Interface hole-doping in cuprate-titanate superlattices

The electronic structure of interfaces between YBa$_2$Cu$_3$O$_6$ and SrTiO$_3$ is studied using local spin density approximation (LSDA) with intra-atomic Coulomb repulsion (LSDA+U). We find a metallic state in cuprate/titanate heterostructures with the hole carriers concentrated substantially in the CuO$_2$-layers and in the first interface TiO$_2$ and SrO planes. This effective interface doping appears due to the polarity of interfaces, caused by the first incomplete copper oxide unit cell. Interface-induced high pre-doping of CuO$_2$-layers is a key mechanism controlling the superconducting properties in engineered field-effect devices realized on the basis of cuprate/titanate superlattices.Comment: 5 pages, 5 figure

Ложка для людей с тремором рук

Болезнь Паркинсона вызвана прогрессирующим разрушением и гибелью нейронов, вырабатывающих нейромедиатор дофамин. Из-за этого нарушается регуляция движений и мышечного тонуса, что проявляется характерным тремором, общей скованностью и нарушением позы и движений. Для паркинсонизма характерен тремор, возникающий в покое. Авторы разработали ложку для людей с болезнью Паркинсона, позволяющую держать её содержимое в неподвижном состоянии при воздействие на нее тремором рук

Increase in Thermal Stability of Hydride of the Titanium

The paper presents the results of studies of the modification of the surface of a fraction of titanium hydride with borosiloxanes in order to increase its thermal stability at high temperatures and protect titanium from oxidation for possible use as a heat-resistant neutron-protective material in nuclear power engineering. A theoretical model has been developed for modifying a fraction of titanium hydride with borosilicate bysol-gel technology from aqueous solutions of sodium organosilicinate and boric acid. The technology for modifying titanium hydride consists in the preliminary chemical activation of the surface of the fraction by a silicone oligomer - sodium organosilicinate (OSN) followed by treatment with boric acid, separation of the solid phase of titanium hydride and subsequent drying at 100 ∘C. During the synthesis of sodium borosilicateand its thermal treatment in the temperature range 100-500 ∘C, complex structuralphase rearrangements were observed. At 100 ∘C, an amorphous-crystalline silicate of CH3 (Si30.4B1.6O64) Na monoclinic syngony with large crystal lattice parameters was formed. The thermal treatment of the borosilicate coating at 300 ∘C led to achange in the radiographic characteristics of the crystalline phase and the formation of a monoclinic NaBSi2O5(OH)2 structure with continuous layers of silicon-oxygen tetrahedra. Further crystallization of borosilicate at a temperature of 500 ∘C leads to the formation of a silicate of the skeleton type NaBSi3O8 of triclinic syngony. Above 500 ∘C, sodium borosilicate passes into a glassy state. &nbsp

Temporal changes of the flare activity of Proxima Cen

We study temporal variations of the emission lines of Halpha, Hepsilon, H and K Ca II, D1 and D2 Na I, 4026 and 5876 A He I in the HARPS spectra of Proxima Centauri across an extended time of 13.2 years, from May 27, 2004, to September 30, 2017. Aims. We analyse the common behaviour and differences in the intensities and profiles of different emission lines in flare and quiet modes of Proxima activity. Methods. We compare the pseudo-equivalent widths (pEW) and profiles of the emission lines in the HARPS high-resolution (R ~ 115,000) spectra observed at the same epochs. Results. All emission lines show variability with a timescale of at least 10 min. The strength of all lines except He I 4026 A correlate with \Halpha. During strong flares the `red asymmetry' appears in the Halpha emission line indicating the infall of hot condensed matter into the chromosphere with velocities greater than 100 km/s disturbing chromospheric layers. As a result, the strength of the Ca II lines anti-correlates with Halpha during strong flares. The He I lines at 4026 and 5876 A appear in the strong flares. The cores of D1 and D2 Na I lines are also seen in emission. During the minimum activity of Proxima Centauri, Ca II lines and Hepsilon almost disappear while the blue part of the Na I emission lines is affected by the absorption in the extending and condensing flows. Conclusions. We see different behaviour of emission lines formed in the flare regions and chromosphere. Chromosphere layers of Proxima Cen are likely heated by the flare events; these layers are cooled in the `non-flare' mode. The self-absorption structures in cores of our emission lines vary with time due to the presence of a complicated system of inward and outward matter flows in the absorbing layers.Comment: 22 pages, 12 Figures, accepted by A

