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Search Results: 1 - 10 of 190429 matches for " G. G. Cortez "
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Ca-Al Hydrotalcites as Catalysts for Methanolysis and Ethanolysis of Soybean Oil  [PDF]
E. A. N. Simonetti, G. P. Thim, G. G. Cortez
Modern Research in Catalysis (MRC) , 2014, DOI: 10.4236/mrc.2014.34015
Abstract: The use of heterogeneous catalysts in the transesterification reaction of vegetable oils has getting emphasis in recent years, mainly by the alternative of obtaining clean fuel derived from renewable sources. Metal oxide such as MgO or CaO, supported ones like \"\" and zeolites are often applied in transesterification process. Among them, hydrotalcite has shown potential as catalysts on this reaction due to their physicochemical properties, such as: thermal stability, porosity, specific surface area, memory effect, basicity, acidity and anion exchange capacity. This work studies the catalytic performance of the calcium and aluminum based hydrotalcite in the transesterification reaction of soybean oil in methanol and ethanol. The hydrotalcite samples treated at 450?C were impregnated with KOH. The efficiency of impregnated and non- impregnated samples was compared and the non-impregnated one showed the best performance. This property was attributed to the higher availability of active sites used in the transesterification process.
Métodos de análise organica do café. II. Compara??o entre métodos de determina??o da cafeína em café verde
Amorim, H. V.;Cortez, J. G.;
Anais da Escola Superior de Agricultura Luiz de Queiroz , 1973, DOI: 10.1590/S0071-12761973000100024
Abstract: the micro bailey-andrew method (official of a. o. a. c, 1970) and the proposed reference method of navellier et al. (1969) for determination of caffeine in coffee were studied. for the caffeine extraction and purification, it was followed the a. o. a. c. (1970) and navellier et al. (1969) procedures, without modification, but for the caffeine estimation, the weight, total nitrogen, spectrofotometry with base line correction and the peak at 273 nm were used. the following conclusion could be drawn: a) the determination of caffeine by using the weight should not be applied by either methods, because it gave high values in comparison with nitrogen and spectrophotometry, and because of the high coeficient of variation. b) the extration and purification procedures used by navellier don't remove all nitrogenous materials which interferes on the total nitrogen determination, whereas the navellier spectrofotometry method gave similar results with the a. o. a. c. (1970) nitrogen and spectrophotometric determinations. c) no diference was found for nitrogen and spetrophotometric (with correction of base line) determination of caffeine when a. o. a. c. (1970) extraction and purification procedures were used.
Influência de cultivar e nível de infesta??o de Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) no rendimento do sorgo
Cortez, Mirko G. R.;Waquil, José M.;
Anais da Sociedade Entomológica do Brasil , 1997, DOI: 10.1590/S0301-80591997000200028
Abstract: an experiment was conducted in the greenhouse to evaluate the effect of sorghum (sorghum bicolor) cultivars and spodoptera frugiperda (j. e. smith) infestations, at different plant developmental stages, on sorghum yield. second instar larvae of s. frugiperda were used to infest plants. significant differences (p ≤ 0,05) were found for the factors cultivar and stage of infestation for panicle (size and weight), grain (volume and weight) and 100 grain weight. no significant differences were observed for grain yield between damaged plant and the checks for the cvs. ag 3001 and cmsxs 375. however, the yield loss for the cv. br 300 ranged from 11,6 to 21,7% for plants infested at 1st (15 days) and 4th stage (15 and 37 days), respectively.
Síntese, caracteriza??o e avalia??o catalítica de Vo x/Mg yAlo x na rea??o de decomposi??o do isopropanol
Cortez, Gilberto G.;Meira, Débora M.;
Química Nova , 2008, DOI: 10.1590/S0100-40422008000600003
Abstract: vanadium oxide supported on hydrotalcite-type precursors was studied in the decomposition of isopropanol. hydrotalcite-type compounds with different y = mg+2/al+3 ratios were synthesized by the method of coprecipitating nitrates of mg+2 and al+3 cations with k2co3 as precipitant. the x-ray diffraction patterns of al-rich hydrotalcite precursors showed the presence of crystalline phases of brucite and gibbsite. it was shown that chemical composition, texture, acid-base properties of the active sites and also mg/al ratio strongly affect the formation of the products in the oxidation of isopropanol. the al-rich catalysts were much more active than the mg-rich ones, converting isopropanol mainly to propylene.
