Shock-induced phase transition of oriented pyrolytic graphite to diamond at pressures up to 15 GPa

In studies of shock-induced phase transition of ordered pyrolytic graphite to a diamond-like phase, the lowest transition onset pressure was observed at 19.6 GPa. The phase transition in that case was considered to be martensitic. In the present study ordered pyrolytic graphite with voids between particles was loaded at pressures up to 15 GPa using a planar shock wave propagating along the basal plane of the graphitic crystal structure. As a result, both diamond-like carbon and diamond were observed in the postshock sample. The phase transition of graphite to diamond was assumed to occur by the release of distortional energy stored in the graphite particles, that is, diffusional-controlled reconstructive mechanism, on the basis of the data by high resolution electron microscopy together with electron energy loss spectroscopy.     

α-Sulfonated fatty acid esters: I. Structural effects of sodium α-sulfonated fatty acid higher alcohol esters on surface-active properties and emulsification ability

The surface-active properties and emulsification ability of sodium α-sulfonated fatty acid esters, C_mH_2m+1CH-(SO₃Na)COOC_nH_2n+1, were studied as a function of the hydrophobic alkyl chainlength in the fatty acid (m=8−16) and the alcohol (n=8−18). As a result, it was discovered that sodium α-sulfonated fatty acid esters have a structural effect on the Krafft point different from that of amphiphiles with short alkyl chains. Moreover, some of the α-sulfonated fatty acid esters have quite low interfacial tensions, as well as non-foaming properties, which depend upon the total (m+n) number of carbon atoms in the alkyl chains.     

Study on the Anti-Coking Nature of Ni/SrTiO3 Catalysts by the CH4 Pyrolysis

A solid phase crystallization (spc) method was applied for the preparation of SrTiO₃-supported Ni catalysts and compared to the impregnation (imp) method. spc-Ni_0.2/SrTiO₃ has highly dispersed and stable Ni metal particles resulting in higher activity and higher sustainability against coking than imp-Ni_0.2/SrTiO₃ in the partial oxidation of CH₄. Both catalysts were tested for the CH₄ pyrolysis in order to elucidate the catalytic nature against coking of spc-Ni_0.2/SrTiO₃. The amount of carbon and the rate of H₂ formation were similar over both catalysts at both 773 and 1073 K. On both catalysts, CH₄ continuously decomposed at 773 K, while the rate of CH₄ pyrolysis quickly decreased at 1073 K. Fibrous carbons grew up with a Ni metal particle on the tip of the fiber at 773 K, while carbon balls and short carbon fibers with a Ni metal particle encapsulated inside formed and no sufficient growth of the fiber was observed at 1073 K. The carbon species formed at 773 K was hydrogenated completely to CH₄ around 873 K, while the hydrogenation of that formed at 1073 K needed higher temperature around 1073 K. However, the carbon species formed on both the catalysts at either 773 or 1073 K was completely oxidized around 773 K. Thus, judging from the anti-coking nature, the behaviors in the CH₄ pyrolysis are similar over both catalysts, nonetheless spc-Ni_0.2/SrTiO₃ was far superior to imp-Ni_0.2/SrTiO₃ in the CH₄ oxidation. It is likely that the high sustainability against coking of spc-Ni_0.2/SrTiO₃ is not due to its intrinsic nature suppressing the coking but due to its high activity of reforming which can quickly eliminate the carbon formed on the catalyst surface.     

Catalytic Rearrangement of Epoxide Compounds

Products formed by rearrangement of epoxide compounds provide useful intermediates in organic syntheses and some of them are valuable as raw materials in the chemical industry. Many studies on the catalytic rearrangement of the epoxides have been made. The reactions which have been used most frequently are homogeneous with acid or base catalysts such as BF3, MgBr2, t-BuOK, or lithium dialkylamides; the acid catalysts form mainly carbonyl compounds (ketone and aldehyde) and the base catalysts in most cases yield allylic alcohols. Recently the heterogeneous reaction over solid catalysts was also investigated, but the catalysts used were just alumina and silica gel, solid acid and base catalysts, and it is very recent that various kinds of the solid acids and bases have been used as catalysts for epoxide isomerization, especially by the authors (Section VI-A). Studies with molten salts are few, and investigations with metal complex and organometal catalysts have just begun.     

