1,891 research outputs found
A pulsational distance to Omega Centauri based on Near-Infrared Period-Luminosity relations of RR Lyrae stars
We present new Near-Infrared (J,K) magnitudes for 114 RR Lyrae stars in the
globular cluster Omega Cen (NGC 5139) which we combine with data from the
literature to construct a sample of 180 RR Lyrae stars with J and K mean
magnitudes on a common photometric system. This is presently the largest such
sample in any stellar system. We also present updated predictions for J,K-band
Period-Luminosity relations for both fundamental and first-overtone RR Lyrae
stars, based on synthetic horizontal branch models with metal abundance ranging
from Z=0.0001 to Z=0.004. By adopting for the Omega Cen variables with measured
metal abundances an alpha-element enhancement of a factor of 3 (about 0.5 dex)
with respect to iron we find a true distance modulus of 13.70 (with a random
error of 0.06 and a systematic error of 0.06), corresponding to a distance
d=5.5 Kpc (with both random and systematic errors equal to 0.03 Kpc). Our
estimate is in excellent agreement with the distance inferred for the eclipsing
binary OGLEGC-17, but differ significantly from the recent distance estimates
based on cluster dynamics and on high amplitude Delta Scuti stars.Comment: 24 pages, 7 figures, accepted for publication on The Astrophysical
Journa
Synthetic properties of bright metal-poor variables. II. BL Her stars
We investigate the properties of the so-called BL Her stars, i.e., Population
II Cepheids with periods shorter than 8 days, using updated pulsation models
and evolutionary tracks computed adopting a metal abundance in the range of
Z=0.0001 to Z=0.004. We derive the predicted Period-Magnitude (PM) and
Period-Wesenheit (PW) relations at the various photometric bands and we show
that the slopes of these relations are in good agreement with the slopes
determined by observed variables in Galactic globular clusters, independently
of the adopted M_V(RR)-[Fe/H] relation to get the cluster RR Lyrae-based
distance. Moreover, we show that also the distances provided by the predicted
PM and PW relations for BL Her stars agree within the errors with the RR Lyrae
based values. The use of the predicted relations with W Vir stars, which are
Population II Cepheids with periods longer than 8 days, provides no clear
evidence for or against a change in the PM and PW slopes around P~10 days.Comment: 12 pages, 6 figures, 6 tables, accepted for publication in A&A on
date 16/05/200
When Viruses Meet Fungi: Tackling the Enemies in Hematology
The association of invasive fungal infections (IFI) and viral infections has been described in patients with hematologic malignancies (HM), in particular in hematopoietic stem cell transplant recipients. Regrettably, the diagnosis is often challenging, making the treatment inappropriate in some circumstances. The present review takes into consideration the viral infections commonly associated with IFI. Clinical presentation of IFI and viral infections, risk factors, and impact on the outcome of HM patients are discussed throughout the paper
Immunotherapy as a turning point in the treatment of acute myeloid leukemia
Acute myeloid leukemia (AML) is a malignant disease of hematopoietic precursors at
the earliest stage of maturation, resulting in a clonalproliferation of myoblasts replacing normal
hematopoiesis. AML represents one of the most common types of leukemia, mostly affecting elderly
patients. To date, standard chemotherapy protocols are only effective in patients at low risk of relapse
and therapy-related mortality. The average 5-year overall survival (OS) is approximately 28%. Allogeneic hematopoietic stem cell transplantation (HSCT) improves prognosis but is limited by donor
availability, a relatively young age of patients, and absence of significant comorbidities. Moreover, it
is associated with significant morbidity and mortality. However, increasing understanding of AML
immunobiology is leading to the development of innovative therapeutic strategies. Immunotherapy
is considered an attractive strategy for controlling and eliminating the disease. It can be a real
breakthrough in the treatment of leukemia, especially in patients who are not eligible forintensive
chemotherapy. In this review, we focused on the progress of immunotherapy in the field of AML by
discussing monoclonal antibodies (mAbs), immune checkpoint inhibitors, chimeric antigen receptor
T cells (CAR-T cells), and vaccine therapeutic choices
Thickness-dependent crystallization on thermal anneal for titania/silica nm-layer composites deposited by ion beam sputter method.
