Near-Infrared [Fe II] and H2 Study of the Galactic Supernova Remnants

NASA Astrophysics Data System (ADS)

Lee, Yong-Hyun; Koo, Bon-Chul; Lee, Jae-Joon; Jaffe, Daniel T.; Burton, Michael G.; Ryder, Stuart D.

2018-01-01

We have searched for near-infrared (NIR) [Fe II] (1.644 μm) and H2 1-0 S(1) (2.122 μm) emission features associated with Galactic supernova remnants (SNRs) using the narrow-band imaging surveys UWIFE / UWISH2 (UKIRT Widefield Infrared Survey for [Fe II] / H2). Both surveys cover about 180 square degrees of the first Galactic quadrant (7° < l < 65° -1.3° < b < +1.3°), and a total of 79 SNRs are falling in the survey area. We have found 19 [Fe II]- and 19 H2-emitting SNRs, giving a detection rate of 24%. Eleven SNRs show both emission features. Some of the SNRs show bright, complex, and interesting structures that have never been reported in previous studies. The brightest SNR in the both emission is W49B, contributing ~70% of the total [Fe II] luminosity of the detected SNRs. The total [Fe II] luminosity, however, is considerably less than what we would expect from the SN rate of our Galaxy.Among the SNRs showing both [Fe II] and H2 emission lines, some SNRs show the “[Fe II]-H2 reversal” phenomenon, i.e., the H2 emission features are detected outside the [Fe II] emission boundary. We carried out high resolution (R~40,000) NIR H- and K-band spectroscopy of the five SNRs showing the [Fe II]-H2 reversal (G11.2-0.3, KES 73, W44, 3C 396, W49B) using IGRINS (Immersion GRating INfrared Spectrograph). Various ro-vibrational H2 lines have been detected, which are used to derive the kinematic distances to the SNRs and to investigate the origin of the H2 emission. The detected H2 lines show broad line width (> 10 km s-1) and line flux ratios of thermal excitation. We discuss the origin of the extended H2 emission features beyond the the [Fe II] emission boundary.

Intense Photosensitized Emission from Stoichiometric Compounds Featuring Mn(2+) in Seven- and Eightfold Coordination Environments.

PubMed

Reid, Howard O. N.; Kahwa, Ishenkumba A.; White, Andrew J. P.; Williams, David J.

1998-07-27

Synthetic, structural and luminescence studies of stoichiometric crown ether compounds of Mn(2+) in well-defined coordination environments were undertaken in an effort to understand the origin of emitting crystal defects found in cubic F23 [(K18C6)(4)MnBr(4)][TlBr(4)](2) crystals (Fender, N. S.; et al. Inorg. Chem. 1997, 36, 5539). The new compound [Mn(12C4)(2)][MnBr(4)](2)[N(CH(3))(4)](2) (3) features Mn(2+) ions in eight- and fourfold coordination environments of [Mn(12C4)(2)](2+) and MnBr(4)(2)(-) respectively, while Mn(2+) in [Mn(15C5)(H(2)O)(2)][TlBr(5)] (4) is in the sevenfold coordination polyhedron of [Mn(15C5)(H(2)O)(2)](2+). Crystal data for 3: monoclinic, P2(1)/c (No. 14); a = 14.131(3) Å, b = 12.158(1) Å, c = 14.239(2) Å, beta = 110.37(1) degrees, Z = 2, R1 = 0.039 and wR2 = 0.083. For 3, long-lived emission (77 K decay rate approximately 3 x 10 s(-)(1)) from [Mn(12C4)(2)](2+) (the first for eight-coordinate Mn(2+) in stoichiometric compounds) is observed (lambda(max) approximately 546 nm) along with that of the sensitizing MnBr(4)(2)(-) (lambda(max) approximately 513 nm), which is partially quenched. Emission from the seven-coordinate [Mn(15C5)(H(2)O)(2)](2+) species of 4 and [Mn(15C5)(H(2)O)(2)][MnBr(4)] (the first for seven-coordinate Mn(2+) in stoichiometric compounds) peaks at lambda(max) approximately 592 nm. Unusually intense absorptions attributable to the seven-coordinate species are observed at 317 ((2)T(2)((2)I) <-- (6)A(1)), 342 ((4)T(1)((4)P) <-- (6)A(1)), 406 ((4)E((4)G) <-- (6)A(1)), and 531 ((4)T(1)((4)G) <-- (6)A(1)) nm.

Phylogenetic and functional potential links pH and N2O emissions in pasture soils.

PubMed

Samad, Md Sainur; Biswas, Ambarish; Bakken, Lars R; Clough, Timothy J; de Klein, Cecile A M; Richards, Karl G; Lanigan, Gary J; Morales, Sergio E

2016-10-26

Denitrification is mediated by microbial, and physicochemical, processes leading to nitrogen loss via N 2 O and N 2 emissions. Soil pH regulates the reduction of N 2 O to N 2 , however, it can also affect microbial community composition and functional potential. Here we simultaneously test the link between pH, community composition, and the N 2 O emission ratio (N 2 O/(NO + N 2 O + N 2 )) in 13 temperate pasture soils. Physicochemical analysis, gas kinetics, 16S rRNA amplicon sequencing, metagenomic and quantitative PCR (of denitrifier genes: nirS, nirK, nosZI and nosZII) analysis were carried out to characterize each soil. We found strong evidence linking pH to both N 2 O emission ratio and community changes. Soil pH was negatively associated with N 2 O emission ratio, while being positively associated with both community diversity and total denitrification gene (nir &nos) abundance. Abundance of nosZII was positively linked to pH, and negatively linked to N 2 O emissions. Our results confirm that pH imposes a general selective pressure on the entire community and that this results in changes in emission potential. Our data also support the general model that with increased microbial diversity efficiency increases, demonstrated in this study with lowered N 2 O emission ratio through more efficient conversion of N 2 O to N 2 .

Phylogenetic and functional potential links pH and N2O emissions in pasture soils

NASA Astrophysics Data System (ADS)

Samad, M. D. Sainur; Biswas, Ambarish; Bakken, Lars R.; Clough, Timothy J.; de Klein, Cecile A. M.; Richards, Karl G.; Lanigan, Gary J.; Morales, Sergio E.

2016-10-01

Denitrification is mediated by microbial, and physicochemical, processes leading to nitrogen loss via N2O and N2 emissions. Soil pH regulates the reduction of N2O to N2, however, it can also affect microbial community composition and functional potential. Here we simultaneously test the link between pH, community composition, and the N2O emission ratio (N2O/(NO + N2O + N2)) in 13 temperate pasture soils. Physicochemical analysis, gas kinetics, 16S rRNA amplicon sequencing, metagenomic and quantitative PCR (of denitrifier genes: nirS, nirK, nosZI and nosZII) analysis were carried out to characterize each soil. We found strong evidence linking pH to both N2O emission ratio and community changes. Soil pH was negatively associated with N2O emission ratio, while being positively associated with both community diversity and total denitrification gene (nir & nos) abundance. Abundance of nosZII was positively linked to pH, and negatively linked to N2O emissions. Our results confirm that pH imposes a general selective pressure on the entire community and that this results in changes in emission potential. Our data also support the general model that with increased microbial diversity efficiency increases, demonstrated in this study with lowered N2O emission ratio through more efficient conversion of N2O to N2.

Phylogenetic and functional potential links pH and N2O emissions in pasture soils

PubMed Central

Samad, M. d. Sainur; Biswas, Ambarish; Bakken, Lars R.; Clough, Timothy J.; de Klein, Cecile A. M.; Richards, Karl G.; Lanigan, Gary J.; Morales, Sergio E.

2016-01-01

Denitrification is mediated by microbial, and physicochemical, processes leading to nitrogen loss via N2O and N2 emissions. Soil pH regulates the reduction of N2O to N2, however, it can also affect microbial community composition and functional potential. Here we simultaneously test the link between pH, community composition, and the N2O emission ratio (N2O/(NO + N2O + N2)) in 13 temperate pasture soils. Physicochemical analysis, gas kinetics, 16S rRNA amplicon sequencing, metagenomic and quantitative PCR (of denitrifier genes: nirS, nirK, nosZI and nosZII) analysis were carried out to characterize each soil. We found strong evidence linking pH to both N2O emission ratio and community changes. Soil pH was negatively associated with N2O emission ratio, while being positively associated with both community diversity and total denitrification gene (nir & nos) abundance. Abundance of nosZII was positively linked to pH, and negatively linked to N2O emissions. Our results confirm that pH imposes a general selective pressure on the entire community and that this results in changes in emission potential. Our data also support the general model that with increased microbial diversity efficiency increases, demonstrated in this study with lowered N2O emission ratio through more efficient conversion of N2O to N2. PMID:27782174

A survey of extended H2 emission from massive YSOs

NASA Astrophysics Data System (ADS)

Navarete, F.; Damineli, A.; Barbosa, C. L.; Blum, R. D.

2015-07-01

We present the results from a survey, designed to investigate the accretion process of massive young stellar objects (MYSOs) through near-infrared narrow-band imaging using the H2 ν=1-0 S(1) transition filter. A sample of 353 MYSO candidates was selected from the Red MSX Source survey using photometric criteria at longer wavelengths (infrared and submillimetre) and chosen with positions throughout the Galactic plane. Our survey was carried out at the Southern Astrophysical Research Telescope Telescope in Chile and Canada-France-Hawaii Telescope in Hawaii covering both hemispheres. The data reveal that extended H2 emission is a good tracer of outflow activity, which is a signpost of accretion process on young massive stars. Almost half of the sample exhibit extended H2 emission and 74 sources (21 per cent) have polar morphology, suggesting collimated outflows. The polar-like structures are more likely to appear on radio-quiet sources, indicating these structures occur during the pre-UCH II phase. We also found an important fraction of sources associated with fluorescent H2 diffuse emission that could be due to a more evolved phase. The images also indicate only ˜23 per cent (80) of the sample is associated with extant (young) stellar clusters. These results support the scenario in which massive stars are formed by accretion discs, since the merging of low-mass stars would not produce outflow structures.

Decreased N2O reduction by low soil pH causes high N2O emissions in a riparian ecosystem.

PubMed

Van den Heuvel, R N; Bakker, S E; Jetten, M S M; Hefting, M M

2011-05-01

Quantification of harmful nitrous oxide (N(2)O) emissions from soils is essential for mitigation measures. An important N(2)O producing and reducing process in soils is denitrification, which shows deceased rates at low pH. No clear relationship between N(2)O emissions and soil pH has yet been established because also the relative contribution of N(2)O as the denitrification end product decreases with pH. Our aim was to show the net effect of soil pH on N(2)O production and emission. Therefore, experiments were designed to investigate the effects of pH on NO(3)(-) reduction, N(2)O production and reduction and N(2) production in incubations with pH values set between 4 and 7. Furthermore, field measurements of soil pH and N(2)O emissions were carried out. In incubations, NO(3)(-) reduction and N(2) production rates increased with pH and net N(2)O production rate was highest at pH 5. N(2)O reduction to N(2) was halted until NO(3)(-) was depleted at low pH values, resulting in a built up of N(2)O. As a consequence, N(2)O:N(2) production ratio decreased exponentially with pH. N(2)O reduction appeared therefore more important than N(2)O production in explaining net N(2)O production rates. In the field, a negative exponential relationship for soil pH against N(2)O emissions was observed. Soil pH could therefore be used as a predictive tool for average N(2)O emissions in the studied ecosystem. The occurrence of low pH spots may explain N(2)O emission hotspot occurrence. Future studies should focus on the mechanism behind small scale soil pH variability and the effect of manipulating the pH of soils. © 2011 Blackwell Publishing Ltd.

Detailed Analysis of Near-IR Water (H2O) Emission in Comet C/2014 Q2 (Lovejoy) with the GIANO/TNG Spectrograph

NASA Astrophysics Data System (ADS)

Faggi, S.; Villanueva, G. L.; Mumma, M. J.; Brucato, J. R.; Tozzi, G. P.; Oliva, E.; Massi, F.; Sanna, N.; Tozzi, A.

2016-10-01

We observed the Oort cloud comet C/2014 Q2 (Lovejoy) on 2015 January 31 and February 1 and 2 at a heliocentric distance of 1.3 au and geocentric distance of 0.8 au during its approach to the Sun. Comet Lovejoy was observed with GIANO, the near-infrared high-resolution spectrograph mounted at the Nasmyth-A focus of the TNG (Telescopio Nazionale Galileo) telescope in La Palma, Canary Islands, Spain. We detected strong emissions of radical CN and water, along with many emission features of unidentified origin, across the 1-2.5 μm region. Spectral lines from eight ro-vibrational bands of H2O were detected, six of them for the first time. We quantified the water production rate [Q(H2O), (3.11 ± 0.14) × 1029 s-1] by comparing the calibrated line fluxes with the Goddard full non-resonance cascade fluorescence model for H2O. The production rates of ortho-water [Q(H2O)ORTHO, (2.33 ± 0.11) × 1029 s-1] and para-water [Q(H2O)PARA, (0.87 ± 0.21) × 1029 s-1] provide a measure of the ortho-to-para ratio (2.70 ± 0.76)). The confidence limits are not small enough to provide a critical test of the nuclear spin temperature.

Detailed Analysis of Near-IR Water (H2O) Emission in Comet C/2014 Q2 (LOVEJOY) with the GIANO/TNG Spectrograph

NASA Technical Reports Server (NTRS)

Faggi, S.; Villanueva, G. L.; Mumma, M. J.; Brucato, J.R.; Tozzi, G. P.; Oliva, E.; Massi, F.; Sanna, N.; Tozzi, A.

2016-01-01

We observed the Oort cloud comet C/2014 Q2 (Lovejoy) on 2015 January 31 and February 1 and 2 at a heliocentric distance of 1.3 au and geocentric distance of 0.8 au during its approach to the Sun. Comet Lovejoy was observed with GIANO, the near-infrared high-resolution spectrograph mounted at the Nasmyth-A focus of the TNG (Telescopio Nazionale Galileo) telescope in La Palma, Canary Islands, Spain. We detected strong emissions of radical CN and water, along with many emission features of unidentified origin, across the 1-2.5 micron region. Spectral lines from eight ro-vibrational bands of H2O were detected, six of them for the first time. We quantified the water production rate [Q(H2O), (3.11+/- 0.14) x 10(exp 29)/s] by comparing the calibrated line fluxes with the Goddard full non-resonance cascade fluorescence model for H2O. The production rates of ortho-water [Q(H2O)ORTHO, (2.33+/- 0.11) x 10(exp 29)/s] and para-water [Q(H2O)PARA, (0.87+/-0.21) x 10(exp 29)/s] provide a measure of the ortho-to-para ratio (2.70+/- 0.76)). The confidence limits are not small enough to provide a critical test of the nuclear spin temperature.

High-resolution spectra of the 3.29 micron interstellar emission feature - A summary

NASA Technical Reports Server (NTRS)

Tokunaga, A. T.; Sellgren, K.; Smith, R. G.; Nagata, T.; Sakata, A.; Nakada, Y.

1991-01-01

High spectral resolution observations of the 3.29-micron interstellar emission feature show two types of profiles. Type 1 has a central wavelength of 3.289-micron and is observed in extended objects such as planetary nebulae and H II regions. Type 2 has a central wavelength of 3.296 microns and is observed around a small number of stellar sources. Type 2 has a full width at half-maximum of 0.020 micron; Type 1 has a broader FWHM, perhaps as much as 0.042 micron, but this is uncertain because of contamination by Pf(delta) emission. These profiles are tabulated for comparison to laboratory data. It is found that no proposed identification for the 3.29-micron emission feature definitely matches the observational spectra, although amorphous aromatic materials and heated polycyclic aromatic hydrocarbons tend to fit the best.

Spatially resolved H2 emission from the disk around T Tau N

NASA Astrophysics Data System (ADS)

Gustafsson, M.; Labadie, L.; Herbst, T. M.; Kasper, M.

2008-09-01

Context: Molecular hydrogen is the main constituent of circumstellar disks and could be an important tracer for the evolution and structure of such disks. So far, H2 has only been detected in a few disks and only through spectroscopic observations, resulting in a limited knowledge of the spatial distribution of the H2 emitting gas. Aims: We report the detection of quiescent H2 emission in a spatially resolved ring-like structure within 100 AU of T Tau N. We present evidence to show that the emission most likely arises from shocks in the atmosphere of a nearly face-on disk around T Tau N. Methods: Using high spatial resolution 3D spectroscopic K-band data, we trace the spatial distribution of several H2 NIR rovibrational lines in the vicinity of T Tau N. We examine the structure of the circumstellar material around the star through SED modeling. Then, we use models of shocks and UV+X-ray irradiation to reproduce the H2 line flux and line ratios in order to test how the H2 is excited. Results: We detect weak H2 emission from the v=1{-}0 S(0), S(1), Q(1) lines and the v=2{-}1 S(1) line in a ring-like structure around T Tau N between 0.1 arcsec ( 15 AU) and 0.7 arcsec ( 100 AU) from the star. The v=1{-}0 S(0) and v=2{-}1 S(1) lines are detected only in the outer parts of the ring structure. Closer to the star, the strong continuum limits our sensitivity to these lines. The total flux of the v=1{-}0 S(1) line is 1.8 × 10-14 erg s-1 cm-2, similar to previous measurements of H2 in circumstellar disks. The velocity of the H2 emitting gas around T Tau N is consistent with the rest velocity of the star, and the H2 does not seem to be part of a collimated outflow. Both shocks impinging on the surface of a disk and irradiation of a disk by UV-photons and X-rays from the central star are plausible candidates for the H2 excitation mechanism. However, irradiation should not create a large degree of excitation at radii larger than 20 AU. Most likely the H2 emission arises in the

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

PubMed

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

2016-10-01

Manganese-induced toxicity has been linked to mitochondrial dysfunction and an increased generation of reactive oxygen species (ROS). We could recently show in mechanistic studies that Mn 2+ ions induce hydrogen peroxide (H 2 O 2 ) production from the ubiquinone binding site of mitochondrial complex II (II Q ) and generally enhance H 2 O 2 formation by accelerating the rate of superoxide dismutation. The present study with intact mitochondria reveals that manganese additionally enhances H 2 O 2 emission by inducing mitochondrial permeability transition (mPT). In mitochondria fed by NADH-generating substrates, the combination of Mn 2+ and different respiratory chain inhibitors led to a dynamically increasing H 2 O 2 emission which was sensitive to the mPT inhibitor cyclosporine A (CsA) as well as Ru-360, an inhibitor of the mitochondrial calcium uniporter (MCU). Under these conditions, flavin-containing enzymes of the mitochondrial matrix, e.g. the mitochondrial 2-oxoglutaratedehydrogenase (OGDH), were major sources of ROS. With succinate as substrate, Mn 2+ stimulated ROS production mainly at complex II, whereby the applied succinate concentration had a marked effect on the tendency for mPT. Also Ca 2+ increased the rate of H 2 O 2 emission by mPT, while no direct effect on ROS-production of complex II was observed. The present study reveals a complex scenario through which manganese affects mitochondrial H 2 O 2 emission: stimulating its production from distinct sites (e.g. site II Q ), accelerating superoxide dismutation and enhancing the emission via mPT which also leads to the loss of soluble components of the mitochondrial antioxidant systems and favors the ROS production from flavin-containing oxidoreductases of the Krebs cycle. Copyright © 2016 Elsevier Inc. All rights reserved.

Overlap corrections for emissivity calculations of H2O-CO2-CO-N2 mixtures

NASA Astrophysics Data System (ADS)

Alberti, Michael; Weber, Roman; Mancini, Marco

2018-01-01

Calculations of total gas emissivities of gas mixtures containing several radiatively active species require corrections for band overlapping. In this paper, we generate such overlap correction charts for H2O-CO2-N2, H2O-CO-N2, and CO2-CO-N2 mixtures. These charts are applicable in the 0.1-40 bar total pressure range and in the 500 K-2500 K temperature range. For H2O-CO2-N2 mixtures, differences between our charts and Hottel's graphs as well as models of Leckner and Modak are highlighted and analyzed.

H2 emission from non-stationary magnetized bow shocks

NASA Astrophysics Data System (ADS)

Tram, L. N.; Lesaffre, P.; Cabrit, S.; Gusdorf, A.; Nhung, P. T.

2018-01-01

When a fast moving star or a protostellar jet hits an interstellar cloud, the surrounding gas gets heated and illuminated: a bow shock is born that delineates the wake of the impact. In such a process, the new molecules that are formed and excited in the gas phase become accessible to observations. In this paper, we revisit models of H2 emission in these bow shocks. We approximate the bow shock by a statistical distribution of planar shocks computed with a magnetized shock model. We improve on previous works by considering arbitrary bow shapes, a finite irradiation field and by including the age effect of non-stationary C-type shocks on the excitation diagram and line profiles of H2. We also examine the dependence of the line profiles on the shock velocity and on the viewing angle: we suggest that spectrally resolved observations may greatly help to probe the dynamics inside the bow shock. For reasonable bow shapes, our analysis shows that low-velocity shocks largely contribute to H2 excitation diagram. This can result in an observational bias towards low velocities when planar shocks are used to interpret H2 emission from an unresolved bow. We also report a large magnetization bias when the velocity of the planar model is set independently. Our 3D models reproduce excitation diagrams in BHR 71 and Orion bow shocks better than previous 1D models. Our 3D model is also able to reproduce the shape and width of the broad H2 1-0S(1) line profile in an Orion bow shock (Brand et al. 1989).

Possible detection of an emission feature near 584 A in the direction of G191-B2B

NASA Technical Reports Server (NTRS)

Green, James; Bowyer, Stuart; Jelinsky, Patrick

1990-01-01

A possible spectral emission feature is reported in the direction of the nearby hot white dwarf G191-B2B at 581.5 + or - 6 A with a significance of 3.8 sigma. This emission has been identified as He I 584.3 A. The emission cannot be due to local geocoronal emission or interplanetary backscatter of solar He I 584 A emission because the feature is not detected in a nearby sky exposure. Possible sources for this emission are examined, including the photosphere of G191-B2B, the comparison star G191-B2A, and a possible nebulosity near or around G191-B2B. The parameters required to explain the emission are derived for each case. All of these explanations require unexpected physical conditions; hence we believe this result must receive confirming verification despite the statistical likelihood of the detection.

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

NASA Technical Reports Server (NTRS)

Leibowitz, L. P.

1977-01-01

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

Feature Modeling of HfO2 Atomic Layer Deposition Using HfCl4/H2O

NASA Astrophysics Data System (ADS)

Stout, Phillip J.; Adams, Vance; Ventzek, Peter L. G.

2003-03-01

A Monte Carlo based feature scale model (Papaya) has been applied to atomic layer deposition (ALD) of HfO2 using HfCl_4/H_20. The model includes physical effects of transport to surface, specular and diffusive reflection within feature, adsorption, surface diffusion, deposition and etching. Discussed will be the 3D feature modeling of HfO2 deposition in assorted features (vias and trenches). The effect of feature aspect ratios, pulse times, cycle number, and temperature on film thickness, feature coverage, and film Cl fraction (surface/bulk) will be discussed. Differences between HfO2 ALD on blanket wafers and in features will be highlighted. For instance, the minimum pulse times sufficient for surface reaction saturation on blanket wafers needs to be increased when depositing on features. Also, HCl products created during the HfCl4 and H_20 pulses are more likely to react within a feature than at the field, reducing OH coverage within the feature (vs blanket wafer) thus limiting the maximum coverage attainable for a pulse over a feature.

The Spacing of the Interstellar 6.2 Microns and 7.7 Microns Emission Features as an Indicator of PAH Size

NASA Technical Reports Server (NTRS)

Hudgins, Douglas M.; Allamandola, L. J.; Mead, Susan (Technical Monitor)

1998-01-01

A database of astrophysically relevant, infrared spectral measurements on a wide variety of neutral as well as positively and negatively charged polycyclic aromatic hydrocarbons ranging in size from C10H8 through C48H20 is now available to extend the interstellar PAH model. Beyond simply indicating general characteristics of the carriers, this collection of data now makes it possible to conduct a more thorough interpretation of the details of the interstellar spectra and thereby derive deeper insights into the nature of the emitting material and conditions in the emission zones. This paper is the first such implementation of this spectral database. The infrared spectra of PAH cations, the main PAH form in the most energetic emission zones, are usually dominated by a few strong features in the 1650 - 1100 per centimeter (6.1 - 9.1 microns) region which tend to cluster in the vicinity of the interstellar emission bands at 1610 per centimeter and 1320 per centimeter (6.2 and 7.6 microns) but with spacings typically somewhat less than that observed in the canonical interstellar spectrum. However, the spectra in the database show that this spacing increases steadily with molecular size. Extrapolation of this trend indicates that PAHS in the 50 to 80 carbon atom size range are entirely consistent with the observed interstellar spacing. Furthermore, the profile of the 1610 per centimeter (6.2 microns) interstellar band indicates that PAHS containing as few as 20 carbon atoms contribute to this feature.

Molecular line emission models of Herbig-Haro objects. I - H2 emission

NASA Technical Reports Server (NTRS)

Wolfire, Mark G.; Konigl, Arieh

1991-01-01

A comprehensive model for molecular hydrogen emssion in Herbig-Haro objects that are associated with the heads of radiative stellar jets is presented by using a simple representation of the jet head as a comprising a leading bow shock and a trailing jet shock, separated by a dense layer of cool shocked gas. Attention is given to collisional excitation in a nondissociative shock and formation pumping in the molecular reformation zone behind a dissociative shock, employing detailed shock and photodissociation-region emission models that incorporate most of the relevant atomic physics and chemistry. The conditions under which each of these excitation mechanisms may be expected to contribute to the observed emission are discussed, and a general diagnostic scheme for discriminating among them is constructed. Applying this scheme to the HH 1-2 system, strong evidence for excitation by the radiation field of a fast shock is found. It is inferred that FUV pumping contributes a significant fraction of the H2 line emission, and it is shown that this can occur only if the UV pump lines are not strongly self-shielded.

DETAILED ANALYSIS OF NEAR-IR WATER (H{sub 2}O) EMISSION IN COMET C/2014 Q2 (LOVEJOY) WITH THE GIANO/TNG SPECTROGRAPH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faggi, S.; Brucato, J. R.; Tozzi, G. P.

We observed the Oort cloud comet C/2014 Q2 (Lovejoy) on 2015 January 31 and February 1 and 2 at a heliocentric distance of 1.3 au and geocentric distance of 0.8 au during its approach to the Sun. Comet Lovejoy was observed with GIANO, the near-infrared high-resolution spectrograph mounted at the Nasmyth-A focus of the TNG (Telescopio Nazionale Galileo) telescope in La Palma, Canary Islands, Spain. We detected strong emissions of radical CN and water, along with many emission features of unidentified origin, across the 1–2.5 μ m region. Spectral lines from eight ro-vibrational bands of H{sub 2}O were detected, sixmore » of them for the first time. We quantified the water production rate [ Q (H{sub 2}O), (3.11 ± 0.14) × 10{sup 29} s{sup −1}] by comparing the calibrated line fluxes with the Goddard full non-resonance cascade fluorescence model for H{sub 2}O. The production rates of ortho-water [ Q (H{sub 2}O){sup ORTHO}, (2.33 ± 0.11) × 10{sup 29} s{sup −1}] and para-water [ Q (H{sub 2}O){sup PARA}, (0.87 ± 0.21) × 1029 s{sup −1}] provide a measure of the ortho-to-para ratio (2.70 ± 0.76)). The confidence limits are not small enough to provide a critical test of the nuclear spin temperature.« less

The spacing of the interstellar 6.2 and 7.7 micron emission features as an indicator of polycyclic aromatic hydrocarbon size

NASA Technical Reports Server (NTRS)

Hudgins, D. M.; Allamandola, L. J.

1999-01-01

A database of astrophysically relevant, infrared spectral measurements on a wide variety of neutral as well as positively and negatively charged polycyclic aromatic hydrocarbons (PAHs), ranging in size from C10H8 through C48H20, is now available to extend the interstellar PAH model. Beyond simply indicating general characteristics of the carriers, this collection of data now makes it possible to conduct a more thorough interpretation of the details of the interstellar spectra and thereby derive deeper insights into the nature of the emitting material and conditions in the emission zones. This Letter is the first such implementation of this spectral database. The infrared spectra of PAH cations, the main PAH form in the most energetic emission zones, are usually dominated by a few strong features in the 1650-1100 cm-1 (6.1-9.1 microns) region that tend to cluster the vicinity of the interstellar emission bands at 1610 and 1320 cm-1 (6.2 and 7.6 microns), but with spacings typically somewhat less than that observed in the canonical interstellar spectrum. However, the spectra in the database show that this spacing increases steadily with molecular size. Extrapolation of this trend indicates that PAHs in the 50-80 carbon atom size range are entirely consistent with the observed interstellar spacing. Furthermore, the profile of the 1610 cm-1 (6.2 microns) interstellar band indicates that PAHs containing as few as 20 carbon atoms contribute to this feature.

The C-H Stretching Features at 3.2--3.5 μm of Polycyclic Aromatic Hydrocarbons with Aliphatic Sidegroups

NASA Astrophysics Data System (ADS)

Yang, X. J.; Li, Aigen; Glaser, R.; Zhong, J. X.

2016-07-01

The so-called “unidentified” infrared emission (UIE) features at 3.3, 6.2, 7.7, 8.6, and 11.3 μm are ubiquitously seen in a wide variety of astrophysical regions. The UIE features are characteristic of the stretching and bending vibrations of aromatic hydrocarbon materials, e.g., polycyclic aromatic hydrocarbon (PAH) molecules. The 3.3 μm aromatic C-H stretching feature is often accompanied by a weaker feature at 3.4 μm. The latter is generally thought to result from the C-H stretch of aliphatic groups attached to the aromatic systems. The ratio of the observed intensity of the 3.3 μm aromatic C-H feature to that of the 3.4 μm aliphatic C-H feature allows one to estimate the aliphatic fraction of the UIE carriers, provided that the intrinsic oscillator strengths of the 3.3 μm aromatic C-H stretch ({A}3.3) and the 3.4 μm aliphatic C-H stretch ({A}3.4) are known. While previous studies on the aliphatic fraction of the UIE carriers were mostly based on the {A}3.4/{A}3.3 ratios derived from the mono-methyl derivatives of small PAH molecules, in this work we employ density functional theory to compute the infrared vibrational spectra of PAH molecules with a wide range of sidegroups including ethyl, propyl, butyl, and several unsaturated alkyl chains, as well as all the isomers of dimethyl-substituted pyrene. We find that, except for PAHs with unsaturated alkyl chains, the corresponding {A}3.4/{A}3.3 ratios are close to that of mono-methyl PAHs. This confirms the predominantly aromatic nature of the UIE carriers previously inferred from the {A}3.4/{A}3.3 ratio derived from mono-methyl PAHs.

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

NASA Astrophysics Data System (ADS)

Aleman, I.; Gruenwald, R.

2011-05-01

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

Effect of H2O on the NO emission characteristics of pulverized coal during oxy-fuel combustion.

PubMed

Lei, Ming; Sun, Cen; Zou, Chan; Mi, Hang; Wang, Chunbo

2018-04-01

The NO emission characteristics of Datong bituminous coal and Yangquan anthracite in O 2 /H 2 O/CO 2 atmospheres were investigated by using a fixed-bed reactor system, and the emission characteristics were compared with the experimental results from O 2 /N 2 and O 2 /CO 2 atmospheres, especially at low O 2 concentrations and high temperatures. The results showed that NO emissions of pulverized coal in O 2 /CO 2 environments were less than those in the O 2 /N 2 environments, regardless of the O 2 concentration and the furnace temperature. Adding H 2 O decreased the possibility of reactions between the reductive groups (NH) and the oxygen radical during devolatilization, which led to a decrease in NO emissions at 1000 °C. However, as the furnace temperature increased, "additional" nitrogen precursors (HCN and NH 3 ) generated by enhanced char-H 2 O gasification were quickly oxidized to generate a large amount of NO during char oxidation that exceeded the amount of NO reduced by NH during devolatilization. Thus, the NO emissions in O 2 /CO 2 /H 2 O atmosphere were higher than those in O 2 /CO 2 atmosphere at a low O 2 concentration. However, as the O 2 concentration increased, the NO emissions in O 2 /CO 2 /H 2 O atmosphere became lower than those in O 2 /CO 2 atmosphere because the effect of H 2 O gasification became weaker. The NO emissions of Yangquan anthracite (YQ) were higher than those of DT, but the changing trend of YQ was similar to that of DT.

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

NASA Astrophysics Data System (ADS)

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

2008-05-01

The mass and dynamics of protoplanetary disks are dominated by molecular hydrogen (H2). However, observationally very little is known about the H2. In this paper, we discuss two projects aimed to constrain the properties of H2 in the disk's planet forming region (R<50AU). First, we present a sensitive survey for pure-rotational H2 emission at 12.278 and 17.035 μm in a sample of nearby Herbig Ae/Be and T Tauri stars using VISIR, ESO's VLT high-resolution mid-infrared spectrograph. Second, we report on a search for H2 ro-vibrational emission at 2.1228, 2.2233 and 2.2477 μm in the classical T Tauri star LkHα 264 and the debris disk 49 Cet employing CRIRES, ESO's VLT high-resolution near-infrared spectrograph. VISIR project: none of the sources show H2 mid-IR emission. The observed disks contain less than a few tenths of MJupiter of optically thin H2 at 150 K, and less than a few MEarth at T>300 K. % and higher T. Our non-detections are consistent with the low flux levels expected from the small amount of H2 gas in the surface layer of a Chiang and Goldreich (1997) Herbig Ae two-layer disk model. In our sources the H2 and dust in the surface layer have not significantly departed from thermal coupling (Tgas/Tdust<2) and the gas-to-dust ratio in the surface layer is very likely <1000. CRIRES project: The H2 lines at 2.1218 μm and 2.2233 μm are detected in LkHα 264. An upper limit on the 2.2477 μm H2 line flux in LkHα 264 is derived. 49 Cet does not exhibit H2 emission in any of observed lines. There are a few MMoon of optically thin hot H2 in the inner disk (0.1 AU) of LkHα 264, and less than a tenth of a MMoon of hot H2 in the inner disk of 49 Cet. The shape of the 1 0 S(0) line indicates that LkHα disk is close to face-on (i<35o). The measured 1 0 S(0)/1 0 S(1) and 2 1 S(1)/1 0 S(1) line ratios in LkHα 264 indicate that the H2 is thermally excited at T<1500 K. The lack of H2 emission in the NIR spectra of 49 Cet and the absence of Hα emission suggest that

High resolution spectroscopy of the disk chromosphere. II - Time sequence observations of Ca II H and K emissions.

NASA Technical Reports Server (NTRS)

Wilson, P. R.; Rees, D. E.; Beckers, J. M.; Brown, D. R.

1972-01-01

Two independent sets of high resolution time series spectra of the Ca II H and K emission obtained at the Solar Tower and at the Big Dome of the Sacramento Peak Observatory on September 11th, 1971 are reported. The evolutionary behavior of the emission first reported by Wilson and Evans is confirmed, but the detail of the evolution is found to be more complex. In one case, a doubly peaked feature showing some K3 emission evolves into a single K2 (red) peak with no K3 emission. Coincidentally, a neighboring doubly peaked feature evolves to a very strong blue peak. In an entirely independent sequence a doubly peaked feature evolves into a single red peak. The K2 emission then fades completely although the continuum threads are still strong. Finally a strong K2 blue peak appears. It is concluded that the observed evolution of the K2 emission is due to temporal variations in the physical conditions which give rise to them.

Spectro-imaging observations of Jupiter's 2-μm auroral emission. I. H 3+ distribution and temperature

NASA Astrophysics Data System (ADS)

Raynaud, E.; Lellouch, E.; Maillard, J.-P.; Gladstone, G. R.; Waite, J. H.; Bézard, B.; Drossart, P.; Fouchet, T.

2004-09-01

We report on spectro-imaging infrared observations of Jupiter's auroral zones, acquired in October 1999 and October 2000 with the FTS/BEAR instrument at the Canada-France-Hawaii Telescope. The use of narrow-band filters at 2.09 and 2.12 μm, combined with high spectral resolution (0.2 cm -1), allowed us to map emission from the H 2S1(1) quadrupole line and from several H 3+ lines. The H 2 and H 3+ emission appears to be morphologically different, especially in the north, where the latter notably exhibits a "hot spot" near 150°-170° System III longitude. This hot spot coincides in position with the region of increased and variable hydrocarbon, FUV and X-ray emission, but is not seen in the more uniform H 2S1(1) emission. We also present the first images of the H 2 emission in the southern polar region. The spectra include a total of 14 H 3+ lines, including two hot lines from the 3 ν2- ν2 band, detected on Jupiter for the first time. They can be used to determine H 3+ column densities, rotational ( Trot) and vibrational ( Tvib) temperatures. We find the mean Tvib of the v2=3 state to be lower (960±50 K) than the mean Trot in v2=2 (1170±75 K), indicating an underpopulation of the v2=3 level with respect to local thermodynamical equilibrium. Rotational temperatures and associated column densities are generally higher and lower, respectively, than inferred previously from ν2 observations. This is a likely consequence of a large positive temperature gradient in the sub-microbar auroral atmosphere. While the signal-to-noise is not sufficient to take full advantage of the 2-D capabilities of the observations, the search for correlations between line intensities, Tvib and column densities, indicates that variations in line intensities are mostly due to correlated variations in the H 3+ column densities. The thermostatic role played by H 3+ at ionospheric levels may provide an explanation. The exception is the northern "hot spot," which exhibits a Tvib about 250 K

Radiative transitions involving the (2p2)(3 Pe) metastable autodetaching of H(-)

NASA Technical Reports Server (NTRS)

Jacobs, V. L.; Bhatia, A. K.; Temkin, A.

1974-01-01

The absorption coefficient for the free-bound transition H (ls) + e(-)+ h omega yields H(-)(2 sq p,(3)P(e)) is calculated (together with the differential emission rate for the inverse process) using ls - 2s - 2p close coupling continuum wave functions and a Hylleraas bound state wave function. A maximum in the absorption and emission spectra is found to occur at a photon wavelength of 1219.5 A, which is 2 A closer to the Lyman alpha line than predicted by the calculations of Drake, and is in closer agreement with the stellar absorption feature identified by Heap and Stecher. The free-bound absorption process appears to be a significant source of continuous ultraviolet opacity.

Broad N2H+ Emission toward the Protostellar Shock L1157-B1

NASA Astrophysics Data System (ADS)

Codella, C.; Viti, S.; Ceccarelli, C.; Lefloch, B.; Benedettini, M.; Busquet, G.; Caselli, P.; Fontani, F.; Gómez-Ruiz, A.; Podio, L.; Vasta, M.

2013-10-01

We present the first detection of N2H+ toward a low-mass protostellar outflow, namely, the L1157-B1 shock, at ~0.1 pc from the protostellar cocoon. The detection was obtained with the IRAM 30 m antenna. We observed emission at 93 GHz due to the J = 1-0 hyperfine lines. Analysis of this emission coupled with HIFI CHESS multiline CO observations leads to the conclusion that the observed N2H+(1-0) line originated from the dense (>=105 cm-3) gas associated with the large (20''-25'') cavities opened by the protostellar wind. We find an N2H+ column density of a few 1012 cm-2 corresponding to an abundance of (2-8) × 10-9. The N2H+ abundance can be matched by a model of quiescent gas evolved for more than 104 yr, i.e., for more than the shock kinematical age (sime2000 yr). Modeling of C-shocks confirms that the abundance of N2H+ is not increased by the passage of the shock. In summary, N2H+ is a fossil record of the pre-shock gas, formed when the density of the gas was around 104 cm-3, and then further compressed and accelerated by the shock.

Ultraviolet continuum and H2 fluorescent emission in Herbig-Haro objects 43 and 47

NASA Technical Reports Server (NTRS)

Schwartz, R. D.

1983-01-01

IUE short wavelength spectra are presented for the low excitation Herbig-Haro objects HH 43 and HH 47. In the former, several emission lines in the Lyman band of H2 from an excited state are observed which are due to fluorescence from the H Ly-alpha line pumping a lower state (that is in turn excited by a low-velocity shock wave). No evidence of highly ionized gas emission is found in the UV spectra, and both objects exhibit a UV continuum which peaks in the vicinity of 1500 A and is probably caused by H two-photon emission enhanced by low velocity shock collisional excitation.

Line Profile of H Lyman-Beta Emission from Dissociative Excitation of H2

NASA Technical Reports Server (NTRS)

Ajello, Joseph M.; Ahmed, Syed M.; Liu, Xian-Ming

1996-01-01

A high-resolution ultraviolet spectrometer was employed for a measurement of the H Lyman-Beta(H L(sub Beta)) emission Doppler line profile at 1025.7 A from dissociative excitation of H2 by electron impact. Analysis of the deconvolved line profile reveals the existence of a narrow central peak, less than 30 mA full width at half maximum (FWHM), and a broad pedestal base about 260 mA FWHM. Analysis of the red wing of the line profile is complicated by a group of Wemer and Lyman rotational lines 160-220 mA from the line center. Analysis of the blue wing of the line profile gives the kinetic-energy distribution. There are two main kinetic-energy components to the H(3p) distribution: (1) a slow distribution with a peak value near 0 eV from singly excited states, and (2) a fast distribution with a peak contribution near 7 eV from doubly excited states. Using two different techniques, the absolute cross section of H L(sub Beta)p is found to be 3.2+/-.8 x 10(exp -19)sq cm at 100-eV electron impact energy. The experimental cross-section and line-profile results can be compared to previous studies of H(alpha) (6563.7 A) for principal quantum number n=3 and L(sub alpha)(1215.7 A) for n=2.

Fabry-Perot Observations of [OI]6300, Hα, H-Beta, and NH2 Emissions from Comet Hyakutake C/1996B2

NASA Astrophysics Data System (ADS)

Scherb, F.; Roesler, F. L.; Tufte, S.; Haffner, M.

