74 research outputs found
Development of improved semi-organic structural adhesives for elevated temperature applications Technical summary report, 1 ~JUL. 1964 - 29 ~FEB. 1968
Titanium chelate polymer adhesive formulation for aluminum joint curing in high temperature application
Evidence of volcanic ash at a K-T boundary section: Ocean drilling program hole 690 C, Maud Rise, Weddell Sea off East Antarctica
Rare vitric volcanogenic ash but more abundant clay minerals considered volcanogenic in origin are associated with an expanded and essentially complete K-T boundary sequence from Ocean Drilling Project (ODP) Hole 690 C on Maud Rise in the Weddell Sea off East Antarctica. Results at this writing are preliminary and are still based to some extent on shipboard descriptions. Further shore-based studies are in progress. It would appear, however, that the presence of volcanic ash and altered ash in the Danian section beginning at the biostratigraphically and paleomagnetically determined K-T boundary on Maud Rise can be cited as evidence of significant volcanic activity within the South Atlantic-Indian Ocean sector of the Southern Ocean coincident with the time of biotic crises at the end of the Maestrichtian. This is a postulated time of tectonic and volcanic activity within this Southern Hemisphere region, including possible initiation of the Reunion hot spot and a peak in explosive volcanism on Walvis Ridge (1) among other events. A causal relationship with the biotic crisis is possible and volcanism should be given serious consideration as a testable working hypothesis to explain these extinctions
The role of depression in the association between mobilisation timing and live discharge after hip fracture surgery: Secondary analysis of the UK National Hip Fracture Database
Purpose
The aim was to compare the probability of discharge after hip fracture surgery conditional on being alive and in hospital between patients mobilised within and beyond 36-hours of surgery across groups defined by depression.
Methods
Data were taken from the National Hip Fracture Database and included patients 60 years of age or older who underwent hip fracture surgery in England and Wales between 2014 and 2016. The conditional probability of postsurgical live discharge was estimated for patients mobilised early and for patients mobilised late across groups with and without depression. The association between mobilisation timing and the conditional probability of live discharge were also estimated separately through adjusted generalized linear models.
Results
Data were analysed for 116,274 patients. A diagnosis of depression was present in 8.31% patients. In those with depression, 7,412 (76.7%) patients mobilised early. In those without depression, 84,085 (78.9%) patients mobilised early. By day 30 after surgery, the adjusted odds ratio of discharge among those who mobilised early compared to late was 1.79 (95% CI: 1.56â2.05, p<0.001) and 1.92 (95% CI: 1.84â2.00, p<0.001) for those with and without depression, respectively.
Conclusion
A similar proportion of patients with depression mobilised early after hip fracture surgery when compared to those without a diagnosis of depression. The association between mobilisation timing and time to live discharge was observed for patients with and without depression
First results from Faint Infrared Grism Survey (FIGS): first simultaneous detection of Lyman-alpha emission and Lyman break from a galaxy at z=7.51
Galaxies at high redshifts provide a valuable tool to study cosmic dawn, and
therefore it is crucial to reliably identify these galaxies. Here, we present
an unambiguous and first simultaneous detection of both the Lyman-alpha
emission and the Lyman break from a z = 7.512+/- 0.004 galaxy, observed in the
Faint Infrared Grism Survey (FIGS). These spectra, taken with G102 grism on
Hubble Space Telescope (HST), show a significant emission line detection (6
sigma) in multiple observational position angles (PA), with total integrated
Ly{\alpha} line flux of 1.06+/- 0.12 e10-17erg s-1cm-2. The line flux is nearly
a factor of four higher than the previous MOSFIRE spectroscopic observations of
faint Ly{\alpha} emission at {\lambda} = 1.0347{\mu}m, yielding z = 7.5078+/-
0.0004. This is consistent with other recent observations implying that
ground-based near-infrared spectroscopy underestimates total emission line
fluxes, and if confirmed, can have strong implications for reionization studies
that are based on ground-based Lyman-{\alpha} measurements. A 4-{\sigma}
detection of the NV line in one PA also suggests a weak Active Galactic Nucleus
(AGN), potentially making this source the highest-redshift AGN yet found. Thus,
this observation from the Hubble Space Telescope clearly demonstrates the
sensitivity of the FIGS survey, and the capability of grism spectroscopy to
study the epoch of reionization.Comment: Published in ApJL; matches published versio
Evolution of the Most Massive Galaxies to z=0.6: I. A New Method for Physical Parameter Estimation
We use principal component analysis (PCA) to estimate stellar masses, mean
stellar ages, star formation histories (SFHs), dust extinctions and stellar
velocity dispersions for ~290,000 galaxies with stellar masses greater than
$10^{11}Msun and redshifts in the range 0.4<z<0.7 from the Baryon Oscillation
Spectroscopic Survey (BOSS). We find the fraction of galaxies with active star
