951 resultados para Cobalt Radioisotopes
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Were synthesized spinel-type ferrites with general formula Ni0,8Mg0.2-xMxFe2O4, where M represents the doping Mn, Co or Mn + Co simultaneously, x ranges for the values 0.02, 0.05 and 0.1. The value of x was divided by 2 in cases where M equals Mn and Co conjugates. We used the citrate precursor method and heat treatment to obtain the phases at 1100°C. The materials were characterized by XRD, TGA/ DTGA, SEM, MAV and reflectivity measurements by the method of waveguide. Powders to 350°C/3.5 h were crystalline and nanosized. According to the results this temperature all powders have a percentage of ferrite phase over 90%. The composition had the addition of Mn and Co simultaneously showed a higher percentage of secondary phase NiO, 5.8%. The TGA/DTGA curves indicate that this sample reached phase (s) crystalline (s) at lowest temperatures. The X-ray diffractograms of the samples calcined at 350°C and 1100°C were treated with the Rietveld refinament technique. The powders calcined at 1100 °C/3h in air show to be 100% except spinel phase composition with 0.02 doping. The micrographs show clusters of particles with sizes smaller than 1 μm in calcination temperature of 1100°C which agreed with the result of Rietveld refinement. In the compositions doped with Mn were higher values of magnetization (45.90 and 53.20 Am2/kg), which did not cause high microwave absorption. The theoretical calculation of magnetization (MT) was consistent with the results, considering that there was agreement between the increase of magnetization experimental and theoretical. It was observed that there was the interrelation of the final effect of absorption with the thickness of MARE, the composition of ferrimagnetic materials and in particular the specific values of frequency. The analysis shows that the reflectivity increases in the concentration of cobalt increased the frequency range and also for absorption 10.17 GHz and 84%, respectively. The best result of chemical homogeneity and the value of 2.96 x 10-2 tesla coercive field were crucial for high performance ferrite absorber with 0.1 cobalt. The Cobalt has high magnetocrystalline anisotropy, it is associated with an increased coercive field, Hc. Therefore, this property improves the results of reflectivity of spinel ferrites
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Metal Organic Frameworks (MOFs) are supramolecular structures consisted of ions or metal clusters coordinated to organic ligands which are repeated in two or three dimensions. These structures have atracted much attention due to their properties such as low density, high specific surface area and large volume of pores. In this work, MOFs consisted of zinc clusters connected by ditopic ligands, terephthalic acid (1,4- H2BDC) or isophthalic acid (1,3-H2BDC) were synthesized. To obtain the proposed materials, different routes and synthetic parameters were tested, such as the molar ratio of the precursors, the addition of template molecules, the type of solvente, the addition of organic base or the type of a counter-ion of Zn salt. It was found that the variation of these parameters led to the formation of different metalorganic structures. The solids obtained were characterized by XRD, SEM and IR. For the samples identified as MOF- 5, it was verified that the structure was composed of both interpenetrated and non interpenetrated structures. These samples showed a low stability, becoming totally transformed into another structure within less than 72 hours. The addition of the nickel and/or cobalt was found to be a promissing method for increasing the stability of MOF- 5, which in this case, still remained unconverted to another structure even after 15 days of exposure to air. The samples prepared from 1,3-H2BDC were probably new, still unknown Metal Organic Frameworks
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In this work, the structures of LaCoO3, La0,8Ba0,2CoO3 and La0,8Ca0,2CoO3 perovskites were characterized as a function of temperature (LaCoO3 structure being analyzed only at room temperature). The characterization of these materials were made by X-Ray Absorption Spectroscopy (XAS), in the cobalt K-edge, taking into account the correlated Einstein model X-ray absorption fine structure (EXAFS). The first part of the absorption spectrum corresponded the X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). These materials were prepared by the combustion method. The combustion products were calcinated at 900 0C, for 6 hours in air. Noted that the sample LaCoO3 at room temperature and samples doped with Calcium and Barium in the temperature range of 50 K to 298 K showed greater distortion to monoclinic symmetry with space group I2/a. However, the sample doped with barium at the temperatures 50 K, 220 K, and 260 K showed a slight distortion to rhombohedral symmetry with space group R-3c. The La0,8Ca0, 2CoO3 structure was few sensitive to temperature variation, showing a higher local distortion in the octahedron and a higher local thermal disorder. These interpretations were in agreement with the information electronic structural on the XANES region and geometric in the EXAFS region
