Structure and solidification of the (Fe0.75B0.15Si0.1)100-xTax (x=0-2) melts: experiment and machine learning

Fe-B-Si system is a matrix for synthesis of new functional materials with exceptional magnetic and mechanical properties. Progress in this area is associated with the search for optimal doping conditions. This theoretical and experimental study is aimed to address the influence of Ta alloying on the structure of undercooled (Fe0.75B0.15Si0.1)100-xTax (x=0-2) melts, their undercoolability and the processes of structure formation during solidification. Small concentration of Ta complicates standard ab initio and machine learning investigations. We developed a technique for fast and stable training of machine learning interatomic potential (MLIP) in this case and uncovered the structure of the undercooled melts. Molecular dynamic simulations with MLIP showed that at Ta concentration of 1 at.% there is a sharp change in the chemical short-range ordering in the melt associated with a change in the interaction of Ta atoms. This effect leads to a restructuring of the cluster formation in the system. At the same time, our experimental investigation shows that melts with a Ta content of 1 at.% have the greatest tendency to undercoolability. Alloying with Ta promotes the formation of primary crystals of Fe2B, and at a concentration of more than 1.5 at.% Ta, also of FeTaB. Herewith, near 1 at.% Ta, the crystallization of the melt proceeds nontrivially: with the formation of two intermediate metastable phases Fe3B and Fe2Ta Laves phase. Also, the highest tendency to amorphization under conditions of quick quenching is exhibited by a melt with a Ta concentration of 1 at.%. The results not only provide understanding of optimal alloying of Fe-B-Si materials but also promote a machine learning method for numerical design of metallic alloys with a small dopant concentration.Comment: 26 pages, 10 figure

Neutron-Capture Elements in Halo, Thick-Disk, and Thin-Disk Stars: Neodymium

We have derived the LTE neodymium abundances in 60 cool stars with metallicities [Fe/H] from 0.25 to -1.71 by applying a synthetic-spectrum analysis to spectroscopic observations of NdII lines with a resolution of λ/Δλ ≃ 60000 and signal-to-noise ratios of 100-200. We have improved the atomic parameters of NdII and blending lines by analyzing the corresponding line profiles in the solar spectrum. Neodymium is overabundant with respect to iron in halo stars, [Nd/Fe] = 0.33 ± 0.09, with the [Nd/Fe] ratio decreasing systematically with metallicity when [Fe/H] > -1. This reflects an onset of efficient iron production in type I supernovae during the formation of the thick disk. The [Nd/Ba] and [Nd/Eu] abundance ratios behave differently in halo, thick-disk, and thin-disk stars. The observed abundance ratios in halo stars, [Nd/Ba] =0.34 ± 0.08 and [Nd/Eu] = -0.27 ± 0.05, agree within the errors with the ratios of the elemental yields for the r-process. These results support the conclusion of other authors based on analyses of other elements that the r-process played the dominant role in the synthesis of heavy elements during the formation of the halo. The [Nd/Ba] and [Nd/Eu] ratios for thick-disk stars are almost independent of metallicity ([Nd/Ba] = 0.28(±0.03)-0.01(±0.04) [Fe/H] and [Nd/Eu] = -0.13(±0.03) + 0.05(±0.04) [Fe/H]) but are smaller in absolute value than the corresponding ratios for halo stars, suggesting that the synthesis of s-process nuclei started during the formation of the thick disk. The s-process is estimated to have contributed ≃30% of the neodymium produced during this stage of the evolution of the Galaxy. The [Nd/Ba] ratio decreases abruptly by 0.17 dex in the transition from the thick to the thin disk. The systematic decrease of [Nd/Ba] and increase of [Nd/Eu] with increasing metallicity of thin-disk stars point toward a dominant role of the s-process in the synthesis of heavy elements during this epoch. © 2004 MAIK "Nauka/Interperiodica"

