Aqueous gels of mixtures of ionic surfactant SDS with pluronic copolymers P123 or F127

Gel diagrams based on tube inversion and oscillatory rheometry are reported for Pluronic copolymers F127 (E98P67E98) and P123 (E21P67E21) in mixtures with anionic surfactant sodium dodecyl sulfate (SDS). Total concentrations (e, SDS+copolymer) were as high as 50 wt% with mole ratios SDS/copolymer (mr) in the ranges 1-5 (F127) a lid 1-7 (PI 23). Temperatures were its high as 90 degrees C. Determination of the temperature dependences of the dynamic moduli served to confirm the gel boundaries from tube inversion and to reveal the high elastic moduli of the gels, e.g., compared at corn parable positions in the gel phase, a 50 wt% SDS/P123 wit h mr = 7 had G' three times that of a corresponding gel of P123 alone. Sin all-angle X-ray scattering (SAX S) was used to show that the structures of all the SDS/F127 gels were bee and that the structures of the SDS/P123 gels with mr = I were either fcc(c = 30 wt%) or hex (c = 40 wt%). Assignment of structures to SDS/P123 gels with values of mr in the range 3-7 was more difficult, as high-order scattering peaks Could be very weak, and at the higher values of c and mr, the SAXS peaks included multiple reflections.

Synthesis of multicarboxylic acid appended imidazolium ionic liquids and their application in palladium-catalyzed selective oxidation of styrene

A series of multicarboxylic acid appended imidazolium ionic liquids ( McaILs) with chloride [ Cl](-) or bromide [ Br](-) as anions have been synthesized and characterized. Deprotonation of these ionic acids gives the corresponding zwitterions. Re-protonation of the zwitterions with strong Bronsted acids gives a series of new ionic acid-adducts, many of which remained as room-temperature ionic liquids. A new catalytic system, McaIL/PdCl2 for the selective catalytic oxidation of styrene to acetophenone with hydrogen peroxide as an oxidant has been attempted. In the presence of McaILs, it is found that the quantity of palladium chloride PdCl2 used can be greatly reduced while the activity ( TOF) and selectivity towards acetophenone are enhanced sharply. It is also shown that the catalytic properties of this system could be finely tuned through the molecular design of the McaILs. The best TOF value obtained so far is 146 h(-1) with 100% conversion of styrene at 93% selectivity to acetophenone. In addition, the catalytic activity has been maintained for at least ten catalytic cycles.

Ultrasonic chemical oxidative degradations of 1,3-dialkylimidazolium ionic liquids and their mechanistic elucidations

A highly efficient process for oxidative degradation of 1,3-dialkylimidazolium ionic liquids in hydrogen peroxide/acetic acid aqueous medium assisted by ultrasonic chemical irradiation is, for the first time, described. It is shown that more than 93% of the 1,3-dialkylimidazolium cation with the corresponding Cl-, Br-, BF4- and PF6- counter-anions at a concentration of 2.5 mM can be degraded at 50 degrees C within 12 h while at 72 h the conversions approach 99%. A tentative mechanism for the degradation of these ILs is for the first time proposed through a detailed kinetic analysis of several characteristic transients and/or immediate products, which are identified during the ILs degradation using GC-MS. The results clearly indicate that three hydrogen atoms in the imidazolium ring are the first sites preferably oxidized, followed by cleavage of the alkyl groups attached to the N atoms from the ring. The nature of the alkyl chain length on the imidazolium ring and the type of counter anion do not seem to affect the degradation process. Further, selective fragmentations of C-N bonds of the imidazolium or derived ring lead to ring opening, forming degraded intermediates. It is also shown that acetoxyacetic acid and biurea are the final kinetically stable degraded products from the ILs under the degradation conditions.

Biomarkers of the intake of dietary polyphenols: strengths, limitations and application in nutrition research

In order to establish firm evidence for the health effects of dietary polyphenol consumption, it is essential to have quantitative information regarding their dietary intake. The usefulness of the current methods, which rely mainly on the assessment of polyphenol intake using food records and food composition tables, is limited as they fail to assess total intake accurately. This review highlights the problems associated with such methods with regard to polyphenol-intake predictions. We suggest that the development of biological biomarkers, measured in both blood and urine, are essential for making accurate estimates of polyphenol intake. However, the relationship between dietary intakes and nutritional biomarkers are often highly complex. This review identifies the criteria that must be considered in the development of such biomarkers. In addition, we provide an assessment of the limited number of potential biomarkers of polyphenol intake currently available.

