4,928 research outputs found
Testing and Learning on Distributions with Symmetric Noise Invariance
Kernel embeddings of distributions and the Maximum Mean Discrepancy (MMD),
the resulting distance between distributions, are useful tools for fully
nonparametric two-sample testing and learning on distributions. However, it is
rarely that all possible differences between samples are of interest --
discovered differences can be due to different types of measurement noise, data
collection artefacts or other irrelevant sources of variability. We propose
distances between distributions which encode invariance to additive symmetric
noise, aimed at testing whether the assumed true underlying processes differ.
Moreover, we construct invariant features of distributions, leading to learning
algorithms robust to the impairment of the input distributions with symmetric
additive noise.Comment: 22 page
Constraints on local primordial non-Gaussianity from large scale structure
Recent work has shown that the local non-Gaussianity parameter f_NL induces a
scale-dependent bias, whose amplitude is growing with scale. Here we first
rederive this result within the context of peak-background split formalism and
show that it only depends on the assumption of universality of mass function,
assuming halo bias only depends on mass. We then use extended Press-Schechter
formalism to argue that this assumption may be violated and the scale dependent
bias will depend on other properties, such as merging history of halos. In
particular, in the limit of recent mergers we find the effect is suppressed.
Next we use these predictions in conjunction with a compendium of large scale
data to put a limit on the value of f_NL. When combining all data assuming that
halo occupation depends only on halo mass, we get a limit of -29 ~ (-65)< f_NL
< +70 ~(+93) at 95% (99.7%) confidence. While we use a wide range of datasets,
our combined result is dominated by the signal from the SDSS photometric quasar
sample. If the latter are modeled as recent mergers then the limits weaken to
-31 ~(-96) < f_NL < +70 ~ (+96) . These limits are comparable to the strongest
current limits from the WMAP 5 year analysis, with no evidence of a positive
signal in f_NL. While the method needs to be thoroughly tested against large
scale structure simulations with realistic quasar and galaxy formation models,
our results indicate that this is a competitive method relative to CMB and
should be further pursued both observationally and theoretically.Comment: 18 pages, 5 figures; v2 matches version accepted by JCAP, several
small changes in the text, added refs and fixed typo
Kinematics of Circumgalactic Gas: Feeding Galaxies and Feedback
We present observations of 50 pairs of redshift z ~ 0.2 star-forming galaxies
and background quasars. These sightlines probe the circumgalactic medium (CGM)
out to half the virial radius, and we describe the circumgalactic gas
kinematics relative to the reference frame defined by the galactic disks. We
detect halo gas in MgII absorption, measure the equivalent-width-weighted
Doppler shifts relative to each galaxy, and find that the CGM has a component
of angular momentum that is aligned with the galactic disk. No net
counter-rotation of the CGM is detected within 45 degrees of the major axis at
any impact parameter. The velocity offset of the circumgalactic gas correlates
with the projected rotation speed in the disk plane out to disk radii of
roughly 70 kpc. We confirm previous claims that the MgII absorption becomes
stronger near the galactic minor axis and show that the equivalent width
correlates with the velocity range of the absorption. We cannot directly
measure the location of any absorber along the sightline, but we explore the
hypothesis that individual velocity components can be associated with gas
orbiting in the disk plane or flowing radially outward in a conical outflow. We
conclude that centrifugal forces partially support the low-ionization gas and
galactic outflows kinematically disturb the CGM producing excess absorption.
Our results firmly rule out schema for the inner CGM that lack rotation and
suggest that angular momentum as well as galactic winds should be included in
any viable model for the low-redshift CGM.Comment: Accepted for publication in the Astrophysical Journa
Re: comparison between two shock wave regimens using frequencies of 60 and 90 impulses per minute for urinary stones
Growth control of oxygen stoichiometry in homoepitaxial SrTiO3 films by pulsed laser epitaxy in high vacuum
In many transition metal oxides (TMOs), oxygen stoichiometry is one of the
most critical parameters that plays a key role in determining the structural,
physical, optical, and electrochemical properties of the material. However,
controlling the growth to obtain high quality single crystal films having the
right oxygen stoichiometry, especially in a high vacuum environment, has been
viewed as a challenge. In this work, we show that through proper control of the
plume kinetic energy, stoichiometric crystalline films can be synthesized
without generating oxygen defects, even in high vacuum. We use a model
homoepitaxial system of SrTiO3 (STO) thin films on single crystal STO
substrates. Physical property measurements indicate that oxygen vacancy
generation in high vacuum is strongly influenced by the energetics of the laser
plume, and it can be controlled by proper laser beam delivery. Therefore, our
finding not only provides essential insight into oxygen stoichiometry control
in high vacuum for understanding the fundamental properties of STO-based thin
films and heterostructures, but expands the utility of pulsed laser epitaxy of
other materials as well
Update on trials examining effects of night-time blood pressure lowering drug treatment on prevention of cardiovascular disease
Current evidence on benefits of night-time blood pressure (BP) lowering drug treatment on cardiovascular disease (CVD) prevention attributable to the Ambulatory Blood Pressure Monitoring in the Prediction of Cardiovascular Events and Effects of Chronotherapy (MAPEC) trial and Bedtime hypertension treatment improves cardiovascular risk reduction (Hygia) trials has raised concern on their validity and methodology. In this commentary, the authors have updated the progress of the ongoing trials that were planned to examine the effect of night-time BP lowering drug treatment on CVD prevention. As compared to MAPEC and Hygia trials, three pragmatic trials the Blood Pressure Medication Timing (BPMedtime) trial (US), the Treatment In Morning versus Evening (TIME) trial (UK), Bedmed and Bedmed-frail (Canada) were planned without ambulatory BP monitoring. The BPMedtime trial was stopped after the pilot phase due to underestimated sample size and insufficient funds. TIME trial (UK) had a similar issue when changing the sample size from 10,269 to more than 20,000 participants. The TIME trial was completed and the initial results showing that protection against heart attack, stroke and vascular death is not affected by whether antihypertensive medications are taken in the morning or evening. The full study of the TIME trial is published in December 2022. Bedmed and Bedmed-frail trials are ongoing and will be completed in 2023. Time of taking BP lowering drug should be determined by patients at their convenience to improve the adherence. There was no difference in adverse effects of taking BP lowering drugs at night or morning. Evidence on the effect of night-time treatment on CVD events is inconsistent. The results from ongoing trials in Canada will contribute evidence to the use of BP lowering drug treatment for the prevention of CVD
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