Efeito da força iônica nas propriedades de fluidos de perfuração aquosos à base de polímeros carboxilados e sulfatados

In the well drilling operations problems caused by contamination of the drilling fluid are common. The dissolution of ions from the geological formations affects the rheological and filtration properties of the fluids. These ions shield the charges of ionic polymers, leading to its precipitation. In this work was performed a detailed study on the stability of the properties of aqueous solutions and aqueous drilling fluids in the presence of sulphated and carboxylated polymers, using carboxymethylcellulose and kappa-carrageenan as polymer compounds carboxylated and sulfated model, respectively. The effects of ionic strength of the aqueous medium containing Na+, Mg2+ and Ca2+ on rheological properties of the polymer and drilling fluids solutions were evaluated by varying the concentration of salts, pH and temperature. It was observed that the fluids with κ-carrageenan suffered less influence against the contamination by the ions at pH 9 to 10, even at higher concentrations, but higher influence on pH> 11. The fluids containing carboxymethylcellulose were more sensitive to contamination, with rapid reduction in viscosity and significant increase of the filtrate volume, while the fluid based polymer sulfated kappa-carrageenan showed evidence of interaction with cations and preserve the rheological properties and improved stability the volume of filtrate.

Ordenamento de cargas e propriedades magnéticas de ortoferritas de lantânio dopadas com estrôncio

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Ordenamento de cargas e propriedades magnéticas de ortoferritas de lantânio dopadas com estrôncio

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeito da adição de WC e Co na sinterização e propriedades mecânicas da alumina

Composites based on alumina (Al2O3), tungsten carbide (WC) and cobalt (Co) exhibit specific properties such as low density, high oxidation resistance, high melting point and high chemical inertia. That composite shows to be a promising material for application in various fields of engineering. In this work, the mechanical properties of the composite (Al2O3 – WC – Co), particularly density and hardness, were evaluated according to the effects of the variables of powder processing parameters, green compact and sintered. Powder composites with the composition of 80 wt% Al2O3, 18 wt% WC and 2 wt% Co were processed by high energy ball milling in a planetary mill for 50 hours as well as mixed by manual mixing in a glass vessel with the same proportion. Samples were collected (2, 10, 20, 30, 40 and 50 hours) during the milling process. Then, the powders were compacted in a cylindrical die with 5 mm in diameter in a uniaxial press with pressures of 200 and 400 MPa. The sintering was in two stages: first, the solid phase sintering was performed at 1126 and 1300 °C for 1 hour with a heating rate of 10 °C/min in a resistive furnace under argon atmosphere for green samples compacted in 200 and 400 MPa; the second sintering was performed on dilatometer in solid phase at 1300 °C for green sample compacted in 200 MPa, another sintering also was performed on dilatometer, this time in liquid phase at 1550 °C for green samples compacted in 200 and 400 MPa, with the same parameters used in resistive furnace. The raw materials were characterized by X – ray diffraction (XRD), X – ray fluorescence (XRF), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and laser particlemeter. The sintered samples were subjected to microhardness testing. The results showed that high energy milling achieved to the objectives regarding the particle size and the dispersion of composite phases. However, the hardness did not achieve to significant results, this is an indication that the composite has low fracture toughness.

Efeito da adição de WC e Co na sinterização e propriedades mecânicas da alumina

Composites based on alumina (Al2O3), tungsten carbide (WC) and cobalt (Co) exhibit specific properties such as low density, high oxidation resistance, high melting point and high chemical inertia. That composite shows to be a promising material for application in various fields of engineering. In this work, the mechanical properties of the composite (Al2O3 – WC – Co), particularly density and hardness, were evaluated according to the effects of the variables of powder processing parameters, green compact and sintered. Powder composites with the composition of 80 wt% Al2O3, 18 wt% WC and 2 wt% Co were processed by high energy ball milling in a planetary mill for 50 hours as well as mixed by manual mixing in a glass vessel with the same proportion. Samples were collected (2, 10, 20, 30, 40 and 50 hours) during the milling process. Then, the powders were compacted in a cylindrical die with 5 mm in diameter in a uniaxial press with pressures of 200 and 400 MPa. The sintering was in two stages: first, the solid phase sintering was performed at 1126 and 1300 °C for 1 hour with a heating rate of 10 °C/min in a resistive furnace under argon atmosphere for green samples compacted in 200 and 400 MPa; the second sintering was performed on dilatometer in solid phase at 1300 °C for green sample compacted in 200 MPa, another sintering also was performed on dilatometer, this time in liquid phase at 1550 °C for green samples compacted in 200 and 400 MPa, with the same parameters used in resistive furnace. The raw materials were characterized by X – ray diffraction (XRD), X – ray fluorescence (XRF), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and laser particlemeter. The sintered samples were subjected to microhardness testing. The results showed that high energy milling achieved to the objectives regarding the particle size and the dispersion of composite phases. However, the hardness did not achieve to significant results, this is an indication that the composite has low fracture toughness.

