6,474 research outputs found
Exploratory wind tunnel tests of a shock-swallowing air data sensor at a Mach number of approximately 1.83
The test probe was designed to measure free-stream Mach number and could be incorporated into a conventional airspeed nose boom installation. Tests were conducted in the Langley 4-by 4-foot supersonic pressure tunnel with an approximate angle of attack test range of -5 deg to 15 deg and an approximate angle of sideslip test range of + or - 4 deg. The probe incorporated a variable exit area which permitted internal flow. The internal flow caused the bow shock to be swallowed. Mach number was determined with a small axially movable internal total pressure tube and a series of fixed internal static pressure orifices. Mach number error was at a minimum when the total pressure tube was close to the probe tip. For four of the five tips tested, the Mach number error derived by averaging two static pressures measured at horizontally opposed positions near the probe entrance were least sensitive to angle of attack changes. The same orifices were also used to derive parameters that gave indications of flow direction
A spectroscopically confirmed z=1.327 galaxy-scale deflector magnifying a z~8 Lyman-Break galaxy in the Brightest of Reionizing Galaxies survey
We present a detailed analysis of an individual case of gravitational lensing
of a Lyman-Break galaxy (LBG) in a blank field, identified in Hubble
Space Telescope imaging obtained as part of the Brightest of Reionizing
Galaxies survey. To investigate the close proximity of the bright
() -dropout to a small group of foreground galaxies, we
obtained deep spectroscopy of the dropout and two foreground galaxies using
VLT/X-Shooter. We detect H-, H-, [OIII] and [OII] emission in
the brightest two foreground galaxies (unresolved at the natural seeing of
arcsec), placing the pair at . We can rule out emission lines
contributing all of the observed broadband flux in band at
, allowing us to exclude the candidate as a low redshift
interloper with broadband photometry dominated by strong emission lines. The
foreground galaxy pair lies at the peak of the luminosity, redshift and
separation distributions for deflectors of strongly lensed objects,
and we make a marginal detection of a demagnified secondary image in the
deepest () filter. We show that the configuration can be accurately
modelled by a singular isothermal ellipsoidal deflector and a S\'{e}rsic source
magnified by a factor of . The reconstructed source in the
best-fitting model is consistent with luminosities and morphologies of
LBGs in the literature. The lens model yields a group mass of
and a stellar mass-to-light ratio for the
brightest deflector galaxy of within its effective radius. The foreground galaxies'
redshifts would make this one of the few strong lensing deflectors discovered
at .Comment: Accepted for publication in MNRAS. 16 pages, 11 figures, 3 table
NEOWISE Reactivation Mission Year One: Preliminary Asteroid Diameters and Albedos
We present preliminary diameters and albedos for 7,959 asteroids detected in
the first year of the NEOWISE Reactivation mission. 201 are near-Earth
asteroids (NEAs). 7,758 are Main Belt or Mars-crossing asteroids. 17% of these
objects have not been previously characterized using WISE or NEOWISE thermal
measurements. Diameters are determined to an accuracy of ~20% or better. If
good-quality H magnitudes are available, albedos can be determined to within
~40% or better.Comment: 42 pages, 5 figure
The Population of Tiny Near-Earth Objects Observed by NEOWISE
Only a very small fraction of the asteroid population at size scales
comparable to the object that exploded over Chelyabinsk, Russia has been
discovered to date, and physical properties are poorly characterized. We
present previously unreported detections of 106 close approaching near-Earth
objects (NEOs) by the Wide-field Infrared Survey Explorer mission's NEOWISE
project. These infrared observations constrain physical properties such as
diameter and albedo for these objects, many of which are found to be smaller
than 100 m. Because these objects are intrinsically faint, they were detected
by WISE during very close approaches to the Earth, often at large apparent
on-sky velocities. We observe a trend of increasing albedo with decreasing
size, but as this sample of NEOs was discovered by visible light surveys, it is
likely that selection biases against finding small, dark NEOs influence this
finding.Comment: Accepted to Ap
The Impact of Strong Gravitational Lensing on Observed Lyman-Break Galaxy Numbers at 4<z<8 in the GOODS and the XDF Blank Fields
Detection of Lyman-Break Galaxies (LBGs) at high-redshift can be affected by
gravitational lensing induced by foreground deflectors not only in galaxy
clusters, but also in blank fields. We quantify the impact of strong
magnification in the samples of , , , LBGs () observed in the XDF and GOODS/CANDELS fields, by investigating the
proximity of dropouts to foreground objects. We find that of bright
LBGs () by
foreground objects. This fraction decreases from at to
at . Since the observed fraction of strongly lensed
galaxies is a function of the shape of the luminosity function (LF), it can be
used to derive Schechter parameters, and , independently
from galaxy number counts. Our magnification bias analysis yields
Schechter-function parameters in close agreement with those determined from
galaxy counts albeit with larger uncertainties. Extrapolation of our analysis
to suggests that future surveys with JSWT, WFIRST and EUCLID
