6,491 research outputs found
The relativistic equations of stellar structure and evolution. Stars with degenerate neutron cores. 1: Structure of equilibrium models
The general relativistic equations of stellar structure and evolution are reformulated in a notation which makes easy contact with Newtonian theory. Also, a general relativistic version of the mixing-length formalism for convection is presented. Finally, it is argued that in previous work on spherical systems general relativity theorists have identified the wrong quantity as "total mass-energy inside radius r.
Transcriptome of the dead: characterisation of immune genes and marker development from necropsy samples in a free-ranging marine mammal
Background
Transcriptomes are powerful resources, providing a window on the expressed portion of the genome that can be generated rapidly and at low cost for virtually any organism. However, because many genes have tissue-specific expression patterns, developing a complete transcriptome usually requires a 'discovery pool' of individuals to be sacrificed in order to harvest mRNA from as many different types of tissue as possible. This hinders transcriptome development in large, charismatic and endangered species, many of which stand the most to gain from such approaches. To circumvent this problem in a model pinniped species, we 454 sequenced cDNA from testis, heart, spleen, intestine, kidney and lung tissues obtained from nine adult male Antarctic fur seals (Arctocephalus gazella) that died of natural causes at Bird Island, South Georgia.
Results
After applying stringent quality control criteria based on length and annotation, we obtained 12,397 contigs which, in combination with 454 data previously obtained from skin, gave a total of 23,096 unique contigs. Homology was found to 77.0% of dog (Canis lupus familiaris) transcripts, suggesting that the combined assembly represents a substantial proportion of this species' transcriptome. Moreover, only 0.5% of transcripts revealed sequence similarity to bacteria, implying minimal contamination, and the percentage of transcripts involved in cell death was low at 2.6%. Transcripts with immune-related annotations were almost five-fold enriched relative to skin and represented 13.2% of all spleen-specific contigs. By reference to the dog, we also identified transcripts revealing homology to five class I, ten class II and three class III genes of the Major Histocompatibility Complex and derived the putative genomic distribution of 17,121 contigs, 2,119 in silico mined microsatellites and 9,382 single nucleotide polymorphisms.
Conclusions
Our findings suggest that transcriptome development based on samples collected post mortem may greatly facilitate genomic studies, not only of marine mammals but also more generally of species that are of conservation concern
The historical and social background of Anthony Trollope’s Phineas Finn and Phineas Redux
This thesis takes the form of an investigation into the amount and type of contemporary material which Trollope incorporated into two of the novels in the Parliamentary series: Phineas Finn and Phineas Redux. The connexion between the historical and political events of the mid-nineteenth century and the events in the novels is demonstrated, particularly with regard to the difficulties of forming governments. Trollope's awareness of the nature of political change and the effect this had on his contemporaries is noted. It is also shown that Trollope took two contemporary events - the passing of the Second Reform Bill of I867 and the Disestablishment of the Irish Church – as the basic political material for the two novels, but that he adapted these events for his own purposes. Trollope's accurate observation of the political society of his time, the difficulties which an 'outsider' (in this case an Irishman) had in penetrating it, and of he role which it forced women to play is discussed. Finally, it is shown that Trollope did, on occasion, use certain characteristics of living politicians, particularly Disraeli, Gladstone and Bright, as the model for his own politicians
Non-monotonic orbital velocity profiles around rapidly rotating Kerr-(anti-)de Sitter black holes
It has been recently demonstrated that the orbital velocity profile around
Kerr black holes in the equatorial plane as observed in the locally
non-rotating frame exhibits a non-monotonic radial behaviour. We show here that
this unexpected minimum-maximum feature of the orbital velocity remains if the
Kerr vacuum is generalized to the Kerr-de Sitter or Kerr-anti-de Sitter metric.
This is a new general relativity effect in Kerr spacetimes with non-vanishing
cosmological constant. Assuming that the profile of the orbital velocity is
known, this effect constrains the spacetime parameters.Comment: 9 pages, 4 figures, accepted for Class. Quant. Gra
R-mode Instability of Slowly Rotating Non-isentropic Relativistic Stars
We investigate properties of -mode instability in slowly rotating
relativistic polytropes. Inside the star slow rotation and low frequency
formalism that was mainly developed by Kojima is employed to study axial
oscillations restored by Coriolis force. At the stellar surface, in order to
take account of gravitational radiation reaction effect, we use a near-zone
boundary condition instead of the usually imposed boundary condition for
asymptotically flat spacetime. Due to the boundary condition, complex
frequencies whose imaginary part represents secular instability are obtained
for discrete -mode oscillations in some polytropic models. It is found that
such discrete -mode solutions can be obtained only for some restricted
polytropic models. Basic properties of the solutions are similar to those
obtained by imposing the boundary condition for asymptotically flat spacetime.
