An experimental approach aiming the production of a gas mixture composed of hydrogen and methane from biomass as natural gas substitute in industrial applications.

PubMed

Kraussler, Michael; Schindler, Philipp; Hofbauer, Hermann

2017-08-01

This work presents an experimental approach aiming the production of a gas mixture composed of H 2 and CH 4 , which should serve as natural gas substitute in industrial applications. Therefore, a lab-scale process chain employing a water gas shift unit, scrubbing units, and a pressure swing adsorption unit was operated with tar-rich product gas extracted from a commercial dual fluidized bed biomass steam gasification plant. A gas mixture with a volumetric fraction of about 80% H 2 and 19% CH 4 and with minor fractions of CO and CO 2 was produced by employing carbon molecular sieve as adsorbent. Moreover, the produced gas mixture had a lower heating value of about 15.5MJ·m -3 and a lower Wobbe index of about 43.4MJ·m -3 , which is similar to the typical Wobbe index of natural gas. Copyright © 2017 Elsevier Ltd. All rights reserved.

Silicon photonic dual-gas sensor for H2 and CO2 detection.

PubMed

Mi, Guangcan; Horvath, Cameron; Van, Vien

2017-07-10

We report a silicon photonic dual-gas sensor based on a wavelength-multiplexed microring resonator array for simultaneous detection of H 2 and CO 2 gases. The sensor uses Pd as the sensing layer for H 2 gas and a novel functional material based on the Polyhexamethylene Biguanide (PHMB) polymer for CO 2 gas sensing. Gas sensing experiments showed that the PHMB-functionalized microring exhibited high sensitivity to CO 2 gas and excellent selectivity against H 2 . However, the Pd-functionalized microring was found to exhibit sensitivity to both H 2 and CO 2 gases, rendering it ineffective for detecting H 2 in a gas mixture containing CO 2 . We show that the dual-gas sensing scheme can allow for accurate measurement of H 2 concentration in the presence of CO 2 by accounting for the cross-sensitivity of Pd to the latter.

Continuous online Fourier transform infrared (FT-IR) spectrometry analysis of hydrogen chloride (HCl), carbon dioxide (CO2), and water (H2O) in nitrogen-rich and ethylene-rich streams.

PubMed

Stephenson, Serena; Pollard, Maria; Boit, Kipchirchir

2013-09-01

The prevalence of optical spectroscopy techniques being applied to the online analysis of continuous processes has increased in the past couple of decades. The ability to continuously "watch" changing stream compositions as operating conditions change has proven invaluable to pilot and world-scale manufacturing in the chemical and petrochemical industries. Presented here is an application requiring continuous monitoring of parts per million (ppm) by weight levels of hydrogen chloride (HCl), water (H2O), and carbon dioxide (CO2) in two gas-phase streams, one nitrogen-rich and one ethylene-rich. Because ethylene has strong mid-infrared (IR) absorption, building an IR method capable of quantifying HCl, H2O, and CO2 posed some challenges. A long-path (5.11m) Fourier transform infrared (FT-IR) spectrometer was used in the mid-infrared region between 1800 and 5000 cm(-1), with a 1 cm(-1) resolution and a 10 s spectral update time. Sample cell temperature and pressure were controlled and measured to minimize measurement variability. Models using a modified classical least squares method were developed and validated first in the laboratory and then using the process stream. Analytical models and process sampling conditions were adjusted to minimize interference of ethylene in the ethylene-rich stream. The predictive capabilities of the measurements were ±0.5 ppm for CO2 in either stream; ±1.1 and ±1.3 ppm for H2O in the nitrogen-rich and ethylene-rich streams, respectively; and ±1.0 and ±2.4 ppm for HCl in the nitrogen-rich and ethylene-rich streams, respectively. Continuous operation of the instrument in the process stream was demonstrated using an automated stream switching sample system set to 10 min intervals. Response time for all components of interest was sufficient to acquire representative stream composition data. This setup provides useful insight into the process for troubleshooting and optimizing plant operating conditions.

Noble-gas-rich separates from ordinary chondrites

NASA Astrophysics Data System (ADS)

Moniot, R. K.

1980-02-01

Acid-resistant residues were prepared by HCl-HF demineralization of three H-type ordinary chondrites: Brownfield 1937 (H3), Dimmitt (H3, 4), and Estacado (H6). These residues were found to contain a large proportion of the planetary-type trapped Ar, Kr, and Xe in the meteorites. The similarity of these acid residues to those from carbonaceous chondrites and LL-type ordinary chondrites suggests that the same phase carries the trapped noble gases in all these diverse meteorite types. Because the H group represents a large fraction of all meteorites, this result indicates that the gas-rich carrier phase is as universal as the trapped noble-gas component itself. When treated with an oxidizing etchant, the acid residues lost almost all their complement of noble gases.

Microbial Reverse-Electrodialysis Electrolysis and Chemical-Production Cell for H2 Production and CO2 Sequestration.

PubMed

Zhu, Xiuping; Hatzell, Marta C; Logan, Bruce E

2014-04-08

Natural mineral carbonation can be accelerated using acid and alkali solutions to enhance atmospheric CO 2 sequestration, but the production of these solutions needs to be carbon-neutral. A microbial reverse-electrodialysis electrolysis and chemical-production cell (MRECC) was developed to produce these solutions and H 2 gas using only renewable energy sources (organic matter and salinity gradient). Using acetate (0.82 g/L) as a fuel for microorganisms to generate electricity in the anode chamber (liquid volume of 28 mL), 0.45 mmol of acid and 1.09 mmol of alkali were produced at production efficiencies of 35% and 86%, respectively, along with 10 mL of H 2 gas. Serpentine dissolution was enhanced 17-87-fold using the acid solution, with approximately 9 mL of CO 2 absorbed and 4 mg of CO 2 fixed as magnesium or calcium carbonates. The operational costs, based on mineral digging and grinding, and water pumping, were estimated to be only $25/metric ton of CO 2 fixed as insoluble carbonates. Considering the additional economic benefits of H 2 generation and possible wastewater treatment, this method may be a cost-effective and environmentally friendly method for CO 2 sequestration.

New places and phases of CO-poor/CI-rich molecular gas in the Universe

NASA Astrophysics Data System (ADS)

Papadopoulos, Padelis P.; Bisbas, Thomas G.; Zhang, Zhiyu

2018-04-01

In this work we extend the work on the recently discovered role of Cosmic Rays (CRs) in regulating the average CO/H_2 abundance ratio in molecular clouds (and thus their CO line visibility) in starburst galaxies, and find that it can lead to a CO-poor/CI-rich H_2 gas phase even in environments with Galactic or in only modestly enhanced CR backgrounds expected in ordinary star-forming galaxies. Furthermore, the same CR-driven astro-chemistry raises the possibility of a widespread phase transition of molecular gas towards a CO-poor/CI-rich phase in: a) molecular gas outflows found in star-forming galaxies, b) active galactic nuclei (AGNs), and c) near synchrotron-emitting radio jets and the radio-loud cores of powerful radio galaxies. For main sequence galaxies we find that CRs can render some of their molecular gas mass CO-invisible, compounding the effects of low metallicities. Imaging the two fine structure lines of atomic carbon with resolution high enough to search beyond the CI/CO-bright line regions associated with central starbursts can reveal such a CO-poor/CI-rich molecular gas phase, provided that relative brightness sensitivity levels of Tb(CI 1 - 0)/Tb(CO J = 1 - 0) ˜0.15 are reached. The capability to search for such gas in the Galaxy is now at hand with the new high-frequency survey telescope HEAT deployed in Antarctica and future ones to be deployed in Dome A. ALMA can search for such gas in star-forming spiral disks, galactic molecular gas outflows and the CR-intense galactic and circumgalactic gas-rich environments of radio-loud objects.

Gas-rich dwarfs and accretion phenomena in early-type galaxies

NASA Technical Reports Server (NTRS)

Silk, J.; Norman, C.

1979-01-01

An analysis is presented of the combined effects of cloud accretion and galactic winds and coronae. An accretion model is developed wherein gas-rich dwarf galaxies are accreted into galactic halos, which provides an adequate source of H I to account for observations of neutral gas in early-type galaxies. Accretion is found to fuel the wind, thereby regulating the accretion flow and yielding a time-dependent model for star formation, enrichment, and nuclear activity. The permissible parameter range for intergalactic gas clouds and galaxy groups is discussed, along with the frequency of gas-rich dwarfs and their large ratios of gas mass to luminosity. Also considered is the occurrence of gas stripping and the consequent formation of dwarf spheroidal systems that remain in the halo, and gas clouds that dissipate and suffer further infall. A cosmological implication of the model is that, because the characteristic time scale of a gas-rich dwarf galaxy to be accreted and lose its gas is comparable to a Hubble time, there may have been a far more extensive primordial distribution of such systems at earlier epochs.

Possible sources of H2 to H2O enrichment at evaporation of parent chondritic material

NASA Technical Reports Server (NTRS)

Makalkin, A. B.; Dorofeyeva, V. A.; Vityazev, A. V.

1993-01-01

One of the results obtained from thermodynamic simulation of recondensation of the source chondritic material is that at 1500-1800 K it's possible to form iron-rich olivine by reaction between enstatite, metallic iron and water vapor in the case of (H2O)/(H2) approximately equal to 0.1. This could be reached if the gas depletion in hydrogen is 200-300 times relative to solar abundance. To get this range of depletion one needs some source material more rich in hydrogen than the carbonaceous CI material which is the richest in volatiles among chondrites. In the case of recondensation at impact heating and evaporation of colliding planetesimals composed of CI material, we obtain insufficiently high value of (H2)/(H2O) ratio. In the present paper we consider some possible source materials and physical conditions necessary to reach gas composition with (H2)/(H2O) approximately 10 at high temperature.

Experimental evidence for non-redox transformations between magnetite and hematite under H 2-rich hydrothermal conditions

NASA Astrophysics Data System (ADS)

Otake, Tsubasa; Wesolowski, David J.; Anovitz, Lawrence M.; Allard, Lawrence F.; Ohmoto, Hiroshi

2007-05-01

Transformations of magnetite (Fe IIFe 2IIIO 4) to hematite (Fe 2IIIO 3) (and vice versa) have been thought by many scientists and engineers to require molecular O 2 and/or H 2. Thus, the presence of magnetite and/or hematite in rocks has been linked to a specific oxidation environment. However, the availability of reductants or oxidants in many geologic and industrial environments appears to have been too low to account for the transformations of iron oxides through redox reactions. Here, we report the results of hydrothermal experiments in mildly acidic and H 2-rich aqueous solutions at 150 °C, which demonstrate that transformations of magnetite to hematite, and hematite to magnetite, occur rapidly without involving molecular O 2 or H 2: Fe3O 4(Mt) + 2H (aq)+ ↔ Fe 2O 3(Hm) + Fe (aq)2+ + H 2O. The transformation products are chemically and structurally homogeneous, and typically occur as euhedral single crystals much larger than the precursor minerals. This suggests that, in addition to the expected release of aqueous ferrous species to solution, the transformations involve release of aqueous ferric species from the precursor oxides to the solution, which reprecipitate without being reduced by H 2. These redox-independent transformations may have been responsible for the formation of some iron oxides in natural systems, such as high-grade hematite ores that developed from Banded Iron Formations (BIFs), hematite-rich deposits formed on Mars, corrosion products in power plants and other industrial systems.

Safety considerations in testing a fuel-rich aeropropulsion gas generator

NASA Technical Reports Server (NTRS)

Rollbuhler, R. James; Hulligan, David D.

1991-01-01

A catalyst containing reactor is being tested using a fuel-rich mixture of Jet A fuel and hot input air. The reactor product is a gaseous fuel that can be utilized in aeropropulsion gas turbine engines. Because the catalyst material is susceptible to damage from high temperature conditions, fuel-rich operating conditions are attained by introducing the fuel first into an inert gas stream in the reactor and then displacing the inert gas with reaction air. Once a desired fuel-to-air ratio is attained, only limited time is allowed for a catalyst induced reaction to occur; otherwise the inert gas is substituted for the air and the fuel flow is terminated. Because there presently is not a gas turbine combustor in which to burn the reactor product gas, the gas is combusted at the outlet of the test facility flare stack. This technique in operations has worked successfully in over 200 tests.

Hydrogen Storage Properties of New Hydrogen-Rich BH3NH3-Metal Hydride (TiH2, ZrH2, MgH2, and/or CaH2) Composite Systems

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

Choi, Young Joon; Xu, Yimin; Shaw, Wendy J.

2012-04-19

Ammonia borane (AB = NH3BH3) is one of the most attractive materials for chemical hydrogen storage due to its high hydrogen contents of 19.6 wt.%, however, impurity levels of borazine, ammonia and diborane in conjunction with foaming and exothermic hydrogen release calls for finding ways to mitigate the decomposition reactions. In this paper we present a solution by mixing AB with metal hydrides (TiH2, ZrH2, MgH2 and CaH2) which have endothermic hydrogen release in order to control the heat release and impurity levels from AB upon decomposition. The composite materials were prepared by mechanical ball milling, and their H2 releasemore » properties were characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The formation of volatile products from decomposition side reactions, such as borazine (N3B3H6) was determined by mass spectrometry (MS). Sieverts type pressure-composition-temperature (PCT) gas-solid reaction instrument was adopted to observe the kinetics of the H2 release reactions of the combined systems and neat AB. In situ 11B MAS-NMR revealed a destabilized decomposition pathway. We found that by adding specific metal hydrides to AB we can eliminate the impurities and mitigate the heat release.« less

Particle Generation And Evolution In Silane (SiH4)/Acetylene (C2H2) Flames In Microgravity

NASA Technical Reports Server (NTRS)

Keil, D. G.

2003-01-01

The objective of this experimental program is to advance the understanding of the coupling of particle formation with gas phase combustion processes. The work utilizes the unique SiH4/C2H2 combustion system which generates particulate products ranging from high purity, white SiC to carbonaceous soot depending on equivalence ratio (Ref. 1). A goal of this work is to identify gas phase or particle formation processes that provide the enthalpy release needed to drive the combustion wave, and to locate the steps of the particle formation process that determine SiC stoichiometry and crystallinity. In a real sense, these SiH4/C2H2 flames act like highly sooty hydrocarbon flames, but with simpler chemistry. This simplification is expected to allow them to be used as surrogates to advance understanding of soot formation in such rich hydrocarbon flames. It is also expected that this improved understanding of SiC particle generation and evolution in these self-sustaining flames will advance the commercial potential of the flame process for the generation of high purity SiC powders.

H2-rich fluids from serpentinization: Geochemical and biotic implications

PubMed Central

Sleep, N. H.; Meibom, A.; Fridriksson, Th.; Coleman, R. G.; Bird, D. K.

2004-01-01

Metamorphic hydration and oxidation of ultramafic rocks produces serpentinites, composed of serpentine group minerals and varying amounts of brucite, magnetite, and/or FeNi alloys. These minerals buffer metamorphic fluids to extremely reducing conditions that are capable of producing hydrogen gas. Awaruite, FeNi3, forms early in this process when the serpentinite minerals are Fe-rich. Olivine with the current mantle Fe/Mg ratio was oxidized during serpentinization after the Moon-forming impact. This process formed some of the ferric iron in the Earth's mantle. For the rest of Earth's history, serpentinites covered only a small fraction of the Earth's surface but were an important prebiotic and biotic environment. Extant methanogens react H2 with CO2 to form methane. This is a likely habitable environment on large silicate planets. The catalytic properties of FeNi3 allow complex organic compounds to form within serpentinite and, when mixed with atmospherically produced complex organic matter and waters that circulated through basalts, constitutes an attractive prebiotic substrate. Conversely, inorganic catalysis of methane by FeNi3 competes with nascent and extant life. PMID:15326313

Exploring the plasma chemistry in microwave chemical vapor deposition of diamond from C/H/O gas mixtures.

PubMed

Kelly, Mark W; Richley, James C; Western, Colin M; Ashfold, Michael N R; Mankelevich, Yuri A

2012-09-27

Microwave (MW)-activated CH(4)/CO(2)/H(2) gas mixtures operating under conditions relevant to diamond chemical vapor deposition (i.e., X(C/Σ) = X(elem)(C)/(X(elem)(C) + X(elem)(O)) ≈ 0.5, H(2) mole fraction = 0.3, pressure, p = 150 Torr, and input power, P = 1 kW) have been explored in detail by a combination of spatially resolved absorption measurements (of CH, C(2)(a), and OH radicals and H(n = 2) atoms) within the hot plasma region and companion 2-dimensional modeling of the plasma. CO and H(2) are identified as the dominant species in the plasma core. The lower thermal conductivity of such a mixture (cf. the H(2)-rich plasmas used in most diamond chemical vapor deposition) accounts for the finding that CH(4)/CO(2)/H(2) plasmas can yield similar maximal gas temperatures and diamond growth rates at lower input powers than traditional CH(4)/H(2) plasmas. The plasma chemistry and composition is seen to switch upon changing from oxygen-rich (X(C/Σ) < 0.5) to carbon-rich (X(C/Σ) > 0.5) source gas mixtures and, by comparing CH(4)/CO(2)/H(2) (X(C/Σ) = 0.5) and CO/H(2) plasmas, to be sensitive to the choice of source gas (by virtue of the different prevailing gas activation mechanisms), in contrast to C/H process gas mixtures. CH(3) radicals are identified as the most abundant C(1)H(x) [x = 0-3] species near the growing diamond surface within the process window for successful diamond growth (X(C/Σ) ≈ 0.5-0.54) identified by Bachmann et al. (Diamond Relat. Mater.1991, 1, 1). This, and the findings of similar maximal gas temperatures (T(gas) ~2800-3000 K) and H atom mole fractions (X(H)~5-10%) to those found in MW-activated C/H plasmas, points to the prevalence of similar CH(3) radical based diamond growth mechanisms in both C/H and C/H/O plasmas.

Hydrogen rich gas generator

NASA Technical Reports Server (NTRS)

Houseman, J.; Rupe, J. H.; Kushida, R. O. (Inventor)

1976-01-01

A process and apparatus is described for producing a hydrogen rich gas by injecting air and hydrocarbon fuel at one end of a cylindrically shaped chamber to form a mixture and igniting the mixture to provide hot combustion gases by partial oxidation of the hydrocarbon fuel. The combustion gases move away from the ignition region to another region where water is injected to be turned into steam by the hot combustion gases. The steam which is formed mixes with the hot gases to yield a uniform hot gas whereby a steam reforming reaction with the hydrocarbon fuel takes place to produce a hydrogen rich gas.

Discovery of an H I-rich Gas Reservoir in the Outskirts of SZ-effect-selected Clusters

NASA Astrophysics Data System (ADS)

Muzahid, Sowgat; Charlton, Jane; Nagai, Daisuke; Schaye, Joop; Srianand, Raghunathan

2017-09-01

We report on the detection of three strong H I absorbers originating in the outskirts (I.e., impact parameter, {ρ }{cl} ≈ (1.6-4.7)r 500) of three massive ({M}500˜ 3× {10}14 M ⊙) clusters of galaxies at redshift {z}{cl}≈ 0.46, in the Hubble Space Telescope Cosmic Origins Spectrograph (HST/COS) spectra of three background UV-bright quasars. These clusters were discovered by the 2500 deg2 South Pole Telescope Sunyaev-Zel’dovich (SZ) effect survey. All three COS spectra show a partial Lyman limit absorber with N(H I) > 1016.5 cm-2 near the photometric redshifts (| {{Δ }}z/(1+z)| ≈ 0.03) of the clusters. The compound probability of the random occurrence of all three absorbers is <0.02%, indicating that the absorbers are most likely related to the targeted clusters. We find that the outskirts of these SZ-selected clusters are remarkably rich in cool gas compared to existing observations of other clusters in the literature. The effective Doppler parameters of the Lyman series lines, obtained using a single-cloud curve-of-growth (COG) analysis, suggest a nonthermal/turbulent velocity of a few×10 km s-1 in the absorbing gas. We emphasize the need for uniform galaxy surveys around these fields and for more UV observations of quasar-cluster pairs in general in order to improve the statistics and gain further insights into the unexplored territory of the largest collapsed cosmic structures.

Peridote-water interaction generating migration pathways of H2-rich fluids in subduction context: Common processes in the ophiolites of Oman, New-Caledonia, Philippines and Turkey

NASA Astrophysics Data System (ADS)

Deville, E. P.; Prinzhofer, A.; Pillot, D.; Vacquand, C.; Sissmann, O.

2010-12-01

The occurrence of H2 flows which were punctually known notably in the ophiolites of Oman, Zambales (Philippines) and Antalya (Turkey) appears to be a widespread phenomenon in these major peridotite massifs associated with ancient or active subduction processes. Similar H2-rich gas flows have been discovered also in the peridotite of New-Caledonia. H2 concentrations are locally high (commonly 60 to90% in Oman). H2 is frequently degassing in hyperalkaline springs but the highest flows were found directly expelled from fractures in the peridotites. Obviously, within the fracture systems, gas and associated hyperalkaline water separate at shallow depth close to the top of the upper aquifer level. Locally high flows of gas migrate vertically in the fractures, whereas water with degassing H2 tends to migrate laterally in the fracture network toward the creeks where most of the hyperalkaline springs are found. The genesis of natural H2 is interpreted as the result of the interaction, at depth, between ultrabasic mantle rocks in the upper plate and water expelled by the subducted sediments by oxidation of metals (Fe2+, Mn2+) and reduction of water during serpentinisation. CH4 is commonly associated to the H2-rich fluids and it is interpreted as the result of the reduction of available CO2 at depth. N2 is also commonly associated to the H2-rich fluids in the ophiolites, whereas N2 flows (within H2) were found in the subducted sediments (below the sole décollement of the peridotite) where it can be observed (Oman and New-Caledonia). Within the peridotites, the hyperalkaline water is rich in ions OH- and Ca2+ and characterized by high pH (between 11 and 12). Most alkaline springs are found in the vicinity of major faults and/or lithological discontinuities like the basal décollement of the ophiolites and the peridotite-gabbro contact (Moho). This hyperalkaline water migration induces a chain of diagenetic reactions starting at depth within the fracture systems by the

H2-rich fluids from serpentinization: geochemical and biotic implications.

