3,256 research outputs found
The RMS Survey: Far-Infrared Photometry of Young Massive Stars
Context: The Red MSX Source (RMS) survey is a multi-wavelength campaign of
follow-up observations of a colour-selected sample of candidate massive young
stellar objects (MYSOs) in the galactic plane. This survey is returning the
largest well-selected sample of MYSOs to date, while identifying other dust
contaminant sources with similar mid-infrared colours including a large number
of new ultra-compact (UC)HII regions. Aims:To measure the far-infrared (IR)
flux, which lies near the peak of the spectral energy distribution (SED) of
MYSOs and UCHII regions, so that, together with distance information, the
luminosity of these sources can be obtained. Methods:Less than 50% of RMS
sources are associated with IRAS point sources with detections at 60 micron and
100 micron, though the vast majority are visible in Spitzer MIPSGAL or IRAS
Galaxy Atlas (IGA) images. However, standard aperture photometry is not
appropriate for these data due to crowding of sources and strong spatially
variable far-IR background emission in the galactic plane. A new technique
using a 2-dimensional fit to the background in an annulus around each source is
therefore used to obtain far-IR photometry for young RMS sources.
Results:Far-IR fluxes are obtained for a total of 1113 RMS candidates
identified as young sources. Of these 734 have flux measurements using IGA 60
micron and 100 micron images and 724 using MIPSGAL 70 micron images, with 345
having measurements in both data sets.Comment: 10 pages, 10 figures, 2 Tables, accepted to A&A. A full version of
table 1 is available from the lead author or at the CDS upon publicatio
RECAST: Extending the Impact of Existing Analyses
Searches for new physics by experimental collaborations represent a
significant investment in time and resources. Often these searches are
sensitive to a broader class of models than they were originally designed to
test. We aim to extend the impact of existing searches through a technique we
call 'recasting'. After considering several examples, which illustrate the
issues and subtleties involved, we present RECAST, a framework designed to
facilitate the usage of this technique.Comment: 13 pages, 4 figure
Surface energy and stability of stress-driven discommensurate surface structures
A method is presented to obtain {\it ab initio} upper and lower bounds to
surface energies of stress-driven discommensurate surface structures, possibly
non-periodic or exhibiting very large unit cells. The instability of the
stressed, commensurate parent of the discommensurate structure sets an upper
bound to its surface energy; a lower bound is defined by the surface energy of
an ideally commensurate but laterally strained hypothetical surface system. The
surface energies of the phases of the Si(111):Ga and Ge(111):Ga systems and the
energies of the discommensurations are determined within eV.Comment: 4 pages RevTeX. 2 Figures not included. Ask for a hard copy (through
regular mail) to [email protected]
IR Dust Bubbles: Probing the Detailed Structure and Young Massive Stellar Populations of Galactic HII Regions
We present an analysis of wind-blown, parsec-sized, mid-infrared bubbles and
associated star-formation using GLIMPSE/IRAC, MIPSGAL/MIPS and MAGPIS/VLA
surveys. Three bubbles from the Churchwell et al. (2006) catalog were selected.
The relative distribution of the ionized gas (based on 20 cm emission), PAH
emission (based on 8 um, 5.8 um and lack of 4.5 um emission) and hot dust (24
um emission) are compared. At the center of each bubble there is a region
containing ionized gas and hot dust, surrounded by PAHs. We identify the likely
source(s) of the stellar wind and ionizing flux producing each bubble based
upon SED fitting to numerical hot stellar photosphere models. Candidate YSOs
are also identified using SED fitting, including several sites of possible
triggered star formation.Comment: 37 pages, 17 figure
Long-Lived Neutralino NLSPs
We investigate the collider signatures of heavy, long-lived, neutral
particles that decay to charged particles plus missing energy. Specifically, we
focus on the case of a neutralino NLSP decaying to Z and gravitino within the
context of General Gauge Mediation. We show that a combination of searches
using the inner detector and the muon spectrometer yields a wide range of
potential early LHC discoveries for NLSP lifetimes ranging from 10^(-1)-10^5
mm. We further show that events from Z(l+l-) can be used for detailed kinematic
reconstruction, leading to accurate determinations of the neutralino mass and
lifetime. In particular, we examine the prospects for detailed event study at
ATLAS using the ECAL (making use of its timing and pointing capabilities)
together with the TRT, or using the muon spectrometer alone. Finally, we also
demonstrate that there is a region in parameter space where the Tevatron could
potentially discover new physics in the delayed Z(l+l-)+MET channel. While our
discussion centers on gauge mediation, many of the results apply to any
scenario with a long-lived neutral particle decaying to charged particles.Comment: 31 pages, 12 figure
Embedded Star Formation in the Eagle Nebula with Spitzer/GLIMPSE
We present new Spitzer photometry of the Eagle Nebula (M16, containing the
optical cluster NGC 6611) combined with near-infrared photometry from 2MASS. We
use dust radiative transfer models, mid-infrared and near-infrared color-color
analysis, and mid-infrared spectral indices to analyze point source spectral
energy distributions, select candidate young stellar objects (YSOs), and
constrain their mass and evolutionary state. Comparison of the different
protostellar selection methods shows that mid-infrared methods are consistent,
but as has been known for some time, near-infrared-only analysis misses some
young objects. We reveal more than 400 protostellar candidates, including one
massive young stellar object (YSO) that has not been previously highlighted.
