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

Superconductivity in 2-2-3 system Y2Ba2Cu2O(8+delta)

Researchers synthesized a new high T(sub c) 2-2-3 superconductor Y2Ba2Cu3O(8+delta) by a special preparation technique and characterized it by ac-susceptibility measurements. Diamagnetism and Meissner effect sets in at low fields and superconducting transition onsets at 90 K. The systematic investigation of the real and imaginary components of ac-susceptibility as a function of temperature and applied ac magnetic field reveals that the magnetic behavior is that of a granular type superconductor

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. ,