Gate-Controlled Skyrmion Chirality

Magnetic skyrmions are localized chiral spin textures, which offer great promise to store and process information at the nanoscale. In the presence of asymmetric exchange interactions, their chirality, which governs their dynamics, is generally considered as an intrinsic parameter set during the sample deposition. In this work, we experimentally demonstrate that this key parameter can be controlled by a gate voltage. We observed that the current-induced skyrmion motion can be reversed by the application of a gate voltage. This local and dynamical reversal of the skyrmion chirality is due to a sign inversion of the interfacial Dzyaloshinskii-Moriya interaction that we attribute to ionic migration of oxygen under gate voltage. Micromagnetic simulations show that the chirality reversal is a continuous transformation, in which the skyrmion is conserved. This gate-controlled chirality provides a local and dynamical degree of freedom, yielding new functionalities to skyrmion-based logic devices.Comment: 4 figure

Surface Layer Thickness Measurement from Eddy Current Profiling of Magnetic Coercivity

The use of eddy currents to measure the depth of surface modified layers in ferromagnetic materials has been the subject of numerous studies which are generally based on changes in impedance associated with differences in permeability (and to a lesser extent resistivity) in the surface modified layer compared to the core material (see for example reference 1). By changing the frequency, the material can be probed at different depths. Recently a different approach has been studied by Theiner et al[2] and others[3, 4] based on using eddy currents of different frequencies to probe spatial distributions of magnetic coercivity. This is obtained by measuring eddy current response while simultaneously cycling an externally applied magnetic field to near saturation. For a uniform material the impedance of the eddy current coil reaches a maximum at a field equal to the coercivity of the material, Hc.</p

Inference of Hardness from Magnetic Measurements in Pearlitic Steels

The possibility of monitoring material properties during the early stages of processing is an area of growing interest which offers potential not only for improving quality but also productivity. Of particular interest is the monitoring of mechanical properties on-line either during intermediate stages of processing or prior to shipping[1, 2].</p

Characterization of 5-ht6 receptor and expression of 5-ht6 mRNA in the rat brain during ontogenetic development

International audienceWe have determined the pharmacological characteristics of the rat 5-ht6 receptor stably expressed in CHO cells. Moreover, using RT-PCR experiments the in vivo expression of the gene encoding this receptor was studied in rat at various embryonic days (ED) starting from ED10 to birth (PN0) and at post-natal days (PN) up to PN36. The pharmacological analysis of the [3H]5-HT binding in stably transfected CHO cells expressing rat 5-ht6 receptors revealed the presence of a single class of high affinity saturable binding sites for 5-HT corresponding to an affinity constant: Kd=27.2+/-3.4 nM. This receptor also exhibited a high affinity for a number of typical and atypical antipsychotics, tricyclic antidepressant drugs and ergot alkaloïds. In stably transfected CHO cells, serotonin elicited a potent stimulation of adenylyl cyclase activity which was blocked by antipsychotic and antidepressant drugs. These results confirm the hypothesis that 5-ht6 receptors may correspond to an important target for atypical antipsychotics and reveal an original pharmacological profile for this receptor. The study of the ontogeny of the 5-ht6 mRNA in rat developing brain showed that 5-ht6 mRNA were first detectable with a high level on ED12, slighly decreased up to ED17 and then remained stable at high level until the adult age. The ontogenetic pattern of 5-ht6 mRNA expression appeared to correlate with the occurence of the first cell bodies of serotonergic neurons; the early expression of 5-ht6 mRNA and the fact that this receptor is positively coupled to the production of cAMP may suggest a role for 5-ht6 receptor in the early growth process involving the serotonergic system

Improved PWR LOCA simulations through refined core 3D simulations - An advanced 3D modelling and the associated METERO validation program

International audienceSystem thermalhydraulic codes have 3D models initially devoted to the prediction of large scale 3D effects during LBLOCAS, which were validated on the 2D-3D experimental program performed in UPTF, SCTF and CCTF facilities. 3D core simulations using one mesh per assembly may become a standard practice in near future and a local refinement of the highest power assemblies with sub-channel analysis becomes also possible. Looking at much finer multi-dimensional physical processes may provide a better accuracy of predictions but also requires more detailed and precise 3D models with a new specific validation. A detailed PIRT identifies all local flow processes to be considered at such a finer scale. Some of these processes may be neglected depending on the sub-component (core, lower plenum, annular downcomer, upper plenum) and depending on the physical situation encountered in accidental transients. An experimental program using the METERO test facility focuses on SLB, IBLOCA and SBLOCA situations in a PWR core to develop models and to validate them in a separateeffect way. Adiabatic water tests and air-water tests will provide information for the development and validation of turbulent diffusion and dispersion of heat and momentum due to time and space averaging, void dispersion, 3D wall friction and interfacial friction forces in non-isotropic media particularly in presence of non axial flows in a core

