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81.
Marina Nídia Ferreira dos Santos Costa Marcos Antônio Pena Muniz Charles Alberto Brito Negrão Carlos Emmerson Ferreira da Costa Maria Louze Nobre Lamarão Luiz Morais José Otávio Carréra Silva Júnior Roseane Maria Ribeiro Costa 《Journal of Thermal Analysis and Calorimetry》2014,115(3):2269-2275
The Pracaxi oil—(Pentaclethra macroloba) contains high concentrations of fatty acids with emollient action that contribute to skin hydration. The use of this oil is supported by the utilization of natural resources thus enabling regional development and social contribution. The objective of this study was to characterize the P. macroloba oil by thermogravimetry (TG, DTG, and DTA), gas chromatography, Fourier transform infrared spectroscopy (FT-IR), and oxidation stability—Rancimat, aiming at the quality control of plant raw material. Three samples of crude oil sold by Amazon Oil Industry (Ananindeua, Pará, Brazil) were studied. The analysis of these oil samples showed different fatty acids, especially the behenic, oleic, linoleic, and lignoceric acids totalizing approximately 96 % of the grease composition and in smaller percentage arachidic, lauric, myristic, palmitic, and linolenic acids were found. The major acids have wide medicinal use. According to the TG/DTG curve, thermal stability was observed up to 220 °C, indicating a greater mass loss related to the dehydration and elimination of volatile substances. The thermal decomposition process occurred in the range of 430–450° C according to the DTG curve. The absorption spectrum in the infrared region (FT-IR) showed well-defined bands confirming the presence of functional groups present in the oil. Tests in a Rancimat have shown an induction period between 8 and 10 h demonstrating that the samples are in agreement with the standards required by ANP No. 14/2012 which requires at least 6 h of testing. 相似文献
82.
Maria I. B. Bernardi Vinícius D. Araújo Caue Ribeiro Waldir Avansi Elson Longo Nilson J. A. de Albuquerque Simoni M. P. Meneghetti Rusiene M. Almeida Humberto V. Fajardo 《Chemical Papers》2014,68(9):1213-1218
Wurtzite-type Zn1?x Mn x O (x = 0, 0.03, 0.05, 0.07) nanostructures were successfully synthesised using a simple microwave-assisted hydrothermal route and their catalytic properties were investigated in the cellulose conversion. The morphology of the nanocatalysts is dopant-dependent. Pure ZnO presented multi-plate morphology with a flower-like shape of nanometric sizes, while the Zn0.97Mn0.03O sample is formed by nanoplates with the presence of spherical nanoparticles; the Zn0.95Mn0.05O and Zn0.93Mn0.07O samples are mainly formed by nanorods with the presence of a small quantity of spherical nanoparticles. The catalyst without Mn did not show any catalytic activity in the cellulose conversion. The Mn doping promoted an increase in the density of weak acid sites which, according to the catalytic results, favoured promotion of the reaction. 相似文献
83.
Manoel Raimundo dos Santos Junior Elinia Castro Costa Caio Campos Ferreira Lucas Pinto Bernar Marcilene Paiva da Silva Andria de Andrade Mncio Marcelo Costa Santos Sílvio Alex Pereira da Mota Douglas Alberto Rocha de Castro Sergio Duvoisin Junior Luiz Eduardo Pizarro Borges Marilena Emmi Araújo Nlio Teixeira Machado 《Molecules (Basel, Switzerland)》2022,27(7)
In this work, the deoxygenation of organic liquid products (OLP) obtained through the thermal catalytic cracking of palm oil at 450 °C, 1.0 atmosphere, with 10% (wt.) Na2CO3 as a catalyst, in multistage countercurrent absorber columns using supercritical carbon dioxide (SC-CO2) as a solvent, with an Aspen-HYSYS process simulator, was systematically investigated. In a previous study, the thermodynamic data basis and EOS modeling necessary to simulate the deoxygenation of OLP was presented. This work addresses a new flowsheet, consisting of 03 absorber columns, 10 expansions valves, 10 flash drums, 08 heat exchanges, 01 pressure pump, and 02 make-ups of CO2, aiming to improve the deacidification of OLP. The simulation was performed at 333 K, 140 bar, and (S/F) = 17; 350 K, 140 bar, and (S/F) = 38; 333 K, 140 bar, and (S/F) = 25. The simulation shows that 81.49% of OLP could be recovered and that the concentrations of hydrocarbons in the extracts of absorber-01 and absorber-02 were 96.95 and 92.78% (wt.) on a solvent-free basis, while the bottom stream of absorber-03 was enriched in oxygenated compounds with concentrations of up to 32.66% (wt.) on a solvent-free basis, showing that the organic liquid products (OLP) were deacidified and SC-CO2 was able to deacidify the OLP and obtain fractions with lower olefin contents. The best deacidifying condition was obtained at 333 K, 140 bar, and (S/F) = 17. 相似文献
84.
de Carvalho Tiago Cristiano Rony Gonçalves Luiz Fernando Tonon Durval José 《Nonlinear dynamics》2020,101(1):719-739
The aim of this paper is to study the qualitative dynamics of a piecewise smooth system modeling the intermittent treatment of the human immunodeficiency virus. Typical singularities and closed orbits are observable, and we quantitatively explore the dynamics around those singularities and closed orbits. Moreover, we conclude that this protocol always will be successful since the trajectory passing through any initial condition converges to one of these distinguished orbits. Our formal mathematical results corroborate the real-world observation, where the virus is not eliminated, but the number of infected cells is controlled around a specific value.
相似文献85.
