Search results for "Solutions"
showing 10 items of 757 documents
Volumes, heat capacities and solubilities of amyl compounds in decyltrimethylammonium bromide aqueous solutions
1989
Apparent molar heat capacities and volumes of amylamine (PentNH2) 0.02m, capronitrile (PentCN) 0.02m and nitropentane (PentNO2) 0.009m in decyltrimethylammonium bromide (DeTAB) micellar solutions, in water and in octane were measured at 25°C. By assuming that their concentration approaches the standard infinite dilution state, heat capacities and volumes were rationalized by means of previously reported equations following which the distribution constant between the aqueous and the micellar phase and heat capacity and volume of the additives in both phases are simultaneously derived. The present results are compared to those we have previously obtained for pentanol (PentOH). The thermodynam…
Enthalpies of mixing of some nitriles aqueous solutions with dodecylsurfactants micellar solutions
1988
The enthalpies of mixing of some n-nitriles (from acetonitrile to valeronitrile) aqueous solutions with dodecyltzimethylammonium bromide, sodium dodecylsulfate and dodecyltzimethylammonium oxide micellar solutions were determined. The measurements were performed by systematically changing the surfactant concentration at a given solute concentration. The experimental enthalpies were rationalized in terms of the standard enthalpy of transfer of solute from the aqueous to the micellar phase and of the distribution constant between the two phase. Information on the effect of the nature of the surfactant on the standard thermodynamic quantities of transfer(ΔG t o , ΔH t o , TΔS t o ) is reported…
Effect of Large Changes in Temperature and Pressure on the Thermodynamic Properties of Micellization and on the Distribution Constant of a Polar Solu…
1996
Density measurements of pentanol (PentOH)−dodecyltrimethylammonium bromide (DTAB)−water mixtures as functions of both alcohol and surfactant (mS) concentrations were carried out at 0.1 MPa from 45 to 75 °C and at 19 MPa from 25 to 130 °C. The standard (infinite dilution) partial molar volumes and expansibilities of DTAB in water and the corresponding properties in the micellar phase were calculated from the experimental data. As far as PentOH in DTAB micellar solutions is concerned, with the exception of the standard partial molar volume (V°R) data at 130 °C and 19 MPa, all the V°R vs mS trends are monotonic curves with mS. The data of V°R as a function of mS were treated by means of an equ…
Thermodynamics of transfer of some nitroalkanes from aqueous to dodecyltrimethylammonium bromide micellar phases
1988
Abstract The enthalpies of mixing of some aqueous n-nitroalkane solutions with dodecyltrimethylammonium bromide micellar solutions were determined. The experimental data were treated by using a previously reported approach giving the enthalpies of transfer of solute from the aqueous to the micellar phases and the distribution constant of solute between the two phases at the same time. From these, the standard thermodynamic quantities of transfer (ΔtrfG°, ΔtrfH° and ΔtrfS°) are derived. In order to study the effect of the nature of both the solvent and the head group of solute, these properties are compared with those from water to octane and with those of alcohols and nitriles from aqueous …
Excess enthalpies of solution of primary and secondary alcohols in dodecyldimethylamine oxide micellar solutions
1987
The excess enthalpies of solution with respect to water of some primary and secondary alcohols in dodecyldimethylamine oxide (DDAO) micellar solutions were measured by mixing aqueous solutions of alcohols with surfactant solutions. Standard free energies, enthalpies and entropies were obtained from the distribution of alcohols between aqueous and micellar phases. It is shown that thermodynamics of transfer of secondary alcohols from aqueous to the DDAO micellar phase differ slightly from those of their corresponding primary alcohols, that the additivity rule holds for free energies of transfer and that enthalpy and entropy display convex curves. The present data are compared with those from…
Double-Shell Vesicles, Strings of Vesicles and Filaments Found in Crosslinked Micellar Solutions of Poly(1,2-butadiene)-block-poly(ethylene oxide) Di…
2001
Micellar structures of amphiphilic poly(1,2-butadiene)-block-poly(ethylene oxide) diblock copolymers have been crosslinked in aqueous solution by γ-irradiation. By transmission electron microscopy (TEM) of neganively stained specimen it is shown that the precominant structures present are sopolymer sesicles (which appear to be double latered. These fived vesules are stable with respect to their share and can be transferred from water into a good solvent for blue filbeks, such as tetrahydrofuran, this demonstrating the effectiveness of the crosslinking. In addition to the resicles a small number of flexible cylindrichl/filimented structures sequentially fused vesicles/strings of vesicles and…
Solutions of the Einstein field equations for a bounded and finite discontinuous source, and its generalization: Metric matching conditions and jumpi…
2019
We consider the metrics of the General Relativity, whose energy-momentum tensor has a bounded support where it is continuous except for a finite step across the corresponding boundary surface. As a consequence, the first derivative of the metric across this boundary could perhaps present a finite step too. However, we can assume that the metric is ${\cal C}^1$ class everywhere. In such a case, although the partial second derivatives of the metric exhibit finite (no Dirac $\delta$ functions) discontinuities, the Dirac $\delta$ functions will still appear in the conservation equation of the energy-momentum tensor. As a consequence, strictly speaking, the corresponding metric solutions of the …
ASYMPTOTIC ANALYSIS OF THE LINEARIZED NAVIER–STOKES EQUATION ON AN EXTERIOR CIRCULAR DOMAIN: EXPLICIT SOLUTION AND THE ZERO VISCOSITY LIMIT
2001
In this paper we study and derive explicit formulas for the linearized Navier-Stokes equations on an exterior circular domain in space dimension two. Through an explicit construction, the solution is decomposed into an inviscid solution, a boundary layer solution and a corrector. Bounds on these solutions are given, in the appropriate Sobolev spaces, in terms of the norms of the initial and boundary data. The correction term is shown to be of the same order of magnitude as the square root of the viscosity. Copyright © 2001 by Marcel Dekker, Inc.
Uveal effusion syndrome complicated by anterior ischemic optic neuropathy
1995
We report on a case of idiopathic uveal effusion syndrome complicated by AION. To our knowledge such an association hasn't been previously described. We suggest that scleral thickening caused obstruction of vortex veins followed by uveal effusion and compression of posterior ciliary arteries within their intrascleral tract, leading to AION. Nevertheless it can't be excluded that AION was the result of mechanical compression on ciliary vessels of optic disc by choroidal detachment. © 1996, Kluwer Academic Publishers. All rights reserved.
Oscillatory Changes of the Heterogeneous Reactive Layer Detected with the Motional Resistance during the Galvanostatic Deposition of Copper in Sulfur…
2015
Metallic copper was galvanostatically deposited on quartz|gold resonant electrodes by applying a constant current in a 0.5 M CuSO4/0.1 M H2SO4 aqueous solution. Galvanostatic copper deposition is one of the best methodologies to calibrate the electrochemical quartz crystal microbalances (EQCM), a gravimetric sensor to evaluate changes in mass during the electrochemical reactions through the Sauerbrey equation. The simultaneous measurement of mass, current density, and motional resistance by an EQCM with motional resistance monitoring allows us to characterize the processes occurring on the electrode surface and at the interfacial regions with unprecedented detail. During the galvanostatic c…