87,894 research outputs found
Effect of β-cyclodextrin on multi-to uni-lamellar thermal transition of catanionic vesicles
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Insights into Catanionic Vesicles Thermal Transition by NMR Spectroscopy
No full textOppositely charged ionic surfactants can self-assemble into hollow structures, called catanionic vesicles,
where the anionic-cationic surfactant pair assumes a double-tailed zwitterionic attitude. In the present
work, multilamellar-to-unilamellar thermal transition of a mixed aqueous system of sodium dodecyl
sulphate (SDS) and cetyl trimethyl ammonium bromide (CTAB), with a slight excess of the anionic one,
has been investigated by 1H, 2H, 14N NMR spectra and 23Na transverse relaxation measurements. It has
been inferred that an increase of the temperature enhances the SDS counterion dissociation, which can be
considered as one of the driving forces of the mentioned transition. Moreover, interesting 23Na T2 changes
with temperature have been detected for unilamellar aggregates
Étude analytique de provenance d'un vase signé C. Cin ( ) Senoviri trouvé à Salelles, Le Bosc (Hérault)
No full textAsaro F., Michel H., Widemann F., Fillières-Kunetz D. Étude analytique de provenance d'un vase signé C. Cin ( ) Senoviri trouvé à Salelles, Le Bosc (Hérault). In: Gallia, tome 33, fascicule 2, 1975. pp. 225-228
Soft nanoonions: A dynamic overview onto catanionic vesicles temperature-driven transition
No full textCatanionic vesicles are emerging interesting structures for bioapplications. They selfgenerate by a pairing of oppositely charged ionic surfactants that assemble into hollow structures. Specifically, the anionic-cationic surfactant pair assumes a double-tailed zwitterionic behavior. In this work, the multilamellar-to-unilamellar thermal transition of several mixed aqueous systems, with a slight excess of the anionic one, were investigated. Interestingly, it was found that the anionic counterion underwent a dissociation as a consequence of a temperature increase, leading to the mentioned thermal transition. The present work proposed the spectroscopic techniques, specifically multinuclear NMR and PGSTE (pulsed gradient stimulated echo), as a key tool to study such systems, with high accuracy and effectiveness, while requiring a small amount of the sample. The results presented herein evidence encouraging perspectives, forecasting the application of the studied vesicular nanoreservoirs, for e.g., drug delivery
Probabilistic typed natural deduction for trustworthy computations
No full textIn this paper we present a typed natural deduction calculus to analyze the formal design of probabilistic computational processes, e.g. in use in machine learning techniques, to model their trustworthiness as a safety property
Solution microstructures of the micellar phase of Pluronic L64/SDS/water system
No full textHere we report on a study dealing with a self-assembling ethylene oxide–propylene oxide–ethylene oxidetriblock copolymer (Pluronic L64) and an anionic surfactant, sodium dodecyl sulfate (SDS), that in water at25 C form an interesting micellar region (L-phase). We have investigated the sequence of micellestructures in this L-phase across a wide interval of copolymer concentrations using phase diagram determination,steady shear, and NMR self-diffusion (pulsed gradient spin–echo, PGSE) experiments. In solutionswhich have been prepared at moderately low copolymer concentrations (ca. 20 wt.% L64) wereport on a transition from discrete micelles to bicontinuous aggregates on the addition of SDS. This changewas mainly inferred from self-diffusion coefficient patterns (i.e., the variation of copolymers and surfactantdiffusivity vs. SDS content). At midrange and at higher polymer concentrations (i.e., in the interval from 50to 80 wt.% L64) the L-phase occurred with a bicontinuous structure which was not modified by theprogressive addition of SDS. Such a bicontinuous structure was identified by the comparison of self-diffusioncoefficients of both cosolutes and the bulk viscosity (i.e., the behavior of zero-shear viscosity vs.SDS)
Micellar crowding and branching in a versatile catanionic system
No full textThe catanionic system didodecyldimethylammonium bromide (DDAB)-sodium taurodeoxycholate(STDC)-D2O is characterized by an exceptionally extended L1region. The comparison of self-diffusioncoefficient of the solvent and the DDAB embedded in the micelles provided information about hydra-tion of the aggregates. Moreover, correlating self-diffusion and14N NMR relaxation measurements newinsight could be obtained regarding the translational and rotational micellar motions in the crowded solu-tions of systems with 0.2 DDAB-STDC molar ratio.1H 2D NMR spectra gave some hints about the mutualarrangement of DDAB and STDC within the aggregates. For samples with 1.8 and 2.6 DDAB/STD molarratios the14N data were in agreement with the presence of somewhat branched, interconnected micelles.23Na and81Br dynamic parameters resulted particularly sensitive to the surrounding environment.The peculiar rheological behaviour of the, highly concentrated, branched micelles samples, namely thesteady oscillations in the step tests, was found to be an example of instability originated by the combinedeffect of material elasticity and slippage at the fixed wall
Complex Formation between Poly(vinylpyrrolidone) and Sodium Decyl Sulfate Studied through NMR
No full textRecent experimental studies have shown a preferential interaction of poly(vinylpyrrolidone) (PVP) toward the alkyl sulfate surfactants rather than toward those belonging to the alkyl sulfonate series. To gain information on the complex formation between PVP and the alkyl sulfate surfactants, we have performed H-1 and C-13 NMR and NOESY measurements on aqueous solutions of sodium decyl sulfate (C10OS) in the presence and absence of PVP at 1wt %. The results show that C10OS interacts with PVP, forming micelle-like clusters bound onto the polymer, and furthermore suggest that the PVP-C10OS complex formation implies the synergic effects of the electrostatic attractions between the surfactant headgroup and the nitrogen and oxygen atoms in the pyrrolidone ring of PVP and of the hydrophobic interaction between the surfactant alkyl moiety and the ring carbons of PVP
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