Coutinho CF Coutinho LF Mazo LH Nixdorf SL Camara CA Lanças FM 《Analytica chimica acta》2007,592(1):30-35
A simple, rapid, and low-cost coulometric method for direct detection of glyphosate using hydrophilic interaction chromatography is presented. The principle of detection is based on the enhancement of the anodic current of copper microelectrode in the presence of complexing agents, such as glyphosate, with the formation of a soluble Cu(II) complex. Under optimized conditions, the limit of detection (S/R = 3) for glyphosate was 0.1 mg L−1 (0.59 μM) without any preconcentration method. The calibration curve has been found linear in all concentration range tested (from limit of detection to 34 mg L−1) with an excellent correlation coefficient (0.9999). The present method was successfully applied for the determination of glyphosate in fruit juices without any kind of extraction, clean-up, or preconcentration step, with recoveries of 92 and 90% for apple and grape juice, respectively. 相似文献
86.
Mariana R. Lopes Carlos J. A. de Souza Marina Q. R. B. Rodrigues Daniela A. Costa Ancély F. dos Santos Leandro L. de Oliveira Humberto J. O. Ramos Valéria M. Guimarães Wendel B. Silveira Flávia M. L. Passos Luciano G. Fietto 《Applied biochemistry and biotechnology》2014,172(5):2412-2424
An extracellular β-glucanase secreted by Kluyveromyces marxianus was identified for the first time. The optimal conditions for the production of this enzyme were evaluated by response surface methodology. The optimal conditions to produce β-glucanase were a glucose concentration of 4 % (w/v), a pH of 5.5, and an incubation temperature of 35 °C. Response surface methodology was also used to determine the pH and temperature required for the optimal enzymatic activity. The highest enzyme activity was obtained at a pH of 5.5 and a temperature of 55 °C. Furthermore, the enzyme was partially purified and sequenced, and its specificity for different substrates was evaluated. The results suggest that the enzyme is an endo-β-1,3(4)-glucanase. After optimizing the conditions for β-glucanase production, the culture supernatant was found to be effective in digesting the cell wall of the yeast Saccharomyces cerevisiae, showing the great potential of β-glucanase in the biotechnological production of soluble β-glucan. 相似文献
87.
Luiz Pereira Ramos Helena Maria Wilhelm 《Applied biochemistry and biotechnology》2005,123(1-3):807-819
In recent years, the concept of producing biodiesel from renewable lipid sources has regained international attention. In
Brazil, a national program was launched in 2002 to evaluate the technical, economic, and environmental competitiveness of
biodiesel in relation to the commercially available diesel oil. Several research projects were initiated nationwide to investigate
and/or optimize biodiesel production from renewable lipid sources and ethanol derived from sugarcane (ethyl esters). Once
implemented, this program will not only decrease our dependence on petroleum derivatives but also create new market opportunities
for agribusiness, opening new jobs in the countryside, improving the sustainability of our energy matrix, and helping the
Brazilian government to support important actions against poverty. This article discusses the efforts to develop the Brazilian
biodiesel program in the context of technical specifications as well as potential oilseed sources. 相似文献
88.
Pereira CF Pimentel MF Galvão RK Honorato FA Stragevitch L Martins MN 《Analytica chimica acta》2008,611(1):41-47
This work presents a comparative study of calibration transfer among three near infrared spectrometers for determination of naphthenes and RON (Research Octane Number) in gasoline. Seven transfer methods are compared: direct standardization (DS), piecewise direct standardization (PDS), orthogonal signal correction (OSC), reverse standardization (RS), piecewise reverse standardization (PRS), slope and bias correction (SBC) and model updating (MU). Two pre-treatment procedures, namely standard normal variate (SNV) and multiplicative scatter correction (MSC), are also investigated. The choice of an appropriate number of transfer samples for each technique, as well as the effect of window size in PDS/PRS and OSC components, are discussed. A broad set of gasoline samples representative of the Northeastern states of Brazil is employed in the investigation. The results show that the use of calibration transfer yields prediction errors comparable to those obtained with complete recalibration of the secondary instrument. Overall, the results point to RS as the best method for the analytical problem under consideration. When storage and/or physical transportation of transfer samples are impractical, MU is more appropriate. The comprehensive investigation carried out in the present work will be of value for practitioners involved in networks of fuel monitoring. 相似文献
89.
Jos Roberto Berretta Wagner de Rossi Maurício David Martins das Neves Ivan Alves de Almeida Nilson Dias Vieira Junior 《Optics and Lasers in Engineering》2007,45(9):960-966
The technique to weld AISI 304 stainless steel to AISI 420 stainless steel with a pulsed Nd:YAG laser has been investigated. The main objective of this study was to determine the influence of the laser beam position, with respect to the joint, on weld characteristics. Specimens were welded with the laser beam incident on the joint and moved 0.1 and 0.2 mm on either side of the joint. The joints were examined in an optical microscope for cracks, pores and to determine the weld geometry. The microstructure of the weld and the heat affected zones were observed in a scanning electron microscope. An energy dispersive spectrometer, coupled to the scanning electron microscope, was used to determine variations in (weight %) the main chemical elements across the fillet weld. Vickers microhardness testing and tensile testing were carried out to determine the mechanical properties of the weld. The results of the various tests and examinations enabled definition of the best position for the incident laser beam with respect to the joint, for welding together the two stainless steels. 相似文献
90.
Luiz C. L. Botelho 《International Journal of Theoretical Physics》2017,56(8):2535-2539
We propose a Fresnel stochastic white noise framework to analyze the nature of the Feynman paths entering on the Feynman Path Integral expression for the Feynman Propagator of a particle quantum mechanically moving under an external electromagnetic time-independent potential. 相似文献