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Sample records for intergalactic cold dust

  1. Intergalactic dust and quasar distribution

    International Nuclear Information System (INIS)

    Soltan, A.

    1979-01-01

    Non-homogeneous intergalactic extinction may considerably affect the quasar distribution. Especially samples of quasars isolated on the basis of B-V colours are subject to this phenomenon. Apparent grouping and close pairs of quasars reported in the literature may be a result of intergalactic dust. Using surface distribution of faint blue objects selected by Hawkins and Reddish it is estimated that intergalactic extinction in B should reach approximately 1 mag out to the redshift of approximately 1. This is slightly larger than predicted by theory and comparable to the mean dust density derived from observations. (Author)

  2. A SEARCH FOR DUST EMISSION IN THE LEO INTERGALACTIC CLOUD

    International Nuclear Information System (INIS)

    Bot, Caroline; Helou, George; Puget, Jeremie; Latter, William B.; Schneider, Stephen; Terzian, Yervant

    2009-01-01

    We present a search for infrared dust emission associated with the Leo cloud, a large intergalactic cloud in the M96 group. Mid-infrared and far-infrared images were obtained with the InfraRed Array Camera and the Multiband Imaging Photometer for Spitzer on the Spitzer Space Telescope. Our analysis of these maps is done at each wavelength relative to the H I spatial distribution. We observe a probable detection at 8 μm and a marginal detection at 24 μm associated with the highest H I column densities in the cloud. At 70 and 160 μm, upper limits on the dust emission are deduced. The level of the detection is low so that the possibility of a fortuitous cirrus clump or of an overdensity of extragalactic sources along the line of sight cannot be excluded. If this detection is confirmed, the quantities of dust inferred imply a dust-to-gas ratio in the intergalactic cloud up to a few times solar but no less than 1/20 solar. A confirmed detection would therefore exclude the possibility that the intergalactic cloud has a primordial origin. Instead, this large intergalactic cloud could therefore have been formed through interactions between galaxies in the group.

  3. Cosmic gamma-ray burst from intergalactic relativistic dust grains

    International Nuclear Information System (INIS)

    Dasgupta, A.K.

    1979-01-01

    Charged dust grains of radii a approximately 3 x 10 -6 approximately 3 x 10 -5 cm may acquire relativistic energy (>10 18 eV) in the intergalactic medium. In order to attain relativistic energy, dust grains have to move in and out ('scattering') of the magnetic field of the medium. A relativistic grain of radius a -5 cm with Lorentz factor γ approximately 10 3 approaching the Earth will break up either due to electrostatic charge or due to sputtering about 150 approximately 100 km, and may scatter solar photons via a fluorescence process. Dust grains may also melt into droplets in the solar vicinity and may contribute towards observed gamma-ray bursts. (Auth.)

  4. THE DISTORTION OF THE COSMIC MICROWAVE BACKGROUND SPECTRUM DUE TO INTERGALACTIC DUST

    Energy Technology Data Exchange (ETDEWEB)

    Imara, Nia; Loeb, Abraham, E-mail: nimara@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2016-07-10

    Infrared emission from intergalactic dust might compromise the ability of future experiments to detect subtle spectral distortions in the Cosmic Microwave Background (CMB) from the early universe. We provide the first estimate of foreground contamination of the CMB signal due to diffuse dust emission in the intergalactic medium. We use models of the extragalactic background light to calculate the intensity of intergalactic dust emission and find that emission by intergalactic dust at z ≲ 0.5 exceeds the sensitivity of the planned Primordial Inflation Explorer to CMB spectral distortions by 1–3 orders of magnitude. In the frequency range ν = 150–2400 GHz, we place an upper limit of 0.06% on the contribution to the far-infrared background from intergalactic dust emission.

  5. The cosmic transparency measured with Type Ia supernovae: implications for intergalactic dust

    Science.gov (United States)

    Goobar, Ariel; Dhawan, Suhail; Scolnic, Daniel

    2018-06-01

    Observations of high-redshift Type Ia supernovae (SNe Ia) are used to study the cosmic transparency at optical wavelengths. Assuming a flat Λ cold dark matter (ΛCDM) cosmological model based on baryon acoustic oscillations and cosmic microwave background measurements, redshift dependent deviations of SN Ia distances are used to constrain mechanisms that would dim light. The analysis is based on the most recent Pantheon SN compilation, for which there is a 0.03 ± 0.01 {({stat})} mag discrepancy in the distant supernova distance moduli relative to the ΛCDM model anchored by supernovae at z < 0.05. While there are known systematic uncertainties that combined could explain the observed offset, here we entertain the possibility that the discrepancy may instead be explained by scattering of supernova light in the intergalactic medium (IGM). We focus on two effects: Compton scattering by free electrons and extinction by dust in the IGM. We find that if the discrepancy is entirely due to dimming by dust, the measurements can be modelled with a cosmic dust density Ω _IGM^dust = 8 × 10^{-5} (1+z)^{-1}, corresponding to an average attenuation of 2 × 10-5 mag Mpc-1 in V band. Forthcoming SN Ia studies may provide a definitive measurement of the IGM dust properties, while still providing an unbiased estimate of cosmological parameters by introducing additional parameters in the global fits to the observations.

  6. Impact of galactic and intergalactic dust on the stellar EBL

    Czech Academy of Sciences Publication Activity Database

    Vavryčuk, Václav

    2016-01-01

    Roč. 361, č. 6 (2016), 198/1-198/8 ISSN 0004-640X Institutional support: RVO:67985530 Keywords : cosmic background radiation * interstellar dust * light extinction * universe opacity Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.622, year: 2016

  7. Effects on the spectrum of the cosmic microwave background due to intergalactic dust

    International Nuclear Information System (INIS)

    Kurtz, R.C.

    1981-01-01

    A model for intergalactic dust composed of graphite grains is presented. The model is examined in the context of the Rayleigh approximation for results due to long-wavelength scattering and absorption by the grains. The temperature of the scattering grains as a function of redshift is found, based on reasonable assumptions of the density of optical wavelength radiation in the universe. Mechanisms for aligning the grains on a scale large enough to produce polarization in the microwave region are discussed. The results are used to predict features that may be present in the observed cosmic microwave background radiation spectrum

  8. Distribution of dark matter, galaxies, and the intergalactic medium in a cold dark matter dominated universe

    International Nuclear Information System (INIS)

    Ryu, D.; Vishniac, E.T.; Chiang, W.H.

    1988-11-01

    The evolution and distribution of galaxies and the intergalactic medium (IGM) have been studied, along with collisionless dark matter in a Universe dominated by cold dark matter. The Einstein-deSitter universe with omega sub 0 = 1 and h = 0.5 was considered (here h = H sub 0 bar 100/kms/Mpc and H sub 0 is the present value of the Hubble constant). It is assumed that initially dark matter composes 90 pct and baryonic matter composes 10 pct of total mass, and that the primordial baryonic matter is comprised of H and He, with the abundance of He equal to 10 pct of H by number. Galaxies are allowed to form out of the IGM, if the total density and baryonic density satisfy an overdensity criterion. Subsequently, the newly formed galaxies release 10 to the 60th ergs of energy into the IGM over a period of 10 to the 8th years. Calculations have been performed with 32 to the 3rd dark matter particles and 32 to the 3rd cells in a cube with comoving side length L = 9.6/h Mpc. Dark matter particles and galaxies have been followed with an N-body code, while the IGM has been followed with a fluid code

  9. Distribution of dark matter, galaxies, and the intergalactic medium in a cold dark matter dominated universe

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, D.; Vishniac, E.T.; Chiang, W.H.

    1988-11-01

    The evolution and distribution of galaxies and the intergalactic medium (IGM) have been studied, along with collisionless dark matter in a Universe dominated by cold dark matter. The Einstein-deSitter universe with omega sub 0 = 1 and h = 0.5 was considered (here h = H sub 0 bar 100/kms/Mpc and H sub 0 is the present value of the Hubble constant). It is assumed that initially dark matter composes 90 pct and baryonic matter composes 10 pct of total mass, and that the primordial baryonic matter is comprised of H and He, with the abundance of He equal to 10 pct of H by number. Galaxies are allowed to form out of the IGM, if the total density and baryonic density satisfy an overdensity criterion. Subsequently, the newly formed galaxies release 10 to the 60th ergs of energy into the IGM over a period of 10 to the 8th years. Calculations have been performed with 32 to the 3rd dark matter particles and 32 to the 3rd cells in a cube with comoving side length L = 9.6/h Mpc. Dark matter particles and galaxies have been followed with an N-body code, while the IGM has been followed with a fluid code.

  10. Reionization in a cold dark matter universe: The feedback of galaxy formation on the intergalactic medium

    Science.gov (United States)

    Shapiro, Paul R.; Giroux, Mark L.; Babul, Arif

    1994-01-01

    We study the coupled evolution of the intergalactic medium (IGM) and the emerging structure in the universe in the context of the cold dark matter (CDM) model, with a special focus on the consequences of imposing reionization and the Gunn-Peterson constraint as a boundary condition on the model. We have calculated the time-varying density of the IGM by coupling our detailed, numerical calculations of the thermal and ionization balance and radiative transfer in a uniform, spatially averaged IGM of H and He, including the mean opacity of an evolving distribution of gas clumps which correspond to quasar absorption line clouds, to the linearized equations for the growth of density fluctuations in both the gaseous and dark matter components in a CDM universe. We use the linear growth equations to identify the fraction of the gas which must have collapsed out at each epoch, an approach similar in spirit to the so-called Press-Schechter formalism. We identify the IGM density with the uncollapsed baryon fraction. The collapsed fraction is postulated to be a source of energy injection into the IGM, by radiation or bulk hydrodynamical heating (e.g., via shocks) or both, at a rate which is marginally enough to satisfy the Gunn-Peterson constraint at z less than 5. Our results include the following: (1) We find that the IGM in a CDM model must have contained a substantial fraction of the total baryon density of the universe both during and after its reionization epoch. (2) As a result, our previous conclusion that the observed Quasi-Stellar Objects (QSOs) at high redshift are not sufficient to ionize the IGM enough to satisfy the Gunn-Peterson constraint is confirmed. (3) We predict a detectable He II Gunn-Peterson effect at 304(1 + z) A in the spectra of quasars at a range of redshift z greater than or approx. 3, depending on the nature of the sources of IGM reionization. (4) We find, moreover, that a CDM model with high bias parameter b (i.e., b greater than or approx. 2

  11. The cosmic transparency measured with Type Ia supernovae: implications for intergalactic dust

    Science.gov (United States)

    Goobar, Ariel; Dhawan, Suhail; Scolnic, Daniel

    2018-04-01

    Observations of high-redshift Type Ia supernovae (SNe Ia) are used to study the cosmic transparency at optical wavelengths. Assuming a flat ΛCDM cosmological model based on BAO and CMB results, redshift dependent deviations of SN Ia distances are used to constrain mechanisms that would dim light. The analysis is based on the most recent Pantheon SN compilation, for which there is a 0.03± 0.01 {(stat)} mag discrepancy in the distant supernova distance moduli relative to the ΛCDM model anchored by supernovae at z measurements can be modeled with a cosmic dust density Ω _IGM^dust = 8 \\cdot 10^{-5} (1+z)^{-1}, corresponding to an average attenuation of 2 . 10-5 mag Mpc-1 in V-band. Forthcoming SN Ia studies may provide a definitive measurement of the IGM dust properties, while still providing an unbiased estimate of cosmological parameters by introducing additional parameters in the global fits to the observations.

  12. The distribution of dark matter, galaxies, and the intergalactic medium in a cold dark matter dominated universe

    Science.gov (United States)

    Ryu, Dongsu; Vishniac, Ethan T.; Chiang, Wei-Hwan

    1988-01-01

    The evolution and distribution of galaxies and the intergalactic medium (IGM) have been studied, along with collisionless dark matter in a Universe dominated by cold dark matter. The Einstein-deSitter universe with omega sub 0 = 1 and h = 0.5 was considered (here h = H sub 0 bar 100/kms/Mpc and H sub 0 is the present value of the Hubble constant). It is assumed that initially dark matter composes 90 pct and baryonic matter composes 10 pct of total mass, and that the primordial baryonic matter is comprised of H and He, with the abundance of He equal to 10 pct of H by number. Galaxies are allowed to form out of the IGM, if the total density and baryonic density satisfy an overdensity criterion. Subsequently, the newly formed galaxies release 10 to the 60th ergs of energy into the IGM over a period of 10 to the 8th years. Calculations have been performed with 32 to the 3rd dark matter particles and 32 to the 3rd cells in a cube with comoving side length L = 9.6/h Mpc. Dark matter particles and galaxies have been followed with an N-body code, while the IGM has been followed with a fluid code.

  13. The distribution of dark matter, galaxies, and the intergalactic medium in a cold dark matter dominated universe

    Science.gov (United States)

    Ryu, Dongsu; Vishniac, Ethan T.; Chiang, Wei-Hwan

    1988-11-01

    The evolution and distribution of galaxies and the intergalactic medium (IGM) have been studied, along with collisionless dark matter in a Universe dominated by cold dark matter. The Einstein-deSitter universe with omega0 = 1 and h = 0.5 was considered (here h = H0 bar 100/kms/Mpc and H0 is the present value of the Hubble constant). It is assumed that initially dark matter composes 90 pct and baryonic matter composes 10 pct of total mass, and that the primordial baryonic matter is comprised of H and He, with the abundance of He equal to 10 pct of H by number. Galaxies are allowed to form out of the IGM, if the total density and baryonic density satisfy an overdensity criterion. Subsequently, the newly formed galaxies release 10 to the 60th ergs of energy into the IGM over a period of 10 to the 8th years. Calculations have been performed with 32 to the 3rd dark matter particles and 32 to the 3rd cells in a cube with comoving side length L = 9.6/h Mpc. Dark matter particles and galaxies have been followed with an N-body code, while the IGM has been followed with a fluid code.

  14. A model for the distribution of dark matter, galaxies, and the intergalactic medium in a cold dark matter-dominated universe

    Science.gov (United States)

    Ryu, Dongsu; Vishniac, Ethan T.; Chiang, Wei-Hwan

    1989-01-01

    The spatial distribution of the cold-dark-matter (CDM) and baryonic components of CDM-dominated cosmological models are characterized, summarizing the results of recent theoretical investigations. The evolution and distribution of matter in an Einstein-de Sitter universe on length scales small enough so that the Newtonian approximation is valid is followed chronologically, assuming (1) that the galaxies, CDM, and the intergalactic medium (IGM) are coupled by gravity, (2) that galaxies form by taking mass and momentum from the IGM, and (3) that the IGM responds to the energy input from the galaxies. The results of the numerical computations are presented in extensive graphs and discussed in detail.

  15. Suprathermal grains: on intergalactic magnetic fields

    International Nuclear Information System (INIS)

    Dasgupta, A.K.

    1979-01-01

    Charged dust grains of radii a approximately equal to 3 x 10 -6 to approximately 3 x 10 -5 cm may be driven out of the galaxy due to radiation pressure of starlight. Once clear of the main gas-dust layer, dust grains may then escape into intergalactic space. Such grains are virtually indestructible-being evaporated only during formation. The dust grains, once injected into the intergalactic medium, may acquire suprathermal energy, thus 'suprathermal grains' in collision with magnetized cloud by the Fermi process. In order to attain relativistic energy, suprathermal grains have to move in and out ('scattering') of the magnetic field of the medium. It is now well established that high energy cosmic rays are of the order 10 20 eV or more. It has been speculated that these high energy (> = 10 18 eV) cosmic ray particles are charged dust grains, of intergalactic origin. This is possible only if there exists a magnetic field in the intergalactic medium. (Auth.)

  16. H2, CO, and dust absorption through cold molecular clouds

    Science.gov (United States)

    Lacy, John H.; Sneden, Chris; Kim, Hwihyun; Jaffe, Daniel Thomas

    2017-06-01

    We have made observations with IGRINS on the Harlan J. Smith telescope at McDonald Observatory of near-infrared absorption by H2, CO, and dust toward stars behind molecular clouds, primarily the TMC. Prior to these observations, the abundance of H2 in molecular clouds, relative to the commonly used tracer CO, had only been measured toward a few embedded stars, which may be surrounded by atypical gas. The new observations provide a representative sample of these molecules in cold molecular gas. We find N(H2)/Av ~ 0.9e+21, N(CO)/Av ~ 1.6e+17, and H2/CO ~ 6000. The measured H2/CO ratio is consistent with that measured toward embedded stars in various molecular clouds, but half that derived from mm-wave observations of CO emission and star counts or other determinations of Av.

  17. Intergalactic extinction and the deceleration parameter

    International Nuclear Information System (INIS)

    Meinel, R.

    1981-01-01

    The deceleration parameter q 0 is calculated from the relation between apparent magnitudes m of the brightest galaxies in clusters and their redshifts z considering an intergalactic extinction. The calculation is valid for a Friedman universe, homogeneously filled with dust grains, assuming the extinction to be 0.5 mag at z = 1 and aΛ -1 -law of extinction (according to Oleak and Schmidt 1976). Using the m,z-values of Kristian, Sandage, and Westphal (1978) a formal value of q 0 approximately 2.1 is obtained instead of q 0 approximately 1.6 without consideration of intergalactic extinction. (author)

  18. Study on coal dust wettability measurement using cold briquetting technique

    Energy Technology Data Exchange (ETDEWEB)

    Li, M.; Xu, H.; Shu, X. [North China Institute of Science and Technology, Beijing (China). Department of Resource and Environmental Engineering

    2008-12-15

    Quantitative measuring of coal dust wettability is essential for the research and development of chemical coal dust suppressants in the field of dust control with wetting-agent-added water. The causes of low repeat rate and poor consistency in present lab testing of coal dust wettability are discussed. The influence of different briquetting pressure (from 0 to 6.5108 Pa) on the wet behavior of coal dust is investigated as a new way to quantitatively evaluate coal dust wettability. The study shows that there is a fairly high coincidence between the coal dust wettability data measured by the briquetting technique and the results gained from the lab dust suppression tests using an MCYZ apparatus designed by the authors. 9 refs., 8 figs., 2 tabs.

  19. Probing the Cold Dust Emission in the AB Aur Disk: A Dust Trap in a Decaying Vortex?

    Science.gov (United States)

    Fuente, Asunción; Baruteau, Clément; Neri, Roberto; Carmona, Andrés; Agúndez, Marcelino; Goicoechea, Javier R; Bachiller, Rafael; Cernicharo, José; Berné, Olivier

    2017-09-01

    One serious challenge for planet formation is the rapid inward drift of pebble-sized dust particles in protoplanetary disks. Dust trapping at local maxima in the disk gas pressure has received much theoretical attention but still lacks observational support. The cold dust emission in the AB Aur disk forms an asymmetric ring at a radius of about 120 au, which is suggestive of dust trapping in a gas vortex. We present high spatial resolution (0".58×0".78 ≈ 80×110 au) NOEMA observations of the 1.12 mm and 2.22 mm dust continuum emission from the AB Aur disk. Significant azimuthal variations of the flux ratio at both wavelengths indicate a size segregation of the large dust particles along the ring. Our continuum images also show that the intensity variations along the ring are smaller at 2.22 mm than at 1.12 mm, contrary to what dust trapping models with a gas vortex have predicted. Our two-fluid (gas+dust) hydrodynamical simulations demonstrate that this feature is well explained if the gas vortex has started to decay due to turbulent diffusion, and dust particles are thus losing the azimuthal trapping on different timescales depending on their size. The comparison between our observations and simulations allows us to constrain the size distribution and the total mass of solid particles in the ring, which we find to be of the order of 30 Earth masses, enough to form future rocky planets.

  20. Probing the Cold Dust Emission in the AB Aur Disk: A Dust Trap in a Decaying Vortex?

    Energy Technology Data Exchange (ETDEWEB)

    Fuente, Asunción; Bachiller, Rafael [Observatorio Astronómico Nacional (OAN, IGN), Apdo 112, E-28803 Alcalá de Henares (Spain); Baruteau, Clément; Carmona, Andrés; Berné, Olivier [IRAP, Université de Toulouse, CNRS, UPS, Toulouse (France); Neri, Roberto [Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, F-38406 Saint Martin d’Hères (France); Agúndez, Marcelino; Goicoechea, Javier R.; Cernicharo, José, E-mail: a.fuente@oan.es [Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), E-28049 Cantoblanco, Madrid (Spain)

    2017-09-01

    One serious challenge for planet formation is the rapid inward drift of pebble-sized dust particles in protoplanetary disks. Dust trapping at local maxima in the disk gas pressure has received much theoretical attention but still lacks observational support. The cold dust emission in the AB Aur disk forms an asymmetric ring at a radius of about 120 au, which is suggestive of dust trapping in a gas vortex. We present high spatial resolution (0.″58 × 0.″78 ≈ 80 × 110 au) NOEMA observations of the 1.12 mm and 2.22 mm dust continuum emission from the AB Aur disk. Significant azimuthal variations of the flux ratio at both wavelengths indicate a size segregation of the large dust particles along the ring. Our continuum images also show that the intensity variations along the ring are smaller at 2.22 mm than at 1.12 mm, contrary to what dust trapping models with a gas vortex have predicted. Our two-fluid (gas+dust) hydrodynamical simulations demonstrate that this feature is well explained if the gas vortex has started to decay due to turbulent diffusion, and dust particles are thus losing the azimuthal trapping on different timescales depending on their size. The comparison between our observations and simulations allows us to constrain the size distribution and the total mass of solid particles in the ring, which we find to be of the order of 30 Earth masses, enough to form future rocky planets.

  1. COLD DUST BUT WARM GAS IN THE UNUSUAL ELLIPTICAL GALAXY NGC 4125

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, C. D.; Cridland, A.; Foyle, K.; Parkin, T. J.; Cooper, E. Mentuch [Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1 (Canada); Roussel, H. [Institut d' Astrophysique de Paris, Université Pierre et Marie Curie, CNRS UMR 7095, F-75014 Paris (France); Sauvage, M.; Lebouteiller, V.; Madden, S. [Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot DAPNIA/Service d' Astrophysique, Bât. 709, CEA-Saclay, F-91191 Gif-sur-Yvette Cedex (France); Smith, M. W. L.; Gear, W. [School of Physics and Astronomy, Cardiff University, The Parade, Cardiff CF24 3AA (United Kingdom); Baes, M.; De Looze, I. [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent (Belgium); Bendo, G. [UK ALMA Regional Centre Node, Jodrell Bank Center for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Boquien, M.; Boselli, A.; Ciesla, L. [Aix-Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Clements, D. L. [Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom); Cooray, A. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Galametz, M. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); and others

    2013-10-20

    Data from the Herschel Space Observatory have revealed an unusual elliptical galaxy, NGC 4125, which has strong and extended submillimeter emission from cold dust but only very strict upper limits to its CO and H I emission. Depending on the dust emissivity, the total dust mass is 2-5 × 10{sup 6} M {sub ☉}. While the neutral gas-to-dust mass ratio is extremely low (<12-30), including the ionized gas traced by [C II] emission raises this limit to <39-100. The dust emission follows a similar r {sup 1/4} profile to the stellar light and the dust to stellar mass ratio is toward the high end of what is found in nearby elliptical galaxies. We suggest that NGC 4125 is currently in an unusual phase where evolved stars produced in a merger-triggered burst of star formation are pumping large amounts of gas and dust into the interstellar medium. In this scenario, the low neutral gas-to-dust mass ratio is explained by the gas being heated to temperatures ≥10{sup 4} K faster than the dust is evaporated. If galaxies like NGC 4125, where the far-infrared emission does not trace neutral gas in the usual manner, are common at higher redshift, this could have significant implications for our understanding of high redshift galaxies and galaxy evolution.

  2. Intergalactic Travel Bureau

    Science.gov (United States)

    Koski, Olivia; Rosin, Mark; Guerilla Science Team

    2014-03-01

    The Intergalactic Travel Bureau is an interactive theater outreach experience that engages the public in the incredible possibilities of space tourism. The Bureau is staffed by professional actors, who play the role of space travel agents, and professional astrophysicists, who play the role of resident scientists. Members of the public of all ages were invited to visit with bureau staff to plan the vacation of their dreams-to space. We describe the project's successful nine day run in New York in August 2013. Funded by the American Physical Society Public Outreach and Informing the Public Grants.

  3. A STUBBORNLY LARGE MASS OF COLD DUST IN THE EJECTA OF SUPERNOVA 1987A

    Energy Technology Data Exchange (ETDEWEB)

    Matsuura, M.; Barlow, M. J. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Dwek, E. [Observational Cosmology Laboratory Code 665, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Babler, B. [Department of Astronomy, 475 North Charter Street, University of Wisconsin, Madison, WI 53706 (United States); Baes, M.; Fritz, Jacopo [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent (Belgium); Meixner, M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Cernicharo, José [Departamento de Astrofísica, Centro de Astrobiología, CSIC-INTA, Ctra. de Torrejón a Ajalvir km 4, E-28850 Madrid (Spain); Clayton, Geoff C. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Dunne, L. [Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8140 (New Zealand); Fransson, C.; Lundqvist, P. [The Oskar Klein Centre, Department of Astronomy, Stockholm University, Albanova, SE-10691 Stockholm (Sweden); Gear, Walter; Gomez, H. L. [School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA (United Kingdom); Groenewegen, M. A. T. [Koninklijke Sterrenwacht van België, Ringlaan 3, 1180 Brussel (Belgium); Indebetouw, R. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904 (United States); Ivison, R. J. [SUPA, Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Jerkstrand, A. [Astrophysics Research Centre, School of Mathematics and Physics, Queen' s University Belfast, Belfast BT7 1NN (United Kingdom); Lebouteiller, V. [AIM, CEA/Saclay, L' Orme des Merisiers, F-91191 Gif-sur-Yvette (France); Lim, T. L., E-mail: mikako@star.ucl.ac.uk [RAL Space, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom); and others

    2015-02-10

    We present new Herschel photometric and spectroscopic observations of Supernova 1987A, carried out in 2012. Our dedicated photometric measurements provide new 70 μm data and improved imaging quality at 100 and 160 μm compared to previous observations in 2010. Our Herschel spectra show only weak CO line emission, and provide an upper limit for the 63 μm [O I] line flux, eliminating the possibility that line contaminations distort the previously estimated dust mass. The far-infrared spectral energy distribution (SED) is well fitted by thermal emission from cold dust. The newly measured 70 μm flux constrains the dust temperature, limiting it to nearly a single temperature. The far-infrared emission can be fitted by 0.5 ± 0.1 M {sub ☉} of amorphous carbon, about a factor of two larger than the current nucleosynthetic mass prediction for carbon. The observation of SiO molecules at early and late phases suggests that silicates may also have formed and we could fit the SED with a combination of 0.3 M {sub ☉} of amorphous carbon and 0.5 M {sub ☉} of silicates, totalling 0.8 M {sub ☉} of dust. Our analysis thus supports the presence of a large dust reservoir in the ejecta of SN 1987A. The inferred dust mass suggests that supernovae can be an important source of dust in the interstellar medium, from local to high-redshift galaxies.

  4. A model for the distribution of dark matter, galaxies, and the intergalactic medium in a cold dark matter-dominated universe

    International Nuclear Information System (INIS)

    Ryu, D.; Vishniac, E.T.; Chiang, W.H.

    1989-01-01

    Until now, most studies on the cold dark matter (CDM) universe have considered only the distribution of the dark matter and compared that with the observed distribution of galaxies. Even though the dark matter determines the overall dynamics of the large-scale structure, galaxies form out of the baryonic matter whose density and velocity distributions can be different from those of the dark matter, depending on the thermal history of the universe. In this paper, the authors study both the dark matter component and the baryonic component, that is, galaxies and the IGM, with several simplifying assumptions, by explicitly following the evolution. The dark matter, galaxies, and IGM are coupled through gravity; galaxies form out of the IGM by taking mass and momentum, whereas the IGM responds to the energy input from the galaxies

  5. Physics of the interstellar and intergalactic medium

    CERN Document Server

    Draine, Bruce T

    2010-01-01

    This is a comprehensive and richly illustrated textbook on the astrophysics of the interstellar and intergalactic medium--the gas and dust, as well as the electromagnetic radiation, cosmic rays, and magnetic and gravitational fields, present between the stars in a galaxy and also between galaxies themselves. Topics include radiative processes across the electromagnetic spectrum; radiative transfer; ionization; heating and cooling; astrochemistry; interstellar dust; fluid dynamics, including ionization fronts and shock waves; cosmic rays; distribution and evolution of the interstellar medium; and star formation. While it is assumed that the reader has a background in undergraduate-level physics, including some prior exposure to atomic and molecular physics, statistical mechanics, and electromagnetism, the first six chapters of the book include a review of the basic physics that is used in later chapters. This graduate-level textbook includes references for further reading, and serves as an invaluable resourc...

  6. Dust grain dynamics due to nonuniform and nonstationary high-frequency radiations in cold magnetoplasmas

    Directory of Open Access Journals (Sweden)

    A. K. Nekrasov

    2006-03-01

    Full Text Available A general nonlinear theory for low-frequency electromagnetic field generation due to high-frequency nonuniform and nonstationary electromagnetic radiations in cold, uniform, multicomponent, dusty magnetoplasmas is developed. This theory permits us to consider the nonlinear action of all waves that can exist in such plasmas. The equations are derived for the dust grain velocities in the low-frequency nonlinear electric fields arising due to the presence of electromagnetic cyclotron waves travelling along the background magnetic field. The dust grains are considered to be magnetized as well as unmagnetized. Different regimes for the dust particle dynamics, depending on the spatio-temporal change of the wave amplitudes and plasma parameters, are discussed. It is shown that induced nonlinear electric fields can have both an electrostatic and electromagnetic nature. Conditions for maximum dust acceleration are found. The results obtained may be useful for understanding the possible mechanisms of dust grain dynamics in astrophysical, cosmic and laboratory plasmas under the action of nonuniform and nonstationary electromagnetic waves.

  7. Spatial and temporal distributions of Martian north polar cold spots before, during, and after the global dust storm of 2001

    Science.gov (United States)

    Cornwall, C.; Titus, T.N.

    2009-01-01

    In the 1970s, Mariner and Viking observed features in the Mars northern polar region that were a few hundred kilometers in diameter with 20 fj,m brightness temperatures as low as 130 K (considerably below C02 ice sublimation temperatures). Over the past decade, studies have shown that these areas (commonly called "cold spots") are usually due to emissivity effects of frost deposits and occasionally to active C02 snowstorms. Three Mars years of Mars Global Surveyor Thermal Emission Spectrometer data were used to observe autumn and wintertime cold spot activity within the polar regions. Many cold spots formed on or near scarps of the perennial cap, probably induced by adiabatic cooling due to orographic lifting. These topographically associated cold spots were often smaller than those that were not associated with topography. We determined that initial grain sizes within the cold spots were on the order of a few millimeters, assuming the snow was uncontaminated by dust or water ice. On average, the half-life of the cold spots was 5 Julian days. The Mars global dust storm in 2001 significantly affected cold spot activity in the north polar region. Though overall perennial cap cold spot activity seemed unaffected, the distribution of cold spots did change by a decrease in the number of topographically associated cold spots and an increase in those not associated with topography. We propose that the global dust storm affected the processes that form cold spots and discuss how the global dust storm may have affected these processes. ?? 2009 by the American Geophysical Union.

  8. Reduction disintegration mechanism of cold briquettes from blast furnace dust and sludge

    Directory of Open Access Journals (Sweden)

    Leandro Rocha Lemos

    2015-07-01

    Full Text Available It is important to understand the reduction disintegration mechanism in ferriferous burden that is used in blast furnaces. The behavior of this burden in the granular zone of this metallurgical reactor is important for smooth operation. The objective of this work was to prepare cold self-reducing briquettes using blast furnace dust and sludge and binders and compare the reduction disintegration index (RDI of these agglomerates with conventional ferriferous burdens such as pellets, sinter and iron ore. In the present work, 25 different mixtures were prepared to produce briquettes in two geometries: pillow and cylindrical. The RDI value was determined for the briquettes that passed the tumbling test.

  9. Herschel and SCUBA-2 observations of dust emission in a sample of Planck cold clumps

    Science.gov (United States)

    Juvela, Mika; He, Jinhua; Pattle, Katherine; Liu, Tie; Bendo, George; Eden, David J.; Fehér, Orsolya; Michel, Fich; Fuller, Gary; Hirano, Naomi; Kim, Kee-Tae; Li, Di; Liu, Sheng-Yuan; Malinen, Johanna; Marshall, Douglas J.; Paradis, Deborah; Parsons, Harriet; Pelkonen, Veli-Matti; Rawlings, Mark G.; Ristorcelli, Isabelle; Samal, Manash R.; Tatematsu, Ken'ichi; Thompson, Mark; Traficante, Alessio; Wang, Ke; Ward-Thompson, Derek; Wu, Yuefang; Yi, Hee-Weon; Yoo, Hyunju

    2018-04-01

    Context. Analysis of all-sky Planck submillimetre observations and the IRAS 100 μm data has led to the detection of a population of Galactic cold clumps. The clumps can be used to study star formation and dust properties in a wide range of Galactic environments. Aims: Our aim is to measure dust spectral energy distribution (SED) variations as a function of the spatial scale and the wavelength. Methods: We examined the SEDs at large scales using IRAS, Planck, and Herschel data. At smaller scales, we compared JCMT/SCUBA-2 850 μm maps with Herschel data that were filtered using the SCUBA-2 pipeline. Clumps were extracted using the Fellwalker method, and their spectra were modelled as modified blackbody functions. Results: According to IRAS and Planck data, most fields have dust colour temperatures TC 14-18 K and opacity spectral index values of β = 1.5-1.9. The clumps and cores identified in SCUBA-2 maps have T 13 K and similar β values. There are some indications of the dust emission spectrum becoming flatter at wavelengths longer than 500 μm. In fits involving Planck data, the significance is limited by the uncertainty of the corrections for CO line contamination. The fits to the SPIRE data give a median β value that is slightly above 1.8. In the joint SPIRE and SCUBA-2 850 μm fits, the value decreases to β 1.6. Most of the observed T-β anticorrelation can be explained by noise. Conclusions: The typical submillimetre opacity spectral index β of cold clumps is found to be 1.7. This is above the values of diffuse clouds, but lower than in some previous studies of dense clumps. There is only tentative evidence of a T-β anticorrelation and β decreasing at millimetre wavelengths. Planck (http://www.esa.int/Planck) is a project of the European Space Agency - ESA - with instruments provided by two scientific consortia funded by ESA member states (in particular the lead countries: France and Italy) with contributions from NASA (USA), and telescope reflectors

  10. VARIATIONS BETWEEN DUST AND GAS IN THE DIFFUSE INTERSTELLAR MEDIUM. II. SEARCH FOR COLD GAS

    Energy Technology Data Exchange (ETDEWEB)

    Reach, William T. [Universities Space Research Association, MS 232-11, Moffett Field, CA 94035 (United States); Heiles, Carl [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Bernard, Jean-Philippe, E-mail: wreach@sofia.usra.edu [Université de Toulouse, Institut de Recherche en Astrophysique et Planétologie, F-31028 Toulouse cedex 4 (France)

    2017-01-01

    The content of interstellar clouds, in particular the inventory of diffuse molecular gas, remains uncertain. We identified a sample of isolated clouds, approximately 100 M {sub ⊙} in size, and used the dust content to estimate the total amount of gas. In Paper I, the total inferred gas content was found significantly larger than that seen in 21 cm emission measurements of H i. In this paper we test the hypothesis that the apparent excess “dark” gas is cold H i, which would be evident in absorption but not in emission due to line saturation. The results show that there is not enough 21 cm absorption toward the clouds to explain the total amount of “dark” gas.

  11. A Comprehensive Study of the Cold Dust and Gas in Galactic Winds

    Science.gov (United States)

    Veilleux, Sylvain

    Galaxies do not evolve statically or in isolation, but instead are being structurally rearranged by stellar and gas motions and are interacting dynamically with their halos and environments. Galactic winds (GWs), or large-scale outflows of material from disks and spheroids, are a primary means by which this structural evolution and ongoing interplay occur. Major outstanding questions remain, however, about the precise impact that GWs make. Both from the ground and from space, our recent effort has focused on the all-important cold gas and dust components of GWs. They are the key to understanding GWs for at least three reasons: i. Outflows have to affect the cold gas and dust out of which stars form if they are to inhibit star formation in the host galaxy. ii. We have found in recent years that the cold gas phase is the energetically dominant phase of many GWs. iii. The kinematics and dynamics of the cold gas phase show trends with AGN luminosity that suggest that we are finally seeing the long-sought ``smoking gun'' of quasar feedback. However, these conclusions rest on very limited samples and are thus tentative. Remarkably, the Herschel and Spitzer Science Archives are treasure troves of high-quality images and spectra on GWs that could drastically improve this sad state of affairs, once these data are analyzed. Here we propose to carry out for the first time a single, self-consistent analysis of all of these data, and combine the results with our extensive ancillary ground-based data (Gemini, VLT, JVLA, ALMA, IRAM, and Keck) to capture all of the gas phases involved in GWs. This multiwavelength approach is unique and goes much beyond individual targeted programs in this area. We are interested in studying all GWs, regardless of redshifts: For the nearest (systems, we will examine deep Herschel and Spitzer images to derive the dust content of GWs and the circumgalactic environment in general. Our sample size (~50 GWs and control galaxies) will allow us to

  12. Observing Interstellar and Intergalactic Magnetic Fields

    Science.gov (United States)

    Han, J. L.

    2017-08-01

    Observational results of interstellar and intergalactic magnetic fields are reviewed, including the fields in supernova remnants and loops, interstellar filaments and clouds, Hii regions and bubbles, the Milky Way and nearby galaxies, galaxy clusters, and the cosmic web. A variety of approaches are used to investigate these fields. The orientations of magnetic fields in interstellar filaments and molecular clouds are traced by polarized thermal dust emission and starlight polarization. The field strengths and directions along the line of sight in dense clouds and cores are measured by Zeeman splitting of emission or absorption lines. The large-scale magnetic fields in the Milky Way have been best probed by Faraday rotation measures of a large number of pulsars and extragalactic radio sources. The coherent Galactic magnetic fields are found to follow the spiral arms and have their direction reversals in arms and interarm regions in the disk. The azimuthal fields in the halo reverse their directions below and above the Galactic plane. The orientations of organized magnetic fields in nearby galaxies have been observed through polarized synchrotron emission. Magnetic fields in the intracluster medium have been indicated by diffuse radio halos, polarized radio relics, and Faraday rotations of embedded radio galaxies and background sources. Sparse evidence for very weak magnetic fields in the cosmic web is the detection of the faint radio bridge between the Coma cluster and A1367. Future observations should aim at the 3D tomography of the large-scale coherent magnetic fields in our Galaxy and nearby galaxies, a better description of intracluster field properties, and firm detections of intergalactic magnetic fields in the cosmic web.

  13. Astronomer's new guide to the galaxy: largest map of cold dust revealed

    Science.gov (United States)

    2009-07-01

    Astronomers have unveiled an unprecedented new atlas of the inner regions of the Milky Way, our home galaxy, peppered with thousands of previously undiscovered dense knots of cold cosmic dust -- the potential birthplaces of new stars. Made using observations from the APEX telescope in Chile, this survey is the largest map of cold dust so far, and will prove an invaluable map for observations made with the forthcoming ALMA telescope, as well as the recently launched ESA Herschel space telescope. ESO PR Photo 24a/09 View of the Galactic Plane from the ATLASGAL survey (annotated and in five sections) ESO PR Photo 24b/09 View of the Galactic Plane from the ATLASGAL survey (annotated) ESO PR Photo 24c/09 View of the Galactic Plane from the ATLASGAL survey (in five sections) ESO PR Photo 24d/09 View of the Galactic Plane from the ATLASGAL survey ESO PR Photo 24e/09 The Galactic Centre and Sagittarius B2 ESO PR Photo 24f/09 The NGC 6357 and NGC 6334 nebulae ESO PR Photo 24g/09 The RCW120 nebula ESO PR Video 24a/09 Annotated pan as seen by the ATLASGAL survey This new guide for astronomers, known as the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) shows the Milky Way in submillimetre-wavelength light (between infrared light and radio waves [1]). Images of the cosmos at these wavelengths are vital for studying the birthplaces of new stars and the structure of the crowded galactic core. "ATLASGAL gives us a new look at the Milky Way. Not only will it help us investigate how massive stars form, but it will also give us an overview of the larger-scale structure of our galaxy", said Frederic Schuller from the Max Planck Institute for Radio Astronomy, leader of the ATLASGAL team. The area of the new submillimetre map is approximately 95 square degrees, covering a very long and narrow strip along the galactic plane two degrees wide (four times the width of the full Moon) and over 40 degrees long. The 16 000 pixel-long map was made with the LABOCA submillimetre

  14. Intergalactic stellar populations in intermediate redshift clusters

    Science.gov (United States)

    Melnick, J.; Giraud, E.; Toledo, I.; Selman, F.; Quintana, H.

    2012-11-01

    A substantial fraction of the total stellar mass in rich clusters of galaxies resides in a diffuse intergalactic component usually referred to as the intracluster light (ICL). Theoretical models indicate that these intergalactic stars originate mostly from the tidal interaction of the cluster galaxies during the assembly history of the cluster, and that a significant fraction of these stars could have formed in situ from the late infall of cold metal-poor gas clouds on to the cluster. However, these models also overpredict the fraction of stellar mass in the ICL by a substantial margin, something that is still not well understood. The models also make predictions about the age distribution of the ICL stars, which may provide additional observational constraints. Here we present population synthesis models for the ICL of an intermediate redshift (z = 0.29) X-ray cluster that we have extensively studied in previous papers. The advantage of observing intermediate redshift clusters rather than nearby ones is that the former fit the field of view of multi-object spectrographs in 8-m telescopes and therefore permit us to encompass most of the ICL with only a few well-placed slits. In this paper we show that by stacking spectra at different locations within the ICL it is possible to reach sufficiently high signal-to-noise ratios to fit population synthesis models and derive meaningful results. The models provide ages and metallicities for the dominant populations at several different locations within the ICL and the brightest cluster galaxies (BCG) halo, as well as measures of the kinematics of the stars as a function of distance from the BCG. We thus find that the ICL in our cluster is dominated by old metal-rich stars, at odds with what has been found in nearby clusters where the stars that dominate the ICL are old and metal poor. While we see weak evidence of a young, metal-poor component, if real, these young stars would amount to less than 1 per cent of the total ICL

  15. Multifrequency survey of the intergalactic cloud in the M96 group

    International Nuclear Information System (INIS)

    Schneider, S.E.; Skrutskie, M.F.; Hacking, P.B.; Young, J.S.; Dickman, R.L.

    1989-01-01

    The intergalactic cloud of neutral hydrogen in the M96 group are examined for signs of emission over a wide range of frequencies, from radio waves to X rays. Past or present stellar activity in the gas might have been expected to produce detectable visual infrared, CO, OH, or radio recombination-line emission. None was detected. The limits are used to study physical conditions in the intergalactic gas. In particular, B and V band limits on starlight and IRAS limits on the presence of dust strongly constrain the presence of stars or stellar by-products. However, given the uncertainties about physical conditions in the intergalactic environment, it is difficult to rule out entirely the presence of stellar-processed materials. Results of neutral hydrogen mapping from a large-scale survey of the intergalactic cloud and surrounding region are also presented. These observations confirm that the gas is confined to a large ringlike structure. The simplest interpretation remains that the intergalactic gas in Leo is primordial. 36 references

  16. Electrical time resolved metrology of dust particles growing in low pressure cold plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Wattieaux, Gaeetan [PRISME, Orleans University, 12 rue de Blois BP 6744, 45067 Orleans cedex 2 (France); Mezeghrane, Abdelaziz [LPCQ, Mouloud Mammeri University, Tizi-Ouzou (Algeria); Boufendi, Laiefa [GREMI, Orleans University, 14 rue d' Issoudun BP 6744, 45067 Orleans cedex 2 (France)

    2011-09-15

    The electrical parameters of a capacitively coupled radiofrequency (CCRF) discharge change significantly when dust arises in the discharge. This work demonstrates the ability to follow in real time the evolution of the size and of the concentration of dust particles forming in a CCRF discharge from the variation of the electron density and of the self-bias voltage of the active electrode. According to experimental findings, it appears that the variation of this self-bias voltage depends on the surface of the dust particles. This trend is confirmed by an analytical modelling considering the low frequency behaviour of the phenomenon.

  17. INTERGALACTIC 'PIPELINE' FUNNELS MATTER BETWEEN COLLIDING GALAXIES

    Science.gov (United States)

    2002-01-01

    This visible-light picture, taken by NASA's Hubble Space Telescope, reveals an intergalactic 'pipeline' of material flowing between two battered galaxies that bumped into each other about 100 million years ago. The pipeline [the dark string of matter] begins in NGC 1410 [the galaxy at left], crosses over 20,000 light-years of intergalactic space, and wraps around NGC 1409 [the companion galaxy at right] like a ribbon around a package. Although astronomers have taken many stunning pictures of galaxies slamming into each other, this image represents the clearest view of how some interacting galaxies dump material onto their companions. These results are being presented today at the 197th meeting of the American Astronomical Society in San Diego, CA. Astronomers used the Space Telescope Imaging Spectrograph to confirm that the pipeline is a continuous string of material linking both galaxies. Scientists believe that the tussle between these compact galaxies somehow created the pipeline, but they're not certain why NGC 1409 was the one to begin gravitationally siphoning material from its partner. And they don't know where the pipeline begins in NGC 1410. More perplexing to astronomers is that NGC 1409 is seemingly unaware that it is gobbling up a steady flow of material. A stream of matter funneling into the galaxy should have fueled a spate of star birth. But astronomers don't see it. They speculate that the gas flowing into NGC 1409 is too hot to gravitationally collapse and form stars. Astronomers also believe that the pipeline itself may contribute to the star-forming draught. The pipeline, a pencil-thin, 500 light-year-wide string of material, is moving a mere 0.02 solar masses of matter a year. Astronomers estimate that NGC 1409 has consumed only about a million solar masses of gas and dust, which is not enough material to spawn some of the star-forming regions seen in our Milky Way. The low amount means that there may not be enough material to ignite star birth

  18. Intergalactic medium heating by dark matter

    NARCIS (Netherlands)

    Ripamonti, E.; Mapelli, M.; Ferrara, A.

    2006-01-01

    Abstract: We derive the evolution of the energy deposition in the intergalactic medium (IGM) by dark matter (DM) decays/annihilations for both sterile neutrinos and light dark matter (LDM) particles. At z > 200 sterile neutrinos transfer a fraction f_abs~0.5 of their rest mass energy into the IGM;

  19. Mid-Infrared Observations of Possible Intergalactic Star Forming Regions in the Leo Ring

    Science.gov (United States)

    Giroux, Mark; Smith, B.; Struck, C.

    2011-05-01

    Within the Leo group of galaxies lies a gigantic loop of intergalactic gas known as the Leo Ring. Not clearly associated with any particular galaxy, its origin remains uncertain. It may be a primordial intergalactic cloud alternatively, it may be a collision ring, or have a tidal origin. Combining archival Spitzer images of this structure with published UV and optical data, we investigate the mid-infrared properties of possible knots of star formation in the ring. These sources are very faint in the mid-infrared compared to star forming regions in the tidal features of interacting galaxies. This suggests they are either deficient in dust, or they may not be associated with the ring.

  20. Use of Cement Kiln Dust, Blast Furnace Slag and Marble Sludge in the Manufacture of Sustainable Artificial Aggregates by Means of Cold Bonding Pelletization.

    Science.gov (United States)

    Colangelo, Francesco; Cioffi, Raffaele

    2013-07-25

    In this work, three different samples of solid industrial wastes cement kiln dust (CKD), granulated blast furnace slag and marble sludge were employed in a cold bonding pelletization process for the sustainable production of artificial aggregates. The activating action of CKD components on the hydraulic behavior of the slag was explored by evaluating the neo-formed phases present in several hydrated pastes. Particularly, the influence of free CaO and sulfates amount in the two CKD samples on slag reactivity was evaluated. Cold bonded artificial aggregates were characterized by determining physical and mechanical properties of two selected size fractions of the granules for each studied mixture. Eighteen types of granules were employed in C28/35 concrete manufacture where coarser natural aggregate were substituted with the artificial ones. Finally, lightweight concretes were obtained, proving the suitability of the cold bonding pelletization process in artificial aggregate sustainable production.

  1. Use of Cement Kiln Dust, Blast Furnace Slag and Marble Sludge in the Manufacture of Sustainable Artificial Aggregates by Means of Cold Bonding Pelletization

    Directory of Open Access Journals (Sweden)

    Raffaele Cioffi

    2013-07-01

    Full Text Available In this work, three different samples of solid industrial wastes cement kiln dust (CKD, granulated blast furnace slag and marble sludge were employed in a cold bonding pelletization process for the sustainable production of artificial aggregates. The activating action of CKD components on the hydraulic behavior of the slag was explored by evaluating the neo-formed phases present in several hydrated pastes. Particularly, the influence of free CaO and sulfates amount in the two CKD samples on slag reactivity was evaluated. Cold bonded artificial aggregates were characterized by determining physical and mechanical properties of two selected size fractions of the granules for each studied mixture. Eighteen types of granules were employed in C28/35 concrete manufacture where coarser natural aggregate were substituted with the artificial ones. Finally, lightweight concretes were obtained, proving the suitability of the cold bonding pelletization process in artificial aggregate sustainable production.

  2. Interactions between intergalactic medium and galaxies

    International Nuclear Information System (INIS)

    Einasto, J.; Saar, E.

    1977-01-01

    The interaction of galaxies with the environmental gas both in clusters and in small groups of galaxies is investigated. Interaction between galaxies and the ambient medium can be considered simply as final touches in the process of galaxy formation. Large relative velocities of galaxies in their clusters and of the intercluster gas result in a loss of the intergalactic gas, that in its turn affects the morphology of cluster galaxies. Interaction between the coronal clouds and the gas in the disk of spiral galaxies may result in regular patterns of star formation and in the bending of planes of galaxies

  3. New photoionization models of intergalactic clouds

    Science.gov (United States)

    Donahue, Megan; Shull, J. M.

    1991-01-01

    New photoionization models of optically thin low-density intergalactic gas at constant pressure, photoionized by QSOs, are presented. All ion stages of H, He, C, N, O, Si, and Fe, plus H2 are modeled, and the column density ratios of clouds at specified values of the ionization parameter of n sub gamma/n sub H and cloud metallicity are predicted. If Ly-alpha clouds are much cooler than the previously assumed value, 30,000 K, the ionization parameter must be very low, even with the cooling contribution of a trace component of molecules. If the clouds cool below 6000 K, their final equilibrium must be below 3000 K, owing to the lack of a stable phase between 6000 and 3000 K. If it is assumed that the clouds are being irradiated by an EUV power-law continuum typical of WSOs, with J0 = 10 exp -21 ergs/s sq cm Hz, typical cloud thicknesses along the line of sight that are much smaller than would be expected from shocks, thermal instabilities, or gravitational collapse are derived.

  4. The physical state of the intergalactic medium

    International Nuclear Information System (INIS)

    Barcons, X.; Fabian, A.C.; Rees, M.J.

    1991-01-01

    Because the process of galaxy formation is most unlikely to be perfectly efficient, there is a strong possibility that some baryonic gas remains outside collapsed structures such as galaxies and clusters of galaxies. What fraction of the baryonic content of the Universe resides in this intergalactic medium (IGM) and what physical state it is in are open questions. Here we use observational limits on the density of neutral hydrogen in the IGM, on the lack of deviations from a black-body spectrum of the cosmic microwave background (MBR), and on the extragalactic component of the soft X-ray background (XRB) to constrain the state of the IGM. From the lack of MBR fluctuations, any energetic IGM (containing as much energy as the binding energy in galaxies) is inferred to be smoothly distributed on scales greater than galactic. This rules out hot IGM models for the origin of the hard X-ray background, as well as the hypothesis that cosmic explosions may have given rise to cosmological structure on scales larger than galaxies. (author)

  5. The Intergalactic Medium as a Cosmological Tool

    Energy Technology Data Exchange (ETDEWEB)

    Viel, Matteo, E-mail: viel@oats.inaf.i [INAF - Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, I-34131 Trieste (Italy); INFN/National Institute for Nuclear Physics, Via Valerio 2, I-34127 Trieste (Italy)

    2009-10-15

    In this talk I will review the capabilities of high-resolution (UVES and Keck) and low resolution (Sloan Digital Sky Survey - SDSS) quasar (QSO) Lyman-alpha absorption spectra as cosmological tools to probe the dark matter distribution in the high redshift universe. I will first summarize the results in terms of cosmological parameters and then discuss consistency with the parameters derived from other large scale structure observable such as the Cosmic Microwave Background (CMB) and weak lensing surveys. When the Lyman-alpha forest data are combined with CMB data and the weak lensing results of the z-COSMOS survey the constraints are: sigma{sub 8}=0.800+-0.023, n{sub s}=0.971+-0.011OMEGA{sub m}=0.247+-0.016 (1-sigma error bars), in perfect agreement with the CMB results of WMAP year five alone. I will briefly address the importance of Lyman-alpha for constraining the neutrino mass fraction. Furthermore, I will present constraints on the mass of warm dark matter (WDM) particles derived from the Lyman-alpha flux power spectrum of 55 high-resolution HIRES Lyman-alpha forest spectra at 2.0=1.2keV (2sigma) if the WDM consists of early decoupled thermal relics and m{sub WDM}>=5.6keV (2sigma) for sterile neutrinos. Adding the SDSS Lyman-alpha flux power spectrum at 2.2=4keV and m{sub WDM}>=28keV (2sigma) for thermal relics and sterile neutrinos. These results improve previous findings by a factor two and are currently the tightest constraints on the coldness of cold dark matter. Finally, I will discuss: i) recent results for a mixture of cold and warm dark matter and the constraints for sterile neutrinos as dark matter candidates in a physically motivated framework (resonant production); ii) perspectives of cross-correlating the Lyman-alpha forest with convergence maps of the cosmic microwave background; iii) fitting of the flux probability distribution function.

  6. Missing dust signature in the cosmic microwave background

    Czech Academy of Sciences Publication Activity Database

    Vavryčuk, Václav

    2017-01-01

    Roč. 470, č. 1 (2017), L44-L48 ISSN 0035-8711 Institutional support: RVO:67985530 Keywords : dust, extinction * galaxies: high redshift * galaxies: ISM * intergalactic medium * cosmic background radiation * early Universe Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 4.961, year: 2016

  7. The physics and early history of the intergalactic medium

    International Nuclear Information System (INIS)

    Barkana, Rennan; Loeb, Abraham

    2007-01-01

    The intergalactic medium-the cosmic gas that fills the great spaces between the galaxies-is affected by processes ranging from quantum fluctuations in the very early Universe to radiative emission from newly formed stars. This gives the intergalactic medium a dual role as a powerful probe both of fundamental physics and of astrophysics. The heading of fundamental physics includes conditions in the very early Universe and cosmological parameters that determine the age of the Universe and its matter content. The astrophysics refers to chapters of the long cosmic history of stars and galaxies that are being revealed through the effects of stellar feedback on the cosmic gas. This review describes the physics of the intergalactic medium, focusing on recent theoretical and observational developments in understanding early cosmic history. In particular, the earliest generation of stars is thought to have transformed the Universe from darkness to light and to have had an enormous impact on the intergalactic medium. Half a million years after the Big Bang the Universe was filled with atomic hydrogen. As gravity pulled gas clouds together, the first stars ignited and their radiation turned the surrounding atoms back into free electrons and ions. From the observed spectral absorption signatures of the gas between us and distant sources, we know that the process of reionization pervaded most of space a billion years after the Big Bang, so that only a small fraction of the primordial hydrogen atoms remained between galaxies. Knowing exactly when and how the reionization process happened is a primary goal of cosmologists, because this would tell us when the early stars and black holes formed and in what kinds of galaxies. The distribution and clustering of these galaxies is particularly interesting since it is driven by primordial density fluctuations in the dark matter. Cosmic reionization is beginning to be understood with the help of theoretical models and computer

  8. A photoionization instability in the early intergalactic medium

    Science.gov (United States)

    Hogan, Craig J.

    1992-01-01

    It is argued that any fairly uniform source of ionizing photons can be the cause of an instability in the pregalactic medium on scales larger than a photon path length. Underdense regions receive more ionizing energy per atom and reach higher temperature and entropy, driving the density down still further. Fluctuations created by this instability can lead to the formation of structures resembling protogalaxies and intergalactic clouds, obviating the need for gas clouds or density perturbations of earlier cosmological provenance, as is usually assumed in theories of galaxy and structure formation. Characteristic masses for clouds produced by the instability, with log mass in solar units plotted against log radius in kpc, are illustrated.

  9. Probing intergalactic magnetic fields with simulations of electromagnetic cascades

    Energy Technology Data Exchange (ETDEWEB)

    Alves Batista, Rafael [Oxford Univ. (United Kingdom). Dept. of Physics and Astrophysics; Saveliev, Andrey [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Russian Academy of Sciences, Moscow (Russian Federation). Keldysh Inst. of Applied Mathematics; Sigl, Guenter [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Vachaspati, Tanmay [Arizona State Univ., Tempe, AZ (United States). Dept. of Physics

    2016-12-15

    We determine the effect of intergalactic magnetic fields on the distribution of high energy gamma rays by performing three-dimensional Monte Carlo simulations of the development of gamma-ray-induced electromagnetic cascades in the magnetized intergalactic medium. We employ the so-called ''Large Sphere Observer'' method to efficiently simulate blazar gamma ray halos. We study magnetic fields with a Batchelor spectrum and with maximal left- and right-handed helicities. We also consider the case of sources whose jets are tilted with respect to the line of sight. We verify the formation of extended gamma ray halos around the source direction, and observe spiral-like patterns if the magnetic field is helical. We apply the Q-statistics to the simulated halos to extract their spiral nature and also propose an alternative method, the S-statistics. Both methods provide a quantative way to infer the helicity of the intervening magnetic fields from the morphology of individual blazar halos for magnetic field strengths B>or similar 10{sup -15} G and magnetic coherence lengths L{sub c}>or similar 100 Mpc. We show that the S-statistics has a better performance than the Q-statistics when assessing magnetic helicity from the simulated halos.

  10. Probing intergalactic magnetic fields with simulations of electromagnetic cascades

    International Nuclear Information System (INIS)

    Alves Batista, Rafael; Saveliev, Andrey; Russian Academy of Sciences, Moscow; Sigl, Guenter; Vachaspati, Tanmay

    2016-12-01

    We determine the effect of intergalactic magnetic fields on the distribution of high energy gamma rays by performing three-dimensional Monte Carlo simulations of the development of gamma-ray-induced electromagnetic cascades in the magnetized intergalactic medium. We employ the so-called ''Large Sphere Observer'' method to efficiently simulate blazar gamma ray halos. We study magnetic fields with a Batchelor spectrum and with maximal left- and right-handed helicities. We also consider the case of sources whose jets are tilted with respect to the line of sight. We verify the formation of extended gamma ray halos around the source direction, and observe spiral-like patterns if the magnetic field is helical. We apply the Q-statistics to the simulated halos to extract their spiral nature and also propose an alternative method, the S-statistics. Both methods provide a quantative way to infer the helicity of the intervening magnetic fields from the morphology of individual blazar halos for magnetic field strengths B>or similar 10"-"1"5 G and magnetic coherence lengths L_c>or similar 100 Mpc. We show that the S-statistics has a better performance than the Q-statistics when assessing magnetic helicity from the simulated halos.

  11. Cosmological simulation with dust formation and destruction

    Science.gov (United States)

    Aoyama, Shohei; Hou, Kuan-Chou; Hirashita, Hiroyuki; Nagamine, Kentaro; Shimizu, Ikkoh

    2018-06-01

    To investigate the evolution of dust in a cosmological volume, we perform hydrodynamic simulations, in which the enrichment of metals and dust is treated self-consistently with star formation and stellar feedback. We consider dust evolution driven by dust production in stellar ejecta, dust destruction by sputtering, grain growth by accretion and coagulation, and grain disruption by shattering, and treat small and large grains separately to trace the grain size distribution. After confirming that our model nicely reproduces the observed relation between dust-to-gas ratio and metallicity for nearby galaxies, we concentrate on the dust abundance over the cosmological volume in this paper. The comoving dust mass density has a peak at redshift z ˜ 1-2, coincident with the observationally suggested dustiest epoch in the Universe. In the local Universe, roughly 10 per cent of the dust is contained in the intergalactic medium (IGM), where only 1/3-1/4 of the dust survives against dust destruction by sputtering. We also show that the dust mass function is roughly reproduced at ≲ 108 M⊙, while the massive end still has a discrepancy, which indicates the necessity of stronger feedback in massive galaxies. In addition, our model broadly reproduces the observed radial profile of dust surface density in the circum-galactic medium (CGM). While our model satisfies the observational constraints for the dust extinction on cosmological scales, it predicts that the dust in the CGM and IGM is dominated by large (>0.03 μm) grains, which is in tension with the steep reddening curves observed in the CGM.

  12. A model for intergalactic filaments and galaxy formation during the first gigayear

    Science.gov (United States)

    Harford, A. Gayler; Hamilton, Andrew J. S.

    2017-11-01

    We propose a physically based, analytic model for intergalactic filaments during the first gigayear of the universe. The structure of a filament is based upon a gravitationally bound, isothermal cylinder of gas. The model successfully predicts for a cosmological simulation the total mass per unit length of a filament (dark matter plus gas) based solely upon the sound speed of the gas component, contrary to the expectation for collisionless dark matter aggregation. In the model, the gas, through its hydrodynamic properties, plays a key role in filament structure rather than being a passive passenger in a preformed dark matter potential. The dark matter of a galaxy follows the classic equation of collapse of a spherically symmetric overdensity in an expanding universe. In contrast, the gas usually collapses more slowly. The relative rates of collapse of these two components for individual galaxies can explain the varying baryon deficits of the galaxies under the assumption that matter moves along a single filament passing through the galaxy centre, rather than by spherical accretion. The difference in behaviour of the dark matter and gas can be simply and plausibly related to the model. The range of galaxies studied includes that of the so-called too big to fail galaxies, which are thought to be problematic for the standard Λ cold dark matter model of the universe. The isothermal-cylinder model suggests a simple explanation for why these galaxies are, unaccountably, missing from the night sky.

  13. Probing the intergalactic medium with fast radio bursts

    International Nuclear Information System (INIS)

    Zheng, Z.; Ofek, E. O.; Kulkarni, S. R.; Neill, J. D.; Juric, M.

    2014-01-01

    The recently discovered fast radio bursts (FRBs), presumably of extragalactic origin, have the potential to become a powerful probe of the intergalactic medium (IGM). We point out a few such potential applications. We provide expressions for the dispersion measure and rotation measure as a function of redshift, and we discuss the sensitivity of these measures to the He II reionization and the IGM magnetic field. Finally, we calculate the microlensing effect from an isolated, extragalactic stellar-mass compact object on the FRB spectrum. The time delays between the two lensing images will induce constructive and destructive interference, leaving a specific imprint on the spectra of FRBs. With a high all-sky rate, a large statistical sample of FRBs is expected to make these applications feasible.

  14. An optical search for the intergalactic HI cloud in Leo

    International Nuclear Information System (INIS)

    Kibblewhite, E.J.; Cawson, M.G.M.; Disney, M.J.; Phillipps, S.

    1985-01-01

    An optical search has been made for the large intergalactic HI cloud discovered from Arecibo by previous authors. A very deep red UKSTU plate of the area has been scanned by the APM machine and deep CCD frames of a small area near a peak in the HI emission have been acquired. No extended emission is found at the limiting surface brightness of the photographic material and no excess of stars above that expected from the Galaxy is found in the CCD data. However, due to the extreme size of the HI cloud, the upper limit on the total luminosity is that of a dwarf galaxy, Msub(B) >approx.-18. As its hydrogen and total masses would not be unusual for a galaxy, a highly extended very low surface brightness galaxy can not be ruled out, at present. (author)

  15. Probing the nature of dark matter through the metal enrichment of the intergalactic medium

    Science.gov (United States)

    Bremer, Jonas; Dayal, Pratika; Ryan-Weber, Emma V.

    2018-06-01

    We focus on exploring the metal enrichment of the intergalactic medium (IGM) in cold and warm (1.5 and 3 keV) dark matter (DM) cosmologies, and the constraints this yields on the DM particle mass, using a semi-analytic model, DELPHI, that jointly tracks the DM and baryonic assembly of galaxies at z ≃ 4-20 including both supernova (SN) and (a range of) reionization feedback (models). We find that while M_{UV}≳ -15 galaxies contribute half of all IGM metals in the cold dark matter (CDM) model by z ≃ 4.5, given the suppression of low-mass haloes, larger haloes with M_{UV}≲ -15 provide about 80 per cent of the IGM metal budget in 1.5 keV warm dark matter (WDM) models using two different models for the metallicity of the interstellar medium. Our results also show that the only models compatible with two different high-redshift data sets, provided by the evolving ultraviolet luminosity function (UV LF) at z ≃ 6-10 and IGM metal density, are standard CDM and 3 keV WDM that do not include any reionization feedback; a combination of the UV LF and the Díaz et al. point provides a weaker constraint, allowing CDM and 3 and 1.5 keV WDM models with SN feedback only, as well as CDM with complete gas suppression of all haloes with v_{circ} ≲ 30 km s^{-1}. Tightening the error bars on the IGM metal enrichment, future observations, at z ≳ 5.5, could therefore represent an alternative way of shedding light on the nature of DM.

  16. MEASURING THE SOURCES OF THE INTERGALACTIC IONIZING FLUX

    International Nuclear Information System (INIS)

    Cowie, L. L.; Barger, A. J.; Trouille, L.

    2009-01-01

    We use a wide-field (0.9 deg 2 ) X-ray sample with optical and Galaxy Evolution Explorer (GALEX) ultraviolet observations to measure the contribution of active galactic nuclei (AGNs) to the ionizing flux as a function of redshift. Our analysis shows that the AGN contribution to the metagalactic ionizing background peaks at around z = 2. The measured values of the ionizing background from the AGNs are lower than previous estimates and confirm that ionization from AGNs is insufficient to maintain the observed ionization of the intergalactic medium (IGM) at z > 3. We show that only X-ray sources with broad lines in their optical spectra have detectable ionizing flux and that the ionizing flux seen in an AGN is not correlated with its X-ray color. We also use the GALEX observations of the GOODS-N region to place a 2σ upper limit of 0.008 on the average ionization fraction f ν (700 A)/f ν (1500 A) for 626 UV selected galaxies in the redshift range z = 0.9-1.4. We then use this limit to estimate an upper bound to the galaxy contribution in the redshift range z = 0-5. If the z ∼ 1.15 ionization fraction is appropriate for higher-redshift galaxies, then contributions from the galaxy population are also too low to account for the IGM ionization at the highest redshifts (z > 4).

  17. Are there really intergalactic hydrogen clouds in the Sculptor group

    International Nuclear Information System (INIS)

    Haynes, M.P.; Roberts, M.S.

