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Sample records for far-ultraviolet h2 emission

  1. Far-Ultraviolet H2 Emission from Circumstellar Disks

    CERN Document Server

    Ingleby, Laura; Bergin, Edwin; Yerasi, Ashwin; Espaillat, Catherine; Herczeg, Gregory; Roueff, Evelyne; Abgrall, Herve; Hernandez, Jesus; Briceno, Cesar; Pascucci, Ilaria; Miller, Jon; Fogel, Jeffrey; Hartmann, Lee; Meyer, Michael; Carpenter, John; Crockett, Nathan; McClure, Melissa

    2009-01-01

    We analyze the far-ultraviolet (FUV) spectra of 33 classical T Tauri stars (CTTS), including 20 new spectra obtained with the Advanced Camera for Surveys Solar Blind Channel (ACS/SBC) on the Hubble Space Telescope. Of the sources, 28 are in the ~1 Myr old Taurus-Auriga complex or Orion Molecular Cloud, 4 in the 8-10 Myr old Orion OB1a complex and one, TW Hya, in the 10 Myr old TW Hydrae Association. We also obtained FUV ACS/SBC spectra of 10 non-accreting sources surrounded by debris disks with ages between 10 and 125 Myr. We use a feature in the FUV spectra due mostly to electron impact excitation of \\h2 to study the evolution of the gas in the inner disk. We find that the \\h2 feature is absent in non-accreting sources, but is detected in the spectra of CTTS and correlates with accretion luminosity. Since all young stars have active chromospheres which produce strong X-ray and UV emission capable of exciting \\h2 in the disk, the fact that the non-accreting sources show no \\h2 emission implies that the \\h2 ga...

  2. Far-ultraviolet florescent molecular hydrogen emission map of the Milky Way Galaxy

    Science.gov (United States)

    Jo, Young-soo; Seon, Kwang-il; Min, Kyoung-wook; Edelstein, Jerry; Han, Wonyong

    2017-01-01

    We present the far-ultraviolet fluorescent molecular hydrogen (H2) emission map observed with FIMS/SPEAR for ~76% of the sky. The fluorescent H2 emission is found to be saturated by strong dust extinction at the optically thick, Galactic plane region. Nevertheless, the extinction-corrected intensity of the fluorescent H2 emission is found to have strong linear correlations with the well-known tracers of the cold interstellar medium, such as the E(B-V) color excess, neutral hydrogen column density N(HI), Hα emission, and CO J=1→0 emission. The all-sky molecular hydrogen column density map is also obtained using a simple photodissociation region model with interstellar radiation fields derived from UV star catalogs. We also estimate the hydrogen molecular fraction (fH2), CO-to-H2 conversion factor (XCO), and the gas-to-dust ratio of the diffuse interstellar medium. fH2 gradually increases from less than 1% at optically thin regions with E(B-V)converges to the Galactic mean value of 1.8×1020 cm-2 K-1 km-1 s at optically thick regions where E(B-V) is larger than 2.0. The estimated gas-to-dust ratio is consistent with the standard value of 5.8×1021 atoms cm-2 mag-1.

  3. Molecular Hydrogen Emission Lines in Far Ultraviolet Spectroscopic Explorer Observations of Mira B

    CERN Document Server

    Wood, B E; Wood, Brian E.; Karovska, Margarita

    2004-01-01

    We present new Far Ultraviolet Spectroscopic Explorer (FUSE) observations of Mira A's wind-accreting companion star, Mira B. We find that the strongest lines in the FUSE spectrum are H2 lines fluoresced by H I Lyman-alpha. A previously analyzed Hubble Space Telescope (HST) spectrum also shows numerous Lyman-alpha fluoresced H2 lines. The HST lines are all Lyman band lines, while the FUSE H2 lines are mostly Werner band lines, many of them never before identified in an astrophysical spectrum. We combine the FUSE and HST data to refine estimates of the physical properties of the emitting H2 gas. We find that the emission can be reproduced by an H2 layer with a temperature and column density of T=3900 K and log N(H2)=17.1, respectively. Another similarity between the HST and FUSE data, besides the prevalence of H2 emission, is the surprising weakness of the continuum and high temperature emission lines, suggesting that accretion onto Mira B has weakened dramatically. The UV fluxes observed by HST on 1999 August ...

  4. A Far-ultraviolet Fluorescent Molecular Hydrogen Emission Map of the Milky Way Galaxy

    Science.gov (United States)

    Jo, Young-Soo; Seon, Kwang-Il; Min, Kyoung-Wook; Edelstein, Jerry; Han, Wonyong

    2017-08-01

    We present the far-ultraviolet (FUV) fluorescent molecular hydrogen (H2) emission map of the Milky Way Galaxy obtained with FIMS/SPEAR covering ˜76% of the sky. The extinction-corrected intensity of the fluorescent H2 emission has a strong linear correlation with the well-known tracers of the cold interstellar medium (ISM), including color excess E(B-V), neutral hydrogen column density N(H i), and Hα emission. The all-sky H2 column density map was also obtained using a simple photodissociation region model and interstellar radiation fields derived from UV star catalogs. We estimated the fraction of H2 (f H2) and the gas-to-dust ratio (GDR) of the diffuse ISM. The f H2 gradually increases from <1% at optically thin regions where E(B-V) < 0.1 to ˜50% for E(B-V) = 3. The estimated GDR is ˜5.1 × 1021 atoms cm-2 mag-1, in agreement with the standard value of 5.8 × 1021 atoms cm-2 mag-1.

  5. Comparison of diffuse infrared and far-ultraviolet emission in the Large Magellanic Cloud: The data

    Science.gov (United States)

    Saikia, Gautam; Shalima, P.; Gogoi, Rupjyoti; Pathak, Amit

    2016-11-01

    Dust scattering is the main source of diffuse emission in the far-ultraviolet (FUV). For several locations in the Large Magellanic Cloud (LMC), Far Ultraviolet Spectroscopic Explorer (FUSE) satellite has observed diffuse radiation in the FUV with intensities ranging from 1000 to 3×105 photon units and diffuse fraction between 5% and 20% at 1100 Å. Here, we compare the FUV diffuse emission with the mid-infrared (MIR) and far-infrared (FIR) diffuse emission observed by the Spitzer Space Telescope and the AKARI satellite for the same locations. The intensity ratios in the different MIR and FIR bands for each of the locations will enable us to determine the type of dust contributing to the diffuse emission as well as to derive a more accurate 3D distribution of stars and dust in the region, which in turn may be used to model the observed scattering in the FUV. In this work we present the infrared (IR) data for two different regions in LMC, namely N11 and 30 Doradus. We also present the FUV IR correlation for different infrared bands.

  6. Comparison of Diffuse Infrared and Far-Ultraviolet emission in the Large Magellanic Cloud: The Data

    CERN Document Server

    Saikia, Gautam; Gogoi, Rupjyoti; Pathak, Amit

    2016-01-01

    Dust scattering is the main source of diffuse emission in the far-ultraviolet (FUV). For several locations in the Large Magellanic Cloud (LMC), Far Ultraviolet Spectroscopic Explorer (FUSE) satellite has observed diffuse radiation in the FUV with intensities ranging from 1000 - 3 X 10^5 photon units and diffuse fraction between 5% - 20% at 1100 {\\deg}A. Here, we compare the FUV diffuse emission with the mid-infrared (MIR) and far-infrared (FIR) diffuse emission observed by the Spitzer Space Telescope and the AKARI satellite for the same locations. The intensity ratios in the different MIR and FIR bands for each of the locations will enable us to determine the type of dust contributing to the diffuse emission as well as to derive a more accurate 3D distribution of stars and dust in the region, which in turn may be used to model the observed scattering in the FUV. In this work we present the infrared (IR) data for two different regions in LMC, namely N11 and 30 Doradus. We also present the FUV~IR correlation fo...

  7. The Far-Ultraviolet Spectra of TW Hya. II. Models of H2 Fluorescence in a Disk

    CERN Document Server

    Herczeg, G J; Linsky, J L; Valenti, J A; Johns-Krull, C M; Herczeg, Gregory J.; Wood, Brian E.; Linsky, Jeffrey L.; Valenti, Jeff A.; Johns-Krull, Chris M.

    2004-01-01

    We measure the temperature of warm gas at planet-forming radii in the disk around the classical T Tauri star (CTTS) TW Hya by modelling the H2 fluorescence observed in HST/STIS and FUSE spectra. Strong Ly-alpha emission irradiates a warm disk surface within 2 AU of the central star and pumps certain excited levels of H2. We simulate a 1D plane-parallel atmosphere to estimate fluxes for the 140 observed H2 emission lines and to reconstruct the Ly-alpha emission profile incident upon the warm H2. The excitation of H2 can be determined from relative line strengths by measuring self-absorption in lines with low-energy lower levels, or by reconstructing the Ly-alpha profile incident upon the warm H2 using the total flux from a single upper level and the opacity in the pumping transition. Based on those diagnostics, we estimate that the warm disk surface has a column density of log N(H2)=18.5^{+1.2}_{-0.8}, a temperature T=2500^{+700}_{-500} K, and a filling factor of H2, as seen by the source of Ly-alpha emission,...

  8. Far Ultraviolet Emission in the A2597 and A2204 Brightest Cluster Galaxies

    CERN Document Server

    Oonk, J B R; Jaffe, W; Bremer, M N; van weeren, R J

    2011-01-01

    We use the Hubble Space Telescope ACS/SBC and Very Large Telescope FORS cameras to observe the Brightest Cluster Galaxies in Abell 2597 and Abell 2204 in the far-ultraviolet (FUV) F150LP and optical U, B, V, R, I Bessel filters. The FUV and U band emission is enhanced in bright, filamentary structures surrounding the BCG nuclei. These filaments can be traced out to 20 kpc from the nuclei in the FUV. Excess FUV and U band light is determined by removing emission due to the underlying old stellar population and mapped with 1 arcsec spatial resolution over the central 20 kpc regions of both galaxies. We find the FUV and U excess emission to be spatially coincident and a stellar interpretation requires the existence of a significant amount of 10000-50000 K stars. Correcting for nebular continuum emission and dust intrinsic to the BCG further increases the FUV to U band emission ratio and implies that stars alone may not suffice to explain the observations. However, lack of detailed information on the gas and dust...

  9. Catching some Sun : Probing the solar wind with cometary X-ray and far-ultraviolet emission

    NARCIS (Netherlands)

    Bodewits, D; Juhasz, Z; Hoekstra, R; Tielens, AGGM

    2004-01-01

    Strong X-ray and far-ultraviolet emission from comets is the direct result of charge exchange reactions of solar wind ions with the neutral coma of comets. Here we report experimental state-selective cross sections of electron capture and use these to predict cometary line emission. Our results show

  10. Catching some Sun : Probing the solar wind with cometary X-ray and far-ultraviolet emission

    NARCIS (Netherlands)

    Bodewits, D; Juhasz, Z; Hoekstra, R; Tielens, AGGM

    2004-01-01

    Strong X-ray and far-ultraviolet emission from comets is the direct result of charge exchange reactions of solar wind ions with the neutral coma of comets. Here we report experimental state-selective cross sections of electron capture and use these to predict cometary line emission. Our results show

  11. The Far-Ultraviolet "Continuum" in Protoplanetary Disk Systems II: CO Fourth Positive Emission and Absorption

    CERN Document Server

    France, Kevin; Burgh, Eric B; Herczeg, Gregory J; Harper, Graham M; Brown, Alexander; Green, James C; Linsky, Jeffrey L; Yang, Hao; Abgrall, Hervé; Ardila, David R; Bergin, Edwin; Bethell, Thomas; Brown, Joanna M; Calvet, Nuria; Espaillat, Catherine; Gregory, Scott G; Hillenbrand, Lynne A; Hussain, Gaitee; Ingleby, Laura; Johns-Krull, Christopher M; Roueff, Evelyne; Valenti, Jeff A; Walter, Frederick M

    2011-01-01

    We exploit the high sensitivity and moderate spectral resolution of the $HST$-Cosmic Origins Spectrograph to detect far-ultraviolet spectral features of carbon monoxide (CO) present in the inner regions of protoplanetary disks for the first time. We present spectra of the classical T Tauri stars HN Tau, RECX-11, and V4046 Sgr, representative of a range of CO radiative processes. HN Tau shows CO bands in absorption against the accretion continuum. We measure a CO column density and rotational excitation temperature of N(CO) = 2 +/- 1 $\\times$ 10$^{17}$ cm$^{-2}$ and T_rot(CO) 500 +/- 200 K for the absorbing gas. We also detect CO A-X band emission in RECX-11 and V4046 Sgr, excited by ultraviolet line photons, predominantly HI LyA. All three objects show emission from CO bands at $\\lambda$ $>$ 1560 \\AA, which may be excited by a combination of UV photons and collisions with non-thermal electrons. In previous observations these emission processes were not accounted for due to blending with emission from the accr...

  12. The far-ultraviolet main auroral emission at Jupiter. Pt. 2. Vertical emission profile

    Energy Technology Data Exchange (ETDEWEB)

    Bonfond, B.; Gustin, J.; Gerard, J.C.; Grodent, D.; Radioti, A. [Liege Univ. (Belgium). Lab. de Physique Atmospherique et Planetaire; Palmaerts, B. [Liege Univ. (Belgium). Lab. de Physique Atmospherique et Planetaire; Max-Planck-Institut fuer Sonnensystemforschung, Goettingen (Germany); Badman, S.V. [Lancaster Univ. (United Kingdom). Dept. of Physics; Khurana, K.K. [California Univ., Los Angeles, CA (United States); Tao, C. [Institut de Recherche en Astrophysique et Planetologie, Toulouse (France)

    2015-07-01

    The aurorae at Jupiter are made up of many different features associated with a variety of generation mechanisms. The main auroral emission, also known as the main oval, is the most prominent of them as it accounts for approximately half of the total power emitted by the aurorae in the ultraviolet range. The energy of the precipitating electrons is a crucial parameter to characterize the processes at play which give rise to these auroral emissions, and the altitude of the emissions directly depends on this energy. Here we make use of far-UV (FUV) images acquired with the Advanced Camera for Surveys on board the Hubble Space Telescope and spectra acquired with the Space Telescope Imaging Spectrograph to measure the vertical profile of the main emissions. The altitude of the brightness peak as seen above the limb is ∝ 400 km, which is significantly higher than the 250 km measured in the post-dusk sector by Galileo in the visible domain. However, a detailed analysis of the effect of hydrocarbon absorption, including both simulations and FUV spectral observations, indicates that FUV apparent vertical profiles should be considered with caution, as these observations are not incompatible with an emission peak located at 250 km. The analysis also calls for spectral observations to be carried out with an optimized geometry in order to remove observational ambiguities.

  13. Origin of the Diffuse, Far Ultraviolet Emission in the Interarm Regions of M101

    CERN Document Server

    Crocker, Alison F; Calzetti, Daniela; Holwerda, Benne Willem; Leitherer, Claus; Popescu, Cristina; Tuffs, R J

    2015-01-01

    We present images from the Solar Blind Channel on HST that resolve hundreds of far ultraviolet (FUV) emitting stars in two ~1 kpc$^2$ interarm regions of the grand-design spiral M101. The luminosity functions of these stars are compared with predicted distributions from simple star formation histories, and are best reproduced when the star formation rate has declined recently (past 10-50 Myr). This pattern is consistent with stars forming within spiral arms and then streaming into the interarm regions. We measure the diffuse FUV surface brightness after subtracting all of the detected stars, clusters and background galaxies. A residual flux is found for both regions which can be explained by a mix of stars below our detection limit and scattered FUV light. The amount of scattered light required is much larger for the region immediately adjacent to a spiral arm, a bright source of FUV photons.

  14. The far-ultraviolet main auroral emission at Jupiter. Pt. 1. Dawn-dusk brightness asymmetries

    Energy Technology Data Exchange (ETDEWEB)

    Bonfond, B.; Gustin, J.; Gerard, J.C.; Grodent, D.; Radioti, A. [Liege Univ. (Belgium). Lab. de Physique Atmospherique et Planetaire; Palmaerts, B. [Liege Univ. (Belgium). Lab. de Physique Atmospherique et Planetaire; Max-Planck-Institut fuer Sonnensystemforschung, Goettingen (Germany); Badman, S.V. [Lancaster Univ. (United Kingdom). Dept. of Physics; Khurana, K.K. [California Univ., Los Angeles, CA (United States); Tao, C. [Institut de Recherche en Astrophysique et Planetologie, Toulouse (France)

    2015-07-01

    The main auroral emission at Jupiter generally appears as a quasi-closed curtain centered around the magnetic pole. This auroral feature, which accounts for approximately half of the total power emitted by the aurorae in the ultraviolet range, is related to corotation enforcement currents in the middle magnetosphere. Early models for these currents assumed axisymmetry, but significant local time variability is obvious on any image of the Jovian aurorae. Here we use far-UV images from the Hubble Space Telescope to further characterize these variations on a statistical basis. We show that the dusk side sector is ∝ 3 times brighter than the dawn side in the southern hemisphere and ∝ 1:1 brighter in the northern hemisphere, where the magnetic anomaly complicates the interpretation of the measurements.We suggest that such an asymmetry between the dawn and the dusk sectors could be the result of a partial ring current in the nightside magnetosphere.

  15. High-resolution far ultraviolet emission spectra of electron-excited molecular deuterium

    Energy Technology Data Exchange (ETDEWEB)

    Abgrall, H.; Roueff, E. [Observatoire de Paris, Section de Meudon, DAEC and CNRS UMR 8631, 92195 Meudon Cedex (France); Xianming Liu; Shemansky, D.E. [Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, CA 90089 (United States); James, G.K. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)

    1999-08-14

    The high-resolution (full width at half maximum {delta} {lambda} = 0.11 A) emission spectrum of the deuterium molecule produced by electron-impact excitation at 100 eV has been measured in the wavelength range 1200-1660 A. In conjunction with the experimental measurement, transition probabilities of B{sup 1}{sigma}{sub u}{sup +}-X{sup 1}{sigma}{sub g}{sup +}, C{sup 1}{pi}{sub u}-X{sup 1}{sigma}{sub g}{sup +}, B'{sup 1}{sigma}{sub u}{sup +}-X{sup 1}{sigma}{sub g}{sup +} and D{sup 1}{pi}{sub u}-X{sup 1}{sigma}{sub g}{sup -} band systems are calculated. Synthetic spectra based on the calculated transition probabilities are in very good agreement with the optically thin experimental spectra. While centrifugal effects on the overall Lyman band emission intensity in D{sub 2} and H{sub 2} are similar, the effect of rotation-vibrational perturbations between the B{sup 1}{sigma}{sub u}{sup +} and C{sup 1}{pi}{sub u}{sup +} states on spectral intensities is found to be less significant in D{sub 2}. Excitations via isotropic ({delta} J = 0) and anisotropic ({delta}J = {+-} 2, and 0) interactions for the dipole forbidden E, F{sup 1}{sigma}{sub g}{sup +}-X{sup 1}{sigma}{sub g}{sup +} transition are inferred from the measured spectra. Excitation cross sections of the B{sup 1}{sigma}{sub u}{sup +}-X{sup 1}{sigma}{sub g}{sup +} and C{sup 1}{pi}{sub u}-X{sup 1}{sigma}{sub g}{sup +} bands, along with the estimated E, F{sup 1}{sigma}{sub g}{sup +}-B{sup 1}{sigma}{sub u}{sup +} cascade cross section, for D{sub 2} are obtained. (author)

  16. Far Ultraviolet Astronomy

    Science.gov (United States)

    Sonneborn, George; Rabin, Douglas M. (Technical Monitor)

    2002-01-01

    The Far Ultraviolet Spectroscopic Explorer (FUSE) is studying a wide range of astronomical problems in the 905-1187 Angstrom wavelength region through the use of high resolution spectroscopy. The FUSE bandpass forms a nearly optimal complement to the spectral coverage provided by the Hubble Space Telescope (HST), which extends down to approximately 1170 Angstroms. The photoionization threshold of atomic hydrogen (911 Angstroms) sets a natural short-wavelength limit for the FUV. FUSE was launched in June 1999 from Cape Canaveral, Florida, on a Delta II rocket into a 768 km circular orbit. Scientific observations started later that year. This spectral region is extremely rich in spectral diagnostics of astrophysical gases over a wide range of temperatures (100 K to over 10 million K). Important strong spectral lines in this wavelength range include those of neutral hydrogen, deuterium, nitrogen, oxygen, and argon (H I, D I, N I, O I, and Ar I), molecular hydrogen (H2), five-times ionized oxygen (O VI), and several ionization states of sulfur (S III - S VI). These elements are essential for understanding the origin and evolution of the chemical elements, the formation of stars and our Solar System, and the structure of galaxies, including our Milky Way. FUSE is one of NASA's Explorer missions and a cooperative project of NASA and the space agencies of Canada and France. These missions are smaller, more scientifically focused missions than the larger observatories, like Hubble and Chandra. FUSE was designed, built and operated for NASA by the Department of Physics and Astronomy at Johns Hopkins University. Hundreds of astronomers world-wide are using FUSE for a wide range of scientific research. Some of the important scientific discoveries from the first two years of the mission are described.

  17. H2O and O2 absorption in the coma of comet 67P/Churyumov-Gerasimenko measured by the Alice far-ultraviolet spectrograph on Rosetta

    Science.gov (United States)

    Keeney, Brian A.; Stern, S. Alan; A'Hearn, Michael F.; Bertaux, Jean-Loup; Feaga, Lori M.; Feldman, Paul D.; Medina, Richard A.; Parker, Joel Wm.; Pineau, Jon P.; Schindhelm, Eric; Steffl, Andrew J.; Versteeg, M.; Weaver, Harold A.

    2017-07-01

    We have detected H2O and O2 absorption against the far-UV continuum of stars located on lines of sight near the nucleus of Comet 67P/Churyumov-Gerasimenko using the Alice imaging spectrograph on Rosetta. These stellar appulses occurred at impact parameters of ρ = 4-20 km, and heliocentric distances ranging from Rh = - 1.8 to 2.3 au (negative values indicate pre-perihelion observations). The measured H2O column densities agree well with nearly contemporaneous values measured by VIRTIS-H. The clear detection of O2 independently confirms the initial detection by the ROSINA mass spectrometer; however, the relative abundance of O2/H2O derived from the stellar spectra (11-68 per cent, with a median value of 25 per cent) is considerably larger than published values found by ROSINA. The cause of this difference is unclear, but potentially related to ROSINA measuring number density at the spacecraft position while Alice measures column density along a line of sight that passes near the nucleus.

  18. Hubble Space Telescope far-ultraviolet imaging of the jet in 3C273: a common emission component from optical to X-rays

    CERN Document Server

    Jester, Sebastian; Martel, Andre'; Perlman, Eric; Sparks, Bill

    2007-01-01

    We present far-ultraviolet (UV) observations at 150 nm of the jet of the quasar 3C 273 obtained with the Advanced Camera for Survey's Solar Blind Channel (ACS/SBC) on board the Hubble Space Telescope. While the jet morphology is very similar to that in the optical and near-ultraviolet, the spectral energy distributions (SEDs) of the jet's sub-regions show an upturn in nu f_nu at 150 nm compared to 300 nm everywhere in the jet. Moreover, the 150 nm flux is compatible with extrapolating the X-ray power-law down to the ultra-violet region. This constitutes strong support for a common origin of the jet's far-UV and X-ray emission. It implies that even a substantial fraction of the *visible light* in the X-ray brightest parts of the jet arises from the same spectral component as the X-rays, as had been suggested earlier based on Spitzer Space Telescope observations. We argue that the identification of this UV/X-ray component opens up the possibility to establish the synchrotron origin of the X-ray emission by opti...

  19. Far-ultraviolet astronomical narrowband imaging.

    Science.gov (United States)

    Cook, Timothy A; Hicks, Brian A; Jung, Paul G; Chakrabarti, Supriya

    2009-04-01

    We describe an all-reflective system for narrowband imaging suitable for imaging emission lines in the far ultraviolet. The system, which we call a monochromatic imager, combines a pupil plane grating monochromator with a telescope and camera to image a scene in one or more very narrow bands. The monochromator uses physical stops at its input and output apertures, and, as a result, the system has excellent rejection of out-of-band and off-axis light.

  20. Thermal Pressure in Diffuse H2 Gas Measured by Herschel [C II] Emission and FUSE UV H2 Absorption

    Science.gov (United States)

    Velusamy, T.; Langer, W. D.; Goldsmith, P. F.; Pineda, J. L.

    2017-04-01

    UV absorption studies with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite have made important observations of H2 molecular gas in Galactic interstellar translucent and diffuse clouds. Observations of the 158 μm [C ii] fine-structure line with Herschel trace the same H2 molecular gas in emission. We present [C ii] observations along 27 lines of sight (LOSs) toward target stars of which 25 have FUSE H2 UV absorption. Two stars have only HST STIS C ii λ2325 absorption data. We detect [C ii] 158 μm emission features in all but one target LOS. For three target LOSs that are close to the Galactic plane, | {\\text{}}b| UV absorption data. We present the H2 gas densities and thermal pressures for 26 target LOSs and from the [C ii] intensities derive a mean thermal pressure in the range of ˜6100-7700 K cm-3 in diffuse H2 clouds. We discuss the thermal pressures and densities toward 14 targets, comparing them to results obtained using the UV absorption data for two other tracers C i and CO. Our results demonstrate the richness of the far-IR [C ii] spectral data which is a valuable complement to the UV H2 absorption data for studying diffuse H2 molecular clouds. While the UV absorption is restricted to the directions of the target star, far-IR [C ii] line emission offers an opportunity to employ velocity-resolved spectral-line mapping capability to study in detail the clouds’ spatial and velocity structures.

  1. $H_{2}$ emission from CRL 618

    CERN Document Server

    Herpin, F; Heras, A

    2000-01-01

    We present a complete study of the H2 infrared emission, including the pure rotational lines, of the proto Planetary Nebulae CRL 618 with the ISO SWS. A large number of lines are detected. The analysis of our observations shows: (i) an OTP ratio very different from the classical value of 3, probably around 1.76-1.87; (ii) a stratification of the emitting region, and more precisely different regions of emission, plausibly located in the lobes, in an intermediate zone, and close to the torus; (iii) different excitation mechanisms, collisions and fluorescence.

  2. Attenuated total reflection far-ultraviolet spectroscopy

    Science.gov (United States)

    Ozaki, Yukihiro; Morisawa, Yusuke; Goto, Takeyoshi; Tanabe, Ichiro

    2016-09-01

    Recently, far-ultraviolet (FUV) spectroscopy of solid and liquid states has been a matter of keen interest because it provides new possibilities for studying electronic structures and transitions of almost all kinds of molecules. It has also great potential for a variety of applications from quantitative and qualitative analysis of aqueous solutions to environmental and geographical analyses. This review describes the state-of- the-art of FUV spectroscopy; an introduction to FUV spectroscopy, the development of FUV spectrometers, investigations on electronic transitions and structure, its various applications, and future prospects.

  3. Planetary Nebulae with H2 Emission

    Directory of Open Access Journals (Sweden)

    Margarita Rosado

    2003-01-01

    Full Text Available Hacemos una revisión de la emisión en hidrogeno molecular (H2 de las nebulosas planetarias (NPs. Vemos como esta emisión se encuentra asociada a objetos de forma bipolar. Describimos los niveles de energía de la molécula de hidrogeno, los principales mecanismos para poblarlos (choques y fluorescencia y las formas en que se puede discriminar que mecanismo opera. Proponemos que la cinemática del H2 también puede ser usada para discriminar el mecanismo de excitación de sus líneas de emisión. Presentamos resultados preliminares sobre el estudio de la cinemática del H2 que estamos realizando para una muestra de cinco NPs bipolares. Este estudio nos ha permitido determinar que los choques son el principal agente en la excitación del H2 y que las masas de los progenitores de estos objetos son mayores que las de los progenitores de NPs típicas.

  4. The Far-Ultraviolet Ups and Downs of Alpha Centauri

    CERN Document Server

    Ayres, Thomas R

    2014-01-01

    Four years (2010-2014) of semiannual pointings by Hubble Space Telescope Imaging Spectrograph (STIS) on nearby Alpha Centauri have yielded a detailed time history of far-ultraviolet emissions of the solar-like primary (A: G2V) and the cooler, but more active, secondary (B: K1V). This period saw A climbing out of a prolonged coronal X-ray minimum, as documented by Chandra, while B was rising to, then falling from, a peak of its long-term (8 yr) starspot cycle. The FUV fluxes of the primary were steady over most of the STIS period, although the [Fe XII] 124 nm coronal forbidden line (T= 1.5 MK) partly mirrored the slowly rising X-ray fluxes. The FUV emissions of the secondary more closely tracked the rise and fall of its coronal luminosities, especially the "hot lines" like Si IV, C IV, and N V (T= 80,000-200,000 K), and coronal [Fe XII] itself. The hot lines of both stars were systematically redshifted, relative to narrow chromospheric emissions, by several km/s, showing little change in amplitude over the 4-y...

  5. Far-Ultraviolet Dust Scattering and Extinction in IC 405

    Science.gov (United States)

    France, Kevin; Burgh, Eric B.; McCandliss, Stephan R.; Feldman, Paul D.

    We present results from a NASA/JHU sounding rocket mission (36.198 UG) during which we acquired a longslit (12" times 200") spectrum of the reflection nebula IC 405 in the 900 - 1400Å wavelength region. Several pointings within the nebula were obtained, including a high quality (S/N ≅10-15 at R = 300) spectrum of the central star, HD 34078. Observations of the nebula reveal a surface brightness to stellar flux ratio that rises by two orders of magnitude to the blue in our bandpass. This is in contrast with the relatively flat nebular dust scattering observed during a prior sounding rocket observation of the reflection nebula NGC 2023. Several possibilities have been suggested to explain the blue rise that is exhibited in IC 405. Differential extinction within the nebula, such as a particular clump of dust along the line of sight, is one possibility. Fluorescent molecular hydrogen, unresolved by the resolution of the rocket experiment, is another possible explanation. Models of nebular dust scattering, similar to those of Burgh et al. 2002, have been compared to the data and results will be discussed. We will explore the possibility of differential extinction with an observing program to measure Balmer line ratios within the nebula with the Dual Imaging Spectrograph at Apache Point Observatory. Additionally, IC 405 has been accepted as a Cycle 4 target of the Far Ultraviolet Spectroscopic Explorer to search for emissions from molecular hydrogen at higher sensitivity and spectral resolution.

  6. Summary of Quantitative Interpretation of Image Far Ultraviolet Auroral Data

    Science.gov (United States)

    Frey, H. U.; Immel, T. J.; Mende, S. B.; Gerard, J.-C.; Hubert, B.; Habraken, S.; Span, J.; Gladstone, G. R.; Bisikalo, D. V.; Shematovich, V. I.; hide

    2002-01-01

    Direct imaging of the magnetosphere by instruments on the IMAGE spacecraft is supplemented by simultaneous observations of the global aurora in three far ultraviolet (FUV) wavelength bands. The purpose of the multi-wavelength imaging is to study the global auroral particle and energy input from thc magnetosphere into the atmosphere. This paper describes provides the method for quantitative interpretation of FUV measurements. The Wide-Band Imaging Camera (WIC) provides broad band ultraviolet images of the aurora with maximum spatial and temporal resolution by imaging the nitrogen lines and bands between 140 and 180 nm wavelength. The Spectrographic Imager (SI), a dual wavelength monochromatic instrument, images both Doppler-shifted Lyman alpha emissions produced by precipitating protons, in the SI-12 channel and OI 135.6 nm emissions in the SI-13 channel. From the SI-12 Doppler shifted Lyman alpha images it is possible to obtain the precipitating proton flux provided assumptions are made regarding the mean energy of the protons. Knowledge of the proton (flux and energy) component allows the calculation of the contribution produced by protons in the WIC and SI-13 instruments. Comparison of the corrected WIC and SI-13 signals provides a measure of the electron mean energy, which can then be used to determine the electron energy fluxun-. To accomplish this reliable modeling emission modeling and instrument calibrations are required. In-flight calibration using early-type stars was used to validate the pre-flight laboratory calibrations and determine long-term trends in sensitivity. In general, very reasonable agreement is found between in-situ measurements and remote quantitative determinations.

  7. Measurements of the Near-Nucleus Coma of Comet 67P/Churyumov-Gerasimenko with the Alice Far-Ultraviolet Spectrograph on Rosetta

    CERN Document Server

    Feldman, Paul D; Bertaux, Jean-Loup; Feaga, Lori M; Parker, Joel Wm; Schindhelm, Eric; Steffl, Andrew J; Stern, S Alan; Weaver, Harold A; Sierks, Holger; Vincent, Jean-Baptiste

    2015-01-01

    Aims. The Alice far-ultraviolet spectrograph onboard Rosetta is designed to observe emissions from various atomic and molecular species from within the coma of comet 67P/ Churyumov-Gerasimenko and to determine their spatial distribution and evolution with time and heliocentric distance. Methods. Following orbit insertion in August 2014, Alice made observations of the inner coma above the limbs of the nucleus of the comet from cometocentric distances varying between 10 and 80 km. Depending on the position and orientation of the slit relative to the nucleus, emissions of atomic hydrogen and oxygen were initially detected. These emissions are spatially localized close to the nucleus and spatially variable with a strong enhancement above the comet's neck at northern latitudes. Weaker emission from atomic carbon and CO were subsequently detected. Results. Analysis of the relative line intensities suggests photoelectron impact dissociation of H2O vapor as the source of the observed H I and O I emissions. The electr...

  8. The far ultraviolet spectrum of Pluto and the discovery of its ionosphere

    Science.gov (United States)

    Steffl, A.; Stern, A.; Gladstone, R.; Parker, J. W.; Greathouse, T. K.; Retherford, K. D.; Young, L. A.; Schindhelm, E.; Kammer, J.; Strobel, D. F.; Summers, M. E.; Versteeg, M.; Olkin, C.; Weaver, H. A., Jr.; Hinson, D. P.; Linscott, I.

    2016-12-01

    During the New Horizons spacecraft's encounter with Pluto in July 2015, the Alice far ultraviolet spectrograph made numerous observations of Pluto and its atmosphere. We present here the far ultraviolet spectrum of Pluto. We observe faint emission ( 34.7 eV; wavelength < 36nm). Notably absent from Pluto's spectrum are emission lines from argon at 104.8 and 106.7 nm. We place upper limits on the amount of argon in Pluto's atmosphere above the tau=1 level (observed to be at 750km tangent altitude) that are significantly lower than previous models. We also identify and derive column densities for various hydrocarbon species such as C2H4 through their absorption of sunlight reflected from Pluto's surface.

  9. Molecular hydrogen (H2) emissions from gasoline and diesel vehicles.

    Science.gov (United States)

    Bond, S W; Alvarez, R; Vollmer, M K; Steinbacher, M; Weilenmann, M; Reimann, S

    2010-08-01

    This study assesses individual-vehicle molecular hydrogen (H2) emissions in exhaust gas from current gasoline and diesel vehicles measured on a chassis dynamometer. Absolute H2 emissions were found to be highest for motorcycles and scooters (141+/-38.6 mg km(-1)), approximately 5 times higher than for gasoline-powered automobiles (26.5+/-12.1 mg km(-1)). All diesel-powered vehicles emitted marginal amounts of H2 ( approximately 0.1 mg km(-1)). For automobiles, the highest emission factors were observed for sub-cycles subject to a cold-start (mean of 53.1+/-17.0 mg km(-1)). High speeds also caused elevated H2 emission factors for sub-cycles reaching at least 150 km h(-1) (mean of 40.4+/-7.1 mg km(-1)). We show that H2/CO ratios (mol mol(-1)) from gasoline-powered vehicles are variable (sub-cycle means of 0.44-5.69) and are typically higher (mean for automobiles 1.02, for 2-wheelers 0.59) than previous atmospheric ratios characteristic of traffic-influenced measurements. The lowest mean individual sub-cycle ratios, which correspond to high absolute emissions of both H2 and CO, were observed during cold starts (for automobiles 0.48, for 2-wheelers 0.44) and at high vehicle speeds (for automobiles 0.73, for 2-wheelers 0.45). This finding illustrates the importance of these conditions to observed H2/CO ratios in ambient air. Overall, 2-wheelers displayed lower H2/CO ratios (0.48-0.69) than those from gasoline-powered automobiles (0.75-3.18). This observation, along with the lower H2/CO ratios observed through studies without catalytic converters, suggests that less developed (e.g. 2-wheelers) and older vehicle technologies are largely responsible for the atmospheric H2/CO ratios reported in past literature. 2010 Elsevier B.V. All rights reserved.

  10. Color enhancement of ten-minute far ultraviolet exposure of Earth

    Science.gov (United States)

    1972-01-01

    An artifically reproduced color enhancement of a ten-minute far-ultraviolet exposure of the Earth, taken with a filter which blocks the glow cause by atomic hydrogen but which transmits the glow caused by atomic oxygen and molecular nitrogen. Note that airglow emission bands are visible on the night side of the Earth, one roughly centered between the two polar auroral zones and one at an angle to this extending northward toward the sunlit side of the Earth.

  11. The brightness ratio of H Lyman‐α/H2 bands in FUV auroral emissions: A diagnosis for the energy of precipitating electrons and associated magnetospheric acceleration processes applied to Saturn

    National Research Council Canada - National Science Library

    Tao, Chihiro; Lamy, Laurent; Prangé, Renée

    2014-01-01

    We propose that the ratio of the auroral brightness of H Lyman‐ α to that of far ultraviolet H 2 and the absolute value of the H 2 brightness provide good indicators of the acceleration versus nonacceleration processes for field...

  12. Far-ultraviolet signatures of the 3He(n,tp) reaction in noble gas mixtures

    CERN Document Server

    Hughes, Patrick P; Thompson, Alan K; Vest, Robert E; Clark, Charles W

    2010-01-01

    Previous work showed that the 3He(n,tp) reaction in a cell of 3He at atmospheric pressure generated tens of far-ultraviolet photons per reacted neutron. Here we report amplification of that signal by factors of 1000 and more when noble gases are added to the cell. Calibrated filter-detector measurements show that this large signal is due to noble-gas excimer emissions, and that the nuclear reaction energy is converted to far-ultraviolet radiation with efficiencies of up to 30%. The results have been placed on an absolute scale through calibrations at the NIST SURF III synchrotron. They suggest possibilities for high-efficiency neutron detectors as an alternative to existing proportional counters.

  13. O2 Emission toward Orion H2 Peak 1 and the Role of FUV-illuminated C-shocks

    Science.gov (United States)

    Melnick, Gary J.; Kaufman, Michael J.

    2015-06-01

    Molecular oxygen (O2) has been the target of ground-based and space-borne searches for decades. Of the thousands of lines of sight surveyed, only those toward Rho Ophiuchus and Orion H2 Peak 1 have yielded detections of any statistical significance. The detection of the O2 NJ = 33-12 and 54-34 lines at 487.249 GHz and 773.840 GHz, respectively, toward Rho Ophiuchus has been attributed to a short-lived peak in the time-dependent, cold-cloud O2 abundance, while the detection of the O2 NJ = 33-12, 54-34 lines, plus the 76-56 line at 1120.715 GHz, toward Orion has been ascribed to time-dependent preshock physical and chemical evolution and low-velocity (12 km s-1) non-dissociative C-type shocks, both of which are fully shielded from far-ultraviolet (FUV) radiation, plus a postshock region that is exposed to an FUV field. We report a re-interpretation of the Orion O2 detection based on new C-type shock models that fully incorporate the significant effects the presence of even a weak FUV field can have on the preshock gas, shock structure, and postshock chemistry. In particular, we show that a family of solutions exists, depending on the FUV intensity, that reproduces both the observed O2 intensities and O2 line ratios. The solution in closest agreement with the shock parameters inferred for H2 Peak 1 from other gas tracers assumes a 23 km s-1 shock impacting gas with a preshock density of 8 × 104 cm-3 and {G}{o} = 1, substantially different from that inferred for the fully shielded shock case. As pointed out previously, the similarity between the LSR velocity of all three O2 lines (≈ 11 km s-1) and recently measured H2O 532-441 maser emission at 620.701 GHz toward H2 Peak 1 suggests that the O2 emission arises behind the same shocks responsible for the maser emission, though the O2 emission is almost certainly more extended than the localized high-density maser spots. Since maser emission arises along lines of sight of low-velocity gradient, indicating shock motion

  14. The Far-Ultraviolet Spectral Signatures of Formaldehyde and Carbon Dioxide in Comets

    Science.gov (United States)

    Feldman, Paul D.; Lupu, Roxana E.; McCandliss, Stephan R.; Weaver, Harold A.

    2009-07-01

    Observations of four comets made with the Far-Ultraviolet Spectroscopic Explorer show the rotational envelope of the (0,0) band of the CO Hopfield-Birge system (C 1Σ+- X 1Σ+) at 1088 Å to consist of both "cold" and "hot" components, the "cold" component accounting for ~75% of the flux and with a rotational temperature in the range 55 K-75 K. We identify the "hot" component as coming from the dissociation of CO2 into rotationally "hot" CO, with electron impact dissociation probably dominant over photodissociation near the nucleus. An additional weak, broad satellite band is seen centered near the position of the P(40) line that we attribute to CO fluorescence from a non-thermal high J rotational population produced by photodissociation of formaldehyde into CO and H2. This process also leaves the H2 preferentially populated in excited vibrational levels which are identified by fluorescent H2 lines in the spectrum excited by solar O VI λ1031.9 and solar Lyα. The amount of H2 produced by H2CO dissociation is comparable to the amount produced by photodissociation of H2O. Electron impact excitation of CO, rather than resonance fluorescence, appears to be the primary source of the observed B 1Σ+- X 1Σ+(0,0) band at 1151 Å.

  15. A Far Ultraviolet Spectroscopic Analysis of BZ Ursae Majoris

    CERN Document Server

    Godon, P; Gaensicke, B T; deMartino, D

    2011-01-01

    We present an analysis of the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) far ultraviolet snapshot spectrum of the dwarf nova BZ UMa taken during quiescence. We find that the flux continuum is consistent with that of a white dwarf atmosphere with a temperature of 15,000K, a projected rotational velocity of 200km/s, non-solar abundances with enhanced N/C ratio, and a distance of about 156pc when assuming a white dwarf gravity of log(g)=7.5. We also show that the hydrogen quasi-molecular satellite lines opacity affects the spectrum around 1300-1400 A and has to be included to fine-tune the spectral modeling, this is self-consistent with the low stellar temperature we find.

  16. Far-ultraviolet Spectroscopy of Recent Comets with the Cosmic Origins Spectrograph on the Hubble Space Telescope

    Science.gov (United States)

    Feldman, Paul D.; Weaver, Harold A.; A'Hearn, Michael F.; Combi, Michael R.; Dello Russo, Neil

    2016-10-01

    Since its launch in 1990, the Hubble Space Telescope (HST) has served as a platform with unique capabilities for remote observations of comets. Successive generations of imagers and spectrographs have seen large advances in sensitivity and spectral resolution enabling observations of the diverse properties of a representative number of comets during the past 25 years. To date, four comets have been observed in the far-ultraviolet by the Cosmic Origins Spectrograph (COS), the last spectrograph to be installed in HST, in 2009: 103P/Hartley 2, C/2009 P1 (Garradd), C/2012 S1 (ISON), and C/2014 Q2 (Lovejoy). COS has unprecedented sensitivity, albeit no spatial resolution, and the principal objective was to determine the relative CO abundance from measurements of the CO Fourth Positive system in the spectral range of 1400 to 1700 Å. In the two brightest comets, nineteen bands of this system were clearly identified. The water production rate was derived from nearly simultaneous observations of the OH (0,0) band at 3085 Å by the Space Telescope Imaging Spectrograph (STIS). The derived CO/H2O production rate ratio ranged from ~0.3% for Hartley 2 (Weaver et al., ApJ 734:L5, 2011) to ~20% for Garradd. In addition, strong partially resolved emission features due to multiplets of S I, centered at 1429 Å and 1479 Å, and of C I at 1561 Å and 1657 Å, were observed in all four comets. Weak emission from several lines of the H2 Lyman band system, excited by solar Lyman-α and Lyman-β pumped fluorescence, were detected in comet Lovejoy.This work is based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Support was provided by NASA through grants from the Space Telescope Science Institute.

  17. The Far Ultraviolet Spectral Signatures of Formaldehyde and Carbon Dioxide in Comets

    CERN Document Server

    Feldman, Paul D; McCandliss, Stephan R; Weaver, Harold A

    2009-01-01

    Observations of four comets made with the Far Ultraviolet Spectroscopic Explorer show the rotational envelope of the (0,0) band of the CO Hopfield-Birge system (C - X) at 1088 A to consist of both "cold" and "hot" components, the "cold" component accounting for ~75% of the flux and with a rotational temperature in the range 55-75 K. We identify the "hot" component as coming from the dissociation of CO2 into rotationally "hot" CO, with electron impact dissociation probably dominant over photodissociation near the nucleus. An additional weak, broad satellite band is seen centered near the position of the P(40) line that we attribute to CO fluorescence from a non-thermal high J rotational population produced by photodissociation of formaldehyde into CO and H2. This process also leaves the H2 preferentially populated in excited vibrational levels which are identified by fluorescent H2 lines in the spectrum excited by solar OVI 1031.9 and solar Lyman-alpha. The amount of H2 produced by H2CO dissociation is compara...

  18. The Nature and Frequency of the Gas Outbursts in Comet 67P/Churyumov-Gerasimenko observed by the Alice Far-ultraviolet Spectrograph on Rosetta

    CERN Document Server

    Feldman, Paul D; Feaga, Lori M; Bertaux, Jean-Loup; Noonan, John; Parker, Joel Wm; Schindhelm, Eric; Steffl, Andrew J; Stern, S Alan; Weaver, Harold A

    2016-01-01

    Alice is a far-ultraviolet imaging spectrograph onboard Rosetta that, amongst multiple objectives, is designed to observe emissions from various atomic and molecular species from within the coma of comet 67P/Churyumov-Gerasimenko. The initial observations, made following orbit insertion in August 2014, showed emissions of atomic hydrogen and oxygen spatially localized close to the nucleus and attributed to photoelectron impact dissociation of H2O vapor. Weaker emissions from atomic carbon were subsequently detected and also attributed to electron impact dissociation, of CO2, the relative H I and C I line intensities reflecting the variation of CO2 to H2O column abundance along the line-of-sight through the coma. Beginning in mid-April 2015, Alice sporadically observed a number of outbursts above the sunward limb characterized by sudden increases in the atomic emissions, particularly the semi-forbidden O I 1356 multiplet, over a period of 10-30 minutes, without a corresponding enhancement in long wavelength so...

  19. Factors affecting temporal H2S emission at construction and demolition (C&D) debris landfills.

    Science.gov (United States)

    Xu, Qiyong; Townsend, Timothy

    2014-02-01

    Odor problems associated with H2S emissions often result in odor complaints from nearby residents of C&D debris landfills, especially in the early morning. As part of a field study conducted on H2S removal ability using different cover materials, daily and seasonal H2S emissions through a soil cover layer were monitored at a C&D debris landfill to investigate factors affecting H2S emissions. H2S emission rates were not a constant, but varied seasonally, with an average emission rate of 4.67×10(-6)mgm(-2)s(-1). During a the 10-month field study, as the H2S concentration increased from 140ppm to about 3500ppm underneath the cover soil in the testing cell, H2S emissions ranged from zero to a maximum emission rate of 1.24×10(-5)mgm(-2)s(-1). Continuous emission monitoring indicated that H2S emissions even changed over time throughout the day, generally increasing from morning to afternoon, and were affected by soil moisture and temperature. Laboratory experiments were also conducted to investigate the effects of H2S concentration and cover soil moisture content on H2S emissions. The results showed that increased soil moisture reduced H2S emissions by retarding H2S migration through cover soil and dissolving H2S into soil water. The field study also indicated that due to atmospheric dispersion, high H2S emissions may not cause odor problems.

  20. The far-ultraviolet spectra of "cool" PG1159 stars

    CERN Document Server

    Werner, K; Kruk, J W

    2015-01-01

    We present a comprehensive study of Far Ultraviolet Spectroscopic Explorer (FUSE) spectra (912-1190 A) of two members of the PG1159 spectral class, which consists of hydrogen-deficient (pre-) white dwarfs with effective temperatures in the range Teff = 75,000-200,000 K. As two representatives of the cooler objects, we have selected PG1707+427 (Teff = 85,000 K) and PG1424+535 (Teff = 110,000 K), complementing a previous study of the hotter prototype PG1159-035 (Teff = 140,000 K). The helium-dominated atmospheres are strongly enriched in carbon and oxygen, therefore, their spectra are dominated by lines from C III-IV and O III-VI, many of which were never observed before in hot stars. In addition, lines of many other metals (N, F, Ne, Si, P, S, Ar, Fe) are detectable, demonstrating that observations in this spectral region are most rewarding when compared to the near-ultraviolet and optical wavelength bands. We perform abundance analyses of these species and derive upper limits for several undetected light and ...

  1. The far-ultraviolet spectra of "cool" PG 1159 stars

    Science.gov (United States)

    Werner, K.; Rauch, T.; Kruk, J. W.

    2015-10-01

    We present a comprehensive study of Far Ultraviolet Spectroscopic Explorer (FUSE) spectra (912-1190 Å) of two members of the PG 1159 spectral class, which consists of hydrogen-deficient (pre-) white dwarfs with effective temperatures in the range Teff = 75 000-200 000 K. As two representatives of the cooler objects, we have selected PG 1707+427 (Teff = 85 000 K) and PG 1424+535 (Teff = 110 000 K), complementing a previous study of the hotter prototype PG 1159-035 (Teff = 140 000 K). The helium-dominated atmospheres are strongly enriched in carbon and oxygen, therefore, their spectra are dominated by lines from C iii-iv and O iii-vi, many of which were never observed before in hot stars. In addition, lines of many other metals (N, F, Ne, Si, P, S, Ar, Fe) are detectable, demonstrating that observations in this spectral region are most rewarding when compared to the near-ultraviolet and optical wavelength bands. We perform abundance analyses of these species and derive upper limits for several undetected light and heavy metals including iron-group and trans-iron elements. The results are compared to predictions of stellar evolution models for neutron-capture nucleosynthesis and good agreement is found. Appendix A is available in electronic form at http://www.aanda.org

  2. The Far Ultraviolet Spectral Signatures of Formaldehyde and Carbon Dioxide in Comets

    Science.gov (United States)

    Feldman, Paul D.; McCandliss, S. R.; Weaver, H. A.

    2006-09-01

    Observations of four comets made with the Far Ultraviolet Spectroscopic Explorer show the rotational envelope of the (0,0) band of the CO Hopfield-Birge system (C 1Σ+ - X 1Σ+) at 1088 Å to consist of both "cold” and "hot” components, the "cold” component accounting for 75% of the flux and with a rotational temperature in the range 55 - 75 K. We identify the rotationally "hot” component (T 500 K) as coming from the dissociation of CO2 into CO, with electron impact dissociation and photodissociation contributing roughly equally. An additional weak, broad satellite band is seen centered near the position of the P(40) line that we attribute to CO fluorescence from a non-thermal high J rotational population produced by photodissociation of formaldehyde into CO and H2. This process, well studied in the laboratory, also leaves the H2 preferentially populated in excited vibrational levels that are identified by fluorescent H2 lines in the spectrum excited by solar O VI λ1031.9. Electron impact excitation of CO, rather than resonance fluorescence, is the primary source of the observed B 1Σ+ - X 1Σ+ (0,0) band at 1151 Å. Financial support was provided by NASA contract NAS5-32985 and NASA grant NAG5-12963.

  3. Far Ultraviolet Spectroscopy of Old Novae. II. RR Pic, V533 Her, and DI Lac

    Science.gov (United States)

    Sion, Edward M.; Godon, Patrick; Jones, Liam

    2017-03-01

    The old novae V533 Her (Nova Her 1963), DI Lac (Nova Lac 1910), and RR Pic (Nova Pic 1891) are in (or near) their quiescent stage, following their nova explosions, and continue to accrete at a high rate in the aftermath of their explosions. They exhibit continua that are steeply rising into the FUV, as well as absorption lines and emission lines of uncertain origin. All three have Far Ultraviolet Spectroscopic Explorer (FUSE) spectra that offer not only higher spectral resolution but also wavelength coverage extending down to the Lyman Limit. For DI Lac, we have matched these FUSE spectra with existing archival International Ultraviolet Explorer spectral coverage to broaden the FUV wavelength coverage. We adopted the newly determined interstellar reddening corrections of Selvelli & Gilmozzi. The dereddened FUV spectra have been modeled with our grids of optically thick accretion disks and hot, NLTE white dwarf (WD) photospheres. The results of our modeling analysis indicate that the hot components in RR Pic and V533 Her are likely to be accretion disks with mass accretion rates of 10‑8 M ⊙ yr‑1 and 10‑9 M ⊙ yr‑1 respectively. However, the disk cannot produce the observed absorption lines. For the WD to be the source of the absorption lines in these two systems, it must be very hot, with a radius several times its expected size (because the WD in these systems is massive, it has a smaller radius). For DI Lac, we find the best fit to be a disk with \\dot{M}={10}-10 {M}ȯ {{yr}}-1 with a 30,000 K WD. Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer (FUSE). FUSE was operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985.

  4. Spectroscopic Measurements of the Far-Ultraviolet Dust Attenuation Curve at z~3

    CERN Document Server

    Reddy, Naveen A; Pettini, Max; Bogosavljevic, Milan

    2016-01-01

    We present the first measurements of the shape of the far-ultraviolet (far-UV; lambda=950-1500 A) dust attenuation curve at high redshift (z~3). Our analysis employs rest-frame UV spectra of 933 galaxies at z~3, 121 of which have very deep spectroscopic observations (>7 hrs) at lambda=850-1300 A, with the Low Resolution Imaging Spectrograph on the Keck Telescope. By using an iterative approach in which we calculate the ratios of composite spectra in different bins of continuum color excess, E(B-V), we derive a dust curve that implies a lower attenuation in the far-UV for a given E(B-V) than those obtained with standard attenuation curves. We demonstrate that the UV composite spectra of z~3 galaxies can be modeled well by assuming our new attenuation curve, a high covering fraction of HI, and absorption from the Lyman-Werner bands of H2 with a small (<20%) covering fraction. The low covering fraction of H2 relative to that of the HI and dust suggests that most of the dust in the ISM of typical galaxies at z...

  5. The Origins of Fluorescent H2 Emission From T Tauri~Stars

    CERN Document Server

    Herczeg, G J; Johns-Krull, C M; Linsky, J L; Walter, F M; Gahm, Gosta F.; Herczeg, Gregory J.; Johns-Krull, Christopher M.; Linsky, Jeffrey L.; Walter, Frederick M.

    2006-01-01

    We survey fluorescent H2 emission in HST/STIS spectra of the classical T Tauri stars (CTTSs) TW Hya, DF Tau, RU Lupi, T Tau, and DG Tau, and the weak-lined T Tauri star (WTTS) V836 Tau. From each of those sources we detect between 41-209 narrow H2 emission lines, most of which are pumped by strong Ly-alpha emission. H2 emission is not detected from the WTTS V410 Tau. The fluorescent H2 emission appears to be common to circumstellar environments around all CTTSs, but high spectral and spatial resolution STIS observations reveal diverse phenomenon. Blueshifted H2 emission detected from RU Lupi, T Tau, and DG Tau is consistent with an origin in an outflow. The H2 emission from TW Hya, DF Tau, and V836 Tau is centered at the radial velocity of the star and is consistent with an origin in a warm disk surface. The H2 lines from RU Lupi, DF Tau, and T Tau also have excess blueshifted H2 emission that extends to as much as -100 km/s. The strength of this blueshifted component from DF Tau and T Tau depends on the uppe...

  6. [Study on the absolute spectral irradiation calibration method for far ultraviolet spectrometer in remote sensing].

    Science.gov (United States)

    Yu, Lei; Lin, Guan-Yu; Chen, Bin

    2013-01-01

    The present paper studied spectral irradiation responsivities calibration method which can be applied to the far ultraviolet spectrometer for upper atmosphere remote sensing. It is difficult to realize the calibration for far ultraviolet spectrometer for many reasons. Standard instruments for far ultraviolet waveband calibration are few, the degree of the vacuum experiment system is required to be high, the stabilities of the experiment are hardly maintained, and the limitation of the far ultraviolet waveband makes traditional diffuser and the integrating sphere radiance calibration method difficult to be used. To solve these problems, a new absolute spectral irradiance calibration method was studied, which can be applied to the far ultraviolet calibration. We build a corresponding special vacuum experiment system to verify the calibration method. The light source system consists of a calibrated deuterium lamp, a vacuum ultraviolet monochromater and a collimating system. We used the calibrated detector to obtain the irradiance responsivities of it. The three instruments compose the calibration irradiance source. We used the "calibration irradiance source" to illuminate the spectrometer prototype and obtained the spectral irradiance responsivities. It realized the absolute spectral irradiance calibration for the far ultraviolet spectrometer utilizing the calibrated detector. The absolute uncertainty of the calibration is 7.7%. The method is significant for the ground irradiation calibration of the far ultraviolet spectrometer in upper atmosphere remote sensing.

  7. Analytic H i-to-H2 Photodissociation Transition Profiles

    Science.gov (United States)

    Bialy, Shmuel; Sternberg, Amiel

    2016-05-01

    We present a simple analytic procedure for generating atomic (H i) to molecular ({{{H}}}2) density profiles for optically thick hydrogen gas clouds illuminated by far-ultraviolet radiation fields. Our procedure is based on the analytic theory for the structure of one-dimensional H i/{{{H}}}2 photon-dominated regions, presented by Sternberg et al. Depth-dependent atomic and molecular density fractions may be computed for arbitrary gas density, far-ultraviolet field intensity, and the metallicity-dependent H2 formation rate coefficient, and dust absorption cross section in the Lyman-Werner photodissociation band. We use our procedure to generate a set of {{H}} {{I}}{-}{to}{-}{{{H}}}2 transition profiles for a wide range of conditions, from the weak- to strong-field limits, and from super-solar down to low metallicities. We show that if presented as functions of dust optical depth, the {{H}} {{I}} and {{{H}}}2 density profiles depend primarily on the Sternberg “α G parameter” (dimensionless) that determines the dust optical depth associated with the total photodissociated {{H}} {{I}} column. We derive a universal analytic formula for the {{H}} {{I}}{-}{to}{-}{{{H}}}2 transition points as a function of just α G. Our formula will be useful for interpreting emission-line observations of H i/{{{H}}}2 interfaces, for estimating star formation thresholds, and for sub-grid components in hydrodynamics simulations.

  8. The Nature and Frequency of the Gas Outbursts in Comet 67P/Churyumov-Gerasimenko Observed by the Alice Far-ultraviolet Spectrograph on Rosetta

    Science.gov (United States)

    Feldman, Paul D.; A'Hearn, Michael F.; Feaga, Lori M.; Bertaux, Jean-Loup; Noonan, John; Parker, Joel Wm.; Schindhelm, Eric; Steffl, Andrew J.; Stern, S. Alan; Weaver, Harold A.

    2016-07-01

    Alice is a far-ultraviolet imaging spectrograph on board Rosetta that, among multiple objectives, is designed to observe emissions from various atomic and molecular species from within the coma of comet 67P/Churyumov-Gerasimenko. The initial observations, made following orbit insertion in 2014 August, showed emissions of atomic hydrogen and oxygen spatially localized close to the nucleus and attributed to photoelectron impact dissociation of H2O vapor. Weaker emissions from atomic carbon were subsequently detected and also attributed to electron impact dissociation, of CO2, the relative H i and C i line intensities reflecting the variation of CO2 to H2O column abundance along the line of sight through the coma. Beginning in 2015 mid-April, Alice sporadically observed a number of outbursts above the sunward limb characterized by sudden increases in the atomic emissions, particularly the semi-forbidden O i λ1356 multiplet, over a period of 10-30 minutes, without a corresponding enhancement in long-wavelength solar reflected light characteristic of dust production. A large increase in the brightness ratio O i λ1356/O i λ1304 suggests O2 as the principal source of the additional gas. These outbursts do not correlate with any of the visible images of outbursts taken with either OSIRIS or the navigation camera. Beginning in 2015 June the nature of the Alice spectrum changed considerably with CO Fourth Positive band emission observed continuously, varying with pointing but otherwise fairly constant in time. However, CO does not appear to be a major driver of any of the observed outbursts.

  9. The impact of H2S emissions on future geothermal power generation - The Geysers region, California

    Science.gov (United States)

    Leibowitz, L. P.

    1977-01-01

    The future potential for geothermal power generation in the Geysers region of California is as much as 10 times the current 502 MW(e) capacity. However, environmental factors such as H2S emissions and institutional considerations may play the primary role in determining the rate and ultimate level of development. In this paper a scenario of future geothermal generation capacity and H2S emissions in the Geysers region is presented. Problem areas associated with H2S emissions, H2S abatement processes, plant operations, and government agency resources are described. The impact of H2S emissions on future development and the views of effected organizations are discussed. Potential actions needed to remove these constraints are summarized.

  10. The impact of H2S emissions on future geothermal power generation - The Geysers region, California

    Science.gov (United States)

    Leibowitz, L. P.

    1977-01-01

    The future potential for geothermal power generation in the Geysers region of California is as much as 10 times the current 502 MW(e) capacity. However, environmental factors such as H2S emissions and institutional considerations may play the primary role in determining the rate and ultimate level of development. In this paper a scenario of future geothermal generation capacity and H2S emissions in the Geysers region is presented. Problem areas associated with H2S emissions, H2S abatement processes, plant operations, and government agency resources are described. The impact of H2S emissions on future development and the views of effected organizations are discussed. Potential actions needed to remove these constraints are summarized.

  11. Pushing the limits: detecting H2 emission from faint bipolar planetary nebulae in the IPHAS sample

    Science.gov (United States)

    Ramos-Larios, G.; Guerrero, M. A.; Sabin, L.; Santamaría, E.

    2017-09-01

    We have obtained deep narrowband images in the near-infrared H2 λ2.122 μm emission line for a sample of 15 faint Isaac Newton Telescope Photometric H α Survey (IPHAS) bipolar planetary nebulae (PNe) to search for molecular material. H2 emission is found in most of them (14 out of 15), mostly associated with rings at their equatorial regions and with their bipolar lobes. These detections add to the high occurrence of H2 emission among bipolar PNe reported in previous works, resulting from the large reservoir of molecular material in these sources and the suitable excitation conditions for H2 emission. The correlation between detailed bipolar morphology and H2 luminosity is also confirmed: bipolar PNe with broad equatorial rings (R-BPNe) have almost no continuum emission, are H2 brighter and have larger H2/Br γ line ratio than bipolar PNe with pinched equatorial waists (W-BPNe). The origin of this dichotomy is unclear. The larger size and age of R-BPNe are consistent with shock excitation of H2, whereas ultraviolet pumping is most likely the excitation mechanism in the smaller and younger W-BPNe, which would explain their lower H2 luminosity. Although both types of bipolar PNe seem to proceed from the same progenitor population, this does not imply that R-BPNe descend from W-BPNe. Otherwise, we note that some of the H2-weak bipolar PNe harbor post-common envelope binary systems and symbiotic stars. Finally, we suggest that the long-living H2 emission from R-BPNe arises from a discrete distribution of compact knots embedded within the ionized gas at the equatorial region.

  12. Modelling the Warm H2 Infrared Emission of the Helix Nebula Cometary Knots

    CERN Document Server

    Aleman, Isabel; Matsuura, Mikako; Gruenwald, Ruth; Kimura, Rafael K

    2011-01-01

    Molecular hydrogen emission is commonly observed in planetary nebulae. Images taken in infrared H2 emission lines show that at least part of the molecular emission is produced inside the ionised region. In the best-studied case, the Helix nebula, the H2 emission is produced inside cometary knots (CKs), comet-shaped structures believed to be clumps of dense neutral gas embedded within the ionised gas. Most of the H2 emission of the CKs seems to be produced in a thin layer between the ionised diffuse gas and the neutral material of the knot, in a mini photodissociation region (PDR). However, PDR models published so far cannot fully explain all the characteristics of the H2 emission of the CKs. In this work, we use the photoionisation code \\textsc{Aangaba} to study the H2 emission of the CKs, particularly that produced in the interface H^+/H^0 of the knot, where a significant fraction of the H2 1-0S(1) emission seems to be produced. Our results show that the production of molecular hydrogen in such a region may ...

  13. Modelling H2 Infrared Emission of the Helix Nebula Cometary Knots

    CERN Document Server

    Aleman, Isabel; Matsuura, Mikako; Gruenwald, Ruth; Kimura, Rafael

    2010-01-01

    In the present work, we use a photoionisation code to study the H2 emission of the Helix nebula (NGC 7293) cometary knots, particularly that produced in the interface H+/H0 of the knot, where a significant fraction of the H2 1-0 S(1) emission seems to be produced. Our results show that the production of molecular hydrogen in such region may explain several characteristics of the observed emission, particularly the high excitation temperature of the H2 infrared lines.

  14. Characteristics of H2S emission from aged refuse after excavation exposure.

    Science.gov (United States)

    Shen, Dong-Sheng; Du, Yao; Fang, Yuan; Hu, Li-Fang; Fang, Cheng-Ran; Long, Yu-Yang

    2015-05-01

    Hydrogen sulfide (H2S(g)) emission from landfills is a widespread problem, especially when aged refuse is excavated. H2S(g) emission from aged refuse exposed to air was investigated and the results showed that large amounts of H2S(g) can be released, especially in the first few hours after excavation, when H2S(g) concentrations in air near refuse could reach 2.00 mg m(-3). Initial exposure to air did not inhibit the emission of H2S(g), as is generally assumed, but actually promoted it. The amounts of H2S(g) emitted in the first 2 d after excavation can be very dangerous, and the risks associated with the emission of H2S(g) could decrease significantly with time. Unlike a large number of sulfide existed under anaerobic conditions, the sulfide in aged municipal solid waste can be oxidized chemically to elemental sulfur (but not sulfate) under aerobic conditions, and its conversion rate was higher than 80%. Only microorganisms can oxidize the reduced sulfur species to sulfate, and the conversion rate could reach about 50%. Using appropriate techniques to enhance these chemical and biological transformations could allow the potential health risks caused by H2S(g) after refuse excavation to be largely avoided. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. The Far Ultraviolet Spectroscopic Explorer Survey of OVI Absorption in the Disk of the Milky Way

    CERN Document Server

    Bowen, D V; Tripp, T M; Sembach, K R; Savage, B D; Moos, H W; Oegerle, W R; Friedman, S D; Gry, C; Kruk, J W; Murphy, E; Sankrit, R; Shull, J M; Sonneborn, G; York, D G

    2007-01-01

    To probe the distribution and physical characteristics of interstellar gas at temperatures T ~ 3e5 K in the disk of the Milky Way, we have used the Far Ultraviolet Spectroscopic Explorer (FUSE) to observe absorption lines of OVI toward 148 early-type stars situated at distances 1 kpc. After subtracting off a mild excess of OVI arising from the Local Bubble, combining our new results with earlier surveys of OVI, and eliminating stars that show conspicuous localized X-ray emission, we find an average OVI mid-plane density n_0 = 1.3e-8 cm^-3. The density decreases away from the plane of the Galaxy in a way that is consistent with an exponential scale height of 3.2 kpc at negative latitudes or 4.6 kpc at positive latitudes. Average volume densities of OVI along different sight lines exhibit a dispersion of about 0.26 dex, irrespective of the distances to the target stars. This indicates that OVI does not arise in randomly situated clouds of a fixed size and density, but instead is distributed in regions that have...

  16. Far-ultraviolet Observations of the Taurus-Perseus-Auriga Complex

    CERN Document Server

    Lim, Tae-Ho; Seon, Kwang-Il

    2013-01-01

    We have constructed a far-ultraviolet (FUV) continuum map of the Taurus-Auriga-Perseus complex, one of the largest local associations of dark clouds, by merging the two data sets of GALEX and FIMS, which made observations at similar wavelengths. The FUV intensity varies significantly across the whole region, but the diffuse FUV continuum is dominated by dust scattering of stellar photons. A diffuse FUV background of $\\sim$1000 CU is observed, part of which may be attributable to the scattered photons of foreground FUV light, located in front of the thick clouds. The fluorescent emission of molecular hydrogen constitutes $\\sim$10% of the total FUV intensity throughout the region, generally proportional to the local continuum level. We have developed a Monte Carlo radiative transfer code and applied it to the present clouds complex to obtain the optical properties of dust grains and the geometrical structures of the clouds. The albedo and the phase function asymmetry factor were estimated to be $0.42^{+0.05}_{-...

  17. A Search for H2CO 6cm Emission toward Young Stellar Objects III: VLA Observations

    CERN Document Server

    Araya, E D; Goss, W M; Linz, H; Kurtz, S; Olmi, L

    2008-01-01

    We report the results of our third survey for formaldehyde (H2CO) 6cm maser emission in the Galaxy. Using the Very Large Array, we detected two new H2CO maser sources (G23.01-0.41 and G25.83-0.18), thus increasing the sample of known H2CO maser regions in the Galaxy to seven. We review the characteristics of the G23.01-0.41 and G25.83-0.18 star forming regions. The H2CO masers in G23.01-0.41 and G25.83-0.18 share several properties with the other known H2CO masers, in particular, emission from rich maser environments and close proximity to very young massive stellar objects.

  18. H2 infrared line emission from the ionized region of planetary nebulae

    CERN Document Server

    Aleman, Isabel

    2010-01-01

    The analysis and interpretation of the H2 line emission from planetary nebulae have been done in the literature assuming that the molecule survives only in regions where the hydrogen is neutral, as in photodissociation, neutral clumps or shocked regions. However, there is strong observational and theoretical evidence that at least part of the H2 emission is produced inside the ionized region of such objects. The aim of the present work is to calculate and analyze the infrared line emission of H2 produced inside the ionized region of planetary nebulae using a one-dimensional photoionization code. The photoionization code Aangaba was improved in order to calculate the statistical population of the H2 energy levels and the intensity of the H2 infrared emission lines in physical conditions typical of planetary nebulae. A grid of models was obtained and the results are analyzed and compared with the observational data. We show that the contribution of the ionized region to the H2 line emission can be important, pa...

  19. Submillimeter H$_2$O and H$_2$O$^+$ emission in lensed ultra- and hyper-luminous infrared galaxies at z ~ 2-4

    CERN Document Server

    Yang, C; Beelen, A; González-Alfonso, E; Neri, R; Gao, Y; van der Werf, P; Weiß, A; Gavazzi, R; Falstad, N; Baker, A J; Bussmann, R S; Cooray, A; Cox, P; Dannerbauer, H; Dye, S; Guélin, M; Ivison, R; Krips, M; Lehnert, M; Michałowski, M J; Riechers, D A; Spaans, M; Valiante, E

    2016-01-01

    (abridged) We report rest-frame submillimeter H2O emission line observations of 11 HyLIRGs/ULIRGs at z~2-4 selected among the brightest lensed galaxies discovered in the Herschel-ATLAS. Using the IRAM NOEMA, we have detected 14 new H2O emission lines. The apparent luminosities of the H2O emission lines are $\\mu L_{\\rm{H_2O}} \\sim 6-21 \\times 10^8 L_\\odot$, with velocity-integrated line fluxes ranging from 4-15 Jy km s$^{-1}$. We have also observed CO emission lines using EMIR on the IRAM 30m telescope in seven sources. The velocity widths for CO and H2O lines are found to be similar. With almost comparable integrated flux densities to those of the high-J CO line, H2O is found to be among the strongest molecular emitters in high-z Hy/ULIRGs. We also confirm our previously found correlation between luminosity of H2O ($L_{\\rm{H_2O}}$) and infrared ($L_{\\rm{IR}}$) that $L_{\\rm{H_2O}} \\sim L_{\\rm{IR}}^{1.1-1.2}$, with our new detections. This correlation could be explained by a dominant role of far-infrared (FIR) ...

