A Cryogenic High-Reynolds Turbulence Experiment at CERN

The potential of cryogenic helium flows for studying high-Reynolds number turbulence in the laboratory has been recognised for a long time and implemented in several small-scale hydrodynamic experiments. With its large superconducting particle accelerators and detector magnets, CERN, the European Laboratory for Particle Physics, has become a major world center in helium cryogenics, with several large helium refrigerators having capacities up to 18 kW @ 4.5 K. Combining a small fraction of these resources with the expertise of three laboratories at the forefront of turbulence research, has led to the design, swift implementation, and successful operation of GReC (Grands Reynolds Cryogéniques) a large axisymmetric turbulent-jet experiment. With flow-rates up to 260 g/s of gaseous helium at ~ 5 K and atmospheric pressure, Reynolds numbers up to 107 have been achieved in a 4.6 m high, 1.4 m diameter cryostat. This paper presents the results of the first runs and describes the experimental set-up comprehensively equipped with "hot" wire micro-anemometers, acoustic scattering vorticity measurements and a large-bandwidth data acquisition system

MicroRNA and Target Protein Patterns Reveal Physiopathological Features of Glioma Subtypes

Gliomas such as oligodendrogliomas (ODG) and glioblastomas (GBM) are brain tumours with different clinical outcomes. Histology-based classification of these tumour types is often difficult. Therefore the first aim of this study was to gain microRNA data that can be used as reliable signatures of oligodendrogliomas and glioblastomas. We investigated the levels of 282 microRNAs using membrane-array hybridisation and real-time PCR in ODG, GBM and control brain tissues. In comparison to these control tissues, 26 deregulated microRNAs were identified in tumours and the tissue levels of seven microRNAs (miR-21, miR-128, miR-132, miR-134, miR-155, miR-210 and miR-409-5p) appropriately discriminated oligodendrogliomas from glioblastomas. Genomic, epigenomic and host gene expression studies were conducted to investigate the mechanisms involved in these deregulations. Another aim of this study was to better understand glioma physiopathology looking for targets of deregulated microRNAs. We discovered that some targets of these microRNAs such as STAT3, PTBP1 or SIRT1 are differentially expressed in gliomas consistent with deregulation of microRNA expression. Moreover, MDH1, the target of several deregulated microRNAs, is repressed in glioblastomas, making an intramitochondrial-NAD reduction mediated by the mitochondrial aspartate-malate shuttle unlikely. Understanding the connections between microRNAs and bioenergetic pathways in gliomas may lead to identification of novel therapeutic targets

An isotropic earth field scalar magnetometer using optically pumped helium 4

Optical pumping was originally suggested by Kastler [1] in 1950 and since the early 1960's numerous helium magnetometers based upon that technique have been developed. Since then the main evolution has consisted in the advent in 1986 of tunable lasers suitable for helium optical pumping. They led to a renewed interest in helium magnetometry essentially because the magnetometer resolution is expected to significantly increase with the optical power. For airborne applications however, these improvements must be associated with a reduction of the anisotropy inherent to optically pumped helium sensors in order to be useful. Our group has therefore recently designed a new helium magnetometer structure which suppresses the sensor orientation effects. To achieve this we perform both the laser optical pumping and the RF resonance excitation in a fixed configuration whatever the sensor orientation with respect to the magnetic field to be measured is. This is performed by rotating simultaneously the laser linear polarization and the RF field direction to maintain them perpendicular to the static field. In this paper, we explain the principles of operation of such a magnetometer and describe this new sensor which drastically reduces the amplitude and frequency anisotropies of standard helium pumped resonance magnetometers. Finally, we present the preliminary sensor isotropy test results which show a perfect amplitude isotropy and frequency effects smaller than 150 pT

Elastic anomalies at the first order transition in Lu5Ir4Si10

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Static and dynamical elastic behavior of Lu5Ir4Si10 around its first-order structural phase transition

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Instabilities by local heating below an interface

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Influence of the gravity on thermal lens oscillations - Results of the 23rd ESA parabolic flight campaign

cited By 2International audienceno abstrac

Instabilities produced by hot-wire heating below a free surface with emphasis on relationships between temporal and spatial dynamics

Bifurcations up to the appearance of temporal chaos are observed when hot-wire heats below a free surface. New observations are reported, and some emphasis is laid on the relationships between temporal dynamics produced by signals averaged along the hot-wire and spatial behaviour of waves generated above it

Elastic properties of the charge density wave system HoTe 3

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