The n-alkylcyclohexanes are poorly evaluated in biodegradation studies of Brazilian petroleum samples. In this context, this work aimed to use the homologue series of alkylcyclohexanes to assess extend of biodegradation of 26 petroleum samples from five Brazilian sedimentary basins, analyzed by gas chromatography coupled to mass spectrometry. The n-alkylcyclohexanes compounds were detected in all samples, with a distribution similar to the n-alkane profile, in which their abundance decreasing with increasing of the biodegradation extent. Based on this, it was suggested the use of the new parameter H30/DC together with the H30/AC already proposed, calculated by the ratio between C30 hopane to the dodecyl-cyclohexane, to assess biodegradation level according Peter and Moldowan scale (PM scale). In addition, it was observed an increasing in the relative abundance of DBE 2 from class O2, analyzed by ESI(-) FT-ICR MS, mainly due to the formation of monocyclic acids with biodegradation, which correlates with the decrease of n-alkylcyclohexanes, a possible precursor of these acids.

Reservoir geochemistry has been effectively used to evaluate compositional heterogeneity in petroleum reservoirs by employing oil fingerprinting technique to assess reservoir continuity, primarily in paraffin oil accumulations. In-reservoir biodegradation has resulted in vast deposits of heavy oils globally; therefore, the application of reservoir geochemistry to such accumulations becomes necessary. We recommend the use of pentacyclic terpanes instead of lower molecular compounds, which are less resistant to biodegradation. Using oil fingerprinting technique in this novel way enabled the differentiation of oil composition among sedimentary facies of tar sands (Pirambóia Formation, Paraná Basin).

Petroleum biodegradation in reservoirs is a process caused by different microorganisms affecting many oil deposits which modifies the oil composition in a quasi-stepwise process starting from n-alkanes and isoprenoids through to diasteranes. This causes oil souring and increased viscosity, sulfur and metal content, having a direct impact on oil production and refining costs.

Esta pesquisa foi conduzida para avaliar a qualidade nutricional das refeições consumida pelas crianças, pertencentes à faixa etária de 2 a 6 anos, matriculadas em creches municipais de Teresina. Os dados foram obtidos durante o período de outubro de 1997 a março de 1998, adotando-se o método da pesagem direta dos alimentos. Para o cálculo da adequação nutricional utilizaram-se as médias do consumo de energia e nutrientes, comparadas às recomendações nacionais. O estudo revelou oferta insuficiente de energia, ferro, cálcio e vitamina A, com um consumo protéico e de vitamina C excedendo as recomendações. Os carboidratos contribuíram com 58,5 ± 3,0% das energias totais, as proteínas com 16,0 ± 1,3% e as gorduras com 25,5 ± 3,7%. A deficiência de energia e a inadequação de proteínas e demais nutrientes demonstram a necessidade de um contínuo monitoramento das metas do programa e o aperfeiçoamento do serviço visando à melhoria da qualidade das dietas, com especial atenção ao atendimento das recomendações nutricionais.

This investigation was carried out to evaluate the nutritional quality of the meal consumed by the children from 2 to 6 years old registered at municipal day-care centers in Teresina. The data were acquired in the period from October/97 to March/98, with the weighing of the food. For the calculation of suitability of the diets it was used the averages of the consumption of energy and nutrients, compared to the national recommendations. The study revealed insufficient offer of energy, iron, calcium and vitamin A. The protein and vitamin C were over the recommendation. The carbohydrate contributed with 58.5 ± 3.0% of the total calories, the proteins with 16.0 ± 1.3% and the fats with 25.5 ± 3.7%. The dietetic information showed a need to adopt a policy of seeking improvement of the quality of the diets, with special attention to the attendance of the nutritional recommendations.