Showing papers by "National Chemical Laboratory published in 1986"
TL;DR: In this article, a review of PET synthesis and its kinetics has been presented, including the network of main reactions and side reactions, as well as thermodynamic and transport data pertaining to PET formation.
117 citations
TL;DR: The optimization of fermentation conditions for Neurospora crassa resulted in yields of 5.5 and 10 g l −1 of ethanol from 1% Avicel and 2% alkali-treated cellulose powder corresponding to 100 and 90% conversion, respectively, in 4 days.
105 citations
99 citations
TL;DR: In this paper, the photodeposition of metal ions onto Pt-loaded titanium dioxide powder was reported, and it was shown that oxygen serves as an electron acceptor, so that the charge separation between the electron and positive hole is promoted.
93 citations
TL;DR: In this paper, the overall nonideality of an aqueous mixed electrolyte solution is characterized in terms of a newly defined parameter Γ*, called the overall reduced ionic activity coefficient.
Abstract: The overall nonideality of an aqueous mixed electrolyte solution is characterized in terms of a newly defined parameter Γ*, called the overall reduced ionic activity coefficient. It is shown that Γ* for the mixed solution is simply related to the properties of single-electrolyte solutions. Γ* is related to the vapor pressure of a mixed-electrolyte solution through well-known thermodynamic equations. This leads to a predictive equation for the vapor pressure of a mixed-electrolyte solution in terms of the vapor pressures of single-electrolyte solutions of the components. This equation is valid over the entire concentration range encountered in practice, without any empirical constants, and has a predictive accuracy of 2%. A predictive equation for the latent heat of vaporization is also developed and tested against experimental data.
85 citations
TL;DR: In this paper, antimony-doped SnO2 films with resistivity as low as 9×10−4 Ωcm were prepared by spray pyrolysis.
Abstract: Antimony-doped SnO2 films with a resistivity as low as 9×10−4 Ωcm were prepared by spray pyrolysis. Structural, electrical and optical properties were studied by varying the antimony concentration, film thickness and deposition temperature. About 94% average transmission in the visible region and about 87% infrared reflectance were obtained for antimony-doped SnO2 films by a systematic optimization of the preparation parameters. As the best combination, an average transmission of 88% in the visible region and an infrared reflectance of 76% was possible for the doped SnO2 films.
79 citations
TL;DR: In this article, the acid and catalytic properties of HZSM-5 zeolites of varying SiO 2 Al 2 O 3 ratios have been investigated, and three types of acid sites, weak, medium and strong, have been identified by temperature programmed desorption of ammonia.
78 citations
TL;DR: A multicopy plasmid was constructed to direct the synthesis and secretion of human lysozyme (HLY) in Saccharomyces cerevisiae, and HLY purified from the culture medium was homogeneous and displayed specific activity identical to that of authentic HLY.
73 citations
TL;DR: The synergistic effect was more pronounced, with the hydrolysis of 68%, when a homogeneous preparation of β‐xylosidase from Sclerotium rolfsii was added to the saccharification system.
Abstract: Extracellular beta-xylosidase (1,4-beta-D-xylan xylohydrolase, EC 3.2.1.37) from culture filtrates of Neurospora crassa was purified to homogeneity by preparative isoelectric focusing followed by gel electrophoresis. The molecular weight of the purified xylosidase was 83,000 D and the K(m) on p-nitrophenyl-beta-D-xyloside was 0.047mM. The homogeneous xylanase (1,4-beta-D-xylan xylanohydrolase, EC 3.2.1.8) and beta-xylosidase showed differences in their mode of action towards xylooligosaccharides. The degree of hydrolysis of D-xylan by xylanase of N. crassa was 18%. Supplementation of beta-xylosidase from the same organism resulted in 48% hydrolysis. The synergistic effect was more pronounced, with the hydrolysis of 68%, when a homogeneous preparation of beta-xylosidase from Sclerotium rolfsii was added to the saccharification system.
69 citations
TL;DR: In this paper, the authors synthesize Pentasil zeolites containing Al 3+ or Fe 3+ in lattice positions using triethyl-n-butylammonium bromide (TEBA-Br) as a template.
67 citations
TL;DR: In this article, core level X-ray photoelectron spectra of Zr76Fe24 metglass have been studied under various oxygen exposures and at different temperatures, and the formation of both ZRO and ZrO2 was observed even at 200 °C.
Abstract: Core level X-ray photoelectron spectra of Zr76Fe24 metglass have been studied under various oxygen exposures and at different temperatures. The formation of both ZrO and ZrO2 was observed even at 200 °C. Angle-dependent studies revealed that the ratio of ZrO to ZrO2 increases as the grazing angle of electron takeoff is approached, up to 100 °C and at 200 °C this ratio decreases as the grazing angle is approached. The Fe 2p32 level did not show any binding energy shift.