1996-05-01

During the period 16-23 March 1996, observations of Comet Hyakutake were carried out with the new WHAM facility at the University of Wisconsin Pine Bluff Observatory, near Madison. WHAM is a second-generation double-Fabry-Perot/CCD spectrometer that is more than ten times as efficient as our previous large-aperture Fabry-Perot instruments. Specifications of WHAM in the spectral mode are: a 1-degree field of view (FOV) on the sky, 10 km/sec velocity resolution, 200 km/sec range, and 20 sigma detection of a 1-Rayleigh H-alpha emission line in about 30 seconds. WHAM can also operate in a mode in which an image of an emission source over a 1-degree FOV can be obtained at a spectral resolution of about 10 km/sec. Spectra of cometary [OI]6300, H-alpha, H-beta, and NH2 emissions were obtained with the FOV centered on the comet head and also located 3/4 degree sunward of the comet head, repectively. This was the first time that cometary H-beta emission has been detected. Images of cometary [OI]6300 and NH2 emissions were obtained with the FOV centered on the comet head. The interpretation of these observations using coma gas dynamic and photochemical models yields values of the H2O production rate from both the [OI]6300 and H-alpha data. Comparison of the cometary H-alpha and H-beta intensities provides unique ground-based information on the EUV solar Lyman-beta and Lyman-gamma emission lines. These results will be presented.

Ozone depletion caused by NO and H2O emissions from hydrazine-fueled rockets

NASA Astrophysics Data System (ADS)

Ross, M. N.; Danilin, M. Y.; Weisenstein, D. K.; Ko, M. K. W.

2004-11-01

Rockets using unsymmetrical dimethyl hydrazine (N(CH3)2NH2) and dinitrogen tetroxide (N2O4) propellants account for about one third of all stratospheric rocket engine emissions, comparable to the solid-fueled rocket emissions. We use plume and global atmosphere models to provide the first estimate of the local and global ozone depletion caused by NO and H2O emissions from the Proton rocket, the largest hydrazine-fueled launcher in use. NO and H2O emission indices are assumed to be 20 and 350 g/kg (propellant), respectively. Predicted maximum ozone loss in the plume of the Proton rocket is 21% at 44 km altitude. Plume ozone loss at 20 km equals 8% just after launch and steadily declines to 2% by model sunset. Predicted steady state global ozone loss from ten Proton launches annually is 1.2 × 10-4%, with nearly all of the loss due to the NO component of the emission. Normalized by stratospheric propellant consumption, the global ozone depletion efficiency of the Proton is approximately 66-90 times less than that of solid-fueled rockets. In situ Proton plume measurements are required to validate assumed emission indices and to assess the role of rocket emissions not considered in these calculations. Such future studies would help to establish a formalism to evaluate the relative ozone depletion caused by different rocket engines using different propellants.

Intrinsic aerobic capacity correlates with greater inherent mitochondrial oxidative and H2O2 emission capacities without major shifts in myosin heavy chain isoform

PubMed Central

Seifert, Erin L.; Bastianelli, Mark; Aguer, Céline; Moffat, Cynthia; Estey, Carmen; Koch, Lauren G.; Britton, Steven L.

2012-01-01

Exercise capacity and performance strongly associate with metabolic and biophysical characteristics of skeletal muscle, factors that also relate to overall disease risk. Despite its importance, the exact mechanistic features that connect aerobic metabolism with health status are unknown. To explore this, we applied artificial selection of rats for intrinsic (i.e., untrained) aerobic treadmill running to generate strains of low- and high-capacity runners (LCR and HCR, respectively), subsequently shown to diverge for disease risk. Concurrent breeding of LCR and HCR per generation allows the lines to serve as reciprocal controls for unknown environmental changes. Here we provide the first direct evidence in mitochondria isolated from skeletal muscle that intrinsic mitochondrial capacity is higher in HCR rats. Maximal phosphorylating respiration was ∼40% greater in HCR mitochondria, independent of substrate and without altered proton leak or major changes in protein levels or muscle fiber type, consistent with altered control of phosphorylating respiration. Unexpectedly, H2O2 emission was ∼20% higher in HCR mitochondria, due to greater reduction of more harmful reactive oxygen species to H2O2; indeed, oxidative modification of mitochondrial proteins was lower. When the higher mitochondrial yield was considered, phosphorylating respiration and H2O2 emission were 70–80% greater in HCR muscle. Greater capacity of HCR muscle for work and H2O2 signaling may result in enhanced and more immediate cellular repair, possibly explaining lowered disease risks. PMID:22995392

Intrinsic aerobic capacity correlates with greater inherent mitochondrial oxidative and H2O2 emission capacities without major shifts in myosin heavy chain isoform.

PubMed

Seifert, Erin L; Bastianelli, Mark; Aguer, Céline; Moffat, Cynthia; Estey, Carmen; Koch, Lauren G; Britton, Steven L; Harper, Mary-Ellen

2012-11-01

Exercise capacity and performance strongly associate with metabolic and biophysical characteristics of skeletal muscle, factors that also relate to overall disease risk. Despite its importance, the exact mechanistic features that connect aerobic metabolism with health status are unknown. To explore this, we applied artificial selection of rats for intrinsic (i.e., untrained) aerobic treadmill running to generate strains of low- and high-capacity runners (LCR and HCR, respectively), subsequently shown to diverge for disease risk. Concurrent breeding of LCR and HCR per generation allows the lines to serve as reciprocal controls for unknown environmental changes. Here we provide the first direct evidence in mitochondria isolated from skeletal muscle that intrinsic mitochondrial capacity is higher in HCR rats. Maximal phosphorylating respiration was ~40% greater in HCR mitochondria, independent of substrate and without altered proton leak or major changes in protein levels or muscle fiber type, consistent with altered control of phosphorylating respiration. Unexpectedly, H(2)O(2) emission was ~20% higher in HCR mitochondria, due to greater reduction of more harmful reactive oxygen species to H(2)O(2); indeed, oxidative modification of mitochondrial proteins was lower. When the higher mitochondrial yield was considered, phosphorylating respiration and H(2)O(2) emission were 70-80% greater in HCR muscle. Greater capacity of HCR muscle for work and H(2)O(2) signaling may result in enhanced and more immediate cellular repair, possibly explaining lowered disease risks.

New Infrared Emission Features and Spectral Variations in Ngc 7023

NASA Technical Reports Server (NTRS)

Werner, M. W.; Uchida, K. I.; Sellgren, K.; Marengo, M.; Gordon, K. D.; Morris, P. W.; Houck, J. R.; Stansberry, J. A.

2004-01-01

We observed the reflection nebula NGC 7023, with the Short-High module and the long-slit Short-Low and Long-Low modules of the Infrared Spectrograph on the Spitzer Space Telescope. We also present Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS) images of NGC 7023 at 3.6, 4.5, 8.0, and 24 m. We observe the aromatic emission features (AEFs) at 6.2, 7.7, 8.6, 11.3, and 12.7 m, plus a wealth of weaker features. We find new unidentified interstellar emission features at 6.7, 10.1, 15.8, 17.4, and 19.0 m. Possible identifications include aromatic hydrocarbons or nanoparticles of unknown mineralogy. We see variations in relative feature strengths, central wavelengths, and feature widths, in the AEFs and weaker emission features, depending on both distance from the star and nebular position (southeast vs. northwest).

ENHANCED WARM H{sub 2} EMISSION IN THE COMPACT GROUP MID-INFRARED ''GREEN VALLEY''

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cluver, M. E.; Ogle, P.; Guillard, P.

2013-03-10

We present results from a Spitzer mid-infrared spectroscopy study of a sample of 74 galaxies located in 23 Hickson Compact Groups (HCGs), chosen to be at a dynamically active stage of H I depletion. We find evidence for enhanced warm H{sub 2} emission (i.e., above that associated with UV excitation in star-forming regions) in 14 galaxies ({approx}20%), with 8 galaxies having extreme values of L(H{sub 2} S(0)-S(3))/L(7.7 {mu}m polycyclic aromatic hydrocarbon), in excess of 0.07. Such emission has been seen previously in the compact group HCG 92 (Stephan's Quintet), and was shown to be associated with the dissipation of mechanicalmore » energy associated with a large-scale shock caused when one group member collided, at high velocity, with tidal debris in the intragroup medium. Similarly, shock excitation or turbulent heating is likely responsible for the enhanced H{sub 2} emission in the compact group galaxies, since other sources of heating (UV or X-ray excitation from star formation or active galactic nuclei) are insufficient to account for the observed emission. The group galaxies fall predominantly in a region of mid-infrared color-color space identified by previous studies as being connected to rapid transformations in HCG galaxy evolution. Furthermore, the majority of H{sub 2}-enhanced galaxies lie in the optical ''green valley'' between the blue cloud and red sequence, and are primarily early-type disk systems. We suggest that H{sub 2}-enhanced systems may represent a specific phase in the evolution of galaxies in dense environments and provide new insight into mechanisms which transform galaxies onto the optical red sequence.« less

Spectral and ion emission features of laser-produced Sn and SnO2 plasmas

NASA Astrophysics Data System (ADS)

Hui, Lan; Xin-Bing, Wang; Du-Luo, Zuo

2016-03-01

We have made a detailed comparison of the atomic and ionic debris, as well as the emission features of Sn and SnO2 plasmas under identical experimental conditions. Planar slabs of pure metal Sn and ceramic SnO2 are irradiated with 1.06 μm, 8 ns Nd:YAG laser pulses. Fast photography employing an intensified charge coupled device (ICCD), optical emission spectroscopy (OES), and optical time of flight emission spectroscopy are used as diagnostic tools. Our results show that the Sn plasma provides a higher extreme ultraviolet (EUV) conversion efficiency (CE) than the SnO2 plasma. However, the kinetic energies of Sn ions are relatively low compared with those of SnO2. OES studies show that the Sn plasma parameters (electron temperature and density) are lower compared to those of the SnO2 plasma. Furthermore, we also give the effects of the vacuum degree and the laser pulse energy on the plasma parameters. Project supported by the National Natural Science Foundation of China (Grant No. 11304235) and the Director Fund of WNLO, China.

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

NASA Astrophysics Data System (ADS)

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

2016-07-01

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

Variations in the Peak Position of the 6.2 micron Interstellar Emission Feature: A Tracer of N in the Interstellar Polycyclic Aromatic Hydrocarbon Population

NASA Technical Reports Server (NTRS)

Hudgins, Douglas M.; Bauschlicher, Charles W.; Allamandola, L. J.

2005-01-01

This paper presents the results of an investigation of the molecular characteristics that underlie the observed peak position and profile of the nominal 6.2 micron interstellar emission band generally attributed to the CC stretching vibrations of polycyclic aromatic hydrocarbons (PAHs). It begins with a summary of recent experimental and theoretical studies ofthe spectroscopic properties of large (>30 carbon atoms) PAH cations as they relate to this aspect of the astrophysical problem. It then continues with an examination of the spectroscopic properties of a number of PAH variants within the context of the interstellar 6.2 micron emission, beginning with a class of compounds known as polycyclic aromatic nitrogen heterocycles (PANHs; PAHs with one or more nitrogen atoms substituted into their carbon skeleton). In this regard, we summarize the results of recent relevant experimental studies involving a limited set of small PANHs and their cations and then report the results of a comprehensive computational study that extends that work to larger PANH cations including many nitrogen-substituted variants of coronene(+) (C24H12(+)), ovalene(+) (C32H14(+)), circumcoronene(+) (C54H18(+)), and circum-circumcoronene(+) (C96H24(+)). Finally, we report the results of more focused computational studies of selected representatives from a number of other classes of PAH variants that share one or more of the key attributes of the PANH species studied. These alternative classes of PAH variants include (1) oxygen- and silicon-substituted PAH cations; (2) PAH-metal ion complexes (metallocenes) involving the cosmically abundant elements magnesium and iron; and (3) large, asymmetric PAH cations. Overall, the studies reported here demonstrate that increasing PAH size alone is insuEcient to account for the position of the shortest wavelength interstellar 6.2 micron emission bands, as had been suggested by earlier studies. On the other hand, this work reveals that substitution of one or

Optical spectrophotometry of Comet P/Giacobini-Zinner and emission profiles of H2O+

NASA Technical Reports Server (NTRS)

Strauss, M. A.; Mccarthy, P. J.; Spinrad, H.

1986-01-01

Two-dimensional CCD spectrograms were obtained of Comet P/Giacobini-Zinner (1984e) on five occasions between July and October 1985. Spatial emission profiles of H2O+ were extracted at 6198 angstroms (the strongest ionic line in the visible spectrum). This emission line traces the extent of the ion, or plasma, tail. The spectrographic slit was placed approximately along the trajectory of the ICE spacecraft on September 11, 1985; the resulting H2O+ profile has a full-width-half-maximum of about 5700 km, about three times that of the plasma density profile measured by ICE, and has a full-width-zero-intensity of about 30,000 km, very similar to the ICE values. H2O production rates for the comet are derived and compared with those of Comet P/Halley (1982i).

JET-SHOCKED H{sub 2} AND CO IN THE ANOMALOUS ARMS OF MOLECULAR HYDROGEN EMISSION GALAXY NGC 4258

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ogle, P. M.; Lanz, L.; Appleton, P. N., E-mail: ogle@ipac.caltech.edu

2014-06-20

We present a Spitzer Infrared Spectrograph map of H{sub 2} emission from the nearby galaxy NGC 4258 (Messier 106). The H{sub 2} emission comes from 9.4 ± 0.4 × 10{sup 6} M {sub ☉} of warm molecular hydrogen heated to 240-1040 K in the inner anomalous arms, a signature of jet interaction with the galaxy disk. The spectrum is that of a molecular hydrogen emission galaxy (MOHEG), with a large ratio of H{sub 2} over 7.7 μm polycyclic aromatic hydrocarbon emission (0.37), characteristic of shocked molecular gas. We find close spatial correspondence between the H{sub 2} and CO emission from the anomalousmore » arms. Our estimate of cold molecular gas mass based on CO emission is 10 times greater than our estimate of 1.0 × 10{sup 8} M {sub ☉} based on dust emission. We suggest that the X {sub CO} value is 10 times lower than the Milky Way value because of high kinetic temperature and enhanced turbulence. The H{sub 2} disk has been overrun and is being shocked by the jet cocoon, and much of the gas originally in the disk has been ejected into the galaxy halo in an X-ray hot outflow. We measure a modest star formation rate of 0.08 M {sub ☉} yr{sup –1} in the central 3.4 kpc{sup 2} that is consistent with the remaining gas surface density.« less

Fluorescent H2 Emission Lines from the Reflection Nebula NGC 7023 Observed with IGRINS

NASA Astrophysics Data System (ADS)

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

2017-05-01

We have analyzed the temperature, velocity, and density of H2 gas in NGC 7023 with a high-resolution near-infrared spectrum of the northwestern filament of the reflection nebula. By observing NGC 7023 in the H and K bands at R ≃ 45,000 with the Immersion GRating INfrared Spectrograph, we detected 68 H2 emission lines within the 1″ × 15″ slit. The diagnostic ratio of 2-1 S(1)/1-0 S(1) is 0.41-0.56. In addition, the estimated ortho-to-para ratio (OPR) is 1.63-1.82, indicating that the H2 emission transitions in the observed region arise mostly from gas excited by UV fluorescence. Gradients in the temperature, velocity, and OPR within the observed area imply motion of the photodissociation region (PDR) relative to the molecular cloud. In addition, we derive the column density of H2 from the observed emission lines and compare these results with PDR models in the literature covering a range of densities and incident UV field intensities. The notable difference between PDR model predictions and the observed data, in high rotational J levels of ν = 1, is that the predicted formation temperature for newly formed H2 should be lower than that of the model predictions. To investigate the density distribution, we combine pixels in 1″ × 1″ areas and derive the density distribution at the 0.002 pc scale. The derived gradient of density suggests that NGC 7023 has a clumpy structure, including a high clump density of ˜105 cm-3 with a size smaller than ˜5 × 10-3 pc embedded in lower-density regions of 103-104 cm-3.

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

NASA Astrophysics Data System (ADS)

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

2009-04-01

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

Continued observations of the H Ly alpha emission from Uranus

NASA Technical Reports Server (NTRS)

Clarke, J.; Durrance, S.; Moos, W.; Murthy, J.; Atreya, S.; Barnes, A.; Mihalov, J.; Belcher, J.; Festou, M.; Imhoff, C.

1986-01-01

Observations of Uranus obtained over four years with the IUE Observatory supports the initial identification of a bright H Ly alpha flux which varies independently of the solar H Ly alpha flux, implying a largely self-excited emission. An average brightness of 1400 Rayleighs is derived, and limits for the possible contribution by reflected solar H Ly alpha emission, estimated to be about 200 Rayleighs, suggest that the remaining self-excited emission is produced by an aurora. Based on comparison with solar wind measurements obtained in the vicinity of Uranus by Voyager 2 and Pioneer 11, no evidence for correlation between the solar wind density and the H Ly alpha brightness is found. The upper limit to H2 emission gives a lower limit to the ratio of H Ly alpha/H2 emissions of about 2.4, suggesting that the precipitating particles may be significantly less energetic on Uranus than those responsible for the aurora on Jupiter. The average power in precipitating particles is estimated to be of the order of 10 to the 12th W.

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

NASA Astrophysics Data System (ADS)

Sánchez-Monge, Á.; Beltrán, M. T.; Cesaroni, R.; Fontani, F.; Brand, J.; Molinari, S.; Testi, L.; Burton, M.

2013-02-01

Aims: We present Australia Telescope Compact Array (ATCA) observations of the H2O maser line and radio continuum at 18.0 GHz and 22.8 GHz toward a sample of 192 massive star-forming regions containing several clumps already imaged at 1.2 mm. The main aim of this study is to investigate the water maser and centimeter continuum emission (that likely traces thermal free-free emission) in sources at different evolutionary stages, using evolutionary classifications previously published. Methods: We used the recently comissioned Compact Array Broadband Backend (CABB) at ATCA that obtains images with ~20'' resolution in the 1.3 cm continuum and H2O maser emission in all targets. For the evolutionary analysis of the sources we used millimeter continuum emission from the literature and the infrared emission from the MSX Point Source Catalog. Results: We detect centimeter continuum emission in 88% of the observed fields with a typical rms noise level of 0.45 mJy beam-1. Most of the fields show a single radio continuum source, while in 20% of them we identify multiple components. A total of 214 cm continuum sources have been identified, that likely trace optically thin H ii regions, with physical parameters typical of both extended and compact H ii regions. Water maser emission was detected in 41% of the regions, resulting in a total of 85 distinct components. The low angular (~20'') and spectral (~14 km s-1) resolutions do not allow a proper analysis of the water maser emission, but suffice to investigate its association with the continuum sources. We have also studied the detection rate of H ii regions in the two types of IRAS sources defined in the literature on the basis of the IRAS colors: High and Low. No significant differences are found, with high detection rates (>90%) for both High and Low sources. Conclusions: We classify the millimeter and infrared sources in our fields in three evolutionary stages following the scheme presented previously: (Type 1) millimeter

Interstellar absorption in the Mg II resonance line k2 and h2 emissions

NASA Technical Reports Server (NTRS)

Boehm-Vitense, E.

1981-01-01

High-resolution (0.2 A) IUE spectra for the long wavelength range (1800-3000 A) have been studied. It is shown that narrow interstellar Mg II lines are seen in the center of the k2 and h2 emissions from nearby stars with large rotational velocities. For all observed stars, the radial velocity of the central k3 absorption component in the rest system of the star is strongly correlated with the mirror image of the radial velocity of the stars; this shows that a major fraction if not all of the k3 absorption is due to interstellar absorption in the solar neighborhood. The violet to red asymmetry of the k2 emission also correlates with the radial velocities of the star; this shows that the shift of k3 is due to the velocity shift of the local interstellar cloud with respect to the star.

Hydrogenated Polycyclic Aromatic Hydrocarbons and the 2940 and 2850 Wavenumber (3.40 and 3.51 micron) Infrared Emission Features

NASA Technical Reports Server (NTRS)

Bernstein, Max P.; Sandford, Scott A.; Allamadola, Louis J.

1996-01-01

The 3150-2700/cm (3.17-3.70 micron) range of the spectra of a number of Ar-matrix-isolated PAHs containing excess H atoms (H(sub n)-PAHS) are presented. This region covers features produced by aromatic and aliphatic C-H stretching vibrations as well as overtone and combination bands involving lower lying fundamentals. The aliphatic C-H stretches in molecules of this type having low to modest excess H coverage provide excellent fits to a number of the weak emission features superposed on the plateau between 3080 and 2700/cm (3.25 and 3.7 micron) in the spectra of many planetary nebulae, reflection nebulae, and H II regions. Higher H coverage is implied for a few objects. We compare these results in context with the other suggested identifications of the emission features in the 2950-2700/cm (3.39-3.70 micron) region and briefly discuss their astrophysical implications.

Detection of H-alpha emission in the hot white dwarf G191-B2B

NASA Astrophysics Data System (ADS)

Reid, Neill; Wegner, Gary

1988-12-01

High-resolution spectra of G191-B2B, the hottest known DA white dwarf were obtained which reveal emission in the core of the H-alpha line. The observations show little variation in the line profile over a period of four days, ruling out line-doubling in a close binary as an explanation. The observed emission cannot be due to a nearby red dwarf companion, while the absence of any spatially extended emission argues against either a planetary nebula remnant or local ionization of the interstellar medium. The determination of the systemic velocity, using the companion red dwarf G191-B2A, is 5 + or - 2 km/s and shows that both the H-alpha emission and the high-excitation species observed in the ultraviolet are redshifted by 19 + or - 3 km/s, suggesting a photospheric origin. The low redshift implies a mass of 0.45 solar mass for this hot white dwarf, although the uncertainties in the effective temperature and parallax permit masses in the range 0.29 to 0.60 solar mass.

High-resolution spectroscopy of Saturn at 3 microns: CH 4, CH 3D, C 2H 2, C 2H 6, PH 3, clouds, and haze

NASA Astrophysics Data System (ADS)

Kim, Joo Hyeon; Kim, Sang J.; Geballe, Thomas R.; Kim, Sungsoo S.; Brown, Linda R.

2006-12-01

We report observation and analysis of a high-resolution 2.87-3.54 μm spectrum of the southern temperate region of Saturn obtained with NIRSPEC at Keck II. The spectrum reveals absorption and emission lines of five molecular species as well as spectral features of haze particles. The ν+ν band of CH 3D is detected in absorption between 2.87 and 2.92 μm; and we derived from it a mixing ratio approximately consistent with the Infrared Space Observatory result. The ν band of C 2H 2 also is detected in absorption between 2.95 and 3.05 μm; analysis indicates a sudden drop in the C 2H 2 mixing ratio at 15 mbar (130 km above the 1 bar level), probably due to condensation in the low stratosphere. The presence of the ν+ν+ν band of C 2H 6 near 3.07 μm, first reported by Bjoraker et al. [Bjoraker, G.L., Larson, H.P., Fink, U., 1981. Astrophys. J. 248, 856-862], is confirmed, and a C 2H 6 condensation altitude of 10 mbar (140 km) in the low stratosphere is determined. We assign weak emission lines within the 3.3 μm band of CH 4 to the ν band of C 2H 6, and derive a mixing ratio of 9±4×10 for this species. Most of the C 2H 6 3.3 μm line emission arises in the altitude range 460-620 km (at ˜μbar pressure levels), much higher than the 160-370 km range where the 12 μm thermal molecular line emission of this species arises. At 2.87-2.90 μm the major absorber is tropospheric PH 3. The cloud level determined here and at 3.22-3.54 is 390-460 mbar (˜30 km), somewhat higher than found by Kim and Geballe [Kim, S.J., Geballe, T.R., 2005. Icarus 179, 449-458] from analysis of a low resolution spectrum. A broad absorption feature at 2.96 μm, which might be due to NH 3 ice particles in saturnian clouds, is also present. The effect of a haze layer at about 125 km (˜12 mbar level) on the 3.20-3.54 μm spectrum, which was not apparent in the low resolution spectrum, is clearly evident in the high resolution data, and the spectral properties of the haze particles suggest that

Fluorescent H{sub 2} Emission Lines from the Reflection Nebula NGC 7023 Observed with IGRINS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le, Huynh Anh N.; Pak, Soojong; Lee, Hye-In

We have analyzed the temperature, velocity, and density of H{sub 2} gas in NGC 7023 with a high-resolution near-infrared spectrum of the northwestern filament of the reflection nebula. By observing NGC 7023 in the H and K bands at R ≃ 45,000 with the Immersion GRating INfrared Spectrograph, we detected 68 H{sub 2} emission lines within the 1″ × 15″ slit. The diagnostic ratio of 2-1 S(1)/1-0 S(1) is 0.41−0.56. In addition, the estimated ortho-to-para ratio (OPR) is 1.63−1.82, indicating that the H{sub 2} emission transitions in the observed region arise mostly from gas excited by UV fluorescence. Gradients inmore » the temperature, velocity, and OPR within the observed area imply motion of the photodissociation region (PDR) relative to the molecular cloud. In addition, we derive the column density of H{sub 2} from the observed emission lines and compare these results with PDR models in the literature covering a range of densities and incident UV field intensities. The notable difference between PDR model predictions and the observed data, in high rotational J levels of ν = 1, is that the predicted formation temperature for newly formed H{sub 2} should be lower than that of the model predictions. To investigate the density distribution, we combine pixels in 1″ × 1″ areas and derive the density distribution at the 0.002 pc scale. The derived gradient of density suggests that NGC 7023 has a clumpy structure, including a high clump density of ∼10{sup 5} cm{sup −3} with a size smaller than ∼5 × 10{sup −3} pc embedded in lower-density regions of 10{sup 3}–10{sup 4} cm{sup −3}.« less

H2 Fluorescence in M Dwarf Systems: A Stellar Origin

NASA Astrophysics Data System (ADS)

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

2017-08-01

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

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

PubMed

Moreno, Lyman; Predicala, Bernardo; Nemati, Mehdi

2010-04-01

The effects of manure age on emission of H(2)S and required level of nitrite or molybdate to control these emissions were investigated in the present work. Molybdate mediated control of H(2)S emission was also studied in semi-pilot scale open systems, and in specifically designed chambers which simulated swine production rooms. With fresh 1-, 3- and 6-month old manures average H(2)S concentration in the headspace gas of the closed systems were 4856+/-460, 3431+/-208, 1037+/-98 ppm and non-detectable, respectively. Moreover, the level of nitrite or molybdate required to control the emission of H(2)S decreased as manure age increased. In the semi-pilot scale open system and chambers, average H(2)S concentration at the surface of agitated fresh manure were 831+/-26 and 88.4+/-5.7 ppm, respectively. Furthermore, 0.1-0.25 mM molybdate was sufficient to control the emission of H(2)S. A cost study for an average size swine operation showed that the cost of treatment with molybdate was less than 1% of the overall production cost for each market hog. Copyright 2009 Elsevier Ltd. All rights reserved.

Observations of CH4, C2H6, and C2H2 in the stratosphere of Jupiter

NASA Technical Reports Server (NTRS)

Sada, P. V.; Bjoraker, G. L.; Jennings, D. E.; McCabe, G. H.; Romani, P. N.

1998-01-01

We have performed high-resolution spectral observations at mid-infrared wavelengths of CH4 (8.14 micrometers), C2H6 (12.16 micrometers), and C2H2 (13.45 micrometers) on Jupiter. These emission features probe the stratosphere of the planet and provide information on the carbon-based photochemical processes taking place in that region of the atmosphere. The observations were performed using our cryogenic echelle spectrometer CELESTE, in conjunction with the McMath-Pierce 1.5-m solar telescope between November 1994 and February 1995. We used the methane observations to derive the temperature profile of the jovian atmosphere in the 1-10 mbar region of the stratosphere. This profile was then used in conjunction with height-dependent mixing ratios of each hydrocarbon to determine global abundances for ethane and acetylene. The resulting mixing ratios are 3.9(+1.9)(-1.3) x 10(-6) for C2H6 (5 mbar pressure level), and 2.3 +/- 0.5 x 10(-8) for C2H2 (8 mbar pressure level), where the quoted uncertainties are derived from model variations in the temperature profile which match the methane observation uncertainties. c1998 Academic Press.

ON THE ORIGINS OF THE DIFFUSE H{alpha} EMISSION: IONIZED GAS OR DUST-SCATTERED H{alpha} HALOS?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seon, Kwang-Il; Witt, Adolf N., E-mail: kiseon@kasi.re.kr

2012-10-20

It is known that the diffuse H{alpha} emission outside of bright H II regions not only are very extended, but also can occur in distinct patches or filaments far from H II regions, and the line ratios of [S II] {lambda}6716/H{alpha} and [N II] {lambda}6583/H{alpha} observed far from bright H II regions are generally higher than those in the H II regions. These observations have been regarded as evidence against the dust-scattering origin of the diffuse H{alpha} emission (including other optical lines), and the effect of dust scattering has been neglected in studies on the diffuse H{alpha} emission. In thismore » paper, we reexamine the arguments against dust scattering and find that the dust-scattering origin of the diffuse H{alpha} emission cannot be ruled out. As opposed to the previous contention, the expected dust-scattered H{alpha} halos surrounding H II regions are, in fact, in good agreement with the observed H{alpha} morphology. We calculate an extensive set of photoionization models by varying elemental abundances, ionizing stellar types, and clumpiness of the interstellar medium (ISM) and find that the observed line ratios of [S II]/H{alpha}, [N II]/H{alpha}, and He I {lambda}5876/H{alpha} in the diffuse ISM accord well with the dust-scattered halos around H II regions, which are photoionized by late O- and/or early B-type stars. We also demonstrate that the H{alpha} absorption feature in the underlying continuum from the dust-scattered starlight ({sup d}iffuse galactic light{sup )} and unresolved stars is able to substantially increase the [S II]/H{alpha} and [N II]/H{alpha} line ratios in the diffuse ISM.« less

Reduction in soil N2O emissions by pH manipulation and enhanced nosZ gene transcription under different water regimes.

PubMed

Shaaban, Muhammad; Wu, Yupeng; Khalid, Muhammad Salman; Peng, Qi-An; Xu, Xiangyu; Wu, Lei; Younas, Aneela; Bashir, Saqib; Mo, Yongliang; Lin, Shan; Zafar-Ul-Hye, Muhammad; Abid, Muhammad; Hu, Ronggui

2018-04-01

Several studies have been carried out to examine nitrous oxide (N 2 O) emissions from agricultural soils in the past. However, the emissions of N 2 O particularly during amelioration of acidic soils have been rarely studied. We carried out the present study using a rice-rapeseed rotation soil (pH 5.44) that was amended with dolomite (0, 1 and 2 g kg -1 soil) under 60% water filled pore space (WFPS) and flooding. N 2 O emissions and several soil properties (pH, NH 4 + N, NO 3 - -N, and nosZ gene transcripts) were measured throughout the study. The increase in soil pH with dolomite application triggered soil N transformation and transcripts of nosZ gene controlling N 2 O emissions under both water regimes (60% WFPS and flooding). The 60% WFPS produced higher soil N 2 O emissions than that of flooding, and dolomite largely reduced N 2 O emissions at higher pH under both water regimes through enhanced transcription of nosZ gene. The results suggest that ameliorating soil acidity with dolomite can substantially mitigate N 2 O emissions through promoting nosZ gene transcription. Copyright © 2017 Elsevier Ltd. All rights reserved.

Measuring H2O and CO2 Emissions in the Mud Volcano region of Yellowstone using Open Path FTIR

NASA Astrophysics Data System (ADS)

Moyer, D. K.; Sealing, C. R.; Carn, S. A.; Vanderkluysen, L.

2017-12-01

Magma degassing is an important factor in many aspects of monitoring active volcanic zones and mitigating associated hazards. The monitoring of these emissions in concentration, flux, and species ratios is important for detecting signs of unrest as well as understanding the natural cycle and budget of volatile species. However, standard gas measurement methods suffer from either low temporal resolution (e.g., direct sampling of fumaroles) or are limited to measuring a small range of species (e.g., MiniDOAS, MultiGAS). In order to establish a carbon budget of active gas sources at a volcano with a dynamic hydrothermal system, we carried out a survey of mud pots and fumaroles at Yellowstone National Park using Open-Path Fourier Transform Infrared Spectroscopy, or OP-FTIR, which allows for a temporal resolution as low as one measurement every 10 seconds. We placed an active infrared (IR) source behind the target gas plume and identified gas species from the presence of their absorption feature in measured spectra in the 2.5 to 25 µm range. From these, we derived pathlength concentrations for a wide range of gases, including: water vapor, carbon dioxide, and methane. During our September 2016 campaign in the Mud Volcano thermal area, we measured CO2 concentrations of 400 ppm in emissions from the Churning Cauldron acid-sulfate mud pot, with an H2O/CO2 ratio of 8; at Sulphur Cauldron and One Hundred Springs Plain, CO2 concentrations reached 200 ppm above background atmospheric values. We derived a CO2 flux of 8.15 T/d, 0.43 T/d and .00025 T/d, respectively, at these three acid-sulfate sources, within range of gas channeling-based estimates from the late 1990s. Previous accumulation chamber studies estimate the CO2 soil diffuse degassing in the Mud Volcano thermal region at 283.15 T/d, indicating that mud pots are minor contributors of CO2 emissions in this area, representing 3% of diffuse emissions. Due to the high acquisition rate and the abundance of water droplets

Differential effects of buffer pH on Ca2+-induced ROS emission with inhibited mitochondrial complexes I and III

PubMed Central

Lindsay, Daniel P.; Camara, Amadou K. S.; Stowe, David F.; Lubbe, Ryan; Aldakkak, Mohammed

2015-01-01

Excessive mitochondrial reactive oxygen species (ROS) emission is a critical component in the etiology of ischemic injury. Complex I and complex III of the electron transport chain are considered the primary sources of ROS emission during cardiac ischemia and reperfusion (IR) injury. Several factors modulate ischemic ROS emission, such as an increase in extra-matrix Ca2+, a decrease in extra-matrix pH, and a change in substrate utilization. Here we examined the combined effects of these factors on ROS emission from respiratory complexes I and III under conditions of simulated IR injury. Guinea pig heart mitochondria were suspended in experimental buffer at a given pH and incubated with or without CaCl2. Mitochondria were then treated with either pyruvate, a complex I substrate, followed by rotenone, a complex I inhibitor, or succinate, a complex II substrate, followed by antimycin A, a complex III inhibitor. H2O2 release rate and matrix volume were compared with and without adding CaCl2 and at pH 7.15, 6.9, or 6.5 with pyruvate + rotenone or succinate + antimycin A to simulate conditions that may occur during in vivo cardiac IR injury. We found a large increase in H2O2 release with high [CaCl2] and pyruvate + rotenone at pH 6.9, but not at pHs 7.15 or 6.5. Large increases in H2O2 release rate also occurred at each pH with high [CaCl2] and succinate + antimycin A, with the highest levels observed at pH 7.15. The increases in H2O2 release were associated with significant mitochondrial swelling, and both H2O2 release and swelling were abolished by cyclosporine A, a desensitizer of the mitochondrial permeability transition pore (mPTP). These results indicate that ROS production by complex I and by complex III is differently affected by buffer pH and Ca2+ loading with mPTP opening. The study suggests that changes in the levels of cytosolic Ca2+ and pH during IR alter the relative amounts of ROS produced at mitochondrial respiratory complex I and complex III. PMID

An alternative mechanism for production of emission features in some infrared objects

NASA Technical Reports Server (NTRS)

Apruzese, J. P.

1975-01-01

Two dust-envelope models of the M supergiant VX Sgr, which exhibits a prominent emission feature at 10 microns, are presented. The models indicate that, for certain envelope sizes, the presence of the observed emission feature does not necessarily indicate that the emitting grains possess a similar feature in their emissivity profile. The mechanism which may in some cases be producing the observed emission feature is discussed.

CO in Hickson compact group galaxies with enhanced warm H2 emission: Evidence for galaxy evolution?

NASA Astrophysics Data System (ADS)

Lisenfeld, U.; Appleton, P. N.; Cluver, M. E.; Guillard, P.; Alatalo, K.; Ogle, P.

2014-10-01

Context. Galaxies in Hickson Compact Groups (HCGs) are believed to experience morphological transformations from blue, star-forming galaxies to red, early-type galaxies. Galaxies with a high ratio between the luminosities of the warm H2 to the 7.7 μm PAH emission (so-called Molecular Hydrogen Emission Galaxies, MOHEGs) are predominantly in an intermediate phase, the green valley. Their enhanced H2 emission suggests that the molecular gas is affected in the transition. Aims: We study the properties of the molecular gas traced by CO in galaxies in HCGs with measured warm H2 emission in order to look for evidence of the perturbations affecting the warm H2 in the kinematics, morphology and mass of the molecular gas. Methods: We observed the CO(1-0) emission of 20 galaxies in HCGs and complemented our sample with 11 CO(1-0) spectra from the literature. Most of the galaxies have measured warm H2 emission, and 14 of them are classified as MOHEGs. We mapped some of these galaxies in order to search for extra-galactic CO emission. We analyzed the molecular gas mass derived from CO(1-0), MH2, and its kinematics, and then compared it to the mass of the warm molecular gas, the stellar mass and star formation rate (SFR). Results: Our results are the following. (i) The mass ratio between the CO-derived and the warm H2 molecular gas is in the same range as found for field galaxies. (ii) Some of the galaxies, mostly MOHEGs, have very broad CO linewidths of up to 1000 km s-1 in the central pointing. The line shapes are irregular and show various components. (iii) In the mapped objects we found asymmetric distributions of the cold molecular gas. (iv) The star formation efficiency (=SFR/MH2) of galaxies in HCGs is very similar to isolated galaxies. No significant difference between MOHEGs and non-MOHEGs or between early-type and spiral galaxies has been found. In a few objects the SFE is significantly lower, indicating the presence of molecular gas that is not actively forming stars

Modelling the ArH+ emission from the Crab nebula

NASA Astrophysics Data System (ADS)

Priestley, F. D.; Barlow, M. J.; Viti, S.

2017-12-01

We have performed combined photoionization and photodissociation region (PDR) modelling of a Crab nebula filament subjected to the synchrotron radiation from the central pulsar wind nebula, and to a high flux of charged particles; a greatly enhanced cosmic-ray ionization rate over the standard interstellar value, ζ0, is required to account for the lack of detected [C I] emission in published Herschel SPIRE FTS observations of the Crab nebula. The observed line surface brightness ratios of the OH+ and ArH+ transitions seen in the SPIRE FTS frequency range can only be explained with both a high cosmic-ray ionization rate and a reduced ArH+ dissociative recombination rate compared to that used by previous authors, although consistent with experimental upper limits. We find that the ArH+/OH+ line strengths and the observed H2 vibration-rotation emission can be reproduced by model filaments with nH = 2 × 104 cm-3, ζ = 107ζ0 and visual extinctions within the range found for dusty globules in the Crab nebula, although far-infrared emission from [O I] and [C II] is higher than the observational constraints. Models with nH = 1900 cm-3 underpredict the H2 surface brightness, but agree with the ArH+ and OH+ surface brightnesses and predict [O I] and [C II] line ratios consistent with observations. These models predict HeH+ rotational emission above detection thresholds, but consideration of the formation time-scale suggests that the abundance of this molecule in the Crab nebula should be lower than the equilibrium values obtained in our analysis.

Uncommon and Emissive {[Au2(C3H6NS2)2][Au(C3H6NS2)2]2(PF6)2} Mixed Au+ and Au3+ Pseudotetranuclear Crystalline Compound: Synthesis, Structural Characterization, and Optical Properties.

PubMed

Langaro, Ana P; Souza, Ana K R; Morassuti, Claudio Y; Lima, Sandro M; Casagrande, Gleison A; Deflon, Victor M; Nunes, Luiz A O; Da Cunha Andrade, Luis H

2016-11-23

An uncommon emissive pseudotetranuclear compound, {[Au 2 (C 3 H 6 NS 2 ) 2 ][Au(C 3 H 6 NS 2 ) 2 ] 2 (PF 6 ) 2 }, was synthesized and characterized in terms of its structure and optical properties. The synthesis produced a crystalline compound composed of four gold atoms with two different oxidation states (Au + and Au 3+ ) in the same crystalline structure. The title complex belonged to a triclinic crystalline system involving the centrosymmetric P1̅ space group. X-ray diffractometry and vibrational spectroscopy (infrared, Raman, and SERS) were used for structural characterization of the new crystal. The vibrational spectroscopy techniques supported the X-ray diffraction results and confirmed the presence of bonds including Au-Au and Au-S. Optical characterization performed using UV-vis spectroscopy showed that under ultraviolet excitation, the emissive crystalline complex presented characteristic broad luminescent bands centered at 420 and 670 nm.

Calibration of H-alpha/H-beta Indexes for Emission Line Objects

NASA Astrophysics Data System (ADS)

Hintz, Eric G.; Joner, Michael D.

2016-01-01

In Joner and Hintz (2015) they report on a standard star system for calibration of H-alpha and H-beta observations. This work was based on data obtained with the Dominion Astrophysical Observatory 1.2-m telescope. As part of the data acquisition for that project, a large number of emission line objects were also observed. We will report on the preliminary results for the emission line data set. This will include a comparison of equivalent width measurements of each line with the matching index. We will also examine the relation between the absorption line objects previously published and the emission line objects, along with a discussion of the transition point. Object types included are Be stars, high mass x-ray binaries, one low mass x-ray binary, Herbig Ae/Be stars, pre-main sequence stars, T Tauri stars, young stellar objects, and one BY Draconis star. Some of these objects come from Cygnus OB-2, NGC 659, NGC 663, NGC 869 and NGC 884.

Intrinsic polarization changes and the H-alpha and CA II emission features in T-Tauri stars

NASA Astrophysics Data System (ADS)

Svatos, J.; Solc, M.

