WorldWideScience

Sample records for high-velocity molecular gas

  1. High Velocity Gas Gun

    Science.gov (United States)

    1988-01-01

    A video tape related to orbital debris research is presented. The video tape covers the process of loading a High Velocity Gas Gun and firing it into a mounted metal plate. The process is then repeated in slow motion.

  2. Survey of high-velocity molecular gas in the vicinity of Herbig-Haro objects. I

    International Nuclear Information System (INIS)

    Edwards, S.; Snell, R.L.

    1983-01-01

    A survey of high-velocity molecular gas toward 49 Herbig-Haro objects is presented. Observations of the 12 CO J = 1-0 transition obtained with the 14 m telescope of the Five College Radio Astronomy Observatory reveal three new spatially extended high-velocity molecular outflows. One is in the NGC 1333 region near HH 12, and two are in the NGC 7129 region, the first near LkHα 234 and the second near a far-infrared source. The relationship between optical Herbin-Haro emission knots and large-scale motions of the ambient molecular material is investigated, and the properties of high-velocity molecular outflows in the vicinity of Herbig-Haro objects are discussed. Of 11 energetic outflows in the vicinity of Herbig-Haro objects, eight are found in four pairs separated by 0.2-1.0 pc. We estimate that energetic outflows characterized by mass loss rates > or =10 -7 M/sub sun/ yr -1 occur for at least 10 4 yr once in the lifetime of all stars with masses greater than 1M/sub sun/

  3. High velocity molecular gas near Herbig-Haro objects HH 7--11

    International Nuclear Information System (INIS)

    Snell, R.L.; Edwards, S.

    1981-01-01

    Observations of the J = 2-1 and J = 1-0 transitions of 12 CO and 13 CO reveal the presence of high velocity molecular gas associated with a low luminosity infrared source in the vicinity of the Herbig-Haro objects HH 7--11. The blueshifted and redshifted wings show peak intensities spatially separated by 1X5 (0.2 pc), suggesting an energetic bipolar outflow of gas from a young low mass star. The mass loss rate implied by these observations is 8 x 10 -6 M/sub sun/ yr -1

  4. Observations of high-velocity molecular gas near Herbig-Haro objects: HH 24--27 and HH 1--2

    International Nuclear Information System (INIS)

    Snell, R.L.; Edwards, S.

    1982-01-01

    High-velocity CO has been detected in the vicinity of the Herbig-Haro objects HH 24--27. These observations indicate that there are two sources of high-velocity outflow; one centered on an infrared source near HH 26, and the second centered roughly 2' south of HH 24. The redshifted and blueshifted wings in both sources are spatially separated suggesting that the high-velocity gas is due to energetic bipolar outflow from young stars embedded in the molecular cloud. The association of Herbig-Haro objects with regions of high-velocity gas suggests a common origin for both in the interaction of a stellar wind with the ambient molecular cloud. The mass loss rates implied by our observations, assuming that the rate of mass loss has been constant throughout the dynamical lifetime of the bipolar lobes, are roughly 10 -6 M/sub sun/ yr -1 for both sources. We have also searched for high-velocity gas near HH 1--2 but found no evidence for mass outflow in this region

  5. MAGNETIZED GAS IN THE SMITH HIGH VELOCITY CLOUD

    International Nuclear Information System (INIS)

    Hill, Alex S.; McClure-Griffiths, Naomi M.; Mao, S. A.; Benjamin, Robert A.; Lockman, Felix J.

    2013-01-01

    We report the first detection of magnetic fields associated with the Smith High Velocity Cloud. We use a catalog of Faraday rotation measures toward extragalactic radio sources behind the Smith Cloud, new H I observations from the Robert C. Byrd Green Bank Telescope, and a spectroscopic map of Hα from the Wisconsin H-Alpha Mapper Northern Sky Survey. There are enhancements in rotation measure (RM) of ≈100 rad m –2 which are generally well correlated with decelerated Hα emission. We estimate a lower limit on the line-of-sight component of the field of ≈8 μG along a decelerated filament; this is a lower limit due to our assumptions about the geometry. No RM excess is evident in sightlines dominated by H I or Hα at the velocity of the Smith Cloud. The smooth Hα morphology of the emission at the Smith Cloud velocity suggests photoionization by the Galactic ionizing radiation field as the dominant ionization mechanism, while the filamentary morphology and high (≈1 Rayleigh) Hα intensity of the lower-velocity magnetized ionized gas suggests an ionization process associated with shocks due to interaction with the Galactic interstellar medium. The presence of the magnetic field may contribute to the survival of high velocity clouds like the Smith Cloud as they move from the Galactic halo to the disk. We expect these data to provide a test for magnetohydrodynamic simulations of infalling gas

  6. Rotational explanation of the high-velocity meolecular emission from the Orion Molecular Cloud

    International Nuclear Information System (INIS)

    Clark, F.O.; Biretta, J.A.; Martin, H.M.

    1979-01-01

    The high-velocity molecular emission of the Orion Molecular Cloud has been sampled using the J/sub N/=2 2 --1 1 rotational spectral line of the SO molecule. The resulting profile, including the high-velocity wings, has been reproduced using only known large-scale properties of the gas and applications of the results of published theoretical calculations. No new physical mechanism is required; observed rotation and conservation of angular momentum are sufficient to reproduce the line profile. The resulting physical state appears to be consistent with all known physical properties. This solution is not unique, but indicates the strengths and weaknesses of such a model for interpretation of Orion as well as the similarities of alternative explanations

  7. Cool C-shocks and high-velocity flows in molecular clouds

    International Nuclear Information System (INIS)

    Smith, M.D.; Brand, P.W.J.L.

    1990-01-01

    C-shocks can be driven through dense clouds when the neutrals and magnetic field interact weakly due to a paucity of ions. We develop a method for calculating C-shock properties with the aim of interpreting the observed high-velocity molecular hydrogen. A high Mach number approximation, corresponding to low temperatures, is employed. Under strong cooling conditions the flow is continuous even though a subsonic region may be present downstream. Analytic expressions for the maximum temperature, dissociation fraction, self-ionization level and J-shock transition are derived. (author)

  8. Hydromagnetic Rayleigh endash Taylor instability in high-velocity gas-puff implosions

    International Nuclear Information System (INIS)

    Roderick, N.F.; Peterkin, R.E. Jr.; Hussey, T.W.; Spielman, R.B.; Douglas, M.R.; Deeney, C.

    1998-01-01

    Experiments using the Saturn pulsed power generator have produced high-velocity z-pinch plasma implosions with velocities over 100 cm/μs using both annular and uniform-fill gas injection initial conditions. Both types of implosion show evidence of the hydromagnetic Rayleigh endash Taylor instability with the uniform-fill plasmas producing a more spatially uniform pinch. Two-dimensional magnetohydrodynamic simulations including unsteady flow of gas from a nozzle into the diode region have been used to investigate these implosions. The instability develops from the nonuniform gas flow field that forms as the gas expands from the injection nozzle. Instability growth is limited to the narrow unstable region of the current sheath. For the annular puff the unstable region breaks through the inner edge of the annulus increasing nonlinear growth as mass ejected from the bubble regions is not replenished by accretion. This higher growth leads to bubble thinning and disruption producing greater nonuniformity at pinch for the annular puff. The uniform puff provides gas to replenish bubble mass loss until just before pinch resulting in less bubble thinning and a more uniform pinch. copyright 1998 American Institute of Physics

  9. Development of high velocity gas gun with a new trigger system-numerical analysis

    Science.gov (United States)

    Husin, Z.; Homma, H.

    2018-02-01

    In development of high performance armor vests, we need to carry out well controlled experiments using bullet speed of more than 900 m/sec. After reviewing trigger systems used for high velocity gas guns, this research intends to develop a new trigger system, which can realize precise and reproducible impact tests at impact velocity of more than 900 m/sec. A new trigger system developed here is called a projectile trap. A projectile trap is placed between a reservoir and a barrel. A projectile trap has two functions of a sealing disk and triggering. Polyamidimide is selected for the trap material and dimensions of the projectile trap are determined by numerical analysis for several levels of launching pressure to change the projectile velocity. Numerical analysis results show that projectile trap designed here can operate reasonably and stresses caused during launching operation are less than material strength. It means a projectile trap can be reused for the next shooting.

  10. Spatially Extended and High-Velocity Dispersion Molecular Component in Spiral Galaxies: Single-Dish Versus Interferometric Observations

    Science.gov (United States)

    Caldú-Primo, Anahi; Schruba, Andreas; Walter, Fabian; Leroy, Adam; Bolatto, Alberto D.; Vogel, Stuart

    2015-02-01

    Recent studies of the molecular medium in nearby galaxies have provided mounting evidence that the molecular gas can exist in two phases: one that is clumpy and organized as molecular clouds and another one that is more diffuse. This last component has a higher velocity dispersion than the clumpy one. In order to investigate these two molecular components further, we compare the fluxes and line widths of CO in NGC 4736 and NGC 5055, two nearby spiral galaxies for which high-quality interferometric as well as single-dish data sets are available. Our analysis leads to two main results: (1) employing three different methods, we determine the flux recovery of the interferometer as compared to the single-dish to be within a range of 35%-74% for NGC 4736 and 81%-92% for NGC 5055, and (2) when focusing on high (S/N ≥ 5) lines of sight (LOSs), the single-dish line widths are larger by ˜(40 ± 20)% than the ones derived from interferometric data, which is in agreement with stacking all LOSs. These results point to a molecular gas component that is distributed over spatial scales larger than 30″(˜1 kpc), and is therefore filtered out by the interferometer. The available observations do not allow us to distinguish between a truly diffuse gas morphology and a uniform distribution of small clouds that are separated by less than the synthesized beam size (˜3″ or ˜100 pc), as they would both be invisible for the interferometer. This high velocity dispersion component has a dispersion similar to what is found in the atomic medium, as traced through observations of the H i line.

  11. Spatially extended and high-velocity dispersion molecular component in spiral galaxies: Single-dish versus interferometric observations

    International Nuclear Information System (INIS)

    Caldú-Primo, Anahi; Walter, Fabian; Schruba, Andreas; Leroy, Adam; Bolatto, Alberto D.; Vogel, Stuart

    2015-01-01

    Recent studies of the molecular medium in nearby galaxies have provided mounting evidence that the molecular gas can exist in two phases: one that is clumpy and organized as molecular clouds and another one that is more diffuse. This last component has a higher velocity dispersion than the clumpy one. In order to investigate these two molecular components further, we compare the fluxes and line widths of CO in NGC 4736 and NGC 5055, two nearby spiral galaxies for which high-quality interferometric as well as single-dish data sets are available. Our analysis leads to two main results: (1) employing three different methods, we determine the flux recovery of the interferometer as compared to the single-dish to be within a range of 35%–74% for NGC 4736 and 81%–92% for NGC 5055, and (2) when focusing on high (S/N ≥ 5) lines of sight (LOSs), the single-dish line widths are larger by ∼(40 ± 20)% than the ones derived from interferometric data, which is in agreement with stacking all LOSs. These results point to a molecular gas component that is distributed over spatial scales larger than 30″(∼1 kpc), and is therefore filtered out by the interferometer. The available observations do not allow us to distinguish between a truly diffuse gas morphology and a uniform distribution of small clouds that are separated by less than the synthesized beam size (∼3″ or ∼100 pc), as they would both be invisible for the interferometer. This high velocity dispersion component has a dispersion similar to what is found in the atomic medium, as traced through observations of the H i line.

  12. Evolution of star-bearing molecular clouds: the high-velocity HCO+ flow in NGC 2071

    International Nuclear Information System (INIS)

    Wootten, A.; Loren, R.B.; Sandqvist, A.; Friberg, P.; Hjalmarson, Aa.

    1984-01-01

    The J = 1-0 and J = 302 lines of HCO + and H 13 CO + have been observed in the molecular cloud NGC 2071, where they map the dense portions of a bidirectional molecular flow. The high resolution (42'') of our observations has enabled us to determine the distribution of mass, momentum , and energy in the flow as a function of projected distance from the cluster. Both momentum and energy diminish with distance from the central cluster of infrared sources. The highest velocities at a given intensity in this dense flow occur in a limited region coincident with an infrared cluster and the densest part of the molecular cloud. Higher resolution (33'') CO and 13 CO observations reveal that the extreme velocities in the flow occur in regions displaced on opposite sides of the cluster, suggesting that the flow only becomes visible in molecular line emission at distances approx.0.1 pc from its supposed source. Lower velocity material containing most of the mass of the flow is found over larger regions, as expected if the flow has decelerated as it has evolved. Assuming conservation of momentum, the historical rate of momentum injection is found to have been roughly constant over a period of 10 4 years, suggesting a constancy of the average luminosity of the central cluster over that time. The J = 3--2 HCO + profile does not show the absorption which is a prominent feature of the J = 1--0 profile, and the J = 3--2 line appears to be a useful probe of conditions specific to the dense cores of clouds. The high velocity HCO + emission correlates very well with spatial and velocity events of molecular hydrogen emission. The abundance of HCO + [X(HCO + )approx.10 -8 ], and by inference the electron density, is similar in material at all velocities

  13. Integral Field Spectroscopy of Markarian 273: Mapping High-Velocity Gas Flows and an Off-Nucleus Seyfert 2 Nebula.

    Science.gov (United States)

    Colina; Arribas; Borne

    1999-12-10

    Integral field optical spectroscopy with the INTEGRAL fiber-based system is used to map the extended ionized regions and gas flows in Mrk 273, one of the closest ultraluminous infrared galaxies. The Hbeta and [O iii] lambda5007 maps show the presence of two distinct regions separated by 4&arcsec; (3.1 kpc) along position angle (P.A.) 240 degrees. The northeastern region coincides with the optical nucleus of the galaxy and shows the spectral characteristics of LINERs. The southwestern region is dominated by [O iii] emission and is classified as a Seyfert 2. Therefore, in the optical, Mrk 273 is an ultraluminous infrared galaxy with a LINER nucleus and an extended off-nucleus Seyfert 2 nebula. The kinematics of the [O iii] ionized gas shows (1) the presence of highly disturbed gas in the regions around the LINER nucleus, (2) a high-velocity gas flow with a peak-to-peak amplitude of 2.4x103 km s-1, and (3) quiescent gas in the outer regions (at 3 kpc). We hypothesize that the high-velocity flow is the starburst-driven superwind generated in an optically obscured nuclear starburst and that the quiescent gas is directly ionized by a nuclear source, similar to the ionization cones typically seen in Seyfert galaxies.

  14. DEPOSITION OF FISSION PRODUCTS FROM HELIUM GAS FLOWING AT HIGH VELOCITIES

    Energy Technology Data Exchange (ETDEWEB)

    Abriss, A.; Ewing, R. A.; Sunderman, D. N.

    1963-11-15

    From American Nuclear Society Meeting, New York, Nov. 1963. Out-of- pile experiments simulating gas cooled reactor flow and temperature conditions were made to correlate by both empirical and theoretical considerations such parameters as Reynolds numbers, velocity, surface conditions, materials of construction, geometry, particulate matter, and fission product diffusion coefficients. It was concluded that all regions of flow disturbance are areas of buildup of activity. No selectivity in deposition among the elements studied, with the exception of I, Te, and Cs, was found. Relative abundances to each other of less volatile isotopes remained constant throughout any particular experiment. Data are tabulated. (P.C.H.)

  15. PRESENT-DAY GALACTIC EVOLUTION: LOW-METALLICITY, WARM, IONIZED GAS INFLOW ASSOCIATED WITH HIGH-VELOCITY CLOUD COMPLEX A

    Energy Technology Data Exchange (ETDEWEB)

    Barger, K. A.; Haffner, L. M.; Wakker, B. P.; Hill, Alex S. [Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706 (United States); Madsen, G. J. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Duncan, A. K., E-mail: kbarger@astro.wisc.edu, E-mail: haffner@astro.wisc.edu, E-mail: Alex.Hill@csiro.au, E-mail: wakker@astro.wisc.edu, E-mail: greg.madsen@sydney.edu.au [Rose-Hulman Institute of Technology, Terre Haute, IN 47803 (United States)

    2012-12-20

    The high-velocity cloud Complex A is a probe of the physical conditions in the Galactic halo. The kinematics, morphology, distance, and metallicity of Complex A indicate that it represents new material that is accreting onto the Galaxy. We present Wisconsin H{alpha} Mapper kinematically resolved observations of Complex A over the velocity range of -250 to -50 km s{sup -1} in the local standard of rest reference frame. These observations include the first full H{alpha} intensity map of Complex A across (l, b) = (124 Degree-Sign , 18 Degree-Sign ) to (171 Degree-Sign , 53 Degree-Sign ) and deep targeted observations in H{alpha}, [S II] {lambda}6716, [N II] {lambda}6584, and [O I] {lambda}6300 toward regions with high H I column densities, background quasars, and stars. The H{alpha} data imply that the masses of neutral and ionized material in the cloud are similar, both being greater than 10{sup 6} M{sub Sun }. We find that the Bland-Hawthorn and Maloney model for the intensity of the ionizing radiation near the Milky Way is consistent with the known distance of the high-latitude part of Complex A and an assumed cloud geometry that puts the lower-latitude parts of the cloud at a distance of 7-8 kpc. This compatibility implies a 5% ionizing photon escape fraction from the Galactic disk. We also provide the nitrogen and sulfur upper abundance solutions for a series of temperatures, metallicities, and cloud configurations for purely photoionized gas; these solutions are consistent with the sub-solar abundances found by previous studies, especially for temperatures above 10{sup 4} K or for gas with a high fraction of singly ionized nitrogen and sulfur.

  16. HIGH-VELOCITY MOLECULAR OUTFLOW IN CO J = 7-6 EMISSION FROM THE ORION HOT CORE

    International Nuclear Information System (INIS)

    Furuya, Ray S.; Shinnaga, Hiroko

    2009-01-01

    Using the Caltech Submillimeter Observatory 10.4 m telescope, we performed sensitive mapping observations of 12 CO J = 7-6 emission at 807 GHz toward Orion IRc2. The image has an angular resolution of 10'', which is the highest angular resolution data toward the Orion Hot Core published for this transition. In addition, thanks to the on-the-fly mapping technique, the fidelity of the new image is rather high, particularly in comparison with previous images. We have succeeded in mapping the northwest-southeast high-velocity molecular outflow, whose terminal velocity is shifted by ∼70-85 km s -1 with respect to the systemic velocity of the cloud. This yields an extremely short dynamical time scale of ∼900 years. The estimated outflow mass loss rate shows an extraordinarily high value, on the order of 10 -3 M sun yr -1 . Assuming that the outflow is driven by Orion IRc2, our result agrees with the picture so far obtained for a 20 M sun (proto)star in the process of formation.

  17. THE EVOLUTION OF GAS CLOUDS FALLING IN THE MAGNETIZED GALACTIC HALO: HIGH-VELOCITY CLOUDS (HVCs) ORIGINATED IN THE GALACTIC FOUNTAIN

    International Nuclear Information System (INIS)

    Kwak, Kyujin; Shelton, Robin L.; Raley, Elizabeth A.

    2009-01-01

    In the Galactic fountain scenario, supernovae and/or stellar winds propel material into the Galactic halo. As the material cools, it condenses into clouds. By using FLASH three-dimensional magnetohydrodynamic simulations, we model and study the dynamical evolution of these gas clouds after they form and begin to fall toward the Galactic plane. In our simulations, we assume that the gas clouds form at a height of z = 5 kpc above the Galactic midplane, then begin to fall from rest. We investigate how the cloud's evolution, dynamics, and interaction with the interstellar medium (ISM) are affected by the initial mass of the cloud. We find that clouds with sufficiently large initial densities (n ≥ 0.1 H atoms cm -3 ) accelerate sufficiently and maintain sufficiently large column densities as to be observed and identified as high-velocity clouds (HVCs) even if the ISM is weakly magnetized (1.3 μG). However, the ISM can provide noticeable resistance to the motion of a low-density cloud (n ≤ 0.01 H atoms cm -3 ) thus making it more probable that a low-density cloud will attain the speed of an intermediate-velocity cloud rather than the speed of an HVC. We also investigate the effects of various possible magnetic field configurations. As expected, the ISM's resistance is greatest when the magnetic field is strong and perpendicular to the motion of the cloud. The trajectory of the cloud is guided by the magnetic field lines in cases where the magnetic field is oriented diagonal to the Galactic plane. The model cloud simulations show that the interactions between the cloud and the ISM can be understood via analogy to the shock tube problem which involves shock and rarefaction waves. We also discuss accelerated ambient gas, streamers of material ablated from the clouds, and the cloud's evolution from a sphere-shaped to a disk- or cigar-shaped object.

  18. Measuring Dark Molecular Gas

    Science.gov (United States)

    Li, Di; Heiles, Carl E.

    2017-01-01

    It is now well known that a substantial fraction of Galactic molecular gas cannot be traced by CO emission. The thus dubbed CO dark molecular gas (DMG) occupy a large volume of ISM with intermediate extinction, where CO is either not self-shielded and/or subthermally excited. We explore the utilities of simple hydrides, such OH, CH, etc., in tracing DMG. We mapped and modeled the transition zone cross a cloud boundary and derived emperical OH abundance and DMG distribution formulae. We also obtained absorption measurements of various species using Arecibo, VLA, ATCA, and ALMA. The absorption technique has the potential to provide systematic quantification of DMG in the next few years.

  19. Gas Phase Molecular Dynamics

    International Nuclear Information System (INIS)

    Hall, G.E.; Prrese, J.M.; Sears, T.J.; Weston, R.E.

    1999-01-01

    The goal of this research is the understanding of elementary chemical and physical processes important in the combustion of fossil fuels. Interest centers on reactions involving short-lived chemical intermediates and their properties. High-resolution high-sensitivity laser absorption methods are augmented by high temperature flow-tube reaction kinetics studies with mass spectrometric sampling. These experiments provide information on the energy levels, structures and reactivity of molecular flee radical species and, in turn, provide new tools for the study of energy flow and chemical bond cleavage in the radicals in chemical systems. The experimental work is supported by theoretical and computational work using time-dependent quantum wave packet calculations that provide insights into energy flow between the vibrational modes of the molecule

  20. The nature of the high-velocity gas in NGC 1275: first results with TAURUS-2 on the William Herschel telescope

    International Nuclear Information System (INIS)

    Unger, S.W.; Taylor, K.; Pedlar, A.; Ghataure, H.S.; Penston, M.V.; Robinson, A.

    1990-01-01

    Observations with a new imaging Fabry-Perot interferometer, TAURUS-2, show that there is a close spatial association between the two systems of emission-line gas in the active galaxy NGC 1275 (Perseus A, 3C84). It therefore seems likely that, as first suggested by previous authors, we are witnessing two galaxies in the process of colliding. We show that this hypothesis is consistent with all available observations of this object. (author)

  1. Southern high-velocity stars

    International Nuclear Information System (INIS)

    Augensen, H.J.; Buscombe, W.

    1978-01-01

    Using the model of the Galaxy presented by Eggen, Lynden-Bell and Sandage (1962), plane galactic orbits have been calculated for 800 southern high-velocity stars which possess parallax, proper motion, and radial velocity data. The stars with trigonometric parallaxes were selected from Buscombe and Morris (1958), supplemented by more recent spectroscopic data. Photometric parallaxes from infrared color indices were used for bright red giants studied by Eggen (1970), and for red dwarfs for which Rodgers and Eggen (1974) determined radial velocities. A color-color diagram based on published values of (U-B) and (B-V) for most of these stars is shown. (Auth.)

  2. High velocity impact experiment (HVIE)

    Energy Technology Data Exchange (ETDEWEB)

    Toor, A.; Donich, T.; Carter, P.

    1998-02-01

    The HVIE space project was conceived as a way to measure the absolute EOS for approximately 10 materials at pressures up to {approximately}30 Mb with order-of-magnitude higher accuracy than obtainable in any comparable experiment conducted on earth. The experiment configuration is such that each of the 10 materials interacts with all of the others thereby producing one-hundred independent, simultaneous EOS experiments The materials will be selected to provide critical information to weapons designers, National Ignition Facility target designers and planetary and geophysical scientists. In addition, HVIE will provide important scientific information to other communities, including the Ballistic Missile Defense Organization and the lethality and vulnerability community. The basic HVIE concept is to place two probes in counter rotating, highly elliptical orbits and collide them at high velocity (20 km/s) at 100 km altitude above the earth. The low altitude of the experiment will provide quick debris strip-out of orbit due to atmospheric drag. The preliminary conceptual evaluation of the HVIE has found no show stoppers. The design has been very easy to keep within the lift capabilities of commonly available rides to low earth orbit including the space shuttle. The cost of approximately 69 million dollars for 100 EOS experiment that will yield the much needed high accuracy, absolute measurement data is a bargain!

  3. A circumstellar molecular gas structure associated with the massive young star Cepheus A-HW 2

    Science.gov (United States)

    Torrelles, Jose M.; Rodriguez, Luis F.; Canto, Jorge; Ho, Paul T. P.

    1993-01-01

    We report the detection via VLA-D observations of ammonia of a circumstellar high-density molecular gas structure toward the massive young star related to the object Cepheus A-HW 2, a firm candidate for the powering source of the high-velocity molecular outflow in the region. We suggest that the circumstellar molecular gas structure could be related to the circumstellar disk previously suggested from infrared, H2O, and OH maser observations. We consider as a plausible scenario that the double radio continuum source of HW 2 could represent the ionized inner part of the circumstellar disk, in the same way as proposed to explain the double radio source in L1551. The observed motions in the circumstellar molecular gas can be produced by bound motions (e.g., infall or rotation) around a central mass of about 10-20 solar masses (B0.5 V star or earlier).

  4. STRUCTURED MOLECULAR GAS REVEALS GALACTIC SPIRAL ARMS

    Energy Technology Data Exchange (ETDEWEB)

    Sawada, Tsuyoshi [Joint ALMA Office, Alonso de Cordova 3107, Vitacura, Santiago 763-0355 (Chile); Hasegawa, Tetsuo [NAOJ Chile Observatory, Joaquin Montero 3000 Oficina 702, Vitacura, Santiago 763-0409 (Chile); Koda, Jin, E-mail: sawada.tsuyoshi@nao.ac.jp [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States)

    2012-11-01

    We explore the development of structures in molecular gas in the Milky Way by applying the analysis of the brightness distribution function and the brightness distribution index (BDI) in the archival data from the Boston University-Five College Radio Astronomy Observatory {sup 13}CO J = 1-0 Galactic Ring Survey. The BDI measures the fractional contribution of spatially confined bright molecular emission over faint emission extended over large areas. This relative quantity is largely independent of the amount of molecular gas and of any conventional, pre-conceived structures, such as cores, clumps, or giant molecular clouds. The structured molecular gas traced by higher BDI is located continuously along the spiral arms in the Milky Way in the longitude-velocity diagram. This clearly indicates that molecular gas changes its structure as it flows through the spiral arms. Although the high-BDI gas generally coincides with H II regions, there is also some high-BDI gas with no/little signature of ongoing star formation. These results support a possible evolutionary sequence in which unstructured, diffuse gas transforms itself into a structured state on encountering the spiral arms, followed by star formation and an eventual return to the unstructured state after the spiral arm passage.

  5. Gas Sensors Based on Molecular Imprinting Technology.

    Science.gov (United States)

    Zhang, Yumin; Zhang, Jin; Liu, Qingju

    2017-07-04

    Molecular imprinting technology (MIT); often described as a method of designing a material to remember a target molecular structure (template); is a technique for the creation of molecularly imprinted polymers (MIPs) with custom-made binding sites complementary to the target molecules in shape; size and functional groups. MIT has been successfully applied to analyze; separate and detect macromolecular organic compounds. Furthermore; it has been increasingly applied in assays of biological macromolecules. Owing to its unique features of structure specificity; predictability; recognition and universal application; there has been exploration of the possible application of MIPs in the field of highly selective gas sensors. In this present study; we outline the recent advances in gas sensors based on MIT; classify and introduce the existing molecularly imprinted gas sensors; summarize their advantages and disadvantages; and analyze further research directions.

  6. Metastable structure formation during high velocity grinding

    International Nuclear Information System (INIS)

    Samarin, A.N.; Klyuev, M.M.

    1984-01-01

    Metastable structures in surface layers of samples are; investigated during force high-velocity abrasive grinding. Samples of martensitic (40Kh13), austenitic (12Kh18N10T), ferritic (05Kh23Yu5) steels and some alloys, in particular KhN77TYuR (EhI437B), were grinded for one pass at treatment depth from 0.17 up to 2.6 mm. It is established that processes of homogenizing, recrystallization and coagulation are; developed during force high-velocity grinding along with polymorphic transformations in the zone of thermomechanical effect, that leads to changes of physical and mechanical properties of the surface

  7. SIMULATIONS OF HIGH-VELOCITY CLOUDS. I. HYDRODYNAMICS AND HIGH-VELOCITY HIGH IONS

    International Nuclear Information System (INIS)

    Kwak, Kyujin; Henley, David B.; Shelton, Robin L.

    2011-01-01

    We present hydrodynamic simulations of high-velocity clouds (HVCs) traveling through the hot, tenuous medium in the Galactic halo. A suite of models was created using the FLASH hydrodynamics code, sampling various cloud sizes, densities, and velocities. In all cases, the cloud-halo interaction ablates material from the clouds. The ablated material falls behind the clouds where it mixes with the ambient medium to produce intermediate-temperature gas, some of which radiatively cools to less than 10,000 K. Using a non-equilibrium ionization algorithm, we track the ionization levels of carbon, nitrogen, and oxygen in the gas throughout the simulation period. We present observation-related predictions, including the expected H I and high ion (C IV, N V, and O VI) column densities on sightlines through the clouds as functions of evolutionary time and off-center distance. The predicted column densities overlap those observed for Complex C. The observations are best matched by clouds that have interacted with the Galactic environment for tens to hundreds of megayears. Given the large distances across which the clouds would travel during such time, our results are consistent with Complex C having an extragalactic origin. The destruction of HVCs is also of interest; the smallest cloud (initial mass ∼ 120 M sun ) lost most of its mass during the simulation period (60 Myr), while the largest cloud (initial mass ∼ 4 x 10 5 M sun ) remained largely intact, although deformed, during its simulation period (240 Myr).

  8. PHOTOCHEMICAL HEATING OF DENSE MOLECULAR GAS

    Energy Technology Data Exchange (ETDEWEB)

    Glassgold, A. E. [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Najita, J. R. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)

    2015-09-10

    Photochemical heating is analyzed with an emphasis on the heating generated by chemical reactions initiated by the products of photodissociation and photoionization. The immediate products are slowed down by collisions with the ambient gas and then heat the gas. In addition to this direct process, heating is also produced by the subsequent chemical reactions initiated by these products. Some of this chemical heating comes from the kinetic energy of the reaction products and the rest from collisional de-excitation of the product atoms and molecules. In considering dense gas dominated by molecular hydrogen, we find that the chemical heating is sometimes as large, if not much larger than, the direct heating. In very dense gas, the total photochemical heating approaches 10 eV per photodissociation (or photoionization), competitive with other ways of heating molecular gas.

  9. Preparation of a pure molecular quantum gas.

    Science.gov (United States)

    Herbig, Jens; Kraemer, Tobias; Mark, Michael; Weber, Tino; Chin, Cheng; Nägerl, Hanns-Christoph; Grimm, Rudolf

    2003-09-12

    An ultracold molecular quantum gas is created by application of a magnetic field sweep across a Feshbach resonance to a Bose-Einstein condensate of cesium atoms. The ability to separate the molecules from the atoms permits direct imaging of the pure molecular sample. Magnetic levitation enables study of the dynamics of the ensemble on extended time scales. We measured ultralow expansion energies in the range of a few nanokelvin for a sample of 3000 molecules. Our observations are consistent with the presence of a macroscopic molecular matter wave.

  10. Galactic hail: the origin of the high-velocity cloud complex C

    NARCIS (Netherlands)

    Fraternali, F.; Marasco, A.; Armillotta, L.; Marinacci, F.

    High-velocity clouds consist of cold gas that appears to be raining down from the halo to the disc of the Milky Way. Over the past 50 years, two competing scenarios have attributed their origin either to gas accretion from outside the Galaxy or to circulation of gas from the Galactic disc powered by

  11. High-velocity frictional properties of gabbro

    Science.gov (United States)

    Tsutsumi, Akito; Shimamoto, Toshihiko

    High-velocity friction experiments have been performed on a pair of hollow-cylindrical specimens of gabbro initially at room temperature, at slip rates from 7.5 mm/s to 1.8 m/s, with total circumferential displacements of 125 to 174 m, and at normal stresses to 5 MPa, using a rotary-shear high-speed friction testing machine. Steady-state friction increases slightly with increasing slip rate at slip rates to about 100 mm/s (velocity strengthening) and it decreases markedly with increasing slip rate at higher velocities (velocity weakening). Steady-state friction in the velocity weakening regime is lower for the non-melting case than the frictional melting case, due perhaps to severe thermal fracturing. A very large peak friction is always recognized upon the initiation of visible frictional melting, presumably owing to the welding of fault surfaces upon the solidification of melt patches. Frictional properties thus change dramatically with increasing displacement at high velocities, and such a non-linear effect must be incorporated into the analysis of earthquake initiation processes.

  12. Consideration of wear rates at high velocity

    Science.gov (United States)

    Hale, Chad S.

    The development of the research presented here is one in which high velocity relative sliding motion between two bodies in contact has been considered. Overall, the wear environment is truly three-dimensional. The attempt to characterize three-dimensional wear was not economically feasible because it must be analyzed at the micro-mechanical level to get results. Thus, an engineering approximation was carried out. This approximation was based on a metallographic study identifying the need to include viscoplasticity constitutive material models, coefficient of friction, relationships between the normal load and velocity, and the need to understand wave propagation. A sled test run at the Holloman High Speed Test Track (HHSTT) was considered for the determination of high velocity wear rates. In order to adequately characterize high velocity wear, it was necessary to formulate a numerical model that contained all of the physical events present. The experimental results of a VascoMax 300 maraging steel slipper sliding on an AISI 1080 steel rail during a January 2008 sled test mission were analyzed. During this rocket sled test, the slipper traveled 5,816 meters in 8.14 seconds and reached a maximum velocity of 1,530 m/s. This type of environment was never considered previously in terms of wear evaluation. Each of the features of the metallography were obtained through micro-mechanical experimental techniques. The byproduct of this analysis is that it is now possible to formulate a model that contains viscoplasticity, asperity collisions, temperature and frictional features. Based on the observations of the metallographic analysis, these necessary features have been included in the numerical model, which makes use of a time-dynamic program which follows the movement of a slipper during its experimental test run. The resulting velocity and pressure functions of time have been implemented in the explicit finite element code, ABAQUS. Two-dimensional, plane strain models

  13. High velocity properties of the dynamic frictional force between ductile metals

    International Nuclear Information System (INIS)

    Hammerberg, James Edward; Hollan, Brad L.; Germann, Timothy C.; Ravelo, Ramon J.

    2010-01-01

    The high velocity properties of the tangential frictional force between ductile metal interfaces seen in large-scale NonEquilibrium Molecular Dynamics (NEMD) simulations are characterized by interesting scaling behavior. In many cases a power law decrease in the frictional force with increasing velocity is observed at high velocities. We discuss the velocity dependence of the high velocity branch of the tangential force in terms of structural transformation and ultimate transition, at the highest velocities, to confined fluid behavior characterized by a critical strain rate. The particular case of an Al/Al interface is discussed.

  14. Rotational temperature determinations in molecular gas lasers

    International Nuclear Information System (INIS)

    Weaver, L.A.; Taylor, L.H.; Denes, L.J.

    1975-01-01

    The small-signal gain expressions for vibrational-rotational transitions are examined in detail to determine possible methods of extracting the rotational temperature from experimental gain measurements in molecular gas lasers. Approximate values of T/subr/ can be deduced from the rotational quantum numbers for which the P- and R-branch gains are maximum. Quite accurate values of T/subr/ and the population inversion density (n/subv//sub prime/-n/subv//sub double-prime/) can be determined by fitting data to suitably linearized gain relationships, or by performing least-squares fits of the P- and R-branch experimental data to the full gain expressions. Experimental gain measurements for 15 P-branch and 12 R-branch transitions in the 10.4-μm CO 2 band have been performed for pulsed uv-preionized laser discharges in CO 2 : N 2 : He=1 : 2 : 3 mixtures at 600 Torr. These data are subjected to the several gain analyses described herein, yielding a rotational temperature of 401plus-or-minus10 degreeK and an inversion density of (3.77plus-or-minus0.07) times10 17 cm -3 for conditions of maximum gain. These techniques provide accurate values of the gas temperature in molecular gas lasers with excellent temporal and spatial resolution, and should be useful in extending the conversion efficiency and arcing limits of high-energy electrically exc []ted lasers

  15. Supernovae-generated high-velocity compact clouds

    Science.gov (United States)

    Yalinewich, A.; Beniamini, P.

    2018-05-01

    Context. A previous study claimed the discovery of an intermediate-mass black hole (IMBH). This hypothetical black hole was invoked in order to explain the high-velocity dispersion in one of several dense molecular clouds near the Galactic center. The same study considered the possibility that this cloud was due to a supernova explosion, but disqualified this scenario because no X-rays were detected. Aims: We here check whether a supernova explosion could have produced that cloud, and whether this explanation is more likely than an IMBH. More specifically, we wish to determine whether a supernova inside a dense molecular cloud would emit in the X-rays. Methods: We have approached this problem from two different directions. First, we performed an analytic calculation to determine the cooling rate by thermal bremsstrahlung and compared this time to the lifetime of the cloud. Second, we estimated the creation rate of these dense clouds in the central molecular zone (CMZ) region near the Galactic center, where they were observed. Based on this rate, we can place lower bounds on the total mass of IMBHs and clouds and compare this to the masses of the components of the CMZ. Results: We find that the cooling time of the supernova remnant inside a molecular cloud is shorter than its dynamical time. This means that the temperature in such a remnant would be much lower than that of a typical supernova remnant. At such a low temperature, the remnant is not expected to emit in the X-rays. We also find that to explain the rate at which such dense clouds are created requires fine-tuning the number of IMBHs. Conclusions: We find the supernova model to be a more likely explanation for the formation of high-velocity compact clouds than an IMBH.

  16. MOLECULAR GAS IN YOUNG DEBRIS DISKS

    International Nuclear Information System (INIS)

    Moor, A.; Abraham, P.; Kiss, Cs.; Juhasz, A.; Kospal, A.; Pascucci, I.; Apai, D.; Henning, Th.; Csengeri, T.; Grady, C.

    2011-01-01

    Gas-rich primordial disks and tenuous gas-poor debris disks are usually considered as two distinct evolutionary phases of the circumstellar matter. Interestingly, the debris disk around the young main-sequence star 49 Ceti possesses a substantial amount of molecular gas and possibly represents the missing link between the two phases. Motivated to understand the evolution of the gas component in circumstellar disks via finding more 49 Ceti-like systems, we carried out a CO J = 3-2 survey with the Atacama Pathfinder EXperiment, targeting 20 infrared-luminous debris disks. These systems fill the gap between primordial and old tenuous debris disks in terms of fractional luminosity. Here we report on the discovery of a second 49 Ceti-like disk around the 30 Myr old A3-type star HD21997, a member of the Columba Association. This system was also detected in the CO(2-1) transition, and the reliable age determination makes it an even clearer example of an old gas-bearing disk than 49 Ceti. While the fractional luminosities of HD21997 and 49 Ceti are not particularly high, these objects seem to harbor the most extended disks within our sample. The double-peaked profiles of HD21997 were reproduced by a Keplerian disk model combined with the LIME radiative transfer code. Based on their similarities, 49 Ceti and HD21997 may be the first representatives of a so far undefined new class of relatively old (∼>8 Myr), gaseous dust disks. From our results, neither primordial origin nor steady secondary production from icy planetesimals can unequivocally explain the presence of CO gas in the disk of HD21997.

  17. Molecular gas species in the lunar atmosphere

    International Nuclear Information System (INIS)

    Hoffman, J.H.; Hodges, R.R. Jr.

    1975-01-01

    There is good evidence for the existence of very small amounts of methane, ammonia and carbon dioxide in the very tenuous lunar atmosphere which consists primarily of the rare gases helium, neon and argon. All of these gases, except 40 Ar, originate from solar wind particles which impinge on the lunar surface and are imbedded in the surface material. Here they may form molecules before being released into the atmosphere, or may be released directly, as is the case for rare gases. Evidence for the existence of the molecular gas species is based on the pre-dawn enhancement of the mass peaks attributable to these compounds in the data from the Apollo 17 Lunar Mass Spectrometer. Methane is the most abundant molecular gas but its concentration is exceedingly low, 1 x 10 3 mol cm -3 , slightly less than 36 Ar, whereas the solar wind flux of carbon is approximately 2000 times that of 36 Ar. Several reasons are advanced for the very low concentration of methane in the lunar atmosphere

  18. High-velocity winds from a dwarf nova during outburst

    Science.gov (United States)

    Cordova, F. A.; Mason, K. O.

    1982-01-01

    An ultraviolet spectrum of the dwarf nova TW Vir during an optical outburst shows shortward-shifted absorption features with edge velocities as high as 4800 km/s, about the escape velocity of a white dwarf. A comparison of this spectrum with the UV spectra of other cataclysmic variables suggests that mass loss is evident only for systems with relatively high luminosities (more than about 10 solar luminosities) and low inclination angles with respect to the observer's line of sight. The mass loss rate for cataclysmic variables is of order 10 to the -11th solar mass per yr; this is from 0.01 to 0.001 of the mass accretion rate onto the compact star in the binary. The mass loss may occur by a mechanism similar to that invoked for early-type stars, i.e., radiation absorbed in the lines accelerates the accreting gas to the high velocities observed.

  19. RESPONSE OF STRUCTURES TO HIGH VELOCITY IMPACTS: A GENERALIZED ALGORITHM

    Directory of Open Access Journals (Sweden)

    Aversh'ev Anatoliy Sergeevich

    2012-10-01

    Full Text Available In this paper, a high velocity impact produced by a spherical striker and a target are considered; different stages of loading and unloading, target deformations and propagation of non-stationary wave surfaces within the target are analyzed. The problem of the strike modeling and subsequent deformations is solved by using not only the equations of mechanics of deformable rigid bodies, but also fluid mechanics equations. The target material is simulated by means of an ideal "plastic gas". Modeling results and theoretical calculations are compared to the experimental results. The crater depth, its correlation with the striker diameter, values of the pressure and deformations of the target underneath the contact area are determined as the main characteristics of dynamic interaction.

  20. High Velocity Oxidation and Hot Corrosion Resistance of Some ODS Alloys

    Science.gov (United States)

    Lowell, C. E.; Deadmore, D. L.

    1977-01-01

    Several oxide dispersion strengthened (ODS) alloys were tested for cyclic, high velocity, oxidation, and hot corrosion resistance. These results were compared to the resistance of an advanced, NiCrAl coated superalloy. An ODS FeCrAl were identified as having sufficient oxidation and hot corrosion resistance to allow potential use in an aircraft gas turbine without coating.

  1. Structure–performance characterization for carbon molecular sieve membranes using molecular scale gas probes

    KAUST Repository

    Rungta, Meha; Xu, Liren; Koros, William J.

    2015-01-01

    © 2015 Elsevier Ltd. All rights reserved. Understanding the relationship between carbon molecular sieve (CMS) pore structure and corresponding gas separation performance enables optimization for a given gas separation application. The final

  2. Gas flow parameter determination by molecular beam method

    International Nuclear Information System (INIS)

    Zarvin, A.E.; Sharafutdinov, R.G.

    1977-01-01

    This paper describes a molecular-beam system intended for studying nonequilibrium processes in supersonic rarefied gas flows. The system represented is a small molecular beam source placed inside the low intensity wind tunnel of the Institute of Thermophysics, Siberian Branch of the USSR Academy of Sciences. The time-of-flight method is used for measuring molecular velocity distribution functions on molecular beam axis. (Auth.)

  3. Gas Sensors Based on Molecular Imprinting Technology

    OpenAIRE

    Zhang, Yumin; Zhang, Jin; Liu, Qingju

    2017-01-01

    Molecular imprinting technology (MIT); often described as a method of designing a material to remember a target molecular structure (template); is a technique for the creation of molecularly imprinted polymers (MIPs) with custom-made binding sites complementary to the target molecules in shape; size and functional groups. MIT has been successfully applied to analyze; separate and detect macromolecular organic compounds. Furthermore; it has been increasingly applied in assays of biological mac...

  4. Experimental and numerical studies of high-velocity impact fragmentation

    Energy Technology Data Exchange (ETDEWEB)

    Kipp, M.E.; Grady, D.E.; Swegle, J.W.

    1993-08-01

    Developments are reported in both experimental and numerical capabilities for characterizing the debris spray produced in penetration events. We have performed a series of high-velocity experiments specifically designed to examine the fragmentation of the projectile during impact. High-strength, well-characterized steel spheres (6.35 mm diameter) were launched with a two-stage light-gas gun to velocities in the range of 3 to 5 km/s. Normal impact with PMMA plates, thicknesses of 0.6 to 11 mm, applied impulsive loads of various amplitudes and durations to the steel sphere. Multiple flash radiography diagnostics and recovery techniques were used to assess size, velocity, trajectory and statistics of the impact-induced fragment debris. Damage modes to the primary target plate (plastic) and to a secondary target plate (aluminum) were also evaluated. Dynamic fragmentation theories, based on energy-balance principles, were used to evaluate local material deformation and fracture state information from CTH, a three-dimensional Eulerian solid dynamics shock wave propagation code. The local fragment characterization of the material defines a weighted fragment size distribution, and the sum of these distributions provides a composite particle size distribution for the steel sphere. The calculated axial and radial velocity changes agree well with experimental data, and the calculated fragment sizes are in qualitative agreement with the radiographic data. A secondary effort involved the experimental and computational analyses of normal and oblique copper ball impacts on steel target plates. High-resolution radiography and witness plate diagnostics provided impact motion and statistical fragment size data. CTH simulations were performed to test computational models and numerical methods.

  5. Hydrogen distribution in a containment with a high-velocity hydrogen-steam source

    International Nuclear Information System (INIS)

    Bloom, G.R.; Muhlestein, L.D.; Postma, A.K.; Claybrook, S.W.

    1982-09-01

    Hydrogen mixing and distribution tests are reported for a modeled high velocity hydrogen-steam release from a postulated small pipe break or release from a pressurizer relief tank rupture disk into the lower compartment of an Ice Condenser Plant. The tests, which in most cases used helium as a simulant for hydrogen, demonstrated that the lower compartment gas was well mixed for both hydrogen release conditions used. The gas concentration differences between any spatial locations were less than 3 volume percent during the hydrogen/steam release period and were reduced to less than 0.5 volume percent within 20 minutes after termination of the hydrogen source. The high velocity hydrogen/steam jet provided the dominant mixing mechanism; however, natural convection and forced air recirculation played important roles in providing a well mixed atmosphere following termination of the hydrogen source. 5 figures, 4 tables

  6. Polymeric molecular sieve membranes for gas separation

    Science.gov (United States)

    Dai, Sheng; Qiao, Zhenan; Chai, Songhai

    2017-08-15

    A porous polymer membrane useful in gas separation, the porous polymer membrane comprising a polymeric structure having crosslinked aromatic groups and a hierarchical porosity in which micropores having a pore size less than 2 nm are present at least in an outer layer of the porous polymer membrane, and macropores having a pore size of over 50 nm are present at least in an inner layer of the porous polymer membrane. Also described are methods for producing the porous polymer membrane in which a non-porous polymer membrane containing aromatic rings is subjected to a Friedel-Crafts crosslinking reaction in which a crosslinking molecule crosslinks the aromatic rings in the presence of a Friedel-Crafts catalyst and organic solvent under sufficiently elevated temperature, as well as methods for using the porous polymer membranes for gas or liquid separation, filtration, or purification.

  7. HIGH VELOCITY THERMAL GUN FOR SURFACE PREPARATION AND TREATMENT

    Directory of Open Access Journals (Sweden)

    I.A. Gorlach

    2012-01-01

    Full Text Available Many surface preparation and treatment processes utilise compressed air to propel particles against surfaces in order to clean and treat them. The effectiveness of the processes depends on the velocity of the particles, which in turn depends on the pressure of the compressed air. This paper describes a thermal gun built on the principles of High Velocity Air Fuel (HVAF and High Velocity Oxy Fuel (HVOF processes. The designed apparatus can be used for abrasive blasting, coating of surfaces, cutting of rocks, removing rubber from mining equipment, cleaning of contaminations etc.

  8. Superconducting spoke cavities for high-velocity applications

    Energy Technology Data Exchange (ETDEWEB)

    Hopper, Christopher S. [Old Dominion U.; Delayen, Jean R. [Old Dominion U., JLAB

    2013-10-01

    To date, superconducting spoke cavities have been designed, developed, and tested for particle velocities up to {beta}{sub 0}~0.6, but there is a growing interest in possible applications of multispoke cavities for high-velocity applications. We have explored the design parameter space for low-frequency, high-velocity, double-spoke superconducting cavities in order to determine how each design parameter affects the electromagnetic properties, in particular the surface electromagnetic fields and the shunt impedance. We present detailed design for cavities operating at 325 and 352 MHz and optimized for {beta}{sub 0}~=0.82 and 1.

  9. The CO Transition from Diffuse Molecular Gas to Dense Clouds

    Science.gov (United States)

    Rice, Johnathan S.; Federman, Steven

    2017-06-01

    The atomic to molecular transitions occurring in diffuse interstellar gas surrounding molecular clouds are affected by the local physical conditions (density and temperature) and the radiation field penetrating the material. Our optical observations of CH, CH^{+}, and CN absorption from McDonald Observatory and the European Southern Observatory are useful tracers of this gas and provide the velocity structure needed for analyzing lower resolution ultraviolet observations of CO and H_{2} absorption from Far Ultraviolet Spectroscopic Explorer. We explore the changing environment between diffuse and dense gas by using the column densities and excitation temperatures from CO and H_{2} to determine the gas density. The resulting gas densities from this method are compared to densities inferred from other methods such as C_{2} and CN chemistry. The densities allow us to interpret the trends from the combined set of tracers. Groupings of sight lines, such as those toward h and χ Persei or Chameleon provide a chance for further characterization of the environment. The Chameleon region in particular helps illuminate CO-dark gas, which is not associated with emission from H I at 21 cm or from CO at 2.6 mm. Expanding this analysis to include emission data from the GOT C+ survey allows the further characterization of neutral diffuse gas, including CO-dark gas.

  10. Molecular gas in dusty high-redshift galaxies

    Science.gov (United States)

    Sharon, Chelsea Electra

    2013-12-01

    We present high-resolution observations of carbon monoxide (CO) emission lines for three high-redshift galaxies in order to determine their molecular gas and star formation properties. These galaxies (SMM J14011+0252, SMM J00266+1708, and SDSS J0901+1814) have large infrared luminosities, which imply high dust enshrouded star formation rates and substantial molecular gas masses. We observed these sources using the Robert C. Byrd Green Bank Telescope, the Karl G. Jansky Very Large Array, the Plateau de Bure Interferometer, and the Submillimeter Array in order to obtain measurements of multiple CO spectral lines, allowing us to determine the physical conditions of the molecular gas. Our high resolution and multi-line CO mapping of SMM J00266+1708 reveals that it is a pair of merging galaxies, whose two components have different gas excitation conditions and different gas kinematics. For SMM J14011+0252 (J14011), we find a near-unity CO(3--2)/CO(1--0) intensity ratio, consistent with a single phase (i.e., a single temperature and density) of molecular gas and different from the average population value for dusty galaxies selected at submillimeter wavelengths. Our radiative transfer modeling (using the large velocity gradient approximation) indicates that converting the CO line luminosity to molecular gas mass requires a Galactic (disk-like) scale factor rather than the typical conversion factor assumed for starbursts. Despite this choice of conversion factor, J14011 falls in the same region of star formation rate surface density and gas mass surface density (the Schmidt-Kennicutt relation) as other starburst galaxies. SDSS J0901+1814 (J0901) was initially selected as a star-forming galaxy at ultraviolet wavelengths, but also has a large infrared luminosity. We use the magnification provided by the strong gravitational lensing affecting this system to examine the spatial variation of the CO excitation within J0901. We find that the CO(3--2)/CO(1--0) line ratio is

  11. Distances, metallicities and origins of high-velocity clouds

    NARCIS (Netherlands)

    van Woerden, H; Wakker, BP; Peletier, RF; Schwarz, UJ; KraanKorteweg, RC; Henning, PA; Andernach, H

    2000-01-01

    A review is given of distances of high-velocity clouds (HVCs) derived from absorption-line measurements, and of the metallicities of HVCs. Chain A definitely lies in the Galactic halo, between 2.5 and 7 kpc above the plane. The distance limits available for other HVCs allow a variety of locations:

  12. On the origin of high-velocity runaway stars

    NARCIS (Netherlands)

    Gvaramadze, V.V.; Gualandris, A.; Portegies Zwart, S.

    2009-01-01

    We explore the hypothesis that some high-velocity runaway stars attain their peculiar velocities in the course of exchange encounters between hard massive binaries and a very massive star (either an ordinary 50-100 M-circle dot star or a more massive one, formed through runaway mergers of ordinary

  13. Laser heating of a molecular gas channel

    International Nuclear Information System (INIS)

    Olsen, J.N.; Baker, L.

    1980-02-01

    The first steps toward laser-initiated discharge channels are outlined, wherein we determine the temperature and density changes which are to be expected with reasonable laser energies. To this end, absorption cross sections were measured as a function of gas pressure, line tuning, and laser energy for NH 3 and C 2 H 4 gases. Based on these values a number of hydrodynamic simulations were performed with the CHARTB hydrocode which show that an efficient conversion of initial vibrational temperature into translational temperature occurs. Moreover, it is seen that the hydrodynamic motion is slow compared to reasonable relaxation times so that this efficiency is not unique to NH 3 with its anomalously fast relaxation time

  14. Energy loss of charged particles to molecular gas targets

    International Nuclear Information System (INIS)

    Sigmund, P.

    1976-01-01

    The energy loss spectrum of fast charged particles penetrating a dilute molecular gas target has been analysed theoretically, with a homogeneous gas mixture in the state of complete dissociation as a reference standard. It is shown that the geometrical structure of molecules causes the energy-loss straggling and higher moments over the energy-loss spectrum to be greater than the corresponding quantities for a completely dissociated gas of equal composition. Such deviations from additivity are shown to be most pronounced at energies around the stopping-power maximum. There is found supporting evidence in the experimental literature. (Auth.)

  15. A New View of Molecular Gas in the Galactic Center

    Science.gov (United States)

    Mills, Elisabeth A.; Morris, M.; Güsten, R.; Requena Torres, M.; Lang, C. C.; Butterfield, N.; Ott, J.

    2013-01-01

    On average, the molecular gas in the center of our Galaxy is significantly hotter (T = 50-300 K), denser (n > 10^4 cm^-3), and more turbulent than gas in the rest of the disk. I will present results from a recent series of observations that indicate that our understanding of the Galactic center (GC) molecular gas is incomplete, and that conditions in some clouds are even more extreme than previously thought. Using the Green Bank telescope, we have measured a very hot molecular gas component (T = 400-500 K ) in three largely quiescent GC giant molecular clouds using metastable inversion lines of ammonia from (8,8) to (15,15) . We further detect the (9,9) line in seven other GC clouds, indicating that this hot gas component may be a common feature of GC clouds, potentially yielding insight into the heating source of the molecular gas in this region. In addition, I will present new density constraints for the circumnuclear disk (CND), a reservoir of gas and dust 1.5 parsecs in radius from the central supermassive black hole, Sgr A*. Recent estimates of the CND density vary by four orders of magnitude, which makes its future evolution uncertain: gas in the CND could either accrete onto the black hole, dissipate, or, if the density is higher than 10^7 cm^-3, exist in gravitationally-stable clumps capable of forming stars. However, our APEX measurements of highly excited lines of HCN and HCO+ indicate that although the CND gas is denser than most other GC clouds, it is not likely to be tidally stable and thus is unlikely to host star formation. Finally, I will present early results from a new Very Large Array study of gas on sub-parsec scales in a sample of GC clouds, all of which exhibit unexpectedly abundant Class I methanol maser emission. The widespread distribution of these masers suggests shocks play an important role in driving cloud evolution throughout this unique region of our Galaxy.

  16. Free-Molecular Gas Flow in Narrow (Nanoscale) Channel

    Czech Academy of Sciences Publication Activity Database

    Levdansky, V.V.; Roldugin, V.I.; Žďanov, V.M.; Ždímal, Vladimír

    2014-01-01

    Roč. 87, č. 4 (2014), s. 802-814 ISSN 1062-0125 Grant - others:BRFFI(BY) T12P-018; RFBR(RU) 12-08-90009 Institutional support: RVO:67985858 Keywords : narrow channels * free-molecular gas flow * surface diffusion Subject RIV: CF - Physical ; Theoretical Chemistry

  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. WARM MOLECULAR GAS IN LUMINOUS INFRARED GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Lu, N.; Zhao, Y.; Xu, C. K.; Mazzarella, J. M.; Howell, J.; Appleton, P.; Lord, S.; Schulz, B. [Infrared Processing and Analysis Center, California Institute of Technology, MS 100-22, Pasadena, CA 91125 (United States); Gao, Y. [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Armus, L.; Díaz-Santos, T.; Surace, J. [Spitzer Science Center, California Institute of Technology, MS 220-6, Pasadena, CA 91125 (United States); Isaak, K. G. [ESA Astrophysics Missions Division, ESTEC, P.O. Box 299, 2200-AG Noordwijk (Netherlands); Petric, A. O. [Gemini Observatory, 670 N. A' ohoku Place, Hilo, HI 96720 (United States); Charmandaris, V. [Department of Physics, University of Crete, GR-71003 Heraklion (Greece); Evans, A. S. [Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, VA 22904 (United States); Inami, H. [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States); Iwasawa, K. [ICREA and Institut de Ciències del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), Martí i Franquès 1, E-08028 Barcelona (Spain); Leech, J. [Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Sanders, D. B., E-mail: lu@ipac.caltech.edu [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); and others

    2014-06-01

    We present our initial results on the CO rotational spectral line energy distribution (SLED) of the J to J–1 transitions from J = 4 up to 13 from Herschel SPIRE spectroscopic observations of 65 luminous infrared galaxies (LIRGs) in the Great Observatories All-Sky LIRG Survey. The observed SLEDs change on average from one peaking at J ≤ 4 to a broad distribution peaking around J ∼ 6 to 7 as the IRAS 60-to-100 μm color, C(60/100), increases. However, the ratios of a CO line luminosity to the total infrared luminosity, L {sub IR}, show the smallest variation for J around 6 or 7. This suggests that, for most LIRGs, ongoing star formation (SF) is also responsible for a warm gas component that emits CO lines primarily in the mid-J regime (5 ≲ J ≲ 10). As a result, the logarithmic ratios of the CO line luminosity summed over CO (5–4), (6–5), (7–6), (8–7) and (10–9) transitions to L {sub IR}, log R {sub midCO}, remain largely independent of C(60/100), and show a mean value of –4.13 (≡log R{sub midCO}{sup SF}) and a sample standard deviation of only 0.10 for the SF-dominated galaxies. Including additional galaxies from the literature, we show, albeit with a small number of cases, the possibility that galaxies, which bear powerful interstellar shocks unrelated to the current SF, and galaxies, in which an energetic active galactic nucleus contributes significantly to the bolometric luminosity, have their R {sub midCO} higher and lower than R{sub midCO}{sup SF}, respectively.

  19. Simple Motor Control Concept Results High Efficiency at High Velocities

    Science.gov (United States)

    Starin, Scott; Engel, Chris

    2013-09-01

    The need for high velocity motors in space applications for reaction wheels and detectors has stressed the limits of Brushless Permanent Magnet Motors (BPMM). Due to inherent hysteresis core losses, conventional BPMMs try to balance the need for torque verses hysteresis losses. Cong-less motors have significantly less hysteresis losses but suffer from lower efficiencies. Additionally, the inherent low inductance in cog-less motors result in high ripple currents or high switching frequencies, which lowers overall efficiency and increases performance demands on the control electronics.However, using a somewhat forgotten but fully qualified technology of Isotropic Magnet Motors (IMM), extremely high velocities may be achieved at low power input using conventional drive electronics. This paper will discuss the trade study efforts and empirical test data on a 34,000 RPM IMM.

  20. High-velocity runaway stars from three-body encounters

    Science.gov (United States)

    Gvaramadze, V. V.; Gualandris, A.; Portegies Zwart, S.

    2010-01-01

    We performed numerical simulations of dynamical encounters between hard, massive binaries and a very massive star (VMS; formed through runaway mergers of ordinary stars in the dense core of a young massive star cluster) to explore the hypothesis that this dynamical process could be responsible for the origin of high-velocity (≥ 200 - 400 km s-1) early or late B-type stars. We estimated the typical velocities produced in encounters between very tight massive binaries and VMSs (of mass of ≥ 200 M⊙) and found that about 3 - 4% of all encounters produce velocities ≥ 400 km s-1, while in about 2% of encounters the escapers attain velocities exceeding the Milky Ways's escape velocity. We therefore argue that the origin of high-velocity (≥ 200 - 400 km s-1) runaway stars and at least some so-called hypervelocity stars could be associated with dynamical encounters between the tightest massive binaries and VMSs formed in the cores of star clusters. We also simulated dynamical encounters between tight massive binaries and single ordinary 50 - 100 M⊙ stars. We found that from 1 to ≃ 4% of these encounters can produce runaway stars with velocities of ≥ 300 - 400 km s-1 (typical of the bound population of high-velocity halo B-type stars) and occasionally (in less than 1% of encounters) produce hypervelocity (≥ 700 km s-1) late B-type escapers.

  1. MXene molecular sieving membranes for highly efficient gas separation.

    Science.gov (United States)

    Ding, Li; Wei, Yanying; Li, Libo; Zhang, Tao; Wang, Haihui; Xue, Jian; Ding, Liang-Xin; Wang, Suqing; Caro, Jürgen; Gogotsi, Yury

    2018-01-11

    Molecular sieving membranes with sufficient and uniform nanochannels that break the permeability-selectivity trade-off are desirable for energy-efficient gas separation, and the arising two-dimensional (2D) materials provide new routes for membrane development. However, for 2D lamellar membranes, disordered interlayer nanochannels for mass transport are usually formed between randomly stacked neighboring nanosheets, which is obstructive for highly efficient separation. Therefore, manufacturing lamellar membranes with highly ordered nanochannel structures for fast and precise molecular sieving is still challenging. Here, we report on lamellar stacked MXene membranes with aligned and regular subnanometer channels, taking advantage of the abundant surface-terminating groups on the MXene nanosheets, which exhibit excellent gas separation performance with H 2 permeability >2200 Barrer and H 2 /CO 2 selectivity >160, superior to the state-of-the-art membranes. The results of molecular dynamics simulations quantitatively support the experiments, confirming the subnanometer interlayer spacing between the neighboring MXene nanosheets as molecular sieving channels for gas separation.

  2. Thermal SiO as a probe of high velocity motions in regions of star formation

    International Nuclear Information System (INIS)

    Downes, D.; Genzel, R.; Hjalmarson, A.; Nyman, L.A.; Roennaeng, B.

    1982-01-01

    New observations of the v = 0, J = = 2→1 line of SiO at 86.8 GHz show a close association of the thermal SiO emission and infrared and maser sources in regions of star formation. In addition to SiO emission with low velocity dispersion (Δν -1 ), we report the first detection of high velocity (''plateau'') emission toward W49 and W51. The low velocity SiO component may come from the core of the molecular cloud which contains the infrared and maser sources. The ''plateau'' may indicate mass clusters. In Orion KL, the positional centroid of the high velocity SiO emission (Vertical BarΔνVertical Bar> or =20 km s -1 ) is near that of the component we identify as the ''18 km s -1 flow''. However, the centriods of the blue- and redshifted wings are displaced from each other by a few arcseconds, to the NW and NE of the position of the 18 km s -1 component. The mass-loss rates of the high velocity flow and the 18 km s -1 flow are similar

  3. Compression of turbulent magnetized gas in giant molecular clouds

    Science.gov (United States)

    Birnboim, Yuval; Federrath, Christoph; Krumholz, Mark

    2018-01-01

    Interstellar gas clouds are often both highly magnetized and supersonically turbulent, with velocity dispersions set by a competition between driving and dissipation. This balance has been studied extensively in the context of gases with constant mean density. However, many astrophysical systems are contracting under the influence of external pressure or gravity, and the balance between driving and dissipation in a contracting, magnetized medium has yet to be studied. In this paper, we present three-dimensional magnetohydrodynamic simulations of compression in a turbulent, magnetized medium that resembles the physical conditions inside molecular clouds. We find that in some circumstances the combination of compression and magnetic fields leads to a rate of turbulent dissipation far less than that observed in non-magnetized gas, or in non-compressing magnetized gas. As a result, a compressing, magnetized gas reaches an equilibrium velocity dispersion much greater than would be expected for either the hydrodynamic or the non-compressing case. We use the simulation results to construct an analytic model that gives an effective equation of state for a coarse-grained parcel of the gas, in the form of an ideal equation of state with a polytropic index that depends on the dissipation and energy transfer rates between the magnetic and turbulent components. We argue that the reduced dissipation rate and larger equilibrium velocity dispersion has important implications for the driving and maintenance of turbulence in molecular clouds and for the rates of chemical and radiative processes that are sensitive to shocks and dissipation.

  4. General physical characteristics of the interstellar molecular gas

    International Nuclear Information System (INIS)

    Turner, B.E.

    1979-01-01

    The interstellar medium may be characterized by several physically rather distinct regimes: coronal gas, intercloud gas, diffuse clouds, isolated dark clouds and globules (of small to modest mass), more massive molecular clouds containing OB (and later) stars, and giant molecular clouds. Values of temperature, density, ionization fraction, mass, size, and velocity field are discussed for each regime. Heating and cooling mechanisms are reviewed. Nearly all molecular clouds exceed the Jeans criteria for gravitational instability, yet detailed models reveal no cases where observations can be interpreted unambiguously in terms of rapid collapse. The possibility that clouds are supported by turbulence, rotation, or magnetic fields is discussed, and it is concluded that none of these agencies suffice. Comments are made about fragmentation and star formation in molecular clouds, with possible explanations for why only low mass stars form in low mass clouds, why early-type stars form only in clouds with masses > approximately 10 3 M solar masses, and why O-stars seem to form near edges of clouds. Finally, large-scale interactions between molecular clouds and the galactic disk stellar population are discussed. (Auth.)

  5. Shocked molecular gas and the origin of cosmic rays

    Science.gov (United States)

    Reach, William; Gusdorf, Antoine; Richter, Matthew

    2018-06-01

    When massive stars reach the end of their ability to remain stable with core nuclear fusion, they explode in supernovae that drive powerful shocks into their surroundings. Because massive stars form in and remain close to molecular clouds they often drive shocks into dense gas, which is now believed to be the origin of a significant fraction of galactic cosmic rays. The nature of the supernova-molecular cloud interaction is not well understood, though observations are gradually elucidating their nature. The range of interstellar densities, and the inclusion of circumstellar matter from the late-phase mass-loss of the stars before their explosions, leads to a wide range of possible appearances and outcomes. In particular, it is not even clear what speed or physical type of shocks are present: are they dense, magnetically-mediated shocks where H2 is not dissociated, or are they faster shocks that dissociate molecules and destroy some of the grains? SOFIA is observing some of the most significant (in terms of cosmic ray production potential and infrared energy output) supernova-molecular cloud interactions for measurement of the line widths of key molecular shocks tracers: H2, [OI], and CO. The presence of gas at speeds 100 km/s or greater would indicate dissociative shocks, while speeds 30 km/s and slower retain most molecules. The shock velocity is a key ingredient in modeling the interaction between supernovae and molecular clouds including the potential for formation of cosmic rays.

  6. MOLECULAR GAS AND STAR FORMATION IN NEARBY DISK GALAXIES

    International Nuclear Information System (INIS)

    Leroy, Adam K.; Munoz-Mateos, Juan-Carlos; Walter, Fabian; Sandstrom, Karin; Meidt, Sharon; Rix, Hans-Walter; Schinnerer, Eva; Schruba, Andreas; Bigiel, Frank; Bolatto, Alberto; Brinks, Elias; De Blok, W. J. G.; Rosolowsky, Erik; Schuster, Karl-Friedrich; Usero, Antonio

    2013-01-01

    We compare molecular gas traced by 12 CO (2-1) maps from the HERACLES survey, with tracers of the recent star formation rate (SFR) across 30 nearby disk galaxies. We demonstrate a first-order linear correspondence between Σ mol and Σ SFR but also find important second-order systematic variations in the apparent molecular gas depletion time, τ dep mol =Σ mol /Σ SFR . At the 1 kpc common resolution of HERACLES, CO emission correlates closely with many tracers of the recent SFR. Weighting each line of sight equally, using a fixed α CO equivalent to the Milky Way value, our data yield a molecular gas depletion time, τ dep mol =Σ mol /Σ SFR ∼2.2 Gyr with 0.3 dex 1σ scatter, in very good agreement with recent literature data. We apply a forward-modeling approach to constrain the power-law index, N, that relates the SFR surface density and the molecular gas surface density, Σ SFR ∝Σ mol N . We find N = 1 ± 0.15 for our full data set with some scatter from galaxy to galaxy. This also agrees with recent work, but we caution that a power-law treatment oversimplifies the topic given that we observe correlations between τ dep mol and other local and global quantities. The strongest of these are a decreased τ dep mol in low-mass, low-metallicity galaxies and a correlation of the kpc-scale τ dep mol with dust-to-gas ratio, D/G. These correlations can be explained by a CO-to-H 2 conversion factor (α CO ) that depends on dust shielding, and thus D/G, in the theoretically expected way. This is not a unique interpretation, but external evidence of conversion factor variations makes this the most conservative explanation of the strongest observed τ dep mol trends. After applying a D/G-dependent α CO , some weak correlations between τ dep mol and local conditions persist. In particular, we observe lower τ dep mol and enhanced CO excitation associated with nuclear gas concentrations in a subset of our targets. These appear to reflect real enhancements in the

  7. Molecular Gas Feeding the Circumnuclear Disk of the Galactic Center

    Energy Technology Data Exchange (ETDEWEB)

    Hsieh, Pei-Ying; Koch, Patrick M.; Ho, Paul T. P.; Tang, Ya-Wen [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China); Kim, Woong-Tae [Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of); Wang, Hsiang-Hsu [Department of Physics and Institute of Theoretical Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong (China); Yen, Hsi-Wei [European Southern Observatory (ESO), Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Hwang, Chorng-Yuan, E-mail: pyhsieh@asiaa.sinica.edu.tw [Institute of Astronomy, National Central University, No.300, Jhongda Road, Jhongli City, Taoyuan County 32001, Taiwan (China)

    2017-09-20

    The interaction between a supermassive black hole (SMBH) and the surrounding material is of primary importance in modern astrophysics. The detection of the molecular 2 pc circumnuclear disk (CND) immediately around the Milky Way SMBH, SgrA*, provides a unique opportunity to study SMBH accretion at subparsec scales. Our new wide-field CS( J = 2 − 1) map toward the Galactic center (GC) reveals multiple dense molecular streamers that originated from the ambient clouds 20 pc further out, and that are connected to the central 2 pc of the CND. These dense gas streamers appear to carry gas directly toward the nuclear region and might be captured by the central potential. Our phase-plot analysis indicates that these streamers show a signature of rotation and inward radial motion with progressively higher velocities as the gas approaches the CND and finally ends up corotating with the CND. Our results might suggest a possible mechanism of gas feeding the CND from 20 pc around 2 pc in the GC. In this paper, we discuss the morphology and the kinematics of these streamers. As the nearest observable Galactic nucleus, this feeding process may have implications for understanding the processes in extragalactic nuclei.

  8. PHIBSS: Unified Scaling Relations of Gas Depletion Time and Molecular Gas Fractions

    Science.gov (United States)

    Tacconi, L. J.; Genzel, R.; Saintonge, A.; Combes, F.; García-Burillo, S.; Neri, R.; Bolatto, A.; Contini, T.; Förster Schreiber, N. M.; Lilly, S.; Lutz, D.; Wuyts, S.; Accurso, G.; Boissier, J.; Boone, F.; Bouché, N.; Bournaud, F.; Burkert, A.; Carollo, M.; Cooper, M.; Cox, P.; Feruglio, C.; Freundlich, J.; Herrera-Camus, R.; Juneau, S.; Lippa, M.; Naab, T.; Renzini, A.; Salome, P.; Sternberg, A.; Tadaki, K.; Übler, H.; Walter, F.; Weiner, B.; Weiss, A.

    2018-02-01

    This paper provides an update of our previous scaling relations between galaxy-integrated molecular gas masses, stellar masses, and star formation rates (SFRs), in the framework of the star formation main sequence (MS), with the main goal of testing for possible systematic effects. For this purpose our new study combines three independent methods of determining molecular gas masses from CO line fluxes, far-infrared dust spectral energy distributions, and ∼1 mm dust photometry, in a large sample of 1444 star-forming galaxies between z = 0 and 4. The sample covers the stellar mass range log(M */M ⊙) = 9.0–11.8, and SFRs relative to that on the MS, δMS = SFR/SFR(MS), from 10‑1.3 to 102.2. Our most important finding is that all data sets, despite the different techniques and analysis methods used, follow the same scaling trends, once method-to-method zero-point offsets are minimized and uncertainties are properly taken into account. The molecular gas depletion time t depl, defined as the ratio of molecular gas mass to SFR, scales as (1 + z)‑0.6 × (δMS)‑0.44 and is only weakly dependent on stellar mass. The ratio of molecular to stellar mass μ gas depends on (1+z{)}2.5× {(δ {MS})}0.52× {({M}* )}-0.36, which tracks the evolution of the specific SFR. The redshift dependence of μ gas requires a curvature term, as may the mass dependences of t depl and μ gas. We find no or only weak correlations of t depl and μ gas with optical size R or surface density once one removes the above scalings, but we caution that optical sizes may not be appropriate for the high gas and dust columns at high z. Based on observations of an IRAM Legacy Program carried out with the NOEMA, operated by the Institute for Radio Astronomy in the Millimetre Range (IRAM), which is funded by a partnership of INSU/CNRS (France), MPG (Germany), and IGN (Spain).

  9. Decision making in high-velocity environments: implications for healthcare.

    Science.gov (United States)

    Stepanovich, P L; Uhrig, J D

    1999-01-01

    Healthcare can be considered a high-velocity environment and, as such, can benefit from research conducted in other industries regarding strategic decision making. Strategic planning is not only relevant to firms in high-velocity environments, but is also important for high performance and survival. Specifically, decision-making speed seems to be instrumental in differentiating between high and low performers; fast decision makers outperform slow decision makers. This article outlines the differences between fast and slow decision makers, identifies five paralyses that can slow decision making in healthcare, and outlines the role of a planning department in circumventing these paralyses. Executives can use the proposed planning structure to improve both the speed and quality of strategic decisions. The structure uses planning facilitators to avoid the following five paralyses: 1. Analysis. Decision makers can no longer afford the luxury of lengthy, detailed analysis but must develop real-time systems that provide appropriate, timely information. 2. Alternatives. Many alternatives (beyond the traditional two or three) need to be considered and the alternatives must be evaluated simultaneously. 3. Group Think. Decision makers must avoid limited mind-sets and autocratic leadership styles by seeking out independent, knowledgeable counselors. 4. Process. Decision makers need to resolve conflicts through "consensus with qualification," as opposed to waiting for everyone to come on board. 5. Separation. Successful implementation requires a structured process that cuts across disciplines and levels.

  10. Ionized gas at the edge of the central molecular zone

    Science.gov (United States)

    Langer, W. D.; Goldsmith, P. F.; Pineda, J. L.; Velusamy, T.; Requena-Torres, M. A.; Wiesemeyer, H.

