What Fraction of the Young Clusters in the Antennae Galaxies are "Missing"?

A reexamination of the correspondence between 6 cm radio continuum sources and young star clusters in the Antennae galaxies indicates that 85 % of the strong thermal sources have optical counterparts, once the optical image is shifted 1.2 arcsec to the southwest. A sample of 37 radio-optical matches are studied in detail showing correlations between radio properties and a variety of optical characteristics. There is a strong correlation between the radio flux and the intrinsic optical brightness. In particular, the brightest radio source is also the intrinsically brightest optical cluster (WS80). It is also the most extincted cluster in the sample, the strongest CO source and the strongest 15 micron source . Furthermore, the brightest ten radio sources are all amongst the youngest clusters with ages in the range 0 - 4 Myr and extinctions from A_V = 0.5 to 7.6 mag (with a median value of 2.6 mag). Only a few of the very red clusters originally discovered by Whitmore & Schweizer are radio sources, contrary to earlier suggestions. Finally, a new hybrid method of determining cluster ages has been developed using both UBVI colors and H_alpha equivalent widths to break the age-reddening degeneracy.Comment: 51 pages, 13 postscript figures, LaTex. To appear in the Astronomical Journal, 124, 2002, Septembe

Air data position-error calibration using state reconstruction techniques

During the highly maneuverable aircraft technology (HiMAT) flight test program recently completed at NASA Ames Research Center's Dryden Flight Research Facility, numerous problems were experienced in airspeed calibration. This necessitated the use of state reconstruction techniques to arrive at a position-error calibration. For the HiMAT aircraft, most of the calibration effort was expended on flights in which the air data pressure transducers were not performing accurately. Following discovery of this problem, the air data transducers of both aircraft were wrapped in heater blankets to correct the problem. Additional calibration flights were performed, and from the resulting data a satisfactory position-error calibration was obtained. This calibration and data obtained before installation of the heater blankets were used to develop an alternate calibration method. The alternate approach took advantage of high-quality inertial data that was readily available. A linearized Kalman filter (LKF) was used to reconstruct the aircraft's wind-relative trajectory; the trajectory was then used to separate transducer measurement errors from the aircraft position error. This calibration method is accurate and inexpensive. The LKF technique has an inherent advantage of requiring that no flight maneuvers be specially designed for airspeed calibrations. It is of particular use when the measurements of the wind-relative quantities are suspected to have transducer-related errors

Flight and wind-tunnel comparisons of the inlet-airframe interaction of the F-15 airplane

The design of inlets and nozzles and their interactions with the airplane which may account for a large percentage of the total drag of modern high performance aircraft is discussed. The inlet/airframe interactions program and the flight tests conducted is described. Inlet drag and lift data from a 7.5% wind-tunnel model are compared with data from an F-15 airplane with instrumentation to match the model. Pressure coefficient variations with variable cowl angles, capture ratios, examples of flow interactions and angles of attack are for Mach numbers of 0.6, 0.9, 1.2, and 1.5 are presented

Evaluation of proposed Skylab and SSP soap products

Three personal hygiene cleansing agents and one laundry detergent (sodium dodecyl benzene sulfonate), which are all candidates for use on long-duration space missions, were evaluated in terms of dermatological effects on human subjects and effects on microbiological species. None of the four materials exhibited adverse dermatological effects from either skin patch tests of two weeks duration or a simulated Skylab personal hygiene regimen of up to four weeks duration. No significant alterations in skin microflora during the use regimen were found. None of the four materials were found to serve as microbiological support media for the species tested, but a species of air-borne mold was observed to grow rapidly in a neutralized aqueous solution. None of the candidate agents was found to be strongly biocidal

Flight and wind-tunnel calibrations of a flush airdata sensor at high angles of attack and sideslip and at supersonic Mach numbers

A nonintrusive airdata-sensing system was calibrated in flight and wind-tunnel experiments to an angle of attack of 70 deg and to angles of sideslip of +/- 15 deg. Flight-calibration data have also been obtained to Mach 1.2. The sensor, known as the flush airdata sensor, was installed on the nosecap of an F-18 aircraft for flight tests and on a full-scale F-18 forebody for wind-tunnel tests. Flight tests occurred at the NASA Dryden Flight Research Facility, Edwards, California, using the F-18 High Alpha Research Vehicle. Wind-tunnel tests were conducted in the 30- by 60-ft wind tunnel at the NASA LaRC, Hampton, Virginia. The sensor consisted of 23 flush-mounted pressure ports arranged in concentric circles and located within 1.75 in. of the tip of the nosecap. An overdetermined mathematical model was used to relate the pressure measurements to the local airdata quantities. The mathematical model was based on potential flow over a sphere and was empirically adjusted based on flight and wind-tunnel data. For quasi-steady maneuvering, the mathematical model worked well throughout the subsonic, transonic, and low supersonic flight regimes. The model also worked well throughout the angles-of-attack and -sideslip regions studied

