882 research outputs found
A catalogue sample of low mass galaxies observed in X-rays with central candidate black holes
We present a sample of -ray selected candidate black holes in 51 low mass
galaxies with {and mass up to M} obtained by
cross-correlating the NASA-SLOAN Atlas with the 3XMM catalogue. {We have also
searched in the available catalogues for radio counterparts of the black hole
candidates and find that 19 of the previously selected sources have also a
radio counterpart.} Our results show that about of the galaxies of our
sample host { an -ray source} (associated to a radio counterpart) spatially
coincident with the galaxy center, in agreement with { other recent works}. For
these {\it nuclear} sources, the -ray/radio fundamental plane relation
allows one to estimate the mass of the (central) candidate black holes which
results to be in the range M (with median
value of M and eight candidates having mass
below M). This result, while suggesting that -ray
emitting black holes in low-mass galaxies may have had a key role in the
evolution of such systems, makes even more urgent to explain how such massive
objects formed in galaxies. {Of course, dedicated follow-up observations both
in the -ray and radio bands, as well as in the optical, are necessary in
order to confirm our resultsComment: 15 Pages, 2 Figures, 3 Table
XMM-Newton observation of a sample of four close dSph galaxies
We present the results of the analysis of deep archival \sat\ observations
towards the dwarf spheroidal galaxies Draco, Leo I, Ursa Major II and Ursa
Minor in the Milky Way neighbourhood. The X-ray source population is
characterized and cross-correlated with available databases with the aim to
infer their nature. We also investigate if intermediate-mass black holes are
hosted in the center of these galaxies. In the case of Draco, we detect 96
high-energy sources, two of them being possibly local stars, while no evidence
for any X-ray emitting central compact object is found. Towards the Leo I and
UMa II field of view we reveal 116 and 49 X-ray sources, respectively. None of
them correlates with the putative central black holes and only one is likely
associated with a UMa II local source. The study of the UMi dwarf galaxy shows
54 high-energy sources and a possible association {with a source at the dSph
center}. We put an upper limit to the central compact object luminosity of
4.0210 erg/s. Furthermore, via the correlation with a radio
source near the galactic center, we get that the putative black hole should
have a mass of and be
radiatively inefficient. This confirms a previous result obtained by using
Chandra data alone.Comment: MNRAS, in press, tables available on lin
Astrometric microlensing
Astrometric microlensing will offer in the next future a new channel for
investigating the nature of both lenses and sources involved in a gravitational
microlensing event. The effect, corresponding to the shift of the position of
the multiple image centroid with respect to the source star location, is
expected to occurr on scales from micro-arcoseconds to milli-arcoseconds
depending on the characteristics of the lens-source system. Here, we consider
different classes of events (single/binary lens acting on a single/binary
source) also accounting for additional effects including the finite source
size, the blending and orbital motion. This is particularly important in the
era of Gaia observations which is making possible astrometric measurements with
unprecedent quality.Comment: On IJMP D, 15 pages, 6 Figure
Penrose-Onsager Criterion Validation in a One-Dimensional Polariton Condensate
We perform quantum tomography on one-dimensional polariton condensates,
spontaneously occurring in linear disorder valleys in a CdTe planar microcavity
sample. By the use of optical interferometric techniques, we determine the
first-order coherence function and the amplitude and phase of the order
parameter of the condensate, providing a full reconstruction of the single
particle density matrix for the polariton system. The experimental data are
used as input to theoretically test the consistency of Penrose-Onsager
criterion for Bose-Einstein condensation in the framework of nonequilibrium
polariton condensates. The results confirm the pertinence and validity of the
criterion for a non equilibrium condensed gas.Comment: 5 pages, 4 figure
The puzzling symbiotic X-ray system 4U1700+24
Symbiotic X-ray binaries form a subclass of low-mass X-ray binary systems
consisting of a neutron star accreting material from a red giant donor star via
stellar wind or Roche lobe overflow. Only a few confirmed members are currently
known; 4U 1700+24 is a good candidate as it is a relatively bright X-ray
object, possibly associated with the late-type star V934 Her. We analysed the
archive {\it XMM}-Newton and Swift/XRT observations of 4U 1700+24 in order to
have a uniform high-energy ( keV) view of the source. We confirmed the
existence of a red-shifted O VIII Ly- transition (already observed in
the 2002 {\it XMM}-Newton data) in the high-resolution spectra collected via
the RGS instruments. The red-shift of the line is found in all the analysed
observations and, on average, it was estimated to be . We also
observed a modulation of the centroid energy of the line on short time scales
(a few days) and discuss the observations in the framework of different
scenarios. If the modulation is due to the gravitational red-shift of the
neutron star, it might arise from a sudden re-organization of the emitting
-ray matter on the scale of a few hundreds of km. Alternatively, we are
witnessing a uni-polar jet of matter (with typical velocity of km
s) possibly emitted by the neutron star in an almost face-on system. The
second possibility seems to be required by the apparent lack of any modulation
in the observed -ray light curve. We also note also that the low-resolution
spectra (both {\it XMM}-Newton and Swift/XRT in the keV band) show the
existence of a black body radiation emitted by a region (possibly associated
with the neutron star polar cap) with typical size from a few tens to hundreds
of meters. The size of this spot-like region reduces as the overall luminosity
of 4U 1700+24 decreases.Comment: In press on A&
Prevention of Dermatologic Side Effects of Bimatoprost 0.03% Topical Therapy
PURPOSE: To investigate the efficacy of reducing the drop-skin contact to prevent dermatologic side effects of bimatoprost 0.03% topical therapy. DESIGN: Prospective, randomized, single-blinded, internally controlled study. METHODS: Enrolled subjects started bimatoprost 0.03% therapy once at night in both eyes and were instructed to wipe selectively only one eye (eye 1) with an adsorbent pad during and after drops administration for four months. The fellow eye acted as the internal control. Eyelash growth, regional skin hypertrichosis, and pigmentation on the periocular skin were assessed at baseline and during the four months of follow-up. RESULTS: A lower incidence of eyelash growth and skin pigmentation in the inferonasal pericanthal region were observed in eye 1. The incidence of pigmentation in the inferotemporal skin region and skin hypertrichosis were similar in the two eyes. CONCLUSION: The reduction of the drop,skin contact affects the regional incidence and the extent of dermatologic skin changes that are related to bimatoprost 0.03% topical therapy
Levels of plasma homocysteine in pseudoexfoliation glaucoma.