1981-12-01

On the basis of the correlation between polarization and emission features observed in certain T-Tauri stars, it is concluded that flaring effects associated with UV and/or X-ray irradiation and with increased magnetic field are responsible for the intrinsic polarization changes in T-Tauri stars. The correlation between emission Ca II lines and polarization degree both in Miras and T-Tau stars is thought to support the contention that the intrinsic polarization changes are due to the irradiation of silicate-like grains. In some T-Tau stars the increase in the magnetic field can be the principal agent causing the polarization increase due to the enhanced orientation of elongated grains.

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

Energetic ion, atom, and molecule reactions and excitation in low-current H2 discharges: H(alpha) Doppler profiles.

PubMed

Petrović, Z Lj; Phelps, A V

2009-12-01

Absolute spectral emissivities for Doppler broadened H(alpha) profiles are measured and compared with predictions of energetic hydrogen ion, atom, and molecule behavior in low-current electrical discharges in H2 at very high electric field E to gas density N ratios E/N and low values of Nd , where d is the parallel-plate electrode separation. These observations reflect the energy and angular distributions for the excited atoms and quantitatively test features of multiple-scattering kinetic models in weakly ionized hydrogen in the presence of an electric field that are not tested by the spatial distributions of H(alpha) emission. Absolute spectral intensities agree well with predictions. Asymmetries in Doppler profiles observed parallel to the electric field at 4H atoms directed toward the cathode and diffusely reflected from the cathode. (1 Td=10(-21) V m(2)) The effects of reflection of hydrogen particles and of changes with cathode material are modeled accurately without adjustable parameters. Maximum measured wavelength shifts result from acceleration of H+ ions and charge transfer to fast H atoms. The Doppler profiles are consistent with models of reactions among H+, H2+, H3 , H, and H2 leading to fast H atoms and then fast excited H(n=3) atoms.

Cesium Platinide Hydride 4Cs 2 Pt-CsH: An Intermetallic Double Salt Featuring Metal Anions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smetana, Volodymyr; Mudring, Anja-Verena

2016-10-24

With Cs9Pt4H a new representative of ionic compounds featuring metal anions can be added to this rare-membered family. Cs 9Pt 4H exhibits a complex crystal structure containing Cs + cations, Pt 2- and H - anions. Being a red, transparent compound its band gap is in the visible range of the electromagnetic spectrum and the ionic type of bonding is confirmed by quantum chemical calculations. This cesium platinide hydride can formally be considered as a double salt of the “alloy” cesium–platinum, or better cesium platinide, Cs2Pt, and the salt cesium hydride CsH according to Cs 9Pt 4H≡4 Cs 2Pt∙CsH.

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

NASA Astrophysics Data System (ADS)

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

2016-06-01

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

PDR MODEL MAPPING OF OBSCURED H{sub 2} EMISSION AND THE LINE-OF-SIGHT STRUCTURE OF M17-SW

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheffer, Y.; Wolfire, M. G.

2013-09-01

We observed H{sub 2} line emission with Spitzer-IRS toward M17-SW and modeled the data with our photon-dominated region (PDR) code. Derived gas density values of up to few times 10{sup 7} cm{sup -3} indicate that H{sub 2} emission originates in high-density clumps. We discover that the PDR code can be utilized to map the amount of intervening extinction obscuring the H{sub 2} emission layers, and thus we obtain the radial profile of A{sub V} relative to the central ionizing cluster NGC 6618. The extinction has a positive radial gradient, varying between 15-47 mag over the projected distance of 0.9-2.5 pcmore » from the primary ionizer, CEN 1. These high extinction values are in good agreement with previous studies of A{sub V} toward stellar targets in M17-SW. The ratio of data to PDR model values is used to infer the global line-of-sight structure of the PDR surface, which is revealed to resemble a concave surface relative to NGC 6618. Such a configuration confirms that this PDR can be described as a bowl-shaped boundary of the central H II region in M17. The derived structure and physical conditions are important for interpreting the fine-structure and rotational line emission from the PDR.« less

The structure of (CENP-A-H4) 2 reveals physical features that mark centromeres

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sekulic, Nikolina; Bassett, Emily A; Rogers, Danielle J

2010-09-20

Centromeres are specified epigenetically, and the histone H3 variant CENP-A is assembled into the chromatin of all active centromeres. Divergence from H3 raises the possibility that CENP-A generates unique chromatin features to mark physically centromere location. Here we report the crystal structure of a subnucleosomal heterotetramer, human (CENP-A-H4) 2, that reveals three distinguishing properties encoded by the residues that comprise the CENP-A targeting domain (CATD; ref. 2): (1) a CENP-A-CENP-A interface that is substantially rotated relative to the H3-H3 interface; (2) a protruding loop L1 of the opposite charge as that on H3; and (3) strong hydrophobic contacts that rigidifymore » the CENP-A-H4 interface. Residues involved in the CENP-A-CENP-A rotation are required for efficient incorporation into centromeric chromatin, indicating specificity for an unconventional nucleosome shape. DNA topological analysis indicates that CENP-A-containing nucleosomes are octameric with conventional left-handed DNA wrapping, in contrast to other recent proposals. Our results indicate that CENP-A marks centromere location by restructuring the nucleosome from within its folded histone core.« less

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

NASA Technical Reports Server (NTRS)

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

1986-01-01

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

Extended analysis of the 5g. -->. 4f emissions in H/sub 2/

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, E.S.; Pulchtopek, S.; Eyler, E.E.

1984-01-15

An analysis starting from Hund's case d has been used to extend the work of Herzberg and Jungen on the 5g..-->..4f emissions in H/sub 2/. A simple analytical expression for the line intensities is presented that agrees with their calculations is about 1%. All of the experimentally observed lines have been accounted for by including higher vibrational levels in our calculations.

The comparison of pathology in ferrets infected by H9N2 avian influenza viruses with different genomic features.

PubMed

Gao, Rongbao; Bai, Tian; Li, Xiaodan; Xiong, Ying; Huang, Yiwei; Pan, Ming; Zhang, Ye; Bo, Hong; Zou, Shumei; Shu, Yuelong

2016-01-15

H9N2 avian influenza virus circulates widely in poultry and has been responsible for sporadic human infections in several regions. Few studies have been conducted on the pathogenicity of H9N2 AIV isolates that have different genomic features. We compared the pathology induced by a novel reassortant H9N2 virus and two currently circulating H9N2 viruses that have different genomic features in ferrets. The results showed that the three viruses can induce infections with various amounts of viral shedding in ferrets. The novel H9N2 induced respiratory infection, but no pathological lesions were observed in lung tissues. The other two viruses induced mild to intermediate pathological lesions in lung tissues, although the clinical signs presented mildly in ferrets. The pathological lesions presented a diversity consistent with viral replication in ferrets. Copyright © 2015 Elsevier Inc. All rights reserved.

Relationship between x-ray emission and absorption spectroscopy and the local H-bond environment in water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhovtobriukh, Iurii; Besley, Nicholas A.; Fransson, Thomas

Here, the connection between specific features in the water X-ray absorption spectrum and X-ray emission spectrum (XES) and the local H-bond coordination is studied based on structures obtained from path-integral molecular dynamics simulations using either the opt-PBE-vdW density functional or the MB-pol force field. Computing the XES spectrum using all molecules in a snapshot results in only one peak in the lone-pair (1b 1) region, while the experiment shows two peaks separated by 0.8-0.9 eV. Different H-bond configurations were classified based on the local structure index (LSI) and a geometrical H-bond cone criterion. We find that tetrahedrally coordinated molecules characterizedmore » by high LSI values and two strong donated and two strong accepted H-bonds contribute to the low energy 1b 1 emission peak and to the post-edge region in absorption. Molecules with the asymmetric H-bond environment with one strong accepted H-bond and one strong donated H-bond and low LSI values give rise to the high energy 1b 1 peak in the emission spectrum and mainly contribute to the pre-edge and main-edge in the absorption spectrum. The 1b 1 peak splitting can be increased to 0.62 eV by imposing constraints on the H-bond length, i.e., for very tetrahedral structures short H-bonds (less than 2.68 Å) and for very asymmetric structures elongated H-bonds (longer than 2.8 Å). Such structures are present, but underrepresented, in the simulations which give more of an average of the two extremes.« less

Relationship between x-ray emission and absorption spectroscopy and the local H-bond environment in water

DOE PAGES

Zhovtobriukh, Iurii; Besley, Nicholas A.; Fransson, Thomas; ...

2018-04-14

Here, the connection between specific features in the water X-ray absorption spectrum and X-ray emission spectrum (XES) and the local H-bond coordination is studied based on structures obtained from path-integral molecular dynamics simulations using either the opt-PBE-vdW density functional or the MB-pol force field. Computing the XES spectrum using all molecules in a snapshot results in only one peak in the lone-pair (1b 1) region, while the experiment shows two peaks separated by 0.8-0.9 eV. Different H-bond configurations were classified based on the local structure index (LSI) and a geometrical H-bond cone criterion. We find that tetrahedrally coordinated molecules characterizedmore » by high LSI values and two strong donated and two strong accepted H-bonds contribute to the low energy 1b 1 emission peak and to the post-edge region in absorption. Molecules with the asymmetric H-bond environment with one strong accepted H-bond and one strong donated H-bond and low LSI values give rise to the high energy 1b 1 peak in the emission spectrum and mainly contribute to the pre-edge and main-edge in the absorption spectrum. The 1b 1 peak splitting can be increased to 0.62 eV by imposing constraints on the H-bond length, i.e., for very tetrahedral structures short H-bonds (less than 2.68 Å) and for very asymmetric structures elongated H-bonds (longer than 2.8 Å). Such structures are present, but underrepresented, in the simulations which give more of an average of the two extremes.« less

The discovery of a new infrared emission feature at 1905 wavenumbers (5.25 microns) in the spectrum of BD +30 degrees 3639 and its relation to the polycyclic aromatic hydrocarbon model

NASA Technical Reports Server (NTRS)

Allamandola, L. J.; Bregman, J. D.; Sandford, S. A.; Tielens, A. G.; Witteborn, F. C.; Wooden, D. H.; Rank, D.

1989-01-01

We have discovered a new IR emission feature at 1905 cm-1 (5.25 microns) in the spectrum of BD +30 degrees 3639. This feature joins the family of well-known IR emission features at 3040, 2940, 1750, 1610, "1310," 1160, and 890 cm-1 (3.3, 3.4, 5.7, 6.2, "7.7," 8.6, and 11.2 microns). The origin of this new feature is discussed and it is assigned to an overtone or combination band involving C-H bending modes of polycyclic aromatic hydrocarbons (PAHs). Laboratory work suggests that spectral studies of the 2000-1650 cm-1 (5.0-6.1 microns) region may be very useful in elucidating the molecular structure of interstellar PAHs. The new feature, in conjunction with other recently discovered spectral structure, suggests that the narrow IR emission features originate in PAH molecules rather than large carbon grains. Larger species are likely to be the source of the broad underlying "plateaus" seen in many of the spectra.

C-H Hot Bands in the Near-IR Emission Spectra of Leonids

NASA Technical Reports Server (NTRS)

Freund, F. T.; Scoville, J.; Holm, R.; Seelemann, R.; Freund, M. M.

2002-01-01

The reported infrared (IR) emission spectra from 1999 Leonid fireballs show a 3.4 micron C-H emission band and unidentified bands at longer wavelengths. Upon atmospheric entry, the Leonid meteorites were flash-heated to temperatures around 2400K, which would destroy any organics on the surface of the meteorite grains. We propose that the nu(sub )CH emission band in the Leonid emission spectra arises from matrix-embedded C(sub n)-H-O entities that are protected from instant pyrolysis. Our model is based on IR absorption nu(sub )CH bands, which we observed in laboratory-grown MgO and natural olivine single crystals, where they arise from C(sub n)-H-O units imbedded in the mineral matrix, indicative of aliphatic -CH2- and -CH3 organics. Instead of being pyrolyzed, the C(sub n)-H-O entities in the Leonid trails become vibrationally excited to higher levels n = 1, 2, 3 etc. During de-excitation they emit at 3.4 microns, due to the (0 => 1) transition, and at longer wavelengths, due to hot bands. As a first step toward verifying this hypothesis we measured the C-H vibrational manifold of hexane (C6H14). The calculated positions of the (2 => l ) , (3 => 2), and possibly (4 => 3) hot bands agree with the Leonid emission bands at 3.5, 3.8 and 4.l microns.

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

NASA Astrophysics Data System (ADS)

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

2012-11-01

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

The IR emission features - Emission from PAH molecules and amorphous carbon particles

NASA Technical Reports Server (NTRS)

Allamandola, L. J.; Tielens, A. G. G. M.; Barker, J. R.

1987-01-01

Given the current understanding of polycyclic aromatic hydrocarbons (PAHs), the spectroscopic data suggest that are at least two components which contribute to the interstellar emission spectrum: (1) free molecule-sized PAHs producing the narrow features and (2) amorphous carbon particles (which are primarily composed of an irregular 'lattice' of PAHs) contributing to the broad underlying components. An exact treatment of the IR fluorescence from highly vibrationally excited large molecules demonstrates that species containing between 20 and 30 carbon atoms are responsible for the narrow features, although the spectra match more closely with the spectra of amorphous carbon particles. It is concluded that, since little is known about the spectroscopic properties of free PAHs and PAH clusters, much laboratory work is required along with an observational program focusing on the spatial characteristics of the spectra.

A Calibrated H-alpha Index to Monitor Emission Line Objects

NASA Astrophysics Data System (ADS)

Hintz, Eric G.; Joner, M. D.

2013-06-01

Over an 8 year period we have developed a calibrated H-alpha index, similar to the more traditional H-beta index, based on spectrophotometric observations (Joner & Hintz, 2013) from the DAO 1.2-m Telescope. While developing the calibration for this filter set we also obtained spectra of a number of emission line systems such as high mass x-ray binaries (HMXB), Be stars, and young stellar objects. From this work we find that the main sequence stars fill a very tight relation in the H-alpha/H-beta plane and that the emission line objects are easily detected. We will present the overall location of these emission line objects. We will also present the changes experiences by these objects over the course of the years of the project.

Origin, Emission, and Propagation of P-H Pulses

NASA Astrophysics Data System (ADS)

Kikuchi, H.

2007-05-01

Origin, Emission, and Propagation of P-H Pulses H. Kikuchi Institute for Environmental Electromagnetics 3-8-18, Komagome, Toshima-ku, Tokyo 170, Japan e-mail: hkikuchi@mars.dti.ne.jp Abstract According to Pulinets, characters of P-H pulses is following. The registered emission has not continuous but pulsed character and has very wide frequency spectrum from kHz to more than hundred MHz. These two facts imply that should be the electric discharge-like emission similar to thunderstorm flashes emission. The emission is connected in some way with seismic activity and the emission intensity increases 12-24 hour before the seismic shock. Another intriguing factor is that emission is registered at large distances up to 500 km (some witness claim up to 1500 km). Taking into account that emission is registered at VHF band also, the source of emission cannot be situated on the ground. This paper puts forwards a model of P-H pulses generation based on "dust dynamics". Rotating ions ascending, for instance erupped metalic ions in the earth's crust into the atmosphere incorporating aerosols might be captured by diffuse dust layers which may exist below or beyond the electric mirror point produced by quadrupole-like thunder- cloud configurations or even form a portion of dust layers and could be a source-origin of P-H pulses that might be emitted by local electric discharges within diffuse dust layers somewhat similar to thundercloud discharges, though emission frequencies and characters are quite different, namely P-H pulses are over a wide range of frequencies, say from kHz to more than hundred MHz with pulsed character in contrast to lightning emission with more continuous character whose frequencies are 1 to 10 kHz. Such diffuse dust layers could be formed over a wide range of height in the troposphere, stratosphere, mesosphere and the thermosphere. Propagation distance of P-H pulses are very large up to 500-1500 km.

Observation of CH A 2X 2Πr and 2Σ--->X 2Πr emissions in gas-phase collisions of fast O(3P) atoms with acetylene

NASA Astrophysics Data System (ADS)

Orient, O. J.; Chutjian, A.; Murad, E.

1995-03-01

Optical emissions in single-collision, beam-beam reactions of fast (3-22-eV translational energy) O(3P) atoms with C2H2 have been measured in the wavelength range 300-850 nm. Two features were observed, one with a peak wavelength at 431 nm, corresponding to the CH A 2X 2Πr transition, and a second weaker emission in the range 380-400 nm corresponding to the B 2Σ--->X 2Πr transition. Both the A-->X and B-->X emissions were fit to a synthetic spectrum of CH(A) at a vibrational temperature Tv of 10 000 K (0.86 eV) and a rotational temperature Tr of approximately 5000 K (0.43 eV); and CH(B) to Tv=2500 K (0.22 eV) and Tr=1000 K (0.09 eV). The energy threshold for the A-->X emission was measured to be 7.3+/-0.4 eV (lab) or 4.5+/-0.2 eV (c.m.). This agrees with the energy threshold of 7.36 eV (lab) for the reaction O(3P)+C2H2-->CH(A)+HCO.

The IR emission features - Emission from PAH molecules and amorphous carbon particles

NASA Technical Reports Server (NTRS)

Allamandola, L. J.; Tielens, A. G. G. M.; Barker, J. R.

1987-01-01

Techniques for the assessment of the importance of the various forms of PAHs, and recent infrared observations concerning the PAH problem, are considered. Spectroscopic data suggest that the observed interstellar spectrum is due to both free molecule-sized PAHs producing the narrow features, and amorphous carbon particles contributing to the broad underlying components. Explanations for the multicomponent emission spectrum are discussed. A model of the emission mechanism for the example of chrysene is presented, and an exact treatment of the IR fluorescence from highly vibrationally excited large molecules shows that species containing 20-30 carbon atoms are responsible for the narrow features, although the spectra more closely resemble those of amorphous carbon particles. It is suggested that future emphasis should be placed on the spatial characteristics of the component spectra.

Solid-State Chemistry as a Formation Mechanism for C 4N 2 Ice and Possibly the Haystack (220 cm -1 ice emission feature) in Titan's Stratosphere as Observed by Cassini CIRS

NASA Astrophysics Data System (ADS)

Anderson, Carrie; Samuelson, Robert E.; McLain, Jason L.; Nna Mvondo, Delphine; Romani, Paul; Flasar, F. Michael

2016-10-01

A profusion of organic ices containing hydrocarbons, nitriles, and combinations of their mixtures comprise Titan's complex stratospheric cloud systems, and are typically formed via vapor condensation. These ice particles are then distributed throughout the mid-to-lower stratosphere, with an increased abundance near the winter poles (see Anderson et al., 2016). The cold temperatures and the associated strong circumpolar winds that isolate polar air act in much the same way as on Earth, giving rise to compositional anomalies and stratospheric clouds that provide heterogeneous chemistry sites.Titan's C4N2 ice emission feature at 478 cm-1 and "the Haystack," a strong unidentified stratospheric ice emission feature centered at 220 cm-1, share a common characteristic. Even though both are distinctive ice emission features evident in Cassini Composite InfraRed (CIRS) far-IR spectra, no associated vapor emission features can be found in Titan's atmosphere. Without a vapor phase, solid-state chemistry provides an alternate mechanism beside vapor condensation for producing these observed stratospheric ices.Anderson et al., (2016) postulated that C4N2 ice formed in Titan's stratosphere via the solid-state photochemical reaction HCN + HC3N → C4N2 + H2 can occur within extant HCN-HC3N composite ice particles. Such a reaction, and potentially similar reactions that may produce the Haystack ice, are specific examples of solid-state chemistry in solar system atmospheres. This is in addition to the reaction HCl + ClONO2 → HNO3 + Cl2, which is known to produce HNO3 coatings on terrestrial water ice particles, a byproduct of the catalytic chlorine chemistry that produces ozone holes in Earth's polar stratosphere (see for example, Molina et al., 1987 Soloman, 1999).A combination of radiative transfer modeling of CIRS far-IR spectra, coupled with optical constants derived from thin film transmittance spectra of organic ice mixtures obtained in our Spectroscopy for Planetary ICes

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

NASA Astrophysics Data System (ADS)

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

2017-10-01

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

New emission features in the 11-13 micron region and their relationship to polycyclic aromatic hydrocarbons

NASA Technical Reports Server (NTRS)

Witteborn, F. C.; Sandford, S. A.; Bregman, J. D.; Allamandola, L. J.; Cohen, M.; Wooden, D. H.; Graps, A. L.

1989-01-01

Moderate-resolution spectra of NGC 7027, HD 44179, IRAS 2182+5050, and BD +30 deg 3639 are presented, showing that the 11.3-micron feature actually peaks at 11.22 microns. Evidence is found for new emission features near 11.9 and 12.7 microns, supporting an origin from PAHs. Also, the observed asymmetry of the 11.3-micron band is consistent with the anharmonicity expected in the C-H out-of-plane bending mode in PAHs. The analysis of the 11-13-micron emission suggests that the molecular structures of the most intensely emitting free PAHs vary between the high-excitation environment in NGC 7027 and the low-excitation but high-flux environment close to HD 44179. In addition, a series of regularly spaced features between 10 and 11 microns is detected in the spectrum of HD 44179, suggesting that a simple polyatomic hydride is present in the object's gas phase.

On the inorganic carriers of the 21 micron emission feature in post-AGB stars

NASA Astrophysics Data System (ADS)

Zhang, Ke; Jiang, Biwei; Li, Aigen

2008-10-01

The mysterious 21 μm emission feature seen in only 12 C-rich proto-planetary nebulae (PPNe) remains unidentified since its discovery in 1989. Over a dozen materials have been suggested as the carrier candidates while none of them has received general acceptance. We investigate the inorganic carrier candidates by applying the observational constraints of the feature strength and associated features. It is found that: (1) three candidates, TiC clusters, fullerenes with Ti impurity atoms, and SiS2, are not abundant enough to account for the emission power of the 21 μm band, (2) five candidates, doped-SiC, SiO2-mantled SiC dust, carbon and silicon mixtures, Fe2O3, and Fe3O4, all show associated features which are either not detected in the 21 μm sources or detected but with a much lower strength, and (3) FeO, which satisfies the abundance constraints, does not display any associated features which are not seen in the 21 μm sources. Moreover, FeO is more likely to survive in the C-rich environment than Fe2O3 and Fe3O4. Thus FeO seems to be the most plausible one among the inorganic carrier candidates.

Crystallographic features of the approximant H (Mn7Si2V) phase in the Mn-Si-V alloy system

NASA Astrophysics Data System (ADS)

Nakayama, Kei; Komatsuzaki, Takumi; Koyama, Yasumasa

2018-07-01

The intermetallic compound H (Mn7Si2V) phase in the Mn-Si-V alloy system can be regarded as an approximant phase of the dodecagonal quasicrystal as one of the two-dimensional quasicrystals. To understand the features of the approximant H phase, in this study, the crystallographic features of both the H phase and the (σ → H) reaction in Mn-Si-V alloy samples were investigated, mainly by transmission electron microscopy. It was found that, in the H phase, there were characteristic structural disorders with respect to an array of a dodecagonal structural unit consisting of 19 dodecagonal atomic columns. Concretely, penetrated structural units consisting of two dodecagonal structural units were presumed to be typical of such disorders. An interesting feature of the (σ → H) reaction was that regions with a rectangular arrangement of penetrated structural units (RAPU) first appeared in the σ matrix as the initial state, and H regions were then nucleated in contact with RAPU regions. The subsequent conversion of RAPU regions into H regions eventually resulted in the formation of the approximant H state as the final state. Furthermore, atomic positions in both the H structure and the dodecagonal quasicrystal were examined using a simple plane-wave model with 12 plane waves.

Guilt by Association: The 13 Micron Dust Emission Feature and Its Correlation to Other Gas and Dust Features

NASA Astrophysics Data System (ADS)

Sloan, G. C.; Kraemer, Kathleen E.; Goebel, J. H.; Price, Stephan D.

2003-09-01

A study of all full-scan spectra of optically thin oxygen-rich circumstellar dust shells in the database produced by the Short Wavelength Spectrometer on ISO reveals that the strength of several infrared spectral features correlates with the strength of the 13 μm dust feature. These correlated features include dust features at 19.8 and 28.1 μm and the bands produced by warm carbon dioxide molecules (the strongest of which are at 13.9, 15.0, and 16.2 μm). The database does not provide any evidence for a correlation of the 13 μm feature with a dust feature at 32 μm, and it is more likely that a weak emission feature at 16.8 μm arises from carbon dioxide gas rather than dust. The correlated dust features at 13, 20, and 28 μm tend to be stronger with respect to the total dust emission in semiregular and irregular variables associated with the asymptotic giant branch than in Mira variables or supergiants. This family of dust features also tends to be stronger in systems with lower infrared excesses and thus lower mass-loss rates. We hypothesize that the dust features arise from crystalline forms of alumina (13 μm) and silicates (20 and 28 μm). Based on observations with the ISO, a European Space Agency (ESA) project with instruments funded by ESA member states (especially the Principal Investigator countries: France, Germany, the Netherlands, and the United Kingdom) and with the participation of the Institute of Space and Astronautical Science (ISAS) and the National Aeronautics and Space Administration (NASA).

Young Debris Disks With Newly Discovered Emission Features

NASA Astrophysics Data System (ADS)

Ballering, N.

2014-04-01

We analyzed the Spitzer/IRS spectra of young A and F stars that host debris disks with previously unidentified silicate emission features. Such features probe small, warm dust grains in the inner regions of these young systems where terrestrial planet formation may be proceeding (Lisse et al. 2009). For most systems, these regions are too near their host star to be directly seen with high-contrast imaging and too warm to be imaged with submillimeter interferometers. Mid-infrared excess spectra - originating from the thermal emission of the debris disk dust - remain the best data to constrain the properties of the debris in these regions. For each target, we fit physically-motivated model spectra to the data. Typical spectra of unresolved debris disks are featureless and suffer severe degeneracies between the dust location and the grain properties; however, spectra with solid-state emission features provide significantly more information, allowing for a more accurate determination of the dust size, composition, and location (e.g. Chen et al. 2006; Olofsson et al. 2012). Our results shed light on the dynamic properties occurring in the terrestrial regions of these systems. For instance, the sizes of the smallest grains and the nature of the grain size distribution reveal whether the dust originates from steady-state collisional cascades or from stochastic collisions. The properties of the dust grains - such as their crystalline or amorphous structure - can inform us of grain processing mechanisms in the disk. The location of this debris illuminates where terrestrial planet forming activity is occurring. We used results from the Beta Pictoris - which has a well-resolved debris disk with emission features (Li et al. 2012) - to place our results in context. References: Chen et al. 2006, ApJS, 166, 351 Li et al. 2012, ApJ, 759, 81 Lisse et al. 2009, ApJ, 701, 2019 Olofsson et al. 2012, A&A, 542, A90

Cigarette Design Features: Effects on Emission Levels, User Perception, and Behavior.

PubMed

Talhout, Reinskje; Richter, Patricia A; Stepanov, Irina; Watson, Christina V; Watson, Clifford H

2018-01-01

This paper describes the effects of non-tobacco, physical cigarette design features on smoke emissions, product appeal, and smoking behaviors - 3 factors that determine smoker's exposure and related health risks. We reviewed available evidence for the impact of filter ventilation, new filter types, and cigarettes dimensions on toxic emissions, smoker's perceptions, and behavior. For evidence sources we used scientific literature and websites providing product characteristics and marketing information. Whereas filter ventilation results in lower machine-generated emissions, it also leads to perceptions of lighter taste and relative safety in smokers who can unwittingly employ more intense smoking behavior to obtain the desired amount of nicotine and sensory appeal. Filter additives that modify smoke emissions can also modify sensory cues, resulting in changes in smoking behavior. Flavor capsules increase the cigarette's appeal and novelty, and lead to misperceptions of reduced harm. Slim cigarettes have lower yields of some smoke emissions, but smoking behavior can be more intense than with standard cigarettes. Physical design features significantly impact machine-measured emission yields in cigarette smoke, product appeal, smoking behaviors, and exposures in smokers. The influence of current and emerging design features is important in understanding the effectiveness of regulatory actions to reduce smoking-related harm.

Sources of the 13 microns Emission Feature Associated with Silicate Dust

NASA Astrophysics Data System (ADS)

Levan, P. D.; Sloan, G. C.; Little-Marenin, I. R.

1993-05-01

We have carefully searched the Atlas of Low-resolution Spectra (IRAS Science Team 1986, A&A Suppl., 65, 607; Volk and Cohen 1989, AJ, 98, 931) for sources of the 13 microns emission feature associated with silicate emission at 10 microns first discussed by Little-Marenin and Little (1988, ApJ, 303, 305). We have identified 73 spectra for which the 13 microns feature is detected at 4sigma or better. In several cases, we have confirmed the existence of the feature using GLADYS, the Air Force long-slit 10 microns spectrometer, at the Wyoming Infrared Observatory. Our sample of 13 microns emission sources are nearly all late M giants, the majority of type M6 or M7. Variability types exist for 54; over half are SRb variables, while the remainder are fairly evenly divided among Miras and classes SRa and Lb. Most of the sources have LRS characterizations of 14, 15, or 21-24, i.e. weak silicate emission at 10 microns. The shape of the silicate emission feature varies from a nearly classic 10 microns profile broadened at longer wavelengths to a double-humped profile with peaks at both 10 and 11 microns. In the scheme of Little-Marenin and Little, these shapes would be characterized as Sil+, Sil++, and 3-component. The root mean square radial velocity of our sample is 31 km/sec. The mean angle from the galactic plane is 29 degrees, and there are no obvious dependencies with galactic longitude. These properties indicate that our sample consists of old Population I AGB stars. We have also investigated how the strength of the 13 microns emission varies with spectral type, class and period of variability, LRS characterization, 10 microns feature width, and galactic position. We find no correlation with any of these properties, indicating that the 13 microns emission is not unique to any specific class of Population I AGB stars. There is no strong evidence for the contention that the 13 microns sources are precursors to S stars.

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

NASA Astrophysics Data System (ADS)

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

2017-08-01

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

Emission of a pulsed purely rotational transition chemical H{sub 2}-F{sub 2} laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Molevich, N E; Pichugin, S Yu

2008-04-30

The possibility of obtaining efficient emission at purely rotational transitions of HF molecules in a pulsed chemical hydrogen fluoride laser is studied theoretically. The operation of a H{sub 2}-F{sub 2} laser with a gas pressure of 1.1 atm emitting at the v, j {yields} v, j - 1 (v = 1 - 6, j = 10 - 14) transitions is simulated taking into account resonance VR processes. The total specific laser energy release calculated over all the vibrational levels is 5.5 J L{sup -1} on purely rotational transitions at {lambda}{approx}17 {mu}m (j = 14), 3.5 J L{sup -1} at {lambda}{approx}18.5more » {mu}m (j = 13), and 2.5 J L{sup -1} at {lambda}{approx}20 {mu}m (j = 12). (lasers and amplifiers)« less

Laboratory measurement of the millimeter wave properties of liquid sulfuric acid (H2SO4). [study of microwave emission from Venus

NASA Technical Reports Server (NTRS)

Fahd, Antoine K.; Steffes, Paul G.

1991-01-01

The methodology and the results of laboratory measurements of the millimeter wave properties of liquid sulfuric acid are presented. Measurements conducted at 30-40 and 90-100 GHz are reported, using different concentrations of liquid H2SO4. The measured data are used to compute the expected opacity of H2SO4 condensates and their effects on the millimeter wave emission from Venus. The cloud condensate is found to have an effect on the emission from Venus. The calculated decrease in brightness temperature is well below the observed decrease in brightness temperature found by de Pater et al. (1991). It is suggested that other constituents such as gaseous H2SO4 also affect the observed variation in the brightness temperature.

SHOCK-ENHANCED C{sup +} EMISSION AND THE DETECTION OF H{sub 2}O FROM THE STEPHAN'S QUINTET GROUP-WIDE SHOCK USING HERSCHEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Appleton, P. N.; Lord, S.; Lu, N.

2013-11-01

We present the first Herschel spectroscopic detections of the [O I] 63 μm and [C II] 158 μm fine-structure transitions, and a single para-H{sub 2}O line from the 35 × 15 kpc{sup 2} shocked intergalactic filament in Stephan's Quintet. The filament is believed to have been formed when a high-speed intruder to the group collided with a clumpy intergroup gas. Observations with the PACS spectrometer provide evidence for broad (>1000 km s{sup –1}) luminous [C II] line profiles, as well as fainter [O I] 63 μm emission. SPIRE FTS observations reveal water emission from the p-H{sub 2}O (1{sub 11}-0{sub 00})more » transition at several positions in the filament, but no other molecular lines. The H{sub 2}O line is narrow and may be associated with denser intermediate-velocity gas experiencing the strongest shock-heating. The [C II]/PAH{sub tot} and [C II]/FIR ratios are too large to be explained by normal photo-electric heating in photodissociation regions. H II region excitation or X-ray/cosmic-ray heating can also be ruled out. The observations lead to the conclusion that a large fraction the molecular gas is diffuse and warm. We propose that the [C II], [O I], and warm H{sub 2} line emission is powered by a turbulent cascade in which kinetic energy from the galaxy collision with the intergalactic medium is dissipated to small scales and low velocities, via shocks and turbulent eddies. Low-velocity magnetic shocks can help explain both the [C II]/[O I] ratio, and the relatively high [C II]/H{sub 2} ratios observed. The discovery that [C II] emission can be enhanced, in large-scale turbulent regions in collisional environments, has implications for the interpretation of [C II] emission in high-z galaxies.« less

Charge Exchange X-Ray Emission due to Highly Charged Ion Collisions with H, He, and H2: Line Ratios for Heliospheric and Interstellar Applications

NASA Astrophysics Data System (ADS)

Cumbee, R. S.; Mullen, P. D.; Lyons, D.; Shelton, R. L.; Fogle, M.; Schultz, D. R.; Stancil, P. C.

2018-01-01

The fundamental collisional process of charge exchange (CX) has been established as a primary source of X-ray emission from the heliosphere, planetary exospheres, and supernova remnants. In this process, X-ray emission results from the capture of an electron by a highly charged ion from a neutral atom or molecule, to form a highly excited, high-charge state ion. As the captured electron cascades down to the lowest energy level, photons are emitted, including X-rays. To provide reliable CX-induced X-ray spectral models to realistically simulate these environments, line ratios and spectra are computed using theoretical CX cross sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, molecular-orbital close-coupling, and classical trajectory Monte Carlo methods for various collisional velocities relevant to astrophysics. X-ray spectra were computed for collisions of bare and H-like C to Al ions with H, He, and H2 with results compared to available experimental data. Using these line ratios, XSPEC models of CX emission in the northeast rim of the Cygnus Loop supernova remnant and the heliosphere are shown as examples with ion velocity dependence.

The CU mobile Solar Occultation Flux instrument: structure functions and emission rates of NH3, NO2 and C2H6

NASA Astrophysics Data System (ADS)

Kille, Natalie; Baidar, Sunil; Handley, Philip; Ortega, Ivan; Sinreich, Roman; Cooper, Owen R.; Hase, Frank; Hannigan, James W.; Pfister, Gabriele; Volkamer, Rainer

2017-02-01

We describe the University of Colorado mobile Solar Occultation Flux instrument (CU mobile SOF). The instrument consists of a digital mobile solar tracker that is coupled to a Fourier transform spectrometer (FTS) of 0.5 cm-1 resolution and a UV-visible spectrometer (UV-vis) of 0.55 nm resolution. The instrument is used to simultaneously measure the absorption of ammonia (NH3), ethane (C2H6) and nitrogen dioxide (NO2) along the direct solar beam from a moving laboratory. These direct-sun observations provide high photon flux and enable measurements of vertical column densities (VCDs) with geometric air mass factors, high temporal resolution of 2 s and spatial resolution of 5-19 m. It is shown that the instrument line shape (ILS) of the FTS is independent of the azimuth and elevation angle pointing of the solar tracker. Further, collocated measurements next to a high-resolution FTS at the National Center for Atmospheric Research (HR-NCAR-FTS) show that the CU mobile SOF measurements of NH3 and C2H6 are precise and accurate; the VCD error at high signal to noise ratio is 2-7 %. During the Front Range Air Pollution and Photochemistry Experiment (FRAPPE) from 21 July to 3 September 2014 in Colorado, the CU mobile SOF instrument measured median (minimum, maximum) VCDs of 4.3 (0.5, 45) × 1016 molecules cm-2 NH3, 0.30 (0.06, 2.23) × 1016 molecules cm-2 NO2 and 3.5 (1.5, 7.7) × 1016 molecules cm-2 C2H6. All gases were detected in larger 95 % of the spectra recorded in urban, semi-polluted rural and remote rural areas of the Colorado Front Range. We calculate structure functions based on VCDs, which describe the variability of a gas column over distance, and find the largest variability for NH3. The structure functions suggest that currently available satellites resolve about 10 % of the observed NH3 and NO2 VCD variability in the study area. We further quantify the trace gas emission fluxes of NH3 and C2H6 and production rates of NO2 from concentrated animal feeding

ON THE 2012 OCTOBER 23 CIRCULAR RIBBON FLARE: EMISSION FEATURES AND MAGNETIC TOPOLOGY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Kai; Guo, Yang; Ding, M. D., E-mail: guoyang@nju.edu.cn, E-mail: dmd@nju.edu.cn

2015-06-20

Circular ribbon flares are usually related to spine-fan type magnetic topology containing null points. In this paper, we investigate an X-class circular ribbon flare on 2012 October 23, using the multiwavelength data from the Solar Dynamics Observatory, Hinode, and RHESSI. In Ca ii H emission, the flare showed three ribbons with two highly elongated ones inside and outside a quasi-circular one, respectively. A hot channel was displayed in the extreme-ultraviolet emissions that infers the existence of a magnetic flux rope. Two hard X-ray (HXR) sources in the 12–25 keV energy band were located at the footpoints of this hot channel. Using amore » nonlinear force-free magnetic field extrapolation, we identify three topological structures: (1) a three-dimensional null point, (2) a flux rope below the fan of the null point, and (3) a large-scale quasi-separatrix layer (QSL) induced by the quadrupolar-like magnetic field of the active region. We find that the null point is embedded within the large-scale QSL. In our case, all three identified topological structures must be considered to explain all the emission features associated with the observed flare. Besides, the HXR sources are regarded as the consequence of the reconnection within or near the border of the flux rope.« less

Simple approximation of total emissivity of CO2-H2O mixture used in the zonal method of calculation of heat transfer by radiation

NASA Astrophysics Data System (ADS)

Lisienko, V. G.; Malikov, G. K.; Titaev, A. A.

2014-12-01

The paper presents a new simple-to-use expression to calculate the total emissivity of a mixture of gases CO2 and H2O used for modeling heat transfer by radiation in industrial furnaces. The accuracy of this expression is evaluated using the exponential wide band model. It is found that the time taken to calculate the total emissivity in this expression is 1.5 times less than in other approximation methods.

Theoretical study of deuteronated PAHs as carriers for IR emission features in the ISM

NASA Astrophysics Data System (ADS)

Buragohain, Mridusmita; Pathak, Amit; Sarre, Peter; Onaka, Takashi; Sakon, Itsuki

2015-11-01

This work proposes deuteronated PAH (DPAH+) molecules as a potential carrier of the 4.4 and 4.65 μm mid-infrared emission bands that have been observationally detected towards the Orion and M17 regions. Density Functional Theory calculations have been carried out on DPAH+ molecules to see the variations in the spectral behaviour from that of a pure polycyclic aromatic hydrocarbon (PAH). DPAH+ molecules show features that arise due to the stretching of the aliphatic C-D bond. Deuterated PAHs have been previously reported as carriers for such features. However, preferred conditions of ionization of PAHs in the interstellar medium (ISM) indicates the possibility of the formation of DPAH+ molecules. Comparison of band positions of DPAH+s shows reasonable agreement with the observations. We report the effect of size of the DPAH+ molecules on band positions and intensities. This study also reports a D/H ratio ([D/H]_{sc}; the ratio of C-D stretch and C-H stretch bands per [D/H]_{num}) that is decreasing with the increasing size of DPAH+s. It is noted that large DPAH+ molecules (no. of C atoms ˜50) match the D/H ratio that has been estimated from observations. This ratio offers prospects to study the deuterium abundance and depletion in the ISM.

Military Aircraft Emissions Research - Case of Hercules Cargo Plane (C-130H) Emissions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Mengdawn; Corporan, E.; DeWitt, M.

2007-01-01

Tactical airlifter like C-130H has been in use for more than 50 years, and is expected to serve for many years to come. However, the emission characteristics data of the aircraft are scarce. To increase our understanding of turboprop engine emissions, emissions from a military C-130H cargo aircraft were characterized in field conditions in the fall of 2005. Particulate and gaseous pollutants were measured by conventional and advanced instrumentation platforms that were built with in-situ extractive or remote optical sensing technologies. The measurements performed at the C-130H engine exhaust exit showed increased levels of emissions as the engine power settingmore » increased. In contrast, there was no such a relationship found for the C-130H emitted particulate matter (as a function of engine power setting) measured at about 15-m downstream of the engine exhaust plane. The emitted gaseous species measured at both locations were, however, proportional to the engine power setting and comparable (at both locations) when corrected for ambient dilution indicating the lack of particulate emission-power setting relationship at the far field is unique. The result clearly indicates that the aircraft emission factor or index for particulate matter cannot be experimentally determined at a downstream location away from the exhaust exit and has to be determined right at the engine exhaust plane. Emission indices that are needed for air quality modeling will be presented.« less

Mapping High-Velocity H-alpha and Lyman-alpha Emission from Supernova 1987A

NASA Technical Reports Server (NTRS)

France, Kevin; McCray, Richard; Fransson, Claes; Larsson, Josefin; Frank, Kari A.; Burrows, David N.; Challis, Peter; Kirshner, Robert P.; Chevalier, Roger A.; Garnavich, Peter;

Near-infrared emission bands of TeH and TeD

NASA Astrophysics Data System (ADS)

Fink, E. H.; Setzer, K. D.; Ramsay, D. A.; Vervloet, M.

1989-11-01

High-resolution emission spectra of TeH and TeD have been obtained in the region 4200 to 3600 cm -1 using a Bomem DA3.002 Fourier transform spectrometer. Analyses are given for the 0-0 and 1-1 bands of the X 22Π{1}/{2}-X 12Π{3}/{2} system of TeH and for the 0-0 band of TeD. In addition the 2-0 vibrational overtone bands of 130TeH, 128TeH, and 126TeH are observed and analyzed. Accurate molecular constants are given for the first time.

Non-Controlled Biogenic Emission of CO, H2S, NH3 and Hg0 from Lazareto's Landfill, Tenerife, Canary Islands

NASA Astrophysics Data System (ADS)

Nolasco, D.; Lima, R.; Salazar, J.; Hernández, P. A.; Pérez, N. M.

2002-12-01

Landfills are important sources of contaminant gases to the surrounding environment and a significant amount of them could be released to the atmosphere through the surface environment in a diffuse form, also known as non-controlled emission of landfill gases. CH4 and CO2 are major components in landfill gases and other gas species are only present in minor amounts. Trace compounds include both inorganic and a large number of volatile organic components. The goal of this study is to evaluate the non-controlled biogenic emission of inorganic toxic gases from Lazareto's landfill. Which is located in the city of Santa Cruz de Tenerife, with a population of about 150,000, and is used as a Palm tree park. Lazareto's landfill has an extension of 0.22 Km2 and it is not operative since 1980. A non-controlled biogenic gas emission survey of 281 sampling sites was carried out from February tod March, 2002. Surface CO2 efflux measurements were performed by means of a portable NDIR sensor according with the accumulation chamber method. Surface CO2 efflux ranged from negligible values up to 30,600 gm-2d-1. At each sampling site, surface landfill gas samples were collected at 40 cm depth using a metallic soil probe. These gas samples were analyzed within 24 hours for major and inorganic toxic gas species by means of microGC and specific electrochemical sensors. The highest concentrations of CO, H2S, NH3 and Hg0 were 3, 20, 2,227, 0.010 ppmV, respectively. Non-controlled biogenic emission rate of CO, H2S, NH3, and Hg0 were estimated by multiplying the observed surface CO2 efflux times (Inorganic Toxic Gas)i/CO2 weight ratio at each sampling site, respectively. The highest surface inorganic toxic gas efllux rates were 699 gm-2d-1 for NH3, 81, 431 and 4 mgm-2d-1 for CO, H2S and Hg0, respectively. Taking into consideration the spatial distribution of the inorganic toxic gas efflux values as well as the extension of the landfill, the non-controlled biogenic emission of CO, H2S, NH3

Estimates of methane emissions from India using CH4-CO-C2H6 relationships from CARIBIC observations in monsoon convective outflow

NASA Astrophysics Data System (ADS)

Baker, A. K.; Rauthe-Schöch, A.; Schuck, T. J.; van Velthoven, P. F.; Slemr, F.; Brenninkmeijer, C. A.

2010-12-01

A large fraction of methane sources are anthropogenic, and include fossil fuel use, biomass/biofuel burning, agriculture and waste treatment. Recently, much attention regarding emissions of greenhouse gases has focused on large, developing nations, as their emissions are expected to rise rapidly over the coming decades. As the second most populous country in the world, and one of the fastest growing economies, India has been of particular interest. Arguably the most important feature of meteorology in India is the Asian summer monsoon. During the monsoon period there exists persistent deep convection over Southern Asia, and the composition of convected air masses is strongly influenced by emissions from India. This ultimately results in a well-mixed air parcel containing air from India being transported to the upper troposphere. Over the course of the 2008 monsoon period the CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) passenger aircraft conducted monthly measurement flights which probed this outflow. Data collected during these flights provides a unique opportunity to examine sources of atmospheric species in India. Here we use measurements of methane (CH4), carbon monoxide (CO) and ethane (C2H6) from whole air samples collected during CARIBIC flights to estimate emissions of methane and to quantify those emissions related to flooding during the monsoon. Methane data from the monsoon period show enhancements inside the monsoon plume, which increase as the monsoon progresses. Using emission data for CO and ΔCH4/ΔCO derived from CARIBIC measurements, we estimate total methane emissions to be ~40 Tg yr-1. Relationships of methane to ethane, which shares the bulk of its sources with methane but lacks a biological component, are further used to estimate the fraction of “extra” emissions from biological activity related to increased monsoon rains. This additional methane is a considerable fraction of

Detection of HCN and C2H2 in ISO Spectra of Oxygen-Rich AGB Stars

NASA Technical Reports Server (NTRS)

Carbon, Duane F.; Chiar, Jean; Goorvitch, David; Kwak, Dochan (Technical Monitor)

2002-01-01

Cool oxygen-rich AGB stars were not expected to have organic molecules like HCN in either their photospheres or circumstellar envelopes (CSEs). The discovery of HCN and CS microwave emission from the shallowest CSE layers of these stars was a considerable surprise and much theoretical effort has been expended in explaining the presence of such organics. To further explore this problem, we have undertaken a systematic search of oxygen-rich AGB stellar spectra in the Infrared Space Observatory (ISO) data archive. Our purposes are to find evidence regarding critical molecular species that could be of value in choosing among the proposed theoretical models, to locate spectral features which might give clues to conditions deeper in the CSEs, and to lay the groundwork for future SIRTF (Space Infrared Telescope Facility) and SOFIA (Stratospheric Observatory for Infrared Astronomy) observations. Using carefully reduced observations, we have detected weak absorption features arising from HCN and possibly C2H2 in a small number of oxygen-rich AGB stars. The most compelling case is NML Cyg which shows both HCN (14 microns) and CO2 (15 microns). VY CMa, a similar star, shows evidence for HCN, but not CO2. Two S-type stars show evidence for the C-H bending transitions: W Aql at 14 microns (HCN) and both W Aql and S Cas at 13.7 microns (C2H2). Both W Aql and S Cas as well as S Lyr, a SC-type star, show 3 micron absorption which may arise from the C-H stretch of HCN and C2H2. In the case of NML Cyg, we show that the HCN and CO2 spectral features are formed in the CSE at temperatures well above those of the outermost CSE layers and derive approximate column densities. In the case of the S-stars, we discuss the evidence for the organic features and their photospheric origin.

Soil pH management without lime, a strategy to reduce greenhouse gas emissions from cultivated soils

NASA Astrophysics Data System (ADS)

Nadeem, Shahid; Bakken, Lars; Reent Köster, Jan; Tore Mørkved, Pål; Simon, Nina; Dörsch, Peter

2015-04-01

For decades, agricultural scientists have searched for methods to reduce the climate forcing of food production by increasing carbon sequestration in the soil and reducing the emissions of nitrous oxide (N2O). The outcome of this research is depressingly meagre and the two targets appear incompatible: efforts to increase carbon sequestration appear to enhance the emissions of N2O. Currently there is a need to find alternative management strategies which may effectively reduce both the CO2 and N2O footprints of food production. Soil pH is a master variable in soil productivity and plays an important role in controlling the chemical and biological activity in soil. Recent investigations of the physiology of denitrification have provided compelling evidence that the emission of N2O declines with increasing pH within the range 5-7. Thus, by managing the soil pH at a near neutral level appears to be a feasible way to reduce N2O emissions. Such pH management has been a target in conventional agriculture for a long time, since a near-neutral pH is optimal for a majority of cultivated plants. The traditional way to counteract acidification of agricultural soils is to apply lime, which inevitably leads to emission of CO2. An alternative way to increase the soil pH is the use of mafic rock powders, which have been shown to counteract soil acidification, albeit with a slower reaction than lime. Here we report a newly established field trail in Norway, in which we compare the effects of lime and different mafic mineral and rock powders (olivine, different types of plagioclase) on CO2 and N2O emissions under natural agricultural conditions. Soil pH is measured on a monthly basis from all treatment plots. Greenhouse gas (GHG) emission measurements are carried out on a weekly basis using static chambers and an autonomous robot using fast box technique. Field results from the first winter (fallow) show immediate effect of lime on soil pH, and slower effects of the mafic rocks. The

The 11 Micron Emissions of Carbon Stars

NASA Technical Reports Server (NTRS)

Goebel, J. H.; Cheeseman, P.; Gerbault, F.

1995-01-01

A new classification scheme of the IRAS LRS carbon stars is presented. It comprises the separation of 718 probable carbon stars into 12 distinct self-similar spectral groupings. Continuum temperatures are assigned and range from 470 to 5000 K. Three distinct dust species are identifiable: SiC, alpha:C-H, and MgS. In addition to the narrow 11 + micron emission feature that is commonly attributed to SiC, a broad 11 + micron emission feature, that is correlated with the 8.5 and 7.7 micron features, is found and attributed to alpha:C-H. SiC and alpha:C-H band strengths are found to correlate with the temperature progression among the Classes. We find a spectral sequence of Classes that reflects the carbon star evolutionary sequence of spectral types, or alternatively developmental sequences of grain condensation in carbon-rich circumstellar shells. If decreasing temperature corresponds to increasing evolution, then decreasing temperature corresponds to increasing C/O resulting in increasing amounts of carbon rich dust, namely alpha:C-H. If decreasing the temperature corresponds to a grain condensation sequence, then heterogeneous, or induced nucleation scenarios are supported. SiC grains precede alpha:C-H and form the nuclei for the condensation of the latter material. At still lower temperatures, MgS appears to be quite prevalent. No 11.3 micron PAH features are identified in any of the 718 carbon stars. However, one of the coldest objects, IRAS 15048-5702, and a few others, displays an 11.9 micron emission feature characteristic of laboratory samples of coronene. That feature corresponds to the C-H out of plane deformation mode of aromatic hydrocarbon. This band indicates the presence of unsaturated, sp(sup 3), hydrocarbon bonds that may subsequently evolve into saturated bonds, sp(sup 2), if, and when, the star enters the planetary nebulae phase of stellar evolution. The effusion of hydrogen from the hydrocarbon grain results in the evolution in wavelength of this

The 11 Micron Emissions of Cabon Stars

NASA Technical Reports Server (NTRS)

Goebel, J. H.; Cheeseman, P.; Gerbault, F.

1995-01-01

A new classification scheme of the IRAS LRS carbon stars is presented. It comprises the separation of 718 probable carbon stars into 12 distinct self-similar spectral groupings. Continuum temperatures are assigned and range from 470 to 5000 K. Three distinct dust species are identifiable: SiC, alpha:C-H, and MgS. In addition to the narrow 11 + micron emission feature that is commonly attributed to SiC, a broad 11 + micron emission feature, that is correlated with the 8.5 and 7.7 micron features, is found and attributed to alpha:C-H. SiC and alpha:C-H band strengths are found to correlate with the temperature progression among the Classes. We find a spectral sequence of Classes that reflects the carbon star evolutionary sequence of spectral types, or alternatively developmental sequences of grain condensation in carbon-rich circumstellar shells. If decreasing temperature corresponds to increasing evolution, then decreasing temperature corresponds to increasing CIO resulting in increasing amounts of carbon rich dust, namely alpha:C-H. If decreasing the temperature corresponds to a grain condensation sequence, then heterogeneous, or induced nucleation scenarios are supported. SiC grains precede alpha:C-H and form the nuclei for the condensation of the latter material. At still lower temperatures, MgS appears to be quite prevalent. No 11.3 micron PAH features are identified in any of the 718 carbon stars. However, one of the coldest objects, IRAS 15048-5702, and a few others, displays an 11.9 micron emission feature characteristic of laboratory samples of coronene. That feature corresponds to the C-H out of plane deformation mode of aromatic hydrocarbon. This band indicates the presence of unsaturated, sp(sup 3), hydrocarbon bonds that may subsequently evolve into saturated bonds, sp(sup 2), if, and when, the star enters the planetary nebulae phase of stellar evolution. The effusion of hydrogen from the hydrocarbon grain results in the evolution in wavelength of this

Jet-ISM Interaction in the Radio Galaxy 3C 293: Jet-driven Shocks Heat ISM to Power X-Ray and Molecular H2 Emission

NASA Astrophysics Data System (ADS)

Lanz, L.; Ogle, P. M.; Evans, D.; Appleton, P. N.; Guillard, P.; Emonts, B.

2015-03-01

We present a 70 ks Chandra observation of the radio galaxy 3C 293. This galaxy belongs to the class of molecular hydrogen emission galaxies (MOHEGs) that have very luminous emission from warm molecular hydrogen. In radio galaxies, the molecular gas appears to be heated by jet-driven shocks, but exactly how this mechanism works is still poorly understood. With Chandra, we observe X-ray emission from the jets within the host galaxy and along the 100 kpc radio jets. We model the X-ray spectra of the nucleus, the inner jets, and the X-ray features along the extended radio jets. Both the nucleus and the inner jets show evidence of 107 K shock-heated gas. The kinetic power of the jets is more than sufficient to heat the X-ray emitting gas within the host galaxy. The thermal X-ray and warm H2 luminosities of 3C 293 are similar, indicating similar masses of X-ray hot gas and warm molecular gas. This is consistent with a picture where both derive from a multiphase, shocked interstellar medium (ISM). We find that radio-loud MOHEGs that are not brightest cluster galaxies (BCGs), like 3C 293, typically have LH2/LX˜ 1 and MH2/MX˜ 1, whereas MOHEGs that are BCGs have LH2/LX˜ 0.01 and MH2/MX˜ 0.01. The more massive, virialized, hot atmosphere in BCGs overwhelms any direct X-ray emission from current jet-ISM interaction. On the other hand, LH2/LX˜ 1 in the Spiderweb BCG at z = 2, which resides in an unvirialized protocluster and hosts a powerful radio source. Over time, jet-ISM interaction may contribute to the establishment of a hot atmosphere in BCGs and other massive elliptical galaxies.

Precursory diffuse CO2 and H2S emission signatures of the 2011-2012 El Hierro submarine eruption, Canary Islands

NASA Astrophysics Data System (ADS)

Pérez, Nemesio M.; Padilla, Germán D.; Padrón, Eleazar; Hernández, Pedro A.; Melián, Gladys V.; Barrancos, José; Dionis, Samara; Nolasco, Dácil; Rodríguez, Fátima; Calvo, David; Hernández, Íñigo

2012-08-01

On October 12, 2011, a submarine eruption began 2 km off the coast of La Restinga, south of El Hierro Island. CO2 and H2S soil efflux were continuously measured during the period of volcanic unrest by using the accumulation chamber method at two different geochemical stations, HIE01 and HIE07. Recorded CO2 and H2S effluxes showed precursory signals that preceded the submarine eruption. Beginning in late August, the CO2 efflux time series started increasing at a relatively constant rate over one month, reaching a maximum of 19 gm-2d-1 one week before the onset of the submarine volcanic eruption. The H2S efflux time series at HIE07 showed a pulse in H2S emission just one day before the initiation of the submarine eruption, reaching peak values of 42 mg m-2 d-1, 10 times the average H2S efflux recorded during the observation period. Since CO2 and H2S effluxes are strongly influenced by external factors, we applied a multiple regression analysis to remove their contribution. A statistical analysis showed that the long-term trend of the filtered data is well correlated with the seismic energy. We find that these geochemical stations are important monitoring sites for evaluating the volcanic activity of El Hierro and that they demonstrate the potential of applying continuous monitoring of soil CO2 and H2S efflux to improve and optimize the detection of early warning signals of future volcanic unrest episodes at El Hierro. Continuous diffuse degassing studies would likely prove useful for monitoring other volcanoes during unrest episodes.

H2S Injection and Sequestration into Basalt - The SulFix Project

NASA Astrophysics Data System (ADS)

Gudbrandsson, S.; Moola, P.; Stefansson, A.

2014-12-01

Atmospheric H2S emissions are among major environmental concern associated with geothermal energy utilization. It is therefore of great importance for the geothermal power sector to reduce H2S emissions. Known solutions for H2S neutralization are both expensive and include production of elemental sulfur and sulfuric acid that needs to be disposed of. Icelandic energy companies that utilize geothermal power for electricity production have decided to try to find an environmentally friendly and economically feasible solution to reduce the H2S emission, in a joint venture called SulFix. The aim of SulFix project is to explore the possibilities of injecting H2S dissolved in water into basaltic formations in close proximity to the power plants for permanent fixation as sulfides. The formation of sulfides is a natural process in geothermal systems. Due to basalt being rich in iron and dissolving readily at acidic conditions, it is feasible to re-inject the H2S dissolved in water, into basaltic formations to form pyrite. To estimate the mineralization rates of H2S, in the basaltic formation, flow through experiments in columns were conducted at various H2S concentrations, temperatures (100 - 240°C) and both fresh and altered basaltic glass. The results indicate that pyrite rapidly forms during injection into fresh basalt but the precipiation in altered basalt is slower. Three different alteration stages, as a function of distance from inlet, can be observed in the column with fresh basaltic glass; (1) dissolution features along with precipitation, (2) precipitation increases, both sulfides and other secondary minerals and (3) the basalt looks to be unaltered and little if any precipitation is observed. The sulfur has precipitated in the first half of the column and thereafter the solution is possibly close to be supersaturated with respect to the rock. These results indicate that the H2S sequestration into basalt is possible under geothermal conditions. The rate limiting

Structure and spectral features of H+(H2O)7: Eigen versus Zundel forms.

PubMed

Shin, Ilgyou; Park, Mina; Min, Seung Kyu; Lee, Eun Cheol; Suh, Seung Bum; Kim, Kwang S

2006-12-21

The two dimensional (2D) to three dimensional (3D) transition for the protonated water cluster has been controversial, in particular, for H(+)(H(2)O)(7). For H(+)(H(2)O)(7) the 3D structure is predicted to be lower in energy than the 2D structure at most levels of theory without zero-point energy (ZPE) correction. On the other hand, with ZPE correction it is predicted to be either 2D or 3D depending on the calculational levels. Although the ZPE correction favors the 3D structure at the level of coupled cluster theory with singles, doubles, and perturbative triples excitations [CCSD(T)] using the aug-cc-pVDZ basis set, the result based on the anharmonic zero-point vibrational energy correction favors the 2D structure. Therefore, the authors investigated the energies based on the complete basis set limit scheme (which we devised in an unbiased way) at the resolution of the identity approximation Moller-Plesset second order perturbation theory and CCSD(T) levels, and found that the 2D structure has the lowest energy for H(+)(H(2)O)(7) [though nearly isoenergetic to the 3D structure for D(+)(D(2)O)(7)]. This structure has the Zundel-type configuration, but it shows the quantum probabilistic distribution including some of the Eigen-type configuration. The vibrational spectra of MP2/aug-cc-pVDZ calculations and Car-Parrinello molecular dynamics simulations, taking into account the thermal and dynamic effects, show that the 2D Zundel-type form is in good agreement with experiments.

Structure and spectral features of H+(H2O)7: Eigen versus Zundel forms

NASA Astrophysics Data System (ADS)

Shin, Ilgyou; Park, Mina; Min, Seung Kyu; Lee, Eun Cheol; Suh, Seung Bum; Kim, Kwang S.

2006-12-01

The two dimensional (2D) to three dimensional (3D) transition for the protonated water cluster has been controversial, in particular, for H+(H2O)7. For H+(H2O)7 the 3D structure is predicted to be lower in energy than the 2D structure at most levels of theory without zero-point energy (ZPE) correction. On the other hand, with ZPE correction it is predicted to be either 2D or 3D depending on the calculational levels. Although the ZPE correction favors the 3D structure at the level of coupled cluster theory with singles, doubles, and perturbative triples excitations [CCSD(T)] using the aug-cc-pVDZ basis set, the result based on the anharmonic zero-point vibrational energy correction favors the 2D structure. Therefore, the authors investigated the energies based on the complete basis set limit scheme (which we devised in an unbiased way) at the resolution of the identity approximation Møller-Plesset second order perturbation theory and CCSD(T) levels, and found that the 2D structure has the lowest energy for H+(H2O)7 [though nearly isoenergetic to the 3D structure for D+(D2O)7]. This structure has the Zundel-type configuration, but it shows the quantum probabilistic distribution including some of the Eigen-type configuration. The vibrational spectra of MP2/aug-cc-pVDZ calculations and Car-Parrinello molecular dynamics simulations, taking into account the thermal and dynamic effects, show that the 2D Zundel-type form is in good agreement with experiments.

Fourier transform emission spectra and deperturbation analysis of the A2Π - X2Σ+ and B2Σ+ - X2Σ+ electronic transitions of ZnH

NASA Astrophysics Data System (ADS)

Abbasi, Mahdi; Shayesteh, Alireza

2017-10-01

A discharge-furnace emission source was used to generate the A2Π → X2Σ+ and B2Σ+ → X2Σ+ spectra of ZnH radical. High resolution emission spectra were recorded with a Fourier transform spectrometer, and several bands have been assigned for the 64ZnH major isotopologue. The data span the v″ = 0-6 levels of the X2Σ+ ground state, the v‧ = 0-3 levels of the A2Π state, and the v‧ = 0-2 levels of the B2Σ+ state, extending to high rotational quantum numbers near and above the dissociation asymptote of the ground state. Large local perturbations were observed in the A2Π and B2Σ+ electronic states, and a deperturbation analysis was carried out using a single Hamiltonian matrix that includes 2Π and 2Σ+ matrix elements, as well as off-diagonal elements coupling vibrational levels of the two electronic states. Band constants and Dunham coefficients were obtained for the A2Π and B2Σ+ excited states by least-squares-fitting of all the experimental data. The equilibrium vibrational constants ωe and ωexe have been determined to be 1907.528(4) and 38.674(2) cm-1, respectively, for the A2Π state, and 1021.135(94) and 17.725(80) cm-1, for the B2Σ+ state, and the equilibrium Zn-H distances (re) are 1.511662(2) Å and 2.26805(7) Å for the A2Π and B2Σ+ states, respectively. The RKR potential curves were constructed for the A2Π and B2Σ+ states, and vibrational radial overlap integrals were computed. The off-diagonal matrix elements coupling the electronic wavefunctions of the A2Π and B2Σ+ states, i.e., a+ and b, were determined to be 228 ± 3 cm-1 and 0.73 ± 0.01, respectively, for the ZnH molecule.

Chromospheres of late-type active and quiescent dwarfs. III - Variability of CA II H emission profiles

NASA Astrophysics Data System (ADS)

Garcia Lopez, R. J.; Crivellari, L.; Beckman, J. E.; Rebolo, R.

1992-08-01

We have used high-resolution spectra of the Ca II H resonance line in late-type dwarfs, obtained with high S:N ratios, over a period of four years to widen our understanding of the dynamical behavior of the Ca II emission cores. All of the stars dealt with in this article, which are chromospherically active, show variability both in core emission flux and line width. They also show significant wavelength shifts with time of order hundreds of meters per second in the mean core wavelength, and with lower amplitude in the H3 self-absorption, compared to the photospheric rest wavelength of Ca II H. Comparing the emission core shifts with those observed in the H3 features, we find, for the first time, direct prima facie evidence for vertical chromospheric velocity fields, which show stability in sense over periods of years in a given star, with notable modulation in gradient, and which differ in gradient from star to star. We present evidence to show that the observed effects are almost certainly not due to projected rotational modulation, and offer new prospects, given spectral measurements closely sampled in time, for investigating the vertical velocity structures of chromospheres.

Radio continuum of galaxies with H2O megamaser disks: 33 GHz VLA data

NASA Astrophysics Data System (ADS)

Kamali, F.; Henkel, C.; Brunthaler, A.; Impellizzeri, C. M. V.; Menten, K. M.; Braatz, J. A.; Greene, J. E.; Reid, M. J.; Condon, J. J.; Lo, K. Y.; Kuo, C. Y.; Litzinger, E.; Kadler, M.

2017-09-01

Context. Galaxies with H2O megamaser disks are active galaxies in whose edge-on accretion disks 22 GHz H2O maser emission has been detected. Because their geometry is known, they provide a unique view into the properties of active galactic nuclei. Aims: The goal of this work is to investigate the nuclear environment of galaxies with H2O maser disks and to relate the maser and host galaxy properties to those of the radio continuum emission of the galaxy. Methods: The 33 GHz (9 mm) radio continuum properties of 24 galaxies with reported 22 GHz H2O maser emission from their disks are studied in the context of the multiwavelength view of these sources. The 29-37 GHz Ka-band observations are made with the Karl Jansky Very Large Array in B, CnB, or BnA configurations, achieving a resolution of 0.2-0.5 arcsec. Hard X-ray data from the Swift/BAT survey and 22 μm infrared data from WISE, 22 GHz H2O maser data and 1.4 GHz data from NVSS and FIRST surveys are also included in the analysis. Results: Eighty-seven percent (21 out of 24) galaxies in our sample show 33 GHz radio continuum emission at levels of 4.5-240σ. Five sources show extended emission (deconvolved source size larger than 2.5 times the major axis of the beam), including one source with two main components and one with three main components. The remaining detected 16 sources (and also some of the above-mentioned targets) exhibit compact cores within the sensitivity limits. Little evidence is found for extended jets (>300 pc) in most sources. Either they do not exist, or our chosen frequency of 33 GHz is too high for a detection of these supposedly steep spectrum features. In NGC 4388, we find an extended jet-like feature that appears to be oriented perpendicular to the H2O megamaser disk. NGC 2273 is another candidate whose radio continuum source might be elongated perpendicular to the maser disk. Smaller 100-300 pc sized jets might also be present, as is suggested by the beam-deconvolved morphology of our

Detection of Interstellar Ortho-D2H+ with SOFIA

NASA Astrophysics Data System (ADS)

Harju, Jorma; Sipilä, Olli; Brünken, Sandra; Schlemmer, Stephan; Caselli, Paola; Juvela, Mika; Menten, Karl M.; Stutzki, Jürgen; Asvany, Oskar; Kamiński, Tomasz; Okada, Yoko; Higgins, Ronan

2017-05-01

We report on the detection of the ground-state rotational line of ortho-D2H+ at 1.477 THz (203 μm) using the German REceiver for Astronomy at Terahertz frequencies (GREAT) on board the Stratospheric Observatory For Infrared Astronomy (SOFIA). The line is seen in absorption against far-infrared continuum from the protostellar binary IRAS 16293-2422 in Ophiuchus. The para-D2H+ line at 691.7 GHz was not detected with the APEX telescope toward this position. These D2H+ observations complement our previous detections of para-H2D+ and ortho-H2D+ using SOFIA and APEX. By modeling chemistry and radiative transfer in the dense core surrounding the protostars, we find that the ortho-D2H+ and para-H2D+ absorption features mainly originate in the cool (T < 18 K) outer envelope of the core. In contrast, the ortho-H2D+ emission from the core is significantly absorbed by the ambient molecular cloud. Analyses of the combined D2H+ and H2D+ data result in an age estimate of ˜5 × 105 yr for the core, with an uncertainty of ˜2 × 105 yr. The core material has probably been pre-processed for another 5 × 105 years in conditions corresponding to those in the ambient molecular cloud. The inferred timescale is more than 10 times the age of the embedded protobinary. The D2H+ and H2D+ ions have large and nearly equal total (ortho+para) fractional abundances of ˜10-9 in the outer envelope. This confirms the central role of {{{H}}}3+ in the deuterium chemistry in cool, dense gas, and adds support to the prediction of chemistry models that also {{{D}}}3+ should be abundant in these conditions.

Abundances and Excitation of H2, H3+ & CO in Star-Forming Regions

NASA Astrophysics Data System (ADS)

Kulesa, Craig A.

Although most of the 123 reported interstellar molecules to date have been detected through millimeter-wave emission-line spectroscopy, this technique is inapplicable to non-polar molecules like H2 and H3+, which are central to our understanding of interstellar chemistry. Thus high resolution infrared absorption-line spectroscopy bears an important role in interstellar studies: chemically important non-polar molecules can be observed, and their abundances and excitation conditions can be referred to the same ``pencil beam'' absorbing column. In particular, through a weak quadrupole absorption line spectrum at near-infrared wavelengths, the abundance of cold H2 in dark molecular clouds and star forming regions can now be accurately measured and compared along the same ``pencil beam'' line of sight with the abundance of its most commonly cited surrogate, CO, and its rare isotopomers. Also detected via infrared line absorption is the pivotal molecular ion H3+, whose abundance provides the most direct measurement of the cosmic ray ionization rate in dark molecular clouds, a process that initiates the formation of many other observed molecules there. Our growing sample of H2 and CO detections now includes detailed multi-beam studies of the ρ Ophiuchi molecular cloud and NGC 2024 in Orion. We explore the excitation and degree of ortho- and para-H2 thermalization in dark clouds, variation of the CO abundance over a cloud, and the relation of H2 column density to infrared extinction mapping, far-infrared/submillimeter dust continuum emission, and large scale submillimeter CO, [C I] and HCO+ line emission -- all commonly invoked to indirectly trace H2 during the past 30+ years. For each of the distinct velocity components seen toward some embedded young stellar objects, we are also able to determine the temperature, density, and a CO/H2 abundance ratio, thus unraveling some of the internal structure of a star-forming cloud. H2 and H3+ continue to surprise and delight us

Halocarbon emissions by selected tropical seaweeds: species-specific and compound-specific responses under changing pH.

PubMed

Mithoo-Singh, Paramjeet Kaur; Keng, Fiona S-L; Phang, Siew-Moi; Leedham Elvidge, Emma C; Sturges, William T; Malin, Gill; Abd Rahman, Noorsaadah

2017-01-01

Five tropical seaweeds, Kappaphycus alvarezii (Doty) Doty ex P.C. Silva, Padina australis Hauck, Sargassum binderi Sonder ex J. Agardh (syn. S. aquifolium (Turner) C. Agardh), Sargassum siliquosum J. Agardh and Turbinaria conoides (J. Agardh) Kützing, were incubated in seawater of pH 8.0, 7.8 (ambient), 7.6, 7.4 and 7.2, to study the effects of changing seawater pH on halocarbon emissions. Eight halocarbon species known to be emitted by seaweeds were investigated: bromoform (CHBr 3 ), dibro-momethane (CH 2 Br 2 ), iodomethane (CH 3 I), diiodomethane (CH 2 I 2 ), bromoiodomethane (CH 2 BrI), bromochlorometh-ane (CH 2 BrCl), bromodichloromethane (CHBrCl 2 ), and dibro-mochloromethane (CHBr 2 Cl). These very short-lived halocarbon gases are believed to contribute to stratospheric halogen concentrations if released in the tropics. It was observed that the seaweeds emit all eight halocarbons assayed, with the exception of K. alvarezii and S. binderi for CH 2 I 2 and CH 3 I respectively, which were not measurable at the achievable limit of detection. The effect of pH on halocarbon emission by the seaweeds was shown to be species-specific and compound specific. The highest percentage changes in emissions for the halocarbons of interest were observed at the lower pH levels of 7.2 and 7.4 especially in Padina australis and Sargassum spp., showing that lower seawater pH causes elevated emissions of some halocarbon compounds. In general the seaweed least affected by pH change in terms of types of halocarbon emission, was P. australis . The commercially farmed seaweed K. alvarezii was very sensitive to pH change as shown by the high increases in most of the compounds in all pH levels relative to ambient. In terms of percentage decrease in maximum quantum yield of photosynthesis ( F v ∕ F m ) prior to and after incubation, there were no significant correlations with the various pH levels tested for all seaweeds. The correlation between percentage decrease in the maximum

Halocarbon emissions by selected tropical seaweeds: species-specific and compound-specific responses under changing pH

PubMed Central

Leedham Elvidge, Emma C.; Sturges, William T.; Malin, Gill; Abd Rahman, Noorsaadah

2017-01-01

Five tropical seaweeds, Kappaphycus alvarezii (Doty) Doty ex P.C. Silva, Padina australis Hauck, Sargassum binderi Sonder ex J. Agardh (syn. S. aquifolium (Turner) C. Agardh), Sargassum siliquosum J. Agardh and Turbinaria conoides (J. Agardh) Kützing, were incubated in seawater of pH 8.0, 7.8 (ambient), 7.6, 7.4 and 7.2, to study the effects of changing seawater pH on halocarbon emissions. Eight halocarbon species known to be emitted by seaweeds were investigated: bromoform (CHBr3), dibro­momethane (CH2Br2), iodomethane (CH3I), diiodomethane (CH2I2), bromoiodomethane (CH2BrI), bromochlorometh­ane (CH2BrCl), bromodichloromethane (CHBrCl2), and dibro­mochloromethane (CHBr2Cl). These very short-lived halocarbon gases are believed to contribute to stratospheric halogen concentrations if released in the tropics. It was observed that the seaweeds emit all eight halocarbons assayed, with the exception of K. alvarezii and S. binderi for CH2I2 and CH3I respectively, which were not measurable at the achievable limit of detection. The effect of pH on halocarbon emission by the seaweeds was shown to be species-specific and compound specific. The highest percentage changes in emissions for the halocarbons of interest were observed at the lower pH levels of 7.2 and 7.4 especially in Padina australis and Sargassum spp., showing that lower seawater pH causes elevated emissions of some halocarbon compounds. In general the seaweed least affected by pH change in terms of types of halocarbon emission, was P. australis. The commercially farmed seaweed K. alvarezii was very sensitive to pH change as shown by the high increases in most of the compounds in all pH levels relative to ambient. In terms of percentage decrease in maximum quantum yield of photosynthesis (Fv∕Fm) prior to and after incubation, there were no significant correlations with the various pH levels tested for all seaweeds. The correlation between percentage decrease in the maximum quantum yield of photosynthesis

On- and off-axis spectral emission features from laser-produced gas breakdown plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harilal, S. S.; Skrodzki, P. J.; Miloshevsky, A.

Laser-heated gas breakdown plasmas or sparks emit profoundly in the ultraviolet and visible region of the electromagnetic spectrum with contributions from ionic, atomic, and molecular species. Laser created kernels expand into a cold ambient with high velocities during its early lifetime followed by confinement of the plasma kernel and eventually collapse. However, the plasma kernels produced during laser breakdown of gases are also capable of exciting and ionizing the surrounding ambient medium. Two mechanisms can be responsible for excitation and ionization of surrounding ambient: viz. photoexcitation and ionization by intense ultraviolet emission from the sparks produced during the early timesmore » of its creation and/or heating by strong shocks generated by the kernel during its expansion into the ambient. In this study, an investigation is made on the spectral features of on- and off-axis emission features of laser-induced plasma breakdown kernels generated in atmospheric pressure conditions with an aim to elucidate the mechanisms leading to ambient excitation and emission. Pulses from an Nd:YAG laser emitting at 1064 nm with 6 ns pulse duration are used to generate plasma kernels. Laser sparks were generated in air, argon, and helium gases to provide different physical properties of expansion dynamics and plasma chemistry considering the differences in laser absorption properties, mass density and speciation. Point shadowgraphy and time-resolved imaging were used to evaluate the shock wave and spark self-emission morphology at early and late times while space and time resolved spectroscopy is used for evaluating the emission features as well as for inferring plasma fundaments at on- and off-axis. Structure and dynamics of the plasma kernel obtained using imaging techniques are also compared to numerical simulations using computational fluid dynamics code. The emission from the kernel showed that spectral features from ions, atoms and molecules are

On- and off-axis spectral emission features from laser-produced gas breakdown plasmas

DOE PAGES

Harilal, S. S.; Skrodzki, P. J.; Miloshevsky, A.; ...

2017-06-01

Laser-heated gas breakdown plasmas or sparks emit profoundly in the ultraviolet and visible region of the electromagnetic spectrum with contributions from ionic, atomic, and molecular species. Laser created kernels expand into a cold ambient with high velocities during its early lifetime followed by confinement of the plasma kernel and eventually collapse. However, the plasma kernels produced during laser breakdown of gases are also capable of exciting and ionizing the surrounding ambient medium. Two mechanisms can be responsible for excitation and ionization of surrounding ambient: viz. photoexcitation and ionization by intense ultraviolet emission from the sparks produced during the early timesmore » of its creation and/or heating by strong shocks generated by the kernel during its expansion into the ambient. In this study, an investigation is made on the spectral features of on- and off-axis emission features of laser-induced plasma breakdown kernels generated in atmospheric pressure conditions with an aim to elucidate the mechanisms leading to ambient excitation and emission. Pulses from an Nd:YAG laser emitting at 1064 nm with 6 ns pulse duration are used to generate plasma kernels. Laser sparks were generated in air, argon, and helium gases to provide different physical properties of expansion dynamics and plasma chemistry considering the differences in laser absorption properties, mass density and speciation. Point shadowgraphy and time-resolved imaging were used to evaluate the shock wave and spark self-emission morphology at early and late times while space and time resolved spectroscopy is used for evaluating the emission features as well as for inferring plasma fundaments at on- and off-axis. Structure and dynamics of the plasma kernel obtained using imaging techniques are also compared to numerical simulations using computational fluid dynamics code. The emission from the kernel showed that spectral features from ions, atoms and molecules are

X-ray and optical emission-line filaments in the cooling flow cluster 2A 0335 + 096

NASA Technical Reports Server (NTRS)

Sarazin, Craig L.; O'Connell, Robert W.; Mcnamara, Brian R.

1992-01-01

We present a new high-resolution X-ray image of the 2A 0335 + 096 cluster of galaxies obtained with the High Resolution Imager (HRI) aboard the ROSAT satellite. The presence of dense gas having a very short cooling time in the central regions confirms its earlier identification as a cooling flow. The X-ray emission from the central regions of the cooling flow shows a great deal of filamentary structure. Using the crude spectral resolution of the HRI, we show that these filaments are the result of excess emission, rather than foreground X-ray absorption. Although there are uncertainties in the pointing, many of the X-ray features in the cooling flow region correspond to features in H-alpha optical line emission. This suggests that the optical emission line gas has resulted directly from the cooling of X-ray-emitting gas. The filament material cannot be in hydrostatic equilibrium, and it is likely that other forces such as rotation, turbulence, and magnetic fields influence the dynamical state of the gas.

Hyperfine excitation of C2H and C2D by para-H2

NASA Astrophysics Data System (ADS)

Dumouchel, Fabien; Lique, François; Spielfiedel, Annie; Feautrier, Nicole

2017-10-01

The [C2H]/[C2D] abundance ratio is a useful tool to explore the physical and chemical conditions of cold molecular clouds. Hence, an accurate determination of both the C2H and C2D abundances is of fundamental interest. Due to the low density of the interstellar medium, the population of the energy levels of the molecules is not at local thermodynamical equilibrium. Thus, the accurate modelling of the emission spectra requires the calculation of collisional rate coefficients with the most abundant interstellar species. Hence, we provide rate coefficients for the hyperfine excitation of C2H and C2D by para-H2(j=0), the most abundant collisional partner in cold molecular clouds. State-to-state rate coefficients between the lowest levels were computed for temperatures ranging from 5 to 80 K. For both isotopologues, the Δj = ΔF propensity rule is observed. The comparison between C2H and C2D rate coefficients shows that differences by up to a factor of two exist, mainly for Δj = ΔN = 1 transitions. The new rate coefficients will significantly help in the interpretation of recent observed spectra.

A Study of Rovibrational H2O, OH, and CO emission from the Herbig Ae/Be star HD 250550

NASA Astrophysics Data System (ADS)

Leiendecker, Harrison; Brittain, Sean; Jensen, Stanley; Najita, Joan R.; Carr, John S.

2018-01-01

We present high-resolution spectroscopy (R∼75,000) of the Herbig Ae/Be star HD 250550. The L-band spectroscopy was obtained with the infrared echelle spectrograph (iSHELL) from The NASA Infrared Telescope Facility. We will describe the performance of the instrument and compare the CO and OH emission and upper limit on H2O emission to other Herbig Ae/Be stars. Specifically, L-band observationsof the ro-vibrational OH emission from the disk surrounding HD 250550 is compared to emission properties of the sources studied by Brittain et al. (2016). The OH 2Π3/2 P4.5 (1+,1-) doublet and the P5.5 (1+) line are spectrally resolved and have the same spectral profile as the CO ro-vibrational lines indicating that they arise from the same emitting region of the disk. The relative fluxes of the ro-vibrational lines from CO indicate that the rotational temperature of the gas is 1060 ± 115 K. The relative fluxes of the ro-vibrational lines from OH are consistent with this temperature.

HIFI Spectroscopy of H2O Submillimeter Lines in Nuclei of Actively Star-forming Galaxies

NASA Astrophysics Data System (ADS)

Liu, L.; Weiß, A.; Perez-Beaupuits, J. P.; Güsten, R.; Liu, D.; Gao, Y.; Menten, K. M.; van der Werf, P.; Israel, F. P.; Harris, A.; Martin-Pintado, J.; Requena-Torres, M. A.; Stutzki, J.

2017-09-01

We present a systematic survey of multiple velocity-resolved H2O spectra using Herschel/Heterodyne Instrument for the Far Infrared (HIFI) toward nine nearby actively star-forming galaxies. The ground-state and low-excitation lines (E up ≤ 130 K) show profiles with emission and absorption blended together, while absorption-free medium-excitation lines (130 K ≤ E up ≤ 350 K) typically display line shapes similar to CO. We analyze the HIFI observation together with archival SPIRE/PACS H2O data using a state-of-the-art 3D radiative transfer code that includes the interaction between continuum and line emission. The water excitation models are combined with information on the dust and CO spectral line energy distribution to determine the physical structure of the interstellar medium (ISM). We identify two ISM components that are common to all galaxies: a warm ({T}{dust}˜ 40{--}70 K), dense (n({{H}})˜ {10}5{--}{10}6 {{cm}}-3) phase that dominates the emission of medium-excitation H2O lines. This gas phase also dominates the far-IR emission and the CO intensities for {J}{up}> 8. In addition, a cold ({T}{dust}˜ 20{--}30 K), dense (n({{H}})˜ {10}4{--}{10}5 {{cm}}-3), more extended phase is present. It outputs the emission in the low-excitation H2O lines and typically also produces the prominent line absorption features. For the two ULIRGs in our sample (Arp 220 and Mrk 231) an even hotter and more compact (R s ≤ 100 pc) region is present, which is possibly linked to AGN activity. We find that collisions dominate the water excitation in the cold gas and for lines with {E}{up}≤slant 300 K and {E}{up}≤slant 800 K in the warm and hot component, respectively. Higher-energy levels are mainly excited by IR pumping.

