7,033 research outputs found
HI 21cm observations of the PG1216+069 sub-DLy-alpha absorber field at z=0.00632
The Westerbork Synthesis Radio Telescope finds a weak 21cm line emission
feature at the coordinates (RA-Dec-velocity) of the sub-Damped Lyman-alpha
absorber observed at z_abs=0.00632 in the spectrum of PG1216+069. The emission
feature, WSRT-J121921+0639, lies within 30" of the quasar sightline, is
detected at 99.8% (3 sigma) confidence level, has M_HI between 5 and 15x10^6
M_solar, and has velocity spread between 20 and 60 km/s. Other HI emitters in
the field include VCC297 at a projected distance of 86/h_75 kpc and a
previously unreported HI cloud, WSRT-J121919+0624 at 112/h_75 kpc with M_HI ~
3x10^8 M_solar. The optically identified, foreground galaxy that is closest to
the quasar sightline appears to be VCC339 (~L*/25) at 29/h_75 kpc and velocity
offset 292 km/s . A low surface brightness galaxy with the HI mass of the
sub-DLA absorber WSRT-J121921+0639 would likely have m_B ~ 17, and its diffuse
optical emission would need to compete with the light of both the background
QSO and a brighter foreground star ~10" from the QSO sight line.Comment: 10 pages, 2 figures, accepted for publication in ApJLet
Estimating the Expected Value of Partial Perfect Information in Health Economic Evaluations using Integrated Nested Laplace Approximation
The Expected Value of Perfect Partial Information (EVPPI) is a
decision-theoretic measure of the "cost" of parametric uncertainty in decision
making used principally in health economic decision making. Despite this
decision-theoretic grounding, the uptake of EVPPI calculations in practice has
been slow. This is in part due to the prohibitive computational time required
to estimate the EVPPI via Monte Carlo simulations. However, recent developments
have demonstrated that the EVPPI can be estimated by non-parametric regression
methods, which have significantly decreased the computation time required to
approximate the EVPPI. Under certain circumstances, high-dimensional Gaussian
Process regression is suggested, but this can still be prohibitively expensive.
Applying fast computation methods developed in spatial statistics using
Integrated Nested Laplace Approximations (INLA) and projecting from a
high-dimensional into a low-dimensional input space allows us to decrease the
computation time for fitting these high-dimensional Gaussian Processes, often
substantially. We demonstrate that the EVPPI calculated using our method for
Gaussian Process regression is in line with the standard Gaussian Process
regression method and that despite the apparent methodological complexity of
this new method, R functions are available in the package BCEA to implement it
simply and efficiently
Constraints on changes in fundamental constants from a cosmologically distant OH absorber/emitter
We have detected the four 18cm OH lines from the gravitational
lens toward PMN J0134-0931. The 1612 and 1720 MHz lines are in conjugate
absorption and emission, providing a laboratory to test the evolution of
fundamental constants over a large lookback time. We compare the HI and OH main
line absorption redshifts of the different components in the
absorber and the lens toward B0218+357 to place stringent
constraints on changes in . We obtain
,
consistent with no evolution over the redshift range . The
measurements have a sensitivity of or to fractional
changes in and over a period of Gyr, half the age of
the Universe. These are among the most sensitive current constraints on changes
in .Comment: 4 pages, 3 figures. Final version, with minor changes to match the
version in print in Phys. Rev. Let
Changing women's roles, changing environmental knowledges: evidence from Upper Egypt
The aim of this paper is to investigate the ways in which changing gender roles in a Bedouin community in Upper Egypt, brought about by settlement over the last 20 years on the shores of Lake Nasser, have impacted on the accumulation and development of indigenous environmental knowledges by Bedouin women. The research was carried out among four groups of Ababda Bedouin in the Eastern Desert of Egypt and involved in-depth monthly conversations carried out over a period of 12 months. The main conclusions of the study are that the women of the study area have had to develop new knowledges which, in some cases, are now different from those held by men because of the different economic circumstances in which many find themselves; that these knowledges are fluid, dynamic and ever-changing with their own internal dynamism; and that socially constructed notions of gender are vital in the development process, notions that are sensitive to both men's and women's interests and their interrelationships
A Deep Look at the T-Type Brown Dwarf Binary Indi Bab with Chandra and ATCA
We present deep observations of the nearby T-type brown dwarf binary
Indi Bab in radio with the Australia Telescope Compact Array and in
X-rays with the Chandra X-ray Observatory. Despite long integration times, the
binary (composed of T1 and T6 dwarfs) was not detected in either wavelength
regime. We reached upper limits of and erg/s/Hz for the radio luminosity at 4.8 GHz and 8.64 GHz,
