Showing papers by "National Chemical Laboratory published in 1988"
TL;DR: In this article, the effect of support on the catalytic activity and properties of molybdenum sulfide catalysts was investigated in order to obtain the fundamental information necessary for designing better hydrotreating catalysts.
152 citations
TL;DR: In this paper, the kinetics of polyesterification of the glycolyzed PET waste with adipic acid was reported, and the reaction conditions were nonisothermal, comparable to the industrial process scheme consisting of two isothermal regions at 170° and 200°C.
Abstract: The kinetics of polyesterification of the glycolyzed PET waste with adipic acid is reported. Glycolysis of PET waste was carried out with ethylene glycol at three different ratios of PET waste to glycol. The glycolyzed products could be readily polyesterified by reacting with adipic acid, to give polyester polyols with low acid number. Kinetics of polyesterification of the glycolyzed product made from 62.5% ethylene glycol (EG) and 37.5% waste were investigated further at different hydroxyl to carboxyl ratios. Reaction conditions were nonisothermal, comparable to the industrial process scheme consisting of two isothermal regions at 170° and 200°C. The kinetic results of the polyesterification of glycolyzed PET waste are compared to the polyesterification of pure diols, namely ethylene glycol and bis(hydroxyethyl) terephthalate (BHET) with adipic acid. The reactions follow second-order kinetics at 170°C and the rate of polyesterification of the mixed diol system from PET waste lies intermediate between those of the pure diols, namely, EG and BHET. Ethylene glycol exhibited the highest reactivity. At 200°C the kinetic plots of the mixed diols from PET waste were nonlinear, and thus the reaction may not follow second-order kinetics. The nonlinearity is explained in terms of the different reactivities of the different diol species in the reaction mixture. The polyester polyols, when cured with polymeric 4,4′ diphenyl methane diisocyanates, gave polyurethane rigid foams and elastomers.
119 citations
TL;DR: In this article, the acid sites of aluminophosphate (AlPO-5) and silicoaluminoph phosphate (SAPO-5)-sieves have been investigated using diffuse reflectance i.r.d. spectroscopy, temperature-programmed desorption (t.p.d.) of NH 3, and catalytic activity in the cracking of cumene and oligomerization of ethylene.
107 citations
TL;DR: Somatic pro-embryos were regenerated from morphogenic protoplasts of cell suspension cultures of Douglas fir and loblolly pine by somatic polyembryogenesis from new ESMs on agar plates and the luciferase (luc) gene was successfully introduced into fir and pine protoplast by electroporation.
95 citations
TL;DR: In this paper, a new type of photochemical Langmuir-Blodgett (LB) film containing azobenzenes (p-phenylazobenzoic acid (PAB), methyl red (MR) and methyl orange (MO)) without long alkyl chains was prepared by the host-guest interaction with an amphiphilic cyclodextrin derivative.
91 citations
TL;DR: In this article, the effects of promoters, solvents, reaction conditions, and pretreatment of catalyst with reactants have been investigated for carbonylation of aniline to N,N′-diphenylurea over 5% Pd C NaI catalyst.
80 citations
TL;DR: In conclusion, inhibition of transmembrane signals associated with autocrine growth control in SCLC by a novel peptide receptor antagonist is demonstrated.
76 citations
TL;DR: Two clerodane type diterpenoids, with antifeedant properties have been isolated from Polyalthia longifolia and identified as 16α-hydroxy-cleroda-3,13(14) Z -dien-15,16-olide and 16-oxo-clerodic acid on the basis of spectral properties.
73 citations
TL;DR: In this paper, a double-tubular membrane reactor equipped with a selective membrane tube as the inner tube was proposed, which makes it possible to obtain a product yield of a reversible reaction beyond its equilibrium value by continuous removal of the products during reaction.
Abstract: A membrane reactor, which is a double-tubular reactor equipped with a selective membrane tube as the inner tube, was proposed Such a reactor makes it possible to obtain a product yield of a reversible reaction beyond its equilibrium value by continuous removal of the products during reaction A microporous glass tube was employed as the selective membrane, through which gases permeate almost according to Knudsen''s law Experiments in the dehydrogenation of cyclohexane to benzene as a model reaction were carried out, using the membrane reactor under atmospheric pressure in the range of 453-493 K It was shown experimentally and theoretically that a marked increase in conversion over that at equilibrium can be achieved
70 citations
TL;DR: It is concluded that a majority of the genotypes that show precocious germination of zygotic embryos have greater embryogenic potential and most of them exhibit a higher frequency and faster rate of plantlet regeneration.