Simple,Mild, and Practical Esterification,Thioesterification, and Amide Formation Utilizing p‐Toluenesulfonyl Chloride and N‐Methylimidazole

We have developed an efficient method for the esterification or thioesterification of equimolar amounts of carboxylic acids and alcohols or thiols using a novel reagent, p‐toluenesulfonyl chloride (TsCl) together with N‐methylimidazole. The present method is simple, mild, and reactive, uses readily available and economical reagents. The choice of amine is critical for the present method. The amine, N‐methylimidazole, has two roles: (i) as an HCl scavenger for the initial smooth generation of mixed anhydrides between carboxylic acids and TsCl and (ii) successive formation of highly reactive ammonium intermediates from mixed anhydrides. This method could be applied to various types of carboxylic acids, alcohols, and thiols: a) several functionalities were tolerated; b) two N‐Cbz amino acids were smoothly esterified without racemization; and c) the labile 1β‐methylcarbapenem key intermediate and a pyrethroid insecticide, prallethrin, were successfully prepared. The related amide formation between carboxylic acids and primary or secondary amines was also performed. The proposed reaction mechanism involves a novel method for producing the reactive acylammonium intermediates. The production of these intermediates was rationally supported by a careful ¹H NMR monitoring study.     

Carbon dioxide reforming of ethanol over Ni/Y2O3–ZrO2 catalysts

Supported nickel catalysts of composition Ni/Y₂O₃–ZrO₂ were synthesized in one step by the polymerization method and compared with a nickel catalyst prepared by wet impregnation. Stronger interactions were observed in the formed catalysts between NiO species and the oxygen vacancies of the Y₂O₃–ZrO₂ in the catalysts made by polymerization, and these were attributed to less agglomeration of the NiO during the synthesis of the catalysts in one step. The dry reforming of ethanol was catalyzed with a maximum CO₂ conversion of 61% on the 5NiYZ catalyst at 800 °C, representing a better response than for the catalyst of the same composition prepared by wet impregnation.     

Preparation and properties of biodegradable network poly(ester-carbonate) elastomers

Biodegradable elastomeric network poly(ester-carbonate)s were prepared from multifunctional aliphatic carboxylic acids such as tricarballylic acid (Y_t) or trimesic acid (Y) and polycarbonate diols (PCD) with molecular weights of 1000 and 2000 g/mol. Prepolymers prepared by a melt polycondensation were cast from dimethylformamide solution and postpolymerized at 270 °C for 40-80 min to form a network. The resultant films were transparent, flexible and insoluble in organic solvents. WAXS exhibited the crystalline peaks due to polycarbonate segments for the network films from PCD₂₀₀₀, while those from PCD₁₀₀₀ were amorphous. The tensile properties were determined for these network films at the temperatures 22, 30, 40 and 50 °C. These films showed elastomeric properties at all temperatures measured. The elongation at break was much higher for the films from PCD₂₀₀₀ (208-434%) than those from PCD₁₀₀₀ (40-120%), and decreased with increasing temperatures. The weight losses of the network films degraded in the buffer solution of Rhizopus delemar lipase at 37 °C increased with time, suggesting that these network films are biodegradable. The degradation rate of the network films from Y_t is faster than that from Y. The GPC curves showed that the lipase hydrolyzed both the ester linkages between Y or Y_t and PCD as well as polycarbonate moiety in the network polymer.     

Preparation of long sticky ends for universal ligation-independent cloning: Sequential T4 DNA polymerase treatments

Ligation-independent cloning (LIC) is a useful method for efficient directional cloning of a PCR product. LIC requires a specially designed vector containing a long stretch of sequence that is missing any one of the four nucleotides. When the linearized vector is treated with T4 DNA polymerase, in the presence of the absent base, long single-stranded overhangs are generated that are suitable for cloning. In this study, long and efficient sticky ends for LIC were produced by sequential T4 DNA polymerase treatments at non-specific sequences on a commercially available vector. All restriction enzyme sites become available in the current LIC.     

Surface properties of TiFe and TiFe-Nb 6.8 at.% electrodes in aqueous solution

Even at ambient pressure and temperature TiFe and TiFe-Nb 6.8 at.% compounds display their outstanding abilities for absorbing hydrogen when cathodically polarized in an aqueous solution. Electrochemical reaction is also highly activated on electrodes made of these intermetallic compounds. This paper describes the results of electrochemical measurement and the surface properties of both TiFe and TiFe-Nb 6.8 at.% electrodes in comparison with those obtained using TiNi_n and TiCo_n (n = 1, 2, 3), emphasizing catalytic activity for the reaction of hydrogen evolution. It was concluded that the electrochemically active site of TiFe or TiFe-Nb 6.8 at.% electrode surface could be formed only after a specified area of the electrode had been covered with hydrogen of one or a few atomic layers. At the same time, this site acts as an entrance and exit for hydrogen into and out of the electrode.