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This study aimed to analyze the phytoremediation potential of Eichhornia crassipes in natural environments, optimize the extraction process of crude protein from plant tissue and, obtain and characterize this process in order to determine its viability of use instead of the protein sources of animal and/or human feed. For this, it has been determined in Apodi/Mossoró river water the concentration of ammonium ions, nitrite, nitrate, calcium, magnesium, potassium, iron, copper, manganese, zinc, nickel, cobalt, sodium, aluminum, cádmium, lead, and total chromium; It was determined in plant tissue of aquatic macrophytes of Eichhornia crassipes species present in Apodi/Mossoró River the moisture content, ash, calcium, magnesium, potassium, iron, copper, manganese, zinc, nickel, cobalt, sodium, aluminum, cadmium, lead, total chromium, total nitrogen and crude protein. It was also determined the translocation factor and bioaccumulation of all the quantified elements; It was developed and optimized the extraction procedure of crude protein based on the isoelectric method and a factorial design 24 with repetition; It was extracted and characterized the extract obtained by determining the moisture content, ash, magnesium, potassium, iron, copper, manganese, zinc, nickel, cobalt, sodium, cadmium, total nitrogen and crude protein. And finally, it was also characterized the protein extract using Thermogravimetric Analysis (TG), Derived Thermogravimetric (DTG), Differential Scanning Calorimetry (DSC), Infrared Spectroscopy (FT-IR) and jelly-like electrophoresis of polyacrylamide (SDS -PAGE) to assess the their molecular weights/mass. Thus, from the results obtained for the translocation and bioaccumulation factors was found that the same can be used as phytoremediation agent in natural environments of all quantified elements. It was also found that the developed method of extraction and protein precipitation was satisfactory for the purpose of the work, which gave the best conditions of extraction and precipitation of proteins as: pH extraction equal to 13.0, extraction temperature equals 60 ° C, reaction time equals to 30 minutes, and pH precipitation equals to 4.0. As for the extract obtained, the total nitrogen and crude protein were quantified higher than those found in the plant, increasing the crude protein content approximately 116.88% in relation to the quantified contente in the vegetal tissue of macrophyte. The levels of nickel and cadmium were the unique that were found below the detection limit of used the equipment. The electrophoretic analysis allowed us to observe that the protein extract obtained is composed of low polypeptide chains by the molecular and phytochelatins, with 6 and 15 kDa bands. Analysis of TG, DTG, DSC and FT-IR showed similarities in protein content of the obtained extracts based on different collection points and 9 parts of the plant under study, as well as commercial soy protein and casein. Finally, based on all these findings, it was concluded that the obtained extract in this work can be used instead of the protein sources of animal feed should, before that, test its digestibility. As human supplementation, it is necessary to conduct more tests associated with the optimization process in the sense of removing undesirable components and constant monitoring of the water body and the raw material used
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The production of oil and gas is usually accompanied by the production of water, also known as produced water. Studies were conducted in platforms that discharge produced water in the Atlantic Ocean due to oil and gas production by Petrobras from 1996 to 2006 in the following basins: Santos (Brazilian south region), Campos (Brazilian southeast region) and Ceara (Brazilian northeast region). This study encompasses chemical composition, toxicological effects, discharge volumes, and produced water behavior after releasing in the ocean, including dispersion plumes modeling and monitoring data of the marine environment. The concentration medians for a sampling of 50 samples were: ammonia (70 mg L-1), boron (1.3 mg L1), iron (7.4 mg L-1), BTEX (4.6 mg L-1), PAH (0.53 mg L-1), TPH (28 mg L-1); phenols (1.3 mg L-1) and radioisotopes (0.15 Bq L-1 for 226Ra and 0.09 Bq L-1 for 228Ra). The concentrations of the organic and inorganic parameters observed for the Brazilian platforms were similar to the international reference data for the produced water in the North Sea and in other regions of the world. It was found significant