High Color Rendering Index White-Light Emission from UV-Driven LEDs Based on Single Luminescent Materials: Two-Dimensional Perovskites (C6H5C2H4NH3)2PbBr xCl4- x.

PubMed

Yang, Shuming; Lin, Zhenghuan; Wang, Jingwei; Chen, Yunxiang; Liu, Zhengde; Yang, E; Zhang, Jian; Ling, Qidan

2018-05-09

Two-dimensional (2D) white-light-emitting hybrid perovskites (WHPs) are promising active materials for single-component white-light-emitting diodes (WLEDs) driven by UV. However, the reported WHPs exhibit low quantum yields (≤9%) and low color rendering index (CRI) values less than 85, which does not satisfy the demand of solid-state lighting applications. In this work, we report a series of mixed-halide 2D layered WHPs (C 6 H 5 C 2 H 4 NH 3 ) 2 PbBr x Cl 4- x (0 < x < 4) obtained from the phenethylammonium cation. Unlike the reported WHPs including (C 6 H 5 C 2 H 4 NH 3 ) 2 PbCl 4 , the mixed-halide perovskites display morphology-dependent white emission for the different extents of self-absorption. Additionally, the amount of Br has a huge influence on the photophysical properties of mixed-halide WHPs. With the increasing content of Br, the quantum yields of WHPs increase gradually from 0.2 to 16.9%, accompanied by tunable color temperatures ranging from 4000 K ("warm" white light) to 7000 K ("cold" white light). When applied to the WLEDs, the mixed-halide perovskite powders exhibit tunable white electroluminescent emission with very high CRI of 87-91.

The discovery of a new infrared emission feature at 1905 wavenumbers (5.25 microns) in the spectrum of BD + 30 deg 3639 and its relation to the polycyclic aromatic hydrocarbon model

NASA Technical Reports Server (NTRS)

Allamandola, L. J.; Bregman, J. D.; Sandford, S. A.; Tielens, A. G. G. M.; Witteborn, F. C.

1989-01-01

A new IR emission feature at 1905/cm (5.25 microns) has been discovered in the spectrum of BD + 30 deg 3639. This feature joins the family of well-known IR emission features at 3040, 2940, 1750, 1610, '1310', 1160, and 890/cm. The origin of this new feature is discussed and it is assigned to an overtone or combination band involving C-H bending modes of polycyclic aromatic hydrocarbons (PAHs). Laboratory work suggests that spectral studies of the 2000-1650/cm region may be very useful in elucidating the molecular structure of interstellar PAHs. The new feature, in conjunction with other recently discovered spectral structures, suggests that the narrow IR emission features originate in PAH molecules rather than large carbon grains.

Infrared and near infrared emission spectra of TeH and TeD

NASA Astrophysics Data System (ADS)

Yu, Shanshan; Shayesteh, Alireza; Fu, Dejian; Bernath, Peter F.

2005-04-01

The vibration-rotation emission spectra for the X2Π ground state and the near infrared emission spectra of the X2Π 1/2- X2Π 3/2 system of the TeH and TeD free radicals have been measured at high resolution using a Fourier transform spectrometer. TeH and TeD were generated in a tube furnace with a DC discharge of a flowing mixture of argon, hydrogen (or deuterium), and tellurium vapor. In the infrared region, for the X2Π 3/2 spin component we observed the 1-0, 2-1, and 3-2 vibrational bands for most of the eight isotopologues of TeH and the 1-0 and 2-1 bands for three isotopologues of TeD. For the X2Π 1/2- X2Π 3/2 transition, we observed the 0-0 and 1-1 bands for TeH and the 0-0, 1-1, and 2-2 bands for TeD. Except for a few lines, the tellurium isotopic shift was not resolved for the X2Π 1/2- X2Π 3/2 transitions of TeH and TeD. Local perturbations with Δ v = 2 between the two spin components of the X2Π state of TeH were found: X2Π 1/2, v = 0 with X2Π 3/2, v = 2; X2Π 1/2, v = 1 with X2Π 3/2, v = 3. The new data were combined with the previous data from the literature and two kinds of fits (Hund's case (a) and Hund's case (c)) were carried out for each of the 10 observed isotopologues: 130TeD, 128TeD, 126TeD, 130TeH, 128TeH, 126TeH, 125TeH, 124TeH, 123TeH, and 122TeH.

N2O, NO, N2 and CO2 emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores

NASA Astrophysics Data System (ADS)

Werner, C.; Reiser, K.; Dannenmann, M.; Hutley, L. B.; Jacobeit, J.; Butterbach-Bahl, K.

2014-11-01

Strong seasonal variability of hygric and thermal soil conditions are a defining environmental feature in northern Australia. However, how such changes affect the soil-atmosphere exchange of nitrous oxide (N2O), nitric oxide (NO) and dinitrogen (N2) is still not well explored. By incubating intact soil cores from four sites (three savanna, one pasture) under controlled soil temperatures (ST) and soil moisture (SM) we investigated the release of the trace gas fluxes of N2O, NO and carbon dioxide (CO2). Furthermore, the release of N2 due to denitrification was measured using the helium gas flow soil core technique. Under dry pre-incubation conditions NO and N2O emissions were very low (<7.0 ± 5.0 μg NO-N m-2 h-1; <0.0 ± 1.4 μg N2O-N m-2 h-1) or in the case of N2O, even a net soil uptake was observed. Substantial NO (max: 306.5 μg N m-2 h-1) and relatively small N2O pulse emissions (max: 5.8 ± 5.0 μg N m-2 h-1) were recorded following soil wetting, but these pulses were short lived, lasting only up to 3 days. The total atmospheric loss of nitrogen was generally dominated by N2 emissions (82.4-99.3% of total N lost), although NO emissions contributed almost 43.2% to the total atmospheric nitrogen loss at 50% SM and 30 °C ST incubation settings (the contribution of N2 at these soil conditions was only 53.2%). N2O emissions were systematically higher for 3 of 12 sample locations, which indicates substantial spatial variability at site level, but on average soils acted as weak N2O sources or even sinks. By using a conservative upscale approach we estimate total annual emissions from savanna soils to average 0.12 kg N ha-1 yr-1 (N2O), 0.68 kg N ha-1 yr-1 (NO) and 6.65 kg N ha-1 yr-1 (N2). The analysis of long-term SM and ST records makes it clear that extreme soil saturation that can lead to high N2O and N2 emissions only occurs a few days per year and thus has little impact on the annual total. The potential contribution of nitrogen released due to pulse events

40 CFR 75.19 - Optional SO2, NOX, and CO2 emissions calculation for low mass emissions (LME) units.

Code of Federal Regulations, 2012 CFR

2012-07-01

... hourly SO2 mass emissions under this section. Alternatively, for fuel oil combustion, a lower, fuel... (or ozone season) prior to the year of the test (g H2O/g air). Ho = Observed humidity ratio during the test run (g H2O/g air). Tr = Average annual atmospheric temperature (or average ozone season...

Redox and pH Dual-Responsive Polymeric Micelles with Aggregation-Induced Emission Feature for Cellular Imaging and Chemotherapy.

PubMed

Zhuang, Weihua; Xu, Yangyang; Li, Gaocan; Hu, Jun; Ma, Boxuan; Yu, Tao; Su, Xin; Wang, Yunbing

2018-05-21

Intelligent polymeric micelles for antitumor drug delivery and tumor bioimaging have drawn a broad attention because of their reduced systemic toxicity, enhanced efficacy of drugs, and potential application of tumor diagnosis. Herein, we developed a multifunctional polymeric micelle system based on a pH and redox dual-responsive mPEG-P(TPE- co-AEMA) copolymer for stimuli-triggered drug release and aggregation-induced emission (AIE) active imaging. These mPEG-P(TPE- co-AEMA)-based micelles showed excellent biocompatibility and emission property, exhibiting great potential application for cellular imaging. Furthermore, the antitumor drug doxorubicin (DOX) could be encapsulated during self-assembly process with high loading efficiency, and a DOX-loaded micelle system with a size of 68.2 nm and narrow size distribution could be obtained. DOX-loaded micelles demonstrated great tumor suppression ability in vitro, and the dual-responsive triggered intracellular drug release could be further traced. Moreover, DOX-loaded micelles could efficiently accumulate at the tumor site because of enhanced permeability and retention effect and long circulation of micelles. Compared with free DOX, DOX-loaded micelles exhibited better antitumor effect and significantly reduced adverse effects. Given the efficient accumulation targeting to tumor tissue, dual-responsive drug release, and excellent AIE property, this polymeric micelle would be a potential candidate for cancer therapy and diagnosis.

Spectroscopic properties of the 1.4 microm emission of Tm3+ ions in TeO2-WO3-PbO glasses.

PubMed

Balda, R; Lacha, L M; Fernández, J; Arriandiaga, M A; Fernández-Navarro, J M; Muñoz-Martin, D

2008-08-04

In this work, we report the spectroscopic properties of the infrared 3H4-->3F4 emission of Tm3+ ions in two different compositions of glasses based on TeO2, WO3, and PbO for three Tm2O3 concentrations (0.1,0.5, and 1 wt%). Judd-Ofelt intensity parameters have been determined and used to calculate the radiative transition probabilities and radiative lifetimes. The infrared emission at around 1490 nm corresponding to the 3H4-->F4 transition has two noticeable features if compared to fluoride glasses used for S-band amplifiers. On one hand, it is broader by nearly 30 nm, and on the other, the stimulated emission cross section is twice the value for fluoride glasses. Both the relative intensity ratio of the 1490 nm emission to 1820 nm and the measured lifetime of the 3H4 level decrease as concentration increases, due to the existence of energy transfer via cross-relaxation among Tm3+ ions. The analysis of the decays from the 3H4 level with increasing concentration indicates the presence of a dipole-dipole quenching process assisted by energy migration.

Detection of Thermal 2 cm and 1 cm Formaldehyde Emission in NGC 7538

NASA Astrophysics Data System (ADS)

Yuan, Liang; Araya, E. D.; Hofner, P.; Kurtz, S.; Pihlstrom, Y.

2011-05-01

Formaldehyde is a tracer of high density gas in massive star forming regions. The K-doublet lines from the three lowest rotational energy levels of ortho-formaldehyde correspond to wavelengths of 6, 2 and 1 cm. Thermal emission of these transitions is rare, and maser emission has only been detected in the 6 cm line. NGC 7538 is an active site of massive star formation in the Galaxy, and one of only a few regions known to harbor 6 cm formaldehyde (H2CO) masers. Using the NRAO 100 m Green Bank Telescope (GBT), we detected 2 cm H2CO emission toward NGC 7538 IRS1. The velocity of the 2 cm H2CO line is very similar to the velocity of one of the 6 cm H2CO masers but the linewidth is greater. To investigate the nature of the 2 cm emission, we conducted observations of the 1 cm H2CO transition, and obtained a cross-scan map of the 2 cm line. We detected 1 cm emission and found that the 2 cm emission is extended (greater than 30"), which implies brightness temperatures of ˜0.2 K. Assuming optically thin emission, LTE, and that the 1 cm and 2 cm lines originate from the same volume of gas, both these detections are consistent with thermal emission of gas at ˜30 K. We conclude that the 1 cm and 2 cm H2CO lines detected with the GBT are thermal, which implies molecular densities above ˜105 cm-3. LY acknowledges support from WIU. PH acknowledges partial support from NSF grant AST-0908901.

Carbon stars with alpha-C:H emission

NASA Technical Reports Server (NTRS)

Gerbault, Florence; Goebel, John H.

1989-01-01

Many carbon stars in the IRS low resolution spectra (LRS) catalog were found which display emission spectra that compare favorable with the absorption spectrum of alpha-C:H. These stars have largely been classified as 4X in the LRS which has led to their interpretation by others in terms of displaying a mixture of the UIRF's 8.6 micron band and SiC at 11.5 microns. It was also found that many of these stars have a spectral upturn at 20+ microns which resembles the MgS band seen in carbon stars and planetary nebulae. It was concluded that this group of carbon stars will evolve into planetary nebulae like NGC 7027 and IC 418. In the presence of hard ultraviolet radiation the UIRF's will light up and be displayed as narrow emission bands on top of the broad alpha-C:H emission bands.

CO2 emissions from German drinking water reservoirs.

PubMed

Saidi, Helmi; Koschorreck, Matthias

2017-03-01

Globally, reservoirs are a significant source of atmospheric CO 2 . However, precise quantification of greenhouse gas emissions from drinking water reservoirs on the regional or national scale is still challenging. We calculated CO 2 fluxes for 39 German drinking water reservoirs during a period of 22years (1991-2013) using routine monitoring data in order to quantify total emission of CO 2 from drinking water reservoirs in Germany and to identify major drivers. All reservoirs were a net CO 2 source with a median flux of 167gCm -2 y -1 , which makes gaseous emissions a relevant process for the carbon budget of each reservoir. Fluxes varied seasonally with median fluxes of 13, 48, and 201gCm -2 y -1 in spring, summer, and autumn respectively. Differences between reservoirs appeared to be primarily caused by the concentration of CO 2 in the surface water rather than by the physical gas transfer coefficient. Consideration of short term fluctuations of the gas transfer coefficient due to varying wind speed had only a minor effect on the annual budgets. High CO 2 emissions only occurred in reservoirs with pH<7 and total alkalinity <0.2mEql -1 . Annual CO 2 emissions correlated exponentially with pH but not with dissolved organic carbon (DOC). There was significant correlation between land use in the catchment and CO 2 emissions. In total, German drinking water reservoirs emit 44000t of CO 2 annually, which makes them a negligible CO 2 source (<0.005% of national CO 2 emissions) in Germany. Copyright © 2017 Elsevier B.V. All rights reserved.

Fumarole/plume and diffuse CO2 emission from Sierra Negra caldera, Galapagos archipelago

NASA Astrophysics Data System (ADS)

Padrón, Eleazar; Hernández, Pedro A.; Pérez, Nemesio M.; Toulkeridis, Theofilos; Melián, Gladys; Barrancos, José; Virgili, Giorgio; Sumino, Hirochika; Notsu, Kenji

2012-08-01

Measurements of visible and diffuse gas emission were conducted in 2006 at the summit of Sierra Negra volcano, Galapagos, with the aim to better characterize degassing after the 2005 eruption. A total SO2 emission of 11 ± 2 t day-1 was derived from miniature differential optical absorption spectrometer (mini-DOAS) ground-based measurements of the plume emanating from the Mini Azufral fumarolic area, the most important site of visible degassing at Sierra Negra volcano. Using a portable multigas system, the H2S/SO2, CO2/SO2, and H2O/SO2 molar ratios in the Mina Azufral plume emissions were found to be 0.41, 52.2, and 867.9, respectively. The corresponding H2O, CO2, and H2S emission rates were 562, 394, and 3 t day-1, respectively. The total output of diffuse CO2 emissions from the summit of Sierra Negra volcano was 990 ± 85 t day-1, with 605 t day-1 being released by a deep source. The diffuse-to-plume CO2 emission ratio was about 1.5. Mina Azufral fumaroles released gasses containing 73.6 mol% of H2O; the main noncondensable components amounted to 97.4 mol% CO2, 1.5 mol% SO2, 0.6 mol% H2S, and 0.35 mol% N2. The higher H2S/SO2 ratio values found in 2006 as compared to those reported before the 2005 eruption reveal a significant hydrothermal contribution to the fumarolic emissions. 3He/4He ratios measured at Mina Azufral fumarolic discharges showed values of 17.88 ± 0.25 R A , indicating a mid-ocean ridge basalts (MORB) and a Galapagos plume contribution of 53 and 47 %, respectively.

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

NASA Technical Reports Server (NTRS)

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

1995-01-01

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

Simultaneous 183 GHz H2O maser and SiO observations towards evolved stars using APEX SEPIA Band 5

NASA Astrophysics Data System (ADS)

Humphreys, E. M. L.; Immer, K.; Gray, M. D.; De Beck, E.; Vlemmings, W. H. T.; Baudry, A.; Richards, A. M. S.; Wittkowski, M.; Torstensson, K.; De Breuck, C.; Møller, P.; Etoka, S.; Olberg, M.

2017-07-01

Aims: The aim is to investigate the use of 183 GHz H2O masers for characterization of the physical conditions and mass loss process in the circumstellar envelopes of evolved stars. Methods: We used APEX SEPIA Band 5 (an ALMA Band 5 receiver on the APEX telescope) to observe the 183 GHz H2O line towards two red supergiant (RSG) and three asymptotic giant branch (AGB) stars. Simultaneously, we observed the J = 4-3 line for 28SiO v = 0, 1, 2 and 3, and for 29SiO v = 0 and 1. We compared the results with simulations and radiative transfer models for H2O and SiO, and examined data for the individual linear orthogonal polarizations. Results: We detected the 183 GHz H2O line towards all the stars with peak flux densities >100 Jy, including a new detection from VY CMa. Towards all five targets, the water line had indications of being caused by maser emission and had higher peak flux densities than for the SiO lines. The SiO lines appear to originate from both thermal and maser processes. Comparison with simulations and models indicate that 183 GHz maser emission is likely to extend to greater radii in the circumstellar envelopes than SiO maser emission and to similar or greater radii than water masers at 22, 321 and 325 GHz. We speculate that a prominent blue-shifted feature in the W Hya 183 GHz spectrum is amplifying the stellar continuum, and is located at a similar distance from the star as mainline OH maser emission. We note that the coupling of an SiO maser model to a hydrodynamical pulsating model of an AGB star yields qualitatively similar simulated results to the observations. From a comparison of the individual polarizations, we find that the SiO maser linear polarization fraction of several features exceeds the maximum fraction allowed under standard maser assumptions and requires strong anisotropic pumping of the maser transition and strongly saturated maser emission. The low polarization fraction of the H2O maser however, fits with the expectation for a non

New Optical Constants for Amorphous and Crystalline H2O-ice and H2O-mixtures.

NASA Technical Reports Server (NTRS)

Mastrapa, Rachel; Bernstein, Max; Sandford, Scott

2006-01-01

We will present the products of new laboratory measurements of ices relevant to Trans-Neptunian Objects. We have calculated the real and imaginary indices of refraction for amorphous and crystalline H2O-ice and also H2O-rich ices containing other molecular species. We create ice samples by condensing gases onto a cold substrate. We measure the thickness of the sample by reflecting a He-Ne laser off of the sample and counting interference fringes as it grows. We then collect transmission spectra of the samples in the wavelength range from 0.7-22 micrometers. Using the thickness and the transmission spectra of the ice we calculate the imaginary part of the index of refraction. We then use a Kramers-Kronig calculation to calculate the real part of the index of refraction (Berland et al. 1994; Hudgins et al. 1993). These optical constants can then be used to create model spectra for comparison to spectra from Solar System objects, including TNOs. We will summarize the difference between the amorphous and crystalline H2O-ice spectra. These changes include weakening of features and shifting of features to shorter wavelength. One important result is that the 2 pm feature is stronger in amorphous H2O ice than it is in crystalline H2O-ice. We will also discuss the changes seen when H2O is mixed with other components, including CO2, CH4, HCN, and NH3 (Bernstein et al. 2005; Bernstein et al. 2006).

H α VARIABILITY IN PTFO 8-8695 AND THE POSSIBLE DIRECT DETECTION OF EMISSION FROM A 2 MILLION YEAR OLD EVAPORATING HOT JUPITER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johns-Krull, Christopher M.; Chen, Wei; Frazier, Sarah A., E-mail: cmj@rice.edu, E-mail: wc2@rice.edu, E-mail: sarah.a.frazier@rice.edu

We use high time cadence, high spectral resolution optical observations to detect excess H α emission from the 2–3 Myr old weak-lined T Tauri star PTFO 8-8695. This excess emission appears to move in velocity as expected if it were produced by the suspected planetary companion to this young star. The excess emission is not always present, but when it is, the predicted velocity motion is often observed. We have considered the possibility that the observed excess emission is produced by stellar activity (flares), accretion from a disk, or a planetary companion; we find the planetary companion to be themore » most likely explanation. If this is the case, the strength of the H α line indicates that the emission comes from an extended volume around the planet, likely fed by mass loss from the planet which is expected to be overflowing its Roche lobe.« less

ALFALFA and WSRT Imaging of Extended H I Features in the Leo Cloud of Galaxies

NASA Astrophysics Data System (ADS)

Leisman, Lukas; Haynes, Martha P.; Giovanelli, Riccardo; Józsa, Gyula; Adams, Elizabeth A. K.; Hess, Kelley M.

2016-12-01

We present Arecibo Legacy Fast ALFA (ALFALFA) H I observations of a well-studied region of the Leo Cloud, which includes the NGC 3227 group and the NGC 3190 group. We detect optically dark H I tails and plumes with extents potentially exceeding 600 kpc, well beyond the field of view of previous observations. These H I features contain ˜40 per cent of the total H I mass in the NGC 3227 group and ˜10 per cent of the NGC 3190 group. We also present Westerbork Synthesis Radio Telescope (WSRT) maps which show the complex morphology of the extended emission in the NGC 3227 group. We comment on previously proposed models of the interactions in these groups and the implications for the scale of group processing through interactions. Motivated by the extent of the H I plumes, we place the H I observations in the context of the larger loose group, demonstrating the need for future sensitive, wide field H I surveys to understand the role of group processing in galaxy evolution.

SWIFT observations and flash ionization features in the spectrum of DLT17h/SN 2017ahn

NASA Astrophysics Data System (ADS)

Tartaglia, L.; Hosseinzadeh, G.; Sand, D.; Valenti, S.; Wyatt, S.; Arcavi, I.; Howell, D. A.; McCully, C.

2017-02-01

We report follow-up observations of the Type II DLT17h/SN 2017ahn (ATels #10058, #10059) in the UV domain with the SWIFT satellite (Gehrels et al. 2004). Three target of opportunity observations were obtained on 2017-02-08.6 ( 3.0 ks), 2017-02-09.2 ( 3.2 ks) and 2017-02-09.6 ( 3.2 ks). DLT17h was detected in the Swift UV/Optical Telescope (UVOT; Roming et al. 2005) data with the following apparent magnitudes: JD | Mag | Err | Filter 2457793.121 | 16.99 | 0.10 | V 2457793.131 | 16.65 | 0.06 | UVM2 2457793.146 | 16.49 | 0.07 | UVW1 2457793.148 | 16.43 | 0.06 | U 2457793.149 | 17.42 | 0.06 | B 2457793.151 | 16.62 | 0.08 | UVW2 2457793.722 | 15.84 | 0.06 | UVM2 2457793.750 | 15.64 | 0.06 | UVW1 2457793.751 | 15.76 | 0.06 | U 2457793.751 | 16.76 | 0.05 | B 2457793.753 | 15.78 | 0.07 | UVW2 2457793.754 | 16.58 | 0.07 | V 2457794.081 | 15.72 | 0.06 | U 2457794.082 | 16.64 | 0.06 | B 2457794.085 | 16.50 | 0.08 | V 2457794.112 | 15.77 | 0.08 | UVW1 2457794.115 | 15.78 | 0.08 | UVW2 2457794.120 | 15.72 | 0.07 | UVM2 We also report the presence of flash ionization features (H-alpha, H-beta, He I, He II, and N IV emission with electron-scattering profiles; see Gal-Yam et al. 2014, Nature, 509, 471) in spectra of DLT17h/SN 2017ahn taken on 2017 February 9 UT with the robotic FLOYDS instrument mounted on the Las Cumbres Observatory 2-meter telescope on Haleakala, Hawai'i.

Analytic H I-to-H2 Photodissociation Transition Profiles

NASA Astrophysics Data System (ADS)

Bialy, Shmuel; Sternberg, Amiel

2016-05-01

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

Satellite Boreal Measurements over Alaska and Canada During June-July 2004: Simultaneous Measurements of Upper Tropospheric CO, C2H6, HCN, CH3Cl, CH4, C2H2, CH2OH, HCOOH, OCS, and SF6 Mixing Ratios

NASA Technical Reports Server (NTRS)

Rinsland, Curtis P.; Dufour, Gaelle; Boone, Chris D.; Bernath, Peter F.; Chiou, Linda; Coheur, Pierre-Francois; Turquety, Solene; Clerbaux, Cathy

2007-01-01

Simultaneous ACE (Atmospheric Chemistry Experiment) upper tropospheric CO, C2H6, HCN, CH3Cl, CH4 , C2H2 , CH30H, HCOOH, and OCS measurements show plumes up to 185 ppbv (10 (exp -9) per unit volume) for CO, 1.36 ppbv for C2H6, 755 pptv (10(exp -12) per unit volume) for HCN, 1.12 ppbv for CH3C1, 1.82 ppmv, (10(exp -6) per unit volume) for CH4, 0.178 ppbv for C2H2, 3.89 ppbv for CH30H, 0.843 ppbv for HCOOH, and 0.48 ppbv for OCS in western Canada and Alaska at 50 deg N-68 deg N latitude between 29 June and 23 July 2004. Enhancement ratios and emission factors for HCOOH, CH30H, HCN, C2H6, and OCS relative to CO at 250-350 hPa are inferred from measurements of young plumes compared with lower mixing ratios assumed to represent background conditions based on a CO emission factor derived from boreal measurements. Results are generally consistent with the limited data reported for various vegetative types and emission phases measured in extratropical forests including boreal forests. The low correlation between fire product emission mixing ratios and the S176 mixing ratio is consistent with no significant SF6 emissions from the biomass fires.

On the carriers of the 21μm emission feature in post-asymptotic giant branch stars

NASA Astrophysics Data System (ADS)

Zhang, Ke; Jiang, B. W.; Li, Aigen

2009-07-01

The mysterious 21μm emission feature seen in sixteen C-rich proto-planetary nebulae (PPNe) remains unidentified since its discovery in 1989. Over a dozen of materials are suggested as the carrier candidates. In this work, we quantitatively investigate eight inorganic and one organic carrier candidates in terms of elemental abundance constraints, while previous studies mostly focus on their spectral profiles (which could be largely affected by grain size, shape and clustering effects). It is found that: (1) five candidates (TiC nanoclusters, fullerenes coordinated with Ti atoms, SiS2, doped-SiC and SiO2-coated SiC dust) violate the abundance constraints (i.e. they require too much Ti, S or Si to account for the emission power of the 21μm band, (2) three candidates (carbon and silicon mixtures, Fe2O3 and Fe3O4), while satisfying the abundance constraints, exhibit secondary features which are not detected in the 21μm sources and (3) nano FeO, neither exceeding the abundance budget nor producing undetected secondary features, seems to be a viable candidate, supporting the suggestions of Posch, Mutschke & Andersen.

Meridional Variations of C2H2 and C2H6 in Jupiter's Atmosphere from Cassini CIRS Infrared Spectra

NASA Technical Reports Server (NTRS)

Nixon, C. A.; Achterberg, R. K.; Conrath, B. J.; Irwin, P. G. J.; Fouchet, T.; Parrish, P. D.; Abbas, M.; LeClaire, A.; Romani, P. N.; Simon-Miller, A. A.

2004-01-01

The abundances of hydrocarbons such as acetylene (C2H2) and ethane (C2H6) in Jupiter's atmosphere are important physical quantities, constraining our models of the chemical and dynamical processes. However, our knowledge of these quantities and their vertical and latitudinal variations has remained sparse. The flyby of the Cassini spacecraft with Jupiter at the end of 2000 provided an excellent opportunity to observe the infrared spectrum with the Composite Infrared Spectrometer (CIRS) instrument, mapping the spatial variation of emissions from 10-1400 cm-1. CIRS spectra taken at the highest resolution (0.5 cm-1) in early December 2000 have been analysed to infer atmospheric temperatures in the stratosphere at 0.5-20 mbar via the v4 of CH4, and in the troposphere at 100-400 mbar, via the hydrogen collision-induced continuum absorption at 600-800 cm. Simultaneously, we have searched for meridional abundance variations in C2H2 and C2H6 via the v5 and vg bands respectively. Tropospheric absorption and stratospheric emission are highly anti-correlated at the CIM resolution, introducing a non-uniqueness into the retrievals, which means that vertical gradient and column abundance cannot be simultaneously found without additional constraints. If we assume the profile shapes from photochemical model calculations, we show that the column abundance of C2H2 must decrease sharply towards the poles, while C2H6 is constant or slightly increasing. The relevance of these results to current photochemical and dynamical knowledge of Jupiter's atmosphere is discussed.

Characterising the VHE diffuse emission in the central 200 parsecs of our Galaxy with H.E.S.S.

NASA Astrophysics Data System (ADS)

H.E.S.S. Collaboration; Abdalla, H.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Andersson, T.; Angüner, E. O.; Arakawa, M.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bonnefoy, S.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Büchele, M.; Bulik, T.; Capasso, M.; Carr, J.; Casanova, S.; Cerruti, M.; Chakraborty, N.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Coffaro, M.; Colafrancesco, S.; Cologna, G.; Condon, B.; Conrad, J.; Cui, Y.; Davids, I. D.; Decock, J.; Degrange, B.; Deil, C.; Devin, J.; deWilt, P.; Dirson, L.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O.'C.; Dutson, K.; Dyks, J.; Edwards, T.; Egberts, K.; Eger, P.; Ernenwein, J.-P.; Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Funk, S.; Füßling, M.; Gabici, S.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goyal, A.; Grondin, M.-H.; Hahn, J.; Haupt, M.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holch, T. L.; Holler, M.; Horns, D.; Ivascenko, A.; Iwasaki, H.; Jacholkowska, A.; Jamrozy, M.; Janiak, M.; Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jogler, T.; Jouvin, L.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katsuragawa, M.; Katz, U.; Kerszberg, D.; Khangulyan, D.; Khélifi, B.; King, J.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lees, J.-P.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; López-Coto, R.; Lypova, I.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Morå, K.; Moulin, E.; Murach, T.; Nakashima, S.; de Naurois, M.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Ohm, S.; Ostrowski, M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Pekeur, N. W.; Pelletier, G.; Perennes, C.; Petrucci, P.-O.; Peyaud, B.; Piel, Q.; Pita, S.; Poon, H.; Prokhorov, D.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Rauth, R.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Richter, S.; Rieger, F.; Romoli, C.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Saito, S.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer, S.; Seglar-Arroyo, M.; Settimo, M.; Seyffert, A. S.; Shafi, N.; Shilon, I.; Simoni, R.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stycz, K.; Sushch, I.; Takahashi, T.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tibaldo, L.; Tiziani, D.; Tluczykont, M.; Trichard, C.; Tsuji, N.; Tuffs, R.; Uchiyama, Y.; van der Walt, D. J.; van Eldik, C.; van Rensburg, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zaborov, D.; Zacharias, M.; Zanin, R.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Żywucka, N.

2018-04-01

The diffuse very high-energy (VHE; >100 GeV) γ-ray emission observed in the central 200 pc of the Milky Way by H.E.S.S. was found to follow dense matter distribution in the central molecular zone (CMZ) up to a longitudinal distance of about 130 pc to the Galactic centre (GC), where the flux rapidly decreases. This was initially interpreted as the result of a burst-like injection of energetic particles 104 yr ago, but a recent more sensitive H.E.S.S. analysis revealed that the cosmic-ray (CR) density profile drops with the distance to the centre, making data compatible with a steady cosmic PeVatron at the GC. In this paper, we extend this analysis to obtain, for the first time, a detailed characterisation of the correlation with matter and to search for additional features and individual γ-ray sources in the inner 200 pc. Taking advantage of 250 h of H.E.S.S. data and improved analysis techniques, we perform a detailed morphology study of the diffuse VHE emission observed from the GC ridge and reconstruct its total spectrum. To test the various contributions to the total γ-ray emission, we used an iterative 2D maximum-likelihood approach that allows us to build a phenomenological model of the emission by summing a number of different spatial components. We show that the emission correlated with dense matter covers the full CMZ and that its flux is about half the total diffuse emission flux. We also detect some emission at higher latitude that is likely produced by hadronic collisions of CRs in less dense regions of the GC interstellar medium. We detect an additional emission component centred on the GC and extending over about 15 pc that is consistent with the existence of a strong CR density gradient and confirms the presence of a CR accelerator at the very centre of our Galaxy. We show that the spectrum of full ridge diffuse emission is compatible with that previously derived from the central regions, suggesting that a single population of particles fills the

Quantum dynamics of the Mu+H2(HD,D2) and H+MuH(MuD) reactions

NASA Astrophysics Data System (ADS)

Tsuda, Ken-ichiro; Moribayashi, Kengo; Nakamura, Hiroki

1995-10-01

Quantum mechanically accurate calculations are carried out for the following reactions involving muonium atom (Mu) using the hyperspherical coordinate approach: Mu+H2→MuH+H, Mu+D2→MuD+D, Mu+HD→MuH(MuD)+D(H), H+MuH→MuH+H, and H+MuD ↔MuH+D. The initial vibrational state is restricted to the ground state (vi=0) and the collision energies considered are up to ˜1.2 eV. The various aspects of the dynamics, such as the isotope effects, the initial rotational state (ji) dependence, and the final rotational state (jf) distribution are analyzed for a wide range of ji and jf. Some of the isotope effects can be interpreted in terms of the variations in reaction barrier and endothermicity. The following two intriguing features are also found: (1) strong enhancement of reaction by initial rotational excitation, and (2) oscillation of integral cross section as a function of collision energy in the case of the Mu-transfer reactions.

The far-ultraviolet /1180-1950 A/ emission spectrum of Arcturus

NASA Technical Reports Server (NTRS)

Mckinney, W. R.; Giles, J. W.; Moos, H. W.

1976-01-01

The far-ultraviolet (1180-1950 A) emission spectrum of the K2 IIIp star, Arcturus, has been obtained with a rocket-borne multichannel spectrometer. The use of multiple detectors gave an increase in effective observing time and permitted an improvement in spectral resolution over two previous rocket measurements. H I at 1216-A and O I at 1304 A are the only identified emissions, and the observed H I 1216-A flux is low compared with previous observations. A third unidentified feature was observed at 1511 A. The absence of many lines found in emission from the sun is striking. The absence of certain features implies that the coronal temperature must be either below 50,000 K or above 350,000 K.

A study of extreme carbon stars. I - Silicon carbide emission features

NASA Technical Reports Server (NTRS)

Cohen, M.

1984-01-01

10-micron spectra of many extreme carbon stars reveal a prominent emission feature near 11 microns. This is compared with laboratory spectra of SiC grains. Two distinct types of features are found, perhaps indicative of different mechanisms of grain formation in different stars. Estimates are made of probable column densities and total masses of SiC in the circumstellar shells.

Apparatus and method for preparing oxygen-15 labeled water H.sub.2 [.sup.15 O] in an injectable form for use in positron emission tomography

DOEpatents

Ferrieri, Richard A.; Schlyer, David J.; Alexoff, David

1996-01-09

A handling and processing apparatus for preparing Oxygen-15 labeled water (H.sub.2 [.sup.15 O]) in injectable form for use in Positron Emission Tomography from preferably H.sub.2 [.sup.15 O] produced by irradiating a flowing gas target of nitrogen and hydrogen. The apparatus includes a collector for receiving and directing a gas containing H.sub.2 [.sup.15 O] gas and impurities, mainly ammonia (NH.sub.3) gas into sterile water to trap the H.sub.2 [.sup.15 O] and form ammonium (NH.sub.4.sup.+) in the sterile water. A device for displacing the sterile water containing H.sub.2 [.sup.15 O] and NH.sub.4.sup.+ through a cation resin removes NH.sub.4.sup.+ from the sterile water. A device for combining the sterile water containing H.sub.2 [.sup.15 O] with a saline solution produces an injectable solution. Preferably, the apparatus includes a device for delivering the solution to a syringe for injection into a patient. Also, disclosed is a method for preparing H.sub.2 [.sup.15 O] in injectable form for use in Positron Emission Tomography in which the method neither requires isotopic exchange reaction nor application of high temperature.

Apparatus and method for preparing oxygen-15 labeled water H{sub 2}[{sup 15}O] in an injectable form for use in positron emission tomography

DOEpatents

Ferrieri, R.A.; Schlyer, D.J.; Alexoff, D.

1996-01-09

A handling and processing apparatus is revealed for preparing Oxygen-15 labeled water (H{sub 2}[{sup 15}O]) in injectable form for use in Positron Emission Tomography from preferably H{sub 2}[{sup 15}O] produced by irradiating a flowing gas target of nitrogen and hydrogen. The apparatus includes a collector for receiving and directing a gas containing H{sub 2}[{sup 15}O] gas and impurities, mainly ammonia (NH{sub 3}) gas into sterile water to trap the H{sub 2}[{sup 15}O] and form ammonium (NH{sub 4}{sup +}) in the sterile water. A device for displacing the sterile water containing H{sub 2}[{sup 15}O] and NH{sub 4}{sup +} through a cation resin removes NH{sub 4}{sup +} from the sterile water. A device for combining the sterile water containing H{sub 2}[{sup 15}O] with a saline solution produces an injectable solution. Preferably, the apparatus includes a device for delivering the solution to a syringe for injection into a patient. Also, disclosed is a method for preparing H{sub 2}[{sup 15}O] in injectable form for use in Positron Emission Tomography in which the method neither requires isotopic exchange reaction nor application of high temperature. 7 figs.

Assessment of Molecular, Antigenic, and Pathological Features of Canine Influenza A(H3N2) Viruses That Emerged in the United States

PubMed Central

Pulit-Penaloza, Joanna A.; Simpson, Natosha; Yang, Hua; Creager, Hannah M.; Jones, Joyce; Carney, Paul; Belser, Jessica A.; Yang, Genyan; Chang, Jessie; Zeng, Hui; Thor, Sharmi; Jang, Yunho; Killian, Mary Lea; Jenkins-Moore, Melinda; Janas-Martindale, Alicia; Dubovi, Edward; Wentworth, David E.; Stevens, James; Tumpey, Terrence M.; Davis, C. Todd; Maines, Taronna R.

2017-01-01

Background A single subtype of canine influenza virus (CIV), A(H3N8), was circulating in the United States until a new subtype, A(H3N2), was detected in Illinois in spring 2015. Since then, this CIV has caused thousands of infections in dogs in multiple states. Methods In this study, genetic and antigenic properties of the new CIV were evaluated. In addition, structural and glycan array binding features of the recombinant hemagglutinin were determined. Replication kinetics in human airway cells and pathogenesis and transmissibility in animal models were also assessed. Results A(H3N2) CIVs maintained molecular and antigenic features related to low pathogenicity avian influenza A(H3N2) viruses and were distinct from A(H3N8) CIVs. The structural and glycan array binding profile confirmed these findings and revealed avian-like receptor-binding specificity. While replication kinetics in human airway epithelial cells was on par with that of seasonal influenza viruses, mild-to-moderate disease was observed in infected mice and ferrets, and the virus was inefficiently transmitted among cohoused ferrets. Conclusions Further adaptation is needed for A(H3N2) CIVs to present a likely threat to humans. However, the potential for coinfection of dogs and possible reassortment of human and other animal influenza A viruses presents an ongoing risk to public health. PMID:28934454

Dynamics of Molecular Emission Features from Nanosecond, Femtosecond Laser and Filament Ablation Plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harilal, Sivanandan S.; Yeak, J.; Brumfield, Brian E.

2016-06-15

The evolutionary paths of molecular species and nanoparticles in laser ablation plumes are not well understood due to the complexity of numerous physical processes that occur simultaneously in a transient laser-plasma system. It is well known that the emission features of ions, atoms, molecules and nanoparticles in a laser ablation plume strongly depend on the laser irradiation conditions. In this letter we report the temporal emission features of AlO molecules in plasmas generated using a nanosecond laser, a femtosecond laser and filaments generated from a femtosecond laser. Our results show that, at a fixed laser energy, the persistence of AlOmore » is found to be highest and lowest in ns and filament laser plasmas respectively while molecular species are formed at early times for both ultrashort pulse (fs and filament) generated plasmas. Analysis of the AlO emission band features show that the vibrational temperature of AlO decays rapidly in filament assisted laser ablation plumes.« less

Polarisation observations of VY Canis Majoris H2O 532-441 620.701 GHz maser emission with HIFI

NASA Astrophysics Data System (ADS)

Harwit, M.; Houde, M.; Sonnentrucker, P.; Boogert, A. C. A.; Cernicharo, J.; De Beck, E.; Decin, L.; Henkel, C.; Higgins, R. D.; Jellema, W.; Kraus, A.; McCoey, C.; Melnick, G. J.; Menten, K. M.; Risacher, C.; Teyssier, D.; Vaillancourt, J. E.; Alcolea, J.; Bujarrabal, V.; Dominik, C.; Justtanont, K.; de Koter, A.; Marston, A. P.; Olofsson, H.; Planesas, P.; Schmidt, M.; Schöier, F. L.; Szczerba, R.; Waters, L. B. F. M.

