Anisotropic static solutions in modelling highly compact bodies

Einstein field equations for anisotropic spheres are solved and exact interior solutions obtained. This paper extends earlier treatments to include anisotropic models which accommodate a wider variety of physically viable energy densities. Two classes of solutions are possible. The first class contains the limiting case $\mu\propto r^{-2}$ for the energy density which arises in many astrophysical applications. In the second class the singularity at the center of the star is not present in the energy density. The models presented in this paper allow for increasing and decreasing profiles in the behavior of the energy density.Comment: 9 pages, to appear in Pramana - J. Phy

A new algorithm for anisotropic solutions

We establish a new algorithm that generates a new solution to the Einstein field equations, with an anisotropic matter distribution, from a seed isotropic solution. The new solution is expressed in terms of integrals of an isotropic gravitational potential; and the integration can be completed exactly for particular isotropic seed metrics. A good feature of our approach is that the anisotropic solutions necessarily have an isotropic limit. We find two examples of anisotropic solutions which generalise the isothermal sphere and the Schwarzschild interior sphere. Both examples are expressed in closed form involving elementary functions only.Comment: 16 pages, to appear in Pramana - J. Phy

General Relativistic Radiant Shock Waves in the Post-Quasistatic Approximation

An evolution of radiant shock wave front is considered in the framework of a recently presented method to study self-gravitating relativistic spheres, whose rationale becomes intelligible and finds full justification within the context of a suitable definition of the post-quasistatic approximation. The spherical matter configuration is divided into two regions by the shock and each side of the interface having a different equation of state and anisotropic phase. In order to simulate dissipation effects due to the transfer of photons and/or neutrinos within the matter configuration, we introduce the flux factor, the variable Eddington factor and a closure relation between them. As we expected the strength of the shock increases the speed of the fluid to relativistic values and for some critical ones is larger than light speed. In addition, we find that energy conditions are very sensible to the anisotropy, specially the strong one. As a special feature of the model, we find that the contribution of the matter and radiation to the radial pressure are the same order of magnitude as in the mant as in the core, moreover, in the core radiation pressure is larger than matter pressure.Comment: To appear in Journal of Physics:Conference Series:"XXIX Spanish Relativity Meeting (ERE 2006): Einstein's Legacy: From the Theoretical Paradise to Astrophysical Observations

Compact anisotropic spheres with prescribed energy density

New exact interior solutions to the Einstein field equations for anisotropic spheres are found. We utilise a procedure that necessitates a choice for the energy density and the radial pressure. This class contains the constant density model of Maharaj and Maartens (Gen. Rel. Grav., Vol 21, 899-905, 1989) and the variable density model of Gokhroo and Mehra (Gen. Rel. Grav., Vol 26, 75-84, 1994) as special cases. These anisotropic spheres match smoothly to the Schwarzschild exterior and gravitational potentials are well behaved in the interior. A graphical analysis of the matter variables is performed which points to a physically reasonable matter distribution.Comment: 22 pages, 3 figures, to appear in Gen. Rel. Gra

On surface tension for compact stars

In an earlier treatment it was demonstrated that general relativity gives higher values of surface tension in strange stars with quark matter than neutron stars.We generate the modified Tolman-Oppenheimer-Volkoff equation to incorporate anisotropic matter and use this to show that pressure anisotropy provides for a wide range of behaviour in the surface tension than is the case with isotropic pressures. In particular it is possible that anisotropy drastically decreases the value of the surface tension.Comment: 8 pages, To appear in J. Astrophys. Astro

Comparison of three nucleic acid-based tests for detecting Anaplasma marginale and Anaplasma centrale in cattle

