Single-step synthesis and characterization of single-walled carbon nanohorns hybridized with Pd nanoparticles using N2 gas-injected arc-in-water method

Single-walled carbon nanohorns (SWCNHs) hybridized with palladium (Pd) nanoparticles were synthesized by a single-step gas-injected arc-in-water method (GI-AIW) with a Pd wire inserted inside the anode hole. In the arc zone, carbon and Pd were vaporized simultaneously, leading to the formation of hybrid material of SWCNHs and Pd nanoparticles due to effective quenching. Based on TEM and CO chemisorption analyses, Pd nanoparticles were found to be embedded inside SWCNH aggregates. The size of Pd nanoparticles, determined by X-ray diffraction, was in the range of 3–6 nm when Pd wires with diameters of 0.1 and 0.3 mm were used. Using a Pd wire with a diameter larger than 0.5 mm results in larger Pd nanoparticles which tend to be exposed to the outer surface of the hybrid material. According to thermogravimetric analyses, the weight fraction of Pd nanoparticles is increased by increasing the Pd wire diameter although the yield of Pd nanoparticles decreased. SWCNHs hybridized with dispersed Pd nanoparticles, synthesized with 0.1 mm Pd wire, exhibited strong anti-oxidation resistance with a highly graphitic structure.     

Rapid Desensitization of Lipolysis in the Visceral and Subcutaneous Adipocytes of Rats

In adipocytes, short and long term stimulation of β adrenergic receptors (βAR) induces the desensitization to catecholamines, leading to a decrease in the intracellular accumulation of cAMP, but the roles played by this in lipolysis is not clear. In this study, we assessed the catecholamine-induced desensitization of lipolysis and compared this in adipocytes isolated from visceral and subcutaneous fat tissues of rats. When adipocytes were pretreated with isoproterenol (ISO), the norepinephrine (NE)-induced lipolysis was significantly reduced dose- and time-dependently. A similar reduction of the lipolytic response was also found in NE-, dobutamine-, terbutaline- or BRL37344-induced lipolysis. The ISO- and each βAR agonist-induced lipolysis in the visceral fat was not only higher than in the subcutaneous fat, but also markedly reduced by ISO- or NE-pretreatment. These results showed that short-term treatment of three subtypes of βAR by each agonist induces a rapid reduction in the lipolytic response to βAR stimulation. This suggests some common mechanism for the rapid desensitization of βAR-agonist-induced lipolysis, in contrast with previous reports on the characteristics of βAR subtypes. In addition, the regional difference of adipose tissue not only in inducing lipolysis but also in rapid desensitization was also apparent.     

Design of High-Quality Pt–CeO2 Composite Anodes Supported by Carbon Black for Direct Methanol Fuel Cell Application

A Pt on nano-sized CeO₂ particles that in turn are supported on carbon black (CB) was synthesized using the co-impregnation method. This potential anode material for fuel cell applications was synthesized in a stepwise process. The pure CeO₂ was synthesized using an ammonium carbonate precipitation method, and the Pt particles dispersed on the CeO₂ in such a way that a uniform dispersion with the CB was obtained (Pt–CeO₂/CB). The electrochemical activity of the methanol (CH₃OH) oxidation reaction on the Pt–CeO₂/CB was investigated using cyclic voltammetry and chronoamperometry experimentation. The onset potential of CH₃OH oxidation reaction on the Pt–CeO₂/CB anode was shifted to a lower potential as compared with that on commercially available Pt–Ru/carbon (C) alloy anode. In addition, the activation energy of the Pt–CeO₂/CB anode was much lower than that of the Pt–Ru/C alloy anode. Moreover, the current density of the Pt–CeO₂/CB anode was much higher than that of the Pt–Ru/C alloy anode at temperatures between 28° and 60°C. These results suggest that the anode performance of the Pt–CeO₂/CB anode at the operating temperature of typical fuel cells (80°C) is superior to that of the more usual Pt–Ru/C alloy anode. Importantly, the rare metal, Ru, is not required in the present anode material and the amount of Pt required is also significantly reduced. As a consequence, we report a promising candidate Pt–CeO₂/CB composite anode for application in the development of direct methanol fuel cells.     

