4,170 research outputs found

    Sea surface temperature of the coastal zones of France

    Get PDF
    Thermal gradients in French coastal zones for the period of one year were mapped in order to enable a coherent study of certain oceanic features detectable by the variations in the sea surface temperature field and their evolution in time. The phenomena examined were mesoscale thermal features in the English Channel, the Bay of Biscay, and the northwestern Mediterranean; thermal gradients generated by French estuary systems; and diurnal heating in the sea surface layer. The investigation was based on Heat Capacity Mapping Mission imagery

    Sea surface temperature of the coastal zones of France

    Get PDF
    The results of an investigation to map the various thermal gradients in the coastal zones of France are presented. Paricular emphasis is given to the natural phenomena and man made thermal effluents. It is shown that a close correlation exist between wind speed direction and the offshore width of the effluent

    Characterization and modeling of precipitation kinetics in an Al-Zn-Mg alloy

    Get PDF
    Abstract The precipitation kinetics in AA7108.70 Al-Zn -Mg alloy have been investigated by small angle X-ray scattering and transmission electron microscopy, and computer modeled by use of an internal state variable model concerning two regimes, (i) precipitation and growth and (ii) growth and coarsening. The modeling and experiments were done for isothermal heat treatment at 120, 140, 150, 160 and 170°C. These treatments were also compared with the industrial two step T6 treatment

    Refractory hypoglycaemia in a dog infected with Trypanosoma congolense

    Get PDF
    A 20 kg German shepherd dog was presented to a French veterinary teaching hospital for seizures and hyperthermia. The dog had returned 1 month previously from a six-month stay in Senegal and sub-Saharan Africa. Biochemistry and haematology showed severe hypoglycaemia (0.12 g/L), anaemia and thrombocytopenia. Despite administration of large amounts of glucose (30 mL of 30% glucose IV and 10 mL of 70% sucrose by gavage tube hourly), 26 consecutive blood glucose measurements were below 0.25 g/L (except one). Routine cytological examination of blood smears revealed numerous free extracytoplasmic protozoa consistent with Trypanosoma congolense. PCR confirmed a Trypanosoma congolense forest-type infection. Treatment consisted of six injections of pentamidine at 48-hour intervals. Trypanosomes had disappeared from the blood smears four days following the first injection. Clinical improvement was correlated with the normalization of laboratory values. The infection relapsed twice and the dog was treated again; clinical signs and parasites disappeared and the dog was considered cured; however, 6 years after this incident, serological examination by ELISA T. congolense was positive. The status of this dog (infected or non-infected) remains unclear. Hypoglycaemia was the most notable clinical feature in this case. It was spectacular in its severity and in its refractory nature; glucose administration seemed only to feed the trypanosomes, indicating that treatment of hypoglycaemia may in fact have been detrimental

    Progress on a spherical TPC for low energy neutrino detection

    Full text link
    The new concept of the spherical TPC aims at relatively large target masses with low threshold and background, keeping an extremely simple and robust operation. Such a device would open the way to detect the neutrino-nucleus interaction, which, although a standard process, remains undetected due to the low energy of the neutrino-induced nuclear recoils. The progress in the development of the fist 1 m3^3 prototype at Saclay is presented. Other physics goals of such a device could include supernova detection, low energy neutrino oscillations and study of non-standard properties of the neutrino, among others.Comment: 3 pages, talk given at the 9th Workshop on Topics in Astroparticle and Underground Physics, Zaragoza, September 10-1

