830 research outputs found
Stellar abundances and molecular hydrogen in high-redshift galaxies -the far-ultraviolet view
FUSE spectra of star-forming regions in nearby galaxies are compared to
composite spectra of Lyman-break galaxies (LBGs), binned by strength of Lyman
alpha emission and by mid-UV luminosity. Several far-UV spectral features,
including lines dominated by stellar wind and by photospheric components, are
very sensitive to stellar abundances. Their measurement in Lyman-break galaxies
is compromised by the strong interstellar absorption features, allowing in some
cases only upper limits. The derived C and N abundances in the LBGs are no
higher than half solar (scaled to oxygen abundance for comparison with
emission-line analyses), independent of the strength of Lyman alpha emission. P
V absorption indicates abundances as low as 0.1 solar, with an upper limit near
0.4 solar in the reddest and weakest-emission galaxies. Unresolved interstellar
absorption components would further lower the derived abundances. Trends of
line strength, and derived abundances, are stronger with mid-UV luminosity than
with Lyman-alpha strength. H2 absorption in the Lyman and Werner bands is very
weak in the LBGs. Template H2 absorption spectra convolved to appropriate
resolution show that strict upper limits N(H2)< 10^18 cm^-2 apply in all cases,
with more stringent values appropriate for the stronger-emission composites and
for mixes of H2 level populations like those on Milky Way sight lines. Since
the UV-bright regions are likely to be widespread in these galaxies, these
results rule out massive diffuse reservoirs of H2, and suggest that the
dust/gas ratio is already fairly large at z~3.Comment: Astron J., in press (June 2006
Ride Utah! Program Guide
Utah State University Extension has developed a therapeutic equine program called Ride Utah! that targets military personnel and a guest. This guide explains that program and contains an in-depth review of Ride Utah! and includes step by step instructions on how to replicate the program
Safety of the Excimer Laser in LASIK and PRK for Patients with Implantable Cardiac Devices: Our Clinical Experience in the Past Two Decades
This is a Letter to the Editor and does not have an abstrac
A Far-Ultraviolet View of Starburst Galaxies
Recent observational and theoretical results on starburst galaxies related to
the wavelength regime below 1200 A are discussed. The review covers stars,
dust, as well as hot and cold gas. This wavelength region follows trends
similar to those seen at longer wavelengths, with several notable exceptions.
Even the youngest stellar populations show a turn-over in their spectral energy
distributions, and line-blanketing is much more pronounced. Furthermore, the O
VI line allows one to probe gas at higher temperatures than possible with lines
at longer wavelengths. Molecular hydrogen lines (if detected) provide a glimpse
of the cold phase. I cover the crucial wavelength regime below 912 A and the
implications of recent attempts to detect the escaping ionizing radiation.Comment: 8 pages, 3 figures, Invited Talk, Starbursts--From 30 Doradus to
Lyman-Break Galaxies, ed. R. de Grijs & R. M. Gonzalez Delgado (Dordrecht:
Kluwer
Delayed-Onset Transient Light Sensitivity Syndrome after Corneal Collagen Cross-Linking: A Case Series
In this case series, we report a potentially novel association of corneal collagen crosslinking (CCL) with the development of photophobia symptoms in a series of patients at a tertiary ophthalmology clinic and describe their clinical course. Photosensitivity is a rare and seemingly unpredictable complication of refractive surgery but can present as a disabling, bilateral ocular pain that requires immediate treatment. This complication, termed transient light-sensitivity syndrome (TLSS), can have a substantially delayed presentation after ocular procedures and is associated with inflammation of structures in the anterior chamber that can be imperceptible on slit-lamp examination. Traditionally, exposure to high-energy femtosecond lasers is hypothesized to create stromal gas bubbles powering postoperative inflammatory reactions. TLSS-like symptoms after CCL may be due to a secondary inflammatory response involving activated keratocytes and cytokine release. However, free radical damage from the interaction of riboflavin and ultraviolet in CCL may also drive this inflammatory process
Management of dental anxiety via distraction technique
The purpose of this study was to evaluate the use of a stress ball as a distraction technique on stress levels of patients undergoing a dental procedure. A randomized, split-mouth design was conducted using 20 adult subjects requiring scaling and root