differences in concentrations of the following parameters: BTEX (p<0.0001), phenols (p=0.0212), boron (p<0.0001), iron (p<0.0001) and toxicological response in sea urchin Lytechinus variegatus (p<0.0001) when considering two distinguished groups, platforms from southeast and northeast Region (PCR-1). Significant differences were not observed among the other parameters. In platforms with large gas production, the monoaromatic concentrations (BTEX from 15.8 to 21.6 mg L-1) and phenols (from 2 to 83 mg L-1) were higher than in oil plataforms (median concentrations of BTEX were 4.6 mg L-1 for n=53, and of phenols were 1.3 mg L-1 for n=46). It was also conducted a study about the influence of dispersion plumes of produced water in the vicinity of six platforms of oil and gas production (P-26, PPG-1, PCR-1, P-32, SS-06), and in a hypothetical critical scenario using the chemical characteristics of each effluent. Through this study, using CORMIX and CHEMMAP models for dispersion plumes simulation of the produced water discharges, it was possible to obtain the dilution dimension in the ocean after those discharges. The dispersion plumes of the produced water modelling in field vicinity showed dilutions of 700 to 900 times for the first 30-40 meters from the platform PCR-1 discharge point; 100 times for the platform P-32, with 30 meters of distance; 150 times for the platform P-26, with 40 meters of distance; 100 times for the platform PPG-1, with 130 meters of distance; 280 to 350 times for the platform SS-06, with 130 meters of distance, 100 times for the hypothetical critical scenario, with the 130 meters of distance. The dilutions continue in the far field, and with the results of the simulations, it was possible to verify that all the parameters presented concentrations bellow the maximum values established by Brazilian legislation for seawater (CONAMA 357/05 - Class 1), before the 500 meters distance of the discharge point. These results were in agreement with the field measurements. Although, in general results for the Brazilian produced water presented toxicological effects for marine organisms, it was verified that dilutions of 100 times were sufficient for not causing toxicological responses. Field monitoring data of the seawater around the Pargo, Pampo and PCR-1 platforms did not demonstrate toxicity in the seawater close to these platforms. The results of environmental monitoring in seawater and sediments proved that alterations were not detected for environmental quality in areas under direct influence of the oil production activities in the Campos and Ceara Basin, as according to results obtained in the dispersion plume modelling for the produced water discharge
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The production of oil and gas is usually accompanied by the production of water, also known as produced water. Studies were conducted in platforms that discharge produced water in the Atlantic Ocean due to oil and gas production by Petrobras from 1996 to 2006 in the following basins: Santos (Brazilian south region), Campos (Brazilian southeast region) and Ceara (Brazilian northeast region). This study encompasses chemical composition, toxicological effects, discharge volumes, and produced water behavior after releasing in the ocean, including dispersion plumes modeling and monitoring data of the marine environment. The concentration medians for a sampling of 50 samples were: ammonia (70 mg L-1), boron (1.3 mg L1), iron (7.4 mg L-1), BTEX (4.6 mg L-1), PAH (0.53 mg L-1), TPH (28 mg L-1); phenols (1.3 mg L-1) and radioisotopes (0.15 Bq L-1 for 226Ra and 0.09 Bq L-1 for 228Ra). The concentrations of the organic and inorganic parameters observed for the Brazilian platforms were similar to the international reference data for the produced water in the North Sea and in other regions of the world. It was found significant differences in concentrations of the following parameters: BTEX (p<0.0001), phenols (p=0.0212), boron (p<0.0001), iron (p<0.0001) and toxicological response in sea urchin Lytechinus variegatus (p<0.0001) when considering two distinguished groups, platforms from southeast and northeast Region (PCR-1). Significant differences were not observed among the other parameters. In platforms with large gas production, the monoaromatic concentrations (BTEX from 15.8 to 21.6 mg L-1) and phenols (from 2 to 83 mg L-1) were higher than in oil plataforms (median concentrations of BTEX were 4.6 mg L-1 for n=53, and of phenols were 1.3 mg L-1 for n=46). It was also conducted a study about the influence of dispersion plumes of produced water in the vicinity of six platforms of oil and gas production (P-26, PPG-1, PCR-1, P-32, SS-06), and in a hypothetical critical scenario using the chemical characteristics of each effluent. Through this study, using CORMIX and CHEMMAP models for dispersion plumes simulation of the produced water discharges, it