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Search Results: 1 - 10 of 252588 matches for " Estêv?o Magno Rodrigues Araújo "
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Solvent Extraction of Citric Acid with Different Organic Phases  [PDF]
Estêvo Magno Rodrigues Araújo, Fabrício Eduardo Bortot Coelho, Julio Cézar Balarini, Tania Lúcia Santos Miranda, Adriane Salum
Advances in Chemical Engineering and Science (ACES) , 2017, DOI: 10.4236/aces.2017.73023
Abstract: The present work aimed at the study of citric acid solvent extraction in order to establish the composition of the organic phase and to obtain thermodynamic and kinetic data for the chosen system. Discontinuous extraction experiments in a single stage were performed from a synthetic solution of citric acid, with the typical concentration (10% w/v) observed in industrial fermented musts. Exploratory experiments were carried out using different organic phases in order to select the most suitable solvent phase to further continuous extraction tests in a mechanically agitated column. The selected organic phase composition was: Alamine 336, ExxalTM 13 tridecyl alcohol, and the aliphatic diluent EscaidTM 110. Next, the effects of the contact time and of the concentrations of extractant and modifier on the citric acid extraction were studied. Among the investigated conditions, the best one was 10 minutes of contact time, 30% w/v of Alamine 336, and 10% w/v of ExxalTM 13 tridecyl alcohol. For this condition, the equilibrium isotherm (28°C ± 2°C) was determined, and the equilibrium constant was calculated (36.8 (mol·L-1)-1.5). It was considered that trioctylamine and citric acid complexation reaction occurs mainly with non-dissociated citric acid form, because the aqueous feed solutions’ pH is lower than the citric acid pKa1. It was found that 1.5 molecules of the extractant, on average, are required to react with one citric acid molecule, which can indicate that reactions with different extractant/citric acid ratios occur simultaneously. Next, the rate constants for the direct and inverse reactions, 2.10 (mol·L-1)-1.5·s-1 and 5.69 × 10-2 s-1, respectively, were calculated. Coefficients of determination (R2) values higher than 0.93 were found in these calculations, suggesting that the results obtained using a computer modeling would be very close to those results obtained experimentally. Therefore, the present work provides data required to future modelling, design, and simulation of citric acid solvent extraction processes.
Individual and Combined Effects of the Extractant, Surfactant and Modifier Concentrations on the Droplet Coalescence Time of the Primary Emulsion in the Liquid Surfactant Membrane Extraction Process  [PDF]
Adriane Salum, Lorena da Costa Nascimento, Tania Lúcia Santos Miranda, Leandro Dornellas Sampaio Andrade, Cibele Konzen, Julio Cézar Balarini, Estêvo Magno Rodrigues Araújo, Fabrício Eduardo Bortot Coelho
Advances in Chemical Engineering and Science (ACES) , 2018, DOI: 10.4236/aces.2018.84014
Abstract: In this work, the individual and combined effects of the extractant, surfactant and modifier concentrations on the droplet coalescence time of the primary emulsion in the liquid surfactant membrane extraction process were evaluated, through emulsification experiments. Adogen 464 was used as extractant (carrier), and Escaid 110, as diluent. Two systems were studied. The first one composed by the extractant, the surfactant and the diluent, and the second one composed by the same reagents, but with the addition of 1-decanol as modifier. It was observed that, when the modifier is not present in the membrane phase, the surfactant not only stabilizes the primary emulsion, but, apparently, it also plays a role similar to that of the alcohol, promoting the solvation of the amine in a low polarity diluent. Furthermore, the extractant, a quaternary amine, helps to stabilize the primary emulsion in systems without a modifier. For membrane phases consisting of 1 or 5% w/w of Adogen 464 and 2% or 5% w/w of ECA 4360, a concentration of 3% w/w of 1-decanol was sufficient to promote the solvation of Adogen 464 in Escaid 110 and to obtain a low droplet coalescence time.
