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[en] We present a transmission electron microscopy study on the room temperature deformation mechanisms in a Mg97Y2Zn1 (at.%) alloy with long-period-stacking-order (LPSO) phase. The alloy consists of α-Mg matrix with platelet-shaped LPSO precipitates 3–5 nm thick and interdendritic LPSO (18R structures) phase grains. The interdendritic LPSO phase was found to deform either by kink-banding in conjunction with basal < a> slip or by basal < a> slip and the formation of dislocation walls. No orientation dependence of these different deformation modes was observed. The α-Mg matrix deforms by basal < a> slip and pyramidal < c + a> slip. No twinning was observed in the α-Mg matrix during room temperature deformation. The elastic modulus mismatch between α-Mg matrix and LPSO plates is suggested to be the main source for activating non-basal dislocations. The combination of the soft α-Mg matrix strengthened by LPSO precipitates and harder “bulk” interdendritic LPSO grains is suggested to contribute to the well-known good mechanical properties of Mg-LPSO alloys at room temperature
[en] An efficient and practical preparation of 2-arylbenzo[b]furan molecules including natural egonol, XH-14, ailanthoidol, and unnatural derivatives is demonstrated using Sonogashira coupling, iodine induced cyclization and Wittig reaction. Anti-inflammatory effects of the prepared benzo[b]furans were examined in lipopolysaccharide (LPS)-stimulated RAW 264-7 macrophages. The results showed that ailanthoidol, XH-14 and three other unnatural derivatives (9-10, 13) inhibited significantly the production of inflammatory mediator nitric oxide without showing cytotoxicity
[en] It has previously been shown that indirubin derivative E804 (IDR-E804) blocks signal transducer and activator of transcription-3 signaling in human breast and prostate cancer cells and inhibits Src kinase activity. To further establish its role in angiogenesis, we tested its potential using human umbilical vein endothelial cells (HUVECs) and analyzed the effects of IDR-E804 on cellular and molecular events related to angiogenesis. The anti-angiogenic effects of IDR-E804 were examined by assessing the proliferation, migration and capillary tube formation of HUVECs were induced by vascular endothelial growth factor (VEGF) with or without various concentrations of IDR-E804. The inhibitory effect of IDR-E804 angiogenesis and tumor growth in vivo was also investigated in Balb/c mice subcutaneously transplanted with CT-26 colon cancer cells. IDR-E804 significantly decreased proliferation, migration and tube formation of vascular endothelial growth factor VEGF-treated HUVECs. These effects were accompanied by decreased phosphorylation of VEGF receptor (VEGFR)-2, AKT and extracellular signal regulated kinase in VEGF-treated HUVECs. Intratumor injections of IDR-E804 inhibited the growth of subcutaneously inoculated CT-26 allografts in syngenic mice. Immunohistochemistry revealed a decreased CD31 microvessel density index and Ki-67 proliferative index, but an increased apoptosis index in IDR-E804-treated tumors. These data revealed that IDR-E804 is an inhibitor of angiogenesis and also provide evidence for the efficacy of IDR-E804 for anti-tumor therapies
[en] Highlights: ► Polyaniline nanocomposites encapsulating gold nanoparticles on the surface of carboxymethyl cellulose were prepared. ► The synthesized composites were characterized by FTIR, SEM, and TEM. ► Temperature-dependent DC conductivity was also studied. ► The new composites may be useful for the applications of biomaterials in molecular electronics and other fields. - Abstract: Polyaniline nanocomposites encapsulating gold nanoparticles on carboxymethyl cellulose surface were prepared via the polymerization of aniline hydrochloride with different carboxymethyl cellulose (CMC) concentrations (wt.%) using HAuCl4 as oxidant. The synthesized composites were characterized by Fourier transform infrared (FTIR) spectroscopy. Surface morphology was studied by electron diffraction scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The embedded crystallinity of the composites was investigated by X-ray diffraction (XRD) analyses. The electrical property of the composites was examined by temperature-dependent DC conductivity in the range of 300–500 K. The composites exhibited higher electrical conductivities with increased CMC concentration under equivalent conditions. Activation energy for electron transport was also calculated based on the conductivity data.