should find excess LBGs at the bright-end, even if there is an intrinsic
exponential cutoff of number counts. Finally, we highlight how the
magnification bias measurement near the detection limit can be used as probe of
the population of galaxies too faint to be detected. Preliminary results using
this novel idea suggest that the magnification bias at is not
as strong as expected if extends well below the current
detection limits in the XDF. At face value this implies a flattening of the LF
at . However, selection effects and completeness estimates
are difficult to quantify precisely. Thus, we do not rule out a steep LF
extending to .Comment: Submitted to ApJ on 18/12/201
Quasi-2D Confinement of a BEC in a Combined Optical and Magnetic Potential
We have added an optical potential to a conventional Time-averaged Orbiting
Potential (TOP) trap to create a highly anisotropic hybrid trap for ultracold
atoms. Axial confinement is provided by the optical potential; the maximum
frequency currently obtainable in this direction is 2.2 kHz for rubidium. The
radial confinement is independently controlled by the magnetic trap and can be
a factor of 700 times smaller than in the axial direction. This large
anisotropy is more than sufficient to confine condensates with ~10^5 atoms in a
Quasi-2D (Q2D) regime, and we have verified this by measuring a change in the
free expansion of the condensate; our results agree with a variational model.Comment: 11 pages, 10 figur
High Redshift Supernovae in the Hubble Deep Field
Two supernovae detected in the Hubble Deep Field using the original December
1995 epoch and data from a shorter (63000 s in F814W) December 1997 visit with
HST are discussed. The supernovae (SNe) are both associated with distinct
galaxies at redshifts of 0.95 (spectroscopic) from Cohen etal. (1996) and 1.32
(photometric) from the work of Fernandez-Soto, Lanzetta, and Yahil (1998).
These redshifts are near, in the case of 0.95, and well beyond for 1.32 the
greatest distance reported previously for SNe. We show that our observations
are sensitive to SNe to z < 1.8 in either epoch for an event near peak
brightness. Detailed simulations are discussed that quantify the level at which
false events from our search phase would start to to arise, and the
completeness of our search as a function of both SN brightness and host galaxy
redshift. The number of Type Ia and Type II SNe expected as a function of
redshift in the two HDF epochs are discussed in relation to several published
predictions and our own detailed calculations. A mean detection frequency of
one SN per epoch for the small HDF area is consistent with expectations from
current theory.Comment: 62 pages, 17 figures, ApJ 1999 in pres
NEOWISE Reactivation Mission Year Three: Asteroid Diameters and Albedos
The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE)
reactivation mission has completed its third year of surveying the sky in the
thermal infrared for near-Earth asteroids and comets. NEOWISE collects
simultaneous observations at 3.4 um and 4.6 um of solar system objects passing
through its field of regard. These data allow for the determination of total
thermal emission from bodies in the inner solar system, and thus the sizes of
these objects. In this paper we present thermal model fits of asteroid
diameters for 170 NEOs and 6110 MBAs detected during the third year of the
survey, as well as the associated optical geometric albedos. We compare our
results with previous thermal model results from NEOWISE for overlapping sample
sets, as well as diameters determined through other independent methods, and
find that our diameter measurements for NEOs agree to within 26% (1-sigma) of
previously measured values. Diameters for the MBAs are within 17% (1-sigma).
This brings the total number of unique near-Earth objects characterized by the
NEOWISE survey to 541, surpassing the number observed during the fully
cryogenic mission in 2010.Comment: Accepted for publication in A
Evaluation of Bleeding Disorders in Patients With Noonan Syndrome: A Systematic Review
Background: Noonan syndrome (NS) is an autosomal dominant genetic condition that has a number of clinical features, including bleeding diathesis and a number of hematological abnormalities including clotting factor deficiencies, von Willebrand disease and abnormal platelet count/function. Methods: We evaluated the frequency/types of bleeding disorders, and associated hematological laboratory findings, in patients with NS, using published data from 1965 to 2014. Results: Of 45 studies identified, 31 included data for 428 patients with NS. Of these patients, 43% had reported bleeding, 26% had no reported bleeding and no bleed data was reported for 31%. Most patients (90%) had bleeding-related laboratory test abnormalities, but only 194 (45%) had a confirmed diagnosis of a specific bleeding disorder. Abnormal laboratory tests included: prolonged prothrombin time, activated partial thromboplastin time, and other platelet-related disorders. Of the 194 patients with a confirmed diagnosis of a specific bleeding disorder, 153 (79%) had single clotting factor deficiencies, von Willebrand disease or platelet-related disorders, and 41 (21%) had multiple deficiencies including platelet-related disorders. Conclusion: As patients with NS can experience multiple bleeding disorders, including abnormal platelet function, clinical evaluations should be performed at diagnosis, after diagnosis, before any surgery is undertaken, and if patients become symptomatic
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