Abstract: Immature embryos of thirty-three genotypes of wheat were cultured on 2,4-D containing medium. Occurrence of precocious germination of the zygotic and somatic embryos simultaneously on the same medium was a striking feature observed during the course of work. The percentage of precocious germination was seen to vary extensively from 0-88% and 0-84% for zygotic and somatic embryos respectively. In the genotypes NI-5439 and NI-5643 which are characterized by a high tillering capacity, the phenomenon of precocious germination seems to take a different path from that observed in the other genotypes. This is evident since these two genotypes require total absence of hormone for shoot elongation although multiple shoot primordia are formed on auxin containing medium.Precocious germination also seems to be relevant to somatic embryogenesis and plantlet regeneration. This conclusion stems from the observation that a majority of the genotypes that show precocious germination of zygotic embryos have greater embryogenic potential. Consecutively, most of the genotypes that show precocious germination of somatic embryos exhibit a higher frequency and faster rate of plantlet regeneration.
62 citations
TL;DR: Owing to the shifts in both ionic strength profiles and pH profiles the Arg74/Arg126 mutant has become a better catalyst than wild-type enzyme under the conditions of high ionsic strength and high pH, and the Gln41/Ser101 mutant has been become aBetter catalyst under the Conditions of low ionicstrength and low pH.
Abstract: The surface positive charges of human lysozyme were either increased or decreased to alter the electrostatic interaction between enzyme and substrate in the lytic action of human lysozyme using site-directed mutagenesis. The amino acid substitutions accompanying either the addition or the removal of two units of positive charge have shifted the optimal ionic strength (NaCl concentration in 10 mM Mes buffer, pH 6.2) for the lysis of Micrococcus lysodeikticus cell from 0.04 M to 0.1 M and from 0.04 M to 0.02 M respectively. In addition to the change in ionic strength-activity profile, the pH-activity profile and the effect of a polycationic electrolyte, poly-L-Lys-HCl, on the lytic activity were significantly changed. Owing to the shifts in both ionic strength profiles and pH profiles the Arg74/Arg126 mutant has become a better catalyst than wild-type enzyme under the conditions of high ionic strength and high pH, and the Gln41/Ser101 mutant has become a better catalyst under the conditions of low ionic strength and low pH.
TL;DR: Bismaleimide ayant un squelette epoxy entre les extremites maleimide as discussed by the authors, avec une resine epoxyde par condensation a l'etat fondu.
Abstract: Bismaleimide ayant un squelette epoxy entre les extremites maleimide. Reaction d'une fonction acide carboxylique contenant un maleimide preforme, avec une resine epoxyde par condensation a l'etat fondu
TL;DR: In this paper, surface pressure area isotherms for 12 amphiphilic cyclodextrins (CDs) with alkyl chains were recorded and the limiting areas per molecule depend on the number of glucose units and the substitution of the secondary hydroxy groups.
TL;DR: In this article, it was shown that not only hydroxyl ions but also sodium ions played an important role in the nucleation of ZSM-23, which was synthesized in the presence of pyrrolidine.
TL;DR: In this article, the thermal and crystallization behavior of blends of three thermoplastic polyesters with different degrees of crystallizability, with an amorphous aromatic polyamide is reported.
Abstract: The thermal and crystallization behavior of blends of three thermoplastic polyesters with different degrees of crystallizability, with an amorphous aromatic polyamide is reported. The thermoplastic polyesters used in the investigation were poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET) and a co-polyester of 1,4 cyclohexane-dimethanol, ethylene glydol and terephthalic acid (PETG). The blends exhibited a single glass transition temperature indicating mlseibility in the amorphous phase. The results of thermal analysis indicated that the crystallization of all the three polyesters is facilitated in the molten phase as a result of blending. The blending significantly Increased the degree of crystallinity of PET, but there was no change in the crystallinity of PBT. It is thus observed that the extent of change in both the crystallization rate and the degree of crystallinity of polyesters depend on the inherent crystallizability of the individual polyester.
TL;DR: The objective of this review is to present a comparative study of the research on cellulase and hemicellulase enzymes from S. rolfsii.
