A Magnetic Flux Tube Oscillation Model for QPOs in SGR Giant Flares

Giant flares from soft gamma-ray repeaters (SGRs) are one of the most violent phenomena in neutron stars. Quasi-periodic oscillations (QPOs) with frequencies ranging from 18 to 1840 Hz have been discovered in the tails of giant flares from two SGRs, and were ascribed to be seismic vibrations or torsional oscillations of magnetars. Here we propose an alternative explanation for the QPOs in terms of standing sausage mode oscillations of flux tubes in the magnetar coronae. We show that most of the QPOs observed in SGR giant flares could be well accounted for except for those with very high frequencies (625 and 1840 Hz).Comment: 15 pages,1 figures,1 table, accepted for publication in The Astrophysical Journa

Nonlinear effects in resonant layers in solar and space plasmas

The present paper reviews recent advances in the theory of nonlinear driven magnetohydrodynamic (MHD) waves in slow and Alfven resonant layers. Simple estimations show that in the vicinity of resonant positions the amplitude of variables can grow over the threshold where linear descriptions are valid. Using the method of matched asymptotic expansions, governing equations of dynamics inside the dissipative layer and jump conditions across the dissipative layers are derived. These relations are essential when studying the efficiency of resonant absorption. Nonlinearity in dissipative layers can generate new effects, such as mean flows, which can have serious implications on the stability and efficiency of the resonance

Temporal Dissociation between Myeloperoxidase (MPO)-Modified LDL and MPO Elevations during Chronic Sleep Restriction and Recovery in Healthy Young Men

OBJECTIVES: Many studies have evaluated the ways in which sleep disturbances may influence inflammation and the possible links of this effect to cardiovascular risk. Our objective was to investigate the effects of chronic sleep restriction and recovery on several blood cardiovascular biomarkers. METHODS AND RESULTS: Nine healthy male non-smokers, aged 22-29 years, were admitted to the Sleep Laboratory for 11 days and nights under continuous electroencephalogram polysomnography. The study consisted of three baseline nights of 8 hours sleep (from 11 pm to 7 am), five sleep-restricted nights, during which sleep was allowed only between 1 am and 6 am, and three recovery nights of 8 hours sleep (11 pm to 7 am). Myeloperoxidase-modified low-density lipoprotein levels increased during the sleep-restricted period indicating an oxidative stress. A significant increase in the quantity of slow-wave sleep was measured during the first recovery night. After this first recovery night, insulin-like growth factor-1 levels increased and myeloperoxidase concentration peaked. CONCLUSIONS: We observed for the first time that sleep restriction and the recovery process are associated with differential changes in blood biomarkers of cardiovascular disease

Néonatalogie bovine, importance du colostrum (hors âge immunologique)

Le colostrum bovin contient moins de lactose mais plus de lipides, protéines et peptides, de vitamines liposolubles, de minéraux, d'enzymes, d'hormones, de facteurs de croissance, de nucléotides que le lait. A parue lactose, ces composants sont particulièrement abondants dans le premier colostrum, mais ils diminuent rapidement environ en huit jours pour atteindre les quantités typiques du lait mature. Le colostrum est un support fondamental pour la croissance et l'adaptation du veau nouveau-né à son nouvel environnement. I1 est responsable du transfert de l'immunité passive, du développement morphologique et fonctionnel du tractus gastro-intestinal, et il influence le statut métabolique, endocrinien et nutritionnel du veau. Cependant l'ingestion suffisante de colostrum est souvent défaillante, les facteurs de variations de sa quantité et qualité sont ainsi détaillés.MAISONS-ALFORT-Ecole Vétérin (940462302) / SudocSudocFranceF

Is microbial reduction of Fe (III) in podzolic soils influencing C release?

Fe(III) oxides stabilize soil organic matter by forming Fe organo-mineral associations (Fe-OMA). Under anoxic conditions, Fe-OMA may be destabilized by microbial dissimilatory iron reduction that releases aqueous Fe(II) and also possibly adsorbed or co-precipitated organic matter. Soil spodic horizons that accumulate Fe-OMA are ideal natural materials to study such impact. Here, we study three spodic horizons from pedons (P) of increasing age: P-270 yrs, P-330 yrs and P-530 yrs. Their contents of total carbon and short range ordered (SRO) Fe oxides increase with soil age from, respectively, 1486 to 3618 and 13 to 249 μmol g−1. The samples were incubated for 96 h under anoxic conditions, with and without Shewanella putrefaciens (a model dissimilatory Fe(III)-reducing bacteria) in a minimal medium devoid of any pH buffer and external electron donor. The concentration of dissolved Fe(II), total Fe and organic C was monitored at 9 time steps. With increasing age, both the rate and extent of microbial Fe(III) reduction increased after S. putrefaciens addition. In P-270 yrs, P-330 yrs and P-530 yrs, respectively, the microbial reduction rates were 0.004, 0.026 and 0.114 fmol Fe(II) h−1 cell−1 while the amounts of released Fe(II) were 0.23, 0.32 and 1.98 μmol Fe(II) g−1, both being strongly correlated with SRO Fe oxides content. Dissolved organic carbon (DOC) was released with or without S. putrefaciens in all samples (up to 73 μmol OC g−1 after 96 h in P-530 yrs). Adding S. putrefaciens significantly increased DOC release, but only in P-270 yrs. Podzol development thus increases the impact of anoxia on Fe(II) release since organic matter accumulation impedes Fe oxide crystallization, thereby amplifying Fe availability for Fe reducing microbes. The evolution of Fe oxide content and crystallinity thus affects the fate of both C and Fe in soils. © 201