Synthesis and property evaluations of highly filled polyimide composites under thermal cycling conditions from -190 °C to +200 °C

This paper presents data on the synthesis of composites based on polyimide and modified tungsten (IV) oxide (WO₂). The resulting, highly filled, polyimide/WO₂ composites were investigated by electron microscopy and thermal analysis in a gas environment of oxygen and argon. The maximum content of modified WO₂, in the studied composites, was 60 wt%. The introduction of WO₂ increases the thermal stability of the composite

Hydrogen transport in superionic system Rb3H(SeO4)2: a revised cooperative migration mechanism

We performed density functional studies of electronic properties and mechanisms of hydrogen transport in Rb3H(SeO4)2 crystal which represents technologically promising class M3H(XO4)2 of proton conductors (M=Rb,Cs, NH4; X=S,Se). The electronic structure calculations show a decisive role of lattice dynamics in the process of proton migration. In the obtained revised mechanism of proton transport, the strong displacements of the vertex oxygens play a key role in the establishing the continuous hydrogen transport and in the achieving low activation energies of proton conduction which is in contrast to the standard two-stage Grotthuss mechanism of proton transport. Consequently, any realistic model description of proton transport should inevitably involve the interactions with the sublattice of the XO4 groups.Comment: 11 pages, 11 figures, to appear in Physical Review

The Gd2−x Mgx Zr2 O7−x/2 Solid Solution: Ionic Conductivity and Chemical Stability in the Melt of LiCl-Li2 O

Materials with pyrochlore structure A2 B2 O7 have attracted considerable attention owing to their various applications as catalysts, sensors, electrolytes, electrodes, and magnets due to the unique crystal structure and thermal stability. At the same time, the possibility of using such materials for electrochemical applications in salt melts has not been studied. This paper presents the new results of obtaining high-density Mg2+-doped ceramics based on Gd2 Zr2 O7 with pyrochlore structure and comprehensive investigation of the electrical properties and chemical stability in a lithium chloride melt with additives of various concentrations of lithium oxide, performed for the first time. The solid solution of Gd2−x Mgx Zr2 O7−x/2 (0 ≤ x ≤ 0.10) with the pyrochlore structure was obtained by mechanically milling stoichiometric mixtures of the corresponding oxides, followed by annealing at 1500◦ C. The lattice parameter changed non-linearly as a result of different mechanisms of Mg2+ incorporation into the Gd2 Zr2 O7 structure. At low dopant concentrations (x ≤ 0.03) some interstitial positions can be substituted by Mg2+, with further increasing Mg2+-content, the decrease in the lattice parameter occurred due to the substitution of host-ion sites with smaller dopant-ion. High-density ceramics 99% was prepared at T = 1500◦ C. According to the results of the measurements of electrical conductivity as a function of oxygen partial pressure, all investigated samples were characterized by the dominant ionic type of conductivity over a wide range of pO2 (1 × 10–18 ≤ pO2 ≤ 0.21 atm) and T < 800◦ C. The sample with the composition of x = 0.03 had the highest oxygen-ion conductivity (10−3 S·cm−1 at 600◦ C). The investigation of chemical stability of ceramics in the melt of LiCl with 2.5 mas.% Li2 O showed that the sample did not react with the melt during the exposed time of one week at the temperature of 650◦ C. This result makes it possible to use these materials as oxygen activity sensors in halide melts. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Russian Foundation for Basic Research, РФФИ: 20-43-660033Funding: The work is financially supported by RFBR and Sverdlovsk region, project number 20-43-660033