Development of a New Bio-Based Insulating Fluid from Jatropha curcas Oil for Power Transformers  [PDF]
José M. G. Evangelista Jr., Fabrício E. Bortot Coelho, Juliana A. O. Carvalho, Estêvo M. R. Araújo, Tania L. S. Miranda, Adriane Salum
Advances in Chemical Engineering and Science (ACES) , 2017, DOI: 10.4236/aces.2017.72018
Abstract: The present work aims to develop a new vegetable insulating fluid for power transformers based on Jatropha curcas oil. Besides its technical benefits, Jatropha curcas oil has a socio-economic role by promoting income to rural families, contributing to the countryside development and avoiding rural exodus. Thus, the entire transformer oil production (extraction, processing, characterization and accelerated aging) was covered and a new process was developed. For oil extraction, the most suitable process was the solvent extraction (5 mL of hexane per gram of crushed non-peeled seeds during 30 minutes) with an oil yield of 32%. In raw oil processing stage, the degumming, with 0.4 g of phosphoric acid per 100 g of oil, at 70°C, was used to remove phosphatides. Then, free fatty acids were 96% neutralized with a sodium hydroxide solution (0.5% w/w) at room temperature. For the oil clarification, the combination of 5% w/woil of activated carbon and 1% w/woil of MgO resulted in a bright, odorless and clear oil with an acid number of 0.04 mgKOH·g1. The oil drying in a vacuum rotary evaporator, at 70°C, for 2 hours reduced the water content to 177 ppm. The processed oil was characterized following ASTM D6871 methods. This oil presented higher dielectric breakdown voltage (55 kV) than commercial transformer fluids (BIOTEMP?, EnvirotempFR3?, and Bivolt?), which increases transformer safety, capacity and lifetime. In addition, the processed oil has a lower viscosity than BIOTEMP? fluid, which can enhance the heat dissipation efficiency in the transformer. Moreover, the processed oil flash and fire points of 310°C and >340°C, respectively, confirm the great security of vegetable insulating fluids. The analyzed properties of the processed oil fulfill all the ASTM D6871, ABNT NBR 15422 and IEC 62770 specifications. Therefore, Jatropha curcas oil is a potential substitute formineral insulating fluids.
Pseudoaneurisma de artéria ilíaca comum como complica??o de cirurgia para hérnia discal lombar: relato de caso
Arquivos de Neuro-Psiquiatria , 1999, DOI: 10.1590/S0004-282X1999000500028
Abstract: surgery for discogenic disease of lumbar region is a challenging and diverse field. the significance of complications in disc surgery arises from the possibility that failure of primary treatment may lead to a permanently disable patient. the most common iatrogenic lesions in the posterior approach to lumbar disc herniation are neurologic, vascular, enteric, ureteral, and sexual dysfunction. abramovitz reports that vascular complications of the posterior approach occur in at least 0.1% of cases. the vascular complications may present during surgery as severe bleeding leading to hypotension. the most common late complication is arteriovenous fistula followed by false aneurysms. we describe the case of a 39 year-old woman who was operated on for a lumbar disc herniation in other hospital. she came to us with a persistent pain in lumbar area. a mri scan of lumbosacral region revealed a paravertebral lesion suggesting abscess. an angiography was performed and showed a false aneurysm of left common iliac artery, which was surgically treated successfully. we discuss the mechanisms of lesion and precautions against vascular ones during lumbar disc surgery.
