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Abstract  

The subject of this work is ethylene polymerisation using Kaminsky type catalysts: Cp2MR2=methylaluminoxane [M=Zr, W, Nb; R=Cl, CH3]. Active center determination and kinetic studies of the (Cp2WCl2+methylaluminoxane) and Cp2ZrCl2+methylaluminoxane) systems are described, using a quenching method with tritiated methanol. The activity of the polymer was determined by liquid scintillation counting. We have found 0.5% and 87% of active centers, respectively for W and Zr system. The catalytic activity of complexes Cp2WCl2 and Cp2NbCl2 was compared with that of Cp2ZrCl2. The W and Nb complexes are found to be less active than the Zr complex.

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Abstract  

The compounds [(LR2Sn)2O] {R=CH3 (Me), n-C4H9(Bn); L=C6H5CH(OH)COO}were studied by thermogravimetric and differential scanning calorimetry in a dynamic atmosphere of helium. The thermal decomposition mechanisms are similar for both compounds and occur in two consecutive steps. The TG curves of the complexes suggest the liberation of the ligand L in the first step, with probable formation of a tin oxide R2SnO intermediate. At the end of the second step free tin is obtained in accordance with the stoichiometry of the related compounds. An inverse relation betweenΔH fusion and solubility of the compounds suggests a polymeric structure for the compound with Bn ligand in relation to the compound with M ligand.

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Summary  

The objective of this study was to determine endogenous phosphorus excretion in sheep fed with different diets. Sixteen male growing sheep, received a basic diet with: 42% hydrolyzed sugarcane bagasse (HSB), 45% lucerne hay (LH) plus 14% hydrolyzed sugarcane bagasse, and 30% citrus pulp (CTP) plus 40% hydrolyzed sugarcane bagasse. A dose of 7.7 MBq 32P was injected into the left jugular vein of each animal. The P endogenous fecal losses were: 1.69, 2.50, 2.33 and 1.45 g/animal for treatments HSB, LH, and CTP respectively (P>0.05). The type of diet influenced slight endogenous P excretion but altered excretion of P in urine. Endogenous P excreted in feces (PF) comes mainly from saliva and represents an important loss of P. The estimation of net requirements of phosphorus (P) for ruminants includes endogenous losses, which is also essential for calculating true absorption of this mineral. Physical structure of the feed may influence endogenous losses, altering the metabolism of P and also the demand of this mineral, therefore being important to know how different feeds affect endogenous P losses.

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Journal of Thermal Analysis and Calorimetry
Authors: Marta C. D. Silva, J. R. Botelho, Marta M. Conceiçăo, B. F. Lira, Monyque A. Coutinho, A. F. Dias, A. G. Souza, and P. F. A. Filho
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Journal of Thermal Analysis and Calorimetry
Authors: Marcelo Kobelnik, Douglas Lopes Cassimiro, Clóvis. A. Ribeiro, Jorge M. V. Capela, Diogines S. Dias, and Marisa S. Crespi

Abstract

The thermal behaviour of Mg-diclofenac compound was evaluated by simultaneous TG-DTA and DSC. The profile of the DSC curves showed that this compound possesses two transition phases: endothermic and exothermic between 170–180 °C and 185–195 °C, respectively. The endothermic reaction is reversible (enantiotropic). Thus, different experimental conditions, i.e. masses sample, open and crimped lids crucible, static and dynamic atmospheres were utilized for DSC analysis for evaluation of this transition phase. In a static atmosphere the enantiotropic reaction was not observed. The obtained data were utilized to obtain the kinetic parameters, which were calculated by the Capela and Ribeiro method. The results show that the activation energy for the transition phase depends on the different experimental conditions.

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Journal of Thermal Analysis and Calorimetry
Authors: Marcelo Kobelnik, Clóvis A. Ribeiro, Diógenes dos Santos Dias, Sonia de Almeida, Marisa Spirandeli Crespi, and Jorge M. V. Capela

Abstract

The Co(II)–diclofenac complex was evaluated by simultaneous thermogravimetry-differential thermal analysis (TG-DTA) and differential scanning calorimetry (DSC). The DTA curve profile shows one exothermic peak because of the transition phase of the compound between 170 and 180 °C, which was confirmed by X-ray powder diffractometry. The transition phase behavior was studied by DSC curves at several heating rates of a sample mass between 1 and 10 mg in nitrogen atmosphere and in a crucible with and without a lid. Thus, the kinetic parameters were evaluated using an isoconversional non-linear fitting proposed by Capela and Ribeiro. The results show that the activation energy and pre-exponential factor for the transition phase is dependant on the different experimental conditions. Nevertheless, these results indicate that the kinetic compensation effect shows a relationship between them.

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Acta Physiologica Hungarica
Authors: S. Baptista, N. Piloto, F. Reis, E. Teixeira-de-Lemos, A.P. Garrido, A. Dias, M. Lourenço, A. Palmeiro, C. Ferrer-Antunes, and F. Teixeira

Physical exercise may improve the metabolic and haemodynamic responses, but the beneficial effects seem to depend on intensity, duration and muscular mass recruitment, which may vary between different types of protocols. This study was performed to evaluate the effects of two distinct moderate/long-term aerobic training protocols in the normal Wistar rat, the treadmill running and the swimming, on several important parameters related to cardiovascular (CV) physiological adaptations, namely: lipid profile, haemorheological measures, lipid peroxidation, peripheral serotonergic system (SS) modulation and sympathetic nervous system (SNS) activation.In both groups under training an HDL-c increment versus the sedentary control was demonstrated. There was a noticeable increase in ADP-induced platelet aggregation in the exercised rats, together with higher PDW and MPV values. The RBC patterns were altered in both groups under training; in the swimming one, however, significantly higher RBC and HCT and lower MCH and MCHC values were found, suggesting renovation of the RBCs. Plasma and platelet SS measures were generally higher in both groups under training, being noticeably relevant the 5-HT and 5-HIAA increment in the treadmill. In opposition, concerning the plasma and platelet NE and E concentrations, the rise was remarkably higher in the rats under a swimming protocol.In conclusion, this study demonstrates that, despite the similar beneficial effects on lipid profile, different aerobic exercise protocols may produce distinct CV physiological adaptations. Therefore, treadmill running was more influent than swimming concerning peripheral SS modulation while swimming was more important on SNS activation, thus recommending a judicious choice of the protocol to be tested in works which make use of rat models of exercise to study physiological or pathophysiological conditions.

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