Release of electrolytes from W/O/W double emulsions stabilized by a soluble complex of modified pectin and whey protein isolate

W/O/W double emulsions (DEs) stabilized by charged soluble complexes of whey protein isolate (WPI) and modified pectins were investigated in relation to their stability and the release of two types of electrolytes, NaCl and sodium ascorbate.WPI alone cannot properly stabilize the DEs. The droplet size is relatively large (100 μm) and increases with time. However, addition of modified pectin to form a soluble complex with WPI significantly improved the stability.DEs prepared with two types of oils (medium chain triglycerides (MCT) and R(+)-limonene) were studied by measuring droplet size, creaming, viscosity, and electrolyte release. Irrespective of their very different oil phase nature, both emulsions were stable against coalescence, but R(+)-limonene formed smaller droplets (25 μm) than MCT (35 μm). The electrolyte release rate was significantly higher from the R(+)-limonene that formed DEs with much lower viscosity. R(+)-limonene-DE released 75% of the NaCl after 28 days, while MCT-DE released only 50%. NaCl was released more slowly than sodium ascorbate.Apparently, the release mechanism from R(+)-limonene-DE was found to be “thinning the outer interface and release of the entire inner droplets” while it seems that the release from MCT-DE was slower and “diffusion controlled”.DEs stabilized by WPI/C63 released 12% of the sodium ascorbate after 1 day in milk and remained stable for at least 8 days. However, DEs stabilized with only WPI released about 50% of the sodium ascorbate after 1 day, and phase separated after 8 days.     

High-resolution NMR "chromatography" using a liquids spectrometer

NMR spectroscopy is an excellent tool for the structural analysis of pure compounds. However, for mixtures it performs poorly because of overlapping signals. Diffusion can be used to separate compounds of widely differing molecular weight but the amount of separation is usually insufficient.Addition of a solid medium, analogous to the stationary phase in chromatography, can preferentially slow the diffusion of some components of a mixture permitting separation in the diffusion dimension. However, this would usually require a solid-state NMR spectrometer otherwise the signals would be too broad.Susceptibility matching the solvent to the solid medium yields a spectrum with narrow signals allowing the measurement of a DOSY spectrum with enhanced separation in the diffusion dimension.     

Harmony in Multiple-Conclusion Natural-Deduction

The paper studies the extension of harmony and stability, major themes in proof-theoretic semantics, from single-conclusion natural-deduction systems to multiple-conclusions natural-deduction, independently of classical logic. An extension of the method of obtaining harmoniously-induced general elimination rules from given introduction rules is suggested, taking into account sub-structurality. Finally, the reductions and expansions of the multiple-conclusions natural-deduction representation of classical logic are formulated.     

Ring-opening polymerization of unsaturated alicyclic compounds

The ring-opening polymerizations of cyclooctene, cyclododecene, 1,5-cyclooctadiene, 1,5,9-cyclododecatriene, 3-methylcyclooctene, and 3-phenylcyclooctene have been carried out by using a two-component catalyst system composed of ethylaluminum dichloride and tungsten hexachloride. NMR and infrared analyses of the respective polymers indicate structures which are consistent with a ring-cleavage mode of propagation. No evidence for double-bond shifts or transannular reactions during the polymerizations of 1,5-cyclooctadiene, 1,5,9-cyclododecatriene, 3-methylcyclooctene, and 3-phenylcyclooctene was found. The polymerizability of substituted, unsaturated, mediumsized alicyclic monomers suggests a convenient method for synthesis of certain perfectly alternating terpolymers. Since polymerizations occurred rapidly with little evolution of heat, it was concluded that entropy is a substantial contributor to the free energy of the ring-opening polymerization of medium-sized, unsaturated alicyclic monomers.     

Sugar-Ester Nonionic Microemulsion: Structural Characterization

Surfactants containing sugar components and fatty acids satisfy the quality standards for food application. The food grade sugar ester in this study is a commercial sucrose monoester of stearic acid (abbreviated SES), the oil phase consists of a 1:1 mixture of n-tetradecane and l-butanol. The originally planned food grade oil, a medium chain triglyceride, is substituted by tetradecane because tetradecane is available as a fully deuterated product, which is necessary for some structural investigations. The investigated system is solid at room temperature, but liquefies and structures into a homogeneous microemulsion when heated to above 37 degrees C. The structural characterization of such microemulsions is the aim of this work. The established methods for this purpose are scattering methods, such as small-angle scattering of X-rays and neutrons and dynamic light scattering. These scattering techniques can be used to obtain valuable information on the size, shape, and internal structure of colloids and complex fluids. We started our investigation with the pseudobinary system SES, tetradecane and l-butanol, varying the SES content. The scattering results show that the sugar ester form inverse globular micelles in the oil phase. The size of these micelles is about 6 nm. While the size is nearly constant in a wide SES concentration regime (5 up to 40% surfactant), the volume or aggregation number increases significantly with SES. This is explained by an increasing replacement of l-butanol molecules by sugar-ester molecules in the micelles formed. Moreover, it can be shown that these micelles strongly overlap. Their center-to-center distance is about 3.8 nm at 40% SES at a micellar diameter of 6 nm. The micellar overlap leads to a highly reduced diffusion of the micelles as was found with dynamic light scattering. When incorporating water in the micellar core, the micelles swell up to about 10 nm and the shape of the aggregates becomes more and more elongated with higher water content. Copyright 2001 Academic Press.     

