6,872 research outputs found
Observability of Forming Planets and their Circumplanetary Disks I. -- Parameter Study for ALMA
We present mock observations of forming planets with ALMA. The possible
detections of circumplanetary disks (CPDs) were investigated around planets of
Saturn, 1, 3, 5, and 10 Jupiter-masses that are placed at 5.2 AU from their
star. The radiative, three dimensional hydrodynamic simulations were then
post-processed with RADMC3D and the ALMA Observation Simulator. We found that
even though the CPDs are too small to be resolved, they are hot due to the
accreting planet in the optically thick limit, therefore the best chance to
detect them with continuum observations in this case is at the shortest ALMA
wavelengths, such as Band 9 (440 microns). Similar fluxes were found in the
case of Saturn and Jupiter-mass planets, as for the 10
gas-giant, due to temperature weighted optical depth effects: when no deep gap
is carved, the planet region is blanketed by the optically thick circumstellar
disk leading to a less efficient cooling there. A test was made for a 52 AU
orbital separation, showed that optically thin CPDs are also detectable in band
7 but they need longer integration times (5hrs). Comparing the gap profiles
of the same simulation at various ALMA bands and the hydro simulation confirmed
that they change significantly, first because the gap is wider at longer
wavelengths due to decreasing optical depth; second, the beam convolution makes
the gap shallower and at least 25% narrower. Therefore, caution has to be made
when estimating planet masses based on ALMA continuum observations of gaps.Comment: Accepted for publication at MNRAS. Typos are corrected since previous
version. 11 pages, 5 tables, 4 figure
No Till and Organic Farming Improve Soil Properties but Reduce Crop Yield Compared to Conventional Farming in a Swiss Farm Network
Soils are of vital importance for sustainable food production. In order to maintain or improve soil quality, it is necessary to develop strategies for a sustainable use of soil. Alternative cropping practices such as reduced tillage and improved crop rotation are more and more adopted with the aim of decreasing the impact of agriculture on the environment. However, their on-the-ground impact in Swiss farming systems still has to be assessed. In this study, we quantified the impact of three farming systems (conventional farming, no-till, and organic farming) on plant and soil chemical, biological and physical properties. Our study included 20 fields for each farming system. All selected fields were cultivated with winter wheat the year of sampling. Soil was sampled at four layers, 0-5 cm, 5-20 cm, 20-25 cm, 25-50 cm. The main variables analysed were grain yield, soil nutrient availability, organic carbon stocks, bulk density, aggregation, porosity and soil biology. This was complemented with a comprehensive survey to collect information about cropping practices at field and farm scale, including organic matter inputs, fertilisation, tillage, phytosanitary treatments, and crop rotation.Our results show a significant influence of cropping practices on plant and soil properties. Wheat yield in no till and organic systems was reduced by 10% and 30% compared to conventional systems. Bulk density was higher in no-till than in ploughed fields in the 5-20 cm layer but similar in the subsoil. A strong stratification with depth of nutrients and soil organic carbon was observed in no-till fields. No-till and organic fields showed larger soil aggregates and higher microbial biomass in the surface layer (0-5 cm). Mycorrhizal colonisation of wheat roots was on average 50% higher in organic fields. However, no differences in carbon stock in the 0-20 cm layer was observed and the ratio organic matter / clay shows a high variability (from poor to good) and was not dependent on the farming system.Our results show that an improvement of soil properties can be achieved with alternative cropping practices such as no-till and organic farming, but also depends on the other practices adopted by the farmers, such as input of organic amendments, crop rotation diversification, residue management
Generation of chirp-free picosecond pulses
The frequency spectrum of moderately chirped laser pulses depends upon the portion of the beam which is accepted by the spectrometer. Observation of the development of the chirp in a mode-locked pulse train allows to determine the small incipient chirp of early pulses. A product, bandwidth times pulse duration, of 0.47 ± 0.03 is consistently observed for single pulses switched from a passively mode-locked Nd-glass system
Embedded disks in Fornax dwarf ellipticals
We present photometric and kinematic evidence for the presence of stellar
disks, seen practically edge-on, in two Fornax dwarf galaxies, FCC204 (dS0(6))
and FCC288 (dS0(7)). This is the first time such structures have been
identified in Fornax dwarfs. FCC2088 has only a small bulge and a bright
flaring and slightly warped disk that can be traced out to 23" from the center
(2.05 kpc for H_0=75 km/s/Mpc). FCC204's disk can be traced out to 20" (1.78
kpc). This galaxy possesses a large bulge. These results can be compared to the
findings of Jerjen et al. (2000) and Barazza et al. (2002) who discovered
nucleated dEs with spiral and bar features in the Virgo Cluster.Comment: 8 pages, 8 figures, accepted for publication in A&
A branch-point approximant for the equation of state of hard spheres
Using the first seven known virial coefficients and forcing it to possess two
branch-point singularities, a new equation of state for the hard-sphere fluid
is proposed. This equation of state predicts accurate values of the higher
virial coefficients, a radius of convergence smaller than the close-packing
value, and it is as accurate as the rescaled virial expansion and better than
the Pad\'e [3/3] equations of state. Consequences regarding the convergence
properties of the virial series and the use of similar equations of state for
hard-core fluids in dimensions are also pointed out.Comment: 6 pages, 4 tables, 3 figures; v2: enlarged version, extension to
other dimensionalities; v3: typos in references correcte
Local Group Dwarf Elliptical Galaxies: II. Stellar Kinematics to Large Radii in NGC 147 and NGC 185
We present kinematic and metallicity profiles for the M31 dwarf elliptical
(dE) satellite galaxies NGC 147 and NGC 185. The profiles represent the most
extensive spectroscopic radial coverage for any dE galaxy, extending to a
projected distance of eight half-light radii (8 r_eff = 14'). We achieve this
coverage via Keck/DEIMOS multislit spectroscopic observations of 520 and 442
member red giant branch stars in NGC 147 and NGC 185, respectively. In contrast
to previous studies, we find that both dEs have significant internal rotation.
