On the generation of internal waves by river plumes in subcritical initial conditions.

Internal waves (IWs) in the ocean span across a wide range of time and spatial scales and are now acknowledged as important sources of turbulence and mixing, with the largest observations having 200 m in amplitude and vertical velocities close to 0.5 m s-1. Their origin is mostly tidal, but an increasing number of non-tidal generation mechanisms have also been observed. For instance, river plumes provide horizontally propagating density fronts, which were observed to generate IWs when transitioning from supercritical to subcritical flow. In this study, satellite imagery and autonomous underwater measurements are combined with numerical modeling to investigate IW generation from an initial subcritical density front originating at the Douro River plume (western Iberian coast). These unprecedented results may have important implications in near-shore dynamics since that suggest that rivers of moderate flow may play an important role in IW generation between fresh riverine and coastal waters.

Uniaxial pressure setup for piezoresistance and magnetoresistance measurements in Heusler materials.

We report on a new uniaxial pressure experimental setup for electrical resistivity measurements working in a 77 K-500 K temperature range and in a magnetic field up to 8 T. Such a continuous uniaxial pressure device enables the study of the piezoresistance and the pressure induced change in electrical properties of bulk samples. Strong influence of uniaxial pressure on transport properties is shown for Ni-Co-Mn-In Heusler single crystal material. A shift of the martensite-austenite first order transformation temperature is measured with an applied uniaxial pressure leading to an electrical resistance changed by up to 120%.

Magneto-optical setup for in situ strain and transport measurements on superconductors.

A recently developed magneto-optical (MO) imaging setup for investigations on superconductors is reported. The main originality of our setup is its ability to combine both strain and transport measurements in the temperature range of 6-300 K with magneto-optical observations. We give here some theoretical considerations on the cryostat conception, which is a key point of our setup. In particular, the thermal and mechanical aspects are discussed. A detailed description of the MO setup and of the associated strain apparatus is given. Additionally, an example of MO strain and transport study on DyBCO coated conductors is given. Evidence of Luders Bands formation under strain in the Hastelloy is revealed by the field penetration inside cracks in the DyBCO and MgO layers. A correlation between the damaging morphology and the critical current at 70 K versus strain has been established.