3,187 research outputs found
Control of ion density distribution by magnetic traps for plasma electrons
The effect of a magnetic field of two magnetic coils on the ion current density distribution in the setup for low-temperature plasma deposition is investigated. The substrate of 400 mm diameter is placed at a distance of 325 mm from the plasma duct exit, with the two magnetic coils mounted symmetrically under the substrate at a distance of 140 mm relative to the substrate centre. A planar probe is used to measure the ion current density distribution along the plasma flux cross-sections at distances of 150, 230, and 325 mm from the plasma duct exit. It is shown that the magnetic field strongly affects the ion current density distribution. Transparent plastic films are used to investigate qualitatively the ion density distribution profiles and the effect of the magnetic field. A theoretical model is developed to describe the interaction of the ion fluxes with the negative space charge regions associated with the magnetic trapping of the plasma electrons. Theoretical results are compared with the experimental measurements, and a reasonable agreement is demonstrated. © 2012 American Institute of Physics
Quantum gases in trimerized kagom\'e lattices
We study low temperature properties of atomic gases in trimerized optical
kagom\'{e} lattices. The laser arrangements that can be used to create these
lattices are briefly described. We also present explicit results for the
coupling constants of the generalized Hubbard models that can be realized in
such lattices. In the case of a single component Bose gas the existence of a
Mott insulator phase with fractional numbers of particles per trimer is
verified in a mean field approach. The main emphasis of the paper is on an
atomic spinless interacting Fermi gas in the trimerized kagom\'{e} lattice with
two fermions per site. This system is shown to be described by a quantum spin
1/2 model on the triangular lattice with couplings that depend on the bond
directions. We investigate this model by means of exact diagonalization. Our
key finding is that the system exhibits non-standard properties of a quantum
spin-liquid crystal: it combines planar antiferromagnetic order in the ground
state with an exceptionally large number of low energy excitations. The
possibilities of experimental verification of our theoretical results are
critically discussed.Comment: 19 pages/14 figures, version to appear in Phys. Rev. A., numerous
minor corrections with respect to former lanl submissio
Dense Plasmas in Magnetic Traps: Generation of Focused Ion Beams With Controlled Ion-to-Neutral Flux Ratios
Customized magnetic traps were developed to produce a domain of dense plasmas with a narrow ion beam directed to a particular area of the processed substrate. A planar magnetron coupled with an arc discharge source created the magnetic traps to confine the plasma electrons and generate the ion beam with the controlled ratio of ion-to-neutral fluxes. Images of the plasma jet patterns and numerical vizualizations help explaining the observed phenomena
Optical linewidth of a low density Fermi-Dirac gas
We study propagation of light in a Fermi-Dirac gas at zero temperature. We
analytically obtain the leading density correction to the optical linewidth.
This correction is a direct consequence of the quantum statistical correlations
of atomic positions that modify the optical interactions between the atoms at
small interatomic separations. The gas exhibits a dramatic line narrowing
already at very low densities.Comment: 4 pages, 2 figure
Central exclusive production of scalar \chi_c meson at the Tevatron, RHIC and LHC energies
We calculate several differential distributions for exclusive double
diffractive production in proton-antiproton collisions at the
Tevatron and in proton-proton collisions at RHIC and LHC in terms of
unintegrated gluon distributions (UGDFs) within the -factorisation
approach. The uncertainties of the Khoze-Martin-Ryskin approach are discussed
in detail. The transition vertex is calculated as
a function of gluon virtualities applying the standard pNRQCD technique. The
off-shell effects are discussed and quantified. They lead to a reduction of the
cross section by a factor 2--5, depending on the position in the phase space
and UGDFs. Different models of UGDFs are used and the results are shown and
discussed. The cross section for diffractive component depends strongly on
UGDFs. We calculate also the differential distributions for the fusion mechanism. The integrated cross section for
photon-photon fusion is much smaller than that of diffractive origin. The two
components have very different dependence on momentum transfers in
the nucleon lines as well as azimuthal-angle correlations between both outgoing
nucleons.Comment: 34 pages, 23 figures, 2 table
Use of a recombinant human follicle-stimulating hormone:recombinant human luteinizing hormone (r-hFSH:r-hLH) 2:1 combination for controlled ovarian stimulation during assisted reproductive technology treatment: A real-world study of routine practice in the Russian Federation
