1,384 research outputs found
Peculiarities of phonon spectra and lattice heat capacity in Ir and Rh
A simple pseudopotential model is proposed, which allows the phonon spectra
and temperature dependence of the lattice heat capacity of Ir and Rh be
described with a high enough accuracy. A careful comparison of the calculated
and experimental values of the lattice heat capacity is carried out, with the
procedure of the identification of the phonon contribution to the heat capacity
and determination of the characteristics (momenta) of the phonon density of
states from the experimental values of the total heat capacity of metal at a
constant pressure being described in detail. The results of the theoretical
calculations explain, in particular, such peculiar feature of Ir and Rh,
unusual for cubic metals, as a sharp (more than by a factor of 1.5) decrease in
the effective Debye temperature with increasing termperature. The temperature
dependence of the mean square amplitude of atomic displacements in Ir and Rh
has been calculated. Basing on the band calculations the manifestation of the
Kohn singularities in the phonon spectra of Ir are discussed.Comment: 15 pages, LaTeX2e, 12 figures in postscrip
Three-particle States in Nonrelativistic Four-fermion Model
On a nonrelativistic contact four-fermion model we have shown that the simple
Lambda-cut-off prescription together with definite fine-tuning of the Lambda
dependency of "bare"quantities lead to self-adjoint semi-bounded Hamiltonian in
one-, two- and three-particle sectors. The fixed self-adjoint extension and
exact solutions in two-particle sector completely define three-particle
problem. The renormalized Faddeev equations for the bound states with Fredholm
properties are obtained and analyzed.Comment: 9 pages, LaTex, no figure
Boron Nitride Monolayer: A Strain-Tunable Nanosensor
The influence of triaxial in-plane strain on the electronic properties of a
hexagonal boron-nitride sheet is investigated using density functional theory.
Different from graphene, the triaxial strain localizes the molecular orbitals
of the boron-nitride flake in its center depending on the direction of the
applied strain. The proposed technique for localizing the molecular orbitals
that are close to the Fermi level in the center of boron nitride flakes can be
used to actualize engineered nanosensors, for instance, to selectively detect
gas molecules. We show that the central part of the strained flake adsorbs
polar molecules more strongly as compared with an unstrained sheet.Comment: 20 pages, 9 figure
Приливы в юго-западной части Карского моря. Результаты применения способа калибровки приливов
The estimates of the tides harmonic constants are given over the period from 1962 to 1993. They were received using a least square method according to AARI. Quality estimation of the sea level observations was performed. The annual series with bad observations were transformed by means of tides calibration. The Estimation of the tides fi ne structure – harmonics of the second and third degree of the potential according to analysis over the period from 1962–1985 was received. The statistical estimations of the sea level in the separate typical years were calculated using initial and corrected series.Приведены оценки гармонических постоянных приливов на станции имени Е.К. Федорова за период с 1962 по 1993 г., полученные с помощью метода наименьших квадратов по версии ААНИИ. Произведена оценка качества наблюдений за уровнем моря. Годовые серии с плохими наблюдениями исправлены по способу калибровки приливов. Получена оценка тонкой структуры приливов — гармоник второй и третьей степени потенциала по анализу за период 1962–1985 гг. По исходным и исправленным рядам рассчитаны статистические оценки уровня моря в отдельные типичные годы
The Unique Origin of Colors of Armchair Carbon Nanotubes
The colors of suspended metallic colloidal particles are determined by their
size-dependent plasma resonance, while those of semiconducting colloidal
particles are determined by their size-dependent band gap. Here, we present a
novel case for armchair carbon nanotubes, suspended in aqueous medium, for
which the color depends on their size-dependent excitonic resonance, even
though the individual particles are metallic. We observe distinct colors of a
series of armchair-enriched nanotube suspensions, highlighting the unique
coloration mechanism of these one-dimensional metals.Comment: 4 pages, 3 figure
Thermochemiluminescent peroxide crystals
Chemiluminescence, a process of transduction of energy stored within chemical bonds of ground-state reactants into light via high-energy excited intermediates, is known in solution, but has remained undetected in macroscopic crystalline solids. By detecting thermally induced chemiluminescence from centimeter-size crystals of an organic peroxide here we demonstrate direct transduction of heat into light by thermochemiluminescence of bulk crystals. Heating of crystals of lophine hydroperoxide to ~115 °C results in detectable emission of blue-green light with maximum at 530 nm with low chemiluminescent quantum yield [(2.1 ± 0.1) × 10 ‒7 E mol ‒1 ]. Spectral comparison of the thermochemiluminescence in the solid state and in solution revealed that the solid-state thermochemiluminescence of lophine peroxide is due to emission from deprotonated lophine. With selected 1,2-dioxetane, endoperoxide and aroyl peroxide we also establish that the thermochemiluminescence is common for crystalline peroxides, with the color of the emitted light varying from blue to green to red
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