5,317 research outputs found
Hyperfine frequency shift in two-dimensional atomic hydrogen
We propose the explanation of a surprisingly small hyperfine frequency shift
in the two-dimensional (2D) atomic hydrogen bound to the surface of superfluid
helium below 0.1 K. Owing to the symmetry considerations, the microwave-induced
triplet-singlet transitions of atomic pairs in the fully spin-polarized sample
are forbidden. The apparent nonzero shift is associated with the
density-dependent wall shift of the hyperfine constant and the pressure shift
due to the presence of H atoms in the hyperfine state not involved in the
observed transition. The interaction of adsorbed atoms with one
another effectively decreases the binding energy and, consequently, the wall
shift by the amount proportional to their density. The pressure shift of the
resonance comes from the fact that the impurity -state atoms
interact differently with the initial -state and final -state atoms and
is also linear in density. The net effect of the two contributions, both
specific for 2D hydrogen, is comparable with the experimental observation. To
our knowledge, this is the first mentioning of the density-dependent wall
shift. We also show that the difference between the triplet and singlet
scattering lengths of H atoms, pm, is exactly twice smaller
than the value reported by Ahokas {\it et al.}, Phys. Rev. Lett. {\bf101},
263003 (2008).Comment: 4 pages, no figure
Higher education competitiveness : definition, assessment and ways of growth
The article is devoted to the search and the description of marketing reserves determining perspective competitiveness of higher educational establishments.
The study refers to highly efficient institutions possessing the development potential and their own operational and marketing possibilities to comparative ways of growth.
The research led to a conclusion that it is necessary to actualize the marketing competence of the Russian higher educational establishments based on the modernization of the educational activity through the development of the full-fledged training and production complexes providing the students with employment experience and real labor activity.peer-reviewe
Shot Noise in Mesoscopic Transport Through Localised States
We show that shot noise can be used for studies of hopping and resonant
tunnelling between localised electron states. In hopping via several states,
shot noise is seen to be suppressed compared with its classical Poisson value
( is the average current) and the suppression depends on the
distribution of the barriers between the localised states. In resonant
tunnelling through a single impurity an enhancement of shot noise is observed.
It has been established, both theoretically and experimentally, that a
considerable increase of noise occurs due to Coulomb interaction between two
resonant tunnelling channels.Comment: 7 pages, 5 figures; Proceedings of the 10th Conference on Hopping and
Related Phenomena (Trieste 2003); requires Wiley style files (included
Adsorption and two-body recombination of atomic hydrogen on He-He mixture films
We present the first systematic measurement of the binding energy of
hydrogen atoms to the surface of saturated He-He mixture films.
is found to decrease almost linearly from 1.14(1) K down to 0.39(1) K, when the
population of the ground surface state of He grows from zero to
cm, yielding the value K cm
for the mean-field parameter of H-He interaction in 2D. The experiments
were carried out with overall He concentrations ranging from 0.1 ppm to 5 %
as well as with commercial and isotopically purified He at temperatures
70...400 mK. Measuring by ESR the rate constants and for
second-order recombination of hydrogen atoms in hyperfine states and we
find the ratio to be independent of the He content and to
grow with temperature.Comment: 4 pages, 4 figures, all zipped in a sigle file. Submitted to Phys.
Rev. Let
Enhanced shot noise in resonant tunnelling via interacting localised states
In a variety of mesoscopic systems shot noise is seen to be suppressed in
comparison with its Poisson value. In this work we observe a considerable
enhancement of shot noise in the case of resonant tunnelling via localised
states. We present a model of correlated transport through two localised states
which provides both a qualitative and quantitative description of this effect.Comment: 4 pages, 4 figure
Fluctuations and Dissipation of Coherent Magnetization
A quantum mechanical model is used to derive a generalized Landau-Lifshitz
equation for a magnetic moment, including fluctuations and dissipation. The
model reproduces the Gilbert-Brown form of the equation in the classical limit.
The magnetic moment is linearly coupled to a reservoir of bosonic degrees of
freedom. Use of generalized coherent states makes the semiclassical limit more
transparent within a path-integral formulation. A general
fluctuation-dissipation theorem is derived. The magnitude of the magnetic
moment also fluctuates beyond the Gaussian approximation. We discuss how the
approximate stochastic description of the thermal field follows from our
result. As an example, we go beyond the linear-response method and show how the
thermal fluctuations become anisotropy-dependent even in the uniaxial case.Comment: 22 page
On Uniqueness of Boundary Blow-up Solutions of a Class of Nonlinear Elliptic Equations
We study boundary blow-up solutions of semilinear elliptic equations
with , or with , where is a second order
elliptic operator with measurable coefficients. Several uniqueness theorems and
an existence theorem are obtained.Comment: To appear in Comm. Partial Differential Equations; 10 page
Behaviour of Ion-modified Cladding Tubes from E110 Alloy in High-temperature Water Steam
Beryllium materials are widely used in science and technology. They are of importance both for nuclear and thermonuclear energy applications. Additionally, metallic beryllium is transparent to x-ray radiation and used in the manufacture of X-ray windows and refractive x-ray lenses. SC “VNIINM” has developed beryllium materialsfor various purposes: for coating of the ITER’s first wall, for focusing and controlling X-ray radiation. Porous beryllium is of particular interest as it is an upcoming trend as a temper and neutron multiplier in blankets of thermonuclear facilities. A unique combination of X-ray optical properties also makes it possible to use porous beryllium in imaging devices in a synchrotron radiation beam (speckle suppressor)
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