Effects of Aging Temperature on Electrical Conductivity and Hardness of Cu-3 at. pct Ti Alloy Aged in a Hydrogen Atmosphere

To improve the balance of the electrical conductivity and mechanical strength for dilute Cu-Ti alloys by aging in a hydrogen atmosphere, the influence of aging temperature ranging from 673 K to 773 K (400 °C to 500 °C) on the properties of Cu-3 at. pct Ti alloy was studied. The Vickers hardness increases steadily with aging time and starts to fall at 3 hours at 773 K (500 °C), 10 hours at 723 K (450 °C), or over 620 hours at 673 K (400 °C), which is the same as the case of conventional aging in vacuum. The maximum hardness increases from 220 to 236 with the decrease of aging temperature, which is slightly lower than aging at the same temperature in vacuum. The electrical conductivity at the maximum hardness also increases from 18 to 32 pct of pure copper with the decrease of the temperature, which is enhanced by a factor of 1.3 to 1.5 in comparison to aging in vacuum. Thus, aging at 673 K (400 °C) in a hydrogen atmosphere renders fairly good balance of strength and conductivity, although it takes nearly a month to achieve. The microstructural changes during aging were examined by transmission electron microscopy (TEM) and atom-probe tomography (APT), and it was confirmed that precipitation of the Cu₄Ti phase occurs first and then particles of TiH₂ form as the third phase, thereby efficiently removing the Ti solutes in the matrix.     

Fabrication of Pd–DNA and Pd–CNT hybrid nanostructures for hydrogen sensors

This review reports fabrication methods for ordered metallic nanostructures such as nanowires and nanoparticles based on deoxyribonucleic acid (DNA) templates. The phosphate groups in DNA are negatively charged; consequently, the DNA conformation may mineralize metals, e.g., palladium (Pd) at a relatively high metal concentration. We successfully form unique spherically shaped moss-like hybrid Pd nanoparticles using the small compacted globular state of DNA by controlling the reductive reaction. Pd can absorb hydrogen to become PdH_x, and hydrogen storage increases the electrical resistance and volume of Pd materials. Hence, the use of this material is attracting growing interest as a reliable, cheap, ultracompact, and safe hydrogen sensor. Pd–DNA hybrid nanoparticles can be used as highly sensitive hydrogen sensors, which exhibit a switch response that depends on the volume expansion in a cyclic atmosphere exchange. This paper also shows the fabrications of Pd–carbon nanotube (CNT) hybrid nanostructures.     

Influence of atmosphere on photoluminescence properties of Eu-doped ZnO nanocrystals

We have fabricated Eu³⁺-doped ZnO (ZnO:Eu) nanocrystals (NCs) by a reverse micelle method, and have studied their photoluminescence (PL) properties in vacuum, nitrogen gas, and oxygen gas atmospheres. The ZnO:Eu NCs exhibit the exciton, defect and Eu³⁺ PL under the inter-band photoexcitation of the ZnO host NCs. The intensity ratio among the three PL peaks is sensitive to the atmosphere for the PL measurements. We discuss the influence of the surrounding gas atmosphere to the PL properties.     

Control of orientation of rhodamine 6G in organic-inorganic hybrid film by capillary electrophoresis doping technique

Rhodamine 6G (R6G) molecules were fixed with oriented transition dipole moment in organic-inorganic hybrid film by capillary electrophoresis doping (CED) technique and their orientation distribution was analyzed quantitatively by using single-molecule fluorescence defocused imaging. The CED technique forces R6G molecules to migrate into the hybrid film with the dipole moments aligned parallel to the electric field of CED. An appropriate pre-baking of the film enables stabilization of the oriented molecules inside the film; the doped molecules have the direction of the transition dipole moment parallel with the film plane.     

Nonlinear two-stage model for color discrimination

We modified a two-stage model for color discrimination proposed in a previous study [Color Res. Appl.25, 105 (2000)]; in order to extend the model to wider conditions, we considered the conditions with luminance modulations in addition to color modulations. Using the modified model, we successfully predicted color discrimination data with test color changes along both the chromatic and luminance axes under a variety of background colors. Both qualitative and quantitative assessments in modeling showed that nonlinearity is required in both the cone and the cone-opponent stages to interpret adaptation effects of both color and luminance on color discrimination. This fact suggests that the nonlinear properties at each stage have different roles in color perception.     