Polymerase Chain Reaction and Its Application in the Diagnosis of Infectious Keratitis
PCR involves a repeating cycle of replication to amplify small segments of deoxyribonucleic acid (DNA). A novel application of this technique is microbial identification in infectious keratitis, one of the leading causes of blindness in the world. PCR is more sensitive than biological stains and culture, which are considered the current gold standards for diagnosing infectious keratitis. The diagnosis and treatment of infectious keratitis cost the United States millions of dollars in health expenditure. PCR may help offset that cost by allowing for individualized disease management and screening for multiple antibiotic-resistant genes. While beneficial, PCR demonstrates lower specificity rates compared to culture and stain, indicating its shortcomings; this can be overcome by performing PCR after narrowing the pool of potential microorganisms. This article examines the clinical utility of PCR in cases of infectious keratitis by evaluating its reliability, validity, associated costs, and indications
Spatially Resolved Spitzer-IRS Spectral Maps of the Superwind in M82
We have mapped the superwind/halo region of the nearby starburst galaxy M82
in the mid-infrared with . The spectral regions covered include
the H, [NeII], [NeIII] emission lines and PAH features. We
estimate the total warm H mass and the kinetic energy of the outflowing
warm molecular gas to be between M and
erg. Using the ratios of the 6.2, 7.7 and 11.3
micron PAH features in the IRS spectra, we are able to estimate the average
size and ionization state of the small grains in the superwind. There are large
variations in the PAH flux ratios throughout the outflow. The 11.3/7.7 and the
6.2/7.7 PAH ratios both vary by more than a factor of five across the wind
region. The Northern part of the wind has a significant population of PAH's
with smaller 6.2/7.7 ratios than either the starburst disk or the Southern
wind, indicating that on average, PAH emitters are larger and more ionized. The
warm molecular gas to PAH flux ratios (H) are enhanced in the outflow
by factors of 10-100 as compared to the starburst disk. This enhancement in the
H ratio does not seem to follow the ionization of the atomic gas (as
measured with the [NeIII]/[NeII] line flux ratio) in the outflow. This suggests
that much of the warm H in the outflow is excited by shocks. The observed
H line intensities can be reproduced with low velocity shocks ( km
s) driven into moderately dense molecular gas (
cm) entrained in the outflow.Comment: 19 pages and 12 figures; accepted in MNRA
Feedback in the local LBG Analog Haro 11 as probed by far-UV and X-ray observations
We have re-analyzed FUSE data and obtained new Chandra observations of Haro
11, a local (D_L=88 Mpc) UV luminous galaxy. Haro 11 has a similar far-UV
luminosity (10^10.3 L_\odot), UV surface brightness (10^9.4 L_\odot kpc^-2),
SFR, and metallicity to that observed in Lyman Break Galaxies (LBGs). We show
that Haro 11 has extended, soft thermal (kT~0.68 keV) X-ray emission with a
luminosity and size which scales with the physical properties (e.g. SFR,
stellar mass) of the host galaxy. An enhanced alpha/Fe, ratio of ~4 relative to
solar abundance suggests significant supernovae enrichment. These results are
consistent with the X-ray emission being produced in a shock between a
supernovae driven outflow and the ambient material. The FUV spectra show strong
absorption lines similar to those observed in LBG spectra. A blueshifted
absorption component is identified as a wind outflowing at ~200-280 km/s.
OVI\lambda\lambda1032,1038 emission, the dominant cooling mechanism for coronal
gas at T~10^5.5 K is also observed. If associated with the outflow, the
luminosity of the OVI emission suggests that <20% of the total mechanical
energy from the supernovae and solar winds is being radiated away. This implies
that radiative cooling through OVI is not significantly inhibiting the growth
of the outflowing gas. In contradiction to the findings of Bergvall et al 2006,
we find no convincing evidence of Lyman continuum leakage in Haro 11. We
conclude that the wind has not created a `tunnel' allowing the escape of a
significant fraction of Lyman continuum photons and place a limit on the escape
fraction of f_{esc}<2%. Overall, both Haro 11 and a previously observed LBG
analogue VV 114, provide an invaluable insight into the X-ray and FUV
properties of high redshift LBGs.Comment: Accepted for publication in ApJ, 40 pages, 17 figure
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