Breaking of Cubic Symmetry in Rare-Earth Dodecaborides with Dynamic Charge Stripes
The effect of symmetry lowering for the parameters of electron transport in rare-earth dodecaborides RB12
(R = Ho, Er, Tm, Lu) with fcc crystal structure at temperatures T ≤ 150 K has been discovered. It has been
shown that the anisotropy of the magnetoresistance increases sharply at the transition to the disordered cageglass
phase below T∗ ∼ 60К. This effect is observed in magnetic and nonmagnetic rare-earth dodecaborides,
including solid solutions RxLu1 – xB12 with high substitutional disorder. The role of the electron phase separation
(charge stripes along the〈110〉direction) in these metals with open trajectories on the Fermi surface is
Precise angle-resolved magnetoresistance (ARM) measurements are applied to reveal the origin of symmetry lowering in electron transport and the emergence of a huge number of magnetic phases in the ground state of the antiferromagnetic metal HoB12 with fcc crystal structure. By analyzing the polar H-θ-ϕ magnetic phase diagrams of this compound reconstructed from the experimental ARM data, we argue that nonequilibrium electron density oscillations (dynamic charge stripes) are responsible for the suppression of the indirect Ruderman-Kittel-Kasuya- Yosida exchange along the <110> directions between the nearest neighboring magnetic moments of Ho3+ ions in this strongly correlated electron system.
The bio-accessibility of 14 elements in welding fume particulate matter was investigated in 325 personal air samples collected during welding in two shipyards and one factory producing heavy machinery. The apparent solubility in a synthetic lung lining fluid (Hatch's solution) was used as proxy for the bio-accessibility. The Hatch solubility of the different elements was highly variable with a median < 1% for Al, Fe, Pb, Ti, between 4 and 6% for Co, Cr, Ni, V, W, between 13 and 27% for Cd, Cu, Mn, Zn, and 41% for Mo. For many elements, the solubility varied over a wide range of several tens of percent. The welding techniques used influenced the solubility of Co, Cr, Cu, Mn and V significantly. The plants investigated (i.e., the welded materials and used electrodes) had a significant influence on the solubility of Co, Cr, Cu, Mn, Mo, V and W. According to principal component analysis (PCA), the variation in solubility can be described by four components, which explain 69% of the variance. The first principal component mostly comprises elements that can predominantly occur as divalent cations, the second principal component elements often forming oxyanions. The principal components are independent of the absolute value of the Hatch solubility. The results of PCA indicate that the co-variation of Hatch solubility is mainly controlled by the most soluble compounds in contrast to the absolute value of apparent solubility, which is strongly influenced by the distribution of the elements between compounds with different equilibrium solubilities. The observed large variability and the significant differences between welding techniques and plants clearly show that the bio-accessibility cannot be obtained from the literature but has to be studied experimentally at each location of interest.
Dear colleagues, The forthcoming ХХVI International scientific – technical conference “Foundry 2019 will be held of the 10-12 April 2019 at “Rostov” hotel in the city of Pleven, Bulgaria. Its aim is to provide a meeting place for scholars from different countries to present their scientific achievements and to discuss the problems of casting production. The conference will provide the opportunity for new ще даде възможност за нови acquaintances and friendships, and this leads to the generation of new ideas. We invite the companies with their own presentations at the conference to present their machines, equipment, technologies, materials and services, which they offer to the market. We also invite the representatives of the casting enterprises to get to know the latest achievements of science and technology in the field of casting production. We hope that in this way, the XVI International conference “Foundry 2019” will fulfill its role of an innovation intermediary between the scientists and researchers from one side and the industry on the other and prompt you to take advantage of this opportunity. We kindly ask you to make the conference information known to other colleagues from here and abroad.
Prof. Dr. Eng. Georgi Popov Chairman of the Scientific-Technical Union of Mechanical Engineering Prof. Dr. Eng. Dimitar Stavrev Chairman of the International Program Committee
This chapter presents a review of the experimental and theoretical investigations of halogen interaction with metal surfaces. The emphasis is on the recent measurements performed with scanning tunneling microscopy in combination with density functional theory calculations. The surface structures formed on metal surface after halogen action are classified into three groups: chemisorbed monolayer, surface halide, bulk-like halide. Formation of monolayer structures is described in terms of surface phase transitions. Surface halide phases are considered as intermediates between chemisorbed halogen and bulk halide. The general conclusion is that, for a number of systems, the picture of halogen/metal interaction is still far from complete.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.