747 research outputs found
Hormonal replacement therapy, prothrombotic mutations and the risk of venous thrombosis
Hormone replacement therapy (HRT) increases the risk of venous thrombosis. We investigated whether this risk is affected by carriership of hereditary prothrombotic abnormalities. Therefore, we determined the two most common prothrombotic mutations, factor V Leiden and prothrombin 20210A in women who participated in a case-control study on venous thrombosis. Relative risks were expressed as odds ratios (OR) with 95% confidence intervals (CI95). Among 7 7 women aged 45-64 years with a first venous thrombosis, 51% were receiving HRT at the time of thrombosis, compared with 24% of control women (OR = 3.3, CI95 1.8-5.8). Among the patients, 23% had a prothrombotic defect, versus 7% among the control women (OR = 3.8, CI95 1.7- 8.5). Women who had factor V Leiden and used HRT had a 15-fold increased risk (OR = 15.5, CI95 3.1-77), which exceeded the expected joint odds ratio of 6.1 (under an additive model). We conclude that the thrombotic risk of HRT may particularly affect women with prothrombotic mutations. Efforts to avoid HRT in women with increased risk of thrombosis are advisable
The origin of hydrogen line emission for five Herbig Ae/Be stars spatially resolved by VLTI/AMBER spectro-interferometry
To trace the accretion and outflow processes around YSOs, diagnostic spectral
lines such as the BrG 2.166 micron line are widely used, although due to a lack
of spatial resolution, the origin of the line emission is still unclear.
Employing the AU-scale spatial resolution which can be achieved with infrared
long-baseline interferometry, we aim to distinguish between theoretical models
which associate the BrG line emission with mass infall or mass outflow
processes. Using the VLTI/AMBER instrument, we spatially and spectrally
(R=1500) resolved the inner environment of five Herbig Ae/Be stars (HD163296,
HD104237, HD98922, MWC297, V921Sco) in the BrG emission line as well as in the
adjacent continuum. All objects (except MWC297) show an increase of visibility
within the BrG emission line, indicating that the BrG-emitting region in these
objects is more compact than the dust sublimation radius. For HD98922, our
quantitative analysis reveals that the line-emitting region is compact enough
to be consistent with the magnetospheric accretion scenario. For HD163296,
HD104237, MWC297, and V921Sco we identify a stellar wind or a disk wind as the
most likely line-emitting mechanism. We search for general trends and find that
the size of the BrG-emitting region does not seem to depend on the basic
stellar parameters, but correlates with the H-alpha line profile shape. We find
evidence for at least two distinct BrG line-formation mechanisms. Stars with a
P-Cygni H-alpha line profile and a high mass-accretion rate seem to show
particularly compact BrG-emitting regions (R_BrG/R_cont<0.2), while stars with
a double-peaked or single-peaked H-alpha-line profile show a significantly more
extended BrG-emitting region (0.6<R_BrG/R_cont<1.4), possibly tracing a stellar
wind or a disk wind.Comment: 20 pages; 11 figures; Accepted by A&A; a high quality version of the
paper can be obtained at
http://www.skraus.eu/papers/kraus.HAeBe-BrGsurvey.pd
What can we learn about protoplanetary disks from analysis of mid-infrared carbonaceous dust emission?
In this Paper we analyze the mid-infrared (mid-IR) emission of very small
dust particles in a sample of 12 protoplanetary disks to see how they are
connected to interstellar dust particles and to investigate the possibility
that their emission can be used as a probe of the physical conditions and
evolution of the disk. We define a basis made of three mid-IR template spectra
PAH, PAH and VSGs that were derived from the analysis of reflection
nebulae, and an additional PAH spectrum that was introduced by Joblin et
al. (2008) for the analysis of the spectra of planetary nebulae. From the
optimization of the fit of 12 star+disk spectra, using a linear combination of
the 4 template spectra, we found that an additional small grain component with
a broad feature at 8.3 m is needed. We find that the fraction of VSG
emission in disks decreases with increasing stellar temperature. VSGs appear to
be destroyed by UV photons at the surface of disks, thus releasing free PAH
molecules, which are eventually ionized as it is observed in photodissociation
regions. On the opposite, we observe that the fraction of PAH increases
with increasing star temperature except in the case of B stars where they are
absent. We argue that this is compatible with the identification of PAH as
large ionized PAHs, most likely emitting in regions of the disk that are close
to the star. Finally, we provide a UV-dependant scheme to explain the evolution
of PAHs and VSGs in protoplanetary disks. We show that A stars modify the size
spectrum of PAHs and VSGs in favor of large PAHs while B stars destroy even the
largest PAHs up to large radii in the disk. These results allow us to put new
constrains on the properties of two sources: IRS 48 and "Gomez's Hamburger"
which are poorly characterized.Comment: Accepted for publication in A&
Dynamical Fermions with Fat Links
We present and test a new method for simulating dynamical fermions with fat
links. Our construction is based on the introduction of auxiliary but dynamical
gauge fields and works with any fermionic action and can be combined with any
fermionic updating. In our simulation we use an over-relaxation step which
makes it effective. For four flavors of staggered fermions first results
indicate that flavor symmetry at a lattice spacing a~0.2 fm is restored to a
few percent. With the standard action this amount of flavor symmetry
restoration is achieved at a~0.07 fm. We estimate that the overall
computational cost is reduced by at least a factor 10.Comment: 11 pages, 4 figures, detailed description of over-relaxation and
references added, figures with more statistic
Warm molecular gas and kinematics in the disc around HD 100546
The disc around the Herbig Ae/Be star HD 100546 is one of the most