Present status and future perspectives on the development of bioartificial kidneys for the treatment of acute and chronic renal failure patients

A bioartificial renal tubule device (BTD) consisting of a hollow-fiber module and human proximal tubular epithelial cells has been completed technically by Humes and colleagues and a few other groups. Humes and colleagues developed BTD, treated acute kidney injury patients with multiorgan failure by continuous hemofiltration (CHF) in conjunction with BTD, and reported a significantly higher survival rate than that by CHF with BTD without cells in the Food and Drug Administration phase IIa trial. However, BTD has never been approved by the US Government, as the CHF+BTD treatment did not show a significant difference from the control group in the phase IIb trial. Human proximal tubular epithelial cells were confirmed to be overgrown on artificial membrane, which resulted in the inhibition of active transports and the metabolism of essential substances. Function of the BTD could be maintained in a U0126-contained medium, even if the BTD had to have been waited by a new acute kidney injury patient for several weeks. For wearable kidneys, heparin-covalently bound membrane or methacryloyloxyethyl phosphorylcholine (MPC) polymer-coated membranes are candidates for antithrombogenic hemofilters, while endothelial progenitor cells from a cord blood, CD133(+) cells-attached hemofilter in which the permeability of the cells was enhanced by the enlarged diameter of fenestrae by treating with cytochalasin B are another candidate. The MPC blend membrane containing 1% of the MPC polymer in polysulfone was developed as a BTD module. MPC was 7 times larger at the sponge layer than at the skin layer of the membrane, resulting in hemocompatibility at the sponge layer and cytocompatibility at the skin layer.     

Flame development along a straight vortex

Flame development along a straight vortex was studied experimentally to elucidate the effects of the maximum circumferential velocity and the density ratio of the flame. A pair of straight vortices was produced in nitrogen-diluted stoichiometric hydrogen-oxygen mixtures with density ratios ranging from 5.3 to 7.2. The velocity field measured by particle image velocimetry (PIV) showed that the vortex tube had a mean maximum circumferential velocity ranging from 18.0 to 35.8 m/s and had a mean core diameter ranging from 5 to 6 mm. One of the vortices was ignited at the core by a focused laser at 193 nm without disturbing the flow field. The flame propagated along the axis of the straight vortex at a speed much higher than in the radial direction or in the quiescent mixture. The axial propagation velocity increased over time and became nearly constant when the half-axial length of the flame was larger than the core diameter of the vortex tube. The axial propagation velocity at steady state was roughly proportional to the maximum circumferential velocity and to the density ratio minus unity. The axial propagation velocity in the initial stage increased with the square root of the half-axial length of the flame as well as with the maximum circumferential velocity and the density ratio minus unity.     

Improved Transport J c in MgB2 Tapes by Graphene Doping

Graphene is a special form of carbon which can effectively enhance the critical current density J _c of MgB₂. In this work, a systematic investigation on the impact of sintering conditions and doping level was carried out for graphene-doped MgB₂ tapes. It is found that an appropriate addition level, i.e., 8 at% in this work, is very critical to obtain a high J _c in graphene-doped samples. The critical field and pinning force are improved obviously due to the graphene doping. The magnetic J _c of samples sintered at 800 °C with 8 at% graphene doping reached 1.78 × 10⁴ A/cm², at 5 T, 20 K. At the same time, the transport J _c was up to 2.38 × 10⁴ A/cm² at 10 T, 4.2 K. The lattice distortion caused by C substitution and residual C at the grain boundaries were thought to be the major factors affecting the J _c of graphene-doped MgB₂ samples.     

Debittering of enzymatic hydrolysates using an aminopeptidase from the edible basidiomycete Grifola frondosa

Bitter peptide solutions, prepared by the enzymatic hydrolysis of soy protein and milk casein, were treated with an aminopeptidase from the edible basidiomycete Grifola frondosa. As the incubation time elapsed, the amount of free amino acids released increased and the bitterness of the enzyme reaction mixtures decreased. However, the debittering of the milk casein hydrolysate by the aminopeptidase was less effective than that observed for the soy protein hydrolysate. Hydrophobic amino acids such as valine, leucine, phenylalanine, tyrosine, and isoleucine were preferentially released from the bitter solutions by the action of the aminopeptidase.     

Preparation of silk protein sericin as mitogenic factor for better mammalian cell culture

We previously reported that sericin small (sericin-S), with a molecular weight that ranges from 5 to 100 kDa, is a cell culture supplement used to accelerate cell proliferation. In this study, a novel preparation method for sericin and several applications of sericin were examined. Sericin large, prepared under nonhydrolyzing conditions and ranging from 50 to 200 kDa, also accelerated cell proliferation, but its effects were inferior to those of sericin-S. Additional sericin preparations with various molecular weights that were differentially hydrolyzed were also tested but none of them was significantly superior to sericin-S, and neither were several recombinant sericin peptides. Sericin-S successfully accelerated the proliferation of hybridoma cells in various serum-free media, implying the mitogenic effect of sericin is independent from media. We also demonstrated that sericin-S successfully induced the proliferation of CTLL-2, an established T lymphocyte cell line, under IL-2 starvation conditions. These results indicate that sericin, particularly sericin-S, improves serum-free mammalian cell culture.