Low viscosity reversed hexagonal mesophases induced by hydrophilic additives

This study reports on the formation of a low viscosity H(II) mesophase at room temperature upon addition of Transcutol (diethylene glycol mono ethyl ether) or ethanol to the ternary mixture of GMO (glycerol monooleate)/TAG (tricaprylin)/water. The microstructure and bulk properties were characterized in comparison with those of the low viscosity HII mesophase formed in the ternary GMO/TAG/water mixture at elevated temperatures (35-40 degrees C). We characterized the role of Transcutol or ethanol as inducers of disorder and surfactant mobility. The techniques used were rheology, differential scanning calorimetry (DSC), wide- and small-angle X-ray scattering (WAXS and SAXS, respectively), NMR (self-diffusion and (2)H NMR), and Fourier transform infrared (FTIR) spectroscopies. The incorporation of either Transcutol or ethanol induced the formation of less ordered HII mesophases with smaller domain sizes and lattice parameters at room temperature (up to 30 degrees C), similar to those found for the GMO/TAG/water mixture at more elevated temperatures (35-40 degrees C). On the basis of our measurements, we suggest that Transcutol or ethanol causes dehydration of the GMO headgroups and enhances the mobility of the GMO chains. As a result, these two small molecules, which compete for water with the GMO polar headgroups, may increase the curvature of the cylindrical micelles and also perhaps reduce their length. This results in the formation of fluid H(II) structures at room temperature (up to 30 degrees C). It is possible that these phases are a prelude to the H(II)-L(2) transformation, which takes place above 35 degrees C.     

Templated cocrystallization of cholesterol and phytosterols from microemulsions

A major cause of cardiovascular disease is high cholesterol (CH) levels in the blood, a potential solution to which is the intake of phytosterols (PS) known as CH-reducing agents. One mechanism proposed for PS activity is the mutual cocrystallization of CH and PS from dietary mixed micelles (DMM), a process that removes excess CH from the transporting micelles. In this study, microemulsions (MEs) were used both as a model system for cocrystallization mimicking DMM and as a possible alternative pathway, based on the competitive solubilization of CH and PS, to reduce solubilized CH transport levels from the ME. The effects of different CH/PS ratios, aqueous dilution, and lecithin-based MEs on sterol crystallization were studied. The precipitated crystals from the ME-loaded system with PS alone and from that loaded with 1:1 or 1:3 CH/PS mixtures were significantly influenced by ME microstructure and by dilution with aqueous phase (X-ray powder diffraction (XRD) and differential scanning calorimetry (DSC) results). No new polymorphic structures were detected apart from the corresponding sterol hydrates. Mixed crystal morphology and the habit of the precipitated sterols were strongly affected by the CH/PS ratio and the structures of the diluted ME. As the amount of PS in the mixture increased or as the ME aqueous dilution proceeded, precipitated crystal shape became more needle-like. The mixed sterols seemed to be forming eutectic solids.     

Phase transition of a second kind in nickel as observed through optical reflection under pressure

The magnetic permeability of materials at optical frequencies is usually suggested in the literature to be $\mu =1$. In this case one cannot expect to measure the magnetic second order phase transition at optical frequencies. The main novel idea of this paper is that the magnetic permeability μ is not equal to 1 for optical frequency and a phase transition of magnetism was measured experimentally with an optical frequency. In particular, this work presents the detection of a magnetic second order phase transition in nickel with temperature and at different pressures, by reflectivity measurements at an optical frequency. Based on our experiments the magnetic permeability is calculated as a function of temperature for pressures of 0.3, 5 and 10 GPa attained in a diamond anvil cell (DAC).     

Electrode kinetics at carbon electrodes and the density of electronic states

Marcus-Hush theory relates the rate of electron transfer to the density of electronic states of the electrode material. Through use of a carbon microelectrode--for which the density of states is expected to vary as a function of potential--this predication is validated for graphitic materials by measurement of a variety of outer-sphere redox systems.