Several nucleic acid-based assays have been developed for detecting Anaplasma marginale and Anaplasma centrale in vectors and hosts, making the choice of method to use in endemic areas difficult. We evaluated the ability of the reverse line blot (RLB) hybridisation assay, two nested polymerase chain reaction (nPCR) assays and a duplex real-time quantitative polymerase chain reaction (qPCR) assay to detect A. marginale and A. centrale infections in cattle (n = 66) in South Africa. The lowest detection limits for A. marginale plasmid DNA were 2500 copies by the RLB assay, 250 copies by the nPCR and qPCR assays and 2500, 250 and 25 copies of A. centrale plasmid DNA by the RLB, nPCR and qPCR assays respectively. The qPCR assay detected more A. marginale- and A. centrale-positive samples than the other assays, either as single or mixed infections. Although the results of the qPCR and nPCR tests were in agreement for the majority (38) of A. marginale-positive samples, 13 samples tested negative for A. marginale using nPCR but positive using qPCR. To explain this discrepancy, the target sequence region of the nPCR assay was evaluated by cloning and sequencing the msp1β gene from selected field samples. The results indicated sequence variation in the internal forward primer (AM100) area amongst the South African A. marginale msp1β sequences, resulting in false negatives. We propose the use of the duplex qPCR assay in future studies as it is more sensitive and offers the benefits of quantification and multiplex detection of both Anaplasma spp.The National Research Foundation (NRF) of South Africa (grant number 81840 awarded to Dr Nicola Collins) and Technology Innovation Agency (TIA), Tshwane Animal Health Cluster (grant TAHC12-00037 awarded to Professor Marinda Oosthuizen).http://www.ojvr.org/am2017GeneticsVeterinary Tropical Disease

Using Lie Symmetry Analysis to Solve a Problem That Models Mass Transfer from a Horizontal Flat Plate

We use Lie symmetry analysis to solve a boundary value problem that arises in chemical engineering, namely, mass transfer during the contact of a solid slab with an overhead flowing fluid. This problem was earlier tackled using Adomian decomposition method (Fatoorehchi and Abolghasemi 2011), leading to the Adomian series form of solution. It turns out that the application of Lie group analysis yields an elegant form of the solution. After introducing the governing mathematical model and some preliminaries of Lie symmetry analysis, we compute the Lie point symmetries admitted by the governing equation and use these to construct the desired solution as an invariant solution

Dataset: Blood parasites of South African cranes

The study investigated the occurrence, systematics, phylogenetic relationships and ecology (geographical distribution and host-parasite relationships) of haemosporidian parasites from selected populations of cranes (order: Gruiformes) in South African in order to document their prevalence and diversity. It contributes to (1) our understanding of the diversity of avian Haemosporidia of priority avian species (2) the expansion of host range and geographical distribution of these parasites (3) additional information on the barcodes of priority avian taxa for which there is paucity of information. Blood samples were collected from three South African cranes species from selected conservation facilities. DNA was extracted from the samples and analysed by PCR. The cytochrome b gene was sequenced from positive samples. The prevalence of the parasites was determined. Genetic distances, haplotype networks and nucleotide diversity (π) were calculated to estimate genetic diversity. Evolutionary relationships of the new sequences were determined by phylogenetic analysis. Parasite DNA was detected in cranes from 10 facilities, with an overall prevalence of 37.41%. Overall haplotype diversity was high (Hd=0.927) with low nucleotide diversity (π=0.099). A total of 15 lineages (cyt b haplotypes) were identified from South African cranes, with 11 being unique South African haplotypes, composed of three Leucocytozoon haplotypes (Hd=0.600; π=0.038), seven for Haemoproteus (Hd=0.81; π=0.046) and five for Plasmodium species (Hd=0.895; π=0.050). Haemoproteus antigonis was the most common and diverse species and is reported for the first time in South African birds by this study. Metadata (locality, date of collection, species, sex, age, Biobank reference number), PCR results, sequence alignment and sequence data (MalAvi lineages, GenBank Accession numbers, genetic distances) are presented. These data contribute valuable information that can be used in subsequent studies. Highlights: haemosporidian infections (Plasmodium, Haemoproteus and Leucocytozoon spp.) in cranes in South Africa are common and genetically diverse; 15 unique lineages and six distinct species are described, two of these are novel species of captive bred cranes in South African; this is the first report on the occurrence of Haemoproteus antigonis in South Africa and confirmation of cranes as the only hosts of H. antigonis.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV