63 research outputs found

    On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

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    A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

    Overview of the JET results in support to ITER

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    Natural Polymers with Antioxidant Properties: Poly-/oligosaccharides of Marine Origin

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    In recent decades, poly- and oligosaccharides derived from marine sources including algae, invertebrates and some bacteria display significant antioxidant activities. Development of therapeutic products based on such bioactive poly-/oligosaccharides has been generating considerable interest. Research has shown that the antioxidant properties of marine polysaccharides depend on a number of structural properties, such as the functional groups, molecular weight, and monosaccharide compositions. Structural characteristics may lead to differing mechanisms responsible for antioxidant activities that can be evaluated by various in vitro approaches including l,l-diphenyl-2-picrylhydrazil radical scavenging, ferric reducing antioxidant power, Superoxide radical and hydroxyl radical scavenging assays. This chapter reviews the research on the antioxidant properties of marine poly- and oligosaccharides, with particular emphasis on the relationship between their structural features and antioxidant mechanism. The antioxidant properties of marine poly- and oligosaccharides may lead to their increased use as natural antioxidant agents in food, medical, cosmetic, and other applications. \ua9 2012 Scrivener Publishing LLC.Peer reviewed: YesNRC publication: Ye
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