    2015-04-01

    Context. The edge of the central molecular zone (CMZ) is the location where massive dense molecular clouds with large internal velocity dispersions transition to the surrounding more quiescent and lower CO emissivity region of the Galaxy. Little is known about the ionized gas surrounding the molecular clouds and in the transition region. Aims: We determine the properties of the ionized gas at the edge of the CMZ near Sgr E using observations of N+ and C+. Methods: We observed a small portion of the edge of the CMZ near Sgr E with spectrally resolved [C ii] 158 μm and [N ii] 205 μm fine structure lines at six positions with the GREAT instrument on SOFIA and in [C ii] using Herschel HIFI on-the-fly strip maps. We use the [N ii] spectra along with a radiative transfer model to calculate the electron density of the gas and the [C ii] maps to illuminate the morphology of the ionized gas and model the column density of CO-dark H2. Results: We detect two [C ii] and [N ii] velocity components, one along the line of sight to a CO molecular cloud at - 207 km s-1 associated with Sgr E and the other at -174 km s-1 outside the edge of another CO cloud. From the [N ii] emission we find that the average electron density is in the range of ~5 to 21 cm-3 for these features. This electron density is much higher than that of the disk's warm ionized medium, but is consistent with densities determined for bright diffuse H ii nebula. The column density of the CO-dark H2 layer in the -207 km s-1 cloud is ~1-2 × 1021 cm-2 in agreement with theoretical models. The CMZ extends further out in Galactic radius by ~7 to 14 pc in ionized gas than it does in molecular gas traced by CO. Conclusions: The edge of the CMZ likely contains dense hot ionized gas surrounding the neutral molecular material. The high fractional abundance of N+ and high electron density require an intense EUV field with a photon flux of order 106 to 107 photons cm-2 s-1, and/or efficient proton charge exchange with

  11. Influences of the Air in Metal Powder High Velocity Compaction

    Directory of Open Access Journals (Sweden)

    Liu Jun

    2017-01-01

    Full Text Available During the process of metal powder high velocity impact compaction, the air is compressed sharply and portion remains in the compacts. In order to study the Influences, a discrete density volleyball accumulation model for aluminium powder was established with the use of ABAQUS. Study found that the powder porosity air obstruct the pressing process because remaining air reduced strength and density of the compacts in the current high-speed pressing (V≤100m/s. When speed further increased (V≥100m/s, the temperature of the air increased sharply, and was even much higher than the melting point of the material. When aluminium powder was compressed at a speed of 200m/s, temperatures of air could reach 2033 K, far higher than the melting point of 877 K. Increased density of powders was a result of local softening and even melt adhesive while air between particles with high temperature and pressure flowed past.

  12. Development of a high velocity rain erosion test method

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Dong Teak; Jin, Doo Han [Korea University of Technology and Education, Cheonan (Korea, Republic of); Kang, Hyung [Agency for Defense Development, Daejeon (Korea, Republic of)

    2009-07-01

    The nose of a missile, flying through raining region with a supersonic speed, is subjected to the rain erosion because the nose is made of a brittle ceramic material. A simple yet very effective rain erosion test method is developed. The sabot assembly similar to the hypodermic syringe carries specific amount of water is launched by a low pressure air gun. After the stopper stop the sabot assembly by impact, the steel plunger continues moving toward to squeeze the silicon rubber in front. The pressurized silicon rubber then is squeezed through the orifice in front of the sabot at high velocity, thus, accelerates the water droplet to higher velocity. The droplet velocity up to 800m/s is successfully attained using a low pressure air gun. The ceramic specimen assembly is placed in front of the high speed water droplet and the rain erosion damage on the surface of the specimen is observed.

  13. Stability and suppression of turbulence in relaxing molecular gas flows

    CERN Document Server

    Grigoryev, Yurii N

    2017-01-01

    This book presents an in-depth systematic investigation of a dissipative effect which manifests itself as the growth of hydrodynamic stability and suppression of turbulence in relaxing molecular gas flows. The work describes the theoretical foundations of a new way to control stability and laminar turbulent transitions in aerodynamic flows. It develops hydrodynamic models for describing thermal nonequilibrium gas flows which allow the consideration of suppression of inviscid acoustic waves in 2D shear flows. Then, nonlinear evolution of large-scale vortices and Kelvin-Helmholtz waves in relaxing shear flows are studied. Critical Reynolds numbers in supersonic Couette flows are calculated analytically and numerically within the framework of both linear and nonlinear classical energy hydrodynamic stability theories. The calculations clearly show that the relaxation process can appreciably delay the laminar-turbulent transition. The aim of the book is to show the new dissipative effect, which can be used for flo...

  14. Gas chromatography-mass spectrometry with supersonic molecular beams.

    Science.gov (United States)

    Amirav, Aviv; Gordin, Alexander; Poliak, Marina; Fialkov, Alexander B

    2008-02-01

    Gas chromatography-mass spectrometry (GC-MS) with supersonic molecular beams (SMBs) (also named Supersonic GC-MS) is based on GC and MS interface with SMBs and on the electron ionization (EI) of vibrationally cold analytes in the SMBs (cold EI) in a fly-through ion source. This ion source is inherently inert and further characterized by fast response and vacuum background filtration capability. The same ion source offers three modes of ionization including cold EI, classical EI and cluster chemical ionization (CI). Cold EI, as a main mode, provides enhanced molecular ions combined with an effective library sample identification, which is supplemented and complemented by a powerful isotope abundance analysis method and software. The range of low-volatility and thermally labile compounds amenable for analysis is significantly increased owing to the use of the contact-free, fly-through ion source and the ability to lower sample elution temperatures through the use of high column carrier gas flow rates. Effective, fast GC-MS is enabled particularly owing to the possible use of high column flow rates and improved system selectivity in view of the enhancement of the molecular ion. This fast GC-MS with SMB can be further improved via the added selectivity of MS-MS, which by itself benefits from the enhancement of the molecular ion, the most suitable parent ion for MS-MS. Supersonic GC-MS is characterized by low limits of detection (LOD), and its sensitivity is superior to that of standard GC-MS, particularly for samples that are hard for analysis. The GC separation of the Supersonic GC-MS can be improved with pulsed flow modulation (PFM) GC x GC-MS. Electron ionization LC-MS with SMB can also be combined with the Supersonic GC-MS, with fast and easy switching between these two modes of operation. (c) 2008 John Wiley & Sons, Ltd.

  15. High-Flux Carbon Molecular Sieve Membranes for Gas Separation.

    Science.gov (United States)

    Richter, Hannes; Voss, Hartwig; Kaltenborn, Nadine; Kämnitz, Susanne; Wollbrink, Alexander; Feldhoff, Armin; Caro, Jürgen; Roitsch, Stefan; Voigt, Ingolf

    2017-06-26

    Carbon membranes have great potential for highly selective and cost-efficient gas separation. Carbon is chemically stable and it is relative cheap. The controlled carbonization of a polymer coating on a porous ceramic support provides a 3D carbon material with molecular sieving permeation performance. The carbonization of the polymer blend gives turbostratic carbon domains of randomly stacked together sp 2 hybridized carbon sheets as well as sp 3 hybridized amorphous carbon. In the evaluation of the carbon molecular sieve membrane, hydrogen could be separated from propane with a selectivity of 10 000 with a hydrogen permeance of 5 m 3 (STP)/(m 2 hbar). Furthermore, by a post-synthesis oxidative treatment, the permeation fluxes are increased by widening the pores, and the molecular sieve carbon membrane is transformed from a molecular sieve carbon into a selective surface flow carbon membrane with adsorption controlled performance and becomes selective for carbon dioxide. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Atomic and molecular physics in the gas phase

    International Nuclear Information System (INIS)

    Toburen, L.H.

    1990-09-01

    The spatial and temporal distributions of energy deposition by high-linear-energy-transfer radiation play an important role in the subsequent chemical and biological processes leading to radiation damage. Because the spatial structures of energy deposition events are of the same dimensions as molecular structures in the mammalian cell, direct measurements of energy deposition distributions appropriate to radiation biology are infeasible. This has led to the development of models of energy transport based on a knowledge of atomic and molecular interactions process that enable one to simulate energy transfer on an atomic scale. Such models require a detailed understanding of the interactions of ions and electrons with biologically relevant material. During the past 20 years there has been a great deal of progress in our understanding of these interactions; much of it coming from studies in the gas phase. These studies provide information on the systematics of interaction cross sections leading to a knowledge of the regions of energy deposition where molecular and phase effects are important and that guide developments in appropriate theory. In this report studies of the doubly differential cross sections, crucial to the development of stochastic energy deposition calculations and track structure simulation, will be reviewed. Areas of understanding are discussed and directions for future work addressed. Particular attention is given to experimental and theoretical findings that have changed the traditional view of secondary electron production for charged particle interactions with atomic and molecular targets

  17. MOLECULAR GAS AND STAR FORMATION IN NEARBY DISK GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Leroy, Adam K.; Munoz-Mateos, Juan-Carlos [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Walter, Fabian; Sandstrom, Karin; Meidt, Sharon; Rix, Hans-Walter; Schinnerer, Eva [Max Planck Institute fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Schruba, Andreas [California Institute for Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Bigiel, Frank [Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Bolatto, Alberto [Department of Astronomy, University of Maryland, College Park, MD (United States); Brinks, Elias [Centre for Astrophysics Research, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); De Blok, W. J. G. [Astrophysics, Cosmology and Gravity Centre, Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa); Rosolowsky, Erik [University of British Columbia, Okanagan Campus, Kelowna, BC (Canada); Schuster, Karl-Friedrich [IRAM, 300 rue de la Piscine, F-38406 St. Martin d' Heres (France); Usero, Antonio [Observatorio Astronomico Nacional, C/ Alfonso XII, 3, E-28014 Madrid (Spain)

    2013-08-01

    We compare molecular gas traced by {sup 12}CO (2-1) maps from the HERACLES survey, with tracers of the recent star formation rate (SFR) across 30 nearby disk galaxies. We demonstrate a first-order linear correspondence between {Sigma}{sub mol} and {Sigma}{sub SFR} but also find important second-order systematic variations in the apparent molecular gas depletion time, {tau}{sub dep}{sup mol}={Sigma}{sub mol}/{Sigma}{sub SFR}. At the 1 kpc common resolution of HERACLES, CO emission correlates closely with many tracers of the recent SFR. Weighting each line of sight equally, using a fixed {alpha}{sub CO} equivalent to the Milky Way value, our data yield a molecular gas depletion time, {tau}{sub dep}{sup mol}={Sigma}{sub mol}/{Sigma}{sub SFR}{approx}2.2 Gyr with 0.3 dex 1{sigma} scatter, in very good agreement with recent literature data. We apply a forward-modeling approach to constrain the power-law index, N, that relates the SFR surface density and the molecular gas surface density, {Sigma}{sub SFR}{proportional_to}{Sigma}{sub mol}{sup N}. We find N = 1 {+-} 0.15 for our full data set with some scatter from galaxy to galaxy. This also agrees with recent work, but we caution that a power-law treatment oversimplifies the topic given that we observe correlations between {tau}{sub dep}{sup mol} and other local and global quantities. The strongest of these are a decreased {tau}{sub dep}{sup mol} in low-mass, low-metallicity galaxies and a correlation of the kpc-scale {tau}{sub dep}{sup mol} with dust-to-gas ratio, D/G. These correlations can be explained by a CO-to-H{sub 2} conversion factor ({alpha}{sub CO}) that depends on dust shielding, and thus D/G, in the theoretically expected way. This is not a unique interpretation, but external evidence of conversion factor variations makes this the most conservative explanation of the strongest observed {tau}{sub dep}{sup mol} trends. After applying a D/G-dependent {alpha}{sub CO}, some weak correlations between {tau}{sub dep

  18. Structure–performance characterization for carbon molecular sieve membranes using molecular scale gas probes

    KAUST Repository

    Rungta, Meha

    2015-04-01

    © 2015 Elsevier Ltd. All rights reserved. Understanding the relationship between carbon molecular sieve (CMS) pore structure and corresponding gas separation performance enables optimization for a given gas separation application. The final pyrolysis temperature and starting polymer precursor are the two critical parameters in controlling CMS performance. This study considers structure and performance changes of CMS derived from a commercially available polymer precursor at different pyrolysis temperatures. As reviewed in this paper, most traditional characterization methods based on microscopy, X-ray diffraction, spectroscopy, sorption-based pore size distribution measurements etc. provide limited information for relating separation performance to the CMS morphology and structural changes. A useful alternative approach based on different sized gases as molecular scale probes of the CMS pore structure was successfully used here in conjunction with separation data to provide critical insights into the structure-performance relationships of the engineered CMS.

  19. TOPICAL REVIEW Warm spraying—a novel coating process based on high-velocity impact of solid particles

    Directory of Open Access Journals (Sweden)

    Seiji Kuroda et al

    2008-01-01

    Full Text Available In recent years, coating processes based on the impact of high-velocity solid particles such as cold spraying and aerosol deposition have been developed and attracting much industrial attention. A novel coating process called 'warm spraying' has been developed, in which coatings are formed by the high-velocity impact of solid powder particles heated to appropriate temperatures below the melting point of the powder material. The advantages of such process are as follows: (1 the critical velocity needed to form a coating can be significantly lowered by heating, (2 the degradation of feedstock powder such as oxidation can be significantly controlled compared with conventional thermal spraying where powder is molten, and (3 various coating structures can be realized from porous to dense ones by controlling the temperature and velocity of the particles. The principles and characteristics of this new process are discussed in light of other existing spray processes such as high-velocity oxy-fuel spraying and cold spraying. The gas dynamics of particle heating and acceleration by the spraying apparatus as well as the high-velocity impact phenomena of powder particles are discussed in detail. Several examples of depositing heat sensitive materials such as titanium, metallic glass, WC–Co cermet and polymers are described with potential industrial applications.

  20. High velocity electromagnetic particle launcher for aerosol production studies

    International Nuclear Information System (INIS)

    Benson, D.A.; Rader, D.J.

    1986-05-01

    This report describes the development of a new device for study of metal combustion, breakup and production of aerosols in a high velocity environment. Metal wires are heated and electromagnetically launched with this device to produce molten metal droplets moving at velocities ranging up to about Mach 1. Such tests are presently intended to simulate the behavior of metal streamers ejected from a high-explosive detonation. A numerical model of the launcher performance in terms of sample properties, sample geometry and pulser electrical parameters is presented which can be used as a tool for design of specific test conditions. Results from several tests showing the range of sample velocities accessible with this device are described and compared with the model. Photographic measurements showing the behavior of tungsten and zirconium metal droplets are presented. Estimates of the Weber breakup and drag on the droplets, as well as calculations of the droplet trajectories, are described. Such studies may ultimately be useful in assessing environmental hazards in the handling and storage of devices containing metallic plutonium

  1. On the origin of high-velocity runaway stars

    Science.gov (United States)

    Gvaramadze, Vasilii V.; Gualandris, Alessia; Portegies Zwart, Simon

    2009-06-01

    We explore the hypothesis that some high-velocity runaway stars attain their peculiar velocities in the course of exchange encounters between hard massive binaries and a very massive star (either an ordinary 50-100Msolar star or a more massive one, formed through runaway mergers of ordinary stars in the core of a young massive star cluster). In this process, one of the binary components becomes gravitationally bound to the very massive star, while the second one is ejected, sometimes with a high speed. We performed three-body scattering experiments and found that early B-type stars (the progenitors of the majority of neutron stars) can be ejected with velocities of >~200-400kms-1 (typical of pulsars), while 3-4Msolar stars can attain velocities of >~300-400kms-1 (typical of the bound population of halo late B-type stars). We also found that the ejected stars can occasionally attain velocities exceeding the Milky Ways's escape velocity.

  2. HERSCHEL* FAR-INFRARED SPECTROSCOPY OF THE GALACTIC CENTER. HOT MOLECULAR GAS: SHOCKS VERSUS RADIATION NEAR Sgr A

    Energy Technology Data Exchange (ETDEWEB)

    Goicoechea, Javier R.; Etxaluze, M.; Cernicharo, J.; Bell, T. A. [Departamento de Astrofisica, Centro de Astrobiologia, CSIC-INTA, Carretera de Ajalvir, Km 4, Torrejon de Ardoz, E-28850 Madrid (Spain); Gerin, M.; De Luca, M.; Encrenaz, P. [LERMA, UMR 8112 du CNRS, Observatoire de Paris, Ecole Normale Superieure (France); Neufeld, D. A.; Indriolo, N. [Johns Hopkins University, Baltimore, MD 21218 (United States); Contursi, A. [Max-Planck-Institut fuer extraterrestrische Physik (MPE), Postfach 1312, D-85741 Garching (Germany); Lis, D. C. [California Institute of Technology, Pasadena, CA 91125 (United States); Polehampton, E. T. [RAL Space, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom); Sonnentrucker, P., E-mail: jr.goicoechea@cab.inta-csic.es [Space Telescope Science Institute, Baltimore, MD 21218 (United States)

    2013-05-20

    We present a {approx}52-671 {mu}m spectral scan toward Sgr A* taken with the PACS and SPIRE spectrometers on board Herschel. The achieved angular resolution allows us to separate, for the first time at far-IR wavelengths, the emission toward the central cavity (gas in the inner central parsec of the galaxy) from that of the surrounding circumnuclear disk. The spectrum toward Sgr A* is dominated by strong [O III], [O I], [C II], [N III], [N II], and [C I] fine-structure lines (in decreasing order of luminosity) arising in gas irradiated by UV photons from the central stellar cluster. In addition, rotationally excited lines of {sup 12}CO (from J = 4-3 to 24-23), {sup 13}CO, H{sub 2}O, OH, H{sub 3}O{sup +}, HCO{sup +}, and HCN, as well as ground-state absorption lines of OH{sup +}, H{sub 2}O{sup +}, H{sub 3}O{sup +}, CH{sup +}, H{sub 2}O, OH, HF, CH, and NH are detected. The excitation of the {sup 12}CO ladder is consistent with a hot isothermal component at T{sub k} {approx_equal} 10{sup 3.1} K and n(H{sub 2}) {approx}< 10{sup 4} cm{sup -3}. It is also consistent with a distribution of temperature components at higher density with most CO at T{sub k} {approx}< 300 K. The detected molecular features suggest that, at present, neither very enhanced X-ray nor cosmic-ray fluxes play a dominant role in the heating of the hot molecular gas. The hot CO component (either the bulk of the CO column or just a small fraction depending on the above scenario) results from a combination of UV- and shock-driven heating. If irradiated dense clumps/clouds do not exist, shocks likely dominate the heating of the hot molecular gas. This is consistent with the high-velocity gas detected toward Sgr A*.

  3. Free energy landscape and molecular pathways of gas hydrate nucleation

    International Nuclear Information System (INIS)

    Bi, Yuanfei; Porras, Anna; Li, Tianshu

    2016-01-01

    Despite the significance of gas hydrates in diverse areas, a quantitative knowledge of hydrate formation at a molecular level is missing. The impediment to acquiring this understanding is primarily attributed to the stochastic nature and ultra-fine scales of nucleation events, posing a great challenge for both experiment and simulation to explore hydrate nucleation. Here we employ advanced molecular simulation methods, including forward flux sampling (FFS), p B histogram analysis, and backward flux sampling, to overcome the limit of direct molecular simulation for exploring both the free energy landscape and molecular pathways of hydrate nucleation. First we test the half-cage order parameter (H-COP) which we developed for driving FFS, through conducting the p B histogram analysis. Our results indeed show that H-COP describes well the reaction coordinates of hydrate nucleation. Through the verified order parameter, we then directly compute the free energy landscape for hydrate nucleation by combining both forward and backward flux sampling. The calculated stationary distribution density, which is obtained independently of nucleation theory, is found to fit well against the classical nucleation theory (CNT). Subsequent analysis of the obtained large ensemble of hydrate nucleation trajectories show that although on average, hydrate formation is facilitated by a two-step like mechanism involving a gradual transition from an amorphous to a crystalline structure, there also exist nucleation pathways where hydrate crystallizes directly, without going through the amorphous stage. The CNT-like free energy profile and the structural diversity suggest the existence of multiple active transition pathways for hydrate nucleation, and possibly also imply the near degeneracy in their free energy profiles among different pathways. Our results thus bring a new perspective to the long standing question of how hydrates crystallize.

  4. Free energy landscape and molecular pathways of gas hydrate nucleation.

    Science.gov (United States)

    Bi, Yuanfei; Porras, Anna; Li, Tianshu

    2016-12-07

    Despite the significance of gas hydrates in diverse areas, a quantitative knowledge of hydrate formation at a molecular level is missing. The impediment to acquiring this understanding is primarily attributed to the stochastic nature and ultra-fine scales of nucleation events, posing a great challenge for both experiment and simulation to explore hydrate nucleation. Here we employ advanced molecular simulation methods, including forward flux sampling (FFS), p B histogram analysis, and backward flux sampling, to overcome the limit of direct molecular simulation for exploring both the free energy landscape and molecular pathways of hydrate nucleation. First we test the half-cage order parameter (H-COP) which we developed for driving FFS, through conducting the p B histogram analysis. Our results indeed show that H-COP describes well the reaction coordinates of hydrate nucleation. Through the verified order parameter, we then directly compute the free energy landscape for hydrate nucleation by combining both forward and backward flux sampling. The calculated stationary distribution density, which is obtained independently of nucleation theory, is found to fit well against the classical nucleation theory (CNT). Subsequent analysis of the obtained large ensemble of hydrate nucleation trajectories show that although on average, hydrate formation is facilitated by a two-step like mechanism involving a gradual transition from an amorphous to a crystalline structure, there also exist nucleation pathways where hydrate crystallizes directly, without going through the amorphous stage. The CNT-like free energy profile and the structural diversity suggest the existence of multiple active transition pathways for hydrate nucleation, and possibly also imply the near degeneracy in their free energy profiles among different pathways. Our results thus bring a new perspective to the long standing question of how hydrates crystallize.

  5. Free energy landscape and molecular pathways of gas hydrate nucleation

    Energy Technology Data Exchange (ETDEWEB)

    Bi, Yuanfei; Porras, Anna; Li, Tianshu, E-mail: tsli@gwu.edu [Department of Civil and Environmental Engineering, George Washington University, Washington DC 20052 (United States)

    2016-12-07

    Despite the significance of gas hydrates in diverse areas, a quantitative knowledge of hydrate formation at a molecular level is missing. The impediment to acquiring this understanding is primarily attributed to the stochastic nature and ultra-fine scales of nucleation events, posing a great challenge for both experiment and simulation to explore hydrate nucleation. Here we employ advanced molecular simulation methods, including forward flux sampling (FFS), p{sub B} histogram analysis, and backward flux sampling, to overcome the limit of direct molecular simulation for exploring both the free energy landscape and molecular pathways of hydrate nucleation. First we test the half-cage order parameter (H-COP) which we developed for driving FFS, through conducting the p{sub B} histogram analysis. Our results indeed show that H-COP describes well the reaction coordinates of hydrate nucleation. Through the verified order parameter, we then directly compute the free energy landscape for hydrate nucleation by combining both forward and backward flux sampling. The calculated stationary distribution density, which is obtained independently of nucleation theory, is found to fit well against the classical nucleation theory (CNT). Subsequent analysis of the obtained large ensemble of hydrate nucleation trajectories show that although on average, hydrate formation is facilitated by a two-step like mechanism involving a gradual transition from an amorphous to a crystalline structure, there also exist nucleation pathways where hydrate crystallizes directly, without going through the amorphous stage. The CNT-like free energy profile and the structural diversity suggest the existence of multiple active transition pathways for hydrate nucleation, and possibly also imply the near degeneracy in their free energy profiles among different pathways. Our results thus bring a new perspective to the long standing question of how hydrates crystallize.

  6. GAS PHASE SELECTIVE PHOTOXIDATION OF ALCOHOLS USING LIGHT-ACTIVATED TITANIUM DIOXIDE AND MOLECULAR OXYGEN

    Science.gov (United States)

    Gas Phase Selective Oxidation of Alcohols Using Light-Activated Titanium Dioxide and Molecular Oxygen Gas phase selective oxidations of various primary and secondary alcohols are studied in an indigenously built stainless steel up-flow photochemical reactor using ultravi...

  7. Complex C: A Low-Metallicity, High-Velocity Cloud Plunging into the Milky Way

    Science.gov (United States)

    Tripp, Todd M.; Wakker, Bart P.; Jenkins, Edward B.; Bowers, C. W.; Danks, A. C.; Green, R. F.; Heap, S. R.; Joseph, C. L.; Kaiser, M. E.; Linsky, J. L.; Woodgate, B. E.

    2003-06-01

    We present evidence that high-velocity cloud (HVC) complex C is a low-metallicity gas cloud that is plunging toward the disk and beginning to interact with the ambient gas that surrounds the Milky Way. This evidence begins with a new high-resolution (7 km s-1 FWHM) echelle spectrum of 3C 351 obtained with the Space Telescope Imaging Spectrograph (STIS). 3C 351 lies behind the low-latitude edge of complex C, and the new spectrum provides accurate measurements of O I, Si II, Al II, Fe II, and Si III absorption lines at the velocity of complex C; N I, S II, Si IV, and C IV are not detected at 3 σ significance in complex C proper. However, Si IV and C IV as well as O I, Al II, Si II and Si III absorption lines are clearly present at somewhat higher velocities associated with a ``high-velocity ridge'' (HVR) of 21 cm emission. This high-velocity ridge has a similar morphology to and is roughly centered on complex C proper. The similarities of the absorption-line ratios in the HVR and complex C suggest that these structures are intimately related. In complex C proper we find [O/H]=-0.76+0.23-0.21. For other species the measured column densities indicate that ionization corrections are important. We use collisional and photoionization models to derive ionization corrections; in both models we find that the overall metallicity Z=0.1-0.3 Zsolar in complex C proper, but nitrogen must be underabundant. The iron abundance indicates that the complex C contains very little dust. The size and density implied by the ionization models indicate that the absorbing gas is not gravitationally confined. The gas could be pressure confined by an external medium, but alternatively we may be viewing the leading edge of the HVC, which is ablating and dissipating as it plunges into the Milky Way. O VI column densities observed with the Far Ultraviolet Spectroscopic Explorer (FUSE) toward nine QSOs/AGNs behind complex C support this conclusion: N(O VI) is highest near 3C 351, and the O VI/H I

  8. Simulation of High Velocity Impact on Composite Structures - Model Implementation and Validation

    Science.gov (United States)

    Schueler, Dominik; Toso-Pentecôte, Nathalie; Voggenreiter, Heinz

    2016-08-01

    High velocity impact on composite aircraft structures leads to the formation of flexural waves that can cause severe damage to the structure. Damage and failure can occur within the plies and/or in the resin rich interface layers between adjacent plies. In the present paper a modelling methodology is documented that captures intra- and inter-laminar damage and their interrelations by use of shell element layers representing sub-laminates that are connected with cohesive interface layers to simulate delamination. This approach allows the simulation of large structures while still capturing the governing damage mechanisms and their interactions. The paper describes numerical algorithms for the implementation of a Ladevèze continuum damage model for the ply and methods to derive input parameters for the cohesive zone model. By comparison with experimental results from gas gun impact tests the potential and limitations of the modelling approach are discussed.

  9. Stability investigations of relaxing molecular gas flows. Results and perspectives

    Science.gov (United States)

    Grigor'ev, Yurii N.; Ershov, Igor V.

    2017-10-01

    This article presents results of systematic investigations of a dissipative effect which manifests itself as the growth of hydrodynamic stability and suppression of turbulence in relaxing molecular gas flows. The effect can be a new way for control stability and laminar turbulent transition in aerodynamic flows. The consideration of suppression of inviscid acoustic waves in 2D shear flows is presented. Nonlinear evolution of large-scale vortices and Kelvin — Helmholtz waves in relaxing shear flows are studied. Critical Reynolds numbers in supersonic Couette flows are calculated analytically and numerically within the framework of both classical linear and nonlinear energy hydrodynamic stability theories. The calculations clearly show that the relaxation process can appreciably delay the laminar-turbulent transition. The aim of this article is to show the new dissipative effect, which can be used for flow control and laminarization.

  10. Dust and gas distribution in molecular clouds: an observational approach

    International Nuclear Information System (INIS)

    Campeggio, Loretta; Elia, Davide; Maiolo, Berlinda M T; Strafella, Francesco; Cecchi-Pestellini, Cesare

    2005-01-01

    The interstellar medium (ISM), gas and dust, appears to be arranged in clouds, whose dimensions, masses and densities span a large range of scales: from giant molecular clouds to small isolated globules. The structure of these objects show a high degree of complexity appearing, in the range of the observed scales, as a non-homogeneous ('clumpy') distribution of matter. The arrangement of the ISM is clearly relevant for the study of the fragmentation of the clouds and then of the star formation processes. To quantify observationally the ISM structure, many methods have been developed and our study is focused on some of them, exploiting multiwavelength observations of IS objects. The investigations presented here have been carried out by considering both the dust absorption (in optical and near IR wavelengths) and the gas emission (in the submm-radio spectral range). We present the maps obtained from the reduction of raw data and a first tentative analysis by means of methods as the structure function, the autocorrelation, and the Δ-variance. These are appropriate tools to highlight the complex structure of the ISM with reference to the paradigm given by the supersonic turbulence. Three observational cases are briefly discussed. In order to analyse the structure of objects characterized by different sizes, we applied the above-mentioned algorithms to the extinction map of the dark globule CB 107 and to the CO(J = 1-0) integrated intensity map of Vela Molecular Ridge, D Cloud. Finally we compare the results obtained with synthetic fractal maps known as 'fractional Brownian motion' fBm images

  11. Molecular gas in the central parsec of the Galaxy

    Science.gov (United States)

    Ciurlo, Anna

    2015-08-01

    In the central parsec of the Galaxy the environment of the black hole presents two different gas structures: the neutral Circumnuclear Disc (CND) and the ionized Minispiral. In order to study the transition between the two structures we have investigated the presence of neutral gas in the inner part of the CND, where the ionized Minispiral lies. Such study is carried out through spectro-imaging data of the central cavity observed with VLT/SPIFFI. Such data cover several H2 lines and the Brγ line. In order to preserve the spatial resolution and avoid edge effects we applied a new line fitting method, which consists on a regularized three- dimensional fit. Thank to the new method we present the highest resolution maps of the H2 emission in the Central parsec, together with velocity and width maps. The analysis of the H2 1-0 S(1) line leads to the detection of three components of the emission: one in the background of the Minispiral, one in the CND, and one in the Minispiral northern arm. This finding is confirmed by others ortho lines 1-0 S(3) and Q(3). Some para lines are detectable, but no complete map can be achieved. However some portion of the field have been studied for all detectable lines and in particular a strong emission at the entrance of the Minicavity is detected. Lines fluxes allow to trace excitation diagrams which lead to excitation temperature of 1200 K in the CND and T>1500 K in the central cavity. The clear higher temperature of the gas in the central cavity is related to the higher density of UV photons and cosmic rays and this means that H2 molecules have thus a shorter mean life during which thermalization cannot fully occur, it is possible for molecular hydrogen to be formed in a state where peculiar state are favoured. The hypothesis is that we are observing not all the H2 but just the one which is situated at the border of the clouds, a mince shell of gas, heated by the UV central field, which gives a new and interesting picture not only of

  12. Molecular Simulation of Gas Solubility in Nitrile Butadiene Rubber.

    Science.gov (United States)

    Khawaja, M; Sutton, A P; Mostofi, A A

    2017-01-12

    Molecular simulation is used to compute the solubility of small gases in nitrile butadiene rubber (NBR) with a Widom particle-insertion technique biased by local free volume. The convergence of the method is examined as a function of the number of snapshots upon which the insertions are performed and the number of insertions per snapshot and is compared to the convergence of the unbiased Widom insertion technique. The effect of varying the definition of local free volume is also investigated. The acrylonitrile content of the polymer is altered to examine its influence on the solubility of helium, CO 2 , and H 2 O, and the solubilities of polar gases are found to be enhanced relative to those of nonpolar gases, in qualitative agreement with experiment. To probe this phenomenon further, the solubilities are decomposed into contributions from the neighborhoods of different atoms, using a Voronoi cell construction, and a strong bias is found for CO 2 and H 2 O in particular to be situated near nitrogen sites in the elastomer. Temperature is shown to suppress the solubility of CO 2 and H 2 O but to increase that of helium. Increasing pressure is found to suppress the solubility of all gases but at different rates, according to a balance between their molecular sizes and electrostatic interactions with the polymer. These results are relevant to the use of NBR seals at elevated temperatures and pressures, such as in oil and gas wells.

  13. Thermally modulated nano-trampoline material as smart skin for gas molecular mass detection

    Science.gov (United States)

    Xia, Hua

    2012-06-01

    Conventional multi-component gas analysis is based either on laser spectroscopy, laser and photoacoustic absorption at specific wavelengths, or on gas chromatography by separating the components of a gas mixture primarily due to boiling point (or vapor pressure) differences. This paper will present a new gas molecular mass detection method based on thermally modulated nano-trampoline material as smart skin for gas molecular mass detection by fiber Bragg grating-based gas sensors. Such a nanomaterial and fiber Bragg grating integrated sensing device has been designed to be operated either at high-energy level (highly thermal strained status) or at low-energy level (low thermal strained status). Thermal energy absorption of gas molecular trigs the sensing device transition from high-thermal-energy status to low-thermal- energy status. Experiment has shown that thermal energy variation due to gas molecular thermal energy absorption is dependent upon the gas molecular mass, and can be detected by fiber Bragg resonant wavelength shift with a linear function from 17 kg/kmol to 32 kg/kmol and a sensitivity of 0.025 kg/kmol for a 5 micron-thick nano-trampoline structure and fiber Bragg grating integrated gas sensing device. The laboratory and field validation data have further demonstrated its fast response characteristics and reliability to be online gas analysis instrument for measuring effective gas molecular mass from single-component gas, binary-component gas mixture, and multi-gas mixture. The potential industrial applications include fouling and surge control for gas charge centrifugal compressor ethylene production, gas purity for hydrogen-cooled generator, gasification for syngas production, gasoline/diesel and natural gas fuel quality monitoring for consumer market.

  14. A dirty window diffuse and translucent molecular gas in the interstellar medium

    CERN Document Server

    Magnani, Loris

    2017-01-01

    This book provides an introduction to the physics of interstellar gas in the Galaxy. It deals with the diffuse interstellar medium which supplies a complex environment for exploring the neutral gas content of a galaxy like the Milky Way and the techniques necessary for studying this non-stellar component. After an initial exposition of the phases of the interstellar medium and the role of gas in a spiral galaxy, the authors discuss the transition from atomic to molecular gas. They then consider basic radiative transfer and molecular spectroscopy with particular emphasis on the molecules useful for studying low-density molecular gas. Observational techniques for investigating the gas and the dust component of the diffuse interstellar medium throughout the electromagnetic spectrum are explored emphasizing results from the recent Herschel and Planck missions. A brief exposition on dust in the diffuse interstellar medium is followed by a discussion of molecular clouds in general and high-latitude molecular clouds...

  15. Fault gouge rheology under confined, high-velocity conditions

    Science.gov (United States)

    Reches, Z.; Madden, A. S.; Chen, X.

    2012-12-01

    We recently developed the experimental capability to investigate the shear properties of fine-grain gouge under confined conditions and high-velocity. The experimental system includes a rotary apparatus that can apply large displacements of tens of meters, slip velocity of 0.001- 2.0 m/s, and normal stress of 35 MPa (Reches and Lockner, 2010). The key new component is a Confined ROtary Cell (CROC) that can shear a gouge layer either dry or under pore-pressure. The pore pressure is controlled by two syringe pumps. CROC includes a ring-shape gouge chamber of 62.5 mm inner diameter, 81.25 mm outer diameter, and up to 3 mm thick gouge sample. The lower, rotating part of CROC contains the sample chamber, and the upper, stationary part includes the loading, hollow cylinder and setting for temperature, and dilation measurements, and pore-pressure control. Each side of the gouge chamber has two pairs of industrial, spring-energized, self-lubricating, teflon-graphite seals, built for particle media and can work at temperature up to 250 ded C. The space between each of the two sets of seals is pressurized by nitrogen. This design generates 'zero-differential pressure' on the inner seal (which is in contact with the gouge powder), and prevents gouge leaks. For the preliminary dry experiments, we used ~2.0 mm thick layers of room-dry kaolinite powder. Total displacements were on the order of meters and normal stress up to 4 MPa. The initial shear was accommodated by multiple internal slip surfaces within the kaolinite layer accommodated as oriented Riedel shear structures. Later, the shear was localized within a thin, plate-parallel Y-surface. The kaolinite layer was compacted at a quasi-asymptotic rate, and displayed a steady-state friction coefficient of ~ 0.5 with no clear dependence on slip velocity up to 0.15 m/s. Further experiments with loose quartz sand (grain size ~ 125 micron) included both dry runs and pore-pressure (distilled water) controlled runs. The sand was

  16. Plane-wave and common-translation-factor treatments of He2++H collisions at high velocities

    International Nuclear Information System (INIS)

    Errea, L.F.; Harel, C.; Jouin, H.; Maidagan, J.M.; Mendez, L.; Pons, B.; Riera, A.

    1992-01-01

    We complement previous work that showed that the molecular approach, modified with plane-wave translation factors, is able to reproduce the fall of charge-exchange cross sections in He 2+ +H collisions, by presenting the molecular data, and studying the corresponding mechanism. We test the accuracy of simplifications of the method that have been employed in the literature, and that lead to very simple calculations. We show that the common-translation-factor method is also successful at high nuclear velocities, provided that sufficiently excited states are included in the basis; moreover, it yields a simple picture of the mechanism and a description of ionization processes at high velocities

  17. Rotational Raman scattering using molecular nitrogen gas for calibration of Thomson-scattering apparatus

    International Nuclear Information System (INIS)

    Yamauchi, Toshihiko; Nakazawa, Ichiro

    1987-01-01

    Anti-Stokes rotational Raman lines in molecular nitrogen gas were used for the calibration of Thomson-scattering apparatus. It was found that molecular nitrogen gas is suitable for a vessel having strong stray light. The polarization ratio was 0.16 using linear-polarized laser light. (author)

  18. Study of the fragmentation of astrophysical interest molecules (CnHm) induced by high velocity collision

    International Nuclear Information System (INIS)

    Tuna, Th.

    2008-07-01

    This work shows the study of atom-molecule collision processes in the high velocity domain (v=4,5 a.u). The molecules concerned by this work are small unsaturated hydrocarbons C 1-4 H and C 3 H 2 . Molecules are accelerated with the Tandem accelerator in Orsay and their fragmentation is analyzed by the 4π, 100% efficient detector, AGAT. Thanks to a shape analysis of the current signal from the silicon detectors in association with the well known grid method, we are able to measure all the fragmentation channels of the incident molecule. These dissociation measurements have been introduced in the modelization of two objects of the interstellar medium in which a lot of hydrocarbon molecules have been observed (TMC1, horse-head nebula). We have extended our branching ratios obtained by high velocity collision to other electronic processes included in the chemical database like photodissociation and dissociative recombination. This procedure is feasible under an assumption of the statistical point of view of the molecular fragmentation. The deviations following our modification are very small in the modelization of TMC1 but significant in the photodissociation region. The first part is dedicated to the description of the experimental setting that has enabled us to study the fragmentation of C n H m molecules: the Orsay's Tandem accelerator and the Agat detector. The second part deals with negative ion sources and particularly with the Sahat source that is based on electronic impact and has shown good features for the production of anions and correct stability for its use with accelerators. The third part is dedicated to the experimental results in terms of cross-sections, number of fragments and branching ratios, associated to the various collisional processes. The last part presents an application of our measurement of fragmentation data to astro-chemistry. In this field, the simulation codes of the inter-stellar medium require databases of chemical reactions that

  19. Molecular analysis of manufactured gas plant soils for naphthalene mineralization

    International Nuclear Information System (INIS)

    Sanseverino, J.; Werner, C.; Fleming, J.; Applegate, B.M.; King, J.M.H.; Sayler, G.S.; Blackburn, J.

    1991-01-01

    New molecular tools are being developed and tested to ascertain the biodegradability of hazardous wastes by soil bacterial population. The potential for manufactured gas plant (MGP) soil bacterial populations to degrade naphthalene, as a component mixture of polynuclear aromatic hydrocarbons, was evaluated by the detection of a naphthalene biodegradative genotype by DNA probe hybridization with DNA extracts and colonies of cultured bacteria of the MGP soils. The activity of the naphthalene-degrading populations was evaluated by mineralization assays, 14 CO 2 production from 14 C-naphthalene. Direct messenger RNA (mRNA) extraction from MGP soil was evaluated as an instantaneous measure of naphthalene catabolic gene expression in MGP soil. The bioavailability of naphthalene for bacterial degradation within the MGP soils was assessed by measuring the bioluminescent response of a naphthalene-lux catabolic reporter strain Pseudomonas fluorescens HK44 (pUTK21). DNA extracted from 5 MGP soils and 1 creosote-contaminated soil and hybridized with a nahA gene probe indicated that the naphthalene degradative genes were present in all samples in the range of 0.06 to 0.95 ng/100 μl DNA extract which was calculated to represent 3.58 x 10 8 to 1.05 x 10 10 nahA positive cells/g soil. Phenanthrene, anthracene, and benzo(a)pyrene were mineralized also by some of the soils. NAH7 homologous messenger RNA transcripts were detectable in one MGP soil and in the creosote-contaminated soil

  20. Molecular structure of tetramethylgermane from gas electron diffraction

    Science.gov (United States)

    Csákvári, Éva; Rozsondai, Béla; Hargittai, István

    1991-05-01

    The molecular structure of Ge(CH 3) 4 has been determined from gas-phase electron diffraction augmented by a normal coordinate analysis. Assuming tetrahedral symmetry for the germanium bond configuration, the following structural parameters are found: rg(GeC) = 1.958 ± 0.004 Å, rg(CH) = 1.111 ± 0.003 Å and ∠(GeCH) = 110.7 ± 0.2° ( R=4.0%). The methyl torsional barrier V 0 is estimated to be 1.3 kJ mol -1 on the basis of an effective angle of torsion 23.0 ± 1.5°, from the staggered form, yielded directly by the analysis. The GeC bond length of Ge(CH 3) 4 is the same, within experimental error, as that of Ge(C 6H 5) 4 and is in agreement with the prediction of a modified Schomaker-Stevenson relationship.

  1. Molecular Communication over Gas Stream Channels using Portable Mass Spectrometry.

    Science.gov (United States)

    Giannoukos, Stamatios; Marshall, Alan; Taylor, Stephen; Smith, Jeremy

    2017-11-01

    The synthetic generation/coding and transmission of olfactory information over a gas stream or an odor network is a new and unexplored field. Application areas vary from the entertainment or advertisement industry to security and telemedicine. However, current technological limitations frustrate the accurate reproduction of decoded and transmitted olfactory data. This study describes the development, testing, and characterization of a novel odor emitter (OE) that is used to investigate the generation-encoding of gaseous standards with odorous characteristics with a regulatable way, for scent transmission purposes. The calibration and the responses of a developed OE were examined using a portable quadrupole mass spectrometer (MS). Experiments were undertaken for a range of volatile organic compounds (VOCs) at different temperatures and flow rates. Individual compounds and mixtures were tested to investigate periodic and dynamic transmission characteristics within two different size tubular containers for distances up to 3 m. Olfactory information transmission is demonstrated using MS as the main molecular sensor for odor detection and monitoring and for the first time spatial encryption of olfactory information is shown. Graphical Abstract ᅟ.

  2. Molecular Communication over Gas Stream Channels using Portable Mass Spectrometry

    Science.gov (United States)

    Giannoukos, Stamatios; Marshall, Alan; Taylor, Stephen; Smith, Jeremy

    2017-07-01

    The synthetic generation/coding and transmission of olfactory information over a gas stream or an odor network is a new and unexplored field. Application areas vary from the entertainment or advertisement industry to security and telemedicine. However, current technological limitations frustrate the accurate reproduction of decoded and transmitted olfactory data. This study describes the development, testing, and characterization of a novel odor emitter (OE) that is used to investigate the generation-encoding of gaseous standards with odorous characteristics with a regulatable way, for scent transmission purposes. The calibration and the responses of a developed OE were examined using a portable quadrupole mass spectrometer (MS). Experiments were undertaken for a range of volatile organic compounds (VOCs) at different temperatures and flow rates. Individual compounds and mixtures were tested to investigate periodic and dynamic transmission characteristics within two different size tubular containers for distances up to 3 m. Olfactory information transmission is demonstrated using MS as the main molecular sensor for odor detection and monitoring and for the first time spatial encryption of olfactory information is shown.

  3. Molecular structure determination of cyclootane by ab initio and electron diffraction methods in the gas phase

    OpenAIRE

    De Almeida, Wagner B.

    2000-01-01

    The determination of the molecular structure of molecules is of fundamental importance in chemistry. X-rays and electron diffraction methods constitute in important tools for the elucidation of the molecular structure of systems in the solid state and gas phase, respectively. The use of quantum mechanical molecular orbital ab initio methods offer an alternative for conformational analysis studies. Comparison between theoretical results and those obtained experimentally in the gas phase can ma...

  4. Stability analysis of confined V-shaped flames in high-velocity streams.

    Science.gov (United States)

    El-Rabii, Hazem; Joulin, Guy; Kazakov, Kirill A

    2010-06-01

    The problem of linear stability of confined V-shaped flames with arbitrary gas expansion is addressed. Using the on-shell description of flame dynamics, a general equation governing propagation of disturbances of an anchored flame is obtained. This equation is solved analytically for V-flames anchored in high-velocity channel streams. It is demonstrated that dynamics of the flame disturbances in this case is controlled by the memory effects associated with vorticity generated by the perturbed flame. The perturbation growth rate spectrum is determined, and explicit analytical expressions for the eigenfunctions are given. It is found that the piecewise linear V structure is unstable for all values of the gas expansion coefficient. Despite the linearity of the basic pattern, however, evolutions of the V-flame disturbances are completely different from those found for freely propagating planar flames or open anchored flames. The obtained results reveal strong influence of the basic flow and the channel walls on the stability properties of confined V-flames.

  5. Method and system for gas flow mitigation of molecular contamination of optics

    Science.gov (United States)

    Delgado, Gildardo; Johnson, Terry; Arienti, Marco; Harb, Salam; Klebanoff, Lennie; Garcia, Rudy; Tahmassebpur, Mohammed; Scott, Sarah

    2018-01-23

    A computer-implemented method for determining an optimized purge gas flow in a semi-conductor inspection metrology or lithography apparatus, comprising receiving a permissible contaminant mole fraction, a contaminant outgassing flow rate associated with a contaminant, a contaminant mass diffusivity, an outgassing surface length, a pressure, a temperature, a channel height, and a molecular weight of a purge gas, calculating a flow factor based on the permissible contaminant mole fraction, the contaminant outgassing flow rate, the channel height, and the outgassing surface length, comparing the flow factor to a predefined maximum flow factor value, calculating a minimum purge gas velocity and a purge gas mass flow rate from the flow factor, the contaminant mass diffusivity, the pressure, the temperature, and the molecular weight of the purge gas, and introducing the purge gas into the semi-conductor inspection metrology or lithography apparatus with the minimum purge gas velocity and the purge gas flow rate.

  6. Molecular Gas Reservoirs in Cluster Galaxies at z = 1.46

    Science.gov (United States)

    Hayashi, Masao; Tadaki, Ken-ichi; Kodama, Tadayuki; Kohno, Kotaro; Yamaguchi, Yuki; Hatsukade, Bunyo; Koyama, Yusei; Shimakawa, Rhythm; Tamura, Yoichi; Suzuki, Tomoko L.

    2018-04-01

    We present molecular gas reservoirs of 18 galaxies associated with the XMMXCS J2215.9–1738 cluster at z = 1.46. From Band 7 and Band 3 data of the Atacama Large Millimeter/submillimeter Array, we detect dust continuum emission at 870 μm and the CO J = 2–1 emission line from 8 and 17 member galaxies, respectively, within a clustercentric radius of R 200. The molecular gas masses derived from the CO and/or dust continuum luminosities show that the fraction of molecular gas mass and the depletion timescale for the cluster galaxies are larger than expected from the scaling relations of molecular gas on stellar mass and offset from the main sequence of star-forming galaxies in general fields. The galaxies closer to the cluster center in terms of both projected position and accretion phase seem to show a larger deviation from the scaling relations. We speculate that the environment of the galaxy cluster helps feed the gas through inflow to the member galaxies and reduce the efficiency of star formation. The stacked Band 3 spectrum of 12 quiescent galaxies with M stellar ∼ 1011 M ⊙ within 0.5R 200 shows no detection of a CO emission line, giving the upper limit of molecular gas mass and molecular gas fraction to be ≲1010 M ⊙ and ≲10%, respectively. Therefore, the massive galaxies in the cluster core quench the star formation activity while consuming most of the gas reservoirs.

  7. Molecular beam photoionization and gas-surface scattering

    International Nuclear Information System (INIS)

    Ceyer, S.T.

    1979-09-01

    The energetics of the ethylene ion-molecule reactions was investigated in more detail than previously possible in two body collision experiments by photoionization of the neutral van der Waals ethylene dimer. The stability of the (C 2 H 4 ) + C 2 H 4 ion-molecule collision complex has been determined to be 18.2 +- 0.5 kcal. The highest potential barriers along the reaction coordinate for decomposition of this collision complex into C 4 H 7 + + H and C 3 H 5 + + CH 3 have been determined to be 0 +- 1.5 and 8.7 +- 1.5 kcal. In a similar manner, the energetics of the solvated ethylene dimer ion was investigated by the photoionization of the ethylene trimer. The absolute proton affinity of NH 3 (203.6 +- 1.3 kcal/mole) and the proton solvation energies by more than one NH 3 have been determined by molecular beam photoionization. In addition, the NH 3 + -NH 3 interaction energy (0.79 +- 0.05 eV) was measured by photoionization of the neutral van der Waals dimer. These experiments have shown that photoionization of van der Waals clusters is a very powerful method of determining the energetics of gas phase proton solvation. The scattering of helium atomic beams from a high Miller index platinum surface that exhibits ordered, periodic steps on the atomic scale to probe the effect of atomic steps on the scattering distribution is explored. Rainbow scattering is observed when the step edges are perpendicular to the incident helium atoms. The design, construction and operation of a beam-surface scattering apparatus are described. The first data obtained in this apparatus are presented and the interesting dynamical aspects of the oxidation of D, D 2 and CO are discussed. 75 references

  8. A Discovery of a Compact High Velocity Cloud-Galactic Supershell System

    Science.gov (United States)

    Park, Geumsook; Koo, Bon-Chul; Kang, Ji-hyun; Gibson, Steven J.; Peek, Joshua Eli Goldston; Douglas, Kevin A.; Korpela, Eric J.; Heiles, Carl E.

    2017-01-01

    High velocity clouds (HVCs) are neutral hydrogen (HI) gas clouds having very different radial velocities from those of the Galactic disk material. While some large HVC complexes are known to be gas streams tidally stripped from satellite galaxies of the Milky Way, there are relatively isolated and small angular-sized HVCs, so called “compact HVCs (CHVCs)”, the origin of which remains controversial. There are about 300 known CHVCs in the Milky Way, and many of them show a head-tail structure, implying a ram pressure interaction with the diffuse Galactic halo gas. It is, however, not clear whether CHVCs are completely dissipated in the Galactic halo to feed the multi-phase circumgalactic medium or they can survive their trip through the halo and collide with the Galactic disk. The colliding CHVCs may leave a gigantic trail in the disk, and it had been suggested that some of HI supershells that require ≧ 3 x 1052 erg may be produced by the collision of such HVCs.Here we report the detection of a kiloparsec (kpc)-size supershell in the outskirts of the Milky Way with the compact HVC 040+01-282 (hereafter, CHVC040) at its geometrical center using the “Inner-Galaxy Arecibo L-band Feed Array” HI 21 cm survey data. The morphological and physical properties of both objects suggest that CHVC040, which is either a fragment of a nearby disrupted galaxy or a cloud that originated from an intergalactic accreting flow, collided with the disk ˜5 Myr ago to form the supershell. Our results show that some compact HVCs can survive their trip through the Galactic halo and inject energy and momentum into the Milky Way disk.

  9. Pumping requirements and options for molecular beam epitaxy and gas source molecular beam epitaxy/chemical beam epitaxy

    International Nuclear Information System (INIS)

    McCollum, M.J.; Plano, M.A.; Haase, M.A.; Robbins, V.M.; Jackson, S.L.; Cheng, K.Y.; Stillman, G.E.

    1989-01-01

    This paper discusses the use of gas sources in growth by MBE as a result of current interest in growth of InP/InGaAsP/InGaAs lattice matched to InP. For gas flows greater than a few sccm, pumping speed requirements dictate the use of turbomolecular or diffusion pumps. GaAs samples with high p-type mobilities have been grown with diffusion pumped molecular beam epitaxial system. According to the authors, this demonstration of the inherent cleanliness of a properly designed diffusion pumping system indicates that a diffusion pump is an excellent inexpensive and reliable choice for growth by molecular beam epitaxy and gas source molecular beam epitaxy/chemical beam epitaxy

  10. Adsorption of gas molecules on a manganese phthalocyanine molecular device and its possibility as a gas sensor.

    Science.gov (United States)

    Zou, Dongqing; Zhao, Wenkai; Cui, Bin; Li, Dongmei; Liu, Desheng

    2018-01-17

    A theoretical investigation of the gas detection performance of manganese(ii) phthalocyanine (MnPc) molecular junctions for six different gases (NO, CO, O 2 , CO 2 , NO 2 , and NH 3 ) is executed through a non-equilibrium Green's function technique in combination with spin density functional theory. Herein, we systematically studied the adsorption structural configurations, the adsorption energy, the charge transfer, and the spin transport properties of the MnPc molecular junctions with these gas adsorbates. Remarkably, NO adsorption can achieve an off-state of the Mn spin; this may be an effective measure to switch the molecular spin. In addition, our results indicate that by measuring spin filter efficiency and the changes in total current through the molecular junctions, the CO, NO, O 2 , and NO 2 gas molecules can be detected selectively. However, the CO 2 and NH 3 gas adsorptions are difficult to be detected due to weak van der Waals interaction between these two gases and central Mn atom. Our findings provide important clues to the application of nanosensors for highly sensitive and selective based on MnPc molecular junction systems.

  11. High-Velocity Ly(Alpha) Emission from SMR 1987A

    Science.gov (United States)

    Michael, Eli; McCray, Richard; Borkowski, Kazimierz J.; Pun, Chu S. J.; Sonneborn, George

    1998-01-01

    The high-velocity Ly(Alpha) emission from SN 1987A observed with the Space Telescope Imaging Spectrograph (STIS) evidently comes from a reverse shock formed where the outer envelope of SN 1987A strikes ionized gas inside the inner circumstellar ring. The observations can be explained by a simple kinematic model, in which the Ly(Alpha) emission comes from hydrogen atoms with radial velocity approximately 15,000 km s(exp -1) crossing a reverse shock in the shape of a slightly prolate ellipsoid with equatorial radius 4.8 x 10(exp 17) cm or approximately 80% of the distance to the inner surface of the inner ring. N v double Lambda 1239, 1243 emission, if present, has a net luminosity approximately less than 30% times that of the Ly(Alpha) emission. Future STIS observations should enable us to predict the time of impact with the inner ring and to determine unambiguously whether or not N v emission is present. These observations will offer a unique opportunity to probe the structure of SN 1987A's circumstellar environment and the hydrodynamics and kinetics of very fast shocks.

  12. Fragmentation of neutral carbon clusters formed by high velocity atomic collision

    International Nuclear Information System (INIS)

    Martinet, G.

    2004-05-01

    The aim of this work is to understand the fragmentation of small neutral carbon clusters formed by high velocity atomic collision on atomic gas. In this experiment, the main way of deexcitation of neutral clusters formed by electron capture with ionic species is the fragmentation. To measure the channels of fragmentation, a new detection tool based on shape analysis of current pulse delivered by semiconductor detectors has been developed. For the first time, all branching ratios of neutral carbon clusters are measured in an unambiguous way for clusters size up to 10 atoms. The measurements have been compared to a statistical model in microcanonical ensemble (Microcanonical Metropolis Monte Carlo). In this model, various structural properties of carbon clusters are required. These data have been calculated with Density Functional Theory (DFT-B3LYP) to find the geometries of the clusters and then with Coupled Clusters (CCSD(T)) formalism to obtain dissociation energies and other quantities needed to compute fragmentation calculations. The experimental branching ratios have been compared to the fragmentation model which has allowed to find an energy distribution deposited in the collision. Finally, specific cluster effect has been found namely a large population of excited states. This behaviour is completely different of the atomic carbon case for which the electron capture in the ground states predominates. (author)

  13. A High-velocity Cloud Impact Forming a Supershell in the Milky Way

    Science.gov (United States)

    Park, Geumsook; Koo, Bon-Chul; Kang, Ji-hyun; Gibson, Steven J.; Peek, J. E. G.; Douglas, Kevin A.; Korpela, Eric J.; Heiles, Carl E.

    2016-08-01

    Neutral atomic hydrogen (H I) gas in interstellar space is largely organized into filaments, loops, and shells, the most prominent of which are “supershells.” These gigantic structures, which require ≳ 3× {10}52 erg to form, are generally thought to be produced by either the explosion of multiple supernovae (SNe) in OB associations or, alternatively, by the impact of high-velocity clouds (HVCs) falling into the Galactic disk. Here, we report the detection of a kiloparsec (kpc)-size supershell in the outskirts of the Milky Way with the compact HVC 040 + 01-282 (hereafter, CHVC040) at its geometrical center using the “Inner-Galaxy Arecibo L-band Feed Array” H I 21 cm survey data. The morphological and physical properties of both objects suggest that CHVC040, which is either a fragment of a nearby disrupted galaxy or a cloud that originated from an intergalactic accreting flow, collided with the disk ˜5 Myr ago to form the supershell. Our results show that some compact HVCs can survive their trip through the Galactic halo and inject energy and momentum into the Milky Way disk.

  14. Molecular gas analysis by Raman scattering in intracavity laser configuration

    International Nuclear Information System (INIS)

    Benner, R.E.; Andrade, J.D.; Van Wagenen, R.A.; Westenskow, D.R.

    1987-01-01

    A system is described for the near simultaneous analysis and quantitation of selected multiple polyatomic gases in a gas sample by Raman light scattering comprising in combination: (a) laser means capable of producing a polarized laser beam of a selected wavelength containing a laser cavity the laser cavity containing a plasma tube and wherein one end of the laser cavity contains a high reflectivity output coupler mirror; (b) a gas sampling cell located within the laser cavity between the plasma tube and the output coupler mirror, the cell having opposing parallel end windows interconnected by a continuous sidewall. The end windows and sidewall define a longitudinal gas chamber oriented such that, when the laser beam is activated, the laser beam is coincident with and traverses the axis of the longitudinal gas chamber, the end windows being positioned to be substantially normal to the axis of the longitudinal gas cell chamber. The cell also has opposing, aligned side windows in the sidewall parallel to and on either side of the axis of the longitudinal gas chamber. The gas cell further contains inlet and outlet means communicating with the chamber to pass a sample gas through the cell

  15. Possibility of gas sensor based on C{sub 20} molecular devices

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Wenkai [School of Physics and Optoelectronics Engineering, Ludong University, Yantai 264025 (China); Yang, Chuanlu, E-mail: yangchuanlu@126.com [School of Physics and Optoelectronics Engineering, Ludong University, Yantai 264025 (China); Zou, Dongqing [School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Sun, Zhaopeng [School of Physics and Optoelectronics Engineering, Ludong University, Yantai 264025 (China); Ji, Guomin [Electrical and Computer Engineering, The University of Oklahoma, Norman, Tulsa, OK 74078 (United States)

    2017-06-09

    We theoretically investigate the possibility of diatomic gas detection (NO, CO, O{sub 2}) by making use of the transport properties of the C{sub 20} molecular junctions. The calculations are performed by using nonequilibrium Green's function (NEGF) formalism in combination with density functional theory (DFT). In this work, we systematically study the most stable adsorption structural configurations, adsorption energy, and the transport properties on C{sub 20} molecular junctions with these diatomic gas molecules. It is found that NO and O{sub 2} gas molecule can be detected selectively. We suggest its possibility of nanosensors for highly sensitive and selective based on C{sub 20} molecular junction systems. - Highlights: • The most favorable adsorption site is investigated. • The mechanism of gas sensors is revealed. • NO and O{sub 2} gas molecules can be detected by C{sub 20} selectively.

  16. Possibility of gas sensor based on C_2_0 molecular devices

    International Nuclear Information System (INIS)

    Zhao, Wenkai; Yang, Chuanlu; Zou, Dongqing; Sun, Zhaopeng; Ji, Guomin

    2017-01-01

    We theoretically investigate the possibility of diatomic gas detection (NO, CO, O_2) by making use of the transport properties of the C_2_0 molecular junctions. The calculations are performed by using nonequilibrium Green's function (NEGF) formalism in combination with density functional theory (DFT). In this work, we systematically study the most stable adsorption structural configurations, adsorption energy, and the transport properties on C_2_0 molecular junctions with these diatomic gas molecules. It is found that NO and O_2 gas molecule can be detected selectively. We suggest its possibility of nanosensors for highly sensitive and selective based on C_2_0 molecular junction systems. - Highlights: • The most favorable adsorption site is investigated. • The mechanism of gas sensors is revealed. • NO and O_2 gas molecules can be detected by C_2_0 selectively.

  17. Origins Space Telescope: Tracing Dark Molecular Gas in the Milky Way

    Science.gov (United States)

    Narayanan, Desika; Li, Qi; Krumholz, Mark; Dave, Romeel; Origins Space Telescope Science and Technology Definition Team

    2018-01-01

    We present theoretical models for quantifying the fraction of CO-dark molecular gas in galaxies. To do this, we combine novel thermal, chemical, and radiative equilibrium calculations with high-resolution cosmological zoom galaxy formation models. We discuss how this dark molecular gas will be uncovered by the Origins Space Telescope, one of the four science and technology definition studies of NASA Headquarters for the 2020 Astronomy and Astrophysics Decadal survey.

  18. HIGH-RESOLUTION OBSERVATIONS AND THE PHYSICS OF HIGH-VELOCITY CLOUD A0

    International Nuclear Information System (INIS)

    Verschuur, Gerrit L.

    2013-01-01

    The neutral hydrogen structure of high-velocity cloud A0 (at about –180 km s –1 ) has been mapped with a 9.'1 resolution. Gaussian decomposition of the profiles is used to separately map families of components defined by similarities in center velocities and line widths. About 70% of the H I gas is in the form of a narrow, twisted filament whose typical line widths are of the order of 24 km s –1 . Many bright features with narrow line widths of the order of 6 km s –1 , clouds, are located in and near the filament. A third category with properties between those of the filament and clouds appears in the data. The clouds are not always co-located with the broader line width filament emission as seen projected on the sky. Under the assumption that magnetic fields underlie the presence of the filament, a theorem is developed for its stability in terms of a toroidal magnetic field generated by the flow of gas along field lines. It is suggested that the axial magnetic field strength may be derived from the excess line width of the H I emission over and above that due to kinetic temperature by invoking the role of Alfvén waves that create what is in essence a form of magnetic turbulence. At a distance of 200 pc the axial and the derived toroidal magnetic field strengths in the filament are then about 6 μG while for the clouds they are about 4 μG. The dependence of the derived field strength on distance is discussed.

  19. High molecular gas fractions in normal massive star-forming galaxies in the young Universe.

    Science.gov (United States)

    Tacconi, L J; Genzel, R; Neri, R; Cox, P; Cooper, M C; Shapiro, K; Bolatto, A; Bouché, N; Bournaud, F; Burkert, A; Combes, F; Comerford, J; Davis, M; Schreiber, N M Förster; Garcia-Burillo, S; Gracia-Carpio, J; Lutz, D; Naab, T; Omont, A; Shapley, A; Sternberg, A; Weiner, B

    2010-02-11

    Stars form from cold molecular interstellar gas. As this is relatively rare in the local Universe, galaxies like the Milky Way form only a few new stars per year. Typical massive galaxies in the distant Universe formed stars an order of magnitude more rapidly. Unless star formation was significantly more efficient, this difference suggests that young galaxies were much more molecular-gas rich. Molecular gas observations in the distant Universe have so far largely been restricted to very luminous, rare objects, including mergers and quasars, and accordingly we do not yet have a clear idea about the gas content of more normal (albeit massive) galaxies. Here we report the results of a survey of molecular gas in samples of typical massive-star-forming galaxies at mean redshifts of about 1.2 and 2.3, when the Universe was respectively 40% and 24% of its current age. Our measurements reveal that distant star forming galaxies were indeed gas rich, and that the star formation efficiency is not strongly dependent on cosmic epoch. The average fraction of cold gas relative to total galaxy baryonic mass at z = 2.3 and z = 1.2 is respectively about 44% and 34%, three to ten times higher than in today's massive spiral galaxies. The slow decrease between z approximately 2 and z approximately 1 probably requires a mechanism of semi-continuous replenishment of fresh gas to the young galaxies.

  20. ULTRA-COMPACT HIGH VELOCITY CLOUDS AS MINIHALOS AND DWARF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Faerman, Yakov; Sternberg, Amiel [Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Ramat Aviv 69978 (Israel); McKee, Christopher F., E-mail: yakovfae@post.tau.ac.il [Department of Physics and Department of Astronomy, University of California at Berkeley, Berkeley, CA 94720 (United States)

    2013-11-10

    We present dark matter minihalo models for the Ultra-Compact, High-Velocity H I Clouds (UCHVCs) recently discovered in the 21 cm ALFALFA survey. We assume gravitational confinement of 10{sup 4} K H I gas by flat-cored dark-matter subhalos within the Local Group. We show that for flat cores, typical (median) tidally stripped cosmological subhalos at redshift z = 0 have dark-matter masses of ∼10{sup 7} M{sub ☉} within the central 300 pc (independent of total halo mass), consistent with the 'Strigari mass scale' observed in low-luminosity dwarf galaxies. Flat-cored subhalos also resolve the mass discrepancy between simulated and observed satellites around the Milky Way. For the UCHVCs, we calculate the photoionization-limited hydrostatic gas profiles for any distance-dependent total observed H I mass and predict the associated (projected) H I half-mass radii, assuming the clouds are embedded in distant (d ∼> 300 kpc) and unstripped subhalos. For a typical UCHVC (0.9 Jy km s{sup –1}), we predict physical H I half-mass radii of 0.18 to 0.35 kpc (or angular sizes of 0.'6 to 2.'1) for distances ranging from 300 kpc to 2 Mpc. As a consistency check, we model the gas-rich dwarf galaxy Leo T, for which there is a well-resolved H I column density profile and a known distance (420 kpc). For Leo T, we find that a subhalo with M{sub 300} = 8 (± 0.2) × 10{sup 6} M{sub ☉} best fits the observed H I profile. We derive an upper limit of P{sub HIM} ∼< 150 cm{sup –3} K for the pressure of any enveloping hot intergalactic medium gas at the distance of Leo T. Our analysis suggests that some of the UCHVCs may in fact constitute a population of 21 cm-selected but optically faint dwarf galaxies in the Local Group.

  1. Probing gas-surface interactions with a molecular beam

    International Nuclear Information System (INIS)

    Spruit, M.E.M.

    1988-01-01

    The dynamics of direct scattering, trapping and sticking in molecular beam scattering is probed. The O 2 /Ag interaction was chosen, using the close-packed (111) plane of Ag as target surface. 170 refs.; 22 figs.; 3 tabs

  2. Management of High-Velocity Injuries of the Head and Neck.

    Science.gov (United States)

    Majors, Jacob S; Brennan, Joseph; Holt, G Richard

    2017-11-01

    Trauma centers must prepare to manage high-velocity injuries resulting from a mass casualty incidents as global terrorism becomes a greater concern and an increasing risk. The most recent conflicts in Iraq and Afghanistan have significantly improved understanding of battlefield trauma and how to appropriately address these injures. This article applies combat surgery experience to civilian situations, outlines the physiology and kinetics of high-velocity injuries, and reviews applicable triage and management strategies. Published by Elsevier Inc.

  3. Molecular structure determination of cyclooctane by Ab Initio and electron diffraction methods in the gas phase

    International Nuclear Information System (INIS)

    Almeida, Wagner B. de

    2000-01-01

    The determination of the molecular structure of molecules is of fundamental importance in chemistry. X-rays and electron diffraction methods constitute in important tools for the elucidation of the molecular structure of systems in the solid state and gas phase, respectively. The use of quantum mechanical molecular orbital ab initio methods offer an alternative for conformational analysis studies. Comparison between theoretical results and those obtained experimentally in the gas phase can make a significant contribution for an unambiguous determination of the geometrical parameters. In this article the determination for an unambiguous determination of the geometrical parameters. In this article the determination of the molecular structure of the cyclooctane molecule by electron diffraction in the gas phase an initio calculations will be addressed, providing an example of a comparative analysis of theoretical and experimental predictions. (author)

  4. The experiment of the elemental mercury was removed from natural gas by 4A molecular sieve

    Science.gov (United States)

    Jiang, Cong; Chen, Yanhao

    2018-04-01

    Most of the world's natural gas fields contain elemental mercury and mercury compounds, and the amount of mercury in natural gas is generally 1μg/m3 200μg/m3. This paper analyzes the mercury removal principle of chemical adsorption process, the characteristics and application of mercury removal gent and the factors that affect the efficiency of mercury removal. The mercury in the natural gas is adsorbed by the mercury-silver reaction of the 4 molecular sieve after the manned treatment. The limits for mercury content for natural gas for different uses and different treatment processes are also different. From the environmental protection, safety and other factors, it is recommended that the mercury content of natural gas in the pipeline is less than 28μg / m3, and the mercury content of the raw material gas in the equipment such as natural gas liquefaction and natural gas condensate recovery is less than 0.01μg/m3. This paper mainly analyzes the existence of mercury in natural gas, and the experimental research process of using 4A molecular sieve to absorb mercury in natural gas.

  5. A molecular gas-rich GRB host galaxy at the peak of cosmic star formation

    Science.gov (United States)

    Arabsalmani, M.; Le Floc'h, E.; Dannerbauer, H.; Feruglio, C.; Daddi, E.; Ciesla, L.; Charmandaris, V.; Japelj, J.; Vergani, S. D.; Duc, P.-A.; Basa, S.; Bournaud, F.; Elbaz, D.

    2018-05-01

    We report the detection of the CO(3-2) emission line from the host galaxy of gamma-ray burst (GRB) 080207 at z = 2.086. This is the first detection of molecular gas in emission from a GRB host galaxy beyond redshift 1. We find this galaxy to be rich in molecular gas with a mass of 1.1 × 10^{11} M_{{\\odot }} assuming αCO = 4.36 M_{{\\odot }} (K km s^{-1} pc^2)^{-1}. The molecular gas mass fraction of the galaxy is ˜0.5, typical of star-forming galaxies (SFGs) with similar stellar masses and redshifts. With an SFR_{FIR} of 260 M_{{\\odot }} yr^{-1}, we measure a molecular gas depletion time-scale of 0.43 Gyr, near the peak of the depletion time-scale distribution of SFGs at similar redshifts. Our findings are therefore in contradiction with the proposed molecular gas deficiency in GRB host galaxies. We argue that the reported molecular gas deficiency for GRB hosts could be the artefact of improper comparisons or neglecting the effect of the typical low metallicities of GRB hosts on the CO-to-molecular-gas conversion factor. We also compare the kinematics of the CO(3-2) emission line to that of the H α emission line from the host galaxy. We find the H α emission to have contributions from two separate components, a narrow and a broad one. The narrow component matches the CO emission well in velocity space. The broad component, with a full width at half-maximum of ˜1100 km s^{-1}, is separated by +390 km s^{-1} in velocity space from the narrow component. We speculate this broad component to be associated with a powerful outflow in the host galaxy or in an interacting system.

  6. Evolution of the Normal State of a Strongly Interacting Fermi Gas from a Pseudogap Phase to a Molecular Bose Gas

    International Nuclear Information System (INIS)

    Perali, A.; Palestini, F.; Pieri, P.; Strinati, G. C.; Stewart, J. T.; Gaebler, J. P.; Drake, T. E.; Jin, D. S.

    2011-01-01

    Wave-vector resolved radio frequency spectroscopy data for an ultracold trapped Fermi gas are reported for several couplings at T c , and extensively analyzed in terms of a pairing-fluctuation theory. We map the evolution of a strongly interacting Fermi gas from the pseudogap phase into a fully gapped molecular Bose gas as a function of the interaction strength, which is marked by a rapid disappearance of a remnant Fermi surface in the single-particle dispersion. We also show that our theory of a pseudogap phase is consistent with a recent experimental observation as well as with quantum Monte Carlo data of thermodynamic quantities of a unitary Fermi gas above T c .

  7. Extending the molecular application range of gas chromatography

    NARCIS (Netherlands)

    Kaal, E.; Janssen, H.-G.

    2008-01-01

    Gas chromatography is an important analytical technique for qualitative and quantitative analysis in a wide range of application areas. It is fast, provides a high peak capacity, is sensitive and allows combination with a wide range of selective detection methods including mass spectrometry.

  8. Gas chromatographic column for the Viking 1975 molecular analysis experiment

    Science.gov (United States)

    Novotny, M.; Hayes, J. M.; Bruner, F.; Simmonds, P. G.

    1975-01-01

    A gas chromatographic column has been developed for use in the remote analysis of the Martian surface. The column, which utilizes a liquid-modified organic adsorbent (Tenax) as the stationary phase, provides efficient transmission and resolution of nanogram quantities of organic materials in the presence of millionfold excesses of water and carbon dioxide.

  9. Energetic molecular outflow near AFGL 961: millimeter-wave and infrared observations

    International Nuclear Information System (INIS)

    Lada, C.J.; Gautier, T.N. III

    1982-01-01

    We report detailed millimeter-wave and near-infrared spectroscopy of the dynamically active region around the infrared source AFGL 961, near the Rosette nebula. Millimeter-wave 12 CO observations are used to study the high-velocity molecular flow around AFGL 961. These observations show that the high-velocity flow has a maximum extent of at least 6' or 2.9 pc at the distance of AFGL 961. The flow is found to be anisotropic, with redshifted high-velocity emission considerably more extended than blueshifted high-velocity emission. However, the flow does not appear to be as highly collimated as some other sources of high-velocity bipolar outflow. We also find the emission profiles to be asymmetric in velocity such that the integrated intensity of the redshifted high-velocity emission is on average 2.5 times greater than that of the blueshifted emission. The mass of the gas involved in the flow is determined to be approximately 19 M/sub sun/, and the kinetic energy of this gas is estimated to be about 8 x 10 46 ergs. These observations are interpreted as evidence that an energetic bipolar outflow of molecular gas is occurring near AFGL 961. The momentum of the outflowing molecular gas is large, and it is shown that this places strong constraints on possible physical mechanisms which may be driving the outflow. The near-infrared spectrum of AFGL 961 from 1.4-2.4 μm was obtained in order to study the conditions immediately around the infrared source which may be driving the molecular outflow

  10. Compaction of Ti–6Al–4V powder using high velocity compaction technique

    International Nuclear Information System (INIS)

    Khan, Dil Faraz; Yin, Haiqing; Li, He; Qu, Xuanhui; Khan, Matiullah; Ali, Shujaat; Iqbal, M. Zubair

    2013-01-01

    Highlights: • We compacted Ti–6Al–4V powder by HVC technique. • As impact force rises up, the green density of the compacts increases gradually. • At impact force 1.857 kN relative sintered density of the compacts reaches 99.88%. • Spring back of the green compact’s decreases gradually with increasing impact force. • Mechanical properties of the samples increases with increasing impact force. - Abstract: High velocity compaction technique was applied to the compaction of pre-alloyed, hydride–dehydride Ti–6Al–4V powder. The powder was pressed in single stroke with a compaction speed of 7.10–8.70 ms −1 . When the speed was 8.70 ms −1 , the relative density of the compacts reaches up to 85.89% with a green density of 3.831 g cm −3 . The green samples were sintered at 1300 °C in Ar-gas atmosphere. Scanning electron microscope (SEM) was used to examine the surface of the sintered samples. Density and mechanical properties such as Vickers micro hardness and bending strength of the powder samples were investigated. Experimental results indicated that with the increase in impact force, the density and mechanical properties of the compacts increased. The sintered compacts exhibited a maximum relative density of 99.88% with a sintered density of 4.415 g cm −3 , hardness of 364–483 HV and the bending strength in the range of 103–126.78 MPa. The springback of the compacts decreased with increasing impact force

  11. Modified molecular sieves: stationary phase for the gas chromatographic separation of hydrogen isotopes

    International Nuclear Information System (INIS)

    Pushpa, K.K.; Annaji Rao, K.; Iyer, R.M.

