Moderating Effects of Posttraumatic Growth On Suicidal Ideation After Combat Exposure

The suicide rate in the United States has risen since 1999 (Curtin, Warner, & Hedegaard, 2016). This increase may be a distinct problem for military service members who may have an additional risk through combat exposure (Bryan et al., 2015). There is a need to identify protective factors for suicide broadly and specifically for military service members and veterans. There is emerging evidence that posttraumatic growth may be a protective factor for suicide ideation possibly buffering the effects of combat exposure on suicide ideation (Bush, Skopp, McCann, & Luxton, 2011). The current study was designed to further examine the relationship between combat exposure and suicide by examining the moderating effects of posttraumatic growth. A sample of 423 veterans participated in this correlational study by completing a series of online measures. Results indicated that posttraumatic growth had a significant inverse relationship with suicide ideation. In addition, combat exposure had a significant positive relationship with posttraumatic growth. Finally, age significantly accounted for variation in posttraumatic growth. However, the interaction effect between combat exposure and posttraumatic growth did not significantly account for variation in suicide ideation scores, suggesting that posttraumatic growth does not moderate the associated effects of combat exposure on suicide ideation. Clinically this suggests posttraumatic growth may be a target to reduce suicide ideation directly. However, posttraumatic growth does not seem to alter the effects of combat exposure on suicide ideation

Digitial Readout for Microwave Kinetic Inductance Detectors and Applications in High Time Resolution Astronomy

This dissertation spans two topics relating to optical tonear-infrared astronomical cameras built around Microwave KineticInductance Detectors (MKIDs). The first topic is the development of adigital readout system for 10- to 30-kilopixel arrays of MKIDs. MKIDs aresuperconducting detectors that can detect individual photons with a widerange of wavelengths with high time resolution (\SI{2}{\micro s}) and low energyresolution. The advantage of MKIDs over other low temperature detectors with similar capabilities is that it is relatively straightforward to multiplex MKIDs into largearrays. All the complexity of readout is in room temperature electronics.This work discusses the implementation and programming of theseelectronics.The second part of this work demonstrates the capabilities of the prototypeoptical and near-infrared MKID instrument with observations ofpulsars. Detecting optical pulsations in these objects require high timeresolution and low noise. The discovery of a correlation between thebrightness of optical pulses from the Crab pulsar and the time of arrivalof coincident giant radio pulses is presented. The search for opticalpulses from a millisecond pulsar J0337+1715 is discussed along with a newupper limit on the brightness of its optical pulses

The interaction of source and post-event misinformation on the accuracy of eyewitness testimony

The recall of an event such as a robbery has been shown to be affected by how closely post-event information corresponds to what the witness actually saw. The purpose of this study was to investigate how the effect of misleading information may be influenced by expertise of the source of the post-event information. Results revealed that subjects recalled less accurately when they received misleading information in the narrative than when the information corresponded with what they had viewed, whereas the accuracy of the recall was unaffected by whether the witness in the narrative was an expert or a non-expert. Subjects rated the narrative witnesses as having equal credibility. This study suggests that the memory for events related to a crime-scene may be impaired by misleading post-event information, but is unaffected by the source of that misleading information when the sources differ in occupational expertise

Evidence That Hydra I is a Tidally Disrupting Milky Way Dwarf Galaxy

The Eastern Banded Structure (EBS) and Hydra I halo overdensities are very nearby (d ~ 10 kpc) objects discovered in Sloan Digital Sky Survey (SDSS) data. Previous studies of the region have shown that EBS and Hydra I are spatially coincident, cold structures at the same distance, suggesting that Hydra I may be the EBS's progenitor. We combine new wide-field Dark Energy Camera (DECam) imaging and MMT/Hectochelle spectroscopic observations of Hydra I with SDSS archival spectroscopic observations to quantify Hydra I's present-day chemodynamical properties, and to infer whether it originated as a star cluster or dwarf galaxy. While previous work using shallow SDSS imaging assumed a standard old, metal-poor stellar population, our deeper DECam imaging reveals that Hydra I has a thin, well-defined main sequence turnoff of intermediate age (~5–6 Gyr) and metallicity ([Fe/H] = −0.9 dex). We measure statistically significant spreads in both the iron and alpha-element abundances of σ_[(Fe)/H}= 0.13 ± 0.02 dex and σ_[ɑ/Fe] = 0.09 ± 0.03 dex, respectively, and place upper limits on both the rotation and its proper motion. Hydra I's intermediate age and [Fe/H]—as well as its low [α/Fe], apparent [Fe/H] spread, and present-day low luminosity—suggest that its progenitor was a dwarf galaxy, which has subsequently lost more than 99.99% of its stellar mass

Chemodynamics of Compact Stellar Systems in NGC 5128: How similar are Globular Clusters, Ultra-Compact Dwarfs, and Dwarf Galaxies?

