183 research outputs found
PynPoint: a modular pipeline architecture for processing and analysis of high-contrast imaging data
The direct detection and characterization of planetary and substellar
companions at small angular separations is a rapidly advancing field. Dedicated
high-contrast imaging instruments deliver unprecedented sensitivity, enabling
detailed insights into the atmospheres of young low-mass companions. In
addition, improvements in data reduction and PSF subtraction algorithms are
equally relevant for maximizing the scientific yield, both from new and
archival data sets. We aim at developing a generic and modular data reduction
pipeline for processing and analysis of high-contrast imaging data obtained
with pupil-stabilized observations. The package should be scalable and robust
for future implementations and in particular well suitable for the 3-5 micron
wavelength range where typically (ten) thousands of frames have to be processed
and an accurate subtraction of the thermal background emission is critical.
PynPoint is written in Python 2.7 and applies various image processing
techniques, as well as statistical tools for analyzing the data, building on
open-source Python packages. The current version of PynPoint has evolved from
an earlier version that was developed as a PSF subtraction tool based on PCA.
The architecture of PynPoint has been redesigned with the core functionalities
decoupled from the pipeline modules. Modules have been implemented for
dedicated processing and analysis steps, including background subtraction,
frame registration, PSF subtraction, photometric and astrometric measurements,
and estimation of detection limits. The pipeline package enables end-to-end
data reduction of pupil-stabilized data and supports classical dithering and
coronagraphic data sets. As an example, we processed archival VLT/NACO L' and
M' data of beta Pic b and reassessed the planet's brightness and position with
an MCMC analysis, and we provide a derivation of the photometric error budget.Comment: 16 pages, 9 figures, accepted for publication in A&A, PynPoint is
available at https://github.com/PynPoint/PynPoin
Genomic Prediction of Single Crosses in the Early Stages of a Maize Hybrid Breeding Pipeline
Prediction of single-cross performance has been a major goal of plant breeders since the beginning of hybrid breeding. Recently, genomic prediction has shown to be a promising approach, but only limited studies have examined the accuracy of predicting single-cross performance. Moreover, no studies have examined the potential of predicting single crosses among random inbreds derived from a series of biparental families, which resembles the structure of germplasm comprising the initial stages of a hybrid maize breeding pipeline. The main objectives of this study were to evaluate the potential of genomic prediction for identifying superior single crosses early in the hybrid breeding pipeline and optimize its application. To accomplish these objectives, we designed and analyzed a novel population of single crosses representing the Iowa Stiff Stalk synthetic/non-Stiff Stalk heterotic pattern commonly used in the development of North American commercial maize hybrids. The performance of single crosses was predicted using parental combining ability and covariance among single crosses. Prediction accuracies were estimated using cross-validation and ranged from 0.28 to 0.77 for grain yield, 0.53 to 0.91 for plant height, and 0.49 to 0.94 for staygreen, depending on the number of tested parents of the single cross and genomic prediction method used. The genomic estimated general and specific combining abilities showed an advantage over genomic covariances among single crosses when one or both parents of the single cross were untested. Overall, our results suggest that genomic prediction of single crosses in the early stages of a hybrid breeding pipeline holds great potential to redesign hybrid breeding and increase its efficiency
Evolution of mud-crack patterns during repeated drying cycles
In mud, crack patterns are frequently seen with either an approximately rectilinear or hexagonal tiling. Here we show, experimentally, how a desiccation crack pattern changes from being dominated by 90° joint angles, to 120° joint angles. Layers of bentonite clay, a few mm thick, were repeatedly wetted and dried. When dried, the layers crack. These cracks visibly close when rewetted, but a similar crack pattern forms when the layer is redried, with cracks forming along the lines of previously open cracks. Time-lapse photography was used to show how the sequence in which individual cracks open is different in each generation of drying. The geometry of the crack pattern was observed after each of 25 generations of wetting and drying. The angles between cracks were found to approach 120°, with a relaxation time of approximately 4 generations. This was accompanied by a gradual change in the position of the crack vertices, as the crack pattern evolved. A simple model of crack behavior in a layer where the positions of previously open cracks define lines of weakness is developed to explain these observations
Suppression of inelastic collisions of polar state molecules in an electrostatic field
Collisions of polar state molecules at ultralow energies are
considered, within a model that accounts for long-range dipole-dipole
interactions, plus rotation of the molecules. We predict a substantial
suppression of dipole-driven inelastic collisions at high values of the applied
electric field, namely, field values of several times . Here is
the rotational constant, and is the electric dipole moment of molecules.
