TÂNIA CARVALHAL E AS TRILHAS DO COMPARATISMO: ESBOÇO DE UM PERFIL

O TEXTO ESTABELECE UM PERFIL DA CRÍTICA LITERÁRIA E TEÓRICA DA LITERATURA COMPARADA TANIA FRANCO CARVALHAL, NA PERSPECTIVA DE UM DE SEUS COLABORADORES MAIS PRÓXIMOS, ENFATIZANDO A RELEVÂNCIA DE SEU TRABALHO PIONEIRO COM A LITERATURA COMPARADA NO BRASIL.

O NOVO COMPARATISMO NA AMÉRICA LATINA: REFLEXOS NO ENSINO E NA HISTORIOGRAFIA LITERÁRIA

As a result of a process of colonization which lasted over three centuries and which can still be felt, though not from the same matrixes, in economical and cultural terms, Latin American intellectuals have always taken Western European ideas and institutions as paradigms and have always sought to internalize their world view. As such, the teaching and research of literature at the Latin American universities have usually been based on European models: at first, by means of Historicism, and later, through the critical currents, especially of an immanent character, that came from that context. In both cases, the idea of national literature was seen as a dominant element and the study of literature was centered upon the canon of each country, founded on nationalistic bases. However, with the advent of Deconstruction and of Cultural and Post-Colonial Studies in the second half of the twentieth century, this model has been deeply queried in Latin America, and has given way to a tension between those who try to maintain the hegemonic concept of nation on the one side, and those who approach literature as one among other expressions of the political affirmation of each group that compose the continent’s ethnic, social, cultural and linguistic mosaic on the other side. Considering the criticisms raised nowadays both to the hegemonic construction of the nation-states and to the responses that they have generated, particularly on the part of minority groups, our purpose in this paper is to draw a few questions regarding the teaching of literature and the writing of literary histories at the present time in Latin America. Em decorrência de um processo de colonização de mais de três séculos e que ainda hoje perdura, embora não mais das mesmas matrizes, do ponto de vista econômico e cultural, os intelectuais da América Latina sempre tomaram idéias e instituições européias como paradigmáticas e buscaram internalizar a visão de mundo desses povos. Desse modo, o ensino e a pesquisa da Literatura nas universidades latino-americanas ateve-se na maioria das vezes aos modelos europeus: primeiro através do historicismo e, mais tarde por meio das correntes teóricas, em especial de cunho imanentista, que provinham daquele contexto. Em ambos os casos, a idéia de literatura nacional constituía uma referência dominante e o estudo da literatura centrava-se no cânone de cada país, erigido em bases nacionalistas. Entretanto, com o advento da Desconstrução e dos Estudos Culturais e Pós-Coloniais na segunda metade do século XX, esses modelos foram amplamente questionados, dando lugar a uma tensão entre os estudiosos que defendiam o conceito hegemônico de nação e os que passaram a abordar a literatura como uma entre as muitas expressões da afirmação política de cada grupo que compõe o mosaico étnico, cultural, social e lingüístico do continente. Com base nas críticas que têm sido feitas atualmente tanto à construção hegemônica de estados nações quanto às respostas daí resultantes, sobretudo da parte dos chamados “grupos minoritários”, teceremos, neste trabalho, alguns comentários sobre o ensino da literatura e sobre a produção de histórias literárias nos dias de hoje na América Latina

Enhanced oil recovery under laboratory conditions using biosurfactant-producing microorganisms

