Long-term creep deformation property of modified 9Cr–1Mo steel Kimura, K.; Kushima, H.; Sawada, K.
Materials science & engineering. A, Structural materials : properties, microstructure and processing,
06/2009, Letnik:
510
Journal Article, Conference Proceeding
Recenzirano
The first volume of “Atlas of Creep Deformation Properties” was published on modified 9Cr–1Mo steels in March 2007, as a part of the NIMS (National Institute for Materials Science) Creep Data Sheet ...series. Creep deformation properties up to about 70,000
h have been investigated. No clear steady-state creep stage has been observed, and creep deformation of the steel consists of transient and accelerating creep stages. Good linear relationships between creep strain vs. time and creep rate vs. time were observed within a transient stage in a log–log plot. It was appropriately expressed by a power law rather than an exponential law, logarithmic law and Blackburn's equation. With decrease in stress, the magnitude of creep strain at the onset of accelerating creep stage decreased from about 2% in the short-term to less than 1% in the long-term region. Life fraction of the time to specific strain of 1% creep strain and 1% total strain, to time to rupture tended to increase with decrease in stress. The time to 1% total strain, that is an important parameter for design of high temperature components, was observed to lie in the transient creep stage in the short-term regime, however, it shifted to the accelerating creep stage in the long-term regime. For evaluation of long-term creep strength properties, an experimental creep test data should be extrapolated in consideration of the stress dependence of creep deformation properties.
•Sexual dimorphic development of gyrification was examined in the ferret cerebrum by MRI-based morphometry.•The global gyrification index (GI) increased linearly from postnatal days (PDs) 4–21, ...reached a peak at PD 42.•Age-dependent sexual difference was obtained by greater global GI in males than in females on PD 21 and thereafter.•Male greater sulcal GI was noted in sulci located on the prefrontal and parietotemporal regions on PD 42 and thereafter.•We concluded that sexually dimorphic ontogenetic trajectory of the sulcal folding in the ferret cortex was biphasic.
The present study characterized quantitatively sexual dimorphic development of gyrification by MRI-based morphometry. High spatial-resolution 3D MR images (using RARE sequence with short TR and minimum TE setting) were acquired from fixed brain of male and female ferrets at postnatal days (PDs) 4–90 using 7-tesla preclinical MRI system. The gyrification index was evaluated either throughout the cerebral cortex (global GI) or in representative primary sulci (sulcal GI). The global GI increased linearly from PD 4, and reached a peak at PD 42, marking 1.486±0.018 in males and 1.460±0.010 in females, respectively. Sexual difference was obtained by greater global GI in males than in females on PD 21 and thereafter. Rostrocaudal GI distribution revealed an overall male-over-female sulcal infolding throughout the cortex on PD 21. Then, an adult pattern of sexually dimorphic cortical convolution was achieved so that gyrification in the temporo-parieto-occipital region was more progressive in males than in females on PD 42, and slightly extended posteriorly in males until PD 90. In the sulcal GI, sulcus-specific male-over-female GI was revealed in the rhinal fissure, and presylvian sulcus on PD 42, and additionally in the coronal, splenial, lateral, and caudal suprasylvian sulci on PD 90. The current results suggest that age-related sexual dimorphism of the gyrification was biphasic in the ferret cortex. A male-over-female gyrification was allometric by PD 21, and was thereafter specific to primary sulci located on phylogenetically newer multimodal cortical regions.
