Oilfields usually represent extreme environments, where physicochemical conditions appear at first sight to be generally unsuitable for living organisms to develop. However, these environments, usually poor in nitrates and oxygen, harbour a rich diverse community of microorganisms. The most widely represented and best-known types are sulfate-reducing, methanogenic and fermentative bacteria.
Nitrate-reducing bacteria, on the other hand, have received little research attention regarding their biology and role. Nevertheless some of their bacteria are known also to have the ability to oxidize sulfates. These components, which can result from metabolic activity of sulfate-reducing bacteria, prove dangerous for the environment and corrosive for drilling equipment. Nitrate injection is practised in some regions of the world in order to restrict the emission of sulfites produced during processes of exploitation of oil deposits. This input of nitrates stimulates nitrate-reducing bacteria, initially present in low quantities in the waters associated with oil reservoirs, to proliferate (2). They thus induce at once inhibition of the development of sulfate-reducing bacteria and oxidation of sulfides that such microorganisms produce.
The question remains of determining whether or not these nitrate inputs into the petroleum reservoir environment can favour the growth of populations of nitrate-reducing microorganisms different from those which oxidize the sulfides, in this way modifying the microbial ecology of oil wells. IRD scientists are therefore investigating in the laboratory the metabolism of novel nitrate-reducing bacteria, especially those able to oxidize organic acids. These acids are often present in the waters of oil reservoirs.
Marie Guillaume | alfa
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The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
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The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
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