404 research outputs found
Revised physical elements of the astrophysically important O9.5+O9.5V eclipsing binary system Y Cyg
Thanks to its long and rich observational history and rapid apsidal motion,
the massive eclipsing binary Y Cyg represents one of the cornestones to
critical tests of stellar evolution theory for massive stars. Yet, the
determination of the basic physical properties is less accurate than it could
be given the existing number of spectral and photometric observations. Our goal
is to analyze all these data simultaneously with the new dedicated series of
our own spectral and photometric observations from observatories widely
separated in longitude. We obtained new series of UBV observations at three
observatories separated in local time to obtain complete light curves of Y Cyg
for its orbital period close to 3 days. This new photometry was reduced and
carefully transformed to the standard UBV system using the HEC22 program. We
also obtained new series of red spectra secured at two observatories and
re-analyzed earlier obtained blue electronic spectra. Our analyses provide the
most accurate so far published value of the apsidal period of 47.805 +/- 0.030
yrs and the following physical elements: M1=17.72+/-0.35$ Msun, M2=17.73+/-0.30
Msun, R1=5.785+/-0.091 Rsun, and R2=5.816+/-0.063 Rsun. The disentangling thus
resulted in the masses, which are somewhat higher than all previous
determinations and virtually the same for both stars, while the light curve
implies a slighly higher radius and luminosity for star 2. The above empirical
values imply the logarithm of the internal structure constant log k2 = -1.937.
A comparison with Claret's stellar interior models implies an age close to 2
millions yrs for both stars. The claimed accuracy of modern element
determination of 1-2 per cent seems still a bit too optimistic and obtaining
new high-dispersion and high-resolution spectra is desirable.Comment: 13 pages; accepted for publication in Astronomy and Astrophysic
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Pre-existing invasive fungal infection is not a contraindication for allogeneic HSCT for patients with hematologic malignancies: a CIBMTR study.
Patients with prior invasive fungal infection (IFI) increasingly proceed to allogeneic hematopoietic cell transplantation (HSCT). However, little is known about the impact of prior IFI on survival. Patients with pre-transplant IFI (cases; n=825) were compared with controls (n=10247). A subset analysis assessed outcomes in leukemia patients pre- and post 2001. Cases were older with lower performance status (KPS), more advanced disease, higher likelihood of AML and having received cord blood, reduced intensity conditioning, mold-active fungal prophylaxis and more recently transplanted. Aspergillus spp. and Candida spp. were the most commonly identified pathogens. 68% of patients had primarily pulmonary involvement. Univariate and multivariable analysis demonstrated inferior PFS and overall survival (OS) for cases. At 2 years, cases had higher mortality and shorter PFS with significant increases in non-relapse mortality (NRM) but no difference in relapse. One year probability of post-HSCT IFI was 24% (cases) and 17% (control, P<0.001). The predominant cause of death was underlying malignancy; infectious death was higher in cases (13% vs 9%). In the subset analysis, patients transplanted before 2001 had increased NRM with inferior OS and PFS compared with later cases. Pre-transplant IFI is associated with lower PFS and OS after allogeneic HSCT but significant survivorship was observed. Consequently, pre-transplant IFI should not be a contraindication to allogeneic HSCT in otherwise suitable candidates. Documented pre-transplant IFI is associated with lower PFS and OS after allogeneic HSCT. However, mortality post transplant is more influenced by advanced disease status than previous IFI. Pre-transplant IFI does not appear to be a contraindication to allogeneic HSCT
Helicobacter pylori-induced inhibition of vascular endothelial cell functions: a role for VacA-dependent nitric oxide reduction
