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  • Author or Editor: M. Pereira x
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Abstract  

The knowledge of the composition of atmospheric aerosols in remote areas, like the Antarctic Peninsula is of great importance for the study of long-range transport of atmospheric contaminants and also from the climatological point of view. Instrumental neutron activation analysis was applied in the present work to determine the elements Al, V, Mn, Na, Cl, Ca, Au, Br, Sb, Sc, Fe, Zn, K, Th and La in aerosol samples collected in the Brazilian Antarctic Station Comandante Ferraz (62° S, 58° W) located on King George Island in the Antarctic Peninsula. The sources of the aerosols were investigated by means of Enrichment Factors and Principal Factor Analysis. Both methods yielded similar results. Sea and soil were identified as the major sources of aerosols, in the samples collected at the Brazilian Station.

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Abstract  

A radiochemical neutron activation analysis procedure is described for the determination of concentration levels of iridium in sedimentary rocks and in the geochemical standard PCC-1. After irradiation, the powdered rock samples and standard are dissolved with a mixture of HF, HNO3 and HClO4 in a teflon bomb. The final solution obtained, in dilute HCl, is passed through a column containing the cationic resin Bio Rad AG 50W-X8. The interfening radionuclides are sorbed by the resin. The effluent solution containing iridium is concentrated for counting by evaporation. Experiments with radioactive tracer for checking radiochemical separation yield are carried out. The accuracy of the method is evaluated by means of analysis of the USGS standard rock peridotite, PCC-1. The precision is about 25% in the ppb range. The method is used for the determination of iridium in 16 samples of sedimentary rocks collected at different depths in the Campos basin-RJ (BRAZIL).

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Abstract  

The thermal decomposition of asphaltenes is mainly responsible for the formation of coke in petroleum processing. Phenomena involved are not clearly understood, because of the difficulties to characterize such heavy components. This paper reports the application of thermal analysis techniques to study the thermal behavior of asphaltenes from Brazilian oil. The approach involves kinetic studies of the thermal decomposition of asphaltenes under controlled conditions by thermogravimetry (TG), characterization of volatile fractions by thermogravimetry and differential thermal analysis coupled with gas chromatography/mass spectrometry (TG-DTA/GC/MS) and by gas chromatography/mass spectrometry (GC/MS) in the volatile recovered. The coke formed was also studied after being decomposed into smaller molecules using selective oxidation.

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Calorimetric methods are becoming important analytical tools in several areas of biochemical and biological research. In this work, a flow microcalorimetric method has been applied to the determination of dihydrofolate reductase (DHFR) activities in rat and human malignant tissue homogenates. In contrast to other commonly used DHFR analytical assays, the sensitivity of flow microcalorimetry allows direct measurements of this enzyme in crude tissue preparations. Our experimental data from rat tissue homogenates show that liver has the highest level of enzyme activity, while lung and brain have lower amounts of DHFR activity. The liver enzyme has a higher activity atpH 4.5, but the optimumpH for the lung and brain enzymes is 6.8. The substrate/cofactor molar ratio which gives the highest levels of DHFR activity is 1/1.5 for the liver and lung enzymes and 1/2.5 for brain DHFR. The DHFR in these rat tissue homogenates is activated by KCl or NaCl: in the presence of these salts (0.6M), the values of enzyme activity are 1.5–3 times higher than in their absence. Using flow microcalorimetry, very low levels of DHFR activity were also measured in human bone tumour homogenates, demonstrating the potential of the technique in the analysis of this enzyme in malignant tissues.

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With a view to increasing the industrial use of bovine blood globin, the extraction of the globin fraction was achieved using the acidified acetone method. Spectrophotometric analysis of the globin and the extracted heme group was performed utilizing the Soret band. The influence of the type of final processing of the globins (freeze drying, gel) on the solubility, the emulsification capacity, the emulsifying activity index and the stability of the emulsion was studied at pH 5, 6 and 7. No behavioural differences between freeze-dried and gel globin forms were observed. The best performance for most of the functional properties was achieved at pH 5.0 for the globin obtained by this method.

