320 research outputs found
MERLIN imaging of the maser flare in Markarian 348
MERLIN images of Mrk 348 at 22 GHz show water maser emission at 0.02 - 0.11
Jy, within approximately 0.8 pc of the nucleus. This is the first direct
confirmation that molecular material exists close to the Seyfert 2 nucleus. Mrk
348 was observed in 2000 May one month after Falcke et al. (2000) first
identified the maser in single-dish spectra. The peak maser flux density has
increased about threefold. The masing region is < 0.6 pc in radius. The flux
density of radio continuum emission from the core has been rising for about 2
years. The maser-core separation is barely resolved but at the 3 sigma
significance level they are not coincident along the line of sight. The masers
lie in the direction of the northern radio lobes and probably emanate from
material shocked by a jet with velocity close to c. The correlation between the
radio continuum increase and maser flare is explained as arising from high
level nuclear activity through a common excitation mechanism although direct
maser amplification of the core by masers tracing a Keplerian disc is not
completely ruled out.Comment: Accepted by MNRAS Letters, 5 pages, 3 figures, corrections in text
and figur
Response of Mouse Breast Cancer Cells to Anastrozole, Tamoxifen, and the Combination
The murine breast cancer cells (4T1) grown both in female BALB/c mice and in culture were treated with anastrozole (50 μg/mL), tamoxifen citrate (5 μg/mL), and the combination of the two drugs in order to determine treatment efficacies, toxic potential, and the mechanism of cell death. The in vivo treatments were evaluated by monitoring tumor growth, development, and life span. The in vitro effects were measured through cell growth kinetics, cell proliferation, mitochondrial membrane potential disruption assay, and light and scanning electron microscopy. All drug treatments extended the mean life span of the 4T1-inoculated tumor-bearing mice; however, only tamoxifen and combination treatments statistically increased the life span when compared to untreated mice. Although the most drug inhibitory effect on cell multiplication was observed in the combination treatment, both anastrozole and tamoxifen individually inhibited cell proliferation significantly at most time periods in this mouse breast cancer cell line. The mitochondrial membrane potential disruption assay demonstrated significant increase in the percent of cells undergoing apoptosis in all treatment groups. However, the combination treatment was the most effective in inducing cell death via apoptosis. Light and scanning electron microscopy of the treated cells revealed characteristics such as rounding, clumping, and shrinkage of the cells as well as formation of cell surface blebbing and apoptotic bodies suggestive of cell death via apoptotic pathway
Linear radio structures in selected Seyfert and LINER galaxies
High resolution MERLIN 5 GHz observations (0.04") of 7 Seyfert galaxies,
selected as the ones previously showing evidence of collimated ejection, have
been compared with high resolution archive HST data. The radio maps reveal rich
structures in all the galaxies. NGC 2639 and TXFS 2226-184 have multiple knot
parsec-scale extended structures, Mrk 1034, Mrk 1210, NGC 4922C and NGC 5506
reveal one-sided jets, while IC 1481 exhibits a jet-like extension. The close
correlation between the radio-emitting relativistic plasma and the ionized gas
in the inner regions of these galaxies allows us to study in detail the physics
close to the center of low luminosity AGN.Comment: American Institute of Physics (AIP) Conference Series "Recent
Advances in Astronomy and Astrophysics
Lovelock black holes with a power-Yang-Mills source
We consider the standard Yang-Mills (YM) invariant raised to the power q,
i.e., as the source of our geometry
and investigate the possible black hole solutions. How does this parameter q
modify the black holes in Einstein-Yang-Mills (EYM) and its extensions such as
Gauss-Bonnet (GB) and the third order Lovelock theories? The advantage of such
a power q (or a set of superposed members of the YM hierarchies) if any, may be
tested even in a free YM theory in flat spacetime. Our choice of the YM field
is purely magnetic in any higher dimensions so that duality makes no sense. In
analogy with the Einstein-power-Maxwell theory, the conformal invariance
provides further reduction, albeit in a spacetime for dimensions of multiples
of 4.Comment: 19 pages, no figure and 2 tables, to appear in Physics Letters
Conformally dressed black hole in 2+1 dimensions