Ethanolamine Is a New Anti-Prion Compound

Prion diseases are a group of fatal neurodegenerative disorders caused by accumulation of proteinaceous infectious particles, or prions, which mainly consist of the abnormally folded, amyloidogenic prion protein, designated PrP^Sc. PrP^Sc is produced through conformational conversion of the cellular isoform of prion protein, PrP^C, in the brain. To date, no effective therapies for prion diseases have been developed. In this study, we incidentally noticed that mouse neuroblastoma N2a cells persistently infected with 22L scrapie prions, termed N2aC24L1-3 cells, reduced PrP^Sc levels when cultured in advanced Dulbecco’s modified eagle medium (DMEM) but not in classic DMEM. PrP^C levels remained unchanged in prion-uninfected parent N2aC24 cells cultured in advanced DMEM. These results suggest that advanced DMEM may contain an anti-prion compound(s). We then successfully identified ethanolamine in advanced DMEM has an anti-prion activity. Ethanolamine reduced PrP^Sc levels in N2aC24L1-3 cells, but not PrP^C levels in N2aC24 cells. Also, oral administration of ethanolamine through drinking water delayed prion disease in mice intracerebrally inoculated with RML scrapie prions. These results suggest that ethanolamine could be a new anti-prion compound.     

Visible-light photocatalytic activity of TiO2−x by heat treatment and plasma-heat treatment

The partial reduction of TiO₂ was attempted by heat treatment and plasma-heat treatment and it was carried out to investigate the photocatalytic characteristics of partially reduced TiO₂ (TiO_2?x) in the visible-light region. As a result, the plasma-heat treatment shows significantly stronger than the heat treatment for the visible-light photocatalytic activity of TiO₂. The red-shifted absorption bands in the visible-light region of TiO_2?x by plasma-heat treatment gave broader than one by heat treatment. The TiO_2?x by heat treatment and plasma-heat treatment was changed white to beige color, and white to navy, respectively.     

Sintering Behavior of Pt Metal Particles Supported on Silica-Coated Alumina Surface

The sintering behavior of Pt metal particles was studied by supporting them on silica-coated alumina. Silica coating was found to be effective for the retention of a large surface area of alumina even after calcination at elevated temperatures. Before sintering, the size of Pt metal particles on all the silica-coated aluminas, including the uncoated alumina, was identical, while the particle size was larger on silica than on alumina. After sintering the Pt catalyst at 1073 K, the particle size increased on uncoated alumina as well as on alumina coated with thicker silica layers, especially on the supports previously calcined at >1473 K. On the other hand, the size of Pt metal particles did not increase much on alumina coated with monolayer silica. The observed suppression of sintering of Pt metal particles resulted from the retention of a large surface area of alumina with a thinner silica layer. In the case of a thicker silica layer, although a large surface area was maintained after calcination at elevated temperatures, the existence of a bulk silica-like property of the support did not favor the suppression of sintering of Pt metal particles.     

N-Alkylation of chitin and some characteristics of the novel derivatives

Summary Introduction of simple alkyl groups at the C-2 nitrogen of chitin and some properties of the resulting N-alkyl-chitins have been examined. Chitosan was fully deacetylated and treated with three kinds of aldehydes, formaldehyde, acetaldehyde, and pentanal. The Schiff bases of chitosan, whose extents of substitution were dependent on the amount of aldehydes, were reduced with sodium cyanoborohydride to N-alkylated chitosans. The N-alkyl-chitosans were then transformed into the corresponding N-alkyl-chitins by acetylation with acetic anhydride followed by transesterification to remove partly formed O-acetyl groups. The resulting N-methyl-, ethyl-, and pentyl-chitins were amorphous and showed improved affinity for organic solvents. Received: 13 December 2001/Revised version: 11 January 2002/Accepted: 17 January 2002     

Adsorption isotherms of pigments from alkali-refined vegetable oils with clay minerals

Adsorption isotherms of pigments from alkali-refined oils (rapeseed, soybean, wheatgerm, safflower, corn, cottonseed and sunflower) were measured to investigate the applicability of the Langmuir and Freundlich equations and to elucidate the adsorption characteristics of pigments on sepiolites and standard activated clay. The Freundlich equation was more applicable to the experimental adsorption isotherms. The equilibrium amount adsorbed, acidity, pore size distribution and inflection of the Freundlich isotherms could be explained by assuming that pigments were adsorbed on the stronger acid sites in smaller pores at low concentration, and then in the larger ones when the concentration increased. The amount adsorbed increased with a rise in adsorption temperatures from 70 to 110°C, and the heat of adsorption was below 10 kcal/mol. The results indicate that pigments were physically adsorbed on the acid sites activated at higher adsorption temperatures.     

Effect of Grain Boundaries on Thermal Conductivity of Silicon Carbide Ceramic at 5 to 1300 K

The thermal conductivity of a SiC ceramic was measured as 270 W·m⁻¹·K⁻¹ at room temperature. At low temperatures ( T < 25 K), the decrease in the conductivity was proportional to T ³ on a logarithmic scale, which indicated that the conductivity was controlled by boundaries. The calculated phonon mean free path in the ceramic increased with decreased temperature, but was limited to ∼4 μm, a length almost equal to the grain size, at temperatures below 30 K. We concluded that the thermal conductivity of the ceramic below 30 K was influenced significantly by grain boundaries and grain junctions.