Éjection de masse coronale

Résumé

350px|vignette|droite|Éjection de masse coronale produite le 31 août 2012. Une éjection de masse coronale (en abrégé EMC ; en anglais coronal mass ejection, CME) est une bulle de plasma produite dans la couronne d'une étoile (par exemple la couronne solaire). Caractéristiques Elle est souvent liée à une éruption solaire ou à l'apparition d'une protubérance solaire, mais ce n'est pas systématique. Les EMC sont des phénomènes à grande échelle : leur taille peut atteindre plusieurs dizaines de rayons solaires. Elles modifient les caractéristiques du vent solaire, se déplaçant à très grande vitesse dans le milieu interplanétaire (entre et ) et peuvent parcourir la distance Terre-Soleil en quelques jours (typiquement trois jours). Le champ magnétique des EMC est très fort : une EMC atteignant la Terre peut donc provoquer des orages magnétiques en interagissant avec le champ magnétique terrestre. On observe alors des phénomènes de reconnexion magnétique et certaines lignes de

Source officielle

https://fr.wikipedia.org/wiki/%C3%89jection_de_masse_coronale

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Large-scale coherent flow structures in rough-bed open-channel flow observed in fluctuations of three-dimensional velocity, skin friction and bed pressure

Fereshteh Bagherimiyab Hunkeler, Ulrich Lemmin

The dynamics of large-scale coherent structures (LSCS) are investigated in a rough-bed flow over the whole water column and longitudinal and transverse turbulent fluxes of momentum are compared. The relation between LSCS and fluctuations of skin friction and near-bed surface pressure is examined in order to understand the effects of LSCS on the bed. The study was carried out in an open channel with a non-moving permeable bed of screeded loose-mixed gravel (D-50 = 1.5 cm) at Reynolds numbers ranging from 3.19 x 10(4) to 1.08 x 10(5). Quasi-instantaneous full-depth three-dimensional (3D) velocity profiles with high spatial and temporal resolution measured with an acoustic Doppler velocity profiler (ADVP) are combined with the signals of a hot-film sensor mounted on the top of the gravel and a piezoresistive pressure transducer placed in the top layer of the bed particles at the centre of the channel. Vertical turbulent momentum flux is clearly dominated by ejections and sweeps over most of the water column. Near the bed, contributions of sweeps are larger than those of ejections. This is reversed at the mid-depth (z/h = 0.5). No preferential quadrant orientation is seen for the transverse momentum flux. A correlation between LSCS dynamics in the water column and data from the sensors on the bed is made evident. Sweeps correlate with positive fluctuations of bottom pressure and skin friction while ejections correlate with negative ones.

TAYLOR & FRANCIS LTD2018

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High Resolution Mass Spectrometry for Studying the Interactions of Cisplatin with Oligonucleotides

Hisham Ben Hamidane, Paul Joseph Dyson, Christian Hartinger, Yury Tsybin

Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been used to probe the interaction of the anticancer drug cisplatin with oligonucleotides. The binding kinetics, the nature of the adducts formed, and the location of the binding site within the specifically designed double-stranded DNA oligonucleotides, ds(GTATTGGCACGTA) and ds(GTACCGGTGTGTA), were detd. by recording mass spectra over time and/or employing tandem mass spectrometry (MS/MS). The FT-ICR MS studies show that binding to DNA takes place via a [Pt(NH3)2Cl]+ intermediate prior to formation of bifunctional [Pt(NH3)2]2+ adducts. Tandem MS reveals that the major binding sites correspond to GG and GTG, the known preferred binding sites for cisplatin, and demonstrates the preference for binding to guanosine within the oligonucleotide. The obtained results are discussed and compared to published data obtained by other mass spectrometric techniques, NMR spectroscopy and x-ray crystallog.

2008

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, ,

With improved B-0 homogeneity along with satisfactory gradient performance at high magnetic fields, snapshot gradient-recalled echo-planar imaging (GRE-EPI) would perform at long echo times (TEs) oil the order of T-2*, which intrinsically allows obtaining strongly T-2*-weighted images with embedded substantial anatomical details in ultrashort time. The aim of this study was to investigate the feasibility and quality of long TE snapshot GRE-EPI images of rat brain at 9.4 T. When compensating for B-0 inhomogeneities, especially second-order shim terms, a 200x200 mu m(2) in-plane resolution image was reproducibly obtained at long TE (> 25 ms). The resulting coronal images at 30 ms had diminished geometric distortions and, thus, embedded Substantial anatomical details. Concurrently with the very consistent stability, such GRE-EPI images should permit to resolve functional data not only with high specificity but also with substantial anatomical details, therefore allowing coregistration of the acquired functional data oil the same image data set. (C) 2008 Elsevier Inc. All rights reserved.

Elsevier2008

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