2,359 research outputs found
Stellar Limb-Darkening Coefficients for CoRot and Kepler
Transiting exoplanets provide unparalleled access to the fundamental
parameters of both extrasolar planets and their host stars. We present
limb-darkening coefficients (LDCs) for the exoplanet hunting CoRot and Kepler
missions. The LDCs are calculated with ATLAS stellar atmospheric model grids
and span a wide range of Teff, log g, and metallically [M/H]. Both CoRot and
Kepler contain wide, nonstandard response functions, and are producing a large
inventory of high-quality transiting lightcurves, sensitive to stellar limb
darkening. Comparing the stellar model limb darkening to results from the first
seven CoRot planets, we find better fits are found when two model intensities
at the limb are excluded in the coefficient calculations. This calculation
method can help to avoid a major deficiency present at the limbs of the 1D
stellar models.Comment: Accepted for publication in A&A. 4 pages, 2 figures, 2 tables. Full
versions of tables 1 and 2 containing limb-darkening coefficients available
at http://vega.lpl.arizona.edu/~sing
Can aerosols be trapped in open flows?
The fate of aerosols in open flows is relevant in a variety of physical
contexts. Previous results are consistent with the assumption that such
finite-size particles always escape in open chaotic advection. Here we show
that a different behavior is possible. We analyze the dynamics of aerosols both
in the absence and presence of gravitational effects, and both when the
dynamics of the fluid particles is hyperbolic and nonhyperbolic. Permanent
trapping of aerosols much heavier than the advecting fluid is shown to occur in
all these cases. This phenomenon is determined by the occurrence of multiple
vortices in the flow and is predicted to happen for realistic particle-fluid
density ratios.Comment: Animation available at
http://www.pks.mpg.de/~rdvilela/leapfrogging.htm
Usability of the SedLine® electroencephalographic monitor of depth of anaesthesia in pigs: a pilot study.
To investigate the usability of the SedLine® monitor in anaesthetized pigs. Five juvenile healthy pigs underwent balanced isoflurane-based general anaesthesia for surgical placement of a subcutaneous jugular venous port. The SedLine® was applied to continuously monitor electroencephalographic (EEG) activity and its modulation during anaesthesia. Computer tomography and magnetic resonance were performed to investigate the relationship between electrodes' positioning and anatomical structures. The pediatric SedLine® EEG-sensor could be easily applied and SedLine®-generated variables collected. An EEG Density Spectral Array (DS) was displayed over the whole procedure. During surgery, the EEG signal was dominated by elevated power in the delta range (0.5-4 Hz), with an underlying broadband signal (where power decreased with increasing frequency). The emergence period was marked by a decrease in delta power, and a more evenly distributed power over the 4-40 Hz frequency range. From incision to end of surgery, mean SedLine®-generated values (± standard deviation) were overall stable [23.0 (± 2.8) Patient State Index (PSI), 1.0% (± 3.8%) Suppression Ratio (SR), 8.8 Hz (± 2.5 Hz) Spectral Edge Frequency 95% (SEF) left, 7.7 Hz (± 2.4 Hz) SEF right], quickly changing during emergence [75.3 (± 11.1) PSI, 0.0 (± 0.0) SR, 12.5 (± 6.6) SEF left 10.4 (± 6.6) SEF right]. Based on the imaging performed, the sensor does not record EEG signals from the same brain areas as in humans. SedLine®-DSA and -generated variables seemed to reflect variations in depth of anaesthesia in pigs. Further studies are needed to investigate this correlation, as well as to define the species-specific brain structures monitored by the EEG-sensor
Machine learning accelerated likelihood-free event reconstruction in dark matter direct detection
Reconstructing the position of an interaction for any dual-phase time projection chamber (TPC) with the best precision is key to directly detecting Dark Matter. Using the likelihood-free framework, a newalgorithm to reconstruct the 2-D (x; y) position and the size of the charge signal (e) of an interaction is presented. The algorithm uses the secondary scintillation light distribution (S2) obtained by simulating events using a waveform generator. To deal with the computational effort required by the likelihood-free approach, we employ the Bayesian Optimization for LikelihoodFree Inference (BOLFI) algorithm. Together with BOLFI, prior distributions for the parameters of interest (x; y; e) and highly informative discrepancy measures to performthe analyses are introduced. We evaluate the quality of the proposed algorithm by a comparison against the currently existing alternative methods using a large-scale simulation study. BOLFI provides a natural probabilistic uncertainty measure for the reconstruction and it improved the accuracy of the reconstruction over the next best algorithm by up to 15% when focusing on events at large radii (R > 30 cm, the outer 37% of the detector). In addition, BOLFI provides the smallest uncertainties among all the tested methods.Peer reviewe
