Interfacial tension of demixed polymer solutions over a wide range of reduced temperature

Interfacial tensions were measured for solutions of polystyrene-methylcyclohexane, polystyrene-heptamethylnonane and poly(dimethyl siloxane)-phenylethyl ether to investigate the behaviour of the interfacial tension from the critical point to a region far away from it. In the polystyrene-heptamethylnonane system, measurements were performed until the concentration of the polymer rich phase became about 70～80%. The molecular weight dependence of the interfacial tension was stronger away from the critical temperature than near to it. Data for polystyrene solutions with different solvents were connected by a scaling law. Recent scaling theories were compared with the results for poly(dimethyl siloxane) solution.     

Electrical properties of sintered EuZrO3  EuNbO3 and EuNbO3

Electrical resistivity of two-phase products [yEuZrO₃ + (1 ? y) EuNbO₃] increased continuously with y, and a transition from a metallic to semiconducting characteristic occured at y = 0.14. The resistivity varied almost linearly with temperaure in the range y = 0 to y = 0.24, and thermal coefficients of resistivity at 300 K for the products decreased from +5.9 × 10^?4 K^?1 to ?7.4 × 10^?4 K^?1 according to the value of y. At y = 0.14, the thermal coefficient was almost zero. Thermal coefficients of electrical resistivity for the niobates with various oxygen contents were all positive in the range $\text{2.55 <}\text{O}\text{Nb}\text{< 3.24}$ and exhibited a sharp minimum at $\text{O}\text{Nb}\text{= 2.92}$. In all these niobates, Eu_xNbO₃ was a major phase and Eu₃NbO₆ or EuNbO₂ was detected as a second phase in the range $\text{O}\text{Nb}\text{> 3}$ or $\text{O}\text{Nb}\text{< 3}$ respectively. Peaks in the resistivity curves were correlated with a magnetic ordering temperature for samples with an overall ratio $\text{O}\text{Nb}\text{> 3}$.     

Electrical properties of sintered EuTiO3  EuNbO3

Two-phase sintered products [yEuTiO₃ + (1?y)EuNbO₃] were investigated as electrical-resistor materials. Electrical resistivities of the products did not depend on y in the range 0 < y < 0.96, and rapidly increased with increasing y over y = 0.96. The sintered products were metallic conductors from y = 0 to y = 0.96, and were semiconductors at y > 0.96. Thermal coefficients of resistivity for sintered products varied continuously with y, and became a maximum of 2.8 × 10^?3 K^?1 at y = 0.75 and a minimum around y = 1.00. The coefficient was positive at y < 0.96 and negative at y > 0.96. The absolute value of the thermal coefficient of resistivity minimized, namely ($\text{1}\text{?}$) ($\text{d}\text{?}\text{dT}\text{) = 0}$, at y = 0.96.     

The preparation of TiO2 nanometer photocatalyst film by a hydrothermal method and its sterilization performance for Giardia lamblia

The photocatalytic property of TiO(2) is utilized to sterilize the Giardia lamblia in an aqueous solution in this study. The TiO(2) colloidal solution used for the film was prepared by the modified hydrothermal method and it was directly coated on a UV-lamp, which was set up using a photoreactor manufactured in our laboratory. The TiO(2) film was very stably attached to the UV-lamp, and it was transparent until 5-time coating. The size of the TiO(2) particle in the film was distributed around 20-30 nm and the film thickness was about 200 nm per 1-time coating.The G. lamblia cell was just partially damaged under UV-irradiation without a TiO(2) photocatalyst, but the dead cell became very small and the dead body finally disappeared with an increase in the intensity of UV-irradiation after 2 h. In addition, under the TiO(2)/UV-irradiation system, the sterilized (dead) rate of G. lamblia was very fast. The sterilizing power increased at lower pH in the initial step, but it rather increased at a higher pH in the final step. And the sterilization of G. lamblia was very sensitive to the temperature, and resulted in an increase in the sterilized rate at higher temperatures. On the basis of these experimental observations, it can be concluded that TiO(2) photocatalyst under UV-irradiation could be adopted as one of the sterilization modalities for the G. lamblia.     

Optimal surface chemistry for peptide immobilization in on-chip phosphorylation analysis

We investigated the optimal surface chemistry of peptide immobilization for on-chip phosphorylation analysis. In our previous study, we used a heterobifunctional cross-linker sulfosuccinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxalate (SSMCC) to immobilize cysteine-terminated peptides on an amine-modified gold surface. The study revealed that the phosphorylation efficiency and rate were low (only 20% at 2 h) comparing with the reaction in solution. In this study, to improve the phosphorylation efficiency, the kinase substrates were immobilized via poly(ethylene glycol) (PEG), a flexible, hydrophilic polymer. An improvement in cSrc phosphorylation was achieved (60% at 1 h) from using a PEG-inserted peptide and SSMCC. However, no phosphorylation could be detected when the peptide was immobilized with a PEG-containing cross-linker. Fluorescence-labeled peptide studies revealed that the use of longer cross-linkers resulted in lower immobilization density. We considered that the flexible PEG linker was preferable to secure high phosphorylation efficiency for the immobilized peptide, probably due to the improvement of cSrc accessibility and peptide mobility, but the immobilization protocol is critical for keeping high density of the peptide immobilization. In addition, such an accelerating effect of PEG linker against on-chip phosphorylation of an immobilized peptide may depend on kinase structures or the position of the active center, because no improvement of on-chip peptide phosphorylation was observed in protein kinase A. However, PEG linker also did not suppress the phosphorylation in protein kinase A. Thus, we concluded that SSMCC and PEGylated peptide will be a good combination for the surface chemistry of on-chip phosphorylation in peptide array.     

