Supernova Remnant in a Stratified Medium: Explicit, Analytical Approximations for Adiabatic Expansion and Radiative Cooling

We propose simple, explicit, analytical approximations for the kinematics of an adiabatic blast wave propagating in an exponentially stratified ambient medium, and for the onset of radiative cooling, which ends the adiabatic era. Our method, based on the Kompaneets implicit solution and the Kahn approximation for the radiative cooling coefficient, gives straightforward estimates for the size, expansion velocity, and progression of cooling times over the surface, when applied to supernova remnants (SNRs). The remnant shape is remarkably close to spherical for moderate density gradients, but even a small gradient in ambient density causes the cooling time to vary substantially over the remnant's surface, so that for a considerable period there will be a cold dense expanding shell covering only a part of the remnant. Our approximation provides an effective tool for identifying the approximate parameters when planning 2-dimensional numerical models of SNRs, the example of W44 being given in a subsequent paper.Comment: ApJ accepted, 11 pages, 2 figures embedded, aas style with ecmatex.sty and lscape.sty package

3D MHD Modeling of the Gaseous Structure of the Galaxy: Synthetic Observations

We generated synthetic observations from the four-arm model presented in Gomez & Cox (2004) for the Galactic ISM in the presence of a spiral gravitational perturbation. We found that velocity crowding and diffusion have a strong effect in the l-v diagram. The v-b diagram presents structures at the expected spiral arm velocities, that can be explained by the off-the-plane structure of the arms presented in previous papers of this series. Such structures are observed in the Leiden/Dwingeloo HI survey. The rotation curve, as measured from the inside of the modeled galaxy, shows similarities with the observed one for the Milky Way Galaxy, although it has large deviations from the smooth circular rotation corresponding to the background potential. The magnetic field inferred from a synthetic synchrotron map shows a largely circular structure, but with interesting deviations in the midplane due to distortion of the field from circularity in the interarm regions.Comment: Accepted for publication in ApJ. Better quality figures in http://www.astro.umd.edu/~gomez/publica/3d_galaxy-3.pd

Models of Veritcal Disturbances in the Interstellar Medium

This paper describes some interesting properties of waves in, and oscillations of, the interstellar medium in the direction normal to the plane of the Galaxy. Our purpose is to examine possible reasons for four observed phenomena: the falling sky in the northern hemisphere; the apparent presence of clouds in absorption spectra when a sightline is occupied primarily only by warm intercloud gas; the peculiar structuring of spiral arms involving clumps, spurs, and feathering; and the existence of an abundance of high stage ions far off the plane of the Galaxy. We explored the reaction of the interstellar medium - in the vertical direction only - to large imposed disturbances (initial displacements, expansive velocities, and compressions), and to the introduction of small amplitude waves via oscillation of the midplane. Our findings included: 1) the anticipated growth in amplitude of high frequency waves with height; 2) the four lowest normal modes for the oscillation of the atmosphere as a whole, as functions of the height of the outer boundary; 3) the time for material to `bounce' from one unusually dense state to the next as a function of height; and 4) the tendency for the disk to develop a hot outer halo, either after the passage of a single shock from a large event, or in response to a continuous stream of small amplitude waves.Comment: This paper contains 31 pages of text and 23 figures. This paper was submitted to The Astrophysical Journal on 6/6/2000. It was revised and resubmitted on 9/29/200

Comparison of NOAA-9 ERBE measurements with Cirrus IFO satellite and aircraft measurements

Earth Radiation Budget Experiment (ERBE) measurements onboard the NOAA-9 are compared for consistency with satellite and aircraft measurements made during the Cirrus Intensive Field Observation (IFO) of October 1986. ERBE scene identification is compared with NOAA-9 TIROS Operational Vertical Sounder (TOVS) cloud retrievals; results from the ERBE spectral inversion algorithms are compared with High resolution Interferometer Sounder (HIS) measurements; and ERBE radiant existance measurements are compared with aircraft radiative flux measurements

Development of a Low-Cost Sub-Scale Aircraft for Flight Research: The FASER Project

An inexpensive unmanned sub-scale aircraft was developed to conduct frequent flight test experiments for research and demonstration of advanced dynamic modeling and control design concepts. This paper describes the aircraft, flight systems, flight operations, and data compatibility including details of some practical problems encountered and the solutions found. The aircraft, named Free-flying Aircraft for Sub-scale Experimental Research, or FASER, was outfitted with high-quality instrumentation to measure aircraft inputs and states, as well as vehicle health parameters. Flight data are stored onboard, but can also be telemetered to a ground station in real time for analysis. Commercial-off-the-shelf hardware and software were used as often as possible. The flight computer is based on the PC104 platform, and runs xPC-Target software. Extensive wind tunnel testing was conducted with the same aircraft used for flight testing, and a six degree-of-freedom simulation with nonlinear aerodynamics was developed to support flight tests. Flight tests to date have been conducted to mature the flight operations, validate the instrumentation, and check the flight data for kinematic consistency. Data compatibility analysis showed that the flight data are accurate and consistent after corrections are made for estimated systematic instrumentation errors

Using Learning Collaboratives to Improve Public Health Emergency Preparedness Systems

