The evolution of a Ku-Band satellite network

The purpose of this study was to undertake the management and development of CTS terminals and time on appropriate Ku-Band satellites was procured. A community of public service users who have readily addressable needs and resources to pay for services on an ad hoc Ku-Band network was developed and a test network for selected users was managed

Ignition characteristics of the iron-based alloy UNS S66286 in pressurized oxygen

The development of ignition and combustion in pressurized oxygen atmospheres was studied for the iron based alloy UNS S66286. Ignition of the alloy was achieved by heating the top surface of a cylindrical specimen with a continuous-wave CO2 laser. Two heating procedures were used. In the first, laser power was adjusted to maintain an approximately linear increase in surface temperature. In the second, laser power was periodically increased until autoheating (self-heating) was established. It was found that the alloy would autoheat to destruction from temperatures below the solidus temperature. In addition endothermic events occurred as the alloy was heated, many at reproducible temperatures. Many endothermic events occurred prior to abrupt increases in surface temperature and appeared to accelerate the rate of increase in specimen temperature to rates greater than what would be expected from increased temperature alone. It is suggested that the source of these endotherms may increase the oxidation rate of the alloy. Ignition parameters are defined and the temperatures at which these parameters occur are given for the oxygen pressure range of 1.72 to 13.8 MPa (25 to 2000 psia)

Ignition characteristics of the nickel-based alloy UNS N07718 in pressurized oxygen

The development of ignition and combustion in pressurized oxygen atmospheres was studied for the nickel based alloy UNS N07718. Ignition of the alloy was achieved by heating the top. It was found that the alloy would autoheat to destruction from temperatures below the solidus temperature. In addition, endothermic events occurred as the alloy was heated, many at reproducible temperatures. Many endothermic events occurred prior to abrupt increases in surface temperature and appeared to accelerate the rate of increase in specimen temperature. It appeared that the source of some endotherms may increase the oxidation rate of the alloy. Ignition parameters are defined and the temperatures at which these parameters occur are given for the oxygen pressure range of 1.72 to 13.8 MPa (250 to 2000 psia)

HII Shells Surrounding Wolf-Rayet stars in M31

We present the results of an ongoing investigation to provide a detailed view of the processes by which massive stars shape the surrounding interstellar medium (ISM), from pc to kpc scales. In this paper we have focused on studying the environments of Wolf-Rayet (WR) stars in M31 to find evidence for WR wind-ISM interactions, through imaging ionized hydrogen nebulae surrounding these stars. We have conducted a systematic survey for HII shells surrounding 48 of the 49 known WR stars in M31. There are 17 WR stars surrounded by single shells, or shell fragments, 7 stars surrounded by concentric limb brightened shells, 20 stars where there is no clear physical association of the star with nearby H-alpha emission, and 4 stars which lack nearby H-alpha emission. For the 17+7 shells above, there are 12 which contain one or two massive stars (including a WR star) and that are <=40 pc in radius. These 12 shells may be classical WR ejecta or wind-blown shells. Further, there may be excess H-alpha point source emission associated with one of the 12 WR stars surrounded by putative ejecta or wind-blown shells. There is also evidence for excess point source emission associated with 11 other WR stars. The excess emission may arise from unresolved circumstellar shells, or within the extended outer envelopes of the stars themselves. In a few cases we find clear morphological evidence for WR shells interacting with each other. In several H-alpha images we see WR winds disrupting, or punching through, the walls of limb-brightened HII shells.Comment: 20 pages, 4 figures (in several parts: some .jpg and others .ps), accepted to AJ (appearing Oct, 1999

The HI and Ionized Gas Disk of the Seyfert Galaxy NGC 1144 = Arp 118: A Violently Interacting Galaxy with Peculiar Kinematics

