Dynamic compressibility and aging in Wigner crystals and quantum glasses

We study the nonequilibrium linear response of quantum elastic systems pinned by quenched disorder with Schwinger-Keldysh real-time techniques complemented by a mean-field variational approach. We find (i) a quasiequilibrium regime in which the analytic continuation from the imaginary-time replica results holds provided the marginality condition is enforced, and (ii) an aging regime. The conductivity and compressibility are computed. The latter is found to cross over from its dynamic to static value on a scale set by the waiting time after a quench, an effect which can be probed in experiments in, e.g., Wigner glasses.     

The Fifth Order Peregrine Breather and Its Eight-Parameter Deformations Solutions of the NLS Equation

We construct here explicitly new deformations of the Peregrine breather of order 5 with 8 real parameters. This gives new families of quasi-rational solutions of the NLS equation and thus one can describe in a more precise way the phenomena of appearance of multi rogue waves. With this method, we construct new patterns of different types of rogue waves. We get at the same time, the triangular configurations as well as rings isolated. Moreover, one sees appearing for certain values of the parameters, new configurations of concentric rings.     

Raman Microspectroscopic study of Iberian pottery from the La Vispesa archaeological site,Spain

Raman microspectroscopy has been employed for the characterization of 16 samples of ancient Iberian pottery. These sherds of vessels were found in the archaeological site of La Vispesa in Tamarite de Litera (Huesca, Spain) and correspond to the Iberian time. The composition of certain mineral phases such as non‐plastic inclusions has been particularly considered with a view to obtaining information on the source materials and their provenance, as well as the technological conditions of ceramic production. Typical minerals such as calcite and quartz were found in most of the samples. The presence of anatase in a group of the samples suggested the use of different clays in the production of the vessels. Furthermore, the absence of rutile in these samples, together with the identification of calcite, is indicative of a mild firing temperature. Hematite was identified in all samples, both in the ceramic body and in the decoration. Differences in the position of the bands and relative intensities characterized hematite in terms of crystallinity and origin. An attempt to assign the samples to different production centers was made according to their chemical composition and morphology. Copyright © 2011 John Wiley & Sons, Ltd.     

B-CALM: An open-source GPU-based 3D-FDTD with multi-pole dispersion for plasmonics

Numerical calculations with finite-difference time-domain (FDTD) on metallic nanostructures in a broad optical spectrum require an accurate approximation of the permittivity of dispersive materials. In this paper, we present the algorithms behind B-CALM (Belgium-California Light Machine), an open-source 3D-FDTD solver operating on Graphical Processing Units with multi-pole dispersion models. Our modified architecture shows a reduction in computing times for multi-pole dispersion models. We benchmark B-CALM by computing the absorption efficiency of a metallic nanosphere on a broad spectral range with a six-poles Drude-Lorentz model and compare it with Mie theory.

     

Morphology and thermal stability of AlF3 thin films grown on Cu(100)

The growth of ultrathin epitaxial layers of aluminum fluoride on Cu(100) has been studied by a combination of surface science techniques. Deposition at room temperature results in step decoration followed by the formation of dendritic two-dimensional islands that coalesce to form porous films. Ultrathin layers (up to 2 monolayers in thickness) are morphologically unstable upon annealing; de-wetting takes place around 430 K with the formation of three-dimensional islands and leaving a large fraction of the Cu surface uncovered. Films several nanometers thick, on the contrary, are stable up to ca. 730 K where desorption in molecular form sets on. The effect of electron irradiation on the AlF₃ has also been characterized by different spectroscopic techniques; we find that even small quantities of stray electrons from rear electron beam heating can provoke significant decomposition of the aluminum fluoride, resulting in the release of molecular fluorine and the formation of deposits of metallic aluminum. These features make AlF₃ an interesting material for spintronic applications.     

