Abstracts

Journal of the American Oil Chemists' Society -     

The structure and dynamics of microparticles at pickering emulsion interfaces

We have employed a laser scanning confocal microscope (LSCM) to study the structure and dynamics of microparticles at Pickering emulsion interfaces. The microparticles can have rich morphology at the emulsion interfaces, ranging from an aggregated structure to colloidal lattices, with a possibility of involving heterogeneous particles. With a specific interest in colloidal lattices, we find that although the enhanced electrostatic repulsion explains the formation of colloidal lattices by sulfate-treated polystyrene (S-PS) particles, it fails to interpret the unsuccessfulness of assembling lattices containing single-species carboxylate-treated polystyrene (C-PS) particles. A small percentage of C-PS particles in the colloidal mixture does not disturb the formation of lattices made of S-PS particles. The LSCM also provides a meaningful way to probe dynamic information. The diffusion of single particles at the emulsion interfaces depends strongly on the oil phase viscosity, particle size, and particle wettability. A highly curved emulsion interface slows the motion of microparticles at oil-water interfaces but the interface curvature effect decreases with increasing oil phase viscosity. Although the confocal microscope was originally used as an imaging tool, we find that the thermodynamic equilibrium of colloidal lattices can be disturbed and even destroyed when increasing the output laser intensity.     

Determination of absorption coefficients for chlorophyll a,phycocyanin, mineral matter and CDOM from three central Indiana reservoirs

Absorption coefficients are used in semi-empirical and bio-optical models to estimate various optically active constituents in water. This study determines the mass-specific absorption coefficients of chlorophyll a (a*_chl), phycocyanin (a*_pc), minerals (a*_m), and chromophoric dissolved organic matter (CDOM; a*_CDOM) and the absorption coefficient for CDOM (a_CDOM) for three central Indiana reservoirs. Absorption spectra were collected using a Shimadzu spectrophotometer equipped with a Spectralon coated integrating sphere. Quantitative measurements from either fluorometric (chlorophyll a, phycocyanin, CDOM) or weight-based (mineral) measurements were used to determine the mass-specific absorption coefficients tested in this study and an exponential function was used to estimate a_CDOM. While a*_chl showed minimum variability between reservoirs, a*_pc, a*_m, a*_CDOM, and a_CDOM showed statistically significant differences between reservoirs; however, for a*_m, there was greater variation within each reservoir. Variability in a*_CDOM and a_CDOM between reservoirs was likely due to different inflows. All absorption coefficients fell within previously published ranges for each constituent examined, with the exception of a*_pc. Differences in a*_pc were likely due to different techniques used in extracting and estimating phycocyanin.     

Ain't misbehavin': The effects of age and intentionality on judgments about misconduct.

In 2 person perception experiments, young and older perceivers read a scenario about a young or old female target who leaves a store without paying for a hat. In Experiment 1, the target claims she forgot she was wearing the hat when questioned by the manager. Perceivers thought the manager would have greater sympathy, less anger, and would recommend less punishment when the target was old. In Experiment 2, the target clearly forgot to pay for the hat, clearly stole it, or had ambiguous intentions. In the ambiguous condition, perceivers attributed the young target's behavior more to stealing and the old target's behavior more to forgetting. In the forget condition, young perceivers had equal sympathy for the young and old targets and held them similarly responsible, but older perceivers had greater sympathy for the forgetful old target and held her less responsible than they did the forgetful young target. (PsycINFO Database Record (c) 2010 APA, all rights reserved)