Frontiers of the physics of dense plasmas and planetary interiors: experiments, theory, applications
Recent developments of dynamic x-ray characterization experiments of dense
matter are reviewed, with particular emphasis on conditions relevant to
interiors of terrestrial and gas giant planets. These studies include
characterization of compressed states of matter in light elements by x-ray
scattering and imaging of shocked iron by radiography. Several applications of
this work are examined. These include the structure of massive "Super Earth"
terrestrial planets around other stars, the 40 known extrasolar gas giants with
measured masses and radii, and Jupiter itself, which serves as the benchmark
for giant planets.Comment: Accepted to Physics of Plasmas special issue. Review from
HEDP/HEDLA-08, April 12-15, 200
A Cross-Flow Ultrasound-Assisted Extraction of Curcuminoids from Curcuma longa L.: Process Design to Avoid Degradation
Rhizomes of Curcuma longa L. are well known for their content of curcuminoids, which are compounds with interesting biological activity against various inflammatory states and diseases. Curcuminoids can degrade during processing. This piece of work investigates fast, efficient and cost-effective metabolite recovery from turmeric under ultrasound-assisted extraction (UAE). An analytical evaluation of curcuminoid stability under sonication in different solvents is reported for the first time. HPLC and quantitative 1H-NMR were used. Under the applied conditions, EtOAc was found to be the optimal extraction medium, rather than EtOH, due to its lower radical generation, which facilitates better curcuminoid stability. Kinetic characterization, by means of the Peleg equation, was applied for single-step UAE on two different rhizome granulometries. Over a time of 90 min, maximum extraction yields were 25.63% and 47.56% for 6 and 2 mm matrix powders, respectively. However, it was observed that the largest portion of curcuminoid recovery was achieved in the first 30 min. Model outcomes were used as the basis for the design of a suitable multi-step cross-flow approach that supports and emphasizes the disruptive role of cavitation. The maximum curcuminoid yield was achieved over three steps (92.10%) and four steps (80.04%), for lower and higher granulometries, respectively. Finally, the central role of the solvent was further confirmed by turmeric oleoresin purification. The EtOAc extract was purified via crystallization, and a 95% pure curcuminoid product was isolated without any chromatographic procedure. No suitable crystallization was observed for the EtOH extract
Collisional Cascades in Planetesimal Disks I. Stellar Flybys
We use a new multiannulus planetesimal accretion code to investigate the
evolution of a planetesimal disk following a moderately close encounter with a
passing star. The calculations include fragmentation, gas and
Poynting-Robertson drag, and velocity evolution from dynamical friction and
viscous stirring. We assume that the stellar encounter increases planetesimal
velocities to the shattering velocity, initiating a collisional cascade in the
disk. During the early stages of our calculations, erosive collisions damp
particle velocities and produce substantial amounts of dust. For a wide range
of initial conditions and input parameters, the time evolution of the dust
luminosity follows a simple relation, L_d/L_{\star} = L_0 / [alpha +
(t/t_d)^{beta}]. The maximum dust luminosity L_0 and the damping time t_d
depend on the disk mass, with L_0 proportional to M_d and t_d proportional to
M_d^{-1}. For disks with dust masses of 1% to 100% of the `minimum mass solar
nebula' (1--100 earth masses at 30--150 AU), our calculations yield t_d approx
1--10 Myr, alpha approx 1--2, beta = 1, and dust luminosities similar to the
range observed in known `debris disk' systems, L_0 approx 10^{-3} to 10^{-5}.
Less massive disks produce smaller dust luminosities and damp on longer
timescales. Because encounters with field stars are rare, these results imply
that moderately close stellar flybys cannot explain collisional cascades in
debris disk systems with stellar ages of 100 Myr or longer.Comment: 33 pages of text, 12 figures, and an animation. The paper will appear
in the March 2002 issue of the Astronmomical Journal. The animation and a
copy of the paper with full resolution figures are at S. Kenyon's planet
formation website: http://cfa-www.harvard.edu/~kenyon/p
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