576 research outputs found
Physical health and the onset and persistence of depression in older adults: an eight-wave prospective community based study.
Background. Poor physical health has long been recognized to be one of the most important risk factors for depression in older adults. Since many aspects of physical health can be targeted for improvement in primary care, it is important to know whether physical health problems predict the onset and/or the persistence of depression. Methods. The study is based on a sample which at the outset consisted of 327 depressed and 325 non-depressed older adults (55-85) drawn from a larger random community-based sample in the Netherlands. Depression was measured using the Center for Epidemiologic Studies Depression scale (CES-D) at eight successive waves. Results. From all incident episodes, the majority (57%) was short-lived. These short episodes could generally not be predicted by physical health problems. The remaining incident episodes (43%) were not short-lived and could be predicted by poor physical health. Chronicity (34%) was also predicted by physical health problems. Conclusions. The study design with its frequent measurements recognized more incident cases than previous studies; these cases however did have a better prognosis than is often assumed. The prognosis of prevalent cases was rather poor. Physical health problems were demonstrated to be a predictor of both the onset and the persistence of depression. This may well have implications for prevention and intervention
Blue Dots Team Transits Working Group Review
Transiting planet systems offer an unique opportunity to observationally
constrain proposed models of the interiors (radius, composition) and
atmospheres (chemistry, dynamics) of extrasolar planets. The spectacular
successes of ground-based transit surveys (more than 60 transiting systems
known to-date) and the host of multi-wavelength, spectro-photometric follow-up
studies, carried out in particular by HST and Spitzer, have paved the way to
the next generation of transit search projects, which are currently ongoing
(CoRoT, Kepler), or planned. The possibility of detecting and characterizing
transiting Earth-sized planets in the habitable zone of their parent stars
appears tantalizingly close. In this contribution we briefly review the power
of the transit technique for characterization of extrasolar planets, summarize
the state of the art of both ground-based and space-borne transit search
programs, and illustrate how the science of planetary transits fits within the
Blue Dots perspective.Comment: 9 pages, 3 figures, to be published in the proceedings (ASP Conf.
Ser.) of the "Pathways Towards Habitable Planets" conference, held in
Barcelona (14-18 Sep 2009
Tumor Necrosis Factor Polymorphism Affects Transplantation Outcome in Patients with Myelodysplastic Syndrome but Not in Those with Chronic Myelogenous Leukemia, Independent of the Presence of HLA-DR15
Both the presence of HLA-DR15 and tumor necrosis factor (TNF)-α levels have been reported to affect outcome after hematopoietic cell transplantation (HCT). Patients with a myelodysplastic syndrome (MDS) show a high prevalence of HLA-DR15 and express high levels of TNF-α in the bone marrow. The present analysis involving 7950 patients showed an HLA-DR15 frequency of 31% in patients with MDS, compared with only 23% in patients with chronic myelogenous leukemia (CML). HLA-DR15 was more prevalent in Caucasian patients than in non-Caucasian patients (P = .01). The numbers of patients in the non-Caucasian subgroups were too small to allow further analysis. Among Caucasian patients with MDS and CML, the presence of HLA-DR15 did not significantly affect the occurrence of graft-versus-host disease, relapse, nonrelapse mortality (NRM), or survival. However, there was a significant correlation between DR15 and TNF polymorphisms at position -308 among patients with MDS, and the TNF-308 AG genotype conferred an increased risk of NRM compared with the GG genotype (hazard ratio [HR], 1.49; P = .02), even after adjusting for DR15. Conversely, the TNF-863 AA genotype was correlated with decreased overall mortality and NRM compared with the CC genotype (HR, 0.36, P = .04 vs HR, 0.13, P = .04), even after adjusting for DR15. There was no significant association between TNF-308 or -863 polymorphisms and transplantation outcome in CML patients. These results suggest that TNF polymorphisms, but not DR15, affect transplantation outcome in a disease-dependent manner
Mid Infrared Properties of Low Metallicity Blue Compact Dwarf Galaxies From Spitzer/IRS
We present a {\em Spitzer}-based mid-infrared study of a large sample of Blue
Compact Dwarf galaxies (BCD) using the Infrared Spectrograph (IRS), including
the first mid-IR spectrum of IZw18, the archetype for the BCD class and among
the most metal poor galaxies known. We show the spectra of Polycyclic Aromatic
Hydrocarbon (PAH) emission in low-metallicity environment. We find that the
equivalent widths (EW) of PAHs at 6.2, 7.7, 8.6 and 11.2 m are generally
weaker in BCDs than in typical starburst galaxies and that the fine structure
line ratio, [NeIII]/[NeII], has a weak anti-correlation with the PAH EW. A much
stronger anti-correlation is shown between the PAH EW and the product of the
[NeIII]/[NeII] ratio and the UV luminosity density divided by the metallicity.
