Heteroramnanas sulfatadas obtidas de Gayralia Oxysperma

Resumo: Estudos prévios realizados no Laboratório de Química de Carboidratos - Algas Marinhas demonostraram que heteroramnanas sulfatadas (OX-6) e seus produtos de menor massa molar (OX-6S, OX-6Sb e OX-6Sc) possuem atividade antitumoral contra linhagens U87MG de glioma humano. Com base nesses resultados, o objetivo do presente trabalho foi investigar o mecanismo pelo qual esses polissacarídeos provocam a diminuição na viabilidade das células de glioma humano. Para tanto, foi avaliado o efeito das frações OX-6, OX-6S, OX-6Sb e OX-6Sc no ciclo, migração e recuperação celular, correlacionando com os níveis de RNAm de p21, p53 e p19. Foi verificado por análise de citometria de fluxo que o tratamento das células U87MG com os polissacarídeos promovem um aumento no número de células da fase G1 do ciclo celular, sem alteração no número de células na fase sub-G1. Ainda, não foi observado alteração na migração celular e na recuperação da proliferação das células após a retirada do tratamento. A análise do perfil de expressão gênica (investigada através do ensaio de PCR quantitativo em Tempo Real) indicou tendência de modulação de p21 e p53. Apesar de não terem sido observadas diferenças em relação ao mecanismo de atividade antitumoral dessas frações, foi observado, dentre os produtos de degradação controlada de Smith homogêneos (OX-6Sb e OX-6Sc) que a fração OX-6Sc é mais citotóxica quando comparada com a fração OX-6Sb. Análises químicas (metilação) realizadas previamente demonstraram que essas frações apresentam diferenças estruturais entre si, o que pode justificar a diferença observada na atividade biológica. Com o objetivo de confirmar os dados estruturais, a fração OX-6Sc foi submetida a uma nova abordagem de metilação, denominada trideuteriometilação. Essa análise confirmou os dados de estrutura química previamente obtidos. Ainda, foram obtidas novas frações polissacarídicas de G. oxysperma, as quais foram caracterizadas quimicamente e mostraram-se semelhantes aos produtos de degradação controlada de Smith utilizados na atividade biológica, demonstrando assim, a reprodutibilidade deste processo

Evaluation of residence time on nitrogen oxides removal in non-thermal plasma reactor

Non-thermal plasma (NTP) has been introduced over the last few years as a promising after- treatment system for nitrogen oxides and particulate matter removal from diesel exhaust. NTP technology has not been commercialised as yet, due to its high rate of energy consumption. Therefore, it is important to seek out new methods to improve NTP performance. Residence time is a crucial parameter in engine exhaust emissions treatment. In this paper, different electrode shapes are analysed and the corresponding residence time and NOx removal efficiency are studied. An axisymmetric laminar model is used for obtaining residence time distribution numerically using FLUENT software. If the mean residence time in a NTP plasma reactor increases, there will be a corresponding increase in the reaction time and consequently the pollutant removal efficiency increases. Three different screw thread electrodes and a rod electrode are examined. The results show the advantage of screw thread electrodes in comparison with the rod electrode. Furthermore,between the screw thread electrodes, the electrode with the thread width of 1 mm has the highest NOx removal due to higher residence time and a greater number of micro-discharges. The results show that the residence time of the screw thread electrode with a thread width of 1 mm is 21% more than for the rod electrode

Waste Foundry Sand/Bauxite Residue for Enhanced NOx Reduction in Diesel Exhaust Pretreated With Plasma/O-3 Injection

The increased usage of diesel fuel of late has led the researchers to pay more attention toward abatement of increased emission of oxides of nitrogen (NOx) in the engine exhaust. The focus is, therefore, lies in providing a technique that is economical, feasible, and long lasting. The combination of electric discharge plasma with adsorbent/catalyst derived out of solid waste can be one such possible technique. In this paper, waste foundry sand from foundry industry and red mud or bauxite residue from aluminum industry have been used. Diesel engine exhaust under dry condition was exposed to an oxidizing discharge plasma environment. The plasma-treated exhaust was subjected to either adsorption over waste foundry sand or catalysis over red mud. Studies were carried out in the laboratory environment with 20% loading of diesel generator. The oxidizing plasma environment was either with direct plasma or with indirect plasma in which case ozone injection into the exhaust was accomplished. The ozone-adsorbent cascading system has resulted in about 87% NOx reduction in the dry exhaust case. The effect of O-3:NO ratio was discussed from the point of NO/NO2

Nonthermal-Plasma-Promoted Catalysis for the Removal of NOx From a Stationary Diesel-Engine Exhaust

