Defect equilibrium in PrBaCo2O5+δ at elevated temperatures

A defect equilibrium model for PrBaCo2O5+δ is suggested based on oxygen non-stoichiometry data. The model includes reactions of oxygen exchange and charge disproportionation of Co3+ cations. The respective equilibrium constants, enthalpies and entropies for the reactions entering the model are obtained from the fitting of the experimental data for oxygen non-stoichiometry. The enthalpies of oxidation Co2+→ Co3+ and Co3+→Co4+ are found to be equal to 115±9 kJ mol-1 and 45±4 kJ mol-1, respectively. The obtained equilibrium constants were used in order to calculate variations in concentration of cobalt species with non-stoichiometry, temperature and oxygen pressure. © 2013 Elsevier Inc

Condensation of Silica Nanoparticles on a Phospholipid Membrane

The structure of the transient layer at the interface between air and the aqueous solution of silica nanoparticles with the size distribution of particles that has been determined from small-angle scattering has been studied by the X-ray reflectometry method. The reconstructed depth profile of the polarizability of the substance indicates the presence of a structure consisting of several layers of nanoparticles with the thickness that is more than twice as large as the thickness of the previously described structure. The adsorption of 1,2-distearoyl-sn-glycero-3-phosphocholine molecules at the hydrosol/air interface is accompanied by the condensation of anion silica nanoparticles at the interface. This phenomenon can be qualitatively explained by the formation of the positive surface potential due to the penetration and accumulation of Na+ cations in the phospholipid membrane.Comment: 7 pages, 5 figure

Spot activiy of dwarf stars FR Cnc and V 772 Her

Представлены новые многоцветные фотометрические наблюдения двух карликовых активных звезд FR Cnc и V772 Her, проведенные в астрономической обсерватории УрФУ и Крымской астрофизической обсерватории. Получены параметры запятненности фотосфер звезд в рамках зональной модели и выполнен анализ эволюционных изменений пятен на протяжении нескольких лет. Также приводится анализ оптической вспышки, зарегистрированной на FR Cnc в 2010 г.We present new multicolor photometric observations of two active dwarf stars FR Cnc and V772 Her. Observations were carried out at the observatory of Ural Federal University and at Crimean astro-physical observatory. We obtained star’s spot parameters according to the zonal model and analyzed evolutionary changes of spots with time. And we present an analysis of an optical flare, detected on FR Cnc in 2010.Работа А. В. Кожевниковой и В. П. Кожевникова была проведена при финансовой поддержке государства в лице Министерства образования и науки Российской Федерации (базовая часть госзадания, РК № AAAAA17-117030310283-7), а также при финансовой поддержке Правительства Российской Федерации (постановление №211, контракт №02.A03.21.0006).Работа И. Ю. Алексеева была выполнена в рамках тематического проекта КРАО РАН «Магнитная активность на звездах»

Theoretical simulation of the picosecond runaway-electron beam in coaxial diode filled with SF6 at atmospheric pressure

This paper presents detailed results of gas discharge theoretical simulation and the explanation of probabilistic mechanism of fast-electrons generation. Within the framework of a hybrid mathematical model, the hydrodynamic and the kinetic approaches are used simultaneously in order to describe the dynamics of different components of a low-temperature discharge plasma. The breakdown of a coaxial diode occurs in the form of a dense plasma region expanding from the cathode. On this background there is a formation of runaway electrons that are initiated by the ensemble of plasma electrons generated in the region of locally enhanced electric field within the front of the dense plasma. It is shown that the power spectrum of fast electrons in the discharge contains the group of electrons with the so-called “anomalous” energies. Comparison of the calculation results with the existent experimental data gives a good agreement for all major process parameters

Full Current Statistics in Diffusive Normal-Superconductor Structures

We study the current statistics in normal diffusive conductors in contact with a superconductor. Using an extension of the Keldysh Green's function method we are able to find the full distribution of charge transfers for all temperatures and voltages. For the non-Gaussian regime, we show that the equilibrium current fluctuations are enhanced by the presence of the superconductor. We predict an enhancement of the nonequilibrium current noise for temperatures below and voltages of the order of the Thouless energy E_Th=D/L^2. Our calculation fully accounts for the proximity effect in the normal metal and agrees with experimental data. We demonstrate that the calculation of the full current statistics is in fact simpler than a concrete calculation of the noise.Comment: 4 pages, 2 figures (included

Measurement of the energy resolution and calibration of hybrid pixel detectors with GaAs:Cr sensor and Timepix readout chip