TL;DR: In this article, high-temperature bulk oxidation between 250 and 650 C goes through distinct steps of formation of intermediate tin oxoselenides, presumably SnOSe or SnSeO2 and its subsequent conversion to SnO2.
Abstract: High-temperature oxidation of SnSe in the temperature interval 25 to 650‡ C has been studied by X-ray photoelectron spectroscopy, X-ray diffraction and thermal analysis techniques. Exposure to dry oxygen (760 torr pressure) at up to 200‡ C leads to the formation of SnO2 on the surface. The high-temperature bulk oxidation between 250 and 650‡ C goes through distinct steps of formation of intermediate tin oxoselenides, presumably SnOSe or SnSeO2 and its subsequent conversion to SnO2.
TL;DR: In this paper, the authors showed that activity for xylene isomerization decreases by a factor of 3 when crystal size of HZSM-5 is increased from 8 to 16 μm.
TL;DR: The best ethanol-producing mutant showed the highest ratio of NADH- to NADPH-linked D-xylose reductase activity and high levels of all other pentose phosphate pathway enzymes assayed.
TL;DR: In this paper, the authors derived predictive equations for several properties in terms of corresponding properties of single-electrolyte solutions containing the component electrolytes, including volume properties such as density and adiabatic compressibility.
Abstract: The overall reduced ionic activity coefficient Γ* is useful in characterizing the overall nonideality of an aqueous mixed-electrolyte solution. It has been shown in Part I that Γ* can be simply related to Γ of single-electrolyte solutions containing the component electrolytes without using empirical constants. This basic relationship is used in this paper for deriving predictive equations for several properties in terms of corresponding properties of single-electrolyte solutions containing the component electrolytes. The predictive equations need no empirical constants. The properties covered include volume properties such as density and adiabatic compressibility, thermal properties such as enthalpy and specific heats, and others such as free energy, expansibility, and depression in freezing point. Comparison with experimental data shows that the predictive equations have an accuracy varying from 0.03% for density to 2% for freezing point depression, and are valid for the entire range of concentrations encountered in practice.
TL;DR: In this article, the authors studied the hydration of CaAl2O4 (CA) by calorimetry, analysis of the liquid phase, measurement of the combined water, and electron microscopy.
Abstract: Hydration of CaAl2O4 (CA) was studied by calorimetry, analysis of the liquid phase, measurement of the combined water, and electron microscopy. During the induction period, the solution remains almost unchanged and is equilibrated temporarily with both superficially intrusion-hydrated CA particles and Al(OH)3 gel formed by dissociation of Al(OH)4– ions, the solubility of the Al(OH)3 gel being 10–4.24 molkg–1 at 25°C, while the intrusion-hydrated layer on the CA particles grows following a nearly linear law to reach a critical thickness (∼3 nm at 10° to 20°C, or 12 nm at 30°C). At this point destruction of the layer occurs, nuclei of hydrous compounds are generated, and the induction period terminates. Subsequent reaction proceeds in accordance with the rate equation of Schiller based on the dissolution-crystallization mechanism.
TL;DR: In this paper, the effect of temperature on the gas hold-up and flow regimes for air-water and air-electrolyte solutions (NaCl and CuCl2) was studied in a bubble column with a sintered glass disc distributor.
Abstract: The effect of temperature on the gas hold-up and flow regimes for air—water and air—electrolyte solutions (NaCl and CuCl2) was studied in a bubble column with a sintered glass disc distributor. For the air—water system, the gas hold-up was found to decrease with increase in temperature. For the air—electrolyte solutions, increase in temperature resulted in increased gas hold-up at lower gas velocity, while at higher gas velocity the gas hold-up was found to decrease with temperature. The gas velocity ugT for transition from bubble flow to churn turbulent flow was found to decrease with increase in temperature as a result of increased coalescence. In the presence of electrolytes, ugT was found to be higher than that for water.
On a etudie 1'influence de la temperature sur la retention des gaz et sur les regimes d'ecoulement pour des solutions air—eau et air–electrolyte (NaCl et CuCl2) dans une colonne a bulles munie d'un disque en verre fritte comme distributeur. La retention des gaz diminue dans le cas du systeme air—eau lorsque la temperature augmente. Pour les solutions air–electrolyte, une augmentation de la temperature provoque une augmentation de la retention des gaz a basse vitesse tandis qu'a plus haute vitesse de circulation des gaz, la retention diminue avec la temperature. On a trouve egalement que la vitesse des gaz ugT correspondant a la transition d'un ecoulement malaxe, diminue lorsque la temperature augmente en raison d'une coalescence accrue. ugT s'avere plus eleve en presence d'electrolyte qu'en presence d'eau.
TL;DR: In this paper, a fast atom bombardment mass spectrometer was used for peptide sequence elucidation, and the result obtained for a given amino acid composition was always satisfactory. But the degree of success depends entirely on the spectrum used in the analysis.