A detailed study on the removal of oxides of nitrogen (NOx) from the exhaust of a stationary diesel engine was carried out using nonthermal-plasma (pulsed electrical-discharge plasma)-promoted catalytic process. In this paper, the filtered exhaust from the diesel engine is made to pass through a combination of nonthermal plasma reactor and a catalytic reactor connected in series. This combination is referred to as cascade. Two types of cascaded systems were studied. In one type, the plasma treating filtered exhaust was cascaded with a reduction catalyst V2O5/TiO2 using ammonia as reducing agent, and in the other type, the plasma treating filtered exhaust was cascaded with activated-alumina catalyst without any additive. Improved NOx-removal performance of both the cascaded processes and the role of nonthermal plasma in promoting catalysis are explained. Along with the NOx, total hydrocarbon and aldehydes were also removed. Furthermore, experiments were conducted at different temperatures and engine-loading conditions

Dielectric Barrier Discharge Cascaded with Red Mud Waste to Enhance NOX Removal from Diesel Engine Exhaust

Red mud is a waste by-product generated during the processing of bauxite, the most common ore of aluminium. With the presence of ferric oxide, high surface area, resistance to poisoning and low cost, red mud made itself a good alternative to the existing commercial automobile catalyst. The cascading of dielectric barrier discharge plasma with red mud improved the NOX removal from diesel engine exhaust significantly. The DeNO(X) efficiency with discharge plasma was 74% and that with red mud was 31%. The efficiency increased to 92% when plasma was cascaded with red mud catalyst operating at a temperature of 400 degrees C. The NOX removal was dominated by NO2 removal. The studies were conducted at different temperatures and the results were discussed

A Laboratory Analysis of Plasma Based Hybrid Techniques for Treating Engine Exhaust

A detailed study on the removal of pollutants (NOx, aldehydes and CO) from the exhaust of a stationary diesel engine is carried out using barrier discharge hybrid plasma techniques. The objective of the study is to make a comparative analysis. For this purpose, the exhaust treatment was carried out in two stages. In the first stage, the exhaust was treated with plasma process and plasma-adsorbent hybrid process. The effectiveness of the two processes with regard to NOx removal and by-product reduction was discussed. In the second stage, the exhaust was treated by plasma and plasma-catalyst hybrid process. The effectiveness of the two processes with regard to pollutants (NOx, CO) removal and by-product reduction was analyzed. Finally, a comprehensive comparison of different techniques has been made and feasible plasma based hybrid techniques for stationary and non-stationary engine exhaust treatments were proposed

Studies on NOX Removal From Diesel Engine Exhaust Using Duct-Type DBD Reactor

With ever more stringent NOX emissions, it is necessary to examine removal of nitrogen oxide from diesel engine exhaust. This paper describes the study of NOX reduction from 5.9-kW stationary diesel engine exhaust under nanosecond pulse energization. Two plasma reactors characterized by dielectric barrier discharge has been designed, built, and evaluated. One of the reactor designs include nine numbers of electrodes kept in parallel, and the exhaust was allowed to pass axially, whereas the second reactor consists of nine parallel electrodes and the exhaust was allowed to pass radially. The reactors were individually tested for the treatment of nitrogen oxides for gas flow rate of 2, 5, and 10 L/min. Both the reactors have been individually tested, and results show an appreciable removal of NOX with equal discharge volume. From the results, it was found that both the reactors were an efficient NOX removal. With consumption of only 36 J/L, the reactors had shown a considerable 45% DeNO(X) efficiency

Studies on nitric oxide removal in simulated gas compositions under plasma-dielectric/catalytic discharges

Application of pulsed electrical discharges for gas cleaning is gaining prominence, mainly from the energy consideration point of view. This present paper presents recent work on applying the electrical discharge plasma technology for treating gaseous pollutants, in general, and nitric oxide, in particular, as this is one of the major contributors to air pollution. The present work focuses attention on pulsed electrical discharge technique for nitric oxide removal from simulated gas compositions and study of effect of packed dielectric pellets, with and without a coating of catalyst, on the removal process. Experiments were conducted in a cylindrical corona reactor energized by repetitive high voltage pulses. The effects of various parameters, viz. pulse voltage magnitude, pulse frequency, initial nitric oxide concentration and gas mixture composition on nitric oxide removal efficiency, are discussed. When the reactors were filled with different dielectric pellets like, barium titanate, alumina, and alumina coated with palladium catalyst, the improvement in nitric oxide removal efficiency is studied and discussed. The power dissipated in the reactor and the energy consumed per nitric oxide molecule removed was calculated. Further results and comparative study of various cases are presented in the paper

Studies on Compact Discharge Plasma Source for NOX Treatment in Engine Exhaust

This paper proposes a compact electric discharge plasma source for controlling NOX emission in diesel engine exhaust. An automobile ignition coil was used to generate the high voltage pulse using flyback topology. This design is aimed at retrofitting the existing catalytic converters with pulse assisted cleaning technique. In this paper we bring out a relative comparison of discharge plasma and plasma-adsorbent process at different gas flow rates. Activated alumina was used as adsorbent. The main emphasis is laid on the development of a compact pulse source from a DC supply for the removal of NOX from the filtered diesel engine exhaust