7,503 research outputs found
Stellar escapers from M67 can reach solar-like Galactic orbits
We investigate the possibility that the Sun could have been born in M67 by
carrying out -body simulations of M67-like clusters in a time-varying
Galactic environment, and following the galactic orbits of stars that escape
from them. We find that model clusters that occupy similar orbits to M67 today
can be divided up into three groups. Hot clusters are born with a high initial
-velocity, depleted clusters are born on cold orbits but are destroyed by
GMC encounters in the Galactic disc, and scattered clusters are born on cold
orbits and survive with more than 1000 stars at an age of 4.6 Gyr. We find that
all cluster models in all three cluster groups have stellar escapers that are
kinematicaly similar to the Sun. Hot clusters having the lowest such fraction
%, whilst depleted clusters have the highest fraction,
%. We calculate that clusters that are destroyed in the
Galactic disc have a specific frequency of escapers that end up on solar-like
orbits that is 2 times that of escapers from clusters that survive their
journey
Violence by clients towards female prostitutes in different work settings: questionnaire survey
No abstract available
Low-Mass X-ray Binaries and Globular Clusters in Early-Type Galaxies. I. Chandra Observations
We present a Chandra survey of LMXBs in 24 early-type galaxies. Correcting
for detection incompleteness, the X-ray luminosity function (XLF) of each
galaxy is consistent with a powerlaw with negative logarithmic differential
slope, beta~2.0. However, beta strongly correlates with incompleteness,
indicating the XLF flattens at low-Lx. The composite XLF is well-fitted by a
powerlaw with a break at 2.21(+0.65,-0.56)E38 erg/s and beta=1.40(+0.10,-0.13)
and 2.84(+0.39,-0.30) below and above it, respectively. The break is close to
the Eddington limit for a 1.4Msun neutron-star, but the XLF shape rules out its
representing the division between neutron-star and black-hole systems. Although
the XLFs are similar, we find evidence of some variation between galaxies. The
high-Lx XLF slope does not correlate with age, but may correlate with
[alpha/Fe]. Considering only LMXBs with Lx>1E37 erg/s, matching the LMXBs with
globular clusters (GCs) identified in HST observations of 19 of the galaxies,
we find the probability a GC hosts an LMXB is proportional to LGC^alpha
ZFe^gamma} where alpha=1.01+/-0.19 and gamma=0.33+/-0.11. Correcting for GC
luminosity and colour effects, and detection incompleteness, we find no
evidence that the fraction of LMXBs with Lx>1e37 erg/s in GCs (40%), or the
fraction of GCs hosting LMXBs (~6.5%) varies between galaxies. The spatial
distribution of LMXBs resembles that of GCs, and the specific frequency of
LMXBs is proportional to the GC specific luminosity, consistent with the
hypothesis that all LMXBs form in GCs. If the LMXB lifetime is tau and the duty
cycle is Fd, our results imply ~1.5 (tau/1E8 yr)^-1 /Fd LMXBs are formed per
Gyr per GC and we place an upper limit of 1 active LMXB in the field per
3.4E9Lsun of V-band luminosity.Comment: 24 pages, 17 figures and 6 tables. Accepted for publication in the
Astrophysical Journal. Expanded discussion and various minor revisions to
improve robustness of results. Conclusions unchange
Identification of the soft X-ray excess in Cygnus X-1 with disc emission
We present results of a study of the soft X-ray excess in the black hole
candidate Cygnus X-1 made with the {\it Rosat PSPC}, using observations taken
during persistent emission at orbital phases close to 0.5. The soft excess can
be well fitted as a blackbody with temperature = keV. did not vary appreciably with intensity of the
source. By assuming that the distance of the source is its lower limit of 2.5
kpc, a luminosity of the soft excess of erg was obtained. From this, disc temperatures were calculated as a
function of radius, assuming the compact object to be a 10 \rm{M_{\sun}}
black hole, in particular, the temperature at 7 Schwarzschild radii expected to
be highly representative of the total disc emission. This was found to be 0.13
keV, in very good agreement with the spectral fitting result. This good
agreement strongly supports the identification of the soft excess with emission
from the disc around a black hole.Comment: PostScript, 3 figures, accepted for publication Astronomy and
Astrophysics Lette
Concept design and alternate arrangements of orbiter mid-deck habitability features
The evaluations and recommendations for habitability features in the space shuttle orbiter mid-deck are summarized. The orbiter mission plans, the mid-deck dimensions and baseline arrangements along with crew compliments and typical activities were defined. Female and male anthropometric data based on zero-g operations were also defined. Evaluations of baseline and alternate feasible concepts provided several recommendations which are discussed
