578 research outputs found
Loop expansion in Yang-Mills thermodynamics
We argue that a selfconsistent spatial coarse-graining, which involves
interacting (anti)calorons of unit topological charge modulus, implies that
real-time loop expansions of thermodynamical quantities in the deconfining
phase of SU(2) and SU(3) Yang-Mills thermodynamics are, modulo 1PI
resummations, determined by a finite number of connected bubble diagrams.Comment: 15 pages, 2 figures, v5: discussion of much more severely constrained
nonplanar situation included in Sec.
Primordial Black Holes: sirens of the early Universe
Primordial Black Holes (PBHs) are, typically light, black holes which can
form in the early Universe. There are a number of formation mechanisms,
including the collapse of large density perturbations, cosmic string loops and
bubble collisions. The number of PBHs formed is tightly constrained by the
consequences of their evaporation and their lensing and dynamical effects.
Therefore PBHs are a powerful probe of the physics of the early Universe, in
particular models of inflation. They are also a potential cold dark matter
candidate.Comment: 21 pages. To be published in "Quantum Aspects of Black Holes", ed. X.
Calmet (Springer, 2014
Energy Content of Colliding Plane Waves using Approximate Noether Symmetries
This paper is devoted to study the energy content of colliding plane waves
using approximate Noether symmetries. For this purpose, we use approximate Lie
symmetry method of Lagrangian for differential equations. We formulate the
first-order perturbed Lagrangian for colliding plane electromagnetic and
gravitational waves. It is shown that in both cases, there does not existComment: 18 pages, accepted for publication in Brazilian J Physic
Immediate response of myocardium to pressure overload includes transient regulation of genes associated with mitochondrial bioenergetics and calcium availability
Ventricular hypertrophy is one of the major myocardial responses to pressure overload (PO). Most studies on early myocardial response focus on the days or even weeks after induction of hypertrophic stimuli. Since mechanotransduction pathways are immediately activated in hearts undergoing increased work load, it is reasonable to infer that the myocardial gene program may be regulated in the first few hours. In the present study, we monitored the expression of some genes previously described in the context of myocardial hypertrophic growth by using the Northern blot technique, to estimate the mRNA content of selected genes in rat myocardium for the periods 1, 3, 6, 12 and 48 h after PO stimuli. Results revealed an immediate switch in the expression of genes encoding alpha and beta isoforms of myosin heavy chain, and up-regulation of the cardiac isoform of alpha actin. We also detected transitory gene regulation as the increase in mitochondrial cytochrome c oxidase 1 gene expression, parallel to down-regulation of genes encoding sarco(endo)plasmic reticulum Ca+2 ATPase and sodium-calcium exchanger. Taken together, these results indicate that initial myocardial responses to increased work load include alterations in the contractile properties of sarcomeres and transitory adjustment of mitochondrial bioenergetics and calcium availability
Semi-analytical approach to magnetized temperature autocorrelations
The cosmic microwave background (CMB) temperature autocorrelations, induced
by a magnetized adiabatic mode of curvature inhomogeneities, are computed with
semi-analytical methods. As suggested by the latest CMB data, a nearly
scale-invariant spectrum for the adiabatic mode is consistently assumed. In
this situation, the effects of a fully inhomogeneous magnetic field are
scrutinized and constrained with particular attention to harmonics which are
relevant for the region of Doppler oscillations. Depending on the parameters of
the stochastic magnetic field a hump may replace the second peak of the angular
power spectrum. Detectable effects on the Doppler region are then expected only
if the magnetic power spectra have quasi-flat slopes and typical amplitude
(smoothed over a comoving scale of Mpc size and redshifted to the epoch of
gravitational collapse of the protogalaxy) exceeding 0.1 nG. If the magnetic
energy spectra are bluer (i.e. steeper in frequency) the allowed value of the
smoothed amplitude becomes, comparatively, larger (in the range of 20 nG). The
implications of this investigation for the origin of large-scale magnetic
fields in the Universe are discussed. Connections with forthcoming experimental
observations of CMB temperature fluctuations are also suggested and partially
explored.Comment: 40 pages, 13 figure
Measuring our universe from galaxy redshift surveys
Galaxy redshift surveys have achieved significant progress over the last
couple of decades. Those surveys tell us in the most straightforward way what
our local universe looks like. While the galaxy distribution traces the bright
side of the universe, detailed quantitative analyses of the data have even
revealed the dark side of the universe dominated by non-baryonic dark matter as
well as more mysterious dark energy (or Einstein's cosmological constant). We
describe several methodologies of using galaxy redshift surveys as cosmological
probes, and then summarize the recent results from the existing surveys.