Epidemiological and clinical studies provide compelling support for a causal relationship between Helicobacter pylori infection and endothelial dysfunction, leading to vascular diseases. However, clear biochemical evidence for this association is limited. In the present study, we have conducted a comprehensive investigation of endothelial injury in bovine aortic endothelial cells (BAECs) induced by H. pylori-conditioned medium (HPCM) prepared from H. pylori 60190 [vacuolating cytotoxin A (Vac(+))]. BAECs were treated with either unconditioned media, HPCM (0-25% vol/vol), or Escherichia coli-conditioned media for 24 h, and cell functions were monitored. Vac(+) HPCM significantly decreased BAEC proliferation, tube formation, and migration (by up to 44%, 65%, and 28%, respectively). Posttreatment, we also observed sporadic zonnula occludens-1 immunolocalization along the cell-cell border, and increased BAEC permeability to FD40 Dextran, indicating barrier reduction. These effects were blocked by 5-nitro-2-(3-phenylpropylamino)benzoic acid (VacA inhibitor) and were not observed with conditioned media prepared from either VacA-deleted H. pylori or E. coli. The cellular mechanism mediating these events was also considered. Vac(+) HPCM (but not Vac(-)) reduced nitric oxide (NO) by \u3e50%, whereas S-nitroso-N-acetylpenicillamine, an NO donor, recovered all Vac(+) HPCM-dependent effects on cell functions. We further demonstrated that laminar shear stress, an endothelial NO synthase/NO stimulus in vivo, could also recover the Vac(+) HPCM-induced decreases in BAEC functions. This study shows, for the first time, a significant proatherogenic effect of H. pylori-secreted factors on a range of vascular endothelial dysfunction markers. Specifically, the VacA-dependent reduction in endothelial NO is indicated in these events. The atheroprotective impact of laminar shear stress in this context is also evident
Astrometry with Hubble Space Telescope: A Parallax of the Fundamental Distance Calibrator RR Lyrae
We present an absolute parallax and relative proper motion for the
fundamental distance scale calibrator, RR Lyr. We obtain these with astrometric
data from FGS 3, a white-light interferometer on HST. We find mas. Spectral classifications and VRIJHKTM and DDO51 photometry of
the astrometric reference frame surrounding RR Lyr indicate that field
extinction is low along this line of sight. We estimate =0.07\pm0.03 for
these reference stars. The extinction suffered by RR Lyr becomes one of the
dominant contributors to the uncertainty in its absolute magnitude. Adopting
the average field absorption, =0.07 \pm 0.03, we obtain M_V^{RR} = 0.61
^{-0.11}_{+0.10}. This provides a distance modulus for the LMC, m-M = 18.38 -
18.53^{-0.11}_{+0.10} with the average extinction-corrected magnitude of RR Lyr
variables in the LMC, , remaining a significant uncertainty. We compare
this result to more than 80 other determinations of the distance modulus of the
LMC.Comment: Several typos corrected. To appear in The Astronomical Journal,
January 200
ALMA and VLA reveal the lukewarm chromospheres of the nearby red supergiants Antares and Betelgeuse
We first present spatially resolved ALMA and VLA continuum observations of
the early-M red supergiant Antares to search for the presence of a chromosphere
at radio wavelengths. We resolve the free-free emission of the Antares
atmosphere at 11 unique wavelengths between 0.7 mm (ALMA band 8) and 10 cm (VLA
S band). The projected angular diameter is found to continually increase with
increasing wavelength, from a low of 50.7 mas at 0.7 mm up to a diameter of 431
mas at 10 cm, which corresponds to 1.35 and 11.6 times the photospheric angular
diameter, respectively. All four ALMA measurements show that the shape of the
atmosphere is elongated, with a flattening of 15% at a similar position angle.
The disk-averaged gas temperature of the atmosphere initially rises from a
value of 2700 K at 1.35 (i.e., 0.35 above the
photosphere) to a peak value of 3800 K at 2.5 , after which it
then more gradually decreases to 1650 K at 11.6 . The rise in gas
temperature between 1.35 and 2.5 is evidence for
a chromospheric temperature rise above the photosphere of a red supergiant. We
detect a clear change in the spectral index across the sampled wavelength
range, with the flux density between 0.7 mm
and 1.4 cm, which we associate with chromosphere-dominated emission, while the
flux density between 4.3 cm and 10 cm, which we
associate with wind-dominated emission. We then perform nonlocal thermal
equilibrium modeling of the far-ultraviolet radiation field of another early-M
red supergiant, Betelgeuse, and find that an additional hot (i.e., K)
chromospheric photoionization component with a much smaller filling factor must
also exist throughout the chromospheres of these stars.Comment: 12 pages, 6 figures, accepted for publication in A&
Vancomycin-intermediate Staphylococcus aureus in a home health-care patient.
