4,073 research outputs found
Black hole solutions in 2+1 dimensions
We give circularly symmetric solutions for null fluid collapse in
2+1-dimensional Einstein gravity with a cosmological constant. The fluid
pressure and energy density are related by . The
long time limit of the solutions are black holes whose horizon structures
depend on the value of . The solution is the
Banados-Teitelboim-Zanelli black hole metric in the long time static limit,
while the solutions give other, `hairy' black hole metrics in this limit.Comment: 8 pages, RevTeX (to appear in Phys. Rev. D) References to Mann and
Ross, and Mann, Chan and Chan adde
Gravitational collapse of quantum matter
We describe a class of exactly soluble models for gravitational collapse in
spherical symmetry obtained by patching dynamical spherically symmetric
exterior spacetimes with cosmological interior spacetimes. These are
generalizations of the Oppenheimer-Snyder type models to include classical and
quantum scalar fields as sources for the interior metric, and null fluids with
pressure as sources for the exterior metric. In addition to dynamical
exteriors, the models exhibit other novel features such as evaporating
horizons, and singularity avoidance without quantum gravity.Comment: 8 pages, 4 figures, revtex 2co
Group study of an 'undercover' test for visuospatial neglect: Invisible cancellation can reveal more neglect than standard cancellation
Visual neglect is a relatively common deficit after brain damage, particularly strokes. Cancellation tests provide standard clinical measures of neglect severity and deficits in daily life. A recent single-case study introduced a new variation on standard cancellation. Instead of making a visible mark on each target found, the patient made invisible marks (recorded with carbon paper underneath, for later scoring). Such invisible cancellation was found to reveal more neglect than cancellation with visible marks. Here we test the generality of this. Twenty three successive cases with suspected neglect each performed cancellation with visible or invisible marks. Neglect of contralesional targets was more pronounced with invisible marks. Indeed, about half of the patients only showed neglect in this version. For cases showing more neglect with invisible marks, stronger neglect of contralesional targets correlated with more revisits to ipsilesional targets for making additional invisible marks upon them. These results indicate that cancellation with invisible marks can reveal more neglect than standard cancellation with visible marks, while still providing a practical bedside test. Our observations may be consistent with recent proposals that demands on spatial working memory (required to keep track of previously found items only when marked invisibly) can exacerbate spatial neglect
Note on flat foliations of spherically symmetric spacetimes
It is known that spherically symmetric spacetimes admit flat spacelike
foliations. We point out a simple method of seeing this result via the
Hamiltonian constraints of general relativity. The method yields explicit
formulas for the extrinsic curvatures of the slicings.Comment: 4 pages, to appear in PRD, reference added, typos correcte
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Nebulized PPARγ agonists: a novel approach to augment neonatal lung maturation and injury repair in rats.
BackgroundBy stimulating lipofibroblast maturation, parenterally administered peroxisome proliferator-activated receptor γ (PPARγ) agonists promote lung homeostasis and injury repair in the neonatal lung. In this study, we determined whether PPARγ agonists could be delivered effectively via nebulization to neonates, and whether this approach would also protect against hyperoxia-induced lung injury.MethodsOne-day old Sprague-Dawley rat pups were administered PPARγ agonists rosiglitazone (RGZ, 3 mg/kg), pioglitazone (PGZ, 3 mg/kg), or the diluent, via nebulization every 24 h; animals were exposed to 21% or 95% O2 for up to 72 h. Twenty-four and 72 h following initial nebulization, the pups were sacrificed for lung tissue and blood collection to determine markers of lung maturation, injury repair, and RGZ and PGZ plasma levels.ResultsNebulized RGZ and PGZ enhanced lung maturation in both males and females, as evidenced by the increased expression of markers of alveolar epithelial and mesenchymal maturation. This approach also protected against hyperoxia-induced lung injury, since hyperoxia-induced changes in bronchoalveolar lavage cell and protein contents and lung injury markers were all blocked by nebulized PGZ.ConclusionNebulized PPARγ agonist administration promotes lung maturation and prevents neonatal hyperoxia-induced lung injury in both males and females
Geographic Information System : Sistem Informasi Embuatan Model Pengendalian Kepemilikan Ternak Sapi Di Wilayah Provinsi NTB
Dengan besarnya potensi yang dimiliki tersebut pemerintah pusat menetapkan Nusa Tenggara Barat (NTB) sebagai salah satu propinsi sumber sapi potong dan sapi bibit diantara 18 propinsi di tanah air, sehingga kiprah NTB diharapkan mampu mempercepat program nasional percepatan pencapaian swasembada daging sapi (P2SDS). Oleh karena itu strategi yang dilakukan dalam mengembangkan potensi peternakan sapi ini adalah dengan memelihara sapi melalui sistem kandang kolektif untuk Pulau Lombok dan pola padang penggembalaan atau lar/so di Pulau Sumbawa. Sampai dengan pertengahan tahun 2010, terdapat sekitar 880 unit kandang kolektif sapi di pulau lombok dari target 1.000 unit kandang kolektif pada tahun 2013. Adanya jumlah sapi yang tiap tahun mengalami peningkatan maka dibutuhkan penelitian pembuatan sistem informasi giografis (SIG) dan database identifikasi peternak sapi. Penelitian ini dilakukan untuk menghasilkan produk SIG peternakan sapi dan database identitfikasi kepemilikan sapi di wilayah NTB. Metodologi penelitian digunakan adalah Model air terjun (waterfall) yaitu metode pengembangan sistem informasi dengan cara perencanaan, analisis, desain sistem, coding dan implementasi, sehingga produk dari SIG diperuntukan dapat menghasilkan pemetaan populasi sapi, database identifikasi kepemilikan sapi, jumlah kelompok tani, jumlah sapi yang dimiliki peternak, jumlah sapi yang terjual pasar tradisional, jumlah sapi yang disalurkan keluar daerah dan jumlah populasi yang ada di kabupaten di provinsi NTB
Two dimensional general covariance from three dimensions
A 3d generally covariant field theory having some unusual properties is
described. The theory has a degenerate 3-metric which effectively makes it a 2d
field theory in disguise. For 2-manifolds without boundary, it has an infinite
number of conserved charges that are associated with graphs in two dimensions
and the Poisson algebra of the charges is closed. For 2-manifolds with boundary
there are additional observables that have a Kac-Moody Poisson algebra. It is
further shown that the theory is classically integrable and the general
solution of the equations of motion is given. The quantum theory is described
using Dirac quantization, and it is shown that there are quantum states
associated with graphs in two dimensions.Comment: 10 pages (Latex), Alberta-Thy-19-9
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