2010-10-01

Context. Water vapour maser emission from evolved oxygen-rich stars remains poorly understood. Additional observations, including polarisation studies and simultaneous observation of different maser transitions may ultimately lead to greater insight. Aims: We have aimed to elucidate the nature and structure of the VY CMa water vapour masers in part by observationally testing a theoretical prediction of the relative strengths of the 620.701 GHz and the 22.235 GHz maser components of ortho H2O. Methods: In its high-resolution mode (HRS) the Herschel Heterodyne Instrument for the Far Infrared (HIFI) offers a frequency resolution of 0.125 MHz, corresponding to a line-of-sight velocity of 0.06 km s-1, which we employed to obtain the strength and linear polarisation of maser spikes in the spectrum of VY CMa at 620.701 GHz. Simultaneous ground based observations of the 22.235 GHz maser with the Max-Planck-Institut für Radioastronomie 100-m telescope at Effelsberg, provided a ratio of 620.701 GHz to 22.235 GHz emission. Results: We report the first astronomical detection to date of H2O maser emission at 620.701 GHz. In VY CMa both the 620.701 and the 22.235 GHz polarisation are weak. At 620.701 GHz the maser peaks are superposed on what appears to be a broad emission component, jointly ejected from the star. We observed the 620.701 GHz emission at two epochs 21 days apart, both to measure the potential direction of linearly polarised maser components and to obtain a measure of the longevity of these components. Although we do not detect significant polarisation levels in the core of the line, they rise up to approximately 6% in its wings. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendix (page 5) is only available in electronic form at http://www.aanda.org

Stellar model chromospheres. IV - The formation of the H-epsilon feature in the sun /G2 V/ and Arcturus /K2 III/

NASA Technical Reports Server (NTRS)

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

1975-01-01

The formation of the Balmer-series member H-epsilon in the near-red wing of the Ca II H line is discussed for two cases: the sun (H-epsilon absorption profile) and Arcturus (H-epsilon emission profile). It is shown that although the H-epsilon source functions in both stars are dominated by the Balmer-continuum radiation field through photoionizations, the line-formation problems in the two stars are quantitatively different, owing to a substantial difference in the relative importance of the stellar chromosphere temperature inversion as compared with the stellar photosphere.

The 3.4 micron emission in comets

NASA Technical Reports Server (NTRS)

Brooke, Tim Y.; Knacke, Roger F.; Owen, T. C.; Tokunaga, Alan T.

1989-01-01

Emission features near 3.4 microns were detected in comet Bradfield (1987s) on 17 Nov. 1987 UT, and, marginally, on two earlier dates, with the Cooled Grating Array Spectrometer at the NASA Infrared Radio Telescope Facility (IRTF) (Brooke et al., 1988b). The central wavelength (3.36 microns) and width (approx. 0.15 microns) of the strongest feature coincide with those observed in comet Halley. A weaker emission feature at 3.52 microns and a strong feature extending shortward of 2.9 microns were also detected. This brings the number of comets in which these three features have been seen to three, two new (Bradfield, Wilson) and one old (Halley). It seems almost certain that the 3.4 micron features are emissions by C-H groups in complex molecules. Based on the similarity of the 3.4 micron features in comets Halley and Wilson, the authors suggest that a particular set of organic compounds may be common to all comets (Brooke et al. 1988a). The absence of the feature in some comets could then be due to photodestruction or evaporation of the organics when the comet approaches the sun, in combination with a predominance of thermal emission from non C-H emitting grains. Detection of the 3.4 micron emission feature in comet Bradfield at 4 = 0.9 AU provides support for this argument. Complex organics in comets could have been formed by particle irradiation of parent ices in the nucleus or been incorporated as grains at the time the comets formed. Since the most heavily irradiated layers of Halley would have been lost in its hundreds of perihelion passages, the authors believe the more likely explanation is that the 3.4 micron emitting material was incorporated in comet nuclei at the time of formation. The 3.4 micron comet feature resembles, but is not identical to, the interstellar 3.29 micron (and longer wavelength) emission features and the broad 3.4 micron feature seen in absorption toward the Galactic center. Detailed comparisons of cometary and interstellar organics

The Luminous Polycyclic Aromatic Hydrocarbon Emission Features: Applications to High Redshift Galaxies and Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Shipley, Heath V.

2016-01-01

For decades, significant work has been applied to calibrating emission from the ultra-violet, nebular emission lines, far-infrared, X-ray and radio as tracers of the star-formation rate (SFR) in distant galaxies. Understanding the exact rate of star-formation and how it evolves with time and galaxy mass has deep implications for how galaxies form. The co-evolution of star-formation and supermassive black hole (SMBH) accretion is one of the key problems in galaxy formation theory. But, many of these SFR indicators are influenced by SMBH accretion in galaxies and result in unreliable SFRs. Utilizing the luminous polycyclic aromatic hydrocarbon (PAH) emission features, I provide a new robust SFR calibration using the luminosity emitted from the PAHs at 6.2μm, 7.7μm and 11.3μm to solve this. The PAH features emit strongly in the mid-infrared (mid-IR; 5-25μm) mitigating dust extinction, containing on average 5-10% of the total IR luminosity in galaxies. I use a sample of 105 star-forming galaxies covering a range of total IR luminosity, LIR = L(8-1000μm) = 109 - 1012 L⊙ and redshift 0 < z < 0.4, with mid-IR spectroscopy from the Spitzer Infrared Spectrograph (IRS), and data covering other SFR indicators (Hα emission and rest-frame 24μm continuum emission). The PAH luminosity correlates linearly with the SFR as measured by the Hα luminosity (corrected for attenuation using the mono-chromatic rest-frame 24μm emission), with a tight scatter of <0.15 dex. The scatter is comparable to that between SFRs derived from the Paα and dust-corrected Hα emission lines. We present a case study in advance of JWST, which will be capable of measuring SFRs (from 8μm rest-frame photometry, i.e. PAHs) in distant galaxies (z ≤ 2) with JWST/MIRI to SFRs as low as ~10 M⊙yr-1, because the PAH features are so bright. We use Spitzer/IRS observations of PAH features in lensed star-forming galaxies at 1 < z < 3 to demonstrate the utility of the PAHs to derive SFRs that agree with

On- and off-axis spectral emission features from laser-produced gas breakdown plasmas

NASA Astrophysics Data System (ADS)

Harilal, S. S.; Skrodzki, P. J.; Miloshevsky, A.; Brumfield, B. E.; Phillips, M. C.; Miloshevsky, G.

2017-06-01

Laser-heated gas breakdown plasmas or sparks emit profoundly in the ultraviolet and visible region of the electromagnetic spectrum with contributions from ionic, atomic, and molecular species. Laser created kernels expand into a cold ambient with high velocities during their early lifetime followed by confinement of the plasma kernel and eventually collapse. However, the plasma kernels produced during laser breakdown of gases are also capable of exciting and ionizing the surrounding ambient medium. Two mechanisms can be responsible for excitation and ionization of the surrounding ambient: photoexcitation and ionization by intense ultraviolet emission from the sparks produced during the early times of their creation and/or heating by strong shocks generated by the kernel during its expansion into the ambient. In this study, an investigation is made on the spectral features of on- and off-axis emission of laser-induced plasma breakdown kernels generated in atmospheric pressure conditions with an aim to elucidate the mechanisms leading to ambient excitation and emission. Pulses from an Nd:YAG laser emitting at 1064 nm with a pulse duration of 6 ns are used to generate plasma kernels. Laser sparks were generated in air, argon, and helium gases to provide different physical properties of expansion dynamics and plasma chemistry considering the differences in laser absorption properties, mass density, and speciation. Point shadowgraphy and time-resolved imaging were used to evaluate the shock wave and spark self-emission morphology at early and late times, while space and time resolved spectroscopy is used for evaluating the emission features and for inferring plasma physical conditions at on- and off-axis positions. The structure and dynamics of the plasma kernel obtained using imaging techniques are also compared to numerical simulations using the computational fluid dynamics code. The emission from the kernel showed that spectral features from ions, atoms, and

Evaluating real-world CO2 and NOX emissions for public transit buses using a remote wireless on-board diagnostic (OBD) approach.

PubMed

Yang, Liuhanzi; Zhang, Shaojun; Wu, Ye; Chen, Qizheng; Niu, Tianlin; Huang, Xu; Zhang, Shida; Zhang, Liangjun; Zhou, Yu; Hao, Jiming

2016-11-01

The challenge to mitigate real-world emissions from vehicles calls for powerful in-use compliance supervision. The remote on-board diagnostic (OBD) approach, with wireless data communications, is one of the promising next-generation monitoring methods. We collected second-by-second profiles of carbon dioxide (CO 2 ) and nitrogen oxides (NO X ) emissions, driving conditions and engine performance for three conventional diesel and three hybrid diesel buses participating in a remote OBD pilot program in Nanjing, China. Our results showed that the average CO 2 emissions for conventional diesel and hybrid diesel buses were 816 ± 83 g km -1 and 627 ± 54 g km -1 , respectively, under a typical driving pattern. An operating mode binning analysis indicated that CO 2 emissions reduction by series-parallel hybrid technology was largely because of the significant benefits of the technology under the modes of low speed and low power demand. However, significantly higher CO 2 emissions were observed for conventional diesel buses during rush hours, higher than 1200 g km -1 . The OBD data suggested no improvement in NO X emission reduction for hybrid buses compared with conventional buses; both were approximately 12 g km -1 because of poor performance of the selective catalyst reduction (SCR) systems in the real world. Speed-dependent functions for real-world CO 2 and NO X emissions were also constructed. The CO 2 emissions of hybrid buses were much less sensitive to the average speed than conventional buses. If the average speed decreased from 20 km h -1 to 10 km h -1 , the estimated CO 2 emission factor for conventional buses would be increased by 34%. Such a change in speed would increase NO X emissions for conventional and hybrid buses by 38% and 56%, respectively. This paper demonstrates the useful features of the remote OBD system and can inform policy makers how to take advantage of these features in monitoring in-use vehicles. Copyright © 2016 Elsevier

The discovery of five new H2O megamasers in active galaxies

NASA Technical Reports Server (NTRS)

Braatz, J. A.; Wilson, A. S.; Henkel, C.

1994-01-01

H2O megamasers with (isotropic) luminosities between 60 and 200 solar luminosity (H(sub 0) = 75 km/s/Mpc) have been detected in the Seyfert 2 galaxies Mrk 1, Mrk 1210, and NGC 5506 and in the LINERs NGC 1052 and NGC 2639. No megamasers have been found in Seyfert 1's. The galaxies have redshifts between 1500 and 4800 km/s and are the most distant H2O sources reported to date. NGC 1052 is also the first elliptical galaxy known to contain an H2O maser. The intensity distribution of an H2O five-point map obtained toward NGC 5506 shows that the H2O emission is pointlike compared to the 40 sec telescope beam. The lack of CO emission in NGC 1052 implies a conservative lower limit to the H2O brightness temperature of 1000 K, thus ruling out a thermal origin for the H2O emission. The success of this survey relative to other recent searches makes it evident that H2O megamasers are preferentially found in galaxies with active nuclei.

Hydrogenation of polycyclic aromatic hydrocarbons as a factor affecting the cosmic 6.2 micron emission band

NASA Technical Reports Server (NTRS)

Beegle, L. W.; Wdowiak, T. J.; Harrison, J. G.

2001-01-01

While many of the characteristics of the cosmic unidentified infrared (UIR) emission bands observed for interstellar and circumstellar sources within the Milky Way and other galaxies, can be best attributed to vibrational modes of the variants of the molecular family known as polycyclic aromatic hydrocarbons (PAH), there are open questions that need to be resolved. Among them is the observed strength of the 6.2 micron (1600 cm(-1)) band relative to other strong bands, and the generally low strength for measurements in the laboratory of the 1600 cm(-1) skeletal vibration band of many specific neutral PAH molecules. Also, experiments involving laser excitation of some gas phase neutral PAH species while producing long lifetime state emission in the 3.3 micron (3000 cm(-1)) spectral region, do not result in significant 6.2 micron (1600 cm(-1)) emission. A potentially important variant of the neutral PAH species, namely hydrogenated-PAH (H(N)-PAH) which exhibit intriguing spectral correlation with interstellar and circumstellar infrared emission and the 2175 A extinction feature, may be a factor affecting the strength of 6.2 micron emission. These species are hybrids of aromatic and cycloalkane structures. Laboratory infrared absorption spectroscopy augmented by density function theory (DFT) computations of selected partially hydrogenated-PAH molecules, demonstrates enhanced 6.2 micron (1600 cm(-1)) region skeletal vibration mode strength for these molecules relative to the normal PAH form. This along with other factors such as ionization or the incorporation of nitrogen or oxygen atoms could be a reason for the strength of the cosmic 6.2 micron (1600 cm(-1)) feature.

Electron Localization in Molecular Fragmentation of H{sub 2} by Carrier-Envelope Phase Stabilized Laser Pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kremer, Manuel; Fischer, Bettina; Feuerstein, Bernold

2009-11-20

Fully differential data for H{sub 2} dissociation in ultrashort (6 fs, 760 nm), linearly polarized, intense (0.44 PW/cm{sup 2}) laser pulses with a stabilized carrier-envelope phase (CEP) were recorded with a reaction microscope. Depending on the CEP, the molecular orientation, and the kinetic energy release (KER), we find asymmetric proton emission at low KERs (0-3 eV), basically predicted by Roudnev and Esry, and much stronger than reported by Kling et al. Wave packet propagation calculations reproduce the salient features and discard, together with the observed KER-independent electron asymmetry, the first ionization step to be the reason for the asymmetric protonmore » emission.« less

MONITORING H{alpha} EMISSION AND CONTINUUM OF UXORs: RR Tauri

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bedell, Megan; Villaume, Alexa; Weiss, Lauren

2011-11-15

The Maria Mitchell Observatory, in collaboration with the Astrokolkhoz Observatory, started a program of photometric monitoring of UX Ori-type stars (UXORs) with narrowband interference filters (IFs; augmented with the traditional broadband filters) aimed at separating the H{alpha} emission variations from those of the continuum. We present the method of separation and the first results for RR Tau obtained in two seasons, each roughly 100 days long (2010 Winter-Spring and 2010 Fall-2011 Spring). We confirm the conclusion from previous studies that the H{alpha} emission in this star is less variable than the continuum. Although some correlation between the two is notmore » excluded, the amplitude of H{alpha} variations is much smaller (factors of 3-5) than that of the continuum. These results are compatible with Grinin's model of UXORs, which postulates the presence of small obscuring circumstellar clouds as the cause of the continuum fading, as well as the presence of a circumstellar reflection/emission nebula, larger than the star and the obscuring clouds, which is responsible for H{alpha} emission and the effect of the 'color reversal' in deep minima. However, the results of both our broadband and narrowband photometry indicate that the obscuration model may be insufficient to explain all of the observations. Disk accretion, the presence of stellar or (proto) planetary companion(s), as well as the intrinsic variations of the star, may contribute to the observed light variations. We argue, in particular, that the H{alpha} emission may be more closely correlated with the intrinsic variations of the star than with the much stronger observed variations caused by the cloud obscuration. If this hypothesis is correct, the close monitoring of H{alpha} emission with IFs, accessible to small-size telescopes, may become an important tool in studying the physical nature of the UXORs' central stars.« less

Warm H2O and OH Disk Emission in V1331 Cyg

NASA Astrophysics Data System (ADS)

Doppmann, Greg W.; Najita, Joan R.; Carr, John S.; Graham, James R.

2011-09-01

We present high-resolution (R = 24, 000) L-band spectra of the young intermediate-mass star V1331 Cyg obtained with NIRSPEC on the Keck II telescope. The spectra show strong, rich emission from water and OH that likely arises from the warm surface region of the circumstellar disk. We explore the use of the new BT2 water line list in fitting the spectra, and we find that it does a much better job than the well-known HITRAN water line list in the observed wavelength range and for the warm temperatures probed by our data. By comparing the observed spectra with synthetic disk emission models, we find that the water and OH emission lines have similar widths (FWHM ~= 18 km s-1). If the line widths are set by disk rotation, the OH and water emission lines probe a similar range of disk radii in this source. The water and OH emission are consistent with thermal emission for both components at a temperature ~1500 K. The column densities of the emitting water and OH are large, ~1021 cm-2 and ~1020 cm-2, respectively. Such a high column density of water is more than adequate to shield the disk midplane from external UV irradiation in the event of complete dust settling out of the disk atmosphere, enabling chemical synthesis to continue in the midplane despite a harsh external UV environment. The large OH-to-water ratio is similar to expectations for UV irradiated disks, although the large OH column density is less easily accounted for. Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

The behaviour of the excess CA II H and K and Hɛ emissions in chromospherically active binaries.

NASA Astrophysics Data System (ADS)

Montes, D.; Fernandez-Figueroa, M. J.; Cornide, M.; de Castro, E.

1996-08-01

In this work we analyze the behaviour of the excess Ca II H and K and Hɛ emissions in a sample of 73 chromospherically active binary systems (RS CVn and BY Dra classes), of different activity levels and luminosity classes. This sample includes the 53 stars analyzed by Fernandez-Figueroa et al. (1994) and the observations of 28 systems described by Montes et al. (1995c). By using the spectral subtraction technique (subtraction of a synthesized stellar spectrum constructed from reference stars of spectral type and luminosity class similar to those of the binary star components) we obtain the active-chromosphere contribution to the Ca II H and K lines in these 73 systems. We have determined the excess Ca II H and K emission equivalent widths and converted them into surface fluxes. The emissions arising from each component were obtained when it was possible to deblend both contributions. We have found that the components of active binaries are generally stronger emitters than single active stars for a given effective temperature and rotation rate. A slight decline of the excess Ca II H and K emissions towards longer rotation periods, P_rot_, and larger Rossby numbers, R_0_, is found. When we use R_0_ instead of P_rot_ the scatter is reduced and a saturation at R_0_=~0.3 is observed. A good correlation between the excess Ca II K and Hɛ chromospheric emission fluxes has been found. The correlations obtained between the excess Ca II K emission and other activity indicators, (C IV in the transition region, and X-rays in the corona) indicate that the exponents of the power-law relations increase with the formation temperature of the spectral features.

[CII] observations of H2 molecular layers in transition clouds

NASA Astrophysics Data System (ADS)

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

2010-10-01

We present the first results on the diffuse transition clouds observed in [CII] line emission at 158 μm (1.9 THz) towards Galactic longitudes near 340° (5 LOSs) & 20° (11 LOSs) as part of the HIFI tests and GOT C+ survey. Out of the total 146 [CII] velocity components detected by profile fitting we identify 53 as diffuse molecular clouds with associated 12CO emission but without 13CO emission and characterized by AV < 5 mag. We estimate the fraction of the [CII] emission in the diffuse HI layer in each cloud and then determine the [CII] emitted from the molecular layers in the cloud. We show that the excess [CII] intensities detected in a few clouds is indicative of a thick H2 layer around the CO core. The wide range of clouds in our sample with thin to thick H2 layers suggests that these are at various evolutionary states characterized by the formation of H2 and CO layers from HI and C+, respectively. In about 30% of the clouds the H2 column densities (“dark gas”) traced by the [CII] is 50% or more than that traced by 12CO emission. On the average ~25% of the total H2 in these clouds is in an H2 layer which is not traced by CO. We use the HI, [CII], and 12CO intensities in each cloud along with simple chemical models to obtain constraints on the FUV fields and cosmic ray ionization rates. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Flooding-related increases in CO2 and N2O emissions from a temperate coastal grassland ecosystem

NASA Astrophysics Data System (ADS)

Gebremichael, Amanuel W.; Osborne, Bruce; Orr, Patrick

2017-05-01

Given their increasing trend in Europe, an understanding of the role that flooding events play in carbon (C) and nitrogen (N) cycling and greenhouse gas (GHG) emissions will be important for improved assessments of local and regional GHG budgets. This study presents the results of an analysis of the CO2 and N2O fluxes from a coastal grassland ecosystem affected by episodic flooding that was of either a relatively short (SFS) or long (LFS) duration. Compared to the SFS, the annual CO2 and N2O emissions were 1.4 and 1.3 times higher at the LFS, respectively. Mean CO2 emissions during the period of standing water were 144 ± 18.18 and 111 ± 9.51 mg CO2-C m-2 h-1, respectively, for the LFS and SFS sites. During the growing season, when there was no standing water, the CO2 emissions were significantly larger from the LFS (244 ± 24.88 mg CO2-C m-2 h-1) than the SFS (183 ± 14.90 mg CO2-C m-2 h-1). Fluxes of N2O ranged from -0.37 to 0.65 mg N2O-N m-2 h-1 at the LFS and from -0.50 to 0.55 mg N2O-N m-2 h-1 at the SFS, with the larger emissions associated with the presence of standing water at the LFS but during the growing season at the SFS. Overall, soil temperature and moisture were identified as the main drivers of the seasonal changes in CO2 fluxes, but neither adequately explained the variations in N2O fluxes. Analysis of total C, N, microbial biomass and Q10 values indicated that the higher CO2 emissions from the LFS were linked to the flooding-associated influx of nutrients and alterations in soil microbial populations. These results demonstrate that annual CO2 and N2O emissions can be higher in longer-term flooded sites that receive significant amounts of nutrients, although this may depend on the restriction of diffusional limitations due to the presence of standing water to periods of the year when the potential for gaseous emissions are low.

Near Infrared Spectra of H2O/HCN Mixtures

NASA Technical Reports Server (NTRS)

Mastrapa, R. M.; Bernstein, M. P.; Sanford, S. A.

2006-01-01

Cassini's VIMS has already returned exciting results interpreting spectra of Saturn's icy satellites. The discovery of unidentified features possibly due to CN compounds inspired the work reported here. We wanted to test HCN as a possibility for explaining these features, and also explore how the features of HCN change when mixed with H2O. We have previously noted that mixing H20 and CO2 produces new spectral features and that those features change with temperature and mixing ratio.

Estimates on the production of CO and H2 from the oxidation of hydrocarbon emissions from vegetation

NASA Technical Reports Server (NTRS)

Zimmerman, P. R.; Chatfield, R. B.; Fishman, J.; Crutzen, P. J.; Hanst, P. L.

1978-01-01

Extrapolating from extensive field measurements on foliar emissions in the U.S. approximate global inputs of isoprene and terpenes of 3.5 times 10 to the 14th power and 4.8 times 10 to the 14th power g(C)/yr, respectively, are obtained. The oxidation of these hydrocarbons could contribute in an important way to the atmospheric sources of CO (4.2-13.3 times 10 to the 14th power g/yr) and H2 (10-35 times 10 to the 12th power g/yr), and to organic species soluble in rainwater

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

USGS Publications Warehouse

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

1990-01-01

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

VizieR Online Data Catalog: H2, D2, and HD c3Πu;

NASA Astrophysics Data System (ADS)

Liu, X.; Shemansky, D. E.; Yoshii, J.; Liu, M. J.; Johnson, P. V.; Malone, C. P.; Khakoo, M. A.

2017-11-01

The c3{Pi}u state of the hydrogen molecule has the triplet-state excitation cross-section, and plays an important role in the heating of the upper thermospheres of outer planets by electron excitation. Precise energies of the H2, D2, and HD c3{Pi}u-(v,N) levels are calculated from highly accurate ab initio potential energy curves that include relativistic, radiative, and empirical non-adiabatic corrections. The emission yields are determined from predissociation rates and refined radiative transition probabilities. The excitation function and excitation cross-section of the c3{Pi}u state are extracted from previous theoretical calculations and experimental measurements. The emission cross-section is determined from the calculated emission yield and the extracted excitation cross-section. The kinetic energy (Ek) distributions of H atoms produced via the predissociation of the c3{Pi}u state, the c3{Pi}u--b3{Sigma}u+ dissociative emission by the magnetic dipole and electric quadrupole, and the c3{Pi}u-a3{Sigma}g+-b3{Sigma}u+ cascade dissociative emission by the electric dipole are obtained. The predissociation of the c3{Pi}u+ and c3{Pi}u- states both produce H(1s) atoms with an average Ek of ~4.1eV/atom, while the c3{Pi}u--b3{Sigma}u+ dissociative emissions by the magnetic dipole and electric quadrupole give an average Ek of ~1.0 and ~0.8eV/atom, respectively. The c3{Pi}u-a3{Sigma}g+-b3{Sigma}u+ cascade and dissociative emission gives an average Ek of ~1.3 eV/atom. On average, each H2 excited to the c3{Pi}u state in an H2-dominated atmosphere deposits ~7.1eV into the atmosphere while each H2 directly excited to the a3{Sigma}g+ and d3{Pi}u states contribute ~2.3 and ~3.3eV, respectively, to the atmosphere. The spectral distribution of the calculated continuum emission arising from the X1{Sigma}g+-c3{Pi}u excitation is significantly different from that of direct a3{Sigma}g+ or d3{Pi}u excitations. (5 data files).

The molecular core in G34.3 + 0.2 - Millimeter interferometric observations of HCO(+), H(C-13)N, H(C-15)N, and SO

NASA Technical Reports Server (NTRS)

Carral, Patricia; Welch, William J.

1992-01-01

This study presents high-resolution observations of the molecular core in the star-forming region G34.3 + 0.2. Maps at 6-arcsec resolution of emission and absorption of the J = 1 - 0 transitions of HCO(+), H (C-13)N, H(C-15)N, and of the 2(2) - 1(1) transition of SO were obtained in addition to a map of the 3.4-mm continuum emission from the compact H II component. The HCL(+) emission toward G34.3 + 0.2 traces a warm molecular core about 0.9 pc in size. Emission from H (C-13)N is detected over about 0.3 pc. The cometary H II region lies near the edge of the molecular core. The blueshift of the radio recombination lines with respect to the molecular emission suggests that gas from the H II region is accelerated in a champagne flow caused by a steep gradient in the ambient gas density.

H2 Fluorescence in M dwarf Systems: A Stellar Origin

NASA Astrophysics Data System (ADS)

Kruczek, Nicholas; France, Kevin; Evonosky, William; Youngblood, Allison; Loyd, R. O. Parke

2017-01-01

Observations of Lyα-driven H2 fluorescence can be a useful tool for measuring the abundance of H2 in exoplanet atmospheres. This emission has been previously observed in M dwarfs with planetary systems but at too low of a signal to determine its origin. It may have been originating in the atmospheres of planets, but conditions within these systems also mean that the H2 could be residing on the stellar surface or in a circumstellar disk. We use observations from the ``Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanet Host Stars" (MUSCLES) Hubble Space Telescope (HST) Treasury Survey to study H2 fluorescence in M dwarfs with and without confirmed planets to determine the origin of the emission. The results are further supported by the direct imaging of a candidate M dwarf system using the HST-Advanced Camera for Surveys/Solar Blind Channel. We constrain the location of the fluorescing H2 through analysis of the line profiles and determine that the emission is originating on the star. We verify that this interpretation is consistent with 1D radiative transfer models that are optimized using the spectra of the MUSCLES stars and find that the H2 likely resides in starspots or a cool region of the lower chromosphere.

Impact of a future H2 transportation on atmospheric pollution in Europe

NASA Astrophysics Data System (ADS)

Popa, M. E.; Segers, A. J.; Denier van der Gon, H. A. C.; Krol, M. C.; Visschedijk, A. J. H.; Schaap, M.; Röckmann, T.

2015-07-01

Hydrogen (H2) is being explored as a fuel for passenger vehicles; it can be used in fuel cells to power electric motors or burned in internal combustion engines. In order to evaluate the potential influence of a future H2-based road transportation on the regional air quality in Europe, we implemented H2 in the atmospheric transport and chemistry model LOTOS-EUROS. We simulated the present and future (2020) air quality, using emission scenarios with different proportions of H2 vehicles and different H2 leakage rates. The reference future scenario does not include H2 vehicles, and assumes that all present and planned European regulations for emissions are fully implemented. We find that, in general, the air quality in 2020 is significantly improved compared to the current situation in all scenarios, with and without H2 cars. In the future scenario without H2 cars, the pollution is reduced due to the strict European regulations: annually averaged CO, NOx and PM2.5 over the model domain decrease by 15%, 30% and 20% respectively. The additional improvement brought by replacing 50% or 100% of traditionally-fueled vehicles by H2 vehicles is smaller in absolute terms. If 50% of vehicles are using H2, the CO, NOx and PM2.5 decrease by 1%, 10% and 1% respectively, compared to the future scenario without H2 cars. When all vehicles run on H2, then additional decreases in CO, NOx and PM2.5 are 5%, 40%, and 5% relative to the no-H2 cars future scenario. Our study shows that H2 vehicles may be an effective pathway to fulfill the strict future EU air quality regulations. O3 has a more complicated behavior - its annual average decreases in background areas, but increases in the high-NOx area in western Europe, with the decrease in NOx. A more detailed analysis shows that the population exposure to high O3 levels decreases nevertheless. In all future scenarios, traffic emissions account for only a small proportion of the total anthropogenic emissions, thus it becomes more important

Meridional Variations of C2H2 and C2H6 in Jupiter's Atmosphere from Cassini CIRS Infrared Spectra

NASA Technical Reports Server (NTRS)

Nixon, C. A.; Achterberg, R. K.; Conrath, B. J.; Irwin, P. G. J.; Fouchet, T.; Parrish, P. D.; Romani, P. N.; Abbas, M.; LeClair, A.; Strobel, D.

2004-01-01

Hydrocarbons such as acetylene (C2H2) and ethane (C2H6) are important tracers in Jupiter's atmosphere, constraining our models of the chemical and dynamical processes. However, our knowledge of the vertical and meridional variations of their abundances has remained sparse. During the flyby of the Cassini spacecraft in December 2000, the Composite Infrared Spectrometer (CIRS) instrument was used to map the spatial variation of emissions from 10-1400 cm(sup -1) (1000-7 microns). In this paper we analyze a zonally-averaged set of CIRS spectra taken at the highest (0.5 cm(sup -1)) resolution, to infer atmospheric temperatures in the stratosphere at 0.5-20 mbar via the v4 band of CH4, and in the troposphere at 150-400 mbar, via the H2 absorption at 600-800 cm(sup -1). Simultaneously, we retrieve the abundances of C2H2 and C2H6 via the v5 and vg bands respectively. Tropospheric absorption and stratospheric emission are highly anti-correlated at the CIRS resolution, introducing a non-uniqueness into the retrievals, such that vertical gradient and column abundance cannot both be found without additional constraints. Assuming profile gradients from photochemical calculations, we show that the column abundance of C2H2 decreases sharply towards the poles by a factor approximately 4, while C2H6 is unchanged in the north and increasing in the south, by a factor approximately 1.8. An explanation for the meridional trends is proposed in terms of a combination of photochemistry and dynamics. Poleward, the decreasing UV flux is predicted to decrease the abundances of C2H2 and C2H6 by factors 2.7 and 3.5 respectively at a latitude 70 deg. However, the lifetime of C2H6 in the stratosphere (5 x 10(exp 9)) is much longer than the dynamical timescale for meridional motions inferred from SL-9 debris (5 x 10(exp 8 s)), and therefore the constant or rising abundance towards high latitudes likely indicates that meridional mixing dominates over photochemical effects. For C2H2, the opposite

Extreme Ultraviolet Emission Spectrum of CO_2 Induced by Electron Impact at 200 eV

NASA Technical Reports Server (NTRS)

Kanik, I.; Ajello, J. M.; James, G. K.

1993-01-01

We present the extreme ultraviolet (EUV) emission spectrum of CO_2 induced by electronimpact at 200 eV. There are 36 spectral features which are identified with a resolution of 0.5 nmover the wavelength range of 40 to 125 nm. Absolute emission cross sections were obtained for eachof these features. The EUV emission spectrum induced by electron impact consist of atomicmultiplets of CI,II and OI,II,III as well as CO and CO^+ molecular band systems produced bydissociative excitation. The CI (119.4 nm) multiplet is the strongest feature of CI with a peak crosssection of 3.61 x 10^(-19) cm^2 at 200 eV. The strongest feature of OI in the EUV spectrum is theOI (99.0 nm) multiplet with a peak cross section of 3.59 x 10^(-19) cm^2 at 200 eV.

Turbulence in Supercritical O2/H2 and C7H16/N2 Mixing Layers

NASA Technical Reports Server (NTRS)

Bellan, Josette; Harstad, Kenneth; Okong'o, Nora

2003-01-01

This report presents a study of numerical simulations of mixing layers developing between opposing flows of paired fluids under supercritical conditions, the purpose of the study being to elucidate chemical-species-specific aspects of turbulence. The simulations were performed for two different fluid pairs O2/H2 and C7H16/N2 at similar reduced initial pressures (reduced pressure is defined as pressure divided by critical pressure). Thermodynamically, O2/H2 behaves more nearly like an ideal mixture and has greater solubility, relative to C7H16/N2, which departs strongly from ideality. Because of a specified smaller initial density stratification, the C7H16/N2 layers exhibited greater levels of growth, global molecular mixing, and turbulence. However, smaller density gradients at the transitional state for the O2/H2 system were interpreted as indicating that locally, this system exhibits enhanced mixing as a consequence of its greater solubility and closer approach to ideality. These thermodynamic features were shown to affect entropy dissipation, which was found to be larger for O2/H2 and concentrated in high-density-gradient-magnitude regions that are distortions of the initial density-stratification boundary. In C7H16/N2, the regions of largest dissipation were found to lie in high-density-gradient-magnitude regions that result from mixing of the two fluids.

Observation of CH A (sup 2)Delta approaches X (sup 2)Pi(sub r) and B (sup 2)Sigma(sup -) approaches X (sup 2)Pi(sub r) emissions in gas-phase collisions of fast O((sup 3)P) atoms with acetylene

NASA Technical Reports Server (NTRS)

Orient, O. J.; Chutjian, A.; Murad, E.

1995-01-01

Optical emissions in single-collision, beam-beam reactions of fast (3-22 eV translational energy) O(P-3) atoms with C2H2 have been measured in the wavelength range 300-850 nm. Two features were observed, one with a peak wavelength at 431 nm, corresponding to the CH A (sup 2)Delta yields X (sup 2)Pi(sub r) transition, and a second weaker emission in the range 380-400 nm corresponding to the B (sup 2)Sigma(sup -) yields X (sup 2)Pi(sub r) transition. Both the A yields X and B yields X emissions were fit to a synthetic spectrum of CH(A) at a vibrational temperature T(sub v) of 10,000 K (0.86 eV) and a rotational temperature T(r) of approximately 5000 K (0.43 eV); and CH(B) to T(sub v) = 2500 K (0.22 eV) and T(sub r) = 1000 K (0.09 eV). The energy threshold for the A yields X emission was measured to be 7.3 +/- 0.4 eV (lab) or 4.5 +/- 0.2 eV (c.m.). This agrees with the energy threshold of 7.36 eV (lab) for the reaction O(P-3) + C2H2 yields CH(A) + HCO.

Infrared spectra of seeded hydrogen clusters: (para-H2)N-N2O and (ortho-H2)N-N2O, N = 2-13.

PubMed

Tang, Jian; McKellar, A R W

2005-09-15

High-resolution infrared spectra of clusters containing para-H2 and/or ortho-H2 and a single nitrous oxide molecule are studied in the 2225-cm(-1) region of the upsilon1 fundamental band of N2O. The clusters are formed in pulsed supersonic jet expansions from a cooled nozzle and probed using a tunable infrared diode laser spectrometer. The simple symmetric rotor-type spectra generally show no resolved K structure, with prominent Q-branch features for ortho-H2 but not para-H2 clusters. The observed vibrational shifts and rotational constants are reported. There is no obvious indication of superfluid effects for para-H2 clusters up to N=13. Sharp transitions due to even larger clusters are observed, but no definite assignments are possible. Mixed (para-H2)N-(ortho-H2)M-N2O cluster line positions can be well predicted by linear interpolation between the corresponding transitions of the pure clusters.

Infrared photodissociation spectroscopy of H(+)(H2O)6·M(m) (M = Ne, Ar, Kr, Xe, H2, N2, and CH4): messenger-dependent balance between H3O(+) and H5O2(+) core isomers.

PubMed

Mizuse, Kenta; Fujii, Asuka

2011-04-21

Although messenger mediated spectroscopy is a widely-used technique to study gas phase ionic species, effects of messengers themselves are not necessarily clear. In this study, we report infrared photodissociation spectroscopy of H(+)(H(2)O)(6)·M(m) (M = Ne, Ar, Kr, Xe, H(2), N(2), and CH(4)) in the OH stretch region to investigate messenger(M)-dependent cluster structures of the H(+)(H(2)O)(6) moiety. The H(+)(H(2)O)(6), the protonated water hexamer, is the smallest system in which both the H(3)O(+) (Eigen) and H(5)O(2)(+) (Zundel) hydrated proton motifs coexist. All the spectra show narrower band widths reflecting reduced internal energy (lower vibrational temperature) in comparison with bare H(+)(H(2)O)(6). The Xe-, CH(4)-, and N(2)-mediated spectra show additional band features due to the relatively strong perturbation of the messenger. The observed band patterns in the Ar-, Kr-, Xe-, N(2)-, and CH(4)-mediated spectra are attributed mainly to the "Zundel" type isomer, which is more stable. On the other hand, the Ne- and H(2)-mediated spectra are accounted for by a mixture of the "Eigen" and "Zundel" types, like that of bare H(+)(H(2)O)(6). These results suggest that a messenger sometimes imposes unexpected isomer-selectivity even though it has been thought to be inert. Plausible origins of the isomer-selectivity are also discussed.

Emission analysis of RE3+ (RE = Sm, Dy):B2O3-TeO2-Li2O-AlF3 glasses.

PubMed

Raju, C Nageswara; Sailaja, S; Kumari, S Pavan; Dhoble, S J; Kumar, V Ramesh; Ramanaiah, M V; Reddy, B Sudhakar

2013-01-01

This article reports on the optical properties of 0.5% mol of Sm(3+), Dy(3+) ion-doped B2O3-TeO2-Li2O-AlF3 (LiAlFBT) glasses. The glass samples were characterized by optical absorption and emission spectra. Judd-Ofelt theory was applied to analyze the optical absorption spectra and calculate the intensity parameters and radiative properties of the emission transitions. The emission spectra of Sm(3+) and Dy(3+):LiAlFBT glasses showed a bright reddish-orange emission at 598 nm ((4)G5/2 → (6)H7/2) and an intense yellow emission at 574 nm ((4)F9/2 → (6)H13/2), respectively. Full width at half maximum (FWHM), stimulated emission cross section, gain bandwidth and optical gain values were also calculated to extend the applications of the Sm(3+) and Dy(3+):LiAlFBT glasses. Copyright © 2012 John Wiley & Sons, Ltd.

Supramolecular features of 2-(chlorophenyl)-3-[(chlorobenzylidene)-amino]-2,3-dihydroquinazolin-4(1H)-ones: A combined experimental and computational study

NASA Astrophysics Data System (ADS)

Mandal, Arkalekha; Patel, Bhisma K.

2018-03-01

The molecular structures of two isomeric 2-(chlorophenyl)-3-[(chlorobenzylidene)-amino] substituted 2,3-dihydroquinazolin-4(1H)-ones have been determined via single crystal XRD. Both isomers contain chloro substitutions on each of the phenyl rings and as a result a broad spectrum of halogen mediated weak interactions are viable in their crystal structures. The crystal packing of these compounds is stabilized by strong N-H⋯O hydrogen bond and various weak, non-classical hydrogen bonds acting synergistically. Both the molecules contain a chiral center and the weak interactions observed in them are either chiral self-discriminatory or chiral self-recognizing in nature. The weak interactions and spectral features of the compounds have been studied through experimental as well as computational methods including DFT, MEP, NBO and Hiresfeld surface analyses. In addition, the effect of different weak interactions to dictate either chiral self-recognition or self-discrimination in crystal packing has been elucidated.

Improvement in thin cirrus retrievals using an emissivity-adjusted CO2 slicing algorithm

NASA Astrophysics Data System (ADS)

Zhang, Hong; Menzel, W. Paul

2002-09-01

CO2 slicing has been generally accepted as a useful algorithm for determining cloud top pressure (CTP) and effective cloud amount (ECA) for tropospheric clouds above 600 hPa. To date, the technique has assumed that the surface emissivity is that of a blackbody in the long-wavelength infrared radiances and that the cloud emissivities in spectrally close bands are approximately equal. The modified CO2 slicing algorithm considers adjustments of both surface emissivity and cloud emissivity ratio. Surface emissivity is adjusted according to the surface types. The ratio of cloud emissivities in spectrally close bands is adjusted away from unity according to radiative transfer calculations. The new CO2 slicing algorithm is examined with Moderate Resolution Imaging Spectroradiometer (MODIS) Airborne Simulator (MAS) CO2 band radiance measurements over thin clouds and validated against Cloud Lidar System (CLS) measurements of the same clouds; it is also applied to Geostationary Operational Environmental Satellite (GOES) Sounder data to study the overall impact on cloud property determinations. For high thin clouds an improved product emerges, while for thick and opaque clouds there is little change. For very thin clouds, the CTP increases by about 10-20 hPa and RMS (root mean square bias) difference is approximately 50 hPa; for thin clouds, the CTP increase is about 10 hPa bias and RMS difference is approximately 30 hPa. The new CO2 slicing algorithm places the clouds lower in the troposphere.

AOI [3] High-Temperature Nano-Derived Micro-H 2 and - H 2S Sensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sabolsky, Edward M.

