Showing papers by "Thomas G. Phillips published in 2013"

Water Absorption in Galactic Translucent Clouds: Conditions and History of the Gas Derived from Herschel/HIFI PRISMAS Observations

Abstract: We present Herschel/HIFI observations of the three ground state transitions of H_2O (556, 1669, and 1113 GHz) and H_2^(18)O (547, 1655, and 1101 GHz)—as well as the first few excited transitions of H_2O (987, 752, and 1661 GHz)—toward six high-mass star-forming regions, obtained as part of the PRISMAS (PRobing InterStellar Molecules with Absorption line Studies) Guaranteed Time Key Program. Water vapor associated with the translucent clouds in Galactic arms is detected in absorption along every line of sight in all the ground state transitions. The continuum sources all exhibit broad water features in emission in the excited and ground state transitions. Strong absorption features associated with the source are also observed at all frequencies except 752 GHz. We model the background continuum and line emission to infer the optical depth of each translucent cloud along the lines of sight. We derive the column density of H_2O or H_2^(18)O for the lower energy level of each transition observed. The total column density of water in translucent clouds is usually about a few 10^(13) cm^(–2). We find that the abundance of water relative to hydrogen nuclei is 1 × 10^(–8) in agreement with models for oxygen chemistry in which high cosmic ray ionization rates are assumed. Relative to molecular hydrogen, the abundance of water is remarkably constant through the Galactic plane with X(H_2O) =5 × 10^(–8), which makes water a good traced of H_2 in translucent clouds. Observations of the excited transitions of H_2O enable us to constrain the abundance of water in excited levels to be at most 15%, implying that the excitation temperature, T_(ex), in the ground state transitions is below 10 K. Further analysis of the column densities derived from the two ortho ground state transitions indicates that T_(ex) ≃ 5 K and that the density n(H_2) in the translucent clouds is below 10^4 cm^(–3). We derive the water ortho-to-para ratio for each absorption feature along the line of sight and find that most of the clouds show ratios consistent with the value of 3 expected in thermodynamic equilibrium in the high-temperature limit. However, two clouds with large column densities exhibit a ratio that is significantly below 3. This may argue that the history of water molecules includes a cold phase, either when the molecules were formed on cold grains in the well-shielded, low-temperature regions of the clouds, or when they later become at least partially thermalized with the cold gas (~25 K) in those regions; evidently, they have not yet fully thermalized with the warmer (~50 K) translucent portions of the clouds.

A randomized controlled trial of the efficacy of autologous platelet therapy for the treatment of osteoarthritis in dogs.

Abstract: Objective—To determine efficacy of a single intra-articular injection of an autologous platelet concentrate for treatment of osteoarthritis in dogs. Design—Randomized, controlled, 2-center clinical trial. Animals—20 client-owned dogs with osteoarthritis involving a single joint. Procedures—Dogs were randomly assigned to a treatment or control group. In all dogs, severity of lameness and pain was scored by owners with the Hudson visual analog scale and the University of Pennsylvania Canine Brief Pain Inventory, respectively, and peak vertical force (PVF) was determined with a force platform. Dogs in the treatment group were then sedated, and a blood sample (55 mL) was obtained. Platelets were recovered by means of a point-of-use filter and injected intra-articularly within 30 minutes. Control dogs were sedated and given an intra-articular injection of saline (0.9% NaCl) solution. Assessments were repeated 12 weeks after injection of platelets or saline solution. Results—Dogs weighed between 18.3 and 63.9 k...

Hydrogen chloride in diffuse interstellar clouds along the line of sight to w31c (g10.6-0.4)

Abstract: We report the detection of hydrogen chloride, HCl, in diffuse molecular clouds on the line of sight toward the star-forming region W31C (G10.6-0.4). The J = 1-0 lines of the two stable HCl isotopologues, H^(35)Cl and H^(37)Cl, are observed using the 1b receiver of the Heterodyne Instrument for the Far-Infrared (HIFI) on board the Herschel Space Observatory. The HCl line is detected in absorption, over a wide range of velocities associated with diffuse clouds along the line of sight to W31C. The analysis of the absorption strength yields a total HCl column density of a few 10^(13) cm^(–2), implying that HCl accounts for ~0.6% of the total gas-phase chlorine, which exceeds the theoretical model predictions by a factor of ~6. This result is comparable to those obtained from the chemically related species H_2Cl^+ and HCl^+, for which large column densities have also been reported on the same line of sight. The source of discrepancy between models and observations is still unknown; however, the detection of these Cl-bearing molecules provides key constraints for the chlorine chemistry in the diffuse gas.

Measurement of the T + T neutron spectrum using the national ignition facility.

Abstract: Neutron time-of-flight spectra from inertial confinement fusion experiments with tritium-filled targets have been measured at the National Ignition Facility. These spectra represent a significant improvement in energy resolution and statistics over previous measurements, and afford the first definitive observation of a peak resulting from sequential decay through the ground state of (5)He at low reaction energies E(c.m.) 100

Determination of the ortho to para ratio of H2Cl+ and H2O+ from submillimeter observations.

Abstract: The opening of the submillimeter sky with the Herschel Space Observatory has led to the detection of new interstellar molecular ions, H2O+, H2Cl+, and HCl+, which are important intermediates in the synthesis of water vapor and hydrogen chloride. In this paper, we report new observations of H2O+ and H2Cl+ performed with both Herschel and ground-based telescopes, to determine the abundances of their ortho and para forms separately and derive the ortho-to-para ratio. At the achieved signal-to-noise ratio, the observations are consistent with an ortho-to-para ratios of 3 for both H2O+ and H2Cl+, in all velocity components detected along the lines-of-sight to the massive star-forming regions W31C and W49N. We discuss the mechanisms that contribute to establishing the observed ortho-to-para ratio and point to the need for a better understanding of chemical reactions, which are important for establishing the H2O+ and H2Cl+ ortho-to-para ratios.