Surface study of a titanium-based ceramic electrode material by X-ray photoelectron spectroscopy

The electrochemical behaviours of the Magneli phase titanium oxides with the general formula TixO2x-1 have been investigated. Surface analysis of these ceramic materials was performed using X-ray photoelectron spectroscopy in order to determine the surface composition. It was shown that the surface layers contain mainly TiIV. When these materials are used as an anode for oxygen evolution, in sulfuric acid, the XPS spectrum shows considerable modification in the O1s region, due to an important contribution of hydroxyl groups and the adsorption of sulfate anions. This revised version was published online in November 2006 with corrections to the Cover Date.     

Mathematical Models of Flavor Release from Liquid Emulsions

The penetration theory of interfacial mass transfer was used to model flavor release from liquid emulsions. The model was used to predict the rates of release and partitioning properties of two volatiles, one hydrophilic (diacetyl) and the other hydrophobic (heptan-2-one), as a function of the oil volume fraction. In general the initial rates of release were faster for emulsions of lower oil content, whereas the equilibrium concentrations depended on the nature of the flavor compound and the volume fraction of oil in the emulsion. Experimental in vitro results suggested that the rate limiting step for flavor release was the resistance to mass transport across the emulsion-gas interface.     

Thermomechanical Mismatch in Ceramic-Fiber-Reinforced Glass-Ceramic Composites

The thermomechanical relationship between mullite and a lithium aluminosilicate (LAS) glass-ceramic has been studied by a technique of bimaterial dilatometry. The viscoelastic behavior of LAS was found to result in a temperature T rvsl below the glass-transformation temperature T_g at which the interfacial stresses between the materials undergo a reversal in sign. The effect of T rvsl on the high-temperature mechanical properties of mullite or SiC fiber-reinforced glass-ceramic composites is discussed. It is suggested that fiber clamping by the matrix at temperatures between T rvsl and T_g contributes to the brittle, high-temperature behavior of such composites.     

PROTEIN AGGREGATION IN INTACT AND DISRUPTED PEROXIDIZING ERYTHROCYTE MEMBRANES

The effects of molecular organization on the interaction of peroxidizing lipids with proteins were studied by using human red cell membranes. Intact and chloroform-disrupted membranes were oxidized. Disruption of membranes was achieved by treatment with chloroform and subsequent elimination of the solvent. Lipid oxidation rates and SDS-electrophoretic protein patterns in the two types of membranes were compared. Specific ³H-DIDS label of band 3 allowed the study of the role of intrinsic proteins in the aggregation process. Lipid oxidation rate is not greatly affected by chloroform disruption although disrupted membranes show a higher rate of protein aggregation. α-Tocopherol decreases lipid oxidation and protein aggregation rates. Band 3 protein dimers (188,000 M.W.) appear earlier than the higher molecular weight protein aggregates (400,000 M.W.). The results suggest that native membrane organization prevents protein damage upon lipid peroxidation.     

REGRESSION ANALYSIS AND THE EVALUATION OF COLOR-DIFFERENCE METRICS

Regression analysis and the use of correlation coefficients have proven to be useful tools in the analysis of experimental data. But unless the proper precautions are taken, erroneous conclusions can easily be reached by their use. Several data patterns are provided to demonstrate this. Examples yielding unrepresentatively high, as well as low, correlations are discussed.     

STUDIES ON MECHANISMS OF RETENTION OF VOLATILE IN FREEZE-DRIED FOOD MODELS: THE SYSTEM PVP-n-PROPANOL

Retention of C¹⁴-labeled n-propanol was studied in a freeze-dried system containing polyvinylpyrrolidone (PVP). Variables affecting retention during freeze drying were: initial concentrations of PVP and n-propanol, rate of freezing and sample thickness. Rehumidification above the BET monolayer value resulted in losses of propanol which increased with increasing water content. Behavior of the model system based on PVP is consistent with the "microregion volatile entrapment theory." The PVP system (and perhaps polymeric carbohydrates) differ from low molecular weight carbohydrates: water sorption below the BET monolayer is reduced by entrapped volatile, and absolute level of retention is lower