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- Author or Editor: L A Carvalho x
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Seismic coda Qattenuation (Q c) in the frequency range from 6 to 20 Hz of two distinct Scoda windows (early and later portions) are compared to analyse the effects of both coda windows on crustal seismic attenuation estimates around Samambaia fault (João CâmaraNortheastern Brazil). Q cvalues associated with the later portion are systematically higher than those related to the early portion. These values follow a frequency (f) function given by Q c(f) = Q 0 f , where Q 0= 11739 and= 1.000.06. In general, Q 0estimate is less sensitive to site effects and stabler than that obtained from the early portion of S coda waves, while its corresponding frequency dependence is similar to that obtained from the early portion of S coda waves. It suggests thatparameter does not depend on coda window's location along the seismic signal. A comparative analysis of both Q 0andvalues with those found recently shows that there is no difference in using early or later portion of S coda waves in the stations located on Pre-Cambrian basement in the João Câmara area. This comparison also shows that the major variations in Q 0values were observed at seismic stations installed on sedimentary terrain. Differences in the seismic attenuation, in both sides of the Samambaia fault, were also observed in this study, and it is in agreement with the hypothesis that Samambaia fault is a kind of boundary between two seismic attenuation zones.
Abstract
The thermal decomposition kinetics of the solid complexes Cd(S2 CNR2 )2 , where R =C2 H5 , n -C3 H7 , n -C4 H9 or iso -C4 H9 , was studied by using isothermal and non-isothermal thermogravimetry. The superimposed TG/DTG/DSC curves revealed that thermal decomposition reactions occur in the liquid phase. The kinetic model that best fitted the experimental isothermal TG data was the one-dimensional phase-boundary reaction-controlled process R1 . The thermal analysis data suggested the thermal stability sequence Cd(S2 CNBun 2 )2 >Cd(S2 CNPrn 2 )2 >Cd(S2 CNBui 2 )2 >Cd(S2 CNEt2 )2 , which accords with the sequence of stability of the apparent activation energies.
Abstract
In this work, the influence of attapulgite concentration on the nucleating efficiency of isotactic polypropylene (iPP) and on the kinetics of non-isothermal crystallization were ascertained.The study was conducted by DSC. The nucleating efficiency was determined according to the procedure described by Fillon and the kinetics of non-isothermal crystallization was determined using Ozawa's method using cooling rates of 2, 5 and 10C min−1.Our results indicate that both the relative crystallinity and the crystallization temperature increase with filler content and that a maximum occurs at 2% mass/mass filler content. Both parameters decrease with increasing cooling rates. The Ozawa's exponent tended to increase with temperature and filler content.
Abstract
Characterization, thermal stability and thermal decomposition of light trivalent lanthanide fumarates, as well as, the thermal behaviour of fumaric acid and its sodium salt were investigated employing simultaneous thermogravimetry and differential thermal analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy (FTIR), TG–FTIR techniques, elemental analysis and complexometry. On heating, sublimation of fumaric acid is observed, while the thermal decomposition of the sodium fumarate occurs with the formation of a mixture of sodium carbonate and carbonaceous residue. The thermal decomposition of light trivalent lanthanide fumarates occurs in consecutive and/or overlapping steps with the formation of the respective oxides: CeO2, Pr6O11, and Ln2O3 (Ln = La, Nd, Sm, Eu, Gd).
Abstract
In this study the effect of Ag additions on the thermal behavior of the Cu–22.55 at.%Al alloy was studied using electrical resistivity measurements, in situ X-ray diffractometry, differential scanning calorimetry, and optical microscopy. The results indicated that Ag additions do not change the phase transformations sequence in the studied alloys, but modify its critical temperatures due to a change on entropy of system. It was verified that at the cooling rate of 10 K/min the decomposition of β phase into (α + γ1) is incomplete, but for lower cooling rates than 1.0 K/min this reaction is completed.
Avocado pulp is widely regarded as a great source of edible oil containing fat-soluble vitamins and omega-3 fatty acids (FA). However, avocado peel and seeds are also good sources of edible oil and are less explored byproducts. This paper aimed at determining the proximal composition, FA and tocopherol contents of the pulp, peel, and seeds of Quintal, Fortuna, Margarida, and Hass avocado cultivars. The pulps presented high concentrations of oleic acid. In addition, peel and seeds presented lower omega-6/omega-3 ratios than the pulp. There was also a considerable amount of tocopherol in the peel and seeds, especially in Hass peel (230.7 mg/100 g). According to the results, the peel and seeds of avocado that are considered byproducts, can be utilized in food industry.
Abstract
Biodiesel is susceptible to autoxidation if exposed to air, light and temperature, during its storage. Physic nut (Jatropha curcas L.) seeds show potential application for biodiesel production since its oil yields high quality biodiesel. This work aims to evaluate the thermal behavior of the physic nut oil and biodiesel, from several Brazilian crops, by means of thermoanalytical techniques. Thermogravimetry (TG) and pressurized-differential scanning calorimetry (PDSC) were used in order to determine the applicability of physic nut biodiesel as fuel. Results suggest that physic nut biodiesel is a practical alternative as renewable and biodegradable fuel able to be used in diesel motors.