Caracterização estrutural e atividades farmacológicas do alginato obtido da alga Dictyopteris delicatula (J.V. Lamouroux., 1809) e seu derivado sulfatado

Marine algae are rich sources of various structural compounds which recently has been increasingly studied as a new source of bioactive substances. The alginate, as come as fucans, are considered the main acidic polysaccharides found in brown seaweed. This molecule consists a linear natural polysaccharide, non-sulfated, and presents monosaccharides: acid β-D-mannuronic (M) and α-L-guluronic acid (G); in a vast amount compositions and threads. Alginate has been widely applied in food and pharmaceutical industries because of its ability to retain water, forming films and gels as well as thickening, stabilizing and form emulsions. In this work we aimed to extract, structurally characterize, compare and analyze the possible pharmacological activities of native alginate molecule obtained from brown seaweed Dyctiopteris delicatula (DYN), and its chemically sulfated derivative (DYS). The alginate structure and composition molecule can be proven through chemical dosing, that showed low protein contamination and high sugar level, existence and separation of M and G blocks in the descending paper chromatography, infrared spectroscopy and nuclear magnetic resonance. Molecule sulfation was proven with sulphate dosage, resulting in 28.56% sulphate in molecule; electrophoresis, verify metachromasia with toluidine blue; and infrared spectroscopy, that showed a characteristic band at 1221cm-1 corresponding a sulfate group vibration. For the pharmacological activities the tests was: antioxidant activity, changes in cell function (MTT test) and anticoagulant test. In the antioxidant activity we observed that DYN showed better results in the kidnapping of hydroxyl radicals and ferric chelation compared to DYS, this had the best result in the total antioxidant capacity. Both showed similar activity in reducing power and the kidnapping radicals DPPH. In MTT test DYN and DYS had not proliferative and cytotoxic activity in fibroblast cells (3T3) and showed antiproliferative and cytotoxic activity in cancer cell lines HeLa and B16 melanoma. In anticoagulant assay DYN showed good activity in the intrinsic pathway of blood coagulation, and a small activity in the extrinsic pathway, in the other hand DYS showed only a very small activity in the extrinsic pathway, but cannot come to be regarded as an anticoagulant agent. From these results it can be concluded that the alginate was extracted and sulfated, revealing a potential compound to be used in the pharmaceutical industry as an anticoagulant agent, antioxidant and antitumor and the sulfation has not been conclusively important to performance in the tested pharmacological activities

Avaliação das atividades farmacológicas de fucoidans obtidos do extrato bruto de fucoidan comercial de Fucus vesiculosus

Fucoidan is a term used to define heteropolysaccharides that are composed of less than 90% L-fucose. The exception to this rule is the homofucoidan obtained from the seaweed Fucus vesiculosus. This fucoidan can be purchased from SIGMA Co. and have been used in various research for evaluation of their pharmacological activities. However, it is not a pure molecule. In fact, it is a mix of several fucoidan molecules. In this work, were obtained, from acetone precipitation, and biochemically characterized, four fucoidan molecules from SIGMA-ALDRICH Co. fucoidan to evaluate their anticoagulant, antioxidant, antiadipogenic, immunomodulatory and antiurolithiatic activities. In anticoagulant activity, evaluated by aPTT assay, fucoidans F0.9, F1.1 and F2.0 increased eightfold the coagulation time, compared to the control, when a mass of 10 μg was used. To PT test, only fucoidan F0.9 was capable of increase the coagulation time, compared to control. In the total antioxidant capacity assay (TAC), the fucoidan F2.0 showed 400 ascorbic acid equivalents, while fucoidan F0.5, the lest effective, 38 equivalents. In respect to the effect on pre-adipocyte cell lines (3T3-L1) adipogenesis, was observed that fucoidan F1.1 and F2.0 reduced the adipogenesis and this effect was associated to the reduction in the expression of regulatoy proteins C/EBPα, C/EBPβ and PPARγ. On the other hand, fucoidans F0.5 and F0.9 induced increased expression of these regulatory proteins. Furthermore, fucoidan F2.0 induced hydrolysis of triglycerides present in the interior of adipocytes. The immunomodulatory effect was evaluated and observed that the presence of fucoidans F0.5 , F1.1 and F2.0 significantly reduced the production of nitric oxide by activated macrophages with LPS specially fucoidan F2.0 that in 100 μg/mL, reduced about 55% the effect caused by LPS. Relative to the effect upon the formation of calcium oxalate crystals, fucoidan F0.5 was more effective in reduce the aggregation of the crystals and this effect it was not significantly different regarding the effect caused by the crude. Besides, fucoidan F0.5 only promoted the formation of COD type crystals, while fucoidans F1.1 and F2.0 did not influence the formation of crystals compared with the control. The results described in this study indicate that the commercial crude fucoidan of Fucus vesiculosus it’s a mix of several fucoidan which, in turn, have different chemical compositions besides having different pharmacological activities. The use of these fucoidans it´s indicated according the pharmacological activity to be evaluated.

