264 research outputs found
Attentional bias for negative, positive, and threat words in current and remitted depression
Background The aim of this study was to improve our understanding of the underlying mechanisms in the maintenance of depression. We examined attentional bias (AB) for negative and positive adjectives and general threat words in strictly-defined clinical groups of participants with pure Major Depressive Disorder (MDD) without a history of anxiety disorders (AD), mixed MDD and AD, and remitted participants. Method We investigated both stimulus specificity and time course of AB in these groups, adopting a cross-sectional design. Data were drawn from the large scale Netherlands Study of Depression and Anxiety (NESDA), from which we selected all participants with pure current MDD without a history of AD (n = 29), all participants with current MDD and co-morbid AD(s) (n = 86), all remitted MDD participants (n = 294), and a comparison group without (a history of) MDD or ADs (n = 474). AB was measured with an Exogenous Cueing Task covering short and long presentation times (500 and 1250 ms) and 4 stimulus types (negative, positive, threat, neutral). Results Both traditional and trial level (dynamic) AB scores failed to show an AB for negative adjectives in participants with MDD or mixed MDD/AD. Specifically for long duration trials (1250 ms), remitted participants showed a larger AB traditional score (albeit the actual score still being negative) than the comparison group. The mixed MDD/AD group showed a higher trial-level AB score away from positive adjectives (1250 ms) than the comparisons. In addition, the mixed MDD/AD group showed higher and more variable trial-level AB scores away from short and towards longer presented general threat words together with a non-significant tendency to show less negative traditional AB scores for threat trials (500 ms) than the comparison group. Conclusions All in all, the findings do not corroborate the view that an AB towards negative or away from positive adjectives is critically involved in currently depressed individuals. Yet, the relatively high (less negative) AB score for negative adjectives in remitted individuals points to the possibility that an AB for negative information may be involved as a risk factor in the recurrence of MDD
The Missing Luminous Blue Variables and the Bistability Jump
We discuss an interesting feature of the distribution of luminous blue
variables on the H-R diagram, and we propose a connection with the bistability
jump in the winds of early-type supergiants. There appears to be a deficiency
of quiescent LBVs on the S Dor instability strip at luminosities between log
L/Lsun = 5.6 and 5.8. The upper boundary, is also where the
temperature-dependent S Dor instability strip intersects the bistability jump
at about 21,000 K. Due to increased opacity, winds of early-type supergiants
are slower and denser on the cool side of the bistability jump, and we
postulate that this may trigger optically-thick winds that inhibit quiescent
LBVs from residing there. We conduct numerical simulations of radiation-driven
winds for a range of temperatures, masses, and velocity laws at log L/Lsun=5.7
to see what effect the bistability jump should have. We find that for
relatively low stellar masses the increase in wind density at the bistability
jump leads to the formation of a modest to strong pseudo photosphere -- enough
to make an early B-type star appear as a yellow hypergiant. Thus, the proposed
mechanism will be most relevant for LBVs that are post-red supergiants. Yellow
hypergiants like IRC+10420 and rho Cas occupy the same luminosity range as the
``missing'' LBVs, and show apparent temperature variations at constant
luminosity. If these yellow hypergiants do eventually become Wolf-Rayet stars,
we speculate that they may skip the normal LBV phase, at least as far as their
apparent positions on the HR diagram are concerned.Comment: 20 pages, 4 figs, accepted by Ap
On the nature of the prototype LBV AG Carinae I. Fundamental parameters during visual minimum phases and changes in the bolometric luminosity during the S-Dor cycle
We present a detailed spectroscopic analysis of the luminous blue variable AG
Carinae during the last two visual minimum phases of its S-Dor cycle (1985-1990
and 2000-2003). The analysis reveals an overabundance of He, N, and Na, and a
depletion of H, C, and O, on the surface of AG Car, indicating the presence of
CNO-processed material. Furthermore, the ratio N/O is higher on the stellar
surface than in the nebula. We found that the minimum phases of AG Car are not
equal to each other, since we derived a noticeable difference between the
maximum effective temperature achieved during 1985-1990 (22,800 K) and
2000-2001 (17,000 K). While the wind terminal velocity was 300 km/s in
