Improved table for cutting and welding

Welding table covered with parallel inverted steel angles improves metal torch cutting of various types and thicknesses

Accretion disks around black holes: dynamical evolution, meridional circulations and gamma ray bursts

We study the hydrodynamical evolution of massive accretion disks around black holes, formed when a neutron star is disrupted by a black hole in a binary system. Initial conditions are taken from 3D calculations of coalescing binaries. Assuming azimuthal symmetry, we follow the time dependence of the disk structure for 0.2 seconds. We use an ideal gas e.o.s., and assume that all the dissipated energy is radiated away. The disks evolve due to viscous stresses, modeled with an alpha law. We study the disk structure, and the strong meridional circulations that are established and persist throughout our calculations. These consist of strong outflows along the equatorial plane that reverse direction close to the surface of the disk and converge on the accretor. In the context of GRBs, we estimate the energy released from the system in neutrinos and through magnetic-dominated mechanisms, and find it can be as high as 10^52 erg and 10^51 erg respectively, during an estimated timescale of 0.1-0.2 seconds. neutrino-anti neutrino annihilation is likely to produce bursts from only an impulsive energy input (the annihilation luminosity scales as t^(-5/2)) and so would be unable to account for a large fraction of bursts with complicated light curves. However a gas mass ~0.1-0.25 Msun survives in the orbiting debris, enabling strong magnetic fields (~10^16 Gauss) to be anchored in the dense matter long enough to power short GRBs. We also investigate the continuous energy injection that arises as the black hole slowly swallows the rest of the disk and discuss its consequences on the GRB afterglow emission.Comment: Accepted for publication in ApJ, 30 pages, 7 figure

The effect of the lateral interactions on the critical behavior of long straight rigid rods on two-dimensional lattices

Using Monte Carlo simulations and finite-size scaling analysis, the critical behavior of attractive rigid rods of length k (k-mers) on square lattices at intermediate density has been studied. A nematic phase, characterized by a big domain of parallel k-mers, was found. This ordered phase is separated from the isotropic state by a continuous transition occurring at a intermediate density \theta_c, which increases linearly with the magnitude of the lateral interactions.Comment: 7 pages, 6 figure