extensively studied discs in the southern sky. Although there is a wealth of
information about its dust content and composition, not much is known about its
gas and large scale kinematics. We detect and study the molecular gas in the
disc at spatial resolution from 7.7" to 18.9" using the APEX telescope. The
lines 12CO J=7-6, J=6-5, J=3-2, 13CO J=3-2 and [C I] 3P2-3P1 are observed,
diagnostic of disc temperature, size, chemistry, and kinematics. We use
parametric disc models that reproduce the low-J 12CO emission from Herbig~Ae
stars and vary the basic disc parameters - temperature, mass and size. Using
the molecular excitation and radiative transfer code RATRAN we fit the observed
spectral line profiles. Our observations are consistent with more than 0.001
Msun of molecular gas in a disc of approximately 400 AU radius in Keplerian
rotation around a 2.5 Msun star, seen at an inclination of 50 degrees. The
detected 12CO lines are dominated by gas at 30-70~K. The non-detection of the
[C I] line indicates excess ultraviolet emission above that of a B9 type model
stellar atmosphere. Asymmetry in the 12CO line emission suggests that one side
of the outer disc is colder by 10-20~K than the other, possibly due to a shadow
by a warped geometry of the inner disc. Pointing offsets, foreground cloud
absorption and asymmetry in the disc extent are excluded scenarios. Efficient
heating of the outer disc ensures that low- and high-J 12CO lines are dominated
by the outermost disc regions, indicating a 400 AU radius. The 12CO J=6--5 line
arises from a disc layer higher above disc midplane, and warmer by 15-20~K than
the layer emitting the J=3--2 line. The existing models of discs around Herbig
Ae stars, assuming a B9.5 type model stellar atmosphere overproduce the [CI]
3P2--3P1 line intensity from HD 100546 by an order of magnitude.Comment: 9pages, 3figures, Accepted for publication in Astronomy &
Astrophysic
Age-related delay in information accrual for faces: Evidence from a parametric, single-trial EEG approach
Background: In this study, we quantified age-related changes in the time-course of face processing
by means of an innovative single-trial ERP approach. Unlike analyses used in previous studies, our
approach does not rely on peak measurements and can provide a more sensitive measure of
processing delays. Young and old adults (mean ages 22 and 70 years) performed a non-speeded
discrimination task between two faces. The phase spectrum of these faces was manipulated
parametrically to create pictures that ranged between pure noise (0% phase information) and the
undistorted signal (100% phase information), with five intermediate steps.
Results: Behavioural 75% correct thresholds were on average lower, and maximum accuracy was
higher, in younger than older observers. ERPs from each subject were entered into a single-trial
general linear regression model to identify variations in neural activity statistically associated with
changes in image structure. The earliest age-related ERP differences occurred in the time window
of the N170. Older observers had a significantly stronger N170 in response to noise, but this age
difference decreased with increasing phase information. Overall, manipulating image phase
information had a greater effect on ERPs from younger observers, which was quantified using a
hierarchical modelling approach. Importantly, visual activity was modulated by the same stimulus
parameters in younger and older subjects. The fit of the model, indexed by R2, was computed at
multiple post-stimulus time points. The time-course of the R2 function showed a significantly slower
processing in older observers starting around 120 ms after stimulus onset. This age-related delay
increased over time to reach a maximum around 190 ms, at which latency younger observers had
around 50 ms time lead over older observers.
Conclusion: Using a component-free ERP analysis that provides a precise timing of the visual
system sensitivity to image structure, the current study demonstrates that older observers
accumulate face information more slowly than younger subjects. Additionally, the N170 appears to
be less face-sensitive in older observers
Analytical case study of the Korean Educational Development Institute
노트 : Korean Educational Development Project(1969-1980)Prokect Documents(Volume VI 15)Learning Systems InstituteComplied December, 1980Florida State Universit
Probing dust grain evolution in IM Lupi's circumstellar disc. Multi-wavelength observations and modelling of the dust disc
We present a panchromatic study, involving a multiple technique approach, of
the circumstellar disc surrounding the T Tauri star IM Lupi (Sz 82). We have
undertaken a comprehensive observational study of IM Lupi using photometry,
spectroscopy, millimetre interferometry and multi-wavelength imaging. For the
first time, the disc is resolved from optical and near-infrared wavelengths in
scattered light, to the millimetre regime in thermal emission. Our data-set, in
conjunction with existing photometric data, provides an extensive coverage of
the spectral energy distribution, including a detailed spectrum of the silicate
emission bands. We have performed a simultaneous modelling of the various
observations, using the radiative transfer code MCFOST, and analysed a grid of
models over a large fraction of the parameter space via Bayesian inference. We
have constructed a model that can reproduce all of the observations of the
disc. Our analysis illustrates the importance of combining a wide range of
observations in order to fully constrain the disc model, with each observation
providing a strong constraint only on some aspects of the disc structure and
dust content. Quantitative evidence of dust evolution in the disc is obtained:
grain growth up to millimetre-sized particles, vertical stratification of dust
grains with micrometric grains close to the disc surface and larger grains
which have settled towards the disc midplane, and possibly the formation of
fluffy aggregates and/or ice mantles around grains.Comment: 20 pages, 13 figures. Accepted for publication in A&
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