150 research outputs found
Vortices in atomic-molecular Bose-Einstein condensates
The structure and stability of vortices in hybrid atomic-molecular
Bose-Einstein condensates is analyzed in the framework of a two-component
Gross-Pitaevskii-type model that describes the stimulated Raman-induced
photoassociation process. New types of topological vortex states are predicted
to exist in the coherently coupled two-component condensates even without a
trap, and their nontrivial dynamics in the presence of losses is demonstrated.Comment: 7 pages, 6 figure
Dipole-Mode Vector Solitons
We find a new type of optical vector soliton that originates from trapping of
a dipole mode by a soliton-induced waveguide. These solitons, which appear as a
consequence of the vector nature of the two component system, are more stable
than the previously found optical vortex-mode solitons and represent a new type
of extremely robust nonlinear vector structure.Comment: Four pages with five eps figure
Observation of dipole-mode vector solitons
We report on the first experimental observation of a novel type of optical
vector soliton, a {\em dipole-mode soliton}, recently predicted theoretically.
We show that these vector solitons can be generated in a photorefractive medium
employing two different processes: a phase imprinting, and a symmetry-breaking
instability of a vortex-mode vector soliton. The experimental results display
remarkable agreement with the theory, and confirm the robust nature of these
radially asymmetric two-component solitary waves.Comment: 4 pages, 8 figures; pictures in the PRL version are better qualit
Efficacy of Various Regimens of Inhibitor-Protected Penicillins on the Basis of Immunospecific Mixed Saliva Proteins in Patients after Dental Implantation: a Randomized Uncontrolled Trial
Background. The available comparative studies on issues of choosing antibiotic regimen in dental implantation are often observational and describe only visible postoperative signs. More objective assessment of postoperative period and comparison of approaches requires laboratory tests. One of the methods to be used at a dental appointment is to study examination of the biochemical properties of saliva.Objective. To carry out comparative evaluation of single and prolonged regimens of amoxicillin/clavulanate administration after dental implantation indicated by nonspecific immunity in mixed saliva.Methods. A randomized uncontrolled trial of 30 partially edentulous patients was conducted. The clinical phase of the study was performed at the Department of Propaedeutics of Surgical Dentistry, MSUMD; the laboratory phase — at the Pharmacology and Biological Chemistry Departments, MSUMD, in 2021–2022. The study included patients aged 18 to 75 years, anatomically suitable for dental implant placement. Patients with somatic diseases in the decompensation stage were excluded from the study. Patients were randomized into 2 groups. The group 1 was prescribed to take amoxicillin/clavulanate pills (875+125 mg) 30 minutes before surgery. The group 2 was to take amoxicillin/clavulanate (875+125 mg) 30 minutes before surgery and then 1 pill of Amoxicillin/ Clavulanate (500+125 mg) 2 times a day for 7 days after surgery. To evaluate the efficacy of the applied antibiotic therapy, unstimulated mixed saliva was collected from all patients on an empty stomach, 1 ml before surgery and on the third day after surgery. The amount of immunoglobulins of G, M, A classes (mg/l) and б-amylase activity (IU/l) were determined spectrophotometrically in the saliva samples. Statistical processing of laboratory data was performed using Welch's t-test by means of Statistica 10 Pro (StatSoft, USA). Intergroup and intragroup differences were considered significant at p ≤ 0.05.Results. Based on the saliva proteins examined, the most pronounced difference between the patient groups was obtained for IgA. For other studied parameters of saliva, no significant difference between the groups was obtained on the third day after the surgery. However, despite the absence of a statistical difference, a tendency to a stronger increase in the amount of IgA, G, IgM, salivary amylase activity was noted for all indicators; moreover, a high correlation between immunoglobulins of class A, G, immunoglobulins of class G, M, and immunoglobulins of class A, M was revealed.Conclusion. Among patients with the prolonged regimen, the groups did not differ significantly in such saliva parameters as immunoglobulins G and M and salivary б-amylase activity, however, a tendency to a stronger increase of the mentioned immunoglobulins in the saliva of group 1 patients was revealed. The most significant difference was recorded for immunoglobulin A in saliva, the amount of which was significantly lower in the group of prolonged antibiotic administration (p < 0.05)