  20. A far-ultraviolet flare on a Pleiades G dwarf

    Science.gov (United States)

    Ayres, T. R.; Stauffer, J. R.; Simon, Theodore; Stern, R. A.; Antiochos, S. K.; Basri, G. S.; Bookbinder, J. A.; Brown, A.; Doschek, G. A.; Linsky, J. L.

    1994-01-01

    The Hubble Space Telescope/Faint Object Spectrograph (HST/FOS) recorded a remarkable transient brightening in the C IV lambda lambda 1548,50 emissions of the rapidly rotating Pleiades G dwarf H II 314. On the one hand the 'flare' might be a rare event luckily observed; on the other hand it might be a bellwether of the coronal heating in very young solar-mass stars. If the latter, flaring provides a natural spin-down mechanism through associated sporadic magnetospheric mass loss.

  1. Spectroscopic Measurements of the Far-Ultraviolet Dust Attenuation Curve at z ˜ 3

    Science.gov (United States)

    Reddy, Naveen A.; Steidel, Charles C.; Pettini, Max; Bogosavljević, Milan

    2016-09-01

    We present the first spectroscopic measurements of the shape of the far-ultraviolet (far-UV; λ =950{--}1500 Å) dust attenuation curve at high redshift (z˜ 3). Our analysis employs rest-frame UV spectra of 933 galaxies at z˜ 3, 121 of which have very deep spectroscopic observations (≳ 7 hr) at λ =850{--}1300 \\mathring{{A}} , with the Low Resolution Imaging Spectrograph on the Keck Telescope. By using an iterative approach in which we calculate the ratios of composite spectra in different bins of continuum color excess, E(B-V), we derive a dust curve that implies a lower attenuation in the far-UV for a given E(B-V) than those obtained with standard attenuation curves. We demonstrate that the UV composite spectra of z˜ 3 galaxies can be modeled well by assuming our new attenuation curve, a high covering fraction of H i, and absorption from the Lyman-Werner bands of {{{H}}}2 with a small (≲ 20 % ) covering fraction. The low covering fraction of {{{H}}}2 relative to that of the {{H}} {{I}} and dust suggests that most of the dust in the ISM of typical galaxies at z˜ 3 is unrelated to the catalysis of {{{H}}}2, and is associated with other phases of the ISM (i.e., the ionized and neutral gas). The far-UV dust curve implies a factor of ≈ 2 lower dust attenuation of Lyman continuum (ionizing) photons relative to those inferred from the most commonly assumed attenuation curves for L* galaxies at z˜ 3. Our results may be utilized to assess the degree to which ionizing photons are attenuated in H ii regions or, more generally, in the ionized or low column density (N({{H}} {{I}})≲ {10}17.2 cm-2) neutral ISM of high-redshift galaxies. Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.

  2. Dense Molecular Gas and H2O Maser Emission in Galaxies

    Indian Academy of Sciences (India)

    F. Huang; J. S. Zhang; R. M. Li; H. K. Li

    2014-09-01

    Extragalactic H2O masers have been found in dense gas circumstance in off-nuclear star formation regions or within parsecs of Active Galactic Nuclei (AGNs). HCN molecular (one of the best dense gas tracers) Emission has been detected in more than 60 galaxies. For HCN-detected galaxy sample, the relation of maser and gas emission was investigated here to identify physical observable properties that differentiate maser and non-maser galaxies. Our analysis results show that there is no significant difference on the infrared and gas emission between maser galaxies and galaxies without maser detection. For maser host HCN-galaxies, maser luminosity is found to be correlated to CO luminosity (a proxy of the total molecular gas) and HCN luminosity, i.e., kilomasers (H2O < 10⊙) with low maser luminosity having low gas emission luminosity, with respect to megamasers (H2O > 10⊙). For normalized maser and HCN luminosity (for removing distance effect), the correlation is still apparent. However, for normalized maser and CO luminosity, the correlation disappeared completely. Thus one proposition that the amount of dense molecular gas should be a good tracer of H2O maser emission can be made.

  3. Spatially resolved H2 emission from the disk around T Tau N

    CERN Document Server

    Gustafsson, M; Herbst, T M; Kasper, M

    2008-01-01

    We report the detection of quiescent H2 emission in a spatially resolved ring-like structure within 100 AU of T Tau N. We present evidence to show that the emission most likely arises from shocks in the atmosphere of a nearly face-on disk around T Tau N. Using high spatial resolution 3D spectroscopic K-band data, we trace the spatial distribution of several H2 NIR rovibrational lines in the vicinity of T Tau N. We detect weak H2 emission from the v=1-0 S(0), S(1), Q(1) lines and the v=2-1 S(1) line in a ring-like structure around T Tau N between 0.1'' (~15 AU) and 0.7'' (~100AU) from the star. The v=1-0 S(0) and v=2-1 S(1) lines are detected only in the outer parts of the ring structure. Closer to the star, the strong continuum limits our sensitivity to these lines. The total flux of the v=1-0 S(1) line is 1.8 *10^{-14} ergs s^{-1}cm^{-2}, similar to previous measurements of H2 in circumstellar disks. The velocity of the H2 emitting gas around T Tau N is consistent with the rest velocity of the star, and the ...

  4. Stratospheric cooling and polar ozone loss due to H2 emissions of a global hydrogen economy

    Science.gov (United States)

    Feck, T.; Grooß, J.-U.; Riese, M.; Vogel, B.

    2009-04-01

    "Green" hydrogen is seen as a major element of the future energy supply to reduce greenhouse gas emissions substantially. However, due to the possible interactions of hydrogen (H2) with other atmospheric constituents there is a need to analyse the implications of additional atmospheric H2 that could result from hydrogen leakage of a global hydrogen infrastructure. Emissions of molecular H2 can occur along the whole hydrogen process chain which increase the tropospheric H2 burden. Across the tropical tropopause H2 reaches the stratosphere where it is oxidised and forms water vapour (H2O). This causes increased IR-emissions into space and hence a cooling of the stratosphere. Both effects, the increase of stratospheric H2O and the cooling, enhances the potential of chlorine activation on liquid sulfate aerosol and polar stratospheric clouds (PSCs), which increase polar ozone destruction. Hence a global hydrogen economy could provoke polar ozone loss and could lead to a substantial delay of the current projected recovery of the stratospheric ozone layer. Our investigations show that even if 90% of the current global fossil primary energy input could be replaced by hydrogen and approximately 9.5% of the product gas would leak to the atmosphere, the ozone loss would be increased between 15 to 26 Dobson Units (DU) if the stratospheric CFC loading would retain unchanged. A consistency check of the used approximation methods with the Chemical Lagrangian Model of the Stratosphere (CLaMS) shows that this additional ozone loss can probably be treated as an upper limit. Towards more realistic future H2 leakage rate assumptions (< 3%) the additional ozone loss would be rather small (? 10 DU). However, in all cases the full damage would only occur if stratospheric CFC-levels would retain unchanged. Due to the CFC-prohibition as a result of the Montreal Protocol the forecasts suggest a decline of the stratospheric CFC loading about 50% until 2050. In this case our calculations

  5. Photoionization Models of the H_2 Emission of the Narrow Line Region of AGNs

    Science.gov (United States)

    Aleman, I.; Gruenwald, R.

    2011-05-01

    The excitation mechanism of the narrow line region (NLR) of AGNs is still an open question. Excitation by UV radiation from O and B stars, x-rays from the central black hole, shock from supernovae or jets, or a combination of these mechanisms have been suggested. In the present work, we use photoionization models to study the excitation mechanisms of the H_2 infrared emission lines in the NLR. In the literature, analyzes of the H_2 emission have been done assuming that the molecules is present only in neutral regions (photodissociation regions, x-ray-dominated regions, or shocks; Veilleux et al. 1997, Krabbe et al. 2000, Rigopoulou et al. 2002, Rodriguez-Ardila et al. 2004, 2005, and Davies et al. 2005). However, they are not conclusive. In previous work (Aleman & Gruenwald 2004, 2011), we show that the H_2 emission from the ionized region of PNe can be significant for planetary nebulae (PNe) with hot central stars (T⋆ > 150000 K). Such stars produce copious amounts of high energy photons, which create an extended partially ionized region that favors the H_2 survival. The conditions in the NLR are similar to those in PNe with hot central stars, so we can expect that the H_2 emission might also be important. We obtain and analyze a grid of photoionization models for different NRL parameters. We study the resulting H_2 density and emission, as well as, the formation, destruction, excitation, and de-excitation mechanisms. The higher values observed for the H_2 1-0 S(1)/Brγ ratio cannot be reproduced by our models. The calculated ratios are between 10^-8 and 10^-1, while the observational ration can be as high as 10. The calculated ratio is strongly anti-correlated with the ionization parameter (U) and only models with U<10-3 result in ratios inside the observational range. We show that the NLR is an environment more hostile to the H_2 molecule than the ionized region of PNe. Another interesting result of our calculations is that the H_2 formation on grain surfaces

  6. On Secondary Electron Emission from Solid H2 and D2

    DEFF Research Database (Denmark)

    Schou, Jørgen; Sørensen, H.

    1978-01-01

    The emission of secondary electrons from solid hydrogen (H2 , D2, T2) is often considered to be of importance for the interaction between a fusion plasma and pellets of solid hydrogens. A set-up was therefore built for studies of interactions between energetic particles and solid hydrogens. Studies...

  7. Control of H2S emissions using an ozone oxidation process: Preliminary results

    Science.gov (United States)

    Defaveri, D.; Ferrando, B.; Ferraiolo, G.

    1986-01-01

    The problem of eliminating industrial emission odors does not have a simple solution, and consequently has not been researched extensively. Therefore, an experimental research program regarding oxidation of H2S through ozone was undertaken to verify the applicable limits of the procedure and, in addition, was designed to supply a useful analytical means of rationalizing the design of reactors employed in the sector.

  8. On Secondary Electron Emission from Solid H2 and D2

    DEFF Research Database (Denmark)

    Schou, Jørgen; Sørensen, H.

    1978-01-01

    The emission of secondary electrons from solid hydrogen (H2 , D2, T2) is often considered to be of importance for the interaction between a fusion plasma and pellets of solid hydrogens. A set-up was therefore built for studies of interactions between energetic particles and solid hydrogens. Studi...

  9. Mapping the Circumstellar Environment of T Tauri with Fluorescent H_2 Emission

    CERN Document Server

    Walter, F M; Brown, A; Ardila, D R; Gahm, G F; Johns-Krull, C M; Lissauer, J J; Simon, M; Valenti, J A; Walter, Frederick M.; Herczeg, Gregory; Brown, Alexander; Ardila, David R.; Gahm, Goesta F.; Johns-Krull, Christopher M.; Lissauer, Jack J.; Simon, Michal; Valenti, Jeff A.

    2003-01-01

    We have obtained three long-slit, far UV spectra of the pre-main sequence system T Tauri. These HST/STIS spectra show a strong and variable on-source spectrum composed of both fluoresced H_2 and stellar chromospheric lines. Extended H_2 emission is seen up to 10" from the T Tau system. The on-source and extended H_2 are both pumped by H I Lyman alpha. The on-source H_2 is pumped by the red wing of a broad, self-absorbed Ly-alpha line, while the progressions seen in the extended gas are pumped from near line center. This suggests that the extended H_2 is pumped locally, and not by the stellar Ly-alpha line. The H_2 to the north and west coincides with the evacuated cavity bounded by the optical reflection nebulosity; to the south the extended H_2 coincides with the HH 255 outflow from the embedded infrared companion T Tau S. The spatial profile of the extended gas shows a prominent dip coincident with the position of T Tau S. This may be absorption by a disk associated with T Tau S. There is no evidence for ab...

  10. [Dynamics of H2S and COS emission fluxes from Calamagrostis different calamagrostis angustifolia wetlands in Sanjiang Plain].

    Science.gov (United States)

    Li, Xin-Hua; Liu, Jing-Shuang; Yang, Ji-Song

    2006-11-01

    Using the static chamber and chromatogram method, H2S and COS emission fluxes from the mash meadow Calamagrostis angustifolia in Sanjiang Plain were measured during growth season(5-9 month), the results showed that the seasonal and diurnal variations of H2S and COS emission fluxes were obvious, the mean H2S and COS emission fluxes from the mash meadow Calamagrostis angustifolia were 0.34 microg x (m2 x h)(-1) and - 0.29 microg x (m2 x h)(-1) respectively, the Calamagrostis angustifolia wetlands were the sources for H2S and the sinks for COS during the growth time. The emission fluxes of H2S and COS were affected by the Calamagrostis angustifolia growth, and there were H2S emission peak and COS absorbed peak during the bloom growth time, meanwhile the integrative correlation of H2S and COS emission fluxes were observed.

  11. Submillimeter H2O and H2O+emission in lensed ultra- and hyper-luminous infrared galaxies at z 2-4

    Science.gov (United States)

    Yang, C.; Omont, A.; Beelen, A.; González-Alfonso, E.; Neri, R.; Gao, Y.; van der Werf, P.; Weiß, A.; Gavazzi, R.; Falstad, N.; Baker, A. J.; Bussmann, R. S.; Cooray, A.; Cox, P.; Dannerbauer, H.; Dye, S.; Guélin, M.; Ivison, R.; Krips, M.; Lehnert, M.; Michałowski, M. J.; Riechers, D. A.; Spaans, M.; Valiante, E.

    2016-11-01

    We report rest-frame submillimeter H2O emission line observations of 11 ultra- or hyper-luminous infrared galaxies (ULIRGs or HyLIRGs) at z 2-4 selected among the brightest lensed galaxies discovered in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). Using the IRAM NOrthern Extended Millimeter Array (NOEMA), we have detected 14 new H2O emission lines. These include five 321-312ortho-H2O lines (Eup/k = 305 K) and nine J = 2 para-H2O lines, either 202-111(Eup/k = 101 K) or 211-202(Eup/k = 137 K). The apparent luminosities of the H2O emission lines are μLH2O 6-21 × 108 L⊙ (3 integrated line fluxes ranging from 4-15 Jy km s-1. We have also observed CO emission lines using EMIR on the IRAM 30 m telescope in seven sources (most of those have not yet had their CO emission lines observed). The velocity widths for CO and H2O lines are found to be similar, generally within 1σ errors in the same source. With almost comparable integrated flux densities to those of the high-J CO line (ratios range from 0.4 to 1.1), H2O is found to be among the strongest molecular emitters in high-redshift Hy/ULIRGs. We also confirm our previously found correlation between luminosity of H2O (LH2O) and infrared (LIR) that LH2O LIR1.1-1.2, with ournew detections. This correlation could be explained by a dominant role of far-infrared pumping in the H2O excitation. Modelling reveals that the far-infrared radiation fields have warm dust temperature Twarm 45-75 K, H2O column density per unit velocity interval NH2O /ΔV ≳ 0.3 × 1015 cm-2 km-1 s and 100 μm continuum opacity τ100> 1 (optically thick), indicating that H2O is likely to trace highly obscured warm dense gas. However, further observations of J ≥ 4 H2O lines are needed to better constrain the continuum optical depth and other physical conditions of the molecular gas and dust. We have also detected H2O+ emission in three sources. A tight correlation between LH2O and LH2O+ has been found in galaxies from low to high

  12. Progesterone increases skeletal muscle mitochondrial H2O2 emission in nonmenopausal women.

    Science.gov (United States)

    Kane, Daniel A; Lin, Chien-Te; Anderson, Ethan J; Kwak, Hyo-Bum; Cox, Julie H; Brophy, Patricia M; Hickner, Robert C; Neufer, P Darrell; Cortright, Ronald N

    2011-03-01

    The luteal phase of the female menstrual cycle is associated with both 1) elevated serum progesterone (P4) and estradiol (E2), and 2) reduced insulin sensitivity. Recently, we demonstrated a link between skeletal muscle mitochondrial H(2)O(2) emission (mE(H2O2)) and insulin resistance. To determine whether serum levels of P4 and/or E(2) are related to mitochondrial function, mE(H2O2) and respiratory O(2) flux (Jo(2)) were measured in permeabilized myofibers from insulin-sensitive (IS, n = 24) and -resistant (IR, n = 8) nonmenopausal women (IR = HOMA-IR > 3.6). Succinate-supported mE(H2O2) was more than 50% greater in the IR vs. IS women (P < 0.05). Interestingly, serum P4 correlated positively with succinate-supported mE(H2O2) (r = 0. 53, P < 0.01). To determine whether P4 or E2 directly affect mitochondrial function, saponin-permeabilized vastus lateralis myofibers biopsied from five nonmenopausal women in the early follicular phase were incubated in P4 (60 nM), E2 (1.4 nM), or both. P4 alone inhibited state 3 Jo(2), supported by multisubstrate combination (P < 0.01). However, E2 alone or in combination with P4 had no effect on Jo(2). In contrast, during state 4 respiration, supported by succinate and glycerophosphate, mE(H2O2) was increased with P4 alone or in combination with E2 (P < 0.01). The results suggest that 1) P4 increases mE(H2O2) with or without E2; 2) P4 alone inhibits Jo(2) but not when E2 is present; and 3) P4 is related to the mE(H2O2) previously linked to skeletal muscle insulin resistance.

  13. Enhanced Warm H2 Emission in the Compact Group Mid-Infrared "Green Valley"

    CERN Document Server

    Cluver, M E; Ogle, P; Jarrett, T H; Rasmussen, J; Lisenfeld, U; Guillard, P; Verdes-Montenegro, L; Antonucci, R; Bitsakis, T; Charmandaris, V; Boulanger, F; Egami, E; Xu, C K; Yun, M S

    2013-01-01

    We present results from a Spitzer, mid-infrared spectroscopy study of a sample of 74 galaxies located in 23 Hickson Compact Groups, chosen to be at a dynamically-active stage of HI depletion. We find evidence for enhanced warm H2 emission (i.e. above that associated with UV excitation in star-forming regions) in 14 galaxies (~20%), with 8 galaxies having extreme values of L(H2 S(0)-S(3))/L(7.7micron PAH), in excess of 0.07. Such emission has been seen previously in the compact group HCG 92 (Stephan's Quintet), and was shown to be associated with the dissipation of mechanical energy associated with a large-scale shock caused when one group member collided, at high velocity, with tidal debris in the intragroup medium. Similarly, shock excitation or turbulent heating is likely responsible for the enhanced H2 emission in the compact group galaxies, since other sources of heating (UV or X-ray excitation from star formation or AGN) are insufficient to account for the observed emission. The group galaxies fall predo...

  14. O$_2$ Emission Toward Orion H$_2$ Peak 1 and the Role of FUV-Illuminated C-Shocks

    CERN Document Server

    Melnick, Gary J

    2015-01-01

    Molecular oxygen, O_2, has been the target of ground-based and space-borne searches for decades. Of the thousands of lines of sight surveyed, only those toward Rho Oph and Orion H_2 Peak 1 have yielded detections of any statistical significance. The detection of the O_2 N_J =3_3 -1_2 and 5_4 - 3_4 lines at 487.249 GHz and 773.840 GHz, respectively, toward Rho Ophiuchus has been attributed to a short-lived peak in the time-dependent, cold-cloud O_2 abundance, while the detection of the O_2 N_J =3_3 - 1_2, 5_4 - 3_4 lines, plus the 7_6 - 5_6 line at 1120.715 GHz, toward Orion has been ascribed to time-dependent preshock physical and chemical evolution and low-velocity (12 km/s) non-dissociative C-type shocks, both of which are fully shielded from far-ultraviolet (FUV) radiation, plus a postshock region that is exposed to a FUV field. We report a re-interpretation of the Orion O_2 detection based on new C-type shock models that fully incorporate the significant effects the presence of even a weak FUV field can h...

  15. Fluorescent H_2 Emission Lines from the Reflection Nebula NGC 7023 Observed with IGRINS

    CERN Document Server

    Le, Huynh Anh N; Kaplan, Kyle F; Mace, Gregory N; Lee, Sungho; Pavel, Michael D; Jeong, Ueejeong; Oh, Heeyoung; Lee, Hye-In; Chun, Moo-Young; Yuk, In-Soo; Pyo, Tae-Soo; Hwang, Narae; Kim, Kang-Min; Park, Chan; Oh, Jae Sok; Yu, Young S; Park, Byeong-Gon; Minh, Young Chol; Jaffe, Daniel T

    2016-01-01

    We have analyzed the temperature, velocity and density of H_2 gas in NGC 7023 with a high-resolution near-infrared spectrum of the northwestern filament of the reflection nebula. By observing NGC 7023 in the H and K bands at R ~ 45,000 with the Immersion GRating INfrared Spectrograph (IGRINS), we detected 70 H_2 emission lines within the 1" x 15" slit. The diagnostic ratios of 2-1 S(1)/1-0 S(1) are 0.39-0.54. In addition, the estimated ortho-to-para ratios (OPR) are 1.57-1.62, indicating that the H_2 transitions in the observed regions are mostly from UV fluorescence. Gradients in the temperature, velocity, and OPR of the observed areas imply motion of the photodissociation region (PDR) relative to the molecular cloud. In addition, we derive the column density of H_2 from the observed emission lines and compare these results with PDR models in the literature covering a range of densities and incident UV field intensities. The notable difference between PDR model predictions and the observed data, in high rota...

  16. Secondary electron emission from solid HD and a solid H2-D2 mixture

    DEFF Research Database (Denmark)

    Sørensen, H.; Børgesen, P.; Hao-Ming, Chen

    1983-01-01

    Secondary electron emission from solid HD and a solid 0.6 H2 + 0.4 D2 mixture has been studied for electron and hydrogen ion bombardment at primary energies from 0.5 to 3 keV and 2 to 10 keV/amu, respectively. The yield for solid HD is well explained by a simple stoichiometric model of the low......-energy stopping power for the internal secondaries. The secondary electron yield from the mixture is somewhat larger than the expected value, but lies between the values for pure solid H2 and D2. The secondary electron emission coefficient for solid tritium may be determined from a linear extrapolation...... of the present data....

  17. Diagnostics of irradiated gas in galaxy nuclei. I: A Far-ultraviolet and X-ray dominated region code

    CERN Document Server

    Meijerink, R; Meijerink, Rowin; Spaans, Marco

    2005-01-01

    We present a far-ultraviolet (PDR) and an X-ray dominated region (XDR) code. We include and discuss thermal and chemical processes that pertain to irradiated gas. An elaborate chemical network is used and a careful treatment of PAHs and H2 formation, destruction and excitation is included. For both codes we calculate four depth-dependent models for different densities and radiation fields, relevant to conditions in starburst galaxies and active galactic nuclei. A detailed comparison between PDR and XDR physics is made for total gas column densities between ~10^20 and ~10^25 cm^-2. We show cumulative line intensities for a number of fine-structure lines (e.g., [CII], [OI], [CI], [SiII], [FeII]), as well as cumulative column densities and column density ratios for a number of species (e.g., CO/H2, CO/C, HCO+/HCN, HNC/HCN). The comparison between the results for the PDRs and XDRs shows that column density ratios are almost constant up to N_H=10^22 cm^-2 for XDRs, unlike those in PDRs. For example, CO/C in PDRs c...

  18. Discovery and imaging of a Galactic cirrus cloud with the far ultraviolet space telescope

    Science.gov (United States)

    Haikala, Lauri K.; Mattila, Kalevi; Bowyer, Stuart; Sasseen, Timothy P.; Lampton, Michael; Knude, Jens

    1995-01-01

    We present new far-ultraviolet (1400-1800 A) data concerning a Galactic cirrus cloud G251.2+73.3 near the north Galactic pole obtained with the space-borne imaging telescope FAUST (Far Ultraviolet Space Telescope). We obtain a good correlation between the far-ultraviolet (FUV) and IRAS 100 micrometers surface brightnesses, their relation being I(sub FUV) = (128 +/- 3) I(sub 100 micrometers) - (264 +/- 9), where the I(sub FUV) flux is given in units of photon/s/sq cm/A/sr and I(sub 100 micrometers) in MJy/sr. Using uvbyH-beta photometry, we get a distance of 120 pc and a visual extinction in the center of the cloud of 0.39 mag corresponding to an extinction of 1.0 mag at 1565 A. We have performed a multiple scattering calculation for the scattered light using the Monte Carlo method. These calculations provide restrictions on the FUV scattering properties of the interstellar dust.

  19. A search for H2 emission in bipolar nebulae and regions of interstellar shock

    Science.gov (United States)

    Phillips, J. P.; White, G. J.; Harten, R.

    1985-04-01

    A H2 emission survey of five bipolar outflow sources (NGC 1333, M2-9, As 353, S106, V645 Cyg), and one region of shock interaction between an H II region and molecular cloud (NGC 281) are presented. Two of the sources (M2-9, NGC 1333) were detected in the v = 1-0S(1), and Q-branch transitions of H2. A detailed analysis and modeling for these cases is provided. The probable mass of shocked H2 is shown to range between 1.4 x 10 to the -6th and 4.2 x 10 to the -8th solar masses for M2-9, and about 0.00025 and 0.00001910 solar masses in the case of NGC 1333, although the latter values may require increasing by a factor of a few when due allowance is made for extinction. A detailed analysis for the core of M2-9 indicates that the ionized zone is extremely compact, and that the Brackett line measures support other evidence in suggesting a high core extinction, large emission measure, and a projected angular radius of about 0.04 arcsec. Similarly, it is apparent from the H2S(1) line strength that the core expansion velocity must be low and less than about 1 km/s (a constraint which is also required on dynamical grounds). Finally, CO J = 3-2 observations of the source failed to detect emission above a 2-sigma limit of about 0.4 K, and this is shown to imply a probable expansion timescale of less than about 2000 yr.

  20. How well does CO emission measure the H2 mass of MCs?

    Science.gov (United States)

    Szűcs, László; Glover, Simon C. O.; Klessen, Ralf S.

    2016-07-01

    We present numerical simulations of molecular clouds (MCs) with self-consistent CO gas-phase and isotope chemistry in various environments. The simulations are post-processed with a line radiative transfer code to obtain 12CO and 13CO emission maps for the J = 1 → 0 rotational transition. The emission maps are analysed with commonly used observational methods, i.e. the 13CO column density measurement, the virial mass estimate and the so-called XCO (also CO-to-H2) conversion factor, and then the inferred quantities (i.e. mass and column density) are compared to the physical values. We generally find that most methods examined here recover the CO-emitting H2 gas mass of MCs within a factor of 2 uncertainty if the metallicity is not too low. The exception is the 13CO column density method. It is affected by chemical and optical depth issues, and it measures both the true H2 column density distribution and the molecular mass poorly. The virial mass estimate seems to work the best in the considered metallicity and radiation field strength range, even when the overall virial parameter of the cloud is above the equilibrium value. This is explained by a systematically lower virial parameter (i.e. closer to equilibrium) in the CO-emitting regions; in CO emission, clouds might seem (sub-)virial, even when, in fact, they are expanding or being dispersed. A single CO-to-H2 conversion factor appears to be a robust choice over relatively wide ranges of cloud conditions, unless the metallicity is low. The methods which try to take the metallicity dependence of the conversion factor into account tend to systematically overestimate the true cloud masses.

  1. A Search for Submillimeter H2O Masers in Active Galaxies: The Detection of 321 GHZ H2O Maser Emission in NGC 4945

    Science.gov (United States)

    Hagiwara, Yoshiaki; Horiuchi, Shinji; Doi, Akihiro; Miyoshi, Makoto; Edwards, Philip G.

    2016-08-01

    We present further results of a search for extragalactic submillimeter H2O masers using the Atacama Large Millimeter/submillimeter Array (ALMA). The detection of a 321 GHz H2O maser in the nearby type 2 Seyfert galaxy, the Circinus galaxy, has previously been reported, and here the spectral analysis of four other galaxies is described. We have discovered H2O maser emission at 321 GHz toward the center of NGC 4945, a nearby type 2 Seyfert. The maser emission shows Doppler-shifted velocity features with velocity ranges similar to those of the previously reported 22 GHz H2O masers however, the non-contemporaneous observations also show differences in velocity offsets. The subparsec-scale distribution of the 22 GHz H2O masers revealed by earlier very long baseline interferometry observations suggests that the submillimeter masers could arise in an edge-on rotating disk. The maser features remain unresolved by the synthesized beam of ˜0.″54 (˜30 pc) and are located toward the 321 GHz continuum peak within errors. A marginally detected (3σ) high-velocity feature is redshifted by 579 km {{{s}}}-1 with respect to the systemic velocity of the galaxy. Assuming that this feature is real and arises from a Keplerian rotating disk in this galaxy, it is located at a radius of ˜0.020 pc (˜1.5 × 105 Schwarzschild radii), which would enable molecular material closer to the central engine to be probed than the 22 GHz H2O masers. This detection confirms that submillimeter H2O masers are a potential tracer of the circumnuclear regions of active galaxies, which will benefit from higher angular resolution studies with ALMA.

  2. Hydrogen sulfide (H2S) emission control by aerobic sulfate reduction in landfill

    Science.gov (United States)

    Long, Yuyang; Fang, Yuan; Shen, Dongsheng; Feng, Huajun; Chen, Ting

    2016-12-01

    H2S emissions from landfill sites resulting from sulfate reduction has become a serious human health and ecological safety issue. This study investigated H2S emission behavior and sulfate metabolism occurring in simulated landfills under different operating conditions. Under aerobic conditions, great attenuation of the original sulfate content (from around 6000 mg kg‑1 dropped to below 800 mg kg‑1) with corresponding accumulation of sulfides and elemental sulfur were observed, indicating that sulfate reduction processes were intense under such conditions. Analysis of the bacterial community in these landfills showed great abundance (1.10%) and diversity of sulfur reducing types, confirming their active involvement in this process. In particular, the total abundance of sulfate-reducing bacteria increased nearly 30 times under aerobic conditions, leading to the transformation of sulfate to sulfide and other reduced sulfur species. Although exposure to air promoted the accumulation of sulfide, it did not lead to an increase in H2S release in these landfills.

  3. On the Possibility of Observing H2 Emission from Primordial Molecular Cloud Kernels

    CERN Document Server

    Kamaya, H; Kamaya, Hideyuki; Silk, Joseph

    2002-01-01

    We study the prospects for observing H$_2$ emission during the assembly of primordial molecular cloud kernels. The primordial molecular cloud cores, which resemble those at the present epoch, can emerge around $1+z=20$ according to recent numerical simulations. The kernels form inside the cores, and the first stars will appear inside the kernels. A kernel typically contracts to form one of the first generation stars with an accretion rate that is as large as $\\sim 0.01 M_\\odot$ year$^{-1}$. This occurs due to the primordial abundances that result in a kernel temperature of order 1000K, and the collapsing kernel emits H$_2$ line radiation at a rate $\\sim 10^{35}$ erg sec$^{-1}$. Principally $J=5-3$ (v=0) rotational emission of H$_2$ is expected. At redshift $1+z=20$, the expected flux is $\\sim 0.01~\\mu$Jy for a single kernel. While an individual object is not observable by any facilities available in the near future, the expected assembly of primordial star clusters on sub-galactic scales can result in fluxes ...

  4. How well does CO emission measure the H$_2$ mass of MCs?

    CERN Document Server

    Szűcs, László; Klessen, Ralf S

    2016-01-01

    We present numerical simulations of molecular clouds (MCs) with self-consistent CO gas-phase and isotope chemistry in various environments. The simulations are post-processed with a line radiative transfer code to obtain $^{12}$CO and $^{13}$CO emission maps for the $J=1\\rightarrow0$ rotational transition. The emission maps are analysed with commonly used observational methods, i.e. the $^{13}$CO column density measurement, the virial mass estimate and the so-called $X_{\\textrm{CO}}$ (also CO-to-H$_2$) conversion factor, and then the inferred quantities (i.e. mass and column density) are compared to the physical values. We generally find that most methods examined here recover the CO-emitting H$_{2}$ gas mass of MCs within a factor of two uncertainty if the metallicity is not too low. The exception is the $^{13}$CO column density method. It is affected by chemical and optical depth issues, and it measures both the true H$_{2}$ column density distribution and the molecular mass poorly. The virial mass estimate...

  5. Study of effect of H2 addition on the production of fluorocarbon radicals in H2/C4F8 inductively coupled plasma via optical emission spectroscopy actinometry

    Institute of Scientific and Technical Information of China (English)

    Huang Song; Xin Yu; Ning Zhao-Yuan

    2005-01-01

    C4F8 plasma with the addition of H2 is generated by the inductively coupled plasma (ICP) method. The relative densities of CF, CF2, H and F radicals are determined by actinometric optical emission spectroscopy (AOES) as a function of the gas flow rate ratio R=H2/(H2+C4F8) at a pressure of 0.8 Pa and an input r.f. power of 400W, while that of HF is measured by quadrupole mass spectrometry (QMS). The results show that plasma activity increases firstly and then decreases with increasing R. As the gas flow rate ratio R changes from 0 to 0.625, relative densities of both CF and CF2 decrease, and the relative [CF] has a similar tendency as the calculated [CF], indicating that CF radicals are generated mainly by the electron impact dissociation of CF2 radicals. Production of HF is also discussed.

  6. The 1600 Å Emission Bump in Protoplanetary Disks: A Spectral Signature of H2O Dissociation

    Science.gov (United States)

    France, Kevin; Roueff, Evelyne; Abgrall, Hervé

    2017-08-01

    The FUV continuum spectrum of many accreting pre-main sequence stars, Classical T Tauri Stars (CTTSs), does not continue smoothly from the well-studied Balmer continuum emission in the NUV, suggesting that additional processes contribute to the short-wavelength emission in these objects. The most notable spectral feature in the FUV continuum of some CTTSs is a broad emission approximately centered at 1600 Å, which has been referred to as the “1600 Å Bump.” The origin of this feature remains unclear. In an effort to better understand the molecular properties of planet-forming disks and the UV spectral properties of accreting protostars, we have assembled archival FUV spectra of 37 disk-hosting systems observed by the Hubble Space Telescope-Cosmic Origins Spectrograph. Clear 1600 Å Bump emission is observed above the smooth, underlying 1100-1800 Å continuum spectrum in 19/37 Classical T Tauri disks in the HST-COS sample, with the detection rate in transition disks (8/8) being much higher than that in primordial or non-transition sources (11/29). We describe a spectral deconvolution analysis to separate the Bump (spanning 1490-1690 Å) from the underlying FUV continuum, finding an average Bump luminosity L(Bump) ≈ 7 × 1029 erg s-1. Parameterizing the Bump with a combination of Gaussian and polynomial components, we find that the 1600 Å Bump is characterized by a peak wavelength λ o = 1598.6 ± 3.3 Å, with FWHM = 35.8 ± 19.1 Å. Contrary to previous studies, we find that this feature is inconsistent with models of H2 excited by electron -impact. We show that this Bump makes up between 5%-50% of the total FUV continuum emission in the 1490-1690 Å band and emits roughly 10%-80% of the total fluorescent H2 luminosity for stars with well-defined Bump features. Energetically, this suggests that the carrier of the 1600 Å Bump emission is powered by Lyα photons. We argue that the most likely mechanism is Lyα-driven dissociation of H2O in the inner disk, r

  7. Pulse laser photolysis of aqueous ozone in the microsecond range studied by time-resolved far-ultraviolet absorption spectroscopy.

    Science.gov (United States)

    Goto, Takeyoshi; Morisawa, Yusuke; Higashi, Noboru; Ikehata, Akifumi; Ozaki, Yukihiro

    2013-05-01

    Chemical dynamics of an ozone (O3) pulse-photolytic reaction in aqueous solutions were studied with pump-probe transient far-ultraviolet (FUV) absorption spectroscopy. With a nanosecond pulse laser of 266 nm as pump light, transient spectra of O3 aqueous solutions (78-480 μM, pH 2.5-11.3) were acquired in the time range from -50 to 50 μs in the wavelength region from 190 to 225 nm. The measured transient spectra were linearly decomposed into the molar absorption coefficients and the concentration-time profiles of constituted chemical components with a multivariate curve resolution method. From the dependences of the time-averaged concentrations for 20 μs of the constituted chemicals on the initial concentration of O3, it was found that the transient spectra involve the decomposition of O3 and the formation of hydrogen peroxide (H2O2) and a third component that is assigned to hydroxyl radical (OH) or perhydroxyl radical (HO2). Furthermore, the pH dependence of the time-averaged concentration of the third components indicates that HO2 is more probable than OH as the third component. The time-averaged concentration ratio of each chemical component to the initial O3 concentration depends on the pH conditions from -0.95 to -0.60 for O3, 0.98 to 1.2 for H2O2, 0.002 to 0.29 for OH, and 0.012 to 0.069 for HO2.

  8. Molecular hydrogen (H2 emissions and their isotopic signatures (H/D from a motor vehicle: implications on atmospheric H2

    Directory of Open Access Journals (Sweden)

    T. Röckmann

    2010-06-01

    Full Text Available Molecular hydrogen (H2, its isotopic signature (deuterium/hydrogen, δD, carbon monoxide (CO, and other compounds were studied in the exhaust of a passenger car engine fuelled with gasoline or methane and run under variable air-fuel ratios and operating modes. H2 and CO concentrations were largely reduced downstream of the three-way catalytic converter (TWC compared to levels upstream, and showed a strong dependence on the air-fuel ratio (expressed as lambda, λ. The isotopic composition of H2 ranged from δD = −140‰ to δD = −195‰ upstream of the TWC but these values decreased to −270‰ to −370‰ after passing through the TWC. Post-TWC δD values for the fuel-rich range showed a strong dependence on TWC temperature with more negative δD for lower temperatures. These effects are attributed to a rapid temperature-dependent H-D isotope equilibration between H2 and water (H2O. In addition, post TWC δD in H2 showed a strong dependence on the fraction of removed H2, suggesting isotopic enrichment during catalytic removal of H2 with enrichment factors (ε ranging from −39.8‰ to −15.5‰ depending on the operating mode. Our results imply that there may be considerable variability in real-world δD emissions from vehicle exhaust, which may mainly depend on TWC technology and exhaust temperature regime. This variability is suggestive of a δD from traffic that varies over time, by season, and by geographical location. An earlier-derived integrated pure (end-member δD from anthropogenic activities of −270‰ (Rahn et al., 2002 can be explained as a mixture of mainly vehicle emissions from cold starts and fully functional TWCs, but enhanced δD values by >50‰ are likely for regions where TWC technology is not fully implemented. Our results also suggest that a full hydrogen isotope analysis on fuel and exhaust gas may greatly aid at understanding process-level reactions in the exhaust gas, in particular in the TWC.

  9. Molecular hydrogen (H2 emissions and their isotopic signatures (H/D from a motor vehicle: implications on atmospheric H2

    Directory of Open Access Journals (Sweden)

    T. Röckmann

    2010-02-01

    Full Text Available Molecular hydrogen (H2, its isotopic signature (deuterium/hydrogen, δD, carbon monoxide (CO and other compounds were studied in the exhaust of a passenger car engine fuelled with gasoline or methane and run under variable air-fuel ratios and operating modes. H2 and CO concentrations were largely reduced downstream of the three-way catalytic converter (TWC compared to levels upstream, and showed a strong dependence on the air-fuel ratio (expressed as lambda, λ. The isotopic composition of H2 ranged from δD=–140‰ to δD=–195‰ upstream of the TWC but these values decreased to –270‰ to –370‰ after passing through the TWC. Post-TWC δD values for the fuel-rich range showed a strong dependence on TWC temperature with more negative δD for lower temperatures. These effects are attributed to a rapid temperature-dependent H-D isotope equilibration between H2 and water (H2O. In addition, post TWC δD in H2 showed a strong dependence on the fraction of removed H2, suggesting isotopic enrichment during catalytic removal of H2 with enrichment factors (ε ranging from –39.8‰ to –15.5‰ depending on the operating mode. Our results imply that there may be considerable variability in real-world δD emissions from vehicle exhaust, which may mainly depend on TWC technology and exhaust temperature regime. This variability is suggestive of a δD from traffic that varies over time, by season, and by geographical location. An earlier-derived integrated pure (end-member δD from anthropogenic activities of –270‰ (Rahn et al., 2002 can be explained as a mixture of mainly vehicle emissions from cold starts and fully functional TWCs, but enhanced δD values by >50‰ are likely for regions where TWC technology is not fully implemented. Our results also suggest that a full hydrogen isotope analysis on fuel and exhaust gas may greatly aid at understanding process-level reactions in the exhaust gas, in particular in the TWC.

  10. VizieR Online Data Catalog: NGC253 near-infrared H2 emission (Rosenberg+,

    Science.gov (United States)

    Rosenberg, M. J. F.; van der Werf, P. P.; Israel, F. P.

    2012-11-01

    All observations were made with SINFONI at the ESO VLT. We observed in the H, and K bands using a spatial pixel scale of 0.25" corresponding to a field of view of 8" by 8" per frame and a spectral resolution of 2000, 3000 and 4000 respectively, which corresponds to a velocity resolution of 149.8, 99.9 and 74.9km/s. All science observations were taken in the ABA'nodding mode (300s of object, 300s of sky, 300s of object), where A' is slightly offset from A. The object exposures are aligned and averaged during the reconstruction of the data cube. The observations of NGC 253 were made in visitor mode on August 28th, 2005. In order to capture the full extent of the H2 emission, consecutive frames were taken in the K band moving further away from the center, along the disk until H2 was no longer detected. This resulted in 6 separate pointings. Since there are also H2 transitions in the H band, a similar strategy was used, resulting in 4 separate pointings. We used the standard reduction techniques of the SINFONI pipeline on all observations, including corrections for flat field, dark current, nonlinearity of pixels, distortion, and wavelength calibration. We obtained the flux calibration and atmospheric corrections from observations of a standard star, namely HR 2058 in the H band and HD 20001 in the K band (2 data files).

  11. H$_2$O maser emission from bright rimmed clouds in the northern hemisphere

    CERN Document Server

    Valdettaro, R; Brand, J; Cesaroni, R

    2005-01-01

    We report the results of a multi-epoch survey of water maser observations at 22.2 GHz with the Medicina radiotelescope from 44 bright rimmed clouds (BRCs) of the northern hemisphere identified by Sugitani et al. (1989) as potential sites of star formation. The data span 16 years of observations and allow to draw conclusions about the maser detection rate in this class of objects. In spite of the relatively high far-infrared luminosities of the embedded sources ($L_{\\rm FIR}\\ga 10^2$ L$_\\odot$), H$_2$O maser emission was detected towards three globules only. Since the occurrence of water masers is higher towards bright IRAS sources, the lack of frequent H$_2$O maser emission is somewhat surprising if the suggestion of induced intermediate- and high-mass star formation within these globules is correct. The maser properties of two BRCs are characteristic of exciting sources of low-mass, while the last one (BRC~38) is consistent with an intermediate-mass object. We argue that most BRCs host young stellar objects ...

  12. The Far Ultraviolet Spectral Signatures of Formaldehyde and Carbon Dioxide in Comets

    OpenAIRE

    Feldman, Paul D.; Lupu, Roxana E.; McCandliss, Stephan R.; Weaver, Harold A.

    2009-01-01

    Observations of four comets made with the Far Ultraviolet Spectroscopic Explorer show the rotational envelope of the (0,0) band of the CO Hopfield-Birge system (C - X) at 1088 A to consist of both "cold" and "hot" components, the "cold" component accounting for ~75% of the flux and with a rotational temperature in the range 55-75 K. We identify the "hot" component as coming from the dissociation of CO2 into rotationally "hot" CO, with electron impact dissociation probably dominant over photod...

  13. On-Orbit Performance of the Far Ultraviolet Spectroscopic Explorer (FUSE) Satellite

    CERN Document Server

    Sahnow, D J; Ake, T; Andersen, J; Andersson, B G; André, M; Artis, D; Berman, A; Blair, W; Brownsberger, K R; Calvani, H; Chayer, P; Conard, S; Feldman, P; Friedman, S; Fullerton, A W; Gaines, G; Gawne, W; Green, J; Gummin, M; Jennings, T; Joyce, J B; Kaiser, M E; Kruk, J W; Lindler, D; Massa, D L; Murphy, E; Oegerle, W R; Ohl, R; Roberts, B; Romelfanger, M; Roth, K C; Sankrit, R; Sembach, K R; Shelton, R; Siegmund, O; Silva, C; Sonneborn, G; Vaclavik, S; Weaver, H; Wilkinson, E

    2000-01-01

    Launch of the Far Ultraviolet Spectroscopic Explorer (FUSE) has been followed by an extensive period of calibration and characterization as part of the preparation for normal satellite operations. Major tasks carried out during this period include initial coalignment, focusing and characterization of the four instrument channels, and a preliminary measurement of the resolution and throughput performance of the instrument. We describe the results from this test program, and present preliminary estimates of the on-orbit performance of the FUSE satellite based on a combination of this data and prelaunch laboratory measurements.

  14. Globular clusters in the far-ultraviolet: evidence for He-enriched second populations in extra-galactic globular clusters?

    CERN Document Server

    Peacock, Mark B; Kundu, Arunav; Chael, Julia

    2016-01-01

    We investigate the integrated far-ultraviolet (FUV) emission from globular clusters. We present new FUV photometry of M~87's clusters based on archival HST WFPC2 F170W observations. We use these data to test the reliability of published photometry based on HST STIS FUV-MAMA observations, which are now known to suffer from significant red-leak. We generally confirm these previous FUV detections, but suggest they may be somewhat fainter. We compare the FUV emission from bright ($M_{V} < -9.0$) clusters in the Milky Way, M~31, M~81 and M~87 to each other and to the predictions from stellar populations models. Metal-rich globular clusters show a large spread in FUV-V, with some clusters in M~31, M~81 and M~87 being much bluer than standard predictions. This requires that some metal-rich clusters host a significant population of blue/extreme horizontal branch (HB) stars. These hot HB stars are not traditionally expected in metal-rich environments, but are a natural consequence of multiple populations in cluster...

  15. Hubble Space Telescope Detection of the Double Pulsar System J0737-3039 in the Far-ultraviolet

    Science.gov (United States)

    Durant, Martin; Kargaltsev, Oleg; Pavlov, George G.

    2014-03-01

    We report on detection of the double pulsar system J0737-3039 in the far-UV with the Advanced Camera for Surveys/Solar-blind Channel detector aboard Hubble Space Telescope. We measured the energy flux F = (4.6 ± 1.0) × 10-17 erg cm-2 s-1 in the 1250-1550 Å band, which corresponds to the extinction-corrected luminosity L ≈ 1.5 × 1028 erg s-1 for the distance d = 1.1 kpc and a plausible reddening E(B - V) = 0.1. If the detected emission comes from the entire surface of one of the neutron stars with a 13 km radius, the surface blackbody temperature is in the range T ~= (2-5) × 105 K for a reasonable range of interstellar extinction. Such a temperature requires an internal heating mechanism to operate in old neutron stars, or, less likely, it might be explained by heating of the surface of the less energetic Pulsar B by the relativistic wind of Pulsar A. If the far-ultraviolet emission is non-thermal (e.g., produced in the magnetosphere of Pulsar A), its spectrum exhibits a break between the UV and X-rays.

  16. Initial Results of a Far-Ultraviolet Spectroscopic Survey of Nearby Star-forming Galaxies with the Cosmic Origins Spectrograph

    Science.gov (United States)

    Redwine, Keith; McCandliss, Stephan R.; Wofford, Aida; Leitherer, Claus; Heckman, Timothy M.; France, Kevin; Fleming, Brian

    2017-01-01

    We present initial results for the HST Cycle 22 proposal 13761. We proposed to observe 75 target star-forming galaxies at a redshift 0.02 COS, spanning a bandpass of 1100 < λ < 2400 angstroms, and have thus far observed 34 of them. The main thrust of this project is to provide a previously unavailable survey of star-forming galaxies in this redshift range, allowing investigation into the factors that determine the Lyman-alpha emission at these low redshifts. We have begun a statistical analysis of the relationship between Lyman-alpha emission and the morphologies of the galaxies, such as absorption line strengths of other species, including various ionization states of oxygen, silicon, and other species to probe intrinsic properties of the emitting galaxy, such as metallicity, the gas-to-dust ratio, and local velocity fields. We have acquired a very rich dataset, with enough samples to try to answer a variety of open questions regarding the far-ultraviolet spectra of bright Lyman-alpha emitters. This work is supported by a NASA Grant HST-GO-13761 to the Johns Hopkins University.

  17. Far-Ultraviolet Spectroscopy of Three Long-Period Novalike Variables

    Science.gov (United States)

    Bisol, Alexandra C.; Godon, Patrick; Sion, Edward M.

    2012-02-01

    We have selected three novalike variables at the long-period extreme of novalike orbital periods: V363 Aur, RZ Gru, and AC Cnc, all with IUE archival far-ultraviolet spectra. All are UX UMa-type novalike variables and all have Porb > 7 hr. V363 Aur is a bona fide SW Sex star, and AC Cnc is a probable one, while RZ Gru has not proven to be a member of the SW Sex subclass. We have carried out the first synthetic spectral analysis of far-ultraviolet spectra of the three systems using state-of-the-art models of both accretion disks and white dwarf photospheres. We find that the FUV spectral energy distribution of both V363 Aur and RZ Gru are in agreement with optically thick steady-state accretion disk models in which the luminous disk accounts for 100% of the FUV light. We present accretion rates and model-derived distances for V363 Aur and RZ Gru. For AC Cnc, we find that a hot accreting white dwarf accounts for ∼60% of the FUV light, with an accretion disk providing the rest. We compare our accretion rates and model-derived distances with estimates in the literature.

  18. Spontaneous Emission Between - and Para-Levels of Water-Ion H_2O^+

    Science.gov (United States)

    Tanaka, Keiichi; Harada, Kensuke; Nanbu, Shinkoh; Oka, Takeshi

    2012-06-01

    Nuclear spin conversion interaction of water ion, H_2O^+, has been studied to derive spontaneous emission lifetime between ortho- and para-levels. H_2O^+ is a radical ion with the ^2B_1 electronic ground state. Its off-diagonal electron spin-nuclear spin interaction term, Tab(S_aΔ I_b + S_bΔ I_a), connects para and ortho levels, because Δ I = I_1 - I_2 has nonvanishing matrix elements between I = 0 and 1. The mixing by this term with Tab = 72 MHz predicted by ab initio theory in the MRD-CI/Bk level, is many orders of magnitude larger than for closed shell molecules because of the large magnetic interaction due to the un-paired electron. Using the molecular constants reported by Mürtz et al. by FIR-LMR, we searched for ortho and para coupling channels below 1000 cm-1 with accidental near degeneracy between para and ortho levels. For example, hyperfine components of the 42,2(ortho) and 33,0(para) levels mix by 1.2 × 10-3 due to their near degeneracy (Δ E = 0.417 cm-1), and give the ortho-para spontaneous emission lifetime of about 0.63 year. The most significant low lying 10,1(para) and 11,1(ortho) levels, on the contrary, mix only by 8.7 × 10-5 because of their large separation (Δ E = 16.267 cm-1) and give the spontaneous emission lifetime from 10,1(para) to 00,0(ortho) of about 100 year.These results qualitatively help to understand the observed high ortho- to para- H_2O^+ ratio of 4.8 ± 0.5 toward Sgr B2 but they are too slow to compete with the conversion by collision unless the number density of the region is very low (n ˜1 cm-3) or radiative temperature is very high (T_r > 100 K). M. Staikova, B. Engels, M. Peric, and S.D. Peyerimhoff, Mol. Phys. 80, 1485 (1993) P. Mürtz, L.R. Zink, K.M. Evenson, and J.M. Brown J. Chem. Phys. 109, 9744 (1998). LP. Schilke, et al., A&A 521, L11 (2010).

  19. A Far-Ultraviolet Survey of 47 Tucanae.II The Long-Period Cataclysmic Variable AKO 9

    CERN Document Server

    Knigge, C; Shara, M M; Long, K S; Gilliland, R L; Knigge, Christian; Zurek, David. R.; Shara, Michael M.; Long, Knox S.; Gilliland, Ronald L.

    2003-01-01

    We present time-resolved, far-ultraviolet (FUV) spectroscopy and photometry of the 1.1 day eclipsing binary system AKO 9 in the globular cluster 47 Tucanae. AKO 9's FUV spectrum is blue and exhibits prominent C IV and He II emission lines. The spectrum broadly resembles that of long-period, cataclysmic variables in the galactic field. Combining our time-resolved FUV data with archival optical photometry of 47 Tuc, we refine AKO 9's orbital period and define an accurate ephemeris for the system. We also place constraints on several other system parameters, using a variety of observational constraints. We find that all of the empirical evidence is consistent with AKO 9 being a long-period dwarf nova in which mass transfer is driven by the nuclear expansion of a sub-giant donor star. We therefore conclude that AKO 9 is the first spectroscopically confirmed cataclysmic variable in 47 Tuc. We also briefly consider AKO 9's likely formation and ultimate evolution. Regarding the former, we find that the system was al...

  20. Far-Ultraviolet to Near-Infrared Spectroscopy of A Nearby Hydrogen Poor Superluminous Supernova Gaia16apd

    CERN Document Server

    Yan, Lin; Gal-Yam, A; Brown, P; Blagorodnova, N; Ofek, E O; Lunnan, R; Cooke, J; Cenko, S B; Jencson, J; Kasliwal, M

    2016-01-01

    We report the first maximum-light far-Ultraviolet to near-infrared spectra (1000A - 1.62um, rest) of a H-poor superluminous supernova, Gaia16apd. At z=0.1018, it is one of the closest and the UV brightest such events, with 17.4 (AB) magnitude in Swift UV band (1928A) at -11days pre-maximum. Assuming an exponential form, we derived the rise time of 33days and the peak bolometric luminosity of 3x10^{44}ergs^-1. At maximum light, the estimated photospheric temperature and velocity are 17,000K and 14,000kms^-1 respectively. The inferred radiative and kinetic energy are roughly 1x10^{51} and 2x10^{52}erg. Gaia16apd is extremely UV luminous, emitting 50% of its total luminosity at 1000 - 2500A. Compared to the UV spectra (normalized at 3100A) of well studied SN1992A (Ia), SN2011fe(Ia), SN1999em (IIP) and SN1993J (IIb), it has orders of magnitude more far-UV emission. This excess is interpreted primarily as a result of weaker metal line blanketing due to much lower abundance of iron-group elements in the outer eject...

  1. Globular clusters in the far-ultraviolet: evidence for He-enriched second populations in extragalactic globular clusters?

    Science.gov (United States)

    Peacock, Mark B.; Zepf, Stephen E.; Kundu, Arunav; Chael, Julia

    2017-01-01

    We investigate the integrated far-ultraviolet (FUV) emission from globular clusters. We present new FUV photometry of M87's clusters based on archival Hubble Space Telescope (HST) Wide Field Planetary Camera 2 F170W observations. We use these data to test the reliability of published photometry based on HST space telescope imaging spectrograph FUV-MAMA observations, which are now known to suffer from significant red-leak. We generally confirm these previous FUV detections, but suggest they may be somewhat fainter. We compare the FUV emission from bright (MV populations models. Metal-rich globular clusters show a large spread in FUV - V, with some clusters in M31, M81 and M87 being much bluer than standard predictions. This requires that some metal-rich clusters host a significant population of blue/extreme horizontal branch (HB) stars. These hot HB stars are not traditionally expected in metal-rich environments, but are a natural consequence of multiple populations in clusters - since the enriched population is observed to be He enhanced and will therefore produce bluer HB stars, even at high metallicity. We conclude that the observed FUV emission from metal-rich clusters in M31, M81 and M87 provides evidence that He-enhanced second populations, similar to those observed directly in the Milky Way, may be a ubiquitous feature of globular clusters in the local Universe. Future HST FUV photometry is required to both confirm our interpretation of these archival data and provide constraints on He-enriched second populations of stars in extragalactic globular clusters.

  2. High-resolution, far-ultraviolet study of Beta Draconis (G2 Ib-II) - Transition region structure and energy balance

    Science.gov (United States)

    Brown, A.; Jordan, C.; Stencel, R. E.; Linsky, J. L.; Ayres, T. R.

    1984-01-01

    High-resolution far ultraviolet spectra of the star Beta Draconis have been obtained with the IUE satellite. The observations and emission line data from the spectra are presented, the interpretation of the emission line widths and shifts is discussed, and the implications are given in terms of atmospheric properties. The emission measure distribution is derived, and density diagnostics involving both line ratios and line opacity arguments is investigated. The methods for calculating spherically symmetric models of the atmospheric structure are outlined, and several such models are presented. The extension of these models to log T(e) greater than 5.3 using the observed X-ray flux is addressed, the energy balance of an 'optimum' model is investigated, and possible models of energy transport and deposition are discussed.

  3. Far Ultraviolet Spectroscopic Explorer(FUSE) Observations Of The Antennae Galaxies (ngc4038/ngc4039)

    Science.gov (United States)

    Iping, Rosina; Sonneborn, G.; Neff, S.

    2006-06-01

    The brightest UV region of the Antennae galaxies (NGC4038/4039), Knots R/S/T, has been observed with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. The observation used a 30x30 arcsec aperture, encompassing several stellar groups. The high-resolution FUV spectrum detects broad ( 150 km/s FWHM) O VI 1032, 1038 absorption blueward of the systemic velocity (1642 km/s) in the galactic outflow. This outflowing gas has a temperature of a few times 105 K and may dominate the radiative cooling of the supernova-heated interstellar medium. Strong C II 1036, H I 1026, S III 1012, 1015, S IV 1062, 1072 and Si IV 1122, 1128 have symmetric absorption features centered at the systemic velocity. These features probably originate from the OB stellar population in the galaxies. This work has been supported in part by a FUSE Guest Investigator grant from NASA (NAG5-13014) to the Catholic University of America.

  4. The Diffuse Interstellar Cloud Experiment: a high-resolution far-ultraviolet spectrograph.

    Science.gov (United States)

    Schindhelm, Eric; Beasley, Matthew; Burgh, Eric B; Green, James C

    2012-03-01

    We have designed, assembled, and launched a sounding rocket payload to perform high-resolution far-ultraviolet spectroscopy. The instrument is functionally a Cassegrain telescope followed by a modified Rowland spectrograph. The spectrograph was designed to achieve a resolving power (R=λ/δλ) of 60,000 in a compact package by adding a magnifying secondary optic. This is enabled by using a holographically ruled grating to minimize aberrations induced by the second optic. We designed the instrument to observe two stars on opposing sides of a nearby hot/cold gas interface. Obtaining spectra of the O VI doublet in absorption toward these stars can provide new insight into the processes governing hot gas in the local interstellar medium. Here we present the optical design and alignment of the telescope and spectrograph, as well as flight results.

  5. A Far Ultraviolet Spectroscopic Analysis of the Old Nova Q Cygni

    Science.gov (United States)

    Kolobow, Craig; Sion, E. M.

    2011-01-01

    Q Cygni (Nova Cygni 1876) is one of the oldest old novae with a long orbital period of 10.08 hours and spectroscopic peculiarities in the optical including the presence of variable wind outflow revealed by optical P Cygni profiles in the He I lines and Halpha (Kafka et al.2003). There has never been a far UV spectroscopic analysis of this system. Therefore, we have carried out a synthetic spectral analysis of a far ultraviolet IUE archival spectrum of Q Cygni using our optically thick, steady state, accretion disk models and model white dwarf photospheres. We report the results of our spectroscopic analysis and compare the physical parameters we derive with those of other old novae. We gratefully acknowledge the support of this by NSF grant 0807892 to Villanova University.

  6. Detection of far ultraviolet radiation by wavelength-shifting tetraphenyl butadiene

    Science.gov (United States)

    Graybill, Joshua R.; Shahi, Chandra B.; Coplan, Michael C.; Vest, Robert E.; Thompson, Alan K.; Clark, Charles W.

    2017-01-01

    Far ultraviolet (FUV) radiation has been used in low-energy particle physics, dark matter searches, and neutron detection, in conjuction with wavelength-shifting (WLS) materials. Tetraphenyl butadiene (TPB) has been found to have high conversion efficiency compared to other WLS fluorophores. We have spin-coated TPB films with high uniformity and optical quality on glass windows and compared the absolute efficiencies of both the spin-coated and vapor deposited films over the incident radiation wavelengths 120 nm < λ < 400 nm at the NIST SURF III Synchrotron Ultraviolet Radiation Facility. While photon efficiencies of 0.7 and 1.35, have been reported, our preliminary results indicate the absolute efficiencies to be between 0.2 and 0.5. The Neutron Observatory was used to compare conversion efficiencies in well-characterized detector platforms.

  7. CalFUSE v3: A Data-Reduction Pipeline for the Far Ultraviolet Spectroscopic Explorer

    CERN Document Server

    Dixon, W V; Barrett, P E; Civeit, T; Dupuis, J; Fullerton, A W; Godard, B; Hsu, J C; Kaiser, M E; Kruk, J W; Lacour, S; Lindler, D J; Massa, D; Robinson, R D; Romelfanger, M L; Sonnentrucker, P

    2007-01-01

    Since its launch in 1999, the Far Ultraviolet Spectroscopic Explorer (FUSE) has made over 4600 observations of some 2500 individual targets. The data are reduced by the Principal Investigator team at the Johns Hopkins University and archived at the Multimission Archive at Space Telescope (MAST). The data-reduction software package, called CalFUSE, has evolved considerably over the lifetime of the mission. The entire FUSE data set has recently been reprocessed with CalFUSE v3.2, the latest version of this software. This paper describes CalFUSE v3.2, the instrument calibrations upon which it is based, and the format of the resulting calibrated data files.

  8. Far-Ultraviolet Rocket Observations of OB Stars and Dust Scattering

    Science.gov (United States)

    Feldman, Paul D.; Lupu, R. E.; McCandliss, S. R.; Fleming, B.; France, K.; Nikzad, S.

    2009-01-01

    The rocket-borne Long-slit Imaging Dual Order Spectrograph (LIDOS) was used to obtain spectra of the Trifid and Orion nebula regions and their illuminating stars in the 900 - 1650 A bandpass during successive flights in 2007 and 2008. The instrument uses both positive and negative diffraction orders, employing a delta-doped CCD in addition to an MCP detector for an expanded dynamic range. We present preliminary extractions of the stellar spectra and the nebular dust scattered light profiles. The chosen lines of sight show little extinction and molecular hydrogen absorption, providing unique observations of stellar atmospheric features below 1200 A, including O VI, C III and He II, and the overall far-ultraviolet continuum output. This work was supported by NASA grants NNG04WC03G and NNX08AM68G to the Johns Hopkins University.

  9. Upper limits for a lunar dust exosphere from far-ultraviolet spectroscopy by LRO/LAMP

    Science.gov (United States)

    Feldman, Paul D.; Glenar, David A.; Stubbs, Timothy J.; Retherford, Kurt D.; Randall Gladstone, G.; Miles, Paul F.; Greathouse, Thomas K.; Kaufmann, David E.; Parker, Joel Wm.; Alan Stern, S.

    2014-05-01

    Since early 2012, the Lyman-Alpha Mapping Project (LAMP) far-ultraviolet spectrograph on the Lunar Reconnaissance Orbiter (LRO) spacecraft has carried out a series of limb observations from within lunar shadow to search for the presence of a high altitude dust exosphere via forward-scattering of sunlight from dust grains. Bright “horizon-glow” was observed from orbit during several Apollo missions and interpreted in terms of dust at altitudes of several km and higher. However, no confirmation of such an exosphere has been made since that time. This raises basic questions about the source(s) of excess brightness in the early measurements and also the conditions for producing observable dust concentrations at km altitudes and higher. Far-ultraviolet measurements between 170 and 190 nm, near the LAMP long wavelength cutoff, are especially sensitive to scattering by small (0.1-0.2 μm radius) dust grains, since the scattering cross-section is near-maximum, and the solar flux is rising rapidly with wavelength. An additional advantage of ultraviolet measurements is the lack of interference by background zodiacal light which must be taken into account at longer wavelengths. As of July 2013, LAMP has completed several limb-observing sequences dedicated to the search for horizon glow, but no clear evidence of dust scattering has yet been obtained. Upper limits for vertical dust column abundance have been estimated at less than 10 grains cm-2 (0.1 μm grain radius), by comparing the measured noise-equivalent brightness with the results of Mie scattering simulations for the same observing geometries. These results indicate that Lunar Atmosphere Dust Environment Explorer (LADEE) UVS lunar dust observations will be considerably more challenging than planned.

  10. Metformin selectively attenuates mitochondrial H2O2 emission without affecting respiratory capacity in skeletal muscle of obese rats.

    Science.gov (United States)

    Kane, Daniel A; Anderson, Ethan J; Price, Jesse W; Woodlief, Tracey L; Lin, Chien-Te; Bikman, Benjamin T; Cortright, Ronald N; Neufer, P Darrell

    2010-09-15

    Metformin is a widely prescribed drug for treatment of type 2 diabetes, although no cellular mechanism of action has been established. To determine whether in vivo metformin treatment alters mitochondrial function in skeletal muscle, respiratory O(2) flux and H(2)O(2) emission were measured in saponin-permeabilized myofibers from lean and obese (fa/fa) Zucker rats treated for 4 weeks with metformin. Succinate- and palmitoylcarnitine-supported respiration generated greater than twofold higher rates of H(2)O(2) emission in myofibers from untreated obese versus lean rats, indicative of an obesity-associated increased mitochondrial oxidant emitting potential. In conjunction with improved glycemic control, metformin treatment reduced H(2)O(2) emission in muscle from obese rats to rates near or below those observed in lean rats during both succinate- and palmitoylcarnitine-supported respiration. Surprisingly, metformin treatment did not affect basal or maximal rates of O(2) consumption in muscle from obese or lean rats. Ex vivo dose-response experiments revealed that metformin inhibits complex I-linked H(2)O(2) emission at a concentration approximately 2 orders of magnitude lower than that required to inhibit respiratory O(2) flux. These findings suggest that therapeutic concentrations of metformin normalize mitochondrial H(2)O(2) emission by blocking reverse electron flow without affecting forward electron flow or respiratory O(2) flux in skeletal muscle. Copyright 2010 Elsevier Inc. All rights reserved.

  11. Effects of sulfur-metabolizing bacterial community diversity on H2S emission behavior in landfills with different operation modes.

    Science.gov (United States)

    Fang, Yuan; Du, Yao; Hu, Lifang; Xu, Jing; Long, Yuyang; Shen, Dongsheng

    2016-11-01

    Hydrogen sulfide (H2S) is one of the major contributors to offensive odors from landfills, and its concentration differs under different operation modes. This study examined the distribution of H2S emission from different landfill depths under different operation modes (anaerobic, semi-aerobic, semi-aerobic transformation, and the three operation modes with additional leachate recirculation). The microbial community (especially the sulfur-metabolizing bacterial community) was investigated using high-throughput sequencing technology. The results showed that the semi-aerobic mode could substantially lower the risks of H2S pollution in landfills, which might be because of the difference in biological processes related to sulfur metabolism driven by functional microbes. A myriad of factors are responsible for mutually shaping the sulfur-metabolizing bacterial community composition in landfills that might subsequently affect the behavior of H2S emission in landfills. The differences in abundance of the genera Acinetobacter and Paracoccus (phylum Proteobacteria) caused by environmental factors might explain the differences in H2S emission. H2S odor control could be realized if the related functional microbe diversity can be influenced by adjustments to landfill operation.

  12. Manganese ions enhance mitochondrial H2O2 emission from Krebs cycle oxidoreductases by inducing permeability transition.

    Science.gov (United States)

    Bonke, Erik; Siebels, Ilka; Zwicker, Klaus; Dröse, Stefan

    2016-10-01

    Manganese-induced toxicity has been linked to mitochondrial dysfunction and an increased generation of reactive oxygen species (ROS). We could recently show in mechanistic studies that Mn(2+) ions induce hydrogen peroxide (H2O2) production from the ubiquinone binding site of mitochondrial complex II (IIQ) and generally enhance H2O2 formation by accelerating the rate of superoxide dismutation. The present study with intact mitochondria reveals that manganese additionally enhances H2O2 emission by inducing mitochondrial permeability transition (mPT). In mitochondria fed by NADH-generating substrates, the combination of Mn(2+) and different respiratory chain inhibitors led to a dynamically increasing H2O2emission which was sensitive to the mPT inhibitor cyclosporine A (CsA) as well as Ru-360, an inhibitor of the mitochondrial calcium uniporter (MCU). Under these conditions, flavin-containing enzymes of the mitochondrial matrix, e.g. the mitochondrial 2-oxoglutaratedehydrogenase (OGDH), were major sources of ROS. With succinate as substrate, Mn(2+) stimulated ROS production mainly at complex II, whereby the applied succinate concentration had a marked effect on the tendency for mPT. Also Ca(2+) increased the rate of H2O2 emission by mPT, while no direct effect on ROS-production of complex II was observed. The present study reveals a complex scenario through which manganese affects mitochondrial H2O2 emission: stimulating its production from distinct sites (e.g. site IIQ), accelerating superoxide dismutation and enhancing the emission via mPT which also leads to the loss of soluble components of the mitochondrial antioxidant systems and favors the ROS production from flavin-containing oxidoreductases of the Krebs cycle.

  13. Extragalactic H2O Megamaser Sources:Central Black Holes,Nuclear X-ray and Maser Emissions

    Institute of Scientific and Technical Information of China (English)

    Jiang-Bo Su; Jiang-Shui Zhang; Jun-Hui Fan

    2008-01-01

    Extragalactic H2O megamasers are typically found within the innermost few parsecs of active galaxy nuclei (AGN) and the maser emission is considered to be excited most likely by the X-ray irradiation of the AGN.We investigate a comprehensive sample of extragalactic H2O masers in a sample of 38 maser host AGN to check potential correlations of the megamaser emission with parameters of the AGN,such as X-ray luminosity and black hole (BH) masses.We find a relation between the maser luminosities and BH masses,LH2O∝ M3.64-0.4 BH,which supports basically the theoretical prediction.The relation between the maser emission and X-ray emission is also confirmed.

  14. Far-ultraviolet and X-ray irradiated protoplanetary disks : a grid of models I. The disk structure

    NARCIS (Netherlands)

    Meijerink, R.; Aresu, G.; Kamp, I.; Spaans, M.; Thi, W. -F.; Woitke, P.

    2012-01-01

    Context. Planets are thought to eventually form from the mostly gaseous (similar to 99% of the mass) disks around young stars. The density structure and chemical composition of protoplanetary disks are affected by the incident radiation field at optical, far-ultraviolet (FUV), and X-ray wavelengths,

  15. Filters for the International Solar Terrestrial Physics (ISTP) mission far ultraviolet imager

    Science.gov (United States)

    Zukic, Muamer; Torr, Douglas G.; Kim, Jongmin; Spann, James F.; Torr, Marsha R.

    1993-01-01

    The far ultraviolet (FUV) imager for the International Solar Terrestrial Physics (ISTP) mission is designed to image four features of the aurora: O I lines at 130.4 nm and 135.6 nm and the N2 Lyman-Birge-Hopfield (LBH) bands between 140 nm - 160 nm (LBH long) and 160 nm - 180 nm (LBH long). In this paper we report the design and fabrication of narrow-band and broadband filters for the ISTP FUV imager. Narrow-band filters designed and fabricated for the O I lines have a bandwidth of less than 5 nm and a peak transmittance of 23.9 percent and 38.3 percent at 130.4 nm and 135.6 nm, respectively. Broadband filters designed and fabricated for LBH bands have the transmittance close to 60 percent. Blocking of out-of-band wavelengths for all filters is better than 5x10(exp -3) percent with the transmittance at 121.6 nm of less than 10(exp -6) percent.

  16. Far ultraviolet filters for the ISTP UV imager. [International Solar-Terrestrial Physics mission

    Science.gov (United States)

    Zukic, Muamer; Torr, Douglas G.; Kim, Jongmin; Spann, James F.; Torr, Marsha R.

    1992-01-01

    The far ultraviolet (FUV) imager for the International Solar-Terrestrial Physics (ISTP) mission is designed to image four features of the aurora: O I lines at 130.4 nm and 135.6 nm and the N2 Lyman-Birge-Hopfield (LBH) bands between 140 nm-160 nm (LBH long) and 160 nm-180 nm (LBH long). We report the design and fabrication of narrow-band and broadband filters for the ISTP FUV imager. Narrow-band filters designed and fabricated for the O I lines have a bandwidth of less than 5 nm and a peak transmittance of 22.3 and 29.6 percent at 130.4 nm and 135.6 nm, respectively. Broadband filters designed and fabricated for LBH bands have the transmittance greater than 40 percent for LBH short and close to 60 percent for LBH long. Blocking of out-of-band wavelengths for all filters is better than 0.001 percent with the transmittance at 121.6 nm of less than 10 exp -6 percent.

