483 research outputs found
The Nuclear Stellar Cluster in the Seyfert~1 Galaxy NGC 3227: High Angular Resolution NIR Imaging and Spectroscopy
NIR high angular resolution speckle imaging and imaging spectroscopy of the
nuclear region (10'' ~ 840pc) of the Seyfert1 galaxy NGC3227 are presented. A
nuclear stellar cluster is slightly resolved in the J and H band with
increasing contribution to the NIR continuum from the K to the J band. The
stellar absorption lines are extended compared to the neighboring continuum
suggesting a cluster size of ~ 70pc FWHM. Analysis of those lines suggests that
the stars are contributing about 65% (40%) of the total continuum emission in
the H (K) band in a 3.6'' aperture. Population synthesis in conjunction with
NIR spectral synthesis indicates an age of 25 to 50 Myr when red supergiants
contribute most to the NIR light. This is supported by published optical data
on the MgIb line and the CaII triplet. Although a higher age of ~ 0.5 Gyr where
AGB stars dominate the NIR light can not be excluded, the observed parameters
are at the limit of those expected for a cluster dominated by AGB stars.
However, in either case the resolved stellar cluster contributes only about ~
15 % of the total dynamical mass in the inner 300pc implying another much older
stellar population. Pure constant star formation over the last 10 Gyr can be
excluded. Therefore, at least two star formation/starburst events took place in
the nucleus of NGC3227. Since such sequences in the nuclear star formation
history are also observed in the nuclei of other galaxies a link between the
activity of the star formation and the AGN itself seems likely.Comment: accepted for publication in the Astrophysical Journal, 46 pages, 15
figure
Response of alluvial systems to Late Pleistocene climate changes recorded by environmental magnetism in the Añavieja Basin (Iberian Range, NE Spain)
Environmental magnetic proxies were analyzed in a relatively monotonous, ~25.3m thick alluvial sedimentary sequence drilled in the Añavieja Basin (NE Spain). Results from the core AĂ2 suggest that the concentrationdependent magnetic parameters mainly reflect variations in the content of detrital magnetite, sourced in the catchment rocks and soils of the basin, via changes in the dynamics of alluvial fans due to temperature changes in the northern hemisphere during the Late Pleistocene. The correspondence between the magnetic proxies and the temperature variations in the North Atlantic region (NGRIP curve) indicates that higher (lower) concentrations and finer (coarser) magnetite grains coincide with warm (cold) periods. We propose that during cold periods, a sparser vegetation cover favored the incoming of higher energy runoff bearing coarser sediments to the basin that are relatively impoverished in magnetite. In contrast, during warm periods, the wider distribution of the vegetation cover associated with the lower runoff energy lead to finer, magnetite-richer sediment input to the basin. Maghemite, presumably of pedogenic origin, appears to be present also in the studied alluvial sediments. Further studies are necessary to unravel its palaeoclimatic significance
Distribution of eosinophils in the gastrointestinal tract of children with no organic disease
Background This study aimed to assess the eosinophil (eos) density of the mucosa of the gastrointestinal (GI) tract in children undergoing endoscopic procedures following an extensive workup, without diagnosis of an organic disease. Methods Biopsies from GI endoscopies performed at 3 major childrenâs hospitals (Athens, Madrid and Rome), between January 2012 and June 2018, were evaluated by a single pathologist in each center. Peak eos counts were expressed /high power field and /mm2. Other histological abnormalities were also reported. Results A total of 111 children (median age 11 years; 48 boys) underwent upper endoscopy (333 biopsies), while 44 (median age 12; 25 boys) underwent ileocolonoscopy (262 biopsies). The median (interquartile range) eos/mm2 were as follows: esophagus 0 (0-0); stomach 0 (0-3); duodenum 22 (13-29); ileum 29 (19-46); cecum 39 (25-71); ascending colon 24 (20-41); transverse colon 27 (21-57); descending colon 21 (13-27); sigmoid colon 22 (13-30); and rectum 10 (6-22). Geographical variations in GI tissue eos counts were found amongst the participating centers, but the causative factors need further evaluation. Functional GI disorders according to the Rome IV criteria were diagnosed in 73 children (37 boys, median age 13 years). No differences were found between children with or without functional GI disorder diagnosis, with regard to eos density in the GI tract. Conclusion The reported peak counts of GI tissue eos in children with no organic diseases provide normative values that may be useful in the evaluation of children with GI symptoms suggestive of eosinophilic GI disorders
The Nature of LINERs
We present -band (m) spectroscopy of a sample of nine
galaxies showing some degree of LINER activity (classical LINERs, weak-[O {\sc
i}] LINERs and transition objects), together with -band spectroscopy for
some of them. A careful subtraction of the stellar continuum allows us to
obtain reliable [Fe {\sc ii}]m/Pa line ratios. We conclude
that different types of LINERs (i.e., photoionized by a stellar continuum or by
an AGN) cannot be easily distinguished based solely on the [Fe {\sc ii}]m/Pa line ratio.
The emission line properties of many LINERs can be explained in terms of an
aging starburst. The optical line ratios of these LINERs are reproduced by a
model with a metal-rich H {\sc ii} region component photoionized with a single
stellar temperature K, plus a supernova remnant (SNR) component.
The [Fe {\sc ii}] line is predominantly excited by shocks produced by SNRs in
starbursts and starburst-dominated LINERs, while Pa tracks H {\sc ii}
regions ionized by massive young stars. The contribution from SNRs to the
overall emission line spectrum is constrained by the [Fe {\sc ii}]m/Pa line ratio. Although our models for aging starbursts are
constrained only by these infrared lines, they consistently explain the optical
spectra of the galaxies also.