The sudden large drop in the inelastic cross section is attributed to the
onset of degeneracy between molecular rotational levels, which dramatically
alters the scattering Hamiltonian. As a result of the large ratio of elastic to
inelastic collision rates, we predict that evaporative cooling may be feasible
for state molecules in weak-field-seeking states, provided a large
bias electric field is present
Field-linked States of Ultracold Polar Molecules
We explore the character of a novel set of ``field-linked'' states that were
predicted in [A. V. Avdeenkov and J. L. Bohn, Phys. Rev. Lett. 90, 043006
(2003)]. These states exist at ultralow temperatures in the presence of an
electrostatic field, and their properties are strongly dependent on the field's
strength. We clarify the nature of these quasi-bound states by constructing
their wave functions and determining their approximate quantum numbers. As the
properties of field-linked states are strongly defined by anisotropic dipolar
and Stark interactions, we construct adiabatic surfaces as functions of both
the intermolecular distance and the angle that the intermolecular axis makes
with the electric field. Within an adiabatic approximation we solve the 2-D
Schrodinger equation to find bound states, whose energies correlate well with
resonance features found in fully-converged multichannel scattering
calculations
Faint Infrared Flares from the Microquasar GRS 1915+105
We present simultaneous infrared and X-ray observations of the Galactic
microquasar GRS 1915+105 using the Palomar 5-m telescope and Rossi X-ray Timing
Explorer on July 10, 1998 UT. Over the course of 5 hours, we observed 6 faint
infrared (IR) flares with peak amplitudes of mJy and durations
of seconds. These flares are associated with X-ray
soft-dip/soft-flare cycles, as opposed to the brighter IR flares associated
with X-ray hard-dip/soft-flare cycles seen in August 1997 by Eikenberry et al.
(1998). Interestingly, the IR flares begin {\it before} the X-ray oscillations,
implying an ``outside-in'' origin of the IR/X-ray cycle. We also show that the
quasi-steady IR excess in August 1997 is due to the pile-up of similar faint
flares. We discuss the implications of this flaring behavior for understanding
jet formation in microquasars.Comment: 10 pages, 4 figures Accepted for publication in ApJ Letter
Cardiovascular Dysfunction Criteria in Critically Ill Children: The PODIUM Consensus Conference
CONTEXT
Cardiovascular dysfunction is associated with poor outcomes in critically ill children.
OBJECTIVE
We aim to derive an evidence-informed, consensus-based definition of cardiovascular dysfunction in critically ill children.
DATA SOURCES
Electronic searches of PubMed and Embase were conducted from January 1992 to January 2020 using medical subject heading terms and text words to define concepts of cardiovascular dysfunction, pediatric critical illness, and outcomes of interest.
STUDY SELECTION
Studies were included if they evaluated critically ill children with cardiovascular dysfunction and assessment and/or scoring tools to screen for cardiovascular dysfunction and assessed mortality, functional status, organ-specific, or other patient-centered outcomes. Studies of adults, premature infants (≤36 weeks gestational age), animals, reviews and/or commentaries, case series (sample size ≤10), and non-English-language studies were excluded. Studies of children with cyanotic congenital heart disease or cardiovascular dysfunction after cardiopulmonary bypass were excluded.
DATA EXTRACTION
Data were abstracted from each eligible study into a standard data extraction form, along with risk-of-bias assessment by a task force member.
RESULTS
Cardiovascular dysfunction was defined by 9 elements, including 4 which indicate severe cardiovascular dysfunction. Cardiopulmonary arrest (>5 minutes) or mechanical circulatory support independently define severe cardiovascular dysfunction, whereas tachycardia, hypotension, vasoactive-inotropic score, lactate, troponin I, central venous oxygen saturation, and echocardiographic estimation of left ventricular ejection fraction were included in any combination. There was expert agreement (>80%) on the definition.
LIMITATIONS
All included studies were observational and many were retrospective.
