CO-activator model for reconstructing Pt(100) surfaces: local microstructures and chemical turbulence

We present the results of the modelling of CO adsorption and catalytic CO oxidation on inhomogeneous Pt(100) surfaces which contain structurally different areas. These areas are formed during the CO-induced transition from a reconstructed phase with hexagonal geometry of the overlayer to a bulk-like (1x1) phase with square atomic arrangement. In the present approach, the surface transition is explained in terms of nonequilibrium bistable behavior. The bistable region is characterized by a coexistence of the hexagonal and (1x1) phases and is terminated in a critical bifurcation point which is located at (T_c ~680 K, p_CO ~10 Torr). Due to increasing fluctuations, the behavior at high temperatures and pressures in the vicinity of this cusp point should be qualitatively different from the hysteresis-type behavior which is typically observed in the experiments under ultrahigh vacuum conditions. On the inhomogeneous surface, we find a regime of nonuniform oscillations characterized by random standing waves of adsorbate concentrations. The resulting spatial deformations of wave fronts allow to gain deeper insight into the nature of irregular oscillations on Pt(100) surface.Comment: 11 pages, 11 figures, to appear in Physical Review

Electrostatic interface tuning in correlated superconducting heterostructures

An electrostatic field, which is applied to a gated high-temperature superconducting (HTSC) film, is believed to affect the film similar to charge doping. Analyzing the pairing in terms of a t-J model, we show that a coupling to electric dipoles and phonons at the interface of film and dielectric gate localizes the injected charge and leads to a superconductor-insulator transition. This results in a dramatic modification of the doping dependent phase diagram close to and above the optimal doping which is expected to shed light on recent electric field-effect experiments with HTSC cuprates.Comment: 6 pages, 6 figures, to appear in Physical Review

Superconductivity Controlled by Polarization in Field-Effect Devices of Confined Geometry

We propose a concept for superconducting electric field-effect devices based on superconducting films sandwiched between ferroelectric layers. We provide theoretical calculations that indicate how the field effect in these devices could be amplified, which can be experimentally probed even at the current stage of film fabrication techniques.Comment: to appear in Applied Physics Letters, 3 pages RevTeX4, 3 figure

Mechanism of orbital reconstruction at the interfaces of transition metal oxides

Orbital reconstruction at interfaces between YBa2Cu3O6 and SrO-terminated SrTiO3 is studied using local spin density approximation (LSDA) with intra-atomic Coulomb repulsion (LSDA+U). The change of population of interfacial Cu 3d orbitals results in stabilization of a new oxidation state $3d^8$ which involves an additional modification of orbital occupancies in the nearest SrO and TiO2 layers. We find that an increase of electron charge in Cu 3d_{x^2-y^2} states counterbalances a depopulation of 3d_{3z^2-r^2} orbitals which induces, on account of the onsite Coulomb repulsion U, a splitting of 3d_{3z^2-r^2} states at CuO2-SrO interfaces.Comment: 7 pages, 7 figures, to appear in Physical Review

Modulation of Superconducting Properties by Ferroelectric Polarization in Confined FE-S-FE Films

We show that the electric polarization at the interface with ultrathin superconducting (S) films sandwiched between ferroelectric (FE) layers allows achievement of substantially stronger modulation of inner carrier density and superconducting transition temperature as compared to FE-S bilayers typically used in superconducting FETs. We find that not only the larger penetration depths but also the pairing symmetry should be responsible for the fact that the electric field effect in high temperature superconductors is much stronger than in conventional systems. Discussing the advantages of multilayers, we propose a novel design concept for superconducting electric field-effect transistors based on ferroelectric films.Comment: 5 pages RevTex4, 6 figure

Вибір зразка безпілотного літального апарату для прийняття на озброєння з урахуванням експертних даних