was possible to obtain the dilution dimension in the ocean after those discharges. The dispersion plumes of the produced water modelling in field vicinity showed dilutions of 700 to 900 times for the first 30-40 meters from the platform PCR-1 discharge point; 100 times for the platform P-32, with 30 meters of distance; 150 times for the platform P-26, with 40 meters of distance; 100 times for the platform PPG-1, with 130 meters of distance; 280 to 350 times for the platform SS-06, with 130 meters of distance, 100 times for the hypothetical critical scenario, with the 130 meters of distance. The dilutions continue in the far field, and with the results of the simulations, it was possible to verify that all the parameters presented concentrations bellow the maximum values established by Brazilian legislation for seawater (CONAMA 357/05 - Class 1), before the 500 meters distance of the discharge point. These results were in agreement with the field measurements. Although, in general results for the Brazilian produced water presented toxicological effects for marine organisms, it was verified that dilutions of 100 times were sufficient for not causing toxicological responses. Field monitoring data of the seawater around the Pargo, Pampo and PCR-1 platforms did not demonstrate toxicity in the seawater close to these platforms. The results of environmental monitoring in seawater and sediments proved that alterations were not detected for environmental quality in areas under direct influence of the oil production activities in the Campos and Ceara Basin, as according to results obtained in the dispersion plume modelling for the produced water discharge
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The aim of this study was to compare the misfit vertical, horizontal and passivity of zirconia and cobalt-chromium frameworks fabricated for CAD / CAM technology and conventional method of casting. Sixteen frameworks in one-piece, were obtained from a metallic matrix containing three Brånemark compatible implants with regular platform (Titamax Cortical Ti, Neodent). Eight frameworks were fabricated by CAD / CAM system (NeoShape, Neodent): four in zirconia (ZirCAD) and four cobalt-chromium (CoCrcad). Eight other frameworks were obtained by conventional casting method: four cobalt-chromium with UCLA abutment premachined Co-Cr (CoCrUCci) and four cobalt-chromium with UCLA abutment castable (CoCrUCc). The fit vertical, horizontal and passivity by one-screw test were measured using scanning electron microscopy with magnification of 250x. Initially evaluated the passivity by one-screw test and subsequently to assess the vertical and horizontal misfit, tightened all the screws with a torque of 20 Ncm. Mean, standard deviation, minimum and maximum values were calculated for each group. Measurements of horizontal misfit were transformed into cumulative frequency for categorization of the variable and the group later comparison groups. To evaluate the existence of quantitative differences between the groups tested for vertical misfit and passivity, we used the Kruskal-Wallis test. The Mann-Whitney test was used to compare group to group statistical differences (p <0.05). Were observed the respective mean and standard deviation for vertical misfit and passivity in micrometers: ZirCAD (5.9 ± 3.6, 107.2 ± 36), CoCrcad (1.2 ± 2.2, 107.5 ± 26 ), CoCrUCci (11.8 ± 9.8, 124.7 ± 74), CoCrUCc (12.9 ± 11.0, 108.8 ± 85). There were statistical differences in measures of vertical misfit (p = 0.000). The Mann-Whitney test revealed statistical differences (p <0.05) between all groups except between CoCrUCci and CoCrUCc (p = 0.619). No statistical difference was observed for the passivity. In relation to the horizontal misfit groups ZirCAD and CoCrcad did not show best values in relation to CoCrUCci and CoCrUCc. Based on the results it can be concluded that frameworks fabricated by CAD / CAM technology had better values of vertical fit than those manufactured by the casting method, nevertheless, the passivity was not influenced by manufacturing technique and material used. The horizontal fit obtained by frameworks manufactured by CAD / CAM was not superior to those manufactured by casting. A lower variability in vertical adjustment and passivity was observed when frameworks were fabricated by CAD / CAM technology
