Fundamental study of narrow-gap welding with oscillation laser beam

Laser welding with oscillation laser beams enables control of the heat input distribution. In this study, we attempted to develop a narrow-gap welding process with oscillation laser welding. This process is expected to prevent a lack of fusion because the entire bottom to the groove can be melted by the oscillation laser. As the first step of the study, bead-on-plate welding experiments with an oscillation laser beam were performed to investigate the relationship between the welding conditions and welding results. The experiments revealed that the oscillation conditions strongly affect the welding penetration shape. It was clarified that the wire melting phenomena in oscillation laser welding differed from those of straight (non-oscillation) laser welding. Additionally, narrow-gap laser welding experiments were performed to investigate the relationship between the oscillation conditions and gap width. The results confirmed the effectiveness of oscillation laser welding for narrow-gap welding.     

Rheological properties of polypropylene/high-density polyethylene blend melts. I. Capillary flow properties

Three kinds of isotactic polypropylenes (PP) with different melt flow indexes (MFIs) were melt-blended with three kinds of high-density polyethylenes (HDPE) with different MFI using a screw extruder, and the morphologies and capillary flow properties such as flow curve, entrance effect, Barus effect, and melt fracture were studied. When HDPE contents were 70 wt % or above and PP particles formed the disperse phase, the size of the particles decreased with decreasing viscosity of PP. When HDPE contents were 30 wt % or below and HDPE particles formed the disperse phase, the size of the particles was minimum when the viscosities of PP and HDPE were similar. The die swell ratios of the blends were higher than those of the components. On the other hand, the entrance correction coefficients of the blends were intermediate between those of the components. There was no correlation between the die swell ratio and the entrance corretion coefficient. Therefore, it is not always appropriate to regard the entrance correction coefficient as a measure of melt elasticity in the case of inhomogeneous polymer systems such as PP/HDPE blend.     

Antibacterial Activity of Photocatalytic Titanium Dioxide Thin Films with Photodeposited Silver on the Surface of Sanitary Ware

The antibacterial activity of photocatalytic titanium dioxide (TiO₂) thin films with photodeposited silver on the surface of sanitary ware was studied. Samples were prepared by coating a TiO₂ sol that was calcined at 880°–980°C and photodeposited with silver ions onto the glazed layer of the sanitary ware. The relationships between the antibacterial activity and the fabrication conditions were investigated by X-ray diffractometry, scanning electron microscopy, and colorimetry. The phase of TiO₂ identified in the thin films was a mixture of anatase and rutile. The amount of rutile phase increased as the calcination temperature increased, and grain growth of the TiO₂ particles was observed. The activity was dependent on the TiO₂ thickness, the calcination temperature, and the amount of silver. These results suggest that the antibacterial activity was strongly affected by the amount of anatase in the thin films.     

Mitochondria‐Targeting Polyamine–Protoporphyrin Conjugates for Photodynamic Therapy

Two polyamine derivatives of protoporphyrin IX (PPIX) were tested as photodynamic therapy (PDT) agents in HT29 colorectal cancer and HEP3B liver cancer cell lines. These compounds exhibit excellent singlet oxygen quantum yields and show strong in vitro PDT efficacy after 660 nm laser irradiation, whereas exogenous PPIX itself exhibits much weaker PDT effects. Confocal microscopy imaging studies reveal that a protoporphyrin derivative with eight amine moieties has excellent water solubility, and localizes mainly in the mitochondria of both HT29 and HEP3B cells, whereas the cellular distribution of a protoporphyrin derivative with four amine moieties is not as specific. This work demonstrates that polyamine moieties on macrocycles can enhance PDT efficacy by targeting mitochondria.     

Synthesis and powder properties of titanium—Zinc phosphate white pigments

Photocatalytically active titanium dioxide and zinc oxide are used as a white pigment for cosmetics, leading to decomposition of a certain degree of sebum on the skin upon exposure to the ultraviolet radiation in sunlight. Herein, as novel white pigments for use in cosmetics, titanium‐zinc phosphates were prepared from titanium sulfate, zinc sulfates, and phosphoric acid. The chemical composition, powder properties, photocatalytic activity, color phase, smoothness, and acid resistance of the titanium‐zinc phosphates were evaluated. Samples prepared at high titanium ratio were easy to be amorphous phase, on the other hand, samples prepared at high zinc ratio indicated the X‐ray diffraction peaks of zinc phosphate dihydrate. The photocatalytic activity of these titanium‐zinc phosphate particles was low; thus these pigments should not induce decomposition of sebum on the skin. All samples prepared in this study exhibited high reflectance within the range of visible light. The substitution with titanium is effective to improve acid resistance of zinc phosphate white pigments.     