The issue of equipping Armed Forces with modern unmanned aerial vehicles and accepting them into service remains unresolved. At present, the needs of Armed Forces of Ukraine in unmanned aerial vehicles have not been clearly identified, as well as the approaches regarding the choice of particular models. Present article proposes to select a model of armament based on the set of basic indicators (criteria) that may have quantitative and qualitative nature. We substantiate the necessity to predict the values of indicators under conditions of nonstochastic uncertainty. It is noted that should the research utilize statistics, then the task of predicting the given characteristics could be solved under conditions of stochastic uncertainty. In this case, it is necessary to take into account the assumption that the set of factors, which defined statistical significance of TTC, remains unchanged over the predicted time period. Under such assumption, long-term prediction of the TTC values cannot be considered satisfactory. It is obvious that the prediction of TTC values of UAV samples is considered under conditions of nonstochastic uncertainty based on the setting of appraisal and processing expert data. We proposed a decomposition of problem into hierarchy that reflects the content of multi-criteria optimization problem, in this case, it is characterized by a fuzzy description of the predicted values of basic UAV TTC, which have distinctly expressed quantitative and qualitative nature and are measured in appropriate magnitudes. An appraisal was performed to determine the predicted values of each characteristics of UAV. When processing expert data, values for each of the quantitative characteristics are represented by a fuzzy triangular number.Regarding the indicators of qualitative nature, we examined relevant linguistic variables. According to the method of hierarchy analysis, we carried out a comparative assessment of the indicators' significance. In order to obtain generalized indicators for the priority UAV model, the principle of synthesis is proposed.Проведена сравнительная характеристика многокритериальных задач оптимизации, критерии которых могут быть количественной и качественной природы. Обоснованно решение относительно выбора образца беспилотного летательного аппарата для принятия на вооружение с характеристиками, значения которых прогнозируются в условиях нестохастической неопределенности на основе экспертных данных. Предложена декомпозиция проблемы в иерархию, которая отражает содержание многокритериальной задачи оптимизацииПроведена порівняльна характеристика багатокритеріальних задач оптимізації, критерії яких можуть мати кількісну і якісну природу. Обґрунтовано рішення щодо вибору зразка безпілотного літального апарату для прийняття на озброєння за характеристиками, значення яких прогнозуються в умовах нестохастичної невизначеності на основі експертних даних. Запропонована декомпозиція проблеми в ієрархію, що відображає зміст багатокритеріальної задачі оптимізаці

Dibromidobis(3,5-dimethyl-1H-pyrazole-κN 2)cobalt(II)

In the mononuclear title complex, [CoBr2(C5H8N2)2], the CoII atom is coordinated by two N atoms from two monodentate 3,5-dimethyl­pyrazole ligands and two Br atoms in a highly distorted tetra­hedral geometry. In the crystal, the complex mol­ecules are linked by inter­molecular N—H⋯Br hydrogen bonds into chains along [101]. An intra­molecular N—H⋯Br hydrogen bond is also present

OT J002656.6+284933 (CSS101212:002657+284933): An SU UMa-Type Dwarf Nova with Longest Superhump Period

We observed the 2016 outburst of OT J002656.6+284933 (CSS101212:002657+284933) and found that it has the longest recorded [0.13225(1) d in average] superhumps among SU UMa-type dwarf novae. The object is the third known SU UMa-type dwarf nova above the period gap. The outburst, however, was unlike ordinary long-period SU UMa-type dwarf novae in that it showed two post-outburst rebrightenings. It showed superhump evolution similar to short-period SU UMa-type dwarf novae. We could constrain the mass ratio to less than 0.15 (most likely between 0.10 and 0.15) by using superhump periods in the early and post-superoutburst stages. These results suggest the possibility that OT J002656.6+284933 has an anomalously undermassive secondary and it should have passed a different evolutionary track from the standard one.Comment: 6 pages, 3 figures, accepted for publication in PASJ (Letters), Note added in proof has been added. Supplementary Information (si.pdf) is available in the source fil