[en] Using higher-order coherence of thermal light sources, the resolution power of standard x-ray imaging techniques can be enhanced. Here in this work, we applied the higher-order measurement to far-field x-ray diffraction and near-field phase contrast imaging (PCI), in order to achieve superresolution in x-ray diffraction and obtain enhanced intensity contrast in PCI. The cost of implementing such schemes is minimal compared to the methods that achieve similar effects by using entangled x-ray photon pairs.

No abstract available

[en] Understanding the electronic properties of actinide oxides under pressure poses a great challenge for experimental and theoretical studies. Here, we investigate the electronic structure of cubic phase uranium dioxide at different volumes using a combination of density functional theory and dynamical mean-field theory. The ab initio calculations predict an orbital-selective insulator-metal transition at a moderate pressure of ~45 GPa. At this pressure the uranium's 5f_5/2 state becomes metallic, while the 5f_7/2 state remains insulating up to about 60 GPa. In the metallic state, we observe a rapid decrease of the 5f occupation and total angular momentum with pressure. Simultaneously, the so-called "Zhang-Rice state", which is of predominantly 5f_5/2 character, quickly disappears after the transition into the metallic phase.

[en] A sodium borosilicate glass was irradiated sequentially and simultaneously with alpha particles and gold ions. Alpha particles induced partial recovery of the network damage and mechanical properties in the gold pre-irradiated glass, while no such recovery effect was observed during gold irradiation of the alpha pre-irradiated glass. The damage capacity of the gold ions was significantly reduced during simultaneous irradiation with alpha particles and gold ions. These results highlight that the irradiation sequence of the ions plays an important role in controlling the final damage level; and if properly employed, irradiation can be employed to induce defect recovery. Such results are of paramount importance to understand the radiation damage in nuclear reactor components and in nuclear waste glass matrices which are subjected to multiple particle irradiations. (authors)

[en] Characterizing the occupation statistics of random walks through confined geometries amounts to assessing the distribution of the travelled length and the number of collisions n performed by the stochastic process in a given region, for which remarkably simple Cauchy-like formulas were established in the case of branching Pearson random walks with exponentially distributed jumps. In this letter, we derive two key results: first, we show that such formulas strikingly carry over to the much broader class of branching processes with arbitrary jumps, and have thus a universal character; second, we obtain a stronger version of these formulas relating the travelled length density and the collision density at any point of the phase space. Our results are key to such technological issues as the analysis of radiation flow for nuclear reactor design and medical diagnosis and apply more broadly to physical and biological systems with diffusion, reproduction and death. (authors)

[en] Building on the complete account of quantum contributions to conductivity, we demonstrate that the resistance of thin superconducting films exhibits a non-monotonic temperature behavior due to the competition between weak localization, electron-electron interaction, and superconducting fluctuations. We show that superconducting fluctuations give rise to an appreciable decrease in the resistance even at temperatures well exceeding the superconducting transition temperature, T_c, with this decrease being dominated by the Maki-Thompson process. The transition to a global phase-coherent superconducting state occurs via the Berezinskii-Kosterlitz-Thouless (BKT) transition, which we observe both by power-law behavior in current-voltage characteristics and by flux flow transport in the magnetic field. The ratio T_BKT/T_c follows the universal relation.

[en] Here we prove, for any state in a conformal field theory defined on a set of boundary manifolds with corresponding classical holographic bulk geometry, that for any bipartition of the boundary into two non-clopen sets, the density matrix cannot be a tensor product of the reduced density matrices on each region of the bipartition. In particular, there must be entanglement across the bipartition surface. We extend this no-go theorem to general, arbitrary partitions of the boundary manifolds into non-clopen parts, proving that the density matrix cannot be a tensor product. Finally, this result gives a necessary condition for states to potentially correspond to holographic duals.

[en] The biphenyl/POPOP couple is known for its scintillation properties, but we describe in this letter its use for the discrimination between fast neutrons and gamma rays. More particularly, the influence of the matrix involved in this process is of interest, and for the first time pulse shape discrimination has been observed in non-common solvents such as heptane or ethanol. The discrimination efficiency of our systems is described in terms of figure of merit, angle between neutron and gamma lobes and scintillation performances. (authors)

[en] Simultaneous high-pressure X-ray diffraction and electrical resistance measurements have been carried out on a PbO-type α-FeSe_0.92 compound to a pressure of 44 GPa and temperatures down to 4 K using designer diamond anvils at synchrotron source. A ambient temperature, a structural phase transition from a tetragonal (P4/nmm) phase to an orthorhombic (Pbnm) phase is observed at 11 GPa and the Pbnm phase persists up to 74 GPa. The superconducting transition temperature (T_c) increases rapidly with pressure reaching a maximum of ∼28 K at ∼6 GPa and decreases at higher pressures, disappearing completely at 14.6 GPa. Simultaneous pressure-dependent X-ray diffraction and resistance measurements at low temperatures show superconductivity only in a low-pressure orthorhombic (Cmma) phase of the α-FeSe_0.92. Upon increasing pressure at 10 K near T_c, crystalline phases change from a mixture of orthorhombic (Cmma) and hexagonal (P63/mmc) phases to a high-pressure orthorhombic (Pbnm) phase near 6.4 GPa where T_c is maximum.

[en] Generalized atomic processes are proposed to establish a consistent description from the free-atom approach to the heated and even up to the cold solid. It is based on a rigorous introduction of the Fermi-Dirac statistics, Pauli blocking factors and on the respect of the principle of detailed balance via the introduction of direct and inverse processes. A probability formalism driven by the degeneracy of the free electrons enables to establish a link of atomic rates valid from the heated atom up to the cold solid. This allows to describe photoionization processes in atomic population kinetics and subsequent solid matter heating on a femtosecond time scale. The Auger effect is linked to the 3-body recombination via a generalized 3-body recombination that is identified as a key mechanism, along with the collisional ionization, that follows energy deposition by photoionization of inner shells when short, intense and high-energy radiation interacts with matter. Detailed simulations are carried out for aluminum that highlight the importance of the generalized approach. (authors)