PubMed

Sleep, N H; Meibom, A; Fridriksson, Th; Coleman, R G; Bird, D K

2004-08-31

Metamorphic hydration and oxidation of ultramafic rocks produces serpentinites, composed of serpentine group minerals and varying amounts of brucite, magnetite, and/or FeNi alloys. These minerals buffer metamorphic fluids to extremely reducing conditions that are capable of producing hydrogen gas. Awaruite, FeNi3, forms early in this process when the serpentinite minerals are Fe-rich. Olivine with the current mantle Fe/Mg ratio was oxidized during serpentinization after the Moon-forming impact. This process formed some of the ferric iron in the Earth's mantle. For the rest of Earth's history, serpentinites covered only a small fraction of the Earth's surface but were an important prebiotic and biotic environment. Extant methanogens react H2 with CO2 to form methane. This is a likely habitable environment on large silicate planets. The catalytic properties of FeNi3 allow complex organic compounds to form within serpentinite and, when mixed with atmospherically produced complex organic matter and waters that circulated through basalts, constitutes an attractive prebiotic substrate. Conversely, inorganic catalysis of methane by FeNi3 competes with nascent and extant life. Copyright 2004 The National Academy of Sciencs of the USA

Quantitative Analysis of Spectral Interference of Spontaneous Raman Scattering in High-Pressure Fuel-Rich H2-Air Combustion

NASA Technical Reports Server (NTRS)

Kojima, Jun; Nguyen, Quang-Viet

2004-01-01

We present a theoretical study of the spectral interferences in the spontaneous Raman scattering spectra of major combustion products in 30-atm fuel-rich hydrogen-air flames. An effective methodology is introduced to choose an appropriate line-shape model for simulating Raman spectra in high-pressure combustion environments. The Voigt profile with the additive approximation assumption was found to provide a reasonable model of the spectral line shape for the present analysis. The rotational/vibrational Raman spectra of H2, N2, and H2O were calculated using an anharmonic-oscillator model using the latest collisional broadening coefficients. The calculated spectra were validated with data obtained in a 10-atm fuel-rich H2-air flame and showed excellent agreement. Our quantitative spectral analysis for equivalence ratios ranging from 1.5 to 5.0 revealed substantial amounts of spectral cross-talk between the rotational H2 lines and the N2 O-/Q-branch; and between the vibrational H2O(0,3) line and the vibrational H2O spectrum. We also address the temperature dependence of the spectral cross-talk and extend our analysis to include a cross-talk compensation technique that removes the nterference arising from the H2 Raman spectra onto the N2, or H2O spectra.

Supersaturation of dissolved H(2) and CO (2) during fermentative hydrogen production with N(2) sparging.

PubMed

Kraemer, Jeremy T; Bagley, David M

2006-09-01

Dissolved H(2) and CO(2) were measured by an improved manual headspace-gas chromatographic method during fermentative H(2) production with N(2) sparging. Sparging increased the yield from 1.3 to 1.8 mol H(2)/mol glucose converted, although H(2) and CO(2) were still supersaturated regardless of sparging. The common assumption that sparging increases the H(2) yield because of lower dissolved H(2) concentrations may be incorrect, because H(2) was not lowered into the range necessary to affect the relevant enzymes. More likely, N(2) sparging decreased the rate of H(2) consumption via lower substrate concentrations.

Hydrogen production from food wastes and gas post-treatment by CO{sub 2} adsorption

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

Redondas, V.; Gomez, X., E-mail: xagomb@unileon.es; Garcia, S.

2012-01-15

Highlights: Black-Right-Pointing-Pointer The dark fermentation process of food wastes was studied over an extended period. Black-Right-Pointing-Pointer Decreasing the HRT of the process negatively affected the specific gas production. Black-Right-Pointing-Pointer Adsorption of CO{sub 2} was successfully attained using a biomass type activated carbon. Black-Right-Pointing-Pointer H{sub 2} concentration in the range of 85-95% was obtained for the treated gas-stream. - Abstract: The production of H{sub 2} by biological means, although still far from being a commercially viable proposition, offers great promise for the future. Purification of the biogas obtained may lead to the production of highly concentrated H{sub 2} streams appropriate formore » industrial application. This research work evaluates the dark fermentation of food wastes and assesses the possibility of adsorbing CO{sub 2} from the gas stream by means of a low cost biomass-based adsorbent. The reactor used was a completely stirred tank reactor run at different hydraulic retention times (HRTs) while the concentration of solids of the feeding stream was kept constant. The results obtained demonstrate that the H{sub 2} yields from the fermentation of food wastes were affected by modifications in the hydraulic retention time (HRT) due to incomplete hydrolysis. The decrease in the duration of fermentation had a negative effect on the conversion of the substrate into soluble products. This resulted in a lower amount of soluble substrate being available for metabolisation by H{sub 2} producing microflora leading to a reduction in specific H{sub 2} production. Adsorption of CO{sub 2} from a gas stream generated from the dark fermentation process was successfully carried out. The data obtained demonstrate that the column filled with biomass-derived activated carbon resulted in a high degree of hydrogen purification. Co-adsorption of H{sub 2}S onto the activated carbon also took place, there being no evidence

Hydrogen gas protects against serum and glucose deprivation‑induced myocardial injury in H9c2 cells through activation of the NF‑E2‑related factor 2/heme oxygenase 1 signaling pathway.

PubMed

Xie, Qiang; Li, Xue-Xiang; Zhang, Peng; Li, Jin-Cao; Cheng, Ying; Feng, Yan-Ling; Huang, Bing-Sheng; Zhuo, Yu-Feng; Xu, Guo-Hua

2014-08-01

Ischemia or hypoxia‑induced myocardial injury is closely associated with oxidative stress. Scavenging free radicals and/or enhancing endogenous antioxidative defense systems may be beneficial for the impediment of myocardial ischemic injury. Hydrogen (H2) gas, as a water‑ and lipid‑soluble small molecule, is not only able to selectively eliminate hydroxyl (·OH) free radicals, but also to enhance endogenous antioxidative defense systems in rat lungs and arabidopsis plants. However, thus far, it has remained elusive whether H2 gas protects cardiomyocytes through enhancement of endogenous antioxidative defense systems. In the present study, the cardioprotective effect of H2 gas against ischemic or hypoxic injury was investigated, along with the underlying molecular mechanisms. H9c2 cardiomyoblasts (H9c2 cells) were treated in vitro with a chemical hypoxia inducer, cobalt chloride (CoCl2), to imitate hypoxia, or by serum and glucose deprivation (SGD) to imitate ischemia. Cell viability and intracellular ·OH free radicals were assessed. The role of an endogenous antioxidative defense system, the NF‑E2‑related factor 2 (Nrf2)/heme oxygenase 1 (HO‑1) signaling pathway, was evaluated. The findings revealed that treatment with CoCl2 or SGD markedly reduced cell viability in H9c2 cells. H2 gas‑rich medium protected against cell injury induced by SGD, but not that induced by CoCl2. When the cells were exposed to SGD, levels of intracellular ·OH free radicals were markedly increased; this was mitigated by H2 gas‑rich medium. Exposure of the cells to SGD also resulted in significant increases in HO‑1 expression and nuclear Nrf2 levels, and the HO‑1 inhibitor ZnPP IX and the Nrf2 inhibitor brusatol aggravated SGD‑induced cellular injury. H2 gas‑rich medium enhanced SGD‑induced upregulation of HO‑1 and Nrf2, and the HO‑1 or Nrf2 inhibition partially suppressed H2 gas‑induced cardioprotection. Furthermore, following genetic silencing of Nrf

C+/H2 gas in star-forming clouds and galaxies

NASA Astrophysics Data System (ADS)

Nordon, Raanan; Sternberg, Amiel

2016-11-01

We present analytic theory for the total column density of singly ionized carbon (C+) in the optically thick photon dominated regions (PDRs) of far-UV irradiated (star-forming) molecular clouds. We derive a simple formula for the C+ column as a function of the cloud (hydrogen) density, the far-UV field intensity, and metallicity, encompassing the wide range of galaxy conditions. When assuming the typical relation between UV and density in the cold neutral medium, the C+ column becomes a function of the metallicity alone. We verify our analysis with detailed numerical PDR models. For optically thick gas, most of the C+ column is mixed with hydrogen that is primarily molecular (H2), and this `C+/H2' gas layer accounts for almost all of the `CO-dark' molecular gas in PDRs. The C+/H2 column density is limited by dust shielding and is inversely proportional to the metallicity down to ˜0.1 solar. At lower metallicities, H2 line blocking dominates and the C+/H2 column saturates. Applying our theory to CO surveys in low-redshift spirals, we estimate the fraction of C+/H2 gas out of the total molecular gas to be typically ˜0.4. At redshifts 1 < z < 3 in massive disc galaxies the C+/H2 gas represents a very small fraction of the total molecular gas (≲ 0.16). This small fraction at high redshifts is due to the high gas surface densities when compared to local galaxies.

Noble gas isotopes and halogens in volatile-rich inclusions in diamonds

NASA Technical Reports Server (NTRS)

Burgess, Raymond; Turner, Grenville

1994-01-01

Application of the (40)Ar-(39)Ar method and noble gas studies to diamonds has increased our understanding of their age relationships to the host kimberlite or lamproite, and of the source and composition of volatile-rich fluids in the upper mantle. The properties of diamond (inert, high mechanical strength and low gas diffusivities) means they are especially useful samples for studying gases trapped deep within the earth (less than 150 km) as they are unlikely to have undergone loss or exchange of entrapped material since formation. Volatile-rich fluids (H2O-CO2) are important agents for metasomatic processes in the upper mantle, and the noble gases and halogens preferentially partition into this phase leading to a strong geochemical coherence between these groups of elements. The abundances of the halogens in the major reservoirs of the Earth shows a marked progression from chlorine, concentrated in the oceans, through to iodine which, through its affinity to organic material, is concentrated mainly in sediments. Abundances in the upper mantle are low. This is particularly true for iodine which is of special interest in view of its potential significance as an indicator of sediment recycling and by way of its link to (129)Xe amomalies in the mantle through the low extinct isotope (129)I. Extensions of the (40)Ar-(39)Ar technique enable measurements of halogens and other elements (K, Ca, Ba, U) by production of noble gas isotopes from these species during neutron irradiation. Samples analyzed in this way include 15 coated stones from an unknown source in Zaire, 3 boarts from the Jwaneng and 1 boart from the Orapa kimberlites, both in Botswana.

Hydrogen generation during serpentinisation in ophiolite complexes: A comparison of H2-rich gases from Oman, Philippines and Turkey.

NASA Astrophysics Data System (ADS)

Beaumont, Valérie; Vacquand, Christèle; Deville, Eric; Prinzhofer, Alain

2013-04-01

H2-rich gas seepages in ultrabasic to basic contexts both in marine and continental environment are by-products of serpentinisation. Hydrothermal systems at MOR expose ultrabasic rocks to thermodynamic conditions favouring oxidation of FeII bearing minerals and water reduction. In continental context such thermodynamic conditions do not exist although active serpentinisation occurs in all known ophiolitic complexes (Barnes et al., 1978; Bruni et al., 2002; Cipolli et al., 2004; Boschetti and Toscani, 2008; Marques et al., 2008). Hyperalkaline springs are reported in these contexts as evidence of this active serpentinisation (Barnes et al., 1967) and are often associated with seepages of reduced gases (Neal and Stanger, 1983; Sano et al., 1993). Dry gas seepages are also observed (Abrajano et al., 1988, 1990; Hosgörmez, 2007; Etiope et al., 2011) Such H2-rich gases from ophiolite complexes were sampled in the Sultanate of Oman, the Philippines and Turkey and were analysed for chemical composition, noble gases contents, stable isotopes of carbon, hydrogen and nitrogen. The conditions for present-day serpentinisation in ophiolites were recognised as low temperature processes in Oman with high rock/water ratios (Neal and Stanger, 1985), while the origin of gases is not as univocal for Philippines and Turkey gas seepages. Although, H2 generation is directly linked with FeII oxidation, different reactions can occur during peridotite hydration (McCollom and Bach, 2009; Marcaillou et al., 2011) and serpentine weathering. Produced H2 can react with carbonate species to produce methane via processes that could be biological or abiotic, while carbon availability depends on water recharge chemistry. In the present study, the geochemical properties of gases sampled from three different ophiolite complexes are compared and provide evidence that weathering reactions producing H2 depend on structural, geological, geomorphologic and hydrological local features. REFERENCES Abrajano

Probing the kinetic energy-release dynamics of H-atom products from the gas-phase reaction of O(3P) with vinyl radical C2H3.

PubMed

Jang, Su-Chan; Choi, Jong-Ho

2014-11-21

The gas-phase radical-radical reaction dynamics of ground-state atomic oxygen O((3)P) with vinyl radicals C2H3 has been studied by combining the results of vacuum-ultraviolet laser-induced fluorescence spectroscopy in a crossed beam configuration with ab initio calculations. The two radical reactants O((3)P) and C2H3 were produced by photolysis of NO2 and supersonic flash pyrolysis of C2H3I, respectively. Doppler profile analysis of the kinetic energy release of the nascent H-atom products from the title reaction O((3)P) + C2H3→ H((2)S) + CH2CO (ketene) revealed that the average translational energy of the products and the average fraction of the total available energy were 7.03 ± 0.30 kcal mol(-1) and 7.2%. The empirical data combined with CBS-QB3 level ab initio theory and statistical calculations demonstrated that the title oxygen-hydrogen exchange reaction is a major reaction channel, through an addition-elimination mechanism involving the formation of a short-lived, dynamical complex on the doublet potential energy surface. On the basis of systematic comparison with several exchange reactions of hydrocarbon radicals, the observed kinetic energy release can be explained in terms of the weak impulse at the moment of decomposition in the loose transition state with a product-like geometry and a small reverse barrier along the exit channel.

Conductivity measurements on H 2O-bearing CO 2-rich fluids

DOE PAGES

Capobianco, Ryan M.; Miroslaw S. Gruszkiewicz; Bodnar, Robert J.; ...

2014-09-10

Recent studies report rapid corrosion of metals and carbonation of minerals in contact with carbon dioxide containing trace amounts of dissolved water. One explanation for this behavior is that addition of small amounts of H 2O to CO 2 leads to significant ionization within the fluid, thus promoting reactions at the fluid-solid interface analogous to corrosion associated with aqueous fluids. The extent of ionization in the bulk CO 2 fluid was determined using a flow-through conductivity cell capable of detecting very low conductivities. Experiments were conducted from 298 to 473 K and 7.39 to 20 MPa with H 2O concentrationsmore » up to ~1600 ppmw (xH 2O ≈ 3.9 x 10 -3), corresponding to the H 2O solubility limit in liquid CO 2 at ambient temperature. All solutions showed conductivities <10 nS/cm, indicating that the solutions were essentially ion-free. Furthermore, this observation suggests that the observed corrosion and carbonation reactions are not the result of ionization in CO 2-rich bulk phase, but does not preclude ionization in the fluid at the fluid-solid interface.« less

H2 production with anaerobic sludge using activated-carbon supported packed-bed bioreactors.

PubMed

Lee, Kuo-Shing; Lo, Yung-Sheng; Lo, Yung-Chung; Lin, Ping-Jei; Chang, Jo-Shu

2003-01-01

Packed-bed bioreactors containing activated carbon as support carrier were used to produce H2 anaerobically from a sucrose-limiting medium while acclimated sewage sludge was used as the H2 producer. The effects of bed porosity (epsilon(b)) and substrate loading rate on H2 fermentation were examined using packed beds with epsilon(b) of 70-90% being operated at hydraulic retention times (HRT) of 0.5-4 h. Higher epsilon(b) and lower HRT favored H2 production. With 20 g COD l(-1) of sucrose in the feed, the optimal H2 production rate (7.4 l h(-1) l(-1)) was obtained when the bed with epsilon(b) = 90% was operated at HRT = 0.5 h. Flocculation of cells enhanced the retention of sludge for stable operations of the bioreactor at low HRTs. The gas products resulting from fermentative H2 production consisted of 30-40% H2 and 60-70% CO2. Butyric acid was the primary soluble product, followed by propionic acid and valeric acid.

Hynol: An economic process for methanol production from biomass and natural gas with reduced CO2 emission

NASA Astrophysics Data System (ADS)

Steinberg, M.; Dong, Yuanji

1993-10-01

The Hynol process is proposed to meet the demand for an economical process for methanol production with reduced CO2 emission. This new process consists of three reaction steps: (1) hydrogasification of biomass, (2) steam reforming of the produced gas with additional natural gas feedstock, and (3) methanol synthesis of the hydrogen and carbon monoxide produced during the previous two steps. The H2-rich gas remaining after methanol synthesis is recycled to gasify the biomass in an energy neutral reactor so that there is no need for an expensive oxygen plant as required by commercial steam gasifiers. Recycling gas allows the methanol synthesis reactor to perform at a relatively lower pressure than conventional while the plant still maintains high methanol yield. Energy recovery designed into the process minimizes heat loss and increases the process thermal efficiency. If the Hynol methanol is used as an alternative and more efficient automotive fuel, an overall 41% reduction in CO2 emission can be achieved compared to the use of conventional gasoline fuel. A preliminary economic estimate shows that the total capital investment for a Hynol plant is 40% lower than that for a conventional biomass gasification plant. The methanol production cost is $0.43/gal for a 1085 million gal/yr Hynol plant which is competitive with current U.S. methanol and equivalent gasoline prices. Process flowsheet and simulation data using biomass and natural gas as cofeedstocks are presented. The Hynol process can convert any condensed carbonaceous material, especially municipal solid waste (MSW), to produce methanol.

High rate dry etching of (BiSb)2Te3 film by CH4/H2-based plasma

NASA Astrophysics Data System (ADS)

Song, Junqiang; Shi, Xun; Chen, Lidong

2014-10-01

Etching characteristics of p-type (BiSb)2Te3 films were studied with CH4/H2/Ar gas mixture using an inductively coupled plasma (ICP)-reactive ion etching (RIE) system. The effects of gas mixing ratio, working pressure and gas flow rate on the etch rate and the surface morphology were investigated. The vertical etched profile with the etch rate of 600 nm/min was achieved at the optimized processing parameters. X-ray photoelectron spectroscopy (XPS) analysis revealed the non-uniform etching of (BiSb)2Te3 films due to disparate volatility of the etching products. Micro-masking effects caused by polymer deposition and Bi-rich residues resulted in roughly etched surfaces. Smooth surfaces can be obtained by optimizing the CH4/H2/Ar mixing ratio.

Mass-production of highly-crystalline few-layer graphene sheets by arc discharge in various H2-inert gas mixtures

NASA Astrophysics Data System (ADS)

Chen, Yani; Zhao, Hongbin; Sheng, Leimei; Yu, Liming; An, Kang; Xu, Jiaqiang; Ando, Yoshinori; Zhao, Xinluo

2012-06-01

Large-scale production of graphene sheets has been achieved by direct current arc discharge evaporation of pure graphite electrodes in various H2-inert gas mixtures. The as-prepared few-layer graphene sheets have high purity, high crystallinity and high oxidation resistance temperature. Their electrochemical characteristics have been evaluated in coin-type cells versus metallic lithium. The first cell discharge capacity reached 1332 mA h g-1 at a current density of 50 mA g-1. After 350 cycles, the discharge capacity still remained at 323 mA h g-1. Graphene sheets produced by this method should be a promising candidate for the electrode material of lithium-ion batteries.

Reactions of CH3SH and CH3SSCH3 with gas-phase hydrated radical anions (H2O)n(•-), CO2(•-)(H2O)n, and O2(•-)(H2O)n.

PubMed

Höckendorf, Robert F; Hao, Qiang; Sun, Zheng; Fox-Beyer, Brigitte S; Cao, Yali; Balaj, O Petru; Bondybey, Vladimir E; Siu, Chi-Kit; Beyer, Martin K

2012-04-19

The chemistry of (H(2)O)(n)(•-), CO(2)(•-)(H(2)O)(n), and O(2)(•-)(H(2)O)(n) with small sulfur-containing molecules was studied in the gas phase by Fourier transform ion cyclotron resonance mass spectrometry. With hydrated electrons and hydrated carbon dioxide radical anions, two reactions with relevance for biological radiation damage were observed, cleavage of the disulfide bond of CH(3)SSCH(3) and activation of the thiol group of CH(3)SH. No reactions were observed with CH(3)SCH(3). The hydrated superoxide radical anion, usually viewed as major source of oxidative stress, did not react with any of the compounds. Nanocalorimetry and quantum chemical calculations give a consistent picture of the reaction mechanism. The results indicate that the conversion of e(-) and CO(2)(•-) to O(2)(•-) deactivates highly reactive species and may actually reduce oxidative stress. For reactions of (H(2)O)(n)(•-) with CH(3)SH as well as CO(2)(•-)(H(2)O)(n) with CH(3)SSCH(3), the reaction products in the gas phase are different from those reported in the literature from pulse radiolysis studies. This observation is rationalized with the reduced cage effect in reactions of gas-phase clusters. © 2012 American Chemical Society

Heavy neutron rich nuclei: production and investigation

NASA Astrophysics Data System (ADS)

Zemlyanoy, S.; Avvakumov, K.; Kazarinov, N.; Fedosseev, V.; Bark, R.; Blazczak, Z.; Janas, Z.

2018-05-01

For production and investigation of heavy neutron rich nuclei devoted the new setup, which is under construction at Flerov Laboratory for Nuclear Reactions (FLNR) - JINR, Dubna now. This setup is planned to exploit available beams from the U-400M cyclotron in low energy multi-nucleon transfer reactions to study exotic neutron-rich nuclei located in the “north-east” region of nuclear map. Products from 4.5 to 9 MeV/nucleon heavy-ion collisions, such as 136Xe on 208Pb, are to be captured in a gas cell and selectively laser-ionized in a sextupole (quadrupole) ion guide extraction system.

Mineral storage of CO2/H2S gas mixture injection in basaltic rocks

NASA Astrophysics Data System (ADS)

Clark, D. E.; Gunnarsson, I.; Aradottir, E. S.; Oelkers, E. H.; Sigfússon, B.; Snæbjörnsdottír, S. Ó.; Matter, J. M.; Stute, M.; Júlíusson, B. M.; Gíslason, S. R.