Estimativa da produ??o microbiana em cabras lactantes alimentadas com diferentes teores de proteína na dieta
Fonseca, Carlos Elysio Moreira da;Valadares, Rilene Ferreira Diniz;Valadares Filho, Sebasti?o de Campos;Le?o, Maria Ignez;Cecon, Paulo Roberto;Rodrigues, Marcelo Teixeira;Pina, Douglas dos Santos;Marcondes, Marcos Inácio;Paix?o, M?nica Lopes;Araújo, Alexandre Magno;
Revista Brasileira de Zootecnia , 2006, DOI: 10.1590/S1516-35982006000400031
Abstract: the objective of this trial was to study the effects of increasing dietary levels of crude protein (cp) on microbial protein synthesis of lactating dairy goats. the microbial markers purines bases and purine derivatives (pd), measured in spot urine samples or in urine samples from total collection, were used to estimate microbial protein synthesis. sixteen lactating goats (four fitted with ruminal cannula) were randomly assigned to four replicated 4 x 4 latin squares and were fed the following dietary cp levels [dry matter (dm) basis]: 11.5, 13.5, 15.5 or 17.5%. no significant differences were observed between techniques for estimating microbial protein synthesis. therefore, 12 non-cannulated goats were used to evaluate the effect of dietary cp level on pd excretion, microbial nitrogen flow and microbial efficiency using either total or spot collection of urine. because creatinine excretion did not differ among treatments, the average value 26.05 mg of urinary creatinine excreted per kg of body weight was used for estimating the volume of urine using spot samples. urinary volume estimated using spot samples was similar to that measured with total urine collection. in both cases, an increase on the amount of absorbed purines was observed when the dietary cp level increased in the diet. in brief, pd can be used for estimating microbial protein synthesis in lactating goats and spot samples were a good alternative for total collection of urine.
Produ??o de proteína microbiana, concentra??o plasmática de uréia e excre??es de uréia em novilhos alimentados com diferentes níveis de uréia ou casca de algod?o
Magalh?es, Karla Alves;Valadares Filho, Sebasti?o de Campos;Valadares, Rilene Ferreira Diniz;Paix?o, M?nica Lopes;Pina, Douglas dos Santos;Paulino, Pedro Veiga Rodrigues;Chizzotti, Mário Luiz;Marcondes, Marcos Inácio;Araújo, Alexandre Magno;Porto, Marlos Oliveira;
Revista Brasileira de Zootecnia , 2005, DOI: 10.1590/S1516-35982005000400038
Abstract: two trials were conducted to study the effects of different levels of urea or cottonseed hulls on yield of microbial protein, estimated by the urinary excretion of purine derivatives, concentration of plasma urea, and excretion of urea in steers. in the first trial, 24 crossbred castrated steers averaging 300 kg of initial live weight (lw) were uniformly assigned to four treatments in a complete randomized design as follows: 0, 0.65, 1.30, or 1.95% of urea (% of dry matter) that replaced soybean meal in the diet. in the second study, 16 crossbred steers averaging 230 kg of initial lw were uniformly assigned to four treatments in a complete randomized design as follows: 0, 10, 20, or 30% of cottonseed hulls (% of dry matter) that replaced elephant grass silage in the diet. spot urine samples were obtained and the concentration of purine derivatives (allantoin plus uric acid) determined. concentrations of creatinine and urea were analyzed in both blood plasma and urine. no significant differences in the urinary concentration of purine derivatives and in the estimation of microbial protein yield were observed by feeding different levels of urea or cottonseed hulls to steers. similarly, no significant differences in the concentration of plasma urea and in the urinary excretion of urea were found by increasing the proportions of urea in the diet. however, concentration of plasma urea decreased linearly by replacing elephantgrass silage with cottonseed hulls in the second trial. it can be concluded that urea as well as cottonseed hulls can be included up to 1.95 and 30% of the diet dry matter, respectively, with no significant change in the efficiency of microbial protein synthesis.
