Quantum Size Effects and Transport Phenomena in PbSe Quantum Wells and PbSe/EuS Superlattices

It is established that the room-temperature dependences of transport properties on the total thickness of PbSe layers d in PbSe/EuS superlattices exhibit an oscillatory behavior. It is shown that the oscillation period Δd practically coincides with the period of the thickness oscillations observed earlier in single PbSe/EuS quantum well. The non-monotonic character of these dependences is attributed to quantum size effects. The theoretically estimated and experimentally determined Δd values are in good agreement

Size Effects in Transport Properties of PbSe Thin Films

This paper presents an overview and analysis of our earlier obtained experimental results on the dependences of kinetic properties of single PbSe quantum wells and PbSe-based superlattices on the PbSe layer thickness d. The observed oscillatory character of these dependences is attributed to quantum size effects due to electron or hole confinement in quantum wells. Some general regularities and factors that determine the character of these quantum size effects are established. The influence of the oxidation processes and doping on the d-dependences of the transport properties is revealed. A periodic change in the conductivity type related to quantum size oscillations is detected. It is shown that the experimentally determined values of the oscillation period Dd are in good agreement with the results of theoretical calculations based on the model of a rectangular quantum well with infinitely high walls, taking into account the dependence of the Fermi energy eF on d and the availability of subbands below eF. It is established that the Dd value for the superlattices is practically equal to the Dd value observed for the single PbSe thin film

Size effects in thin PbSe films

The objects of the study are thin PbSe films with thicknesses d in the range of d = 5.5 – 410 nm, grown by thermal evaporation in vacuum of stoichiometric p-PbSe crystals on KCl substrates and covered with a EuSe layer. The room-temperature d-dependences of the Seebeck coefficient, Hall coefficient, electrical conductivity, charge carrier mobility, thermoelectric power factor are obtained. When d increases to ~ 20 nm, an inversion of the conductivity sign from p to n is observed. In the d-dependences of the transport properties one can isolate a monotonic and oscillatory components, whose presence is attributed to the manifestation of classical and quantum size effects, respectively. The oscillation periods Δd for electronic and hole gases are determined. Theoretically calculated Δd, assuming a size quantization of the electronic and hole spectra, and our estimate of the monotonic component of the electrical conductivity, using the Fuchs-Sondheimer theory, are in good agreement with the experimental data

Business administration as a basis for development of global entrepreneurship

The purpose of the article is to determine the role and meaning of business administration in development of global entrepreneurship. The work uses the proprietary methodology of evaluation of global competitiveness of enterprise and the proprietary methodology of evaluation of efficiency of business administration of enterprise, as well as method of correlation analysis. The authors determine the role of business administration in management of factors of development of global enterprise and offer the proprietary structural and logical model of organization of the process of business administration of global enterprise as a perspective tool for provision of global competitiveness of business and development of global entrepreneurship on the whole. The authors come to the conclusion that business administration is a basis for development of global entrepreneurship and plays an important role in this process, which consists in managing other internal and external factors of functioning of global business.peer-reviewe

A variable kinematic doubly-curved MITC9 shell element for the analysis of laminated composites

The present article considers the linear static analysis of composite shell structures with double-curvature geometry by means of a shell finite element with variable through-the-thickness kinematic. The refined models used are grouped in the Unified Formulation by Carrera (CUF) and they permit the distribution of displacements and stresses along the thickness of the multilayered shell to be accurately described. The shell element has nine nodes and the mixed interpolation of tensorial components (MITC) method is used to contrast the membrane and shear locking phenomenon. The governing equations are derived from the principle of virtual displacement (PVD) and the finite element method (FEM) is employed to solve them. Cross-ply spherical shells with simply-supported edges and subjected to bi-sinusoidal pressure are analyzed. Various laminations, thickness ratios, and curvature ratios are considered. The results, obtained with different theories contained in the CUF, are compared with both the elasticity solutions given in the literature and the analytical solutions obtained using the CUF and the Navier's method. From the analysis, one can conclude that the shell element based on the CUF is very efficient and its use is mandatory with respect to the classical models in the study of composite structures. Finally, shells with different lamination, boundary conditions, and loads are also analyzed using high-order layer-wise theories in order to provide FEM benchmark solution

Prediction of Anisotropic Single-Dirac-Cones in Bi1−x{}_{1-x}Sbx{}_{x} Thin Films

The electronic band structures of Bi${}_{1-x}$Sb${}_{x}$ thin films can be varied as a function of temperature, pressure, stoichiometry, film thickness and growth orientation. We here show how different anisotropic single-Dirac-cones can be constructed in a Bi${}_{1-x}$Sb${}_{x}$ thin film for different applications or research purposes. For predicting anisotropic single-Dirac-cones, we have developed an iterative-two-dimensional-two-band model to get a consistent inverse-effective-mass-tensor and band-gap, which can be used in a general two-dimensional system that has a non-parabolic dispersion relation as in a Bi${}_{1-x}$Sb${}_{x}$ thin film system

