1,848 research outputs found
On the Creation of the Universe out of Nothing
We explain how the Universe was created with no expenditure of energy or
initial mass.Comment: To be presented at IWARA 2009 (4th International Workshop on
Astronomy and Relativistic Astrophysics), to be held in Brazil, October 200
Deep Chandra Observations of HCG 16 - I. Active Nuclei, Star formation and Galactic Winds
We present new, deep Chandra X-ray and Giant Metrewave Radio Telescope
610~MHz observations of the spiral-galaxy-rich compact group HCG 16, which we
use to examine nuclear activity, star formation and the high luminosity X-ray
binary populations in the major galaxies. We confirm the presence of obscured
active nuclei in NGC 833 and NGC 835, and identify a previously unrecognized
nuclear source in NGC 838. All three nuclei are variable on timescales of
months to years, and for NGC 833 and NGC 835 this is most likely caused by
changes in accretion rate. The deep Chandra observations allow us to detect for
the first time an Fe-K emission line in the spectrum of the Seyfert 2
nucleus of NGC 835. We find that NGC 838 and NGC 839 are both
starburst-dominated systems, with only weak nuclear activity, in agreement with
previous optical studies. We estimate the star formation rates in the two
galaxies from their X-ray and radio emission, and compare these results with
estimates from the infra-red and ultra-violet bands to confirm that star
formation in both galaxies is probably declining after galaxy-wide starbursts
were triggered ~400-500 Myr ago. We examine the physical properties of their
galactic superwinds, and find that both have temperatures of ~0.8 keV. We also
examine the X-ray and radio properties of NGC 848, the fifth largest galaxy in
the group, and show that it is dominated by emission from its starburst.Comment: 18 pages, 11 figures, 11 tables, accepted for publication in ApJ;
updated references and fixed typos identified at proof stag
Dynamical analysis of the cluster pair: A3407 + A3408
We carried out a dynamical study of the galaxy cluster pair A3407 \& A3408
based on a spectroscopic survey obtained with the 4 meter Blanco telescope at
the CTIO, plus 6dF data, and ROSAT All-Sky-Survey. The sample consists of 122
member galaxies brighter than . Our main goal is to probe the galaxy
dynamics in this field and verify if the sample constitutes a single galaxy
system or corresponds to an ongoing merging process. Statistical tests were
applied to clusters members showing that both the composite system A3407 +
A3408 as well as each individual cluster have Gaussian velocity distribution. A
velocity gradient of was identified around
the principal axis of the projected distribution of galaxies, indicating that
the global field may be rotating. Applying the KMM algorithm to the
distribution of galaxies we found that the solution with two clusters is better
than the single unit solution at the 99\% c.l. This is consistent with the
X-ray distribution around this field, which shows no common X-ray halo
involving A3407 and A3408. We also estimated virial masses and applied a
two-body model to probe the dynamics of the pair. The more likely scenario is
that in which the pair is gravitationally bound and probably experiences a
collapse phase, with the cluster cores crossing in less than 1
Gyr, a pre-merger scenario. The complex X-ray morphology, the gas temperature,
and some signs of galaxy evolution in A3408 suggests a post-merger scenario,
with cores having crossed each other Gyr ago, as an
alternative solution.Comment: 17 pages, 12 figures, submitted to MNRAS, accepted 2016 May 9.
Received 2016 May 9; in original form 2016 April 1
Effect of nitrogen supply on trans-resveratrol concentration in berries of Vitis vinifera L. cv. Cabernet Sauvignon
Research Note
High-resolution abundance analysis of red giants in the globular cluster NGC 6522
The [Sr/Ba] and [Y/Ba] scatter observed in some galactic halo stars that are
very metal-poor stars and in a few individual stars of the oldest known Milky
Way globular cluster NGC 6522,have been interpreted as evidence of early
enrichment by massive fast-rotating stars (spinstars). Because NGC 6522 is a
bulge globular cluster, the suggestion was that not only the very-metal poor
halo stars, but also bulge stars at [Fe/H]~-1 could be used as probes of the
stellar nucleosynthesis signatures from the earlier generations of massive
stars, but at much higher metallicity. For the bulge the suggestions were based
on early spectra available for stars in NGC 6522, with a medium resolution of
R~22,000 and a moderate signal-to-noise ratio. The main purpose of this study
is to re-analyse the NGC 6522 stars previously reported using new
high-resolution (R~45,000) and high signal-to-noise spectra (S/N>100). We aim
at re-deriving their stellar parameters and elemental ratios, in particular the
abundances of the neutron-capture s-process-dominated elements such as Sr, Y,
Zr, La, and Ba, and of the r-element Eu. High-resolution spectra of four giants
belonging to the bulge globular cluster NGC 6522 were obtained at the 8m VLT
UT2-Kueyen telescope with the UVES spectrograph in FLAMES-UVESconfiguration.
