815 research outputs found
Determination of Gd concentration profile in UO2-Gd2O3 fuel pellets
A transversal mapping of the Gd concentration was measured in UO2-Gd2O3
nuclear fuel pellets by electron paramagnetic resonance spectroscopy (EPR). The
quantification was made from the comparison with a Gd2O3 reference sample. The
nominal concentration in the pellets is UO2: 7.5 % Gd2O3. A concentration
gradient was found, which indicates that the Gd2O3 amount diminishes towards
the edges of the pellets. The concentration varies from (9.3 +/- 0.5)% in the
center to (5.8 +/- 0.3)% in one of the edges. The method was found to be
particularly suitable for the precise mapping of the distribution of Gd3+ ions
in the UO2 matrix.Comment: 10 pages, 5 figures, 2 tables. Submitted to Journal of Nuclear
Material
Pure spin current manipulation in antiferromagnetically exchange coupled heterostructures
We present a model to describe the spin currents generated by ferromagnet/spacer/ferromagnet exchange coupled trilayer systems and heavy metal layers with strong spin-orbit coupling. By exploiting the magnitude of the exchange coupling (oscillatory RKKY-like coupling) and the spin-flop transition in the magnetization process, it has been possible to produce spin currents polarized in arbitrary directions. The spin-flop transition of the trilayer system originates pure spin currents whose polarization vector depends on the exchange field and the magnetization equilibrium angles. We also discuss a protocol to control the polarization sign of the pure spin current injected into the metallic layer by changing the initial conditions of magnetization of the ferromagnetic layers previously to the spin pumping and inverse spin Hall effect experiments. The small differences in the ferromagnetic layers lead to a change in the magnetization vector rotation that permits the control of the sign of the induced voltage components due to the inverse spin Hall effect. Our results can lead to important advances in hybrid spintronic devices with new functionalities, particularly, the ability to control microscopic parameters such as the polarization direction and the sign of the pure spin current through the variation of macroscopic parameters, such as the external magnetic field or the thickness of the spacer in antiferromagnetic exchange coupled systems.Fil: Avilés Félix, L.. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Butera, Alejandro Ricardo. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Resonancias Magnéticas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: González Chávez, D. E.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Sommer, R. L.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Gomez, Javier Enrique. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Resonancias Magnéticas; Argentin
Updated tests of scaling and universality for the spin-spin correlations in the 2D and 3D spin-S Ising models using high-temperature expansions
We have extended, from order 12 through order 25, the high-temperature series
expansions (in zero magnetic field) for the spin-spin correlations of the
spin-S Ising models on the square, simple-cubic and body-centered-cubic
lattices. On the basis of this large set of data, we confirm accurately the
validity of the scaling and universality hypotheses by resuming several tests
which involve the correlation function, its moments and the exponential or the
second-moment correlation-lengths.Comment: 21 pages, 8 figure
A study of logarithmic corrections and universal amplitude ratios in the two-dimensional 4-state Potts model
Monte Carlo (MC) and series expansion (SE) data for the energy, specific
heat, magnetization and susceptibility of the two-dimensional 4-state Potts
model in the vicinity of the critical point are analysed. The role of
logarithmic corrections is discussed and an approach is proposed in order to
account numerically for these corrections in the determination of critical
amplitudes. Accurate estimates of universal amplitude ratios ,
, and are given, which arouse
new questions with respect to previous works
High-temperature expansions through order 24 for the two-dimensional classical XY model on the square lattice
The high-temperature expansion of the spin-spin correlation function of the
two-dimensional classical XY (planar rotator) model on the square lattice is
extended by three terms, from order 21 through order 24, and analyzed to
improve the estimates of the critical parameters.Comment: 7 pages, 2 figure
Effect of boundaries on vacuum field fluctuations and radiation-mediated interactions between atoms
In this paper we discuss and review several aspects of the effect of boundary
conditions and structured environments on dispersion and resonance interactions
