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Search Results: 1 - 10 of 660061 matches for " CARVALHO A. G. V. "
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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, Estêv?o 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.
Effect of La doping on the structural, electrical, magnetic and morphological properties of the BSCCO system
V. D. Rodrigues,G. A. de Souza,R. G. de Lima,C. L. Carvalho,R. Zadorosny
Physics , 2013,
Abstract: Effect of La doping on the structural, electrical, magnetic and morphological properties of the BSCCO system
Field experimental evaluation of secondary metabolites from marine invertebrates as antifoulants
PEREIRA, R. C;CARVALHO, A. G. V.;GAMA, B. A. P.;COUTINHO, R.;
Brazilian Journal of Biology , 2002, DOI: 10.1590/S1519-69842002000200015
Abstract: the crude organic extracts of the endemic gorgonian phyllogorgia dilatata and two sponge species aplysina fulva and mycale microsigmatosa were evaluated for anti-fouling properties through field experiments. to investigate this property in ecologically meaningful conditions, crude extracts from these invertebrates were incorporated at concentrations naturally found in these marine organisms into a stable gel used as a substratum for fouling settlement. crude extract from a. fulva showed no significant anti-fouling property at the natural concentrations used in the field experiments. in fact, fouling organisms settled significantly more on gels treated with a. fulva extract than on the control gel. on the other hand, both m. microsigmatosa and p. dilatata yielded crude extracts that exhibited a selective action inhibiting only the settlement of barnacles. the evidences obtained here by means of field experiments can provide a basis for future development of one kind of natural antifoulant technology to prevent marine biofouling.
Field experimental evaluation of secondary metabolites from marine invertebrates as antifoulants
PEREIRA R. C,CARVALHO A. G. V.,GAMA B. A. P.,COUTINHO R.
Brazilian Journal of Biology , 2002,
Abstract: The crude organic extracts of the endemic gorgonian Phyllogorgia dilatata and two sponge species Aplysina fulva and Mycale microsigmatosa were evaluated for anti-fouling properties through field experiments. To investigate this property in ecologically meaningful conditions, crude extracts from these invertebrates were incorporated at concentrations naturally found in these marine organisms into a stable gel used as a substratum for fouling settlement. Crude extract from A. fulva showed no significant anti-fouling property at the natural concentrations used in the field experiments. In fact, fouling organisms settled significantly more on gels treated with A. fulva extract than on the control gel. On the other hand, both M. microsigmatosa and P. dilatata yielded crude extracts that exhibited a selective action inhibiting only the settlement of barnacles. The evidences obtained here by means of field experiments can provide a basis for future development of one kind of natural antifoulant technology to prevent marine biofouling.
Spin waves scattering on a Bloch point
R. G. Elías,V. L. Carvalho-Santos,A. S. Nú?ez,A. D. Verga
Physics , 2014, DOI: 10.1103/PhysRevB.90.224414
Abstract: We show that, after a transformation, the dynamics of linear perturbations (spin waves) around a singular Bloch point soliton is formally equivalent to a quantum system of an electron in a magnetic monopole field. The analytical solution to this problem is known and allows us to find the spectrum and the scattering of a wave in a Bloch point field.
Further studies on the synergistic effect of Ni(II) and Co(II) ions on the sulfite induced autoxidation of Cu(II) penta and hexaglycine complexes
Carvalho, Luciana B.;Alipázaga, María V.;Moreno, Rubén G. M.;Coichev, Nina;
Journal of the Brazilian Chemical Society , 2007, DOI: 10.1590/S0103-50532007000600021
Abstract: the autoxidation of cu(ii)/penta and hexaglycine complexes at ph = 9 is very slow showing a large induction period (about 4 h). the presence of s(iv) practically does not affect the rate of this reaction. addition of small amounts of ni(ii) or co(ii) increases significantly the reaction rate and the effectiveness of cu(iii) formation, the induction period becomes as short as 0.5 s. the observed rate constant for cu(iii) formation also depends on the s(iv) concentration. the mechanism is discussed based on the available literature information and involves a radical chain and redox cycling of the metal ion complexes.
ECF BLEACHING WITH A FINAL HYDROGEN PEROXIDE STAGE: IMPACT ON THE CHEMICAL COMPOSITION OF Eucalyptus globulus KRAFT PULPS
Pedro E. G. Loureiro,Eva F. Domingues,Dmitry V. Evtuguin,M. Gra?a Videira Sousa Carvalho
BioResources , 2010,
Abstract: Two industrial elemental chlorine free (ECF) bleaching sequences, D0(EOP)D1(EP)D2 and OQ(PO)DP, are compared with respect to the bulk content of lignin, carboxyl, hexeneuronic acids (HexA), and reducing groups after each bleaching stage. HexA groups contribute significantly to the total content of carboxyl groups, and their degradation during chlorine dioxide bleaching is reflected by a decrease of the carboxyl content. The higher degradation using an enhanced use of oxygen-based bleaching chemicals is associated with a higher fiber charge reduction, mainly due to xylan depletion. Additionally, the effect of process variables of a laboratory final hydrogen peroxide stage on the chemical composition of the fully bleached pulp (D0(EOP)D1P and OQ(PO)DP) is studied. The ability of final peroxide bleaching to raise the content of carboxyl groups is dependent on the operating conditions and pulp bleaching history. A balance between carbohydrate oxidation and dissolution of oxidized groups determines the effect on fiber charge. The effect of hydrogen peroxide stabilizers added into the final stage on the content of carboxyl groups is also reported.