Abstract: This paper proposes an efficient method for computer-aided peptide sequencing based on fast atom bombardment mass spectrometry. The method allows us to analyse peptides much larger than 1000 u within a reasonable cpu time and to have a set of amino acid sequences which are consistent with the observed fast atom bombardment mass spectrum to varying degrees. Another feature is that there is no need to pick sequence ion peaks out of the spectrum; all the ions observed are equally taken into account in the analysis so that one can exhaust the possibilities expected from the whole spectrum. For most samples of penta- to tridecapeptides, parts of an amino acid sequence could be reproduced satisfactorily without prior knowledge of amino acid composition. The degree of success in sequence elucidation depends entirely on the spectrum used in the analysis. When fragment ion peaks are clearly observed, the sequence can be predicted successfully. The result obtained for a given amino acid composition was always satisfactory.
TL;DR: In this article, new procedures for acylation of active methylene compounds via palladium complex-catalyzed carbonylation of organic halides are disclosed. But these procedures are restricted to the case of methylene.
TL;DR: In this paper, the viscosity of ferrite-filled polymers at high levels of loading has been investigated and the differences in relative viscosities between the filled and unfilled systems for various matrices have been explained on the basis of polymer filler affinity and filler-filler interaction.
Abstract: This paper presents new experimental data on the viscosity of ferrite-filled polymers at high levels of loading. The choice of matrix and the choice of filler and filler loading has direct relevance to commercially important systems of magnetic plastics and rubbers. The effect of shear rate, concentration, and temperature on the rheological behavior of such highly loaded systems has been discussed in detail. The differences in the relative viscosities between the filled and unfilled systems for various matrices have been explained on the basis of polymer filler affinity and filler-filler interaction.
TL;DR: In this article, the thermal and crystallization behavior of alloys of two semicrystalline thermoplastics, namely, polyphenylene sulfide (PPS) and high-density polyethylene (HDPE), were studied by differential scanning calorimetry (DSC).
Abstract: The thermal and crystallization behavior of alloys of two semicrystalline thermoplastics, namely, polyphenylene sulfide (PPS) and high-density polyethylene (HDPE) were studied by differential scanning calorimetry (DSC). The presence of a second component in the alloy was found to influence the nonisothermal crystallization process of both the component polymers. The crystallization temperature of PPS in the DSC cooling scan is significantly affected, whereas there is little variation in case of HDPE in the composition range studied. The morphological changes observed in both PPS and HDPE are similar. These include larger crystallite size, a narrower crystallite size distribution, and a lower degree of crystallinity in the alloys as compared to the homopolymers. The isothermal crystallization of the component polymers in the alloys is significantly different from that of the homopolymer. The composition dependence of the overall rate of isothermal crystallization is explained in terms of the competing processes of nucleation and crystal growth. The results show that blending of a high melting polymer with a low melting polymer accelerates the crystallization of the high melting polymer, even at low levels of about 10% of the lower melting component.
TL;DR: In this article, the effect of supports on the molybdenum catalysts used for upgrading coal-derived liquids was investigated using X-ray photoelectron spectrometer and Raman spectrometers.
TL;DR: In this paper, a regiospecific and convergent synthesis of Lavendamycin (1) starting from 8-hydroxyquinoline and indole via Bischler-Napieralski cyclisation is described.
TL;DR: In this paper, a gas chromatograph was used to study the effect of the Si/Al ratio, nature of cation and its degree of exchange, pretreatment temperature, and hydrothermal treatment on benzene diffusion in H-ZSM-5 zeolites.
TL;DR: It was found that the segment encompassing the 86-bp region worked equally well in an inverted orientation, but the tandem duplication of the sequence did not enhance the expression of the fused gene.
TL;DR: In this paper, the authors reported that the best results were obtained with mycelium entrapped in κ-carrageenan and in cubes of polyurethane sponge, and that the maximum protease activity secreted in the tenth cycle being about 85% of that produced in the initial use.
TL;DR: In this paper, it was suggested that pyrrolidine might stabilize certain aluminosilicate polyanions which have building units of oxygen five-membered rings, and it was also presumed that all zeolites, except ZSM-39, have a pore opening of oxygen ten-armed rings.
TL;DR: In this article, the authors investigated the effect of catalyst loading, H 2 pressure, concentrations of reactants and products on the rate of hydrogenation as well as the concentration profile in a batch reactor.
TL;DR: In this paper, the Rietveld refinement of gallosilicate zeolite in the sodium form in the space group P 4 3n (a = 8.856 A) converged with RF = 0.084 and Rwp =0.182.
TL;DR: In this article, the factors contributing to the high conductivity of doped thick films of Cd2SnO4 were identified and their influence on the character of the films is explained.