BACKGROUND: To examine levels of serum homocysteine (Hcy), vitamin B12 and folic acid in patients with pseudoexfoliation glaucoma (PEXG), primary open-angle glaucoma (POAG), and healthy control subjects.
METHODS: This study included 36 patients with PEXG, 40 with POAG, and 40 age-matched healthy subjects. Fasting plasma Hcy concentrations and levels of serum vitamin B12 and folic acid were measured using competitive chemiluminescent enzyme immunoassay; values exceeding 14 ÎŒm/l were considered elevated. RESULTS:
Mean plasma Hcy was significantly higher in PEXG (16.55â±â7.23 ÎŒm/l) compared with POAG (13.91â±â3.61 ÎŒm/l) and controls (13.12â±â5.13 ÎŒm/l) (pâ=â0.03 and pâ=â0.0007 respectively). There were no statistical differences in serum vitamin B12 and folic acid levels among PEXG, POAG and control subjects (pâ>â0.05). A moderate, although statistically significant, relationship between Hcy and folic acid levels was found in the PEXG group (R(2)â=â0.23, pâ=â0.003). Hcy levels were found not to be related with folic acid or vitamin B12 in either POAG or control subjects.
CONCLUSIONS: In this study, plasma Hcy is significantly higher in PEXG group than the POAG and control groups. Hyper-Hcy might play a role in the pathogenesis of PEXG. Hyper-Hcy may be an independent factor stressing vasculopathy in addition to pseudoexfoliation, so might be a modifiable risk factor for PEXG
Exploring the Heidelberg Retinal Tomograph 3 diagnostic accuracy across disc sizes and glaucoma stages: a multicenter study
To investigate and compare the diagnostic accuracy of the Heidelberg Retinal Tomograph 3 (HRT3) diagnostic algorithms and establish whether they are affected by optic disc size and glaucoma severity
Learning effect of humphrey matrix frequency doubling technology perimetry in patients with ocular hypertension
Aim: To evaluate the learning effect of Frequency Doubling Technology (FDT) perimetry using the Humphrey Matrix-FDT perimetry (Matrix) 24-2 full-threshold program on patients with 7 ocular hypertension experienced with standard automated perimetry. Methods: Twenty-four patients with Ocular hypertension underwent 5 full-threshold Matrix tests at intervals of 5 2 days. Learning effect was defined as an improvement at results for duration, perimetric indices, foveal sensitivity, Glaucoma Hemifield Test, and the number of points with a P < 5% and < 1% in the total and pattern deviation maps. Eccentricity, hemifield, and quadrant sensitivities were also addressed as Sources of differences in learning effect. Test-retest variability was also calculated for each repetition as the mean of the point-to-point interindividual standard deviations. Results: A learning effect was demonstrated for mean defect (P = 0.031, analysis of variance) and foveal sensitivity (P = 0.009) and it only affected the first test for both parameters. All the other parameters did not show any significant learning effect. The effect was independent From eccentricity and quadrant or hemifield sensitivities. Conclusions: The results of this study demonstrate that the learning effect for Matrix-FDT is mild and it may affect only the first test. Caution is needed in the analysis of the first Matrix-FDT examination and retest may be advisable in the presence of low mean defect
Promoter methylation and downregulated expression of the TBX15 gene in ovarian carcinoma.
TBX15 is a gene involved in the development of mesodermal derivatives. As the ovaries and the female reproductive system are of mesodermal origin, the aim of the present study was to determine the methylation status of the TBX15 gene promoter and the expression levels of TBX15 in ovarian carcinoma, which is the most lethal and aggressive type of gynecological tumor, in order to determine the role of TBX15 in the pathogenesis of ovarian carcinoma. This alteration could be used to predict tumor development, progression, recurrence and therapeutic effects. The study was conducted on 80 epithelial ovarian carcinoma and 17 control cases (normal ovarian and tubal tissues). TBX15 promoter methylation was first determined by pyrosequencing following bisulfite modification, then by cloning and sequencing, in order to obtain information about the epigenetic haplotype. Immunohistochemical analysis was performed to evaluate the correlation between the methylation and protein expression levels. Data revealed a statistically significant increase of the TBX15 promoter region methylation in 82% of the tumor samples and in various histological subtypes. Immunohistochemistry showed an inverse correlation between methylation levels and the expression of the TBX15 protein. Furthermore, numerous tumor samples displayed varying degrees of intratumor heterogeneity. Thus, the present study determined that ovarian carcinoma typically expresses low levels of TBX15 protein, predominantly due to an epigenetic mechanism. This may have a role in the pathogenesis of ovarian carcinoma independent of the histological subtype
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