Influence of boron on ferrite formation in copper-added spheroidal graphite cast iron

This paper reviews the original work of the authors published recently,describing the influence of B on the matrix of the Cuadded spheroidal graphite cast iron.The effect of Cu has been corrected as a ferrite formation promoter in the matrix of the grey cast iron by the usage of high-purity material.Also,this paper focuses on the ferrite formation and the observation of the Cu distribution in the B-added and B-free Cu-containing spheroidal graphite cast iron.The Cu film on the spheroidal graphite can be successfully observed in the B-free sample using a special etching method.However,in the B-added sample,no Cu film could be found,while the secondary graphite was formed on the surface of the spheroidal graphite.The interaction between B and Cu is stressed as a peculiar phenomenon by the employment of a contrast experiment of B and Mn.The heat treatment could make Cu precipitate more significantly in the eutectic cells and in the matrix in the form of large Cu particles because of the limited solubility of Cu.     

A methodology to predict a fission gas release ratio of MOX fuel with heterogeneous microstructure

The objective of this study is to formulate a methodology to predict a fission gas release ratio of MIMAS MOX. An irradiated MIMAS MOX fuel with plutonium rich agglomerates was subjected to elemental analyses by electron probe micro analysis and secondary ion mass spectrometry in order to investigate xenon distribution. The results of the elemental analyses showed that the plutonium rich agglomerates at the periphery of the fuel pellet sample retained a high concentration of xenon as gas bubbles. Then, the results were used as reference data for modification of models in a fuel rod analysis code, FEMAXI-7. Using the modified FEMAXI-7, we applied an approach to prediction of fission gas release ratio of MOX fuel with plutonium rich agglomerates. In the approach, two separated analyses using FEMAXI-7 were performed for the plutonium rich agglomerates and the matrix. Fission gas release ratios obtained from the two analyses were processed through weighted-average with burnup ratios of the plutonium rich agglomerates and the matrix. Finally, the fission gas release ratios were compared with results of rod puncture tests. As a result of the comparison, it was confirmed that the proposed approach could well predict fission gas release ratio of MOX fuel with plutonium rich agglomerates.     

Effects of roughness pitch of surfaces on their wettability

The surface roughness factors, such as the Wenzel roughness factor and so on, are very interrelated to each other. Therefore, it makes a precise discussion difficult on how the surface roughness affects the wettability. We already reported the effect of the surface roughness on the wettability at a constant Wenzel roughness factor using two kinds of models, the hemisphere close packing model and the hemiround rod close lining model. Nevertheless, the pitch is proportional to the height in these models. Therefore, we could not independently discuss the influence of roughness height and roughness pitch on the wettability. We developed our new models which can independently describe the influence of the surface roughness height and the roughness pitch on the wettability. We simulated loose packing sphere models by periodically placing small ball bearings and the loose lining round rod models by winding fine wires. The wettability was measured by the sessile drop method for the non-wetting system using paraffin coated samples and aqueous solutions. These results show that there is a critical pitch which determines the maximum contact angle in both systems. These results can be explained by the ratio of the solid/liquid/vapor and liquid/vapor line length at the three phase line.     

Formation Mechanism of Chunky Graphite and Its Preventive Measures

The formation mechanism of chunky graphite has been reviewed and studied. The study consisted of a unidirectional solidification method, a small droplet method and a furnace cooling method. Four kinds of iron samples were prepared, namely, the pure Fe-C, Fe-C-S, Fe-C-Ce and Fe-C-Si-Ce alloys, and three kinds of nickel samples, namely the Ni-C, Ni-C-S and Ni-C-Mg alloys. The results of the unidirectional solidification of the Ni-C alloys showed that spheroidal graphite is not observed in the continuous solidified region, in which only flake-like graphite is observed, while spheroidal graphite is usually observed in the quenched liquid region. The existence of spheroidal graphite in the solidified phase is recognized only in the discontinuous growth mode of the Ni-C-Mg alloy solidified at 150 mm/h. This means that the spheroidal graphite is directly crystallized from the melt and entrapped by the flake-like chunky graphite that is formed by the continuous growth mode. In the small droplet method, a small piece of the Fe-C or Fe-C-Ce sample was melted on a pure graphite plate then cooled at a different cooling rate in a He-3%H2 atmosphere. The graphite in the Fe-C-Ce alloy is usually spherical. Nevertheless, the graphite morphology of the final solidified area changed from spherical to chunky and chunky to ledeburite with an increase in the cooling rate. This means that the chunky graphite is formed in the residual liquid region by the solidification into Fe-graphite system. The sample was cooled in a furnace, and the graphite morphology changes from spherical to chunky and chunky to ledeburite with the decrease in the Si content. These phenomena can be confirmed by the cooling curves of these samples.     

Regulatory T Cells Exhibit Interleukin-33-Dependent Migratory Behavior during Skin Barrier Disruption

Regulatory T cells (Tregs) suppress immune responses and maintain immunological self-tolerance and homeostasis. We currently investigated relationships between skin barrier condition and Treg behavior using skin barrier-disrupted mice. Skin barrier disruption was induced by repeated topical application of 4% sodium dodecyl sulfate (SDS) on mice. The number of CD4⁺ forkhead box protein P3 (Foxp3)⁺ Tregs was higher in 4% SDS-treated skins than in controls. This increasing was correlated with the degree of acanthosis. The numbers of interleukin (IL)-10⁺ and transforming growth factor (TGF)-β⁺ Tregs also increased in 4% SDS-treated skins. Localization of IL-33 in keratinocytes shifted from nucleus to cytoplasm after skin barrier disruption. Notably, IL-33 promoted the migration of Tregs in chemotaxis assay. The skin infiltration of Tregs was cancelled in IL-33 neutralizing antibody-treated mice and IL-33 knockout mice. Thus, keratinocyte-derived IL-33 may induce Treg migration into barrier-disrupted skin to control the phase transition between healthy and inflammatory conditions.     

