Publications

Abstract Four typical soils of the Porto (Portugal) area were characterized and used to study the decomposition of buried pieces of pork meat under controlled laboratory experiments (an 8 month experiment with a relatively high soilmoisture and a 1 month experiment with relatively low soilmoisture). The soils types were: organic, sandy, gravel and clay-gravel soils. Soils were characterized for their grain size distribution, pH, water content, organicmatter percentage and mineral composition. Four free fatty acids (myristic, palmitic, oleic and stearic) were analysed (using a methodology based on an extraction step followed by a derivatization reaction and high performance liquid chromatography analysis) in soil samples as a sign of adipocere formation. The direct sensorial analysis of the buried sample residues and the free fatty acids profiles of the sampled soils showed that sandy and clay-gravel soils (in a low moisture environment) slowed the normal decomposition process promoting the formation of adipocere. Nevertheless, this apparent soil effect is indirect and a consequence of the different water retention and permeability of the soils. Thus, the water content of the soils is a crucial factor for adipocere formation.

Abstract The standard (p degrees = 0.1 MPa) molar enthalpies of formation. of the 2-, 3-, and 4-monobromonitrobenzene isomers, in the crystalline phase, at T = 298.15 K, were derived from the standard massic energies of combustion, in oxygen, at T = 298.15 K. measured by rotating bomb combustion calorimetry From the temperature dependence of the vapour pressures of these compounds, measured by the Knudsen effusion technique, their standard molar enthalpies of sublimation, at T = 298.15 K, were derived using the Clausius-Clapeyron equation. [GRAPHICS] The combination of the values of the standard molar enthalpies of formation in the crystalline phase, and of the standard molar enthalpies of sublimation. yielded the standard molar enthalpies of formation in the gaseous phase. The results were interpreted in terms of enthalpic increments, and compared with estimated Values applying the empirical scheme developed by Cox.

Abstract The standard gas-phase enthalpies of formation of difluoro-substituted phenols have been determined experimentally, and have also been predicted by means of computational and empirical estimative methods. Combustion calorimetric studies were used to determine the standard molar enthalpies of formation of the six difluorophenol isomers, whereas their standard molar enthalpies of sublimation or vaporization, at T = 298.15 K was measured by the Calvet drop calorimetric technique. [GRAPHICS] From the values obtained for Delta(f)H(m)degrees (cr, I) and Delta(g)(cr,I)H(m)degrees(298.15 K), the standard molar enthalpies of formation in the gas-phase, at T = 298.15 K, were derived for the six isomers. Moreover, the standard gas-phase enthalpies of formation of difluorophenols have been predicted based on two different methodologies: one using the empirical scheme developed by Cox and the other one based on density functional theory calculations performed at the B3LYP/6-311++G(d,p) level of theory coupled with suitable homodesmic reactions and were compared to the experimental values.

Abstract The present work is part of a research program on the energetics of the linear 4-n-alkoxybenzoic acids, aiming the study of the enthalpic effect of the introduction of an alkoxy chain in the position 4- of the benzoic acid ring. In this work, we present the results of the thermochemical research on 4-n-alkoxybenzoic acids with the alkoxy chain length n = 2, 4, and 8. The standard (p degrees = 0.1 MPa) molar enthalpy of formation of crystalline 4-ethoxybenzoic acid, 4-butoxybenzoic acid, and 4-(octyloxy)benzoic acid was measured, at T = 298.15 K, by static-bomb calorimetry. These values, combined with the values of standard molar enthalpies of sublimation, were used to derive the standard molar enthalpies of formation in the gaseous phase. [GRAPHICS] From those experimental values, the standard molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, are interpreted in terms of structural contributions to the energetics of the substituted benzoic acids and compared with the same parameters estimated from the Benson's Group Method.

Abstract A computational study of the structural and thermochemical properties of N-phenyl (open) and N-alkyl (cyclic) ureas, through the use of M05-2X and B3LYP density functional theory calculations has been carried out. The consistency of the literature experimental results has been confirmed, and using mainly isodesmic reactions, the unknown Delta fH(0)(g) of the other urea derivatives were estimated. The experimental results together with the theoretical information have permitted the study of the effect of phenyl, p- and m-chlorophenyl, alkyl, and carbonyl substitutions on the thermodynamical stability of urea and its cyclic derivatives. The peculiar behavior of the N-tert-butyl substituent in cyclic ureas has been related to geometric deformations.

