1,577 research outputs found
Economic evaluation of the eradication program for bovine viral diarrhea in the Swiss dairy sector
The aim of this study was to conduct an economic evaluation of the BVD eradication program in the Swiss dairy sector. The situation before the start of the program (herd-level prevalence: 20%) served as a baseline scenario. Production models for three dairy farm types were used to estimate gross margins as well as net production losses and expenditures caused by BVD. The total economic benefit was estimated as the difference in disease costs between the baseline scenario and the implemented eradication program and was compared to the total eradication costs in a benefit-cost analysis. Data on the impact of BVD virus (BVDV) infection on animal health, fertility and production parameters were obtained empirically in a retrospective epidemiological case-control study in Swiss dairy herds and complemented by literature. Economic and additional production parameters were based on benchmarking data and published agricultural statistics. The eradication costs comprised the cumulative expenses for sampling and diagnostics. The economic model consisted of a stochastic simulation in @Risk for Excel with 20,000 iterations and was conducted for a time period of 14 years (2008–2021)
Older Citizens' Opinions on Long-Term Care Options: A Vignette Survey.
Older citizens are directly concerned, as potential beneficiaries and informal caregivers, by access to long-term care (LTC) services matching their expectations. The aim of this research was to collect their opinions regarding LTC arrangements for a diversity of disability profiles.
Mailed vignette survey in a representative population-based sample of 3133 community-dwelling persons 68 years or older residing in a Swiss region.
All persons received a set of 10 vignettes. For each vignette, they considered 2 social situations successively: a person (1) living with an able-bodied spouse, and (2) living alone or with a spouse unable to help (resulting in 20 vignettes). Subjects selected a care setting (home, sheltered housing, or nursing home) and specified the preferred type of caregivers (spouse, professionals, or both) after community-based care options. Population estimates were based on weighted data accounting for the stratification of the survey sample.
A total of 2985 participants (95.3%) expressed opinions on 55,178 vignettes (mean 18.5 vignettes, SD 4.1) Institutionalization was selected by 0.8% (95% confidence interval 0.3-1.4) of the population for the vignette of lowest disability with able-bodied spouse and 78.8% (76.1-81.6) for the vignette of highest disability and no possible help from a spouse. Continence, cognitive, and behavioral difficulties further influenced the preferences expressed for LTC options. Community-based LTC choices involved professionals mostly as a complement to informal help by the spouse, except for vignettes describing isolated moderate cognitive impairment or difficulties in instrumental activities of daily living. In these cases, most favored help provided by spouses only.
This survey had high acceptance. Responses to variations in the disability and social profile displayed in the vignettes suggested the validity of measurements
The Luminosity Function of Omega Centauri
Deep HST-WFPC2 observations of the stellar population in the globular cluster
Omega Cen (NGC 5139) have been used to measure the luminosity function of main
sequence stars at the low-mass end. Two fields have been investigated, located
respectively ~4.6' and ~7' away from the cluster center, or near the half-light
radius of this cluster (~4.8'). The color-magnitude diagrams derived from these
data show the cluster main sequence extending to the detection limit at I ~ 24.
Information on both color and magnitude is used to build the luminosity
functions of main sequence stars in these fields and the two independent
determinations are found to agree very well with each other within the
observational uncertainty. Both functions show a peak in the stellar
distribution around M_I ~ 9 followed by a drop at fainter magnitudes well
before photometric incompleteness becomes significant, as is typical of other
globular clusters observed with the HST. This result is at variance with
previous claims that the luminosity function of Omega Cen stays flat at low
masses, but is in excellent agreement with recent near-IR NICMOS observations
of the same cluster.Comment: To appear in The Astronomical Journal. Contains 7 pages, 4 figures,
prepared with the AAS LaTeX macr
Intervals between response choices on a single-item measure of quality of life.
BACKGROUND: A single overall rating of quality of life (QoL) is a sensitive method that is often used in population surveys. However, the exact meaning of response choices is unclear. In particular, uneven spacing may affect the way QoL ratings should be analyzed and interpreted. This study aimed to determine the intervals between response choices to a single-item QoL assessment.