2017-12-01

Carbon capture and storage is one solution to reducing CO2 emissions in the atmosphere. The long-term geological storage of buoyant supercritical CO2 requires high integrity cap rock. Some of the risk associated with CO2 buoyancy can be overcome by dissolving CO2 into water during its injection, thus eliminating its buoyancy. This enables injection into fractured rocks, such as basaltic rocks along oceanic ridges and on continents. Basaltic rocks are rich in divalent cations, Ca2+, Mg2+ and Fe2+, which react with CO2 dissolved in water to form stable carbonate minerals. This possibility has been successfully tested as a part of the CarbFix CO2storage pilot project at the Hellisheiði geothermal power plant in Iceland, where they have shown mineralization occurs in less than two years [1, 2]. Reykjavik Energy and the CarbFix group has been injecting a mixture of CO2 and H2S at 750 m depth and 240-250°C since June 2014; by 1 January 2016, 6290 tons of CO2 and 3530 tons of H2S had been injected. Once in the geothermal reservoir, the heat exchange and sufficient dissolution of the host rock neutralizes the gas-charged water and saturates the formation water respecting carbonate and sulfur minerals. A thermally stable inert tracer was also mixed into the stream to monitor the subsurface transport and to assess the degree of subsurface carbonation and sulfide precipitation [3]. Water and gas samples have been continuously collected from three monitoring wells and geochemically analyzed. Based on the results, mineral saturation stages have been defined. These results and tracer mass balance calculations are used to evaluate the rate and magnitude of CO2 and H2S mineralization in the subsurface, with indications that mineralization of carbon and sulfur occurs within months. [1] Gunnsarsson, I., et al. (2017). Rapid and cost-effective capture and subsurface mineral storage of carbon and sulfur. Manuscript submitted for publication. [2] Matter, J., et al. (2016). Rapid

Metagenomic Evidence for H2 Oxidation and H2 Production by Serpentinite-Hosted Subsurface Microbial Communities

PubMed Central

Brazelton, William J.; Nelson, Bridget; Schrenk, Matthew O.

2012-01-01

Ultramafic rocks in the Earth’s mantle represent a tremendous reservoir of carbon and reducing power. Upon tectonic uplift and exposure to fluid flow, serpentinization of these materials generates copious energy, sustains abiogenic synthesis of organic molecules, and releases hydrogen gas (H2). In order to assess the potential for microbial H2 utilization fueled by serpentinization, we conducted metagenomic surveys of a marine serpentinite-hosted hydrothermal chimney (at the Lost City hydrothermal field) and two continental serpentinite-hosted alkaline seeps (at the Tablelands Ophiolite, Newfoundland). Novel [NiFe]-hydrogenase sequences were identified at both the marine and continental sites, and in both cases, phylogenetic analyses indicated aerobic, potentially autotrophic Betaproteobacteria belonging to order Burkholderiales as the most likely H2-oxidizers. Both sites also yielded metagenomic evidence for microbial H2 production catalyzed by [FeFe]-hydrogenases in anaerobic Gram-positive bacteria belonging to order Clostridiales. In addition, we present metagenomic evidence at both sites for aerobic carbon monoxide utilization and anaerobic carbon fixation via the Wood–Ljungdahl pathway. In general, our results point to H2-oxidizing Betaproteobacteria thriving in shallow, oxic–anoxic transition zones and the anaerobic Clostridia thriving in anoxic, deep subsurface habitats. These data demonstrate the feasibility of metagenomic investigations into novel subsurface habitats via surface-exposed seeps and indicate the potential for H2-powered primary production in serpentinite-hosted subsurface habitats. PMID:22232619

Metagenomic evidence for h(2) oxidation and h(2) production by serpentinite-hosted subsurface microbial communities.

PubMed

Brazelton, William J; Nelson, Bridget; Schrenk, Matthew O

2012-01-01

Ultramafic rocks in the Earth's mantle represent a tremendous reservoir of carbon and reducing power. Upon tectonic uplift and exposure to fluid flow, serpentinization of these materials generates copious energy, sustains abiogenic synthesis of organic molecules, and releases hydrogen gas (H(2)). In order to assess the potential for microbial H(2) utilization fueled by serpentinization, we conducted metagenomic surveys of a marine serpentinite-hosted hydrothermal chimney (at the Lost City hydrothermal field) and two continental serpentinite-hosted alkaline seeps (at the Tablelands Ophiolite, Newfoundland). Novel [NiFe]-hydrogenase sequences were identified at both the marine and continental sites, and in both cases, phylogenetic analyses indicated aerobic, potentially autotrophic Betaproteobacteria belonging to order Burkholderiales as the most likely H(2)-oxidizers. Both sites also yielded metagenomic evidence for microbial H(2) production catalyzed by [FeFe]-hydrogenases in anaerobic Gram-positive bacteria belonging to order Clostridiales. In addition, we present metagenomic evidence at both sites for aerobic carbon monoxide utilization and anaerobic carbon fixation via the Wood-Ljungdahl pathway. In general, our results point to H(2)-oxidizing Betaproteobacteria thriving in shallow, oxic-anoxic transition zones and the anaerobic Clostridia thriving in anoxic, deep subsurface habitats. These data demonstrate the feasibility of metagenomic investigations into novel subsurface habitats via surface-exposed seeps and indicate the potential for H(2)-powered primary production in serpentinite-hosted subsurface habitats.

Gas Production at Comet 67P/Churyumov-Gerasimenko as Measured by the ROSINA Instrument: Long Term Trends and Correlations with H2O and CO2

NASA Astrophysics Data System (ADS)

Hansen, K. C.; Altwegg, K.; Berthelier, J. J.; Combi, M. R.; De Keyser, J.; Fiethe, B.; Fougere, N.; Fuselier, S. A.; Gombosi, T. I.; Huang, Z.; Rubin, M.; Tenishev, V.; Toth, G.; Tzou, C. Y.

2017-12-01

The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument onboard the Rosetta spacecraft measured the in situ gas density of comet 67P/Churyumov-Gerasimenko during the full perihelion passage of the comet within 3.5au. During this time, ROSINA sampled the neutral coma, measuring the broad range of cometary species including both the major constituents such as H2O, CO2, CO as well as many other species that are interesting to the general astrophysical community, such as O2, Xe, Si and even amino acids. Many of these species are hard to detect and therefore measurements are limited to when the spacecraft was close to the comet or the production rate was high. In contrast, in this work we will consider species that are most easily measured due to either their higher production rates or the ease with which their mass peaks are located (H2O, CO2, CO, O2, 18OH, HDO, OCS, SO2, H2S, CN, HCN, NH3, CH4, C2H2, C2H3, CH3OH and F). The advantage of examining these species is that we are able to present measurements over the entire perihelion passage at reasonably high time resolution. In this work we will present two important results. First, we will examine the long-term trend and heliocentric distance dependence of the production of these species over the entire perihelion passage of 67P. Second we will consider the correlation of the production of each species with the production of H2O and CO2. The study will consider both the long term correspondence between production of different species as well as the shorter term correlation.

Chlorobium limicola forma thiosulfatophilum: Biocatalyst in the Production of Sulfur and Organic Carbon from a Gas Stream Containing H2S and CO2

PubMed Central

Cork, Douglas J.; Garunas, Ruta; Sajjad, Ashfaq

1983-01-01

Chlorobium limicola forma thiosulfatophilum (ATCC 17092) was grown in a 1-liter continuously stirred tank reactor (800-ml liquid volume) at pH 6.8, 30°C, saturated light intensity, and a gas flow rate of 23.6 ml/min from a gas cylinder blend consisting of 3.9 mol% H2S, 9.2 mol% CO2, 86.4 mol% N2, and 0.5 mol% H2. This is the first demonstration of photoautotrophic growth of a Chlorobium sp. on a continuous inorganic gas feed. A significant potential exists for applying this photoautotrophic process to desulfurization and CO2 fixation of gases containing acidic components (H2S and CO2). PMID:16346255

Hydrogen cyanide production due to mid-size impacts in a redox-neutral N2-rich atmosphere.

PubMed

Kurosawa, Kosuke; Sugita, Seiji; Ishibashi, Ko; Hasegawa, Sunao; Sekine, Yasuhito; Ogawa, Nanako O; Kadono, Toshihiko; Ohno, Sohsuke; Ohkouchi, Naohiko; Nagaoka, Yoichi; Matsui, Takafumi

2013-06-01

Cyanide compounds are amongst the most important molecules of the origin of life. Here, we demonstrate the importance of mid-size (0.1-1 km in diameter) hence frequent meteoritic impacts to the cyanide inventory on the early Earth. Subsequent aerodynamic ablation and chemical reactions with the ambient atmosphere after oblique impacts were investigated by both impact and laser experiments. A polycarbonate projectile and graphite were used as laboratory analogs of meteoritic organic matter. Spectroscopic observations of impact-generated ablation vapors show that laser irradiation to graphite within an N2-rich gas can produce a thermodynamic environment similar to that produced by oblique impacts. Thus, laser ablation was used to investigate the final chemical products after this aerodynamic process. We found that a significant fraction (>0.1 mol%) of the vaporized carbon is converted to HCN and cyanide condensates, even when the ambient gas contains as much as a few hundred mbar of CO2. As such, the column density of cyanides after carbon-rich meteoritic impacts with diameters of 600 m would reach ~10 mol/m(2) over ~10(2) km(2) under early Earth conditions. Such a temporally and spatially concentrated supply of cyanides may have played an important role in the origin of life.

A green desulfurization technique: utilization of flue gas SO2 to produce H2 via a photoelectrochemical process based on Mo-doped BiVO4

NASA Astrophysics Data System (ADS)

Han, Jin; Li, Kejian; Cheng, Hanyun; Zhang, Liwu

2017-12-01

A green photoelectrochemical (PEC) process with simultaneous SO2 removal and H2 production has attracted an increasing attention. The proposed process uses flue gas SO2 to improve H2 production. The improvement of the efficiency of this process is necessary before it can become industrial viable. Herein, we reported a Mo modified BiVO4 photocatalysts for a simultaneous SO2 removal and H2 production. And the PEC performance could be significantly improved with doping and flue gas removal. The evolution rate of H2 and removal of SO2 could be enhanced by almost 3 times after Mo doping as compared with pristine BiVO4. The enhanced H2 production and SO2 removal is attributed to the improved bulk charge carrier transportation after Mo doping, and greatly enhanced oxidation reaction kinetics on the photoanode due to the formation of SO32- after SO2 absorption by the electrolyte. Due to the utilization of SO2 to improve the production of H2, the proposed PEC process may become a profitable desulfurization technique.

A Green Desulfurization Technique: Utilization of Flue Gas SO2 to Produce H2 via a Photoelectrochemical Process Based on Mo-Doped BiVO4

PubMed Central

Han, Jin; Li, Kejian; Cheng, Hanyun; Zhang, Liwu

2017-01-01

A green photoelectrochemical (PEC) process with simultaneous SO2 removal and H2 production has attracted an increasing attention. The proposed process uses flue gas SO2 to improve H2 production. The improvement of the efficiency of this process is necessary before it can become industrial viable. Herein, we reported a Mo modified BiVO4 photocatalysts for a simultaneous SO2 removal and H2 production. And the PEC performance could be significantly improved with doping and flue gas removal. The evolution rate of H2 and removal of SO2 could be enhanced by almost three times after Mo doping as compared with pristine BiVO4. The enhanced H2 production and SO2 removal is attributed to the improved bulk charge carrier transportation after Mo doping, and greatly enhanced oxidation reaction kinetics on the photoanode due to the formation of SO32− after SO2 absorption by the electrolyte. Due to the utilization of SO2 to improve the production of H2, the proposed PEC process may become a profitable desulfurization technique. PMID:29312924

A Green Desulfurization Technique: Utilization of Flue Gas SO2 to Produce H2 via a Photoelectrochemical Process Based on Mo-Doped BiVO4.

PubMed

Han, Jin; Li, Kejian; Cheng, Hanyun; Zhang, Liwu

2017-01-01

A green photoelectrochemical (PEC) process with simultaneous SO 2 removal and H 2 production has attracted an increasing attention. The proposed process uses flue gas SO 2 to improve H 2 production. The improvement of the efficiency of this process is necessary before it can become industrial viable. Herein, we reported a Mo modified BiVO 4 photocatalysts for a simultaneous SO 2 removal and H 2 production. And the PEC performance could be significantly improved with doping and flue gas removal. The evolution rate of H 2 and removal of SO 2 could be enhanced by almost three times after Mo doping as compared with pristine BiVO 4 . The enhanced H 2 production and SO 2 removal is attributed to the improved bulk charge carrier transportation after Mo doping, and greatly enhanced oxidation reaction kinetics on the photoanode due to the formation of [Formula: see text] after SO 2 absorption by the electrolyte. Due to the utilization of SO 2 to improve the production of H 2 , the proposed PEC process may become a profitable desulfurization technique.

U2 8 + -intensity record applying a H2 -gas stripper cell

NASA Astrophysics Data System (ADS)

Barth, Winfried; Adonin, Aleksey; Düllmann, Christoph E.; Heilmann, Manuel; Hollinger, Ralph; Jäger, Egon; Khuyagbaatar, Jadambaa; Krier, Joerg; Scharrer, Paul; Vormann, Hartmut; Yakushev, Alexander

2015-04-01

To meet the Facility for Antiproton and Ion Research science requirements higher beam intensity has to be achieved in the present GSI-accelerator complex. For this an advanced upgrade program for the UNILAC is ongoing. Stripping is a key technology for all heavy ion accelerators. For this an extensive research and development program was carried out to optimize for high brilliance heavy ion operation. After upgrade of the supersonic N2 -gas jet (2007), implementation of high current foil stripping (2011) and preliminary investigation of H2 -gas jet operation (2012), recently (2014) a new H2 -gas cell using a pulsed gas regime synchronized with arrival of the beam pulse has been developed. An obviously enhanced stripper gas density as well as a simultaneously reduced gas load for the pumping system result in an increased stripping efficiency, while the beam emittance remains the same. A new record intensity (7.8 emA) for 238U2 8 + beams at 1.4 MeV /u has been achieved applying the pulsed high density H2 stripper target to a high intensity 238U4 + beam from the VARIS ion source with a newly developed extraction system. The experimental results are presented in detail.

Room-temperature H2S Gas Sensor Based on Au-doped ZnFe2O4 Yolk-shell Microspheres.

PubMed

Yan, Yin; Nizamidin, Patima; Turdi, Gulmira; Kari, Nuerguli; Yimit, Abliz

2017-01-01

Room-temperature type H 2 S sensing devices that use Au-doped ZnFe 2 O 4 yolk-shell microspheres as the active material have been fabricated using a solvothermal method as well as subsequent annealing and a chemical etching process. The samples are characterized using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), field-emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). The results demonstrate that the doping of Au does not change the spinel structure of the products, which were yolk-shell microspheres, while the particle size varied with the Au doping concentration. Also, the as-fabricated sensor device exhibited excellent selectivity toward H 2 S gas at the room temperature; the gas-sensing property of 2 wt% Au-doped ZnFe 2 O 4 microspheres was the best. The Au-doped ZnFe 2 O 4 yolk-shell microspheres can be promising as a sensing material for H 2 S gas detecting at room temperature.

The unusual ISM in Blue and Dusty Gas Rich Galaxies (BADGRS).

NASA Astrophysics Data System (ADS)

Dunne, L.; Zhang, Z.; De Vis, P.; Clark, C. J. R.; Oteo, I.; Maddox, S. J.; Cigan, P.; de Zotti, G.; Gomez, H. L.; Ivison, R. J.; Rowlands, K.; Smith, M. W. L.; van der Werf, P.; Vlahakis, C.; Millard, J. S.

2018-06-01

The Herschel-ATLAS unbiased survey of cold dust in the local Universe is dominated by a surprising population of very blue (FUV - K < 3.5), dust-rich galaxies with high gas fractions ({f_{HI}=M_{HI}/({ M_{\\ast }}+M_{HI})}>0.5). Dubbed `Blue and Dusty Gas Rich Sources' (BADGRS) they have cold diffuse dust temperatures, and the highest dust-to-stellar mass ratios of any galaxies in the local Universe. Here, we explore the molecular ISM in a representative sample of BADGRS, using very deep {CO(J_{up}=1,2,3)} observations across the central and outer disk regions. We find very low CO brightnesses (Tp = 5 - 30 mK), despite the bright far-infrared emission and metallicities in the range 0.5 < Z/Z⊙ < 1.0. The CO line ratios indicate a range of conditions with R_{21}={T_b^{21}/T_b^{10}=0.6-2.1} and R_{31}={T_b^{32}/T_b^{10}=0.2-1.2}. Using a metallicity dependent conversion from CO luminosity to molecular gas mass we find M_{H2}/{M_d}˜ 7-27 and Σ _{H2} = 0.5-6 M_{⊙} {pc^{-2}}, around an order of magnitude lower than expected. The BADGRS have lower molecular gas depletion timescales (τd ˜ 0.5 Gyr) than other local spirals, lying offset from the Kennicutt-Schmidt relation by a similar factor to Blue Compact Dwarf galaxies. The cold diffuse dust temperature in BADGRS (13-16 K) requires an interstellar radiation field 10-20 times lower than that inferred from their observed surface brightness. We speculate that the dust in these sources has either a very clumpy geometry or a very different opacity in order to explain the cold temperatures and lack of CO emission. BADGRS also have low UV attenuation for their UV colour suggestive of an SMC-type dust attenuation curve, different star formation histories or different dust/star geometry. They lie in a similar part of the IRX-β space as z ˜ 5 galaxies and may be useful as local analogues for high gas fraction galaxies in the early Universe.

Production and investigation of heavy neutron rich nuclei

NASA Astrophysics Data System (ADS)

Zemlyanoy, Sergey; Avvakumov, Konstantin; Kozulin, Eduard; Fedosseev, Valentin; Bark, Robert; Janas, Zenon

2017-11-01

A project devoted to the production and study of neutron rich heavy nuclei (GALS - project) is being realized at Flerov Laboratory for Nuclear Reactions (FLNR) - JINR. GALS is planned to exploit available beams from the U-400M cyclotron in low energy multi-nucleon transfer reactions to study exotic neutron rich nuclei located in the "north-east" region of nuclear map. Products from 4.5 to 9 MeV/nucleon heavy-ion collisions, such as 136Xe on 208Pb, are to be captured in a gas cell and selectively laser-ionized in a sextupole (quadrupole) ion guide extraction system.

Production of conjugated linoleic acid-rich potato chips.

PubMed

Jain, Vishal P; Proctor, Andrew

2007-01-01

Conjugated linoleic acid (CLA) is found primarily in diary and beef products, but the health benefits of CLA can only be realized if they are consumed at much greater levels than a normal healthy dietary intake. We have recently shown that a CLA-rich soy oil can be produced by simple isomerization of linoleic acid in soy oil by photoirradiation. This oil may allow greatly increased dietary CLA without significantly elevating fat intake. The objective of this study was to prepare CLA-rich potato chips by frying in CLA-rich soy oil. Soy oil was photoisomerized in the presence of iodine catalyst with UV/visible light. The irradiated oil was clay processed to remove the residual iodine and this oil was then used to fry potato chips. Oil was extracted from fried chips and analyzed for its CLA content with gas chromatography. A 1-oz serving of CLA-rich potato chips contained approximately 2.4 g CLA as compared to 0.1 g CLA in 3-oz serving of steak fillet and 0.06 g CLA in 8-oz serving of whole milk. The peroxide value of the oil extracted from potato chips was found to be 1 meq/1000 g sample, which was within the acceptable commercial standards. This study may lead to the commercialization of CLA-rich food products.

Non-absorbable antibiotics for managing intestinal gas production and gas-related symptoms.

PubMed

Di Stefano, M; Strocchi, A; Malservisi, S; Veneto, G; Ferrieri, A; Corazza, G R

2000-08-01

Simethicone, activated charcoal and antimicrobial drugs have been used to treat gas-related symptoms with conflicting results. To study the relationship between gaseous symptoms and colonic gas production and to test the efficacy of rifaximin, a new non-absorbable antimicrobial agent, on these symptoms. Intestinal gas production was measured by hydrogen (H2) and methane (CH4) breath testing after lactulose in 21 healthy volunteers and 34 functional patients. Only the 34 functional patients took part in a double-blind, double-dummy controlled trial, receiving, at random, rifaximin (400 mg b.d per 7 days), or activated charcoal (400 mg b.d per 7 days). The following parameters were evaluated at the start of the study and 1 and 10 days after therapy: bloating, abdominal pain, number of flatus episodes, abdominal girth, and cumulative breath H2 excretion. Hydrogen excretion was greater in functional patients than in healthy volunteers. Rifaximin, but not activated charcoal, led to a significant reduction in H2 excretion and overall severity of symptoms. In particular, in patients treated with rifaximin, a significant reduction in the mean number of flatus episodes and of mean abdominal girth was evident. In patients with gas-related symptoms the colonic production of H2 is increased. Rifaximin significantly reduces this production and the excessive number of flatus episodes.

Dissolution Rates and Reaction Products of Olivine Interaction with Ammonia-Rich Fluid

NASA Astrophysics Data System (ADS)

Zandanel, A. E.; Truche, L.; Hellmann, R.; Tobie, G.; Marrocchi, Y.

2018-05-01

Olivine dissolution rates and reaction products in NH3-rich fluids are determined from experiments simulating H2O-rock interaction on Enceladus. Kinetic rates are calculated from flow through experiments and reaction products from static experiments.

Effect of SiO2 coating layer morphology on TiH2 gas release characteristic.

PubMed

Yang, Zhimao; Fang, Jixiang; Ding, Bingjun

2005-10-15

In this study, a uniform and compact SiO2 film-coating layer was prepared on the surface of TiH2 particles by sol-gel method using inexpensive raw materials. The preparation process of SiO2-coated TiH2 particles and the effect of the coating layer morphology on the gas release characteristic were investigated in detail. When the pH value of TiH2 suspending solution is about 4.0 and the concentration of silicic acid is more than 0.5 mol/L, the coating layer shows a SiO2 particle-coating morphology. While a homogeneous and dense film-coating layer can be obtained when the solution pH value and concentration of silicic acid are about 4.0 and 0.5 mol/L. The results of gas release at 700 degrees C show that TiH2 particles coated with silicon dioxide layers can efficiently delay the starting time of gas release of TiH2 powders to 60-100 s. Comparing the particle-coating layer, the SiO2 film-coating layer has a better delaying effect on gas release of TiH2 particles.