    1979-01-01

    High-sensitivity 21 cm observations of the region of the Sculptor group of galaxies reveal at least 30 H I clouds distributed over only the southern sector of the group. These new data add two striking complications to the picture of the clouds as H I companions of Sculptor galaxies: first, a much wider spatial distribution of clouds in marked contrast with the clustering of clouds around NGC 55 and NGC 300 previously reported by Mathewson, Cleary, and Murray; and second, a cloud velocity distribution which does not match that of the galaxies.We cannot reconcile the spatial and velocity distributions of the H I clouds with those of the group or of any subgroup. We conclude that there are no intergalactic H I clouds of > or =10 8 M/sub sun/ and galactic dimensions within the Sculptor group. Of a number of explanations alternative to group membership, we favor the identification of the clouds as a component of the Magellanic Stream which is seen in projection. Observations reported here of other nearby groups, combined with those of Sculptor, rule out the existence of a significant population of discrete H I clouds having the above properties

  18. STAR FORMATION FEEDBACK AND METAL-ENRICHMENT HISTORY OF THE INTERGALACTIC MEDIUM

    International Nuclear Information System (INIS)

    Cen Renyue; Chisari, Nora Elisa

    2011-01-01

    Using the state-of-the-art cosmological hydrodynamic simulations of the standard cold dark matter model with star formation feedback strength normalized to match the observed star formation history of the universe at z= 0-6, we compute the metal-enrichment history of the intergalactic medium (IGM). Overall we show that galactic superwind (GSW) feedback from star formation can transport metals to the IGM and that the properties of simulated metal absorbers match current observations. The distance of influence of GSW from galaxies is typically limited to about ≤0.5 Mpc and within regions of overdensity δ ≥ 10. Most C IV and O VI absorbers are located within shocked regions of elevated temperature (T ≥ 2 x 10 4 K), overdensity (δ ≥ 10), and metallicity ([Z/Z sun ] = [ - 2.5, - 0.5]), enclosed by double shocks propagating outward. O VI absorbers have typically higher metallicity, lower density, and higher temperature than C IV absorbers. For O VI absorbers, collisional ionization dominates over the entire redshift range z= 0-6, whereas for C IV absorbers the transition occurs at moderate redshift z ∼ 3 from collisionally dominated to photoionization dominated. We find that the observed column density distributions for C IV and O VI in the range log N cm 2 =12-15 are reasonably reproduced by the simulations. The evolution of mass densities contained in C IV and O VI lines, Ω CIV and Ω OVI , is also in good agreement with observations, which shows a near constancy at low redshifts and an exponential drop beyond redshift z= 3-4. For both C IV and O VI, most absorbers are transient and the amount of metals probed by C IV and O VI lines of column log N cm 2 =12-15 is only ∼2% of total metal density at any epoch. While gravitational shocks from large-scale structure formation dominate the energy budget (80%-90%) for turning about 50% of the IGM to the warm-hot intergalactic medium (WHIM) by z = 0, GSW feedback shocks are energetically dominant over

  19. Simulating the interaction of galaxies and the intergalactic medium

    Science.gov (United States)

    Carin, Robert A.

    2008-11-01

    The co-evolution of galaxies and the intergalactic medium as a function of environment is studied using hydrodynamic simulations of the ΛCDM cosmogony. It is demonstrated with non-radiative calculations that, in the absence of non-gravitational mechanisms, dark matter haloes accrete a near-universal fraction (˜ 0.9Ω_{b}/&Omega_;{m}) of baryons. The absence of a mass or redshift dependence of this fraction augurs well for parameter tests that use X-ray clusters as cosmological probes. Moreover, this result indicates that non-gravitational processes must efficiently regulate the formation of stars in dark matter haloes if the halo mass function is to be reconciled with the observed galaxy luminosity function. Simulations featuring stellar evolution and non-gravitational feedback mechanisms (photo-heating by the ultraviolet background, and thermal and kinetic supernovae feedback) are used to follow the evolution of star formation, and the thermo- and chemo-dynamical evolution of baryons. The observed star formation history of the Universe is reproduced, except at low redshift where it is overestimated by a factor of a few, possibly indicating the need for feedback from active galactic nuclei to quench cooling flows around massive galaxies. The simulations more accurately reproduce the observed abundance of galaxies with late-type morphologies than has been reported elsewhere. The unique initial conditions of these simulations, based on the Millennium Simulation, allow an unprecedented study of the role of large-scale environment to be conducted. The cosmic star formation rate density is found to vary by an order of magnitude across the extremes of environment expected in the local Universe. The mass fraction of baryons in the observationally elusive warm-hot intergalactic medium (WHIM), and the volume filling factor that this gas occupies, is also shown to vary by a factor of a few across such environments. This variation is attributed to differences in the halo

  20. The effect of UV stars on the intergalactic medium. II

    International Nuclear Information System (INIS)

    Sonnanstine, A.E.; Hills, J.G.

    1976-01-01

    The effect of ionizing radiation from the UV stars (hot prewhite dwarfs) on the intergalactic medium (IGM) has been investigated. If the UV stars are powered only by gravitational contraction they radiate most of their energy at a typical surface temperature of 1.5 x 10 5 K which produces a very highly ionized IGM in which the elements carbon, nitrogen and oxygen are left with only one or two electrons. This result in these elements being very inefficient coolants. The gas is cooled principally by free-free emission and the collisional ionization of hydrogen and helium. For a typical UV star temperature of T=1.5 x 10 5 K, the temperature of the ionized gas in the IGM is Tsub(g)=1.2 x 10 5 K for a Hubble constant H 0 =75 kms -1 Mpc -1 and a hydrogen density nsub(H)=10 -6 cm -3 . Heating by cosmic rays and X-rays is insignificant in the IGM except perhaps in the H I clouds because when a hydrogen atom recombines in the IGM it is far more likely to be re-ionized by a UV-star photon than by either of the other two types of particles due to the greater space density of UV-star photons and their appreciably larger ionization cross sections. If the UV stars radiate a substantial fraction of their energy in a helium-burning stage in which they have surface temperatures of about 5 x 10 4 K, the temperature of the IGM could be lowered to about 5 x 10 4 K. (Auth.)

  1. TEMPORAL SMEARING OF TRANSIENT RADIO SOURCES BY THE INTERGALACTIC MEDIUM

    International Nuclear Information System (INIS)

    Macquart, Jean-Pierre; Koay, Jun Yi

    2013-01-01

    The temporal smearing of impulsive radio events at cosmological redshifts probes the properties of the ionized intergalactic medium (IGM). We relate the degree of temporal smearing and the profile of a scattered source to the evolution of a turbulent structure in the IGM as a function of redshift. We estimate the degree of scattering expected by analyzing the contributions to the scattering measure of the various components of baryonic matter embedded in the IGM, including the diffuse IGM, intervening galaxies, and intracluster gas. These estimates predict that the amount of temporal smearing expected at 300 MHz is typically as low as ∼1 ms and suggests that these bursts may be detectable with low-frequency widefield arrays. A generalization of the dispersion-measure-scattering-measure relation observed for Galactic scattering to the densities and turbulent conditions relevant to the IGM suggests that scattering measures on the order of 10 –6 kpc m –20/3 would be expected at z ∼ 1. This scattering is sufficiently low enough that its effects would not, for most lines of sight, be manifested in existing observations of the scatter broadening in images of extragalactic compact sources. The redshift dependence on the temporal smearing discriminates between scattering that occurs in the host galaxy of the burst and the IGM, with τ host ∝(1 + z) –3 if the scattering probes length scales below the inner scale of the turbulence or τ host ∝(1 + z) –17/5 if the turbulence follows a Kolmogorov spectrum. This differs strongly from the expected IGM scaling τ IGM ∼ z 2 for z ∼ 0.2–0.5 for z ∼> 1

  2. X-ray ionization of the intergalactic medium by quasars

    Science.gov (United States)

    Graziani, Luca; Ciardi, B.; Glatzle, M.

    2018-06-01

    We investigate the impact of quasars on the ionization of the surrounding intergalactic medium (IGM) with the radiative transfer code CRASH4, now accounting for X-rays and secondary electrons. After comparing with analytic solutions, we post-process a cosmic volume (≈1.5 × 104 Mpc3h-3) containing a ULAS J1120+0641-like quasar (QSO) hosted by a 5 × 1011M⊙h-1 dark matter (DM) halo. We find that: (i) the average HII region (R ˜ 3.2 pMpc in a lifetime tf = 107 yrs) is mainly set by UV flux, in agreement with semi-analytic scaling relations; (ii) a largely neutral (xHII < 0.001), warm (T ˜ 103 K) tail extends up to few Mpc beyond the ionization front, as a result of the X-ray flux; (iii) LyC-opaque inhomogeneities induce a line of sight (LOS) scatter in R as high as few physical Mpc, consistent with the DLA scenario proposed to explain the anomalous size of the ULAS J1120+0641 ionized region. On the other hand, with an ionization rate \\dot{N}_{γ ,0} ˜ 10^{57} s-1, the assumed DLA clustering and gas opacity, only one LOS shows an HII region compatible with the observed one. We deduce that either the ionization rate of the QSO is at least one order of magnitude lower or the ULAS J1120+0641 bright phase is shorter than 107 yrs.

  3. Evolution of the intergalactic medium - What happened during the epoch z = 3-10?

    Science.gov (United States)

    Ikeuchi, S.; Ostriker, J. P.

    1986-01-01

    An attempt is made to model consistently the thermal and dynamic history of the intergalactic medium (IGM) from the era of reheating (z = 10-5) to the present, and to provide a unified explanation for the origin of ordinary galaxies, blue compact objects, and Lyman-alpha clouds. The evolution of the intergalactic gas is analyzed, treating the IGM as perfectly homogeneous at every epoch and taking into account radiative and Compton cooling, adiabatic cooling, shock heating, and heating produced by the diffuse UV flux. It is suggested that the IGM must have been heated to higher than a 10 to the 6th K by shock heasting caused either by explosions of pregalactic objects or expanding voids. The formation of intergalactic clouds by fragmentation of the resulting shells and the subsequent collapse of the shells to form galaxies are studied. An attempt is made to determine model parameters on the basis of an analysis of Lyman-alpha absorption lines.

  4. Cold Stress

    Science.gov (United States)

    ... Publications and Products Programs Contact NIOSH NIOSH COLD STRESS Recommend on Facebook Tweet Share Compartir Workers who ... cold environments may be at risk of cold stress. Extreme cold weather is a dangerous situation that ...

  5. Dust in planetary nebulae

    International Nuclear Information System (INIS)

    Kwok, S.

    1980-01-01

    A two-component dust model is suggested to explain the infrared emission from planetary nebulae. A cold dust component located in the extensive remnant of the red-giant envelope exterior to the visible nebula is responsible for the far-infrared emission. A ward dust component, which is condensed after the formation of the planetary nebula and confined within the ionized gas shell, emits most of the near- and mid-infrared radiation. The observations of NGC 7027 are shown to be consisten with such a model. The correlation of silicate emission in several planetary nebulae with an approximately +1 spectral index at low radio frequencies suggests that both the silicate and radio emissions originate from the remnant of the circumstellar envelope of th precursor star and are observable only while the planetary nebula is young. It is argued that oxygen-rich stars as well as carbon-rich stars can be progenitors of planetary nebulae

  6. Wood Dust

    Science.gov (United States)

    Learn about wood dust, which can raise the risk of cancers of the paranasal sinuses and nasal cavity. High amounts of wood dust are produced in sawmills, and in the furniture-making, cabinet-making, and carpentry industries.

  7. Counts of galaxies in the region of the 'intergalactic dark cloud' near iota Microscopii

    International Nuclear Information System (INIS)

    Meinunger, I.

    1976-01-01

    The distribution of the total numbers of galaxies down to about 18th magnitude on 84 squares is largely in agreement with the structure of the hypothetic intergalactic absorbing cloud near iota Microscopii found by C. Hoffmeister. The counts of galaxies were performed on the Whiteoak prints covering that region. (author)

  8. Cometary Dust

    Science.gov (United States)

    Levasseur-Regourd, Anny-Chantal; Agarwal, Jessica; Cottin, Hervé; Engrand, Cécile; Flynn, George; Fulle, Marco; Gombosi, Tamas; Langevin, Yves; Lasue, Jérémie; Mannel, Thurid; Merouane, Sihane; Poch, Olivier; Thomas, Nicolas; Westphal, Andrew

    2018-04-01

    This review presents our understanding of cometary dust at the end of 2017. For decades, insight about the dust ejected by nuclei of comets had stemmed from remote observations from Earth or Earth's orbit, and from flybys, including the samples of dust returned to Earth for laboratory studies by the Stardust return capsule. The long-duration Rosetta mission has recently provided a huge and unique amount of data, obtained using numerous instruments, including innovative dust instruments, over a wide range of distances from the Sun and from the nucleus. The diverse approaches available to study dust in comets, together with the related theoretical and experimental studies, provide evidence of the composition and physical properties of dust particles, e.g., the presence of a large fraction of carbon in macromolecules, and of aggregates on a wide range of scales. The results have opened vivid discussions on the variety of dust-release processes and on the diversity of dust properties in comets, as well as on the formation of cometary dust, and on its presence in the near-Earth interplanetary medium. These discussions stress the significance of future explorations as a way to decipher the formation and evolution of our Solar System.

  9. Nonlinear periodic waves in dusty plasma with variable dust charge

    International Nuclear Information System (INIS)

    Yadav, Lakhan Lal; Bharuthram, R.

    2002-01-01

    Using the reductive perturbation method, we present a theory of nonlinear periodic waves, viz. the cnoidal waves, in a dusty plasma consisting of electrons, ions, and cold dust grains with charge fluctuations, which in the limiting case reduce to dust acoustic solitons. It is found that the frequency of the dust acoustic cnoidal wave increases with its amplitude. The dust charge fluctuations are found to affect the characteristics of the cnoidal waves

  10. Allergies, asthma, and dust

    Science.gov (United States)

    Reactive airway disease - dust; Bronchial asthma - dust; Triggers - dust ... Things that make allergies or asthma worse are called triggers. Dust is a common trigger. When your asthma or allergies become worse due to dust, you are ...

  11. Formation of hot intergalactic gas by gas ejection from a galaxy in an early explosive era

    International Nuclear Information System (INIS)

    Ikeuchi, Satoru

    1977-01-01

    Chemical evolution of a galaxy in an early explosive era is studied by means of one zone model. Calculating the thermal properties of interstellar gas and the overlapping factor of expanding supernova-remnant shells, the gas escape conditions from a galaxy are examined. From these, it is shown that the total mass of ejected gas from a galaxy amounts to 10 -- 40% of the initial mass of a galaxy. The ejected gas extends to the intergalactic space and the whole universe. The mass, the heavy-element abundance and other physical properties of thus formed intergalactic gas are investigated for various parameters of galactic evolution. Some other effects of gas release on the evolution of a galaxy and the evolution of the universe are discussed. (auth.)

  12. Dimming of supernovae by photon-pseudoscalar conversion and the intergalactic plasma

    International Nuclear Information System (INIS)

    Deffayet, Cedric; Harari, Diego; Uzan, Jean-Philippe; Zaldarriaga, Matias

    2002-01-01

    It has been suggested recently that the observed dimming of distant type Ia supernovae may be a consequence of mixing of the photons with very light axions. We point out that the effect of the plasma, in which the photons are propagating, must be taken into account. This effect changes the oscillation probability and renders the dimming frequency dependent, contrary to observations. One may hope to accommodate the data by averaging the oscillations over many different coherence domains. We estimate the effect of coherence loss, either due to the inhomogeneities of the magnetic field or of the intergalactic plasma. These estimates indicate that the achromaticity problem can be resolved only with very specific, and probably unrealistic, properties of the intergalactic medium

  13. IGMtransmission: A Java GUI to model the effects of the Intergalactic Medium on the colours of high redshift galaxies

    OpenAIRE

    Harrison, Christopher M.; Meiksin, Avery; Stock, David

    2011-01-01

    IGMtransmission is a Java graphical user interface that implements Monte Carlo simulations to compute the corrections to colours of high-redshift galaxies due to intergalactic attenuation based on current models of the Intergalactic Medium. The effects of absorption due to neutral hydrogen are considered, with particular attention to the stochastic effects of Lyman Limit Systems. Attenuation curves are produced, as well as colours for a wide range of filter responses and model galaxy spectra....

  14. Supergalactic studies. II. Supergalactic distribution of the nearest intergalactic gas clouds

    International Nuclear Information System (INIS)

    de Vaucouleurs, G.; Corwin, H.G. Jr.

    1975-01-01

    The report by Mathewson, Cleary, and Murray that the nearby ''high velocity'' H i clouds, and in particular the Magellanic Stream, are strongly concentrated toward the supergalactic plane is confirmed. The observed concentration within +-30degree from the supergalactic equator of 21 out of 25 clouds in the north galactic hemisphere and 27 out of 31 clouds in the south galactic hemisphere could occur by chance in less than 7 and 3 percent of random samples from a population having a statistically isotropic Poisson distribution. Since the two galactic hemispheres are substantially independent samples, the combined probability of the chance hypothesis is P -3 . It is found that actually the high-velocity clouds are not so much concentrated toward the supergalactic equator (SGE) as toward the equator of the ''Local Cloud'' of galaxies inclined 14degree to the main supergalactic plane. Both galaxies and H i clouds define the same small circle of maximum concentration and exhibit the same standard deviation (15degree) from it, demonstrating closely related space distributions. It is concluded that, with the possible exception of a few of the largest and probably nearest cloud complexes (MS, AC, C), most of the high-velocity clouds are truly intergalactic and associated with the Local Group and nearer groups of galaxies. Half the population in a total sample of 115 nearby galaxies and intergalactic gas coulds is within 11degree from the Local equator, indicating a half-thickness of approx.0.75 Mpc for the Local Cloud. Intergalactic gas clouds have already been identified near 10 of the nearest galaxies (including our Galaxy and the Magellanic Clouds), most within approx.3 Mpc. The estimated space density of intergalactic gas clouds is Napprox. =20--25 Mpc -3 , in approximate agreement with the densities required by the collision theory of ring galaxies

  15. Extended H I regions around spiral galaxies: a probe for galactic structure and the intergalactic medium

    International Nuclear Information System (INIS)

    Bergeron, J.

    1977-01-01

    The H I disks observed at large radii around nearby spiral galaxies provide sensitive probes for the mass distributions in these galaxies and of their environments. We show, for a few well-observed systems, that there is an unseen component which dominates the mass at large radii. This additional matter cannot be gas, either neutral or ionized. The data do not distinguish strongly between flat and spherical spatial distributions for this mass, though they suggest that the distribution is spherical. An observational test is proposed to differentiate the two. We investigate the thermal interaction between a hot intergalactic medium near the closure density and these extended H I regions in the assumption of magnetic field lines extended outward into the intergalactic medium (IGM). We show that, with plausible initial conditions, the intergalactic temperature at present cannot exceed 1 x 10 7 K if the H I is to have survived until now. Consideration of conditions in the past places even more stringent limits on the temperature and density of the IGM. Survival of the H I disk also implies that these galaxies cannot have persistent hot, dense halos. The X-ray observations of M31, in particular, cannot be interpreted in terms of a thermal bremsstrahlung halo model, unless this halo is younger than about 10 7 yr

  16. Intergalactic Leadership: Practical Tips for Leading Where No One Has Gone Before

    Directory of Open Access Journals (Sweden)

    Peg A Lonnquist

    2015-07-01

    Full Text Available Most of the transformational, inclusive, partnership leadership literature, while brilliant and inspirational, does not provide day-to-day ideas for practitioners. Drawing on several key leadership theories and theorists (Kouzes and Posner’s five core behaviors of successful leaders, the Athena Model based on research on women leaders, Centered Leadership from the McKinsey Project, the Research-Productivity and Engagement Model, Burn’s and Bass’ Transformational Leadership Theory, Riane Eisler’s partnership leadership, multicultural leadership theorist Juana Bordas, and feminist leadership theorists, the author describes how she has translated and implemented day-to-day leadership practices which she calls Intergalactic Leadership.

  17. Cold plate

    Energy Technology Data Exchange (ETDEWEB)

    Marroquin, Christopher M.; O' Connell, Kevin M.; Schultz, Mark D.; Tian, Shurong

    2018-02-13

    A cold plate, an electronic assembly including a cold plate, and a method for forming a cold plate are provided. The cold plate includes an interface plate and an opposing plate that form a plenum. The cold plate includes a plurality of active areas arranged for alignment over respective heat generating portions of an electronic assembly, and non-active areas between the active areas. A cooling fluid flows through the plenum. The plenum, at the non-active areas, has a reduced width and/or reduced height relative to the plenum at the active areas. The reduced width and/or height of the plenum, and exterior dimensions of cold plate, at the non-active areas allow the non-active areas to flex to accommodate surface variations of the electronics assembly. The reduced width and/or height non-active areas can be specifically shaped to fit between physical features of the electronics assembly.

  18. Does Light from Steady Sources Bear Any Observable Imprint of the Dispersive Intergalactic Medium?

    Science.gov (United States)

    Lieu, Richard; Duan, Lingze

    2018-02-01

    There has recently been some interest in the prospect of detecting ionized intergalactic baryons by examining the properties of incoherent light from background cosmological sources, namely quasars. Although the paper by Lieu et al. proposed a way forward, it was refuted by the later theoretical work of Hirata & McQuinn and the observational study of Hales et al. In this paper we investigate in detail the manner in which incoherent radiation passes through a dispersive medium both from the frameworks of classical and quantum electrodynamics, leading us to conclude that the premise of Lieu et al. would only work if the pulses involved are genuinely classical ones containing many photons per pulse; unfortunately, each photon must not be treated as a pulse that is susceptible to dispersive broadening. We are nevertheless able to change the tone of the paper at this juncture by pointing out that because current technology allows one to measure the phase of individual modes of radio waves from a distant source, the most reliable way of obtaining irrefutable evidence of dispersion, namely via the detection of its unique signature of a quadratic spectral phase, may well be already accessible. We demonstrate how this technique is only applied to measure the column density of the ionized intergalactic medium.

  19. On modeling and measuring the temperature of the z ∼ 5 intergalactic medium

    International Nuclear Information System (INIS)

    Lidz, Adam; Malloy, Matthew

    2014-01-01

    The temperature of the low-density intergalactic medium (IGM) at high redshift is sensitive to the timing and nature of hydrogen and He II reionization, and can be measured from Lyman-alpha (Lyα) forest absorption spectra. Since the memory of intergalactic gas to heating during reionization gradually fades, measurements as close as possible to reionization are desirable. In addition, measuring the IGM temperature at sufficiently high redshifts should help to isolate the effects of hydrogen reionization since He II reionization starts later, at lower redshift. Motivated by this, we model the IGM temperature at z ≳ 5 using semi-numeric models of patchy reionization. We construct mock Lyα forest spectra from these models and consider their observable implications. We find that the small-scale structure in the Lyα forest is sensitive to the temperature of the IGM even at redshifts where the average absorption in the forest is as high as 90%. We forecast the accuracy at which the z ≳ 5 IGM temperature can be measured using existing samples of high resolution quasar spectra, and find that interesting constraints are possible. For example, an early reionization model in which reionization ends at z ∼ 10 should be distinguishable—at high statistical significance—from a lower redshift model where reionization completes at z ∼ 6. We discuss improvements to our modeling that may be required to robustly interpret future measurements.

  20. DETECTING THE WARM-HOT INTERGALACTIC MEDIUM THROUGH X-RAY ABSORPTION LINES

    International Nuclear Information System (INIS)

    Yao Yangsen; Shull, J. Michael; Cash, Webster; Wang, Q. Daniel

    2012-01-01

    The warm-hot intergalactic medium (WHIM) at temperatures 10 5 -10 7 K is believed to contain 30%-50% of the baryons in the local universe. However, all current X-ray detections of the WHIM at redshifts z > 0 are of low statistical significance (∼ Ovii ∼10 15 cm -2 (corresponding to an equivalent width of 2.5 mÅ for a Doppler velocity of 50 km s –1 ) at ∼> 3σ significance level. The simulation results also suggest that it would take >60 Ms for Chandra and 140 Ms for XMM-Newton to measure the N Ovii at ≥4σ from a spectrum of a background QSO with flux of ∼0.2 mCrab (1 Crab = 2 × 10 –8 erg s –1 cm –2 at 0.5-2 keV). Future X-ray spectrographs need to be equipped with spectral resolution R ∼ 4000 and effective area A ≥ 100 cm 2 to accomplish the similar constraints with an exposure time of ∼2 Ms and would require ∼11 Ms to survey the 15 QSOs with flux ∼> 0.2 mCrab along which clear intergalactic O VI absorbers have been detected.

  1. High Latitude Dust in the Earth System

    Science.gov (United States)

    Bullard, Joanna E.; Baddock, Matthew; Bradwell, Tom; Crusius, John; Darlington, Eleanor; Gaiero, Diego; Gasso, Santiago; Gisladottir, Gudrun; Hodgkins, Richard; McCulloch, Robert; hide

    2016-01-01

    Natural dust is often associated with hot, subtropical deserts, but significant dust events have been reported from cold, high latitudes. This review synthesizes current understanding of high-latitude (> or = 50degN and > or = 40degS) dust source geography and dynamics and provides a prospectus for future research on the topic. Although the fundamental processes controlling aeolian dust emissions in high latitudes are essentially the same as in temperate regions, there are additional processes specific to or enhanced in cold regions. These include low temperatures, humidity, strong winds, permafrost and niveo-aeolian processes all of which can affect the efficiency of dust emission and distribution of sediments. Dust deposition at high latitudes can provide nutrients to the marine system, specifically by contributing iron to high-nutrient, low-chlorophyll oceans; it also affects ice albedo and melt rates. There have been no attempts to quantify systematically the expanse, characteristics, or dynamics of high-latitude dust sources. To address this, we identify and compare the main sources and drivers of dust emissions in the Northern (Alaska, Canada, Greenland, and Iceland) and Southern (Antarctica, New Zealand, and Patagonia) Hemispheres. The scarcity of year-round observations and limitations of satellite remote sensing data at high latitudes are discussed. It is estimated that under contemporary conditions high-latitude sources cover >500,000 sq km and contribute at least 80-100 Tg/yr1 of dust to the Earth system (approx. 5% of the global dust budget); both are projected to increase under future climate change scenarios.

  2. Cold injuries.

    Science.gov (United States)

    Kruse, R J

    1995-01-01

    There are two categories of cold injury. The first is hypothermia, which is a systemic injury to cold, and the second is frostbite, which is a local injury. Throughout history, entire armies, from George Washington to the Germans on the Russian Front in World War II, have fallen prey to prolonged cold exposure. Cold injury is common and can occur in all seasons if ambient temperature is lower than the core body temperature. In the 1985 Boston Marathon, even though it was 76 degrees and sunny, there were 75 runners treated for hypothermia. In general, humans adapt poorly to cold exposure. Children are at particular risk because of their relatively greater surface area/body mass ratio, causing them to cool even more rapidly than adults. Because of this, the human's best defense against cold injury is to limit his/her exposure to cold and to dress appropriately. If cold injury has occurred and is mild, often simple passive rewarming such as dry blankets and a warm room are sufficient treatment.

  3. A SUBMILLIMETER CONTINUUM SURVEY OF LOCAL DUST-OBSCURED GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jong Chul [Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055 (Korea, Republic of); Hwang, Ho Seong [School of Physics, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 02455 (Korea, Republic of); Lee, Gwang-Ho, E-mail: jclee@kasi.re.kr [Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of)

    2016-12-20

    We conduct a 350 μ m dust continuum emission survey of 17 dust-obscured galaxies (DOGs) at z = 0.05–0.08 with the Caltech Submillimeter Observatory (CSO). We detect 14 DOGs with S{sub 350μm} = 114–650 mJy and signal-to-noise > 3. By including two additional DOGs with submillimeter data in the literature, we are able to study dust content for a sample of 16 local DOGs, which consist of 12 bump and four power-law types. We determine their physical parameters with a two-component modified blackbody function model. The derived dust temperatures are in the range 57–122 K and 22–35 K for the warm and cold dust components, respectively. The total dust mass and the mass fraction of the warm dust component are 3–34 × 10{sup 7} M {sub ⊙} and 0.03%–2.52%, respectively. We compare these results with those of other submillimeter-detected infrared luminous galaxies. The bump DOGs, the majority of the DOG sample, show similar distributions of dust temperatures and total dust mass to the comparison sample. The power-law DOGs show a hint of smaller dust masses than other samples, but need to be tested with a larger sample. These findings support that the reason DOGs show heavy dust obscuration is not an overall amount of dust content, but probably the spatial distribution of dust therein.

  4. A SUBMILLIMETER CONTINUUM SURVEY OF LOCAL DUST-OBSCURED GALAXIES

    International Nuclear Information System (INIS)

    Lee, Jong Chul; Hwang, Ho Seong; Lee, Gwang-Ho

    2016-01-01

    We conduct a 350 μ m dust continuum emission survey of 17 dust-obscured galaxies (DOGs) at z = 0.05–0.08 with the Caltech Submillimeter Observatory (CSO). We detect 14 DOGs with S 350μm = 114–650 mJy and signal-to-noise > 3. By including two additional DOGs with submillimeter data in the literature, we are able to study dust content for a sample of 16 local DOGs, which consist of 12 bump and four power-law types. We determine their physical parameters with a two-component modified blackbody function model. The derived dust temperatures are in the range 57–122 K and 22–35 K for the warm and cold dust components, respectively. The total dust mass and the mass fraction of the warm dust component are 3–34 × 10 7 M ⊙ and 0.03%–2.52%, respectively. We compare these results with those of other submillimeter-detected infrared luminous galaxies. The bump DOGs, the majority of the DOG sample, show similar distributions of dust temperatures and total dust mass to the comparison sample. The power-law DOGs show a hint of smaller dust masses than other samples, but need to be tested with a larger sample. These findings support that the reason DOGs show heavy dust obscuration is not an overall amount of dust content, but probably the spatial distribution of dust therein.

  5. Infrared astronomy and the galactic dust

    International Nuclear Information System (INIS)

    Pecker, J.C.

    1977-01-01

    The existence, in the Galaxy, of small absorbing dust grains has been known for a long time, as they redden the light of stars located behind them, and obscure by amounts which can often even be several magnitudes... In the infrared, where absorption is smaller, one can see through the dust, while at the same time, one can observe the emission of cold dust clouds. After a brief review of technical developments, the reasons for studying the infrared, and the principles of diagnostics, are given. The analysis of the spectral features leads to identification of ice, graphite, and various silicates, as main constituents of the dust. In the fifth section, examples are given of the various sources that one meets when travelling in the Galaxy: protostars, cold and dilute, dense envelopes of young stars (cold or hot), dilute envelopes of not so young stars, and ejected clouds surrounding evolved objects... The simultaneous observation of dust, molecules and atoms, in the same regions, shows that the knowledge of the circumstellar dense regions might be of a great interest, in the study of the origin of life, and of the evolution of the Universe. (Auth.)

  6. Probing stochastic inter-galactic magnetic fields using blazar-induced gamma ray halo morphology

    Energy Technology Data Exchange (ETDEWEB)

    Duplessis, Francis [Physics Department, Arizona State University, Tempe, AZ 85287 (United States); Vachaspati, Tanmay, E-mail: fdupless@asu.edu, E-mail: tvachasp@asu.edu [Maryland Center for Fundamental Physics, University of Maryland, College Park, MD 20742 (United States)

    2017-05-01

    Inter-galactic magnetic fields can imprint their structure on the morphology of blazar-induced gamma ray halos. We show that the halo morphology arises through the interplay of the source's jet and a two-dimensional surface dictated by the magnetic field. Through extensive numerical simulations, we generate mock halos created by stochastic magnetic fields with and without helicity, and study the dependence of the halo features on the properties of the magnetic field. We propose a sharper version of the Q-statistics and demonstrate its sensitivity to the magnetic field strength, the coherence scale, and the handedness of the helicity. We also identify and explain a new feature of the Q-statistics that can further enhance its power.

  7. The Magnetic Field in Galaxies, Galaxy Clusters, and the InterGalactic Space

    CERN Document Server

    Dar, A; Dar, Arnon

    2005-01-01

    Magnetic fields of debated origin appear to permeate the Universe on all large scales. There is mounting evidence that supernovae produce not only roughly spherical ejecta and winds, but also highly relativistic jets of ordinary matter. These jets, which travel long distances, slow down by accelerating the matter encountered on their path to cosmic-ray energies. We show that, if the turbulent motions induced by the winds and the cosmic rays generate magnetic fields in rough energy equipartition, the predicted magnetic-field strengths coincide with the ones observed not only in galaxies (5 $\\mu$G in the Milky Way) but also in galaxy clusters (6 $\\mu$G in Coma). The prediction for the intergalactic (or inter-cluster) field is 50 nG.

  8. Measurement of the small-scale structure of the intergalactic medium using close quasar pairs.

    Science.gov (United States)

    Rorai, Alberto; Hennawi, Joseph F; Oñorbe, Jose; White, Martin; Prochaska, J Xavier; Kulkarni, Girish; Walther, Michael; Lukić, Zarija; Lee, Khee-Gan

    2017-04-28

    The distribution of diffuse gas in the intergalactic medium (IGM) imprints a series of hydrogen absorption lines on the spectra of distant background quasars known as the Lyman-α forest. Cosmological hydrodynamical simulations predict that IGM density fluctuations are suppressed below a characteristic scale where thermal pressure balances gravity. We measured this pressure-smoothing scale by quantifying absorption correlations in a sample of close quasar pairs. We compared our measurements to hydrodynamical simulations, where pressure smoothing is determined by the integrated thermal history of the IGM. Our findings are consistent with standard models for photoionization heating by the ultraviolet radiation backgrounds that reionized the universe. Copyright © 2017, American Association for the Advancement of Science.

  9. The evolution of the intergalactic medium and the origin of the galaxy luminosity function

    Science.gov (United States)

    Valls-Gabaud, David; Blanchard, Alain; Mamon, Gary

    1993-01-01

    The coupling of the Press and Schechter prescription with the CDM scenario and the Hoyle-Rees-Ostriker cooling criterion leads to a galaxy formation scenario in which galaxies are overproduced by a large factor. Although star formation might be suppressed in the smaller halos, a large amount of energy per galactic mass is needed to account for the present number density of galaxies. The evolution of the intergalactic medium (IGM) provides a simple criterion to prevent galaxy formation without requiring feedback, since halos with small virial temperatures are not able to retain the infalling hot gas of the IGM. If the ionizing background has decreased since z is approximately 1 - 2, then this criterion explains the slope of the luminosity function at the faint end. In addition, this scenario predicts two populations of dwarf galaxies, well differentiated in age, gas content, stellar populations, and clustering properties, which can be identified with dE and dIm galaxies.

  10. Power-law to Power-law Mapping of Blazar Spectra from Intergalactic Absorption

    International Nuclear Information System (INIS)

    Stecker, F W; Scully, S T

    2007-01-01

    We have derived a useful analytic approximation for determining the effect of intergalactic absorption on the γ-ray spectra of TeV blazars the energy range 0.2 TeV γ γ ) is approximately logarithmic. The effect of this energy dependence is to steepen intrinsic source spectra such that a source with an approximate power-law spectral index Γ s is converted to one with an observed spectral index Γ o ≅ Γ s + ΔΓ(z) where ΔΓ(z) is a linear function of z in the redshift range 0.05-0.4. We apply this approximation to the spectra of 7 TeV blazars

  11. New limits on 21 cm epoch of reionization from paper-32 consistent with an x-ray heated intergalactic medium at z = 7.7

    International Nuclear Information System (INIS)

    Parsons, Aaron R.; Liu, Adrian; Ali, Zaki S.; Pober, Jonathan C.; Aguirre, James E.; Moore, David F.; Bradley, Richard F.; Carilli, Chris L.; DeBoer, David R.; Dexter, Matthew R.; MacMahon, David H. E.; Gugliucci, Nicole E.; Jacobs, Daniel C.; Klima, Pat; Manley, Jason R.; Walbrugh, William P.; Stefan, Irina I.

    2014-01-01

    We present new constraints on the 21 cm Epoch of Reionization (EoR) power spectrum derived from three months of observing with a 32 antenna, dual-polarization deployment of the Donald C. Backer Precision Array for Probing the Epoch of Reionization in South Africa. In this paper, we demonstrate the efficacy of the delay-spectrum approach to avoiding foregrounds, achieving over eight orders of magnitude of foreground suppression (in mK 2 ). Combining this approach with a procedure for removing off-diagonal covariances arising from instrumental systematics, we achieve a best 2σ upper limit of (41 mK) 2 for k = 0.27 h Mpc –1 at z = 7.7. This limit falls within an order of magnitude of the brighter predictions of the expected 21 cm EoR signal level. Using the upper limits set by these measurements, we generate new constraints on the brightness temperature of 21 cm emission in neutral regions for various reionization models. We show that for several ionization scenarios, our measurements are inconsistent with cold reionization. That is, heating of the neutral intergalactic medium (IGM) is necessary to remain consistent with the constraints we report. Hence, we have suggestive evidence that by z = 7.7, the H I has been warmed from its cold primordial state, probably by X-rays from high-mass X-ray binaries or miniquasars. The strength of this evidence depends on the ionization state of the IGM, which we are not yet able to constrain. This result is consistent with standard predictions for how reionization might have proceeded.

  12. New limits on 21 cm epoch of reionization from paper-32 consistent with an x-ray heated intergalactic medium at z = 7.7

    Energy Technology Data Exchange (ETDEWEB)

    Parsons, Aaron R.; Liu, Adrian; Ali, Zaki S.; Pober, Jonathan C. [Astronomy Department, University of California, Berkeley, CA (United States); Aguirre, James E.; Moore, David F. [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA (United States); Bradley, Richard F. [Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA (United States); Carilli, Chris L. [National Radio Astronomy Observatory, Socorro, NM (United States); DeBoer, David R.; Dexter, Matthew R.; MacMahon, David H. E. [Radio Astronomy Laboratory, University of California, Berkeley, CA (United States); Gugliucci, Nicole E. [Department of Astronomy, University of Virginia, Charlottesville, VA (United States); Jacobs, Daniel C. [School of Earth and Space Exploration, Arizona State University, Tempe, AZ (United States); Klima, Pat [National Radio Astronomy Observatory, Charlottesville, VA (United States); Manley, Jason R.; Walbrugh, William P. [Square Kilometer Array, South Africa Project, Cape Town (South Africa); Stefan, Irina I. [Cavendish Laboratory, Cambridge (United Kingdom)

    2014-06-20

    We present new constraints on the 21 cm Epoch of Reionization (EoR) power spectrum derived from three months of observing with a 32 antenna, dual-polarization deployment of the Donald C. Backer Precision Array for Probing the Epoch of Reionization in South Africa. In this paper, we demonstrate the efficacy of the delay-spectrum approach to avoiding foregrounds, achieving over eight orders of magnitude of foreground suppression (in mK{sup 2}). Combining this approach with a procedure for removing off-diagonal covariances arising from instrumental systematics, we achieve a best 2σ upper limit of (41 mK){sup 2} for k = 0.27 h Mpc{sup –1} at z = 7.7. This limit falls within an order of magnitude of the brighter predictions of the expected 21 cm EoR signal level. Using the upper limits set by these measurements, we generate new constraints on the brightness temperature of 21 cm emission in neutral regions for various reionization models. We show that for several ionization scenarios, our measurements are inconsistent with cold reionization. That is, heating of the neutral intergalactic medium (IGM) is necessary to remain consistent with the constraints we report. Hence, we have suggestive evidence that by z = 7.7, the H I has been warmed from its cold primordial state, probably by X-rays from high-mass X-ray binaries or miniquasars. The strength of this evidence depends on the ionization state of the IGM, which we are not yet able to constrain. This result is consistent with standard predictions for how reionization might have proceeded.

  13. Cold Sore

    Science.gov (United States)

    ... may reduce how often they return. Symptoms A cold sore usually passes through several stages: Tingling and itching. Many people feel an itching, burning or tingling sensation around their lips for a day or so ...

  14. Dust collector

    Energy Technology Data Exchange (ETDEWEB)

    Sahourin, H.

    1988-03-22

    This invention relates to a dust collector or filter which may be used for large volume cleaning air for gases or for separating out industrial byproducts such as wood chips, sawdust, and shavings. It relies on filtration or separation using only a uniquely configured medium. A primary, but not exclusive, purpose of the invention is to enable very large throughput, capable of separating or filtering of gases containing up to three or more tons of byproduct with a minimum pressure-drop across the device. No preliminary cycloning, to remove major particulates is necessary. The collector generally comprises a continuous and integral filter medium which is suspended from a plurality of downwardly extending frames forming a series of separate elements having a triangular cross-section, each element being relatively wide at the top and narrow at the bottom to define, between adjacent elements, a divergent collecting space which is wide at the bottom. 11 figs.

  15. Dust Measurements in Tokamaks

    International Nuclear Information System (INIS)

    Rudakov, D; Yu, J; Boedo, J; Hollmann, E; Krasheninnikov, S; Moyer, R; Muller, S; Yu, A; Rosenberg, M; Smirnov, R; West, W; Boivin, R; Bray, B; Brooks, N; Hyatt, A; Wong, C; Fenstermacher, M; Groth, M; Lasnier, C; McLean, A; Stangeby, P; Ratynskaia, S; Roquemore, A; Skinner, C; Solomon, W M

    2008-01-01

    Dust production and accumulation impose safety and operational concerns for ITER. Diagnostics to monitor dust levels in the plasma as well as in-vessel dust inventory are currently being tested in a few tokamaks. Dust accumulation in ITER is likely to occur in hidden areas, e.g. between tiles and under divertor baffles. A novel electrostatic dust detector for monitoring dust in these regions has been developed and tested at PPPL. In DIII-D tokamak dust diagnostics include Mie scattering from Nd:YAG lasers, visible imaging, and spectroscopy. Laser scattering resolves size of particles between 0.16-1.6 (micro)m in diameter; the total dust content in the edge plasmas and trends in the dust production rates within this size range have been established. Individual dust particles are observed by visible imaging using fast-framing cameras, detecting dust particles of a few microns in diameter and larger. Dust velocities and trajectories can be determined in 2D with a single camera or 3D using multiple cameras, but determination of particle size is problematic. In order to calibrate diagnostics and benchmark dust dynamics modeling, pre-characterized carbon dust has been injected into the lower divertor of DIII-D. Injected dust is seen by cameras, and spectroscopic diagnostics observe an increase of carbon atomic, C2 dimer, and thermal continuum emissions from the injected dust. The latter observation can be used in the design of novel dust survey diagnostics

  16. Dust Evolution in Galaxy Cluster Simulations

    Science.gov (United States)

    Gjergo, Eda; Granato, Gian Luigi; Murante, Giuseppe; Ragone-Figueroa, Cinthia; Tornatore, Luca; Borgani, Stefano

    2018-06-01

    We implement a state-of-the-art treatment of the processes affecting the production and Interstellar Medium (ISM) evolution of carbonaceous and silicate dust grains within SPH simulations. We trace the dust grain size distribution by means of a two-size approximation. We test our method on zoom-in simulations of four massive (M200 ≥ 3 × 1014M⊙) galaxy clusters. We predict that during the early stages of assembly of the cluster at z ≳ 3, where the star formation activity is at its maximum in our simulations, the proto-cluster regions are rich in dusty gas. Compared to the case in which only dust production in stellar ejecta is active, if we include processes occurring in the cold ISM,the dust content is enhanced by a factor 2 - 3. However, the dust properties in this stage turn out to be significantly different from those observationally derived for the average Milky Way dust, and commonly adopted in calculations of dust reprocessing. We show that these differences may have a strong impact on the predicted spectral energy distributions. At low redshift in star forming regions our model reproduces reasonably well the trend of dust abundances over metallicity as observed in local galaxies. However we under-produce by a factor of 2 to 3 the total dust content of clusters estimated observationally at low redshift, z ≲ 0.5 using IRAS, Planck and Herschel satellites data. This discrepancy does not subsist by assuming a lower sputtering efficiency, which erodes dust grains in the hot Intracluster Medium (ICM).

  17. 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

  18. DUST PROPERTIES OF LOCAL DUST-OBSCURED GALAXIES WITH THE SUBMILLIMETER ARRAY

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Ho Seong; Andrews, Sean M.; Geller, Margaret J., E-mail: hhwang@cfa.harvard.edu, E-mail: sandrews@cfa.harvard.edu, E-mail: mgeller@cfa.harvard.edu [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)

    2013-11-01

    We report Submillimeter Array observations of the 880 μm dust continuum emission for four dust-obscured galaxies (DOGs) in the local universe. Two DOGs are clearly detected with S{sub ν}(880 μm) =10-13 mJy and S/N > 5, but the other two are not detected with 3σ upper limits of S{sub ν}(880 μm) =5-9 mJy. Including an additional two local DOGs with submillimeter data from the literature, we determine the dust masses and temperatures for six local DOGs. The infrared luminosities and dust masses for these DOGs are in the ranges of 1.2-4.9 × 10{sup 11}(L{sub ☉}) and 4-14 × 10{sup 7}(M{sub ☉}), respectively. The dust temperatures derived from a two-component modified blackbody function are 23-26 K and 60-124 K for the cold and warm dust components, respectively. Comparison of local DOGs with other infrared luminous galaxies with submillimeter detections shows that the dust temperatures and masses do not differ significantly among these objects. Thus, as argued previously, local DOGs are not a distinctive population among dusty galaxies, but simply represent the high-end tail of the dust obscuration distribution.

  19. DUST PROPERTIES OF LOCAL DUST-OBSCURED GALAXIES WITH THE SUBMILLIMETER ARRAY

    International Nuclear Information System (INIS)

    Hwang, Ho Seong; Andrews, Sean M.; Geller, Margaret J.

    2013-01-01

    We report Submillimeter Array observations of the 880 μm dust continuum emission for four dust-obscured galaxies (DOGs) in the local universe. Two DOGs are clearly detected with S ν (880 μm) =10-13 mJy and S/N > 5, but the other two are not detected with 3σ upper limits of S ν (880 μm) =5-9 mJy. Including an additional two local DOGs with submillimeter data from the literature, we determine the dust masses and temperatures for six local DOGs. The infrared luminosities and dust masses for these DOGs are in the ranges of 1.2-4.9 × 10 11 (L ☉ ) and 4-14 × 10 7 (M ☉ ), respectively. The dust temperatures derived from a two-component modified blackbody function are 23-26 K and 60-124 K for the cold and warm dust components, respectively. Comparison of local DOGs with other infrared luminous galaxies with submillimeter detections shows that the dust temperatures and masses do not differ significantly among these objects. Thus, as argued previously, local DOGs are not a distinctive population among dusty galaxies, but simply represent the high-end tail of the dust obscuration distribution

  20. DETECTING THE WARM-HOT INTERGALACTIC MEDIUM THROUGH X-RAY ABSORPTION LINES

    Energy Technology Data Exchange (ETDEWEB)

    Yao Yangsen; Shull, J. Michael; Cash, Webster [Center for Astrophysics and Space Astronomy, Department of Astrophysical and Planetary Sciences, University of Colorado, 389 UCB, Boulder, CO 80309 (United States); Wang, Q. Daniel, E-mail: yaoys@colorado.edu [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States)

    2012-02-20

    The warm-hot intergalactic medium (WHIM) at temperatures 10{sup 5}-10{sup 7} K is believed to contain 30%-50% of the baryons in the local universe. However, all current X-ray detections of the WHIM at redshifts z > 0 are of low statistical significance ({approx}< 3{sigma}) and/or controversial. In this work, we aim to establish the detection limits of current X-ray observatories and explore requirements for next-generation X-ray telescopes for studying the WHIM through X-ray absorption lines. We analyze all available grating observations of Mrk 421 and obtain spectra with signal-to-noise ratios (S/Ns) of {approx}90 and 190 per 50 mA spectral bin from Chandra and XMM-Newton observations, respectively. Although these spectra are two of the best ever collected with Chandra and XMM-Newton, we cannot confirm the two WHIM systems reported by Nicastro et al. in 2005. Our bootstrap simulations indicate that spectra with such high S/N cannot constrain the WHIM with O VII column densities N{sub Ovii}{approx}10{sup 15} cm{sup -2} (corresponding to an equivalent width of 2.5 mA for a Doppler velocity of 50 km s{sup -1}) at {approx}> 3{sigma} significance level. The simulation results also suggest that it would take >60 Ms for Chandra and 140 Ms for XMM-Newton to measure the N{sub Ovii} at {>=}4{sigma} from a spectrum of a background QSO with flux of {approx}0.2 mCrab (1 Crab = 2 Multiplication-Sign 10{sup -8} erg s{sup -1} cm{sup -2} at 0.5-2 keV). Future X-ray spectrographs need to be equipped with spectral resolution R {approx} 4000 and effective area A {>=} 100 cm{sup 2} to accomplish the similar constraints with an exposure time of {approx}2 Ms and would require {approx}11 Ms to survey the 15 QSOs with flux {approx}> 0.2 mCrab along which clear intergalactic O VI absorbers have been detected.

  1. Properties of the Intergalactic Magnetic Field Constrained by Gamma-Ray Observations of Gamma-Ray Bursts

    Energy Technology Data Exchange (ETDEWEB)

    Veres, P.; Dermer, C. D.; Dhuga, K. S. [Department of Physics, George Washington University, Washington, DC 20052 (United States)

    2017-09-20

    The magnetic field in intergalactic space gives important information about magnetogenesis in the early universe. The properties of this field can be probed by searching for radiation of secondary e {sup +} e {sup −} pairs created by TeV photons that produce GeV range radiation by Compton-scattering cosmic microwave background photons. The arrival times of the GeV “echo” photons depend strongly on the magnetic field strength and coherence length. A Monte Carlo code that accurately treats pair creation is developed to simulate the spectrum and time-dependence of the echo radiation. The extrapolation of the spectrum of powerful gamma-ray bursts (GRBs) like GRB 130427A to TeV energies is used to demonstrate how the intergalactic magnetic field can be constrained if it falls in the 10{sup −21}–10{sup −17} G range for a 1 Mpc coherence length.

  2. Cold fusion

    International Nuclear Information System (INIS)

    Koster, J.

    1989-01-01

    In this contribution the author the phenomenom of so-called cold fusion, inspired by the memorable lecture of Moshe Gai on his own search for this effect. Thus much of what follows was presented by Dr. Gai; the rest is from independent reading. What is referred to as cold fusion is of course the observation of possible products of deuteron-deuteron (d-d) fusion within deuterium-loaded (dentended) electrodes. The debate over the two vanguard cold fusion experiments has raged under far more public attention than usually accorded new scientific phenomena. The clamor commenced with the press conference of M. Fleishmann and S. Pons on March 23, 1989 and the nearly simultaneous wide circulation of a preprint of S. Jones and collaborators. The majority of work attempting to confirm these observations has at the time of this writing yet to appear in published form, but contributions to conferences and electronic mail over computer networks were certainly filled with preliminary results. To keep what follows to a reasonable length the author limit this discussion to the searches for neutron (suggested by ref. 2) or for excessive heat production (suggested by ref. 1), following a synopsis of the hypotheses of cold fusion

  3. Project COLD.

    Science.gov (United States)

    Kazanjian, Wendy C.

    1982-01-01

    Describes Project COLD (Climate, Ocean, Land, Discovery) a scientific study of the Polar Regions, a collection of 35 modules used within the framework of existing subjects: oceanography, biology, geology, meterology, geography, social science. Includes a partial list of topics and one activity (geodesic dome) from a module. (Author/SK)

  4. Cold fusion

    International Nuclear Information System (INIS)

    Seo, Suk Yong; You, Jae Jun

    1996-01-01

    Nearly every technical information is chased in the world. All of them are reviewed and analyzed. Some of them are chosen to study further more to review every related documents. And a probable suggestion about the excitonic process in deuteron absorbed condensed matter is proposed a way to cold fusion. 8 refs. (Author)

  5. Diagnosing the reionization of the universe - The absorption spectrum of the intergalactic medium and Lyman alpha clouds

    Science.gov (United States)

    Giroux, Mark L.; Shapiro, Paul R.

    1991-01-01

    The thermal and ionization evolution of a uniform intergalactic medium composed of H and He and undergoing reionization is studied. The diagnosis of the metagalactic ionizing radiation background at z of about three using metal line ratios for Lyman limit quasar absorption line systems is addressed. The use of the He II Gunn-Peterson effect to diagnose the reionization source and/or nature of the Hy-alpha forest clouds is considered.

  6. Probing the Intergalactic Medium with Ly α and 21 cm Fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Heneka, Caroline [Dark Cosmology Center, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Cooray, Asantha; Feng, Chang [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)

    2017-10-10

    We study 21 cm and Ly α fluctuations, as well as H α , while distinguishing between Ly α emission of galactic, diffuse, and scattered intergalactic medium (IGM) origin. Cross-correlation information about the state of the IGM is obtained, testing neutral versus ionized medium cases with different tracers in a seminumerical simulation setup. In order to pave the way toward constraints on reionization history and modeling beyond power spectrum information, we explore parameter dependencies of the cross-power signal between 21 cm and Ly α , which displays a characteristic morphology and a turnover from negative to positive correlation at scales of a couple Mpc{sup −1}. In a proof of concept for the extraction of further information on the state of the IGM using different tracers, we demonstrate the use of the 21 cm and H α cross-correlation signal to determine the relative strength of galactic and IGM emission in Ly α . We conclude by showing the detectability of the 21 cm and Ly α cross-correlation signal over more than one decade in scale at high signal-to-noise ratio for upcoming probes like SKA and the proposed all-sky intensity mapping satellites SPHEREx and CDIM, while also including the Ly α damping tail and 21 cm foreground avoidance in the modeling.

  7. A new measurement of the intergalactic temperature at z ˜ 2.55-2.95

    Science.gov (United States)

    Rorai, Alberto; Carswell, Robert F.; Haehnelt, Martin G.; Becker, George D.; Bolton, James S.; Murphy, Michael T.

    2018-03-01

    We present two measurements of the temperature-density relationship (TDR) of the intergalactic medium (IGM) in the redshift range 2.55 law parameters T0 and γ describing the TDR. This approach yields T0/103 K = 15.6 ± 4.4 and γ = 1.45 ± 0.17 independent of the assumed pressure smoothing of the small-scale density field. In order to explore the information contained in the overall b-N_{H I} distribution rather than only the lower cut-off, we obtain a second measurement based on a similar Bayesian analysis of the median Doppler parameter for separate column-density ranges of the absorbers. In this case, we obtain T0/103 K = 14.6 ± 3.7 and γ = 1.37 ± 0.17 in good agreement with the first measurement. Our Bayesian analysis reveals strong anticorrelations between the inferred T0 and γ for both methods as well as an anticorrelation of the inferred T0 and the pressure smoothing length for the second method, suggesting that the measurement accuracy can in the latter case be substantially increased if independent constraints on the smoothing are obtained. Our results are in good agreement with other recent measurements of the thermal state of the IGM probing similar (over-)density ranges.

  8. Atomic Data Revisions for Transitions Relevant to Observations of Interstellar, Circumgalactic, and Intergalactic Matter

    Energy Technology Data Exchange (ETDEWEB)

    Cashman, Frances H.; Kulkarni, Varsha P. [Department of Physics and Astronomy, University of South Carolina, Columbia, SC 29208 (United States); Kisielius, Romas; Bogdanovich, Pavel [Institute of Theoretical Physics and Astronomy, Vilnius University, Saulėtekio al. 3, LT-10222 Vilnius (Lithuania); Ferland, Gary J. [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506 (United States)

    2017-05-01

    Measurements of element abundances in galaxies from astrophysical spectroscopy depend sensitively on the atomic data used. With the goal of making the latest atomic data accessible to the community, we present a compilation of selected atomic data for resonant absorption lines at wavelengths longward of 911.753 Å (the H i Lyman limit), for key heavy elements (heavier than atomic number 5) of astrophysical interest. In particular, we focus on the transitions of those ions that have been observed in the Milky Way interstellar medium (ISM), the circumgalactic medium (CGM) of the Milky Way and/or other galaxies, and the intergalactic medium (IGM). We provide wavelengths, oscillator strengths, associated accuracy grades, and references to the oscillator strength determinations. We also attempt to compare and assess the recent oscillator strength determinations. For about 22% of the lines that have updated oscillator strength values, the differences between the former values and the updated ones are ≳0.1 dex. Our compilation will be a useful resource for absorption line studies of the ISM, as well as studies of the CGM and IGM traced by sight lines to quasars and gamma-ray bursts. Studies (including those enabled by future generations of extremely large telescopes) of absorption by galaxies against the light of background galaxies will also benefit from our compilation.

  9. Discovery of intergalactic radio emission in the Coma-A1367 supercluster

    International Nuclear Information System (INIS)

    Kim, K.T.; Kronberg, P.P.; Venturi, T.

    1989-01-01

    The Coma cluster is a rich cluster of galaxies nested in an even larger super cluster of galaxies. The plane of the supercluster seems to be defined by the Coma cluster itself and another galaxy cluster, Abell 1367, which lies ∼ 40 Mpc farther west. The largest structures known are the giant voids and superclusters which are as large as 70h 75 -1 Mpc (refs 3-5). The Coma cluster of galaxies seems to be located on the rim of a giant void in the three-dimensional distribution of galaxies. Here we describe the detection of faint, supercluster-scale radio emission at 326 MHz that extends between the Coma cluster of galaxies and the Abell 1367 cluster and which is apparently not associated with any individual galaxy system in the complex. The radiation's synchrotron origin implies the existence of a large-scale intercluster magnetic field with an estimated strength of 0.3-0.6 μG, which is remarkably strong. The synchrotron-emitting relativistic electrons cannot be older than a few times 10 8 yr, but we speculate that the magnetic field is the fossil of a pre-galactic primaeval field, which was amplified in the course of the formation of intergalactic voids and superclusters. (author)

  10. An intergalactic absorbing cloud in the neighbourhood of the North galactic pole

    International Nuclear Information System (INIS)

    Murawski, W.

    1983-01-01

    The purpose of this investigation is to study the possibility that the lack of galaxies in the area between the Virgo and Coma clusters, to which OKROY (1965) drew attention, is due to an intergalactic cloud. Using Zwicky's Catalogue of Galaxies and Clusters of Galaxies, it is shown that there is a shortage of galaxies in the suspected area for all magnitude classes. The absorption of the cloud is calculated to be 0.45+-05 mag. A quantity called the areal colour index (ACI) is introduced and defined as ACI=a sub(b) b sub(b)/(a sub(r) b sub(r)) where a and b are the lengths of the major and minor axes of a galaxy, respectively, and the subscripts b and r respectively refer to measurements on the blue and red prints of the Palomar survey, given in the Uppsala Catalogue of Galaxies. The average ACI is found to be 1.25 for the control area, and 1.04 for the area covered by Okroy's alleged obscuring cloud. On the basis of this colour data an approximate map showing the shape of the cloud is given. The effect of the alleged cloud on the shape frequency of types of galaxies is discussed. It is found that the cloud significantly increases the ratio of elliptical and dwarf galaxies to SO's. The determination of the distance to the cloud and its density is discussed. (author)

  11. A NEWLY FORMING COLD FLOW PROTOGALACTIC DISK, A SIGNATURE OF COLD ACCRETION FROM THE COSMIC WEB

    International Nuclear Information System (INIS)

    Martin, D. Christopher; Matuszewski, Mateusz; Morrissey, Patrick; Neill, James D.; Moore, Anna; Steidel, Charles C.; Trainor, Ryan

    2016-01-01

    How galaxies form from, and are fueled by, gas from the intergalactic medium (IGM) remains one of the major unsolved problems in galaxy formation. While the classical Cold Dark Matter paradigm posits galaxies forming from cooling virialized gas, recent theory and numerical simulations have highlighted the importance of cold accretion flows—relatively cool ( T ∼ few × 104 K) unshocked gas streaming along filaments into dark matter halos, including hot, massive, high-redshift halos. These flows are thought to deposit gas and angular momentum into the circumgalactic medium resulting in disk- or ring-like structures, eventually coalescing into galaxies forming at filamentary intersections. We earlier reported a bright, Ly α emitting filament near the QSO HS1549+19 at redshift z = 2.843 discovered with the Palomar Cosmic Web Imager. We now report that the bright part of this filament is an enormous ( R > 100 kpc) rotating structure of hydrogen gas with a disk-like velocity profile consistent with a 4 × 10"1"2 M _⊙ halo. The orbital time of the outer part of the what we term a “protodisk” is comparable to the virialization time and the age of the universe at this redshift. We propose that this protodisk can only have recently formed from cold gas flowing directly from the cosmic web.

  12. A NEWLY FORMING COLD FLOW PROTOGALACTIC DISK, A SIGNATURE OF COLD ACCRETION FROM THE COSMIC WEB

    Energy Technology Data Exchange (ETDEWEB)

    Martin, D. Christopher; Matuszewski, Mateusz; Morrissey, Patrick; Neill, James D. [Cahill Center for Astrophysics, California Institute of Technology, 1216 East California Boulevard, Mail Code 278-17, Pasadena, California 91125 (United States); Moore, Anna [Caltech Optical Observatories, Cahill Center for Astrophysics, California Institute of Technology, 1216 East California Boulevard, Mail Code 11-17, Pasadena, California 91125 (United States); Steidel, Charles C. [Cahill Center for Astrophysics, California Institute of Technology, 1216 East California Boulevard, Mail Code 249-17, Pasadena, California 91125 (United States); Trainor, Ryan, E-mail: cmartin@srl.caltech.edu [Department of Astronomy, University of California, Berkeley, 501 15 Campbell Hall, Berkeley, CA 94720 (United States)

    2016-06-10

    How galaxies form from, and are fueled by, gas from the intergalactic medium (IGM) remains one of the major unsolved problems in galaxy formation. While the classical Cold Dark Matter paradigm posits galaxies forming from cooling virialized gas, recent theory and numerical simulations have highlighted the importance of cold accretion flows—relatively cool ( T ∼ few × 104 K) unshocked gas streaming along filaments into dark matter halos, including hot, massive, high-redshift halos. These flows are thought to deposit gas and angular momentum into the circumgalactic medium resulting in disk- or ring-like structures, eventually coalescing into galaxies forming at filamentary intersections. We earlier reported a bright, Ly α emitting filament near the QSO HS1549+19 at redshift z = 2.843 discovered with the Palomar Cosmic Web Imager. We now report that the bright part of this filament is an enormous ( R > 100 kpc) rotating structure of hydrogen gas with a disk-like velocity profile consistent with a 4 × 10{sup 12} M {sub ⊙} halo. The orbital time of the outer part of the what we term a “protodisk” is comparable to the virialization time and the age of the universe at this redshift. We propose that this protodisk can only have recently formed from cold gas flowing directly from the cosmic web.

  13. Cold fusion

    International Nuclear Information System (INIS)

    Suh, Suk Yong; Sung, Ki Woong; Kang, Joo Sang; Lee, Jong Jik

    1995-02-01

    So called 'cold fusion phenomena' are not confirmed yet. Excess heat generation is very delicate one. Neutron generation is most reliable results, however, the records are erratic and the same results could not be repeated. So there is no reason to exclude the malfunction of testing instruments. The same arguments arise in recording 4 He, 3 He, 3 H, which are not rich in quantity basically. An experiment where plenty of 4 He were recorded is attached in appendix. The problem is that we are trying to search cold fusion which is permitted by nature or not. The famous tunneling effect in quantum mechanics will answer it, however, the most fusion rate is known to be negligible. The focus of this project is on the theme that how to increase that negligible fusion rate. 6 figs, 4 tabs, 1512 refs. (Author)

  14. Cold fusion

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Suk Yong; Sung, Ki Woong; Kang, Joo Sang; Lee, Jong Jik [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1995-02-01

    So called `cold fusion phenomena` are not confirmed yet. Excess heat generation is very delicate one. Neutron generation is most reliable results, however, the records are erratic and the same results could not be repeated. So there is no reason to exclude the malfunction of testing instruments. The same arguments arise in recording {sup 4}He, {sup 3}He, {sup 3}H, which are not rich in quantity basically. An experiment where plenty of {sup 4}He were recorded is attached in appendix. The problem is that we are trying to search cold fusion which is permitted by nature or not. The famous tunneling effect in quantum mechanics will answer it, however, the most fusion rate is known to be negligible. The focus of this project is on the theme that how to increase that negligible fusion rate. 6 figs, 4 tabs, 1512 refs. (Author).

  15. Long-term variability of dust events in Iceland (1949-2011)

    Science.gov (United States)

    Dagsson-Waldhauserova, P.; Arnalds, O.; Olafsson, H.

    2014-12-01

    The long-term frequency of atmospheric dust observations was investigated for the southern part of Iceland and interpreted together with earlier results obtained from northeastern (NE) Iceland (Dagsson-Waldhauserova et al., 2013). In total, over 34 dust days per year on average occurred in Iceland based on conventionally used synoptic codes for dust observations. However, frequent volcanic eruptions, with the re-suspension of volcanic materials and dust haze, increased the number of dust events fourfold (135 dust days annually). The position of the Icelandic Low determined whether dust events occurred in the NE (16.4 dust days annually) or in the southern (S) part of Iceland (about 18 dust days annually). The decade with the most frequent dust days in S Iceland was the 1960s, but the 2000s in NE Iceland. A total of 32 severe dust storms (visibility typically warm, occurring during summer/autumn (May-September) and during mild southwesterly winds, while the subarctic dust events (S Iceland) were mainly cold, occurring during winter/spring (March-May) and during strong northeasterly winds. About half of the dust events in S Iceland occurred in winter or at sub-zero temperatures. A good correlation was found between particulate matter (PM10) concentrations and visibility during dust observations at the stations Vík and Stórhöfði. This study shows that Iceland is among the dustiest areas of the world and that dust is emitted year-round.

  16. INFRARED LUMINOSITIES AND DUST PROPERTIES OF z ∼ 2 DUST-OBSCURED GALAXIES

    International Nuclear Information System (INIS)

    Bussmann, R. S.; Dey, Arjun; Jannuzi, B. T.; Borys, C.; Desai, V.; Sheth, K.; Soifer, B. T.; Le Floc'h, E.; Melbourne, J.

    2009-01-01

    We present SHARC-II 350 μm imaging of twelve 24 μm bright (F 24μm > 0.8 mJy) Dust-Obscured Galaxies (DOGs) and Combined Array for Research in Millimeter-wave Astronomy (CARMA) 1 mm imaging of a subset of two DOGs. These objects are selected from the Booetes field of the NOAO Deep Wide-Field Survey. Detections of four DOGs at 350 μm imply infrared (IR) luminosities which are consistent to within a factor of 2 of expectations based on a warm-dust spectral energy distribution (SED) scaled to the observed 24 μm flux density. The 350 μm upper limits for the 8 non-detected DOGs are consistent with both Mrk 231 and M82 (warm-dust SEDs), but exclude cold dust (Arp 220) SEDs. The two DOGs targeted at 1 mm were not detected in our CARMA observations, placing strong constraints on the dust temperature: T dust > 35-60 K. Assuming these dust properties apply to the entire sample, we find dust masses of ∼3 x 10 8 M sun . In comparison to other dusty z ∼ 2 galaxy populations such as submillimeter galaxies (SMGs) and other Spitzer-selected high-redshift sources, this sample of DOGs has higher IR luminosities (2 x 10 13 L sun versus 6 x 10 12 L sun for the other galaxy populations) that are driven by warmer dust temperatures (>35-60 K versus ∼30 K) and lower inferred dust masses (3 x 10 8 M sun versus 3 x 10 9 M sun ). Wide-field Herschel and Submillimeter Common-User Bolometer Array-2 surveys should be able to detect hundreds of these power-law-dominated DOGs. We use the existing Hubble Space Telescope and Spitzer/InfraRed Array Camera data to estimate stellar masses of these sources and find that the stellar to gas mass ratio may be higher in our 24 μm bright sample of DOGs than in SMGs and other Spitzer-selected sources. Although much larger sample sizes are needed to provide a definitive conclusion, the data are consistent with an evolutionary trend in which the formation of massive galaxies at z ∼ 2 involves a submillimeter bright, cold-dust, and star

  17. LADEE LUNAR DUST EXPERIMENT

    Data.gov (United States)

    National Aeronautics and Space Administration — This archive bundle includes data taken by the Lunar Dust Experiment (LDEX) instrument aboard the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft....

  18. Construction dust amelioration techniques.

    Science.gov (United States)

    2012-04-01

    Dust produced on seasonal road construction sites in Alaska is both a traffic safety and environmental concern. Dust emanating from : unpaved road surfaces during construction severely reduces visibility and impacts stopping sight distance, and contr...

  19. On Dust Charging Equation

    OpenAIRE

    Tsintsadze, Nodar L.; Tsintsadze, Levan N.

    2008-01-01

    A general derivation of the charging equation of a dust grain is presented, and indicated where and when it can be used. A problem of linear fluctuations of charges on the surface of the dust grain is discussed.