Transverse-momentum-dependent Multiplicities of Charged Hadrons in Muon-Deuteron Deep Inelastic Scattering

A semi-inclusive measurement of charged hadron multiplicities in deep inelastic muon scattering off an isoscalar target was performed using data collected by the COMPASS Collaboration at CERN. The following kinematic domain is covered by the data: photon virtuality $Q^{2}>1$ (GeV/$c$)$^2$, invariant mass of the hadronic system $W > 5$ GeV/$c^2$, Bjorken scaling variable in the range $0.003 < x < 0.4$, fraction of the virtual photon energy carried by the hadron in the range $0.2 < z < 0.8$, square of the hadron transverse momentum with respect to the virtual photon direction in the range 0.02 (GeV/$c)^2 < P_{\rm{hT}}^{2} < 3$ (GeV/$c$)$^2$. The multiplicities are presented as a function of $P_{\rm{hT}}^{2}$ in three-dimensional bins of $x$, $Q^2$, $z$ and compared to previous semi-inclusive measurements. We explore the small-$P_{\rm{hT}}^{2}$ region, i.e. $P_{\rm{hT}}^{2} < 1$ (GeV/$c$)$^2$, where hadron transverse momenta are expected to arise from non-perturbative effects, and also the domain of larger $P_{\rm{hT}}^{2}$, where contributions from higher-order perturbative QCD are expected to dominate. The multiplicities are fitted using a single-exponential function at small $P_{\rm{hT}}^{2}$ to study the dependence of the average transverse momentum $\langle P_{\rm{hT}}^{2}\rangle$ on $x$, $Q^2$ and $z$. The power-law behaviour of the multiplicities at large $P_{\rm{hT}}^{2}$ is investigated using various functional forms. The fits describe the data reasonably well over the full measured range.Comment: 28 pages, 20 figure

Инвазивный микоз с поражением центральной нервной системы, обусловленный редкими дрожжевыми грибами Malassezia spp., у пациентов с острым лейкозом: описание клинических случаев и обзор литературы

Malassezia spp. is a commensal yeast that represents normal microflora in humans and some animals. However, Malassezia spp. can cause life-threatening invasive mycosis. Evidence on Malassezia spp. infections is limited mostly to a case reports describing disease in newborns and premature infants, because lipid infusions (total parenteral nutrition) given through central venous catheter is a major risk factor. Here, we report two cases of CNS infection caused by Malassezia species in non-neonates with acute leukemia.Malassezia spp. — дрожжевые грибы, которые представлены в составе нормальной микрофлоры кожи человека и как симбионт препятствуют развитию инфекций, обусловленных опасными патогенами. Однако Malassezia spp. также может стать причиной тяжелого инвазивного микоза и привести к летальному исходу. Данные литературы ограничены, представлены преимущественно публикациями об инфекциях у новорожденных и недоношенных детей, что, в первую очередь, связывают с известным фактором риска — применение парентерального питания, включающего в себя жировую эмульсию, с использованием центрального венозного катетера. Мы представляем клинические случаи инфекции центральной нервной системы, обусловленной редкими возбудителями, дрожжевыми грибами рода Malassezia, у детей с острым лейкозом

Light isovector resonances in π-p →π-π-π+p at 190 GeV/c

We have performed the most comprehensive resonance-model fit of π-π-π+ states using the results of our previously published partial-wave analysis (PWA) of a large data set of diffractive-dissociation events from the reaction π-+p→π-π-π++precoil with a 190 GeV/c pion beam. The PWA results, which were obtained in 100 bins of three-pion mass, 0.5<2.5 GeV/c2, and simultaneously in 11 bins of the reduced four-momentum transfer squared, 0.1<1.0 (GeV/c)2, are subjected to a resonance-model fit using Breit-Wigner amplitudes to simultaneously describe a subset of 14 selected waves using 11 isovector light-meson states with JPC=0-+, 1++, 2++, 2-+, 4++, and spin-exotic 1-+ quantum numbers. The model contains the well-known resonances π(1800), a1(1260), a2(1320), π2(1670), π2(1880), and a4(2040). In addition, it includes the disputed π1(1600), the excited states a1(1640), a2(1700), and π2(2005), as well as the resonancelike a1(1420). We measure the resonance parameters mass and width of these objects by combining the information from the PWA results obtained in the 11 t′ bins. We extract the relative branching fractions of the ρ(770)π and f2(1270)π decays of a2(1320) and a4(2040), where the former one is measured for the first time. In a novel approach, we extract the t′ dependence of the intensity of the resonances and of their phases. The t′ dependence of the intensities of most resonances differs distinctly from the t′ dependence of the nonresonant components. For the first time, we determine the t′ dependence of the phases of the production amplitudes and confirm that the production mechanism of the Pomeron exchange is common to all resonances. We have performed extensive systematic studies on the model dependence and correlations of the measured physical parameters

Corrigendum to "Transverse extension of partons in the proton probed in the sea-quark range by measuring the DVCS cross section" [Phys. Lett. B 793 (2019) 188]

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