Phase selection and microstructure of slowly solidified Al-Cu-Fe alloys

The search for effective methods to fabricate bulk single-phase quasicrystalline Al-Cu-Fe alloys is currently an important task. Crucial to solving this problem is to understand the mechanisms of phase formation in this system. Here we study the crystallization sequence during solidification as well as the conditions of solid phase formation in slowly solidified Al-Cu-Fe alloys in a wide range of compositions. We have also constructed concentration dependencies of undercoolability by differential thermal analysis method. These experimental results are compared with data on chemical short-range order in the liquid state determined from ab initio molecular dynamic simulations. We observe that the main features of interatomic interaction in the Al-Cu-Fe alloys are similar for both liquid and solid states and they change in the vicinity of i-phase composition. In the concentration region, where the i-phase is formed from the melt, both the undercoolability and the crystallization character depend on the temperature of the melts before cooling. © 2019 Elsevier B.V.This work was supported by supercomputer of IMM UB RAS and computing resources of the federal collective usage center Complex for Simulation and Data Processing for Mega-science Facilities at NRC “Kurchatov Institute” Russian Science Foundation (grant RNF 18-12-00438 ). The experimental study was perfomed using equipment of the Shared Use Centre of Physical and Physicochemical Methods of Analysis and Study of the Properties and Surface Characteristics of Nanostructures, Materials, and Products, UdmFRC UB RAS. AIMD simulations have been carried out using ”Uran” http://ckp.nrcki.ru

Neutron-Capture Elements in Halo, Thick-Disk, and Thin-Disk Stars: Neodymium

We have derived the LTE neodymium abundances in 60 cool stars with metallicities [Fe/H] from 0.25 to -1.71 by applying a synthetic-spectrum analysis to spectroscopic observations of NdII lines with a resolution of λ/Δλ ≃ 60000 and signal-to-noise ratios of 100-200. We have improved the atomic parameters of NdII and blending lines by analyzing the corresponding line profiles in the solar spectrum. Neodymium is overabundant with respect to iron in halo stars, [Nd/Fe] = 0.33 ± 0.09, with the [Nd/Fe] ratio decreasing systematically with metallicity when [Fe/H] > -1. This reflects an onset of efficient iron production in type I supernovae during the formation of the thick disk. The [Nd/Ba] and [Nd/Eu] abundance ratios behave differently in halo, thick-disk, and thin-disk stars. The observed abundance ratios in halo stars, [Nd/Ba] =0.34 ± 0.08 and [Nd/Eu] = -0.27 ± 0.05, agree within the errors with the ratios of the elemental yields for the r-process. These results support the conclusion of other authors based on analyses of other elements that the r-process played the dominant role in the synthesis of heavy elements during the formation of the halo. The [Nd/Ba] and [Nd/Eu] ratios for thick-disk stars are almost independent of metallicity ([Nd/Ba] = 0.28(±0.03)-0.01(±0.04) [Fe/H] and [Nd/Eu] = -0.13(±0.03) + 0.05(±0.04) [Fe/H]) but are smaller in absolute value than the corresponding ratios for halo stars, suggesting that the synthesis of s-process nuclei started during the formation of the thick disk. The s-process is estimated to have contributed ≃30% of the neodymium produced during this stage of the evolution of the Galaxy. The [Nd/Ba] ratio decreases abruptly by 0.17 dex in the transition from the thick to the thin disk. The systematic decrease of [Nd/Ba] and increase of [Nd/Eu] with increasing metallicity of thin-disk stars point toward a dominant role of the s-process in the synthesis of heavy elements during this epoch. © 2004 MAIK "Nauka/Interperiodica"

