404 research outputs found
Behavior of materials in vacuum Final report, Jun. 1967 - Sep. 1968
Outgassed materials condensed on magnesium overcoated aluminum mirrors irradiated with ultraviolet radiation in vacuu
Irradiation of thermal control coatings Final report, Feb. 1967 - Feb. 1968
Irradiation effects on thermal control coatings of OA
Periodontal effects of the reversible dipeptidyl peptidase 1 inhibitor brensocatib in bronchiectasis
Aims: Brensocatib is a reversible inhibitor of dipeptidyl peptidase 1 (cathepsin C), in development to treat chronic non-cystic fibrosis bronchiectasis. The phase 2, randomized, placebo-controlled WILLOW trial (NCT03218917) was conducted to examine whether brensocatib reduced the incidence of pulmonary exacerbations. Brensocatib prolonged the time to the first exacerbation and led to fewer exacerbations than placebo. Because brensocatib potentially affects oral tissues due to its action on neutrophil-mediated inflammation, we analyzed periodontal outcomes in the trial participants.Materials and Methods: Patients with bronchiectasis were randomized 1:1:1 to receive once-daily oral brensocatib 10 or 25 mg or placebo. Periodontal status was monitored throughout the 24-week trial in a prespecified safety analysis. Periodontal pocket depth (PPD) at screening, week 8, and week 24 was evaluated. Gingival inflammation was evaluated by a combination of assessing bleeding upon probing and monitoring the Löe-Silness Gingival Index on 3 facial surfaces and the mid-lingual surface.Results: At week 24, mean ± SE PPD reductions were similar across treatment groups: -0.07 ± 0.007, -0.06 ± 0.007, and -0.15 ± 0.007 mm with brensocatib 10 mg, brensocatib 25 mg, and placebo, respectively. The distribution of changes in PPD and the number of patients with multiple increased PPD sites were similar across treatment groups at weeks 8 and 24. The frequencies of gingival index values were generally similar across treatment groups at each assessment. An increase in index values 0-1 and a decrease in index values 2-3 over time and at the end of the study were observed in all groups, indicating improved oral health.Conclusions: In patients with non-cystic fibrosis bronchiectasis, brensocatib 10 or 25 mg had an acceptable safety profile after 6 months' treatment, with no changes in periodontal status noted. Improvement in oral health at end of the study may be due to regular dental care during the trial and independent of brensocatib treatment.Knowledge Transfer Statement: The results of this study suggest that 24 weeks of treatment with brensocatib does not affect periodontal disease progression. This information can be used by clinicians when considering treatment approaches for bronchiectasis and suggests that the use of brensocatib will not be limited by periodontal disease risks. Nevertheless, routine dental/periodontal care should be provided to patients irrespective of brensocatib treatment.</p
Quasars: What turns them off?
(Abridged) We explore the idea that the anti-hierarchical turn-off observed
in the quasar population arises from self-regulating feedback, via an outflow
mechanism. Using a detailed hydrodynamic simulation we calculate the luminosity
function of quasars down to a redshift of z=1 in a large, cosmologically
representative volume. Outflows are included explicitly by tracking halo
mergers and driving shocks into the surrounding intergalactic medium. Our
results are in excellent agreement with measurements of the spatial
distribution of quasars, and we detect an intriguing excess of galaxy-quasar
pairs at very short separations. We also reproduce the anti-hierarchical
turnoff in the quasar luminosity function, however, the magnitude of the
turn-off falls short of that observed as well as that predicted by analogous
semi-analytic models. The difference can be traced to the treatment of gas
heating within galaxies. The simulated galaxy cluster L_X-T relationship is
close to that observed for z~1 clusters, but the simulated galaxy groups at z=1
are significantly perturbed by quasar outflows, suggesting that measurements of
X-ray emission in high-redshift groups could well be a "smoking gun" for the
AGN heating hypothesis.Comment: 16 pages, 11 figures, submitted to ApJ, comments welcome
The effect of galaxy mass ratio on merger--driven starbursts
We employ numerical simulations of galaxy mergers to explore the effect of
galaxy mass ratio on merger--driven starbursts. Our numerical simulations
include radiative cooling of gas, star formation, and stellar feedback to
follow the interaction and merger of four disk galaxies. The galaxy models span
a factor of 23 in total mass and are designed to be representative of typical
galaxies in the local Universe. We find that the merger--driven star formation
is a strong function of merger mass ratio, with very little, if any, induced
star formation for large mass ratio mergers. We define a burst efficiency that
is useful to characterize the merger--driven star formation and test that it is
insensitive to uncertainties in the feedback parameterization. In accord with
previous work we find that the burst efficiency depends on the structure of the
primary galaxy. In particular, the presence of a massive stellar bulge
stabilizes the disk and suppresses merger--driven star formation for large mass
ratio mergers. Direct, co--planar merging orbits produce the largest tidal
disturbance and yield that most intense burst of star formation. Contrary to
naive expectations, a more compact distribution of gas or an increased gas
fraction both decrease the burst efficiency. Owing to the efficient feedback
model and the newer version of SPH employed here, the burst efficiencies of the
mergers presented here are smaller than in previous studies.Comment: 26 pages, 21 figures, submitted to MNRA
Lensing-Induced Structure of Submillimeter Sources: Implications for the Microwave Background
We consider the effect of lensing by galaxy clusters on the angular
distribution of submillimeter wavelength objects. While lensing does not change
the total flux and number counts of submillimeter sources, it can affect the
number counts and fluxes of flux-limited samples. Therefore imposing a flux cut
on point sources not only reduces the overall Poisson noise, but imprints the
correlations between lensing clusters on the unresolved flux distribution.