  17. Deuterium Toward WD1634-573 Results from the Far Ultraviolet Spectroscopic Explorer (FUSE) Mission

    CERN Document Server

    Wood, B E; Hébrard, G; Vidal-Madjar, A; Lemoine, M; Moos, H W; Sembach, K R; Jenkins, E B

    2002-01-01

    We use Far Ultraviolet Spectrocopic Explorer (FUSE) observations to study interstellar absorption along the line of sight to the white dwarf WD1634-573 (d=37.1+/-2.6 pc). Combining our measurement of D I with a measurement of H I from Extreme Ultraviolet Explorer data, we find a D/H ratio toward WD1634-573 of D/H=(1.6+/-0.5)e-5. In contrast, multiplying our measurements of D I/O I=0.035+/-0.006 and D I/N I=0.27+/-0.05 with published mean Galactic ISM gas phase O/H and N/H ratios yields D/H(O)=(1.2+/-0.2)e-5 and D/H(N)=(2.0+/-0.4)e-5, respectively. Note that all uncertainties quoted above are 2 sigma. The inconsistency between D/H(O) and D/H(N) suggests that either the O I/H I and/or the N I/H I ratio toward WD1634-573 must be different from the previously measured average ISM O/H and N/H values. The computation of D/H(N) from D I/N I is more suspect, since the relative N and H ionization states could conceivably vary within the LISM, while the O and H ionization states will be more tightly coupled by charge e...

  18. An Online Catalog of Cataclysmic Variable Spectra from the Far Ultraviolet Spectroscopic Explorer

    CERN Document Server

    Godon, P; Levay, K; Linnell, A P; Szkody, P; Barrett, P E; Hubeny, I; Blair, W P

    2012-01-01

    We present an online catalog containing spectra and supporting information for cataclysmic variables that have been observed with the Far Ultraviolet Spectroscopic Explorer (FUSE). For each object in the catalog we list some of the basic system parameters such as (RA,Dec), period, inclination, white dwarf mass, as well as information on the available FUSE spectra: data ID, observation date and time, and exposure time. In addition, we provide parameters needed for the analysis of the FUSE spectra such as the reddening E(B-V), distance, and state (high, low, intermediate) of the system at the time it was observed. For some of these spectra we have carried out model fits to the continuum with synthetic stellar and/or disk spectra using the codes TLUSTY and SYNSPEC. We provide the parameters obtained from these model fits; this includes the white dwarf temperature, gravity, projected rotational velocity and elemental abundances of C, Si, S and N, together with the disk mass accretion rate, the resulting inclinati...

  19. SSUSI-lite: next generation far-ultraviolet sensor for characterizing geospace

    Science.gov (United States)

    Paxton, Larry J.; Hicks, John E.; Grey, Matthew P.; Parker, Charles W.; Hourani, Ramsay S.; Marcotte, Kathryn M.; Carlsson, Uno P.; Kerem, Samuel; Osterman, Steven N.; Maas, Bryan J.; Ogorzalek, Bernard S.

    2016-10-01

    SSUSI-Lite is an update of an existing sensor, SSUSI. The current generation of Defense Meteorological Satellite Program (DMSP) satellites (Block 5D3) includes a hyperspectral, cross-tracking imaging spectrograph known as the Special Sensor Ultraviolet Spectrographic Imager (SSUSI). SSUSI has been part of the DMSP program since 1990. SSUSI is designed to provide space weather information such as: auroral imagery, ionospheric electron density profiles, and neutral density composition changes. The sensors that are flying today (see http://ssusi.jhuapl.edu) were designed in 1990 - 1992. There have been some significant improvements in flight hardware since then. The SSUSI-Lite instrument is more capable than SSUSI yet consumes ½ the power and is ½ the mass. The total package count (and as a consequence, integration cost and difficulty) was reduced from 7 to 2. The scan mechanism was redesigned and tested and is a factor of 10 better. SSUSI-Lite can be flown as a hosted payload or a rideshare - it only needs about 10 watts and weighs under 10 kg. We will show results from tests of an interesting intensified position sensitive anode pulse counting detector system. We use this approach because the SSUSI sensor operates in the far ultraviolet - from about 110 to 180 nm or 0.11 to 0.18 microns.

  20. The far-ultraviolet spectra of two hot PG1159 stars

    CERN Document Server

    Werner, K; Kruk, J W

    2016-01-01

    PG1159 stars are hot, hydrogen-deficient (pre-) white dwarfs with atmospheres mainly composed of helium, carbon, and oxygen. The unusual surface chemistry is the result of a late helium-shell flash. Observed element abundances enable us to test stellar evolution models quantitatively with respect to their nucleosynthesis products formed near the helium-burning shell of the progenitor asymptotic giant branch stars. Because of the high effective temperatures (Teff), abundance determinations require ultraviolet spectroscopy and non-local thermodynamic equilibrium model atmosphere analyses. Up to now, we have presented results for the prototype of this spectral class and two cooler members (Teff in the range 85,000-140,000 K). Here we report on the results for two even hotter stars (PG1520+525 and PG1144+005, both with Teff = 150,000 K) which are the only two objects in this temperature-gravity region for which useful far-ultraviolet spectra are available, and revisit the prototype star. Previous results on the a...

  1. A Far Ultraviolet Spectroscopic Explorer Survey of Coronal Forbidden Lines in Late-Type Stars

    CERN Document Server

    Redfield, S; Linsky, J L; Ake, T B; Dupree, A K; Robinson, R D; Young, P R; Redfield, Seth; Ayres, Thomas R.; Linsky, Jeffrey L.; Ake, Thomas B.; Robinson, Richard D.; Young, Peter R.

    2002-01-01

    We present a survey of coronal forbidden lines detected in Far Ultraviolet Spectroscopic Explorer (FUSE) spectra of nearby stars. Two strong coronal features, Fe XVIII 974 A and Fe XIX 1118 A, are observed in 10 of the 26 stars in our sample. Various other coronal forbidden lines, observed in solar flares, also were sought but not detected. The Fe XVIII feature, formed at log T (K) = 6.8, appears to be free of blends, whereas the Fe XIX line can be corrupted by a C I multiplet. FUSE observations of these forbidden iron lines at spectral resolution R ~ 15,000 provides the opportunity to study dynamics of hot coronal plasmas. We find that the velocity centroid of the Fe XVIII feature deviates little from the stellar rest frame, confirming that the hot coronal plasma is confined. The observed line widths generally are consistent with thermal broadening at the high temperatures of formation and show little indication of additional turbulent broadening. The fastest rotating stars, 31 Com, alpha Aur Ab, and AB Dor,...

  2. Far-Ultraviolet Observations of the Spica Nebula and the Interaction Zone

    CERN Document Server

    Choi, Yeon-Ju; Seon, Kwang-Il; Lim, Tae-Ho; Jo, Young-Soo; Park, Jae-Woo

    2013-01-01

    We report the analysis results of far ultraviolet (FUV) observations, made for a broad region around $\\alpha$ Vir (Spica) including the interaction zone of Loop I and the Local Bubble. The whole region was optically thin and a general correlation was seen between the FUV continuum intensity and the dust extinction, except in the neighborhood of the bright central star, indicating the dust scattering nature of the FUV continuum. We performed Monte-Carlo radiative transfer simulations to obtain the optical parameters related to the dust scattering as well as the geometrical structure of the region. The albedo and asymmetry factor were found to be 0.38$\\pm$0.06 and 0.46$\\pm$0.06, respectively, in good agreement with the Milky Way dust grain models. The distance to and the thickness of the interaction zone were estimated to be 70$^{+4}_{-8}$ pc and 40$^{+8}_{-10}$ pc, respectively. The diffuse FUV continuum in the northern region above Spica was mostly the result of scattering of the starlight from Spica, while t...

  3. Analysis of H2 Emission from Mira B in UV Spectra from HST

    CERN Document Server

    Wood, B E; Raymond, J C; Wood, Brian E.; Karovska, Margarita; Raymond, John C.

    2002-01-01

    We analyze Ly-alpha fluoresced H2 lines observed in the UV spectrum of Mira B. We identify 13 different sequences fluoresced by 13 different H2 transitions within the Ly-alpha line. The observed H2 line ratios within these sequences imply significant line opacity, so we use a Monte Carlo radiative transfer code to model the line ratios, correcting for opacity effects. We find the observed line ratios can best be reproduced by assuming that the H2 is fluoresced in a layer between the observer and Mira B with a temperature and column density of T=3600 K and log N(H2)=17.3, respectively. The strengths of H2 absorption features within the Ly-alpha line are roughly consistent with this temperature and column. We use the total flux fluoresced within the 13 sequences to infer the Ly-alpha profile seen by the H2. In order to explain differences between the shape of this and the observed profile, we have to assume that the observed profile suffers additional interstellar (or circumstellar) H I Ly-alpha absorption with...

  4. The gaseous debris disk of the white dwarf SDSS J1228+1040. HST/COS search for far-ultraviolet signatures

    CERN Document Server

    Hartmann, S; Rauch, T; Werner, K

    2016-01-01

    Gaseous and dust debris disks around white dwarfs (WDs) are formed from tidally disrupted planetary bodies. This offers an opportunity to determine the composition of exoplanetary material by measuring element abundances in the accreting WD's atmosphere. A more direct way to do this is through spectral analysis of the disks themselves. Currently, the number of chemical elements detected through disk emission-lines is smaller than that of species detected through lines in the WD atmospheres. We assess the far-ultraviolet (FUV) spectrum of one well-studied object (SDSS J122859.93+104032.9) to search for disk signatures at wavelengths <1050 angstrom, where the broad absorption lines of the Lyman series effectively block the WD photospheric flux. We performed FUV observations (950-1240 angstrom) with the Hubble Space Telescope/Cosmic Origins Spectrograph and used archival optical spectra. We compared them with non-local thermodynamic equilibrium model spectra. In addition, we investigate the Ca II infrared tri...

  5. Detection of polychlorinated biphenyls in transformer oils in Vietnam by multiphoton ionization mass spectrometry using a far-ultraviolet femtosecond laser as an ionization source.

    Science.gov (United States)

    Vu, Thi Thuy Duong; Vu, Duong; Nghiem, Thi Ha Lien; Imasaka, Tomoko; Tang, Yuanyuan; Shibuta, Shinpei; Hamachi, Akifumi; Do, Quang Hoa; Imasaka, Totaro

    2016-03-01

    Polychlorinated biphenyls (PCBs) in transformer and food oils were measured using gas chromatography combined with multiphoton ionization mass spectroscopy. An ultrashort laser pulse emitting in the far-ultraviolet region was utilized for efficient ionization of the analytes. Numerous signal peaks were clearly observed for a standard sample mixture of PCBs when the third and fourth harmonic emissions (267 and 200nm) of a femtosecond Ti:sapphire laser (800nm) were employed. The signal intensities were found to be greater when measured at 200nm compared with those measured at 267nm, providing lower detection limits especially for highly chlorinated PCBs at shorter wavelengths. After simple pretreatment using disposable columns, PCB congeners were measured and found to be present in the transformer oils used in Vietnam.

  6. The far-ultraviolet spectra of two hot PG 1159 stars

    Science.gov (United States)

    Werner, K.; Rauch, T.; Kruk, J. W.

    2016-09-01

    PG 1159 stars are hot, hydrogen-deficient (pre-) white dwarfs with atmospheres mainly composed of helium, carbon, and oxygen. The unusual surface chemistry is the result of a late helium-shell flash. Observed element abundances enable us to test stellar evolution models quantitatively with respect to their nucleosynthesis products formed near the helium-burning shell of the progenitor asymptotic giant branch stars. Because of the high effective temperatures (Teff), abundance determinations require ultraviolet spectroscopy and non-local thermodynamic equilibrium model atmosphere analyses. Up to now, we have presented results for the prototype of this spectral class and two cooler members (Teff in the range 85 000-140 000 K). Here we report on the results for two even hotter stars (PG 1520+525 and PG 1144+005, both with Teff = 150 000 K) which are the only two objects in this temperature-gravity region for which useful far-ultraviolet spectra are available, and revisit the prototype star. Previous results on the abundances of some species are confirmed, while results on others (Si, P, S) are revised. In particular, a solar abundance of sulphur is measured in contrast to earlier claims of a strong S deficiency that contradicted stellar evolution models. For the first time, we assess the abundances of Na, Al, and Cl with newly constructed non-LTE model atoms. Besides the main constituents (He, C, O), we determine the abundances (or upper limits) of N, F, Ne, Na, Al, Si, P, S, Cl, Ar, and Fe. Generally, good agreement with stellar models is found.

  7. AN ONLINE CATALOG OF CATACLYSMIC VARIABLE SPECTRA FROM THE FAR-ULTRAVIOLET SPECTROSCOPIC EXPLORER

    Energy Technology Data Exchange (ETDEWEB)

    Godon, Patrick; Sion, Edward M. [Astronomy and Astrophysics, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085 (United States); Levay, Karen [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Linnell, Albert P.; Szkody, Paula [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); Barrett, Paul E. [United States Naval Observatory, Washington, DC 20392 (United States); Hubeny, Ivan [Steward Observatory and Department of Astronomy and Astrophysics, University of Arizona, Tucson, AZ 85721 (United States); Blair, William P., E-mail: patrick.godon@villanova.edu, E-mail: edward.sion@villanova.edu, E-mail: klevay@stsci.edu, E-mail: linnell@astro.washington.edu, E-mail: szkody@astro.washington.edu, E-mail: barrett.paul@usno.navy.mil, E-mail: hubeny@as.arizona.edu, E-mail: wpb@pha.jhu.edu [Henry A. Rowland Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218 (United States)

    2012-12-15

    We present an online catalog containing spectra and supporting information for cataclysmic variables that have been observed with the Far-Ultraviolet Spectroscopic Explorer (FUSE). For each object in the catalog we list some of the basic system parameters such as (R.A., decl.), period, inclination, and white dwarf mass, as well as information on the available FUSE spectra: data ID, observation date and time, and exposure time. In addition, we provide parameters needed for the analysis of the FUSE spectra such as the reddening E(B - V), distance, and state (high, low, intermediate) of the system at the time it was observed. For some of these spectra we have carried out model fits to the continuum with synthetic stellar and/or disk spectra using the codes TLUSTY and SYNSPEC. We provide the parameters obtained from these model fits; this includes the white dwarf temperature, gravity, projected rotational velocity, and elemental abundances of C, Si, S, and N, together with the disk mass accretion rate, the resulting inclination, and model-derived distance (when unknown). For each object one or more figures are provided (as gif files) with line identification and model fit(s) when available. The FUSE spectra and the synthetic spectra are directly available for download as ASCII tables. References are provided for each object, as well as for the model fits. In this article we present 36 objects, and additional ones will be added to the online catalog in the future. In addition to cataclysmic variables, we also include a few related objects, such as a wind-accreting white dwarf, a pre-cataclysmic variable, and some symbiotics.

  8. Different evolutionary stages in massive star formation. Centimeter continuum and H2O maser emission with ATCA

    CERN Document Server

    Sanchez-Monge, A; Cesaroni, R; Fontani, F; Brand, J; Molinari, S; Testi, L; Burton, M

    2012-01-01

    We present ATCA observations of the H2O maser line and radio continuum at 18.0GHz and 22.8GHz, toward a sample of 192 massive star forming regions containing several clumps already imaged at 1.2mm. The main aim of this study is to investigate the water maser and centimeter continuum emission (likely tracing thermal free-free emission) in sources at different evolutionary stages, using the evolutionary classifications proposed by Palla et al (1991) and Molinari et al (2008). We used the recently comissioned CABB backend at ATCA obtaining images with 20arcsec resolution in the 1.3cm continuum and H2O maser emission, in all targets. For the evolutionary analysis of the sources we used the millimeter continuum emission from Beltran et al (2006) and the infrared emission from the MSX Point Source Catalogue. We detect centimeter continuum emission in 88% of the observed fields with a typical rms noise level of 0.45mJy/beam. Most of the fields show a single radio continuum source, while in 20% of them we identify mu...

  9. Molecular hydrogen (H2) emissions and their isotopic signatures (H/D) from a motor vehicle : implications on atmospheric H2

    NARCIS (Netherlands)

    Vollmer, M.K.; Walter, S.; Bond, S.W.; Soltic, P.; Röckmann, T.

    2010-01-01

    Molecular hydrogen (H2), its isotopic signature (deuterium/hydrogen, δD), carbon monoxide (CO) and other compounds were studied in the exhaust of a passenger car engine fuelled with gasoline or methane and run under variable air-fuel ratios and operating modes. H2 and CO concentrations were largely

  10. Molecular hydrogen (H2) emissions and their isotopic signatures (H/D) from a motor vehicle : implications on atmospheric H2

    NARCIS (Netherlands)

    Vollmer, M.K.; Walter, S.; Bond, S.W.; Soltic, P.; Röckmann, T.

    2010-01-01

    Molecular hydrogen (H2), its isotopic signature (deuterium/hydrogen, δD), carbon monoxide (CO) and other compounds were studied in the exhaust of a passenger car engine fuelled with gasoline or methane and run under variable air-fuel ratios and operating modes. H2 and CO concentrations were largely

  11. Far Ultraviolet Refractive Index of Optical Materials for Solar Blind Channel (SBC) Filters for HST Advanced Camera for Surveys

    Science.gov (United States)

    Leviton, Douglas B.; Madison, Timothy J.; Petrone, Peter

    1998-01-01

    Refractive index measurements using the minimum deviation method have been carried out for prisms of a variety of far ultraviolet optical materials used in the manufacture of Solar Blind Channel (SBC) filters for the HST Advanced Camera for Surveys (ACS). Some of the materials measured are gaining popularity in a variety of high technology applications including high power excimer lasers and advanced microlithography optics operating in a wavelength region where high quality knowledge of optical material properties is sparse. Our measurements are of unusually high accuracy and precision for this wavelength region owing to advanced instrumentation in the large vacuum chamber of the Diffraction Grating Evaluation Facility (DGEF) at Goddard Space Flight Center (GSFC). Index values for CaF2, BaF2, LiF, and far ultraviolet grades of synthetic sapphire and synthetic fused silica are reported and compared with values from the literature.

  12. Far Ultraviolet Refractive Index of Optical Materials for Solar Blind Channel (SBC) Filters for HST Advanced Camera for Surveys

    Science.gov (United States)

    Leviton, Douglas B.; Madison, Timothy J.; Petrone, Peter

    1998-01-01

    Refractive index measurements using the minimum deviation method have been carried out for prisms of a variety of far ultraviolet optical materials used in the manufacture of Solar Blind Channel (SBC) filters for the HST Advanced Camera for Surveys (ACS). Some of the materials measured are gaining popularity in a variety of high technology applications including high power excimer lasers and advanced microlithography optics operating in a wavelength region where high quality knowledge of optical material properties is sparse. Our measurements are of unusually high accuracy and precision for this wavelength region owing to advanced instrumentation in the large vacuum chamber of the Diffraction Grating Evaluation Facility (DGEF) at Goddard Space Flight Center (GSFC). Index values for CaF2, BaF2, LiF, and far ultraviolet grades of synthetic sapphire and synthetic fused silica are reported and compared with values from the literature.

  13. Far-Ultraviolet Surveys of Globular Clusters: Searching for the Products of Stellar Collisions and Near Misses

    CERN Document Server

    Knigge, C; Shara, M M; Long, K S; Gilliland, R L; Charles, P A

    2004-01-01

    Far-ultraviolet (FUV) observations with the Hubble Space Telescope are an excellent way to find and study the hot, blue stellar populations in the cores of globular clusters. These populations include dynamically-formed blue stragglers and interacting binaries (such as cataclysmic variables), i.e. the products of stellar collisions and near misses. Using the cluster 47 Tuc as an example, we show how the combination of FUV imaging and slitless spectroscopy can be used to uncover and study these populations.

  14. H2S and CO2 emissions from Cerro Prieto geothermal power plant, Mexico

    Science.gov (United States)

    Peralta, Oscar; Franco, Luis; Castro, Telma; Taran, Yuri; Bernard, Ruben; Inguaggiato, Salvatore; Navarro, Rafael; Saavedra, Isabel

    2014-05-01

    Cerro Prieto geothermal power plant has an operation capacity of 570 MW distributed in four powerhouses being the largest geothermal plant in Mexico. The geothermal field has 149 production wells. It is located in Cerro Prieto, Baja California, 30 km to the south of the Mexico-US border. Two sampling campaigns were performed in December 2012 and May 2013 where geothermal fluids from 46 production wells and 10 venting stacks were obtained and analyzed by gas chromatography coupled to mass spectrometry. Average CO2 and H2S composition of samples from venting stacks were 49.4% and 4.79%, respectively. Based on the chemical composition of samples, the geothermal power plant emits every day from venting stacks 869 tons of CO2, plus 68 tons of H2S, among other non-condensable gases.

  15. The use of Ks band photometric excesses to Investigate H2 emission in planetary nebulae

    Directory of Open Access Journals (Sweden)

    G. Ramos-Larios

    2006-01-01

    Full Text Available Se ha determinado la distribución de emisión H2 en 14 (NP`s, usando imágenes y fotometría publicadas en el catálogo infrarrojo de 2MASS. Esta técnica es aplicable solo bajo ciertas condiciones y requiere fonometría precisa, así como un exacto registro espacial entre las imágenes de banda KS y H. Es, además, sólo aplicable para algunas fuentes, y excluye flujos en los cuales, la estrella central y el exceso de polvo caliente son apreciables. Los resultados para NGC 3132, NGC 6720, IC 4406 y M 2_9 son muy similares a imágenes previas de banda angosta, y confirman que la emisión H2 está confinada a una envoltura delgada muy fragmentada. Se obtienen resultados similares para M 1-7, M 1-8 y M 3-5. Los perfiles espaciales también confirman que la emisión se extiende fuera de las cáscaras ionizadas primarias. Cuando las cáscaras son mayores y las NP`s son más evolucionadas, entonces las extensiones fraccionales O=O parecen ser más pequeñas. También son similares a los anchos radiales predichos para los perfiles de abundancias de H2, y a los valores R/R determinados a través de modelación magnetohidrodinámica de choques. Finalmente, parece haber evidencia para una evolución en este parámetro, tal que O/O varía con el incremento de la medida de la envoltura d(H como O/O d(H_2:2.

  16. Warm H2O and OH disk emission in V1331 Cyg

    CERN Document Server

    Doppmann, Greg W; Carr, John S; Graham, James R

    2011-01-01

    We present high resolution (R=24,000) L-band spectra of the young intermediate mass star V1331 Cyg obtained with NIRSPEC on the Keck II telescope. The spectra show strong, rich emission from water and OH that likely arises from the warm surface region of the circumstellar disk. We explore the use of the new BT2 (Barber et al. 2006) water line list in fitting the spectra, and we find that it does a much better job than the well-known HITRAN (Rothman et al. 1998) water line list in the observed wavelength range and for the warm temperatures probed by our data. By comparing the observed spectra with synthetic disk emission models, we find that the water and OH emission lines have similar widths (FWHM ~ 18 km s-1). If the line widths are set by disk rotation, the OH and water emission lines probe a similar range of disk radii in this source. The water and OH emission are consistent with thermal emission for both components at a temperature ~ 1500 K. The column densities of the emitting water and OH are large, ~ 1...

  17. Diffuse H_{2} emission: a useful geochemical tool to monitor the volcanic activity at El Hierro volcano system

    Science.gov (United States)

    Pérez, Nemesio M.; Melián, Gladys; González-Santana, Judit; Barrancos, José; Padilla, Germán; Rodríguez, Fátima; Padrón, Eleazar; Hernández, Pedro A.

    2016-04-01

    The occurrence of interfering processes affecting reactive gases as CO2 during its ascent from magmatic bodies or hydrothermal systems toward the surface environment hinders the interpretation of their enrichments in the soil atmosphere and fluxes for volcano monitoring purposes (Marini and Gambardella, 2005). These processes include gas scrubbing by ground-waters and interaction with rocks, decarbonatation processes, biogenic production, etc. Within the rest of the soil gases, particularly interest has been addressed to light and highly mobile gases. They offer important advantages for the detection of vertical permeability structures, because their interaction with the surrounding rocks or fluids during the ascent toward the surface is minimum. H2 is one of the most abundant trace species in volcano-hydrothermal systems and is a key participant in many redox reactions occurring in the hydrothermal reservoir gas (Giggenbach, 1987). Although H2 can be produced in soils by N2-fixing and fertilizing bacteria, soils are considered nowadays as sinks of molecular hydrogen (Smith-Downey et al., 2006). Because of its chemical and physical characteristics, H2 generated within the crust moves rapidly and escapes to the atmosphere. These characteristics make H2 one of the best geochemical indicators of magmatic and geothermal activity at depth. El Hierro is the youngest and the SW-most of the Canary Islands and the scenario of the last volcanic eruption of the archipelago, a submarine eruption that took place 2 km off the southern coast of the island from October 2011 to March 2012. Since at El Hierro Island there are not any surface geothermal manifestations (fumaroles, etc), we have focused our studies on soil degassing surveys. Here we show the results of soil H2 emission surveys that have been carried out regularly since mid-2012. Soil gas samples were collected in ˜600 sites selected based on their accessibility and geological criteria. Soil gases were sampled at ˜40

  18. Partial covering of emission regions of Q 0528-250 by intervening H$_2$ clouds

    CERN Document Server

    Klimenko, V V; Ivanchik, A V; Ledoux, C; Noterdaeme, P; Petitjean, P; Srianand, R; Varshalovich, D A

    2015-01-01

    We present an analysis of the molecular hydrogen absorption system at z$_{\\rm abs}$ = 2.811 in the spectrum of the blazar Q0528-250. We demonstrate that the molecular cloud does not cover the background source completely. The partial coverage reveals itself as a residual flux in the bottom of saturated H_2 absorption lines. This amounts to about (2.22$\\pm$0.54)% of the continuum and does not depend on the wavelength. This value is small and it explains why this effect has not been detected in previous studies of this quasar spectrum. However, it is robustly detected and significantly higher than the zero flux level in the bottom of saturated lines of the Ly-alpha forest, (-0.21$\\pm$0.22)%. The presence of the residual flux could be caused by unresolved quasar multicomponents, by light scattered by dust, and/or by jet-cloud interaction. The H$_2$ absorption system is very well described by a two-component model without inclusion of additional components when we take partial coverage into account. The derived t...

  19. A Low-Mass H2 Component to the AU Microscopii Circumstellar Disk

    CERN Document Server

    France, Kevin; Lupu, Roxana E; Redfield, Seth; Feldman, Paul D

    2007-01-01

    We present a determination of the molecular gas mass in the AU Microscopii circumstellar disk. Direct detection of a gas component to the AU Mic disk has proven elusive, with upper limits derived from ultraviolet absorption line and submillimeter CO emission studies. Fluorescent emission lines of H2, pumped by the OVI 1032 resonance line through the C-X (1 -- 1) Q(3) 1031.87 \\AA\\ transition, are detected by the Far Ultraviolet Spectroscopic Explorer. These lines are used to derive the H2 column density associated with the AU Mic system. The derived column density is in the range N(H2) = 1.9 x 10^{17} - 2.8 x 10^{15} cm^{-2}, roughly two orders of magnitude lower than the upper limit inferred from absorption line studies. This range of column densities reflects the range of H2 excitation temperature consistent with the observations, T(H2) = 800 -- 2000 K, derived from the presence of emission lines excited by OVI in the absence of those excited by LyA. Within the observational uncertainties, the data are consi...

  20. Laboratory studies of UV emissions of H2 by electron impact - The Werner- and Lyman-band systems

    Science.gov (United States)

    Ajello, J. M.; Srivastava, S. K.; Yung, Y. L.

    1982-01-01

    The vacuum ultraviolet electron-impact-induced fluorescence emissions of H2 were studied for the Lyman and Werner band systems in the range of 120-170 nm, using an optical system containing a photomultiplier and a spectrometer, over an energy range from threshold to 400 eV. The emission cross sections for the Lyman and Werner transitions at 100 eV are determined. The cross-section ratio is in excellent agreement with theoretical calculations and experimental data for the optical oscillator strengths. The cross-section for cascading to the B state is stated as a percentage of the total emission cross section at both 100 and 300 eV, increasing substantially at 20 eV. The vibrational population distribution of the B state is found to be a function of electron-impact energy as the importance of cascading relative to direct excitation changes with electron-impact energy.

  1. Molecular hydrogen (H2 combustion emissions and their isotope (D/H signatures from domestic heaters, diesel vehicle engines, waste incinerator plants, and biomass burning

    Directory of Open Access Journals (Sweden)

    T. Röckmann

    2012-03-01

    Full Text Available Molecular hydrogen (H2, its stable isotope signature (δD, and the key combustion parameters carbon monoxide (CO, carbon dioxide (CO2, and methane (CH4 were measured from various combustion processes. H2 in the exhaust of gas and oil-fired heaters and of waste incinerator plants was generally depleted compared to ambient intake air, while CO was significantly elevated. These findings contradict the often assumed co-occurring net H2 and CO emissions in combustion processes and suggest that previous H2 emissions from combustion may have been overestimated when scaled to CO emissions. For the heater exhausts, H2 and δD generally decrease with increasing fuel-to-air ratio, from ambient values of ∼0.5 ppm and +130‰ to 0.2 ppm and −206‰, respectively. These results are interpreted as a combination of an isotopically light H2 source from fossil fuel combustion and a D/H kinetic isotope fractionation of hydrogen in the advected ambient air during its partial removal during combustion. Diesel exhaust measurements from dynamometer test stand driving cycles show elevated H2 and CO emissions during cold-start and some acceleration phases. Their molar H2/CO ratios are 2/CO emission ratios, along with CO global emission inventories, we estimate global H2 emissions for 2000, 2005, and 2010. For road transportation (gasoline and diesel, we calculate 8.6 ± 2.1 Tg, 6.3 ± 1.5 Tg, and 4.1 ± 1.0 Tg, respectively, whereas the contribution from diesel vehicles has increased from 5% to 8% over this time. Other fossil fuel emissions are believed to be negligible but H2 emissions from coal combustion are unknown. For residential (domestic emissions, which are likely dominated by biofuel combustion, emissions for the same years are estimated at 2.7 ± 0.7 Tg, 2.8 ± 0.7 Tg, and 3.0 ± 0.8 Tg, respectively. Our wood combustion measurements are combined with results from the literature to calculate biomass burning emissions. For these estimates, we propose a

  2. The 2.4 micron spectrum of Comet Halley - A search for H2 emission

    Science.gov (United States)

    Smith, W. Hayden; Wolstencroft, Ramon D.; Lutz, Barry L.

    1989-01-01

    A 2.4-micron spectrum of Comet Halley was obtained on April 1, 1986 with the UKIRT scanning Fabry-Perot-CVF equipped with an InSb detector. From the ratio of the measured flux from comet Halley to Zeta Her in the 8.8 x 10 to the -4th micron bandwidth, Comet Halley produced a detected flux of about 1.3 x 10 to the 5th photons/sec with a 1-sigma variance of 385 photons. The flux detected in the same spectral region by Maillard et al. (1986) agrees with the measurements reported here to within a factor of two. The data obtained are examined from the standpoint of the possible mechanisms of H2 production.

  3. Advances in far-ultraviolet reflective and transmissive coatings for space applications

    Science.gov (United States)

    Rodríguez-de Marcos, Luis; Aznárez, José A.; Méndez, José A.; Larruquert, Juan I.; Vidal-Dasilva, M.; Malvezzi, A. Marco; Giglia, Angelo; Capobianco, Gerardo; Massone, Giuseppe; Fineschi, Silvano; Nannarone, Stefano

    2016-07-01

    Exploitation of far ultraviolet (FUV, 100-200 nm) observations extends to most areas of modern astronomy, from detailed observations of Solar System objects, the interstellar medium, exoplanets, stars and galaxies, to studies of crucial cosmological relevance. Despite several developments in recent decades, yet many observations are not possible due to technical limitations, of which one of the most important is the lack of optical coatings with high throughput. Development and optimization of such efficient FUV coatings have been identified in several roadmap reports as a key goal for future missions. The success of this development will ultimately improve the performance of nowadays feasible optical instruments and will enable new scientific imaging capabilities. GOLD's research is devoted to developing novel coatings with enhanced performance for space optics. Several deposition systems are available for the deposition of multilayer coatings. A deposition system was developed to deposit FUV coatings to satisfy space requirements. It consists of a 75-cm-diameter deposition chamber pumped with a cryo-pump and placed in an ISO-6 clean room. This chamber is available for deposition by evaporation of top-requirement coatings such as Al/ MgF2 mirrors or (Al/MgF2)n multilayer coatings for transmittance filters. A plan to add an Ion-Beam-Sputtering system in this chamber is under way. In this and other chambers at GOLD the following FUV coatings can be prepared: Transmittance filters based on (Al/MgF2)n multilayer coatings. These filters can be designed to have a peak at the FUV spectral line or band of interest and a high peak-to-visible transmittance ratio. Filters can be designed with a peak transmittance at a wavelength as short as 120 nm and with a transmittance in the visible smaller than 10-5. Narrowband reflective coatings peaked close to H Lyman β (102.6 nm) with a reflectance at H Lyman α (121.6 nm) two orders of magnitude below the one at 102.6 nm. Other

  4. Online diagnosis of electron excitation temperature in CH4+H2 discharge plasma at atmospheric pressure by optical emission spectra

    Institute of Scientific and Technical Information of China (English)

    CUI JinHua; XU ZhenFeng; ZHANG JiaLiang; NIE QiuYue; XU GenHui; REN LongLiang

    2008-01-01

    Methane coupling under low temperature plasmas at atmospheric pressure is a green process by use of renewable sources of energy.In this study,CH4+H2 dis-charge plasma was on-line diagnosed by optical emission spectra so as to char-acterize the discharge system and to do spade work for the optimization of the technical parameters for future commercial production of methane coupling under plasmas.The study was focused on a calculation method for the online diagnosis of the electron excitation temperature in CH4+H2 discharge plasma at atmospheric pressure.The diagnostic method is easy,efficient and fairly precise.A serious er-ror in a literature was corrected during the reasoning of its series of equations formerly used to calculate electron temperatures in plasmas.

  5. Online diagnosis of electron excitation temperature in CH4+H2 discharge plasma at atmospheric pressure by optical emission spectra

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Methane coupling under low temperature plasmas at atmospheric pressure is a green process by use of renewable sources of energy. In this study, CH4+H2 dis- charge plasma was on-line diagnosed by optical emission spectra so as to char- acterize the discharge system and to do spade work for the optimization of the technical parameters for future commercial production of methane coupling under plasmas. The study was focused on a calculation method for the online diagnosis of the electron excitation temperature in CH4+H2 discharge plasma at atmospheric pressure. The diagnostic method is easy, efficient and fairly precise. A serious er- ror in a literature was corrected during the reasoning of its series of equations formerly used to calculate electron temperatures in plasmas.

  6. An IUE Atlas of Pre-Main-Sequence Stars. II. Far-Ultraviolet Accretion Diagnostics in T Tauri Stars

    Science.gov (United States)

    Johns-Krull, Christopher M.; Valenti, Jeff A.; Linsky, Jeffrey L.

    2000-08-01

    We use our ultraviolet (UV) atlas of pre-main-sequence stars constructed from all useful, short-wavelength, low-resolution spectra in the International Ultraviolet Explorer (IUE) satellite Final Archive to analyze the short-wavelength UV properties of 49 T Tauri stars (TTSs). We compare the line and continuum fluxes in these TTSs with each other and with previously published parameters of these systems, including rotation rate, infrared excess, and mass accretion rate. The short-wavelength continuum in the classical TTSs (CTTSs) appears to originate in a ~10,000 K optically thick plasma, while in the naked TTSs (NTTSs-stars without dusty disks) the continuum appears to originate in the stellar atmosphere. We show that all of the TTSs in our sample lie in the regime of ``saturated'' magnetic activity due to their small Rossby numbers. However, while some of the TTSs show emission line surface fluxes consistent with this saturation level, many CTTSs show significantly stronger emission than predicted by saturation. In these stars, the emission line luminosity in the high ionization lines present in the spectrum between 1200 and 2000 Å correlates well with the mass accretion rate. Therefore, we conclude that the bulk of the short-wavelength emission seen in CTTSs results from accretion related processes and not from dynamo-driven magnetic activity. Using CTTSs with known mass accretion rates, we calibrate the relationship between M and LC IV to derive the mass accretion rate for some CTTSs which for various reasons have never had their mass accretion rates measured. Finally, several of the CTTSs show strong emission from molecular hydrogen. While emission from H2 cannot form in gas at a temperature of ~105 K, the strength of the molecular hydrogen emission is nevertheless well correlated with all the other emissions displayed in the IUE short-wavelength bandpass. This suggests that the H2 emission is in fact fluorescent emission pumped by the emission (likely Ly

  7. Time-resolved OES of nanosecond pulsed discharges in N$_{2}$ and N$_{2}$/H$_{2}$O mixtures]{Time-resolved optical emission spectroscopy of nanosecond pulsed discharges in atmospheric pressure N$_{2}$ and N$_{2}$/H$_{2}$O mixtures

    CERN Document Server

    van der Horst, R M; van Veldhuizen, E M; Bruggeman, P J

    2014-01-01

    In this contribution, nanosecond pulsed discharges in N$_{2}$ and N$_{2}$/0.9% H$_{2}$O at atmospheric pressure (at 300 K) are studied with time-resolved imaging, optical emission spectroscopy and Rayleigh scattering. A 170 ns high voltage pulse is applied across two pin-shaped electrodes at a frequency of 1 kHz. The discharge consists of three phases: an ignition phase, a spark phase and a recombination phase. During the ignition phase the emission is mainly caused by molecular nitrogen (N$_{2}$(C-B)). In the spark and recombination phase mainly atomic nitrogen emission is observed. The emission when H$_{2}$O is added is very similar, except the small contribution of H$_{\\alpha}$ and the intensity of the molecular N$_{2}$(C-B) emission is less.

  8. The molecular H2 emission and the stellar kinematics in the nuclear region of the Sombrero galaxy

    CERN Document Server

    Menezes, R B

    2015-01-01

    We analyze the molecular H$_2$ emission and the stellar kinematics in a data cube of the nuclear region of M104, the Sombrero galaxy, obtained with NIFS on the Gemini-north telescope. After a careful subtraction of the stellar continuum, the only emission line we detected in the data cube was H$_2 \\lambda 21218$. An analysis of this emission revealed the existence of a rotating molecular torus/disk, aproximately co-planar with a dusty structure detected by us in a previous work. We interpret these two structures as being associated with the same obscuring torus/disk. The kinematic maps provided by the Penalized Pixel Fitting method revealed that the stellar kinematics in the nuclear region of M104 appears to be the result of the superposition of a "cold" rotating disk and a "hot" bulge. Using a model of a thin eccentric disk, we reproduced the main properties of the maps of the stellar radial velocity and of the stellar velocity dispersion, specially within a distance of 0.2" from the kinematic axis (in regio...

  9. FUV Irradiated Disk Atmospheres: Ly$\\alpha$ and the Origin of Hot H$_2$ Emission

    CERN Document Server

    Ádámkovics, Máté; Glassgold, Alfred E

    2015-01-01

    Protoplanetary disks are strongly irradiated by a stellar FUV spectrum that is dominated by Ly$\\alpha$ photons. We investigate the impact of stellar Ly$\\alpha$ irradiation on the terrestrial planet region of disks ($\\lesssim 1$AU) using an updated thermal-chemical model of a disk atmosphere irradiated by stellar FUV and X-rays. The radiative transfer of Ly$\\alpha$ is implemented in a simple approach that includes scattering by H I and absorption by molecules and dust. Because of their non-radial propagation path, scattered Ly$\\alpha$ photons deposit their energy deeper in the disk atmosphere than the radially propagating FUV continuum photons. We find that Ly$\\alpha$ has a significant impact on the thermal structure of the atmosphere. Photochemical heating produced by scattered Ly$\\alpha$ photons interacting with water vapor and OH leads to a layer of hot (1500 - 2500 K) molecular gas. The temperature in the layer is high enough to thermally excite the H$_2$ to vibrational levels from which they can be fluore...

  10. Control of H2S emission from swine manure using Na-nitrite and Na-molybdate.

    Science.gov (United States)

    Predicala, Bernardo; Nemati, Mehdi; Stade, Sarah; Laguë, Claude

    2008-06-15

    Biogenic production of hydrogen sulphide (H2S) in oil reservoirs (souring) has been shown to be controlled effectively using nitrite and molybdate salts. In the present work the effects of addition of nitrite and molybdate on reducing the emission of H2S from swine manure slurry was investigated in the laboratory and semi-pilot scale systems. Addition of 80 mM nitrite or 2 mM molybdate (final concentration in the manure slurry) to fresh manure in the laboratory scale closed systems (125 mL and 4 L) reduced the concentration of H2S in the headspace gas from 1500 microL L(-1) to 10 microL L(-1) which maintained during the remaining period of trials (40-60 days). With aged manure, similar results were achieved with a lower level of nitrite (10 mM). Simultaneous or sequential additions of nitrite and molybdate to fresh manure had similar effects. Contrary to the systems simulating biological conditions in oil reservoirs in which simultaneous addition of nitrite and molybdate has been reported to have a synergistic effect, no synergism was observed when nitrite and molybdate were added to the manure simultaneously. Experiments with fresh manure slurry in the semi-pilot scale systems (200 L) confirmed the effectiveness of this approach in which addition of 80 mM nitrite or 2 mM molybdate or a combination of 80 mM nitrite and 2 mM molybdate decreased the concentration of the H2S in the headspace gas from an initial value of 500 microL L(-1) to a low level in the range 2-25 microL L(-1) and maintained these low levels during the remaining period of trials (16 days). The concentration of ammonia (NH3) in the headspace gas of the treated systems was similar to that observed in the control system (untreated), indicating that the treatment did not have an effect on the level of present NH3. Although the addition of nitrite or molybdate reduced emissions of H2S from swine manure and the associated health and safety concerns, it had little impact on the intensity of odour in the

  11. Molecular hydrogen (H2) combustion emissions and their isotope (D/H) signatures from domestic heaters, diesel vehicle engines, waste incinerator plants, and biomass burning

    Science.gov (United States)

    Vollmer, M. K.; Walter, S.; Mohn, J.; Steinbacher, M.; Bond, S. W.; Röckmann, T.; Reimann, S.

    2012-07-01

    Molecular hydrogen (H2), its stable isotope signature (δD), and the key combustion parameters carbon monoxide (CO), carbon dioxide (CO2), and methane (CH4) were measured from various combustion processes. H2 in the exhaust of gas and oil-fired heaters and of waste incinerator plants was generally depleted compared to ambient intake air, while CO was significantly elevated. These findings contradict the often assumed co-occurring net H2 and CO emissions in combustion processes and suggest that previous H2 emissions from combustion may have been overestimated when scaled to CO emissions. For the gas and oil-fired heater exhausts, H2 and δD generally decrease with increasing CO2, from ambient values of ~0.5 ppm and +130‰ to 0.2 ppm and -206‰, respectively. These results are interpreted as a combination of an isotopically light H2 source from fossil fuel combustion and a D/H kinetic isotope fractionation of hydrogen in the advected ambient air during its partial removal during combustion. Diesel exhaust measurements from dynamometer test stand driving cycles show elevated H2 and CO emissions during cold-start and some acceleration phases. While H2 and CO emissions from diesel vehicles are known to be significantly less than those from gasoline vehicles (on a fuel-energy base), we find that their molar H2/CO ratios (median 0.026, interpercentile range 0.12) are also significantly less compared to gasoline vehicle exhaust. Using H2/CO emission ratios, along with CO global emission inventories, we estimate global H2 emissions for 2000, 2005, and 2010. For road transportation (gasoline and diesel), we calculate 8.3 ± 2.2 Tg, 6.0 ± 1.5 Tg, and 3.8 ± 0.94 Tg, respectively, whereas the contribution from diesel vehicles is low (0.9-1.4%). Other fossil fuel emissions are believed to be negligible but H2 emissions from coal combustion are unknown. For residential (domestic) emissions, which are likely dominated by biofuel combustion, emissions for the same years are

  12. Variations of electric resistance and H2 and Rn emissions of concrete blocks under increasing uniaxial compression

    Science.gov (United States)

    King, C.-Y.; Luo, G.

    1990-01-01

    Electric resistance and emissions of hydrogen and radon isotopes of concrete (which is somewhat similar to fault-zone materials) under increasing uniaxial compression were continuously monitored to check whether they show any pre- and post-failure changes that may correspond to similar changes reported for earthquakes. The results show that all these parameters generally begin to increase when the applied stresses reach 20% to 90% of the corresponding failure stresses, probably due to the occurrence and growth of dilatant microcracks in the specimens. The prefailure changes have different patterns for different specimens, probably because of differences in spatial and temporal distributions of the microcracks. The resistance shows large co-failure increases, and the gas emissions show large post-failure increases. The post-failure increase of radon persists longer and stays at a higher level than that of hydrogen, suggesting a difference in the emission mechanisms for these two kinds of gases. The H2 increase may be mainly due to chemical reaction at the crack surfaces while they are fresh, whereas the Rn increases may be mainly the result of the increased emanation area of such surfaces. The results suggest that monitoring of resistivity and gas emissions may be useful for predicting earthquakes and failures of concrete structures. ?? 1990 Birkha??user Verlag.

  13. A Tropospheric Emission Spectrometer HDO/H2O Retrieval Simulator for Climate Models

    Science.gov (United States)

    Field, R. D.; Risi, C.; Schmidt, G. A.; Worden, J.; Voulgarakis, A.; LeGrande, A. N.; Sobel, A. H.; Healy, R. J.

    2012-01-01

    Retrievals of the isotopic composition of water vapor from the Aura Tropospheric Emission Spectrometer (TES) have unique value in constraining moist processes in climate models. Accurate comparison between simulated and retrieved values requires that model profiles that would be poorly retrieved are excluded, and that an instrument operator be applied to the remaining profiles. Typically, this is done by sampling model output at satellite measurement points and using the quality flags and averaging kernels from individual retrievals at specific places and times. This approach is not reliable when the model meteorological conditions influencing retrieval sensitivity are different from those observed by the instrument at short time scales, which will be the case for free-running climate simulations. In this study, we describe an alternative, categorical approach to applying the instrument operator, implemented within the NASA GISS ModelE general circulation model. Retrieval quality and averaging kernel structure are predicted empirically from model conditions, rather than obtained from collocated satellite observations. This approach can be used for arbitrary model configurations, and requires no agreement between satellite-retrieved and model meteorology at short time scales. To test this approach, nudged simUlations were conducted using both the retrieval-based and categorical operators. Cloud cover, surface temperature and free-tropospheric moisture content were the most important predictors of retrieval quality and averaging kernel structure. There was good agreement between the D fields after applying the retrieval-based and more detailed categorical operators, with increases of up to 30 over the ocean and decreases of up to 40 over land relative to the raw model fields. The categorical operator performed better over the ocean than over land, and requires further refinement for use outside of the tropics. After applying the TES operator, ModelE had D biases of 8

  14. The fine structure of the solar atmosphere in the far ultraviolet

    Science.gov (United States)

    Brueckner, G. E.; Bartoe, J.-D. F.

    1974-01-01

    The paper describes qualitatively the spatial distribution of UV emission obtained from high resolution spectroheliograms in the UV emission lines He I, He II, O IV, O V, and Ne VII photographed during a sounding rocket flight. Broad band filtergrams of the far UV solar corona were also obtained. The results confirmed that spicules are the location of UV emission. Most of the UV emission in the temperature range from 100,000 to 200,000 K is concentrated in and around the spicules and this concentration decreases with increasing temperatures. Four different areas of UV emission are discussed. The He I and He II spectroheliogram observations showed He to be suppressed in the coronal holes, polar caps, and sunspots.

  15. Far-ultraviolet Observations of Comet C/2012 S1 (ISON) from FORTIS

    CERN Document Server

    McCandliss, Stephan R; Weaver, Harold; Fleming, Brian; Redwine, Keith; Li, Mary J; Kutyrev, Alexander; Moseley, S Harvey

    2016-01-01

    We have used the unique far-UV imaging capability offered by a sounding rocket borne instrument to acquire observations of C/2012 S1 (ISON) when its angular separation with respect to the sun was 26.3deg, on 2013 November 20.49. At the time of observation the comet's heliocentric distance and velocity relative to the sun were rh = 0.43 AU and rh_dot = -62.7 km s^-1. Images dominated by C I 1657 A and H I 1216 A were acquired over a 1e6 x 1e6 km^2 region. The water production rate implied by the Lyman alpha observations is constrained to be Q_H2O approximately 8e29 s^-1 while the neutral carbon production rate was Q_C approximately 4e28 s^-1. The radial profile of C I was consistent with it being a dissociation product of a parent molecule with a lifetime approximately 5e4 seconds, favoring a parent other than CO. We constrain the Q_CO production rate to 5(+1.5, -7.5)e28 s^-1 with 1sigma errors derived from photon statistics. The upper limit on the Q_CO/Q_H2O < 6%.

  16. Far-ultraviolet Observations of Comet C/2012 S1 (ISON) from FORTIS

    Science.gov (United States)

    McCandliss, Stephan R.; Feldman, Paul D.; Weaver, Harold; Fleming, Brian; Redwine, Keith; Li, Mary J.; Kutyrev, Alexander; Moseley, S. Harvey

    2016-09-01

    We have used the unique far-UV imaging capability offered by a sounding-rocket-borne instrument to acquire observations of C/2012 S1 (ISON) when its angular separation with respect to the Sun was 26.°3 on 2013 November 20.49. At the time of observation, the comet’s heliocentric distance and velocity relative to the Sun were r h = 0.43 au and {\\dot{r}}h = -62.7 km s-1. Images dominated by C i λ1657 and H i λ1216 were acquired over a 106 × 106 km2 region. The water production rate implied by the Lyα observations is constrained to be {Q}{{{H}}2{{O}}}≈ 8 × 1029 s-1 while the neutral carbon production rate was {Q}C ≈ 4 ×1028 s-1. The radial profile of C i was consistent with it being a dissociation product of a parent molecule with a lifetime τ ˜ 5 × 104 s, favoring a parent other than CO. We constrain the Q CO production rate to {5}-7.5+1.5 × 1028 s-1 with 1σ errors derived from photon statistics. The upper limit on the Q CO/{Q}{{{H}}2{{O}}} is ≲6%.

  17. Multi-frequency radiation hydrodynamics simulations of H2 line emission in primordial, star-forming clouds

    CERN Document Server

    Greif, Thomas H

    2014-01-01

    We investigate the collapse of primordial gas in a minihalo with three-dimensional radiation hydrodynamics simulations that accurately model the transfer of H2 line emission. For this purpose, we have implemented a multi-line, multi-frequency ray-tracing scheme in the moving-mesh code Arepo that is capable of adaptively refining rays based on the Healpix algorithm, as well as a hybrid equilibrium/non-equilibrium primordial chemistry solver. We find that the chemical and thermal evolution of the central gas cloud is similar to the case where an escape probability formalism with a fit to detailed one-dimensional calculations is used, with the exception that the suppression of density perturbations due to the diffusion of radiation is only present in the full radiation hydrodynamics simulations. A multi-frequency treatment of the individual H2 lines is essential, since for high optical depths the smaller cross section in the wings of the lines greatly increases the amount of energy that can escape. The influence...

  18. Far-Ultraviolet Surveys of Globular Clusters: Hunting for the Products of Stellar Collisions and Near Misses

    CERN Document Server

    Knigge, C

    2004-01-01

    Globular clusters are gravitationally bound stellar systems containing on the order of 100,000 stars. Due to the high stellar densities in the cores of these clusters, close encounters and even physical collisions between stars are inevitable. These dynamical interactions can produce exotic types of single and binary stars that are extremely rare in the galactic field, but which may be important to the dynamical evolution of their host clusters. A common feature of these dynamically-formed stellar populations is that many of their members are relatively hot, and thus bright in the far-ultraviolet (FUV) waveband. In this short review, I describe how space-based FUV observations are being used to find and study these populations.

  19. A Study of Far-Ultraviolet Extinction in the Upper Scorpius Cloud Using the SPINR Sounding Rocket Experiment

    Science.gov (United States)

    Lewis, N. K.; Cook, T. A.; Chakrabarti, S.

    2005-01-01

    In this study, six new interstellar extinction curves in the far-ultraviolet are presented using data from a sounding rocket experiment. The sounding rocket data were combined with IUE data for six lines of sight in the Upper Scorpius group to cover the wavelength range of 912-3030 Å. The extinction curves were produced using the pair comparison method with B stars of similar spectral types. Parameterizations from Fitzpatrick & Massa, Cardelli et al., and Fitzpatrick were then fitted to the derived extinction curves. From the derived extinction curves, their corresponding fits, and the dust model of Weingartner & Draine, it is concluded that the dust population in the Upper Scorpius region exhibits a larger than average grain population with a depletion of smaller grains.

  20. Laboratory, semi-pilot and room scale study of nitrite and molybdate mediated control of H(2)S emission from swine manure.

    Science.gov (United States)

    Moreno, Lyman; Predicala, Bernardo; Nemati, Mehdi

    2010-04-01

    The effects of manure age on emission of H(2)S and required level of nitrite or molybdate to control these emissions were investigated in the present work. Molybdate mediated control of H(2)S emission was also studied in semi-pilot scale open systems, and in specifically designed chambers which simulated swine production rooms. With fresh 1-, 3- and 6-month old manures average H(2)S concentration in the headspace gas of the closed systems were 4856+/-460, 3431+/-208, 1037+/-98 ppm and non-detectable, respectively. Moreover, the level of nitrite or molybdate required to control the emission of H(2)S decreased as manure age increased. In the semi-pilot scale open system and chambers, average H(2)S concentration at the surface of agitated fresh manure were 831+/-26 and 88.4+/-5.7 ppm, respectively. Furthermore, 0.1-0.25 mM molybdate was sufficient to control the emission of H(2)S. A cost study for an average size swine operation showed that the cost of treatment with molybdate was less than 1% of the overall production cost for each market hog.

  1. Far-Ultraviolet Imaging of the Field Star Population in the Large Magellanic Cloud with HST

    CERN Document Server

    Brosch, N; MacKenty, J W; Zurek, D R; McLean, B J; Brosch, Noah; Shara, Michael; Kenty, John Mac; Zurek, David; Lean, Brian Mc

    1999-01-01

    We present an analysis of the deepest pure-UV observations with the highest angular resolution ever performed, a set of 12 exposures with the HST WFPC2 and F160BW filter obtained in parallel observing mode, which cover $\\sim$12 square arcminutes in the LMC, North of the bar and in the ``general field'' regime of the LMC. The 341 independent measurements of 198 objects represent an accumulated exposure of $\\geq 2 10^4$ sec and reveal stars as faint as m$_{UV}\\simeq$22 mag. The observations show that $\\sim 2/3$ of the UV emission from the LMC is emitted by our HST-detected UV stars in the field, i.e., not in clusters or associations. We identified optical counterparts in the ROE/NRL photometric catalog for $\\sim 1/3$ of the objects. The results are used to discuss the nature of these UV sources, to estimate the diffuse UV emission from the LMC as a prototype of dwarf galaxies, and to evaluate the contamination by field stars of UV observations of globular and open clusters in the LMC. We find that the projected...

  2. Searching for H2 emission from protoplanetary disks using near- and mid-infrared high-resolution spectroscopy

    NARCIS (Netherlands)

    Carmona, A.; van den Ancker, M.E.; Henning, T.; Pavlyuchenkov, Y.; Dullemond, C.P.; Goto, M.; Fedele, D.; Stecklum, B.; Thi, W.F.; Bouwman, J.; Waters, L.B.F.M.

    2008-01-01

    The mass and dynamics of protoplanetary disks are dominated by molecular hydrogen (H2). However, observationally very little is known about the H2. In this paper, we discuss two projects aimed to constrain the properties of H2 in the disk's planet forming region (R<50AU). First, we present a

  3. The Southwest Research Institute ultraviolet reflectance chamber (SwURC): a far ultraviolet reflectometer

    Science.gov (United States)

    Winters, Gregory S.; Retherford, Kurt D.; Davis, Michael W.; Escobedo, Stephen M.; Bassett, Eric C.; Patrick, Edward L.; Nagengast, Maggie E.; Fairbanks, Matthew H.; Miles, Paul F.; Parker, Joel W.; Gladstone, G. Randall; Slater, David C.; Stern, S. Alan

    2012-10-01

    We designed and assembled a highly capable UV reflectometer chamber and data acquisition system to provide bidirectional scattering data of various surfaces and materials. This chamber was initially conceived to create laboratory-based UV reflectance measurements of water frost on lunar soil/regolith simulants, to support interpretation of UV reflectance data from the Lyman Alpha Mapping Project ("LAMP") instrument on-board the NASA Lunar Reconnaissance Orbiter spacecraft. A deuterium lamp illuminates surfaces and materials at a fixed 45° incident beam angle over the 115 to 200 nm range via a monochromator, while a photomultiplier tube detector is scanned to cover emission angles -85° to +85° (with a gap from -60° to -30°, due to the detector blocking the incident beam). Liquid nitrogen cools the material/sample mount when desired. The chamber can be configured to test a wide range of samples and materials using sample trays and holders. Test surfaces to date include aluminum mirrors, water ice, reflectance standards, and frozen mixtures of water and lunar soil/regolith stimulant. Future UV measurements planned include Apollo lunar samples, meteorite samples, other ices, minerals, and optical surfaces. Since this chamber may well be able to provide useful research data for groups outside Southwest Research Institute, we plan to take requests from and collaborate with others in the UV and surface reflection research community.

  4. A Far-Ultraviolet Spectroscopic Survey of the Globular Cluster 47 Tuc

    CERN Document Server

    Knigge, C; Zurek, D R; Long, K S; Gilliland, R L

    2000-01-01

    We present preliminary results from a FUV spectroscopic and photometric survey of the globular cluster 47 Tuc. Our main goal is to either confirm or rule out the existence of a large population of CVs in the core of this cluster. We have so far identified approximately 425 FUV sources, most of which are probably hot, young WDs. However, we have also found approximately 30 FUV sources whose position in a FUV-optical color-magnitude diagram makes them strong CV candidates. If most or all of these objects are eventually confirmed as CVs, the large CV population predicted by tidal capture theory has finally been found. Our data has also allowed us to resolve the long-standing puzzle surrounding AKO 9, a UV-bright and highly variable 1.1 day binary system in 47 Tuc. AKO 9 is the brightest FUV source in our data and presents a blue FUV spectrum with strong CIV and HeII emission lines. Its spectrum is similar to that of the long-period, DN-type field CV GK Per. Based on this similarity and other evidence, we suggest...

  5. Ex Lupi from Quiescence to Outburst: Exploring the LTE Approach in Modelling Blended H2O and OH Mid-Infrared Emission

    CERN Document Server

    Banzatti, A; Bruderer, S; Geers, V; Pascucci, I; Lahuis, F; Juhasz, A; Henning, T; Abraham, P

    2011-01-01

    We present a comparison of archival Spitzer spectra of the strongly variable T Tauri EX Lupi, observed before and during its 2008 outburst. We analyze the mid-infrared emission from gas-phase molecules thought to originate in a circumstellar disk. In quiescence the emission shows a forest of H2O lines, highly excited OH lines, and the Q branches of the organics C2H2, HCN, and CO2, similar to the emission observed toward several T Tauri systems. The outburst emission shows instead remarkable changes: H2O and OH line fluxes increase, new OH, H2, and HI transitions are detected, and organics are no longer seen. We adopt a simple model of a single-temperature slab of gas in local thermal equilibrium, a common approach for molecular analyses of Spitzer spectra, and derive the excitation temperature, column density, and emitting area of H2O and OH. We show how model results strongly depend on the selection of emission lines fitted, and that spectrally-resolved observations are essential for a correct interpretation...

  6. Resolving shocked and UV excited components of H2 emission in planetary nebulae with high-resolution near-infrared spectroscopy

    Science.gov (United States)

    Kaplan, Kyle; Dinerstein, Harriet L.; Jaffe, Daniel Thomas

    2016-06-01

    Planetary nebulae (PNe) form when low and intermediate-mass stars eject their outer layers into the ISM at the end of the AGB phase. Many PNe exhibit near-infrared (NIR) emission from molecular hydrogen (H2). This NIR emission arises from radiative decay out of excited rotation-vibration (rovibrational) states. The rovibrational states can be populated by excitation to higher electronic states through absorption of a far-UV photon followed by a radiative cascade to the electronic ground state, or by collisions (e.g., in a hot gas). The two processes populate the rovibrational levels of H2 differently, so the observed emergent emission spectrum provides an effective probe of the mechanisms that excite the H2. Many PNe display line intensity ratios that are intermediate between these two processes (Otsuka et al. 2013). With the advantages of the high spectral resolution (R~40000), broad wavelength coverage (1.45-2.45 μm), and high spatial resolution of the Immersion GRating Infrared Spectrometer (IGRINS, Park et al. 2014), we are able to differentiate components in position-velocity space: we see a slowly expanding UV-excited H2 shell in the PN M 1-11 and two faster moving “bullets” of thermalized H2 that we interpret as shocked gas from a bipolar outflow. We also present observations of several other PNe that exhibit similar morphologies of thermalized and UV-excited H2 components.

  7. Diffuse Hydrogen (H2) emissions from the summit crater of Pico do Fogo before the 2014-15 eruption, Cape Verde

    Science.gov (United States)

    Dionis, Samara; Padrón, Eleazar; Melián, Gladys V.; Asensio-Ramos, María; Fernandes, Paulo; Barrancos, José; Rodríguez, Fátima; Padilla, Germán; Calvo, David; Hernández, Pedro A.; Silva, Sónia; Cabral, Jeremias; Bandomo, Zuleyka; Pereira, José Manuel; Semedo, Helio; Pérez, Nemesio M.

    2015-04-01

    Pico do Fogo is an active stratovolcano rising 2,829 m above sea level, situated in Fogo Island (476 km2), Cape Verde. Pico do Fogo has a long eruptive history with about 30 eruptions since its discovery (~1500 AD). On November 23, 2014 a new volcanic eruption started at the southwestern flank of the volcano after 19 years of the last eruptive event on 1995. Diffuse hydrogen (H2) emission from the summit crater of Pico do Fogo has been regularly estimated since 2007 to improve the geochemical monitoring program for the volcano surveillance. H2 is one of the most abundant trace species in volcano-hydrothermal systems and is a key participant in many redox reactions occurring in the volcano-hydrothermal reservoir. Because of its chemical and physical characteristics, H2 moves rapidly though the crust and escapes to the atmosphere. These characteristics make H2 an excellent tracer for processes that occurs in the volcano-hydrothermal systems. The first published data on diffuse H2 degassing rate from Pico do Fogo volcano (37.3 ± 11.3 kg d-1) is related to a field work performed on February 2010 (Dionis et al., 2015). A total of seven diffuse H2 degassing surveys have been carried out during the period 2007-2014. Soil gas H2 concentration measured at 40 cm depth, allowed the computation of its emission rate in about 50 sampling sites selected in the surface environment of Pico do Fogo summit crater (0.14 km2). Both advective (convective) and diffuse components were estimated. The sampling sites were selected to cover homogeneously the study area, allowing the computation of the total H2 emission by sequential Gaussian simulation (sGs). During the study period diffuse H2 emission rate ranged between 2.9 and 163.6 kg d-1. On February 2010, it was observed the first relatively high diffuse H2 emission value which suggests the occurrence of an increase in the heat flow. However, higher observed diffuse H2 emission values than February 2010 were detected on April 2013 (75

  8. Optical emission measurements of H 2 and D 2 molecules in the divertor region of ASDEX Upgrade

    Science.gov (United States)

    Fantz, U.; Behringer, K.; Gafert, J.; Coster, D.; ASDEX Upgrade Team

    A spectroscopic method has been developed for measuring molecular influxes and particle densities in fusion edge plasmas, which is based on the H 2 and D 2 Fulcher emission bands around 600 nm wavelength. A first application to the ASDEX Upgrade divertor plasma is described. The influx of hydrogen molecules was determined from the population of the upper Fulcher state using the theoretical number of ionization and dissociation events per Fulcher photon ( Seff + Deff)/XB Ful, as calculated by a collisional-radiative model. These results were compared with expectations on the basis of the atomic hydrogen fluxes and a typical molecule/atom ratio. Measurements and calculations agree in their time dependence, but the experimental values are somewhat lower, which may be within the error margin or of more significance. The Fulcher radiation was also compared directly to B2-EIRENE predictions, resulting in a higher discrepancy. In addition, the vibrational population of the ground state molecules was determined from that of the excited state using a method based on Franck-Condon factors. It can be characterized by a Tvib between 3000 and 9000 K, inversely correlated with electron temperature. This variation is predicted by the collisional-radiative code and even allows an estimate of Te. Vibrational excitation increases ionization and dissociation rate coefficients, as clearly demonstrated by the code calculations. It is therefore very likely that the observed discrepancy in molecular intensity is mainly caused by the omission of vibrational excitation in the present version of B2-EIRENE. The described flux measurements are expected to be accurate above Te=5 eV, but are more difficult at lower temperatures due to the strong Te dependence of ( Seff + Deff)/XB Ful in that region.

  9. The far-ultraviolet dust albedo in the Upper Scorpius subgroup of the Scorpius OB2 association

    Science.gov (United States)

    Gordon, Karl D.; Witt, Adolf N.; Carruthers, George R.; Christensen, Susan A.; Dohne, Brian C.

    1994-01-01

    During NRL's Far Ultraviolet Cameras experiemnt on STS-39, four images of the giant reflection nebula encompassing the Upper Scorpius subgroup of the Sco OB2 association were obtained in two ultraviolet bandpasses with lambda(sub eff) = 1362 A and 1769 A. From these images and IUE and TD-1 stellar spectra, the ratio of nebular to stellar flux was calculated. The ratio ranged from 0.577 to 0.921 at 1362 A and 0.681 to 0.916 at 1769 A with the spread in the ratio arising mainly from uncertainties in the sky background. In order to analyze these images, a model utilizing Monte Carlo techniques to describe radiative transfer in a spherical nebula with asymmetrically distributed stars was developed by elaborating on previous work by Witt. This model was used to determine the range of albedos reproducing the observed nebular-to-stellar flux ratios while allowing the scattering phase function asymmetry to vary between 0.0 and 0.8. The resulting albedos were 0.47-0.70 at 1362 A and 0.55-0.72 at 1769 A.

  10. Far-Ultraviolet Imaging of the Hubble Deep Field North: Star Formation in Normal Galaxies at z<1

    CERN Document Server

    Teplitz, H I; Brown, T M; Chary, R; Colbert, J W; Conselice, C J; De Mello, D F; Dickinson, M; Ferguson, H C; Gardner, J P; Menanteau, F; Gardner, Jonathan P.

    2006-01-01

    We present far-ultraviolet (FUV) imaging of the Hubble Deep Field North (HDF-N) taken with the Solar Blind Channel of the Advanced Camera for Surveys (ACS/SBC) and the FUV MAMA detector of the Space Telescope Imaging Spectrograph (STIS) onboard the Hubble Space Telescope. The full WFPC2 deep field has been observed at 1600 Angstroms. We detect 134 galaxies and one star down to a limit of FUV_{AB} ~ 29. All sources have counterparts in the WFPC2 image. Redshifts (spectroscopic or photometric) for the detected sources are in the range 0

  11. Taming the Invisible Monster: System Parameter Constraints for Epsilon Aurigae from the Far-Ultraviolet to the Mid-Infrared

    CERN Document Server

    Hoard, D W; Stencel, R E

    2010-01-01

    We have assembled new Spitzer Space Telescope Infrared Array Camera observations of the mysterious binary star Epsilon Aurigae, along with archival far-ultraviolet to mid-infrared data, to form an unprecedented spectral energy distribution spanning three orders of magnitude in wavelength from 0.1 microns to 100 microns. The observed spectral energy distribution can be reproduced using a three component model consisting of a 2.2+0.9/-0.8 Msun F type post-asymptotic giant branch star, and a 5.9+/-0.8 Msun B5+/-1 type main sequence star that is surrounded by a geometrically thick, but partially transparent, disk of gas and dust. At the nominal HIPPARCOS parallax distance of 625 pc, the model normalization yields a radius of 135+/-5 Rsun for the F star, consistent with published interferometric observations. The dusty disk is constrained to be viewed at an inclination of i > 87 deg, and has effective temperature of 550+/-50 K with an outer radius of 3.8 AU and a thickness of 0.95 AU. The dust content of the disk ...

  12. Far-ultraviolet and X-ray irradiated protoplanetary disks : a grid of models II. Gas diagnostic line emission

    NARCIS (Netherlands)

    Aresu, G.; Meijerink, R.; Kamp, I.; Spaans, M.; Thi, W. -F.; Woitke, P.

    2012-01-01

    Context. Most of the mass in protoplanetary disks is in the form of gas. The study of the gas and its diagnostics is of fundamental importance in order to achieve a detailed description of the thermal and chemical structure of the disk. Both radiation from the central star (from optical to X-ray wav

  13. Far-ultraviolet and X-ray irradiated protoplanetary disks: a grid of models. II. Gas diagnostic line emission

    NARCIS (Netherlands)

    Aresu, G.; Meijerink, R.; Kamp, I.; Spaans, M.; Thi, W.-F.; Woitke, P.

    2012-01-01

    Context. Most of the mass in protoplanetary disks is in the form of gas. The study of the gas and its diagnostics is of fundamental importance in order to achieve a detailed description of the thermal and chemical structure of the disk. Both radiation from the central star (from optical to X-ray wav

  14. Far-ultraviolet and X-ray irradiated protoplanetary disks: a grid of models : II. Gas diagnostic line emission

    NARCIS (Netherlands)

    Aresu, G.; Meijerink, R.; Kamp, I.; Spaans, M.; Thi, W. -F; Woitke, P.

    2012-01-01

    Context. Most of the mass in protoplanetary disks is in the form of gas. The study of the gas and its diagnostics is of fundamental importance in order to achieve a detailed description of the thermal and chemical structure of the disk. Both radiation from the central star (from optical to X-ray wav

  15. Far ultraviolet auroral imager

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Reviewing the technology development of imaging the global FUV auroral morphology,we introduce a space-based FUV auroral imager prototype developed by the Center for Space Science and Applied Research(CSSAR).It is designed to obtain continuous observations on the temporal and spatial morphology of the aurora which occupies highly elliptical high-altitude near-polar orbits.Primarily composed of a telescope system,image intensifier system,CCD,and collection and control system,the instrument works in the spectral region from 140―190 nm in the field of view 25°×25°,and the spatial resolution is better than 0.1°.

  16. Far ultraviolet auroral imager

    Institute of Scientific and Technical Information of China (English)

    FU LiPing; WANG YongMei; WANG YingJian; ZHANG ZhongMou; LU JianGong

    2009-01-01

    Reviewing the technology development of imaging the global FUV auroral morphology,we introduce a space-based FUV auroral imager prototype developed by the Center for Space Science and Applied Research(CSSAR).It is designed to obtain continuous observations on the temporal and spatial morphology of the aurora which occupies highly elliptical high-altitude near-polar orbits.Primarily composed of a telescope system,image intensifier system,CCD,and collection and control system,the instrument works in the spectral region from 140-190 nm in the field of view 25°×25°,and the spatial resolution is better than 0.1°.

  17. Comparison of Global Cerebral Blood Flow Measured by Phase-Contrast Mapping MRI with O-15-H2O Positron Emission Tomography

    DEFF Research Database (Denmark)

    Vestergaard, Mark Bitsch; Lindberg, Ulrich; Aachmann-Andersen, Niels Jacob

    2017-01-01

    Purpose To compare mean global cerebral blood flow (CBF) measured by phase-contrast mapping magnetic resonance imaging (PCM MRI) and by 15O-H2O positron emission tomography (PET) in healthy subjects. PCM MRI is increasingly being used to measure mean global CBF, but has not been validated in vivo...

