759 research outputs found
Tachyonic potential in Bianchi type-I universe
Motivated from recent string theoretic results, a tachyonic potential is
constructed for a spatially homogeneous and anisotropic background cosmology.Comment: 5 pages,LATEX,Typos in the text corrected, more references adde
Cosmological Models with Shear and Rotation
Cosmological models involving shear and rotation are considered, first in the
General Relat ivistic and then in the Newtonian framework with the aim of
investigating singularities in them by using numerical and analytical
techniques. The dynamics of these rotating models ar e studied. It is shown
that singularities are unavoidable in such models and that the centr ifugal
force arising due to rotation can never overcome the gravitational and shearing
forc e over a length of time.Comment: 17 pages, 6 figures Journal Ref: J. Astrophys. Astr. (1999) 20, 79-8
A phase 3 multicenter, prospective, open-label efficacy and safety study of immune globulin (human) 10% caprylate/chromatography purified in patients with myasthenia gravis exacerbations
Background: Myasthenia gravis (MG) is an autoimmune disorder affecting neuromuscular transmission. Exacerbations may involve increasing bulbar weakness and/or sudden respiratory failure, both of which can be critically disabling. Management of MG exacerbations includes plasma exchange and intravenous immunoglobulin (IVIG); they are equally effective, but patients experience fewer side effects with IVIG. The objective of this study was to assess the efficacy and safety of immune globulin caprylate/chromatography purified (IGIV-C) in subjects with MG exacerbations. Methods: This prospective, open-label, non-controlled 28-day clinical trial was conducted in adults with MG Foundation of America class IVb or V status. Subjects received IGIV-C 2 g/kg over 2 consecutive days (1 g/kg/day) and were assessed for efficacy/safety on Days 7, 14, 21, and 28. The primary efficacy endpoint was the change from Baseline in quantitative MG (QMG) score to Day 14. Secondary endpoints of clinical response, Baseline to Day 14, included at least a 3-point decrease in QMG and MG Composite and a 2-point decrease in MG-activities of daily living (MG-ADL). Results: Forty-nine subjects enrolled. The change in QMG score at Day 14 was significant (p < 0.001) in the Evaluable (-6.4, n = 43) and Safety (-6.7, n = 49) populations. Among evaluable subjects, Day 14 response rates were 77, 86, and 88% for QMG, MG Composite, and MG-ADL, respectively. IGIV-C showed good tolerability with no serious adverse events. Conclusions: The results of this study show that IGIV-C was effective, safe, and well tolerated in the treatment of MG exacerbations
Anisotropy and inflation in Bianchi I brane worlds
After a more general assumption on the influence of the bulk on the brane, we
extend some conclusions by Maartens et al. and Santos et al. on the asymptotic
behavior of Bianchi I brane worlds. As a consequence of the nonlocal
anisotropic stresses induced by the bulk, in most of our models, the brane does
not isotropize and the nonlocal energy does not vanish in the limit in which
the mean radius goes to infinity. We have also found the intriguing possibility
that the inflation due to the cosmological constant might be prevented by the
interaction with the bulk. We show that the problem for the mean radius can be
completely solved in our models, which include as particular cases those in the
references above.Comment: 10 pages, improved discussion on the likeliness of
non-isotropization, completed list of references, matches version to appear
in Class. Quantum Gra
Program transformations using temporal logic side conditions
This paper describes an approach to program optimisation based on transformations, where temporal logic is used to specify side conditions, and strategies are created which expand the repertoire of transformations and provide a suitable level of abstraction. We demonstrate the power of this approach by developing a set of optimisations using our transformation language and showing how the transformations can be converted into a form which makes it easier to apply them, while maintaining trust in the resulting optimising steps. The approach is illustrated through a transformational case study where we apply several optimisations to a small program
Newtonian Cosmology in Lagrangian Formulation: Foundations and Perturbation Theory
The ``Newtonian'' theory of spatially unbounded, self--gravitating,
pressureless continua in Lagrangian form is reconsidered. Following a review of
the pertinent kinematics, we present alternative formulations of the Lagrangian
evolution equations and establish conditions for the equivalence of the
Lagrangian and Eulerian representations. We then distinguish open models based
on Euclidean space from closed models based (without loss of generality)
on a flat torus \T^3. Using a simple averaging method we show that the
spatially averaged variables of an inhomogeneous toroidal model form a
spatially homogeneous ``background'' model and that the averages of open
models, if they exist at all, in general do not obey the dynamical laws of
homogeneous models. We then specialize to those inhomogeneous toroidal models
whose (unique) backgrounds have a Hubble flow, and derive Lagrangian evolution
equations which govern the (conformally rescaled) displacement of the
inhomogeneous flow with respect to its homogeneous background. Finally, we set
up an iteration scheme and prove that the resulting equations have unique
solutions at any order for given initial data, while for open models there
exist infinitely many different solutions for given data.Comment: submitted to G.R.G., TeX 30 pages; AEI preprint 01
Possible extensions of the standard cosmological model: anisotropy, rotation, and magnetic field
We show that the difference between the theoretically expected and measured
by WMAP amplitude of the quadrupole fluctuations of CMB can be related to the
impact of the anisotropic curvature of the homogeneous universe dominated by
the dark energy. In such universe the matter expansion becomes practically
isotropic just after the period of inflation and only at small redshifts the
anisotropic expansion is generated again by the small curvature . For such models the possible deviations
from the parameters derived for the standard cosmological model are evidently
negligible but the correlations of large scale perturbations and distortions of
their Gaussianity are possible. Such models are also compatible with existence
of a homogeneous magnetic field and matter rotation which contribute to the low
anisotropy and can be considered as ``hidden parameters'' of the model.
Their influence can be observed as, for example, special correlations of small
scale fluctuations and the Faraday rotation of the CMB and radiation of the
farthest quasars. However, both the magnetic field and matter rotation require
also modifications of the simple models of isotropic inflation and they change
the evolutionary history of the early Universe.Comment: 7 page
Anti-phosphorylated histone H2AThr120: A universal microscopic marker for centromeric chromatin of mono- and holocentric plant species
Based on the analysis of 20 different monocot and eudicot species, we propose that the centromeric distribution of the phosphorylated histone H2AThr120 is evolutionary highly conserved across species with mono- and holocentric chromosomes. Therefore, antibodies recognizing the phosphorylated threonine 120 of the histone H2A can serve as a universal marker for the cytological detection of centromeres of mono- and holokinetic plant species. In addition, super resolution microscopy of signals specific to the centromere-specific histone H3 variant CENH3 and to H2AThr120ph revealed that these histone variants are incorporated into different nucleosomes, which form distinct, partly intermingled chromatin domains. This specific arrangement of both histone variants suggests different centromeric functions during the cell cycle
- …