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The objective of this research was to evaluate the passivity and strain induced in infrastructures screwed on abutments, made by CAD/CAM technology, and to compare these samples with parts manufactured by conventional casting. Using CAD/CAM technology, 4 samples were made from zirconia (Zircad) and 4 samples were manufactured from cobaltchrome (CoCrcad). The control groups were 4 specimens of cobalt-chrome, made by onepiece casting (CoCrci), for a total of 12 infrastructures. To evaluate the passivity, the infraestructures were installed on the abutments. One end was tightened and the vertical gap between the infrastructure and the prosthetic abutment was measured with scanning electron microscopy (250×). The mean strain in these infrastructures was analyzed via the photoelasticity test. A significant difference (p = 0.000) in passivity was observed between the control (CoCrci) and sample groups (CoCrcad and CoCrci). CoCrcad exhibited the best value of passivity (48.76 ± 13.45 μm) and CoCrci the worst (187.55 ± 103.63 μm), Zircad presented an intermediate value (103.81 ± 43.15 μm). When compared to the other groups, CoCrci showed the highest mean strain around the implants (17.19 ± 7.22 kPa). It was concluded that the zirconia infrastructure made by CAD / CAM showed a higher vertical marginal misfit than those made in cobalt-chromium alloy with the same methodology, however, the tension generated in the implants was similar. The CAD/CAM technology is more accurate for passivity and mean strain of infrastructure screwed on abutments than conventional manufacturing techniques
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Ceramic powders based on oxides of perovskite-type structure is of fundamental interest nowadays, since they have important ionic-electronic conductivity in the use of materials with technological applications such as gas sensors, oxygen permeation membranes, catalysts and electrolytes for solid oxide fuel cells (SOFC). The main objective of the project is to develop nanostructured ceramic compounds quaternary-based oxide Barium (Br), Strontium (Sr), Cobalt (Co) and Iron (Fe). In this project were synthesized compounds BaxSr(1-x)Co0, 8Fe0,2O3- (x = 0.2, 0.5 and 0.8) through the oxalate co-precipitation method. The synthesized powders were characterized by thermogravimetric analysis and differential thermal analysis (TGADTA), X-ray diffraction (XRD) with the Rietveld refinement using the software MAUD and scanning electron microscopy (SEM). The results showed that the synthesis technique used was suitable for production of nanostructured ceramic solid solutions. The powders obtained had a crystalline phase with perovskite-type structure. The TGA-DTA results showed that the homogeneous phase of interest was obtained temperature above 1034°C. It was also observed that the heating rate of the calcination process did not affect the elimination of impurities present in the ceramic powder. The variation in the addition of barium dopant promoted changes in the average crystallite size in the nanometer range, the composition being BSCF(5582) obtained the lowest value (179.0nm). The results obtained by oxalate co-precipitation method were compared with those synthesis methods in solid state and EDTA-citrate method
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This pilot study uses concentrations of metals in maternal and cord blood at delivery, in seven selected geographical areas of South Africa, to determine prenatal environmental exposure to toxic metals. Samples of maternal and cord whole blood were analysed for levels of cadmium, mercury, lead, manganese, cobalt, copper, zinc, arsenic and selenium. Levels of some measured metals differed by site, indicating different environmental pollution levels in the regions selected for the study. Mercury levels were elevated in two coastal populations studied (Atlantic and Indian Ocean sites) with mothers from the Atlantic site having the highest median concentration of 1.78 mu g/L ranging from 0.44 to 8.82 mu g/L, which was found to be highly significant (p < 0.001) when compared to other sites, except the Indian Ocean site. The highest concentration of cadmium was measured in maternal blood from the Atlantic site with a median value of 0.25 mu g/L (range 0.05-0.89 mu g/L), and statistical significance of p < 0.032, when compared to all other sites studied, and p < 0.001 and p < 0.004 when compared to rural and industrial sites respectively, confounding factor for elevated cadmium levels was found to be cigarette smoking. Levels of lead were highest in the urban site, with a median value of 32.9 mu g/L (range 16-81.5 mu g/L), and statistically significant when compared with other sites (p < 0.003). Levels of selenium were highest in the Atlantic site reaching statistical significance (p < 0.001). All analysed metals were detected in umbilical cord blood samples and differed between sites, with mercury being highest in the Atlantic site (p < 0.001), lead being highest in the urban site (p < 0.004) and selenium in the Atlantic site (p < 0.001). To the best of our knowledge this pilot investigation is the first study performed in South Africa that measured multiple metals in delivering mothers and umbilical cord blood samples. These results will inform the selection of the geographical sites requiring further investigation in the main study.