589 research outputs found
Variable stars and stellar populations in Andromeda XXI: II. Another merged galaxy satellite of M31?
B and V time-series photometry of the M31 dwarf spheroidal satellite
Andromeda XXI (And XXI) was obtained with the Large Binocular Cameras at the
Large Binocular Telescope. We have identified 50 variables in And XXI, of which
41 are RR Lyrae stars (37 fundamental-mode RRab, and 4 first-overtone RRc,
pulsators) and 9 are Anomalous Cepheids (ACs). The average period of the RRab
stars ( = 0.64 days) and the period-amplitude diagram place And~XXI in the
class of Oosterhoff II - Oosterhoff-Intermediate objects. From the average
luminosity of the RR Lyrae stars we derived the galaxy distance modulus of
(m-M)= mag, which is smaller than previous literature
estimates, although still consistent with them within 1 . The galaxy
color-magnitude diagram shows evidence for the presence of three different
stellar generations in And~XXI: 1) an old ( 12 Gyr) and metal poor
([Fe/H]=1.7 dex) component traced by the RR Lyrae stars; 2) a slightly
younger (10-6 Gyr) and more metal rich ([Fe/H]=1.5 dex) component populating
the red horizontal branch, and 3) a young age ( 1 Gyr) component with
same metallicity, that produced the ACs. Finally, we provide hints that And~XXI
could be the result of a minor merging event between two dwarf galaxies.Comment: accepted for publications in Ap
New pulsational properties of eight "anomalous" RR Lyrae variables
CCD photometry in the V band is presented for 7 field RR Lyrae stars selected
from a sample of eight variables which, according to data collected in the
literature, are expected to be {\it ab}-type pulsators, to have short periods
and hence high metallicity, and to be located at high {\it z} from the galactic
plane. New periods and epochs are derived for them. The new periods are only
slightly shorter than the values published on the last edition of the General
Catalog of Variable Stars (GCVS4). Instead, in six cases our amplitude of the
light variation is significantly smaller than that published on the GCVS4, and
in at least three cases the actual pulsation appears to be in the first
harmonic rather than in the fundamental mode. All the suggested {\it c}-type
pulsators show variations in the amplitude and/or quite scattered light curves.
Possible explanations are given. From a spectro-photometric analysis of the
sample, only DL Com is confirmed to pulsate in the fundamental mode, to have
short period, and to be located at relatively high {\it z}. A single object
cannot be taken as evidence for a significant metal rich population at large
distance from the galactic plane.Comment: 28 pages including text and tables, plain tex. Figures available
through anonymous ftp at ftp://astbo3.bo.astro.it/pub/bap/files/ (get
bap95-12-fig1.ps and bap95-12-figures.ps
Anomalous RR Lyrae stars(?). III. CM Leonis
Time series of B,V,I CCD photometry and radial velocity measurements from
high resolution spectroscopy (R=30,000) covering the full pulsation cycle are
presented for the field RR Lyrae star CM Leonis. The photometric data span a 6
year interval from 1994 to 1999, and allow us to firmly establish the pulsation
mode and periodicity of the variable. The derived period P=0.361699 days (+/-
0.000001) is very close to the value published in the Fourth Edition of the
General Catalogue of Variable Stars (P=0.361732 days). However, contrary to
what was previously found, the amplitude and shape of the light curve qualify
CM Leo as a very regular first overtone pulsator with a prominent hump on the
rising branch of its multicolour light curves. According to an abundace
analysis performed on three spectra taken near minimum light (0.42 < phase <
0.61), CM Leo is a metal-poor star with metal abundance [Fe/H]=-1.93 +/- 0.20.
The photometric and radial velocity curves of CM Leo have been compared with
the predictions of suitable pulsational models to infer tight constraints on
the stellar mass, effective temperature, and distance modulus of the star. We
derive a true distance modulus of CM Leo of (m-M)0=13.11 +/- 0.02 mag and a
corresponding absolute magnitude of Mv=0.47 +/- 0.04. This absolute magnitude,
once corrected for evolutionary and metallicity effects, leads to a true
distance modulus of the Large Magellanic Cloud of (m-M)0=18.43 +/- 0.06 mag, in
better agreement with the long astronomical distance scale.Comment: 14 pages, 10 figures, accepted for publication in MNRA
Cytokine Profiling in Myeloproliferative Neoplasms: Overview on Phenotype Correlation, Outcome Prediction, and Role of Genetic Variants
Among hematologic malignancies, the classic Philadelphia-negative chronic myeloproliferative neoplasms (MPNs) are considered a model of inflammation-related cancer development. In this context, the use of immune-modulating agents has recently expanded the MPN therapeutic scenario. Cytokines are key mediators of an auto-amplifying, detrimental cross-talk between the MPN clone and the tumor microenvironment represented by immune, stromal, and endothelial cells. This review focuses on recent advances in cytokine-profiling of MPN patients, analyzing different expression patterns among the three main Philadelphia-negative (Ph-negative) MPNs, as well as correlations with disease molecular profile, phenotype, progression, and outcome. The role of the megakaryocytic clone as the main source of cytokines, particularly in myelofibrosis, is also reviewed. Finally, we report emerging intriguing evidence on the contribution of host genetic variants to the chronic pro-inflammatory state that typifies MPNs
The ESO Slice Project (ESP) galaxy redshift survey: III. The Sample
The ESO Slice Project (ESP) is a galaxy redshift survey extending over about
23 square degrees, in a region near the South Galactic Pole. The survey is ~85%
complete to the limiting magnitude b_J=19.4 and consists of 3342 galaxies with
redshift determination.