In June 2000, vancomycin-intermediate Staphylococcus aureus (VISA) was isolated from a 27-year-old home health-care patient following a complicated cholecystectomy. Two VISA strains were identified with identical MICs to all antimicrobials tested except oxacillin and with closely related pulsed-field gel electrophoresis types. The patient was treated successfully with antimicrobial therapy, biliary drainage, and reconstruction. Standard precautions in the home health setting appear successful in preventing transmission
Evolution in Binary and Triple Stars, with an application to SS Lac
We present equations governing the way in which both the orbit and the
intrinsic spins of stars in a close binary should evolve subject to a number of
perturbing forces, including the effect of a third body in a possibly inclined
wider orbit. We illustrate the solutions in some binary-star and triple-star
situations: tidal friction in a wide but eccentric orbit of a radio pulsar
about a B star, the Darwin and eccentricity instabilities in a more massive but
shorter-period massive X-ray binary, and the interaction of tidal friction with
Kozai cycles in a triple such as Algol (beta-Per), at an early stage in that
star's life when all 3 components were ZAMS stars. We also attempt to model in
some detail the interesting triple system SS Lac, which stopped eclipsing in
about 1950. We find that our model of SS Lac is quite constrained by the
relatively good observational data of this system, and leads to a specific
inclination (29 deg) of the outer orbit relative to the inner orbit at epoch
zero (1912). Although the intrinsic spins of the stars have little effect on
the orbit, the converse is not true: the spin axes can vary their orientation
relative to the close binary by up to 120 deg on a timescale of about a
century.Comment: 30 pages, 6 figure
Heterosexual and Homosexual Patients with the Acquired Immunodeficiency Syndrome: A Comparison of Surveillance, Interview, and Laboratory Data
Homosexual and heterosexual patients with the acquired immunodeficiency syndrome were compared by risk group. Race; diagnoses; history of sexually transmitted diseases, sexual behavior, and drug use; and socioeconomic indicators differed considerably among the risk groups, suggesting different risk factors for acquisition of the syndrome. Patients in the homosexual, intravenous drug user, and Haitian risk groups differed in their serologic response to cytomegalovirus and syphilis testing, presumably due to lifestyle-related exposures. Differences in the rate of recovery of cytomegalovirus, serum levels of IgA and IgG, and antibody titers to Epstein-Barr virus were noted among patients with different diagnoses. We conclude that in studies of risk factors for the acquired immunodeficiency syndrome, patients should be analyzed by risk group and diagnoses
Kepler eclipsing binary stars. VII. the catalogue of eclipsing binaries found in the entire Kepler data set
The primary Kepler Mission provided nearly continuous monitoring of ~200,000 objects with unprecedented photometric precision. We present the final catalog of eclipsing binary systems within the 105 deg2 Kepler field of view. This release incorporates the full extent of the data from the primary mission (Q0-Q17 Data Release). As a result, new systems have been added, additional false positives have been removed, ephemerides and principal parameters have been recomputed, classifications have been revised to rely on analytical models, and eclipse timing variations have been computed for each system. We identify several classes of systems including those that exhibit tertiary eclipse events, systems that show clear evidence of additional bodies, heartbeat systems, systems with changing eclipse depths, and systems exhibiting only one eclipse event over the duration of the mission. We have updated the period and galactic latitude distribution diagrams and included a catalog completeness evaluation. The total number of identified eclipsing and ellipsoidal binary systems in the Kepler field of view has increased to 2878, 1.3% of all observed Kepler targets
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