We describe the APERture Tile In Focus (Apertif) system, a phased array feed (PAF) upgrade of the Westerbork Synthesis Radio Telescope that transforms this telescope into a high-sensitivity, ...wide-field-of-view
L
-band imaging and transient survey instrument. Using novel PAF technology, up to 40 partially overlapping beams are formed on the sky simultaneously, significantly increasing the survey speed of the telescope. With this upgraded instrument, an imaging survey covering an area of 2300 deg
2
is being performed that will deliver both continuum and spectral line datasets, of which the first data have been publicly released. In addition, a time domain transient and pulsar survey covering 15 000 deg
2
is in progress. An overview of the Apertif science drivers, hardware, and software of the upgraded telescope is presented, along with its key performance characteristics.
Context.A complex environment exists in the inner few astronomical units of planet-forming disks. High-angular-resolution observa-tions play a key role in our understanding of the disk structure and ...the dynamical processes at work.Aims.In this study we aim to characterize the mid-infrared brightness distribution of the inner disk of the young intermediate-massstar HD 163296 from early VLTI/MATISSE observations taken in theL- andN-bands. We put special emphasis on the detection ofpotential disk asymmetries.Methods.We use simple geometric models to fit the interferometric visibilities and closure phases. Our models include a smoothedring, a flat disk with an inner cavity, and a 2D Gaussian. The models can account for disk inclination and for azimuthal asymmetriesas well. We also perform numerical hydrodynamical simulations of the inner edge of the disk.Results.Our modeling reveals a significant brightness asymmetry in theL-band disk emission. The brightness maximum of the asym-metry is located at the NW part of the disk image, nearly at the position angle of the semimajor axis. The surface brightness ratio inthe azimuthal variation is3.5±0.2. Comparing our result on the location of the asymmetry with other interferometric measurements,we confirm that the morphology of ther<0.3au disk region is time-variable. We propose that this asymmetric structure, located in ornear the inner rim of the dusty disk, orbits the star. To find the physical origin of the asymmetry, we tested a hypothesis where a vortexis created by Rossby wave instability, and we find that a unique large-scale vortex may be compatible with our data. The half-lightradius of theL-band-emitting region is0.33±0.01au, the inclination is52◦+5◦−7◦, and the position angle is143◦±3◦. Our models predictthat a non-negligible fraction of theL-band disk emission originates inside the dust sublimation radius forμm-sized grains. Refractorygrains or large (&10μm-sized) grains could be the origin of this emission.N-band observations may also support a lack of smallsilicate grains in the innermost disk (r.0.6au), in agreement with our findings fromL-band data.
Context.
The nature of circumstellar envelopes (CSEs) around Cepheids is a matter of ongoing debate. The physical origin of their infrared (IR) excess could be shown to either be made up of a shell ...of ionized gas, a dust envelope, or a combination of both.
Aims.
This study is aimed at constraining the geometry and the IR excess of the environment of the bright long-period Cepheid
ℓ
Car (
P
= 35.5 days) at mid-IR wavelengths in order to understand its physical nature.
Methods.
We first used photometric observations in various bands (from the visible domain to the infrared) and
Spitzer
Space Telescope spectroscopy to constrain the IR excess of
ℓ
Car. Then we analyzed the VLTI/MATISSE measurements at a specific phase of observation in order to determine the flux contribution as well as the size and shape of the environment of the star in the
L
band. Finally, we tested the hypothesis of a shell of ionized gas in order to model the IR excess.
Results.
We report the first detection in the
L
band of a centro-symmetric extended emission around
ℓ
Car, of about 1.7
R
⋆
in full width at half maximum, producing an excess of about 7.0% in this band.This latter value is used to calibrate the IR excess found when comparing the photometric observations in various bands and quasi-static atmosphere models. In the
N
band, there is no clear evidence for dust emission from VLTI/MATISSE correlated flux and
Spitzer
data. On the other side, the modeled shell of ionized gas implies a more compact CSE (1.13 ± 0.02
R
⋆
) that is also fainter (IR excess of 1% in the
L
band).
Conclusions.
We provide new evidence supporting a compact CSE for
ℓ
Car and we demonstrate the capabilities of VLTI/MATISSE for determining common properties of CSEs. While the compact CSE of
ℓ
Car is likely to be of a gaseous nature, the tested model of a shell of ionized gas is not able to simultaneously reproduce the IR excess and the interferometric observations. Further Galactic Cepheid observations with VLTI/MATISSE are necessary for determining the properties of CSEs, which may also depend on both the pulsation period and the evolutionary state of the stars.
We describe the APERture Tile In Focus (Apertif) system, a phased array feed (PAF) upgrade of the Westerbork Synthesis Radio Telescope that transforms this telescope into a high-sensitivity, ...wide-field-of-view L-band imaging and transient survey instrument. Using novel PAF technology, up to 40 partially overlapping beams are formed on the sky simultaneously, significantly increasing the survey speed of the telescope. With this upgraded instrument, an imaging survey covering an area of 2300 deg2 is being performed that will deliver both continuum and spectral line datasets, of which the first data have been publicly released. In addition, a time domain transient and pulsar survey covering 15 000 deg2 is in progress. An overview of the Apertif science drivers, hardware, and software of the upgraded telescope is presented, along with its key performance characteristics.
Context. A complex environment exists in the inner few astronomical units of planet-forming disks. High-angular-resolution observations play a key role in our understanding of the disk structure and ...the dynamical processes at work. Aims. In this study we aim to characterize the mid-infrared brightness distribution of the inner disk of the young intermediate-mass star HD 163296 from early VLTI/MATISSE observations taken in the L - and N -bands. We put special emphasis on the detection of potential disk asymmetries. Methods. We use simple geometric models to fit the interferometric visibilities and closure phases. Our models include a smoothed ring, a flat disk with an inner cavity, and a 2D Gaussian. The models can account for disk inclination and for azimuthal asymmetries as well. We also perform numerical hydrodynamical simulations of the inner edge of the disk. Results. Our modeling reveals a significant brightness asymmetry in the L -band disk emission. The brightness maximum of the asymmetry is located at the NW part of the disk image, nearly at the position angle of the semimajor axis. The surface brightness ratio in the azimuthal variation is 3.5 ± 0.2. Comparing our result on the location of the asymmetry with other interferometric measurements, we confirm that the morphology of the r < 0.3 au disk region is time-variable. We propose that this asymmetric structure, located in or near the inner rim of the dusty disk, orbits the star. To find the physical origin of the asymmetry, we tested a hypothesis where a vortex is created by Rossby wave instability, and we find that a unique large-scale vortex may be compatible with our data. The half-light radius of the L -band-emitting region is 0.33 ±0.01 au, the inclination is 52° −7° +5° , and the position angle is 143° ± 3°. Our models predict that a non-negligible fraction of the L -band disk emission originates inside the dust sublimation radius for μ m-sized grains. Refractory grains or large (≳10 μ m-sized) grains could be the origin of this emission. N -band observations may also support a lack of small silicate grains in the innermost disk ( r ≲ 0.6 au), in agreement with our findings from L -band data.
The paper describes the system developed by researchers from MIT for the Defense Advanced Research Projects Agency's (DARPA) Virtual Robotics Challenge (VRC), held in June 2013. The VRC was the first ...competition in the DARPA Robotics Challenge (DRC), a program that aims to "develop ground robotic capabilities to execute complex tasks in dangerous, degraded, human-engineered environments". The VRC required teams to guide a model of Boston Dynamics' humanoid robot, Atlas, through driving, walking, and manipulation tasks in simulation. Team MIT's user interface, the Viewer, provided the operator with a unified representation of all available information. A 3D rendering of the robot depicted its most recently estimated body state with respect to the surrounding environment, represented by point clouds and texture-mapped meshes as sensed by on-board LIDAR and fused over time.
The Maxwell-Stefan mass transfer description is applied to two electrodialysis systems. Firstly, a model system involving NaCl and HCl is investigated. For this system, all the model parameters are ...obtained either from separate experiments or existing correlations. Although it is not possible to determine all the parameters accurately, the values found are all within the ranges expected.
Secondly, a two amino acid system is investigated. The separation of two amino acids using electrodialysis is found to be feasible. Unfortunately, it is too difficult to obtain sufficient data for a proper quantitative description of the process.
In both cases, the Maxwell-Stefan description appears to provide a thorough model of the electrodialysis process.
The Dutch Working Party on Antibiotic Policy (SWAB) in collaboration with relevant professional societies, has updated their evidence-based guidelines on empiric antibacterial therapy of sepsis in ...adults. Our multidisciplinary guideline committee generated ten population, intervention, comparison, and outcome (PICO) questions relevant for adult patients with sepsis. For each question, a literature search was performed to obtain the best available evidence and assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system. The quality of evidence for clinically relevant outcomes was graded from high to very low. In structured consensus meetings, the committee formulated recommendations as strong or weak. When evidence could not be obtained, recommendations were provided based on expert opinion and experience (good practice statements). Fifty-five recommendations on the antibacterial therapy of sepsis were generated. Recommendations on empiric antibacterial therapy choices were differentiated for sepsis according to the source of infection, the potential causative pathogen and its resistance pattern. One important revision was the distinction between low, increased and high risk of infection with Enterobacterales resistant to third generation cephalosporins (3GRC-E) to guide the choice of empirical therapy. Other new topics included empirical antibacterial therapy in patients with a reported penicillin allergy and the role of pharmacokinetics and pharmacodynamics to guide dosing in sepsis. We also established recommendations on timing and duration of antibacterial treatment. Our multidisciplinary committee formulated evidence-based recommendations for the empiric antibacterial therapy of adults with sepsis in The Netherlands.
In suspected hypercortisolism, the 1 mg dexamethasone suppression test is the usual initial test. In fertile women, false-positive test results are often due to the use of oral contraceptives. By ...elevating cortisol-binding globulin these contraceptives increase the total serum cortisol concentration. The aim of this study was to assess the duration and degree of influence of oral contraceptives on the low-dose dexamethasone suppression test.
Thirteen healthy female volunteers without symptoms or signs of overt hypercortisolism, aged 18-55 years, who were using oral contraceptives, underwent a 1 mg dexamethasone suppression test. Tests were repeated one and six weeks after withdrawal of the contraceptive. In addition, 24-hour urinary cortisol excretion and late-night salivary cortisol were measured.
Of the 13 volunteers (62%) eight had inadequate suppression of cortisol by 1 mg dexamethasone while using oral contraceptives. One week after the contraceptive was withdrawn, the number of false-positive results significantly decreased to 1 (8%, p < 0.02). Six weeks after discontinuation, all tests were normal. None of the 24-hour urinary cortisol samples and just one late-night salivary cortisol level was elevated.
The results of the 1 mg dexamethasone suppression test performed one week after cessation of oral contraceptives are accurate in almost all subjects. In case of inadequate suppression, a second test may be performed after six weeks. In this manner the 1 mg dexamethasone suppression test can reliably be done at the end of a seven-day break from contraceptive use in nearly all cases.
PDF