respectively; in the X-rays, the upper limit in the keV band was erg/s. We discuss the above results in the framework of
magnetic activity in ultracool, low-mass dwarfs.Comment: Accepted for publication in the Astrophysical Journal Letter
Transfer of memory retrieval cues attenuates the context specificity of latent inhibition
Previous studies have demonstrated that the transfer of retrieval cues for original acquisition memories, old \u27reactivatedâ memories, and extinction memories attenuated the context shift effect. This study examined whether latent inhibition (CS preexposure) cues would also transfer, thus alleviating the context specificity. Rats preexposed to a particular context were immediately exposed to a different, novel context. When these rats were trained and tested in the shifted context following preexposure/exposure they showed the latent inhibition effect, i.e., retarded learning in the context that differed from preexposure. That the rats treated the shifted context as the preexposure context demonstrates that the preexposure retrieval cues transferred. These results are consistent with other findings that a novel context can serve as retrieval cues for an event learned in a different setting
The line-of-sight warp of the spiral galaxy ESO 123-G23
We present 3-D modelling of the distribution and kinematics of the neutral
hydrogen in the spiral galaxy ESO 123-G23. The optical appearance of this
galaxy is an almost perfectly edge-on disk, while the neutral hydrogen is found
to extend vertically out to about 15 kpc on either side of the galactic plane.
The HI layer and the major features of the HI data cube can be successfully
explained by a model dominated by a strong (about 30 degrees) line-of-sight
warp. Other models were tried, including a flare model and a two-component
model, but they clearly do not reproduce the data. This is the first
unambiguous detection of a galactic warp that has the maximum deviation from
the central plane almost along the line-of-sight. No evidence for the presence
of any companion galaxy is found in the HI data cube. Line-of-sight warps in
edge-on galaxies are probably frequent, but escape detection as they are too
weak. Moreover they may easily be mistaken as flares or 'thick disks'. A 3-D
modelling of the HI layer as the one presented here is needed in order to
distinguish between these possibilities.Comment: 5 pages, 5 figures, accepted by A&
The Ulysses Supplement to the BATSE 3B Catalog of Cosmic Gamma-Ray Bursts
We present Interplanetary Network localization information for 218 gamma-ray
bursts in the 3rd BATSE catalog, obtained by analyzing the arrival times of
these bursts at the Ulysses and Compton Gamma-Ray Observatory (CGRO)
spacecraft. For any given burst observed by these two spacecraft, arrival time
analysis (or "triangulation") results in an annulus of possible arrival
directions whose half-width varies between 7 arcseconds and 32 arcminutes,
depending on the intensity and time history of the burst, and the distance of
the Ulysses spacecraft from Earth. This annulus generally intersects the BATSE
error circle, resulting in an average reduction of the error box area of a
factor of 30.Comment: Accepted for publication in the Astrophysical Journal Supplemen
A novel multigrid method for electronic structure calculations
A general real-space multigrid algorithm for the self-consistent solution of
the Kohn-Sham equations appearing in the state-of-the-art electronic-structure
calculations is described. The most important part of the method is the
multigrid solver for the Schroedinger equation. Our choice is the Rayleigh
quotient multigrid method (RQMG), which applies directly to the minimization of
the Rayleigh quotient on the finest level. Very coarse correction grids can be
used, because there is no need to be able to represent the states on the coarse
levels. The RQMG method is generalized for the simultaneous solution of all the
states of the system using a penalty functional to keep the states orthogonal.
The performance of the scheme is demonstrated by applying it in a few molecular
and solid-state systems described by non-local norm-conserving
pseudopotentials.Comment: 9 pages, 3 figure
Optical absorption and photoluminescence spectroscopy of the growth of silver nanoparticles
Results obtained from the optical absorption and photoluminescence (PL)
spectroscopy experiments have shown the formation of excitons in the
silver-exchanged glass samples. These findings are reported here for the first
time. Further, we investigate the dramatic changes in the photoemission
properties of the silver-exchanged glass samples as a function of postannealing
temperature. Observed changes are thought to be due to the structural
rearrangements of silver and oxygen bonding during the heat treatments of the
glass matrix. In fact, photoelectron spectroscopy does reveal these chemical
transformations of silver-exchanged soda glass samples caused by the thermal
effects of annealing in a high vacuum atmosphere. An important correlation
between temperature-induced changes of the PL intensity and thermal growth of
the silver nanoparticles has been established in this Letter through precise
spectroscopic studies.Comment: 15 pages,4 figures,PDF fil
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