  20. Efficient adiabatic hydrodynamical simulations of the high-redshift intergalactic medium

    Science.gov (United States)

    Gaikwad, Prakash; Choudhury, Tirthankar Roy; Srianand, Raghunathan; Khaire, Vikram

    2018-02-01

    We present a post-processing tool for GADGET-2 adiabatic simulations to model various observed properties of the Ly α forest at 2.5 ≤ z ≤ 4 that enables an efficient parameter estimation. In particular, we model the thermal and ionization histories that are not computed self-consistently by default in GADGET-2. We capture the effect of pressure smoothing by running GADGET-2 at an elevated temperature floor and using an appropriate smoothing kernel. We validate our procedure by comparing different statistics derived from our method with those derived using self-consistent simulations with GADGET-3. These statistics are: line-of-sight density field power spectrum, flux probability distribution function, flux power spectrum, wavelet statistics, curvature statistics, H I column density (N_{H I}) distribution function, linewidth (b) distribution and b versus log N_{H I} scatter. For the temperature floor of 104 K and typical signal-to-noise ratio of 25, the results agree well within 20 per cent of the self-consistent GADGET-3 simulation. However, this difference is smaller than the expected 1σ sample variance for an absorption path length of ˜5.35 at z = 3. Moreover for a given cosmology, we gain a factor of ˜N in computing time for modelling the intergalactic medium under N ≫ 1 different thermal histories. In addition, our method allows us to simulate the non-equilibrium evolution of thermal and ionization state of the gas and include heating due to non-standard sources like cosmic rays and high-energy γ-rays from Blazars.

  1. Agnostic stacking of intergalactic doublet absorption: measuring the Ne VIII population

    Science.gov (United States)

    Frank, Stephan; Pieri, Matthew M.; Mathur, Smita; Danforth, Charles W.; Shull, J. Michael

    2018-05-01

    We present a blind search for doublet intergalactic metal absorption with a method dubbed `agnostic stacking'. Using a forward-modelling framework, we combine this with direct detections in the literature to measure the overall metal population. We apply this novel approach to the search for Ne VIII absorption in a set of 26 high-quality COS spectra. We probe to an unprecedented low limit of log N>12.3 at 0.47≤z ≤1.34 over a path-length Δz = 7.36. This method selects apparent absorption without requiring knowledge of its source. Stacking this mixed population dilutes doublet features in composite spectra in a deterministic manner, allowing us to measure the proportion corresponding to Ne VIII absorption. We stack potential Ne VIII absorption in two regimes: absorption too weak to be significant in direct line studies (12.3 13.7). We do not detect Ne VIII absorption in either regime. Combining our measurements with direct detections, we find that the Ne VIII population is reproduced with a power-law column density distribution function with slope β = -1.86 ^{+0.18 }_{ -0.26} and normalization log f_{13.7} = -13.99 ^{+0.20 }_{ -0.23}, leading to an incidence rate of strong Ne VIII absorbers dn/dz =1.38 ^{+0.97 }_{ -0.82}. We infer a cosmic mass density for Ne VIII gas with 12.3 value significantly lower that than predicted by recent simulations. We translate this density into an estimate of the baryon density Ωb ≈ 1.8 × 10-3, constituting 4 per cent of the total baryonic mass.

  2. PATCHY BLAZAR HEATING: DIVERSIFYING THE THERMAL HISTORY OF THE INTERGALACTIC MEDIUM

    International Nuclear Information System (INIS)

    Lamberts, Astrid; Chang, Philip; Pfrommer, Christoph; Puchwein, Ewald; Broderick, Avery E.; Shalaby, Mohamad

    2015-01-01

    TeV-blazars potentially heat the intergalactic medium (IGM) as their gamma rays interact with photons of the extragalactic background light to produce electron–positron pairs, which lose their kinetic energy to the surrounding medium through plasma instabilities. This results in a heating mechanism that is only weakly sensitive to the local density, and therefore approximately spatially uniform, naturally producing an inverted temperature–density relation in underdense regions. In this paper we go beyond the approximation of uniform heating and quantify the heating rate fluctuations due to the clustered distribution of blazars and how this impacts the thermal history of the IGM. We analytically compute a filtering function that relates the heating rate fluctuations to the underlying dark matter density field. We implement it in the cosmological code GADGET-3 and perform large-scale simulations to determine the impact of inhomogeneous heating. We show that because of blazar clustering, blazar heating is inhomogeneous for z ≳ 2. At high redshift, the temperature–density relation shows an important scatter and presents a low temperature envelope of unheated regions, in particular at low densities and within voids. However, the median temperature of the IGM is close to that in the uniform case, albeit slightly lower at low redshift. We find that blazar heating is more complex than initially assumed and that the temperature–density relation is not unique. Our analytic model for the heating rate fluctuations couples well with large-scale simulations and provides a cost-effective alternative to subgrid models

  3. Thermal Sunyaev-Zel'dovich effect in the intergalactic medium with primordial magnetic fields

    Science.gov (United States)

    Minoda, Teppei; Hasegawa, Kenji; Tashiro, Hiroyuki; Ichiki, Kiyotomo; Sugiyama, Naoshi

    2017-12-01

    The presence of ubiquitous magnetic fields in the universe is suggested from observations of radiation and cosmic ray from galaxies or the intergalactic medium (IGM). One possible origin of cosmic magnetic fields is the magnetogenesis in the primordial universe. Such magnetic fields are called primordial magnetic fields (PMFs), and are considered to affect the evolution of matter density fluctuations and the thermal history of the IGM gas. Hence the information of PMFs is expected to be imprinted on the anisotropies of the cosmic microwave background (CMB) through the thermal Sunyaev-Zel'dovich (tSZ) effect in the IGM. In this study, given an initial power spectrum of PMFs as P (k )∝B1Mpc 2knB , we calculate dynamical and thermal evolutions of the IGM under the influence of PMFs, and compute the resultant angular power spectrum of the Compton y -parameter on the sky. As a result, we find that two physical processes driven by PMFs dominantly determine the power spectrum of the Compton y -parameter; (i) the heating due to the ambipolar diffusion effectively works to increase the temperature and the ionization fraction, and (ii) the Lorentz force drastically enhances the density contrast on small scale just after the recombination epoch. These facts result in making the anisotropies of the CMB temperature on small scales, and we find that the signal goes up to 10 μ K2 around ℓ˜106 with B1 Mpc=0.1 nG and nB=0.0 . Therefore, CMB measurements on such small scales may provide a hint for the existence of the PMFs.

  4. Physics of interstellar dust

    CERN Document Server

    Krugel, Endrik

    2002-01-01

    The dielectric permeability; How to evaluate grain cross sections; Very small and very big particles; Case studies of Mie calculus; Particle statistics; The radiative transition probability; Structure and composition of dust; Dust radiation; Dust and its environment; Polarization; Grain alignment; PAHs and spectral features of dust; Radiative transport; Diffuse matter in the Milky Way; Stars and their formation; Emission from young stars. Appendices Mathematical formulae; List of symbols.

  5. Dust as a surfactant

    International Nuclear Information System (INIS)

    Ignatov, A M; Schram, P P J M; Trigger, S A

    2003-01-01

    We argue that dust immersed in a plasma sheath acts as a surfactant. By considering the momentum balance in a plasma sheath, we evaluate the dependence of the plasma surface pressure on the dust density. It is shown that the dust may reduce the surface pressure, giving rise to a sufficiently strong tangential force. The latter is capable of confining the dust layer inside the sheath in the direction perpendicular to the ion flow

  6. Dust grains from the heart of supernovae

    Science.gov (United States)

    Bocchio, M.; Marassi, S.; Schneider, R.; Bianchi, S.; Limongi, M.; Chieffi, A.

    2016-03-01

    Dust grains are classically thought to form in the winds of asymptotic giant branch (AGB) stars. However, there is increasing evidence today for dust formation in supernovae (SNe). To establish the relative importance of these two classes of stellar sources of dust, it is important to know the fraction of freshly formed dust in SN ejecta that is able to survive the passage of the reverse shock and be injected in the interstellar medium. With this aim, we have developed a new code, GRASH_Rev, that allows following the dynamics of dust grains in the shocked SN ejecta and computing the time evolution of the mass, composition, and size distribution of the grains. We considered four well-studied SNe in the Milky Way and Large Magellanic Cloud: SN 1987A, CasA, the Crab nebula, and N49. These sources have been observed with both Spitzer and Herschel, and the multiwavelength data allow a better assessment the mass of warm and cold dust associated with the ejecta. For each SN, we first identified the best explosion model, using the mass and metallicity of the progenitor star, the mass of 56Ni, the explosion energy, and the circumstellar medium density inferred from the data. We then ran a recently developed dust formation model to compute the properties of freshly formed dust. Starting from these input models, GRASH_Rev self-consistently follows the dynamics of the grains, considering the effects of the forward and reverse shock, and allows predicting the time evolution of the dust mass, composition, and size distribution in the shocked and unshocked regions of the ejecta. All the simulated models aagree well with observations. Our study suggests that SN 1987A is too young for the reverse shock to have affected the dust mass. Hence the observed dust mass of 0.7-0.9 M⊙ in this source can be safely considered as indicative of the mass of freshly formed dust in SN ejecta. Conversely, in the other three SNe, the reverse shock has already destroyed between 10-40% of the

  7. Nonlinear propagation of dust-acoustic solitary waves in a dusty ...

    Indian Academy of Sciences (India)

    component unmag- netized dusty plasma consisting of trapped electrons, Maxwellian ions, and arbitrarily charged cold mobile dust was done. It has been found that, owing to the departure from the Maxwellian elec- tron distribution to a vortex-like ...

  8. A fluid dynamic approach to the dust-acoustic soliton

    International Nuclear Information System (INIS)

    McKenzie, J.F.; Doyle, T.B.

    2002-01-01

    The properties of dust-acoustic solitons are derived from a fluid dynamic viewpoint in which conservation of total momentum, combined with the Bernoulli-like energy equations for each species, yields the structure equation for the heavy (or dust) speed in the stationary wave. This fully nonlinear approach reveals the crucial role played by the heavy sonic point in limiting the collective dust-acoustic Mach number, above which solitons cannot exist. An exact solution illustrates that the cold heavy species is compressed and this implies concomitant contraints on the potential and on the flow speed of the electrons and protons in the wave

  9. A Fluid Dynamic Approach to the Dust-Acoustic Soliton

    Science.gov (United States)

    McKenzie, J. F.; Doyle, T. B.

    2002-12-01

    The properties of dust-acoustic solitons are derived from a fluid dynamic viewpoint in which conservation of total momentum, combined with the Bernoulli-like energy equations for each species, yields the structure equation for the heavy (or dust) speed in the stationary wave. This fully nonlinear approach reveals the crucial role played by the heavy sonic point in limiting the collective dust-acoustic Mach number, above which solitons cannot exist. An exact solution illustrates that the cold heavy species is compressed and this implies concomitant contraints on the potential and on the flow speed of the electrons and protons in the wave.

  10. Existence domains of dust-acoustic solitons and supersolitons

    International Nuclear Information System (INIS)

    Maharaj, S. K.; Bharuthram, R.; Singh, S. V.; Lakhina, G. S.

    2013-01-01

    Using the Sagdeev potential method, the existence of large amplitude dust-acoustic solitons and supersolitons is investigated in a plasma comprising cold negative dust, adiabatic positive dust, Boltzmann electrons, and non-thermal ions. This model supports the existence of positive potential supersolitons in a certain region in parameter space in addition to regular solitons having negative and positive potentials. The lower Mach number limit for supersolitons coincides with the occurrence of double layers whereas the upper limit is imposed by the constraint that the adiabatic positive dust number density must remain real valued. The upper Mach number limits for negative potential (positive potential) solitons coincide with limiting values of the negative (positive) potential for which the negative (positive) dust number density is real valued. Alternatively, the existence of positive potential solitons can terminate when positive potential double layers occur

  11. Probing the Metal Enrichment of the Intergalactic Medium at z = 5–6 Using the Hubble Space Telescope

    International Nuclear Information System (INIS)

    Cai, Zheng; Fan, Xiaohui; Dave, Romeel; Finlator, Kristian; Oppenheimer, Ben

    2017-01-01

    We test the galactic outflow model by probing associated galaxies of four strong intergalactic C iv absorbers at z = 5–6 using the Hubble Space Telescope ( HST ) Advanced Camera for Surveys (ACS) ramp narrowband filters. The four strong C iv absorbers reside at z = 5.74, 5.52, 4.95, and 4.87, with column densities ranging from N Civ = 10 13.8 to 10 14.8 cm −2 . At z = 5.74, we detect an i-dropout Ly α emitter (LAE) candidate with a projected impact parameter of 42 physical kpc from the C iv absorber. This LAE candidate has a Ly α -based star formation rate (SFR Lyα ) of 2 M ⊙ yr −1 and a UV-based SFR of 4 M ⊙ yr −1 . Although we cannot completely rule out that this i-dropout emitter may be an [O ii] interloper, its measured properties are consistent with the C iv powered galaxy at z = 5.74. For C iv absorbers at z = 4.95 and z = 4.87, although we detect two LAE candidates with impact parameters of 160 and 200 kpc, such distances are larger than that predicted from the simulations. Therefore, we treat them as nondetections. For the system at z = 5.52, we do not detect LAE candidates, placing a 3 σ upper limit of SFR Lyα ≈ 1.5 M ⊙ yr −1 . In summary, in these four cases, we only detect one plausible C iv source at z = 5.74. Combining the modest SFR of the one detection and the three nondetections, our HST observations strongly support that smaller galaxies (SFR Lyα ≲ 2 M ⊙ yr −1 ) are main sources of intergalactic C iv absorbers, and such small galaxies play a major role in the metal enrichment of the intergalactic medium at z ≳ 5.

  12. High-latitude dust in the Earth system

    Science.gov (United States)

    Bullard, Joanna E; Baddock, Matthew; Bradwell, Tom; Crusius, John; Darlington, Eleanor; Gaiero, Diego; Gasso, Santiago; Gisladottir, Gudrun; Hodgkins, Richard; McCulloch, Robert; NcKenna Neuman, Cheryl; Mockford, Tom; Stewart, Helena; Thorsteinsson, Throstur

    2016-01-01

    Natural dust is often associated with hot, subtropical deserts, but significant dust events have been reported from cold, high latitudes. This review synthesizes current understanding of high-latitude (≥50°N and ≥40°S) dust source geography and dynamics and provides a prospectus for future research on the topic. Although the fundamental processes controlling aeolian dust emissions in high latitudes are essentially the same as in temperate regions, there are additional processes specific to or enhanced in cold regions. These include low temperatures, humidity, strong winds, permafrost and niveo-aeolian processes all of which can affect the efficiency of dust emission and distribution of sediments. Dust deposition at high latitudes can provide nutrients to the marine system, specifically by contributing iron to high-nutrient, low-chlorophyll oceans; it also affects ice albedo and melt rates. There have been no attempts to quantify systematically the expanse, characteristics, or dynamics of high-latitude dust sources. To address this, we identify and compare the main sources and drivers of dust emissions in the Northern (Alaska, Canada, Greenland, and Iceland) and Southern (Antarctica, New Zealand, and Patagonia) Hemispheres. The scarcity of year-round observations and limitations of satellite remote sensing data at high latitudes are discussed. It is estimated that under contemporary conditions high-latitude sources cover >500,000 km2 and contribute at least 80–100 Tg yr−1 of dust to the Earth system (~5% of the global dust budget); both are projected to increase under future climate change scenarios.

  13. Planck early results. XXIII. The first all-sky survey of Galactic cold clumps

    DEFF Research Database (Denmark)

    Poutanen, T.; Natoli, P.; Polenta, G.

    2011-01-01

    We present the statistical properties of the Cold Clump Catalogue of Planck Objects (C3PO), the first all-sky catalogue of cold objects, in terms of their spatial distribution, dust temperature, distance, mass, and morphology. We have combined Planck and IRAS data to extract 10342 cold sources...... dark clouds where the latter have been catalogued. These cold clumps are not isolated but clustered in groups. Dust temperature and emissivity spectral index values are derived from their spectral energy distributions using both Planck and IRAS data. The temperatures range from 7K to 19K...

  14. Dust-acoustic solitons in quantum plasma with kappa-distributed ions

    Indian Academy of Sciences (India)

    Abstract. Arbitrary amplitude dust-acoustic (DA) solitary waves in an unmagnetized and col- lisionless quantum dusty plasma comprising cold dust particles, kappa (κ)-distributed ions and degenerate electrons are investigated. The influence of suprathermality and quantum effects on the linear dispersion relation of DA ...

  15. The dust-acoustic mode in two-temperature electron plasmas with ...

    Indian Academy of Sciences (India)

    ... charging fluctuations, the dispersion peculiarities of dust-acoustic waves are studied based on dust fluid dynamics. The present results show that the effect will introduce a dissipation on the mode, and the dispersion and the dissipation depend on the temperature ratio and number density ratio of hot and cold electrons.

  16. PAPER-64 CONSTRAINTS ON REIONIZATION. II. THE TEMPERATURE OF THE z = 8.4 INTERGALACTIC MEDIUM

    Energy Technology Data Exchange (ETDEWEB)

    Pober, Jonathan C. [Physics Dept., U. Washington, Seattle, WA (United States); Ali, Zaki S.; Parsons, Aaron R.; Cheng, Carina; Liu, Adrian [Astronomy Dept., University of California, Berkeley, CA (United States); McQuinn, Matthew [Astronomy Dept., University of Washington, Seattle, WA (United States); Aguirre, James E.; Kohn, Saul A. [Dept. of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA (United States); Bernardi, Gianni; Grobbelaar, Jasper; Horrell, Jasper; Maree, Matthys [Square Kilometre Array South Africa (SKA SA), Pinelands (South Africa); Bradley, Richard F. [Dept. of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA (United States); Carilli, Chris L. [National Radio Astronomy Obs., Socorro, NM (United States); DeBoer, David R.; Dexter, Matthew R.; MacMahon, David H. E. [Radio Astronomy Lab., University of California, Berkeley, CA (United States); Furlanetto, Steven R. [Dept. of Physics and Astronomy, University of California, Los Angeles, CA (United States); Jacobs, Daniel C. [School of Earth and Space Exploration, Arizona State U., Tempe, AZ (United States); Klima, Patricia J. [National Radio Astronomy Obs., Charlottesville, VA (United States); and others

    2015-08-10

    We present constraints on both the kinetic temperature of the intergalactic medium (IGM) at z = 8.4, and on models for heating the IGM at high-redshift with X-ray emission from the first collapsed objects. These constraints are derived using a semi-analytic method to explore the new measurements of the 21 cm power spectrum from the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER), which were presented in a companion paper, Ali et al. Twenty-one cm power spectra with amplitudes of hundreds of mK{sup 2} can be generically produced if the kinetic temperature of the IGM is significantly below the temperature of the cosmic microwave background (CMB); as such, the new results from PAPER place lower limits on the IGM temperature at z = 8.4. Allowing for the unknown ionization state of the IGM, our measurements find the IGM temperature to be above ≈5 K for neutral fractions between 10% and 85%, above ≈7 K for neutral fractions between 15% and 80%, or above ≈10 K for neutral fractions between 30% and 70%. We also calculate the heating of the IGM that would be provided by the observed high redshift galaxy population, and find that for most models, these galaxies are sufficient to bring the IGM temperature above our lower limits. However, there are significant ranges of parameter space that could produce a signal ruled out by the PAPER measurements; models with a steep drop-off in the star formation rate density at high redshifts or with relatively low values for the X-ray to star formation rate efficiency of high redshift galaxies are generally disfavored. The PAPER measurements are consistent with (but do not constrain) a hydrogen spin temperature above the CMB temperature, a situation which we find to be generally predicted if galaxies fainter than the current detection limits of optical/NIR surveys are included in calculations of X-ray heating.

  17. Interstellar and ejecta dust in the cas a supernova remnant

    Energy Technology Data Exchange (ETDEWEB)

    Arendt, Richard G. [CRESST, University of Maryland, Baltimore County, Baltimore, MD 21250 (United States); Dwek, Eli; Kober, Gladys [NASA Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States); Rho, Jeonghee [SETI Institute, 189 Bernardo Avenue, Mountain View, CA 94043 (United States); Hwang, Una, E-mail: Richard.G.Arendt@nasa.gov [NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771 (United States)

    2014-05-01

    Infrared continuum observations provide a means of investigating the physical composition of the dust in the ejecta and swept up medium of the Cas A supernova remnant (SNR). Using low-resolution Spitzer IRS spectra (5-35 μm), and broad-band Herschel PACS imaging (70, 100, and 160 μm), we identify characteristic dust spectra, associated with ejecta layers that underwent distinct nuclear burning histories. The most luminous spectrum exhibits strong emission features at ∼9 and 21 μm and is closely associated with ejecta knots with strong Ar emission lines. The dust features can be reproduced by magnesium silicate grains with relatively low Mg to Si ratios. Another dust spectrum is associated with ejecta having strong Ne emission lines. It has no indication of any silicate features and is best fit by Al{sub 2}O{sub 3} dust. A third characteristic dust spectrum shows features that are best matched by magnesium silicates with a relatively high Mg to Si ratio. This dust is primarily associated with the X-ray-emitting shocked ejecta, but it is also evident in regions where shocked interstellar or circumstellar material is expected. However, the identification of dust composition is not unique, and each spectrum includes an additional featureless dust component of unknown composition. Colder dust of indeterminate composition is associated with emission from the interior of the SNR, where the reverse shock has not yet swept up and heated the ejecta. Most of the dust mass in Cas A is associated with this unidentified cold component, which is ≲ 0.1 M {sub ☉}. The mass of warmer dust is only ∼0.04 M {sub ☉}.

  18. The Lunar Dust Environment

    Science.gov (United States)

    Szalay, Jamey Robert

    Planetary bodies throughout the solar system are continually bombarded by dust particles, largely originating from cometary activities and asteroidal collisions. Surfaces of bodies with thick atmospheres, such as Venus, Earth, Mars and Titan are mostly protected from incoming dust impacts as these particles ablate in their atmospheres as 'shooting stars'. However, the majority of bodies in the solar system have no appreciable atmosphere and their surfaces are directly exposed to the flux of high speed dust grains. Impacts onto solid surfaces in space generate charged and neutral gas clouds, as well as solid secondary ejecta dust particles. Gravitationally bound ejecta clouds forming dust exospheres were recognized by in situ dust instruments around the icy moons of Jupiter and Saturn, and had not yet been observed near bodies with refractory regolith surfaces before NASA's Lunar Dust and Environment Explorer (LADEE) mission. In this thesis, we first present the measurements taken by the Lunar Dust Explorer (LDEX), aboard LADEE, which discovered a permanently present, asymmetric dust cloud surrounding the Moon. The global characteristics of the lunar dust cloud are discussed as a function of a variety of variables such as altitude, solar longitude, local time, and lunar phase. These results are compared with models for lunar dust cloud generation. Second, we present an analysis of the groupings of impacts measured by LDEX, which represent detections of dense ejecta plumes above the lunar surface. These measurements are put in the context of understanding the response of the lunar surface to meteoroid bombardment and how to use other airless bodies in the solar system as detectors for their local meteoroid environment. Third, we present the first in-situ dust measurements taken over the lunar sunrise terminator. Having found no excess of small grains in this region, we discuss its implications for the putative population of electrostatically lofted dust.

  19. Cough & Cold Medicine Abuse

    Science.gov (United States)

    ... Videos for Educators Search English Español Cough & Cold Medicine Abuse KidsHealth / For Teens / Cough & Cold Medicine Abuse ... resfriado Why Do People Use Cough and Cold Medicines to Get High? There's an ingredient in many ...

  20. Cold fusion

    International Nuclear Information System (INIS)

    Bush, R.T.

    1991-01-01

    The transmission resonance model (TRM) is combined with some electrochemistry of the cathode surface and found to provide a good fit to new data on excess heat. For the first time, a model for cold fusion not only fits calorimetric data but also predicts optimal trigger points. This suggests that the model is meaningful and that the excess heat phenomenon claimed by Fleischmann and Pons is genuine. A crucial role is suggested for the overpotential and, in particular, for the concentration overpotential, i.e., the hydrogen overvoltage. Self-similar geometry, or scale invariance, i.e., a fractal nature, is revealed by the relative excess power function. Heat bursts are predicted with a scale invariance in time, suggesting a possible link between the TRM and chaos theory. The model describes a near-surface phenomenon with an estimated excess power yield of ∼1 kW/cm 3 Pd, as compared to 50 W/cm 3 of reactor core for a good fission reactor. Transmission resonance-induced nuclear transmutation, a new type of nuclear reaction, is strongly suggested with two types emphasized: transmission resonance-induced neutron transfer reactions yielding essentially the same end result as Teller's hypothesized catalytic neutron transfer and a three-body reaction promoted by standing de Broglie waves. In this paper suggestions for the anomalous production of heat, particles, and radiation are given

  1. Solitons in dusty plasmas with positive dust grains

    International Nuclear Information System (INIS)

    Baluku, T. K.; Hellberg, M. A.; Mace, R. L.

    2008-01-01

    Although ''typical'' micrometer-sized dust grains in a space or laboratory plasma are often negatively charged because of collisions with the mobile electrons, there are environments in which grains may take on a positive charge. We consider a dusty plasma composed of electrons, positive ions and positive dust grains, and use the fluid dynamic paradigm to identify existence domains in parameter space for both dust-acoustic (DA) and dust-modified ion-acoustic (DIA) solitons. Only positive potential DA solitons are found. This represents an expected antisymmetry with the case of negative dust, where previously only negative solitons were reported. However, whereas for negative dust DIA solitons of either sign of potential may exist, we find that for the case of positive dust, DIA solitons are restricted to positive potentials only. The results for both positive and negative dust are consistent with an hypothesis that, in the absence of flows, the sign(s) of the soliton potential coincide(s) with the sign(s) of the species whose inertia is included in the calculation; i.e., the cold, supersonic species present in the plasma

  2. Analysis of synoptic situation for dust storms in Iraq

    Energy Technology Data Exchange (ETDEWEB)

    Al-Jumaily, Kais J.; Ibrahim, Morwa K. [Department of Atmospheric Sciences, College of Science, Al-Mustansiriyah University, Baghdad (Iraq)

    2013-07-01

    Dust storms are considered major natural disasters that cause many damages to society and environment in Iraq and surrounded deserted regions. The aim of this research is to analyze and study the synoptic patterns leading to the formation of dust storms in Iraq. Analysis are based on satellite images, aerosols index and synoptic weather maps. Two severe dust storms occurred over Iraq on February 22, 2010, and on December 10, 2011 were analyzed. The results showed that dust storms form when a low-pressure system forms over Iran causing Shamal winds blow; they carry cool air from that region towards warmer regions like eastern Syria and Iraq. In some cases, this low-pressure system is followed by a high-pressure system brining more cold air to the region and pushing dust toward south. Dust storms are initiated from source regions near Iraq-Syria borders by the existence of negative vertical velocity, which causes dust particles to be lifted upwards, and the strong westerly wind drives dust to travel eastward.

  3. Dust Devil Tracks

    Science.gov (United States)

    2002-01-01

    (Released 8 May 2002) The Science This image, centered near 50.0 S and 17.7 W displays dust devil tracks on the surface. Most of the lighter portions of the image likely have a thin veneer of dust settled on the surface. As a dust devil passes over the surface, it acts as a vacuum and picks up the dust, leaving the darker substrate exposed. In this image there is a general trend of many of the tracks running from east to west or west to east, indicating the general wind direction. There is often no general trend present in dust devil tracks seen in other images. The track patterns are quite ephemeral and can completely change or even disappear over the course of a few months. Dust devils are one of the mechanisms that Mars uses to constantly pump dust into the ubiquitously dusty atmosphere. This atmospheric dust is one of the main driving forces of the present Martian climate. The Story Vrrrrooooooooom. Think of a tornado, the cartoon Tasmanian devil, or any number of vacuum commercials that powerfully suck up swirls of dust and dirt. That's pretty much what it's like on the surface of Mars a lot of the time. Whirlpools of wind called

  4. Intergalactic medium emission observations with the cosmic web imager. II. Discovery of extended, kinematically linked emission around SSA22 Lyα BLOB 2

    International Nuclear Information System (INIS)

    Christopher Martin, D.; Chang, Daphne; Matuszewski, Matt; Morrissey, Patrick; Rahman, Shahin; Moore, Anna; Steidel, Charles C.; Matsuda, Yuichi

    2014-01-01

    The intergalactic medium (IGM) is the dominant reservoir of baryons, delineates the large-scale structure of the universe at low to moderate overdensities, and provides gas from which galaxies form and evolve. Simulations of a cold-dark-matter- (CDM-) dominated universe predict that the IGM is distributed in a cosmic web of filaments and that galaxies should form along and at the intersections of these filaments. While observations of QSO absorption lines and the large-scale distribution of galaxies have confirmed the CDM paradigm, the cosmic web of IGM has never been confirmed by direct imaging. Here we report our observation of the Lyα blob 2 (LAB2) in SSA22 with the Cosmic Web Imager (CWI). This is an integral field spectrograph optimized for low surface brightness, extended emission. With 22 hr of total on- and off-source exposure, CWI has revealed that LAB2 has extended Lyα emission that is organized into azimuthal zones consistent with filaments. We perform numerous tests with simulations and the data to secure the robustness of this result, which relies on data with modest signal-to-noise ratios. We have developed a smoothing algorithm that permits visualization of data cube slices along image or spectral image planes. With both raw and smoothed data cubes we demonstrate that the filaments are kinematically associated with LAB2 and display double-peaked profiles characteristic of optically thick Lyα emission. The flux is 10-20 times brighter than expected for the average emission from the IGM but is consistent with boosted fluorescence from a buried QSO or gravitation cooling radiation. Using simple emission models, we infer a baryon mass in the filaments of at least 1-4 × 10 11 M ☉ , and the dark halo mass is at least 2 × 10 12 M ☉ . The spatial-kinematic morphology is more consistent with inflow from the cosmic web than outflow from LAB2, although an outflow feature maybe present at one azimuth. LAB2 and the surrounding gas have significant and

  5. Intergalactic medium emission observations with the cosmic web imager. II. Discovery of extended, kinematically linked emission around SSA22 Lyα BLOB 2

    Energy Technology Data Exchange (ETDEWEB)

    Christopher Martin, D.; Chang, Daphne; Matuszewski, Matt; Morrissey, Patrick; Rahman, Shahin [Cahill Center for Astrophysics, California Institute of Technology, 1216 East California Boulevard, Mail Code 278-17, Pasadena, CA 91125 (United States); Moore, Anna [Caltech Optical Observatories, Cahill Center for Astrophysics, California Institute of Technology, 1216 East California Boulevard, Mail Code 11-17, Pasadena, CA 91125 (United States); Steidel, Charles C.; Matsuda, Yuichi, E-mail: cmartin@srl.caltech.edu [Cahill Center for Astrophysics, California Institute of Technology, 1216 East California Boulevard, Mail Code 249-17, Pasadena, CA 91125 (United States)

    2014-05-10

    The intergalactic medium (IGM) is the dominant reservoir of baryons, delineates the large-scale structure of the universe at low to moderate overdensities, and provides gas from which galaxies form and evolve. Simulations of a cold-dark-matter- (CDM-) dominated universe predict that the IGM is distributed in a cosmic web of filaments and that galaxies should form along and at the intersections of these filaments. While observations of QSO absorption lines and the large-scale distribution of galaxies have confirmed the CDM paradigm, the cosmic web of IGM has never been confirmed by direct imaging. Here we report our observation of the Lyα blob 2 (LAB2) in SSA22 with the Cosmic Web Imager (CWI). This is an integral field spectrograph optimized for low surface brightness, extended emission. With 22 hr of total on- and off-source exposure, CWI has revealed that LAB2 has extended Lyα emission that is organized into azimuthal zones consistent with filaments. We perform numerous tests with simulations and the data to secure the robustness of this result, which relies on data with modest signal-to-noise ratios. We have developed a smoothing algorithm that permits visualization of data cube slices along image or spectral image planes. With both raw and smoothed data cubes we demonstrate that the filaments are kinematically associated with LAB2 and display double-peaked profiles characteristic of optically thick Lyα emission. The flux is 10-20 times brighter than expected for the average emission from the IGM but is consistent with boosted fluorescence from a buried QSO or gravitation cooling radiation. Using simple emission models, we infer a baryon mass in the filaments of at least 1-4 × 10{sup 11} M {sub ☉}, and the dark halo mass is at least 2 × 10{sup 12} M {sub ☉}. The spatial-kinematic morphology is more consistent with inflow from the cosmic web than outflow from LAB2, although an outflow feature maybe present at one azimuth. LAB2 and the surrounding gas

  6. Tracing the cosmic metal evolution in the low-redshift intergalactic medium

    Energy Technology Data Exchange (ETDEWEB)

    Michael Shull, J. [Also at Institute of Astronomy, University of Cambridge, Cambridge CB3 OHA, UK. (United Kingdom); Danforth, Charles W.; Tilton, Evan M., E-mail: michael.shull@colorado.edu, E-mail: danforth@colorado.edu, E-mail: evan.tilton@colorado.edu [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States)

    2014-11-20

    Using the Cosmic Origins Spectrograph aboard the Hubble Space Telescope, we measured the abundances of six ions (C III, C IV, Si III, Si IV, N V, and O VI) in the low-redshift (z ≤ 0.4) intergalactic medium (IGM). Both C IV and Si IV have increased in abundance by a factor of ∼10 from z ≈ 5.5 to the present. We derive ion mass densities, ρ{sub ion} ≡ Ω{sub ion}ρ{sub cr}, with Ω{sub ion} expressed relative to the closure density. Our models of mass-abundance ratios, (Si III/Si IV) =0.67{sub −0.19}{sup +0.35}, (C III/C IV) =0.70{sub −0.20}{sup +0.43}, and (Ω{sub C} {sub III}+Ω{sub C} {sub IV})/(Ω{sub Si} {sub III}+Ω{sub Si} {sub IV})=4.9{sub −1.1}{sup +2.2}, are consistent with the photoionization parameter log U = –1.5 ± 0.4, hydrogen photoionization rate Γ{sub H} = (8 ± 2) × 10{sup –14} s{sup –1} at z < 0.4, and specific intensity I {sub 0} = (3 ± 1) × 10{sup –23} erg cm{sup –2} s{sup –1} Hz{sup –1} sr{sup –1} at the Lyman limit. Consistent ionization corrections for C and Si are scaled to an ionizing photon flux Φ{sub 0} = 10{sup 4} cm{sup –2} s{sup –1}, baryon overdensity Δ {sub b} ≈ 200 ± 50, and ''alpha-enhancement'' (Si/C enhanced to three times its solar ratio). We compare these metal abundances to the expected IGM enrichment and abundances in higher photoionized states of carbon (C V) and silicon (Si V, Si VI, and Si VII). Our ionization modeling infers IGM metal densities of (5.4 ± 0.5) × 10{sup 5} M {sub ☉} Mpc{sup –3} in the photoionized Lyα forest traced by the C and Si ions and (9.1 ± 0.6) × 10{sup 5} M {sub ☉} Mpc{sup –3} in hotter gas traced by O VI. Combining both phases, the heavy elements in the IGM have mass density ρ {sub Z} = (1.5 ± 0.8) × 10{sup 6} M {sub ☉} Mpc{sup –3} or Ω {sub Z} ≈ 10{sup –5}. This represents 10% ± 5% of the metals produced by (6 ± 2) × 10{sup 8} M {sub ☉} Mpc{sup –3} of integrated star formation with yield y{sub m} = 0

  7. Whither Cometary Dust?

    Science.gov (United States)

    Lisse, Carey M.

    2010-10-01

    In this paper I will discuss recent findings that have important implications for our understanding of the formation and evolution of primitive solar system dust, including: - Nesvorny et al. (2010), following up on their dynamical analyses of the zodiacal dust bands as sourced by the breakup of the Karin (5Mya) and Veritas (8Mya) asteroid families, argue that over 90% of the interplanetary dust cloud at 1 AU comes from JFC comets with near-circularized, low inclination orbits. This implies that the noted IPD collections of anhydrous and hydrous dust particles are likely to be from Oort cloud and JFC comets, respectively, not from asteroids and comets as thought in the past. Hydrous dust particles from comets like 85P/Wild2 and 9P/Tempel 1 would be consistent with results from the STARDUST and Deep Impact experiments. - Estimates of the dust particle size distributions (PSDs) in the comae of 85P/Wild2 (Green et al. 2004, 2007) and 73P/SW-3 (Sitko et al. 2010, Vaubaillon & Reach 2010) and in the trails of comets (Reach et al. 2007) have broken power law structure, with a plateau enhancement of particles of 1 mm - 1 cm in size. This size is also the size of most chondritic inclusions, and the predicted size range of the "aggregational barrier", where collisions between dust particles become destructive. - Studies of the albedo and polarization properties of cometary dust (Kolokolova et al. 2007) suggest there are 2 major groupings, one with low scattering capability and one with high. While these families could possibly have been explained by systematics in the PSDs of the emitted dust, independent work by Lisse et al. (2008) on the mineralogy of a number of highly dusty comets has shown evidence for one family of comets with highly crystalline dust and another with highly amorphous dust.

  8. Communication plan for windblown dust.

    Science.gov (United States)

    2015-05-01

    Windblown dust events occur in Arizona, and blowing dust has been considered a contributing factor to serious crashes on the : segment of Interstate 10 (I10) between Phoenix and Tucson, as well as on other Arizona roadways. Arizonas dust events...

  9. Probing the Metal Enrichment of the Intergalactic Medium at z = 5–6 Using the Hubble Space Telescope

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Zheng [UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Fan, Xiaohui [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Dave, Romeel [Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom); Finlator, Kristian [New Mexico State University, Las Cruces, NM 88003 (United States); Oppenheimer, Ben, E-mail: zcai@ucolick.org [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, 389 UCB, Boulder, CO 80309 (United States)

    2017-11-01

    We test the galactic outflow model by probing associated galaxies of four strong intergalactic C iv absorbers at z = 5–6 using the Hubble Space Telescope ( HST ) Advanced Camera for Surveys (ACS) ramp narrowband filters. The four strong C iv absorbers reside at z = 5.74, 5.52, 4.95, and 4.87, with column densities ranging from N {sub Civ} = 10{sup 13.8} to 10{sup 14.8} cm{sup −2}. At z = 5.74, we detect an i-dropout Ly α emitter (LAE) candidate with a projected impact parameter of 42 physical kpc from the C iv absorber. This LAE candidate has a Ly α -based star formation rate (SFR{sub Lyα} ) of 2 M {sub ⊙} yr{sup −1} and a UV-based SFR of 4 M {sub ⊙} yr{sup −1}. Although we cannot completely rule out that this i-dropout emitter may be an [O ii] interloper, its measured properties are consistent with the C iv powered galaxy at z = 5.74. For C iv absorbers at z = 4.95 and z = 4.87, although we detect two LAE candidates with impact parameters of 160 and 200 kpc, such distances are larger than that predicted from the simulations. Therefore, we treat them as nondetections. For the system at z = 5.52, we do not detect LAE candidates, placing a 3 σ upper limit of SFR{sub Lyα} ≈ 1.5 M {sub ⊙} yr{sup −1}. In summary, in these four cases, we only detect one plausible C iv source at z = 5.74. Combining the modest SFR of the one detection and the three nondetections, our HST observations strongly support that smaller galaxies (SFR{sub Lyα} ≲ 2 M {sub ⊙} yr{sup −1}) are main sources of intergalactic C iv absorbers, and such small galaxies play a major role in the metal enrichment of the intergalactic medium at z ≳ 5.

  10. The HOSTS Survey—Exozodiacal Dust Measurements for 30 Stars

    Science.gov (United States)

    Ertel, S.; Defrère, D.; Hinz, P.; Mennesson, B.; Kennedy, G. M.; Danchi, W. C.; Gelino, C.; Hill, J. M.; Hoffmann, W. F.; Rieke, G.; Shannon, A.; Spalding, E.; Stone, J. M.; Vaz, A.; Weinberger, A. J.; Willems, P.; Absil, O.; Arbo, P.; Bailey, V. P.; Beichman, C.; Bryden, G.; Downey, E. C.; Durney, O.; Esposito, S.; Gaspar, A.; Grenz, P.; Haniff, C. A.; Leisenring, J. M.; Marion, L.; McMahon, T. J.; Millan-Gabet, R.; Montoya, M.; Morzinski, K. M.; Pinna, E.; Power, J.; Puglisi, A.; Roberge, A.; Serabyn, E.; Skemer, A. J.; Stapelfeldt, K.; Su, K. Y. L.; Vaitheeswaran, V.; Wyatt, M. C.

    2018-05-01

    The Hunt for Observable Signatures of Terrestrial Systems survey searches for dust near the habitable zones (HZs) around nearby, bright main-sequence stars. We use nulling interferometry in the N band to suppress the bright stellar light and to probe for low levels of HZ dust around the 30 stars observed so far. Our overall detection rate is 18%, including four new detections, among which are the first three around Sun-like stars and the first two around stars without any previously known circumstellar dust. The inferred occurrence rates are comparable for early-type and Sun-like stars, but decrease from {60}-21+16% for stars with previously detected cold dust to {8}-3+10% for stars without such excess, confirming earlier results at higher sensitivity. For completed observations on individual stars, our sensitivity is five to ten times better than previous results. Assuming a lognormal excess luminosity function, we put upper limits on the median HZ dust level of 13 zodis (95% confidence) for a sample of stars without cold dust and of 26 zodis when focusing on Sun-like stars without cold dust. However, our data suggest that a more complex luminosity function may be more appropriate. For stars without detectable Large Binocular Telescope Interferometer (LBTI) excess, our upper limits are almost reduced by a factor of two, demonstrating the strength of LBTI target vetting for future exo-Earth imaging missions. Our statistics are limited so far, and extending the survey is critical to informing the design of future exo-Earth imaging surveys.

  11. Dust in planetary nebulae

    International Nuclear Information System (INIS)

    Mathis, J.S.

    1978-01-01

    The author's review concentrates on theoretical aspects of dust in planetary nebulae (PN). He considers the questions: how much dust is there is PN; what is its composition; what effects does it have on the ionization structure, on the dynamics of the nebula. (Auth.)

  12. Toxicity of lunar dust

    NARCIS (Netherlands)

    Linnarsson, D.; Carpenter, J.; Fubini, B.; Gerde, P.; Loftus, D.; Prisk, K.; Staufer, U.; Tranfield, E.; van Westrenen, W.

    2012-01-01

    The formation, composition and physical properties of lunar dust are incompletely characterised with regard to human health. While the physical and chemical determinants of dust toxicity for materials such as asbestos, quartz, volcanic ashes and urban particulate matter have been the focus of

  13. Combustible dust tests

    Science.gov (United States)

    The sugar dust explosion in Georgia on February 7, 2008 killed 14 workers and injured many others (OSHA, 2009). As a consequence of this explosion, OSHA revised its Combustible Dust National Emphasis (NEP) program. The NEP targets 64 industries with more than 1,000 inspections and has found more tha...

  14. Respirable dust measured downwind during rock dust application.

    Science.gov (United States)

    Harris, M L; Organiscak, J; Klima, S; Perera, I E

    2017-05-01

    The Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health (NIOSH) conducted underground evaluations in an attempt to quantify respirable rock dust generation when using untreated rock dust and rock dust treated with an anticaking additive. Using personal dust monitors, these evaluations measured respirable rock dust levels arising from a flinger-type application of rock dust on rib and roof surfaces. Rock dust with a majority of the respirable component removed was also applied in NIOSH's Bruceton Experimental Mine using a bantam duster. The respirable dust measurements obtained downwind from both of these tests are presented and discussed. This testing did not measure miners' exposure to respirable coal mine dust under acceptable mining practices, but indicates the need for effective continuous administrative controls to be exercised when rock dusting to minimize the measured amount of rock dust in the sampling device.

  15. Lunar Dust Mitigation Screens

    Science.gov (United States)

    Knutson, Shawn; Holloway, Nancy

    With plans for the United States to return to the moon, and establish a sustainable human presence on the lunar surface many issues must be successfully overcome. Lunar dust is one of a number of issues with the potential to create a myriad of problems if not adequately addressed. Samples of dust brought back from Apollo missions show it to be soft, yet sharp and abrasive. The dust consists of a variety of morphologies including spherical, angular blocks, shards, and a number of irregular shapes. One of the main issues with lunar dust is its attraction to stick to anything it comes in contact with (i.e. astronauts, equipment, habitats, etc.). Ionized radiation from the sun strikes the moon's surface and creates an electrostatic charge on the dust. Further, the dust harbors van der Waals forces making it especially difficult to separate once it sticks to a surface. During the Apollo missions, it was discovered that trying to brush the lunar dust from spacesuits was not effective, and rubbing it caused degradation of the suit material. Further, when entering the lunar module after moonwalks, the astronauts noted that the dust was so prolific inside the cabin that they inhaled and ingested it, causing at least one of them, Harrison "Jack" Schmidt, to report irritation of the throat and lungs. It is speculated that the dust could also harm an astronaut's nervous and cardiovascular systems, especially during an extended stay. In addition to health issues, the dust can also cause problems by scouring reflective coatings off of thermal blankets, and roughening surfaces of windows and optics. Further, panels on solar cells and photovoltaics can also be compromised due to dust sticking on the surfaces. Lunar dust has the capacity to penetrate seals, interfere with connectors, as well as mechanisms on digging machines, all of which can lead to problems and failure. To address lunar dust issues, development of electrostatic screens to mitigate dust on sur-faces is currently

  16. Influence of Non-Maxwellian Particles on Dust Acoustic Waves in a Dusty Magnetized Plasma

    International Nuclear Information System (INIS)

    Nouri Kadijani, M.; Zareamoghaddam, H.

    2013-01-01

    In this paper an investigation into dust acoustic solitary waves (DASWs) in the presence of superthermal electrons and ions in a magnetized plasma with cold dust grains and trapped electrons is discussed. The dynamic of both electrons and ions is simulated by the generalized Lorentzian (κ) distribution function (DF). The dust grains are cold and their dynamics are studied by hydrodynamic equations. The basic set of fluid equations is reduced to modified Korteweg-de Vries (mKdV) equation using Reductive Perturbation Theory (RPT). Two types of solitary waves, fast and slow dust acoustic soliton (DAS) exist in this plasma. Calculations reveal that compressive solitary structures are possibly propagated in the plasma where dust grains are negatively (or positively) charged. The properties of DASs are also investigated numerically. (physics of gases, plasmas, and electric discharges)

  17. Compacting of fly dusts from cupola and electric arc furnace

    Directory of Open Access Journals (Sweden)

    D. Baricová

    2012-01-01

    Full Text Available Recycling and utilization of dust waste is important not only from the point of view of its usage as an alternative source of raw materials, but regarding the environmental problems also. Dust emissions arise from thermal and chemical or physical processes and mechanical actions. Two kinds of fl y dusts from cupola furnaces (hot and cold blast cupola furnace and fl y dust from electric arc furnace were used by experiments. They were pelletized only with addition of water and briquetted with diff erent addition of water glass, bentonite and cement. Quality of briquettes was tested by compression – strength test and by break down test in green state, after drying and afterstoring (1 month.

  18. TeV gamma rays from 3C 279 - A possible probe of origin and intergalactic infrared radiation fields

    Science.gov (United States)

    Stecker, F. W.; De Jager, O. C.; Salamon, M. H.

    1992-01-01

    The gamma-ray spectrum of 3C 279 during 1991 June exhibited a near-perfect power law between 50 MeV and over 5 GeV with a differential spectral index of -(2.02 +/- 0.07). If extrapolated, the gamma-ray spectrum of 3C 279 should be easily detectable with first-generation air Cerenkov detectors operating above about 0.3 TeV provided there is no intergalactic absorption. However, by using model-dependent lower and upper limits for the extragalactic infrared background radiation field, a sharp cutoff of the 3C 279 spectrum is predicted at between about 0.1 and about 1 TeV. The sensitivity of present air Cerenkov detectors is good enough to measure such a cutoff, which would provide the first opportunity to obtain a measurement of the extragalactic background infrared radiation field.

  19. Planck early results. XXII. The submillimetre properties of a sample of Galactic cold clumps

    DEFF Research Database (Denmark)

    Poutanen, T.; Natoli, P.; Polenta, G.

    2011-01-01

    We perform a detailed investigation of sources from the Cold Cores Catalogue of Planck Objects (C3PO). Our goal is to probe the reliability of the detections, validate the separation between warm and cold dust emission components, provide the first glimpse at the nature, internal morphology and p...

  20. Gathering dust: A galaxy-wide study of dust emission from cloud complexes in NGC 300

    Science.gov (United States)

    Riener, M.; Faesi, C. M.; Forbrich, J.; Lada, C. J.

    2018-05-01

    Aims: We use multi-band observations by the Herschel Space Observatory to study the dust emission properties of the nearby spiral galaxy NGC 300. We compile a first catalogue of the population of giant dust clouds (GDCs) in NGC 300, including temperature and mass estimates, and give an estimate of the total dust mass of the galaxy. Methods: We carried out source detection with the multiwavelength source extraction algorithm getsources. We calculated physical properties, including mass and temperature, of the GDCs from five-band Herschel PACS and SPIRE observations from 100 to 500 μm; the final size and mass estimates are based on the observations at 250 μm that have an effective spatial resolution of 170 pc. We correlated our final catalogue of GDCs to pre-existing catalogues of HII regions to infer the number of GDCs associated with high-mass star formation and determined the Hα emission of the GDCs. Results: Our final catalogue of GDCs includes 146 sources, 90 of which are associated with known HII regions. We find that the dust masses of the GDCs are completely dominated by the cold dust component and range from 1.1 × 103 to 1.4 × 104 M⊙. The GDCs have effective temperatures of 13-23 K and show a distinct cold dust effective temperature gradient from the centre towards the outer parts of the stellar disk. We find that the population of GDCs in our catalogue constitutes 16% of the total dust mass of NGC 300, which we estimate to be about 5.4 × 106 M⊙. At least about 87% of our GDCs have a high enough average dust mass surface density to provide sufficient shielding to harbour molecular clouds. We compare our results to previous pointed molecular gas observations in NGC 300 and results from other nearby galaxies and also conclude that it is very likely that most of our GDCs are associated with complexes of giant molecular clouds. The catalogue is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc

  1. Quantifying Anthropogenic Dust Emissions

    Science.gov (United States)

    Webb, Nicholas P.; Pierre, Caroline

    2018-02-01

    Anthropogenic land use and land cover change, including local environmental disturbances, moderate rates of wind-driven soil erosion and dust emission. These human-dust cycle interactions impact ecosystems and agricultural production, air quality, human health, biogeochemical cycles, and climate. While the impacts of land use activities and land management on aeolian processes can be profound, the interactions are often complex and assessments of anthropogenic dust loads at all scales remain highly uncertain. Here, we critically review the drivers of anthropogenic dust emission and current evaluation approaches. We then identify and describe opportunities to: (1) develop new conceptual frameworks and interdisciplinary approaches that draw on ecological state-and-transition models to improve the accuracy and relevance of assessments of anthropogenic dust emissions; (2) improve model fidelity and capacity for change detection to quantify anthropogenic impacts on aeolian processes; and (3) enhance field research and monitoring networks to support dust model applications to evaluate the impacts of disturbance processes on local to global-scale wind erosion and dust emissions.

  2. COLLISIONAL GROOMING MODELS OF THE KUIPER BELT DUST CLOUD

    International Nuclear Information System (INIS)

    Kuchner, Marc J.; Stark, Christopher C.

    2010-01-01

    We modeled the three-dimensional structure of the Kuiper Belt (KB) dust cloud at four different dust production rates, incorporating both planet-dust interactions and grain-grain collisions using the collisional grooming algorithm. Simulated images of a model with a face-on optical depth of ∼10 -4 primarily show an azimuthally symmetric ring at 40-47 AU in submillimeter and infrared wavelengths; this ring is associated with the cold classical KB. For models with lower optical depths (10 -6 and 10 -7 ), synthetic infrared images show that the ring widens and a gap opens in the ring at the location of Neptune; this feature is caused by trapping of dust grains in Neptune's mean motion resonances. At low optical depths, a secondary ring also appears associated with the hole cleared in the center of the disk by Saturn. Our simulations, which incorporate 25 different grain sizes, illustrate that grain-grain collisions are important in sculpting today's KB dust, and probably other aspects of the solar system dust complex; collisions erase all signs of azimuthal asymmetry from the submillimeter image of the disk at every dust level we considered. The model images switch from being dominated by resonantly trapped small grains ('transport dominated') to being dominated by the birth ring ('collision dominated') when the optical depth reaches a critical value of τ ∼ v/c, where v is the local Keplerian speed.

  3. Collisional Grooming Models of the Kuiper Belt Dust Cloud

    Science.gov (United States)

    Kuchner, Marc J.; Stark, Christopher C.

    2010-01-01

    We modeled the three-dimensional structure of the Kuiper Belt (KB) dust cloud at four different dust production rates, incorporating both planet-dust interactions and grain-grain collisions using the collisional grooming algorithm. Simulated images of a model with a face-on optical depth of approximately 10 (exp -4) primarily show an azimuthally- symmetric ring at 40-47 AU in submillimeter and infrared wavelengths; this ring is associated with the cold classical KB. For models with lower optical depths (10 (exp -6) and 10 (exp-7)), synthetic infrared images show that the ring widens and a gap opens in the ring at the location of Neptune; this feature is caused by trapping of dust grains in Neptune's mean motion resonances. At low optical depths, a secondary ring also appears associated with the hole cleared in the center of the disk by Saturn. Our simulations, which incorporate 25 different grain sizes, illustrate that grain-grain collisions are important in sculpting today's KB dust, and probably other aspects of the solar system dust complex; collisions erase all signs of azimuthal asymmetry from the submillimeter image of the disk at every dust level we considered. The model images switch from being dominated by resonantly trapped small grains ("transport dominated") to being dominated by the birth ring ("collision dominated") when the optical depth reaches a critical value of r approximately v/c, where v is the local Keplerian speed.

  4. Acoustic solitary waves in dusty and/or multi-ion plasmas with cold, adiabatic, and hot constituents

    International Nuclear Information System (INIS)

    Verheest, Frank; Hellberg, Manfred A.; Kourakis, Ioannis

    2008-01-01

    Large nonlinear acoustic waves are discussed in a four-component plasma, made up of two superhot isothermal species, and two species with lower thermal velocities, being, respectively, adiabatic and cold. First a model is considered in which the isothermal species are electrons and ions, while the cooler species are positive and/or negative dust. Using a Sagdeev pseudopotential formalism, large dust-acoustic structures have been studied in a systematic way, to delimit the compositional parameter space in which they can be found, without restrictions on the charges and masses of the dust species and their charge signs. Solitary waves can only occur for nonlinear structure velocities smaller than the adiabatic dust thermal velocity, leading to a novel dust-acoustic-like mode based on the interplay between the two dust species. If the cold and adiabatic dust are oppositely charged, only solitary waves exist, having the polarity of the cold dust, their parameter range being limited by infinite compression of the cold dust. However, when the charges of the cold and adiabatic species have the same sign, solitary structures are limited for increasing Mach numbers successively by infinite cold dust compression, by encountering the adiabatic dust sonic point, and by the occurrence of double layers. The latter have, for smaller Mach numbers, the same polarity as the charged dust, but switch at the high Mach number end to the opposite polarity. Typical Sagdeev pseudopotentials and solitary wave profiles have been presented. Finally, the analysis has nowhere used the assumption that the dust would be much more massive than the ions and hence, one or both dust species can easily be replaced by positive and/or negative ions and the conclusions will apply to that plasma model equally well. This would cover a number of different scenarios, such as, for example, very hot electrons and ions, together with a mix of adiabatic ions and dust (of either polarity) or a very hot electron

  5. Spirit Feels Dust Gust

    Science.gov (United States)

    2007-01-01

    On sol 1149 (March 28, 2007) of its mission, NASA's Mars Exploration Rover Spirit caught a wind gust with its navigation camera. A series of navigation camera images were strung together to create this movie. The front of the gust is observable because it was strong enough to lift up dust. From assessing the trajectory of this gust, the atmospheric science team concludes that it is possible that it passed over the rover. There was, however, no noticeable increase in power associated with this gust. In the past, dust devils and gusts have wiped the solar panels of dust, making it easier for the solar panels to absorb sunlight.

  6. Grooved cold moderator tests

    International Nuclear Information System (INIS)

    Inoue, K.; Kiyanagi, Y.; Iwasa, H.; Watanabe, N.; Ikeda, S.; Carpenter, J.M.; Ishikawa, Y.

    1983-01-01

    We performed some grooved cold moderator experiments for methane at 20 K by using the Hokkaido University linac to obtain information to be used in the planning of the KENS-I' project. Cold neutron gains, spatial distribution of emitted beams and time distribution of the neutrons in the grooved cold moderator were measured. Furthermore, we assessed the effects of the grooved cold moderator on the performances of the spectrometers presently installed at the KENS-I cold source. We concluded that the grooved cold moderator benefited appreciably the performances of the spectrometers

  7. Carbon dust formation in a cold plasma from cathode sputtering

    International Nuclear Information System (INIS)

    Arnas, C.; Mouberi, A.; Hassouni, K.; Michau, A.; Lombardi, G.; Bonnin, X.; Benedic, F.; Pegourie, B.

    2009-01-01

    Nanoparticles are produced in argon glow plasmas where carbon is introduced by sputtering of a graphite cathode. A scaling law of growth is reported on as a function of the discharge time. Two successive stages of growth of concomitant agglomeration and carbon deposition are observed, followed by a final stage of growth by carbon deposition. A model of formation of molecular precursors by coagulation of neutral clusters on the one hand and of neutral-negative clusters on the other hand is presented, based on formation enthalpy and cluster geometry.

  8. Carbon dust formation in a cold plasma from cathode sputtering

    Science.gov (United States)

    Arnas, C.; Mouberi, A.; Hassouni, K.; Michau, A.; Lombardi, G.; Bonnin, X.; Bénédic, F.; Pégourié, B.

    2009-06-01

    Nanoparticles are produced in argon glow plasmas where carbon is introduced by sputtering of a graphite cathode. A scaling law of growth is reported on as a function of the discharge time. Two successive stages of growth of concomitant agglomeration and carbon deposition are observed, followed by a final stage of growth by carbon deposition. A model of formation of molecular precursors by coagulation of neutral clusters on the one hand and of neutral-negative clusters on the other hand is presented, based on formation enthalpy and cluster geometry.

  9. Galactic dust and extinction

    International Nuclear Information System (INIS)

    Lyngaa, G.

    1979-01-01

    The ratio R between visual extinction and colour excess, is slightly larger than 3 and does not vary much throughout our part of the Galaxy. The distribution of dust in the galactic plane shows, on the large scale, a gradient with higher colour excesses towards l=50 0 than towards l=230 0 . On the smaller scale, much of the dust responsible for extinction is situated in clouds which tend to group together. The correlation between positions of interstellar dust clouds and positions of spiral tracers seems rather poor in our Galaxy. However, concentrated dark clouds as well as extended regions of dust show an inclined distribution similar to the Gould belt of bright stars. (Auth.)

  10. Radioisotope dust pollution monitor

    International Nuclear Information System (INIS)

    Szepke, R.; Harasimczuk, J.; Dobrowiecki, J.

    1990-01-01

    Measuring principles and specification of two dust monitors: station-type AMIZ and portable-type PIK-10 for ambient air pollution are presented. The first one, a fully automatic instrument is destined for permanent monitoring of air pollution in preset sampling time from .25 to 24 hours. The second one was developed as a portable working model. Both instruments display their results in digital form in dust concentration units. (author)

  11. Coal dust symposium

    Energy Technology Data Exchange (ETDEWEB)

    1981-03-01

    This paper gives a report of the paper presented at the symposium held in Hanover on 9 and 10 February 1981. The topics include: the behaviour of dust and coal dust on combustion and explosion; a report on the accidents which occurred at the Laegerdorf cement works' coal crushing and drying plant; current safety requirements at coal crushing and drying plant; and coal crushing and drying. Four papers are individually abstracted. (In German)

  12. Dust devil generation

    International Nuclear Information System (INIS)

    G Onishchenko, O; A Pokhotelov, O; Horton, W; Stenflo, L

    2014-01-01

    The equations describing axi-symmetric nonlinear internal gravity waves in an unstable atmosphere are derived. A hydrodynamic model of a dust devil generation mechanism in such an atmosphere is investigated. It is shown that in an unstably stratified atmosphere the convective plumes with poloidal motion can grow exponentially. Furthermore, it is demonstrated that these convective plumes in an atmosphere with weak large scale toroidal motion are unstable with respect to three-dimensional dust devil generation. (papers)

  13. Conceptualizing Cold Disasters

    DEFF Research Database (Denmark)

    Lauta, Kristian Cedervall; Dahlberg, Rasmus; Vendelø, Morten Thanning

    2017-01-01

    In the present article, we explore in more depth the particular circumstances and characteristics of governing what we call ‘cold disasters’, and thereby, the paper sets out to investigate how disasters in cold contexts distinguish themselves from other disasters, and what the implications hereof...... are for the conceptualization and governance of cold disasters. Hence, the paper can also be viewed as a response to Alexander’s (2012a) recent call for new theory in the field of disaster risk reduction. The article is structured in four overall parts. The first part, Cold Context, provides an overview of the specific...... conditions in a cold context, exemplified by the Arctic, and zooms in on Greenland to provide more specific background for the paper. The second part, Disasters in Cold Contexts, discusses “cold disasters” in relation to disaster theory, in order to, elucidate how cold disasters challenge existing...

  14. Working in the Cold

    Centers for Disease Control (CDC) Podcasts

    During the winter, many workers are outdoors, working in cold, wet, icy, or snowy conditions. Learn how to identify symptoms that tell you there may be a problem and protect yourself from cold stress.

  15. Colds and the Flu

    Science.gov (United States)

    ... disease (COPD). What medicines can I give my child? There is no cure for the cold or the flu, and antibiotics do not work against the viruses that cause colds and the flu. Pain relievers such as ...

  16. Cold knife cone biopsy

    Science.gov (United States)

    ... biopsy; Pap smear - cone biopsy; HPV - cone biopsy; Human papilloma virus - cone biopsy; Cervix - cone biopsy; Colposcopy - cone biopsy Images Female reproductive anatomy Cold cone biopsy Cold cone removal References Baggish ...

  17. Cold medicines and children

    Science.gov (United States)

    ... ingredient. Avoid giving more than one OTC cold medicine to your child. It may cause an overdose with severe side ... the dosage instructions strictly while giving an OTC medicine to your child. When giving OTC cold medicines to your child: ...

  18. Extended dust in dwarf galaxies - solving an energy-budget paradox?

    Science.gov (United States)

    Keel, William C.; Holwerda, Benne; Lintott, Chris; Schawinski, Kevin

    2012-02-01

    The role of dust in shaping the emerging spectral energy distributions of galaxies remains poorly understood; recent Herschel results suggest large amounts of cold dust coupled with only modest optical extinction for much of the galaxy population. Previous work has used the discovery of a silhouetted-galaxy pair of a backlit dwarf galaxy with dust features extending beyond the de Vaucouleurs radius to investigate this question. We propose to examine a larger set of galaxies of this type drawn from the Galaxy Zoo catalog of silhouetted-galaxy pairs, to see whether a significant fraction of dwarfs have such extensive dust distributions. The catalog contains ~ 150 candidate backlit dwarfs; if such dust distributions are common enough to account for the Herschel results, we would see many additional cases of silhouetted dust beyond their stellar disks.

  19. Fractal dust grains in plasma

    International Nuclear Information System (INIS)

    Huang, F.; Peng, R. D.; Liu, Y. H.; Chen, Z. Y.; Ye, M. F.; Wang, L.

    2012-01-01

    Fractal dust grains of different shapes are observed in a radially confined magnetized radio frequency plasma. The fractal dimensions of the dust structures in two-dimensional (2D) horizontal dust layers are calculated, and their evolution in the dust growth process is investigated. It is found that as the dust grains grow the fractal dimension of the dust structure decreases. In addition, the fractal dimension of the center region is larger than that of the entire region in the 2D dust layer. In the initial growth stage, the small dust particulates at a high number density in a 2D layer tend to fill space as a normal surface with fractal dimension D = 2. The mechanism of the formation of fractal dust grains is discussed.

  20. Using gamma-ray bursts to probe the cosmic intergalactic medium

    International Nuclear Information System (INIS)

    Sudilovsky, Vladimir

    2014-01-01

    Gamma-ray bursts (GRBs) rapidly liberate enormous amounts of energy through the cataclysmic destruction of an individual massive object. GRBs are the most energetic events in the Universe, boasting isotropic equivalent energy releases of E∝10 51-54 erg in time scales of seconds - more energy than even active galaxies in the same time-frame. These transient events represent the ultimate high energy laboratories, and their afterglows are readily detectable from ground-based observatories out to cosmological distances out to z∝8. For this reason, GRBs are a natural tool to probe the early universe. To this end, programs to quickly measure the photometric and spectroscopic properties of GRB afterglows are providing a wealth of data that enable us to characterize the physical properties of both the burst itself and its host environment. In addition to providing extremely poignant information on the burst and its medium, GRB afterglow spectra show the presence of matter intervening along the line of sight. MgII, an important tracer of α-element processes and thus of star formation and galaxies, has been measured in ∝ 60% of GRB afterglow spectra. Surprisingly, MgII is only found in ∝30% of quasar spectra. This discrepancy in the number density dn/dz of intervening MgII absorbers implies that there are significant observational biases in either the spectroscopic samples of either GRB afterglows or quasars. In this work, we review the MgII issue and the biases proposed to explain it. We find that observations of other tracer systems (namely CIV) do not show the same overdensity, and thus conclude that solution to the MgII problem is related to the geometry of the sight-line relative to the absorbers. We conclude that an observational bias stemming from dust extinction arising from MgII cannot explain such a large discrepancy. Finally, we search for a signal of the MgII discrepancy in the transverse direction by computing the GRB-galaxy two point correlation

  1. Using gamma-ray bursts to probe the cosmic intergalactic medium

    Energy Technology Data Exchange (ETDEWEB)

    Sudilovsky, Vladimir

    2014-05-28

    Gamma-ray bursts (GRBs) rapidly liberate enormous amounts of energy through the cataclysmic destruction of an individual massive object. GRBs are the most energetic events in the Universe, boasting isotropic equivalent energy releases of E∝10{sup 51-54} erg in time scales of seconds - more energy than even active galaxies in the same time-frame. These transient events represent the ultimate high energy laboratories, and their afterglows are readily detectable from ground-based observatories out to cosmological distances out to z∝8. For this reason, GRBs are a natural tool to probe the early universe. To this end, programs to quickly measure the photometric and spectroscopic properties of GRB afterglows are providing a wealth of data that enable us to characterize the physical properties of both the burst itself and its host environment. In addition to providing extremely poignant information on the burst and its medium, GRB afterglow spectra show the presence of matter intervening along the line of sight. MgII, an important tracer of α-element processes and thus of star formation and galaxies, has been measured in ∝ 60% of GRB afterglow spectra. Surprisingly, MgII is only found in ∝30% of quasar spectra. This discrepancy in the number density dn/dz of intervening MgII absorbers implies that there are significant observational biases in either the spectroscopic samples of either GRB afterglows or quasars. In this work, we review the MgII issue and the biases proposed to explain it. We find that observations of other tracer systems (namely CIV) do not show the same overdensity, and thus conclude that solution to the MgII problem is related to the geometry of the sight-line relative to the absorbers. We conclude that an observational bias stemming from dust extinction arising from MgII cannot explain such a large discrepancy. Finally, we search for a signal of the MgII discrepancy in the transverse direction by computing the GRB-galaxy two point correlation

  2. Revealing the meteorological drivers of the September 2015 severe dust event in the Eastern Mediterranean

    Directory of Open Access Journals (Sweden)

    P. Gasch

    2017-11-01

    Full Text Available In September 2015 one of the severest and most unusual dust events on record occurred in the Eastern Mediterranean. Surprisingly, operational dust transport models were unable to forecast the event. This study details the reasons for this failure and presents simulations of the event at convection-permitting resolution using the modelling system ICON-ART. The results allow for an in-depth analysis of the influence of the synoptic situation, the complex interaction of multiple driving atmospheric systems and the mineral dust radiative effect on the dust event. A comparison of the results with observations reveals the quality of the simulation results with respect to structure and timing of the dust transport. The forecast of the dust event is improved decisively. The event is triggered by the unusually early occurrence of an active Red Sea trough situation with an easterly axis over Mesopotamia. The connected sustained organized mesoscale convection produces multiple cold-pool outflows responsible for intense dust emissions. Complexity is added by the interaction with an intense heat low, the inland-penetrating Eastern Mediterranean sea breeze and the widespread occurrence of supercritical flow conditions and subsequent hydraulic jumps in the vicinity of the Dead Sea Rift Valley. The newly implemented mineral dust radiation interaction leads to systematically more intense and faster propagating cold-pool outflows.