2014-08-01

The emissions from coal-fired power plants remain a significant concern for air quality. This environmental challenge must be overcome by controlling the emission of sulfur dioxide (SO 2) and hydrogen sulfide (H 2S) throughout the entire coal combustion process. One of the processes which could specifically benefit from robust, low cost, and high temperature compatible gas sensors is the coal gasification process which converts coal and/or biomass into syngas. Hydrogen (H 2), carbon monoxide (CO) and sulfur compounds make up 33%, 43% and 2% of syngas, respectively. Therefore, development of a high temperature (>500°C) chemical sensor for in-situ monitoring ofmore » H 2, H 2S and SO2 2 levels during coal gasification is strongly desired. The selective detection of SO 2/H 2S in the presence of H 2, is a formidable task for a sensor designer. In order to ensure effective operation of these chemical sensors, the sensor system must inexpensively function within harsh temperature and chemical environment. Currently available sensing approaches, which are based on gas chromatography, electrochemistry, and IR-spectroscopy, do not satisfy the required cost and performance targets. This work focused on the development microsensors that can be applied to this application. In order to develop the high- temperature compatible microsensor, this work addressed various issues related to sensor stability, selectivity, and miniaturization. In the research project entitled “High-Temperature Nano-Derived Micro-H 2 and -H 2S Sensors”, the team worked to develop micro-scale, chemical sensors and sensor arrays composed of nano-derived, metal-oxide composite materials to detect gases like H 2, SO 2, and H 2S within high-temperature environments (>500°C). The research was completed in collaboration with NexTech Materials, Ltd. (Lewis Center, Ohio). NexTech assisted in the testing of the sensors in syngas with contaminate levels of H 2S. The idea of including nanomaterials as the

A set of new transition metal-based coordination complexes dependent upon Hpztza ligand (Hpztza=2-(5-(pyrazin-2-yl)-2H-tetrazol-2-yl) acetic acid)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang Jie; Shen Lei; Yang Gaowen, E-mail: ygwsx@126.com

2012-02-15

Reaction of MCl{sub 2}{center_dot}4H{sub 2}O (M=Zn, Cd, Mn, Co, Ni) with 2-(5-(pyrazin-2-yl)-2H-tetrazol-2-yl) acetic acid (Hpztza) yielded a set of new M(II)/pztza complexes, [Cd(pztza){sub 2}(H{sub 2}O){sub 6}]{center_dot}3H{sub 2}O{center_dot}(Hpztza) (1), [M(pztza){sub 2}(H{sub 2}O){sub 2}; M=Cd(2), Zn(7), Mn(9)], [Cd(pztza){sub 2}]{center_dot}2(CH{sub 3}OH) (3), [Co(pztza){sub 2}(H{sub 2}O){sub 2}]{center_dot}6H{sub 2}O (4), [Co(pztza)(H{sub 2}O)Cl] (6) and [M(pztza){sub 2}(H{sub 2}O){sub 2}]{center_dot}2H{sub 2}O [M=Co(5), Zn(8), Ni(10)]. These compounds were structurally characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction. Complex 1 featured a mononuclear structure, complexes 4, 5, 7, 8, 10 showed 1D chains and complexes 2, 3, 6, 9 displayed 2D layer structures. Furthermore, the luminescence propertiesmore » of 1-10 were investigated at room temperature in the solid state. - Graphical abstract: Ten new coordination polymers with 2-(5-(pyrazin-2-yl)-2H-tetrazol-2-yl) acetic acid (Hpztza) ligand have been synthesized and their structures have been characterized. All of the complexes show photoluminescence at room temperature. Highlights: Black-Right-Pointing-Pointer Ten novel transition metal-based coordination complexes with 2-(5-(pyrazin-2-yl)-2H-tetrazol-2-yl) acetic acid (Hpztza) are reported. Black-Right-Pointing-Pointer Complexes 1-10 are described as mononuclear structure, 1D and 2D frameworks with diverse architecture. Black-Right-Pointing-Pointer Six coordination complexes show emission at room temperature in the solid state.« less

Regulated deficit irrigation can decrease soil CO2 emissions in fruit orchards

NASA Astrophysics Data System (ADS)

Zornoza, Raul; Acosta, José Alberto; Martínez-Martínez, Silvia; De la Rosa, Jose M.°; Faz, Angel; Pérez-Pastor, Alejandro

2016-04-01

Irrigation water restrictions in the Mediterranean area have created a growing interest in water conservation. Apart from environmental and economic benefits by water savings, regulated deficit irrigation (RDI) may contribute to reduce soil CO2 emissions and enhance C sequestration in soils, by decreasing microbial and root activity in response to decreased soil moisture levels. An experiment was established in four orchards (peach, apricot, Saturn peach and grape) to investigate the effects of regulated deficit irrigation (RDI) on soil CO2 emissions. Two irrigation treatments were assayed: full irrigation (FI), and RDI, irrigated as FI except for postharvest period (peach, apricot, Saturn peach) or post-veraison period (grape) were 50% of FI was applied. The application of deficit caused a significant decrease in CO2 emission rates, with rates in average of 90 mg CO2-C m-2 h-1, 120 mg CO2-C m-2 h-1, 60 mg CO2-C m-2 h-1 and 60 mg CO2-C m-2 h-1 lower than FI during the period when deficit was applied for peach, apricot, Saturn peach and grape. This confirms the high effectiveness of the RDI strategies not only to save water consumption but also to decrease soil CO2 emissions. However, monitoring during longer periods is needed to verify that this trend is long-term maintained, and assess if soil carbon stocks are increase or most CO2 emissions derive from root respiration. Acknowledgements This work has been funded by the European Union LIFE+ project IRRIMAN (LIFE13 ENV/ES/000539).

HST STIS Images of the H-Lyman Alpha Emission and Disk-Reflected FUV Sunlight from the Upper Atmosphere of Uranus

NASA Astrophysics Data System (ADS)

Ballester, G. E.; Ben-Jaffel, L.; Clarke, J. T.; Gladstone, R.; Miller, S.; Trafton, L. M.; Trauger, J. T.

1998-09-01

An excess of H-Lyalpha emission from Uranus' sunlit hemisphere was detected by the IUE satellite in 1982, and some excess was confirmed with the Voyager 2 UVS during the 1986 encounter with Uranus. Radiative transfer modeling has shown that the Voyager H-Lyalpha observations did require emission additional to the scattered solar and IPM H-Lyalpha , and thus produced by internal processes in the upper atmosphere, such as aurora or other unidentified mechanisms. Subsequent IUE observations showed very large short- and long-term intensity variations that support an auroral source. However, although Voyager did identify UV auroral emissions by H_2 in the sunlit hemisphere, it did not detect a large H-Lyalpha auroral emission there, making it impossible to provide conclusive evidence that the H-Lyalpha enhancements observed by IUE are due to aurora. Auroral emissions are spatially confined, and resolution of the emission distribution could yield the needed evidence, or could alternatively provide observational clues to other possible causes of dayglow variations in the upper atmosphere. Uranus intrinsically weak H-Lyalpha emission ( ~ 1600 R on average) had not allowed for such an experiment in the past, but the high sensitivity in the FUV of the Space Telescope Imaging Spectrograph (STIS) on HST has now provided first images of Uranus in the FUV. The observations made on 29-30 July 1998 consisted of a FUV MAMA image in the open mode (25MAMA) and a consecutive image filtering out the H-Lyalpha (F25SRF2) to measure and subtract the disk reflected sunlight above 1250 Ang. A quick look at the data shows the H-Lyalpha emission and disk-reflected sunlight, with additional noise from the geocoronal background. We will present the results from these data, taking advantage of the time-tagging information to subtract the geocoronal background, and modeling of the underlying disk background. Four new observations will hopefully be made before October 1998 which will cover the

Synthesis and structural features of U VI and V IV chelate complexes with (hhmmbH)Cl·H 2O [hhmmb = {3-hydroxyl-5-(hydroxymethyl)-2-methylpyridine-4-yl-methylene}benzohydrazide], a new Schiff base ligand derived from vitamin B6

NASA Astrophysics Data System (ADS)

Back, Davi Fernando; Ballin, Marco Aurélio; de Oliveira, Gelson Manzoni

2009-10-01

The Schiff base ligand {3-hydroxyl-5-(hydroxymethyl)-2-methylpyridine-4-yl-methylene}benzohydrazide hydrochloride monohydrated {(hhmmbH)Cl·H 2O} ( 1) was prepared by reaction of pyridoxine hydrochloride with benzoic acid hydrazide. The reaction of 1 with [VO(acac) 2] and triethylamine yields the neutral vanadium IV complex [VO 2(hhmmb)]·Py ( 2), with a distorted quadratic pyramidal configuration. The Schiff base 1 reacts also with UO 2(NO 3) 2·6H 2O and triethylamine under deprotonation giving the uranium VI cationic complexes [UO 2(hhmmb)(H 2O)Cl] + ( 3) and [UO 2(hhmmb)(CH 3OH)Cl] + ( 4), both showing the classical pentagonal bipyrimidal geometry of UO22+ complexes. The structural features of all compounds are discussed.

Aggregation-induced emission spectral shift as a measure of local concentration of a pH-activatable rhodamine-based smart probe

NASA Astrophysics Data System (ADS)

Arsov, Zoran; Urbančič, Iztok; Štrancar, Janez

2018-02-01

Generating activatable probes that report about molecular vicinity through contact-based mechanisms such as aggregation can be very convenient. Specifically, such probes change a particular spectral property only at the intended biologically relevant target. Xanthene derivatives, for example rhodamines, are able to form aggregates. It is typical to examine aggregation by absorption spectroscopy but for microscopy applications utilizing fluorescent probes it is very important to perform characterization by measuring fluorescence spectra. First we show that excitation spectra of aqueous solutions of rhodamine 6G can be very informative about the aggregation features. Next we establish the dependence of the fluorescence emission spectral maximum shift on the dimer concentration. The obtained information helped us confirm the possibility of aggregation of a recently designed and synthesized rhodamine 6G-based pH-activatable fluorescent probe and to study its pH and concentration dependence. The size of the aggregation-induced emission spectral shift at specific position on the sample can be measured by fluorescence microspectroscopy, which at particular pH allows estimation of the local concentration of the observed probe at microscopic level. Therefore, we show that besides aggregation-caused quenching and aggregation-induced emission also aggregation-induced emission spectral shift can be a useful photophysical phenomenon.

A Survey of Extended H_{2} Emission Towards a Sample of Massive YSOs

NASA Astrophysics Data System (ADS)

Navarete, F.; Damineli, A.; Barbosa, C. L.; Blum, R. D.

2014-10-01

Very few massive stars in early formation stages were clearly identified in the Milky Way and moreover, the processes of formation of such objects lacks of observational evidences. Two theories predict the formation of massive star: i) by merging of low mass stars or ii) by an accretion disk. One of the most prominent evidences for the accretion scenario is the presence of bipolar outflows associated to the central sources. Those structures were found on both intermediate and low-mass YSOs, but there are no evidences for associations with MYSOs. Based on that, a survey was designed to investigate the earliest stages of massive star formation through the molecular hydrogen transition at 2.12μm. A sample of ˜ 300 MYSOs candidates was selected from the Red MSX Source program and the sources were observed with the IR cameras Spartan (SOAR, Chile) and WIRCam (CFHT, Hawaii). Extended H_{2} emission was found toward 55% of the sample and 30% of the positive detections (50 sources) have bipolar morphology, suggesting collimated outflows. These results support the accretion scenario, since the merging of low mass stars would not produce jet-like structures.

Outflow of chromospheric emission features from the rim of a sunspot

NASA Technical Reports Server (NTRS)

Liu, S.-Y.

1973-01-01

In viewing a 16 mm movie made from a time sequence of spectroheliograms, some of these emission features are found to move outward from the rim of the sunspot until they are eventually lost in the small plage. There are two interpretations for the streaming of the magnetic features. It is possible that kinks in the line of force propagate along a horizontal extension of the penumbral magnetic field. Alternatively, fragments of the sunspot magnetic field are carried away by the photospheric velocity field.

Unidentified emission features in the R Coronae Borealis star V854 Centauri

NASA Astrophysics Data System (ADS)

Oostrum, L. C.; Ochsendorf, B. B.; Kaper, L.; Tielens, A. G. G. M.

2018-02-01

During its 2012 decline, the R Coronae Borealis star (RCB) V854 Cen was spectroscopically monitored with X-shooter on the ESO Very Large Telescope. The obscured optical and near-infrared spectrum exhibits many narrow and several broad emission features, as previously observed. The envelope is spatially resolved along the slit and allows for a detailed study of the circumstellar material. In this Letter, we report on the properties of a number of unidentified visual emission features (UFs), including the detection of a new feature at 8692 Å. These UFs have been observed in the Red Rectangle (RR), but their chemical and physical nature is still a mystery. The previously known UFs behave similarly in the RR and in V854 Cen, but are not detected in six other observed RCBs. Some hydrogen might be required for the formation of their carrier(s). The λ8692 UF is present in all RCBs. Its carrier is likely of a carbonaceous molecular nature, presumably different from that of the other UFs.

DETECTION OF H i IN EMISSION IN THE LY α EMITTING GALAXY HARO 11

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pardy, Stephen A.; Cannon, John M.; Östlin, Göran

We present the first robust detection of H i 21 cm emission in the blue compact galaxy Haro 11 using the 100 m Robert C. Byrd Green Bank Telescope (GBT). Haro 11 is a luminous blue compact galaxy with emission in both Ly α and the Lyman continuum. We detect (5.1 ± 0.7 × 10{sup 8}) M {sub ⊙} of H i gas at an assumed distance of 88 Mpc, making this galaxy H i deficient compared to other local galaxies with similar optical properties. Given this small H i mass, Haro 11 has an elevated M{sub H2}/ M{sub Hi} ratio and a verymore » low gas fraction compared to most local galaxies, and contains twice as much mass in ionized hydrogen as in neutral hydrogen. The H i emission has a linewidth of 71 km s{sup −}1 and is offset 60 km s{sup −1} redward of the optical line center. It is undergoing a starburst after a recent merger that has elevated the star formation rate, and will deplete the gas supply in <0.2 Gyr. Although this starburst has elevated the star formation rate (SFR) compared to galaxies with similar H i masses and line widths, Haro 11 matches a trend of lower gas fractions toward higher SFRs and is below the general trend of increasing H i mass with increasing luminosity. Taken together, our results paint Haro 11 as a standard low-mass galaxy that is undergoing an unusually efficient star formation episode.« less

Infrared atmospheric sounding interferometer correlation interferometry for the retrieval of atmospheric gases: the case of H2O and CO2.

PubMed

Grieco, Giuseppe; Masiello, Guido; Serio, Carmine; Jones, Roderic L; Mead, Mohammed I

2011-08-01

Correlation interferometry is a particular application of Fourier transform spectroscopy with partially scanned interferograms. Basically, it is a technique to obtain the difference between the spectra of atmospheric radiance at two diverse spectral resolutions. Although the technique could be exploited to design an appropriate correlation interferometer, in this paper we are concerned with the analytical aspects of the method and its application to high-spectral-resolution infrared observations in order to separate the emission of a given atmospheric gas from a spectral signal dominated by surface emission, such as in the case of satellite spectrometers operated in the nadir looking mode. The tool will be used to address some basic questions concerning the vertical spatial resolution of H2O and to develop an algorithm to retrieve the columnar amount of CO2. An application to complete interferograms from the Infrared Atmospheric Sounding Interferometer will be presented and discussed. For H2O, we have concluded that the vertical spatial resolution in the lower troposphere mostly depends on broad features associated with the spectrum, whereas for CO2, we have derived a technique capable of retrieving a CO2 columnar amount with accuracy of ≈±7 parts per million by volume at the level of each single field of view.

Unique Structural Features of Influenza Virus H15 Hemagglutinin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tzarum, Netanel; McBride, Ryan; Nycholat, Corwin M.

Influenza A H15 viruses are members of a subgroup (H7-H10-H15) of group 2 hemagglutinin (HA) subtypes that include H7N9 and H10N8 viruses that were isolated from humans during 2013. The isolation of avian H15 viruses is, however, quite rare and, until recently, geographically restricted to wild shorebirds and waterfowl in Australia. The HAs of H15 viruses contain an insertion in the 150-loop (loop beginning at position 150) of the receptor-binding site common to this subgroup and a unique insertion in the 260-loop compared to any other subtype. Here, we show that the H15 HA has a high preference for avianmore » receptor analogs by glycan array analyses. The H15 HA crystal structure reveals that it is structurally closest to H7N9 HA, but the head domain of the H15 trimer is wider than all other HAs due to a tilt and opening of the HA1 subunits of the head domain. The extended 150-loop of the H15 HA retains the conserved conformation as in H7 and H10 HAs. Furthermore, the elongated 260-loop increases the exposed HA surface and can contribute to antigenic variation in H15 HAs. Since avian-origin H15 HA viruses have been shown to cause enhanced disease in mammalian models, further characterization and immune surveillance of H15 viruses are warranted. IMPORTANCEIn the last 2 decades, an apparent increase has been reported for cases of human infection by emerging avian influenza A virus subtypes, including H7N9 and H10N8 viruses isolated during 2013. H15 is the other member of the subgroup of influenza A virus group 2 hemagglutinins (HAs) that also include H7 and H10. H15 viruses have been restricted to Australia, but recent isolation of H15 viruses in western Siberia suggests that they could be spread more globally via the avian flyways that converge and emanate from this region. Here we report on characterization of the three-dimensional structure and receptor specificity of the H15 hemagglutinin, revealing distinct features and specificities that can aid in global

Simultaneous measurement of stratospheric O3, H2O, CH4, and N2O profiles from infrared limb thermal emissions

NASA Technical Reports Server (NTRS)

Abbas, M. M.; Glenn, M. J.; Kunde, V. G.; Brasunas, J.; Conrath, B. J.; Maguire, W. C.; Herman, J. R.

1987-01-01

Thermal emission measurements of the earth's stratospheric limb were made with a cryogenically cooled high-resolution Michelson interferometer on a balloon flight launched from Palestine, TX, on Nov. 6, 1984. Infrared spectra for complete limb sequences were obtained over portions of the 700-1940/cm range with an unapodized spectral resolution of 0.03/cm for tangent heights varying from 13 to 39 km. The observed data from 1125 to 1425/cm have been analyzed for simultaneous measurement of O3, H2O, CH4, and N2O profiles. The analysis employs line-by-line and layer-by-layer radiative-transfer calculations, including curvature and refraction effects. The optimum use of geometric and spectral effects is made to obtain sharply peaked weighting functions. Contributions from stratospheric aerosol are included by measuring the light extinction within the window regions of the observed spectra. The retrieved constituent profiles are compared with measurements made with a variety of techniques by other groups. The comparison shows good agreement with the published data for all gases, indicating the capability of retrieving trace gas profiles from high-resolution thermal emission limb measurements.

Intramolecular H-transfer reactions in Si 2H n (for n=3-5)

NASA Astrophysics Data System (ADS)

Ernst, M. C.; Sax, A. F.; Kalcher, J.

1993-12-01

Intramolecular rearrangement reactions for doublet Si 2H 5 and Si 2H 3, quartet Si 2H 3, and singlet Si 2H 4 have been studied. aim of the study was to characterize a series of intramolecular H-transfer reactions in silicon hydrides with vrying degrees of saturation. The transition states belonging to the reactions presented in this work possess a monobridged Si 2H moiety. Structural features of the transition states and relative barrier heights have been examined; the geometry optimizations were performed with the use of CAS-SCF wavefunctions and the barrier height estimates were obtained with single-point CI calculations.

Subpart H: National Emission Standards for Emissions of Radionuclides Other Than Radon From Department of Energy Facilities

EPA Pesticide Factsheets

Subpart H sets a limit on the emission of radionuclides that ensures no member of the public receives an effective dose equivalent of more than 10 mrem/year emissions from Department of Energy (DOE) facilities.

Wavelet-based Characterization of Small-scale Solar Emission Features at Low Radio Frequencies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suresh, A.; Sharma, R.; Oberoi, D.

Low radio frequency solar observations using the Murchison Widefield Array have recently revealed the presence of numerous weak short-lived narrowband emission features, even during moderately quiet solar conditions. These nonthermal features occur at rates of many thousands per hour in the 30.72 MHz observing bandwidth, and hence necessarily require an automated approach for their detection and characterization. Here, we employ continuous wavelet transform using a mother Ricker wavelet for feature detection from the dynamic spectrum. We establish the efficacy of this approach and present the first statistically robust characterization of the properties of these features. In particular, we examine distributionsmore » of their peak flux densities, spectral spans, temporal spans, and peak frequencies. We can reliably detect features weaker than 1 SFU, making them, to the best of our knowledge, the weakest bursts reported in literature. The distribution of their peak flux densities follows a power law with an index of −2.23 in the 12–155 SFU range, implying that they can provide an energetically significant contribution to coronal and chromospheric heating. These features typically last for 1–2 s and possess bandwidths of about 4–5 MHz. Their occurrence rate remains fairly flat in the 140–210 MHz frequency range. At the time resolution of the data, they appear as stationary bursts, exhibiting no perceptible frequency drift. These features also appear to ride on a broadband background continuum, hinting at the likelihood of them being weak type-I bursts.« less

The Detection of 6.9 μm Emission Features in the Infrared Spectra of IRAS 04296+3429, IRAS 05341+0852, and IRAS 22272+5435: Evidence for the Presence of Hn-PAHs in Post-AGB Stars

NASA Astrophysics Data System (ADS)

Materese, Christopher K.; Bregman, Jesse D.; Sandford, Scott A.

2017-12-01

Polycyclic aromatic hydrocarbons (PAHs) are generally believed to be ubiquitous in space and responsible for numerous telltale interstellar infrared emission bands. In Sandford et al., we suggested that PAHs with excess hydrogenation at their periphery ({{{H}}}{{n}}-PAHs) may be an important subclass of these molecules in some astrophysical environments. These molecules are candidates to explain objects with anomalously large 3.4 μm features, which are presumed to be associated with the aliphatic C-H stretching vibrations of the excess hydrogen. In that work, we suggest that for Hn-PAHs to be a viable candidate as the source for this 3.4 μm feature, we must also expect to observe methylene scissoring modes at 6.9 μm. In this work, we continue to develop the {{{H}}}{{n}} - {PAH} hypothesis with a focus on the 6.9 μm feature. We also present some new observations of three post-asymptotic giant branch (post-AGB) objects with abnormally large 3.4 μm features, IRAS 04296+3429, IRAS 05341+0852, and IRAS 22272+5435, in addition to one post-AGB object with normal PAH emissions, IRAS 20000+3239. These observations were made using the FORCAST instrument in grism mode on the Stratospheric Observatory for Infrared Astronomy aircraft and demonstrate the presence of a 6.9 μm feature for the three objects with abnormally large 3.4 μm features and no detectable 6.9 μm feature for the normal PAH emitter. These results are consistent with the hypothesis that Hn-PAHs are a possible source of these infrared emission bands.

Supernova Remnants in the UWIFE and UWISH2 Surveys

NASA Astrophysics Data System (ADS)

Lee, Yong-Hyun; Koo, Bon-Chul; Lee, Jae-Joon

2016-06-01

We have searched for near-infrared [Fe II] (1.644 µm) and H2 1-0 S(1) (2.122 µm) emission features associated with Galactic supernova remnants (SNRs) using the narrow-band imaging surveys UWIFE/ UWISH2 (UKIRT Widefield Infrared Survey for [Fe II] / H2). Both surveys cover about 180 square degrees of the first Galactic quadrant (7° < l < 62°; -1.5° < b < +1.5°), and a total of 79 SNRs are falling in the survey area among the currently known 294 Galactic SNRs. The images show diffuse structures as deep as the surface brightness limit of 10-19 W m-2 arcsec-2 which is comparable with a 5σ detection limit of point sources of 18 mag. In order to inspect the narrow-band features, we subtracted H and K-band continuum images obtained from the UKIDSS GPS (UKIRT Infrared Deep Sky Survey of the Galactic Plane) from the [Fe II] and H2 narrow-band images, respectively. By this time, we have found 19 [Fe II]- and 18 H2-emitting SNRs, and these are likely to increase in future as we inspect the images in more detail. Some of the SNRs show bright, complex, and interesting structures that have never been reported in previous studies. Since [Fe II] and H2 lines trace dense atomic and molecular gases associated with SNR shocks, our results can help us understand the environment and evolution of individual SNRs. Among the SNRs showing both [Fe II] and H2 emission lines, some SNRs show the “[Fe II]-H2 reversal” phenomenon, i.e., the H2 emission features are detected outside the [Fe II] emission boundary. This is opposite to the standard picture: If the shocks are driven by the same blast wave, we expect the H2 filaments to be closer to the explosion center than the [Fe II] filaments. In this presentation, we show several examples of such SNRs detected in our study, and present high resolution (R ˜ 40,000) H and K-band spectra of H2 emission features obtained by using IGRINS (Immersion Grating Infrared Spectrograph).

Supernova Remnants in the UWIFE and UWISH2 Surveys

NASA Astrophysics Data System (ADS)

Lee, Yong-Hyun

2016-06-01

We have searched for near-infrared [Fe II] (1.644 μm) and H2 1-0 S(1) (2.122 μm) emission features associated with Galactic supernova remnants (SNRs) using the narrow-band imaging surveys UWIFE/ UWISH2 (UKIRT Widefield Infrared Survey for [Fe II] / H2 ). Both surveys cover about 180 square degrees of the first Galactic quadrant (7 {circ} < l < 62 {circ} ; -1.5 {circ} < b < +1.5 {circ} ), and a total of 79 SNRs are falling in the survey area among the currently known 294 Galactic SNRs. The images show diffuse structures as deep as the surface brightness limit of 10^(-19) W m^(-2) arcsec^(-2) which is comparable with a 5σ detection limit of point sources of 18 mag. In order to inspect the narrow-band features, we subtracted H and K-band continuum images obtained from the UKIDSS GPS (UKIRT Infrared Deep Sky Survey of the Galactic Plane) from the [Fe II] and H2 narrow-band images, respectively. By this time, we have found 19 [Fe II]- and 18 H2 -emitting SNRs, and these are likely to increase in future as we inspect the images in more detail. Some of the SNRs show bright, complex, and interesting structures that have never been reported in previous studies. Since [Fe II] and H2 lines trace dense atomic and molecular gases associated with SNR shocks, our results can help us understand the environment and evolution of individual SNRs. Among the SNRs showing both [Fe II] and H2 emission lines, some SNRs show the “[Fe II]-H2 reversal” phenomenon, i.e., the H2 emission features are detected outside the [Fe II] emission boundary. This is opposite to the standard picture: If the shocks are driven by the same blast wave, we expect the H2 filaments to be closer to the explosion center than the [Fe II] filaments. In this presentation, we show several examples of such SNRs detected in our study, and present high resolution (R 40,000) H and K-band spectra of H2 emission features obtained by using IGRINS (Immersion Grating Infrared Spectrograph).

A Study of the 3.3 and 3.4 μm Emission Features in Proto-Planetary Nebulae

NASA Astrophysics Data System (ADS)

Hrivnak, Bruce J.; Geballe, T. R.; Kwok, Sun

2007-06-01

Medium-resolution spectra have been obtained of seven carbon-rich proto-planetary nebulae (PPNs) and one young planetary nebula from 3.2 to 3.8 μm, an interval containing the prominent hydrocarbon CH stretches at 3.3 and 3.4 μm due to aromatic and aliphatic structures, respectively. The 3.3 μm feature is newly identified in IRAS 23304+6147, 22223+4327, and 06530-0213 and is confirmed in Z02229+6208. Three of the PPNs emit in the 3.4 μm feature, two of these being new identifications, IRAS 20000+3239 and 01005+7910, with two others showing possible detections. The 3.3 and 3.4 μm emission features in IRAS 22272+5435 are seen in the nebula offset from the star but not at the position of the central star, consistent with the 2003 results of Goto et al. A similar distribution is seen for the 3.3 μm feature in IRAS 22223+4327. All of the PPNs except IRAS 22272+5435 show Class A 3 μm emission features. These observations, when combined with those of the approximately equal number of other carbon-rich PPNs previously observed, demonstrate that there are large differences in the 3 μm emission bands, even for PPNs with central stars of similar spectral type, and thus that the behavior of the bands does not depend solely on spectral type. We also investigated other possible correlations to help explain these differences. These differences do not depend on the C/O value, since the Class B sources fall within the C/O range found for Class A. All of these 3.3 μm sources also show C2 absorption and 21 μm emission features, except IRAS 01005+7910, which is the hottest source at B0. This research is based on observations made at the W. M. Keck Observatory by Gemini staff, supported by the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., on behalf of the international Gemini partnership of Argentina, Australia, Brazil, Canada, Chile, the United Kingdom, and the United States of America. The W. M. Keck Observatory is

Laboratory simulation of infrared astrophysical features. Ph.D. Thesis; [emission spectra of comets

NASA Technical Reports Server (NTRS)

Rose, L. A.

1977-01-01

Intermediate resolution emission spectroscopy was used to study a group of 9 terrestrial silicates, 1 synthetic silicate, 6 meteorites and 2 lunar soils; comparisons were made with the intermediate resolution spectra of Comet Kohoutek in order to determine which materials best simulate the 10um astrophysical feature. Mixtures of silicates which would yield spectra matching the spectrum of the comet in the 10um region include: (1) A hydrous layer lattice silicate in combination with a high temperature condensate; (2) an amorphous magnesium silicate in combination with a high temperature condensate and (3) glassy olivine and glassy anorthite in approximately equal proportions.

Hydrogen atom abstraction from aldehydes - OH + H2CO and O + H2CO

NASA Technical Reports Server (NTRS)

Dupuis, M.; Lester, W. A., Jr.

1984-01-01

The essential features of the potential energy surfaces governing hydrogen abstraction from formaldehyde by oxygen atom and hydroxyl radical have been characterized with ab inito multiconfiguration Hartree-Fock (MCHF) and configuration interaction (CI) wave functions. The results are consistent with a very small activation energy for the OH + H2CO reaction, and an activation energy of a few kcal/mol for the O + H2CO reaction. In the transition state structure of both systems, the attacking oxygen atom is nearly collinear with the attacked CH bond.

Herschel/HIFI observations of CO, H2O and NH3 in Monoceros R2

NASA Astrophysics Data System (ADS)

Pilleri, P.; Fuente, A.; Cernicharo, J.; Ossenkopf, V.; Berné, O.; Gerin, M.; Pety, J.; Goicoechea, J. R.; Rizzo, J. R.; Montillaud, J.; González-García, M.; Joblin, C.; Le Bourlot, J.; Le Petit, F.; Kramer, C.

2012-08-01

Context. Mon R2, at a distance of 830 pc, is the only ultracompact H ii region (UCH ii) where the associated photon-dominated region (PDR) can be resolved with Herschel. Owing to its brightness and proximity, it is one of the best-suited sources for investigating the chemistry and physics of highly UV-irradiated PDRs. Aims: Our goal is to estimate the abundance of H2O and NH3 in this region and investigate their origin. Methods: We present new observations ([C ii], 12CO, 13CO, C18O, o-H2O, p-H2O, o-H_218O and o-NH3) obtained with the HIFI instrument onboard Herschel and the IRAM-30 m telescope. We investigated the physical conditions in which these lines arise by analyzing their velocity structure and spatial variations. Using a large velocity gradient approach, we modeled the line intensities and derived an average abundance of H2O and NH3 across the region. Finally, we modeled the line profiles with a non-local radiative transfer model and compared these results with the abundance predicted by the Meudon PDR code. Results: The variations of the line profiles and intensities indicate complex geometrical and kinematical patterns. In several tracers ([C ii], CO 9 → 8 and H2O) the line profiles vary significantly with position and have broader line widths toward the H ii region. The H2O lines present strong self-absorption at the ambient velocity and emission in high-velocity wings toward the H ii region. The emission in the o-H_218O ground state line reaches its maximum value around the H ii region, has smaller linewidths and peaks at the velocity of the ambient cloud. Its spatial distribution shows that the o-H_218O emission arises in the PDR surrounding the H ii region. By modeling the o-H_218O emission and assuming the standard [16O] / [18O] = 500, we derive a mean abundance of o-H2O of ~10-8 relative to H2. The ortho-H2O abundance, however, is larger (~1 × 10-7) in the high-velocity wings detected toward the H ii region. Possible explanations for this larger

Syntheses, crystal structures and luminescent properties of two salts with 2-((1H-imidazol-1-yl)methyl)-1H-benzimidazole

NASA Astrophysics Data System (ADS)

Wang, Yong-Tao; Lü, Lin-Rui; Tang, Gui-Mei

2018-03-01

Two new benzimidazole salts, namely, [H2IBI]2+ 2X (X = NO3- (1), ClO4- (2) [IBI = 2-((1H-imidazol-1-yl)methyl)-1H-benzimidazole], were grown through reacting IBI and two different inorganic acids by slow evaporation method, respectively. Compounds 1 and 2 have been characterized by single-crystal X-ray diffraction, IR, UV-Vis, and thermogravimetric analyses (TGA). In both compounds, a set of hydrogen bonds (C/Nsbnd H⋯O) can be clearly observed, through which a three-dimensional framework will be generated. The luminescent spectra show the emission peaks in compounds 1 and 2 are found at 375 and 371 nm, respectively. By comparison with the free IBI, the emission maxima of compounds 1 and 2 are obviously red-shifted about 67 and 63 nm, respectively.

Inelastic rate coefficients for collisions of C6H- with H2 and He

NASA Astrophysics Data System (ADS)

Walker, Kyle M.; Lique, François; Dumouchel, Fabien; Dawes, Richard

2017-04-01

The recent detection of anions in the interstellar medium has shown that they exist in a variety of astrophysical environments - circumstellar envelopes, cold dense molecular clouds and star-forming regions. Both radiative and collisional processes contribute to molecular excitation and de-excitation in these regions so that the 'local thermodynamic equilibrium' approximation, where collisions cause the gas to behave thermally, is not generally valid. Therefore, along with radiative coefficients, collisional excitation rate coefficients are needed to accurately model the anionic emission from these environments. We focus on the calculation of state-to-state rate coefficients of the C6H- molecule in its ground vibrational state in collisions with para-H2, ortho-H2 and He using new potential energy surfaces. Dynamical calculations for the pure rotational excitation of C6H- were performed for the first 11 rotational levels (up to j1 = 10) using the close-coupling method, while the coupled-states approximation was used to extend the H2 rate coefficients to j1 = 30, where j1 is the angular momentum quantum number of C6H-. State-to-state rate coefficients were obtained for temperatures ranging from 2 to 100 K. The rate coefficients for H2 collisions for Δj1 = -1 transitions are of the order of 10-10 cm3 s-1, a factor of 2 to 3 greater than those of He. Propensity rules are discussed. The collisional excitation rate coefficients produced here impact astrophysical modelling since they are required for obtaining accurate C6H- level populations and line emission for regions that contain anions.

An Integrated Modeling Study for Coordinated Observations of H, O, OH, and H2O(+) Emissions in the Coma and Ion Tail of the Comet Hale-Bopp

NASA Technical Reports Server (NTRS)

Smyth, William H.

2001-01-01

This project has two overall objectives. One objective is to advance our general understanding of both the comet neutral atmosphere and the cometary plasma in the atmosphere and ion tall. The other objective is to obtain specific key information about comet Hale-Bopp that is generally important for Hale-Bopp studies. The primary emphasis in this project is to analyze, in a self-consistent manner, excellent quality high resolution image and line profile observations obtained by the University of Wisconsin for H, O, OH, and H2O+ emissions from the inner coma, outer coma, and ion tail of Hale-Bopp. The information on the spatial and velocity distributions of H2O neutral and ionized photo-products in the inner coma, outer coma, and in the H2O+ ion tail is of substantial and direct importance in the development of an integrated understanding of the complex structure and dynamics of the neutral and plasma species in the atmosphere of Hale-Bopp in particular and comets in general. The H2O production rate of Hale-Bopp is determined and, together with the other information related to the structure and dynamics of the neutral and plasma atmospheres obtained in this study, provide critical information important for a wide variety of research conducted by other groups.

Optical emission spectroscopic study of plasma plumes generated by IR CO2 pulsed laser on carbon targets

NASA Astrophysics Data System (ADS)

Camacho, J. J.; Díaz, L.; Santos, M.; Reyman, D.; Poyato, J. M. L.

2008-05-01

Optical emission spectroscopy studies, in the spectral range ultraviolet-visible-near infrared (UV-Vis-NIR), were performed to investigate thermal and dynamical properties of a plume produced by laser ablation of a graphite target. Ablation is carried out using a high-power IR CO2 pulsed laser at λ = 9.621 µm, power density ranging from 0.22 to 5.36 GW cm-2 and air pressures around 4 Pa. The strong emission observed in the plasma region is mainly due to electronic relaxation of excited C, ionic fragments C+, C2+ and C3+ and molecular features of C2(d 3Πg-a 3Πu Swan band system). The medium-weak emission is mainly due to excited atomic N, H, O, ionic fragment C4+ and molecular features of C2( E\\,^1\\Sigma _g^+\\--A\\,^{1}\\Pi _u ; Freymark system), C2( D\\,^1\\Sigma _u^+\\--X\\,^1\\Sigma _g^+ ; Mulliken system), CN(D 2Π-A 2Π), C2(e 3Πg-a 3Πu Fox-Herzberg system), C2(C 1Πg-A 1Πu Deslandres-d'Azambuja system), OH(A 2Σ+-X 2Π), CH(C 2Σ+-X 2Π), NH(A 3Π-X 3Σ-), CN(B 2Σ+-X 2Σ+ violet system), CH(B 2Σ+-X 2Π), CH(A 2Δ-X 2Π), C2( A\\,^{1}\\Pi_u\\--X\\,^{1}\\Sigma ^{+}_g ; Phillips system) and CN(A 2Π-X 2Σ+ red system). An excitation temperature Texc = 23 000 ± 1900 K and electron densities in the range (0.6-5.6) × 1016 cm-3 were estimated by means of C+ ionic lines. The characteristics of the spectral emission intensities from different species have been investigated as functions of the ambient pressure and laser irradiance. Estimates of vibrational temperatures of C2 and CN electronically excited species under various laser irradiance conditions are made.

Exploring H2O Prominence in Reflection Spectra of Cool Giant Planets

NASA Astrophysics Data System (ADS)

MacDonald, Ryan J.; Marley, Mark S.; Fortney, Jonathan J.; Lewis, Nikole K.

2018-05-01

The H2O abundance of a planetary atmosphere is a powerful indicator of formation conditions. Inferring H2O in the solar system giant planets is challenging, due to condensation depleting the upper atmosphere of water vapor. Substantially warmer hot Jupiter exoplanets readily allow detections of H2O via transmission spectroscopy, but such signatures are often diminished by the presence of clouds composed of other species. In contrast, highly scattering water clouds can brighten planets in reflected light, enhancing molecular signatures. Here, we present an extensive parameter space survey of the prominence of H2O absorption features in reflection spectra of cool (Teff < 400 K) giant exoplanetary atmospheres. The impact of effective temperature, gravity, metallicity, and sedimentation efficiency is explored. We find prominent H2O features around 0.94 μm, 0.83 μm, and across a wide spectral region from 0.4 to 0.73 μm. The 0.94 μm feature is only detectable where high-altitude water clouds brighten the planet: Teff ∼ 150 K, g ≳ 20 ms‑2, fsed ≳ 3, m ≲ 10× solar. In contrast, planets with g ≲ 20 ms‑2 and Teff ≳ 180 K display substantially prominent H2O features embedded in the Rayleigh scattering slope from 0.4 to 0.73 μm over a wide parameter space. High fsed enhances H2O features around 0.94 μm, and enables these features to be detected at lower temperatures. High m results in dampened H2O absorption features, due to water vapor condensing to form bright, optically thick clouds that dominate the continuum. We verify these trends via self-consistent modeling of the low-gravity exoplanet HD 192310c, revealing that its reflection spectrum is expected to be dominated by H2O absorption from 0.4 to 0.73 μm for m ≲ 10× solar. Our results demonstrate that H2O is manifestly detectable in reflected light spectra of cool giant planets only marginally warmer than Jupiter, providing an avenue to directly constrain the C/O and O/H ratios of a hitherto

The Orion Fingers: H2 Temperatures and Excitation in an Explosive Outflow

NASA Astrophysics Data System (ADS)

Youngblood, Allison; France, Kevin; Ginsburg, Adam; Hoadley, Keri; Bally, John

2018-04-01

We measure H2 temperatures and column densities across the Orion Becklin-Neugebauer/Kleinmann-Low (BN/KL) explosive outflow from a set of 13 near-infrared (IR) H2 rovibrational emission lines observed with the TripleSpec spectrograph on Apache Point Observatory’s 3.5 m telescope. We find that most of the region is well characterized by a single temperature (∼2000–2500 K), which may be influenced by the limited range of upper-energy levels (6000–20,000 K) probed by our data set. The H2 column density maps indicate that warm H2 comprises 10‑5–10‑3 of the total H2 column density near the center of the outflow. Combining column density measurements for co-spatial H2 and CO at T = 2500 K, we measure a CO/H2 fractional abundance of 2 × 10‑3 and discuss possible reasons why this value is in excess of the canonical 10‑4 value, including dust attenuation, incorrect assumptions on co-spatiality of the H2 and CO emission, and chemical processing in an extreme environment. We model the radiative transfer of H2 in this region with ultraviolet (UV) pumping models to look for signatures of H2 fluorescence from H I Lyα pumping. Dissociative (J-type) shocks and nebular emission from the foreground Orion H II region are considered as possible Lyα sources. From our radiative transfer models, we predict that signatures of Lyα pumping should be detectable in near-IR line ratios given a sufficiently strong source, but such a source is not present in the BN/KL outflow. The data are consistent with shocks as the H2 heating source.

Observations of Ellerman bomb emission features in He I D3 and He I 10 830 Å

NASA Astrophysics Data System (ADS)

Libbrecht, Tine; Joshi, Jayant; Rodríguez, Jaime de la Cruz; Leenaarts, Jorrit; Ramos, Andrés Asensio

2017-02-01

Context. Ellerman bombs (EBs) are short-lived emission features, characterised by extended wing emission in hydrogen Balmer lines. Until now, no distinct signature of EBs has been found in the He I 10 830 Å line, and conclusive observations of EBs in He I D3 have never been reported. Aims: We aim to study the signature of EBs in neutral helium triplet lines. Methods: The observations consisted of ten consecutive SST/TRIPPEL raster scans close to the limb, featuring the Hβ, He I D3 and He I 10 830 Å spectral regions. We also obtained raster scans with IRIS and made use of the SDO/AIA 1700 Å channel. We used Hazel to invert the neutral helium triplet lines. Results: Three EBs in our data show distinct emission signatures in neutral helium triplet lines, most prominently visible in the He I D3 line. The helium lines have two components: a broad and blueshifted emission component associated with the EB, and a narrower absorption component formed in the overlying chromosphere. One of the EBs in our data shows evidence of strong velocity gradients in its emission component. The emission component of the other two EBs could be fitted using a constant slab. Our analysis hints towards thermal Doppler motions having a large contribution to the broadening for helium and IRIS lines. We conclude that the EBs must have high temperatures to exhibit emission signals in neutral helium triplet lines. An order of magnitude estimate places our observed EBs in the range of T 2 × 104-105 K. Movies associated to Figs. 3-5 are available at http://www.aanda.org

Emissions of ammonia, carbon dioxide, and hydrogen sulfide from swine wastewater during and after acidification treatment: effect of pH, mixing and aeration.