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Natural (NV) and Cobalto60-irradiated (IrV) Crotalus durissus terrificus venom were used to evaluate serum production capacity of sheep and possible hematological and biochemical effects. Freeze-dried venom aliquots were diluted in acidified saline solution (NaCl 150 mM, pH 3.0) and irradiated by a Cobalt 60 source at a dose of 5.54 x 102 Gy/h and a concentration of 2.000 Gy. Twelve sheep were divided into two groups of six animals. One group received irradiated venom (IrV) and the other natural venom (NV). Three antigen doses (venom) were administered at monthly intervals. Blood samples were collected weekly for analysis of serum neutralization potency and capacity, complete blood count (CBC), total plasma protein, fibrinogen, albumin, and globulin. At the end of the experiment, the animals were challenged with a LD50 for sheep and showed no signs of envenoming. The two groups did not present clinical alterations. Results of the total leukocyte count did not present interaction or time factor effect for both groups, but there was a different action between them, with the NV group presenting more cells than the IrV group. The leukocyte increase to 13,000/ml indicates that slight leukocytosis occurred in the week after the first inoculation in the NV group. There was no statistically significant difference between groups in the absolute count of segmented neutrophils, eosinophils, and lymphocytes but there were statistically significant oscillations in values at the different collecting times. The NV group presented an increase in the absolute neutrophil count after the first inoculation that persisted for 5 weeks. In the IrV group, the increase in neutrophils occurred only in the first week returning to normal in the following weeks. The alterations in the neutrophil count are indicative of systemic inflammatory response related to cytokine release; response was more marked in the NV group, showing its greater toxicity.
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Purpose: This study compared the maintenance of tightening torque in different retention screw types of implant-supported crowns.Materials and Methods: Twelve metallic crowns in UCLA abutments cast with cobalt-chromium alloy were attached to external hexagon osseointegrated implants with different retention screws: group A: titanium alloy retention screw; group B: gold alloy retention screw with gold coating; group C: titanium alloy retention screw with diamond-like carbon film coating; and group D: titanium alloy retention screw with aluminum titanium nitride coating. Three detorque measurements were obtained after torque insertion in each replica. Data were evaluated by analysis of variance (ANOVA), Tukey's test (P < 0.05), and t test (P < 0.05).Results: Detorque value reduced in all groups (P < 0.05). Group A retained the highest percentage of torque in comparison with the other groups (P < 0.05). Groups B and D retained the lowest percentage of torque without statistically significant difference between them (P < 0.05).Conclusions: All screw types exhibited reduction in the detorque value. The titanium screw maintained the highest percentage of torque whereas the gold-coated screw and the titanium screw with aluminum titanium nitride coating retained the lowest percentage. (Implant Dent 2012;21:46-50)
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Purpose: The aim of this study was to evaluate the effect of mechanical cycling and different misfit levels on Vicker's microhardness of retention screws for single implant-supported prostheses.Materials and Methods: Premachined UCLA abutments were cast with cobalt-chromium alloy to obtain 48 crowns divided into four groups (n = 12). The crowns presented no misfit in group A (control group) and unilateral misfits of 50 mu m, 100 mu m, and 200 mu m in groups B, C, and D, respectively. The crowns were screwed to external hexagon implants with titanium retention screws (torque of 30 N/cm), and the sets were submitted to three different periods of mechanical cycling: 2 x 10(4), 5 x 10(4), and 1 x 10(6) cycles. Screw microhardness values were measured before and after each cycling period. Data were evaluated by two-way ANOVA and Tukey's test (p < 0.05).Results: Mechanical cycling statistically reduced microhardness values of retention screws regardless of cycling periods and groups. In groups A, B, and C, initial microhardness values were statistically different from final microhardness values (p < 0.05). There was no statistically significant difference for initial screw microhardness values (p > 0.05) among the groups; however, when the groups were compared after mechanical cycling, a statistically significant difference was observed between groups B and D (p < 0.05).Conclusions: Mechanical cycling reduced the Vicker's microhardness values of the retention screws of all groups. The crowns with the highest misfit level presented the highest Vicker's microhardness values.