Vanadium oxides supported on hydrotalcite-type precursors: the effect of acid-base properties on the oxidation of isopropanol
Meira, D. M.;Cortez, G. G.;Monteiro, W. R.;Rodrigues, J. A. J.;
Brazilian Journal of Chemical Engineering , 2006, DOI: 10.1590/S0104-66322006000300008
Abstract: vanadium oxide supported on hydrotalcite-type precursors was studied in the oxidation of isopropanol. hydrotalcites with different y = mg/al ratios were synthesized by the method of coprecipitation nitrates of mg and al cations with k2co3 as precipitant. the decomposition of these hydrotalcite precursors at 450°c yielded homogeneous mgyalox mixed oxides that contain the al+3 cations totally incorporated into the mgo framework. the materials were characterized by chemical analysis, bet superficial area, x-ray diffraction, temperature-programmed reduction (tpr) and the reaction of isopropanol, a probe molecule used to evaluate the acid-base properties. the results of tpr showed that the reducibility of v+5 decreased with the increase in magnesium loading in catalysts. the x-ray diffraction patterns of al-rich hydrotalcite precursors showed the presence of crystalline phases of brucite and gibbsite. it was shown that chemical composition, texture, acid-base properties of the active sites and also mg/al ratio strongly affect the formation of the products in the oxidation of isopropanol. the al-rich catalysts were much more active than the mg-rich ones, converting isopropanol mainly to propylene.
Purification of the Drosophila melanogaster Proteins Inscuteable and Staufen Expressed in Escherichia coli  [PDF]
Xristo Zárate, Megan M. McEvoy, Teresa Vargas-Cortez, Jéssica J. Gómez-Lugo, Claudia J. Barahona, Elena Cantú- Cárdenas, Alberto Gómez -Trevi?o
Advances in Bioscience and Biotechnology (ABB) , 2015, DOI: 10.4236/abb.2015.67050
Abstract: The proteins Inscuteable and Staufen are key components during asymmetric cell division of neuroblasts for the development of Drosophila melanogaster. Expression and purification of both proteins has been a difficult task for structure-function studies. Based on codon optimization for protein expression in Escherichia coli, we have been able to produce, in soluble form, the C-terminal domains of Inscuteable and Staufen as chimeras with N-terminal maltose binding protein tag that contains a rigid linker between them for feasible crystallization. In addition, using an optimized synthetic gene, corresponding to the amino acid region 250 - 623 of Inscuteable fused to glutathione-S-transferase, low-scale expression experiments showed production of soluble protein. Finally, eukaryotic expression of Inscuteable in the methylothropic yeast Pichia pastoris failed to produce the Drosophila protein at detectable amounts, reinforcing the fact that E. coli still was the microorganism of choice for high-yield protein expression.
Sazonalidade na produ??o de raízes e teor de β-ecdisona em acessos de fáfia
Corrêa Júnior, Cirino;Ming, Lin Chau;Cortez, Diógenes Aparício G;
Horticultura Brasileira , 2008, DOI: 10.1590/S0102-05362008000300020
Abstract: roots of pfaffia sp. are used in the brazilian popular medicine, especially for their tonic, aphrodisiac, and anti-diabetic properties. sides and islands of the paraná river are the natural habitat of p. glomerata (spreng.) pedersen, a species threatened due to intensive harvests. therefore, its preservation demands the development of sustainable exploitation systems. in this framework, the seasonal variation of root biomass production and β-ecdisone contents were evaluated, using different pfaffia glomerata accessions. accessions were collected along the rivers paraná (a1 and a3), ivaí (a2), and paranapanema (a4). plantlets obtained out of these accessions were transplanted to its natural habitat, in a complete random blocks experimental design, with split-plots (accessions in the plots; harvests in the split-plots), and four six-plant replications. four root harvests took place: at the eighth (may), tenth (july), twelfth (october), and fourteenth (december) month after planting. the highest root yield, assessed as dry mass, was found in the third harvest, 38.41 g plant-1. accession a4 significantly outyielded the others, both in root fresh (94.67 g plant-1) and dry mass (26.39 g plant-1) yield. the ratio root fresh:dry mass, with an average of 26.91% (3.7:1), suffered little influence of accession origin. however, it was significantly altered along harvests (from 4.1:1, in the first harvest, to 3.3:1, in the third harvest, where it reached its peak). β-ecdisone content in roots was similar in the first three harvests, ranging from 0.26 to 0.38%, but with a sharp drop in the last harvest (0.16%). accessions a2 and a3 had the highest β-ecdisone contents in roots, respectively 0.36 and 0.30%. taking into account the results obtained in this work, we suggest the third harvest, twelve months after planting, as the most adequate for harvesting pfaffia roots.