The role of the fibronectin receptor, α(5)β(1)-integrin, as an adhesion receptor and in angiogenesis is well established. However, its role in cancer cell invasion and metastasis is less clear. We ...describe a novel mechanism by which fibronectin regulates ovarian cancer cell signaling and promotes metastasis. Fibronectin binding to α(5)β(1)-integrin led to a direct association of α(5)-integrin with the receptor tyrosine kinase, c-Met, activating it in a hepatocyte growth factor/scatter factor (HGF/SF) independent manner. Subsequently, c-Met associated with Src, and activated Src and focal adhesion kinase (FAK). Inhibition of α(5)β(1)-integrin decreased the phosphorylation of c-Met, FAK and Src, both in vitro and in vivo. Independent activation of c-Met by its native ligand, HGF/SF, or overexpression of a constitutively active FAK in HeyA8 cells could overcome the effect of α(5)β(1)-integrin inhibition on tumor cell invasion, indicating that α(5)β(1)-integrin is upstream of c-Met, Src and FAK. Inhibition of α(5)β(1)-integrin on cancer cells in two xenograft models of ovarian cancer metastasis resulted in a significant decrease of tumor burden, which was independent of the effect of α(5)β(1)-integrin on angiogenesis. These data suggest that fibronectin promotes ovarian cancer invasion and metastasis through an α(5)β(1)-integrin/c-Met/FAK/Src-dependent signaling pathway, transducing signals through c-Met in an HGF/SF-independent manner.
In the hole-doped cuprates, a small number of carriers suppresses antiferromagnetism and induces superconductivity. In the electron-doped cuprates, on the other hand, superconductivity appears only ...in a narrow window of high-doped Ce concentration after reduction annealing, and strong antiferromagnetic correlation persists in the superconducting phase. Recently, Pr(1.3-x)La0.7Ce(x)CuO4 (PLCCO) bulk single crystals annealed by a protect annealing method showed a high critical temperature of around 27 K for small Ce content down to 0.05. Here, by angle-resolved photoemission spectroscopy measurements of PLCCO crystals, we observed a sharp quasi-particle peak on the entire Fermi surface without signature of an antiferromagnetic pseudogap unlike all the previous work, indicating a dramatic reduction of antiferromagnetic correlation length and/or of magnetic moments. The superconducting state was found to extend over a wide electron concentration range. The present results fundamentally challenge the long-standing picture on the electronic structure in the electron-doped regime.
► In Gr.91 steel, premature creep failure occurred in the long-term at 600
°C and 650
°C. ► Dislocation structure slightly recovered during creep up to later stage of tertiary creep. ► Number density ...of MX particles abruptly decreased in tertiary stage due to the Z-phase formation. ► The decrease in number density of MX particles causes decrease in creep resistance.
Microstructural changes during creep at 600
°C under 70
MPa were investigated in the case of interrupted Gr.91 steel samples by taking into account the dislocation structure and Z-phase formation. The creep life monotonically increased with a decrease in the applied stress at each temperature considered in the study. However, the long-term creep life was shorter than that determined from the short-term creep data at 600
°C and 650
°C, meaning premature failure. The subgrain size gradually increased during creep up to 70,000
h, after which rapid subgrain coarsening occurred. Preferential recovery of the subgrain structure occurred around the prior-austenite grain boundary (PAGB) after 50,000
h and 70,000
h. After creep rupture, subgrain recovery was observed over the entire area of each sample. Z-phase formation was clearly visible for 30,000
h after creep. The number density of the MX particles gradually decreased after 30,000
h because of Z-phase formation. After creep rupture, the number density of the MX particles was almost the same as that of the Z-phase particles. During creep, the V content of the Z-phase gradually increased but the Nb content decreased. Changes in the chemical composition of the Z-phase occurred after a longer time in Gr.91 steel than in 12Cr steel.
MicroRNA (miRNA; miR) is a class of small regulatory RNA molecules, the aberrant expression of which can lead to the development of cancer. We recently reported that overexpression of miR-21 and/or ...miR-155 leads to activation of the phosphoinositide 3-kinase (PI3K)-AKT pathway in malignant lymphomas expressing CD3(-)CD56(+) natural killer (NK) cell antigen. Through expression analysis, we show in this study that in both NK/T-cell lymphoma lines and samples of primary lymphoma, levels of miR-150 expression are significantly lower than in normal NK cells. To examine its role in lymphomagenesis, we transduced miR-150 into NK/T-cell lymphoma cells, which increased the incidence of apoptosis and reduced cell proliferation. Moreover, the miR-150 transductants appeared senescent and showed lower telomerase activity, resulting in shortened telomeric DNA. We also found that miR-150 directly downregulated expression of DKC1 and AKT2, reduced levels of phosphorylated AKT(ser473/4) and increased levels of tumor suppressors such as Bim and p53. Collectively, these results suggest that miR-150 functions as a tumor suppressor, and that its aberrant downregulation induces continuous activation of the PI3K-AKT pathway, leading to telomerase activation and immortalization of cancer cells. These findings provide new insight into the pathogenesis of malignant lymphoma.
