Electric-field control of the magnetic anisotropy in an ultrathin (Ga,Mn)As/(Ga,Mn)(As,P) bilayer

We report on the electric control of the magnetic anisotropy in an ultrathin ferromagnetic (Ga,Mn)As/(Ga,Mn)(As,P) bilayer with competing in-plane and out-of-plane anisotropies. The carrier distribution and therefore the strength of the effective anisotropy is controlled by the gate voltage of a field effect device. Anomalous Hall Effect measurements confirm that a depletion of carriers in the upper (Ga,Mn)As layer results in the decrease of the in-plane anisotropy. The uniaxial anisotropy field is found to decrease by a factor ~ 4 over the explored gate-voltage range, so that the transition to an out-of-plane easy-axis configuration is almost reached

Surface acoustic wave driven ferromagnetic resonance in (Ga,Mn)(As,P) epilayers

Interdigitated transducers were used to generate and detect surface acoustic waves on a thin layer of (Ga,Mn)(As,P). The out-of-plane uniaxial magnetic anisotropy of this dilute magnetic semiconductor is very sensitive to the strain of the layer, making it an ideal test material for the dynamic control of magnetization via magneto-striction. The time-domain measurement of the amplitude and phase of the transmitted SAW during magnetic field sweeps indicated a clear resonant behavior at a field close to the one calculated to give a precession frequency equal to the SAW frequency. A resonance was observed from 5K to 85K, just below the Curie temperature of the layer. A full analytical treatment of the coupled magnetization/acoustic dynamics showed that the magneto-strictive coupling modifies the elastic constants of the material and accordingly the wave-vector solution to the elastic wave equation. The shape and position of the resonance were well reproduced by the calculations, in particular the fact that velocity (phase) variations resonated at lower fields than the acoustic attenuation variations

Strain-Control of the magnetic anisotropy in (Ga,Mn)(As,P) ferromagnetic semiconductor layers

A small fraction of phosphorus (up to 10 %) was incorporated in ferromagnetic (Ga,Mn)As epilayers grown on a GaAs substrate. P incorporation allows reducing the epitaxial strain or even change its sign, resulting in strong modifications of the magnetic anisotropy. In particular a reorientation of the easy axis toward the growth direction is observed for high P concentration. It offers an interesting alternative to the metamorphic approach, in particular for magnetization reversal experiments where epitaxial defects stongly affect the domain wall propagation

Stabilisation of HF soluble and HCL resistant organic matter in sloping tropical soils under slash and burn agriculture

Soil organic matter (SOM) stabilisation on tropical sloping land can be influenced by slash burning and erosion processes. However, information on the behaviour of potentially stable components of organic matter on burned sites is scarce. This study is focused on organic matter soluble after demineralisation of the samples with hydrofluoric acid (HF soluble) and organic matter remaining after hydrolysis with hydrochloric acid (HCl resistant), which are both part of the potentially stabile OM fraction in tropical soils. The objective was to examine their contribution to carbon stabilisation along a toposequence of soil profiles sampled in a small cultivated catchment in Northern Laos with slash burning as common agricultural practice. Bulk soil as well as residues after acid hydrolysis using HCl have been analysed for chemical composition and mean residence time of SOM. The tropical soils showed similar amounts of HIP soluble and HCl resistant OC, representing between 20 and 60% of the total OC of the soils. OC stabilisation at the sites is chiefly determined by mineral interactions as shown by the good correlations of the clay and the HF soluble OC contents with C-14 activity. Analysis of the chemical structure by solid state C-13 nuclear magnetic resonance spectroscopy (C-13 CPMAS NMR) showed that aromatic carbon contributes substantially to HCl resistant organic matter. The C-14 activity of the hydrolysis residue was lower compared to the untreated soil, reaching a C-14 age of around 1000 years B.P. in B horizons. This is consistent with the observation that chemical recalcitrant black carbon, produced by slash burning, may remain on site for a long time, once it is incorporated into the mineral soil

Recent progress in tetravalent terbium chemistry

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Autophagy mediates phosphatidylserine exposure and phagosome degradation during apoptosis through specific functions of GABARAP/LGG-1 and LC3/LGG-2

International audiencePhagocytosis and macroautophagy/autophagy are 2 processes involved in lysosome-mediated clearance of extracellular and intracellular components, respectively. Recent studies have identified the recruitment of the autophagic protein LC3 during phagocytosis of apoptotic corpses in what is now called LC3-associated phagocytosis (LAP). LAP is a distinct process from autophagy but it relies on some members of the autophagy pathway to allow efficient degradation of the phagocytosed cargo. We investigated whether both LC3/LGG-2 and GABARAP/LGG-1 are involved in phagocytosis of apoptotic corpses during embryonic development of Caenorhabditis elegans. We discovered that both LGG-1 and LGG-2 are involved in the correct elimination of apoptotic corpses, but that they have different functions. lgg-1 and lgg-2 mutants present a delay in phagocytosis of apoptotic cells but genetic analyses indicate that LGG-1 and LGG-2 act upstream and downstream of the engulfment pathways, respectively. Moreover, LGG-1 and LGG-2 display different cellular localizations with enrichment in apoptotic corpses and phagocytic cells, respectively. For both LGG-1 and LGG-2, subcellular localization is vesicular and dependent on UNC-51/ULK1, BEC-1/BECN1 and the lipidation machinery, indicating that their functions during phagocytosis of apoptotic corpses mainly rely on autophagy. Finally, we show that LGG-1 is involved in the exposure of the 'eat-me signal' phosphatidylserine at the surface of the apoptotic cell to allow its recognition by the phagocytic cell, whereas LGG-2 is involved in later steps of phagocytosis to allow efficient cell corpse clearance by mediating the maturation/degradation of the phagosome

Synthesis and single-crystal structural study of an original low-temperatureform α of BaTbF6

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Utilisation digestive des graines protéagineuses traitées et leur valorisation par les vaches laitières

National audienc

Evaluation des rejets d’azote vers l'environnement chez le jeune bovin en engraissement par une approche isotopique

Numéro Hors-Série ; Session : Empreinte environnementale de la viande et des produits carnésAnimals are 15N-enriched compared to the diet they consume and the extent of this isotopic enrichment ( 15N) has been shown to vary according to different animal and environmental factors. We investigated the relationship between 15N, the efficiency of N utilization (ENU) and N excretion in young finishing beef cattle. Young bulls (n=35) were individually fed after weaning one of the 4 experimental diets based on either corn silage or pre-wilted grass silage offered at two different intake levels (high and low) according to a complete block design experiment. Plasma was sampled from all animals the day before the first slaughter and diet ingredients were sampled throughout the experiment. The natural abundance of 15N in plasma protein and diets was analyzed and 15N was calculated. The N balance of 8 extra animals fed the same diets was conducted according to a replicated 4 × 4 Latin square design to evaluate the fecal and urinary N excretion. Animals on the corn silage diets had higher ENU and lower total N excretion and 15N compared to grass silage fed animals. The 15N had a good correlation with ENU and could be used to evaluate the environmental N excretion of beef cattle in different feeding conditions