1985-1990, it was as low as 105 km/s in 2001. The mass-loss rate, however, was
lower from 1985-1990 (1.5 x 10^(-5) Msun/yr) than from 2000-2001 (3.7 x 10^(-5)
Msun/yr). We found that the wind of AG Car is significantly clumped (f=0.10 -
0.25) and that clumps must be formed deep in the wind. We derived a bolometric
luminosity of 1.5 x 10^6 Lsun during both minimum phases which, contrary to the
common assumption, decreases to 1.0 x 10^6 Lsun as the star moves towards
maximum flux in the V band. Assuming that the decrease in the bolometric
luminosity of AG Car is due to the energy used to expand the outer layers of
the star (Lamers 1995), we found that the expanding layers contain roughly 0.6
- 2 Msun. Such an amount of mass is an order of magnitude lower than the
nebular mass around AG Car, but is comparable to the nebular mass found around
lower-luminosity LBVs and to that of the Little Homunculus of Eta Car. If such
a large amount of mass is indeed involved in the S Dor-type variability, we
speculate that such instability could be a failed Giant Eruption, with several
solar masses never becoming unbound from the star.(abridged)Comment: 22 pages, 13 figures, ApJ in press. A high-resolution PDF version is
also available at http://www.mpifr-bonn.mpg.de/staff/jgroh/agcar.htm
A High-Quality Bonobo Genome Refines The Analysis Of Hominid Evolution
The divergence of chimpanzee and bonobo provides one of the few examples of recent hominid speciation(1,2). Here we describe a fully annotated, high-quality bonobo genome assembly, which was constructed without guidance from reference genomes by applying a multiplatform genomics approach. We generate a bonobo genome assembly in which more than 98% of genes are completely annotated and 99% of the gaps are closed, including the resolution of about half of the segmental duplications and almost all of the full-length mobile elements. We compare the bonobo genome to those of other great apes(1,3-5) and identify more than 5,569 fixed structural variants that specifically distinguish the bonobo and chimpanzee lineages. We focus on genes that have been lost, changed in structure or expanded in the last few million years of bonobo evolution. We produce a high-resolution map of incomplete lineage sorting and estimate that around 5.1% of the human genome is genetically closer to chimpanzee or bonobo and that more than 36.5% of the genome shows incomplete lineage sorting if we consider a deeper phylogeny including gorilla and orangutan. We also show that 26% of the segments of incomplete lineage sorting between human and chimpanzee or human and bonobo are non-randomly distributed and that genes within these clustered segments show significant excess of amino acid replacement compared to the rest of the genome
Molecular cloning and analysis of functional envelope genes from human immunodeficiency virus type 1 sequence subtypes A through G
Astrophysical parameters of the peculiar X-ray transient IGR J11215−5952
Context. The current generation of X-ray satellites has discovered many new X-ray sources that are difficult to classify within the well-described subclasses. The hard X-ray source IGR J11215-5952 is a peculiar transient, displaying very short X-ray outbursts every 165 days.
Aims: To characterise the source, we obtained high-resolution spectra of the optical counterpart, HD 306414, at different epochs, spanning a total of three months, before and around the 2007 February outburst with the combined aims of deriving its astrophysical parameters and searching for orbital modulation.
Methods: We fit model atmospheres generated with the FASTWIND code to the spectrum, and used the interstellar lines in the spectrum to estimate its distance. We also cross-correlated each individual spectrum to the best-fit model to derive radial velocities.
Results: From its spectral features, we classify HD 306414 as B0.5 Ia. From the model fit, we find Teff ≈ 24 700 K and log g ≈ 2.7, in good agreement with the morphological classification. Using the interstellar lines in its spectrum, we estimate a distance to HD 306414 d ≳ 7 kpc. Assuming this distance, we derive R∗ ≈ 40 R⊙ and Mspect ≈ 30 M⊙ (consistent, within errors, with Mevol ≈ 38 M⊙, and in good agreement with calibrations for the spectral type). Analysis of the radial velocity curve reveals that radial velocity changes are not dominated by the orbital motion, and provide an upper limit on the semi-amplitude for the optical component Kopt ≲ 11 ± 6 km s-1. Large variations in the depth and shape of photospheric lines suggest the presence of strong pulsations, which may be the main cause of the radial velocity changes. Very significant variations, uncorrelated with those of the photospheric lines are seen in the shape and position of the Hα emission feature around the time of the X-ray outburst, but large excursions are also observed at other times.
