41 research outputs found
The influence of quintessence on the motion of a binary system in cosmology
We employ the metric of Schwarzschild space surrounded by quintessential
matter to study the trajectories of test masses on the motion of a binary
system. The results, which are obtained through the gradually approximate
approach, can be used to search for dark energy via the difference of the
azimuth angle of the pericenter. The classification of the motion is discussed.Comment: 7 pages, 1 figur
Particle Motion and Electromagnetic Fields of Rotating Compact Gravitating Objects with Gravitomagnetic Charge
The exact solution for the electromagnetic field occuring when the
Kerr-Taub-NUT compact object is immersed (i) in an originally uniform magnetic
field aligned along the axis of axial symmetry (ii) in dipolar magnetic field
generated by current loop has been investigated. Effective potential of motion
of charged test particle around Kerr-Taub-NUT gravitational source immersed in
magnetic field with different values of external magnetic field and NUT
parameter has been also investigated. In both cases presence of NUT parameter
and magnetic field shifts stable circular orbits in the direction of the
central gravitating object. Finally we find analytical solutions of Maxwell
equations in the external background spacetime of a slowly rotating magnetized
NUT star. The star is considered isolated and in vacuum, with monopolar
configuration model for the stellar magnetic field.Comment: 18 pages, 6 figures, new results in section 2 added, section 3 is
revised, 3 references are adde
Electromagnetic Effects in Superconductors in Gravitational Field
The general relativistic modifications to the resistive state in
superconductors of second type in the presence of a stationary gravitational
field are studied. Some superconducting devices that can measure the
gravitational field by its red-shift effect on the frequency of radiation are
suggested. It has been shown that by varying the orientation of a
superconductor with respect to the earth gravitational field, a corresponding
varying contribution to AC Josephson frequency would be added by gravity. A
magnetic flux (being proportional to angular velocity of rotation )
through a rotating hollow superconducting cylinder with the radial gradient of
temperature is theoretically predicted. The magnetic flux is
assumed to be produced by the azimuthal current arising from Coriolis force
effect on radial thermoelectric current. Finally the magnetic flux through the
superconducting ring with radial heat flow located at the equatorial plane
interior the rotating neutron star is calculated. In particular it has been
shown that nonvanishing magnetic flux will be generated due to the general
relativistic effect of dragging of inertial frames on the thermoelectric
current.Comment: 11 pages 2 figure
Mesenchymal stromal cells of bone marrow and azathioprine in Crohn's disease therapy
Crohn's disease (CD) is a chronic, recurring disease of the gastrointestinal tract of unclear etiology. One of the new approaches to CD therapy is the use of the possibilities of stem cells, in particular, mesenchymal stromal cells (MSCs). Currently, the use of MSC in clinical practice for the treatment of chronic inflammatory and autoimmune diseases is being studied in patients who receive concomitant therapy with other immunomodulatory medications. Aim. To evaluate the effectiveness of MSCs therapy in patients with CD receiving azathioprine (AZA). Materials and methods. The study included 34 patients with inflammatory (luminal) form of CD. The 1st group of patients (n=15) received anti-inflammatory therapy using MSCs culture in combination with AZA. The 2nd group (n=19) received MSCs without AZA. The severity of the attack was assessed in points in accordance with the of Crohn's disease activity index (CDAI). Immunoglobulins (IgA, IgG, IgM), interleukins (IL) 1β, 4, 10, tumor necrosis factor-α (TNF-α), interferon-γ (INF-γ), transforming growth factor-1β (TGF-1β), C-reactive protein (CRP), platelets and erythrocyte sedimentation rate (ESR) at 2, 6 and 12 months from the beginning of MSCs therapy. Results. The initial mean CDAI in the 1st group was 337.6±17.1 points, in the 2nd group - 332.7±11.0 points (p=0.3). In both groups of patients there was a significant decrease in CDAI after 2 months. From the beginning of therapy MSCs: in the 1st group to 118.9±12.4 points, in the 2nd - 120.3±14.1 points (p=0.7), after 6 months - 110.3±11.1 and 114.3±11.8 points (p=0.8), respectively. After 12 months CDAI in the 1st group was 99.9±10.8 points, in the 2nd group it was 100.6±12.1 points (p=0.8). The level of IgA, IgG, IgM was significantly lower in the group of patients with a longer history of the disease and long-term ASA. After the introduction of MSC in both groups of patients with BC, there was a tendency for the growth of pro - and anti-inflammatory cytokines, with a significantly lower level of pro-inflammatory cytokines - INF-γ, TNF-α, IL-1β - in the 1st group, indicating potentiation of the immunosuppressive effect of MSCs and AZA, which provides a more pronounced anti-inflammatory effect. Conclusion. Transplantation of MSCs promotes an increase in the serum of patients with CD initially reduced concentration of IG, cytokines and restoring their balance as the onset of clinical remission. The combination with AZA has a more pronounced anti-inflammatory effect
