Spin–state transition in the layered barium cobaltite derivatives and their thermoelectric properties

Ba1.9Me0.1Co9O14 (Me = Ba, Sr, Ca) (BCO) layered cobaltites were prepared by means of solid-state reactions method. Crystal structure, microstructure, thermal expansion, electrical conductivity, and thermo-EMF for the obtained oxides were studied; the values of their linear thermal expansion coefficient, activation energy of electrical transport, and power factor values were calculated. It was found that BCO are p-type semiconductors, in which the spin-state transition occurs within 460-700 K temperature interval due to change in spin state of cobalt ions, which accompanied the sharp increase in electrical conductivity, activation energy of electrical conductivity, and linear thermal expansion coefficient, while thermo-EMF coefficient decreased. Partial substitution of barium by strontium or calcium in BCO leads to the increase in spin-state transition temperature and electrical conductivity of the samples, and, at the same time, thermo-EMF coefficient; consequently, their power factor values decrease

Optical Study of GaAs quantum dots embedded into AlGaAs nanowires

We report on the photoluminescence characterization of GaAs quantum dots embedded into AlGaAs nano-wires. Time integrated and time resolved photoluminescence measurements from both an array and a single quantum dot/nano-wire are reported. The influence of the diameter sizes distribution is evidenced in the optical spectroscopy data together with the presence of various crystalline phases in the AlGaAs nanowires.Comment: 5 page, 5 figure

Integrated indicators of the quality of the system as the solution to the problem of separation of useful signal from noisy data

A stable modification of the principal component method is considered, which uses a quantitative estimation of the input data noise – the signal to noise ratio in determining the structure of the principal components and the principal factors for different observationsРассматривается устойчивая модификация метода главных компонент, использующая количественную оценку шума входных данных — отношение сигнал/шум, при определении структуры главных компонент и главных факторов для разных наблюдени

Size quantization of Dirac fermions in graphene constrictions

Quantum point contacts (QPCs) are cornerstones of mesoscopic physics and central building blocks for quantum electronics. Although the Fermi wave-length in high-quality bulk graphene can be tuned up to hundreds of nanometers, the observation of quantum confinement of Dirac electrons in nanostructured graphene systems has proven surprisingly challenging. Here we show ballistic transport and quantized conductance of size-confined Dirac fermions in lithographically-defined graphene constrictions. At high charge carrier densities, the observed conductance agrees excellently with the Landauer theory of ballistic transport without any adjustable parameter. Experimental data and simulations for the evolution of the conductance with magnetic field unambiguously confirm the identification of size quantization in the constriction. Close to the charge neutrality point, bias voltage spectroscopy reveals a renormalized Fermi velocity ($v_F \approx 1.5 \times 10^6 m/s$) in our graphene constrictions. Moreover, at low carrier density transport measurements allow probing the density of localized states at edges, thus offering a unique handle on edge physics in graphene devices.Comment: 24 pages including 20 figures and 1 table. Corrected typos. To appear in Nature Communication

Electrostatically Confined Monolayer Graphene Quantum Dots with Orbital and Valley Splittings

The electrostatic confinement of massless charge carriers is hampered by Klein tunneling. Circumventing this problem in graphene mainly relies on carving out nanostructures or applying electric displacement fields to open a band gap in bilayer graphene. So far, these approaches suffer from edge disorder or insufficiently controlled localization of electrons. Here we realize an alternative strategy in monolayer graphene, by combining a homogeneous magnetic field and electrostatic confinement. Using the tip of a scanning tunneling microscope, we induce a confining potential in the Landau gaps of bulk graphene without the need for physical edges. Gating the localized states toward the Fermi energy leads to regular charging sequences with more than 40 Coulomb peaks exhibiting typical addition energies of 7-20 meV. Orbital splittings of 4-10 meV and a valley splitting of about 3 meV for the first orbital state can be deduced. These experimental observations are quantitatively reproduced by tight binding calculations, which include the interactions of the graphene with the aligned hexagonal boron nitride substrate. The demonstrated confinement approach appears suitable to create quantum dots with well-defined wave function properties beyond the reach of traditional techniques

Electrostatically confined monolayer graphene quantum dots with orbital and valley splittings

The electrostatic confinement of massless charge carriers is hampered by Klein tunneling. Circumventing this problem in graphene mainly relies on carving out nanostructures or applying electric displacement fields to open a band gap in bilayer graphene. So far, these approaches suffer from edge disorder or insufficiently controlled localization of electrons. Here we realize an alternative strategy in monolayer graphene, by combining a homogeneous magnetic field and electrostatic confinement. Using the tip of a scanning tunneling microscope, we induce a confining potential in the Landau gaps of bulk graphene without the need for physical edges. Gating the localized states towards the Fermi energy leads to regular charging sequences with more than 40 Coulomb peaks exhibiting typical addition energies of 7-20 meV. Orbital splittings of 4-10 meV and a valley splitting of about 3 meV for the first orbital state can be deduced. These experimental observations are quantitatively reproduced by tight binding calculations, which include the interactions of the graphene with the aligned hexagonal boron nitride substrate. The demonstrated confinement approach appears suitable to create quantum dots with well-defined wave function properties beyond the reach of traditional techniques