Structural Characteristics of Mulato Grass I under Different Cutting Heights  [PDF]
Leonardo Assis Dutra, Fabianno Cavalcante de Carvalho, Eneas Reis Leite, Magno José Duarte Candido, Joo Ambrósio de Araújo Filho
American Journal of Plant Sciences (AJPS) , 2014, DOI: 10.4236/ajps.2014.55077

This work aimed to evaluate the effects of different individual heights of cut on structural characteristics of Brachiaria hibrida cv. Mulato I in four periods of the year. The study was carried out at the Fazenda Experimental Vale do Acaraú, in Sobral, Ceará, Brazil, from January to December, 2008. The experimental design was a split plot, with the plots representing four pasture conditions through manual cuts of 10 cm, 20 cm, 30 cm and 40 cm heights, which were done every 30 days. Each treatment had three replications. The subplots were represented by four periods of evaluation: January-February-March, April-May-June, July-August-September and October-November-December. Fertilization was performed with 350 kg of N/ha, divided into monthly applications. Irrigation was conducted in alternate days during the dry season. The variables studied were: mean height before cutting (cm); dry matter content (%); total dry matter production (t/ha); percentage of leaves; percentage of stems; percentage of dead material; leaf blade/stem ratios; number of total leaves per tiller; number of live leaves per tiller; average size of leaves; and tiller density. Cutting at 10 cm caused a decrease in total dry matter production, underestimating the potential production. Cutting heights between 20 and 30 cm contributed positively to increase the total number of leaves, number of green leaves, average size of the leafs and total dry matter production. Under the present experimental conditions, cutting around 40 cm was not recommended because of a decreasing in the leaf/stem ratio and a increasing in stem fraction and dry matter content, compromising the structure of the canopy.

Qualidade das silagens de três híbridos de sorgo ensilados em cinco diferentes estádios de matura??o
Araújo, V.L.;Rodriguez, N.M.;Gon?alves, L.C.;Rodrigues, J.A.S.;Borges, I.;Borges, A.L.C.C.;Saliba, E.O.S.;
Arquivo Brasileiro de Medicina Veterinária e Zootecnia , 2007, DOI: 10.1590/S0102-09352007000100028
Abstract: three hybrids of sorghum with medium height (br700, br701 e massa 03) for silage production were evaluated. hybrids were harvest at five different maturation stages. dry matter content, ph, ammonia nitrogen, crude protein, fibrous fractions, in vitro dry matter digestibility and organic acids were determined in silage. a completely randomized block design with three replicates was used. the treatments consisted in a factorial arrangement 5x3 (maturation stages x hybrids). the means were compared by snk test (p<0.05). dry matter content and ph values increased with the maturation stage; ph values were always lower than 4.09. no effects of maturation stage of the plant on ammonia nitrogen, fibrous fractions and in vitro dry matter digestibility were found. organic acids contents suggested that the fermentation inside the silo was enough for preservation of the forage.
Sinopse das espécies neotropicais do grupo nitida do gênero Apenesia (Hymenoptera, Bethylidae)
Ramos, Magno S.;Araújo, Brenda O. P. de;Azevedo, Celso O.;
Iheringia. Série Zoologia , 2010, DOI: 10.1590/S0073-47212010000400005
Abstract: two species are described and illustrated: apenesia quelata sp. nov. and a. trivisa sp. nov. new geographic records and data on morphostructural variation of a. membranaceus lanes & azevedo, 2004, a. paraensis kieffer, 1910, a. quadrata evans, 1963, a. serrulata azevedo & batista, 2002, e a. williamsi evans, 1966 are provided. two species are synonymyzed: a. laticeps evans, 1963 as junior synonym of a. quadrata evans, 1963; a. truncaticeps (kieffer, 1910) as junior synonym of a. paraensis kieffer, 1910. the female of a. quadrata is described and illustrated for the first time. key to the species of the nitida species-group based on males is provided.
Geometric approach to nonvariational singular elliptic equations
Dami?o Araújo,Eduardo V. Teixeira
Mathematics , 2012, DOI: 10.1007/s00205-013-0633-9
Abstract: In this work we develop a systematic geometric approach to study fully nonlinear elliptic equations with singular absorption terms as well as their related free boundary problems. The magnitude of the singularity is measured by a negative parameter $(\gamma -1)$, for $0 < \gamma < 1$, which reflects on lack of smoothness for an existing solution along the singular interface between its positive and zero phases. We establish existence as well sharp regularity properties of solutions. We further prove that minimal solutions are non-degenerate and obtain fine geometric-measure properties of the free boundary $\mathfrak{F} = \partial \{u > 0 \}$. In particular we show sharp Hausdorff estimates which imply local finiteness of the perimeter of the region $\{u > 0 \}$ and $\mathcal{H}^{n-1}$ a.e. weak differentiability property of $\mathfrak{F}$.
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