    1993-01-01

    Gas chromatographic separation of hydrogen isotopes on different molecular sieves at liquid nitrogen temperature has been investigated. Normal molecular sieves 5A, 13X and AW500 are not satisfactory for the purpose both in the partially dehydrated as well as totally dehydrated state. Molecular sieve 4A in partially dehydrated state separated H 2 and D 2 while H 2 and HD are not well resolved. Iron exchanged or coated molecular sieves 4A, 5A, 13X and AW500 in the partially dehydrated state separated the isotopic mixtures H 2 , HD, D 2 and H 2 , HT, T 2 . The resolution varied depending on the amount of iron content and the residual moisture in the molecular sieves. Good separations were obtained on 15% Fe coated molecular sieve 5A and 5% Fe coated molecular sieve 4A. (author). 18 refs., 6 figs., 3 tabs

  12. Application of an Arbitrary Lagrangian Eulerian Method to Describe High Velocity Gas-Particle Flow Behavior

    Science.gov (United States)

    2011-09-01

    applied in this work was based on some of the standard definitions of soil constitutive properties as found in, e.g., Chen and Baladi [20], and...Livermore, CA. [20] Chen, W. F., and Baladi , G. Y., 1985. Soil Plasticity: Theory and Implementation. Elsevier Science, New York. [21] Zimmerman, H.D

  13. LLAMA: normal star formation efficiencies of molecular gas in the centres of luminous Seyfert galaxies

    Science.gov (United States)

    Rosario, D. J.; Burtscher, L.; Davies, R. I.; Koss, M.; Ricci, C.; Lutz, D.; Riffel, R.; Alexander, D. M.; Genzel, R.; Hicks, E. H.; Lin, M.-Y.; Maciejewski, W.; Müller-Sánchez, F.; Orban de Xivry, G.; Riffel, R. A.; Schartmann, M.; Schawinski, K.; Schnorr-Müller, A.; Saintonge, A.; Shimizu, T.; Sternberg, A.; Storchi-Bergmann, T.; Sturm, E.; Tacconi, L.; Treister, E.; Veilleux, S.

    2018-02-01

    Using new Atacama Pathfinder Experiment and James Clerk Maxwell Telescope spectroscopy of the CO 2→1 line, we undertake a controlled study of cold molecular gas in moderately luminous (Lbol = 1043-44.5 erg s-1) active galactic nuclei (AGN) and inactive galaxies from the Luminous Local AGN with Matched Analogs (LLAMA) survey. We use spatially resolved infrared photometry of the LLAMA galaxies from 2MASS, the Wide-field Infrared Survey Explorer the Infrared Astronomical Satellite and the Herschel Space Observatory (Herschel), corrected for nuclear emission using multicomponent spectral energy distribution fits, to examine the dust-reprocessed star formation rates, molecular gas fractions and star formation efficiencies (SFEs) over their central 1-3 kpc. We find that the gas fractions and central SFEs of both active and inactive galaxies are similar when controlling for host stellar mass and morphology (Hubble type). The equivalent central molecular gas depletion times are consistent with the discs of normal spiral galaxies in the local Universe. Despite energetic arguments that the AGN in LLAMA should be capable of disrupting the observable cold molecular gas in their central environments, our results indicate that nuclear radiation only couples weakly with this phase. We find a mild preference for obscured AGN to contain higher amounts of central molecular gas, which suggests connection between AGN obscuration and the gaseous environment of the nucleus. Systems with depressed SFEs are not found among the LLAMA AGN. We speculate that the processes that sustain the collapse of molecular gas into dense pre-stellar cores may also be a prerequisite for the inflow of material on to AGN accretion discs.

  14. The mobilies of chiral molecular cluster ions in He gas

    International Nuclear Information System (INIS)

    Saito, Kazuyuki; Matoba, Shiro; Koizumi, Tetsuo; Kojima, Takao M; Tanuma, Hajime; Shiromaru, Haruo

    2012-01-01

    We measured the mobilities of Li + -(2-butanol) and Li + -(limonene) ions in He gas at room temperature using a drift tube mass spectrometer. The zero field mobilities of Li + -(2-Butanol) and Li + -(Limonene) were much lower than the polarization limit, indicating that the geometric collision cross-sections between the cluster ions and He atom were larger than the cross-sections predicted by the presence of a polarization force alone.

  15. Hybrid continuum–molecular modelling of multiscale internal gas flows

    International Nuclear Information System (INIS)

    Patronis, Alexander; Lockerby, Duncan A.; Borg, Matthew K.; Reese, Jason M.

    2013-01-01

    We develop and apply an efficient multiscale method for simulating a large class of low-speed internal rarefied gas flows. The method is an extension of the hybrid atomistic–continuum approach proposed by Borg et al. (2013) [28] for the simulation of micro/nano flows of high-aspect ratio. The major new extensions are: (1) incorporation of fluid compressibility; (2) implementation using the direct simulation Monte Carlo (DSMC) method for dilute rarefied gas flows, and (3) application to a broader range of geometries, including periodic, non-periodic, pressure-driven, gravity-driven and shear-driven internal flows. The multiscale method is applied to micro-scale gas flows through a periodic converging–diverging channel (driven by an external acceleration) and a non-periodic channel with a bend (driven by a pressure difference), as well as the flow between two eccentric cylinders (with the inner rotating relative to the outer). In all these cases there exists a wide variation of Knudsen number within the geometries, as well as substantial compressibility despite the Mach number being very low. For validation purposes, our multiscale simulation results are compared to those obtained from full-scale DSMC simulations: very close agreement is obtained in all cases for all flow variables considered. Our multiscale simulation is an order of magnitude more computationally efficient than the full-scale DSMC for the first and second test cases, and two orders of magnitude more efficient for the third case

  16. Experimental Investigation of Multi-layer Insulation Effect on Damage of Stuffed Shield by High-velocity Impact

    Directory of Open Access Journals (Sweden)

    GUAN Gong-shun

    2016-09-01

    Full Text Available The stuffed shield with multi-layer insulation(MLI was designed by improving on Al Whipple shield, and a series of high-velocity impact tests were practiced with a two-stage light gas gun facility at vacuum environment. The damage model of the stuffed shield with different MLI location by Al-sphere projectile impacting was obtained. The effect of MLI on damage of the stuffed shield by high-velocity impact was studied. The results indicate when the MLI is located at front side of the first Al-plate, the protection performance of the stuffed shield is improved with the larger perforation diameter of the first Al-plate and more impact kinetic energy dissipation of the projectile. When MLI is arranged at back side of the first Al-plate, the expansion of the secondary debris cloud from projectile impacting the first Al-plate is restrained, it is not good to improve the protection performance of the stuffed shield. When MLI is arranged at front side of the stuffed wall, the perforation size of the stuffed wall increases; when MLI is arranged at front side of the rear wall, the distribution range of crater on the rear wall decreases.

  17. Theoretical aspects of gas-phase molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Muckerman, J.T. [Brookhaven National Laboratory, Upton, NY (United States)

    1993-12-01

    Research in this program is focused on the development and application of time-dependent quantum mechanical and semiclassical methods for treating inelastic and reactive molecular collisions, and the photochemistry and photophysics of atoms and molecules in laser fields. Particular emphasis is placed on the development and application of grid methods based on discrete variable representations, on time-propagation methods, and, in systems with more that a few degrees of freedom, on the combined use of quantal wavepackets and classical trajectories.

  18. Multiple-electron excitation, ionization, and transfer in high-velocity atomic and molecular collisions

    International Nuclear Information System (INIS)

    McGuire, J.H.

    1992-01-01

    This paper reports that the many-body and many-electron problem is common in various areas of physics as well as in chemistry and biology. Basic understanding of phenomena ranging from the nature of matter at the creation of time to the properties of useful materials in the human environment is limited by the boundaries of our knowledge of the many-body problem. There is an advantage in studying the many-body problem in atomic physics since the two-body and parts of the three-body problem are understood. Furthermore, both the mystery of the meanings of quantum mechanics and the mystery of the transition from microscopic time-reversible atomic processes to the dynamics of macroscopic time-irreversible aggregates of atomic particles is inherent in the many-body problems of atomic interactions. Thus, by studying the many-body problem in atomic physics we are able to develop effective tools to discover insights that provide both meaning and utility in our lives

  19. Atomic and molecular hydrogen gas temperatures in a low-pressure helicon plasma

    Science.gov (United States)

    Samuell, Cameron M.; Corr, Cormac S.

    2015-08-01

    Neutral gas temperatures in hydrogen plasmas are important for experimental and modelling efforts in fusion technology, plasma processing, and surface modification applications. To provide values relevant to these application areas, neutral gas temperatures were measured in a low pressure (radiofrequency helicon discharge using spectroscopic techniques. The atomic and molecular species were not found to be in thermal equilibrium with the atomic temperature being mostly larger then the molecular temperature. In low power operation (measurements near a graphite target demonstrated localised cooling near the sample surface. The temporal evolution of the molecular gas temperature during a high power 1.1 ms plasma pulse was also investigated and found to vary considerably as a function of pressure.

  20. Molecular Laser Spectroscopy as a Tool for Gas Analysis Applications

    Directory of Open Access Journals (Sweden)

    Javis Anyangwe Nwaboh

    2011-01-01

    Full Text Available We have used the traceable infrared laser spectrometric amount fraction measurement (TILSAM method to perform absolute concentration measurements of molecular species using three laser spectroscopic techniques. We report results performed by tunable diode laser absorption spectroscopy (TDLAS, quantum cascade laser absorption spectroscopy (QCLAS, and cavity ring down spectroscopy (CRDS, all based on the TILSAM methodology. The measured results of the different spectroscopic techniques are in agreement with respective gravimetric values, showing that the TILSAM method is feasible with all different techniques. We emphasize the data quality objectives given by traceability issues and uncertainty analyses.

  1. Unexpected mobility of OH+ and OD+ molecular ions in cooled helium gas

    International Nuclear Information System (INIS)

    Isawa, R; Yamazoe, J; Tanuma, H; Ohtsuki, K

    2012-01-01

    Mobilities of OH + and OD + ions in cooled helium gas have been measured at gas temperature of 4.3 K. Measured mobilities of both ions as a function of an effective temperature T eff show a minimum around 80 K, and they are approaching to the polarization limits at very low T eff . These findings will be related to the extremely strong anisotropy of the interaction potential between the molecular ion and helium atom.

  2. Warm and cold molecular gas conditions modeled in 87 galaxies observed by the Herschel SPIRE FTS

    Science.gov (United States)

    Kamenetzky, Julia; Rangwala, Naseem; Glenn, Jason

    2018-01-01

    Molecular gas is the raw material for star formation, and like the interstellar medium (ISM) in general, it can exist in regions of higher and lower excitation. Rotational transitions of the CO molecule are bright and sensitive to cold molecular gas. While the majority of the molecular gas exists in the very cold component traced by CO J=1-0, the higher-J lines trace the highly excited gas that may be more indicative of star formation processes. The atmosphere is opaque to these lines, but the launch of the Herschel Space Observatory made them accessible for study of Galactic and extragalactic sources. We have conducted two-component, non-local thermodynamic equilibrium (non-LTE) modeling of the CO lines from J=1‑0 through J=13‑12 in 87 galaxies observed by the Herschel SPIRE Fourier Transform Spectrometer (FTS). We used the nested sampling algorithm Multinest to compare the measured CO spectral line energy distributions (SLEDs) to the ones produced by a custom version of the non-LTE code RADEX. This allowed us to fully examine the degeneracies in parameter space for kinetic temperature, molecular gas density, CO column density, and area filling factor.Here we discuss the major findings of our study, as well as the important implications of two-component molecular gas modeling. The average pressure of the warm gas is slightly correlated with galaxy LFIR, but that of the cold gas is not. A high-J (such as J=11-10) to J=1-0 line ratio is diagnostic of warm component pressure. We find a very large spread in our derived values of "alpha-CO," with no discernable trend with LFIR, and average molecular gas depletion times that decrease with LFIR. If only a few molecular lines are available in a galaxy's SLED, the limited ability to model only one component will change the results. A one-component fit often underestimates the flux of carbon monoxide (CO) J=1‑0 and the mass. If low-J lines are not included, mass is underestimated by an order of magnitude. Even when

  3. Theoretical Research Progress in High-Velocity/Hypervelocity Impact on Semi-Infinite Targets

    Directory of Open Access Journals (Sweden)

    Yunhou Sun

    2015-01-01

    Full Text Available With the hypervelocity kinetic weapon and hypersonic cruise missiles research projects being carried out, the damage mechanism for high-velocity/hypervelocity projectile impact on semi-infinite targets has become the research keystone in impact dynamics. Theoretical research progress in high-velocity/hypervelocity impact on semi-infinite targets was reviewed in this paper. The evaluation methods for critical velocity of high-velocity and hypervelocity impact were summarized. The crater shape, crater scaling laws and empirical formulae, and simplified analysis models of crater parameters for spherical projectiles impact on semi-infinite targets were reviewed, so were the long rod penetration state differentiation, penetration depth calculation models for the semifluid, and deformed long rod projectiles. Finally, some research proposals were given for further study.

  4. A molecular study of gas solubility in nitrile rubber

    Science.gov (United States)

    Khawaja, Musab; Mostofi, Arash; Sutton, Adrian

    2015-03-01

    One of the most important uses of elastomers in the oil industry is for seals to encase and protect sensitive monitoring equipment from contamination by gases and liquids at the high pressures and temperatures in the well. Failure of such seals sometimes occurs on decompression when they are returned to the surface. The conditions in the well lead to gases being absorbed by Nitrile rubber (NBR) seals. NBR exhibits a strong permselectivity towards CO2 compared to other gases; something attributed experimentally to the enhanced solubility of CO2. In this study an explanation is sought at the molecular level for this phenomenon. A series of molecular mechanics calculations are performed to compute solubilities of different gases in NBR. The effect of acrylonitrile content on their solubilities is studied for the first time by simulation, and we discuss the important issue of convergence with respect to the sampling of different elastomer configurations. It is observed that the presence of cyano groups has a marked impact on the solubility of CO2 and an explanation is offered.

  5. Unsupervised Learning Through Randomized Algorithms for High-Volume High-Velocity Data (ULTRA-HV).

    Energy Technology Data Exchange (ETDEWEB)

    Pinar, Ali [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Kolda, Tamara G. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Carlberg, Kevin Thomas [Wake Forest Univ., Winston-Salem, MA (United States); Ballard, Grey [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Mahoney, Michael [Univ. of California, Berkeley, CA (United States)

    2018-01-01

    Through long-term investments in computing, algorithms, facilities, and instrumentation, DOE is an established leader in massive-scale, high-fidelity simulations, as well as science-leading experimentation. In both cases, DOE is generating more data than it can analyze and the problem is intensifying quickly. The need for advanced algorithms that can automatically convert the abundance of data into a wealth of useful information by discovering hidden structures is well recognized. Such efforts however, are hindered by the massive volume of the data and its high velocity. Here, the challenge is developing unsupervised learning methods to discover hidden structure in high-volume, high-velocity data.

  6. High-Pressure Shock Compression of Solids VIII The Science and Technology of High-Velocity Impact

    CERN Document Server

    Chhabildas, Lalit C; Horie, Yasuyuki

    2005-01-01

    Research in the field of shock physics and ballistic impact has always been intimately tied to progress in development of facilities for accelerating projectiles to high velocity and instrumentation for recording impact phenomena. The chapters of this book, written by leading US and European experts, cover a broad range of topics and address researchers concerned with questions of material behaviour under impulsive loading and the equations of state of matter, as well as the design of suitable instrumentation such as gas guns and high-speed diagnostics. Applications include high-speed impact dynamics, the inner composition of planets, syntheses of new materials and materials processing. Among the more technologically-oriented applications treated is the testing of the flight characteristics of aeroballistic models and the assessment of impacts in the aerospace industry.

  7. An approach to spin-resolved molecular gas microscopy

    Science.gov (United States)

    Covey, Jacob P.; De Marco, Luigi; Acevedo, Óscar L.; Rey, Ana Maria; Ye, Jun

    2018-04-01

    Ultracold polar molecules are an ideal platform for studying many-body physics with long-range dipolar interactions. Experiments in this field have progressed enormously, and several groups are pursuing advanced apparatus for manipulation of molecules with electric fields as well as single-atom-resolved in situ detection. Such detection has become ubiquitous for atoms in optical lattices and tweezer arrays, but has yet to be demonstrated for ultracold polar molecules. Here we present a proposal for the implementation of site-resolved microscopy for polar molecules, and specifically discuss a technique for spin-resolved molecular detection. We use numerical simulation of spin dynamics of lattice-confined polar molecules to show how such a scheme would be of utility in a spin-diffusion experiment.

  8. Low pressure gas detectors for molecular-ion break up studies

    International Nuclear Information System (INIS)

    Breskin, A.; Chechik, R.; Zwang, N.

    1981-01-01

    Two detector systems for Molecular ions like OH + and CH 2 + and like H 2 + and H 3 + were developed and are described. The first detector is installed in a magnetic spectrometer. Both systems are made of various types of gas detectors operating at low pressures. In the study of the Coulomb explosion of molecular ions like OH + , CH 2 + or H 3 + these detectors provide the position and time coordinates of all the fragments of the molecular ion, in coincidence, in order to determine their energy and angular distribution. In the case of molecules containing atoms other than hydrogen, information on the electronic charge state is obtained. (H.K.)

  9. Comparison of molecular dynamics and kinetic modeling of gas-surface interactions

    NARCIS (Netherlands)

    Frezzotti, A.; Gaastra - Nedea, S.V.; Markvoort, A.J.; Spijker, P.; Gibelli, L.

    2008-01-01

    The interaction of a dilute monatomic gas with a solid surface is studied byMolecular Dynamics (MD) simulations and by numerical solutions of a recently proposed kinetic model. Following previous investigations, the heat transport between parallel walls and Couette flow have been adopted as test

  10. Molecular dynamics study of the influence of wall-gas interactions on heat flow in nanochannels

    NARCIS (Netherlands)

    Markvoort, Albert. J.; Hilbers, P.A.J.; Nedea, S.V.

    2005-01-01

    Especially at the nanometer scale interfaces play an important role. The effect of the wettability on the solid-liquid interface has already been studied with molecular dynamics. In this paper we study the dependence of wetting on the solid-gas interface for different density gases and investigate

  11. Distribution and kinematics of atomic and molecular gas inside the solar circle

    NARCIS (Netherlands)

    Marasco, A.; Fraternali, F.; van der Hulst, J. M.; Oosterloo, T.

    2017-01-01

    The detailed distribution and kinematics of the atomic and the CO-bright molecular hydrogen in the disc of the Milky Way inside the solar circle are derived under the assumptions of axisymmetry and pure circular motions. We divide the Galactic disc into a series of rings, and assume that the gas in

  12. DISTRIBUTION AND ORIGIN OF HIGH-VELOCITY CLOUDS .3. CLOUDS, COMPLEXES AND POPULATIONS

    NARCIS (Netherlands)

    WAKKER, BP; VANWOERDEN, H

    1991-01-01

    We present the first complete catalogue of high-velocity clouds (HVCs), followed by a classification of these clouds into complexes and populations. The catalogue will form the basis for comparisons with theoretical models. The study described here yields the following conclusions: (1) Differential

  13. Cold Molecular Gas Along the Merger Sequence in Local Luminous Infrared Galaxies

    Science.gov (United States)

    Yamashita, Takuji; Komugi, Shinya; Matsuhara, Hideo; Armus, Lee; Inami, Hanae; Ueda, Junko; Iono, Daisuke; Kohno, Kotaro; Evans, Aaron S.; Arimatsu, Ko

    2017-08-01

    We present an initial result from the 12CO (J = 1-0) survey of 79 galaxies in 62 local luminous and ultraluminous infrared galaxy (LIRG and ULIRG) systems obtained using the 45 m telescope at the Nobeyama Radio Observatory. This is a systematic 12CO (J = 1-0) survey of the Great Observatories All-sky LIRGs Survey (GOALS) sample. The molecular gas mass of the sample is in the range 2.2× {10}8{--}7.0× {10}9 {M}⊙ within the central several kiloparsecs subtended by the 15\\prime\\prime beam. A method to estimate the size of a CO gas distribution is introduced, which is combined with the total CO flux in the literature. This method is applied to part of our sample, and we find that the median CO radius is 1-4 kpc. From the early stage to the late stage of mergers, we find that the CO size decreases while the median value of the molecular gas mass in the central several-kiloparsec region is constant. Our results statistically support a scenario where molecular gas inflows toward the central region from the outer disk to replenish gas consumed by starburst, and that such a process is common in merging LIRGs.

  14. Carbon-fiber composite molecular sieves for gas separation

    Energy Technology Data Exchange (ETDEWEB)

    Jagtoyen, M.; Derbyshire, F. [Univ. of Kentucky, Lexington, KY (United States)

    1996-08-01

    This report describes continuing work on the activation and characterization of formed carbon fiber composites. The composites are produced at the Oak Ridge National Laboratory (ORNL) and activated at the Center for Applied Energy Research (CAER) using steam, CO{sub 2}, or O{sub 2} at different conditions of temperature and time, and with different furnace configurations. The general aims of the project are to produce uniformly activated samples with controlled pore structures for specialist applications such as gas separation and water treatment. In previous work the authors reported that composites produced from isotropic pitch fibers weighing up to 25g can be uniformly activated through the appropriate choice of reaction conditions and furnace configurations. They have now succeeded in uniformly activating composites of dimensions up to 12 x 7 x 6 cm, or up to about 166 gram - a scale-up factor of about six. Part of the work has involved the installation of a new furnace that can accommodate larger composites. Efforts were made to achieve uniform activation in both steam and CO{sub 2}. The authors have also succeeded in producing materials with very uniform and narrow pore size distributions by using a novel method involving low temperature oxygen chemisorption in combination with heat treatment in N{sub 2} at high temperatures. Work has also started on the activation of PAN based carbon fibers and fiber composites with the aim of producing composites with wide pore structures for use as catalyst supports. So far activation of the PAN fiber composites supplied by ORNL has been difficult which is attributed to the low reactivity of the PAN fibers. As a result, studies are now being made of the activation of the PAN fibers to investigate the optimum carbonization and activation conditions for PAN based fibers.

  15. Ultra-compact high velocity clouds in the ALFALFA HI survey: Candidate Local Group galaxies?

    Science.gov (United States)

    Adams, Elizabeth Ann Kovenz

    The increased sensitivity and spatial resolution of the ALFALFA HI survey has resulted in the detection of ultra-compact high velocity clouds (UCHVCs). These objects are good candidates to represent low mass gas-rich galaxies in the Local Group and Local Volume with stellar populations that are too faint to be detected in extant optical surveys. This idea is referred to as the "minihalo hypothesis". We identify the UCHVCs within the ALFALFA dataset via the use of a 3D matched filtering signal identification algorithm. UCHVCs are selected based on a compact size ( 120 km s-1) and isolation. Within the 40% complete ALFALFA survey (alpha.40), 59 UCHVCs are identified; 19 are in a most-isolated subset and are the best galaxy candidates. Due to the presence of large HVC complexes in the fall sky, most notably the Magellanic Stream, the association of UCHVCs with existing structure cannot be ruled out. In the spring sky, the spatial and kinematic distribution of the UCHVCs is consistent with simulations of dark matter halos within the Local Group. In addition, the HI properties of the UCHVCs (if placed at 1 Mpc) are consistent with both theoretical and observational predictions for low mass gas-rich galaxies. Importantly, the HI properties of the UCHVCs are consistent with those of two recently discovered low mass gas-rich galaxies in the Local Group and Local Volume, Leo T and Leo P. Detailed follow-up observations are key for addressing the minihalo hypothesis. High resolution HI observations can constrain the environment of a UCHVC and offer evidence for a hosting dark matter halo through evidence of rotation support and comparison to theoretical models. Observations of one UCHVC at high resolution (15'') reveal the presence of a clumpy HI distribution, similar to both low mass galaxies and circumgalactic compact HVCs. An extended envelope containing ˜50% of the HI flux is resolved out by the array configuration; observations at lower spatial resolution can recover

  16. Gas Source Techniques for Molecular Beam Epitaxy of Highly Mismatched Ge Alloys

    Directory of Open Access Journals (Sweden)

    Chad A. Stephenson

    2016-12-01

    Full Text Available Ge and its alloys are attractive candidates for a laser compatible with silicon integrated circuits. Dilute germanium carbide (Ge1−xCx offers a particularly interesting prospect. By using a precursor gas with a Ge4C core, C can be preferentially incorporated in substitutional sites, suppressing interstitial and C cluster defects. We present a method of reproducible and upscalable gas synthesis of tetrakis(germylmethane, or (H3Ge4C, followed by the design of a hybrid gas/solid-source molecular beam epitaxy system and subsequent growth of defect-free Ge1−xCx by molecular beam epitaxy (MBE. Secondary ion mass spectroscopy, transmission electron microscopy and contactless electroreflectance confirm the presence of carbon with very high crystal quality resulting in a decrease in the direct bandgap energy. This technique has broad applicability to growth of highly mismatched alloys by MBE.

  17. Where is OH and Does It Trace the Dark Molecular Gas (DMG)?

    Science.gov (United States)

    Li, Di; Tang, Ningyu; Nguyen, Hiep; Dawson, J. R.; Heiles, Carl; Xu, Duo; Pan, Zhichen; Goldsmith, Paul F.; Gibson, Steven J.; Murray, Claire E.; Robishaw, Tim; McClure-Griffiths, N. M.; Dickey, John; Pineda, Jorge; Stanimirović, Snežana; Bronfman, L.; Troland, Thomas; PRIMO Collaboration

    2018-03-01

    Hydroxyl (OH) is expected to be abundant in diffuse interstellar molecular gas because it forms along with H2 under similar conditions and forms within a similar extinction range. We have analyzed absorption measurements of OH at 1665 MHz and 1667 MHz toward 44 extragalactic continuum sources, together with the J = 1–0 transitions of 12CO, 13CO, and C18O, and the J = 2–1 transition of 12CO. The excitation temperatures of OH were found to follow a modified lognormal distribution f({T}ex})\\propto \\tfrac{1}{\\sqrt{2π }σ }\\exp ≤ft[-\\tfrac{{[{ln}({T}ex})-{ln}(3.4{{K}})]}2}{2{σ }2}\\right], the peak of which is close to the temperature of the Galactic emission background (CMB+synchrotron). In fact, 90% of the OH has excitation temperatures within 2 K of the Galactic background at the same location, providing a plausible explanation for the apparent difficulty of mapping this abundant molecule in emission. The opacities of OH were found to be small and to peak around 0.01. For gas at intermediate extinctions (AV ∼ 0.05–2 mag), the detection rate of OH with a detection limit N(OH) ≃ 1012 cm‑2 is approximately independent of AV. We conclude that OH is abundant in the diffuse molecular gas and OH absorption is a good tracer of “dark molecular gas (DMG).” The measured fraction of DMG depends on the assumed detection threshold of the CO data set. The next generation of highly sensitive low-frequency radio telescopes, such as FAST and SKA, will make feasible the systematic inventory of diffuse molecular gas through decomposing, in velocity, the molecular (e.g., OH and CH) absorption profiles toward background continuum sources with numbers exceeding what is currently available by orders of magnitude.

  18. DETECTION OF MOLECULAR GAS IN VOID GALAXIES: IMPLICATIONS FOR STAR FORMATION IN ISOLATED ENVIRONMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Das, M.; Honey, M. [Indian Institute of Astrophysics, Bangalore (India); Saito, T. [Department of Astronomy, Graduate school of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 133-0033 (Japan); Iono, D. [Chile Observatory, NAOJ (Japan); Ramya, S., E-mail: mousumi@iiap.res.in [Shanghai Astronomical Observatory, Shanghai (China)

    2015-12-10

    We present the detection of molecular gas from galaxies located in nearby voids using the CO(1–0) line emission as a tracer. The observations were performed using the 45 m single dish radio telescope of the Nobeyama Radio Observatory. Void galaxies lie in the most underdense parts of our universe and a significant fraction of them are gas rich, late-type spiral galaxies. Although isolated, they have ongoing star formation but appear to be slowly evolving compared to galaxies in denser environments. Not much is known about their star formation properties or cold gas content. In this study, we searched for molecular gas in five void galaxies. The galaxies were selected based on their relatively high IRAS fluxes or Hα line luminosities, both of which signify ongoing star formation. All five galaxies appear to be isolated and two lie within the Bootes void. We detected CO(1–0) emission from four of the five galaxies in our sample and their molecular gas masses lie between 10{sup 8} and 10{sup 9} M{sub ⊙}. We conducted follow-up Hα imaging observations of three detected galaxies using the Himalayan Chandra Telescope and determined their star formation rates (SFRs) from their Hα fluxes. The SFR varies from 0.2 to 1 M{sub ⊙} yr{sup −1}; which is similar to that observed in local galaxies. Our study indicates that although void galaxies reside in underdense regions, their disks contain molecular gas and have SFRs similar to galaxies in denser environments. We discuss the implications of our results.

  19. STAR FORMATION SUPPRESSION DUE TO JET FEEDBACK IN RADIO GALAXIES WITH SHOCKED WARM MOLECULAR GAS

    International Nuclear Information System (INIS)

    Lanz, Lauranne; Ogle, Patrick M.; Appleton, Philip N.; Alatalo, Katherine

    2016-01-01

    We present Herschel observations of 22 radio galaxies, selected for the presence of shocked, warm molecular hydrogen emission. We measured and modeled spectral energy distributions in 33 bands from the ultraviolet to the far-infrared to investigate the impact of jet feedback on star formation activity. These galaxies are massive, early-type galaxies with normal gas-to-dust ratios, covering a range of optical and infrared colors. We find that the star formation rate (SFR) is suppressed by a factor of ∼3–6, depending on how molecular gas mass is estimated. We suggest that this suppression is due to the shocks driven by the radio jets injecting turbulence into the interstellar medium (ISM), which also powers the luminous warm H 2 line emission. Approximately 25% of the sample shows suppression by more than a factor of 10. However, the degree of SFR suppression does not correlate with indicators of jet feedback including jet power, diffuse X-ray emission, or intensity of warm molecular H 2 emission, suggesting that while injected turbulence likely impacts star formation, the process is not purely parameterized by the amount of mechanical energy dissipated into the ISM. Radio galaxies with shocked warm molecular gas cover a wide range in SFR–stellar mass space, indicating that these galaxies are in a variety of evolutionary states, from actively star-forming and gas-rich to quiescent and gas-poor. SFR suppression appears to have the largest impact on the evolution of galaxies that are moderately gas-rich.

  20. Physical properties of CO-dark molecular gas with C+ and OH observations

    Science.gov (United States)

    Tang, Ningyu; Li, Di; Heiles, Carl E.; ISM Group in National Astronomical Observatories, CAS

    2017-01-01

    The lifecycle of interstellar medium (ISM) is critical for understanding galaxy evolution. The transition between atomic neutral medium and dense molecular gas, however, cannot be traced adequately by either HI or CO emission. Results from dust observations of Planck all-sky mission and gamma-ray observations of Energetic Gamma Ray Experiment Telescope (EGRET) have revealed the existence of “CO dark molecular gas” (DMG) - molecular gas without CO emission. The physical conditions of DMG including density, temperature, and molecular composition are basis of understanding the ISM evolution. We analyzed physical properties of DMG with HI-self absorption and C+ fine line emission at 158 um toward the lines of sight of Galactic Observations of Terahertz C+ (GOTC+). DMG clouds have a median excitation temperature of 56 K and median volume density of 230 cm2, showing intermediate physical properties between atomic and molecular gas. Sixteen DMG clouds with high visual extinction (AV>=2.7 mag) were found. CO abundance compared to H2 in these clouds is two orders magnitude smaller than the cannonical value in the Milky Way and cannot be explained by the chemical evolutionary model. They may be formed through the agglomeration of pre-existing molecular gas in the Milky Way. We have finished a follow up survey of OH 18 cm lines toward 51 sightlines of GOTC+ including sightlines with DMG clouds through Arecibo telescope. DMG may result in the absence of correlation between CO and OH column density. A possible correlation was found between C+ and OH column density in tracing DMG.

  1. Laser-induced breakdown spectroscopy at a water/gas interface: A study of bath gas-dependent molecular species

    International Nuclear Information System (INIS)

    Adamson, M.; Padmanabhan, A.; Godfrey, G.J.; Rehse, S.J.

    2007-01-01

    Single-pulse laser-induced breakdown spectroscopy has been performed on the surface of a bulk water sample in an air, argon, and nitrogen gas environment to investigate emissions from hydrogen-containing molecules. A microplasma was formed at the gas/liquid interface by focusing a Nd:YAG laser beam operating at 1064 nm onto the surface of an ultra-pure water sample. A broadband Echelle spectrometer with a time-gated intensified charge-coupled device was used to analyze the plasma at various delay times (1.0-40.0 μs) and for incident laser pulse energies ranging from 20-200 mJ. In this configuration, the dominant atomic spectral features at short delay times are the hydrogen H-alpha and H-beta emission lines at 656 and 486 nm, respectively, as well as emissions from atomic oxygen liberated from the water and air and nitrogen emission lines from the air bath gas. For delay times exceeding approximately 8 μs the emission from molecular species (particularly OH and NH) created after the ablation process dominates the spectrum. Molecular emissions are found to be much less sensitive to variations in pulse energy and exhibit a temporal decay an order of magnitude slower than the atomic emission. The dependence of both atomic hydrogen and OH emission on the bath gas above the surface of the water was studied by performing the experiment at standard pressure in an atmospheric purge box. Electron densities calculated from the Stark broadening of the H-beta and H-gamma lines and plasma excitation temperatures calculated from the ratio of H-beta to H-gamma emission were measured for ablation in the three bath gases

  2. A CATALOG OF ULTRA-COMPACT HIGH VELOCITY CLOUDS FROM THE ALFALFA SURVEY: LOCAL GROUP GALAXY CANDIDATES?

    International Nuclear Information System (INIS)

    Adams, Elizabeth A. K.; Giovanelli, Riccardo; Haynes, Martha P.

    2013-01-01

    We present a catalog of 59 ultra-compact high velocity clouds (UCHVCs) extracted from the 40% complete ALFALFA HI-line survey. The ALFALFA UCHVCs have median flux densities of 1.34 Jy km s –1 , median angular diameters of 10', and median velocity widths of 23 km s –1 . We show that the full UCHVC population cannot easily be associated with known populations of high velocity clouds. Of the 59 clouds presented here, only 11 are also present in the compact cloud catalog extracted from the commensal GALFA-HI survey, demonstrating the utility of this separate dataset and analysis. Based on their sky distribution and observed properties, we infer that the ALFALFA UCHVCs are consistent with the hypothesis that they may be very low mass galaxies within the Local Volume. In that case, most of their baryons would be in the form of gas, and because of their low stellar content, they remain unidentified by extant optical surveys. At distances of ∼1 Mpc, the UCHVCs have neutral hydrogen (H I) masses of ∼10 5 -10 6 M ☉ , H I diameters of ∼2-3 kpc, and indicative dynamical masses within the H I extent of ∼10 7 -10 8 M ☉ , similar to the Local Group ultra-faint dwarf Leo T. The recent ALFALFA discovery of the star-forming, metal-poor, low mass galaxy Leo P demonstrates that this hypothesis is true in at least one case. In the case of the individual UCHVCs presented here, confirmation of their extragalactic nature will require further work, such as the identification of an optical counterpart to constrain their distance.

  3. A CATALOG OF ULTRA-COMPACT HIGH VELOCITY CLOUDS FROM THE ALFALFA SURVEY: LOCAL GROUP GALAXY CANDIDATES?

    Energy Technology Data Exchange (ETDEWEB)

    Adams, Elizabeth A. K.; Giovanelli, Riccardo; Haynes, Martha P., E-mail: betsey@astro.cornell.edu, E-mail: riccardo@astro.cornell.edu, E-mail: haynes@astro.cornell.edu [Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853 (United States)

    2013-05-01

    We present a catalog of 59 ultra-compact high velocity clouds (UCHVCs) extracted from the 40% complete ALFALFA HI-line survey. The ALFALFA UCHVCs have median flux densities of 1.34 Jy km s{sup -1}, median angular diameters of 10', and median velocity widths of 23 km s{sup -1}. We show that the full UCHVC population cannot easily be associated with known populations of high velocity clouds. Of the 59 clouds presented here, only 11 are also present in the compact cloud catalog extracted from the commensal GALFA-HI survey, demonstrating the utility of this separate dataset and analysis. Based on their sky distribution and observed properties, we infer that the ALFALFA UCHVCs are consistent with the hypothesis that they may be very low mass galaxies within the Local Volume. In that case, most of their baryons would be in the form of gas, and because of their low stellar content, they remain unidentified by extant optical surveys. At distances of {approx}1 Mpc, the UCHVCs have neutral hydrogen (H I) masses of {approx}10{sup 5}-10{sup 6} M{sub Sun }, H I diameters of {approx}2-3 kpc, and indicative dynamical masses within the H I extent of {approx}10{sup 7}-10{sup 8} M{sub Sun }, similar to the Local Group ultra-faint dwarf Leo T. The recent ALFALFA discovery of the star-forming, metal-poor, low mass galaxy Leo P demonstrates that this hypothesis is true in at least one case. In the case of the individual UCHVCs presented here, confirmation of their extragalactic nature will require further work, such as the identification of an optical counterpart to constrain their distance.

  4. A new all-sky map of Galactic high-velocity clouds from the 21-cm HI4PI survey

    Science.gov (United States)

    Westmeier, Tobias

    2018-02-01

    High-velocity clouds (HVCs) are neutral or ionized gas clouds in the vicinity of the Milky Way that are characterized by high radial velocities inconsistent with participation in the regular rotation of the Galactic disc. Previous attempts to create a homogeneous all-sky H I map of HVCs have been hampered by a combination of poor angular resolution, limited surface brightness sensitivity and suboptimal sampling. Here, a new and improved H I map of Galactic HVCs based on the all-sky HI4PI survey is presented. The new map is fully sampled and provides significantly better angular resolution (16.2 versus 36 arcmin) and column density sensitivity (2.3 versus 3.7 × 1018 cm-2 at the native resolution) than the previously available LAB survey. The new HVC map resolves many of the major HVC complexes in the sky into an intricate network of narrow H I filaments and clumps that were not previously resolved by the LAB survey. The resulting sky coverage fraction of high-velocity H I emission above a column density level of 2 × 1018 cm-2 is approximately 15 per cent, which reduces to about 13 per cent when the Magellanic Clouds and other non-HVC emission are removed. The differential sky coverage fraction as a function of column density obeys a truncated power law with an exponent of -0.93 and a turnover point at about 5 × 1019 cm-2. H I column density and velocity maps of the HVC sky are made publicly available as FITS images for scientific use by the community.

  5. The Molecular Gas Environment in the 20 km s{sup −1} Cloud in the Central Molecular Zone

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Xing; Gu, Qiusheng [School of Astronomy and Space Science, Nanjing University, Nanjing, Jiangsu 210093 (China); Zhang, Qizhou; Battersby, Cara [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kauffmann, Jens; Pillai, Thushara [Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Longmore, Steven N. [Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF (United Kingdom); Kruijssen, J. M. Diederik [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, D-69120 Heidelberg (Germany); Liu, Hauyu Baobab; Zhang, Zhi-Yu [European Southern Observatory, Karl-Schwarzschild-Straße 2, D-85748 Garching (Germany); Ginsburg, Adam [National Radio Astronomy Observatory, Socorro, NM 87801 (United States); Mills, Elisabeth A. C., E-mail: xinglv.nju@gmail.com [Department of Physics and Astronomy, San Jose State University, One Washington Square, San Jose, CA 95192 (United States)

    2017-04-10

    We recently reported a population of protostellar candidates in the 20 km s{sup −1} cloud in the Central Molecular Zone of the Milky Way, traced by H{sub 2}O masers in gravitationally bound dense cores. In this paper, we report molecular line studies with high angular resolution (∼3″) of the environment of star formation in this cloud. Maps of various molecular line transitions as well as the continuum at 1.3 mm are obtained using the Submillimeter Array. Five NH{sub 3} inversion lines and the 1.3 cm continuum are observed with the Karl G. Jansky Very Large Array. The interferometric observations are complemented with single-dish data. We find that the CH{sub 3}OH, SO, and HNCO lines, which are usually shock tracers, are better correlated spatially with the compact dust emission from dense cores among the detected lines. These lines also show enhancement in intensities with respect to SiO intensities toward the compact dust emission, suggesting the presence of slow shocks or hot cores in these regions. We find gas temperatures of ≳100 K at 0.1 pc scales based on RADEX modeling of the H{sub 2}CO and NH{sub 3} lines. Although no strong correlations between temperatures and linewidths/H{sub 2}O maser luminosities are found, in high-angular-resolution maps we note several candidate shock-heated regions offset from any dense cores, as well as signatures of localized heating by protostars in several dense cores. Our findings suggest that at 0.1 pc scales in this cloud star formation and strong turbulence may together affect the chemistry and temperature of the molecular gas.

  6. WISDOM Project - II. Molecular gas measurement of the supermassive black hole mass in NGC 4697

    Science.gov (United States)

    Davis, Timothy A.; Bureau, Martin; Onishi, Kyoko; Cappellari, Michele; Iguchi, Satoru; Sarzi, Marc

    2017-07-01

    As part of the mm-Wave Interferometric Survey of Dark Object Masses (WISDOM) project, we present an estimate of the mass of the supermassive black hole (SMBH) in the nearby fast-rotating early-type galaxy NGC 4697. This estimate is based on Atacama Large Millimeter/submillimeter Array (ALMA) cycle-3 observations of the 12CO(2-1) emission line with a linear resolution of 29 pc (0.53 arcsec). We find that NGC 4697 hosts a small relaxed central molecular gas disc with a mass of 1.6 × 107 M⊙, co-spatial with the obscuring dust disc visible in optical Hubble Space Telescope imaging. We also resolve thermal 1 mm continuum emission from the dust in this disc. NGC 4697 is found to have a very low molecular gas velocity dispersion, σgas = 1.65^{+0.68}_{-0.65} km s-1. This seems to be partially because the giant molecular cloud mass function is not fully sampled, but other mechanisms such as chemical differentiation in a hard radiation field or morphological quenching also seem to be required. We detect a Keplerian increase of the rotation of the molecular gas in the very centre of NGC 4697, and use forward modelling of the ALMA data cube in a Bayesian framework with the KINematic Molecular Simulation (kinms) code to estimate an SMBH mass of (1.3_{-0.17}^{+0.18}) × 108 M⊙ and an I-band mass-to-light ratio of 2.14_{-0.05}^{+0.04} M⊙/L⊙ (at the 99 per cent confidence level). Our estimate of the SMBH mass is entirely consistent with previous measurements from stellar kinematics. This increases confidence in the growing number of SMBH mass estimates being obtained in the ALMA era.

  7. COLD MOLECULAR GAS IN THE INNER TWO KILOPARSECS OF NGC 4151

    International Nuclear Information System (INIS)

    Dumas, G.; Schinnerer, E.; Mundell, C. G.

    2010-01-01

    We present the first spatially resolved spectroscopic imaging observations of the 12 CO (1-0) line emission in the central 2.5 kpc of the Seyfert 1 galaxy NGC 4151, obtained with the IRAM Plateau de Bure Interferometer (PdBI). Most of the cold molecular gas is distributed along two curved gas lanes about 1 kpc north and south of the active nucleus, coincident with the circumnuclear dust ring noted by previous authors. These CO arcs lie within the Inner Lindblad Resonance of the large scale oval bar and have kinematics consistent with those derived from neutral hydrogen observations of the disk and the bar. Two additional gas clumps are detected that show non-circular motion-one associated with the southern gas lane and the other lying ∼600 pc north of the nucleus. Closer to the nucleus, no cold molecular gas is detected in the central 300 pc where abundant near-IR H 2 line emission arises. This suggests that the H 2 line emission is not a good indicator of a cold gas reservoir in NGC 4151 and that the H 2 is likely photo-excited by the active galactic nucleus (AGN). The upper limit of the CO mass in the central 300 pc is sufficient to support the AGN activity at its current level for 10 7 yr. The total cold molecular mass detected by PdBI is 4.3 x 10 7 M sun . Finally, 3 mm continuum emission arising from the location of the AGN is detected with a flux of S 3 m m ∼ 14 mJy and appears to be unresolved at an angular resolution of 2.''8 (∼180 pc).

  8. Recent progress in molecular simulation of nanoporous graphene membranes for gas separation

    Science.gov (United States)

    Fatemi, S. Mahmood; Baniasadi, Aminreza; Moradi, Mahrokh

    2017-07-01

    If an ideal membrane for gas separation is to be obtained, the following three characteristics should be considered: the membrane should be as thin as possible, be mechanically robust, and have welldefined pore sizes. These features will maximize its solvent flux, preserve it from fracture, and guarantee its selectivity. Graphene is made up of a hexagonal honeycomb lattice of carbon atoms with sp 2 hybridization state forming a one-atom-thick sheet of graphite. Following conversion of the honeycomb lattices into nanopores with a specific geometry and size, a nanoporous graphene membrane that offers high efficiency as a separation membrane because of the ultrafast molecular permeation rate as a result of its one-atom thickness is obtained. Applications of nanoporous graphene membranes for gas separation have been receiving remarkably increasing attention because nanoporous graphene membranes show promising results in this area. This review focuses on the recent advances in nanoporous graphene membranes for applications in gas separation, with a major emphasis on theoretical works. The attractive properties of nanoporous graphene membranes introduce make them appropriate candidates for gas separation and gas molecular-sieving processes in nanoscale dimensions.

  9. A review of recent advances in molecular simulation of graphene-derived membranes for gas separation

    Science.gov (United States)

    Fatemi, Seyyed Mahmood; Abbasi, Zeynab; Rajabzadeh, Halimeh; Hashemizadeh, Seyyed Ali; Deldar, Amir Noori

    2017-07-01

    To obtain an ideal membrane for gas separation the following three characteristics should be considered: the membrane should be as thin as possible, be mechanically robust, and have well-defined pore sizes. These features will maximize its solvent flux, preserve it from fracture, and guarantee its selectivity. These attractive properties of graphene-derived membranes introduce them as appropriate candidates for gas separation and gas molecular-sieving processes in nanoscale dimensions. The current effort has focused on two issues, including the review of the most newly progression on drilling holes in single graphene membranes for making ultrathin membranes for gas separation, and studying functionalized nanoporous sheet and graphene-derived membranes, including doped graphene, graphene oxide, fluorographene, and reduced graphene oxide from theoretical perspectives for making functional coatings for nano ultrafiltration for gas separation. We investigated the basic mechanism of separation by membranes derived from graphene and relevant possible applications. Functionalized nanoporous membranes as novel approach are characterized by low energy cost in realizing high throughput molecular-sieving separation.

  10. Adsorption separation of carbon dioxide from flue gas by a molecularly imprinted adsorbent.

    Science.gov (United States)

    Zhao, Yi; Shen, Yanmei; Ma, Guoyi; Hao, Rongjie

    2014-01-01

    CO2 separation by molecularly imprinted adsorbent from coal-fired flue gas after desulfurization system has been studied. The adsorbent was synthesized by molecular imprinted technique, using ethanedioic acid, acrylamide, and ethylene glycol dimethacrylate as the template, functional monomer, and cross-linker, respectively. According to the conditions of coal-fired flue gas, the influencing factors, including adsorption temperature, desorption temperature, gas flow rate, and concentrations of CO2, H2O, O2, SO2, and NO, were studied by fixed bed breakthrough experiments. The experimental conditions were optimized to gain the best adsorption performance and reduce unnecessary energy consumption in future practical use. The optimized adsorption temperature, desorption temperature, concentrations of CO2, and gas flow rate are 60 °C, 80 °C, 13%, and 170 mL/min, respectively, which correspond to conditions of practical flue gases to the most extent. The CO2 adsorption performance was nearly unaffected by H2O, O2, and NO in the flue gas, and was promoted by SO2 within the emission limit stipulated in the Chinese emission standards of air pollutants for a thermal power plant. The maximum CO2 adsorption capacity, 0.57 mmol/g, was obtained under the optimized experimental conditions, and the SO2 concentration was 150 mg/m(3). The influence mechanisms of H2O, O2, SO2, and NO on CO2 adsorption capacity were investigated by infrared spectroscopic analysis.

  11. The Association of Molecular Gas and Natal Super Star Clusters in Henize 2–10

    Science.gov (United States)

    Johnson, Kelsey E.; Brogan, Crystal L.; Indebetouw, Remy; Testi, Leonardo; Wilner, David J.; Reines, Amy E.; Chen, C.-H. Rosie; Vanzi, Leonardo

    2018-02-01

    We present ALMA observations of the dwarf starburst galaxy He 2–10 in combination with previous SMA CO observations to probe the molecular environments of natal super star clusters (SSCs). These observations include the HCO+(1-0), HCN(1-0), HNC(1-0), and CCH(1-0) molecular lines, as well as 88 GHz continuum with a spatial resolution of 1\\buildrel{\\prime\\prime}\\over{.} 7× 1\\buildrel{\\prime\\prime}\\over{.} 6. After correcting for the contribution from free–free emission to the 88 GHz continuum flux density (∼60% of the 88 GHz emission), we derive a total gas mass for He 2–10 of {M}{gas}=4{--}6× {10}8 M ⊙, roughly 5%–20% of the dynamical mass. Based on a principle component analysis, HCO+ is found to be the best “general” tracer of molecular emission. The line widths and luminosities of the CO emission suggests that the molecular clouds could either be as small as ∼8 pc, or alternately have enhanced line widths. The CO emission and 88 GHz continuum are anti-correlated, suggesting that either the dust and molecular gas are not cospatial, which could reflect that the 88 GHz continuum is dominated by free–free emission. The CO and CCH emission are also relatively anti-correlated, which is consistent with the CCH being photo-enhanced, and/or the CO being dissociated in the regions near the natal SSCs. The molecular line ratios of regions containing the natal star clusters are different from the line ratios observed for regions elsewhere in the galaxy. In particular, the regions with thermal radio emission all have {CO}(2{--}1)/{{HCO}}+(1-0)correlated with the evolutionary stage of the clusters.

  12. Molecular gas in the x-ray bright group NGC 5044 as revealed by ALMA

    Energy Technology Data Exchange (ETDEWEB)

    David, Laurence P.; Forman, William; Vrtilek, Jan; Jones, Christine; O' Sullivan, Ewan [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Lim, Jeremy [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong); Combes, Francoise [Observatoire de Paris, LERMA, CNRS, 61 Avenue de l' Observatoire, F-75014 Paris (France); Salome, Philippe [LERMA Observatoire de paris, CNRS, 61 rue de l' Observatoire, F-75014 Paris (France); Edge, Alastair; Hamer, Stephen [Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Sun, Ming [Department of Physics, University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Gastaldello, Fabio; Bardelli, Sandro [INAF - IASF-Milano, Via E. Bassini 15, I-20133 Milano (Italy); Temi, Pasquale [Astrophysics Branch, NASA/Ames Research Center, MS 245-6, Moffett Field, CA 94035 (United States); Schmitt, Henrique [Remote Sensing Division, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375 (United States); Ohyama, Youichi [Academia Sinica, Institute of Astronomy and Astrophysics, Taiwan (China); Mathews, William [University of California Observatories/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Brighenti, Fabrizio [Dipartimento di Astronomia, Universit di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Giacintucci, Simona [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Trung, Dinh-V, E-mail: ldavid@head.cfa.harvard.edu [Institute of Physics, Vietnamese Academy of Science and Technology, 10 DaoTan Street, BaDinh, Hanoi (Viet Nam)

    2014-09-10

    An ALMA observation of the early-type galaxy NGC 5044, which resides at the center of an X-ray bright group with a moderate cooling flow, detected 24 molecular structures within the central 2.5 kpc. The masses of the molecular structures vary from 3 × 10{sup 5} M {sub ☉} to 10{sup 7} M {sub ☉} and the CO(2-1) linewidths vary from 15 to 65 km s{sup –1}. Given the large CO(2-1) linewidths, the observed structures are likely giant molecular associations (GMAs) and not individual giant molecular clouds (GMCs). Only a few of the GMAs are spatially resolved and the average density of these GMAs yields a GMC volume filling factor of about 15%. The masses of the resolved GMAs are insufficient for them to be gravitationally bound, however, the most massive GMA does contain a less massive component with a linewidth of 5.5 km s{sup –1} (typical of an individual virialized GMC). We also show that the GMAs cannot be pressure confined by the hot gas. Given the CO(2-1) linewidths of the GMAs (i.e., the velocity dispersion of the embedded GMCs) they should disperse on a timescale of about 12 Myr. No disk-like molecular structures are detected and all indications suggest that the molecular gas follows ballistic trajectories after condensing out of the thermally unstable hot gas. The 230 GHz luminosity of the central continuum source is 500 times greater than its low frequency radio luminosity and probably reflects a recent accretion event. The spectrum of the central continuum source also exhibits an absorption feature with a linewidth typical of an individual GMC and an infalling velocity of 250 km s{sup –1}.

  13. The influence of slip velocity and temperature on permeability during and after high-velocity fault slip

    Science.gov (United States)

    Tanikawa, W.; Mukoyoshi, H.; Tadai, O.; Hirose, T.; Lin, W.

    2011-12-01

    Fluid transport properties in fault zones play an important role in dynamic processes during large earthquakes. If the permeability in a fault zone is low, high pore-fluid pressures caused by thermal pressurization (Sibson, 1973) or shear-induced compaction (Blanpied et al., 1992) can lead to an apparent reduction of fault strength. Changes in porosity and permeability of fault rocks within a fault zone during earthquakes and the subsequent progressive recovery of these properties may have a large influence on earthquake recurrence (Sleep and Blanpied, 1992). A rotary shear apparatus was used to investigate changes of fluid transport properties in a fault zone by real-time measurement of gas flow rates during and after shearing of hollow sandstone and granite cylinders at various slip rates. Our apparatus measures permeability parallel to the slip plane in both the slip zone and wall rocks. In all cases, permeability decreased rapidly with an increase of friction, but recovered soon after slip, reaching a steady state within several tens of minutes. The rate of reduction of permeability increased with increasing slip velocity. Permeability did not recover to pre-slip levels after low-velocity tests but recovered to exceed them after high-velocity tests. Frictional heating of gases at the slip surface increased gas viscosity, which increased gas flow rate to produce an apparent permeability increase. The irreversible permeability changes of the low-velocity tests were caused by gouge formation due to wearing and smoothing of the slip surface. The increase of permeability after high-velocity tests was caused by mesoscale fracturing in response to rapid temperature rise. Changes of pore fluid viscosity contributed more to changes of flow rate than did permeability changes caused by shear deformation, although test results from different rocks and pore fluids might be different. References Blanpied, M.L., Lockner, D.A., Byerlee, J.D., 1992. An earthquake mechanism

  14. The efficiency of ceramic-faced metal targets at high-velocity impact

    Science.gov (United States)

    Tolkachev, V. F.; Konyaev, A. A.; Pakhnutova, N. V.

    2017-11-01

    The paper represents experimental results and engineering evaluation concerning the efficiency of composite materials to be used as an additional protection during the high- velocity interaction of a tungsten rod with a target in the velocity range of 1...5 km/s. The main parameter that characterizes the high-velocity interaction of a projectile with a layered target is the penetration depth. Experimental data, numerical simulation and engineering evaluation by modified models are used to determine the penetration depth. Boron carbide, aluminum oxide, and aluminum nickelide are applied as a front surface of targets. Based on experimental data and numerical simulation, the main characteristics of ceramics are determined, which allows composite materials to be effectively used as additional elements of protection.

  15. Towards high velocity deformation characterisation of metals and composites using Digital Image Correlation

    DEFF Research Database (Denmark)

    Eriksen, Rasmus Normann Wilken; Berggreen, Christian; Boyd, S.W

    2010-01-01

    images and then extracting deformation data using Digital Image Correlation (DIC) from tensile testing in the intermediate strain rate regime available with the test machines. Three different materials, aluminium alloy 1050, S235 steel and glass fibre reinforced plastic (GFRP) were tested at different......Characterisation of materials subject to high velocity deformation is necessary as many materials behave differently under such conditions. It is particularly important for accurate numerical simulation of high strain rate events. High velocity servo-hydraulic test machines have enabled material...... testing in the strain rate regime from 1 – 500 ε/s. The range is much lower than that experienced under ballistic, shock or impact loads, nevertheless it is a useful starting point for the application of optical techniques. The present study examines the possibility of using high speed cameras to capture...

  16. Treatment Protocol for High Velocity/High Energy Gunshot Injuries to the Face

    Science.gov (United States)

    Peled, Micha; Leiser, Yoav; Emodi, Omri; Krausz, Amir

    2011-01-01

    Major causes of facial combat injuries include blasts, high-velocity/high-energy missiles, and low-velocity missiles. High-velocity bullets fired from assault rifles encompass special ballistic properties, creating a transient cavitation space with a small entrance wound and a much larger exit wound. There is no dispute regarding the fact that primary emergency treatment of ballistic injuries to the face commences in accordance with the current advanced trauma life support (ATLS) recommendations; the main areas in which disputes do exist concern the question of the timing, sequence, and modes of surgical treatment. The aim of the present study is to present the treatment outcome of high-velocity/high-energy gunshot injuries to the face, using a protocol based on the experience of a single level I trauma center. A group of 23 injured combat soldiers who sustained bullet and shrapnel injuries to the maxillofacial region during a 3-week regional military conflict were evaluated in this study. Nine patients met the inclusion criteria (high-velocity/high-energy injuries) and were included in the study. According to our protocol, upon arrival patients underwent endotracheal intubation and were hemodynamically stabilized in the shock-trauma unit and underwent total-body computed tomography with 3-D reconstruction of the head and neck and computed tomography angiography. All patients underwent maxillofacial surgery upon the day of arrival according to the protocol we present. In view of our treatment outcomes, results, and low complication rates, we conclude that strict adherence to a well-founded and structured treatment protocol based on clinical experience is mandatory in providing efficient, appropriate, and successful treatment to a relatively large group of patients who sustain various degrees of maxillofacial injuries during a short period of time. PMID:23449809

  17. Auditory velocity discrimination in the horizontal plane at very high velocities.

    Science.gov (United States)

    Frissen, Ilja; Féron, François-Xavier; Guastavino, Catherine

    2014-10-01

    We determined velocity discrimination thresholds and Weber fractions for sounds revolving around the listener at very high velocities. Sounds used were a broadband white noise and two harmonic sounds with fundamental frequencies of 330 Hz and 1760 Hz. Experiment 1 used velocities ranging between 288°/s and 720°/s in an acoustically treated room and Experiment 2 used velocities between 288°/s and 576°/s in a highly reverberant hall. A third experiment addressed potential confounds in the first two experiments. The results show that people can reliably discriminate velocity at very high velocities and that both thresholds and Weber fractions decrease as velocity increases. These results violate Weber's law but are consistent with the empirical trend observed in the literature. While thresholds for the noise and 330 Hz harmonic stimulus were similar, those for the 1760 Hz harmonic stimulus were substantially higher. There were no reliable differences in velocity discrimination between the two acoustical environments, suggesting that auditory motion perception at high velocities is robust against the effects of reverberation. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. A survey of high-velocity H I in the Cetus region

    International Nuclear Information System (INIS)

    Cohen, R.J.

    1982-01-01

    The region 02sup(h) 16sup(m) 0 0 surrounding the Cohen and Davies complex of high-velocity clouds has been surveyed in the 21-cm line of H I using the Jodrell Bank MK II radio telescope (beamwidth 31 x 34 arcmin). The high-velocity cloud complex was sampled every 2sup(m) in right ascension and every 0 0 .5 in declination. The observations cover a velocity range of 2100 km s -1 with a resolution of 7.3 km s -1 and an rms noise level of 0.025 K. No HVCs were found outside the velocity range -400 to +100 km s -1 . The data are presented on microfiche as a set of contour maps showing 21-cm line temperature as a function of declination and radial velocity at constant values of right ascension. Discussion is centred on the very-high-velocity clouds at velocities of -360 to -190 km s -1 . It is concluded that they are probably debris from the tidal interaction between our Galaxy and the Magellanic Clouds. (author)

  19. Survivability of bare, individual Bacillus subtilis spores to high-velocity surface impact: Implications for microbial transfer through space

    Science.gov (United States)

    Barney, Brandon L.; Pratt, Sara N.; Austin, Daniel E.

    2016-06-01

    Laboratory experiments show that endospores of Bacillus subtilis survive impact against a solid surface at velocities as high as 299 ±28 m/s. During impact, spores experience and survive accelerations of at least 1010 m/s2. The spores were introduced into a vacuum chamber using an electrospray source and accelerated to a narrow velocity distribution by entrainment in a differentially pumped gas flow. Different velocity ranges were studied by modifying the gas flow parameters. The spores were electrically charged, allowing direct measurement of the velocity of each spore as it passed through an image charge detector prior to surface impact. Spores impacted a glass surface and were collected for subsequent analysis by culturing. Most spores survived impact at all measured velocities. These experiments differ fundamentally from other studies that show either shock or impact survivability of bacteria embedded within or on the surface of a projectile. Bacteria in the present experiments undergo a single interaction with a solid surface at the full impact velocity, in the absence of any other effects such as cushioning due to microbe agglomerations, deceleration due to air or vapor, or transfer of impact shock through solid or liquid media. During these full-velocity impact events, the spores experience extremely high decelerations. This study is the first reported instance of accelerations of this magnitude experienced during a bacteria impact event. These results are discussed in the context of potential transfer of viable microbes in space and other scenarios involving surface impacts at high velocities.

  20. Damage characterization of E-glass and C-glass fibre polymer composites after high velocity impact

    Science.gov (United States)

    Razali, N.; Sultan, M. T. H.; Cardona, F.; Jawaid, M.

    2017-12-01

    The purpose of this work is to identify impact damage on glass fibre reinforced polymer composite structures after high velocity impact. In this research, Type C-glass (600 g/m2) and Type E-glass (600 g/m2) were used to fabricate Glass Fibre-Reinforced Polymer composites (GFRP) plates. The panels were fabricated using a vacuum bagging and hot bounder method. Single stage gas gun (SSGG) was used to do the testing and data acquisition system was used to collect the damage data. Different types of bullets and different pressure levels were used for the experiment. The obtained results showed that the C-glass type of GFRP experienced more damage in comparison to E-glass type of materials based on the amount of energy absorbed on impact and the size of the damage area. All specimens underwent a partial fibre breakage but the laminates were not fully penetrated by the bullets. This indicated that both types of materials have high impact resistance even though the applied pressures of the gas gun were on the high range. We concluded that within the material specifications of the laminates including the type of glass fibre reinforcement and the thickness of the panels, those composite materials are safe to be applied in structural and body armour applications as an alternative to more expensive materials such as Kevlar and type S-glass fibre based panels.

  1. Comparative characteristic and erosion behavior of NiCr coatings deposited by various high-velocity oxyfuel spray processes

    Science.gov (United States)

    Sidhu, Hazoor Singh; Sidhu, Buta Singh; Prakash, S.

    2006-12-01

    The purpose of this study is to analyze and compare the mechanical properties and microstructure details at the interface of high-velocity oxyfuel (HVOF)-sprayed NiCr-coated boiler tube steels, namely ASTM-SA-210 grade A1, ASTM-SA213-T-11, and ASTM-SA213-T-22. Coatings were developed by two different techniques, and in these techniques liquefied petroleum gas was used as the fuel gas. First, the coatings were characterized by metallographic, scanning electron microscopy/energy-dispersive x-ray analysis, x-ray diffraction, surface roughness, and microhardness, and then were subjected to erosion testing. An attempt has been made to describe the transformations taking place during thermal spraying. It is concluded that the HVOF wire spraying process offers a technically viable and cost-effective alternative to HVOF powder spraying process for applications in an energy generation power plant with a point view of life enhancement and to minimize the tube failures because it gives a coating having better resistance to erosion.

  2. A low thermal mass fast gas chromatograph and its implementation in fast gas chromatography mass spectrometry with supersonic molecular beams.

    Science.gov (United States)

    Fialkov, Alexander B; Moragn, Mati; Amirav, Aviv

    2011-12-30

    A new type of low thermal mass (LTM) fast gas chromatograph (GC) was designed and operated in combination with gas chromatography mass spectrometry (GC-MS) with supersonic molecular beams (SMB), including GC-MS-MS with SMB, thereby providing a novel combination with unique capabilities. The LTM fast GC is based on a short capillary column inserted inside a stainless steel tube that is resistively heated. It is located and mounted outside the standard GC oven on its available top detector port, while the capillary column is connected as usual to the standard GC injector and supersonic molecular beam interface transfer line. This new type of fast GC-MS with SMB enables less than 1 min full range temperature programming and cooling down analysis cycle time. The operation of the fast GC-MS with SMB was explored and 1 min full analysis cycle time of a mixture of 16 hydrocarbons in the C(10)H(22) up to C(44)H(90) range was achieved. The use of 35 mL/min high column flow rate enabled the elution of C(44)H(90) in less than 45 s while the SMB interface enabled splitless acceptance of this high flow rate and the provision of dominant molecular ions. A novel compound 9-benzylazidanthracene was analyzed for its purity and a synthetic chemistry process was monitored for the optimization of the chemical reaction yield. Biodiesel was analyzed in jet fuel (by both GC-MS and GC-MS-MS) in under 1 min as 5 ppm fatty acid methyl esters. Authentic iprodion and cypermethrin pesticides were analyzed in grapes extract in both full scan mode and fast GC-MS-MS mode in under 1 min cycle time and explosive mixture including TATP, TNT and RDX was analyzed in under 1 min combined with exhibiting dominant molecular ion for TATP. Fast GC-MS with SMB is based on trading GC separation for speed of analysis while enhancing the separation power of the MS via the enhancement of the molecular ion in the electron ionization of cold molecules in the SMB. This paper further discusses several features of

  3. Molecular dynamics simulations of classical sound absorption in a monatomic gas

    Science.gov (United States)

    Ayub, M.; Zander, A. C.; Huang, D. M.; Cazzolato, B. S.; Howard, C. Q.

    2018-05-01

    Sound wave propagation in argon gas is simulated using molecular dynamics (MD) in order to determine the attenuation of acoustic energy due to classical (viscous and thermal) losses at high frequencies. In addition, a method is described to estimate attenuation of acoustic energy using the thermodynamic concept of exergy. The results are compared against standing wave theory and the predictions of the theory of continuum mechanics. Acoustic energy losses are studied by evaluating various attenuation parameters and by comparing the changes in behavior at three different frequencies. This study demonstrates acoustic absorption effects in a gas simulated in a thermostatted molecular simulation and quantifies the classical losses in terms of the sound attenuation constant. The approach can be extended to further understanding of acoustic loss mechanisms in the presence of nanoscale porous materials in the simulation domain.

  4. Description of the electrodynamics of a gas by molecular-electromagnetic correlation functions

    International Nuclear Information System (INIS)

    Coulter, C.A.; Howgate, D.W.

    1985-01-01

    Starting from basic principles, we develop a description of the electromagnetic interactions of a molecular gas in terms of a set of correlation functions which we call the molecular-electromagnetic correlation functions (MECF's). First we use the energy eigenfunctions for an isolated molecule of the species of interest to define a set of molecular creation and annihilation operators. We then derive a closed set of operator equations for these molecular creation and annihilation operators and the electromagnetic vector potential. Explicit definitions of the lowest-order MECF's are given in terms of these operators, and it is shown how the operator equations which have been obtained can be used to derive equations of motion for the MECF's. Finally, we illustrate the use of the MECF's in describing physical properties of the molecular gas and the electromagnetic field. Brief indications are given of the application of the MECF formulation to the semiclassical approximation and to the description of quantum emission of radiation, topics which are treated in greater detail in subsequent papers. The basic MECF formulation described here contains three rather mild approximations: (1) Atomic nuclei are treated as elementary particles; (2) nuclei and electrons are treated nonrelativistically; and (3) the effect of molecular collisions with the container walls on the internal molecular state is neglected. Consequently, the physical description contained in the formulation is rather complete; and the MECF results can be used both to provide a sound basis for some aspects of the usual heuristic models, and to ascertain the ways in which those models are incomplete

  5. Dynamics of gas-phase transient species studied by dissociative photodetachment of molecular anions

    OpenAIRE

    Lu, Zhou

    2007-01-01

    Gas-phase transient species, such as the CH₃CO₂ and HOCO free radicals, play important roles in combustion and environment chemistry. In this thesis work, the dynamics of these two radicals were studied by dissociative photodetachment (DPD) of the negative ions, CH₃CO₂-С and HOCO⁻, respectively. The experiments were carried out with a fast-ion-beam photoelectron-photofragment coincidence (PPC) spectrometer. Mass-selected molecular anions in a fast ion beam were intercepted by a linearly polar...

  6. Separation and Molecular Identification of Resistant Bacteria to Lead from Behbahan Bidboland Gas Refinery Wastewater (Iran)

    OpenAIRE

    Azam Mehrbakhsh; Monir Doudi; Hossein Motamedi

    2016-01-01

    Heavy metals are one of the pollution sources in environment. The pollution due to these metals is the problem that could have negative impact on water. Human is faced with these poisons effects due to occupational reasons. The lead is regarded as heavy metal whose industrial applications cause environmental pollution in high rate.The aim of this project was Separation and Molecular Identification of Resistant Bacteria to Lead from Behbahan Bidboland Gas Refinery Wastewater (Iran). For thi...

  7. AGN feedback on molecular gas reservoirs in quasars at z 2.4

    Science.gov (United States)

    Carniani, S.; Marconi, A.; Maiolino, R.; Feruglio, C.; Brusa, M.; Cresci, G.; Cano-Díaz, M.; Cicone, C.; Balmaverde, B.; Fiore, F.; Ferrara, A.; Gallerani, S.; La Franca, F.; Mainieri, V.; Mannucci, F.; Netzer, H.; Piconcelli, E.; Sani, E.; Schneider, R.; Shemmer, O.; Testi, L.

    2017-09-01

    We present new ALMA observations aimed at mapping molecular gas reservoirs through the CO(3-2) transition in three quasars at z ≃ 2.4, LBQS 0109+0213, 2QZ J002830.4-281706, and [HB89] 0329-385. Previous [Oiii]λ5007 observations of these quasars showed evidence for ionised outflows quenching star formation in their host galaxies. Systemic CO(3-2) emission has been detected only in one quasar, LBQS 0109+0213, where the CO(3-2) emission is spatially anti-correlated with the ionised outflow, suggesting that most of the molecular gas may have been dispersed or heated in the region swept by the outflow. In all three sources, including the one detected in CO, our constraints on the molecular gas mass indicate a significantly reduced reservoir compared to main-sequence galaxies at the same redshift, supporting a negative feedback scenario. In the quasar 2QZ J002830.4-281706, we tentatively detect an emission line blob blue-shifted by v - 2000 km s-1 with respect to the galaxy systemic velocity and spatially offset by 0.2'' (1.7 kpc) with respect to the ALMA continuum peak. Interestingly, such emission feature is coincident in both velocity and space with the ionised outflow as seen in [Oiii]λ5007. This tentative detection must be confirmed with deeper observations but, if real, it could represent the molecular counterpart of the ionised gas outflow driven by the Active Galactic Nucleus (AGN). Finally, in all ALMA maps we detect the presence of serendipitous line emitters within a projected distance 160 kpc from the quasars. By identifying these features with the CO(3-2) transition, we find that the serendipitous line emitters would be located within | Δv | < 500 km s-1 from the quasars, hence suggesting an overdensity of galaxies in two out of three quasars.

  8. Black hole mass measurement using molecular gas kinematics: what ALMA can do

    Science.gov (United States)

    Yoon, Ilsang

    2017-04-01

    We study the limits of the spatial and velocity resolution of radio interferometry to infer the mass of supermassive black holes (SMBHs) in galactic centres using the kinematics of circum-nuclear molecular gas, by considering the shapes of the galaxy surface brightness profile, signal-to-noise ratios (S/Ns) of the position-velocity diagram (PVD) and systematic errors due to the spatial and velocity structure of the molecular gas. We argue that for fixed galaxy stellar mass and SMBH mass, the spatial and velocity scales that need to be resolved increase and decrease, respectively, with decreasing Sérsic index of the galaxy surface brightness profile. We validate our arguments using simulated PVDs for varying beam size and velocity channel width. Furthermore, we consider the systematic effects on the inference of the SMBH mass by simulating PVDs including the spatial and velocity structure of the molecular gas, which demonstrates that their impacts are not significant for a PVD with good S/N unless the spatial and velocity scale associated with the systematic effects are comparable to or larger than the angular resolution and velocity channel width of the PVD from pure circular motion. Also, we caution that a bias in a galaxy surface brightness profile owing to the poor resolution of a galaxy photometric image can largely bias the SMBH mass by an order of magnitude. This study shows the promise and the limits of ALMA observations for measuring SMBH mass using molecular gas kinematics and provides a useful technical justification for an ALMA proposal with the science goal of measuring SMBH mass.

  9. Reversed thermo-switchable molecular sieving membranes composed of two-dimensional metal-organic nanosheets for gas separation

    Science.gov (United States)

    Wang, Xuerui; Chi, Chenglong; Zhang, Kang; Qian, Yuhong; Gupta, Krishna M.; Kang, Zixi; Jiang, Jianwen; Zhao, Dan

    2017-02-01

    It is highly desirable to reduce the membrane thickness in order to maximize the throughput and break the trade-off limitation for membrane-based gas separation. Two-dimensional membranes composed of atomic-thick graphene or graphene oxide nanosheets have gas transport pathways that are at least three orders of magnitude higher than the membrane thickness, leading to reduced gas permeation flux and impaired separation throughput. Here we present nm-thick molecular sieving membranes composed of porous two-dimensional metal-organic nanosheets. These membranes possess pore openings parallel to gas concentration gradient allowing high gas permeation flux and high selectivity, which are proven by both experiment and molecular dynamics simulation. Furthermore, the gas transport pathways of these membranes exhibit a reversed thermo-switchable feature, which is attributed to the molecular flexibility of the building metal-organic nanosheets.

  10. Conversion of a Degenerate Fermi Gas of 6Li Atoms to a Molecular BEC

    International Nuclear Information System (INIS)

    Strecker, K.E.; Partridge, G.B.; Kamar, R.I.; Jack, M.W.; Hulet, R.G.

    2005-01-01

    Atomic Feshbach resonances have recently been used to produce a strongly interacting Fermi gas, where the BCS/BEC crossover can be explored. We have used both narrow and broad Feshbach resonances to convert a quantum degenerate Fermi gas of 6Li atoms into an ultracold gas of Li2 molecules. For the narrow resonances, the molecules are formed by coherent adiabatic passage through the resonance. We find that 50% of the atoms are converted to molecules. Furthermore, the lifetime of these molecules was measured to be surprisingly long, 1 s. We will discuss these measurements in the context of the present theoretical understanding. Molecules can also be formed using static fields near the broad Feshbach resonance. The lifetime of these molecules is again long, and sufficient to enable their evaporation to a Bose-Einstein condensate. Phase contrast images of the molecular condensate are presented. The BCS/BEC crossover may be explored by starting with a pure molecular condensate on the low-field side of the Feshbach resonance, and adiabatically changing the field to any final value around resonance. We combine this ability with optical spectroscopy on a bound-bound molecular transition to probe the nature of the many-body wavefunction in the crossover regime

  11. The Curious Molecular Gas Conditions in a z=2.6 Radio-loud Quasar

    Science.gov (United States)

    Sharon, Chelsea; Riechers, Dominik A.; Kuk Leung, Tsz; Weiss, Axel; Walter, Fabian; Carilli, Chris; Kraiburg Knudsen, Kirsten; Hodge, Jacqueline

    2018-01-01

    Theoretical work suggests that AGN play an important role in quenching star formation in massive galaxies. In addition to molecular outflows observed in the local universe, emission from very high-J CO rotational transitions has been one of the key pieces of evidence for AGN directly affecting the molecular gas reservoirs that fuel star formation. However, very few observations of Jupper>9 transitions exist for galaxies in the early universe. Here we will present the peculiar molecular gas conditions in MG 0414+0534 (MG 0414 hereafter), one of the few high-z galaxies with very high-J CO detections. MG 0414 is a strongly lensed IR-bright radio-loud quasar with broad Hα emission at z=2.6390. We recently confirmed the CO(3–2) detection from Barvainis et al. (1998), but were unable to detect the CO(1–0) line. The 3σ lower limit on the 3–2/1–0 line ratio (in units of brightness temperature) is r3,1>5.72, which is significantly higher than the r3,1≤1 typical for thermalized optically thick emission in other z˜2–3 AGN host galaxies. In addition, the CO(11–10) line was detected to high significance using the Atacama Large Millimeter/submillimeter Array, and the CO(11–10) line FWHM is nearly double that of the CO(3–2) line. We will discuss possible explanations for the peculiar line ratios in MG 0414 (such as optically thin emission, molecular outflows, and differential lensing) and what the origin of these ratios imply for molecular gas observations of other high-z AGN host galaxies.