Small Employer Perspectives On The Affordable Care Act's Premiums, SHOP Exchanges, And Self-Insurance

Beginning January 1, 2014, small businesses having no more than fifty full-time-equivalent workers will be able to obtain healthinsurance for their employees through Small Business Health OptionsProgram (SHOP) exchanges in every state. Although the Affordable Care Act intended the exchanges to make the purchasing of insurance moreattractive and affordable to small businesses, it is not yet known how they will respond to the exchanges. Based on a telephone survey of 604 randomly selected private firms having 3 -- 50 employees, we found that both firms that offered health coverage and those that did not rated most features of SHOP exchanges highly but were also very price sensitive.More than 92 percent of nonoffering small firms said that if they were to offer coverage, it would be "very" or "somewhat" important to them that premium costs be less than they are today. Eighty percent of offering firms use brokers who commonly perform functions of benefit managers -- functions that the SHOP exchanges may assume. Twenty-six percent of firms using brokers reported discussing self-insuring with their brokers. An increase in the number of self-insured small employers could pose a threat to SHOP exchanges and other small-group insurance reforms

Gold Creek Dam and its Unusual Waste Waterway (1890-1997): Design, Operation, Maintenance

Completed in 1885, the Gold Creek dam is an earthen dam located on the outskirts of Brisbane, Australia. The spillway system was refurbished three times, each time to increase the maximum overflow capacity. In 1890, a concrete stepped waterway was built to replace the damaged unlined-rock channel. This staircase chute is an unique structure : it is the first large man-made waste waterway built in Queensland, it is the only stepped weir built in Queensland before 1900, and it is, so far as the writers are aware, the first concrete-stepped spillway built for a large dam. The characteristics of the dam and its unusual stepped spillway are reviewed in a historical context. The design is compared with contemporary structures and present knowledge in stepped spillway design. The authors believe that the Queensland engineers gained expertise from overseas and within Australia for the stepped spillway design. However the selection of concrete for the step construction was made by the local engineers and the reasons behind the decision are not yet understoo

The Infrared Massive Stellar Content of M83

We present an analysis of archival Spitzer images and new ground-based and Hubble Space Telescope (HST) near-infrared (IR) and optical images of the field of M83 with the goal of identifying rare, dusty, evolved massive stars. We present point source catalogs consisting of 3778 objects from $Spitzer$ Infrared Array Camera (IRAC) Band 1 (3.6 $\mu$m) and Band 2 (4.5 $\mu$m), and 975 objects identified in Magellan 6.5m FourStar near-IR $J$ and $K_{\rm s}$ images. A combined catalog of coordinate matched near- and mid-IR point sources yields 221 objects in the field of M83. Using this photometry we identify 185 massive evolved stellar candidates based on their location in color-magnitude and color-color diagrams. We estimate the background contamination to our stellar candidate lists and further classify candidates based on their appearance in $HST$ Wide Field Camera 3 (WFC3) observations of M83. We find 49 strong candidates for massive stars which are very promising objects for spectroscopic follow-up. Based on their location in a $B-V$ versus $V-I$ diagram, we expect at least 24, or roughly 50%, to be confirmed as red supergiants.Comment: 32 pages, 23 figures, accepted for publication in A&

Effects of Radiation Heating on Additively Printed Hybrid Fuel Grain Oxidizer-To-Fuel Ratio Shift

Utah State University has researched and developed a hybrid rocket system that uses a non-toxic, simple, and 3D printed plastic as the fuel. This plastic is ABS (acrylonitrile butadiene styrene) which is a common material used in pipe systems, automotive components, and toys such as Lego bricks. As a fuel, ABS has structural properties that outweigh other polymer fuels; has matching or better performance than most commonly used propellants; is an environmentally-friendly fuel; and is easily manufactured and assembled. Furthermore, Utah State University has developed a novel ignition technology for hybrid rocket systems that involves pyrolyzing a marginal portion of the ABS fuel into a vapor rich in hydrocarbons which, when introduced to an oxidizer, initiates rapid combustion. Thus, the system simply requires a valve and spark command which grants restart and throttle capability. Although this technology has the potential to become a game-changing propulsion system for both the launch vehicles and small satellite communities, its performance and stability are still relatively uncharacterized. Many tests have been implemented at Utah State University and the performance model continues to be improved still. Recently, we have conducted tests on smaller-scale motors suited towards small spacecraft and have noticed a surprising trend in the oxidizer-to-fuel (O/F) ratio. Most results for hybrid rocket performance indicate that this ratio increases as the fuel is burned away, meaning that the combustion product becomes more oxidizer-rich as the motor is being fired. However, the results from the smaller-scale motors indicate that the oxidizer-to-fuel ratio decreases as the fuel is burned away. We believe that this trend towards a more fuel-rich burn is due to a neglected radiation effect that enhances the fuel regression rate. The goal of this research is to investigate this phenomena through running extensive tests as well as redevelop the equations describing fuel regression rate