PubMed

Dai, X R; Blanes-Vidal, V

2013-01-30

This study aimed at evaluating the effect of swine slurry acidification and acidification-aeration treatments on ammonia (NH(3)), carbon dioxide (CO(2)) and hydrogen sulfide (H(2)S) emissions during slurry treatment and subsequent undisturbed storage. The study was conducted in an experimental setup consisting of nine dynamic flux chambers. Three pH levels (pH = 6.0, pH = 5.8 and pH = 5.5), combined with short-term aeration and venting (with an inert gas) treatments were studied. Acidification reduced average NH(3) emissions from swine slurry stored after acidification treatment compared to emissions during storage of non-acidified slurry. The reduction were 50%, 62% and 77% when pH was reduce to 6.0, 5.8 and 5.5, respectively. However, it had no significant effect on average CO(2) and H(2)S emissions during storage of slurry after acidification. Aeration of the slurry for 30 min had no effect on average NH(3), CO(2) and H(2)S emissions both during the process and from stored slurry after venting treatments. During aeration treatment, the NH(3), CO(2) and H(2)S release pattern observed was related to the liquid turbulence caused by the gas bubbles rather than to biological oxidation processes in this study. Copyright © 2012 Elsevier Ltd. All rights reserved.

Characterization of NOx, SO2, ethene, and propene from industrial emission sources in Houston, Texas

NASA Astrophysics Data System (ADS)

Washenfelder, R. A.; Trainer, M.; Frost, G. J.; Ryerson, T. B.; Atlas, E. L.; de Gouw, J. A.; Flocke, F. M.; Fried, A.; Holloway, J. S.; Parrish, D. D.; Peischl, J.; Richter, D.; Schauffler, S. M.; Walega, J. G.; Warneke, C.; Weibring, P.; Zheng, W.

2010-08-01

The Houston-Galveston-Brazoria urban area contains industrial petrochemical sources that emit volatile organic compounds and nitrogen oxides, resulting in rapid and efficient ozone production downwind. During September to October 2006, the NOAA WP-3D aircraft conducted research flights as part of the second Texas Air Quality Study (TexAQS II). We use measurements of NOx, SO2, and speciated hydrocarbons from industrial sources in Houston to derive source emission ratios and compare these to emission inventories and the first Texas Air Quality Study (TexAQS) in 2000. Between 2000 and 2006, NOx/CO2 emission ratios changed by an average of -29% ± 20%, while a significant trend in SO2/CO2 emission ratios was not observed. We find that high hydrocarbon emissions are routine for the isolated petrochemical facilities. Ethene (C2H4) and propene (C3H6) are the major contributors to ozone formation based on calculations of OH reactivity for organic species including C2-C10 alkanes, C2-C5 alkenes, ethyne, and C2-C5 aldehydes and ketones. Measured ratios of C2H4/NOx and C3H6/NOx exceed emission inventory values by factors of 1.4-20 and 1-24, respectively. We examine trends in C2H4/NOx and C3H6/NOx ratios between 2000 and 2006 for the isolated petrochemical sources and estimate a change of -30% ± 30%, with significant day-to-day and within-plume variability. Median ambient mixing ratios of ethene and propene in Houston show decreases of -52% and -48%, respectively, between 2000 and 2006. The formaldehyde, acetaldehyde, and peroxyacetyl nitrate products produced by alkene oxidation are observed downwind, and their time evolution is consistent with the rapid photochemistry that also produces ozone.

Preliminary JIRAM results from Juno polar observations: 2. Analysis of the Jupiter southern H3+ emissions and comparison with the north aurora

NASA Astrophysics Data System (ADS)

Adriani, A.; Mura, A.; Moriconi, M. L.; Dinelli, B. M.; Fabiano, F.; Altieri, F.; Sindoni, G.; Bolton, S. J.; Connerney, J. E. P.; Atreya, S. K.; Bagenal, F.; Gérard, J.-C. M. C.; Filacchione, G.; Tosi, F.; Migliorini, A.; Grassi, D.; Piccioni, G.; Noschese, R.; Cicchetti, A.; Gladstone, G. R.; Hansen, C.; Kurth, W. S.; Levin, S. M.; Mauk, B. H.; McComas, D. J.; Olivieri, A.; Turrini, D.; Stefani, S.; Amoroso, M.

2017-05-01

The Jupiter InfraRed Auroral Mapper (JIRAM) aboard Juno observed the Jovian South Pole aurora during the first orbit of the mission. H3+ (trihydrogen cation) and CH4 (methane) emissions have been identified and measured. The observations have been carried out in nadir and slant viewing both by a L-filtered imager and a 2-5 μm spectrometer. Results from the spectral analysis of the all observations taken over the South Pole by the instrument are reported. The coverage of the southern aurora during these measurements has been partial, but sufficient to determine different regions of temperature and abundance of the H3+ ion from its emission lines in the 3-4 μm wavelength range. Finally, the results from the southern aurora are also compared with those from the northern ones from the data taken during the same perijove pass and reported by Dinelli et al. (2017).

Electronic structure and energetics of the tetragonal distortion for TiH2, ZrH2 and HfH2: a first principles study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quijano, Ramiro; DeCoss, Romeo; Singh, David J

2009-01-01

The electronic structure and energetics of the tetragonal distortion for the fluorite-type dihydrides TiH{sub 2}, ZrH{sub 2}, and HfH{sub 2} are studied by means of highly accurate first-principles total-energy calculations. For HfH{sub 2}, in addition to the calculations using the scalar relativistic (SR) approximation, calculations including the spin-orbit coupling have also been performed. The results show that TiH{sub 2}, ZrH{sub 2}, and HfH{sub 2} in the cubic phase are unstable against tetragonal strain. For the three systems, the total energy shows two minima as a function of the c/a ratio with the lowest-energy minimum at c/a < 1 in agreementmore » with the experimental observations. The band structure of TiH{sub 2}, ZrH{sub 2}, and HfH{sub 2} (SR) around the Fermi level shows two common features along the two major symmetry directions of the Brillouin zone, {Lambda}?L and {Lambda}?K, a nearly flat doubly degenerate band, and a van Hove singularity, respectively. In cubic HfH{sub 2} the spin-orbit coupling lifts the degeneracy of the partially filled bands in the {Lambda}?L path, while the van Hove singularity in the {Lambda}?K path remains unchanged. The density of states of the three systems in the cubic phase shows a sharp peak at the Fermi level. We found that the tetragonal distortion produces a strong reduction in the density of states at the Fermi level resulting mainly from the splitting of the doubly-degenerate bands in the {Lambda}?L direction and the shift of the van Hove singularity to above the Fermi level. The validity of the Jahn-Teller model in explaining the tetragonal distortion in this group of dihydrides is discussed.« less

Biogenic emissions and CO 2 gas exchange investigated on four Mediterranean shrubs

NASA Astrophysics Data System (ADS)

Hansen, U.; van Eijk, J.; Bertin, N.; Staudt, M.; Kotzias, D.; Seufert, G.; Fugit, J.-L.; Torres, L.; Cecinato, A.; Brancaleoni, E.; Ciccioli, P.; Bomboi, T.

In order to investigate the impact of plant physiology on emissions of biogenic volatile organic compounds monoterpene emission rates from Rosmarinus officinalis (L.) and Pistacia lentiscus (L.) and isoprene emission rates from Erica arborea (L.) and Myrtus communis (L.) were determined. The study, an activity in the framework of BEMA (Biogenic Emissions in the Mediterranean Area), was carried out in May 1994 at Castelporziano near Rome in Italy, using a dynamic enclosure technique combined with recording CO 2 gas exchange, temperature and irradiance data. The monoterpenes dominating the emission pattern were 1,8-cineol, α-pinene and β-pinene for rosemary and α-pinene, linalool and β-pinene + sabinene for pistachio. Total monoterpene emission rates standardized to 30°C of 1.84 ± 0.24 and 0.35 ± 0.04 μg Cg -1 dw h -1 were found for rosemary and pistachio, respectively (on a leaf dry weight basis). Myrtle emitted 22.2 ± 4.9 μg C g -1 dw h -1 at standard conditions (30°C, PAR 1000 μmol photons m -2 s -1 as isoprene and erica 5.61 μg C g -1 dw h -1 The carbon loss due to terpenoid emissions per photosynthetically carbon uptake was about 0.01-0.1% for the monoterpene emitters. The isoprene emitting shrubs lost 0-0.9% of the assimilated carbon. The rapid induction of emissions in the sun after temporary shading indicates that isoprene emissions were closely linked to photosynthesis. A higher proportion of the assimilated carbon was lost as isoprene under conditions of high light and temperature compared to the morning and evening hours.

Outsourcing CO2 Emissions

NASA Astrophysics Data System (ADS)

Davis, S. J.; Caldeira, K. G.

2009-12-01

CO2 emissions from the burning of fossil fuels are the primary cause of global warming. Much attention has been focused on the CO2 directly emitted by each country, but relatively little attention has been paid to the amount of emissions associated with consumption of goods and services in each country. This consumption-based emissions inventory differs from the production-based inventory because of imports and exports of goods and services that, either directly or indirectly, involved CO2 emissions. Using the latest available data and reasonable assumptions regarding trans-shipment of embodied carbon through third-party countries, we developed a global consumption-based CO2 emissions inventory and have calculated associated consumption-based energy and carbon intensities. We find that, in 2004, 24% of CO2 emissions are effectively outsourced to other countries, with much of the developed world outsourcing CO2 emissions to emerging markets, principally China. Some wealthy countries, including Switzerland and Sweden, outsource over half of their consumption-based emissions, with many northern Europeans outsourcing more than three tons of emissions per person per year. The United States is both a big importer and exporter of emissions embodied in trade, outsourcing >2.6 tons of CO2 per person and at the same time as >2.0 tons of CO2 per person are outsourced to the United States. These large flows indicate that CO2 emissions embodied in trade must be taken into consideration when considering responsibility for increasing atmospheric greenhouse gas concentrations.

Influence of H2O2 on LPG fuel performance evaluation

NASA Astrophysics Data System (ADS)

Khan, Muhammad Saad; Ahmed, Iqbal; Mutalib, Mohammad Ibrahim bin Abdul; Nadeem, Saad; Ali, Shahid

2014-10-01

The objective of this mode of combustion is to insertion of hydrogen peroxide (H2O2) to the Liquefied Petroleum Gas (LPG) combustion on spark plug ignition engines. The addition of hydrogen peroxide may probably decrease the formation of NOx, COx and unburned hydrocarbons. Hypothetically, Studies have shown that addition of hydrogen peroxide to examine the performance of LPG/H2O2 mixture in numerous volumetric compositions starting from lean LPG until obtaining a better composition can reduce the LPG fuel consumption. The theory behind this idea is that, the addition of H2O2 can cover the lean operation limit, increase the lean burn ability, diminution the burn duration along with controlling the exhaust emission by significantly reducing the greenhouse gaseous.

Orientation and temperature dependent adsorption of H 2S on GaAs: Valence band photoemission

NASA Astrophysics Data System (ADS)

Ranke, W.; Kuhr, H. J.; Finster, J.

A cylindrically shaped GaAs single crystal was used to study the adsorption of H 2S on the six inequivalent orientations (001), (113), (111), (110), (111) and (113) by angle resolved valence band photoelectron spectroscopy and surface dipole measurements. Adsorption at 150 K on the surface prepared by molecular beam epitaxy (MBE) yields similar adsorbate induced emission on all orientations which were ascribed to SH radicals. On (110), where preferential adsorption occurs additional features from molecular H 2S are observed. The adsorbate spectra at 720 K are ascribed to atomic sulphur. On the surface prepared by ion bombardment and annealing, defect enhanced adsorption occurs in the range (111)-(113). The adsorbate spectra are very similar to those on the MBE surface at 720 K. Thus, no new species are adsorbed on defects but only sticking probability and penetration capability are increased.

Fumarole/plume and diffuse CO2 emission from Sierra Negra volcano, Galapagos archipelago

NASA Astrophysics Data System (ADS)

Padron, E.; Hernandez Perez, P. A.; Perez, N.; Theofilos, T.; Melian, G.; Barrancos, J.; Virgil, G.; Sumino, H.; Notsu, K.

2009-12-01

The active shield-volcano Sierra Negra is part of the Galapagos hotspot. Sierra Negra is the largest shield volcano of Isabela Island, hosting a 10 km diameter caldera. Ten historic eruptions have occurred and some involved a frequently visited east caldera rim fissure zone called Volcan Chico. The last volcanic event occurred in October 2005 and lasted for about a week, covering approximately twenty percent of the eastern caldera floor. Sierra Negra volcano has experienced some significant changes in the chemical composition of its volcanic gas discharges after the 2005 eruption. This volcanic event produced an important SO2 degassing that depleted the magmatic content of this gas. Not significant changes in the MORB and plume-type helium contribution were observed after the 2005 eruption, with a 65.5 % of MORB and 35.5 % of plume contribution. In 2006 a visible and diffuse gas emission study was performed at the summit of Sierra Negra volcano, Galapagos, to evaluate degassing rate from this volcanic system. Diffuse degassing at Sierra Negra was mainly confined in three different DDS: Volcan Chico, the southern inner margin of the caldera, and Mina Azufral. These areas showed also visible degassing, which indicates highly fractured areas where volcano-hydrothermal fluids migrate towards surface. A total fumarole/plume SO2 emission of 11 ± 2 td-1 was calculated by mini-DOAS ground-based measurements at Mina Azufral fumarolic area. Molar ratios of major volcanic gas components were also measured in-situ at Mina Azufral with a portable multisensor. The results showed H2S/SO2, CO2/SO2 and H2O/SO2 molar ratios of 0.41, 52.2 and 867.9, respectively. Multiplying the observed SO2 emission rate times the observed (gas)i/SO2 mass ratio we have estimated other volatiles emission rates. The results showed that H2O, CO2 and H2S emission rates from Sierra Negra are 562, 394, and 2.4 t d-1, respectively. The estimated total output of diffuse CO2 emission from the summit of

Guilt by Association: The 13 micron Dust Feature in Circumstellar Shells and Related Spectral Features

NASA Astrophysics Data System (ADS)

Sloan, G. C.; Kraemer, K. E.; Goebel, J. H.; Price, S. D.

A study of spectra from the SWS on ISO of optically thin oxygen-rich dust shells shows that the strength of the 13 micron dust emission feature is correlated with the CO2 bands (13--17 microns) and dust emission features at 19.8 and 28.1 microns. SRb variables tend to show stronger 13 micron features than Mira variables, suggesting that the presence of the 13 micron and related features depends on pulsation mode and mass-loss rate. The absence of any correlation to dust emission features at 16.8 and 32 microns makes spinel an unlikely carrier. The most plausible carrier of the 13 micron feature remains crystalline alumina, and we suggest that the related dust features may be crystalline silicates. When dust forms in regions of low density, it may condense into crystalline grain structures.

A TALE OF THREE MYSTERIOUS SPECTRAL FEATURES IN CARBON-RICH EVOLVED STARS: THE 21 μm, 30 μm, AND “UNIDENTIFIED INFRARED” EMISSION FEATURES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, Ajay; Li, Aigen; Jiang, B. W., E-mail: amishra@mail.missouri.edu, E-mail: lia@missouri.edu, E-mail: bjiang@bnu.edu.cn

2015-03-20

The mysterious “21 μm” emission feature seen almost exclusively in the short-lived protoplanetary nebula (PPN) phase of stellar evolution remains unidentified since its discovery two decades ago. This feature is always accompanied by the equally mysterious, unidentified “30 μm” feature and the so-called “unidentified infrared” (UIR) features at 3.3, 6.2, 7.7, 8.6, and 11.3 μm which are generally attributed to polycyclic aromatic hydrocarbon (PAH) molecules. The 30 μm feature is commonly observed in all stages of stellar evolution from the asymptotic giant branch through PPN to the planetary nebula phase. We explore the interrelations among the mysterious 21, 30 μm,more » and UIR features of the 21 μm sources. We derive the fluxes emitted in the observed UIR, 21, and 30 μm features from published Infrared Space Observatory or Spitzer/IRS spectra. We find that none of these spectral features correlate with each other. This argues against a common carrier (e.g., thiourea) for both the 21 μm feature and the 30 μm feature. This also does not support large PAH clusters as a possible carrier for the 21 μm feature.« less

Validation of a novel Multi-Gas sensor for volcanic HCl alongside H2S and SO2 at Mt. Etna

NASA Astrophysics Data System (ADS)

Roberts, T. J.; Lurton, T.; Giudice, G.; Liuzzo, M.; Aiuppa, A.; Coltelli, M.; Vignelles, D.; Salerno, G.; Couté, B.; Chartier, M.; Baron, R.; Saffell, J. R.; Scaillet, B.

2017-05-01

Volcanic gas emission measurements inform predictions of hazard and atmospheric impacts. For these measurements, Multi-Gas sensors provide low-cost in situ monitoring of gas composition but to date have lacked the ability to detect halogens. Here, two Multi-Gas instruments characterized passive outgassing emissions from Mt. Etna's (Italy) three summit craters, Voragine (VOR), North-east Crater (NEC) and Bocca Nuova (BN) on 2 October 2013. Signal processing (Sensor Response Model, SRM) approaches are used to analyse H2S/SO2 and HCl/SO2 ratios. A new ability to monitor volcanic HCl using miniature electrochemical sensors is here demonstrated. A "direct-exposure" Multi-Gas instrument contained SO2, H2S and HCl sensors, whose sensitivities, cross-sensitivities and response times were characterized by laboratory calibration. SRM analysis of the field data yields H2S/SO2 and HCl/SO2 molar ratios, finding H2S/SO2 = 0.02 (0.01-0.03), with distinct HCl/SO2 for the VOR, NEC and BN crater emissions of 0.41 (0.38-0.43), 0.58 (0.54-0.60) and 0.20 (0.17-0.33). A second Multi-Gas instrument provided CO2/SO2 and H2O/SO2 and enabled cross-comparison of SO2. The Multi-Gas-measured SO2-HCl-H2S-CO2-H2O compositions provide insights into volcanic outgassing. H2S/SO2 ratios indicate gas equilibration at slightly below magmatic temperatures, assuming that the magmatic redox state is preserved. Low SO2/HCl alongside low CO2/SO2 indicates a partially outgassed magma source. We highlight the potential for low-cost HCl sensing of H2S-poor HCl-rich volcanic emissions elsewhere. Further tests are needed for H2S-rich plumes and for long-term monitoring. Our study brings two new advances to volcano hazard monitoring: real-time in situ measurement of HCl and improved Multi-Gas SRM measurements of gas ratios.

New crystals of the CsHSO{sub 4}–CsH{sub 2}PO{sub 4}–H{sub 2}O system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Makarova, I. P., E-mail: makarova@crys.ras.ru; Grebenev, V. V.; Komornikov, V. A.

2016-11-15

Cs{sub 6}H(HSO{sub 4}){sub 3}(H{sub 2}PO{sub 4}){sub 4} crystals, grown for the first time based on an analysis of the phase diagram of the CsHSO{sub 4}–CsH{sub 2}PO{sub 4}–H{sub 2}O ternary system, have been investigated by structural analysis using synchrotron radiation. The atomic structure of the crystals is determined and its specific features are analyzed.

Emission-line diagnostics of nearby H II regions including interacting binary populations

NASA Astrophysics Data System (ADS)

Xiao, Lin; Stanway, Elizabeth R.; Eldridge, J. J.

2018-06-01

We present numerical models of the nebular emission from H II regions around young stellar populations over a range of compositions and ages. The synthetic stellar populations include both single stars and interacting binary stars. We compare these models to the observed emission lines of 254 H II regions of 13 nearby spiral galaxies and 21 dwarf galaxies drawn from archival data. The models are created using the combination of the BPASS (Binary Population and Spectral Synthesis) code with the photoionization code CLOUDY to study the differences caused by the inclusion of interacting binary stars in the stellar population. We obtain agreement with the observed emission line ratios from the nearby star-forming regions and discuss the effect of binary-star evolution pathways on the nebular ionization of H II regions. We find that at population ages above 10 Myr, single-star models rapidly decrease in flux and ionization strength, while binary-star models still produce strong flux and high [O III]/H β ratios. Our models can reproduce the metallicity of H II regions from spiral galaxies, but we find higher metallicities than previously estimated for the H II regions from dwarf galaxies. Comparing the equivalent width of H β emission between models and observations, we find that accounting for ionizing photon leakage can affect age estimates for H II regions. When it is included, the typical age derived for H II regions is 5 Myr from single-star models, and up to 10 Myr with binary-star models. This is due to the existence of binary-star evolution pathways, which produce more hot Wolf-Rayet and helium stars at older ages. For future reference, we calculate new BPASS binary maximal starburst lines as a function of metallicity, and for the total model population, and present these in Appendix A.

Hydrogen sulfide (H 2S) in urban ambient air

NASA Astrophysics Data System (ADS)

Kourtidis, K.; Kelesis, A.; Petrakakis, M.

Despite indications of high hydrogen sulfide levels in some urban environments, only sparse measurements have been reported in the literature. Here we present one full year of hydrogen sulfide measurements in an urban traffic site in the city of Thessaloniki, Greece. In this 1-million-population city the H 2S concentrations were surprisingly high, with a mean annual concentration of 8 μg m -3 and wintertime mean monthly concentrations up to 20 μg m -3 (12.9 ppb). Daily mean concentrations in the winter were up to 30 μg m -3 (19.3 ppb), while hourly concentrations were up to 54 μg m -3 (34.8 ppb). During calm (wind velocity < 0.5 m s -1) conditions, mainly encountered during night-time hours, hourly values of H 2S were highly correlated with those of CO ( r2 = 0.75) and SO 2 ( r2 = 0.70), pointing to a common traffic source from catalytic converters. Annual mean concentrations are above the WHO recommendation for odor annoyance; hence, H 2S might play a role to the malodorous episodes that the city occasionally experiences. The high ambient H 2S levels might also be relevant to the implementation of preservation efforts for outdoor marble and limestone historical monuments that have been targeting SO 2 emissions as an atmospheric acidity source, since the measurements presented here suggest that about 19% of the annual sulfur (SO 2 + H 2S) emissions in Thessaloniki are in the form of H 2S.

Detection of silicate emission features in the 8- to 13-micron spectra of main belt asteroids

NASA Technical Reports Server (NTRS)

Feierberg, M. A.; Witteborn, F. C.; Lebofsky, L. A.

1983-01-01

A presentation is given of 8.0-13.0 micron spectra (Delta lambda/lambda = 0.02-0.03) for six main belt asteroids, which range from 58 to 220 km in diameter and sample the five principal taxonomic classes (C, S, M, R and E). Narrow, well-defined silicate emission features are present on two of the asteroids, the C-type 19 Fortuna and the M-type 21 Lutetia. No comparable emission features are observed on the S-types 11 Parthenope and 14 Irene, the R-type 349 Dembowska or the E-type 64 Angelina.

Laboratory IR Detection of H2O, CO2 in Ion-Irradiated Ices Relevant to Europa

NASA Technical Reports Server (NTRS)

Moore, Marla H.; Hudson, R. L.

1999-01-01

Hydrogen peroxide has been identified on Europa (Carlson et al. 1999) based in part on the 3.50 micron absorption feature observed in Galileo NIMS spectra. The observed feature was fitted with laboratory reflectance spectra of H2O + H2O2. Since condensed phase molecules on Europa (H2O, CO2, SO2, and H2O2) are bombarded with a significant flux of energetic particles (H(+), O(n+), S(n+) and e-), we examined the proton irradiation of H2O at 80 K and the conditions for the IR detection of H2O2 near 3.5 microns. Contrary to expectations, H2O2 was not detected if pure H2O ice was irradiated at 80 K. This was an unexpected result since, H2O2 was detected if pure H2O was irradiated at 18 K. We find, however, that if H2O ice contains either O2 or CO2 then H2O2 is detected after irradiation at 80 K (Moore and Hudson, 1999). The source of O2 for the H2O ice on Europa could come from surface interactions with the tenuous oxygen atmosphere, or from the bombardment of the surface by O(n+).

Fourier transform infrared emission spectra of MnH and MnD

NASA Astrophysics Data System (ADS)

Gordon, Iouli E.; Appadoo, Dominique R. T.; Shayesteh, Alireza; Walker, Kaley A.; Bernath, Peter F.

2005-01-01

Fourier transform infrared emission spectra of MnH and MnD were observed in the ground X7Σ + electronic state. The vibration-rotation bands from v = 1 → 0 to v = 3 → 2 for MnH and from v = 1 → 0 to v = 4 → 3 for MnD were recorded at an instrumental resolution of 0.0085 cm -1. Spectroscopic constants were determined for each vibrational level and equilibrium constants were found from a Dunham-type fit. The equilibrium vibrational constant ( ωe) for MnH was found to be 1546.84518(65) cm -1, the equilibrium rotational constant ( Be) is 5.6856789(103) cm -1 and the eqilibrium bond distance ( re) was determined to be 1.7308601(47) Å.

IUE detection of bursts of H Ly-alpha emission from Saturn

NASA Technical Reports Server (NTRS)

Clarke, J. T.; Moos, H. W.; Atreya, S. K.; Lane, A. L.

1981-01-01

A new investigation is reported of the potential sources of Ly-alpha emission in a series of observations of the Saturnian system carried out between January and July 1980 using the short wavelength spectrograph of the IUE Observatory. It is noted that north-south maps of the Ly-alpha emission across the planet disk show pronounced spatial asymmetries in emission brightness. These asymmetries vary to a marked extent on a time scale of days and are interpreted as bursts of Ly-alpha emission of as much as 1 kR brightness averaged over a 6 x 10 arcsec area, above a constant planetary emission level of 700-800 R. In fact, the Ly-alpha emission peaks manifest themselves as essentially point source features in these data; it is pointed out that if the emitting region is smaller than the 6 x 10 arcsec instrumental resolution, the surface brightness must be proportionally higher.

Raindrop Impact, Disaggregation & CO2 emissions

NASA Astrophysics Data System (ADS)

Gao, Xin; Wang, Rui; Hu, Yaxian; Guo, Shengli

2017-04-01

On the Chinese Loess Plateau, heave storms often occur from July to September, which happens to be fallow season. Without protections from crop coverage, soil surface is completely exposed to rainfalls, receives much more enhanced raindrop impact, thus potentially experience advanced disaggregation. After breaking into smaller fragments, and exposing those previously encapsulated soil organic carbon (SOC), soil surface is very likely to release additional CO2 emissions. However, the possible addition of CO2 emissions from fallow season on the Chinese Loess Plateau, and its potential contribution to local carbon balances, have not yet been systematically investigated. In order to compare the effects of raindrop impacts to CO2 emissions on bare soil during fallow season, two erosion plots (100 cm * 40 cm *35 cm) were set up. Both plots were filled with the loess soil. One plot was covered with two meshes (1 mm * 1mm)overlapping each other, to simulate crop coverage; the other plot was directly exposed to raindrops. Both plots were placed underneath simulated rainfalls (intensity of 90 mm h-1), for 5 min and 10 min. After 24 hours post rainfalls, soil moisture and CO2 emissions from both plots were measured every day for one week. Soil particle size distributions from surface soil were also determined to compare the changes of soil composition. Our results show that raindrop impacted soil in general released more CO2 emissions than the covered soil, and this pattern was more pronounced after experiencing longer period of rainfall events (20.6% more after 5 min; 48.3% more after 10 min). This agreed well with the increase of soil particles < 0.01 mm observed on the raindrop impacted soil surface.

Quantifying global fossil-fuel CO2 emissions: from OCO-2 to optimal observing designs

NASA Astrophysics Data System (ADS)

Ye, X.; Lauvaux, T.; Kort, E. A.; Oda, T.; Feng, S.; Lin, J. C.; Yang, E. G.; Wu, D.; Kuze, A.; Suto, H.; Eldering, A.

2017-12-01

Cities house more than half of the world's population and are responsible for more than 70% of the world anthropogenic CO2 emissions. Therefore, quantifications of emissions from major cities, which are only less than a hundred intense emitting spots across the globe, should allow us to monitor changes in global fossil-fuel CO2 emissions, in an independent, objective way. Satellite platforms provide favorable temporal and spatial coverage to collect urban CO2 data to quantify the anthropogenic contributions to the global carbon budget. We present here the optimal observation design for future NASA's OCO-2 and Japanese GOSAT missions, based on real-data (i.e. OCO-2) experiments and Observing System Simulation Experiments (OSSE's) to address different error components in the urban CO2 budget calculation. We identify the major sources of emission uncertainties for various types of cities with different ecosystems and geographical features, such as urban plumes over flat terrains, accumulated enhancements within basins, and complex weather regimes in coastal areas. Atmospheric transport errors were characterized under various meteorological conditions using the Weather Research and Forecasting (WRF) model at 1-km spatial resolution, coupled to the Open-source Data Inventory for Anthropogenic CO2 (ODIAC) emissions. We propose and discuss the optimized urban sampling strategies to address some difficulties from the seasonality in cloud cover and emissions, vegetation density in and around cities, and address the daytime sampling bias using prescribed diurnal cycles. These factors are combined in pseudo data experiments in which we evaluate the relative impact of uncertainties on inverse estimates of CO2 emissions for cities across latitudinal and climatological zones. We propose here several sampling strategies to minimize the uncertainties in target mode for tracking urban fossil-fuel CO2 emissions over the globe for future satellite missions, such as OCO-3 and future

The Wardle Instability in Interstellar Shocks. 2; Gas Temperture and Line Emission

NASA Technical Reports Server (NTRS)

Neufeld, David A.; Stone, James M.

1997-01-01

We have modeled the gas temperature structure in unstable C-type shocks and obtained predictions for the resultant CO and H2 rotational line emissions, using numerical simulations of the Wardle instability. Our model for the thermal balance of the gas includes ion-neutral frictional heating; compressional heating; radiative cooling due to rotational and ro-vibrational transitions of the molecules CO, H2O, and H2; and gas-grain collisional cooling. We obtained results for the gas temperature distribution in-and H2 and CO line emission from-shocks of neutral Alfvenic Mach number 10 and velocity 20 or 40 km/ s in which the Wardle instability has saturated. Both two- and three-dimensional simulations were carried out for shocks in which the preshock magnetic field is perpendicular to the shock propagation direction, and a two-dimensional simulation was carried out for the case in which the magnetic field is obliquely oriented with respect to the shock propagation direction. Although the Wardle instability profoundly affects the density structure behind C-type shocks, most of the shock-excited molecular line emission is generated upstream of the region where the strongest effects of the instability are felt. Thus the Wardle instability has a relatively small effect on the overall gas temperature distribution in-and the emission-line spectrum from-C-type shocks, at least for the cases that we have considered. In none of the cases that we have considered thus far did any of the predicted emission-line luminosities change by more than a factor of 2.5, and in most cases the effects of instability were significantly smaller than that. Slightly larger changes in the line luminosities seem likely for three-dimensional simulations of oblique shocks, although such simulations have yet to be carried out and lie beyond the scope of this study. Given the typical uncertainties that are always present when model predictions are compared with real astronomical data, we conclude that

Can the bump in the composite spectrum of GRB 910503 be an emission line feature of gamma-ray bursts?

NASA Astrophysics Data System (ADS)

Qin, Yi-Ping; Zhang, Fu-Wen

2005-12-01

Appearing in the composite spectral data of BATSE, EGRET and COMPTEL for GRB 910503, there is a bump at around 1600 keV. We perform a statistical analysis on the spectral data, trying to find out if the bump could be accounted for by a blue-shifted and significantly broadened rest frame line due to the Doppler effect of an expanding fireball surface. We made an F-test and adopted previously proposed criteria. The study reveals that the criteria are well satisfied and the feature can be interpreted as the blue shifted 6.4 keV line. From the fit with this line taken into account, we find the Lorentz factor of this source to be Γ = 116+9-9 (at the 68% confident level, triangleχ2 = 1) and the rest frame spectral peak energy to be E0,p = 2.96+0.24-0.18 keV. Although the existence of the emission line feature requires other independent tests to confirm, the analysis suggests that it is feasible to detect emission line features in the high energy range of GRB spectra when taking into account the Doppler effect of fireball expansion.

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

PubMed

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

2013-12-15

The impact of ambient concentrations in the vicinity of a plant can only be assessed if the emission rate is known. In this study, based on measurements of ambient H2S concentrations and meteorological parameters, the a priori unknown emission rates of a tannery wastewater treatment plant are calculated by an inverse dispersion technique. The calculations are determined using the Gaussian Austrian regulatory dispersion model. Following this method, emission data can be obtained, though only for a measurement station that is positioned such that the wind direction at the measurement station is leeward of the plant. Using the inverse transform sampling, which is a Monte Carlo technique, the dataset can also be completed for those wind directions for which no ambient concentration measurements are available. For the model validation, the measured ambient concentrations are compared with the calculated ambient concentrations obtained from the synthetic emission data of the Monte Carlo model. The cumulative frequency distribution of this new dataset agrees well with the empirical data. This inverse transform sampling method is thus a useful supplement for calculating emission rates using the inverse dispersion technique. Copyright © 2013 Elsevier B.V. All rights reserved.

Low-Lying Energy Isomers and Global Minima of Aqueous Nanoclusters: Structures and Spectroscopic Features of the Pentagonal Dodecahedron (H2O)20 and (H3O)+(H2O)20

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xantheas, Sotiris S.

We rely on a hierarchy of methods to identify the low-lying isomers for the pentagonal dodecahedron (H2O)20 and the H3O+(H2O)20 clusters. Initial screening of isomers was performed with classical potentials [TIP4P, TTM2-F, TTM2.1-F for (H2O)20 and ASP for H3O+(H2O)20] and the networks obtained with those potentials were subsequently reoptimized at the DFT (B3LYP) and MP2 levels of theory. For the pentagonal dodecahedron (H2O)20 it was found that DFT (B3LYP) and MP2 produced the same global minimum. However, this was not the case for the H3O+(H2O)20 cluster, for which MP2 produced a different network for the global minimum when compared tomore » DFT (B3LYP). All low-lying minima of H3O+(H2O)20 correspond to hydrogen bonding networks having 9 ''free'' OH bonds and the hydronium ion on the surface of the cluster. The fact that DFT (B3LYP) and MP2 produce different results and issues related to the use of a smaller basis set, explains the discrepancy between the current results and the structure previously suggested [Science 304, 1137 (2004)] for the global minimum of the H3O+(H2O)20 cluster. Additionally, the IR spectra of the MP2 global minimum are closer to the experimentally measured ones than the spectra of the previously suggested DFT global minimum. The latter exhibit additional bands in the most red-shifted region of the OH stretching vibrations (corresponding to the ''fingerprint'' of the underlying hydrogen bonding network), which are absent from both the experimental as well as the spectra of the new structure suggested for the global minimum of this cluster.« less

Exploring the engines of molecular outflows. Radio continuum and H_2_O maser observations.

NASA Astrophysics Data System (ADS)

Tofani, G.; Felli, M.; Taylor, G. B.; Hunter, T. R.

1995-09-01

We present A-configuration VLA observations of the 22GHz H_2_O maser line and 8.4GHz continuum emission of 22 selected CO bipolar outflows associated with water masers. These observations allow us to study the region within 10^4^AU of the engine powering the outflow. The positions of the maser spots are compared with those of ultra-compact (UC) continuum sources found in our observations, with IRAS data and with data from the literature on the molecular outflows. Weak unresolved continuum sources are found in several cases associated with the maser. Most probably they represent the ionized envelope surrounding the young stellar object (YSO) which powers the maser and the outflow. These weak radio continuum sources are not necessarily associated with the IRAS sources, which are more representative of the global emission from the star forming region. A comparison of the velocity pattern of the CO outflow with those of the maser spots detected with the VLA is also made. Asymmetries in the H_2_O velocities are found on opposite sides of the YSO, suggesting that the outflow acceleration begins from the YSO itself. In a few cases we find evidence for two outflows in different evolutionary stages. The H_2_O masers in these sources are always found at the centre of the younger outflow. The degree of variability of each maser is derived from single dish observations obtained with the Medicina radiotelescope before and after the VLA observations. Velocity drifts of some features are interpreted as acceleration of the maser.

H2@Scale Resource and Market Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruth, Mark

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

An experimental study on premixed CNG/H2/CO2 mixture flames

NASA Astrophysics Data System (ADS)

Yilmaz, Ilker; Yilmaz, Harun; Cam, Omer

2018-03-01

In this study, the effect of swirl number, gas composition and CO2 dilution on combustion and emission behaviour of CNG/H2/CO2 gas mixtures was experimentally investigated in a laboratory scale combustor. Irrespective of the gas composition, thermal power of the combustor was kept constant (5 kW). All experiments were conducted at or near stoichiometric and the local atmospheric conditions of the city of Kayseri, Turkey. During experiments, swirl number was varied and the combustion performance of this combustor was analysed by means of centreline temperature distributions. On the other hand, emission behaviour was examined with respect to emitted CO, CO2 and NOx levels. Dynamic flame behaviour was also evaluated by analysing instantaneous flame images. Results of this study revealed the great impact of swirl number and gas composition on combustion and emission behaviour of studied flames.

Heterodyne detection of CO2 emission lines and wind velocities in the atmosphere of Venus

NASA Technical Reports Server (NTRS)

Betz, A. L.; Johnson, M. A.; Mclaren, R. A.; Sutton, E. C.

1975-01-01

Strong 10 micrometer line emission from (c-12)(o-16)2 in the upper atmosphere of Venus was detected by heterodyne techniques. Observations of the absolute Doppler shift of the emission features indicate mean zonal wind velocities less than 10 m/sec in the upper atmosphere near the equator. No evidence was found of the 100 m/sec wind velocity implied by the apparent 4-day rotation period of ultraviolet cloud features.

Stability of field emission current from porous n-GaAs(110)

NASA Astrophysics Data System (ADS)

Tondare, V. N.; Naddaf, M.; Bhise, A. B.; Bhoraskar, S. V.; Joag, D. S.; Mandale, A. B.; Sainkar, S. R.

2002-02-01

Field electron emission from porous GaAs has been investigated. The emitter was prepared by anodic etching of n-GaAs (110) in 0.1 M HCl solution. The as-etched porous GaAs shows nonlinear Fowler-Nordheim (FN) characteristics, with a low onset voltage. The emitter, after operating for 6 h at the residual gas pressure of 1×10-8 mbar, shows a linear FN characteristics with a relatively high onset voltage and poor field emission current stability as compared to the as-etched emitter. The change in the behavior was attributed to the residual gas ion bombardment during field electron emission. X-ray photoelectron spectroscopic investigations were carried out on as-etched sample and the one which was studied for field emission. The studies indicate that the as-etched surface contains As2O3 and the surface after field electron emission for about 6 h becomes gallium rich. The presence of As2O3 seems to be a desirable feature for the stable field emission current.

Environmental Impact of H2 from Hydrogen Fuel Cell on the Stratosphere

NASA Astrophysics Data System (ADS)

Tromp, T. K.

2002-12-01

Hydrogen fuel cell technology seems poised to replace the internal combustion engine in the upcoming decade. Environmentalists tout the technology as environmentally friendly and stress its low tailpipe emissions resulting in cleaner urban air. At face value the technology should have a negligible impact because the major byproduct is water. What has not been considered is that it will take billions of liters of H2 to power the future national (and international) fleet of fuel-cell vehicles and that the leading contenders to make that H2 are the very fossil fuels that cause smog and greenhouse gases. If that does happen, there will be two important consequences. First, the current fossil fuel pollutants will not disappear, rather they will be shifted from tailpipe sources to where the fossil fuels are extracted and the hydrogen is made. In addition, the fuel to make the cells work, H2, is an important trace constituent (~0.5 ppmv) of the atmosphere [Novelli et al., 1999] and participates in reactions involving pollutants and greenhouse gases [Crutzen, 1977]. Thus, anthropogenic H2 emissions could have significant indirect environmental consequences. The global annual H2 production from current sources, anthropogenic plus natural, could be doubled in coming decades with the development of a hydrogen fuel economy [Zittel, 1996]. Such an increase could significantly impact the hydrogen cycle and other cycles with which it interacts in both the atmosphere and biosphere. We have examined the potential environmental impact of additional H2 release for several emission scenarios. We calculated the ODP of H2. Given that the oxidation of H2 is an important source of water vapor in the stratosphere, which is otherwise isolated from direct sources of H2O by the `cold trap' at the tropopause. We calculated what kind of elevated concentrations of stratospheric water vapor could occur for the different emission scenarios. Not only will additional water vapor cool the

Suggestion for search of cyclopropenone (c-C3H2O) in a cosmic object

NASA Astrophysics Data System (ADS)

Sharma, M. K.; Sharma, M.; Chandra, S.

2017-03-01

Following Minimum Energy Principle, out of the three isomers of chemical formula C3H2O, the cyclopropenone (c-C3H2O) is the most stable and therefore may be the most abundant and easily detectable in a cosmic object. The cyclopropenone is detected in Sgr B2(N). Owing to half-spin of each of two hydrogen atoms, the c-C3H2O has two distinct ortho and para species. Using the rotational and centrifugal distortion constants along with the electric dipole moment, we have calculated energies of 100 rotational levels of each of the ortho and para species of c-C3H2O and the Einstein A-coefficients for radiative transitions between the levels. The values of Einstein A-coefficients along with the scaled values for collisional rate coefficients are used for solving a set of statistical equilibrium equations coupled with the equations of radiative transfer. Brightness temperatures of seven rotational transitions of each of the ortho and para species of c-C3H2O are investigated. Out of fourteen transitions, seven are found to show anomalous absorption and rest seven are found to show emission feature. We find that the transitions 110 -111 (1.544 GHz) may play important role in identification of cyclopropenone in a cosmic object.