  12. Dense Molecular Gas Around Protostars and in Galactic Nuclei European Workshop on Astronomical Molecules 2004

    CERN Document Server

    Baan, W A; Langevelde, H J

    2004-01-01

    The phenomena observed in young stellar objects (YSO), circumstellar regions and extra-galactic nuclei show some similarity in their morphology, dynamical and physical processes, though they may differ in scale and energy. The European Workshop on Astronomical Molecules 2004 gave astronomers a unique opportunity to discuss the links among the observational results and to generate common interpretations of the phenomena in stars and galaxies, using the available diagnostic tools such as masers and dense molecular gas. Their theoretical understanding involves physics, numerical simulations and chemistry. Including a dozen introductory reviews, topics of papers in this book also cover: maser and dense gas diagnostics and related phenomena, evolution of circumstellar regions around protostars, evolution of circumnuclear regions of active galaxies, diagnostics of the circumnuclear gas in stars and galactic nuclei. This book summarizes our present knowledge in these topics, highlights major problems to be addressed...

  13. A black-hole mass measurement from molecular gas kinematics in NGC4526.

    Science.gov (United States)

    Davis, Timothy A; Bureau, Martin; Cappellari, Michele; Sarzi, Marc; Blitz, Leo

    2013-02-21

    The masses of the supermassive black holes found in galaxy bulges are correlated with a multitude of galaxy properties, leading to suggestions that galaxies and black holes may evolve together. The number of reliably measured black-hole masses is small, and the number of methods for measuring them is limited, holding back attempts to understand this co-evolution. Directly measuring black-hole masses is currently possible with stellar kinematics (in early-type galaxies), ionized-gas kinematics (in some spiral and early-type galaxies) and in rare objects that have central maser emission. Here we report that by modelling the effect of a black hole on the kinematics of molecular gas it is possible to fit interferometric observations of CO emission and thereby accurately estimate black-hole masses. We study the dynamics of the gas in the early-type galaxy NGC 4526, and obtain a best fit that requires the presence of a central dark object of 4.5(+4.2)(-3.1) × 10(8) solar masses (3σ confidence limit). With the next-generation millimetre-wavelength interferometers these observations could be reproduced in galaxies out to 75 megaparsecs in less than 5 hours of observing time. The use of molecular gas as a kinematic tracer should thus allow one to estimate black-hole masses in hundreds of galaxies in the local Universe, many more than are accessible with current techniques.

  14. Molecular mechanism of adsorption/desorption hysteresis: dynamics of shale gas in nanopores

    Science.gov (United States)

    Chen, Jie; Wang, FengChao; Liu, He; Wu, HengAn

    2017-01-01

    Understanding the adsorption and desorption behavior of methane has received considerable attention since it is one of the crucial aspects of the exploitation of shale gas. Unexpectedly, obvious hysteresis is observed from the ideally reversible physical sorption of methane in some experiments. However, the underlying mechanism still remains an open problem. In this study, Monte Carlo (MC) and molecular dynamics (MD) simulations are carried out to explore the molecular mechanisms of adsorption/desorption hysteresis. First, a detailed analysis about the capillary condensation of methane in micropores is presented. The influence of pore width, surface strength, and temperature on the hysteresis loop is further investigated. It is found that a disappearance of hysteresis occurs above a temperature threshold. Combined with the phase diagram of methane, we explicitly point out that capillary condensation is inapplicable for the hysteresis of shale gas under normal temperature conditions. Second, a new mechanism, variation of pore throat size, is proposed and studied. For methane to pass through the throat, a certain energy is required due to the repulsive interaction. The required energy increases with shrinkage of the throat, such that the originally adsorbed methane cannot escape through the narrowed throat. These trapped methane molecules account for the hysteresis. Furthermore, the hysteresis loop is found to increase with the increasing pressure and decreasing temperature. We suggest that the variation of pore throat size can explain the adsorption/desorption hysteresis of shale gas. Our conclusions and findings are of great significance for guiding the efficient exploitation of shale gas.

  15. Dense gas and star formation in individual Giant Molecular Clouds in M31

    Science.gov (United States)

    Viaene, S.; Forbrich, J.; Fritz, J.

    2018-04-01

    Studies both of entire galaxies and of local Galactic star formation indicate a dependency of a molecular cloud's star formation rate (SFR) on its dense gas mass. In external galaxies, such measurements are derived from HCN(1-0) observations, usually encompassing many Giant Molecular Clouds (GMCs) at once. The Andromeda galaxy (M31) is a unique laboratory to study the relation of the SFR and HCN emission down to GMC scales at solar-like metallicities. In this work, we correlate our composite SFR determinations with archival HCN, HCO+, and CO observations, resulting in a sample of nine reasonably representative GMCs. We find that, at the scale of individual clouds, it is important to take into account both obscured and unobscured star formation to determine the SFR. When correlated against the dense-gas mass from HCN, we find that the SFR is low, in spite of these refinements. We nevertheless retrieve an SFR-dense-gas mass correlation, confirming that these SFR tracers are still meaningful on GMC scales. The correlation improves markedly when we consider the HCN/CO ratio instead of HCN by itself. This nominally indicates a dependency of the SFR on the dense-gas fraction, in contradiction to local studies. However, we hypothesize that this partly reflects the limited dynamic range in dense-gas mass, and partly that the ratio of single-pointing HCN and CO measurements may be less prone to systematics like sidelobes. In this case, the HCN/CO ratio would importantly be a better empirical measure of the dense-gas content itself.

  16. Sticking efficiency of nanoparticles in high-velocity collisions with various target materials

    International Nuclear Information System (INIS)

    Reissaus, Philipp; Waldemarsson, Tomas; Blum, Juergen; Clement, Dominik; Llamas, Isabel; Mutschke, Harald; Giovane, Frank

    2006-01-01

    In order to find reliable collector surfaces for the Mesospheric Aerosol - Genesis, Interaction and Composition (MAGIC) sounding rocket experiment, intended to collect atmospheric nanoparticles, the sticking efficiency of nanoparticles was measured on several targets of different materials. The nanoparticles were generated by a molecular beam apparatus in Jena, Germany, by laser ablation (Al 2 O 3 particles, diameter 5-50 nm) and by laser pyrolysis (carbon particles, diameter 10-20 nm). In a vacuum environment (>10 -5 mbar) the particles condensed from the gas phase, formed a particle beam, and were accelerated to ∼∼1 km/s. The sticking efficiency on the target materials carbon, gold and grease was measured by a microbalance. Results demonstrate moderate to high sticking probabilities. Thus, the capture and retrieval of atmospheric nanoparticles was found to be quantitatively feasible

  17. Toward Measuring Galactic Dense Molecular Gas Properties and 3D Distribution with Hi-GAL

    Science.gov (United States)

    Zetterlund, Erika; Glenn, Jason; Maloney, Phil

    2016-01-01

    The Herschel Space Observatory's submillimeter dust continuum survey Hi-GAL provides a powerful new dataset for characterizing the structure of the dense interstellar medium of the Milky Way. Hi-GAL observed a 2° wide strip covering the entire 360° of the Galactic plane in broad bands centered at 70, 160, 250, 350, and 500 μm, with angular resolution ranging from 10 to 40 arcseconds. We are adapting a molecular cloud clump-finding algorithm and a distance probability density function distance-determination method developed for the Bolocam Galactic Plane Survey (BGPS) to the Hi-GAL data. Using these methods we expect to generate a database of 105 cloud clumps, derive distance information for roughly half the clumps, and derive precise distances for approximately 20% of them. With five-color photometry and distances, we will measure the cloud clump properties, such as luminosities, physical sizes, and masses, and construct a three-dimensional map of the Milky Way's dense molecular gas distribution.The cloud clump properties and the dense gas distribution will provide critical ground truths for comparison to theoretical models of molecular cloud structure formation and galaxy evolution models that seek to emulate spiral galaxies. For example, such models cannot resolve star formation and use prescriptive recipes, such as converting a fixed fraction of interstellar gas to stars at a specified interstellar medium density threshold. The models should be compared to observed dense molecular gas properties and galactic distributions.As a pilot survey to refine the clump-finding and distance measurement algorithms developed for BGPS, we have identified molecular cloud clumps in six 2° × 2° patches of the Galactic plane, including one in the inner Galaxy along the line of sight through the Molecular Ring and the termination of the Galactic bar and one toward the outer Galaxy. Distances have been derived for the inner Galaxy clumps and compared to Bolocam Galactic Plane

  18. High-velocity-oxidation performance of metal-chromium-aluminum (MCrAl), cermet, and modified aluminide coatings on IN-100 and type VIA alloys at 1093 C

    Science.gov (United States)

    Deadmore, D. L.

    1974-01-01

    Cermet, MCrAl, and modified aluminide types of coatings applied to IN-100 and NASA-TRW-VIA alloy specimens were cyclically oxidation tested in a high velocity (Mach 1) gas flame at 1093 C. Several coating compositions of each type were evaluated for oxidation resistance. The modified aluminide coating, Pt-Al, applied to alloy 6A proved to be the best, providing oxidation protection to approximately 750 hours based on weight change measurements. The second best, a CoCrAlY coating applied to 6A, provided protection to 450 hours. The third best was a cermet + aluminide coating on 6A with a protection time to 385 hours.

  19. Towards Breath Gas Analysis Based on Millimeter-Wave Molecular Spectroscopy

    Science.gov (United States)

    Rothbart, Nick; Hübers, Heinz-Wilhelm; Schmalz, Klaus; Borngräber, Johannes; Kissinger, Dietmar

    2018-03-01

    Breath gas analysis is a promising non-invasive tool for medical diagnosis as there are thousands of Volatile Organic Compounds (VOCs) in human breath that can be used as health monitoring markers. Millimeter-wave/terahertz molecular spectroscopy is highly suitable for breath gas analysis due to unique fingerprint spectra of many VOCs in that frequency range. We present our recent work on sensor systems for gas spectroscopy based on integrated transmitters (TX) and receivers (RX) fabricated in IHP's 0.13 μm SiGe BiCMOS technology. For a single-band system, spectroscopic measurements and beam profiles are presented. The frequency is tuned by direct voltage-frequency tuning and by a fractional-n PLL, respectively. The spectroscopic system includes a folded gas absorption cell with gas pre-concentration abilities demonstrating the detection of a 50 ppm mixture of ethanol in ambient air corresponding to a minimum detectable concentration of 260 ppb. Finally, the design of a 3-band system covering frequencies from 225 to 273 GHz is introduced.

  20. Comparison between gas puffing and supersonic molecular beam injection in plasma density feedback experiments in EAST

    International Nuclear Information System (INIS)

    Zheng, Xingwei; Li, Jiangang; Hu, Jiansheng; Li, Jiahong; Ding, Rui; Cao, Bin; Wu, Jinhua

    2013-01-01

    To achieve desirable plasma density control, a supersonic molecular beam injection (SMBI) feedback control system has been developed recently for the EAST tokamak. The performance of the SMBI and gas puffing (GP) feedback systems were used and compared. The performance of pulse width mode is better than that of pulse amplitude mode when GP was used for density feedback control. During one-day experiments, the variation of gas input and wall retention can be clarified into two stages. In the first stage the retention ratio is as high as 80–90%, and the gas input is about an order of 10 22 D 2 . However, in the second stage, the retention ratio is at a range of 50–70%. The gas input of a single discharge is small and the net wall retention grows slowly. The results of the SMBI feedback control experiment was analyzed. The shorter delay time of SMBI makes it faster at feeding back control the plasma density. The result showed that, compared with GP, the gas input of SMBI was decreased ∼30% and the wall retention was reduced ∼40%. This shows SMBI's advantage for the long pulse high density discharges in EAST. (paper)

  1. Novel studies of molecular orientation in synthetic polymeric membranes for gas separation

    International Nuclear Information System (INIS)

    Ismail, Ahmad Fauzi

    1998-01-01

    The main objective of this investigation was to produce a super-selective asymmetric membrane for gas separation. To achieve this, molecular orientation induced by rheological conditions during membrane fabrication was investigated and related to the gas separation performance of flat sheet and hollow fiber membranes. Infrared dichroism, a spectroscopic technique, was developed in the first phase of the research to directly measure molecular orientation in flat sheet membranes. The degree of molecular orientation was found to increase with increasing shear during fabrication which enhanced both pressure-normalised flux and selectivity of the coated membranes. The rheology of polymer solutions and the mechanism of molecular orientation have been treated in detail for membrane production. This is a novel approach since previous fundamental work has focused on the phase inversion process. The current study showed that rheological conditions during membrane fabrication have the utmost importance in enhancing membrane selectivity. The effects of molecular orientation at greater shear, as experienced by hollow fiber membranes during extrusion through the spinneret channel, were investigated in the second phase of this research. In order to produce a good quality fiber, a unique tube-in-orifice spinneret and a modified hollow fiber spinning rig were designed and fabricated. Thus the combined effects of reduced water activity in the bore coagulant during hollow fiber spinning and rheologically induced molecular orientation were investigated. The selectivity of the coated high shear hollow fiber membranes was heightened and even surpassed the recognised intrinsic selectivity of the polymer. Pressure-normalised flux also increased with increasing shear rate. In the third phase of this research phase inversion conditions were further optimised to give a superior skin layer and thus provide an even better platform for the advantageous effects of molecular orientation. These

  2. High-velocity penetrating thoracic trauma with suspected cardiac involvement in a combat support hospital

    International Nuclear Information System (INIS)

    Dominguez, F.; Gentlesk, P.J.; Eckart, R.E.; Beekley, A.C.; Huffer, L.L.

    2011-01-01

    The most common cardiac injuries in the United States are blunt trauma from motor vehicle accidents or low-velocity trauma from stabbings. During military conflict, high-velocity injuries, including gunshot wounds (GSW) and fragment injury from improvised explosive devices (IED), are relatively more common. This is a retrospective review of cases with high-velocity penetrating injury and suspected myocardial involvement during a 6-month period in Baghdad, Iraq, at a United States Army hospital during Operation Iraqi Freedom. Eleven cases survived to admission (GSW in 5, IED in 6). The mean age of the all-male cohort was 27 years (range, 3-54 years). Eight of the 11 patients (73%) were victims of polytrauma. The entrance involved the right ventricle (n=3), right atrium (n=2), left ventricle (n=1), or mediastinum and pericardial reflections (n=5). Echocardiography was performed in all 11 patients. In 7 patients, no foreign body was identifiable, and in 2 patients the foreign body was identified within the pericardial fat pad. Three patients were identified as having a suspected ventricular septal defect, ranging in size from 2 to 8 mm. The most common electrocardiographic abnormality was atrioventricular block and right bundle branch block. In 4 patients, the management of the chest injury was nonsurgical, and in 1 patient the treatment was a chest tube only. Four of the patients underwent median sternotomy, 1 underwent emergent lateral thoracotomy, and 1 underwent an infradiaphragmatic approach. This case series is too small to draw definitive conclusions; however, a multidisciplinary approach to high-velocity injuries with potential for cardiac involvement augments preoperative assessment for myocardial injury and may allow selective nonoperative management. (author)

  3. Total molecular gas masses of Planck - Herschel selected strongly lensed hyper luminous infrared galaxies

    Science.gov (United States)

    Harrington, K. C.; Yun, M. S.; Magnelli, B.; Frayer, D. T.; Karim, A.; Weiß, A.; Riechers, D.; Jiménez-Andrade, E. F.; Berman, D.; Lowenthal, J.; Bertoldi, F.

    2018-03-01

    We report the detection of CO(1-0) line emission from seven Planck and Herschel selected hyper luminous ({L_{IR (8-1000{μ m})} > 10^{13} L_{⊙}) infrared galaxies with the Green Bank Telescope (GBT). CO(1-0) measurements are a vital tool to trace the bulk molecular gas mass across all redshifts. Our results place tight constraints on the total gas content of these most apparently luminous high-z star-forming galaxies (apparent IR luminosities of LIR > 1013 - 14 L⊙), while we confirm their predetermined redshifts measured using the Large Millimeter Telescope, LMT (zCO = 1.33-3.26). The CO(1-0) lines show similar profiles as compared to Jup = 2-4 transitions previously observed with the LMT. We report enhanced infrared to CO line luminosity ratios of = 110 ± 22 L_{⊙} (K km s^{-1} pc^{-2})^{-1} compared to normal star-forming galaxies, yet similar to those of well-studied IR-luminous galaxies at high-z. We find average brightness temperature ratios of 〈 r21〉 = 0.93 (2 sources), 〈 r31〉 = 0.34 (5 sources), and 〈 r41〉 = 0.18 (1 source). The r31 and r41 values are roughly half the average values for SMGs. We estimate the total gas mass content as {μ M_{H2} = (0.9-27.2) × 10^{11} (α _CO/0.8) M_{⊙}, where μ is the magnification factor and αCO is the CO line luminosity to molecular hydrogen gas mass conversion factor. The rapid gas depletion times, = 80} Myr, reveal vigorous starburst activity, and contrast the Gyr depletion time-scales observed in local, normal star-forming galaxies.

  4. Molecular Simulation of Ionic Polyimides and Composites with Ionic Liquids as Gas-Separation Membranes.

    Science.gov (United States)

    Abedini, Asghar; Crabtree, Ellis; Bara, Jason E; Turner, C Heath

    2017-10-24

    Polyimides are at the forefront of advanced membrane materials for CO 2 capture and gas-purification processes. Recently, ionic polyimides (i-PIs) have been reported as a new class of condensation polymers that combine structural components of both ionic liquids (ILs) and polyimides through covalent linkages. In this study, we report CO 2 and CH 4 adsorption and structural analyses of an i-PI and an i-PI + IL composite containing [C 4 mim][Tf 2 N]. The combination of molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulations is used to compute the gas solubility and the adsorption performance with respect to the density, fractional free volume (FFV), and surface area of the materials. Our results highlight the polymer relaxation process and its correlation to the gas solubility. In particular, the surface area can provide meaningful guidance with respect to the gas solubility, and it tends to be a more sensitive indicator of the adsorption behavior versus only considering the system density and FFV. For instance, as the polymer continues to relax, the density, FFV, and pore-size distribution remain constant while the surface area can continue to increase, enabling more adsorption. Structural analyses are also conducted to identify the nature of the gas adsorption once the ionic liquid is added to the polymer. The presence of the IL significantly displaces the CO 2 molecules from the ligand nitrogen sites in the neat i-PI to the imidazolium rings in the i-PI + IL composite. However, the CH 4 molecules move from the imidazolium ring sites in the neat i-PI to the ligand nitrogen atoms in the i-PI + IL composite. These molecular details can provide critical information for the experimental design of highly selective i-PI materials as well as provide additional guidance for the interpretation of the simulated adsorption systems.

  5. Penetration of Liquid Jets into a High-velocity Air Stream

    Science.gov (United States)

    Chelko, Louis J

    1950-01-01

    Data are presented showing the penetration characteristics of liquid jets directed approximately perpendicular to a high-velocity air stream for jet-nozzle-throat diameters from 0.0135 to 0.0625 inch, air stream densities from 0.0805 to 0.1365 pound per cubic foot, liquid jet velocities from 168.1 to 229.0 feet per second and a liquid jet density of approximately 62 pounds per cubic foot. The data were analyzed and a correlation was developed that permitted the determination of the penetration length of the liquid jet for any operation condition within the range of variables investigated.

  6. Deposition of magnetite particles from high velocity water onto isothermal tubes

    International Nuclear Information System (INIS)

    Burrill, K.A.

    1977-02-01

    The deposition rate of magnetite particles from a high velocity water slurry onto isothermal metal tubes was measured. The effects of velocity (5 to 100 m/s), slurry concentration (200 to 1000 mg Fe/kg H 2 O), temperature (25 0 to 90 0 C), pH (4 to 10 at 25 0 C), and tube material (nickel, Zircaloy-4) on deposition rate were studied. The data are interpreted in terms of two steps in series for deposition: a mass transfer step followed by a deposition or inertial coasting step. Mass transfer of particles through the bulk water phase apparently limits the deposition of particles at high Reynolds number

  7. Measurements of low density, high velocity flow by electron beam fluorescence technique

    International Nuclear Information System (INIS)

    Soga, Takeo; Takanishi, Masaya; Yasuhara, Michiru

    1981-01-01

    A low density chamber with an electron gun system was made for the measurements of low density, high velocity (high Mach number) flow. This apparatus is a continuous running facility. The number density and the rotational temperature in the underexpanding free jet of nitrogen were measured along the axis of the jet by the electron beam fluorescence technique. The measurements were carried out from the vicinity of the exit of the jet to far downstream of the first Mach disk. Rotational nonequilibrium phenomena were observed in the hypersonic flow field as well as in the shock wave (Mach disk). (author)

  8. Evaluation of a Candidate Trace Contaminant Control Subsystem Architecture: The High Velocity, Low Aspect Ratio (HVLA) Adsorption Process

    Science.gov (United States)

    Kayatin, Matthew J.; Perry, Jay L.

    2017-01-01

    Traditional gas-phase trace contaminant control adsorption process flow is constrained as required to maintain high contaminant single-pass adsorption efficiency. Specifically, the bed superficial velocity is controlled to limit the adsorption mass-transfer zone length relative to the physical adsorption bed; this is aided by traditional high-aspect ratio bed design. Through operation in this manner, most contaminants, including those with relatively high potential energy are readily adsorbed. A consequence of this operational approach, however, is a limited available operational flow margin. By considering a paradigm shift in adsorption architecture design and operations, in which flows of high superficial velocity are treated by low-aspect ratio sorbent beds, the range of well-adsorbed contaminants becomes limited, but the process flow is increased such that contaminant leaks or emerging contaminants of interest may be effectively controlled. To this end, the high velocity, low aspect ratio (HVLA) adsorption process architecture was demonstrated against a trace contaminant load representative of the International Space Station atmosphere. Two HVLA concept packaging designs (linear flow and radial flow) were tested. The performance of each design was evaluated and compared against computer simulation. Utilizing the HVLA process, long and sustained control of heavy organic contaminants was demonstrated.

  9. EXTREMELY BROAD RADIO RECOMBINATION MASER LINES TOWARD THE HIGH-VELOCITY IONIZED JET IN CEPHEUS A HW2

    International Nuclear Information System (INIS)

    Jimenez-Serra, I.; Patel, N.; Martin-Pintado, J.; Baez-Rubio, A.; Thum, C.

    2011-01-01

    We present the first detection of the H40α, H34α, and H31α radio recombination lines (RRLs) at millimeter wavelengths toward the high-velocity ionized jet in the Cepheus A HW2 star-forming region. From our single-dish and interferometric observations, we find that the measured RRLs show extremely broad asymmetric line profiles with zero-intensity line widths of ∼1100 km s -1 . From the line widths, we estimate a terminal velocity for the ionized gas in the jet of ≥500 km s -1 , consistent with that obtained from the proper motions of the HW2 radio jet. The total integrated line-to-continuum flux ratios of the H40α, H34α, and H31α lines are 43, 229, and 280 km s -1 , clearly deviating from LTE predictions. These ratios are very similar to those observed for the RRL masers toward MWC349A, suggesting that the intensities of the RRLs toward HW2 are affected by maser emission. Our radiative transfer modeling of the RRLs shows that their asymmetric profiles could be explained by maser emission arising from a bi-conical radio jet with a semi-opening angle of 18 deg., electron density distribution varying as r -2.11 , and turbulent and expanding wind velocities of 60 and 500 km s -1 .

  10. Molecular analysis of petroleum derived compounds that adsorb onto gas hydrate surfaces

    International Nuclear Information System (INIS)

    Borgund, Anna E.; Hoiland, Sylvi; Barth, Tanja; Fotland, Per; Askvik, Kjell M.

    2009-01-01

    Field observations have shown that some streams of water, gas and crude oil do not form gas hydrate plugs during petroleum production even when operating within thermodynamic conditions for hydrate formation. Also, when studied under controlled laboratory conditions, some oils are found to form hydrate dispersed systems whereas others form plugs. Oils with low tendency to form hydrate plugs are believed to contain natural hydrate plug inhibiting components (NICs) that adsorb onto the hydrate surface, making them less water-wet and preventing the particles from agglomerating into large hydrate clusters. The molecular structure of the NICs is currently unknown. In this work, hydrate adsorbing components were extracted from crude oils using freon hydrates as an extraction phase. The fractions were found to be enriched in polar material, and more polar material is associated with hydrates generated in biodegraded crude oils than in non-biodegraded oils. Various fractionation schemes and analytical techniques have been applied in the search for molecular characterisation. The average molecular weights were found to be approximately 500 g/mole. GC-MS chromatograms show a large UCM (Unresolved Complex Mixture). Thus, GC-MS has a limited potential for identification of compounds. A commercial biosurfactant was used as a model compound in the search for similar structures in the extracts. The results from analysis of the hydrate adsorbing components suggest that the type and structure are more important for hydrate morphology than the amount of material adsorbed.

  11. Gas, dust, stars, star formation, and their evolution in M 33 at giant molecular cloud scales

    Science.gov (United States)

    Komugi, Shinya; Miura, Rie E.; Kuno, Nario; Tosaki, Tomoka

    2018-04-01

    We report on a multi-parameter analysis of giant molecular clouds (GMCs) in the nearby spiral galaxy M 33. A catalog of GMCs identifed in 12CO(J = 3-2) was used to compile associated 12CO(J = 1-0), dust, stellar mass, and star formation rate. Each of the 58 GMCs are categorized by their evolutionary stage. Applying the principal component analysis on these parameters, we construct two principal components, PC1 and PC2, which retain 75% of the information from the original data set. PC1 is interpreted as expressing the total interstellar matter content, and PC2 as the total activity of star formation. Young (activity compared to intermediate-age and older clouds. Comparison of average cloud properties in different evolutionary stages imply that GMCs may be heated or grow denser and more massive via aggregation of diffuse material in their first ˜ 10 Myr. The PCA also objectively identified a set of tight relations between ISM and star formation. The ratio of the two CO lines is nearly constant, but weakly modulated by massive star formation. Dust is more strongly correlated with the star formation rate than the CO lines, supporting recent findings that dust may trace molecular gas better than CO. Stellar mass contributes weakly to the star formation rate, reminiscent of an extended form of the Schmidt-Kennicutt relation with the molecular gas term substituted by dust.

  12. Aerosol formation from high-velocity uranium drops: Comparison of number and mass distributions. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Rader, D.J.; Benson, D.A.

    1995-05-01

    This report presents the results of an experimental study of the aerosol produced by the combustion of high-velocity molten-uranium droplets produced by the simultaneous heating and electromagnetic launch of uranium wires. These tests are intended to simulate the reduction of high-velocity fragments into aerosol in high-explosive detonations or reactor accidents involving nuclear materials. As reported earlier, the resulting aerosol consists mainly of web-like chain agglomerates. A condensation nucleus counter was used to investigate the decay of the total particle concentration due to coagulation and losses. Number size distributions based on mobility equivalent diameter obtained soon after launch with a Differential Mobility Particle Sizer showed lognormal distributions with an initial count median diameter (CMD) of 0.3 {mu}m and a geometric standard deviation, {sigma}{sub g} of about 2; the CMD was found to increase and {sigma}{sub g} decrease with time due to coagulation. Mass size distributions based on aerodynamic diameter were obtained for the first time with a Microorifice Uniform Deposit Impactor, which showed lognormal distributions with mass median aerodynamic diameters of about 0.5 {mu}m and an aerodynamic geometric standard deviation of about 2. Approximate methods for converting between number and mass distributions and between mobility and aerodynamic equivalent diameters are presented.

  13. HIGH-VELOCITY RESISTANCE EXERCISE PROTOCOLS IN OLDER WOMEN: EFFECTS ON CARDIOVASCULAR RESPONSE

    Directory of Open Access Journals (Sweden)

    Rodrigo P. da Silva

    2007-12-01

    Full Text Available Acute cardiovascular responses to different high-velocity resistance exercise protocols were compared in untrained older women. Twelve apparently healthy volunteers (62.6 ± 2.9 y performed three different protocols in the bench press (BP. All protocols involved three sets of 10 repetitions performed with a 10RM load and 2 minutes of rest between sets. The continuous protocol (CP involved ten repetitions with no pause between repetitions. The discontinuous protocols were performed with a pause of five (DP5 or 15 (DP15 seconds between the fifth and sixth repetitions. Heart rate (HR, systolic blood pressure (SBP, rate pressure product (RPP, Rating of Perceived Exertion (RPE, and blood lactate (BLa were assessed at baseline and at the end of all exercise sets. Factorial ANOVA was used to compare the cardiovascular response among different protocols. Compared to baseline, HR and RPP were significantly (p < 0.05 higher after the third set in all protocols. HR and RPP were significantly (p < 0.05 lower in DP5 and DP15 compared with CP for the BP exercise. Compared to baseline, RPE increased significantly (p < 0.05 with each subsequent set in all protocols. Blood lactate concentration during DP5 and DP15 was significantly lower than CP. It appears that discontinuous high-velocity resistance exercise has a lower cardiovascular demand than continuous resistance exercise in older women

  14. Aerosol formation from high-velocity uranium drops: Comparison of number and mass distributions. Final report

    International Nuclear Information System (INIS)

    Rader, D.J.; Benson, D.A.

    1995-05-01

    This report presents the results of an experimental study of the aerosol produced by the combustion of high-velocity molten-uranium droplets produced by the simultaneous heating and electromagnetic launch of uranium wires. These tests are intended to simulate the reduction of high-velocity fragments into aerosol in high-explosive detonations or reactor accidents involving nuclear materials. As reported earlier, the resulting aerosol consists mainly of web-like chain agglomerates. A condensation nucleus counter was used to investigate the decay of the total particle concentration due to coagulation and losses. Number size distributions based on mobility equivalent diameter obtained soon after launch with a Differential Mobility Particle Sizer showed lognormal distributions with an initial count median diameter (CMD) of 0.3 μm and a geometric standard deviation, σ g of about 2; the CMD was found to increase and σ g decrease with time due to coagulation. Mass size distributions based on aerodynamic diameter were obtained for the first time with a Microorifice Uniform Deposit Impactor, which showed lognormal distributions with mass median aerodynamic diameters of about 0.5 μm and an aerodynamic geometric standard deviation of about 2. Approximate methods for converting between number and mass distributions and between mobility and aerodynamic equivalent diameters are presented

  15. PTF 12gzk—A rapidly declining, high-velocity type Ic radio supernova

    Energy Technology Data Exchange (ETDEWEB)

    Horesh, Assaf; Kulkarni, Shrinivas R. [Cahill Center for Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Corsi, Alessandra [Department of Physics, The George Washington University, 725 21st Street, NW, Washington, DC 20052 (United States); Frail, Dale A. [National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801 (United States); Cenko, S. Bradley [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Ben-Ami, Sagi; Gal-Yam, Avishay; Yaron, Ofer; Arcavi, Iair; Ofek, Eran O. [Department of Particle Physics and Astrophysics, The Weizmann Institute of Science, Rehovot 76100 (Israel); Kasliwal, Mansi M. [Carnegie Institution for Science, Department of Terrestrial Magnetism, 5241 Broad Branch Road, Washington, DC 20008 (United States)

    2013-11-20

    Only a few cases of Type Ic supernovae (SNe) with high-velocity ejecta (≥0.2 c) have been discovered and studied. Here, we present our analysis of radio and X-ray observations of the Type Ic SN PTF 12gzk. The radio emission declined less than 10 days after explosion, suggesting SN ejecta expanding at high velocity (∼0.3 c). The radio data also indicate that the density of the circumstellar material (CSM) around the supernova is lower by a factor of ∼10 than the CSM around normal Type Ic SNe. PTF 12gzk may therefore be an intermediate event between a 'normal' SN Ic and a gamma-ray-burst-SN-like event. Our observations of this rapidly declining radio SN at a distance of 58 Mpc demonstrates the potential to detect many additional radio SNe, given the new capabilities of the Very Large Array (improved sensitivity and dynamic scheduling), which are currently missed, leading to a biased view of radio SNe Ic. Early optical discovery followed by rapid radio observations would provide a full description of the ejecta velocity distribution and CSM densities around stripped massive star explosions as well as strong clues about the nature of their progenitor stars.

  16. PTF 12gzk—A rapidly declining, high-velocity type Ic radio supernova

    International Nuclear Information System (INIS)

    Horesh, Assaf; Kulkarni, Shrinivas R.; Corsi, Alessandra; Frail, Dale A.; Cenko, S. Bradley; Ben-Ami, Sagi; Gal-Yam, Avishay; Yaron, Ofer; Arcavi, Iair; Ofek, Eran O.; Kasliwal, Mansi M.

    2013-01-01

    Only a few cases of Type Ic supernovae (SNe) with high-velocity ejecta (≥0.2 c) have been discovered and studied. Here, we present our analysis of radio and X-ray observations of the Type Ic SN PTF 12gzk. The radio emission declined less than 10 days after explosion, suggesting SN ejecta expanding at high velocity (∼0.3 c). The radio data also indicate that the density of the circumstellar material (CSM) around the supernova is lower by a factor of ∼10 than the CSM around normal Type Ic SNe. PTF 12gzk may therefore be an intermediate event between a 'normal' SN Ic and a gamma-ray-burst-SN-like event. Our observations of this rapidly declining radio SN at a distance of 58 Mpc demonstrates the potential to detect many additional radio SNe, given the new capabilities of the Very Large Array (improved sensitivity and dynamic scheduling), which are currently missed, leading to a biased view of radio SNe Ic. Early optical discovery followed by rapid radio observations would provide a full description of the ejecta velocity distribution and CSM densities around stripped massive star explosions as well as strong clues about the nature of their progenitor stars.

  17. A Microchannel Inlet to Reduce High-Velocity Impact Fragmentation of Molecules in Orbital and Fly-by Mass Spectrometers

    Science.gov (United States)

    Turner, Brandon; Anupriya, Anupriya; Sevy, Eric; Austin, Daniel E.

    2017-10-01

    Closed source neutral mass spectrometers are often used on flyby missions to characterize the molecular components of planetary exospheres. In a typical closed source, neutrals are thermalized as they deflect off the walls within a spherical antechamber prior to ionization and mass analysis. However, the high kinetic energy of each molecule as it impacts the chamber can lead to fragmentation before the ionization region is reached. Due to this fragmentation, the original composition of the molecule can be altered, leading to ambiguous identification.Even knowing the fragmentation pathways that occur may not allow deconvolution of data to give the correct composition. Only stable, volatile fragments will be observed in the subsequent mass spectrometer and different organic compounds likely give similar fragmentation products. Simply detecting these products will not lead to unambiguous identication of the precursor molecules. Here, we present a hardware solution to this problem—an inlet that reduces the fragmentation of molecules that impact at high velocities.We present a microchannel inlet that reduces the impact fragmentation by allowing the molecules to dissipate kinetic energy faster than their respective dissociation lifetimes. Preliminary calculations indicate that impact-induced fragmentation will be reduced up to three orders of magnitude compared with conventional closed sources by using this inlet. The benefits of such an inlet apply to any orbital or flyby velocity. The microchannel inlet enables detection of semi-volatile molecules that were previously undetectable due to impact fragmentation.

  18. Physical properties of CO-dark molecular gas traced by C+

    Science.gov (United States)

    Tang, Ningyu; Li, Di; Heiles, Carl; Wang, Shen; Pan, Zhichen; Wang, Jun-Jie

    2016-09-01

    Context. Neither Hi nor CO emission can reveal a significant quantity of so-called dark gas in the interstellar medium (ISM). It is considered that CO-dark molecular gas (DMG), the molecular gas with no or weak CO emission, dominates dark gas. Determination of physical properties of DMG is critical for understanding ISM evolution. Previous studies of DMG in the Galactic plane are based on assumptions of excitation temperature and volume density. Independent measurements of temperature and volume density are necessary. Aims: We intend to characterize physical properties of DMG in the Galactic plane based on C+ data from the Herschel open time key program, namely Galactic Observations of Terahertz C+ (GOT C+) and Hi narrow self-absorption (HINSA) data from international Hi 21 cm Galactic plane surveys. Methods: We identified DMG clouds with HINSA features by comparing Hi, C+, and CO spectra. We derived the Hi excitation temperature and Hi column density through spectral analysis of HINSA features. The Hi volume density was determined by utilizing the on-the-sky dimension of the cold foreground Hi cloud under the assumption of axial symmetry. The column and volume density of H2 were derived through excitation analysis of C+ emission. The derived parameters were then compared with a chemical evolutionary model. Results: We identified 36 DMG clouds with HINSA features. Based on uncertainty analysis, optical depth of HiτHi of 1 is a reasonable value for most clouds. With the assumption of τHi = 1, these clouds were characterized by excitation temperatures in a range of 20 K to 92 K with a median value of 55 K and volume densities in the range of 6.2 × 101 cm-3 to 1.2 × 103 cm-3 with a median value of 2.3 × 102 cm-3. The fraction of DMG column density in the cloud (fDMG) decreases with increasing excitation temperature following an empirical relation fDMG =-2.1 × 10-3Tex,(τHi = 1) + 1.0. The relation between fDMG and total hydrogen column density NH is given by f

  19. Doppler-free laser spectroscopy of buffer-gas-cooled molecular radicals

    International Nuclear Information System (INIS)

    Skoff, S M; Hendricks, R J; Sinclair, C D J; Tarbutt, M R; Hudson, J J; Segal, D M; Sauer, B E; Hinds, E A

    2009-01-01

    We demonstrate Doppler-free saturated absorption spectroscopy of cold molecular radicals formed by laser ablation inside a cryogenic buffer gas cell. By lowering the temperature, congested regions of the spectrum can be simplified, and by using different temperatures for different regions of the spectrum a wide range of rotational states can be studied optimally. We use the technique to study the optical spectrum of YbF radicals with a resolution of 30 MHz, measuring the magnetic hyperfine parameters of the electronic ground state. The method is suitable for high-resolution spectroscopy of a great variety of molecules at controlled temperature and pressure, and is particularly well suited to those that are difficult to produce in the gas phase.

  20. A UV-to-NIR Study of Molecular Gas in the Dust Cavity around RY Lupi

    Science.gov (United States)

    Arulanantham, N.; France, K.; Hoadley, K.; Manara, C. F.; Schneider, P. C.; Alcalá, J. M.; Banzatti, A.; Günther, H. M.; Miotello, A.; van der Marel, N.; van Dishoeck, E. F.; Walsh, C.; Williams, J. P.

    2018-03-01

    We present a study of molecular gas in the inner disk (rgas in a surface layer between r = 0.1–10 au, as traced by Lyα-pumped H2. The result shows H2 emission originating in a ring centered at ∼3 au that declines within r gas emitting from radially separated disk regions ( ∼ 0.4+/- 0.1 {au}; ∼ 3+/- 2 {au}). The 4.7 μm 12CO emission lines are also well fit by two-component profiles ( =0.4+/- 0.1 {au}; =15+/- 2 {au}). We combine these results with 10 μm observations to form a picture of gapped structure within the mm-imaged dust cavity, providing the first such overview of the inner regions of a young disk. The HST SED of RY Lupi is available online for use in modeling efforts.

  1. Reactive molecular dynamic simulations on the gas separation performance of porous graphene membrane.

    Science.gov (United States)

    Esfandiarpoor, Somaye; Fazli, Mostafa; Ganji, Masoud Darvish

    2017-11-29

    The separation of gases molecules with similar diameter and shape is an important area of research. For example, the major challenge to set up sweeping carbon dioxide capture and storage (CCS) in power plants is the energy requisite to separate the CO 2 from flue gas. Porous graphene has been proposed as superior material for highly selective membranes for gas separation. Here we design some models of porous graphene with different sizes and shape as well as employ double layers porous graphene for efficient CO 2 /H 2 separation. The selectivity and permeability of gas molecules through various nanopores were investigated by using the reactive molecular dynamics simulation which considers the bond forming/breaking mechanism for all atoms. Furthermore, it uses a geometry-dependent charge calculation scheme that accounts appropriately for polarization effect which can play an important role in interacting systems. It was found that H-modified porous graphene membrane with pore diameter (short side) of about 3.75 Å has excellent selectivity for CO 2 /H 2 separation. The mechanism of gas penetration through the sub-nanometer pore was presented for the first time. The accuracy of MD simulation results validated by valuable DFT method. The present findings show that reactive MD simulation can propose an economical means of separating gases mixture.

  2. Carbon molecular sieve gas separation membranes based on an intrinsically microporous polyimide precursor

    KAUST Repository

    Ma, Xiaohua

    2013-10-01

    We report the physical characteristics and gas transport properties for a series of pyrolyzed membranes derived from an intrinsically microporous polyimide containing spiro-centers (PIM-6FDA-OH) by step-wise heat treatment to 440, 530, 600, 630 and 800 C, respectively. At 440 C, the PIM-6FDA-OH was converted to a polybenzoxazole and exhibited a 3-fold increase in CO2 permeability (from 251 to 683 Barrer) with a 50% reduction in selectivity over CH4 (from 28 to 14). At 530 C, a distinct intermediate amorphous carbon structure with superior gas separation properties was formed. A 56% increase in CO2-probed surface area accompanied a 16-fold increase in CO2 permeability (4110 Barrer) over the pristine polymer. The graphitic carbon membrane, obtained by heat treatment at 600 C, exhibited excellent gas separation properties, including a remarkable CO2 permeability of 5040 Barrer with a high selectivity over CH4 of 38. Above 600 C, the strong emergence of ultramicroporosity (<7 Å) as evidenced by WAXD and CO2 adsorption studies elicits a prominent molecular sieving effect, yielding gas separation performance well above the permeability-selectivity trade-off curves of polymeric membranes. © 2013 Elsevier Ltd. All rights reserved.

  3. CONSTRAINING DUST AND MOLECULAR GAS PROPERTIES IN Lyα BLOBS AT z ∼ 3

    International Nuclear Information System (INIS)

    Yang Yujin; Decarli, Roberto; Walter, Fabian; Leipski, Christian; Dannerbauer, Helmut; Le Floc'h, Emeric; Weiss, Axel; Menten, Karl M.; Dey, Arjun; Chapman, Scott C.; Prescott, Moire K. M.; Neri, Roberto; Borys, Colin; Matsuda, Yuichi; Yamada, Toru; Hayashino, Tomoki; Tapken, Christian

    2012-01-01

    In order to constrain the bolometric luminosities, dust properties, and molecular gas content of giant Lyα nebulae, the so-called Lyα blobs, we have carried out a study of dust continuum and CO line emission in two well-studied representatives of this population at z ∼ 3: an Lyα blob discovered by its strong Spitzer Multiband Infrared Photometer 24 μm detection (LABd05) and the Steidel blob 1 (SSA22-LAB01). We find that the spectral energy distribution of LABd05 is well described by an active-galactic-nucleus-starburst composite template with L FIR = (4.0 ± 0.5) × 10 12 L ☉ , comparable to high-z submillimeter galaxies and ultraluminous infrared galaxies. New Large APEX Bolometer Camera 870 μm measurements rule out the reported Submillimeter Common-User Bolometer Array detection of the SSA22-LAB01 (S 850μm = 16.8 mJy) at the >4σ level. Consistent with this, ultradeep Plateau de Bure Interferometer observations with ∼2'' spatial resolution also fail to detect any 1.2 mm continuum source down to ≈0.45 mJy beam –1 (3σ). Combined with the existing (sub)millimeter observations in the literature, we conclude that the FIR luminosity of SSA22-LAB01 remains uncertain. No CO line is detected in either case down to integrated flux limits of S ν ΔV ∼ –1 , indicating a modest molecular gas reservoir, M(H 2 ) 10 M ☉ . The non-detections exclude, with high significance (12σ), the previous tentative detection of a CO J = 4-3 line in the SSA22-LAB01. The increased sensitivity afforded by the Atacama Large Millimeter/submillimeter Array will be critical in studying molecular gas and dust in these interesting systems.

  4. Seismic Technology Adapted to Analyzing and Developing Geothermal Systems Below Surface-Exposed High-Velocity Rocks Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Hardage, Bob A. [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; DeAngelo, Michael V. [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Ermolaeva, Elena [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Hardage, Bob A. [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Remington, Randy [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Sava, Diana [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Wagner, Donald [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Wei, Shuijion [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology

    2013-02-01

    The objective of our research was to develop and demonstrate seismic data-acquisition and data-processing technologies that allow geothermal prospects below high-velocity rock outcrops to be evaluated. To do this, we acquired a 3-component seismic test line across an area of exposed high-velocity rocks in Brewster County, Texas, where there is high heat flow and surface conditions mimic those found at numerous geothermal prospects. Seismic contractors have not succeeded in creating good-quality seismic data in this area for companies who have acquired data for oil and gas exploitation purposes. Our test profile traversed an area where high-velocity rocks and low-velocity sediment were exposed on the surface in alternating patterns that repeated along the test line. We verified that these surface conditions cause non-ending reverberations of Love waves, Rayleigh waves, and shallow critical refractions to travel across the earth surface between the boundaries of the fast-velocity and slow-velocity material exposed on the surface. These reverberating surface waves form the high level of noise in this area that does not allow reflections from deep interfaces to be seen and utilized. Our data-acquisition method of deploying a box array of closely spaced geophones allowed us to recognize and evaluate these surface-wave noise modes regardless of the azimuth direction to the surface anomaly that backscattered the waves and caused them to return to the test-line profile. With this knowledge of the surface-wave noise, we were able to process these test-line data to create P-P and SH-SH images that were superior to those produced by a skilled seismic data-processing contractor. Compared to the P-P data acquired along the test line, the SH-SH data provided a better detection of faults and could be used to trace these faults upward to the boundaries of exposed surface rocks. We expanded our comparison of the relative value of S-wave and P-wave seismic data for geothermal

  5. Simulating the control of molecular reactions via modulated light fields: from gas phase to solution

    Science.gov (United States)

    Thallmair, Sebastian; Keefer, Daniel; Rott, Florian; de Vivie-Riedle, Regina

    2017-04-01

    Over the past few years quantum control has proven to be very successful in steering molecular processes. By combining theory with experiment, even highly complex control aims were realized in the gas phase. In this topical review, we illustrate the past achievements on several examples in the molecular context. The next step for the quantum control of chemical processes is to translate the fruitful interplay between theory and experiment to the condensed phase and thus to the regime where chemical synthesis can be supported. On the theory side, increased efforts to include solvent effects in quantum control simulations were made recently. We discuss two major concepts, namely an implicit description of the environment via the density matrix algorithm and an explicit inclusion of solvent molecules. By application to chemical reactions, both concepts conclude that despite environmental perturbations leading to more complex control tasks, efficient quantum control in the condensed phase is still feasible.

  6. Solvation of ions in the gas-phase: a molecular dynamics simulation

    Science.gov (United States)

    Cabarcos, Orlando M.; Lisy, James M.

    1996-07-01

    Molecular dynamics simulations have been performed on the collision between a cesium ion and a cluster of twenty methanol molecules. This process, generating a solvated ion, was studied over a range (1 to 25 eV) of eight collision energies. Preliminary analysis of this gas phase solvation has included the distribution of final ion cluster sizes, fragmentation patterns, solvation timescales and energetics. Two distinct patterns have emerged: a ballistic penetration of the neutral cluster at the higher collision energies and an evaporative evolution of the cluster ion at lower collision energies.

  7. Gas-Phase Molecular Dynamics: Theoretical Studies In Spectroscopy and Chemical Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Yu H. G.; Muckerman, J.T.

    2012-05-29

    The main goal of this program is the development and application of computational methods for studying chemical reaction dynamics and molecular spectroscopy in the gas phase. We are interested in developing rigorous quantum dynamics algorithms for small polyatomic systems and in implementing approximate approaches for complex ones. Particular focus is on the dynamics and kinetics of chemical reactions and on the rovibrational spectra of species involved in combustion processes. This research also explores the potential energy surfaces of these systems of interest using state-of-the-art quantum chemistry methods, and extends them to understand some important properties of materials in condensed phases and interstellar medium as well as in combustion environments.

  8. Gas-Phase Molecular Dynamics: Theoretical Studies in Spectroscopy and Chemical Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Yu, H.G.; Muckerman, J.T.

    2010-06-01

    The goal of this program is the development and application of computational methods for studying chemical reaction dynamics and molecular spectroscopy in the gas phase. We are interested in developing rigorous quantum dynamics algorithms for small polyatomic systems and in implementing approximate approaches for complex ones. Particular focus is on the dynamics and kinetics of chemical reactions and on the rovibrational spectra of species involved in combustion processes. This research also explores the potential energy surfaces of these systems of interest using state-of-the-art quantum chemistry methods.

  9. Molecular theory of mass transfer kinetics and dynamics at gas-water interface

    International Nuclear Information System (INIS)

    Morita, Akihiro; Garrett, Bruce C

    2008-01-01

    The mass transfer mechanism across gas-water interface is studied with molecular dynamics (MD) simulation. The MD results provide a robust and qualitatively consistent picture to previous studies about microscopic aspects of mass transfer, including interface structure, free energy profiles for the uptake, scattering dynamics and energy relaxation of impinging molecules. These MD results are quantitatively compared with experimental uptake measurements, and we find that the apparent inconsistency between MD and experiment could be partly resolved by precise decomposition of the observed kinetics into elemental steps. Remaining issues and future perspectives toward constructing a comprehensive multi-scale description of interfacial mass transfer are summarized.

  10. Theoretical analysis of fluorescence signals in filamentation of femtosecond laser pulses in nitrogen molecular gas

    International Nuclear Information System (INIS)

    Arevalo, E.; Becker, A.

    2005-01-01

    We study numerically and analytically the role of the combined effect of self-focusing, geometrical focusing, and the plasma defocusing in the formation of the fluorescence signal during the filamentation of a Ti:sapphire laser pulse in nitrogen molecular gas. Results of numerical simulations are used to estimate the number of excited ions in the focal volume, which is proportional to the fluorescence signal. We find good agreement between the theoretical results and the experimental data, showing that such data can be used to get further insight into the effective focal volume during filamentation of femtosecond laser pulses in transparent media

  11. A MOLECULAR STAR FORMATION LAW IN THE ATOMIC-GAS-DOMINATED REGIME IN NEARBY GALAXIES

    International Nuclear Information System (INIS)

    Schruba, Andreas; Walter, Fabian; Dumas, Gaelle; Sandstrom, Karin; Leroy, Adam K.; Bigiel, Frank; Brinks, Elias; De Blok, W. J. G.; Kramer, Carsten; Rosolowsky, Erik; Schuster, Karl; Usero, Antonio; Weiss, Axel; Wiesemeyer, Helmut

    2011-01-01

    We use the IRAM HERACLES survey to study CO emission from 33 nearby spiral galaxies down to very low intensities. Using 21 cm line atomic hydrogen (H I) data, mostly from THINGS, we predict the local mean CO velocity based on the mean H I velocity. By re-normalizing the CO velocity axis so that zero corresponds to the local mean H I velocity we are able to stack spectra coherently over large regions. This enables us to measure CO intensities with high significance as low as I CO ∼ 0.3 K km s -1 (Σ H 2 ∼1 M sun pc -2 ), an improvement of about one order of magnitude over previous studies. We detect CO out to galactocentric radii r gal ∼ r 25 and find the CO radial profile to follow a remarkably uniform exponential decline with a scale length of ∼0.2 r 25 . Here we focus on stacking as a function of radius, comparing our sensitive CO profiles to matched profiles of H I, Hα, far-UV (FUV), and Infrared (IR) emission at 24 μm and 70 μm. We observe a tight, roughly linear relationship between CO and IR intensity that does not show any notable break between regions that are dominated by molecular gas (Σ H 2 >Σ H i ) and those dominated by atomic gas (Σ H 2 H i ). We use combinations of FUV+24 μm and Hα+24 μm to estimate the recent star formation rate (SFR) surface density, Σ SFR , and find approximately linear relations between Σ SFR and Σ H 2 . We interpret this as evidence of stars forming in molecular gas with little dependence on the local total gas surface density. While galaxies display small internal variations in the SFR-to-H 2 ratio, we do observe systematic galaxy-to-galaxy variations. These galaxy-to-galaxy variations dominate the scatter in relationships between CO and SFR tracers measured at large scales. The variations have the sense that less massive galaxies exhibit larger ratios of SFR-to-CO than massive galaxies. Unlike the SFR-to-CO ratio, the balance between atomic and molecular gas depends strongly on the total gas surface density

  12. Testing the universality of the star-formation efficiency in dense molecular gas

    Science.gov (United States)

    Shimajiri, Y.; André, Ph.; Braine, J.; Könyves, V.; Schneider, N.; Bontemps, S.; Ladjelate, B.; Roy, A.; Gao, Y.; Chen, H.

    2017-08-01

    Context. Recent studies with, for example, Spitzer and Herschel have suggested that star formation in dense molecular gas may be governed by essentially the same "law" in Galactic clouds and external galaxies. This conclusion remains controversial, however, in large part because different tracers have been used to probe the mass of dense molecular gas in Galactic and extragalactic studies. Aims: We aimed to calibrate the HCN and HCO+ lines commonly used as dense gas tracers in extragalactic studies and to test the possible universality of the star-formation efficiency in dense gas (≳104 cm-3), SFEdense. Methods: We conducted wide-field mapping of the Aquila, Ophiuchus, and Orion B clouds at 0.04 pc resolution in the J = 1 - 0 transition of HCN, HCO+, and their isotopomers. For each cloud, we derived a reference estimate of the dense gas mass MHerschelAV > 8, as well as the strength of the local far-ultraviolet (FUV) radiation field, using Herschel Gould Belt survey data products, and estimated the star-formation rate from direct counting of the number of Spitzer young stellar objects. Results: The H13CO+(1-0) and H13CN(1-0) lines were observed to be good tracers of the dense star-forming filaments detected with Herschel. Comparing the luminosities LHCN and LHCO+ measured in the HCN and HCO+ lines with the reference masses MHerschelAV > 8, the empirical conversion factors αHerschel - HCN (=MHerschelAV > 8/LHCN) and αHerschel - HCO+ (=MHerschelAV > 8/LHCO+) were found to be significantly anti-correlated with the local FUV strength. In agreement with a recent independent study of Orion B by Pety et al., the HCN and HCO+ lines were found to trace gas down to AV ≳ 2. As a result, published extragalactic HCN studies must be tracing all of the moderate density gas down to nH2 ≲ 103 cm-3. Estimating the contribution of this moderate density gas from the typical column density probability distribution functions in nearby clouds, we obtained the following G0

  13. Molecular simulation of excess isotherm and excess enthalpy change in gas-phase adsorption.

    Science.gov (United States)

    Do, D D; Do, H D; Nicholson, D

    2009-01-29

    We present a new approach to calculating excess isotherm and differential enthalpy of adsorption on surfaces or in confined spaces by the Monte Carlo molecular simulation method. The approach is very general and, most importantly, is unambiguous in its application to any configuration of solid structure (crystalline, graphite layer or disordered porous glass), to any type of fluid (simple or complex molecule), and to any operating conditions (subcritical or supercritical). The behavior of the adsorbed phase is studied using the partial molar energy of the simulation box. However, to characterize adsorption for comparison with experimental data, the isotherm is best described by the excess amount, and the enthalpy of adsorption is defined as the change in the total enthalpy of the simulation box with the change in the excess amount, keeping the total number (gas + adsorbed phases) constant. The excess quantities (capacity and energy) require a choice of a reference gaseous phase, which is defined as the adsorptive gas phase occupying the accessible volume and having a density equal to the bulk gas density. The accessible volume is defined as the mean volume space accessible to the center of mass of the adsorbate under consideration. With this choice, the excess isotherm passes through a maximum but always remains positive. This is in stark contrast to the literature where helium void volume is used (which is always greater than the accessible volume) and the resulting excess can be negative. Our definition of enthalpy change is equivalent to the difference between the partial molar enthalpy of the gas phase and the partial molar enthalpy of the adsorbed phase. There is no need to assume ideal gas or negligible molar volume of the adsorbed phase as is traditionally done in the literature. We illustrate this new approach with adsorption of argon, nitrogen, and carbon dioxide under subcritical and supercritical conditions.

  14. Large turbulent reservoirs of cold molecular gas around high-redshift starburst galaxies.

    Science.gov (United States)

    Falgarone, E; Zwaan, M A; Godard, B; Bergin, E; Ivison, R J; Andreani, P M; Bournaud, F; Bussmann, R S; Elbaz, D; Omont, A; Oteo, I; Walter, F

    2017-08-24

    Starburst galaxies at the peak of cosmic star formation are among the most extreme star-forming engines in the Universe, producing stars over about 100 million years (ref. 2). The star-formation rates of these galaxies, which exceed 100 solar masses per year, require large reservoirs of cold molecular gas to be delivered to their cores, despite strong feedback from stars or active galactic nuclei. Consequently, starburst galaxies are ideal for studying the interplay between this feedback and the growth of a galaxy. The methylidyne cation, CH + , is a most useful molecule for such studies because it cannot form in cold gas without suprathermal energy input, so its presence indicates dissipation of mechanical energy or strong ultraviolet irradiation. Here we report the detection of CH + (J = 1-0) emission and absorption lines in the spectra of six lensed starburst galaxies at redshifts near 2.5. This line has such a high critical density for excitation that it is emitted only in very dense gas, and is absorbed in low-density gas. We find that the CH + emission lines, which are broader than 1,000 kilometres per second, originate in dense shock waves powered by hot galactic winds. The CH + absorption lines reveal highly turbulent reservoirs of cool (about 100 kelvin), low-density gas, extending far (more than 10 kiloparsecs) outside the starburst galaxies (which have radii of less than 1 kiloparsec). We show that the galactic winds sustain turbulence in the 10-kiloparsec-scale environments of the galaxies, processing these environments into multiphase, gravitationally bound reservoirs. However, the mass outflow rates are found to be insufficient to balance the star-formation rates. Another mass input is therefore required for these reservoirs, which could be provided by ongoing mergers or cold-stream accretion. Our results suggest that galactic feedback, coupled jointly to turbulence and gravity, extends the starburst phase of a galaxy instead of quenching it.

  15. Close entrainment of massive molecular gas flows by radio bubbles in the central galaxy of Abell 1795

    Science.gov (United States)

    Russell, H. R.; McNamara, B. R.; Fabian, A. C.; Nulsen, P. E. J.; Combes, F.; Edge, A. C.; Hogan, M. T.; McDonald, M.; Salomé, P.; Tremblay, G.; Vantyghem, A. N.

    2017-12-01

    We present new ALMA observations tracing the morphology and velocity structure of the molecular gas in the central galaxy of the cluster Abell 1795. The molecular gas lies in two filaments that extend 5-7 kpc to the N and S from the nucleus and project exclusively around the outer edges of two inner radio bubbles. Radio jets launched by the central active galactic nucleus have inflated bubbles filled with relativistic plasma into the hot atmosphere surrounding the central galaxy. The N filament has a smoothly increasing velocity gradient along its length from the central galaxy's systemic velocity at the nucleus to -370 km s^{-1}, the average velocity of the surrounding galaxies, at the furthest extent. The S filament has a similarly smooth but shallower velocity gradient and appears to have partially collapsed in a burst of star formation. The close spatial association with the radio lobes, together with the ordered velocity gradients and narrow velocity dispersions, shows that the molecular filaments are gas flows entrained by the expanding radio bubbles. Assuming a Galactic XCO factor, the total molecular gas mass is 3.2 ± 0.2 × 109 M⊙. More than half lies above the N radio bubble. Lifting the molecular clouds appears to require an infeasibly efficient coupling between the molecular gas and the radio bubble. The energy required also exceeds the mechanical power of the N radio bubble by a factor of 2. Stimulated feedback, where the radio bubbles lift low-entropy X-ray gas that becomes thermally unstable and rapidly cools in situ, provides a plausible model. Multiple generations of radio bubbles are required to lift this substantial gas mass. The close morphological association then indicates that the cold gas either moulds the newly expanding bubbles or is itself pushed aside and shaped as they inflate.

  16. Spectral characteristics of aurorae connected with high-velocity flows of the solar wind from coronal holes

    International Nuclear Information System (INIS)

    Khviyuzova, T.A.; Leont'ev, S.V.

    1997-01-01

    Bright electron aurorae almost always followed by red lower edge occur when the Earth is being passed by high-velocity flows from coronal holes within the auroral range at the night meridian. In contrast to other types of the solar wind the high-velocity flows from coronal holes do not cause the occurrence of A type red polar aurorae, that is, the spectrum of electrons pouring into the Earth atmosphere in these cases is shifted towards higher energies

  17. A study of human liver ferritin and chicken liver and spleen using Moessbauer spectroscopy with high velocity resolution

    Energy Technology Data Exchange (ETDEWEB)

    Oshtrakh, M. I., E-mail: oshtrakh@mail.utnet.ru [Ural State Technical University-UPI, Faculty of Physical Techniques and Devices for Quality Control (Russian Federation); Milder, O. B.; Semionkin, V. A. [Ural State Technical University-UPI, Faculty of Experimental Physics (Russian Federation)

    2008-01-15

    Lyophilized samples of human liver ferritin and chicken liver and spleen were measured at room temperature using Moessbauer spectroscopy with high velocity resolution. An increase in the velocity resolution of Moessbauer spectroscopy permitted us to increase accuracy and decrease experimental error in determining the hyperfine parameters of human liver ferritin and chicken liver and spleen. Moessbauer spectroscopy with high velocity resolution may be very useful for revealing small differences in hyperfine parameters during biomedical research.

  18. Atomic beam formed by the vaporization of a high velocity pellet

    International Nuclear Information System (INIS)

    Foster, C.A.; Hendricks, C.D.

    1974-01-01

    A description of an atomic beam formed by vaporizing an electrostatically accelerated high velocity pellet is given. Uniformly sized droplets of neon will be formed by the mechanical disintegration of liquid jet and frozen by adiabatic vaporization in vacuum. The pellets produced will be charged and accelerated by contacting a needle held at high potential. The accelerated pellets will be vaporized forming a pulse of mono-energetic atoms. The advantages are that a wide range of energies will be possible. The beam will be mono-energetic. The beam is inheretly pulsed, allowing a detailed time of flight velocity distribution measurement. The beam will have a high instantaneous intensity. The beam will be able to operate into an ultra high vacuum chamber

  19. Microstructure Characterization of WCCo-Mo Based Coatings Produced Using High Velocity Oxygen Fuel

    Directory of Open Access Journals (Sweden)

    Serkan Islak

    2015-12-01

    Full Text Available The present study has been carried out in order to investigate the microstructural properties of WCCo-Mo composite coatings deposited onto a SAE 4140 steel substrate by high velocity oxygen fuel (HVOF thermal spray. For this purpose, the Mo quantity added to the WCCo was changed as 10, 20, 30 and 40 wt. % percents. The coatings are compared in terms of their phase composition, microstructure and hardness. Phase compound and microstructure of coating layers were examined using X-ray diffractometer (XRD and scanning electron microscope (SEM. XRD results showed that WCCo-Mo composite coatings were mainly composed of WC, W2C, Co3W3C, Mo2C, MoO2, Mo and Co phases. The average hardness of the coatings increased with increasing Mo content.

  20. Diagnostic of N2(A) concentration in high velocity nitrogen afterglow at atmospheric pressure

    Science.gov (United States)

    Pointu, Anne-Marie; Mintusov, Evgeny

    2009-10-01

    An optical emission diagnostic was used to measure N2(A) concentration in a high velocity (1000 cm/s) N2 flowing afterglow of corona discharge at atmospheric pressure, used for biological decontamination. Introducing impurities of NO (measured at different axial distances and for different values of NO injected flow. Moreover, it has been demonstrated that N2(A) creation comes from N+N+N2 atom recombination with a global rate around 2e-33 cm^6/s, a result which agrees with literature, as well as N2(A) loss mechanisms were confirmed to go via quenching with O and N atoms. The order of magnitude of obtained N2(A) concentration, about 1e11 cm-3, coincides with the results of direct measurement (by Vegard-Kaplan band), using a spectrometer of better resolution.

  1. High-velocity facial gunshot wounds: multidisciplinary care from prehospital to discharge.

    Science.gov (United States)

    Sinnott, J D; Morris, G; Medland, P J; Porter, K

    2016-01-28

    A case is presented in which a high velocity rifle (shotgun) was fired into the inferior part of a patient's face in an attempted suicide causing widespread trauma to the inferior and left side of the patient's face. He presented to his general practitioner where an ambulance was called. The patient is followed from prehospital care (air ambulance) to resuscitation in accident and emergency and through the first stages of reconstructive surgery. The article focuses on the multidisciplinary approach to the patient's prehospital care and initial resuscitation at a major trauma centre. CT reconstruction images of the patient's skull allow visualisation of the extent of bone damage at presentation. Medical photography allows visualisation of the extent of the initial damage and shows how reconstructive surgery was undertaken early and in progressive stages. A literature review was performed allowing discussion of the current evidence and best practice in the management of facial gunshot wounds. 2016 BMJ Publishing Group Ltd.

  2. Introducing a novel gravitation-based high-velocity compaction analysis method for pharmaceutical powders.

    Science.gov (United States)

    Tanner, Timo; Antikainen, Osmo; Ehlers, Henrik; Yliruusi, Jouko

    2017-06-30

    With modern tableting machines large amounts of tablets are produced with high output. Consequently, methods to examine powder compression in a high-velocity setting are in demand. In the present study, a novel gravitation-based method was developed to examine powder compression. A steel bar is dropped on a punch to compress microcrystalline cellulose and starch samples inside the die. The distance of the bar is being read by a high-accuracy laser displacement sensor which provides a reliable distance-time plot for the bar movement. In-die height and density of the compact can be seen directly from this data, which can be examined further to obtain information on velocity, acceleration and energy distribution during compression. The energy consumed in compact formation could also be seen. Despite the high vertical compression speed, the method was proven to be cost-efficient, accurate and reproducible. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. LP 400-22, A Very Low Mass and High-Velocity White Dwarf

    Science.gov (United States)

    Kawka, Adela; Vennes, Stephane; Oswalt, Terry D.; Smith, J. Allyn; Silvestri, Nicole M.

    2006-01-01

    We report the identification of LP 400-22 (WD 2234+222) as a very low mass and high-velocity white dwarf. The ultraviolet GALEX and optical photometric colors and a spectral line analysis of LP 400-22 show this star to have an effective temperature of 11,080+/-140 K and a surface gravity of log g = 6.32 +/-0.08. Therefore, this is a helium-core white dwarf with a mass of 0.17 M,. The tangential velocity of this white dwarf is 414+/-43 km/s, making it one of the fastest moving white dwarfs known. We discuss probable evolutionary scenarios for this remarkable object.

  4. Combustion of a high-velocity hydrogen microjet effluxing in air

    Science.gov (United States)

    Kozlov, V. V.; Grek, G. R.; Korobeinichev, O. P.; Litvinenko, Yu. A.; Shmakov, A. G.

    2016-09-01

    This study is devoted to experimental investigation of hydrogen-combustion modes and the structure of a diffusion flame formed at a high-velocity efflux of hydrogen in air through round apertures of various diameters. The efflux-velocity range of the hydrogen jet and the diameters of nozzle apertures at which the flame is divided in two zones with laminar and turbulent flow are found. The zone with the laminar flow is a stabilizer of combustion of the flame as a whole, and in the zone with the turbulent flow the intense mixing of fuel with an oxidizer takes place. Combustion in these two zones can occur independently from each other, but the steadiest mode is observed only at the existence of the flame in the laminar-flow zone. The knowledge obtained makes it possible to understand more deeply the features of modes of microjet combustion of hydrogen promising for various combustion devices.

  5. The deposition of magnetite particles from high velocity water onto isothermal tubes

    International Nuclear Information System (INIS)

    Burrill, K.A.

    1977-02-01

    The deposition rate of magnetite particles from a high velocity water slurry onto isothermal metal tubes was measured. The effects of velocity (5 to 100 m/s), slurry concentration (200 to 1000 mg Fe/kg H 2 O), temperature (25 to 90 deg C), pH (4 to 10 at 25 deg C), and tube material (nickel, Zircaloy-4) on deposition rate were studied. The data are interpreteω in terms of two steps in series for deposition: a mass transfer step followed by a deposition or ''inertial coasting'' step. Mass transfer of particles through the bulk water phase apparently limits the deposition of particles at high Reynolds number (10 5 ). (author)

  6. Minimally-invasive treatment of high velocity intra-articular fractures of the distal tibia.

    LENUS (Irish Health Repository)

    Leonard, M

    2012-02-01

    The pilon fracture is a complex injury. The purpose of this study was to evaluate the outcome of minimally invasive techniques in management of these injuries. This was a prospective study of closed AO type C2 and C3 fractures managed by early (<36 hours) minimally invasive surgical intervention and physiotherapist led rehabilitation. Thirty patients with 32 intra-articular distal tibial fractures were treated by the senior surgeon (GK). Our aim was to record the outcome and all complications with a minimum two year follow-up. There were two superficial wound infections. One patient developed a non-union which required a formal open procedure. Another patient was symptomatic from a palpable plate inferiorly. An excellent AOFAS result was obtained in 83% (20\\/24) of the patients. Early minimally invasive reduction and fixation of complex high velocity pilon fractures gave very satisfactory results at a minimum of two years follow-up.

  7. St 2-22 - Another Symbiotic Star with High-Velocity Bipolar Jets

    Science.gov (United States)

    Tomov, T.; Zamanov, R.; Gałan, C.; Pietrukowicz, P.

    2017-09-01

    We report the detection of high-velocity components in the wings of Hα emission line in spectra of symbiotic binary star St 2-22 obtained in 2005. This finding encouraged us to start the present investigation in order to show that this poorly-studied object is a jet-producing system. We have used high-resolution optical and low-resolution near-infrared spectra, as well as available optical and infrared photometry, to evaluate some physical parameters of the St 2-22 components and characteristics of the jets. We confirm that St 2-22 is a S-type symbiotic star. Our results demonstrate that an unnoticed outburst, similar to those in classical symbiotic systems, occurred in the first half of 2005. During the outburst, collimated bipolar jets were ejected by the hot component of St 2-22 with an average velocity of about 1700 km/s.

  8. High-Velocity Impact Behaviour of Prestressed Composite Plates under Bird Strike Loading

    Directory of Open Access Journals (Sweden)

    Sebastian Heimbs

    2012-01-01

    Full Text Available An experimental and numerical analysis of the response of laminated composite plates under high-velocity impact loads of soft body gelatine projectiles (artificial birds is presented. The plates are exposed to tensile and compressive preloads before impact in order to cover realistic loading conditions of representative aeronautic structures under foreign object impact. The modelling methodology for the composite material, delamination interfaces, impact projectile, and preload using the commercial finite element code Abaqus are presented in detail. Finally, the influence of prestress and of different delamination modelling approaches on the impact response is discussed and a comparison to experimental test data is given. Tensile and compressive preloading was found to have an influence on the damage pattern. Although this general behaviour could be predicted well by the simulations, further numerical challenges for improved bird strike simulation accuracy are highlighted.

  9. Optimization and Characterization of High Velocity Oxy-fuel Sprayed Coatings: Techniques, Materials, and Applications

    Directory of Open Access Journals (Sweden)

    Maria Oksa

    2011-09-01

    Full Text Available In this work High Velocity Oxy-fuel (HVOF thermal spray techniques, spraying process optimization, and characterization of coatings are reviewed. Different variants of the technology are described and the main differences in spray conditions in terms of particle kinetics and thermal energy are rationalized. Methods and tools for controlling the spray process are presented as well as their use in optimizing the coating process. It will be shown how the differences from the starting powder to the final coating formation affect the coating microstructure and performance. Typical properties of HVOF sprayed coatings and coating performance is described. Also development of testing methods used for the evaluation of coating properties and current status of standardization is presented. Short discussion of typical applications is done.

  10. A systematic search for dwarf counterparts to ultra compact high velocity clouds

    Science.gov (United States)

    Bennet, Paul; Sand, David J.; Crnojevic, Denija; Strader, Jay

    2015-01-01

    Observations of the Universe on scales smaller than typical, massive galaxies challenge the standard Lambda Cold Dark Matter paradigm for structure formation. It is thus imperative to discover and characterize the faintest dwarf galaxy systems, not just within the Local Group, but in relatively isolated environments as well in order to properly connect them with models of structure formation. Here we report on a systematic search of public ultraviolet and optical archives for dwarf galaxy counterparts to so-called Ultra Compact High Velocity Clouds (UCHVCs), which are compact, isolated HI sources recently found in the Galactic Arecibo L-band Feed Array-HI (GALFA-HI) and Arecibo Legacy Fast ALFA (ALFALFA-HI) surveys. Our search has uncovered at least three strong dwarf galaxy candidates, and we present their inferred star formation rate and structural properties here.

  11. Moessbauer spectroscopy with a high velocity resolution: advances in biomedical, pharmaceutical, cosmochemical and nano technological research

    International Nuclear Information System (INIS)

    Oshtrakha, M.I.; Semionkina, V.A.

    2011-01-01

    Full text: Velocity resolution is a term denoted the smallest velocity step (2V/2 n ) in velocity driving system of Moessbauer spectrometer and velocity step for the one point in Moessbauer spectrum. Velocity resolution coefficient 1/2 n in velocity driving system is constant and velocity resolution value depends on velocity range (2V) only while velocity resolution in Moessbauer spectrum may be the same or less. Moessbauer spectroscopy with a high velocity resolution is a new method to measure precision high quality spectra. It is well known that one of the main parts of Moessbauer spectrometer is velocity driving system. Usual spectrometers are used sinusoidal or triangular velocity reference signal and 256 or 512 channels to form velocity signal. Such velocity driving system provides spectra measurement with a low velocity resolution (2 n =256 or 512 channels) with possibility to decrease measurement time and reach needed signal/noise ratio by spectra folding on the direct and reverse motion. However, these driving systems do not provide a low systematic error for velocity signal while folding increases integral velocity error due to different velocity errors on the direct and reverse motions. These problems can be neglected if a high precision is not required for spectra measurement. Nevertheless, further development of Moessbauer spectroscopy may be related to increase in precision and quality of spectra measurement with less instrumental (systematic) velocity error and to increase in velocity resolution for both spectrometer and spectrum. A new velocity driving system was developed for Moessbauer spectrometer SM- 2201. This system uses saw-tooth shape velocity reference signal and 2 n =4096 channels to form velocity signal. On the basis of SM-2201 and liquid nitrogen cryostat with moving absorber and temperature variation in the range of 295-85 K a new automated precision Moessbauer spectrometric system with a high velocity resolution was created

  12. KINETIC TEMPERATURES OF THE DENSE GAS CLUMPS IN THE ORION KL MOLECULAR CORE

    International Nuclear Information System (INIS)

    Wang, K.-S.; Kuan, Y.-J.; Liu, S.-Y.; Charnley, Steven B.

    2010-01-01

    High angular-resolution images of the J = 18 K -17 K emission of CH 3 CN in the Orion KL molecular core were observed with the Submillimeter Array (SMA). Our high-resolution observations clearly reveal that CH 3 CN emission originates mainly from the Orion Hot Core and the Compact Ridge, both within ∼15'' of the warm and dense part of Orion KL. The clumpy nature of the molecular gas in Orion KL can also be readily seen from our high-resolution SMA images. In addition, a semi-open cavity-like kinematic structure is evident at the location between the Hot Core and the Compact Ridge. We performed excitation analysis with the 'population diagram' method toward the Hot Core, IRc7, and the northern part of the Compact Ridge. Our results disclose a non-uniform temperature structure on small scales in Orion KL, with a range of temperatures from 190-620 K in the Hot Core. Near the Compact Ridge, the temperatures are found to be 170-280 K. Comparable CH 3 CN fractional abundances of 10 -8 to 10 -7 are found around both in the Hot Core and the Compact Ridge. Such high abundances require that a hot gas phase chemistry, probably involving ammonia released from grain mantles, plays an important role in forming these CH 3 CN molecules.

  13. A simple measurement method of molecular relaxation in a gas by reconstructing acoustic velocity dispersion

    Science.gov (United States)

    Zhu, Ming; Liu, Tingting; Zhang, Xiangqun; Li, Caiyun

    2018-01-01

    Recently, a decomposition method of acoustic relaxation absorption spectra was used to capture the entire molecular multimode relaxation process of gas. In this method, the acoustic attenuation and phase velocity were measured jointly based on the relaxation absorption spectra. However, fast and accurate measurements of the acoustic attenuation remain challenging. In this paper, we present a method of capturing the molecular relaxation process by only measuring acoustic velocity, without the necessity of obtaining acoustic absorption. The method is based on the fact that the frequency-dependent velocity dispersion of a multi-relaxation process in a gas is the serial connection of the dispersions of interior single-relaxation processes. Thus, one can capture the relaxation times and relaxation strengths of N decomposed single-relaxation dispersions to reconstruct the entire multi-relaxation dispersion using the measurements of acoustic velocity at 2N  +  1 frequencies. The reconstructed dispersion spectra are in good agreement with experimental data for various gases and mixtures. The simulations also demonstrate the robustness of our reconstructive method.

  14. WISDOM project - I. Black hole mass measurement using molecular gas kinematics in NGC 3665

    Science.gov (United States)

    Onishi, Kyoko; Iguchi, Satoru; Davis, Timothy A.; Bureau, Martin; Cappellari, Michele; Sarzi, Marc; Blitz, Leo

    2017-07-01

    As a part of the mm-Wave Interferometric Survey of Dark Object Masses (WISDOM) project, we present an estimate of the mass of the supermassive black hole (SMBH) in the nearby fast-rotator early-type galaxy NGC 3665. We obtained the Combined Array for Research in Millimeter Astronomy (CARMA) B and C array observations of the 12CO(J = 2 - 1) emission line with a combined angular resolution of 0.59 arcsec. We analysed and modelled the three-dimensional molecular gas kinematics, obtaining a best-fitting SMBH mass M_BH=5.75^{+1.49}_{-1.18} × 108 M⊙, a mass-to-light ratio at H-band (M/L)H = 1.45 ± 0.04 (M/L)⊙,H and other parameters describing the geometry of the molecular gas disc (statistical errors, all at 3σ confidence). We estimate the systematic uncertainties on the stellar M/L to be ≈0.2 (M/L)⊙,H, and on the SMBH mass to be ≈0.4 × 108 M⊙. The measured SMBH mass is consistent with that estimated from the latest correlations with galaxy properties. Following our older works, we also analysed and modelled the kinematics using only the major-axis position-velocity diagram, and conclude that the two methods are consistent.

  15. Collisional energy dependence of molecular ionization by metastable rare gas atoms

    International Nuclear Information System (INIS)

    Martin, R.M.; Parr, T.P.

    1979-01-01

    The collisional energy dependence of several molecular total ionization cross sections by metastable rare gas atoms was studied over the thermal energy region using the crossed molecular beam time-of-flight method. Results are reported for the collision systems He, Ne, and Ar ionizing the geometric isomers cis- and trans-dichloroethylene and ortho- and para-dichlorobenzene. The He ionization cross sections oscillate about an energy dependence of E/sup -1/2/ over the energy range 0.004--1.0 eV, and the Ar*+para-dichlorobenzene cross section oscillates about an energy dependence of E/sup -2/5/ over the energy range 0.011--0.64 eV. The remaining systems are characterized by ''bent'' E/sup -m/ dependences with m values of 0.56--0.70 at low energies changing to 0.07--0.29 at higher energies. Comparison with the slopes of the He* systems and the Ar*+para-dichlorobenzene system shows that the ''bent'' and ''oscillating'' energy dependences are similar except for the form of the cross section functions at the lowest energies. No systematic differences are found between the cross section energy dependences for ionization of different geometric isomers or for ionization by the different metastable rare gas atoms

  16. Treatment of open tibial fracture with bone defect caused by high velocity missiles: A case report

    Directory of Open Access Journals (Sweden)

    Golubović Zoran

    2013-01-01

    Full Text Available Introduction .Tibia fracture caused by high velocity missiles is mostly comminuted and followed by bone defect which makes their healing process extremely difficult and prone to numerous complications. Case Outline. A 34-year-old male was wounded at close range by a semi-automatic gun missile. He was wounded in the distal area of the left tibia and suffered a massive defect of the bone and soft tissue. After the primary treatment of the wound, the fracture was stabilized with an external fixator type Mitkovic, with convergent orientation of the pins. The wound in the medial region of the tibia was closed with the secondary stitch, whereas the wound in the lateral area was closed with the skin transplant after Thiersch. Due to massive bone defect in the area of the rifle-missile wound six months after injury, a medical team placed a reconstructive external skeletal fixator type Mitkovic and performed corticotomy in the proximal metaphyseal area of the tibia. By the method of bone transport (distractive osteogenesis, the bone defect of the tibia was replaced. After the fracture healing seven months from the secondary surgery, the fixator was removed and the patient was referred to physical therapy. Conclusion. Surgical treatment of wounds, external fixation, performing necessary debridement, adequate antibiotic treatment and soft and bone tissue reconstruction are essential in achieving good results in patients with the open tibial fracture with bone defect caused by high velocity missiles. Reconstruction of bone defect can be successfully treated by reconstructive external fixator Mitkovic. [Projekat Ministarstva nauke Republike Srbije, br. III 41017 i br. III 41004

  17. Numerical simulation of a high velocity impact on fiber reinforced materials

    International Nuclear Information System (INIS)

    Thoma, Klaus; Vinckier, David

    1994-01-01

    Whereas the calculation of a high velocity impact on isotropical materials can be done on a routine basis, the simulation of the impact and penetration process into nonisotropical materials such as reinforced concrete or fiber reinforced materials still is a research task.We present the calculation of an impact of a metallic fragment on a modern protective wall structure. Such lightweight protective walls typically consist of two layers, a first outer layer made out of a material with high hardness and a backing layer. The materials for the backing layer are preferably fiber reinforced materials. Such types of walls offer a protection against fragments in a wide velocity range.For our calculations we used a non-linear finite element Lagrange code with explicit time integration. To be able to simulate the high velocity penetration process with a continuous erosion of the impacting metallic fragment, we used our newly developed contact algorithm with eroding surfaces. This contact algorithm is vectorized to a high degree and especially robust as it was developed to work for a wide range of contact-impact problems. To model the behavior of the fiber reinforced material under the highly dynamic loads, we present a material model which initially was developed to calculate the crash behavior (automotive applications) of modern high strength fiber-matrix systems. The model can describe the failure and the postfailure behavior up to complete material crushing.A detailed simulation shows the impact of a metallic fragment with a velocity of 750ms -1 on a protective wall with two layers, the deformation and erosion of fragment and wall material and the failure of the fiber reinforced material. ((orig.))

  18. Modeling of liquid ceramic precursor droplets in a high velocity oxy-fuel flame jet

    International Nuclear Information System (INIS)

    Basu, Saptarshi; Cetegen, Baki M.

    2008-01-01

    Production of coatings by high velocity oxy-fuel (HVOF) flame jet processing of liquid precursor droplets can be an attractive alternative method to plasma processing. This article concerns modeling of the thermophysical processes in liquid ceramic precursor droplets injected into an HVOF flame jet. The model consists of several sub-models that include aerodynamic droplet break-up, heat and mass transfer within individual droplets exposed to the HVOF environment and precipitation of ceramic precursors. A parametric study is presented for the initial droplet size, concentration of the dissolved salts and the external temperature and velocity field of the HVOF jet to explore processing conditions and injection parameters that lead to different precipitate morphologies. It is found that the high velocity of the jet induces shear break-up into several μm diameter droplets. This leads to better entrainment and rapid heat-up in the HVOF jet. Upon processing, small droplets (<5 μm) are predicted to undergo volumetric precipitation and form solid particles prior to impact at the deposit location. Droplets larger than 5 μm are predicted to form hollow or precursor containing shells similar to those processed in a DC arc plasma. However, it is found that the lower temperature of the HVOF jet compared to plasma results in slower vaporization and solute mass diffusion time inside the droplet, leading to comparatively thicker shells. These shell-type morphologies may further experience internal pressurization, resulting in possibly shattering and secondary atomization of the trapped liquid. The consequences of these different particle states on the coating microstructure are also discussed in this article

  19. Physical conditions of the molecular gas in metal-poor galaxies

    Science.gov (United States)

    Hunt, L. K.; Weiß, A.; Henkel, C.; Combes, F.; García-Burillo, S.; Casasola, V.; Caselli, P.; Lundgren, A.; Maiolino, R.; Menten, K. M.; Testi, L.

    2017-10-01

    Studying the molecular component of the interstellar medium (ISM) in metal-poor galaxies has been challenging because of the faintness of carbon monoxide emission, the most common proxy of H2. Here we present new detections of molecular gas at low metallicities, and assess the physical conditions in the gas through various CO transitions for 8 galaxies. For one, NGC 1140 (Z/Z⊙ 0.3), two detections of 13CO isotopologues and atomic carbon, [Ci](1-0) and an upper limit for HCN(1-0) are also reported. After correcting to a common beam size, we compared 12CO(2-1)/12CO(1-0) (R21) and 12CO(3-2)/12CO(1-0) (R31) line ratios of our sample with galaxies from the literature and find that only NGC 1140 shows extreme values (R21 R31 2). Fitting physical models to the 12CO and 13CO emission in NGC 1140 suggests that the molecular gas is cool (kinetic temperature Tkin ≲ 20 K), dense (H2 volume density nH2 ≳ 106 cm-3), with moderate CO column density (NCO 1016 cm-2) and low filling factor. Surprisingly, the [12CO]/[13CO] abundance ratio in NGC 1140 is very low ( 8-20), lower even than the value of 24 found in the Galactic Center. The young age of the starburst in NGC 1140 precludes 13CO enrichment from evolved intermediate-mass stars; instead we attribute the low ratio to charge-exchange reactions and fractionation, because of the enhanced efficiency of these processes in cool gas at moderate column densities. Fitting physical models to 12CO and [Ci](1-0) emission in NGC 1140 gives an unusually low [12CO]/[12C] abundance ratio, suggesting that in this galaxy atomic carbon is at least 10 times more abundant than 12CO. Based on observations carried out with the IRAM 30 m and the Atacama Pathfinder Experiment (APEX). IRAM is supported by the INSU/CNRS (France), MPG (Germany), and IGN (Spain), and APEX is a collaboration between the Max-Planck-Institut fur Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory.

  20. A More Extreme View of Molecular Gas in the Center of the Milky Way galaxy

    Science.gov (United States)

    Mills, Elisabeth Anne Crossfield

    This thesis examines the molecular gas properties in the central 600 parsecs of the Galaxy (the CMZ). I first present a study of a group of HII regions in the central 10 parsecs embedded within the M-0.02-0.07 cloud, adjacent to the Sgr A East supernova remnant. To better depict the physical relationship between these sources, I use archival VLA observations and Paschen-alpha images from the Hubble Space telescope to determine the extinction toward the HII regions. From the measured extinctions and source morphologies, I determine that three of the HII regions lie on the front side of the cloud and formed in the eastern part of the cloud which is unaffected by the supernova remnant's expansion. The higher extinction of the fourth HII region indicates it is embedded in the supernova-compressed ridge, and though younger than the other HII regions, is still older than the supernova. This work is an important determination of the their line-of-sight placement of these sources which helps to define their interaction and strengthens the case that the supernova did not trigger the formation of the HII regions. I next present results from a project I led to survey a sample of CMZ clouds for hot gas using the Green Bank Telescope. I observe multiple highly-excited lines of ammonia, and detect emission from the (9,9) line of ammonia, (excitation energy = 840 K) in 13 of 17 clouds, many of which have no associated star formation. For the three strongest sources, I derive rotation temperatures of 400-500 K, substantially higher than previous temperatures of 200-300 K measured for these clouds. The widespread detections of gas hotter than 400 K indicates for the first time that his hot gas must be heated by global processes in the CMZ. These extremely high temperatures also suggest that cosmic rays are not responsible for the heating of this gas. I also present a determination of the density of the Circumnuclear disk (CND) in the central two parsecs using multiple transitions

  1. The Gas-Phase Formation of Methyl Formate in Hot Molecular Cores

    Science.gov (United States)

    Horn, Anne; Møllendal, Harald; Sekiguchi, Osamu; Uggerud, Einar; Roberts, Helen; Herbst, Eric; Viggiano, A. A.; Fridgen, Travis D.

    2004-08-01

    Methyl formate, HCOOCH3, is a well-known interstellar molecule prominent in the spectra of hot molecular cores. The current view of its formation is that it occurs in the gas phase from precursor methanol, which is synthesized on the surfaces of grain mantles during a previous colder era and evaporates while temperatures increase during the process of high-mass star formation. The specific reaction sequence thought to form methyl formate, the ion-molecule reaction between protonated methanol and formaldehyde followed by dissociative recombination of the protonated ion [HCO(H)OCH3]+, has not been studied in detail in the laboratory. We present here the results of both a quantum chemical study of the ion-molecule reaction between [CH3OH2]+ and H2CO as well as new experimental work on the system. In addition, we report theoretical and experimental studies for a variety of other possible gas-phase reactions leading to ion precursors of methyl formate. The studied chemical processes leading to methyl formate are included in a chemical model of hot cores. Our results show that none of these gas-phase processes produces enough methyl formate to explain its observed abundance.

  2. [Removal of toluene from waste gas by honeycomb adsorption rotor with modified 13X molecular sieves].

    Science.gov (United States)

    Wang, Jia-De; Zheng, Liang-Wei; Zhu, Run-Ye; Yu, Yun-Feng

    2013-12-01

    The removal of toluene from waste gas by Honeycomb Adsorption Rotor with modified 13X molecular sieves was systematically investigated. The effects of the rotor operating parameters and the feed gas parameters on the adsorption efficiency were clarified. The experimental results indicated that the honeycomb adsorption rotor had a good humidity resistance. The removal efficiency of honeycomb adsorption rotor achieved the maximal value with optimal rotor speed and optimal generation air temperature. Moreover, for an appropriate flow rate ratio the removal efficiency and energy consumption should be taken into account. When the recommended operating parameters were regeneration air temperature of 180 degrees C, rotor speed of 2.8-5 r x h(-1), flow rate ratio of 8-12, the removal efficiency kept over 90% for the toluene gas with concentration of 100 mg x m(-3) and inlet velocity of 2 m x s(-1). The research provided design experience and operating parameters for industrial application of honeycomb adsorption rotor. It showed that lower empty bed velocity, faster rotor speed and higher temperature were necessary to purify organic waste gases of higher concentrations.

  3. Molecular bio-dosimetry for carcinogenic risk assessment in survivors of Bhopal gas tragedy

    Directory of Open Access Journals (Sweden)

    Pradyumna Kumar Mishra

    2015-12-01

    Full Text Available December 2014 marked the 30th year anniversary of Bhopal gas tragedy. This sudden and accidental leakage of deadly poisonous methyl isocyanate (MIC gas instigated research efforts to understand the nature, severity of health damage and sufferings of 570 000 ailing survivors of this tragedy. In a decade-long period, our systematic laboratory investigations coupled with long-term molecular surveillance studies have comprehensively demonstrated that the risk of developing an environmental associated aberrant disease phenotype, including cancer, involves complex interplay of genomic and epigenetic reprogramming. These findings poised us to translate this knowledge into an investigative framework of “molecular biodosimetry” in a strictly selected cohort of MIC exposed individuals. A pragmatic cancer risk-assessment strategy pursued in concert with a large-scale epidemiological study might unfold molecular underpinnings of host-susceptibility and exposureresponse relationship. The challenges are enormous, but we postulate that the study will be necessary to establish a direct initiation-promotion paradigm of environmental carcinogenesis. Given that mitochondrial retrograde signaling-induced epigenetic reprogramming is apparently linked to neoplasticity, a cutting-edge tailored approach by an expert pool of biomedical researchers will be fundamental to drive these strategies from planning to execution. Validating the epigenomic signatures will hopefully result in the development of biomarkers to better protect human lives in an overburdened ecosystem, such as India, which is continuously challenged to meet population demands. Besides, delineating the mechanistic links between MIC exposure and cancer morbidity, our investigative strategy might help to formulate suitable regulatory policies and measures to reduce the overall burden of occupational and environmental carcinogenesis.

  4. Classical electron ionization mass spectra in gas chromatography/mass spectrometry with supersonic molecular beams.

    Science.gov (United States)

    Gordin, Alexander; Fialkov, Alexander B; Amirav, Aviv

    2008-09-01

    A major benefit of gas chromatography/mass spectrometry (GC/MS) with a supersonic molecular beam (SMB) interface and its fly-through ion source is the ability to obtain electron ionization of vibrationally cold molecules (cold EI), which show enhanced molecular ions. However, GC/MS with an SMB also has the flexibility to perform 'classical EI' mode of operation which provides mass spectra to mimic those in commercial 70 eV electron ionization MS libraries. Classical EI in SMB is obtained through simple reduction of the helium make-up gas flow rate, which reduces the SMB cooling efficiency; hence the vibrational temperatures of the molecules are similar to those in traditional EI ion sources. In classical EI-SMB mode, the relative abundance of the molecular ion can be tuned and, as a result, excellent identification probabilities and very good matching factors to the NIST MS library are obtained. Classical EI-SMB with the fly-through dual cage ion source has analyte sensitivity similar to that of the standard EI ion source of a basic GC/MS system. The fly-through EI ion source in combination with the SMB interface can serve for cold EI, classical EI-SMB, and cluster chemical ionization (CCI) modes of operation, all easily exchangeable through a simple and quick change (not involving hardware). Furthermore, the fly-through ion source eliminates sample scattering from the walls of the ion source, and thus it offers full sample inertness, tailing-free operation, and no ion-molecule reaction interferences. It is also robust and enables increased column flow rate capability without affecting the sensitivity.

  5. Experience of molecular monitoring techniques in upstream oil and gas operations

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, Anthony F.; Anfindsen, Hilde; Liengen, Turid; Molid, Solfrid [Statoil ASA (Denmark)

    2011-07-01

    For a numbers of years, molecular monitoring tools have been used in upstream oil and gas operations but the results have given only limited added value. This paper discusses the various techniques available for upstream molecular monitoring which provides scope for identification of microbial influenced problems. The methodology, which consists of analyzing solid samples using traditional as well as molecular techniques, is detailed. Two cases were studied with the objective of determining if microbial contamination was contributing to the problem. The first case was a study of amorphous deposits in production wells and mainly iron sulphide was found. The second study was of amorphous deposits in water injection wells and the analysis showed typical components of drilling and completion fluids with some organic material. Two more cases, corrosion of tubing in a water injection well and flow line corrosion, are discussed and the results are given. From the study, it can be concluded that failure can be due to several factors, chemical and biological.

  6. PHIBSS: MOLECULAR GAS, EXTINCTION, STAR FORMATION, AND KINEMATICS IN THE z = 1.5 STAR-FORMING GALAXY EGS13011166

    Energy Technology Data Exchange (ETDEWEB)

    Genzel, R.; Tacconi, L. J.; Kurk, J.; Wuyts, S.; Foerster Schreiber, N. M.; Gracia-Carpio, J. [Max-Planck-Institut fuer extraterrestrische Physik (MPE), Giessenbachstr., D-85748 Garching (Germany); Combes, F.; Freundlich, J. [Observatoire de Paris, LERMA, CNRS, 61 Av. de l' Observatoire, F-75014 Paris (France); Bolatto, A. [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Cooper, M. C. [Department of Physics and Astronomy, Frederick Reines Hall, University of California, Irvine, CA 92697 (United States); Neri, R. [IRAM, 300 Rue de la Piscine, F-38406 St. Martin d' Heres, Grenoble (France); Nordon, R. [Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel); Bournaud, F. [Service d' Astrophysique, DAPNIA, CEA/Saclay, F-91191 Gif-sur-Yvette Cedex (France); Burkert, A. [Universitaetssternwarte der Ludwig-Maximiliansuniversitaet, Scheinerstr. 1, D-81679 Muenchen (Germany); Comerford, J. [Department of Astronomy and McDonald Observatory, 1 University Station, C1402 Austin, TX 78712-0259 (United States); Cox, P. [Department of Physics, Le Conte Hall, University of California, 94720 Berkeley, CA (United States); Davis, M. [Department of Astronomy, Campbell Hall, University of California, Berkeley, CA 94720 (United States); Garcia-Burillo, S. [Observatorio Astronomico Nacional-OAN, Observatorio de Madrid, Alfonso XII, 3, E-28014 Madrid (Spain); Naab, T. [Max-Planck Institut fuer Astrophysik, Karl Schwarzschildstrasse 1, D-85748 Garching (Germany); Lutz, D., E-mail: genzel@mpe.mpg.de, E-mail: linda@mpe.mpg.de; and others

    2013-08-10

    We report matched resolution imaging spectroscopy of the CO 3-2 line (with the IRAM Plateau de Bure millimeter interferometer) and of the H{alpha} line (with LUCI at the Large Binocular Telescope) in the massive z = 1.53 main-sequence galaxy EGS 13011166, as part of the ''Plateau de Bure high-z, blue-sequence survey'' (PHIBSS: Tacconi et al.). We combine these data with Hubble Space Telescope V-I-J-H-band maps to derive spatially resolved distributions of stellar surface density, star formation rate, molecular gas surface density, optical extinction, and gas kinematics. The spatial distribution and kinematics of the ionized and molecular gas are remarkably similar and are well modeled by a turbulent, globally Toomre unstable, rotating disk. The stellar surface density distribution is smoother than the clumpy rest-frame UV/optical light distribution and peaks in an obscured, star-forming massive bulge near the dynamical center. The molecular gas surface density and the effective optical screen extinction track each other and are well modeled by a ''mixed'' extinction model. The inferred slope of the spatially resolved molecular gas to star formation rate relation, N = dlog{Sigma}{sub starform}/dlog{Sigma}{sub molgas}, depends strongly on the adopted extinction model, and can vary from 0.8 to 1.7. For the preferred mixed dust-gas model, we find N = 1.14 {+-} 0.1.

  7. The SAMI Galaxy Survey: a new method to estimate molecular gas surface densities from star formation rates

    Science.gov (United States)

    Federrath, Christoph; Salim, Diane M.; Medling, Anne M.; Davies, Rebecca L.; Yuan, Tiantian; Bian, Fuyan; Groves, Brent A.; Ho, I.-Ting; Sharp, Robert; Kewley, Lisa J.; Sweet, Sarah M.; Richards, Samuel N.; Bryant, Julia J.; Brough, Sarah; Croom, Scott; Scott, Nicholas; Lawrence, Jon; Konstantopoulos, Iraklis; Goodwin, Michael

    2017-07-01

    Stars form in cold molecular clouds. However, molecular gas is difficult to observe because the most abundant molecule (H2) lacks a permanent dipole moment. Rotational transitions of CO are often used as a tracer of H2, but CO is much less abundant and the conversion from CO intensity to H2 mass is often highly uncertain. Here we present a new method for estimating the column density of cold molecular gasgas) using optical spectroscopy. We utilize the spatially resolved Hα maps of flux and velocity dispersion from the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey. We derive maps of Σgas by inverting the multi-freefall star formation relation, which connects the star formation rate surface density (ΣSFR) with Σgas and the turbulent Mach number (M). Based on the measured range of ΣSFR = 0.005-1.5 {M_{⊙} yr^{-1} kpc^{-2}} and M=18-130, we predict Σgas = 7-200 {M_{⊙} pc^{-2}} in the star-forming regions of our sample of 260 SAMI galaxies. These values are close to previously measured Σgas obtained directly with unresolved CO observations of similar galaxies at low redshift. We classify each galaxy in our sample as 'star-forming' (219) or 'composite/AGN/shock' (41), and find that in 'composite/AGN/shock' galaxies the average ΣSFR, M and Σgas are enhanced by factors of 2.0, 1.6 and 1.3, respectively, compared to star-forming galaxies. We compare our predictions of Σgas with those obtained by inverting the Kennicutt-Schmidt relation and find that our new method is a factor of 2 more accurate in predicting Σgas, with an average deviation of 32 per cent from the actual Σgas.

  8. Galaxy pairs in the SDSS - XIII. The connection between enhanced star formation and molecular gas properties in galaxy mergers

    Science.gov (United States)

    Violino, Giulio; Ellison, Sara L.; Sargent, Mark; Coppin, Kristen E. K.; Scudder, Jillian M.; Mendel, Trevor J.; Saintonge, Amelie

    2018-05-01

    We investigate the connection between star formation and molecular gas properties in galaxy mergers at low redshift (z ≤ 0.06). The study we present is based on IRAM 30-m CO(1-0) observations of 11 galaxies with a close companion selected from the Sloan Digital Sky Survey (SDSS). The pairs have mass ratios ≤4, projected separations rp ≤ 30 kpc and velocity separations ΔV ≤ 300 km s-1, and have been selected to exhibit enhanced specific star formation rates (sSFRs). We calculate molecular gas (H2) masses, assigning to each galaxy a physically motivated conversion factor αCO, and we derive molecular gas fractions and depletion times. We compare these quantities with those of isolated galaxies from the extended CO Legacy Data base for the GALEX Arecibo SDSS Survey sample (xCOLDGASS; Saintonge et al.) with gas quantities computed in an identical way. Ours is the first study which directly compares the gas properties of galaxy pairs and those of a control sample of normal galaxies with rigorous control procedures and for which SFR and H2 masses have been estimated using the same method. We find that the galaxy pairs have shorter depletion times and an average molecular gas fraction enhancement of 0.4 dex compared to the mass matched control sample drawn from xCOLDGASS. However, the gas masses (and fractions) in galaxy pairs and their depletion times are consistent with those of non-mergers whose SFRs are similarly elevated. We conclude that both external interactions and internal processes may lead to molecular gas enhancement and decreased depletion times.

  9. Design Optimization of Liquid Fueled High Velocity Oxy- Fuel Thermal Spraying Technique for Durable Coating for Fossil Power Systems

    Energy Technology Data Exchange (ETDEWEB)

    Choudhuri, Ahsan [Univ. of Texas, El Paso, TX (United States); Love, Norman [Univ. of Texas, El Paso, TX (United States)

    2016-11-04

    High-velocity oxy–fuel (HVOF) thermal spraying was developed in 1930 and has been commercially available for twenty-five years. HVOF thermal spraying has several benefits over the more conventional plasma spray technique including a faster deposition rate which leads to quicker turn-around, with more durable coatings and higher bond strength, hardness and wear resistance due to a homogeneous distribution of the sprayed particles. HVOF thermal spraying is frequently used in engineering to deposit cermets, metallic alloys, composites and polymers, to enhance product life and performance. HVOF thermal spraying system is a highly promising technique for applying durable coatings on structural materials for corrosive and high temperature environments in advanced ultra-supercritical coal- fired (AUSC) boilers, steam turbines and gas turbines. HVOF thermal spraying is the preferred method for producing coatings with low porosity and high adhesion. HVOF thermal spray process has been shown to be one of the most efficient techniques to deposit high performance coatings at moderate cost. Variables affecting the deposit formation and coating properties include hardware characteristics such as nozzle geometry and spraying distance and process parameters such as equivalence ratio, gas flow density, and powder feedstock. In the spray process, the powder particles experience very high speeds combined with fast heating to the powder material melting point or above. This high temperature causes evaporation of the powder, dissolution, and phase transformations. Due to the complex nature of the HVOF technique, the control and optimization of the process is difficult. In general, good coating quality with suitable properties and required performance for specific applications is the goal in producing thermal spray coatings. In order to reach this goal, a deeper understanding of the spray process as a whole is needed. Although many researchers studied commercial HVOF thermal spray

  10. STRUCTURAL VARIATION OF MOLECULAR GAS IN THE SAGITTARIUS ARM AND INTERARM REGIONS

    Energy Technology Data Exchange (ETDEWEB)

    Sawada, Tsuyoshi; Hasegawa, Tetsuo; Sugimoto, Masahiro [Joint ALMA Office, Alonso de Cordova 3107, Vitacura, Santiago 763-0355 (Chile); Koda, Jin [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States); Handa, Toshihiro, E-mail: sawada.tsuyoshi@nao.ac.jp [Department of Physics, Faculty of Science, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065 (Japan)

    2012-06-20

    We have carried out survey observations toward the Galactic plane at l Almost-Equal-To 38 Degree-Sign in the {sup 12}CO and {sup 13}CO J = 1-0 lines using the Nobeyama Radio Observatory 45 m telescope. A wide area (0.{sup 0}8 Multiplication-Sign 0.{sup 0}8) was mapped with high spatial resolution (17''). The line of sight samples the gas in both the Sagittarius arm and the interarm regions. The present observations reveal how the structure and physical conditions vary across a spiral arm. We classify the molecular gas in the line of sight into two distinct components based on its appearance: the bright and compact B component and the fainter and diffuse (i.e., more extended) D component. The B component is predominantly seen at the spiral arm velocities, while the D component dominates at the interarm velocities and is also found at the spiral arm velocities. We introduce the brightness distribution function and the brightness distribution index (BDI, which indicates the dominance of the B component) in order to quantify the map's appearance. The radial velocities of BDI peaks coincide with those of high {sup 12}CO J = 3-2/{sup 12}CO J = 1-0 intensity ratio (i.e., warm gas) and H II regions, and tend to be offset from the line brightness peaks at lower velocities (i.e., presumably downstream side of the arm). Our observations reveal that the gas structure at small scales changes across a spiral arm: bright and spatially confined structures develop in a spiral arm, leading to star formation at the downstream side, while extended emission dominates in the interarm region.

  11. MOLECULAR SPECTROSCPY AND REACTIONS OF ACTINIDES IN THE GAS PHASE AND CRYOGENIC MATRICES

    Energy Technology Data Exchange (ETDEWEB)

    Heaven, Michael C.; Gibson, John K.; Marcalo, Joaquim

    2009-02-01

    In this chapter we review the spectroscopic data for actinide molecules and the reaction dynamics for atomic and molecular actinides that have been examined in the gas phase or in inert cryogenic matrices. The motivation for this type of investigation is that physical properties and reactions can be studied in the absence of external perturbations (gas phase) or under minimally perturbing conditions (cryogenic matrices). This information can be compared directly with the results from high-level theoretical models. The interplay between experiment and theory is critically important for advancing our understanding of actinide chemistry. For example, elucidation of the role of the 5f electrons in bonding and reactivity can only be achieved through the application of experimentally verified theoretical models. Theoretical calculations for the actinides are challenging due the large numbers of electrons that must be treated explicitly and the presence of strong relativistic effects. This topic has been reviewed in depth in Chapter 17 of this series. One of the goals of the experimental work described in this chapter has been to provide benchmark data that can be used to evaluate both empirical and ab initio theoretical models. While gas-phase data are the most suitable for comparison with theoretical calculations, there are technical difficulties entailed in generating workable densities of gas-phase actinide molecules that have limited the range of species that have been characterized. Many of the compounds of interest are refractory, and problems associated with the use of high temperature vapors have complicated measurements of spectra, ionization energies, and reactions. One approach that has proved to be especially valuable in overcoming this difficulty has been the use of pulsed laser ablation to generate plumes of vapor from refractory actinide-containing materials. The vapor is entrained in an inert gas, which can be used to cool the actinide species to room

  12. xGASS: total cold gas scaling relations and molecular-to-atomic gas ratios of galaxies in the local Universe

    Science.gov (United States)

    Catinella, Barbara; Saintonge, Amélie; Janowiecki, Steven; Cortese, Luca; Davé, Romeel; Lemonias, Jenna J.; Cooper, Andrew P.; Schiminovich, David; Hummels, Cameron B.; Fabello, Silvia; Geréb, Katinka; Kilborn, Virginia; Wang, Jing

    2018-05-01

    We present the extended GALEX Arecibo SDSS Survey (xGASS), a gas fraction-limited census of the atomic hydrogen (H I) gas content of 1179 galaxies selected only by stellar mass (M⋆ = 109-1011.5 M⊙) and redshift (0.01 new Arecibo observations of 208 galaxies, for which we release catalogues and H I spectra. In addition to extending the GASS H I scaling relations by one decade in stellar mass, we quantify total (atomic+molecular) cold gas fractions and molecular-to-atomic gas mass ratios, Rmol, for the subset of 477 galaxies observed with the IRAM 30 m telescope. We find that atomic gas fractions keep increasing with decreasing stellar mass, with no sign of a plateau down to log M⋆/M⊙ = 9. Total gas reservoirs remain H I-dominated across our full stellar mass range, hence total gas fraction scaling relations closely resemble atomic ones, but with a scatter that strongly correlates with Rmol, especially at fixed specific star formation rate. On average, Rmol weakly increases with stellar mass and stellar surface density μ⋆, but individual values vary by almost two orders of magnitude at fixed M⋆ or μ⋆. We show that, for galaxies on the star-forming sequence, variations of Rmol are mostly driven by changes of the H I reservoirs, with a clear dependence on μ⋆. Establishing if galaxy mass or structure plays the most important role in regulating the cold gas content of galaxies requires an accurate separation of bulge and disc components for the study of gas scaling relations.

  13. CONSTRAINING DUST AND MOLECULAR GAS PROPERTIES IN Ly{alpha} BLOBS AT z {approx} 3

    Energy Technology Data Exchange (ETDEWEB)

    Yang Yujin; Decarli, Roberto; Walter, Fabian; Leipski, Christian [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, Heidelberg (Germany); Dannerbauer, Helmut; Le Floc' h, Emeric [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, Irfu/Service d' Astrophysique, CEA-Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette Cedex (France); Weiss, Axel; Menten, Karl M. [Max-Planck-Insitut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Dey, Arjun [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Chapman, Scott C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Prescott, Moire K. M. [Department of Physics, Broida Hall, Mail Code 9530, University of California, Santa Barbara, CA 93106 (United States); Neri, Roberto [IRAM-Institut de Radio Astronomie Millimetrique, 300 rue de la Piscine, 38406 Saint-Martin d' Heres (France); Borys, Colin [IPAC, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Matsuda, Yuichi [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Yamada, Toru [Astronomical Institute, Tohoku University, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578 (Japan); Hayashino, Tomoki [Research Center for Neutrino Science, Graduate School of Science, Tohoku University, Sendai 980-8578 (Japan); Tapken, Christian [Leibnitz-Institut fuer Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam (Germany)

    2012-01-10

    In order to constrain the bolometric luminosities, dust properties, and molecular gas content of giant Ly{alpha} nebulae, the so-called Ly{alpha} blobs, we have carried out a study of dust continuum and CO line emission in two well-studied representatives of this population at z {approx} 3: an Ly{alpha} blob discovered by its strong Spitzer Multiband Infrared Photometer 24 {mu}m detection (LABd05) and the Steidel blob 1 (SSA22-LAB01). We find that the spectral energy distribution of LABd05 is well described by an active-galactic-nucleus-starburst composite template with L{sub FIR} = (4.0 {+-} 0.5) Multiplication-Sign 10{sup 12} L{sub Sun }, comparable to high-z submillimeter galaxies and ultraluminous infrared galaxies. New Large APEX Bolometer Camera 870 {mu}m measurements rule out the reported Submillimeter Common-User Bolometer Array detection of the SSA22-LAB01 (S{sub 850{mu}m} = 16.8 mJy) at the >4{sigma} level. Consistent with this, ultradeep Plateau de Bure Interferometer observations with {approx}2'' spatial resolution also fail to detect any 1.2 mm continuum source down to Almost-Equal-To 0.45 mJy beam{sup -1} (3{sigma}). Combined with the existing (sub)millimeter observations in the literature, we conclude that the FIR luminosity of SSA22-LAB01 remains uncertain. No CO line is detected in either case down to integrated flux limits of S{sub {nu}}{Delta}V {approx}< 0.25-1.0 Jy km s{sup -1}, indicating a modest molecular gas reservoir, M(H{sub 2}) < (1-3) Multiplication-Sign 10{sup 10} M{sub Sun }. The non-detections exclude, with high significance (12{sigma}), the previous tentative detection of a CO J = 4-3 line in the SSA22-LAB01. The increased sensitivity afforded by the Atacama Large Millimeter/submillimeter Array will be critical in studying molecular gas and dust in these interesting systems.

  14. Electron Scattering Studies of Gas Phase Molecular Structure at High Temperature

    Science.gov (United States)

    Mawhorter, Richard J., Jr.

    A high precision counting electron diffraction study of the structure of gaseous sulfur dioxide as a function of temperature from 300(DEGREES) to 1000(DEGREES)K is presented. The results agree well with current theory, and yield insight into the effects of anharmonicity on molecular structure. Another aspect of molecular structure is the molecular charge density distribution. The difference (DELTA)(sigma) is between the electron scattering cross sections for the actual molecule and independent atom model (IAM) are a sensitive measure of the change in this distribution due to bond formation. These difference cross sections have been calculated using ab initio methods, and the results for a wide range of simple polyatomic molecules are presented. Such calculations are routinely done for a single, fixed molecular geometry, an approach which neglects the effects of the vibrational motion of real molecules. The effect of vibrational averaging is studied in detail for the three normal vibrational modes of H(,2)O in the ground state. The effects are small, lending credence to the practice of comparing cross sections calculated at a fixed geometry with inherently averaged experimental data. The efficacy of the standard formula used to account for vibrational averaging in the IAM is also examined. Finally, the nature of the ionic bond is probed with an experimental study of the structure of alkali chlorides, NaCl, KCl, RbCl, and CsCl, in the gas phase. Temperatures from 840-960(DEGREES)K were required to achieve the necessary vapor pressures of approximately 0.01 torr. A planar rhombic structure for the dimer molecule is confirmed, with a fairly uniform decrease of the chlorine-alkali-chlorine angle as the alkalis increase in size. The experiment also yields information on the amount of dimer present in the vapor, and these results are compared with thermodynamic values.

  15. MILKY WAY STAR-FORMING COMPLEXES AND THE TURBULENT MOTION OF THE GALAXY'S MOLECULAR GAS

    International Nuclear Information System (INIS)

    Lee, Eve J.; Rahman, Mubdi; Murray, Norman

    2012-01-01

    We analyze Spitzer GLIMPSE, Midcourse Space Experiment (MSX), and Wilkinson Microwave Anisotropy Probe (WMAP) images of the Milky Way to identify 8 μm and free-free sources in the Galaxy. Seventy-two of the 88 WMAP sources have coverage in the GLIMPSE and MSX surveys suitable for identifying massive star-forming complexes (SFCs). We measure the ionizing luminosity functions of the SFCs and study their role in the turbulent motion of the Galaxy's molecular gas. We find a total Galactic free-free flux f ν = 46,177.6 Jy; the 72 WMAP sources with full 8 μm coverage account for 34,263.5 Jy (∼75%), with both measurements made at ν = 94 GHz (W band). We find a total of 280 SFCs, of which 168 have unique kinematic distances and free-free luminosities. We use a simple model for the radial distribution of star formation to estimate the free-free and ionizing luminosity for the sources lacking distance determinations. The total dust-corrected ionizing luminosity is Q = (2.9 ± 0.5) × 10 53 photons s –1 , which implies a Galactic star formation rate of M-dot * = 1.2±0.2 M ☉ yr -1 . We present the (ionizing) luminosity function of the SFCs and show that 24 sources emit half the ionizing luminosity of the Galaxy. The SFCs appear as bubbles in GLIMPSE or MSX images; the radial velocities associated with the bubble walls allow us to infer the expansion velocity of the bubbles. We calculate the kinetic luminosity of the bubble expansion and compare it to the turbulent luminosity of the inner molecular disk. SFCs emitting 80% of the total Galactic free-free luminosity produce a kinetic luminosity equal to 65% of the turbulent luminosity in the inner molecular disk. This suggests that the expansion of the bubbles is a major driver of the turbulent motion of the inner Milky Way molecular gas.

  16. Molecular Line Emission as a Tool for Galaxy Observations (LEGO). I. HCN as a tracer of moderate gas densities in molecular clouds and galaxies

    Science.gov (United States)

    Kauffmann, Jens; Goldsmith, Paul F.; Melnick, Gary; Tolls, Volker; Guzman, Andres; Menten, Karl M.

    2017-09-01

    Trends observed in galaxies, such as the Gao & Solomon relation, suggest a linear relationship between the star formation rate and the mass of dense gas available for star formation. Validation of such trends requires the establishment of reliable methods to trace the dense gas in galaxies. One frequent assumption is that the HCN (J = 1-0) transition is unambiguously associated with gas at H2 densities ≫ 104 cm-3. If so, the mass of gas at densities ≫ 104 cm-3 could be inferred from the luminosity of this emission line, LHCN (1-0). Here we use observations of the Orion A molecular cloud to show that the HCN (J = 1-0) line traces much lower densities 103 cm-3 in cold sections of this molecular cloud, corresponding to visual extinctions AV ≈ 6 mag. We also find that cold and dense gas in a cloud like Orion produces too little HCN emission to explain LHCN (1-0) in star forming galaxies, suggesting that galaxies might contain a hitherto unknown source of HCN emission. In our sample of molecules observed at frequencies near 100 GHz (also including 12CO, 13CO, C18O, CN, and CCH), N2H+ is the only species clearly associated with relatively dense gas.

  17. Probing Conditions at Ionized/Molecular Gas Interfaces With High Resolution Near-Infrared Spectroscopy

    Science.gov (United States)

    Kaplan, Kyle Franklin

    2017-08-01

    Regions of star formation and star death in our Galaxy trace the cycle of gas and dust in the interstellar medium (ISM). Gas in dense molecular clouds collapses to form stars, and stars at the end of their lives return the gas that made up their outer layers back out into the Galaxy. Hot stars generate copious amounts of ultraviolet photons which interact with the surrounding medium and dominate the energetics, ionization state, and chemistry of the gas. The interface where molecular gas is being dissociated into neutral atomic gas by far-UV photons from a nearby hot source is called a photodissociation or photon-dominated region (PDR). PDRs are found primarily in star forming regions where O and B stars serve as the source of UV photons, and in planetary nebulae where the hot core of the dying star acts as the UV source. The main target of this dissertation is molecular hydrogen (H2), the most abundant molecule in the Universe, made from hydrogen formed during the Big Bang. H2 makes up the overwhelming majority of molecules found in the ISM and in PDRs. Far-UV radiation absorbed by H2 will excite an electron in the molecule. The molecule then either dissociates ( 10% of the time; Field et al. 1966) or decays into excited rotational and vibrational ("rovibrational") levels of the electronic ground state. These excited rovibrational levels then decay via a radiative cascade to the ground rovibrational state (v = 0, J = 0), giving rise to a large number of transitions observable in emission from the mid-IR to the optical (Black & van Dishoeck, 1987). These transitions provide an excellent probe of the excitation and conditions within the gas. These transitions are also observed in warm H2, such as in shocks, where collisions excite H2 to higher rovibrational levels. High resolution near-infrared spectroscopy, with its ability to see through dust, and avoid telluric absorption and emission, serves as an effective tool to detect emission from ions, atoms, and molecules

  18. Detection of a noble gas molecular ion, 36ArH+, in the Crab Nebula.

    Science.gov (United States)

    Barlow, M J; Swinyard, B M; Owen, P J; Cernicharo, J; Gomez, H L; Ivison, R J; Krause, O; Lim, T L; Matsuura, M; Miller, S; Olofsson, G; Polehampton, E T

    2013-12-13

    Noble gas molecules have not hitherto been detected in space. From spectra obtained with the Herschel Space Observatory, we report the detection of emission in the 617.5- and 1234.6-gigahertz J = 1-0 and 2-1 rotational lines of (36)ArH(+) at several positions in the Crab Nebula, a supernova remnant known to contain both molecular hydrogen and regions of enhanced ionized argon emission. Argon-36 is believed to have originated from explosive nucleosynthesis in massive stars during core-collapse supernova events. Its detection in the Crab Nebula, the product of such a supernova event, confirms this expectation. The likely excitation mechanism for the observed (36)ArH(+) emission lines is electron collisions in partially ionized regions with electron densities of a few hundred per centimeter cubed.

  19. Gas-Transport-Property Performance of Hybrid Carbon Molecular Sieve−Polymer Materials

    KAUST Repository

    Das, Mita

    2010-10-06

    High-performance hybrid materials using carbon molecular sieve materials and 6FDA-6FpDA were produced. A detailed analysis of the effects of casting processes and the annealing temperature is reported. Two existing major obstacles, sieve agglomeration and residual stress, were addressed in this work, and subsequently a new membrane formation technique was developed to produce high-performing membranes. The successfully improved interfacial region of the hybrid membranes allows the sieves to increase the selectivity of the membranes above the neat polymer properties. Furthermore, an additional performance enhancement was seen with increased sieve loading in the hybrid membranes, leading to an actual performance above the upper bound for pure polymer membranes. The membranes were also tested under a mixed-gas environment, which further demonstrated promising results. © 2010 American Chemical Society.

  20. Selective vibrational pumping of molecular hydrogen via gas phase atomic recombination.

    Science.gov (United States)

    Esposito, Fabrizio; Capitelli, Mario

    2009-12-31

    Formation of rovibrational excited molecular hydrogen from atomic recombination has been computationally studied using three body dynamics and orbiting resonance theory. Each of the two methods in the frame of classical mechanics, that has been used for all of the calculations, appear complementary rather than complete, with similar values in the low temperature region, and predominance of three body dynamics for temperatures higher than about 1000 K. The sum of the two contributions appears in fairly good agreement with available data from the literature. Dependence of total recombination on the temperature over pressure ratio is stressed. Detailed recombination toward rovibrational states is presented, with large evidence of importance of rotation in final products. Comparison with gas-surface recombination implying only physiadsorbed molecules shows approximate similarities at T = 5000 K, being on the contrary different at lower temperature.

  1. ALLSMOG, the APEX Low-redshift Legacy Survey for MOlecular Gas

    Science.gov (United States)

    Bothwell, M.; Cicone, C.; Wagg, J.; De Breuck, C..

    2017-09-01

    We report the completion of the APEX Low-redshift Legacy Survey for MOlecular Gas (ALLSMOG), an ESO Large Programme, carried out with the Atacama Pathfinder EXperiment (APEX) between 2013 and 2016. With a total of 327 hours of APEX observing time, we observed the 12CO(2-1) line in 88 nearby low-mass star-forming galaxies. We briefly outline the ALLSMOG goals and design, and describe a few science highlights that have emerged from the survey so far. We outline future work that will ensure that the ALLSMOG dataset continues to provide scientific value in the coming years. ALLSMOG was designed to be a reference legacy survey and as such all reduced data products are publicly available through the ESO Science Archive Phase 3 interface.

  2. Advances in the application of molecular microbiological methods in the oil and gas industry and links to microbiologically influenced corrosion

    DEFF Research Database (Denmark)

    Eckert, Rickard; Skovhus, Torben Lund

    2018-01-01

    While the oil and gas industry has witnessed increased applications of molecular microbiological methods (MMMs) for diagnosing and managing microbiologically influenced corrosion (MIC) in the past decade, the process for establishing clear links between microbiological conditions and corrosion...... mechanisms is still emerging. Different MMMs provide various types of information about microbial diversity, abundance, activity and function, all of which are quite different from the culture-based results that are familiar to oil and gas industry corrosion professionals. In addition, a multidisciplinary...

  3. Pure and Modified Co-Poly(amide-12-b-ethylene oxide) Membranes for Gas Separation Studied by Molecular Investigations.

    Science.gov (United States)

    De Lorenzo, Luana; Tocci, Elena; Gugliuzza, Annarosa; Drioli, Enrico

    2012-06-28

    This paper deals with a theoretical investigation of gas transport properties in a pure and modified PEBAX block copolymer membrane with N-ethyl-o/p-toluene sulfonamide (KET) as additive molecules. Molecular dynamics simulations using COMPASS force field, Gusev-Suter Transition State Theory (TST) and Monte Carlo methods were used. Bulk models of PEBAX and PEBAX/KET in different copolymer/additive compositions were assembled and analyzed to evaluate gas permeability and morphology to characterize structure-performance relationships.

  4. The Dense Molecular Gas and Nuclear Activity in the ULIRG IRAS 13120–5453

    Energy Technology Data Exchange (ETDEWEB)

    Privon, G. C.; Treister, E. [Instituto de Astrofśica, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22 (Chile); Aalto, S.; Falstad, N.; Muller, S.; Costagliola, F. [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-439 94 Onsala (Sweden); González-Alfonso, E. [Universidad de Alcalá, Departamento de Física y Matemáticas, Campus Universitario, E-28871 Alcalá de Henares, Madrid (Spain); Sliwa, K. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Armus, L. [Spitzer Science Center, California Institute of Technology, MS 220-6, Pasadena, CA, 91125 (United States); Evans, A. S. [Department of Astronomy, University of Virginia, Charlottesville, VA 22903 (United States); Garcia-Burillo, S. [Observatorio de Madrid, OAN-IGN, Alfonso XII, 3, E-28014-Madrid (Spain); Izumi, T. [Institute of Astronomy, School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Sakamoto, K. [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, 10617, Taipei, Taiwan (China); Werf, P. van der [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Chu, J. K. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2017-02-01

    We present new Atacama Large Millimeter/submillimeter Array Band 7 (∼340 GHz) observations of the dense gas tracers HCN, HCO{sup +}, and CS in the local, single-nucleus, ultraluminous infrared galaxy IRAS 13120–5453. We find centrally enhanced HCN (4–3) emission, relative to HCO{sup +} (4–3), but do not find evidence for radiative pumping of HCN. Considering the size of the starburst (0.5 kpc) and the estimated supernovae rate of ∼1.2 yr{sup −1}, the high HCN/HCO{sup +} ratio can be explained by an enhanced HCN abundance as a result of mechanical heating by the supernovae, though the active galactic nucleus and winds may also contribute additional mechanical heating. The starburst size implies a high Σ{sub IR} of 4.7 × 10{sup 12} L {sub ⊙} kpc{sup −2}, slightly below predictions of radiation-pressure limited starbursts. The HCN line profile has low-level wings, which we tentatively interpret as evidence for outflowing dense molecular gas. However, the dense molecular outflow seen in the HCN line wings is unlikely to escape the Galaxy and is destined to return to the nucleus and fuel future star formation. We also present modeling of Herschel observations of the H{sub 2}O lines and find a nuclear dust temperature of ∼40 K. IRAS 13120–5453 has a lower dust temperature and Σ{sub IR} than is inferred for the systems termed “compact obscured nuclei (CONs)” (such as Arp 220 and Mrk 231). If IRAS 13120–5453 has undergone a CON phase, we are likely witnessing it at a time when the feedback has already inflated the nuclear ISM and diluted star formation in the starburst/active galactic nucleus core.

  5. HERSCHEL-SPIRE IMAGING SPECTROSCOPY OF MOLECULAR GAS IN M82

    Energy Technology Data Exchange (ETDEWEB)

    Kamenetzky, J.; Glenn, J.; Rangwala, N.; Maloney, P. [Center for Astrophysics and Space Astronomy, 389-UCB, University of Colorado, Boulder, CO 80303 (United States); Bradford, M. [NASA Jet Propulsion Laboratory, Pasadena, CA 91109 (United States); Wilson, C. D.; Schirm, M. R. P. [Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Bendo, G. J. [UK ALMA Regional Centre Node, Jordell Bank Center for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Baes, M. [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, 9000 Gent (Belgium); Boselli, A. [Laboratoire d' Astrophysique de Marseille, UMR6110 CNRS, 38 rue F. Joliot-Curie, 13388 Marseille (France); Cooray, A. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Isaak, K. G. [ESA Astrophysics Missions Division, ESTEC, P.O. Box 299, 2200 AG Noordwijk (Netherlands); Lebouteiller, V.; Madden, S.; Panuzzo, P.; Wu, R. [CEA, Laboratoire AIM, Irfu/SAp, Orme des Merisiers, 91191 Gif-sur-Yvette (France); Spinoglio, L. [Istituto di Fisica dello Spazio Interplanetario, INAF, Via del Fosso del Cavaliere 100, 00133 Roma (Italy)

    2012-07-01

    We present new Herschel-SPIRE imaging spectroscopy (194-671 {mu}m) of the bright starburst galaxy M82. Covering the CO ladder from J = 4 {yields} 3 to J = 13 {yields} 12, spectra were obtained at multiple positions for a fully sampled {approx}3 Multiplication-Sign 3 arcmin map, including a longer exposure at the central position. We present measurements of {sup 12}CO, {sup 13}CO, [C I], [N II], HCN, and HCO{sup +} in emission, along with OH{sup +}, H{sub 2}O{sup +}, and HF in absorption and H{sub 2}O in both emission and absorption, with discussion. We use a radiative transfer code and Bayesian likelihood analysis to model the temperature, density, column density, and filling factor of multiple components of molecular gas traced by {sup 12}CO and {sup 13}CO, adding further evidence to the high-J lines tracing a much warmer ({approx}500 K), less massive component than the low-J lines. The addition of {sup 13}CO (and [C I]) is new and indicates that [C I] may be tracing different gas than {sup 12}CO. No temperature/density gradients can be inferred from the map, indicating that the single-pointing spectrum is descriptive of the bulk properties of the galaxy. At such a high temperature, cooling is dominated by molecular hydrogen. Photon-dominated region (PDR) models require higher densities than those indicated by our Bayesian likelihood analysis in order to explain the high-J CO line ratios, though cosmic-ray-enhanced PDR models can do a better job reproducing the emission at lower densities. Shocks and turbulent heating are likely required to explain the bright high-J emission.

  6. The au-scale structure in diffuse molecular gas towards ζ Persei

    Science.gov (United States)

    Boissé, P.; Federman, S. R.; Pineau des Forêts, G.; Ritchey, A. M.

    2013-11-01

    Context. Spatial structure in molecular material has a strong impact on its physical and chemical evolution and is still poorly known, especially on very small scales. Aims: To better characterize the small-scale structure in diffuse molecular gas and in particular to investigate the CH+ production mechanism, we study the spatial distribution of CH+, CH, and CN towards the bright star ζ Per on scales in the range 1-20 AU. Methods: We use ζ Per's proper motion and the implied drift of the line of sight through the foreground gas at a rate of about 2 AU yr-1 to probe absorption line variations between adjacent lines of sight. The good S/N, high or intermediate resolution spectra of ζ Per, obtained in the interval 2003-2011, allow us to search for low column-density and line width variations for CH+, CH, and CN. Results: CH and CN lines appear remarkably stable in time, implying an upper limit δN/N ≤ 6% for CH and CN (3σ limit). The weak CH+λ4232 line shows a possible increase of 11% during the interval 2004-2007, which appears to be correlated with a comparable increase in the CH+ velocity dispersion over the same period. Conclusions: The excellent stability of CH and CN lines implies that these species are distributed uniformly to good accuracy within the cloud. The small size implied for the regions associated with the CH+ excess is consistent with scenarios in which this species is produced in very small (a few AU) localized active regions, possibly weakly magnetized shocks or turbulent vortices. Based on observations made at McDonald Observatory (USA) and Observatoire de Haute-Provence (France).

  7. Evidence for mass loss at moderate to high velocity in Be stars

    International Nuclear Information System (INIS)

    Snow, T.P. Jr.; Marlborough, J.M.

    1976-01-01

    Ultraviolet spectra of intermediate resolution have been obtained with Copernicus of 12 objects classified as Be or shell stars, and 19 additional early B dwarfs. Some of these spectra show marked asymmetries in certain resonance lines, especially the Si iv doublet at 1400 A, indicating the presence in some cases of outflowing material with maximum velocities of nearly 1000 km s -1 . Direct evidence for mass loss at these velocities is seen for the first time in dwarf stars as late as B1.5; the only objects later than B0.5 which show this effect are Be or shell stars. Among the stars considered there is a correlation between the presence of mass-loss effects and projected rotational velocity, suggesting that the ultraviolet flux from B1-B2 dwarfs is sufficient to drive high-velocity stellar winds only if rotation effects reduce the effective gravity near the equator. The mass loss rate for one of the most active Be stars, 59 Cyg, is crudely estimated to be 10 -10 --10 -9 M/sub sun/ yr -1 . The data are suggestive that the extended atmospheres associated with Be star phenomena may be formed by mass ejection

  8. Evidence for mass loss at moderate to high velocity in Be stars

    Science.gov (United States)

    Snow, T. P., Jr.; Marlborough, J. M.

    1976-01-01

    Ultraviolet spectra of intermediate resolution have been obtained with Copernicus for 12 objects classified as Be or shell stars and for 19 additional early B dwarfs. Some of these spectra show marked asymmetries in certain resonance lines, especially the Si IV doublet at 1400 A, indicating the presence in some cases of outflowing material with maximum velocities of nearly 1000 km/s. Direct evidence for mass loss at these velocities is seen for the first time in dwarf stars as late as B1.5; the only objects later than B0.5 which show this effect are Be or shell stars. Among the stars considered, there is a correlation between the presence of mass-loss effects and projected rotational velocity, suggesting that the ultraviolet flux from B1-B2 dwarfs is sufficient to drive high-velocity stellar winds only if rotational effects reduce the effective gravity near the equator. The mass-loss rate for one of the most active Be stars, 59 Cyg, is crudely estimated to be one billionth or one ten-billionth of a solar mass per year. The data suggest that the extended atmospheres associated with Be-star phenomena may be formed by mass ejection.

  9. Joint Manipulation: Toward a General Theory of High-Velocity, Low-Amplitude Thrust Techniques.

    Science.gov (United States)

    Harwich, Andrew S

    2017-12-01

    The objective of this study was to describe the initial stage of a generalized theory of high-velocity, low-amplitude thrust (HVLAT) techniques for joint manipulation. This study examined the movements described by authors from the fields of osteopathy, chiropractic, and physical therapy to produce joint cavitation in both the metacarpophalangeal (MCP) joint and the cervical spine apophysial joint. This study qualitatively compared the kinetics, the similarities, and the differences between MCP cavitation and cervical facet joint cavitation. A qualitative vector analysis of forces and movements was undertaken by constructing computer-generated, simplified graphical models of the MCP joint and a typical cervical apophysial joint and imposing the motions dictated by the clinical technique. Comparing the path to cavitation of 2 modes of HVLAT for the MCP joint, namely, distraction and hyperflexion, it was found that the hyperflexion method requires an axis of rotation, the hinge axis, which is also required for cervical HVLAT. These results show that there is an analogue of cervical HVLAT in one of the MCP joint HVLATs. The study demonstrated that in a theoretical model, the path to joint cavitation is the same for asymmetric separation of the joint surfaces in the cervical spine and the MCP joints.

  10. Searching for Dark Matter Annihilation in the Smith High-Velocity Cloud

    Science.gov (United States)

    Drlica-Wagner, Alex; Gomez-Vargas, German A.; Hewitt, John W.; Linden, Tim; Tibaldo, Luigi

    2014-01-01

    Recent observations suggest that some high-velocity clouds may be confined by massive dark matter halos. In particular, the proximity and proposed dark matter content of the Smith Cloud make it a tempting target for the indirect detection of dark matter annihilation. We argue that the Smith Cloud may be a better target than some Milky Way dwarf spheroidal satellite galaxies and use gamma-ray observations from the Fermi Large Area Telescope to search for a dark matter annihilation signal. No significant gamma-ray excess is found coincident with the Smith Cloud, and we set strong limits on the dark matter annihilation cross section assuming a spatially extended dark matter profile consistent with dynamical modeling of the Smith Cloud. Notably, these limits exclude the canonical thermal relic cross section (approximately 3 x 10 (sup -26) cubic centimeters per second) for dark matter masses less than or approximately 30 gigaelectronvolts annihilating via the B/B- bar oscillation or tau/antitau channels for certain assumptions of the dark matter density profile; however, uncertainties in the dark matter content of the Smith Cloud may significantly weaken these constraints.

  11. High-velocity Penetration of Concrete Targets with Three Types of Projectiles: Experiments and Analysis

    Directory of Open Access Journals (Sweden)

    Shuang Zhang

    Full Text Available Abstract This study conducted high-velocity penetration experiments using conventional ogive-nose, double-ogive-nose, and grooved-tapered projectiles of approximately 2.5 kg and initial velocities between 1000 and 1360 m/s to penetrate or perforate concrete targets with unconfined compressive strengths of nominally 40MPa. The penetration performance data of these three types of projectiles with two different types of materials (i.e., AerMet100 and DT300 were obtained. The crater depth model considering both the projectile mass and the initial velocity was proposed based on the test results and a theoretical analysis. The penetration ability and the trajectory stability of these three projectile types were compared and analyzed accordingly. The results showed that, under these experimental conditions, the effects of these two different kinds of projectile materials on the penetration depth and mass erosion rate of projectile were not obvious. The existing models could not reflect the crater depths for projectiles of greater weights or higher velocities, whereas the new model established in this study was reliable. The double-ogive-nose has a certain effect of drag reduction. Thus, the double-ogive-nose projectile has a higher penetration ability than the conventional ogive-nose projectile. Meanwhile, the grooved-tapered projectile has a better trajectory stability, because the convex parts of tapered shank generated the restoring moment to stabilize the trajectory.

  12. Scaling invariance of spherical projectile fragmentation upon high-velocity impact on a thin continuous shield

    Energy Technology Data Exchange (ETDEWEB)

    Myagkov, N. N., E-mail: nn-myagkov@mail.ru [Russian Academy of Sciences, Institute of Applied Mechanics (Russian Federation)

    2017-01-15

    The problem of aluminum projectile fragmentation upon high-velocity impact on a thin aluminum shield is considered. A distinctive feature of this description is that the fragmentation has been numerically simulated using the complete system of equations of deformed solid mechanics by a method of smoothed particle hydrodynamics in three-dimensional setting. The transition from damage to fragmentation is analyzed and scaling relations are derived in terms of the impact velocity (V), ratio of shield thickness to projectile diameter (h/D), and ultimate strength (σ{sub p}) in the criterion of projectile and shield fracture. Analysis shows that the critical impact velocity V{sub c} (separating the damage and fragmentation regions) is a power function of σ{sub p} and h/D. In the supercritical region (V > V{sub c}), the weight-average fragment mass asymptotically tends to a power function of the impact velocity with exponent independent of h/D and σ{sub p}. Mean cumulative fragment mass distributions at the critical point are scale-invariant with respect to parameters h/D and σ{sub p}. Average masses of the largest fragments are also scale-invariant at V > V{sub c}, but only with respect to variable parameter σ{sub p}.

  13. Rebound mechanics of micrometre-scale, spherical particles in high-velocity impacts.

    Science.gov (United States)

    Yildirim, Baran; Yang, Hankang; Gouldstone, Andrew; Müftü, Sinan

    2017-08-01

    The impact mechanics of micrometre-scale metal particles with flat metal surfaces is investigated for high-velocity impacts ranging from 50 m s -1 to more than 1 km s -1 , where impact causes predominantly plastic deformation. A material model that includes high strain rate and temperature effects on the yield stress, heat generation due to plasticity, material damage due to excessive plastic strain and heat transfer is used in the numerical analysis. The coefficient of restitution e is predicted by the classical work using elastic-plastic deformation analysis with quasi-static impact mechanics to be proportional to [Formula: see text] and [Formula: see text] for the low and moderate impact velocities that span the ranges of 0-10 and 10-100 m s -1 , respectively. In the elastic-plastic and fully plastic deformation regimes the particle rebound is attributed to the elastic spring-back that initiates at the particle-substrate interface. At higher impact velocities (0.1-1 km s -1 ) e is shown to be proportional to approximately [Formula: see text]. In this deeply plastic deformation regime various deformation modes that depend on plastic flow of the material including the time lag between the rebound instances of the top and bottom points of particle and the lateral spreading of the particle are identified. In this deformation regime, the elastic spring-back initiates subsurface, in the substrate.

  14. Experimental and analytical study of high velocity impact on Kevlar/Epoxy composite plates

    Science.gov (United States)

    Sikarwar, Rahul S.; Velmurugan, Raman; Madhu, Velmuri

    2012-12-01

    In the present study, impact behavior of Kevlar/Epoxy composite plates has been carried out experimentally by considering different thicknesses and lay-up sequences and compared with analytical results. The effect of thickness, lay-up sequence on energy absorbing capacity has been studied for high velocity impact. Four lay-up sequences and four thickness values have been considered. Initial velocities and residual velocities are measured experimentally to calculate the energy absorbing capacity of laminates. Residual velocity of projectile and energy absorbed by laminates are calculated analytically. The results obtained from analytical study are found to be in good agreement with experimental results. It is observed from the study that 0/90 lay-up sequence is most effective for impact resistance. Delamination area is maximum on the back side of the plate for all thickness values and lay-up sequences. The delamination area on the back is maximum for 0/90/45/-45 laminates compared to other lay-up sequences.

  15. Cleansing technique using high-velocity steam-air micromist jet spray.

    Science.gov (United States)

    Fukuda, Koichi; Ishihara, Masayuki; Murakami, Kaoru; Nakamura, Shingo; Sato, Yoko; Kuwabara, Masahiro; Fujita, Masanori; Kiyosawa, Tomoharu; Yokoe, Hidetaka

    2017-10-01

    Application of a high-velocity steam-air micromist jet spray (HVS-AMJS; micromist average diameter: 2.4 μm) for cleansing the skin is proposed. Low-pressure steam is mixed with compressed air (pH 6.5) in a nozzle, and then sprayed at a pressure of ≦0.25 MPa and a velocity of ≧0.34 m/s on the skin or surface of material located approximately 5-10 cm from the nozzle. The temperature on the sprayed surface and water flow rate could be controlled between 42 °C and 46 °C and at approximately 50 mL/min, respectively. Compared with ultrasonic cleansing with tap water and rubbing with only tap water, the HVS-AMJS successfully removed fluorescent lotion covering pieces of wood and significantly reduced both the number of coliforms and the total viable counts on pieces of wood and gauze. Furthermore, the HVS-AMJS effectively removed oily ink from the skin of hairless rats, and temporarily elevated the skin temperature and blood flow, indicating massage effects. The striking characteristics of this cleansing technique using HVS-AMJS are not only its ability to remove microbes and residue without using any chemicals or detergents but also its massage effects.

  16. High-velocity low-amplitude manipulation (thrust and athletic performance: a systematic review

    Directory of Open Access Journals (Sweden)

    Mikhail Santos Cerqueira

    Full Text Available Abstract Introduction: The high demand level in sports has encouraged the search for strategies to increase the yield. In this context, manual therapy through high-velocity low-amplitude (thrust has been employed in many sports. Despite the adhesion of manual therapists in clinical practice, there were no systematic reviews on this topic. Objective: To evaluate the effects of thrust on the performance of athletes in relation to the outcomes hand-grip strength, jump height and running speed. Methods: The databases used in the search were MEDLINE / PUBMED, LILACS, CINAHL, PEDro, WEB OF SCIENCE, CENTRAL and SCOPUS, and Randomized controlled trials were included, whose participants were professionals or recreational athletes and had thrust as intervention. The methodological quality of the studies was assessed using the PEDro scale of 10 points. Intervention effects were determined by the mean difference and confidence interval. The data analysis was done in the descriptive form due to the heterogeneity found among studies. Results: Five trials were included with a total of 95 individuals. The methodological quality of studies was low, with an average value of 5.6 on the PEDro scale. It was found two articles for each outcome, but in none of them was presented differences between the experimental and control groups considering the confidence interval. Conclusion: The current evidence is insufficient to determine the use or nonuse the MAVBA in sports in order to improve performance.

  17. Remote Numerical Simulations of the Interaction of High Velocity Clouds with Random Magnetic Fields

    Science.gov (United States)

    Santillan, Alfredo; Hernandez--Cervantes, Liliana; Gonzalez--Ponce, Alejandro; Kim, Jongsoo

    The numerical simulations associated with the interaction of High Velocity Clouds (HVC) with the Magnetized Galactic Interstellar Medium (ISM) are a powerful tool to describe the evolution of the interaction of these objects in our Galaxy. In this work we present a new project referred to as Theoretical Virtual i Observatories. It is oriented toward to perform numerical simulations in real time through a Web page. This is a powerful astrophysical computational tool that consists of an intuitive graphical user interface (GUI) and a database produced by numerical calculations. In this Website the user can make use of the existing numerical simulations from the database or run a new simulation introducing initial conditions such as temperatures, densities, velocities, and magnetic field intensities for both the ISM and HVC. The prototype is programmed using Linux, Apache, MySQL, and PHP (LAMP), based on the open source philosophy. All simulations were performed with the MHD code ZEUS-3D, which solves the ideal MHD equations by finite differences on a fixed Eulerian mesh. Finally, we present typical results that can be obtained with this tool.

  18. In vitro performance of ceramic coatings obtained by high velocity oxy-fuel spray.

    Science.gov (United States)

    Melero, H; Garcia-Giralt, N; Fernández, J; Díez-Pérez, A; Guilemany, J M

    2014-01-01

    Hydroxyapatite coatings obtained by plasma-spraying have been used for many years to improve biological performance of bone implants, but several studies have drawn attention to the problems arising from high temperatures and the lack of mechanical properties. In this study, plasma-spraying is substituted by high velocity oxy-fuel (HVOF) spray, with lower temperatures reached, and TiO2 is added in low amounts to hydroxyapatite in order to improve the mechanical properties. Four conditions have been tested to evaluate which are those with better biological properties. Viability and proliferation tests, as well as differentiation assays and morphology observation, are performed with human osteoblast cultures onto the studied coatings. The hydroxyapatite-TiO2 coatings maintain good cell viability and proliferation, especially the cases with higher amorphous phase amount and specific surface, and promote excellent differentiation, with a higher ALP amount for these cases than for polystyrene controls. Observation by SEM corroborates this excellent behaviour. In conclusion, these coatings are a good alternative to those used industrially, and an interesting issue would be improving biological behaviour of the worst cases, which in turn show the better mechanical properties.

  19. THE FIRST DISTANCE CONSTRAINT ON THE RENEGADE HIGH-VELOCITY CLOUD COMPLEX WD

    Energy Technology Data Exchange (ETDEWEB)

    Peek, J. E. G.; Roman-Duval, Julia; Tumlinson, Jason [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Bordoloi, Rongmon [MIT-Kavli Center for Astrophysics and Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Sana, Hugues [Institute of Astronomy, KU Leuven, Celestijnenlaan 200 D, B-3001 Leuven (Belgium); Zheng, Yong [Department of Astronomy, Columbia University, New York, NY 10027 (United States)

    2016-09-10

    We present medium-resolution, near-ultraviolet Very Large Telescope/FLAMES observations of the star USNO-A0600-15865535. We adapt a standard method of stellar typing to our measurement of the shape of the Balmer ϵ absorption line to demonstrate that USNO-A0600-15865535 is a blue horizontal branch star, residing in the lower stellar halo at a distance of 4.4 kpc from the Sun. We measure the H and K lines of singly ionized calcium and find two isolated velocity components, one originating in the disk, and one associated with the high-velocity cloud complex WD. This detection demonstrated that complex WD is closer than ∼4.4 kpc and is the first distance constraint on the +100 km s{sup −1} Galactic complex of clouds. We find that complex WD is not in corotation with the Galactic disk, which has been assumed for decades. We examine a number of scenarios and find that the most likely scenario is that complex WD was ejected from the solar neighborhood and is only a few kiloparsecs from the Sun.

  20. Searching for dark matter annihilation in the Smith high-velocity cloud

    International Nuclear Information System (INIS)

    Drlica-Wagner, Alex; Gómez-Vargas, Germán A.; Hewitt, John W.; Linden, Tim; Tibaldo, Luigi

    2014-01-01

    Recent observations suggest that some high-velocity clouds may be confined by massive dark matter halos. In particular, the proximity and proposed dark matter content of the Smith Cloud make it a tempting target for the indirect detection of dark matter annihilation. We argue that the Smith Cloud may be a better target than some Milky Way dwarf spheroidal satellite galaxies and use γ-ray observations from the Fermi Large Area Telescope to search for a dark matter annihilation signal. No significant γ-ray excess is found coincident with the Smith Cloud, and we set strong limits on the dark matter annihilation cross section assuming a spatially extended dark matter profile consistent with dynamical modeling of the Smith Cloud. Notably, these limits exclude the canonical thermal relic cross section (∼ 3 × 10 –26 cm 3 s –1 ) for dark matter masses ≲ 30 GeV annihilating via the b b-bar or τ + τ – channels for certain assumptions of the dark matter density profile; however, uncertainties in the dark matter content of the Smith Cloud may significantly weaken these constraints.

  1. Kinematics of Local, High-Velocity K dwarfs in the SUPERBLINK Proper Motion Catalog

    Science.gov (United States)

    Kim, Bokyoung; Lepine, Sebastien

    2018-01-01

    We present a study of the kinematics of 345,480 K stars within 2 kpc of the Sun, based on data from the SUPERBLINK catalog of stars with high proper motions (> 40 mas/yr), combined with data from the 2MASS survey and from the first GAIA release, which together yields proper motions accurate to ~2 mas/yr. All K dwarfs were selected based on their G-K colors, and photometric distances were estimated from a re-calibrated color-magnitude relationship for K dwarfs. We plot transverse velocities VT in various directions on the sky, to examine the local distribution of K dwarfs in velocity space. We have also obtained radial velocity information for a subsample of 10,128 stars, from RAVE and SDSS DR12, which we use to construct spatial velocity (U, V, W) plots. About a third (123,350) of the stars are high-velocity K dwarfs, with motions consistent with the local Galactic halo population. Our kinematic analysis suggests that their velocity-space distribution is very uniform, and we find no evidence of substructure that might arise, e.g., from local streams or moving groups.

  2. Searching for dark matter annihilation in the Smith high-velocity cloud

    Energy Technology Data Exchange (ETDEWEB)

    Drlica-Wagner, Alex [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Gómez-Vargas, Germán A. [Departamento de Fisíca, Pontificia Universidad Católica de Chile, Avenida Vicuña Mackenna 4860, Santiago (Chile); Hewitt, John W. [CRESST, University of Maryland, Baltimore County, Baltimore, MD 21250 (United States); Linden, Tim [The Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637 (United States); Tibaldo, Luigi [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States)

    2014-07-20

    Recent observations suggest that some high-velocity clouds may be confined by massive dark matter halos. In particular, the proximity and proposed dark matter content of the Smith Cloud make it a tempting target for the indirect detection of dark matter annihilation. We argue that the Smith Cloud may be a better target than some Milky Way dwarf spheroidal satellite galaxies and use γ-ray observations from the Fermi Large Area Telescope to search for a dark matter annihilation signal. No significant γ-ray excess is found coincident with the Smith Cloud, and we set strong limits on the dark matter annihilation cross section assuming a spatially extended dark matter profile consistent with dynamical modeling of the Smith Cloud. Notably, these limits exclude the canonical thermal relic cross section (∼ 3 × 10{sup –26} cm{sup 3} s{sup –1}) for dark matter masses ≲ 30 GeV annihilating via the b b-bar or τ{sup +}τ{sup –} channels for certain assumptions of the dark matter density profile; however, uncertainties in the dark matter content of the Smith Cloud may significantly weaken these constraints.

  3. Numerical Material Model for Composite Laminates in High-Velocity Impact Simulation

    Directory of Open Access Journals (Sweden)

    Tao Liu

    Full Text Available Abstract A numerical material model for composite laminate, was developed and integrated into the nonlinear dynamic explicit finite element programs as a material user subroutine. This model coupling nonlinear state of equation (EOS, was a macro-mechanics model, which was used to simulate the major mechanical behaviors of composite laminate under high-velocity impact conditions. The basic theoretical framework of the developed material model was introduced. An inverse flyer plate simulation was conducted, which demonstrated the advantage of the developed model in characterizing the nonlinear shock response. The developed model and its implementation were validated through a classic ballistic impact issue, i.e. projectile impacting on Kevlar29/Phenolic laminate. The failure modes and ballistic limit velocity were analyzed, and a good agreement was achieved when comparing with the analytical and experimental results. The computational capacity of this model, for Kevlar/Epoxy laminates with different architectures, i.e. plain-woven and cross-plied laminates, was further evaluated and the residual velocity curves and damage cone were accurately predicted.

  4. Integrity of high-velocity water slug generated by an impacting technique

    Science.gov (United States)

    Dehkhoda, Sevda; Bourne, Neil

    2013-06-01

    A pulsed water jet is a series of discrete water slugs travelling at high velocity. Immediately after striking a target, these slugs apply high-intensity, short-duration transient stress known as the water hammer pressure, followed by low-intensity, long-duration stationary stress at the stagnation pressure. The magnitude and duration of the water hammer and stagnation pressures are controlled by the size and quality of the water slugs. The use of water jets for rock cutting in mining operations is a centuries-old technology; however, practical methods for producing high-energy water slugs repeatedly have proven difficult. This can be partly due to the fact that the geometrical properties of a jet and so its effectiveness in creating damage is controlled and influenced by the method that is employed to generate the water slugs. This paper investigates the integrity of a single water slug produced using an impacting technique where a hammer strikes a piston, resting on top of a water-filled chamber. The coherence of the generated water pulse was of concern in this study. If repeated shock reflections within the chamber were transmitted or were carried into the internal geometry of nozzle, the emerging jet could pulsate. The impact impulse of the formed water jet was measured in a Kel-F target material using an embedded PVDF (Polyvinylidene fluoride) shock gauge. The recorded stress waveform was then used to study the quality and endurance of the water pulse stream as it travelled through air.