Oil recovery comprises a primary phase, which produces oil using the natural pressure drive of the reservoir, and a secondary phase, which includes the injection of water to improve the flow of oil to the wellhead [1,2]. While primary recovery produces 5-10% of the original oil in place, recovery efficiencies in the secondary stage vary from 10% to 40% [1]. Most of the unrecovered oil (up to two-thirds of the total oil reserves) is trapped in the reservoir pores by high capillary forces [2]. Microbial Enhanced Oil Recovery (MEOR) is a tertiary oil recovery process where microorganisms and their metabolites are used to retrieve unrecoverable oil from mature reservoirs. Stimulation of biosurfactant production by indigenous or injected microorganisms can reduce the capillary forces that retain the oil into the reservoir. In this work, a sand pack column model was designed to simulate the oil recovery operations in oil reservoirs and evaluate the mobilization of residual oil by microorganisms. Three Bacillus subtilis strains (309, 311 and 573), previously isolated from crude oil samples, were used in this study. They grow and produce extracellular biosurfactants at 40ºC under anaerobic conditions in medium supplemented with hydrocarbons. Biosurfactants produced by those isolates reduce the surface tension of water from 72 to 30 mN/m, exhibit emulsifying activity and are not affected by exposure to high temperatures (121ºC) which makes them good candidates for application in biosurfactant mediated MEOR. Acrylic columns (250 ml) packed with acid washed sand were first flooded with water, after that saturated with paraffin, and then washed with water to remove the excess of paraffin. Afterwards, the isolates were injected into the columns with the optimized medium and incubated at 40ºC. After 14 days, the columns were flooded with water and the additional oil recovery (AOR) was calculated as the percentage of paraffin recovered. AOR using B. subtilis 309, 311 and 573 was 35.0 ± 1.0 %, 23.5 ± 1.2 % and 19.8 ± 1.9 %, respectively. The results obtained suggest that stimulation of biosurfactant production by these strains in the oil reservoir can contribute to mobilize entrapped oi

Isolation and study of microorganisms from oil samples for application in Microbial Enhanced Oil Recovery

"Author's personal copy"Microbial Enhanced Oil Recovery (MEOR) is potentially useful to increment oil recovery from a reservoir beyond primary and secondary recovery operations using microorganisms and their metabolites. Stimulation of bacterial growth for biosurfactant production and degradation of heavy oil fractions by indigenous microorganisms can enhance the fluidity and reduce the capillary forces that retain the oil into the reservoir. MEOR offers major advantages over conventional EOR, namely low energy consumption and independence of the price of crude oil. In this work, the isolation and identification of microorganisms capable of producing biosurfactants and promote degradation of long-chain n-alkanes under conditions existent in oil reservoirs were addressed. Among the isolated microorganisms, five Bacillus strains were able to produce extracellular biosurfactants at 40 C under anaerobic conditions in medium supplemented with hydrocarbons. Three isolates were selected as the higher biosurfactant producers. The obtained biosurfactants reduced the surface tension of water from 72 to 30 mN/m, exhibited emulsifying activity and were not affected by exposure to high temperatures (121 C). These characteristics make them good candidates for use at conditions usually existing in oil reservoirs. Furthermore, it was here shown for the first time that Bacillus strains were able to degrade large alkyl chains and reduce the viscosity of hydrocarbon mixtures under anaerobic conditions. The results obtained show that the isolated microorganisms are promising candidates for the development of enhanced oil recovery processes.This work was supported by PARTEX OIL AND GAS. Jorge F. B. Pereira acknowledges the financial support from Fundacao para a Ciencia e a Tecnologia through doctoral research grant SFRH/BD/60228/2009

Microbial degradation of hydrocarbons and its applications to enhanced oil recovery at lab scale

The renewed interest in Enhanced Oil Recovery (EOR) techniques as a consequence of the current oil prices is boosting the development of the Microbial Enhanced Oil Recovery (MEOR). This technique is useful to recover incremental oil from a reservoir beyond primary and secondary recovery operations and can be carried by the injection of exogenous or stimulation of indigenous microorganisms. This last approach is here investigated. In this work we address the isolation and identification of microorganisms from Brazilian heavy oil samples capable of producing biosurfactants and to promote the degradation of heavy oil fractions, in particular long-chain hydrocarbons.Different crude oil samples obtained from an oil reservoir were used to isolate microorganisms for application in MEOR. Most of isolates were Pseudomonas and Bacillus strains. The growth of different microbial isolates was studied under both aerobic and anaerobic conditions at 40ºC. These isolates were found to produce extracellular biosurfactants, reduce surface tension and showed a high emulsifying activity. In addition to these capabilities, we studied the ability of these microorganisms to degrade the heavy oil fraction, in particular long-chain hydrocarbons. Several parameters were studied, such as nutritional conditions, incubation time and paraffinic composition of the mixture. Our results show that some of the isolates displayed a capacity to degrade, under aerobic and anaerobic conditions, the large alkyl chains (18+ carbons in alkyl chains) and to reduce the viscosity of hydrocarbon mixtures. Our results, show the ability of the Bacillus subtilis strains to enhance the recovery of paraffinic oil on sand pack columns. These results suggest that the microorganisms’ here isolated have interesting characteristics to be applied for MEOR