  3. Sahara Dust Cloud

    Science.gov (United States)

    2005-01-01

    [figure removed for brevity, see original site] Dust Particles Click on the image for Quicktime movie from 7/15-7/24 A continent-sized cloud of hot air and dust originating from the Sahara Desert crossed the Atlantic Ocean and headed towards Florida and the Caribbean. A Saharan Air Layer, or SAL, forms when dry air and dust rise from Africa's west coast and ride the trade winds above the Atlantic Ocean. These dust clouds are not uncommon, especially during the months of July and August. They start when weather patterns called tropical waves pick up dust from the desert in North Africa, carry it a couple of miles into the atmosphere and drift westward. In a sequence of images created by data acquired by the Earth-orbiting Atmospheric Infrared Sounder ranging from July 15 through July 24, we see the distribution of the cloud in the atmosphere as it swirls off of Africa and heads across the ocean to the west. Using the unique silicate spectral signatures of dust in the thermal infrared, AIRS can detect the presence of dust in the atmosphere day or night. This detection works best if there are no clouds present on top of the dust; when clouds are present, they can interfere with the signal, making it much harder to detect dust as in the case of July 24, 2005. In the Quicktime movie, the scale at the bottom of the images shows +1 for dust definitely detected, and ranges down to -1 for no dust detected. The plots are averaged over a number of AIRS observations falling within grid boxes, and so it is possible to obtain fractional numbers. [figure removed for brevity, see original site] Total Water Vapor in the Atmosphere Around the Dust Cloud Click on the image for Quicktime movie The dust cloud is contained within a dry adiabatic layer which originates over the Sahara Desert. This Saharan Air Layer (SAL) advances Westward over the Atlantic Ocean, overriding the cool, moist air nearer the surface. This burst of very dry air is visible in the AIRS retrieved total water

  4. Charging of dust grains in a plasma with negative ions

    International Nuclear Information System (INIS)

    Kim, Su-Hyun; Merlino, Robert L.

    2006-01-01

    The effect of negative ions on the charging of dust particles in a plasma is investigated experimentally. A plasma containing a very low percentage of electrons is formed in a single-ended Q machine when SF 6 is admitted into the vacuum system. The relatively cold Q machine electrons (T e ≅0.2 eV) readily attach to SF 6 molecules to form SF 6 - negative ions. Calculations of the dust charge indicate that for electrons, negative ions, and positive ions of comparable temperatures, the charge (or surface potential) of the dust can be positive if the positive ion mass is smaller than the negative ion mass and if ε, the ratio of the electron to positive ion density, is sufficiently small. The Q machine plasma is operated with K + positive ions (mass 39 amu) and SF 6 - negative ions (mass 146 amu), and also utilizes a rotating cylinder to dispense dust into the plasma column. Analysis of the current-voltage characteristics of a Langmuir probe in the dusty plasma shows evidence for the reduction in the (magnitude) of the negative dust charge and the transition to positively charged dust as the relative concentration of the residual electrons is reduced. Some remarks are offered concerning experiments that could become possible in a dusty plasma with positive grains

  5. Charging of dust grains in a plasma with negative ions

    Science.gov (United States)

    Kim, Su-Hyun; Merlino, Robert L.

    2006-05-01

    The effect of negative ions on the charging of dust particles in a plasma is investigated experimentally. A plasma containing a very low percentage of electrons is formed in a single-ended SF6 is admitted into the vacuum system. The relatively cold (Te≈0.2eV ) readily attach to SF6 molecules to form SF6- negative ions. Calculations of the dust charge indicate that for electrons, negative ions, and positive ions of comparable temperatures, the charge (or surface potential) of the dust can be positive if the positive ion mass is smaller than the negative ion mass and if ɛ, the ratio of the electron to positive ion density, is sufficiently small. The K+ positive ions (mass 39amu) and SF6- negative ions (mass 146amu), and also utilizes a rotating cylinder to dispense dust into the plasma column. Analysis of the current-voltage characteristics of a Langmuir probe in the dusty plasma shows evidence for the reduction in the (magnitude) of the negative dust charge and the transition to positively charged dust as the relative concentration of the residual electrons is reduced. Some remarks are offered concerning experiments that could become possible in a dusty plasma with positive grains.

  6. Electrodynamic Dust Shield Demonstrator

    Science.gov (United States)

    Stankie, Charles G.

    2013-01-01

    The objective of the project was to design and manufacture a device to demonstrate a new technology developed by NASA's Electrostatics and Surface Physics Laboratory. The technology itself is a system which uses magnetic principles to remove regolith dust from its surface. This project was to create an enclosure that will be used to demonstrate the effectiveness of the invention to The Office of the Chief Technologist. ONE of the most important challenges of space exploration is actually caused by something very small and seemingly insignificant. Dust in space, most notably on the moon and Mars, has caused many unforeseen issues. Dirt and dust on Earth, while a nuisance, can be easily cleaned and kept at bay. However, there is considerably less weathering and erosion in space. As a result, the microscopic particles are extremely rough and abrasive. They are also electrostatically charged, so they cling to everything they make contact with. This was first noted to be a major problem during the Apollo missions. Dust would stick to the spacesuits, and could not be wiped off as predicted. Dust was brought back into the spacecraft, and was even inhaled by astronauts. This is a major health hazard. Atmospheric storms and other events can also cause dust to coat surfaces of spacecraft. This can cause abrasive damage to the craft. The coating can also reduce the effectiveness of thermal insulation and solar panels.' A group of engineers at Kennedy Space Center's Electrostatics and Surface Physics Laboratory have developed a new technology, called the Electrodynamic Dust Shield, to help alleviate these problems. It is based off of the electric curtain concept developed at NASA in 1967. "The EDS is an active dust mitigation technology that uses traveling electric fields to transport electrostatically charged dust particles along surfaces. To generate the traveling electric fields, the EDS consists of a multilayer dielectric coating with an embedded thin electrode grid

  7. How cold is cold dark matter?

    International Nuclear Information System (INIS)

    Armendariz-Picon, Cristian; Neelakanta, Jayanth T.

    2014-01-01

    If cold dark matter consists of particles, these must be non-interacting and non-relativistic by definition. In most cold dark matter models however, dark matter particles inherit a non-vanishing velocity dispersion from interactions in the early universe, a velocity that redshifts with cosmic expansion but certainly remains non-zero. In this article, we place model-independent constraints on the dark matter temperature to mass ratio, whose square root determines the dark matter velocity dispersion. We only assume that dark matter particles decoupled kinetically while non-relativistic, when galactic scales had not entered the horizon yet, and that their momentum distribution has been Maxwellian since that time. Under these assumptions, using cosmic microwave background and matter power spectrum observations, we place upper limits on the temperature to mass ratio of cold dark matter today (away from collapsed structures). These limits imply that the present cold dark matter velocity dispersion has to be smaller than 54 m/s. Cold dark matter has to be quite cold, indeed

  8. Filling the Void: A Comprehensive Survey of the Intergalactic Medium at z 1 Using STIS/COS Archival Spectra

    Science.gov (United States)

    Khaire, Vikram

    2017-08-01

    There exists a large void in our understanding of the intergalactic medium (IGM) at z=0.5-1.5, spanning a significant cosmic time of 4 Gyr. This hole resulted from a paucity of near-UV QSO spectra, which were historically very expensive to obtain. However, with the advent of COS and the HST UV initiative, sufficient STIS/COS NUV spectra have finally become available, enabling the first statistical analyses. We propose a comprehensive study of the z 1 IGM using the Ly-alpha forest of 26 archival QSO spectra. This analysis will: (1) measure the distribution of HI absorbers to several percent precision down to log NHI science cases. These results, along with our state-of-the-art hydrodynamical simulations, and theoretical models of the UVB, will fill the 4 Gyr hole in our understanding of the IGM. When combined with existing HST and ground-based data from lower and higher z, they will lead to a complete, empirical description of the IGM from HI reionization to the present, spanning more than 10 Gyr of cosmic history, adding substantially to Hubble's legacy of discovery on the IGM.

  9. Interstellar dust and extinction

    International Nuclear Information System (INIS)

    Mathis, J.S.

    1990-01-01

    It is noted that the term interstellar dust refers to materials with rather different properties, and that the mean extinction law of Seaton (1979) or Savage and Mathis (1979) should be replaced by the expression given by Cardelli et al. (1989), using the appropriate value of total-to-selective extinction. The older laws were appropriate for the diffuse ISM but dust in clouds differs dramatically in its extinction law. Dust is heavily processed while in the ISM by being included within clouds and cycled back into the diffuse ISM many times during its lifetime. Hence, grains probably reflect only a trace of their origin, although meteoritic inclusions with isotopic anomalies demonstrate that some tiny particles survive intact from a supernova origin to the present. 186 refs

  10. Dust control for draglines

    Energy Technology Data Exchange (ETDEWEB)

    Grad, P.

    2009-09-15

    Monitoring dust levels inside draglines reveals room for improvement in how filtration systems are used and maintained. The Australian firm BMT conducted a field test program to measure airflow parameters, dust fallout rates and dust concentrations, inside and outside the machine house, on four draglines and one shovel. The study involved computational fluid dynamics (CFD) simulations. The article describes how the tests were made and gives results. It was not possible to say which of the two main filtration systems currently used on Australian draglines - Dynavane or Floseps - performs better. It would appear that more frequent maintenance and cleaning would increase the overall filtration performance and systems could be susceptible to repeat clogging in a short time. 2 figs., 1 photos.

  11. DustEM: Dust extinction and emission modelling

    Science.gov (United States)

    Compiègne, M.; Verstraete, L.; Jones, A.; Bernard, J.-P.; Boulanger, F.; Flagey, N.; Le Bourlot, J.; Paradis, D.; Ysard, N.

    2013-07-01

    DustEM computes the extinction and the emission of interstellar dust grains heated by photons. It is written in Fortran 95 and is jointly developed by IAS and CESR. The dust emission is calculated in the optically thin limit (no radiative transfer) and the default spectral range is 40 to 108 nm. The code is designed so dust properties can easily be changed and mixed and to allow for the inclusion of new grain physics.

  12. Comet Dust: The Story of Planet Formation as Told by the Tiniest of Particles

    Science.gov (United States)

    Wooden, D. H.

    2005-01-01

    Our planetary system formed out of a gas-rich disk-shaped nebula with the early Sun at its center. Many small icy bodies were consumed by the formation of the giant planets. However, many km-size icy bodies were tossed out of the giant-planet region to the cold, distant reaches of our solar system. Comets remained in their places of cold storage until perturbed into orbits that carry them into the inner solar system where they pass relatively close to the Sun. Comets are warmed by the Sun and shed material from their outer layers. The ices and gases shed by comets reveal simple and complex organic molecules were present at the time and in the region of the formation of the giant planets. Where the Earth was forming was too hot and had too intense sunlight for many of these ices and molecules to survive. The dust shed by comets tells us that some stardust survived unaltered but much of the dust was heated and crystallized before becoming part of the comet. Therefore, comet dust grains tell of large radial migrations from the cold outer reaches near Neptune into the hot regions near the forming Sun, and then back out to the cold regions where icy comets were accreting and forming. On 2005 July 4, the NASA Deep Impact Mission hit a comet and ejected primitive materials fiom its interior. These materials were not released into the comet s coma during normal activity. Despite the many passages of this comet close to the Sun, these primitive volatile gases and dust grains survived in its interior. Comet dust grains show that cold and hot materials were mixed into the same tiny particle very early in the formation of the solar system, and these aggregate dust grains never saw high temperatures again. The survival of primitive materials in comet nuclei suggests comets could have delivered organic molecules and primitive dust grains to early Earth.

  13. The dust-acoustic mode in two-temperature electron plasmas with ...

    Indian Academy of Sciences (India)

    and the Poisson equation. ∇2ϕ1 = −. [. 4π e (ni1 − nec1 − neh1) + 4πqd0nd1 + 4πqd1nd0. ] ,. (3) where nd1, nec1, neh1 and ni1 are the perturbed dust, cold electron, hot electron and ion number density, vd1, ϕ1 are the perturbed dust fluid velocity and the electrostatic poten- tial, nd0 and qd0 are the equilibrium number ...

  14. Dust-Plasma Interactions

    International Nuclear Information System (INIS)

    Rosenberg, M.

    2010-01-01

    The objective of our theoretical research under this grant over the past 3 years was to develop new understanding in a range of topics in the physics of dust-plasma interactions, with application to space and the laboratory. We conducted studies related to the physical properties of dust, waves and instabilities in both weakly coupled and strongly coupled dusty plasmas, and innovative possible applications. A major consideration in our choice of topics was to compare theory with experiments or observations, and to motivate new experiments, which we believe is important for developing this relatively new field. Our research is summarized, with reference to our list of journal publications.

  15. Ventilation in homes infested by house-dust mites.

    Science.gov (United States)

    Sundell, J; Wickman, M; Pershagen, G; Nordvall, S L

    1995-02-01

    Thirty single-family homes with either high (> or = 2000 ng/g) or low (< or = 1000 ng/g) house-dust mite (HDM) allergen levels in mattress dust were examined for ventilation, thermal climate, and air quality (formaldehyde and total volatile organic compounds (TVOC). Elevated concentrations of HDM allergen in mattress and floor dust were associated with the difference in absolute humidity between indoor and outdoor air, as well as with low air-change rates of the home, particularly the bedroom. No correlation was found between concentration of TVOC or formaldehyde in bedroom air and HDM allergen concentration. In regions with a cold winter climate, the air-change rate of the home and the infiltration of outdoor air into the bedroom appear to be important for the infestation of HDM.

  16. Analysis of Dust and Fission Products in PBMR Turbine

    International Nuclear Information System (INIS)

    Stempniewicz, M.M.; Wessels, D.

    2014-01-01

    A 400 MWth direct cycle Pebble Bed Modular reactor was under development in South Africa. The work performed included design and safety analyses. In HTR/PBMR, graphite dust is generated during normal reactor operation due to pebble-to-pebble scratching. This dust will be deposited throughout the primary system. Furthermore, the dust will become radioactive due to sorption of fission products released, although in very small quantities, during normal operation. This paper presents a model and analyses of the PBMR turbine with the SPECTRA code. The purpose of the present work was to estimate the amount and distribution of deposited dust and the fission products, namely cesium, iodine, and silver, during plant life-time, which was assumed to be 40 full-power years. The performed work showed that after 40 years of plant life-time deposited layers are very small. The largest deposition is of course observed on the dust filters. Apart from the dust filters, the largest dust deposition is observed on the: • Outer Casing (inner walls) • Turbine Rotor Cooling Cavity (inner walls) • HPC Cold Cooling Gas Header (inner walls) This is caused by relatively low gas velocities in these volumes. The low velocities allow a continuous build-up of the dust layer. About 90% of cesium, 40% of iodine, and 99.9% of silver is adsorbed on the metallic structures of the turbine. The sorption rate increases along the turbine due to decreasing temperatures. In case of cesium and iodine the highest concentrations are observed in the last stage (stage 12) of the turbine. In the case of silver the sorption is so large that the silver vapor is significantly depleted in the last stages of the turbine. This is a reason for having a maximum in silver concentration in the stage 10. In the following stages the concentration decreases due to very small silver vapor fraction in the gas. (author)

  17. Control of harmful dust in coal mines

    Energy Technology Data Exchange (ETDEWEB)

    Goddard, B; Bower, K; Mitchell, D

    1973-01-01

    This handbook consists of a series of short chapters devoted to: sources of airborne dust; dust standards and methods of sampling; dust prevention on mechanized faces; ventilation and dust extraction; distribution and use of water; dust control on mechanized faces; dust control in drivages and headings; drilling and shotfiring; dust control in transport; some outbye dust control techniques (hygroscopic salts, impingement curtains); water infusion; personal protective equipment. (CIS Abstr.)

  18. Cold formability of steels

    International Nuclear Information System (INIS)

    Lafond, G.; Leclerq, G.; Moliexe, F.; Namdar, R.; Roesch, L.; Sanz, G.

    1977-01-01

    This work was essentially aimed to the study of the following three questions. Is it possible to assess the cold formability of steels using simple material properties as criteria. What values of mechanical properties can one expect to reach in cold formed parts. Are there simple ways of characterizing the speroidization treatments carried out on steels before cold forming operations. The present report describes the results obtained during this investigation. It is logically divided into three separate parts. Experimental study of cold formability in wire drawing. Influence of metallurgical variables on mechanical properties of high carbon cold drawn wires. Contribution to the study of characterization methods of cold forming steels subjected to a spheroidization heat treatment

  19. Dust evolution in protoplanetary disks

    OpenAIRE

    Gonzalez , Jean-François; Fouchet , Laure; T. Maddison , Sarah; Laibe , Guillaume

    2007-01-01

    6 pages, 5 figures, to appear in the Proceedings of IAU Symp. 249: Exoplanets: Detection, Formation and Dynamics (Suzhou, China); International audience; We investigate the behaviour of dust in protoplanetary disks under the action of gas drag using our 3D, two-fluid (gas+dust) SPH code. We present the evolution of the dust spatial distribution in global simulations of planetless disks as well as of disks containing an already formed planet. The resulting dust structures vary strongly with pa...

  20. Respirable versus inhalable dust sampling

    International Nuclear Information System (INIS)

    Hondros, J.

    1987-01-01

    The ICRP uses a total inhalable dust figure as the basis of calculations on employee lung dose. This paper was written to look at one aspect of the Olympic Dam dust situation, namely, the inhalable versus respirable fraction of the dust cloud. The results of this study will determine whether it is possible to use respirable dust figures, as obtained during routine monitoring to help in the calculations of employee exposure to internal radioactive contaminants

  1. Paleo-dust insights onto dust-climate interactions

    Science.gov (United States)

    Albani, S.; Mahowald, N. M.

    2017-12-01

    Mineral dust emissions are affected by changing climate conditions, and in turn dust impacts the atmospheric radiation budget, clouds and biogeochemical cycles. Climate and public health dust-related issues call for attention on the fate of the dust cycle in the future, and the representation of the dust cycle is now part of the strategy of the Paleoclimate Modelling Intercomparison Project phase 4 and the Coupled Model Intercomparison Project phase 6 (PMIP4-CMIP6). Since mineral aerosols are one of the most important natural aerosols, understanding past dust responses to climate in the paleoclimate will allow us to better understand mineral aerosol feedbacks with climate and biogeochemistry in the Anthropocene. Modern observations and paleoclimate records offer the possibility of multiple, complementary views on the global dust cycle, and allow to validate and/or constrain the numerical representation of dust in climate and Earth system models. We present our results from a set of simulations with the Community Earth System Model for different climate states, including present and past climates such as the pre-industrial, the mid-Holocene and the Last Glacial Maximum. A set of simulations including a prognostic dust cycle was thoroughly compared with a wide set of present day observations from different platforms and regions, in order to realistically constrain the magnitude of dust load, surface concentration, deposition, optical properties, and particle size distributions. The magnitude of emissions for past climate regimes was constrained based on compilations of paleodust mass accumulation rates and size distributions, as well as based on information on dust provenance. The comparison with a parallel set of simulations without dust allows estimating the impacts of dust on surface climate. We analyze impacts of dust on the mean and variability of surface temperature and precipitation in each climate state, as well as the impacts that changing dust emissions had

  2. The impact of dust storms on the Arabian Peninsula and the Red Sea

    KAUST Repository

    Jish Prakash, P.

    2015-01-12

    Located in the dust belt, the Arabian Peninsula is a major source of atmospheric dust. Frequent dust outbreaks and some 15 to 20 dust storms per year have profound effects on all aspects of human activity and natural processes in this region. To quantify the effect of severe dust events on radiation fluxes and regional climate characteristics, we simulated the storm that occurred from 18 to 20 March 2012 using a regional weather research forecast model fully coupled with the chemistry/aerosol module (WRF–Chem). This storm swept over a remarkably large area affecting the entire Middle East, northeastern Africa, Afghanistan, and Pakistan. It was caused by a southward propagating cold front, and the associated winds activated the dust production in river valleys of the lower Tigris and Euphrates in Iraq; the coastal areas in Kuwait, Iran, and the United Arab Emirates; the Rub al Khali, An Nafud, and Ad Dahna deserts; and along the Red Sea coast on the west side of the Arabian Peninsula. Our simulation results compare well with available ground-based and satellite observations. We estimate the total amount of dust generated by the storm to have reached 94 Mt. Approximately 78% of this dust was deposited within the calculation domain. The Arabian Sea and Persian Gulf received 5.3 Mt and the Red Sea 1.2 Mt of dust. Dust particles bring nutrients to marine ecosystems, which is especially important for the oligotrophic Northern Red Sea. However, their contribution to the nutrient balance in the Red Sea remains largely unknown. By scaling the effect of one storm to the number of dust storms observed annually over the Red Sea, we estimate the annual dust deposition to the Red Sea, associated with major dust storms, to be 6 Mt.

  3. The impact of dust storms on the Arabian Peninsula and the Red Sea

    KAUST Repository

    Jish Prakash, P.; Stenchikov, Georgiy L.; Kalenderski, Stoitchko; Osipov, Sergey; Bangalath, Hamza Kunhu

    2015-01-01

    Located in the dust belt, the Arabian Peninsula is a major source of atmospheric dust. Frequent dust outbreaks and some 15 to 20 dust storms per year have profound effects on all aspects of human activity and natural processes in this region. To quantify the effect of severe dust events on radiation fluxes and regional climate characteristics, we simulated the storm that occurred from 18 to 20 March 2012 using a regional weather research forecast model fully coupled with the chemistry/aerosol module (WRF–Chem). This storm swept over a remarkably large area affecting the entire Middle East, northeastern Africa, Afghanistan, and Pakistan. It was caused by a southward propagating cold front, and the associated winds activated the dust production in river valleys of the lower Tigris and Euphrates in Iraq; the coastal areas in Kuwait, Iran, and the United Arab Emirates; the Rub al Khali, An Nafud, and Ad Dahna deserts; and along the Red Sea coast on the west side of the Arabian Peninsula. Our simulation results compare well with available ground-based and satellite observations. We estimate the total amount of dust generated by the storm to have reached 94 Mt. Approximately 78% of this dust was deposited within the calculation domain. The Arabian Sea and Persian Gulf received 5.3 Mt and the Red Sea 1.2 Mt of dust. Dust particles bring nutrients to marine ecosystems, which is especially important for the oligotrophic Northern Red Sea. However, their contribution to the nutrient balance in the Red Sea remains largely unknown. By scaling the effect of one storm to the number of dust storms observed annually over the Red Sea, we estimate the annual dust deposition to the Red Sea, associated with major dust storms, to be 6 Mt.

  4. Cold fusion, Alchemist's dream

    International Nuclear Information System (INIS)

    Clayton, E.D.

    1989-09-01

    In this report the following topics relating to cold fusion are discussed: muon catalysed cold fusion; piezonuclear fusion; sundry explanations pertaining to cold fusion; cosmic ray muon catalysed cold fusion; vibrational mechanisms in excited states of D 2 molecules; barrier penetration probabilities within the hydrogenated metal lattice/piezonuclear fusion; branching ratios of D 2 fusion at low energies; fusion of deuterons into 4 He; secondary D+T fusion within the hydrogenated metal lattice; 3 He to 4 He ratio within the metal lattice; shock induced fusion; and anomalously high isotopic ratios of 3 He/ 4 He

  5. Erosion of dust aggregates

    NARCIS (Netherlands)

    Seizinger, A.; Krijt, S.; Kley, W.

    2013-01-01

    Aims: The aim of this work is to gain a deeper insight into how much different aggregate types are affected by erosion. Especially, it is important to study the influence of the velocity of the impacting projectiles. We also want to provide models for dust growth in protoplanetary disks with simple

  6. Dust-Plasma Interactions

    International Nuclear Information System (INIS)

    Rosenberg, Marelene

    2005-01-01

    Our theoretical research on dust-plasma interactions has concentrated on three main areas: (a)studies of grain charging and applications; (b) waves and instabilities in weakly correlated dusty plasma with applications to space and laboratory plasmas; (c) waves in strongly coupled dusty plasmas.

  7. From dust to life

    Science.gov (United States)

    Wickramasinghe, Chandra

    After initially challenging the dirty-ice theory of interstellar grains, Fred Hoyle and the present author proposed carbon (graphite) grains, mixtures of refractory grains, organic polymers, biochemicals and finally bacterial grains as models of interstellar dust. The present contribution summarizes this trend and reviews the main arguments supporting a modern version of panspermia.

  8. Cold Antimatter Plasmas, and Aspirations for Cold Antihydrogen

    Science.gov (United States)

    2002-06-24

    UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP012494 TITLE: Cold Antimatter Plasmas, and Aspirations for Cold...part numbers comprise the compilation report: ADP012489 thru ADP012577 UNCLASSIFIED Cold Antimatter Plasmas, and Aspirations for Cold Antihydrogen G...and positrons. The antiprotons come initially from the new Antiproton Decel- erator facility at CERN. Good control of such cold antimatter plasmas is

  9. Modelling dust transport in tokamaks

    International Nuclear Information System (INIS)

    Martin, J.D.; Martin, J.D.; Bacharis, M.; Coppins, M.; Counsell, G.F.; Allen, J.E.; Counsell, G.F.

    2008-01-01

    The DTOKS code, which models dust transport through tokamak plasmas, is described. The floating potential and charge of a dust grain in a plasma and the fluxes of energy to and from it are calculated. From this model, the temperature of the dust grain can be estimated. A plasma background is supplied by a standard tokamak edge modelling code (B2SOLPS5.0), and dust transport through MAST (the Mega-Amp Spherical Tokamak) and ITER plasmas is presented. We conclude that micron-radius tungsten dust can reach the separatrix in ITER. (authors)

  10. DUST LOADING OF THE ATMOSPHERE AND GLACIERS IN THE KUMTOR MINING AREA (AKSHYYRAK, TIEN SHAN

    Directory of Open Access Journals (Sweden)

    V. A. Kuzmichenok

    2012-01-01

    Full Text Available Industrial development of the Kumtor Gold Mine in the nival-glacial zone of Tien Shan (altitude ranging from 4000 to 4500 m a.s.l. is inevitably accompanied by the release of some additional amounts of dust in atmosphere. Sampling in 7 points and an analysis of the quantity (weight of dust in the seasonal snow (September–April on glaciers show that the dust pollution does not substantially exceed the natural level of dust in Tien Shan. An analysis of almost 3 000 daily measurements of dust in the surface layer of air at 4 points around the gold mine has also shown that the economic activity has no significant impact on dust production. It is likely that the manmade component of overall dust in the immediate vicinity of the deposit and the gob pile does not exceed 20%. No increase in the content of dust and in its anthropogenic component with time has been found. Thus, we suggest that the principal amount of dust in the area is brought during the cold season from snow-free areas of Central Asia.

  11. Development of a Severe Sand-dust Storm Model and its Application to Northwest China

    International Nuclear Information System (INIS)

    Zhang Xiaoling; Cheng, Linsheng; Chung, Yong-Seung

    2003-01-01

    A very strong sand-dust storm occurred on 5 May, 1993 in Northwest China. In order to give a detailed description of the evolution of a mesoscale system along with the heavy sand-dust storm, a complex model including improved physical processes and a radiation parameterization scheme was developed based on a simulation model. The improved model introduced a sand-dust transport equation as well as a lifting transport model, sand-dust aerosols and radiation parameterization scheme.Using this model, the super sand-dust storm case on 5 May was simulated. Results indicated that the coupled mesoscale model successfully simulated the mesoscale vortex, its strong upward movement and the warm core structure of PBL. The generation and development of these structures were consistent with that of the sand-dust storm and dry squall-line (which was different with normal squall-line). Simulated sand-dust concentration and its radiative effect corresponded with observation data. The radiative effect of sand-dust aerosols caused the air to heat on the top of aerosol layer with a heating rate amounting to 2 K hr -1 . As a result, solar radiation flux that reached the surface, net radiation flux and surface temperature all suddenly went down. The temperature gradient across the cold front became obviously larger. Therefore, enhancing the development of the mesoscale system. The simulation generally reflected features during the squall-line passage of this strong sand-dust storm

  12. The Dispersion of Fast Radio Bursts from a Structured Intergalactic Medium at Redshifts z < 1.5

    Science.gov (United States)

    Shull, J. Michael; Danforth, Charles W.

    2018-01-01

    We analyze the sources of free electrons that produce the large dispersion measures, {DM}≈ 300{--}1600 (in units of cm‑3 pc), observed toward fast radio bursts (FRBs). Individual galaxies typically produce {DM}∼ 25{--}60 {{cm}}-3 {pc} from ionized gas in their disk, disk-halo interface, and circumgalactic medium. Toward an FRB source at redshift z, a homogeneous intergalactic medium (IGM) containing a fraction {f}{IGM} of cosmological baryons will produce {DM}=(935 {{cm}}-3 {pc}){f}{IGM} {h}70-1I(z), where I{(z)=(2/3{{{Ω }}}m)[\\{{{{Ω }}}m(1+z)}3+{{{Ω }}}{{Λ }}\\}{}1/2-1]. A structured IGM of photoionized Lyα absorbers in the cosmic web produces similar dispersion, modeled from the observed distribution, {f}b(N,z), of H I (Lyα-forest) absorbers in column density and redshift with ionization corrections and scaling relations from cosmological simulations. An analytic formula for DM(z) applied to observed FRB dispersions suggests that {z}{FRB}≈ 0.2{--}1.5 for an IGM containing a significant baryon fraction, {f}{IGM}=0.6+/- 0.1. Future surveys of the statistical distribution, DM(z), of FRBs identified with specific galaxies and redshifts can be used to calibrate the IGM baryon fraction and distribution of Lyα absorbers. Fluctuations in DM at the level ±10 cm‑3 pc will arise from filaments and voids in the cosmic web.

  13. The concerted impact of galaxies and QSOs on the ionization and thermal state of the intergalactic medium

    Science.gov (United States)

    Kakiichi, Koki; Graziani, Luca; Ciardi, Benedetta; Meiksin, Avery; Compostella, Michele; Eide, Marius B.; Zaroubi, Saleem

    2017-07-01

    We present a detailed analysis of the ionization and thermal structure of the intergalactic medium (IGM) around a high-redshift (z = 10) QSO, using a large suite of cosmological, multifrequency radiative transfer simulations, exploring the contribution from galaxies as well as the QSO, and the effect of X-rays and secondary ionization. We show that in high-z QSO environments both the central QSO and the surrounding galaxies concertedly control the reionization morphology of hydrogen and helium and have a non-linear impact on the thermal structure of the IGM. A QSO imprints a distinctive morphology on H II regions if its total ionizing photon budget exceeds that of the surrounding galaxies since the onset of hydrogen reionization; otherwise, the morphology shows little difference from that of H II regions produced only by galaxies. In addition, the spectral shape of the collective radiation field from galaxies and QSOs controls the thickness of the I-fronts. While a UV-obscured QSO can broaden the I-front, the contribution from other UV sources, either galaxies or unobscured QSOs, is sufficient to maintain a sharp I-front. X-ray photons from the QSO are responsible for a prominent extended tail of partial ionization ahead of the I-front. QSOs leave a unique imprint on the morphology of He II/He III regions. We suggest that, while the physical state of the IGM is modified by QSOs, the most direct test to understand the role of galaxies and QSOs during reionization is to perform galaxy surveys in a region of sky imaged by 21 cm tomography.

  14. Finite Cosmology and a CMB Cold Spot

    Energy Technology Data Exchange (ETDEWEB)

    Adler, R.J.; /Stanford U., HEPL; Bjorken, J.D.; /SLAC; Overduin, J.M.; /Stanford U., HEPL

    2006-03-20

    The standard cosmological model posits a spatially flat universe of infinite extent. However, no observation, even in principle, could verify that the matter extends to infinity. In this work we model the universe as a finite spherical ball of dust and dark energy, and obtain a lower limit estimate of its mass and present size: the mass is at least 5 x 10{sup 23}M{sub {circle_dot}} and the present radius is at least 50 Gly. If we are not too far from the dust-ball edge we might expect to see a cold spot in the cosmic microwave background, and there might be suppression of the low multipoles in the angular power spectrum. Thus the model may be testable, at least in principle. We also obtain and discuss the geometry exterior to the dust ball; it is Schwarzschild-de Sitter with a naked singularity, and provides an interesting picture of cosmogenesis. Finally we briefly sketch how radiation and inflation eras may be incorporated into the model.

  15. Working in the Cold

    Centers for Disease Control (CDC) Podcasts

    2016-02-08

    During the winter, many workers are outdoors, working in cold, wet, icy, or snowy conditions. Learn how to identify symptoms that tell you there may be a problem and protect yourself from cold stress.  Created: 2/8/2016 by National Institute for Occupational Safety and Health (NIOSH).   Date Released: 2/8/2016.

  16. Cold-Weather Sports

    Science.gov (United States)

    ... Videos for Educators Search English Español Cold-Weather Sports KidsHealth / For Teens / Cold-Weather Sports What's in this article? What to Do? Classes ... weather. What better time to be outdoors? Winter sports can help you burn calories, increase your cardiovascular ...

  17. Cold fusion research

    International Nuclear Information System (INIS)

    1989-11-01

    I am pleased to forward to you the Final Report of the Cold Fusion Panel. This report reviews the current status of cold fusion and includes major chapters on Calorimetry and Excess Heat, Fusion Products and Materials Characterization. In addition, the report makes a number of conclusions and recommendations, as requested by the Secretary of Energy

  18. COLD-WORKED HARDWARE

    Directory of Open Access Journals (Sweden)

    N. M. Strizhak

    2007-01-01

    Full Text Available The different types of cold-worked accessory are examined in the article. The necessity of development of such type of accessory in the Republic of Belarus due to requirements of market is shown. High emphasis is placed on the methods of increase of plasticity of cold-worked accessory from usual mill of RUP and CIS countries.

  19. Liquid metal cold trap

    International Nuclear Information System (INIS)

    Hundal, R.

    1976-01-01

    A cold trap assembly for removing impurities from a liquid metal is described. A hole between the incoming impure liquid metal and purified outgoing liquid metal acts as a continuous bleed means and thus prevents the accumulation of cover gases within the cold trap assembly

  20. Climatology of atmospheric circulation patterns of Arabian dust in western Iran.

    Science.gov (United States)

    Najafi, Mohammad Saeed; Sarraf, B S; Zarrin, A; Rasouli, A A

    2017-08-28

    Being in vicinity of vast deserts, the west and southwest of Iran are characterized by high levels of dust events, which have adverse consequences on human health, ecosystems, and environment. Using ground based dataset of dust events in western Iran and NCEP/NCAR reanalysis data, the atmospheric circulation patterns of dust events in the Arabian region and west of Iran are identified. The atmospheric circulation patterns which lead to dust events in the Arabian region and western Iran were classified into two main categories: the Shamal dust events that occurs in warm period of year and the frontal dust events as cold period pattern. In frontal dust events, the western trough or blocking pattern at mid-level leads to frontogenesis, instability, and air uplift at lower levels of troposphere in the southwest of Asia. Non-frontal is other pattern of dust event in the cold period and dust generation are due to the regional circulation systems at the lower level of troposphere. In Shamal wind pattern, the Saudi Arabian anticyclone, Turkmenistan anticyclone, and Zagros thermal low play the key roles in formation of this pattern. Summer and transitional patterns are two sub-categories of summer Shamal wind pattern. In summer trough pattern, the mid-tropospheric trough leads to intensify the surface thermal systems in the Middle East and causes instability and rising of wind speed in the region. In synthetic pattern of Shamal wind and summer trough, dust is created by the impact of a trough in mid-levels of troposphere as well as existing the mentioned regional systems which are contributed in formation of summer Shamal wind pattern.

  1. Dust storm, northern Mexico

    Science.gov (United States)

    1983-01-01

    This large dust storm along the left side of the photo, covers a large portion of the state of Coahuila, Mexico (27.5N, 102.0E). The look angle of this oblique photo is from the south to the north. In the foreground is the Sierra Madre Oriental in the states Coahuila and Nuevo Leon with the Rio Grande River, Amistad Reservoir and Texas in the background.

  2. Human whole body cold adaptation.

    NARCIS (Netherlands)

    Daanen, Hein A.M.; Van Marken Lichtenbelt, Wouter D.

    2016-01-01

    Reviews on whole body human cold adaptation generally do not distinguish between population studies and dedicated acclimation studies, leading to confusing results. Population studies show that indigenous black Africans have reduced shivering thermogenesis in the cold and poor cold induced

  3. Dust acoustic shock wave at high dust density

    International Nuclear Information System (INIS)

    Ghosh, Samiran; Sarkar, Susmita; Khan, Manoranjan; Avinash, K.; Gupta, M. R.

    2003-01-01

    Dust acoustic (DA) shock wave at high dust density, i.e., the dust electroacoustic (DEA) or dust Coulomb (DC) shock wave has been investigated incorporating the nonadiabatic dust charge variation. The nonlinear DEA (DC) shock wave is seen to be governed by the Korteweg-de Vries Burger equation, in which the Burger term is proportional to the nonadiabaticity generated dissipation. It is seen that the shock strength decreases but after reaching minimum, it increases as the dust space charge density |q d n d | increases and the shock strength of DA wave is greater than that of DEA (DC) wave. Moreover the DEA (DC) shock width increases appreciably with increase mass m i of the ion component of the dusty plasma but for DA shock wave the effect is weak

  4. Dust, Climate, and Human Health

    Science.gov (United States)

    Maynard, Nancy G.

    2003-01-01

    Air pollution from both natural and anthropogenic causes is considered to be one of the most serious world-wide environment-related health problems, and is expected to become worse with changes in the global climate. Dust storms from the atmospheric transport of desert soil dust that has been lifted and carried by the winds - often over significant distances - have become an increasingly important emerging air quality issue for many populations. Recent studies have shown that the dust storms can cause significant health impacts from the dust itself as well as the accompanying pollutants, pesticides, metals, salt, plant debris, and other inorganic and organic materials, including viable microorganisms (bacteria, viruses and fungi). For example, thousands of tons of Asian desert sediments, some containing pesticides and herbicides from farming regions, are commonly transported into the Arctic during dust storm events. These chemicals have been identified in animal and human tissues among Arctic indigenous populations. Millions of tons of airborne desert dust are being tracked by satellite imagery, which clearly shows the magnitude as well as the temporal and spatial variability of dust storms across the "dust belt" regions of North Africa, the Middle East, and China. This paper summarizes the most recent findings on the effects of airborne desert dust on human health as well as potential climate influences on dust and health.

  5. Parameterizing the interstellar dust temperature

    Science.gov (United States)

    Hocuk, S.; Szűcs, L.; Caselli, P.; Cazaux, S.; Spaans, M.; Esplugues, G. B.

    2017-08-01

    The temperature of interstellar dust particles is of great importance to astronomers. It plays a crucial role in the thermodynamics of interstellar clouds, because of the gas-dust collisional coupling. It is also a key parameter in astrochemical studies that governs the rate at which molecules form on dust. In 3D (magneto)hydrodynamic simulations often a simple expression for the dust temperature is adopted, because of computational constraints, while astrochemical modelers tend to keep the dust temperature constant over a large range of parameter space. Our aim is to provide an easy-to-use parametric expression for the dust temperature as a function of visual extinction (AV) and to shed light on the critical dependencies of the dust temperature on the grain composition. We obtain an expression for the dust temperature by semi-analytically solving the dust thermal balance for different types of grains and compare to a collection of recent observational measurements. We also explore the effect of ices on the dust temperature. Our results show that a mixed carbonaceous-silicate type dust with a high carbon volume fraction matches the observations best. We find that ice formation allows the dust to be warmer by up to 15% at high optical depths (AV> 20 mag) in the interstellar medium. Our parametric expression for the dust temperature is presented as Td = [ 11 + 5.7 × tanh(0.61 - log 10(AV) ]χuv1/5.9, where χuv is in units of the Draine (1978, ApJS, 36, 595) UV field.

  6. Dust in H II regions

    International Nuclear Information System (INIS)

    Isobe, S.

    1977-01-01

    Several pieces of evidence indicate that H II regions may contain dust: 1) the continuum light scattered by dust grains (O'Dell and Hubbard, 1965), 2) thermal radiation from dust grains at infrared wavelengths (Ney and Allen, 1969), 3) the abnormal helium abundance in some H II regions (Peimbert and Costero, 1969), etc. Although observations of the scattered continuum suggest that the H II region cores may be dust-free, dust grains and gas must be well mixed in view of the infrared observations. This difficulty may be solved by introducing globules with sizes approximately 0.001 pc. These globules and the molecular clouds adjacent to H II regions are the main sources supplying dust to H II regions. (Auth.)

  7. Large Aperture Electrostatic Dust Detector

    International Nuclear Information System (INIS)

    Skinner, C.H.; Hensley, R.; Roquemore, A.L.

    2007-01-01

    Diagnosis and management of dust inventories generated in next-step magnetic fusion devices is necessary for their safe operation. A novel electrostatic dust detector, based on a fine grid of interlocking circuit traces biased to 30 or 50 v has been developed for the detection of dust particles on remote surfaces in air and vacuum environments. Impinging dust particles create a temporary short circuit and the resulting current pulse is recorded by counting electronics. Up to 90% of the particles are ejected from the grid or vaporized suggesting the device may be useful for controlling dust inventories. We report measurements of the sensitivity of a large area (5x5 cm) detector to microgram quantities of dust particles and review its applications to contemporary tokamaks and ITER.

  8. THE COSMOLOGICAL IMPACT OF LUMINOUS TeV BLAZARS. II. REWRITING THE THERMAL HISTORY OF THE INTERGALACTIC MEDIUM

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Philip; Broderick, Avery E; Pfrommer, Christoph [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, Toronto, ON M5S 3H8 (Canada)

    2012-06-10

    The universe is opaque to extragalactic very high energy gamma rays (VHEGRs, E > 100 GeV) because they annihilate and pair produce on the extragalactic background light. The resulting ultrarelativistic pairs are commonly assumed to lose energy primarily through inverse Compton scattering of cosmic microwave background (CMB) photons, reprocessing the original emission from TeV to GeV energies. In Broderick et al., we argued that this is not the case; powerful plasma instabilities driven by the highly anisotropic nature of the ultrarelativistic pair distribution provide a plausible way to dissipate the kinetic energy of the TeV-generated pairs locally, heating the intergalactic medium (IGM). Here, we explore the effect of this heating on the thermal history of the IGM. We collate the observed extragalactic VHEGR sources to determine a local VHEGR heating rate. Given the pointed nature of VHEGR observations, we estimate the correction for the various selection effects using Fermi observations of high- and intermediate-peaked BL Lac objects. As the extragalactic component of the local VHEGR flux is dominated by TeV blazars, we then estimate the evolution of the TeV blazar luminosity density by tying it to the well-observed quasar luminosity density and producing a VHEGR heating rate as a function of redshift. This heating is relatively homogeneous for z {approx}< 4, but there is greater spatial variation at higher redshift (order unity at z {approx} 6) because of the reduced number of blazars that contribute to local heating. We show that this new heating process dominates photoheating in the low-redshift evolution of the IGM and calculate the effect of this heating in a one-zone model. As a consequence, the inclusion of TeV blazar heating qualitatively and quantitatively changes the structure and history of the IGM. Due to the homogeneous nature of the extragalactic background light, TeV blazars produce a uniform volumetric heating rate. This heating is sufficient to

  9. THE COSMOLOGICAL IMPACT OF LUMINOUS TeV BLAZARS. II. REWRITING THE THERMAL HISTORY OF THE INTERGALACTIC MEDIUM

    International Nuclear Information System (INIS)

    Chang, Philip; Broderick, Avery E.; Pfrommer, Christoph

    2012-01-01

    The universe is opaque to extragalactic very high energy gamma rays (VHEGRs, E > 100 GeV) because they annihilate and pair produce on the extragalactic background light. The resulting ultrarelativistic pairs are commonly assumed to lose energy primarily through inverse Compton scattering of cosmic microwave background (CMB) photons, reprocessing the original emission from TeV to GeV energies. In Broderick et al., we argued that this is not the case; powerful plasma instabilities driven by the highly anisotropic nature of the ultrarelativistic pair distribution provide a plausible way to dissipate the kinetic energy of the TeV-generated pairs locally, heating the intergalactic medium (IGM). Here, we explore the effect of this heating on the thermal history of the IGM. We collate the observed extragalactic VHEGR sources to determine a local VHEGR heating rate. Given the pointed nature of VHEGR observations, we estimate the correction for the various selection effects using Fermi observations of high- and intermediate-peaked BL Lac objects. As the extragalactic component of the local VHEGR flux is dominated by TeV blazars, we then estimate the evolution of the TeV blazar luminosity density by tying it to the well-observed quasar luminosity density and producing a VHEGR heating rate as a function of redshift. This heating is relatively homogeneous for z ∼< 4, but there is greater spatial variation at higher redshift (order unity at z ∼ 6) because of the reduced number of blazars that contribute to local heating. We show that this new heating process dominates photoheating in the low-redshift evolution of the IGM and calculate the effect of this heating in a one-zone model. As a consequence, the inclusion of TeV blazar heating qualitatively and quantitatively changes the structure and history of the IGM. Due to the homogeneous nature of the extragalactic background light, TeV blazars produce a uniform volumetric heating rate. This heating is sufficient to increase

  10. The Column Density Distribution and Continuum Opacity of the Intergalactic and Circumgalactic Medium at Redshift langzrang = 2.4

    Science.gov (United States)

    Rudie, Gwen C.; Steidel, Charles C.; Shapley, Alice E.; Pettini, Max

    2013-06-01

    We present new high-precision measurements of the opacity of the intergalactic and circumgalactic medium (IGM; CGM) at langzrang = 2.4. Using Voigt profile fits to the full Lyα and Lyβ forests in 15 high-resolution high-S/N spectra of hyperluminous QSOs, we make the first statistically robust measurement of the frequency of absorbers with H I column densities 14 \\lesssim log (N_H\\,\\scriptsize{ I}/ {cm}^{-2}) \\lesssim 17.2. We also present the first measurements of the frequency distribution of H I absorbers in the volume surrounding high-z galaxies (the CGM, 300 pkpc), finding that the incidence of absorbers in the CGM is much higher than in the IGM. In agreement with Rudie et al., we find that there are fractionally more high-N H I absorbers than low-N H I absorbers in the CGM compared to the IGM, leading to a shallower power law fit to the CGM frequency distribution. We use these new measurements to calculate the total opacity of the IGM and CGM to hydrogen-ionizing photons, finding significantly higher opacity than most previous studies, especially from absorbers with log (N_H\\,\\scriptsize{ I}/ {cm}^{-2}) law parameterization of the frequency distribution with a break near N H I ≈1015 cm-2. We compute new estimates of the mean free path (λmfp) to hydrogen-ionizing photons at z em = 2.4, finding λmfp = 147 ± 15 Mpc when considering only IGM opacity. If instead, we consider photons emanating from a high-z star-forming galaxy and account for the local excess opacity due to the surrounding CGM of the galaxy itself, the mean free path is reduced to λmfp = 121 ± 15 Mpc. These λmfp measurements are smaller than recent estimates and should inform future studies of the metagalactic UV background and of ionizing sources at z ≈ 2-3. 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 the National Aeronautics and Space

  11. Photoelectric charging of dust grains

    International Nuclear Information System (INIS)

    Ignatov, A. M.

    2009-01-01

    Photoemission from the surface of a dust grain in vacuum is considered. It is shown that the cutoff in the energy spectrum of emitted electrons leads to the formation of a steady-state electron cloud. The equation describing the distribution of the electric potential in the vicinity of a dust grain is solved numerically. The dust grain charge is found as a function of the grain size.

  12. Chilling Out With Colds

    Science.gov (United States)

    ... and use the time to read, listen to music, or watch a movie. In other words, chill out and you might prevent a cold! Reviewed by: Patricia ... Policy Permissions Guidelines Privacy Policy & Terms of Use Notice ...

  13. Cold Vacuum Drying Facility

    Data.gov (United States)

    Federal Laboratory Consortium — Located near the K-Basins (see K-Basins link) in Hanford's 100 Area is a facility called the Cold Vacuum Drying Facility (CVDF).Between 2000 and 2004, workers at the...

  14. Dence Cold Matter

    Directory of Open Access Journals (Sweden)

    Stavinskiy Alexey

    2014-04-01

    Full Text Available Possible way to create dense cold baryonic matter in the laboratory is discussed. The density of this matter is comparable or even larger than the density of neutron star core. The properties of this matter can be controlled by trigger conditions. Experimental program for the study of properties of dense cold matter for light and heavy ion collisions at initial energy range √sNN~2-3GeV is proposed..

  15. Dust in cosmic plasma environments

    International Nuclear Information System (INIS)

    Mendis, D.A.

    1979-01-01

    Cosmic dust is invariably immersed in a plasma and a radiative environment. Consequently, it is charged to some electrostatic potential which depends on the properties of the environment as well as the nature of the dust. This charging affects the physical and dynamical properties of the dust. In this paper the basic aspects of this dust-plasma interaction in several cosmic environments - including planetary magnetospheres, the heliosphere and the interstellar medium - are discussed. The physical and dynamical consequences of the interaction, as well as the pertinent observational evidence, are reviewed. Finally, the importance of the surface charge during the condensation process in plasma environments is stressed. (Auth.)

  16. Hypothermic general cold adaptation induced by local cold acclimation.

    Science.gov (United States)

    Savourey, G; Barnavol, B; Caravel, J P; Feuerstein, C; Bittel, J H

    1996-01-01

    To study relationships between local cold adaptation of the lower limbs and general cold adaptation, eight subjects were submitted both to a cold foot test (CFT, 5 degrees C water immersion, 5 min) and to a whole-body standard cold air test (SCAT, 1 degree C, 2 h, nude at rest) before and after a local cold acclimation (LCA) of the lower limbs effected by repeated cold water immersions. The LCA induced a local cold adaptation confirmed by higher skin temperatures of the lower limbs during CFT and a hypothermic insulative general cold adaptation (decreased rectal temperature and mean skin temperature P adaptation was related to the habituation process confirmed by decreased plasma concentrations of noradrenaline (NA) during LCA (P general cold adaptation was unrelated either to local cold adaptation or to the habituation process, because an increased NA during SCAT after LCA (P syndrome" occurring during LCA.

  17. Biological response to millennial variability of dust and nutrient supply in the Subantarctic South Atlantic Ocean.

    Science.gov (United States)

    Anderson, Robert F; Barker, Stephen; Fleisher, Martin; Gersonde, Rainer; Goldstein, Steven L; Kuhn, Gerhard; Mortyn, P Graham; Pahnke, Katharina; Sachs, Julian P

    2014-07-13

    Fluxes of lithogenic material and fluxes of three palaeo-productivity proxies (organic carbon, biogenic opal and alkenones) over the past 100,000 years were determined using the (230)Th-normalization method in three sediment cores from the Subantarctic South Atlantic Ocean. Features in the lithogenic flux record of each core correspond to similar features in the record of dust deposition in the EPICA Dome C ice core. Biogenic fluxes correlate with lithogenic fluxes in each sediment core. Our preferred interpretation is that South American dust, most probably from Patagonia, constitutes a major source of lithogenic material in Subantarctic South Atlantic sediments, and that past biological productivity in this region responded to variability in the supply of dust, probably due to biologically available iron carried by the dust. Greater nutrient supply as well as greater nutrient utilization (stimulated by dust) contributed to Subantarctic productivity during cold periods, in contrast to the region south of the Antarctic Polar Front (APF), where reduced nutrient supply during cold periods was the principal factor limiting productivity. The anti-phased patterns of productivity on opposite sides of the APF point to shifts in the physical supply of nutrients and to dust as cofactors regulating productivity in the Southern Ocean. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  18. Gravitational radiation from dust

    International Nuclear Information System (INIS)

    Isaacson, R.A.; Welling, J.S.; Winicour, J.

    1985-01-01

    A dust cloud is examined within the framework of the general relativistic characteristic initial value problem. Unique gravitational initial data are obtained by requiring that the space-time be quasi-Newtonian. Explicit calculations of metric and matter fields are presented, which include all post-Newtonian corrections necessary to discuss the major physical properties of null infinity. These results establish a curved space version of the Einstein quadrupole formula, in the form ''news function equals third time derivative of transverse quadrupole moment,'' for this system. However, these results imply that some weakened notion of asymptotic flatness is necessary for the description of quasi-Newtonian systems

  19. Dust coagulation in ISM

    Science.gov (United States)

    Chokshi, Arati; Tielens, Alexander G. G. M.; Hollenbach, David

    1989-01-01

    Coagulation is an important mechanism in the growth of interstellar and interplanetary dust particles. The microphysics of the coagulation process was theoretically analyzed as a function of the physical properties of the coagulating grains, i.e., their size, relative velocities, temperature, elastic properties, and the van der Waal interaction. Numerical calculations of collisions between linear chains provide the wave energy in individual particles and the spectrum of the mechanical vibrations set up in colliding particles. Sticking probabilities are then calculated using simple estimates for elastic deformation energies and for the attenuation of the wave energy due to absorption and scattering processes.

  20. IRAS constraints on a cold cloud around the solar system

    International Nuclear Information System (INIS)

    Aumann, H.H.; Good, J.C.

    1990-01-01

    IRAS 60- and 100-micron observations of G-stars in the solar neighborhood indicate that the typical G star is surrounded by a cold cloud. The assumption that the sun is archetypical requires that a cloud of typical G star extent and temperature surrounds our solar system. IRAS ecliptic plane scans, which are dominated by a 40-deg wide band of zodiacal dust, asteroid debris trails, and the Galactic plane, are consistent with a larger than typical G star cold cloud. Consistency with the typical G star and the direct observations constrain the width of the cold cloud perpendicular to the ecliptic plane to be larger than 5 deg. The 100-150 AU radius of this cloud is larger, but not inconsistent with the inner boundary of a cloud of comets, postulated previously at a radius of 50 AU based on Neptune orbital perturbations and models of short period comets. 17 refs

  1. Dust confinement and dust acoustic waves in a magnetized plasma

    Science.gov (United States)

    Piel, A.

    2005-10-01

    Systematic laboratory experiments on dust acoustic waves require the confinement of dust particles. Here we report on new experiments in a magnetized plasma region in front of an additional positively biased disk electrode in a background plasma which is generated in argon at 27MHz between a disk and grid electrode. The plasma diffuses through the grid along the magnetic field. The three-dimensional dust distribution is measured with a horizontal sheet of laser light and a CCD camera, which are mounted on a vertical translation stage. Depending on magnetic field and discharge current, cigar or donut-shaped dust clouds are generated, which tend to rotate about the magnetic field direction. Measurements with emissive probes show that the axial confinement of dust particles with diameters between 0.7-2 μm is achieved by a balance of ion-drag force and electric field force. Dust levitation and radial confinement is due to a strong radial electric field. Dust acoustic waves are destabilized by the ion flow or can be stimulated by a periodic bias on the disk electrode. The observed wave dispersion is compared with fluid and kinetic models of the dust acoustic wave.

  2. Gravimetric dust sampling for control purposes and occupational dust sampling.

    CSIR Research Space (South Africa)

    Unsted, AD

    1997-02-01

    Full Text Available Prior to the introduction of gravimetric dust sampling, konimeters had been used for dust sampling, which was largely for control purposes. Whether or not absolute results were achievable was not an issue since relative results were used to evaluate...

  3. Emission, transport, and radiative effects of mineral dust from the Taklimakan and Gobi deserts: comparison of measurements and model results

    Science.gov (United States)

    Chen, Siyu; Huang, Jianping; Kang, Litai; Wang, Hao; Ma, Xiaojun; He, Yongli; Yuan, Tiangang; Yang, Ben; Huang, Zhongwei; Zhang, Guolong

    2017-02-01

    The Weather Research and Forecasting Model with chemistry (WRF-Chem model) was used to investigate a typical dust storm event that occurred from 18 to 23 March 2010 and swept across almost all of China, Japan, and Korea. The spatial and temporal variations in dust aerosols and the meteorological conditions over East Asia were well reproduced by the WRF-Chem model. The simulation results were used to further investigate the details of processes related to dust emission, long-range transport, and radiative effects of dust aerosols over the Taklimakan Desert (TD) and Gobi Desert (GD). The results indicated that weather conditions, topography, and surface types in dust source regions may influence dust emission, uplift height, and transport at the regional scale. The GD was located in the warm zone in advance of the cold front in this case. Rapidly warming surface temperatures and cold air advection at high levels caused strong instability in the atmosphere, which strengthened the downward momentum transported from the middle and low troposphere and caused strong surface winds. Moreover, the GD is located in a relatively flat, high-altitude region influenced by the confluence of the northern and southern westerly jets. Therefore, the GD dust particles were easily lofted to 4 km and were the primary contributor to the dust concentration over East Asia. In the dust budget analysis, the dust emission flux over the TD was 27.2 ± 4.1 µg m-2 s-1, which was similar to that over the GD (29 ± 3.6 µg m-2 s-1). However, the transport contribution of the TD dust (up to 0.8 ton d-1) to the dust sink was much smaller than that of the GD dust (up to 3.7 ton d-1) because of the complex terrain and the prevailing wind in the TD. Notably, a small amount of the TD dust (PM2.5 dust concentration of approximately 8.7 µg m-3) was lofted to above 5 km and transported over greater distances under the influence of the westerly jets. Moreover, the direct radiative forcing induced by dust

  4. Cold moderators at ORNL

    International Nuclear Information System (INIS)

    Lucas, A. T.

    1997-09-01

    The Advanced Neutron Source (ANS) cold moderators were not an 'Oak Ridge first', but would have been the largest both physically and in terms of cold neutron flux. Two cold moderators were planned each 410 mm in diameter and containing about 30L of liquid deuterium. They were to be completely independent of each other. A modular system design was used to provide greater reliability and serviceability. When the ANS was terminated, upgrading of the resident High Flux Isotope Reactor (HFIR) was examined and an initial study was made into the feasibility of adding a cold source. Because the ANS design was modular, it was possible to use many identical design features. Sub-cooled liquid at 4 bar abs was initially chosen for the HFIR design concept, but this was subsequently changed to 15 bar abs to operate above the critical pressure. As in the ANS, the hydrogen will operate at a constant pressure throughout the temperature range and a completely closed loop with secondary containment was adopted. The heat load of 2 kW made the heat flux comparable with that of the ANS. Subsequent studies into the construction of cryogenic moderators for the proposed new Synchrotron Neutron source indicated that again many of the same design concepts could be used. By connecting the two cold sources together in series, the total heat load of 2 kW is very close to that of the HFIR allowing a very similar supercritical hydrogen system to be configured. The two hydrogen moderators of the SNS provide a comparable heat load to the HFIR moderator. It is subsequently planned to connect the two in series and operate from a single cold loop system, once again using supercritical hydrogen. The spallation source also provided an opportunity to re-examine a cold pellet solid methane moderator operating at 20K.

  5. Comet Dust: The Diversity of "Primitive" Particles and Implications

    Science.gov (United States)

    Wooden, Diane H.; Ishii, Hope A.; Bradley, John P.; Zolensky, Michael E.

    2016-01-01

    Comet dust is primitive and shows significant diversity. Our knowledge of the properties of primitive particles has expanded significantly through microscale investigations of cosmic dust samples ( IDP's(Interplanetary Dust Particles) and AMM's (Antarctic Micrometeorites)) and of comet dust samples (Stardust and Rosetta's COSIMA), as well as through remote sensing (spectroscopy and imaging) via Spitzer and via spacecraft encounters with 103P/Hartley 2 and 67P/Churyumov-Gerasimenko. Microscale investigations show that comet dust and cosmic dust are particles of unequilibrated materials, including aggregates of materials unequilibrated at submicron scales. We call unequilibrated materials "primitive" and we deduce they were incorporated into ice-rich (H2O-, CO2-, and CO-ice) parent bodies that remained cold, i.e., into comets, because of the lack of aqueous or thermal alteration since particle aggregation; yet some Stardust olivines suggest mild thermal metamorphism. Primitive particles exhibit a diverse range of: structure and typology; size and size distribution of constituents; concentration and form of carbonaceous and organic matter; D-, N-, and O- isotopic enhancements over solar; Mg-, Fe-contents of the silicate minerals; the compositions and concentrations of sulfides, and of less abundant mineral species such as chondrules, CAIs and carbonates. The uniformity within a group of samples points to: aerodynamic sorting of particles and/or particle constituents; the inclusion of a limited range of oxygen fugacities; the inclusion or exclusion of chondrules; a selection of organics. The properties of primitive particles imply there were disk processes that resulted in different comets having particular selections of primitive materials. The diversity of primitive particles has implications for the diversity of materials in the protoplanetary disk present at the time and in the region where the comets formed.

  6. Astrochemical Properties of Planck Cold Clumps

    Energy Technology Data Exchange (ETDEWEB)

    Tatematsu, Ken’ichi; Sanhueza, Patricio; Nguyễn Lu’o’ng, Quang; Hirota, Tomoya [National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Liu, Tie; Choi, Minho; Kang, Miju; Kim, Kee-Tae [Korea Astronomy and Space Science Institute, Daedeokdaero 776, Yuseong, Daejeon 305-348 (Korea, Republic of); Ohashi, Satoshi [Department of Astronomy, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Liu, Sheng-Yuan; Hirano, Naomi [Academia Sinica Institute of Astronomy and Astrophysics, 11F of Astronomy-Mathematics Building, AS/NTU. No.1, Section 4, Roosevelt Rd, Taipei 10617, Taiwan (China); Thompson, Mark A. [Centre for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, Hatfield, AL10 9AB (United Kingdom); Fuller, Gary [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Wu, Yuefang [Department of Astronomy, Peking University, 100871, Beijing (China); Li, Di [National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012 (China); Francesco, James Di [NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Wang, Ke [European Southern Observatory (Germany); Ristorcelli, Isabelle [IRAP, CNRS (UMR5277), Universite Paul Sabatier, 9 avenue du Colonel Roche, BP 44346, F-31028, Toulouse Cedex 4 (France); Juvela, Mika [Department of physics, University of Helsinki, FI-00014, Helsinki (Finland); Shinnaga, Hiroko, E-mail: k.tatematsu@nao.ac.jp [Department of Physics, Kagoshima University, 1-21-35, Korimoto, Kagoshima, 890-0065 (Japan); Collaboration: JCMT Large Program “SCOPE” collaboration; TRAO Key Science Program “TOP” collaboration; and others

    2017-02-01

    We observed 13 Planck cold clumps with the James Clerk Maxwell Telescope/SCUBA-2 and with the Nobeyama 45 m radio telescope. The N{sub 2}H{sup +} distribution obtained with the Nobeyama telescope is quite similar to SCUBA-2 dust distribution. The 82 GHz HC{sub 3}N, 82 GHz CCS, and 94 GHz CCS emission are often distributed differently with respect to the N{sub 2}H{sup +} emission. The CCS emission, which is known to be abundant in starless molecular cloud cores, is often very clumpy in the observed targets. We made deep single-pointing observations in DNC, HN{sup 13}C, N{sub 2}D{sup +}, and cyclic-C{sub 3}H{sub 2} toward nine clumps. The detection rate of N{sub 2}D{sup +} is 50%. Furthermore, we observed the NH{sub 3} emission toward 15 Planck cold clumps to estimate the kinetic temperature, and confirmed that most targets are cold (≲20 K). In two of the starless clumps we observed, the CCS emission is distributed as it surrounds the N{sub 2}H{sup +} core (chemically evolved gas), which resembles the case of L1544, a prestellar core showing collapse. In addition, we detected both DNC and N{sub 2}D{sup +}. These two clumps are most likely on the verge of star formation. We introduce the chemical evolution factor (CEF) for starless cores to describe the chemical evolutionary stage, and analyze the observed Planck cold clumps.

  7. Of data and dust

    CERN Multimedia

    Stephanie Hills

    2016-01-01

    The traditional image of an archive is one of dusty old boxes, books and papers. When your archive is digital, dust spells disaster. An innovative environmental sensor designed and built by a CERN IT specialist has become an essential element in the Laboratory’s data-preservation strategy.   The novel air particle monitoring sensor designed by CERN's Julien Leduc. CERN’s archive holds more than 130 petabytes of data from past and present high-energy physics experiments. Some of it is 40 years old, most of it needs to be kept forever, and all of it is held on tape cartridges (over 20,000 of them). The cartridges are held inside tape libraries with robotic arms that load them into tape drives where they can be read and written. Tape cartridges have many advantages over other data storage media, notably cost and long-term reliability, but topping the list of drawbacks is their vulnerability to contamination from airborne dust particles; a tiny piece of g...

  8. Radionuclides in house dust

    Energy Technology Data Exchange (ETDEWEB)

    Fry, F A; Green, N; Dodd, N J; Hammond, D J

    1985-04-01

    Discharges of radionuclides from the British Nuclear Fuel plc (BNFL) reprocessing plant at Sellafield in Cumbria have led to elevated concentrations radionuclides in the local environment. The major routes of exposure of the public are kept under review by the appropriate authorising Government departments and monitoring is carried out both by the departments and by BNFL itself. Recently, there has been increasing public concern about general environmental contamination resulting from the discharges and, in particular, about possible exposure of members of the public by routes not previously investigated in detail. One such postulated route of exposure that has attracted the interest of the public, the press and Parliament arises from the presence of radionuclides within houses. In view of this obvious and widespread concern, the Board has undertaken a sampling programme in a few communities in Cumbria to assess the radiological significance of this source of exposure. From the results of our study, we conclude that, although radionuclides originating rom the BNFL site can be detected in house dust, this source of contamination is a negligible route of exposure for members of the public in West Cumbria. This report presents the results of the Board's study of house dust in twenty homes in Cumbria during the spring and summer of 1984. A more intensive investigation is being carried out by Imperial College. (author)

  9. Health hazards of cement dust

    International Nuclear Information System (INIS)

    Meo, Sultan A.

    2004-01-01

    ven in the 21st century, millions of people are working daily in a dusty environment. They are exposed to different types of health hazards such as fume, gases and dust, which are risk factors in developing occupational disease. Cement industry is involved in the development of structure of this advanced and modern world but generates dust during its production. Cement dust causes lung function impairment, chronic obstructive lung disease, restrictive lung disease, pneumoconiosis and carcinoma of the lungs, stomach and colon. Other studies have shown that cement dust may enter into the systemic circulation and thereby reach the essentially all the organs of body and affects the different tissues including heart, liver, spleen, bone, muscles and hairs and ultimately affecting their micro-structure and physiological performance. Most of the studies have been previously attempted to evaluate the effects of cement dust exposure on the basis of spirometry or radiology, or both. However, collective effort describing the general effects of cement dust on different organ and systems in humans or animals, or both has not been published. Therefore, the aim of this review is to gather the potential toxic effects of cement dust and to minimize the health risks in cement mill workers by providing them with information regarding the hazards of cement dust. (author)

  10. Dust forecasting system in JMA

    International Nuclear Information System (INIS)

    Mikami, M; Tanaka, T Y; Maki, T

    2009-01-01

    JMAs dust forecasting information, which is based on a GCM dust model, is presented through the JMA website coupled with nowcast information. The website was updated recently and JMA and MOE joint 'KOSA' website was open from April 2008. Data assimilation technique will be introduced for improvement of the 'KOSA' information.

  11. Cold water injection nozzles

    International Nuclear Information System (INIS)

    Kura, Masaaki; Maeda, Masamitsu; Endo, Takio.

