Improvement in Thermoelectric Characteristics of n-type Iron Disilicide by Local Composition Modification

High thermoelectric figure of merit semiconducting ceramics of n -type iron disilicide with modified local compositions have been developed. Sintering and annealing of the composite powder composed of iron disilicide and precipitated cobalt (II) hydroxide resulted in the dissolution of excess Co and oxygen into the iron disilicide phase. Excess Co segregated to the grain boundary region, while interstitially incorporated oxygen was distributed homogeneously in the microstructure. The maximum figure of merit achieved was 5.2 × 10⁻⁴/K at 673 K.     

An absolute requirement of fructose 1,6-bisphosphate for the Lactobacillus caseiL-lactate dehydrogenase activity induced by a single amino acid substitution

Lactobacillus casei allosteric L-lactate dehydrogenase (L-LDH)absolutely requires fructose 1,6-bisphosphate [Fru(1,6)P2] forits catalytic activity under neutral conditions, but exhibitsmarked catalytic activity in the absence of Fru(1,6)P₂ underacidic conditions through the homotropic activation effect ofsubstrate pyruvate. In this enzyme, a single amino acid replacement,i.e. that of His205 conserved in the Fru(1,6)P₂-binding siteof certain allosteric L-LDHs of lactic acid bacteria with Thr,did not induce a marked loss of the activation effect of Fru(1,6)P₂or divalent metal ions, which are potent activators that improvethe activation function of Fru(1,6)P₂ under neutral conditions.However, this replacement induced a great loss of the Fru(1,6)P₂-independentactivation effect of pyruvate or pyruvate analogs under acidicconditions, consequently indicating an absolute Fru(1,6)P₂ requirementfor the enzyme activity. The replacement also induced a significantreduction in the pH-dependent sensitivity of the enzyme to Fru(1,6)P₂,through a slight decrease and increase of the Fru(1,6)P₂ sensitivityunder acidic and neutral conditions, respectively, indicatingthat His205 is also largely involved in the pH-dependent sensitivityof L.casei L-LDH to Fru(1,6)P₂. The role of His205 in the allostericregulation of the enzyme is discussed on the basis of the knowncrystal structures of L-LDHs.     

Resistance to sulfur poisoning of hot gas cleaning catalysts for the removal of tar from the pyrolysis of cedar wood

In the partial oxidation of tar derived from the pyrolysis of cedar wood, the effect of H₂S addition was investigated over non-catalyst, steam reforming Ni catalyst, and Rh/CeO₂/SiO₂ using a fluidized bed reactor. In the non-catalytic gasification, the product distribution was not influenced by the presence of H₂S. Steam reforming Ni catalyst was effective for the tar removal without H₂S addition, however, the addition of H₂S deactivated drastically. In contrast, Rh/CeO₂/SiO₂ exhibited higher and more stable activity than the Ni catalyst even under the presence of high concentration of H₂S (280 ppm). On the Ni catalyst, the adsorption of sulfur was observed by XPS and Ni species was oxidized during the partial oxidation of tar. In the case of Rh/CeO₂/SiO₂, the adsorption of sulfur was below the detection limit of XPS. This can be related to the self-cleaning of catalyst surface during the circulation in the fluidized bed reactor for the partial oxidation of tar derived from cedar pyrolysis.     

New class of cellulose fiber spun from the novel solution of cellulose by wet spinning method

A novel cellulose solution, prepared by dissolving an alkali-soluble cellulose, which was obtained by the steam explosion treatment on almost pure natural cellulose (soft wood pulp), into the aqueous sodium hydroxide solution with specific concentration (9.1 wt %) was employed for the first time to prepare a new class of multifilament-type cellulose fiber. For this purpose a wet spinning system with acid coagulation bath was applied. The mechanical properties and structural characteristics of the resulting cellulose fibers were compared with those of regenerated cellulose fibers such as viscose rayon and cuprammonium rayon commercially available. X-ray analysis shows that the new cellulose fiber is crystallographically cellulose II, and its crystallinity is higher but its crystalline orientation is slightly lower than those of other commercial regenerated fibers. The degree of breakdown of intramolecular hydrogen bond at C₃[X_am(C₃)] of the cellulose fiber, as determined by solid-state cross-polarization magic-angle sample spinning (CP/MAS) ¹³C NMR, is much lower than other, and the NMR spectra of its dry and wet state were significantly different from each other, indicating that cellulose molecules in the new cellulose fiber are quite mobile when wet. This phenomenon has not been reported for so-called regenerated cellulose fibers.     

The structure of acetylene flames for diamond synthesis

An acetylene flame was photographed with an SIT camera through optical filters, and the signals were Abel transformed to obtain two-dimensional emission-intensity profiles. It was found that the intensive emissions of CH* and C*₂ are localized at the feather boundary, while the OH* emission is localized at the intermediate zone. The structure of the acetylene flame was made clear: it consists of a carbon-radical-rich feather and an oxygen-radical-rich intermediate zone. The carbon-radical concentrations are approximately in equilibrium near the burner exit while they decrease almost linearly via interdiffusion and reactions with the oxygen-radicals in the intermediate zone.Numerical simulations including detailed gaseous and surface reactions reproduced well previous preliminary calculations showing that CH₄ is rapidly produced in the boundary layer near the substrate followed by an increase in CH₃. This result satisfactorily explains the measured dependence of growth rate on the substrate temperature and ratio.     

