Etude par diffraction neutronique des composés Mn23Y6D x

Neutron diffraction experiments have permitted us to locate hydrogen (deuterium) atoms in the compounds Mn23Y6Dx, x = 8.3; 18; 23 whose magnetic behavior is appreciably different from that of the alloy Mn23Y6. No evidence of a Mn-Mn critical distance corresponding to a Pauli-paramagnetic behavior of the hydride (deuteride) has been found.La localisation des atomes d'hydrogène (deutérium) a été déterminée par diffraction neutronique sur les phases de composition Mn23Y 6Dx, x = 8,3; 18; 23, dont le comportement magnétique est sensiblement différent de celui de l'alliage Mn23Y 6. On montre qu'il n'existe pas de distance critique Mn-Mn au-delà de laquelle l'hydrure (deutérure) devient un paramagnétique de Pauli

Rochechouart 2017-Drilling Campaign: First Results

No abstract available

Factors affecting body temperatures of toads

Factors influencing levels and rates of variation of body temperature ( T b ) in montane Bufo boreas boreas and in lowland Bufo boreas halophilus were investigated as an initial step toward understanding the role of natural thermal variation in the physiology and energetics of these ectothermic animals. Body temperatures of boreas can vary 25–30° C over 24-h periods. Such variation is primarily due to both nocturnal and diurnal activity and the physical characteristics of the montane environment. Bufo boreas halophilus are primarily nocturnal except during breeding and are voluntarily active at body temperatures ranging between 10 and 25° C. Despite variation in T b encountered in the field, boreas select a narrow range of T b in a thermal gradient, averaging 23.5 and 26.2° C for fasted individuals maintained under field conditions or acclimated to 20° C, respectively. In a thermal gradient the mean T b of fasted halophilus acclimated to 20° C is 23.9° C. Skin color of boreas varies in the field from very dark to light. The dark skins absorb approximately 4% more radiation than the light ones. Light colored boreas should absorb approximately 5% more radiation than similarly colored halophilus . Evaporative water losses increase directly with skin temperatures and vapor pressure deficit in both subspecies. Larger individuals heat and cool more slowly than smaller ones. Calculation of an enery budget for boreal toads suggests that they could sit in direct sunlight for long periods without fatally overheating, providing the skin was continually moist.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47722/1/442_2004_Article_BF00344732.pd

Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω0T<5.58×10-8, Ω0V<6.35×10-8, and Ω0S<1.08×10-7 at a reference frequency f0=25 Hz. © 2018 American Physical Society

Mechanical Properties and Microstructural Characterization of Aged Nickel-based Alloy 625 Weld Metal

The aim of this work was to evaluate the different phases formed during solidification and after thermal aging of the as-welded 625 nickel-based alloy, as well as the influence of microstructural changes on the mechanical properties. The experiments addressed aging temperatures of 650 and 950 A degrees C for 10, 100, and 200 hours. The samples were analyzed by electron microscopy, microanalysis, and X-ray diffraction in order to identify the secondary phases. Mechanical tests such as hardness, microhardness, and Charpy-V impact test were performed. Nondestructive ultrasonic inspection was also conducted to correlate the acquired signals with mechanical and microstructural properties. The results show that the alloy under study experienced microstructural changes when aged at 650 A degrees C. The aging was responsible by the dissolution of the Laves phase formed during the solidification and the appearance of gamma aEuro(3) phase within interdendritic region and fine carbides along the solidification grain boundaries. However, when it was aged at 950 A degrees C, the Laves phase was continuously dissolved and the excess Nb caused the precipitation of the delta-phase (Ni3Nb), which was intensified at 10 hours of aging, with subsequent dissolution for longer periods such as 200 hours. Even when subjected to significant microstructural changes, the mechanical properties, especially toughness, were not sensitive to the dissolution and/or precipitation of the secondary phases

On the progenitor of binary neutron star merger GW170817

On 2017 August 17 the merger of two compact objects with masses consistent with two neutron stars was discovered through gravitational-wave (GW170817), gamma-ray (GRB 170817A), and optical (SSS17a/AT 2017gfo) observations. The optical source was associated with the early-type galaxy NGC 4993 at a distance of just ∼40 Mpc, consistent with the gravitational-wave measurement, and the merger was localized to be at a projected distance of ∼2 kpc away from the galaxy's center. We use this minimal set of facts and the mass posteriors of the two neutron stars to derive the first constraints on the progenitor of GW170817 at the time of the second supernova (SN). We generate simulated progenitor populations and follow the three-dimensional kinematic evolution from binary neutron star (BNS) birth to the merger time, accounting for pre-SN galactic motion, for considerably different input distributions of the progenitor mass, pre-SN semimajor axis, and SN-kick velocity. Though not considerably tight, we find these constraints to be comparable to those for Galactic BNS progenitors. The derived constraints are very strongly influenced by the requirement of keeping the binary bound after the second SN and having the merger occur relatively close to the center of the galaxy. These constraints are insensitive to the galaxy's star formation history, provided the stellar populations are older than 1 Gyr

Antibodies to surface epitopes of the carbohydrate larval antigen CarLA are associated with passive protection in strongylid nematode challenge infections

Sheep were immunized by multiple truncated infections with the gastrointestinal nematodes Trichostrongylus colubriformis, Haemonchus contortus and Teladorsagia circumcincta. Three infections with T. colubriformis of 14 days plus five booster doses of L3 stimulated highly effective protection against challenge (99%). Three infections of 14 days plus three booster doses with H. contortus also resulted in significant protection against challenge infection (87%), but the same procedure was not effective for T. circumcincta. Antibodies derived from gastrointestinal mucus of these immunized sheep were tested for their ability to reduce worm burden following injection of antibody-coated exsheathed larvae into the abomasum (H. contortus and T. circumcincta) or duodenum (T. colubriformis) of nematode-naive sheep in a passive immunity test. The IgG fraction from the mucus of immunized sheep reduced worm burdens by 62%, 76% and 91% in three tests with T. colubriformis but was not effective for either of the abomasal dwelling nematodes H. contortus and T. circumcincta. Antibodies in immune mucus predominantly recognized two larval surface antigens on immunoblots of L3 extract, a high MW surface glycoprotein and the carbohydrate larval antigen (CarLA). Antibodies raised against purified T. colubriformis glycoprotein Tc-120 and CarLA were tested in the passive immunity model and it was found that only the antibody against CarLA resulted in a significant reduction of infection (87%). The protective anti-CarLA antibodies strongly recognized the surface of living T. colubriformis L3. Antibodies from abomasal mucus of sheep immunized by H. contortus and T. circumcincta infections reacted weakly with CarLA and the larval surface and did not reduce worm counts in a passive immunity test. The results provide further evidence that the larval surface carbohydrate antigen CarLA has potential as a mucosal immunogen for a strongylid nematode vaccine