Catalytic activity of Cu4-cluster to adsorb H2S gas: h-BN nanosheet

NASA Astrophysics Data System (ADS)

Kansara, Shivam; Gupta, Sanjeev K.; Sonvane, Yogesh

2018-05-01

We have investigated the electronic properties, adsorptions strength and charge transfer using first principles calculations using density functional theory (DFT). The hexagonal boron nitride (h-BN) substrate shows metallic behavior, which helps to enhance the absorption process. The adsorption of three different orientations (S, D and T) of the H2S gas molecules to analyze the maximum adsorption strength from them onto a copper cluster (Cu4) based on h-BN nanosheet. The maximum adsorption energy of the H2S gas molecule is -1.50 eV for the S orientation and for D and U, it is -0.71 eV and -0.78 eV, respectively. The results show that Cu4 cluster helps to capture H2S gas from the environment and results are useful for the cleaning environment from the toxic gases.

Effects of H{sub 2} and H preferential diffusion and unity Lewis number on superadiabatic flame temperatures in rich premixed methane flames

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

Liu, Fengshan; Guelder, OEmer L.

2005-11-01

The structures of freely propagating rich CH{sub 4}/air and CH{sub 4}/O{sub 2} flames were studied numerically using a relatively detailed reaction mechanism. Species diffusion was modeled using five different methods/assumptions to investigate the effects of species diffusion, in particular H{sub 2} and H, on superadiabatic flame temperature. With the preferential diffusion of H{sub 2} and H accounted for, significant amount of H{sub 2} and H produced in the flame front diffuse from the reaction zone to the preheat zone. The preferential diffusion of H{sub 2} from the reaction zone to the preheat zone has negligible effects on the phenomenon ofmore » superadiabatic flame temperature in both CH{sub 4}/air and CH{sub 4}/O{sub 2} flames. It is therefore demonstrated that the superadiabatic flame temperature phenomenon in rich hydrocarbon flames is not due to the preferential diffusion of H{sub 2} from the reaction zone to the preheat zone as recently suggested by Zamashchikov et al. [V.V. Zamashchikov, I.G. Namyatov, V.A. Bunev, V.S. Babkin, Combust. Explosion Shock Waves 40 (2004) 32]. The suppression of the preferential diffusion of H radicals from the reaction zone to the preheat zone drastically reduces the degree of superadiabaticity in rich CH{sub 4}/O{sub 2} flames. The preferential diffusion of H radicals plays an important role in the occurrence of superadiabatic flame temperature. The assumption of unity Lewis number for all species leads to the suppression of H radical diffusion from the reaction zone to the preheat zone and significant diffusion of CO{sub 2} from the postflame zone to the reaction zone. Consequently, the degree of superadiabaticity of flame temperature is also significantly reduced. Through reaction flux analyses and numerical experiments, the chemical nature of the superadiabatic flame temperature phenomenon in rich CH{sub 4}/air and CH{sub 4}/O{sub 2} flames was identified to be the relative scarcity of H radical, which leads to

The Interplay of Proton, Electron, and Metabolite Supply for Photosynthetic H2 Production in Chlamydomonas reinhardtii*

PubMed Central

Doebbe, Anja; Keck, Matthias; La Russa, Marco; Mussgnug, Jan H.; Hankamer, Ben; Tekçe, Ercan; Niehaus, Karsten; Kruse, Olaf

2010-01-01

To obtain a detailed picture of sulfur deprivation-induced H2 production in microalgae, metabolome analyses were performed during key time points of the anaerobic H2 production process of Chlamydomonas reinhardtii. Analyses were performed using gas chromatography coupled to mass spectrometry (GC/MS), two-dimensional gas chromatography combined with time-of-flight mass spectrometry (GCxGC-TOFMS), lipid and starch analysis, and enzymatic determination of fermentative products. The studies were designed to provide a detailed metabolite profile of the solar Bio-H2 production process. This work reports on the differential analysis of metabolic profiles of the high H2-producing strain Stm6Glc4 and the wild-type cc406 (WT) before and during the H2 production phase. Using GCxGC-TOFMS analysis the number of detected peaks increased from 128 peaks, previously detected by GC/MS techniques, to ∼1168. More detailed analysis of the anaerobic H2 production phase revealed remarkable differences between wild-type and mutant cells in a number of metabolic pathways. Under these physiological conditions the WT produced up to 2.6 times more fatty acids, 2.2 times more neutral lipids, and up to 4 times more fermentation products compared with Stm6Glc4. Based on these results, specific metabolic pathways involving the synthesis of fatty acids, neutral lipids, and fermentation products during anaerobiosis in C. reinhardtii have been identified as potential targets for metabolic engineering to further enhance substrate supply for the hydrogenase(s) in the chloroplast. PMID:20581114

Numerical Analysis of Extremely-rich CH4/O2/H2O Premixed Flames at High Pressure and High Temperature Considering Production of Higher Hydrocarbons

NASA Astrophysics Data System (ADS)

Kumagami, Manabu; Ogami, Yasuhiro; Tamaki, Yuichi; Kobayashi, Hideaki

Numerical analysis of CH4/O2/H2O laminar premixed flame under various conditions of pressure, equivalence ratio and steam concentration was performed using GRI-Mech 3.0 and the mechanism proposed by Davis and Law, which consists of C1 to C6 hydrocarbons in addition to GRI-Mech 3.0. The pressure dependence of laminar burning velocity and flame structure under fuel-rich conditions was focused on. Effects of the formation of higher hydrocarbons under fuel-rich conditions were also clarified using the mechanism proposed by Davis and Law. Results showed that for extremely fuel-rich conditions, laminar burning velocity increases as pressure increases for both mechanisms. The increase of laminar burning velocity is caused by the shift of the oxidation pathway of CH3 radical from the C2 Route to the C1 Route. The formation of C3-C6 hydrocarbons has only a small effect on laminar burning velocity. Under fuel-rich conditions, super-adiabatic flame temperature (SAFT) occurs and its pressure dependency was clarified.

RADIOLYTIC GAS PRODUCTION RATES OF POLYMERS EXPOSED TO TRITIUM GAS

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

Clark, E.

Data from previous reports on studies of polymers exposed to tritium gas is further analyzed to estimate rates of radiolytic gas production. Also, graphs of gas release during tritium exposure from ultrahigh molecular weight polyethylene (UHMW-PE), polytetrafluoroethylene (PTFE, a trade name is Teflon®), and Vespel® polyimide are re-plotted as moles of gas as a function of time, which is consistent with a later study of tritium effects on various formulations of the elastomer ethylene-propylene-diene monomer (EPDM). These gas production rate estimates may be useful while considering using these polymers in tritium processing systems. These rates are valid at least formore » the longest exposure times for each material, two years for UHMW-PE, PTFE, and Vespel®, and fourteen months for filled and unfilled EPDM. Note that the production “rate” for Vespel® is a quantity of H{sub 2} produced during a single exposure to tritium, independent of length of time. The larger production rate per unit mass for unfilled EPDM results from the lack of filler- the carbon black in filled EPDM does not produce H{sub 2} or HT. This is one aspect of how inert fillers reduce the effects of ionizing radiation on polymers.« less

Enhanced visible light photocatalytic H2-production of g-C3N4/WS2 composite heterostructures

NASA Astrophysics Data System (ADS)

Akple, Maxwell Selase; Low, Jingxiang; Wageh, S.; Al-Ghamdi, Ahmed. A.; Yu, Jiaguo; Zhang, Jun

2015-12-01

As a clean and renewable solar H2-production system to address the increasing global environmental crisis and energy demand, photocatalytic hydrogen production from water splitting using earth abundant materials has received a lot of attention. In this study, WS2-graphitic carbon nitride (g-C3N4) composites were prepared using WO3 and thiourea as precursors through a gas-solid reaction. Different amount of WS2 were loaded on g-C3N4 to form the heterostructures and the composite samples exhibited enhanced photocatalytic activity for H2 production under visible light. The composite sample with 0.01 wt% WS2 exhibited the highest H2-production rate of 101 μmol g-1 h-1, which was even better than that of the Pt-C3N4 sample with the same loading content. The high photocatalytic activity was attributed to the formation of heterojunction between g-C3N4 and WS2 cocatalyst which allowed for effective separation of photogenerated charge carriers. This work showed the possibility for the utilization of low cost WS2 as an efficient cocatalyst to promote the photocatalytic H2 production of g-C3N4.

Ternary recombination of H3+, H2D+, HD2+, and D3+ with electrons in He/Ar/H2/D2 gas mixtures

NASA Astrophysics Data System (ADS)

Kalosi, Abel; Dohnal, Petr; Plasil, Radek; Johnsen, Rainer; Glosik, Juraj

2016-09-01

The temperature dependence of the ternary recombination rate coefficients of H2D+ and HD2+ ions has been studied in the temperature range of 80-150 K at pressures from 500 to 1700 Pa in a stationary afterglow apparatus equipped with a cavity ring-down spectrometer. Neutral gas mixtures consisting of He/Ar/H2/D2 (with typical number densities 1017 /1014 /1014 /1014 cm-3) were employed to produce the desired ionic species and their fractional abundances were monitored as a function of helium pressure and the [D2]/[H2] ratio of the neutral gas. In addition, the translational and the rotational temperature and the ortho to para ratio were monitored for both H2D+ and HD2+ ions. A fairly strong pressure dependence of the effective recombination rate coefficient was observed for both ion species, leading to ternary recombination rate coefficients close to those previously found for (helium assisted) ternary recombination of H3+ and D3+. Work supported by: Czech Science Foundation projects GACR 14-14649P, GACR 15-15077S, GACR P209/12/0233, and by Charles University in Prague Project Nr. GAUK 692214.

Investigation of Gas-Sensing Property of Acid-Deposited Polyaniline Thin-Film Sensors for Detecting H2S and SO2

PubMed Central

Dong, Xingchen; Zhang, Xiaoxing; Wu, Xiaoqing; Cui, Hao; Chen, Dachang

2016-01-01

Latent insulation defects introduced in manufacturing process of gas-insulated switchgears can lead to partial discharge during long-time operation, even to insulation fault if partial discharge develops further. Monitoring of decomposed components of SF6, insulating medium of gas-insulated switchgear, is a feasible method of early-warning to avoid the occurrence of sudden fault. Polyaniline thin-film with protonic acid deposited possesses wide application prospects in the gas-sensing field. Polyaniline thin-film sensors with only sulfosalicylic acid deposited and with both hydrochloric acid and sulfosalicylic acid deposited were prepared by chemical oxidative polymerization method. Gas-sensing experiment was carried out to test properties of new sensors when exposed to H2S and SO2, two decomposed products of SF6 under discharge. The gas-sensing properties of these two sensors were compared with that of a hydrochloric acid deposited sensor. Results show that the hydrochloric acid and sulfosalicylic acid deposited polyaniline thin-film sensor shows the most outstanding sensitivity and selectivity to H2S and SO2 when concentration of gases range from 10 to 100 μL/L, with sensitivity changing linearly with concentration of gases. The sensor also possesses excellent long-time and thermal stability. This research lays the foundation for preparing practical gas-sensing devices to detect H2S and SO2 in gas-insulated switchgears at room temperature. PMID:27834895

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.

Fuel-Flexible Gasification-Combustion Technology for Production of H2 and Sequestration-Ready CO2

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

Parag Kulkarni; Jie Guan; Raul Subia

In the near future, the nation will continue to rely on fossil fuels for electricity, transportation, and chemicals. It is necessary to improve both the process efficiency and environmental impact of fossil fuel utilization including greenhouse gas management. GE Global Research (GEGR) investigated an innovative fuel-flexible Unmixed Fuel Processor (UFP) technology with potential to produce H{sub 2}, power, and sequestration-ready CO{sub 2} from coal and other solid fuels. The UFP technology offers the long-term potential for reduced cost, increased process efficiency relative to conventional gasification and combustion systems, and near-zero pollutant emissions. GE was awarded a contract from U.S. DOEmore » NETL to investigate and develop the UFP technology. Work started on the Phase I program in October 2000 and on the Phase II effort in April 2005. In the UFP technology, coal, water and air are simultaneously converted into (1) hydrogen rich stream that can be utilized in fuel cells or turbines, (2) CO{sub 2} rich stream for sequestration, and (3) high temperature/pressure vitiated air stream to produce electricity in a gas turbine expander. The process produces near-zero emissions with an estimated efficiency higher than Integrated Gasification Combined Cycle (IGCC) process with conventional CO{sub 2} separation. The Phase I R&D program established the chemical feasibility of the major reactions of the integrated UFP technology through lab-, bench- and pilot-scale testing. A risk analysis session was carried out at the end of Phase I effort to identify the major risks in the UFP technology and a plan was developed to mitigate these risks in the Phase II of the program. The Phase II effort focused on three high-risk areas: economics, lifetime of solids used in the UFP process, and product gas quality for turbines (or the impact of impurities in the coal on the overall system). The economic analysis included estimating the capital cost as well as the costs of

Stoichiometry and possible mechanism of SiH/sub 4/-O/sub 2/ explosions

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

Hartman, J.R.; Famil-Ghiriha, J.; Ring, M.A.

1987-04-01

The products of silane-O/sub 2/ mixture explosions vary with mixture composition. For O/sub 2/-rich mixtures (>70% O/sub 2/), the products are H/sub 2/O and SiO/sub 2/. As the mixtures become richer in silane, H/sub 2/ replaces H/sub 2/O as a final product. For very SiH/sub 4/-rich mixtures (>70% SiH/sub 4/), the products are H/sub 2/, SiO/sub x/, and Si. The fact that silane is totally consumed in silane-rich mixtures (70-90% silane) demonstrates that solid particle formation (SiO/sub 2/, SiO, and Si) occurs very rapidly and that the accompanying heat release is essential to drive the reactions to completion. It ismore » also clear that the explosion of a silane-rich mixture is primarily a thermal explosion of silane. Effects due to problems associated with upper pressure limit measurements and mechanistic aspects of the SiH/sub 4/-O/sub 2/ explosion reaction are discussed.« less

A Thermodynamic Model for Predicting Mineral Reactivity in Supercritical Carbon Dioxide: I. Phase Behavior of Carbon Dioxide - Water - Chloride Salt Systems Across the H2O-Rich to the CO2-Rich Regions

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

Springer, Ronald D.; Wang, Zheming; Anderko, Andre

Phase equilibria in mixtures containing carbon dioxide, water, and chloride salts have been investigated using a combination of solubility measurements and thermodynamic modeling. The solubility of water in the CO2-rich phase of ternary mixtures of CO2, H2O and NaCl or CaCl2 was determined, using near infrared spectroscopy, at 90 atm and 40 to 100 °C. These measurements fill a gap in the experimental database for CO2 water salt systems, for which phase composition data have been available only for the H2O-rich phases. A thermodynamic model for CO2 water salt systems has been constructed on the basis of the previously developedmore » Mixed-Solvent Electrolyte (MSE) framework, which is capable of modeling aqueous solutions over broad ranges of temperature and pressure, is valid to high electrolyte concentrations, treats mixed-phase systems (with both scCO2 and water present) and can predict the thermodynamic properties of dry and partially water-saturated supercritical CO2 over broad ranges of temperature and pressure. Within the MSE framework the standard-state properties are calculated from the Helgeson-Kirkham-Flowers equation of state whereas the excess Gibbs energy includes a long-range electrostatic interaction term expressed by a Pitzer-Debye-Hückel equation, a virial coefficient-type term for interactions between ions and a short-range term for interactions involving neutral molecules. The parameters of the MSE model have been evaluated using literature data for both the H2O-rich and CO2-rich phases in the CO2 - H2O binary and for the H2O-rich phase in the CO2 - H2O - NaCl / KCl / CaCl2 / MgCl2 ternary and multicompontent systems. The model accurately represents the properties of these systems at temperatures from 0°C to 300 °C and pressures up to ~4000 atm. Further, the solubilities of H2O in CO2-rich phases that are predicted by the model are in agreement with the new measurements for the CO2 - H2O - NaCl and CO2 - H2O - CaCl2 systems. Thus, the model

Natural flows of H2-rich fluids in the ophiolites of Oman and the Philippines: Tectonic control of migration pathways and associated diagenetic processes

NASA Astrophysics Data System (ADS)

Deville, E. P.; Prinzhofer, A.; Vacquand, C.; Chavagnac, V.; Monnin, C.; Ceuleneer, G.; Arcilla, C. A.

2009-12-01

We compare the geological environments of sites of emission of natural hydrogen in the Oman ophiolite and the Zambales ophiolite (Luzon, Philippines). The genesis of natural H2 results from the interaction between ultrabasic rocks and aqueous solutions circulating in deep fracture networks, by oxidation of metals (Fe2+, Mn2+) and reduction of water, probably under high temperature conditions. This process generates very reducing conditions capable of destabilizing other molecules (notably reduction of deep CO2 being transformed into CH4 by Fisher-Tropsch type reactions). Nitrogen is also commonly associated to the H2-rich fluids. H2 flows are associated with the expulsion of hyperalkaline waters rich in ions OH- and Ca2+ and characterized by high pH (between 11 and 12). Most alkaline springs are found in the vicinity of major faults and/or lithological discontinuities like the basal thrust plane of the ophiolites and the peridotite-gabbro contact (Moho). Within the fracture networks, gas and water separate probably at shallow depth, i.e. close to the top of the upper aquifer level. Locally high flows of gas migrate vertically through fracture pathways and they are able to inflame spontaneously on the surface. Aqueous fluids tends to migrate laterally in the fracture network toward the creeks where most of the hyperalkaline springs are found. This water circulation induces a chain of diagenetic reactions starting in the fracture systems and continuing at the surface where it leads to the precipitation of calcite, aragonite, brucite and more rarely portlandite. This chain of diagenetic reactions is associated with the capture of the atmospheric CO2 during the precipitation of carbonates.

Si-rich W silicide films composed of W-atom-encapsulated Si clusters deposited using gas-phase reactions of WF6 with SiH4.

PubMed

Okada, Naoya; Uchida, Noriyuki; Kanayama, Toshihiko

2016-02-28

We formed Si-rich W silicide films composed of Sin clusters, each of which encapsulates a W atom (WSi(n) clusters with 8 < n ≤ ∼ 12), by using a gas-phase reaction between WF6 and SiH4 in a hot-wall reactor. The hydrogenated WSi(n)H(x) clusters with reduced F concentration were synthesized in a heated gas phase and subsequently deposited on a substrate heated to 350-420 °C, where they dehydrogenated and coalesced into the film. Under a gas pressure of SiH4 high enough for the WSi(n)H(x) reactant to collide a sufficient number of times with SiH4 molecules before reaching the substrate, the resulting film was composed of WSi(n) clusters with a uniform n, which was determined by the gas temperature. The formed films were amorphous semiconductors with an optical gap of ∼0.8-1.5 eV and an electrical mobility gap of ∼0.05-0.12 eV, both of which increased as n increased from 8 to 12. We attribute this dependence to the reduction of randomness in the Si network as n increased, which decreased the densities of band tail states and localized states.

Insights into the structure of mixed CO 2/CH 4 in gas hydrates

DOE PAGES

Everett, S. Michelle; Rawn, Claudia J.; Chakoumakos, Bryan C.; ...

2015-05-12

The exchange of carbon dioxide for methane in natural gas hydrates is an attractive approach to harvesting CH 4 for energy production while simultaneously sequestering CO 2. In addition to the energy and environmental implications, the solid solution of clathrate hydrate (CH 4) 1-x(CO 2) x·5.75H 2O provides a model system to study how the distinct bonding and shapes of CH 4 and CO 2 influence the structure and properties of the compound. In this paper, high-resolution neutron diffraction was used to examine mixed CO 2/CH 4 gas hydrates. CO 2-rich hydrates had smaller lattice parameters, which were attributed tomore » the higher affinity of the CO 2 molecule interacting with H 2O molecules that form the surrounding cages, and resulted in a reduction in the unit-cell volume. Experimental nuclear scattering densities illustrate how the cage occupants and energy landscape change with composition. Finally, these results provide important insights on the impact and mechanisms for the structure of mixed CH 4/CO 2 gas hydrate.« less

Promotion of hydrogen-rich gas and phenolic-rich bio-oil production from green macroalgae Cladophora glomerata via pyrolysis over its bio-char.

PubMed

Norouzi, Omid; Jafarian, Sajedeh; Safari, Farid; Tavasoli, Ahmad; Nejati, Behnam

2016-11-01

Conversion of Cladophora glomerata (C. glomerata) as a Caspian Sea's green macroalgae into gaseous, liquid and solid products was carried out via pyrolysis at different temperatures to determine its potential for bio-oil and hydrogen-rich gas production for further industrial utilization. Non-catalytic tests were performed to determine the optimum condition for bio-oil production. The highest portion of bio-oil was retrieved at 500°C. The catalytic test was performed using the bio-char derived at 500°C as a catalyst. Effect of the addition of the algal bio-char on the composition of the bio-oil and also gaseous products was investigated. Pyrolysis derived bio-char was characterized by BET, FESEM and ICP method to show its surface area, porosity, and presence of inorganic metals on its surface, respectively. Phenols were increased from 8.5 to 20.76area% by the addition of bio-char. Moreover, the hydrogen concentration and hydrogen selectivity were also enhanced by the factors of 1.37, 1.59 respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

Increased H2CO production in the outer disk around HD 163296

NASA Astrophysics Data System (ADS)

Carney, M. T.; Hogerheijde, M. R.; Loomis, R. A.; Salinas, V. N.; Öberg, K. I.; Qi, C.; Wilner, D. J.