Conclusions: HD 306414 is a normal B0.5 Ia supergiant. Its radial velocity curve is dominated by an effect that is different from binary motion, and is most likely stellar pulsations. The data available suggest that the X-ray outbursts are caused by the close passage of the neutron star in a very eccentric orbit, perhaps leading to localised mass outflow
DOT Tomography of the Solar Atmosphere VII. Chromospheric Response to Acoustic Events
We use synchronous movies from the Dutch Open Telescope sampling the
G band, Ca II and Halpha with five-wavelength profile sampling to study the
response of the chromosphere to acoustic events in the underlying photosphere.
We first compare the visibility of the chromosphere in Ca II H and Halpha,
demonstrate that studying the chromosphere requires Halpha data, and summarize
recent developments in understanding why this is so. We construct divergence
and vorticity maps of the photospheric flow field from the G-band images and
locate specific events through the appearance of bright Ca II H grains. The
reaction of the Halpha chromosphere is diagnosed in terms of brightness and
Doppler shift. We show and discuss three particular cases in detail: a regular
acoustic grain marking shock excitation by granular dynamics, a persistent
flasher which probably marks magnetic-field concentration, and an exploding
granule. All three appear to buffet overlying fibrils, most clearly in
Dopplergrams. Although our diagnostic displays to dissect these phenomena are
unprecedentedly comprehensive, adding even more information (photospheric
Doppler tomography and magnetograms, chromospheric imaging and Doppler mapping
in the ultraviolet) is warranted.Comment: accepted by Solar Physic
Scientific assessment of the quality of OSIRIS images
OSIRIS, the scientific imaging system onboard the ESA Rosetta spacecraft, has been imaging the nucleus of comet 67P/Churyumov-Gerasimenko and its dust and gas environment since March 2014. The images serve different scientific goals, from morphology and composition studies of the nucleus surface, to the motion and trajectories of dust grains, the general structure of the dust coma, the morphology and intensity of jets, gas distribution, mass loss, and dust and gas production rates. We present the calibration of the raw images taken by OSIRIS and address the accuracy that we can expect in our scientific results based on the accuracy of the calibration steps that we have performed. Methods. We describe the pipeline that has been developed to automatically calibrate the OSIRIS images. Through a series of steps, radiometrically calibrated and distortion corrected images are produced and can be used for scientific studies. Calibration campaigns were run on the ground before launch and throughout the years in flight to determine the parameters that are used to calibrate the images and to verify their evolution with time. We describe how these parameters were determined and we address their accuracy. Results. We provide a guideline to the level of trust that can be put into the various studies performed with OSIRIS images, based on the accuracy of the image calibration
Solar Spectroscopy and (Pseudo-)Diagnostics of the Solar Chromosphere
I first review trends in current solar spectrometry and then concentrate on
comparing various spectroscopic diagnostics of the solar chromosphere. Some are
actually not at all chromospheric but just photospheric or clapotispheric and
do not convey information on chromospheric heating, even though this is often
assumed. Balmer Halpha is the principal displayer of the closed-field
chromosphere, but it is unclear how chromospheric fibrils gain their large
Halpha opacity. The open-field chromosphere seems to harbor most if not all
coronal heating and solar wind driving, but is hardly seen in optical
diagnostics.Comment: To appear in "Recent Advances in Spectroscopy: Astrophysical,
Theoretical and Experimental Perspectives", eds. R.K. Chaudhuri, M.V.
Mekkaden, A.V. Raveendran and A. Satya Narayanan, Astrophysics and Space
Science Proceedings, Springer, Heidelberg, 2009. Revision: references
corrected, new references added, minor text correction
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