  18. Elucidating electronic transitions from σ orbitals of liquid n- and branched alkanes by far-ultraviolet spectroscopy and quantum chemical calculations.

    Science.gov (United States)

    Morisawa, Yusuke; Tachibana, Shin; Ehara, Masahiro; Ozaki, Yukihiro

    2012-12-01

    Attenuated total reflection far-ultraviolet (ATR-FUV) spectra containing Rydberg states of n-alkanes (C(m)H(2m+2); m varies in the range 5-9) and branched alkanes observed in the liquid phase were investigated by quantum chemical calculations with the aim of elucidating electronic transitions from σ orbitals of liquid n- and branched alkanes. New assignments are proposed based on the time-dependent density functional theory (TD-DFT) and symmetry-adapted cluster configuration interaction (SAC-CI) calculations, and the differences in these spectra are analyzed in detail. The FUV spectra of n-alkanes show a broad asymmetric feature near 8.3 eV. The strong band at ∼8.3 eV shows a red shift with a significant increase in intensity as the carbon chain length increases, which is attributed to the overlapping transitions from the third (or fourth) highest occupied molecular orbitals HOMO-2 (or HOMO-3) and HOMO-1 to Rydberg 3p(y) by the TD-DFT and SAC-CI calculations. This band was previously assigned to the overlap of two peaks arising from the transition from the HOMO to 3p and from the HOMO-1 to 3s based on their term values. Although the most intense transition, T1, is from HOMO-2 for m = 5 and 6 and HOMO-3 for m varying in the range of 7-9, the shape of Kohn-Sham molecular orbital for T1 is similar among the all-alkanes investigated. The theoretical result also has demonstrated that the red shift originates in both stabilization of the Rydberg 3p(y) and destabilization of the occupied orbitals. The intensity of the shoulder at 7.7 eV drastically increases in the spectra of the branched alkanes, especially for those with quaternary carbon atoms such as 2,2-dimethyl butane. This increase in intensity is caused by a reduction in symmetry in the branched alkanes, which leads the forbidden transitions to Rydberg 3s to allowed transitions. In this way, the present study has provided new insight into the existence of their Rydberg transitions and the shape of the relevant

  19. Airborne Measurement of CO2, SO2, and H2S Emission Rates During the 2004-2005 Eruption of Mount St. Helens

    Science.gov (United States)

    Doukas, M. P.; McGee, K. A.; Gerlach, T. M.

    2005-12-01

    Volcanic gas measurements by helicopter and fixed-wing aircraft began on 27 September 2004 during the initial unrest. Target gases included CO2, SO2, and H2S measured by remote (COSPEC, FLYSPEC) and extraction (LI-COR, Interscan) techniques. These measurements defined periods of negligible, wet, and dry volcanic degassing. Measurements during the period of early seismic unrest on September 2-30 showed little or no CO2 above atmospheric levels; SO2 and H2S were absent. These results suggest involvement of degassed magma, confinement of gases because of reduction in permeability since the 1980-86 dome eruptions, or almost complete gas scrubbing at high water to gas mass ratios. Following the first steam and ash explosion on October 1, a large increase in the number of fumaroles on the 1980-86 dome and frequent detection of CO2 above atmospheric levels together with more frequent detection of H2S characterized the period of wet volcanic degassing. Wet degassing of CO2 and H2S included observed emission by ejection of large bubbles through pools of water, however the few CO2 emission rates available for this period were rose, steaming increased, and rock adjacent to the invading magma dried out. These conditions enabled a buoyant plume to rise above the crater and enter higher elevation winds, facilitating airborne measurements of gas emission rates. Gas emission rates have been notably low and declined gradually throughout the eruption. Emission rates of CO2 were mostly in the 500-1000 t/d range until early February 2005, when they fell to 150-500 t/d and remained there. Emission rates of SO2 rose to 240 t/d during 2004 then declined and remained below 100 t/d (often CO2) and 100 t/d (SO2).

  20. New Gas Carburizing Method for Minimizing CO2 Emission by Saving Resources and Selective Removal of H2 in Furnace

    Science.gov (United States)

    Mizukoshi, Tomoyuki; Yokoyama, Yujiro; Hoshino, Hideaki; Ishigami, Itsuo; Usui, Tateo

    An attempt has been made to develop a new gas carburizing furnace with the system that discharges H2 gas selectively from the atmosphere in the furnace. Polyimide hollow-fiber membrane filter on the market was selected as a filter that was expected to have good H2 gas permeability and selectivity. The results of the various gas permeability measurements of this filter showed that it had superior H2 gas permeability and selectivity. Using this gas filter module, a new industrial gas carburizing furnace that had ‘H2 gas selective discharging system’ was produced as a trial. Use of this furnace made possible to stabilize the gas carburizing atmosphere in the furnace under the lower carrier gas flow rate condition (below 25% of standard condition). It was confirmed that the carbon concentration profile of the steel carburized with the new carburizing furnace under lower carrier gas flow rate condition was comparable to that of the specimen carburized under standard carrier gas flow rate condition.

  1. On the detection of high-redshift black holes with ALMA through CO and H(2) emission

    NARCIS (Netherlands)

    Spaans, Marco; Meijerink, Rowin

    2008-01-01

    Many present-day galaxies are known to harbor supermassive, >= 10(6) M(circle dot), black holes. These central black holes must have grown through accretion from less massive seeds in the early universe. The molecules CO and H 2 can be used to trace this young population of accreting massive black h

  2. A Study of H2 Emission in Three Bipolar Proto-Planetary Nebulae: IRAS 16594-4656, Hen 3-401, and Rob 22

    CERN Document Server

    Hrivnak, Bruce J; Su, Kate Y L; Sahai, Raghvendra

    2008-01-01

    We have carried out a spatial-kinematical study of three proto-planetary nebulae, IRAS 16594-4656, Hen 3-401, and Rob 22. High-resolution H2 images were obtained with NICMOS on the HST and high-resolution spectra were obtained with the Phoenix spectrograph on Gemini-South. IRAS 16594-4656 shows a "peanut-shaped" bipolar structure with H2 emission from the walls and from two pairs of more distant, point-symmetric faint blobs. The velocity structure shows the polar axis to be in the plane of the sky, contrary to the impression given by the more complex visual image and the visibility of the central star, with an ellipsoidal velocity structure. Hen 3-401 shows the H2 emission coming from the walls of the very elongated, open-ended lobes seen in visible light, along with a possible small disk around the star. The bipolar lobes appear to be tilted 10-15 deg with respect to the plane of the sky and their kinematics display a Hubble-like flow. In Rob 22, the H2 appears in the form of an "S" shape, approximately trac...

  3. Secondary ion emission from CO2-H2O ice irradiated by energetic heavy ions: Part I. Measurement of the mass spectra

    Science.gov (United States)

    Farenzena, L. S.; Collado, V. M.; Ponciano, C. R.; da Silveira, E. F.; Wien, K.

    2005-05-01

    Secondary ion mass spectrometry is used to investigate ion emission from a frozen-gas mixture (T = 80-90 K) of CO2 and H2O bombarded by MeV nitrogen ions and by 252Cf fission fragments (FF). The aim of the experiments is to produce organic molecules in the highly excited material around the nuclear track and to detect them in the flux of sputtered particles. Such sputter processes are known to occur at the icy surfaces of planetary or interstellar objects. Time-of-flight (TOF) mass spectrometry is employed to identify the desorbed ions. Mass spectra of positive and negative ions were taken for several molecular H2O/CO2 ratios. In special, positive ions induced by MeV nitrogen beam were analyzed for 9 and 18% H2O concentrations of the CO2-H2O ice and negative ions for ~5% H2O. The ion peaks are separated to generate exclusive the spectra of CO2 specific ions, H2O specific ions and hybrid molecular ions, the latter ones corresponding to ions that contain mostly H and C atoms. In the mass range from 10 to 320 u, the latter exhibits 35 positive and 58 negative ions. The total yield of the positive ions is 0.35 and 0.57 ions/impact, respectively, and of negative ions 0.066 ions/impact. Unexpected effects of secondary ion sputtering yields on H2O/CO2 ratio are attributed to the influence of water molecules concentration on the ionization process.

  4. Intracavity CO laser photoacoustic trace gas detection: cyclic CH 4 , H 2 O and CO 2 emission by cockroaches and scarab beetles

    Science.gov (United States)

    Bijnen, F. G. C.; Harren, F. J. M.; Hackstein, J. H. P.; Reuss, J.

    1996-09-01

    A liquid-nitrogen-cooled CO laser and an intracavity resonant photoacoustic cell are employed to monitor trace gases. The setup was designed to monitor trace gas emissions of biological samples on line. The arrangement offers the possibility to measure gases at the 10 9 by volume (ppbv) level (e.g., CH 4 , H 2 O) and to detect rapid changes in trace gas emission. A detection limit of 1 ppbv for CH 4 in N 2 equivalent to a minimal detectable absorption of 3 10 9 cm 1 can be achieved. Because of the kinetic cooling effect we lowered the detection limit for CH 4 in air is decreased to 10 ppbv. We used the instrument in a first application to measure the CH 4 and H 2 O emission of individual cockroaches and scarab beetles. These emissions could be correlated with CO 2 emissions that were recorded simultaneously with an infrared gas analyzer. Characteristic breathing patterns of the insects could be observed; unexpectedly methane was also found to be released.

  5. Spitzer spectral line mapping of protostellar outflows: III - H_2 emission in L1448, BHR71, and NGC2071

    CERN Document Server

    Giannini, T; Neufeld, D; Yuan, Y; Antoniucci, S; Gusdorf, A

    2011-01-01

    Spitzer-IRS maps of H_2 pure rotational lines from S(0) to S(7) in 3 outflows from Class 0 sources - L1448, BHR71, and NGC2071 - are presented. These lines are used, in conjunction with available rovibrational, near-IR H_2 lines, to probe the physical conditions of the warm gas between hundreds and thousands of Kelvin. We have constructed maps of the molecular hydrogen column density, ortho-to-para ratio and volume density, together with the index beta of the power law describing the distribution of gas temperature. In all three outflows, the present ortho-to-para ratio significantly deviates from the high temperature equilibrium of 3, being on average between 2.0 and 2.3. These low values, that reflect the young age of these flows, are found also in regions of relatively high temperature (~ 1000 K), likely indicating that shocks are occurring in a time shorter than that needed for a complete para to ortho conversion. Density maps indicate upper limits close to LTE conditions, i.e. between 10^6-10^7 cm^-3; mo...

  6. Mitochondrial H2O2 emission and cellular redox state link excess fat intake to insulin resistance in both rodents and humans.

    Science.gov (United States)

    Anderson, Ethan J; Lustig, Mary E; Boyle, Kristen E; Woodlief, Tracey L; Kane, Daniel A; Lin, Chien-Te; Price, Jesse W; Kang, Li; Rabinovitch, Peter S; Szeto, Hazel H; Houmard, Joseph A; Cortright, Ronald N; Wasserman, David H; Neufer, P Darrell

    2009-03-01

    High dietary fat intake leads to insulin resistance in skeletal muscle, and this represents a major risk factor for type 2 diabetes and cardiovascular disease. Mitochondrial dysfunction and oxidative stress have been implicated in the disease process, but the underlying mechanisms are still unknown. Here we show that in skeletal muscle of both rodents and humans, a diet high in fat increases the H(2)O(2)-emitting potential of mitochondria, shifts the cellular redox environment to a more oxidized state, and decreases the redox-buffering capacity in the absence of any change in mitochondrial respiratory function. Furthermore, we show that attenuating mitochondrial H(2)O(2) emission, either by treating rats with a mitochondrial-targeted antioxidant or by genetically engineering the overexpression of catalase in mitochondria of muscle in mice, completely preserves insulin sensitivity despite a high-fat diet. These findings place the etiology of insulin resistance in the context of mitochondrial bioenergetics by demonstrating that mitochondrial H(2)O(2) emission serves as both a gauge of energy balance and a regulator of cellular redox environment, linking intracellular metabolic balance to the control of insulin sensitivity.

  7. Redox Potential as a Means to Control the Treatment of Slurry to Lower H2S Emissions

    Directory of Open Access Journals (Sweden)

    Anders Feilberg

    2012-04-01

    Full Text Available Slurry can be oxidized to eliminate undesirable emissions, including malodorous hydrogen sulfide (H2S. However, it is difficult to assess the optimal amount of oxidizing agent required. In this study, one cow and one pig manure, each in three particle size ranges were oxidized with 0–350 mg ozone/L manure. Redox and H2S concentration were measured continuously. During ozonation the manures gave equivalent redox potential curves. A relatively rapid rise in redox potential was observed within a range of −275 mV to −10 mV, with all manures changing as a minimum from −200 mV to −80 mV. The gaseous H2S emissions were decreased by 99.5% during the redox increase (−200 mV to −80 mV. This is attributed to H2S oxidation by ozone and oxygen, and is not due to H2S deprotonation or gas flushing. By identifying the initiation of the final redox level following the rise, the amount of ozone required to remove H2S from the manure samples was estimated to be in the range of 6–24 mg O3/L manure, depending on the type of manure. Hence, continuous monitoring of redox potential (termination of the redox rise during the oxidation treatment is a simple method of achieving cost-effective minimization of H2S emissions from slurry.

  8. Use of a Monte Carlo technique to complete a fragmented set of H2S emission rates from a wastewater treatment plant.

    Science.gov (United States)

    Schauberger, Günther; Piringer, Martin; Baumann-Stanzer, Kathrin; Knauder, Werner; Petz, Erwin

    2013-12-15

    The impact of ambient concentrations in the vicinity of a plant can only be assessed if the emission rate is known. In this study, based on measurements of ambient H2S concentrations and meteorological parameters, the a priori unknown emission rates of a tannery wastewater treatment plant are calculated by an inverse dispersion technique. The calculations are determined using the Gaussian Austrian regulatory dispersion model. Following this method, emission data can be obtained, though only for a measurement station that is positioned such that the wind direction at the measurement station is leeward of the plant. Using the inverse transform sampling, which is a Monte Carlo technique, the dataset can also be completed for those wind directions for which no ambient concentration measurements are available. For the model validation, the measured ambient concentrations are compared with the calculated ambient concentrations obtained from the synthetic emission data of the Monte Carlo model. The cumulative frequency distribution of this new dataset agrees well with the empirical data. This inverse transform sampling method is thus a useful supplement for calculating emission rates using the inverse dispersion technique.

  9. Secondary ion emission from CO2-H2O ice irradiated by energetic heavy ions: Part II: Analysis-search for organic ions

    Science.gov (United States)

    Ponciano, C. R.; Farenzena, L. S.; Collado, V. M.; da Silveira, E. F.; Wien, K.

    2005-06-01

    Secondary ion mass spectrometry is used to investigate ion emission from a frozen-gas mixture of CO2 and H2O (T = 80-90 K) bombarded by MeV nitrogen ions and by 252Cf fission fragments. The aim of the experiment is to detect organic molecules, produced in the highly excited material around the nuclear track, which appear as ions in the flux of sputtered particles. Part I of the present work [L.S. Farenzena, V.M. Collado, C.R Ponciano, E.F. da Silveira, K. Wien. Int. J. Mass Spectrom. 243 (2005) 85-93] described the method and presented the time-of-flight mass spectra; a list of the CO2 specific and H2O specific reaction products was provided. In Part II, the peaks of the TOF mass spectra are analyzed. Projectile-ice direct coulomb interaction leads to the production in the track of the H+, C+, O+, O2+, CO+ and CO2+ primarily ions, which react in the highly energized nuclear track plasma mainly with CO2 and H2O or H2CO3. The positive molecular hybrid ions formed are identified as organic species like COH+, COOH+, CHn = 1-3+, Hn = 1,2COOH+ and cluster ions. Similarly, the negative primarily ions O- and OH- formed by electron capture produce negative hybrid ions such as (CO2)nOH-, the four ions (CO4Hm = 0-3)- and the corresponding cluster ions. By far, most of the molecular ions have been formed by one-step reactions; exceptions are eventually the CO4Hm- ions created by a reaction between CO3- and water molecules. An intense mass line corresponding to HCO3+ has been observed, but not the one due to formaldehyde ion. Weak signals of ionic ketene, hydrogen peroxide and carbonic acid were seen.

  10. 三江平原小叶章湿地H2S和COS排放动态%Dynamics of H2S and COS Emission Fluxes from Different Calamagrostis angustifolia Wetlands in Sanjiang Plain

    Institute of Scientific and Technical Information of China (English)

    李新华; 刘景双; 杨继松

    2006-01-01

    利用静态箱/气相色谱法,观测了生长季(5~9月)三江平原小叶章沼泽化草甸H2S和COS的释放动态,结果表明,H2S、COS的排放通量具有季节和日变化规律,小叶章沼泽化草甸H2S的平均释放通量为0.34μg·(m2·h)-1,COS的平均释放通量为-0.29μg·(m2·h)-1;在生长季,小叶章沼泽化草甸表现为H2S的源,COS的汇小叶章的生长过程对H2S、COS的排放影响显著,在小叶章生长旺盛期,H2S出现排放峰值,COS出现吸收高峰,H2S和COS的释放通量呈负相关.

  11. Resonances in the Photoionization Cross Sections of Atomic Nitrogen Shape the Far-Ultraviolet Spectrum of the Bright Star in 47 Tucanae

    CERN Document Server

    Dixon, William V

    2013-01-01

    The far-ultraviolet (FUV) spectrum of the Bright Star (B8 III) in 47 Tuc (NGC 104) shows a remarkable pattern: it is well fit by LTE models at wavelengths longer than Lyman beta, but at shorter wavelengths it is fainter than the models by a factor of two. A spectrum of this star obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) shows broad absorption troughs with sharp edges at 995 and 1010 A and a deep absorption feature at 1072 A, none of which are predicted by the models. We find that these features are caused by resonances in the photoionization cross sections of the first and second excited states of atomic nitrogen (2s$^2$ 2p$^3$ $^2$D$^0$ and $^2$P$^0$). Using cross sections from the Opacity Project, we can reproduce these features, but only if we use the cross sections at their full resolution, rather than the resonance-averaged cross sections usually employed to model stellar atmospheres. These resonances are strongest in stellar atmospheres with enhanced nitrogen and depleted carbon ab...

  12. Emission of H2S and Prevention of Harmfulness in Wastewater Treatment Plant%城市污水处理厂H2S气体的产生、危害及预防

    Institute of Scientific and Technical Information of China (English)

    牛克胜; 张建峰

    2003-01-01

    本文主要介绍了城市污水处理厂H2S的产生的根源,对人体的危害和对设备的损害,中毒预防、中毒后急救和治疗措施.只要了解了H2S的性质,采取必要的措施可完全避免H2S对人体造成伤害和对设备造成损害.

  13. Comparison of global cerebral blood flow measured by phase‐contrast mapping MRI with 15O‐H2O positron emission tomography

    Science.gov (United States)

    Lindberg, Ulrich; Aachmann‐Andersen, Niels Jacob; Lisbjerg, Kristian; Christensen, Søren Just; Rasmussen, Peter; Olsen, Niels Vidiendal; Law, Ian; Larsson, Henrik Bo Wiberg; Henriksen, Otto Mølby

    2016-01-01

    Purpose To compare mean global cerebral blood flow (CBF) measured by phase‐contrast mapping magnetic resonance imaging (PCM MRI) and by 15O‐H2O positron emission tomography (PET) in healthy subjects. PCM MRI is increasingly being used to measure mean global CBF, but has not been validated in vivo against an accepted reference technique. Materials and Methods Same‐day measurements of CBF by 15O‐H2O PET and subsequently by PCM MRI were performed on 22 healthy young male volunteers. Global CBF by PET was determined by applying a one‐tissue compartment model with measurement of the arterial input function. Flow was measured in the internal carotid and vertebral arteries by a noncardiac triggered PCM MRI sequence at 3T. The measured flow was normalized to total brain weight determined from a volume‐segmented 3D T 1‐weighted anatomical MR‐scan. Results Mean CBF was 34.9 ± 3.4 mL/100 g/min measured by 15O‐H2O PET and 57.0 ± 6.8 mL/100 g/min measured by PCM MRI. The measurements were highly correlated (P = 0.0008, R2 = 0.44), although values obtained by PCM MRI were higher compared to 15O‐H2O PET (absolute and relative differences were 22.0 ± 5.2 mL/100 g/min and 63.4 ± 14.8%, respectively). Conclusion This study confirms the use of PCM MRI for quantification of global CBF, but also that PCM MRI systematically yields higher values relative to 15O‐H2O PET, probably related to methodological bias. Level of Evidence: 3 J. Magn. Reson. Imaging 2017;45:692–699. PMID:27619317

  14. Microbial monitoring and performance evaluation for H2S biological air emissions control at a wastewater lift station in South Texas, USA.

    Science.gov (United States)

    Jones, Kim D; Yadavalli, Naga; Karre, Anand K; Paca, Jan

    2012-01-01

    A pilot-scale biological sequential treatment system consisting of a biotrickling filter and two biofilters was installed at Waste Water Lift Station # 64 in Brownsville, Texas, USA to evaluate the performance of the system being loaded with variable concentrations of wastewater hydrogen sulfide (H(2)S) emissions. In this study, the effectiveness of sulfur oxidizing bacteria along with the distribution of various sulfur species and their correlation with the performance of the biofilters was evaluated. The biofilters were packed with engineered media consisting of plastic cylinders with compacted organic material which was supplied by Met-Pro Environmental Air Solutions (formerly Bio·Reaction Industries). The overall performance of the pilot-scale biological sequential treatment system with an Empty Bed Residence Time (EBRT) of 60s and the overall performance of the biofilter unit with an EBRT of 35s developed a removal efficiency of > 99% at H(2)S levels up to 500 ppm. A decrease in performance over time was observed in the first and second sections of the first biofilter unit with the third section of the biofilter unit ultimately becoming the most robust unit removing most of the pollutant. The second biofilter unit was not needed and subsequently removed from the system. The number of CFUs in sulfur oxidizing T.thioparus selective media grew significantly in all four sections of the biofilter over the two months of pilot operation of the biological unit. The sulfur oxidizer growth rates appeared to be highest at low total sulfur content and at slightly acidic pH levels. This study has implications for improving the understanding of the distribution of sulfur oxidizing bacteria throughout the length of the biofilter columns, which can be used to further optimize performance and estimate breakthrough at these very high H(2)S input loadings.

  15. Comparison of global cerebral blood flow measured by phase-contrast mapping MRI with (15) O-H2 O positron emission tomography

    DEFF Research Database (Denmark)

    Vestergaard, Mark Bitsch; Lindberg, Ulrich; Aachmann-Andersen, Niels Jacob;

    2017-01-01

    PURPOSE: To compare mean global cerebral blood flow (CBF) measured by phase-contrast mapping magnetic resonance imaging (PCM MRI) and by (15) O-H2 O positron emission tomography (PET) in healthy subjects. PCM MRI is increasingly being used to measure mean global CBF, but has not been validated...... of the arterial input function. Flow was measured in the internal carotid and vertebral arteries by a noncardiac triggered PCM MRI sequence at 3T. The measured flow was normalized to total brain weight determined from a volume-segmented 3D T1 -weighted anatomical MR-scan. RESULTS: Mean CBF was 34.9 ± 3.4 mL/100 g...... in vivo against an accepted reference technique. MATERIALS AND METHODS: Same-day measurements of CBF by (15) O-H2 O PET and subsequently by PCM MRI were performed on 22 healthy young male volunteers. Global CBF by PET was determined by applying a one-tissue compartment model with measurement...

  16. A HIFI preview of warm molecular gas around chi Cyg : first detection of H2O emission toward an S-type AGB star

    CERN Document Server

    Justtanont, K; Schoier, F L; Maercker, M; Olofsson, H; Bujarrabal, V; Marston, A P; Teyssier, D; Alcolea, J; Cernicharo, J; Dominik, C; de Koter, A; Melnick, G; Menten, K; Neufeld, D; Planesas, P; Schmidt, M; Szczerba, R; Waters, R; de Graauw, Th; Whyborn, N; Finn, T; Helmich, F; Siebertz, O; Schmulling, F; Ossenkopf, V; Lai, R

    2010-01-01

    A set of new, sensitive, and spectrally resolved, sub-millimeter line observations are used to probe the warm circumstellar gas around the S-type AGB star chi Cyg. The observed lines involve high rotational quantum numbers, which, combined with previously obtained lower-frequency data, make it possible to study in detail the chemical and physical properties of, essentially, the entire circumstellar envelope of chi Cyg. The data were obtained using the HIFI instrument aboard Herschel, whose high spectral resolution provides valuable information about the line profiles. Detailed, non-LTE, radiative transfer modelling, including dust radiative transfer coupled with a dynamical model, has been performed to derive the temperature, density, and velocity structure of the circumstellar envelope. We report the first detection of circumstellar H2O rotational emission lines in an S-star. Using the high-J CO lines to derive the parameters for the circumstellar envelope, we modelled both the ortho- and para-H2O lines. Our...

  17. AN ATLAS OF FAR-ULTRAVIOLET SPECTRA OF THE ZETA AURIGAE BINARY 31 CYGNI WITH LINE IDENTIFICATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Wendy Hagen [Whitin Observatory, Wellesley College, 106 Central Street, Wellesley, MA 02481 (United States); Bennett, Philip D., E-mail: wbauer@wellesley.edu [Department of Astronomy and Physics, Saint Mary' s University, Halifax, NS B3H 3C3 (Canada)

    2014-04-01

    The ζ Aurigae system 31 Cygni (K4 Ib + B4 V) was observed by the FUSE satellite during total eclipse and at three phases during chromospheric eclipse. We present the coadded, calibrated spectra and atlases with line identifications. During total eclipse, emission from high ionization states (e.g., Fe III and Cr III) shows asymmetric profiles redshifted from the systemic velocity, while emission from lower ionization states (e.g., Fe II and O I) appears more symmetric and is centered closer to the systemic velocity. Absorption from neutral and singly ionized elements is detected during chromospheric eclipse. Late in chromospheric eclipse, absorption from the K star wind is detected at a terminal velocity of ∼80 km s{sup –1}. These atlases will be useful for interpreting the far-UV spectra of other ζ Aur systems, as the observed FUSE spectra of 32 Cyg, KQ Pup, and VV Cep during chromospheric eclipse resemble that of 31 Cyg.

  18. Selective Ag(I) binding, H2S sensing, and white-light emission from an easy-to-make porous conjugated polymer.

    Science.gov (United States)

    Liu, Jie; Yee, Ka-Kit; Lo, Kenneth Kam-Wing; Zhang, Kenneth Yin; To, Wai-Pong; Che, Chi-Ming; Xu, Zhengtao

    2014-02-19

    Separating silver (Ag(+)) from lead (Pb(2+)) is one of the many merits of the porous polymer framework reported here. The selective metal binding stems from the well-defined chelating unit of N-heterocycles, which consists of a triazine (C3N3) ring bonded to three 3,5-dimethylpyrazole moieties. Such a rigid and open triad also serves as the distinct building unit in the fully conjugated 3D polymer scaffold. Because of its strong fluorescence and porosity (e.g., BET surface area: 355 m(2)/g), and because of the various types of metal species that can be readily taken up, this versatile framework is especially fit for functionalization. For example, with AgNO3 loaded, the framework solid exhibits a brown color in response to water solutions of H2S, even at the dilution of 5.0 μM (0.17 ppm); whereas cysteine and other biologically relevant thiols do not cause notable change in color. In another example, tunable white-light emission was produced when an Ir(III) complex was doped (e.g., about 0.02% of the polymer weight) onto the framework. Mechanistically, the bound Ir(III) centers become highly emissive in the orange-red region, complementing the broad, bluish emission from the polymer host to result in the overall white-light quality: the color attributes of the emission are therefore easily tunable by the Ir(III) dopant concentration. With this exemplary study, we intend to highlight metal uptake as an effective approach to modify and enrich the properties of porous polymer frameworks and to stimulate interest in further examining metal-polymer interactions in the context of sensing, separation, catalyzes, and other applications.

  19. Powerful H2 Line Cooling in Stephan’s Quintet. II. Group-wide Gas and Shock Modeling of the Warm H2 and a Comparison with [C II] 157.7 μm Emission and Kinematics

    Science.gov (United States)

    Appleton, P. N.; Guillard, P.; Togi, A.; Alatalo, K.; Boulanger, F.; Cluver, M.; Pineau des Forêts, G.; Lisenfeld, U.; Ogle, P.; Xu, C. K.

    2017-02-01

    We map for the first time the two-dimensional H2 excitation of warm intergalactic gas in Stephan's Quintet on group-wide (50 × 35 kpc2) scales to quantify the temperature, mass, and warm H2 mass fraction as a function of position using Spitzer. Molecular gas temperatures are seen to rise (to T > 700 K) and the slope of the power-law density–temperature relation flattens along the main ridge of the filament, defining the region of maximum heating. We also performed MHD modeling of the excitation properties of the warm gas, to map the velocity structure and energy deposition rate of slow and fast molecular shocks. Slow magnetic shocks were required to explain the power radiated from the lowest-lying rotational states of H2, and strongly support the idea that energy cascades down to small scales and low velocities from the fast collision of NGC 7318b with group-wide gas. The highest levels of heating of the warm H2 are strongly correlated with the large-scale stirring of the medium as measured by [C ii] spectroscopy with Herschel. H2 is also seen associated with a separate bridge that extends toward the Seyfert nucleus in NGC 7319, from both Spitzer and CARMA CO observations. This opens up the possibility that both galaxy collisions and outflows from active galactic nuclei can turbulently heat gas on large scales in compact groups. The observations provide a laboratory for studying the effects of turbulent energy dissipation on group-wide scales, which may provide clues about the heating and cooling of gas at high z in early galaxy and protogalaxy formation.

  20. ORFEUS-II Far-Ultraviolet Observations of 3C273; 1, Interstellar and Intergalactic Absorption Lines

    CERN Document Server

    Hurwitz, M; Barnstedt, J; Bowyer, S; Van Dixon, W D; Grewing, M; Kappelmann, N; Krämer, G; Krautter, J; Mandel, H; Hurwitz, Mark; Appenzeller, Immo; Barnstedt, Juergen; Bowyer, Stuart; Grewing, Michael; Kappelmann, Norbert; Kraemer, Gerhard; Krautter, Joachim; Mandel, Holger

    1998-01-01

    We present the first intermediate-resolution (lambda / 3000) spectrum of the bright quasi-stellar object 3C273 at wavelengths between 900 and 1200 A. Observations were performed with the Berkeley spectrograph aboard the ORFEUS-SPAS II mission. We detect Lyman beta counterparts to previously-identified intergalactic Lyman-alpha features at cz = 19900, 1600, and 1000 km/s; counterparts to other putative Lyman-alpha clouds along the sight line are below our detection limit. The strengths of the two very low redshift Lyman-beta features, which are believed to arise in Virgo intracluster gas, exceed preflight expectations, suggesting that the previous determination of the cloud parameters may underestimate the true column densities. A curve-of-growth analysis sets a minimum H I column density of 4 E14/cm^2 for the 1600 km/s cloud. We find marginally significant evidence for Galactic H_2 along the sight line, with a total column density of about 1 E15/cm^2. We detect the stronger interstellar O VI doublet member un...

  1. Hubble Space Telescope detection of the double pulsar system J0737-3039 in the far-ultraviolet

    CERN Document Server

    Durant, Martin; Pavlov, George G

    2014-01-01

    We report on detection of the double pulsar system J0737-3039 in the far-UV with the ACS/SBC detector aboard HST. We measured the energy flux F = 4.5+/-1.0e-17 erg cm-2s-1 in the 1250-1550 AA band, which corresponds to the extinction-corrected luminosity L~1.5e28 erg s-1 for the distance d=1.1 kpc and a plausible reddening E(B-V)=0.1. If the detected emission comes from the entire surface of one of the neutron stars with a 13 km radius, the surface blackbody temperature is in the range T~2-5e5 K for a reasonable range of interstellar extinction. Such a temperature requires an internal heating mechanism to operate in old neutron stars, or it might be explained by heating of the surface of the less energetic Pulsar B by the relativistic wind of Pulsar A. If the far-UV emission is non-thermal (e.g., produced in the magnetosphere of Pulsar A), its spectrum exhibits a break between the UV and X-rays.

  2. Interstellar H I and H2 in the Magellanic Clouds: An Expanded Sample Based on Ultraviolet Absorption-line Data

    Science.gov (United States)

    Welty, Daniel E.; Xue, Rui; Wong, Tony

    2012-02-01

    We have determined column densities of H I and/or H2 for sight lines in the Magellanic Clouds from archival Hubble Space Telescope and Far-Ultraviolet Spectroscopic Explorer spectra of H I Lyα and H2 Lyman-band absorption. Together with some similar data from the literature, we now have absorption-based N(H I) and/or N(H2) for 285 Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) sight lines (114 with a detection or limit for both species)—enabling more extensive, direct, and accurate determinations of molecular fractions, gas-to-dust ratios, and elemental depletions in these two nearby, low-metallicity galaxies. For sight lines where the N(H I) estimated from 21 cm emission is significantly higher than the value derived from Lyα absorption (presumably due to emission from gas beyond the target stars), integration of the 21 cm profile only over the velocity range seen in Na I or H2 absorption generally yields much better agreement. Conversely, N(21 cm) can be lower than N(Lyα) by factors of 2-3 in some LMC sight lines—suggestive of small-scale structure within the 21 cm beam(s) and/or some saturation in the emission. The mean gas-to-dust ratios obtained from N(Htot)/E(B - V) are larger than in our Galaxy, by factors of 2.8-2.9 in the LMC and 4.1-5.2 in the SMC—i.e., factors similar to the differences in metallicity. The N(H2)/E(B - V) ratios are more similar in the three galaxies, but with considerable scatter within each galaxy. These data may be used to test models of the atomic-to-molecular transition at low metallicities and predictions of N(H2) based on comparisons of 21 cm emission and the IR emission from dust. ), the MAST archive at STScI (FUSE data), and the University of Bonn (LAB and GASS 21 cm surveys).

  3. Hubble Space Telescope Detection of the Millisecond Pulsar J2124-3358 and its Far-ultraviolet Bow Shock Nebula

    Science.gov (United States)

    Rangelov, B.; Pavlov, G. G.; Kargaltsev, O.; Reisenegger, A.; Guillot, S.; van Kerkwijk, M. H.; Reyes, C.

    2017-02-01

    We observed the nearby millisecond pulsar J2124–3358 with the Hubble Space Telescope in broad far-UV (FUV) and optical filters. The pulsar is detected in both bands with fluxes F(1250–2000 Å) = (2.5 ± 0.3) × 10‑16 erg s‑1 cm‑2 and F(3800–6000 Å) = (6.4 ± 0.4) × 10‑17 erg s‑1 cm‑2, which corresponds to luminosities of ≈5.8 × 1027 and 1.4 × 1027 erg s‑1, for d = 410 pc and E(B ‑ V) = 0.03. The optical-FUV spectrum can be described by a power-law model, {f}ν \\propto {ν }α , with slope α = 0.18–0.48 for a conservative range of color excess, E(B ‑ V) = 0.01–0.08. Since a spectral flux rising with frequency is unusual for pulsar magnetospheric emission in this frequency range, it is possible that the spectrum is predominantly magnetospheric (power law with α neutron star surface in the FUV. For a neutron star radius of 12 km, the surface temperature would be between 0.5 × 105 and 2.1 × 105 K for α ranging from ‑1 to 0, E(B ‑ V) = 0.01–0.08, and d = 340–500 pc. In addition to the pulsar, the FUV images reveal extended emission that is spatially coincident with the known Hα bow shock, making PSR J2124–3358 the second pulsar (after PSR J0437‑4715) with a bow shock detected in the FUV.

  4. Effects Of Electrons and Heavy Particles On Halpha Emission In Pure H2O DC Discharge At High E/N (E-Electric Field, N-Gas Density)

    Science.gov (United States)

    Petrovic, Zoran; Stojanovic, Vladimir; Skoro, Nikola; Sivos, Jelena; Maric, Dragana; Malovic, Gordana

    2016-09-01

    In this work we present results of Monte Carlo simulations for spatially resolved emission due to the transport of electrons and heavy particles (fast H, H+, OH+, H2O+,H3O+) in pure H2O for the conditions used in plasma assisted technologies. Monte Carlo technique, already used for similar discharges in nitrogen, argon and hydrogen is used to obtain spatially resolved Halpha emission in H2O. Data for anisotropic scattering of electrons, ions and fast neutrals are used to obtain contribution to Halpha spatially resolved emission. Agreement with experimental data for drift velocities for all charged particles and effective electron ionization for the conditions of moderate E/N allowed us to study production of heavy particles and subsequently spatial emission as a consequence of their transport. Acknowledgment to Ministry of Education, Science and Technology of Republic Serbia, Projects No. 171037 and 410011.

  5. The Structure and Kinematics of the Circumgalactic Medium from Far-ultraviolet Spectra of z ~= 2-3 Galaxies

    Science.gov (United States)

    Steidel, Charles C.; Erb, Dawn K.; Shapley, Alice E.; Pettini, Max; Reddy, Naveen; Bogosavljević, Milan; Rudie, Gwen C.; Rakic, Olivera

    2010-07-01

    We present new results on the kinematics and spatial distribution of metal-enriched gas within ~125 kpc of star-forming ("Lyman break") galaxies at redshifts 2 background galaxies provide new information on the spatial distribution of circumgalactic gas surrounding the foreground galaxies. The close pairs sample galactocentric impact parameters 3-125 kpc (physical) at langzrang = 2.2, providing for the first time a robust map of cool gas as a function of galactocentric distance for a well-characterized population of galaxies. We propose a simple model of circumgalactic gas that simultaneously matches the kinematics, depth, and profile shape of IS absorption and Lyα emission lines, as well as the observed variation of absorption line strength (H I and several metallic species) versus galactocentric impact parameter. Within the model, cool gas is distributed symmetrically around every galaxy, accelerating radially outward with v out(r) increasing with r (i.e., the highest velocities are located at the largest galactocentric distances r). The inferred radial dependence of the covering fraction of cool gas (which modulates the absorption line strength) is fc (r) vprop r -γ with 0.2 Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation.

  6. Observed changes of the diffuse H_{2} emission at the summit cone of Teide volcano (Tenerife, Canary Islands): a geochemical evidence of processes operating deep in the magmatic system

    Science.gov (United States)

    Pérez, Nemesio M.; Melián, Gladys V.; Padrón, Eleazar; Asensio-Ramos, María; Padilla, Germán; Rodríguez, Fátima; Calvo, David; Barrancos, José; Hernández, Pedro A.

    2017-04-01

    Hydrogen is one of the most abundant trace species in volcano-hydrothermal systems and is a key participant in many redox reactions occurring in the hydrothermal reservoir gas (Giggenbach 1987; Chiodini and Marini 1998). Because of its chemical and physical characteristics such as low weight and low solubility in groundwater and hydrothermal fluids, H2 moves rapidly within the crust and escapes easily to the atmosphere. These characteristics make H2a potentially excellent tracer of processes operating deep in magmatic systems. Most of the diffuse degassing studies on active volcanic-hydrothermal systems is primarily focused on CO2, the second major component of volcanic gases. Unfortunately however, few studies of surface H2efflux measurements at active volcanoes have been performed to evaluate diffuse H2 emission rates from active volcanic systems. Here, we report a time series on diffuse H2 emission rates from surveys carried out in yearly basis at the summit cone of Teide volcano, where most obvious geothermal features at Tenerife occurs, during the 2006-2016 period. Thousands of samples of volcanic gases from the surface environment, at 40 cm depth, have been collected during this 2006-2016 period to estimate surface H2 efflux values from 150 observation sites selected to cover the 0.5 Km2 area of the summit cone Teide volcano. Most of the surveys showed diffuse H2 emission rate values lower than 40 kgṡd-1 from the summit cone of Teide volcano. On the contrary, an increasing trend of diffuse H2 emission rate from 35 ± 7 to 122 ± 36 kgṡd-1 was observed during the 2006 to 2009 period. This increase trend of diffuse H2 emission rate was detected before a raise of seismic activity in and around Tenerife from November 2009 to June 2011, with about 1176 seismic events recorded by Spanish-IGN in 2010 (Pérez and Schmincke, 2016). The observed increased trend of diffuse H2 emission occurs simultaneously with an increase trend of diffuse CO2 emission at the summit

  7. Far ultraviolet imaging from the IMAGE spacecraft. 3. Spectral imaging of Lyman-α and OI 135.6 nm

    Science.gov (United States)

    Mende, S. B.; Heetderks, H.; Frey, H. U.; Stock, J. M.; Lampton, M.; Geller, S. P.; Abiad, R.; Siegmund, O. H. W.; Habraken, S.; Renotte, E.; Jamar, C.; Rochus, P.; Gerard, J.-C.; Sigler, R.; Lauche, H.

    2000-01-01

    Two FUV Spectral imaging instruments, the Spectrographic Imager (SI) and the Geocorona Photometer (GEO) provide IMAGE with simultaneous global maps of the hydrogen (121.8 nm) and oxygen 135.6 nm components of the terrestrial aurora and with observations of the three dimensional distribution of neutral hydrogen in the magnetosphere (121.6 nm). The SI is a novel instrument type, in which spectral separation and imaging functions are independent of each other. In this instrument, two-dimensional images are produced on two detectors, and the images are spectrally filtered by a spectrograph part of the instrument. One of the two detectors images the Doppler-shifted Lyman-α while rejecting the geocoronal `cold' Ly-α, and another detector images the OI 135.6 nm emission. The spectrograph is an all-reflective Wadsworth configuration in which a grill arrangement is used to block most of the cold, un-Doppler-shifted geocoronal emission at 121.567 nm. The SI calibration established that the upper limit of transmission at cold geocoronal Ly-α is less than 2%. The measured light collecting efficiency was 0.01 and 0.008 cm^2 at 121.8 and at 135.6 nm, respectively. This is consistent with the size of the input aperture, the optical transmission, and the photocathode efficiency. The expected sensitivity is 1.8x10^-2 and 1.3x10^-2 counts per Rayleigh per pixel for each 5 s viewing exposure per satellite revolution (120 s). The measured spatial resolution is better than the 128x128 pixel matrix over the 15 degx15 deg field of view in both wavelength channels. The SI detectors are photon counting devices using the cross delay line principle. In each detector a triple stack microchannel plate (MCP) amplifies the photo-electronic charge which is then deposited on a specially configured anode array. The position of the photon event is measured by digitizing the time delay between the pulses detected at each end of the anode structures. This scheme is intrinsically faster than systems

  8. H- and He-like Charge-Exchange Induced X-ray Emission due to Ion Collisions with H, He, and H2

    Science.gov (United States)

    Cumbee, Renata; Mullen, Patrick; Miller, Ansley; Lyons, David; Shelton, Robin L.; Schultz, David R.; Stancil, Phillip C.; Leutenegger, Maurice A.

    2017-08-01

    When a hot plasma collides with a cold neutral gas interactions occur between the microscopic constituents including charge exchange (CX). CX is a process in which an electron can be transferred from a neutral atom or molecule into an excited energy level of an ion. Following this transfer, the excited electron relaxes to lower energy levels, emitting X-rays. This process has been established as a primary source of X-ray emission within our solar system, such as when the solar wind interacts with cometary and planetary atmospheres, and outside of our solar system, such as in the hot outflows of starburst galaxies.Since the CX X-ray emission spectrum varies greatly with collision velocity, it is critical that realistic CX data are included in X-ray spectral models of astrophysical environments in which CX might be significant in order to correctly estimate the ion abundance and plasma velocities. Here, line ratios and spectra are computed using theoretical CX cross sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, and classical-trajectory Monte Carlo methods for a variety of collision energies relevant to various astrophysical environments. Collisions of bare and H-like C, N, O, Ne, Mg, Al, Si, P, S, and Cl ions are shown with H, He, and H2 as the neutral collision targets. An X-ray model using line ratios for C-Si ions is then performed within XSPEC for a region of the Cygnus Loop supernova remnant for 8 collision energies in order to highlight the variation in CX spectral models with collision energy.R. Cumbee’s research was partially supported by an appointment to the NASA Postdoctoral Program at NASA GSFC, administered by Universities Space Research Association under contract with NASA. Work at UGA was partially supported by NASA grants NNX09AC46G and NNG09WF24I.

  9. Characterization of mid-infrared emissions from C2H2, CO, CO2, and HCN-filled hollow fiber lasers

    Science.gov (United States)

    Jones, A. M.; Fourcade-Dutin, C.; Mao, C.; Baumgart, B.; Nampoothiri, A. V. V.; Campbell, N.; Wang, Y.; Benabid, F.; Rudolph, W.; Washburn, B. R.; Corwin, K. L.

    2012-02-01

    We have now demonstrated and characterized gas-filled hollow-core fiber lasers based on population inversion from acetylene (12C2H2) and HCN gas contained within the core of a kagome-structured hollow-core photonic crystal fiber. The gases are optically pumped via first order rotational-vibrational overtones near 1.5 μm using 1-ns pulses from an optical parametric amplifier. Transitions from the pumped overtone modes to fundamental C-H stretching modes in both molecules create narrow-band laser emissions near 3 μm. High gain resulting from tight confinement of the pump and laser light together with the active gas permits us to operate these lasers in a single pass configuration, without the use of any external resonator structure. A delay between the emitted laser pulse and the incident pump pulse has been observed and is shown to vary with pump pulse energy and gas pressure. Furthermore, we have demonstrated lasing beyond 4 μm from CO and CO2 using silver-coated glass capillaries, since fused silica based fibers do not transmit in this spectral region and chalcogenide fibers are not yet readily available. Studies of the laser pulse energy as functions of the pump pulse energy and gas pressure were performed. Efficiencies reaching ~ 20% are observed for both acetylene and CO2.

  10. A Correction Method for Attenuated Total Reflection-Far Ultraviolet Spectra Via the Use of Charge Transfer to Solvent Band Intensities of Iodide in the Ultraviolet Region.

    Science.gov (United States)

    Ikehata, Akifumi; Goto, Takeyoshi; Morisawa, Yusuke

    2017-07-01

    Attenuated total reflection (ATR) spectra, which are often used in IR analysis, can be transformed into extinction and refraction spectra by Kramers-Kronig transformation (KKT) with Fresnel equations. However, it is often difficult to obtain correct optical indices due to the inherent instrumental functions. This paper proposes a simple practical method for correction of KKT with two parameters, which include all the effects of the instrumental function. In order to obtain the parameters of the instrumental function, absorption ratios of charge transfer to solvent (CTTS) transitions of aqueous iodide ions observed at 195 nm and 230 nm were used as a standard. The absorption indices calculated from the ATR spectra with the parameters correspond reasonably well to those given by the transmittance spectra not only in the UV region but also in the far-ultraviolet (FUV, 120-200 nm) region. By applying the corrected KKT to the ATR-FUV spectra of aqueous potassium halide solutions in the range of 0-2 M, correct features of the absorption spectra of KCl and KBr, whose CTTS bands are thought to be observed in FUV region, were confirmed. It is possible to use the parameters representing the instrument function as long as the instrument is not changed.

  11. Molecular hydrogen (H2) combustion emissions and their isotope (D/H) signatures from domestic heaters, diesel vehicle engines, waste incinerator plants, and biomass burning

    NARCIS (Netherlands)

    Vollmer, M.K.; Walter, S.; Mohn, J.; Steinbacher, M.; Bond, S.W.; Röckmann, T.; Reimann, S.

    2012-01-01

    Molecular hydrogen (H2), its stable isotope signature ( D), and the key combustion parameters carbon monoxide (CO), carbon dioxide (CO2), and methane (CH4) were measured from various combustion processes. H2 in the exhaust of gas and oil-fired heaters and of waste incinerator plants was generally de

  12. Molecular hydrogen (H2) combustion emissions and their isotope (D/H) signatures from domestic heaters, diesel vehicle engines, waste incinerator plants, and biomass burning

    NARCIS (Netherlands)

    Vollmer, M.K.; Walter, S.; Mohn, J.; Steinbacher, M.; Bond, S.W.; Röckmann, T.; Reimann, S.

    2012-01-01

    Molecular hydrogen (H2), its stable isotope signature ( D), and the key combustion parameters carbon monoxide (CO), carbon dioxide (CO2), and methane (CH4) were measured from various combustion processes. H2 in the exhaust of gas and oil-fired heaters and of waste incinerator plants was generally

  13. The R136 star cluster dissected with Hubble Space Telescope/STIS. I. Far-ultraviolet spectroscopic census and the origin of He II λ1640 in young star clusters

    Science.gov (United States)

    Crowther, Paul A.; Caballero-Nieves, S. M.; Bostroem, K. A.; Maíz Apellániz, J.; Schneider, F. R. N.; Walborn, N. R.; Angus, C. R.; Brott, I.; Bonanos, A.; de Koter, A.; de Mink, S. E.; Evans, C. J.; Gräfener, G.; Herrero, A.; Howarth, I. D.; Langer, N.; Lennon, D. J.; Puls, J.; Sana, H.; Vink, J. S.

    2016-05-01

    We introduce a Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) stellar census of R136a, the central ionizing star cluster of 30 Doradus. We present low resolution far-ultraviolet STIS spectroscopy of R136 using 17 contiguous 52 arcsec × 0.2 arcsec slits which together provide complete coverage of the central 0.85 parsec (3.4 arcsec). We provide spectral types of 90 per cent of the 57 sources brighter than mF555W = 16.0 mag within a radius of 0.5 parsec of R136a1, plus 8 additional nearby sources including R136b (O4 If/WN8). We measure wind velocities for 52 early-type stars from C IVλλ1548-51, including 16 O2-3 stars. For the first time, we spectroscopically classify all Weigelt and Baier members of R136a, which comprise three WN5 stars (a1-a3), two O supergiants (a5-a6) and three early O dwarfs (a4, a7, a8). A complete Hertzsprung-Russell diagram for the most massive O stars in R136 is provided, from which we obtain a cluster age of 1.5^{+0.3}_{-0.7} Myr. In addition, we discuss the integrated ultraviolet spectrum of R136, and highlight the central role played by the most luminous stars in producing the prominent He II λ1640 emission line. This emission is totally dominated by very massive stars with initial masses above ˜100 M⊙. The presence of strong He II λ1640 emission in the integrated light of very young star clusters (e.g. A1 in NGC 3125) favours an initial mass function extending well beyond a conventional upper limit of 100 M⊙. We include montages of ultraviolet spectroscopy for Large Magellanic Cloud O stars in the appendix. Future studies in this series will focus on optical STIS medium resolution observations.

  14. Analyze and solve the problem of excessive hydrogen sulfide content in CO2 emissions gas%CO2排放气中H2S超标的问题分析及解决

    Institute of Scientific and Technical Information of China (English)

    乔景红

    2013-01-01

    针对低温甲醇洗系统中排放气中H2S超标的问题,采用人、机、料、法、环的方法进行分析,并对分析出的主要原因制定相应的措施,使排放气的H2S含量达到设计值以内,解决了排放气中H2S超标的问题.%For the problem of excessive hydrogen sulfide as the emission gas in low temperature methanol washing system. This paper analyses the causes of this phenomena by human, machine, material, method and environment. Some advice about how to ensure that the concentration of hydrogen sulfide in the setting within were put forward. In this way, The problem of excessive hydrogen sulfide as the emission gas was solved.

  15. 固氮添加剂降低厨余垃圾堆肥中NH3和H2S排放%Nitrogen fixation additive reducing emission of NH3 and H2S during composting of kitchen waste and cornstalk

    Institute of Scientific and Technical Information of China (English)

    张红玉; 李国学; 袁京; 臧冰; 杨青原

    2013-01-01

    In order to reduce odor emissions such as NH3 and H2S, this study designed experiments to investigate the effects of H3PO4+Mg(OH)2, Ca(H2PO4)2, FeCl3, andβcyclodextrin on producing and releasing NH3 and H2S during kitchen waste composting. The composting treatment without adding chemical materials was used as control. The kitchen waste consisted of 53%vegetation waste, 24%fruit wall, 19%meat, and 4%leaves. For all treatments, cornstalks as an additive using the wet weight ration of 1:5.7 were added to the kitchen waste composting. All treatments were analyzed using 60 L heat insulated composting vessels with forced aeration systems. The vessels were controlled by the C-LGX program, which enables aeration to be controlled automatically by time or inside temperature. Aeration consisted of pumping ambient air into the reactor continuously at a rate of 0.2 L/(kg·min) dry matter. The TKN and TOC were determined according to the Chinese national standard (NY 525-2002). The pH, EC, and GI were determined in water extracts (20 g of dry weight compost were extracted with 200 ml of distilled water, stirred for 1 h, and then centrifuged at 4000 rpm). pH value was measured with a pH meter, electrical conductivity (EC) was measured by a DDS-12A conductivity meter. The moisture content was determined by drying the samples at 105℃, until the weight was unvarying. The boric acid titration method was used to determine ammonia emission. The H2S content was analyzed daily using a portable biogas analyzer. Composting gas samples were extracted using a suction pump (built-in biogas analyzer, gas flow:550 mL/min), and then transferred to the inlet port of the biogas analyzer via a Teflon hose that contained a filter element (2.0μm PTFE) installed in the middle of the pipe. The measurement was taken for about 90 seconds, and the measured value of H2S was read directly from the screen. The results showed that adding nitrogen control material reduced the pH of the composting systems

  16. Evaluation of a hand-held far-ultraviolet radiation device for decontamination of Clostridium difficile and other healthcare-associated pathogens

    Directory of Open Access Journals (Sweden)

    Nerandzic Michelle M

    2012-05-01

    Full Text Available Abstract Background Environmental surfaces play an important role in transmission of healthcare-associated pathogens. There is a need for new disinfection methods that are effective against Clostridium difficile spores, but also safe and rapid. The Sterilray™ Disinfection Wand device is a hand-held room decontamination technology that utilizes far-ultraviolet radiation (185-230 nm to kill pathogens. Methods We examined the efficacy of disinfection using the Sterilray device in the laboratory, in rooms of hospitalized patients, and on surfaces outside of patient rooms (i.e. keyboards and portable medical equipment. Cultures for C. difficile, methicillin-resistant Staphylococcus aureus (MRSA, and vancomycin-resistant Enterococcus (VRE were collected from commonly-touched surfaces before and after use of the Sterilray device. Results On inoculated surfaces in the laboratory, application of the Sterilray device at a radiant dose of 100 mJ/cm2 for ~ 5 seconds consistently reduced recovery of C. difficile spores by 4.4 CFU log10, MRSA by 5.4 log10CFU and of VRE by 6.9 log10CFU. A >3 log10 reduction of MRSA and VRE was achieved in ~2 seconds at a lower radiant dose, but killing of C. difficile spores was significantly reduced. On keyboards and portable medical equipment that were inoculated with C. difficile spores, application of the Sterilray device at a radiant dose of 100���mJ/cm2 for ~ 5 seconds reduced contamination by 3.2 log10CFU. However, the presence of organic material reduced the lethal effect of the far-UV radiation. In hospital rooms that were not pre-cleaned, disinfection with the Sterilray device significantly reduced the frequency of positive C. difficile and MRSA cultures (P =0.007. Conclusions The Sterilray™ Disinfection Wand is a novel environmental disinfection technology that rapidly kills C. difficile spores and other healthcare-associated pathogens on surfaces. However, the presence of organic matter

  17. A collimated jet and an infalling-rotating disk in G192.16-3.84 traced by H2O maser emission

    CERN Document Server

    Imai, H; Hirota, T; Umemoto, T; Sorai, K; Kondo, T; Imai, Hiroshi; Omodaka, Toshihiro; Hirota, Tomoya; Umemoto, Tomofumi; Sorai, Kazuo; Kondo, Tetsuro

    2006-01-01

    We report H2O masers associated with the massive-star forming region G192.16-3.84 observed with the new Japan VLBI network at three epochs spanned for two months, which have revealed the three-dimensional kinematical structure of the whole \\h2o maser region in G192.16-3.84, containing two young stellar objects separated by ~1200 AU. The maser spatio-kinematical structure has well persisted since previous observations, in which the masers are expected to be associated with a highly-collimated bipolar jet and an infalling-rotating disk in the northern and southern clusters of H2O maser features, respectively. We estimated a jet expansion speed of ~100 km/s and re-estimated a dynamical age of the whole jet to be 5.6x10^4 yrs. We have investigated the spatial distribution of Doppler velocities during the previous and present observations and relative proper motions of H2O maser features in the southern cluster, and a relative bulk motion between the two maser clusters. They are well explained by a model of an inf...

  18. H-2 incompatible chimera

    Energy Technology Data Exchange (ETDEWEB)

    Matzinger, P.; Mirkwood, G.

    1978-07-01

    Fully H-2 incompatible radiation chimeras were prepared using BALB congenic mice. Such chimeric mice were immunized in vivo against histocompatibility antigens of the C57BL/10Sn (B10) background in association with either the parental H-2 haplotypes, and their spleen cells subsequently boosted in vitro with the same minor antigens. Strong H-2-restricted cytotoxic activity against minor antigens was detected, and the specificity of the restriction could be to the H-2 haplotype of the donor or the host depending on the cells used for priming or boosting. Cross priming could also be demonstrated in these mice. The results show that fully allogenic radiation chimeras can produce H-2-restricted T-cell responses to minor histocompatibility (H) antigens, and are discussed in relation to contrasting results.

  19. Effect of number concentration of soot and H2SO4 on aerosol based emissions from a post combustion capture plant

    NARCIS (Netherlands)

    Khakharia, P.M.; Brachert, L.; Schaber, K.; Huizinga, A.; Vlugt, T.; Mertens, J.; Schallert, B.; Goetheer, E.L.V.

    2013-01-01

    It is known that the use of volatile solvents for a post combustion capture process can lead to emission of the solvent due to their high vapour pressure. More recently, the issue of emission due to the formation of aerosols has been observed at different pilot plants. Therefore, it is of high impor

  20. On the Emission of Electrons from Solid H_2 and D_2 by Bombardment with 1-3 keV Electrons up to Very Large Angles of Incidence

    DEFF Research Database (Denmark)

    Schou, Jørgen; Sørensen, H.

    1982-01-01

    Electron emission, i.e. electron reflection (ER) and secondary electron emission (SEE), was studied for solid H2 and D2 for oblique incidence of 1-3 keV electrons up to an angle of incidence θ of 83°. The ER coefficient η was small at low angles, and rose rapidly with increasing θ above 60......-65°. Only at large angles and low energies were the results different for H2 and D2, those for H2 being the lower ones. The angular variation of the SEE coefficient δ may be written as δ(θ)=δ(0)(cos θ)3/2 up to an angle of 65-75°. For H2 the SEE coefficient is around 0.65 times that the D2 except...... at the largest angles. The results agree well with the existing qualitative tendencies described in the literature. The variation with the angle of incidence shows a fair agreement with an estimate based on data for the angular distribution of electrons ejected from ionized hydrogen molecules. In addition...

  1. Quasi-white light emission involving Förster resonance energy transfer in a new organic inorganic tin chloride based material (AMPS)[SnCl6]H2O

    Science.gov (United States)

    Dammak, Thameur; Abid, Younes

    2017-04-01

    This work deals with optical properties of a new organic inorganic material: 3, 3‧-Diaminodiphenyl-sulfone tin chloride with the formula (C12H14N2O2S)[SnCl6]H2O abbreviated as (AMPS)[SnCl6]H2O. Single crystals of (AMPS)[SnCl6]H2O were elaborated by the solvent evaporation method and investigated by X-ray diffraction, optical absorption (OA), photoluminescence (PL) and photoluminescence excitation (PLE). The crystal structure is composed of discrete [SnCl6] anions surrounded by organic (AMPS) cations and H2O molecules. For optical investigations, thin films have been prepared by spin-coating method from the ethanol solution of the material. Photoluminescence measurements show a quasi-white light and intense emission which can be observed even with naked eye at room temperature. This emission is believed to be due to excitonic recombination involving a Förster resonance energy transfer mechanism in which (AMPS) molecule acts as a donor and [SnCl6] molecule acts as an acceptor. Moreover, the temperature dependence study of the photoluminescence in term of Varshni and Arrhenius models reveals the free character of the inorganic exciton and shows that the organic exciton is rather localized.

  2. {{\\rm{H}}}_{2}\\,X{}^{1}{{\\rm{\\Sigma }}}_{g}^{+}-c{}^{3}{{\\rm{\\Pi }}}_{u} Excitation by Electron Impact: Energies, Spectra, Emission Yields, Cross-sections, and H(1s) Kinetic Energy Distributions

    Science.gov (United States)

    Liu, Xianming; Shemansky, Donald E.; Yoshii, Jean; Liu, Melinda J.; Johnson, Paul V.; Malone, Charles P.; Khakoo, Murtadha A.

    2017-10-01

    The c{}3{{{\\Pi }}}u state of the hydrogen molecule has the second largest triplet-state excitation cross-section, and plays an important role in the heating of the upper thermospheres of outer planets by electron excitation. Precise energies of the H2, D2, and HD c{}3{{{\\Pi }}}u-(v,N) levels are calculated from highly accurate ab initio potential energy curves that include relativistic, radiative, and empirical non-adiabatic corrections. The emission yields are determined from predissociation rates and refined radiative transition probabilities. The excitation function and excitation cross-section of the c{}3{{{\\Pi }}}u state are extracted from previous theoretical calculations and experimental measurements. The emission cross-section is determined from the calculated emission yield and the extracted excitation cross-section. The kinetic energy (E k ) distributions of H atoms produced via the predissociation of the c{}3{{{\\Pi }}}u state, the c{}3{{{\\Pi }}}u- – b{}3{{{Σ }}}u+ dissociative emission by the magnetic dipole and electric quadrupole, and the c{}3{{{\\Pi }}}u – a{}3{{{Σ }}}g+ – b{}3{{{Σ }}}u+ cascade dissociative emission by the electric dipole are obtained. The predissociation of the c{}3{{{\\Pi }}}u+ and c{}3{{{\\Pi }}}u- states both produce H(1s) atoms with an average E k of ∼4.1 eV/atom, while the c{}3{{{\\Pi }}}u- – b{}3{{{Σ }}}u+ dissociative emissions by the magnetic dipole and electric quadrupole give an average E k of ∼1.0 and ∼0.8 eV/atom, respectively. The c{}3{{{\\Pi }}}u – a{}3{{{Σ }}}g+ – b{}3{{{Σ }}}u+ cascade and dissociative emission gives an average E k of ∼1.3 eV/atom. On average, each H2 excited to the c{}3{{{\\Pi }}}u state in an H2-dominated atmosphere deposits ∼7.1 eV into the atmosphere while each H2 directly excited to the a{}3{{{Σ }}}g+ and d{}3{{{\\Pi }}}u states contribute ∼2.3 and ∼3.3 eV, respectively, to the atmosphere. The spectral distribution of the calculated continuum emission

  3. High spectral and spatial resolution observations of the 12.28 micron emission from H2 in the Orion Molecular Cloud

    Science.gov (United States)

    Beck, S. C.; Tokunaga, A. T.; Bloemhof, E. E.; Serabyn, E.; Townes, C. H.; Lacy, J. H.; Smith, H. A.

    1982-01-01

    The pure rotational S(2) line of H2 at 12.28 microns was sought in 44 positions in the Orion Molecular Cloud with 6-arcsec beams and 35 km/s spectral resolution; and it was detected in 27 positions. The lines are approximately symmetric and have full widths at half-maximum ranging from 100 km/s down to the resolution limit. The distribution of intensities and line shapes is largely consistent with that observed in the 2-micron hydrogen transitions; however, unexpectedly complex line profiles and point-to-point variations in line shapes appear, particularly in the region near IRc9.

  4. Hydrogen Two-Photon Continuum Emission from the Horseshoe Filament in NGC 1275

    CERN Document Server

    Johnstone, R M; Fabian, A C; Ferland, G J; Lykins, M; Porter, R L; van Hoof, P A M; Williams, R J R

    2012-01-01

    Far ultraviolet emission has been detected from a knot of Halpha emission in the Horseshoe filament, far out in the NGC 1275 nebula. The flux detected relative to the brightness of the Halpha line in the same spatial region is very close to that expected from Hydrogen two-photon continuum emission in the particle heating model of Ferland et al. (2009) if reddening internal to the filaments is taken into account. We find no need to invoke other sources of far ultraviolet emission such as hot stars or emission lines from CIV in intermediate temperature gas to explain these data.

  5. Computational Modeling of Laboratory X-ray Emission due to Low-Energy Collisions of H-like and He-like ions with H2

    Science.gov (United States)

    Miller, Ansley; Mullen, Patrick Dean; Cumbee, Renata; Stancil, Phillip C.; Leutenegger, Maurice A.

    2016-06-01

    Charge exchange between highly-charged ions and neutral molecules occurs when the solar wind, or other astrophysical plasmas, collide with cool gas. This process emits observable X-rays with specific line intensities. Recent CX experiments at Lawrence Livermore National Laboratory measured the X-ray hardness ratios of low-energy collisions between hydrogen- and helium-like ions with H2 (Leutenegger et al. 2010). Using our recently developed X-ray modeling package, Kronos_v2 (Mullen et al. 2016), which utilizes multi-channel Landau-Zener charge exchange cross sections, we have computed theoretical hydrogen-like hardness ratios to aid in interpretation of the experimental data. While the computed hardness ratios are somewhat smaller than the experiment, it shows better agreement than earlier classical trajectory predictions. We are also in the process of building Kronos_v3; further enhancing the comprehensive charge exchange database to include helium-like and multielectron ions to allow for comparison with experiments and for models of hot astrophysical environments such as supernova remnants, star-forming galaxies, and galaxy clusters.Leutenegger, M. et al. 2010, Phys. Rev. Lett., 105, 063201Mullen, P. D. et al., 2016, ApJS, in press

  6. Cooling of Dense Gas by H2O Line Emission and an Assessment of its Effects in Chondrule-Forming Shocks

    CERN Document Server

    Morris, M A; Ciesla, F J

    2008-01-01

    We consider gas at densities appropriate to protoplanetary disks and calculate its ability to cool due to line radiation emitted by H2O molecules within the gas. Our work follows that of Neufeld & Kaufman (1993; ApJ, 418, 263), expanding on their work in several key aspects, including use of a much expanded line database, an improved escape probability formulism, and the inclusion of dust grains, which can absorb line photons. Although the escape probabilities formally depend on a complicated combination of optical depth in the lines and in the dust grains, we show that the cooling rate including dust is well approximated by the dust-free cooling rate multiplied by a simple function of the dust optical depth. We apply the resultant cooling rate of a dust-gas mixture to the case of a solar nebula shock pertinent to the formation of chondrules, millimeter-sized melt droplets found in meteorites. Our aim is to assess whether line cooling can be neglected in chondrule-forming shocks or if it must be included....

  7. H2@Scale Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ruth, Mark

    2017-07-12

    'H2@Scale' is a concept based on the opportunity for hydrogen to act as an intermediate between energy sources and uses. Hydrogen has the potential to be used like the primary intermediate in use today, electricity, because it too is fungible. This presentation summarizes the H2@Scale analysis efforts performed during the first third of 2017. Results of technical potential uses and supply options are summarized and show that the technical potential demand for hydrogen is 60 million metric tons per year and that the U.S. has sufficient domestic resources to meet that demand. A high level infrastructure analysis is also presented that shows an 85% increase in energy on the grid if all hydrogen is produced from grid electricity. However, a preliminary spatial assessment shows that supply is sufficient in most counties across the U.S. The presentation also shows plans for analysis of the economic potential for the H2@Scale concept. Those plans involve developing supply and demand curves for potential hydrogen generation options and as compared to other options for use of that hydrogen.

  8. H2 Reconstitution

    Science.gov (United States)

    Skipper, Mike

    2002-02-01

    The high power microwave program at the Air Force Research Laboratory (AFRL) includes high power source development in narrow band and wideband technologies. The H2 source is an existing wideband source that was developed at the AFRL. A recent AFRL requirement for a wideband impulse generator to use in materials tests has provided the need to update the H2 source for the current test requirements. The H2 source is composed of a dual resonant transformer that charges a short length of coaxial transmission line. The transmission line is then discharged into an output coaxial transmission line with a self-break hydrogen switch. The dual resonant transformer is driven by a low inductance primary capacitor bank operating through a self-break gas switch. The upgrade of the coaxial hydrogen output switch is the focus of this report. The hydrogen output switch was developed through extensive electrical and mechanical simulations. The switch insulator is made of Ultem 2300 and is designed to operate with a mechanical factor of safety equal to 4.0 at 1,000 psi. The design criteria, design data and operational data will be presented.

  9. On the Emission of Electrons from Solid H_2 and D_2 by Bombardment with 1-3 keV Electrons up to Very Large Angles of Incidence

    DEFF Research Database (Denmark)

    Schou, Jørgen; Sørensen, H.

    1982-01-01

    Electron emission, i.e. electron reflection (ER) and secondary electron emission (SEE), was studied for solid H2 and D2 for oblique incidence of 1-3 keV electrons up to an angle of incidence θ of 83°. The ER coefficient η was small at low angles, and rose rapidly with increasing θ above 60...... at the largest angles. The results agree well with the existing qualitative tendencies described in the literature. The variation with the angle of incidence shows a fair agreement with an estimate based on data for the angular distribution of electrons ejected from ionized hydrogen molecules. In addition......, an ionization cascade treatment leads to an expression for the behavior of the yield of those secondary electrons that are generated directly by the primaries. The agreement with experimental data is good...

  10. Impact of D2O/H2O Solvent Exchange on the Emission of HgTe and CdTe Quantum Dots: Polaron and Energy Transfer Effects.

    Science.gov (United States)

    Wen, Qiannan; Kershaw, Stephen V; Kalytchuk, Sergii; Zhovtiuk, Olga; Reckmeier, Claas; Vasilevskiy, Mikhail I; Rogach, Andrey L

    2016-04-26

    We have studied light emission kinetics and analyzed carrier recombination channels in HgTe quantum dots that were initially grown in H2O. When the solvent is replaced by D2O, the nonradiative recombination rate changes highlight the role of the vibrational degrees of freedom in the medium surrounding the dots, including both solvent and ligands. The contributing energy loss mechanisms have been evaluated by developing quantitative models for the nonradiative recombination via (i) polaron states formed by strong coupling of ligand vibration modes to a surface trap state (nonresonant channel) and (ii) resonant energy transfer to vibration modes in the solvent. We conclude that channel (i) is more important than (ii) for HgTe dots in either solution. When some of these modes are removed from the relevant spectral range by the H2O to D2O replacement, the polaron effect becomes weaker and the nonradiative lifetime increases. Comparisons with CdTe quantum dots (QDs) served as a reference where the resonant energy loss (ii) a priori was not a factor, also confirmed by our experiments. The solvent exchange (H2O to D2O), however, is found to slightly increase the overall quantum yield of CdTe samples, probably by increasing the fraction of bright dots in the ensemble. The fundamental study reported here can serve as the foundation for the design and optimization principles of narrow bandgap quantum dots aimed at applications in long wavelength colloidal materials for infrared light emitting diodes and photodetectors.

  11. Laser-induced positive ion and neutral atom/molecule emission from single-crystal CaHPO4.2H2O: The role of electron-beam-induced defects

    Science.gov (United States)

    Dawes, M. L.; Hess, W.; Kawaguchi, Y.; Langford, S. C.; Dickinson, J. T.

    We examine laser-induced ion and neutral emissions from single-crystal CaHPO4.2H2O (brushite), a wide-band-gap, hydrated inorganic single crystal, with 248-nm excimer laser radiation. Both laser-induced ion and neutral emissions are several orders of magnitude higher following exposure to 2 keV electrons at current densities of 200 μA/cm2 and doses of 1 C/cm2. In addition to intense Ca+ signals, electron-irradiated surfaces yield substantial CaO+, PO+, and P+ signals. As-grown and as-cleaved brushite show only weak neutral O2 and Ca emissions, whereas electron-irradiated surfaces yield enhanced O2, Ca, PO, PO2, and P emissions. Electron irradiation (i) significantly heats the sample, leading to thermal dehydration (CaHPO4 formation) and pyrolysis (Ca2P2O7 formation) and (ii) chemically reduces the surface via electron stimulated desorption. The thermal effects are accompanied by morphological changes, including recrystallization. Although complex, these changes lead to high defect densities, which are responsible for the dramatic enhancements in the observed laser desorption.

