Radical-initiator-Induced solid-state polymerization of butadiyne nanocrystals in water and their dispersion stabilization

Butadiyne nanocrystals in water are usually polymerized by UV or gamma-ray irradiation to give polydiacetylene (PDA) nanocrystals. In this study, we confirmed that solid-state polymerization of 1,6-di(N-carbazolyl)-2,4-hexadiyne (DCHD) and 5,7-dodecadiyn-1,12-diyl bis[N-(butoxycarbonyl-methyl)carbamate] (4BCMU) could be stimulated by water-soluble radical initiators. The radical initiators used were potassium peroxodisulfate, three kinds of azo-type compounds and a redox initiator. In all cases, the solid-state polymerization was confirmed by color change into blue indicating that PDA modified by the radical residues at the end was formed. However, nanocrystal cohesion occurred especially when the concentration of the initiators was high or the dispersion was kept for a long time. In order to improve the dispersion stability, two kinds of surfactants, i.e., sodium dodecyl sulfate (SDS) or dodecyltrimethylammonium chloride (DTMAC), were added to the DCHD nanocrystal aqueous dispersion. As a result, when anionic SDS was added, the solid-state polymerization of nanocrystals proceeded without coagulation and quantitative conversion was confirmed for all initiators. Cationic DTMAC has no effect on dispersion stabilization. PDA nanocrystal surfaces in water are negatively charged in nature and electric interaction of nanocrystals with the cations results in decrease of surface charge and aggregation of nanocrystals.     

High copy number mutants derived from Corynebacterium glutamicum cryptic plasmid pAM330 and copy number control

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Ultrafast nonlinear optical effect in CdTe-doped glasses fabricated by the laser evaporation method

The laser evaporation method is an attractive technology to synthesize composite materials. We tried to apply the laser evaporation method on fabrication of CdTe-doped glasses for the first time. CdTe microcrystallites embedded in SiO₂ films were confirmed by transmission electron microscope images. The third-order nonlinear susceptibility χ⁽³⁾ and the decay time τ of CdTe-doped glasses were measured by three-beam forward type degenerate four-wave mixing. The maximum value of χ⁽³⁾ was estimated 4.2 x 10^-7 esu when the absorption coefficient was 6000 cm^-1. From the limitation of pulse duration of 5 ps, τ was not exactly measured but imagined to be shorter than 10 ps, which was much faster than the other semiconductor-doped glasses ever reported. The figure of merit defined as χ^(3)/τ is probably larger than 7.     

Capillary rise properties of porous mullite ceramics prepared by an extrusion method using organic fibers as the pore former

Porous mullite ceramics with unidirectionally oriented pores were prepared by an extrusion method to investigate their capillary rise properties. Rayon fibers 16.5 μm in diameter and 800 μm long were used as the pore formers by kneading with alumina powder, kaolin clay, China earthen clay and binder with varying Fe₂O₃ contents of 0, 5 and 7 mass%. The resulting pastes were extruded into cylindrical tubes (outer diameter (OD) 30–50 mm and inner diameter (ID) 20–30 mm), dried at room temperature and fired at 1500 °C for 4 h. The bulk densities of the resulting porous ceramics ranged from 1.31 to 1.67 g/cm³, with apparent porosities of 43.2–59.3%. The pore size distributions measured by Hg porosimetry showed a sharp peak at 10.0 μm in the sample without Fe₂O₃ and at 15.6 μm in the samples containing Fe₂O₃; these pores, which arose from the burnt-out rayon fibers, corresponded to total pore volumes ranging from 0.24 to 0.34 ml/g. SEM showed a microstructure consisting of unidirectionally oriented pores in a porous mullite matrix. Prismatic mullite crystals were well developed on the surfaces of the pore walls owing to the liquid phase formed by the Fe₂O₃ component added to color the samples. The bending strengths of the tubular samples ranged from 15.6 to 26.3 MPa. The height of capillary rise, measured under controlled relative humidities (RH) of 50, 65 and 85%, was greater in the ceramics containing Fe₂O₃ than in those without Fe₂O₃, especially in the thinner samples. The maximum capillary rise reached about 1300 mm, much higher than previously reported. This excellent capillary rise ability is thought to be due to the controlled pore size, pore distribution and pore orientation in these porous mullite ceramics.     

Effects of Cu, Zn-superoxide dismutase delivered by genetically modified skin fibroblasts on cold-induced skin edema in rats

The effects of Cu, Zn-superoxide disumutase (SOD) delivered by genetically modified skin fibroblasts on cold-induced skin edema were studied in rats. Cold-induced skin edema was induced on the dorsal skin following transplantation of ILSOD cells, genetically modified skin fibroblasts which release secretable SOD protein into the extracellular space. The degree of skin edema induced by cold injury was estimated by measuring the amounts of Evans' blue (EB) leaking into the injured skin following intravenously administration. The amounts of EB leakage were significantly reduced by transplantation of ILSOD cells relative to that observed following transplantation of host cells as a control. The degrees and durability of these effects of ILSOD cells were dependent on the number of cells transplanted. Also, the increases of lipid peroxidation following cold injury were significantly reduced by transplantation of ILSOD cells but not of host cells. These findings suggested that transplantation of ILSOD cells was a suitable delivery system for obtaining efficient and continuous effects of SOD. This strategy using genetically modified skin fibroblasts may also be useful as a drug delivery system for other therapeutic proteins.     

Technology and corporate culture of industrial robots in Japan

This paper describes with examples of some typical industrial robots developed in Japan the process of development, which industrial robots in Japan took. It also describes citing the differences of cultural basis between Japan and western countries the influences of automation to man, culture and society, and survey the future industrial robots.     

Effects of interaction between molten zircaloy and irradiated MOX fuel on the fission product release behavior

As a first step for obtaining experimental data on the effects of high-temperature chemical interaction on fission product release behavior, we focused on the dissolution of irradiated uranium plutonium mixed oxide (MOX) fuel by molten zircaloy (Zry) and carried out a heating test under the reducing atmosphere. Pieces of an irradiated MOX fuel pellet and cladding were subjected to the heating test at 2373 K for five minutes. The fractional release rate of cesium (specifically ¹³⁷Cs) was monitored during the test and its release behavior was evaluated. The observation of microstructures and measurements of elemental distribution in the heated specimen were also performed. We demonstrated experimentally that the fuel dissolution by molten Zry accelerated the release of Cs from the fuel pellets.     

Observation of Magnetic‐Switching and Multiferroic‐Like Behavior of Co Nanoparticles in a C60 Matrix

A novel magnetoelectric effect is found to appear in a C₆₀‐Co nanocomposite. Although Co is well‐known as a ferromagnet, its nanoparticles embedded in a C₆₀ matrix can exhibit multiferroic‐like behavior, i.e., an electric field controls magnetic alignment of the nanoparticles and a magnetic field controls their charged states. This novel effect enables a strong magnetic switching effect for which the on/off ratio is ca. 10⁴. Such an effect has been expected to exist and these findings show this magnetoelectric coupling for the first time.