121 research outputs found
The brightest OH maser in the sky: a flare of emission in W75 N
A flare of maser radio emission in the OH-line 1665 MHz has been discovered
in the star forming region W75 N in 2003, with the flux density of about 1000
Jy. At the time it was the strongest OH maser detected during the whole history
of observations since the discovery of cosmic masers in 1965. The flare
emission is linearly polarized with a degree of polarization near 100%. A
weaker flare with a flux of 145 Jy was observed in this source in 2000 - 2001,
which was probably a precursor of the powerful flare. Intensity of two other
spectral features has decreased after beginning of the flare. Such variation of
the intensity of maser condensation emission (increasing of one and decreasing
of the other) can be explained by passing of the magneto hydrodynamic shock
across regions of enhanced gas concentration.Comment: 9 pages with 2 figures, accepted for publication in Astronomy Letter
Clustered Star Formation in W75 N
We present 2" to 7" resolution 3 mm continuum and CO(J=1-0) line emission and
near infrared Ks, H2, and [FeII] images toward the massive star forming region
W75 N. The CO emission uncovers a complex morphology of multiple, overlapping
outflows. A total flow mass of greater than 255 Msun extends 3 pc from
end-to-end and is being driven by at least four late to early-B protostars.
More than 10% of the molecular cloud has been accelerated to high velocities by
the molecular flows (> 5.2 km/s relative to v{LSR}) and the mechanical energy
in the outflowing gas is roughly half the gravitational binding energy of the
cloud. The W75 N cluster members represent a range of evolutionary stages, from
stars with no apparent circumstellar material to deeply embedded protostars
that are actively powering massive outflows. Nine cores of
millimeter-wavelength emission highlight the locations of embedded protostars
in W75 N. The total mass of gas & dust associated with the millimeter cores
ranges from 340 Msun to 11 Msun. The infrared reflection nebula and shocked H2
emission have multiple peaks and extensions which, again, suggests the presence
of several outflows. Diffuse H2 emission extends about 0.6 parsecs beyond the
outer boundaries of the CO emission while the [FeII] emission is only detected
close to the protostars. The infrared line emission morphology suggests that
only slow, non-dissociative J-type shocks exist throughout the pc-scale
outflows. Fast, dissociative shocks, common in jet-driven low-mass outflows,
are absent in W75 N. Thus, the energetics of the outflows from the late to
early B protostars in W75 N differ from their low-mass counterparts -- they do
not appear to be simply scaled-up versions of low-mass outflows.Comment: Astrophysical Journal, in press. 23 pages plus 10 figures (jpg
format). See http://www.aoc.nrao.edu/~dshepher/science.shtml for reprint with
full resolution figure
Total linear polarization in the OH maser W75N: VLBA polarization structure
W75N is a star-forming region containing various ultracompact HII regions and
OH, water, and methanol maser emission. Our VLBA map shows that the OH masers
are located in a thin disk rotating around an O-star which is the exciting star
of the ultracompact HII region VLA1. A separate set of maser spots is connected
with the ultracompact HII region VLA2. The radial velocity of OH maser spots
varies across the disk from 3.7 km/s to 10.9 km/s. The diameter of the disk is
4000 A.U. All maser spots are strongly polarized. This are the first OH masers
showing nearly 100 per cent linear polarization in several spots. Two maser
spots seem to be Zeeman pairs corresponding to a magnetic field of 5.2 mgauss
and 7.7 mgauss, and in one case we tentatively found a Zeeman pair consisting
of two linearly polarized components. The linearly polarized maser spots are
shown to be sigma-components which is the case of the magnetic field being
perpendicular to the line of sight. The direction of the magnetic field as
determined from linearly polarized spots is perpendicular to the plane of the
disk, although the galactic Faraday rotation may significantly affect this
conclusion.Comment: 14 figures, 1 table, 27 pages. accepted for publication in ApJ,
scheduled for v.564, N1, 200
Identifying Biomarkers in Lymph Node Metastases of Esophageal Adenocarcinoma for Tumor-Targeted Imaging
INTRODUCTION: Tumor-targeted imaging is a promising technique for the detection of lymph node metastases (LNM) and primary tumors. It remains unclear which biomarker is the most suitable target to distinguish malignant from healthy tissue in esophageal adenocarcinoma (EAC). OBJECTIVE: We performed an immunohistochemistry study to identify viable tumor markers for tumor-targeted imaging of EAC. METHODS: We used samples from 72 patients with EAC to determine the immunohistochemical expression of ten potential tumor biomarkers for EAC (carbonic anhydrase IX [CA-IX], carcinoembryonic antigen [CEA], hepatic growth factor receptor, epidermal growth factor receptor, epithelial membrane antigen [EMA], epithelial cell adhesion molecule [EpCAM], human epidermal growth factor receptor 2 [HER-2], urokinase plasminogen activator receptor, vascular endothelial growth factor-A [VEGF-A], and VEGF receptor 2). Immunohistochemistry was performed on tissue microarrays of LNM (n = 48), primary EACs (n = 62), fibrotic tissues (n = 11), nonmalignant lymph nodes (n = 24), and normal esophageal and gastric tissues (n = 40). Tumor marker staining was scored on intensity and percentage of positive cells. RESULTS: EMA and EpCAM showed strong expression in LNM (> 95%) and primary EACs (> 95%). Significant expression was also observed for LNM and EAC using VEGF-A (85 and 92%), CEA (68 and 54%), and CA-IX (4 and 34%). The other tumor biomarkers showed expression of 0-15% for LNM and primary EAC. Except for VEGF-A, nonmalignant lymph node staining was scored as slight or absent. CONCLUSIONS: High expression rates and correlation between LNM in EAC combined with low expression rates in healthy lymph nodes and esophagus tissues were observed for EpCAM and CEA, meaning these are promising targets for tumor-targeted imaging approaches for lymph nodes in patients with EAC
Observations of Massive Star Forming Regions with Water Masers: Mid-Infrared Imaging
We present here a mid-infrared imaging survey of 26 sites of water maser