Parasitismo e preda??o em ovos de Euschistus heros (Fab.) (Heteroptera: Pentatomidae) no Distrito Federal, Brasil
Medeiros, Maria A.;Schimidt, Francisco V.G.;Loiácono, Marta S.;Carvalho, Vinícius F.;Borges, Miguel;
Anais da Sociedade Entomológica do Brasil , 1997, DOI: 10.1590/S0301-80591997000200026
Abstract: the mortality of euschistus heros (f.) at the egg stage was studied at the field. the experiments were carried out in planaltina - d.f., brazil, in 1993 and 1994, on sunflower (helianthus annuus) cultivated following the soybean (glycine max) crop season. egg masses found in the field were marked and checked daily for four days, and taken to the laboratory to check the total number of eggs, eggs that failed to hatch and those parasitized or destroyed by predators. the incidence of parasitism in eggs of e. heros was high in 1993 (65%) and in 1994 (80%). five species of parasitoids were recovered: telenomus podisi ashmead, trissolcus basalis (wollaston), trissolcus teretis johnson, trissolcus urichi crawford (scelionidae) and eupelmus sp. (eupelmidae). t. podisi was the most frequent species. egg mortality due to predators was 17% in 1993 and 13% in 1994.
Spatio-temporal distribution and target species in a longline fishery off the southeastern coast of Brazil
Mourato, Bruno L.;Arfelli, Carlos A.;Amorim, Alberto F.;Hazin, Humberto G.;Carvalho, Felipe C.;Hazin, Fábio H. V.;
Brazilian Journal of Oceanography , 2011, DOI: 10.1590/S1679-87592011000200007
Abstract: in the present study, a cluster analysis, in relation to the species composition of the catches, was used to classify 6,486 fishing sets by a longline fleet based in s?o paulo state, brazil, from 1998 to 2006. based on the proportions of 12 species and three broader species groups, three clusters were identified: c1: other fishes; c2: blue shark; c3: swordfish. results indicated that the fleet targeted mainly blue shark and swordfish and also showed that the blue shark importance in this fishery has been growing progressively trough the years. offshore areas were exploited mainly in the first and fourth quarters (from 2001 mainly), while the fishing effort was more concentrated near the continental shelf break, during the second and third quarters (for the whole period). the longline fishery based in sao paulo state changed fishing strategy to target different species which produced important changes in catch-per-unit-effort (cpue) of the main species caught. cluster analysis seems to have appropriately identified these changes over time, which is an important information, often missing in logbooks.
Optimization of Extraction Conditions and Antioxidant Activity of Solanum lycocarpum Fruits
G.Z. Martins,A.N. dos Santos,M.V. Ribeiro Vilela,M. de Carvalho Ferreira
Journal of Applied Sciences , 2013,
Abstract: Antioxidants are substances that may protect cells from the damage caused by unstable molecules known as free radicals. The capacity of natural antioxidant from phytochemical has increase attention from researchers and public. However, the extraction process is affecting the activity and the bioavailability of bioactive compounds. The Solanum lycocarpum is a plant of the Brazilian cerrado, popularly used as a hypoglycemic, hypocholesterolemic and control of metabolic diseases. Its effects are attributed to the presence of several glycoalkaloids (solamargine, solasonina) and solasodine. Therefore, the purpose of this communication was, investigate the optimization of extraction condition and evaluation of antioxidant activity from fruits of Solanum lycocarpum. The extracts were obtained using different solvent systems, i.e., water, 50% ethanol, ethanol absolute and ethyl ether (1:10 and 1:20) and different extraction processes: maceration with constant agitation at room temperature, maceration with constant agitation and heating at 30C and ultrasound. The extracts were characterized by the amount of material extracted (1, 6 and 24 h) and the action of antioxidant activity by DPPH method. The results showed that the polar solvent (50% ethanol) and extractive process maceration with agitation to ambient temperature showed higher contents of extractable of fruits of S. lycocarpum (3.4 g %) and also showed higher antioxidant activity (88.572.41% de inhibition). This action whether the presence of glycoalkaloids (solamargine, solasonine and solasodine) in fruits S. lycocarpum which are polar compounds and may explain this increased antioxidant action of this extract.
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