Decoupled and unidirectional asymptotic models for the propagation of internal waves

We study the relevance of various scalar equations, such as inviscid Burgers', Korteweg-de Vries (KdV), extended KdV, and higher order equations (of Camassa-Holm type), as asymptotic models for the propagation of internal waves in a two-fluid system. These scalar evolution equations may be justified with two approaches. The first method consists in approximating the flow with two decoupled, counterpropagating waves, each one satisfying such an equation. One also recovers homologous equations when focusing on a given direction of propagation, and seeking unidirectional approximate solutions. This second justification is more restrictive as for the admissible initial data, but yields greater accuracy. Additionally, we present several new coupled asymptotic models: a Green-Naghdi type model, its simplified version in the so-called Camassa-Holm regime, and a weakly decoupled model. All of the models are rigorously justified in the sense of consistency

Radiative rates and opacity calculations in Ce II-IV Multiconfiguration Dirac-Hartree-Fock radiative parameters for emission lines in Ce II-IV ions and cerium opacity calculations for kilonovae

Large-scale calculations of atomic structures and radiative properties have been carried out for singly, doubly- and trebly ionized cerium. For this purpose, the purely relativistic multiconfiguration Dirac-Hartree-Fock (MCDHF) method was used, taking into account the effects of valence-valence and core-valence electronic correlations in detail. The results obtained were then used to calculate the expansion opacities characterizing the kilonovae observed as a result of neutron star mergers. Comparisons with previously published experimental and theoretical studies have shown that the results presented in this work are the most complete currently available, in terms of quantity and quality, concerning the atomic data and monochromatic opacities for Ce II, Ce III and Ce IV ions.Comment: Submitted to MNRA

Epidemiology and control of Salmonella in the pork production chain: the approach in a high prevalence country (Spain)

The present study summarises the insights yielded by different studies focused on the epidemiology of the infection by Salmonella through the pig production (breeders, finishers and post-farm stages). The final objective is to determine the best strategies for successful control of Salmonella in a highly prevalent country such as Spain. The study in breeders evidenced a high seroprevalence. There were differences among some of the 10 most common serotypes detected in breeders compared to previous studies in finishers, although the two most common were shared by both populations. Type of feed and type of floor were the factors associated to the presence of Salmonella. A Salmonella Typhimurium inactivated vaccine and two organic acids demonstrated to be good tools to reduce the prevalence in finishers. Finally a study of the contamination in post-farm stages evidenced the high contamination of transport, lairage and the contamination of the slaughter line, accounting for 70% of carcass cross-contamination

Sharp global well-posedness for the higher order non-linear Schr\"odinger equation on modulations spaces

We consider the initial value problem (IVP) associated to a higher order nonlinear Schr\"odinger (h-NLS) equation $\partial_{t}u+ia \partial^{2}_{x}u+ b\partial^{3}_{x}u+ic_1|u|^{2}u+c_2 |u|^{2}\partial_{x}u=0, \quad x,t \in \mathbb{R},$ for given data in the modulation space $M_s^{2,p}(\mathbb{R})$. Using ideias of Killip, Visan, Zhang, Oh, Wang, we prove that the IVP associated to the h-NLS equation is globally well-posed in the modulation spaces $M^{s,p}$ for $s\geq\frac14$ and $p\geq2$

Study of CeNi4Mn by neutron diffraction

We report neutron diffraction measurements on CeNi4Mn, which has recently been identified as a soft ferromagnet (Tc ~ 140 K) with a sizeable spin-transport polarization. Our data show conclusively that the Mn atoms occupy a unique site (4c) in the unit cell, which has the symmetry of the cubic MgCu4Sn-type structure. We infer a moment of 4.6 mu_B on Mn at 17 K, which is oriented ferromagnetically along the {101} plane. The amplitude of the Mn vibrational motion is found to be larger than that of Ce and Ni atoms at all temperatures, thereby lending support to theoretical prediction of rattling phonon modes in this compound.Comment: Accepted for publication in Solid State Commu

High-temperature oxygen non-stoichiometry, conductivity and structure in strontium-rich nickelates La2-xSrxNiO4-\delta (x = 1 and 1.4)

Oxygen nonstoichiometry, electrical conductivity and thermal expansion of La2 xSrxNiO4-\delta phases with high levels of strontium substitution (1 =< x =< 1.4) have been investigated in air and oxygen atmosphere in the temperature range 20-1050 degrees C. These phases retain the K2NiF4-type structure of La2NiO4 (tetragonal, space group I4/mmm). The oxygen vacancy fraction was determined independently from thermogravimetric and neutron diffraction experiments, and is found to increase considerably on heating. The electrical resistivity, thermal expansion and cell parameters with temperature show peculiar variations with temperature, and differ notably from La2NiO4$\pm$\delta in this respect. These variations are tentatively correlated with the evolution of nickel oxidation state, which crosses from a Ni3+/Ni4+ to a Ni2+/Ni3+ equilibrium on heating

Effect of Particle Interactions on Powder Flow Behavior

The study of powder flow behavior is essential for the development of processing technologies in many industries. In fact, powders have a major function in diverse types of manufacturing, such as pharmaceuticals, foods, chemicals, materials, minerals and cosmetics. This leads to an increasing demand for the development of reliable methods to assess powder flow problems in industry. This research intends to provide a general insight into how surface interactions and particle properties may alter powder flowability. The materials used for this study were lactose, starch, milk powder, cocoa and chocolate. These vary in their interparticle forces as well as on their manufacturing process. Powder flow behavior of these materials was measured by using a 502 Twin Drive Anton Paar Modular Compact Rheometer. The collected sets of data were used to identify how particle characteristics affect powder flow behavior. The results suggest that powder flow is affected by a combination of particle size, morphology, environmental conditions and composition. The obtained flowability profiles were compared with previous results obtained using the Freeman FT4 Powder Rheometer. Although the flow tendency is somewhat similar, the results have some differences that are attributed to the principle of operation of each of the measurement systems. The findings represent a starting point for the understanding of particle interactions involved in complex materials. It is envisioned that the results will assist in the development of models to predict how to alter particle characteristics, using processing techniques and additives, in order to tune in a desired powder flow behavior

Molecular epidemiology of Salmonella Typhimurium and Salmonella 4,5,12:i:- isolated from pig farms in Spain

The genetic diversity of 194 salmonella isolates belonging to different phagetypes of S. Typhimurium and S 4,5, 12:i- isolated from both healthy slaughter (157) and diarrhoea-affected (37) pigs was assessed using molecular typing (plasmid profiling and PFGE). The aim of this study was to elucidate the sources of infection, and to follow the spread of specific clones within the infected farms. In spite of the genetic diversity observed amongst the isolates, some clones were more prevalent and widely distributed in the pig population, being detected in several slaughter batches from the same and different farms. This finding suggests the existence of multiple and recurrent infection sources, as well as mechanisms favouring survival, persistence and spreading of certam clones within and between pig farms