We measure a maximum rotational velocity of 17+/-2 km/s for NGC 147 and 15+/-5
km/s for NGC 185. The velocity dispersions decrease gently with radius with an
average dispersion of 16+/-1 km/s for NGC 147 and 24+/-1 km/s for NGC 185. Both
dEs have internal metallicity dispersions of 0.5 dex, but show no evidence for
a radial metallicity gradient. We construct two-integral axisymmetric dynamical
models and find that the observed kinematical profiles cannot be explained
without modest amounts of non-baryonic dark matter. We measure central
mass-to-light ratios of ML_V = 4.2+/-0.6 and ML_V = 4.6+/-0.6 for NGC 147 and
NGC 185, respectively. Both dE galaxies are consistent with being primarily
flattened by their rotational motions, although some anisotropic velocity
dispersion is needed to fully explain their observed shapes. The velocity
profiles of all three Local Group dEs (NGC 147, NGC 185 and NGC 205) suggest
that rotation is more prevalent in the dE galaxy class than previously assumed,
but is often manifest only at several times the effective radius. Since all dEs
outside the Local Group have been probed to only inside the effective radius,
this opens the door for formation mechanisms in which dEs are transformed or
stripped versions of gas-rich rotating progenitor galaxies.Comment: 16 pages, 7 figures. accepted to A
The effectiveness of metacognitive therapy in comparison to exposure and response prevention for obsessive-compulsive disorder:A randomized controlled trial
Background: The recommended psychological treatment of choice for obsessive-compulsive disorder (OCD) is exposure with response prevention (ERP). Although this treatment is quite effective, recovery rates are modest and attrition rate is relatively high. Also, ERP treatment requires amounts of therapist time. A possible way to improve OCD treatment is by taking into account key cognitive processes involved in the development and maintenance of the disorder. The metacognitive model is such an account and pilot findings suggest that the associated metacognitive therapy (MCT) might be an effective treatment for OCD. Methods: In the present study, a randomized controlled trial (RCT) is used to assess the effectiveness of MCT in comparison to ERP in an outpatient clinical sample of patients with OCD. Results: Both MCT and ERP produced significant pre-treatment to post-treatment decreases in obsessive-compulsive, comorbid psychological symptoms and metacognitive beliefs, both with moderate to large within-group effect sizes and high proportions of significant clinical change. Drop-out rates were low and treatment gains were maintained at six-month follow-up. There were no differences in efficacy observed between MCT and ERP treatments. Conclusions: MCT proves to be a promising treatment of OCD.</p
Combining astrometry with the light-time effect: The case of VW Cep, zeta Phe and HT Vir
Three eclipsing binary systems with astrometric orbit have been studied. For
a detailed analysis two circular-orbit binaries (VW Cep and HT Vir) and one
binary with an eccentric orbit (zeta Phe) have been chosen. Merging together
astrometry and the analysis of the times of minima, one is able to describe the
orbit of such a system completely. The O-C diagrams and the astrometric orbits
of the third bodies were analysed simultaneously for these three systems by the
least-squares method. The introduced algorithm is useful and powerful, but also
time consuming, due to many parameters which one is trying to derive. The new
orbits for the third bodies in these systems were found with periods 30, 221,
and 261 yr, and eccentricities 0.63, 0.37, and 0.64 for VW Cep, zeta Phe, and
HT Vir, respectively. Also an independent approach to compute the distances to
these systems was used. The use of this algorithm to VW Cep gave the distance
d=(27.90 +/- 0.29) pc, which is in excellent agreement with the previous
Hipparcos result.Comment: 10 pages, 8 figures, 3 tables, submitted to A
The effectiveness of metacognitive therapy in comparison to exposure and response prevention for obsessive-compulsive disorder:A randomized controlled trial
Background: The recommended psychological treatment of choice for obsessive-compulsive disorder (OCD) is exposure with response prevention (ERP). Although this treatment is quite effective, recovery rates are modest and attrition rate is relatively high. Also, ERP treatment requires amounts of therapist time. A possible way to improve OCD treatment is by taking into account key cognitive processes involved in the development and maintenance of the disorder. The metacognitive model is such an account and pilot findings suggest that the associated metacognitive therapy (MCT) might be an effective treatment for OCD. Methods: In the present study, a randomized controlled trial (RCT) is used to assess the effectiveness of MCT in comparison to ERP in an outpatient clinical sample of patients with OCD. Results: Both MCT and ERP produced significant pre-treatment to post-treatment decreases in obsessive-compulsive, comorbid psychological symptoms and metacognitive beliefs, both with moderate to large within-group effect sizes and high proportions of significant clinical change. Drop-out rates were low and treatment gains were maintained at six-month follow-up. There were no differences in efficacy observed between MCT and ERP treatments. Conclusions: MCT proves to be a promising treatment of OCD.</p
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