  12. HST/COS Spectra of DF Tau and V4046 SGR: First Detection of Molecular Hydrogen Absorption Against the Ly$\\alpha$ Emission Line

    CERN Document Server

    Yang, Hao; France, Kevin

    2011-01-01

    We report the first detection of molecular hydrogen (H$_{2}$) absorption in the Lyman-$\\alpha$ emission line profiles of two classical T Tauri stars (CTTSs), DF Tau and V4046 Sgr, observed by \\emph{HST}/COS. This absorption is the energy source for many of the Lyman-band H$_{2}$ fluorescent lines commonly seen in the far-ultraviolet spectra of CTTSs. We find that the absorbed energy in the H$_{2}$ pumping transitions from a portion of the Lyman-$\\alpha$ line significantly differ from the amount of energy in the resulting fluorescent emission. By assuming additional absorption in the H I Lyman-$\\alpha$ profile along our light of sight, we can correct the H$_{2}$ absorption/emission ratios so that they are close to unity. The required H I absorption for DF Tau is at a velocity close to the radial velocity of the star, consistent with H I absorption in the edge-on disk and interstellar medium. For V4046 Sgr, a nearly face-on system, the required absorption is between +100 km/s and +290 km/s, most likely resultin...

  13. Associated Absorption Lines in the Radio-Loud Quasar 3C 351 Far-Ultraviolet Echelle Spectroscopy from the Hubble Space Telescope

    CERN Document Server

    Yuan, Q; Brotherton, M; Tripp, T M; Kaiser, M E; Kriss, G A

    2002-01-01

    As one of the most luminous radio-loud quasars showing intrinsic ultraviolet (UV) and X-ray absorption, 3C 351 provides a laboratory for studying the kinematics and physical conditions of such ionized absorbers. We present an analysis of the intrinsic absorption lines in the high-resolution ($\\sim$ 7 km/s) far-UV spectrum which was obtained from observations with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST). The spectrum spans wavelengths from 1150 \\AA to 1710 \\AA, and shows strong emission lines from O VI and Ly$\\alpha$. Associated absorption lines are present on the blue wings of the high-ionization emission doublets O VI $\\lambda\\lambda$ 1032,1038 and N V $\\lambda\\lambda$ 1238,1242, as well as the Lyman lines through Ly$\\epsilon$. These intrinsic absorption features are resolved into several distinct kinematic components, covering rest-frame velocities from -40 to -2800 km/s, with respect to the systemic redshift of $z_{em}=0.3721$. For the majority of these abs...

  14. Origin of warm and hot gas emission from low-mass protostars: Herschel-HIFI observations of CO J = 16-15. I. Line profiles, physical conditions, and H2O abundance

    Science.gov (United States)

    Kristensen, L. E.; van Dishoeck, E. F.; Mottram, J. C.; Karska, A.; Yıldız, U. A.; Bergin, E. A.; Bjerkeli, P.; Cabrit, S.; Doty, S.; Evans, N. J.; Gusdorf, A.; Harsono, D.; Herczeg, G. J.; Johnstone, D.; Jørgensen, J. K.; van Kempen, T. A.; Lee, J.-E.; Maret, S.; Tafalla, M.; Visser, R.; Wampfler, S. F.

    2017-09-01

    Context. Through spectrally unresolved observations of high-J CO transitions, Herschel Photodetector Array Camera and Spectrometer (PACS) has revealed large reservoirs of warm (300 K) and hot (700 K) molecular gas around low-mass protostars. The excitation and physical origin of this gas is still not understood. Aims: We aim to shed light on the excitation and origin of the CO ladder observed toward protostars, and on the water abundance in different physical components within protostellar systems using spectrally resolved Herschel-HIFI data. Methods: Observations are presented of the highly excited CO line J = 16-15 (Eup/kB = 750 K) with the Herschel Heterodyne Instrument for the Far Infrared (HIFI) toward a sample of 24 low-mass protostellar objects. The sources were selected from the Herschel "Water in Star-forming regions with Herschel" (WISH) and "Dust, Ice, and Gas in Time" (DIGIT) key programs. Results: The spectrally resolved line profiles typically show two distinct velocity components: a broad Gaussian component with an average FWHM of 20 km s-1 containing the bulk of the flux, and a narrower Gaussian component with a FWHM of 5 km s-1 that is often offset from the source velocity. Some sources show other velocity components such as extremely-high-velocity features or "bullets". All these velocity components were first detected in H2O line profiles. The average rotational temperature over the entire profile, as measured from comparison between CO J = 16-15 and 10-9 emission, is 300 K. A radiative-transfer analysis shows that the average H2O/CO column-density ratio is 0.02, suggesting a total H2O abundance of 2 × 10-6, independent of velocity. Conclusions: Two distinct velocity profiles observed in the HIFI line profiles suggest that the high-J CO ladder observed with PACS consists of two excitation components. The warm PACS component (300 K) is associated with the broad HIFI component, and the hot PACS component (700 K) is associated with the offset HIFI

  15. H2@Scale Resource and Market Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ruth, Mark

    2017-05-04

    The 'H2@Scale' concept is based on the potential for wide-scale utilization of hydrogen as an energy intermediate where the hydrogen is produced from low cost energy resources and it is used in both the transportation and industrial sectors. H2@Scale has the potential to address grid resiliency, energy security, and cross-sectoral emissions reductions. This presentation summarizes the status of an ongoing analysis effort to quantify the benefits of H2@Scale. It includes initial results regarding market potential, resource potential, and impacts of when electrolytic hydrogen is produced with renewable electricity to meet the potential market demands. It also proposes additional analysis efforts to better quantify each of the factors.

  16. The R136 star cluster dissected with Hubble Space Telescope/STIS. I. Far-ultraviolet spectroscopic census and the origin of HeII 1640 in young star clusters

    CERN Document Server

    Crowther, Paul A; Bostroem, K A; Apellaniz, J Maiz; Schneider, F R N; Walborn, N R; Angus, C R; Brott, I; Bonanos, A; de Koter, A; de Mink, S E; Evans, C J; Grafener, G; Herrero, A; Howarth, I D; Langer, N; Lennon, D J; Puls, J; Sana, H; Vink, J S

    2016-01-01

    We introduce a HST/STIS stellar census of R136a, the central ionizing star cluster of 30 Doradus. We present low resolution far-ultraviolet STIS/MAMA spectroscopy of R136 using 17 contiguous 52x0.2 arcsec slits which together provide complete coverage of the central 0.85 parsec (3.4 arcsec). We provide spectral types of 90% of the 57 sources brighter than m_F555W = 16.0 mag within a radius of 0.5 parsec of R136a1, plus 8 additional nearby sources including R136b (O4\\,If/WN8). We measure wind velocities for 52 early-type stars from CIV 1548-51, including 16 O2-3 stars. For the first time we spectroscopically classify all Weigelt & Baier members of R136a, which comprise three WN5 stars (a1-a3), two O supergiants (a5-a6) and three early O dwarfs (a4, a7, a8). A complete Hertzsprung-Russell diagram for the most massive O stars in R136 is provided, from which we obtain a cluster age of 1.5+0.3_-0.7 Myr. In addition, we discuss the integrated ultraviolet spectrum of R136, and highlight the central role played b...

  17. H2 Temperatures in the Crab Nebula

    CERN Document Server

    Loh, E D; Ferland, G J; Curtis, Z K; Richardson, C T; Fabian, A C; Salomé, P

    2011-01-01

    We used K-band spectra to measure the H2 excitation temperatures in six molecular knots associated with the filaments in the Crab Nebula. The temperatures are quite high - in the range T ~ 2000-3000K, just below the H2 dissociation temperature. This is the temperature range over which the H2 1-0 S(1) line at 2.121\\mum has its maximum emissivity per unit mass, so there may be many additional H2 cores with lower temperatures that are too faint to detect. We also measured the electron density in adjacent ionized gas, which on the assumption of gas pressure balance indicates densities in the molecular region n_mol ~ 20,000 H baryons cm-3, although this really is just a lower limit since the H2 gas may be confined by other means. The excited region may be just a thin skin on a much more extensive blob of molecular gas that does not have the correct temperature and density to be as easily detectable. At the opposite extreme, the observed knots could consist of a fine mist of molecular gas in which we are detecting ...

  18. Far-ultraviolet spectrophotometry of Spica

    Science.gov (United States)

    Cook, Timothy A.; Cash, Webster; Snow, Theodore P.

    1989-01-01

    A spectrum of the star Spica (Alpha Virginis) from 960 to 1270 A was recorded by a rocket-borne spectrograph March 13, 1988. The spectrum, which has 3.4 A resolution, shows a much sharper drop-off in intensity near 1050 A than similar measurements made by the Voyager UVS, but is in good agreement with the spectrum obtained by Brune et al. in a 1977 sounding rocket. The disagreement with Voyager is a factor of 1.5 at 1100 A and grows to a factor of 5.7 at 960 A. This implies that the photometric standards between 912 and 1100 A may need some revision, and that the standard photospheric models for hot stars may err significantly near the Lyman limit.

  19. Far ultraviolet spectrophotometry of BD +28 4211

    Science.gov (United States)

    Cook, Timothy A.; Cash, Webster; Green, James C.

    1991-01-01

    The results are reported of a November 1989 rocket flight which recorded a flux-calibrated spectrum of BD +28 4211 from 912 to 1150 A with 1A resolution. BD +28 4211, an SdO-type star, is commonly used as an ultraviolet calibration source in the IUE wavelength band. The present work extends the useful range of this standard shortward of Lyman-alpha. Since previous experiments show marked disparity, this study can be useful in determining a standard in the 912 to 1216 A band.

  20. CO and H2 Absorption in the AA Tauri Circumstellar Disk

    CERN Document Server

    France, Kevin; Herczeg, Gregory J; Schindhelm, Eric; Yang, Hao; Abgrall, Herve; Roueff, Evelyne; Brown, Alexander; Brown, Joanna; Linsky, Jeffrey L

    2011-01-01

    The direct study of molecular gas in inner protoplanetary disks is complicated by uncertainties in the spatial distribution of the gas, the time-variability of the source, and the comparison of observations across a wide range of wavelengths. Some of these challenges can be mitigated with far-ultraviolet spectroscopy. Using new observations obtained with the HST-Cosmic Origins Spectrograph, we measure column densities and rovibrational temperatures for CO and H2 observed on the line-of-sight through the AA Tauri circumstellar disk. CO A-X absorption bands are observed against the far-UV continuum. The CO absorption is characterized by log(N(^{12}CO)) = 17.5 +/- 0.5 cm^{-2} and T_rot(CO) = 500$^{+500}_{-200} K, although this rotational temperature may underestimate the local kinetic temperature of the CO-bearing gas. We also detect ^{13}CO in absorption with an isotopic ratio of ~20. We do not observe H2 absorption against the continuum; however, hot H2 (v > 0) is detected in absorption against the LyA emissio...

  1. Ultraviolet Survey of CO and H_2 in Diffuse Molecular Clouds: The Reflection of Two Photochemistry Regimes in Abundance Relationships

    CERN Document Server

    Sheffer, Y; Federman, S R; Abel, N P; Gredel, R; Lambert, D L; Shaw, G

    2008-01-01

    (Abridged) We carried out a comprehensive far-ultraviolet (UV) survey of ^12CO and H_2 column densities along diffuse molecular Galactic sight lines in order to explore in detail the relationship between CO and H_2. We measured new CO abundances from HST spectra, new H_2 abundances from FUSE data, and new CH, CH^+, and CN abundances from the McDonald and European Southern Observatories. A plot of log N(CO) versus log N(H_2) shows that two power-law relationships are needed for a good fit of the entire sample, with a break located at log N(CO, cm^-2) = 14.1 and log N(H_2) = 20.4, corresponding to a change in production route for CO in higher-density gas. Similar logarithmic plots among all five diatomic molecules allow us to probe their relationships, revealing additional examples of dual slopes in the cases of CO versus CH (break at log N = 14.1, 13.0), CH^+ versus H_2 (13.1, 20.3), and CH^+ versus CO (13.2, 14.1). These breaks are all in excellent agreement with each other, confirming the break in the CO ver...

  2. [Bi2Cl10(H2-Norf)4(H2O)8] where H-Norf is Norfloxacin(R)%[Bi2Cl10(H2-Norf)4(H2O)8](H-Norf是诺氟沙星)

    Institute of Scientific and Technical Information of China (English)

    李咏华; 熊仁根

    2005-01-01

    The crystal structure of [Bi2Cl10(H2-Norf)4(H2O)s] (1) comprises [H2-Norf]+ cations and [Bi2Cl10]4- anions,that are loosely associated via H-bonding interactions, as well as water molecules that also participate in H-bond-ing interactions. Strong blue-fluorescent emission of 1 at solid state is observed at the room temperature. CCDC:238237.

  3. H2@Scale Workshop Report

    Energy Technology Data Exchange (ETDEWEB)

    Pivovar, Bryan

    2017-03-31

    Final report from the H2@Scale Workshop held November 16-17, 2016, at the National Renewable Energy Laboratory in Golden, Colorado. The U.S. Department of Energy's National Renewable Energy Laboratory hosted a technology workshop to identify the current barriers and research needs of the H2@Scale concept. H2@Scale is a concept regarding the potential for wide-scale impact of hydrogen produced from diverse domestic resources to enhance U.S. energy security and enable growth of innovative technologies and domestic industries. Feedback received from a diverse set of stakeholders at the workshop will guide the development of an H2@Scale roadmap for research, development, and early stage demonstration activities that can enable hydrogen as an energy carrier at a national scale.

  4. H2O Formation in C-rich AGB Winds

    NARCIS (Netherlands)

    R. Lombaert; L. Decin; P. Royer; A. de Koter; N.L.J. Cox; J. De Ridder; T. Khouri; M. Agúndez; J.A.D.L. Blommaert; J. Gernicharo; E. González-Alfonso; M.A.T. Groenewegen; F. Kerschbaum; D. Neufeld; B. Vandenbussche; C. Waelkens

    2014-01-01

    The Herschel detection of warm H2O vapor emission from C-rich winds of AGB stars challenges the current understanding of circumstellar chemistry. Two mechanisms have been invoked to explain warm H2O formation. In the first, penetration of UV interstellar radiation through a clumpy circumstellar medi

  5. Influence of H2S poisoned biomethane on catalyst performance

    NARCIS (Netherlands)

    Bruijstens, A.J.; Beuman, W.P.H.; Molen, M. van de; Bleuanus, W.A.J.

    2008-01-01

    The influence of the level of H2S in the fuel on catalyst performance was investigated. The main conclusion is that at H2S levels of 30ppm and above, it is probable that the exhaust gas emissions of NGV’s are negatively influenced. Further research is suggested to: 1) Determine the effect of differe

  6. Influence of H2S poisoned biomethane on catalyst performance

    NARCIS (Netherlands)

    Bruijstens, A.J.; Beuman, W.P.H.; Molen, M. van de; Bleuanus, W.A.J.

    2008-01-01

    The influence of the level of H2S in the fuel on catalyst performance was investigated. The main conclusion is that at H2S levels of 30ppm and above, it is probable that the exhaust gas emissions of NGV’s are negatively influenced. Further research is suggested to: 1) Determine the effect of

  7. HI-to-H2 Transitions and H I Column Densities in Galaxy Star-Forming Regions

    CERN Document Server

    Sternberg, Amiel; Roueff, Evelyne; Bourlot, Jacques Le

    2014-01-01

    We present new analytic theory and radiative transfer computations for the atomic to molecular (HI-to-H2) transitions, and the build-up of atomic-hydrogen (HI) gas columns, in optically thick interstellar clouds, irradiated by far-ultraviolet photodissociating radiation fields. We derive analytic expressions for the total HI column densities for (1D) planar slabs, for beamed or isotropic radiation fields, from the weak- to strong-field limits, for gradual or sharp atomic to molecular transitions, and for arbitrary metallicity. Our expressions may be used to evaluate the HI column densities as functions of the radiation field intensity and the H2-dust-limited dissociation flux, the hydrogen gas density, and the metallicity-dependent H2 formation rate-coefficient and far-UV dust-grain absorption cross-section. We make the distinction between "HI-dust" and "H2-dust" opacity, and we present computations for the "universal H2-dust-limited effective dissociation bandwidth". We validate our analytic formulae with Me...

  8. Kinetic Energy Distribution of H(2p) Atoms from Dissociative Excitation of H2

    Science.gov (United States)

    Ajello, Joseph M.; Ahmed, Syed M.; Kanik, Isik; Multari, Rosalie

    1995-01-01

    The kinetic energy distribution of H(2p) atoms resulting from electron impact dissociation of H2 has been measured for the first time with uv spectroscopy. A high resolution uv spectrometer was used for the measurement of the H Lyman-alpha emission line profiles at 20 and 100 eV electron impact energies. Analysis of the deconvolved 100 eV line profile reveals the existence of a narrow line peak and a broad pedestal base. Slow H(2p) atoms with peak energy near 80 meV produce the peak profile, which is nearly independent of impact energy. The wings of H Lyman-alpha arise from dissociative excitation of a series of doubly excited Q(sub 1) and Q(sub 2) states, which define the core orbitals. The fast atom energy distribution peaks at 4 eV.

  9. H2@Scale Resource and Market Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ruth, Mark

    2017-07-12

    This presentation overviews progress to date on the H2@Scale resource and market analysis work. The work finds, for example, that hydrogen demand of 60 MMT/yr is possible when transportation and industry are considered; resources are available to meet that demand; using renewable resources would reduce emissions and fossil use by over 15%; further impacts are possible when considering synergistic benefits; additional analysis is underway to improve understanding of potential markets and synergistic impacts; and further analysis will be necessary to estimate impacts due to spatial characteristics, feedback effects in the economy, and inertia characteristics.

  10. Effects of mirror surface roughness on encircled energy for far ultraviolet telescopes%镜面粗糙度对远紫外望远镜能量集中度的影响

    Institute of Scientific and Technical Information of China (English)

    付怀洋; 周泗忠; 姜凯; 梅超; 张惠

    2014-01-01

    The image quality was degraded by the surface roughness of astronomy imaging applications, and it might be specified in terms of fractional encircled energy. Relationship between the encircled energy and roughness RMS was qualitatively analysed by cosine phase grating model,moreover,the effective transfer function of the surface was built drew on Fourier optical linear systems theory, then the associated angle spread function as well as encircled energy were deduced. For 1 216Å (1Å=0.1 nm) far ultraviolet telescope which closed to diffraction limit and in the terms of primary and secondary mirrors roughness RMS were far less than one wavelength, encircled energy versus RMS roughness and autocovariance width could be infered. So resolution error caused by surface roughness was limited in 0.171 5, the manufacturing requirement for mirrors roughness RMS was less than 31 Å and autocovariance width was longer than one wavelength. It′s useful for our manufacturing guiding significance.%远紫外空间成像设备镜面粗糙度严重影响成像质量,成像质量可用能量集中度来表征。拟用余弦相位调制光栅分析方法定性说明镜面粗糙度 RMS 对能量集中度的影响;通过傅里叶光学线性系统理论建立了普遍的面传递函数,得到了角度能量和能量集中度的分布情况,并以设计上达到衍射极限的1216Å(1Å=0.1 nm)远紫外望远镜为对象,在镜面粗糙度 RMS 值远小于波长的假定情况下,得到了能量集中度与主次镜面粗糙度 RMS 和面自相关长度的关系,并预测了镜面粗糙度引起的分辨率误差在0.1715″时对镜面加工的要求,即主次镜镜面 RMS 小于31Å,面自相关宽度大于1波长,这对于实际的加工具有指导意义。

  11. Effects of lanthanoid cations on the first electronic transition of liquid water studied using attenuated total reflection far-ultraviolet spectroscopy: ligand field splitting of lanthanoid hydrates in aqueous solutions.

    Science.gov (United States)

    Goto, Takeyoshi; Ikehata, Akifumi; Morisawa, Yusuke; Higashi, Noboru; Ozaki, Yukihiro

    2012-10-15

    The effects of the lanthanoid cations (Ln(3+)) on the first electronic transition (à ← X̃) of liquid water were studied from the attenuated total reflection far-ultraviolet (ATR-FUV) spectra of trivalent Ln(3+) electrolyte solutions (1 M), except Pm(3+). The à ← X̃ transition energies of the Ln(3+) electrolyte solutions show a distinct tetrad in their dependence on the number of 4f electrons of the Ln(3+) cations. For the half occupation period of the 4f electrons, the à ← X̃ transition energies decrease from La(3+) (4f(0), 8.0375 eV) to Nd(3+) (4f(3), 8.0277 eV) and increase from Sm(3+) (4f(5), 8.0279 eV) to Gd(3+) (4f(7), 8.0374 eV). For the complete occupation period, there are two local minima at Dy(3+) (4f(9), 8.0349 eV) and Yb(3+) (4f(13), 8.0355 eV). The à ← X̃ transition energies of the tetrad nodes (La(3+), Gd(3+), Ho(3+) (4f(10)), and Lu(3+) (4f(14))) increase slightly, as the nuclear charge increases in accordance with the hydration energies of the Ln(3+) cations. The energy difference (ΔE) between the à ← X̃ transition energies and the line between La(3+) and Lu(3+) is largest at Nd(3+) (80.5 cm(-1)) for the half occupation period and at Dy(3+) (26.1 cm(-1)) and Yb(3+) (24.5 cm(-1)) for the complete occupation period. The order of magnitude of ΔE is comparable to the ligand field splitting (LFS) of the ground state multiplets of Ln(3+) complexes. The observed tetrad trend of the à ← X̃ transition energies of the Ln(3+) electrolyte solutions across the 4f period reflects the hydration energies of the Ln(3+) cations and the LFS induced by water ligands.

  12. ISO Spectroscopy of H2 in Star Forming Regions

    NARCIS (Netherlands)

    Van den Ancker, M. E.; Wesselius, P. R.; Tielens, A. G. G. M.

    2000-01-01

    Abstract: We have studied molecular hydrogen emission in a sample of 21 YSOs using spectra obtained with the Infrared Space Observatory (ISO). H2 emission was detected in 12 sources and can be explained as arising in either a shock, caused by the interaction of an outflow from an embedded YSO with

  13. H2 in low-ionization structures of planetary nebulae

    Science.gov (United States)

    Akras, Stavros; Gonçalves, Denise R.; Ramos-Larios, Gerardo

    2017-02-01

    We report the detection of near-IR H2 emission from the low-ionization structures (knots) in two planetary nebulae. The deepest ever high-angular-resolution H2 (1-0) S(1) at 2.122 μm, H2 (2-1) S(1) at 2.248 μm and Brγ images of K 4-47 and NGC 7662, obtained using the Near InfraRed Imager and Spectrometer (NIRI) at Gemini-North, are analysed here. K 4-47 reveals a remarkable highly collimated bipolar structure not only in the optical but also in the molecular hydrogen emission. The H2 emission emanates from the walls of the bipolar outflows and also from the pair of knots at the tip of the outflows. The H2 (1-0) S(1)/(2-1) S(1) line ratio ranges from ˜7 to ˜10, suggesting the presence of shock interactions. Our findings can be explained by the interaction of a jet/bullet ejected from the central star with the surrounding asymptotic giant branch material. The strongest H2 line, (1-0) S(1), is also detected in several low-ionization knots located at the periphery of the elliptical planetary nebula NGC 7662, but only four of these knots are detected in the H2 (2-1) S(1) line. These four knots exhibit an H2 line ratio between 2 and 3.5, which suggests that the emission is caused by the UV ionizing flux of the central star. Our data confirm the presence of H2 gas in both fast- and slow-moving low-ionization knots, which has only been confirmed before in the nearby Helix nebula and Hu 1-2. Overall, the low-ionization structures of planetary nebulae are found to have similar traits to photodissociation regions.

  14. H2 Fluorescence in M Dwarf Systems: A Stellar Origin

    Science.gov (United States)

    Kruczek, Nicholas; France, Kevin; Evonosky, William; Parke Loyd, R. O.; Youngblood, Allison; Roberge, Aki; Wittenmyer, Robert A.; Stocke, John T.; Fleming, Brian; Hoadley, Keri

    2017-08-01

    Observations of molecular hydrogen (H2) fluorescence are a potentially useful tool for measuring the H2 abundance in exoplanet atmospheres. This emission was previously observed in {{M}} dwarfs with planetary systems. However, low signal-to-noise prevented a conclusive determination of its origin. Possible sources include exoplanetary atmospheres, circumstellar gas disks, and the stellar surface. We use observations from the “Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanet Host Stars” Treasury Survey to study H2 fluorescence in {{M}} dwarfs. We detect fluorescence in Hubble Space Telescope spectra of 8/9 planet-hosting and 5/6 non-planet-hosting {{M}} dwarfs. The detection statistics, velocity centroids, and line widths of the emission suggest a stellar origin. We calculate H2-to-stellar-ion flux ratios to compare flux levels between stars. For stars with planets, we find an average ratio of 1.7+/- 0.9, using the fluxes of the brightest H2 feature and two stellar C iv lines. This is compared to 0.9+/- 0.4 for stars without planets, showing that the planet-hosting {{M}} dwarfs do not have significant excess H2 emission. This claim is supported by the direct FUV imaging of GJ 832, where no fluorescence is observed at the expected star-planet separation. Additionally, the 3σ upper limit of 4.9 × 10-17 erg cm-2 s-1 from these observations is two orders of magnitude below the spectroscopically observed H2 flux. We constrain the location of the fluorescing H2 using 1D radiative transfer models, and find that it could reside in starspots or a ˜2500-3000 {{K}} region in the lower chromosphere. The presence of this emission could complicate efforts to quantify the atmospheric abundance of H2 in exoplanets orbiting {{M}} dwarfs.

  15. On Robust H2 Estimation

    Institute of Scientific and Technical Information of China (English)

    Lihua Xie

    2005-01-01

    The problem of state estimation for uncertain systems has attracted a recurring interest in the past decade. In this paper, we shall give an overview on some of the recent development in the area by focusing on the robust H2 (Kaiman) filtering of uncertain discrete-time systems. The robust H2 estimation is concerned with the design of a fixed estimator for a family of plants under consideration such that the estimation error covariance is of a minimal upper bound. The uncertainty under consideration includes norm-bounded uncertainty and polytopic uncertainty. In the finite horizon case, we shall discuss a parameterized difference Riccati equation approach for systems with normbounded uncertainty and pinpoint the difference of state estimation between systems without uncertainty and those with uncertainty. In the infinite horizon case, we shall deal with both the norm-bounded and polytopic uncertainties using a linear matrix inequality (LMI) approach. In particular, we shall demonstrate how the conservatism of design can be improved using a slack variable technique. We also propose an iterative algorithm to refine a designed estimator. An example will be given to compare estimators designed using various techniques.

  16. H$_2$ in low-ionization structures of planetary nebulae

    CERN Document Server

    Akras, Stavros; Ramos-Larios, Gerardo

    2016-01-01

    We report the detection of near-IR H$_2$ emission from the low-ionization structures (knots) in two planetary nebulae. The deepest ever, high-angular resolution H$_2$ 1-0 S(1) at 2.122$\\mu$, H$_2$ 2-1 S(1) at 2.248$\\mu$ and Br$\\gamma$ images of K 4-47 and NGC 7662, obtained using the Near InfraRed Imager and Spectrometer (NIRI) at Gemini-North, are analyzed here. K 4-47 reveals a remarkable highly collimated bipolar structure not only in the optical but also in the molecular hydrogen emission. The H$_2$ emission emanates from the walls of the bipolar outflows and also from the pair of knots at the tip of the outflows. The H$_2$ 1-0 S(1)/2-1 S(1) line ratio ranges from ~7 to ~10 suggesting the presence of shock interactions. Our findings can be explained by the interaction of a jet/bullet ejected from the central star with the surrounding asymptotic giant branch material. The strongest H$_2$ line, v=1-0 S(1) is also detected in several low-ionization knots located at the periphery of the elliptical planetary n...

  17. Odin observations of H2O in the Galactic Centre

    CERN Document Server

    Sandqvist, A; Black, J; Sandqvist, Aa.

    2003-01-01

    The Odin satellite has been used to detect emission and absorption in the 557-GHz H2O line in the Galactic Centre towards the Sgr A* Circumnuclear Disk (CND), and the Sgr A +20 km/s and +50 km/s molecular clouds. Strong broad H2O emission lines have been detected in all three objects. Narrow H2O absorption lines are present at all three positions and originate along the lines of sight in the 3-kpc Spiral Arm, the -30 km/s Spiral Arm and the Local Sgr Spiral Arm. Broad H2O absorption lines near -130 km/s are also observed, originating in the Expanding Molecular Ring. A new molecular feature (the ``High Positive Velocity Gas'' - HPVG) has been identified in the positive velocity range of ~ +120 to +220 km/s, seen definitely in absorption against the stronger dust continuum emission from the +20 km/s and +50 km/s clouds and possibly in emission towards the position of Sgr A* CND. The 548-GHz H2_18O isotope line towards the CND is not detected at the 0.02 K (rms) level.

  18. Endogenous mitigation of H2S inside of the landfills.

    Science.gov (United States)

    Fang, Yuan; Zhong, Zhong; Shen, Dongsheng; Du, Yao; Xu, Jing; Long, Yuyang

    2016-02-01

    Vast quantities of hydrogen sulfide (H2S) emitted from landfill sites require urgent disposal. The current study focused on source control and examined the migration and conversion behavior of sulfur compounds in two lab-scale simulated landfills with different operation modes. It aimed to explore the possible strategies and mechanisms for H2S endogenous mitigation inside of landfills during decomposition. It was found that the strength of H2S emissions from the landfill sites was dependent on the municipal solid waste (MSW) degradation speed and vertical distribution of sulfide. Leachate recirculation can shorten both the H2S influence period and pollution risk to the surrounding environment. H2S endogenous mitigation may be achieved by chemical oxidation, biological oxidation, adsorption, and/or precipitation in different stages. Migration and conversion mainly affected H2S release behavior during the initial stabilization phase in the landfill. Microbial activities related to sulfur, nitrogen, and iron can further promote H2S endogenous mitigation during the high reducing phase. Thus, H2S endogenous mitigation can be effectively enhanced via control of the aforementioned processes.

  19. The Production of HI in Photodissociation Regions and A Comparison with CO(1-0) Emission

    CERN Document Server

    Allen, R J; Kaufman, M J; Allen, Ronald J.; Heaton, Harold I.; Kaufman, Michael J.

    2004-01-01

    The gas at the surfaces of molecular clouds in galaxies is heated and dissociated by photons from young stars both near and far. HI resulting from the dissociation of molecular hydrogen H2 emits hyperfine line emission at 21 cm, and warmed CO emits dipole rotational lines such as the 2.6 mm line of CO(1-0). We use previously developed models for photodissociation regions (PDRs) to compute the intensities of these HI and CO(1-0) lines as a function of the total volume density n in the cloud and the far ultraviolet flux G0 incident upon it and present the results in units familiar to observers. The intensities of these two lines behave differently with changing physical conditions in the PDR, and, taken together, the two lines can provide a ground-based radio astronomy diagnostic for determining n and G0 separately in distant molecular clouds. This diagnostic is particularly useful in the range Gzero <~ 100, 10 cm^{-3} <~ n <~ 10^5 cm^{-3}, which applies to a large fraction of the volume of the interst...

  20. Near-Infrared H2 and Continuum Survey of Extended Green Objects

    CERN Document Server

    Lee, Hsu-Tai; Duan, Hao-Yuan; Karr, Jennifer; Su, Yu-Nung; Liu, Sheng-Yuan; Froebrich, Dirk; Yeh, Cosmos C

    2012-01-01

    The Spitzer GLIMPSE survey has revealed a number of "Extended Green Objects" (EGOs) which display extended emission at 4.5 micron. These EGOs are potential candidates for high mass protostellar outflows. We have used high resolution (< 1") H2 1-0 S(1) line, K, and H-band images from the United Kingdom Infrared Telescope to study 34 EGOs to investigate their nature. We found that 12 EGOs exhibit H2 outflows (two with chains of H2 knotty structures; five with extended H2 bipolar structures; three with extended H2 lobes; two with pairs of H2 knots). In the 12 EGOs with H2 outflows, three of them exhibit similar morphologies between the 4.5 micron and H2 emission. However, the remaining 9 EGOs show that the H2 features are more extended than the continuum features, and the H2 emission is seldom associated with continuum emission. Furthermore, the morphologies of the near-infrared continuum and 4.5 micron emission are similar to each other for those EGOs with K-band emission, implying that at least a part of th...

  1. Bolometric Luminosity Correction of H2O Maser AGNs

    Indian Academy of Sciences (India)

    Q. Guo; J. S. Zhang; J. Wang

    2014-09-01

    For the H2O maser host AGN sample, we derived their bolometric luminosity corrections, based on their X-ray data and [O III] emission line luminosities. Our results for maser AGNs is comparable to that of non-maser AGNs.

  2. Glitters of warm H2 in cold diffuse molecular gas

    NARCIS (Netherlands)

    Falgarone, Edith; Beichman, Chaz; Boulanger, Francois; Combes, Francoise; Gry, Cecile; Helou, Georges; Laureijs, Rene; Pineau Des Forets, Guillaume; Valentijn, Edwin; Verstraete, Laurent

    2004-01-01

    Cold molecular hydrogen, a possibly dominant gas fraction in galaxies, does not radiate due to the symmetry and small moment of inertia of the molecule. The only tracers of cold H2, the rotational lines of CO and dust thermal emission operate only in metal-rich environments. By detecting the lowest

  3. Interpolatory Weighted-H2 Model Reduction

    CERN Document Server

    Anic, Branimir; Gugercin, Serkan; Antoulas, Athanasios C

    2012-01-01

    This paper introduces an interpolation framework for the weighted-H2 model reduction problem. We obtain a new representation of the weighted-H2 norm of SISO systems that provides new interpolatory first order necessary conditions for an optimal reduced-order model. The H2 norm representation also provides an error expression that motivates a new weighted-H2 model reduction algorithm. Several numerical examples illustrate the effectiveness of the proposed approach.

  4. Crystal structures of heterotypic nucleosomes containing histones H2A.Z and H2A.

    Science.gov (United States)

    Horikoshi, Naoki; Arimura, Yasuhiro; Taguchi, Hiroyuki; Kurumizaka, Hitoshi

    2016-06-01

    H2A.Z is incorporated into nucleosomes located around transcription start sites and functions as an epigenetic regulator for the transcription of certain genes. During transcriptional regulation, the heterotypic H2A.Z/H2A nucleosome containing one each of H2A.Z and H2A is formed. However, previous homotypic H2A.Z nucleosome structures suggested that the L1 loop region of H2A.Z would sterically clash with the corresponding region of canonical H2A in the heterotypic nucleosome. To resolve this issue, we determined the crystal structures of heterotypic H2A.Z/H2A nucleosomes. In the H2A.Z/H2A nucleosome structure, the H2A.Z L1 loop structure was drastically altered without any structural changes of the canonical H2A L1 loop, thus avoiding the steric clash. Unexpectedly, the heterotypic H2A.Z/H2A nucleosome is more stable than the homotypic H2A.Z nucleosome. These data suggested that the flexible character of the H2A.Z L1 loop plays an essential role in forming the stable heterotypic H2A.Z/H2A nucleosome.

  5. Spitzer Mapping of PAHs and H2 in Photodissociation Regions

    CERN Document Server

    Fleming, Brian T; Lupu, Roxana E; McCandliss, Stephan R

    2010-01-01

    The mid-infrared (MIR) spectra of dense photodissociation regions (PDRs) are typically dominated by emission from polycyclic aromatic hydrocarbons (PAHs) and the lowest pure rotational states of molecular hydrogen (H2); two species which are probes of the physical properties of gas and dust in intense UV radiation fields. We utilize the high angular resolution of the Infrared Spectrograph on the Spitzer Space Telescope to construct spectral maps of the PAH and H2 features for three of the best studied PDRs in the galaxy, NGC 7023, NGC 2023 and IC 63. We present spatially resolved maps of the physical properties, including the H2 ortho-to-para ratio, temperature, and G_o/n_H. We also present evidence for PAH dehydrogenation, which may support theories of H2 formation on PAH surfaces, and a detection of preferential self-shielding of ortho-H2. All PDRs studied exhibit average temperatures of ~500 - 800K, warm H2 column densities of ~10^20 cm^-2, G_o/n_H ~ 0.1 - 0.8, and ortho-to-para ratios of ~ 1.8. We find th...

  6. Hyperfine excitation of linear molecules by para- and ortho-H2: application to the HCl-H2 system.

    Science.gov (United States)

    Lanza, Mathieu; Lique, François

    2014-10-28

    The determination of hyperfine structure resolved excitation cross sections and rate coefficients due to H2 collisions is required to interpret astronomical spectra. In this paper, we present several theoretical approaches to compute these data. An almost exact recoupling approach and approximate sudden methods are presented. We apply these different approaches to the HCl-H2 collisional system in order to evaluate their respective accuracy. HCl-H2 hyperfine structure resolved cross sections and rate coefficients are then computed using recoupling and approximate sudden methods. As expected, the approximate sudden approaches are more accurate when the collision energy increases and the results suggest that these approaches work better for para-H2 than for ortho-H2 colliding partner. For the first time, we present HCl-H2 hyperfine structure resolved rate coefficients, computed here for temperatures ranging from 5 to 300 K. The usual Δj1 = ΔF1 propensity rules are observed for the hyperfine transitions. The new rate coefficients will significantly help the interpretation of interstellar HCl emission lines observed with current and future telescopes. We expect that these new data will allow a better determination of the HCl abundance in the interstellar medium, that is crucial to understand the interstellar chlorine chemistry.

  7. H2− formation in electron impact ionization of H2 near threshold

    NARCIS (Netherlands)

    Boesten, L.G.J.; Heideman, H.G.M.; Schowengerdt, F.D.; Golden, D.E.; Ormonde, S.

    1974-01-01

    New features in near threshold ionization spectra of H2 which can be correlated with two series of H2− states proceeding across the H2+ threshold, indicate a need for coincidence experiments that differentiate between one and two electron decay modes of H2−.

  8. H2− formation in electron impact ionization of H2 near threshold

    NARCIS (Netherlands)

    Boesten, L.G.J.; Heideman, H.G.M.; Schowengerdt, F.D.; Golden, D.E.; Ormonde, S.

    1974-01-01

    New features in near threshold ionization spectra of H2 which can be correlated with two series of H2− states proceeding across the H2+ threshold, indicate a need for coincidence experiments that differentiate between one and two electron decay modes of H2−.

  9. Photolysis of H2O-H2O2 Mixtures: The Destruction of H2O2

    Science.gov (United States)

    Loeffler, M. J.; Fama, M.; Baragiola, R. A.; Carlson, R. W.

    2013-01-01

    We present laboratory results on the loss of H2O2 in solid H2O + H2O2 mixtures at temperatures between 21 and 145 K initiated by UV photolysis (193 nm). Using infrared spectroscopy and microbalance gravimetry, we measured the decrease of the 3.5 micrometer infrared absorption band during UV irradiation and obtained a photodestruction cross section that varies with temperature, being lowest at 70 K. We use our results, along with our previously measured H2O2 production rates via ionizing radiation and ion energy fluxes from the spacecraft to compare H2O2 creation and destruction at icy satellites by ions from their planetary magnetosphere and from solar UV photons. We conclude that, in many cases, H2O2 is not observed on icy satellite surfaces because the H2O2 photodestruction rate is much higher than the production rate via energetic particles, effectively keeping the H2O2 infrared signature at or below the noise level.

  10. Rotationally Excited H2 in the Magellanic Clouds

    Science.gov (United States)

    Xue, Rui; Wong, T. H.; Welty, D. E.

    2014-01-01

    We have performed a systematic analysis of excited-state (up to J=5) H2 Lyman-Werner absorption lines using archival spectra in the FUSE Magellanic Clouds Legacy Project. The H2 column densities at different ground state J-levels and the Doppler broadening parameter b are determined for both Magellanic and Galactic components along each line of sight. Combining the results with previously measured total gas column densities of HI and H2, we derive the H2 excitation temperature, volume density, and local UV field strength for the absorbing gas. The physical and chemical properties of the absorbers are compared with Galactic samples, and also used to test predictions from multiple-phase ISM equilibrium models. Finally, we compare the absorbing gas from the Magellanic Clouds with its larger-scale ISM environment as revealed in previous surveys of gas and dust emission, extending our results from the UV data measured along moderately reddened sight lines to more dense gas detected in emission.

  11. NMR Evidence of Cage-to-Cage Diffusion of H2 in H2-Clathrates

    Science.gov (United States)

    Senadheera, Lasitha; Conradi, Mark

    2008-03-01

    H2 and heavy-ice at P>1 kbar and T ˜250 K form H2-D2O clathrate; four and one H2 may occupy each large (L) and small (S) cage, respectively. In H2-THF-H2O clathrate, H2 occupies singly and only S cages. Previous electronic-structure calculations estimate the barriers for H2 passage though hexagonal and pentagonal faces of cages as ˜6 and ˜25 kcal/mol, respectively. Our H2 NMR linewidth data reflect random crystal fields from frozen cage-wall D2O orientations. We find dramatic reductions in linewidth starting at 120 K (175 K) for H2-D2O (H2-TDF-D2O) indicating time-averaging of the crystal fields. Assuming Arrhenius behavior, our data imply energies for escape from L (S) cages of about ˜4 (˜6) kcal/mol. For L cages, the agreement with the calculated (cages were treated as rigid) barrier is reasonable. For H2 in S cages, in H2-TDF-D2O, the extreme disagreement with theory points to another mechanism of time-averaging, reorientations of the cage-wall D2O molecules, as suggested by previous work in TDH-H2O clathrate. Our limited NMR spectra at high T ˜145 K in H2-D2O show evidence of distinct resonances from diffusionally mobile and immobile H2 molecules, as expected.

  12. Evolution of chromospheres and coronae in solar mass stars - A far-ultraviolet and soft X-ray comparison of Arcturus /K2 III/ and Alpha Centauri A /G2 V/

    Science.gov (United States)

    Ayres, T. R.; Simon, T.; Linsky, J. L.

    1982-01-01

    IUE far-UV and Einstein Observatory soft X-ray observations for the red giant Arcturus and the nearby yellow dwarf Alpha-Centauri A, which are archetypes of solar mass stars in different stages of evolution, are compared. Evidence is found for neither coronal soft X-ray emission from the red giant, at surface flux levels of only 0.0006 that detected previously for the yellow dwarf, nor C II and IV resonance line emission at surface flux levels of only 0.02 those of the yellow dwarf. The resonance line upper limits and previous detections of the C II intersystem UV multiplet 0.01 near 2325 A provide evidence for an Arcturus outer atmosphere that is geometrically extended, tenuous and cool. The red giant has, in addition, a prominent cool stellar wind. An extensive tabulation of line identifications, widths and fluxes for the IUE far-UV echelle spectra of the two stars is given, and two competing explanations for the Wilson-Bappu effect are discussed.

  13. Robust H2 estimation and control

    Institute of Scientific and Technical Information of China (English)

    Lihua XIE; Yeng Chai SOH; Chunling DU; Yun ZOU

    2004-01-01

    This paper is concerned with the H2 estimation and control problems for uncertain discretetime systems with norm-bounded parameter uncertainty. We first present an analysis result on H2 norm bound for a stable uncertain system in terms of linearmatrix inequalities (LMIs). A solution to the robust H2 estimation problem is then derived in terms of two LMIs. As compared tothe existing results, our result on robust H2 estimation is more general. In addition, explicit search of appropriate scaling parametersis not needed as the optimization is convex in the scaling parameters. The LMI approach is also extended to solve the robust H2control problem which has been difficult for the traditional Riccati equation approach since no separation principle has been knownfor uncertain systems. The design approach is demonstrated through a simple example.

  14. Impact of a future H2 transportation on atmospheric pollution in Europe

    Science.gov (United States)

    Popa, Maria Elena; Segers, Arjo; Denier van der Gon, Hugo; Schaap, Martijn; Krol, Maarten; Visschedijk, Antoon; Röckmann, Thomas

    2014-05-01

    Traditionally fuelled road traffic is a major source of greenhouse gases and pollutants. Greenhouse gases (e.g. CO2 and CH4) affect the global atmosphere and contribute to global warming. The pollutants emitted by vehicles (e.g. CO, NOx, SO2, particulate matter, volatile organic compounds) are toxic for man and environment and decrease air quality especially in highly populated areas. Burning H2 produces only water, thus H2-powered vehicles are seen as a possibility to reduce greenhouse gas emissions and improve air quality; because of this, H2 usage as a fuel is foreseen to significantly increase in the future. Large scale usage of H2 as a fuel has the potential to affect the atmospheric composition in different ways. On one hand, emissions associated to fossil fuel burning will decrease. On the other hand, large quantities of H2 used will likely lead to increased H2 emissions from leakages during production, transport and storage. Additional H2 in the atmosphere will affect the chemistry of many species, in principal by decreasing the availability of OH radicals, with the result of increasing the lifetime of greenhouse gases and pollutants. Thus the net effect of H2 vehicles on the atmospheric composition depends on the relative strength of these two contrary effects. In order to evaluate the potential influence of a future H2 road transportation on local and regional air quality, we implemented H2 in the atmospheric transport and chemistry model LOTOS-EUROS. We simulated the future (2020) using emission scenarios with different proportions of H2 vehicles and different H2 leakage rates. The reference future scenario does not include H2 vehicles, and assumes that all present and planned European regulations for emissions are fully implemented. We find that in general the air quality in 2020 will be significantly better than at present in all scenarios, with and without H2 cars. In the future scenario without H2 cars, the pollution is reduced due to the strict

  15. Triazine-based H2S Scavenging

    DEFF Research Database (Denmark)

    Madsen, Henrik Tækker; Vestergaard Jensen, Carina; Søgaard, Erik Gydesen

    2014-01-01

    The authors studied the applicability of a previously suggested model to describe the reaction between 1,3,5-tri-(2-hydroxypropyl)-hexahydro-s-triazine and H2S and thereby predict formation of fouling. To investigate the reaction system, electrospray ionization mass spectrometry was employed...... to analyze the composition of the generated mixture as H2S is bubbled through the scavenger. The results of the study confirm that the suggested model is capable of explaining how the scavenger reacts with H2S, which may be used to explain from where and how the fouling originates, and how a scavenging...

  16. An H2A Histone Isotype, H2ac, Associates with Telomere and Maintains Telomere Integrity.

    Directory of Open Access Journals (Sweden)

    Chia-Hsin Su

    Full Text Available Telomeres are capped at the ends of eukaryotic chromosomes and are composed of TTAGGG repeats bound to the shelterin complex. Here we report that a replication-dependent histone H2A isotype, H2ac, was associated with telomeres in human cells and co-immunoprecipitates with telomere repeat factor 2 (TRF2 and protection of telomeres protein 1 (POT1, whereas other histone H2A isotypes and mutations of H2ac did not bind to telomeres or these two proteins. The amino terminal basic domain of TRF2 was necessary for the association with H2ac and for the recruitment of H2ac to telomeres. Depletion of H2ac led to loss of telomeric repeat sequences, the appearance of dysfunctional telomeres, and chromosomal instability, including chromosomal breaks and anaphase bridges, as well as accumulation of telomere-associated DNA damage factors in H2ac depleted cells. Additionally, knockdown of H2ac elicits an ATM-dependent DNA damage response at telomeres and depletion of XPF protects telomeres against H2ac-deficiency-induced G-strand overhangs loss and DNA damage response, and prevents chromosomal instability. These findings suggest that the H2A isotype, H2ac, plays an essential role in maintaining telomere functional integrity.

  17. Rovibrational states of the H2O-H2 complex: An ab initio calculation

    Science.gov (United States)

    van der Avoird, Ad; Nesbitt, David J.

    2011-01-01

    All bound rovibrational levels of the H2O-H2 dimer are calculated for total angular momentum J = 0-5 on two recent intermolecular potential surfaces reported by Valiron et al. [J. Chem. Phys. 129, 134306 (2008)] and Hodges et al. [J. Chem. Phys. 120, 710 (2004)] obtained through ab initio calculations. The method used handles correctly the large amplitude internal motions in this complex; it involves a discrete variable representation of the intermolecular distance coordinate R and a basis of coupled free rotor wave functions for the hindered internal rotations and the overall rotation of the dimer. The basis is adapted to the permutation symmetry associated with the para/ortho (p/o) nature of both H2O and H2 as well as to inversion symmetry. Dimers containing oH2 are more strongly bound than dimers with pH2, as expected, with dissociation energies D_0 of 33.57, 36.63, 53.60, and 59.04 cm^{-1}for pH2O-pH2, oH2O-pH2, pH2O-oH2, and oH2O-oH2, respectively, on the potential of Valiron et al. that corresponds to a binding energy D_e of 235.14 cm^{-1}. Rovibrational wave functions are computed as well and the nature of the bound states in the four different dimer species is discussed. Converged rovibrational levels on both potentials agree well with the high-resolution spectrum reported by Weida and Nesbitt [J. Chem. Phys. 110, 156 (1999)]; the hindered internal rotor model that was used to interpret this spectrum is qualitatively correct.

  18. Variations in H2O+/H2O ratios toward massive star-forming regions

    CERN Document Server

    Wyrowski, F; Herpin, F; Baudry, A; Bontemps, S; Chavarria, L; Frieswijk, W; Jacq, T; Marseille, M; Shipman, R; van Dishoeck, E F; Benz, A O; Caselli, P; Hogerheijde, M R; Johnstone, D; Liseau, R; Bachiller, R; Benedettini, M; Bergin, E; Bjerkeli, P; Blake, G; Braine, J; Bruderer, S; Cernicharo, J; Codella, C; Daniel, F; di Giorgio, A M; Dominik, C; Doty, S D; Encrenaz, P; Fich, M; Fuente, A; Giannini, T; Goicoechea, J R; de Graauw, Th; Helmich, F; Herczeg, G J; Jørgensen, J K; Kristensen, L E; Larsson, B; Lis, D; McCoey, C; Melnick, G; Nisini, B; Olberg, M; Parise, B; Pearson, J C; Plume, R; Risacher, C; Santiago, J; Saraceno, P; Tafalla, M; van Kempen, T A; Visser, R; Wampfler, S; Yıldız, U A; Black, J H; Falgarone, E; Gerin, M; Roelfsema, P; Dieleman, P; Beintema, D; De Jonge, A; Whyborn, N; Stutzki, J; Ossenkopf, V

    2010-01-01

    Early results from the Herschel Space Observatory revealed the water cation H2O+ to be an abundant ingredient of the interstellar medium. Here we present new observations of the H2O and H2O+ lines at 1113.3 and 1115.2 GHz using the Herschel Space Observatory toward a sample of high-mass star-forming regions to observationally study the relation between H2O and H2O+ . Nine out of ten sources show absorption from H2O+ in a range of environments: the molecular clumps surrounding the forming and newly formed massive stars, bright high-velocity outflows associated with the massive protostars, and unrelated low-density clouds along the line of sight. Column densities per velocity component of H2 O+ are found in the range of 10^12 to a few 10^13 cm-2 . The highest N(H2O+) column densities are found in the outflows of the sources. The ratios of H2O+/H2O are determined in a range from 0.01 to a few and are found to differ strongly between the observed environments with much lower ratios in the massive (proto)cluster e...

  19. Thermal modeling of NiH2 batteries

    Science.gov (United States)

    Ponthus, Agnes-Marie; Alexandre, Alain

    1994-01-01

    The following are discussed: NiH2 battery mission and environment; NiH2 cell heat dissipation; Nodal software; model development general philosophy; NiH2 battery model development; and NiH2 experimental developments.

  20. Chemiluminescent ion-molecule reactions B + +H2

    Science.gov (United States)

    Ottinger, Ch.; Reichmuth, J.

    1981-01-01

    Emission spectra resulting from impact of low-energy (1-10 eVc.m.) B+ ions in a beam on an H2 target were measured. Numerous new bands of the BH+(A 2Π-X 2Σ+) transition were observed besides the previously known (0,0) and (1,1) bands. Also, at higher energy a new band system was discovered which is ascribed to the BH+(B' 2Σ+-X 2Σ+) transition. It was identified by analogy with BeH and MgH. The results are discussed in terms of electronic state and molecular orbital correlation diagrams.

  1. EPA H2O Software Tool

    Science.gov (United States)

    EPA H2O allows user to: Understand the significance of EGS in Tampa Bay watershed; visually analyze spatial distribution of the EGS in Tampa Bay watershed; obtain map and summary statistics of EGS values in Tampa Bay watershed; analyze and compare potential impacts of development...

  2. EPA H2O User Manual

    Science.gov (United States)

    EPA H2O is a software tool designed to support research being conducted in the Tampa Bay watershed to provide information, data, and approaches and guidance that communities can use to examine alternatives when making strategic decisions to support a prosperous and environmentall...

  3. Triazine-based H2S Scavenging

    DEFF Research Database (Denmark)

    Madsen, Henrik Tækker; Vestergaard Jensen, Carina; Søgaard, Erik Gydesen

    2014-01-01

    The authors studied the applicability of a previously suggested model to describe the reaction between 1,3,5-tri-(2-hydroxypropyl)-hexahydro-s-triazine and H2S and thereby predict formation of fouling. To investigate the reaction system, electrospray ionization mass spectrometry was employed to a...

  4. Advanced Colloids Experiment (ACE-H-2)

    Science.gov (United States)

    Meyer, William V.; Sicker, Ron; Chmiel, Alan J.; Eustace, John; LaBarbera, Melissa

    2015-01-01

    Increment 43 - 44 Science Symposium presentation of Advanced Colloids Experiment (ACE-H-2) to RPO. The purpose of this event is for Principal Investigators to present their science objectives, testing approach, and measurement methods to agency scientists, managers, and other investigators.

  5. When sticking influences H2 formation

    NARCIS (Netherlands)

    Cazaux, S.; Morisset, S.; Spaans, M.; Allouche, A.

    2011-01-01

    Aims: Because of their catalytic properties, interstellar dust grains are crucial to the formation of H2, the most abundant molecule in the Universe. The formation of molecular hydrogen strongly depends on the ability of H atoms to stick on dust grains. In this study we determine the sticking coeffi

  6. SOLARNET & LAIME: Imaging & Spectroscopy in the Far Ultraviolet

    Science.gov (United States)

    Damé, Luc; Koutchmy, Serge

    SOLARNET is a medium size high resolution solar physics mission proposed to CNES and ESA for a new start in 2007 and a possible launch in 2012 (CNES) or later (ESA Cosmic Vision framework: 2015-2016). Partnerships with India and China are under discussion, and several European contributions are considered. At the center of the SOLARNET mission is a 3-telescope interferometer of 1 meter baseline capable to provide 40 times the best ever spatial resolution achieved in Space with previous, current or even planned solar missions: 20 mas - 20 km on the Sun in the FUV. The interferometer is associated to an on-axis Subtractive Double Monochromator coupled to an Imaging Fourier Transform Spectrometer capable of high spectral (0.01 nm) and high temporal resolutions (50 ms) on a field of view of 40 arcsec and covering the FUV and UV spectral domains (from 117.5 to 400 nm). This will allow to access process scales of magnetic reconnection, dissipation, emerging flux and much more, from the chromosphere to the low corona with emphasis on the transition zone where the magnetic confinement is expected to be maximum. A whole new chapter of the physics of solar magnetic field structuring, evolution and mapping from the photosphere to the high atmosphere will be opened. The interferometer is completed by instruments providing larger field of view and higher temperature (EUV-XUV coronal imaging & spectroscopy) to define the context and extension of the solar phenomena. The 3-telescope interferometer design results of an extensive laboratory demonstration program of interferometric imaging of extended objects. We will review the scientific program of SOLARNET, describe the interferometer concept and design, present the results of the breadboard and give a short overview of the mission aspects. In a different category, LAIME, the Lyman Alpha Imaging-Monitor Experiment, is a remarkably simple (no mechanisms) and compact full Sun imager to be flown with TESIS on the CORONAS-PHOTON mission in 2008. It could be the only chromospheric imager to be flown in the next years, supporting Solar-B, STEREO, SDO and the Belgian LYRA Lyman Alpha flux monitor. We will give a short description of this unique 60 mm aperture imaging telescope, dedicated to the investigation of the UV sources of solar variability and of the chromospheric and coronal disruptive events (Moreton waves, prominences, CMEs, etc.).

  7. Far Ultraviolet Spectra of B Stars near the Ecliptic

    CERN Document Server

    Morales, C; Gómez, J F; Trapero, J; Talavera, A; Bowyer, S; Edelstein, J D; Korpela, E J; Lampton, M; Drake, J J

    2000-01-01

    Spectra of B stars in the wavelength range of 911-1100 A have been obtained with the EURD spectrograph onboard the Spanish satellite MINISAT-01 with ~5 A spectral resolution. IUE spectra of the same stars have been used to normalize Kurucz models to the distance, reddening and spectral type of the corresponding star. The comparison of 8 main-sequence stars studied in detail (alpha Vir, epsilon Tau, lambda Tau, tau Tau, alpha Leo, zeta Lib, theta Oph, and sigma Sgr) shows agreement with Kurucz models, but observed fluxes are 10-40% higher than the models in most cases. The difference in flux between observations and models is higher in the wavelength range between Lyman alpha and Lyman beta. We suggest that Kurucz models underestimate the FUV flux of main-sequence B stars between these two Lyman lines. Computation of flux distributions of line-blanketed model atmospheres including non-LTE effects suggests that this flux underestimate could be due to departures from LTE, although other causes cannot be ruled ou...

  8. S201 Catalog of Far-Ultraviolet Objects. Revised.

    Science.gov (United States)

    1982-05-06

    I 0> 00~ -C z TS.-o w~r W2 u0 W -* O rw00 , 2az oo~ o2o m aoooocooa OO w w w w w w wwoo o~~o 0~ CC 09a0M 1! MMM11 !TI0 I!! O O 0000. 0 000 0 00...N0 0 - -- 0 0 0 zw m o o o2o woZZ 2 00 02 0 w 2w0 M M0 0 0 OC r- r - ,0a0 640MgCC U S0 n~e -CMOI-gr-rI-± S 5 ±14 08 U 1SSCCu0 M004ISCCCCCC~- * NRL

  9. A year of H2 measurements at Weybourne Atmospheric Observatory, UK

    Directory of Open Access Journals (Sweden)

    Grant L. Forster

    2012-07-01

    Full Text Available We present a year-long high precision time series of atmospheric molecular hydrogen (H2 measured at the UK North Sea coast from March 2008 to February 2009. We observed a pronounced seasonal cycle in H2 with mean values in late winter/early spring ~40 ppb higher than those in late summer/early autumn. Background-subtracted molar H2/CO ratios (ΔH2/ΔCO averaged 0.35±0.002 for all data combined and 0.25±0.002 when ΔH2 was above 10 ppb. The ΔH2/ΔCO ratio was highest in summer, possibly as a result of larger photochemical production. Using simultaneous measurements of ozone, we estimated the deposition velocity of H2 during nocturnal inversion events to average 3.5±0.7×10−4 m s−1 for June 2008 and 1.9±1×10−4 m s−1 for July 2008, in good agreement with other reported estimates. In May 2008, we observed an episode of exceptionally clean air being transported from the tropics but arriving from the north, in which H2 was slightly elevated indicating minimal surface loss. On another occasion with south-easterly winds, we believe we detected emissions from H2 production facilities in the near-continent characterised by H2 mixing ratios reaching 1450 ppb.

  10. Assessment of the perfusion of glioblastomas before and during radiotherapy: longitudinal comparison between H{sub 2}-{sup 15}O positron emission tomography and perfusion MRI; Evaluation de la perfusion des glioblastomes en avant et pendant la radiotherapie: comparaison longitudinale entre la tomographie par emission de positons H2 15O et l'IRM de perfusion

    Energy Technology Data Exchange (ETDEWEB)

    Laprie, A.; Ken, S.; Moyal Cohen-Jonathan, E. [Departement de radiotherapie, institut Claudius-Regaud, 31 - Toulouse (France); Laprie, A.; Ken, S.; Lotterie, J.A.; Franceries, X.; Celsis, P.; Payoux, P.; Berry, I. [Inserm imagerie cerebrale et handicaps neurologiques UMR 825, 31 - Toulouse (France); Lotterie, J.A.; Berry, I. [Departement de biophysique, centre hospitalier universitaire de Rangueil, 31 - Toulouse (France); Barcelo, C. [Departement de radiologie, centre hospitalier universitaire de Purpan, 31 - Toulouse (France)

    2010-10-15

    The authors report the comparison of different perfusion imagery modalities for patients suffering form glioblastomas and included in a phase-1 clinic trial comprising conformational radiotherapy concomitant with the use of a farnesyl-transferase inhibitor (tipifarnib). With these different techniques, perfusion MRI and perfusion positron emission tomography, the authors made respectively a qualitative and quantitative assessment of the tumour vascularisation. Short communication

  11. High purity H2/H2O/Ni/SZ electrodes at 500º C

    DEFF Research Database (Denmark)

    Høgh, Jens Valdemar Thorvald; Hansen, Karin Vels; Norrman, Kion

    2013-01-01

    of stabilized zirconia (SZ) with 10, 13 and 18 mol% yttria and one with 6 mol% scandia plus 4 mol% yttria were studied at open circuit voltage at 400-500 C in mixtures of H2/H2O over 46 days. The polarization resistances (Rp) for all samples increased significantly during the first 10-20 days at 500 C...

  12. H2O Paradox and its Implications on H2O in Moon

    Science.gov (United States)

    Zhang, Youxue

    2017-04-01

    The concentration of H2O in the mantle of a planetary body plays a significant role in the viscosity and partial melting and hence the convection and evolution of the planetary body. Even though the composition of the primitive terrestrial mantle (PTM) is thought to be well known [1-2], the concentration of H2O in PTM remains paradoxial because different methods of estimation give different results [3]: Using H2O/Ce ratio in MORB and OIB and Ce concentration in PTM, the H2O concentration in PTM would be (300÷×1.5) ppm; using mass balance by adding surface water to the mantle [3-4], H2O concentration in PTM would be (900÷×1.3) ppm [2-3]. The inconsistency based on these two seemingly reliable methods is referred to as the H2O paradox [3]. For Moon, H2O contents in the primitive lunar mantle (PLM) estimated from H2O in plagioclase in lunar anorthosite and that from H2O/Ce ratio in melt inclusions are roughly consistent at ˜110 ppm [5-6] even though there is still debate about the volatile depletion trend [7]. One possible solution to the H2O paradox in PTM is to assume that early Earth experienced whole mantle degassing, which lowered the H2O/Ce ratio in the whole mantle but without depleting Ce in the mantle. The second possible solution is that some deep Earth reservoirs with high H2O/Ce ratios have not been sampled by MORB and OIB. Candidates include the transition zone [8] and the D" layer. The third possible solution is that ocean water only partially originated from mantle degassing, but partially from extraterrestrial sources such as comets [9-10]. At present, there is not enough information to determine which scenario is the answer to the H2O paradox. On the other hand, each scenario would have its own implications to H2O in PLM. If the first scenario applies to Moon, because degassed H2O or H2 would have escaped from the lunar surface, the very early lunar mantle could have much higher H2O [11] than that obtained using the H2O/Ce ratio method. The

  13. Editing of H2BC NMR spectra.

    Science.gov (United States)

    Nyberg, Nils T; Duus, Jens Ø; Sørensen, Ole W

    2005-12-01

    New versions of the H2BC pulse sequence (Nyberg NT, Duus JØ, Sørensen OW. J. Am. Chem. Soc. 2005; 127: 6154) that edit into two subspectra according to the number of protons attached to 13C nuclei being odd or even are introduced. These sequences can be useful for resolving spectral overlap, which is demonstrated on the molecule prednisolone [(11 beta)-11,17,21-trihydroxypregna-1,4-diene-3,20-dione].

  14. Electron mass stopping power in H2

    Science.gov (United States)

    Fursa, Dmitry V.; Zammit, Mark C.; Threlfall, Robert L.; Savage, Jeremy S.; Bray, Igor

    2017-08-01

    Calculations of electron mass stopping power (SP) of electrons in H2 have been performed using the convergent close-coupling method for incident electron energies up to 2000 eV. Convergence of the calculated SP has been established by increasing the size of the close-coupling expansion from 9 to 491 states. Good agreement was found with the SP measurements of Munoz et al. [Chem. Phys. Lett. 433, 253 (2007), 10.1016/j.cplett.2006.10.114].

  15. Flux-Velocity Relation for H2 Outflows

    Science.gov (United States)

    Salas, Luis; Cruz-González, Irene

    2002-06-01

    We present an analysis of velocity-resolved near-IR molecular hydrogen observations of a variety of protostellar outflows with very different energetics, degrees of collimation, and morphologies. Observations in the 2.12 μm line of H2 were obtained using an IR Fabry-Pérot interferometer with a spectral resolution of 23 km s-1. The integrated flux-velocity diagrams for each outflow show a flat spectrum for low velocities followed by a decreasing power law dF/dv~vγ, with γ between -1.8 and -2.6, for velocities higher than a clearly defined break velocity at 2-17 km s-1. Contrary to shock model predictions, it is shown that the H2 intensity is constant with velocity. We argue that the flux-velocity relation can then be interpreted as a mass-velocity relation, in striking similarity to the power-law mass spectra observed in CO outflows. By comparing H2 and CO mass-velocity spectra, it is shown that there is a velocity regime in which both molecules coexist and produce similar γ-values. Evolution effects in outflows appear as a correlation between outflow length and γ as outflows age, the spectra becomes steeper. Our results support a common physical origin for both CO and H2 emission and a strong association between the molecular outflows traced in each molecule. Based on observations obtained at the Observatorio Astronómico Nacional at San Pedro Mártir, Mexico.

  16. Cysteine Activated Hydrogen Sulfide (H2S) Donors

    OpenAIRE

    Zhao, Yu; Wang, Hua; Xian, Ming

    2010-01-01

    H2S, the newly discovered gasotransmitter, plays important roles in biological systems. However, the research on H2S has been hindered by lacking controllable H2S donors which could mimic the slow and continuous H2S generation process in vivo. Herein we report a series of cysteine-activated H2S donors. Structural modifications on these molecules can regulate the rates of H2S generation. These compounds can be useful tools in H2S research.

  17. When sticking influences H2 formation

    CERN Document Server

    Cazaux, S; Spaans, M; Allouche, A

    2011-01-01

    Aims. Interstellar dust grains, because of their catalytic properties, are crucial to the formation of H2, the most abundant molecule in the Universe. The formation of molecular hydrogen strongly depends on the ability of H atoms to stick on dust grains. In this study we determine the sticking coefficient of H atoms chemisorbed on graphitic surfaces, and estimate its impact on the forma- tion of H2. Methods. The sticking probability of H atoms chemisorbed onto graphitic surfaces is obtained using a mixed classical-quantum dynamics method. In this, the H atom is treated quantum- mechanically and the vibrational modes of the surface are treated classically. The implications of sticking for the formation of H2 are addressed by using Kinetic Monte Carlo simulations that follow how atoms stick, move and associate with each other on dust surfaces of different temper- ature. Results. In our model, molecular hydrogen forms very efficiently for dust temperatures lower than 15 K through the involvement of physisorbed H...

  18. Ion desorption from frozen H 2O irradiated by MeV heavy ions

    Science.gov (United States)

    Collado, V. M.; Farenzena, L. S.; Ponciano, C. R.; Silveira, E. F. da; Wien, K.

    2004-10-01

    Nitrogen (0.13-0.85 MeV) and 252Cf fission fragments (˜65 MeV) beams are employed to sputter positive and negative secondary ions from frozen water. Desorption yields are measured for different ice temperatures and projectile energies. Target surface is continuously refreshed by condensed water while the target temperature varies and ice thickness changes. In both projectile energy ranges, the preferentially ejected ions are H +, H2+ and (H 2O) nH +-cluster ions. The yields of the corresponding negative ions H - and (H 2O) nO - or (H 2O) nOH - are 1-2 orders of magnitude lower. The (H 2O) nH + desorption yields decrease exponentially as the cluster size, n, increases. In the low energy range, the desorption of positive ion clusters may occur in a two-step process: first, desorption of preformed H 2O clusters and, then, ionization by H + or H 3O + capture. For 0.81 MeV N + projectile ions, the cluster ion emission contributes with 0.05% to the total H 2O desorbed yield. There are indications that emission of the (H 2O) nH + disappears for an electronic energy loss lower than 20 eV/Å. For the high energy range, desorption of small ion clusters is particularly enhanced, revealing that a fragmentation process also exists.

  19. Proof of shock-excited H$_2$ in low-ionization structures of PNe

    CERN Document Server

    Akras, Stavros; Ramos-Larios, Gerardo

    2016-01-01

    We report the detection of near-IR H$_2$ lines emission from low-ionization structures (LISs) in planetary nebulae. The deepest, high-angular resolution H$_2$ 1-0 S(1) at 2.122 $\\mu$m, and H$_2$ 2-1 S(1) at 2.248 $\\mu$m images of K 4-47 and NGC 7662, obtained using NIRI@Gemini-North, are presented here. K 4-47 reveals a remarkable high-collimated bipolar structure. The H$_2$ emission emanates from the walls of the bipolar outflows and a pair of knots at the tips of these outflows. The H$_2$ 1-0 S(1)/2-1 S(1) line ratio is $\\sim$7-10 which indicates shock interaction due to both the lateral expansion of the gas in the outflows and the high-velocity knots. The strongest line, H$_2$ v=1-0 S(1), is also detected in several LISs located at the periphery of the outer shell of the elliptical PN NGC 7662, whereas only four knots are detected in the H$_2$ v=2-1 S(1) line. These knots have H$_2$ v=1-0 S(1)/v=2-1 S(1) values between 2 and 3. These data confirm the presence of molecular gas in both highly (K 4-47) and sl...

  20. A novel source of atmospheric H2: abiotic degradation of organic material

    Science.gov (United States)

    Lee, H.; Rahn, T.; Throop, H. L.

    2012-11-01

    Molecular hydrogen (H2) plays an important role in atmospheric chemistry by competing for reactions with the hydroxyl radical (OH·) and contributing to the production of H2O in the stratosphere, indirectly influencing stratospheric ozone concentrations. The dominant pathway for loss of H2 from the atmosphere is via microbially-mediated soil uptake, although the magnitude of this loss is still regarded as highly uncertain. Recent studies have shown that abiotic processes such as photochemically mediated degradation (photodegradation) of organic material result in direct emissions of carbon (C) and nitrogen (N)-based trace gases as well as H2. This H2 production has important implications on source-sink dynamics of H2 at the soil-atmosphere interface and thus it is important to quantify its variability over a range of plant types and materials. Here, we show laboratory observations of H2 production and its temperature dependence during abiotic degradation of four plant litter types as well as pure cellulose and high lignin content woody material. A greater amount of H2 was produced in the absence of solar radiation than from photodegradation alone, verifying that low temperature thermal degradation of plant litter is a source of H2. In addition, we measured a significant release of H2 both in the presence and absence of O2. Our results suggest that abiotic release of H2 during organic matter degradation is ubiquitous in arid ecosystems and may also occur in other terrestrial ecosystems. We propose that because these processes occur at the soil-atmosphere interface, they provide a previously unrecognized proximal source of H2 for microbial uptake and confound interpretation of direct measurements of atmospheric uptake that are important for constraining the global H2 budget.

  1. Near-infrared H2 and Continuum Survey of Extended Green Objects. II. Complete Census for the Northern Galactic Plane

    CERN Document Server

    Lee, Hsu-Tai; Froebrich, Dirk; Karr, Jennifer; Ioannidis, Georgios; Lee, Yong-Hyun; Su, Yu-Nung; Liu, Sheng-Yuan; Duan, Hao-Yuan; Takami, Michihiro

    2013-01-01

    We discuss 94 Extended Green Objects (EGOs) in the northern Galactic plane cataloged by Cyganowski et al, based on near-infrared narrowband H2 (2.122 {\\mu}m and continuum observations from the United Kingdom Infrared Telescope. This data set is three times larger than our previous study, and is unbiased by preselection. As discussed in the previous paper, the morphologies of the 4.5 {\\mu}m emission generally resemble those of the near-infrared continuum, but are different from those of the H2 emission. Of our sample, only 28% of EGOs with H2 emission show similar morphologies between 4.5 {\\mu}m and H2 emission. These results suggest that the 4.5 {\\mu}m emission mainly comes from scattered continuum from the embedded young stellar object (YSO), and partially from H2 emission. About half of EGOs are associated with H2 outflows, if the H2 outflow incompleteness is considered. The H2 outflow detection rate for EGOs with K-band detections (61%) is significantly higher than for those without K-band detections (36%)...