formation first declines with increasing stellar mass, but then flattens above
a stellar mass of 10^{11.5}Msun at z~0.6. This is in striking contrast to
z~0.1, where the fraction of galaxies with active star formation declines
monotonically with stellar mass. At stellar masses of 10^{12}Msun, therefore,
the evolution in the fraction of star-forming galaxies from z~0.6 to the
present-day reaches a factor of ~10. When we stack the spectra of the most
massive, star-forming galaxies at z~0.6, we find that half of their [OIII]
emission is produced by AGNs. The black holes in these galaxies are accreting
on average at ~0.01 the Eddington rate. To obtain these results, we use the
stellar population synthesis models of Bruzual & Charlot (2003) to generate a
library of model spectra with a broad range of SFHs, metallicities, dust
extinctions and stellar velocity dispersions. The PCA is run on this library to
identify its principal components over the rest-frame wavelength range
3700-5500A. We demonstrate that linear combinations of these components can
recover information equivalent to traditional spectral indices such as the
4000A break strength and HdA, with greatly improved S/N. This method is able to
recover physical parameters such as stellar mass-to-light ratio, mean stellar
age, velocity dispersion and dust extinction from the relatively low S/N BOSS
spectra. We examine the sensitivity of our stellar mass estimates to the input
parameters in our model library and the different stellar population synthesis
models.Comment: 20 pages, 18 Figures, submitted to MNRA
New Quantum Theory of Laser Cooling Mechanisms
In this paper, we study the laser cooling mechanisms with a new quantum
theory approach by applying a new Schrodinger equation, which can describe a
particle in conservative and non-conservative force field. With the new theory,
we prove the atom in laser field can be cooled, and give the atom cooling
temperature, which is accordance with experiment result. Otherwise, we give new
prediction that the atom cooling temperature is directly proportional to the
atom vibration frequency. By calculation, we find they are: .Comment: arXiv admin note: text overlap with arXiv:physics/0601097,
arXiv:0710.5078, arXiv:0707.2280 by other authors without attributio
Spectroscopic study of blue compact galaxies III. Empirical population synthesis
This is the third paper of a series dedicated to the study of the star
formation rates, star formation histories, metallicities and dust contents of a
sample of blue compact galaxies (BCGs). We constrain the stellar contents of 73
blue compact galaxies by analyzing their continuum spectra and the equivalent
widths of strong stellar absorption features using a technique of empirical
population synthesis based on a library of observed star-cluster spectra. Our
results indicate that blue compact galaxies are typically age-composite stellar
systems; in addition to young stars, intermediate-age and old stars contribute
significantly to the 5870 A continuum emission of most galaxies in our sample.
The stellar populations of blue compact galaxies also span a variety of
metallicities. The ongoing episodes of star formation started typically less
than a billion years ago. Some galaxies may be undergoing their first global
episode of star formation, while for most galaxies in our sample, older stars
are found to contribute up to half the optical emission. Our results suggest
that BCGs are primarily old galaxies with discontinuous star formation
histories. The absorption equivalent widths measured in the synthetic spectra
range from typically 1.5 A for Halpha, to 2 -- 5 A for Hbeta, Hgamma, and
Hdelta. The implied accurate measurements of emission-line intensities will be
used in a later study to constrain the star formation rates and gas-phase
chemical element abundances of blue compact galaxies.Comment: 23 pages, 5 figures, accepted for publication in Astronomy and
Astrophysic
Star forming dwarf galaxies
Star forming dwarf galaxies (SFDGs) have a high gas content and low
metallicities, reminiscent of the basic entities in hierarchical galaxy
formation scenarios. In the young universe they probably also played a major
role in the cosmic reionization. Their abundant presence in the local volume
and their youthful character make them ideal objects for detailed studies of
the initial stellar mass function (IMF), fundamental star formation processes
and its feedback to the interstellar medium. Occasionally we witness SFDGs
involved in extreme starbursts, giving rise to strongly elevated production of
super star clusters and global superwinds, mechanisms yet to be explored in
more detail. SFDGs is the initial state of all dwarf galaxies and the relation
to the environment provides us with a key to how different types of dwarf
galaxies are emerging. In this review we will put the emphasis on the exotic
starburst phase, as it seems less important for present day galaxy evolution
but perhaps fundamental in the initial phase of galaxy formation.Comment: To appear in JENAM Symposium "Dwarf Galaxies: Keys to Galaxy
Formation and Evolution", P. Papaderos, G. Hensler, S. Recchi (eds.). Lisbon,
September 2010, Springer Verlag, in pres
Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial
Background
Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy
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