Coalescence during emulsification. 3. Effect of gelatin on rupture and coalescence

An oil-soluble fluorescent probe, undecyl pyrene (UDP), is used to measure the amount of coalescence that occurs during the emulsification of tri-2-ethylhexyl phosphate using a high-pressure homogenizer. From these measurements, the roles of anionic surfactant (SDS) and gelatin in stabilizing drops against coalescence and promoting drop rupture during emulsification are deduced. It is found that gelatin aids in reducing coalescence, whereas SDS aids in rupture of drops. The effect of variables such as gelatin MW, surfactant type, and pH on coalescence and final drop size is investigated.     

Geochemical aspects and distribution of long-lived radionuclides in marine sediments from Palomares

The main objective of this paper is to point out problems associated with interpretation of bioassay monitoring in view of the existing biokinetic models. The exposure to thorium in Brazil is given in this paper as an example of the seriousness of the problem.     

Transport of solutes through calix[4]pyrrole-containing cellulose acetate films

Films of cellulose acetate containing different concentrations of meso-octamethyl-porphyrinogen (calix[4]pyrrole) were prepared and characterized using UV-vis and FTIR spectroscopy, DSC and SEM. Incorporation of calix[4]pyrrole into cellulose acetate leads to a decrease in the degree of hydrophilicity of the polymeric matrix. However, a slight increase in the percentage of water uptake of the polymer is found with an increase of the initial amount of calix[4]pyrrole in the composite composition. This effect can be related to the plasticizing effect that the calix[4]pyrrole provokes in the cellulose acetate. A comparative study of transport parameters of oxygen and some non-associated electrolytes (sodium, copper(II) and nickel chlorides) was carried out. The diffusion coefficients of molecular oxygen through cellulose acetate films decrease with an increase of the concentration of calix[4]pyrrole in the composite films. The transport (diffusion and permeation) of the above mentioned electrolytes through a set of composite films shows a decrease of permeability and diffusion coefficients with an increase of calix[4]pyrrole concentration. Such behaviour is typical of systems where interactions between the polymer and diffusing species occur. However, from the analysis of the distribution coefficient, it was found that those interactions are only dependent on the calix[4]pyrrole content for 2:1 electrolytes.     

Determination of Diclofenac in Urine Samples by Molecularly‐Imprinted Solid‐Phase Extraction and Adsorptive Differential Pulse Voltammetry

A molecularly imprinted polymer for diclofenac (DCF) was prepared by thermal polymerization over silica beads using 2‐(dimethylamino)ethyl‐methacrylate as functional monomer. After silica elimination by HF treatment, the polymer was applied to the selective solid‐phase extraction of the drug from urine followed by its quantification by adsorptive differential pulse voltammetry. Results indicate that the drug could be selectively extracted from the sample and quantified at clinically relevant concentrations (μg/mL).     

Mean distance of closest approach of ions: Lithium salts in aqueous solutions

Numerical values for the mean distance of closest approach of ions, “a”, for lithium salts in aqueous solutions are presented and discussed. These values were obtained from both experimental activity and diffusion coefficients, and estimated by using different theoretical approaches.     

Asymptotics for models of non‐stationary diffusion in domains with a surface distribution of obstacles

We consider a time‐dependent model for the diffusion of a substance through an incompressible fluid in a perforated domain Ω_?, with n = 3,4. The fluid flows in a domain containing a periodical set of “obstacles” (Ω\Ω_?) placed along an inner (n ? 1)‐dimensional manifold . The size of the obstacles is much smaller than the size of the characteristic period ?. An advection term appears in the partial differential equation linking the fluid velocity with the concentration, while we assume a nonlinear adsorption law on the boundary of the obstacles. This law involves a monotone nonlinear function σ of the concentration and a large adsorption parameter. The “critical adsorption parameter” depends on the size of the obstacles , and, for different sizes, we derive the time‐dependent homogenized models. These models contain a “strange term” in the transmission conditions on Σ, which is a nonlinear function and inherits the properties of σ. The case in which the fluid velocity and the concentration do not interact is also considered for n ≥ 3.     

On the solvability of implicit differential inclusions

In the paper, the set-valued covering mappings are studied. The statements on solvability, solution estimates, and well-posedness of inclusions with conditionally covering mappings are proved. The results obtained are applied to the investigation of differential inclusions unsolved for the unknown function. The statements on solvability, solution estimates, and well-posedness of these inclusions are derived.