Ultrasound diagnostics of consequences of traumatic injuries of liver

The results of ultrasound diagnostics of consequences of traumatic injuries of liver in 122 patients were analyzed. Contours, structure and. texture of intrahepatic formations depended on the type of tissue substrate (haematoma, haemobylema, bylema), terms of formation and infection of traumatic focus. At aseptic course of haematomas and haemobylemas of liver we divided pathological process into 4 stages: stage of latest hemorrhage, stage of formed clot, hemolytic stage and reparative stage. The differences at the infection way of development started from the second week after appearance of intrahepatic injury on the stage of "bacterial lysis of a clot" and. incapsulation. Ultrasound semiotics of intrahepatic bylemas depended only on the infection of contents

Expert Assessment of a Ratio of Expenses at Construction of Oil Transport Infrastructure in the Arctic

When assessing the cost of construction and operation of transport infrastructure in the early stages of the investment process, there is a problem in the formalization of some indicators of the factors influencing decision-making. The temporary impossibility to express them in monetary or comparable natural quantities leads to uncertainty in the ratio between these two groups of factors. On the example of one of the discussed objects of oil transport infrastructure in the territory of the Russian Arctic, quantitative estimates of such uncertainties are obtained, the value of which was very weighty and variable depending on the considered alternative. The authors propose an approach based on the vector representation of factors, fuzzy set theory and expert estimates, which allows developing a criterion of the limit value of uncertainty, allowing making management decisions in the problems of choice. The corresponding model giving the possibility of calculation of such criterion is constructed

Morphometric characteristics of effects induced by <i>Ensifer meliloti</i> lipopolysaccharide fractions on parenchymatous organs in laboratory rats with secondary immunodeficiency

Introduction. Gram-negative bacteria-derived lipopolysaccharides (LPS) are better known as bacterial endotoxins. However, an increasing body of evidence has been accumulated regarding a whole range of LPS-bound physiological effects also observed in normal settings. In particular, LPS derived from some bacterial species was shown to exhibit an immunomodulating activity.Study objective — to characterize physiological effects of Ensifer meliloti lipopolysaccharides in modelled rat induced immunodeficiency.Materials and methods. Biological activity of intraperitoneally administered E. meliloti LPS fractions was studied for 21 days in 60 outbred male rats after induction of a minimal immunodeficiency state 24 hours later after inoculating cytostatic agent cyclophosphamide (CF). Animals were euthanized on day 22 followed by conducting an autopsy and morphometric study of internal organs. Later, paraffin-embedded sections of parenchymal organs were stained with hematoxylin-eosin and examined histologically by light microscopy.Results. It was found that at the end of the experiment cyclophosphamide applied to laboratory animals insignificantly decreased weight of liver and kidney, but not that of heart and spleen (compared to intact animals). In contrast, lung weight was solely significantly increased in immunodeficient rats compared to control. Intraperitoneally administered LPS fractions during secondary immunodeficiency affected weight parameters in the liver and kidney as the most intensively blood supplied organs suggesting its systemic effects. Quantity of follicles with large germinal centers as well as secondary follicles and lymphatic sheath formation in splenic stroma was increased that features activated immune response. Moreover, hepatic lymphoid infiltration in the portal tracts and reversal to normal vascular pattern were found as well. In contrast, LPS and Licopid administered to rats resulted in marked lung hyperplasia of lymphoid tissue containing large germinal centers.Conclusion. The data obtained indicate that E. meliloti-derived LPS fractions administered to rats with secondary immunodeficiency positively affected immunoreactivity

The state of indicators of the angio-OCT of the macular area in pregnant women with preeclampsia in conjunction with the content of the factor of endothelial dysfunction, their importance for predicting vascular retinal pathology in the postpartum period

Purpose. Clinical assessment of the hemodynamic state of the macula in pregnant women with preeclampsia in conjunction with the content of endothelial dysfunction factors, their importance in predicting vascular retinal pathology in the postpartum period.Material and methods. The main group consisted of 46 pregnant women with preeclampsia (PE) from 19 to 40 years. 36 women had a moderate degree of PE, and 10 women had a severe degree. The 1st comparison group included 20 pregnant women with a physiological course of pregnancy, from 18 to 38 years. The 2nd comparison group included 16 non-pregnant women with occlusions of the branches of the central retinal vein (CRV), aged 34 to 45 years. The control group consisted of 20 healthy, non-pregnant women from 19 to 38 years. All patients underwent determination of the level of endothelin-1 (E) in the lacrimal fluid (LF), the state of hemodynamics of the macular area was investigated using optical coherent tomography with angiography function (angio-OCT).Results. The highest values of the average level of E in LF occurred in the main group and in the 2nd comparison group (2.5±1.1 and 2.6±0.4 ng / ml, respectively). In the 1st comparison group in the 3rd trimester of pregnancy, the indicators of the total average density of the superficial vascular plexus in the macular region (DS), the density of the superficial vascular plexus in the fovea (DF), the density of the superficial vascular plexus in the parafova (DP), the area of the retinal avascular area (NFA) and subfoveal thickness of the choroid (CTX) had statistically significant differences from the control (p&lt;0.01), but after 6–9 months after birth, these differences disappeared, although the difference in DS, DP values remained.Conclusion. In women with PE in the 3rd trimester of pregnancy, there was a statistically significant increase in E level in the LF and the deterioration of the angio-OCT of the macular ar ea