398 research outputs found
APM 08279+5255: an ultraluminous BAL quasar at a redshift z=3.87
We report on the discovery of a highly luminous, broad absorption line quasar
at a redshift of which is positionally coincident, within one
arcsecond, with the IRAS FSC source F08279+5255. A chance alignment of the
quasar and the IRAS source is extremely unlikely and we argue that the optical
and FIR flux are different manifestations of the same object. With an R-band
magnitude of 15.2, and an IRAS 60\mum flux of 0.51\jy, APM 08279+5255 is
(apparently) easily the most intrinsically luminous object known, with
L_{Bol}\sim5\times10^{15}L_{\odot}}. Imaging suggests that gravitational
lensing may play a role in amplifying the intrinsic properties of the system.
The optical spectrum of the quasar clearly reveals the presence of three
potential lensing galaxies, \mg absorption systems at and ,
and a \ly absorption system at . We estimate the total amplification of
the optical component to be , but, due to the larger scale of the
emitting region, would expect the infrared amplification to be significantly
less. Even making the conservative assumption that all wavelengths are
amplified by a factor 40, APM 08279+5255 still possesses a phenomenal
luminosity of \simgt 10^{14L_{\odot}}, indicating that it belongs to a small,
but significant population of high--redshift, hyperluminous objects with
copious infrared emission.Comment: 15 Pages with Four figures. Accepted for publication in the
Astrophysical Journa
NICMOS and VLA Observations of the Gravitatonally Lensed Ultraluminous BAL Quasar APM~08279+5255: Detection of a Third Image
We present a suite of observations of the recently identified ultraluminous
BAL quasar APM 08279+5255, taken both in the infra-red with the NICMOS high
resolution camera on board the Hubble Space Telescope, and at 3.5cm with the
Very Large Array. With an inferred luminosity of ~5x10^15 Solar luminosities,
APM 08279+5255 is apparently the most luminous system known. Extant
ground-based images show that APM 08279+5255 is not point-like, but is instead
separated into two components, indicative of gravitational lensing. The much
higher resolution images presented here also reveal two point sources, A and B,
of almost equal brightness (f_B/f_A=0.782 +/- 0.010), separated by 0."378 +/-
0."001, as well as a third, previously unknown, fainter image, C, seen between
the brighter images. While the nature of C is not fully determined, several
lines of evidence point to it being a third gravitationally lensed image of the
quasar, rather than being the lensing galaxy. Simple models which recover the
relative image configuration and brightnesses are presented. While proving to
be substantially amplified, APM 08279+5255 possesses an intrinsic bolometric
luminosity of ~10^14 to 10^15 Solar luminosities and remains amongst the most
luminous objects known.Comment: 21 pages, 5 figures (2 as GIF files); accepted for publication in the
Astronomical Journa
Intranasal nanoemulsion vaccine confers longâlasting immunomodulation and sustained unresponsiveness in a murine model of milk allergy
BackgroundImmunotherapy for food allergy requires prolonged treatment protocols and, in most cases, does not lead to durable modulation of the allergic immune response. We have demonstrated an intranasal (IN) nanoemulsion adjuvant that redirects allergenâspecific Th2 responses toward Th1 and Th17 immunity, and protects from allergen challenge after only 2â4 monthly administrations. Here, we investigate the ability of this technology to provide longâterm modulation of allergy in a murine model of cowâs milk allergy.MethodsSix weeks after sensitization to bovine casein, mice received four, monthly IN immunizations with nanoemulsion formulated with casein. Protection from casein challenge was assessed at 4 and 16Â weeks after the final vaccine administration.ResultsThe NE vaccine significantly blunted the physiological responses to allergen challenge, and this effect persisted for at least 16Â weeks. The protection from challenge was associated with the suppression of caseinâspecific Th2 immunity and induced Th1 and Th17 cytokines as well as induction of ILâ10. Of interest, while immunized animals showed significantly decreased Th2 cytokine responses, cowâs milkâspecific IgE remained elevated in the serum at levels associated with reactivity in control sensitized animals. Protection was associated with suppressed mast cell activation and markedly reduced mast cell infiltration into the small intestine.ConclusionThe sustained unresponsiveness of at least 16Â weeks after vaccination suggests that the nanoemulsion vaccine alters the allergic phenotype in a persistent manner different from traditional desensitization, and this leads to longâterm suppressive effects on allergic disease without eliminating serum IgE.This study evaluates the ability of an intranasal nanoemulsionâbased vaccine to induce longâterm modulation of allergic reactions in a mouse model of cowâs milk allergy. Intranasal immunization with nanoemulsion adjuvant suppresses Th2 responses and anaphylaxis. The sustained unresponsiveness of at least 16Â weeks after vaccination suggests that the nanoemulsion vaccine alters the allergic phenotype.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154959/1/all14064_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154959/2/all14064.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154959/3/all14064-sup-0003-FigS3.pd