Our results suggest that existence of a continuous part of spectrum cannot be
avoided even when its frequency becomes complex due to the emission of
gravitational radiation.Comment: 10 pages, 4 figures, accepted for publlication in PR
Red giants and supergiants with degenerate neutron cores
A new type of stellar model is constructed. It is related to neutron stars as ordinary red giants are related to white dwarfs. Its external appearance is similar to that of an ordinary M supergiant, but its evolutionary lifetime is 10 times longer.
Our models are constrained to be relativistic but nonrotating, to constrain a degenerate neutron core of mass 1 M⊙ and radius 10 km, surrounded by a nondegenerate, massive, diffuse envelope. The core and envelope turn out to be separated by a thin (~40 m) energy-generation layer. The envelope convects from this layer all the way out to the photosphere. The effective temperatures and radii are ~2700 K and ~1000 R⊙. Within a fairly narrow range of effective temperatures and radii, two families of models were found: "red giants" and "red supergiants" with luminosities and masses less than and greater than ~65,000 L⊙ and ~10 M⊙, respectively. The luminosity of a giant comes 97 percent from gravitational contraction and 3 percent from nuclear burning. That of a supergiant is 5 percent from gravitational contraction and 95 percent from hydrogen burning by nonequilibrium, hot CNO reactions. The CNO reaction products are convected directly from the hydrogen-burning shell out to the photosphere of the supergiant, where they should be observable
Chorus acceleration of radiation belt relativistic electrons during March 2013 geomagnetic storm
Abstract The recent launching of Van Allen probes provides an unprecedent opportunity to investigate variations of the radiation belt relativistic electrons. During the 17-19 March 2013 storm, the Van Allen probes simultaneously detected strong chorus waves and substantial increases in fluxes of relativistic (2 - 4.5 MeV) electrons around L = 4.5. Chorus waves occurred within the lower band 0.1-0.5fce (theelectron equatorial gyrofrequency), with a peak spectral density ∼10-4 nT 2/Hz. Correspondingly, relativistic electron fluxes increased by a factor of 102-103 during the recovery phase compared to the main phase levels. By means of a Gaussian fit to the observed chorus spectra, the drift and bounce-averaged diffusion coefficients are calculated and then used to solve a 2-D Fokker-Planck diffusion equation. Numerical simulations demonstrate that the lower-band chorus waves indeed produce such huge enhancements in relativistic electron fluxes within 15 h, fitting well with the observation. Key Points Initial RBSP correlated data of chorus waves and relativistic electron fluxes A realistic simulation to examine effect of chorus on relativistic electron flux Chorus yields huge increases inelectron flux rapidly, consistent with data
What is the maximum rate at which entropy of a string can increase?
According to Susskind, a string falling toward a black hole spreads
exponentially over the stretched horizon due to repulsive interactions of the
string bits. In this paper such a string is modeled as a self-avoiding walk and
the string entropy is found. It is shown that the rate at which
information/entropy contained in the string spreads is the maximum rate allowed
by quantum theory. The maximum rate at which the black hole entropy can
increase when a string falls into a black hole is also discussed.Comment: 11 pages, no figures; formulas (18), (20) are corrected (the quantum
constant is added), a point concerning a relation between the Hawking and
Hagedorn temperatures is corrected, conclusions unchanged; accepted by
Physical Review D for publicatio
Shell sources as a probe of relativistic effects in neutron star models
A perturbing shell is introduced as a device for studying the excitation of
fluid motions in relativistic stellar models. We show that this approach allows
a reasonably clean separation of radiation from the shell and from fluid
motions in the star, and provides broad flexibility in the location and
timescale of perturbations driving the fluid motions. With this model we
compare the relativistic and Newtonian results for the generation of even
parity gravitational waves from constant density models. Our results suggest
that relativistic effects will not be important in computations of the
gravitational emission except possibly in the case of excitation of the neutron
star on very short time scales.Comment: 16 pages LaTeX with 6 eps figures; submitted to Phys. Rev.
Source integrals of asymptotic multipole moments
We derive source integrals for multipole moments that describe the behaviour
of static and axially symmetric spacetimes close to spatial infinity. We assume
isolated non-singular sources but will not restrict the matter content
otherwise. Some future applications of these source integrals of the asymptotic
multipole moments are outlined as well.Comment: 9 pages, 1 figure, contribution to the proceedings of the conference
"Relativity and Gravitation - 100 Years after Einstein in Prague", June
25-29, 2012, Pragu
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