The Ephemeris and Dipping Spectral Behavior of X1624-490
We present striking results from Rossi X-ray Timing Explorer (RXTE)
observations of the 21-hr low mass X-ray binary X1624-490, showing five complex
dips in unprecedented detail. For the first time, dipping is detected up to 15
keV. Prominent flares are also observed in the light curves, limited to
energies above 8 keV. Spectra selected by intensity during dip episodes can be
well fit with a two-component model consisting of a point-like blackbody from
the neutron star and progressive covering of an extended Comptonized region,
presumably an accretion disk corona (ADC), corrected for photons scattered into
and out of the X-ray beam by a interstellar dust halo. We find that the outer
regions of the absorber are highly ionized and that electron scattering is
totally responsible for the X-ray attenuation during shallow dipping. The
timescales of dip ingress and egress indicate that the envelope of material
absorbing the ADC has smaller angular size than the ADC itself, and that the
ADC is likely limited to a height-to-radius ratio of 10%, rather than being
spherical in extent. In addition, we have analyzed 4.5 yrs of RXTE All Sky
Monitor (ASM) coverage to derive the first accurate orbital ephemeris for
X1624-490, with phase zero (the time of dip centers) well-described by the
relation 2450088.63918(69) + N*0.869907(12) (JD).Comment: 12 pages, 5 figure
Longevity and mortality of owned dogs in England
Improved understanding of longevity represents a significant welfare opportunity for the domestic dog, given its unparalleled morphological diversity. Epidemiological research using electronic patient records (EPRs) collected from primary veterinary practices overcomes many inherent limitations of referral clinic, owner questionnaire and pet insurance data. Clinical health data from 102,609 owned dogs attending first opinion veterinary practices (n = 86) in central and southeast England were analysed, focusing on 5095 confirmed deaths.
Of deceased dogs with information available, 3961 (77.9%) were purebred, 2386 (47.0%) were female, 2528 (49.8%) were neutered and 1105 (21.7%) were insured. The overall median longevity was 12.0 years (IQR 8.9–14.2). The longest-lived breeds were the Miniature poodle, Bearded collie, Border collie and Miniature dachshund, while the shortest-lived were the Dogue de Bordeaux and Great Dane. The most frequently attributed causes of death were neoplastic, musculoskeletal and neurological disorders. The results of multivariable modelling indicated that longevity in crossbred dogs exceeded purebred dogs by 1.2 years (95% confidence interval 0.9–1.4; P < 0.001) and that increasing bodyweight was negatively correlated with longevity. The current findings highlight major breed differences for longevity and support the concept of hybrid vigour in dogs
Approaches to canine health surveillance
Effective canine health surveillance systems can be used to monitor disease in the general population, prioritise disorders for strategic control and focus clinical research, and to evaluate the success of these measures. The key attributes for optimal data collection systems that support canine disease surveillance are representativeness of the general population, validity of disorder data and sustainability. Limitations in these areas present as selection bias, misclassification bias and discontinuation of the system respectively. Canine health data sources are reviewed to identify their strengths and weaknesses for supporting effective canine health surveillance. Insurance data benefit from large and well-defined denominator populations but are limited by selection bias relating to the clinical events claimed and animals covered. Veterinary referral clinical data offer good reliability for diagnoses but are limited by referral bias for the disorders and animals included. Primary-care practice data have the advantage of excellent representation of the general dog population and recording at the point of care by veterinary professionals but may encounter misclassification problems and technical difficulties related to management and analysis of large datasets. Questionnaire surveys offer speed and low cost but may suffer from low response rates, poor data validation, recall bias and ill-defined denominator population information. Canine health scheme data benefit from well-characterised disorder and animal data but reflect selection bias during the voluntary submissions process. Formal UK passive surveillance systems are limited by chronic under-reporting and selection bias. It is concluded that active collection systems using secondary health data provide the optimal resource for canine health surveillance
Distribution des éléments alcalino-terreux dans les eaux interstitielles d'une carotte de Méditerranée occidentale
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