2,374 research outputs found
A Near-Solar Metallicity, Nitrogen-Deficient Lyman Limit Absorber Associated with two S0 Galaxies
From UV spectra of the bright quasar PHL 1811 recorded by FUSE and the E140M
configuration on STIS, we have determined the abundances of various atomic
species in a Lyman limit system at z = 0.0809 with log N(H I) = 17.98.
Considerably more hydrogen may be in ionized form, since the abundances of C
II, Si II, S II and Fe II are very large compared to that of O I, when compared
to their respective solar abundance ratios. Our determination [O/H] = -0.19 in
the H I-bearing gas indicates that the chemical enrichment of the gas is
unusually high for an extragalactic QSO absorption system. However, this same
material has an unusually low abundance of nitrogen, [N/O] < -0.59, indicating
that there may not have been enough time during this enrichment for secondary
nitrogen to arise from low and intermediate mass stars. In an earlier
investigation we found two galaxies at nearly the same redshift as this
absorption system and displaced by 34 and 87 kpc from the line of sight. An
r-band image recorded by the ACS on HST indicates these are S0 galaxies. One or
both of these galaxies may be the source of the gas, which might have been
expelled in a fast wind, by tidal stripping, or by ram-pressure stripping.
Subtraction of the ACS point-spread function from the image of the QSO reveals
the presence of a face-on spiral galaxy under the glare of the quasar; although
it is possible that this galaxy may be responsible for the Lyman limit
absorption, the exact alignment of the QSO with the center of the galaxy
suggests that the spiral is the quasar host.Comment: 74 pages, 14 figures; to be published in the Astrophysical Journal
(Part 1) May 1, 2005 issue. A version of the paper with figures of better
quality may be found at http://www.astro.princeton.edu/~ebj/PHL1811_paper.ps
(postscript) or http://www.astro.princeton.edu/~ebj/PHL1811_paper.pdf (pdf
The effect of high dose antibiotic impregnated cement on rate of surgical site infection after hip hemiarthroplasty for fractured neck of femur : a protocol for a double-blind quasi randomised controlled trial
Background:
Mortality following hip hemiarthroplasty is in the range of 10-40% in the first year, with much attributed to post-operative complications. One such complication is surgical site infection (SSI), which at the start of this trial affected 4.68% of patients in the UK having this operation. Compared to SSI rates of elective hip surgery, at less than 1%, this figure is elevated. The aim of this quasi randomised controlled trial (RCT) is to determine if high dose antibiotic impregnated cement can reduce the SSI in patients at 12-months after hemiarthroplasty for intracapsular fractured neck of femur.
Methods:
848 patients with an intracapsular fractured neck of femur requiring a hip hemiarthroplasty are been recruited into this two-centre double-blind quasi RCT. Participants were recruited before surgery and quasi randomised to standard care or intervention group. Participants, statistician and outcome assessors were blind to treatment allocation throughout the study. The intervention consisted of high dose antibiotic impregnated cement consisting of 1 gram Clindamycin and 1 gram of Gentamicin. The primary outcome is Health Protection Agency (HPA) defined deep surgical site infection at 12 months. Secondary outcomes include HPA defined superficial surgical site infection at 30 days, 30 and 90-day mortality, length of hospital stay, critical care stay, and complications.