Abstract The Knudsen mass-loss effusion technique was used to measure the vapor pressures at different temperatures of the following dihydroxybenzoic acids: 2,3-dihydroxybenzoic acid, between (345.22 and 363.18) K; 2,4-dihydroxybenzoic acid, between (376.22 and 392.11) K; 2,5-dihydroxybenzoic acid, between (372.14 and 388.92) K; 2,6-dihydroxybenzoic acid, between (347.14 and 365.17) K; 3,4-dihydroxybenzoic acid, between (387.12 and 403.26) K; and 3,5-dihydroxybenzoic acid, between (345.22 and 363.18) K. From the temperature dependences of the vapor pressure of the crystalline compounds, the standard (p(0) = 10(5) Pa) molar enthalpies and Gibbs energies of sublimation, at T = 298.15 K, were derived. For each of the six isomers the standard (p(0) = 0.1 MPa) molar enthalpy of formation in the crystalline phase was derived from the experimental standard molar energy of combustion, in oxygen, measured by static-bomb combustion calorimetry at T = 298.15 K. The combination of the standard molar enthalpy of formation in the crystalline phase with the standard enthalpy of sublimation yields the standard molar enthalpy of formation in the gaseous phase of the studied compounds.

Abstract The present work reports the thermodynamic study performed on three monofluorinated nitrobenzene derivatives by a combination of experimental techniques and computational approaches. The standard (p degrees = 0.1 MPa) molar enthalpies of formation in the liquid phase of the three isomers of fluoronitrobenzene were derived from the standard molar energies of combustion, in oxygen, at T = 298.15 K, measured by rotating bomb combustion calorimetry. The vapor pressure study of the referred compounds was done by a static method and, from the obtained results, the phase diagrams were elaborated, and the respective triple point coordinates, as well as the standard molar enthalpies of vaporization, sublimation and fusion, at T = 298.15 K, were determined. The combination of some of the referred thermodynamic parameters yielded the standard (p degrees = 0.1 MPa) molar enthalpies of formation in the gaseous phase, at T = 298.15 K, of the studied compounds: Delta(f)H(m)degrees(2-fluoronitrobenzene, g) = -(102.4 +/- 1.5) kJ.mol(-1), Delta(f)H(m)degrees(3-fluoronitrobenzene, g) = -(128.0 +/- 1.7) kJ.mol(-1), and Delta(f)H(m)degrees(4-fluoronitrobenzene, g) = -(133.9 +/- 1.4) kJ.mol(-1). Using the empirical scheme developed by Cox, values of standard molar enthalpies of formation in the gaseous phase were estimated and afterwards compared with the ones obtained experimentally, and both were interpreted in terms of the molecular structure of the compounds. The theoretically estimated gas-phase enthalpies of formation were calculated from high-level ab initio molecular orbital calculations at the G3(MP2)//B3LYP level of theory. The computed values compare very well with the experimental results obtained in this work and show that 4-fluoronitrobenzene is the most stable isomer from the thermodynamic point of view. Furthermore, this composite approach was also used to obtain information about the gas-phase basicities, proton and electron affinities and, finally, adiabatic ionization enthalpies.

Abstract Methamphetamine (METH) causes irreversible damage to brain cells leading to neurological and psychiatric abnormalities. However, the mechanisms underlying life-threatening effects of acute METH intoxication remain unclear. Indeed, most of the hypotheses focused on intra-neuronal events, such as dopamine oxidation, oxidative stress and excitotoxicity. Yet, recent reports suggested that glia may contribute to METH-induced neuropathology. In the present study, we investigated the hippocampal dysfunction induced by an acute high dose of METH (30 mg/kg; intraperitoneal injection), focusing on the inflammatory process and changes in several neuronal structural proteins. For that, 3-month-old male wild-type C57BL/6J mice were killed at different time-points post-METH. We observed that METH caused an inflammatory response characterized by astrocytic and microglia reactivity, and tumor necrosis factor (TNF) system alterations. Indeed, glial fibrillary acidic protein (GFAP) and CD11b immunoreactivity were upregulated, likewise TNF-alpha and TNF receptor 1 protein levels. Furthermore, the effect of METH on hippocampal neurons was also investigated, and we observed a downregulation in beta III tubulin expression. To clarify the possible neuronal dysfunction induced by METH, several neuronal proteins were analysed. Syntaxin-1, calbindin D28k and tau protein levels were downregulated, whereas synaptophysin was upregulated. We also evaluated whether an anti-inflammatory drug could prevent or diminish METH-induced neuroinflammation, and we concluded that indomethacin (10 mg/kg; i.p.) prevented METH-induced glia activation and both TNF system and beta III tubulin alterations. In conclusion, we demonstrated that METH triggers an inflammatory process and leads to neuronal dysfunction in the hippocampus, which can be prevented by an anti-inflammatory treatment.