    1979-01-01

    Purpose: To inject cold water in a reactor without applying heat cycles to a reactor container and to the inner wall of a feedwater nozzle by securing a perforated plate at the outlet of the cold water injection nozzle. Constitution: A disc-like cap is secured to the final end of a return nozzle of a control rod drive. The cap prevents the flow of a high temperature water flowing downward in the reactor from entering into the nozzle. The cap is perforated with a plurality of bore holes for injecting cold water into the reactor. The cap is made to about 100 mm in thickness so that the cold water passing through the bore holes is heated by the heat conduction in the cap. Accordingly, the flow of high temperature water flowing downwardly in the reactor is inhibited by the cap from backward flowing into the nozzle. Moreover, the flow of the cold water in the nozzle is controlled and rectified when passed through the bore holes in the cap and then injected into the reactor. (Yoshino, Y.)

  12. Dust in flowing magnetized plasma

    International Nuclear Information System (INIS)

    Pandey, Birendra P.; Samarian, Alex A.; Vladimirov, Sergey V.

    2009-01-01

    Plasma flows occur in almost every laboratory device and interactions of flowing plasmas with near-wall impurities and/or dust significantly affects the efficiency and lifetime of such devices. The charged dust inside the magnetized flowing plasma moves primarily under the influence of the plasma drag and electric forces. Here, the charge on the dust, plasma potential, and plasma density are calculated self-consistently. The electrons are assumed non-Boltzmannian and the effect of electron magnetization and electron-atom collisions on the dust charge is calculated in a self-consistent fashion. For various plasma magnetization parameters viz. the ratio of the electron and ion cyclotron frequencies to their respective collision frequencies, plasma-atom and ionization frequencies, the evolution of the plasma potential and density in the flow region is investigated. The variation of the dust charge profile is shown to be a sensitive function of plasma parameters. (author)

  13. Nonlinear acoustic waves in nonthermal plasmas with negative and positive dust

    International Nuclear Information System (INIS)

    Verheest, Frank

    2009-01-01

    Using a Sagdeev pseudopotential formalism where nonlinear structures are stationary in a co-moving frame, large dust-acoustic solitary waves and double layers have been studied in plasmas with negative and positive cold dust, in the presence of nonthermal electrons and ions. This has been done in a systematic way, to delimit the compositional parameter space in which such modes can be found. The existence domain of negative/positive solitary waves is limited by infinite compression of the negative/positive dust or by the occurrence of negative/positive double layers. These double layers require a sufficient nonthermality of the electrons/ions and the presence of enough positive/negative dust. There are parameter ranges where both negative and positive solitary structures coexist, sometimes both of the solitary wave type, sometimes one a solitary wave and the other a double layer. Typical Sagdeev pseudopotentials and solitary wave profiles have been presented.

  14. Dust in protoplanetary disks: observations*

    Directory of Open Access Journals (Sweden)

    Waters L.B.F.M.

    2015-01-01

    Full Text Available Solid particles, usually referred to as dust, are a crucial component of interstellar matter and of planet forming disks surrounding young stars. Despite the relatively small mass fraction of ≈1% (in the solar neighborhood of our galaxy; this number may differ substantially in other galaxies that interstellar grains represent of the total mass budget of interstellar matter, dust grains play an important role in the physics and chemistry of interstellar matter. This is because of the opacity dust grains at short (optical, UV wavelengths, and the surface they provide for chemical reactions. In addition, dust grains play a pivotal role in the planet formation process: in the core accretion model of planet formation, the growth of dust grains from the microscopic size range to large, cm-sized or larger grains is the first step in planet formation. Not only the grain size distribution is affected by planet formation. Chemical and physical processes alter the structure and chemical composition of dust grains as they enter the protoplanetary disk and move closer to the forming star. Therefore, a lot can be learned about the way stars and planets are formed by observations of dust in protoplanetary disks. Ideally, one would like to measure the dust mass, the grain size distribution, grain structure (porosity, fluffiness, the chemical composition, and all of these as a function of position in the disk. Fortunately, several observational diagnostics are available to derive constrains on these quantities. In combination with rapidly increasing quality of the data (spatial and spectral resolution, a lot of progress has been made in our understanding of dust evolution in protoplanetary disks. An excellent review of dust evolution in protoplanetary disks can be found in Testi et al. (2014.

  15. A NEW METHOD TO DIRECTLY MEASURE THE JEANS SCALE OF THE INTERGALACTIC MEDIUM USING CLOSE QUASAR PAIRS

    International Nuclear Information System (INIS)

    Rorai, Alberto; Hennawi, Joseph F.; White, Martin

    2013-01-01

    Although the baryons in the intergalactic medium (IGM) trace dark matter fluctuations on megaparsec scales, on smaller scales ∼100 kpc, fluctuations are suppressed because the finite temperature gas is pressure supported against gravity, analogous to the classical Jeans argument. This Jeans filtering scale, which quantifies the small-scale structure of the IGM, has fundamental cosmological implications. First, it provides a thermal record of heat injected by ultraviolet photons during cosmic reionization events, and thus constrains the thermal and reionization history of the universe. Second, the Jeans scale determines the clumpiness of the IGM, a critical ingredient in models of cosmic reionization. Third, it sets the minimum mass scale for gravitational collapse from the IGM, and hence plays a pivotal role in galaxy formation. Unfortunately, it is extremely challenging to measure the Jeans scale via the standard technique of analyzing purely longitudinal Lyα forest spectra, because the thermal Doppler broadening of absorption lines along the line-of-sight, is highly degenerate with Jeans smoothing. In this work, we show that the Jeans filtering scale can be directly measured by characterizing the coherence of correlated Lyα forest absorption in close quasar pairs, with separations small enough ∼100 kpc to resolve it. We present a novel technique for this purpose, based on the probability density function (PDF) of phase angle differences of homologous longitudinal Fourier modes in close quasar pair spectra. A Bayesian formalism is introduced based on the phase angle PDF, and Markov Chain Monte Carlo techniques are used to characterize the precision of a hypothetical Jeans scale measurement, and explore degeneracies with other thermal parameters governing the IGM. A semi-analytical model of the Lyα forest is used to generate a large grid (500) of thermal models from a dark matter only simulation. Our full parameter study indicates that a realistic sample of

  16. A NEW METHOD TO DIRECTLY MEASURE THE JEANS SCALE OF THE INTERGALACTIC MEDIUM USING CLOSE QUASAR PAIRS

    Energy Technology Data Exchange (ETDEWEB)

    Rorai, Alberto; Hennawi, Joseph F. [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); White, Martin [Department of Astronomy, University of California at Berkeley, 601 Campbell Hall, Berkeley, CA 94720-3411 (United States)

    2013-10-01

    Although the baryons in the intergalactic medium (IGM) trace dark matter fluctuations on megaparsec scales, on smaller scales ∼100 kpc, fluctuations are suppressed because the finite temperature gas is pressure supported against gravity, analogous to the classical Jeans argument. This Jeans filtering scale, which quantifies the small-scale structure of the IGM, has fundamental cosmological implications. First, it provides a thermal record of heat injected by ultraviolet photons during cosmic reionization events, and thus constrains the thermal and reionization history of the universe. Second, the Jeans scale determines the clumpiness of the IGM, a critical ingredient in models of cosmic reionization. Third, it sets the minimum mass scale for gravitational collapse from the IGM, and hence plays a pivotal role in galaxy formation. Unfortunately, it is extremely challenging to measure the Jeans scale via the standard technique of analyzing purely longitudinal Lyα forest spectra, because the thermal Doppler broadening of absorption lines along the line-of-sight, is highly degenerate with Jeans smoothing. In this work, we show that the Jeans filtering scale can be directly measured by characterizing the coherence of correlated Lyα forest absorption in close quasar pairs, with separations small enough ∼100 kpc to resolve it. We present a novel technique for this purpose, based on the probability density function (PDF) of phase angle differences of homologous longitudinal Fourier modes in close quasar pair spectra. A Bayesian formalism is introduced based on the phase angle PDF, and Markov Chain Monte Carlo techniques are used to characterize the precision of a hypothetical Jeans scale measurement, and explore degeneracies with other thermal parameters governing the IGM. A semi-analytical model of the Lyα forest is used to generate a large grid (500) of thermal models from a dark matter only simulation. Our full parameter study indicates that a realistic sample of

  17. THE ORIGIN OF DUST IN EARLY-TYPE GALAXIES AND IMPLICATIONS FOR ACCRETION ONTO SUPERMASSIVE BLACK HOLES

    Energy Technology Data Exchange (ETDEWEB)

    Martini, Paul [Department of Astronomy and Center for Cosmology and Astroparticle Physics, The Ohio State University, Columbus, OH 43210 (United States); Dicken, Daniel [Institut de Astrophysique Spatiale, Paris (France); Storchi-Bergmann, Thaisa [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, Caixa Postal 15051, 91501-970 Porto Alegre, RS (Brazil)

    2013-04-01

    We have conducted an archival Spitzer study of 38 early-type galaxies in order to determine the origin of the dust in approximately half of this population. Our sample galaxies generally have good wavelength coverage from 3.6 {mu}m to 160 {mu}m, as well as visible-wavelength Hubble Space Telescope (HST) images. We use the Spitzer data to estimate dust masses, or establish upper limits, and find that all of the early-type galaxies with dust lanes in the HST data are detected in all of the Spitzer bands and have dust masses of {approx}10{sup 5}-10{sup 6.5} M{sub Sun }, while galaxies without dust lanes are not detected at 70 {mu}m and 160 {mu}m and typically have <10{sup 5} M{sub Sun} of dust. The apparently dust-free galaxies do have 24 {mu}m emission that scales with the shorter-wavelength flux, yet substantially exceeds the expectations of photospheric emission by approximately a factor of three. We conclude this emission is dominated by hot, circumstellar dust around evolved stars that does not survive to form a substantial interstellar component. The order-of-magnitude variations in dust masses between galaxies with similar stellar populations rule out a substantial contribution from continual, internal production in spite of the clear evidence for circumstellar dust. We demonstrate that the interstellar dust is not due to purely external accretion, unless the product of the merger rate of dusty satellites and the dust lifetime is at least an order of magnitude higher than expected. We propose that dust in early-type galaxies is seeded by external accretion, yet the accreted dust is maintained by continued growth in externally accreted cold gas beyond the nominal lifetime of individual grains. The several Gyr depletion time of the cold gas is long enough to reconcile the fraction of dusty early-type galaxies with the merger rate of gas-rich satellites. As the majority of dusty early-type galaxies are also low-luminosity active galactic nuclei and likely fueled

  18. COAL DUST EMISSION PROBLEM

    Directory of Open Access Journals (Sweden)

    M. M. Biliaiev

    2016-12-01

    Full Text Available Purpose. The article aims to develop 2D numerical models for the prediction of atmospheric pollution during transportation of coal in the railway car, as well as the ways to protect the environment and the areas near to the mainline from the dust emission due to the air injection installation. Methodology. To solve this problem there were developed numerical models based on the use of the equations of motion of an inviscid incompressible fluid and mass transfer. For the numerical integration of the transport equation of the pollutant the implicit alternating-triangular difference scheme was used. For numerical integration of the 2D equation for the velocity potential the method of total approximation was used. The developed numerical models are the basis of established software package. On the basis of the constructed numerical models it was carried out a computational experiment to assess the level of air pollution when transporting bulk cargo by rail when the railway car has the air injection. Findings. 2D numerical models that belong to the class «diagnostic models» were developed. These models take into account the main physical factors affecting the process of dispersion of dust pollution in the atmosphere during transportation of bulk cargo. The developed numerical models make it possible to calculate the dust loss process, taking into account the use of the air injection of the car. They require a small cost of the computer time during practical realization at the low and medium power machines. There were submitted computational calculations to determine pollutant concentrations and the formation of the zone of pollution near the train with bulk cargo in «microscale» scale taking into account the air curtains. Originality. 2D numerical models taking into account the relevant factors influencing the process of dispersion of pollutants in the atmosphere, and the formation of the zone of pollution during transportation of bulk cargo by

  19. Cold Milky Way HI Gas in Filaments

    Science.gov (United States)

    Kalberla, P. M. W.; Kerp, J.; Haud, U.; Winkel, B.; Ben Bekhti, N.; Flöer, L.; Lenz, D.

    2016-04-01

    We investigate data from the Galactic Effelsberg-Bonn H I Survey, supplemented with data from the third release of the Galactic All Sky Survey (GASS III) observed at Parkes. We explore the all-sky distribution of the local Galactic H I gas with | {v}{{LSR}}| \\lt 25 km s-1 on angular scales of 11‧-16‧. Unsharp masking is applied to extract small-scale features. We find cold filaments that are aligned with polarized dust emission and conclude that the cold neutral medium (CNM) is mostly organized in sheets that are, because of projection effects, observed as filaments. These filaments are associated with dust ridges, aligned with the magnetic field measured on the structures by Planck at 353 GHz. The CNM above latitudes | b| \\gt 20^\\circ is described by a log-normal distribution, with a median Doppler temperature TD = 223 K, derived from observed line widths that include turbulent contributions. The median neutral hydrogen (H I) column density is NH I ≃ 1019.1 cm-2. These CNM structures are embedded within a warm neutral medium with NH I ≃ 1020 cm-2. Assuming an average distance of 100 pc, we derive for the CNM sheets a thickness of ≲0.3 pc. Adopting a magnetic field strength of Btot = (6.0 ± 1.8) μG, proposed by Heiles & Troland, and assuming that the CNM filaments are confined by magnetic pressure, we estimate a thickness of 0.09 pc. Correspondingly, the median volume density is in the range 14 ≲ n ≲ 47 cm-3. The authors thank the Deutsche Forschungsgemeinschaft (DFG) for support under grant numbers KE757/11-1, KE757/7-3, KE757/7-2, KE757/7-1, and BE4823/1-1.

  20. Cold regions isotope applications

    International Nuclear Information System (INIS)

    Perrigo, L.D.; Divine, T.E.

    1976-04-01

    Pacific Northwest Laboratories (PNL) started the Cold Regions Isotope Applications Program in FY-1975 to identify special conditions in the Arctic and similar geographic areas (Cold Regions) where radioisotope power, heater, or sterilization systems would be desirable and economically viable. Significant progress was made in the first year of this program and all objectives for this initial 12-month period were achieved. The major conclusions and recommendations resulting for this effort are described below. The areas of interest covered include: radiosterilization of sewage; heating of septic tanks; and radioisotope thermoelectric generators as power sources for meteorological instruments and navigational aids

  1. Exploring the Dust Content of Galactic Winds with Herschel. II. Nearby Dwarf Galaxies*

    Science.gov (United States)

    McCormick, Alexander; Veilleux, Sylvain; Meléndez, Marcio; Martin, Crystal L.; Bland-Hawthorn, Joss; Cecil, Gerald; Heitsch, Fabian; Müller, Thomas; Rupke, David S. N.; Engelbracht, Chad

    2018-03-01

    We present results from analysis of deep Herschel Space Observatory observations of six nearby dwarf galaxies known to host galactic-scale winds. The superior far-infrared sensitivity and angular resolution of Herschel have allowed detection of cold circumgalactic dust features beyond the stellar components of the host galaxies traced by Spitzer 4.5 μm images. Comparisons of these cold dust features with ancillary data reveal an imperfect spatial correlation with the ionized gas and warm dust wind components. We find that typically ˜10-20% of the total dust mass in these galaxies resides outside of their stellar disks, but this fraction reaches ˜60% in the case of NGC 1569. This galaxy also has the largest metallicity (O/H) deficit in our sample for its stellar mass. Overall, the small number of objects in our sample precludes drawing strong conclusions on the origin of the circumgalactic dust. We detect no statistically significant trends with star formation properties of the host galaxies, as might be expected if the dust were lifted above the disk by energy inputs from on-going star formation activity. Although a case for dust entrained in a galactic wind is seen in NGC 1569, in all cases, we cannot rule out the possibility that some of the circumgalactic dust might be associated instead with gas accreted or removed from the disk by recent galaxy interaction events, or that it is part of the outer gas-rich portion of the disk that lies below the sensitivity limit of the Spitzer 4.5 μm data.

  2. Exploring the dust content of galactic winds with Herschel - II. Nearby dwarf galaxies

    Science.gov (United States)

    McCormick, Alexander; Veilleux, Sylvain; Meléndez, Marcio; Martin, Crystal L.; Bland-Hawthorn, Joss; Cecil, Gerald; Heitsch, Fabian; Müller, Thomas; Rupke, David S. N.; Engelbracht, Chad

    2018-06-01

    We present the results from an analysis of deep Herschel Space Observatory observations of six nearby dwarf galaxies known to host galactic-scale winds. The superior far-infrared sensitivity and angular resolution of Herschel have allowed detection of cold circumgalactic dust features beyond the stellar components of the host galaxies traced by Spitzer 4.5 μm images. Comparisons of these cold dust features with ancillary data reveal an imperfect spatial correlation with the ionized gas and warm dust wind components. We find that typically ˜10-20 per cent of the total dust mass in these galaxies resides outside of their stellar discs, but this fraction reaches ˜60 per cent in the case of NGC 1569. This galaxy also has the largest metallicity (O/H) deficit in our sample for its stellar mass. Overall, the small number of objects in our sample precludes drawing strong conclusions on the origin of the circumgalactic dust. We detect no statistically significant trends with star formation properties of the host galaxies, as might be expected if the dust were lifted above the disc by energy inputs from ongoing star formation activity. Although a case for dust entrained in a galactic wind is seen in NGC 1569, in all cases, we cannot rule out the possibility that some of the circumgalactic dust might be associated instead with gas accreted or removed from the disc by recent galaxy interaction events, or that it is part of the outer gas-rich portion of the disc that lies below the sensitivity limit of the Spitzer 4.5 μm data.

  3. Dust of dark energy

    International Nuclear Information System (INIS)

    Lim, Eugene A.; Sawicki, Ignacy; Vikman, Alexander

    2010-01-01

    We introduce a novel class of field theories where energy always flows along timelike geodesics, mimicking in that respect dust, yet which possess non-zero pressure. This theory comprises two scalar fields, one of which is a Lagrange multiplier enforcing a constraint between the other's field value and derivative. We show that this system possesses no wave-like modes but retains a single dynamical degree of freedom. Thus, the sound speed is always identically zero on all backgrounds. In particular, cosmological perturbations reproduce the standard behaviour for hydrodynamics in the limit of vanishing sound speed. Using all these properties we propose a model unifying Dark Matter and Dark Energy in a single degree of freedom. In a certain limit this model exactly reproduces the evolution history of ΛCDM, while deviations away from the standard expansion history produce a potentially measurable difference in the evolution of structure

  4. Simulating southwestern U.S. desert dust influences on supercell thunderstorms

    Science.gov (United States)

    Lerach, David G.; Cotton, William R.

    2018-05-01

    Three-dimensional numerical simulations were performed to evaluate potential southwestern U.S. dust indirect microphysical and direct radiative impacts on a real severe storms outbreak. Increased solar absorption within the dust plume led to modest increases in pre-storm atmospheric stability at low levels, resulting in weaker convective updrafts and less widespread precipitation. Dust microphysical impacts on convection were minor in comparison, due in part to the lofted dust concentrations being relatively few in number when compared to the background (non-dust) aerosol population. While dust preferentially serving as cloud condensation nuclei (CCN) versus giant CCN had opposing effects on warm rain production, both scenarios resulted in ample supercooled water and subsequent glaciation aloft, yielding larger graupel and hail. Associated latent heating from condensation and freezing contributed little to overall updraft invigoration. With reduced rain production overall, the simulations that included dust effects experienced slightly reduced grid-cumulative precipitation and notably warmer and spatially smaller cold pools. Dust serving as ice nucleating particles did not appear to play a significant role. The presence of dust ultimately reduced the number of supercells produced but allowed for supercell evolution characterized by consistently higher values of relative vertical vorticity within simulated mesocyclones. Dust radiative and microphysical effects were relatively small in magnitude when compared to those from altering the background convective available potential energy and vertical wind shear. It is difficult to generalize such findings from a single event, however, due to a number of case-specific environmental factors. These include the nature of the low-level moisture advection and characteristics of the background aerosol distribution.

  5. Dust modeling over East Asia during the summer of 2010 using the WRF-Chem model

    Science.gov (United States)

    Zhang, B.; Huang, J.; Chen, S.

    2017-12-01

    An intense summer dust storm over East Asia during June 24-27, 2010, was systematically analyzed using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) and a variety of in situ measurements and satellite retrievals. The results showed that the WRF-Chem model captured the spatial and temporal distributions of meteorological factors and dust aerosols over East Asia. This summer dust storm was initiated by the approach of a transverse trough in the northwestern Xinjiang. Because of the passage of the cutoff-low, a large amount of cold air was transported southward and further enhanced in the narrow valleys of the Altai and Tianshan Mountains, which resulted in higher wind speeds and huge dust emissions over the Taklimakan Desert (TD). Dust emission fluxes over the TD were as high as 54 μg m-2 s-1 on June 25th. The dust aerosols from the TD then swept across Inner Mongolia, Ningxia and Mongolia, and some were also transported eastward to Beijing, Tianjin, the Hebei region, and even South Korea and Japan. The simulations further showed that summer dust over East Asia exerts an important influence on the radiation budget in the Earth-atmosphere system. Dust heat the atmosphere at a maximum heating rate of 0.14 k day-1, effectively changing the vertical stability of the atmosphere and affecting climate change at regional and even global scales. The dust event-averaged direct radiative forcing induced by dust particles over the TD at all-sky was -6.0, -16.8 and 10.8 W m-2 at the top of the atmosphere, the surface, and in the atmosphere, respectively.

  6. Dust emission mechanisms in the central Sahara: new insights from remote field observations

    Science.gov (United States)

    Allen, C.; Washington, R.; Engelstaedter, S.

    2013-12-01

    North Africa is the world's largest source of mineral aerosol (dust). The Fennec Project, an international consortium led by the University of Oxford, is the first project to systematically instrument the remote central Sahara Desert. These observations have, among others, provided new insights into the atmospheric mechanisms of dust emission. Bordj Badji Mokhtar, in south-west Algeria, is within kilometres of the centre of the global mean summer dust maximum. The site, operated by Fennec partners ONM Algerie, has been heavily instrumented since summer 2011. During the Intensive Observation Period (IOP) in June 2011, four main emission mechanisms were observed and documented: cold pool outflows, low level jets (LLJs), monsoon surges and dry convective plumes. Establishing the relative importance of dust emission mechanisms has been a long-standing research goal. A detailed partitioning exercise of dust events during the IOP shows that 45% of the dust over BBM was generated by local emission in cold pool outflows, 14% by LLJs and only 2% by dry convective plumes. 27% of the dust was advected to the site rather than locally emitted and 12% of the dust was residual or ';background' dust. The work shows the primacy of cold pool outflows for dust emission in the region and also the important contribution of dust advection. In accordance with long-held ideas, the cube of wind speed is strongly correlated with dust emission. Surprisingly however, particles in long-range advection (>500km) were found to be larger than locally emitted dust. Although a clear LLJ wind structure is evident in the mean diurnal cycle during the IOP (12m/s peak winds at 935hPa between 04-05h), LLJs are only responsible for a relatively small amount of dust emission. There is significant daily variability in LLJ strength; the strongest winds are produced by a relatively small number of events. The position and strength of the Saharan Heat Low is strongly associated with the development (or

  7. Ulysses dust measurements near Jupiter.

    Science.gov (United States)

    Grün, E; Zook, H A; Baguhl, M; Fechtig, H; Hanner, M S; Kissel, J; Lindblad, B A; Linkert, D; Linkert, G; Mann, I B

    1992-09-11

    Submicrometer- to micrometer-sized particles were recorded by the Ulysses dust detector within 40 days of the Jupiter flyby. Nine impacts were recorded within 50 Jupiter radii with most of them recorded after closest approach. Three of these impacts are consistent with particles on prograde orbits around Jupiter and the rest are believed to have resulted from gravitationally focused interplanetary dust. From the ratio of the impact rate before the Jupiter flyby to the impact rate after the Jupiter flyby it is concluded that interplanetary dust particles at the distance of Jupiter move on mostly retrograde orbits. On 10 March 1992, Ulysses passed through an intense dust stream. The dust detector recorded 126 impacts within 26 hours. The stream particles were moving on highly inclined and apparently hyperbolic orbits with perihelion distances of >5 astronomical units. Interplanetary dust is lost rather quickly from the solar system through collisions and other mechanisms and must be almost continuously replenished to maintain observed abundances. Dust flux measurements, therefore, give evidence of the recent rates of production from sources such as comets, asteroids, and moons, as well as the possible presence of interstellar grains.

  8. Experiments on Dust Grain Charging

    Science.gov (United States)

    Abbas, M. N.; Craven, P. D.; Spann, J. F.; Tankosic, D.; LeClair, A.; West, E. A.

    2004-01-01

    Dust particles in various astrophysical environments are charged by a variety of mechanisms generally involving collisional processes with other charged particles and photoelectric emission with UV radiation from nearby sources. The sign and the magnitude of the particle charge are determined by the competition between the charging processes by UV radiation and collisions with charged particles. Knowledge of the particle charges and equilibrium potentials is important for understanding of a number of physical processes. The charge of a dust grain is thus a fundamental parameter that influences the physics of dusty plasmas, processes in the interplanetary medium and interstellar medium, interstellar dust clouds, planetary rings, cometary and outer atmospheres of planets etc. In this paper we present some results of experiments on charging of dust grains carried out on a laboratory facility capable levitating micron size dust grains in an electrodynamic balance in simulated space environments. The charging/discharging experiments were carried out by exposing the dust grains to energetic electron beams and UV radiation. Photoelectric efficiencies and yields of micron size dust grains of SiO2, and lunar simulates obtained from NASA-JSC will be presented.

  9. Iron: A Key Element for Understanding the Origin and Evolution of Interstellar Dust

    Science.gov (United States)

    Dwek, Eli

    2016-01-01

    The origin and depletion of iron differ from all other abundant refractory elements that make up the composition of the interstellar dust. Iron is primarily synthesized in Type Ia supernovae (SNe Ia) and in core collapse supernovae (CCSN), and is present in the outflows from AGB (Asymptotic Giant Branch) stars. Only the latter two are observed to be sources of interstellar dust, since searches for dust in SN Ia have provided strong evidence for the absence of any significant mass of dust in their ejecta. Consequently, more than 65 percent of the iron is injected into the ISM (Inter-Stellar Matter) in gaseous form. Yet, ultraviolet and X-ray observations along many lines of sight in the ISM show that iron is severely depleted in the gas phase compared to expected solar abundances. The missing iron, comprising about 90 percent of the total, is believed to be locked up in interstellar dust. This suggests that most of the missing iron must have precipitated from the ISM gas by cold accretion onto preexisting silicate, carbon, or composite grains. Iron is thus the only element that requires most of its growth to occur outside the traditional stellar condensation sources. This is a robust statement that does not depend on our evolving understanding of the dust destruction efficiency in the ISM. Reconciling the physical, optical, and chemical properties of such composite grains with their many observational manifestations is a major challenge for understanding the nature and origin of interstellar dust.

  10. Commemoration of a cold war

    DEFF Research Database (Denmark)

    Farbøl, Rosanna

    2015-01-01

    This article brings together the fields of Cold War studies and memory studies. In Denmark, a remarkable institutionalisation of Cold War memory has taken place in the midst of a heated ideological battle over the past and whether to remember the Cold War as a ‘war’. Using Danish Cold War museums...... and heritage sites as case studies, this article sheds new light on the politics of history involved in Cold War commemoration. It suggests that the Cold War is commemorated as a war, yet this war memory is of a particular kind: it is a war memory without victims....

  11. Paracas dust storms: Sources, trajectories and associated meteorological conditions

    Science.gov (United States)

    Briceño-Zuluaga, F.; Castagna, A.; Rutllant, J. A.; Flores-Aqueveque, V.; Caquineau, S.; Sifeddine, A.; Velazco, F.; Gutierrez, D.; Cardich, J.

    2017-09-01

    Dust storms that develop along the Pisco-Ica desert in Southern Peru, locally known as ;Paracas; winds have ecological, health and economic repercussions. Here we identify dust sources through MODIS (Moderate Resolution Imaging Spectroradiometer) imagery and analyze HYSPLIT (Hybrid Single Particles Lagrangian Integrated Trajectory) model trajectories and dispersion patterns, along with concomitant synoptic-scale meteorological conditions from National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis (NCEP/NCAR). Additionally, surface pressure data from the hourly METeorological Aerodrome Report (METAR) at Arica (18.5°S, 70.3°W) and Pisco (13.7°S, 76.2°W) were used to calculate Alongshore (sea-level) Pressure Gradient (APG) anomalies during Paracas dust storms, their duration and associated wind-speeds and wind directions. This study provides a review on the occurrence and strength of the Paracas dust storms as reported in the Pisco airfield for five-year period and their correspondence with MODIS true-color imagery in terms of dust-emission source areas. Our results show that most of the particle fluxes moving into the Ica-Pisco desert area during Paracas wind events originate over the coastal zone, where strong winds forced by steep APGs develop as the axis of a deep mid-troposphere trough sets in along north-central Chile. Direct relationships between Paracas wind intensity, number of active dust-emission sources and APGs are also documented, although the scarcity of simultaneous METAR/MODIS data for clearly observed MODIS dust plumes prevents any significant statistical inference. Synoptic-scale meteorological composites from NCEP/NCAR reanalysis data show that Paracas wind events (steep APGs) are mostly associated with the strengthening of anticyclonic conditions in northern Chile, that can be attributed to cold air advection associated with the incoming trough. Compared to the MODIS images, HYSPLIT outputs were able

  12. Cold welding of organic light emitting diode: Interfacial and contact models

    Directory of Open Access Journals (Sweden)

    J. Asare

    2016-06-01

    Full Text Available This paper presents the results of an analytical and computational study of the contacts and interfacial fracture associated with the cold welding of Organic Light Emitting diodes (OLEDs. The effects of impurities (within the possible interfaces are explored for contacts and interfacial fracture between layers that are relevant to model OLEDs. The models are used to study the effects of adhesion, pressure, thin film layer thickness and dust particle modulus (between the contacting surfaces on contact profiles around impurities between cold-welded thin films. The lift-off stage of thin films (during cold welding is then modeled as an interfacial fracture process. A combination of adhesion and interfacial fracture theories is used to provide new insights for the design of improved contact and interfacial separation during cold welding. The implications of the results are discussed for the design and fabrication of cold welded OLED structures.

  13. Cold spray nozzle design

    Science.gov (United States)

    Haynes, Jeffrey D [Stuart, FL; Sanders, Stuart A [Palm Beach Gardens, FL

    2009-06-09

    A nozzle for use in a cold spray technique is described. The nozzle has a passageway for spraying a powder material, the passageway having a converging section and a diverging section, and at least the diverging section being formed from polybenzimidazole. In one embodiment of the nozzle, the converging section is also formed from polybenzimidazole.

  14. Cold fusion - todays situation

    International Nuclear Information System (INIS)

    Malmqvist, K.

    1993-01-01

    A brief review of the history of cold fusion is given. It is noted that it is not possible to draw any definite conclusions about all the experimental and theoretical details, but that some of the results presented do not seem to be reached according to the normal scientific methods. 6 figs

  15. Recent Cold War Studies

    Science.gov (United States)

    Pineo, Ronn

    2003-01-01

    Cold War historiography has undergone major changes since the 1991 collapse of the Soviet Union. For two years (1992-1993) the principal Soviet archives fell open to scholars, and although some of the richest holdings are now once again closed, new information continues to find its way out. Moreover, critical documentary information has become…

  16. Expert Cold Structure Development

    Science.gov (United States)

    Atkins, T.; Demuysere, P.

    2011-05-01

    The EXPERT Program is funded by ESA. The objective of the EXPERT mission is to perform a sub-orbital flight during which measurements of critical aero- thermodynamic phenomena will be obtained by using state-of-the-art instrumentation. As part of the EXPERT Flight Segment, the responsibility of the Cold Structure Development Design, Manufacturing and Validation was committed to the Belgian industrial team SONACA/SABCA. The EXPERT Cold Structure includes the Launcher Adapter, the Bottom Panel, the Upper Panel, two Cross Panels and the Parachute Bay. An additional Launcher Adapter was manufactured for the separation tests. The selected assembly definition and manufacturing technologies ( machined parts and sandwich panels) were dictated classically by the mass and stiffness, but also by the CoG location and the sensitive separation interface. Used as support for the various on-board equipment, the Cold Structure is fixed to but thermally uncoupled from the PM 1000 thermal shield. It is protect on its bottom panel by a thermal blanket. As it is a protoflight, analysis was the main tool for the verification. Low level stiffness and modal analysis tests have also been performed on the Cold Structure equipped with its ballast. It allowed to complete its qualification and to prepare SONACA/SABCA support for the system dynamic tests foreseen in 2011. The structure was finally coated with a thermal control black painting and delivered on time to Thales Alenia Space-Italy end of March 201.

  17. A dust-free dock

    Energy Technology Data Exchange (ETDEWEB)

    Merrion, D. [E & F Services Ltd. (United Kingdom)

    2002-10-01

    This paper describes the process of unloading coal, petcoke and other dusty products in environmentally-sensitive areas. It presents a case study of the deepwater Port of Foynes on the west coast of Ireland which imports animal feed, fertiliser, coal and cement clinker, where dockside mobile loaders (DMLs) have eliminated spillage and controlled dust, and a record case study of the Humber International Terminal in the UK, where air curtinas, dust suppression grids and EFFEX{reg_sign} filters overcome the dust problems. 2 photos.

  18. Triton's streaks as windblown dust

    Science.gov (United States)

    Sagan, Carl; Chyba, Christopher

    1990-01-01

    Explanations for the surface streaks observed by Voyager 2 on Triton's southern hemisphere are discussed. It is shown that, despite Triton's tenuous atmosphere, low-cohesion dust trains with diameters of about 5 micron or less may be carried into suspension by aeolian surface shear stress, given expected geostrophic wind speeds of about 10 m/s. For geyser-like erupting dust plumes, it is shown that dust-settling time scales and expected wind velocities can produce streaks with length scales in good agreement with those of the streaks. Thus, both geyserlike eruptions or direct lifting by surface winds appear to be viable mechanisms for the origin of the streaks.

  19. [Asthma due to grain dust].

    Science.gov (United States)

    Baur, X; Preisser, A; Wegner, R

    2003-06-01

    The actual literature as well as two case reports described in detail show that grain dust induces asthmatic reactions and ODTS which are obviously not of allergic origin. For diagnosis occupational-type exposure tests are decisive whereas allergological testing usually is not. Endotoxins which are present in the grain dust samples in high concentrations have to be regarded as the major causative components. To avoid irreversible lung function impairment a comprehensive early diagnosis is necessary. Generally, a remarkable reduction of exposure to dust with high levels of airborne endotoxin in agriculture has to be achieved since in many workplaces corresponding exposures are still rather high.

  20. Detection of cold pain, cold allodynia and cold hyperalgesia in freely behaving rats

    Directory of Open Access Journals (Sweden)

    Woolf Clifford J

    2005-12-01

    Full Text Available Abstract Background Pain is elicited by cold, and a major feature of many neuropathic pain states is that normally innocuous cool stimuli begin to produce pain (cold allodynia. To expand our understanding of cold induced pain states we have studied cold pain behaviors over a range of temperatures in several animal models of chronic pain. Results We demonstrate that a Peltier-cooled cold plate with ± 1°C sensitivity enables quantitative measurement of a detection withdrawal response to cold stimuli in unrestrained rats. In naïve rats the threshold for eliciting cold pain behavior is 5°C. The withdrawal threshold for cold allodynia is 15°C in both the spared nerve injury and spinal nerve ligation models of neuropathic pain. Cold hyperalgesia is present in the spared nerve injury model animals, manifesting as a reduced latency of withdrawal response threshold at temperatures that elicit cold pain in naïve rats. We also show that following the peripheral inflammation produced by intraplantar injection of complete Freund's adjuvant, a hypersensitivity to cold occurs. Conclusion The peltier-cooled provides an effective means of assaying cold sensitivity in unrestrained rats. Behavioral testing of cold allodynia, hyperalgesia and pain will greatly facilitate the study of the neurobiological mechanisms involved in cold/cool sensations and enable measurement of the efficacy of pharmacological treatments to reduce these symptoms.

  1. Burning Cold: Involvement of TRPA1 in Noxious Cold Sensation

    OpenAIRE

    Kwan, Kelvin Y.; Corey, David P.

    2009-01-01

    Soon after its discovery ten years ago, the ion channel TRPA1 was proposed as a sensor of noxious cold. Evidence for its activation by painfully cold temperatures (below ~15° C) has been mixed, however. Some groups found that cold elicits a nonselective conductance in cells expressing TRPA1; others found no activation, or argued that activation is an indirect effect of elevated \\(Ca^{ 2+}\\) . Sensory cells from the trigeminal and dorsal root ganglia that are activated by cold were sometimes c...

  2. Dust Dynamics Near Planetary Surfaces

    Science.gov (United States)

    Colwell, Joshua; Hughes, Anna; Grund, Chris

    Observations of a lunar "horizon glow" by several Surveyor spacecraft in the 1960s opened the study of the dynamics of charged dust particles near planetary surfaces. The surfaces of the Moon and other airless planetary bodies in the solar system (asteroids, and other moons) are directly exposed to the solar wind and ionizing solar ultraviolet radiation, resulting in a time-dependent electric surface potential. Because these same objects are also exposed to bombardment by micrometeoroids, the surfaces are usually characterized by a power-law size distribution of dust that extends to sub-micron-sized particles. Individual particles can acquire a charge different from their surroundings leading to electrostatic levitation. Once levitated, particles may simply return to the surface on nearly ballistic trajectories, escape entirely from the moon or asteroid if the initial velocity is large, or in some cases be stably levitated for extended periods of time. All three outcomes have observable consequences. Furthermore, the behavior of charged dust near the surface has practical implications for planned future manned and unmanned activities on the lunar surface. Charged dust particles also act as sensitive probes of the near-surface plasma environment. Recent numerical modeling of dust levitation and transport show that charged micron-sized dust is likely to accumulate in topographic lows such as craters, providing a mechanism for the creation of dust "ponds" observed on the asteroid 433 Eros. Such deposition can occur when particles are supported by the photoelectron sheath above the dayside and drift over shadowed regions of craters where the surface potential is much smaller. Earlier studies of the lunar horizon glow are consistent with those particles being on simple ballistic trajectories following electrostatic launching from the surface. Smaller particles may be accelerated from the lunar surface to high altitudes consistent with observations of high altitude

  3. A Determination of the Intergalactic Redshift Dependent UV-Optical-NIR Photon Density Using Deep Galaxy Survey Data and the Gamma-ray Opacity of the Universe

    Science.gov (United States)

    Stecker, Floyd W.; Malkan, Matthew A.; Scully, Sean T.

    2012-01-01

    We calculate the intensity and photon spectrum of the intergalactic background light (IBL) as a function of redshift using an approach based on observational data obtained in many different wavelength bands from local to deep galaxy surveys. This allows us to obtain an empirical determination of the IBL and to quantify its observationally based uncertainties. Using our results on the IBL, we then place 68% confidence upper and lower limits on the opacity of the universe to gamma-rays, free of the theoretical assumptions that were needed for past calculations. We compare our results with measurements of the extragalactic background light and upper limits obtained from observations made by the Fermi Gamma-ray Space Telescope.

  4. Bounded dust-acoustic waves in a cylindrically bounded collisional dusty plasma with dust charge variation

    International Nuclear Information System (INIS)

    Wei Nanxia; Xue Jukui

    2006-01-01

    Taking into account the boundary, particle collisions, and dust charging effects, dust-acoustic waves in a uniform cylindrically bounded dusty plasma is investigated analytically, and the dispersion relation for the dust-acoustic wave is obtained. The effects of boundary, dust charge variation, particle collision, and dust size on the dust-acoustic wave are discussed in detail. Due to the bounded cylindrical boundary effects, the radial wave number is discrete, i.e., the spectrum is discrete. It is shown that the discrete spectrum, the adiabatic dust charge variation, dust grain size, and the particle collision have significant effects on the dust-acoustic wave

  5. Dust particle formation in silane plasmas

    NARCIS (Netherlands)

    Sorokin, M.

    2005-01-01

    Dust can be found anywhere: in the kitchen, in the car, in space… Not surprisingly we also see dust in commercial and laboratory plasmas. Dust can be introduced in the plasma, but it can also grow there by itself. In the microelectronics industry, contamination of the processing plasma by dust is an

  6. PERSPECTIVE: Dust, fertilization and sources

    Science.gov (United States)

    Remer, Lorraine A.

    2006-11-01

    Aerosols, tiny suspended particles in the atmosphere, play an important role in modifying the Earth's energy balance and are essential for the formation of cloud droplets. Suspended dust particles lifted from the world's arid regions by strong winds contain essential minerals that can be transported great distances and deposited into the ocean or on other continents where productivity is limited by lack of usable minerals [1]. Dust can transport pathogens as well as minerals great distance, contributing to the spread of human and agricultural diseases, and a portion of dust can be attributed to human activity suggesting that dust radiative effects should be included in estimates of anthropogenic climate forcing. The greenish and brownish tints in figure 1 show the wide extent of monthly mean mineral dust transport, as viewed by the MODerate resolution Imaging Spectroradiometer (MODIS) satellite sensor. The monthly mean global aerosol system for February 2006 from the MODIS aboard the Terra satellite Figure 1. The monthly mean global aerosol system for February 2006 from the MODIS aboard the Terra satellite. The brighter the color, the greater the aerosol loading. Red and reddish tints indicate aerosol dominated by small particles created primarily from combustion processes. Green and brownish tints indicate larger particles created from wind-driven processes, usually transported desert dust. Note the bright green band at the southern edge of the Saharan desert, the reddish band it must cross if transported to the southwest and the long brownish transport path as it crosses the Atlantic to South America. Image courtesy of the NASA Earth Observatory (http://earthobservatory.nasa.gov). Even though qualitatively we recognize the extent and importance of dust transport and the role that it plays in fertilizing nutrient-limited regions, there is much that is still unknown. We are just now beginning to quantify the amount of dust that exits one continental region and the

  7. COINCIDENCES BETWEEN O VI AND O VII LINES: INSIGHTS FROM HIGH-RESOLUTION SIMULATIONS OF THE WARM-HOT INTERGALACTIC MEDIUM

    International Nuclear Information System (INIS)

    Cen Renyue

    2012-01-01

    With high-resolution (0.46 h –1 kpc), large-scale, adaptive mesh-refinement Eulerian cosmological hydrodynamic simulations we compute properties of O VI and O VII absorbers from the warm-hot intergalactic medium (WHIM) at z = 0. Our new simulations are in broad agreement with previous simulations with ∼40% of the intergalactic medium being in the WHIM. Our simulations are in agreement with observed properties of O VI absorbers with respect to the line incidence rate and Doppler-width-column-density relation. It is found that the amount of gas in the WHIM below and above 10 6 K is roughly equal. Strong O VI absorbers are found to be predominantly collisionally ionized. It is found that (61%, 57%, 39%) of O VI absorbers of log N(O VI) cm 2 = (12.5-13, 13-14, > 14) have T 5 K. Cross correlations between galaxies and strong [N(O VI) > 10 14 cm –2 ] O VI absorbers on ∼100-300 kpc scales are suggested as a potential differentiator between collisional ionization and photoionization models. Quantitative prediction is made for the presence of broad and shallow O VI lines that are largely missed by current observations but will be detectable by Cosmic Origins Spectrograph observations. The reported 3σ upper limit on the mean column density of coincidental O VII lines at the location of detected O VI lines by Yao et al. is above our predicted value by a factor of 2.5-4. The claimed observational detection of O VII lines by Nicastro et al., if true, is 2σ above what our simulations predict.

  8. THE COSMOLOGICAL IMPACT OF LUMINOUS TeV BLAZARS. I. IMPLICATIONS OF PLASMA INSTABILITIES FOR THE INTERGALACTIC MAGNETIC FIELD AND EXTRAGALACTIC GAMMA-RAY BACKGROUND

    Energy Technology Data Exchange (ETDEWEB)

    Broderick, Avery E; Chang, Philip; Pfrommer, Christoph [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, Toronto, ON M5S 3H8 (Canada)

    2012-06-10

    Inverse Compton cascades (ICCs) initiated by energetic gamma rays (E {approx}> 100 GeV) enhance the GeV emission from bright, extragalactic TeV sources. The absence of this emission from bright TeV blazars has been used to constrain the intergalactic magnetic field (IGMF), and the stringent limits placed on the unresolved extragalactic gamma-ray background (EGRB) by Fermi have been used to argue against a large number of such objects at high redshifts. However, these are predicated on the assumption that inverse Compton scattering is the primary energy-loss mechanism for the ultrarelativistic pairs produced by the annihilation of the energetic gamma rays on extragalactic background light photons. Here, we show that for sufficiently bright TeV sources (isotropic-equivalent luminosities {approx}> 10{sup 42} erg s{sup -1}) plasma beam instabilities, specifically the 'oblique' instability, present a plausible mechanism by which the energy of these pairs can be dissipated locally, heating the intergalactic medium. Since these instabilities typically grow on timescales short in comparison to the inverse Compton cooling rate, they necessarily suppress the ICCs. As a consequence, this places a severe constraint on efforts to limit the IGMF from the lack of a discernible GeV bump in TeV sources. Similarly, it considerably weakens the Fermi limits on the evolution of blazar populations. Specifically, we construct a TeV-blazar luminosity function from those objects currently observed and find that it is very well described by the quasar luminosity function at z {approx} 0.1, shifted to lower luminosities and number densities, suggesting that both classes of sources are regulated by similar processes. Extending this relationship to higher redshifts, we show that the magnitude and shape of the EGRB above {approx}10 GeV are naturally reproduced with this particular example of a rapidly evolving TeV-blazar luminosity function.

  9. Flu and Colds: In Depth

    Science.gov (United States)

    ... to prevent colds or relieve cold symptoms. Andrographis (Andrographis paniculata) Chinese herbal medicines Green tea Guided imagery Hydrotherapy ... measurements (VAS) to assess the effectiveness of standardized Andrographis paniculata extract SHA-10 in reducing the symptoms of ...

  10. Herpes Simplex Virus (Cold Sores)

    Science.gov (United States)

    ... Print Share Cold Sores in Children: About the Herpes Simplex Virus Page Content ​A child's toddler and ... Cold sores (also called fever blisters or oral herpes) start as small blisters that form around the ...

  11. Imaging with cold neutrons

    International Nuclear Information System (INIS)

    Lehmann, E.H.; Kaestner, A.; Josic, L.; Hartmann, S.; Mannes, D.

    2011-01-01

    Neutrons for imaging purposes are provided mainly from thermal beam lines at suitable facilities around the world. The access to cold neutrons is presently limited to very few places only. However, many challenging options for imaging with cold neutrons have been found out, given by the interaction behavior of the observed materials with neutrons in the cold energy range (3-10 A). For absorbing materials, the interaction probability increases proportionally with the wavelength with the consequence of more contrast but less transmission with cold neutrons. Many materials are predominantly scattering neutrons, in particular most of crystalline structural materials. In these cases, cold neutrons play an important role by covering the energy range of the most important Bragg edges given by the lattice planes of the crystallites. This particular behavior can be used for at least two important aspects-choosing the right energy of the initial beam enables to have a material more or less transparent, and a direct macroscopic visualization of the crystalline structure and its change in a manufacturing process. Since 2006, PSI operates its second beam line for neutron imaging, where cold neutrons are provided from a liquid deuterium cold source (operated at 25 K). It has been designed to cover the most current aspects in neutron imaging research with the help of high flexibility. This has been done with changeable inlet apertures, a turbine based velocity selector, two beam positions and variable detector systems, satisfying the demands of the individual investigation. The most important detection system was found to be a micro-tomography system that enables studies in the presently best spatial resolution. In this case, the high contrast from the sample interaction process and the high detection probability for the cold neutrons combines in an ideal combination for the best possible performance. Recently, it was found out that the energy selective studies might become a

  12. Loess and Eolian Dust Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Records of past environment derived from Loess and Eolian dust (silt-sized material deposited on the Earth surface by the surface winds. Parameter keywords describe...

  13. 75 FR 3881 - Combustible Dust

    Science.gov (United States)

    2010-01-25

    ..., rubber, drugs, dried blood, dyes, certain textiles, and metals (such as aluminum and magnesium..., furniture manufacturing, metal processing, fabricated metal products and machinery manufacturing, pesticide... standard that will comprehensively address the fire and explosion hazards of combustible dust. The Agency...

  14. Rethinking wood dust safety standards

    OpenAIRE

    Ratnasingam, Jega; Wai, Lim Tau; Ramasamy, Geetha; Ioras, Florin; Tadin, Ishak; Universiti Putra Malaysia; Buckinghamshire New University; Centre for Occupational Safety and Health Singapore

    2015-01-01

    The current universal work safety and health standards pertaining to wood dust in factories lack the localisation required. As a study has shown, there is a urgent need to reevaluate the current guidelines and practices.

  15. Comet Dust: The Diversity of Primitive Particles and Implications

    Science.gov (United States)

    John Bradley; Zolensky, Michael E.

    2016-01-01

    Comet dust is primitive and shows significant diversity. Our knowledge of the properties of primitive particles has expanded significantly through microscale investigations of cosmic dust samples (IDPs and AMMs) and of comet dust samples (Stardust and Rosetta's COSIMA), as well as through remote sensing (spectroscopy and imaging) via Spitzer and via spacecraft encounters with 103P/Hartley 2 and 67P/Churyumov-Gerasimenko. Microscale investigations show that comet dust and cosmic dust are particles of unequilibrated materials, including aggregates of materials unequilibrated at submicron scales. We call unequilibrated materials "primitive" and we deduce they were incorporated into ice-­-rich (H2O-, CO2-, and CO-ice) parent bodies that remained cold, i.e., into comets, because of the lack of aqueous or thermal alteration since particle aggregation; yet some Stardust olivines suggest mild thermal metamorphism. Primitive particles exhibit a diverse range of: structure and typology; size and size distribution of constituents; concentration and form of carbonaceous and organic matter; D-, N-, and O- isotopic enhancements over solar; Mg-, Fe-contentsof thesilicate minerals; the compositions and concentrations of sulfides, and of less abundant mineral species such as chondrules, CAIs and carbonates. The unifomity within a group of samples points to: aerodynamic sorting of particles and/or particle constituents; the inclusion of a limited range of oxygen fugacities; the inclusion or exclusion of chondrules; a selection of organics. The properites of primitive particles imply there were disk processes that resulted in different comets having particular selections of primitive materials. The diversity of primitive particles has implications for the diversity of materials in the protoplanetary disk present at the time and in the region where the comets formed.

  16. The Diversity of Carbon in Cometary Refractory Dust Particles

    Science.gov (United States)

    Wooden, D. H.

    2018-01-01

    When comparing the dark icy surfaces of outer solar system small bodies and the composition of carbonaceous chondrites derived from dark asteroids we find a significant discrepancy in the assessed amounts of elemental carbon: up to 80% amorphous carbon is used to model the dark surfaces of Kuiper Belt Objects and Centaurs whereas at most 5% of elemental carbon is found in carbonaceous chondrites. If we presume that regimes of comet nuclei formation are analogous to disk regimes where other outer solar system ice-rich bodies formed then we can turn to comet dust to gain insights into the diversity in the concentration and forms of carbon available in the outer disk. Comet dust offers important insights into the diversity in the amounts and forms of carbon that were incorporated into aggregate dust particles in the colder parts of the protoplanetary disk out of which comet nuclei accreted. Comet nuclei are amongst the most primitive bodies because they have remained cold and unequilibrated. Comet dust particles reveal the presence of forms of elemental carbon and of soluble and insoluble organic matter, and in a great diversity of concentrations from very little, e.g., Stardust samples of comet 81P/Wild 2, to 80% by volume for Ultra Carbonaceous Antarctic Micro Meteorites (UCAMMs). Cometary outbursts and/or jet activity also demonstrate variations in the concentration of carbon in the grains at different grain sizes within a single comet. We review the diversity of carbon-bearing dust grains in cometary samples, flyby measurements and deduced from remote-sensing to enrich the discussion about the diversity of carbonaceous matter available in the outer ice-rich disk at the time of comet nuclei formation.

  17. Human whole body cold adaptation.

    OpenAIRE

    Daanen, Hein A.M.; Van Marken Lichtenbelt, Wouter D.

    2016-01-01

    ABSTRACT Reviews on whole body human cold adaptation generally do not distinguish between population studies and dedicated acclimation studies, leading to confusing results. Population studies show that indigenous black Africans have reduced shivering thermogenesis in the cold and poor cold induced vasodilation in fingers and toes compared to Caucasians and Inuit. About 40,000?y after humans left Africa, natives in cold terrestrial areas seems to have developed not only behavioral adaptations...

  18. Global Scale Attribution of Anthropogenic and Natural Dust Sources and their Emission Rates Based on MODIS Deep Blue Aerosol Products

    Science.gov (United States)

    Ginoux, Paul; Prospero, Joseph M.; Gill, Thomas E.; Hsu, N. Christina; Zhao, Ming

    2012-01-01

    Our understanding of the global dust cycle is limited by a dearth of information about dust sources, especially small-scale features which could account for a large fraction of global emissions. Here we present a global-scale high-resolution (0.1 deg) mapping of sources based on Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue estimates of dust optical depth in conjunction with other data sets including land use. We ascribe dust sources to natural and anthropogenic (primarily agricultural) origins, calculate their respective contributions to emissions, and extensively compare these products against literature. Natural dust sources globally account for 75% of emissions; anthropogenic sources account for 25%. North Africa accounts for 55% of global dust emissions with only 8% being anthropogenic, mostly from the Sahel. Elsewhere, anthropogenic dust emissions can be much higher (75% in Australia). Hydrologic dust sources (e.g., ephemeral water bodies) account for 31% worldwide; 15% of them are natural while 85% are anthropogenic. Globally, 20% of emissions are from vegetated surfaces, primarily desert shrublands and agricultural lands. Since anthropogenic dust sources are associated with land use and ephemeral water bodies, both in turn linked to the hydrological cycle, their emissions are affected by climate variability. Such changes in dust emissions can impact climate, air quality, and human health. Improved dust emission estimates will require a better mapping of threshold wind velocities, vegetation dynamics, and surface conditions (soil moisture and land use) especially in the sensitive regions identified here, as well as improved ability to address small-scale convective processes producing dust via cold pool (haboob) events frequent in monsoon regimes.

  19. Physical properties of five grain dust types.

    OpenAIRE

    Parnell, C B; Jones, D D; Rutherford, R D; Goforth, K J

    1986-01-01

    Physical properties of grain dust derived from five grain types (soybean, rice, corn, wheat, and sorghum) were measured and reported. The grain dusts were obtained from dust collection systems of terminal grain handling facilities and were assumed to be representative of grain dust generated during the handling process. The physical properties reported were as follows: particle size distributions and surface area measurements using a Coulter Counter Model TAII; percent dust fractions less tha...

  20. Efficient radiative transfer in dust grain mixtures

    OpenAIRE

    Wolf, S.

    2002-01-01

    The influence of a dust grain mixture consisting of spherical dust grains with different radii and/or chemical composition on the resulting temperature structure and spectral energy distribution of a circumstellar shell is investigated. The comparison with the results based on an approximation of dust grain parameters representing the mean optical properties of the corresponding dust grain mixture reveal that (1) the temperature dispersion of a real dust grain mixture decreases substantially ...

  1. Human whole body cold adaptation.

    Science.gov (United States)

    Daanen, Hein A M; Van Marken Lichtenbelt, Wouter D

    2016-01-01

    Reviews on whole body human cold adaptation generally do not distinguish between population studies and dedicated acclimation studies, leading to confusing results. Population studies show that indigenous black Africans have reduced shivering thermogenesis in the cold and poor cold induced vasodilation in fingers and toes compared to Caucasians and Inuit. About 40,000 y after humans left Africa, natives in cold terrestrial areas seems to have developed not only behavioral adaptations, but also physiological adaptations to cold. Dedicated studies show that repeated whole body exposure of individual volunteers, mainly Caucasians, to severe cold results in reduced cold sensation but no major physiological changes. Repeated cold water immersion seems to slightly reduce metabolic heat production, while repeated exposure to milder cold conditions shows some increase in metabolic heat production, in particular non-shivering thermogenesis. In conclusion, human cold adaptation in the form of increased metabolism and insulation seems to have occurred during recent evolution in populations, but cannot be developed during a lifetime in cold conditions as encountered in temperate and arctic regions. Therefore, we mainly depend on our behavioral skills to live in and survive the cold.

  2. Grain dust and the lungs.

    Science.gov (United States)

    Chan-Yeung, M.; Ashley, M. J.; Grzybowski, S.

    1978-01-01

    Grain dust is composed of a large number of materials, including various types of grain and their disintegration products, silica, fungi, insects and mites. The clinical syndromes described in relation to exposure to grain dust are chronic bronchitis, grain dust asthma, extrinsic allergic alveolitis, grain fever and silo-filler's lung. Rhinitis and conjunctivitis are also common in grain workers. While the concentration and the quality of dust influence the frequency and the type of clinical syndrome in grain workers, host factors are also important. Of the latter, smoking is the most important factor influencing the frequency of chronic bronchitis. The role of atopy and of bronchial hyperreactivity in grain dust asthma has yet to be assessed. Several well designed studies are currently being carried out in North America not only to delineate the frequency of the respiratory abnormalities, the pathogenetic mechanisms and the host factors, but also to establish a meaningful threshold limit concentration for grain dust. Images p1272-a PMID:348288

  3. Charged dust structures in plasmas

    International Nuclear Information System (INIS)

    Cramer, N.F.; Vladimirov, S.V.

    1999-01-01

    We report here on theoretical investigations of the mechanical-electrostatic modes of vibration of a dust-plasma crystal, extending earlier work on the transverse modes of a horizontal line of grains (where the ions flow vertically downward to a plane horizontal cathode), the modes of two such lines of grains, and the modes of a vertical string of grains. The last two arrangements have the unique feature that the effect of the background plasma on the mutual grain interaction is asymmetric because of the wake downstream of the grains studied in. The characteristic frequencies of the vibrations are dependent on the parameters of the plasma and the dust grains, such as the Debye length and the grain charge, and so measurement of the frequencies could provide diagnostics of these quantities. Although the current boom in dusty plasma research is driven mainly by such industrial applications as plasma etching, sputtering and deposition, the physical outcomes of investigations in this rapidly expanding field cover many important topics in space physics and astrophysics as well. Examples are the interaction of dust with spacecraft, the structure of planetary rings, star formation, supernova explosions and shock waves. In addition, the study of the influence of dust in environmental research, such as in the Earth's ionosphere and atmosphere, is important. The unique binding of dust particles in a plasma opens possibilities for so-called super-chemistry, where the interacting bound elements are not atoms but dust grains

  4. Suspended dust in Norwegian cities

    International Nuclear Information System (INIS)

    2001-01-01

    According to calculations, at least 80 000 people in Oslo and 8 000 in Trondheim were annoyed by too much suspended dust in 2000. The dust concentration is greatest in the spring, presumably because dust is swirling up from melting snow and ice on the streets. Car traffic is the main source of the dust, except for some of the most highly exposed regions where wood-firing from old stoves contributes up to 70 percent of the dust. National targets for air quality include suspended dust, nitrogen dioxide, sulphur dioxide and benzene. Calculations show that nitrogen dioxide emissions exceeding the limit affected 4 000 people in Oslo and 1 000 people in Trondheim. The sulphur dioxide emissions in the major cities did non exceed the national quality limit; they did exceed the limit in some of the smaller industrial centres. In Trondheim, measurements show that the national limit for benzene was exceeded. Most of the emission of nitrogen dioxide comes from the road traffic. Local air pollution at times causes considerable health- and well-being problems in the larger cities and industrial centres, where a great part of the population may be at risk of early death, infection of the respiratory passage, heart- and lung diseases and cancer

  5. The need to be cold : cold warriors

    Energy Technology Data Exchange (ETDEWEB)

    Gregoire, L.

    2008-10-15

    This article discussed the changing climate of Ellesmere Island and the adaptation of the Inuit in response to the climate change, with particular reference to Canada's most northern community of Grise Fiord. Because of the changing climate, the vast northern landscape that the Inuit navigated for centuries by reading its subtle signs is becoming warmer, softer, and unpredictable. The geographic history and demographics of Grise Fiord were described. The community's main water supply comes from a glacier which is sinking. The negative impacts of ice shrinkage on this northern community and on the environment were presented. These included more international shipping through the Arctic, more resource exploration, a greater risk of environmental contamination, and reduced habitat for the polar bears and seals that eat, mate, and reproduce on the ice. Climate change impacts on the sea and sea ice were also discussed. Several photographs illustrating the changing climate were presented. The article noted that climate change could destroy the Inuit culture, making climate change an issue of human rights, notably the right to live connected to the land and the right to be cold. It was concluded that in one generation, Inuit were swept up by both a social and an economic upheaval. In one more generation, they will undergo an environmental shift. 13 figs.

  6. Direct radiative effects during intense Mediterranean desert dust outbreaks

    Directory of Open Access Journals (Sweden)

    A. Gkikas

    2018-06-01

    temperature at 2 m by up to 4 K during day-time, whereas a reverse tendency of similar magnitude is found during night-time. Depending on the vertical distribution of dust loads and time, mineral particles heat (cool the atmosphere by up to 0.9 K (0.8 K during day-time (night-time within atmospheric dust layers. Beneath and above the dust clouds, mineral particles cool (warm the atmosphere by up to 1.3 K (1.2 K at noon (night-time. On a regional mean basis, negative feedbacks on the total emitted dust (reduced by 19.5 % and dust AOD (reduced by 6.9 % are found when dust interacts with the radiation. Through the consideration of dust radiative effects in numerical simulations, the model positive and negative biases for the downward surface SW or LW radiation, respectively, with respect to Baseline Surface Radiation Network (BSRN measurements, are reduced. In addition, they also reduce the model near-surface (at 2 m nocturnal cold biases by up to 0.5 K (regional averages, as well as the model warm biases at 950 and 700 hPa, where the dust concentration is maximized, by up to 0.4 K. However, improvements are relatively small and do not happen in all episodes because other model first-order errors may dominate over the expected improvements, and the misrepresentation of the dust plumes' spatiotemporal features and optical properties may even produce a double penalty effect. The enhancement of dust forecasts via data assimilation techniques may significantly improve the results.

  7. WISPy cold dark matter

    Energy Technology Data Exchange (ETDEWEB)

    Arias, Paola [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Pontificia Univ. Catolica de Chile, Santiago (Chile). Facultad de Fisica; Cadamuro, Davide; Redondo, Javier [Max-Planck-Institut fuer Physik, Muenchen (Germany); Goodsell, Mark [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); European Organization for Nuclear Research (CERN), Geneva (Switzerland); Jaeckel, Joerg [Durham Univ. (United Kingdom). Inst. for Particle Physics Phenomenology; Ringwald, Andreas [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2012-01-15

    Very weakly interacting slim particles (WISPs), such as axion-like particles (ALPs) or hidden photons (HPs), may be non-thermally produced via the misalignment mechanism in the early universe and survive as a cold dark matter population until today. We find that, both for ALPs and HPs whose dominant interactions with the standard model arise from couplings to photons, a huge region in the parameter spaces spanned by photon coupling and ALP or HP mass can give rise to the observed cold dark matter. Remarkably, a large region of this parameter space coincides with that predicted in well motivated models of fundamental physics. A wide range of experimental searches - exploiting haloscopes (direct dark matter searches exploiting microwave cavities), helioscopes (searches for solar ALPs or HPs), or light-shining-through-a-wall techniques - can probe large parts of this parameter space in the foreseeable future. (orig.)

  8. Progress with cold antihydrogen

    CERN Document Server

    Charlton, M; Amsler, C; Bonomi, G; Bowe, P D; Canali, C; Carraro, C; Cesar, C L; Doser, M; Fontana, A; Fujiwara, M C; Funakoshi, R; Genova, P; Hangst, J S; Hayano, R S; Johnson, I; Jørgensen, L V; Kellerbauer, A G; Lagomarsino, V; Landua, Rolf; Lodi-Rizzini, E; Macri, M; Madsen, N; Manuzio, G; Mitchard, D; Montagna, P; Pruys, H; Regenfus, C; Rotondi, A; Testera, G; Variola, A; Venturelli, L; Van der Werf, D P; Yamazaki, Y; Zurlo, N

    2006-01-01

    The creation of cold antihydrogen by the ATHENA and ATRAP collaborations, working at CERN's unique Antiproton Decelerator (AD) facility, has ushered in a new era in atomic physics. This contribution will briefly review recent results from the ATHENA experiment. These include discussions of antiproton slowing down in a cold positron gas during antihydrogen formation, information derived on the dependence of the antihydrogen formation rate upon the temperature of the stored positron plasma and, finally, upon the spatial distribution of the emitted anti-atoms. We will discuss the implications of these studies for the major outstanding goal of trapping samples of antihydrogen for precise spectroscopic comparisons with hydrogen. The physics motivations for undertaking these challenging experiments will be briefly recalled.

  9. Cold nuclear fusion device

    International Nuclear Information System (INIS)

    Ogino, Shinji.

    1991-01-01

    Selection of cathode material is a key to the attainment of cold nuclear fusion. However, there are only few reports on the cathode material at present and an effective development has been demanded. The device comprises an anode and a cathode and an electrolytic bath having metal salts dissolved therein and containing heavy water in a glass container. The anode is made of gold or platinum and the cathode is made of metals of V, Sr, Y, Nb, Hf or Ta, and a voltage of 3-25V is applied by way of a DC power source between them. The metal comprising V, Sr, Y, Nb, Hf or Ta absorbs deuterium formed by electrolysis of heavy water effectively to cause nuclear fusion reaction at substantially the same frequency and energy efficiency as palladium and titanium. Accordingly, a cold nuclear fusion device having high nuclear fusion generation frequency can be obtained. (N.H.)

  10. Cold source economic study

    International Nuclear Information System (INIS)

    Fuster, Serge.

    1975-01-01

    This computer code is intended for the statement of the general economic balance resulting from using a given cold source. The balance includes the investments needed for constructing the various materials, and also production balances resulting from their utilization. The case of either using an open circuit condenser on sea or river, or using air cooling systems with closed circuits or as auxiliaries can be dealt with. The program can be used to optimize the characteristics of the various parts of the cold source. The performance of the various materials can be evaluated for a given situation from using very full, precise economic balances, these materials can also be classified according to their possible uses, the outer constraints being taken into account (limits for heat disposal into rivers or seas, water temperature, air temperature). Technical choices whose economic consequences are important have been such clarified [fr

  11. The CMS COLD BOX

    CERN Multimedia

    Brice, Maximilien

    2015-01-01

    The CMS detector is built around a large solenoid magnet. This takes the form of a cylindrical coil of superconducting cable that generates a field of 3.8 Tesla: about 100,000 times the magnetic field of the Earth. To run, this superconducting magnet needs to be cooled down to very low temperature with liquid helium. Providing this is the job of a compressor station and the so-called “cold box”.

  12. Clumpy cold dark matter

    Science.gov (United States)

    Silk, Joseph; Stebbins, Albert

    1993-01-01

    A study is conducted of cold dark matter (CDM) models in which clumpiness will inhere, using cosmic strings and textures suited to galaxy formation. CDM clumps of 10 million solar mass/cu pc density are generated at about z(eq) redshift, with a sizable fraction surviving. Observable implications encompass dark matter cores in globular clusters and in galactic nuclei. Results from terrestrial dark matter detection experiments may be affected by clumpiness in the Galactic halo.

