Redox‐Active Catalyst Based on Poly(Anilinesulfonic Acid)‐ Supported Gold Nanoparticles for Aerobic Alcohol Oxidation in Water

The hybrid consisting of gold nanoparticles and poly(2‐methoxyaniline‐5‐sulfonic acid), which works as a redox mediator for transferring protons and electrons, catalyzed the oxidation reaction of various alcohols in water under molecular oxygen.     

Generation of Brønsted Acid Over Alumina-Supported Niobia Calcined at High Temperatures

Nb₂O₅/Al₂O₃ catalysts calcined at high temperatures exhibited the Brønsted acid property. A monolayer of niobic acid-like compound, which has distorted octahedral symmetry, was stabilized over 16 wt% Nb₂O₅/Al₂O₃ catalyst calcined at 1,173 K. The two-dimensional Nb–O–Nb network of stabilized niobic acid-like compound probably accounts for the generation of Brønsted acid.     

Effect of microstructures on dielectric breakdown strength of sintered reaction-bonded silicon nitride ceramics

Silicon nitride (Si₃N₄) was prepared from silicon by a sintered reaction-bonded silicon nitride method using yttria and magnesia as sintering additives. Post-sintering (PS) of nitrided compacts was carried out at 1850°C under a nitrogen pressure of 1 MPa. Effect of PS time on microstructure and dielectric breakdown strength (DBS) of the prepared Si₃N₄ ceramics was evaluated. The DBS was measured using specimens with four different thicknesses (0.30, 0.20, 0.10, and 0.05 mm) in order to examine the thickness dependence. The porosity of the sintered Si₃N₄ decreased by prolonging the PS time, and the full density could be achieved at the PS time of over 6 h. After full densification, rod-like β-Si₃N₄ grains grew up, and their maximum grain size increased from 45.1 to 154.7 μm by prolonging the PS time from 6 to 48 h. The DBS of the thick Si₃N₄ substrates (0.30 mm) showed little variation from 35.4 to 47.0 kV/mm, regardless of the PS time. On the other hand, that of the thin ones (0.05 mm) dramatically decreased from 99.5 to 9.8 kV/mm with increased the PS time from 6 to 48 h. Because the DBS sharply decreased at the thin substrate sintered for longer time in which some large-elongated grains might span the substrate thickness-wise throughout, it was inferred that the interface between β-Si₃N₄ grains and grain boundary phase/intergranular glassy films might be a path of the dielectric breakdown.     

Isolation and identification of xenobiotic aryl hydrocarbon receptor ligands in dyeing wastewater

Dyeing wastewater collected in Kyoto city, Japan, was investigated for the occurrence of aryl hydrocarbon receptor (AhR) ligands by using an AhR-responsive reporter gene assay. Concentrated extracts of wastewater samples elicited a dose-dependent increase in AhR ligand activity, and several hydrophobic HPLC fractions of the extracts were highly effective in inducing AhR ligand activity. Three potential AhR ligands were isolated from these fractions and identified to be Disperse Red 92, Disperse Yellow 64, and 3'-hydroxybenzo[b]quinophthalone by using HPLC and LC-MS/MS. Disperse Red 92, which has also been detected in the treated effluent from a sewage plant receiving the wastewater, is an anthraquinone disperse dye showing weak AhR binding affinity in the assay. Disperse Yellow 64 and 3'-hydroxybenzo[b]quinophthalone are quinoline disperse dyes capable of activating the AhR at nanomolar concentrations. In particular, Disperse Yellow 64 is a highly potent AhR ligand that was 3 times more effective in inducing AhR ligand activity than beta-naphthoflavone in the assay. Quinoline disperse dyes are suggested to be a new class of xenobiotic AhR ligands which pose a danger to aquatic biota and human health.     