[en] To increase the production of RI and labelled compounds utilizing the Korea Multipurpose Research Reactor (KMRR), development of P-32 production process, devices and tools of neutron irradiation use, GMP facilities of radiopharmaceuticals, Dy-165/Ho-166 macroaggregate of radiation synovectomy use for rheumatoid archritis have been carried out, respectively. To utilize NAA in analysis of environmental samples, experimental studies on air borne samples have also been carried out. An efficient P-32 production process obtaining high recovery of >98% with sufficiently high radionuclidic purity of >99% has been established through reaction 32S(n,p)32P and subsequent reduced pressure distillation purification. Various capsules, loading/unloading device for capsule/rigs, cole-welder for capsules, checking instrument for capsule sealing, working table/tools, transfer cask for the irradiated targets, etc. have been developed. To maintain cleanliness inside of hot cells, a modification has been proposed, and a two door type autoclave usable in GMP facility has been prepared. An efficient way of preparation of the Dy-165/Ho-166 macroaggregate of radiation synovectomy use as well as its clinical application scheme has been developed. A suitable process of environmental sample analyses has been established by carrying out NAA of standard/reference samples as well as airborne dust samples. (Author)
[en] We investigated the effect of Nb micro-alloying in the range of 0.01 to 0.l wt% on the microstructures and mechanical properties of Fe17Mn0.6C1.5Al (wt%) TWIP steel. EBSD analysis shows that the Nb addition retards recrystallization in both the hot-rolled steels and cold-rolled and annealed steels. The Nb addition in the cold-rolled and annealed TWIP steel leads to an increase in yield strength. This phenomenon is due to a combined effect of precipitation hardening and a low degree of recrystallization. Recovery annealing of the cold-rolled TWIP steels at 650 °C results in a good combination of yield strength and ductility. The steels containing 0.01 wt% and 0.025 wt% of Nb show a superior combination of UTS×TE exceeding 40,000 MPa∙% and yield strength higher than 800 MPa. The design of TWIP steels utilizing both precipitation hardening and partial recrystallization opens a way to develop steels with a superior combination of yield strength and ductility.
[en] We present a systematic atomic scale analysis of the structural evolution of long-period-stacking-ordered (LPSO) structures in the (i) α-Mg matrix and in the (ii) interdendritic LPSO phase of an Mg_9_7Y_2Zn_1 (at. %) alloy annealed at 500 °C, using high resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Various types of metastable LPSO building block clusters have been observed in both regions. The thermodynamic phase stabilities computed by density-functional-theory calculations explain the diversity of the LPSO structures which are distinguished by their different arrangements of the Y/Zn enriched LPSO building blocks that have a local fcc stacking sequence on the close packed planes. A direct evidence of the transformation from 18R to 14H is presented. This finding suggests that LPSO structures can change their separation distance — quantified by the number of α-Mg layers between them — at a low energy penalty by generating the necessary Shockley partial dislocation on a specific glide plane. Based on our results the most probable transformation sequence of LPSO precipitate plates in the α-Mg matrix is: single building block → various metastable LPSO building block clusters → 14H, and the most probable transformation sequence in the interdendritic LPSO phase is: 18R→ various metastable LPSO building block clusters → 14H. The thermodynamically most stable structures in both the α-Mg matrix and the interdendritic LPSO phase are a mixture of 14H and α-Mg.
[en] The plasticity mechanisms of press hardening steel with a fully lath martensite microstructure were examined experimentally by strain rate sensitivity measurements, repeated relaxation tests and internal friction measurements. The analysis of relaxation tests suggests that the micro-plasticity could be due to the motion of mobile non-screw dislocations, based on mobile dislocation exhaustion observed in the micro-plastic range. In the macro-plastic range, the plasticity is thought to be due to the generation of mobile screw dislocations. The solute carbon-dislocation interaction results in a negative strain rate sensitivity and a Snoek-Köster-Kê peak in the internal friction spectrum of the lath martensitic press hardening steel. The magnitude of the effective activation volume and its stress dependence indicate that plastic deformation is most likely controlled by screw dislocation motion by formation and lateral movement of kink pairs dragging solute carbon atom atmospheres. Both isotropic and kinematical hardening seem to play a role in the strain hardening behavior of lath martensitic steel.
[en] Mg alloys containing long-period stacking ordered (LPSO) structures are strong and ductile compared to conventional Mg alloys. We study here the compositional evolution of LPSO structures in a Mg97Y2Zn1 (at.%) alloy upon annealing at 500 °C using atom probe tomography. In the material annealed for 2.5 h, the Zn/Y ratio of the building blocks in the interdendritic LPSO phase (0.73) is close to the stoichiometric composition of Y8Zn6 L12 clusters while that in plate-type LPSO structures (0.66) slightly deviates from the ideal value. The Y/Zn enrichment in LPSO structures in the α-Mg matrix slightly decreases with increasing annealing time.
[en] Chrysin (5,7-dihydroxyflavone) is a natural flavone commonly found in many plants. It has previously been shown to be an anti-tumor agent. In this study, we investigated whether chrysin could alleviate the symptoms of dextran sodium sulfate (DSS)-induced colitis in mice and whether chrysin has an inhibitory effect on nuclear factor (NF)-κB activation in vitro. A significant blunting of weight loss and clinical signs was observed in DSS-exposed, chrysin-treated mice when compared to vehicle-treated mice. This was associated with a remarkable amelioration of the disruption of the colonic architecture, a significant reduction in colonic myeloperoxidase (MPO) activity, and a decrease in the production of inflammatory mediators such as nitric oxide (NO), prostaglandin (PG) E2, and pro-inflammatory cytokines. In addition, chrysin inhibited tumor necrosis factor (TNF)-α-induced activation of NF-κB in IEC-6 cells. These findings suggest that chrysin exerts potentially clinically useful anti-inflammatory effects mediated through the suppression of NF-κB activation.