The LINER-starburst connection is tested by predicting the time dependence of
the ratio of the ionizing luminosity () to the supernova rate
(SNr), /(SNr). We predict the relative number of starbursts to
starburst-dominated LINERs (aging starbursts) and show that it is in
approximate agreement with survey findings for nearby galaxies.Comment: Accepted in ApJ (19 pages, 8 figures, uses emulateapj.sty
Towards a metallic top contact electrode in molecular electronic devices exhibiting a large surface coverage by photoreduction of silver cations
In this contribution the photoreduction of silver ions coordinated onto a LangmuirâBlodgett monolayer is presented as an effective method for the deposition of the top contact electrode in metal/monolayer/metal devices. Silver cations were incorporated from an aqueous AgNO3 sub-phase of Langmuir films of 4,4'-(1,4-phenylenebis(ethyne-2,1-diyl))dibenzoic acid upon the transference of these films onto a metallic substrate. Subsequent irradiation of the silver-ion functionalized LangmuirâBlodgett films with 254 nm light results in the photoreduction of silver cations to produce metallic silver nanoparticles, which are distributed over the organic monolayer and exhibit a surface coverage as large as 76% of the monolayer surface. Electrical properties of these metal/monolayer/metal devices were determined by recording IâV curves, which show a sigmoidal behaviour indicative of well-behaved junctions free of metallic filaments and short-circuits. The integrity of the organic monolayer upon the irradiation process and formation of the silver top-contact electrode has also been demonstrated through cyclic voltammetry experiments
Development of fluorogenic probe-based PCR assays for the detection and quantification of bovine piroplasmids.
This paper reports two new quantitative PCR (qPCR) assays, developed in an attempt to improve the detection of bovine piroplasmids. The first of these techniques is a duplex TaqMan assay for the simultaneous diagnosis of Babesia bovis and B. bigemina. This technique is ideal for use in South America where bovids harbour no theilerids. The second technique, which is suitable for the diagnosis of both babesiosis and theileriosis worldwide, involves fluorescence resonance energy transfer (FRET) probes. In FRET assays, Babesia bovis, B. divergens, Babesia sp. (B. major or B. bigemina), Theileria annae and Theileria sp. were all identifiable based on the melting temperatures of their amplified fragments. Both techniques provided linear calibration curves over the 0.1fg/microl to 0.01ng/microl DNA range. The assays showed good sensitivity and specificity. To assess their performance, both procedures were compared in two separate studies: the first was intended to monitor the experimental infection of calves with B. bovis and the second was a survey where 200 bovid/equine DNA samples from different countries were screened for piroplasmids. Comparative studies showed that duplex TaqMan qPCR was more sensitive than FRET qPCR in the detection of babesids
GIANO-TNG spectroscopy of red supergiants in the young star cluster RSGC2
The inner disk of the Galaxy has a number of young star clusters dominated by
red supergiants that are heavily obscured by dust extinction and observable
only at infrared wavelengths. These clusters are important tracers of the
recent star formation and chemical enrichment history in the inner Galaxy.
During the technical commissioning and as a first science verification of the
GIANO spectrograph at the Telescopio Nazionale Galileo, we secured
high-resolution (R~50,000) near-infrared spectra of three red supergiants in
the young Scutum cluster RSGC2. Taking advantage of the full YJHK spectral
coverage of GIANO in a single exposure, we were able to identify several tens
of atomic and molecular lines suitable for chemical abundance determinations.
By means of spectral synthesis and line equivalent width measurements, we
obtained abundances of Fe and other iron-peak elements such as V, Cr, Ni, of
alpha (O, Mg, Si, Ca and Ti) and other light elements (C, N, Na, Al, K, Sc),
and of some s-process elements (Y, Sr). We found iron abundances between half
and one third solar and solar-scaled [X/Fe] abundance patterns of iron-peak,
alpha and most of the light elements, consistent with a thin-disk chemistry. We
found a depletion of [C/Fe] and enhancement of [N/Fe], consistent with CN
burning, and low 12C/13C abundance ratios (between 9 and 11), requiring
extra-mixing processes in the stellar interiors during the post-main sequence
evolution. Finally, we found a slight [Sr/Fe] enhancement and a slight [Y/Fe]
depletion (by a factor of <=2), with respect to solar.Comment: Paper accepted on A&
Asymptotically Lifshitz wormholes and black holes for Lovelock gravity in vacuum
Static asymptotically Lifshitz wormholes and black holes in vacuum are shown
to exist for a class of Lovelock theories in d=2n+1>7 dimensions, selected by
requiring that all but one of their n maximally symmetric vacua are AdS of
radius l and degenerate. The wormhole geometry is regular everywhere and
connects two Lifshitz spacetimes with a nontrivial geometry at the boundary.
The dynamical exponent z is determined by the quotient of the curvature radii
of the maximally symmetric vacua according to n(z^2-1)+1=(l/L)^2, where L
corresponds to the curvature radius of the nondegenerate vacuum. Light signals
are able to connect both asymptotic regions in finite time, and the
gravitational field pulls towards a fixed surface located at some arbitrary
proper distance to the neck. The asymptotically Lifshitz black hole possesses
the same dynamical exponent and a fixed Hawking temperature given by T=z/(2^z
pi l). Further analytic solutions, including pure Lifshitz spacetimes with a
nontrivial geometry at the spacelike boundary, and wormholes that interpolate
between asymptotically Lifshitz spacetimes with different dynamical exponents
are also found.Comment: 19 pages, 1 figur
- âŠ