Two observational studies in the Russian Federation described patient demographics/clinical decision for treatment with recombinant human follicle-stimulating hormone:recombinant human luteinizing hormone (r-hFSH:r-hLH) 2:1 combination for ovarian stimulation (OS) during assisted reproductive technology (ART) and outcomes, respectively. The first (prospective) study enrolled 500 patients. After post-hoc regrouping to assign patients to discrete groups, 378 (75.6%) met the local Russian label for an r-hFSH:r-hLH 2:1 combination, 105 (21%) were treated according to other physician preference, and 17 (3.4%) met only the ESHRE Bologna criteria for a poor ovarian response. The clinical pregnancy rate per cycle was 30.4%. A total of 158/175 (90.3%) women achieving clinical pregnancy in the prospective study participated in the second (retrospective) study. The live birth rate per cycle was 25.8%. No new safety concerns were reported. These results support the use of the r-hFSH:r-hLH 2:1 combination in patients with a poor/suboptimal response to OS for ART treatment in the Russian Federation
Scissors mode of trapped dipolar gases
We study the scissors modes of dipolar boson and fermion gases trapped in a
spherically symmetric potential. We use the harmonic oscillator states to solve
the time-dependent Gross-Pitaevskii equation for bosons and the time-dependent
Hartree-Fock equation for fermions. It is pointed out that the scissors modes
of bosons and fermions can be of quite different nature
Differentiated approach to diagnosis and treatment to combined pathology of the pharynx, larynx and rhino-orbital zone: interdisciplinary interaction
Background. The main complaint of patients with inflammatory diseases of the pharynx is a sore throat; rhino-orbital pathology, in turn, is manifested by symptoms associated with impaired nasal breathing, lacrimal drainage and other ophthalmological disorders. With pathology of the larynx, dysphonia is often present. As a rule, such patients initially fall into the hands of general practitioners, therapists and pediatricians, less often otolaryngologists, however, periodically the clinical situation requires the involvement of other specialists and additional laboratory and instrumental studies. The article presents a number of clinical observations of patients with combined pathology of the pharynx, larynx and rhino-orbital zone, who initially turned to an otolaryngologist, who subsequently required a team approach from various specialists.
Aim. Demonstration of a differentiated approach to the diagnosis and treatment of combined pathology of the pharynx, larynx and rhino-orbital zone within the framework of interdisciplinary interaction of specialists based on clinical observations of patients.
Materials and methods. We observed 5 patients who initially sought consultation with an otorhinolaryngologist with complaints of pain or discomfort in the throat, impaired nasal breathing, lacrimal drainage, itching in the eye area, and dysphonia.
Results. The article presents clinical cases of syphilis, leptotrichosis of the oropharynx, herpesvirus infection type VI, infectious mononucleosis, infectious-toxic paresis of the larynx, the diagnosis and treatment of which was carried out through interdisciplinary interaction of otorhinolaryngologists with doctors of other specialties. The presented observations demonstrate that, despite the reason for treatment, patients with combined pathology of the pharynx, larynx and rhino-orbital zone require the help of not only otolaryngologists, but also other specialists, primarily infectious disease specialists.
Conclusion. In order to improve the quality of diagnosis, routing and treatment of patients with combined pathology of the pharynx and rhino-orbital zone, it is necessary to develop interdisciplinary interaction and create conditions for expanding the professional erudition of doctors dealing with the problems of pathology of the same anatomical areas
Sympathetic cooling of an atomic Bose-Fermi gas mixture
Sympathetic cooling of an atomic Fermi gas by a Bose gas is studied by
solution of the coupled quantum Boltzmann equations for the confined gas
mixture. Results for equilibrium temperatures and relaxation dynamics are
presented, and some simple models developed. Our study illustrate that a
combination of sympathetic and forced evaporative cooling enables the Fermi gas
to be cooled to the degenerate regime where quantum statistics, and mean field
effects are important. The influence of mean field effects on the equilibrium
spatial distributions is discussed qualitatively.Comment: 8 pages, 9 figures, accepted for publication in Phys.Rev.Let
Collective oscillations of an interacting trapped Fermi gas
We calculate the effects of two-body interactions on the low frequency
oscillations of a normal Fermi gas confined in a harmonic trap. The mean field
contribution to the collective frequencies is evaluated in the collisionless
regime using a sum rule approach. We also discuss the transition between the
collisionless and hydrodynamic regime with special emphasis to the spin dipole
mode in which two atomic clouds occupying different spin states oscillate in
opposite phase. The spin dipole mode is predicted to be overdamped in the
hydrodynamic regime. The relaxation time is calculated as a function of
temperature and the effects of Fermi statistics are explicitly pointed out.Comment: 4 pages, 1 figure include
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