Diamines prevent thermal aggregation and inactivation of lysozyme

Protein aggregation is a major obstacle in both biological applications and biomedical fields involving proteins. In this study, we investigated the essential structure of small additives that function as chemical chaperones. Aggregation-suppressing competent additives were 1,3-diaminopropane, 1,4-diaminobutane, and 1,5-diaminopentane, which suppressed aggregation in the given order; whereas no diols or monoamines prevented the thermal aggregation and the inactivation of lysozyme. The heat-inactivation rate of lysozyme with 1,3-diaminopropane was almost identical to that of lysozyme with spermine and arginine ethylester, which are the most prominent additives reported yet.     

Monte Carlo simulation of diffusive-to-ballistic transition in phonon transport

Heat conduction properties in Si nanostructures are analyzed using a Monte Carlo method developed for solving the phonon Boltzmann transport equation. The thermal resistances are evaluated for the systems with various sizes, and the transition from the diffusive to the ballistic heat conduction are investigated. We compare the two different phonon dispersion models (the realistic dispersion relation based on the adiabatic bond charge model and the analytically approximated model), and it is shown that the correct implementation of the phonon dispersion relation is essential to accurately simulate the quasi-ballistic heat conduction properties, which becomes obvious in the structures smaller than the phonon mean free path.     

Burning velocities and kinetics of H2/NF3/N2, CH4/NF3/N2, and C3H8/NF3/N2 flames

The combustion characteristics and reaction mechanism of mixtures containing nitrogen trifluoride (NF₃) were investigated. Burning velocities for H₂/NF₃/N₂, CH₄/NF₃/N₂, and C₃H₈/NF₃/N₂ flames were determined for the first time at various equivalence ratios and N₂ mole fractions. The burning velocities of the latter two flames were similar and showed peaks at equivalence ratios of ∼1.0, while those of the H₂/NF₃/N₂ flames had the pronounced peak at low equivalence ratios where the formation of the wrinkled flames was observed. A detailed kinetic model was constructed to simulate the laminar burning velocities of H₂/NF₃/N₂ and CH₄/NF₃/N₂ flames. The model accurately reproduced the experimental results. Analyses of the reaction mechanism revealed the major reaction pathways that involve the decomposition of NF₃, the oxidation and chain-fluoridation of H₂ and CH₄, and the formation of N₂.     

Experimental study of several types of ground heat exchanger using a steel pile foundation

An experimental study of several types of ground heat exchangers (GHEs) installed in a steel pile foundation, including double-tube, U-tube, and multi-tube GHEs, was carried out at Saga University. Water flows through the heat exchangers and exchanges heat to or from the ground. The performance of GHEs was investigated under actual operation in the cooling mode with flow rates of 2, 4, and 8 l/min. Temperatures of the ground and GHE tube wall were measured to find the temperature distributions according to the depth of the ground and depth of the GHE tube wall. The temperatures of the inlet and outlet of circulated water were also measured to calculate the heat exchange rate. The double-tube had the highest heat exchange rate, followed by the multi-tube and U-tube GHEs. For example, the average heat exchange rate of GHEs over 24 h of continuous operation with a flow rate of 4 l/min was 49.6 W/m for the double-tube, 34.8 W/m for the multi-tube, and 30.4 W/m for the U-tube. An increasing flow rate increased the heat exchange rate of the GHEs. The heat exchange rates increased significantly for flow rate increases from 2 to 4 l/min, but only slightly changed from 4 to 8 l/min.     

Tribological Properties and Film Formation Behavior of Thermoreversible Gel Lubricants

The tribological properties of a new and unique thermoreversible gel lubricant (TR gel lube) were investigated. TR gel lube, which includes 10–40% of amide-type gelling agent in base fluid, is able to repeatedly alter or convert phase from gel state to liquid state at the melting point of the gelling agent. High-pressure rheological tests were performed in order to characterize the behavior of base oil and TR gel lube as a function of pressure and temperature. The effect of TR gel lube on ball bearing fatigue life was carried out by systematic tests using thrust ball bearings. The results of L ₁₀ life tests of TR gel lube showed a longer life than the conventional greases. This result was investigated from the oil film formation. It was found that the gelling agent played a key role in the lubricating properties. Some mechanisms such as adsorbed film formation and solid-like formation are proposed.