The ESP survey is intermediate between shallow, wide angle samples and very
deep, one-dimensional pencil beams; the spanned volume is ~ 5 x 10^4 Mpc^3 at
the sensitivity peak (z ~ 0.1).
In this paper we present the description of the observations and of the data
reduction, the ESP redshift catalogue and the analysis of the quality of the
velocity determinations.Comment: 10 pages, 4 encapsulated figures, uses A&A LATEX; A&A Supplements in
press (June 1998 issue
CU Comae: a new field double-mode RR Lyrae, the most metal poor discovered to date
We report the discovery of a new double-mode RR Lyrae variable (RRd) in the
field of our Galaxy: CU Comae. CU Comae is the sixth such RRd identified to
date and is the most metal-poor RRd ever detected. Based on BVI CCD photometry
spanning eleven years of observations, we find that CU Comae has periods
P0=0.5441641 +/-0.0000049d and P1=0.4057605 +/-0.0000018d. The amplitude of the
primary (first-overtone) period of CU Comae is about twice the amplitude of the
secondary (fundamental) period. The combination of the fundamental period of
pulsation P0 and the period ratio of P1/P0=0.7457 places the variable on the
metal-poor side of the Petersen diagram, in the region occupied by M68 and M15
RRd's. A mass of 0.83 solar masses is estimated for CU Comae using an updated
theoretical calibration of the Petersen diagram. High resolution spectroscopy
(R=30,000) covering the full pulsation cycle of CU Comae was obtained with the
2.7 m telescope of the Mc Donald Observatory, and has been used to build up the
radial velocity curve of the variable. Abundance analysis done on the four
spectra taken near minimum light (phase: 0.54 -- 0.71) confirms the metal poor
nature of CU Comae, for which we derive [Fe/H]=-2.38 +/-0.20. This value places
this new RRd at the extreme metal-poor edge of the metallicity distribution of
the RR Lyrae variables in our Galaxy.Comment: 21 pages including 8 Tables, Latex, 11 Figures. Accepted for
publication in The Astronomical Journal, October 2000 issu
Pharmacological characterization of P2X1 and P2X3 purinergic receptors in bovine chondrocytes
SummaryObjectiveThe aim of the present study is that of characterizing, for the first time in a quantitative way, from a biochemical, physico chemical and functional point of view P2X1 and P2X3 purinergic receptors in bovine chondrocytes. The affinity and the potency of typical purinergic ligands were studied through competition binding experiments and their role in modulating chondrocyte actvities was investigated by analyzing nitric oxide (NO) and prostaglandin E2 (PGE2) release.MethodsSaturation, competition binding experiments, western blotting and immunohistochemistry assays on the P2X1 and P2X3 purinergic receptors in bovine chondrocytes were performed. Thermodynamic analysis of the P2X1 and P2X3 purinergic binding was studied to investigate the forces driving drug-receptor coupling. In the functional assays (NO and PGE2 release) the potency of purinergic agonists and antagonists was evaluated.ResultsBovine chondrocytes expressed P2X1 and P2X3 purinergic receptors and thermodynamic parameters indicated that purinergic binding is enthalpy- and entropy-driven for agonists and totally entropy-driven for antagonists. Typical purinergic agonists such as adenosine 5âČ-triphosphate (ATP) and α,ÎČ-methyleneATP were able to increase NO and PGE2 release. A purinergic antagonist, A317491, was able to block the stimulatory effect on functional experiments mediated by the agonists.ConclusionsThese data demonstrate for the first time the presence of functional P2X1 and P2X3 purinergic receptors in bovine chondrocytes. Agonists and antagonists are thermodynamically discriminated and are able to modulate functional responses such as NO and PGE2 release. These results suggest the potential role of novel purinergic antagonists in the treatment of pathophysiological diseases linked to the inflammation and involved in articular cartilage resorption
Human Red Blood Cells as Oxygen Carriers to Improve Ex-Situ Liver Perfusion in a Rat Model
Ex-situ machine perfusion (MP) has been increasingly used to enhance liver quality in different settings. Small animal models can help to implement this procedure. As most normothermic MP (NMP) models employ sub-physiological levels of oxygen delivery (DO2), the aim of this study was to investigate the effectiveness and safety of different DO2, using human red blood cells (RBCs) as oxygen carriers on metabolic recovery in a rat model of NMP. Four experimental groups (n = 5 each) consisted of (1) native (untreated/control), (2) liver static cold storage (SCS) 30 min without NMP, (3) SCS followed by 120 min of NMP with Dulbecco-Modified-Eagle-Medium as perfusate (DMEM), and (4) similar to group 3, but perfusion fluid was added with human RBCs (hematocrit 15%) (BLOOD). Compared to DMEM, the BLOOD group showed increased liver DO2 (p = 0.008) and oxygen consumption ( V O \u2d9 2) (p < 0.001); lactate clearance (p < 0.001), potassium (p < 0.001), and glucose (p = 0.029) uptake were enhanced. ATP levels were likewise higher in BLOOD relative to DMEM (p = 0.031). V O \u2d9 2 and DO2 were highly correlated (p < 0.001). Consistently, the main metabolic parameters were directly correlated with DO2 and V O \u2d9 2. No human RBC related damage was detected. In conclusion, an optimized DO2 significantly reduces hypoxic damage-related effects occurring during NMP. Human RBCs can be safely used as oxygen carriers
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