2017-09-01

Context. The gas and dust in circumstellar disks provide the raw materials to form planets. The study of organic molecules and their building blocks in such disks offers insight into the origin of the prebiotic environment of terrestrial planets. Aims: We aim to determine the distribution of formaldehyde, H2CO, in the disk around HD 163296 to assess the contribution of gas- and solid-phase formation routes of this simple organic. Methods: Three formaldehyde lines were observed (H2CO 303-202, H2CO 322-221, and H2CO 321-220) in the protoplanetary disk around the Herbig Ae star HD 163296 with ALMA at 0.5″ (60 AU) spatial resolution. Different parameterizations of the H2CO abundance were compared to the observed visibilities, using either a characteristic temperature, a characteristic radius or a radial power law index to describe the H2CO chemistry. Similar models were applied to ALMA Science Verification data of C18O. In each scenario, χ2 minimization on the visibilities was used to determine the best-fit model in each scenario. Results: H2CO 303-202 was readily detected via imaging, while the weaker H2CO 322-221 and H2CO 321-220 lines required matched filter analysis to detect. H2CO is present throughout most of the gaseous disk, extending out to 550 AU. An apparent 50 AU inner radius of the H2CO emission is likely caused by an optically thick dust continuum. The H2CO radial intensity profile shows a peak at 100 AU and a secondary bump at 300 AU, suggesting increased production in the outer disk. In all modeling scenarios, fits to the H2CO data show an increased abundance in the outer disk. The overall best-fit H2CO model shows a factor of two enhancement beyond a radius of 270 ± 20 AU, with an inner abundance (relative to H2) of 2 - 5 × 10-12. The H2CO emitting region has a lower limit on the kinetic temperature of T> 20 K. The C18O modeling suggests an order of magnitude depletion of C18O in the outer disk and an abundance of 4 - 12 × 10-8 in the inner disk

Cold parsec-scale gas in a zabs ˜ 0.1 sub-damped Lyman α with disparate H2 and 21-cm absorption

NASA Astrophysics Data System (ADS)

Dutta, R.; Srianand, R.; Muzahid, S.; Gupta, N.; Momjian, E.; Charlton, J.

2015-04-01

We present a detailed analysis of a H2-bearing metal-rich sub-damped Lyman α system at zabs = 0.10115 towards the radio-loud quasar J0441-4313, at a projected separation of ˜7.6 kpc from a star-forming galaxy. The H2, {C I}} and {Na I} absorption are much stronger in the redder of the two components seen in the Hubble Space Telescope/Cosmic Origins Spectrograph spectrum. The best single-component fit to the strong H2 component gives log N(H2) = 16.61 ± 0.05. However, possible hidden saturation in the medium-resolution spectrum can allow for log N(H2) to be as high as 18.9. The rotational excitation temperature of H2 in this component is 133^{+33}_{-22} K. Photoionization models suggest 30-80 per cent of the total N(H I) is associated with the strong H2 component that has a density ≤100 cm-3 and is subject to a radiation field that is ≤0.5 times the Galactic mean field. The Very Long Baseline Array 1.4 GHz continuum image of the radio source contains only 27 per cent of the arcsecond scale emission. Using a previously published spectrum, no 21-cm absorption is found to be associated with the strong H2 component. This suggests that either the N(H I)) associated with this component is ≤50 per cent of the total N(H I)) or the gas covering factor is ≤0.27. This is consistent with the results of the photoionization model that uses ultraviolet radiation due to stars in the associated galaxy. The 21-cm absorption previously reported from the weaker H2 component suggests a spin temperature of ≤90 K, at odds with the weakness of H2, {C I} and {Na I} absorption in this component. From the inferred physical and chemical conditions, we suggest that the gas may be tracing a recent metal-rich outflow from the host galaxy.

Diffusion Monte Carlo simulations of gas phase and adsorbed D2-(H2)n clusters

NASA Astrophysics Data System (ADS)

Curotto, E.; Mella, M.

2018-03-01

We have computed ground state energies and analyzed radial distributions for several gas phase and adsorbed D2(H2)n and HD(H2)n clusters. An external model potential designed to mimic ionic adsorption sites inside porous materials is used [M. Mella and E. Curotto, J. Phys. Chem. A 121, 5005 (2017)]. The isotopic substitution lowers the ground state energies by the expected amount based on the mass differences when these are compared with the energies of the pure clusters in the gas phase. A similar impact is found for adsorbed aggregates. The dissociation energy of D2 from the adsorbed clusters is always much higher than that of H2 from both pure and doped aggregates. Radial distributions of D2 and H2 are compared for both the gas phase and adsorbed species. For the gas phase clusters, two types of hydrogen-hydrogen interactions are considered: one based on the assumption that rotations and translations are adiabatically decoupled and the other based on nonisotropic four-dimensional potential. In the gas phase clusters of sufficiently large size, we find the heavier isotopomer more likely to be near the center of mass. However, there is a considerable overlap among the radial distributions of the two species. For the adsorbed clusters, we invariably find the heavy isotope located closer to the attractive interaction source than H2, and at the periphery of the aggregate, H2 molecules being substantially excluded from the interaction with the source. This finding rationalizes the dissociation energy results. For D2-(H2)n clusters with n ≥12 , such preference leads to the desorption of D2 from the aggregate, a phenomenon driven by the minimization of the total energy that can be obtained by reducing the confinement of (H2)12. The same happens for (H2)13, indicating that such an effect may be quite general and impact on the absorption of quantum species inside porous materials.

FUEL RICH SULFUR CAPTURE IN A COMBUSTION ENVIRONMENT

EPA Science Inventory

A refractory-lined, natural gas furnace was used to study fuel rich sulfur capture reactions of calcium sorbents under typical combustion conditions. The fuel rich sulfur species H2S and COS were monitored in a near-continuous fashion using a gas chromatograph equipped with a fl...

H2 enrichment from synthesis gas by Desulfotomaculum carboxydivorans for potential applications in synthesis gas purification and biodesulfurization.

PubMed

Sipma, Jan; Osuna, M Begoña; Parshina, Sofiya N; Lettinga, Gatze; Stams, Alfons J M; Lens, Piet N L

2007-08-01

Desulfotomaculum carboxydivorans, recently isolated from a full-scale anaerobic wastewater treatment facility, is a sulfate reducer capable of hydrogenogenic growth on carbon monoxide (CO). In the presence of sulfate, the hydrogen formed is used for sulfate reduction. The organism grows rapidly at 200 kPa CO, pH 7.0, and 55 degrees C, with a generation time of 100 min, producing nearly equimolar amounts of H(2) and CO(2) from CO and H(2)O. The high specific CO conversion rates, exceeding 0.8 mol CO (g protein)(-1) h(-1), makes this bacterium an interesting candidate for a biological alternative of the currently employed chemical catalytic water-gas shift reaction to purify synthesis gas (contains mainly H(2), CO, and CO(2)). Furthermore, as D. carboxydivorans is capable of hydrogenotrophic sulfate reduction at partial CO pressures exceeding 100 kPa, it is also a good candidate for biodesulfurization processes using synthesis gas as electron donor at elevated temperatures, e.g., in biological flue gas desulfurization. Although high maximal specific sulfate reduction rates (32 mmol (g protein)(-1) h(-1)) can be obtained, its sulfide tolerance is rather low and pH dependent, i.e., maximally 9 and 5 mM sulfide at pH 7.2 and pH 6.5, respectively.

Evolution of gas-rich meteorites: Clues from cosmogenic nuclides

NASA Technical Reports Server (NTRS)

Goswami, J. N.

1986-01-01

The evolution of gas-rich meteorites in general, and the setting in which the observed solar-wind, solar-flare irradiation records were imprinted in individual components of these meteorites are understood only in qualitative terms, although contrary viewpoints do exist. The regolith irradiation hypothesis, bolstered by the observations of irradiation features in lunar regolith materials, similar to those observed in gas-rich meteorites, is accepted by many workers in this field. However, a close analysis of the problem suggests that the regolith irradiation may not be the dominant mode in producing the observed precompaction irradiation features in the gas-rich meteorites.

CO2 and H2O Contents of Melt Inclusions from the 1891 Basaltic Balloon Eruption of Foerstner Submarine Volcano, Italy

NASA Astrophysics Data System (ADS)

Balcanoff, J. R.; Carey, S.; Kelley, K. A.; Boesenberg, J. S.

2016-12-01

Eruptions that produce basaltic balloon products are an uncommon eruption style only observed in five cases during historical times. Basaltic balloon products form in gas rich shallow submarine eruptions, which produce large hollow clasts with sufficient buoyancy to float on seawater. Foerstner submarine volcano, off the coast of Pantelleria (Italy), erupted with this style in 1891 and is the only eruption where the vent site (250 m water depth) has been studied and sampled in detail with remotely operated vehicles (ROVs). Here, we report Fournier Transform Infrared Spectroscopy (FTIR) and electron microprobe (EMP) analyses of major elements and dissolved volatiles in melt inclusions from olivine and plagioclase phenocrysts picked from highly vesicular clasts recovered from the seafloor. The trachybasaltic melt is enriched in alkalis with notably high phosphorus (1.82-2.38 wt%), and melt inclusions show elevated H2O concentrations of 0.17 to 1.2 wt.% and highly elevated CO2 concentrations of 928 to 1864 ppm. Coexisting matrix glass is completely degassed with respect to carbon dioxide but has variable water contents up to 0.19 %. The maximum carbon dioxide value implies saturation at 1.5 kb, or 4.5 km below the volcano. Trends in the CO2 and H2O data are most compatible with calculated open system degassing behavior. This is consistent with a proposed balloon formation mechanism involving a hybrid strombolian eruption style with the potential accumulation of gas-rich pockets below the vent as gas bubbles moved upwards independent of the low viscosity basaltic melt. Discharge of the gas-rich pockets led to the discharge of meter-sized slugs of magma with large internal vesicles (several tens of centimeters). A subset of these clasts had bulk densities that were lower than seawater, allowing them to rise to the sea surface where they either exploded or became water saturated and sank back to the seafloor.

Mass-independent fractionation of oxygen isotopes during H2O2 formation by gas-phase discharge from water vapour

NASA Astrophysics Data System (ADS)

Velivetskaya, Tatiana A.; Ignatiev, Alexander V.; Budnitskiy, Sergey Y.; Yakovenko, Victoria V.; Vysotskiy, Sergey V.

2016-11-01

Hydrogen peroxide is an important atmospheric component involved in various gas-phase and aqueous-phase transformation processes in the Earth's atmosphere. A study of mass-independent 17O anomalies in H2O2 can provide additional insights into the chemistry of the modern atmosphere and, possibly, of the ancient atmosphere. Here, we report the results of laboratory experiments to study the fractionation of three oxygen isotopes (16O, 17O, and 18O) during H2O2 formation from products of water vapour dissociation. The experiments were carried out by passing an electrical discharge through a gaseous mixture of helium and water at atmospheric pressure. The effect of the presence of O2 in the gas mixture on the isotopic composition of H2O2 was also investigated. All of the experiments showed that H2O2 produced under two different conditions (with or without O2 added in the gas mixtures) was mass-independently fractionated (MIF). We found a positive MIF signal (∼1.4‰) in the no-O2 added experiments, and this signal increased to ∼2.5‰ once O2 was added (1.6% mixing ratio). We suggest that if O2 concentrations are very low, the hydroxyl radical recombination reaction is the dominant pathway for H2O2 formation and is the source of MIF in H2O2. Although H2O2 formation via a hydroxyl radical recombination process is limited in the modern atmosphere, it would be possible in the Archean atmosphere when O2 was a trace constituent, and H2O2 would be mass-independently fractionated. The anomalous 17O excess, which was observed in H2O2 produced by spark discharge experiments, may provide useful information about the radical chemistry of the ancient atmosphere and the role of H2O2 in maintaining and controlling the atmospheric composition.

High H2O/Ce of K-rich MORB from Lena Trough and Gakkel Ridge, Arctic Ocean

NASA Astrophysics Data System (ADS)

Snow, J. E.; Feig, S. T.

2014-12-01

Lena Trough in the Arctic ocean is the oblique spreading continuation of Gakkel Ridge through the Fram Strait (eg Snow et al. 2011). Extreme trace element and isotopic compositions seen in Lena Trough basalt appear to be the enriched end member dominating the geochemistry of the Western Volcanic Zone of the Western Gakkel Ridge as traced by Pb isotopes, K2O/TiO2, Ba/Nb and other isotopic, major and trace element indicators of mixing (Nauret et al., 2011). This is in contrast to neighboring Gakkel Ridge which has been spreading for 50-60 million years. Basalts from Lena Trough also show a pure MORB noble gas signature (Nauret et al., 2010) and peridotites show no evidence of ancient components in their Os isotopes (Lassiter, et al., in press). The major and trace element compositions of the basalts, however are very distinct from MORB, being far more potassic than all but a single locality on the SW Indian Ridge. We determined H2O and trace element composiitions of a suite of 17 basalt glasses from the Central Lena Trough (CLT) and the Gakkel Western Volcanic Zone, including many of those previously analyzed by Nauret et al. (2012). The Western Gakkel glasses have high H2O/Ce for MORB (>300) suggesting a water rich source consistent with the idea that the northernmost Atlantic mantle is enriched in water (Michael et al., 1995). They are within the range of Eastern Gakkel host glasses determined by Wanless et al, 2013. The Lena Trough (CLT) glasses are very rich in water for MORB (>1% H2O) and are among the highest H2O/Ce (>400) ever measured in MORB aside from melt inclusions in olivine. Mantle melting dynamics and melt evolution cannot account for the H2O/Ce variations in MORB, as these elements have similar behavior during melting and crustal evolution. Interestingly, the H2O/K2O ratios in the basalts are only around 1. This is because the K2O levels in the CLT glasses are very high as well relative to REE. The absolutely linear relationship between H2O and K2O

Quantifying Hydrate Formation in Gas-rich Environments Using the Method of Characteristics

NASA Astrophysics Data System (ADS)

You, K.; Flemings, P. B.; DiCarlo, D. A.

2015-12-01

Methane hydrates hold a vast amount of methane globally, and have huge energy potential. Methane hydrates in gas-rich environments are the most promising production targets. We develop a one-dimensional analytical solution based on the method of characteristics to explore hydrate formation in such environments (Figure 1). Our solution shows that hydrate saturation is constant with time and space in a homogeneous system. Hydrate saturation is controlled by the initial thermodynamic condition of the system, and changed by the gas fractional flow. Hydrate saturation increases with the initial distance from the hydrate phase boundary. Different gas fractional flows behind the hydrate solidification front lead to different gas saturations at the hydrate solidification front. The higher the gas saturation at the front, the less the volume available to be filled by hydrate, and hence the lower the hydrate saturation. The gas fractional flow depends on the relative permeability curves, and the forces that drive the flow. Viscous forces (the drive for flow induced from liquid pressure gradient) dominate the flow, and hydrate saturation is independent on the gas supply rates and the flow directions at high gas supply rates. Hydrate saturation can be estimated as one minus the ratio of the initial to equilibrium salinity. Gravity forces (the drive for flow induced from the gravity) dominate the flow, and hydrate saturation depends on the flow rates and the flow directions at low gas supply rates. Hydrate saturation is highest for upward flow, and lowest for downward flow. Hydrate saturation decreases with the flow rate for upward flow, and increases with the flow rate for downward flow. This analytical solution illuminates how hydrate is formed by gas (methane, CO2, ethane, propane) flowing into brine-saturated sediments at both the laboratory and geological scales (Figure 1). It provides an approach to generalize the understanding of hydrate solidification in gas-rich

Production of Excess CO2 relative to methane in peatlands: a new H2 sink

NASA Astrophysics Data System (ADS)

Wilson, R.; Woodcroft, B. J.; Varner, R. K.; Tyson, G. W.; Tfaily, M. M.; Sebestyen, S.; Saleska, S. R.; Rogers, K.; Rich, V. I.; McFarlane, K. J.; Kostka, J. E.; Kolka, R. K.; Keller, J.; Iversen, C. M.; Hodgkins, S. B.; Hanson, P. J.; Guilderson, T. P.; Griffiths, N.; de La Cruz, F.; Crill, P. M.; Chanton, J.; Bridgham, S. D.; Barlaz, M.

2015-12-01

Methane is generated as the end product of anaerobic organic matter degradation following a series of reaction pathways including fermentation and syntrophy. Along with acetate and CO2, syntrophic reactions generate H2 and are only thermodynamically feasible when coupled to an exothermic reaction that consumes H2. The usual model of organic matter degradation in peatlands has assumed that methanogenesis is that exothermic H2-consuming reaction. If correct, this paradigm should ultimately result in equimolar production of CO2 and methane from the degradation of the model organic compound cellulose: i.e. C6H12O6 à 3CO2 + 3CH4. However, dissolved gas measurement and modeling results from field and incubation experiments spanning peatlands across the northern hemisphere have failed to demonstrate equimolar production of CO2 and methane. Instead, in a flagrant violation of thermodynamics, these studies show a large bias favoring CO2 production over methane generation. In this talk, we will use an array of complementary analytical techniques including FT-IR, cellulose and lignin measurements, 13C-NMR, fluorescence spectroscopy, and ultra-high resolution mass spectrometry to describe organic matter degradation within a peat column and identify the important degradation mechanisms. Hydrogenation was the most common transformation observed in the ultra-high resolution mass spectrometry data. From these results we propose a new mechanism for consuming H2 generated during CO2 production, without concomitant methane formation, consistent with observed high CO2/CH4 ratios. While homoacetogenesis is a known sink for H2 in these systems, this process also consumes CO2 and therefore does not explain the excess CO2 measured in field and incubation samples. Not only does the newly proposed mechanism consume H2 without generating methane, but it also yields enough energy to balance the coupled syntrophic reactions, thereby restoring thermodynamic order. Schematic of organic matter

Hot gas, regenerative, supported H.sub.2 S sorbents

NASA Technical Reports Server (NTRS)

Voecks, Gerald E. (Inventor); Sharma, Pramod K. (Inventor)

1993-01-01

Efficient, regenerable sorbents for removal of H.sub.2 S from moderately high temperature (usually 200.degree. C.-550.degree.C.) gas streams comprise a porous, high surface area aluminosilicate support, suitably a zeolite, and most preferably a sodium deficient zeolite containing 1 to 20 weight percent of binary metal oxides. The binary oxides are a mixture of a Group VB or VIB metal oxide with a Group IB, IIB or VIII metal oxide such as V-Zn-O, V-Cu-O, Cu-Mo-O, Zn-Mo-O or Fe-Mo-O contained in the support. The sorbent effectively removes H.sub.2 S from the host gas stream in high efficiency and can be repetitively regenerated at least 10 times without loss of activity.

Production of B atoms and BH radicals from B2H6/He/H2 mixtures activated on heated W wires.

PubMed

Umemoto, Hironobu; Kanemitsu, Taijiro; Tanaka, Akihito

2014-07-17

B atoms and BH radicals could be identified by laser-induced fluorescence when B2H6/He/H2 mixtures were activated on heated tungsten wires. The densities of these radical species increased not only with the wire temperature but also with the partial pressure of H2. The densities in the presence of 0.026 Pa of B2H6 and 2.6 Pa of H2 were on the order of 10(11) cm(-3) both for B and BH when the wire temperature was 2000 K. Densities in the absence of a H2 flow were much smaller, suggesting that the direct production of these species on wire surfaces is minor. B and BH must be produced in the H atom shifting reactions, BH(x) + H → BH(x-1) + H2 (x = 1-3), in the gas phase, while H atoms are produced from H2 on wire surfaces. The B atom density increased monotonously with the H atom density, while the BH density showed saturation. These tendencies could be reproduced by simple modeling based on ab initio potential energy calculations and the transition-state theoretical calculations of the rate constants. The absolute densities could also be reproduced within a factor of 2.5.

Synthetic CO, H2 and H I surveys of the second galactic quadrant, and the properties of molecular gas

NASA Astrophysics Data System (ADS)

Duarte-Cabral, A.; Acreman, D. M.; Dobbs, C. L.; Mottram, J. C.; Gibson, S. J.; Brunt, C. M.; Douglas, K. A.

2015-03-01

We present CO, H2, H I and HISA (H I self-absorption) distributions from a set of simulations of grand design spirals including stellar feedback, self-gravity, heating and cooling. We replicate the emission of the second galactic quadrant by placing the observer inside the modelled galaxies and post-process the simulations using a radiative transfer code, so as to create synthetic observations. We compare the synthetic data cubes to observations of the second quadrant of the Milky Way to test the ability of the current models to reproduce the basic chemistry of the Galactic interstellar medium (ISM), as well as to test how sensitive such galaxy models are to different recipes of chemistry and/or feedback. We find that models which include feedback and self-gravity can reproduce the production of CO with respect to H2 as observed in our Galaxy, as well as the distribution of the material perpendicular to the Galactic plane. While changes in the chemistry/feedback recipes do not have a huge impact on the statistical properties of the chemistry in the simulated galaxies, we find that the inclusion of both feedback and self-gravity are crucial ingredients, as our test without feedback failed to reproduce all of the observables. Finally, even though the transition from H2 to CO seems to be robust, we find that all models seem to underproduce molecular gas, and have a lower molecular to atomic gas fraction than is observed. Nevertheless, our fiducial model with feedback and self-gravity has shown to be robust in reproducing the statistical properties of the basic molecular gas components of the ISM in our Galaxy.

Advanced oxidation technology for H2S odor gas using non-thermal plasma

NASA Astrophysics Data System (ADS)

Tao, ZHU; Ruonan, WANG; Wenjing, BIAN; Yang, CHEN; Weidong, JING

2018-05-01

Non-thermal plasma technology is a new type of odor treatment processing. We deal with H2S from waste gas emission using non-thermal plasma generated by dielectric barrier discharge. On the basis of two criteria, removal efficiency and absolute removal amount, we deeply investigate the changes in electrical parameters and process parameters, and the reaction process of the influence of ozone on H2S gas removal. The experimental results show that H2S removal efficiency is proportional to the voltage, frequency, power, residence time and energy efficiency, while it is inversely proportional to the initial concentration of H2S gas, and ozone concentration. This study lays the foundations of non-thermal plasma technology for further commercial application.

Fluid inclusion volatile analysis by gas chromatography with photoionization micro-thermal conductivity detectors: Applications to magmatic MoS 2 and other H 2O-CO 2 and H 2O-CH 4 fluids

NASA Astrophysics Data System (ADS)

Bray, C. J.; Spooner, E. T. C.