  13. Engine Cold Start

    Science.gov (United States)

    2015-09-01

    matching pre- calibrated amplifier • BEI Shaft Encoder (0.2 CAD) • Wolff Instrumented Injector The high speed data was recorded and post-processed by...14. ABSTRACT These fuels were used for testing a GEP 6.5L turbocharged V-8 diesel engine operation in a cold box. This engine architecture is...Z39.18 UNCLASSIFIED UNCLASSIFIED v EXECUTIVE SUMMARY A fuel’s cetane number is very important for the operation of modern diesel

  14. Investigation of dust storms entering Western Iran using remotely sensed data and synoptic analysis.

    Science.gov (United States)

    Boloorani, Ali D; Nabavi, Seyed O; Bahrami, Hosain A; Mirzapour, Fardin; Kavosi, Musa; Abasi, Esmail; Azizi, Rasoul

    2014-01-01

    One of the natural phenomena which have had considerable impacts on various regions of the world, including Iran, is "dust storm". In recent years, this phenomenon has taken on new dimensions in Iran and has changed from a local problem to a national issue. This study is an attempt to investigate the formation of the dust storms crossing the Western Iran. To find the sources of the dust storms entering Iran, first we examine three determined dust paths in the region and their temporal activities, using MODIS satellite images. Then, four regions were identified as dust sources through soil, land cover and wind data. Finally, atmospheric analyses are implemented to find synoptic patterns inducing dust storms. Source 1 has covered the region between the eastern banks of Euphrates and western banks of Tigris. Source 2 is in desert area of western and south-western Iraq. Finally source 3 is bounded in eastern and south-eastern deserts of Saudi Arabia called Rub-Al-Khali desert, or Empty Quarter. Moreover, south-eastern part of Iraq (source 4) was also determined as a secondary source which thickens the dust masses originating from the above mentioned sources. The study of synoptic circulations suggests that the dust storms originating from source 1 are formed due to the intense pressure gradient between the low-pressure system of Zagros and a high-pressure cell formed on Mediterranean Sea. The dust events in sources 2 and 3 are outcomes of the atmospheric circulations dominant in the cold period of the year in mid-latitudes.

  15. Support for cold neutron utilization

    International Nuclear Information System (INIS)

    Lee, Kye Hong; Han, Young Soo; Choi, Sungmin; Choi, Yong; Kwon, Hoon; Lee, Kwang Hee

    2012-06-01

    - Support for experiments by users of cold neutron scattering instrument - Short-term training of current and potential users of cold neutron scattering instrument for their effective use of the instrument - International collaboration for advanced utilization of cold neutron scattering instruments - Selection and training of qualified instrument scientists for vigorous research endeavors and outstanding achievements in experiments with cold neutron - Research on nano/bio materials using cold neutron scattering instruments - Bulk nano structure measurement using small angle neutron scattering and development of analysis technique

  16. CONSTRAINING DUST AND COLOR VARIATIONS OF HIGH-z SNe USING NICMOS ON THE HUBBLE SPACE TELESCOPE

    International Nuclear Information System (INIS)

    Nobili, S.; Amanullah, R.; Goobar, A.

    2009-01-01

    We present data from the Supernova Cosmology Project for five high redshift Type Ia supernovae (SNe Ia) that were obtained using the NICMOS infrared camera on the Hubble Space Telescope. We add two SNe from this sample to a rest-frame I-band Hubble diagram, doubling the number of high redshift supernovae on this diagram. This I-band Hubble diagram is consistent with a flat universe (Ω M , Ω Λ ) = (0.29, 0.71). A homogeneous distribution of large grain dust in the intergalactic medium (replenishing dust) is incompatible with the data and is excluded at the 5σ confidence level, if the SN host galaxy reddening is corrected assuming R V = 1.75. We use both optical and infrared observations to compare photometric properties of distant SNe Ia with those of nearby objects. We find generally good agreement with the expected color evolution for all SNe except the highest redshift SN in our sample (SN 1997ek at z = 0.863) which shows a peculiar color behavior. We also present spectra obtained from ground-based telescopes for type identification and determination of redshift.

  17. Cold neutron production and application

    International Nuclear Information System (INIS)

    Inoue, Kazuhiko; Watanabe, Noboru.

    1976-01-01

    The first part gives general introduction to cold neutrons, namely the definition and the role as a probe in basic science and technology. The second part reviews various methods of cold neutron production. Some physical characteristics required for cold moderators are presented, and a list summarizes a number of cold moderators and their reactor physics constants. The definition of flux gain factor and the measured values for liquid light- and heavy-hydrogen are also given. The cold neutron spectra in methane and liquid hydrogen measured by LINAC time-of-flight method are presented to show the advantage of solid methane. The cold neutron sources using experimental reactors or linear accelerators are explained along with the examples of existing facilities. Two Japanese programs, the one is the use of a high flux reactor and the other is the use of a LINAC, are also presented. The third part of this report reviews the application areas of cold neutrons. (Aoki, K.)

  18. Childhood to adolescence: dust and gas clearing in protoplanetary disks

    Science.gov (United States)

    Brown, Joanna Margaret

    Disks are ubiquitous around young stars. Over time, disks dissipate, revealing planets that formed hidden by their natal dust. Since direct detection of young planets at small orbital radii is currently impossible, other tracers of planet formation must be found. One sign of disk evolution, potentially linked to planet formation, is the opening of a gap or inner hole in the disk. In this thesis, I have identified and characterized several cold disks with large inner gaps but retaining massive primordial outer disks. While cold disks are not common, with ~5% of disks showing signs of inner gaps, they provide proof that at least some disks evolve from the inside-out. These large gaps are equivalent to dust clearing from inside the Earth's orbit to Neptune's orbit or even the inner Kuiper belt. Unlike more evolved systems like our own, the central star is often still accreting and a large outer disk remains. I identified four cold disks in Spitzer 5-40 μm spectra and modeled these disks using a 2-D radiative transfer code to determine the gap properties. Outer gap radii of 20-45 AU were derived. However, spectrophotometric identification is indirect and model-dependent. To validate this interpretation, I observed three disks with a submillimeter interferometer and obtained the first direct images of the central holes. The images agree well with the gap sizes derived from the spectrophotometry. One system, LkH&alpha 330, has a very steep outer gap edge which seems more consistent with gravitational perturbation rather than gradual processes, such as grain growth and settling. Roughly 70% of cold disks show CO v=1&rarr 0 gas emission from the inner 1 AU and therefore are unlikely to have evolved due to photoevaporation. The derived rotation temperatures are significantly lower for the cold disks than disks without gaps. Unresolved (sub)millimeter photometry shows that cold disks have steeper colors, indicating that they are optically thin at these wavelengths, unlike

  19. Study on treatment of dust by dismantling

    International Nuclear Information System (INIS)

    Torikai, K.; Suzuki, K.

    1987-01-01

    In dismantling of nuclear reactors, various kinds of treatment of dust generated by cutting or dismantling concrete structures of components of reactors are evaluated for safety, cost, and performance comparing the work in air with water. A method of dust treatment for work in air is discussed. The dry method has an easy operation in practice and a good performance in the equipment, but has problem on the prevention from radioactive contamination by diffusion of dust in air. For the purpose of advancing the strong points and eliminating the weak points in dry method, an improved venturi scrubber system is proposed for dismantling work as a dust collecting system. The system consists of dust absorbing pipe, dust collector, separator of dust and water and dust transfer equipment to a storage of waste. This system would be expected to have better performance and lower operating cost in decommissioning nuclear reactors, especially, the number of dust filters, for example, HEPA filters, will be considerably saved

  20. Four Interstellar Dust Candidates from the Stardust Interstellar Dust Collector

    Science.gov (United States)

    Westphal, A. J.; Allen, C.; Bajt, S.; Bechtel, H. A.; Borg, J.; Brenker, F.; Bridges, J.; Brownlee, D. E.; Burchell, M.; Burghammer, M.; hide

    2011-01-01

    In January 2006, the Stardust sample return capsule returned to Earth bearing the first solid samples from a primitive solar system body, Comet 81P/Wild2, and a collector dedicated to the capture and return of contemporary interstellar dust. Both collectors were approx. 0.1 sq m in area and were composed of aerogel tiles (85% of the collecting area) and aluminum foils. The Stardust Interstellar Dust Collector (SIDC) was exposed to the interstellar dust stream for a total exposure factor of 20 sq m/day. The Stardust Interstellar Preliminary Examination (ISPE) is a consortium-based project to characterize the collection using nondestructive techniques. The goals and restrictions of the ISPE are described . A summary of analytical techniques is described.

  1. DUST PRODUCTION AND PARTICLE ACCELERATION IN SUPERNOVA 1987A REVEALED WITH ALMA

    Energy Technology Data Exchange (ETDEWEB)

    Indebetouw, R.; Chevalier, R. [Department of Astronomy, University of Virginia, PO Box 400325, Charlottesville, VA 22904 (United States); Matsuura, M.; Barlow, M. J. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Dwek, E. [NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States); Zanardo, G. [International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, Crawley, WA 6009 (Australia); Baes, M. [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent (Belgium); Bouchet, P. [CEA-Saclay, F-91191 Gif-sur-Yvette (France); Burrows, D. N. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Clayton, G. C. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Fransson, C.; Lundqvist, P. [Department of Astronomy and the Oskar Klein Centre, Stockholm University, AlbaNova, SE-106 91 Stockholm (Sweden); Gaensler, B. [Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO) (Australia); Kirshner, R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Lakićević, M. [Lennard-Jones Laboratories, Keele University, ST5 5BG (United Kingdom); Long, K. S.; Meixner, M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Martí-Vidal, I. [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-43992 Onsala (Sweden); Marcaide, J. [Universidad de Valencia, C/Dr. Moliner 50, E-46100 Burjassot (Spain); McCray, R., E-mail: remy@virginia.edu [Department of Astrophysical and Planetary Sciences, University of Colorado at Boulder, UCB 391, Boulder, CO 80309 (United States); and others

    2014-02-10

    Supernova (SN) explosions are crucial engines driving the evolution of galaxies by shock heating gas, increasing the metallicity, creating dust, and accelerating energetic particles. In 2012 we used the Atacama Large Millimeter/Submillimeter Array to observe SN 1987A, one of the best-observed supernovae since the invention of the telescope. We present spatially resolved images at 450 μm, 870 μm, 1.4 mm, and 2.8 mm, an important transition wavelength range. Longer wavelength emission is dominated by synchrotron radiation from shock-accelerated particles, shorter wavelengths by emission from the largest mass of dust measured in a supernova remnant (>0.2 M {sub ☉}). For the first time we show unambiguously that this dust has formed in the inner ejecta (the cold remnants of the exploded star's core). The dust emission is concentrated at the center of the remnant, so the dust has not yet been affected by the shocks. If a significant fraction survives, and if SN 1987A is typical, supernovae are important cosmological dust producers.

  2. Star Formation in High Pressure, High Energy Density Environments: Laboratory Experiments of ISM Dust Analogs

    International Nuclear Information System (INIS)

    Breugel, W. van; Bajt, S.; Bradley, J.; Bringa, E.; Dai, Z.; Felter, T.; Graham, G.; Kucheyev, S.; Torres, D.; Tielens, A.; Baragiola, R.; Dukes, C.; Loeffler, M.

    2005-01-01

    Dust grains control the chemistry and cooling, and thus the gravitational collapse of interstellar clouds. Energetic particles, shocks and ionizing radiation can have a profound influence on the structure, lifetime and chemical reactivity of the dust, and therefore on the star formation efficiency. This would be especially important in forming galaxies, which exhibit powerful starburst (supernovae) and AGN (active galactic nucleus) activity. How dust properties are affected in such environments may be crucial for a proper understanding of galaxy formation and evolution. The authors present the results of experiments at LLNL which show that irradiation of the interstellar medium (ISM) dust analog forsterite (Mg 2 SiO 4 ) with swift heavy ions (10 MeV Xe) and a large electronic energy deposition amorphizes its crystalline structure, without changing its chemical composition. From the data they predict that silicate grains in the ISM, even in dense and cold giant molecular clouds, can be amorphized by heavy cosmic rays (CR's). This might provide an explanation for the observed absence of crystalline dust in the ISM clouds of the Milky Way galaxy. This processing of dust by CR's would be even more important in forming galaxies and galaxies with active black holes

  3. Cosmic dust investigations. Pt. 2

    International Nuclear Information System (INIS)

    Simpson, J.A.; Tuzzolino, A.J.

    1989-01-01

    A series of experiments have been completed using accelerator dust particles in the mass range ≅ 10 -9 -10 -6 g and velocity range ≅ 2-12 km/s to measure the velocity loss and degree of fragmentation for dust particles penetrating 6 and 28 μm thick polyvinylidene fluoride (PVDF) dust detectors. These measurements prove that even for a ratio of PVDF foil thickness to particle diameter as large as 0.6, the velocity loss and fragmentation is far less than expected from earlier reports in the literature. For 6 μm thick foils the velocity loss is ≤5%. These experiments are based on an extension of our earlier work which showed that two PVDF foils spaced a given distance apart could provide accurate time-of-flight (TOF) information due to the fast pulse rise time of PVDF detector response. We also report on our present state of development of PVDF position-sensing detectors which identify the x, y coordinates of particle impact, using detector and electronic pulse techniques adapted from our semiconductor position-sensing cosmic-ray detectors. Typical position errors of ≅ 1 mm are readily achieved. Finally, we have combined the above developments into a dust-particle telescope which accurately (≅ 1 0 angular accuracy) measures the trajectory of the incident particle as well as its mass and incident velocity, irrespective of whether it is a charged or neutral particle. We discuss how this practical dust telescope can be combined with dust capture cells for space flight and later recovery for laboratory determination of elemental and isotopic composition of captured dust. We also describe a simpler trajectory array based on discrete mosaics of thin detectors which would measure trajectories with a mean angular error of ≅ 4 0 . We discuss the application of these instruments for distinguishing between interplanetary dust of cometary and asteroidal origin, and for measurements on a space station, from near-Earth trapped dust of artificial origin. (orig.)

  4. Charged dust in saturn's magnetosphere

    International Nuclear Information System (INIS)

    Mendis, D.A.; Hill, J.R.; Houpis, H.L.F.

    1983-01-01

    Gravito-electrodynamic theory of charged dust grains is used to explain a variety of phenomena in those portions of the Saturnian ring system that are known to be dominated by fine (micron- and submicron-sized) dust, and in which collisional forces and Coulomb drag can be neglected. Among the phenomena discussed are the formation and evolution of the rotating near-radial spokes in the B-ring, the formation of waves in the F-ring, the cause of eccentricities of certain isolated ringlets, and the origin and morphology of the broad diffuse E-ring. Several novel processes predicted by the gravitoelectrodynamic theory, including 'magneto-gravitational capture' of exogenic dust by the magnetosphere, '1:1 magneto-gravitational orbital resonances' of charged dust with nearby satellites, and 'gyro-orbital resonances,' are used to explain individual observations. The effect of a ring current associated with this charged dust is also evaluated. Finally, the cosmogonic implications of the magneto-gravitational theory are briefly discussed. While several (although not all) of these processes have been discussed by one or more of the present authors elsewhere, the purpose of this paper is to synthesize all these processes within the framework of gravito-electrodynamics, and also to show its range of applicability within Saturn's ring system

  5. Spring Dust Storm Smothers Beijing

    Science.gov (United States)

    2002-01-01

    A few days earlier than usual, a large, dense plume of dust blew southward and eastward from the desert plains of Mongolia-quite smothering to the residents of Beijing. Citizens of northeastern China call this annual event the 'shachenbao,' or 'dust cloud tempest.' However, the tempest normally occurs during the spring time. The dust storm hit Beijing on Friday night, March 15, and began coating everything with a fine, pale brown layer of grit. The region is quite dry; a problem some believe has been exacerbated by decades of deforestation. According to Chinese government estimates, roughly 1 million tons of desert dust and sand blow into Beijing each year. This true-color image was made using two adjacent swaths (click to see the full image) of data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), flying aboard the OrbView-2 satellite, on March 17, 2002. The massive dust storm (brownish pixels) can easily be distinguished from clouds (bright white pixels) as it blows across northern Japan and eastward toward the open Pacific Ocean. The black regions are gaps between SeaWiFS' viewing swaths and represent areas where no data were collected. Image courtesy the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  6. Physical properties of five grain dust types.

    Science.gov (United States)

    Parnell, C B; Jones, D D; Rutherford, R D; Goforth, K J

    1986-01-01

    Physical properties of grain dust derived from five grain types (soybean, rice, corn, wheat, and sorghum) were measured and reported. The grain dusts were obtained from dust collection systems of terminal grain handling facilities and were assumed to be representative of grain dust generated during the handling process. The physical properties reported were as follows: particle size distributions and surface area measurements using a Coulter Counter Model TAII; percent dust fractions less than 100 micron of whole dust; bulk density; particle density; and ash content. PMID:3709482

  7. Gone with the heat: a fundamental constraint on the imaging of dust and molecular gas in the early Universe.

    Science.gov (United States)

    Zhang, Zhi-Yu; Papadopoulos, Padelis P; Ivison, R J; Galametz, Maud; Smith, M W L; Xilouris, Emmanuel M

    2016-06-01

    Images of dust continuum and carbon monoxide (CO) line emission are powerful tools for deducing structural characteristics of galaxies, such as disc sizes, H2 gas velocity fields and enclosed H2 and dynamical masses. We report on a fundamental constraint set by the cosmic microwave background (CMB) on the observed structural and dynamical characteristics of galaxies, as deduced from dust continuum and CO-line imaging at high redshifts. As the CMB temperature rises in the distant Universe, the ensuing thermal equilibrium between the CMB and the cold dust and H2 gas progressively erases all spatial and spectral contrasts between their brightness distributions and the CMB. For high-redshift galaxies, this strongly biases the recoverable H2 gas and dust mass distributions, scale lengths, gas velocity fields and dynamical mass estimates. This limitation is unique to millimetre/submillimetre wavelengths and unlike its known effect on the global dust continuum and molecular line emission of galaxies, it cannot be addressed simply. We nevertheless identify a unique signature of CMB-affected continuum brightness distributions, namely an increasing rather than diminishing contrast between such brightness distributions and the CMB when the cold dust in distant galaxies is imaged at frequencies beyond the Raleigh-Jeans limit. For the molecular gas tracers, the same effect makes the atomic carbon lines maintain a larger contrast than the CO lines against the CMB.

  8. Contribution to the study of the intergalactic medium physical properties through infrared, sub-millimetric and millimetric observations

    International Nuclear Information System (INIS)

    Pointecouteau, Etienne

    1999-01-01

    This work concerns the largest self-gravitating structures of the Universe, clusters of galaxies. Due to its thermodynamical conditions, their intracluster atmosphere is completely ionised. This gas is observed at X-ray wavelengths through its free-free emission, and at submillimeter-millimeter wavelengths through the Sunyaev-Zel'dovich (SZ) effect. This effect is due to the inverse Compton scattering of the cosmic microwave background photons by the hot intracluster electrons. First, taking into account the weakly relativistic behaviour of the electrons, we performed exact calculations of the SZ spectrum. The resulting spectra show the strong dependency of the SZ effect spectral shape with respect to the gas temperature. Making use of this work, we analysed the millimeter data from the DiaBolo spectrophotometer in the direction of a massive and distant cluster, RXJ1347-1145. With a high angular resolution, we have mapped the centre and the extended emission of this cluster, leading to the detection of the strongest SZ effect measured to date. The comparison with the X-ray data shows some very exciting and puzzling differences. In the third part, we present for the first time the spectrum of a galaxy cluster, A2163, from far infrared (90 μm) to millimeter (2.1 mm) wavelengths. The constraints set by the FIR measurements on the residual dust emission, allowed us put strong constraints on the SZ parameters. Finally, we propose a new method which allows to extract the intracluster gas temperature from a set of SZ data. We have quantified the reliability of this method in case of observations obtained from the Planck surveyor and the Herschel space missions. (author) [fr

  9. Cold fusion in perspective

    International Nuclear Information System (INIS)

    Sanford, L.

    1989-01-01

    Since early April a great deal of excitement has been created over the Fleischmann/Pons cold fusion experiment, which if it performs as advertised, could turn out to be mankind's best hope of heading off the energy crisis scheduled for early in the next century. Dozens of groups around the world are now attempting to duplicate the experiment to see if Fleischmann and Pons' discovery is an experimental mistake, an unknown electrochemical effect or a new kind of fusion reaction. This article puts the experiment into the perspective of today and looks at how it might affect the energy scene tomorrow if it should turn out to be commercially exploitable. (author)

  10. Glass Frit Clumping And Dusting

    International Nuclear Information System (INIS)

    Steimke, J. L.

    2013-01-01

    DWPF mixes a slurry of glass frit (Frit 418) and dilute (1.5 wt%) formic acid solution with high level waste in the Slurry Mix Evaporator (SME). There would be advantages to introducing the frit in a non-slurry form to minimize water addition to the SME, however, adding completely dry frit has the potential to generate dust which could clog filters or condensers. Prior testing with another type of frit, Frit 320, and using a minimal amount of water reduced dust generation, however, the formation of hard clumps was observed. To examine options and behavior, a TTQAP [McCabe and Stone, 2013] was written to initiate tests that would address these concerns. Tests were conducted with four types of glass frit; Frit 320, DWPF Frit 418, Bekeson Frit 418 and Multi-Aspirator Frit 418. The last two frits are chemically identical to DWPF Frit 418 but smaller particles were removed by the respective vendors. Test results on Frit Clumping and Dusting are provided in this report. This report addresses the following seven questions. Short answers are provided below with more detailed answers to follow. 1. Will the addition of a small amount of water, 1.5 wt%, to dry DWPF Frit 418 greatly reduce the dust generation during handling at DWPF? a. Yes, a small scale test showed that adding a little water to the frit greatly reduced dust generation during handling. 2. Will the addition of small amounts of water to the frit cause clumping that will impair frit handling at DWPF? a. No, not with Frit 418. Although clumps were observed to form when 1.5 wt% water was mixed with DWPF Frit 418, then compressed and air-dried overnight, the clumps were easily crushed and did not form the hardened material noted when Frit 320 was tested. 3. What is the measured size distribution of dust generated when dry frit is handled? (This affects the feasibility and choice of processing equipment for removing the dust generating fraction of the frit before it is added to the SME.) a. The size distribution for

  11. Glass Frit Clumping And Dusting

    Energy Technology Data Exchange (ETDEWEB)

    Steimke, J. L.

    2013-09-26

    DWPF mixes a slurry of glass frit (Frit 418) and dilute (1.5 wt%) formic acid solution with high level waste in the Slurry Mix Evaporator (SME). There would be advantages to introducing the frit in a non-slurry form to minimize water addition to the SME, however, adding completely dry frit has the potential to generate dust which could clog filters or condensers. Prior testing with another type of frit, Frit 320, and using a minimal amount of water reduced dust generation, however, the formation of hard clumps was observed. To examine options and behavior, a TTQAP [McCabe and Stone, 2013] was written to initiate tests that would address these concerns. Tests were conducted with four types of glass frit; Frit 320, DWPF Frit 418, Bekeson Frit 418 and Multi-Aspirator Frit 418. The last two frits are chemically identical to DWPF Frit 418 but smaller particles were removed by the respective vendors. Test results on Frit Clumping and Dusting are provided in this report. This report addresses the following seven questions. Short answers are provided below with more detailed answers to follow. 1. Will the addition of a small amount of water, 1.5 wt%, to dry DWPF Frit 418 greatly reduce the dust generation during handling at DWPF? a. Yes, a small scale test showed that adding a little water to the frit greatly reduced dust generation during handling. 2. Will the addition of small amounts of water to the frit cause clumping that will impair frit handling at DWPF? a. No, not with Frit 418. Although clumps were observed to form when 1.5 wt% water was mixed with DWPF Frit 418, then compressed and air-dried overnight, the clumps were easily crushed and did not form the hardened material noted when Frit 320 was tested. 3. What is the measured size distribution of dust generated when dry frit is handled? (This affects the feasibility and choice of processing equipment for removing the dust generating fraction of the frit before it is added to the SME.) a. The size distribution for

  12. Dust deposit in recirculation regions

    International Nuclear Information System (INIS)

    Griemert, R.

    1985-03-01

    The present report shows investigations, which have been carried out in a closed duct at forward and backward facing steps. Distribution of fluid velocity and fluid fluctuations in and normal to main flow direction as well as the distribution of Reynolds shear stress have been measured. The mass transfer downstream of a backward facing step has been investigated as well. By using graphite-, copper-, tin- and rubber dust, conditions of deposition have been defined experimentally. A serie of photos shows the filling of a recirculation region downstream of a backward facing step with graphite dust. The present investigations allow to avoid deposition of dust in recirculation regions by selecting the fluid numbers in an appropriate way. (orig.) [de

  13. Dust Storm Hits Canary Islands

    Science.gov (United States)

    2002-01-01

    A thick pall of sand and dust blew out from the Sahara Desert over the Atlantic Ocean yesterday (January 6, 2002), engulfing the Canary Islands in what has become one of the worst sand storms ever recorded there. In this scene, notice how the dust appears particularly thick in the downwind wake of Tenerife, the largest of the Canary Islands. Perhaps the turbulence generated by the air currents flowing past the island's volcanic peaks is churning the dust back up into the atmosphere, rather than allowing it to settle toward the surface. This true-color image was captured by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA's Terra satellite, on January 7, 2002. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

  14. Mechanisms of metal dusting corrosion

    DEFF Research Database (Denmark)

    Hummelshøj, Thomas Strabo

    In this thesis the early stages of metal dusting corrosion is addressed; the development of carbon expanded austenite, C, and the decomposition hereof into carbides. Later stages of metal dusting corrosion are explored by a systematic study of stainless steel foils exposed to metal dusting...... deformed stainless steel flakes is transformed to expanded martensite/austenite during low-temperature carburization. Various experimental procedures to experimentally determine the concentration dependent diffusion coefficient of carbon in expanded austenite are evaluated. The most promising procedure...... powders and flakes. The nature of the decomposition products, carbides of the form M23C6 and M7C3, were evaluated by X-ray diffraction, light optical microscopy, scanning electron microscopy and thermodynamic modelling. The decomposition was found to be dependent on several parameters such as thermal...

  15. The distribution of interstellar dust

    International Nuclear Information System (INIS)

    Clocchiatti, A.; Marraco, H.G.

    1986-01-01

    We propose the interstellar matter structural function as a tool to derive the features of the interstellar dust distribution. We study that function resolving some ideal dust distribution models. Later we describe the method used to find a reliable computing algorithm for the observational case. Finally, we describe the steps to build a model for the interstellar matter composed by spherically symmetrical clouds. The density distribution for each of these clouds is D(r) = D 0 .esup(-r/r 0 ) 2 . The preliminary results obtained are summarised. (author)

  16. A spectroscopic study of absorption and emission features of interstellar dust components

    International Nuclear Information System (INIS)

    Zwet, G.P. van der.

    1986-01-01

    The spectroscopic properties of silicate interstellar dust grains are the subject of this thesis. The process of accretion and photolysis is simulated in the laboratory by condensing mixtures of gases onto a cold substrate (T ∼ 12 K) in a vacuum chamber and photolyzing these mixtures with a vacuum ultraviolet source. Alternatively, the gas mixtures may be passed through a microwave discharge first, before deposition. The spectroscopic properties of the ices are investigated using ultraviolet, visible and infrared spectroscopy. (Auth.)

  17. Modeling the Transport and Radiative Forcing of Taklimakan Dust over the Tibetan Plateau: A case study in the summer of 2006

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Siyu; Huang, J.; Zhao, Chun; Qian, Yun; Leung, Lai-Yung R.; Yang, Ben

    2013-01-30

    The Weather Research and Forecasting model with chemistry (WRF-Chem) is used to investigate an intense dust storm event during 26 to 30 July 2006 that originated over the Taklimakan Desert (TD) and transported to the northern slope of Tibetan Plateau (TP). The dust storm is initiated by the approach of a strong cold frontal system over the TD. In summer, the meridional transport of TD dust to the TP is favored by the thermal effect of the TP and the weakening of the East Asian westerly winds. During this dust storm, the transport of TD dust over the TP is further enhanced by the passage of the cold front. As a result, TD dust breaks through the planetary boundary layer and extends to the upper troposphere over the northern TP. TD dust flux arrived at the TP with a value of 6.6 Gg/day in this 5 day event but decays quickly during the southward migration over the TP due to dry deposition. The simulations show that TD dust cools the atmosphere near the surface and heats the atmosphere above with a maximum heating rate of 0.11 K day-1 at ~7 km over the TP. The event-averaged net radiative forcings of TD dust over the TP are -3.97, 1.61, and -5.58 Wm-2 at the top of the atmosphere (TOA), in the atmosphere, and at the surface, respectively. The promising performance of WRF-Chem in simulating dust and its radiative forcing provides confidence for use in further investigation of climatic impact of TD dust over the TP.

  18. Extinction Mapping and Dust-to-Gas Ratios of Nearby Galaxies using LEGUS

    Science.gov (United States)

    Kahre, Lauren; Walterbos, Rene; Kim, Hwihyun; Thilker, David; Lee, Janice; LEGUS Team

    2018-01-01

    Dust is commonly used as a tracer for cold dense gas, either through IR and NIR emission maps or through extinction mapping, and dust abundance and gas metallicity are critical constraints for chemical and galaxy evolution models. Extinction mapping has been used to trace dust column densities in the Milky Way, the Magellanic Clouds, and M31. The maps for M31 use IR and NIR photometry of red giant branch stars, which is more difficult to obtain for more distant galaxies. Work by Kahre et al. (in prep) uses the extinctions derived for individual massive stars using the isochrone-matching method described by Kim et al. (2012) to generate extinction maps for these more distant galaxies.Isochrones of massive stars lie in the same location on a color-color diagram with little dependence on metallicity and luminosity class, so the extinction can be directly derived from the observed photometry. We generate extinction maps using photometry of massive stars from the Hubble Space Telescope for several of the nearly 50 galaxies observed by the Legacy Extragalactic Ultraviolet Survey (LEGUS). The derived extinction maps will allow us to correct ground-based and HST Halpha maps for extinction, and will be used to constrain changes in the dust-to-gas ratio across the galaxy sample and in different star formation, metallicity and morphological environments. Previous studies have found links between galaxy metallicity and the dust-to-gas mass ratio. We present a study of LEGUS galaxies spanning a range of distances, metallicities, and galaxy morphologies, expanding on our previous study of metal-poor dwarfs Holmberg I and II and giant spirals NGC 6503 and NGC 628. We see clear evidence for changes in the dust-to-gas mass ratio with changing metallicity. We also examine changes in the dust-to-gas mass ratio with galactocentric radius. Ultimately, we will provide constraints on the dust-to-gas mass ratio across a wide range of galaxy environments.

  19. Electrostatic Dust Detector with Improved Sensitivity

    International Nuclear Information System (INIS)

    Boyle, D.P.; Skinner, C.H.; Roquemore, A.L.

    2008-01-01

    Methods to measure the inventory of dust particles and to remove dust if it approaches safety limits will be required in next-step tokamaks such as ITER. An electrostatic dust detector, based on a fine grid of interlocking circuit traces, biased to 30 or 50 V, has been developed for the detection of dust on remote surfaces in air and vacuum environments. Gaining operational experience of dust detection on surfaces in tokamaks is important, however the level of dust generated in contemporary short-pulse tokamaks is comparatively low and high sensitivity is necessary to measure dust on a shot-by-shot basis. We report on modifications in the detection electronics that have increased the sensitivity of the electrostatic dust detector by a factor of up to 120, - a level suitable for measurements on contemporary tokamaks.

  20. Infrared Observations of Cometary Dust and Nuclei

    Science.gov (United States)

    Lisse, Carey

    2004-01-01

    This bibliography lists citations for publications published under the grant. Subjects of the publications include cometary dust, instellar and interplanetary dust, comet nuclei and comae, Comet Hale-Bopp, infrared observations of comets, mass loss, and comet break-up.

  1. The global distribution of mineral dust

    International Nuclear Information System (INIS)

    Tegen, I; Schepanski, K

    2009-01-01

    Dust aerosol particles produced by wind erosion in arid and semi arid regions affect climate and air quality, but the magnitude of these effects is largely unquantified. The major dust source regions include the Sahara, the Arabian and Asian deserts; global annual dust emissions are currently estimated to range between 1000 and 3000 Mt/yr. Dust aerosol can be transported over long distances of thousands of kilometers, e.g. from source regions in the Saharan desert over the North Atlantic, or from the Asian deserts towards the Pacific Ocean. The atmospheric dust load varies considerably on different timescales. While dust aerosol distribution and dust effects are important on global scales, they strongly depend on dust emissions that are controlled on small spatial and temporal scales.

  2. Stochastic histories of dust grains in the interstellar medium

    International Nuclear Information System (INIS)

    Liffman, K.; Clayton, D.D.

    1989-01-01

    The purpose is to study an evolving system of refractory dust grains within the Interstellar Medium (ISM). This is done via a combination of Monte Carlo processes and a system of partial differential equations, where refractory dust grains formed within supernova remnants and ejecta from high mass loss stars are subjected to the processes of sputtering and collisional fragmentation in the diffuse media and accretion within the cold molecular clouds. In order to record chemical detail, the authors take each new particle to consist of a superrefractory core plus a more massive refractory mantle. The particles are allowed to transfer to and fro between the different phases of the interstellar medium (ISM) - on a time scale of 10(exp 8) years - until either the particles are destroyed or the program finishes at a Galaxy time of 6x10(exp 9) years. The resulting chemical and size spectrum(s) are then applied to various astrophysical problems with the following results. For an ISM which has no collisional fragmentation of the dust grains, roughly 10 percent by mass of the most refractory material survives the rigors of the ISM intact, which leaves open the possibility that fossilized isotopically anomalous material may have been present within the primordial solar nebula. Stuctured or layered refractory dust grains within the model cannot explain the observed interstellar depletions of refractory material. Fragmentation due to grain-grain collisions in the diffuse phase plus the accretion of material in the molecular cloud phase can under certain circumstances cause a bimodal distribution in grain size

  3. Exact solutions for rotating charged dust

    International Nuclear Information System (INIS)

    Islam, J.N.

    1984-01-01

    Earlier work by the author on rotating charged dust is summarized. An incomplete class of exact solutions for differentially rotating charged dust in Newton-Maxwell theory for the equal mass and charge case that was found earlier is completed. A new global exact solution for cylindrically symmetric differentially rotating charged dust in Newton-Maxwell theory is presented. Lastly, a new exact solution for cylindrically symmetric rigidly rotating charged dust in general relativity is given. (author)

  4. Studies of dust shells around stars

    International Nuclear Information System (INIS)

    Bedijn, P.J.

    1977-01-01

    This thesis deals with some aspects of circumstellar dust shells. This dust shell, emitting infrared radiation, is described by way of its absorptive and emissive properties as well as by the transfer of radiation through the dust shell itself. Model calculations are compared to experimental results and agree reasonably well. The author also discusses the dynamics of the extended shells of gas and dust around newly formed stars

  5. Impacts of interactive dust and its direct radiative forcing on interannual variations of temperature and precipitation in winter over East Asia: Impacts of Dust on IAVs of Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Lou, Sijia [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Russell, Lynn M. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Yang, Yang [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Liu, Ying [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Singh, Balwinder [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Ghan, Steven J. [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA

    2017-08-24

    We used 150-year pre-industrial simulations of the Community Earth System Model (CESM) to quantify the impacts of interactively-modeled dust emissions on the interannual variations of temperature and precipitation over East Asia during the East Asian Winter Monsoon (EAWM) season. The simulated December-January-February dust column burden and dust optical depth are lower over northern China in the strongest EAWM years than those of the weakest years, with regional mean values lower by 38.3% and 37.2%, respectively. The decrease in dust over the dust source regions (the Taklamakan and Gobi Deserts) and the downwind region (such as the North China Plain) leads to an increase in direct radiative forcing (RF) both at the surface and top of atmosphere by up to 1.5 and 0.75 W m-2, respectively. The effects of EAWM-related variations in surface winds, precipitation and their effects on dust emissions and wet removal contribute about 67% to the total dust-induced variations of direct RF at the surface and partly offset the cooling that occurs with the EAWM strengthening by heating the surface. The variations of surface air temperature induced by the changes in wind and dust emissions increase by 0.4-0.6 K over eastern coastal China, northeastern China, and Japan, which weakens the impact of EAWM on surface air temperature by 3–18% in these regions. The warming results from the combined effects of changes in direct RF and easterly wind anomalies that bring warm air from the ocean to these regions. Moreover, the feedback of the changes in wind on dust emissions weakens the variations of the sea level pressure gradient on the Siberian High while enhancing the Maritime Continent Low. Therefore, cold air is prevented from being transported from Siberia, Kazakhstan, western and central China to the western Pacific Ocean and decreases surface air temperature by 0.6 K and 2 K over central China and the Tibetan Plateau, respectively. Over eastern coastal China, the variations of

  6. Radio frequency discharge with dust particles

    NARCIS (Netherlands)

    Chutov, Y. I.; W. J. Goedheer,; Kravchenko, O. Y.; Zuz, V. M.; Yan, M.; Martins, R.; Ferreira, I.; Fortunato, E.; Kroesen, G.

    2000-01-01

    A 1D PIC/MCC method has been developed for computer simulations of low-pressure RF discharges with dust particles using the method for dust-free discharges. A RF discharge in argon with dust particles distributed uniformly in the interelectrode gap is simulated at parameters providing a possibility

  7. Thirteen years of Aeolian dust dynamics in a desert region (Negev desert, Israel): analysis of horizontal and vertical dust flux, vertical dust distribution and dust grain size

    NARCIS (Netherlands)

    Offer, Z.Y.; Goossens, D.

    2004-01-01

    At Sede Boqer (northern Negev desert, Israel), aeolian dust dynamics have been measured during the period 1988–2000. This study focuses on temporal records of the vertical and horizontal dust flux, the vertical distribution of the dust particles in the atmosphere, and the grain size of the

  8. Dust Measurements Onboard the Deep Space Gateway

    Science.gov (United States)

    Horanyi, M.; Kempf, S.; Malaspina, D.; Poppe, A.; Srama, R.; Sternovsky, Z.; Szalay, J.

    2018-02-01

    A dust instrument onboard the Deep Space Gateway will revolutionize our understanding of the dust environment at 1 AU, help our understanding of the evolution of the solar system, and improve dust hazard models for the safety of crewed and robotic missions.

  9. Properties of interstellar dust in reflection nebulae

    International Nuclear Information System (INIS)

    Sellgren, K.

    1988-01-01

    Observations of interstellar dust in reflection nebulae are the closest analog in the interstellar medium to studies of cometary dust in our solar system. The presence of a bright star near the reflection nebula dust provides the opportunity to study both the reflection and emission characteristics of interstellar dust. At 0.1 to 1 micrometer, the reflection nebula emission is due to starlight scattered by dust. The albedo and scattering phase function of the dust is determined from observations of the scattered light. At 50 to 200 micrometers, thermal emission from the dust in equilibrium with the stellar radiation field is observed. The derived dust temperature determines the relative values of the absorption coefficient of the dust at wavelengths where the stellar energy is absorbed and at far infrared wavelengths where the absorbed energy is reradiated. These emission mechanisms directly relate to those seen in the near and mid infrared spectra of comets. In a reflection nebula the dust is observed at much larger distances from the star than in our solar system, so that the equilibrium dust temperature is 50 K rather than 300 K. Thus, in reflection nebulae, thermal emission from dust is emitted at 50 to 200 micrometer

  10. House dust extracts contain potent immunological adjuvants

    NARCIS (Netherlands)

    Beukelman, C.J.; Dijk, H. van; Aerts, P.C.; Rademaker, P.M.; Berrens, L.; Willers, J.M.N.

    1987-01-01

    A crude aqueous extract of house dust and two house dust subfractions were tested for adjuvant activity in a sensitivity assay performed in mice. Evidence is presented that house dust contains at least two potent immunological adjuvants. One of these, present in both subfractions, was probably

  11. Observed spectral features of dust

    International Nuclear Information System (INIS)

    Willner, S.P.

    1984-01-01

    The author concentrates on the observed properties of dust spectral features. Identifications, based on laboratory data, are given whenever plausible ones exist. There are a very large number of papers in the literature of even such a young field as infrared spectroscopy, and therefore the author refers only to the most recent paper on a topic or to another review. (Auth.)

  12. Meteors, meteorites and cosmic dust

    International Nuclear Information System (INIS)

    Lebedinets, V.N.

    1987-01-01

    The problem of meteorite origin and meteorite composition is discussed. Nowadays, most scientists suppose that the giant Oort cloud consisting of ice comet nuclei is the sourse of the meteor matter. A principle unity of the matter of meteorites falling to the Earth and cosmic dust is noted as well as that of meteorite bodies evaporating in the atmosphere and bearing meteors and bodies

  13. Occupational diseases of dust etiology

    International Nuclear Information System (INIS)

    Sokolik, L.I.; Shkondin, A.N.

    1981-01-01

    Detailed etiologic and clinico-roentgenological characteristics of pneumoconiosis, as widely spread occupational disease caused by different kinds of dust, are given. The course of pneumoconiosis is discussed depending on working conditions of patients after the disease had been ascertained, as well as its complications, taking into account roentgeno-morphological types of fibrosis and the stages of the disease [ru

  14. 75 FR 32142 - Combustible Dust

    Science.gov (United States)

    2010-06-07

    .... Contact Mat Chibbaro, P.E., Fire Protection Engineer, Office of Safety Systems, OSHA Directorate of..., and metals (such as aluminum and magnesium). Industries that may have combustible dust hazards include..., chemical manufacturing, textile manufacturing, furniture manufacturing, metal processing, fabricated metal...

  15. Cold moderator scattering kernels

    International Nuclear Information System (INIS)

    MacFarlane, R.E.

    1989-01-01

    New thermal-scattering-law files in ENDF format have been developed for solid methane, liquid methane liquid ortho- and para-hydrogen, and liquid ortho- and para-deuterium using up-to-date models that include such effects as incoherent elastic scattering in the solid, diffusion and hindered vibration and rotations in the liquids, and spin correlations for the hydrogen and deuterium. These files were generated with the new LEAPR module of the NJOY Nuclear Data Processing System. Other modules of this system were used to produce cross sections for these moderators in the correct format for the continuous-energy Monte Carlo code (MCNP) being used for cold-moderator-design calculations at the Los Alamos Neutron Scattering Center (LANSCE). 20 refs., 14 figs

  16. Experiments in cold fusion

    International Nuclear Information System (INIS)

    Palmer, E.P.

    1986-01-01

    The work of Steve Jones and others in muon-catalyzed cold fusion of deuterium and hydrogen suggests the possibility of such fusion catalyzed by ions, or combinations of atoms, or more-or-less free electrons in solid and liquid materials. A hint that this might occur naturally comes from the heat generated in volcanic action in subduction zones on the earth. It is questionable whether the potential energy of material raised to the height of a midocean ridge and falling to the depth of an ocean trench can produce the geothermal effects seen in the volcanoes of subduction zones. If the ridge, the trench, the plates, and the asthenosphere are merely visible effects of deeper density-gradient driven circulations, it is still uncertain that observed energy-concentration effects fit the models

  17. Trapping Dust to Form Planets

    Science.gov (United States)

    Kohler, Susanna

    2017-10-01

    Growing a planet from a dust grain is hard work! A new study explores how vortices in protoplanetary disks can assist this process.When Dust Growth FailsTop: ALMA image of the protoplanetary disk of V1247 Orionis, with different emission components labeled. Bottom: Synthetic image constructed from the best-fit model. [Kraus et al. 2017]Gradual accretion onto a seed particle seems like a reasonable way to grow a planet from a grain of dust; after all, planetary embryos orbit within dusty protoplanetary disks, which provides them with plenty of fuel to accrete so they can grow. Theres a challenge to this picture, though: the radial drift problem.The radial drift problem acknowledges that, as growing dust grains orbit within the disk, the drag force on them continues to grow as well. For large enough dust grains perhaps around 1 millimeter the drag force will cause the grains orbits to decay, and the particles drift into the star before they are able to grow into planetesimals and planets.A Close-Up Look with ALMASo how do we overcome the radial drift problem in order to form planets? A commonly proposed mechanism is dust trapping, in which long-lived vortices in the disk trap the dust particles, preventing them from falling inwards. This allows the particles to persist for millions of years long enough to grow beyond the radial drift barrier.Observationally, these dust-trapping vortices should have signatures: we would expect to see, at millimeter wavelengths, specific bright, asymmetric structures where the trapping occurs in protoplanetary disks. Such disk structures have been difficult to spot with past instrumentation, but the Atacama Large Millimeter/submillimeter Array (ALMA) has made some new observations of the disk V1247 Orionis that might be just what were looking for.Schematic of the authors model for the disk of V1247 Orionis. [Kraus et al. 2017]Trapped in a Vortex?ALMAs observations of V1247 Orionis are reported by a team of scientists led by Stefan

  18. Scientists Detect Radio Emission from Rapidly Rotating Cosmic Dust Grains

    Science.gov (United States)

    2001-11-01

    current radio astronomy research, and the idea was largely forgotten. In the 1990s this perception began to change when scientists and engineers designed sensitive instruments to detect the faint afterglow of the Big Bang, which is seen in the Universe as the Cosmic Microwave Background Radiation. While making detailed maps of this faint and cold radiation, scientists also detected signals at approximately the same wavelength and intensity as the background radiation, but clearly emanating from within the Milky Way's galactic plane. The researchers expected to detect some emission from the Milky Way, but what they encountered was much brighter than anticipated. This discovery caused some concern among researchers because of the need to have a very clear "window" on the Universe to study the background radiation in great detail. If there were a source of radio emission in our own galactic "back yard," then studies of the microwave background radiation would need to recognize these emissions and correct for them. "We want to be clear, however, that nothing we have found invalidates the current interpretation of the Cosmic Microwave Background Radiation," assured Finkbeiner. "Nobody has done anything wrong in neglecting these signals - so far." Scientists considered several plausible mechanisms for this anomalous emission, but these theories failed to explain the observed spatial distribution of this emission across the sky. This predicament prompted theorists to rethink the spinning dust idea, leading to a 1998 model by Bruce Draine (Princeton University) and Alex Lazarian (University of Wisconsin), which proposed rotational dust-grain emission as an important mechanism. Draine and Lazarian assumed that small dust grains, perhaps having no more than 100 atoms each, would populate many interstellar dust clouds in the Galaxy. Each grain would have a small electric dipole and would therefore react to the charged ions that race through the clouds at tremendous speeds. As an ion

  19. Respiratory Toxicity of Lunar Highland Dust

    Science.gov (United States)

    James, John T.; Lam, Chiu-wing; Wallace, William T.

    2009-01-01

    Lunar dust exposures occurred during the Apollo missions while the crew was on the lunar surface and especially when microgravity conditions were attained during rendezvous in lunar orbit. Crews reported that the dust was irritating to the eyes and in some cases respiratory symptoms were elicited. NASA s vision for lunar exploration includes stays of 6 months on the lunar surface hence the health effects of periodic exposure to lunar dust need to be assessed. NASA has performed this assessment with a series of in vitro and in vivo tests on authentic lunar dust. Our approach is to "calibrate" the intrinsic toxicity of lunar dust by comparison to a nontoxic dust (TiO2) and a highly toxic dust (quartz) using intratrachael instillation of the dusts in mice. A battery of indices of toxicity is assessed at various time points after the instillations. Cultures of selected cells are exposed to test dusts to assess the adverse effects on the cells. Finally, chemical systems are used to assess the nature of the reactivity of various dusts and to determine the persistence of reactivity under various environmental conditions that are relevant to a space habitat. Similar systems are used to assess the dissolution of the dust. From these studies we will be able to set a defensible inhalation exposure standard for aged dust and predict whether we need a separate standard for reactive dust. Presently-available data suggest that aged lunar highland dust is slightly toxic, that it can adversely affect cultured cells, and that the surface reactivity induced by grinding the dust persists for a few hours after activation.

  20. Design and development of a dust dispersion chamber to quantify the dispersibility of rock dust.

    Science.gov (United States)

    Perera, Inoka E; Sapko, Michael J; Harris, Marcia L; Zlochower, Isaac A; Weiss, Eric S

    2016-01-01

    Dispersible rock dust must be applied to the surfaces of entries in underground coal mines in order to inert the coal dust entrained or made airborne during an explosion and prevent propagating explosions. 30 CFR. 75.2 states that "… [rock dust particles] when wetted and dried will not cohere to form a cake which will not be dispersed into separate particles by a light blast of air …" However, a proper definition or quantification of "light blast of air" is not provided. The National Institute for Occupational Safety and Health (NIOSH) has, consequently, designed a dust dispersion chamber to conduct quantitative laboratory-scale dispersibility experiments as a screening tool for candidate rock dusts. A reproducible pulse of air is injected into the chamber and across a shallow tray of rock dust. The dust dispersed and carried downwind is monitored. The mass loss of the dust tray and the airborne dust measurements determine the relative dispersibility of the dust with respect to a Reference rock dust. This report describes the design and the methodology to evaluate the relative dispersibility of rock dusts with and without anti-caking agents. Further, the results of this study indicate that the dispersibility of rock dusts varies with particle size, type of anti-caking agent used, and with the untapped bulk density. Untreated rock dusts, when wetted and dried forming a cake that was much less dispersible than the reference rock dust used in supporting the 80% total incombustible content rule.

  1. Monitoring the vaccine cold chain.

    OpenAIRE

    Cheriyan, E

    1993-01-01

    Maintaining the vaccine cold chain is an essential part of a successful immunisation programme. A continuous electronic temperature monitor helped to identify breaks in the cold chain in the community and the study led to the issue of proper guidelines and replacement of faulty equipment.

  2. Cold gelation of globular proteins

    NARCIS (Netherlands)

    Alting, A.C.

    2003-01-01

    Keywords : globular proteins, whey protein, ovalbumin, cold gelation, disulfide bonds, texture, gel hardnessProtein gelation in food products is important to obtain desirable sensory and textural properties. Cold gelation is a novel method to produce protein-based gels. It is a two step process in

  3. Initial heating in cold cars

    NARCIS (Netherlands)

    Daanen, H.A.M.; Teunissen, L.P.J.; Hoogh, I.M. de

    2012-01-01

    During the initial minutes after entering a cold car, people feel uncomfortably cold. Six different warming systems were investigated in a small car in order to find out how to improve the feeling of comfort using 16 volunteers. The methods were: no additional warming next to a standard heating

  4. The status of cold fusion

    Science.gov (United States)

    Storms, E.

    This report attempts to update the status of the phenomenon of cold fusion. The new field is continuing to grow as a variety of nuclear reactions are discovered to occur in a variety of chemical environments at modest temperatures. However, it must be cautioned that most scientists consider cold fusion as something akin to UFO's, ESP, and numerology.

  5. Facts about the Common Cold

    Science.gov (United States)

    ... different viruses. Rhinovirus is the most common cause, accounting for 10 to 40 percent of colds. Other common cold viruses include coronavirus and ... RSS | Terms Of Use | Privacy | Sitemap Our Family Of Sites ... Introduction Risk Factors Screening Symptoms Tumor Testing Summary '; var ...

  6. Step by step in dust control

    Energy Technology Data Exchange (ETDEWEB)

    Archer, N. [Arch Environmental Equipment, Inc. (United States)

    2003-05-01

    The paper examines the different stages in identifying delegating and controlling dust before it becomes a serious problem for a facility. Material handling, processing, storage and traffic are the major dust producing sources. All industries that convey dry, light material need to install a dust control system. The confine-seal-suppress method of dust control has provided excellent results in numerous applications, only with the combination of all three will maximum dust control. When a system is properly engineered and correctly installed, meeting the EPA Government standards becomes very easy, and is necessary in to the operation of a quality facility. 5 photos.

  7. Dust bands in the asteroid belt

    International Nuclear Information System (INIS)

    Sykes, M.V.; Greenberg, R.; Dermott, S.F.; Nicholson, P.D.; Burns, J.A.

    1989-01-01

    This paper describes the original IRAS observations leading to the discovery of the three dust bands in the asteroid belt and the analysis of data. Special attention is given to an analytical model of the dust band torus and to theories concerning the origin of the dust bands, with special attention given to the collisional equilibrium (asteroid family), the nonequilibrium (random collision), and the comet hypotheses of dust-band origin. It is noted that neither the equilibrium nor nonequilibrium models, as currently formulated, present a complete picture of the IRAS dust-band observations. 32 refs

  8. Linear Alkylbenzenesulfonates in indoor Floor Dust

    DEFF Research Database (Denmark)

    Madsen, Jørgen Øgaard; Wolkoff, Peder; Madsen, Jørgen Øgaard

    1999-01-01

    The amount of Linear Alkylbenzenesulfonates (LAS) in the particle fraction of floor dust sampled from 7 selected public buildings varied between 34 and 1500 microgram per gram dust, while the contents of the fibre fractions generally were higher with up to 3500 microgram LAS/g dust. The use...... of a cleaning agent with LAS resulted in an increase of the amount of LAS in the floor dust after floor wash relative to just before floor wash. However, the most important source of LAS in the indoor floor dust appears to be residues of detergent in clothing. Thus, a newly washed shirt contained 2960 microgram...

  9. Time-Dependent Dust Formation in Novae

    Directory of Open Access Journals (Sweden)

    Kyung-Won Suh

    1991-06-01

    Full Text Available The dust formation processes in novae are investigated with close attention to recent infrared observations. Using mainly the classical nucleation theory, we have calculated the time scales of dust formation and growth in the environments of novae. Those time scales roughly resemble the typical observations. We have classified the dust-forming novae into three classes according to their explosion properties and the thermodynamic properties of dust grains. Oxygen grains from much later than carbon grains because of their thermodynamic properties. The effect of grain formation to the efficiency of stellar winds to drive the material outward is tested with newly obtained Planck mean values of dust grains.

  10. Numerical Prediction of Dust. Chapter 10

    Science.gov (United States)

    Benedetti, Angela; Baldasano, J. M.; Basart, S.; Benincasa, F.; Boucher, O.; Brooks, M.; Chen, J. P.; Colarco, P. R.; Gong, S.; Huneeus, N.; hide

    2013-01-01

    Covers the whole breadth of mineral dust research, from a scientific perspective Presents interdisciplinary work including results from field campaigns, satellite observations, laboratory studies, computer modelling and theoretical studies Explores the role of dust as a player and recorder of environmental change This volume presents state-of-the-art research about mineral dust, including results from field campaigns, satellite observations, laboratory studies, computer modelling and theoretical studies. Dust research is a new, dynamic and fast-growing area of science and due to its multiple roles in the Earth system, dust has become a fascinating topic for many scientific disciplines. Aspects of dust research covered in this book reach from timescales of minutes (as with dust devils, cloud processes, and radiation) to millennia (as with loess formation and oceanic sediments), making dust both a player and recorder of environmental change. The book is structured in four main parts that explore characteristics of dust, the global dust cycle, impacts of dust on the Earth system, and dust as a climate indicator. The chapters in these parts provide a comprehensive, detailed overview of this highly interdisciplinary subject. The contributions presented here cover dust from source to sink and describe all the processes dust particles undergo while travelling through the atmosphere. Chapters explore how dust is lifted and transported, how it affects radiation, clouds, regional circulations, precipitation and chemical processes in the atmosphere, and how it deteriorates air quality. The book explores how dust is removed from the atmosphere by gravitational settling, turbulence or precipitation, how iron contained in dust fertilizes terrestrial and marine ecosystems, and about the role that dust plays in human health. We learn how dust is observed, simulated using computer models and forecast. The book also details the role of dust deposits for climate reconstructions

  11. Dust removal system for fusion experimental reactors

    International Nuclear Information System (INIS)

    Onozuka, M.; Ueda, Y.; Takahashi, K.; Oda, Y.; Seki, Y.; Ueda, S.; Aoki, I.

    1995-01-01

    Development of a dust removal system using static electricity has been conducted. It is envisioned that the system can collect and transport dust under vacuum. In the system, the dust is charged by dielectric polarization and floated by an electrostatic attraction force that is generated by the DC electric field. The dust is then transported by the electric curtain formed by the three-phase AC electric field. Experimental investigation has been conducted to examine the characteristics of the system. Current research results indicate that the dust removal system using static electricity can be used for fusion experimental reactors

  12. Dust removal system for fusion experimental reactors

    Energy Technology Data Exchange (ETDEWEB)

    Onozuka, M.; Ueda, Y.; Takahashi, K.; Oda, Y. [Mitsubishi Heavy Industries, Ltd., Yokohama (Japan); Seki, Y.; Ueda, S.; Aoki, I. [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan)

    1995-12-31

    Development of a dust removal system using static electricity has been conducted. It is envisioned that the system can collect and transport dust under vacuum. In the system, the dust is charged by dielectric polarization and floated by an electrostatic attraction force that is generated by the DC electric field. The dust is then transported by the electric curtain formed by the three-phase AC electric field. Experimental investigation has been conducted to examine the characteristics of the system. Current research results indicate that the dust removal system using static electricity can be used for fusion experimental reactors.

  13. Development of cold neutron spectrometers

    International Nuclear Information System (INIS)

    Lee, Changhee; Lee, C. H.; So, J. Y.; Park, S.; Han, Y. S.; Cho, S. J.; Moon, M. K.; Choi, Y. H.; Sun, G. M.

    2012-03-01

    Cold Neutron Triple Axsis Spectrometer (Cold-TAS) Development Ο Fabrication and Installation of the Major Cold-TAS Components Ο Performance Test of the Cold-TAS □ Cold Neutron Time-of-Flight Spectrometer(DC-TOF) Development Ο Fabrication of the Major DC-TOF Components Ο Development DC-TOF Data Reduction Software □ Expected Contribution The two world-class inelastic neutron scattering instruments measure atomic or molecular scale dynamics of meV energy range. This unprecedented measurement capability in the country will enable domestic and international scientists to observe new phenomena in their materials research to obtain world class results. Especially those who work in the fields of magnetic properties of superconductors and multiferroics, molecular dynamics, etc. will get more benefit from these two instruments

  14. ORIGIN OF DUST AROUND V1309 SCO

    International Nuclear Information System (INIS)

    Zhu, Chunhua; Lü, Guoliang; Wang, Zhaojun

    2013-01-01

    The origin of dust grains in the interstellar medium is still an unanswered problem. Nicholls et al. found the presence of a significant amount of dust around V1309 Sco, which may originate from the merger of a contact binary. We investigate the origin of dust around V1309 Sco and suggest that these dust grains are produced in the binary-merger ejecta. By means of the AGBDUST code, we estimate that ∼5.2 × 10 –4 M ☉ dust grains are produced with a radii of ∼10 –5 cm. These dust grains are mainly composed of silicate and iron grains. Because the mass of the binary merger ejecta is very small, the contribution of dust produced by binary merger ejecta to the overall dust production in the interstellar medium is negligible. However, it is important to note that the discovery of a significant amount of dust around V1309 Sco offers a direct support for the idea that common-envelope ejecta provides an ideal environment for dust formation and growth. Therefore, we confirm that common envelope ejecta can be important source of cosmic dust

  15. Engineering-scale dust control experiments

    International Nuclear Information System (INIS)

    Winberg, M.R.; Pawelko, R.J.; Jacobs, N.C.; Thompson, D.N.

    1990-12-01

    This report presents the results of engineering scale dust-control experiments relating to contamination control during handling of transuranic waste. These experiments focused on controlling dust during retrieval operations of buried waste where waste and soil are intimately mixed. Sources of dust generation during retrieval operations include digging, dumping, and vehicle traffic. Because contaminants are expected to attach to soil particles and move with the generated dust, control of the dust spread may be the key to contamination control. Dust control techniques examined in these experiments include the use of misting systems, soil fixatives, and dust suppression agents. The Dryfog Ultrasonic Misting Head, manufactured by Sonics, Incorporated, and ENTAC, an organic resin derived from tree sap manufactured by ENTAC Corporation, were tested. The results of the experiments include product performance and recommended application methods. 19 figs., 7 refs., 6 tabs

  16. COSMIC DUST AGGREGATION WITH STOCHASTIC CHARGING

    International Nuclear Information System (INIS)

    Matthews, Lorin S.; Hyde, Truell W.; Shotorban, Babak

    2013-01-01

    The coagulation of cosmic dust grains is a fundamental process which takes place in astrophysical environments, such as presolar nebulae and circumstellar and protoplanetary disks. Cosmic dust grains can become charged through interaction with their plasma environment or other processes, and the resultant electrostatic force between dust grains can strongly affect their coagulation rate. Since ions and electrons are collected on the surface of the dust grain at random time intervals, the electrical charge of a dust grain experiences stochastic fluctuations. In this study, a set of stochastic differential equations is developed to model these fluctuations over the surface of an irregularly shaped aggregate. Then, employing the data produced, the influence of the charge fluctuations on the coagulation process and the physical characteristics of the aggregates formed is examined. It is shown that dust with small charges (due to the small size of the dust grains or a tenuous plasma environment) is affected most strongly

  17. The parametric decay of dust ion acoustic waves in non-uniform quantum dusty magnetoplasmas

    International Nuclear Information System (INIS)

    Jamil, M.; Ali, Waris; Shah, H. A.; Shahid, M.; Murtaza, G.; Salimullah, M.

    2011-01-01

    The parametric decay instability of a dust ion acoustic wave into low-frequency electrostatic dust-lower-hybrid and electromagnetic shear Alfven waves has been investigated in detail in an inhomogeneous cold quantum dusty plasma in the presence of external/ambient uniform magnetic field. The quantum magnetohydrodynamic model of plasmas with quantum effect arising through the Bohm potential and Fermi degenerate pressure has been employed in order to find the linear and nonlinear responses of the plasma particles for three-wave nonlinear coupling in a dusty magnetoplasma. A relatively high frequency electrostatic dust ion acoustic wave has been taken as the pump wave. It couples with two other low-frequency internal possible modes of the dusty magnetoplasma, viz., the dust-lower-hybrid and shear Alfven waves. The nonlinear dispersion relation of the dust-lower-hybrid wave has been solved to obtain the growth rate of the parametric decay instability. The growth rate is at a maximum for a small value of the external magnetic field B 0 . It is noted that the growth rate is proportional to the unperturbed electron number density n oe and is independent of inhomogeneity beyond L e =2 cm. An extraordinary growth rate is observed with the quantum effect.

  18. Coupling Mars' Dust and Water Cycles: Effects on Dust Lifting Vigor, Spatial Extent and Seasonality

    Science.gov (United States)

    Kahre, M. A.; Hollingsworth, J. L.; Haberle, R. M.; Montmessin, F.

    2012-01-01

    The dust cycle is an important component of Mars' current climate system. Airborne dust affects the radiative balance of the atmosphere, thus greatly influencing the thermal and dynamical state of the atmosphere. Dust raising events on Mars occur at spatial scales ranging from meters to planet-wide. Although the occurrence and season of large regional and global dust storms are highly variable from one year to the next, there are many features of the dust cycle that occur year after year. Generally, a low-level dust haze is maintained during northern spring and summer, while elevated levels of atmospheric dust occur during northern autumn and winter. During years without global-scale dust storms, two peaks in total dust loading were observed by MGS/TES: one peak occurred before northern winter solstice at Ls 200-240, and one peak occurred after northern winter solstice at L(sub s) 305-340. These maxima in dust loading are thought to be associated with transient eddy activity in the northern hemisphere, which has been observed to maximize pre- and post-solstice. Interactive dust cycle studies with Mars General Circulation Models (MGCMs) have included the lifting, transport, and sedimentation of radiatively active dust. Although the predicted global dust loadings from these simulations capture some aspects of the observed dust cycle, there are marked differences between the simulated and observed dust cycles. Most notably, the maximum dust loading is robustly predicted by models to occur near northern winter solstice and is due to dust lifting associated with down slope flows on the flanks of the Hellas basin. Thus far, models have had difficulty simulating the observed pre- and post- solstice peaks in dust loading. Interactive dust cycle studies typically have not included the formation of water ice clouds or their radiative effects. Water ice clouds can influence the dust cycle by scavenging dust from atmosphere and by interacting with solar and infrared radiation

  19. Observed trend in Asian dust days in South Korea and its geo-physiographical implications

    Science.gov (United States)

    Yang, Soohyun; Paik, Kyungrock

    2015-04-01

    South Korea has experienced significant socio-economic damages by Asian dust (also called Yellow sand or Yellow dust). Asian dust is a wind-driven natural phenomenon that carries fine sand particles along with surface pollutants from semi-arid areas in northern China, Inner Mongolia, the Gobi Desert, and the Taklimakan Desert to the East Asia. Its occurrence requires three necessary conditions: dry soil in source areas, strong ascending air current to lift sand particles up, and intense wind speed to transport the particles. Accordingly, the drier source areas are, the larger amount of source materials for Asian dust becomes. Further, regional wind speed and direction are key elements that determine the influencing boundary and level of damage. In this study, we investigate number of Asian dust days over South Korea. We utilize monthly data over 50 years (from 1961 to 2013) recorded at 12 stations, operated by the Korean Meteorological Administration, which are evenly distributed over the country. We find that annual number of Asian dust days in South Korea tends to increase until early 2000s and the increasing trend is ceased since then. Interestingly, this transition time (early 2000s) matches the time when the surface wind speed trend has reversed (Kim and Paik, 2015). Hence, we hypothesize that occurrence of Asian dust in South Korea can be largely captured by surface wind, instead of air circulation at high altitude. We also hypothesize that the transition in the trend around early 2000s is associated with expansion of cold air system during winter over the East Asia. Detailed analysis to support these findings will be presented. Reference Kim, JC., & Paik, K. (2015). Recent recovery of surface wind speed after decadal decrease: A focus on South Korea. Climate Dynamics, (Under review).

  20. Cold fusion method

    International Nuclear Information System (INIS)

    Takahashi, Akihito.

    1994-01-01

    A Pt wire electrode is supported from the periphery relative to a Pd electrode by way of a polyethylene or teflon plate in heavy water, and electrolysis is applied while varying conditions successively in a sawteeth fashion at an initial stage, and after elapse of about one week, a pulse current is supplied to promote nuclear reaction and to generate excess heat greater than a charged electric power. That is, small amount of neutron emission is increased and electrolytic cell temperature is elevated by varying the electrolysis conditions successively in the sawteeth fashion at the initial stage. In addition, when the pulse electric current is supplied after elapse of about one week, the electrolytic cell temperature is abnormally elevated, so that the promotion of nuclear reaction phenomenon and the generation of excess heat greater than the charged electric power are recognized. Then, a way to control power level and time fluctuation of cold fusion is attained, thereby contributing to development of a further method for generating excess heat as desired. In addition, it contributes to a development for a method of obtaining such an excess heat that can be taken as a new energy. (N.H.)

  1. Cold Rydberg molecules

    Science.gov (United States)

    Raithel, Georg; Zhao, Jianming

    2017-04-01

    Cold atomic systems have opened new frontiers at the interface of atomic and molecular physics. These include research on novel types of Rydberg molecules. Three types of molecules will be reviewed. Long-range, homonuclear Rydberg molecules, first predicted in [1] and observed in [2], are formed via low-energy electron scattering of the Rydberg electron from a ground-state atom within the Rydberg atom's volume. The binding mostly arises from S- and P-wave triplet scattering. We use a Fermi model that includes S-wave and P-wave singlet and triplet scattering, the fine structure coupling of the Rydberg atom and the hyperfine structure coupling of the 5S1/2 atom (in rubidium [3]). The hyperfine structure gives rise to mixed singlet-triplet potentials for both low-L and high-L Rydberg molecules [3]. A classification into Hund's cases [3, 4, 5] will be discussed. The talk further includes results on adiabatic potentials and adiabatic states of Rydberg-Rydberg molecules in Rb and Cs. These molecules, which have even larger bonding length than Rydberg-ground molecules, are formed via electrostatic multipole interactions. The leading interaction term of neutral Rydberg-Rydberg molecules is between two dipoles, while for ionic Rydberg molecules it is between a dipole and a monopole. NSF (PHY-1506093), NNSF of China (61475123).

  2. Cold-Adapted Enzymes

    Science.gov (United States)

    Georlette, D.; Bentahir, M.; Claverie, P.; Collins, T.; D'amico, S.; Delille, D.; Feller, G.; Gratia, E.; Hoyoux, A.; Lonhienne, T.; Meuwis, M.-a.; Zecchinon, L.; Gerday, Ch.