METHODS: A secondary analysis was conducted on data from the Lc65+ cohort study and two additional, population-based, stratified random samples of older people (N = 5,300). Overall QoL was rated as excellent, very good, good, fair or poor. A QoL score (range 0-100) was derived from participants' answers to a 28-item QoL assessment tool. A transformed QoL score ranging from 1 (poor) to 5 (excellent) was calculated. The same procedure was repeated to compute seven domain-specific QoL subscores (Feeling of safety; Health and mobility; Autonomy; Close entourage; Material resources; Esteem and recognition; Social and cultural life).
RESULTS: Mean (95 % confidence intervals) QoL scores were 96.23 (95.81-96.65) for excellent, 93.09 (92.74-93.45) for very good, 81.45 (80.63-82.27) for good, 65.44 (62.67-68.20) for fair and 54.52 (45.31-63.73) for poor overall QoL, corresponding to transformed QoL scores of respectively 5.00, 4.70, 3.58, 2.05, and 1.00. Ordinality of the categories excellent to poor was preserved in all seven QoL subscores.
CONCLUSIONS: The excellent-to-poor rating scale provides an ordinal measure of overall QoL. The intervals between response choices are unequal, but an interval scale can be obtained after adequate recoding of excellent, very good, good, fair and poor
A Consistent Picture Emerges: A Compact X-ray Continuum Emission Region in the Gravitationally Lensed Quasar SDSS J0924+0219
We analyze the optical, UV, and X-ray microlensing variability of the lensed
quasar SDSS J0924+0219 using six epochs of Chandra data in two energy bands
(spanning 0.4-8.0 keV, or 1-20 keV in the quasar rest frame), 10 epochs of
F275W (rest-frame 1089A) Hubble Space Telescope data, and high-cadence R-band
(rest-frame 2770A) monitoring spanning eleven years. Our joint analysis
provides robust constraints on the extent of the X-ray continuum emission
region and the projected area of the accretion disk. The best-fit half-light
radius of the soft X-ray continuum emission region is between 5x10^13 and 10^15
cm, and we find an upper limit of 10^15 cm for the hard X-rays. The best-fit
soft-band size is about 13 times smaller than the optical size, and roughly 7
GM_BH/c^2 for a 2.8x10^8 M_sol black hole, similar to the results for other
systems. We find that the UV emitting region falls in between the optical and
X-ray emitting regions at 10^14 cm < r_1/2,UV < 3x10^15 cm. Finally, the
optical size is significantly larger, by 1.5*sigma, than the theoretical
thin-disk estimate based on the observed, magnification-corrected I-band flux,
suggesting a shallower temperature profile than expected for a standard disk.Comment: Replaced with accepted version to Ap
Young and intermediate-age massive star clusters
An overview of our current understanding of the formation and evolution of
star clusters is given, with main emphasis on high-mass clusters. Clusters form
deeply embedded within dense clouds of molecular gas. Left-over gas is cleared
within a few million years and, depending on the efficiency of star formation,
the clusters may disperse almost immediately or remain gravitationally bound.
Current evidence suggests that a few percent of star formation occurs in
clusters that remain bound, although it is not yet clear if this fraction is
truly universal. Internal two-body relaxation and external shocks will lead to
further, gradual dissolution on timescales of up to a few hundred million years
for low-mass open clusters in the Milky Way, while the most massive clusters (>
10^5 Msun) have lifetimes comparable to or exceeding the age of the Universe.
The low-mass end of the initial cluster mass function is well approximated by a
power-law distribution, dN/dM ~ M^{-2}, but there is mounting evidence that
quiescent spiral discs form relatively few clusters with masses M > 2 x 10^5
Msun. In starburst galaxies and old globular cluster systems, this limit
appears to be higher, at least several x 10^6 Msun. The difference is likely
related to the higher gas densities and pressures in starburst galaxies, which
allow denser, more massive giant molecular clouds to form. Low-mass clusters
may thus trace star formation quite universally, while the more long-lived,
massive clusters appear to form preferentially in the context of violent star
formation.Comment: 21 pages, 3 figures. To appear as invited review article in a special
issue of the Phil. Trans. Royal Soc. A: Ch. 9 "Star clusters as tracers of
galactic star-formation histories" (ed. R. de Grijs). Fully peer reviewed.