We conclude that PAH EW in metal-poor high-excitation environments is
determined by a combination of PAH formation and destruction effects.Comment: 41 pages, 14 figure
High angular resolution imaging and infrared spectroscopy of CoRoT candidates
Studies of transiting extrasolar planets are of key importance for
understanding the nature of planets outside our solar system because their
masses, diameters, and bulk densities can be measured. An important part of
transit-search programmes is the removal of false-positives. The critical
question is how many of the candidates that passed all previous tests are false
positives. For our study we selected 25 CoRoT candidates that have already been
screened against false-positives using detailed analysis of the light curves
and seeing-limited imaging, which has transits that are between 0.7 and 0.05%
deep. We observed 20 candidates with the adaptive optics imager NaCo and 18
with the high-resolution infrared spectrograph CRIRES. We found previously
unknown stars within 2 arcsec of the targets in seven of the candidates. All of
these are too faint and too close to the targets to have been previously
detected with seeing-limited telescopes in the optical. Our study thus leads to
the surprising results that if we remove all candidates excluded by the
sophisticated analysis of the light-curve, as well as carrying out deep imaging
with seeing-limited telescopes, still 28-35% of the remaining candidates are
found to possess companions that are bright enough to be false-positives. Given
that the companion-candidates cluster around the targets and that the J-K
colours are consistent with physical companions, we conclude that the
companion-candidates are more likely to be physical companions rather than
unrelated field stars.Comment: 12 pages, 12 figures, A&A in pres
Possible detection of phase changes from the non-transiting planet HD 46375b by CoRoT
The present work deals with the detection of phase changes in an exoplanetary
system. HD 46375 is a solar analog known to host a non-transiting Saturn-mass
exoplanet with a 3.0236 day period. It was observed by the CoRoT satellite for
34 days during the fall of 2008. We attempt to identify at optical wavelengths,
the changing phases of the planet as it orbits its star. We then try to improve
the star model by means of a seismic analysis of the same light curve and the
use of ground-based spectropolarimetric observations. The data analysis relies
on the Fourier spectrum and the folding of the time series. We find evidence of
a sinusoidal signal compatible in terms of both amplitude and phase with light
reflected by the planet. Its relative amplitude is Delta Fp/F* = [13.0, 26.8]
ppm, implying an albedo A=[0.16, 0.33] or a dayside visible brightness
temperature Tb ~ [1880,2030] K by assuming a radius R=1.1 R_Jup and an
inclination i=45 deg. Its orbital phase differs from that of the
radial-velocity signal by at most 2 sigma_RV. However, the tiny planetary
signal is strongly blended by another signal, which we attribute to a telluric
signal with a 1 day period. We show that this signal is suppressed, but not
eliminated, when using the time series for HD 46179 from the same CoRoT run as
a reference. This detection of reflected light from a non-transiting planet
should be confirmable with a longer CoRoT observation of the same field. In any
case, it demonstrates that non-transiting planets can be characterized using
ultra-precise photometric lightcurves with present-day observations by CoRoT
and Kepler. The combined detection of solar-type oscillations on the same
targets (Gaulme et al. 2010a) highlights the overlap between exoplanetary
science and asteroseismology and shows the high potential of a mission such as
Plato.Comment: 4 pages, 6 figure
Absolute properties of the low-mass eclipsing binary CM Draconis
Spectroscopic and eclipsing binary systems offer the best means for
determining accurate physical properties of stars, including their masses and
radii. The data available for low-mass stars have yielded firm evidence that
stellar structure models predict smaller radii and higher effective
temperatures than observed, but the number of systems with detailed analyses is
still small. In this paper we present a complete reanalysis of one of such
eclipsing systems, CM Dra, composed of two dM4.5 stars. New and existing light
curves as well as a radial velocity curve are modeled to measure the physical