  2. H2 formation and excitation in the Stephan's Quintet galaxy-wide collision

    CERN Document Server

    Guillard, P; Forets, G Pineau des; Appleton, P N

    2009-01-01

    Context. The Spitzer Space Telescope has detected a powerful (L(H2)~10^41 erg s-1) mid-infrared H2 emission towards the galaxy-wide collision in the Stephan's Quintet (SQ) galaxy group. This discovery was followed by the detection of more distant H2-luminous extragalactic sources, with almost no spectroscopic signatures of star formation. These observations set molecular gas in a new context where one has to describe its role as a cooling agent of energetic phases of galaxy evolution. Aims. The SQ postshock medium is observed to be multiphase, with H2 gas coexisting with a hot (~ 5 10^6 K), X-ray emitting plasma. The surface brightness of H2 lines exceeds that of the X-rays and the 0-0 S(1) H2 linewidth is ~ 900 km s-1, of the same order of the collision velocity. These observations raise three questions we propose to answer: (i) Why H2 is present in the postshock gas ? (ii) How can we account for the H2 excitation ? (iii) Why H2 is a dominant coolant ? Methods. We consider the collision of two flows of multi...

  3. Dissecting a Molecular Shock: Spatially Resolved H2 Line Ratios Across the HH7 Bow Shock

    Science.gov (United States)

    Pike, Rosemary E.; Geballe, Thomas R.; Burton, Michael G.; Chrysostomou, Antonio; Brand, Peter

    2015-01-01

    We report on a detailed study of the physics of molecular shocks using Gemini NIFS (Near-Infrared Field Spectrometer) K-band spectra of a 3.'2 x 2.'9 region near the tip of the HH7 bow shock. The IFU data have an angular resolution of 0.3", much higher resolution then in any previous study of a molecular shock, and a velocity resolution of 60 km/s. We have detected 20 H2 emission lines with upper state energies as high as 28,000 K, and 6 additional unidentified lines which share the same bow shock morphology as the H2. We use excitation temperatures derived from line pairs measured in 0.15' x 0.15' bins to attempt to constrain the shock type and distinguish between low velocity jump shocks, continuous shocks, and dissociative shocks in which the H2 line emission arises from newly reformed H2.

  4. Experimental study of CH4/H2 mixtures-LPG-gasoline in internal combustion engines

    Energy Technology Data Exchange (ETDEWEB)

    Bayrak, Mehmet; Albayrak Ceper, Bilge; Kahraman, Nafiz; Orhan Akansu, Selahaddin [Dept. of Mechanical Engineering, Erciyes University Engineering Faculty (Turkey)], e-mail: akansu@erciyes.edu.tr

    2011-07-01

    With the depletion of fossil fuel and the rising concerns about the environment, there is an urgent need for alternative fuels with low environmental impact. Research has been carried out world-wide to determine the energetic and environmental performance of alternative fuels in existing engines and the aim of this paper is to study the performance of engines using CH4/H2 (90% CH4 and 10% H2), liquefied petroleum gas (LPG) and gasoline. Experiments were conducted on a Kathana engine running at between 1500 and 3500 rotations per minutes and with spark timing between 10 and 35 BTDC. It was found that the CH4/H2 mix provides the lowest pollutant emission values of the studied fuels and the lowest brake thermal efficiency. This study provided a better understanding of the exhaust emission and combustion performances of CH4/H2 and LPG compared to gasoline.

  5. Wave-function inspired density functional applied to the H$_2$/H$_2^+$ challenge

    CERN Document Server

    Zhang, Igor Ying; Scheffler, Matthias

    2016-01-01

    We start from the Bethe-Goldstone equation (BGE) to derive a simple orbital-dependent correlation functional -- BGE2 -- which terminates the BGE expansion at the second-order, but retains the self-consistent coupling of electron-pair orrelations. We demonstrate that BGE2 is size consistent and one-electron "self-correlation" free. The electron-pair correlation coupling ensures the correct H$_2$ dissociation limit and gives a finite correlation energy for any system even if it has a no energy gap. BGE2 provides a good description of both H$_2$ and H$_2^+$ dissociation, which is regarded as a great challenge in density functional theory (DFT). We illustrate the behavior of BGE2 analytically by considering H$_2$ in a minimal basis. Our analysis shows that BGE2 captures essential features of the adiabatic connection path that current state-of-the-art DFT approximations do not.

  6. Histone H2A and H2B Deubiquitinase in Developmental Disease and Cancer

    Directory of Open Access Journals (Sweden)

    Demeng Chen

    2015-01-01

    Full Text Available Histone H2A and H2B ubiquitination represents a widely used mechanism for a variety of regulatory transcriptional programs. In this review, structural and functional studies of histone H2A and histone H2B deubiquitinase (DUB, DUB including 2A-DUB, BRCA1-associated protein-1, USP3, UBP8, and USP16, and their role in developmental disease and carcinogenesis were recapitulated. Also the progress in developing small molecular inhibitors targeting DUBs and their application in colon cancer, B-cell lymphoma, and multiple myeloma were summarized. Overall, the study seek to strengthen the understanding on how these DUBs contribute to normal and malignant tissue development thus aiding in improving the design of therapeutic strategies used for diagnosis and prognosis of the disease.

  7. Theoretical study of the rovibrational spectrum of H2O-H2

    Science.gov (United States)

    Wang, Xiao-Gang; Carrington, Tucker

    2011-01-01

    In this paper we report transition frequencies and line strengths computed for H_2O-H_2 and compare with the experimental observations of [M. J. Weida and D. J. Nesbitt, J. Chem. Phys. 110, 156 (1999)]. To compute the spectra we use a symmetry adapted Lanczos algorithm and an uncoupled product basis set. Our results corroborate the assignments of Weida and Nesbitt and there is good agreement between calculated and observed transitions. Possible candidates for lines that Weida and Nesbitt were not able to assign are presented. Several other bands that may be observable are also discovered. Although all the observed bands are associated with states localized near the global potential minimum, at which H_2O acts as proton acceptor, a state with significant amplitude near the T-shape secondary potential minimum at which H_2O acts as proton donor is identified by examining many different probability density plots.

  8. Rydberg and π-π* transitions in film surfaces of various kinds of nylons studied by attenuated total reflection far-ultraviolet spectroscopy and quantum chemical calculations: peak shifts in the spectra and their relation to nylon structure and hydrogen bondings.

    Science.gov (United States)

    Morisawa, Yusuke; Yasunaga, Manaka; Sato, Harumi; Fukuda, Ryoichi; Ehara, Masahiro; Ozaki, Yukihiro

    2014-10-09

    Attenuated total reflection far-ultraviolet (ATR-FUV) spectra in the 145-260 nm region were measured for surfaces (thickness 50-200 nm) of various kinds of nylons in cast films to explore their electronic transitions in the FUV region. ATR-FUV spectra show two major bands near 150 and 200 nm in the surface condensed phase of nylons. Transmittance (Tr) spectra were also observed in particular for the analysis of valence excitations. Time-dependent density functional theory (TD-DFT/CAM-B3LYP) calculations were carried out using the model systems to provide the definitive assignments of their absorption spectra and to elucidate their peak shifts in several nylons, in particular, focusing on their crystal alignment structures and intermolecular hydrogen bondings. Two major bands of nylon films near 150 and 200 nm are characterized as σ-Rydberg 3p and π-π* transitions of nylons, respectively. These assignments are also coherent with those of liquid n-alkanes (n = 5-14) and liquid amides observed previously. The Rydberg transitions are delocalized over the hydrocarbon chains, while the π-π* transitions are relatively localized at the amide group. Differences in the peak positions and intensity were found in both ATR- and Tr-FUV spectra for different nylons. A red-shift of the π-π* amide band in the FUV spectra of nylon-6 and nylon-6/6 models in α-form is attributed to the crystal structure pattern and the intermolecular hydrogen bondings, which result in the different delocalization character of the π-π* transitions and transition dipole coupling.

  9. Microstructural and Kinetic Evolution of Fe Doped MgH2 during H2 Cycling

    Directory of Open Access Journals (Sweden)

    Annalisa Aurora

    2012-09-01

    Full Text Available The effect of extended H2 sorption cycles on the structure and on the hydrogen storage performances of MgH2 powders with 5 wt% of Fe particle catalyst is reported. MgH2 powders with and without Fe have been ball milled under Argon, the doped MgH2 nanocomposite has been cycled under hydrogen pressure up to a maximum of 47 desorption and absorption cycles at 300 °C. After acceleration during the first 10 cycles, the kinetics behavior of doped MgH2 is constant after extended cycling, in terms of maximum storage capacity and rate of sorption. The major effect of cycling on particle morphology is the progressive extraction of Mg from the MgO shell surrounding the powder particles. The Mg extraction from the MgO shell leaves the catalyst particles inside the hydride particles. Many empty MgO shells are observed in the pure ball milled MgH2 upon cycling at higher temperature, suggesting that this enhancement of the extraction efficiency is related to the higher operating temperature which favors Mg diffusivity with respect to the H ion one.

  10. Raman scattering study of α-MgH2 and γ-MgH2

    Science.gov (United States)

    Kuzovnikov, M. A.; Efimchenko, V. S.; Filatov, E. V.; Maksimov, A. A.; Tartakovskii, I. I.; Ramirez-Cuesta, A. J.

    2013-01-01

    Two modifications of MgH2 have been studied by Raman spectroscopy: α-MgH2 with the P42/mnm space group and γ-MgH2 with the Pbcn space group. The latter was prepared from α-MgH2 by exposing it to a pressure of 5.6 GPa at 470 °C for 1.5 h. A comparison of the experimental spectra with ab-initio calculations allowed identification of a few phonon modes. A broad feature in the Raman spectrum of α-MgH2 in the range 1470-1790 cm-1 was identified as the B2g phonon mode. A Raman spectrum of γ-MgH2 consists of five discernible peaks at 186 cm-1, 313 cm-1, 509 cm-1, 660 cm-1, 706 cm-1 and of three broad features in the regions 890-980 cm-1, 1010-1220 cm-1 and 1240-1430 cm-1. The peaks are identified as the 1Ag (186 cm-1), 3B3g (509 cm-1), 2Ag (660 cm-1) and 3B1g (706 cm-1) phonon modes.

  11. Refinements in an Mg/MgH2/H2O-Based Hydrogen Generator

    Science.gov (United States)

    Kindler, Andrew; Huang, Yuhong

    2010-01-01

    Some refinements have been conceived for a proposed apparatus that would generate hydrogen (for use in a fuel cell) by means of chemical reactions among magnesium, magnesium hydride, and steam. The refinements lie in tailoring spatial and temporal distributions of steam and liquid water so as to obtain greater overall energy-storage or energy-generation efficiency than would otherwise be possible. A description of the prior art is prerequisite to a meaningful description of the present refinements. The hydrogen-generating apparatus in question is one of two versions of what was called the "advanced hydrogen generator" in "Fuel-Cell Power Systems Incorporating Mg-Based H2 Generators" (NPO-43554), NASA Tech Briefs, Vol. 33, No. 1 (January 2009), page 52. To recapitulate: The apparatus would include a reactor vessel that would be initially charged with magnesium hydride. The apparatus would exploit two reactions: The endothermic decomposition reaction MgH2-->Mg + H2, which occurs at a temperature greater than or equal to 300 C, and The exothermic oxidation reaction MgH2 + H2O MgO + 2H2, which occurs at a temperature greater than or equal to 330 C.

  12. The Hydrogen Futures Simulation Model (H[2]Sim) technical description.

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Scott A.; Kamery, William; Baker, Arnold Barry; Drennen, Thomas E.; Lutz, Andrew E.; Rosthal, Jennifer Elizabeth

    2004-10-01

    ) vehicles (0.55$/mile), hybrids (0.56 $/mile), and electric vehicles (0.82-0.84 $/mile) with 2020 fuel cell vehicles (FCVs) (0.64-0.66 $/mile), fuel cell vehicles with onboard gasoline reformation (FCVOB) (0.70 $/mile), and direct combustion hydrogen hybrid vehicles (H2Hybrid) (0.55-0.59 $/mile). The results suggests that while the H2Hybrid vehicle may be competitive with ICE vehicles, it will be difficult for the FCV to compete without significant increases in gasoline prices, reduced predicted vehicle costs, stringent carbon policies, or unless they can offer the consumer something existing vehicles can not, such as on demand power, lower emissions, or better performance.

  13. Detection of local H2O exposed at the surface of Ceres

    Science.gov (United States)

    Combe, Jean-Philippe; McCord, Thomas B.; Tosi, Federico; Ammannito, Eleonora; Carrozzo, Filippo Giacomo; De Sanctis, Maria Cristina; Raponi, Andrea; Byrne, Shane; Landis, Margaret E.; Hughson, Kynan H. G.; Raymond, Carol A.; Russell, Christopher T.

    2016-09-01

    The surface of dwarf planet Ceres contains hydroxyl-rich materials. Theories predict a water ice-rich mantle, and water vapor emissions have been observed, yet no water (H2O) has been previously identified. The Visible and InfraRed (VIR) mapping spectrometer onboard the Dawn spacecraft has now detected water absorption features within a low-illumination, highly reflective zone in Oxo, a 10-kilometer, geologically fresh crater, on five occasions over a period of 1 month. Candidate materials are H2O ice and mineral hydrates. Exposed H2O ice would become optically undetectable within tens of years under current Ceres temperatures; consequently, only a relatively recent exposure or formation of H2O would explain Dawn’s findings. Some mineral hydrates are stable on geological time scales, but their formation would imply extended contact with ice or liquid H2O.

  14. Velocity Dispersion of Excited H2

    CERN Document Server

    Lacour, S; Hébrard, G; Oliveira, C; André, M K; Ferlet, R; Vidal-Madjar, A

    2005-01-01

    We present a study of the high rotational bands (J > 2) of H2 toward 4 early type galactic stars: HD 73882, HD 192639, HD 206267, and HD 207538. In each case, the velocity dispersion - characterized by the spectrum fitting parameter b - increases with the level of excitation, a phenomenon that has previously been detected by the Copernicus and IMAPS observatories. In particular, we show with 4 sigma confidence that for HD 192639 it is not possible to fit all J levels with a single b value, and that higher b values are needed for the higher levels. The amplitude of the line broadening, which can be as high as 10 km s^-1, makes explanations such as inhomogeneous spatial distribution unlikely. We investigate a mechanism in which the broadening is due to the molecules that are rotationally excited through the excess energy acquired after their formation on a grain (H2-formation pumping). We show that different dispersions would be a natural consequence of this mechanism. We note however that such process would re...

  15. H2 Energetics in Galaxy-wide Shocks: Insights in Starburst Triggering and Galaxy Formation

    CERN Document Server

    Guillard, P

    2008-01-01

    Spitzer space telescope observations led to the surprising detection of a diverse set of extragalactic sources whose infrared spectra are dominated by line emission of molecular hydrogen (H2). The absence or relative weakness of typical signs of star formation (like dust features, lines of ionized gas) suggest the presence of large quantities of H2 gas with no (or very little) associated star formation. We use the Stephan's Quintet (SQ) galaxy collision to define a physical framework to describe the H2 formation and emission in galaxy-wide shocks. SQ observations show that exceptionally turbulent H2 gas is coexisting with a hot, X-ray emitting plasma. The extreme mid-IR H2 emission from the shock exceeds that of the X-rays. These observations set a new light on the contribution of H2 to the cooling of the interstellar medium, on the relation between molecular gas and star formation, and on the energetics of galaxy formation. These observations can be interpreted by considering that the shock is moving through...

  16. High-Velocity H2O Masers Associated Massive Star Formation Regions

    Institute of Scientific and Technical Information of China (English)

    徐烨; 蒋栋荣; 郑兴武; 顾敏峰; 俞志尧; 裴春传

    2001-01-01

    We report on the results of 12 CO (1-0) emission associated with H2O masers and massive star formation regions to identify high-velocity H2O masers. Several masers have a large blueshift, even up to 120 km.s-1, with respect to the CO peak, but no large redshifted maser appears. This result suggests that high-velocity H2O masers can most probably occur in high mass star-forming regions and quite a number of masers stem from the amplifications of a background source, which may enable those undetectable weak masers to come to an observable level.

  17. Kinetics of the atrazine degradation process using H2O2-UVC.

    Science.gov (United States)

    Sarmento, Sandra M; Miranda, José T G

    2014-01-01

    This work is concerned with the intrinsic reaction kinetic of the degradation of atrazine (ATZ) using H2O2-UVC. Experimental runs were carried out in annular photoreactor. The initial concentration of ATZ was 2.2 × 10(-2) mol m(-3) while the H2O2-ATZ molar ratio range was 0-578 mol H2O2 mol(-1) ATZ. The ATZ molecules are decomposed by means of free-radical attack (95.2%) and direct photolysis (4.8%). There is an optimal H2O2/ATZ molar ratio (ROP = 347 H2O2 mol(-1) ATZ) which maximizes the initial degradation rate and conversion at 300 s at 83% and 77%, respectively. The process is economically feasible as the values of the energy requirement, energy and H2O2 costs at ROP are 0.14 KWh m(-3) order(-1), US$0.02 kWh(-1) m(-3) and US$1.0 m(-3), respectively. The kinetic model proposed is based on Lea's reaction scheme for the H2O2 direct photolysis, the hypothesis that unknown ATZ sub-products that absorb UVC radiation are generated, and the local volumetric rate of photon absorption. The radiation transport equation was solved and the linear spherical source emission model was used to represent the lamp emission. Intrinsic reaction kinetic parameters were estimated and the model was validated. The model predicted the data in a range of 90 to 98%.

  18. NICMOS Observations of Shocked H_2 in Orion

    CERN Document Server

    Colgan, Sean W J; Kaufman, M J; Erickson, E F; Hollenbach, D J

    2007-01-01

    HST NICMOS narrowband images of the shocked molecular hydrogen emission in OMC-1 are analyzed to reveal new information on the BN/KL outflow. The outstanding morphological feature of this region is the array of molecular hydrogen ``fingers'' emanating from the general vicinity of IRc2 and the presence of several Herbig-Haro objects. The NICMOS images appear to resolve individual shock fronts. This work is a more quantitative and detailed analysis of our data from a previous paper (Schultz etal. 1999). Line strengths for the H_2 1--0 S(4) plus 2--1 S(6) lines at 1.89 micron are estimated from measurements with the Paschen_alpha continuum filter F190N at 1.90 micron, and continuum measurements at 1.66 and 2.15 micron. We compare the observed H_2 line strengths and ratios of the 1.89 micron and 2.12 micron 1--0 S(1) lines with models for molecular cloud shock waves. Most of the data cannot be fit by J-shocks, but are well matched by C-shocks with shock velocities in the range of 20--45 km/s and preshock densitie...

  19. Miles Technicon H.2 automated hematology analyzer.

    Science.gov (United States)

    1992-11-01

    Automated hematology analyzers are used in all large hospitals and most commercial laboratories, as well as in most smaller hospitals and laboratories, to perform complete blood counts (including white blood cell, red blood cell, and platelet counts; hemoglobin concentration; and RBC indices) and white blood cell differential counts. Our objectives in this study are to provide user guidance for selecting, purchasing, and using an automated hematology analyzer, as well as to present an overview of the technology used in an automated five-part differential unit. Specifications for additional automated units are available in ECRI's Clinical Laboratory Product Comparison System. We evaluated the Miles Technicon H.2 unit and rated it Acceptable. The information in this Single Product Evaluation is also useful for purchasing other models; our criteria will guide users in assessing components, and our findings and discussions on some aspects of automated hematology testing are common to many available systems. We caution readers not to base purchasing decisions on our rating of the Miles unit alone, but on a thorough understanding of the issues surrounding automated hematology analyzers, which can be gained only by reading this report in its entirety. The willingness of manufacturers to cooperate in our studies and the knowledge they gain through participating lead to the development of better products. Readers should refer to the Guidance Section, "Selecting and Purchasing an Automated Hematology Analyzer," where we discuss factors such as standardization, training, human factors, manufacturer support, patient population, and special features that the laboratory must consider before obtaining any automated unit; we also provide an in-depth review of cost issues, including life-cycle cost analyses, acquisition methods and costs of hardware and supplies, and we describe the Hemacost and Hemexmpt cost worksheets for use with our PresValu and PSV Manager CAHDModel software

  20. Constraints on the H2O formation mechanism in the wind of carbon-rich AGB stars

    CERN Document Server

    Lombaert, R; Royer, P; de Koter, A; Cox, N L J; González-Alfonso, E; Neufeld, D; De Ridder, J; Agúndez, M; Blommaert, J A D L; Khouri, T; Groenewegen, M A T; Kerschbaum, F; Cernicharo, J; Vandenbussche, B; Waelkens, C

    2016-01-01

    Context. The recent detection of warm H$_2$O vapor emission from the outflows of carbon-rich asymptotic giant branch (AGB) stars challenges the current understanding of circumstellar chemistry. Two mechanisms have been invoked to explain warm H$_2$O vapor formation. In the first, periodic shocks passing through the medium immediately above the stellar surface lead to H$_2$O formation. In the second, penetration of ultraviolet interstellar radiation through a clumpy circumstellar medium leads to the formation of H$_2$O molecules in the intermediate wind. Aims. We aim to determine the properties of H$_2$O emission for a sample of 18 carbon-rich AGB stars and subsequently constrain which of the above mechanisms provides the most likely warm H$_2$O formation pathway. Methods, Results, and Conclusions. See paper.

  1. HCl-H2S-H2O体系中HCl与H2S对20碳钢腐蚀的交互作用

    Institute of Scientific and Technical Information of China (English)

    郭金彪; 李艳

    2013-01-01

    目前有关HCl-H2S-H2O体系中HCl与H2S对碳钢腐蚀的交互作用的试验数据较少.利用电化学方法测试了20碳钢在90℃,不同浓度的HCl,H2S单一腐蚀液及HCl和H2S混合腐蚀液中的腐蚀速率,分析了HCl-H2S-H2O体系中HCl与H2S对20碳钢腐蚀的交互作用.结果表明:20碳钢在单一的HCl或H2S腐蚀液中的腐蚀速率随HCl或H2S浓度的增大而增大;在HCl-H2S-H2O体系中,不论H2S浓度高低,HCl的存在均会促进H2S对20碳钢的腐蚀;只有当HCl的浓度较低(≤248.72 mg/L)时,H2S的存在才会促进HCl对20碳钢的腐蚀;而当HCl浓度较高(≥499.16 mg/L)时,H2S的存在不仅不会促进HCl对20碳钢的腐蚀,还会在一定程度上起阻碍作用.

  2. The H2O2-H2O Hypothesis: Extremophiles Adapted to Conditions on Mars?

    Science.gov (United States)

    Houtkooper, Joop M.; Schulze-Makuch, Dirk

    2007-08-01

    The discovery of extremophiles on Earth is a sequence of discoveries of life in environments where it had been deemed impossible a few decades ago. The next frontier may be the Martian surface environment: could life have adapted to this harsh environment? What we learned from terrestrial extremophiles is that life adapts to every available niche where energy, liquid water and organic materials are available so that in principle metabolism and propagation are possible. A feasible adaptation mechanism to the Martian surface environment would be the incorporation of a high concentration of hydrogen peroxide in the intracellular fluid of organisms. The H2O2-H2O hypothesis suggests the existence of Martian organisms that have a mixture of H2O2 and H2O instead of salty water as their intracellular liquid (Houtkooper and Schulze-Makuch, 2007). The advantages are that the freezing point is low (the eutectic freezes at 56.5°C) and that the mixture is hygroscopic. This would enable the organisms to scavenge water from the atmosphere or from the adsorbed layers of water molecules on mineral grains, with H2O2 being also a source of oxygen. Moreover, below its freezing point the H2O2-H2O mixture has the tendency to supercool. Hydrogen peroxide is not unknown to biochemistry on Earth. There are organisms for which H2O2 plays a significant role: the bombardier beetle, Brachinus crepitans, produces a 25% H2O2 solution and, when attacked by a predator, mixes it with a fluid containing hydroquinone and a catalyst, which produces an audible steam explosion and noxious fumes. Another example is Acetobacter peroxidans, which uses H2O2 in its metabolism. H2O2 plays various other roles, such as the mediation of physiological responses such as cell proliferation, differentiation, and migration. Moreover, most eukaryotic cells contain an organelle, the peroxisome, which mediates the reactions involving H2O2. Therefore it is feasible that in the course of evolution, water-based organisms

  3. Isotopic signatures of production and uptake of H2 by soil

    Directory of Open Access Journals (Sweden)

    Q. Chen

    2015-09-01

    Full Text Available Molecular hydrogen (H2 is the second most abundant reduced trace gas (after methane in the atmosphere, but its biogeochemical cycle is not well understood. Our study focuses on the soil production and uptake of H2 and the associated isotope effects. Air samples from a grass field and a forest site in the Netherlands were collected using soil chambers. The results show that uptake and emission of H2 occurred simultaneously at all sampling sites, with strongest emission at the grassland sites where clover (N2 fixing legume was present. The H2 mole fraction and deuterium content were measured in the laboratory to determine the isotopic fractionation factor during H2 soil uptake (αsoil and the isotopic signature of H2 that is simultaneously emitted from the soil (δDsoil. By considering all net-uptake experiments, an overall fractionation factor for deposition of αsoil = kHD/kHH = 0.945 ± 0.004 (95 % CI was obtained. The difference in mean αsoil between the forest soil 0.937 ± 0.008 and the grassland 0.951 ± 0.025 is not statistically significant. For two experiments, the removal of soil cover increased the deposition velocity (vd and αsoil simultaneously, but a general positive correlation between vd and αsoil was not found in this study. When the data are evaluated with a model of simultaneous production and uptake, the isotopic composition of H2 that is emitted at the grassland site is calculated as δDsoil = (−530 ± 40 ‰. This is less deuterium-depleted than what is expected from isotope equilibrium between H2O and H2.

  4. Increased H2CO production in the outer disk around HD 163296

    Science.gov (United States)

    Carney, M. T.; Hogerheijde, M. R.; Loomis, R. A.; Salinas, V. N.; Öberg, K. I.; Qi, C.; Wilner, D. J.

    2017-09-01

    Context. The gas and dust in circumstellar disks provide the raw materials to form planets. The study of organic molecules and their building blocks in such disks offers insight into the origin of the prebiotic environment of terrestrial planets. Aims: We aim to determine the distribution of formaldehyde, H2CO, in the disk around HD 163296 to assess the contribution of gas- and solid-phase formation routes of this simple organic. Methods: Three formaldehyde lines were observed (H2CO 303-202, H2CO 322-221, and H2CO 321-220) in the protoplanetary disk around the Herbig Ae star HD 163296 with ALMA at 0.5″ (60 AU) spatial resolution. Different parameterizations of the H2CO abundance were compared to the observed visibilities, using either a characteristic temperature, a characteristic radius or a radial power law index to describe the H2CO chemistry. Similar models were applied to ALMA Science Verification data of C18O. In each scenario, χ2 minimization on the visibilities was used to determine the best-fit model in each scenario. Results: H2CO 303-202 was readily detected via imaging, while the weaker H2CO 322-221 and H2CO 321-220 lines required matched filter analysis to detect. H2CO is present throughout most of the gaseous disk, extending out to 550 AU. An apparent 50 AU inner radius of the H2CO emission is likely caused by an optically thick dust continuum. The H2CO radial intensity profile shows a peak at 100 AU and a secondary bump at 300 AU, suggesting increased production in the outer disk. In all modeling scenarios, fits to the H2CO data show an increased abundance in the outer disk. The overall best-fit H2CO model shows a factor of two enhancement beyond a radius of 270 ± 20 AU, with an inner abundance (relative to H2) of 2 - 5 × 10-12. The H2CO emitting region has a lower limit on the kinetic temperature of T> 20 K. The C18O modeling suggests an order of magnitude depletion of C18O in the outer disk and an abundance of 4 - 12 × 10-8 in the inner disk

  5. Chemiluminescent Detection of Enzymatically Produced H2S

    OpenAIRE

    Bailey, T. Spencer; Pluth, Michael D.

    2015-01-01

    Hydrogen sulfide (H2S) has emerged as an important biological signaling molecule. To better understand the multifaceted biological roles of H2S, the development of selective and sensitive biocompatible assays for H2S is becoming increasingly important. Motivated by these challenges, our laboratory is developing new methods to further detect and monitor biological H2S. Here, we describe in detail our recent advances in the development and the use of chemiluminescence-based H2S sensors to assis...

  6. 20 CFR 655.132 - H-2A labor contractor (H-2ALC) filing requirements.

    Science.gov (United States)

    2010-04-01

    ... LABOR TEMPORARY EMPLOYMENT OF FOREIGN WORKERS IN THE UNITED STATES Labor Certification Process for Temporary Agricultural Employment in the United States (H-2A Workers) Application for Temporary Employment... and activities the workers are expected to perform at such fixed site. (2) A copy of the Migrant...

  7. H2O2 space shuttle APU

    Science.gov (United States)

    1975-01-01

    A cryogenic H2-O2 auxiliary power unit (APU) was developed and successfully demonstrated. It has potential application as a minimum weight alternate to the space shuttle baseline APU because of its (1) low specific propellant consumption and (2) heat sink capabilities that reduce the amount of expendable evaporants. A reference system was designed with the necessary heat exchangers, combustor, turbine-gearbox, valves, and electronic controls to provide 400 shp to two aircraft hydraulic pumps. Development testing was carried out first on the combustor and control valves. This was followed by development of the control subsystem including the controller, the hydrogen and oxygen control valves, the combustor, and a turbine simulator. The complete APU system was hot tested for 10 hr with ambient and cryogenic propellants. Demonstrated at 95 percent of design power was 2.25 lb/hp-hr. At 10 percent design power, specific propellant consumption was 4 lb/hp-hr with space simulated exhaust and 5.2 lb/hp-hr with ambient exhaust. A 10 percent specific propellant consumption improvement is possible with some seal modifications. It was demonstrated that APU power levels could be changed by several hundred horsepower in less than 100 msec without exceeding allowable turbine inlet temperatures or turbine speed.

  8. Modeling Ice Giant Interiors Using Constraints on the H2-H2O Critical Curve

    Science.gov (United States)

    Bailey, E.; Stevenson, D. J.

    2015-12-01

    We present a range of models of Uranus and Neptune, taking into account recent experimental data (Bali, 2013) implying the location of the critical curve of the H2-H2O system at pressures up to 2.6 GPa. The models presented satisfy the observed total mass of each planet and the radius at the observed 1-bar pressure level. We assume the existence of three regions at different depths: an outer adiabatic envelope composed predominately of H2 and He, with a helium mass fraction 0.26, a water-rich layer including varied amounts of rock and hydrogen, and a chemically homogeneous rock core. Using measured rotation rates of Uranus and Neptune, and a density profile obtained for each model using constituent equations of state and the assumption of hydrostatic equilibrium, we calculate the gravitational harmonics J2 and J4 for comparison with observed values as an additional constraint. The H2-H2O critical curve provides information about the nature of the boundary between the outer, hydrogen-rich envelope and underlying water-rich layer. The extrapolated critical curve for hydrogen-water mixtures crosses the adiabat of the outer atmospheric shell in these models at two depths, implying a shallow outer region of limited miscibility, an intermediate region between ~90 and 98 percent of the total planet radius within which hydrogen and water can mix in all proportions, and another, deeper region of limited miscibility at less than ~90 percent of the total planet radius. The pressure and temperature of the gaseous adiabatic shell at the depth of the shallowest extent of the water-rich layer determines whether a gradual compositional transition or an ocean surface boundary may exist at depth in these planets. To satisfy the observed J2, the outer extent of the water-rich layer in these models must be located between approximately 80 and 85 percent of the total planet radius, within the deep region of limited H2-H2O miscibility, implying an ocean surface is possible within the

  9. Methodological aspects of breath hydrogen (H2) analysis. Evaluation of a H2 monitor and interpretation of the breath H2 test

    DEFF Research Database (Denmark)

    Rumessen, J J; Kokholm, G; Gudmand-Høyer, E

    1987-01-01

    The reliability of end-expiratory hydrogen (H2) breath tests were assessed and the significance of some important pitfalls were studied, using a compact, rapid H2-monitor with electrochemical cells. The H2 response was shown to be linear and stable. The reproducibility of the breath collection...... were studied in 10 healthy adults during a 4-month period and they showed very marked inter- and intra-individual variability (16% above 40 p.p.m.). Initial peaks (early, short-lived H2 rises unrelated to carbohydrate malabsorption) were identified in 25% of the breath tests (in 4% above 20 p.......p.m). It is concluded that the technique used for interval sampling of end-expiratory breath samples for H2 concentration gives reliable results. The biological significance of H2 concentration increments can only be evaluated if the limitations of the technical procedures and the individual ability to produce H2...

  10. Phase transition and optoelectronic properties of MgH2

    Science.gov (United States)

    Nayak, Vikas; Verma, U. P.

    2016-05-01

    In this article, structural and electronic properties of MgH2 have been studied. The aim behind this study was to find out the ground state crystal structure of MgH2. For the purpose, density functional theory (DFT)-based full-potential linearized augmented plane wave (FP-LAPW) calculations have been performed in three different space groups: P42/mnm (α-MgH2), Pa3 (β-MgH2) and Pbcn (γ-MgH2). It has been found that the ground state structure of MgH2 is α-MgH2. The present study shows that α-MgH2 transforms into γ-MgH2 at a pressure of 0.41 GPa. After further increase in pressure, γ-MgH2 transforms into β-MgH2 at a pressure of 3.67 GPa. The obtained results are in good agreement with previously reported experimental data. In all the studied phases, the behavior of MgH2 is insulating and its optical conductivity is around 6.0 eV. The α-MgH2 and γ-MgH2 are anisotropic materials while β-MgH2 is isotropic in nature.

  11. Lighting the dark molecular gas: H$_{2}$ as a direct tracer

    CERN Document Server

    Togi, Aditya

    2016-01-01

    Robust knowledge of molecular gas mass is critical for understanding star formation in galaxies. The H$_{2}$ molecule does not emit efficiently in the cold interstellar medium, hence the molecular gas content of galaxies is typically inferred using indirect tracers. At low metallicity and in other extreme environments, these tracers can be subject to substantial biases. We present a new method of estimating total molecular gas mass in galaxies directly from pure mid-infrared rotational H$_{2}$ emission. By assuming a power-law distribution of H$_{2}$ rotational temperatures, we can accurately model H$_{2}$ excitation and reliably obtain warm ($T\\!\\gtrsim\\!100$ K) H$_{2}$ gas masses by varying only the power law's slope. With sensitivities typical of Spitzer/IRS, we are able to directly probe the H$_{2}$ content via rotational emission down to ~80 K, accounting for ~15% of the total molecular gas mass in a galaxy. By extrapolating the fitted power law temperature distributions to a calibrated \\emph{single} low...

  12. The Distribution and Chemistry of H$_2$CO in the DM Tau Protoplanetary Disk

    CERN Document Server

    Loomis, Ryan A; Öberg, Karin I; Guzman, Viviana V; Andrews, Sean M

    2015-01-01

    H$_2$CO ice on dust grains is an important precursor of complex organic molecules (COMs). H$_2$CO gas can be readily observed in protoplanetary disks and may be used to trace COM chemistry. However, its utility as a COM probe is currently limited by a lack of constraints on the relative contributions of two different formation pathways: on icy grain-surfaces and in the gas-phase. We use archival ALMA observations of the resolved distribution of H$_2$CO emission in the disk around the young low-mass star DM Tau to assess the relative importance of these formation routes. The observed H$_2$CO emission has a centrally peaked and radially broad brightness profile (extending out to 500 AU). We compare these observations with disk chemistry models with and without grain-surface formation reactions, and find that both gas and grain-surface chemistry are necessary to explain the spatial distribution of the emission. Gas-phase H$_2$CO production is responsible for the observed central peak, while grain-surface chemist...

  13. Experimental evidence of twin fast metastable H(2S) atoms from dissociation of cold H_2 induced by electrons

    CERN Document Server

    Robert, J; Carvalho, C R; Jalbert, Ginette; Nascimento, R F; Trimeche, A; Dulieu, O; Medina, Aline; Carvalho, Carla; Faria, N V de Castro

    2013-01-01

    We report the direct detection of two metastable H(2S) atoms coming from the dissociation of a single cold H_2 molecule, in coincidence measurements. The molecular dissociation was induced by electron impact in order to avoid limitations by the selection rules governing radiative transitions. Two detectors, placed close from the collision center, measure the neutral metastable H(2S) through a localized quenching process, which mixes the H(2S) state with the H(2P), leading to a Lyman-\\alpha detection. Our data show the accomplishment of a coincidence measurement which proves for the first time the existence of the H(2S)-H(2S) dissociation channel.

  14. Heavy hydrides: H2Te ultraviolet photochemistry

    Science.gov (United States)

    Underwood, J.; Chastaing, D.; Lee, S.; Wittig, C.

    2005-08-01

    The room-temperature ultraviolet absorption spectrum of H2Te has been recorded. Unlike other group-6 hydrides, it displays a long-wavelength tail that extends to 400 nm. Dissociation dynamics have been examined at photolysis wavelengths of 266 nm (which lies in the main absorption feature) and 355 nm (which lies in the long-wavelength tail) by using high-n Rydberg time-of-flight spectroscopy to obtain center-of-mass translational energy distributions for the channels that yield H atoms. Photodissociation at 355 nm yields TeH(Π1/22) selectively relative to the TeH(Π3/22) ground state. This is attributed to the role of the 3A' state, which has a shallow well at large RH-TeH and correlates to H +TeH(Π1/22). Note that the Π1/22 state is analogous to the P1/22 spin-orbit excited state of atomic iodine, which is isoelectronic with TeH. The 3A' state is crossed at large R only by 2A″, with which it does not interact. The character of 3A' at large R is influenced by a strong spin-orbit interaction in the TeH product. Namely, Π1/22 has a higher degree of spherical symmetry than does Π3/22 (recall that I(P1/22) is spherically symmetric), and consequently Π1/22 is not inclined to form either strongly bonding or antibonding orbitals with the H atom. The 3A'←X transition dipole moment dominates in the long-wavelength region and increases with R. Structure observed in the absorption spectrum in the 380-400 nm region is attributed to vibrations on 3A'. The main absorption feature that is peaked at ˜240nm might arise from several excited surfaces. On the basis of the high degree of laboratory system spatial anisotropy of the fragments from 266 nm photolysis, as well as high-level theoretical studies, the main contribution is believed to be due to the 4A″ surface. The 4A″←X transition dipole moment dominates in the Franck-Condon region, and its polarization is in accord with the experimental observations. An extensive secondary photolysis (i.e., of nascent TeH) is

  15. Identification of H2S3 and H2S produced by 3-mercaptopyruvate sulfurtransferase in the brain.

    Science.gov (United States)

    Kimura, Yuka; Toyofuku, Yukiko; Koike, Shin; Shibuya, Norihiro; Nagahara, Noriyuki; Lefer, David; Ogasawara, Yuki; Kimura, Hideo

    2015-10-06

    Hydrogen polysulfides (H2Sn) have a higher number of sulfane sulfur atoms than hydrogen sulfide (H2S), which has various physiological roles. We recently found H2Sn in the brain. H2Sn induced some responses previously attributed to H2S but with much greater potency than H2S. However, the number of sulfur atoms in H2Sn and its producing enzyme were unknown. Here, we detected H2S3 and H2S, which were produced from 3-mercaptopyruvate (3 MP) by 3-mercaptopyruvate sulfurtransferase (3MST), in the brain. High performance liquid chromatography with fluorescence detection (LC-FL) and tandem mass spectrometry (LC-MS/MS) analyses showed that H2S3 and H2S were produced from 3 MP in the brain cells of wild-type mice but not 3MST knockout (3MST-KO) mice. Purified recombinant 3MST and lysates of COS cells expressing 3MST produced H2S3 from 3 MP, while those expressing defective 3MST mutants did not. H2S3 was localized in the cytosol of cells. H2S3 was also produced from H2S by 3MST and rhodanese. H2S2 was identified as a minor H2Sn, and 3 MP did not affect the H2S5 level. The present study provides new insights into the physiology of H2S3 and H2S, as well as novel therapeutic targets for diseases in which these molecules are involved.

  16. Pressure-induced structural transitions in MgH2.

    Science.gov (United States)

    Vajeeston, P; Ravindran, P; Kjekshus, A; Fjellvåg, H

    2002-10-21

    The stability of MgH2 has been studied up to 20 GPa using density-functional total-energy calculations. At ambient pressure alpha-MgH2 takes a TiO2-rutile-type structure. alpha-MgH2 is predicted to transform into gamma-MgH2 at 0.39 GPa. The calculated structural data for alpha- and gamma-MgH2 are in very good agreement with experimental values. At equilibrium the energy difference between these modifications is very small, and as a result both phases coexist in a certain volume and pressure field. Above 3.84 GPa gamma-MgH2 transforms into beta-MgH2, consistent with experimental findings. Two further transformations have been identified at still higher pressure: (i) beta- to delta-MgH2 at 6.73 GPa and (ii) delta- to epsilon-MgH2 at 10.26 GPa.

  17. Modeling the Interaction of H2 on Root Exudate Degradation and Methanogenesis in Wetland Sediments

    Science.gov (United States)

    Pal, D. S.; Jaffe, P. R.

    2014-12-01

    CH4 is produced in wetland sediments from the microbial degradation of organic carbon through multiple fermentation steps and methanogenesis pathways. There are many potential sources of carbon for methananogenesis; in vegetated wetland sediments, microbial communities consume root exudates as a major source of organic carbon. In many methane models propionate is used as a model carbon molecule. This simple sugar is fermented into acetate and H2, acetate is transformed to methane and CO2 while the H2 and CO2 is synthesized to form an additional CH4 molecule. The hydrogenotrophic pathway involves the equilibrium of two dissolved gases, CH4 and H2. In an effort to limit CH4 emissions from wetlands, there has been growing interest in finding ways to limit plant transport of soil gases through root systems. While this may decrease the direct emissions of methane, there is little understanding about how H2 dynamics may feedback into overall methane production. Since H2 is used in methane production and produced in propionate fermentation, increased subsurface H2 concentrations can simultaneously inhibit propionate fermentation and acetate production and enhance hydrogenotrophic methanogenesis. For this study, we incubated soil samples from vegetated wetland sediments with propionate or acetate and four different hydrogen concentrations. The headspaces from these incubations were simultaneously analyzed for H2 and CH4 at multiple time points over two months. The comparison of methane production between different hydrogen concentrations and different carbon sources can indicate which process is most affected by increased hydrogen concentrations. The results from this study were combined with a newly formulated steady-state model of propionate degradation and formation of methane, that also accounts for the venting off both gases via plants. The resulting model indicates how methane production and emissions would be affected by plant volatilization.

  18. HE-2+-H2 COLLISIONS - NONDISSOCIATIVE AND DISSOCIATIVE ONE-ELECTRON CAPTURE

    NARCIS (Netherlands)

    HOEKSTRA, R; FOLKERTS, HO; BEIJERS, JPM; MORGENSTERN, R; DEHEER, FJ

    1994-01-01

    Electron-redistribution processes in collisions of He-2+ ions on H-2 are studied for energies from 1 to 25 keV amu-1. One-electron capture and target excitation cross sections are determined by photon-emission spectroscopy. At energies exceeding approximately 5 keV amu-1 capture into excited states

  19. Some empirical estimates of the H2 formation rate in photon-dominated regions

    CERN Document Server

    Habart, E; Verstraete, L; Walmsley, C M; Pineau des Forêts, G

    2004-01-01

    We combine recent ISO observations of the vibrational ground state lines of H2 towards Photon-Dominated Regions (PDRs) with observations of vibrationally excited states made with ground-based telescopes in order to constrain the formation rate of H2 on grain surfaces under the physical conditions in the layers responsible for H2 emission. We use steady state PDR models in order to examine the sensitivity of different H2 line ratios to the H2 formation rate Rf. We show that the ratio of the 0-0 S(3) to the 1-0 S(1) line increases with Rf but that one requires independent estimates of the radiation field incident upon the PDR and the density in order to infer Rf from the H2 line data. We confirm the earlier result of Habart et al. (2003) that the H2 formation rate in regions of moderate excitation such as Oph W, S140 and IC 63 is a factor of 5 times larger than the standard rate inferred from UV observations of diffuse clouds. On the other hand, towards regions of higher radiation field such as the Orion Bar an...

  20. Some empirical estimates of the H2 formation rate in photon-dominated regions

    Science.gov (United States)

    Habart, E.; Boulanger, F.; Verstraete, L.; Walmsley, C. M.; Pineau des Forêts, G.

    2004-02-01

    We combine recent ISO observations of the vibrational ground state lines of H2 towards Photon-Dominated Regions (PDRs) with observations of vibrationally excited states made with ground-based telescopes in order to constrain the formation rate of H2 on grain surfaces under the physiconditions in the layers responsible for H2 emission. We briefly review the data available for five nearby PDRs. We use steady state PDR models in order to examine the sensitivity of different H2 line ratios to the H2 formation rate R_f. We show that the ratio of the 0-0 S(3) to the 1-0 S(1) line increases with Rf but that one requires independent estimates of the radiation field incident upon the PDR and the density in order to infer Rf from the H2 line data. We confirm earlier work by \\cite{habart2003a} on the Oph W PDR which showed that an H2 formation rate higher than the standard value of 3 × 10-17 cm3 s-1 inferred from UV observations of diffuse clouds is needed to explain the observed H2 excitation. From comparison of the ISO and ground-based data, we find that moderately excited PDRs such as Oph W, S140 and IC 63 require an H2 formation rate of about five times the standard value whereas the data for PDRs with a higher incident radiation field such as NGC 2023 and the Orion Bar can be explained with the standard value of Rf. We compare also the H21-0 S(1) line intensities with the emission in PAH features and find a rough scaling of the ratio of these quantities with the ratio of local density to radiation field. This suggests but does not prove that formation of H2 on PAHs is important in PDRs. We also consider some empirical models of the H2 formation process with the aim of explaining these results. Here we consider both formation on classical grains of size roughly 0.1 μm and on very small (˜10 Å) grains by either direct recombination from the gas phase (Eley-Rideal mechanism) or recombination of physisorbed H atoms with atoms in a chemisorbed site. We conclude that

  1. An accurate H2-H2 interaction potential from first principles

    Science.gov (United States)

    Diep, Phong; Johnson, J. Karl

    2000-03-01

    We have calculated the potential energy surface extrapolated to the complete basis set limit using coupled-cluster theory with singles, doubles, and perturbational triples excitations [CCSD(T)] for the rigid monomer model of (H2)2. There is significant anisotropy among the 37 unique angular configurations selected to represent the surface. A four term spherical harmonics expansion model was chosen to fit the surface. The calculated potential energy surface reproduces the quadrupole moment to within 0.58% and the experimental well depth to within 1%. The second virial coefficient has been computed from the fitted potential energy surface. The usual semiclassical treatment of quantum mechanical effects on the second virial coefficient was applied in the temperature range of 100-500 K. We have developed a new technique for computing the quantum second virial coefficient by combining Feynman's path integral formalism and Monte Carlo integration. The calculated virial coefficient compares very well with published experimental measurements. Integral elastic cross sections were calculated for the scattering of para-H2/para-H2 by use of the close-coupling method. The interaction potential model from this work is able to reproduce the experimental cross sections in the relative kinetic velocity range of 900-2300 m/s.

  2. Submillimeter spectroscopy of H$_2$C$^{17}$O and a revisit of the rotational spectra of H$_2$C$^{18}$O and H$_2$C$^{16}$O

    CERN Document Server

    Müller, Holger S P

    2016-01-01

    The rotational spectrum of the formaldehyde isotopologue H2C(17)O was investigated between 0.56 and 1.50 THz using a sample of natural isotopic composition. In addition, transition frequencies were determined for H2C(18)O and H2C(16)O between 1.37 and 1.50 THz. The data were combined with critically evaluated literature data to derive improved sets of spectroscopic parameters which include (17)O or H nuclear hyperfine structure parameters.

  3. Near-resonance scattering of the para-H2 vibrons in (ortho-H2)x(para-H2)1-x mixed crystals

    Science.gov (United States)

    de Kinder, J.; Bouwen, A.; Schoemaker, D.; Boukahil, A.; Huber, D. L.

    1994-05-01

    The p-H2 vibrons hae been studied by high-resolution Raman scattering in mixed crystals of (o-H2)x(p-H2)1-x, (HD)x(p-H2)1-x, and (o-D2)0.069(p-H2)0.931. For increasing o-H2 concentration, the line shape broadens and becomes asymmetric with a tail towards higher frequencies. This effect is less pronounced in the HD- and the o-D2-doped crystals, where the energy difference between the p-H2 vibron and the stretching vibration of the impurity is much larger. Isolated impurities still have a symmetrical line shape, showing that the asymmetry is not due to inhomogeneities. Calculated line shapes by the coherent-potential-approximation technique are in very good qualitative agreement with the experimental results. The theory also accounts for previously published experimental data on the variations of the relative positions and intensities of the ortho and para peaks in (o-H2)x(p-H2)1-x.

  4. Proteome analysis of protein partners to nucleosomes containing canonical H2A or the variant histones H2A.Z or H2A.X.

    Science.gov (United States)

    Fujimoto, Satoru; Seebart, Corrine; Guastafierro, Tiziana; Prenni, Jessica; Caiafa, Paola; Zlatanova, Jordanka

    2012-01-01

    Although the existence of histone variants has been known for quite some time, only recently are we grasping the breadth and diversity of the cellular processes in which they are involved. Of particular interest are the two variants of histone H2A, H2A.Z and H2A.X because of their roles in regulation of gene expression and in DNA double-strand break repair, respectively. We hypothesize that nucleosomes containing these variants may perform their distinct functions by interacting with different sets of proteins. Here, we present our proteome analysis aimed at identifying protein partners that interact with nucleosomes containing H2A.Z, H2A.X or their canonical H2A counterpart. Our development of a nucleosome-pull down assay and analysis of the recovered nucleosome-interacting proteins by mass spectrometry allowed us to directly compare nuclear partners of these variant-containing nucleosomes to those containing canonical H2A. To our knowledge, our data represent the first systematic analysis of the H2A.Z and H2A.X interactome in the context of nucleosome structure.

  5. Fluorescent Probes for H2S Detection and Quantification.

    Science.gov (United States)

    Feng, Wei; Dymock, Brian W

    2015-01-01

    Many diverse, sensitive and structurally novel fluorescent probes have recently been reported for H2S detection. Quantification of H2S requires a selective chemosensor which will react only with H2S against a background of high concentrations of other thiols or reducing agents. Most published probes are able to quantify H2S selectively in a simple in vitro system with the most sensitive probes able to detect H2S at below 100 nM concentrations. A subset of probes also have utility in sensing H2S in living cells, and there are now several with specific sub-cellular localization and a few cases of in vivo applications. Biologists studying H2S now have a wide range of tools to assist them to aid further understanding of the role of H2S in biology.

  6. Analysis list: Suv39h2 [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Suv39h2 Pluripotent stem cell + mm9 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Suv...39h2.1.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Suv39h2.5.tsv http://dbarchive.bi...osciencedbc.jp/kyushu-u/mm9/target/Suv39h2.10.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Suv39h

  7. The Nature of the H2-Emitting Gas in the Crab Nebula

    CERN Document Server

    Richardson, C T; Ferland, G J; Loh, E D; Kuehn, C A; Fabian, A C; Salomé, Philippe

    2012-01-01

    Understanding how molecules and dust might have formed within a rapidly expanding young supernova remnant is important because of the obvious application to vigorous supernova activity at very high redshift. In previous papers, we found that the H2 emission is often quite strong, correlates with optical low-ionization emission lines, and has a surprisingly high excitation temperature. Here we study Knot 51, a representative, bright example, for which we have available long slit optical and NIR spectra covering emission lines from ionized, neutral, and molecular gas, as well as HST visible and SOAR Telescope NIR narrow-band images. We present a series of CLOUDY simulations to probe the excitation mechanisms, formation processes and dust content in environments that can produce the observed H2 emission. We do not try for an exact match between model and observations given Knot 51's ambiguous geometry. Rather, we aim to explain how the bright H2 emission lines can be formed from within the volume of Knot 51 that...

  8. Acetate enhances startup of a H2-producing microbial biocathode

    NARCIS (Netherlands)

    Jeremiasse, A.W.; Hamelers, H.V.M.; Croese, E.; Buisman, C.J.N.

    2012-01-01

    H2 can be produced from organic matter with a microbial electrolysis cell (MEC). To decrease MEC capital costs, a cathode is needed that is made of low-cost material and produces H2 at high rate. A microbial biocathode is a low-cost candidate, but suffers from a long startup and a low H2 production

  9. Dynamics of yeast histone H2A and H2B phosphorylation in response to a double-strand break.

    Science.gov (United States)

    Lee, Cheng-Sheng; Lee, Kihoon; Legube, Gaëlle; Haber, James E

    2014-01-01

    In budding yeast, a single double-strand break (DSB) triggers extensive Tel1 (ATM)- and Mec1 (ATR)-dependent phosphorylation of histone H2A around the DSB, to form γ-H2AX. We describe Mec1- and Tel1-dependent phosphorylation of histone H2B at T129. γ-H2B formation is impaired by γ-H2AX and its binding partner Rad9. High-density microarray analyses show similar γ-H2AX and γ-H2B distributions, but γ-H2B is absent near telomeres. Both γ-H2AX and γ-H2B are strongly diminished over highly transcribed regions. When transcription of GAL7, GAL10 and GAL1 genes is turned off, γ-H2AX is restored within 5 min, in a Mec1-dependent manner; after reinduction of these genes, γ-H2AX is rapidly lost. Moreover, when a DSB is induced near CEN2, γ-H2AX spreads to all other pericentromeric regions, again depending on Mec1. Our data provide new insights in the function and establishment of phosphorylation events occurring on chromatin after DSB induction.

  10. First detection of 22 GHz H2O masers in TX Camelopardalis

    CERN Document Server

    Cho, Se-Hyung; Yun, Youngjoo

    2014-01-01

    Simultaneous time monitoring observations of H$_{2}$O $6_{16}-5_{23}$, SiO $J$ = 1--0, 2--1, 3--2, and $^{29}$SiO $v$ = 0, $J$ = 1--0 lines were carried out in the direction of the Mira variable star TX Cam with the Korean VLBI Network single dish radio telescopes. For the first time, the H$_{2}$O maser emission from TX Cam was detected near the stellar velocity at five epochs from April 10, 2013 ($\\phi$ = 3.13) to June 4, 2014 ($\\phi$ = 3.89) including minimum optical phases. The intensities of H$_{2}$O masers are very weak compared to SiO masers. The variation of peak antenna temperature ratios among SiO $v$ = 1, $J$ = 1--0, $J$ = 2--1, and $J$ = 3--2 masers is investigated according to their phases. The shift of peak velocities of H$_{2}$O and SiO masers with respect to the stellar velocity is also investigated according to observed optical phases. The H$_{2}$O maser emission occurs around the stellar velocity during our monitoring interval. On the other hand, the peak velocities of SiO masers show a sprea...

  11. Design of a MT-DBD reactor for H2S control

    Science.gov (United States)

    Xu, CAO; Weixuan, ZHAO; Renxi, ZHANG; Huiqi, HOU; Shanping, CHEN; Ruina, ZHANG

    2017-04-01

    This study aimed to discuss the removal of hydrogen sulfide (H2S) with non-thermal plasma produced by a multilayer tubular dielectric barrier discharge reactor, which is useful in the field of plasma environmental applications. We explored the influence of various factors upon H2S removal efficiency ({η }{{{H}}2{{S}}}) and energy yield (Ey), such as specific energy density (SED), initial concentration, gas flow velocity and the reactor configuration. The study showed that we can achieve {η }{{{H}}2{{S}}} of 91% and the best Ey of 3100 mg kWh‑1 when we set the SED, gas flow velocity, initial H2S concentration and layers of quartz tubes at 33.2 J l‑1, 8.0 m s‑1, 30 mg m‑3 and five layers, correspondingly. The average rate constant for the decomposition of hydrogen sulfide was 0.206 g m‑3 s‑1. In addition, we also presented the optimized working conditions, by-product analysis and decomposition mechanism. Supported by programs of Research on the Technology and Equipment of Gaseous Pollutant Removal from the Emission of Household Garbage (15DZ12055904) and Jointly Decomposition of Odorous Compounds by Dielectric Combined with Excimer Ultraviolet Emission (21577023).

  12. Design of a MT-DBD reactor for H2S control

    Science.gov (United States)

    Cao, Xu; Zhao, Weixuan; Zhang, Renxi; Hou, Huiqi; Chen, Shanping; Zhang, Ruina

    2017-04-01

    This study aimed to discuss the removal of hydrogen sulfide (H2S) with non-thermal plasma produced by a multilayer tubular dielectric barrier discharge reactor, which is useful in the field of plasma environmental applications. We explored the influence of various factors upon H2S removal efficiency ({η }{{{H}}2{{S}}}) and energy yield (Ey), such as specific energy density (SED), initial concentration, gas flow velocity and the reactor configuration. The study showed that we can achieve {η }{{{H}}2{{S}}} of 91% and the best Ey of 3100 mg kWh-1 when we set the SED, gas flow velocity, initial H2S concentration and layers of quartz tubes at 33.2 J l-1, 8.0 m s-1, 30 mg m-3 and five layers, correspondingly. The average rate constant for the decomposition of hydrogen sulfide was 0.206 g m-3 s-1. In addition, we also presented the optimized working conditions, by-product analysis and decomposition mechanism. Supported by programs of Research on the Technology and Equipment of Gaseous Pollutant Removal from the Emission of Household Garbage (15DZ12055904) and Jointly Decomposition of Odorous Compounds by Dielectric Combined with Excimer Ultraviolet Emission (21577023).

  13. Toeplitz Operators on H2(T2)%H2(T2)上的Toeplitz算子

    Institute of Scientific and Technical Information of China (English)

    杨立敏

    2001-01-01

    给出了H2(T2)上Toeplitz算子的特征方程:T*zTTz=T,T*wTTw=T,及两个Toeplitz算子ψ,ψ∈L∞(T2),Tψ和Tφ的乘积TψTφ仍为Toeplitz算子的充要条件是:ψ对z、w中零个、一个或两个变量共轭解析,φ对余下变量解析,且乘积为Tψφ.

  14. EERE-SBIR technology transfer opportunity. H2 Safety Sensors for H2

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, Mariann R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-12-01

    The Office of Energy Efficiency and Renewable Energy’s Fuel Cell Technologies Office (FCTO) works in partnership with industry (including small businesses), academia, and DOE's national laboratories to establish fuel cell and hydrogen energy technologies as economically competitive contributors to U.S. transportation needs. The work that is envisioned between the SBIR/STTR grantee and Los Alamos National Laboratory would involve Technical Transfer of Los Alamos Intellectual Property (IP) on Thin-film Mixed Potential Sensor (U.S. Patent 7,264,700) and associated know-how for H2 sensor manufacturing and packaging.

  15. Methodological aspects of breath hydrogen (H2) analysis. Evaluation of a H2 monitor and interpretation of the breath H2 test

    DEFF Research Database (Denmark)

    Rumessen, J J; Kokholm, G; Gudmand-Høyer, E

    1987-01-01

    technique was determined in 20 patients following ingestion of lactulose. The increment between consecutive means of duplicate samples indicative of a significant rise of H2 concentration never exceeded 10 p.p.m., the mean coefficient of variation of the duplicate samples was below 5%. Fasting H2 levels...

  16. Organelle-Targeted H2S Probes Enable Visualization of the Subcellular Distribution of H2S Donors.

    Science.gov (United States)

    Montoya, Leticia A; Pluth, Michael D

    2016-06-07

    Hydrogen sulfide (H2S) is an essential biological signaling molecule in diverse biological regulatory pathways. To provide new chemical tools for H2S imaging, we report here a fluorescent H2S detection platform (HSN2-BG) that is compatible with subcellular localization SNAP-tag fusion protein methodologies and use appropriate fusion protein constructs to demonstrate mitochondrial and lysosomal localization. We also demonstrate the efficacy of this detection platform to image endogenous H2S in Chinese hamster ovary (CHO) cells and use the developed constructs to report on the subcellular H2S distributions provided by common H2S donor molecules AP39, ADT-OH, GYY4137, and diallyltrisulfide (DATS). The developed constructs provide a platform poised to provide new insights into the subcellular distribution of common H2S donors and a useful tool for investigating H2S biochemistry.

  17. Photochemical generation of H2NCNX, H2NNCX, H2NC(NX) (X = O, S) in low-temperature matrices.

    Science.gov (United States)

    Vörös, Tamás; Lajgút, Győző György; Magyarfalvi, Gábor; Tarczay, György

    2017-01-14

    The [NH2, C, N, O] and the [NH2, C, N, S] molecular systems were investigated by computational and matrix-isolation spectroscopic methods. The determination of the equilibrium structures and relative energies by CCSD(T) method was followed by the computation of the harmonic and anharmonic vibrational wavenumbers, infrared intensities, relative Raman activities, and UV excitation energies. These computed data were used to assist the identification of products obtained by UV laser photolysis of 3,4-diaminofurazan and 3,4-diaminothiadiazole in low-temperature Ar and Kr matrices. It is shown that two open-chain H2NNCX and H2NCNX and one cyclic H2NC(NX) (X = O, S) isomers are generated in the case of both systems. Except for H2NNCO and H2NCNS, the present study reports the first generation and spectroscopic identification of these compounds.

  18. Warm H2O and OH in the disk around the Herbig star HD 163296

    CERN Document Server

    Fedele, D; van Dishoeck, E F; Herczeg, G J; Evans, N J; Bouwman, J; Henning, Th; Green, J

    2012-01-01

    We present observations of far-infrared (50-200 micron) OH and H2O emission of the disk around the Herbig Ae star HD 163296 obtained with Herschel/PACS in the context of the DIGIT key program. In addition to strong [OI] emission, a number of OH doublets and a few weak highly excited lines of H2O are detected. The presence of warm H2O in this Herbig disk is confirmed by a line stacking analysis, enabled by the full PACS spectral scan, and by lines seen in Spitzer data. The line fluxes are analyzed using an LTE slab model including line opacity. The water column density is 10^14 - 10^15 cm^-2, and the excitation temperature is 200-300 K implying warm gas with a density n > 10^5 cm^-3. For OH we find a column density of 10^14 - 2x10^15 cm^-2 and T_ex ~ 300-500 K. For both species we find an emitting region of r ~ 15-20 AU from the star. We argue that the molecular emission arises from the protoplanetary disk rather than from an outflow. This far-infrared detection of both H2O and OH contrasts with near- and mid-...

  19. An exact calculation of the N2+ and H2+ influx at cathode surface in N2-H2 discharges

    Science.gov (United States)

    Suraj, K. S.; Alex, Prince

    An exact calculation of N2+ and H2+ influx, at cathode surface in N2-H2 discharge, has been derived using electron impact ionization cross-section at plasma sheath boundary. The analytical formula is very convenient in practical applications. Through the analysis of experimental parameters for glow discharge plasma nitriding, the formula explains, why treatment in an N2-H2 mixture with H2 percentage ∼70% gives most enhanced result.

  20. The Role of Endogenous H(2)S in Cardiovascular Physiology

    DEFF Research Database (Denmark)

    Skovgaard, Nini; Gouliaev, Anja; Aalling, Mathilde

    2011-01-01

    Recent research has shown that the endogenous gas hydrogen sulphide (H(2)S) is a signalling molecule of considerable biological potential and has been suggested to be involved in a vast number of physiological processes. In the vascular system, H(2)S is synthesized from cysteine by cystathionine......-γ-lyase (CSE) in smooth muscle cells (SMC) and 3-mercaptopyruvate sulfuresterase (3MST) and CSE in the endothelial cells. In pulmonary and systemic arteries, H(2)S induces relaxation and/or contraction dependent on the concentration of H(2)S, type of vessel and species. H(2)S relaxes SMC through a direct...

  1. Analysis list: Cap-H2 [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Cap-H2 Cell line + dm3 http://dbarchive.biosciencedbc.jp/kyushu-u/dm3/target/Cap-H2....1.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/dm3/target/Cap-H2.5.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/dm3/target/Cap...-H2.10.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/dm3/colo/Cap-H2.Cell_line.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/dm3/colo/Cell_line.gml ...

  2. Analysis list: Nr1h2 [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Nr1h2 Blood + mm9 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Nr1h2.1.tsv... http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Nr1h2.5.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Nr1h...2.10.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Nr1h2.Blood.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Blood.gml ...

  3. H2S regulation of nitric oxide metabolism

    Science.gov (United States)

    Kolluru, Gopi K.; Yuan, Shuai; Shen, Xinggui; Kevil, Christopher G.

    2015-01-01

    Nitric oxide (NO) and hydrogen sulfide (H2S) are two major gaseous signaling molecules that regulate diverse physiological functions. Recent publications indicate the regulatory role of H2S on NO metabolism. In this chapter, we discuss the latest findings on H2S-NO interactions through formation of novel chemical derivatives, and experimental approaches to study these adducts. This chapter also addresses potential H2S interference on various NO detection techniques, along with precautions for analyzing biological samples from various sources. This information will facilitate critical evaluation and clearer insight into H2S regulation of NO signaling and its influence on various physiological functions. PMID:25725527

  4. Observations of the H2S toward OMC-1

    Science.gov (United States)

    Minh, Y. C.; Irvine, W. M.; Mcgonagle, D.; Ziurys, L. M.

    1990-01-01

    Observations of the 1(10) - 1(01) transition of interstellar H2S and its isotopes toward OMC-1 are reported. The fractional abundance of H2S in the quiescent regions of OMC-1 seems difficult to explain by currently known ion-molecular reactions. The fractional abundance of H2S relative to H2 is enhanced by a factor of 1000 in the hot core and the plateau relative to the quiescent clouds. The (HDS)/(H2S) abundance ratio in the hot core is estimated at 0.02 or less.

  5. Observations of the H2S toward OMC-1

    Science.gov (United States)

    Minh, Y. C.; Irvine, W. M.; Mcgonagle, D.; Ziurys, L. M.

    1990-01-01

    Observations of the 1(10) - 1(01) transition of interstellar H2S and its isotopes toward OMC-1 are reported. The fractional abundance of H2S in the quiescent regions of OMC-1 seems difficult to explain by currently known ion-molecular reactions. The fractional abundance of H2S relative to H2 is enhanced by a factor of 1000 in the hot core and the plateau relative to the quiescent clouds. The (HDS)/(H2S) abundance ratio in the hot core is estimated at 0.02 or less.

  6. H2S: A Novel Gasotransmitter that Signals by Sulfhydration.

    Science.gov (United States)

    Paul, Bindu D; Snyder, Solomon H

    2015-11-01

    Hydrogen sulfide (H2S) is a member of the growing family of gasotransmitters. Once regarded as a noxious molecule predominantly present in the atmosphere, H2S is now known to be synthesized endogenously in mammals. H2S participates in a myriad of physiological processes ranging from regulation of blood pressure to neuroprotection. Its chemical nature precludes H2S from being stored in vesicles and acting on receptor proteins in the fashion of other chemical messengers. Thus, novel cellular mechanisms have evolved to mediate its effects. This review focuses on sulfhydration (or persulfidation), which appears to be the principal post-translational modification elicited by H2S.

  7. Lighting the Dark Molecular Gas: H2 as a Direct Tracer

    Science.gov (United States)

    Togi, Aditya; Smith, J. D. T.

    2016-10-01

    Robust knowledge of molecular gas mass is critical for understanding star formation in galaxies. The {{{H}}}2 molecule does not emit efficiently in the cold interstellar medium, hence the molecular gas content of galaxies is typically inferred using indirect tracers. At low metallicity and in other extreme environments, these tracers can be subject to substantial biases. We present a new method of estimating total molecular gas mass in galaxies directly from pure mid-infrared rotational {{{H}}}2 emission. By assuming a power-law distribution of {{{H}}}2 rotational temperatures, we can accurately model {{{H}}}2 excitation and reliably obtain warm (T ≳ 100 K) {{{H}}}2 gas masses by varying only the power law’s slope. With sensitivities typical of Spitzer/IRS, we are able to directly probe the {{{H}}}2 content via rotational emission down to ∼80 K, accounting for ∼15% of the total molecular gas mass in a galaxy. By extrapolating the fitted power-law temperature distributions to a calibrated single lower cutoff temperature, the model also recovers the total molecular content within a factor of ∼2.2 in a diverse sample of galaxies, and a subset of broken power-law models performs similarly well. In ULIRGs, the fraction of warm {{{H}}}2 gas rises with dust temperature, with some dependency on α CO. In a sample of five low-metallicity galaxies ranging down to 12+{log}[{{O}}/{{H}}]=7.8, the model yields molecular masses up to ∼100× larger than implied by CO, in good agreement with other methods based on dust mass and star formation depletion timescale. This technique offers real promise for assessing molecular content in the early universe where CO and dust-based methods may fail.

  8. FACT Disrupts Nucleosome Structure by Binding H2A-H2B with Conserved Peptide Motifs.

    Science.gov (United States)

    Kemble, David J; McCullough, Laura L; Whitby, Frank G; Formosa, Tim; Hill, Christopher P

    2015-10-15

    FACT, a heterodimer of Spt16 and Pob3, is an essential histone chaperone. We show that the H2A-H2B binding activity that is central to FACT function resides in short acidic regions near the C termini of each subunit. Mutations throughout these regions affect binding and cause correlated phenotypes that range from mild to lethal, with the largest individual contributions unexpectedly coming from an aromatic residue and a nearby carboxylate residue within each domain. Spt16 and Pob3 bind overlapping sites on H2A-H2B, and Spt16-Pob3 heterodimers simultaneously bind two H2A-H2B dimers, the same stoichiometry as the components of a nucleosome. An Spt16:H2A-H2B crystal structure explains the biochemical and genetic data, provides a model for Pob3 binding, and implies a mechanism for FACT reorganization that we confirm biochemically. Moreover, unexpected similarity to binding of ANP32E and Swr1 with H2A.Z-H2B reveals that diverse H2A-H2B chaperones use common mechanisms of histone binding and regulating nucleosome functions.

  9. Hydrogen generation via hydrolysis of nanocrystalline MgH2 and MgH2-based composites

    Institute of Scientific and Technical Information of China (English)

    HU Lian-xi; WANG Er-de

    2005-01-01

    Nanocrystalline MgH2 and MgH2-based composites with 25% (mass fraction) of Al, Ca, or CaH2 as an individual additive respectively were prepared by ball milling. The crystallite size and morphology of the as-milled powders were characterized and their hydrolysis behaviours were investigated in comparison with commercial polycrystalline MgH2. The results show that the crystallite size of both MgH2 and MgH2-based composites is reduced to less than 13 nm after milling for 15 h. Due to its enhanced specific surface area and unique nanocrystalline structure, the as-milled MgH2 shows much better hydrolysis kinetics than the commercial polycrystalline MgH2, with the hydrolysed fraction upon hydrolysing for 70 min enhances from 7.5% to about 25%. As compared with the as-milled MgH2, the MgH2-based composites with either CaH2 or Ca as an additive present further greatly improved hydrolysis kinetics, with the hydrolysed fraction for 80 min achieving about 76% and 62% respectively.However, the addition of Al doesn't show any positive effect on the improvement of the hydrolysis kinetics of MgH2.

  10. H2SO4/HNO3/H2O Phase Diagram in Regions of Stratospheric Importance

    Science.gov (United States)

    Beyer, K. D.; Hansen, A. R.; Raddatz, N.

