138 research outputs found
Clumpy dust clouds and extended atmosphere of the AGB star W Hya revealed with VLT/SPHERE-ZIMPOL and VLTI/AMBER II. Time variations between pre-maximum and minimum light
Our recent visible polarimetric images of the well-studied AGB star W Hya
taken at pre-maximum light (phase 0.92) with VLT/SPHERE-ZIMPOL have revealed
clumpy dust clouds close to the star at ~2 Rstar. We present second-epoch
SPHERE-ZIMPOL observations of W Hya at minimum light (phase 0.54) in the
continuum (645, 748, and 820 nm), in the Halpha line (656.3 nm), and in the TiO
band (717 nm) as well as high-spectral resolution long-baseline interferometric
observations in 2.3 micron CO lines with the AMBER instrument at the Very Large
Telescope Interferometer (VLTI). The high-spatial resolution polarimetric
images have allowed us to detect clear time variations in the clumpy dust
clouds as close as 34--50~mas (1.4--2.0 Rstar) to the star. We detected the
formation of a new dust cloud and the disappearance of one of the dust clouds
detected at the first epoch. The Halpha and TiO emission extends to ~150 mas
(~6 Rstar), and the Halpha images reveal time variations. The degree of linear
polarization is higher at minimum light (13--18%) than that at pre-maximum
light. The power-law-type limb-darkened disk fit to the AMBER data in the
continuum results in a limb-darkened disk diameter of 49.1+/-1.5 mas and a
limb-darkening parameter of 1.16+/-0.49, indicating that the atmosphere is more
extended with weaker limb-darkening compared to pre-maximum light. Our Monte
Carlo radiative transfer modeling suggests the predominance of small (0.1
micron) grains of Al2O3, Mg2SiO4, and MgSiO3 at minimum light, in marked
contrast to the predominance of large (0.5 micron) grains at pre-maximum light.
The variability phase dependence of the grain size implies that small grains
might just have started to form at minimum light in the wake of a shock, while
the pre-maximum light phase might have corresponded to the phase of efficient
grain growth.Comment: 14 pages, 9 figures, accepted for publication in Astronomy and
Astrophysic
Using Copper in Organic Viticulture: Doing it best with less?
For many years, applications of copper fungicides have been used to control downy mildew on grapes. Nowadays, its intensive use is under consideration due to ecotoxicological aspects, especially in organic viticulture. As a result, this project made allowance for consumer perception about organic viticulture and is seeking suitable alternatives. The project includes an association of six research facilities, four organic wineries, several consultant agencies for organic viticulture as well as SME (small and medium-sized enterprise) partners, which are working together in four work packages. The aim of this work is to obtain an array of products that provide sufficient control of Plasmopara viticola with the lowest possible input of copper. As a longterm intention, copper-containing products should be totally replaced by other effective agents. Progress to-date suggests that some non-copper products and several copper-based products using less than 3 kg/(ha*a) have potential to effectively control the disease with less ecological residue
Gas dynamics in the inner few AU around the Herbig B[e] star MWC297: Indications of a disk wind from kinematic modeling and velocity-resolved interferometric imaging
We present near-infrared AMBER (R = 12, 000) and CRIRES (R = 100, 000)
observations of the Herbig B[e] star MWC297 in the hydrogen Br-gamma-line.
Using the VLTI unit telescopes, we obtained a uv-coverage suitable for aperture
synthesis imaging. We interpret our velocity-resolved images as well as the
derived two-dimensional photocenter displacement vectors, and fit kinematic
models to our visibility and phase data in order to constrain the gas velocity
field on sub-AU scales. The measured continuum visibilities constrain the
orientation of the near-infrared-emitting dust disk, where we determine that
the disk major axis is oriented along a position angle of 99.6 +/- 4.8 degrees.
