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11.
A rapid and simplified method for the determination of phase inversion temperature (PIT) and the stability of oil in water emulsions, stabilized by nonionic emulsifiers, is described. The method is based on the use of any thermogravimetric apparatus from which the rate of loss of water can be measured as a function of linear increase in the emulsion temperature. A DTG peak is obtained at the PIT: the emulsion in which the lowest PIT is observed is also the less stable one. 相似文献
12.
This article is the first part of a two-part study that exemplifies how to treat the solubilization of water in multicomponent surfactant-based systems. In particular, it aims at clarifying the role of cosurfactants in water solubilization in these systems. The judicious selection of the components in such systems to maximize water solubilization is occasionally thought to be dictated by the chain length compatibility principle, which may be expressed quantitatively by the BSO (Bansal, Shah, O'Connell) equation. Here we demonstrate some limitations of the equation. For example, in our best model system, C12(EO)8/dodecane+pentanol=1:1 (by weight)/water at 27+/-0.2 degrees C, the BSO equation predicts that no alcohol is needed for maximum water solubilization, contrary to our experimental findings. We discuss how to optimize the alcohol/oil weight ratio needed for stabilizing four-component microemulsions. In our model systems C12(EO)8 or C(18:1)(EO)10/pentanol/dodecane/water, this optimal weight ratio is 1:1. We also highlight the difference between the effect of normal alcohols on water solubilization-which passes via a maximum-and their effect on percolation processes and structured changes of proteins, which depends solely upon the alcohol hydrophobicity. For the investigation of the effect of branching on phase behavior the utilization of an extended form of the geometrical branching factor F(b) is suggested. The meaning of this factor is elucidated by comparing it with topological indices. 相似文献
13.
Kogan A Popov I Uvarov V Cohen S Aserin A Garti N 《Langmuir : the ACS journal of surfaces and colloids》2008,24(3):722-733
Crystallization of carbamazepine (CBZ), an antiepileptic drug, precipitated from confined spaces of nonionic microemulsions was investigated. The study was aimed to correlate the structure of the microemulsion [water-in-oil (W/O), bicontinuous, and oil-in-water (O/W)] with the crystalline structure and morphology of solid CBZ. The precipitated CBZ was studied by DSC, TGA, powder XRD, single-crystal XRD, SEM, and optical microscopy. The results suggest that the microstructure of the microemulsions influences the crystallization process and allows crystallizing polymorphs that exhibit different crystal structure and habits. W/O nanodroplets orient the crystallizing CBZ molecules to form a prismlike anhydrous polymorphic form with monoclinic unit cell and P21/n space group. Bicontinuous structures lead to platelike dihydrate crystals with orthorhombic unit cell and Cmca space group. The O/W nanodroplets cause the formation of needlelike dihydrate crystals with monoclinic unit cell and P21/c space group. The morphological features of solid CBZ remain predetermined by the basic symmetry and parameters of its unit cell. Precipitation of CBZ pseudopolymorphs from supersaturated microemulsion is discussed in terms of oriented attachment that provides perfect packing of numerous separately nucleated ordered nuclei of CBZ into microscale platelets and then into macroscopic crystals. Crystallization from microemulsion media enabling one to obtain the drug (CBZ) with predicted structure and morphology should be of great significance for pharmaceutical applications. 相似文献
14.
Shimon Garti 《Order》2016,33(3):411-417
Let κ = 2 ω , and assume \(f:\mathbb {R}\rightarrow \mathcal {P}(\mathbb {R})\) satisfies the intersection properties C(ω,κ) and C(κ,ω). We prove that if \(\mathfrak {r}<\text {cf}(\kappa )\) then there exists a dense free set for f. 相似文献
15.
Competitive solubilization of cholesterol and phytosterols in nonionic microemulsions 总被引:1,自引:0,他引:1
It is well documented that phytosterols inhibit the uptake of exogenic cholesterol and do not interfere with cholesterol synthesis or cause side effects. The mechanism by which phytosterols interfere with cholesterol absorption is not completely clear and there are at least three hypotheses for their beneficial activity. Among these is that of competitive solubilization of phytosterols and cholesterol in dietary mixed micelles. In the present study we investigated the competitive solubilization of phytosterols (approximately 50% beta-sitosterol) and cholesterol in a nonionic microemulsion system constructed as a model for the dietary mixed micelles. We studied the effect of the competitive solubilization of cholesterol and phytosterols on the structural transformations and physical properties of the microemulsion and evaluated the locus of the solubilizates within the nanodroplets of each sterol separately and when they are loaded together at different weight ratios along one dilution line. Our results show that chemical and structural differences between cholesterol and phytosterols significantly influence the solubilization capacity of the nonionic microemulsion. Cholesterol, being more amphiphilic, is solubilized more efficiently at the W/O microemulsion interface, while in the O/W microemulsion phytosterols are dissolved somewhat more efficiently in the droplet core. 相似文献
16.