A Process and Outcome Evaluation of a Shelter for Homeless Young Women
To evaluate the processes and outcomes of a short-term shelter, both quantitative and qualitative data were gathered via participant observation, focus group interviews with shelter staff and residents, and individual interviews with a sample of 40 young women who had been homeless prior to using the shelter. The process evaluation showed that the shelter staff strived to utilize an empowerment philosophy in their relationships with residents, but that there were many challenges to implementing this philosophy. The outcome evaluation showed that, at a 3-month follow-up, the participants reported significant improvements in housing, income, independence, and life satisfaction, but most continued to experience poverty and a number of other difficulties. The results were discussed in terms of the implications for future research and the value and limitations of shelters for dealing with homeless youth. The need for more sustained and comprehensive program interventions and supportive social policies was underscored
Great Circle tidal streams: evidence for a nearly spherical massive dark halo around the Milky Way
An all high-latitude sky survey for cool carbon giant stars in the Galactic
halo has revealed 75 such stars, of which the majority are new detections. Of
these, more than half are clustered on a Great Circle on the sky which
intersects the center of Sagittarius dwarf galaxy (Sgr) and is parallel to its
proper motion vector, while many of the remainder are outlying Magellanic Cloud
C-stars. A pole-count analysis of the carbon star distribution clearly
indicates that the Great Circle stream we have isolated is statistically
significant, being a 5-6 sigma over-density. These two arguments strongly
support our conclusion that a large fraction of the Halo carbon stars
originated in Sgr. The stream orbits the Galaxy between the present location of
Sgr, 16 kpc from the Galactic center, and the most distant stream carbon star,
at ~60 kpc. It follows neither a polar nor a Galactic plane orbit, so that a
large range in both Galactic R and z distances are probed. That the stream is
observed as a Great Circle indicates that the Galaxy does not exert a
significant torque upon the stream, so the Galactic potential must be nearly
spherical in the regions probed by the stream. We present N-body experiments
simulating this disruption process as a function of the distribution of mass in
the Galactic halo. A likelihood analysis shows that, in the Galactocentric
distance range 16 kpc < R < 60 kpc, the dark halo is most likely almost
spherical. We rule out, at high confidence levels, the possibility that the
Halo is significantly oblate, with isodensity contours of aspect q_m < 0.7.
This result is quite unexpected and contests currently popular galaxy formation
models. (Abridged)Comment: 26 pages, 13 figures (6 in color, 8 chunky due to PS compression),
minor revisions, accepted by Ap
X-ray Source Populations in the Region of the Open Clusters NGC 6633 and IC 4756
Using deep exposures (~10^5 s) with the ROSAT HRI, we have performed
flux-limited surveys for X-ray sources in the vicinity of the Hyades-age open
stellar clusters NGC 6633 and IC 4756, detecting 31 and 13 sources
respectively. Our primary aim is to search for so-far unrecognised cluster
members. We propose identifications or classifications (cluster member, field
star, extragalactic field object) for the X-ray sources, based on published
membership lists, and on X-ray:optical flux ratios and optical
colour--magnitude diagrams. Results of simulating the expected X-ray-emitting
source populations are compared with the ROSAT measurements and with the
expected capabilities of the XMM mission. The simulations provide a novel
method of comparing the activity levels of NGC 6633 and IC 4756 with that of
the Hyades. The measurements and simulations confirm that cluster members are
the major class of X-ray emitter in these fields at flux levels f_x >
10^{-14}/erg/cm^2/s (0.1--2.4 keV), contributing ~40 per cent of the total
X-ray sources. We find 6 possible new members in NGC 6633, and 4 candidates in
