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.     

Development and evaluation of qualitative detection methods for unapproved genetically modified rice (LLRice)

We developed a specific method to extract DNA from rice grain samples and modified the qualitative real-time PCR method provided by Bayer Co., Ltd. for reliable detection of the genetically modified (GM) rice variety, LLRice601, which has not undergone safety assessment for regulatory approval in Japan. Moreover, we conducted a data analysis to confirm the results obtained with real-time PCR. The yields of DNA extracted from powdered samples of rice grains were almost equal among 5 different varieties of rice, and there was no significant difference in the yield over three days. Reliable results were obtained using 50 ng of the extracted DNA as the template for real-time PCR. To examine the adequacy of the methods, we organized an interlaboratory study with the participation of 2 laboratories, in which 80 test samples were analyzed in a blinded manner. The statistical analysis revealed no significant difference in the Ct value for the endogenous gene of the DNA samples and for the targeted DNA sequence of 0.1% samples. The limit of detection of the method was approximately 0.1%. Analysis of the fluorescence intensity of the PCR-amplified product of the construct-specific DNA sequence suggested that it may be reasonable to judge a sample as positive when a Ct value of less than 40 is obtained.     

Initial stage of carbon nanotube formation process by surface decomposition of SiC: STM and NEXAFS study

Formation process of carbon nanocaps, which are formed at the beginning of carbon nanotube (CNT) growth by surface decomposition of SiC, was investigated by scanning tunneling microscopy (STM) and in situ near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. As Si atoms were desorbed, carbon nanoparticles 1-2 nm in diameter were accumulated on SiC(000-1) surfaces. At around 1200 °C, these were coalesced and crystallized to carbon nanocaps. In addition, just before the crystallization, majority of C-C bonds were directed nearly parallel to the surface. Based on these experimental results, we proposed a model for carbon nanocap formation, which plays an important role to determine the CNTs.