1992-01-01

the Cretaceous Boss Mtn. monzogranite stock-related MoS 2 deposit, central British Columbia of ~97 mol% H 2O, ~3% CO 2, ~ 140-150 ppm N 2, and ~16-39 ppm CH 4 (~300-350°C) are reasonable in comparison with high temperature (~400-900°C) volcanic gas analyses from four, active calc-alkaline volcanoes; e.g., the H 2O contents of volcanic gases from the White Island (New Zealand), Mount St. Helens (Washington, USA), Merapi (Bali, Indonesia), and Momotombo (Nicaragua) volcanoes are 88-95%, >90% (often >95%), 88-95% and ~93%, respectively; CO 2 contents are ~3-10%, 1-10%, 3-8%, and ~3.5%. CO 2/N 2 ratios for the Boss Mtn. MoS 2 fluids of ~ 190-220 are in the range for known volcanic gas ratios (e.g., ~ 150- 240; White Island). The ∑S content of the Boss Mtn. MoS 2 fluid prior to S loss by sulphide precipitation may have been ~2 mol% since CO 2/∑S molar ratios of analysed high-temperature volcanic gases are ~ 1.5. This estimate is supported by ∑S contents for White Island, Merapi and Momotombo volcanic gases of ~2%, ~0.5-2.5%, and ~2%. COS has been determined in H 2O-CO 2 fluid inclusions of interpreted magmatic origin from the Boss Mtn. MoS 2 deposit and the Tanco zoned granitic pegmatite, S.E. Manitoba at ~50-100 ppm molar levels, which are consistent with levels in volcanic gases. It appears that low, but significant, concentrations of C 2-C 4 alkanes (~ 1-20 ppm), C 2-C 4 alkenes (~ 1-480 ppb) and alkynes (e.g., C 3H 4) have been detected in magmatically derived fluids (Boss Mtn. MoS 2 deposit; Tanco granitic pegmatite). Significantly higher, low molecular weight hydrocarbon concentrations have been determined in a CH 4-rich (~ 2%), externally derived fluid of possible metamorphic or deep crustal origin trapped as inclusions in metasomatic wall-rock tourmaline adjacent to the Tanco pegmatite (e.g., 300/470 ppm C 2H 6; 50/90 ppm C 3H 8; 3-60 ppm C 2H 4/C 3H 6 n-C 4H 10).

Minimization of steam requirements and enhancement of water-gas shift reaction with warm gas temperature CO2 removal

DOEpatents

Siriwardane, Ranjani V; Fisher, II, James C

2013-12-31

The disclosure utilizes a hydroxide sorbent for humidification and CO.sub.2 removal from a gaseous stream comprised of CO and CO.sub.2 prior to entry into a water-gas-shift reactor, in order to decrease CO.sub.2 concentration and increase H.sub.2O concentration and shift the water-gas shift reaction toward the forward reaction products CO.sub.2 and H.sub.2. The hydroxide sorbent may be utilized for absorbtion of CO.sub.2 exiting the water-gas shift reactor, producing an enriched H.sub.2 stream. The disclosure further provides for regeneration of the hydroxide sorbent at temperature approximating water-gas shift conditions, and for utilizing H.sub.2O product liberated as a result of the CO.sub.2 absorption.

Molecular gas in low-metallicity starburst galaxies:. Scaling relations and the CO-to-H2 conversion factor

NASA Astrophysics Data System (ADS)

Amorín, R.; Muñoz-Tuñón, C.; Aguerri, J. A. L.; Planesas, P.

2016-04-01

Context. Tracing the molecular gas-phase in low-mass star-forming galaxies becomes extremely challenging due to significant UV photo-dissociation of CO molecules in their low-dust, low-metallicity ISM environments. Aims: We aim to study the molecular content and the star-formation efficiency of a representative sample of 21 blue compact dwarf galaxies (BCDs), previously characterized on the basis of their spectrophotometric properties. Methods: We present CO (1-0) and (2-1) observations conducted at the IRAM-30m telescope. These data are further supplemented with additional CO measurements and multiwavelength ancillary data from the literature. We explore correlations between the derived CO luminosities and several galaxy-averaged properties. Results: We detect CO emission in seven out of ten BCDs observed. For two galaxies these are the first CO detections reported so far. We find the molecular content traced by CO to be correlated with the stellar and Hi masses, star formation rate (SFR) tracers, the projected size of the starburst, and its gas-phase metallicity. BCDs appear to be systematically offset from the Schmidt-Kennicutt (SK) law, showing lower average gas surface densities for a given ΣSFR, and therefore showing extremely low (≲0.1 Gyr) H2 and H2 +Hi depletion timescales. The departure from the SK law is smaller when considering H2 +Hi rather than H2 only, and is larger for BCDs with lower metallicity and higher specific SFR. Thus, the molecular fraction (ΣH2/ ΣHI) and CO depletion timescale (ΣH2/ ΣSFR) of BCDs is found to be strongly correlated with metallicity. Using this, and assuming that the empirical correlation found between the specific SFR and galaxy-averaged H2 depletion timescale of more metal-rich galaxies extends to lower masses, we derive a metallicity-dependent CO-to-H2 conversion factor αCO,Z ∝ (Z/Z⊙)- y, with y = 1.5(±0.3)in qualitative agreement with previous determinations, dust-based measurements, and recent model

Microbial production of natural gas from coal and organic-rich shale

USGS Publications Warehouse

Orem, William

2013-01-01

Natural gas is an important component of the energy mix in the United States, producing greater energy yield per unit weight and less pollution compared to coal and oil. Most of the world’s natural gas resource is thermogenic, produced in the geologic environment over time by high temperature and pressure within deposits of oil, coal, and shale. About 20 percent of the natural gas resource, however, is produced by microorganisms (microbes). Microbes potentially could be used to generate economic quantities of natural gas from otherwise unexploitable coal and shale deposits, from coal and shale from which natural gas has already been recovered, and from waste material such as coal slurry. Little is known, however, about the microbial production of natural gas from coal and shale.

DIRECT DETERMINATION OF THE HF/H{sub 2} ABUNDANCE RATIO IN INTERSTELLAR GAS

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

Indriolo, Nick; Neufeld, D. A.; Seifahrt, A.

2013-02-20

We report the first detection of the v = 1-0, R(0) ro-vibrational transition of HF at 2.499385 {mu}m arising from interstellar gas. The line is seen in absorption toward three background sources-HD 154368, Elias 29, and AFGL 2136 IRS 1-all of which have reported H{sub 2} column densities determined from observations of H{sub 2}. This allows for the first direct determination of the HF/H{sub 2} abundance ratio. We find values of N(HF)/N(H{sub 2}) = 1.15 Multiplication-Sign 10{sup -8} and 0.69 Multiplication-Sign 10{sup -8} for HD 154368 and Elias 29, respectively. The sight line toward AFGL 2136 IRS 1 also showsmore » absorption from the v = 1-0, R(1) transition of HF, indicating warm, dense (n {sub H} {approx}> 10{sup 9} cm{sup -3}) gas, likely very close to the central protostar. Ascribing portions of the HF absorption to warm and cold gas, we find N(HF)/N(H{sub 2}) = (1.7-2.9) Multiplication-Sign 10{sup -8} and (0.33-0.58) Multiplication-Sign 10{sup -8} for the two components, respectively. Except for the warm component toward AFGL 2136 IRS 1, all observed HF/H{sub 2} ratios are well below N(HF)/N(H{sub 2}) = 3.6 Multiplication-Sign 10{sup -8}, the value predicted if nearly all gas phase fluorine is in the form of HF. Models of fluorine chemistry that account for depletion onto grains are able to reproduce the results toward HD 154368, but not in the cold, dense gas toward AFGL 2136 IRS 1 and Elias 29. Most likely, some combinations of simplifying assumptions made in the chemical models are responsible for these discrepancies.« less

Metal Oxide/Zeolite Combination Absorbs H2S

NASA Technical Reports Server (NTRS)

Voecks, Gerald E.; Sharma, Pramod K.

1989-01-01

Mixed copper and molybdenum oxides supported in pores of zeolite found to remove H2S from mixture of gases rich in hydrogen and steam, at temperatures from 256 to 538 degree C. Absorber of H2S needed to clean up gas streams from fuel processors that incorporate high-temperature steam reformers or hydrodesulfurizing units. Zeolites chosen as supporting materials because of their high porosity, rigidity, alumina content, and variety of both composition and form.

Effects of gas composition in headspace and bicarbonate concentrations in media on gas and methane production, degradability, and rumen fermentation using in vitro gas production techniques.

PubMed

Patra, Amlan Kumar; Yu, Zhongtang

2013-07-01

Headspace gas composition and bicarbonate concentrations in media can affect methane production and other characteristics of rumen fermentation in in vitro gas production systems, but these 2 important factors have not been evaluated systematically. In this study, these 2 factors were investigated with respect to gas and methane production, in vitro digestibility of feed substrate, and volatile fatty acid (VFA) profile using in vitro gas production techniques. Three headspace gas compositions (N2+ CO2+ H2 in the ratio of 90:5:5, CO2, and N2) with 2 substrate types (alfalfa hay only, and alfalfa hay and a concentrate mixture in a 50:50 ratio) in a 3×2 factorial design (experiment 1) and 3 headspace compositions (N2, N2 + CO2 in a 50:50 ratio, and CO2) with 3 bicarbonate concentrations (80, 100, and 120 mM) in a 3×3 factorial design (experiment 2) were evaluated. In experiment 1, total gas production (TGP) and net gas production (NGP) was the lowest for CO2, followed by N2, and then the gas mixture. Methane concentration in headspace gas after fermentation was greater for CO2 than for N2 and the gas mixture, whereas total methane production (TMP) and net methane production (NMP) were the greatest for CO2, followed by the gas mixture, and then N2. Headspace composition did not affect in vitro digestibility or the VFA profile, except molar percentages of propionate, which were greater for CO2 and N2 than for the gas mixture. Methane concentration in headspace gas, TGP, and NGP were affected by the interaction of headspace gas composition and substrate type. In experiment 2, increasing concentrations of CO2 in the headspace decreased TGP and NGP quadratically, but increased the concentrations of methane, NMP, and in vitro fiber digestibility linearly, and TMP quadratically. Fiber digestibility, TGP, and NGP increased linearly with increasing bicarbonate concentrations in the medium. Concentrations of methane and NMP were unaffected by bicarbonate concentration, but

First Scattered-Light Images of the Gas-Rich Debris Disk Around 49 Ceti

NASA Technical Reports Server (NTRS)

Choquet, Elodie; Milli, Julien; Wahhaj, Zahed; Soummer, Remi; Roberge, Aki; Augereau, Jean-Charles; Booth, Mark; Absil, Olivier; Boccaletti, Anthony; Chen, Christine H.;

Hydrogen-rich gas generator

NASA Technical Reports Server (NTRS)

Houseman, J.; Cerini, D. J. (Inventor)

1976-01-01

A process and apparatus are described for producing hydrogen-rich product gases. A spray of liquid hydrocarbon is mixed with a stream of air in a startup procedure and the mixture is ignited for partial oxidation. The stream of air is then heated by the resulting combustion to reach a temperature such that a signal is produced. The signal triggers a two way valve which directs liquid hydrocarbon from a spraying mechanism to a vaporizing mechanism with which a vaporized hydrocarbon is formed. The vaporized hydrocarbon is subsequently mixed with the heated air in the combustion chamber where partial oxidation takes place and hydrogen-rich product gases are produced.

Numerical simulations of CO2 -assisted gas production from hydrate reservoirs

NASA Astrophysics Data System (ADS)

Sridhara, P.; Anderson, B. J.; Myshakin, E. M.

2015-12-01

A series of experimental studies over the last decade have reviewed the feasibility of using CO2 or CO2+N2 gas mixtures to recover CH4 gas from hydrates deposits. That technique would serve the dual purpose of CO2 sequestration and production of CH4 while maintaining the geo-mechanical stability of the reservoir. In order to analyze CH4 production process by means of CO2 or CO2+N2 injection into gas hydrate reservoirs, a new simulation tool, Mix3HydrateResSim (Mix3HRS)[1], was previously developed to account for the complex thermodynamics of multi-component hydrate phase and to predict the process of CH4 substitution by CO2 (and N2) in the hydrate lattice. In this work, Mix3HRS is used to simulate the CO2 injection into a Class 2 hydrate accumulation characterized by a mobile aqueous phase underneath a hydrate bearing sediment. That type of hydrate reservoir is broadly confirmed in permafrost and along seashore. The production technique implies a two-stage approach using a two-well design, one for an injector and one for a producer. First, the CO2 is injected into the mobile aqueous phase to convert it into immobile CO2 hydrate and to initiate CH4 release from gas hydrate across the hydrate-water boundary (generally designating the onset of a hydrate stability zone). Second, CH4 hydrate decomposition is induced by the depressurization method at a producer to estimate gas production potential over 30 years. The conversion of the free water phase into the CO2 hydrate significantly reduces competitive water production in the second stage, thereby improving the methane gas production. A base case using only the depressurization stage is conducted to compare with enhanced gas production predicted by the CO2-assisted technique. The approach also offers a possibility to permanently store carbon dioxide in the underground formation to greater extent comparing to a direct injection of CO2 into gas hydrate sediment. Numerical models are based on the hydrate formations at the

Influence of Background H2O on the Collision-Induced Dissociation Products Generated from [UO2NO3]+

NASA Astrophysics Data System (ADS)

Van Stipdonk, Michael J.; Iacovino, Anna; Tatosian, Irena

2018-04-01

Developing a comprehensive understanding of the reactivity of uranium-containing species remains an important goal in areas ranging from the development of nuclear fuel processing methods to studies of the migration and fate of the element in the environment. Electrospray ionization (ESI) is an effective way to generate gas-phase complexes containing uranium for subsequent studies of intrinsic structure and reactivity. Recent experiments by our group have demonstrated that the relatively low levels of residual H2O in a 2-D, linear ion trap (LIT) make it possible to examine fragmentation pathways and reactions not observed in earlier studies conducted with 3-D ion traps (Van Stipdonk et al. J. Am. Soc. Mass Spectrom. 14, 1205-1214, 2003). In the present study, we revisited the dissociation of complexes composed of uranyl nitrate cation [UVIO2(NO3)]+ coordinated by alcohol ligands (methanol and ethanol) using the 2-D LIT. With relatively low levels of background H2O, collision-induced dissociation (CID) of [UVIO2(NO3)]+ primarily creates [UO2(O2)]+ by the ejection of NO. However, CID (using He as collision gas) of [UVIO2(NO3)]+ creates [UO2(H2O)]+ and UO2 + when the 2-D LIT is used with higher levels of background H2O. Based on the results presented here, we propose that product ion spectrum in the previous experiments was the result of a two-step process: initial formation of [UVIO2(O2)]+ followed by rapid exchange of O2 for H2O by ion-molecule reaction. Our experiments illustrate the impact of residual H2O in ion trap instruments on the product ions generated by CID and provide a more accurate description of the intrinsic dissociation pathway for [UVIO2(NO3)]+. [Figure not available: see fulltext.

Catalase activity is stimulated by H2O2 in rich culture medium and is required for H2O2 resistance and adaptation in yeast☆

PubMed Central

Martins, Dorival; English, Ann M.

2014-01-01

Catalases are efficient scavengers of H2O2 and protect cells against H2O2 stress. Examination of the H2O2 stimulon in Saccharomyces cerevisiae revealed that the cytosolic catalase T (Ctt1) protein level increases 15-fold on H2O2 challenge in synthetic complete media although previous work revealed that deletion of the CCT1 or CTA1 genes (encoding peroxisomal/mitochondrial catalase A) does not increase the H2O2 sensitivity of yeast challenged in phosphate buffer (pH 7.4). This we attributed to our observation that catalase activity is depressed when yeast are challenged with H2O2 in nutrient-poor media. Hence, we performed a systematic comparison of catalase activity and cell viability of wild-type yeast and of the single catalase knockouts, ctt1∆ and cta1∆, following H2O2 challenge in nutrient-rich medium (YPD) and in phosphate buffer (pH 7.4). Ctt1 but not Cta1 activity is strongly induced by H2O2 when cells are challenged in YPD but suppressed when cells are challenged in buffer. Consistent with the activity results, exponentially growing ctt1∆ cells in YPD are more sensitive to H2O2 than wild-type or cta1∆ cells, whereas in buffer all three strains exhibit comparable H2O2 hypersensitivity. Furthermore, catalase activity is increased during adaptation to sublethal H2O2 concentrations in YPD but not in buffer. We conclude that induction of cytosolic Ctt1 activity is vital in protecting yeast against exogenous H2O2 but this activity is inhibited by H2O2 when cells are challenged in nutrient-free media. PMID:24563848

Low Cost High-H 2 Syngas Production for Power and Liquid Fuels

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

Zhou, S. James

2015-07-31

This report summarizes the technical progress made of the research project entitled “Low Cost High-H2 Syngas Production for Power and Liquid Fuels,” under DOE Contract No. DE-FE-0011958. The period of performance was October 1, 2013 through July 30, 2015. The overall objectives of this project was to determine the technical and economic feasibility of a systems approach for producing high hydrogen syngas from coal with the potential to reduce significantly the cost of producing power, chemical-grade hydrogen or liquid fuels, with carbon capture to reduce the environmental impact of gasification. The project encompasses several areas of study and the resultsmore » are summarized here. (1) Experimental work to determine the technical feasibility of a novel hybrid polymer/metal H2-membrane to recover pure H2 from a coal-derived syngas was done. This task was not successful. Membranes were synthesized and show impermeability of any gases at required conditions. The cause of this impermeability was most likely due to the densification of the porous polymer membrane support made from polybenzimidazole (PBI) at test temperatures above 250 °C. (2) Bench-scale experimental work was performed to extend GTI's current database on the University of California Sulfur Recovery Process-High Pressure (UCSRP-HP) and recently renamed Sulfur Removal and Recovery (SR2) process for syngas cleanup including removal of sulfur and other trace contaminants, such as, chlorides and ammonia. The SR2 process tests show >90% H2S conversion with outlet H2S concentrations less than 4 ppmv, and 80-90% ammonia and chloride removal with high mass transfer rates. (3) Techno-economic analyses (TEA) were done for the production of electric power, chemical-grade hydrogen and diesel fuels, from a mixture of coal- plus natural gas-derived syngas using the Aerojet Rocketdyne (AR) Advanced Compact coal gasifier and a natural gas partial oxidation reactor (POX) with SR2 technology. Due to the

Serpentinization and the Formation of H2 and CH4 on Celestial Bodies (Planets, Moons, Comets).

PubMed

Holm, N G; Oze, C; Mousis, O; Waite, J H; Guilbert-Lepoutre, A

2015-07-01

Serpentinization involves the hydrolysis and transformation of primary ferromagnesian minerals such as olivine ((Mg,Fe)2SiO4) and pyroxenes ((Mg,Fe)SiO3) to produce H2-rich fluids and a variety of secondary minerals over a wide range of environmental conditions. The continual and elevated production of H2 is capable of reducing carbon, thus initiating an inorganic pathway to produce organic compounds. The production of H2 and H2-dependent CH4 in serpentinization systems has received significant interdisciplinary interest, especially with regard to the abiotic synthesis of organic compounds and the origins and maintenance of life in Earth's lithosphere and elsewhere in the Universe. Here, serpentinization with an emphasis on the formation of H2 and CH4 are reviewed within the context of the mineralogy, temperature/pressure, and fluid/gas chemistry present in planetary environments. Whether deep in Earth's interior or in Kuiper Belt Objects in space, serpentinization is a feasible process to invoke as a means of producing astrobiologically indispensable H2 capable of reducing carbon to organic compounds.

On-line estimation of O2 production, CO2 uptake, and growth kinetics of microalgal cultures in a gas-tight photobioreactor

PubMed Central

Riisgård, Frederik Kier; Gunther, William Stuart; Lønsmann Iversen, Jens Jørgen

2006-01-01

Growth of the green algae Chlamydomonas reinhardtii and Chlorella sp. in batch cultures was investigated in a novel gas-tight photobioreactor, in which CO2, H2, and N2 were titrated into the gas phase to control medium pH, dissolved oxygen partial pressure, and headspace pressure, respectively. The exit gas from the reactor was circulated through a loop of tubing and re-introduced into the culture. CO2 uptake was estimated from the addition of CO2 as acidic titrant and O2 evolution was estimated from titration by H2, which was used to reduce O2 over a Pd catalyst. The photosynthetic quotient, PQ, was estimated as the ratio between O2 evolution and CO2 up-take rates. NH4+, NO2−, or NO3− was the final cell density limiting nutrient. Cultures of both algae were, in general, characterised by a nitrogen sufficient growth phase followed by a nitrogen depleted phase in which starch was the major product. The estimated PQ values were dependent on the level of oxidation of the nitrogen source. The PQ was 1 with NH4+ as the nitrogen source and 1.3 when NO3− was the nitrogen source. In cultures grown on all nitrogen sources, the PQ value approached 1 when the nitrogen source was depleted and starch synthesis became dominant, to further increase towards 1.3 over a period of 3–4 days. This latter increase in PQ, which was indicative of production of reduced compounds like lipids, correlated with a simultaneous increase in the degree of reduction of the biomass. When using the titrations of CO2 and H2 into the reactor headspace to estimate the up-take of CO2, the production of O2, and the PQ, the rate of biomass production could be followed, the stoichiometrical composition of the produced algal biomass could be estimated, and different growth phases could be identified. PMID:19396354

Gas-rich galaxy pair unveiled in the lensed quasar 0957+561

PubMed

Planesas; Martin-Pintado; Neri; Colina

1999-12-24

Molecular gas in the host galaxy of the lensed quasar 0957+561 (QSO 0957+561) at the redshift of 1.41 has been detected in the carbon monoxide (CO) line. This detection shows the extended nature of the molecular gas distribution in the host galaxy and the pronounced lensing effects due to the differentially magnified CO luminosity at different velocities. The estimated mass of molecular gas is about 4 x 10(9) solar masses, a molecular gas mass typical of a spiral galaxy like the Milky Way. A second, weaker component of CO is interpreted as arising from a close companion galaxy that is rich in molecular gas and has remained undetected so far. Its estimated molecular gas mass is 1.4 x 10(9) solar masses, and its velocity relative to the main galaxy is 660 kilometers per second. The ability to probe the molecular gas distribution and kinematics of galaxies associated with high-redshift lensed quasars can be used to improve the determination of the Hubble constant H(0).

Corrosion of 310 stainless steel in H2-H2O-H2S gas mixtures: Studies at constant temperature and fixed oxygen potential

NASA Technical Reports Server (NTRS)

Rao, D. B.; Jacob, K. T.; Nelson, H. G.

1981-01-01

Corrosion of SAE 310 stainless steel in H2-H2O-H2S gas mixtures was studied at a constant temperature of 1150 K. Reactive gas mixtures were chosen to yield a constant oxygen potential of approximately 6 x 10 to the minus 13th power/cu Nm and sulfur potentials ranging from 0.19 x 10 to the minus 2nd power/cu Nm to 33 x 10 to the minus 2nd power/cu Nm. The kinetics of corrosion were determined using a thermobalance, and the scales were analyzed using metallography, scanning electron microscopy, and energy dispersive X-ray analysis. Two corrosion regimes, which were dependent on sulfur potential, were identified. At high sulfur potentials (p sub S sub 2 less than or equal to 2.7 x 10 to the minus 2nd power/cu Nm) the corrosion rates were high, the kinetics obeyed a linear rate equation, and the scales consisted mainly of sulfide phases similar to those observed from pure sulfication. At low sulfur potentials (P sub S sub 2 less than or equal to 0.19 x 10 to the minus 2nd power/cu Nm) the corrosion rates were low, the kinetics obeyed a parabolic rate equation, and scales consisted mainly of oxide phases.

