Analysis of XANES for identification of highly dispersed transition metal oxides on supports

XANES of vanadium and niobium oxide on silica or alumina have been analyzed quantitatively by a deconvolution technique. Based on the results for reference compounds, local structures of supported vanadium and niobium species were identified. The composition was estimated from difference spectra for the samples which consisted of two kinds of species.     

X-ray absorption fine structure analysis of local structure of CeO2–ZrO2 mixed oxides with the same composition ratio (Ce/Zr=1)

Three types of CeO₂–ZrO₂ (Ce:Zr=1:1 molar ratio) compounds with different oxygen storage/release capacities (OSCs) were characterized by means of the Ce K-edge and Zr K-edge X-ray absorption fine structure (XAFS). In order to investigate the relationship between the OSC and local structure, the quantitative EXAFS curve-fitting analysis was applied. By enhancing the homogeneity of the Ce and Zr atoms in the CeO₂–ZrO₂ solid solution, the OSC performance increased. Especially, the atomically homogeneous Ce_0.5Zr_0.5O₂ solid solution exhibited the highest OSC among these CeO₂–ZrO₂ samples. Additionally, the local oxygen environment around Ce and Zr was remarkably modified by enhancing the homogeneity of the CeO₂–ZrO₂ solid solution. It was postulated that the enhancement of the homogeneity of the CeO₂–ZrO₂ solid solution and the modification of the oxygen environment would be the source for the OSC improvement.     

Photocatalytic oxidation of alkane at a steady rate over alkali-ion-modified vanadium oxide supported on silica

Photocatalysts were applied to photocatalytic oxidation of propane in a fixed bed flow reactor. Titanium dioxide exhibited fairly high activity but the deep oxidation was predominant. Silica-supported vanadium oxide (VS) favors the partial oxidation to form propanone and variety of aldehydes and the fast deactivation took place accompanied by reduction of vanadium ions. On the other hand, alkali-ion-modified VS exhibited the highest activity and high selectivity to propanone. The activity was stable because vanadates in alkali-ion-modified VS do not change their structure or are not poisoned by water molecules throughout the reaction. The cleavage of C=C double bond to form aldehydes predominantly proceeded in the case of photo-oxidation of 1-butene over VS while in the case of photo-oxidation of Rb-modified VS, the oxidation of secondary carbon atom to form methyl vinyl ketone is favored. Methyl ethyl ketone was produced at a steady rate over Rb-VS in the photo-oxidation of n-butane.     

Plasma behavior and characteristics of a pulsed‐laser‐driven MHD electrical power generation

The fundamental electrical power generation experiment of a pulsed‐laser‐driven magnet hydrodynamics generator with a divergent channel and segmented electrodes has been conducted with a rough estimate of gas heating efficiency of laser energy. The output energy is increased with the decrease in the initial filling gas pressure because of the increase in the gas velocity and the electrical conductivity with the gas temperature. The output power is surely improved in comparison with the previously examined generator with constant height channel and continuous electrode. About 70% of the incident laser energy is absorbed and less than 20% is transferred to the blast wave energy at low initial filling gas pressure in the present experimental setup.     

Studies on local structure in hydrogenated amorphous LaNi5.0 films using extended X-ray absorption fine structure

The local structure in hydrogenated amorphous LaNi_5.0 film was analysed by means of extended X-ray absorption fine structure. The short-range order in the amorphous LaNi_5.0 film was found to be little affected by the absorption of hydrogen. The lengthening of the interatomic distance with an increase in hydrogen concentration was much smaller for an amorphous film than for a crystalline bulk, so that the amorphous film appears to have excellent durability with regard to the hydrogen absorption-desorption process.     

XAFS and XRD Analysis of Ceria–Zirconia Oxygen Storage Promoters for Automotive Catalysts

