59 research outputs found
Dual equilibrium in a finite aspect ratio tokamak
A new approach to high pressure magnetically-confined plasmas is necessary to
design efficient fusion devices. This paper presents an equilibrium combining
two solutions of the Grad-Shafranov equation, which describes the
magnetohydrodynamic equilibrium in toroidal geometry. The outer equilibrium is
paramagnetic and confines the inner equilibrium, whose strong diamagnetism
permits to balance large pressure gradients. The existence of both equilibria
in the same volume yields a dual equilibrium structure. Their combination also
improves free-boundary mode stability
True optical spacial derivatives for plasma density measurements
This paper shows analytically and numerically that a vortex plate coupled to
a neutral density filter can deliver a true optical derivative when placed at
the focal plane of a lens pair. This technique turns spatial variations in
intensity into an intensity, which square root is the spatial derivative of the
initial intensity variation. More surprisingly, it also turns any spatial
variations in phase into an intensity, which square root is the spatial
derivative of the initial phase variation. Since the optical derivative drops
the DC component of the signal, it is possible to measure the full electron
plasma turbulence spectrum optically, without using any interferometer
Using LES to Study Reacting Flows and Instabilities in Annular Combustion Chambers
Great prominence is put on the design of aeronautical gas turbines due to increasingly stringent regulations and the need to tackle rising fuel prices. This drive towards innovation has resulted sometimes in new concepts being prone to combustion instabilities. In the particular field of annular combustion chambers, these instabilities often take the form of azimuthal modes. To predict these modes, one must compute the full combustion chamber, which remained out of reach until very recently and the development of massively parallel computers. Since one of the most limiting factors in performing Large Eddy Simulation (LES) of real combustors is estimating the adequate grid, the effects of mesh resolution are investigated by computing full annular LES of a realistic helicopter combustion chamber on three grids, respectively made of 38, 93 and 336 million elements. Results are compared in terms of mean and fluctuating fields. LES captures self-established azimuthal modes. The presence and structure of the modes is discussed. This study therefore highlights the potential of LES for studying combustion instabilities in annular gas turbine combustors
Prion Protein Is a Key Determinant of Alcohol Sensitivity through the Modulation of N-Methyl-D-Aspartate Receptor (NMDAR) Activity
The prion protein (PrP) is absolutely required for the development of prion diseases; nevertheless, its physiological functions in the central nervous system remain elusive. Using a combination of behavioral, electrophysiological and biochemical approaches in transgenic mouse models, we provide strong evidence for a crucial role of PrP in alcohol sensitivity. Indeed, PrP knock out (PrP−/−) mice presented a greater sensitivity to the sedative effects of EtOH compared to wild-type (wt) control mice. Conversely, compared to wt mice, those over-expressing mouse, human or hamster PrP genes presented a relative insensitivity to ethanol-induced sedation. An acute tolerance (i.e. reversion) to ethanol inhibition of N-methyl-D-aspartate (NMDA) receptor-mediated excitatory post-synaptic potentials in hippocampal slices developed slower in PrP−/− mice than in wt mice. We show that PrP is required to induce acute tolerance to ethanol by activating a Src-protein tyrosine kinase-dependent intracellular signaling pathway. In an attempt to decipher the molecular mechanisms underlying PrP-dependent ethanol effect, we looked for changes in lipid raft features in hippocampus of ethanol-treated wt mice compared to PrP−/− mice. Ethanol induced rapid and transient changes of buoyancy of lipid raft-associated proteins in hippocampus of wt but not PrP−/− mice suggesting a possible mechanistic link for PrP-dependent signal transduction. Together, our results reveal a hitherto unknown physiological role of PrP on the regulation of NMDAR activity and highlight its crucial role in synaptic functions
DON content in oat grains in Norway related to weather conditions at different growth stages
High concentrations of the mycotoxin deoxynivalenol (DON), produced by Fusarium graminearum have occurred frequently in Norwegian oats recently. Early prediction of DON levels is important for farmers, authorities and the Cereal Industry. In this study, the main weather factors influencing myco-toxin accumulation were identified and two models to predict the risk of DON in oat grains in Norway were developed: (1) as a warning system for farmers to decide if and when to treat with fungicide, and (2) for authorities and industry to use at harvest to identify potential food safety problems. Oat grain samples from farmers’ fields were collected together with weather data (2004–2013)\ud
A mathematical model was developed and used to esti-\ud
mate phenology windows of growth stages in oats (til-\ud
lering, flowering etc.). Weather summarisations were\ud
then calculated within these windows, and the Spearman\ud
rank correlation factor calculated between DON-\ud
contamination in oats at harvest and the weather\ud
summarisations for each phenological window. DON\ud
contamination was most clearly associated with the\ud
weather conditions around flowering and close to har-\ud
vest. Warm, rainy and humid weather during and around\ud
flowering increased the risk of DON accumulation in\ud
oats, as did dry periods during germination/seedling\ud
growth and tillering. Prior to harvest, warm and humid\ud
weather conditions followed by cool and dry conditions\ud
were associated with a decreased risk of DON accumu-\ud
lation. A prediction model, including only pre-flowering\ud
weather conditions, adequately forecasted risk of DON\ud
contamination in oat, and can aid in decisions about\ud
fungicide treatments
Unsteady simulation of an axial compressor stage with casing and blade passive treatments
International audienc
Numerical analysis of the tip leakage flow field in a transonic axial compressor with circumferential casing treatment
International audienc
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