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

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

First Scattered-light Images of the Gas-rich Debris Disk around 49 Ceti

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

Choquet, Élodie; Milli, Julien; Wahhaj, Zahed

We present the first scattered-light images of the debris disk around 49 Ceti, a ∼40 Myr A1 main-sequence star at 59 pc, famous for hosting two massive dust belts as well as large quantities of atomic and molecular gas. The outer disk is revealed in reprocessed archival Hubble Space Telescope NICMOS-F110W images, as well as new coronagraphic H-band images from the Very Large Telescope SPHERE instrument. The disk extends from 1.″1 (65 au) to 4.″6 (250 au) and is seen at an inclination of 73°, which refines previous measurements at lower angular resolution. We also report no companion detection largermore » than 3 M {sub Jup} at projected separations beyond 20 au from the star (0.″34). Comparison between the F110W and H-band images is consistent with a gray color of 49 Ceti’s dust, indicating grains larger than ≳2 μ m. Our photometric measurements indicate a scattering efficiency/infrared excess ratio of 0.2–0.4, relatively low compared to other characterized debris disks. We find that 49 Ceti presents morphological and scattering properties very similar to the gas-rich HD 131835 system. From our constraint on the disk inclination we find that the atomic gas previously detected in absorption must extend to the inner disk, and that the latter must be depleted of CO gas. Building on previous studies, we propose a schematic view of the system describing the dust and gas structure around 49 Ceti and hypothetical scenarios for the gas nature and origin.« less

Solar flare neon and solar cosmic ray fluxes in the past using gas-rich meteorites

NASA Technical Reports Server (NTRS)

Nautiyal, C. M.; Rao, M. N.

1986-01-01

Methods were developed earlier to deduce the composition of solar flare neon and to determine the solar cosmic ray proton fluxes in the past using etched lunar samples and at present, these techniques are extended to gas rich meteorites. By considering high temperature Ne data points for Pantar, Fayetteville and other gas rich meteorites and by applying the three component Ne-decomposition methods, the solar cosmic ray and galactic cosmic ray produced spallation Ne components from the trapped SF-Ne was resolved. Using appropiate SCR and GCR production rates, in the case of Pantar, for example, a GCR exposure age of 2 m.y. was estimated for Pantar-Dark while Pantar-Light yielded a GCR age of approx. 3 m.y. However the SCR exposure age of Pantar-Dark is two orders of magnitude higher than the average surface exposure ages of lunar soils. The possibility of higher proton fluxes in the past is discussed.

Relative Importance of H2 and H2S as Energy Sources for Primary Production in Geothermal Springs▿ †

PubMed Central

D'Imperio, Seth; Lehr, Corinne R.; Oduro, Harry; Druschel, Greg; Kühl, Michael; McDermott, Timothy R.

2008-01-01

Geothermal waters contain numerous potential electron donors capable of supporting chemolithotrophy-based primary production. Thermodynamic predictions of energy yields for specific electron donor and acceptor pairs in such systems are available, although direct assessments of these predictions are rare. This study assessed the relative importance of dissolved H2 and H2S as energy sources for the support of chemolithotrophic metabolism in an acidic geothermal spring in Yellowstone National Park. H2S and H2 concentration gradients were observed in the outflow channel, and vertical H2S and O2 gradients were evident within the microbial mat. H2S levels and microbial consumption rates were approximately three orders of magnitude greater than those of H2. Hydrogenobaculum-like organisms dominated the bacterial component of the microbial community, and isolates representing three distinct 16S rRNA gene phylotypes (phylotype = 100% identity) were isolated and characterized. Within a phylotype, O2 requirements varied, as did energy source utilization: some isolates could grow only with H2S, some only with H2, while others could utilize either as an energy source. These metabolic phenotypes were consistent with in situ geochemical conditions measured using aqueous chemical analysis and in-field measurements made by using gas chromatography and microelectrodes. Pure-culture experiments with an isolate that could utilize H2S and H2 and that represented the dominant phylotype (70% of the PCR clones) showed that H2S and H2 were used simultaneously, without evidence of induction or catabolite repression, and at relative rate differences comparable to those measured in ex situ field assays. Under in situ-relevant concentrations, growth of this isolate with H2S was better than that with H2. The major conclusions drawn from this study are that phylogeny may not necessarily be reliable for predicting physiology and that H2S can dominate over H2 as an energy source in terms of

Octupole Deformation Bands of πh11/2 in Neutron-Rich 145,147La Nuclei

NASA Astrophysics Data System (ADS)

Zhu, Sheng-jiang; S, Zhu J.; Wang, Mu-ge; J, Hamilton H.; A, Ramayya V.; B, Babu R. S.; W, Ma C.; Long, Gui-lu; Zhu, Ling-yan; Li, Ming; A, Sakhaee; Gan, Cui-yun; Yang, Li-ming; J, Komicki; J, Cole D.; R, Aryaeinejad; M, Drigert W.; J, Rasmussen O.; M, Stoyer A.; S, Chu Y.; K, Gregorich E.; M, Mohar F.; S, Prussin G.; I, Lee Y.; Yu, Oganessian Ts; G, Ter-Akopian M.; A, Daniel V.

1999-03-01

Octupole deformation bands built on πh11/2 orbital in neutron-rich odd-Z 145,147La nuclei have been investigated by measuring the prompt γ-rays emitted from the 252Cf source. The alternating parity band structures and strong E1 transitions observed between negative- and positive-parity bands in both nuclei indicate the octupole deformation enhanced by the h11/2 single proton coupling. According to observed energy displacements the octupole deformation becomes stable at the intermediate spin states.

Fuel-Flexible Gasification-Combustion Technology for Production of H2 and Sequestration-Ready CO2

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

George Rizeq; Janice West; Raul Subia

GE Global Research is developing an innovative energy technology for coal gasification with high efficiency and near-zero pollution. This Unmixed Fuel Processor (UFP) technology simultaneously converts coal, steam and air into three separate streams of hydrogen-rich gas, sequestration-ready CO{sub 2}, and high-temperature, high-pressure vitiated air to produce electricity in gas turbines. This is the draft final report for the first stage of the DOE-funded Vision 21 program. The UFP technology development program encompassed lab-, bench- and pilot-scale studies to demonstrate the UFP concept. Modeling and economic assessments were also key parts of this program. The chemical and mechanical feasibility weremore » established via lab and bench-scale testing, and a pilot plant was designed, constructed and operated, demonstrating the major UFP features. Experimental and preliminary modeling results showed that 80% H{sub 2} purity could be achieved, and that a UFP-based energy plant is projected to meet DOE efficiency targets. Future work will include additional pilot plant testing to optimize performance and reduce environmental, operability and combined cycle integration risks. Results obtained to date have confirmed that this technology has the potential to economically meet future efficiency and environmental performance goals.« less

Methane-rich syngas production from hydrocarbon fuels using multi-functional catalyst/capture agent

DOEpatents

Siefert, Nicholas S.; Shekhawat, Dushyant; Berry, David A.; Surdoval, Wayne A.

2017-02-07

The disclosure provides a gasification process for the production of a methane-rich syngas at temperatures exceeding 400.degree. C. through the use of an alkali hydroxide MOH, using a gasification mixture comprised of at least 0.25 moles and less than 2 moles of water for each mole of carbon, and at least 0.15 moles and less than 2 moles of alkali hydroxide MOH for each mole of carbon. These relative amounts allow the production of a methane-rich syngas at temperatures exceeding 400.degree. C. by enabling a series of reactions which generate H.sub.2 and CH.sub.4, and mitigate the reforming of methane. The process provides a methane-rich syngas comprised of roughly 20% (dry molar percentage) CH.sub.4 at temperatures above 400.degree. C., and may effectively operate within an IGFC cycle at reactor temperatures between 400-900.degree. C. and pressures in excess of 10 atmospheres.

Method for making hydrogen rich gas from hydrocarbon fuel

DOEpatents

Krumpelt, M.; Ahmed, S.; Kumar, R.; Doshi, R.

1999-07-27

A method of forming a hydrogen rich gas from a source of hydrocarbon fuel in which the hydrocarbon fuel contacts a two-part catalyst comprising a dehydrogenation portion and an oxide-ion conducting portion at a temperature not less than about 400 C for a time sufficient to generate the hydrogen rich gas while maintaining CO content less than about 5 volume percent. There is also disclosed a method of forming partially oxidized hydrocarbons from ethanes in which ethane gas contacts a two-part catalyst comprising a dehydrogenation portion and an oxide-ion conducting portion for a time and at a temperature sufficient to form an oxide. 4 figs.

Method for making hydrogen rich gas from hydrocarbon fuel

DOEpatents

Krumpelt, Michael; Ahmed, Shabbir; Kumar, Romesh; Doshi, Rajiv

1999-01-01

A method of forming a hydrogen rich gas from a source of hydrocarbon fuel in which the hydrocarbon fuel contacts a two-part catalyst comprising a dehydrogenation portion and an oxide-ion conducting portion at a temperature not less than about 400.degree. C. for a time sufficient to generate the hydrogen rich gas while maintaining CO content less than about 5 volume percent. There is also disclosed a method of forming partially oxidized hydrocarbons from ethanes in which ethane gas contacts a two-part catalyst comprising a dehydrogenation portion and an oxide-ion conducting portion for a time and at a temperature sufficient to form an oxide.

Yield of H2O2 in Gas-Liquid Phase with Pulsed DBD

NASA Astrophysics Data System (ADS)

Jiang, Song; Wen, Yiyong; Liu, Kefu

2014-01-01

Electric discharge in water can generate a large number of oxidants such as ozone, hydrogen peroxide and hydroxyl radicals. In this paper, a non-thermal plasma processing system was established by means of pulsed dielectric barrier discharge in gas-liquid phase. The electrodes of discharge reactor were staggered. The yield of H2O2 was enhanced after discharge. The effects of discharge time, discharge voltage, frequency, initial pH value, and feed gas were investigated. The concentration of hydrogen peroxide and ozone was measured after discharge. The experimental results were fully analyzed. The chemical reaction equations in water were given as much as possible. At last, the water containing Rhodamine B was tested in this system. The degradation rate came to 94.22% in 30 min.

Two-step gasification of cattle manure for hydrogen-rich gas production: Effect of biochar preparation temperature and gasification temperature.

PubMed

Xin, Ya; Cao, Hongliang; Yuan, Qiaoxia; Wang, Dianlong

2017-10-01

Two-step gasification process was proposed to dispose cattle manure for hydrogen rich gas production. The effect of temperature on product distribution and biochar properties were first studied in the pyrolysis-carbonization process. The steam gasification of biochar derived from different pyrolysis-carbonization temperatures was then performed at 750°C and 850°C. The biochar from the pyrolysis-carbonization temperatures of 500°C had high carbon content and low volatiles content. According to the results of gasification stage, the pyrolysis-carbonization temperature of 500°C and the gasification temperature of 850°C were identified as the suitable conditions for hydrogen production. We obtained 1.61m 3 /kg of syngas production, 0.93m 3 /kg of hydrogen yield and 57.58% of hydrogen concentration. This study shows that two-step gasification is an efficient waste-to-hydrogen energy process. Copyright © 2017 Elsevier Ltd. All rights reserved.

Novel Gas Sensor Based on ZnO Nanorod Circular Arrays for C2H5OH Gas Detection.

PubMed

Jianjiao, Zhang; Hongyan, Yue; Erjun, Guo; Shaolin, Zhang; Liping, Wang; Chunyu, Zhang; Xin, Gao; Jing, Chang; Hong, Zhang

2015-03-01

Novel side-heating gas sensor based on ZnO nanorod circular arrays was firstly fabricated by hydrothermal treatment assisted with a kind of simple dip-coating technique. The structure and morphologies of ZnO nanorods were characterized by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), respectively. XRD result indicates that the obtained ZnO nanorods have good crystalline with the hexagonal wurtzite structure. SEM result indicates that ZnO nanorod arrays are vertically growth on the surface of ceramic tube of side-heating sensor with controlled diameter and length, narrow size distribution and high orientation. The gas sensing properties of ZnO nanorod circular arrays are also evaluated. Comparative to the sensor based on scattered ZnO nanorods responding to 25 ppm H2, CO, C6H5CH3 and C2H5OH gas, respectively, the sensing values of high orientation gas sensor are generally increased by 5%. This novel sensor has good application promising for the fabrication of cost effective and high performance gas sensors.

Gas-phase evolution of Ar/H2O and Ar/CH4 dielectric barrier discharge plasmas

NASA Astrophysics Data System (ADS)

Barni, Ruggero; Riccardi, Claudia

2018-04-01

We present some experimental results of an investigation aimed to hydrogen production with atmospheric pressure plasmas, based on the use of dielectric barrier discharges, fed with a high-voltage alternating signal at frequency 30-50 kHz, in mixtures of methane or water vapor diluted in argon. The plasma gas-phase of the discharge was investigated by means of optical and electrical diagnostics. The emission spectra of the discharges was measured with a wide band spectrometer and a photosensor module, based on a photomultiplier tube. A Rogowski coil allowed to measure the electric current flowing into the circuit and a high voltage probe was employed for evaluating the voltage at the electrodes. The analysis of the signals of voltage and current shows the presence of microdischarges between the electrodes in two alternating phases during the period of oscillation of the applied voltage. The hydrogen concentration in the gaseous mixture was measured too. Besides this experimental campaign, we present also results from a numerical modeling of chemical kinetics in the gas-phase of Ar/H2O and Ar/CH4 plasmas. The simulations were conducted under conditions of single discharge to study the evolution of the system and of fixed frequency repeated discharging. In particular in Ar/H2O mixtures we could study the evolution from early atomic dissociation in the discharge, to longer time scales, when chemical reactions take place producing an increase of the density of species such as OH, H2O2 and subsequently of H and H2. The results of numerical simulations provide some insights into the evolution happening in the plasma gas-phase during the hydrogen reforming process.

State-to-state, multi-collision, energy transfer in H-H2 gas ensembles.

PubMed

McCaffery, Anthony J; Marsh, Richard J

2013-12-21

We use our recently developed computational model of energy flow in gas ensembles to study translation-to-internal energy conversion in an ensemble consisting of H2(0; 0) in a bath of H atoms. This mixture is found in plasmas of industrial importance and also in interstellar clouds. The storage of energy of relative motion as rovibrational energy of H2 represents a potential mechanism for cooling translation. This may have relevance in astrophysical contexts such as the post-recombination epoch of the early universe when hydrogenic species dominated and cooling was a precondition for the formation of structured objects. We find that conversion of translational motion to H2 vibration and rotation is fast and, in our closed system, is complete within around 100 cycles of ensemble collisions. Large amounts of energy become stored as H2 vibration and a tentative mechanism for this unequal energy distribution is suggested. The "structured dis-equilibrium" we observe is found to persist through many collision cycles. In contrast to the rapidity of excitation, the relaxation of H2(6; 10) in H is very slow and not complete after 10(5) collision cycles. The quasi-equilibrium modal temperatures of translation, rotation, and vibration are found to scale linearly with collision energy but at different rates. This may be useful in estimating the partitioning of energy within a given H + H2 ensemble.

The Gas-rich Circumbinary Disk of HR 4049. II. A Detailed Study of the Near-infrared Spectrum

NASA Astrophysics Data System (ADS)

Malek, S. E.; Cami, J.

2014-10-01

HR 4049 is a peculiar evolved binary surrounded by a circumbinary disk. Mid-infrared observations show that the disk is rich in molecular gas and radially extended. To study the properties of this disk, we re-analyzed a set of near-infrared observations at high spectral resolution obtained with Gemini-Phoenix. These data cover absorption lines originating from the first overtone of CO and from H2O in the 2.3 μm region as well as more complex emission-absorption profiles from H2O and the fundamental mode of CO near 4.6 μm. By using an excitation diagram and from modeling the spectrum, we find that most of the CO overtone and H2O absorption originates from hot gas (T ex ≈ 1000 K) with high column densities, consistent with the mid-infrared data. The strong emission in the wavelength range of the CO fundamental furthermore suggests that there is a significant quantity of gas in the inner cavity of the disk. In addition, there is a much colder component in the line of sight to the disk. A detailed analysis of the overtone line profiles reveals variations in the line widths that are consistent with a radially extended disk in Keplerian rotation with hotter gas closer to the central star. We estimate the mass of the primary to be ~0.34 M ⊙ and discuss the implications for its evolutionary status.

Hydrogen Abundances in Metal Grains from the Hammadah Al Hamra (HaH) 237 Metal-rich Chondrite: A Test of the Nebular-Formation Theory

NASA Technical Reports Server (NTRS)

Lauretta, D. S.; Guan, Y.; Leshin, L. A.

2005-01-01

The Bencubbin-like (CB) chondrites are metal-rich, primitive meteorites [1,2]. Some of these chondrites (HaH 237, QUE 94411) contain compositionally zoned metal grains with near-chondritic bulk compositions. Thermodynamic modeling of the zoning patterns in these grains suggests that they were formed by condensation in a region of the solar nebula with enhanced dust/gas ratios and a total pressure of 10(exp -4) bars at temperatures between 1400 - 1500 K [3]. If these predictions are correct than the metal grains would have been exposed to abundant H2 gas, which comprises the bulk of nebular systems. Since Fe-based alloys can absorb significant quantities of H, metal grains formed in the solar nebula should contain measurable abundances of H.

CO-dark molecular gas at high redshift: very large H2 content and high pressure in a low-metallicity damped Lyman alpha system

NASA Astrophysics Data System (ADS)

Balashev, S. A.; Noterdaeme, P.; Rahmani, H.; Klimenko, V. V.; Ledoux, C.; Petitjean, P.; Srianand, R.; Ivanchik, A. V.; Varshalovich, D. A.

2017-09-01

We present a detailed analysis of an H2-rich, extremely strong intervening damped Ly α absorption system (DLA) at zabs = 2.786 towards the quasar J 0843+0221, observed with the Ultraviolet and Visual Echelle Spectrograph on the Very Large Telescope. The total column density of molecular (resp. atomic) hydrogen is log N(H2) = 21.21 ± 0.02 (resp. log N(H I) = 21.82 ± 0.11), making it to be the first case in quasar absorption line studies with H2 column density as high as what is seen in 13CO-selected clouds in the Milky Way. We find that this system has one of the lowest metallicity detected among H2-bearing DLAs, with [Zn/H] = -1.52^{+0.08}_{-0.10}. This can be the reason for the marked differences compared to systems with similar H2 column densities in the local Universe: (I) the kinetic temperature, T ˜ 120 K, derived from the J = 0, 1 H2 rotational levels is at least twice higher than expected; (II) there is little dust extinction with AV < 0.1; (III) no CO molecules are detected, putting a constraint on the XCO factor XCO > 2 × 1023 cm-2/(km s-1 K), in the very low metallicity gas. Low CO and high H2 contents indicate that this system represents 'CO-dark/faint' gas. We investigate the physical conditions in the H2-bearing gas using the fine-structure levels of C I, C II, Si II and the rotational levels of HD and H2. We find the number density to be about n ˜ 260-380 cm-3, implying a high thermal pressure of 3-5 × 104 cm-3 K. We further identify a trend of increasing pressure with increasing total hydrogen column density. This independently supports the suggestion that extremely strong DLAs (with log N(H) ˜22) probe high-z galaxies at low impact parameters.

The RealGas and RealGasH2O options of the TOUGH+ code for the simulation of coupled fluid and heat flow in tight/shale gas systems

EPA Science Inventory

We developed two new EOS additions to the TOUGH+ family of codes, the RealGasH2O and RealGas. The RealGasH2O EOS option describes the non-isothermal two-phase flow of water and a real gas mixture in gas reservoirs, with a particular focus in ultra-tight (such as tight-sand and sh...

Pyrolysis process for producing fuel gas

NASA Technical Reports Server (NTRS)

Serio, Michael A. (Inventor); Kroo, Erik (Inventor); Wojtowicz, Marek A. (Inventor); Suuberg, Eric M. (Inventor)

2007-01-01

Solid waste resource recovery in space is effected by pyrolysis processing, to produce light gases as the main products (CH.sub.4, H.sub.2, CO.sub.2, CO, H.sub.2O, NH.sub.3) and a reactive carbon-rich char as the main byproduct. Significant amounts of liquid products are formed under less severe pyrolysis conditions, and are cracked almost completely to gases as the temperature is raised. A primary pyrolysis model for the composite mixture is based on an existing model for whole biomass materials, and an artificial neural network models the changes in gas composition with the severity of pyrolysis conditions.

Bar quenching in gas-rich galaxies

NASA Astrophysics Data System (ADS)

Khoperskov, S.; Haywood, M.; Di Matteo, P.; Lehnert, M. D.; Combes, F.

2018-01-01

Galaxy surveys have suggested that rapid and sustained decrease in the star-formation rate (SFR), "quenching", in massive disk galaxies is frequently related to the presence of a bar. Optical and near-IR observations reveal that nearly 60% of disk galaxies in the local universe are barred, thus it is important to understand the relationship between bars and star formation in disk galaxies. Recent observational results imply that the Milky Way quenched about 9-10 Gyr ago, at the transition between the cessation of the growth of the kinematically hot, old, metal-poor thick disk and the kinematically colder, younger, and more metal-rich thin disk. Although perhaps coincidental, the quenching episode could also be related to the formation of the bar. Indeed the transfer of energy from the large-scale shear induced by the bar to increasing turbulent energy could stabilize the gaseous disk against wide-spread star formation and quench the galaxy. To explore the relation between bar formation and star formation in gas rich galaxies quantitatively, we simulated gas-rich disk isolated galaxies. Our simulations include prescriptions for star formation, stellar feedback, and for regulating the multi-phase interstellar medium. We find that the action of stellar bar efficiently quenches star formation, reducing the star-formation rate by a factor of ten in less than 1 Gyr. Analytical and self-consistent galaxy simulations with bars suggest that the action of the stellar bar increases the gas random motions within the co-rotation radius of the bar. Indeed, we detect an increase in the gas velocity dispersion up to 20-35 km s-1 at the end of the bar formation phase. The star-formation efficiency decreases rapidly, and in all of our models, the bar quenches the star formation in the galaxy. The star-formation efficiency is much lower in simulated barred compared to unbarred galaxies and more rapid bar formation implies more rapid quenching.