Métodos de análise organica do café. I. Compara??o entre métodos de determina??o do ácido clorogênico
Amorim, H. V.;Guercio, M. A.;Cortez, J. G.;Malavolta, E.;
Anais da Escola Superior de Agricultura Luiz de Queiroz , 1973, DOI: 10.1590/S0071-12761973000100021
Abstract: three methods of total chlorogenic acid determination in green coffee were studied. six coffee samples, three soft (best) and three rio (worst) were used. the method of moores et al. (1948), weiss (1957) and gnagy (1961, 1962) adapted by amorim (1972) gave no statistic difference when rio coffees were used, however, the method of moores et al. (1948) and weiss (1957) gave lower values than the gnagy - amorim procedure, for the solft coffees. no statistical difference was found between moores and weiss methods. it was infered that the higher enzymatic activities of polyphenol oxidase found in the best coffees (solft), oxidize the chlorogenic acids in the extraction procedure of the moores and weiss methods, leading to the lower chlorogenic acid values observed.
Morphology and anatomy of a leaf mine in Vismia guianensis (Aubl.) Choisy (Clusiaceae) in a fragment of Brazilian Atlantic forest
Almeida-Cortez, J. S.;Melo-de-Pinna, G. F. A.;
Brazilian Journal of Biology , 2006, DOI: 10.1590/S1519-69842006000400021
Abstract: mines or hyponomes are channels caused by larva miners consuming internal plant tissues. these miners live on the leaf and feed from these tissues. leaf mines are usually visible on the exterior of the leaf as serpentine paths, blotches, or other characteristic shapes of discolored tissues. morphological and structural modifications undergone by mined leaves of vismia guianensis (aubl.) choisy are presented here with the purpose of elucidating their structure and to contribute to studies about insect-plant interactions. healthy and mined leaves were harvested from thirty plants and taken to the laboratory. for each branch, the total number of young and mature leaves, the number of leaves with mines and the number of mine per leaf were counted. transverse sections of healthy and mined leaves were obtained to observe the morpho-anatomic aspects. from the 1,438 mature leaves and 379 young leaves analyzed, 214 (14.9%) and 70 (18.5%) were mined, where most of the leaves (67%) presented one mine per leaf. transverse sections of the mine revealed that the larva consumed only mesophyll parenchyma tissue and the epidermis remains intact. there is not a pattern of leaf mining, but the larvae did not consume the druses observed on mesophyll and the vascular tissues of the mid-vein and lateral vein.
ESTUDO TEóRICO DO RESFRIAMENTO COM AR FOR?ADO DE FRUTAS DE GEOMETRIAS DIFERENTES
TERUEL, Bárbara;CORTEZ, Luís A.;LEAL, Paulo;LIMA, Antonio G. B.;
Ciência e Tecnologia de Alimentos , 2001, DOI: 10.1590/S0101-20612001000200019
Abstract: this paper presents a numerical study for obtaining cooling curves of orange valência (citrus sinensis o.) and banana prata (mussa balbisiana colla), in different positions along the bed and conditioned in package with 40% of effective opening area. the fruits were pre-cooled in a forced-air system (1.933m3/h), at 1°c and 7°c, rh= 88,4 ± 2,0% and air velocity around 1m/s. a two-dimensional mathematical model was applied, assuming prolate spheroid coordinate, to characterize the transient heat transfer process inside the fruits considering convective profile conditions at the surface of the body. the generated equations were numerically solved by finite-volume method. the convective heat transfer coefficients were obtained using the least square method by comparison between experimental and numerical data. the comparative analysis of the theoretical and experimental curves presented a satisfactory agreement, with error between 5% and 7%. it was noted that the convective heat transfer coefficient changes with the fruits position in the bed and cooling time present a variation of approximately 38% among the different points. the spatial distributions of temperature inside the fruits, for three times, demonstrate the existence of a temperature differential between the center and the surface of 30%, approximately. the model predicts that the cooling rate is in the extremes of the banana. the bi and fo numbers obtained represent very well the heat transfer process in the fruits under different relationships of volume/area.
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