Finally we present our views on the future of redshift surveys in the era of
Precision Cosmology.Comment: 82 pages, 31 figures, invited review article published in Living
Reviews in Relativity, http://www.livingreviews.org/lrr-2004-
Elevated Uptake of Plasma Macromolecules by Regions of Arterial Wall Predisposed to Plaque Instability in a Mouse Model
Atherosclerosis may be triggered by an elevated net transport of lipid-carrying
macromolecules from plasma into the arterial wall. We hypothesised that whether
lesions are of the thin-cap fibroatheroma (TCFA) type or are less fatty and more
fibrous depends on the degree of elevation of transport, with greater uptake leading
to the former. We further hypothesised that the degree of elevation can depend on
haemodynamic wall shear stress characteristics and nitric oxide synthesis. Placing
a tapered cuff around the carotid artery of apolipoprotein E -/- mice modifies
patterns of shear stress and eNOS expression, and triggers lesion development at
the upstream and downstream cuff margins; upstream but not downstream lesions
resemble the TCFA. We measured wall uptake of a macromolecular tracer in the
carotid artery of C57bl/6 mice after cuff placement. Uptake was elevated in the
regions that develop lesions in hyperlipidaemic mice and was significantly more
elevated where plaques of the TCFA type develop. Computational simulations and
effects of reversing the cuff orientation indicated a role for solid as well as fluid
mechanical stresses. Inhibiting NO synthesis abolished the difference in uptake
between the upstream and downstream sites. The data support the hypothesis that
excessively elevated wall uptake of plasma macromolecules initiates the
development of the TCFA, suggest that such uptake can result from solid and fluid
mechanical stresses, and are consistent with a role for NO synthesis. Modification
of wall transport properties might form the basis of novel methods for reducing
plaque rupture
Therapeutic efficacy of sulphadoxine-pyrimethamine and chloroquine for the treatment of uncomplicated malaria in pregnancy in Burkina Faso
BACKGROUND: A reduction in the therapeutic efficacy of chloroquine (CQ) and sulphadoxine-pyrimethamine (SP) has recently been observed in Burkina Faso. As these two drugs are used in pregnancy, their efficacy in pregnant women was studied to directly assess the level of drug resistance in this specific population, rather than to extrapolate results of studies conducted in children < 5 years of age. METHODS: During the malaria transmission season of 2003 in Ouagadougou, the clinical efficacy of SP and CQ, using the WHO 28-day protocol, was assessed in primigravidae and secundigravidae presenting with uncomplicated malaria. RESULTS: PCR-corrected results by day 28 showed that among 62 women treated with SP, eight (12.9%) experienced late parasitological failure, but no clinical failures. Among 60 women treated with CQ, the overall failure rate was 46.7% including 1.7% early treatment failures, 5% late clinical failures and 40% late parasitological failures. SP induced a haemoglobin gain of 0.3 g/dL by day 14 and 0.9 g/dL by day 28. Treatment responses were independent of gravidity, gestational age and prior antenatal care visits. CONCLUSION: While CQ should no longer be used, the efficacy of SP is still compatible with use for intermittent preventive treatment (IPT) in pregnancy. However, given the possible spread of resistance, the drug should be restricted in its use
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