2,315 research outputs found
Magneto-optics in pure and defective Ga_{1-x}Mn_xAs from first-principles
The magneto-optical properties of GaMnAs including their most
common defects were investigated with precise first--principles
density-functional FLAPW calculations in order to: {\em i}) elucidate the
origin of the features in the Kerr spectra in terms of the underlying
electronic structure; {\em ii}) perform an accurate comparison with
experiments; and {\em iii}) understand the role of the Mn concentration and
occupied sites in shaping the spectra. In the substitutional case, our results
show that most of the features have an interband origin and are only slightly
affected by Drude--like contributions, even at low photon energies. While not
strongly affected by the Mn concentration for the intermediately diluted range
( 10%), the Kerr factor shows a marked minimum (up to 1.5) occurring
at a photon energy of 0.5 eV. For interstitial Mn, the calculated
results bear a striking resemblance to the experimental spectra, pointing to
the comparison between simulated and experimental Kerr angles as a valid tool
to distinguish different defects in the diluted magnetic semiconductors
framework.Comment: 10 pages including 2 figures, submitted to Phys. Rev.
Spinning BTZ Black Hole versus Kerr Black Hole : A Closer Look
By applying Newman's algorithm, the AdS_3 rotating black hole solution is
``derived'' from the nonrotating black hole solution of Banados, Teitelboim,
and Zanelli (BTZ). The rotating BTZ solution derived in this fashion is given
in ``Boyer-Lindquist-type'' coordinates whereas the form of the solution
originally given by BTZ is given in a kind of an ``unfamiliar'' coordinates
which are related to each other by a transformation of time coordinate alone.
The relative physical meaning between these two time coordinates is carefully
studied. Since the Kerr-type and Boyer-Lindquist-type coordinates for rotating
BTZ solution are newly found via Newman's algorithm, next, the transformation
to Kerr-Schild-type coordinates is looked for. Indeed, such transformation is
found to exist. And in this Kerr-Schild-type coordinates, truely maximal
extension of its global structure by analytically continuing to ``antigravity
universe'' region is carried out.Comment: 17 pages, 1 figure, Revtex, Accepted for publication in Phys. Rev.
Kinematic Distances to Molecular Clouds identified in the Galactic Ring Survey
Kinematic distances to 750 molecular clouds identified in the 13CO J=1-0
Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
(BU-FCRAO GRS) are derived assuming the Clemens rotation curve of the Galaxy.
The kinematic distance ambiguity is resolved by examining the presence of HI
self-absorption toward the 13CO emission peak of each cloud using the Very
Large Array Galactic Plane Survey (VGPS). We also identify 21 cm continuum
sources embedded in the GRS clouds in order to use absorption features in the
HI 21 cm continuum to distinguish between near and far kinematic distances. The
Galactic distribution of GRS clouds is consistent with a four-arm model of the
Milky Way. The locations of the Scutum-Crux and Perseus arms traced by GRS
clouds match star count data from the Galactic Legacy Infrared Mid-Plane Survey
Extraordinaire (GLIMPSE) star-count data. We conclude that molecular clouds
must form in spiral arms and be short-lived (lifetimes < 10 Myr) in order to
explain the absence of massive, 13CO bright molecular clouds in the inter-arm
space
Post-Foucauldian governmentality: what does it offer critical social policy analysis?
This article considers the theoretical perspective of post-Foucauldian governmentality, especially the insights and challenges it poses for applied researchers within the critical social policy tradition. The article firstly examines the analytical strengths of this approach to understanding power and rule in contemporary society, before moving on to consider its limitations for social policy. It concludes by arguing that these insights can be retained, and some of the weaknesses overcome, by adopting a ârealist governmentalityâ approach (Stenson 2005, 2008). This advocates combining traditional discursive analysis with more ethnographic methods in order to render visible the concrete activity of governing, and unravel the messiness, complexity and unintended consequences involved in the struggles around subjectivity
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Toward vicarious calibration of microwave remote-sensing satellites in arid environments
The Soil Moisture and Ocean Salinity (SMOS)
satellite marks the commencement of dedicated global surface
soil moisture missions, and the first mission to make passive microwave observations at L-band. On-orbit calibration is an essential part of the instrument calibration strategy, but on-board beam-filling targets are not practical for such large apertures. Therefore, areas to serve as vicarious calibration targets need to be identified. Such sites can only be identified through field
experiments including both in situ and airborne measurements. For this purpose, two field experiments were performed in central Australia. Three areas are studied as follows: 1) Lake Eyre, a typically dry salt lake; 2) Wirrangula Hill, with sparse vegetation and a dense cover of surface rock; and 3) Simpson Desert, characterized by dry sand dunes. Of those sites, only Wirrangula
Hill and the Simpson Desert are found to be potentially
suitable targets, as they have a spatial variation in brightness temperatures of <4 K under normal conditions. However, some limitations are observed for the Simpson Desert, where a bias of 15 K in vertical and 20 K in horizontal polarization exists between model predictions and observations, suggesting a lack of understanding of the underlying physics in this environment.