    2003-12-01

    We have investigated the region of the H2SO4/HNO3/H2O ternary liquid/solid phase diagram bounded by ice, nitric acid trihydrate (NAT), and sulfuric acid tetrahydrate (SAT) using differential scanning calorimetry (DSC) and infrared spectroscopy of thin films. We report measurements and analysis of the eutectic melting curves in the ternary system of the hydrates mentioned as well as the temperature of the eutectics: ice/SAT/NAT, ice/sulfuric acid hemihexahydrate (SAH)/NAT, and SAT/NAT. We report for the first time an analysis of the content of the solid phase of completely frozen samples and find that sulfuric acid octahydrate (SAO) is often present in frozen ternary samples and can be a significant portion of the solid phase. We provide a description of how the melting path of a frozen ternary sample can be predicted using the ternary phase diagram. We have parameterized our melting point data and provide equations to generate the ternary melting surface. Finally, we compare our results to the historic work of Carpenter & Lehrmann (Carpenter, C. D.; Lehrman, A. Trans. AIChE 1925, 17, 35) and to other more recent work.

  11. Chemiluminescent Detection of Enzymatically Produced H2S

    Science.gov (United States)

    Bailey, T. Spencer; Pluth, Michael D.

    2015-01-01

    Hydrogen sulfide (H2S) has emerged as an important biological signaling molecule. To better understand the multifaceted biological roles of H2S, the development of selective and sensitive biocompatible assays for H2S is becoming increasingly important. Motivated by these challenges, our laboratory is developing new methods to further detect and monitor biological H2S. Here, we describe in detail our recent advances in the development and the use of chemiluminescence-based H2S sensors to assist other investigators with use of these chemical tools. We highlight the use of these tools use by displaying their selectivity and high sensitivity toward H2S and provide examples of assays we have developed to detect enzymatically produced H2S. PMID:25725517

  12. A proposal for climate stability on H2-greenhouse planets

    CERN Document Server

    Abbot, Dorian S

    2015-01-01

    A terrestrial planet in an orbit far outside of the standard habitable zone could maintain surface liquid water as a result of H2-H2 collision-induced absorption by a thick H2 atmosphere. Without a stabilizing climate feedback, however, habitability would be accidental and likely brief. In this letter I propose stabilizing climate feedbacks for such a planet that require only that biological functions have an optimal temperature and operate less efficiently at other temperatures. For example, on a planet with a net source of H2 from its interior, H2-consuming life (such as methanogens) could establish a stable climate. If a positive perturbation is added to the equilibrium temperature, H2 consumption by life will increase (cooling the planet) until the equilibrium climate is reestablished. The potential existence of such feedbacks makes H2-warmed planets more attractive astrobiological targets.

  13. H2S Injection and Sequestration into Basalt - The SulFix Project

    Science.gov (United States)

    Gudbrandsson, S.; Moola, P.; Stefansson, A.

    2014-12-01

    Atmospheric H2S emissions are among major environmental concern associated with geothermal energy utilization. It is therefore of great importance for the geothermal power sector to reduce H2S emissions. Known solutions for H2S neutralization are both expensive and include production of elemental sulfur and sulfuric acid that needs to be disposed of. Icelandic energy companies that utilize geothermal power for electricity production have decided to try to find an environmentally friendly and economically feasible solution to reduce the H2S emission, in a joint venture called SulFix. The aim of SulFix project is to explore the possibilities of injecting H2S dissolved in water into basaltic formations in close proximity to the power plants for permanent fixation as sulfides. The formation of sulfides is a natural process in geothermal systems. Due to basalt being rich in iron and dissolving readily at acidic conditions, it is feasible to re-inject the H2S dissolved in water, into basaltic formations to form pyrite. To estimate the mineralization rates of H2S, in the basaltic formation, flow through experiments in columns were conducted at various H2S concentrations, temperatures (100 - 240°C) and both fresh and altered basaltic glass. The results indicate that pyrite rapidly forms during injection into fresh basalt but the precipiation in altered basalt is slower. Three different alteration stages, as a function of distance from inlet, can be observed in the column with fresh basaltic glass; (1) dissolution features along with precipitation, (2) precipitation increases, both sulfides and other secondary minerals and (3) the basalt looks to be unaltered and little if any precipitation is observed. The sulfur has precipitated in the first half of the column and thereafter the solution is possibly close to be supersaturated with respect to the rock. These results indicate that the H2S sequestration into basalt is possible under geothermal conditions. The rate limiting

  14. Photochemical Generation of H_{2}NCNX, H_{2}NNCX, H_{2}NC(NX) (x = O, s) in Low-Temperature Matrices

    Science.gov (United States)

    Voros, Tamas; Lajgut, Gyozo Gyorgy; Magyarfalvi, Gabor; Tarczay, Gyorgy

    2017-06-01

    The [NH_{2}, C, N, O] and the [NH_{2}, C, N, S] systems were investigated by quantum-chemical computations and matrix-isolation spectroscopic methods. The equilibrium structures of the isomers and their relative energies were determined by CCSD(T) method. This was followed by the computation of the harmonic and anharmonic vibrational wavenumbers, infrared intensities, relative Raman activities and UV excitation energies. These computed data were used to assist the identification of products obtained by UV laser photolysis of 3,4-diaminofurazan, 3,4-diaminothiadiazole and 1,2,4-thiadiazole-3,5-diamine in low-temperature Ar and Kr matrices. Experimentally, first the precursors were studied by matrix-isolation IR and UV spectroscopic methods. Based on these UV spectra, different wavelengths were selected for photolysis. The irradiations, carried out by a tunable UV laser-light source, resulted in the decomposition of the precursors, and in the appearance of new bands in the IR spectra. Some of these bands were assigned to cyanamide (H_{2}NCN) and its isomer, the carbodiimide molecule (HNCNH), generated from H_{2}NCN. By the analysis of the relative absorbance vs. photolysis time curves, the other bands were grouped to three different species both for the O- and the S-containing systems. In the case of the O-containing isomers, these bands were assigned to the H_{2}NNCO:H_{2}NCN, and H_{2}NCNO:H_{2}NCN complexes, and to the ring-structure H_{2}NC(NO) isomer. In a similar way, the complexes of H_{2}NNCS and H_{2}NCNS with the H_{2}NCN, and H_{2}NC(NS) were also identified. 1,2,4-thiadiazole-3,5-diamine was also investigated in similar way like the above mentioned precursors. The results of this study also support the identification of the new S-containing isomers. Except for H_{2}NNCO and H_{2}NCNS, these molecules were not identified previously. It is expected that at least some of these species, like the methyl isocyanate (CH_{3}CNO) isomer, are present and could be

  15. H2CO and N2H+ in Protoplanetary Disks: Evidence for a CO-ice Regulated Chemistry

    CERN Document Server

    Qi, Chunhua; Wilner, David

    2013-01-01

    We present Submillimeter Array observations of H2CO and N2H+ emission in the disks around the T Tauri star TW Hya and the Herbig Ae star HD 163296 at 2"-6" resolution and discuss the distribution of these species with respect to CO freeze-out. The H2CO and N2H+ emission toward HD 163296 does not peak at the continuum emission center that marks the stellar position but is instead significantly offset. Using a previously developed model for the physical structure of this disk, we show that the H2CO observations are reproduced if H2CO is present predominantly in the cold outer disk regions. A model where H2CO is present only beyond the CO snow line (estimated at a radius of 160 AU) matches the observations well. We also show that the average H2CO excitation temperature, calculated from two transitions of H2CO observed in these two disks and a larger sample of disks around T Tauri stars in the DISCS (the Disk Imaging Survey of Chemistry with SMA) program, is consistent with the CO freeze-out temperature of 20 K. ...

  16. Hydrogen polysulfide (H2S n ) signaling along with hydrogen sulfide (H2S) and nitric oxide (NO).

    Science.gov (United States)

    Kimura, Hideo

    2016-11-01

    Hydrogen sulfide (H2S) is a physiological mediator with various roles, including neuro-modulation, vascular tone regulation, and cytoprotection against ischemia-reperfusion injury, angiogenesis, and oxygen sensing. Hydrogen polysulfide (H2S n ), which possesses a higher number of sulfur atoms than H2S, recently emerged as a potential signaling molecule that regulates the activity of ion channels, a tumor suppressor, transcription factors, and protein kinases. Some of the previously reported effects of H2S are now attributed to the more potent H2S n . H2S n is produced by 3-mercaptopyruvate sulfurtransferase (3MST) from 3-mercaptopyruvate (3MP) and is generated by the chemical interaction of H2S with nitric oxide (NO). H2S n sulfhydrates (sulfurates) cysteine residues of target proteins and modifies their activity, whereas H2S sulfurates oxidized cysteine residues as well as reduces cysteine disulfide bonds. This review focuses on the recent progress made in studies concerning the production and physiological roles of H2S n and H2S.

  17. Photochemistry in Terrestrial Exoplanet Atmospheres II: H2S and SO2 Photochemistry in Anoxic Atmospheres

    CERN Document Server

    Hu, Renyu; Bains, William

    2013-01-01

    Sulfur gases are common components in the volcanic and biological emission on Earth, and are expected to be important input gases for atmospheres on terrestrial exoplanets. We study the atmospheric composition and the spectra of terrestrial exoplanets with sulfur compounds (i.e., H2S and SO2) emitted from their surfaces. We use a comprehensive one-dimensional photochemistry model and radiative transfer model to investigate the sulfur chemistry in atmospheres ranging from reducing to oxidizing. The most important finding is that both H2S and SO2 are chemically short-lived in virtually all types of atmospheres on terrestrial exoplanets, based on models of H2, N2, and CO2 atmospheres. This implies that direct detection of surface sulfur emission is unlikely, as their surface emission rates need to be extremely high (>1000 times Earth's volcanic sulfur emission) for these gases to build up to a detectable level. We also find that sulfur compounds emitted from the surface lead to photochemical formation of element...

  18. Neutron spectroscopy of gamma-MgH2

    Science.gov (United States)

    Kolesnikov, Alexander; Antonov, Vladimir; Efimchenko, Vadim; Granroth, Garrett; Klyamkin, S. N.; Levchenko, A. V.; Sakharov, Michael; Ren, Yang; Ramirez-Cuesta, Timmy

    2011-03-01

    Under ambient conditions, magnesium dihydride exists in two forms, alpha-MgH2 (the most stable modification) and gamma-MgH2 (a less stable modification). The alpha-phase partly transforms to gamma-MgH2 in the course of ball-milling and under high pressure and temperature. Due to the high hydrogen content of 7.6 wt.%, MgH2 has been intensively studied as a prospective material for hydrogen storage. By exposing of alpha-MgH2 to a pressure of 5 GPa and temperature 840 K, we prepared a sample, in which about 60% of the alpha-MgH2 was transformed to gamma-MgH2. We have measured inelastic neutron scattering (INS) spectra of both the high pressure treated MgH2 and starting alpha-MgH2, and extracted the spectrum for gamma-MgH2. The differences between the INS spectra and their agreement with the first-principles calculations for these compounds will be discussed.

  19. H(2)S signaling in redox regulation of cellular functions.

    Science.gov (United States)

    Ju, Youngjun; Zhang, Weihua; Pei, Yanxi; Yang, Guangdong

    2013-01-01

    Hydrogen sulfide (H(2)S) is traditionally recognized as a toxic gas with a rotten-egg smell. In just the last few decades, H(2)S has been found to be one of a family of gasotransmitters, together with nitric oxide and carbon monoxide, and various physiologic effects of H(2)S have been reported. Among the most acknowledged molecular mechanisms for the cellular effects of H(2)S is the regulation of intracellular redox homeostasis and post-translational modification of proteins through S-sulfhydration. On the one side, H(2)S can promote an antioxidant effect and is cytoprotective; on the other side, H(2)S stimulates oxidative stress and is cytotoxic. This review summarizes our current knowledge of the antioxidant versus pro-oxidant effects of H(2)S in mammalian cells and describes the Janus-faced properties of this novel gasotransmitter. The redox regulation for the cellular effects of H(2)S through S-sulfhydration and the role of H(2)S in glutathione generation is also recapitulated. A better understanding of H(2)S-regualted redox homeostasis will pave the way for future design of novel pharmacological and therapeutic interventions for various diseases.

  20. The role of endogenous H2S in cardiovascular physiology.

    Science.gov (United States)

    Skovgaard, Nini; Gouliaev, Anja; Aalling, Mathilde; Simonsen, Ulf

    2011-09-01

    Recent research has shown that the endogenous gas hydrogen sulphide (H2S) is a signalling molecule of considerable biological potential and has been suggested to be involved in a vast number of physiological processes. In the vascular system, H2S is synthesized from cysteine by cystathionine-γ-lyase (CSE) in smooth muscle cells (SMC) and 3- mercaptopyruvate sulfuresterase (3MST) and CSE in the endothelial cells. In pulmonary and systemic arteries, H2S induces relaxation and/or contraction dependent on the concentration of H2S, type of vessel and species. H2S relaxes SMC through a direct effect on KATP-channels or Kv-channels causing hyperpolarization and closure of voltage-dependent Ca2+-channels followed by a reduction in intracellular calcium. H2S also relaxes SMC through the release of endothelium- derived hyperpolarizing factor (EDHF) and nitric oxide (NO) from the endothelium. H2S contracts SMC through a reduction in nitric oxide (NO) availability by reacting with NO forming a nitrosothiol compound and through an inhibitory effect on endothelial nitric oxide synthase (eNOS) as well as a reduction in SMC cyclic AMP concentration. Evidence supports a role for H2S in oxygen sensing. Furthermore, reduced endogenous H2S production may also play a role in ischemic heart diseases and hypertension, and treatment with H2S donors and cysteine analogues may be beneficial in treatment of cardiovascular disease.

  1. Working with "H2S": facts and apparent artifacts.

    Science.gov (United States)

    Wedmann, Rudolf; Bertlein, Sarah; Macinkovic, Igor; Böltz, Sebastian; Miljkovic, Jan Lj; Muñoz, Luis E; Herrmann, Martin; Filipovic, Milos R

    2014-09-15

    Hydrogen sulfide (H2S) is an important signaling molecule with physiological endpoints similar to those of nitric oxide (NO). Growing interest in its physiological roles and pharmacological potential has led to large sets of contradictory data. The principle cause of these discrepancies can be the common neglect of some of the basic H2S chemistry. This study investigates how the experimental outcome when working with H2S depends on its source and dose and the methodology employed. We show that commercially available NaHS should be avoided and that traces of metal ions should be removed because these can reduce intramolecular disulfides and change protein structure. Furthermore, high H2S concentrations may lead to a complete inhibition of cell respiration, mitochondrial membrane potential depolarization and superoxide generation, which should be considered when discussing the biological effects observed upon treatment with high concentrations of H2S. In addition, we provide chemical evidence that H2S can directly react with superoxide. H2S is also capable of reducing cytochrome c(3+) with the concomitant formation of superoxide. H2S does not directly react with nitrite but with NO electrodes that detect H2S. In addition, H2S interferes with the Griess reaction and should therefore be removed from the solution by Cd(2+) or Zn(2+) precipitation prior to nitrite quantification. 2-Phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO) is reduced by H2S, and its use should be avoided in combination with H2S. All these constraints must be taken into account when working with H2S to ensure valid data.

  2. Quantum calculations of H2-H2 collisions: from ultracold to thermal energies

    CERN Document Server

    Quéméner, Goulven

    2008-01-01

    We present quantum dynamics of collisions between two para-H2 molecules from low (1 mK) to high collision energies (1 eV). The calculations are carried out using a quantum scattering code that solves the time-independent Schrodinger equation in its full dimensionality without any decoupling approximations. The six-dimensional potential energy surface for the H4 system developed by Boothroyd et al. [J. Chem. Phys. 116, 666 (2002)] is used in the calculations. Elastic, inelastic and state-to-state cross sections as well as rate coefficients from T = 1 K to 400 K obtained from our calculations are compared with available experimental and theoretical results. Overall, good agreement is obtained with previous studies.

  3. Incorporating H2 Dynamics and Inhibition into a Microbially Based Methanogenesis Model for Restored Wetland Sediments

    Science.gov (United States)

    Pal, David; Jaffe, Peter

    2015-04-01

    Estimates of global CH4 emissions from wetlands indicate that wetlands are the largest natural source of CH4 to the atmosphere. In this paper, we propose that there is a missing component to these models that should be addressed. CH4 is produced in wetland sediments from the microbial degradation of organic carbon through multiple fermentation steps and methanogenesis pathways. There are multiple sources of carbon for methananogenesis; in vegetated wetland sediments, microbial communities consume root exudates as a major source of organic carbon. In many methane models propionate is used as a model carbon molecule. This simple sugar is fermented into acetate and H2, acetate is transformed to methane and CO2, while the H2 and CO2 are used to form an additional CH4 molecule. The hydrogenotrophic pathway involves the equilibrium of two dissolved gases, CH4 and H2. In an effort to limit CH4 emissions from wetlands, there has been growing interest in finding ways to limit plant transport of soil gases through root systems. Changing planted species, or genetically modifying new species of plants may control this transport of soil gases. While this may decrease the direct emissions of methane, there is little understanding about how H2 dynamics may feedback into overall methane production. The results of an incubation study were combined with a new model of propionate degradation for methanogenesis that also examines other natural parameters (i.e. gas transport through plants). This presentation examines how we would expect this model to behave in a natural field setting with changing sulfate and carbon loading schemes. These changes can be controlled through new plant species and other management practices. Next, we compare the behavior of two variations of this model, with or without the incorporation of H2 interactions, with changing sulfate, carbon loading and root volatilization. Results show that while the models behave similarly there may be a discrepancy of nearly

  4. Nucleosome adaptability conferred by sequence and structural variations in histone H2A-H2B dimers.

    Science.gov (United States)

    Shaytan, Alexey K; Landsman, David; Panchenko, Anna R

    2015-06-01

    Nucleosome variability is essential for their functions in compacting the chromatin structure and regulation of transcription, replication and cell reprogramming. The DNA molecule in nucleosomes is wrapped around an octamer composed of four types of core histones (H3, H4, H2A, H2B). Nucleosomes represent dynamic entities and may change their conformation, stability and binding properties by employing different sets of histone variants or by becoming post-translationally modified. There are many variants of histones H2A and H2B. Specific H2A and H2B variants may preferentially associate with each other resulting in different combinations of variants and leading to the increased combinatorial complexity of nucleosomes. In addition, the H2A-H2B dimer can be recognized and substituted by chaperones/remodelers as a distinct unit, can assemble independently and is stable during nucleosome unwinding. In this review we discuss how sequence and structural variations in H2A-H2B dimers may provide necessary complexity and confer the nucleosome functional variability.

  5. Communication: the origin of rotational enhancement effect for the reaction of H2O(+) + H2 (D2).

    Science.gov (United States)

    Li, Anyang; Li, Yongle; Guo, Hua; Lau, Kai-Chung; Xu, Yuntao; Xiong, Bo; Chang, Yih-Chung; Ng, C Y

    2014-01-01

    We have measured the absolute integral cross sections (σ's) for H3O(+) formed by the reaction of rovibrationally selected H2O(+)(X(2)B1; v1 (+)v2 (+)v3 (+) = 000; N(+) K a (+) K c (+) = 000, 111, and 211) ion with H2 at the center-of-mass collision energy (Ecm) range of 0.03-10.00 eV. The σ(000), σ(111), and σ(211) values thus obtained reveal rotational enhancements at low Ecm Communication presents important progress concerning the high-level ab initio quantum calculation of the potential energy surface for the H2O(+)(X(2)B1) + H2 (D2) reactions, which has provided valuable insight into the origin of the rotational enhancement effect. Governed by the charge and dipole-induced-multipole interactions, the calculation shows that H2 (D2) approaches the H end of H2O(+)(X(2)B1) in the long range, whereas chemical force in the short range favors the orientation of H2 (D2) toward the O side of H2O(+). The reorientation of H2O(+) reactant ion facilitated by rotational excitation thus promotes the H2O(+) + H2 (D2) reaction along the minimum energy pathway, rendering the observed rotational enhancement effects. The occurrence of this effect at low Ecm indicates that the long range charge and dipole-induced-multipole interactions of the colliding pair play a significant role in the dynamics of the exothermic H2O(+) + H2 (D2) reactions.

  6. A shock tube study of OH + H(2)O(2) --> H(2)O + HO(2) and H(2)O(2) + M --> 2OH + M using laser absorption of H(2)O and OH.

    Science.gov (United States)

    Hong, Zekai; Cook, Robert D; Davidson, David F; Hanson, Ronald K

    2010-05-13

    The rate constants of the reactions: (1) H2O2+M-->2OH+M, (2) OH+H2O2-->H2O+HO2 were measured in shock-heated H(2)O(2)/Ar mixtures using laser absorption diagnostics for H(2)O and OH. Time-histories of H(2)O were monitored using tunable diode laser absorption at 2550.96 nm, and time-histories of OH were achieved using ring dye laser absorption at 306 nm. Initial H(2)O(2) concentrations were also determined utilizing the H(2)O diagnostic. On the basis of simultaneous time-history measurements of OH and H(2)O, k(2) was found to be 4.6 x 10(13) exp(-2630 K/T) [cm(3) mol(-1) s(-1)] over the temperature range 1020-1460 K at 1.8 atm; additional measurements of k(2) near 1 atm showed no significant pressure dependence. Similarly, k(1) was found to be 9.5 x 10(15) exp(-21 250 K/T) [cm(3) mol(-1) s(-1)] over the same temperature and pressure range.

  7. The Role of Endogenous H(2)S in Cardiovascular Physiology

    DEFF Research Database (Denmark)

    Skovgaard, Nini; Gouliaev, Anja; Aalling, Mathilde

    2011-01-01

    Recent research has shown that the endogenous gas hydrogen sulphide (H(2)S) is a signalling molecule of considerable biological potential and has been suggested to be involved in a vast number of physiological processes. In the vascular system, H(2)S is synthesized from cysteine by cystathionine...... in oxygen sensing. Furthermore, reduced endogenous H(2)S production may also play a role in ischemic heart diseases and hypertension, and treatment with H(2)S donors and cysteine analogues may be beneficial in treatment of cardiovascular disease....

  8. Development of immunoaffinity chromatographic method for Ara h 2 isolation.

    Science.gov (United States)

    Wu, Zhihua; Zhang, Ying; Zhan, Shaode; Lian, Jun; Zhao, Ruifang; Li, Kun; Tong, Ping; Li, Xin; Yang, Anshu; Chen, Hongbing

    2017-03-01

    Ara h 2 is considered a major allergen in peanut. Due to the difficulty of separation, Ara h 2 had not been fully studied. Immunoaffinity chromatography (IAC) column can separate target protein with high selectivity, which made it possible to purify Ara h 2 from different samples. In this study, IAC method was developed to purify Ara h 2 and its effect was evaluated. By coupling polyclonal antibody (pAb) on CNBr-activated Sepharose 4B, the column for specific extraction was constructed. The coupling efficiency of the IAC column was higher than 90%, which made the capacity of column reached 0.56 mg per 0.15 g medium (dry weight). The recovery of Ara h 2 ranged from 93% to 100% for different concentrations of pure Ara h 2 solutions in 15 min. After using a column 10 times, about 88% of the column capacity remained. When applied to extract Ara h 2 from raw peanut protein extract and boiled peanut protein extract, the IAC column could recovery 94% and 88% target protein from the mixture. SDS-PAGE and Western blotting analysis confirmed the purified protein was Ara h 2, its purity reached about 90%. Significantly, the IAC column could capture dimer of Ara h 2, which made it feasible to prepared derivative of protein after processing. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. Particulate filtration for sorbent-based H2 storage

    Science.gov (United States)

    van Hassel, Bart A.; Karra, Jagadeswara R.

    2016-01-01

    A method was developed for sizing the particulate filter that can be used inside a sorption-based onboard hydrogen storage system for light-duty vehicles. The method is based on a trade-off between the pressure drop across the particulate filter (during the fill of the H2 storage tank or during its discharge while driving) and the effect of this pressure drop on the usable amount of H2 gas from the H2 storage system. The permeability and filtration efficiency of the particulate filters (in the absence and presence of MOF-5 particulates) was quantified in this study, with an emphasis on meeting DOE's H2 purity requirements.

  10. H2S and Blood Vessels: An Overview.

    Science.gov (United States)

    Yang, Guangdong; Wang, Rui

    2015-01-01

    The physiological and biomedical importance of hydrogen sulfide (H2S) has been fully recognized in the cardiovascular system as well as in the rest of the body. In blood vessels, cystathionine γ-lyase (CSE) is a major H2S-producing enzyme expressed in both smooth muscle and endothelium as well as periadventitial adipose tissues. Regulation of H2S production from CSE is controlled by a complex integration of transcriptional, posttranscriptional, and posttranslational mechanisms in blood vessels. In smooth muscle cells, H2S regulates cell apoptosis, phenotypic switch, relaxation and contraction, and calcification. In endothelial cells, H2S controls cell proliferation, cellular senescence, oxidative stress, inflammation, etc. H2S interacts with nitric oxide and acts as an endothelium-derived relaxing factor and an endothelium-derived hyperpolarizing factor. H2S generated from periadventitial adipose tissues acts as an adipocyte-derived relaxing factor and modulates the vascular tone. Extensive evidence has demonstrated the beneficial roles of the CSE/H2S system in various blood vessel diseases, such as hypertension, atherosclerosis, and aortic aneurysm. The important roles signaling in the cardiovascular system merit further intensive and extensive investigation. H2S-releasing agents and CSE activators will find their great applications in the prevention and treatment of blood vessel-related disorders.

  11. Secondary electron emission of thin carbon foils under the impact of hydrogen atoms, ions and molecular ions, under energies within the MeV range; Multiplicite des electrons secondaires emis par des cibles minces de carbone sous l'impact de projectiles H0, H2+, H3+ d'energie de l'ordre du MeV

    Energy Technology Data Exchange (ETDEWEB)

    Vidovic, Z

    1997-06-15

    This work focuses on the study of the emission statistics of secondary electrons from thin carbon foils bombarded with H{sup 0}, H{sub 2}{sup +} and H{sub 3}{sup +} projectiles in the 0.25-2.2 MeV energy range. The phenomenon of secondary electron emission from solids under the impact of swift ions is mainly due to inelastic interactions with target electrons. The phenomenological and theoretical descriptions, as well as a summary of the main theoretical models are the subject of the first chapter. The experimental set-up used to measure event by event the electron emission of the two faces of a thin carbon foil traversed by an energetic projectile is described in the chapter two. In this chapter are also presented the method and algorithms used to process experimental spectra in order to obtain the statistical distribution of the emitted electrons. Chapter three presents the measurements of secondary electron emission induced by H atoms passing through thin carbon foils. The secondary electron yields are studied in correlation with the emergent projectile charge state. We show the peculiar role of the projectile electron, whether it remains or not bound to the incident proton. The fourth chapter is dedicated to the secondary electron emission induced by H{sub 2}{sup +} and H{sub 3}{sup +} polyatomic ions. The results are interpreted in terms of collective effects in the interactions of these ions with solids. The role of the proximity of the protons, molecular ion fragments, upon the amplitude of these collective effects is evidenced from the study of the statistics of forward emission. These experiences allowed us to shed light on various aspects of atom and polyatomic ion inter-actions with solid surfaces. (author)

  12. An Unsymmetrical Trinickel Metal Complex with 4-Sulfobenzoate Axial Ligand: [Ni3(dpa4(4-sb(H2O]×3H2O

    Directory of Open Access Journals (Sweden)

    Xiao-Feng Zheng

    2011-08-01

    Full Text Available An unsymmetrical trinickel metal complex, [Ni3(dpa4(4-sb(H2O]×3H2O (1, where dpa is a 2,2’-dipyridylamine anion and 4-sb is 4-sulfobenzoate dianion, was synthesized and characterized by X-ray crystallography, IR, elemental analysis, fluorescence, and cyclic voltammetry. The molecular structure of 1 is a cluster with a linear trimer. The extended structure is a 3D architecture assembled by hydrogen bonds. The 4-sulfobenzoate axial replacement leads to the change of Ni-Ni distances, the shift of the fluorescence emission, and the reversible one-electron reduction process without oxidation process.

  13. Relative importance of H2 and H2S as energy sources for primary production in geothermal springs.

    Science.gov (United States)

    D'Imperio, Seth; Lehr, Corinne R; Oduro, Harry; Druschel, Greg; Kühl, Michael; McDermott, Timothy R

    2008-09-01

    Geothermal waters contain numerous potential electron donors capable of supporting chemolithotrophy-based primary production. Thermodynamic predictions of energy yields for specific electron donor and acceptor pairs in such systems are available, although direct assessments of these predictions are rare. This study assessed the relative importance of dissolved H(2) and H(2)S as energy sources for the support of chemolithotrophic metabolism in an acidic geothermal spring in Yellowstone National Park. H(2)S and H(2) concentration gradients were observed in the outflow channel, and vertical H(2)S and O(2) gradients were evident within the microbial mat. H(2)S levels and microbial consumption rates were approximately three orders of magnitude greater than those of H(2). Hydrogenobaculum-like organisms dominated the bacterial component of the microbial community, and isolates representing three distinct 16S rRNA gene phylotypes (phylotype = 100% identity) were isolated and characterized. Within a phylotype, O(2) requirements varied, as did energy source utilization: some isolates could grow only with H(2)S, some only with H(2), while others could utilize either as an energy source. These metabolic phenotypes were consistent with in situ geochemical conditions measured using aqueous chemical analysis and in-field measurements made by using gas chromatography and microelectrodes. Pure-culture experiments with an isolate that could utilize H(2)S and H(2) and that represented the dominant phylotype (70% of the PCR clones) showed that H(2)S and H(2) were used simultaneously, without evidence of induction or catabolite repression, and at relative rate differences comparable to those measured in ex situ field assays. Under in situ-relevant concentrations, growth of this isolate with H(2)S was better than that with H(2). The major conclusions drawn from this study are that phylogeny may not necessarily be reliable for predicting physiology and that H(2)S can dominate over H(2

  14. Numerical simulation of H2S and CO2 generation during SAGD

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Perez, A.; Kamp, A.M. [CHLOE, UFR Science, University of Pau, 64000, Pau (France); Soleimani, H. (IFP School (France)); Darche, G. (TOTAL, Pau (France))

    2011-07-01

    In the heavy oil industry, the steam assisted gravity drainage process is often used to enhance oil recovery but the production of undesirable gases occurs during this process. These gases are mainly hydrogen sulphide and carbon dioxide, generated through chemical reactions triggered by high temperatures and water presence. The aim of this paper is to create a kinetic model for H2S and CO2 generation and to insert it in a reservoir simulation. This model was then tested under steam injection conditions in an SAGD system using experimental data available in the literature. The model developed successfully reproduced gas plateaus at different temperatures and results from the test showed that the model's predicted gas emissions are of the same order of magnitude as the field results. This paper presented a new kinetic model which can predict H2S and CO2 emissions of a SAGD system and could thus be used in the design of treatment facilities.

  15. Equations of state for H2, H2O, and H2-H2O fluid mixtures at temperatures above 0.01° C and at high pressures

    Science.gov (United States)

    Rimbach, Helmut; Chatterjee, Niranjan D.

    1987-11-01

    Modified Redlich-Kwong (MRK) equations of state have been derived for the pure fluid species H2 and H2O by expressing the parameter a as a function of T and P, and b as as a function of P only. These equations are valid above 0° and 0.01° C, respectively. For H2O, the prediction of volumes is successful not only in the supercritical, but also in the subcritical range. As a result of this, the saturation curve of H2O can be calculated with a maximum deviation of ±1.4 bar in the range 100 350° C. Between 350° C and the critical point (374.15° C), the uncertainty increases somewhat; this is due to a fundamental inadequacy of the Redlich-Kwong equation itself. These equations of state permit extrapolations to pressures of 100 kbar for H2 and at least 200 kbar for H2O and are, therefore, eminently suited for geochemical applications. Formulation of the MRK of the binary H2-H2O mixtures was achieved by assuming the quadratic mixing rule for the parameters a mix and b+mix. To derive the cross coefficients, aH2-H2Oand b H 2-H 2O, adjustable corrective factors ɛ and τ had to be introduced. The T- and P-dependences of ɛ and τ are based on P-V-T-X H 2 data (Seward and Franck 1981) to 440° C and 2500 bar. The resulting equation of state very satisfactorily reproduces the volumes observed experimentally at various sets of T, P, and X H 2. At a total pressure of 2 kbar, positive deviation from ideal mixing behaviour is still perceptible at as high a temperature as 1000° C. At some temperature around 380° C, phase separation sets in, an aqueous solution with dissolved H2 coexisting in equilibrium with an H2-rich fluid with dissolved H2O. The computed P-T-X H 2 surface of this two-phase region agrees well with that observed in Seward and Franck's (1981) experiments. An independent proof of the validity of this equation of state is the accuracy with which H {m/ex}can be predicted. Calorimetric measurements of H {m/ex}(Smith et al. 1983, Wormald and Colling 1985

  16. Communication: The origin of rotational enhancement effect for the reaction of H2O+ + H2 (D2)

    Science.gov (United States)

    Li, Anyang; Li, Yongle; Guo, Hua; Lau, Kai-Chung; Xu, Yuntao; Xiong, Bo; Chang, Yih-Chung; Ng, C. Y.

    2014-01-01

    We have measured the absolute integral cross sections (σ's) for H3O+ formed by the reaction of rovibrationally selected H2O+(X2B1; v1+v2+v3+ = 000; N+Ka+Kc+ = 000, 111, and 211) ion with H2 at the center-of-mass collision energy (Ecm) range of 0.03-10.00 eV. The σ(000), σ(111), and σ(211) values thus obtained reveal rotational enhancements at low Ecm reactant ion facilitated by rotational excitation thus promotes the H2O+ + H2 (D2) reaction along the minimum energy pathway, rendering the observed rotational enhancement effects. The occurrence of this effect at low Ecm indicates that the long range charge and dipole-induced-multipole interactions of the colliding pair play a significant role in the dynamics of the exothermic H2O+ + H2 (D2) reactions.

  17. CFD Recombiner Modelling and Validation on the H2-Par and Kali-H2 Experiments

    Directory of Open Access Journals (Sweden)

    Stéphane Mimouni

    2011-01-01

    Full Text Available A large amount of Hydrogen gas is expected to be released within the dry containment of a pressurized water reactor (PWR, shortly after the hypothetical beginning of a severe accident leading to the melting of the core. According to local gas concentrations, the gaseous mixture of hydrogen, air and steam can reach the flammability limit, threatening the containment integrity. In order to prevent mechanical loads resulting from a possible conflagration of the gas mixture, French and German reactor containments are equipped with passive autocatalytic recombiners (PARs which preventively oxidize hydrogen for concentrations lower than that of the flammability limit. The objective of the paper is to present numerical assessments of the recombiner models implemented in CFD solvers NEPTUNE_CFD and Code_Saturne. Under the EDF/EPRI agreement, CEA has been committed to perform 42 tests of PARs. The experimental program named KALI-H2, consists checking the performance and behaviour of PAR. Unrealistic values for the gas temperature are calculated if the conjugate heat transfer and the wall steam condensation are not taken into account. The combined effects of these models give a good agreement between computational results and experimental data.

  18. Metallo-Dielectric Multilayer Structure for Lactose Malabsorption Diagnosis through H2 Breath Test

    CERN Document Server

    Cioffi, N; De Sario, M; D'Orazio, A; Petruzzelli, V; Prudenzano, F; Scalora, M; Trevisi, S; Vincenti, M A

    2007-01-01

    A metallo-dielectric multilayer structure is proposed as a novel approach to the analysis of lactose malabsorption. When lactose intolerance occurs, the bacterial overgrowth in the intestine causes an increased spontaneous emission of H2 in the human breath. By monitoring the changes in the optical properties of a multilayer palladium-polymeric structure, one is able to detect the patient's disease and the level of lactose malabsorption with high sensitivity and rapid response.

  19. Synthesis of CuO nanoflower and its application as a H2O2 sensor

    Indian Academy of Sciences (India)

    Aixia Gu; Guangfeng Wang; Xiaojun Zhang; Bin Fang

    2010-02-01

    CuO three-dimensional (3D) flower-like nanostructures were successfully synthesized by a simple method at 100°C with Cu(NO3)2.3H2O and NH3.H2O for 6 h in the absence of any additives. We found that NH3.H2O amount was critical for CuO morphology evolution. The phase analysis was carried out using X-ray diffraction (XRD) and the result confirmed that the CuO nanoflowers were single-phase. The morphological investigations by field emission scanning electron microscope (FESEM) revealed that the CuO nanoflowers were mono-dispersed in a large quantity and consisted of nanosheets. And then, CuO nanoflowers were successfully used to modify a gold electrode to detect H2O2 with cyclic voltammetry (CV) and amperometric (AC). It was found that CuO nanoflowers may be of great potential for H2O2 electrochemical sensing.

  20. Optimal estimation of tropospheric H2O and δD with IASI/METOP

    Directory of Open Access Journals (Sweden)

    F. Hase

    2011-11-01

    Full Text Available We present optimal estimates of tropospheric H2O and δD derived from radiances measured by the instrument IASI (Infrared Atmospheric Sounding Interferometer flown on EUMETSAT's polar orbiter METOP. We document that the IASI spectra allow for retrieving H2O profiles between the surface and the upper troposphere as well as middle tropospheric δD values. A theoretical error estimation suggests a precision for H2O of better than 35% in the lower troposphere and of better than 15% in the middle and upper troposphere, respectively, whereby surface emissivity and atmospheric temperature uncertainties are the leading error sources. For the middle tropospheric δD values we estimate a precision of 15–20‰ with the measurement noise being the dominating error source. The accuracy of the IASI products is estimated to about 20–10% and 10‰ for lower to upper tropospheric H2O and middle tropospheric δD, respectively. It is limited by systematic uncertainties in the applied spectroscopic parameters and the a priori atmospheric temperature profiles. We compare our IASI products to a large number of near coincident radiosonde in-situ and ground-based FTS (Fourier Transform Spectrometer remote sensing measurements. The bias and the scatter between the different H2O and δD data sets are consistent with the combined theoretical uncertainties of the involved measurement techniques.

  1. Herschel images of NGC 6720: H2 formation on dust grains

    CERN Document Server

    van Hoof, P A M; Barlow, M J; Exter, K M; Sibthorpe, B; Ueta, T; Peris, V; Groenewegen, M A T; Blommaert, J A D L; Cohen, M; De Meester, W; Ferland, G J; Gear, W K; Gomez, H L; Hargrave, P C; Huygen, E; Ivison, R J; Jean, C; Leeks, S J; Lim, T L; Olofsson, G; Polehampton, E T; Regibo, S; Royer, P; Swinyard, B M; Vandenbussche, B; Van Winckel, H; Waelkens, C; Walker, H J; Wesson, R

    2010-01-01

    Herschel PACS and SPIRE images have been obtained of NGC 6720 (the Ring Nebula). This is an evolved planetary nebula with a central star that is currently on the cooling track, due to which the outer parts of the nebula are recombining. From the PACS and SPIRE images we conclude that there is a striking resemblance between the dust distribution and the H2 emission, which appears to be observational evidence that H2 forms on grain surfaces. We have developed a photoionization model of the nebula with the Cloudy code which we used to determine the physical conditions of the dust and investigate possible formation scenarios for the H2. We conclude that the most plausible scenario is that the H2 resides in high density knots which were formed after the recombination of the gas started when the central star entered the cooling track. Hydrodynamical instabilities due to the unusually low temperature of the recombining gas are proposed as a mechanism for forming the knots. H2 formation in the knots is expected to be...

  2. Dirty H2 Molecular Clusters as the DIB Sources: Spectroscopic and Physical Properties

    Science.gov (United States)

    Bernstein, L. S.; Clark, F. O.; Lynch, D. K.

    2014-02-01

    We propose that the diffuse interstellar bands (DIBs) arise from absorption lines of electronic transitions in molecular clusters primarily composed of a single molecule, atom, or ion (``seed''), embedded in a single-layer shell of H2 molecules (Bernstein et al. 2013). Less abundant variants of the cluster, including two seed molecules and/or a two-layer shell of H2 molecules may also occur. The lines are broadened, blended, and wavelength-shifted by interactions between the seed and surrounding H2 shell. We refer to these clusters as CHCs (Contaminated H2 Clusters). CHC spectroscopy matches the diversity of observed DIB spectral profiles, and provides good fits to several DIB profiles based on a rotational temperature of 10 K. CHCs arise from ~cm-sized, dirty H2 ice balls, called CHIMPs (Contaminated H2 Ice Macro-Particles), formed in cold, dense, Giant Molecular Clouds (GMCs), and later released into the interstellar medium (ISM) upon GMC disruption. Attractive interactions, arising from Van der Waals and ion-induced dipole potentials, between the seeds and H2 molecules enable CHIMPs to attain cm-sized dimensions. When an ultraviolet (UV) photon is absorbed in the outer layer of a CHIMP, it heats the icy matrix and expels CHCs into the ISM. While CHCs are quickly destroyed by absorbing UV photons, they are replenished by the slowly eroding CHIMPs. Since CHCs require UV photons for their release, they are most abundant at, but not limited to, the edges of UV-opaque molecular clouds, consistent with the observed, preferred location of DIBs. An inherent property of CHCs, which can be characterized as nanometer size, spinning, dipolar dust grains, is that they emit in the radio-frequency region. Thus, CHCs offer a natural explanation to the anomalous microwave emission (AME) feature in the ~10-100 GHz spectral region.

  3. Dissociation path for H2 on Al(110)

    DEFF Research Database (Denmark)

    Hammer, Bjørk; Jacobsen, Karsten Wedel; Nørskov, Jens Kehlet

    1992-01-01

    The minimum energy path is calculated for an H2 molecule dissociating on an Al(110) surface within local density functional theory. The properties of the potential energy surface along the five H2 ionic coordinates perpendicular to the reaction path are also determined and shown to be essential...

  4. Molecular adsorption of H2 on small cationic nickel clusters

    NARCIS (Netherlands)

    Swart, I.; Gruene, P.; Fielicke, A.; Meijer, G.; Weckhuysen, B.M.; de Groot, F.M.F.

    2008-01-01

    The adsorption of H2 on metal clusters is of interest in several fields, including metallurgy, catalysis and hydrogen storage. Hydrogen interacting with small Ni clusters is of special interest, as Ni is widely used as a hydrogenation catalyst. In general, reactions of H2 with extended Ni surfaces a

  5. H2-rich interstellar grain mantles: An equilibrium description

    Science.gov (United States)

    Dissly, Richard W.; Allen, Mark; Anicich, Vincent G.

    1994-01-01

    Experiments simulating the codeposition of molecular hydrogen and water ice on interstellar grains demonstrate that amorphous water ice at 12 K can incorporate a substantial amount of H2, up to a mole ratio of H2/H2O = 0.53. We find that the physical behavior of approximately 80% of the hydrogen can be explained satisfactorily in terms of an equilibrium population, thermodynamically governed by a wide distribution of binding site energies. Such a description predicts that gas phase accretion could lead to mole fractions of H2 in interstellar grain mantles of nearly 0.3; for the probable conditions of WL5 in the rho Ophiuchi cloud, an H2 mole fraction of between 0.05 and 0.3 is predicted, in possible agreement with the observed abundance reported by Sandford, Allamandola, & Geballe. Accretion of gas phase H2 onto grain mantles, rather than photochemical production of H2 within the ice, could be a general explanation for frozen H2 in interstellar ices. We speculate on the implications of such a composition for grain mantle chemistry and physics.

  6. H2 cycling and microbial bioenergetics in anoxic sediments

    Science.gov (United States)

    Hoehler, Tori M.; DeVincenzi, Donald (Technical Monitor)

    2001-01-01

    The simple biochemistry of H2 is central to a large number of microbial processes, affecting the interaction of organisms with each other and with the environment. In anoxic sediments, the great majority of microbial redox processes involve H2 as a reactant, product, or potential by-product, and the thermodynamics of these processes are thus highly sensitive to fluctuations in environmental H2 concentrations. In turn, H2 concentrations are controlled by the activity of H2-consuming microorganisms, which efficiently utilize this substrate down to levels which correspond to their bioenergetic limitations. Consequently, any environmental change which impacts the thermodynamics of H2-consuming organisms is mirrored by a corresponding change in H2 concentrations. This phenomenon is illustrated in anoxic sediments from Cape Lookout Bight, NC, USA: H2 concentrations are controlled by a suite of environmental parameters (e.g., temperature, sulfate concentrations) in a fashion which can be quantitatively described by a simple thermodynamic model. These findings allow us to calculate the apparent minimum quantity of biologically useful energy in situ. We find that sulfate reducing bacteria are not active at energy yields below -18 kJ per mole sulfate, while methanogenic archaea exhibit a minimum close to -10 kJ per mole methane.

  7. Molecular adsorption of H2 on small cationic nickel clusters

    NARCIS (Netherlands)

    Swart, I.; Gruene, P.; Fielicke, A.; Meijer, G.; Weckhuysen, B.M.; de Groot, F.M.F.

    2008-01-01

    The adsorption of H2 on metal clusters is of interest in several fields, including metallurgy, catalysis and hydrogen storage. Hydrogen interacting with small Ni clusters is of special interest, as Ni is widely used as a hydrogenation catalyst. In general, reactions of H2 with extended Ni surfaces

  8. Role of H2S Donors in Cancer Biology.

    Science.gov (United States)

    Lee, Zheng-Wei; Deng, Lih-Wen

    2015-01-01

    Hydrogen sulfide (H2S) donors including organosulfur compounds (OSC), inorganic sulfide salts, and synthetic compounds are useful tools in studies to elucidate the effects of H2S in cancer biology. Studies using such donors have shown the ability of H2S to suppress tumor growth both in vitro and in vivo, with some of them suggesting the selectivity of its cytotoxic effects to cancer cells. In addition to promoting cancer cell death, H2S donors were also found to inhibit cancer angiogenesis and metastasis. The underlying mechanisms for the anticancer activities of H2S involve (1) cell signaling pathways, such as MAPK and STAT; (2) cell cycle regulation; (3) microRNAs regulation; and (4) cancer metabolism and pH regulation. Altogether, compiling evidences have demonstrated the great potential of using H2S donors as anticancer agents. Nevertheless, the application and development of H2S for therapy are still facing challenges as identification of molecular targets of H2S awaits further investigation.

  9. H2S, a novel gasotransmitter, involves in gastric accommodation.

    Science.gov (United States)

    Xiao, Ailin; Wang, Hongjuan; Lu, Xin; Zhu, Jianchun; Huang, Di; Xu, Tonghui; Guo, Jianqiang; Liu, Chuanyong; Li, Jingxin

    2015-11-04

    H2S is produced mainly by two enzymes:cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE), using L-cysteine (L-Cys) as the substrate. In this study, we investigated the role of H2S in gastric accommodation using CBS(+/-) mice, immunohistochemistry, immunoblot, methylene blue assay, intragastric pressure (IGP) recording and electrical field stimulation (EFS). Mouse gastric fundus expressed H2S-generating enzymes (CBS and CSE) and generated detectable amounts of H2S. The H2S donor, NaHS or L-Cys, caused a relaxation in either gastric fundus or body. The gastric compliance was significantly increased in the presence of L-Cys (1 mM). On the contrary, AOAA, an inhibitor for CBS, largely inhibited gastric compliance. Consistently, CBS(+/-) mice shows a lower gastric compliance. However, PAG, a CSE inhibitor, had no effect on gastric compliances. L-Cys enhances the non-adrenergic, non-cholinergic (NANC) relaxation of fundus strips, but AOAA reduces the magnitude of relaxations to EFS. Notably, the expression level of CBS but not CSE protein was elevated after feeding. Consistently, the production of H2S was also increased after feeding in mice gastric fundus. In addition, AOAA largely reduced food intake and body weight in mice. Furthermore, a metabolic aberration of H2S was found in patients with functional dyspepsia (FD). In conclusion, endogenous H2S, a novel gasotransmitter, involves in gastric accommodation.

  10. PET imaging of DNA damage using {sup 89}Zr-labelled anti-γH2AX-TAT immunoconjugates

    Energy Technology Data Exchange (ETDEWEB)

    Knight, James C.; Topping, Caitriona; Mosley, Michael; Kersemans, Veerle; Cornelissen, Bart [University of Oxford, CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, Oxford (United Kingdom); Falzone, Nadia [University of Oxford, CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, Oxford (United Kingdom); Royal Marsden Hospital, Sutton, Surrey (United Kingdom); Fernandez-Varea, Jose M. [Universitat de Barcelona, Facultat de Fisica (ECM and ICC), Barcelona (Spain)

    2015-10-15

    The efficacy of most anticancer treatments, including radiotherapy, depends on an ability to cause DNA double-strand breaks (DSBs). Very early during the DNA damage signalling process, the histone isoform H2AX is phosphorylated to form γH2AX. With the aim of positron emission tomography (PET) imaging of DSBs, we synthesized a {sup 89}Zr-labelled anti-γH2AX antibody, modified with the cell-penetrating peptide, TAT, which includes a nuclear localization sequence. {sup 89}Zr-anti-γH2AX-TAT was synthesized using EDC/NHS chemistry for TAT peptide linkage. Desferrioxamine conjugation allowed labelling with {sup 89}Zr. Uptake and retention of {sup 89}Zr-anti-γH2AX-TAT was evaluated in the breast adenocarcinoma cell line MDA-MB-468 in vitro or as xenografts in athymic mice. External beam irradiation was used to induce DSBs and expression of γH2AX. Since {sup 89}Zr emits ionizing radiation, detailed radiobiological measurements were included to ensure {sup 89}Zr-anti-γH2AX-TAT itself does not cause any additional DSBs. Uptake of {sup 89}Zr-anti-γH2AX-TAT was similar to previous results using {sup 111}In-anti-γH2AX-TAT. Retention of {sup 89}Zr-anti-γH2AX-TAT was eightfold higher at 1 h post irradiation, in cells expressing γH2AX, compared to non-irradiated cells or to non-specific IgG control. PET imaging of mice showed higher uptake of {sup 89}Zr-anti-γH2AX-TAT in irradiated xenografts, compared to non-irradiated or non-specific controls (12.1 ± 1.6 vs 5.2 ± 1.9 and 5.1 ± 0.8 %ID/g, respectively; p < 0.0001). The mean absorbed dose to the nucleus of cells taking up {sup 89}Zr-anti-γH2AX-TAT was twofold lower compared to {sup 111}In-anti-γH2AX-TAT. Additional exposure of neither irradiated nor non-irradiated cells nor tissues to {sup 89}Zr-anti-γH2AX-TAT resulted in any significant changes in the number of observable DNA DSBs, γH2AX foci or clonogenic survival. {sup 89}Zr-anti-γH2AX-TAT allows PET imaging of DNA DSBs in a tumour xenograft mouse model

  11. Herschel observations of EXtra-Ordinary Sources (HEXOS): Observations of H2O and its isotopologues towards Orion KL

    CERN Document Server

    Melnick, G J; Neufeld, D A; Bergin, E A; Phillips, T G; Wang, S; Crockett, N R; Bell, T A; Blake, G A; Cabrit, S; Caux, E; Ceccarelli, C; Cernicharo, J; Comito, C; Daniel, F; Dubernet, M -L; Emprechtinger, M; Encrenaz, P; Falgarone, E; Gerin, M; Giesen, T F; Goicoechea, J R; Goldsmith, P F; Herbst, E; Joblin, C; Johnstone, D; Langer, W D; Latter, W D; Lis, D C; Lord, S D; Maret, S; Martin, P G; Menten, K M; Morris, P; Muller, H S P; Murphy, J A; Ossenkopf, V; Pagani, L; Pearson, J C; Perault, M; Plume, R; Qin, S -L; Salez, M; Schilke, P; Schlemmer, S; Stutzki, J; Trappe, N; van der Tak, F F S; Vastel, C; Yorke, H W; Yu, S; Zmuidzinas, J

    2010-01-01

    We report the detection of more than 48 velocity-resolved ground rotational state transitions of H2(16)O, H2(18)O, and H2(17)O - most for the first time - in both emission and absorption toward Orion KL using Herschel/HIFI. We show that a simple fit, constrained to match the known emission and absorption components along the line of sight, is in excellent agreement with the spectral profiles of all the water lines. Using the measured H2(18)O line fluxes, which are less affected by line opacity than their H2(16)O counterparts, and an escape probability method, the column densities of H2(18)O associated with each emission component are derived. We infer total water abundances of 7.4E-5, 1.0E-5, and 1.6E-5 for the plateau, hot core, and extended warm gas, respectively. In the case of the plateau, this value is consistent with previous measures of the Orion-KL water abundance as well as those of other molecular outflows. In the case of the hot core and extended warm gas, these values are somewhat higher than wate...

  12. Sulfur fertilization and fungal infections affect the exchange of H(2)S and COS from agricultural crops.

    Science.gov (United States)

    Bloem, Elke; Haneklaus, Silvia; Kesselmeier, Jürgen; Schnug, Ewald

    2012-08-08

    The emission of gaseous sulfur (S) compounds by plants is related to several factors, such as the plant S status or fungal infection. Hydrogen sulfide (H(2)S) is either released or taken up by the plant depending on the ambient air concentration and the plant demand for S. On the contrary, carbonyl sulfide (COS) is normally taken up by plants. In a greenhouse experiment, the dependence of H(2)S and COS exchange with ambient air on the S status of oilseed rape (Brassica napus L.) and on fungal infection with Sclerotinia sclerotiorum was investigated. Thiol contents were determined to understand their influence on the exchange of gaseous S compounds. The experiment revealed that H(2)S emissions were closely related to pathogen infections as well as to S nutrition. S fertilization caused a change from H(2)S consumption by S-deficient oilseed rape plants to a H(2)S release of 41 pg g(-1) (dw) min(-1) after the addition of 250 mg of S per pot. Fungal infection caused an even stronger increase of H(2)S emissions with a maximum of 1842 pg g(-1) (dw) min(-1) 2 days after infection. Healthy oilseed rape plants acted as a sink for COS. Fungal infection caused a shift from COS uptake to COS releases. The release of S-containing gases thus seems to be part of the response to fungal infection. The roles the S-containing gases may play in this response are discussed.

  13. Scavenging of H2O2 by mouse brain mitochondria.

    Science.gov (United States)

    Starkov, Anatoly A; Andreyev, Alexander Yu; Zhang, Steven F; Starkova, Natalia N; Korneeva, Maria; Syromyatnikov, Mikhail; Popov, Vasily N

    2014-12-01

    Mitochondrial reactive oxygen species (ROS) metabolism is unique in that mitochondria both generate and scavenge ROS. Recent estimates of ROS scavenging capacity of brain mitochondria are surprisingly high, ca. 9-12 nmol H2O2/min/mg, which is ~100 times higher than the rate of ROS generation. This raises a question whether brain mitochondria are a source or a sink of ROS. We studied the interaction between ROS generation and scavenging in mouse brain mitochondria by measuring the rate of removal of H2O2 added at a concentration of 0.4 μM, which is close to the reported physiological H2O2 concentrations in tissues, under conditions of low and high levels of mitochondrial H2O2 generation. With NAD-linked substrates, the rate of H2O2 generation by mitochondria was ~50-70 pmol/min/mg. The H2O2 scavenging dynamics was best approximated by the first order reaction equation. H2O2 scavenging was not affected by the uncoupling of mitochondria, phosphorylation of added ADP, or the genetic ablation of glutathione peroxidase 1, but decreased in the absence of respiratory substrates, in the presence of thioredoxin reductase inhibitor auranofin, or in partially disrupted mitochondria. With succinate, the rate of H2O2 generation was ~2,200-2,900 pmol/min/mg; the scavenging of added H2O2 was masked by a significant accumulation of generated H2O2 in the assay medium. The obtained data were fitted into a simple model that reasonably well described the interaction between H2O2 scavenging and production. It showed that mitochondria are neither a sink nor a source of H2O2, but can function as both at the same time, efficiently stabilizing exogenous H2O2 concentration at a level directly proportional to the ratio of the H2O2 generation rate to the rate constant of the first order scavenging reaction.

  14. Altered Sulfide (H2S) Metabolism in Ethylmalonic Encephalopathy

    Science.gov (United States)

    Tiranti, Valeria; Zeviani, Massimo

    2013-01-01

    Hydrogen sulfide (sulfide, H2S) is a colorless, water-soluble gas with a typical smell of rotten eggs. In the past, it has been investigated for its role as a potent toxic gas emanating from sewers and swamps or as a by-product of industrial processes. At high concentrations, H2S is a powerful inhibitor of cytochrome c oxidase; in trace amounts, it is an important signaling molecule, like nitric oxide (NO) and carbon monoxide (CO), together termed “gasotransmitters.” This review will cover the physiological role and the pathogenic effects of H2S, focusing on ethylmalonic encephalopathy, a human mitochondrial disorder caused by genetic abnormalities of sulfide metabolism. We will also discuss the options that are now conceivable for preventing genetically driven chronic H2S toxicity, taking into account that a complete understanding of the physiopathology of H2S has still to be achieved. PMID:23284046

  15. Altered sulfide (H(2)S) metabolism in ethylmalonic encephalopathy.

    Science.gov (United States)

    Tiranti, Valeria; Zeviani, Massimo

    2013-01-01

    Hydrogen sulfide (sulfide, H(2)S) is a colorless, water-soluble gas with a typical smell of rotten eggs. In the past, it has been investigated for its role as a potent toxic gas emanating from sewers and swamps or as a by-product of industrial processes. At high concentrations, H(2)S is a powerful inhibitor of cytochrome c oxidase; in trace amounts, it is an important signaling molecule, like nitric oxide (NO) and carbon monoxide (CO), together termed "gasotransmitters." This review will cover the physiological role and the pathogenic effects of H(2)S, focusing on ethylmalonic encephalopathy, a human mitochondrial disorder caused by genetic abnormalities of sulfide metabolism. We will also discuss the options that are now conceivable for preventing genetically driven chronic H(2)S toxicity, taking into account that a complete understanding of the physiopathology of H(2)S has still to be achieved.

  16. H2S分压对油管钢CO2/H2S腐蚀的影响%EFFECT OF H2S PARTIAL PRESSURE ON CO2/H2S CORROSION OF OIL TUBE STEELS

    Institute of Scientific and Technical Information of China (English)

    张清; 李全安; 文九巴; 白真权

    2004-01-01

    采用高温高压釜,辅以失重法和扫描电镜,对不同H2S分压下(1.4 kPa,20 kPa,60 kPa,120kPa)油管钢N80、P110的CO2/H2S腐蚀进行了研究.结果表明,在试验H2S分压范围内,随着H2S分压的升高,两种钢的腐蚀速率先增后降,且都在H2S分压为20 kPa时取得最大值.

  17. H2O line mapping at high spatial and spectral resolution - Herschel observations of the VLA1623 outflow

    CERN Document Server

    Bjerkeli, P; Larsson, B; Rydbeck, G; Nisini, B; Tafalla, M; Antoniucci, S; Benedettini, M; Bergman, P; Cabrit, S; Giannini, T; Melnick, G; Neufeld, D; Santangelo, G; van Dishoeck, E F

    2012-01-01

    Apart from being an important coolant, H2O is known to be a tracer of high-velocity molecular gas. Recent models predict relatively high abundances behind interstellar shockwaves. The dynamical and physical conditions of the H2O emitting gas, however, are not fully understood yet. We aim to determine the abundance and distribution of H2O, its kinematics and the physical conditions of the gas responsible for the H2O emission. The observed line profile shapes help us understand the dynamics in molecular outflows. We mapped the VLA1623 outflow, in the ground-state transitions of o-H2O, with the HIFI and PACS instruments. We also present observations of higher energy transitions of o-H2O and p-H2O obtained with HIFI and PACS towards selected outflow positions. From comparison with non-LTE radiative transfer calculations, we estimate the physical parameters of the water emitting regions. The observed water emission line profiles vary over the mapped area. Spectral features and components, tracing gas in different ...

  18. Spatial distribution of far-infrared rotationally excited CH+ and OH emission lines in the Orion Bar photodissociation region

    Science.gov (United States)

    Parikka, A.; Habart, E.; Bernard-Salas, J.; Goicoechea, J. R.; Abergel, A.; Pilleri, P.; Dartois, E.; Joblin, C.; Gerin, M.; Godard, B.

    2017-02-01

    Context. The methylidyne cation (CH+) and hydroxyl (OH) are key molecules in the warm interstellar chemistry, but their formation and excitation mechanisms are not well understood. Their abundance and excitation are predicted to be enhanced by the presence of vibrationally excited H2 or hot gas ( 500-1000 K) in photodissociation regions (PDRs) with high incident far-ultraviolet (FUV) radiation field. The excitation may also originate in dense gas (>105 cm-3) followed by nonreactive collisions with H2, H, and electrons. Previous observations of the Orion Bar suggest that the rotationally excited CH+ and OH correlate with the excited CO, which is a tracer of dense and warm gas, and that formation pumping contributes to CH+ excitation. Aims: Our goal is to examine the spatial distribution of the rotationally excited CH+ and OH emission lines in the Orion Bar to establish their physical origin and main formation and excitation mechanisms. Methods: We present spatially sampled maps of the CH+J = 3-2 transition at 119.8 μm and the OH Λ doublet at 84 μm in the Orion Bar over an area of 110″× 110″ with Herschel/PACS. We compare the spatial distribution of these molecules with those of their chemical precursors, C+, O and H2, and tracers of warm and dense gas (high-J CO). We assess the spatial variation of the CH+J = 2-1 velocity-resolved line profile at 1669 GHz with Herschel/HIFI spectrometer observations. Results: The OH and especially CH+ lines correlate well with the high-J CO emission and delineate the warm and dense molecular region at the edge of the Bar. While notably similar, the differences in the CH+ and OH morphologies indicate that CH+ formation and excitation are strongly related to the observed vibrationally excited H2. This, together with the observed broad CH+ line widths, indicates that formation pumping contributes to the excitation of this reactive molecular ion. Interestingly, the peak of the rotationally excited OH 84 μm emission coincides

  19. Probing 67P/Churyumov-Gerasimenko's Electron Environment Through Ultraviolet Emission by Rosetta Alice Observations

    Science.gov (United States)

    Schindhelm, Eric; Noonan, John; Keeney, Brian A.; Broiles, Thomas; Bieler, Andre; A'Hearn, Michael F.; Bertaux, Jean-Loup; Feaga, Lori M.; Feldman, Paul D.; Parker, Joel Wm.; Steffl, Andrew Joseph; Stern, S. Alan; Weaver, Harold A.

    2016-10-01

    The Alice Far-Ultraviolet (FUV) Spectrograph onboard ESA's Rosetta spacecraft has observed the coma of comet 67P/Churyumov-Gerasimenko from far approach in summer 2014 until the end of mission in September 2016. We present an overall perspective of the bright FUV emission lines (HI 1026 Å, OI 1302/1305/1306 Å multiplet, OI] 1356 Å, CO 1510 (1-0) Å, and CI 1657 Å) above the sunward hemisphere, detailing their spatial extent and brightness as a function of time and the heliocentric distance of the comet. We compare our observed gas column densities derived using electron temperatures and densities from the Ion Electron Sensor (IES) with those derived using the Inner Coma Environment Simulator (ICES) models in periods when electron-impact excited emission dominates over solar fluorescence emission. The electron population is characterized with 2 three-dimensional kappa functions, one dense and warm, one rarefied and hot.

  20. A role for nucleosome assembly protein 1 in the nuclear transport of histones H2A and H2B.

    Science.gov (United States)

    Mosammaparast, Nima; Ewart, Courtney S; Pemberton, Lucy F

    2002-12-02

    Import of core histones into the nucleus is a prerequisite for their deposition onto DNA and the assembly of chromatin. Here we demonstrate that nucleosome assembly protein 1 (Nap1p), a protein previously implicated in the deposition of histones H2A and H2B, is also involved in the transport of these two histones. We demonstrate that Nap1p can bind directly to Kap114p, the primary karyopherin/importin responsible for the nuclear import of H2A and H2B. Nap1p also serves as a bridge between Kap114p and the histone nuclear localization sequence (NLS). Nap1p acts cooperatively to increase the affinity of Kap114p for these NLSs. Nuclear accumulation of histone NLS-green fluorescent protein (GFP) reporters was decreased in deltanap1 cells. Furthermore, we demonstrate that Nap1p promotes the association of the H2A and H2B NLSs specifically with the karyopherin Kap114p. Localization studies demonstrate that Nap1p is a nucleocytoplasmic shuttling protein, and genetic experiments suggest that its shuttling is important for maintaining chromatin structure in vivo. We propose a model in which Nap1p links the nuclear transport of H2A and H2B to chromatin assembly.

  1. A novel H2S/H2O2 fuel cell operating at the room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Sanli, Ayse Elif [Gazi University (Turkey)], email: aecsanli@gmail.com; Aytac, Aylin [Department of Chemistry, Faculty of Science, Gazi University, Teknikokullar (Turkey)], email: aytaca@gazi.edu.tr

    2011-07-01

    This study concerns the oxidation mechanism of hydrogen sulfide and a fuel cell; acidic peroxide is used as the oxidant and basic hydrogen sulfide is the fuel. A solid state H2S/H2O2 stable fuel cell was produced at room temperature. A cell potential of 0.85 V was reached; this is quite remarkable in comparison to the H2S/O2 fuel cell potential of 0.85 V obtained at 850-1000 degree celsius. The hydrogen sulfide goes through an oxidation reaction in the alkaline fuel cell (H2S/H2O2 fuel cell) which opens up the possibility of using the cheaper nickel as a catalyst. As a result, the fuel cell becomes a potentially low cost technology. A further benefit from using H2S as the alkaline liquid H2S/H2O2 fuel cell, is that sulfide ions are oxidized at the anode, releasing electrons. Sulfur produced reacts with the other sulfide ions and forms disulfide and polysulfide ions in basic electrolytes (such as Black Sea water).

  2. Resonant Enhancement of Ground State H2+ Formation in Low Energy Charge Transfer between Protons and H2

    Science.gov (United States)

    Andrianarijaona, V. M.; King, J. G.; Martin, M. F.; de Ruette, N.; Urbain, X.

    2013-05-01

    We investigated the charge transfer (CT) from an H2 or D2 target to various fast atomic/molecular ions for a wide span of collision energies in the laboratory frame (eV to keV). Vibrationally resolved cross sections have been obtained on a relative scale, by dissociative charge transfer of the product H2+ ions with potassium atoms, and 3-D imaging of the fragments. An absolute value of the total CT cross section has been inferred from the measured ratio of the CT yield for protons and H2+, combined with the recommended H2+ + H2 cross section (ORNL). Our results on the (H2, H+) system benchmark state-to-state calculations at 10eV and above (Phys. Rev. A 75 032703, 2007 and J. Phys. B 42, 105207 2009). In particular, they confirm the vibrational excitation mechanism responsible for the resonance at 50eV, characterized by a dominant population of the ground vibrational state of H2++. The spectra for the isotopic system (D2, H+) will be also presented along with the results of CT performed with H2++ and D2+ projectiles. Research supported by the Fund for Scientific Research - FNRS through IISN Grant No. 4.4504.10, and the National Science Foundation through Grant No. PHY-106887.

  3. H2S2014 in Kyoto: the 3rd International Conference on H2S in Biology and Medicine.

    Science.gov (United States)

    Kimura, Hideo

    2015-04-30

    About 20 years ago, a pungent gas was found to be the physiological mediator of cognitive function and vascular tone. Since then, studies on hydrogen sulfide (H2S) have uncovered its numerous physiological roles such as protecting various tissues/organs from ischemia and regulating inflammation, cell growth, oxygen sensing, and senescence. These effects of H2S were extensively studied, and some of the corresponding mechanisms were also studied in detail. Previous studies on the synergistic interaction between H2S and nitric oxide (NO) have led to the discovery of several potential signaling molecules. Polysulfides are considerably potent and are one of the most active forms of H2S. H2S has a significant therapeutic potential, which is evident from the large number of novel H2S-donating compounds and substances developed for manipulating endogenous levels of H2S. The Third International Conference on H2S was held in Kyoto in June 2014. One hundred and sixty participants from 21 countries convened in Kyoto to report new advances, discuss conflicting findings, and make plans for future research. This article summarizes each oral presentation presented at the conference. Copyright © 2014 Elsevier Inc. All rights reserved.

  4. Revealing H2D+ depletion and compact structure in starless and protostellar cores with ALMA

    DEFF Research Database (Denmark)

    Friesen, R. K.; Di Francesco, J.; Bourke, T. L.;

    2014-01-01

    We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the submillimeter dust continuum and H2D+ 110-111 emission toward two evolved, potentially protostellar cores within the Ophiuchus molecular cloud, Oph A SM1 and SM1N. The data reveal small-scale condensations within...... hydrostatic core, or HD (and consequently H2D+) depletion in the cold center of the condensation. We propose that SM1 is protostellar and that the condensation detected by ALMA is a warm (T ~ 30-50 K) accretion disk. The less concentrated emission of the SM1N condensation suggests that it is still starless...

  5. Methanol synthesis on potassium modified Cu(100) from CO + H2 and CO + CO2 +H2

    DEFF Research Database (Denmark)

    Maack, M.; Friis-Jensen, Henriette; Sckerl, Susanne Quist;

    2003-01-01

    Methanol cannot be produced from CO + H-2 on a clean copper surface, but a promotional effect of potassium on methanol synthesis from mixtures of CO + H-2 and CO = CO2 + H-2 at a total pressure of 1.5 bar on a Cu(100) surface is shown in this work. The experiments are performed in a UHV chamber...... connected with a high-pressure cell (HPC). The methanol produced is measured with a gas chromatograph and the surface is characterized with surface science techniques. The results show that potassium is a promoter for the methanol synthesis from CO + H-2, and that the influence of CO2 is negligible....... Investigation of the post-reaction surface with TPD indicates that potassium carbonate is present and plays an important role. The activation energy is determined as 42 +/- 3 kJ/mol for methanol synthesis on K/Cu(100) from CO + H-2....

  6. Adriamycin induces H2AX phosphorylation in human spermatozoa

    Institute of Scientific and Technical Information of China (English)

    Zhong-Xiang Li; Ting-Ting Wang; Yan-Ting Wu; Chen-Ming Xu; Min-Yue Dong; Jian-Zhong Sheng; He-Feng Huang

    2008-01-01

    Aim: To investigate whether adriamycin induces DNA damage and the formation of γH2AX (the phosphorylated form of histone H2AX) foci in mature spermatozoa. Methods: Human spermatozoa were treated with adriamycin at different concentrations. γH2AX was analyzed by immunofluorescent staining and flow cytometry and double- strand breaks (DSB) were detected by the comet assay. Results: The neutral comet assay revealed that the treatment with adriamycin at 2 μg/mL for different times (0.5, 2, 8 and 24 h), or for 8 h at different concentrations (0.4, 2 and 10 μg/mL), induced significant DSB in spermatozoa. Immunofluorent staining and flow cytometry showed that the expression of γH2AX was increased in a dose-dependent and time-dependant manner after the treatment of adriamycin. Adriamycin also induced the concurrent appearance of DNA maintenance/repair proteins RAD50 and 53BP1 with γH2AX in spermatozoa. Wortmannin, an inhibitor of the phosphatidylinositol 3-kinase (PI3K) family, abolished the co-appearance of these two proteins with γH2AX. Conclusion: Human mature spermatozoa have the same response to DSB-induced H2AX phosphorylation and subsequent recruitment of DNA maintenance/repair proteins as somatic cells.