    In the last few years, increased attention has been focused on enzymes produced by cold-adapted micro-organisms. It has emerged that psychrophilic enzymes represent an extremely powerful tool in both protein folding investigations and for biotechnological purposes. Such enzymes are characterised by an increased thermosensitivity and, most of them, by a higher catalytic efficiency at low and moderate temperatures, when compared to their mesophilic counterparts. The high thermosensitivity probably originates from an increased flexibility of either a selected area of the molecular edifice or the overall protein structure, providing enhanced abilities to undergo conformational changes during catalysis at low temperatures. Structure modelling and recent crystallographic data have allowed to elucidate the structural parameters that could be involved in this higher resilience. It was demonstrated that each psychrophilic enzyme adopts its own adaptive strategy. It appears, moreover, that there is a continuum in the strategy of protein adaptation to temperature, as the previously mentioned structural parameters are implicated in the stability of thermophilic proteins. Additional 3D crystal structures, site-directed and random mutagenesis experiments should now be undertaken to further investigate the stability-flexibility-activity relationship.

  3. Observations of cold antihydrogen

    CERN Document Server

    Tan, J N; Gabrielse, G; Oxley, P; Speck, A; Storry, C H; Wessels, M; Grzonka, D; Oelert, W; Schepers, G; Sefzick, T; Walz, J; Pittner, H; Hänsch, T W; Hessels, E A

    2004-01-01

    ATRAP's e/sup +/ cooling of p in a nested Penning trap has led to reports of cold H produced during such cooling by the ATHENA and ATRAP collaborations. To observe H, ATHENA uses coincident annihilation detection and ATRAP uses field ionization followed by p storage. Advantages of ATRAP's field ionization method include the complete absence of any background events, and the first way to measure which H states are produced. ATRAP enhances the H production rate by driving many cycles of e/sup +/ cooling in the nested trap, with more H counted in an hour than the sum of all the other antimatter atoms ever reported. The number of H counted per incident high energy p is also higher than ever observed. The first measured distribution of H states is made using a pre-ionizing electric field between separated production and detection regions. The high rate and the high Rydberg states suggest that the H is formed via three-body recombination, as expected. (22 refs).

  4. Observations of cold antihydrogen

    International Nuclear Information System (INIS)

    Tan, J.N.; Bowden, N.S.; Gabrielse, G.; Oxley, P.; Speck, A.; Storry, C.H.; Wessels, M.; Grzonka, D.; Oelert, W.; Schepers, G.; Sefzick, T.; Walz, J.; Pittner, H.; Haensch, T.W.; Hessels, E.A.

    2004-01-01

    ATRAP's e + cooling of p-bar in a nested Penning trap has led to reports of cold H-bar produced during such cooling by the ATHENA and ATRAP collaborations. To observe H-bar, ATHENA uses coincident annihilation detection and ATRAP uses field ionization followed by p-bar storage. Advantages of ATRAP's field ionization method include the complete absence of any background events, and the first way to measure which H-bar states are produced. ATRAP enhances the H-bar production rate by driving many cycles of e + cooling in the nested trap, with more H-bar counted in an hour than the sum of all the other antimatter atoms ever reported. The number of H-bar counted per incident high energy p-bar is also higher than ever observed. The first measured distribution of H-bar states is made using a pre-ionizing electric field between separated production and detection regions. The high rate and the high Rydberg states suggest that the H-bar is formed via three-body recombination, as expected

  5. House Dust Mite Respiratory Allergy

    DEFF Research Database (Denmark)

    Calderón, Moisés A; Kleine-Tebbe, Jörg; Linneberg, Allan

    2015-01-01

    Although house dust mite (HDM) allergy is a major cause of respiratory allergic disease, specific diagnosis and effective treatment both present unresolved challenges. Guidelines for the treatment of allergic rhinitis and asthma are well supported in the literature, but specific evidence on the e......Although house dust mite (HDM) allergy is a major cause of respiratory allergic disease, specific diagnosis and effective treatment both present unresolved challenges. Guidelines for the treatment of allergic rhinitis and asthma are well supported in the literature, but specific evidence...... not extend beyond the end of treatment. Finally, allergen immunotherapy has a poor but improving evidence base (notably on sublingual tablets) and its benefits last after treatment ends. This review identifies needs for deeper physician knowledge on the extent and impact of HDM allergy in respiratory disease...... and therapy of HDM respiratory allergy in practice....

  6. Global-scale attribution of anthropogenic and natural dust sources and their emission rates based on MODIS Deep Blue aerosol products

    Science.gov (United States)

    Ginoux, Paul; Prospero, Joseph M.; Gill, Thomas E.; Hsu, N. Christina; Zhao, Ming

    2012-09-01

    Our understanding of the global dust cycle is limited by a dearth of information about dust sources, especially small-scale features which could account for a large fraction of global emissions. Here we present a global-scale high-resolution (0.1°) mapping of sources based on Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue estimates of dust optical depth in conjunction with other data sets including land use. We ascribe dust sources to natural and anthropogenic (primarily agricultural) origins, calculate their respective contributions to emissions, and extensively compare these products against literature. Natural dust sources globally account for 75% of emissions; anthropogenic sources account for 25%. North Africa accounts for 55% of global dust emissions with only 8% being anthropogenic, mostly from the Sahel. Elsewhere, anthropogenic dust emissions can be much higher (75% in Australia). Hydrologic dust sources (e.g., ephemeral water bodies) account for 31% worldwide; 15% of them are natural while 85% are anthropogenic. Globally, 20% of emissions are from vegetated surfaces, primarily desert shrublands and agricultural lands. Since anthropogenic dust sources are associated with land use and ephemeral water bodies, both in turn linked to the hydrological cycle, their emissions are affected by climate variability. Such changes in dust emissions can impact climate, air quality, and human health. Improved dust emission estimates will require a better mapping of threshold wind velocities, vegetation dynamics, and surface conditions (soil moisture and land use) especially in the sensitive regions identified here, as well as improved ability to address small-scale convective processes producing dust via cold pool (haboob) events frequent in monsoon regimes.

  7. Mechanisms and Effects of Summertime Transport of African Dust Through the Tokar Mountain Gap to the Red Sea and Arabian Peninsula

    Science.gov (United States)

    Kalenderski, S.; Stenchikov, G. L.

    2015-12-01

    Very high dust loading over the Red Sea region in summer strongly affects the nutrition balance and thermal and dynamic regimes of the sea. The observations suggest that small-scale local dynamic and orographic effects, from both the Arabian and African sides, strongly contribute to dust plume formation. To better understand and quantify these processes we present here the first high resolution modeling study of the dust outbreak phenomena in June 2012 over East Africa, the Red Sea, and the Arabian Peninsula using the WRF-Chem model. We identified several dust generating dynamical processes that range from convective to synoptic scales, including: synoptic cyclones, nocturnal low-level jets, and cold pools of mesoscale convective systems. The simulations reveal an eastward transport of African dust across the Red Sea. Over the northern part of the Red Sea most of the dust transport occurs beyond 2 km above ground level and is strengthened by a pressure gradient formed by low pressure over the eastern Mediterranean and high pressure over the Arabian Peninsula. Across the central and southern parts of the Red Sea dust is mostly transported below 2 km height. During the study period dust is a dominant contributor (87%) to aerosol optical depth (AOD), producing a domain average cooling effect of -12.1 W m-2 at surface, a warming of 7.1 W m-2 in the atmosphere, and a residual cooling of -4.9 W m-2 at the top of the atmosphere. WRF-Chem simulations demonstrate that both dry and wet deposition processes contribute significantly to dust removal from the atmosphere. During the dust outbreak 49.2 Tg of dust deposits within the calculation domain, which is approximately 90% of the total dust emission of 54.5 Tg. Model results compare well with available ground-based and satellite observations but generally underestimate the observed AOD maximum values.

  8. Collisionless damping of nonlinear dust ion acoustic wave due to dust charge fluctuation

    International Nuclear Information System (INIS)

    Ghosh, Samiran; Chaudhuri, Tushar K.; Sarkar, Susmita; Khan, Manoranjan; Gupta, M.R.

    2002-01-01

    A dissipation mechanism for the damping of the nonlinear dust ion acoustic wave in a collisionless dusty plasma consisting of nonthermal electrons, ions, and variable charge dust grains has been investigated. It is shown that the collisionless damping due to dust charge fluctuation causes the nonlinear dust ion acoustic wave propagation to be described by the damped Korteweg-de Vries equation. Due to the presence of nonthermal electrons, the dust ion acoustic wave admits both positive and negative potential and it suffers less damping than the dust acoustic wave, which admits only negative potential

  9. Cold-formed steel design

    CERN Document Server

    Yu, Wei-Wen

    2010-01-01

    The definitive text in the field, thoroughly updated and expanded Hailed by professionals around the world as the definitive text on the subject, Cold-Formed Steel Design is an indispensable resource for all who design for and work with cold-formed steel. No other book provides such exhaustive coverage of both the theory and practice of cold-formed steel construction. Updated and expanded to reflect all the important developments that have occurred in the field over the past decade, this Fourth Edition of the classic text provides you with more of the detailed, up-to-the-minute techni

  10. Respiratory effects of borax dust.

    Science.gov (United States)

    Garabrant, D H; Bernstein, L; Peters, J M; Smith, T J; Wright, W E

    1985-12-01

    The relation of respiratory symptoms, pulmonary function, and abnormalities of chest radiographs to estimated exposures of borax dust has been investigated in a cross sectional study of 629 actively employed borax workers. Ninety three per cent of the eligible workers participated in the study and exposures ranged from 1.1 mg/m3 to 14.6 mg/m3. Symptoms of acute respiratory irritation such as dryness of the mouth, nose, or throat, dry cough, nose bleeds, sore throat, productive cough, shortness of breath, and chest tightness were related to exposures of 4.0 mg/m3 or more, and were infrequent at exposures of 1.1 mg/m3. Symptoms of persistent respiratory irritation meeting the definition of chronic simple bronchitis were related to exposure among non-smokers. Decrements in the FEV1 as a percentage of predicted were seen among smokers who had heavy cumulative borax exposures (greater than or equal to 80 mg/m3 years) but were not seen among less exposed smokers or among non-smokers. Radiographic abnormalities were uncommon and were not related to dust exposure. Borax dust appears to act as a simple respiratory irritant and perhaps causes small changes in the FEV1 among smokers who are heavily exposed.

  11. Dust-Tolerant Intelligent Electrical Connection System

    Science.gov (United States)

    Lewis, Mark; Dokos, Adam; Perotti, Jose; Calle, Carlos; Mueller, Robert; Bastin, Gary; Carlson, Jeffrey; Townsend, Ivan, III; Immer, Chirstopher; Medelius, Pedro

    2012-01-01

    Faults in wiring systems are a serious concern for the aerospace and aeronautic (commercial, military, and civilian) industries. Circuit failures and vehicle accidents have occurred and have been attributed to faulty wiring created by open and/or short circuits. Often, such circuit failures occur due to vibration during vehicle launch or operation. Therefore, developing non-intrusive fault-tolerant techniques is necessary to detect circuit faults and automatically route signals through alternate recovery paths while the vehicle or lunar surface systems equipment is in operation. Electrical connector concepts combining dust mitigation strategies and cable diagnostic technologies have significant application for lunar and Martian surface systems, as well as for dusty terrestrial applications. The dust-tolerant intelligent electrical connection system has several novel concepts and unique features. It combines intelligent cable diagnostics (health monitoring) and automatic circuit routing capabilities into a dust-tolerant electrical umbilical. It retrofits a clamshell protective dust cover to an existing connector for reduced gravity operation, and features a universal connector housing with three styles of dust protection: inverted cap, rotating cap, and clamshell. It uses a self-healing membrane as a dust barrier for electrical connectors where required, while also combining lotus leaf technology for applications where a dust-resistant coating providing low surface tension is needed to mitigate Van der Waals forces, thereby disallowing dust particle adhesion to connector surfaces. It also permits using a ruggedized iris mechanism with an embedded electrodynamic dust shield as a dust barrier for electrical connectors where required.

  12. Ocular toxicity of authentic lunar dust.

    Science.gov (United States)

    Meyers, Valerie E; Garcìa, Hector D; Monds, Kathryn; Cooper, Bonnie L; James, John T

    2012-07-20

    Dust exposure is a well-known occupational hazard for terrestrial workers and astronauts alike and will continue to be a concern as humankind pursues exploration and habitation of objects beyond Earth. Humankind's limited exploration experience with the Apollo Program indicates that exposure to dust will be unavoidable. Therefore, NASA must assess potential toxicity and recommend appropriate mitigation measures to ensure that explorers are adequately protected. Visual acuity is critical during exploration activities and operations aboard spacecraft. Therefore, the present research was performed to ascertain the ocular toxicity of authentic lunar dust. Small (mean particle diameter = 2.9 ± 1.0 μm), reactive lunar dust particles were produced by grinding bulk dust under ultrapure nitrogen conditions. Chemical reactivity and cytotoxicity testing were performed using the commercially available EpiOcularTM assay. Subsequent in vivo Draize testing utilized a larger size fraction of unground lunar dust that is more relevant to ocular exposures (particles lunar dust was minimally irritating. Minor irritation of the upper eyelids was noted at the 1-hour observation point, but these effects resolved within 24 hours. In addition, no corneal scratching was observed using fluorescein stain. Low-titanium mare lunar dust is minimally irritating to the eyes and is considered a nuisance dust for ocular exposure. No special precautions are recommended to protect against ocular exposures, but fully shielded goggles may be used if dust becomes a nuisance.

  13. Dust characterisation for hot gas filters

    Energy Technology Data Exchange (ETDEWEB)

    Dockter, B.; Erickson, T.; Henderson, A.; Hurley, J.; Kuehnel, V.; Katrinak, K.; Nowok, J.; O`Keefe, C.; O`Leary, E.; Swanson, M.; Watne, T. [University of North Dakota, Grand Forks, ND (United States). Energy and Environmental Research Center (UNDEERC)

    1998-03-01

    Hot gas filtration to remove particulates from the gas flow upstream of the gas turbine is critical to the development of many of the advanced coal-fired power generation technologies such as the Air Blown Gasification Cycle (ABGC), a hybrid gasification combined cycle being developed in the UK. Ceramic candle filters are considered the most promising technology for this purpose. Problems of mechanical failure and of `difficult-to-clean` dusts causing high pressure losses across the filter elements need to be solved. The project investigated the behaviour of high-temperature filter dusts, and the factors determining the ease with which they can be removed from filters. The high-temperature behaviour of dusts from both combustion and gasification systems was investigated. Dust samples were obtained from full-scale demonstration and pilot-scale plant operating around the world. Dust samples were also produced from a variety of coals, and under several different operating conditions, on UNDEERC`s pilot-scale reactor. Key factors affecting dust behaviour were examined, including: the rates of tensile strength developing in dust cakes; the thermochemical equilibria pertaining under filtration conditions; dust adhesivity on representative filter materials; and the build-up and cleaning behaviour of dusts on representative filter candles. The results obtained confirmed the importance of dust temperature, dust cake porosity, cake liquid content, and particle size distribution in determining the strength of a dust cake. An algorithm was developed to indicate the likely sticking propensity of dusts as a function of coal and sorbent composition and combustion conditions. This algorithm was incorporated into a computer package which can be used to judge the degree of difficulty in filter cleaning that can be expected to arise in a real plant based on operating parameters and coal analyzes. 6 figs.

  14. Reconstructing the Mineralogy and Bioavailability of Dust-Borne Iron Deposited to the Southern Ocean through the Last Glacial Cycle

    Science.gov (United States)

    Shoenfelt, E. M.; Winckler, G.; Lamy, F.; Bostick, B. C.

    2017-12-01

    The iron (Fe) in dust deposited to the Fe-limited Southern Ocean plays an important role in ocean biogeochemistry and global climate. For instance, increases in dust-borne Fe deposition in the subantarctic Southern Ocean have been linked to increases in productivity and part of the CO2 drawdown of the last glacial cycle [1]. Notably, bioavailable Fe impacts productivity rather than total Fe. While it has long been understood that Fe mineralogy impacts Fe bioavailability in general, our understanding of the mineralogy of Fe in dust in specific is limited to that in modern dust sources. Reduced mineral Fe in dust has been shown to be more bioavailable than oxidized mineral iron, as it is more readily dissolved [2], and it is more easily utilized directly by a model diatom [3]. Our previous work focusing on South American dust sources shows that glacial activity is associated with higher Fe(II) fractions in dust-borne minerals, due to the physical weathering of Fe(II)-rich silicates in bedrock [3]. Thus, we hypothesize that there were higher Fe(II) fractions in dust deposited during cold glacial periods where ice sheets were more widespread. Using synchrotron-based X-ray absorption spectroscopy, we have reconstructed the mineralogy of Fe deposited to Southern Ocean sediment cores from the subantarctic South Atlantic (TN057-6/ODP Site 1090) and South Pacific (PS7/56-1) through the last glacial cycle, creating the first paleorecord of Fe mineralogy and its associated bioavailability. During cold glacial periods there is a higher fraction of reduced Fe - in the form of Fe(II) silicates - deposited to the sediments compared to warm interglacial periods. Thus, Fe(II) content is directly correlated with dust input. The presence of Fe(II) silicates rather than products of diagenesis such as pyrite suggests that these Fe(II) minerals are physically weathered from bedrock and preserved rather than produced in the sediment. This result suggests that not only was there more dust

  15. Surface properties of activated carbon treated by cold plasma heating

    Energy Technology Data Exchange (ETDEWEB)

    Norikazu, Kurano [Shigematsu works Co. Ltd., 267 Yashita, Iwatsuki 3390046 (Japan); Yamada, Hiroshi [Shigematsu works Co. Ltd., 267 Yashita, Iwatsuki 3390046 (Japan); Yajima, Tatsuhiko [Faculty of Engineering, Saitama Institute of Technology, 1690 Fusoiji, Okabe 3690293 (Japan); Sugiyama, Kazuo [Faculty of Engineering, Saitama University, 255 Shimo-okubo, Sakura-Ku, Saitama 3388570 (Japan)]. E-mail: sugi@apc.saitama-u.ac.jp

    2007-03-12

    To modify the surface properties of activated carbon powders, we have applied the cold plasma treatment method. The cold plasma was used to be generated in the evacuated reactor vessel by 2.45 GHz microwave irradiation. In this paper, changes of surface properties such as distribution of acidic functional groups and roughness morphology were examined. By the cold plasma treatment, activated carbons with large specific surface area of ca. 2000 m{sup 2}/g or more could be prepared in a minute. The amount of every gaseous organic compound adsorbed on the unit gram of treated activated carbons was more increased that on the unit gram of untreated carbons. Especially, the adsorbed amount of carbon disulfide was remarkably increased even if it was compared by the amount per unit surface area. These results suggest that the surface property of the sample was modified by the plasma treatment. It became apparent by observing SEM photographs that dust and impure particles in macropores of activated carbons were far more reduced by the plasma treatment than by the conventional heating in an electric furnace under vacuum. In addition, a bubble-like surface morphology of the sample was observed by AEM measurement. The amount of acidic functional groups at the surface was determined by using the Boehm's titration method. Consequently, the increase of lactone groups and the decrease of carboxyl groups were also observed.

  16. GRB 130606A AS A PROBE OF THE INTERGALACTIC MEDIUM AND THE INTERSTELLAR MEDIUM IN A STAR-FORMING GALAXY IN THE FIRST Gyr AFTER THE BIG BANG

    International Nuclear Information System (INIS)

    Chornock, Ryan; Berger, Edo; Lunnan, Ragnhild; Drout, Maria R.; Fong Wenfai; Laskar, Tanmoy; Fox, Derek B.; Roth, Katherine C.

    2013-01-01

    We present high signal-to-noise ratio Gemini and MMT spectroscopy of the optical afterglow of the gamma-ray burst (GRB) 130606A at redshift z = 5.913, discovered by Swift. This is the first high-redshift GRB afterglow to have spectra of comparable quality to those of z ≈ 6 quasars. The data exhibit a smooth continuum at near-infrared wavelengths that is sharply cut off blueward of 8410 Å due to absorption from Lyα at redshift z ≈ 5.91, with some flux transmitted through the Lyα forest between 7000 and 7800 Å. We use column densities inferred from metal absorption lines to constrain the metallicity of the host galaxy between a lower limit of [Si/H] ∼> –1.7 and an upper limit of [S/H] ∼ GP eff (Lyα) > 6.4). This is comparable to the lowest-redshift Gunn-Peterson troughs found in quasar spectra. Some Lyβ and Lyγ transmission is detected in this redshift window, indicating that it is not completely opaque, and hence that the intergalactic medium (IGM) is nonetheless mostly ionized at these redshifts. We set a 2σ upper limit of 0.11 on the neutral fraction of the IGM at the redshift of the GRB from the lack of a Lyα red damping wing, assuming a model with a constant neutral density. GRB 130606A thus for the first time realizes the promise of GRBs as probes of the first galaxies and cosmic reionization

  17. The Faint End of the Quasar Luminosity Function at z ~ 4: Implications for Ionization of the Intergalactic Medium and Cosmic Downsizing

    Science.gov (United States)

    Glikman, Eilat; Djorgovski, S. G.; Stern, Daniel; Dey, Arjun; Jannuzi, Buell T.; Lee, Kyoung-Soo

    2011-02-01

    We present an updated determination of the z ~ 4 QSO luminosity function (QLF), improving the quality of the determination of the faint end of the QLF presented by Glikman et al. (2010). We have observed an additional 43 candidates from our survey sample, yielding one additional QSO at z = 4.23 and increasing the completeness of our spectroscopic follow-up to 48% for candidates brighter than R = 24 over our survey area of 3.76 deg2. We study the effect of using K-corrections to compute the rest-frame absolute magnitude at 1450 Å compared with measuring M 1450 directly from the object spectra. We find a luminosity-dependent bias: template-based K-corrections overestimate the luminosity of low-luminosity QSOs, likely due to their reliance on templates derived from higher luminosity QSOs. Combining our sample with bright quasars from the Sloan Digital Sky Survey and using spectrum-based M 1450 for all the quasars, we fit a double power law to the binned QLF. Our best fit has a bright-end slope, α = 3.3 ± 0.2, and faint-end slope, β = 1.6+0.8 -0.6. Our new data revise the faint-end slope of the QLF down to flatter values similar to those measured at z ~ 3. The break luminosity, though poorly constrained, is at M* = -24.1+0.7 -1.9, approximately 1-1.5 mag fainter than at z ~ 3. This QLF implies that QSOs account for about half the radiation needed to ionize the intergalactic medium at these redshifts. The data presented herein were 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 the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  18. Cold nuclear fusion

    Energy Technology Data Exchange (ETDEWEB)

    Tsyganov, E.N., E-mail: edward.tsyganov@coldfusion-power.com [Cold Fusion Power, International (United States); Bavizhev, M.D. [LLC “Radium”, Moscow (Russian Federation); Buryakov, M.G. [Joint Institute for Nuclear Research (JINR), Dubna (Russian Federation); Dabagov, S.B. [RAS P.N. Lebedev Physical Institute, Leninsky pr. 53, 119991 Moscow (Russian Federation); National Research Nuclear University MEPhI, Kashirskoe shosse 31, 115409 Moscow (Russian Federation); Golovatyuk, V.M.; Lobastov, S.P. [Joint Institute for Nuclear Research (JINR), Dubna (Russian Federation)

    2015-07-15

    If target deuterium atoms were implanted in a metal crystal in accelerator experiments, a sharp increase in the probability of DD-fusion reaction was clearly observed when compared with the reaction’s theoretical value. The electronic screening potential, which for a collision of free deuterium atoms is about 27 eV, reached 300–700 eV in the case of the DD-fusion in metallic crystals. These data leads to the conclusion that a ban must exist for deuterium atoms to be in the ground state 1s in a niche filled with free conduction electrons. At the same time, the state 2p whose energy level is only 10 eV above that of state 1s is allowed in these conditions. With anisotropy of 2p, 3p or above orbitals, their spatial positions are strictly determined in the lattice coordinate system. When filling out the same potential niches with two deuterium atoms in the states 2p, 3p or higher, the nuclei of these atoms can be permanently positioned without creating much Coulomb repulsion at a very short distance from each other. In this case, the transparency of the potential barrier increases dramatically compared to the ground state 1s for these atoms. The probability of the deuterium nuclei penetrating the Coulomb barrier by zero quantum vibration of the DD-system also increases dramatically. The so-called cold nuclear DD-fusion for a number of years was registered in many experiments, however, was still rejected by mainstream science for allegedly having no consistent scientific explanation. Finally, it received the validation. Below, we outline the concept of this explanation and give the necessary calculations. This paper also considers the further destiny of the formed intermediate state of {sup 4}He{sup ∗}.

  19. Hydrothermal Cold Sintering

    Science.gov (United States)

    Kang, Xiaoyu

    C, respectively. Process variables were defined and effects of individual parameters were studied systematically through control variable method with Li2MoO4-water system. Crystalline structure, fractured surface morphology and chemical bonding information of the cold sintered pellets were studied with X-ray diffraction (XRD), field effect scanning electron microscopy (FE-SEM) and Raman spectroscopy, etc. Densification mechanism studies were conducted on ZnO. Through comparison experiments, it was found that the Zn2+ concentration in the solution is critical for densification, while dissolution of grains only serves as a means to the former. Through pressure dependent studies, a critical value was found, which correlated well with the hydrostatic pressure keeping liquid water from thermal expansion. These results confirmed establishment of hydrothermal condition that would be important for mass transport in densification. Densification rate variations with process time was estimated and similar time dependence to Kingery's model was found. The densification process was proposed to be consist of three consecutive stages, which are quick initial compaction, grain rearrangement and dissolution-reprecipitation events. Binary metal oxides with different acidities were subjected to cold sintering with various aqueous solutions in establishing a criteria for material selection. It was found that in general materials with high solubility at around neutral pH, high dissolution kinetics and similar free energy to their hydroxides or hydrates at ambient would be more likely for full densification with high phase purity. The anions in solution should also be wisely selected to avoid stable compound or complex formation. To extend the applicable material list for full densification, non-aqueous solvent of dimethyl sulfoxide (DMSO) based solution was studied for cold sintering. Both improvement of pellet density and suppression of hydroxide formation were achieved for MnO by using DMSO

  20. Phonon forces and cold denaturatio

    DEFF Research Database (Denmark)

    Bohr, Jakob

    2003-01-01

    Protein unfolds upon temperature reduction as Well as upon In increase in temperature, These phenomena are called cold denaturation and hot denaturation, respectively. The contribution from quantum mode forces to denaturation is estimated using a simple phenomenological model describing the molec......Protein unfolds upon temperature reduction as Well as upon In increase in temperature, These phenomena are called cold denaturation and hot denaturation, respectively. The contribution from quantum mode forces to denaturation is estimated using a simple phenomenological model describing...... the molecule Is a continuum. The frequencies of the vibrational modes depend on the molecular dimensionality; hence, the zero-point energies for the folded and the denatured protein are estimated to differ by several electron volts. For a biomolecule such an energy is significant and may contribute to cold...... denaturing. This is consistent with the empirical observation that cold denaturation is exothermic anti hot denaturation endothermic....

  1. Cold Weather and Cardiovascular Disease

    Science.gov (United States)

    ... Venous Thromboembolism Aortic Aneurysm More Cold Weather and Cardiovascular Disease Updated:Sep 16,2015 Th is winter ... and procedures related to heart disease and stroke. Cardiovascular Conditions • Conditions Home • Arrhythmia and Atrial Fibrillation • Cardiac ...

  2. Magnesium Repair by Cold Spray

    National Research Council Canada - National Science Library

    Champagne, V. K; Leyman, P.F; Helfritch, D. J

    2008-01-01

    .... Army Research Laboratory has developed a cold spray process to reclaim magnesium components that shows significant improvement over existing methods and is in the process of qualification for use on rotorcraft...

  3. House dust in seven Danish offices

    Science.gov (United States)

    Mølhave, L.; Schneider, T.; Kjærgaard, S. K.; Larsen, L.; Norn, S.; Jørgensen, O.

    Floor dust from Danish offices was collected and analyzed. The dust was to be used in an exposure experiment. The dust was analyzed to show the composition of the dust which can be a source of airborne dust indoors. About 11 kg of dust from vacuum cleaner bags from seven Danish office buildings with about 1047 occupants (12 751 m 2) was processed according to a standardized procedure yielding 5.5 kg of processed bulk dust. The bulk dust contained 130.000-160.000 CFU g -1 microorganisms and 71.000-90.000 CFU g -1 microfungi. The content of culturable microfungi was 65-123 CFU 30 g -1 dust. The content of endotoxins ranged from 5.06-7.24 EU g -1 (1.45 ng g -1 to 1.01 ng g -1). Allergens (ng g -1) were from 147-159 (Mite), 395-746 (dog) and 103-330 (cat). The macro molecular organic compounds (the MOD-content) varied from 7.8-9.8 mg g -1. The threshold of release of histamine from basophil leukocytes provoked by the bulk dust was between 0.3 and 1.0 mg ml -1. The water content was 2% (WGT) and the organic fraction 33%. 6.5-5.9% (dry) was water soluble. The fiber content was less than 0.2-1.5% (WGT) and the desorbable VOCs was 176-319 μg g -1. Most of the VOC were aldehydes. However, softeners for plastic (DBP and DEHP) were present. The chemical composition includes human and animal skin fragments, paper fibers, glass wool, wood and textilefibers and inorganic and metal particles. The sizes ranged from 0.001-1 mm and the average specific density was 1.0 g m -3. The bulk dust was resuspended and injected into an exposure chamber. The airborne dust was sampled and analyzed to illustrate the exposures that can result from sedimented dirt and dust. The airborne dust resulting from the bulk dust reached concentrations ranging from 0.26-0.75 mg m -3 in average contained 300-170 CFU m -3. The organic fraction was from 55-70% and the water content about 2.5% (WGT). The content of the dust was compared to the similar results reported in the literature and its toxic potency is

  4. Nonfreezing Cold-Induced Injuries

    Science.gov (United States)

    2012-01-01

    cold injury. ( Modi - fi ed from Jia J, Pollock M: The pathogenesis of non-freezing cold nerve injury: Observations in the rat, Brain 120:631, 1997...myelitis and sinus development ( Figures 7-17 to 7-19 ). Appearance and behavior of the neuropathic foot have many similarities to those of the diabetic ...foot. In the diabetic foot, infections tend to be polymicrobial with Staphylococcus aureus, Staphylococcus epidermidis, and Enterococcus and

  5. Tip model of cold fission

    International Nuclear Information System (INIS)

    Goennenwein, F.; Boersig, B.

    1991-01-01

    Cold fission is defined to be the limiting case of nuclear fission where virtually all of the available energy is converted into the total kinetic energy of the fragments. The fragments have, therefore, to be born in or at least close to their respective ground states. Starting from the viewpoint that cold fission corresponds to most compact scission configurations, energy constraints have been exploited to calculate minimum tip distances between the two nascent fragments in binary fission. Crucial input parameters to this tip model of cold fission are the ground-state deformations of fragment nuclei. It is shown that the minimum tip distances being compatible with energy conservation vary strongly with both the mass and charge fragmentation of the fission prone nucleus. The tip distances refer to nuclei with equivalent sharp surfaces. In keeping with the size of the surface width of leptodermous nuclei, only configurations where the tip distances are smaller than a few fm may be considered as valid scission configurations. From a comparison with experimental data on cold fission this critical tip distance appears to be 3.0 fm for the model parameters chosen. Whenever the model calculation yields tip distances being smaller than the critical value, a necessary condition for attaining cold fission is considered to be fulfilled. It is shown that this criterion allows to understand in fair agreement with experiment which mass fragmentations are susceptible to lead to cold fission and which fragment-charge divisions are the most favored in each isobaric mass chain. Being based merely on energy arguments, the model cannot aim at predicting fragment yields in cold fission. However, the tip model proposed appears well suited to delineate the phase space where cold fission phenomena may come into sight. (orig.)

  6. Stochastic histories of dust grains in the interstellar medium

    International Nuclear Information System (INIS)

    Liffman, K.

    1988-01-01

    The purpose of this thesis is to study an evolving system of SU-perNOva CONdensateS (SUNOCONS) within the Interstellar Medium (ISM). This is done via a Monte Carlo process where refractory dust grains formed within supernova remnants are subjected to the processes of sputtering and collisional fragmentation in the diffuse phase and accretion within the cold molecular cloud phase. In order to record chemical detail, we take each new particle to consist of a superrefractory core plus a more massive refractory mantle. The particles are allowed to transfer to and from between the different phases of the ISM until either the particles are destroyed or the program finishes. The resulting chemical and size spectrum(s) are then applied to various astrophysical problems with the following results: (1) after six thousand million years roughly 10 to 20% by mass of the most refractory material (Al 2 O 3 ) survives the rigors of the ISM intact, which leaves open the possibility that fossilized isotopically anomalous material may have been present within the primordial solar nebula. (2) structured or layered refractory dust grains within our model cannot explain the observed interstellar depletions of refractory material. (3) fragmentation due to grain-grain collisions in the diffuse phase plus the accretion of material in the molecular cloud phase can under certain circumstances cause a biomodal distribution in grain size

  7. High-resolution regional modeling of summertime transport and impact of African dust over the Red Sea and Arabian Peninsula

    KAUST Repository

    Kalenderski, Stoitchko Dimitrov

    2016-05-23

    Severe dust outbreaks and high dust loading over Eastern Africa and the Red Sea are frequently detected in the summer season. Observations suggest that small-scale dynamic and orographic effects, from both the Arabian and African sides, strongly contribute to dust plume formation. To better understand these processes, we present here the first high resolution modeling study of a dust outbreak in June 2012 developed over East Africa, the Red Sea, and the Arabian Peninsula. Using the Weather Research and Forecasting model coupled with Chemistry component (WRF-Chem), we identified several dust generating dynamical processes that range from convective to synoptic scales, including synoptic cyclones, nocturnal low-level jets, and cold pools of mesoscale convective systems. The simulations reveal an eastward transport of African dust across the Red Sea. Over the northern part of the Red Sea, most of the dust transport occurs above 2 km height, whereas across the central and southern parts of the sea, dust is mostly transported below 2 km height. Dust is the dominant contributor (87%) to the aerosol optical depth, producing a domain average cooling effect of -12.1 W m-2 at the surface, a warming of 7.1 W m-2 in the atmosphere, and a residual cooling of -4.9 W m-2 at the top of the atmosphere. Both dry and wet deposition processes contribute significantly to dust removal from the atmosphere. Model results compare well with available ground-based and satellite observations, but generally underestimate the observed maximum values of aerosol optical depth. The satellite-retrieved mean optical depth at some locations are underestimated by a factor of two. A sensitive experiment suggests that these large local differences may result from poor characterization of dust emissions in some areas of the modeled domain. In this case study we successfully simulate the major fine-scale dust generating dynamical processes, explicitly resolving convection and haboob

  8. Characterization of high concentration dust generator

    International Nuclear Information System (INIS)

    Shimura, Toichiro; Yokochi, Akira

    1999-01-01

    This paper describes the development of fluidized bed type high concentration dust generator that keeps for long period dust concentration range of about 10 mg/m 3 for the study of working place monitoring system and evaluation of respirator. The generator is keeping constant powder in fluidized bed for keeping the dust concentration. It is necessary to keep constant feeding rate of powder in order to keep the quantity of dust in the fluidized bed. Our generator enables to obtain constant feeding rate by a screw feeder and by using mixed powder with fluidising particles (glass beads) before feeding. The generator produces high concentration dust of 11.3 mg/m 3 ± 1.0 mg/m 3 for about 5 hours and keeps the dust size 4.2-4.6 μm in mass median aerodynamic diameter with reasonable reproducibility. (author)

  9. Molecules and dust in Cassiopeia A

    DEFF Research Database (Denmark)

    Biscaro, Chiara; Cherchneff, Isabelle

    2016-01-01

    We study the dust evolution in the supernova remnant Cassiopeia A. We follow the processing of dust grains that formed in the Type II-b supernova ejecta by modelling the sputtering of grains. The dust is located in dense ejecta clumps that are crossed by the reverse shock. We also investigate......-rich clumps that correspond to the outermost carbon-rich ejecta zone. We consider the various dust components that form in the supernova, several reverse shock velocities and inter-clump gas temperatures, and derive grain-size distributions and masses for the dust as a function of time. Both non...... and size, and the shock velocity in the clump. A Type II-b SN forms small grains that are sputtered within the clumps and in the inter-clump medium. For Cas A, silicate grains do not survive thermal sputtering in the inter-clump medium, while alumina, silicon carbide, and carbon dust may survive...

  10. Active Dust Experiment in the Mesosphere

    International Nuclear Information System (INIS)

    Norberg, Carol; Pellinen-Wannberg, Asta

    2008-01-01

    The mesosphere stretches from an altitude of about 50 to 90 km above the Earth's surface. Meteors entering the Earth's atmosphere are believed to ablate and hence give rise to a thin layer of dust particles in the upper part of the Earth's mesosphere. It seems that the dust is most dense in a layer that lies between 80 and 90 km. The dust particles are thought to have sizes of a few to tens of nanometers. Efforts have been made to measure these particles using rockets and radar techniques with limited success. We propose to release dust into the mesosphere over northern Sweden at a height of about 90 km and observe the released dust using the EISCAT radar system. The dust will be launched from the Swedish Space Corporation Esrange Space Centre on a single-stage Improved-Orion rocket that will be launched so that its flight path will be in the radar field of view.

  11. Dust observations by PFS on Mars Express

    Science.gov (United States)

    Zasova, L. V.; Formisano, V.; Moroz, V. I.; Grassi, D.; Ignatiev, N. I.; Blecka, M. I.; Maturilli, A.; Palomba, E.; Piccioni, G.; Pfs Team

    Dust is always present in the Martian atmosphere with opacity, which changes from values below 0.1 (at 9 μ m) up to several units during the dust storms. From the thermal IR (LW channel of PFS) the dust opacity is retrieved in a self consistent way together with the temperature profile from the same spectrum A preliminary investigation along the orbit, which comes through Hellas, shows that the value of dust opacity anticorrelates with surface altitude. From -70 to +25 of latitude the vertical dust distribution follows the exponential low with the scale of 12 km, which corresponds to the gaseous scale height near noon and indicates for well mixed condition. The dust opacity, corresponding to the zero surface altitude, is found of 0.25+-0.05. More detailed investigations of all available data will be presented, including analysis of both short- and long- wavelength spectra of PFS.

  12. Formation and dissociation of dust molecules in dusty plasma

    International Nuclear Information System (INIS)

    Yan Jia; Feng Fan; Liu Fucheng; Dong Lifang; He Yafeng

    2016-01-01

    Dust molecules are observed in a dusty plasma experiment. By using measurements with high spatial resolution, the formation and dissociation of the dust molecules are studied. The ion cloud in the wake of an upper dust grain attracts the lower dust grain nearby. When the interparticle distance between the upper dust grain and the lower one is less than a critical value, the two dust grains would form a dust molecule. The upper dust grain always leads the lower one as they travel. When the interparticle distance between them is larger than the critical value, the dust molecule would dissociate. (paper)

  13. Trace metals in urban road dust

    International Nuclear Information System (INIS)

    Randazzo, Loredana Antonella; Dongarra, Gaetano; Manno, Emanuela; Varrica, Daniela

    2006-01-01

    Heavy metals associated with urban road dust is a matter for concern as they may have serious effects on biological systems. The bioavailability and potential toxicity of metals bound to urban dust is related to the specific chemical form of the element. In the present article are reported the determinations and chemical speciation of As, Ba, Cr, Cu, Mo, Ni, Pb and Zn in six samples of road dust collected within the urban centre and the outskirts of Palermo [it

  14. Cylindrical dust acoustic waves with transverse perturbation

    International Nuclear Information System (INIS)

    Xue Jukui

    2003-01-01

    The nonlinear dust acoustic waves in dusty plasmas with the combined effects of bounded cylindrical geometry and the transverse perturbation are studied. Using the perturbation method, a cylindrical Kadomtsev-Petviashvili (CKP) equation that describes the dust acoustic waves is deduced for the first time. A particular solution of this CKP equation is also obtained. It is shown that the dust acoustic solitary waves can exist in the CKP equation

  15. The control and prevention of dust explosions

    Energy Technology Data Exchange (ETDEWEB)

    1982-01-01

    Papers presented discussed: explosion characteristics and hybrid mixtures explosion characteristics and influencing factors, propagation of dust explosions in ducts, prevention of dust explosions, desensitization, explosion-proof type of construction, explosion pressure relief, optical flame barriers, slide-valves for explosion protection, Ventex explosion barrier valves, grinding and mixing plants, spray driers, dust explosions in silos, and explosion-proof bucket elevators. One paper has been abstracted separately.

  16. [Particle numbers in classified sizes of roadside dust caused by studded tires in the air at different heights from the pavement surface].

    Science.gov (United States)

    Sato, T; Niioka, T; Kurasaki, M; Kojima, Y

    1996-07-01

    Increased use of motor vehicles has produced various risks to human health due to air pollution by noxious gases, heavy metals and roadside dust. Since the late 1970s, the wide spread use of studded tires for cars has caused pavement wear, resulting in not only economic losses, but also roadside air pollution in cold and snowy regions in Japan. The most serious environmental problem in Sapporo, a city with heavy snowfall, in the 1980s, was roadside dust derived from studded tires. The inhabitants suffered from this dust in the early winter and in the early spring when the streets were not covered with snow. To investigate the influence of such roadside dust upon human health, particle numbers in classified sizes of roadside dust were counted after the roadside dust in the air was collected with a device we constructed at 30, 60, 90, 120, 150, and 180 cm above the pavement surface. The results indicated that the concentration of roadside dust in the air did not greatly vary according to the height from the pavement surface. The results also suggested that xenogranuloma, reported in lungs of stray dogs, under roadside dust-pollution conditions such as those examined here, may occur in humans in the future.

  17. Dust control at Yucca Mountain project

    International Nuclear Information System (INIS)

    Kissell, F.; Jurani, R.; Dresel, R.; Reaux, C.

    1999-01-01

    This report describes actions taken to control silica dust at the Yucca Mountain Exploratory Studies Facility, a tunnel located in Southern Nevada that is part of a scientific program to determine site suitability for a potential nuclear waste repository. The rock is a volcanic tuff containing significant percentages of both quartz and cristobalite. Water use for dust control was limited because of scientific test requirements, and this limitation made dust control a difficult task. Results are reported for two drifts, called the Main Loop Drift and the Cross Drift. In the Main Loop Drift, dust surveys and tracer gas tests indicated that air leakage from the TBM head, the primary ventilation duct, and movement of the conveyor belt were all significant sources of dust. Conventional dust control approaches yielded no significant reductions in dust levels. A novel alternative was to install an air cleaning station on a rear deck of the TBM trailing gear. It filtered dust from the contaminated intake air and discharged clean air towards the front of the TBM. The practical effect was to produce dust levels below the exposure limit for all TBM locations except close to the head. In the Cross Drift, better ventilation and an extra set of dust seals on the TBM served to cut down the leakage of dust from the TBM cutter head. However, the conveyor belt was much dustier than the belt in the main loop drift. The problem originated with dirt on the bottom of the belt return side and much spillage from the belt top side. Achieving lower dust levels in hard rock tunneling operations will require new approaches as well as a more meticulous application of existing technology. Planning for dust control will require specific means to deal with dust that leaks from the TBM head, dust that originates with leaky ventilation systems, and dust that comes from conveyor belts. Also, the application of water could be more efficient if automatic controls were used to adjust the water flow

  18. Beryllium dust generation resulting from plasma bombardment

    International Nuclear Information System (INIS)

    Doerner, R.; Mays, C.

    1997-01-01

    The beryllium dust resulting from erosion of beryllium samples subjected to plasma bombardment has been measured in PISCES-B. Loose surface dust was found to be uniformly distributed throughout the device and accounts for 3% of the eroded material. A size distribution measurement of the loose surface dust shows an increasing number of particles with decreasing diameter. Beryllium coatings on surfaces with a line of sight view of the target interaction region account for an additional 33% of the eroded beryllium material. Flaking of these surface layers is observed and is thought to play a significant role in dust generation inside the vacuum vessel. (orig.)

  19. Control of dust production in ITER

    International Nuclear Information System (INIS)

    Rodriguez-Rodrigo, L.; Ciattaglia, S.; Elbez-Uzan, J.

    2006-01-01

    In the last years dust has been observed in a number of fusion devices and is being studied more in detail for understanding in particular the physical phenomena related to its formation, its composition, physical and chemical characteristics, and the amount of produced dust. The extrapolation of dust formation to ITER predicts (with large error bars), a large mass of dust production with a scattered size distribution. To evaluate the impact of dust on safety, assumptions have also been made on radionuclide inventory, and mobility in off-normal events, as well as any postulated contributions the dust may make to effluents or accidental releases. Solid activation products in structures are generally not readily mobilisable in incidental and accidental situations, so that activated dust, tritium and activated corrosions products are the important in-vessel source terms in postulated scenarios that assume a mobilisation and release of some fraction of this inventory. Such a release would require the simultaneous leak or bypass of several robust confinement barriers. Further concerns for dust may be the potential for chemical reactions between dust and coolant in the event of an in-vessel leak, and the theoretical possibility of a dust explosion, either of which could in principle cause a pressure rise that challenges one or more of the confinement barriers. Although these hazards can - and will - be controlled by other measures in the ITER design, application of the principle of Defence in Depth dictates that the dust inventory should also be minimised and controlled to prevent the potential hazard. A well-coordinated R-and-D programme is required to support this dust production control. This document provides from the safety point of view, an overview of existing data given in '' Dossier d'Options de Surete '', the first safety report presented in 2001 to the French Safety Authorities, and ITER documents; it also gathers information on status of studies on activated

  20. Cold urticaria. Dissociation of cold-evoked histamine release and urticara following cold challenge.

    Science.gov (United States)

    Keahey, T M; Greaves, M W

    1980-02-01

    Nine patients with acquired cold urticaria were studied to assess the effects of beta-adrenergic agents, xanthines, and corticosteroids on cold-evoked histamine release from skin in vivo. The patients, in all of whom an immediate urticarial response developed after cooling of the forearm, demonstrated release of histamine into the venous blood draining that forearm. Following treatment with aminophylline and albuterol in combination or prednisone alone, suppression of histamine release occurred in all but one patient. In some patients, this was accompanied by a subjective diminution in pruritus or buring, but there was no significant improvement in the ensuing edema or erythema. In one patient, total suppression of histamine release was achieved without any effect on whealing and erythema in response to cold challenge. Our results suggest that histamine is not central to the pathogenesis of vascular changes in acquired cold urticaria.

  1. Cold acclimation and cognitive performance: A review.

    Science.gov (United States)

    Jones, Douglas M; Bailey, Stephen P; Roelands, Bart; Buono, Michael J; Meeusen, Romain

    2017-12-01

    Athletes, occupational workers, and military personnel experience cold temperatures through cold air exposure or cold water immersion, both of which impair cognitive performance. Prior work has shown that neurophysiological pathways may be sensitive to the effects of temperature acclimation and, therefore, cold acclimation may be a potential strategy to attenuate cold-induced cognitive impairments for populations that are frequently exposed to cold environments. This review provides an overview of studies that examine repeated cold stress, cold acclimation, and measurements of cognitive performance to determine whether or not cold acclimation provides beneficial protection against cold-induced cognitive performance decrements. Studies included in this review assessed cognitive measures of reaction time, attention, logical reasoning, information processing, and memory. Repeated cold stress, with or without evidence of cold acclimation, appears to offer no added benefit of improving cognitive performance. However, research in this area is greatly lacking and, therefore, it is difficult to draw any definitive conclusions regarding the use of cold acclimation to improve cognitive performance during subsequent cold exposures. Given the current state of minimal knowledge on this topic, athletes, occupational workers, and military commands looking to specifically enhance cognitive performance in cold environments would likely not be advised to spend the time and effort required to become acclimated to cold. However, as more knowledge becomes available in this area, recommendations may change. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Integrative Analysis of Desert Dust Size and Abundance Suggests Less Dust Climate Cooling

    Science.gov (United States)

    Kok, Jasper F.; Ridley, David A.; Zhou, Qing; Miller, Ron L.; Zhao, Chun; Heald, Colette L.; Ward, Daniel S.; Albani, Samuel; Haustein, Karsten

    2017-01-01

    Desert dust aerosols affect Earths global energy balance through interactions with radiation, clouds, and ecosystems. But the magnitudes of these effects are so uncertain that it remains unclear whether atmospheric dust has a net warming or cooling effect on global climate. Consequently, it is still uncertain whether large changes in atmospheric dust loading over the past century have slowed or accelerated anthropogenic climate change, and the climate impact of possible future alterations in dust loading is similarly disputed. Here we use an integrative analysis of dust aerosol sizes and abundance to constrain the climatic impact of dust through direct interactions with radiation. Using a combination of observational, experimental, and model data, we find that atmospheric dust is substantially coarser than represented in current climate models. Since coarse dust warms global climate, the dust direct radiative effect (DRE) is likely less cooling than the 0.4 W m superscript 2 estimated by models in a current ensemble. We constrain the dust DRE to -0.20 (-0.48 to +0.20) W m superscript 2, which suggests that the dust DRE produces only about half the cooling that current models estimate, and raises the possibility that dust DRE is actually net warming the planet.

  3. Carbohydrate and protein contents of grain dusts in relation to dust morphology.

    Science.gov (United States)

    Dashek, W V; Olenchock, S A; Mayfield, J E; Wirtz, G H; Wolz, D E; Young, C A

    1986-01-01

    Grain dusts contain a variety of materials which are potentially hazardous to the health of workers in the grain industry. Because the characterization of grain dusts is incomplete, we are defining the botanical, chemical, and microbial contents of several grain dusts collected from grain elevators in the Duluth-Superior regions of the U.S. Here, we report certain of the carbohydrate and protein contents of dusts in relation to dust morphology. Examination of the gross morphologies of the dusts revealed that, except for corn, each dust contained either husk or pericarp (seed coat in the case of flax) fragments in addition to respirable particles. When viewed with the light microscope, the fragments appeared as elongated, pointed structures. The possibility that certain of the fragments within corn, settled, and spring wheat were derived from cell walls was suggested by the detection of pentoses following colorimetric assay of neutralized 2 N trifluoroacetic acid hydrolyzates of these dusts. The presence of pentoses together with the occurrence of proteins within water washings of grain dusts suggests that glycoproteins may be present within the dusts. With scanning electron microscopy, each dust was found to consist of a distinct assortment of particles in addition to respirable particles. Small husk fragments and "trichome-like" objects were common to all but corn dust. Images FIGURE 4. FIGURE 5. PMID:3709476

  4. The turbulent life of dust grains in the supernova-driven, multiphase interstellar medium

    Science.gov (United States)

    Peters, Thomas; Zhukovska, Svitlana; Naab, Thorsten; Girichidis, Philipp; Walch, Stefanie; Glover, Simon C. O.; Klessen, Ralf S.; Clark, Paul C.; Seifried, Daniel

    2017-06-01

    Dust grains are an important component of the interstellar medium (ISM) of galaxies. We present the first direct measurement of the residence times of interstellar dust in the different ISM phases, and of the transition rates between these phases, in realistic hydrodynamical simulations of the multiphase ISM. Our simulations include a time-dependent chemical network that follows the abundances of H+, H, H2, C+ and CO and take into account self-shielding by gas and dust using a tree-based radiation transfer method. Supernova explosions are injected either at random locations, at density peaks, or as a mixture of the two. For each simulation, we investigate how matter circulates between the ISM phases and find more sizeable transitions than considered in simple mass exchange schemes in the literature. The derived residence times in the ISM phases are characterized by broad distributions, in particular for the molecular, warm and hot medium. The most realistic simulations with random and mixed driving have median residence times in the molecular, cold, warm and hot phase around 17, 7, 44 and 1 Myr, respectively. The transition rates measured in the random driving run are in good agreement with observations of Ti gas-phase depletion in the warm and cold phases in a simple depletion model. ISM phase definitions based on chemical abundance rather than temperature cuts are physically more meaningful, but lead to significantly different transition rates and residence times because there is no direct correspondence between the two definitions.

  5. 77 FR 43117 - Meeting of the Cold War Advisory Committee for the Cold War Theme Study

    Science.gov (United States)

    2012-07-23

    ... the Cold War Advisory Committee for the Cold War Theme Study AGENCY: National Park Service, Interior... Committee Act, 5 U.S.C. Appendix, that the Cold War Advisory Committee for the Cold War Theme Study will... National Park Service (NPS) concerning the Cold War Theme Study. DATES: The teleconference meeting will be...

  6. The Electric Environment of Martian Dust Devils

    Science.gov (United States)

    Barth, E. L.; Farrell, W. M.; Rafkin, S. C.

    2017-12-01

    While Martian dust devils have been monitored through decades of observations, we have yet to study their possible electrical effects from in situ instrumentation. However, evidence for the existence of active electrodynamic processes on Mars is provided by laboratory studies of analog material and field campaigns of dust devils on Earth. We have enabled our Mars regional scale atmospheric model (MRAMS) to estimate an upper limit on electric fields generated through dust devil circulations by including charged particles as defined from the Macroscopic Triboelectric Simulation (MTS) code. MRAMS is used to investigate the complex physics of regional, mesoscale, and microscale atmospheric phenomena on Mars; it is a 3-D, nonhydrostatic model, which permits the simulation of atmospheric flows with large vertical accelerations, such as dust devils. MTS is a 3-D particle code which quantifies charging associated with swirling, mixing dust grains; grains of pre-defined sizes and compositions are placed in a simulation box and allowed to move under the influence of winds and gravity. Our MRAMS grid cell size makes our results most applicable to dust devils of a few hundred meters in diameter. We have run a number of simulations to understand the sensitivity of the electric field strength to the particle size and abundance and the amount of charge on each dust grain. We find that Efields can indeed develop in Martian dust convective features via dust grain filtration effects. The overall value of these E-fields is strongly dependent upon dust grain size, dust load, and lifting efficiency, and field strengths can range from 100s of mV/m to 10s of kV/m.

  7. A SPITZER c2d LEGACY SURVEY TO IDENTIFY AND CHARACTERIZE DISKS WITH INNER DUST HOLES

    International Nuclear Information System (INIS)

    Merin, Bruno; Brown, Joanna M.; Herczeg, Gregory J.; Van Dishoeck, Ewine F.; Oliveira, Isa; Lahuis, Fred; Bottinelli, Sandrine; Augereau, Jean-Charles; Olofsson, Johan; Evans, Neal J.; Harvey, Paul M.; Cieza, Lucas; Spezzi, Loredana; Prusti, Timo; Alcala, Juan M.; Blake, Geoffrey A.; Bayo, Amelia; Geers, Vincent G.; Walter, Frederick M.; Chiu, Kuenley

    2010-01-01

    Understanding how disks dissipate is essential to studies of planet formation. However, identifying exactly how dust and gas dissipate is complicated due to the difficulty of finding objects that are clearly in the transition phase of losing their surrounding material. We use Spitzer Infrared Spectrograph (IRS) spectra to examine 35 photometrically selected candidate cold disks (disks with large inner dust holes). The infrared spectra are supplemented with optical spectra to determine stellar and accretion properties and 1.3 mm photometry to measure disk masses. Based on detailed spectral energy distribution modeling, we identify 15 new cold disks. The remaining 20 objects have IRS spectra that are consistent with disks without holes, disks that are observed close to edge-on, or stars with background emission. Based on these results, we determine reliable criteria to identify disks with inner holes from Spitzer photometry, and examine criteria already in the literature. Applying these criteria to the c2d surveyed star-forming regions gives a frequency of such objects of at least 4% and most likely of order 12% of the young stellar object population identified by Spitzer. We also examine the properties of these new cold disks in combination with cold disks from the literature. Hole sizes in this sample are generally smaller than in previously discovered disks and reflect a distribution in better agreement with exoplanet orbit radii. We find correlations between hole size and both disk and stellar masses. Silicate features, including crystalline features, are present in the overwhelming majority of the sample, although the 10 μm feature strength above the continuum declines for holes with radii larger than ∼7 AU. In contrast, polycyclic aromatic hydrocarbons are only detected in 2 out of 15 sources. Only a quarter of the cold disk sample shows no signs of accretion, making it unlikely that photoevaporation is the dominant hole-forming process in most cases.

  8. Lyα Profile, Dust, and Prediction of Lyα Escape Fraction in Green Pea Galaxies

    Science.gov (United States)

    Yang, Huan; Malhotra, Sangeeta; Gronke, Max; Rhoads, James E.; Leitherer, Claus; Wofford, Aida; Jiang, Tianxing; Dijkstra, Mark; Tilvi, V.; Wang, Junxian

    2017-08-01

    We studied Lyman-α (Lyα) escape in a statistical sample of 43 Green Peas with HST/COS Lyα spectra. Green Peas are nearby star-forming galaxies with strong [O III]λ5007 emission lines. Our sample is four times larger than the previous sample and covers a much more complete range of Green Pea properties. We found that about two-thirds of Green Peas are strong Lyα line emitters with rest-frame Lyα equivalent width > 20 \\mathringA . The Lyα profiles of Green Peas are diverse. The Lyα escape fraction, defined as the ratio of observed Lyα flux to intrinsic Lyα flux, shows anti-correlations with a few Lyα kinematic features—both the blue peak and red peak velocities, the peak separations, and the FWHM of the red portion of the Lyα profile. Using properties measured from Sloan Digital Sky Survey optical spectra, we found many correlations—the Lyα escape fraction generally increases at lower dust reddening, lower metallicity, lower stellar mass, and higher [O III]/[O II] ratio. We fit their Lyα profiles with the H I shell radiative transfer model and found that the Lyα escape fraction is anti-correlated with the best-fit N H I . Finally, we fit an empirical linear relation to predict {f}{esc}{Lyα } from the dust extinction and Lyα red peak velocity. The standard deviation of this relation is about 0.3 dex. This relation can be used to isolate the effect of intergalactic medium (IGM) scatterings from Lyα escape and to probe the IGM optical depth along the line of sight of each z> 7 Lyα emission-line galaxy in the James Webb Space Telescope era.

  9. Spectroscopy with cold and ultra-cold neutrons

    Directory of Open Access Journals (Sweden)

    Abele Hartmut

    2015-01-01

    Full Text Available We present two new types of spectroscopy methods for cold and ultra-cold neutrons. The first method, which uses the R×B drift effect to disperse charged particles in a uniformly curved magnetic field, allows to study neutron β-decay. We aim for a precision on the 10−4 level. The second method that we refer to as gravity resonance spectroscopy (GRS allows to test Newton’s gravity law at short distances. At the level of precision we are able to provide constraints on any possible gravity-like interaction. In particular, limits on dark energy chameleon fields are improved by several orders of magnitude.

  10. HERSCHEL OBSERVATIONS OF GAS AND DUST IN THE UNUSUAL 49 Ceti DEBRIS DISK

    Energy Technology Data Exchange (ETDEWEB)

    Roberge, A. [Exoplanets and Stellar Astrophysics Laboratory, NASA Goddard Space Flight Center, Code 667, Greenbelt, MD 20771 (United States); Kamp, I. [Kapteyn Astronomical Institute, University of Groningen, 9700 AV Groningen (Netherlands); Montesinos, B. [Departamento de Astrofisica, Centro de Astrobiologia (INTA-CSIC), ESAC Campus, PO Box 78, E-28691 Villanueva de la Canada, Madrid (Spain); Dent, W. R. F. [ALMA, Avda Apoquindo 3846, Piso 19, Edificio Alsacia, Las Condes, Santiago (Chile); Meeus, G.; Eiroa, C. [Departmento Fisica Teorica, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Donaldson, J. K. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Olofsson, J. [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117, Heidelberg (Germany); Moor, A. [Konkoly Observatory of the Hungarian Academy of Sciences, P.O. Box 67, H-1525 Budapest (Hungary); Augereau, J.-C.; Thi, W.-F. [UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d' Astrophysique de Grenoble, UMR 5274, F-38041, Grenoble (France); Howard, C.; Sandell, G. [SOFIA-USRA, NASA Ames Research Center, Building N232, PO Box 1, Moffett Field, CA 94035 (United States); Ardila, D. R. [NASA Herschel Science Center, California Institute of Technology, 1200 E. California Blvd., Mail Stop 220-6, Pasadena, CA 91125 (United States); Woitke, P., E-mail: Aki.Roberge@nasa.gov [University of Vienna, Department of Astronomy, Tuerkenschanzstr. 17, A-1180, Vienna (Austria)

    2013-07-01

    We present far-IR/sub-mm imaging and spectroscopy of 49 Ceti, an unusual circumstellar disk around a nearby young A1V star. The system is famous for showing the dust properties of a debris disk, but the gas properties of a low-mass protoplanetary disk. The data were acquired with the Herschel Space Observatory PACS and SPIRE instruments, largely as part of the ''Gas in Protoplanetary Systems'' (GASPS) Open Time Key Programme. Disk dust emission is detected in images at 70, 160, 250, 350, and 500 {mu}m; 49 Cet is significantly extended in the 70 {mu}m image, spatially resolving the outer dust disk for the first time. Spectra covering small wavelength ranges centered on eight atomic and molecular emission lines were obtained, including [O I] 63 {mu}m and [C II] 158 {mu}m. The C II line was detected at the 5{sigma} level-the first detection of atomic emission from the disk. No other emission lines were seen, despite the fact that the O I line is the brightest one observed in Herschel protoplanetary disk spectra. We present an estimate of the amount of circumstellar atomic gas implied by the C II emission. The new far-IR/sub-mm data fills in a large gap in the previous spectral energy distribution (SED) of 49 Cet. A simple model of the new SED confirms the two-component structure of the disk: warm inner dust and cold outer dust that produces most of the observed excess. Finally, we discuss preliminary thermochemical modeling of the 49 Cet gas/dust disk and our attempts to match several observational results simultaneously. Although we are not yet successful in doing so, our investigations shed light on the evolutionary status of the 49 Cet gas, which might not be primordial gas but rather secondary gas coming from comets.

  11. GLOBAL STAR FORMATION RATES AND DUST EMISSION OVER THE GALAXY INTERACTION SEQUENCE

    Energy Technology Data Exchange (ETDEWEB)

    Lanz, Lauranne; Zezas, Andreas; Smith, Howard A.; Ashby, Matthew L. N.; Fazio, Giovanni G.; Hernquist, Lars [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Brassington, Nicola [School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield, AL10 9AB (United Kingdom); Da Cunha, Elisabete [Max Planck Institute for Astronomy (MPIA), Koenigstuhl 17, D-69117, Heidelberg (Germany); Hayward, Christopher C. [Heidelberger Institut fuer Theoretische Studien, Schloss-Wolfsbrunnenweg 35, D-69118, Heidelberg (Germany); Jonsson, Patrik, E-mail: llanz@head.cfa.harvard.edu [Space Exploration Technologies, 1 Rocket Road, Hawthorne, CA 90250 (United States)

    2013-05-01

    We measured and modeled spectral energy distributions (SEDs) in 28 bands from the ultraviolet to the far-infrared (FIR) for 31 interacting galaxies in 14 systems. The sample is drawn from the Spitzer Interacting Galaxy Survey, which probes a range of galaxy interaction parameters at multiple wavelengths with an emphasis on the infrared bands. The subset presented in this paper consists of all galaxies for which FIR Herschel SPIRE observations are publicly available. Our SEDs combine the Herschel photometry with multi-wavelength data from Spitzer, GALEX, Swift UVOT, and 2MASS. While the shapes of the SEDs are broadly similar across our sample, strongly interacting galaxies typically have more mid-infrared emission relative to their near-infrared and FIR emission than weakly or moderately interacting galaxies. We modeled the full SEDs to derive host galaxy star formation rates (SFRs), specific star formation rates (sSFRs), stellar masses, dust temperatures, dust luminosities, and dust masses. We find increases in the dust luminosity and mass, SFR, and cold (15-25 K) dust temperature as the interaction progresses from moderately to strongly interacting and between non-interacting and strongly interacting galaxies. We also find increases in the SFR between weakly and strongly interacting galaxies. In contrast, the sSFR remains unchanged across all the interaction stages. The ultraviolet photometry is crucial for constraining the age of the stellar population and the SFR, while dust mass is primarily determined by SPIRE photometry. The SFR derived from the SED modeling agrees well with rates estimated by proportionality relations that depend on infrared emission.

  12. Hesitant birth of cold fusion

    International Nuclear Information System (INIS)

    Bockris, J.O.

    1992-01-01

    John O'M. Bockris, a distinguished chemistry professor at Texas A ampersand M University, finds the reaction to the announcement of the discovery of cold fusion curious. Two years earlier, he notes, there had been a comparable announcement concerning the discovery of high-temperature superconductivity; it received favorable press coverage for months. The cold-fusion announcement, on the other hand, was met with dour skepticism. When other researchers failed in efforts to duplicate the findings of Martin Fleischmann and B. Stanley Pons, Bockris says, the two scientists were held up to ridicule. Bockris says he found a deep emotional opposition to cold fusion, even within his own department and university. This opposition is fueled in large part, he believes, by big science and the hot fusion lobby. A key indicator of cold fusion is the presence of tritium, Brockis claims. At Texas A ampersand M, large amounts of tritium have been found in some experiments; this also has occurred in experiments at more than 40 laboratories in nine countries, he says. Excess heat production is more difficult to attain, he acknowledges. The cold-fusion controversy has uncovered some unflattering characteristics of the scientific community, Bockris says. Among them are: scientists are no less driven by emotion that business people or politicians; research funding decisions serve to perpetuate the goals of politically powerful interest groups; and ideas have great inertia once planted in a scientist's mind

  13. Steel weldability. Underbead cold cracking

    International Nuclear Information System (INIS)

    Marquet, F.; Defourny, J.; Bragard, A.

    1977-01-01

    The problem of underbead cold cracking has been studied by the implant technique. This approach allows to take into account in a quantitative manner the different factors acting on the cold cracking phenomenon: structure under the weld bead, level of restraint, hydrogen content in the molten metal. The influence of the metallurgical factors depending from the chemical composition of the steel has been examined. It appeared that carbon equivalent is an important factor to explain cold cracking sensitivity but that it is not sufficient to characterize the steel. The results have shown that vanadium may have a deleterious effect on the resistance to cold cracking when the hydrogen content is high and that small silicon additions are beneficient. The influence of the diffusible hydrogen content has been checked and the important action of pre- and postheating has been shown. These treatments allow the hydrogen to escape from the weld before the metal has been damaged. Some inclusions (sulphides) may also decrease the influence of hydrogen. A method based on the implant tests has been proposed which allows to choose and to control safe welding conditions regarding cold cracking

  14. The dust acoustic wave in a bounded dusty plasma with strong electrostatic interactions between dust grains

    International Nuclear Information System (INIS)

    Shukla, Nitin; Shukla, P.K.

    2011-01-01

    The dispersion relation for the dust acoustic wave (DAW) in an unmagnetized dusty plasma cylindrical waveguide is derived, accounting for strong electrostatic interactions between charged dust grains. It is found that the boundary effect limits the radial extent of the DAW. The present result should be helpful for understanding the frequency spectrum of the DAW in a dusty plasma waveguide with strongly coupled charged dust grains. - Highlights: → We study the dust acoustic wave (DAW) in a bounded plasma. → We account for interactions between dust grains. → The boundary effect limits the radial extent of the DAW.