properties of both components. The masses and radii determined for the
components of CM Dra are M1=0.2310+/-0.0009 Msun, M2=0.2141+/-0.0010 Msun,
R1=0.2534+/-0.0019 Rsun, and R2=0.2396+/-0.0015 Rsun. With relative
uncertainties well below the 1% level, these values constitute the most
accurate properties to date for fully convective stars. This makes CM Dra a
valuable benchmark for testing theoretical models. In comparing our
measurements with theory, we confirm the discrepancies reported previously for
other low-mass eclipsing binaries. These discrepancies seem likely to be due to
the effects of magnetic activity. We find that the orbit of this system is
slightly eccentric, and we have made use of eclipse timings spanning three
decades to infer the apsidal motion and other related properties.Comment: 19 pages, 9 figures. Accepted for publication in Ap
Reanalysis of two eclipsing binaries: EE Aqr and Z Vul
We study the radial-velocity and light curves of the two eclipsing binaries
EE Aqr and Z Vul. Using the latest version of the Wilson & Van Hamme (2003)
model, absolute parameters for the systems are determined. We find that EE Aqr
and Z Vul are near-contact and semi-detached systems, respectively. The primary
component of EE Aqr fills about 96% of its 'Roche lobe', while its secondary
one appears close to completely filling this limiting volume. In a similar way,
we find fill-out proportions of about 72 and 100% of these volumes for the
primary and secondary components of Z Vul respectively. We compare our results
with those of previous authors.Comment: 13 pages, 8 figures, 10 table
Multi-object spectroscopy of stars in the CoRoT fields II: The stellar population of the CoRoT fields IRa01, LRa01, LRa02, and LRa06
With now more than 20 exoplanets discovered by CoRoT, it has often been
considered strange that so many of them are orbiting F-stars, and so few of
them K or M-stars. Although transit search programs are mostly sensitive to
short-period planets, they are ideal for verifying these results. To determine
the frequency of planets as a function of stellar mass, we also have to
characterize the sample of stars that was observed. We study the stellar
content of the CoRoT-fields IRa01, LRa01 (=LRa06), and LRa02 by determining the
spectral types of 11466 stars. We used spectra obtained with the multi-object
spectrograph AAOmega and derived the spectral types by using template spectra
with well-known parameters. We find that 34.8+/-0.7% of the stars observed by
CoRoT in these fields are F-dwarfs, 15.1+/-0.5% G-dwarfs, and 5.0+/-0.3%
K-dwarfs. We conclude that the apparent lack of exoplanets of K- and M-stars is
explained by the relatively small number of these stars in the observed sample.
We also show that the apparently large number of planets orbiting F-stars is
similarly explained by the large number of such stars in these fields. Our
study also shows that the difference between the sample of stars that CoRoT
observes and a sample of randomly selected stars is relatively small, and that
the yield of CoRoT specifically is the detection one hot Jupiter amongst
2100+/-700 stars. We conclude that transit search programs can be used to study
the relation between the frequency of planets and the mass of the host stars,
and that the results obtained so far generally agree with those of radial
velocity programs.Comment: 231 pages with 6 figures, A&A accepte
Linear response within the projection-based renormalization method: Many-body corrections beyond the random phase approximation
The explicit evaluation of linear response coefficients for interacting
many-particle systems still poses a considerable challenge to theoreticians. In
this work we use a novel many-particle renormalization technique, the so-called
projector-based renormalization method, to show how such coefficients can
systematically be evaluated. To demonstrate the prospects and power of our
approach we consider the dynamical wave-vector dependent spin susceptibility of
the two-dimensional Hubbard model and also determine the subsequent magnetic
phase diagram close to half-filling. We show that the superior treatment of
(Coulomb) correlation and fluctuation effects within the projector-based
renormalization method significantly improves the standard random phase
approximation results.Comment: 17 pages, 7 figures, revised versio
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