Particle motion in the field of a five-dimensional charged black hole
In this paper, we have investigated the geodesics of neutral particles near a
five-dimensional charged black hole using a comparative approach. The effective
potential method is used to determine the location of the horizons and to study
radial and circular trajectories. This also helps us to analyze the stability
of radial and circular orbits. The radius of the innermost stable circular
orbits have also been determined. Contrary to the case of massive particles for
which, the circular orbits may have up to eight possible values of specific
radius, we find that the photons will only have two distinct values for the
specific radii of circular trajectories. Finally we have used the dynamical
systems analysis to determine the critical points and the nature of the
trajectories for the timelike and null geodesics.Comment: 15 pages, accepted for publication in Astrophysics and Space Scienc
Report on workshop A1: Exact solutions and their interpretation
I report on the communications and posters presented on exact solutions and
their interpretation at the GRG18 Conference, Sydney.Comment: 9 pages, no figures. Many typos corrected. Report submitted to the
Proceedings of GR18. To appear in CQ
Pathway to the Square Kilometre Array - The German White Paper -
The Square Kilometre Array (SKA) is the most ambitious radio telescope ever
planned. With a collecting area of about a square kilometre, the SKA will be
far superior in sensitivity and observing speed to all current radio
facilities. The scientific capability promised by the SKA and its technological
challenges provide an ideal base for interdisciplinary research, technology
transfer, and collaboration between universities, research centres and
industry. The SKA in the radio regime and the European Extreme Large Telescope
(E-ELT) in the optical band are on the roadmap of the European Strategy Forum
for Research Infrastructures (ESFRI) and have been recognised as the essential
facilities for European research in astronomy.
This "White Paper" outlines the German science and R&D interests in the SKA
project and will provide the basis for future funding applications to secure
German involvement in the Square Kilometre Array.Comment: Editors: H. R. Kl\"ockner, M. Kramer, H. Falcke, D.J. Schwarz, A.
Eckart, G. Kauffmann, A. Zensus; 150 pages (low resolution- and colour-scale
images), published in July 2012, language English (including a foreword and
an executive summary in German), the original file is available via the MPIfR
homepag
Magnetized Particle Capture Cross Section for Braneworld Black Hole
Capture cross section of magnetized particle (with nonzero magnetic moment)
by braneworld black hole in uniform magnetic field is considered. The magnetic
moment of particle was chosen as it was done by \citet{rs99} and for the
simplicity particle with zero electric charge is chosen. It is shown that the
spin of particle as well as the brane parameter are to sustain the stability of
particles circularly orbiting around the black hole in braneworld i.e. spin of
particles and brane parameter try to prevent the capture by black hole.Comment: 7 pages, 4 figures, Accepted for publication in Astrophysics & Space
Scienc
The Influence of Free Quintessence on Gravitational Frequency Shift and Deflection of Light with 4D momentum
Based on the 4D momentum, the influence of quintessence on the gravitational
frequency shift and the deflection of light are examined in modified
Schwarzschild space. We find that the frequency of photon depends on the state
parameter of quintessence : the frequency increases for and
decreases for . Meanwhile, we adopt an integral power number
() to solve the orbital equation of photon. The photon's
potentials become higher with the decrease of . The behavior of
bending light depends on the state parameter sensitively. In
particular, for the case of , there is no influence on the
deflection of light by quintessence. Else, according to the H-masers of GP-A
redshift experiment and the long-baseline interferometry, the constraints on
the quintessence field in Solar system are presented here.Comment: 12 pages, 2 figures, 4 tables. European Physical Journal C in pres