3,627 research outputs found
The Small Magellanic Cloud Investigation of Dust and Gas Evolution (SMIDGE): The Dust Extinction Curve from Red Clump Stars
We use Hubble Space Telescope (HST) observations of red clump stars taken as
part of the Small Magellanic Cloud Investigation of Dust and Gas Evolution
(SMIDGE) program to measure the average dust extinction curve in a ~ 200 pc x
100 pc region in the southwest bar of the Small Magellanic Cloud (SMC). The
rich information provided by our 8-band ultra-violet through near-infrared
photometry allows us to model the color-magnitude diagram of the red clump
accounting for the extinction curve shape, a log-normal distribution of
, and the depth of the stellar distribution along the line of sight. We
measure an extinction curve with = 2.65
0.11. This measurement is significantly larger than the equivalent values
of published Milky Way = 3.1 () and SMC Bar =
2.74 () extinction curves. Similar extinction curve offsets in
the Large Magellanic Cloud (LMC) have been interpreted as the effect of large
dust grains. We demonstrate that the line-of-sight depth of the SMC (and LMC)
introduces an apparent "gray" contribution to the extinction curve inferred
from the morphology of the red clump. We show that no gray dust component is
needed to explain extinction curve measurements when a full-width half-max
depth of 10 2 kpc in the stellar distribution of the SMC (5 1 kpc
for the LMC) is considered, which agrees with recent studies of Magellanic
Cloud stellar structure. The results of our work demonstrate the power of
broad-band HST imaging for simultaneously constraining dust and galactic
structure outside the Milky Way.Comment: 16 pages, 12 figures, 5 tables. Accepted for publication in Ap
Continuous infusion of an agonist of the tumor necrosis factor receptor 2 in the spinal cord improves recovery after traumatic contusive injury.
AimThe activation of the TNFR2 receptor is beneficial in several pathologies of the central nervous system, and this study examines whether it can ameliorate the recovery process following spinal cord injury.MethodsEHD2-sc-mTNFR2 , an agonist specific for TNFR2, was used to treat neurons exposed to high levels of glutamate in vitro. In vivo, it was infused directly to the spinal cord via osmotic pumps immediately after a contusion to the cord at the T9 level. Locomotion behavior was assessed for 6Â weeks, and the tissue was analyzed (lesion size, RNA and protein expression, cell death) after injury. Somatosensory evoked potentials were also measured in response to hindlimb stimulation.ResultsThe activation of TNFR2 protected neurons from glutamate-mediated excitotoxicity through the activation of phosphoinositide-3 kinase gamma in vitro and improved the locomotion of animals following spinal cord injury. The extent of the injury was not affected by infusing EHD2-sc-mTNFR2 , but higher levels of neurofilament H and 2', 3'-cyclic-nucleotide 3'-phosphodiesterase were observed 6Â weeks after the injury. Finally, the activation of TNFR2 after injury increased the neural response recorded in the cortex following hindlimb stimulation.ConclusionThe activation of TNFR2 in the spinal cord following contusive injury leads to enhanced locomotion and better cortical responses to hindlimb stimulation
Star formation towards the Scutum tangent region and the effects of Galactic environment
By positional matching to the catalogue of Galactic Ring Survey molecular
clouds, we have derived distances to 793 Bolocam Galactic Plane Survey (BGPS)
sources out of a possible 806 located within the region defined by Galactic
longitudes l = 28.5 degr to 31.5 degr and latitudes |b| < 1 degr. This section
of the Galactic Plane contains several major features of Galactic structure at
different distances, mainly mid-arm sections of the Perseus and Sagittarius
spiral arms and the tangent of the Scutum-Centarus arm, which is coincident
with the end of the Galactic Long Bar. By utilising the catalogued cloud
distances plus new kinematic distance determinations, we are able to separate
the dense BGPS clumps into these three main line-of-sight components to look
for variations in star-formation properties that might be related to the
different Galactic environments. We find no evidence of any difference in
either the clump mass function or the average clump formation efficiency (CFE)
between these components that might be attributed to environmental effects on
scales comparable to Galactic-structure features.
