Publications

Abstract The electrochemical oxidation of CO has been studied on Pt(S)[(n - 1)(1 0 0) x (1 1 0)] electrodes to investigate the effect of the step density in the reaction. This series shows two different trends for long (n >= 7) and short terraces. For long terraces, the voltammetric peak shifts towards higher potential as the step density increases, unlike the behaviour observed for other stepped surfaces, which exhibit the opposite behaviour in agreement with the Smoluchowski effect. For short terraces, the "normal" behaviour is observed, that is, as the step density increases the peak shifts towards lower potentials. Chronoamperometric measurements were used to determine rate constants and Tafel slopes using the mean field Langmuir-Hinselwood kinetics. Rate constants follow the same trends as the peak potentials in voltammetry. A Tafel slope of 75 +/- 4 mV has been obtained for the surfaces with long terraces whereas a value of the surfaces with short terraces showed a value of 100-120 mV is obtained. This change of slopes is interpreted as a change in the electrochemical behaviour of the species involved in the mechanism, probably, a change in the adsorption isotherm of adsorbed OH. Pt(5 10) electrode exhibits an intermediate behaviour between those of long and short terraces with two different peaks that can be associated with both behaviours previously described.

Abstract The standard (p degrees = 0.1 MPa) molar energies of combustion in oxygen at T = 298.15 K of 5-hydroxy- and 6-hydroxy-alpha-tetralone were measured by static bomb calorimetry. The values of the standard molar enthalpies of sublimation at T = 298.15 K were obtained by Calvet microcalorimetry. Combining these results, the standard molar enthalpies of formation of the compounds in the gas-phase at T = 298.15 K have been calculated: 5-hydroxy-alpha-tetralone -(262.5 +/- 2.3) kJ.mol(-1) and 6-hydroxy-alpha-tetralone -(268.1 +/- 2.2) kJ.mol(-1). Additionally, high-level single-point calculations based on density functional theory with the B3LYP hybrid exchange-correlation energy functional and extended basis sets as well as on two more accurate correlated computational techniques of the MCCM/3 suite have been performed for the studied compounds. The agreement between experiment and theory gives us confidence to estimate the enthalpies of formation of 7-hydroxy and 8-hydroxy-alpha-tetralone. Similar calculations were done for 5-, 6, 7-, and 8-hydroxy-beta-tetralone, for which experimental work was not done.

Abstract The standard (p degrees = 0.1 MPa) molar energies of combustion in oxygen, at T = 298.15 K, of solid 3,3-tetramethyleneglutaric acid and the related 3,3-tetramethyleneglutaric anhydride and 3,3-tetramethylenegiutarimide were measured by static bomb combustion calorimetry. The values of the standard molar enthalpies of sublimation, at T = 298.15 K, were obtained by Calvet microcalorimetry, allowing the calculation of the standard molar enthalpies of formation of the compounds, in the gaseous state, at T = 298.15 K. The geometries of the experimentally studied compounds were fully optimized using density functional theory with the B3LYP functional and extended basis sets. More accurate energies were also obtained from single-point calculations at the most stable B3LYP/6-311G** geometries, using the cc-pVTZ basis set. From these calculations the standard molar enthalpies of formation of 3,3-tetramethyleneglutaric acid, 3,3-tetramethyleneglutaric anhydride, and 3,3-tetramethyleneglutarimide were estimated using isodesmic reactions involving glutaric acid, glutaric anhydride, and glutarimide, respectively. Experimental and computational results were used in the discussion of the interrelation of energetics and structure in these compounds and compared with other structurally related compounds.

Abstract Nanocomposite films comprising walled carbon nanotubes (MWCNTs) embedded within poly [Ni(3-Mesalophen-b15-c5)] were deposited on Pt and ITO electrode surfaces by the potentiodynamic polyrnerisation of [Ni(3-Mesalophen-b15-c5)] from solutions containing dispersed MWCNTs. Composites incorporating carbon nanotubes subject to a range of oxidising pre-treatments were compared with those incorporating untreated carbon nanotubes and with the pure polymer. In both cases the use CH3CN and CH2Cl2 as fabrication and characterization media were explored. Films were characterized by voltammetry. electrochemical impedance spectroscopy and scanning electron microscope (SEM). The coating of the carbon nanotubes with polymer varied significantly with pre-treatment and solvent medium; this influenced the final composite morphology and electrical properties. Performance enhancement of the polymer component by the presence of the carbon nanotubes was manifested through the ability to store charge and the ease with which this Could he accomplished; these were parameterized via increased redox capacitance and decreased charge-transfer resistance, respectively. Correlation of impedance parameters with SEM images provided a morphological rationale for composite electrical properties.

Abstract The mechanisms by which methamphetamine (METH) causes neurotoxicity are not well understood. Recent studies have suggested that METH-induced neuropathology may result from a multicellular response in which glial cells play a prominent role, and so it is plausible to suggest that cytokines may participate in the toxic effects of METH. Therefore, in the present work we evaluated the effect of an acute administration of METH (30 mg/kg in a single intraperitoneal injection) on the interleukin (IL)-1 beta, IL-6, and tumor necrosis factor (TNF)-alpha mRNA expression levels in the hippocampus, frontal cortex, and striatum of mice. We observed that METH did not induce changes in the IL-1 beta mRNA expression levels in both hippocampus and striatum, with immeasurable levels in the frontal cortex. Regarding IL-6, METH induced an increase in the expression levels of this cytokine in the hippocampus and striatum, 1 h and 30 min post injection, respectively. In the frontal cortex, the increase in IL-6 mRNA levels was more significant and remained high even after 2 h. Moreover, the expression levels of TNF-alpha were increased in both hippocampus and frontal cortex 30 min post METH administration, with immeasurable levels in the striatum. We conclude that the pro-inflammatory cytokines IL-6 and TNF-alpha rapidly increase after METH administration, providing a new insight for understanding the effect of this drug of abuse in the brain.