231 research outputs found
Innovative preparation route for uranium carbide using citric acid as a carbon source
No full textThe preparation of uranium carbide (UC) by carbothermal reduction and its sintering into dense pellets by conventional means require high temperatures for long periods. We have developed a preparation route yielding fine UC powder with significantly increased sinterability. At first, a mixture of nanocrystalline UO2 embedded in amorphous carbon (nano-UO2/C) was obtained by thermal decomposition of a gel containing solubilised uranyl nitrate and citric acid. Later, the nano-UO2/C powder was treated in a conventional furnace or in a modified spark plasma sintering facility at elevated temperatures (≥1200°C) in order to obtain uranium carbide powder. The effects of initial composition, temperature, gas/vacuum atmosphere and the overall reaction kinetics are reported
On a contradiction between the classical (idealised) quantum theory of measurement and the conservation of the square of the total angular momentum in the Einstein-Podolsky-Rosen paradox
No full textExperimental investigation and thermodynamic modelling of the ThF4-PuF3 phase diagram
No full textPhase equilibria in the system ThF4-PuF3 were measured by DSC. Samples were encapsulated to prevent leak during the measurements and to protect the internal parts of the device from the corrosive fluoride vapours. Formation of intermediate compounds and solid solutions was investigated by XRD. A thermodynamic model based on CALPHAD approach was developed for the measured system. Good fit between measurements and phase equilibria calculated using the model was achieved
Norman barley
No full text Legge, W. G., Tucker, J. R., Bizimungu, B., Tekauz, A., Noll, J. S., Fetch Jr., T. G., Menzies, J. G., Haber, S., Savard, M. E., Vigier, B. J., Choo, T. M., Martin, R. A., Turkington, T. K., Rossnagel, B. G. and Harvey, B. L. 2011. Norman barley. Can. J. Plant Sci. 91: 1105–1113. Norman is a hulled two-row spring malting barley (Hordeum vulgare L.) cultivar derived from the cultivar CDC Kendall that was widely grown in western Canada and utilized commercially by the malting and brewing industry. Developed in 2000 by in vitro selection using deoxynivalenol mycotoxin in the medium of an anther culture system, Norman was evaluated in the Western Cooperative Two-row Barley Registration Test in 2005 and 2006, and the malting and brewing industry Collaborative Malting Barley Trials in 2006 and 2007, before being registered in 2009. Norman was also evaluated extensively for deoxynivalenol concentration in fusarium head blight (Fusarium graminearum Schwabe) nurseries from 2001 to 2009. Norman accumulates 25 to 30% less deoxynivalenol than its parent cultivar, CDC Kendall, but is similar in all other traits including malting quality. </jats:p
Hf and Nd isotopes in marine sediments: Constraints on global silicate weathering
No full textThe combined use of Lu–Hf and Sm–Nd isotope systems potentially offers a unique perspective for investigating continental erosion, but little is known about whether, and to what extent, the Hf–Nd isotope composition of sediments is related to silicate weathering intensity. In this study, Hf and Nd elemental and isotope data are reported for marine muds, leached Fe-oxide fractions and zircon-rich turbidite sands collected off the Congo River mouth, and from other parts of the SE Atlantic Ocean. All studied samples from the Congo fan (muds, Fe-hydroxides, sands) exhibit indistinguishable Nd isotopic composition (?Nd ~ ? 16), indicating that Fe-hydroxides leached from these sediments correspond to continental oxides precipitated within the Congo basin. In marked contrast, Hf isotope compositions for the same samples exhibit significant variations. Leached Fe-hydroxide fractions are characterized by ?Hf values (from ? 1.1 to + 1.3) far more radiogenic than associated sediments (from ? 7.1 to ? 12.0) and turbidite sands (from ? 27.2 to ? 31.6). ?Hf values for Congo fan sediments correlate very well with Al/K (i.e. a well-known index for the intensity of chemical weathering in Central Africa). Taken together, these results indicate that (1) silicate weathering on continents leads to erosion products having very distinctive Hf isotope signatures, and (2) a direct relationship exists between ?Hf of secondary clay minerals and chemical weathering intensity.These results combined with data from the literature have global implications for understanding the Hf–Nd isotope variability in marine precipitates and sediments. Leached Fe-hydroxides from Congo fan sediments plot remarkably well on an extension of the ‘seawater array’ (i.e. the correlation defined by deep-sea Fe–Mn precipitates), providing additional support to the suggestion that the ocean Hf budget is dominated by continental inputs. Fine-grained sediments define a diffuse trend, between that for igneous rocks and the ‘seawater array’, which we refer to as the ‘zircon-free sediment array’ (?Hf = 0.91 ?Nd + 3.10). Finally, we show that the Hf–Nd arrays for seawater, unweathered igneous rocks, zircon-free and zircon-bearing sediments (?Hf = 1.80 ?Nd + 2.35) can all be reconciled, using Monte Carlo simulations, with a simple weathering model of the continental crust.<br/
Neurosciences mathématiques / Mathematical neuroscience
No full text Responsable : Jonathan Touboul Publications del Molino L.C.G., Pakdaman K., Touboul J. et Wainrib G., « The real ginibre ensemble with real eigenvalues », Journal of Statistical Physics, vol. 163, n° 2, 2016, p. 303-323, DOI : 10.1007/s10955-016-1485-0. Freret-Hodara B., Cui Y., Griveau A., Vigier L., Arai Y., Touboul J. et Pierani A., « Enhanced abventricular proliferation compensates cell death in the embryonic cerebral cortex », Cerebral Cortex, vol. 27, n° 10, 2017, p. 4701-4718, DOI ..
DISTRIBUTION OF Al IN Nd-Fe-Al-B PERMANENT MAGNETS
No full text57Fe Mössbauer spectroscopy and electron microprobe analysis are used to determine the Al-distribution in the Nd-Fe-Al-B alloys ; Mössbauer spectroscopy gives the Al distribution between the J2 and K2 sites of Nd2Fe14B-like-phase ; microprobe analysis gives the composition of both matrix and minor phases and their evolution with sintering
Introduction
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Non-infectious causes of uveitis in 70 Swiss children
No full textMany diseases are linked with uveitis, but few studies have specifically looked at the noninfectious triggers of childhood uveitis in Central Europe. The charts of 70 paediatric patients with non-infectious uveitis admitted to the Department of Pediatrics, University of Bern, Switzerland, between 1983 and 1998 were therefore reviewed. In the patients the age at presentation with uveitis ranged between 0.3 and 16 y, median 8.5 y. Based on the localization, uveitis anterior was diagnosed in most cases (n = 40; 57%), followed by panuveitis (n = 20; 29%) and uveitis posterior (n = 10; 14%). Uveitis was chronic in 54 (77%) and acute in 16 (23%), bilateral in 38 (54%) and unilateral in 32 (46%) cases. An associated condition was noted in 32 (46%) cases: juvenile idiopathic arthritis in 24 cases, sarcoidosis and juvenile spondyloarthropathy in 3 cases, and Sjögren's syndrome and Behçet's disease in 1 case each. In the remaining 38 (54%) patients, no associated condition was diagnosed. It is concluded that in Swiss children, uveitis can be due to a wide spectrum of non-infectious diseases, juvenile idiopathic arthritis being the leading cause. In the majority of the children, no associated condition was recognized
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