involving atoms or molecules, as well as on vacuum field fluctuations. We first
consider the case of a perfect mirror, which is free to move around an
equilibrium position and whose mechanical degrees of freedom are treated
quantum mechanically. We investigate how the quantum fluctuations of the
mirror's position affect vacuum field fluctuations for both a one-dimensional
scalar and electromagnetic field, showing that the effect is particularly
significant in the proximity of the moving mirror. This result can be also
relevant for possible gravitational effects, since the field energy density
couples to gravity. We stress that this interaction-induced modification of the
vacuum field fluctuations can be probed through the Casimir-Polder interaction
with a polarizable body, thus allowing to detect the effect of the mirror's
quantum position fluctuations. We then consider the effect of an environment
such as an isotropic photonic crystal or a metallic waveguide, on the resonance
interaction between two entangled identical atoms, one excited and the other in
the ground state. We discuss the strong dependence of the resonance interaction
with the relative position of the atomic transition frequency with the gap of
the photonic crystal in the former case, and with the cut-off frequency of
waveguide in the latter.Comment: 8 pages, 2 figures, Proceedings of the Eighth International Workshop
DICE 2016 Spacetime - Matter - Quantum Mechanic
The RANLUX generator: resonances in a random walk test
Using a recently proposed directed random walk test, we systematically
investigate the popular random number generator RANLUX developed by Luescher
and implemented by James. We confirm the good quality of this generator with
the recommended luxury level. At a smaller luxury level (for instance equal to
1) resonances are observed in the random walk test. We also find that the
lagged Fibonacci and Subtract-with-Carry recipes exhibit similar failures in
the random walk test. A revised analysis of the corresponding dynamical systems
leads to the observation of resonances in the eigenvalues of Jacobi matrix.Comment: 18 pages with 14 figures, Essential addings in the Abstract onl
A mindset of competition versus cooperation moderates the impact of social comparison on self-evaluation
International audienc
Cytoprotective effects of the antioxidant phytochemical indicaxanthin in beta-thalassemia red blood cells
Antioxidant phytochemicals are investigated as novel treatments for supportive therapy in b-thalassemia. The dietary
indicaxanthin was assessed for its protective effects on human b-thalassemic RBCs submitted in vitro to oxidative haemolysis
by cumene hydroperoxide. Indicaxanthin at 1.0\u201310 mMenhanced the resistance to haemolysis dose-dependently. In addition,
it prevented lipid and haemoglobin (Hb) oxidation, and retarded vitamin E and GSH depletion. After ex vivo spiking of blood
from thalassemia patients with indicaxanthin, the phytochemical was recovered in the soluble cell compartment of the RBCs.
A spectrophotometric study showed that indicaxanthin can reduce perferryl-Hb generated in solution from met-Hb and
hydrogen peroxide (H2O2), more effectively than either Trolox or vitamin C.
Collectively our results demonstrate that indicaxanthin can be incorporated into the redox machinery of b-thalassemic RBC
and defend the cell from oxidation, possibly interfering with perferryl-Hb, a reactive intermediate in the hydroperoxidedependent
Hb degradation. Opportunities of therapeutic interest for b-thalassemia may be considered
Field observables near a fluctuating boundary
We review several aspects related to the confinement of a massless scalar field in a cavity with a movable conducting wall of finite mass, free to move around its equilibrium position to which it is bound by a harmonic potential, and whose mechanical degrees of freedom are described quantum mechanically. This system, for small displacements of the movable wall from its equilibrium position, can be described by an e↵ective interaction Hamiltonian between the field and the mirror, quadratic in the field operators and linear in the mirror operators. In the interacting, i.e. dressed, ground state, we first consider local field observables such as the field energy density: we evaluate changes of the field energy density in the cavity with the movable wall with respect to the case of a fixed wall, and corrections to the usual Casimir forces between the two walls. We then investigate the case of two one-dimensional cavities separated by a movable wall of finite mass, with two massless scalar fields defined in the two cavities. We show that in this case correlations between the squared fields in the two cavities exist, mediated by the movable wall, at variance with the fixed-wall case
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