Melt synthesis of oxide phosphors with K2NiF4 structures: CaLa1? x Eu x GaO4

In order to synthesize compounds of various Perovskite-related structures, we have utilized a novel “melt synthesis technique” for phosphors rather than the conventional solid state reaction techniques. The solid state reactions require multi-step processes of heating/cooling with intermediate grindings to make homogeneous samples. However, for the melt synthesis, it is possible to make a homogeneous sample in a single step within a short period of time (1–60 s) due to the liquid phase reaction in the molten samples, which were melted by strong light radiation in an imaging furnace. In this study, we have prepared a red-phosphor CaLaGaO₄:Eu³⁺ which has a perovskite—related layered K₂NiF₄ structure. Well-crystallized CaLa_1−x Eu _x GaO₄ samples with the K₂NiF₄ structure have been obtained up to x = 0.25, but there was the formation of an olivine phase when x = 0.5–1.0. The red emission at 618 nm increased with the increasing value of x up to x = 0.25.

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Hydrogen embrittlement susceptibility of microstructures formed in multipass weld metal for HT780 class steel

The effect of reheating by following passes on the hydrogen embrittlement of MAG weld metal for HT780 class steels has been investigated by using specimens subjected to simulated thermal cycles. The hydrogen-charged specimens exhibited transgranular quasi-cleavage fracture and intergranular fracture along prior austenite grain boundaries on slow strain rate tensile (SSRT) tests, depending on the reheated temperature and charged hydrogen content. The reduction in elongation of hydrogen-charged specimens became more significant when intergranular fracture occurred. When specimens in as-welded state and precedently reheated at coarse grained HAZ temperature of 1,623 K were reheated at a tempering temperature of 873 K, significant amount of intergranular fracture occurred at charged hydrogen contents above 3 ppm in spite of the decrease in hardness. The specimen reheated at 1,173 K showed no intergranular fracture even after receiving the reheating at 873 K at a hydrogen content of 6 ppm, suggesting the strong influence of the prior austenite grain size on the hydrogen-induced intergranular embrittlement. The measurement of hydrogen content desorbed from the hydrogen-charged specimen at room temperature suggested that the intergranular fracture caused by the reheating at 873 K was associated with an increase in susceptibility to hydrogen embrittlement of the prior austenite grain boundary itself rather than a decrease in the amounts of trapping sites such as dislocation and retained austenite.     

Microstructure of interface for high-adhesion DLC film on metal substrates by plasma-based ion implantation

The diamond-like carbon (DLC) film was prepared on various metal substrates with a plasma-based ion implantation and deposition using superimposed RF and negative high-voltage pulses. The adhesion strength of DLC film was enhanced above the epoxy resin strength by implantation of carbon ions or mixed ions of carbon and silicon to the substrate surface before DLC deposition. In order to clarify the mechanism for improvement in adhesive strength, the microstructure of an interface between DLC film and substrate was examined in detail by transmission electron microscopy (TEM) observations in combination with EDS analysis. As a result, the enhancement in adhesion strength of DLC film by C ion implantation resulted from the formation of amorphous-like phase in the ion-implanted region of substrate, the production of carbon-component graded interface, the destruction of the oxide layer on the top surface of substrate, and the reduction of residual stress in DLC film by ion implantation during the deposition. The production of stress-free DLC film allowed us to demonstrate a supra-thick DLC film of more than 400 μm in thickness.     

Luminescent passive-oxidized silicon quantum dots as biological staining labels and their cytotoxicity effects at high concentration

Semiconductor quantum dots (QDs) hold some advantages over conventional organic fluorescent dyes. Due to these advantages, they are becoming increasingly popular in the field of bioimaging. However, recent work suggests that cadmium based QDs affect cellular activity. As a substitute for cadmium based QDs, we have developed photoluminescent stable silicon quantum dots (Si-QDs) with a passive-oxidation technique. Si-QDs (size: 6.5 ± 1.5?nm) emit green light, and they have been used as biological labels for living cell imaging. In order to determine the minimum concentration for cytotoxicity, we investigated the response of HeLa cells. We have shown that the toxicity of Si-QDs was not observed at 112?μg?ml(-1) and that Si-QDs were less toxic than CdSe-QDs at high concentration in mitochondrial assays and with lactate dehydrogenase (LDH) assays. Especially under UV exposure, Si-QDs were more than ten times safer than CdSe-QDs. We suggest that one mechanism for the cytotoxicity is that Si-QDs can generate oxygen radicals and these radicals are associated with membrane damages. This work has demonstrated the suitability of Si-QDs for bioimaging in lower concentration, and their cytotoxicity and one toxicity mechanism at high concentration.