Difference in the reactivity of acetaldehyde intermediates in the dehydrogenation of ethanol over supported Pd catalysts

Catalytic performances of supported Pd catalysts for the dehydrogenation of ethanol were greatly modified upon the formation of Pd alloy phases. Over Pd–Zn, Pd–Ga and Pd–In alloys, acetaldehyde was selectively produced at lower conversion levels. With the increased conversion level, ethyl acetate was produced at the expense of acetaldehyde. The selectivities for the ethyl acetate formation exceeded that over a Cu/ZnO catalyst. Over metallic Pd, the decomposition of ethanol, C₂H₅OH → CO + CH₄ + H₂, occurred to a considerable extent. It was shown that the reactivity of acetaldehyde species over the Pd alloys was markedly different from that over metallic Pd. Over the Pd alloys, acetaldehyde species were stabilized and transformed into ethyl acetate by the nucleophilic addition of ethanol. By contrast, over metallic Pd, aldehyde species were rapidly decarbonylated to methane and carbon monoxide. This revised version was published online in July 2006 with corrections to the Cover Date.     

Driving plasmonic nanoantennas with triangular lasers and slot waveguides

Plasmonic nanoantennas can generate high-intensity electric fields in a very small area. However, being passive devices, they need to be excited by external laser sources. The excitation of nanoantennas by semiconductor lasers can be inefficient and a significant amount of light may return back to the laser source after being scattered by the nanoantenna. In this paper, it is shown that the amount of light being returned to the semiconductor laser can be reduced by using dielectric slot waveguides. These waveguides can transport the incident light to the nanoantennas, but the amount of nondirectional back-scattered light is reduced after propagation through the slot waveguide.     

Microstructure and mechanical properties of commercial purity titanium severely deformed by ARB process

Commercial purity titanium was deformed by accumulative roll-bonding (ARB) process up to 8 cycles (equivalent strain of 6.4) at ambient temperature. This is the first study on ultra-high straining of h.c.p. metals by the ARB process. The microstructure of the ARB-processed specimens showed two kinds of characteristic ultrafine microstructures. One was the lamellar boundary structure elongated along RD, which has been also reported in the ARB-processed cubic metals. The lamellar boundary spacing decreased with increasing ARB strain and reached about 80 nm after 5 ARB cycles. The other microstructure was the equiaxed grains having mean grain size of 80–100 nm. Such a fine and equiaxed grain structure has not yet been reported in the as-ARB-processed materials before. The fraction of the equiaxed grains increased as the ARB process proceeded, and 90% of the specimen was filled with the equiaxed grains after 8 ARB cycles. As the number of the ARB process increased, the tensile strength increased and the total elongation decreased gradually. After 6 ARB cycles, the specimen exhibited almost the same mechanical properties as that of commercial Ti-6Al-4V alloy.     

Natural convective heat transfer in uniformly heated vertical pipe annuli

Natural convective heat transfer in vertical concentric pipe annuli is investigated both numerically and experimentally for a fluid having a Prandtl number of 0.7. Numerical calculations for three cases of different heating conditions for pipes (heated inner pipe, heated outer pipe, both pipes heated) are made of laminar flows for different inner‐to‐outer‐pipe diameter ratios d_i/d_o from 0.2 to 0.8. For each case, the thermal entrance length x/b at the modified Grashof numbers Gr^*=10² to 5 × 10⁵ is well correlated with Grashof number Gr^* and annulus length to clearance ratio L/b. Local Nusselt numbers Nu_i and Nu_o in the thermally fully developed region have certain constant values dependent on the diameter ratio d_i/d_o, regardless of Gr^* and L/b. Average Nusselt numbers Nu_i and Nu_o in the thermal entrance region are also independent of Gr^* and L/b. © 2001 Scripta Technica, Heat Trans Asian Res, 30(8): 676–688, 2001     

Synergistic Effect of a Palladium‐on‐Carbon/Platinum‐on‐Carbon Mixed Catalyst in Hydrogen/Deuterium Exchange Reactions of Alkyl‐Substituted Aromatic Compounds

We have found a synergistic effect in the H‐D exchange reaction of alkyl‐substituted aromatic compounds using the Pd/C‐Pt/C‐D₂O‐H₂ system. This system would lead to fully H‐D exchange results even on the sterically hindered sites which were only low‐deuterium incorporated by Pd/C or Pt/C independently. Since the reaction was general for a variety of aromatic compounds, it could be applied to the deuteration of dianiline derivatives as raw materials for polyimides.     