The spectroscopic parameters were derived based on the excitation and
ionization equilibrium of \ion{Fe}{I} and \ion{Fe}{II}. Our analysis confirms a
metallicity [Fe/H] = -0.95+-0.15 for NGC 6522, and the overabundance of the
studied stars in Eu (with +~0.2 < [Eu/Fe] < +~0.4) and alpha-elements O and Mg.
The neutron-capture s-element-dominated Sr, Y, Zr, Ba, La now show less
pronounced variations from star to star. Enhancements are in the range 0.0 <
[Sr/Fe] < +0.4, +0.23 < [Y/Fe] < +0.43, 0.0 < [Zr/Fe] < +0.4, 0.0 < [La/Fe] <
+0.35,and 0.05 < [Ba/Fe] < +0.55.Comment: date of acceptation: 31/07/2014, in press, 24 pages, 19
figures,Astronomy & Astrophysics, 201
Immunoexpression Of Cd95 In Chronic Gastritis And Gastric Mucosa-associated Lymphomas.
CD95 (Fas/APO-1)-mediated apoptosis plays an important role in immunological regulation and is related to the pathogenesis of autoimmune diseases. Immunoexpression of CD95 has been reported to frequently occur in low grade non-Hodgkin lymphomas, especially of post-germinal center histogenesis, among which those originating in mucosa-associated lymphoid tissue (MALT lymphomas). However, there is no report comparing in situ immunoexpression of this marker in lymphomas and the hyperplastic lymphoid reaction (chronic gastritis) related to Helicobacter pylori infection. The purpose of the present research was to compare the intensity of lymphoid CD95 immunoexpression in 15 cases of H. pylori-related chronic gastritis and 15 gastric MALT lymphomas. CD95 (anti-CD95) was detected by an immunoperoxidase technique in paraffin sections using the catalyzed amplification system. Graduation of reaction intensity (percentage of CD95-positive cells) was semiquantitative, from 1+ to 4+. Nine cases of chronic gastritis were 4+, five 2+ and one 1+. Three lymphomas were 4+, three 3+, four 2+, four 1+, and one was negative. Although 14 of 15 lymphomas were positive for CD95, the intensity of the reaction was significantly weaker compared to that obtained with gastric tissue for patients with gastritis (P = 0.03). The difference in CD95 immunoexpression does not seem to be useful as an isolated criterion in the differential diagnosis between chronic gastritis and MALT lymphomas since there was overlapping of immunostaining patterns. However, it suggests the possibility of a pathogenetic role of this apoptosis-regulating protein in MALT lymphomas.371397-40
Nuclear phytochrome a signaling promotes phototropism in Arabidopsis.
Phototropin photoreceptors (phot1 and phot2 in Arabidopsis thaliana) enable responses to directional light cues (e.g., positive phototropism in the hypocotyl). In Arabidopsis, phot1 is essential for phototropism in response to low light, a response that is also modulated by phytochrome A (phyA), representing a classical example of photoreceptor coaction. The molecular mechanisms underlying promotion of phototropism by phyA remain unclear. Most phyA responses require nuclear accumulation of the photoreceptor, but interestingly, it has been proposed that cytosolic phyA promotes phototropism. By comparing the kinetics of phototropism in seedlings with different subcellular localizations of phyA, we show that nuclear phyA accelerates the phototropic response, whereas in the fhy1 fhl mutant, in which phyA remains in the cytosol, phototropic bending is slower than in the wild type. Consistent with this data, we find that transcription factors needed for full phyA responses are needed for normal phototropism. Moreover, we show that phyA is the primary photoreceptor promoting the expression of phototropism regulators in low light (e.g., PHYTOCHROME KINASE SUBSTRATE1 [PKS1] and ROOT PHOTO TROPISM2 [RPT2]). Although phyA remains cytosolic in fhy1 fhl, induction of PKS1 and RPT2 expression still occurs in fhy1 fhl, indicating that a low level of nuclear phyA signaling is still present in fhy1 fhl
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