A biosurfactant-producing and oil-degrading Bacillus subtilis strain enhances oil recovery under simulated reservoir conditions

Microbial Enhanced Oil Recovery (MEOR) is potentially useful to increment oil recovery from reservoirs beyond primary and secondary recovery operations using microorganisms and their metabolites. In situ stimulation of microorganisms that produce biosurfactants and degrade heavy oil fractions reduces the capillary forces that retain the oil inside the reservoir and decreases oil viscosity, thus promoting its flow and increasing oil production. Bacillus subtilis #573, isolated from crude oil samples obtained from a Brazilian oil field with a moderate temperature (40ºC), was selected for further use in MEOR. This isolate can grow at temperatures up to 55ºC and salinities up to 100 g/l, and produces extracellular biosurfactants under both aerobic and anaerobic conditions in the presence of hydrocarbons. The biosurfactants produced reduced the surface tension to 30 mN/m, decrease the interfacial tension oil-water and exhibited a high emulsifying activity, as well as thermo- and salt-tolerance. The microbial isolate also showed the ability of degrading long-chain n-alkanes under aerobic and anaerobic conditions. Mobilization of heavy crude oil by this isolate was evaluated using sand-pack columns at 40ºC. Growing in situ B. subtilis #573 for 14 days allowed a 17% recovery of the entrapped crude oil. The recovered crude oil showed a decrease in the percentage of n-alkanes higher than C25 and its viscosity was reduced about 32%, which contributed to enhance its mobility. A core flooding equipment was used for a better simulation of the oil reservoir conditions (40ºC and 32.4 bars). Preliminary results showed an additional oil recovery of 4%. The results obtained demonstrated that the selected isolate can be useful to recover residual oil from mature reservoirs

Evaluation and characterization of biosurfactants produced by microorganisms isolated from Brazilian oils

Surface-active agents or surfactants are amphiphilic molecules that comprise both hydrophilic and hydrophobic moieties, allowing the reduction of the surface and interfacial tensions, as well as the formation of oil in water or water in oil emulsions. Due to their interesting properties, surfactants are widely used by petroleum industries to reduce the capillary forces that retain the oil inside the reservoir. However, since chemical surfactants present some limitations related to environmental issues and restrictive laws, the biosurfactants constitute a reliable alternative due to their lower toxicity, higher biodegradability and effectiveness at extreme temperature, salinity and pH conditions. In this work, different biosurfactant-producing microorganisms under reservoir conditions were isolated from Brazilian oils. Biosurfactant production was evaluated by measuring surface tensions, interfacial oil-water tensions and emulsification activities. Among the isolated microorganisms, two Pseudomonas and three Bacillus strains were able to grow and produce extracellular biosurfactants at 40ºC. Furthermore, the biosurfactants were characterized using different spectroscopic techniques, namely FTIR, 1H NMR, ESI/MS and MS/MS. Structural characterization of these molecules is important to understand their surface-active properties, as well as the formation of molecular aggregates. Biosurfactants produced by Pseudomonas and Bacillus strains were found to be rhamnolipids and surfactins, respectively. The results obtained show that it is important to characterize the biosurfactants in order to optimize their application in bioremediation with crude oil, or in microbial enhanced oil recovery processes

A mathematical model for optimizing the indications of liver transplantation in patients with hepatocellular carcinoma