Compatibility of cassava starch films as nitric oxide carrier for potential medical device

Films prepared with bioabsorbable materials (cassava starch, glycerol, and carboxymethyl cellulose (CMC)) can be used as an external support in the myocardial revascularization surgery, releasing nitric oxide (NO) during the tissue regeneration. In the present study, these materials submitted to in vitro degradation tests under physiological conditions, presented the reduction of 38% of weight loss by the modification of native starch using sodium trimetaphosphate (STMP) (15 g/100g of starch). The CMC addition of 10 g/100g of cassava starch increased 119% of the tensile strength of the films in comparison with films prepared without CMC. It was verified that the ruthenium complex trans‐[Ru(NH₃)₄(isn)(NO)](BF₄)₃ incorporated in the starch based films behave similarly as in aqueous solution, releasing NO by photochemical reaction. Macrophage cells were detected in in vivo degradation tests in rats around the implant after 1 and 7 days, and complete biodegradation was observed after 30 days. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41382.     

Fundamental safety strategy against severe accidents on prototype sodium-cooled fast reactor

The accident categories of severe accidents (SAs) for prototype sodium-cooled fast reactor (SFR) which need proper measures were investigated through the internal event probabilistic risk assessment (PRA) and event tree analysis for the external event and six accident categories, unprotected loss of flow (ULOF), unprotected transient over power (UTOP), unprotected loss of heat sink (ULOHS), loss of reactor sodium level (LORL), protected loss of heat sink (PLOHS) and station blackout (SBO), were identified. Fundamental safety strategy against these accidents is studied and clearly stated considering the characteristics and existing accident measures of prototype SFR, and concrete measures based on this safety strategy are investigated and organized. The sufficiency of these SA measures is confirmed by comparing the evaluated core damage frequency (CDF) and containment failure frequency (CFF) to the target value, 1×10^?5 and 1×10^?6 per plant operating year, respectively, which were selected based on the IAEA's safety target. However, the target value of CDF and CFF should be satisfied considering all the SAs caused by both internal and external events. External event PRA for prototype SFR is now under evaluation and we set out to satisfy the target value of CDF and CFF considering both internal and external events.     

Chemical composition of the terpenoids in wood and knots of Abies species

Oily constituents were obtained from sapwood and knots of Abies balsamea and A. alba using steam-distillation, and the chemical compositions were determined by gas chromatography and gas chromatography–mass spectrometry. The oily constituents of sapwood and knots of A. balsamea were mainly oxygenated diterpenes with manoyl oxide (1), epi-13-manoyl oxide (2), manool (3), and epi-13-manool (4). Moreover, 2 and 3 were found to be components in A. alba. The constituents of sound knots were dominated by oxygenated diterpenes, together with 2 and 3. Comparison of the content of oxygenated diterpenes from the material revealed that dead knots of A. balsamea contained a large quantity of 4, which was higher than in sapwood. Knots of both Abies spp. contained large quantities of oxygenated diterpenes that were also higher than in sapwood.     

Using promoter replacement and selection for loss of heterozygosity to generate an industrially applicable sake yeast strain that homozygously overproduces isoamyl acetate

By application of the high-efficiency loss of heterozygosity (HELOH) method for disrupting genes in diploid sake yeast (Kotaka et al., Appl. Microbiol. Biotechnol., 82, 387–395 (2009)), we constructed, from a heterozygous integrant, a homozygous diploid that overexpresses the alcohol acetyltransferase gene ATF2 from the SED1 promoter, without the need for sporulation and mating. Under the conditions of sake brewing, the homozygous integrant produced 1.4 times more isoamyl acetate than the parental, heterozygous strain. Furthermore, the homozygous integrant was more genetically stable than the heterozygous recombinant. Thus, the HELOH method can produce homozygous, recombinant sake yeast that is ready to be grown on an industrial scale using the well-established procedures of sake brewing. The HELOH method, therefore, facilitates genetic modification of this rarely sporulating diploid yeast strain while maintaining those characteristics required for industrial applications.