Abstract This work reports the experiunental and computational thermochemical study performed on time dilluorinated nitrobenzene isomers: 2,4-dilluoronitrobenzene (2,4-DFNB), 2,5-di fluoronitrobenzene (2.5-DFN13), and 3,4difluoronitrobenzene (3.4-DFNI3). The standard (p(o) = 0.1 WIN) molar enthalpies of formation in the liquid phase of these compounds were derived from the standard molar energies of combustion, in oxygen, at 7' = 298.15 K, measured by rotating bomb combustion ealorimetry. A static method was used to perform the vapor pressure study of the referred compounds allowing the construction of the phase diagrams and determination of the respective triple point coordinates, as well as the standard molar enthalpies of vaporization, sublimation, and fusion for two of the isomers (2,4-DFN13 and 3,4-DFN113). For 2,5-dilluoronitrobenzene, only liquid vapor pressures were measured enabling the determination of the standard molar enthalpies of vaporization. Combining the thermodynamic parameters of the compounds studied, the following standard (p(o) = 0.1 MN) molar enthalpies of formation in the gaseous phase, at T = 298.15 K, were derived: Delta(f)H(m)(o)(2,4-DFNB, g) = (296.3 +/- 1.8) kJ.mol(-1), Delta(f)H(m)(o)(2,5-DFNB, g) = (288.2 +/- 2.1) kJ.mol(-1), and Delta(f)H(m)(o)(3,4-DFNB, g) = -(302.4 +/- 2.1) kJ.mol(-1). Using the empirical scheme developed by Cox, several approaches were evaluated in order to identify the best method for estimating the standard molar gas phase enthalpies of.formation of these compounds. The estimated values were compared to the ones obtained experirrientally, and the approach providing the best comparison with experiment was used to estimate the thermodynamic behavior of the other difluorinated nitrobenzene isomers not included in this study. Additionally, the enthalpies of formation of these compounds along with the enthalpies of formation of the other isomers not studied experimentally, i.e., 2,3-DFNB, 2,6-DFNB, and 3,5-DFNB, were estimated using the composite G3MP2B3 approach together with adequate gas-phase working reactions. Furthermore, we also used this computational approach to calculate the gas-phase hasicities, proton and electron affinities, and, finally, adiabatic ionization enthalpies.

Abstract The energetic study of 1,2,3-triphenylbenzene (1.2,3-TPhB) and 1,3,5 -triphenylbenzene (1,3,5-TPhB) isomers was carried out by making use of the mini-bomb combustion calorimetry and Knudsen mass-loss effusion techniques. The mini-bomb combustion calorimetry technique was used to derive the standard (p degrees = 0.1 MPa) molar enthalpies of formation in the crystalline state from the measured standard molar energies of combustion for both isomers. The Knudsen mass-loss effusion technique was used to measure the dependence with the temperature of the vapour pressure of crystalline 1.2.3-TPhB, which allowed the derivation of the standard molar enthalpy of sublimation, by application of the Clausius-Clapeyron equation. The sublimation study of 1,3,5-TPhB had been performed previously. From the combination of data obtained by both techniques, the standard molar enthalpies of formation in the gaseous state, for both isomers. at T = 298.15 K, were calculated. The results indicate a higher stability of the 1,3,5-TPhB isomer relative to 1,2,3-TPhB, similarly to the terphenyls. Nevertheless, the 1,2,3-TPhB isomer is not as energetically destabilized as one might expect, supporting the existence of a pi-pi displacive stacking interaction between both pairs of outer phenyl rings. The volatility difference between the two isomers is ruled by the enthalpy of sublimation. The volatility of the 1,2,3-TPhB is two orders of magnitude higher than the 1,3,5-TPhB isomer, at T = 298.15 K. [GRAPHICS]