  5. Production of a high-velocity water slug using an impacting technique

    Science.gov (United States)

    Dehkhoda, S.; Bourne, N. K.

    2014-02-01

    A pulsed water jet consists of a series of discrete water slugs travelling at high velocity. Immediately after striking a target, these slugs apply high-intensity, short-duration transient stress pulses reaching an amplitude known as the water hammer pressure, followed by low-intensity, long-duration stationary stress at a lower stagnation pressure. The magnitude and duration of the water hammer and stagnation pressures are controlled by the size and quality of the water slugs. The use of water jets for rock cutting in mining operations is a centuries-old technology; however, practical methods for producing high-energy water slugs repeatedly have proven difficult. This can be partly due to the fact that the geometrical properties of a jet and so its effectiveness in creating damage is controlled and influenced by the method that is employed to generate the water slugs. This paper investigates the quality of a single water slug produced using an impacting technique where a hammer strikes a piston, resting on top of a water-filled chamber. The coherence and integrity of the jet core was of concern in this study. The impact impulse of the formed water jet was measured in a Kel-F target material using an embedded PVDF (Polyvinylidene fluoride) shock gauge. The recorded stress waveform was then used to determine the unity and endurance of the water slug stream once travelled through air.

  6. Magnetic Circuit Design and Multiphysics Analysis of a Novel MR Damper for Applications under High Velocity

    Directory of Open Access Journals (Sweden)

    Jiajia Zheng

    2014-02-01

    Full Text Available A novel magnetorheological (MR damper with a multistage piston and independent input currents is designed and analyzed. The equivalent magnetic circuit model is investigated along with the relation between magnetic induction density in the working gap and input currents of the electromagnetic coils. Finite element method (FEM is used to analyze the distribution of magnetic field through the MR fluid region. Considering the real situation, coupling equations are presented to analyze the electromagnetic-thermal-flow coupling problems. Software COMSOL is used to analyze the multiphysics, that is, electromagnetic, thermal dynamic, and fluid mechanic. A measurement index involving total damping force, dynamic range, and induction time needed for magnetic coil is put forward to evaluate the performance of the novel multistage MR damper. The simulation results show that it is promising for applications under high velocity and works better when more electromagnetic coils are applied with input currents separately. Besides, in order to reduce energy consumption, it is recommended to apply more electromagnetic coils with relative low currents based on the analysis of pressure drop along the annular gap.

  7. Effect of molecular weight and density of ambient gas on shock wave in laser-induced surface nanostructuring

    International Nuclear Information System (INIS)

    Guo Liying; Wang Xinwei

    2009-01-01

    This paper presents the results of molecular dynamics studies about the shock wave during laser-induced surface nanostructuring. A quasi-three dimensional model is constructed to study systems consisting of over 2 million atoms. Detailed studies are carried out about the shock wave front and Mach number, evolution of plume and ambient gas interaction zone, and energy exchange between the ambient gas and plume. Under an ambience of lower pressure or lighter molecular mass, the plume affects a larger area while the strength of the shock wave front is weaker. With the same ambient pressure, the ablated material features the same kinetic energy at the late stage regardless of the molecular weight of the ambient gas. The same conclusion holds for the energy increase of the ambient gas as well. When the ambient pressure is reduced, more kinetic energy is carried out by the ablated material while less energy is transferred to the ambient gas. It is observed that heavier ambient gas could bounce back the ablated material to the target surface.

  8. ALMA Shows that Gas Reservoirs of Star-forming Disks over the Past 3 Billion Years Are Not Predominantly Molecular

    Energy Technology Data Exchange (ETDEWEB)

    Cortese, Luca; Catinella, Barbara; Janowiecki, Steven, E-mail: luca.cortese@uwa.edu.au [International Centre for Radio Astronomy Research, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia)

    2017-10-10

    Cold hydrogen gas is the raw fuel for star formation in galaxies, and its partition into atomic and molecular phases is a key quantity for galaxy evolution. In this Letter, we combine Atacama Large Millimeter/submillimeter Array and Arecibo single-dish observations to estimate the molecular-to-atomic hydrogen mass ratio for massive star-forming galaxies at z ∼ 0.2 extracted from the HIGHz survey, i.e., some of the most massive gas-rich systems currently known. We show that the balance between atomic and molecular hydrogen in these galaxies is similar to that of local main-sequence disks, implying that atomic hydrogen has been dominating the cold gas mass budget of star-forming galaxies for at least the past three billion years. In addition, despite harboring gas reservoirs that are more typical of objects at the cosmic noon, HIGHz galaxies host regular rotating disks with low gas velocity dispersions suggesting that high total gas fractions do not necessarily drive high turbulence in the interstellar medium.

  9. Membrane separation study for methane-hydrogen gas mixtures by molecular simulations

    Directory of Open Access Journals (Sweden)

    T. Kovács

    2017-06-01

    Full Text Available Direct simulation results for stationary gas transport through pure silica zeolite membranes (MFI, LTA and DDR types are presented using a hybrid, non-equilibrium molecular dynamics simulation methodology introduced recently. The intermolecular potential models for the investigated CH_4 and H_2 gases were taken from literature. For different zeolites, the same atomic (Si and O interaction parameters were used, and the membranes were constructed according to their real (MFI, LTA, or DDR crystal structures. A realistic nature of the applied potential parameters was tested by performing equilibrium adsorption simulations and by comparing the calculated results with the data of experimental adsorption isotherms. The results of transport simulations carried out at 25°C and 125°C, and at 2.5, 5 or 10 bar clearly show that the permeation selectivities of CH_4 are higher than the corresponding permeability ratios of pure components, and significantly differ from the equilibrium selectivities in mixture adsorptions. We experienced a transport selectivity in favor of CH_4 in only one case. A large discrepancy between different types of selectivity data can be attributed to dissimilar mobilities of the components in a membrane, their dependence on the loading of a membrane, and the unlike adsorption preferences of the gas molecules.

  10. Galaxy evolution in extreme environments: Molecular gas content star formation and AGN in isolated void galaxies

    Science.gov (United States)

    Das, Mousumi; Iono, Daisuke; Saito, Toshiki; Subramanian, Smitha

    Since the early redshift surveys of the large scale structure of our universe, it has become clear that galaxies cluster along walls, sheet and filaments leaving large, empty regions called voids between them. Although voids represent the most under dense parts of our universe, they do contain a sparse but significant population of isolated galaxies that are generally low luminosity, late type disk galaxies. Recent studies show that most void galaxies have ongoing star formation and are in an early stage of evolution. We present radio, optical studies of the molecular gas content and star formation in a sample of void galaxies. Using SDSS data, we find that AGN are rare in these systems and are found only in the Bootes void; their black hole masses and radio properties are similar to bright spirals galaxies. Our studies suggest that close galaxy interactions and gas accretion are the main drivers of galaxy evolution in these systems despite their location in the underdense environment of the voids.

  11. Condensation and dissociation rates for gas phase metal clusters from molecular dynamics trajectory calculations

    Science.gov (United States)

    Yang, Huan; Goudeli, Eirini; Hogan, Christopher J.

    2018-04-01

    In gas phase synthesis systems, clusters form and grow via condensation, in which a monomer binds to an existing cluster. While a hard-sphere equation is frequently used to predict the condensation rate coefficient, this equation neglects the influences of potential interactions and cluster internal energy on the condensation process. Here, we present a collision rate theory-molecular dynamics simulation approach to calculate condensation probabilities and condensation rate coefficients. We use this approach to examine atomic condensation onto 6-56-atom Au and Mg clusters. The probability of condensation depends upon the initial relative velocity (v) between atom and cluster and the initial impact parameter (b). In all cases, there is a well-defined region of b-v space where condensation is highly probable, and outside of which the condensation probability drops to zero. For Au clusters with more than 10 atoms, we find that at gas temperatures in the 300-1200 K range, the condensation rate coefficient exceeds the hard-sphere rate coefficient by a factor of 1.5-2.0. Conversely, for Au clusters with 10 or fewer atoms and for 14- and 28-atom Mg clusters, as cluster equilibration temperature increases, the condensation rate coefficient drops to values below the hard-sphere rate coefficient. Calculations also yield the self-dissociation rate coefficient, which is found to vary considerably with gas temperature. Finally, calculations results reveal that grazing (high b) atom-cluster collisions at elevated velocity (>1000 m s-1) can result in the colliding atom rebounding (bounce) from the cluster surface or binding while another atom dissociates (replacement). The presented method can be applied in developing rate equations to predict material formation and growth rates in vapor phase systems.

  12. THE RELATION BETWEEN GAS AND DUST IN THE TAURUS MOLECULAR CLOUD

    International Nuclear Information System (INIS)

    Pineda, Jorge L.; Goldsmith, Paul F.; Chapman, Nicholas; Li Di; Snell, Ronald L.; Cambresy, Laurent; Brunt, Chris

    2010-01-01

    We report a study of the relation between dust and gas over a 100 deg 2 area in the Taurus molecular cloud. We compare the H 2 column density derived from dust extinction with the CO column density derived from the 12 CO and 13 CO J = 1 → 0 lines. We derive the visual extinction from reddening determined from 2MASS data. The comparison is done at an angular size of 200'' corresponding to 0.14 pc at a distance of 140 pc. We find that the relation between visual extinction A V and N(CO) is linear between A V ≅ 3 and 10 mag in the region associated with the B213-L1495 filament. In other regions, the linear relation is flattened for A V ∼> 4 mag. We find that the presence of temperature gradients in the molecular gas affects the determination of N(CO) by ∼30%-70% with the largest difference occurring at large column densities. Adding a correction for this effect and accounting for the observed relation between the column density of CO and CO 2 ices and A V , we find a linear relationship between the column of carbon monoxide and dust for observed visual extinctions up to the maximum value in our data ≅23 mag. We have used these data to study a sample of dense cores in Taurus. Fitting an analytical column density profile to these cores we derive an average volume density of about 1.4 x 10 4 cm -3 and a CO depletion age of about 4.2 x 10 5 yr. At visual extinctions smaller than ∼3 mag, we find that the CO fractional abundance is reduced by up to two orders of magnitude. The data show a large scatter suggesting a range of physical conditions of the gas. We estimate the H 2 mass of Taurus to be about 1.5 x 10 4 M sun , independently derived from the A V and N(CO) maps. We derive a CO integrated intensity to H 2 conversion factor of about 2.1 x 10 20 cm -2 (K km s -1 ) -1 , which applies even in the region where the [CO]/[H 2 ] ratio is reduced by up to two orders of magnitude. The distribution of column densities in our Taurus maps resembles a log

  13. The effects of loaded and unloaded high-velocity resistance training on functional fitness among community-dwelling older adults.

    Science.gov (United States)

    Glenn, Jordan M; Gray, Michelle; Binns, Ashley

    2015-11-01

    Physical function declines up to 4% per year after the age of 65. High-velocity training is important for maintaining muscular power and ultimately, physical function; however, whether performing high-velocity training without external resistance increases functional fitness among older adults remains unclear. The purpose of this investigation was to evaluate loaded and unloaded high-velocity training on lower body muscular power and functional fitness in older adults. Fifty-seven community-dwelling older adults (n = 16 males, n = 41 females) participated in this study. Inclusion criteria comprised ≥65 years of age, ≥24 on the Mini-mental state examination and no falls within past year. Two groups completed a 20-week high-velocity training intervention. The non-weighted group (UNLOAD, n = 27) performed the protocol without external load while the intervention group (LOAD, n = 30) used external loads via exercise machines. Functional fitness was assessed using the Short Physical Performance Battery (SPPB), Senior Fitness Test (SFT), hand-grip and lower body power measures. Multivariate ANOVA revealed that both groups had significant improvements for average (17.21%) and peak (9.26%) lower body power, along with the SFT arm curl (16.94%), chair stand (20.10%) and 8 ft. up-and-go (15.67%). Improvements were also noticed for SPPB 8 ft. walk (25.21%). However, improvements for all functional fitness measures were independent of training group. Unloaded high-velocity training increased functional fitness and power the same as loaded training. The ability of high-velocity movements to elicit gains in functional fitness without external loads may help health professionals develop fitness programs when time/space is limiting factor. © The Author 2015. Published by Oxford University Press on behalf of the British Geriatrics Society. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  14. AXAOTHER XL -- A spreadsheet for determining doses for incidents caused by tornadoes or high-velocity straight winds

    International Nuclear Information System (INIS)

    Simpkins, A.A.

    1996-09-01

    AXAOTHER XL is an Excel Spreadsheet used to determine dose to the maximally exposed offsite individual during high-velocity straight winds or tornado conditions. Both individual and population doses may be considered. Potential exposure pathways are inhalation and plume shine. For high-velocity straight winds the spreadsheet has the capability to determine the downwind relative air concentration, however for the tornado conditions, the user must enter the relative air concentration. Theoretical models are discussed and hand calculations are performed to ensure proper application of methodologies. A section has also been included that contains user instructions for the spreadsheet

  15. An HST/COS legacy survey of high-velocity ultraviolet absorption in the Milky Way's circumgalactic medium and the Local Group

    Science.gov (United States)

    Richter, P.; Nuza, S. E.; Fox, A. J.; Wakker, B. P.; Lehner, N.; Ben Bekhti, N.; Fechner, C.; Wendt, M.; Howk, J. C.; Muzahid, S.; Ganguly, R.; Charlton, J. C.

    2017-11-01

    Context. The Milky Way is surrounded by large amounts of diffuse gaseous matter that connects the stellar body of our Galaxy with its large-scale Local Group (LG) environment. Aims: To characterize the absorption properties of this circumgalactic medium (CGM) and its relation to the LG we present the so-far largest survey of metal absorption in Galactic high-velocity clouds (HVCs) using archival ultraviolet (UV) spectra of extragalactic background sources. The UV data are obtained with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope (HST) and are supplemented by 21 cm radio observations of neutral hydrogen. Methods: Along 270 sightlines we measure metal absorption in the lines of Si II, Si III, C II, and C iv and associated H I 21 cm emission in HVCs in the velocity range | vLSR | = 100-500 km s-1. With this unprecedented large HVC sample we were able to improve the statistics on HVC covering fractions, ionization conditions, small-scale structure, CGM mass, and inflow rate. For the first time, we determine robustly the angular two point correlation function of the high-velocity absorbers, systematically analyze antipodal sightlines on the celestial sphere, and compare the HVC absorption characteristics with that of damped Lyman α absorbers (DLAs) and constrained cosmological simulations of the LG (CLUES project). Results: The overall sky-covering fraction of high-velocity absorption is 77 ± 6 percent for the most sensitive ion in our survey, Si III, and for column densities log N(Si III)≥ 12.1. This value is 4-5 times higher than the covering fraction of 21 cm neutral hydrogen emission at log N(H I)≥ 18.7 along the same lines of sight, demonstrating that the Milky Way's CGM is multi-phase and predominantly ionized. The measured equivalent-width ratios of Si II, Si III, C II, and C iv are inhomogeneously distributed on large and small angular scales, suggesting a complex spatial distribution of multi-phase gas that surrounds the

  16. Evolution of the 1963 Vajont landslide (Northern Italy) from low and high velocity friction experiments

    Science.gov (United States)

    Ferri, F.; di Toro, G.; Hirose, T.; Han, R.; Noda, H.; Shimamoto, T.; Pennacchioni, G.

    2009-04-01

    The final slip at about 30 m/s of the Vajont landslide (Northern Italy) on 9th October 1963 was preceded by a long creeping phase which was monitored over about three years. Creep was localized in cm-thick clay-rich (50% Ca-montmorillonite + smectite + illite + vermiculite, 40% calcite and 10% quartz) gouge layers. The velocity results in thermoviscoplastic model of the landslide (Veveakis et al., 2007) suggested that during creep, compaction and frictional heating released water from the clay-rich layer and, by increasing the pore-pressure in the slipping zone, determined the final collapse of the landslide. Here we investigated the frictional evolution of the clay-rich layers and the transition towards the final collapse. Experiments were carried out on the clayey gouge from the slipping zone at atmospheric humidity conditions ("dry") and in the presence of excess water ("saturated"). High velocity friction experiments were performed in a rotary shear apparatus at 1 MPa normal stress (about the normal stress at the sliding surface of the Vajont landslide), velocity v from 0.006 m/s to 1.31 m/s and displacements up to 34 m. The 1 mm-thick clayey gouges were sandwiched between marble cylindrical specimens (24.95 mm in diameter) and confined by Teflon rings to avoid gouge expulsion during the experiments. The fluid release during the experiments was monitored with a humidity sensor. Low velocity friction experiments were performed in a biaxial apparatus at 5 MPa normal stress, v from 1.0 10E-7 m/s to 1.0 10E-4 m/s (within the range at which the slide became critical, 2.0 10E-7 m/s, Veveakis et al., 2007) and displacements up to 0.02 m. In dry experiments, friction is 0.43-0.47 at v Vajont clays), and decreases to 0.03-0.05 at v > 0.006 m/s. At dry conditions, dilatancy was observed for v > 0.7 m/s suggesting fault pressurization by water release due to smectite-to-illite decomposition. Decomposition occurred at temperatures above 300°C, as confirmed by the

  17. Discovery of Molecular Gas Shells around the Unusual Galaxy Centaurus A

    Science.gov (United States)

    2000-03-01

    photometric and spectrographic studies of their light, it has been known since the early 1980's that such shells are made up of stars. It appears that they are quite common - about half of the nearby large elliptical galaxies have been found to be surrounded by stellar shells. More recently, in 1994, atomic hydrogen gas was discovered to be associated with some of the stellar shells. This discovery was a bit of a surprise, because the current theory predicts that when two galaxies merge, their gas and stars will behave very differently. While the individual stars hardly ever hit each other, the interstellar gas clouds collide violently. They will lose all their energy and the gas will fall towards the common centre where it is soon consumed in vigorous bursts of star formation. Why would there then be hydrogen gas in the outer shells of some elliptical galaxies? A possible origin of gaseous shells The astronomer team, headed by Vassilis Charmandaris [1] decided to look into this serious discrepancy between theory and observations. They believed that a possible explanation might be that this diffuse atomic gas is located, not in vast, very dilute clouds, but rather in smaller, much denser molecular clouds , such as these are known in our own galaxy, the Milky Way. Due to their relative compactness (more than 1000 molecules/cm 3 , i.e,. at least 100 times more than that of larger diffuse clouds), molecular clouds would behave more like the stars during the galaxy collision event. Indeed, realistic calculations showed that the dynamical behavior of such dense clouds would be intermediate between the stars and the diffuse hydrogen gas. Thus, while most of the gas would still end up in the centre of the remaining galaxy after a merger, a larger fraction of it would be able to survive at large distances from the nucleus. This would then be the origin of the observed hydrogen shells. During the merger, gas that originates from regions in the outskirts of the "cannibalized" galaxy

  18. Energy Productivity of the High Velocity Algae Raceway Integrated Design (ARID-HV)

    Energy Technology Data Exchange (ETDEWEB)

    Attalah, Said; Waller, Peter M.; Khawam, George; Ryan, Randy D.; Huesemann, Michael H.

    2015-06-03

    The original Algae Raceway Integrated Design (ARID) raceway was an effective method to increase algae culture temperature in open raceways. However, the energy input was high and flow mixing was poor. Thus, the High Velocity Algae Raceway Integrated Design (ARID-HV) raceway was developed to reduce energy input requirements and improve flow mixing in a serpentine flow path. A prototype ARID-HV system was installed in Tucson, Arizona. Based on algae growth simulation and hydraulic analysis, an optimal ARID-HV raceway was designed, and the electrical energy input requirement (kWh ha-1 d-1) was calculated. An algae growth model was used to compare the productivity of ARIDHV and conventional raceways. The model uses a pond surface energy balance to calculate water temperature as a function of environmental parameters. Algae growth and biomass loss are calculated based on rate constants during day and night, respectively. A 10 year simulation of DOE strain 1412 (Chlorella sorokiniana) showed that the ARID-HV raceway had significantly higher production than a conventional raceway for all months of the year in Tucson, Arizona. It should be noted that this difference is species and climate specific and is not observed in other climates and with other algae species. The algae growth model results and electrical energy input evaluation were used to compare the energy productivity (algae production rate/energy input) of the ARID-HV and conventional raceways for Chlorella sorokiniana in Tucson, Arizona. The energy productivity of the ARID-HV raceway was significantly greater than the energy productivity of a conventional raceway for all months of the year.

  19. Search for auroral belt Eparallel fields with high-velocity barium ion injections

    International Nuclear Information System (INIS)

    Heppner, J.P.; Ledley, B.G.; Miller, M.L.; Marionni, P.A.; Pongratz, M.B.; Slater, D.W.; Hallinan, T.J.; Rees, D.

    1989-01-01

    Four high-velocity shaped charge Ba + injections were conducted from two Black Brant-10 rockets at collision-free altitudes (770-975 km) over northern Alaska (L = 7.4-10.6) in April 1984 under active auroral and magnetic disturbance (Kp 4+ and 5) conditions. The motions of the Ba + pencil beams from these injections were accurately triangulated to altitudes ranging from 9,000 to 14,000 km from multistation image observations. Well-defined initial conditions and improved software for predicting the unperturbed. E = 0, trajectories in the presence of convection, E perpendicular , fields permitted an accurate detection of changes in the motion which could be attributed to E parallel fields. Large (> 1 keV) potential changes that might be anticipated from double-layer or V-, U- and S-shaped potential structures were not encountered even though the Ba + rays were clearly located on auroral arc flux tubes on at least several occasions and were at various times in close proximity to auroral flux tubes for many minutes. Abnormally intense E perpendicular fields that might also indicate that the above potential structures were also not observed. Transient accelerations and/or decelerations involving magnetic field-aligned energy changes ≤ 375 eV were, however, encountered by each of the seven principal Ba + rays tracked to high altitudes. Acceleration events were only slightly more frequent than deceleration events. Interpretation, taking into account limits on the duration of the events and simultaneous auroral conditions, favors explanation in terms of propagating waves, soliton trains, or other pulse forms provided that the propagation is primarily field-aligned

  20. Building America Case Study: High-Velocity Small-Diameter Duct System, Pittsburgh, Pennsylvania

    Energy Technology Data Exchange (ETDEWEB)

    2017-04-01

    This study tests the performance of a variable airflow small-diameter duct heating, ventilation, and air conditioning (HVAC) system in a new construction unoccupied low-load test house in Pittsburgh, Pennsylvania. The duct system was installed entirely in conditioned space and was operated from the winter through summer seasons. Measurements were collected on the in-room temperatures and energy consumed by the air handler and heat pump unit. Operation modes with three different volumes of airflow were compared to determine the ideal airflow scenario that maximizes room-to-room thermal uniformity while minimizing fan energy consumption. Black felt infrared imagery was used as a measure of diffuser throw and in-room air mixing. Measured results indicate the small-diameter, high velocity airflow system can provide comfort under some conditions. Solar heat gains resulted in southern rooms drifting beyond acceptable temperature limits. Insufficient airflow to some bedrooms also resulted in periods of potential discomfort. Homebuilders or HVAC contractors can use these results to assess whether this space conditioning strategy is an attractive alternative to a traditional duct system. The team performed a cost analysis of two duct system configurations: (1) a conventional diameter and velocity duct system, and (2) the small-diameter duct system. This work applies to both new and retrofit homes that have achieved a low heating and cooling density either by energy conservation or by operation in a mild climate with few heating or cooling degree days. Guidance is provided on cost trade-offs between the conventional duct system and the small-diameter duct system.

  1. High-energy radiation from collisions of high-velocity clouds and the Galactic disc

    Science.gov (United States)

    del Valle, Maria V.; Müller, A. L.; Romero, G. E.

    2018-04-01

    High-velocity clouds (HVCs) are interstellar clouds of atomic hydrogen that do not follow normal Galactic rotation and have velocities of a several hundred kilometres per second. A considerable number of these clouds are falling down towards the Galactic disc. HVCs form large and massive complexes, so if they collide with the disc a great amount of energy would be released into the interstellar medium. The cloud-disc interaction produces two shocks: one propagates through the cloud and the other through the disc. The properties of these shocks depend mainly on the cloud velocity and the disc-cloud density ratio. In this work, we study the conditions necessary for these shocks to accelerate particles by diffusive shock acceleration and we study the non-thermal radiation that is produced. We analyse particle acceleration in both the cloud and disc shocks. Solving a time-dependent two-dimensional transport equation for both relativistic electrons and protons, we obtain particle distributions and non-thermal spectral energy distributions. In a shocked cloud, significant synchrotron radio emission is produced along with soft gamma rays. In the case of acceleration in the shocked disc, the non-thermal radiation is stronger; the gamma rays, of leptonic origin, might be detectable with current instruments. A large number of protons are injected into the Galactic interstellar medium, and locally exceed the cosmic ray background. We conclude that under adequate conditions the contribution from HVC-disc collisions to the galactic population of relativistic particles and the associated extended non-thermal radiation might be important.

  2. The effects of varying resistance-training loads on intermediate- and high-velocity-specific adaptations.

    Science.gov (United States)

    Jones, K; Bishop, P; Hunter, G; Fleisig, G

    2001-08-01

    The purpose of this study was to compare changes in velocity-specific adaptations in moderately resistance-trained athletes who trained with either low or high resistances. The study used tests of sport-specific skills across an intermediate- to high-velocity spectrum. Thirty NCAA Division I baseball players were randomly assigned to either a low-resistance (40-60% 1 repetition maximum [1RM]) training group or a high-resistance (70-90% 1RM) training group. Both of the training groups intended to maximallv accelerate each repetition during the concentric phase (IMCA). The 10 weeks of training consisted of 4 training sessions a week using basic core exercises. Peak force, velocity, and power were evaluated during set angle and depth jumps as well as weighted jumps using 30 and 50% 1RM. Squat 1RMs were also tested. Although no interactions for any of the jump tests were found, trends supported the hypothesis of velocity-specific training. Percentage gains suggest that the combined use of heavier training loads (70-90% 1RM) and IMCA tend to increase peak force in the lower-body leg and hip extensors. Trends also show that the combined use of lighter training loads (40-60% 1RM) and IMCA tend to increase peak power and peak velocity in the lower-body leg and hip extensors. The high-resistance group improved squats more than the low-resistance group (p training loads and IMCA to increase 1RM strength in the lower bodies of resistance-trained athletes.

  3. HIGH-VELOCITY LINE FORMING REGIONS IN THE TYPE Ia SUPERNOVA 2009ig

    International Nuclear Information System (INIS)

    Marion, G. H.; Foley, Ryan J.; Challis, Peter; Kirshner, Robert P.; Vinko, Jozsef; Wheeler, J. Craig; Silverman, Jeffrey M.; Hsiao, Eric Y.; Brown, Peter J.; Filippenko, Alexei V.; Garnavich, Peter; Landsman, Wayne B.; Parrent, Jerod T.; Pritchard, Tyler A.; Roming, Peter W. A.; Wang, Xiaofeng

    2013-01-01

    We report measurements and analysis of high-velocity (HVF) (>20,000 km s –1 ) and photospheric absorption features in a series of spectra of the Type Ia supernova (SN) 2009ig obtained between –14 days and +13 days with respect to the time of maximum B-band luminosity (B-max). We identify lines of Si II, Si III, S II, Ca II, and Fe II that produce both HVF and photospheric-velocity (PVF) absorption features. SN 2009ig is unusual for the large number of lines with detectable HVF in the spectra, but the light-curve parameters correspond to a slightly overluminous but unexceptional SN Ia (M B = –19.46 mag and Δm 15 (B) = 0.90 mag). Similarly, the Si II λ6355 velocity at the time of B-max is greater than 'normal' for an SN Ia, but it is not extreme (v Si = 13,400 km s –1 ). The –14 days and –13 days spectra clearly resolve HVF from Si II λ6355 as separate absorptions from a detached line forming region. At these very early phases, detached HVF are prevalent in all lines. From –12 days to –6 days, HVF and PVF are detected simultaneously, and the two line forming regions maintain a constant separation of about 8000 km s –1 . After –6 days all absorption features are PVF. The observations of SN 2009ig provide a complete picture of the transition from HVF to PVF. Most SNe Ia show evidence for HVF from multiple lines in spectra obtained before –10 days, and we compare the spectra of SN 2009ig to observations of other SNe. We show that each of the unusual line profiles for Si II λ6355 found in early-time spectra of SNe Ia correlate to a specific phase in a common development sequence from HVF to PVF

  4. Modelling and Simulation of Tensile Fracture in High Velocity Compacted Metal Powder

    International Nuclear Information System (INIS)

    Jonsen, P.; Haeggblad, H.-A.

    2007-01-01

    In cold uniaxial powder compaction, powder is formed into a desired shape with rigid tools and a die. After pressing, but before sintering, the compacted powder is called green body. A critical property in the metal powder pressing process is the mechanical properties of the green body. Beyond a green body free from defects, desired properties are high strength and uniform density. High velocity compaction (HVC) using a hydraulic operated hammer is a production method to form powder utilizing a shock wave. Pre-alloyed water atomised iron powder has been HVC-formed into circular discs with high densities. The diametral compression test also called the Brazilian disc test is an established method to measure tensile strength in low strength material like e.g. rock, concrete, polymers and ceramics. During the test a thin disc is compressed across the diameter to failure. The compression induces a tensile stress perpendicular to the compressed diameter. In this study the test have been used to study crack initiation and the tensile fracture process of HVC-formed metal powder discs with a relative density of 99%. A fictitious crack model controlled by a stress versus crack-width relationship is utilized to model green body cracking. Tensile strength is used as a failure condition and limits the stress in the fracture interface. The softening rate of the model is obtained from the corresponding rate of the dissipated energy. The deformation of the powder material is modelled with an elastic-plastic Cap model. The characteristics of the tensile fracture development of the central crack in a diametrically loaded specimen is numerically studied with a three dimensional finite element simulation. Results from the finite element simulation of the diametral compression test shows that it is possible to simulate fracturing of HVC-formed powder. Results from the simulation agree reasonably with experiments

  5. Cognate xenoliths in Mt. Etna lavas: witnesses of the high-velocity body beneath the volcano

    Science.gov (United States)

    Corsaro, Rosa Anna; Rotolo, Silvio Giuseppe; Cocina, Ornella; Tumbarello, Gianvito

    2014-01-01

    Various xenoliths have been found in lavas of the 1763 ("La Montagnola"), 2001, and 2002-03 eruptions at Mt. Etna whose petrographic evidence and mineral chemistry exclude a mantle origin and clearly point to a cognate nature. Consequently, cognate xenoliths might represent a proxy to infer the nature of the high-velocity body (HVB) imaged beneath the volcano by seismic tomography. Petrography allows us to group the cognate xenoliths as follows: i) gabbros with amphibole and amphibole-bearing mela-gabbros, ii) olivine-bearing leuco-gabbros, iii) leuco-gabbros with amphibole, and iv) Plg-rich leuco gabbros. Geobarometry estimates the crystallization pressure of the cognate xenoliths between 1.9 and 4.1 kbar. The bulk density of the cognate xenoliths varies from 2.6 to 3.0 g/cm3. P wave velocities (V P ), calculated in relation to xenolith density, range from 4.9 to 6.1 km/s. The integration of mineralogical, compositional, geobarometric data, and density-dependent V P with recent literature data on 3D V P seismic tomography enabled us to formulate the first hypothesis about the nature of the HVB which, in the depth range of 3-13 km b.s.l., is likely made of intrusive gabbroic rocks. These are believed to have formed at the "solidification front", a marginal zone that encompasses a deep region (>5 km b.s.l.) of Mt. Etna's plumbing system, within which magma crystallization takes place. The intrusive rocks were afterwards fragmented and transported as cognate xenoliths by the volatile-rich and fast-ascending magmas of the 1763 "La Montagnola", 2001 and 2002-03 eruptions.

  6. Molecular analysis of intact preen waxes of Calidris canutus (Aves : Scolopacidae) by gas chromatography/mass spectrometry

    NARCIS (Netherlands)

    Dekker, MHA; Piersma, T; Damste, JSS; Dekker, Marlèn H.A.; Sinninghe Damsté, Jaap S.

    The intact preen wax esters of the red knot Calidris canutus were studied with gas chromatography/mass spectrometry (GC/MS) and GC/MS/MS. In this latter technique, transitions from the molecular ion to fragment ions representing the fatty acid moiety of the wax esters were measured, providing

  7. Facilitating Students' Interaction with Real Gas Properties Using a Discovery-Based Approach and Molecular Dynamics Simulations

    Science.gov (United States)

    Sweet, Chelsea; Akinfenwa, Oyewumi; Foley, Jonathan J., IV

    2018-01-01

    We present an interactive discovery-based approach to studying the properties of real gases using simple, yet realistic, molecular dynamics software. Use of this approach opens up a variety of opportunities for students to interact with the behaviors and underlying theories of real gases. Students can visualize gas behavior under a variety of…

  8. A New Radio Spectral Line Survey of Planetary Nebulae: Exploring Radiatively-driven Heating and Chemistry of Molecular Gas

    Science.gov (United States)

    Bublitz, Jesse; Kastner, Joel H.; Santander-García, Miguel; Montez, Rodolfo; Alcolea, Javier; Balick, Bruce; Bujarrabal, Valentín

    2018-01-01

    We report the results of a survey of mm-wave molecular line emission from nine nearby (Radioastronomie Millimétrique (IRAM) 30 m telescope. Our sample comprises molecule-rich PNe spanning a wide range of central star UV luminosities as well as central star and nebular X-ray emission properties. Nine molecular line frequencies were chosen to investigate the molecular chemistry of these nebulae. New detections of one or more of five molecules -- the molecular mass tracer 13CO and the chemically important trace species HCO+, CN, HCN, and HNC -- were made in at least one PN. We present analysis of emission line flux ratios that are potential diagnostics of the influence that ultraviolet and X-ray radiation have on the chemistry of residual molecular gas in PNe.

  9. MOLECULAR GAS ALONG A BRIGHT H α FILAMENT IN 2A 0335+096 REVEALED BY ALMA

    Energy Technology Data Exchange (ETDEWEB)

    Vantyghem, A. N.; McNamara, B. R.; Hogan, M. T. [Department of Physics and Astronomy, University of Waterloo, Waterloo, ON N2L 3G1 (Canada); Russell, H. R.; Fabian, A. C. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Edge, A. C. [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Nulsen, P. E. J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Combes, F.; Salomé, P. [LERMA, Observatoire de Paris, CNRS, UPMC, PSL Univ., 61 avenue de l’Observatoire, 75014 Paris (France); Baum, S. A.; O’Dea, C. P. [Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB R3T 2N2 (Canada); Donahue, M.; Voit, G. M. [Department of Physics and Astronomy, Michigan State University, 567 Wilson Road, East Lansing, MI 48824 (United States); Main, R. A.; Murray, N. W.; Parrish, I. J [Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8 (Canada); O’Connell, R. W. [Department of Astronomy, University of Virginia, P.O. Box 400235, Charlottesville, VA 22904 (United States); Oonk, J. B. R. [ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, NL-7990 AA Dwingeloo (Netherlands); Sanders, J. S. [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany); Tremblay, G., E-mail: a2vantyg@uwaterloo.ca [Department of Physics and Yale Center for Astronomy and Astrophysics, Yale University, 217 Prospect Street, New Haven, CT 06511 (United States)

    2016-12-01

    We present ALMA CO(1–0) and CO(3–2) observations of the brightest cluster galaxy (BCG) in the 2A 0335+096 galaxy cluster ( z  = 0.0346). The total molecular gas mass of 1.13 ± 0.15 × 10{sup 9} M {sub ⊙} is divided into two components: a nuclear region and a 7 kpc long dusty filament. The central molecular gas component accounts for 3.2 ± 0.4 × 10{sup 8} M {sub ⊙} of the total supply of cold gas. Instead of forming a rotationally supported ring or disk, it is composed of two distinct, blueshifted clumps south of the nucleus and a series of low-significance redshifted clumps extending toward a nearby companion galaxy. The velocity of the redshifted clouds increases with radius to a value consistent with the companion galaxy, suggesting that an interaction between these galaxies <20 Myr ago disrupted a pre-existing molecular gas reservoir within the BCG. Most of the molecular gas, 7.8 ± 0.9 × 10{sup 8} M {sub ⊙}, is located in the filament. The CO emission is co-spatial with a 10{sup 4} K emission-line nebula and soft X-rays from 0.5 keV gas, indicating that the molecular gas has cooled out of the intracluster medium over a period of 25–100 Myr. The filament trails an X-ray cavity, suggesting that the gas has cooled from low-entropy gas that has been lifted out of the cluster core and become thermally unstable. We are unable to distinguish between inflow and outflow along the filament with the present data. Cloud velocities along the filament are consistent with gravitational free-fall near the plane of the sky, although their increasing blueshifts with radius are consistent with outflow.

  10. Cyclic oxidation of coated Oxide Dispersion Strengthened (ODS) alloys in high velocity gas streams at 1100 deg C

    Science.gov (United States)

    Gedwill, M. A.

    1978-01-01

    Several overlay coatings on ODS NiCrAl's were tested in Mach 1 and Mach 0.3 burner rigs to examine oxidation and thermal fatigue performance. The coatings were applied by various methods. Based on weight change, macroscopic, and metallographic observations in Mach 1 tests Nascoat 70 on TD-NiCrAl exhibited the best oxidation resistance. In Mach 0.3 tests PWA 267 and ATD-1, about equally, were the best coatings on YD-NiCrAl (Nascoat 70 was not tested in Mach 0.3 rigs).

  11. WISDOM Project - III. Molecular gas measurement of the supermassive black hole mass in the barred lenticular galaxy NGC4429

    Science.gov (United States)

    Davis, Timothy A.; Bureau, Martin; Onishi, Kyoko; van de Voort, Freeke; Cappellari, Michele; Iguchi, Satoru; Liu, Lijie; North, Eve V.; Sarzi, Marc; Smith, Mark D.

    2018-01-01

    As part of the mm-Wave Interferometric Survey of Dark Object Masses project we present an estimate of the mass of the supermassive black hole (SMBH) in the nearby fast-rotating early-type galaxy NGC4429, that is barred and has a boxy/peanut-shaped bulge. This estimate is based on Atacama Large Millimeter/submillimeter Array (ALMA) cycle-2 observations of the 12CO(3-2) emission line with a linear resolution of ≈13 pc (0.18 arcsec × 0.14 arcsec). NGC4429 has a relaxed, flocculent nuclear disc of molecular gas that is truncated at small radii, likely due to the combined effects of gas stability and tidal shear. The warm/dense 12CO(3-2) emitting gas is confined to the inner parts of this disc, likely again because the gas becomes more stable at larger radii, preventing star formation. The gas disc has a low velocity dispersion of 2.2^{+0.68}_{-0.65} km s-1. Despite the inner truncation of the gas disc, we are able to model the kinematics of the gas and estimate a mass of (1.5 ± 0.1^{+0.15}_{-0.35}) × 108 M⊙ for the SMBH in NGC4429 (where the quoted uncertainties reflect the random and systematic uncertainties, respectively), consistent with a previous upper limit set using ionized gas kinematics. We confirm that the V-band mass-to-light ratio changes by ≈30 per cent within the inner 400 pc of NGC4429, as suggested by other authors. This SMBH mass measurement based on molecular gas kinematics, the sixth presented in the literature, once again demonstrates the power of ALMA to constrain SMBH masses.

  12. DENSE GAS IN MOLECULAR CORES ASSOCIATED WITH PLANCK GALACTIC COLD CLUMPS

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Jinghua; Li, Jin Zeng; Liu, Hong-Li [National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012 (China); Wu, Yuefang; Chen, Ping; Hu, Runjie [Department of Astronomy, Peking University, 100871 Beijing (China); Liu, Tie [Korea Astronomy and Space Science Institute 776, Daedeokdae-ro, Yuseong-gu, Daejeon, 305-348 (Korea, Republic of); Zhang, Tianwei [Peking University Health Science Center, Xueyuan Road 38th, Haidian District, Beijing 100191 (China); Meng, Fanyi [Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 (Germany); Wang, Ke, E-mail: ywu@pku.edu.cn [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München (Germany)

    2016-03-20

    We present the first survey of dense gas toward Planck Galactic Cold Clumps (PGCCs). Observations in the J = 1–0 transitions of HCO{sup +} and HCN toward 621 molecular cores associated with PGCCs were performed using the Purple Mountain Observatory’s 13.7 m telescope. Among them, 250 sources were detected, including 230 cores detected in HCO{sup +} and 158 in HCN. Spectra of the J = 1–0 transitions from {sup 12}CO, {sup 13}CO, and C{sup 18}O at the centers of the 250 cores were extracted from previous mapping observations to construct a multi-line data set. The significantly low detection rate of asymmetric double-peaked profiles, together with the good consistency among central velocities of CO, HCO{sup +}, and HCN spectra, suggests that the CO-selected Planck cores are more quiescent than classical star-forming regions. The small difference between line widths of C{sup 18}O and HCN indicates that the inner regions of CO-selected Planck cores are no more turbulent than the exterior. The velocity-integrated intensities and abundances of HCO{sup +} are positively correlated with those of HCN, suggesting that these two species are well coupled and chemically connected. The detected abundances of both HCO{sup +} and HCN are significantly lower than values in other low- to high-mass star-forming regions. The low abundances may be due to beam dilution. On the basis of an inspection of the parameters given in the PGCC catalog, we suggest that there may be about 1000 PGCC objects that have a sufficient reservoir of dense gas to form stars.

  13. CUTLASS HF radar observations of high-velocity E-region echoes

    Directory of Open Access Journals (Sweden)

    M. V. Uspensky

    Full Text Available A short event of high-velocity E-region echo observations by the Pykkvibaer HF radar is analysed to study echo parameters and the echo relation to the Farley-Buneman plasma instability. The echoes were detected in several beams aligned closely to the magnetic L-shell direction. Two echo groups were identified: one group corresponded to the classical type 1 echoes with velocities close to the nominal ion-acoustic speed of 400 ms1 , while the other group had significantly larger velocities, of the order of 700 ms1 . The mutual relationship between the echo power, Doppler velocity, spectral width and elevation angles for these two groups was studied. Plotting of echo parameters versus slant range showed that all ~700 ms1 echoes originated from larger heights and distances of 500–700 km, while all ~400 ms1 echoes came from lower heights and from farther distances; 700–1000 km. We argue that both observed groups of echoes occurred due to the Farley-Buneman plasma instability excited by strong ( ~70 mVm1 and uniformly distributed electric fields. We show that the echo velocities for the two groups were different because the echoes were received from different heights. Such a separation of echo heights occurred due to the differing amounts of ionospheric refraction at short and large ranges. Thus, the ionospheric refraction and related altitude modulation of ionospheric parameters are the most important factors to consider, when various characteristics of E-region decametre irregularities are derived from HF radar measurements.

    Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; polar ionosphere

  14. Conformal and highly luminescent monolayers of Alq3 prepared by gas-phase molecular layer deposition.

    Science.gov (United States)

    Räupke, André; Albrecht, Fabian; Maibach, Julia; Behrendt, Andreas; Polywka, Andreas; Heiderhoff, Ralf; Helzel, Jonatan; Rabe, Torsten; Johannes, Hans-Hermann; Kowalsky, Wolfgang; Mankel, Eric; Mayer, Thomas; Görrn, Patrick; Riedl, Thomas

    2014-01-22

    The gas-phase molecular layer deposition (MLD) of conformal and highly luminescent monolayers of tris(8-hydroxyquinolinato)aluminum (Alq3) is reported. The controlled formation of Alq3 monolayers is achieved for the first time by functionalization of the substrate with amino groups, which serve as initial docking sites for trimethyl aluminum (TMA) molecules binding datively to the amine. Thereby, upon exposure to 8-hydroxyquinoline (8-HQ), the self-limiting formation of highly luminescent Alq3 monolayers is afforded. The growth process and monolayer formation were studied and verified by in situ quartz crystal monitoring, optical emission and absorption spectroscopy, and X-ray photoelectron spectroscopy. The nature of the MLD process provides an avenue to coat arbitrarily shaped 3D surfaces and porous structures with high surface areas, as demonstrated in this work for silica aerogels. The concept presented here paves the way to highly sensitive luminescent sensors and dye-sensitized metal oxides for future applications (e.g., in photocatalysis and solar cells).

  15. Effect of molecular structure on fragmentation of isolated organic molecules in solid rare gas matrices

    International Nuclear Information System (INIS)

    Kobzarenko, A.V.; Sukhov, F.F.; Orlov, A.Yu.; Kovalev, G.V.; Baranova, I.A.; Feldman, V.I.

    2012-01-01

    The effect of excess energy on the primary radical cations of bifunctional carbonyl compounds and aliphatic alkynes was simulated by matrix isolation method using rare gas matrices with various ionization potentials. The formation of fragmentation products was monitored by EPR and FTIR spectroscopy. It was shown that the radical cations of bifunctional compounds (CH 3 OCH 2 COCH 3 and CH 3 COCOCH 3 ) dissociated effectively yielding · CH 3 radicals upon irradiation in solid argon matrix at T≤16 K. In addition to isolated methyl radicals, the radical pairs consisting of two methyl radicals separated by two CO molecules were detected in the case of diacetyl. The probability of fragmentation decreases with the decreasing excess energy by switching from Ar to Xe. In general, bifunctional molecules were found to be less stable to “hot” ionic fragmentation in low-temperature solids in comparison with simple prototype compounds. In the case of alkynes of the R--C≡CH type, a noticeable yield of fragmentation products was observed when R=–C(CH 3 ) 3 , but it was negligible for R=–CH 3 . The mechanisms of “hot” reactions and excess energy relaxation are discussed. - Highlights: ► Radiolysis of bifunctional organic compounds and alkynes. ► Dependence of “hot” fragmentation probability from molecular structure. ► Ions of bifunctional compounds are less stable than those of monofunctional ones. ► Alkynes are rather stable to “hot” fragmentation.

  16. Positrons in gas filled traps and their transport in molecular gases

    Energy Technology Data Exchange (ETDEWEB)

    Petrovic, Z Lj; Bankovic, A; Marjanovic, S; Suvakov, M; Dujko, S; Malovic, G [Institute of Physics, University of Belgrade, Pregrevica 118, POB 68, Zemun (Serbia); White, R D [ARC Centre for Antimatter-Matter Studies, James Cook University, Townsville 4810, QLD (Australia); Buckman, S J, E-mail: zoran@ipb.ac.rs [ARC Centre for Antimatter-Matter Studies, Australian National University, Canberra, ACT, 0200 (Australia)

    2011-01-01

    In this paper we give a review of two recent developments in positron transport, calculation of transport coefficients for a relatively complete set of collision cross sections for water vapour and for application of they Monte Carlo technique to model gas filled subexcitation positron traps such as Penning Malmberg Surko (Surko) trap. Calculated transport coefficients, very much like those for argon and other molecular gases show several new kinetic phenomena. The most important is the negative differential conductivity (NDC) for the bulk drift velocity when the flux drift velocity shows no sign of NDC. These results in water vapour are similar to the results in argon or hydrogen. The same technique that has been used for positron (and previously electron) transport may be applied to model development of particles in a Surko trap. We have provided calculation of the ensemble of positrons in the trap from an initial beam like distribution to the fully thermalised distribution. This model, however, does not include plasma effects (interaction between charged particles) and may be applied for lower positron densities.

  17. A Molecularly Imprinted Electrochemical Gas Sensor to Sense Butylated Hydroxytoluene in Air

    Directory of Open Access Journals (Sweden)

    Shadi Emam

    2018-01-01

    Full Text Available Alzheimer’s disease (AD is a neurodegenerative disease, which affects millions of people worldwide. Curing this disease has not gained much success so far. Exhaled breath gas analysis offers an inexpensive, noninvasive, and immediate method for detecting a large number of diseases, including AD. In this paper, a new method is proposed to detect butylated hydroxytoluene (BHT in the air, which is one of the chemicals found in the breath print of AD patients. A three-layer sensor was formed through deposition of a thin layer of graphene onto a glassy carbon substrate. Selective binding of the analyte was facilitated by electrochemically initiated polymerization of a solution containing the desired target molecule. Subsequent polymerization and removal of the analyte yielded a layer of polypyrrole, a conductive polymer, on top of the sensor containing molecularly imprinted cavities selective for the target molecule. Two sets of sensors have been developed. First, the graphene sensor has been fabricated with a layer of reduced graphene oxide (RGO and tested over 5–100 part per million (ppm. For the second batch, Prussian blue was added to graphene before polymerization, mainly for enhancing the electrochemical properties. The sensor was tested over 0.02-1 parts per billion (ppb level of concentration while the sensor resistance has been monitored.

  18. Molecular insights of Gas6/TAM in cancer development and therapy.

    Science.gov (United States)

    Wu, Guiling; Ma, Zhiqiang; Hu, Wei; Wang, Dongjin; Gong, Bing; Fan, Chongxi; Jiang, Shuai; Li, Tian; Gao, Jianyuan; Yang, Yang

    2017-03-23

    Since growth arrest-specific gene 6 (Gas6) was discovered in 1988, numerous studies have highlighted the role of the Gas6 protein and its receptors Tyro3, Axl and Mer (collectively referred to as TAM), in proliferation, apoptosis, efferocytosis, leukocyte migration, sequestration and platelet aggregation. Gas6 has a critical role in the development of multiple types of cancers, including pancreatic, prostate, oral, ovarian and renal cancers. Acute myelocytic leukaemia (AML) is a Gas6-dependent cancer, and Gas6 expression predicts poor prognosis in AML. Interestingly, Gas6 also has a role in establishing tumour dormancy in the bone marrow microenvironment and in suppressing intestinal tumorigenesis. Numerous studies regarding cancer therapy have targeted Gas6 and TAM receptors with good results. However, some findings have suggested that Gas6 is associated with the development of resistance to cancer therapies. Concerning these significant effects of Gas6 in numerous cancers, we discuss the roles of Gas6 in cancer development in this review. First, we introduce basic knowledge on Gas6 and TAM receptors. Next, we describe and discuss the involvement of Gas6 and TAM receptors in cancers from different organ systems. Finally, we highlight the progress in therapies targeting Gas6 and TAM receptors. This review presents the significant roles of Gas6 in cancers from different systems and may contribute to the continued promotion of Gas6 as a therapeutic target.

  19. Dynamics in ion-molecule collisions at high velocities: One- and two-electron processes

    International Nuclear Information System (INIS)

    Wang, Yudong.

    1992-01-01

    This dissertation addresses the dynamic interactions in ion-molecule collisions. Theoretical methods are developed for single and multiple electron transitions in fast collisions with diatomic molecules by heavy-ion projectiles. Various theories and models are developed to treat the three basic inelastic processes (excitation, ionization and charge transfer) involving one and more electrons. The development, incorporating the understanding of ion-atom collision theories with some unique characteristics for molecular targets, provides new insights into phenomena that are absent from collisions with atomic targets. The influence from the multiple scattering centers on collision dynamics is assessed. For diatomic molecules, effects due to a fixed molecular orientation or alignment are calculated and compared with available experimental observations. Compared with excitation and ionization, electron capture, which probes deeper into the target, presents significant two-center interference and strong orientation dependence. Attention has been given in this dissertation to exploring mechanisms for two-and multiple electron transitions. Application of independent electron approximation to transfer excitation from molecular hydrogen is studied. Electron-electron interaction originated from projectile and target nuclear centers is studied in conjunction with the molecular nature of target. Limitations of the present theories and models as well as possible new areas for future theoretical and experimental applications are also discussed. This is the first attempt to describe multi-electron processes in molecular dynamics involving fast highly charged ions

  20. Friction in Carborane-Based Molecular Rotors Driven by Gas Flow or Electric Field: Classical Molecular Dynamics

    Czech Academy of Sciences Publication Activity Database

    Prokop, Alexandr; Vacek, Jaroslav; Michl, Josef

    2012-01-01

    Roč. 6, č. 3 (2012), s. 1901-1914 ISSN 1936-0851 R&D Projects: GA ČR GA203/09/1802; GA MŠk ME09020 Institutional research plan: CEZ:AV0Z40550506 Keywords : molecular rotors * molecular dynamics * potential energy barriers * friction * intramolecular vibrational redistribution Subject RIV: CC - Organic Chemistry Impact factor: 12.062, year: 2012

  1. Molecular dynamics simulation of chemical vapor deposition of amorphous carbon. Dependence on H/C ratio of source gas

    International Nuclear Information System (INIS)

    Ito, Atsushi M.; Takayama, Arimichi; Nakamura, Hiroaki; Saito, Seiki; Ohno, Noriyasu; Kajita, Shin

    2011-01-01

    By molecular dynamics simulation, the chemical vapor deposition of amorphous carbon onto graphite and diamond surfaces was studied. In particular, we investigated the effect of source H/C ratio, which is the ratio of the number of hydrogen atoms to the number of carbon atoms in a source gas, on the deposition process. In the present simulation, the following two source gas conditions were tested: one was that the source gas was injected as isolated carbon and hydrogen atoms, and the other was that the source gas was injected as hydrocarbon molecules. Under the former condition, we found that as the source H/C ratio increases, the deposition rate of carbon atoms decreases exponentially. This exponential decrease in the deposition rate with increasing source H/C ratio agrees with experimental data. However, under the latter molecular source condition, the deposition rate did not decrease exponentially because of a chemical reaction peculiar to the type of hydrocarbon in the source gas. (author)

  2. 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.

  3. Pure and Modified Co-Poly(amide-12-b-ethylene oxide Membranes for Gas Separation Studied by Molecular Investigations

    Directory of Open Access Journals (Sweden)

    Luana De Lorenzo

    2012-06-01

    Full Text Available This paper deals with a theoretical investigation of gas transport properties in a pure and modified PEBAX block copolymer membrane with N-ethyl-o/p-toluene sulfonamide (KET as additive molecules. Molecular dynamics simulations using COMPASS force field, Gusev-Suter Transition State Theory (TST and Monte Carlo methods were used. Bulk models of PEBAX and PEBAX/KET in different copolymer/additive compositions were assembled and analyzed to evaluate gas permeability and morphology to characterize structure-performance relationships.

  4. A New Radio Spectral Line Survey of Planetary Nebulae: Exploring Radiatively Driven Heating and Chemistry of Molecular Gas

    Science.gov (United States)

    Bublitz, Jesse

    Planetary nebulae contain shells of cold gas and dust whose heating and chemistry is likely driven by UV and X-ray emission from their central stars and from wind-collision-generated shocks. We present the results of a survey of molecular line emissions in the 88 - 235 GHz range from nine nearby (Radioastronomie Millimetrique. Rotational transitions of nine molecules, including the well-studied CO isotopologues and chemically important trace species, were observed and the results compared with and augmented by previous studies of molecular gas in PNe. Lines of the molecules HCO+, HNC, HCN, and CN, which were detected in most objects, represent new detections for five planetary nebulae in our study. Flux ratios were analyzed to identify correlations between the central star and/or nebular ultraviolet/X-ray luminosities and the molecular chemistries of the nebulae. Analysis reveals the apparent dependence of the HNC/HCN line ratio on PN central star UV luminosity. There exists no such clear correlation between PN X-rays and various diagnostics of PN molecular chemistry. The correlation between HNC/HCN ratio and central star UV luminosity hints at the potential of molecular emission line studies of PNe for improving our understanding of the role that high-energy radiation plays in the heating and chemistry of photodissociation regions.

  5. Mapping the Diffusion Potential of a Reconstructed Au(111) Surface at Nanometer Scale with 2D Molecular Gas

    International Nuclear Information System (INIS)

    Yan Shi-Chao; Xie Nan; Gong Hui-Qi; Guo Yang; Shan Xin-Yan; Lu Xing-Hua; Sun Qian

    2012-01-01

    The adsorption and diffusion behaviors of benzene molecules on an Au(111) surface are investigated by low-temperature scanning tunneling microscopy. A herringbone surface reconstruction of the Au(111) surface is imaged with atomic resolution, and significantly different behaviors are observed for benzene molecules adsorbed on step edges and terraces. The electric field induced modification in the molecular diffusion potential is revealed with a 2D molecular gas model, and a new method is developed to map the diffusion potential over the reconstructed Au(111) surface at the nanometer scale. (condensed matter: structure, mechanical and thermal properties)

  6. Subarcsecond observations of NGC 7538 IRS 1: Continuum distribution and dynamics of molecular gas

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Lei; Shi, Hui [National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing 100012 (China); Zhao, Jun-Hui [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Wright, M. C. H. [Department of Astronomy, University of California, Berkeley, Berkeley, CA 94720 (United States); Sandell, Göran [SOFIA-USRA, NASA Ames Research Center, MS 232-12, Building N232, Rm. 146, P.O. Box 1, Moffett Field, CA 94035-0001 (United States); Wu, Yue-Fang [Department of Astronomy, Peking University, Beijing 100871 (China); Brogan, Crystal; Corder, Stuartt, E-mail: lzhu@nao.cas.cn [NRAO, 520 Edgemont Road, Charlottesville, VA 22903 (United States)

    2013-12-10

    We report new results based on the analysis of the Submillimeter Array (SMA) and Combined Array for Research in Millimeter-wave Astronomy (CARMA) observations of NGC 7538 IRS 1 at 1.3 and 3.4 mm with subarcsecond resolutions. With angular resolutions ∼0.''7, the SMA and CARMA observations show that the continuum emission at 1.3 and 3.4 mm from the hyper-compact H II region IRS 1 is dominated by a compact source with a tail-like extended structure to the southwest of IRS 1. With a CARMA B-array image at 1.3 mm convolved to 0.''1, we resolve the hyper-compact H II region into two components: an unresolved hyper-compact core, and a north-south extension with linear sizes of <270 AU and ∼2000 AU, respectively. The fine structure observed with CARMA is in good agreement with the previous Very Large Array results at centimeter wavelengths, suggesting that the hyper-compact H II region at the center of IRS 1 is associated with an ionized bipolar outflow. We image the molecular lines OCS(19-18) and CH{sub 3}CN(12-11) as well as {sup 13}CO(2-1) surrounding IRS 1, showing a velocity gradient along the southwest-northeast direction. The spectral line profiles in {sup 13}CO(2-1), CO(2-1), and HCN(1-0) observed toward IRS 1 show broad redshifted absorption, providing evidence for gas infall with rates in the range of 3-10 × 10{sup –3} M {sub ☉} yr{sup –1} inferred from our observations.

  7. H ii REGION G46.5-0.2: THE INTERPLAY BETWEEN IONIZING RADIATION, MOLECULAR GAS, AND STAR FORMATION

    International Nuclear Information System (INIS)

    Paron, S.; Ortega, M. E.; Dubner, G.; Petriella, A.; Giacani, E.; Yuan, Jing-Hua; Li, Jin Zeng; Liu, Hongli; Huang, Ya Fang; Zhang, Si-Ju; Wu, Yuefang

    2015-01-01

    H ii regions are particularly interesting because they can generate dense layers of gas and dust, elongated columns or pillars of gas pointing toward the ionizing sources, and cometary globules of dense gas where triggered star formation can occur. Understanding the interplay between the ionizing radiation and the dense surrounding gas is very important to explain the origin of these peculiar structures, and hence to characterize triggered star formation. G46.5-0.2 (G46), a poorly studied galactic H ii region located at about 4 kpc, is an excellent target for performing this kind of study. Using public molecular data extracted from the Galactic Ring Survey ( 13 CO J = 1–0) and from the James Clerk Maxwell Telescope data archive ( 12 CO, 13 CO, C 18 O J = 3–2, HCO + , and HCN J = 4–3), and infrared data from the GLIMPSE and MIPSGAL surveys, we perform a complete study of G46, its molecular environment, and the young stellar objects (YSOs) placed around it. We found that G46, probably excited by an O7V star, is located close to the edge of the GRSMC G046.34-00.21 molecular cloud. It presents a horse-shoe morphology opening in the direction of the cloud. We observed a filamentary structure in the molecular gas likely related to G46 and not considerable molecular emission toward its open border. We found that about 10′ to the southwest of G46 there are some pillar-like features, shining at 8 μm and pointing toward the H ii region open border. We propose that the pillar-like features were carved and sculpted by the ionizing flux from G46. We found several YSOs likely embedded in the molecular cloud grouped in two main concentrations: one, closer to the G46 open border consisting of Class II type sources, and another mostly composed of Class I type YSOs located just ahead of the pillar-like features, strongly suggesting an age gradient in the YSO distribution

  8. H ii REGION G46.5-0.2: THE INTERPLAY BETWEEN IONIZING RADIATION, MOLECULAR GAS, AND STAR FORMATION

    Energy Technology Data Exchange (ETDEWEB)

    Paron, S.; Ortega, M. E.; Dubner, G.; Petriella, A.; Giacani, E. [Instituto de Astronomía y Física del Espacio (IAFE, CONICET-UBA), CC 67, Suc. 28, 1428 Buenos Aires (Argentina); Yuan, Jing-Hua; Li, Jin Zeng; Liu, Hongli; Huang, Ya Fang; Zhang, Si-Ju [National Astronomical Observatories, Chinese Academy of Sciences, 20 A Datun Road, Chaoyang District, Beijing 100012 (China); Wu, Yuefang, E-mail: sparon@iafe.uba.ar [Department of Astronomy, Peking University, 100871 Beijing (China)

    2015-06-15

    H ii regions are particularly interesting because they can generate dense layers of gas and dust, elongated columns or pillars of gas pointing toward the ionizing sources, and cometary globules of dense gas where triggered star formation can occur. Understanding the interplay between the ionizing radiation and the dense surrounding gas is very important to explain the origin of these peculiar structures, and hence to characterize triggered star formation. G46.5-0.2 (G46), a poorly studied galactic H ii region located at about 4 kpc, is an excellent target for performing this kind of study. Using public molecular data extracted from the Galactic Ring Survey ({sup 13}CO J = 1–0) and from the James Clerk Maxwell Telescope data archive ({sup 12}CO, {sup 13}CO, C{sup 18}O J = 3–2, HCO{sup +}, and HCN J = 4–3), and infrared data from the GLIMPSE and MIPSGAL surveys, we perform a complete study of G46, its molecular environment, and the young stellar objects (YSOs) placed around it. We found that G46, probably excited by an O7V star, is located close to the edge of the GRSMC G046.34-00.21 molecular cloud. It presents a horse-shoe morphology opening in the direction of the cloud. We observed a filamentary structure in the molecular gas likely related to G46 and not considerable molecular emission toward its open border. We found that about 10′ to the southwest of G46 there are some pillar-like features, shining at 8 μm and pointing toward the H ii region open border. We propose that the pillar-like features were carved and sculpted by the ionizing flux from G46. We found several YSOs likely embedded in the molecular cloud grouped in two main concentrations: one, closer to the G46 open border consisting of Class II type sources, and another mostly composed of Class I type YSOs located just ahead of the pillar-like features, strongly suggesting an age gradient in the YSO distribution.

  9. H II Region G46.5-0.2: The Interplay between Ionizing Radiation, Molecular Gas, and Star Formation

    Science.gov (United States)

    Paron, S.; Ortega, M. E.; Dubner, G.; Yuan, Jing-Hua; Petriella, A.; Giacani, E.; Zeng Li, Jin; Wu, Yuefang; Liu, Hongli; Huang, Ya Fang; Zhang, Si-Ju

    2015-06-01

    H ii regions are particularly interesting because they can generate dense layers of gas and dust, elongated columns or pillars of gas pointing toward the ionizing sources, and cometary globules of dense gas where triggered star formation can occur. Understanding the interplay between the ionizing radiation and the dense surrounding gas is very important to explain the origin of these peculiar structures, and hence to characterize triggered star formation. G46.5-0.2 (G46), a poorly studied galactic H ii region located at about 4 kpc, is an excellent target for performing this kind of study. Using public molecular data extracted from the Galactic Ring Survey (13CO J = 1-0) and from the James Clerk Maxwell Telescope data archive (12CO, 13CO, C18O J = 3-2, HCO+, and HCN J = 4-3), and infrared data from the GLIMPSE and MIPSGAL surveys, we perform a complete study of G46, its molecular environment, and the young stellar objects (YSOs) placed around it. We found that G46, probably excited by an O7V star, is located close to the edge of the GRSMC G046.34-00.21 molecular cloud. It presents a horse-shoe morphology opening in the direction of the cloud. We observed a filamentary structure in the molecular gas likely related to G46 and not considerable molecular emission toward its open border. We found that about 10‧ to the southwest of G46 there are some pillar-like features, shining at 8 μm and pointing toward the H ii region open border. We propose that the pillar-like features were carved and sculpted by the ionizing flux from G46. We found several YSOs likely embedded in the molecular cloud grouped in two main concentrations: one, closer to the G46 open border consisting of Class II type sources, and another mostly composed of Class I type YSOs located just ahead of the pillar-like features, strongly suggesting an age gradient in the YSO distribution.

  10. A Comprehensive Pitting Study of High Velocity Oxygen Fuel Inconel 625 Coating by Using Electrochemical Testing Techniques

    Science.gov (United States)

    Niaz, Akbar; Khan, Sajid Ullah

    2016-01-01

    In the present work, Inconel 625 was coated on a mild steel substrate using a high velocity oxygen fuel coating process. The pitting propensity of the coating was tested by using open circuit potential versus time, potentiodynamic polarization, electrochemical potentiokinetic reactivation, and scanning electrochemical microscopy. The pitting propensity of the coating was compared with bulk Inconel 625 alloy. The results confirmed that there were regions of different electrochemical activities on the coating which have caused pitting corrosion.

  11. Anomalous resistivity due to low-frequency turbulence. [of collisionless plasma with limited acceleration of high velocity runaway electrons

    Science.gov (United States)

    Rowland, H. L.; Palmadesso, P. J.

    1983-01-01

    Large amplitude ion cyclotron waves have been observed on auroral field lines. In the presence of an electric field parallel to the ambient magnetic field these waves prevent the acceleration of the bulk of the plasma electrons leading to the formation of a runaway tail. It is shown that low-frequency turbulence can also limit the acceleration of high-velocity runaway electrons via pitch angle scattering at the anomalous Doppler resonance.

  12. Building America Case Study: Standard- Versus High-Velocity Air Distribution in High-Performance Townhomes, Denver, Colorado

    Energy Technology Data Exchange (ETDEWEB)

    A. Poerschke, R. Beach, T. Begg

    2017-06-01

    IBACOS investigated the performance of a small-diameter high-velocity heat pump system compared to a conventional system in a new construction triplex townhouse. A ductless heat pump system also was installed for comparison, but the homebuyer backed out because of aesthetic concerns about that system. In total, two buildings, having identical solar orientation and comprised of six townhomes, were monitored for comfort and energy performance.

  13. Gas kinematics and star formation in the filamentary molecular cloud G47.06+0.26

    Science.gov (United States)

    Xu, Jin-Long; Xu, Ye; Zhang, Chuan-Peng; Liu, Xiao-Lan; Yu, Naiping; Ning, Chang-Chun; Ju, Bing-Gang

    2018-01-01

    Aims: We performed a multi-wavelength study toward the filamentary cloud G47.06+0.26 to investigate the gas kinematics and star formation. Methods: We present the 12CO (J = 1-0), 13CO (J = 1-0) and C18O (J = 1-0) observations of G47.06+0.26 obtained with the Purple Mountain Observation (PMO) 13.7 m radio telescope to investigate the detailed kinematics of the filament. Radio continuum and infrared archival data were obtained from the NRAO VLA Sky Survey (NVSS), the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL), the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) survey, and the Multi-band Imaging Photometer Survey of the Galaxy (MIPSGAL). To trace massive clumps and extract young stellar objects in G47.06+0.26, we used the BGPS catalog v2.0 and the GLIMPSE I catalog, respectively. Results: The 12CO (J = 1-0) and 13CO (J = 1-0) emission of G47.06+0.26 appear to show a filamentary structure. The filament extends about 45' (58.1 pc) along the east-west direction. The mean width is about 6.8 pc, as traced by the 13CO (J = 1-0) emission. G47.06+0.26 has a linear mass density of 361.5 M⊙pc-1. The external pressure (due to neighboring bubbles and H II regions) may help preventing the filament from dispersing under the effects of turbulence. From the velocity-field map, we discern a velocity gradient perpendicular to G47.06+0.26. From the Bolocam Galactic Plane Survey (BGPS) catalog, we found nine BGPS sources in G47.06+0.26, that appear to these sources have sufficient mass to form massive stars. We obtained that the clump formation efficiency (CFE) is 18% in the filament. Four infrared bubbles were found to be located in, and adjacent to, G47.06+0.26. Particularly, infrared bubble N98 shows a cometary structure. CO molecular gas adjacent to N98 also shows a very intense emission. H II regions associated with infrared bubbles can inject the energy to surrounding gas. We calculated the kinetic energy, ionization energy, and thermal energy

  14. THE FAR-INFRARED, UV, AND MOLECULAR GAS RELATION IN GALAXIES UP TO z = 2.5

    International Nuclear Information System (INIS)

    Nordon, R.; Lutz, D.; Saintonge, A.; Berta, S.; Wuyts, S.; Förster Schreiber, N. M.; Genzel, R.; Magnelli, B.; Poglitsch, A.; Popesso, P.; Rosario, D.; Sturm, E.; Tacconi, L. J.

    2013-01-01

    We use the infrared excess (IRX) FIR/UV luminosity ratio to study the relation between the effective UV attenuation (A IRX ) and the UV spectral slope (β) in a sample of 450 1 * ) > 9.3. Thus, we are able to study galaxies on and even below the main SFR-stellar mass relation (main sequence). We find that main-sequence galaxies form a tight sequence in the IRX-β plane, which has a flatter slope than commonly used relations. This slope favors a Small-Magellanic-Cloud-like UV extinction curve, though the interpretation is model dependent. The scatter in the A IRX -β plane correlates with the position of the galaxies in the SFR-M * plane. Using a smaller sample of galaxies with CO gas masses, we study the relation between the UV attenuation and the molecular gas content. We find a very tight relation between the scatter in the IRX-β plane and the specific attenuation S A , a quantity that represents the attenuation contributed by the molecular gas mass per young star. S A is sensitive to both the geometrical arrangement of stars and dust and to the compactness of the star-forming regions. We use this empirical relation to derive a method for estimating molecular gas masses using only widely available integrated rest-frame UV and FIR photometry. The method produces gas masses with an accuracy between 0.12 and 0.16 dex in samples of normal galaxies between z ∼ 0 and z ∼ 1.5. Major mergers and submillimeter galaxies follow a different S A relation.

  15. Gas sorption and barrier properties of polymeric membranes from molecular dynamics and Monte Carlo simulations.

    Science.gov (United States)

    Cozmuta, Ioana; Blanco, Mario; Goddard, William A

    2007-03-29

    It is important for many industrial processes to design new materials with improved selective permeability properties. Besides diffusion, the molecule's solubility contributes largely to the overall permeation process. This study presents a method to calculate solubility coefficients of gases such as O2, H2O (vapor), N2, and CO2 in polymeric matrices from simulation methods (Molecular Dynamics and Monte Carlo) using first principle predictions. The generation and equilibration (annealing) of five polymer models (polypropylene, polyvinyl alcohol, polyvinyl dichloride, polyvinyl chloride-trifluoroethylene, and polyethylene terephtalate) are extensively described. For each polymer, the average density and Hansen solubilities over a set of ten samples compare well with experimental data. For polyethylene terephtalate, the average properties between a small (n = 10) and a large (n = 100) set are compared. Boltzmann averages and probability density distributions of binding and strain energies indicate that the smaller set is biased in sampling configurations with higher energies. However, the sample with the lowest cohesive energy density from the smaller set is representative of the average of the larger set. Density-wise, low molecular weight polymers tend to have on average lower densities. Infinite molecular weight samples do however provide a very good representation of the experimental density. Solubility constants calculated with two ensembles (grand canonical and Henry's constant) are equivalent within 20%. For each polymer sample, the solubility constant is then calculated using the faster (10x) Henry's constant ensemble (HCE) from 150 ps of NPT dynamics of the polymer matrix. The influence of various factors (bad contact fraction, number of iterations) on the accuracy of Henry's constant is discussed. To validate the calculations against experimental results, the solubilities of nitrogen and carbon dioxide in polypropylene are examined over a range of

  16. Gas

    International Nuclear Information System (INIS)

    1996-01-01

    The French government has decided to modify the conditions of extension of local natural gas authorities to neighbouring districts. The European Union is studying the conditions of internal gas market with the objective of more open markets although considering public service requirements

  17. Carbon Molecular Sieve Membranes Derived from Tröger's Base-Based Microporous Polyimide for Gas Separation.

    Science.gov (United States)

    Wang, Zhenggong; Ren, Huiting; Zhang, Shenxiang; Zhang, Feng; Jin, Jian

    2018-03-09

    Carbon molecular sieve (CMS)-based membranes have attracted great attention because of their outstanding gas-separation performance. The polymer precursor is a key point for the preparation of high-performance CMS membranes. In this work, a microporous polyimide precursor containing a Tröger's base unit was used for the first time to prepare CMS membranes. By optimizing the pyrolysis procedure and the soaking temperature, three TB-CMS membranes were obtained. Gas-permeation tests revealed that the comprehensive gas-separation performance of the TB-CMS membranes was greatly enhanced relative to that of most state-of-the-art CMS membranes derived from polyimides reported so far. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Gas-chromatographic separation of hydrogen isotopes mixtures on capillary molecular sieve 5 A column at 173 K

    International Nuclear Information System (INIS)

    Bidica, N.; Preda, A.; Stanciu, V.

    2002-01-01

    Analysis of a gas mixture of hydrogen species, is not too easy because the differences in their physical-chemical properties are very small; the most different are their masses, and consequently most common analytical method appear to be the mass-spectrometry. However, the impossibility to distinguish between two ions (atomic or molecular) with the same mass renders this method as unapplicable. Another problem is the decay of tritium with production of 3 He. These disadvantages of mass-spectrometry have made that other analytical methods, like gas chromatography, to be considered and developed. Thus, there are many papers about various chromatographic columns especially prepared for hydrogen species separation but the preparation and treatment of these columns are very difficult to reproduce. Besides these, there are two other main disadvantages: column operating temperature is very low and long retention times for hydrogen species (more than half an hour) are required. However, the gas-chromatography method still remains an appropriate one. The method described in this paper was based on using a capillary molecular sieve 5A column which has been operated for this kind of separation. The retention times were relatively short, about 8-9 minutes. The carrier gas was Ne and the detector - TCD. In the paper chromatograms for various carrier flow rates and various hydrogen isotope mixtures are presented. The results demonstrated a quite good efficiency for H 2 , HD, D 2 and a not very good one for orthoH 2 -paraH 2 . (authors)

  19. [Gas chromatography with a Pulsed discharge helium ionization detector for measurement of molecular hydrogen(H2) in the atmosphere].

    Science.gov (United States)

    Luan, Tian; Fang, Shuang-xi; Zhou, Ling-xi; Wang, Hong-yang; Zhang, Gen

    2015-01-01

    A high precision GC system with a pulsed discharge helium ionization detector was set up based on the commercial Agilent 7890A gas chromatography. The gas is identified by retention time and the concentration is calculated through the peak height. Detection limit of the system is about 1 x 10(-9) (mole fraction, the same as below). The standard deviation of 140 continuous injections with a standard cylinder( concentration is roughly 600 x 10(-9)) is better than 0.3 x 10(-9). Between 409.30 x 10(-9) and 867.74 x 10(-9) molecular hydrogen mole fractions and peak height have good linear response. By using two standards to quantify the air sample, the precision meets the background molecular hydrogen compatibility goal within the World Meteorological Organization/Global Atmosphere Watch (WMO/GAW) program. Atmospheric molecular hydrogen concentration at Guangzhou urban area was preliminarily measured by this method from January to November 2013. The results show that the atmospheric molecular hydrogen mole fraction varies from 450 x 10(-9) to 700 x 10(-9) during the observation period, with the lowest value at 14:00 (Beijing time, the same as below) and the peak value at 20:00. The seasonal variation of atmospheric hydrogen at Guangzhou area was similar with that of the same latitude stations in northern hemisphere.

  20. Seeing the Forest Through the Trees: The Distribution and Properties of Dense Molecular Gas in the Milky Way Galaxy

    Science.gov (United States)

    Ellsworth-Bowers, Timothy P.

