Model Development of Slag Foaming Ghag, Surinder S.; Hayes, Peter C.; Lee, Hae-Geon
ISIJ International,
01/1998, Letnik:
38, Številka:
11
Journal Article
Recenzirano
Odprti dostop
A general model of foaming has been developed which relates the structure of a foam stabilised by viscoelastic forces to the bubble rupturing processes. For the specific case of negligible bubble ...coalescence within the foam it has been shown that, in the region of linearity between the foam height and gas flux, the residence time of gas in the foam (Σ) is solely a function of the bubble diameter (d), the liquid phase density (ρ) and viscosity (μ), and the effective elasticity (Eeff) resulting from the dynamic adsorption of surface active species: Σ=1×106((pg)2d3 μ·Eeff) The model, which shows that the gas bubble diameter has the greatest effect on the retention of gas bubbles within the foam, has been found to be applicable to a range of system in which foams are stabilised by viscoelastic forces.
A dynamic, non-equilibrium model of foaming: Σ=1×106((pg)2d3 μ·Eeff) which relates the residence times of gas bubbles in foams (Σ) to the viscosity of the liquid phase (μ); the effective elasticity ...(Eeff) resulting from the dynamic adsorption of surface active species; the liquid phase density (ρ); and the mean bubble diameter (d ); has been applied to foaming in the CaO–SiO2–FeO system at 1823 K. In agreement with industrial observations, the model shows a transition from a foaming regime to a non-foaming regime as the slag basicity increase above 1.5. This is due to poor surface elasticity resulting from the negligible adsorption of silica in this region.
The gene for bifunctional deacetoxycephalosporin C synthetase/hydroxylase of Cephalosporium acremonium was cloned and overexpressed as an insoluble and inactive enzyme in granules of recombinant ...Escherichia coli. About 40-60% of expected synthetase activity along with 50-80% protein purity could be recovered directly from granular extracts with only a single empirically optimized refolding step. Further purification to homogeneity was achieved by a single anion-exchange-chromatographic step in the presence of denaturing concentrations of urea. The main obstacle to converting the homogeneous unfolded protein into the active enzyme was a urea-dependent aggregation during refolding that led to irreversible enzyme inactivation. Information obtained from refolding studies using gel-filtration HPLC, fluorescence spectroscopy and disulphide analysis led to an optimal enzyme refolding scheme that resulted in a highly active (i.e. 65-75% of the expected activity) and moderately stable fungal synthetase/hydroxylase.
A dynamic, non-equilibrium model of foaming which relates the residence times of gas bubbles in foams ( Sigma ) to the viscosity of the liquid phase ( mu ); the effective elasticity (E sub eff ) ...resulting from the dynamic adsorption of surface active species; the liquid phase density ( rho ); and the mean bubble diameter (d); has been applied to foaming in the CaO-SiO sub 2 -FeO system at 1823K. In agreement with industrial observations, the model shows a transition from a foaming regime to a non-foaming regime as the slag basicity increase > 1.5. This is due to poor surface elasticity resulting from the negligible adsorption of silica in this region.
Specific syntheses of 2'(3')-O-aminoacyl oligoribonucleotides C-C-A-Gly (12), C-C-A(AcGly) (7), U-C-C-A-Gly (17), and C-U-C-C-A-Gly (19), which are the 3'-terminal sequences of Escherichia coli ...Gly-tRNA (or AcGly-tRNA, respectively) are described. Compounds 12, 17, and 19 were synthesized by employing the benzotriazolyl phosphotriester approach with the following protection groups on the components: benzoyl for the heterocyclic amino groups, 2-chlorophenyl group for internucleotide phosphate protection, dimethoxytrityl and levulinoyl groups for blocking of the 5'-hydroxyl, methoxytetrahydropyranyl group for protection of the 2'-hydroxyl functions, and N-(benzyloxycarbonyl)orthoglycinate as the masked aminoacyl group simultaneously protecting the 2',3'-cis diol group of the 3'-terminal adenosine moiety. The fully protected tri-, tetra-, and pentanucleotides were obtained via 5'-extension of di- and trinucleotide blocks after prior selective removal of the 5'-O-levulinoyl group with hydrazine. The blocked derivatives 11, 16, and 18 were totally deprotected by reactions with NH4OH, H+, and H2/Pd to yield the target compounds 12, 17, and 19 in good yields. C-C-A(AcGly) (7) was synthesized according to a stepwise procedure via activation of preformed diesters with (mesitylenesulfonyl)tetrazole. C-C-A-Gly (12), U-C-C-A-Gly (17), and C-U-C-C-A-Gly (19) were all acceptor substrates in the peptidyltransferase reaction with the Ac-Phe-tRNA-70S ribosome-poly(U) system. All three models also promoted EF-Tu-70S ribosome GTP hydrolysis.
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