The near-infrared continuum emission is 3.6 times more compact than the
expected dust-sublimation radius, possibly indicating the presence of highly
refractory dust grains or optically thick gas emission in the inner disk. Our
velocity-resolved channel maps and moment maps reveal the motion of the
Br-gamma-emitting gas in six velocity channels, marking the first time that
kinematic effects in the sub-AU inner regions of a protoplanetary disk could be
directly imaged. We find a rotation-dominated velocity field, where the blue-
and red-shifted emissions are displaced along a position angle of 24 +/- 3
degrees and the approaching part of the disk is offset west of the star. The
visibility drop in the line as well as the strong non-zero phase signals can be
modeled reasonably well assuming a Keplerian velocity field, although this
model is not able to explain the 3 sigma difference that we measure between the
position angle of the line photocenters and the position angle of the dust
disk. We find that the fit can be improved by adding an outflowing component to
the velocity field, as inspired by a magneto-centrifugal disk-wind scenario.Comment: 15 pages, 13 Figure
Infrared interferometric imaging of the compact dust disk around the AGB star HR3126 with the bipolar Toby Jug Nebula
The asymptotic giant branch (AGB) star HR3126, associated with the
arcminute-scale bipolar Toby Jug Nebula, provides a rare opportunity to study
the emergence of bipolar structures at the end of the AGB phase. We carried out
long-baseline interferometric observations with AMBER and GRAVITY (2--2.45
micron) at the Very Large Telescope Interferometer, speckle interferometric
observations with VLT/NACO (2.24 micron), and imaging with SPHERE-ZIMPOL (0.55
micron) and VISIR (7.9--19.5 micron). The images reconstructed in the continuum
at 2.1--2.29 micron from the AMBER+GRAVITY data reveal the central star
surrounded by an elliptical ring-like structure with a semimajor and semiminor
axis of 5.3 and 3.5 mas, respectively. The ring is interpreted as the inner rim
of an equatorial dust disk viewed from an inclination angle of ~50 degrees, and
its axis is approximately aligned with the bipolar nebula. The disk is
surprisingly compact, with an inner radius of a mere 3.5 Rstar (2 au). Our 2-D
radiative transfer modeling shows that an optically thick flared disk with
silicate grains as large as ~4 micron can reproduce the observed continuum
images and the spectral energy distribution. The images obtained in the CO
first overtone bands reveal elongated extended emission around the central
star, suggesting the oblateness of the star's atmosphere or the presence of a
CO gas disk inside the dust cavity. The object is unresolved with
SPHERE-ZIMPOL, NACO, and VISIR. If the disk formed together with the bipolar
nebula, the grain growth from sub-micron to a few microns should have taken
place over the nebula's dynamical age of ~3900 yrs. The non-detection of a
companion in the reconstructed images implies that either its 2.2 micron
brightness is more than ~30 times lower than that of the red giant or it might
have been shredded due to binary interaction.Comment: 24 pages, 14 figures, published in Astronomy and Astrophysic
On the nature of the Herbig B[e] star binary system V921 Scorpii: Geometry and kinematics of the circumprimary disk on sub-AU scales
V921 Scorpii is a close binary system (separation 0.025") showing the
B[e]-phenomenon. The system is surrounded by an enigmatic bipolar nebula, which
might have been shaped by episodic mass-loss events, possibly triggered by
dynamical interactions between the companion and the circumprimary disk (Kraus
et al. 2012a). In this paper, we investigate the spatial structure and
kinematics of the circumprimary disk, with the aim to obtain new insights into
the still strongly debated evolutionary stage. For this purpose, we combine,
for the first time, infrared spectro-interferometry (VLTI/AMBER, R=12,000) and
spectro-astrometry (VLT/CRIRES, R=100,000), which allows us to study the
AU-scale distribution of circumstellar gas and dust with an unprecedented
velocity resolution of 3 km*s^-1. Using a model-independent photocenter
analysis technique, we find that the Br-gamma-line emission rotates in the same
plane as the dust disk. We can reproduce the wavelength-differential
visibilities and phases and the double-peaked line profile using a
Keplerian-rotating disk model. The derived mass of the central star is
5.4+/-0.4 M_sun*(d/1150 pc), which is considerably lower than expected from the
spectral classification, suggesting that V921 Sco might be more distant (d
approx 2kpc) than commonly assumed. Using the geometric information provided by
our Br-gamma spectro-interferometric data and Paschen, Brackett, and Pfund line
decrement measurements in 61 hydrogen recombination line transitions, we derive
the density of the line-emitting gas (N_e=2...6*10^19 m^-3). Given that our
measurements can be reproduced with a Keplerian velocity field without
outflowing velocity component and the non-detection of age-indicating
spectroscopic diagnostics, our study provides new evidence for the
pre-main-sequence nature of V921 Sco.Comment: 17 pages, 11 figures, 3 tables, accepted by Ap
Wolf-Rayet stars probed by AMBER/VLTI
Massive stars deeply influence their surroundings by their luminosity and the
injection of kinetic energy. So far, they have mostly been studied with
spatially unresolved observations, although evidence of geometrical complexity
of their wind are numerous. Interferometry can provide spatially resolved
observations of massive stars and their immediate vicinity. Specific geometries
(disks, jets, latitude-dependent winds) can be probed by this technique. The
first observation of a Wolf-Rayet (WR) star (\gamma^2 Vel) with the AMBER/VLTI
instrument yielded to a re-evaluation of its distance and an improved
characterization of the stellar components, from a very limited data-set. This
motivated our team to increase the number of WR targets observed with AMBER. We
present here new preliminary results that encompass several spectral types,
ranging from early WN to evolved dusty WC. We present unpublished data on
WR79a, a massive star probably at the boundary between the O and Wolf- Rayet
type, evidencing some Wolf-Rayet broad emission lines from an optically thin
wind. We also present new data obtained on \gamma^2 Vel that can be compared to
the up-to-date interferometry-based orbital parameters from North et al.