Subsequent comparison with model predictions indicates a SMOS bias of 5 K in vertical and 11 K in horizontal polarization, and an unbiased root mean square difference of 10 K in both polarizations for Wirrangula Hill. Most importantly, the SMOS observations show that the brightness temperature evolution is dominated by regular seasonal patterns and that precipitation events have only little impact
A Gravitational Redshift Determination of the Mean Mass of White Dwarfs. DA Stars
We measure apparent velocities (v_app) of the Halpha and Hbeta Balmer line
cores for 449 non-binary thin disk normal DA white dwarfs (WDs) using optical
spectra taken for the ESO SN Ia Progenitor surveY (SPY; Napiwotzki et al.
2001). Assuming these WDs are nearby and co-moving, we correct our velocities
to the Local Standard of Rest so that the remaining stellar motions are random.
By averaging over the sample, we are left with the mean gravitational redshift,
: we find = = 32.57 +/- 1.17 km/s. Using the mass-radius
relation from evolutionary models, this translates to a mean mass of 0.647
+0.013 -0.014 Msun. We interpret this as the mean mass for all DAs. Our results
are in agreement with previous gravitational redshift studies but are
significantly higher than all previous spectroscopic determinations except the
recent findings of Tremblay & Bergeron (2009). Since the gravitational redshift
method is independent of surface gravity from atmosphere models, we investigate
the mean mass of DAs with spectroscopic Teff both above and below 12000 K; fits
to line profiles give a rapid increase in the mean mass with decreasing Teff.
Our results are consistent with no significant change in mean mass: ^hot =
0.640 +/- 0.014 Msun and ^cool = 0.686 +0.035 -0.039 Msun.Comment: Accepted for publication in ApJ, 14 pages, 12 figure
Entropies of Rotating Charged Black Holes from Conformal Field Theory at Killing Horizons
The covariant phase technique is used to compute the constraint algebra of
the stationary axisymmetric charged black hole. A standard Virasoro subalgebra
with corresponding central charge is constructed at a Killing horizon with
Carlip's boundary conditions. For the Kerr-Newman black hole and the
Kerr-Newman-AdS black hole, the density of states determined by conformal
fields theory methods yields the statistical entropy which agrees with the
Bekenstein-Hawking entropy.Comment: 12 pages, no figure, RevTe
The impact of hyperhidrosis on patients' daily life and quality of life : A qualitative investigation
Background: An understanding of the daily life impacts of hyperhidrosis and how patients deal with them, based on qualitative research, is lacking. This study investigated the impact of hyperhidrosis on the daily life of patients using a mix of qualitative research methods. Methods: Participants were recruited through hyperhidrosis patient support groups such as the Hyperhidrosis Support Group UK. Data were collected using focus groups, interviews and online surveys. A grounded theory approach was used in the analysis of data transcripts. Data were collected from 71 participants, out of an initial 100 individuals recruited. Results: Seventeen major themes capturing the impacts of hyperhidrosis were identified; these covered all areas of life including daily life, psychological well-being, social life, professional /school life, dealing with hyperhidrosis, unmet health care needs and physical impact. Conclusions: Psychosocial impacts are central to the overall impacts of hyperhidrosis, cutting across and underlying the limitations experienced in other areas of life.Peer reviewe
Development of a decision support tool to facilitate primary care management of patients with abnormal liver function tests without clinically apparent liver disease [HTA03/38/02]. Abnormal Liver Function Investigations Evaluation (ALFIE)
Liver function tests (LFTs) are routinely performed in primary care, and are often the gateway to further invasive and/or expensive investigations. Little is known of the consequences in people with an initial abnormal liver function (ALF) test in primary care and with no obvious liver disease. Further investigations may be dangerous for the patient and expensive for Health Services. The aims of this study are to determine the natural history of abnormalities in LFTs before overt liver disease presents in the population and identify those who require minimal further investigations with the potential for reduction in NHS costs
Higher dimensional flat embeddings of (2+1) dimensional black holes
We obtain the higher dimensional global flat embeddings of static, rotating,
and charged BTZ black holes. On the other hand, we also study the similar
higher dimensional flat embeddings of the (2+1) de Sitter black holes which are
the counterparts of the anti-de Sitter BTZ black holes. As a result, the
charged dS black hole is shown to be embedded in (3+2) GEMS, contrast to the
charged BTZ one having (3+3) GEMS structure.Comment: 16pages, revtex, no figures, to appear in Phys. Rev.
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