Photo-physical and structural interactions between viologen phosphorus-based dendrimers and human serum albumin

This work deals with photo-physical and structural interactions between viologen phosphorus dendrimers and human serum albumin (HSA). Viologens are derivatives of 4,4′-bipyridinium salts. Aiming to rationalize the parameters governing such interactions eight types of these polycationic dendrimers in which the generation, the number of charges, the nature of the core and of the terminal groups vary from one to another, were designed and used. The influence of viologen-based dendrimers' on human serum albumin has been investigated. The photo-physical interactions of the two systems have been monitored by fluorescence quenching of free l-tryptophan and of HSA tryptophan residue. Additionally, using circular dichroism (CD) the effect of dendrimers on the secondary structure of albumin was measured. The obtained results show that viologen dendrimers interact with human serum albumin quenching its fluorescence either by collisional (dynamic) way or by forming complexes in a ground state (static quenching). In some cases the quenching is accompanied by changes of the secondary structure of HSA.     

Effect of Precipitation Temperature and Number of Iron Atoms per Molecule on the Structure of Hydrated Iron(III) Oxyhydroxide Ferritin Cores Synthesised in vitro

Hyperfine Interactions - Horse spleen apoferritin was reconstituted with varying numbers of iron atoms per protein shell at 25 and 50°C. Samples with mean particle sizes ranging from...     

Comparison between lattice Boltzmann method and Navier–Stokes high order schemes for computational aeroacoustics

Computational aeroacoustic (CAA) simulation requires accurate schemes to capture the dynamics of acoustic fluctuations, which are weak compared with aerodynamic ones. In this paper, two kinds of schemes are studied and compared: the classical approach based on high order schemes for Navier–Stokes-like equations and the lattice Boltzmann method. The reference macroscopic equations are the 3D isothermal and compressible Navier–Stokes equations. A Von Neumann analysis of these linearized equations is carried out to obtain exact plane wave solutions. Three physical modes are recovered and the corresponding theoretical dispersion relations are obtained. Then the same analysis is made on the space and time discretization of the Navier–Stokes equations with the classical high order schemes to quantify the influence of both space and time discretization on the exact solutions. Different orders of discretization are considered, with and without a uniform mean flow. Three different lattice Boltzmann models are then presented and studied with the Von Neumann analysis. The theoretical dispersion relations of these models are obtained and the error terms of the model are identified and studied. It is shown that the dispersion error in the lattice Boltzmann models is only due to the space and time discretization and that the continuous discrete velocity Boltzmann equation yield the same exact dispersion as the Navier–Stokes equations. Finally, dispersion and dissipation errors of the different kind of schemes are quantitatively compared. It is found that the lattice Boltzmann method is less dissipative than high order schemes and less dispersive than a second order scheme in space with a 3-step Runge–Kutta scheme in time. The number of floating point operations at a given error level associated with these two kinds of schemes are then compared.     

Asymptotic-Preserving Particle-In-Cell method for the Vlasov–Poisson system near quasineutrality

This paper deals with the numerical resolution of the Vlasov–Poisson system in a nearly quasineutral regime by Particle-In-Cell (PIC) methods. In this regime, Classical PIC methods are subject to stability constraints on the time and space steps related to the small Debye length and large plasma frequency. Here, we propose an “Asymptotic-Preserving” PIC scheme which is not subjected to these limitations. Additionally, when the plasma period and Debye length are small compared to the time and space steps, this method provides a consistent PIC discretization of the quasineutral Vlasov equation. We perform several one-dimensional numerical experiments which provide a solid validation of the method and its underlying concepts, and compare the method with Classical PIC and Direct-Implicit methods.     

A fast and light stream cipher for smartphones

We present a stream cipher based on a chaotic dynamical system. Using a chaotic trajectory sampled under certain rules in order to avoid any attempt to reconstruct the original one, we create a binary pseudo-random keystream that can only be exactly reproduced by someone that has fully knowledge of the communication system parameters formed by a transmitter and a receiver, sharing the same initial conditions. The plaintext is XOR’ed with the keystream creating the ciphertext, the encrypted message. This keystream passes the NIST’s randomness test and has been implemented in a videoconference App for smartphones, in order to show the fast and light nature of the proposed encryption system.