(2007). We discuss the presence of a wind-wind collision zone in the system and
provide preliminary analysis suggesting the presence of such a structure in the
data. Then, we present data obtained on 2 dusty Wolf-Rayet stars: WR48a-b and
WR118, the latter exhibiting some clues of a pinwheel-like structure from the
visibility variations.Comment: This paper will be published in the proceeding of SPIE ``astronomical
Telescopes and Instrumentation: Optical and Infrared Interferometry'
Age-related differences of microRNA-21 in leukocytes and its association with physical performance
INTRODUCTION: Several studies suggest chronic inflammation as an underlying biological mechanism for the decline in physical performance of elderly (Cesari et al., 2004; Tiainen et al., 2010). Moreover, it has been shown that habitual exercise ameliorates the higher proinflammatory gene expression in leukocytes of elderly (Gano et al., 2011). Within the last years several microRNAs (short, non-coding RNAs) have been demonstrated to regulate gene expression also in the context of exercise immunology (Wessner et al., 2010). Interestingly, some of these microRNAs (miRs) such as miR-21 and miR-146 are involved in pathways important for ageing as well as inflammatory processes (Olivieri et al. 2012). Therefore, the main aims of the current study were (1) to investigate whether miR-21 and miR-146 levels in leukocytes are affected by age and (2) to correlate performance levels of elderly to miR gene expression levels.
METHODS: Healthy young (n=7, age: 25.28 ± 2.3 years) and old (n=25, age: 83.40 ± 5.63 years) females participated in the study. After an overnight fast, leukocytes were isolated from heparinized blood using BD Vacutainer CPT tubes. miR-21 and miR146 gene expression in leukocytes was determined by quantitative RT-PCR using miScript Primer Assays (Qiagen, Hilden, Germany). Additonally, leukocyte numbers and inflammatory markers (hs-CRP, hs-IL6, IL1-ra) were quantified. In order to relate potential inflammtaory markers to the fitness level of the elderly, several functional tests were performed (handgrip, 6min walking test, chair-rise test, isokinetic measurement of knee extension and flexion). Differences between groups were detected by unpaired t-tests. Correlations between markers were characterized using Pearson correlation coefficients.
RESULTS: Interestingly, miR-21 expression in leukocytes was significantly enhanced in the elderly (+55.1%, p=0.036) while miR-146a levels were not affected by age (p=0.492). However, miR-21 correlated signifantly with hs-CRP levels (r=0.352; p=0.033), we did not detect any associations between miR-21 expression and performance parameters of the elderly: Handgrip (r=0.533; p=0.121), 6-min Walking Test (r=0.231; p=0.220), Chair Rise (r=0.336; p=0.070), Peak Torque knee extension (r=0.589; p=0.105) as well as flexion (r=0.203; p=0.291).
CONCLUSION: In conclusion these preliminary results show that miR-21 seems to be enhanced with age but not influenced by fitness level of the elderly. Gene targets of miR-21 have been identified in the TGF-β signaling pathway. Therefore, next steps would be to associate the changes in miR-21with its potential targets to further elucidate its role in the ageing process
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