Despite having a very high star-formation rate, and containing at least one
cloud with a very high CFE, the star formation associated with the
Scutum-Centarus tangent does not appear to be in any way abnormal or different
to that in the other two spiral-arm sections. Large variations in the CFE are
found on the scale of individual clouds, however, which may be due to local
triggering agents as opposed to the large-scale Galactic structure.Comment: 11 pages, 8 figures. Accepted for publication in the Monthly Notices
of the Royal Astronomical Societ
The Value of In Vivo Reflectance Confocal Microscopy as an Assessment Tool in Chemotherapy-Induced Peripheral Neuropathy:A Pilot Study
Chemotherapy-induced peripheral neuropathy (CIPN) is a common dose-limiting toxicity with significant sequelae. There is a lack of standardized objective and reliable assessment tools in CIPN. In vivo reflectance confocal microscopy (RCM) imaging offers a non-invasive method to identify peripheral neuropathy markers, namely Meissner's corpuscles. This article reports on the feasibility and value of RCM in CIPN.Background There is a lack of standardized objective and reliable assessment tools for chemotherapy-induced peripheral neuropathy (CIPN). In vivo reflectance confocal microscopy (RCM) imaging offers a non-invasive method to identify peripheral neuropathy markers, namely Meissner's corpuscles (MC). This study investigated the feasibility and value of RCM in CIPN. Patients and Methods Reflectance confocal microscopy was performed on the fingertip to evaluate MC density in 45 healthy controls and 9 patients with cancer (prior, during, and post-chemotherapy). Quantification was completed by 2 reviewers (one blinded), with maximum MC count/3 x 3 mm image reported. Quantitative Sensory Testing (QST; thermal and mechanical detection thresholds), Grooved pegboard test, and patient-reported outcomes measures (PROMS) were conducted for comparison. Results In controls (25 females, 20 males; 24-81 years), females exhibited greater mean MC density compared with males (49.9 +/- 7.1 vs 30.9 +/- 4.2 MC/3 x 3 mm; P = .03). Differences existed across age by decade (P < .0001). Meissner's corpuscle density was correlated with mechanical detection (rho = -0.51), warm detection (rho = -0.47), cold pain (rho = 0.49) thresholds (P < .01); and completion time on the Grooved pegboard test in both hands (P <= .02). At baseline, patients had reduced MC density vs age and gender-matched controls (P = .03). Longitudinal assessment of MC density revealed significant relationships with QST and PROMS. Inter-rater reliability of MC count showed an intraclass correlation of 0.96 (P < .0001). Conclusions The findings support the clinical utility of RCM in CIPN as it provides meaningful markers of sensory nerve dysfunction. Novel, prospective assessment demonstrated the ability to detect subclinical deficits in patients at risk of CIPN and potential to monitor neuropathy progression
PHAT Stellar Cluster Survey I. Year 1 Catalog and Integrated Photometry
The Panchromatic Hubble Andromeda Treasury (PHAT) survey is an on-going
Hubble Space Telescope (HST) multi-cycle program to obtain high spatial
resolution imaging of one-third of the M31 disk at ultraviolet through
near-infrared wavelengths. In this paper, we present the first installment of
the PHAT stellar cluster catalog. When completed, the PHAT cluster catalog will
be among the largest and most comprehensive surveys of resolved star clusters
in any galaxy. The exquisite spatial resolution achieved with HST has allowed
us to identify hundreds of new clusters that were previously inaccessible with
existing ground-based surveys. We identify 601 clusters in the Year 1 sample,
representing more than a factor of four increase over previous catalogs within
the current survey area (390 arcmin^2). This work presents results derived from
the first \sim25% of the survey data; we estimate that the final sample will
include \sim2500 clusters. For the Year 1 objects, we present a catalog with
positions, radii, and six-band integrated photometry. Along with a general
characterization of the cluster luminosities and colors, we discuss the cluster
luminosity function, the cluster size distributions, and highlight a number of
individually interesting clusters found in the Year 1 search.Comment: 26 pages, 22 figures, Accepted by Ap
Stratified dispersal and increasing genetic variation during the invasion of Central Europe by the western corn rootworm, Diabrotica virgifera virgifera
Invasive species provide opportunities for investigating evolutionary aspects of colonization processes, including initial foundations of populations and geographic expansion. Using microsatellite markers and historical information, we characterized the genetic patterns of the invasion of the western corn rootworm (WCR), a pest of corn crops, in its largest area of expansion in Europe: Central and South-Eastern (CSE) Europe. We found that the invaded area probably corresponds to a single expanding population resulting from a single introduction of WCR and that gene flow is geographically limited within the population. In contrast to what is expected in classical colonization processes, an increase in genetic variation was observed from the center to the edge of the outbreak. Control measures against WCR at the center of the outbreak may have decreased effective population size in this area which could explain this observed pattern of genetic variation. We also found that small remote outbreaks in southern Germany and north-eastern Italy most likely originated from long-distance dispersal events from CSE Europe. We conclude that the large European outbreak is expanding by stratified dispersal, involving both continuous diffusion and discontinuous long-distance dispersal. This latter mode of dispersal may accelerate the expansion of WCR in Europe in the future
Genetic Variants in Arhgef11 Are Associated With Kidney Injury in the Dahl Salt-Sensitive Rat
A previous genetic analysis comparing the Dahl salt-sensitive (S) rat to the spontaneously hypertensive rat (SHR) identified a major locus on chromosome 2 that influences proteinuria in the S rat. In the present study, blood pressure, proteinuria, and renal hemodynamics were evaluated in congenic strains with small segments of the protective SHR genome on the S background. Proteinuria and renal function were significantly improved in the congenic strains compared to the S. The causative locus interval was narrowed to Arhgef11, Pear1, and Sh2d2 were identified as important candidate genes that may be linked to kidney injury in the S rat. In particular, Arhgef11 plays an important role in the activation of the Rho-ROCK signaling pathway. Inhibition of this pathway using fasudil resulted in a significant reduction of proteinuria in treated S rats (compared to untreated S). However, no difference was observed between treated or untreated SHR or congenic strains. The homologous region in humans was found to be associated with estimated glomerular filtration rate (eGFR) in the Candidate Gene Association Resource (CARe) population. In summary, these findings demonstrate that allelic variants in Arhgef11, acting through the Rho-ROCK pathway, could influence kidney injury in the S as well as provide insight into human kidney disease
The Global Evolution of Giant Molecular Clouds II: The Role of Accretion
We present virial models for the global evolution of giant molecular clouds.
Focusing on the presence of an accretion flow, and accounting for the amount of
mass, momentum, and energy supplied by accretion and star formation feedback,
we are able to follow the growth, evolution, and dispersal of individual giant
molecular clouds. Our model clouds reproduce the scaling relations observed in
both galactic and extragalactic clouds. We find that accretion and star
formation contribute contribute roughly equal amounts of turbulent kinetic
energy over the lifetime of the cloud. Clouds attain virial equilibrium and
grow in such a way as to maintain roughly constant surface densities, with
typical surface densities of order 50 - 200 Msun pc^-2, in good agreement with
observations of giant molecular clouds in the Milky Way and nearby external
galaxies. We find that as clouds grow, their velocity dispersion and radius
must also increase, implying that the linewidth-size relation constitutes an
age sequence. Lastly, we compare our models to observations of giant molecular
clouds and associated young star clusters in the LMC and find good agreement
between our model clouds and the observed relationship between H ii regions,
young star clusters, and giant molecular clouds.Comment: 23 Pages, 9 Figures. Accepted to Ap
The RMS Survey: Distribution and properties of a sample of massive young stars
The Red MSX Source (RMS) survey has identified a large sample of massive
young stellar objects (MYSOs) and ultra compact (UC) HII regions from a sample
of ~2000 MSX and 2MASS colour selected sources. Using a recent catalogue of
molecular clouds derived from the Boston University-Five College Radio
Astronomy Observatory Galactic Ring Survey (GRS), and by applying a Galactic
scaleheight cut off of 120 pc, we solve the distance ambiguity for RMS sources
located within 18\degr 54\degr. These two steps yield kinematic
distances to 291 sources out of a possible 326 located within the GRS longitude
range. Combining distances and integrated fluxes derived from spectral energy
distributions, we estimate luminosities to these sources and find that > 90%
are indicative of the presence of a massive star. We find the completeness
limit of our sample is ~10^4 Lsun, which corresponds to a zero age main
sequence (ZAMS) star with a mass of ~12 Msun. Selecting only these sources, we
construct a complete sample of 196 sources. Comparing the properties of the
sample of young massive stars with the general population, we find the
RMS-clouds are generally larger, more massive, and more turbulent. We examine
the distribution of this sub-sample with respect to the location of the spiral
arms and the Galactic bar and find them to be spatially correlated. We identify
three significant peaks in the source surface density at Galactocentric radii
of approximately 4, 6 and 8 kpc, which correspond to the proposed positions of
the Scutum, Sagittarius and Perseus spiral arms, respectively. Fitting a scale
height to the data we obtain an average value of ~29+-0.5 pc, which agrees well
with other reported values in the literature, however, we note a dependence of
the scale height on galactocentric radius with it increases from 30 pc to 45 pc
between 2.5 and 8.5 kpc.Comment: Accepted for publication by MNRAS. Paper consists of 15 pages
including 12 figures and four tables. Full versions of Tables 2 and 3 will
only be available online. The resolution of Figure 9 has been reduced - a
full resolution version of the paper can be download from here:
http://www.ast.leeds.ac.uk/cgi-bin/RMS/RMS_PUBLICATIONS.cg
The BLAST View of the Star Forming Region in Aquila (ell=45deg,b=0deg)
We have carried out the first general submillimeter analysis of the field
towards GRSMC 45.46+0.05, a massive star forming region in Aquila. The
deconvolved 6 deg^2 (3\degree X 2\degree) maps provided by BLAST in 2005 at
250, 350, and 500 micron were used to perform a preliminary characterization of
the clump population previously investigated in the infrared, radio, and
molecular maps. Interferometric CORNISH data at 4.8 GHz have also been used to
characterize the Ultracompact HII regions (UCHIIRs) within the main clumps. By
means of the BLAST maps we have produced an initial census of the submillimeter
structures that will be observed by Herschel, several of which are known
Infrared Dark Clouds (IRDCs). Our spectral energy distributions of the main
clumps in the field, located at ~7 kpc, reveal an active population with
temperatures of T~35-40 K and masses of ~10^3 Msun for a dust emissivity index
beta=1.5. The clump evolutionary stages range from evolved sources, with
extended HII regions and prominent IR stellar population, to massive young
stellar objects, prior to the formation of an UCHIIR.The CORNISH data have
revealed the details of the stellar content and structure of the UCHIIRs. In
most cases, the ionizing stars corresponding to the brightest radio detections
are capable of accounting for the clump bolometric luminosity, in most cases
powered by embedded OB stellar clusters
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