Abstract Background The criteria for organ sharing has developed a system that prioritizes liver transplantation (LT) for patients with hepatocellular carcinoma (HCC) who have the highest risk of wait-list mortality. In some countries this model allows patients only within the Milan Criteria (MC, defined by the presence of a single nodule up to 5 cm, up to three nodules none larger than 3 cm, with no evidence of extrahepatic spread or macrovascular invasion) to be evaluated for liver transplantation. This police implies that some patients with HCC slightly more advanced than those allowed by the current strict selection criteria will be excluded, even though LT for these patients might be associated with acceptable long-term outcomes. Methods We propose a mathematical approach to study the consequences of relaxing the MC for patients with HCC that do not comply with the current rules for inclusion in the transplantation candidate list. We consider overall 5-years survival rates compatible with the ones reported in the literature. We calculate the best strategy that would minimize the total mortality of the affected population, that is, the total number of people in both groups of HCC patients that die after 5 years of the implementation of the strategy, either by post-transplantation death or by death due to the basic HCC. We illustrate the above analysis with a simulation of a theoretical population of 1,500 HCC patients with tumor size exponentially. The parameter λ obtained from the literature was equal to 0.3. As the total number of patients in these real samples was 327 patients, this implied in an average size of 3.3 cm and a 95% confidence interval of [2.9; 3.7]. The total number of available livers to be grafted was assumed to be 500. Results With 1500 patients in the waiting list and 500 grafts available we simulated the total number of deaths in both transplanted and non-transplanted HCC patients after 5 years as a function of the tumor size of transplanted patients. The total number of deaths drops down monotonically with tumor size, reaching a minimum at size equals to 7 cm, increasing from thereafter. With tumor size equals to 10 cm the total mortality is equal to the 5 cm threshold of the Milan criteria. Conclusion We concluded that it is possible to include patients with tumor size up to 10 cm without increasing the total mortality of this population

Biosurfactant producing microorganisms and its application to enhanced oil recovery at lab scale

Microbial Enhanced Oil Recovery (MEOR) is a tertiary oil recovery process where microorganisms and their metabolites are used to retrieve unrecoverable oil from mature reservoirs. Stimulation of biosurfactant production by indigenous microorganisms can reduce the capillary forces that retain the oil into the reservoir. The studied reservoir is characterized by alternated oil and water sand layers, with an average porosity of 25% and a permeability of 50 mD. It’s a flat structure at 450 m depth, with an initial pressure of 32.4 bars and a temperature of 42.5ºC. The oil is paraffinic, with low viscosity, high pour point and a gravity of 25º API, with no gas dissolved. Due to these properties, the wells can’t flow naturally and the production has to be lifted, making this reservoir a good candidate for MEOR application. This work addresses the isolation and identification of microorganisms capable of producing biosurfactants and degrading heavy oil fractions at the oil reservoir conditions. Five Bacillus subtilis strains isolated from oil samples were able to grow and produce extracellular biosurfactants at 40ºC under anaerobic conditions in medium supplemented with hydrocarbons. In addition, some of the isolates displayed a capacity to degrade, both in aerobic and anaerobic conditions, the large alkyl chains, and reduce the viscosity of hydrocarbon mixtures. A sand-pack column model was designed to simulate the oil recovery operations and evaluate the mobilization of residual oil by microorganisms. Additional oil recovery using B. subtilis isolates ranged from 19.8 to 35.0%, suggesting that stimulation of biosurfactant production by these strains in situ can contribute to mobilize entrapped oil. The novelty of this technique, compared to the conventional EOR methods, is the application of indigenous microorganisms to increase the oil recovery.(undefined

Production and characterization of biosurfactants produced by microorganisms isolated from brazilian oils

Surfactants are amphiphilic molecules that comprise both hydrophilic and hydrophobic moieties, allowing the reduction the surface and interfacial tensions, as well as the formation of oil in water or water in oil emulsions. These surface-active compounds are extensively used by petroleum industries in order to reduce the capillary forces that entrapped the oil inside the reservoir. The compounds synthetized chemically, chemical surfactants, have some applicability limitations according some environmental restrictions. Contrarily, sustainable surfactants compounds can be produced naturally by microorganisms, designed by biosurfactants. The biosurfactants are a reliable alternative, since they exhibit lower toxicity, higher biodegradability, and effectiveness at extreme temperature, salinity and pH conditions. This work studies the production of different biosurfactant produced by microorganisms isolated from Brazilian oils. It was evaluated their abilities by measuring surface tensions, interfacial oil-water tensions and emulsification activities. Two Pseudomonas and three Bacillus strains demonstrated capability to grow and produce extracellular biosurfactants at 40ºC. Additionally, the biosurfactants produced were characterized using different spectroscopic techniques, namely FTIR, 1H NMR, ESI/MS and MS/MS, being the biosurfactants produced by Pseudomonas and Bacillus strains characterized as rhamnolipids and surfactins, respectively. The results obtained show that it is important to characterize the biosurfactants in order to understand their surface-active properties, as well as their formation of molecular aggregates: The biosurfactants chemical characterization allows the optimization of their application in bioremediation with crude oil, or in microbial enhanced oil recovery processes