Measurement of ionic calcium in milk

There are many reports in the literature regarding the effects of ionic calcium on reactions related to casein micelle stability, such as heat stability, ethanol stability and susceptibility to gelation, sediment formation and fouling. However, experimental evidence supporting these assertions is much less readily available. This paper evaluates three selective ion electrode systems for measuring ionic calcium directly in milk as well as looking at the effects on pH reduction and addition of calcium chloride. The best electrode system was the Ciba Corning 634 system, which was designed for blood but has been modified for milk. This was found to be reproducible and stable when calibrated daily and allowed direct measurements to be taken on milk in 70 s. This has been found to perform well now for 3 years. The other systems were not so useful, as they took longer to stabilize, but may be useful for higher ionic calcium concentrations, which are found in acidified milk products. Reducing the pH increased ionic calcium and reduced ethanol stability. Calcium chloride addition reduced pH, increased ionic calcium and reduced the ethanol stability. Readjusting the pH to its value before calcium addition reduced the ionic calcium, but not back to its original value. Milks from individual cows showed wide variations in their ionic calcium concentrations. This establishes the methodology for a more detailed investigation on measurement of ionic calcium in milks from individual cows and from bulk milks, to allow a better understanding of its role in casein micelle stability.

An insight into the mechanism of protein separation by colloidal gas aphrons (CGA) generated from ionic surfactants

Colloidal gas aphrons (CGA), which are surfactant stabilised microbubbles, have been previously applied for the recovery of proteins from model mixtures and a few studies have demonstrated the potential of these dispersions for the selective recovery of proteins from complex mixtures. However there is a lack of understanding of the mechanism of separation and forces governing the selectivity of the separation. In this paper a mechanistic study is carried out to determine the main factors and forces influencing the selectivity of separation of whey proteins with CGA generated from ionic surfactants. Two different separation strategies were followed: (i) separation of lactoferrin and lactoperoxidase by anionic CGA generated from a solution of sodium bis-(2-ethyl hexyl) sulfosuccinate (AOT); (ii) separation of beta-lactoglobulin by cationic CGA generated from a solution of cetyltrimethylammonium bromide (CTAB). Separation results indicate that electrostatic interactions are the main forces determining the selectivity however these could not completely explain the selectivities obtained following both strategies. Protein-surfactant interactions were studied by measuring the zeta potential changes on individual proteins upon addition of surfactant and at varying pH. Interestingly strongest electrostatic interactions were measured at those pH and surfactant to protein mass ratios which were optimum for protein separation. Effect of surfactant on protein conformation was determined by measuring the change in fluorescence intensity upon addition of surfactant at varying pH. Differences in the fluorescence patterns were detected among proteins which were correlated to differences in their conformational features which could in turn explain their different separation behaviour. The effect of conformation on selectivity was further proven by experiments in which conformational changes were induced by pre-treatment of whey (heating) and by storage at 4 degrees C. Overall it can be concluded that separation of proteins by ionic CGA is driven mainly by electrostatic interactions however conformational features will finally determine the selectivity of the separation with competitive adsorption having also an effect. (c) 2006 Elsevier B.V. All rights reserved.

Visuospatial cognition in Williams syndrome: reviewing and accounting for the strengths and weaknesses in performance

Individuals with Williams syndrome typically show relatively poor visuospatial abilities in comparison to stronger verbal skills. However, individuals' level of performance is not consistent across all visuospatial tasks. The studies assessing visuospatial functioning in Williams syndrome are critically reviewed, to provide a clear pattern of the relative difficulty of these tasks. This prompts a possible explanation of the variability in performance seen, which focuses on the processing demands of some of these tasks. Individuals with Williams syndrome show an atypical processing style on tests of construction, which does not affect tests of perception.

Influence of a non-ionic amphiphilic copolymer on the self-assembly of a peptide amphiphile that forms nanotapes

The influence of a non-ionic polymeric surfactant on the self-assembly of a peptide amphiphile (PA) that forms nanotapes is investigated using a combination of microscopic, scattering and spectroscopic techniques. Mixtures of Pluronic copolymer P123 with the PA C16-KTTKS in aqueous solution were studied at a fixed concentration of the PA at which it is known to self-assemble into extended nanotapes, but varying P123 concentration. We find that P123 can disrupt the formation of C16- KTTKS nanotapes, leading instead to cylindrical nanofibril structures. The spherical micelles formed by P123 at room temperature are disrupted in the presence of the PA. There is a loss of cloudiness in the solutions as the large nanotape aggregates formed by C16-KTTKS are broken up, by P123 solubilization. At least locally, b-sheet structure is retained, as confirmed by XRD and FTIR spectroscopy, even for solutions containing 20 wt% P123. This indicates, unexpectedly, that peptide secondary structure can be retained in solutions with high concentration of non-ionic surfactant. Selfassembly in this system exhibits slow kinetics towards equilibrium, the initial self-assembly being dependent on the order of mixing. Heating above the lipid chain melting temperature assists in disrupting trapped non-equilibrium states.