Electrolytic production of NF3 with a LiNiO2 coated nickel sheet anode prepared by atmospheric plasma spraying technique

A nickel sheet coated with LiNiO₂ powder having average particle sizes of 40 and 50 μm in diameter by atmospheric plasma spraying technique was employed as the anode for electrolytic production of NF₃. In electrolysis of a molten NH₄F·2HF at 100 °C and 25 mA cm⁻², the anode gas generated at the LiNiO₂ coated Ni sheet anode was composed of N₂, O₂, NF₃, N₂F₂, N₂F₄, and N₂O, and its composition was almost the same as that at the Ni sheet anode. The current efficiency for the NF₃ formation on the LiNiO₂ coated Ni sheet anode was increased to reach the constant value of ca. 55% during electrolysis for 100 h, and it was almost the same as that on the Ni sheet anode. The anode consumption of the LiNiO₂ coated Ni sheet was small compared with that of the Ni sheet. Also, the oxygen content in the oxidized layer formed on the LiNiO₂ coated Ni sheet anode was high compared with that on the Ni sheet anode, and the surface of the LiNiO₂ coated Ni sheet anode was covered with a compact and adhesive film having some defects. Although the bottom of the hollow was covered with a thinner layer, no pore penetrated through the oxidized layer. Hence, the LiNiO₂ coated Ni sheet anode is favorable for the electrolytic production of NF₃, and the oxidized layer on the LiNiO₂ coated Ni sheet anode has the higher resistance to corrosion, because of the compact and adhesive film containing the higher content of oxygen formed on the anode.     

Reaction of methyl thioglycolate with chloromethylstyrene microgel: Preparation of core–shell-type microgel by chemical modification

A uniform spherical polychloromethylstyrene (PCMS) microgel whose average diameter was 2.3 μm was prepared by dispersion copolymerization of chloromethylstyrene and divinylbenzene in ethanol–DMSO (25/3 v/v) in the presence of polyvinylpyrrolidinone. When the PCMS microgel was treated with an excess amount of methyl thioglycolate (MTG) in the presence of 1,8-diazabicylco[5.4.0]undec-7-ene (DBU) at room temperature in THF for 4 h, sulfenylated microgel was obtained. The introduction ratio of MTG corresponded well to the amount of DBU used. A transmission electron microscope (TEM) photograph and thermal analysis of the PCMS microgel partially modified by MTG showed that it had a core–shell structure, that is, an MTG-modified shell and an unchanged core. Since the reaction of the chloromethyl group and MTG was a diffusion-limited one, MTG was introduced into the PCMS microgel from the outer side layer by layer. The PCMS microgel in which 52% of the MTG was introduced was treated with an excess amount of pyridine in DMAc at 50°C for 48 h followed by acid-catalyzed hydrolysis in dioxane–water at 80°C for 48 h to give a zwitterionic microgel that formed a stable suspension. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1863–1873, 1998     

Rice embryo globulins: amino-terminal amino acid sequences, cDNA cloning and expression

A globulin fraction prepared from rice embryos contained polypeptides or polypeptide groups of 49 kDa (designated REG1), 46 kDa (designated REG2), about 35 kDa, 32 kDa and 25 kDa. The amino-terminal sequences of REG1 and the major polypeptide in the 35-kDa group were identical, suggesting that the REG1 polypeptide undergoes partial proteolytic processing that removes a carboxy-terminal region. A cDNA clone, designated pcREG2, encoding REG2 was isolated, and its nucleotide sequence was determined. The deduced amino acid sequence of REG2 was found to be 68% identical to that of the maize GLB2 globulin. Reg2 mRNA was present at high levels during embryo development for up to 14 days after flowering (DAF). Lower levels were found 20 DAF when the maturation of embryos was almost completed, and at the dry mature stage. Reg2 mRNA almost disappeared upon imbibition of isolated dry mature embryos but it was re-induced at a low level by further treatment with ABA. The expression of Reg2 was not induced by ABA in suspension-cultured cells, unlike that of Osem, one of the late embryogenesis abundant protein (LEA) genes.     

Novel liquid‐crystal materials for AMLCDs

Abstract— We have developed novel liquid‐crystal (LC) materials with a difluoromethyleneoxy CF₂O) moiety as the linkage group in order to satisfy the various requirements of active‐matrix liquid‐crystal displays (AMLCDs). We measured the physical properties of the CF₂O LC materials. The novel CF₂O LC materials have excellent physical properties, that is, high dielectric anisotropy, low viscosity, a broad nematic range, high reliability, etc. It was revealed that several advantages can be obtained by the introduction of CF₂O moiety into the LC molecules. The mixture containing CF₂O LC materials for various applications indicated a decrease in rotational viscosity of about 15–25% compared with that for conventional LC mixtures. Also, these novel mixtures with CF₂O LCM demonstrated a higher voltage‐holding ratio (VHR). It was confirmed that mixtures containing CF₂O LC materials have suitable characteristics for various applications, for example, low‐driving‐voltage note‐book PCs, quick response monitors, and transflective applications.