Neutron-Capture Elements in Halo, Thick-Disk, and Thin-Disk Stars: Neodymium

We have derived the LTE neodymium abundances in 60 cool stars with metallicities [Fe/H] from 0.25 to -1.71 by applying a synthetic-spectrum analysis to spectroscopic observations of NdII lines with a resolution of λ/Δλ ≃ 60000 and signal-to-noise ratios of 100-200. We have improved the atomic parameters of NdII and blending lines by analyzing the corresponding line profiles in the solar spectrum. Neodymium is overabundant with respect to iron in halo stars, [Nd/Fe] = 0.33 ± 0.09, with the [Nd/Fe] ratio decreasing systematically with metallicity when [Fe/H] > -1. This reflects an onset of efficient iron production in type I supernovae during the formation of the thick disk. The [Nd/Ba] and [Nd/Eu] abundance ratios behave differently in halo, thick-disk, and thin-disk stars. The observed abundance ratios in halo stars, [Nd/Ba] =0.34 ± 0.08 and [Nd/Eu] = -0.27 ± 0.05, agree within the errors with the ratios of the elemental yields for the r-process. These results support the conclusion of other authors based on analyses of other elements that the r-process played the dominant role in the synthesis of heavy elements during the formation of the halo. The [Nd/Ba] and [Nd/Eu] ratios for thick-disk stars are almost independent of metallicity ([Nd/Ba] = 0.28(±0.03)-0.01(±0.04) [Fe/H] and [Nd/Eu] = -0.13(±0.03) + 0.05(±0.04) [Fe/H]) but are smaller in absolute value than the corresponding ratios for halo stars, suggesting that the synthesis of s-process nuclei started during the formation of the thick disk. The s-process is estimated to have contributed ≃30% of the neodymium produced during this stage of the evolution of the Galaxy. The [Nd/Ba] ratio decreases abruptly by 0.17 dex in the transition from the thick to the thin disk. The systematic decrease of [Nd/Ba] and increase of [Nd/Eu] with increasing metallicity of thin-disk stars point toward a dominant role of the s-process in the synthesis of heavy elements during this epoch. © 2004 MAIK "Nauka/Interperiodica"

Neutron-Capture Elements in Halo, Thick-Disk, and Thin-Disk Stars: Neodymium

We have derived the LTE neodymium abundances in 60 cool stars with metallicities [Fe/H] from 0.25 to -1.71 by applying a synthetic-spectrum analysis to spectroscopic observations of NdII lines with a resolution of λ/Δλ ≃ 60000 and signal-to-noise ratios of 100-200. We have improved the atomic parameters of NdII and blending lines by analyzing the corresponding line profiles in the solar spectrum. Neodymium is overabundant with respect to iron in halo stars, [Nd/Fe] = 0.33 ± 0.09, with the [Nd/Fe] ratio decreasing systematically with metallicity when [Fe/H] > -1. This reflects an onset of efficient iron production in type I supernovae during the formation of the thick disk. The [Nd/Ba] and [Nd/Eu] abundance ratios behave differently in halo, thick-disk, and thin-disk stars. The observed abundance ratios in halo stars, [Nd/Ba] =0.34 ± 0.08 and [Nd/Eu] = -0.27 ± 0.05, agree within the errors with the ratios of the elemental yields for the r-process. These results support the conclusion of other authors based on analyses of other elements that the r-process played the dominant role in the synthesis of heavy elements during the formation of the halo. The [Nd/Ba] and [Nd/Eu] ratios for thick-disk stars are almost independent of metallicity ([Nd/Ba] = 0.28(±0.03)-0.01(±0.04) [Fe/H] and [Nd/Eu] = -0.13(±0.03) + 0.05(±0.04) [Fe/H]) but are smaller in absolute value than the corresponding ratios for halo stars, suggesting that the synthesis of s-process nuclei started during the formation of the thick disk. The s-process is estimated to have contributed ≃30% of the neodymium produced during this stage of the evolution of the Galaxy. The [Nd/Ba] ratio decreases abruptly by 0.17 dex in the transition from the thick to the thin disk. The systematic decrease of [Nd/Ba] and increase of [Nd/Eu] with increasing metallicity of thin-disk stars point toward a dominant role of the s-process in the synthesis of heavy elements during this epoch. © 2004 MAIK "Nauka/Interperiodica"

CHANGES OF IMMUNE INDEXES DURING SUBLINGUAL ALLERGEN-SPECIFIC IMMUNOTHERAPY IN CHILDREN WITH HAY FEVER

Aims of study: evaluation of immunological parameters in course of sublingual allergen-specific immunotherapy with tree pollen mixture in children with hay fever.Materials and methods: the study included one-hundred patients 5 to 18 years of age with hay fever (pollen rhinitis, rhinoconjunctivitis and/or asthma). Allergen-specific immunotherapy was administered pre-seasonally for three consecutive years. Cytokinechanges were studied in blood serum and in lavages from nasal cavity. Samples assessed before treatment and after 2nd and 3rd courses SLIT completion.Results: increased serum concentrations of IL-10, IFNγ, and decreased IL-4 contents were revealed in the course of treatment. No significant changes in cytokineconcentrations were detectable in nasal lavages.Conclusions: the changes revealed correspond to a shift of T cell response profile towards Th1 pathway, thus confirming pathogenetic effects of sublingual allergen-specifi