CONCLUSIONS
The Pediatric Organ Dysfunction Information Update Mandate panel propose this evidence-informed definition of cardiovascular dysfunction
Applying a temporal systematics model to vector Apodizing Phase Plate coronagraphic data: TRAP4vAPP
The vector Apodizing Phase Plate (vAPP) is a pupil plane coronagraph that
suppresses starlight by forming a dark hole in its point spread function (PSF).
The unconventional and non-axisymmetrical PSF arising from the phase
modification applied by this coronagraph presents a special challenge to
post-processing techniques. We aim to implement a recently developed
post-processing algorithm, temporal reference analysis of planets (TRAP) on
vAPP coronagraphic data. The property of TRAP that uses non-local training
pixels, combined with the unconventional PSF of vAPP, allows for more
flexibility than previous spatial algorithms in selecting reference pixels to
model systematic noise. Datasets from two types of vAPPs are analysed: a double
grating-vAPP (dgvAPP360) that produces a single symmetric PSF and a
grating-vAPP (gvAPP180) that produces two D-shaped PSFs. We explore how to
choose reference pixels to build temporal systematic noise models in TRAP for
them. We then compare the performance of TRAP with previously implemented
algorithms that produced the best signal-to-noise ratio (S/N) in companion
detections in these datasets. We find that the systematic noise between the two
D-shaped PSFs is not as temporally associated as expected. Conversely, there is
still a significant number of systematic noise sources that are shared by the
dark hole and the bright side in the same PSF. We should choose reference
pixels from the same PSF when reducing the dgvAPP360 dataset or the gvAPP180
dataset with TRAP. In these datasets, TRAP achieves results consistent with
previous best detections, with an improved S/N for the gvAPP180 dataset.Comment: 15 pages, 10 figures, accepted to A&
Genetic interaction mapping informs integrative structure determination of protein complexes
Determining structures of protein complexes is crucial for understanding cellular functions. Here, we describe an integrative structure determination approach that relies on in vivo measurements of genetic interactions. We construct phenotypic profiles for point mutations crossed against gene deletions or exposed to environmental perturbations, followed by converting similarities between two profiles into an upper bound on the distance between the mutated residues. We determine the structure of the yeast histone H3-H4 complex based on similar to 500,000 genetic interactions of 350 mutants. We then apply the method to subunits Rpb1-Rpb2 of yeast RNA polymerase II and subunits RpoB-RpoC of bacterial RNA polymerase. The accuracy is comparable to that based on chemical cross-links; using restraints from both genetic interactions and cross-links further improves model accuracy and precision. The approach provides an efficient means to augment integrative structure determination with in vivo observations
The B-Star Exoplanet Abundance Study: a co-moving 16-25 Mjup companion to the young binary system HIP 79098
Wide low-mass substellar companions are known to be very rare among low-mass
stars, but appear to become increasingly common with increasing stellar mass.
However, B-type stars, which are the most massive stars within ~150 pc of the
Sun, have not yet been examined to the same extent as AFGKM-type stars in that
regard. In order to address this issue, we launched the ongoing B-star
Exoplanet Abundance Study (BEAST) to examine the frequency and properties of
planets, brown dwarfs, and disks around B-type stars in the Scorpius-Centaurus
(Sco-Cen) association; we also analyzed archival data of B-type stars in
Sco-Cen. During this process, we identified a candidate substellar companion to
the B9-type spectroscopic binary HIP 79098 AB, which we refer to as HIP 79098
(AB)b. The candidate had been previously reported in the literature, but was
classified as a background contaminant on the basis of its peculiar colors.
Here we demonstrate that the colors of HIP 79098 (AB)b are consistent with
several recently discovered young and low-mass brown dwarfs, including other
companions to stars in Sco-Cen. Furthermore, we show unambiguous common proper
motion over a 15-year baseline, robustly identifying HIP 79098 (AB)b as a bona
fide substellar circumbinary companion at a 345+/-6 AU projected separation to
the B9-type stellar pair. With a model-dependent mass of 16-25 Mjup yielding a
mass ratio of <1%, HIP 79098 (AB)b joins a growing number of substellar
companions with planet-like mass ratios around massive stars. Our observations
underline the importance of common proper motion analysis in the identification
of physical companionship, and imply that additional companions could
potentially remain hidden in the archives of purely photometric surveys.Comment: 9 pages, 6 figures, accepted for publication in A&
- …