2,096 research outputs found
Features of epigenetic dolomite transformations in the Syukeyevskoye bitumen field
Syukeyevskoye bitumen field is one of perspective for development of open pit mining in western part of the Republic of Tatarstan. Basically two predominant stages in the process of epigenetic rock transformations were discriminated on the basis of field and laboratory data. The first stage associates with the fluids penetration in biomicritic dolomites and the hydrocarbon accumulation. The second stage associates with hydrocarbon oxidation. One can resume that leaching processes dominate at the stage of hydrocarbons penetration within dolomite rocks, and metasomatic processes dominate at hydrocarbon oxidation stage. These features can be used as key for understanding rock formation history in other similar cases
Excitonic instability and electric-field-induced phase transition towards a two dimensional exciton condensate
We present an InAs-GaSb-based system in which the electric-field tunability
of its 2D energy gap implies a transition towards a thermodynamically stable
excitonic condensed phase. Detailed calculations show a 3 meV BCS-like gap
appearing in a second-order phase transition with electric field. We find this
transition to be very sharp, solely due to exchange interaction, and so, the
exciton binding energy is greatly renormalized even at small condensate
densities. This density gradually increases with external field, thus enabling
the direct probe of the Bose-Einstein to BCS crossover.Comment: LaTex, 11 pages, 3 ps figures, To appear in PR
Method for measuring the hadron-proton scattering cross-section in the coulomb interference region
X-ray microtomography and grain size analysis of bituminous sandstones from Ashalchinskoye oil field
X-ray microtomography on 4.6 mm long 4.7 mm diameter samples of bituminous sandstones from Ashalchinskoye oil field was performed with a spatial resolution of 5.8?m. The representative elementary volumes for grain size distribution were estimated along with porosity and permeability coefficients for digital cube geometry ranged between 0.3 and 3.5 mm (0.03-43 mm3).The representative elementary volume for grain size distribution was achieved at cube edge length of 2.3 mm (12.2 mm3). This value is almost 2 times higher than the estimation of representative elementary volume for absolute permeability tensor and almost 4 times higher than the estimation for porosity coefficient. It is shown that Kozeny's formula characterizing the dependence of the effective permeability coefficient on the grain diameter and the porosity gives lower values, compared with the permeability coefficients obtained by modeling flow processes on digital images
Unconventional magnetism of non-uniform distribution of Co in TiO2 nanoparticles
High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) analysis, electron paramagnetic resonance (EPR), X-ray absorption spectroscopy (XAS), magnetic methods, and density-functional theory (DFT) calculations were applied for the investigations of Co-doped anatase TiO2 nanoparticles (∼20 nm). It was found that high-spin Co2+ ions prefer to occupy the interstitial positions in the TiO2 lattice which are the most energetically favourable in compare to the substitutional those. A quantum mechanical model which operates mainly on two types of Co2+ – Co2+ dimers with different negative exchange interactions and the non-interacting paramagnetic Co2+ ions provides a satisfactorily description of magnetic properties for the TiO2:Co system. © 2020 Elsevier B.V.Russian Foundation for Basic Research. Ministry of Science and Higher Education of the Russian Federatio
Skyrmionic excitons
We investigate the properties of a Skyrmionic exciton consisting of a
negatively charged Skyrmion bound to a mobile valence hole. A variational wave
function is constructed which has the generalized total momentum P as a good
quantum number. It is shown that the Skyrmionic exciton can have a larger
binding energy than an ordinary magnetoexciton and should therefore dominate
the photoluminescence spectrum in high-mobility quantum wells and
heterojunctions where the electron-hole separation exceeds a critical value.
The dispersion relation for the Skyrmionic exciton is discussed.Comment: 9 pages, RevTex, 2 PostScript figures. Replaced with version to
appear in Phys. Rev. B Rapid Communications. Short discussion of variational
state adde
Hydrogen Molecules In Superstrong Magnetic Field: II. Excitation Levels
We study the energy levels of H molecules in a superstrong magnetic field
(B\go 10^{12} G), typically found on the surfaces of neutron stars. The
interatomic interaction potentials are calculated by a Hartree-Fock method with
multi-configurations assuming electrons are in the ground Landau state. Both
the aligned configurations and arbitrary orientations of the molecular axis
with respect to the magnetic field axis are considered. Different types of
molecular excitations are then studied: electronic excitations, aligned (along
the magnetic axis) vibrational excitations, transverse vibrational excitations
(a constrained rotation of the molecular axis around the magnetic field line).
Similar results for the molecular ion H are also obtained and compared
with previous variational calculations. Both numerical results and analytical
fitting formulae are given for a wide range of field strengths. In contrast to
the zero-field case, it is found that the transverse vibrational excitation
energies can be larger than the aligned vibration excitation, and they both can
be comparable or larger than the electronic excitations. For B\go
B_{crit}=4.23\times 10^{13} G, the Landau energy of proton is appreciable and
there is some controversy regarding the dissociation energy of H. We show
that H is bound even for and that neither proton has a Landau
excitation in the ground molecular state.Comment: Revtex (45 pages), 3 postscript figures; Phys. Rev. A in pres
Hydrogen molecule in a magnetic field: The lowest states of the Pi manifold and the global ground state of the parallel configuration
The electronic structure of the hydrogen molecule in a magnetic field is
investigated for parallel internuclear and magnetic field axes. The lowest
states of the manifold are studied for spin singlet and triplet as well as gerade and ungerade parity for a broad range of field
strengths For both states with gerade parity we
observe a monotonous decrease in the dissociation energy with increasing field
strength up to and metastable states with respect to the
dissociation into two H atoms occur for a certain range of field strengths. For
both states with ungerade parity we observe a strong increase in the
dissociation energy with increasing field strength above some critical field
strength . As a major result we determine the transition field strengths
for the crossings among the lowest , and
states. The global ground state for is the strongly
bound state. The crossings of the with the
and state occur at and , respectively. The transition between the and
state occurs at Therefore, the global ground state of the
hydrogen molecule for the parallel configuration is the unbound
state for The ground state for is the strongly bound state. This result is of great
relevance to the chemistry in the atmospheres of magnetic white dwarfs and
neutron stars.Comment: submitted to Physical Review
Second-order -regularity in nonlinear elliptic problems
A second-order regularity theory is developed for solutions to a class of
quasilinear elliptic equations in divergence form, including the -Laplace
equation, with merely square-integrable right-hand side. Our results amount to
the existence and square integrability of the weak derivatives of the nonlinear
expression of the gradient under the divergence operator. This provides a
nonlinear counterpart of the classical -coercivity theory for linear
problems, which is missing in the existing literature. Both local and global
estimates are established. The latter apply to solutions to either Dirichlet or
Neumann boundary value problems. Minimal regularity on the boundary of the
domain is required. If the domain is convex, no regularity of its boundary is
needed at all
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