Discussion:
Large randomised controlled trials assessing the effectiveness of a surgical intervention are uncommon, particularly in the speciality of orthopaedics. The results from this trial will inform evidence-based recommendations for antibiotic impregnated cement in the management of patients with a fractured neck of femur undergoing a hip hemiarthroplasty. If high dose antibiotic impregnated cement is found to be an effective intervention, implementation into clinical practice could improve long-term outcomes for patients undergoing hip hemiarthroplasty
Production and calibration of the first HEFT hard x-ray optics module
Complete hard X-ray optics modules are currently being produced for the High Energy Focusing Telescope (HEFT), a balloon born mission that will observe a wide range of objects including young supernova remnants, active galactic nuclei, and galaxy clusters at energies between 20 and 70 keV. Large collecting areas are achieved by tightly nesting layers of grazing incidence mirrors in a conic approximation Wolter-I design. The segmented layers are made of thermally-formed glass substrates coated with depth-graded multilayer films for enhanced reflectivity. Our novel mounting technique involves constraining these mirror segments to successive layers of precisely machined graphite spacers. We report the production and calibration of the first HEFT optics module
The speed of parietal theta frequency drives visuospatial working memory capacity
The speed of theta brain oscillatory activity is thought to play a key role in determining working memory (WM) capacity. Individual differences in the length of a theta cycle (ranging between 4 and 7 Hz) might determine how many gamma cycles (>30 Hz) can be nested into a theta wave. Gamma cycles are thought to represent single memory items; therefore, this interplay could determine individual memory capacity. We directly tested this hypothesis by means of parietal transcranial alternating current stimulation (tACS) set at slower (4 Hz) and faster (7 Hz) theta frequencies during a visuospatial WM paradigm. Accordingly, we found that 4-Hz tACS enhanced WM capacity, while 7-Hz tACS reduced WM capacity. Notably, these effects were found only for items presented to the hemifield contralateral to the stimulation site. This provides causal evidence for a frequency-dependent and spatially specific organization of WM storage, supporting the thetaâgamma phase coupling theory of WM capacity
TESS Discovery of an ultra-short-period planet around the nearby M dwarf LHS 3844
Data from the newly-commissioned \textit{Transiting Exoplanet Survey
Satellite} (TESS) has revealed a "hot Earth" around LHS 3844, an M dwarf
located 15 pc away. The planet has a radius of and
orbits the star every 11 hours. Although the existence of an atmosphere around
such a strongly irradiated planet is questionable, the star is bright enough
(, ) for this possibility to be investigated with transit and
occultation spectroscopy. The star's brightness and the planet's short period
will also facilitate the measurement of the planet's mass through Doppler
spectroscopy.Comment: 10 pages, 4 figures. Submitted to ApJ Letters. This letter makes use
of the TESS Alert data, which is currently in a beta test phase, using data
from the pipelines at the TESS Science Office and at the TESS Science
Processing Operations Cente
The GALEX Ultraviolet Atlas of Nearby Galaxies
We present images, integrated photometry, surface-brightness and color
profiles for a total of 1034 nearby galaxies recently observed by the GALEX
satellite in its far-ultraviolet (FUV; 1516A) and near-ultraviolet (NUV; 2267A)
bands. (...) This data set has been complemented with archival optical,
near-infrared, and far-infrared fluxes and colors. We find that the integrated
(FUV-K) color provides robust discrimination between elliptical and
spiral/irregular galaxies and also among spiral galaxies of different
sub-types. Elliptical galaxies with brighter K-band luminosities (i.e. more
massive) are redder in (NUV-K) color but bluer in (FUV-NUV) than less massive
ellipticals. In the case of the spiral/irregular galaxies our analysis shows
the presence of a relatively tight correlation between the (FUV-NUV) color and
the total infrared-to-UV ratio. The correlation found between (FUV-NUV) color
and K-band luminosity (with lower luminosity objects being bluer than more
luminous ones) can be explained as due to an increase in the dust content with
galaxy luminosity.
The images in this Atlas along with the profiles and integrated properties
are publicly available through a dedicated web page at
http://nedwww.ipac.caltech.edu/level5/GALEX_Atlas/Comment: 181 pages, 10 figures, accepted for publication in ApJS (abstract
abridged
The LHC Injection Tests
A series of LHC injection tests was performed in August and September 2008. The first saw beam injected into sector 23; the second into sectors 78 and 23; the third into sectors 78-67 and sectors 23-34-45. The fourth, into sectors 23-34-45, was performed the evening before the extended injection test on the 10th September which saw both beams brought around the full circumference of the LHC. The tests enabled the testing and debugging of a number of critical control and hardware systems; testing and validation of instrumentation with beam for the first time; deployment, and validation of a number of measurement procedures. Beam based measurements revealed a number of machine configuration issues that were rapidly resolved. The tests were undoubtedly an essential precursor to the successful start of LHC beam commissioning. This paper provides an outline of preparation for the tests, the machine configuration and summarizes the measurements made and individual system performance
- âŠ