Advanced Next-Generation Emergency Locator (ANGEL) MEOSAR Applications to NASA Human Spaceflight

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Nuclear Rings in Galaxies---A Kinematic Perspective

We combine DensePak integral field unit and TAURUS Fabry-Perot observations of 13 nuclear rings to show an interconnection between the kinematic properties of the rings and their resonant origin. The nuclear rings have regular and symmetric kinematics, and lack strong non-circular motions. This symmetry, coupled with a direct relationship between the position angles and ellipticities of the rings and those of their host galaxies, indicate the rings are in the same plane as the disc and are circular. From the rotation curves derived, we have estimated the compactness (v^2/r) up to the turnover radius, which is where the nuclear rings reside. We find that there is evidence of a correlation between compactness and ring width and size. Radially wide rings are less compact, and thus have lower mass concentration. The compactness increases as the ring width decreases. We also find that the nuclear ring size is dependent on the bar strength, with weaker bars allowing rings of any size to form.Comment: 19 pages, 7 figures, accepted for publication into Ap

Emergency Locator Transmitter Survivability and Reliability Study

A comprehensive study of Emergency Locator Transmitter (ELT) performance was conducted over a three year period concluding in 2016 in support of the Search and Rescue (SAR) Mission Office at National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC). The study began with a review of reported performance cited in a collection of works published as early as 1980 as well as analysis of a focused set of contemporary aviation crash reports. Based on initial research findings, a series of subscale and fullscale system tests were performed at NASA Langley Research Center (LaRC) with the goals of investigating ELT system failure modes and developing recommended improvements to the Radio Technical Commission for Aeronautics (RTCA) Minimum Operational Performance Specification (MOPS) that will result in improved system performance. Enhanced performance of ELT systems in aviation accidents will reduce unnecessary loss of human life and make SAR operations safer and less costly by reducing the amount of time required to locate accident sites

A Connection between Star Formation in Nuclear Rings and their Host Galaxies

We present results from a photometric H-alpha survey of 22 nuclear rings, aiming to provide insight into their star formation properties, including age distribution, dynamical timescales, star formation rates, and galactic bar influence. We find a clear relationship between the position angles and ellipticities of the rings and those of their host galaxies, which indicates the rings are in the same plane as the disk and circular. We use population synthesis models to estimate ages of each H-alpha emitting HII region, which range from 1 Myr to 10 Myrs throughout the rings. We find that approximately half of the rings contain azimuthal age gradients that encompass at least 25% of the ring, although there is no apparent relationship between the presence or absence of age gradients and the morphology of the rings or their host galaxies. NGC1343, NGC1530, and NGC4321 show clear bipolar age gradients, where the youngest HII regions are located near the two contact points of the bar and ring. We speculate in these cases that the gradients are related to an increased mass inflow rate and/or an overall higher gas density in the ring, which would allow for massive star formation to occur on short timescales, after which the galactic rotation would transport the HII regions around the ring as they age. Two-thirds of the barred galaxies show correlation between the locations of the youngest HII region(s) in the ring and the location of the contact points, which is consistent with predictions from numerical modeling.Comment: 23 pages, 10 figures (7 color), 23 tables, accepted for publication in ApJS (Feb 08); NASA-GSFC, IAC, University of Maryland, STSc

A Young Stellar Cluster in the Nucleus of NGC 4449

We have obtained 1-2 A resolution optical Echellette spectra of the nuclear star cluster in the nearby starburst galaxy NGC 4449. The light is clearly dominated by a very young (6-10 Myr) population of stars. For our age dating, we have used recent population synthesis models to interpret the observed equivalent width of stellar absorption features such as the HI Balmer series and the CaII triplet around 8500 A. We also compare the observed spectrum of the nuclear cluster to synthesized spectra of simple stellar populations of varying ages. All these approaches yield a consistent cluster age. Metallicity estimates based on the relative intensities of various ionization lines yield no evidence for significant enrichment in the center of this low mass galaxy: the metallicity of the nuclear cluster is about one fourth of the solar value, in agreement with independent estimates for the disk material of NGC 4449.Comment: 24 pages (incl. 7 figures), accepted by AJ, March 2001 issue revised version with minor changes and additions, one additional figur

Morphology, Star Formation, and Kinematics of Nuclear Rings

This thesis presents a detailed optical study with the goal of better understanding the elusive physical nature of nuclear rings. We use H-alpha imaging of the central kilo-parsec region of a large sample of spiral galaxies to verify that nuclear rings occur primarily in spiral types Sa-Sbc. Late-type galaxies have a patchy and more diffuse circumnuclear appearance in H-alpha. From the parent sample, we identify 22 nuclear rings and analyze the HII regions that comprise them. We derive the ages throughout each nuclear ring, and find that the stellar content is consistently very young, with ages ranging from 1 Myr to 10 Myrs. Approximately half of the rings contain azimuthal age gradients that encompass at least 25% of the ring. Two-thirds of the galaxies containing a nuclear ring and a bar show a link between the youngest HII region(s) and the location along the ring where the bar dust lanes merge. We show that regions of enhanced star formation, as seen in nuclear rings, correspond to regions with (1) the strongest H-alpha emission, (2) high luminosities of order 10^40 erg/s - 10^42 erg/s, (3) low residual velocities of order 10 km/s, and (4) low velocity dispersions ranging from 20 km/s- 50 km/s. The lack of strong non-circular motions in the rings, coupled with a direct relationship between the position angles and ellipticities of the rings and those of their host galaxies, indicate the rings are in the same plane as the disk and are circular. We find a correlation between the largest velocity deviations (just outside of the rings) and the location of the bar minor axis, where the dominant family of stellar orbits transitions from the x1 family to the x2 family. Lastly, we apply two-dimensional line ratio diagnostics to separate the physical environments of the nuclear ring and an AGN present in NGC 7742. Results indicate very low gas densities in the nuclear ring, and show the transition from star formation in the ring to excitation by high-velocity shocks or by a central AGN towards the center. Comparison to starburst population models reveals that the HII regions comprising the ring are of roughly solar metallicity

Functional gains and maintenance in residents of complex continuing care: implications for physical therapy

Affiliated institutions include: Baycrest (M. Huijbregts, C. Nisan, S. Wong), University of Toronto (K. Berg)BACKGROUND:There is a lack of evidence to guide clinical physical therapy (PT) intervention and resource allocation in the Complex Continuing Care (CCC) population in Canada. OBJECTIVE: To investigate physical and psychosocial changes in residents receiving PT services for one year in a CCC program. METHODS: Data from nursing notes, the Continuing Care Activity Measure (CCAM) and the Minimum Data Set (MDS) were extracted from Praxia© and Meditech© databases. Residents were divided into groups (increased, stable, and decreased CCAM scores) and average change in total score from admission to one year for pain, depression, and activities of daily living (ADLs) was determined. Descriptive analysis for trajectory of changes in pain, depression, and ADLs over a year, and potential influences of baseline factors was completed. RESULTS: Twenty-five CCC residents receiving PT were included. Significant improvement in CCAM scores occurred from admission to one year (p?0.05). Individuals who improved tended to be younger, have lower CCAM scores, be more socially engaged and be medically stable at admission. Discrepancies existed between functional measurement tools in the MDS and CCAM. CONCLUSION: PT intervention provided to CCC residents may maintain or improve functional mobility over a year