363 research outputs found
The use of composite ferrocyanide materials for the treatment of high salinity liquid radioactive wastes rich in cesium isotopes
Several factors affecting the removal of cesium from LRW, namely total salt content, pH
and organic matter content, were also investigated. High concentrations of complexing organic matter
significantly reduced the sorption capacity of ferrocyanide sorbents
Delay and distortion of slow light pulses by excitons in ZnO
Light pulses propagating through ZnO undergo distortions caused by both bound
and free excitons. Numerous lines of bound excitons dissect the pulse and
induce slowing of light around them, to the extend dependent on their nature.
Exciton-polariton resonances determine the overall pulse delay and attenuation.
The delay time of the higher-energy edge of a strongly curved light stripe
approaches 1.6 ns at 3.374 eV with a 0.3 mm propagation length. Modelling the
data of cw and time-of-flight spectroscopies has enabled us to determine the
excitonic parameters, inherent for bulk ZnO. We reveal the restrictions on
these parameters induced by the light attenuation, as well as a discrepancy
between the parameters characterizing the surface and internal regions of the
crystal.Comment: 4 pages, 4 figure
Quantum corrections to the conductivity and Hall coefficient of a 2D electron gas in a dirty AlGaAs/GaAs/AlGaAs quantum well: transition from diffusive to ballistic regime
We report an experimental study of the quantum corrections to the
longitudinal conductivity and the Hall coefficient of a low mobility, high
density two-dimensional two-dimensional electron gas in a AlGaAs/GaAs/AlGaAs
quantum well in a wide temperature range (1.5 K - 110 K). This temperature
range covers both the diffusive and the ballistic interaction regimes for our
samples. It was therefore possible to study the crossover region for the
longitudinal conductivity and the Hall effect
Quantum Hall Effect induced by electron-electron interaction in disordered GaAs layers with 3D spectrum
It is shown that the observed Quantum Hall Effect in epitaxial layers of
heavily doped n-type GaAs with thickness (50-140 nm) larger the mean free path
of the conduction electrons (15-30 nm) and, therefore, with a three-dimensional
single-particle spectrum is induced by the electron-electron interaction. The
Hall resistance R_xy of the thinnest sample reveals a wide plateau at small
activation energy E_a=0.4 K found in the temperature dependence of the
transverse resistance R_xx. The different minima in the transverse conductance
G_xx of the different samples show a universal temperature dependence
(logarithmic in a large range of rescaled temperatures T/T_0) which is
reminiscent of electron-electron-interaction effects in coherent diffusive
transport.Comment: 6 pages, 3 figures, 1 tabl
Nano-QSAR: Model of mutagenicity of fullerene as a mathematical function of different conditions
The experimental data on the bacterial reverse mutation test (under various conditions) on C60 nanoparticles for the cases (i) TA100, and (ii) WP2uvrA/pkM101 are examined as endpoints. By means of the optimal descriptors calculated with the Monte Carlo method a mathematical model of these endpoints has been built up. The models are a mathematical function of eclectic data such as (i) dose (g/plate); (ii) metabolic activation (i.e. with mix S9 or without mix S9); and (iii) illumination (i.e. darkness or irradiation). The eclectic data on different conditions were represented by so-called quasi-SMILES. In contrast to the traditional SMILES which are representation of molecular structure, the quasi-SMILES are representation of conditions by sequence of symbols. The calculations were carried out with the CORAL software, available on the Internet at http://www.insilico.eu/coral. The main idea of the suggested descriptors is the accumulation of all available eclectic information in the role of logical and digital basis for building up a model. The computational experiments have shown that the described approach can be a tool to build up models of mutagenicity of fullerene under different conditions
Excitonic parameters of GaN studied by time-of-flight spectroscopy
We refine excitonic parameters of bulk GaN by means of time-of-flight
spectroscopy of light pulses propagating through crystals. The influence of
elastic photon scattering is excluded by using the multiple reflections of the
pulses from crystal boundaries. The shapes of these reflexes in the time-energy
plane depict the variation of the group velocity induced by excitonic
resonances. Modeling of the shapes, as well as other spectra, shows that a
homogeneous width of the order of 10 \mu eV characterizes the exciton-polariton
resonances within the crystal. The oscillator strength of A and B
exciton-polaritons is determined as 0.0022 and 0.0016, respectively.Comment: 12 pages, 2 figure
MATHEMATICAL MODELING OF ROCK CRUSHING AND MULTIPHASE FLOW OF DRILLING FLUID IN WELL DRILLING
The aim of the work is a mathematical modeling of the rock crushing during drilling and removal of the drilling cuttings (sludge) to the surface by drilling fluid. The process of rock destruction is described using the mathematical theory of fragmentation. The distribution of sludge particles in size and mass depends on such factors as the properties of the drilled rock, the rate of penetration, the type of bit, and the output power. After the formation of sludge, the process of its removal to the surface is modeled. The drilling fluid together with the rock particles is considered as a heterogeneous multiphase medium in which the carrier phase – the drilling fluid – is a non-Newtonian fluid. The flow of such a medium is described using a mixture model in the framework of the multi-fluid approach. This results in a system of nonlinear partial differential equations, for which a new closure relation is derived. To solve the system, the SIMPLE algorithm is used. As a result, the flow properties are studied with the inclusion of particles of various sizes. In particular, for particles of small size due to the action of plastic stresses in a non-Newtonian drilling fluid, an equilibrium mode arises in which the particles move with the drilling fluid without slipping. This is the fastest mode of delivery of sludge to the surface. The specific dimensions of such particles depend on the parameters of the drilling process. In particular, the appropriate size range can be adjusted by changing the parameters of the drilling fluid
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