodes and converted to (+/-)-1,16-bis(diphenylphosphino)tetraphenylene (BPTP) (26), whose platinum complex BPTP-PtCl(2) (27) was also obtained. As a hydrogen bond donor, racemic and optically active DHTP 2 was allowed to assemble with 4,4'-bipyridine to form single crystals of good quality. X-ray Diffraction studies of these crystals revealed that the crystallographic packing of the hydrogen bonded complex between (+/-)-2 and 4,4'-bipyridine was different from the one formed from (S)-2 and 4,4'-bipyridine. It was found that an infinite zigzag chain with alternate chirality was formed in the assembly of (+/-)-2 and 4,4'-bipyridine, while (S)-2 and 4,4'-bipyridine failed to show the same assembly pattern. The reason (+/-)-2 formed an alternate and zigzag chain with 4,4'-bipyridine was most likely due to the inherent stability of this supramolecular assembly. The chiral recognition between 2 and optically active BINAP under the direction of platinum(II) has also been examined. (1)H and (31)P NMR spectroscopic studies demonstrated that there was an obvious discrimination of 2 between the enantiomers of BINAP-PtCO(3).