Un modelo simple del fenómeno de difusión que tiene lugar durante el proceso de desamarizado de aceitunas verdes de mesa

The change in the concentration of sodium and calcium ions in the olive flesh and in the lye during the debittering process was quantified. The average concentration of Na increased from 0.0045 to 0,395 meq Na/g of olive flesh and the concentration of Ca increased from 0.018 to 0.0252 meq Ca/g of olive flesh. The firmness of the olives decreased almost linearly from 375 gf to 235 gf during the alkali treatment. The olives also suffered a 25.9% loss in their initial content of reducing sugars. A hypothetical simplified description of the dynamic of ionic charge changes and unwinding of the pectinic structure during the debittering process of green olives has been proposed. In addition, the effective diffusion coefficients were calculated for sodium and calcium using a diffusion model for a composite flat plate and constant diffusion coefficients. The coefficients for both solutes were in the order of 10–12 m2/s for the skin and 10–10 m2/s for the flesh. In both cases, the diffusion coefficients of Na were larger than the diffusion coefficients of Ca.Se ha cuantificado el cambio en la concentración de sodio y calcio en la pulpa y en la lejía durante el tratamiento alcalino de aceitunas. La concentración promedio de sodio en la pulpa aumentó de 0,0045 a 0,395 meq Na/g mientras que la de calcio creció de 0,018 a 0,0252 meq Ca/g. La textura de las aceitunas disminuyó casi linealmente de 375 gf a 235 gf durante el tratamiento alcalino. Las aceitunas sufrieron una perdida de azúcares reductores del 25.9%. Se ha propuesto una hipotética y simplificada descripción de la dinámica de los cambios de carga iónica y el desenrrollamiento de las pectinas durante el desamarizado de las aceitunas. También se calculó el coeficiente efectivo de difusión para sodio y calcio usando un modelo de difusión para una placa compuesta. Los coeficientes resultaron en el orden de 10–12 m2/s para la piel y 10–10 m2/s para pulpa. En ambos casos el coeficiente de difusión de Na fue mayor que el de Ca

The Kondo Resonance in Electron Spectroscopy

The Kondo resonance is the spectral manifestation of the Kondo properties of the impurity Anderson model, and also plays a central role in the dynamical mean-field theory (DMFT) for correlated electron lattice systems. This article presents an overview of electron spectroscopy studies of the resonance for the 4f electrons of cerium compounds, and for the 3d electrons of V_2O_3, including beginning efforts at using angle resolved photoemission to determine the k-dependence of the resonance. The overview includes the comparison and analysis of spectroscopy data with theoretical spectra as calculated for the impurity model and as obtained by DMFT, and the Kondo volume collapse calculation of the cerium alpha-gamma phase transition boundary, with its spectroscopic underpinnings.Comment: 32 pages, 11 figures, 151 references; paper for special issue of J. Phys. Soc. Jpn. on "Kondo Effect--40 Years after the Discovery

Dynamical Mean-Field Theory and Its Applications to Real Materials

Dynamical mean-field theory (DMFT) is a non-perturbative technique for the investigation of correlated electron systems. Its combination with the local density approximation (LDA) has recently led to a material-specific computational scheme for the ab initio investigation of correlated electron materials. The set-up of this approach and its application to materials such as (Sr,Ca)VO_3, V_2O_3, and Cerium is discussed. The calculated spectra are compared with the spectroscopically measured electronic excitation spectra. The surprising similarity between the spectra of the single-impurity Anderson model and of correlated bulk materials is also addressed.Comment: 20 pages, 9 figures, invited paper for the JPSJ Special Issue "Kondo Effect - 40 Years after the Discovery"; final version, references adde

The cientificWorldJOURNAL Research Article Stabilizing Agents for Calibration in the Determination of Mercury Using Solid Sampling Electrothermal Atomic Absorption Spectrometry

Tetramethylene dithiocarbamate (TMDTC), diethyldithiocarbamate (DEDTC), and thiourea were investigated as stabilizing agents for calibration purposes in the determination of mercury using solid sampling electrothermal atomic absorption spectrometry (SS-ETAAS). These agents were used for complexation of mercury in calibration solutions and its thermal stabilization in a solid sampling platform. The calibration solutions had the form of methyl isobutyl ketone (MIBK) extracts or MIBK-methanol solutions with the TMDTC and DEDTC chelates and aqueous solutions with thiourea complexes. The best results were obtained for MIBK-methanol solutions in the presence of 2.5 g L −1 TMDTC. The surface of graphite platforms for solid sampling was modified with palladium or rhenium by using electrodeposition from a drop of solutions. The Re modifier is preferable due to a higher lifetime of platform coating. A new SS-ETAAS procedure using the direct sampling of solid samples into a platform with an Re modified graphite surface and the calibration against MIBK-methanol solutions in the presence of TMDTC is proposed for the determination of mercury content in solid environmental samples, such as soil and plants