This paper describes an iterative method of per-pixel energy calibration of hybrid pixel detectors with GaAs:Cr sensor and Timepix readout chip. A convolution of precisely measured spectra of characteristic X-rays of different metals with the resolution and the efficiency of the pixel detector is used for the calibration. The energy resolution of the detector is also measured during the calibration. The use of per-pixel calibration allows to achieve a good energy resolution of the Timepix detector with GaAs:Cr sensor: 8% and 13% at 60 keV and 20 keV, respectively

Classification of the electronic correlation strength in the Fe-pnictides: The case of the parent compound BaFe2As2

Electronic correlations in the Fe-pnictide BaFe2As2 are explored within LDA+DMFT, the combination of density functional theory with dynamical mean-field theory. While the correlated band structure is substantially renormalized there is only little transfer of spectral weight. The computed k-integrated and k-resolved spectral functions are in good agreement with photoemission spectroscopy (PES) and angular resolved PES experiments. Making use of a general classification scheme for the strength of electronic correlations we conclude that BaFe2As2 is a moderately correlated system.Comment: 4 pages, 3 figure

Non-equilibrium current noise in mesoscopic disordered SNS junctions

Current noise in superconductor-normal metal-superconductor (SNS) junctions is calculated within the scattering theory of multiple Andreev reflections (MAR). It is shown that the noise exhibits subharmonic gap singularities at $eV=2\Delta/n$, $n=1,2,...$ both in single-mode junctions with arbitrary transparency $D$ and in multi-mode disordered junctions. The subharmonic structure is superimposed with monotonic increase of the effective transferred charge $q^*=S_I(0)/2I$ with decreasing bias voltage. Other features of the noise include a step-like increase of $q^*$ in junctions with small $D$, and a divergence $S_I(0) \propto V^{-1/2}$ at small voltages and excess noise $S_{ex} = 2eI_{ex}$, where $I_{ex}$ is the excess current, at large voltages, in junctions with diffusive transport.Comment: 5 page

EXPERIENCE OF SURGICAL TREATMENT OF BENIGN TUMORS AND DYSPLATIC PROCESSES OF THE MANDIBLE BY THE METHOD OF REPLANTATION OF THE RECTURAL BONE, SUBJECTED TO FREEZING

The purpose of the study is the development of indications and evaluation of the long-term results of surgical treatment of benign tumors and dysplastic processes of the mandible by the method of replantation of resected bone exposed to extraorganic freezing. Material and methods. A method for the surgical treatment of benign tumors and dysplastic processes of the mandible has been developed. It involves resection of an afflicted by pathological process segment of bone within healthy tissues, its mechanical processing, freezing in liquid nitrogen followed by slow thawing, and replantation. The evaluation of the treatment results has been carried out on the base of clinical, radiation and functional research methods. Long-term follow-up after surgery has been ranged from one to 25 years. Results and discussion. Positive results of surgical treatment were recorded in 72 patients (88,9 %). The indications for the developed method use have been established. It was found that the reconstruction of the mandible with a resected bone segment exposed to extraorganic cryosurgery, eliminates the recurrence of a benign tumor, provides for the restoration of the anatomical integrity of the jaw, and reduces the invasiveness of the operation. Conclusion. Long-term clinical experience has shown that mandible direct reconstruction in the surgical treatment of benign tumors and dysplastic processes with the method of resection, external freezing of the afflicted jaw area and its replantation is available, simple, and highly effective and can be recommended in the practice of medical institutions

Peculiarities of Long-Term Spot Activity of Variable Stars of Late Spectral Types

В работе представлен анализ многолетних фотометрических наблюдений нескольких десятков хромосферно-активных звезд, обладающих активностью солнечного типа (как наших собственных наблюдений, так и имеющихся в литературе). Выполнено моделирование распределения холодных фотосферных пятен на основе зональной модели — получено несколько сотен моделей. Показано, что у ряда звезд наблюдается дрейф пятен по широте как в сторону экватора, так и в сторону полюса, однако скорость дрейфа ниже в несколько раз, чем у солнечных пятен. Выявлены циклы звездной активности длительностью от 6 до 40 лет.The paper presents an analysis of long-term photometric observations of several dozen chromospherically active stars with solar-type activity (both our own observations and those available in the literature). The distribution of cold photospheric spots has been modeled on the basis of a zonal model — several hundred models have been obtained. It is shown that a number of stars exhibit a latitude drift of spots, both towards the equator and towards the pole, however, the drift velocity is several times lower than that of sunspots. Cycles of stellar activity lasting from 6 to 40 years have been revealed.Работа выполнена при финансовой поддержке Министерства науки и высшего образования Российской Федерации, тема FEUZ-2023-0019