Using a simple model, we quantify the lensing anisotropy induced in
flux-limited samples and compare this to Poisson noise. We find that while the
level of induced anisotropies on the scale of the cluster angular correlation
length is comparable to Poisson noise for a slowly evolving cluster model, it
is negligible for more realistic models of cluster evolution. Thus the removal
of point sources is not expected to induce measurable structure in the
microwave or far-infrared backgrounds.Comment: 22 pages, 9 figures, accepted to Astrophysical Journa
Evolution of shocks and turbulence in major cluster mergers
We performed a set of cosmological simulations of major mergers in galaxy
clusters to study the evolution of merger shocks and the subsequent injection
of turbulence in the post-shock region and in the intra-cluster medium (ICM).
The computations were done with the grid-based, adaptive mesh refinement hydro
code Enzo, using an especially designed refinement criteria for refining
turbulent flows in the vicinity of shocks. A substantial amount of turbulence
energy is injected in the ICM due to major merger. Our simulations show that
the shock launched after a major merger develops an ellipsoidal shape and gets
broken by the interaction with the filamentary cosmic web around the merging
cluster. The size of the post-shock region along the direction of shock
propagation is about 300 kpc h^-1, and the turbulent velocity dispersion in
this region is larger than 100 km s^-1. Scaling analysis of the turbulence
energy with the cluster mass within our cluster sample is consistent with
M^(5/3), i.e. the scaling law for the thermal energy in the self-similar
cluster model. This clearly indicates the close relation between virialization
and injection of turbulence in the cluster evolution. We found that the ratio
of the turbulent to total pressure in the cluster core within 2 Gyr after the
major merger is larger than 10%, and it takes about 4 Gyr to get relaxed, which
is substantially longer than typically assumed in the turbulent re-acceleration
models, invoked to explain the statistics of observed radio halos. Striking
similarities in the morphology and other physical parameters between our
simulations and the "symmetrical radio relics" found at the periphery of the
merging cluster A3376 are finally discussed. In particular, the interaction
between the merger shock and the filaments surrounding the cluster could
explain the presence of "notch-like" features at the edges of the double
relics.Comment: 16 pages, 19 figures, Published in Astrophysical Journal (online) and
printed version will be published on 1st January, 201
The RAVE survey: the Galactic escape speed and the mass of the Milky Way
We construct new estimates on the Galactic escape speed at various
Galactocentric radii using the latest data release of the Radial Velocity
Experiment (RAVE DR4). Compared to previous studies we have a database larger
by a factor of 10 as well as reliable distance estimates for almost all stars.
Our analysis is based on the statistical analysis of a rigorously selected
sample of 90 high-velocity halo stars from RAVE and a previously published data
set. We calibrate and extensively test our method using a suite of cosmological
simulations of the formation of Milky Way-sized galaxies. Our best estimate of
the local Galactic escape speed, which we define as the minimum speed required
to reach three virial radii , is km/s (90%
confidence) with an additional 5% systematic uncertainty, where is
the Galactocentric radius encompassing a mean over-density of 340 times the
critical density for closure in the Universe. From the escape speed we further
derive estimates of the mass of the Galaxy using a simple mass model with two
options for the mass profile of the dark matter halo: an unaltered and an
adiabatically contracted Navarro, Frenk & White (NFW) sphere. If we fix the
local circular velocity the latter profile yields a significantly higher mass
than the un-contracted halo, but if we instead use the statistics on halo
concentration parameters in large cosmological simulations as a constraint we
find very similar masses for both models. Our best estimate for , the
mass interior to (dark matter and baryons), is M (corresponding to M). This estimate is in good agreement with recently published
independent mass estimates based on the kinematics of more distant halo stars
and the satellite galaxy Leo I.Comment: 16 pages, 15 figures; accepted for publication in Astronomy &
Astrophysic
The Role of Heating and Enrichment in Galaxy Formation
We show that the winds identified with high-redshift low-mass galaxies may
strongly affect the formation of stars in more massive galaxies that form
later. With 3D realizations of a simple linear growth model we track gas
shocking, metal enrichment, and cooling, together with dark halo formation. We
show that outflows typically strip baryonic material out of collapsing
intermediate mass halos, suppressing star formation. More massive halos can
trap the heated gas but collapse late, leading to a broad bimodal redshift
distribution, with a larger characteristic mass associated with the lower
redshift peak. This scenario accounts for the observed bell-shaped luminosity
function of early type galaxies, explains the small number of Milky Way
satellite galaxies relative to Cold Dark Matter models predictions, and
provides a possible explanation for the lack of metal poor G-dwarfs in the
solar neighborhood and the more general lack of low-metallicity stars in
massive galaxies relative to ``closed-box'' models of chemical enrichment.
Intergalactic medium heating from outflows should produce spectral distortions
in the cosmic microwave background that will be measurable with the next
generation of experiments.Comment: 19 pages, 12 figures, accepted to ApJ, models refined and minor
revisions mad
Measurement of a Peak in the Cosmic Microwave Background Power Spectrum from the North American test flight of BOOMERANG
We describe a measurement of the angular power spectrum of anisotropies in
the Cosmic Microwave Background (CMB) from 0.3 degrees to ~10 degrees from the
North American test flight of the BOOMERANG experiment. BOOMERANG is a
balloon-borne telescope with a bolometric receiver designed to map CMB
anisotropies on a Long Duration Balloon flight. During a 6-hour test flight of
a prototype system in 1997, we mapped > 200 square degrees at high galactic
latitudes in two bands centered at 90 and 150 GHz with a resolution of 26 and
16.6 arcmin FWHM respectively. Analysis of the maps gives a power spectrum with
a peak at angular scales of ~1 degree with an amplitude ~70 uK.Comment: 5 pages, 1 figure LaTeX, emulateapj.st
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