The proto-oncogene BMI1 and its product, Bmi1, is overexpressed in various types of tumors, particularly in aggressive tumors and tumors resistant to conventional chemotherapy. BMI1/Bmi1 is also ...crucially involved in cancer-initiating cell maintenance, and is recurrently upregulated in mantle cell lymphoma (MCL), especially aggressive variants. Recently, side population (SP) cells were shown to exhibit tumor-initiating characteristics in various types of tumors. In this study, we show that recurrent MCL cases significantly exhibit upregulation of BMI1/Bmi1. We further demonstrate that clonogenic MCL SP shows such tumor-initiating characteristics as high tumorigenicity and self-renewal capability, and that BMI1 was upregulated in the SP from recurrent MCL cases and MCL cell lines. On screening for upstream regulators of BMI1, we found that expression of microRNA-16 (miR-16) was downregulated in MCL SP cells by regulating Bmi1 in the SPs, leading to reductions in tumor size following lymphoma xenografts. Moreover, to investigate downstream targets of BMI1 in MCL, we performed cross-linking/chromatin immunoprecipitation assay against MCL cell lines and demonstrated that Bmi1 directly regulated pro-apoptotic genes such as BCL2L11/Bim and PMAIP1/Noxa, leading to enhance anti-apoptotic potential of MCL. Finally, we found that a proteasome inhibitor bortezomib, which has been recently used for relapsed MCL, effectively induced apoptosis among MCL cells while reducing expression of Bmi1 and increasing miR-16 in MCL SP. These results suggest that upregulation of BMI1 and downregulation of miR-16 in MCL SP has a key role in the disease's progression by reducing MCL cell apoptosis. Our results provide important new insight into the pathogenesis of MCL and strongly suggest that targeting BMI1/Bmi1 might be an effective approach to treating MCL, particularly refractory and recurrent cases.
We report a proof of concept experiment illustrating the implementation of several simple quantum logic gates on D-level quantum systems (quDits) using the Talbot effect. A number of QuDit states are ...encoded into the transverse profile of a paraxial laser beam using a spatial light modulator. These states are transformed through a diagonal phase element and then free-propagation via the fractional Talbot effect, demonstrating the realization of some well-known single quDit gates in quantum computation. Our classical optics experiment allows us to identify several important technical details, and serves as a first experimental step in performing D-dimensional quantum operations with single photons or other quantum systems using this scheme.
The microstructure of the heat affected zone after welding was investigated in Mod.9Cr–1Mo steel, using TEM and STEM-EDX. The microstructure of thin foil was observed at the fusion line, and at the ...positions of 0.5mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm and 3.5mm to the base metal side of the fusion line. Martensite structure with very fine lath and high dislocation density was confirmed at all positions. Twins with a twin plane of (112) were locally observed at all positions. Elemental mapping was obtained for all positions by means of STEM-EDX. Inclusions of mainly Si were formed at the fusion line but not at the other positions. No precipitates could be detected at the fusion line or at the position of 0.5mm. On the other hand, MX particles were observed at the positions of 1.0mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm and 3.5mm even after welding. M23C6 particles were also confirmed at the positions of 2.0mm, 2.5mm, 3.0mm and 3.5mm. Very fine equiaxed grains were locally observed at the positions of 2.0mm and 2.5mm. The Cr content of the equiaxed grains was about 12mass%, although the martensite area included about 8mass% Cr.
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•Nonequilibrium microstructure of heat affected zone was observed after welding in Mod.9Cr–1Mo steel.•Inclusions containing Si were detected at the fusion line.•Undissolved M23C6 and MX particles were confirmed in heat affected zone.•Twins with a twin plane of (112) were locally observed at all positions.•Very fine ferrite grains with high Cr content were observed in fine grained heat affected zone.
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