518 research outputs found
Quantum interference in the classically forbidden region: a parametric oscillator
We study tunneling between period two states of a parametrically modulated
oscillator. The tunneling matrix element is shown to oscillate with the varying
frequency of the modulating field. The effect is due to spatial oscillations of
the wave function and the related interference in the classically forbidden
region. The oscillations emerge already in the ground state of the oscillator
Hamiltonian in the rotating frame, which is quartic in the momentum.Comment: Submitted to PR
Low temperature magnetic structure of CeRhIn by neutron diffraction on absorption-optimized samples
Two aspects of the ambient pressure magnetic structure of heavy fermion
material CeRhIn have remained under some debate since its discovery:
whether the structure is indeed an incommensurate helix or a spin density wave,
and what is the precise magnitude of the ordered magnetic moment. By using a
single crystal sample optimized for hot neutrons to minimize neutron absorption
by Rh and In, here we report an ordered moment of . In
addition, by using spherical neutron polarimetry measurements on a similar
single crystal sample, we have confirmed the helical nature of the magnetic
structure, and identified a single chiral domain
Multiphoton antiresonance in large-spin systems
We study nonlinear response of a spin with easy-axis anisotropy. The
response displays sharp dips or peaks when the modulation frequency is
adiabatically swept through multiphoton resonance. The effect is a consequence
of a special symmetry of the spin dynamics in a magnetic field for the
anisotropy energy . The occurrence of the dips or peaks is
determined by the spin state. Their shape strongly depends on the modulation
amplitude. Higher-order anisotropy breaks the symmetry, leading to sharp steps
in the response as function of frequency. The results bear on the dynamics of
molecular magnets in a static magnetic field.Comment: Submitted to PR
Several New Active Galactic Nuclei Among X-ray Sources Detected by INTEGRAL and SWIFT Observatories
We present the results of the optical identifications of a set of X-ray
sources from the all-sky surveys of INTEGRAL and SWIFT observatories. Optical
data were obtained with Russian-Turkish 1.5-m Telescope (RTT150). Nine X-ray
sources were identified as active galactic nuclei (AGNs). Two of them are
hosted by nearby, nearly exactly edge-on, spiral galaxies MCG -01-05-047 and
NGC 973. One source, IGR J16562-3301, is most probably BL Lac object (blazar).
Other AGNs are observed as stellar-like nuclei of spiral galaxies, with broad
emission lines in their spectra.
For the majority of our hard X-ray selected AGNs, their hard X-ray
luminosities are well-correlated with the luminosities in [OIII],5007 optical
emission line. However, the luminosities of some AGNs deviate from this
correlation. The fraction of these objects can be as high as 20%. In
particular, the flux in [OIII] line turns to be lower in two nearby edge-on
spiral galaxies, which can be explained by the extinction in their galactic
disks.Comment: 9 pages, 3 figures, accepted for publication in Astronomy Letters,
the original text in Russian can be found at
http://hea.iki.rssi.ru/~rodion/poptid.pd
Organizational aspects of neurorehabilitation at the outpatient stage
The study was aimed to evaluate the effectiveness of IRP implementation in patients of a specialized clinic providing long-term care to neurological and neurosurgical patients.
Material and methods. The study was conducted in 2020-2021. on the basis of the MC "Expert Health" (Odessa, Ukraine). 83 patients undergoing neurorehabilitation program were examined. The correspondence of the fulfillment of key rehabilitation tasks in terms of time and quality was assessed. Additionally, the level of motivation and compliance of the patient was assessed using the MOT-Q questionnaires (for patients with previous TBI (n = 13), SRMS (for patients with stroke (n = 54) and with SRQ-E (for patients with other types of neurological pathology (n = 16). The overall level of compliance was assessed using the General Rehabilitation Adherence Scale (GRAS). The level of safety was assessed according to the following criteria: the presence of FAST certificates for personnel, a system for monitoring vital functions, equipment and consumables for the provision of emergency care. Statistical processing was carried out by methods of variance and correlation analysis, using the MedCalc 1.3 software.
