Ecological hazard, typology, morphometry and quantity of waste dumps of coal mines in Ukraine

As a result of coal mining, a large number of waste rock dumps have been created on the earth's surface around the world. As a result of deflation and water erosion of the dump surface, extensive contamination of the soil cover of agricultural land with heavy metals occurs, threatening the food security of many countries. The article proposes a method for determining the area of potentially contaminated land in coal-mining regions. The area of such land in Ukraine has been estimated. A scheme for the dispersion of pollutants from waste dumps is proposed, which makes it possible to identify four types of polluted areas. Using the Google Earth service, the exact modern number of dumps in the Donetsk coal basin (Donbass) as a whole (1600) and separately in its western, central and eastern parts was determined. The average height, the average and total area of the base and surface, and the forest cover of the dumps in the Central Donbass were determined. It was found that the area of potentially contaminated land as a result of surface deflation of dumps in Central Donbass is 30,605 hectares. Taking into account the discharge of pollutants both from the surface of the dumps and from the deflationary pollution zone, the area of such land is 35,765 hectares. The mathematical modelling of the processes of pollutant removal by wind and deposition on the soil surface showed that it is possible to radically reduce the area of pollution by afforestation of waste dumps and, first of all, their flat tops

Electron dynamics in the normal state of cuprates: spectral function, Fermi surface and ARPES data

An influence of the electron-phonon interaction on excitation spectrum and damping in a narrow band electron subsystem of cuprates has been investigated. Within the framework of the t-J model an approach to solving a problem of account of both strong electron correlations and local electron-phonon binding with characteristic Einstein mode $\omega _0$ in the normal state has been presented. In approximation Hubbard-I it was found an exact solution to the polaron bands. We established that in the low-dimensional system with a pure kinematic part of Hamiltonian a complicated excitation spectrum is realized. It is determined mainly by peculiarities of the lattice Green's function. In the definite area of the electron concentration and hopping integrals a correlation gap may be possible on the Fermi level. Also, in specific cases it is observed a doping evolution of the Fermi surface. We found that the strong electron-phonon binding enforces a degree of coherence of electron-polaron excitations near the Fermi level and spectrum along the nodal direction depends on wave vector module weakly. It corresponds to ARPES data. A possible origin of the experimentally observed kink in the nodal direction of cuprates is explained by fine structure of the polaron band to be formed near the mode -$\omega _0$

Glass transition in fullerenes: mode-coupling theory predictions

We report idealized mode-coupling theory results for the glass transition of ensembles of model fullerenes interacting via phenomenological two-body potentials. Transition lines are found for C60, C70 and C96 in the temperature-density plane. We argue that the observed glass-transition behavior is indicative of kinetic arrest that is strongly driven by the inter-particle attraction in addition to excluded-volume repulsion. In this respect, these systems differ from most standard glass-forming liquids. They feature arrest that occurs at lower densities and that is stronger than would be expected for repulsion-dominated hard-sphere-like or Lennard-Jones-like systems. The influence of attraction increases with increasing the number of carbon atoms per molecule. However, unrealistically large fullerenes would be needed to yield behavior reminiscent of recently investigated model colloids with strong short-ranged attraction (glass-glass transitions and logarithmic decay of time-correlation functions).Comment: 10 pages, 5 figure