Abstract: Microbial degradation of native cellulose to glucose is catalysed by cellulases which refers to a group of enzymes acting in concert. The extracellular enzyme systems of Trichoderma reesei, Sporotrichum pulverulentum, Aspergillus niger and Sclerotium rolfsii have been examined more extensively than other microbial sources. The objective of this review is to present a comparative study of the research on cellulase and hemicellulase enzymes from S. rolfsii.
TL;DR: In this paper, the electron affinities of the acceptors of TMTTF-CnTCNQ (n=14, 18 or 22) in solution are reported.
TL;DR: In this paper, an integrated spectral data base system named SDBS was constructed, in which six kinds of spectral data, i.e., data of IR, MS, 1H-NMR, 13C- NMR, ESR and Raman spectra were compiled in an integrated way under the control of a directory data base.
Abstract: An integrated spectral data base system named SDBS was constructed, in which six kinds of spectral data, i.e., data of IR, MS, 1H-NMR, 13C-NMR, ESR and Raman spectra were compiled in an integrated way under the control of a directory data base. The spectra data are full pattern data and/or numerical data depending on the features of the spectra, most of which were obtained in our laboratory. Three options are provided as mode of access. In LOOK option the spectra for a given compound are displayed; in SEARCH option the identification of unknown compounds as well as the estimation of NMR chemical shifts and/or of the sub-structure of a molecule are possible; and in SIMULATE option, 1H-NMR and ESR spectra are generated from the NMR and ESR parameters, respectively. At present, approximately 17000 compounds are registered in the directory data base.
TL;DR: The structure of an intermediate phase (LaNi5D3) in the LaNi5-D2 system was refined using high resolution time-of-flight neutron powder diffraction data.
Abstract: The structure of an intermediate phase (LaNi5D3) in the LaNi5-D2 system was refined using high resolution time-of-flight neutron powder diffraction data. The structure is described in the space group P6/mmm and the unit cell dimensions are a = 5.302(5) A and c = 4.066(3) A . Two of the three deuterium atoms of LaNi5D3 occupy the 6i site (0.5, 0, 0.088) and the remaining deuterium atom occupies the 6m site (0.131, 0.262, 0.5). Measurements of the hydrogen content of the specimen confirmed the composition LaNi5D3.
TL;DR: In this paper, the authors measured the sorption capacity of a number of sorbates, viz. alcohols and hydrocarbons, and the isotherms of sorption of methanol, n -hexane, and benzene in AlPO 4 -5 at 313 K.
TL;DR: In this paper, the co-transport mechanism of amino acids with lipophilic anions through supported liquid membranes (SLMs), composed of o-nitrophenyl phenyl ether containing achiral or chiral crown ether, was investigated.
TL;DR: Sulfurization and selenation reactions of 1,1,4,4-tetraaryl-1,2,3-butatrienes were examined to give novel 1 2,3, 4,5-pentathiepane and 1 2 5 triselenepane ring systems as mentioned in this paper.
TL;DR: In this article, a comparison of the catalytic activity of [HRu(CO) 4 ] − with those of the known catalyst systems ([HRu 3 (CO) 11 ] − and Ru 3 (Co) 12 ] − has revealed that the system is an active catalyst for hydroformylation of 1-pentene, styrene, and ethyl acrylate.
TL;DR: In this paper, high molecular weight polyacrylamides were synthesized and successfully modified to contain up to 8·3% hydroxamate functional groups, which confirmed the possibility of enhancing selectivity through introduction of iron chelating functional groups in commercially available polymers.
Abstract: High molecular weight polyacrylamides were synthesized and successfully modified to contain up to 8·3% hydroxamate functional groups. The selective flocculation tests carried out on 1:1 iron oxide/kaolin mixtures using parent polyacrylamide, polyacrylic acid and the modified polyacrylamide, confirm the possibility of enhancing selectivity through introduction of iron chelating functional groups in commercially available polymers. Starting with a feed grade of 35% iron, 92% recovery with acceptable grade of 60% iron has been achieved using the modified polyacrylamide.
TL;DR: In this article, the thermal and crystallization behavior of blends of glass fiber reinforced polyphenylene sulfide (PPS) with polyethylene terephthalate (PET) has been reported.