Stabilization of poly(vinyl chloride). I. Change in color of poly(vinyl chloride) compounded with some metal soaps

Poly(vinyl chloride) (PVC) with one or more metal salts added was colored by the action of heat to investigate the stabilization mechanism. The coloration and the color difference of heated PVC compound films varied according to the metal salt added. The decoloration of the colored compound films was advanced markedly in THF, DMF, acetone, and ammonia. On the other hand, the heated achromatic PVC film containing Cd/Ba soaps underwent an opposite change, from colorless to yellow orange, in the above materials. This means that the coloration of heated compound films may result from the formation of some complex (for example, π complex of the polyene with the metal chloride). Furthermore, the colored film with cadmium stearate was decolored by roll mixing with the colored film containing barium stearate. These results indicate that the stabilization with metal soaps may be founded on a physical phenomenon such aa an effect of complementary color.     

Copolymerization of ethanesultam with 2-methyl-2-oxazoline

Summary This paper describes the so-called No Catalyst Copolymerization between dioxo-1,1-thiazetidine-1,2(Ethanesultam; ESm) and 2-methyl-2-oxazoline. The copolymerization took place without any added initiator to produce copolymers of MeOZO and ESm. The structure of the copolymer was determined by the IR and NMR spectra, elemental analysis, as well as by the result of an alkaline hydrolysis of the copolymer. The reaction scheme of the copolymerization via zwitterion mechanism (Eq 3–5) was proposed.     

Radiation-induced polymerization of ethylene in pilot plant. III. Heavy-phase recycling process

Radiation-induced polymerization of ethylene using aqueous tert-butyl alcohol as medium was carried out in a large-scale pilot plant with a 50-liter central source-type reactor at a pressure of 105 to 395 kg/cm², temperature of 30° to 80°C, mean dose rate of 4.5 × 10⁴ to 1.9 × 10⁵ rads/hr, ethylene feed rate of 5.5 to 23.5 kg/hr, and medium feed rate of 21 to 102 l./hr. The space–time yield and molecular weight of the polymer were in the range of 4.7 to 16.8 g/l.-hr and 1.3 × 10⁴ to 8.9 × 10⁴, respectively. The space–time yield and molecular weight increased with mean residence time at 30°C, whereas at 80°C they became almost independent of the time. The space–time yield increased with pressure and dose rate, slightly decreased with temperature, and was maximum at ethylene molar fraction of 0.5. The polymer molecular weight increased with pressure and ethylene molar fraction, and decreased with dose rate and temperature. The total amount of deposited polymer on the reactor wall, source case wall, and scraping blades was usually less than 1 kg, which was negligibly small for the analysis of polymerization. Continuous discharge of the polymer slurry and production of fine-powder polyethylene were successfully carried out. In the central source-type reactor, a dose rate of 1.9 × 10⁵ rads/hr was obtained with a ⁶⁰Co source of ca. 12 kCi.     

Sintering Kinetics at Isothermal Shrinkage: II, Effect of Y2O3 Concentration on the Initial Sintering Stage of Fine Zirconia Powder

The shrinkage behavior of fine zirconia powders containing 2.9 and 7.8 mol% Y₂O₃ was investigated to clarify the effect of Y₂O₃ concentration on the initial sintering stage. The shrinkage of powder compact was measured under both conditions of constant rates of heating (CRH) and constant temperatures. CRH measurements revealed that when the Y₂O₃ concentration of fine zirconia powder increased, the starting temperature of shrinkage shifted to a high temperature. Isothermal shrinkage measurements revealed that the increase in Y₂O₃ concentration causes the shrinkage rate to decrease. The values of activation energy ( Q ) and frequency-factor term (β₀) of diffusion at initial sintering were estimated by applying the sintering-rate equation to the isothermal shrinkage data. When the Y₂O₃ concentration increases, both Q and β₀ of diffusion increase. It is, therefore, concluded that the increase in Y₂O₃ concentration of fine zirconia powder decreases the shrinkage rate because of increasing Q of diffusion at the initial stage of sintering.     

Reaction products of α-tocopherol with methyl linoleate-peroxyl radicals

α-Tocopherol was reacted with methyl linoleateperoxyl radicals at 37°C. The peroxyl radicals were generated by the reaction of methyl linoleate with a free radical initiator, 2,2′-azobis(2,4-dimethylvaleronitrile). The primary products of α-tocopherol with methyl linoleate-peroxyl radicals were isolated by reversephase and normal-phase high performance liquid chromatography (HPLC), and their structures were characterized by ultraviolet (UV), infrared (IR),¹H and¹³C nuclear magnetic resonance (NMR) and mass spectrometry (MS). There were four stereoisomers of methyl 13-(8a-peroxy-α-tocopherone)-9(Z),11(E)-octadecadienoate and four stereoisomers of methyl9-(8a-peroxy-α-tocopherone)-10(E),12(Z)-octadecadienoate.