emission. Observations were obtained at the InfraRed Telescope Facility 3-m
telescope with the University of Florida mid-infrared imager/spectrometer
OSCIR, and the JPL mid-infrared camera MIRLIN. The main purpose of the survey
was to explore the relationship between water masers and the massive star
formation process. It is generally believed that water masers predominantly
trace outflows and embedded massive stellar objects, but may also exist in
circumstellar disks around young stars. We investigate each of these
possibilities in light of our mid-infrared imaging. We find that mid-infrared
emission seems to be more closely associated with water and OH maser emission
than cm radio continuum emission from UC HII regions. We also find from the
sample of sources in our survey that, like groups of methanol masers, both
water and OH masers have a proclivity for grouping into linear or elongated
distributions. We conclude that the vast majority of linearly distributed
masers are not tracing circumstellar disks, but outflows and shocks instead.Comment: 49 pages; 23 figures; To appear in February 2005 ApJS; To download a
version with better quality figures, go to
http://www.ctio.noao.edu/~debuizer
Meiotic arrest occurs most frequently at metaphase and is often incomplete in azoospermic men
Objective: To establish which meiotic checkpoints are activated in males with severe spermatogenic impairment to improve phenotypic characterization of meiotic defects. Design: Retrospective observational study. Setting: University medical center research laboratory and andrology clinic. Patient(s): Forty-eight patients with confirmed spermatogenic impairment (Johnsen scores 3–6) and 15 controls (Johnsen score 10). Intervention(s): None. Main Outcome Measure(s): Quantitative assessment of immunofluorescent analyses of specific markers to determine meiotic entry, chromosome pairing, progression of DNA double-strand break repair, crossover formation, formation of meiotic metaphases, metaphase arrest, and spermatid formation, resulting in a novel classification of human meiotic arrest types. Result(s): Complete metaphase arrest was observed most frequently (27%), and the patients with the highest frequency of apoptotic metaphases also displayed a reduction in crossover number. Incomplete metaphase arrest was observed in 17% of the patients. Only four patients (8%) displayed a failure to complete meiotic chromosome pairin
Full-Polarization Observations of OH Masers in Massive Star-Forming Regions: II. Maser Properties and the Interpretation of Polarization
We analyze full-polarization VLBA data of ground-state, main-line OH masers
in 18 massive star-forming regions previously presented in a companion paper.
The OH masers often arise in the shocked neutral gas surrounding ultracompact
Hii regions. Magnetic fields as deduced from OH maser Zeeman splitting are
highly ordered, both on the scale of a source as well as the maser clustering
scale of ~10^15 cm. Results from our large sample show that this clustering
scale appears to be universal to these masers. OH masers around ultracompact
Hii regions live ~10^4 years and then turn off abruptly, rather than weakening
gradually with time. These masers have a wide range of polarization properties.
At one extreme (e.g., W75 N), pi-components are detected and the polarization
position angles of maser spots show some organization. At the other extreme
(e.g., W51 e1/e2), almost no linear polarization is detected and total
polarization fractions can be substantially less than unity. A typical source
has properties intermediate to these two extremes. In contrast to the well
ordered magnetic field inferred from Zeeman splitting, there is generally no
clear pattern in the distribution of polarization position angles. This can be
explained if Faraday rotation in a typical OH maser source is large on a maser
amplification length but small on a single (e-folding) gain length. Increasing
or decreasing Faraday rotation by a factor of ~5 among different sources can
explain the observed variation in polarization properties. We suggest that
almost all pi-components acquire a signficant amount of circular polarization
from low-gain stimulated emission of a sigma-component from OH appropriately
shifted in velocity and lying along the propagation path.Comment: AASTeX, 57 pages including 2 tables and 21 figures (1 color),
accepted for publication in ApJ
An overview of the cutaneous porphyrias
This is an overview of the cutaneous porphyrias. It is a narrative review based on the published literature and my personal experience; it is not based on a formal systematic search of the literature. The cutaneous porphyrias are a diverse group of conditions due to inherited or acquired enzyme defects in the porphyrin–haem biosynthetic pathway. All the cutaneous porphyrias can have (either as a consequence of the porphyria or as part of the cause of the porphyria) involvement of other organs as well as the skin. The single commonest cutaneous porphyria in most parts of the world is acquired porphyria cutanea tarda, which is usually due to chronic liver disease and liver iron overload. The next most common cutaneous porphyria, erythropoietic protoporphyria, is an inherited disorder in which the accumulation of bile-excreted protoporphyrin can cause gallstones and, rarely, liver disease. Some of the porphyrias that cause blistering (usually bullae) and fragility (clinically and histologically identical to porphyria cutanea tarda) can also be associated with acute neurovisceral porphyria attacks, particularly variegate porphyria and hereditary coproporphyria. Management of porphyria cutanea tarda mainly consists of visible-light photoprotection measures while awaiting the effects of treating the underlying liver disease (if possible) and treatments to reduce serum iron and porphyrin levels. In erythropoietic protoporphyria, the underlying cause can be resolved only with a bone marrow transplant (which is rarely justifiable in this condition), so management consists particularly of visible-light photoprotection and, in some countries, narrowband ultraviolet B phototherapy. Afamelanotide is a promising and newly available treatment for erythropoietic protoporphyria and has been approved in Europe since 2014
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