Three types of CeO₂–ZrO₂ (Ce:Zr = 1:1 molar ratio) compounds with different oxygen storage/release capacity (OSC) were characterized by means of the Ce K-edge and Zr K-edge XAFS. In order to investigate the relationship between the OSC and local structure, the quantitative EXAFS curve-fitting analysis was applied. By enhancing the homogeneity of the Ce and Zr atoms in the CeO₂–ZrO₂ solid solution, the OSC performance increased. Additionally, from the XRD analysis, the homogeneous CeO₂–ZrO₂ solid solution has an ordered cation arrangement, and exhibits the highest OSC. The crystal structure of this CeO₂–ZrO₂ solid solution is usually termed as “κ-CeZrO₄ phase”. However, the OSC performance of κ-CeZrO₄ degrades upon a high-temperature treatment under an oxidative atmosphere. The fresh κ-CeZrO₄ was aged at 973, 1,273 and 1,473 K under an oxidative atmosphere, respectively. The OSC performance deteriorated as: the fresh sample ≈973 > 1,273 > 1,473 K-aged samples. We also found that, if the temperature was beyond 1,273 K, the Ce/Zr ordered arrangement would collapse and the local structure around Ce and Zr ions would also changed remarkably. These results indicated that OSC was strongly dependent on its atomic structure.     

Insect-type MEMS microrobot with mountable bare chip IC of artificial neural networks

This paper discussed insect-type MEMS microrobot system which could locomote without using computer programs. Locomotion of the MEMS microrobot was generated using the analog circuit of artificial neural networks. We constructed the artificial neural networks as a bare chip integrated circuit (IC) which could mount on top of the MEMS microrobot. As a result, the MEMS microrobot system could perform the locomotion using constructed bare chip IC of artificial neural networks. The insect-type MEMS microrobot system was 0.079 g in weight and less than 5.0 mm in size. Only the power source was outside of the robot. In addition, we analyze the heat conduction of the shape memory alloy-type actuator. It was shown that the heat of shape memory alloy conducts to the mechanical parts of the MEMS microrobot; therefore, locomotion becomes slowly after 30 s. The slow locomotion was 2 mm/min. We constructed the less conduction shape memory alloy-type actuator. The locomotion speed of the insect-type MEMS microrobot using less conduction shape memory alloy-type actuator was 90.8 mm/min.     

Preparation of highly dispersed niobium oxide on silica by equilibrium adsorption method

Two series of Nb₂O₅/SiO₂ catalysts are prepared by an equilibrium adsorption method (type A) and a conventional evaporation to dryness method (type E). The loading amounts of type A catalysts were low ( ˜ 0.2 wt% as Nb₂O₅) and those of type E catalysts were varied from 0.1 to 10 wt%. UV/VIS diffuse reflectance spectra of the catalyst samples show that micro particles of Nb₂O₅) are present on the catalysts with high-loading and monomeric or oligomeric niobate species are present on the catalysts with low-loading. By analyzing luminescence spectra of the low-loading samples, we conclude that the type A catalyst contains monomeric NbO₄ tetrahedra and the type E catalyst oligomeric NbO₄ tetrahedra. Propene photo-oxidation on type A catalysts yields propene oxide selectively, formed on monomeric NbO₄, whereas the photo-oxidation on the type E catalyst with low-loading yields propanal selectively. Propanal is the product in decomposition of propene oxide on oligomeric NbO₄ tetrahedra.     

Urinary Dopamine as a Potential Index of the Transport Activity of Multidrug and Toxin Extrusion in the Kidney

Dopamine is a cationic natriuretic catecholamine synthesized in proximal tubular cells (PTCs) of the kidney before secretion into the lumen, a key site of its action. However, the molecular mechanisms underlying dopamine secretion into the lumen remain unclear. Multidrug and toxin extrusion (MATE) is a H⁺/organic cation antiporter that is highly expressed in the brush border membrane of PTCs and mediates the efflux of organic cations, including metformin and cisplatin, from the epithelial cells into the urine. Therefore, we hypothesized that MATE mediates dopamine secretion, a cationic catecholamine, into the tubule lumen, thereby regulating natriuresis. Here, we show that [³H]dopamine uptake in human (h) MATE1-, hMATE-2K- and mouse (m) MATE-expressing cells exhibited saturable kinetics. Fluid retention and decreased urinary excretion of dopamine and Na⁺ were observed in Mate1-knockout mice compared to that in wild-type mice. Imatinib, a MATE inhibitor, inhibited [³H]dopamine uptake by hMATE1-, hMATE2-K- and mMATE1-expressing cells in a concentration-dependent manner. At clinically-relevant concentrations, imatinib inhibited [³H]dopamine uptake by hMATE1- and hMATE2-K-expressing cells. The urinary excretion of dopamine and Na⁺ decreased and fluid retention occurred in imatinib-treated mice. In conclusion, MATE transporters secrete renally-synthesized dopamine, and therefore, urinary dopamine has the potential to be an index of the MATE transporter activity.