Monte Carlo simulation of the KCl : OH dipole glass

Monte Carlo simulation of electric dipole correlations in KCl doped with OH at a concentration of 0.2 at.% are reported. Using a classical model the calculated dielectric susceptibility and specific heat show good agreement with the experimental results obtained around the temperature T_F corresponding to the maximum of the dielectric dispersion and characterizing the freezing of the electric dipole system.     

On the lattice scattering and effective mass of holes in natural diamond

Drift mobility and high-field drift velocity of holes in natural diamond are investigated with the time-of-flight technique. A theoretical interpretation based on Monte Carlo simulation suggests possible values for the deformation potential parameters and effective masses.     

Mössbauer Study of Serpentine Minerals in the Ultramafic Body of Tehuitzingo,Southern Mexico

Hyperfine Interactions - Serpentine “polymorph” minerals (chrysotile, lizardite, and antigorite) are hydrous Mg–Fe silicates that commonly form serpentine rock (serpentinite) by...     

High-performance liquid chromatographic evaluation of 2-(alpha-thenoylthio)propionylglycine and its two metabolites in biological fluids

A high-performance liquid chromatographic (HPLC) method for determining 2-(alpha-thenoylthio)propionylglycine (TTPG) and its two main metabolites, thiophenecarboxylic acid and thiopronine, in biological samples was developed. TTPG and its metabolites were extracted by solvent partition and then determined by reversed-phase HPLC with UV detection at 245, 295 and 360 nm. This procedure was validated in order to allow the assay of these compounds in plasma and urine samples with sufficiently low detection limits (50 ng/ml for TTPG and TCA and 100 ng/ml for thiopronine) and with good linearity within the concentration range investigated. It was applied to a comprehensive pharmacokinetic investigation of TTPG in healthy volunteers.     

Structural Instabilities in Passivated Gold Nanoclusters Induced by Electron Irradiation

In the new nanotechnology devices design, the stability of the systems is very important, in the present work we report evidences of internal and external changes of nanoparticles passivated by thiol molecules when they are irradiated under a high flux of an electron beam in the transmission electron microscope. High Resolution images were digitized and processed in order to identify the contrast changes produced by the atomic inside the nanoparticles. Fcc and decahedral nanoparticles cases are shown. Molecular dynamics calculations are also included in order to compare the experimental evidences with the cluster conditions of stabilities. Both theoretical and experimental results imply the occurrence of atomic and twining movements, and indicate that the n-alkyl thiol molecules prevent atomic movement and changes on the particle structure are not observed.     

Mössbauer Study of the Structure of Fe - Zircon System

Iron-doped silicate (zircon), prepared by a ceramic method with the addition of LiF as mineralizer, was analyzed by X-ray powder diffraction (XRD) and ⁵⁷Fe Mössbauer spectroscopy to obtain information on the solid solution formation. The results of X-ray diffraction and Mössbauer spectroscopy have shown that only a small fraction of iron, about 1.5 mol%, is incorporated in the zircon structure as paramagnetic Fe³⁺ species while the remaining Fe³⁺ cations form magnetic -Fe₂O₃ particles which are trapped within the zircon matrix.     

Poly(ε-caprolactone) + unsaturated isophtalic polyester blends: Thermal properties and morphology

Miscibility of blends composed by a linear unsaturated polyester (LUP) with poly(ε-caprolactone) (PCL) of different molecular weights (M_w = 50 × 10³, 18 × 10³ and 2 × 10³) has been studied. The blends were subjected to different thermal treatments and have been studied by FT-IR spectroscopy, differential scanning calorimetry (DSC) and scanning electronic microscopy (ESEM). FT-IR results allow proving the miscibility of the blends at temperatures above the melting temperature of neat PCL. DSC measurements confirm the existence of a crystalline phase corresponding to neat PCL. The crystallization of PCL is observed in a wide range of blends composition, being detected in all the blend compositions when the crystallization time increases. Thermograms show clearly the glass transition temperatures of samples that have been rapidly quenched from the melt. However, the change in the heat flow corresponding to the glass transition temperatures is difficult to detect in samples with high PCL crystallization degree. The analysis of the results indicates that the morphology of the amorphous phase is heterogeneous for LUP + PCL blends and changes depending on the thermal treatment. The ESEM measurements, confirm the heterogeneity of the amorphous phase. The decrease of the molecular weight of the PCL favours the miscibility of the blends.