METERO-V experimental set-up: presentation and first results. Uniform flows through a 8x34 PWR-type rod bundle with mixing grids at Reynolds number ranging from 800 to 70000: pressure loss measurements

International audienceWe present the METERO-V set-up and preliminary results from the first set of experiments performed. METERO-V is a closed loop, equipped with a test section made of two halves of PWR-type rod bundles (8x34 rods) at full scale. The set up allows independent injection of different flow rates and temperatures at the inlet of each half of rod bundles. METERO-V experimental program focuses on IBLOCA (Intermediate Break Loss of Coolant Accident), SBLOCA (Small Break) and SLB (Steam Line Break) situations where significant 3D effects may occur in the core, with the aim to develop models and to validate them in a separated-effect way for CFD to system thermal-hydraulic scales. We present the preliminary results for a homogeneous inflow, varying the Reynolds number from laminar regime to fully turbulent regime. We measure pressure loss along the flow, across the grids and for the bare bundle. The axial pressure drop is successfully compared with available literature models and experimental data. Reproducibility and accuracy of the measurements is also very good. Future work will consist in non-symmetrical injections: velocities and/or temperatures

Uniform and non-uniform flows through a PWR-type rod bundle with mixing grids at Reynolds number ranging from 800 up to 70000: pressure loss measurements

International audienceWe present two sets of experiments performed on the METERO-V set-up. METERO-V is a closed loop, equipped with a test section made of two halves of PWR-type rod bundles (8x34 rods) at full scale. The set up allows injection of different flow rates and temperatures at the inlet of each half of rod bundles. METERO-V experimental program focuses on IBLOCA (Intermediate Break Loss of Coolant Accident), SBLOCA (Small Break) and SLB (Steam Line Break) situations where significant 3D effects may occur in the core, with the aim to develop models and to validate them in a separated-effect way for CFD to system thermal-hydraulic scales. We present preliminary results for a homogeneous inflow, varying the Reynolds number from laminar regime to fully turbulent regime. We measure pressure loss along the flow, across the grids and for the bare bundle. For non-symmetrical inlet velocity, we measure also transverse pressure across the test section at different elevations. For the homogeneous injections, the axial pressure drop is successfully compared with available literature models and experimental data. Principle of tests in non-symmetrical configuration is presented

Isolation and characterization of an endogenous peptide from rat brain interacting specifically with the serotoninergic 1B receptor subtypes

International audienceThe existence of endogenous compounds interacting with the serotonergic system was previously postulated. In the present work, rat brain tissues were extracted by acidic and organic procedures. The resulting extract was tested for its capacity to interact with the binding of [3H]5-hydroxytryptamine ([3H]5-HT) to 5-HT1 receptors. Compounds responsible for the observed inhibitory activities were isolated and purified by high pressure liquid chromatography.A tetrapeptide corresponding to a novel amino acid sequence Leu-Ser-Ala-Leu (LSAL) was identified. It reduces the binding of [3H]5-HT to 5-HT1 receptors at low concentration (IC50 = 10−10M). This effect corresponds to a specific interaction at 5-HT1B receptors since LSAL does not significantly affect other neurotransmitter bindings. LSAL appears heterogeneously distributed throughout the brain (hippocampus > cerebellum > striatum > brain stem) and in peripheral tissues (kidney > lung > stomach > blood > liver > spleen).Two other peptides, Leu-Ser (LS) and Ala-Leu (AL), were also purified. They hardly affected [3H]5-HT binding compared with LSAL. They presumably represent degradation products of the functional peptide LSAL. The fact that LSAL interacts specifically with 5-HT1B receptors that inhibit the release of neurotransmitters and particularly that of 5-HT itself suggests that this peptide may be involved in mechanisms controlling 5-HT neurotransmission and, accordingly, may play an important role in pathophysiological functions related to 5-HT activity