  7. Herschel/HIFI discovery of interstellar chloronium (H$_2$Cl$^+$)

    CERN Document Server

    Lis, D C; Neufeld, D A; Schilke, P; Müller, H S P; Gupta, H; Bell, T A; Comito, C; Phillips, T G; Bergin, E A; Ceccarelli, C; Goldsmith, P F; Blake, G A; Bacmann, A; Baudry, A; Benedettini, M; Benz, A; Black, J; Boogert, A; Bottinelli, S; Cabrit, S; Caselli, P; Castets, A; Caux, E; Cernicharo, J; Codella, C; Coutens, A; Crimier, N; Crockett, N R; Daniel, F; Demyk, K; Dominic, C; Dubernet, M -L; Emprechtinger, M; Encrenaz, P; Falgarone, E; Fuente, A; Gerin, M; Giesen, T F; Goicoechea, J R; Helmich, F; Hennebelle, P; Henning, Th; Herbst, E; Hily-Blant, P; Hjalmarson, Å; Hollenbach, D; Jack, T; Joblin, C; Johnstone, D; Kahane, C; Kama, M; Kaufman, M; Klotz, A; Langer, W D; Larsson, B; Bourlot, J Le; Lefloch, B; Petit, F Le; Li, D; Liseau, R; Lord, S D; Lorenzani, A; Maret, S; Martin, P G; Melnick, G J; Menten, K M; Morris, P; Murphy, J A; Nagy, Z; Nisini, B; Ossenkopf, V; Pacheco, S; Pagani, L; Parise, B; Pérault, M; Plume, R; Qin, S -L; Roueff, E; Salez, M; Sandqvist, A; Saraceno, P; Schlemmer, S; Schuster, K; Snell, R; Stutzki, J; Tielens, A; Trappe, N; van der Tak, F F S; van der Wiel, M H D; van Dishoeck, E; Vastel, C; Viti, S; Wakelam, V; Walters, A; Wang, S; Wyrowski, F; Yorke, H W; Yu, S; Zmuidzinas, J; Delorme, Y; Desbat, J -P; Güsten, R; Krieg, J -M; Delforge, B

    2010-01-01

    We report the first detection of chloronium, H$_2$Cl$^+$, in the interstellar medium, using the HIFI instrument aboard the \\emph{Herschel} Space Observatory. The $2_{12}-1_{01}$ lines of ortho-H$_2^{35}$Cl$^+$ and ortho-H$_2^{37}$Cl$^+$ are detected in absorption towards NGC~6334I, and the $1_{11}-0_{00}$ transition of para-H$_2^{35}$Cl$^+$ is detected in absorption towards NGC~6334I and Sgr~B2(S). The H$_2$Cl$^+$ column densities are compared to those of the chemically-related species HCl. The derived HCl/H$_2$Cl$^+$ column density ratios, $\\sim$1--10, are within the range predicted by models of diffuse and dense Photon Dominated Regions (PDRs). However, the observed H$_2$Cl$^+$ column densities, in excess of $10^{13}$~cm$^{-2}$, are significantly higher than the model predictions. Our observations demonstrate the outstanding spectroscopic capabilities of HIFI for detecting new interstellar molecules and providing key constraints for astrochemical models.

  8. H2 formation and excitation in the diffuse interstellar medium

    CERN Document Server

    Gry, C; Nehme, C; Pineau des Forêts, G; Habart, E; Falgarone, E; Gry, Cecile; Boulanger, Francois; Nehme, Cyrine; Forets, Guillaume Pineau Des; Habart, Emilie; Falgarone, Edith

    2002-01-01

    We use far-UV absorption spectra obtained with FUSE towards three late B stars to study the formation and excitation of H2 in the diffuse ISM. The data interpretation relies on a model of the chemical and thermal balance in photon-illuminated gas. The data constrain well the nR product between gas density and H2 formation rate on dust grains: nR = 1 to 2.2 e-15 s-1. For each line of sight the mean effective H2 density n, assumed uniform, is obtained by the best fit of the model to the observed N(J=1)/N(J=0) ratio, since the radiation field is known. Combining n with the nR values, we find similar H2 formation rates for the three stars of about R = 4 e-17 cm3/s. Because the target stars do not interact with the absorbing matter we can show that the H2 excitation in the J>2 levels cannot be accounted for by the UV pumping of the cold H2 but implies collisional excitation in regions where the gas is much warmer. The existence of warm H2 is corroborated by the fact that the star with the largest column density of...

  9. Time-dependent H2 formation and protonation

    CERN Document Server

    Liszt, H S

    2009-01-01

    Methods: The microscopic equations of H2-formation and protonation are integrated numerically over time in such a manner that the overall structures evolve self-consistently under benign conditions. Results: The equilibrium H2 formation timescale in an H I cloud with N(H) ~ 4x10^{20}/cm^2 is 1-3 x 10^7 yr, nearly independent of the assumed density or H2 formation rate constant on grains, etc. Attempts to speed up the evolution of the H2-fraction would require densities well beyond the range usually considered typical of diffuse gas. The calculations suggest that, under benign, quiescent conditions, formation of H2 is favored in larger regions having moderate density, consistent with the rather high mean kinetic temperatures measured in H2, 70-80 K. Formation of H3+ is essentially complete when H2-formation equilibrates but the final abundance of H3+ appears more nearly at the very last instant. Chemistry in a weakly-molecular gas has particular properties so that the abundance patterns change appreciably as g...

  10. H2 reformation in post-shock regions

    CERN Document Server

    Cuppen, H M; Gavardi, E

    2010-01-01

    H2 formation is an important process in post-shock regions, since H2 is an active participant in the cooling and shielding of the environment. The onset of H2 formation therefore has a strong effect on the temperature and chemical evolution in the post shock regions. We recently developed a model for H2 formation on a graphite surface in warm conditions. The graphite surface acts as a model system for grains containing large areas of polycyclic aromatic hydrocarbon structures. Here this model is used to obtain a new description of the H2 formation rate as a function of gas temperature that can be implemented in molecular shock models. The H2 formation rate is substantially higher at high gas temperatures as compared to the original implementation of this rate in shock models, because of the introduction of H atoms which are chemically bonded to the grain (chemisorption). Since H2 plays such a key role in the cooling, the increased rate is found to have a substantial effect on the predicted line fluxes of an i...

  11. Pyruvate protects pathogenic spirochetes from H2O2 killing.

    Directory of Open Access Journals (Sweden)

    Bryan Troxell

    Full Text Available Pathogenic spirochetes cause clinically relevant diseases in humans and animals, such as Lyme disease and leptospirosis. The causative agent of Lyme disease, Borrelia burgdorferi, and the causative agent of leptospirosis, Leptospria interrogans, encounter reactive oxygen species (ROS during their enzootic cycles. This report demonstrated that physiologically relevant concentrations of pyruvate, a potent H2O2 scavenger, and provided passive protection to B. burgdorferi and L. interrogans against H2O2. When extracellular pyruvate was absent, both spirochetes were sensitive to a low dose of H2O2 (≈0.6 µM per h generated by glucose oxidase (GOX. Despite encoding a functional catalase, L. interrogans was more sensitive than B. burgdorferi to H2O2 generated by GOX, which may be due to the inherent resistance of B. burgdorferi because of the virtual absence of intracellular iron. In B. burgdorferi, the nucleotide excision repair (NER and the DNA mismatch repair (MMR pathways were important for survival during H2O2 challenge since deletion of the uvrB or the mutS genes enhanced its sensitivity to H2O2 killing; however, the presence of pyruvate fully protected ΔuvrB and ΔmutS from H2O2 killing further demonstrating the importance of pyruvate in protection. These findings demonstrated that pyruvate, in addition to its classical role in central carbon metabolism, serves as an important H2O2 scavenger for pathogenic spirochetes. Furthermore, pyruvate reduced ROS generated by human neutrophils in response to the Toll-like receptor 2 (TLR2 agonist zymosan. In addition, pyruvate reduced neutrophil-derived ROS in response to B. burgdorferi, which also activates host expression through TLR2 signaling. Thus, pathogenic spirochetes may exploit the metabolite pyruvate, present in blood and tissues, to survive H2O2 generated by the host antibacterial response generated during infection.

  12. Structural basis of histone H2A-H2B recognition by the essential chaperone FACT.

    Science.gov (United States)

    Hondele, Maria; Stuwe, Tobias; Hassler, Markus; Halbach, Felix; Bowman, Andrew; Zhang, Elisa T; Nijmeijer, Bianca; Kotthoff, Christiane; Rybin, Vladimir; Amlacher, Stefan; Hurt, Ed; Ladurner, Andreas G

    2013-07-04

    Facilitates chromatin transcription (FACT) is a conserved histone chaperone that reorganizes nucleosomes and ensures chromatin integrity during DNA transcription, replication and repair. Key to the broad functions of FACT is its recognition of histones H2A-H2B (ref. 2). However, the structural basis for how histones H2A-H2B are recognized and how this integrates with the other functions of FACT, including the recognition of histones H3-H4 and other nuclear factors, is unknown. Here we reveal the crystal structure of the evolutionarily conserved FACT chaperone domain Spt16M from Chaetomium thermophilum, in complex with the H2A-H2B heterodimer. A novel 'U-turn' motif scaffolded onto a Rtt106-like module embraces the α1 helix of H2B. Biochemical and in vivo assays validate the structure and dissect the contribution of histone tails and H3-H4 towards Spt16M binding. Furthermore, we report the structure of the FACT heterodimerization domain that connects FACT to replicative polymerases. Our results show that Spt16M makes several interactions with histones, which we suggest allow the module to invade the nucleosome gradually and block the strongest interaction of H2B with DNA. FACT would thus enhance 'nucleosome breathing' by re-organizing the first 30 base pairs of nucleosomal histone-DNA contacts. Our snapshot of the engagement of the chaperone with H2A-H2B and the structures of all globular FACT domains enable the high-resolution analysis of the vital chaperoning functions of FACT, shedding light on how the complex promotes the activity of enzymes that require nucleosome reorganization.

  13. H2 metabolism in the photosynthetic bacterium Rhodopseudomonas capsulata: production and utilization of H2 by resting cells.

    Science.gov (United States)

    Hillmer, P; Gest, H

    1977-02-01

    Photoproduction of H2 and activation of H2 for CO2 reduction (photoreduction) by Rhodopseudomonas capsulata are catalyzed by different enzyme systems. Formation of H2 from organic compounds is mediated by nitrogenase and is nto inhibited by an atmosphere of 99% H2. Cells grown photoheterotrophically on C4 dicarboxylic acids (with glutamate as N source) evolve H2 from the C4 acids and also from lactate and pyruvate; cells grown on C3 carbon sources, however, are inactive with the C4 acids, presumably because they lack inducible transport systems. Ammonia is known to inhibit N2 fixation by photosynthetic bacteria, and it also effectively prevents photoproduction of H2; these effects are due to inhibition and, in part, inactivation of nitrogenase. Biosynthesis of the latter, as measured by both H2 production and acetylene reduction assays, is markedly increased when cells are grown at high light intensity; synthesis of the photoreduction system, on the other hand, is not appreciably influenced by light intensity during photoheterotrophic growth. The photoreduction activity of cells grown on lactate + glutamate (which contain active nitrogenase) is greatly activated by NH4+, but this effect is not observed in cells grown with NH4+ as N source (nitrogenase repressed) or in a Nif- mutant that is unable to produce H2. Lactate, malate, and succinate, which are readily used as growth substrates by R. capsulata and are excellent H donors for photoproduction of H2, abolish photoreduction activity. The physiological significances of this phenomenon and of the reciprocal regulatory effects of NH4+ on H2 production and photoreduction are discussed.

  14. H2S concentrations in the heart after acute H2S administration: methodological and physiological considerations.

    Science.gov (United States)

    Sonobe, Takashi; Haouzi, Philippe

    2016-12-01

    In this study, we have tried to characterize the limits of the approach typically used to determine H2S concentrations in the heart based on the amount of H2S evaporating from heart homogenates-spontaneously, after reaction with a strong reducing agent, or in a very acidic solution. Heart homogenates were prepared from male rats in control conditions or after H2S infusion induced a transient cardiogenic shock (CS) or cardiac asystole (CA). Using a method of determination of gaseous H2S with a detection limit of 0.2 nmol, we found that the process of homogenization could lead to a total disappearance of free H2S unless performed in alkaline conditions. Yet, after restoration of neutral pH, free H2S concentration from samples processed in alkaline and nonalkaline milieus were similar and averaged ∼0.2-0.4 nmol/g in both control and CS homogenate hearts and up to 100 nmol/g in the CA group. No additional H2S was released from control, CS, or CA hearts by using the reducing agent tris(2-carboxyethyl)phosphine or a strong acidic solution (pH H2S from combined pools. Of note, the reducing agent DTT produced a significant sulfide artifact and was not used. These data suggest that 1) free H2S found in heart homogenates is not a reflection of H2S present in a "living" heart and 2) the pool of combined sulfides, released in a strong reducing or acidic milieu, does not increase in the heart in a measurable manner even after toxic exposure to sulfide. Copyright © 2016 the American Physiological Society.

  15. Histamine H2 receptor - Involvement in gastric ulceration

    Science.gov (United States)

    Brown, P. A.; Vernikos-Danellis, J.; Brown, T. H.

    1976-01-01

    The involvement of the H1 and H2 receptors for histamine in the pathogenesis of gastric ulcers was investigated in rats. Metiamide, an H2 receptor antagonist, reliably reduced ulceration produced by stress alone or by a combination of stress and aspirin. In contrast, pyrilamine, which blocks only the H1 receptor, was without effect under these same conditions. The results support the hypothesis that histamine mediates both stress and stress plus aspirin induced ulceration by a mechanism involving the H2 receptor.

  16. Histamine H2 receptor - Involvement in gastric ulceration

    Science.gov (United States)

    Brown, P. A.; Vernikos-Danellis, J.; Brown, T. H.

    1976-01-01

    The involvement of the H1 and H2 receptors for histamine in the pathogenesis of gastric ulcers was investigated in rats. Metiamide, an H2 receptor antagonist, reliably reduced ulceration produced by stress alone or by a combination of stress and aspirin. In contrast, pyrilamine, which blocks only the H1 receptor, was without effect under these same conditions. The results support the hypothesis that histamine mediates both stress and stress plus aspirin induced ulceration by a mechanism involving the H2 receptor.

  17. Measurements of Molecular Cloud Ages using the HI/ H2 Ratio

    Science.gov (United States)

    Krco, Marko; Li, Di

    2017-01-01

    We utilize a new chemical evolution model in conjunction with the HI and H2 mass measurements of 9 nearby molecular clouds in order to place lower limits on their chemical ages (the time since the cloud first attained sufficient self-shielding for molecules to persist). HI masses are measured using HI Narrow Self-Absorption (HINSA) features with data taken with the GBT. H2 masses are estimated using 13CO emission data obtained with FCRAO.Since the clouds' geometry (and volume density) are unknown, we examine each cloud under a range of assumptions. Under conditions that favor the lowest age limits, where each cloud is assumed to resemble a sheet and has the highest reasonable volume density, we arrive at age lower limits between 0.3 and 1.5 Myrs. Assuming that the clouds have no preferential orientation yields age lower limits of 4.4 Myrs or older. HI/H2 cloud mass ratios between 0.13x10-3 and 3.8x10-3 were observed. The lack of any observed clouds with higher HI/H2 ratios leaves open the question of why the youngest clouds are not observed. Our models reveal that the clouds studied here should reach a steady-state, where the only remaining HI is due to cosmic ray dissociation, within approximately 7 to 15 Myrs.We determine the HI/H2 ratio, and age lower limit for all clumps and velocity components within each cloud. Though individual clumps within a single cloud, and even along the same line of sight may exhibit very different HI/H2 ratios, they most often exhibit similar ages. This would indicate that the mixing timescale for different clumps within cloud are generally longer than the cloud ages.Ultimately we conclude that the cloud collapse timescale is at least on the order of 10Myrs.

  18. Toeplitz and composition operators on H~2 (B_n)

    Institute of Scientific and Technical Information of China (English)

    曹广福; 孙顺华

    1997-01-01

    The composition operators with closed range on H2( Bn) are characterized, and the Frcdholmness of products of Toeplitz and composition operators discussed. Moreover, using composition operators, the spectra of Toeplitz operators are studied.

  19. The role of H2S bioavailability in endothelial dysfunction

    Science.gov (United States)

    Wang, Rui; Szabo, Csaba; Ichinose, Fumito; Ahmed, Asif; Whiteman, Matthew; Papapetropoulos, Andreas

    2015-01-01

    Endothelial dysfunction reflects pathophysiological changes in the phenotype and functions of endothelial cells that result from and/or contribute to a plethora of cardiovascular diseases. Here we review the role of hydrogen sulfide (H2S) in the pathogenesis of endothelial dysfunction, one of the fastest advanced and hottest research topics. Conventionally treated as an environment pollutant, H2S is also produced in endothelial cells and participates in the fine regulation of endothelial integrity and functions. Disturbed H2S bioavailability has been suggested to be a novel indicator of the progress and prognosis of endothelial dysfunction. Endothelial dysfunction appears to exhibit in different forms in different pathologies but therapeutics aimed at remedying the altered H2S bioavailability may benefit all. PMID:26071118

  20. Constraints on the H2O formation mechanism in the wind of carbon-rich AGB stars

    Science.gov (United States)

    Lombaert, R.; Decin, L.; Royer, P.; de Koter, A.; Cox, N. L. J.; González-Alfonso, E.; Neufeld, D.; De Ridder, J.; Agúndez, M.; Blommaert, J. A. D. L.; Khouri, T.; Groenewegen, M. A. T.; Kerschbaum, F.; Cernicharo, J.; Vandenbussche, B.; Waelkens, C.

    2016-04-01

    Context. The recent detection of warm H2O vapor emission from the outflows of carbon-rich asymptotic giant branch (AGB) stars challenges the current understanding of circumstellar chemistry. Two mechanisms have been invoked to explain warm H2O vapor formation. In the first, periodic shocks passing through the medium immediately above the stellar surface lead to H2O formation. In the second, penetration of ultraviolet interstellar radiation through a clumpy circumstellar medium leads to the formation of H2O molecules in the intermediate wind. Aims: We aim to determine the properties of H2O emission for a sample of 18 carbon-rich AGB stars and subsequently constrain which of the above mechanisms provides the most likely warm H2O formation pathway. Methods: Using far-infrared spectra taken with the PACS instrument onboard the Herschel telescope, we combined two methods to identify H2O emission trends and interpreted these in terms of theoretically expected patterns in the H2O abundance. Through the use of line-strength ratios, we analyzed the correlation between the strength of H2O emission and the mass-loss rate of the objects, as well as the radial dependence of the H2O abundance in the circumstellar outflow per individual source. We computed a model grid to account for radiative-transfer effects in the line strengths. Results: We detect warm H2O emission close to or inside the wind acceleration zone of all sample stars, irrespective of their stellar or circumstellar properties. The predicted H2O abundances in carbon-rich environments are in the range of 10-6 up to 10-4 for Miras and semiregular-a objects, and cluster around 10-6 for semiregular-b objects. These predictions are up to three orders of magnitude greater than what is predicted by state-of-the-art chemical models. We find a negative correlation between the H2O/CO line-strength ratio and gas mass-loss rate for Ṁg> 5 × 10-7 M⊙ yr-1, regardless of the upper-level energy of the relevant transitions

  1. Clinical Applications of CO2 and H2 Breath Test

    OpenAIRE

    ZHAO Si-qian; Chen, Bao-Jun; LUO Zhi-fu

    2016-01-01

    Breath test is non-invasive, high sensitivity and high specificity. In this article, CO2 breath test, H2 breath test and their clinical applications were elaborated. The main applications of CO2 breath test include helicobacter pylori test, liver function detection, gastric emptying test, insulin resistance test, pancreatic exocrine secretion test, etc. H2 breath test can be applied in the diagnosis of lactose malabsorption and detecting small intestinal bacterial overgrowth. With further res...

  2. Robust H2 control for uncertain sampled-data systems

    Institute of Scientific and Technical Information of China (English)

    Xie Weinan; Ma Guangcheng; Li Qinghua; Wang Changhong

    2009-01-01

    A new approach is proposed for robust H2 problem of uncertain sampled-data systems. Through introducing a free variable, a new Lyapunov asymptotical stability criterion with less conservativeness is established. Based on this criterion, some sufficient conditions on two classes of robust H2 problems for uncertain sampled-data control systems are presented through a set of coupled linear matrix inequalities, Finally, the less conservatism and potential of the developed results are illustrated via a numerical example.

  3. The interstellar chemistry of H2C3O isomers

    Science.gov (United States)

    Loison, Jean-Christophe; Agúndez, Marcelino; Marcelino, Núria; Wakelam, Valentine; Hickson, Kevin M.; Cernicharo, José; Gerin, Maryvonne; Roueff, Evelyne; Guélin, Michel

    2016-01-01

    We present the detection of two H2C3O isomers, propynal and cyclopropenone, toward various starless cores and molecular clouds, together with upper limits for the third isomer propadienone. We review the processes controlling the abundances of H2C3O isomers in interstellar media showing that the reactions involved are gas-phase ones. We show that the abundances of these species are controlled by kinetic rather than thermodynamic effects. PMID:27013768

  4. Metal Oxide/Zeolite Combination Absorbs H2S

    Science.gov (United States)

    Voecks, Gerald E.; Sharma, Pramod K.

    1989-01-01

    Mixed copper and molybdenum oxides supported in pores of zeolite found to remove H2S from mixture of gases rich in hydrogen and steam, at temperatures from 256 to 538 degree C. Absorber of H2S needed to clean up gas streams from fuel processors that incorporate high-temperature steam reformers or hydrodesulfurizing units. Zeolites chosen as supporting materials because of their high porosity, rigidity, alumina content, and variety of both composition and form.

  5. PLASMA POLYMERIZATION OF ACETYLENE/CO2/H2

    Institute of Scientific and Technical Information of China (English)

    ZHENG Ji; FANG Yuee; SHI Tianyi; SHOHEI INOUE

    1989-01-01

    A study has been made on the plasma polymerization of acetylene/CO2/H2 in a capacitively coupled RF plasma. The monomer mixture yielded a crosslinked film with light brown color. A kinetic study is reported for the plasma polymerization of acetylene/CO2/H2. The effects of discharge power level and reactor geometry on the rate of polymer formation are reported. The structure of the plasma polymer is investigated by IR study.

  6. H2S-mediated thermal and photochemical methane activation.

    Science.gov (United States)

    Baltrusaitis, Jonas; de Graaf, Coen; Broer, Ria; Patterson, Eric V

    2013-12-02

    Sustainable, low-temperature methods for natural gas activation are critical in addressing current and foreseeable energy and hydrocarbon feedstock needs. Large portions of natural gas resources are still too expensive to process due to their high content of hydrogen sulfide gas (H2S) mixed with methane, deemed altogether as sub-quality or "sour" gas. We propose a unique method of activation to form a mixture of sulfur-containing hydrocarbon intermediates, CH3SH and CH3SCH3 , and an energy carrier such as H2. For this purpose, we investigated the H2S-mediated methane activation to form a reactive CH3SH species by means of direct photolysis of sub-quality natural gas. Photoexcitation of hydrogen sulfide in the CH4 + H2S complex resulted in a barrierless relaxation by a conical intersection to form a ground-state CH3SH + H2 complex. The resulting CH3SH could further be coupled over acidic catalysts to form higher hydrocarbons, and the resulting H2 used as a fuel. This process is very different from conventional thermal or radical-based processes and can be driven photolytically at low temperatures, with enhanced control over the conditions currently used in industrial oxidative natural gas activation. Finally, the proposed process is CO2 neutral, as opposed to the current industrial steam methane reforming (SMR).

  7. Double strand break repair functions of histone H2AX

    Energy Technology Data Exchange (ETDEWEB)

    Scully, Ralph, E-mail: rscully@bidmc.harvard.edu; Xie, Anyong

    2013-10-15

    Chromosomal double strand breaks provoke an extensive reaction in neighboring chromatin, characterized by phosphorylation of histone H2AX on serine 139 of its C-terminal tail (to form “γH2AX”). The γH2AX response contributes to the repair of double strand breaks encountered in a variety of different contexts, including those induced by ionizing radiation, physiologically programmed breaks that characterize normal immune cell development and the pathological exposure of DNA ends triggered by telomere dysfunction. γH2AX also participates in the evolutionarily conserved process of sister chromatid recombination, a homologous recombination pathway involved in the suppression of genomic instability during DNA replication and directly implicated in tumor suppression. At a biochemical level, the γH2AX response provides a compelling example of how the “histone code” is adapted to the regulation of double strand break repair. Here, we review progress in research aimed at understanding how γH2AX contributes to double strand break repair in mammalian cells.

  8. Hydrogen Storage Properties of New Hydrogen-Rich BH3NH3-Metal Hydride (TiH2, ZrH2, MgH2, and/or CaH2) Composite Systems

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Young Joon; Xu, Yimin; Shaw, Wendy J.; Ronnebro, Ewa

    2012-04-19

    Ammonia borane (AB = NH3BH3) is one of the most attractive materials for chemical hydrogen storage due to its high hydrogen contents of 19.6 wt.%, however, impurity levels of borazine, ammonia and diborane in conjunction with foaming and exothermic hydrogen release calls for finding ways to mitigate the decomposition reactions. In this paper we present a solution by mixing AB with metal hydrides (TiH2, ZrH2, MgH2 and CaH2) which have endothermic hydrogen release in order to control the heat release and impurity levels from AB upon decomposition. The composite materials were prepared by mechanical ball milling, and their H2 release properties were characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The formation of volatile products from decomposition side reactions, such as borazine (N3B3H6) was determined by mass spectrometry (MS). Sieverts type pressure-composition-temperature (PCT) gas-solid reaction instrument was adopted to observe the kinetics of the H2 release reactions of the combined systems and neat AB. In situ 11B MAS-NMR revealed a destabilized decomposition pathway. We found that by adding specific metal hydrides to AB we can eliminate the impurities and mitigate the heat release.

  9. How Universal is the SFR - H2 Relation?

    CERN Document Server

    Feldmann, R; Kravtsov, A V

    2010-01-01

    It is a well established empirical fact that the surface density of the star formation rate, Sigma_SFR, strongly correlates with the surface density of molecular hydrogen, Sigma_H2, at least when averaged over large (~kpc) scales. Much less is known, however, if (and how) the Sigma_SFR-Sigma_H2 relation depends on environmental parameters, such as the metallicity or the UV radiation field in the interstellar medium (ISM). Furthermore, observations indicate that the scatter in the Sigma_SFR-Sigma_H2 relation increases rapidly with decreasing averaging scale. How the scale dependent scatter is generated and how one recovers a tight ~ kpc scale Sigma_SFR-Sigma_H2 relation in the first place is still largely debated. Here, we explore these questions with hydrodynamical simulations that follow the formation and destruction of H2, include radiative transfer of UV radiation, and resolve the ISM on ~60 pc scales. We find that within the considered range of H2 surface densities (10-100 Msun/pc^2) the Sigma_SFR-Sigma_H...

  10. H2 Velocity Maps of Orion: Destruction of the Environment of the BN-KL Nebula

    Directory of Open Access Journals (Sweden)

    Luis Salas

    2001-01-01

    Full Text Available We present the velocity structure of the 2.12 micron H2 emission in Orion, obtained with an IR Fabry-Perot interferometer with a spectral resolution of 24 km/s and a 2arcsec spatial resolution, covering a region of 3.6´ by 3.6´ (0.46 by 0.46 pc2 that contains the H2 filamentary finger system. A simple model is proposed to explain the observed low velocity structure as described by its radial moments: intensity, velocity centroid, velocity dispersion and skewness. We assume a strong wind of 230 km/s produced by IRc2 interacting with a set of molecular clumps with density of 5.6×105 cm-3. The scenario provides a good match to the observed moments is obtained, gives clues to the development of filaments or fingers and entrainment of the molecular material, and associates the observed high velocity blueshifted emission to the region. The H2 line emission is produced by a slow J-shock (20 km/s in the clumps with an emissivity proportional to v1.8 . Estimates for the total wind mass and clumps mass yield 0.5 Msolar and 15 Msolar inside a radius of 1arcmin (0.1 pc. The individual clumps have masses and sizes of few × 10-3 Msolar and 0.007 pc, respectively. We conclude that the central 0.1 pc region surrounding the BN-KL nebula in front of OMC-1 is in the process of being disrupted by the strong wind of IRc2 on a time scale of 2000 yr.

  11. Multi-Wavelength Studies on H2O Maser Host Galaxies

    Indian Academy of Sciences (India)

    J. S. Zhang; J. Wang

    2011-03-01

    H2O maser emissions have been found in external galaxies for more than 30 years. Main sciences associated with extragalactic H2O masers can be summarized roughly into three parts: maser emission itself, AGN sciences and cosmology exploration. Our work in this field focusses on two projects: X-ray data analysis of individual maser source using X-ray penetrability to explore maser host obscured AGN; multi-wavelength statistical properties of the whole published H2O maser sample. Here their nuclear radio properties were investigated in detail, based on their 6-cm and 20-cm radio observation data. Comparing the radio properties between maser-detected sources and non-detected sources at similar distance scale, we find that: (1) maser host galaxies tend to have higher nuclear radio luminosity; (2) the spectral index of both samples is comparable (∼ 0.6), within the error ranges. In addition, for AGN-maser sources, the isotropic maser luminosity tends to increase with rising radio luminosity. Thus we propose the nuclear radio luminosity as one good indicator for searching AGN-masers in the future.

  12. Highly Excited H2 in Herbig-Haro 7: Formation Pumping in Shocked Molecular Gas?

    CERN Document Server

    Pike, R E; Burton, M G; Chrysostomou, A

    2016-01-01

    We have obtained K-band spectra at R~5,000 and angular resolution 0.3" of a section of the Herbig-Haro 7 (HH7) bow shock, using the Near-Infrared Integral Field Spectrograph at Gemini North. Present in the portion of the data cube corresponding to the brightest part of the bow shock are emission lines of H2 with upper state energies ranging from ~6,000 K up to the dissociation energy of H2, ~50,000 K. Because of low signal-to-noise ratios, the highest excitation lines cannot be easily seen elsewhere in the observed region. However, excitation temperatures, measured throughout much of the observed region using lines from levels as high as 25,000 K, are a strong function of upper level energy, indicating that the very highest levels are populated throughout. The level populations in the brightest region are well fit by a two-temperature model, with 98.5% of the emitting gas at T=1800 K and 1.5% at T=5200 K. The bulk of the H2 line emission in HH7, from the 1,800 K gas, has previously been well modeled by a cont...

  13. H2 active jets in the near IR as a probe of protostellar evolution

    CERN Document Server

    Garatti, A C; Nisini, B; Lorenzetti, D

    2005-01-01

    We present a NIR analysis of a sample of H2 outflows from young embedded sources to compare the physical properties and cooling mechanisms of the different flows. The sample comprises 23 outflows driven by Class 0 and I sources having low-intermediate luminosity. We have obtained narrow band images in H2 2.12um and FeII 1.64um and spectroscopic observations in the range 1-2.5um. H2 line ratios have been used to estimate the visual extinction and average temperature of the molecular gas. Av values range from 2 to 15mag; average temperatures range between 2000 and 4000K. In several knots a stratification of temperatures is found with maximum values up to 5000K. Such a stratification is more commonly observed in those knots which also show FeII emission, while a thermalized gas at a single temperature is generally found in knots emitting only in molecular lines. Combining narrow band imaging with the parameters derived from the spectral analysis, we are able to measure the total luminosity of the H2 and FeII sho...

  14. Sulfide oxidation and nitrate reduction for potential mitigation of H2S in landfills.

    Science.gov (United States)

    Fang, Yuan; Du, Yao; Feng, Huan; Hu, Li-Fang; Shen, Dong-Sheng; Long, Yu-Yang

    2015-04-01

    Because H2S emitted by landfill sites has seriously endangered human health, its removal is urgent. H2S removal by use of an autotrophic denitrification landfill biocover has been reported. In this process, nitrate-reducing and sulfide-oxidizing bacteria use a reduced sulfur source as electron donor when reducing nitrate to nitrogen gas and oxidizing sulfur compounds to sulfate. The research presented here was performed to investigate the possibility of endogenous mitigation of H2S by autotrophic denitrification of landfill waste. The sulfide oxidation bioprocess accompanied by nitrate reduction was observed in batch tests inoculated with mineralized refuse from a landfill site. Repeated supply of nitrate resulted in rapid oxidation of the sulfide, indicating that, to a substantial extent, the bioprocess may be driven by functional microbes. This bioprocess can be realized under conditions suitable for the autotrophic metabolic process, because the process occurred without addition of acetate. H2S emissions from landfill sites would be substantially reduced if this bioprocess was introduced.

  15. Different reaction of the core histones H2A and H2B to red laser irradiation

    Science.gov (United States)

    Brill, G. E.; Egorova, A. V.; Bugaeva, I. O.; Postnov, D. E.; Ushakova, O. V.

    2017-03-01

    Analysis of the influence of red laser irradiation on the processes of self-assembly of the core histones H2A and H2B was performed using a wedge dehydration method. Image-analysis of facies included their qualitative characteristics and calculation of quantitative parameters with subsequent statistical processing. It was established that linearly polarized red laser light (λ - 660 nm, 1 J/cm2) significantly modified the process of self-assembly of core histone H2B, whereas the structure of the facies of H2A histone changed to a lesser extent. Histones were used in the form of aqueous salt solutions. The effect of red light seems to result from the formation of singlet oxygen by direct laser excitation of molecular oxygen.

  16. Destruction and Sequestration of H2O on Mars

    Science.gov (United States)

    Clark, Benton

    2016-07-01

    The availability of water in biologically useable form on any planet is a quintessential resource, even if the planet is in a zone habitable with temperature regimes required for growth of organisms (above -18 °C). Mars and most other planetary objects in the solar system do not have sufficient liquid water at their surfaces that photosynthesis or chemolithoautotrophic metabolism could occur. Given clear evidence of hydrous mineral alteration and geomorphological constructs requiring abundant supplies of liquid water in the past, the question arises whether this H2O only became trapped physically as ice, or whether there could be other, more or less accessible reservoirs that it has evolved into. Salts containing S or Cl appear to be ubiquitous on Mars, having been measured in soils by all six Mars landed missions, and detected in additional areas by orbital investigations. Volcanoes emit gaseous H2S, S, SO2, HCl and Cl2. A variety of evidence indicates the geochemical fate of these gases is to be transformed into sulfates, chlorides, chlorates and perchlorates. Depending on the gas, the net reaction causes the destruction of between one and up to eight molecules of H2O per atom of S or Cl (although hydrogen atoms are also released, they are lost relatively rapidly to atmospheric escape). Furthermore, the salt minerals formed often incorporate H2O into their crystalline structures, and can result in the sequestration of up to yet another six (sometimes, more) molecules of H2O. In addition, if the salts are microcrystalline or amorphous, they are potent adsorbents for H2O. In certain cases, they are even deliquescent under martian conditions. Finally, the high solubility of the vast majority of these salts (with notable exception of CaSO4) can result in dense brines with low water activity, aH, as well as cations which can be inimical to microbial metabolism, effectively "poisoning the well." The original geologic materials on Mars, igneous rocks, also provide some

  17. Enhanced stability of histone octamers from plant nucleosomes: role of H2A and H2B histones.

    Science.gov (United States)

    Moehs, C P; Baxevanis, A D; Moudrianakis, E N; Spiker, S

    1992-11-10

    Gel filtration and sedimentation studies have previously established that the vertebrate animal core histone octamer is in equilibrium with an (H3-H4)2 tetramer and an H2A-H2B dimer [Eickbush, T. H., & Moudrianakis, E. N. (1978) Biochemistry 17, 4955-4964; Godfrey, J. E., Eickbush, T. H., & Moudrianakis, E. N. (1980) Biochemistry 19, 1339-1346]. We have investigated the core histone octamer of wheat (Triticum aestivum L.) and have found it to be much more stable than its vertebrate animal counterpart. When vertebrate animal histone octamers are subjected to gel filtration in 2 M NaCl, a trailing peak of H2A-H2B dimer can be clearly resolved from the main octamer peak. When the plant octamer is subjected to the identical procedure, there is no trailing peak of H2A-H2B dimer, but rather a single peak containing the octamer. A sampling across the octamer peak from leading to trailing edge shows no change in the ratio of H2A-H2B to (H3-H4)2. Surprisingly, the plant octamer shows the same stability at 0.6 M NaCl, a salt concentration in which the vertebrate animal octamer dissociates into dimers and tetramers. Equilibrium sedimentation data indicate that the assembly potential of the wheat histones in 2 M NaCl is very high at all protein concentrations above 0.1 mg mL-1. In order to disrupt the forces stabilizing the plant histone octamer at high histone concentrations, the concentration of NaCl must be lowered to approximately 0.3 M.(ABSTRACT TRUNCATED AT 250 WORDS)

  18. NMR structure of chaperone Chz1 complexed with histones H2A.Z-H2B.

    Science.gov (United States)

    Zhou, Zheng; Feng, Hanqiao; Hansen, D Flemming; Kato, Hidenori; Luk, Ed; Freedberg, Daron I; Kay, Lewis E; Wu, Carl; Bai, Yawen

    2008-08-01

    The NMR structure of budding yeast chaperone Chz1 complexed with histones H2A.Z-H2B has been determined. Chz1 forms a long irregular chain capped by two short alpha-helices, and uses both positively and negatively charged residues to stabilize the histone dimer. A molecular model that docks Chz1 onto the nucleosome has implications for its potential functions.

  19. Quantum dynamics of rovibrational transitions in H2-H2 collisions: internal energy and rotational angular momentum conservation effects.

    Science.gov (United States)

    Fonseca dos Santos, S; Balakrishnan, N; Lepp, S; Quéméner, G; Forrey, R C; Hinde, R J; Stancil, P C

    2011-06-01

    We present a full dimensional quantum mechanical treatment of collisions between two H(2) molecules over a wide range of energies. Elastic and state-to-state inelastic cross sections for ortho-H(2) + para-H(2) and ortho-H(2) + ortho-H(2) collisions have been computed for different initial rovibrational levels of the molecules. For rovibrationally excited molecules, it has been found that state-to-state transitions are highly specific. Inelastic collisions that conserve the total rotational angular momentum of the diatoms and that involve small changes in the internal energy are found to be highly efficient. The effectiveness of these quasiresonant processes increases with decreasing collision energy and they become highly state-selective at ultracold temperatures. They are found to be more dominant for rotational energy exchange than for vibrational transitions. For non-reactive collisions between ortho- and para-H(2) molecules for which rotational energy exchange is forbidden, the quasiresonant mechanism involves a purely vibrational energy transfer albeit with less efficiency. When inelastic collisions are dominated by a quasiresonant transition calculations using a reduced basis set involving only the quasiresonant channels yield nearly identical results as the full basis set calculation leading to dramatic savings in computational cost.

  20. Solubility of ammonium paratungstate in the system NH3·H2O-H2O

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The equilibrium solubilities of 5(NH4)O@ 12WO3 @ 5H2O (APT@ 5H2O) were determined at the terminal ammoniaconcentration of 2 mol/L at 87-95℃. Experimental data were regressed. The linear functional relation between the solubilityof APT@ 5H2O and the temperature (t / ℃) is given as y = - 588.08 + 7.28t. The solubility of the species as a function of theterminal ammonia concentration (x / mol@ L-1) is also achieved: y = 36.76 + 18.86x. The solubility of APT@ 5H2O producedby ion-exchange method in China is much lower, which is due to much lower silica, much higher NH4C1, and a smallamount of APT@ 7H2O with low solubility in the APT crystals. APT@ 7H2O forms because of a large amount of NH4Cl andthe low activity of water in the crystallization.

  1. Transcription-coupled eviction of histones H2A/H2B governs V(D)J recombination.

    Science.gov (United States)

    Bevington, Sarah; Boyes, Joan

    2013-05-15

    Initiation of V(D)J recombination critically relies on the formation of an accessible chromatin structure at recombination signal sequences (RSSs) but how this accessibility is generated is poorly understood. Immunoglobulin light-chain loci normally undergo recombination in pre-B cells. We show here that equipping (earlier) pro-B cells with the increased pre-B-cell levels of just one transcription factor, IRF4, triggers the entire cascade of events leading to premature light-chain recombination. We then used this finding to dissect the critical events that generate RSS accessibility and show that the chromatin modifications previously associated with recombination are insufficient. Instead, we establish that non-coding transcription triggers IgL RSS accessibility and find that the accessibility is transient. Transcription transiently evicts H2A/H2B dimers, releasing 35-40 bp of nucleosomal DNA, and we demonstrate that H2A/H2B loss can explain the RSS accessibility observed in vivo. We therefore propose that the transcription-mediated eviction of H2A/H2B dimers is an important mechanism that makes RSSs accessible for the initiation of recombination.

  2. Corrosion of 310 stainless steel in H2-H2O-H2S gas mixtures: Studies at constant temperature and fixed oxygen potential

    Science.gov (United States)

    Rao, D. B.; Jacob, K. T.; Nelson, H. G.

    1981-01-01

    Corrosion of SAE 310 stainless steel in H2-H2O-H2S gas mixtures was studied at a constant temperature of 1150 K. Reactive gas mixtures were chosen to yield a constant oxygen potential of approximately 6 x 10 to the minus 13th power/cu Nm and sulfur potentials ranging from 0.19 x 10 to the minus 2nd power/cu Nm to 33 x 10 to the minus 2nd power/cu Nm. The kinetics of corrosion were determined using a thermobalance, and the scales were analyzed using metallography, scanning electron microscopy, and energy dispersive X-ray analysis. Two corrosion regimes, which were dependent on sulfur potential, were identified. At high sulfur potentials (p sub S sub 2 less than or equal to 2.7 x 10 to the minus 2nd power/cu Nm) the corrosion rates were high, the kinetics obeyed a linear rate equation, and the scales consisted mainly of sulfide phases similar to those observed from pure sulfication. At low sulfur potentials (P sub S sub 2 less than or equal to 0.19 x 10 to the minus 2nd power/cu Nm) the corrosion rates were low, the kinetics obeyed a parabolic rate equation, and scales consisted mainly of oxide phases.

  3. HIFI Spectroscopy of H2O Submillimeter Lines in Nuclei of Actively Star-forming Galaxies

    Science.gov (United States)

    Liu, L.; Weiß, A.; Perez-Beaupuits, J. P.; Güsten, R.; Liu, D.; Gao, Y.; Menten, K. M.; van der Werf, P.; Israel, F. P.; Harris, A.; Martin-Pintado, J.; Requena-Torres, M. A.; Stutzki, J.

    2017-09-01

    We present a systematic survey of multiple velocity-resolved H2O spectra using Herschel/Heterodyne Instrument for the Far Infrared (HIFI) toward nine nearby actively star-forming galaxies. The ground-state and low-excitation lines (E up ≤ 130 K) show profiles with emission and absorption blended together, while absorption-free medium-excitation lines (130 K ≤ E up ≤ 350 K) typically display line shapes similar to CO. We analyze the HIFI observation together with archival SPIRE/PACS H2O data using a state-of-the-art 3D radiative transfer code that includes the interaction between continuum and line emission. The water excitation models are combined with information on the dust and CO spectral line energy distribution to determine the physical structure of the interstellar medium (ISM). We identify two ISM components that are common to all galaxies: a warm ({T}{dust}∼ 40{--}70 K), dense (n({{H}})∼ {10}5{--}{10}6 {{cm}}-3) phase that dominates the emission of medium-excitation H2O lines. This gas phase also dominates the far-IR emission and the CO intensities for {J}{up}> 8. In addition, a cold ({T}{dust}∼ 20{--}30 K), dense (n({{H}})∼ {10}4{--}{10}5 {{cm}}-3), more extended phase is present. It outputs the emission in the low-excitation H2O lines and typically also produces the prominent line absorption features. For the two ULIRGs in our sample (Arp 220 and Mrk 231) an even hotter and more compact (R s ≤ 100 pc) region is present, which is possibly linked to AGN activity. We find that collisions dominate the water excitation in the cold gas and for lines with {E}{up}≤slant 300 K and {E}{up}≤slant 800 K in the warm and hot component, respectively. Higher-energy levels are mainly excited by IR pumping.

  4. The hydrocarbon ring C3H2 is ubiquitous in the Galaxy

    Science.gov (United States)

    Matthews, H. E.; Irvine, W. M.

    1985-01-01

    The discovery of a strong microwave (1.6 cm-wavelength) spectral line, the carrier of which is common and widespread throughout the Galaxy is reported. A survey of a large number of sources shows that the line appears in emission in cold dust clouds, in absorption in the direction of the Galactic center, and exhibits complex profiles toward H II regions. Toward Cas A and distant H II regions, intervening 'spiral arm' clouds produce absorption. For almost all cases, the absorption features show a striking 1:1 radial velocity correspondence with those seen, e.g., in H2CO spectra of the same objects. The data indicate that the line arises between low-lying energy states of a rather polar molecule. Recent work by Thaddeus, Vrtilek, and Gottlieb (1985) incorporating the present data, shows that the line in question is the 1(10)-1(01) transition of the small hydrocarbon ring C3H2.

  5. Density Distributions of H and H2 in Pulsed Microwave hydrogen Plasmas

    Institute of Scientific and Technical Information of China (English)

    DUAN Xu-Ru(段旭如); H.Lange; QIAN shang-Jie(钱尚介); N.Lang

    2003-01-01

    Temporal distribution of the H atom and Hz densities in a pulsed microwave hydrogen plasmas has been measured simultaneously by two-photon absorption laser-induced fluorescence (TALIF). The measurement of the H-atom absolute density obtained by NO2 titration in a flow tube reactor shows that the density of H2 could be determined by the measured effective lifetime of the TALIF signal via the quenching equation. The H-atom density of about 1.5×1015cm-3 in both pulsed and stationary phases does not obviously change. It is found that the gas temperature volume effect plays an important role in governing the distributions of the H-atom density and it is mole fraction. The calculated gas temperature is in good consistent with the rotational temperature of H2measured by optical emission spectroscopy in pulsed phase.

  6. Interstellar H I and H2 in the Magellanic Clouds: An Expanded Sample Based on UV Absorption-Line Data

    Science.gov (United States)

    Welty, Daniel E.; Xue, Rui; Wong, Tony

    2010-11-01

    We have determined column densities of H I and/or H2 for sight lines in the Magellanic Clouds from archival HST and FUSE spectra of H I Lyman-α and H2 Lyman-band absorption. Together with (some) similar data from the literature, we now have absorption-based N(H I) and/or N(H2) for about 250 Magellanic Clouds sight lines - enabling more extensive, direct, and accurate determinations of molecular fractions, dust-to-gas ratios, and elemental depletions. The N(H I) estimated from 21 cm emission (for the same sight lines) can be lower by factors of 2-3 in the LMC - suggestive of small-scale structure within the 21 cm beam(s) and/or some saturation in the emission. Both E(B-V)/N(H I) and E(B-V)/N(Htot) are smaller than in our Galaxy, by factors of 2.7-3.4 in the LMC and 4.3-4.9 in the SMC - similar to the differences in metallicity. The E(B-V)/N(N2) ratio is more similar in the three galaxies, however. These data may be used to test models of the atomic-to-molecular transition at low metallicities and predictions of N(H2) based on comparisons of 21 cm emission and the IR emission from dust.

  7. Ortho-para-H$_2$ conversion processes in astrophysical media

    CERN Document Server

    Lique, François; Faure, Alexandre

    2014-01-01

    We report in this review recent fully-quantum time-independent calculations of cross sections and rate constants for the gas phase ortho-to-para conversion of H$_2$ by H and H$^+$. Such processes are of crucial interest and importance in various astrophysical environments. The investigated temperature ranges was 10$-$1500 K for H+H$_2$ and 10$-$100 K for H$^+$+H$_2$. Calculations were based on highly accurate H$_3$ and H$_3^+$ global potential energy surfaces. Comparisons with previous calculations and with available measurements are presented and discussed. It is shown that the existence of a long-lived intermediate complex H$_3^+$ in the (barrierless) H$^+$+H$_2$ reaction give rise to a pronounced resonance structure and a statistical behaviour, in contrast to H+H$_2$ which proceeds through a barrier of $\\sim 5000$ K. In the cold interstellar medium ($T\\leq 100$ K), the ortho-to-para conversion is thus driven by proton exchange while above $\\sim$300 K, the contribution of hydrogen atoms become significant o...

  8. CO diffusion into amorphous H2O ices

    CERN Document Server

    Lauck, Trish; Shulenberger, Katherine; Rajappan, Mahesh; Oberg, Karin I; Cuppen, Herma M

    2015-01-01

    The mobility of atoms, molecules and radicals in icy grain mantles regulate ice restructuring, desorption, and chemistry in astrophysical environments. Interstellar ices are dominated by H2O, and diffusion on external and internal (pore) surfaces of H2O-rich ices is therefore a key process to constrain. This study aims to quantify the diffusion kinetics and barrier of the abundant ice constituent CO into H2O dominated ices at low temperatures (15-23 K), by measuring the mixing rate of initially layered H2O(:CO2)/CO ices. The mixed fraction of CO as a function of time is determined by monitoring the shape of the infrared CO stretching band. Mixing is observed at all investigated temperatures on minute time scales, and can be ascribed to CO diffusion in H2O ice pores. The diffusion coefficient and final mixed fraction depend on ice temperature, porosity, thickness and composition. The experiments are analyzed by applying Fick's diffusion equation under the assumption that mixing is due to CO diffusion into an i...

  9. Rotational Spectroscopy of the NH3-H2 Molecular Complex

    Science.gov (United States)

    Surin, L. A.; Tarabukin, I. V.; Schlemmer, S.; Breier, A. A.; Giesen, T. F.; McCarthy, M. C.; van der Avoird, A.

    2017-03-01

    We report the first high resolution spectroscopic study of the NH3–H2 van der Waals molecular complex. Three different experimental techniques, a molecular beam Fourier transform microwave spectrometer, a millimeter-wave intracavity jet OROTRON spectrometer, and a submillimeter-wave jet spectrometer with multipass cell, were used to detect pure rotational transitions of NH3–H2 in the wide frequency range from 39 to 230 GHz. Two nuclear spin species, (o)-NH3–(o)-H2 and (p)-NH3–(o)-H2, have been assigned as carriers of the observed lines on the basis of accompanying rovibrational calculations performed using the ab initio intermolecular potential energy surface (PES) of Maret et al. The experimental spectra were compared with the theoretical bound state results, thus providing a critical test of the quality of the NH3–H2 PES, which is a key issue for reliable computations of the collisional excitation and de-excitation of ammonia in the dense interstellar medium.

  10. Dwarf galaxy formation with H2-regulated star formation

    CERN Document Server

    Kuhlen, M; Madau, P; Smith, B; Wise, J

    2011-01-01

    We describe cosmological galaxy formation simulations with the adaptive mesh refinement code Enzo that incorporate a star formation prescription regulated by the local abundance of molecular hydrogen. We show that this H2-regulated prescription leads to a suppression of star formation in low mass halos (M_h 4, alleviating some of the dwarf galaxy problems faced by theoretical galaxy formation models. H2 regulation modifies the efficiency of star formation of cold gas directly, rather than indirectly reducing the cold gas content with "supernova feedback". We determine the local H2 abundance in our most refined grid cells (76 proper parsec in size at z=4) by applying the model of Krumholz, McKee, & Tumlinson, which is based on idealized 1D radiative transfer calculations of H2 formation-dissociation balance in ~100 pc atomic--molecular complexes. Our H2-regulated simulations are able to reproduce the empirical (albeit lower z) Kennicutt-Schmidt relation, including the low Sigma_gas cutoff due to the transi...

  11. Radio continuum of galaxies with H2O megamaser disks: 33 GHz VLA data

    Science.gov (United States)

    Kamali, F.; Henkel, C.; Brunthaler, A.; Impellizzeri, C. M. V.; Menten, K. M.; Braatz, J. A.; Greene, J. E.; Reid, M. J.; Condon, J. J.; Lo, K. Y.; Kuo, C. Y.; Litzinger, E.; Kadler, M.

    2017-09-01

    Context. Galaxies with H2O megamaser disks are active galaxies in whose edge-on accretion disks 22 GHz H2O maser emission has been detected. Because their geometry is known, they provide a unique view into the properties of active galactic nuclei. Aims: The goal of this work is to investigate the nuclear environment of galaxies with H2O maser disks and to relate the maser and host galaxy properties to those of the radio continuum emission of the galaxy. Methods: The 33 GHz (9 mm) radio continuum properties of 24 galaxies with reported 22 GHz H2O maser emission from their disks are studied in the context of the multiwavelength view of these sources. The 29-37 GHz Ka-band observations are made with the Karl Jansky Very Large Array in B, CnB, or BnA configurations, achieving a resolution of 0.2-0.5 arcsec. Hard X-ray data from the Swift/BAT survey and 22 μm infrared data from WISE, 22 GHz H2O maser data and 1.4 GHz data from NVSS and FIRST surveys are also included in the analysis. Results: Eighty-seven percent (21 out of 24) galaxies in our sample show 33 GHz radio continuum emission at levels of 4.5-240σ. Five sources show extended emission (deconvolved source size larger than 2.5 times the major axis of the beam), including one source with two main components and one with three main components. The remaining detected 16 sources (and also some of the above-mentioned targets) exhibit compact cores within the sensitivity limits. Little evidence is found for extended jets (>300 pc) in most sources. Either they do not exist, or our chosen frequency of 33 GHz is too high for a detection of these supposedly steep spectrum features. In NGC 4388, we find an extended jet-like feature that appears to be oriented perpendicular to the H2O megamaser disk. NGC 2273 is another candidate whose radio continuum source might be elongated perpendicular to the maser disk. Smaller 100-300 pc sized jets might also be present, as is suggested by the beam-deconvolved morphology of our

  12. Excitation of the low lying vibrational levels of H2O by O(3P) as measured on Spacelab 2

    Science.gov (United States)

    Meyerott, R. E.; Swenson, G. R.; Schweitzer, E. L.; Koch, D. G.

    1994-01-01

    The data from the infrared telescope (IRT), which was flown on space shuttle Challenger Spacelab 2 mission (July 1985), were originally reported by Koch et al. (1987) as originating from near orbital emissions, primarily H2O. In this study, analysis of this data was extended to determine the collisional cross sections for the excitation of the low lying vibrational levels of H2O, present in the orbiter cloud, by atmospheric O(3P). The evaluation of the contribution to the measured signal from solar excitation and ram O excitation of outgassing H2O permits the determination of the H2O column density and the excitation cross section of the (101) level at an O(3P) velocity of approximately 7.75 km/s. Contributions to the radiation in the 1.7-3.0 micron band by transitions from the (100), (001), and multiquantum excited levels are discussed. The findings of the study are (1) the IRT data for the 4.5-9.5 micron and the nighttime data for the 1.7-3.0 micron sensors are consistent with being explained by collision excitation of H2O by O(3P), (2) diurnal variations of 4.5-9.5 micron intensities follow the model predicted O density for a full orbit, (3) daytime increases in the H2O cloud density were not evident, (4) the cross sections for the collisional excitation process are derived and compared to values computated by Johnson (1986) and Redmon et al. (1986), (5) theoretical investigation suggests greater than 60% of the radiation from H2O is a result of multiphoton emission resulting from collisional multiquanta excitation, and (6) the large daytime increase in the 1.7-3.0 micron intensity data suggests that O(+) may likely be instrumental in producing excited H2O(+) through charge exchange.

  13. Mapping of [HDO]/[H2O] in the Martian Atmosphere

    Science.gov (United States)

    Novak, R. E.; Mumma, M. J.; Villanueva, G.; Bonev, B.; Disanti, M.

    Observations of the Martian atmosphere were taken for several seasonal dates at NASA's IRTF using CSHELL. Column densities of HDO and H2O were extracted from individual spectral lines near 3.67 ìm and 3.29 ìm. The slit was positioned N-S on Mars centered at the sub-earth point producing spectral/spatial images. Spectra were extracted at 0.6 arc-sec. intervals and analyzed with models created from GENLN2 atmospheric software; the models include solar Fraunhofer lines, a two-way transmission through Mars' atmosphere, thermal emission from Mars' surface and atmosphere, and a one way transmission through the Earth's atmosphere. From these, latitudinal maps of HDO/H2O were constructed across the observable planet. The HDO/H2O ratios have been found to be larger than those on Earth and they vary with both latitude and season. The higher global HDO/H2O value on Mars compared to that of the Earth is attributed to differential Jeans escape of D and H over geologic time. The ratio in the southern Martian hemisphere is found to be larger than that in the north. This difference could be the signature of Rayleigh distillation, a process in which the different mean temperatures of the polar caps causes a different degree of HDO sequestration resulting in different degrees of enrichment in the polar caps. Detailed results for Ls= 357o in 2006 will be presented when both the HDO and the H2O column densities were obtain from CSHELL data. These will be compared to results from other seasons.Observations of the Martian atmosphere were taken for several seasonal dates at NASA's IRTF using CSHELL. Column densities of HDO and H2O were extracted from individual spectral lines near 3.67 ìm and 3.29 ìm. The slit was positioned N-S on Mars centered at the sub-earth point producing spectral/spatial images. Spectra were extracted at 0.6 arc-sec. intervals and analyzed with models created from GENLN2 atmospheric software; the models include solar Fraunhofer lines, a two-way transmission

  14. Dynamics of H2 dissociation on the close-packed (111) surface of the noblest metal: H2 + Au(111)

    Science.gov (United States)

    Wijzenbroek, Mark; Helstone, Darcey; Meyer, Jörg; Kroes, Geert-Jan

    2016-10-01

    We have performed calculations on the dissociative chemisorption of H2 on un-reconstructed and reconstructed Au(111) with density functional theory, and dynamics calculations on this process on un-reconstructed Au(111). Due to a very late barrier for dissociation, H2 + Au(111) is a candidate H2-metal system for which the dissociative chemisorption could be considerably affected by the energy transfer to electron-hole pairs. Minimum barrier geometries and potential energy surfaces were computed for six density functionals. The functionals tested yield minimum barrier heights in the range of 1.15-1.6 eV, and barriers that are even later than found for the similar H2 + Cu(111) system. The potential energy surfaces have been used in quasi-classical trajectory calculations of the initial (v,J) state resolved reaction probability for several vibrational states v and rotational states J of H2 and D2. Our calculations may serve as predictions for state-resolved associative desorption experiments, from which initial state-resolved dissociative chemisorption probabilities can be extracted by invoking detailed balance. The vibrational efficacy ηv=0→1 reported for D2 dissociating on un-reconstructed Au(111) (about 0.9) is similar to that found in earlier quantum dynamics calculations on H2 + Ag(111), but larger than found for D2 + Cu(111). With the two functionals tested most extensively, the reactivity of H2 and D2 exhibits an almost monotonic increase with increasing rotational quantum number J. Test calculations suggest that, for chemical accuracy (1 kcal/mol), the herringbone reconstruction of Au(111) should be modeled.

  15. Oxidation of H2S in mammalian cells and mitochondria.

    Science.gov (United States)

    Abou-Hamdan, Abbas; Guedouari-Bounihi, Hala; Lenoir, Véronique; Andriamihaja, Mireille; Blachier, François; Bouillaud, Frédéric

    2015-01-01

    Hydrogen sulfide (H2S) is the third gasotransmitter described in mammals. These gasotransmitters (H2S, CO, and NO) are small molecules able to diffuse freely across membranes and thus susceptible to reach easily intracellular targets, one of which is the respiratory enzyme cytochrome oxidase subject to complete inhibition by low micromolar concentrations of these gases. However in contrast to NO or CO, H2S can be metabolized by a sulfide quinone reductase feeding the mitochondrial respiratory chain with the hydrogen atoms of sulfide. Sulfide is thus a two-sided molecule: substrate or poison according to the concentration. The aim of this chapter is to present a mean to monitor sulfide oxidation by isolated mitochondria or cells and to summarize how the properties of this amazing couple (mitochondria and sulfide) translate into practical and conceptual consequences.

  16. Substrate Recognition of Histone H2B by DUBm

    Science.gov (United States)

    Henderson, Elizabeth; Berndsen, Christopher; Wolberger, Cynthia

    2011-03-01

    The SAGA complex is a transcriptional coactivator that regulates gene expression in eukaryotes via histone acetylation and deubiquitination, which are crucial for transcription. Our lab is investigating the SAGA-dependent deubiquitination of histone H2B. The deubiquitinating module (DUBm) of SAGA is comprised of a ubiquitin-specific protease, Ubp8, and three other proteins. It is known that Ubp8 cleaves ubiquitin from histone H2B, however, the specific way in which the enzyme binds to the substrate remains elusive. In order to unravel this mechanism, we attempted to determine the crystal structure of the substrate binding complex. We obtained this substrate by exploiting the techniques of intein chemistry to artificially ubiquitinate a histone H2B peptide, which we then co-crystallized with DUBm. Additionally, we synthesized Ub-K63R-linked chains and Ub-K48-linked chains and co-crystallized them with DUBm.

  17. Atmospheric photochemical loss of H and H2 from formaldehyde

    DEFF Research Database (Denmark)

    Simonsen, Jens Bæk; Rusteika, Nerijus; Johnson, Matthew Stanley;

    2008-01-01

    We have performed ab initio calculations to examine the potential energy along the normal modes of ground-state HCHO and along the reaction coordinates for loss of H2 and atomic hydrogen, respectively. This exploration showed that there are no specific features that will lead to reaction on the e......We have performed ab initio calculations to examine the potential energy along the normal modes of ground-state HCHO and along the reaction coordinates for loss of H2 and atomic hydrogen, respectively. This exploration showed that there are no specific features that will lead to reaction...... on the excited-state surfaces for excitations that are relevant to the troposphere and stratosphere. The calculations did however lead to the localization of a conical intersection point through which a specific loss of H2 could take place. However, the conical intersection lies at 5.4 eV relative to the ground...

  18. Robust generalized H2 control:time-delay case

    Institute of Scientific and Technical Information of China (English)

    刘飞

    2004-01-01

    Generalized H2 control problem is considered for a class of linear time-delay systems covering linear timeinvariant (LTI) case and time-varying but norm-bounded linear differential inclusion (NLDI) case. The issues focus on the synthesis of so-called generalized H2 controller, which guarantees internal/robust stability and a certain performance level of generalized H2 norm of resulting closed-loop system. By using Lyapunov functional technique, sufficient conditions for the existence of such a kind of controllers are obtained in terms of two linear matrix inequalities (LMIs).In the state space, for memoryless state feedback case, we treat the controller design in a unified framework for both LTI and NLDI. The presented results are illustrated by numerical examples.

  19. Vibrational predissociation of ArH2O

    Science.gov (United States)

    Bissonnette, C.; Clary, D. C.

    1992-12-01

    Accurate close-coupling calculations are used to investigate the vibrational predissociation of ArH2O as a function of the overall rotation J of the van der Waals complex. A full vibrational and rotational basis of H2O states is used in the calculation. The potential energy surface is of a form due to Cohen and Saykally and derived from far-infrared spectra, with an additional term to introduce the dependence on the vibrations of H2O. The linewidths calculated in this work show a maximum at J=6 and it is found that Fermi resonances affect dramatically the magnitude of the calculated linewidths. Good agreement with experimentally measured linewidths of Nesbitt and Lascola is achieved and the calculations provide a simple picture for the J dependence of the linewidths.

  20. H2-optimal approximation of MIMO linear dynamical systems

    CERN Document Server

    Van Dooren, Paul; Absil, P -A

    2008-01-01

    We consider the problem of approximating a multiple-input multiple-output (MIMO) $p\\times m$ rational transfer function $H(s)$ of high degree by another $p\\times m$ rational transfer function $\\hat H(s)$ of much smaller degree, so that the ${\\cal H}_2$ norm of the approximation error is minimized. We characterize the stationary points of the ${\\cal H}_2$ norm of the approximation error by tangential interpolation conditions and also extend these results to the discrete-time case. We analyze whether it is reasonable to assume that lower-order models can always be approximated arbitrarily closely by imposing only first-order interpolation conditions. Finally, we analyze the ${\\cal H}_2$ norm of the approximation error for a simple case in order to illustrate the complexity of the minimization problem.

  1. Data-Driven Controller Design The H2 Approach

    CERN Document Server

    Sanfelice Bazanella, Alexandre; Eckhard, Diego

    2012-01-01

    Data-driven methodologies have recently emerged as an important paradigm alternative to model-based controller design and several such methodologies are formulated as an H2 performance optimization. This book presents a comprehensive theoretical treatment of the H2 approach to data-driven control design. The fundamental properties implied by the H2 problem formulation are analyzed in detail, so that common features to all solutions are identified. Direct methods (VRFT) and iterative methods (IFT, DFT, CbT) are put under a common theoretical framework. The choice of the reference model, the experimental conditions, the optimization method to be used, and several other designer’s choices are crucial to the quality of the final outcome, and firm guidelines for all these choices are derived from the theoretical analysis presented. The practical application of the concepts in the book is illustrated with a large number of practical designs performed for different classes of processes: thermal, fluid processing a...

  2. A Global PLASIMO Model for H2O Chemistry

    Science.gov (United States)

    Tadayon Mousavi, Samaneh; Koelman, Peter; Graef, Wouter; Mihailova, Diana; van Dijk, Jan; EPG/ Applied Physics/ Eindhoven University of Technology Team; Plasma Matters B. V. Team

    2016-09-01

    Global warming is one of the critical contemporary problems for mankind. Transformation of CO2 into fuels, like CH4, that are transportable with the current infrastructure seems a promising idea to solve this threatening issue. The final aim of this research is to produce CH4 by using microwave plasma in CO2 -H2 O mixture and follow-up catalytic processes. In this contribution we present a global model for H2 O chemistry that is based on the PLASIMO plasma modeling toolkit. The time variation of the electron energy and the species' densities are calculated based on the source and loss terms in plasma due to chemical reactions. The short simulation times of such models allow an efficient assessment and chemical reduction of the H2O chemistry, which is required for full spatially resolved simulations.

  3. The rotational excitation of the HCN and HNC molecules by H2 revisited

    Science.gov (United States)

    Hernández Vera, M.; Lique, F.; Dumouchel, F.; Hily-Blant, P.; Faure, A.

    2017-06-01

    HCN and HNC are two fundamental molecules in the dense interstellar medium. The HNC/HCN abundance ratio depends on the kinetic temperature and can be used to explore the physical and chemical conditions of star-forming regions. Modelling of HCN and HNC emissions from interstellar clouds requires to model their collisional and radiative excitations. We report the calculation of the HCN and HNC excitation rate coefficients among the first 26 rotational levels due to H2 collisions, for temperatures ranging from 5 to 500 K, using the exact close coupling and the approximate coupled states methods. We found a propensity for even Δj transitions in the case of HCN-para-H2 collisions, whereas a propensity for odd Δj transitions is observed in the case of HNC-para-H2 collisions. For collisions with ortho-H2, both molecules show a propensity rule favouring transitions with odd Δj. The rate coefficients for HCN and HNC differ significantly, showing clearly that the collisional excitation of the two isomers is different, especially for para-H2. We also evaluate the impact of these new data on the astrophysical modelling through radiative transfer calculations. It is shown that specific calculations have to be performed for the two isomers and that the HNC/HCN abundance ratio in cold molecular clouds cannot be estimated from line intensity ratio. Finally, observations of the two isotopologues H13CN and HN13C towards a sample of prestellar cores are presented, and the larger excitation temperature of HN13C is well reproduced by our excitation model.

  4. Thermodynamics of the formation of sulfuric acid dimers in the binary (H2SO4-H2O and ternary (H2SO4-H2O-NH3 system

    Directory of Open Access Journals (Sweden)

    A. Kürten

    2015-05-01

    Full Text Available Sulfuric acid is an important gas influencing atmospheric new particle formation (NPF. Both the binary (H2SO4-H2O system, and the ternary system involving ammonia (H2SO4-H2O-NH3 may be important in the free troposphere. An essential step in the nucleation of aerosol particles from gas-phase precursors is the formation of a dimer, so an understanding of the thermodynamics of dimer formation over a wide range of atmospheric conditions is essential to describe NPF. We have used the CLOUD chamber to conduct nucleation experiments for these systems at temperatures from 208 to 248 K. Neutral monomer and dimer concentrations of sulfuric acid were measured using a Chemical Ionization Mass Spectrometer (CIMS. From these measurements dimer evaporation rates in the binary system were derived for temperatures of 208 and 223 K. We compare these results to literature data from a previous study that was conducted at higher temperatures but is in good agreement with the present study. For the ternary system the formation of H2SO4 • NH3 is very likely an essential step in the formation of sulfuric acid dimers, which were measured at 210, 223, and 248 K. We estimate the thermodynamic properties (dH and dS of the H2SO4 • NH3 cluster using a simple heuristic model and the measured data. Furthermore, we report the first measurements of large neutral sulfuric acid clusters containing as many as 10 sulfuric acid molecules for the binary system using Chemical Ionization-Atmospheric Pressure interface-Time Of Flight (CI-APi-TOF mass spectrometry.

  5. The intriguing near-ultraviolet photochemistry of H 2Te

    Science.gov (United States)

    Underwood, J.; Chastaing, D.; Lee, S.; Boothe, P.; Flood, T. C.; Wittig, C.

    2002-08-01

    The ultraviolet absorption spectrum of H 2Te has a long wavelength tail that extends to 400 nm. Photodissociation at 355 nm yields TeH( 2Π 1/2) selectively relative to the 2Π 3/2 ground state; the transition moments for these channels lie in, and perpendicular to, the molecular plane, respectively. Vibrational structure in the region 380-400 nm is consistent with a shallow well in the adiabat leading to 2Π 1/2, akin to the one in HI leading to I( 2P 1/2). These effects have no counterparts with the light Group 6A dihydrides.

  6. Altered Sulfide (H2S) Metabolism in Ethylmalonic Encephalopathy

    OpenAIRE

    2013-01-01

    Hydrogen sulfide (sulfide, H2S) is a colorless, water-soluble gas with a typical smell of rotten eggs. In the past, it has been investigated for its role as a potent toxic gas emanating from sewers and swamps or as a by-product of industrial processes. At high concentrations, H2S is a powerful inhibitor of cytochrome c oxidase; in trace amounts, it is an important signaling molecule, like nitric oxide (NO) and carbon monoxide (CO), together termed “gasotransmitters.” This review will cover th...

  7. Assay Methods for H2S Biogenesis and Catabolism Enzymes

    Science.gov (United States)

    Banerjee, Ruma; Chiku, Taurai; Kabil, Omer; Libiad, Marouane; Motl, Nicole; Yadav, Pramod K.

    2015-01-01

    H2S is produced from sulfur-containing amino acids, cysteine and homocysteine, or a catabolite, 3-mercaptopyruvate, by three known enzymes: cystathionine β-synthase, γ-cystathionase, and 3-mercaptopyruvate sulfurtransferase. Of these, the first two enzymes reside in the cytoplasm and comprise the transsulfuration pathway, while the third enzyme is found both in the cytoplasm and in the mitochondrion. The following mitochondrial enzymes oxidize H2S: sulfide quinone oxidoreductase, sulfur dioxygenase, rhodanese, and sulfite oxidase. The products of the sulfide oxidation pathway are thiosulfate and sulfate. Assays for enzymes involved in the production and oxidative clearance of sulfide to thiosulfate are described in this chapter. PMID:25725523

  8. Counterintuitive alignment of H2(+) in intense femtosecond laser fields.

    Science.gov (United States)

    Frasinski, L J; Plumridge, J; Posthumus, J H; Codling, K; Taday, P F; Divall, E J; Langley, A J

    2001-03-19

    The multiphoton ionization of H2 has been studied using laser pulses of 266 nm wavelength, 250 fs duration, and 5x10(13) W/cm(2) peak intensity. Dissociation of H2(+) via one-photon absorption proceeds through two channels with markedly different proton angular distributions. The lower-energy channel (2.6 eV kinetic energy release) is produced in the bond softening mechanism, which generates parallel alignment. The higher-energy channel (3.5 eV) originates from population trapping in a light-induced bound state, where bond hardening generates orthogonal, counterintuitive alignment.

  9. Robust Schur Stability and Robust H^2 Performance

    DEFF Research Database (Denmark)

    Stoustrup, Jakob; Zhao, K.-Y.

    1996-01-01

    In this paper we address the problems of robust stability androbust QTR H^2 performance for uncertain discrete time systemswith nonlinear parametric uncertainties. We consider two families ofsystems with parametric uncertainties described by state space modelswhich offer a fairly general...... representation of most uncertain systemswith one or two parameters (the approach can be extended to more parameters).For these two families we obtain explicit expressions for the Schurstability radius and for the QTR H^2 robust performance radiusin the case of uncertainties with a single parameter. Moreover, we...

  10. H∞ /H2 model reduction through dilated linear matrix inequalities

    DEFF Re