Abstract: The thermal and crystallization behavior of blends of glass fiber reinforced polyphenylene sulfide (PPS) with polyethylene terephthalate (PET) has been reported. The blends showed two overlapping melting peaks and two separate crystallization peaks. The heat of crystallization of PPS was found to decrease continuously with increasing PET content, whereas the heat of crystallization of PET was found to increase with increasing PPS content. This indicates that the degree of crystallinity of PPS is reduced whereas that of PET is increased as a result of blending. It is interesting to note that the combined heats of fusion of the blends were marginally higher than those calculated by proportional additivity rule in spite of the drop in the heat of crystallization of PPS. The temperature onset of crystallization of PET in the blends shifted to higher temperature whereas there was no significant change in the crystallization temperature of PPS. The increase in the temperature of crystallization of PET indicates enhanced nucleation. The isothermal crystallization studies of the component polymers revealed that both the component polymers crystallized at a relatively faster rate in the blend. The crystallization rate of PPS was found to increase significantly with increasing PET content. A significant increase in the rate of crystallization of PET was also observed in the blends. The acceleration of crystallization rate of PET in the blends was more pronounced as compared to that of PPS. The acceleration in the PET crystallization rate was attributed to the presence of glass fibers and crystallized PPS.
TL;DR: Using a gel retardation assay it was shown that the 87 bp DNA fragment (UAS87) containing the upstream activating sequence of S. cerevisiae EN01 gene and a nuclear extract gave rise to three migration-retarded species specific to UAS87.
Abstract: Using a gel retardation assay it was shown that the 87 bp DNA fragment (UAS87) containing the upstream activating sequence (UAS) of S. cerevisiae EN01 gene and a nuclear extract gave rise to three migration-retarded species specific to UAS87. Heat- or proteinase-treatment of the nuclear extract revealed that these species were protein-DNA complexes. The precise binding region of the protein identified by DNaseI protection analysis was found to include a CCAAACA sequence which forms a dyad-symmetrical structure. The amount of one of the three migration-retarded species significantly increased when cells were grown in medium containing a gluconeogenic carbon source. The introduction of pGCR8, a multicopy plasmid containing GCR1 gene, a regulatory gene controlling the expression of several glycolytic enzymes, showed no effect on the amount of three migration-retarded species.
TL;DR: The separation of the five principal alkaloids, three minor alkaloidal components, meconic acid and some unidentified constituents in gum opium samples has been achieved on a reversed-phase phenyl column by gradient high-performance liquid chromatography using a simple and inexpensive mobile phase system.
TL;DR: The results suggest that the gene expression for poly(ADP-ribose) synthetase is depressed during the interferon-gamma-induced activation process of macrophage tumor cells.
Abstract: A 2.7-kb cDNA clone coding for bovine poly(ADP-ribose) synthetase was isolated from a λgt11 expression library by direct immunological screening with an antiserum to the enzyme. The cDNA hybridizes to an approximately 3.8-kb bovine thymus polyadenylated RNA, which translates an immunoprecipitable 120-kDa protein with the antibody to the enzyme. The partial DNA sequence of the cDNA was determined and portions of the predicted amino acid sequence matched the sequence of 26 amino acids at the N terminal of the 41-kDa α-chymotryptic fragment and two cyanogen-bromide-cleaved peptides of the enzyme.
A subcloned fragment from the coding region of the cDNA was used as a probe to estimate the level of mRNA for the enzyme during the interferon-γ-induced activation process of the murine macrophage tumor P388D1 cell line. The amount of mRNA for the enzyme decreased nearly completely within 24 h after incubation in a medium containing interferon-γ, while mRNA of the Ia antigen, one of the major histocompatibility gene products, was increased in the macrophage tumor cells by interferon-γ as confirmed by the I-Aβ cDNA as a probe. These results suggest that the gene expression for poly(ADP-ribose) synthetase is depressed during the interferon-γ-induced activation process of macrophage tumor cells.
TL;DR: A new electron donor C 7 TET-TTF of which the molecular structure is expressed by substituting one ethylenedithio moiety of BEDT- TTF with two heptylthio groups was synthesized (m.p.
TL;DR: Dimethylphenylsilane was catalytically dehydrogenated and condensed in the presence of platinum complexes to give 1,1,2,2-tetramethyl-1, 2-diphenyl-disilane.
Abstract: Dimethylphenylsilane was catalytically dehydrogenated and condensed in the presence of platinum complexes to give 1,1,2,2-tetramethyl-1,2-diphenyl-disilane.