  15. GRB 130606A AS A PROBE OF THE INTERGALACTIC MEDIUM AND THE INTERSTELLAR MEDIUM IN A STAR-FORMING GALAXY IN THE FIRST Gyr AFTER THE BIG BANG

    Energy Technology Data Exchange (ETDEWEB)

    Chornock, Ryan; Berger, Edo; Lunnan, Ragnhild; Drout, Maria R.; Fong Wenfai; Laskar, Tanmoy [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Fox, Derek B. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Roth, Katherine C., E-mail: rchornock@cfa.harvard.edu [Gemini Observatory, 670 North Aohoku Place, Hilo, HI 96720 (United States)

    2013-09-01

    We present high signal-to-noise ratio Gemini and MMT spectroscopy of the optical afterglow of the gamma-ray burst (GRB) 130606A at redshift z = 5.913, discovered by Swift. This is the first high-redshift GRB afterglow to have spectra of comparable quality to those of z Almost-Equal-To 6 quasars. The data exhibit a smooth continuum at near-infrared wavelengths that is sharply cut off blueward of 8410 A due to absorption from Ly{alpha} at redshift z Almost-Equal-To 5.91, with some flux transmitted through the Ly{alpha} forest between 7000 and 7800 A. We use column densities inferred from metal absorption lines to constrain the metallicity of the host galaxy between a lower limit of [Si/H] {approx}> -1.7 and an upper limit of [S/H] {approx}< -0.5 set by the non-detection of S II absorption. We demonstrate consistency between the dramatic evolution in the transmission fraction of Ly{alpha} seen in this spectrum over the redshift range z = 4.9-5.85 with that previously measured from observations of high-redshift quasars. There is an extended redshift interval of {Delta}z = 0.12 in the Ly{alpha} forest at z = 5.77 with no detected transmission, leading to a 3{sigma} upper limit on the mean Ly{alpha} transmission fraction of {approx}<0.2% (or {tau}{sub GP}{sup eff} (Ly{alpha}) > 6.4). This is comparable to the lowest-redshift Gunn-Peterson troughs found in quasar spectra. Some Ly{beta} and Ly{gamma} transmission is detected in this redshift window, indicating that it is not completely opaque, and hence that the intergalactic medium (IGM) is nonetheless mostly ionized at these redshifts. We set a 2{sigma} upper limit of 0.11 on the neutral fraction of the IGM at the redshift of the GRB from the lack of a Ly{alpha} red damping wing, assuming a model with a constant neutral density. GRB 130606A thus for the first time realizes the promise of GRBs as probes of the first galaxies and cosmic reionization.

  16. Radioactive dust in the air

    Energy Technology Data Exchange (ETDEWEB)

    Yano, N

    1956-01-01

    An electric precipitator is used to collect dust in the air because its collection efficiency for radioactive substances is up to 10 times that of the impactor of filter-paper types. About 10 cu m of air is filtered during 5 hours, and the trapped dust is measured more than 24 hours after collection to avoid the influence of naturally active substances. The average radioactivity of the air is approximately 10/sup -16/ c/cc. During the period of observation 4 peaks occurred. The dates and maximum levels of artificial activity, respectively, are November 4 to 10, 1954, 1.2 x 10/sup -7/ uc/l; April 11 to 13, 1955, 4.3 x 10/sup -8/ uc/l; November 25 to 28, 1955, maximum unknown; and March 22 to 25, 1956, 1.- x 10/sup -7/ uc/l. The presumed dates and places of detonation corresponding to the peaks are October 31, 1954 northwest of Japan; March 29, 1955, Nevada, US; November 22, 1955, near L. Baikal, USSR; and March 13 to 15, 1956 unknown.

  17. THE 1.1 mm CONTINUUM SURVEY OF THE SMALL MAGELLANIC CLOUD: PHYSICAL PROPERTIES AND EVOLUTION OF THE DUST-SELECTED CLOUDS

    Energy Technology Data Exchange (ETDEWEB)

    Takekoshi, Tatsuya; Minamidani, Tetsuhiro; Sorai, Kazuo [Department of Cosmosciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Komugi, Shinya; Muller, Erik; Mizuno, Norikazu; Kawamura, Akiko; Ezawa, Hajime [Chile Observatory, National Astronomical Observatory of Japan (NAOJ), National Institutes of Natural Sciences (NINS), 2-21-1, Osawa, Mitaka, Tokyo 181-8588 (Japan); Kohno, Kotaro [Institute of Astronomy, The University of Tokyo, 2-21-1, Osawa, Mitaka, Tokyo 181-0015 (Japan); Tosaki, Tomoka [Joetsu University of Education, Joetsu, Niigata 943-8512 (Japan); Onishi, Toshikazu [Department of Physical Science, Osaka Prefecture University, Gakuen 1-1, Sakai, Osaka 599-8531 (Japan); Fukui, Yasuo [Department of Astrophysics, Nagoya University, Chikusa-ku, Nagoya 464-8602 (Japan); Oshima, Tai; Kawabe, Ryohei [Nobeyama Radio Observatory, National Astronomical Observatory of Japan (NAOJ), National Institutes of Natural Sciences (NINS), 462-2, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305 (Japan); Scott, Kimberly S.; Austermann, Jason E.; Wilson, Grant W. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Matsuo, Hiroshi [Department of Astronomical Science, School of Physical Science, SOKENDAI (The Graduate University for Advanced Studies), 2-21-1, Osawa, Mitaka, Tokyo 181-8588 (Japan); Aretxaga, Itziar; Hughes, David H. [Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE), 72000 Puebla (Mexico); and others

    2017-01-20

    The first 1.1 mm continuum survey toward the Small Magellanic Cloud (SMC) was performed using the AzTEC instrument installed on the ASTE 10 m telescope. This survey covered 4.5 deg{sup 2} of the SMC with 1 σ noise levels of 5–12 mJy beam{sup −1}, and 44 extended objects were identified. The 1.1 mm extended emission has good spatial correlation with Herschel 160 μ m, indicating that the origin of the 1.1 mm extended emission is thermal emission from a cold dust component. We estimated physical properties using the 1.1 mm and filtered Herschel data (100, 160, 250, 350, and 500 μ m). The 1.1 mm objects show dust temperatures of 17–45 K and gas masses of 4 × 10{sup 3}–3 × 10{sup 5} M {sub ⊙}, assuming single-temperature thermal emission from the cold dust with an emissivity index, β , of 1.2 and a gas-to-dust ratio of 1000. These physical properties are very similar to those of giant molecular clouds (GMCs) in our galaxy and the Large Magellanic Cloud. The 1.1 mm objects also displayed good spatial correlation with the Spitzer 24 μ m and CO emission, suggesting that the 1.1 mm objects trace the dense gas regions as sites of massive star formation. The dust temperature of the 1.1 mm objects also demonstrated good correlation with the 24 μ m flux connected to massive star formation. This supports the hypothesis that the heating source of the cold dust is mainly local star-formation activity in the 1.1 mm objects. The classification of the 1.1 mm objects based on the existence of star-formation activity reveals the differences in the dust temperature, gas mass, and radius, which reflects the evolution sequence of GMCs.

  18. The early summertime Saharan heat low: sensitivity of the radiation budget and atmospheric heating to water vapour and dust aerosol

    Science.gov (United States)

    Alamirew, Netsanet K.; Todd, Martin C.; Ryder, Claire L.; Marsham, John H.; Wang, Yi

    2018-01-01

    The Saharan heat low (SHL) is a key component of the west African climate system and an important driver of the west African monsoon across a range of timescales of variability. The physical mechanisms driving the variability in the SHL remain uncertain, although water vapour has been implicated as of primary importance. Here, we quantify the independent effects of variability in dust and water vapour on the radiation budget and atmospheric heating of the region using a radiative transfer model configured with observational input data from the Fennec field campaign at the location of Bordj Badji Mokhtar (BBM) in southern Algeria (21.4° N, 0.9° E), close to the SHL core for June 2011. Overall, we find dust aerosol and water vapour to be of similar importance in driving variability in the top-of-atmosphere (TOA) radiation budget and therefore the column-integrated heating over the SHL (˜ 7 W m-2 per standard deviation of dust aerosol optical depth - AOD). As such, we infer that SHL intensity is likely to be similarly enhanced by the effects of dust and water vapour surge events. However, the details of the processes differ. Dust generates substantial radiative cooling at the surface (˜ 11 W m-2 per standard deviation of dust AOD), presumably leading to reduced sensible heat flux in the boundary layer, which is more than compensated by direct radiative heating from shortwave (SW) absorption by dust in the dusty boundary layer. In contrast, water vapour invokes a radiative warming at the surface of ˜ 6 W m-2 per standard deviation of column-integrated water vapour in kg m-2. Net effects involve a pronounced net atmospheric radiative convergence with heating rates on average of 0.5 K day-1 and up to 6 K day-1 during synoptic/mesoscale dust events from monsoon surges and convective cold-pool outflows (haboobs). On this basis, we make inferences on the processes driving variability in the SHL associated with radiative and advective heating/cooling. Depending on the

  19. Cosmic rays, gas and dust in nearby anticentre clouds. I. CO-to-H2 conversion factors and dust opacities

    Science.gov (United States)

    Remy, Q.; Grenier, I. A.; Marshall, D. J.; Casandjian, J. M.

    2017-05-01

    four to six in the cold molecular regions that are well shielded from stellar radiation. Consequently, the XCO factor derived from dust is systematically larger by 30% to 130% than the γ-ray estimate. We also evaluate the average γ-ray XCO factor for each cloud, and find that XCO tends to decrease from diffuse to more compact molecular clouds, as expected from theory. We find XCO factors in the anti-centre clouds close to or below 1020 cm-2 K-1 km-1 s, in agreement with other estimates in the solar neighbourhood. Together, they confirm the long-standing unexplained discrepancy, by a factor of two, between the mean XCO values measured at parsec scales in nearby clouds and those obtained at kiloparsec scale in the Galaxy. Our results also highlight large quantitative discrepancies in 12CO intensities between simulations and observations at low molecular gas densities.

  20. A Climatology of dust emission in northern Africa using surface observations from 1984-2012

    Science.gov (United States)

    Cowie, Sophie; Knippertz, Peter; Marsham, John

    2014-05-01

    The huge quantity of mineral dust emitted annually from northern Africa makes this area crucial to the global dust cycle. Once in the atmosphere, dust aerosols have a significant impact on the global radiation budget, clouds, the carbon cycle and can even act as a fertilizer to rain forests in South America. Current model estimates of dust production from northern Africa are uncertain. At the heart of this problem is insufficient understanding of key dust emitting processes such as haboobs (cold pools generated through evaporation of convective precipitation), low-level jets (LLJs) and dry convection (dust devils and dust plumes). Scarce observations in this region, in particular in the Sahara, make model evaluation difficult. This work uses long-term surface observations from 70 stations situated in the Sahara and Sahel to explore the diurnal, seasonal and geographical variations in dust emission events and thresholds. Quality flags are applied to each station to indicate a day-time bias or gaps in the time period 1984-2012. The frequency of dust emission (FDE) is calculated using the present weather codes (WW) of SYNOP reports, where WW = 07,08,09,30-35 and 98. Thresholds are investigated by estimating the wind speeds for which there is a 25%, 50% and 75% probability of dust emission. The 50% threshold is used to calculate strong wind frequency (SWF) and the diagnostic parameter dust uplift potential (DUP); a thresholded cubic function of wind-speed which quantifies the dust generating power of winds. Stations are grouped into 6 areas (North Algeria, Central Sahara, Egypt, West Sahel, Central Sahel and Sudan) for more in-depth analysis of these parameters. Spatially, thresholds are highest in northern Algeria and lowest in the Sahel around the latitude band 16N-21N. Annual mean FDE is anti-correlated with the threshold, showing the importance of spatial variations in thresholds for mean dust emission. The annual cycles of FDE and SWF for the 6 grouped areas are

  1. Comet Dust After Deep Impact

    Science.gov (United States)

    Wooden, Diane H.; Harker, David E.; Woodward, Charles E.

    2006-01-01

    When the Deep Impact Mission hit Jupiter Family comet 9P/Tempel 1, an ejecta crater was formed and an pocket of volatile gases and ices from 10-30 m below the surface was exposed (A Hearn et aI. 2005). This resulted in a gas geyser that persisted for a few hours (Sugita et al, 2005). The gas geyser pushed dust grains into the coma (Sugita et a1. 2005), as well as ice grains (Schulz et al. 2006). The smaller of the dust grains were submicron in radii (0-25.3 micron), and were primarily composed of highly refractory minerals including amorphous (non-graphitic) carbon, and silicate minerals including amorphous (disordered) olivine (Fe,Mg)2SiO4 and pyroxene (Fe,Mg)SiO3 and crystalline Mg-rich olivine. The smaller grains moved faster, as expected from the size-dependent velocity law produced by gas-drag on grains. The mineralogy evolved with time: progressively larger grains persisted in the near nuclear region, having been imparted with slower velocities, and the mineralogies of these larger grains appeared simpler and without crystals. The smaller 0.2-0.3 micron grains reached the coma in about 1.5 hours (1 arc sec = 740 km), were more diverse in mineralogy than the larger grains and contained crystals, and appeared to travel through the coma together. No smaller grains appeared at larger coma distances later (with slower velocities), implying that if grain fragmentation occurred, it happened within the gas acceleration zone. These results of the high spatial resolution spectroscopy (GEMINI+Michelle: Harker et 4. 2005, 2006; Subaru+COMICS: Sugita et al. 2005) revealed that the grains released from the interior were different from the nominally active areas of this comet by their: (a) crystalline content, (b) smaller size, (c) more diverse mineralogy. The temporal changes in the spectra, recorded by GEMIM+Michelle every 7 minutes, indicated that the dust mineralogy is inhomogeneous and, unexpectedly, the portion of the size distribution dominated by smaller grains has

  2. The management of house dust mite allergies

    NARCIS (Netherlands)

    Bronswijk, van J.E.M.H.; Schober, G.; Kniest, F.M.

    1990-01-01

    A safe and practical home sanitation procedure for the removal of house dust mites (Dermatophagoides pteronyssinus) and their allergens is described. The severity of mite infestation was assessed with the use of the Acarex test, which measures the concentration of guanine in house dust, and all

  3. A rotating dust cloud in general relativity

    International Nuclear Information System (INIS)

    Bonnor, W.B.

    1977-01-01

    An axially symmetric, stationary exact solution of Einstein's equations for dust is studied. It is asymptotically flat, and represents a rotating dust cloud extending tenuously to infinity, containing a singularity at the centre. An explanation is given as to why there exists no corresponding solution in Newtonian theory. (author)

  4. Dust coagulation in protoplanetary disks : porosity matters

    NARCIS (Netherlands)

    Ormel, C. W.; Spaans, M.; Tielens, A. G. G. M.

    Context. Sticking of colliding dust particles through van der Waals forces is the first stage in the grain growth process in protoplanetary disks, eventually leading to the formation of comets, asteroids and planets. A key aspect of the collisional evolution is the coupling between dust and gas

  5. Correlation between Yellow Dust and Radioactivity

    Energy Technology Data Exchange (ETDEWEB)

    AIZaabia, Mouza A [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Kim, Byoung-Jik [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2015-10-15

    In East Asia, yellow dust or Asian Dust (AD) outbreaks are among the largest contributors of wind-blown dust that carry natural and anthropogenic radionuclides and subsequently alter their concentration and distribution throughout the environment. Although the Korean Peninsula has been experiencing AD events since ancient times, the research has tended to focus on the transport routes and characteristics of AD, rather than on its impact on radionuclide activity levels. This paper examines the relationship between radionuclide concentration in the air and the frequency of dusty days in South Korea during AD intrusion events. It also investigates whether increased radionuclide concentration is a function of either more mass or more dust contamination. In this study, significant linear correlations of gamma-emitting radionuclides were found with mass of dust and occurrence frequency of AD. Regardless of the source origin of the dust, {sup 137}Cs and {sup 7}Be concentration primarily depended on dust mass in the filter. Nonetheless, the correlations were greatly distorted in 2011 and in the spring season, particularly the correlations with AD days that were far below that of the correlations obtained for the whole study period. A possible explanation of these conflicting results is that a change in the dust source could appreciably alter the concentration, deposition, and distribution of airborne radionuclides.

  6. Correlation between Yellow Dust and Radioactivity

    International Nuclear Information System (INIS)

    AIZaabia, Mouza A; Kim, Byoung-Jik

    2015-01-01

    In East Asia, yellow dust or Asian Dust (AD) outbreaks are among the largest contributors of wind-blown dust that carry natural and anthropogenic radionuclides and subsequently alter their concentration and distribution throughout the environment. Although the Korean Peninsula has been experiencing AD events since ancient times, the research has tended to focus on the transport routes and characteristics of AD, rather than on its impact on radionuclide activity levels. This paper examines the relationship between radionuclide concentration in the air and the frequency of dusty days in South Korea during AD intrusion events. It also investigates whether increased radionuclide concentration is a function of either more mass or more dust contamination. In this study, significant linear correlations of gamma-emitting radionuclides were found with mass of dust and occurrence frequency of AD. Regardless of the source origin of the dust, 137 Cs and 7 Be concentration primarily depended on dust mass in the filter. Nonetheless, the correlations were greatly distorted in 2011 and in the spring season, particularly the correlations with AD days that were far below that of the correlations obtained for the whole study period. A possible explanation of these conflicting results is that a change in the dust source could appreciably alter the concentration, deposition, and distribution of airborne radionuclides

  7. Measurement of nicotine in household dust

    International Nuclear Information System (INIS)

    Kim, Sungroul; Aung, Ther; Berkeley, Emily; Diette, Gregory B.; Breysse, Patrick N.

    2008-01-01

    An analytical method of measuring nicotine in house dust was optimized and associations among three secondhand smoking exposure markers were evaluated, i.e., nicotine concentrations of both house dust and indoor air, and the self-reported number of cigarettes smoked daily in a household. We obtained seven house dust samples from self-reported nonsmoking homes and 30 samples from smoking homes along with the information on indoor air nicotine concentrations and the number of cigarettes smoked daily from an asthma cohort study conducted by the Johns Hopkins Center for Childhood Asthma in the Urban Environment. House dust nicotine was analyzed by isotope dilution gas chromatography-mass spectrometry (GC/MS). Using our optimized method, the median concentration of nicotine in the dust of self-reported nonsmoking homes was 11.7 ng/mg while that of smoking homes was 43.4 ng/mg. We found a substantially positive association (r=0.67, P<0.0001) between house dust nicotine concentrations and the numbers of cigarettes smoked daily. Optimized analytical methods showed a feasibility to detect nicotine in house dust. Our results indicated that the measurement of nicotine in house dust can be used potentially as a marker of longer term SHS exposure

  8. 30 CFR 56.9315 - Dust control.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Dust control. 56.9315 Section 56.9315 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND... control. Dust shall be controlled at muck piles, material transfer points, crushers, and on haulage roads...

  9. Role of dust in H II regions

    International Nuclear Information System (INIS)

    Sarazin, C.L.

    1975-01-01

    The purpose of this dissertation is to determine quantitatively the effects of U.V. absorbing dust on H II regions, and compare these effects with observations. Many observations indicate that dust grains are present within H II regions. An analytic theory is presented which describes all three of the effects of dust in H II regions. Although this model is relatively crude, it is useful in determining the approximate size of the modifications due to dust. In order to explore this problem more carefully, detailed numerical models of H II regions with dust were constructed. The ionization and thermal structure of these model H II regions is discussed. The observational consequences of the presence of dust are explored; the optical line intensities, radio continuum and line fluxes, and infrared emission of model H II regions with dust are given. These numerical models are compared with observations of diffuse nebulae. The optical line ratios are compared to several nearby bright H II regions, and it is found that the dust models may explain several anomalies in their spectrum

  10. Raman lidar measurement of water vapor and ice clouds associated with Asian dust layer over Tsukuba, Japan

    Science.gov (United States)

    Sakai, Tetsu; Nagai, Tomohiro; Nakazato, Masahisa; Matsumura, Takatsugu

    2004-03-01

    The vertical distributions of particle extinction, backscattering, depolarization, and water vapor mixing ratio were measured using a Raman lidar over Tsukuba (36.1°N, 140.1°E), Japan, on 23-24 April 2001. Ice clouds associated with the Asian dust layer were observed at an altitude of ~6-9 km. The relative humidities in the cloud layer were close to the ice saturation values and the temperature at the top of the cloud layer was ~-35°C, suggesting that the Asian dust acted as ice nuclei at the high temperatures. The meteorological analysis suggested that the ice-saturated region was formed near the top of the dust layer where the moist air ascended in slantwise fashion above the cold-frontal zone associated with extratropical cyclone.

  11. Dust-acoustic solitary modes in plasmas with isothermal and nonthermal ions: Polarity switches and coexistence domains

    International Nuclear Information System (INIS)

    Verheest, Frank

    2011-01-01

    Large dust-acoustic waves are investigated in a multispecies plasma model consisting of cold negative dust in the presence of cooler Boltzmann and hotter nonthermal Cairns positive ions, in a Sagdeev pseudopotential formalism. Use of the pseudopotential at the acoustic speed itself yields in a systematic way compositional parameter values where negative/positive solitons interchange polarities and also where both polarities coexist. The latter requires that solitons at the acoustic speed exist, with finite amplitudes, compared to superacoustic solitons of the opposite polarity. The coexistence region starts when the pseudopotential at the acoustic speed has a negative root at the limit of infinite dust compression and ends when a positive double root is encountered. Outside the coexistence domain, only negative or positive superacoustic solitons can exist. Thus, the discussion and numerical evaluations are guided by precise physical and analytic arguments rather than mere numerical experimentation. Graphs of relevant Sagdeev pseudopotentials illustrate the link with the analytical constraints.

  12. Dust-acoustic solitary modes in plasmas with isothermal and nonthermal ions: Polarity switches and coexistence domains

    Energy Technology Data Exchange (ETDEWEB)

    Verheest, Frank [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281, B-9000 Gent, Belgium and School of Physics, University of KwaZulu-Natal, Private Bag X54001, Durban 4000 (South Africa)

    2011-08-15

    Large dust-acoustic waves are investigated in a multispecies plasma model consisting of cold negative dust in the presence of cooler Boltzmann and hotter nonthermal Cairns positive ions, in a Sagdeev pseudopotential formalism. Use of the pseudopotential at the acoustic speed itself yields in a systematic way compositional parameter values where negative/positive solitons interchange polarities and also where both polarities coexist. The latter requires that solitons at the acoustic speed exist, with finite amplitudes, compared to superacoustic solitons of the opposite polarity. The coexistence region starts when the pseudopotential at the acoustic speed has a negative root at the limit of infinite dust compression and ends when a positive double root is encountered. Outside the coexistence domain, only negative or positive superacoustic solitons can exist. Thus, the discussion and numerical evaluations are guided by precise physical and analytic arguments rather than mere numerical experimentation. Graphs of relevant Sagdeev pseudopotentials illustrate the link with the analytical constraints.

  13. The Continuous Monitoring of Desert Dust using an Infrared-based Dust Detection and Retrieval Method

    Science.gov (United States)

    Duda, David P.; Minnis, Patrick; Trepte, Qing; Sun-Mack, Sunny

    2006-01-01

    Airborne dust and sand are significant aerosol sources that can impact the atmospheric and surface radiation budgets. Because airborne dust affects visibility and air quality, it is desirable to monitor the location and concentrations of this aerosol for transportation and public health. Although aerosol retrievals have been derived for many years using visible and near-infrared reflectance measurements from satellites, the detection and quantification of dust from these channels is problematic over bright surfaces, or when dust concentrations are large. In addition, aerosol retrievals from polar orbiting satellites lack the ability to monitor the progression and sources of dust storms. As a complement to current aerosol dust retrieval algorithms, multi-spectral thermal infrared (8-12 micron) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Meteosat-8 Spinning Enhanced Visible and Infrared Imager (SEVIRI) are used in the development of a prototype dust detection method and dust property retrieval that can monitor the progress of Saharan dust fields continuously, both night and day. The dust detection method is incorporated into the processing of CERES (Clouds and the Earth s Radiant Energy System) aerosol retrievals to produce dust property retrievals. Both MODIS (from Terra and Aqua) and SEVERI data are used to develop the method.

  14. Dust plume formation in the free troposphere and aerosol size distribution during the Saharan Mineral Dust Experiment in North Africa

    KAUST Repository

    Khan, Basit Ali; Stenchikov, Georgiy L.; Weinzierl, Bernadett; Kalenderski, Stoitchko; Osipov, Sergey

    2015-01-01

    , this study combines model simulations and dust observations collected during the first stage of the Saharan Mineral Dust Experiment (SAMUM-I), which sampled dust events that extended from Morocco to Portugal, and investigated the spatial distribution

  15. Extracting lunar dust parameters from image charge signals produced by the Lunar Dust Experiment

    Science.gov (United States)

    Stanley, J.; Kempf, S.; Horanyi, M.; Szalay, J.

    2015-12-01

    The Lunar Dust Experiment (LDEX) onboard the Lunar Atmosphere and Dust Environment Explorer (LADEE) is an impact ionization dust detector used to characterize the lunar dust exosphere generated by the impacts of large interplanetary particles and meteor streams (Horanyi et al., 2015). In addition to the mass and speed of these lofted particles, LDEX is sensitive to their charge. The resulting signatures of impact events therefore provide valuable information about not only the ambient plasma environment, but also the speed vectors of these dust grains. Here, impact events produced from LDEX's calibration at the Dust Accelerator Laboratory are analyzed using an image charge model derived from the electrostatic simulation program, Coulomb. We show that parameters such as dust grain speed, size, charge, and position of entry into LDEX can be recovered and applied to data collected during LADEE's seven-month mission.

  16. Dust effect on the collisional pumping of the H2O cosmic maser

    International Nuclear Information System (INIS)

    Bolgova, G.T.; Strel'nitskij, V.S.; Shmeld, I.K.

    1977-01-01

    The rate equations for the pupulations of 48 ortho-H 2 O rotational levels are solved simultaneously with the equations of the radiative transfer in the rotational lines, accounting for the continuous absorption and emission of resonance photon by dust grains. The radiative transport was treated in a model of a homogeneous isothermal plane-parallel slab, approximating the region of collisional pumping behind a shock front. It is found, that continuous absorption and emission may strongly influence the character of the distribution of the rotational level populations. Depending on the relation between the kinetic temperature Tsub(k) and the dust temperature Tsub(d) the ''turning on'' of the dust may either greatly increase the inversion of the 6 16 -5 23 transition (when Tsub(d) < Tsub(k)) or, on the contrary, greatly decrease and even liquidate the inversion (when Tsub(d)=Tsub(k)). The sink of the rotational photons on the cold dust reduces the thermalizing effect of the radiation trapping, reestablishing the inversion of many transitions provided by the collisional pumping

  17. Heating of Porous Icy Dust Aggregates

    Energy Technology Data Exchange (ETDEWEB)

    Sirono, Sin-iti [Earth and Environmental Sciences, Nagoya University, Tikusa-ku, Furo-cho, Nagoya 464-8601 (Japan)

    2017-06-10

    At the beginning of planetary formation, highly porous dust aggregates are formed through coagulation of dust grains. Outside the snowline, the main component of an aggregate is H{sub 2}O ice. Because H{sub 2}O ice is formed in amorphous form, its thermal conductivity is extremely small. Therefore, the thermal conductivity of an icy dust aggregate is low. There is a possibility of heating inside an aggregate owing to the decay of radionuclides. It is shown that the temperature increases substantially inside an aggregate, leading to crystallization of amorphous ice. During the crystallization, the temperature further increases sufficiently to continue sintering. The mechanical properties of icy dust aggregates change, and the collisional evolution of dust aggregates is affected by the sintering.

  18. The relaxation of plasmas with dust particles

    International Nuclear Information System (INIS)

    Chutov, Yu.I.; Kravchenko, A.Yu.; Schram, P.P.J.M.

    1997-01-01

    Various parameters of relaxing plasmas with dust particles including the electron and ion energy distributions function are numerically simulated at various parameters of the dust particles using the PIC method and taking into account the dynamics of the dust particle charge without the assumption about the equilibrium of electrons and ions. Coulomb collisions are taken into account in the framework of the method of stochastic differential equations. The relaxation of bounded plasma clouds expanding into a vacuum as well as the relaxation of a uniform plasma, in which dust particles appear at some initial time, are investigated. The obtained results show that the relaxation of plasmas can be accompanied by a deviation of the ion distribution function from equilibrium as well as a change of the mean energy of electrons and ions because of the dependence of the collection of electrons and ions by dust particles on their energy. (author)

  19. Recycling of steelmaking dusts: The Radust concept

    Directory of Open Access Journals (Sweden)

    Jalkanen H.

    2005-01-01

    Full Text Available Recycling of dusts and other wastes of steelmaking is becoming to a necessity of two reasons: due to high contents of iron oxides dusts are valuable raw material for steelmaking and tightening environmental legislation makes the landfill disposal of wastes more expensive. Fine dust fractions from various stages of steelmaking route contain besides iron and carbon heavy metals especially zinc and lead and heavy hydrocarbons that are acceptable neither for landfill disposal nor for recycling back to processes without any spe4cial treatments. Some theoretical and practical aspects concerning high temperature treatments of steelmaking dusts for removal of hazardous components and production of clean high iron raw material for recycling is discussed in this paper. The Radust technology developed at Koverhar steelwork in Finland for treatment of the most problematic fine fractions of blast furnace and oxygen converter dusts is shortly presented and discussed.

  20. Dust storm events over Delhi: verification of dust AOD forecasts with satellite and surface observations

    Science.gov (United States)

    Singh, Aditi; Iyengar, Gopal R.; George, John P.

    2016-05-01

    Thar desert located in northwest part of India is considered as one of the major dust source. Dust storms originate in Thar desert during pre-monsoon season, affects large part of Indo-Gangetic plains. High dust loading causes the deterioration of the ambient air quality and degradation in visibility. Present study focuses on the identification of dust events and verification of the forecast of dust events over Delhi and western part of IG Plains, during the pre-monsoon season of 2015. Three dust events have been identified over Delhi during the study period. For all the selected days, Terra-MODIS AOD at 550 nm are found close to 1.0, while AURA-OMI AI shows high values. Dust AOD forecasts from NCMRWF Unified Model (NCUM) for the three selected dust events are verified against satellite (MODIS) and ground based observations (AERONET). Comparison of observed AODs at 550 nm from MODIS with NCUM predicted AODs reveals that NCUM is able to predict the spatial and temporal distribution of dust AOD, in these cases. Good correlation (~0.67) is obtained between the NCUM predicted dust AODs and location specific observations available from AERONET. Model under-predicted the AODs as compared to the AERONET observations. This may be mainly because the model account for only dust and no anthropogenic activities are considered. The results of the present study emphasize the requirement of more realistic representation of local dust emission in the model both of natural and anthropogenic origin, to improve the forecast of dust from NCUM during the dust events.

  1. Galactic and intergalactic magnetic fields

    CERN Document Server

    Klein, Ulrich

    2014-01-01

    This course-tested textbook conveys the fundamentals of magnetic fields and relativistic plasma in diffuse cosmic media, with a primary focus on phenomena that have been observed at different wavelengths. Theoretical concepts are addressed wherever necessary, with derivations presented in sufficient detail to be generally accessible.In the first few chapters the authors present an introduction to various astrophysical phenomena related to cosmic magnetism, with scales ranging from molecular clouds in star-forming regions and supernova remnants in the Milky Way, to clusters of galaxies. Later c

  2. Dust in the Quasar Wind (Artist Concept)

    Science.gov (United States)

    2007-01-01

    Dusty grains -- including tiny specks of the minerals found in the gemstones peridot, sapphires and rubies -- can be seen blowing in the winds of a quasar, or active black hole, in this artist's concept. The quasar is at the center of a distant galaxy. Astronomers using NASA's Spitzer Space Telescope found evidence that such quasar winds might have forged these dusty particles in the very early universe. The findings are another clue in an ongoing cosmic mystery: where did all the dust in our young universe come from? Dust is crucial for efficient star formation as it allows the giant clouds where stars are born to cool quickly and collapse into new stars. Once a star has formed, dust is also needed to make planets and living creatures. Dust has been seen as far back as when the universe was less than a tenth of its current age, but how did it get there? Most dust in our current epoch forms in the winds of evolved stars that did not exist when the universe was young. Theorists had predicted that winds from quasars growing in the centers of distant galaxies might be a source of this dust. While the environment close to a quasar is too hot for large molecules like dust grains to survive, dust has been found in the cooler, outer regions. Astronomers now have evidence that dust is created in these outer winds. Using Spitzer's infrared spectrograph instrument, scientists found a wealth of dust grains in a quasar called PG2112+059 located at the center of a galaxy 8 billion light-years away. The grains - including corundum (sapphires and rubies); forsterite (peridot); and periclase (naturally occurring in marble) - are not typically found in galaxies without quasars, suggesting they might have been freshly formed in the quasar's winds.

  3. Absorption by Spinning Dust: A Contaminant for High-redshift 21 cm Observations

    Science.gov (United States)

    Draine, B. T.; Miralda-Escudé, Jordi

    2018-05-01

    Spinning dust grains in front of the bright Galactic synchrotron background can produce a weak absorption signal that could affect measurements of high-redshift 21 cm absorption. At frequencies near 80 MHz where the Experiment to Detect the Global EoR Signature (EDGES) has reported 21 cm absorption at z≈ 17, absorption could be produced by interstellar nanoparticles with radii a≈ 50 \\mathringA in the cold interstellar medium (ISM), with rotational temperature T ≈ 50 K. Atmospheric aerosols could contribute additional absorption. The strength of the absorption depends on the abundance of such grains and on their dipole moments, which are uncertain. The breadth of the absorption spectrum of spinning dust limits its possible impact on measurement of a relatively narrow 21 cm absorption feature.

  4. Asian dust events of April 1998

    Science.gov (United States)

    Husar, R.B.; Tratt, D.M.; Schichtel, B.A.; Falke, S.R.; Li, F.; Jaffe, D.; Gasso, S.; Gill, T.; Laulainen, N.S.; Lu, F.; Reheis, M.C.; Chun, Y.; Westphal, D.; Holben, B.N.; Gueymard, C.; McKendry, I.; Kuring, N.; Feldman, G.C.; McClain, C.; Frouin, R.J.; Merrill, J.; DuBois, D.; Vignola, F.; Murayama, T.; Nickovic, S.; Wilson, W.E.; Sassen, K.; Sugimoto, N.; Malm, W.C.

    2001-01-01

    On April 15 and 19, 1998, two intense dust storms were generated over the Gobi desert by springtime low-pressure systems descending from the northwest. The windblown dust was detected and its evolution followed by its yellow color on SeaWiFS satellite images, routine surface-based monitoring, and through serendipitous observations. The April 15 dust cloud was recirculating, and it was removed by a precipitating weather system over east Asia. The April 19 dust cloud crossed the Pacific Ocean in 5 days, subsided to the surface along the mountain ranges between British Columbia and California, and impacted severely the optical and the concentration environments of the region. In east Asia the dust clouds increased the albedo over the cloudless ocean and land by up to 10-20%, but it reduced the near-UV cloud reflectance, causing a yellow coloration of all surfaces. The yellow colored backscattering by the dust eludes a plausible explanation using simple Mie theory with constant refractive index. Over the West Coast the dust layer has increased the spectrally uniform optical depth to about 0.4, reduced the direct solar radiation by 30-40%, doubled the diffuse radiation, and caused a whitish discoloration of the blue sky. On April 29 the average excess surface-level dust aerosol concentration over the valleys of the West Coast was about 20-50 ??g/m3 with local peaks >100 ??g/m3. The dust mass mean diameter was 2-3 ??m, and the dust chemical fingerprints were evident throughout the West Coast and extended to Minnesota. The April 1998 dust event has impacted the surface aerosol concentration 2-4 times more than any other dust event since 1988. The dust events were observed and interpreted by an ad hoc international web-based virtual community. It would be useful to set up a community-supported web-based infrastructure to monitor the global aerosol pattern for such extreme aerosol events, to alert and to inform the interested communities, and to facilitate collaborative

  5. Austrian emission inventory for dust

    International Nuclear Information System (INIS)

    Winiwarter, W.; Trenker, C.; Hoeflinger, W.

    2001-09-01

    For the first time, Austrian emissions of anthropogenic particulate matter emissions to the atmosphere have been estimated. Results have been reported as total suspended particles (TSP) as well as for the fractions of particles smaller than 10 μm or 2.5 μm aerodynamic diameter (PM 10 , PM 2.5 ), respectively. Base years for the inventory were 1990, 1995 and 1999. Excluded from this assessment is wind blown dust, which has been considered a natural source here. National statistics have been applied, specifically those also used previously in the Austrian air pollution inventory (OLI). Emission factors have been taken from literature compilations, only for exceptional cases specific Austrian assessments were performed or original literature on emission measurements was consulted. Resuspension of dust by road traffic emerged as the most important source. For the size fraction of PM 10 this source contributed about half of the emissions, when applying the calculation scheme by the U.S. EPA. While this scheme is widely used and well documented, its validity is currently subject of intense scientific debate. As these results do not seem to coincide with ambient air measurements, resuspension of road dust is considered separately and not now included in the national total. The sum of all other sources increases from 75,000 t of TSP in 1990 and 1995 to 77,000 t in 1999, while both PM 10 and PM 2.5 exhibit decreasing tendency (at 45,000 t and 26,000 t in 1999, respectively). The increase in TSP derives from increasing traffic and friction related emissions (tire wear, break wear), decrease of the finer particulate matter is due to reductions in firewood consumption for domestic heating. Most important source sectors are fugitive emissions from material transfer in industry as well as the building industry and the tilling of agricultural land. Common to these sources is the high uncertainty of available data. Wood combustion is the most important of the non

  6. Scientists study 'cold war' fallout

    International Nuclear Information System (INIS)

    Stone, R.

    1993-01-01

    This article describes the epidemiological studies being carried out to determine radiation doses to the public from intentional and accidental releases of radioactive compounds during the Cold War. These studies at present are focused on Hanford, Oak Ridge, and Fernald, with studies beginning at Rocky Flats and Savannah

  7. Encyclopedia of the Cold War

    NARCIS (Netherlands)

    van Dijk, R.

    2008-01-01

    Between 1945 and 1991, tension between the USA, its allies, and a group of nations led by the USSR, dominated world politics. This period was called the Cold War - a conflict that stopped short to a full-blown war. Benefiting from the recent research of newly open archives, the Encyclopedia of the

  8. Cold gas accretion in galaxies

    NARCIS (Netherlands)

    Sancisi, Renzo; Fraternali, Filippo; Oosterloo, Tom; van der Hulst, Thijs

    Evidence for the accretion of cold gas in galaxies has been rapidly accumulating in the past years. HI observations of galaxies and their environment have brought to light new facts and phenomena which are evidence of ongoing or recent accretion: (1) A large number of galaxies are accompanied by

  9. Cold fusion and hot history

    International Nuclear Information System (INIS)

    Lewenstein, B.

    1996-01-01

    The history of cold fusion research following the announcement of the Pons-Fleischmann experiment is described in detail, including all the confusion, responses of scientists, personal impressions, personal quotations, reactions of the media, references to contemporary sources, etc. (P.A.). 5 figs

  10. Probing the impact of metallicity on the dust properties in galaxies

    International Nuclear Information System (INIS)

    Remy-Ruyer, Aurelie

    2013-01-01

    As galaxies evolve, their Interstellar Medium (ISM) becomes continually enriched with metals, and this metal enrichment influences the subsequent star formation. Low metallicity dwarf galaxies of the local Universe are ideal candidates to study the influence of metal enrichment on the ISM properties of galaxies and gives us insight into the enrichment process and star formation under ISM conditions that may provide clues to conditions in early universe metal-poor systems. Previous studies have shown that the ISM of dwarf galaxies poses a number of interesting puzzles in terms of the abundance of dust grains, the dust composition and even the FIR emission processes. However these studies were limited to the warmer dust emitting at wavelengths shorter than 200 microns and were done only on a small number of dwarf galaxies. Thanks to its increased sensitivity and resolution in FIR and submillimeter (sub-mm) wavelengths, Herschel gives us a new view on the cold dust properties in galaxies and enables us to study the lowest metallicity galaxies in a systematic way. In this work, I carry out a study of the dust properties in dwarf galaxies and compare with more metal rich environments, in order to address the question of the impact of metallicity on the dust properties. The novelty of this work lays in the fact that dwarf galaxies are studied here in a systematic way, enabling us to derive and quantify the general properties that are representative of these systems. This study is conducted over the full IR-to-sub-mm range, using new FIR/sub-mm Herschel observations, Spitzer, WISE, IRAS and 2MASS data. We complete this set of data with longer sub-mm measurements from ground-based facilities such as APEX and JCMT to study the presence and characteristics of the sub-mm excess in my sample of galaxies. I also collect Hi and CO data to access the gas properties of the galaxies and study the evolution of the G/D with metallicity. Our study reveal different dust properties in

  11. The Spatial Variation of Dust Particulate Matter Concentrations during Two Icelandic Dust Storms in 2015

    Directory of Open Access Journals (Sweden)

    Pavla Dagsson-Waldhauserova

    2016-06-01

    Full Text Available Particulate matter mass concentrations and size fractions of PM1, PM2.5, PM4, PM10, and PM15 measured in transversal horizontal profile of two dust storms in southwestern Iceland are presented. Images from a camera network were used to estimate the visibility and spatial extent of measured dust events. Numerical simulations were used to calculate the total dust flux from the sources as 180,000 and 280,000 tons for each storm. The mean PM15 concentrations inside of the dust plumes varied from 10 to 1600 µg·m−3 (PM10 = 7 to 583 µg·m−3. The mean PM1 concentrations were 97–241 µg·m−3 with a maximum of 261 µg·m−3 for the first storm. The PM1/PM2.5 ratios of >0.9 and PM1/PM10 ratios of 0.34–0.63 show that suspension of volcanic materials in Iceland causes air pollution with extremely high PM1 concentrations, similar to polluted urban areas in Europe or Asia. Icelandic volcanic dust consists of a higher proportion of submicron particles compared to crustal dust. Both dust storms occurred in relatively densely inhabited areas of Iceland. First results on size partitioning of Icelandic dust presented here should challenge health authorities to enhance research in relation to dust and shows the need for public dust warning systems.

  12. Kuiper Belt Dust Grains as a Source of Interplanetary Dust Particles

    Science.gov (United States)

    Liou, Jer-Chyi; Zook, Herbert A.; Dermott, Stanley F.

    1996-01-01

    The recent discovery of the so-called Kuiper belt objects has prompted the idea that these objects produce dust grains that may contribute significantly to the interplanetary dust population. In this paper, the orbital evolution of dust grains, of diameters 1 to 9 microns, that originate in the region of the Kuiper belt is studied by means of direct numerical integration. Gravitational forces of the Sun and planets, solar radiation pressure, as well as Poynting-Robertson drag and solar wind drag are included. The interactions between charged dust grains and solar magnetic field are not considered in the model. Because of the effects of drag forces, small dust grains will spiral toward the Sun once they are released from their large parent bodies. This motion leads dust grains to pass by planets as well as encounter numerous mean motion resonances associated with planets. Our results show that about 80% of the Kuiper belt grains are ejected from the Solar System by the giant planets, while the remaining 20% of the grains evolve all the way to the Sun. Surprisingly, the latter dust grains have small orbital eccentricities and inclinations when they cross the orbit of the Earth. This makes them behave more like asteroidal than cometary-type dust particles. This also enhances their chances of being captured by the Earth and makes them a possible source of the collected interplanetary dust particles; in particular, they represent a possible source that brings primitive/organic materials from the outer Solar System to the Earth. When collisions with interstellar dust grains are considered, however, Kuiper belt dust grains around 9 microns appear likely to be collisionally shattered before they can evolve toward the inner part of the Solar System. The collision destruction can be applied to Kuiper belt grains up to about 50 microns. Therefore, Kuiper belt dust grains within this range may not be a significant part of the interplanetary dust complex in the inner Solar

  13. Dust limit management strategy in tokamaks

    International Nuclear Information System (INIS)

    Rosanvallon, S.; Grisolia, C.; Andrew, P.; Ciattaglia, S.; Delaporte, P.; Douai, D.; Garnier, D.; Gauthier, E.; Gulden, W.; Hong, S.H.; Pitcher, S.; Rodriguez, L.; Taylor, N.; Tesini, A.; Vartanian, S.; Vatry, A.; Wykes, M.

    2009-01-01

    Dust is produced in tokamaks by the interaction between the plasma and the plasma facing components. Dust has not yet been of a major concern in existing tokamaks mainly because the quantity is small and these devices are not nuclear facilities. However, in ITER and in future reactors, it will represent operational and potential safety issues. From a safety point of view, in order to control the potential dust hazard, the current ITER strategy is based on a defense in depth approach designed to provide reliable confinement systems, to avoid failures, and to measure and minimise the dust inventory. In addition, R and D is put in place for optimisation of the proposed methods, such as improvement of measurement, dust cleaning and the reduction of dust production. The aim of this paper is to present the approach for the control of the dust inventory, relying on the monitoring of envelope values and the development of removal techniques already developed in the existing tokamaks or plasma dedicated devices or which will need further research and development in order to be integrated in ITER.

  14. Dust limit management strategy in tokamaks

    Science.gov (United States)

    Rosanvallon, S.; Grisolia, C.; Andrew, P.; Ciattaglia, S.; Delaporte, P.; Douai, D.; Garnier, D.; Gauthier, E.; Gulden, W.; Hong, S. H.; Pitcher, S.; Rodriguez, L.; Taylor, N.; Tesini, A.; Vartanian, S.; Vatry, A.; Wykes, M.

    2009-06-01

    Dust is produced in tokamaks by the interaction between the plasma and the plasma facing components. Dust has not yet been of a major concern in existing tokamaks mainly because the quantity is small and these devices are not nuclear facilities. However, in ITER and in future reactors, it will represent operational and potential safety issues. From a safety point of view, in order to control the potential dust hazard, the current ITER strategy is based on a defense in depth approach designed to provide reliable confinement systems, to avoid failures, and to measure and minimise the dust inventory. In addition, R&D is put in place for optimisation of the proposed methods, such as improvement of measurement, dust cleaning and the reduction of dust production. The aim of this paper is to present the approach for the control of the dust inventory, relying on the monitoring of envelope values and the development of removal techniques already developed in the existing tokamaks or plasma dedicated devices or which will need further research and development in order to be integrated in ITER.

  15. Hypervelocity Dust Injection for Plasma Diagnostic Applications

    Science.gov (United States)

    Ticos, Catalin

    2005-10-01

    Hypervelocity micron-size dust grain injection was proposed for high-temperature magnetized plasma diagnosis. Multiple dust grains are launched simultaneously into high temperature plasmas at several km/s or more. The hypervelocity dust grains are ablated by the electron and ion fluxes. Fast imaging of the resulting luminous plumes attached to each grain is expected to yield local magnetic field vectors. Combination of multiple local magnetic field vectors reproduces 2D or even 3D maps of the internal magnetic field topology. Key features of HDI are: (1) a high spatial resolution, due to a relatively small transverse size of the elongated tail, and (2) a small perturbation level, as the dust grains introduce negligible number of particles compared to the plasma particle inventory. The latter advantage, however, could be seriously compromised if the gas load from the accelerator has an unobstructed access to the diagnosed plasma. Construction of a HDI diagnostic for National Spherical Torus Experiment (NSTX), which includes a coaxial plasma gun for dust grain acceleration, is underway. Hydrogen and deuterium gas discharges inside accelerator are created by a ˜ 1 mF capacitor bank pre-charged up to 10 kV. The diagnostic apparatus also comprises a dust dispenser for pre-loading the accelerator with dust grains, and an imaging system that has a high spatial and temporal resolution.

  16. Testing of a Plasmadynamic Hypervelocity Dust Accelerator

    Science.gov (United States)

    Ticos, Catalin M.; Wang, Zhehui; Dorf, Leonid A.; Wurden, G. A.

    2006-10-01

    A plasmadynamic accelerator for microparticles (or dust grains) has been designed, built and tested at Los Alamos National laboratory. The dust grains are expected to be accelerated to hypervelocities on the order of 1-30 km/s, depending on their size. The key components of the plasmadynamic accelerator are a coaxial plasma gun operated at 10 kV, a dust dispenser activated by a piezoelectric transducer, and power and remote-control systems. The coaxial plasma gun produces a high density (10^18 cm-3) and low temperature (˜ 1 eV) plasma in deuterium ejected by J x B forces, which provides drag on the dust particles in its path. Carbon dust particles will be used, with diameters from 1 to 50 μm. The plasma parameters produced in the coaxial gun are presented and their implication to dust acceleration is discussed. High speed dust will be injected in the National Spherical Torus Experiment to measure the pitch angle of magnetic field lines.

  17. Featured Image: Making Dust in the Lab

    Science.gov (United States)

    Kohler, Susanna

    2017-12-01

    This remarkable photograph (which spans only 10 m across; click for a full view) reveals what happens when you form dust grains in a laboratory under conditions similar to those of interstellar space. The cosmic life cycle of dust grains is not well understood we know that in the interstellar medium (ISM), dust is destroyed at a higher rate than it is produced by stellar sources. Since the amount of dust in the ISM stays constant, however, there must be additional sources of dust production besides stars. A team of scientists led by Daniele Fulvio (Pontifical Catholic University of Rio de Janeiro and the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena) have now studied formation mechanisms of dust grains in the lab by mimicking low-temperature ISM conditions and exploring how, under these conditions, carbonaceous materials condense from gas phase to form dust grains. To read more about their results and see additional images, check out the paper below.CitationDaniele Fulvio et al 2017 ApJS 233 14. doi:10.3847/1538-4365/aa9224

  18. THE MEASUREMENT AND DISTRIBUTION OF WOOD DUST

    Directory of Open Access Journals (Sweden)

    Andrea Rosario Proto

    2010-03-01

    Full Text Available In Italy, the woodworking industry presents many issues in terms of occupational health and safety. This study on exposure to wood dust could contribute to the realization of a prevention model in order to limit exposure to carcinogenic agents to the worker. The sampling methodology illustrated the analysis of dust emissions from the woodworking machinery in operation throughout the various processing cycles. The quantitative and qualitative assessment of exposure was performed using two different methodologies. The levels of wood dust were determined according to EN indications and sampling was conducted using IOM and Cyclon personal samplers. The qualitative research of wood dust was performed using an advanced laser air particle counter. This allowed the number of particles present to be counted in real time. The results obtained allowed for an accurate assessment of the quality of the dust emitted inside the workplace during the various processing phases. The study highlighted the distribution of air particles within the different size classes, the exact number of both thin and ultra-thin dusts, and confirmed the high concentration of thin dust particles which can be very harmful to humans.

  19. Cold atoms in singular potentials

    International Nuclear Information System (INIS)

    Denschlag, J. P.

    1998-09-01

    We studied both theoretically and experimentally the interaction between cold Li atoms from a magnetic-optical trap (MOT) and a charged or current-carrying wire. With this system, we were able to realize 1/r 2 and 1/r potentials in two dimensions and to observe the motion of cold atoms in both potentials. For an atom in an attractive 1/r 2 potential, there exist no stable trajectories, instead there is a characteristic class of trajectories for which atoms fall into the singularity. We were able to observe this falling of atoms into the center of the potential. Moreover, by probing the singular 1/r 2 potential with atomic clouds of varying size and temperature we extracted scaling properties of the atom-wire interaction. For very cold atoms, and very thin wires the motion of the atoms must be treated quantum mechanically. Here we predict that the absorption cross section for the 1/r 2 potential should exhibit quantum steps. These quantum steps are a manifestation of the quantum mechanical decomposition of plane waves into partial waves. For the second part of this work, we realized a two dimensional 1/r potential for cold atoms. If the potential is attractive, the atoms can be bound and follow Kepler-like orbits around the wire. The motion in the third dimension along the wire is free. We were able to exploit this property and constructed a novel cold atom guide, the 'Kepler guide'. We also demonstrated another type of atom guide (the 'side guide'), by combining the magnetic field of the wire with a homogeneous offset magnetic field. In this case, the atoms are held in a potential 'tube' on the side of the wire. The versatility, simplicity, and scaling properties of this guide make it an interesting technique. (author)

  20. Detection of HC11N in the cold dust cloud TMC-1

    International Nuclear Information System (INIS)

    Bell, M.B.; Matthews, H.E.

    1985-01-01

    The detection of the J = 41 = 40 rotational transition of HC11N in the direction of the Taurus molecular cloud complex is reported. The line strength is in good agreement with predicted values, and the rotational parameters, althrough determined more accurately with these results, remain unchanged from those obtained previously using observations of IRC + 10 deg 216 alone. 14 references

  1. Pebble Bed Reactor Dust Production Model

    Energy Technology Data Exchange (ETDEWEB)

    Abderrafi M. Ougouag; Joshua J. Cogliati

    2008-09-01

    The operation of pebble bed reactors, including fuel circulation, can generate graphite dust, which in turn could be a concern for internal components; and to the near field in the remote event of a break in the coolant circuits. The design of the reactor system must, therefore, take the dust into account and the operation must include contingencies for dust removal and for mitigation of potential releases. Such planning requires a proper assessment of the dust inventory. This paper presents a predictive model of dust generation in an operating pebble bed with recirculating fuel. In this preliminary work the production model is based on the use of the assumption of proportionality between the dust production and the normal force and distance traveled. The model developed in this work uses the slip distances and the inter-pebble forces computed by the authors’ PEBBLES. The code, based on the discrete element method, simulates the relevant static and kinetic friction interactions between the pebbles as well as the recirculation of the pebbles through the reactor vessel. The interaction between pebbles and walls of the reactor vat is treated using the same approach. The amount of dust produced is proportional to the wear coefficient for adhesive wear (taken from literature) and to the slip volume, the product of the contact area and the slip distance. The paper will compare the predicted volume with the measured production rates. The simulation tallies the dust production based on the location of creation. Two peak production zones from intra pebble forces are predicted within the bed. The first zone is located near the pebble inlet chute due to the speed of the dropping pebbles. The second peak zone occurs lower in the reactor with increased pebble contact force due to the weight of supported pebbles. This paper presents the first use of a Discrete Element Method simulation of pebble bed dust production.

  2. Pebble Bed Reactor Dust Production Model

    International Nuclear Information System (INIS)

    Abderrafi M. Ougouag; Joshua J. Cogliati

    2008-01-01

    The operation of pebble bed reactors, including fuel circulation, can generate graphite dust, which in turn could be a concern for internal components; and to the near field in the remote event of a break in the coolant circuits. The design of the reactor system must, therefore, take the dust into account and the operation must include contingencies for dust removal and for mitigation of potential releases. Such planning requires a proper assessment of the dust inventory. This paper presents a predictive model of dust generation in an operating pebble bed with recirculating fuel. In this preliminary work the production model is based on the use of the assumption of proportionality between the dust production and the normal force and distance traveled. The model developed in this work uses the slip distances and the inter-pebble forces computed by the authors PEBBLES. The code, based on the discrete element method, simulates the relevant static and kinetic friction interactions between the pebbles as well as the recirculation of the pebbles through the reactor vessel. The interaction between pebbles and walls of the reactor vat is treated using the same approach. The amount of dust produced is proportional to the wear coefficient for adhesive wear (taken from literature) and to the slip volume, the product of the contact area and the slip distance. The paper will compare the predicted volume with the measured production rates. The simulation tallies the dust production based on the location of creation. Two peak production zones from intra pebble forces are predicted within the bed. The first zone is located near the pebble inlet chute due to the speed of the dropping pebbles. The second peak zone occurs lower in the reactor with increased pebble contact force due to the weight of supported pebbles. This paper presents the first use of a Discrete Element Method simulation of pebble bed dust production

  3. Cold acclimation increases cold tolerance independently of diapause programing in the bean bug, Riptortus pedestris.

    Science.gov (United States)

    Rozsypal, J; Moos, M; Goto, S G

    2017-10-17

    The bean bug (Riptortus pedestris) is a pest of soybeans and other legumes in Japan and other Asian countries. It enters a facultative adult diapause on exposure to short days. While photoperiodism and diapause are well understood in R. pedestris, knowledge of cold tolerance is very limited, as is information on the effect of diapause on cold tolerance. We examined the effect of photoperiod, cold acclimation, and feeding status on cold tolerance in R. pedestris. We found that cold acclimation significantly increased survival at -10°C in both long- and short-day adult R. pedestris. Since the difference in cold survival between long- and short-day cold-acclimated groups was only marginal, we conclude that entering diapause is not crucial for R. pedestris to successfully pass through cold acclimation and become cold tolerant. We observed similar effects in 5th instar nymphs, with both long- and short-day cold-acclimated groups surviving longer cold exposures compared with non-acclimated groups. Starvation, which was tested only in adult bugs, had only a negligible and negative impact on cold survival. Although cold tolerance significantly increased with cold acclimation in adult bugs, supercooling capacity unexpectedly decreased. Our results suggest that changes in supercooling capacity as well as in water content are unrelated to cold tolerance in R. pedestris. An analysis of metabolites revealed differences between the treatments, and while several metabolites markedly increased with cold acclimation, their concentrations were too low to have a significant effect on cold tolerance.

  4. Simulation of dust-acoustic waves

    International Nuclear Information System (INIS)

    Winske, D.; Murillo, M.S.; Rosenberg, M.

    1998-01-01

    The authors use molecular dynamics (MD) and particle-in-cell (PIC) simulation methods to investigate the dispersion relation of dust-acoustic waves in a one-dimensional, strongly coupled (Coulomb coupling parameter Λ = ratio of the Coulomb energy to the thermal energy = 120) dusty plasma. They study both cases where the dust is represented by a small number of simulation particles that form into a regular array structure (crystal limit) as well as where the dust is represented by a much larger number of particles (fluid limit)

  5. Backscattering Moessbauer spectroscopy of Martian dust

    International Nuclear Information System (INIS)

    Bertelsen, P.; Madsen, M. B.; Binau, C. S.; Goetz, W.; Gunnlaugsson, H. P.; Hviid, S. F.; Kinch, K. M.; Klingelhoefer, G.; Leer, K.; Madsen, D. E.; Merrison, J.; Olsen, M.; Squyres, S. W.

    2005-01-01

    We report on the determination of the mineralogy of the atmospherically suspended Martian dust particles using backscattering 57 Fe Moessbauer spectroscopy on dust accumulated onto the magnets onboard the Mars Exploration Rovers. The spectra can be interpreted in terms of minerals of igneous origin, and shows only limited, if any, amounts of secondary minerals that may have formed in the presence of liquid water. These findings suggest that the dust has formed in a dry environment over long time in the history of the planet.

  6. Dust and radon: the legal implications

    International Nuclear Information System (INIS)

    Van Sittert, J.M.O.

    1990-01-01

    It is known that radon gas is not generally considered to be a major problem when encountered in the working environment. However, in its process of decay, a series of four short lived daughter products are formed. In a dust-laden atmosphere these daughter products, which are ionized readily, attach to the particulate material and when inhaled are deposited in the alveoli of the lungs. Therefore, if respirable dust is controlled, the effects of radon daughters will also be minimized. The legal requirements for dust control in South Africa and their implications are discussed. 1 ill

  7. Is there dust in galactic haloes

    International Nuclear Information System (INIS)

    Greenberg, J.M.; Ferrini, F.; Pisa Univ.; Barsella, B.; Aiello, S.

    1987-01-01

    The ubiquitous presence of dust within the disks of spiral galaxies is well established. The authors predict that the presence of dust in these regions may be revealed in bright edge-on galaxies, especially by using the polarization of the scattered light from the symmetric lanes. The detection of scattered light above the galactic plane may be an indicator that the parent galaxy has not suffered close encounters with other galaxies at least within the timescale required to establish the dust layers. (author)

  8. Residual dust charges in discharge afterglow

    International Nuclear Information System (INIS)

    Coueedel, L.; Mikikian, M.; Boufendi, L.; Samarian, A. A.

    2006-01-01

    An on-ground measurement of dust-particle residual charges in the afterglow of a dusty plasma was performed in a rf discharge. An upward thermophoretic force was used to balance the gravitational force. It was found that positively charged, negatively charged, and neutral dust particles coexisted for more than 1 min after the discharge was switched off. The mean residual charge for 200-nm-radius particles was measured. The dust particle mean charge is about -5e at a pressure of 1.2 mbar and about -3e at a pressure of 0.4 mbar

  9. Genetics Home Reference: familial cold autoinflammatory syndrome

    Science.gov (United States)

    ... inflammatory response. Monarch-1 is involved in the inhibition of the inflammatory response. Mutations in the NLRP12 ... cold autoinflammatory syndrome Orphanet: Familial cold urticaria Patient Support and Advocacy Resources (3 links) Autoinflammatory Alliance National ...

  10. Center for Cold Spray Research and Development

    Data.gov (United States)

    Federal Laboratory Consortium — This is the only DoD facility capable of cold spray research and development, production, and field-repair. It features three stationary cold spray systems used for...

  11. Understanding Colds: Anatomy of the Nose

    Science.gov (United States)

    ... Complications Special Features References Common Cold Understanding Colds Anatomy of the Nose The nose contains shelf-like ... white). Soft tissue, such as the eye, is gray. The maxillary sinus of adults has a volume ...

  12. Effect of non-Maxwellian particle trapping and dust grain charging on dust acoustic solitary waves

    International Nuclear Information System (INIS)

    Rubab, N.; Murtaza, G.; Mushtaq, A.

    2006-01-01

    The role of adiabatic trapped ions on a small but finite amplitude dust acoustic wave, including the effect of adiabatic dust charge variation, is investigated in an unmagnetized three-component dusty plasma consisting of electrons, ions and massive micron sized negatively charged dust particulates. We have assumed that electrons and ions obey (r,q) velocity distribution while the dust species is treated fluid dynamically. It is found that the dynamics of dust acoustic waves is governed by a modified r dependent Korteweg-de Vries equation. Further, the spectral indices (r,q) affect the charge fluctuation as well as the trapping of electrons and ions and consequently modify the dust acoustic solitary wave

  13. Cold moderators for pulsed neutron sources

    International Nuclear Information System (INIS)

    Carpenter, J.M.

    1990-01-01

    This paper reviews cold moderators in pulsed neutron sources and provides details of the performance of different cold moderator materials and configurations. Analytical forms are presented which describe wavelength spectra and emission time distributions. Several types of cooling arrangements used in pulsed source moderators are described. Choices of materials are surveyed. The author examines some of the radiation damage effects in cold moderators, including the phenomenon of ''burping'' in irradiated cold solid methane. 9 refs., 15 figs., 4 tabs

  14. A transcription factor for cold sensation!

    OpenAIRE

    Kim, Susan J; Qu, Zhican; Milbrandt, Jeffrey; Zhuo, Min

    2005-01-01

    Abstract The ability to feel hot and cold is critical for animals and human beings to survive in the natural environment. Unlike other sensations, the physiology of cold sensation is mostly unknown. In the present study, we use genetically modified mice that do not express nerve growth factor-inducible B (NGFIB) to investigate the possible role of NGFIB in cold sensation. We found that genetic deletion of NGFIB selectively affected behavioral responses to cold stimuli while behavioral respons...

  15. Dust storm detection using random forests and physical-based ...

    Indian Academy of Sciences (India)

    arid areas of the Middle. East. Due to the influences of dust aerosols on climate and human daily activities, dust detection plays a crucial role in environmental and climatic studies. Detection of dust storms is critical to accurately under- stand dust ...

  16. Dust analysis on board the Destiny+ mission to 3200 Phaethon

    Science.gov (United States)

    Krüger, H.; Kobayashi, M.; Arai, T.; Srama, R.; Sarli, B. V.; Kimura, H.; Moragas-Klostermeyer, G.; Soja, R.; Altobelli, N.; Grün, E.

    2017-09-01

    The Japanese Destiny+ spacecraft will be launched to the active asteroid 3200 Phaethon in 2022. Among the proposed core payload is an in-situ dust instrument based on the Cassini Cosmic Dust Analyzer. We use the ESA Interplanetary Meteoroid Engineering Model (IMEM), to study detection conditions and fluences of interplanetary and interstellar dust with a dust analyzer on board Destiny+.

  17. Respirable quartz hazard associated with coal mine roof bolter dust

    International Nuclear Information System (INIS)

    Joy, G.J.; Beck, T.W.; Listak, J.M.

    2010-01-01

    Pneumoconiosis has been reported to be increasing among underground coal miners in the Southern Appalachian Region. The National Institute for Occupational Safety and Health conducted a study to examine the particle size distribution and quartz content of dust generated by the installation of roof bolts in mines. Forty-six bulk samples of roof bolting machine pre-cleaner cyclone dump dust and collector box dust were collected from 26 underground coal mines. Real-time and integrated airborne respirable dust concentrations were measured on 3 mining sections in 2 mines. The real-time airborne dust concentrations profiles were examined to identify any concentration changes that might be associated with pre-cleaner cyclone dust discharge events. The study showed that bolter dust is a potential inhalation hazard due to the fraction of dust less than 10 μm in size, and the quartz content of the dust. The pre-cleaner cyclone dust was significantly larger than the collector box dust, indicating that the pre-cleaner functioned properly in removing the larger dust size fraction from the airstream. However, the pre-cleaner dust still contained a substantial amount of respirable dust. It was concluded that in order to maintain the effectiveness of a roof bolter dust collector, periodic removal of dust is required. Appropriate work procedures and equipment are necessary to minimize exposure during this cleaning task. 13 refs., 3 tabs., 2 figs.

  18. Plasma particle lofting : experimental investigation of dust removal force

    NARCIS (Netherlands)

    Heijmans, L.C.J.; Nijdam, S.

    2015-01-01

    Dust is everywhere. Sometimes it's harmless, but sometimes it needs to be removed. Especially in modern optical machinery, dust control can be of vital importance. In this research we look at dust on a surface. We focus on the behaviour under influence of a plasma. The dust particles will stick to a

  19. QUANTIFYING THE HEATING SOURCES FOR MID-INFRARED DUST EMISSIONS IN GALAXIES: THE CASE OF M 81

    Energy Technology Data Exchange (ETDEWEB)

    Lu, N.; Zhao, Y. [Infrared Processing and Analysis Center, California Institute of Technology, MS 100-22, Pasadena, CA 91125 (United States); Bendo, G. J. [Jordrell Bank Center for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Boselli, A. [Laboratoire d' Astrophysique de Marseille-LAM, Université d' Aix-Marseille and CNRS, UMR7326, 38 rue F. Joliot-Curie, F-13388 Marseille Cedex 13 (France); Baes, M.; De Looze, I. [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent (Belgium); Wu, H.; Lam, M. I. [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Beijing 100012 (China); Madden, S. C.; Rémy-Ruyer, A. [Laboratoire AIM, CEA, Université Paris VII, IRFU/Service d' Ástrophysique, Bat. 709, F-91191 Gif-sur-Yvette (France); Boquien, M. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA (United Kingdom); Wilson, C. D. [Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Galametz, M. [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching-bei-Mnchen (Germany); Cooray, A. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Spinoglio, L., E-mail: lu@ipac.caltech.edu [Istituto di Astrofisica e Planetologia Spaziali, INAF, Via Fosso del Cavaliere 100, I-00133 Roma (Italy)

    2014-12-20

    With the newly available photometric images at 250 and 500 μm from the Herschel Space Observatory, we study quantitative correlations over a sub-kiloparsec scale among three distinct emission components in the interstellar medium of the nearby spiral galaxy M 81 (NGC 3031): (1) I {sub 8} or I {sub 24}, the surface brightness of the mid-infrared emission observed in the Spitzer Space Telescope 8 or 24 μm band, with I {sub 8} and I {sub 24} being dominated by the emissions from polycyclic aromatic hydrocarbons (PAHs) and very small grains (VSGs) of dust, respectively; (2) I {sub 500}, that of the cold dust continuum emission in the Herschel Space Observatory 500 μm band, dominated by the emission from large dust grains heated by evolved stars; and (3) I {sub Hα}, a nominal surface brightness of the Hα line emission, from gas ionized by newly formed massive stars. The results from our correlation study, free from any assumption on or modeling of dust emissivity law or dust temperatures, present solid evidence for significant heating of PAHs and VSGs by evolved stars. In the case of M 81, about 67% (48%) of the 8 μm (24 μm ) emission derives its heating from evolved stars, with the remainder attributed to radiation heating associated with ionizing stars.

  20. Limited production of sulfate and nitrate on front-associated dust storm particles moving from desert to distant populated areas in northwestern China

    Science.gov (United States)

    Wu, Feng; Zhang, Daizhou; Cao, Junji; Guo, Xiao; Xia, Yao; Zhang, Ting; Lu, Hui; Cheng, Yan

    2017-12-01

    particles following cold fronts is likely limited when the particles move from the desert to populated areas within the continent. For an accurate quantification of sulfate and nitrate formed on long-distance-transported desert dust particles at downwind populated areas in eastern China, dust collection efforts are indispensable to minimize any possible influence by locally emitted particles or at least to ensure that the samples are collected after dust arrival.