Tetragonal and helical morphologies from polyferrocenylsilane block polyelectrolytes via ionic self-assembly

The use of ionic self-assembly, a facile noncovalent approach, to access non-conventional block copolymer morphologies, including tetragonal and helical structures, from a combination of polyferrocenylsilane diblock copolymer polyelectrolytes and AOT-based surfactants, is described.

Desert dust deposition on Mt. Elbrus, Caucasus Mountains, Russia in 2009-2012 as recorded in snow and shallow ice core: high-resolution "provenancing", transport patterns, physical properties and soluble ionic composition

A record of dust deposition events between 2009 and 2012 on Mt. Elbrus, Caucasus Mountains derived from a snow pit and a shallow ice core is presented for the first time for this region. A combination of isotopic analysis, SEVIRI red-green-blue composite imagery, MODIS atmospheric optical depth fields derived using the Deep Blue algorithm, air mass trajectories derived using the HYSPLIT model and analysis of meteorological data enabled identification of dust source regions with high temporal (hours) and spatial (cf. 20–100 km) resolution. Seventeen dust deposition events were detected; fourteen occurred in March–June, one in February and two in October. Four events originated in the Sahara, predominantly in north-eastern Libya and eastern Algeria. Thirteen events originated in the Middle East, in the Syrian Desert and northern Mesopotamia, from a mixture of natural and anthropogenic sources. Dust transportation from Sahara was associated with vigorous Saharan depressions, strong surface winds in the source region and mid-tropospheric south-westerly flow with daily winds speeds of 20–30 m s−1 at 700 hPa level and, although these events were less frequent, they resulted in higher dust concentrations in snow. Dust transportation from the Middle East was associated with weaker depressions forming over the source region, high pressure centered over or extending towards the Caspian Sea and a weaker southerly or south-easterly flow towards the Caucasus Mountains with daily wind speeds of 12–18 m s−1 at 700 hPa level. Higher concentrations of nitrates and ammonium characterise dust from the Middle East deposited on Mt. Elbrus in 2009 indicating contribution of anthropogenic sources. The modal values of particle size distributions ranged between 1.98 μm and 4.16 μm. Most samples were characterised by modal values of 2.0–2.8 μm with an average of 2.6 μm and there was no significant difference between dust from the Sahara and the Middle East.

Fluorinated ionic surfactant microemulsions in hydrofluorocarbon 134a (HFC 134a)

The factors influencing the formation of water-in-134a-propellant microemulsions using the fluorinated ionic surfactants ammonium perfluorooctanoate, ammonium perfluoroheptanoate, and sodium perfluorooctanoate has been determined. None of the fluorinated ionic surfactants could be used to prepare clear, one-phase systems when used as sole surfactant, but they could be when combined with a short-chain fluoro- or hydrocarbon alcohol in surfactant:cosurfactant weight-mixing ratios (K(m)) in the range 1:2 to 2:1. When hydrocarbon alcohols were used this clear region extended over a wide range of compositions and was confirmed by means of photon correlation spectroscopy (PCS) to contain microemulsion droplets in the propellant-rich part of the phase diagram. PCS studies performed in the presence of the water-soluble drug terbutaline sulfate showed that it was possible to solubilize the drug within water-in-propellant microemulsion droplets. These studies confirm for the first time that it is possible to prepare water-in-propellant 134a microemulsions using fluorinated ionic surfactants and to solubilize water-soluble drugs within these systems.

Salt and ionic cocrystalline forms of amides: protonation of carbamazepine in aqueous media

The products of reactions of the pharmaceutical amide carbamazepine (CBZ) with strong acids under aqueous conditions were investigated by both powder and single crystal X-ray diffraction. Despite previous claims to the contrary, it was found that salt forms with CBZ protonated at the amide O atom could be isolated from reactions with both HCl and HBr. These forms include the newly identified hydrate phase [CBZ(H)][Cl]·H O. Reactions with other mineral acids (HI and HBF ) gave ionic cocrystalline (ICC) forms (CBZ· [acridinium][I ]·2.5I and CBZ·[H O ] [BF ] ·H O) as well as the salt form CBZ·[CBZ(H)][BF ]·0.5H O. Reaction 2 4 3 2 5 2 0.25 4 0.25 2 4 2 of CBZ with a series of sulfonic acids also gave salt forms, namely, [CBZ(H)][O SC H ], [CBZ(H)][O SC H (OH)]· 3 6 5 3 6 4 0.5H O, [CBZ(H)] [O SCH CH SO ], and [CBZ(H)][O SC H (OH) (COOH)]·H O. CBZ and protonated CBZ(H) 2 2 3 2 2 3 3 6 3 2 moieties can be differentiated in the solid state both by changes to molecular geometry and by differing packing preferences