Nonlinear Dynamic Phenomena in Macroscopic Tunneling
Numerical simulations of the NLSE (or GPE) are presented demonstrating
emission of short pulses of the matter (light) density formed in the course of
tunneling in wave-guided light and/or trapped BEC. The phenomenon is observed
under various conditions, for nonlinearities of different signs, zero
nonlinearity included. We study, both numerically and analytically, pulsations
of matter (light) remaining within the trap and use the results in order to
induce emission of sequential pulses by properly narrowing the trap. This
allows us to propose a mechanism for a realization of Atom Pulse Laser.Comment: 14 pages, 6 figure
Modulational instability of spinor condensates
We demonstrate, analytically and numerically, that the ferromagnetic phase of
the spinor Bose-Einstein condenstate may experience modulational instability of
the ground state leading to a fragmentation of the spin domains. Together with
other nonlinear effects in the atomic optics of ultra-cold gases (such as
coherent photoassociation and four-wave mixing) this effect provides one more
analogy between coherent matter waves and light waves in nonlinear optics.Comment: 4 pages, 4 figures. Accepted for Phys. Rev. A Rapid Communication
Higher-order nonlinear modes and bifurcation phenomena due to degenerate parametric four-wave mixing
We demonstrate that weak parametric interaction of a fundamental beam with
its third harmonic field in Kerr media gives rise to a rich variety of families
of non-fundamental (multi-humped) solitary waves. Making a comprehensive
comparison between bifurcation phenomena for these families in bulk media and
planar waveguides, we discover two novel types of soliton bifurcations and
other interesting findings. The later includes (i) multi-humped solitary waves
without even or odd symmetry and (ii) multi-humped solitary waves with large
separation between their humps which, however, may not be viewed as bound
states of several distinct one-humped solitons.Comment: 9 pages, 17 figures, submitted to Phys. Rev.
The dynamics of a strongly driven two component Bose-Einstein Condensate
We consider a two component Bose-Einstein condensate in two spatially
localized modes of a double well potential, with periodic modulation of the
tunnel coupling between the two modes. We treat the driven quantum field using
a two mode expansion and define the quantum dynamics in terms of the Floquet
Operator for the time periodic Hamiltonian of the system. It has been shown
that the corresponding semiclassical mean-field dynamics can exhibit regions of
regular and chaotic motion. We show here that the quantum dynamics can exhibit
dynamical tunneling between regions of regular motion, centered on fixed points
(resonances) of the semiclassical dynamics
Dark-in-Bright Solitons in Bose-Einstein Condensates with Attractive Interactions
We demonstrate a possibility to generate localized states in effectively
one-dimensional Bose-Einstein condensates with a negative scattering length in
the form of a dark soliton in the presence of an optical lattice (OL) and/or a
parabolic magnetic trap. We connect such structures with twisted localized
modes (TLMs) that were previously found in the discrete nonlinear
Schr{\"o}dinger equation. Families of these structures are found as functions
of the OL strength, tightness of the magnetic trap, and chemical potential, and
their stability regions are identified. Stable bound states of two TLMs are
also found. In the case when the TLMs are unstable, their evolution is
investigated by means of direct simulations, demonstrating that they transform
into large-amplitude fundamental solitons. An analytical approach is also
developed, showing that two or several fundamental solitons, with the phase
shift between adjacent ones, may form stable bound states, with
parameters quite close to those of the TLMs revealed by simulations. TLM
structures are found numerically and explained analytically also in the case
when the OL is absent, the condensate being confined only by the magnetic trap.Comment: 13 pages, 7 figures, New Journal of Physics (in press
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