3,674 research outputs found
Improving the Sensitivity of Advanced LIGO Using Noise Subtraction
This paper presents an adaptable, parallelizable method for subtracting
linearly coupled noise from Advanced LIGO data. We explain the features
developed to ensure that the process is robust enough to handle the variability
present in Advanced LIGO data. In this work, we target subtraction of noise due
to beam jitter, detector calibration lines, and mains power lines. We
demonstrate noise subtraction over the entirety of the second observing run,
resulting in increases in sensitivity comparable to those reported in previous
targeted efforts. Over the course of the second observing run, we see a 30%
increase in Advanced LIGO sensitivity to gravitational waves from a broad range
of compact binary systems. We expect the use of this method to result in a
higher rate of detected gravitational-wave signals in Advanced LIGO data.Comment: 15 pages, 6 figure
The Issues of Mismodelling Gravitational-Wave Data for Parameter Estimation
Bayesian inference is used to extract unknown parameters from gravitational
wave signals. Detector noise is typically modelled as stationary, although data
from the LIGO and Virgo detectors is not stationary. We demonstrate that the
posterior of estimated waveform parameters is no longer valid under the
assumption of stationarity. We show that while the posterior is unbiased, the
errors will be under- or overestimated compared to the true posterior. A
formalism was developed to measure the effect of the mismodelling, and found
the effect of any form of non-stationarity has an effect on the results, but
are not significant in certain circumstances. We demonstrate the effect of
short-duration Gaussian noise bursts and persistent oscillatory modulation of
the noise on binary-black-hole-like signals. In the case of short signals,
non-stationarity in the data does not have a large effect on the parameter
estimation, but the errors from non-stationary data containing signals lasting
tens of seconds or longer will be several times worse than if the noise was
stationary. Accounting for this limiting factor in parameter sensitivity could
be very important for achieving accurate astronomical results, including an
estimation of the Hubble parameter. This methodology for handling the
non-stationarity will also be invaluable for analysis of waveforms that last
minutes or longer, such as those we expect to see with the Einstein Telescope.Comment: 15 pages, 5 figures. Comments welcom
Molecular depletion times and the CO-to-H2 conversion factor in metal-poor galaxies
Tracing molecular hydrogen content with carbon monoxide in low-metallicity
galaxies has been exceedingly difficult. Here we present a new effort, with
IRAM 30-m observations of 12CO(1-0) of a sample of 8 dwarf galaxies having
oxygen abundances ranging from 12+logO/H=7.7 to 8.4. CO emission is detected in
all galaxies, including the most metal-poor galaxy of our sample (0.1 Zsun); to
our knowledge this is the largest number of 12CO(1-0) detections ever reported
for galaxies with 12+logO/H<=8 (0.2 Zsun) outside the Local Group. We calculate
stellar masses (Mstar) and star-formation rates (SFRs), and analyze our results
by combining our observations with galaxy samples from the literature.
Extending previous results for a correlation of the molecular gas depletion
time, tau(dep), with Mstar and specific SFR (sSFR), we find a variation in
tau(dep) of a factor of 200 or more (from <50 Myr to 10 Gyr) over a spread of
1000 in sSFR and Mstar. We exploit the variation of tau(dep) to constrain the
CO-to-H2 mass conversion factor alpha(CO) at low metallicity, and assuming a
power-law variation find alpha(CO) \propto (Z/Zsun)^1.9, similar to results
based on dust continuum measurements compared with gas mass. By including HI
measurements, we show that the fraction of total gas mass relative to the
baryonic mass is higher in galaxies that are metal poor, of low mass, and of
high sSFR. Finally, comparisons of the data with star-formation models of the
molecular gas phases suggest that, at metallicities Z/Zsun<=0.2, there are some
discrepancies with model predictions.Comment: 18 pages, 15 figures, accepted for publication in A&
Transcript expression of vesicular glutamate transporters in lumbar dorsal root ganglia and the spinal cord of mice – Effects of peripheral axotomy or hindpaw inflammation
Using specific riboprobes, we characterized the expression of vesicular glutamate transporter (VGLUT)1–VGLUT3 transcripts in lumbar 4–5 (L4–5) dorsal root ganglions (DRGs) and the thoracolumbar to lumbosacral spinal cord in male BALB/c mice after a 1- or 3-day hindpaw inflammation, or a 7-day sciatic nerve axotomy. Sham animals were also included. In sham and contralateral L4–5 DRGs of injured mice, VGLUT1-, VGLUT2- and VGLUT3 mRNAs were expressed in ∼45%, ∼69% or ∼17% of neuron profiles (NPs), respectively. VGLUT1 was expressed in large and medium-sized NPs, VGLUT2 in NPs of all sizes, and VGLUT3 in small and medium-sized NPs. In the spinal cord, VGLUT1 was restricted to a number of NPs at thoracolumbar and lumbar segments, in what appears to be the dorsal nucleus of Clarke, and in mid laminae III–IV. In contrast, VGLUT2 was present in numerous NPs at all analyzed spinal segments, except the lateral aspects of the ventral horns, especially at the lumbar enlargement, where it was virtually absent. VGLUT3 was detected in a discrete number of NPs in laminae III–IV of the dorsal horn. Axotomy resulted in a moderate decrease in the number of DRG NPs expressing VGLUT3, whereas VGLUT1 and VGLUT2 were unaffected. Likewise, the percentage of NPs expressing VGLUT transcripts remained unaltered after hindpaw inflammation, both in DRGs and the spinal cord. Altogether, these results confirm previous descriptions on VGLUTs expression in adult mice DRGs, with the exception of VGLUT1, whose protein expression was detected in a lower percentage of mouse DRG NPs. A detailed account on the location of neurons expressing VGLUTs transcripts in the adult mouse spinal cord is also presented. Finally, the lack of change in the number of neurons expressing VGLUT1 and VGLUT2 transcripts after axotomy, as compared to data on protein expression, suggests translational rather than transcriptional regulation of VGLUTs after injury.Fil: Malet, Mariana. Universidad Austral. Facultad de Ciencias Biomédicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vieytes, C. A.. Universidad Austral. Facultad de Ciencias Biomédicas; ArgentinaFil: Lundgren, K. H.. University of Cincinnati; Estados UnidosFil: Seal, R. P.. University of Pittsburgh; Estados UnidosFil: Tomasella, María Eugenia. Universidad Austral. Facultad de Ciencias Biomédicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Seroogy, K. B.. University of Cincinnati; Estados UnidosFil: Hökfelt, T.. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Gebhart, G. F.. University of Pittsburgh; Estados UnidosFil: Brumovsky, Pablo Rodolfo. Universidad Austral. Facultad de Ciencias Biomédicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. University of Pittsburgh; Estados Unido
Relaxation of the field-cooled magnetization of an Ising spin glass
The time and temperature dependence of the field-cooled magnetization of a
three dimensional Ising spin glass, Fe_{0.5}Mn_{0.5}TiO_{3}, has been
investigated. The temperature and cooling rate dependence is found to exhibit
memory phenomena that can be related to the memory behavior of the low
frequency ac-susceptibility. The results add some further understanding on how
to model the three dimensional Ising spin glass in real space.Comment: 8 pages RevTEX, 5 figure
Simulation of CCN distributions on the regional scale and their impact on clouds and warm precipitation
Kinetic hindrance during the initial oxidation of Pd(100) at ambient pressures
The oxidation of the Pd(100) surface at oxygen pressures in the 10^-6 to 10^3
mbar range and temperatures up to 1000 K has been studied in-situ by surface
x-ray diffraction (SXRD). The results provide direct structural information on
the phases present in the surface region and on the kinetics of the oxide
formation. Depending on the (T,p) environmental conditions we either observe a
thin sqrt(5) x sqrt(5) R27 surface oxide or the growth of a rough, poorly
ordered bulk oxide film of PdO predominantly with (001) orientation. By either
comparison to the surface phase diagram from first-principles atomistic
thermodynamics or by explicit time-resolved measurements we identify a strong
kinetic hindrance to the bulk oxide formation even at temperatures as high as
675 K.Comment: 4 pages including 4 figures, Related publications can be found at
http://www.fhi-berlin.mpg.de/th/paper.htm
Spatially Extended Low Ionization Emission Regions (LIERs) at
We present spatially resolved emission diagnostics for eight
galaxies that demonstrate extended low ionization emission-line regions (LIERs)
over kpc scales. Eight candidates are selected based on their spatial extent
and emission line fluxes from slitless spectroscopic observations with the
HST/WFC3 G141 and G800L grisms in the well-studied GOODS survey fields. Five of
the candidates (62.5%) are matched to X-ray counterparts in the \textit{Chandra
X-Ray Observatory} Deep Fields. We modify the traditional
Baldwin-Philips-Terlevich (BPT) emission line diagnostic diagram to use
[SII]/(H+[NII]) instead of [NII]/H to overcome the blending of
[NII] and H+[NII] in the low resolution slitless grism spectra. We
construct emission line ratio maps and place the individual pixels in the
modified BPT. The extended LINER-like emission present in all of our
candidates, coupled with X-Ray properties consistent with star-forming galaxies
and weak [OIII]5007\AA\ detections, is inconsistent with purely
nuclear sources (LINERs) driven by active galactic nuclei. While recent
ground-based integral field unit spectroscopic surveys have revealed
significant evidence for diffuse LINER-like emission in galaxies within the
local universe , this work provides the first evidence for the
non-AGN origin of LINER-like emission out to high redshifts.Comment: 11 pages, 1 table, 6 figures, accepted for publication in the
Astrophysics Journal (ApJ
Dense Cloud Formation and Star Formation in a Barred Galaxy
We investigate the properties of massive, dense clouds formed in a barred
galaxy and their possible relation to star formation, performing a
two-dimensional hydrodynamical simulation with the gravitational potential
obtained from the 2Mass data from the barred spiral galaxy, M83. Since the
environment for cloud formation and evolution in the bar region is expected to
be different from that in the spiral arm region, barred galaxies are a good
target to study the environmental effects on cloud formation and the subsequent
star formation. Our simulation uses for an initial 80 Myr an isothermal flow of
non-self gravitating gas in the barred potential, then including radiative
cooling, heating and self-gravitation of the gas for the next 40 Myr, during
which dense clumps are formed. We identify many cold, dense gas clumps for
which the mass is more than (a value corresponding to the
molecular clouds) and study the physical properties of these clumps. The
relation of the velocity dispersion of the identified clump's internal motion
with the clump size is similar to that observed in the molecular clouds of our
Galaxy. We find that the virial parameters for clumps in the bar region are
larger than that in the spiral arm region. From our numerical results, we
estimate star formation in the bar and spiral arm regions by applying the
simple model of Krumholtz and McKee (2005). The mean relation between star
formation rate and gas surface density agrees well with the observed
Kennicutt-Schmidt relation. The SFE in the bar region is of the
spiral arm region. This trend is consistent with observations of barred
galaxies.Comment: 9 pages, 16 figures. Accepted for publication in the MNRA
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