IC 4756; all require further observation to establish membership probability.Comment: 12 pages, 4 figure
Cool carbon stars in the halo: a new survey based on 2MASS
We present the first results of a new survey for finding cool N-type carbon
(C) stars in the halo of the Galaxy. Candidates were first selected in the
2MASS Second Incremental Release database with JHKs colours typical of red AGB
C stars and Ks < 13, and susequently checked through slit spectroscopy. 27 new
halo C stars were discovered, and a detailed study of their properties are
given (distance, radial velocity, variablility, proper motion, colors etc). It
is found that most probably all these stars are true luminous AGB stars, rather
than C dwarfs. It is finally found that about half of these stars belong to the
Sgr Stream. (this abstract was shortened)Comment: 21 pages, 12 figs, accepted by Astron. & Astrophysic
Serendipitous discovery of seven new southern L-dwarfs
We report the discovery of seven hitherto unknown L-dwarfs found as a result
of a spectroscopic search for distant AGB stars. Their far-red and
near-infrared colours are very similar to known dwarfs of the same spectral
type. One new object is among the ~30 brightest L-dwarfs, with K_s=12.12, and
is nearby, ~20pc. Using low resolution spectroscopy from the Danish 1.54 m ESO
telescope, spectral types in the range L0.5 - L5 are derived for these seven
L-dwarfs by direct comparison to L-type standards taken from Kirkpatrick et al.
(1999). Distances are determined from existing calibrations, and together with
measured proper motions, yield kinematics for the seven new dwarfs consistent
with that expected for the solar neighbourhood disk population.Comment: 8 pages, 11 figures, accepted by A&
Cool carbon stars in the halo II. A study of 25 new objects
We present new results from an ongoing survey of carbon-rich asymptotic giant
(AGB) stars in the halo of our Galaxy. After selecting candidates primarily
through their 2MASS colours, slit spectroscopy was achieved at the ESO NTT
telescope. Twenty-one new AGB carbon stars were discovered, increasing the
total of presently known similar AGB C stars to about 120. A further four were
observed again in order to confirm their carbon-rich nature and measure radial
velocities. Two main findings emerge from this work. First, we found a C star
located at about 130 kpc from the Sun and at b = -62 degrees. This distant star
is remarkably close (5 kpc) to the principal plane of the Stream of the
Sagittarius dwarf galaxy, and is likely to be a tracer of a distant poorly
populated southern warp of the Stream. etc etcComment: accepted by Astronomy and Astrophysic
Comparative genomics of isolates of a pseudomonas aeruginosa epidemic strain associated with chronic lung infections of cystic fibrosis patients
Pseudomonas aeruginosa is the main cause of fatal chronic lung infections among individuals suffering from cystic fibrosis (CF). During the past 15 years, particularly aggressive strains transmitted among CF patients have been identified, initially in Europe and more recently in Canada. The aim of this study was to generate high-quality genome sequences for 7 isolates of the Liverpool epidemic strain (LES) from the United Kingdom and Canada representing different virulence characteristics in order to: (1) associate comparative genomics results with virulence factor variability and (2) identify genomic and/or phenotypic divergence between the two geographical locations. We performed phenotypic characterization of pyoverdine, pyocyanin, motility, biofilm formation, and proteolytic activity. We also assessed the degree of virulence using the Dictyostelium discoideum amoeba model. Comparative genomics analysis revealed at least one large deletion (40-50 kb) in 6 out of the 7 isolates compared to the reference genome of LESB58. These deletions correspond to prophages, which are known to increase the competitiveness of LESB58 in chronic lung infection. We also identified 308 non-synonymous polymorphisms, of which 28 were associated with virulence determinants and 52 with regulatory proteins. At the phenotypic level, isolates showed extensive variability in production of pyocyanin, pyoverdine, proteases and biofilm as well as in swimming motility, while being predominantly avirulent in the amoeba model. Isolates from the two continents were phylogenetically and phenotypically undistinguishable. Most regulatory mutations were isolate-specific and 29% of them were predicted to have high functional impact. Therefore, polymorphism in regulatory genes is likely to be an important basis for phenotypic diversity among LES isolates, which in turn might contribute to this strain's adaptability to varying conditions in the CF lung
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