Electrical Conductance of Bolted Copper Joints for Cryogenic Applications

International audienceWe present the results of electric contact resistance measurements at low temperatures on copper-to-copper bolted joints. Our accurate and systematic data display a rather small dispersion, and maybe a useful tool for cryogenic applications like pulse-tubes, dilution refrigerators and nuclear refrigerators

Three-dimensional tomographic imaging of the magnetization vector field using Fourier transform holography

In recent years, interest in expanding from 2D to 3D systems has grown in the magnetism community, from exploring new geometries to broadening the knowledge on the magnetic textures present in thick samples, and with this arises the need for new characterization techniques, in particular tomographic imaging. Here, we present a new tomographic technique based on Fourier transform holography, a lensless imaging technique that uses a known reference in the sample to retrieve the object of interest from its diffraction pattern in one single step of the calculation, overcoming the phase problem inherent to reciprocal-space-based techniques. Moreover, by exploiting the phase contrast instead of the absorption contrast, thicker samples can be investigated. We obtain a 3D full-vectorial image of a 800-nm-thick extended Fe/Gd multilayer in a 5 − µ m -diameter circular field of view with a resolution of approximately 80 nm. The 3D image reveals wormlike domains with magnetization pointing mostly out of plane near the surface of the sample but that falls in-plane near the substrate. Since the FTH setup is fairly simple, it allows modifying the sample environment. Therefore this technique could enable in particular a 3D view of the magnetic configuration's response to an external magnetic field

Cardiolipin content controls mitochondrial coupling and energetic efficiency in muscle

International audienceUnbalanced energy partitioning participates in the rise of obesity, a major public health concern in many countries. Increasing basal energy expenditure has been proposed as a strategy to fight obesity yet raises efficiency and safety concerns. Here, we show that mice deficient for a muscle-specific enzyme of very-long-chain fatty acid synthesis display increased basal energy expenditure and protection against high-fat diet–induced obesity. Mechanistically, muscle-specific modulation of the very-long-chain fatty acid pathway was associated with a reduced content of the inner mitochondrial membrane phospholipid cardiolipin and a blunted coupling efficiency between the respiratory chain and adenosine 5′-triphosphate (ATP) synthase, which was restored by cardiolipin enrichment. Our study reveals that selective increase of lipid oxidative capacities in skeletal muscle, through the cardiolipin-dependent lowering of mitochondrial ATP production, provides an effective option against obesity at the whole-body level