The U.S. National Health Security Strategy calls for the development and wide-spread implementation of quality improvement (QI) tools in public health emergency preparedness (PHEP), including the development of “learning collaboratives,” a structured way for organizations with common interests to close the gap between potential and practice by learning from each other. To test this approach, we developed and assessed separate learning collaboratives focused on PHEP emergency communications and on the use of Medical Reserve Corps (MRC) volunteers. Although participants carried out improvement projects that they felt were useful, each collaborative struggled to identify a common theme, participation was limited, and leadership buy-in was not strong. This suggests that the learning collaborative model may not be appropriate in this context. Because some of the factors that limited their success are inherent (the lack of an established evidence base and agreed upon outcome and performance measures and the difficulty of carrying out rapid Plan-Do-Study-Act (PDSA) cycles and measuring the results), this suggests that the learning collaborative model may not be appropriate in this context

Rubella Immunization of Adult Females Using HPV-77 DK-12 Live Attenuated Rubella Virus

This study demonstrates the serologic response as measured by the HAl test and the side reactions of the HPV-77 DK-12 live rubella vaccine in a small group of adult females. One hundred percent seroconversion was obtained using this vaccine. The mean titers obtained in two separate time periods post-vaccination are higher than those reported for several other rubella virus vaccines. A 66% occurrence of joint symptomatology was recorded post-vaccination with a mean duration of 11.6 days; 24% of women who received placebo reported joint complaints which had a mean duration of 2.0 days. The difference between these two rates is somewhat greater than that reported for other HPV-77 strain vaccines and the average duration of these complaints is longer. The other symptoms reported postvaccination seemed insignificant when comparing both the placebo and the vaccine group. One woman became pregnant three months after vaccination and was subsequently therapeutically aborted. At the time of therapeutic abortion, attempts were unsuccessful to recover rubella virus from the products of conception and cervical swabs

Proceedings of the 2008 Center for Homeland Defense and Security Security Annual Conference

This article appeared in Homeland Security Affairs (April 2008), Supplement no.2The 2008 Center for Homeland Defense and Security (CHDS) Annual Conference was conducted January 29-30, 2008, at the Naval Postgraduate School in Monterey, California. Its theme, Five Years of Meeting the Homeland Security Challenge, was tied to the fifth anniversary of the establishment of CHDS. More than 230 CHDS master's degree and Executive Leadership Program alumni, partners, sponsors and stakeholders participated in the event. The conference featured a keynote speaker; a question and answer plenary session with a panel of senior Homeland Defense and Security government executives; and three breakout sessions dealing with issues in Intelligence and Information Sharing, Border Security, and Public and Private Integration. These proceedings summarize the presentations and sessions from the conference.Approved for public release; distribution is unlimited

Sensitive observations at 1.4 and 250 GHz of z > 5 QSOs

We present 1.4 and 5 GHz observations taken with the Very Large Array (VLA), and observations at 250 GHz obtained with the Max-Planck millimeter bolometer (MAMBO) at the IRAM 30~m telescope, of ten optically selected Quasi-stellar Objects (QSOs) at 5.0 < z < 6.28. Four sources are detected at 1.4 GHz two of which are radio loud and are also detected at 5 GHz. These results are roughly consistent with there being no evolution of the radio-loud QSO fraction out to z~6. Three sources have been detected at 250 GHz or 350 GHz at much higher levels than their 1.4 GHz flux densities suggesting that the observed mm emission is likely thermal emission from warm dust, although more exotic possibilities cannot be precluded. The highest redshift source in our sample (J1030+0524 at z=6.28) is not detected at 1.4 or 250 GHz, but four fairly bright radio sources (flux density at 1.4GHz > 0.2 mJy) are detected in a 2' field centered on the QSO, including an edge-brightened ('FRII') double radio source with an extent of about 1'. A similar over-density of radio sources is seen in the field of the highest redshift QSO J1148+5251. We speculate that these over-densities of radio sources may indicate clusters along the lines-of-sight, in which case gravitational lensing by the cluster could magnify the QSO emission by a factor 2 or so without giving rise to arcsecond-scale distortions in the optical images of the QSOs.Comment: 25 pages, 12 figures. accepted by A

The Evolution of Adiabatic Supernova Remnants in a Turbulent, Magnetized Medium

(Abridged) We present the results of three dimensional calculations for the MHD evolution of an adiabatic supernova remnant in both a uniform and turbulent interstellar medium using the RIEMANN framework of Balsara. In the uniform case, which contains an initially uniform magnetic field, the density structure of the shell remains largely spherical, while the magnetic pressure and synchrotron emissivity are enhanced along the plane perpendicular to the field direction. This produces a bilateral or barrel-type morphology in synchrotron emission for certain viewing angles. We then consider a case with a turbulent external medium as in Balsara & Pouquet, characterized by $v_{A}(rms)/c_{s}=2$. Several important changes are found. First, despite the presence of a uniform field, the overall synchrotron emissivity becomes approximately spherically symmetric, on the whole, but is extremely patchy and time-variable, with flickering on the order of a few computational time steps. We suggest that the time and spatial variability of emission in early phase SNR evolution provides information on the turbulent medium surrounding the remnant. The shock-turbulence interaction is also shown to be a strong source of helicity-generation and, therefore, has important consequences for magnetic field generation. We compare our calculations to the Sedov-phase evolution, and discuss how the emission characteristics of SNR may provide a diagnostic on the nature of turbulence in the pre-supernova environment.Comment: ApJ, in press, 5 color figure