PDFLaTeX, requires rspublic.cls style fil
Surface Brightness Profiles of Galactic Globular Clusters from Hubble Space Telescope Images
Hubble Space Telescope allows us to study the central surface brightness
profiles for globular clusters at unprecedented detail. We have mined the HST
archives to obtain 38 WFPC2 images of galactic globular clusters with adequate
exposure times and filters, which we use to measure their central structure. We
outline a reliable method to obtain surface brightness profiles from integrated
light that we test on an extensive set of simulated images. Most clusters have
central surface brightness about 0.5 mag brighter than previous measurements
made from ground-based data, with the largest differences around 2 magnitudes.
Including the uncertainties in the slope estimates, the surface brightness
slope distribution is consistent with half of the sample having flat cores and
the remaining half showing a gradual decline from 0 to -0.8
(dlog(Sigma)/dlogr). We deproject the surface brightness profiles in a
non-parametric way to obtain luminosity density profiles. The distribution of
luminosity density logarithmic slopes show similar features with half of the
sample between -0.4 and -1.8. These results are in contrast to our theoretical
bias that the central regions of globular clusters are either isothermal (i.e.
flat central profiles) or very steep (i.e. luminosity density slope ~-1.6) for
core-collapse clusters. With only 50% of our sample having central profiles
consistent with isothermal cores, King models appear to poorly represent most
globular clusters in their cores.Comment: 23 pages, 14 figures, AJ accepte
Binary formation within globular clusters : X-ray clues
We have investigated the effect of the number of primordial binaries on the
relationship between the total number of detected binaries within globular
cluster and its collision rate. We have used simulated populations of binary
stars in globular clusters : primordial binaries and binaries formed through
gravitational interactions. We show that the initial number of primordial
binaries influences the relationship between the number of detected sources and
the collision rate, which we find to be a power law. We also show that
observing an incomplete sample provides the same results as those obtained with
a complete sample. We use observations made by XMM-Newton and Chandra to
constrain the formation mechanism of sources with X-ray luminosities larger
than 10^{31} erg/s, and show that some of the cataclysmic variables within
globular clusters should be primordial objects. We point out a possibly hidden
population of neutron stars within high mass globular clusters with a low
collision rate.Comment: 6 pages, no figure, accepted for publication in Astronomy &
Astrophysic
No Increase of the Red-Giant-Branch Tip Luminosity Toward the Center of M31
We present observations with the Hubble Space Telescope Wide Field Planetary
Camera 2 of three fields centered on super-metal-rich globular clusters in the
bulge of M31. Our (I,V-I) color-magnitude diagrams reach as faint as I ~ 26.5
mag and clearly reveal the magnitude of the first ascent red giant branch (RGB)
tip. We find that the apparent I magnitude of the RGB tip does not become
brighter near the center of M31 as concluded by previous investigators. Our
observations and artificial star experiments presented in this study strongly
support the idea that previous very bright stars were likely the result of
spurious detections of blended stars due to crowding in lower resolution
images. On the contrary, our observations indicate that, at a mean projected
galactocentric distance of 1.1 kpc, the RGB tip is some 1.3 magnitudes fainter
than it is at 7 kpc. An analysis of this difference in RGB tip magnitude
suggests that the M31 bulge stellar population has a mean metallicity close to
that of the Sun.Comment: Accepted for publication in ApJ, June 20, 1999 issu
The redshift of the gravitationally lensed radio source PKS1830-211
We report on the spectroscopic identification and the long awaited redshift
measurement of the heavily obscured, gravitationally lensed radio source PKS
1830-211, which was first observed as a radio Einstein ring. The NE component
of the doubly imaged core is identified, in our infrared spectrum covering the
wavelength range 1.5-2.5 microns, as an impressively reddened quasar at
z=2.507. Our redshift measurement, together with the recently measured time
delay (Lovell et al.), means that we are a step closer to determining the
Hubble constant from this lens. Converting the time delay into the Hubble
constant by using existing models leads to high values for the Hubble constant.
Since the lensing galaxy lies very close to the center of the lensed ring,
improving the error bars on the Hubble constant will require not only a more
precise time delay measurement, but also very precise astrometry of the whole
system.Comment: 11 pages, 2 figures, Accepted ApJ
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