Dima Libster Abraham Aserin Doron Yariv Gil Shoham Nissim Garti 《Colloids and surfaces. B, Biointerfaces》2009,74(1):202-215
This paper describes the formation and characterization of liquid crystalline dispersions based on the hexagonal phase of GMO/tricaprylin/water. As a stabilizer of the soft particles dispersed in the aqueous phase, a non-ionic, non-polymeric surfactant—ethoxylated phytosterol with 30 oxyethylene units (PhEO) was utilized. In contrast to Pluronic copolymers, normally utilized in the stabilization of liquid crystalline dispersions with ordered inner structure, use of such non-polymeric surfactant is not a common practice in this field. We revealed how properties of these particles, such as internal structure, size, and stability, can be rationally modified by the concentration of the stabilizing agent and processing conditions. The physical stability of the hexosomes was further examined by the LUMiFuge technique.Structural effect of PhEO solubilization on the properties of the bulk HII mesophase system showed that phase behavior was greatly influenced following phase transitions: HII → HII + cubic → cubic + Lα → Lα. The decrease of hydrogen bonding of the hydroxyl and carbonyl groups of monoolein with water and simultaneous hydration of EO groups of PhEO appeared to be important for the observed behavior. The use of PhEO as a dispersant resulted in a soft matter multi-phase water dispersion with bimodal distribution of the particle population. Effective stabilization of hexosomes was obtained in an extremely narrow concentration range of PhEO (0.1–0.2 wt%), coexisting with small vesicles and disordered particles. At higher PhEO content, particles had disordered inner structure, and unilamellar and multilamellar vesicles, at the expense of hexosomes in consequence of incorporation of the dispersant into the hexosome structure. PhEO was found to induce lamellar phase formation, introducing disorder into the hexagonal LLC and reducing their domain size.Finally, hexosomes were evaluated as delivery vehicles for the therapeutic peptide desmopressin. Sustained release of this drug was observed during the first 10 h; however, permeation drastically increased in the 10–24 h range. 相似文献
17.
In
this study we used differential scanning calorimetry to clarify the role of
water activity within the nano-droplets, and to explore phase transitions
in novel phospholipids based fully dilutable food-grade microemulsions.
The microstructure
transitions were investigated along two water dilution lines (50:50 and 80:20
mass% surfactant mixture/oil phase). From the water thermal behavior we learned
that three structural regions can be identified along the water dilution lines.
The thermal transition points coincide with the structural phase transition
of the microemulsions as measured by other methods (electrical conductivity
and SD-NMR measurements).
The structural transitions were detected at 20 and 45 mass%
of water along dilution line 55, where along dilution line 82 it occurs at
40 and 50 mass% of water.
The microemulsions along dilution line 82 seem to have
more compact surfactant packing film, thus the film has stronger resistance
to transformation upon dilution, resulting in a smaller bicontinuous region
than the one formed at dilution line 55. The difference in phase transition
point can be used for triggering the release of future solubilizate. 相似文献
18.
An infinite cardinal λ is Magidor if and only if . It is known that if λ is Magidor then for some , and the first such α is denoted by . In this paper we try to understand some of the properties of . We prove that can be the successor of a supercompact cardinal, when λ is a Magidor cardinal. From this result we obtain the consistency of being a successor of a singular cardinal with uncountable cofinality. 相似文献
19.
Garti Shimon Hayut Yair Horowitz Haim Magidor Menachem 《Periodica Mathematica Hungarica》2022,84(2):250-258
Periodica Mathematica Hungarica - We study the Galvin property. We show that various square principles imply that the cofinality of the Galvin number is uncountable (or even greater than $$\aleph... 相似文献
20.
We introduce a model-theoretic characterization of Magidor cardinals, from which we infer that Magidor filters are beyond ZFC-inconsistency. 相似文献