Anisotropic Compacts Stars on Paraboloidal Spacetime with Linear Equation of State

New exact solutions of Einstein's field equations (EFEs) by assuming linear equation of state, $p_r = \alpha (\rho - \rho_R)$ where $p_r$ is the radial pressure and $\rho_R$ is the surface density, are obtained on the background of a paraboloidal spacetime. By assuming estimated mass and radius of strange star candidate 4U 1820-30, various physical and energy conditions are used for estimating the range of parameter $\alpha$. The suitability of the model for describing pulsars like PSR J1903+327, Vela X-1, Her X-1 and SAX J1804.3658 has been explored and respective ranges of $\alpha$, for which all physical and energy conditions are satisfied throughout the distribution, are obtained.Comment: 10 pages, 12 figures, 1 tabl

Six billion and counting

In 1999 global population surpassed 6 billion people, and this number rises by about 70-80 million people each year. "Six Billion and Counting" examines the consequences of continuing population growth for the world's resource systems and for national and global food security. Leisinger, Schmitt, and Pandya-Lorch offer here a sober analysis of a complex and alarming situation. They assess the progress the world has made in controlling population growth and point to the areas where future difficulties will lie. They describe the effects of rapid population growth on social and economic conditions and on natural resources, and they consider what population growth will mean for the food security of poor people and poor countries. In addition, the authors make clear how the roles of women and children in traditional societies affect birth rates. "Six Billion and Counting" shows that neither the population pessimists, who predict a catastrophic exhaustion of natural resources, nor the population optimists, who foresee technological solutions for all of the problems raised by population growth, offer the most useful approach to this problem. Instead, Leisinger and his coauthors argue that new technologies mitigating the harmful effects of rapid population growth can give the world valuable time to take the complex and multifaceted steps needed to reduce population growth rates to sustainable levels.Population forecasting. ,Population Economic aspects. ,Food security. ,Population Environmental aspects ,Technological innovations. ,Population policy. ,

Trypanosoma Brucei Telomere Functions in Antigenic Variation

Trypanosoma brucei is a protozoan parasite that causes sleeping sickness in humans and Nagana in cattle. They evade the host\u27s immune defense by periodically switching their major surface antigen, variant surface glycoprotein (VSG), a phenomenon termed antigenic variation. Inside its mammalian host, bloodstream form (BF) T. brucei monoallelically expresses its major surface molecule VSG from the VSG Expression Sites (ESs) located at subtelomeric loci. Monoallelic VSG expression ensures effective antigenic variation and maximizes the efficiency of T. brucei pathogenesis. In the mid-gut of its insect host (tsetse), procyclic form (PF) T. brucei expresses procyclins as the major surface molecules and all VSGs are silent. After the migration to the salivary glands of the tsetse fly, T. brucei cells differentiate into metacyclic forms and express metacyclic VSGs (mVSGs). Therefore, VSG silencing is important for the normal development of T. brucei. Telomeres are important for the regulation of antigenic variation. TbRAP1 was previously identified as an intrinsic component of the T. brucei telomere complex and was shown to be important for ES-linked VSG silencing in BF cells. Our studies further established that TbRAP1 is essential for cell proliferation and required for VSG silencing in PF cells. Apart form ES-linked VSGs, TbRAP1 also regulates the silencing of mVSGs in both BF and PF cells. The strength of TbRAP1 mediated VSG silencing is stronger in PF cells compared to that in the BF cells. In addition, the TbRAP1-mediated VSG silencing in PF cells involves chromatin remodeling. TbTRF, a duplex telomere DNA binding protein that interacts with TbRAP1, does not affect VSG silencing but regulates telomere structure. TbTRFH (TRF homology domain) is required for the homodimerization of TbTRF as well as for interaction with TbRAP1. We established several TbTRFH mutants and determined the critical regions required for homodimerization of TbTRF by performing yeast two-hybrid analysis. TERRA (telomeric repeat- c

Trypanosoma Brucei Telomere Functions in Antigenic Variation

Trypanosoma brucei is a protozoan parasite that causes sleeping sickness in humans and Nagana in cattle. They evade the host\u27s immune defense by periodically switching their major surface antigen, variant surface glycoprotein (VSG), a phenomenon termed antigenic variation. Inside its mammalian host, bloodstream form (BF) T. brucei monoallelically expresses its major surface molecule VSG from the VSG Expression Sites (ESs) located at subtelomeric loci. Monoallelic VSG expression ensures effective antigenic variation and maximizes the efficiency of T. brucei pathogenesis. In the mid-gut of its insect host (tsetse), procyclic form (PF) T. brucei expresses procyclins as the major surface molecules and all VSGs are silent. After the migration to the salivary glands of the tsetse fly, T. brucei cells differentiate into metacyclic forms and express metacyclic VSGs (mVSGs). Therefore, VSG silencing is important for the normal development of T. brucei. Telomeres are important for the regulation of antigenic variation. TbRAP1 was previously identified as an intrinsic component of the T. brucei telomere complex and was shown to be important for ES-linked VSG silencing in BF cells. Our studies further established that TbRAP1 is essential for cell proliferation and required for VSG silencing in PF cells. Apart form ES-linked VSGs, TbRAP1 also regulates the silencing of mVSGs in both BF and PF cells. The strength of TbRAP1 mediated VSG silencing is stronger in PF cells compared to that in the BF cells. In addition, the TbRAP1-mediated VSG silencing in PF cells involves chromatin remodeling. TbTRF, a duplex telomere DNA binding protein that interacts with TbRAP1, does not affect VSG silencing but regulates telomere structure. TbTRFH (TRF homology domain) is required for the homodimerization of TbTRF as well as for interaction with TbRAP1. We established several TbTRFH mutants and determined the critical regions required for homodimerization of TbTRF by performing yeast two-hybrid analysis. TERRA (telomeric repeat- c