The YSO distribution supports a picture of distributed low-level star
formation, with no strong evidence of triggered star formation in the
``pillars''. We confirm the youth of NGC 6611 by a large fraction of
infrared-excess sources, and reveal a younger cluster of YSOs in the nearby
molecular cloud. Analysis of the YSO clustering properties shows a possible
imprint of the molecular cloud's Jeans length. Multiwavelength mid-IR imaging
thus allows us to analyze the protostellar population, to measure the dust
temperature and column density, and to relate these in a consistent picture of
star formation in M16.Comment: 16p preprint - ApJ accepte
Natural Supersymmetry at the LHC
If the minimal supersymmetric standard model is the solution to the hierarchy
problem, the scalar top quark (stop) and the Higgsino should weigh around the
electroweak scale such as 200 GeV. A low messenger scale, which results in a
light gravitino, is also suggested to suppress the quantum corrections to the
Higgs mass parameters. Therefore the minimal model for natural supersymmetry is
a system with stop/Higgsino/gravitino whereas other superparticles are heavy.
We study the LHC signatures of the minimal system and discuss the discovery
potential and methods for the mass measurements.Comment: 19 pages, 6 figures, 1 tabl
Bandgap properties of two-dimensional low-index photonic crystals
We study the bandgap properties of two-dimensional photonic crystals created
by a lattice of rods or holes conformed in a symmetric or asymmetric triangular
structure. Using the plane-wave analysis, we calculate a minimum value of the
refractive index contrast for opening both partial and full two-dimensional
spectral gaps for both TM and TE polarized waves. We also analyze the effect of
ellipticity of rods and holes and their orientation on the threshold value and
the relative size of the bandgap.Comment: 5 pages, 6 figures, App. Phys. B. styl
Revealing the footprints of squark gluino production through Higgs search experiments at the Large Hadron Collider at 7 TeV and 14 TeV
The invariant mass distribution of the di-photons from the decay of the
lighter scalar Higgs boson(h) to be carefully measured by dedicated h search
experiments at the LHC may be distorted by the di-photons associated with the
squark-gluino events with much larger cross sections in Gauge Mediated
Supersymmetry Breaking (GMSB) models. This distortion if observed by the
experiments at the Large Hadron Collider at 7 TeV or 14 TeV, would disfavour
not only the standard model but various two Higgs doublet models with
comparable h - masses and couplings but without a sector consisting of new
heavy particles decaying into photons. The minimal GMSB (mGMSB) model
constrained by the mass bound on h from LEP and that on the lightest neutralino
from the Tevatron, produce negligible effects. But in the currently popular
general GMSB(GGMSB) models the tail of the above distribution may show
statistically significant excess of events even in the early stages of the LHC
experiments with integrated luminosity insufficient for the discovery of h. We
illustrate the above points by introducing several benchmark points in various
GMSB models - minimal as well as non-minimal. The same conclusion follows from
a detailed parameter scan in a simplified GGMSB model recently employed by the
CMS collaboration to interpret their searches in the di-photon + \etslash
channel. Other observables like the effective mass distribution of the
di-photon + X events may also reveal the presence of new heavy particles beyond
the Higgs sector. The contamination of the h mass peak and simple remedies are
also discussed.Comment: 23 pages, 7 figures, title and organization of the paper is changed,
detailed parameter scan in a simplified GGMSB model is added, conclusions and
old numerical results remain unchange
Feasibility of Conducting a Web-Based Survey of Patient-Reported Outcomes and Rehabilitation Progress
Background: Web-based surveys provide an efficient means to track clinical outcomes over time without the use of clinician time for additional paperwork. Our purpose was to determine the feasibility of utilizing web-based surveys to capture rehabilitation compliance and clinical outcomes among postoperative orthopedic patients. The study hypotheses were that (a) recruitment rate would be high (\u3e 90%), (b) patients receiving surveys every two weeks would demonstrate higher response rates than patients that receive surveys every four weeks, and (c) response rates would decrease over time.
Methods: The study design involved a longitudinal cohort. Surgical knee patients were recruited for study participation during their first post-operative visit (n = 59, 34.9 ± 12.0 years of age). Patients with Internet access, an available email address and willingness to participate were counter-balanced into groups to receive surveys either every two or four weeks for 24 weeks post-surgery. The surveys included questions related to rehabilitation and questions from standard patient-reported outcome measures. Outcome measures included recruitment rate (participants consented/patients approached), eligibility (participants with email/participants consented), willingness (willing participants/participants eligible), and response rate (percentage of surveys completed by willing participants).
Results: Fifty-nine patients were approached regarding participation. Recruitment rate was 98% (n = 58). Eligibility was 95% (n = 55), and willingness was 91% (n = 50). The average response rate was 42% across both groups. There was no difference in the median response rates between the two-week (50%, range 0–100%) and four-week groups (33%, range 0–100%; p = 0.55).
Conclusions: Although patients report being willing and able to participate in a web-based survey, response rates failed to exceed 50% in both the two-week and four-week groups. Furthermore, response rates began to decrease after the first three months postoperatively. Therefore, supplementary data collection procedures may be necessary to meet established research quality standards
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