    The Milky Way Galaxy serves as a vast laboratory for studying the dynamics and evolution of the dense interstellar medium and the processes of and surrounding massive star formation. From our vantage point within the Galactic plane, however, it has been extremely difficult to construct a coherent picture of Galactic structure; we cannot see the forest for the trees. The principal difficulties in studying the structure of the Galactic disk have been obscuration by the ubiquitous dust and molecular gas and confusion between objects along a line of sight. Recent technological advances have led to large-scale blind surveys of the Galactic plane at (sub-)millimeter wavelengths, where Galactic dust is generally optically thin, and have opened a new avenue for studying the forest. The Bolocam Galactic Plane Survey (BGPS) observed over 190 deg 2 of the Galactic plane in dust continuum emission near lambda = 1.1 mm, producing a catalog of over 8,000 dense molecular cloud structures across a wide swath of the Galactic disk. Deriving the spatial distribution and physical properties of these objects requires knowledge of distance, a component lacking in the data themselves. This thesis presents a generalized Bayesian probabilistic distance estimation method for dense molecular cloud structures, and demonstrates it with the BGPS data set. Distance probability density functions (DPDFs) are computed from kinematic distance likelihoods (which may be double- peaked for objects in the inner Galaxy) and an expandable suite of prior information to produce a comprehensive tally of our knowledge (and ignorance) of the distances to dense molecular cloud structures. As part of the DPDF formalism, this thesis derives several prior DPDFs for resolving the kinematic distance ambiguity in the inner Galaxy. From the collection of posterior DPDFs, a set of objects with well-constrained distance estimates is produced for deriving Galactic structure and the physical properties of dense molecular

  1. ALMA Observations of the Water Fountain Pre-Planetary Nebula IRAS 16342-3814: High-Velocity Bipolar Jets and an Expanding Torus.

    Science.gov (United States)

    Sahai, R; Vlemmings, W H T; Gledhill, T; Sánchez Contreras, C; Lagadec, E; Nyman, L-Å; Quintana-Lacaci, G

    2017-01-20

    We have mapped 12 CO J=3-2 and other molecular lines from the "water-fountain" bipolar pre-planetary nebula (PPN) IRAS 16342-3814 with [Formula: see text] resolution using ALMA. We find (i) two very high-speed knotty, jet-like molecular outflows, (ii) a central high-density (> few × 10 6 cm -3 ), expanding torus of diameter 1300 AU, and (iii) the circumstellar envelope of the progenitor AGB, generated by a sudden, very large increase in the mass-loss rate to > 3.5 × 10 -4 M ⊙ yr -1 in the past ~455 yr. Strong continuum emission at 0.89 mm from a central source (690 mJy), if due to thermally-emitting dust, implies a substantial mass (0.017 M ⊙ ) of very large (~mm-sized) grains. The measured expansion ages of the above structural components imply that the torus (age~160 yr) and the younger high-velocity outflow (age~110 yr) were formed soon after the sharp increase in the AGB mass-loss rate. Assuming a binary model for the jets in IRAS 16342, the high momentum rate for the dominant jet-outflow in IRAS 16342 implies a high minimum accretion rate, ruling out standard Bondi-Hoyle-Lyttleton wind accretion and wind Roche lobe overflow (RLOF) models with white-dwarf or main-sequence companions. Most likely, enhanced RLOF from the primary or accretion modes operating within common envelope evolution are needed.

  2. Titan's organic aerosols: Molecular composition and structure of laboratory analogues inferred from pyrolysis gas chromatography mass spectrometry analysis

    Science.gov (United States)

    Morisson, Marietta; Szopa, Cyril; Carrasco, Nathalie; Buch, Arnaud; Gautier, Thomas

    2016-10-01

    Analogues of Titan's aerosols are of primary interest in the understanding of Titan's atmospheric chemistry and climate, and in the development of in situ instrumentation for future space missions. Numerous studies have been carried out to characterize laboratory analogues of Titan aerosols (tholins), but their molecular composition and structure are still poorly known. If pyrolysis gas chromatography mass spectrometry (pyr-GCMS) has been used for years to give clues about their chemical composition, highly disparate results were obtained with this technique. They can be attributed to the variety of analytical conditions used for pyr-GCMS analyses, and/or to differences in the nature of the analogues analyzed, that were produced with different laboratory set-ups under various operating conditions. In order to have a better description of Titan's tholin's molecular composition by pyr-GCMS, we carried out a systematic study with two major objectives: (i) exploring the pyr-GCMS analytical parameters to find the optimal ones for the detection of a wide range of chemical products allowing a characterization of the tholins composition as comprehensive as possible, and (ii) highlighting the role of the CH4 ratio in the gaseous reactive medium on the tholin's molecular structure. We used a radio-frequency plasma discharge to synthetize tholins with different concentrations of CH4 diluted in N2. The samples were pyrolyzed at temperatures covering the 200-700°C range. The extracted gases were then analyzed by GCMS for their molecular identification. The optimal pyrolysis temperature for characterizing the molecular composition of our tholins by GCMS analysis is found to be 600°C. This temperature choice results from the best compromise between the number of compounds released, the quality of the signal and the appearance of pyrolysis artifacts. About a hundred molecules are identified as pyrolysates. A common major chromatographic pattern appears clearly for all the

  3. Direct coupling of a dense (supercritical) gas chromatograph to a mass spectrometer using a supersonic molecular beam interface

    International Nuclear Information System (INIS)

    Randall, L.G.; Wahrhaftig, A.L.

    1981-01-01

    A detecting mass spectrometer has been successfully coupled to a dense gas (supercritical fluid) chromatograph to produce an instrument (DGC/MS) that may be an alternative to high performance liquid chromatograph/mass spectrometer instruments (HPLC/MS) and gas chromatograph/mass spectrometer instruments (GC/MS) for analysis of involatile and/or thermally labile compounds. The mobile phase in DGC is a gas held at temperatures above the critical temperature and at pressures sufficient to obtain nearly liquid-like densities. DGC combines advantages of GC and HPLC: rapid separations, moderate operating temperatures, and analysis of involatile compounds. An advantage unique to DGC is the solvent power dependence upon pressure. While several groups have studied DGC, its development has been limited by the lack of a sensitive and selective detector. Hence, work has been directed towards the design and construction of a DGC/MS resulting in a trial instrument capable of chromatographic pressures of at least 300 atm and temperatures from 10 0 to 60 0 C. The DGC/MS coupling has been accomplished by the use of a supersonic molecular beam interface. This application of molecular beam formation appears to be unique in its requirements of a large pressure ratio (approx.10 8 ), low flow rates, and low final pressures. The authors outline characteristics of supersonic jets and molecular beams pertinent to the design of such an instrument. The interface which uses pumping speeds of 2400 and 1200 l/s in the beam forming chambers is described in detail, while the other components: the detecting mass spectrometer, the dense gas supply, and the DGC: are briefly described. Preliminary work with this instrument has established the feasibility of DGC/MS as an analytical technique and further development is recommended

  4. Distribution and kinematics of atomic and molecular gas inside the solar circle

    Science.gov (United States)

    Marasco, A.; Fraternali, F.; van der Hulst, J. M.; Oosterloo, T.

    2017-11-01

    The detailed distribution and kinematics of the atomic and the CO-bright molecular hydrogen in the disc of the Milky Way inside the solar circle are derived under the assumptions of axisymmetry and pure circular motions. We divide the Galactic disc into a series of rings, and assume that the gas in each ring is described by four parameters: its rotation velocity, velocity dispersion, midplane density and its scale height. We fit these parameters to the Galactic H I and 12CO (J = 1-0) data by producing artificial H I and CO line-profiles and comparing them with the observations. Our approach allows us to fit all parameters to the data simultaneously without assuming a-priori a radial profile for one of the parameters. We present the distribution and kinematics of the H I and H2 in both the approaching (QIV) and the receding (QI) regions of the Galaxy. Our best-fit models reproduces remarkably well the observed H I and CO longitude-velocity diagrams up to a few degrees of distance from the midplane. With the exception of the innermost 2.5 kpc, QI and QIV show very similar kinematics. The rotation curves traced by the H I and H2 follow each other closely, flattening beyond R = 6.5 kpc. Both the H I and the H2 surface densities show a) a deep depression at 0.5 < R < 2.5 kpc, analogous to that shown by some nearby barred galaxies, b) local overdensities that can be interpreted in terms of spiral arms or ring-like features in the disc. The H I (H2) properties are fairly constant in the region outside the depression, with typical velocity dispersion of 8.9 ± 1.1 (4.4 ± 1.2) km s-1, density of 0.43 ± 0.11 (0.42 ± 0.22) cm-3 and HWHM scale height of 202 ± 28 (64 ± 12) pc. We also show that the H I opacity in the LAB data can be accounted for by using an "effective" spin temperature of 150 K: assuming an optically thin regime leads to an underestimate of the H I mass by about 30%.

  5. Spectroscopic studies of molecular iodine emitted into the gas phase by seaweed

    Directory of Open Access Journals (Sweden)

    S. M. Ball

    2010-07-01

    Full Text Available Time profiles of molecular iodine emissions from seven species of seaweed have been measured at high time resolution (7.5 s by direct spectroscopic quantification of the gas phase I2 using broadband cavity enhanced absorption spectroscopy. Substantial differences were found between species, both in the amounts of I2 emitted when the plants were exposed to air and in the shapes of their emission time profiles. Two species of kelp, Laminaria digitata and Laminaria hyperborea, were found to be the most potent emitters, producing an intense burst of I2 when first exposed to air. I2 was also observed from Saccharina latissima and Ascophyllum nodosum but in lower amounts and with broader time profiles. I2 mixing ratios from two Fucus species and Dictyopteris membranacea were at or below the detection limit of the present instrument (25 pptv. A further set of experiments investigated the time dependence of I2 emissions and aerosol particle formation when fragments of L. digitata were exposed to desiccation in air, to ozone and to oligoguluronate stress factors. Particle formation occurred in all L. digitata stress experiments where ozone and light were present, subject to the I2 mixing ratios being above certain threshold amounts. Moreover, the particle number concentrations closely tracked variations in the I2 mixing ratios, confirming the results of previous studies that the condensable particle-forming gases derive from the photochemical oxidation of the plant's I2 emissions. This work also supports the theory that particle nucleation in the coastal atmosphere occurs in "hot-spot" regions of locally elevated concentrations of condensable gases: the greatest atmospheric concentrations of I2 and hence of condensable iodine oxides are likely to be above plants of the most efficiently

  6. Molecular Gas toward the Gemini OB1 Molecular Cloud Complex. II. CO Outflow Candidates with Possible WISE Associations

    Science.gov (United States)

    Li, Yingjie; Li, Fa-Cheng; Xu, Ye; Wang, Chen; Du, Xin-Yu; Yang, Wenjin; Yang, Ji

    2018-03-01

    We present a large-scale survey of CO outflows in the Gem OB1 molecular cloud complex and its surroundings, using the Purple Mountain Observatory Delingha 13.7 m telescope. A total of 198 outflow candidates were identified over a large area (∼58.5 square degrees), of which 193 are newly detected. Approximately 68% (134/198) are associated with the Gem OB1 molecular cloud complex, including clouds GGMC 1, GGMC 2, BFS 52, GGMC 3, and GGMC 4. Other regions studied are: the Local arm (Local Lynds, West Front), Swallow, Horn, and Remote cloud. Outflow candidates in GGMC 1, BFS 52, and Swallow are mainly located at ring-like or filamentary structures. To avoid excessive uncertainty in distant regions (≳3.8 kpc), we only estimated the physical parameters for clouds in the Gem OB1 molecular cloud complex and in the Local arm. In those clouds, the total kinetic energy and the energy injection rate of the identified outflow candidates are ≲1% and ≲3% of the turbulent energy and the turbulent dissipation rate of each cloud, indicating that the identified outflow candidates cannot provide enough energy to balance turbulence of their host cloud at the scale of the entire cloud (several to dozens of parsecs). The gravitational binding energy of each cloud is ≳135 times the total kinetic energy of the identified outflow candidates within the corresponding cloud, indicating that the identified outflow candidates cannot cause major disruptions to the integrity of their host cloud at the scale of the entire cloud.

  7. Gas-surface interactions using accommodation coefficients for a dilute and a dense gas in a micro/nano-channel : heat flux predictions using combined molecular dynamics and Monte Carlo techniques

    NARCIS (Netherlands)

    Gaastra - Nedea, S.V.; Steenhoven, van A.A.; Markvoort, A.J.; Spijker, P.; Giordano, D.

    2014-01-01

    The influence of gas-surface interactions of a dilute gas confined between two parallel walls on the heat flux predictions is investigated using a combined Monte Carlo (MC) and molecular dynamics (MD) approach. The accommodation coefficients are computed from the temperature of incident and

  8. Large Area, High Resolution N2H+ studies of dense gas in the Perseus and Serpens Molecular Clouds

    Science.gov (United States)

    Storm, Shaye; Mundy, Lee

    2014-07-01

    Star formation in molecular clouds occurs over a wide range of spatial scales and physical densities. Understanding the origin of dense cores thus requires linking the structure and kinematics of gas and dust from cloud to core scales. The CARMA Large Area Star Formation Survey (CLASSy) is a CARMA Key Project that spectrally imaged five diverse regions of the Perseus and Serpens Molecular Clouds in N2H+ (J=1-0), totaling over 800 square arcminutes. The observations have 7’’ angular resolution (~0.01 pc spatial resolution) to probe dense gas down to core scales, and use combined interferometric and single-dish data to fully recover line emission up to parsec scales. CLASSy observations are complete, and this talk will focus on three science results. First, the dense gas in regions with existing star formation has complex hierarchical structure. We present a non-binary dendrogram analysis for all regions and show that dense gas hierarchy correlates with star formation activity. Second, well-resolved velocity information for each dendrogram-identified structure allows a new way of looking at linewidth-size relations in clouds. Specifically, we find that non-thermal line-of-sight velocity dispersion varies weakly with structure size, while rms variation in the centroid velocity increases strongly with structure size. We argue that the typical line-of-sight depth of a cloud can be estimated from these relations, and that our regions have depths that are several times less than their extent on the plane of the sky. This finding is consistent with numerical simulations of molecular cloud turbulence that show that high-density sheets are a generic result. Third, N2H+ is a good tracer of cold, dense gas in filaments; we resolve multiple beams across many filaments, some of which are narrower than 0.1 pc. The centroid velocity fields of several filaments show gradients perpendicular to their major axis, which is a common feature in filaments formed from numerical

  9. Application of Homochiral Alkylated Organic Cages as Chiral Stationary Phases for Molecular Separations by Capillary Gas Chromatography.

    Science.gov (United States)

    Xie, Shengming; Zhang, Junhui; Fu, Nan; Wang, Bangjin; Hu, Cong; Yuan, Liming

    2016-11-08

    Molecular organic cage compounds have attracted considerable attention due to their potential applications in gas storage, catalysis, chemical sensing, molecular separations, etc. In this study, a homochiral pentyl cage compound was synthesized from a condensation reaction of ( S , S )-1,2-pentyl-1,2-diaminoethane and 1,3,5-triformylbenzene. The imine-linked pentyl cage diluted with a polysiloxane (OV-1701) was explored as a novel stationary phase for high-resolution gas chromatographic separation of organic compounds. Some positional isomers were baseline separated on the pentyl cage-coated capillary column. In particular, various types of enantiomers including chiral alcohols, esters, ethers and epoxides can be resolved without derivatization on the pentyl cage-coated capillary column. The reproducibility of the pentyl cage-coated capillary column for separation was investigated using nitrochlorobenzene and styrene oxide as analytes. The results indicate that the column has good stability and separation reproducibility after being repeatedly used. This work demonstrates that molecular organic cage compounds could become a novel class of chiral separation media in the near future.

  10. Application of Homochiral Alkylated Organic Cages as Chiral Stationary Phases for Molecular Separations by Capillary Gas Chromatography

    Directory of Open Access Journals (Sweden)

    Shengming Xie

    2016-11-01

    Full Text Available Molecular organic cage compounds have attracted considerable attention due to their potential applications in gas storage, catalysis, chemical sensing, molecular separations, etc. In this study, a homochiral pentyl cage compound was synthesized from a condensation reaction of (S,S-1,2-pentyl-1,2-diaminoethane and 1,3,5-triformylbenzene. The imine-linked pentyl cage diluted with a polysiloxane (OV-1701 was explored as a novel stationary phase for high-resolution gas chromatographic separation of organic compounds. Some positional isomers were baseline separated on the pentyl cage-coated capillary column. In particular, various types of enantiomers including chiral alcohols, esters, ethers and epoxides can be resolved without derivatization on the pentyl cage-coated capillary column. The reproducibility of the pentyl cage-coated capillary column for separation was investigated using nitrochlorobenzene and styrene oxide as analytes. The results indicate that the column has good stability and separation reproducibility after being repeatedly used. This work demonstrates that molecular organic cage compounds could become a novel class of chiral separation media in the near future.

  11. Gas Source Techniques for Molecular Beam Epitaxy of Highly Mismatched Ge Alloys

    OpenAIRE

    Chad A. Stephenson; Miriam Gillett-Kunnath; William A. O’Brien; Robert Kudrawiec; Mark A. Wistey

    2016-01-01

    Ge and its alloys are attractive candidates for a laser compatible with silicon integrated circuits. Dilute germanium carbide (Ge1−xCx) offers a particularly interesting prospect. By using a precursor gas with a Ge4C core, C can be preferentially incorporated in substitutional sites, suppressing interstitial and C cluster defects. We present a method of reproducible and upscalable gas synthesis of tetrakis(germyl)methane, or (H3Ge)4C, followed by the design of a hybrid gas/solid-source molecu...

  12. Molecular analysis of sulphur-rich brown coals by flash pyrolysis-gas chromatography-mass spectrometry: The type III-S kerogen

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Las Heras, F.X.C. de; Leeuw, J.W. de

    1992-01-01

    The molecular composition of five brown coals from three different basins (Maestrazgo, Mequinenza and Rubielos) in Spain was investigated by flash pyrolysis-gas chromatography and flash pyrolysis-gas chromatography-mass spectrometry. In these techniques, the macromolecular material is thermally

  13. Dynamic Contraction of the Positive Column of a Self-Sustained Glow Discharge in Molecular Gas Flow

    Science.gov (United States)

    Shneider, Mikhail

    2014-10-01

    Contraction of the gas discharge, when current contracts from a significant volume of weakly ionized plasma into a thin arc channel, was attracted attention of scientists for more than a century. Studies of the contraction (also called constriction) mechanisms, besides carrying interesting science, are of practical importance, especially when contraction should be prevented. A set of time-dependent two-dimensional equations for the non-equilibrium weakly-ionized nitrogen/ air plasma is formulated. The process is described by a set of time-dependent continuity equations for the electrons, positive and negative ions; gas and vibrational temperature; by taking into account the convective heat and plasma losses by the transverse flux. Transition from the uniform to contracted state was analyzed. It was shown that such transition experiences a hysteresis, and that the critical current of the transition increases when the pressure (gas density) drops. Possible coexistence of the contracted and uniform state of the plasma in the discharge where the current flows along the density gradient of the background gas was discussed. In this talk the problems related to the dynamic contraction of the current channel inside a quasineutral positive column of a self-sustained glow discharge in molecular gas in a rectangular duct with convection cooling will be discussed. Study presented in this talk was stimulated by the fact that there are large number of experiments on the dynamic contraction of a glow discharge in nitrogen and air flows and a many of possible applications. Similar processes play a role in the powerful gas-discharge lasers. In addition, the problem of dynamic contraction in the large volume of non-equilibrium weakly ionized plasma is closely related to the problem of streamer to leader transitions in lightning and blue jets.

  14. On recent progress using QCLs for molecular trace gas detection - from basic research to industrial applicaitons

    NARCIS (Netherlands)

    Röpcke, J.; Davies, P.; Hempel, F.; Hübner, M.; Glitsch, S.; Lang, N.; Nägele, M.; Rousseau, A.; Wege, S.; Welzel, S.

    2010-01-01

    Quantum Cascade Lasers offer attractive options for applications of MIR absorption spectroscopy for basic research and industrial process control. The contribution reviews applications for plasma diagnostics and trace gas monitoring in research and industry.

  15. Characterisation of uremic "Middle molecular"fractions by gas chromatography mass spectrometry, isotachophoresis, and liquid chromatography

    NARCIS (Netherlands)

    Schoots, A.C.; Mikkers, F.E.P.; Claessens, H.A.; Smet, de R.; Landschoot, van N.; Ringoir, S.M.G.

    1982-01-01

    Uremic ultrafiltrates (and normal serum, for comparison) were fractionated by means of gel filtration. The collected fractions were further investigated by combined analytical techniques: "high- performance" liquid chromatography, gas chromatography, mass spectrometry, and isotachophoresis.

  16. Preparation and electrical properties of boron and boron phosphide films obtained by gas source molecular beam deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kumashiro, Y.; Yokoyama, T.; Sakamoto, T.; Fujita, T. [Yokohama National Univ. (Japan)

    1997-10-01

    Boron and boron phosphide films were prepared by gas source molecular beam deposition on sapphire crystal at various substrate temperatures up to 800{degrees}C using cracked B{sub 2}H{sub 6} (2% in H{sub 2}) at 300{degrees}C and cracked PH{sub 3} (20% in H{sub 2}) at 900{degrees}C. The substrate temperatures and gas flow rates of the reactant gases determined the film growth. The boron films with amorphous structure are p type. Increasing growth times lead to increasing mobilities and decreasing carrier concentrations. Boron phosphide film with maximum P/B ratio is obtained at a substrate temperature of 600{degrees}C, below and above which they become phosphorous deficient due to insufficient supply of phosphorus and thermal desorption of the phosphorus as P{sub 2}, respectively, but they are all n type conductors due to phosphorus vacancies.

  17. Synthetic CO, H2 and H I surveys of the second galactic quadrant, and the properties of molecular gas

    Science.gov (United States)

    Duarte-Cabral, A.; Acreman, D. M.; Dobbs, C. L.; Mottram, J. C.; Gibson, S. J.; Brunt, C. M.; Douglas, K. A.

    2015-03-01

    We present CO, H2, H I and HISA (H I self-absorption) distributions from a set of simulations of grand design spirals including stellar feedback, self-gravity, heating and cooling. We replicate the emission of the second galactic quadrant by placing the observer inside the modelled galaxies and post-process the simulations using a radiative transfer code, so as to create synthetic observations. We compare the synthetic data cubes to observations of the second quadrant of the Milky Way to test the ability of the current models to reproduce the basic chemistry of the Galactic interstellar medium (ISM), as well as to test how sensitive such galaxy models are to different recipes of chemistry and/or feedback. We find that models which include feedback and self-gravity can reproduce the production of CO with respect to H2 as observed in our Galaxy, as well as the distribution of the material perpendicular to the Galactic plane. While changes in the chemistry/feedback recipes do not have a huge impact on the statistical properties of the chemistry in the simulated galaxies, we find that the inclusion of both feedback and self-gravity are crucial ingredients, as our test without feedback failed to reproduce all of the observables. Finally, even though the transition from H2 to CO seems to be robust, we find that all models seem to underproduce molecular gas, and have a lower molecular to atomic gas fraction than is observed. Nevertheless, our fiducial model with feedback and self-gravity has shown to be robust in reproducing the statistical properties of the basic molecular gas components of the ISM in our Galaxy.

  18. Fragmentation of neutral carbon clusters formed by high velocity atomic collision; Fragmentation d'agregats de carbone neutres formes par collision atomique a haute vitesse

    Energy Technology Data Exchange (ETDEWEB)

    Martinet, G

    2004-05-01

    The aim of this work is to understand the fragmentation of small neutral carbon clusters formed by high velocity atomic collision on atomic gas. In this experiment, the main way of deexcitation of neutral clusters formed by electron capture with ionic species is the fragmentation. To measure the channels of fragmentation, a new detection tool based on shape analysis of current pulse delivered by semiconductor detectors has been developed. For the first time, all branching ratios of neutral carbon clusters are measured in an unambiguous way for clusters size up to 10 atoms. The measurements have been compared to a statistical model in microcanonical ensemble (Microcanonical Metropolis Monte Carlo). In this model, various structural properties of carbon clusters are required. These data have been calculated with Density Functional Theory (DFT-B3LYP) to find the geometries of the clusters and then with Coupled Clusters (CCSD(T)) formalism to obtain dissociation energies and other quantities needed to compute fragmentation calculations. The experimental branching ratios have been compared to the fragmentation model which has allowed to find an energy distribution deposited in the collision. Finally, specific cluster effect has been found namely a large population of excited states. This behaviour is completely different of the atomic carbon case for which the electron capture in the ground states predominates. (author)

  19. Stellar feedback as the origin of an extended molecular outflow in a starburst galaxy.

    Science.gov (United States)

    Geach, J E; Hickox, R C; Diamond-Stanic, A M; Krips, M; Rudnick, G H; Tremonti, C A; Sell, P H; Coil, A L; Moustakas, J

    2014-12-04

    Recent observations have revealed that starburst galaxies can drive molecular gas outflows through stellar radiation pressure. Molecular gas is the phase of the interstellar medium from which stars form, so these outflows curtail stellar mass growth in galaxies. Previously known outflows, however, involve small fractions of the total molecular gas content and have typical scales of less than a kiloparsec. In at least some cases, input from active galactic nuclei is dynamically important, so pure stellar feedback (the momentum return into the interstellar medium) has been considered incapable of rapidly terminating star formation on galactic scales. Molecular gas has been detected outside the galactic plane of the archetypal starburst galaxy M82 (refs 4 and 5), but so far there has been no evidence that starbursts can propel substantial quantities of cold molecular gas to the same galactocentric radius (about 10 kiloparsecs) as the warmer gas that has been traced by metal ion absorbers in the circumgalactic medium. Here we report observations of molecular gas in a compact (effective radius 100 parsecs) massive starburst galaxy at redshift 0.7, which is known to drive a fast outflow of ionized gas. We find that 35 per cent of the total molecular gas extends approximately 10 kiloparsecs, and one-third of this extended gas has a velocity of up to 1,000 kilometres per second. The kinetic energy associated with this high-velocity component is consistent with the momentum flux available from stellar radiation pressure. This demonstrates that nuclear bursts of star formation are capable of ejecting large amounts of cold gas from the central regions of galaxies, thereby strongly affecting their evolution by truncating star formation and redistributing matter.

  20. Gas Separation Performance of Carbon Molecular Sieve Membranes Based on 6FDA-mPDA/DABA (3:2) Polyimide

    KAUST Repository

    Qiu, Wulin

    2014-02-23

    6FDA-mPDA/DABA (3:2) polyimide was synthesized and characterized for uncross-linked, thermally crosslinked, and carbon molecular sieve (CMS) membranes. The membranes were characterized with thermogravimetric analysis, FTIR spectroscopy, wide-angle X-ray diffraction, and gas permeation tests. Variations in the d spacing, the formation of pore structures, and changes in the pore sizes of the CMS membranes were discussed in relation to pyrolysis protocols. The uncross-linked polymer membranes showed high CO 2/CH4 selectivity, whereas thermally crosslinked membranes exhibited significantly improved CO2 permeability and excellent CO2 plasticization resistance. The CMS membranes showed even higher CO2 permeability and CO2/CH4 selectivity. An increase in the pyrolysis temperature resulted in CMS membranes with lower gas permeability but higher selectivity. The 550 °C pyrolyzed CMS membranes showed CO2 permeability as high as 14 750 Barrer with CO 2/CH4 selectivity of approximately 52. Even 800 °C pyrolyzed CMS membranes still showed high CO2 permeability of 2610 Barrer with high CO2/CH4 selectivity of approximately 118. Both polymer membranes and the CMS membranes are very attractive in aggressive natural gas purification applications. Permeating through: Polyimide-based uncross-linked, thermally crosslinked, and carbon molecular sieve (CMS) membranes are prepared. Variations in the d spacing, the formation of pore structures, and changes in the pore sizes of the CMS membranes are discussed in relation to pyrolysis protocols. Both the polymer and CMS membranes are very attractive in aggressive natural gas purification applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. SUB-KILOPARSEC IMAGING OF COOL MOLECULAR GAS IN TWO STRONGLY LENSED DUSTY, STAR-FORMING GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Spilker, J. S.; Marrone, D. P. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Aravena, M. [Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército 441, Santiago (Chile); Béthermin, M.; Breuck, C. de [European Southern Observatory, Karl Schwarzschild Straße 2, D-85748 Garching (Germany); Bothwell, M. S. [Cavendish Laboratory, University of Cambridge, JJ Thompson Ave, Cambridge CB3 0HA (United Kingdom); Carlstrom, J. E. [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Chapman, S. C.; Rotermund, K. M. [Dalhousie University, Halifax, Nova Scotia (Canada); Collier, J. D.; Galvin, T.; Grieve, K.; O’Brien, A. [University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751 (Australia); Fassnacht, C. D. [Department of Physics, University of California, One Shields Avenue, Davis, CA 95616 (United States); Gonzalez, A. H.; Ma, J. [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); González-López, J. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago (Chile); Hezaveh, Y. [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305 (United States); Malkan, M., E-mail: jspilker@as.arizona.edu [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547 (United States); and others

    2015-10-01

    We present spatially resolved imaging obtained with the Australia Telescope Compact Array (ATCA) of three CO lines in two high-redshift gravitationally lensed dusty star-forming galaxies, discovered by the South Pole Telescope. Strong lensing allows us to probe the structure and dynamics of the molecular gas in these two objects, at z = 2.78 and z = 5.66, with effective source-plane resolution of less than 1 kpc. We model the lensed emission from multiple CO transitions and the dust continuum in a consistent manner, finding that the cold molecular gas as traced by low-J CO always has a larger half-light radius than the 870 μm dust continuum emission. This size difference leads to up to 50% differences in the magnification factor for the cold gas compared to dust. In the z = 2.78 galaxy, these CO observations confirm that the background source is undergoing a major merger, while the velocity field of the other source is more complex. We use the ATCA CO observations and comparable resolution Atacama Large Millimeter/submillimeter Array dust continuum imaging of the same objects to constrain the CO–H{sub 2} conversion factor with three different procedures, finding good agreement between the methods and values consistent with those found for rapidly star-forming systems. We discuss these galaxies in the context of the star formation—gas mass surface density relation, noting that the change in emitting area with observed CO transition must be accounted for when comparing high-redshift galaxies to their lower redshift counterparts.

  2. xCOLD GASS: The Complete IRAM 30 m Legacy Survey of Molecular Gas for Galaxy Evolution Studies

    Science.gov (United States)

    Saintonge, Amélie; Catinella, Barbara; Tacconi, Linda J.; Kauffmann, Guinevere; Genzel, Reinhard; Cortese, Luca; Davé, Romeel; Fletcher, Thomas J.; Graciá-Carpio, Javier; Kramer, Carsten; Heckman, Timothy M.; Janowiecki, Steven; Lutz, Katharina; Rosario, David; Schiminovich, David; Schuster, Karl; Wang, Jing; Wuyts, Stijn; Borthakur, Sanchayeeta; Lamperti, Isabella; Roberts-Borsani, Guido W.

    2017-12-01

    We introduce xCOLD GASS, a legacy survey providing a census of molecular gas in the local universe. Building on the original COLD GASS survey, we present here the full sample of 532 galaxies with CO (1–0) measurements from the IRAM 30 m telescope. The sample is mass-selected in the redshift interval 0.01 {10}9 {M}ȯ . The CO (1–0) flux measurements are complemented by observations of the CO (2–1) line with both the IRAM 30 m and APEX telescopes, H I observations from Arecibo, and photometry from SDSS, WISE, and GALEX. Combining the IRAM and APEX data, we find that the ratio of CO (2–1) to CO (1–0) luminosity for integrated measurements is {r}21=0.79+/- 0.03, with no systematic variations across the sample. The CO (1–0) luminosity function is constructed and best fit with a Schechter function with parameters {L}{CO}* =(7.77+/- 2.11)× {10}9 {{K}} {km} {{{s}}}-1 {{pc}}2, {φ }* =(9.84+/- 5.41)× {10}-4 {{Mpc}}-3, and α =-1.19+/- 0.05. With the sample now complete down to stellar masses of 109 {M}ȯ , we are able to extend our study of gas scaling relations and confirm that both molecular gas fractions ({f}{{{H}}2}) and depletion timescale ({t}{dep}({{{H}}}2)) vary with specific star formation rate (or offset from the star formation main sequence) much more strongly than they depend on stellar mass. Comparing the xCOLD GASS results with outputs from hydrodynamic and semianalytic models, we highlight the constraining power of cold gas scaling relations on models of galaxy formation.

  3. Giant galaxy growing from recycled gas: ALMA maps the circumgalactic molecular medium of the Spiderweb in [C I

    Science.gov (United States)

    Emonts, B. H. C.; Lehnert, M. D.; Dannerbauer, H.; De Breuck, C.; Villar-Martín, M.; Miley, G. K.; Allison, J. R.; Gullberg, B.; Hatch, N. A.; Guillard, P.; Mao, M. Y.; Norris, R. P.

    2018-06-01

    The circumgalactic medium (CGM) of the massive Spiderweb Galaxy, a conglomerate of merging proto-cluster galaxies at z = 2.2, forms an enriched interface where feedback and recycling act on accreted gas. This is shown by observations of [C I], CO(1-0), and CO(4-3) performed with the Atacama Large Millimeter Array and Australia Telescope Compact Array. [C I] and CO(4-3) are detected across ˜50 kpc, following the distribution of previously detected low-surface-brightness CO(1-0) across the CGM. This confirms our previous results on the presence of a cold molecular halo. The central radio galaxy MRC 1138-262 shows a very high global L^'_CO(4-3)/L^'_CO(1-0) ˜ 1, suggesting that mechanisms other than FUV-heating by star formation prevail at the heart of the Spiderweb Galaxy. Contrary, the CGM has L^'_CO(4-3)/L^'_CO(1-0) and L^'_[C I]/L^'_CO(1-0) similar to the ISM of five galaxies in the wider proto-cluster, and its carbon abundance, X_[C I]/X_H_2, resembles that of the Milky Way and star-forming galaxies. The molecular CGM is thus metal-rich and not diffuse, confirming a link between the cold gas and in situ star formation. Thus, the Spiderweb Galaxy grows not directly through accretion of gas from the cosmic web, but from recycled gas in the CGM.

  4. Effect of gas adsorption on acoustic wave propagation in MFI zeolite membrane materials: experiment and molecular simulation.

    Science.gov (United States)

    Manga, Etoungh D; Blasco, Hugues; Da-Costa, Philippe; Drobek, Martin; Ayral, André; Le Clezio, Emmanuel; Despaux, Gilles; Coasne, Benoit; Julbe, Anne

    2014-09-02

    The present study reports on the development of a characterization method of porous membrane materials which consists of considering their acoustic properties upon gas adsorption. Using acoustic microscopy experiments and atomistic molecular simulations for helium adsorbed in a silicalite-1 zeolite membrane layer, we showed that acoustic wave propagation could be used, in principle, for controlling the membranes operando. Molecular simulations, which were found to fit experimental data, showed that the compressional modulus of the composite system consisting of silicalite-1 with adsorbed He increases linearly with the He adsorbed amount while its shear modulus remains constant in a large range of applied pressures. These results suggest that the longitudinal and Rayleigh wave velocities (VL and VR) depend on the He adsorbed amount whereas the transverse wave velocity VT remains constant.

  5. Study of the molecular and ionized gas in a possible precursor of an ultra-compact H II region

    Science.gov (United States)

    Ortega, M. E.; Paron, S.; Giacani, E.; Celis Peña, M.; Rubio, M.; Petriella, A.

    2017-10-01

    Aims: We aim to study the molecular and the ionized gas in a possible precursor of an ultra-compact H II region to contribute to the understanding of how high-mass stars build-up their masses once they have reached the zero-age main sequence. Methods: We carried out molecular observations toward the position of the Red MSX source G052.9221-00.4892, using the Atacama Submillimeter Telescope Experiment (ASTE; Chile) in the 12CO J = 3-2, 13CO J = 3-2, C18O J = 3-2, and HCO+J = 4-3 lines with an angular resolution of about 22''. We also present radio continuum observations at 6 GHz carried out with the Jansky Very Large Array (JVLA; USA) interferometer with a synthesized beam of 4.8 arcsec × 4.1 arcsec. The molecular data were used to study the distribution and kinematics of the molecular gas, while the radio continuum data were used to characterize the ionized gas in the region. Combining these observations with public infrared data allowed us to inquire about the nature of the source. Results: The analysis of the molecular observations reveals the presence of a kinetic temperature and H2 column density gradients across the molecular clump in which the Red MSX source G052.9221-00.4892 is embedded, with the hotter and less dense gas in the inner region. The 12CO J = 3-2 emission shows evidence of misaligned massive molecular outflows, with the blue lobe in positional coincidence with a jet-like feature seen at 8 μm. The radio continuum emission shows a slightly elongated compact radio source, with a flux density of about 0.9 mJy, in positional coincidence with the Red MSX source. The polar-like morphology of this compact radio source perfectly matches the hourglass-like morphology exhibited by the source in the Ks band. Moreover, the axes of symmetry of the radio source and the near-infrared nebula are perfectly aligned. Thus, based on the presence of molecular outflows, the slightly elongated morphology of the compact radio source matching the hourglass

  6. Energy harvesting through gas dynamics in the free molecular flow regime between structured surfaces at different temperatures

    DEFF Research Database (Denmark)

    Baier, Tobias; Dölger, Julia; Hardt, Steffen

    2014-01-01

    For a gas confined between surfaces held at different temperatures the velocity distribution shows a significant deviation from the Maxwell distribution when the mean free path of the molecules is comparable to or larger than the channel dimensions. If one of the surfaces is suitably structured...... from the thermal creep flow that has gained more attention so far. This situation is studied in the limit of free-molecular flow for the case that an unstructured surface is allowed to move tangentially with respect to a structured surface. Parameter studies are conducted, and configurations...

  7. Flow analysis-hydride generation-gas phase derivative molecular absorption spectrophotometric determination of antimony in antileishmanial drugs

    Directory of Open Access Journals (Sweden)

    Máximo Gallignani

    2009-01-01

    Full Text Available In the present work, the development of a method based on the coupling of flow analysis (FA, hydride generation (HG, and derivative molecular absorption spectrophotometry (D-EAM in gas phase (GP, is described in order to determine total antimony in antileishmanial products. Second derivative order (D²224nm of the absorption spectrum (190 - 300 nm is utilized as measurement criterion. Each one of the parameters involved in the development of the proposed method was examined and optimized. The utilization of the EAM in GP as detection system in a continuous mode instead of atomic absorption spectrometry represents the great potential of the analytic proposal.

  8. Determination of Some Low Molecular Weight Carbohydrates in the Fruits of Wild Cherry Laurel (Laurocerasus officinalis Roem.) Using Gas Chromatography

    OpenAIRE

    AYAZ, F. Ahmet; KADIOĞLU, Asım; HAYIRLIOĞLU-AYAZ, Sema

    1998-01-01

    Some low-molecular-weight carbohydrates extracted with ethanol and water from the fruits of Laurocerasus officinalis Roem. ( Rosaceae), from two different regions in Trabzon, were analysed using gas chromatography. In one population, the analysis in the ethanol extraction showed the occurence of fructose, glucose, sorbitol and sucrose in concentrations (w/w) of 25.20; 23.00; 14.00 and 0.024 %, respectively. The same sugars, in the water extraction were found in concentrations (w/w) of 24.6...

  9. Turbulence, dynamic similarity and scale effects in high-velocity free-surface flows above a stepped chute

    Science.gov (United States)

    Felder, Stefan; Chanson, Hubert

    2009-07-01

    In high-velocity free-surface flows, air entrainment is common through the interface, and intense interactions take place between turbulent structures and entrained bubbles. Two-phase flow properties were measured herein in high-velocity open channel flows above a stepped chute. Detailed turbulence measurements were conducted in a large-size facility, and a comparative analysis was applied to test the validity of the Froude and Reynolds similarities. The results showed consistently that the Froude similitude was not satisfied using a 2:1 geometric scaling ratio. Lesser number of entrained bubbles and comparatively greater bubble sizes were observed at the smaller Reynolds numbers, as well as lower turbulence levels and larger turbulent length and time scales. The results implied that small-size models did underestimate the rate of energy dissipation and the aeration efficiency of prototype stepped spillways for similar flow conditions. Similarly a Reynolds similitude was tested. The results showed also some significant scale effects. However a number of self-similar relationships remained invariant under changes of scale and confirmed the analysis of Chanson and Carosi (Exp Fluids 42:385-401, 2007). The finding is significant because self-similarity may provide a picture general enough to be used to characterise the air-water flow field in large prototype channels.

  10. Molecular structure determination of cyclooctane by Ab Initio and electron diffraction methods in the gas phase; Determinacao da estrutura molecular do ciclooctano por metodos Ab Initio e difracao de eletrons na fase gasosa

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, Wagner B. de [Minas Gerais Univ., Belo Horizonte, MG (Brazil). Dept. de Quimica

    2000-10-01

    The determination of the molecular structure of molecules is of fundamental importance in chemistry. X-rays and electron diffraction methods constitute in important tools for the elucidation of the molecular structure of systems in the solid state and gas phase, respectively. The use of quantum mechanical molecular orbital ab initio methods offer an alternative for conformational analysis studies. Comparison between theoretical results and those obtained experimentally in the gas phase can make a significant contribution for an unambiguous determination of the geometrical parameters. In this article the determination for an unambiguous determination of the geometrical parameters. In this article the determination of the molecular structure of the cyclooctane molecule by electron diffraction in the gas phase an initio calculations will be addressed, providing an example of a comparative analysis of theoretical and experimental predictions. (author)

  11. Energetics of the molecular gas in the H2 luminous radio galaxy 3C 326: Evidence for negative AGN feedback

    Science.gov (United States)

    Nesvadba, N. P. H.; Boulanger, F.; Salomé, P.; Guillard, P.; Lehnert, M. D.; Ogle, P.; Appleton, P.; Falgarone, E.; Pineau Des Forets, G.

    2010-10-01

    We present a detailed analysis of the gas conditions in the H2 luminous radio galaxy 3C 326 N at z ~ 0.1, which has a low star-formation rate (SFR ~ 0.07 M⊙ yr-1) in spite of a gas surface density similar to those in starburst galaxies. Its star-formation efficiency is likely a factor ~10-50 lower than those of ordinary star-forming galaxies. Combining new IRAM CO emission-line interferometry with existing Spitzer mid-infrared spectroscopy, we find that the luminosity ratio of CO and pure rotational H2 line emission is factors 10-100 lower than what is usually found. This suggests that most of the molecular gas is warm. The Na D absorption-line profile of 3C 326 N in the optical suggests an outflow with a terminal velocity of ~-1800 km s-1 and a mass outflow rate of 30-40 M⊙ yr-1, which cannot be explained by star formation. The mechanical power implied by the wind, of order 1043 erg s-1, is comparable to the bolometric luminosity of the emission lines of ionized and molecular gas. To explain these observations, we propose a scenario where a small fraction of the mechanical energy of the radio jet is deposited in the interstellar medium of 3C 326 N, which powers the outflow, and the line emission through a mass, momentum and energy exchange between the different gas phases of the ISM. Dissipation times are of order 107-8 yrs, similar or greater than the typical jet lifetime. Small ratios of CO and PAH surface brightnesses in another 7 H2 luminous radio galaxies suggest that a similar form of AGN feedback could be lowering star-formation efficiencies in these galaxies in a similar way. The local demographics of radio-loud AGN suggests that secular gas cooling in massive early-type galaxies of ≥1011 M⊙ could generally be regulated through a fundamentally similar form of “maintenance-phase” AGN feedback. Based on observations carried out with the IRAM Plateau de Bure Interferometer.

  12. Production of ultrapure D-T gas by removal of molecular tritium by selective adsorption

    International Nuclear Information System (INIS)

    Maienschein, J.L.; Hudson, R.S.; Tsugawa, R.T.; Fearon, E.M.; Souers, P.C.; Collins, G.W.

    1991-07-01

    The application of selective adsorption to purification of D-T gas by removal of T 2 has been demonstrated for small quantities of gas typical in research applications. This represents a variation on the production of pure spin isomers of deuterium and hydrogen. The use of an adsorption column offers several advantages over conventional separation techniques, such as low tritium inventory, rapid delivery to prevent radiation damage of the accumulated product, compact size, simplicity of design, construction, and operation, and operation without carrier gas. Because a column can have several thousand equilibrium stages, the purity of the product can be very high. The adsorption column has been shown to be an attractive separation tool for small quantities of hydrogen isotopes

  13. Molecular Gas Clumps from the Destruction of Icy Bodies in the beta Pictoris Debris Disk

    Science.gov (United States)

    Dent, W. R. F.; Wyatt, M. C.; Roberge, A.; Augereau, J. -C.; Casassus, S.; Corder, S.; Greaves, J. S.; DeGregorio-Monsalvo, I.; Hales, A.; Jackson, A. P.; hide

    2014-01-01

    Many stars are surrounded by disks of dusty debris formed in the collisions of asteroids, comets and dwarf planets. But is gas also released in such events? Observations at sub-mm wavelengths of the archetypal debris disk around ß Pictoris show that 0.3% of a Moon mass of carbon monoxide orbits in its debris belt. The gas distribution is highly asymmetric, with 30% found in a single clump 85 AU from the star, in a plane closely aligned with the orbit of the inner planet, beta Pic b. This gas clump delineates a region of enhanced collisions, either from a mean motion resonance with an unseen giant planet, or from the remnants of a collision of Mars-mass planets.

  14. SOFIA Observations of S106: Dynamics of the Warm Gas

    Science.gov (United States)

    Simon, R.; Schneider, N.; Stutzki, J.; Gusten, R.; Graf, U. U.; Hartogh, P.; Guan, X.; Staguhn, J. G.; Benford, D. J.

    2012-01-01

    Context The H II region/PDR/molecular cloud complex S106 is excited by a single O-star. The full extent of the warm and dense gas close to the star has not been mapped in spectrally resolved high-J CO or [C II] lines, so the kinematics of the warm. partially ionized gas, are unknown. Whether the prominent dark lane bisecting the hourglass-shaped nebula is due solely to the shadow cast by a small disk around the exciting star or also to extinction in high column foreground gas was an open question until now. Aims. To disentangle the morphology and kinematics of warm neutral and ionized gas close to the star, study their relation to the bulk of the molecular gas. and to investigate the nature of the dark lane. Methods. We use the heterodyne receiver GREAT on board SOFIA to observe velocity resolved spectral lines of [C II] and CO 11 yields 10 in comparison with so far unpublished submm continuum data at 350 micron (8HARC-Il) and complementary molecular line data. Results. The high angular and spectral resolution observations show a very complex morphology and kinematics of the inner S106 region, with many different components at different excitation conditions contributing to the observed emission. The [C II] lines are found to be bright and very broad. tracing high velocity gas close to the interface of molecular cloud and H II region. CO 11 yields 10 emission is more confined.. both spatially and in velocity, to the immediate surroundings of S 106 IR showing the presence of warm, high density (clumpy) gas. Our high angular resolution submm continuum observations rule out the scenario where the dark lane separating the two lobes is due solely to the shadow cast by a small disk close to the star. The lane is clearly seen also as warm, high column density gas at the boundary of the molecular cloud and H II region.

  15. Microscopic molecular dynamics characterization of the second-order non-Navier-Fourier constitutive laws in the Poiseuille gas flow

    Energy Technology Data Exchange (ETDEWEB)

    Rana, A.; Ravichandran, R. [School of Mechanical and Aerospace Engineering, Gyeongsang National University, Jinju, Gyeongnam 52828 (Korea, Republic of); Park, J. H.; Myong, R. S., E-mail: myong@gnu.ac.kr [School of Mechanical and Aerospace Engineering, Gyeongsang National University, Jinju, Gyeongnam 52828 (Korea, Republic of); Research Center for Aircraft Parts Technology, Gyeongsang National University, Jinju, Gyeongnam 52828 (Korea, Republic of)

    2016-08-15

    The second-order non-Navier-Fourier constitutive laws, expressed in a compact algebraic mathematical form, were validated for the force-driven Poiseuille gas flow by the deterministic atomic-level microscopic molecular dynamics (MD). Emphasis is placed on how completely different methods (a second-order continuum macroscopic theory based on the kinetic Boltzmann equation, the probabilistic mesoscopic direct simulation Monte Carlo, and, in particular, the deterministic microscopic MD) describe the non-classical physics, and whether the second-order non-Navier-Fourier constitutive laws derived from the continuum theory can be validated using MD solutions for the viscous stress and heat flux calculated directly from the molecular data using the statistical method. Peculiar behaviors (non-uniform tangent pressure profile and exotic instantaneous heat conduction from cold to hot [R. S. Myong, “A full analytical solution for the force-driven compressible Poiseuille gas flow based on a nonlinear coupled constitutive relation,” Phys. Fluids 23(1), 012002 (2011)]) were re-examined using atomic-level MD results. It was shown that all three results were in strong qualitative agreement with each other, implying that the second-order non-Navier-Fourier laws are indeed physically legitimate in the transition regime. Furthermore, it was shown that the non-Navier-Fourier constitutive laws are essential for describing non-zero normal stress and tangential heat flux, while the classical and non-classical laws remain similar for shear stress and normal heat flux.

  16. A review of molecular effects in gas-phase KL X-ray emission

    Energy Technology Data Exchange (ETDEWEB)

    Guillemin, Renaud; Carniato, Stéphane; Journel, Loïc [UPMC Univ Paris 06, UMR 7614, Laboratoire de Chimie Physique Matière et Rayonnement, F-75005 Paris (France); CNRS, UMR 7614, Laboratoire de Chimie Physique Matière et Rayonnement, F-75005 Paris (France); Stolte, Wayne C. [Department of Chemistry, University of Nevada, Las Vegas, NV 89154-4003 (United States); Marchenko, Tatiana; Khoury, Lara El; Kawerk, Elie; Piancastelli, Maria Novella [UPMC Univ Paris 06, UMR 7614, Laboratoire de Chimie Physique Matière et Rayonnement, F-75005 Paris (France); CNRS, UMR 7614, Laboratoire de Chimie Physique Matière et Rayonnement, F-75005 Paris (France); Hudson, Amanda C.; Lindle, Dennis W. [Department of Chemistry, University of Nevada, Las Vegas, NV 89154-4003 (United States); Simon, Marc, E-mail: marc.simon@upmc.fr [UPMC Univ Paris 06, UMR 7614, Laboratoire de Chimie Physique Matière et Rayonnement, F-75005 Paris (France); CNRS, UMR 7614, Laboratoire de Chimie Physique Matière et Rayonnement, F-75005 Paris (France)

    2013-06-15

    The unique capabilities of resonant inelastic X-ray scattering (RIXS) to provide a deep insight into molecular dynamics following core excitation are reviewed here. Characteristic features of molecular X-ray emission are experimentally observed and theoretically interpreted. Some of our most significant results on molecular dynamics following deep core excitation are presented. In particular, we provide several examples of nuclear dynamics on the femtosecond or subfemtosecond time scale; line-narrowing effects related to the quenching of vibrational structure due to parallelism of intermediate and final state curves; anomalous line dispersion across a resonance, which is due to core-hole lifetime effects; spin–orbit-state populations derived from polarized RIXS experiments. We also show how to connect the RIXS results to the general chemical properties of the investigated systems.

  17. A review of molecular effects in gas-phase KL X-ray emission

    International Nuclear Information System (INIS)

    Guillemin, Renaud; Carniato, Stéphane; Journel, Loïc; Stolte, Wayne C.; Marchenko, Tatiana; Khoury, Lara El; Kawerk, Elie; Piancastelli, Maria Novella; Hudson, Amanda C.; Lindle, Dennis W.; Simon, Marc

    2013-01-01

    The unique capabilities of resonant inelastic X-ray scattering (RIXS) to provide a deep insight into molecular dynamics following core excitation are reviewed here. Characteristic features of molecular X-ray emission are experimentally observed and theoretically interpreted. Some of our most significant results on molecular dynamics following deep core excitation are presented. In particular, we provide several examples of nuclear dynamics on the femtosecond or subfemtosecond time scale; line-narrowing effects related to the quenching of vibrational structure due to parallelism of intermediate and final state curves; anomalous line dispersion across a resonance, which is due to core-hole lifetime effects; spin–orbit-state populations derived from polarized RIXS experiments. We also show how to connect the RIXS results to the general chemical properties of the investigated systems

  18. Competetive clustering in a bidisperse granular gas : experiment, molecular dynamics, and flux model

    NARCIS (Netherlands)

    Mikkelsen, René; van der Meer, Devaraj; van der Weele, Ko; Lohse, Detlef

    2004-01-01

    A compartmentalized bidisperse granular gas clusters competitively [R. Mikkelsen, D. van der Meer, K. van der Weele, and D. Lohse, Phys. Rev. Lett. 89, 214301 (2002)]: By tuning the shaking strength, the clustering can be directed either towards the compartment initially containing mainly small

  19. Dense Molecular Gas and H2O Maser Emission in Galaxies F ...

    Indian Academy of Sciences (India)

    2School of Physics and Telecommunication Engineering, South China Normal University,. Guangzhou 510006, China. ∗ e-mail: jszhang@gzhu.edu.cn. Abstract. Extragalactic H2O masers have been found in dense gas cir- cumstance in off-nuclear star formation regions or within parsecs of. Active Galactic Nuclei (AGNs).

  20. Gas phase polymerization of propylene. Reaction kinetics and molecular weight distribution

    NARCIS (Netherlands)

    Meier, G.B.; Weickert, G.; van Swaaij, Willibrordus Petrus Maria

    2001-01-01

    Gas-phase polymerizations have been executed at different temperatures, pressures, and hydrogen concentrations using Me2Si[Ind]2ZrCl2 / methylaluminoxane / SiO2(Pennsylvania Quarts) as a catalyst. The reaction rate curves have been described by a kinetic model, which takes into account the initially

  1. Imaging Molecular Structure through Femtosecond Photoelectron Diffraction on Aligned and Oriented Gas-Phase Molecules

    DEFF Research Database (Denmark)

    Boll, Rebecca; Rouzee, Arnaud; Adolph, Marcus

    2014-01-01

    This paper gives an account of our progress towards performing femtosecond time-resolved photoelectron diffraction on gas-phase molecules in a pump-probe setup combining optical lasers and an X-ray Free-Electron Laser. We present results of two experiments aimed at measuring photoelectron angular...

  2. Molecular gas properties of a lensed star-forming galaxy at z 3.6: a case study

    Science.gov (United States)

    Dessauges-Zavadsky, M.; Zamojski, M.; Rujopakarn, W.; Richard, J.; Sklias, P.; Schaerer, D.; Combes, F.; Ebeling, H.; Rawle, T. D.; Egami, E.; Boone, F.; Clément, B.; Kneib, J.-P.; Nyland, K.; Walth, G.

    2017-09-01

    We report on the galaxy MACSJ0032-arc at zCO = 3.6314 discovered during the Herschel Lensing snapshot Survey of massive galaxy clusters, and strongly lensed by the cluster MACS J0032.1+1808. The successful detections of its rest-frame ultraviolet (UV), optical, far-infrared (FIR), millimeter, and radio continua, and of its CO emission enable us to characterize, for the first time at such a high redshift, the stellar, dust, and molecular gas properties of a compact star-forming galaxy with a size smaller than 2.5 kpc, a fairly low stellar mass of 4.8+ 0.5-1.0 × 109M⊙, and a moderate IR luminosity of 4.8+ 1.2-0.6 × 1011L⊙. By combining the stretching effect of the lens with the high angular resolution imaging of the CO(1-0) line emission and the radio continuum at 5 GHz, we find that the bulk of the molecular gas mass and star formation seems to be spatially decoupled from the rest-frame UV emission. About 90% of the total star formation rate is undetected at rest-frame UV wavelengths because of severe obscuration by dust, but is seen through the thermal FIR dust emission and the radio synchrotron radiation. The observed CO(4-3) and CO(6-5) lines demonstrate that high-J transitions, at least up to J = 6, remain excited in this galaxy, whose CO spectral line energy distribution resembles that of high-redshift submm galaxies, even though the IR luminosity of MACSJ0032-arc is ten times lower. This high CO excitation is possibly due to the compactness of the galaxy. We find evidence that this high CO excitation has to be considered in the balance when estimating the CO-to-H2 conversion factor. Indeed, the respective CO-to-H2 conversion factors as derived from the correlation with metallicity and the FIR dust continuum can only be reconciled if excitation is accounted for. The inferred depletion time of the molecular gas in MACSJ0032-arc supports the decrease in the gas depletion timescale of galaxies with redshift, although to a lesser degree than predicted by

  3. Quantifying the Effects of the Influence of a Tungsten Long-rod Projectile into Confined Ceramics at High-velocity Impact

    National Research Council Canada - National Science Library

    Gorsich, Tara J; Templeton, Douglas W

    2008-01-01

    .... The finite element simulations were performed using Elastic Plastic Impact Code (EPIC) [Johnson (2006)], which simulates the failure and particle breakup of the target once the long-rod penetrator strikes at high-velocity impact...

  4. Warm and cold molecular gas conditions modelled in 87 galaxies observed by the Herschel SPIRE Fourier transform spectrometer

    Science.gov (United States)

    Kamenetzky, J.; Rangwala, N.; Glenn, J.

    2017-11-01

    We have conducted two-component, non-local thermodynamic equilibrium modelling of the CO lines from J = 1-0 through J = 13-12 in 87 galaxies observed by the Herschel SPIRE Fourier Transform Spectrometer (FTS). We find the average pressure of the cold molecular gas, traced especially by CO J = 1-0, is ˜105.0±0.5 K cm-3. The mid- to high-J lines of CO trace higher pressure gas at 106.5 ± 0.6 K cm-3; this pressure is slightly correlated with LFIR. Two components are often necessary to accurately fit the Spectral Line Energy Distributions; a one-component fit often underestimates the flux of carbon monoxide (CO) J = 1-0 and the mass. If low-J lines are not included, mass is underestimated by an order of magnitude. Even when modelling the low-J lines alone or using an αCO conversion factor, the mass should be considered to be uncertain to a factor of at least 0.4 dex, and the vast majority of the CO luminosity will be missed (median, 65 per cent). We find a very large spread in our derived values of αCO, though they do not have a discernible trend with LFIR; the best fit is a constant 0.7 M⊙ (K km s- 1 pc2)-1, with a standard deviation of 0.36 dex, and a range of 0.3-1.6 M⊙ (K km s- 1 pc2)-1. We find average molecular gas depletion times (τdep) of 108 yr that decrease with increasing star formation rate. Finally, we note that the J = 11-10/J = 1-0 line flux ratio is diagnostic of the warm component pressure, and discuss the implications of this comprehensive study of SPIRE FTS extragalactic spectra for future study post-Herschel.

  5. Gas separation performance of carbon molecular sieve membranes based on 6FDA-mPDA/DABA (3:2) polyimide.

    Science.gov (United States)

    Qiu, Wulin; Zhang, Kuang; Li, Fuyue Stephanie; Zhang, Ke; Koros, William J

    2014-04-01

    6FDA-mPDA/DABA (3:2) polyimide was synthesized and characterized for uncross-linked, thermally crosslinked, and carbon molecular sieve (CMS) membranes. The membranes were characterized with thermogravimetric analysis, FTIR spectroscopy, wide-angle X-ray diffraction, and gas permeation tests. Variations in the d spacing, the formation of pore structures, and changes in the pore sizes of the CMS membranes were discussed in relation to pyrolysis protocols. The uncross-linked polymer membranes showed high CO2 /CH4 selectivity, whereas thermally crosslinked membranes exhibited significantly improved CO2 permeability and excellent CO2 plasticization resistance. The CMS membranes showed even higher CO2 permeability and CO2 /CH4 selectivity. An increase in the pyrolysis temperature resulted in CMS membranes with lower gas permeability but higher selectivity. The 550 °C pyrolyzed CMS membranes showed CO2 permeability as high as 14 750 Barrer with CO2 /CH4 selectivity of approximately 52. Even 800 °C pyrolyzed CMS membranes still showed high CO2 permeability of 2610 Barrer with high CO2 /CH4 selectivity of approximately 118. Both polymer membranes and the CMS membranes are very attractive in aggressive natural gas purification applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Molecular simulation of steady-state evaporation and condensation in the presence of a non-condensable gas

    Science.gov (United States)

    Liang, Zhi; Keblinski, Pawel

    2018-02-01

    Using molecular dynamics simulations, we study evaporation and condensation of fluid Ar in the presence of a non-condensable Ne gas in a nanochannel. The evaporation and condensation are driven by the temperature difference, ΔTL, between the evaporating and condensing liquid surfaces. The steady-state evaporation and condensation fluxes (JMD) are also affected by the Ne concentration, ρNe, and the nanochannel length. We find that across a wide range of ΔTL and ρNe, JMD is in good agreement with the prediction from Stefan's law and from Schrage relationships. Furthermore, for ΔTL less than ˜20% of the absolute average temperature, we find that both steady-state heat and mass fluxes are proportional to ΔTL. This allows us to determine the interfacial resistance to the heat and mass transfer and compare it with the corresponding resistances in the gas phase. In this context, we derive an analytical expression for the effective thermal conductivity of the gas region in the nanochannel and the mass transport interfacial resistance equivalent length, i.e., the length of the nanochannel for which the resistance to the mass flow is the same as the interfacial resistance to the mass flow.

  7. Accessing the molecular frame through strong-field alignment of distributions of gas phase molecules

    Science.gov (United States)

    Reid, Katharine L.

    2018-03-01

    A rationale for creating highly aligned distributions of molecules is that it enables vector properties referenced to molecule-fixed axes (the molecular frame) to be determined. In the present work, the degree of alignment that is necessary for this to be achieved in practice is explored. Alignment is commonly parametrized in experiments by a single parameter, ?, which is insufficient to enable predictive calculations to be performed. Here, it is shown that, if the full distribution of molecular axes takes a Gaussian form, this single parameter can be used to determine the complete set of alignment moments needed to characterize the distribution. In order to demonstrate the degree of alignment that is required to approach the molecular frame, the alignment moments corresponding to a few chosen values of ? are used to project a model molecular frame photoelectron angular distribution into the laboratory frame. These calculations show that ? needs to approach 0.9 in order to avoid significant blurring to be caused by averaging. This article is part of the theme issue `Modern theoretical chemistry'.

  8. Radiative and mechanical feedback into the molecular gas of NGC 253

    NARCIS (Netherlands)

    Rosenberg, M. J. F.; Kazandjian, M. V.; van der Werf, P. P.; Israel, F. P.; Meijerink, R.; Weiß, A.; Requena-Torres, M. A.; Güsten, R.

    Starburst galaxies are galaxies or regions of galaxies undergoing intense periods of star formation. Understanding the heating and cooling mechanisms in these galaxies can give us insight to the driving mechanisms that fuel the starburst. Molecular emission lines play a crucial role in the cooling

  9. Free-Molecular Gas Flow in Channels (Pores) with Physico-Chemical Transformation on the Surface

    Czech Academy of Sciences Publication Activity Database

    Levdansky, V.V.; Smolík, Jiří; Moravec, Pavel

    2006-01-01

    Roč. 49, 13-14 (2006), s. 2356-2365 ISSN 0017-9310 Institutional research plan: CEZ:AV0Z40720504 Keywords : free-molecular flow * surface * spatial distribution Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.482, year: 2006

  10. Feedback from deeply embedded low- and high-mass protostars. Surveying hot molecular gas with Herschel

    NARCIS (Netherlands)

    Karska, Agata

    2014-01-01

    Protostars interact violently with their natal cocoons within dense molecular clouds. Characterizing this feedback is key to understanding the efficiency of the star formation process and the chemical processing of material that will be available for planet formation. In this thesis, the imprints

  11. Evolution of the atomic and molecular gas content of galaxies in dark matter haloes

    NARCIS (Netherlands)

    Popping, Gergö; Behroozi, Peter S.; Peeples, Molly S.

    We present a semi-empirical model to infer the atomic and molecular hydrogen content of galaxies as a function of halo mass and time. Our model combines the star formation rate (SFR)-halo mass-redshift relation (constrained by galaxy abundances) with inverted SFR-surface density relations to infer

  12. Molecular hydrogen line ratios in four regions of shock-excited gas

    International Nuclear Information System (INIS)

    Burton, M.G.

    1989-01-01

    Five emission lines of molecular hydrogen, with wavelengths in the ranges of 2.10-2.25 and 3.80-3.85 μm, have been observed in four objects of different type in which the line emission is believed to be excited by shocks. (author)

  13. High velocity missile-related colorectal injuries: In-theatre application of injury scores and their effects on ostomy rates.

    Science.gov (United States)

    Kaymak, Şahin; Ünlü, Aytekin; Harlak, Ali; Ersöz, Nail; Şenocak, Rahman; Coşkun, Ali Kağan; Zeybek, Nazif; Lapsekili, Emin; Kozak, Orhan

    2016-03-01

    Treatment of colorectal injuries (CRIs) remains a significant cause of morbidity and mortality. The aim of the present study was to analyze treatment trends of Turkish surgeons and effects of the American Association for the Surgery of Trauma (AAST), Injury Severity (ISS), and Penetrating Abdominal Trauma Index (PATI) scoring systems on decision-making processes and clinical outcomes. Data regarding high velocity missile (HVM)-related CRIs were retrospectively gathered. Four patient groups were included: Group 1 (stoma), Group 2 (no stoma in primary surgery), Group 2a (conversion to stoma in secondary surgery), and Group 2b (remaining Group 2 patients). Groups 1, 2, 2a, and 2b included 39 (66%), 20 (34%), 6 (30%), and 14 (70%) casualties, respectively. Ostomies were performed in casualties with significantly higher AAST scores (pcolon/rectum injury scores.

  14. Titanium K-Shell X-Ray Production from High Velocity Wire Arrays Implosions on the 20-MA Z Accelerator

    International Nuclear Information System (INIS)

    Apruzese, J.P.; Beg, F.N.; Clark, R.C.; Coverdale, C.A.; Davis, J.; Deeney, C.; Douglas, M.R.; Nash, T.J.; Ruiz-Comacho, J.; Spielman, R.B.; Struve, K.W.; Thornhill, J.W.; Whitney, K.G.

    1999-01-01

    The advent of the 20-MA Z accelerator [R.B. Spielman, C. Deeney, G.A. Chandler, et al., Phys. Plasmas 5, 2105, (1997)] has enabled implosions of large diameter, high-wire-number arrays of titanium to begin testing Z-pinch K-shell scaling theories. The 2-cm long titanium arrays, which were mounted on a 40-mm diameter, produced between 75±15 to 125±20 kJ of K-shell x-rays. Mass scans indicate that, as predicted, higher velocity implosions in the series produced higher x-ray yields. Spectroscopic analyses indicate that these high velocity implosions achieved peak electron temperatures from 2.7±0.1 to 3.2±0.2 keV and obtained a K-shell emission mass participation of up to 12%

  15. Optimizing pulse shaping and zooming for acceleration to high velocities and fusion neutron production on the Nike laser

    Science.gov (United States)

    Karasik, Max; Weaver, J. L.; Aglitskiy, Y.; Zalesak, S. T.; Velikovich, A. L.; Oh, J.; Obenschain, S. P.; Arikawa, Y.; Watari, T.

    2010-11-01

    We will present results from follow-on experiments to the record-high velocities of 1000 km/s achieved on Nike [Karasik et al., Phys. Plasmas 17, 056317 (2010) ], in which highly accelerated planar foils of deuterated polystyrene were made to collide with a witness foil to produce extreme shock pressures and result in heating of matter to thermonuclear temperatures. Still higher velocities and higher target densities are required for impact fast ignition. The aim of these experiments is shaping the driving pulse to minimize shock heating of the accelerated target and using the focal zoom capability of Nike to achieve higher densities and velocities. Spectroscopic measurements of electron temperature achieved upon impact will complement the neutron time-of-flight ion temperature measurement. Work is supported by US DOE and Office of Naval Research.

  16. Use of zooming and pulseshaping for acceleration to high velocities and fusion neutron production on the Nike laser

    Science.gov (United States)

    Karasik, Max; Weaver, J. L.; Aglitskiy, Y.; Kehne, D. M.; Zalesak, S. T.; Velikovich, A. L.; Oh, J.; Obenschain, S. P.; Arikawa, Y.

    2011-10-01

    We will present results from follow-on experiments to the record-high velocities of 1000 km/s achieved on Nike [Karasik et al, Phys. Plasmas 17, 056317(2010)], in which highly accelerated planar foils of deuterated polystyrene were made to collide with a witness foil to produce ~ 1 Gbar shock pressures and result in heating of matter to thermonuclear temperatures. Still higher velocities and higher target densities are required for impact fast ignition. The aim of these experiments is using the focal zoom capability of Nike and shaping the driving pulse to minimize shock heating of the accelerated target to achieve higher densities and velocities. In-flight target density is inferred from target heating upon collision via DD neutron time-of-flight ion temperature measurement. Work is supported by US DOE (NNSA) and Office of Naval Research. SAIC

  17. A study of the condensation of a high-velocity vapor jet on a coflowing turbulent liquid jet

    Science.gov (United States)

    Ovsiannikov, V. A.; Levin, A. A.

    A method for the experimental determination of the local value of the heat transfer coefficient under conditions of jet condensation is proposed which employs a heat balance expression in differential form. The method is used in an experimental study of the heat transfer characteristics of the condensation of a high-velocity coaxial jet of a slightly superheated (3 percent) steam on a coflowing cylindrical turbulent water jet. In the experiment, the relative velocities reach hundreds of m/s; the temperature nonequilibrium of the phases is high, as is the steam flow mass density during the initial contact; heat transfer between the phases is significant. The results can be used as the basis for determining experimental criterial dependences for jet condensation.

  18. The molecular structure of 4-methylpyridine-N-oxide: Gas-phase electron diffraction and quantum chemical calculations

    Science.gov (United States)

    Belova, Natalya V.; Girichev, Georgiy V.; Kotova, Vitaliya E.; Korolkova, Kseniya A.; Trang, Nguyen Hoang

    2018-03-01

    The molecular structure of 4-methylpiridine-N-oxide, 4-MePyO, has been studied by gas-phase electron diffraction monitored by mass spectrometry (GED/MS) and quantum chemical (DFT) calculations. Both, quantum chemistry and GED analyses resulted in CS molecular symmetry with the planar pyridine ring. Obtained molecular parameters confirm the hyperconjugation in the pyridine ring and the sp2 hybridization concept of the nitrogen and carbon atoms in the ring. The experimental geometric parameters are in a good agreement with the parameters for non-substituted N-oxide and reproduced very closely by DFT calculations. The presence of the electron-donating CH3 substituent in 4-MePyO leads to a decrease of the ipso-angle and to an increase of r(N→O) in comparison with the non-substituted PyO. Electron density distribution analysis has been performed in terms of natural bond orbitals (NBO) scheme. The nature of the semipolar N→O bond is discussed.

  19. Application of TiC reinforced Fe-based coatings by means of High Velocity Air Fuel Spraying

    Science.gov (United States)

    Bobzin, K.; Öte, M.; Knoch, M. A.; Liao, X.; Sommer, J.

    2017-03-01

    In the field of hydraulic applications, different development trends can cause problems for coatings currently used as wear and corrosion protection for piston rods. Aqueous hydraulic fluids and rising raw material prices necessitate the search for alternatives to conventional coatings like galvanic hard chrome or High Velocity Oxygen Fuel (HVOF)-sprayed WC/Co coatings. In a previous study, Fe/TiC coatings sprayed by a HVOF-process, were identified to be promising coating systems for wear and corrosion protection in hydraulic systems. In this feasibility study, the novel High Velocity Air Fuel (HVAF)-process, a modification of the HVOF-process, is investigated using the same feedstock material, which means the powder is not optimized for the HVAF-process. The asserted benefits of the HVAF-process are higher particle velocities and lower process temperatures, which can result in a lower porosity and oxidation of the coating. Further benefits of the HVAF process are claimed to be lower process costs and higher deposition rates. In this study, the focus is set on to the applicability of Fe/TiC coatings by HVAF in general. The Fe/TiC HVAF coating could be produced, successfully. The HVAF- and HVOF-coatings, produced with the same powder, were investigated using micro-hardness, porosity, wear and corrosion tests. A similar wear coefficient and micro-hardness for both processes could be achieved. Furthermore the propane/hydrogen proportion of the HVAF process and its influence on the coating thickness and the porosity was investigated.

  20. Ultrafast Magnetization of a Dense Molecular Gas with an Optical Centrifuge

    Science.gov (United States)

    Milner, A. A.; Korobenko, A.; Milner, V.

    2017-06-01

    Strong laser-induced magnetization of oxygen gas at room temperature and atmospheric pressure is achieved experimentally on the subnanosecond time scale. The method is based on controlling the electronic spin of paramagnetic molecules by means of manipulating their rotation with an optical centrifuge. Spin-rotational coupling results in a high degree of spin polarization on the order of one Bohr magneton per centrifuged molecule. Owing to the nonresonant interaction with the laser pulses, the demonstrated technique is applicable to a broad class of paramagnetic rotors. Executed in a high-density gas, it may offer an efficient way of generating macroscopic magnetic fields remotely (as shown in this work) and producing a large amount of spin-polarized electrons.

  1. Comparative studies of high-frequency and direct current molecular gas discharges

    International Nuclear Information System (INIS)

    Goichman, V.H.; Goldfarb, V.M.; Tendler, M.B.

    1975-01-01

    Electron gas parameters, gas temperatures, ionization and thermal instability are found to be markedly different in direct current glow discharges from capactive electrodless high frequency discharge even when equal net power input is provided. It is reasonable to expect that the combined discharge containing both types of discharges mentioned above may be expected to improve significantly both the steady-state and transient characteristics of the plasma. The characteristics of different discharges in air, nitrogen air-CO 2 -He mixture have been compared. Because of the lack of the direct electrical methods for measurements of the hf plasma, exphasis in this investigation has been laid on both theoretical) based on the analytical expression for electron energy distribution function received previously and experimental spectroscopic evaluations of the plasma parameters. (Auth.)

  2. Molecularly Designed Stabilized Asymmetric Hollow Fiber Membranes for Aggressive Natural Gas Separation.

    Science.gov (United States)

    Liu, Gongping; Li, Nanwen; Miller, Stephen J; Kim, Danny; Yi, Shouliang; Labreche, Ying; Koros, William J

    2016-10-24

    New rigid polyimides with bulky CF 3 groups were synthesized and engineered into high-performance hollow fiber membranes. The enhanced rotational barrier provided by properly positioned CF 3 side groups prohibited fiber transition layer collapse during cross-linking, thereby greatly improving CO 2 /CH 4 separation performance compared to conventional materials for aggressive natural gas feeds. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Ionized and Molecular Gas Kinematics in a z = 1.4 Star-forming Galaxy

    Science.gov (United States)

    Übler, H.; Genzel, R.; Tacconi, L. J.; Förster Schreiber, N. M.; Neri, R.; Contursi, A.; Belli, S.; Nelson, E. J.; Lang, P.; Shimizu, T. T.; Davies, R.; Herrera-Camus, R.; Lutz, D.; Plewa, P. M.; Price, S. H.; Schuster, K.; Sternberg, A.; Tadaki, K.; Wisnioski, E.; Wuyts, S.

    2018-02-01

    We present deep observations of a z = 1.4 massive, star-forming galaxy (SFG) in molecular and ionized gas at comparable spatial resolution (CO 3–2, NOrthern Extended Millimeter Array (NOEMA); Hα, Large Binocular Telescope (LBT)). The kinematic tracers agree well, indicating that both gas phases are subject to the same gravitational potential and physical processes affecting the gas dynamics. We combine the one-dimensional velocity and velocity dispersion profiles in CO and Hα to forward-model the galaxy in a Bayesian framework, combining a thick exponential disk, a bulge, and a dark matter halo. We determine the dynamical support due to baryons and dark matter, and find a dark matter fraction within one effective radius of {f}DM}(≤slant {R}e)={0.18}-0.04+0.06. Our result strengthens the evidence for strong baryon-dominance on galactic scales of massive z ∼ 1–3 SFGs recently found based on ionized gas kinematics alone. Based on observations carried out with the IRAM Interferometer NOEMA. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). Based on observations carried out with the LBT. The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are: LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, The Leibniz Institute for Astrophysics Potsdam, and Heidelberg University; The University of Arizona on behalf of the Arizona Board of Regents; Istituto Nazionale di Astrofisica, Italy; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota and University of Virginia.

  4. Submm Observations of Massive Star Formation in the Giant Molecular Cloud NGC 6334 : Gas Kinematics with Radiative Transfer Models

    Science.gov (United States)

    Zernickel, A.