Crystallization following thermal annealing of thin film stacks consisting of alternating nm-thick titania/silica layers was investigated. Several prototypes were designed, featuring a different number of titania/silica layer pairs, and different thicknesses (in the range from 4 to 40 nm, for the titania layers), but the same nominal refractive index (2.09) and optical thickness (a quarter of wavelength at 1064 nm). The prototypes were deposited by ion beam sputtering on silicon substrates. All prototypes were found to be amorphous as-deposited. Thermal annealing in air at progressive temperatures was subsequently performed. It was found that the titania layers eventually crystallized forming the anatase phase, while the silica layers remained always amorphous. However, progressively thinner layers exhibited progressively higher threshold temperatures for crystallization onset. Accordingly it can be expected that composites with thinner layers will be able to sustain higher annealing temperatures without crystallizing, and likely yielding better optical and mechanical properties for advanced coatings application. These results open the way to the use of materials like titania and hafnia, that crystallize easily under thermal anneal, but ARE otherwise promising candidate materials for HR coatings necessary for cryogenic 3rd generation laser interferometric gravitational wave detectors
CD90/Thy-1 is preferentially expressed on blast cells of high risk acute myeloid leukaemias
Different transformation mechanisms have been proposed for elderly acute myeloid leukaemia (AML) and secondary AML (sAML) when compared with de novo AML or AML of younger patients. However, little is known regarding differences in the immunophenotypic profile of blast cells in these diseases. We systematically analysed, by flow cytometry, 148 patients affected by de novo (100 cases) or sAML (48 cases). By defining a cut-off level of 20% of CD34+ cells co-expressing CD90, the frequency of CD90+ cases was higher in sAML (40%) versus de novo AML (6%, P < 0.001), elderly AML (>60 years) (24%) versus AML of younger patients (10%, P = 0.010) and poor- versus good-risk karyotypes (according to the Medical Research Council classification, P < 0.001). The correlation between CD90 expression, sAML and unfavourable karyotypes was confirmed by analysing the subset of CD34+ AML cases alone (91/148). Consistently, univariate analysis showed that expression of CD90 was statistically relevant in predicting a shorter survival in CD90+ AML patients (P = 0.042). Our results, demonstrating CD90 expression in AML with unfavourable clinical and biological features, suggest an origin of these diseases from a CD90-expressing haemopoietic progenitor and indicate the use of CD90 as an additional marker of prognostic value in AML
B, V, I photometry of the complete sample of 23 Cepheids in the field of NGC 1866
We present the result of BVI photometry, obtained by using FORS@VLT, of the
Cepheids present in the field of the Large Magellanic Cloud cluster NGC 1866.
We found the 22 known variables plus an additional new Cepheid located about
10' from the cluster center. The accuracy of the photometry allowed us to
derive B, V and I mean magnitudes with an uncertainty lower than 0.02 mag for
22 out of the 23 objects, with the exception of only one Cepheid (WS9) which
presents a noisy light curve due to the probable occurrence of image blending.
As a result, we provide accurate observational data for a substantial sample of
variables all lying at the same distance and with a common original
composition. The resulting period-luminosity relations are presented and
briefly discussed.Comment: 4 pages, 6 figure, to appear in the proceedings of the Workshop
"Stellar pulsation and evolution", 2005. Monte Porzio Catone, Italy. Eds.: A.
R. Walker and G. Bon
Star Counts in the Globular Cluster Omega Centauri. I. Bright Stellar Components
We present an extensive photometry on HB, RGB, and MSTO stars in Omega Cen.
The central regions of the cluster were covered with a mosaic of F435W, F625W,
and F658N-band data collected with ACS/HST. The outer reaches were covered with
a large set of U,B,V,I-band data collected with the [email protected] ESO/MPI telescope.
The final catalogue includes ~1.7 million stars. We identified ~3,200 likely HB
stars and ~12,500 stars brighter than the subgiant branch and fainter than the
RGB bumps. The HB morphology changes with the radial distance. The relative
number of extreme HB stars decreases from ~30% to ~21% when moving from the
center toward the outer regions of the cluster, while the fraction of less hot
HB stars increases from ~62% to ~72%. We performed a detailed comparison
between observed ratios of different stellar tracers and predictions based on
canonical evolutionary models with a primordial helium (Y=0.23) content and
metal abundances (Z=0.0002,0.001) that bracket the observed spread in
metallicity of Omega Cen stars. We found that the empirical star counts of HB
stars are on average larger (30%-40%) than predicted. Moreover, the rate of HB
stars is 43% larger than the MSTO rate. The discrepancy between the rate of HB
compared with the rate of RG and MSTO stars supports the evidence that we are
facing a true excess of HB stars. The same comparison was performed by assuming
a mix of stellar populations made with 70% of canonical stars and 30% of
He-enhanced stars. The discrepancy between theory and observations decreases by
a factor of two when compared with rates predicted by canonical He content
models, but still 15%-25% (Y=0.42) and 15%-20% (Y=0.33) higher than observed.
Furthermore, the ratio between HB and MSTO star counts are ~24% (Y=0.42) and
30% (Y=0.33) larger than predicted lifetime ratios.Comment: 54 pages, 17 figures,to be published in ApJ, see link at
http://stellari.wiki.zoho.co
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