Velocity dispersion measurements are presented for luminous GCs in NGC 5128 derived from high-res. UVES spectra. The measurements are made with the pPXF code that parametrically recovers line-of-sight velocity dispersions. Combining the measured velocity dispersions with surface photometry and structural parameter data from HST enables both dynamical masses and M/L ratios to be derived. The fundamental plane relations of these clusters are investigated in order to fill the apparent gap between the relations of Local Group GCs and more massive early-type galaxies. It is found that the properties of these massive stellar systems match those of nuclear clusters in dwarf elliptical galaxies and UCDs better than those of Local Group GCs, and that all objects share similarly old (>8 Gyr) ages, suggesting a possible link between the formation and evolution of dE,Ns, UCDs and massive GCs. We find a very steep correlation between dynamical (M/L) ratio and dynamical mass of the form (M/L)_dyn ~ M_dyn^(0.24+/-0.02) above M_dyn = 2x10^6 Msol. Formation scenarios are investigated with a chemical abundance analysis using absorption line strengths calibrated to the Lick/IDS index system. The results lend support to two scenarios contained within a single general formation scheme. Old, massive, super-solar [alpha/Fe] systems are formed on short (<100 Myr) timescales through the merging of single-collapse GCs which themselves are formed within single, giant molecular clouds. More intermediate- and old-aged (~3-10 Gyr), solar- to sub-solar [alpha/Fe] systems are formed on much longer (~Gyr) timescales through the stripping of dE,Ns in the 10^13-10^15 Msol potential wells of massive galaxies and galaxy clusters.Comment: 12 pages (ApJ style) with 11 figures and 7 tables, accepted for publication in Ap

Signatures of Tidal Disruption in Ultra-Faint Dwarf Galaxies: A Combined HST, Gaia, and MMT/Hectochelle Study of Leo V

The ultra-faint dwarf galaxy Leo V has shown both photometric overdensities and kinematic members at large radii, along with a tentative kinematic gradient, suggesting that it may have undergone a close encounter with the Milky Way. We investigate these signs of disruption through a combination of i) high-precision photometry obtained with the Hubble Space Telescope (HST), ii) two epochs of stellar spectra obtained with the Hectochelle Spectrograph on the MMT, and iii) measurements from the Gaia mission. Using the HST data, we examine one of the reported stream-like overdensities at large radii, and conclude that it is not a true stellar stream, but instead a clump of foreground stars and background galaxies. Our spectroscopic analysis shows that one known member star is likely a binary, and challenges the membership status of three others, including two distant candidates that had formerly provided evidence for overall stellar mass loss. We also find evidence that the proposed kinematic gradient across Leo V might be due to small number statistics. We update the systemic proper motion of Leo V, finding $(\mu_\alpha \cos\delta, \mu_\delta)= (0.009\pm0.560$, $-0.777\pm0.314)$ mas yr$^{-1}$, which is consistent with its reported orbit that did not put Leo V at risk of being disturbed by the Milky Way. These findings remove most of the observational clues that suggested Leo V was disrupting, however, we also find new plausible member stars, two of which are located >5 half-light radii from the main body. These stars require further investigation. Therefore, the nature of Leo V still remains an open question.Comment: Higher resolution figures are available upon request. Submitted to the Ap

An open source, FPGA-based LeKID readout for BLAST-TNG: Pre-flight results

We present a highly frequency multiplexed readout for large-format superconducting detector arrays intended for use in the next generation of balloon-borne and space-based sub-millimeter and far-infrared missions. We will demonstrate this technology on the upcoming NASA Next Generation Balloon-borne Large Aperture Sub-millimeter Telescope (BLAST-TNG) to measure the polarized emission of Galactic dust at wavelengths of 250, 350 and 500 microns. The BLAST-TNG receiver incorporates the first arrays of Lumped Element Kinetic Inductance Detectors (LeKID) along with the first microwave multiplexing readout electronics to fly in a space-like environment and will significantly advance the TRL for these technologies. After the flight of BLAST-TNG, we will continue to improve the performance of the detectors and readout electronics for the next generation of balloon-borne instruments and for use in a future FIR Surveyor. Read More: http://www.worldscientific.com/doi/abs/10.1142/S225117171641003

Three Hypervelocity White Dwarfs in Gaia DR2: Evidence for Dynamically Driven Double-Degenerate Double-Detonation Type Ia Supernovae

Double detonations in double white dwarf (WD) binaries undergoing unstable mass transfer have emerged in recent years as one of the most promising Type Ia supernova (SN Ia) progenitor scenarios. One potential outcome of this "dynamically driven double-degenerate double-detonation" (D^6) scenario is that the companion WD survives the explosion and is flung away with a velocity equal to its > 1000 km/s pre-SN orbital velocity. We perform a search for these hypervelocity runaway WDs using Gaia's second data release. In this paper, we discuss seven candidates followed up with ground-based instruments. Three sources are likely to be some of the fastest known stars in the Milky Way, with total Galactocentric velocities between 1000 and 3000 km/s, and are consistent with having previously been companion WDs in pre-SN Ia systems. However, although the radial velocity of one of the stars is > 1000 km/s, the radial velocities of the other two stars are puzzlingly consistent with 0. The combined five-parameter astrometric solutions from Gaia and radial velocities from follow-up spectra yield tentative 6D confirmation of the D^6 scenario. The past position of one of these stars places it within a faint, old SN remnant, further strengthening the interpretation of these candidates as hypervelocity runaways from binary systems that underwent SNe Ia.Comment: Accepted for publication in ApJ. Minor corrections for clarity. D6 spectra are available as ancillary data file