Pitavastatin Reduces Lectin-Like Oxidized Low-Density Lipoprotein Receptor-1 Ligands in Hypercholesterolemic Humans

The aim of this study was to determine the impact of pitavastatin on low-density lipoprotein cholesterol (LDL-C) and lectin-like oxidized LDL receptor-1 (LOX-1) in patients with hypercholesterolemia. Twenty-five hypercholesterolemic patients (8 male, 17 female; age 66 ± 13, 21–80 years) who had not received anti-dyslipidemic agents and had LDL-C levels of more than 160 mg/dL were examined. Biochemical factors were measured at baseline and after treatment with pitavastatin (2 mg/day) for 6 months. Serum levels of LOX-1 with apolipoprotein B-100 particle ligand and a soluble form of LOX-1 (sLOX-1) were measured by ELISA. All subjects completed the study with no adverse side effects. Total-C (268 ± 26 vs. 176 ± 17 mg/dL), LDL-C (182 ± 21 vs. 96 ± 14 mg/dL), and LOX-1 ligand (867 ± 452 vs. 435 ± 262 ng/mL) were reduced with pitavastatin treatment (P < 0.0001 for each). Significant decreases in triacylglycerols were noted (P < 0.0001), but there were no changes in high-density lipoprotein cholesterol. After 6 months, there were no significant changes in high-sensitivity CRP or soluble LOX-1. At baseline, there were no significant correlations between LOX-1 ligand and either LDL-C or sLOX-1. The decrease in LOX-1 ligand was not correlated with the decrease in LDL-C, but was correlated with the decrease in sLOX-1 (r = 0.47, P < 0.05). In conclusion, pitavastatin therapy had beneficial effects on markers of oxidative stress in hypercholesterolemic subjects. Serum levels of LOX-1 ligand may be a useful biomarker of the pleiotropic effects of statins.     

Effect of modification and ceramic particles on solidification behavior of aluminum-matrix composites

Thermal analysis is used to establish the relationship between solidification history and the microstructure of SiC particulate reinforced Al-Si alloy-matrix composites. The results show that cooling curves are influenced by the presence of SiC particles and by strontium modification. The eutectic growth temperature of SiC_P/359 composites modified with Sr lies in the range of 840 to 843 K, i.e., about 5 to 7 K higher than that of Sr-modified unreinforced 359. For the same composite, the eutectic undercooling is higher with Sr modification than without. The eutectic solidification time of the composites is shorter than that of the unreinforced base alloy because of the presence of the ceramic particles. Strontium modification has the tendency to extend the eutectic solidification time. Microstructure analysis reveals that Sr modification has a refining effect on eutectic silicon for the composites, and SiC particles in the composite melt serve as the substrates for eutectic Si phase nucleation.     

The role of mex-gene products in antibiotic extrusion in Pseudomonas aeruginosa

The antibiotic extrusion machinery in Pseudomonas aeruginosa is assembled from the mex-operon encoded proteins, OprM and MexA-MexB, connecting the outer and inner membranes. To envisage the role of these proteins in antibiotic extrusion and resistance, we employed the gene replacement technique to construct mutants deficient in mexA, mexB, or oprM, and all possible combinations of these genes. Using the Southern and the Western blotting methods, we confirmed that only the target genes were disrupted. All the mutants deficient in OprM exhibited a 4 to 16 times higher susceptibility against quinolone antibiotics, chloramphenicol, and gentamicin than the parent strain. The mutants deficient in MexA or MexB or both MexA and MexB were only 2 to 4 times more susceptible to these antibiotics than the parent strain. All the mutants lacking MexA, MexB, or OprM showed stereospecific hypersusceptibility to beta-lactam antibiotics than the parent strain. However, the extent of susceptibility to each beta-lactam was comparable among the mutants. Strains lacking OprM accumulated the highest level of ciprofloxacin among all these isogenic strains. The strains lacking either MexA or MexB accumulated lower levels of ciprofloxacin than the mutant lacking OprM, but the levels were still higher than in the parent strain. The results are consistent with the antibiotic susceptibility of these strains. These results suggest that the extrusion of antibiotics occurs most efficiently with a whole assembly of MexA/B-OprM, but it remains a possibility that OprM interacts with a putative inner membrane pump(s).     

The feasibility study on perfect burning reactor system

The system of 100% natural uranium burning with once-through fuel cycle is defined as the Perfect Burning Reactor System (PBRS). This kind of nuclear system can be expected to have some good characteristic such as resource efficiency, radiotoxicity reduction, proliferation and nuclear safety. Therefore, the feasibility of the concept is studied in this paper. The preliminary results show that the system of 100% natural uranium burning with once-through fuel cycle is physically possible with a plenty supply of external neutron, and that the system demands no activities concerning with fuel cycle such as uranium enrichment, fuel fabrication, spent fuel reprocessing and radioactive waste treatment. The study also quantitatively clarifies the external neutron source strength, the nuclear criticality safety, the demanded accelerator performance and the energy balance. In addition, the more precise analysis is requested for well understanding and improving the characteristic and economical rationality of the system.