Results. There were not recorded any significant violations of safety principles in the provision of rehabilitation assistance in the certification of personnel according to FAST. The frequency of detecting cases of improper implementation of IRP did not exceed 6.0% (5 cases out of 83 analyzed). When assessing the relationship between the effectiveness of IRP and the level of compliance, a strong positive correlation was found - r = 0.78
Conclusion. 1. Provision of rehab services for neurological patients in the long term requires coordination of the actions of specialists at the intra-, inter-, and transdisciplinary levels. 2. A necessary condition for the functioning of a multidisciplinary team in the provision of rehabilitation care is certification of staff in the BLS systems - for allied health specialists and ACLS for physicians. 3. The effectiveness of IRP depends on the patient's compliance level (r = 0.78). 4. For the continuity of the rehabilitation process, it is necessary to involve relatives and facilitate their training in the basics of "home" rehabilitation
New Kinds of Acoustic Solitons
We find that the modified sine-Gordon equation belonging to the class of the
soliton equations describes the propagation of extremely short transverse
acoustic pulses through the low-temperature crystal containing paramagnetic
impurities with effective spin S=1/2 in the Voigt geometry case. The features
of nonlinear dynamics of strain field and effective spins, which correspond to
the different kinds of acoustic solitons, are studied.Comment: 9 pages, 1 figur
X-ray line formation in the spectrum of SS 433
The mechanisms for the formation of X-ray lines in the spectrum of SS 433 are
investigated by taking into account the radiative transfer inside the jets. The
results of Monte Carlo numerical simulations are presented. The effect of a
decrease in line intensity due to scattering inside the jet turns out to be
pronounced, but it does not exceed 60% in magnitude on the entire grid of
parameters. The line broadening due to scattering, nutational motion, and the
contribution of satellites can lead to overestimates of the jet opening angle
from the line widths in Chandra X-ray observations. The fine structure
of the lines turns out to be very sensitive to the scattering effects. This
makes its investigation by planned X-ray observatories equipped with
high-resolution spectrometers (primarily Astro-H) a powerful tool for
diagnosing the parameters of the jets in SS 433.Comment: 23 pages, 14 figures, to be published in Astronomy Letters, v. 38, n.
7, p. 443 (2012
Positron annihilation spectrum from the Galactic Center region observed by SPI/INTEGRAL
The electron-positron annihilation spectrum observed by SPI/INTEGRAL during
deep Galactic Center region exposure is reported. The line energy
(510.9540.075 keV) is consistent with the unshifted annihilation line. The
width of the annihilation line is 2.370.25 keV (FWHM), while the strength
of the ortho-positronium continuum suggests that the dominant fraction of
positrons (946%) form positronium before annihilation. Compared to the
previous missions these deep INTEGRAL observations provide the most stringent
constraints on the line energy and width.
Under the assumption of an annihilation in a single-phase medium these
spectral parameters can be explained by a warm K gas with
the degree of ionization larger than a few . One of the wide-spread
ISM phases - warm ( K) and weakly ionized (degree of ionization
0.1) medium satisfies these criteria. Other single-phase solutions are
also formally allowed by the data (e.g. cold, but substantially ionized ISM),
but such solutions are believed to be astrophysically unimportant.
The observed spectrum can also be explained by the annihilation in a
multi-phase ISM. The fraction of positrons annihilating in a very hot ( K) phase is constrained to be less than 8%. Neither a moderately
hot ( K) ionized medium nor a very cold ( K)
neutral medium can make a dominant contribution to the observed annihilation
spectrum. However, a combination of cold/neutral, warm/neutral and warm/ionized
phases in comparable proportions could also be consistent with the data.Comment: 11 pages, 11 figures, MNRAS, accepte
Asymptotic description of solutions of the exterior Navier Stokes problem in a half space
We consider the problem of a body moving within an incompressible fluid at
constant speed parallel to a wall, in an otherwise unbounded domain. This
situation is modeled by the incompressible Navier-Stokes equations in an
exterior domain in a half space, with appropriate boundary conditions on the
wall, the body, and at infinity. We focus on the case where the size of the
body is small. We prove in a very general setup that the solution of this
problem is unique and we compute a sharp decay rate of the solution far from
the moving body and the wall
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