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In 2005, a severe drought occurred in Portugal, with several reservoirs becoming dry in the southern region. A set of 20 Portuguese water bodies were analysed through denaturing gradient gel electrophoresis (16SrDNA-DGGE) and DNA sequencing to assess its bacterioplankton diversity under these particular conditions. Environmental parameters were determined to assess the trophic conditions of each water body. Most water bodies fell into the meso-to eutrophic and hypereutrophic state. In general, the levels for conductivity, pH and total suspended solids were higher than the average data from previous years. Dominant phylotypes belonged to Cyanobacteria, Actinobacteria Alphaproteobacteria, Betaproteobacteria and Bacteroidetes groups. Despite the geographic distance, common phylotypes could be recorded among water bodies. Bacteroidetes dominated at Sousa River and were related to high nutrient levels. Cyanobacteria dominated at Alentejo reservoirs and correlated with higher conductivity values. However, Actinobacteria showed ubiquitous phylotypes throughout several samples, suggesting its persistence over geographically distant water bodies. This study showed a clear deterioration of water quality, from a physico-chemical point of view; furthermore, dominance of Cyanobacteria and Actinobacteria in reservoirs used for drinking water supply were also detected, which may become a concerning issue. However, the most severe bacterial community composition variations between summer 2005 and others were mainly related to higher water residence times. Thus, along with the expected intensification of drought episodes, with severe effects particularly in Southern Europe, it is clearly predictable an intensification in risks for water quality maintenance and even Public Health.

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Abstract  

In order to assess the elemental concentration level in a galvanizing industry and alert for the need to assess the outcome of a long-term exposure, scalp hair and toenail samples were used as bioindicators and the industry environment was evaluated through airborne particulate matter. The elemental concentration results have pointed out a high exposure to pollutant at workplaces and a high elemental concentration in biomonitors suggesting endogenous contamination. The majority of the elements determined in airborne particulate matter were also determined in hair and toenail samples. The results evidence the efficiency of these matrixes as biomonitors and the importance to carry out the airborne particulate matter sampling in parallel to these biomonitors mainly in occupational epidemiological studies.

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Abstract  

The effects of processing time and concentration of cobalt acetylacetonate III complex in poly(ethylene terephthalate)/polycarbonate reactive blending were investigated. The blend was prepared in an internal mixer at 270C, 60 rpm, at different processing times (5–20 min) and catalyst concentration (0.00625–0.075 mass%). The reaction product was evaluated by differential scanning calorimetry (DSC), thermogravimetry (TG) and wide angle X-rays scattering (WAXS). In general, the DSC curves showed two glass transition temperatures (T g’s) close to each homopolymer, independent of the processing time and complex’s concentration, suggesting the presence of two phases: one rich in PET and other one rich in PC. In all cases, melting temperature (T m), cold crystallization temperature (T cc) and crystallinity degree (X c) were progressively reduced with blending conditions. The TG curves presented two decays. The first one represented the PET rich phase and the other one was related to the PC phase. The WAXS diffractograms showed that the Bragg’s angle and interplanar spacing of PET remaining practically unchanged.

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Abstract  

The increased pollution in the aquatic ecosystem has led to the investigation of toxic elements in sea water by using marine organisms to assess marine pollution from human activities. Among these organisms, the mollusks bivalves have been used as biomonitors since they can accumulate trace elements and other substances, without the occurrence of their death. In this study, Perna perna mussels were transplanted from a mussel farm (reference region) to four sites located in coastal regions of São Paulo State, Brazil, close to anthropic discharge areas. Vanadium was determined in mussel tissues by instrumental neutron activation analysis (INAA). Quality control of V analysis was checked by analyzing biological reference materials and the results obtained were precise and in good agreement with the certified values. Comparisons between the V concentrations obtained in transplanted mussels indicated that those from São Sebastião region, close to an oil terminal presented the highest concentration of this element, during spring.

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