    2015-05-01

    Context. How massive stars (M>8 Ms) form and how they accrete gas is still an open research field, but it is known that their influence on the interstellar medium (ISM) is immense. Star formation involves the gravitational collapse of gas from scales of giant molecular clouds (GMCs) down to dense hot molecular cores (HMCs). Thus, it is important to understand the mass flows and kinematics in the ISM. Aims. This dissertation focuses on the detailed study of the region NGC 6334, located in the Galaxy at a distance of 1.7 kpc. It is aimed to trace the gas velocities in the filamentary, massive star-forming region NGC 6334 at several scales and to explain its dynamics. For that purpose, different scales are examined from 0.01-10 pc to collect information about the density, molecular abundance, temperature and velocity, and consequently to gain insights about the physio-chemical conditions of molecular clouds. The two embedded massive protostellar clusters NGC 6334I and I(N), which are at different stages of development, were selected to determine their infall velocities and mass accretion rates. Methods. This astronomical source was surveyed by a combination of different observatories, namely with the Submillimeter Array (SMA), the single-dish telescope Atacama Pathfinder Experiment (APEX), and the Herschel Space Observatory (HSO). It was mapped with APEX in carbon monoxide (13CO and C18O, J=2-1) at 220.4 GHz to study the filamentary structure and turbulent kinematics on the largest scales of 10 pc. The spectral line profiles are decomposed by Gaussian fitting and a dendrogram algorithm is applied to distinguish velocity-coherent structures and to derive statistical properties. The velocity gradient method is used to derive mass flow rates. The main filament was mapped with APEX in hydrogen cyanide (HCN) and oxomethylium (HCO+, J=3-2) at 267.6 GHz to trace the dense gas. To reproduce the position- velocity diagram (PVD), a cylindrical model with the radiative transfer

  5. Production of ultrapure D-T gas by removal of molecular tritium by selective adsorption

    International Nuclear Information System (INIS)

    Maienschein, J.L.; Hudson, R.S.; Tsugawa, R.T.; Fearon, E.M.; Souers, P.C.; Collins, G.W.

    1992-01-01

    Production of molecular deuterium-tritium (D-T) with very low molecular tritium (T 2 ) is necessary for application as a nuclear spin polarized fuel. Selective adsorption of hydrogen isotopes on zeolites or alumina can provide the separation needed to produce D-T with very low T 2 . Use of an absorption column at 20-25 K offers low inventory, compact size, and rapid operation, in comparison with conventional separation techniques such as cryogenic distillation or thermal diffusion. In this paper, the authors discuss principles of absorption, and describe a calculational model of the absorption column and operational implications revealed by it. The authors show experimental proof-of-principle data for removal of T 2 from D-T with an adsorption column operated at 23 K

  6. MILKY WAY STAR-FORMING COMPLEXES AND THE TURBULENT MOTION OF THE GALAXY'S MOLECULAR GAS

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Eve J.; Rahman, Mubdi [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON, M5S 3H4 (Canada); Murray, Norman, E-mail: elee@astro.utoronto.ca, E-mail: rahman@astro.utoronto.ca, E-mail: elee@cita.utoronto.ca, E-mail: murray@cita.utoronto.ca [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, University of Toronto, Toronto, ON, M5S 3H8 (Canada)

    2012-06-20

    We analyze Spitzer GLIMPSE, Midcourse Space Experiment (MSX), and Wilkinson Microwave Anisotropy Probe (WMAP) images of the Milky Way to identify 8 {mu}m and free-free sources in the Galaxy. Seventy-two of the 88 WMAP sources have coverage in the GLIMPSE and MSX surveys suitable for identifying massive star-forming complexes (SFCs). We measure the ionizing luminosity functions of the SFCs and study their role in the turbulent motion of the Galaxy's molecular gas. We find a total Galactic free-free flux f{sub {nu}} = 46,177.6 Jy; the 72 WMAP sources with full 8 {mu}m coverage account for 34,263.5 Jy ({approx}75%), with both measurements made at {nu} = 94 GHz (W band). We find a total of 280 SFCs, of which 168 have unique kinematic distances and free-free luminosities. We use a simple model for the radial distribution of star formation to estimate the free-free and ionizing luminosity for the sources lacking distance determinations. The total dust-corrected ionizing luminosity is Q = (2.9 {+-} 0.5) Multiplication-Sign 10{sup 53} photons s{sup -1}, which implies a Galactic star formation rate of M-dot{sub *}= 1.2{+-}0.2 M{sub Sun} yr{sup -1}. We present the (ionizing) luminosity function of the SFCs and show that 24 sources emit half the ionizing luminosity of the Galaxy. The SFCs appear as bubbles in GLIMPSE or MSX images; the radial velocities associated with the bubble walls allow us to infer the expansion velocity of the bubbles. We calculate the kinetic luminosity of the bubble expansion and compare it to the turbulent luminosity of the inner molecular disk. SFCs emitting 80% of the total Galactic free-free luminosity produce a kinetic luminosity equal to 65% of the turbulent luminosity in the inner molecular disk. This suggests that the expansion of the bubbles is a major driver of the turbulent motion of the inner Milky Way molecular gas.

  7. Hubble Space Telescope Imaging of the Ultra-compact High Velocity Cloud AGC 226067: A Stripped Remnant in the Virgo Cluster

    Energy Technology Data Exchange (ETDEWEB)

    Sand, D. J.; Crnojević, D. [Texas Tech University, Physics and Astronomy Department, Box 41051, Lubbock, TX 79409-1051 (United States); Seth, A. C. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Spekkens, K. [Royal Military College of Canada, Department of Physics, P.O. Box 17000, Station Forces, Kingston, Ontario, K7K 7B4 (Canada); Strader, J. [Center for Data Intensive and Time Domain Astronomy, Department of Physics and Astronomy, Michigan State University, 567 Wilson Road, East Lansing, MI 48824 (United States); Adams, E. A. K. [ASTRON, Netherlands Institute for Radio Astronomy, Postbus 2, 7900 AA Dwingeloo (Netherlands); Caldwell, N.; Randall, S. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Guhathakurta, P. [UCO/Lick Observatory, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Kenney, J. [Yale University Astronomy Department, P.O. Box 208101, New Haven, CT 06520-8101 (United States); Simon, J. D. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Toloba, E. [Department of Physics, University of the Pacific, 3601 Pacific Avenue, Stockton, CA 95211 (United States); Willman, B., E-mail: david.sand@ttu.edu [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

    2017-07-10

    We analyze the optical counterpart to the ultra-compact high velocity cloud AGC 226067, utilizing imaging taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope . The color–magnitude diagram of the main body of AGC 226067 reveals an exclusively young stellar population, with an age of ∼7–50 Myr, and is consistent with a metallicity of [Fe/H] ∼ −0.3 as previous work has measured via H ii region spectroscopy. Additionally, the color–magnitude diagram is consistent with a distance of D ≈ 17 Mpc, suggesting an association with the Virgo cluster. A secondary stellar system located ∼1.′6 (∼8 kpc) away in projection has a similar stellar population. The lack of an old red giant branch (≳5 Gyr) is contrasted with a serendipitously discovered Virgo dwarf in the ACS field of view (Dw J122147+132853), and the total diffuse light from AGC 226067 is consistent with the luminosity function of the resolved ∼7–50 Myr stellar population. The main body of AGC 226067 has a M {sub V} = −11.3 ± 0.3, or M {sub stars} = 5.4 ± 1.3 × 10{sup 4} M {sub ⊙} given the stellar population. We searched 20 deg{sup 2} of imaging data adjacent to AGC 226067 in the Virgo Cluster, and found two similar stellar systems dominated by a blue stellar population, far from any massive galaxy counterpart—if this population has star-formation properties that are similar to those of AGC 226067, it implies ∼0.1 M {sub ⊙} yr{sup −1} in Virgo intracluster star formation. Given its unusual stellar population, AGC 226067 is likely a stripped remnant and is plausibly the result of compressed gas from the ram pressure stripped M86 subgroup (∼350 kpc away in projection) as it falls into the Virgo Cluster.

  8. observations of hot molecular gas emission from embedded low-mass protostars

    DEFF Research Database (Denmark)

    Visser, R.; Kristensen, L. E.; Bruderer, S.

    2012-01-01

    Aims. Young stars interact vigorously with their surroundings, as evident from the highly rotationally excited CO (up to Eu/k = 4000 K) and H2O emission (up to 600 K) detected by the Herschel Space Observatory in embedded low-mass protostars. Our aim is to construct a model that reproduces...... the observations quantitatively, to investigate the origin of the emission, and to use the lines as probes of the various heating mechanisms. Methods. The model consists of a spherical envelope with a power-law density structure and a bipolar outflow cavity. Three heating mechanisms are considered: passive heating...... such as luminosity and envelope mass. Results. The bulk of the gas in the envelope, heated by the protostellar luminosity, accounts for 3–10% of the CO luminosity summed over all rotational lines up to J = 40–39; it is best probed by low-J CO isotopologue lines such as C18O 2–1 and 3–2. The UV-heated gas and the C...

  9. Molecular gas and star formation in the centers of Virgo spirals

    International Nuclear Information System (INIS)

    Canzian, B.

    1990-01-01

    The CO and H alpha flux distributions for a sample of Virgo spirals were mapped out in an attempt to understand the coupling between gas dynamics and star formation in spiral galaxies. A broad range of morphological types were observed (types Sab through Scd) under the hypothesis that the gas dynamics is most influential in determining the overall appearance of a spiral galaxy. Only non-barred spirals were considered so that the well-studied but complicated properties of bars and their role in inducing star formation would not be a factor. All galaxies were chosen from the Virgo cluster to eliminate uncertainties due to distance errors. Since the dynamical seat of a spiral is at its center, it was expected that the dynamics of the central region would influence global properties of the rest of the disk. This could happen through the existence or absence of an inner Lindblad resonance (according to the degree of central concentration of mass) to modulate swing amplification of spiral waves, or the persistence of an oval distortion to initiate an instability which leads to spiral structure

  10. Size and molecular weight determination of polysaccharides by means of nano electrospray gas-phase electrophoretic mobility molecular analysis (nES GEMMA).

    Science.gov (United States)

    Weiss, Victor U; Golesne, Monika; Friedbacher, Gernot; Alban, Susanne; Szymanski, Wladyslaw W; Marchetti-Deschmann, Martina; Allmaier, Günter

    2018-02-21

    Size, size distribution and molecular weight (MW) determination of nanoparticles and that are for example large polymers, are of great interest and pose an analytical challenge. In this context, nano electrospray gas-phase electrophoretic mobility molecular analysis (nES GEMMA) is a valuable tool with growing impact. Separation of single-charged analytes according to their electrophoretic mobility diameter (EMD) starting from single-digit EMDs up to several hundred nm diameters is possible. In case of spherical analytes, the EMD corresponds to the dry nanoparticle size. Additionally, the instrument is capable of number-based, single-particle detection following the recommendation of the European Commission for nanoparticle characterization (2011/696/EU). In case an EMD/MW correlation for a particular compound class (based on availability of well-defined standards) exists, a nanoparticle's MW can be determined from its EMD. In the present study, we focused on nES GEMMA of linear and branched, water-soluble polysaccharides forming nanoparticles and were able to obtain spectra for both analyte classes regarding single-charged species. Based on EMDs for corresponding analytes, an excellent EMD/MW correlation could be obtained in case of the branched natural polymer (dextran). This enables the determination of dextran MWs from nES GEMMA spectra despite high analyte polydispersity and in a size/MW range, where classical mass spectrometry is limited. EMD/MW correlations based on linear (pullulans, oat-ß-glucans) polymers were significantly different, possibly indicating challenges in the exact MW determination of these compounds by, for example, chromatographic and light scattering means. Despite these observations, nES GEMMA of linear, monosaccharide-based polymers enabled the determination of size and size-distribution of such dry bionanoparticles. © 2018 The Authors. Electrophoresis published by Wiley-VCH Verlag GmbH & Co. KGaA.

  11. Molecular Gas-Filled Hollow Optical Fiber Lasers in the Near Infrared

    Science.gov (United States)

    2012-01-12

    Benabid, F., Roberts , P. J., Light, P. S., and Raymer , M. G., “Generation and photonic guidance of multi-octave optical-frequency combs,” Science, 318...scattering in molecular hydrogen," Phys. Rev. Lett. 93, 123903 (2004). 16. F. Couny, F. Benabid, P. J. Roberts , P. S. Light, and M. G. Raymer ...Couny, F., Wang, Y. Y., Wheeler, N. V., Roberts , P. J., and Benabid, F., “Double photonic bandgap hollow-core photonic crystal fiber,” Opt

  12. Molecular Hydrogen as an Emerging Therapeutic Medical Gas for Neurodegenerative and Other Diseases

    Directory of Open Access Journals (Sweden)

    Kinji Ohno

    2012-01-01

    Full Text Available Effects of molecular hydrogen on various diseases have been documented for 63 disease models and human diseases in the past four and a half years. Most studies have been performed on rodents including two models of Parkinson's disease and three models of Alzheimer's disease. Prominent effects are observed especially in oxidative stress-mediated diseases including neonatal cerebral hypoxia; Parkinson's disease; ischemia/reperfusion of spinal cord, heart, lung, liver, kidney, and intestine; transplantation of lung, heart, kidney, and intestine. Six human diseases have been studied to date: diabetes mellitus type 2, metabolic syndrome, hemodialysis, inflammatory and mitochondrial myopathies, brain stem infarction, and radiation-induced adverse effects. Two enigmas, however, remain to be solved. First, no dose-response effect is observed. Rodents and humans are able to take a small amount of hydrogen by drinking hydrogen-rich water, but marked effects are observed. Second, intestinal bacteria in humans and rodents produce a large amount of hydrogen, but an addition of a small amount of hydrogen exhibits marked effects. Further studies are required to elucidate molecular bases of prominent hydrogen effects and to determine the optimal frequency, amount, and method of hydrogen administration for each human disease.

  13. Molecular Hydrogen as an Emerging Therapeutic Medical Gas for Neurodegenerative and Other Diseases

    Science.gov (United States)

    Ohno, Kinji; Ito, Mikako; Ichihara, Masatoshi; Ito, Masafumi

    2012-01-01

    Effects of molecular hydrogen on various diseases have been documented for 63 disease models and human diseases in the past four and a half years. Most studies have been performed on rodents including two models of Parkinson's disease and three models of Alzheimer's disease. Prominent effects are observed especially in oxidative stress-mediated diseases including neonatal cerebral hypoxia; Parkinson's disease; ischemia/reperfusion of spinal cord, heart, lung, liver, kidney, and intestine; transplantation of lung, heart, kidney, and intestine. Six human diseases have been studied to date: diabetes mellitus type 2, metabolic syndrome, hemodialysis, inflammatory and mitochondrial myopathies, brain stem infarction, and radiation-induced adverse effects. Two enigmas, however, remain to be solved. First, no dose-response effect is observed. Rodents and humans are able to take a small amount of hydrogen by drinking hydrogen-rich water, but marked effects are observed. Second, intestinal bacteria in humans and rodents produce a large amount of hydrogen, but an addition of a small amount of hydrogen exhibits marked effects. Further studies are required to elucidate molecular bases of prominent hydrogen effects and to determine the optimal frequency, amount, and method of hydrogen administration for each human disease. PMID:22720117

  14. Flow-injection analysis of nitrate by reduction to nitrite and gas-phase molecular absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Haghighi, B.; Tavassoli, A. [Dept. of Chemistry, Inst. for Advanced Studies in Basic Sciences, Zanjan (Iran)

    2001-12-01

    Two flow-injection manifolds have been investigated for the determination of nitrate. These manifolds are based on the reduction of nitrate to nitrite and determination of nitrite by gas-phase molecular absorption spectrophotometry. Nitrate sample solution (300 {mu}L) which is injected to the flow line, is reduced to nitrite by reaction with hydrazine or passage through the on-line copperized cadmium (Cd-Cu) reduction column. The nitrite produced reacts with a stream of hydrochloric acid and the evolved gases are purged into the stream of O{sub 2}carrier gas. The gaseous phase is separated from the liquid phase using a gas-liquid separator and then swept into a flow-through cell which has been positioned in the cell compartment of an UV-visible spectrophotometer. The absorbance of the gaseous phase is measured at 204.7 nm. A linear relationship was obtained between the intensity of absorption signals and concentration of nitrate when Cd-Cu reduction method was used, but a logarithmic relationship was obtained when the hydrazine reduction method was used. By use of the Cd-Cu reduction method, up to 330 {mu}g of nitrate was determined. The limit of detection was 2.97 {mu}g nitrate and the relative standard deviations for the determination of 12.0, 30.0 and 150 {mu}g nitrate were 3.32, 3.87 and 3.6%, respectively. Maximum sampling rate was approximately 30 samples per hour. The Cd-Cu reduction method was applied to the determination of nitrate and the simultaneous determination of nitrate and nitrite in meat products, vegetables, urine, and a water sample. (orig.)

  15. Numerical Simulations of Turbulent Molecular Clouds Regulated by Radiation Feedback Forces. II. Radiation-Gas Interactions and Outflows

    Science.gov (United States)

    Raskutti, Sudhir; Ostriker, Eve C.; Skinner, M. Aaron

    2017-12-01

    Momentum deposition by radiation pressure from young, massive stars may help to destroy molecular clouds and unbind stellar clusters by driving large-scale outflows. We extend our previous numerical radiation hydrodynamic study of turbulent star-forming clouds to analyze the detailed interaction between non-ionizing UV radiation and the cloud material. Our simulations trace the evolution of gas and star particles through self-gravitating collapse, star formation, and cloud destruction via radiation-driven outflows. These models are idealized in that we include only radiation feedback and adopt an isothermal equation of state. Turbulence creates a structure of dense filaments and large holes through which radiation escapes, such that only ˜50% of the radiation is (cumulatively) absorbed by the end of star formation. The surface density distribution of gas by mass as seen by the central cluster is roughly lognormal with {σ }{ln{{Σ }}}=1.3{--}1.7, similar to the externally projected surface density distribution. This allows low surface density regions to be driven outwards to nearly 10 times their initial escape speed {v}{esc}. Although the velocity distribution of outflows is broadened by the lognormal surface density distribution, the overall efficiency of momentum injection to the gas cloud is reduced because much of the radiation escapes. The mean outflow velocity is approximately twice the escape speed from the initial cloud radius. Our results are also informative for understanding galactic-scale wind driving by radiation, in particular, the relationship between velocity and surface density for individual outflow structures and the resulting velocity and mass distributions arising from turbulent sources.

  16. A study of the thermal activation of synthetic zeolites (molecular sieve) for gas-solid chromatography

    International Nuclear Information System (INIS)

    Walker, J.A.J.

    1978-10-01

    The thermal activation of synthetic zeolites from two sources has been investigated with reference to the adsorption chromatography of inorganic gases. It was found that the heats of adsorption for oxygen and carbon monoxide increased with activation temperatures. Limits of detection for oxygen in argon and conversely argon in oxygen were determined as well as the chromatographic stability of the activated zeolite. The practical implications and importance of the results are discussed and the application to the analysis of fast reactor blanket gas is mentioned. An explanation is proposed for the adsorption behaviour of these activated materials, based on an electrostatic mechanism, and this has suggested a reason for the separation characteristics of oxygen and argon on polar zeolites. Further work is identified including the investigation of energy states of the oxygen molecule adsorbed on activated zeolite by means of ultra-violet photoelectron spectroscopy. (author)

  17. A study of the thermal activation of synthetic zeolites (molecular sieve) for gas-solid chromatography

    International Nuclear Information System (INIS)

    Walker, J.A.J.

    1978-10-01

    The thermal activation of synthetic zeolites from two sources has been investigated with reference to the adsorption chromatography of inorganic gases. It was found that the heats of adsorption for oxygen and carbon monoxide increased with activation temperature. Limits of detection for oxygen in argon and conversely argon in oxygen were determined as well as the chromatographic stability of the activated zeolite. The practical implications and importance of the results are discussed and the application to the analysis of fast reactor blanket gas is mentioned. An explanation is proposed for the adsorption behaviour of these activated materials, based on an electrostatic mechanism, and this has suggested a reason for the separation characteristics of oxygen and argon on polar zeolites. Further work is identified including the investigation of energy states of the oxygen molecule adsorbed on activated zeolite by means of ultra-violet photoelectron spectroscopy. (author)

  18. HIGHLY EXCITED H2 IN HERBIG–HARO 7: FORMATION PUMPING IN SHOCKED MOLECULAR GAS?

    International Nuclear Information System (INIS)

    Pike, R. E.; Geballe, T. R.; Burton, M. G.; Chrysostomou, A.

    2016-01-01

    We have obtained K -band spectra at R ∼ 5000 and an angular resolution of 0.″3 of a section of the Herbig–Haro 7 (HH7) bow shock, using the Near-Infrared Integral Field Spectrograph at Gemini North. Present in the portion of the data cube corresponding to the brightest part of the bow shock are emission lines of H 2 with upper state energies ranging from ∼6000 K to the dissociation energy of H 2 , ∼50,000 K. Because of low signal-to-noise ratios, the highest excitation lines cannot be easily seen elsewhere in the observed region. However, excitation temperatures, measured throughout much of the observed region using lines from levels as high as 25,000 K, are a strong function of upper level energy, indicating that the very highest levels are populated throughout. The level populations in the brightest region are well fit by a two-temperature model, with 98.5% of the emitting gas at T = 1800 K and 1.5% at T = 5200 K. The bulk of the H 2 line emission in HH7, from the 1800 K gas, has previously been well-modeled by a continuous shock, but the 5200 K cozmponent is inconsistent with standalone standard continuous shock models. We discuss various possible origins for the hot component and suggest that this component is H 2 newly reformed on dust grains and then ejected from them, presumably following dissociation of some of the H 2 by the shock.

  19. Shocked POststarburst Galaxy Survey. II. The Molecular Gas Content and Properties of a Subset of SPOGs

    Science.gov (United States)

    Alatalo, Katherine; Lisenfeld, Ute; Lanz, Lauranne; Appleton, Philip N.; Ardila, Felipe; Cales, Sabrina L.; Kewley, Lisa J.; Lacy, Mark; Medling, Anne M.; Nyland, Kristina; Rich, Jeffrey A.; Urry, C. Meg

    2016-08-01

    We present CO(1-0) observations of objects within the Shocked POststarburst Galaxy Survey taken with the Institut de Radioastronomie Millimétrique 30 m single dish and the Combined Array for Research for Millimeter Astronomy interferometer. Shocked poststarburst galaxies (SPOGs) represent a transitioning population of galaxies, with deep Balmer absorption ({{EW}}{{H}δ }\\gt 5 {\\mathring{{A}}} ), consistent with an intermediate-age (A-star) stellar population, and ionized gas line ratios inconsistent with pure star formation. The CO(1-0) subsample was selected from SPOGs detected by the Wide-field Infrared Survey Explorer with 22 μm flux detected at a signal-to-noise ratio (S/N) > 3. Of the 52 objects observed in CO(1-0), 47 are detected with S/N > 3. A large fraction (37%-46% ± 7%) of our CO-SPOG sample were visually classified as morphologically disrupted. The H2 masses detected were between {10}8.7-10.8 {M}⊙ , consistent with the gas masses found in normal galaxies, though approximately an order of magnitude larger than the range seen in poststarburst galaxies. When comparing the 22 μm and CO(1-0) fluxes, SPOGs diverge from the normal star-forming relation, having 22 μm fluxes in excess of the relation by a factor of ={4.91}-0.39+0.42, suggestive of the presence of active galactic nuclei (AGNs). The Na I D characteristics of CO-SPOGs show that it is likely that many of these objects host interstellar winds. Objects with large Na I D enhancements also tend to emit in the radio, suggesting possible AGN driving of neutral winds.

  20. Detectability of molecular gas signatures on Jupiter’s moon Europa from ground and space-based facilities

    Science.gov (United States)

    Paganini, Lucas; Villanueva, Geronimo Luis; Hurford, Terry; Mandell, Avi; Roth, Lorenz; Mumma, Michael J.

    2017-10-01

    Plumes and their effluent material could provide insights into Europa’s subsurface chemistry and relevant information about the prospect that life could exist, or now exists, within the ocean. In 2016, we initiated a strong observational campaign to characterize the chemical composition of Europa’s surface and exosphere using high-resolution infrared spectroscopy. While several studies have focused on the detection of water, or its dissociation products, there could be a myriad of complex molecules released by erupting plumes. Our IR survey has provided a serendipitous search for several key molecular species, allowing a chemical characterization that can aid the investigation of physical processes underlying its surface. Since our tentative water detection, presented at the 2016 DPS meeting, we have continued the observations of Europa during 2017 covering a significant extent of the moon’s terrain and orbital position (true anomaly), accounting for over 50 hr on source. Current analyses of these data are showing spectral features that grant further investigation. In addition to analysis algorithms tailored to the examination of Europan data, we have developed simulation tools to predict the possible detection of molecular species using ground-based facilities like the Keck Observatory, NASA’s Infrared Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA). In this presentation we will discuss the detectability of key molecular species with these remote sensing facilities, as well as expected challenges and future strategies with upcoming spacecrafts such as the James Webb Space Telescope (JWST), the Large UV/Optical/Infrared Surveyor (LUVOIR), and a possible gas spectrometer onboard an orbiter.This work is supported by NASA’s Keck PI Data Award (PI L.P.) and Solar System Observation Program (PI L.P.), and by the NASA Astrobiology Institute through funding awarded to the Goddard Center for Astrobiology (PI M.J.M.).

  1. Pulsed flow modulation two-dimensional comprehensive gas chromatography-tandem mass spectrometry with supersonic molecular beams.

    Science.gov (United States)

    Poliak, Marina; Fialkov, Alexander B; Amirav, Aviv

    2008-11-07

    Pulsed flow modulation (PFM) two-dimensional comprehensive gas chromatography (GC x GC) was combined with quadrupole-based mass spectrometry (MS) via a supersonic molecular beam (SMB) interface using a triple-quadrupole system as the base platform, which enabled tandem mass spectrometry (MS-MS). PFM is a simple GC x GC modulator that does not consume cryogenic gases while providing tunable second GC x GC column injection time for enabling the use of quadrupole-based mass spectrometry regardless its limited scanning speed. The 20-ml/min second column flow rate involved with PFM is handled, splitless, by the SMB interface without affecting the sensitivity. The combinations of PFM GC x GC-MS with SMB and PFM GC x GC-MS-MS with SMB were explored with the analysis of diazinon and permethrin in coriander. PFM GC x GC-MS with SMB is characterized by enhanced molecular ion and tailing-free fast ion source response time. It enables universal pesticide analysis with full scan and data analysis with reconstructed single ion monitoring on the enhanced molecular ion and another prominent high mass fragment ion. The elimination of the third fragment ion used in standard three ions method results in significantly reduced matrix interference. GC x GC-MS with SMB improves the GC separation, and thereby our ability for sample identification using libraries. GC-MS-MS with SMB provides better reduction (elimination) of matrix interference than GC x GC-MS. However, it is a target method, which is not always applicable. GC x GC-MS-MS does not seem to further reduce matrix interferences over GC-MS-MS and unlike GC x GC-MS, it is incompatible with library identification, but it is beneficial to have both GC x GC and MS-MS capabilities in the same system.

  2. Rational extended thermodynamics of a rarefied polyatomic gas with molecular relaxation processes

    Science.gov (United States)

    Arima, Takashi; Ruggeri, Tommaso; Sugiyama, Masaru

    2017-10-01

    We present a more refined version of rational extended thermodynamics of rarefied polyatomic gases in which molecular rotational and vibrational relaxation processes are treated individually. In this case, we need a triple hierarchy of the moment system and the system of balance equations is closed via the maximum entropy principle. Three different types of the production terms in the system, which are suggested by a generalized BGK-type collision term in the Boltzmann equation, are adopted. In particular, the rational extended thermodynamic theory with seven independent fields (ET7) is analyzed in detail. Finally, the dispersion relation of ultrasonic wave derived from the ET7 theory is confirmed by the experimental data for CO2, Cl2, and Br2 gases.

  3. Contribution to the study of the simultaneous emission phenomena in molecular gas lasers

    International Nuclear Information System (INIS)

    Garnier, Jean-Pierre

    1974-01-01

    A selectively or simultaneously laser emission had been improved in a 12 CO 2 - 13 CO 2 -N 2 -He laser. 12 CO 2 wavelength near 945 cm -1 (10,58 μm), 13 CO 2 wavelength near 895 cm -1 (11,17 μm). The effect of CO 2 pressure, current intensity and isotopic enrichment in 13 C on the phenomena has been studied by measuring gain of a sealed laser amplifier containing CO 2 and its decomposition products (CO and O 2 ). A theoretical model has been established. A good agreement between theory and experiment has been obtained. The generalization of the phenomena to non-isotopic molecular systems has been experimentally verified with a mixture of CO 2 and N 2 O.(author) [fr

  4. Molecular recognition applied to gas detection: the contribution of Langmuir-Blodgett films

    International Nuclear Information System (INIS)

    Clemendot, Sylvain

    1992-01-01

    In the first part of this research thesis, the author presents the Langmuir-Blodgett technique and outlines how it can face the challenge of molecular electronics. Then, he proposes an overview of the state-of-the-art of chemical sensors based on LB films, and an assessment of the state of the art of conductive LB films based on TCNQ (tetracyanoquinodimethane) and on tetrathiafulvalene for which the author proposes a modelling. He describes how phosphine sensors with varying conductivity based on TCNQ-based conductive LB films have been developed and reports the study of electric performance of these sensors. He describes and compares mechanisms of interaction of phosphine with conductive LB films for films based on TCNQ and those based on tetrathiafulvalene [fr

  5. Effect of molecular structure on fragmentation of isolated organic molecules in solid rare gas matrices

    International Nuclear Information System (INIS)

    Kobrazenko, A.V.; Sukhov, F.F.; Orlov, A.Yu.; Kovalev, G.V.; Baranova, I.A.; Feldman, V.I.

    2011-01-01

    Complete text of publication follows. Elucidation of high-energy reaction pathways in the condensed phase is an important issue for basic understanding of the radiation stability of complex organic molecules. As was shown previously, organic radical cations (RC) may undergo fragmentation or rearrangement in solid matrices due to excess energy. The probability of this process depends on both ionization potential (IP) of the molecule and molecular structure. In the present work we have studied the role of 'hot' ionic reaction channels for RC of some bifunctional compounds and alkynes. The effect of excess energy was simulated by matrix isolation method as described in detail earlier. The formation of fragmentation products was monitored by EPR and FTIR spectroscopy. In the present work it was shown that the RC of bifunctional compounds (CH 3 OCH 2 COCH 3 , CH 3 CO(CH 2 ) n COCH 3 , n 0/2) dissociated efficiently producing · CH 3 radicals upon irradiation in solid argon matrix at T ≤ 16 K. The probability of fragmentation decreases with decrease of excess energy by switching from Ar to Xe. It is worth noting that acetone RC does not show fragmentation under these conditions. Thus, bifunctional molecules were found to be less stable to 'hot' ionic fragmentation in low-temperature solids in comparison with simple prototype carbonyl compounds. In the case of alkynes of the R-C ≡ CH type, a noticeable yield of fragmentation products was observed when R = -C(CH 3 ) 3 , but it was negligible for R = -CH 3 . It means that the presence of triple bond stabilizes the molecular skeleton of linear alkynes toward 'hot' fragmentation, similarly as it was shown for alkenes. The mechanisms of 'hot' reactions and excess energy relaxation are discussed. This work was supported by the Russian Foundation for Basic Research (project 09-03-00848a).

  6. Influence of Particle Size Distribution on the Morphology and Cavitation Resistance of High-Velocity Oxygen Fuel Coatings

    Science.gov (United States)

    Silveira, L. L.; Sucharski, G. B.; Pukasiewicz, A. G. M.; Paredes, R. S. C.

    2018-02-01

    The cavitation wear process is one of the major wear mechanisms in turbines and rotors of hydroelectric power plants in Brazil. An effective way to increase the cavitation resistance is the use of coatings, applied by thermal spraying. The high-velocity oxy-fuel process (HVOF) is one of the most used thermal spraying processes, and it is widely adopted for applying coatings for protection against wear and in maintenance components. A FeCrMnSiB experimental alloy was deposited onto SAE 1020 substrate by HVOF process, in order to evaluate the influence of the powder particle size range on the morphology and cavitation resistance of the coatings. The morphology of the coatings showed an increase in oxide content with powder size reduction. The increase in the powder particle size reduced the wettability of the particles, observed by the increase in the quantity of non-melted particles. Higher particle size distribution led to an increase in erosion rate, due to higher presence of non-melted particles in the coatings and consequently reduction of splats adhesion. The cavitation damage was perceived mainly by the mechanism of lamellae detachment; however, part of the damage was also absorbed by strain hardening due to the γ-ɛ martensitic transformation.

  7. Influence of Particle Size Distribution on the Morphology and Cavitation Resistance of High-Velocity Oxygen Fuel Coatings

    Science.gov (United States)

    Silveira, L. L.; Sucharski, G. B.; Pukasiewicz, A. G. M.; Paredes, R. S. C.

    2018-04-01

    The cavitation wear process is one of the major wear mechanisms in turbines and rotors of hydroelectric power plants in Brazil. An effective way to increase the cavitation resistance is the use of coatings, applied by thermal spraying. The high-velocity oxy-fuel process (HVOF) is one of the most used thermal spraying processes, and it is widely adopted for applying coatings for protection against wear and in maintenance components. A FeCrMnSiB experimental alloy was deposited onto SAE 1020 substrate by HVOF process, in order to evaluate the influence of the powder particle size range on the morphology and cavitation resistance of the coatings. The morphology of the coatings showed an increase in oxide content with powder size reduction. The increase in the powder particle size reduced the wettability of the particles, observed by the increase in the quantity of non-melted particles. Higher particle size distribution led to an increase in erosion rate, due to higher presence of non-melted particles in the coatings and consequently reduction of splats adhesion. The cavitation damage was perceived mainly by the mechanism of lamellae detachment; however, part of the damage was also absorbed by strain hardening due to the γ- ɛ martensitic transformation.

  8. Application of High-Velocity Oxygen-Fuel (HVOF Spraying to the Fabrication of Yb-Silicate Environmental Barrier Coatings

    Directory of Open Access Journals (Sweden)

    Emine Bakan

    2017-04-01

    Full Text Available From the literature, it is known that due to their glass formation tendency, it is not possible to deposit fully-crystalline silicate coatings when the conventional atmospheric plasma spraying (APS process is employed. In APS, rapid quenching of the sprayed material on the substrate facilitates the amorphous deposit formation, which shrinks when exposed to heat and forms pores and/or cracks. This paper explores the feasibility of using a high-velocity oxygen-fuel (HVOF process for the cost-effective fabrication of dense, stoichiometric, and crystalline Yb2Si2O7 environmental barrier coatings. We report our findings on the HVOF process optimization and its resultant influence on the microstructure development and crystallinity of the Yb2Si2O7 coatings. The results reveal that partially crystalline, dense, and vertical crack-free EBCs can be produced by the HVOF technique. However, the furnace thermal cycling results revealed that the bonding of the Yb2Si2O7 layer to the Silicon bond coat needs to be improved.

  9. Burst Speed of Wild Fishes under High-Velocity Flow Conditions Using Stamina Tunnel with Natural Guidance System in River

    Science.gov (United States)

    Izumi, Mattashi; Yamamoto, Yasuyuki; Yataya, Kenichi; Kamiyama, Kohhei

    Swimming experiments were conducted on wild fishes in a natural guidance system stamina tunnel (cylindrical pipe) installed in a fishway of a local river under high-velocity flow conditions (tunnel flow velocity : 211 to 279 cm·s-1). In this study, the swimming characteristics of fishes were observed. The results show that (1) the swimming speeds of Tribolodon hakonensis (Japanese dace), Phoxinus lagowshi steindachneri (Japanese fat-minnow), Plecoglossus altivelis (Ayu), and Zacco platypus (Pale chub) were in proportion to their body length under identical water flow velocity conditions; (2) the maximum burst speed of Japanese dace and Japanese fat-minnow (measuring 4 to 6 cm in length) was 262 to 319 cm·s-1 under high flow velocity conditions (225 to 230 cm·s-1), while the maximum burst speed of Ayu and Pale chub (measuring 5 cm to 12 cm in length) was 308 to 355 cm·s-1 under high flow velocity conditions (264 to 273 cm·s-1) ; (3) the 50cm-maximum swimming speed of swimming fishes was 1.07 times faster than the pipe-swimming speed; (4) the faster the flow velocity, the shorter the swimming distance became.

  10. Structure and performance of anisotropic nanocrystalline Nd-Fe-B magnets fabricated by high-velocity compaction followed by deformation

    Science.gov (United States)

    Zhao, L. Z.; Deng, X. X.; Yu, H. Y.; Guan, H. J.; Li, X. Q.; Xiao, Z. Y.; Liu, Z. W.; Greneche, J. M.

    2017-12-01

    High-velocity compaction (HVC) has been proposed as an effective approach for the fabrication of nanocrystalline Nd-Fe-B magnets. In this work, the effect of powder size on the density of HVCed magnets has been studied and the anisotropic nanocrystalline Nd-Fe-B magnets were prepared by HVC followed by hot deformation (HD). It is found that a proper particle size range is beneficial to high density. The investigations on the microstructure, magnetic domain structure, and hyperfine structure, indicate that the deformed grain structure and the magnetic domain structure with uniform paramagnetic grain boundary phase give good magnetic properties of HVC + HDed magnets. These magnets also have good mechanical and anti-corrosion properties. The results indicate that HVC is not only a near-net-shape, room temperature and binder-free process but is also able to maintain uniform nanostructure and to achieve good magnetic properties in both isotropic and anisotropic magnets. As a result, HVC can be employed as an ideal alternative process for bonding or hot pressing for the conventional MQI, MQII and MQIII magnets.

  11. AN EXTREME HIGH-VELOCITY BIPOLAR OUTFLOW IN THE PRE-PLANETARY NEBULA IRAS 08005-2356

    Energy Technology Data Exchange (ETDEWEB)

    Sahai, R. [Jet Propulsion Laboratory, California Institute of Technology, MS 183-900, Pasadena, CA 91109 (United States); Patel, N. A., E-mail: raghvendra.sahai@jpl.nasa.gov [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)

    2015-09-01

    We report interferometric mapping of the bipolar pre-planetary nebula IRAS 08005-2356 (I 08005) with an angular resolution of ∼1″–5″, using the Submillimeter Array, in the {sup 12}CO J = 2–1, 3–2, {sup 13}CO J = 2–1, and SiO J = 5–4 (v = 0) lines. Single-dish observations, using the SMT 10 m, were made in these lines as well as in the CO J = 4–3 and SiO J = 6–5 (v = 0) lines. The line profiles are very broad, showing the presence of a massive (>0.1 M{sub ⊙}), extreme high velocity outflow (V ∼ 200 km s{sup −1}) directed along the nebular symmetry axis derived from the Hubble Space Telescope imaging of this object. The outflow's scalar momentum far exceeds that available from radiation pressure of the central post-AGB star, and it may be launched from an accretion disk around a main-sequence companion. We provide indirect evidence for such a disk from its previously published, broad Hα emission profile, which we propose results from Lyβ emission generated in the disk followed by Raman-scattering in the innermost regions of a fast, neutral wind.

  12. Seismic site-response characterization of high-velocity sites using advanced geophysical techniques: application to the NAGRA-Net

    Science.gov (United States)

    Poggi, V.; Burjanek, J.; Michel, C.; Fäh, D.

    2017-08-01

    The Swiss Seismological Service (SED) has recently finalised the installation of ten new seismological broadband stations in northern Switzerland. The project was led in cooperation with the National Cooperative for the Disposal of Radioactive Waste (Nagra) and Swissnuclear to monitor micro seismicity at potential locations of nuclear-waste repositories. To further improve the quality and usability of the seismic recordings, an extensive characterization of the sites surrounding the installation area was performed following a standardised investigation protocol. State-of-the-art geophysical techniques have been used, including advanced active and passive seismic methods. The results of all analyses converged to the definition of a set of best-representative 1-D velocity profiles for each site, which are the input for the computation of engineering soil proxies (traveltime averaged velocity and quarter-wavelength parameters) and numerical amplification models. Computed site response is then validated through comparison with empirical site amplification, which is currently available for any station connected to the Swiss seismic networks. With the goal of a high-sensitivity network, most of the NAGRA stations have been installed on stiff-soil sites of rather high seismic velocity. Seismic characterization of such sites has always been considered challenging, due to lack of relevant velocity contrast and the large wavelengths required to investigate the frequency range of engineering interest. We describe how ambient vibration techniques can successfully be applied in these particular conditions, providing practical recommendations for best practice in seismic site characterization of high-velocity sites.

  13. Isotropic and anisotropic nanocrystalline NdFeB bulk magnets prepared by binder-free high-velocity compaction technique

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Xiangxing [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Liu, Zhongwu, E-mail: zwliu@scut.edu.cn [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Yu, Hongya [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Xiao, Zhiyu [School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640 (China); Zhang, Guoqing [Science and Technology on Advanced High Temperature Structural Materials Laboratory, Beijing Institute of Aeronautical Materials, Beijing 100095 (China)

    2015-09-15

    NdFeB powders were consolidated into nanocrystalline bulk magnets by a near-net-shape process of high-velocity compaction (HVC) at room temperature with no binder employed. The nanostructure can be maintained after compaction. The compacted magnets with relatively high density can inherit the coercivity of the starting powders. The mechanical strength of the HVCed magnet after heat treatment is comparable to that of the conventional bonded NdFeB magnets. The anisotropic magnet has also been prepared by hot deformation using HVCed magnet as the precursor. The remanence value along the pressing direction increased from 0.64 to 0.95 T and maximum energy product (BH){sub max} increased from 65 to 120 kJ/m{sup 3} after hot deformation. The processing–structure–properties relationships for both isotropic and anisotropic magnets are discussed. - Highlights: • HVC is a feasible binder-free approach for preparing NdFeB magnets. • The compacted magnets can inherit the coercivity of the starting powders. • The magnets post heat treatment have compression strength higher than bonded magnets. • The approach of HVC is a potential pre-process for anisotropic NdFeB bulk magnets.

  14. Isotropic and anisotropic nanocrystalline NdFeB bulk magnets prepared by binder-free high-velocity compaction technique

    International Nuclear Information System (INIS)

    Deng, Xiangxing; Liu, Zhongwu; Yu, Hongya; Xiao, Zhiyu; Zhang, Guoqing

    2015-01-01

    NdFeB powders were consolidated into nanocrystalline bulk magnets by a near-net-shape process of high-velocity compaction (HVC) at room temperature with no binder employed. The nanostructure can be maintained after compaction. The compacted magnets with relatively high density can inherit the coercivity of the starting powders. The mechanical strength of the HVCed magnet after heat treatment is comparable to that of the conventional bonded NdFeB magnets. The anisotropic magnet has also been prepared by hot deformation using HVCed magnet as the precursor. The remanence value along the pressing direction increased from 0.64 to 0.95 T and maximum energy product (BH) max increased from 65 to 120 kJ/m 3 after hot deformation. The processing–structure–properties relationships for both isotropic and anisotropic magnets are discussed. - Highlights: • HVC is a feasible binder-free approach for preparing NdFeB magnets. • The compacted magnets can inherit the coercivity of the starting powders. • The magnets post heat treatment have compression strength higher than bonded magnets. • The approach of HVC is a potential pre-process for anisotropic NdFeB bulk magnets

  15. High-velocity DC-VPS for diffusion and protecting barrier layers in solid oxide fuel cells (SOFCs)

    Science.gov (United States)

    Henne, R. H.; Franco, T.; Ruckdäschel, R.

    2006-12-01

    High-temperature fuel cells of the solid oxide fuel cell (SOFC) type as direct converter of chemical into electrical energy show a high potential for reducing considerably the specific energy consumption in different application fields. Of particular interest are advanced lightweight planar cells for electricity supply units in cars and other mobile systems. Such cells, in one new design, consist mainly of metallic parts, for example, of ferrite steels. These cells shall operate in the temperature range of 700 to 800 °C where oxidation and diffusion processes can be of detrimental effect on cell performance for long-term operation. Problems arise in particular by diffusion of chromium species from the interconnect or the cell containment into the electrolyte/cathode interface forming insulating phases and by the mutual diffusion of substrate and anode material, for example, iron and chromium from the ferrite into the anode and nickel from the anode into the ferrite, which in both cases reduces performance and system lifetime. Additional intermediate layers of perovskite-type material, (e.g., doped LaCrO3) applied with high-velocity direct-current vacuum plasma spraying (DC-VPS) can reduce such effects considerably if they are stable and of high electronic conductivity.

  16. Teaching and Assessment of High-Velocity, Low-Amplitude Techniques for the Spine in Predoctoral Medical Education.

    Science.gov (United States)

    Channell, Millicent King

    2016-09-01

    Although national didactic criteria have been set for predoctoral education and assessment in osteopathic manipulative treatment, there is no criterion standard for teaching methods and assessments of osteopathic manipulative treatment competence in colleges of osteopathic medicine. This issue is more pressing with the creation of the single graduate medical education accreditation system by the American Osteopathic Association and Accreditation Council for Graduate Medical Education, which introduced the creation of "osteopathic recognition" for residencies that want to incorporate osteopathic principles and practice into their programs. Residencies with osteopathic recognition may include both osteopathic and allopathic graduates. Increased standardization at the predoctoral level, however, is recommended as osteopathic principles and practice training applications are expanded. The objectives of this article are to review the standards for teaching osteopathic medical students high-velocity, low-amplitude (HVLA) techniques for the spine; to review and discuss the methods used to assess medical students' proficiency in using HVLA; and to propose baseline standards for teaching and assessing HVLA techniques among medical students.

  17. THE APACHE POINT OBSERVATORY GALACTIC EVOLUTION EXPERIMENT: FIRST DETECTION OF HIGH-VELOCITY MILKY WAY BAR STARS

    Energy Technology Data Exchange (ETDEWEB)

    Nidever, David L.; Zasowski, Gail; Majewski, Steven R.; Beaton, Rachael L.; Wilson, John C.; Skrutskie, Michael F.; O' Connell, Robert W. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States); Bird, Jonathan; Schoenrich, Ralph; Johnson, Jennifer A.; Sellgren, Kris [Department of Astronomy and the Center for Cosmology and Astro-Particle Physics, The Ohio State University, Columbus, OH 43210 (United States); Robin, Annie C.; Schultheis, Mathias [Institut Utinam, CNRS UMR 6213, OSU THETA, Universite de Franche-Comte, 41bis avenue de l' Observatoire, F-25000 Besancon (France); Martinez-Valpuesta, Inma; Gerhard, Ortwin [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Shetrone, Matthew [McDonald Observatory, University of Texas at Austin, Fort Davis, TX 79734 (United States); Schiavon, Ricardo P. [Gemini Observatory, 670 North A' Ohoku Place, Hilo, HI 96720 (United States); Weiner, Benjamin [Steward Observatory, 933 North Cherry Street, University of Arizona, Tucson, AZ 85721 (United States); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Allende Prieto, Carlos, E-mail: dln5q@virginia.edu [Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife (Spain); and others

    2012-08-20

    Commissioning observations with the Apache Point Observatory Galactic Evolution Experiment (APOGEE), part of the Sloan Digital Sky Survey III, have produced radial velocities (RVs) for {approx}4700 K/M-giant stars in the Milky Way (MW) bulge. These high-resolution (R {approx} 22, 500), high-S/N (>100 per resolution element), near-infrared (NIR; 1.51-1.70 {mu}m) spectra provide accurate RVs ({epsilon}{sub V} {approx} 0.2 km s{sup -1}) for the sample of stars in 18 Galactic bulge fields spanning -1 Degree-Sign -32 Degree-Sign . This represents the largest NIR high-resolution spectroscopic sample of giant stars ever assembled in this region of the Galaxy. A cold ({sigma}{sub V} {approx} 30 km s{sup -1}), high-velocity peak (V{sub GSR} Almost-Equal-To +200 km s{sup -1}) is found to comprise a significant fraction ({approx}10%) of stars in many of these fields. These high RVs have not been detected in previous MW surveys and are not expected for a simple, circularly rotating disk. Preliminary distance estimates rule out an origin from the background Sagittarius tidal stream or a new stream in the MW disk. Comparison to various Galactic models suggests that these high RVs are best explained by stars in orbits of the Galactic bar potential, although some observational features remain unexplained.

  18. Building America Case Study: Standard- Versus High-Velocity Air Distribution in High-Performance Townhomes, Denver, Colorado

    Energy Technology Data Exchange (ETDEWEB)

    2017-06-09

    IBACOS investigated the performance of a small-diameter high velocity heat pump system compared to a conventional system in a new construction triplex townhouse. A ductless heat pump system also was installed for comparison, but the homebuyer backed out because of aesthetic concerns about that system. In total, two buildings, having identical solar orientation and comprised of six townhomes, were monitored for comfort and energy performance. Results show that the small-diameter system provides more uniform temperatures from floor to floor in the three-story townhome. No clear energy consumption benefit was observed from either system. The builder is continuing to explore the small-diameter system as its new standard system to provide better comfort and indoor air quality. The homebuilder also explored the possibility of shifting its townhome product to meet the U.S. Department of Energy Challenge Home National Program Requirements. Ultimately, the builder decided that adoption of these practices would be too disruptive midstream in the construction cycle. However, the townhomes met the ENERGY STAR Version 3.0 program requirements.

  19. A modified compressible smoothed particle hydrodynamics method and its application on the numerical simulation of low and high velocity impacts

    International Nuclear Information System (INIS)

    Amanifard, N.; Haghighat Namini, V.

    2012-01-01

    In this study a Modified Compressible Smoothed Particle Hydrodynamics method is introduced which is applicable in problems involving shock wave structures and elastic-plastic deformations of solids. As a matter of fact, algorithm of the method is based on an approach which descritizes the momentum equation into three parts and solves each part separately and calculates their effects on the velocity field and displacement of particles. The most exclusive feature of the method is exactly removing artificial viscosity of the formulations and representing good compatibility with other reasonable numerical methods without any rigorous numerical fractures or tensile instabilities while Modified Compressible Smoothed Particle Hydrodynamics does not use any extra modifications. Two types of problems involving elastic-plastic deformations and shock waves are presented here to demonstrate the capability of Modified Compressible Smoothed Particle Hydrodynamics in simulation of such problems and its ability to capture shock. The problems that are proposed here are low and high velocity impacts between aluminum projectiles and semi infinite aluminum beams. Elastic-perfectly plastic model is chosen for constitutive model of the aluminum and the results of simulations are compared with other reasonable studies in these cases.

  20. The effect of reported high-velocity small raindrops on inferred drop size distributions and derived power laws

    Directory of Open Access Journals (Sweden)

    H. Leijnse

    2010-07-01

    Full Text Available It has recently been shown that at high rainfall intensities, small raindrops may fall with much larger velocities than would be expected from their diameters. These were argued to be fragments of recently broken-up larger drops. In this paper we quantify the effect of this phenomenon on raindrop size distribution measurements from a Joss-Waldvogel disdrometer, a 2-D Video Distrometer, and a vertically-pointing Doppler radar. Probability distributions of fall velocities have been parameterized, where the parameters are functions of both rainfall intensity and drop size. These parameterizations have been used to correct Joss-Waldvogel disdrometer measurements for this phenomenon. The effect of these corrections on fitted scaled drop size distributions are apparent but not major. Fitted gamma distributions for three different types of rainfall have been used to simulate drop size measurements. The effect of the high-velocity small drops is shown to be minor. Especially for the purpose of remote sensing of rainfall using radar, microwave links, or optical links, the errors caused by using the slightly different retrieval relations will be masked completely by other error sources.

  1. Looking for Galaxies in All the Right Places: A Search for Stellar Populations in ALFALFA’s Ultra-compact High Velocity Clouds

    Science.gov (United States)

    Janesh, William; Rhode, Katherine L.; Salzer, John J.; Janowiecki, Steven; Adams, Elizabeth; Haynes, Martha P.; Giovanelli, Riccardo; Cannon, John M.

    2018-01-01

    Nearby gas-rich dwarf galaxies are excellent laboratories for investigating the baryonic feedback processes that govern star formation and galaxy evolution in galaxies at the extreme end of the mass function. Detecting and studying such objects may help resolve the well-known tension between cosmological model predictions for low-mass dark matter halos and observations. The ALFALFA neutral hydrogen (Hi) survey has detected a sample of isolated ultra-compact high-velocity Hi clouds (UCHVCs) with kinematic properties that make them likely members of the Local Volume, but that have no optical counterparts in existing optical surveys. This UCHVC sample possesses Hi properties (at 1 Mpc, Hi masses of ~105-106 M⊙, Hi diameters of ~2-3 kpc, and dynamical masses of ~107-108 M⊙) similar to other known ultra-faint dwarf galaxies like Leo T. Following the discovery of Leo P, an extremely metal-poor, gas-rich star-forming dwarf galaxy associated with an ALFALFA UCHVC, we have initiated a campaign to obtain deep optical imaging of 56 UCHVCs using the wide field-of-view, high-resolution ODI camera on the WIYN 3.5-m telescope. Here we present a brief overview of our campaign to search for resolved stellar populations associated with the UCHVCs in our optical images, and initial results from our survey.After creating a stellar catalog from the pipeline-reduced and stacked ODI g- and i-band images, we apply a color-magnitude filter tuned for old, metal-poor stellar populations to select red giant branch stars at distances between 250 kpc and 2 Mpc. The spatial distribution of the stars selected by the filter is then smoothed, and overdensities in the fields are identified. Of the 22 targets analyzed to date, seven have associated stellar populations detected at a high confidence (92% to 99.9% significance). The detected objects have a range of distances (from 350 kpc to 1.6 Mpc) and have optical properties similar to those of ultra-faint dwarf galaxies. These objects have

  2. TRACING MOLECULAR GAS MASS IN EXTREME EXTRAGALACTIC ENVIRONMENTS: AN OBSERVATIONAL STUDY

    International Nuclear Information System (INIS)

    Zhu Ming; Papadopoulos, Padeli P.; Xilouris, Emmanuel M.; Kuno, Nario; Lisenfeld, Ute

    2009-01-01

    We present a new observational study of the 12 CO(1-0) line emission as an H 2 gas mass tracer under extreme conditions in extragalactic environments. Our approach is to study the full neutral interstellar medium (H 2 , H I, and dust) of two galaxies whose bulk interstellar medium (ISM) resides in environments that mark (and bracket) the excitation extremes of the ISM conditions found in infrared luminous galaxies, the starburst NGC 3310, and the quiescent spiral NGC 157. Our study maintains a robust statistical notion of the so-called X = N(H 2 )/I CO factor (i.e., a large ensemble of clouds is involved) while exploring its dependence on the very different average ISM conditions prevailing within these two systems. These are constrained by fully sampled 12 CO(3-2) and 12 CO(1-0) observations, at a matched beam resolution of half-power beam width ∼15'', obtained with the James Clerk Maxwell Telescope (JCMT) on Mauna Kea (Hawaii) and the 45 m telescope of the Nobeyama Radio Observatory in Japan, combined with sensitive 850 μm and 450 μm dust emission and H I interferometric images which allow a complete view of all the neutral ISM components. Complementary 12 CO(2-1) observations were obtained with the JCMT toward the center of the two galaxies. We found an X factor varying by a factor of 5 within the spiral galaxy NGC 157 and about two times lower than the Galactic value in NGC 3310. In addition, the dust emission spectrum in NGC 3310 shows a pronounced submillimeter 'excess'. We tried to fit this excess by a cold dust component but very low temperatures were required (T C ∼ 5-11 K) with a correspondingly low gas-to-dust mass ratio of ∼5-43. We furthermore show that it is not possible to maintain the large quantities of dust required at these low temperatures in this starburst galaxy. Instead, we conclude that the dust properties need to be different from Galactic dust in order to fit the submillimeter 'excess'. We show that the dust spectral energy

  3. CHEMICALLY DISTINCT NUCLEI AND OUTFLOWING SHOCKED MOLECULAR GAS IN Arp 220

    Energy Technology Data Exchange (ETDEWEB)

    Tunnard, R.; Greve, T. R. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Garcia-Burillo, S.; Fuente, A.; Usero, A.; Planesas, P. [Observatorio Astronómico Nacional, Observatorio de Madrid, Alfonso XII, 3, E-28014 Madrid (Spain); Carpio, J. Graciá; Hailey-Dunsheath, S.; Sturm, E. [Max-Planck-Institute for Extraterrestrial Physics (MPE), Giessenbachstraße 1, D-85748 Garching (Germany); Fischer, J. [Naval Research Laboratory, Remote Sensing Division, 4555 Overlook Ave SW, Washington, DC 20375 (United States); González-Alfonso, E.; Neri, R., E-mail: richard.tunnard.13@ucl.ac.uk [Universidad de Alcalá de Henares, Departamento de Física y Matemáticas, Campus Universitario, E-28871 Alcalá de Henares, Madrid (Spain)

    2015-02-10

    We present the results of interferometric spectral line observations of Arp 220 at 3.5 mm and 1.2 mm from the Plateau de Bure Interferometer, imaging the two nuclear disks in H{sup 13}CN(1-0) and (3-2), H{sup 13}CO{sup +}(1-0) and (3-2), and HN{sup 13}C(3-2) as well as SiO(2-1) and (6-5), HC{sup 15}N(3-2), and SO(6{sub 6}-5{sub 5}). The gas traced by SiO(6-5) has a complex and extended kinematic signature including a prominent P Cygni profile, almost identical to previous observations of HCO{sup +}(3-2). Spatial offsets 0.''1 north and south of the continuum center in the emission and absorption of the SiO(6-5) P Cygni profile in the western nucleus (WN) imply a bipolar outflow, delineating the northern and southern edges of its disk and suggesting a disk radius of ∼40 pc, consistent with that found by ALMA observations of Arp 220. We address the blending of SiO(6-5) and H{sup 13}CO{sup +}(3-2) by considering two limiting cases with regards to the H{sup 13}CO{sup +} emission throughout our analysis. Large velocity gradient modeling is used to constrain the physical conditions of the gas and to infer abundance ratios in the two nuclei. Our most conservative lower limit on the [H{sup 13}CN]/[H{sup 13}CO{sup +}] abundance ratio is 11 in the WN, compared with 0.10 in the eastern nucleus (EN). Comparing these ratios to the literature we argue on chemical grounds for an energetically significant active galactic nucleus in the WN driving either X-ray or shock chemistry, and a dominant starburst in the EN.

  4. Early stage oxynitridation process of Si(001) surface by NO gas: Reactive molecular dynamics simulation study

    International Nuclear Information System (INIS)

    Cao, Haining; Kim, Seungchul; Lee, Kwang-Ryeol; Srivastava, Pooja; Choi, Keunsu

    2016-01-01

    Initial stage of oxynitridation process of Si substrate is of crucial importance in fabricating the ultrathin gate dielectric layer of high quality in advanced MOSFET devices. The oxynitridation reaction on a relaxed Si(001) surface is investigated via reactive molecular dynamics (MD) simulation. A total of 1120 events of a single nitric oxide (NO) molecule reaction at temperatures ranging from 300 to 1000 K are statistically analyzed. The observed reaction kinetics are consistent with the previous experimental or calculation results, which show the viability of the reactive MD technique to study the NO dissociation reaction on Si. We suggest the reaction pathway for NO dissociation that is characterized by the inter-dimer bridge of a NO molecule as the intermediate state prior to NO dissociation. Although the energy of the inter-dimer bridge is higher than that of the intra-dimer one, our suggestion is supported by the ab initio nudged elastic band calculations showing that the energy barrier for the inter-dimer bridge formation is much lower. The growth mechanism of an ultrathin Si oxynitride layer is also investigated via consecutive NO reactions simulation. The simulation reveals the mechanism of self-limiting reaction at low temperature and the time evolution of the depth profile of N and O atoms depending on the process temperature, which would guide to optimize the oxynitridation process condition.

  5. Early stage oxynitridation process of Si(001) surface by NO gas: Reactive molecular dynamics simulation study

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Haining; Kim, Seungchul; Lee, Kwang-Ryeol, E-mail: krlee@kist.re.kr [Computational Science Research Center, Korea Institute of Science and Technology, 5, Hwarangno 14-gil, Seongbuk-gu, Seoul 02792 (Korea, Republic of); Department of Nanomaterial Science and Technology, Korea University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113 (Korea, Republic of); Srivastava, Pooja; Choi, Keunsu [Computational Science Research Center, Korea Institute of Science and Technology, 5, Hwarangno 14-gil, Seongbuk-gu, Seoul 02792 (Korea, Republic of)

    2016-03-28

    Initial stage of oxynitridation process of Si substrate is of crucial importance in fabricating the ultrathin gate dielectric layer of high quality in advanced MOSFET devices. The oxynitridation reaction on a relaxed Si(001) surface is investigated via reactive molecular dynamics (MD) simulation. A total of 1120 events of a single nitric oxide (NO) molecule reaction at temperatures ranging from 300 to 1000 K are statistically analyzed. The observed reaction kinetics are consistent with the previous experimental or calculation results, which show the viability of the reactive MD technique to study the NO dissociation reaction on Si. We suggest the reaction pathway for NO dissociation that is characterized by the inter-dimer bridge of a NO molecule as the intermediate state prior to NO dissociation. Although the energy of the inter-dimer bridge is higher than that of the intra-dimer one, our suggestion is supported by the ab initio nudged elastic band calculations showing that the energy barrier for the inter-dimer bridge formation is much lower. The growth mechanism of an ultrathin Si oxynitride layer is also investigated via consecutive NO reactions simulation. The simulation reveals the mechanism of self-limiting reaction at low temperature and the time evolution of the depth profile of N and O atoms depending on the process temperature, which would guide to optimize the oxynitridation process condition.

  6. Electrospun Nanofibers from a Tricyanofuran-Based Molecular Switch for Colorimetric Recognition of Ammonia Gas.

    Science.gov (United States)

    Khattab, Tawfik A; Abdelmoez, Sherif; Klapötke, Thomas M

    2016-03-14

    A chromophore based on tricyanofuran (TCF) with a hydrazone (H) recognition moiety was developed. Its molecular-switching performance is reversible and has differential sensitivity towards aqueous ammonia at comparable concentrations. Nanofibers were fabricated from the TCF-H chromophore by electrospinning. The film fabricated from these nanofibers functions as a solid-state optical chemosensor for probing ammonia vapor. Recognition of ammonia vapor occurs by proton transfer from the hydrazone fragment of the chromophore to the ammonia nitrogen atom and is facilitated by the strongly electron withdrawing TCF fragment. The TCF-H chromophore was added to a solution of poly(acrylic acid), which was electrospun to obtain a nanofibrous sensor device. The morphology of the nanofibrous sensor was determined by SEM, which showed that nanofibers with a diameter range of 200-450 nm formed a nonwoven mat. The resultant nanofibrous sensor showed very good sensitivity in ammonia-vapor detection. Furthermore, very good reversibility and short response time were also observed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Gas Phase Chemistry and Molecular Complexity: How Far Do They Go?

    Science.gov (United States)

    Balucani, Nadia

    2016-07-01

    The accumulation of organic molecules of increasing complexity is believed to be an important step toward the emergence of life. But how massive organic synthesis could occur in primitive Earth, i.e. a water-dominated environment, is a matter of debate. Two alternative theories have been suggested so far: endogenous and exogenous synthesis. In the first theory, the synthesis of simple organic molecules having a strong prebiotic potential (simple prebiotic molecules SPMs, such as H2CO, HCN, HC3N, NH2CHO) occurred directly on our planet starting from simple parent molecules of the atmosphere, liquid water and various energy sources. Miller's experiment was a milestone in this theory, but it was later recognized that the complexity of a planet cannot be reproduced in a single laboratory experiment. Some SPMs have been identified in the N2-dominated atmosphere of Titan (a massive moon of Saturn), which is believed to be reminiscent of the primitive terrestrial atmosphere. As such, the atmosphere of Titan represents a planetary scale laboratory for the comprehension of SPM formation in an environment close enough to primitive Earth and is the current frontier in the endogenous theory exploration. In the exogenous theory, SPMs came from space, the carriers being comets, asteroids and meteorites. The rationale behind this suggestion is that plenty of SPMs have been observed in interstellar clouds (ISCs), including star-forming regions, and in small bodies like comets, asteroids and meteorites. Therefore, the basic idea is that SPMs were formed in the solar nebula, preserved during the early phases of the Solar System formation in the body of comets/asteroids/meteorites and finally delivered to Earth by cometary and meteoritic falls. In this contribution, the status of our knowledge on how SPMs can be formed in the gas phase, either in the primitive terrestrial atmosphere or in the cold nebula from which the Solar System originated, will be presented. Particular attention

  8. Hydrogen separation from high temperature CO-containing syn-gas flow using molecular ceramic membranes

    Energy Technology Data Exchange (ETDEWEB)

    Soudarev, A.; Konakov, G.; Souryaninov, A.; Molchanov, A. [Boyko Research Engineering Ceramic Heat Engines Center Ltd., St. Petersburg (Russian Federation); Lelait, L.; Stevens, P.H. [European Inst. for Power Studies, Karlsruhe (Germany)

    2006-07-01

    Poisoning of the platinum (Pt) metals used as catalysts for proton exchange membrane fuel cells (PEMFCs) can negatively impact on PEMFC operation efficiency. In order to address this issue, a supply of hydrogen with a carbon monoxide (CO) admixtures is required. This paper provided details of a new type of molecular ceramic membrane (MCM) that allows the separation of hydrogen (H{sub 2}) from the hydrocarbon fuel reforming products that contain CO and has higher temperature and pressure capacity than other membranes. After various tests, alumo-magnesium spinel (AMS) was selected as the most promising porous material for the ceramic multi-layer membrane. The crystalline structure of the AMS showed good thermo-dynamic stability during tests that ranged between 20 and 1400 degrees C, as well as a chemical resistance relative to the effects of the aggressive fuel cell environment, and no exposure to the oxidation-recovery processes in the CO and H{sub 2} flow. The macroporous substrate of the AMS and the membrane selection layers have the same composition. The formation of the carrier was conducted by a semi-dry molding on a hydraulic press. Formation of the nano-porous structure in the carrier macro-pores by the polysilicon acid sol solution treatment allowed the synthesis of the amorphous silica and crystobalite crystals with a developed surface and nano-dimension subporosity. Test results have shown that the MCM has optimum penetrability and selectivity values as well as admissible thermo-mechanical properties. H{sub 2} flow through the membrane was 1.5-1.7 times greater than the CO flow. It was concluded that the AMS-based membrane devices will increase the efficiency of the PEMFC power plants and reduce their degradation capacity. 2 refs., 1 tab., 1 fig.

  9. Gas phase detection of explosives such as 2,4,6-trinitrotoluene by molecularly imprinted polymers.

    Science.gov (United States)

    Bunte, Gudrun; Hürttlen, Jürgen; Pontius, Heike; Hartlieb, Kerstin; Krause, Horst

    2007-05-15

    Fast, reliable and inexpensive analytical techniques for trace detection of explosive components are in high demand. Our approach is to develop specific sensor coating materials based on molecularly imprinted polymers (MIPs). Despite the known inhibition of radical polymerisations by nitro groups and the known shrinkage of the polymer lattice during/after drying we were able to synthesize particulate MIPs by suspension polymerisation as well as thin MIP coatings by direct surface polymerisation on quartz crystal microbalances (QCM). The best method to purify the porous beads was Soxhlet extraction followed by supercritical carbon dioxide extraction (SFE with sc-CO2) at mild conditions (150 bar, 50 degrees C). At least a removal of >99.7% of the template was achieved. Performance tests of TNT imprinted polymer beads showed that acrylamide (AA) and more pronounced also methacrylic acid (MAA) possessed an enhanced adsorption tendency for gaseous TNT. An adsorption of 2,4-DNT, dinitrotoluene, by these MIPs was not detected. Using 2,4-DNT as template and methacrylamide, MAAM, a positive imprint effect for gaseous 2,4-DNT was achieved with no measurable cross-sensitivity for 2,4,6-TNT. The thin MIP coatings directly synthesized on the QCMs showed thicknesses of 20 to up to 500 nm. Preliminary screening experiments were performed for five different monomers and three different solvents (acetonitrile, chloroform and dimethylformamide). Best adsorption properties for TNT vapour until now showed a PAA-MIP synthesized with chloroform. Direct measurements of the mass attachment, respectively frequency decrease of the coated QCMs during vapour treatment showed a TNT-uptake of about 150 pg per microg MIP per hour. Results look worthy for further studies.

  10. Friction and wear properties of high-velocity oxygen fuel sprayed WC-17Co coating under rotational fretting conditions

    Science.gov (United States)

    Luo, Jun; Cai, Zhenbing; Mo, Jiliang; Peng, Jinfang; Zhu, Minhao

    2016-05-01

    Rotational fretting which exist in many engineering applications has incurred enormous economic loss. Thus, accessible methods are urgently needed to alleviate or eliminate damage by rotational fretting. Surface engineering is an effective approach that is successfully adopted to enhance the ability of components to resist the fretting damage. In this paper, using a high-velocity oxygen fuel sprayed (HVOF) technique WC-17Co coating is deposited on an LZ50 steel surface to study its properties through Vickers hardness testing, scanning electric microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffractrometry (XRD). Rotational fretting wear tests are conducted under normal load varied from 10 N to 50 N, and angular displacement amplitudes vary from 0.125° to 1°. Wear scars are examined using SEM, EDX, optical microscopy (OM), and surface topography. The experimental results reveal that the WC-17Co coating adjusted the boundary between the partial slip regime (PSR) and the slip regime (SR) to the direction of smaller amplitude displacement. As a result, the coefficients of friction are consistently lower than the substrate's coefficients of friction both in the PSR and SR. The damage to the coating in the PSR is very slight. In the SR, the coating exhibits higher debris removal efficiency and load-carrying capacity. The bulge is not found for the coating due to the coating's higher hardness to restrain plastic flow. This research could provide experimental bases for promoting industrial application of WC-17Co coating in prevention of rotational fretting wear.

  11. Solvation theory to provide a molecular interpretation of the hydrophobic entropy loss of noble-gas hydration

    International Nuclear Information System (INIS)

    Irudayam, Sheeba Jem; Henchman, Richard H

    2010-01-01

    An equation for the chemical potential of a dilute aqueous solution of noble gases is derived in terms of energies, force and torque magnitudes, and solute and water coordination numbers, quantities which are all measured from an equilibrium molecular dynamics simulation. Also derived are equations for the Gibbs free energy, enthalpy and entropy of hydration for the Henry's law process, the Ostwald process, and a third proposed process going from an arbitrary concentration in the gas phase to the equivalent mole fraction in aqueous solution which has simpler expressions for the enthalpy and entropy changes. Good agreement with experimental hydration free energies is obtained in the TIP4P and SPC/E water models although the solute's force field appears to affect the enthalpies and entropies obtained. In contrast to other methods, the approach gives a complete breakdown of the entropy for every degree of freedom and makes possible a direct structural interpretation of the well-known entropy loss accompanying the hydrophobic hydration of small non-polar molecules under ambient conditions. The noble-gas solutes experience only a small reduction in their vibrational entropy, with larger solutes experiencing a greater loss. The vibrational and librational entropy components of water actually increase but only marginally, negating any idea of water confinement. The term that contributes the most to the hydrophobic entropy loss is found to be water's orientational term which quantifies the number of orientational minima per water molecule and how many ways the whole hydrogen-bond network can form. These findings help resolve contradictory deductions from experiments that water structure around non-polar solutes is similar to bulk water in some ways but different in others. That the entropy loss lies in water's rotational entropy contrasts with other claims that it largely lies in water's translational entropy, but this apparent discrepancy arises because of different

  12. Electron induced formation and stability of molecular and cluster ions in gas phase and superfluid helium nanodroplets

    International Nuclear Information System (INIS)

    Aleem, M. A.

    2010-01-01

    The present PhD thesis represents a broad range study of electron induced formation and stability of positive and negative ions in gas phase and superfluid helium nanodroplets. The molecules studied are of industrial, environmental, plasma and biological relevance. The knowledge obtained from the study provides new insight for the proper understanding and control on energetics and dynamics of the reactions involved in the formation and fragmentation processes of the studied molecules and clusters. The experiments are accomplished and investigated using mass spectrometric techniques for the formation of molecular and cluster ions using different mass spectrometers available in our laboratory. One part of the work is focused on electron-induced reactions of the molecules in gas phase. Especially focus is laid to electron attachment to the isomers of mononitrotolouene used as an additive to explosives. The fragile nature and high internal energy of these molecules has lead to extensive fragmentation following the ionisation process. Dissociative electron attachment to the three different isomers has shown different resonances and therefore this process can be utilized to explicitly distinguish these isomers. Anion efficiency curves of the isomers have been studied using effusive molecular beam source in combination with a hemispherical electron monochromator as well as a Nier-type ion source attached to a sector field mass spectrometer. The outcome of the experiment is a reliable and effective detection method highly desirable for environmental and security reasons. Secondly, dissociative electron ionization of acetylene and propene is studied and their data is directly related to the plasma modelling for plasma fusion and processing reactors. Temperature effects for dissociative electron attachment to halo-hydrocarbons are also measured using a trochoidal electron monochromator. The second part of the work is concerned with the investigation of electron

  13. Molecular characterization of primary humic-like substances in fine smoke particles by thermochemolysis-gas chromatography-mass spectrometry

    Science.gov (United States)

    Fan, Xingjun; Wei, Siye; Zhu, Mengbo; Song, Jianzhong; Peng, Ping'an

    2018-05-01

    In this study, the molecular structures of primary humic-like substances (HULIS) in fine smoke particles emitted from the combustion of biomass materials (including rice straw, corn straw, and pine branches) and coal, and atmospheric HULIS were determined by off-line tetramethylammonium hydroxide thermochemolysis coupled with gas chromatography and mass spectrometry (TMAH-GC/MS). A total of 89 pyrolysates were identified by the thermochemolysis of primary and atmospheric HULIS. The main groups were polysaccharide derivatives, N-containing compounds, lignin derivatives, aromatic acid methyl ester, aliphatic acid methyl ester, and diterpenoid derivatives. Both the type and distribution of pyrolysates among primary HULIS were comparable to those in atmospheric HULIS. This indicates that primary HULIS from combustion processes are important contributors to atmospheric HULIS. Some distinct differences were also observed. The aromatic compounds, including lignin derivatives and aromatic acid methyl ester, were the major pyrolysates (53.0%-84.9%) in all HULIS fractions, suggesting that primary HULIS significantly contributed aromatic structures to atmospheric HULIS. In addition, primary HULIS from biomass burning (BB) contained a relatively high abundance of lignin and polysaccharide derivatives, which is consistent with the large amounts of lignin and cellulose structures contained in biomass materials. Aliphatic acid methyl ester and benzyl methyl ether were prominent pyrolysates in atmospheric HULIS. Moreover, some molecular markers of specific sources were obtained from the thermochemolysis of primary and atmospheric HULIS. For example, polysaccharide derivatives, pyridine and pyrrole derivatives, and lignin derivatives can be used as tracers of fresh HULIS emitted from BB. Diterpenoid derivatives are important markers of HULIS from pine wood combustion sources. Finally, the differences in pyrolysate types and the distributions between primary and atmospheric HULIS

  14. ALMA REVEALS THE ANATOMY OF THE mm-SIZED DUST AND MOLECULAR GAS IN THE HD 97048 DISK

    Energy Technology Data Exchange (ETDEWEB)

    Walsh, Catherine; Maud, Luke T. [Leiden Observatory, Leiden University, P.O. Box 9531, 2300 RA Leiden (Netherlands); Juhász, Attila [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Meeus, Gwendolyn [Departamento de Física Teórica, Universidad Autonoma de Madrid, Campus Cantoblanco, E-28049 Madrid (Spain); Dent, William R. F. [Joint ALMA Observatory (JAO), Alonso de Córdova 3107, Vitacura, Santiago (Chile); Aikawa, Yuri [Center for Computer Sciences, University of Tsukuba, 305-8577 Tsukuba (Japan); Millar, Tom J. [School of Mathematics and Physics, Queen’s University Belfast, University Road, Belfast BT7 1NN (United Kingdom); Nomura, Hideko, E-mail: cwalsh@strw.leidenuniv.nl, E-mail: c.walsh1@leeds.ac.uk [Department of Earth and Planetary Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, 152-8551 Tokyo (Japan)

    2016-11-10

    Transitional disks show a lack of excess emission at infrared wavelengths due to a large dust cavity, that is often corroborated by spatially resolved observations at ∼ mm wavelengths. We present the first spatially resolved ∼ mm-wavelength images of the disk around the Herbig Ae/Be