We present observations of the distribution and kinematics of neutral and ionized gas in NGC 1144, a galaxy that forms part of the Arp 118 system. Ionized gas is present over a huge spread in velocity (1100 km/s) in the disk of NGC 1144, but HI emission is detected over only 1/3 of this velocity range, in an area that corresponds to the NW half of the disk. In the nuclear region of NGC 1144, a jump in velocity in the ionized gas component of 600 km/s is observed. Faint, narrow HI absorption lines are also detected against radio sources in the SE part of the disk of NGC 1144, which includes regions of massive star formation and a Seyfert nucleus. The peculiar HI distribution, which is concentrated in the NW disk, seems to be the inverse of the molecular distribution which is concentrated in the SE disk. Although this may partly be the result of the destruction of HI clouds in the SE disk, there is circumstantial evidence that the entire HI emission spectrum of NGC 1144 is affected by a deep nuclear absorption line covering a range of 600 km/s, and is likely blueshifted with respect to the nucleus. In this picture, a high column-density HI stream is associated with the nuclear ionized gas velocity discontinuity, and the absorption effectively masks any HI emission that would be present in the SE disk of NGC 1144.Comment: manuscript, arp118.ps: 28 pages; 1 Table: arp118.tab1.ps; 16 Figures: arp118.fig1-16.ps; Accepted to Ap

Radio-Luminous Southern Seyfert Galaxies. I. Radio Images and Selected Optical/Near-Infrared Spectroscopy

This is the first of two papers in which a study is made of a sample of 12 southern radio-luminous Seyfert galaxies. Our aim is to investigate possible correlations between radio morphology and nuclear/circumnuclear emission-line properties. In this paper we present radio images at 13, 6, and 3 cm taken with the Australia Telescope Compact Array (ATCA), global far-infrared (FIR) properties for the whole sample, and optical and near-infrared (NIR) spectroscopy of an interesting subset. We find a mixture of radio morphologies, including linear, diffuse and compact sources. When the FIR colors of the galaxies are considered there is an indication that the compact radio sources have warmer FIR colors than the diffuse sources, whereas the linear sources span a wide range of FIR colors. There is a wide variation in radio spectral-indices, suggesting that free-free absorption is significant in some systems, particularly IRAS 11249-2859, NGC 4507, and NGC 7213. Detailed emission-line studies are presented of 4 galaxies IC 3639, NGC 5135, NGC 3393 & IRAS 11249-2859. In IC 3639 we present evidence of vigorous, compact star formation enclosed by very extended [OI]6300 emission, suggestive of the boundary between a diffuse outflow and the surrounding ISM. In another galaxy, IC 5063, we see evidence for the possible interaction of a highly collimated outflow and the surrounding rotating inner disk. Of the 5 galaxies which show compact radio emission, 4 have radio/FIR flux ratios consistent with an energetically dominant AGN, whereas IC 4995 exhibits evidence for a very compact starburst.Comment: 42 pages, including 7 tables, latex, 19 jpeg figures, Accepted to ApJ. Replacement updates coordintes of galaxies in Table

Azimuthal and Kinematic Segregation of Neutral and Molecular Gas in Arp 118: The Yin-Yang Galaxy NGC 1144

We present new high-resolution HI observations of the disk of the collisional infrared luminous (L$_{\rm IR}=2.2\times10^{11}$ L_{\sun}) galaxy NGC 1144, which reveal an apparent large-scale azimuthal and kinematic segregation of neutral hydrogen relative to the molecular gas distribution. Even among violently collisional galaxies, the CO/HI asymmetry in NGC 1144 is unusual, both in the inner regions, and in the outer disk. We suggest that we are observing Arp 118 at a special moment, shortly after a high-speed collision between NGC 1144 and its elliptical companion NGC 1143. HI emission with an average molecular fraction f$_{mol}$ $<$ 0.5 is observed on one side (NW) of the rotating disk of NGC 1144, while the other side (SE) is dominated by dense molecular complexes in which f$_{mol}$ is almost unity. The interface region between the warm-- and cool--cloud dominated regions, lies on a deep spiral-like dust-lane which we identify as a shock-wave responsible for the relative shift in the dominance of HI and H$_2$ gas. A strong shock being fed by diffuse HI clouds with unusually large ($>$ 400 km s$^{-1}$) rotational velocities can explain: 1) the CO/HI asymmetries, 2) a large velocity jump (185 km s$^{-1}$) across the arm as measured by HI absorption against a radio bright continuum source which straddles the arm, and 3) the asymmetric distribution of star formation and off-nuclear molecular gas resulting from likely streaming motions associated with the strong-shock. The new results provide for the first time a coherent picture of Arp 118's many peculiarities, and underlines the potentially complex changes in the gas-phase that can accompany large gravitational perturbations of gas-rich galaxies.Comment: 20 pages, two tables, 9 Figure