Planar Heterostructure Graphene -- Narrow-Gap Semiconductor -- Graphene

We investigate a planar heterostructure composed of two graphene films separated by a narrow-gap semiconductor ribbon. We show that there is no the Klein paradox when the Dirac points of the Brillouin zone of graphene are in a band gap of a narrow-gap semiconductor. There is the energy range depending on an angle of incidence, in which the above-barrier damped solution exists. Therefore, this heterostructure is a "filter" transmitting particles in a certain range of angles of incidence upon a potential barrier. We discuss the possibility of an application of this heterostructure as a "switch".Comment: 9 pages, 2 figure

Moving zero-gap Wannier-Mott excitons in graphene

We demonstrate the possibility of existence of indirect moving Wannier-Mott excitons in graphene. Electron-hole binding is conditioned by the trigonal warping of conic energy spectrum. The binding energies are found for the lowest exciton states. These energies essentially depend on the value and direction of exciton momentum and vanish when the exciton momentum tends to the conic points. The ways to observe the exciton states are discussed. The opportunity of experimental observation of zero-gap excitons by means of external electron scattering is examined.Comment: 6 pages, 7 figure

Quantum Well Based on Graphene and Narrow-Gap Semiconductors

We consider the energy spectrum of the planar quantum well which consisted of two ribbons of narrow-gap semiconductors and a graphene ribbon between ones. It is shown that the gapless mode appears only in case of inverted narrow-gap semiconductors. Spin splitting of the energy spectrum for a nonsymmetric quantum well is calculated taking into account a specificity of graphene. We investigate interface states and optical transitions. It is shown that the optical transitions are possible only with a conservation of a parity.Comment: 13 pages, 2 figures, 1 tabl

NEW MOLECULAR COMPLEX OF AMMONIUM GLYCYRRHIZATE WITH RUTIN

This study was carried out on the experimental equipment of the Sevastopol State University (project PR/807-42/2017)

Review on uranium in soil: levels, migration

The problems of radioactive contamination of biosphere with the 238U in recent years have attracted a large number of experts in various fields of knowledge. Natural radionuclides are an integral part of the biosphere. They are concentrated everywhere: in rocks, in soil, water, air and food. Various types of phosphorus fertilizers and other natural ameliorants used in agriculture are also an additional source of heavy natural radionuclides. The review describes the behaviour and migration of 238U in biosphere, which depend on various factors acting simultaneously. It is noted that the behaviour of 238U in the soil depends on the forms of its presence in it and the physical and chemical properties of the soil. The processes of sorption and desorption of 238U by different soil types are significant indicators

New Molecular Complex of Ammonium Glycyrrhizate with Rutin

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.Received:03.11.2021. Revised: 21.12.2021. Accepted: 21.12.2021. Available online: 11.01.2022.A new 1:1 molecular complex of triterpene glycoside ammonium glycyrrhizate (GC) with flavonoid glycoside rutin (Rut) was obtained in aqueous ethanol. The stability constant (9.70.2)104 (mol/L)–1 was calculated for the complex via isomolar curves. The complexation was studied by UV- and ATR IR-Fourier spectroscopy and a method of isomolar series. The hydrogen bonds and hydrophobic interactions are formed in the molecular complex. A preliminary antioxidant activity assessment of the complex was made.This study was carried out with the experimental equipment of the Sevastopol State University (project PR/807-42/2017)

A transverse current rectification in graphene superlattice

A model for energy spectrum of superlattice on the base of graphene placed on the striped dielectric substrate is proposed. A direct current component which appears in that structure perpendicularly to pulling electric field under the influence of elliptically polarized electromagnetic wave was derived. A transverse current density dependence on pulling field magnitude and on magnitude of component of elliptically polarized wave directed along the axis of a superlattice is analyzed.Comment: 12 pages, 6 figure

Assessment of the role of the state in the management of mineral resources

Mineral resources as natural capital can be transformed into human, social and physical capital, that guarantees the sustainable development of a country, exclusively through professional public management. Public management of a country's mineral resource potential is seen as an element of transnational governance. Regulation involves the use of laws, rules and regulations within the jurisdictional and sectoral capabilities of the state, minimizing its involvement as a producer. The features of the ideology of economic liberalism, which polarizes the societies of raw material producing countries by imposing austerity, as well as lowering trade barriers have been studied. The analysis of the influence of the radical new order of neoliberal world ideology on the development of the extractive sector and the strengthening of state regulation has been presented

Inclusive V0V^0 Production Cross Sections from 920 GeV Fixed Target Proton-Nucleus Collisions

Inclusive differential cross sections $d\sigma_{pA}/dx_F$ and $d\sigma_{pA}/dp_t^2$ for the production of \kzeros, \lambdazero, and \antilambda particles are measured at HERA in proton-induced reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to $\sqrt {s} = 41.6$ GeV in the proton-nucleon system. The ratios of differential cross sections \rklpa and \rllpa are measured to be $6.2\pm 0.5$ and $0.66\pm 0.07$, respectively, for \xf $\approx-0.06$. No significant dependence upon the target material is observed. Within errors, the slopes of the transverse momentum distributions $d\sigma_{pA}/dp_t^2$ also show no significant dependence upon the target material. The dependence of the extrapolated total cross sections $\sigma_{pA}$ on the atomic mass $A$ of the target material is discussed, and the deduced cross sections per nucleon $\sigma_{pN}$ are compared with results obtained at other energies.Comment: 17 pages, 7 figures, 5 table