A three dimensional black hole solution of Einstein equations with negative
cosmological constant coupled to a conformal scalar field is given. The
solution is static, circularly symmetric, asymptotically anti-de Sitter and
nonperturbative in the conformal field. The curvature tensor is singular at the
origin while the scalar field is regular everywhere. The condition that the
Euclidean geometry be regular at the horizon fixes the temperature to be
. Using the Hamiltonian formulation including
boundary terms of the Euclidean action, the entropy is found to be
of the standard value (), and in agreement with
the first law of thermodynamics.Comment: LaTeX ,RevTeX, 13pages, no figure
Conformal Black Hole Solutions of Axi-Dilaton Gravity in D-dimensions
Static, spherically symmetric solutions of axi-dilaton gravity in
dimensions is given in the Brans-Dicke frame for arbitrary values of the
Brans-Dicke constant and an axion-dilaton coupling parameter . The
mass and the dilaton and axion charges are determined and a BPS bound is
derived. There exists a one parameter family of black hole solutions in the
scale invariant limit.Comment: 6 PAGES, Rev-tex file, no figures, to appear in Phys-Rev
Dipole Perturbations of the Reissner-Nordstrom Solution: The Polar Case
The formalism developed by Chandrasekhar for the linear polar perturbations
of the Reissner-Nordstrom solution is generalized to include the case of dipole
(l=1) perturbations. Then, the perturbed metric coefficients and components of
the Maxwell tensor are computed.Comment: 16 pages, LaTeX, no figures. Submitted for publication in Physical
Review
Chaos in black holes surrounded by gravitational waves
The occurrence of chaos for test particles moving around Schwarzschild black
holes perturbed by a special class of gravitational waves is studied in the
context of the Melnikov method. The explicit integration of the equations of
motion for the homoclinic orbit is used to reduce the application of this
method to the study of simple graphics.Comment: 15 pages, LaTex
Critical gradient turbulence optimization toward a compact stellarator reactor concept
Integrating turbulence into stellarator optimization is shown by targeting
the onset for the ion-temperature-gradient mode, highlighting effects of
parallel connection length, local magnetic shear, and flux surface expansion.
The result is a compact quasihelically symmetric stellarator configuration,
admitting a set of uncomplicated coils, with significantly reduced turbulent
heat fluxes compared to a known stellarator. The new configuration combines low
values of neoclassical transport, good alpha particle confinement, and Mercier
stability at a plasma beta of almost 2.Comment: 5 pages, 5 figures. Phys. Rev. Research 5, L032030 (2023
NICMOS images of JVAS/CLASS gravitational lens systems
We present Hubble Space Telescope (HST) infrared images of four gravitational
lens systems from the JVAS/CLASS gravitational lens survey and compare the new
infrared HST pictures with previously published WFPC2 HST optical images and
radio maps. Apart from the wealth of information that we get from the flux
ratios and accurate positions and separations of the components of the lens
systems that we can use as inputs for better constraints on the lens models we
are able to discriminate between reddening and optical/radio microlensing as
the possible cause of differences observed in the flux ratios of the components
across the three wavelength bands. Substantial reddening has been known to be
present in the lens system B1600+434 and has been further confirmed by the
present infrared data. In the two systems B0712+472 and B1030+074 microlensing
has been pinpointed down as the main cause of the flux ratio discrepancy both
in the optical/infrared and in the radio, the radio possibly caused by the
substructure revealed in the lensing galaxies. In B0218+357 however the results
are still not conclusive. If we are actually seeing the two "true" components
of the lens system then the flux ratio differences are attributed to a
combination of microlensing and reddening or alternatively due to some
variability in at least one of the images. Otherwise the second "true"
component of B0218+357 maybe completely absorbed by a molecular cloud and the
anomalous flux density ratios and large difference in separation between the
optical/infrared and radio that we see can be explained by emission from either
a foreground object or from part of the lensing galaxy.Comment: 10 pages, 4 figures (original higher resolution figures can be
obtained at the e-mail above), to appear in MNRAS (accepted
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