Gravitational Instability in Collisionless Cosmological Pancakes

The gravitational instability of cosmological pancakes composed of collisionless dark matter in an Einstein-de Sitter universe is investigated numerically to demonstrate that pancakes are unstable with respect to fragmentation and the formation of filaments. A ``pancake'' is defined here as the nonlinear outcome of the growth of a 1D, sinusoidal, plane-wave, adiabatic density perturbation. We have used high resolution, 2D, N-body simulations by the Particle-Mesh (PM) method to study the response of pancakes to perturbation by either symmetric (density) or antisymmetric (bending or rippling) modes, with corresponding wavevectors k_s and k_a transverse to the wavevector k_p of the unperturbed pancake plane-wave. We consider dark matter which is initially ``cold'' (i.e. with no random thermal velocity in the initial conditions). We also investigate the effect of a finite, random, isotropic, initial velocity dispersion (i.e. initial thermal velocity) on the fate of pancake collapse and instability. Pancakes are shown to be gravitationally unstable with respect to all perturbations of wavelength l<l_p (where l_p= 2pi/k_p). These results are in contradiction with the expectations of an approximate, thin-sheet energy argument.Comment: To appear in the Astrophysical Journal (1997), accepted for publication 10/10/96, single postscript file, 61 pages, 19 figure

Propfan test assessment testbed aircraft stability and control/performance 1/9-scale wind tunnel tests

One-ninth scale wind tunnel model tests of the Propfan Test Assessment (PTA) aircraft were performed in three different NASA facilities. Wing and propfan nacelle static pressures, model forces and moments, and flow field at the propfan plane were measured in these tests. Tests started in June 1985 and were completed in January 1987. These data were needed to assure PTA safety of flight, predict PTA performance, and validate analytical codes that will be used to predict flow fields in which the propfan will operate

On the Dynamical Ferromagnetic, Quantum Hall, and Relativistic Effects on the Carbon Nanotubes Nucleation and Growth Mechanism

The mechanism of carbon nanotube (CNT) nucleation and growth has been a mystery for over 15 years. Prior models have attempted the extension of older classical transport mechanisms. In July 2000, a more detailed and accurate nonclassical, relativistic mechanism was formulated considering the detailed dynamics of the electronics of spin and orbital rehybridization between the carbon and catalyst via novel mesoscopic phenomena and quantum dynamics. Ferromagnetic carbon was demonstrated. Here, quantum (Hall) effects and relativistic effects of intense many body spin-orbital interactions for novel orbital rehybridization dynamics (Little Effect) are proposed in this new dynamical magnetic mechanism. This dynamic ferromagnetic mechanism is proven by imposing dynamic and static magnetic fields during CNT syntheses and observing the different influence of these external magnetic environments on the catalyzing spin currents and spin waves and the resulting CNT formation

7-Li(p,n) Nuclear Data Library for Incident Proton Energies to 150 MeV

We describe evaluation methods that make use of experimental data, and nuclear model calculations, to develop an ENDF-formatted data library for the reaction p + Li7 for incident protons with energies up to 150 MeV. The important 7-Li(p,n_0) and 7-Li(p,n_1) reactions are evaluated from the experimental data, with their angular distributions represented using Lengendre polynomial expansions. The decay of the remaining reaction flux is estimated from GNASH nuclear model calculations. The evaluated ENDF-data are described in detail, and illustrated in numerous figures. We also illustrate the use of these data in a representative application by a radiation transport simulation with the code MCNPX.Comment: 11 pages, 8 figures, LaTeX, submitted to Proc. 2000 ANS/ENS International Meeting, Nuclear Applications of Accelerator Technology (AccApp00), November 12-16, Washington, DC, US