Search results for "Opera"

1990

Taking into account the dependency on molar mass of the viscometric interaction parameter B, the modified Stockmayer-Fixman-Burchard equation ([η]/M1/2) = KΘ + C″ · A2 · M1/2 is obtained. It relates the intrinsic viscosity, [η], to the second virial coefficient, A2, and to the unperturbed dimensions parameter, KΘ, with C″ being a constant. Hereupon, KΘ can be determined from [η] and A2 data of any binary (solvent/polymer) and/or ternary (solvent 1/solvent 2/polymer) system, BPS and/or TPS. Because of the scarcity of reliable sets of [η] and A2 values mostly for TPS, the application of the above equation to obtain KΘ coefficients rests limited. This limitation can be surmounted by an A2 eval…

1972

The determination of reactivity ratios is simplified by using an excess of one monomer (M1) at a time large enough that the copolymers will have a very small content of the other monomer (M2). In this case chain propagation takes place almost exclusively by addition to polymer radicals with a terminal M1-unit (P) and monomer consumption by propagation of P may be neglected. One reactivity ratio (r1) is obtained from monomer conversions by means of a simple integrated equation which is valid up to high conversions. A calculation is proposed in order to account for the neglected propagation via P. The other reactivity ratio (r2) is obtained from copolymerizations with excess M2. As the new me…

MbCO embedded in trehalosyldextrin matrices: thermal effects and protein-matrix coupling

2010

Saccharide-based biopreservation is widely studied because of its scientific importance and possible technological outcomes for food and pharmaceutical industries. Ternary protein/saccharide/water systems have been extensively exploited to model the characteristics of the in vivo biopreservation process. A tight, water dependent, protein–matrix coupling has been shown to occur in various simple saccharide amorphous matrices, which is stronger in trehalose. The efficiency as bioprotectant of trehalose has been ascribed to this tight coupling, since the appearance of damages on biological structures will more involve structural variations of the surrounding matrix. Here we present, as an appl…

Corrigendum to “Phase equilibria for the ternary systems ethanol, water + ethylene glycol or + glycerol at 101.3 kPa” [Fluid Phase Equilib. 341 (2013…

2013

Rotational spectra of isotopic species of silyl fluoride. Part II: theoretical and empirical equilibrium structure

2010

Abstract The equilibrium structure of silyl fluoride, SiH 3 F, has been reinvestigated using both theoretical and experimental data. With respect to the former, quantum-chemical calculations at the coupled-cluster level have been employed together with extrapolation to the basis set limit, consideration of higher excitations in the cluster operator, and inclusion of core correlation as well as relativistic corrections ( r (Si–F) = 1.5911 A, r (Si–H) = 1.4695 A, and ∠FSiH = 108.30°). A semi-experimental equilibrium structure has been determined based on the available rotational constants for the various isotopic species of silyl fluoride ( 28 SiH 3 F, 28 SiD 3 F, 29 SiH 3 F, 29 SiD 3 F, 30 S…

1978

For the three different cases (R=polybutadiene, polypropylene oxide and EPDM) the isothermal cloud point curves of the system styrene/polystyrene/rubber (S/PS/R) show that at 25°C a decomposition into two phases occurs already in the presence of a few percents of polystyrene and rubber. By separating the phases (centrifuge) and analysis of coexisting phases, tie lines and thus critical points could be fixed. Evaluation of the results was made on the basis of the Flory and Huggins theory by means of approximations given for such systems by Scott. The interaction parameters resulting for 25°C are well in agreement with literature data—as far as available. By means of the approximations mentio…

Isobaric Vapor−Liquid Equilibria for Binary and Ternary Mixtures with Cyclohexane, Cyclohexene, and 2-Methoxyethanol at 100 kPa

2009

Consistent vapor−liquid equilibria (VLE) data at 100 kPa have been determined for the ternary system cyclohexane + cyclohexene + 2-methoxyethanol and two constituent binary systems: cyclohexane + 2-methoxyethanol and cyclohexene + 2-methoxyethanol. Both binary systems deviate remarkably from ideal behavior presenting a minimum boiling point azeotrope. The VLE data have been correlated by the Wilson, UNIQUAC, and NRTL equations. The ternary system does not present an azeotrope and is well predicted from binary interaction parameters. Prediction with the UNIFAC method has been also obtained.

Genetic Systems for Monitoring Interactions of Transmembrane Domains in Bacterial Membranes

2013

In recent years several systems have been developed to study interactions of TM domains within the inner membrane of the Gram-negative bacterium Escherichia coli. Mostly, a transmembrane domain of interest is fused to a soluble DNA-binding domain, which dimerizes in E. coli cytoplasm after interactions of the transmembrane domains. The dimeric DNA-binding domain subsequently binds to a promoter/operator region and thereby activates or represses a reporter gene. In 1996 the first bacterial system has been introduced to measure interactions of TM helices within a bacterial membrane, which is based on fusion of a transmembrane helix of interest to the DNA-binding domain of the Vibrio cholerae …

Isobaric Vapor−Liquid Equilibria for Binary and Ternary Mixtures of Ethanol, Methylcyclohexane, and p-Xylene

2004

Consistent vapor−liquid equilibria (VLE) were determined for the ternary system ethanol + methylcyclohexane + p-xylene and the three binary subsystems at 101.3 kPa at temperatures in the range from 345 to 408 K. The binary systems exhibit positive deviation from ideal behavior, and the system ethanol + methylcyclohexane presents a minimum-boiling-point azeotrope. The VLE data have been correlated by the Wilson, NRTL, and UNIQUAC equations. The ternary system does not present an azeotrope and is well predicted from binary interaction parameters.

1990

Intrinsic viscosities, [η], second virial coefficients, A2, and interaction potentials, g12, for the ternary systems alcohol (1)/3-heptanone (2)/poly(1-vinyl-2-pyrrolidone) (3), with the unbranched alcohols methanol, ethanol and 1-propanol, were determined at 25°C. Taking into account the dependence of the viscometric interaction parameter, B, with the molecular weight of the polymer, the unperturbed dimensions parameter, KΘ, of the polymer was unambiguously obtained. Relationships between ΔKΘ (defined as ΔKΘ = ΔK − KΘ) and excess Gibbs energies, GE, and between excess viscosity, Δ[η], and GE allow to obtain equations relating A2 to ΔKΘ or to Δ[η]. Therefore, A2 can be evaluated from experi…