Effect of roasting on the antioxidant activity of coffee brews

Colombian Arabica coffee beans were roasted to give light, medium, and dark samples. Their aqueous extracts were analyzed by gel filtration chromatography, UV-visible spectrophotometry, capillary electrophoresis, and the ABTS(.+) assay. A progressive decrease in antioxidant activity (associated mainly with chlorogenic acids in the green beans) with degree of roasting was observed with the simultaneous generation of high (HMM) and low molecular mass (LMM) compounds possessing antioxidant activity. Maximum antioxidant activity was observed for the medium-roasted coffee; the dark coffee had a lower antioxidant activity despite the increase in color. Analysis of the gel filtration chromatography fractions showed that the LMM fraction made a greater contribution to total antioxidant activity than the HMM components.

The effect of SO2 on the activity of Pd-based catalysts in methane combustion

The effect of SO2 on Pd-based catalysts for the combustion of methane has been investigated. It is shown that while SO2 poisons Al2O3- and SiO2-supported catalysts. pre-treatment of Pd/ZrO2 by SO2 enhances the activity substantially.

The effect of volition on the stability of bimanual coordination

The authors investigated how the intention to passively perform a behavior and the intention to persist with a behavior impact upon the spatial and temporal properties of bimanual coordination. Participants (N = 30) were asked to perform a bimanual coordination task that demanded the continuous rhythmic extension-flexion of the wrists. The frequency of movement was scaled by an auditory metronome beat from 1.5 Hz, increasing to 3.25 Hz in .25-Hz increments. The task was further defined by the requirement that the movements be performed initially in a prescribed pattern of coordination (in-phase or antiphase) while the participants assumed one of two different intentional states: stay with the prescribed pattern should it become unstable or do not intervene should the pattern begin to change. Transitions away from the initially prescribed pattern were observed only in trials conducted in the antiphase mode of coordination. The time at which the antiphase pattern of coordination became unstable was not found to be influenced by the intentional state. In addition, the do-not-intervene set led to a switch to an in-phase pattern of coordination whereas the stay set led to phase wandering. Those findings are discussed within the framework of a dynamic account of bimanual coordination.

Effect of acetonitrile on the solubility of carbon dioxide in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide

The effect of the addition of acetonitrile on the solubility of carbon dioxide in an ionic liquid, the 1-ethyl-3- methylimidazolium bis(trifluoromethanesulfonyl)amide, [C(2)mim][NTf2], was studied experimentally at pressures close to atmospheric and as a function of temperature between 290 and 335 K. It was observed that the solubility of carbon dioxide decreases linearly with the mole fraction of acetonitrile from a value of 2.6 x 10(-2) in the pure ionic liquid at 303 K to a mole fraction of 1.3 x 10(-2) in the mixture [C(2)mim][NTf2] + CH3CN with x(CH3CN) = 0.77 at the same temperature. The gas solubility decreases with temperature, and the thermodynamic properties of solvation could be calculated. The vapor pressures of the [ C2mim][ NTf2] + CH3CN mixtures were measured in the same temperature range, and strong negative deviations from Raoult's law were obtained: up to 36% for a mixture with x(CH3CN) = 0.46 at 334 K. Negative excess molar volumes of approximately -1 cm(3) mol(-1) at equimolar composition could also be calculated from density measurements of the pure components and of the mixtures. These observations are confirmed by neutron diffraction studies and are compatible with the existence of strong ion-dipole interactions in the mixed liquid solvent.

Effect of Water on the Electrochemical Window and Potential Limits of Room-Temperature Ionic Liquids

The effect of water content on room-temperature ionic liquids (RTILs) was studied by Karl Fischer titration and cyclic voltammetry in the following ionic liquids: tris(P-hexyl)tetradecylphosphonium trifluorotris(pentafluoroethyl)phosphate [P-14,P-6,P-6,P-6][NTf2], N-butyl-N-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide [C(4)mpyrr][NTf2], 1-hexyl-3-methylimidazolium tris(perfluoroethyl)trifluorophosphate [C(6)mim][FAP], 1-butyl3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C(4)mim][NTf2], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C(4)dmim][NTf2], N-hexyltriethylammonium bis(trifluoromethylsolfonyl)imide [N-6,N-2,N-2,N-2][NTf2], 1-butyl-3-methylirnidazolium hexafluorophosphate [C(4)mim][PF6], F6], 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C(2)mim][NTf2], 1-butyl-3-methylimidazolium tetrafluoroborate [C(4)mim][BF4], 1-hexyl-3-methylimidazolium iodide [C(4)mim][I], 1-butyl-3-methylimidazolium trifluoromethylsulfonate [C(4)mim][OTf], and 1-hexyl-3-methylimidazolium chloride [C(6)mim][Cl]. In addition, electrochemically relevant properties such as viscosity, conductivity, density, and melting point of RTILs are summarized from previous literature and are discussed. Karl Fisher titrations were carried out to determine the water content of RTILs for vacuum-dried, atmospheric, and wet samples. The anion in particular was found to affect the level of water uptake. The hydrophobicity of the anions adhered to the following trend: [FAP](-) > [NTf2](-) > [PF6](-) > [BF4](-) > halides. Cyclic voltammetry shows that an increase in water content significantly narrows the electrochemical window of each ionic liquid. The electrochemical window decreases in the following order: vacuum-dried > atmospheric > wet at 298 K > 318 K > 338 K. The anodic and cathodic potentials vs ferrocene internal reference are also listed under vacuum-dried and atmospheric conditions. The data obtained may aid the selection of a RTIL for use as a solvent in electrochemical applications.

The Effect of Antinotches on Domain Wall Mobility in Single Crystal Ferroelectric Nanowires

Changes in domain wall mobility, caused by the presence of antinotches in single crystal BaTiO3 nanowires, have been investigated. While antinotches appeared to cause a slight broadening in the distribution of switching events, observed as a function of applied electric field (inferred from capacitance-voltage measurements), the effect was often subtle. Greater clarity of information was obtained from Rayleigh analysis of the capacitance variation with ac field amplitude. Here the magnitude of the domain wall mobility parameter (R) associated with irreversible wall movements was found to be reduced by the presence of antinotches - an effect which became more noticeable on heating toward the Curie temperature. The reduction in this domain wall mobility was contrasted with the noticeable enhancement found previously in ferroelectric wires with notches. Finite element modeling of the electric field, developed in the nanowires during switching, revealed regions of increased and decreased local field at the center of the notch and antinotch structures, respectively; the absolute magnitude of field enhancement in the notch centers was considerably greater than the field reduction in the center of the antinotches and this was commensurate with the manner in, and degree to, which domain wall mobility appeared to be affected. We therefore conclude that the main mechanism by which morphology alters the irreversible component of the domain wall mobility in ferroelectric wire structures is via the manner in which morphological variations alter the spatial distribution of the electric field.