Avaliação das atividades farmacológicas de fucoidans obtidos do extrato bruto de fucoidan comercial de Fucus vesiculosus

Fucoidan is a term used to define heteropolysaccharides that are composed of less than 90% L-fucose. The exception to this rule is the homofucoidan obtained from the seaweed Fucus vesiculosus. This fucoidan can be purchased from SIGMA Co. and have been used in various research for evaluation of their pharmacological activities. However, it is not a pure molecule. In fact, it is a mix of several fucoidan molecules. In this work, were obtained, from acetone precipitation, and biochemically characterized, four fucoidan molecules from SIGMA-ALDRICH Co. fucoidan to evaluate their anticoagulant, antioxidant, antiadipogenic, immunomodulatory and antiurolithiatic activities. In anticoagulant activity, evaluated by aPTT assay, fucoidans F0.9, F1.1 and F2.0 increased eightfold the coagulation time, compared to the control, when a mass of 10 μg was used. To PT test, only fucoidan F0.9 was capable of increase the coagulation time, compared to control. In the total antioxidant capacity assay (TAC), the fucoidan F2.0 showed 400 ascorbic acid equivalents, while fucoidan F0.5, the lest effective, 38 equivalents. In respect to the effect on pre-adipocyte cell lines (3T3-L1) adipogenesis, was observed that fucoidan F1.1 and F2.0 reduced the adipogenesis and this effect was associated to the reduction in the expression of regulatoy proteins C/EBPα, C/EBPβ and PPARγ. On the other hand, fucoidans F0.5 and F0.9 induced increased expression of these regulatory proteins. Furthermore, fucoidan F2.0 induced hydrolysis of triglycerides present in the interior of adipocytes. The immunomodulatory effect was evaluated and observed that the presence of fucoidans F0.5 , F1.1 and F2.0 significantly reduced the production of nitric oxide by activated macrophages with LPS specially fucoidan F2.0 that in 100 μg/mL, reduced about 55% the effect caused by LPS. Relative to the effect upon the formation of calcium oxalate crystals, fucoidan F0.5 was more effective in reduce the aggregation of the crystals and this effect it was not significantly different regarding the effect caused by the crude. Besides, fucoidan F0.5 only promoted the formation of COD type crystals, while fucoidans F1.1 and F2.0 did not influence the formation of crystals compared with the control. The results described in this study indicate that the commercial crude fucoidan of Fucus vesiculosus it’s a mix of several fucoidan which, in turn, have different chemical compositions besides having different pharmacological activities. The use of these fucoidans it´s indicated according the pharmacological activity to be evaluated.

Estudo teórico das propriedades eletrônicas e termodinâmicas de nanofitas quasiperiódicas BCN

Nanoscale materials composed of boron, nitrogen, and carbon have unique properties and may be useful in new technologies. In this thesis, we investigate some properties of BCN nanoribbons constructed according to the Fibonacci quasiperiodic sequence. We analyze properties such as structural stability, electronic density of states, electronic specific heat, band structure, and energy band gap. We have performed first-principles calculations based on density functional theory implemented in the SIESTA code. The results showed that nanoribbons present a fixed value of the formation energy. The electronic density of states was used to calculate the specific heat. We found an oscillatory behavior of the electronic specific heat, in the low temperature regime. We analyze the electronic band structure to determine the energy band gap. The energy band gap oscillates as a function of the Fibonacci generation index n. Our work suggest that appropriate choice of the building block materials of the quasiperiodic sequence, may lead to a tuneable band gap of the quasiperiodic nanoribbons.