    Dynamics of Fluid Vesicles in Oscillatory Shear Flow

    Full text link
    The dynamics of fluid vesicles in oscillatory shear flow was studied using differential equations of two variables: the Taylor deformation parameter and inclination angle θ\theta. In a steady shear flow with a low viscosity ηin\eta_{\rm {in}} of internal fluid, the vesicles exhibit steady tank-treading motion with a constant inclination angle θ0\theta_0. In the oscillatory flow with a low shear frequency, θ\theta oscillates between ±θ0\pm \theta_0 or around θ0\theta_0 for zero or finite mean shear rate γ˙m\dot\gamma_{\rm m}, respectively. As shear frequency fγf_{\gamma} increases, the vesicle oscillation becomes delayed with respect to the shear oscillation, and the oscillation amplitude decreases. At high fγf_{\gamma} with γ˙m=0\dot\gamma_{\rm m}=0, another limit-cycle oscillation between θ0π\theta_0-\pi and θ0-\theta_0 is found to appear. In the steady flow, θ\theta periodically rotates (tumbling) at high ηin\eta_{\rm {in}}, and θ\theta and the vesicle shape oscillate (swinging) at middle ηin\eta_{\rm {in}} and high shear rate. In the oscillatory flow, the coexistence of two or more limit-cycle oscillations can occur for low fγf_{\gamma} in these phases. For the vesicle with a fixed shape, the angle θ\theta rotates back to the original position after an oscillation period. However, it is found that a preferred angle can be induced by small thermal fluctuations.Comment: 11 pages, 13 figure

    POLDER observations of cloud bidirectional reflectances compared to a plane-parallel model using the International Satellite Cloud Climatology Project cloud phase functions

    Full text link
    International audienceThis study investigates the validity of the plane-parallel cloud model and in addition the suitability of water droplet and ice polycrystal phase functions for stratocumulus and cirrus clouds, respectively. To do that, we take advantage of the multidirectional viewing capability of the Polarization and Directionality of the Earth's Reflectances (POLDER) instrument which allows us to characterize the anisotropy of the reflected radiation field. We focus on the analysis of airborne-POLDER data acquired over stratocumulus and cirrus clouds during two selected flights (on April 17 and April 18, 1994) of the European Cloud and Radiation Experiment (EUCREX'94) campaign. The bidirectional reflectances measured in the 0.86 μm channel are compared to plane-parallel cloud simulations computed with the microphysical models used by the International Satellite Cloud Climatology Project (ISCCP). Although clouds are not homogeneous plane-parallel layers, the extended cloud layers under study appear to act, on average, as a homogeneous plane-parallel layer. The standard water droplet model (with an effective radius of 10 μm) used in the ISCCP analysis seems to be suitable for stratocumulus clouds. The relative root-mean-square difference between the observed bidirectional reflectances and the model is only 2%. For cirrus clouds, the water droplet cloud model is definitely inadequate since the rms difference rises to 9%; when the ice polycrystal model chosen for the reanalysis of ISCCP data is used instead, the rms difference is reduced to 3%

    Nucleation of Al3Zr and Al3Sc in aluminum alloys: from kinetic Monte Carlo simulations to classical theory

    Get PDF
    Zr and Sc precipitate in aluminum alloys to form the compounds Al3Zr and Al3Sc which for low supersaturations of the solid solution have the L12 structure. The aim of the present study is to model at an atomic scale this kinetics of precipitation and to build a mesoscopic model based on classical nucleation theory so as to extend the field of supersaturations and annealing times that can be simulated. We use some ab-initio calculations and experimental data to fit an Ising model describing thermodynamics of the Al-Zr and Al-Sc systems. Kinetic behavior is described by means of an atom-vacancy exchange mechanism. This allows us to simulate with a kinetic Monte Carlo algorithm kinetics of precipitation of Al3Zr and Al3Sc. These kinetics are then used to test the classical nucleation theory. In this purpose, we deduce from our atomic model an isotropic interface free energy which is consistent with the one deduced from experimental kinetics and a nucleation free energy. We test di erent mean-field approximations (Bragg-Williams approximation as well as Cluster Variation Method) for these parameters. The classical nucleation theory is coherent with the kinetic Monte Carlo simulations only when CVM is used: it manages to reproduce the cluster size distribution in the metastable solid solution and its evolution as well as the steady-state nucleation rate. We also find that the capillary approximation used in the classical nucleation theory works surprisingly well when compared to a direct calculation of the free energy of formation for small L12 clusters.Comment: submitted to Physical Review B (2004
    corecore