Effect of simethicone on lactulose-induced H2 production and gastrointestinal symptoms.

PubMed

Friis, H; Bodé, S; Rumessen, J J; Gudmand-Høyer, E

1991-01-01

The results of studies of the effect of simethicone on abdominal gas-related symptoms have been contradictory. In a randomized, double-blind cross-over study, 10 healthy volunteers were given 30 g lactulose and 600 mg simethicone or placebo. End-expiratory breath samples were collected and analyzed for H2 and gastrointestinal symptoms registered. There were no differences in biochemical parameters or symptom score between simethicone and placebo. In contrast to previous studies, we used a sufficiently large dose of lactulose to produce gastrointestinal symptoms, a higher dose of simethicone and placebo tablets containing the same additives as the simethicone tablets. There was no demonstrable effect of simethicone on symptoms or intestinal gas production caused by carbohydrate malabsorption.

Delayed addition of nitrogen-rich substrates during composting of municipal waste: Effects on nitrogen loss, greenhouse gas emissions and compost stability.

PubMed

Nigussie, Abebe; Bruun, Sander; Kuyper, Thomas W; de Neergaard, Andreas

2017-01-01

Municipal waste is usually composted with an N-rich substrate, such as manure, to increase the N content of the product. This means that a significant amount of nitrogen can be lost during composting. The objectives of this study were (i) to investigate the effect of split addition of a nitrogen-rich substrate (poultry manure) on nitrogen losses and greenhouse gas emissions during composting and to link this effect to different bulking agents (coffee husks and sawdust), and (ii) to assess the effect of split addition of a nitrogen-rich substrate on compost stability and sanitisation. The results showed that split addition of the nitrogen-rich substrate reduced nitrogen losses by 9% when sawdust was used and 20% when coffee husks were used as the bulking agent. Depending on the bulking agent used, split addition increased cumulative N 2 O emissions by 400-600% compared to single addition. In contrast, single addition increased methane emissions by up to 50% compared to split addition of the substrate. Hence, the timing of the addition of the N-rich substrate had only a marginal effect on total non-CO 2 greenhouse gas emissions. Split addition of the N-rich substrate resulted in compost that was just as stable and effective at completely eradicating weed seeds as single addition. These findings therefore show that split addition of a nitrogen-rich substrate could be an option for increasing the fertilising value of municipal waste compost without having a significant effect on total greenhouse gas emissions or compost stability. Copyright © 2016 Elsevier Ltd. All rights reserved.

Production of H2 from aluminium/water reaction and its potential for CO2 methanation

NASA Astrophysics Data System (ADS)

Khai Phung, Khor; Sethupathi, Sumathi; Siang Piao, Chai

2018-04-01

Carbon dioxide (CO2) is a natural gas that presents in excess in the atmosphere. Owing to its ability to cause global warming, capturing and conversion of CO2 have attracted much attention worldwide. CO2 methanation using hydrogen (H2) is believed to be a promising route for CO2 removal. In the present work, H2 is produced using aluminum-water reaction and tested for its ability to convert CO2 to methane (CH4). Different type of water i.e. tap water, distilled water, deionized water and ultrapure water, concentration of sodium hydroxide (NaOH) (0.2 M to 1.0 M) and particle size of aluminum (45 m to 500 μm) were varied as parameter study. It was found that the highest yield of H2 was obtained using distilled water, 1.0 M of NaOH and 45μm particle size of aluminium. However, the highest yield of methane was achieved using a moderate and progressive H2 production (distilled water, 0.6 M of NaOH and 45 μm particle size of aluminium) which allowed sufficient time for H2 to react with CO2. It was concluded that 1130 ml of H2 can produce about 560 ppm of CH4 within 25 min of batch reaction using nickel catalyst.

Serpentinization and the Formation of H2 and CH4 on Celestial Bodies (Planets, Moons, Comets)

PubMed Central

Oze, C.; Mousis, O.; Waite, J.H.; Guilbert-Lepoutre, A.

2015-01-01

Abstract Serpentinization involves the hydrolysis and transformation of primary ferromagnesian minerals such as olivine ((Mg,Fe)2SiO4) and pyroxenes ((Mg,Fe)SiO3) to produce H2-rich fluids and a variety of secondary minerals over a wide range of environmental conditions. The continual and elevated production of H2 is capable of reducing carbon, thus initiating an inorganic pathway to produce organic compounds. The production of H2 and H2-dependent CH4 in serpentinization systems has received significant interdisciplinary interest, especially with regard to the abiotic synthesis of organic compounds and the origins and maintenance of life in Earth's lithosphere and elsewhere in the Universe. Here, serpentinization with an emphasis on the formation of H2 and CH4 are reviewed within the context of the mineralogy, temperature/pressure, and fluid/gas chemistry present in planetary environments. Whether deep in Earth's interior or in Kuiper Belt Objects in space, serpentinization is a feasible process to invoke as a means of producing astrobiologically indispensable H2 capable of reducing carbon to organic compounds. Key Words: Serpentinization—Fischer-Tropsch-type synthesis—Hydrogen formation—Methane formation—Ultramafic rocks. Astrobiology 15, 587–600. PMID:26154779

Effect of simulated coal-derived gas composition on H{sub 2}S poisoning behavior evaluated using a disaggregation scheme

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

Li, T.S.; Miao, H.; Chen, T.

2009-07-01

H{sub 2}S poisoning is an important issue for solid oxide fuel cells (SOFCs) operated with syngas. The effect of simulated coal-derived gas composition on H{sub 2}S poisoning behavior was evaluated using a disaggregation scheme where the influence of H{sub 2} content was determined separately using a typical anode-supported SOFC operated with a N2/H{sub 2} mixture gas, while the effect of other compositions (CO, CO{sub 2}, and H{sub 2}O) was investigated with simulated coal-derived gas having constant H{sub 2} and CO flow rates balanced by a H{sub 2}/N2 mixture gas (83% H{sub 2} and 17% N2). The results indicated that themore » extent of H{sub 2}S poisoning was not pertinent to H{sub 2} content when the cell was tested galvanostatically with a current density of 0.3 A/cm{sup 2} at 800{sup o}C using a N2/H{sub 2} mixture gas containing 10 ppm H{sub 2}S, and the H{sub 2}S poisoning impact can be completely removed by switching to sulfur-free gas. The CO, CO{sub 2}, and high water vapor content aggravated the H{sub 2}S poisoning effect, and the performance was almost irrecoverable when the cell was tested with a 35% H{sub 2}-46% CO-16% N2-3% H{sub 2}O mixture gas containing 12.5 ppm H{sub 2}S. However, the introduction of 10% CO{sub 2} and an increase in H{sub 2}O content from 3 to 10% in the mixture gas can promote the performance recoverability to a larger extent.« less

Simultaneous high efficiency capture of CO.sub.2 and H.sub.2S from pressurized gas

DOEpatents

Gal, Eli; Krishnan, Gopala N.; Jayaweera, Indira S.

2016-10-11

Low-cost and energy-efficient CO.sub.2 and H.sub.2S capture is provided obtaining greater than 99.9% capture efficiency from pressurized gas. The acid species are captured in an ammonia solution, which is then regenerated by stripping the absorbed species. The solution can capture as much as 330 grams of CO.sub.2 and H.sub.2S per 1000 gram of water and when regenerated it produces pure pressurized acid gas containing more than 99.7% CO.sub.2 and H2S. The absorption of the acid species is accomplished in two absorbers in-series, each having multiple stages. More than 95% of the acid species are captured in the first absorber and the balance is captured in the second absorber to below 10 ppm concentration in the outlet gas. The two absorbers operate at temperatures ranging from 20-70 degrees Celsius. The two absorbers and the main stripper of the alkaline solution operate at similar pressures ranging from 5-200 bara.

Conversion of H2 and CO2 to CH4 and acetate in fed-batch biogas reactors by mixed biogas community: a novel route for the power-to-gas concept.

PubMed

Szuhaj, Márk; Ács, Norbert; Tengölics, Roland; Bodor, Attila; Rákhely, Gábor; Kovács, Kornél L; Bagi, Zoltán

2016-01-01

Applications of the power-to-gas principle for the handling of surplus renewable electricity have been proposed. The feasibility of using hydrogenotrophic methanogens as CH4 generating catalysts has been demonstrated. Laboratory and scale-up experiments have corroborated the benefits of the CO2 mitigation via biotechnological conversion of H2 and CO2 to CH4. A major bottleneck in the process is the gas-liquid mass transfer of H2. Fed-batch reactor configuration was tested at mesophilic temperature in laboratory experiments in order to improve the contact time and H2 mass transfer between the gas and liquid phases. Effluent from an industrial biogas facility served as biocatalyst. The bicarbonate content of the effluent was depleted after some time, but the addition of stoichiometric CO2 sustained H2 conversion for an extended period of time and prevented a pH shift. The microbial community generated biogas from the added α-cellulose substrate with concomitant H2 conversion, but the organic substrate did not facilitate H2 consumption. Fed-batch operational mode allowed a fourfold increase in volumetric H2 load and a 6.5-fold augmentation of the CH4 formation rate relative to the CSTR reactor configuration. Acetate was the major by-product of the reaction. Fed-batch reactors significantly improve the efficiency of the biological power-to-gas process. Besides their storage function, biogas fermentation effluent reservoirs can serve as large-scale bio CH4 reactors. On the basis of this recognition, a novel concept is proposed, which merges biogas technology with other means of renewable electricity production for improved efficiency and sustainability.

A Novel Study of Methane-Rich Gas Reforming to Syngas and Its Kinetics over Semicoke Catalyst

PubMed Central

Zhang, Guojie; Su, Aiting; Qu, Jiangwen; Du, Yannian

2014-01-01

A small-size gasification unit is improved through process optimization to simulate industrial United Gas Improvement Company gasification. It finds that the reaction temperature has important impacts on semicoke catalyzed methane gas mixture. The addition of water vapor can enhance the catalytic activity of reforming, which is due to the fact that addition of water vapor not only removes carbon deposit produced in the reforming and gasification reaction processes, but also participates in gasification reaction with semicoke to generate some active oxygen-containing functional groups. The active oxygen-containing functional groups provide active sites for carbon dioxide reforming of methane, promoting the reforming reaction. It also finds that the addition of different proportions of methane-rich gas can yield synthesis gas with different H2/CO ratio. The kinetics study shows that the semicoke can reduce the activation energy of the reforming reaction and promote the occurrence of the reforming reaction. The kinetics model of methane reforming under the conditions of steam gasification over semicoke is as follows: k-=5.02×103·pCH40.71·pH20.26·exp(−74200/RT). PMID:24959620

Gas-phase hydrogen atom abstraction reactions of S- with H2, CH4, and C2H6

NASA Astrophysics Data System (ADS)

Angel, Laurence A.; Dogbevia, Moses K.; Rempala, Katarzyna M.; Ervin, Kent M.

2003-11-01

Reaction cross sections, product axial velocity distributions, and potential energy surfaces are presented for the hydrogen atom abstraction reactions S-+RH→R+HS- (R=H, CH3, C2H5) as a function of collision energy. The observed threshold energy, E0, for S-+H2→H+HS- agrees with the reaction endothermicity, ΔrH0. At low collision energies, the H+HS- products exhibit symmetric, low-recoil-velocity scattering, consistent with statistical reaction behavior. The S-+CH4→CH3+HS- and S-+C2H6→C2H5+HS reactions, in contrast, show large excess threshold energies when compared to ΔrH0. The excess energies are partly explained by a potential energy barrier separating products from reactants. However, additional dynamical constraints must account for more than half of the excess threshold energy. The observed behavior seems to be general for collisional activation of anion-molecule reactions that proceed through a tight, late transition state. For RH=CH4 and C2H6, the HS- velocity distributions show anisotropic backward scattering at low collision energies indicating small impact parameters and a direct rebound reaction mechanism. At higher collision energies, there is a transition to HS- forward scattering and high velocities consistent with grazing collisions and a stripping mechanism.

Scalable fabrication of SnO2 thin films sensitized with CuO islands for enhanced H2S gas sensing performance

NASA Astrophysics Data System (ADS)

Van Toan, Nguyen; Chien, Nguyen Viet; Van Duy, Nguyen; Vuong, Dang Duc; Lam, Nguyen Huu; Hoa, Nguyen Duc; Van Hieu, Nguyen; Chien, Nguyen Duc

2015-01-01

The detection of H2S, an important gaseous molecule that has been recently marked as a highly toxic environmental pollutant, has attracted increasing attention. We fabricate a wafer-scale SnO2 thin film sensitized with CuO islands using microelectronic technology for the improved detection of the highly toxic H2S gas. The SnO2-CuO island sensor exhibits significantly enhanced H2S gas response and reduced operating temperature. The thickness of CuO islands strongly influences H2S sensing characteristics, and the highest H2S gas response is observed with 20 nm-thick CuO islands. The response value (Ra/Rg) of the SnO2-CuO island sensor to 5 ppm H2S is as high as 128 at 200 °C and increases nearly 55-fold compared with that of the bare SnO2 thin film sensor. Meanwhile, the response of the SnO2-CuO island sensor to H2 (250 ppm), NH3 (250 ppm), CO (250 ppm), and LPG (1000 ppm) are low (1.3-2.5). The enhanced gas response and selectivity of the SnO2-CuO island sensor to H2S gas is explained by the sensitizing effect of CuO islands and the extension of electron depletion regions because of the formation of p-n junctions.

Online analysis of H2S and SO2 via advanced mid-infrared gas sensors.

PubMed

Petruci, João Flavio da Silveira; Wilk, Andreas; Cardoso, Arnaldo Alves; Mizaikoff, Boris

2015-10-06

Volatile sulfur compounds (VSCs) are among the most prevalent emitted pollutants in urban and rural atmospheres. Mainly because of the versatility of sulfur regarding its oxidation state (2- to 6+), VSCs are present in a wide variety of redox-environments, concentration levels, and molar ratios. Among the VSCs, hydrogen sulfide and sulfur dioxide are considered most relevant and have simultaneously been detected within naturally and anthropogenically caused emission events (e.g., volcano emissions, food production and industries, coal pyrolysis, and various biological activities). Next to their presence as pollutants, changes within their molar ratio may also indicate natural anomalies. Prior to analysis, H2S- and SO2-containing samples are usually preconcentrated via solid sorbents and are then detected by gas chromatographic techniques. However, such analytical strategies may be of limited selectivity, and the dimensions and operation modalities of the involved instruments prevent routine field usage. In this contribution, we therefore describe an innovative portable mid-infrared chemical sensor for simultaneously determining and quantifying gaseous H2S and SO2 via coupling a substrate-integrated hollow waveguides (iHWG) serving as a highly miniaturized mid-infrared photon conduit and gas cell with a custom-made preconcentration tube and an in-line UV-converter device. Both species were collected onto a solid sorbent within the preconcentrator and then released by thermal desorption into the UV-device. Hydrogen sulfide is detected by UV-assisted quantitative conversion of the rather weak IR-absorber H2S into SO2, which provides a significantly more pronounced and distinctively detectable rovibrational signature. Modulation of the UV-device system (i.e., UV-lamp on/off) enables discriminating between SO2 generated from H2S conversion and abundant SO2 signals. After optimization of the operational parameters, calibrations in the range of 0.75-10 ppmv with a limit

Production of methane-rich syngas from hydrocarbon fuels using multi-functional catalyst/capture agent

DOEpatents

Siefert, Nicholas S; Shekhawat, Dushyant; Berry, David A; Surdoval, Wayne A

2014-12-30

The disclosure provides a gasification process for the production of a methane-rich syngas at temperatures exceeding 700.degree. C. through the use of an alkali hydroxide MOH, using a gasification mixture comprised of at least 0.25 moles and less than 2 moles of water for each mole of carbon, and at least 0.15 moles and less than 2 moles of alkali hydroxide MOH for each mole of carbon. These relative amounts allow the production of a methane-rich syngas at temperatures exceeding 700.degree. C. by enabling a series of reactions which generate H.sub.2 and CH.sub.4, and mitigate the reforming of methane. The process provides a methane-rich syngas comprised of roughly 20% (dry molar percentage) CH.sub.4 at temperatures above 700.degree. C., and may effectively operate within an IGFC cycle at reactor temperatures between 700-900.degree. C. and pressures in excess of 10 atmospheres.

Recent observations of interstellar molecules - Detection of CCO and a limit on H2C3O

NASA Technical Reports Server (NTRS)

Brown, R. D.; Cragg, D. M.; Godfrey, P. D.; Irvine, W. M.; Mcgonagle, D.; Ohishi, M.

1992-01-01

In order to test gas-phase reaction schemes for the production of small oxides of carbon in cold, dense interstellar clouds, we have searched for the radical CCO and for propadienone (H2C3O) in Taurus Molecular Cloud 1, a nearby cloud which exhibits a rich organic chemistry. The radical CCO has been detected with a fractional abundance some two orders of magnitude less than that of CCS, about one order of magnitude less than that of H2CCO, and slightly less than that of C3O. An upper limit has been obtained on the abundance of propadienone which is slightly less than that of its isomer propynal (HC2CHO).

Gas41 links histone acetylation to H2A.Z deposition and maintenance of embryonic stem cell identity.

PubMed

Hsu, Chih-Chao; Zhao, Dan; Shi, Jiejun; Peng, Danni; Guan, Haipeng; Li, Yuanyuan; Huang, Yaling; Wen, Hong; Li, Wei; Li, Haitao; Shi, Xiaobing

2018-01-01

The histone variant H2A.Z is essential for maintaining embryonic stem cell (ESC) identity in part by keeping developmental genes in a poised bivalent state. However, how H2A.Z is deposited into the bivalent domains remains unknown. In mammals, two chromatin remodeling complexes, Tip60/p400 and SRCAP, exchange the canonical histone H2A for H2A.Z in the chromatin. Here we show that Glioma Amplified Sequence 41 (Gas41), a shared subunit of the two H2A.Z-depositing complexes, functions as a reader of histone lysine acetylation and recruits Tip60/p400 and SRCAP to deposit H2A.Z into specific chromatin regions including bivalent domains. The YEATS domain of Gas41 bound to acetylated histone H3K27 and H3K14 both in vitro and in cells. The crystal structure of the Gas41 YEATS domain in complex with the H3K27ac peptide revealed that, similar to the AF9 and ENL YEATS domains, Gas41 YEATS forms a serine-lined aromatic cage for acetyllysine recognition. Consistently, mutations in the aromatic residues of the Gas41 YEATS domain abrogated the interaction. In mouse ESCs, knockdown of Gas41 led to flattened morphology of ESC colonies, as the result of derepression of differentiation genes. Importantly, the abnormal morphology was rescued by expressing wild-type Gas41, but not the YEATS domain mutated counterpart that does not recognize histone acetylation. Mechanically, we found that Gas41 depletion led to reduction of H2A.Z levels and a concomitant reduction of H3K27me3 levels on bivalent domains. Together, our study reveals an essential role of the Gas41 YEATS domain in linking histone acetylation to H2A.Z deposition and maintenance of ESC identity.

Effectiveness and reaction networks of H2O2 vapor with NH3 gas for decontamination of the toxic warfare nerve agent, VX on a solid surface.

PubMed

Gon Ryu, Sam; Wan Lee, Hae

2015-01-01

The nerve agent, O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX) must be promptly eliminated following its release into the environment because it is extremely toxic, can cause death within a few minutes after exposure, acts through direct skin contact as well as inhalation, and persists in the environment for several weeks after release. A mixture of hydrogen peroxide vapor and ammonia gas was examined as a decontaminant for the removal of VX on solid surfaces at ambient temperature, and the reaction products were analyzed by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance spectrometry (NMR). All the VX on glass wool filter disks was found to be eliminated after 2 h of exposure to the decontaminant mixtures, and the primary decomposition product was determined to be non-toxic ethyl methylphosphonic acid (EMPA); no toxic S-[2-(diisopropylamino)ethyl] methylphosphonothioic acid (EA-2192), which is usually produced in traditional basic hydrolysis systems, was found to be formed. However, other by-products, such as toxic O-ethyl S-vinyl methylphosphonothioate and (2-diisopropylaminoethyl) vinyl disulfide, were detected up to 150 min of exposure to the decontaminant mixture; these by-products disappeared after 3 h. The two detected vinyl byproducts were identified first in this study with the decontamination system of liquid VX on solid surfaces using a mixture of hydrogen peroxide vapor and ammonia gas. The detailed decontamination reaction networks of VX on solid surfaces produced by the mixture of hydrogen peroxide vapor and ammonia gas were suggested based on the reaction products. These findings suggest that the mixture of hydrogen peroxide vapor and ammonia gas investigated in this study is an efficient decontaminant mixture for the removal of VX on solid surfaces at ambient temperature despite the formation of a toxic by-product in the reaction process.

Optimization of operating parameters for gas-phase photocatalytic splitting of H2S by novel vermiculate packed tubular reactor.

PubMed

Preethi, V; Kanmani, S

2016-10-01

Hydrogen production by gas-phase photocatalytic splitting of Hydrogen Sulphide (H2S) was investigated on four semiconductor photocatalysts including CuGa1.6Fe0.4O2, ZnFe2O3, (CdS + ZnS)/Fe2O3 and Ce/TiO2. The CdS and ZnS coated core shell particles (CdS + ZnS)/Fe2O3 shows the highest rate of hydrogen (H2) production under optimized conditions. Packed bed tubular reactor was used to study the performance of prepared photocatalysts. Selection of the best packing material is a key for maximum removal efficiency. Cheap, lightweight and easily adsorbing vermiculate materials were used as a novel packing material and were found to be effective in splitting H2S. Effect of various operating parameters like flow rate, sulphide concentration, catalyst dosage, light irradiation were tested and optimized for maximum H2 conversion of 92% from industrial waste H2S. Copyright © 2016 Elsevier Ltd. All rights reserved.

Molecular hydrogen consumption in the human body during the inhalation of hydrogen gas.

PubMed

Shimouchi, Akito; Nose, Kazutoshi; Mizukami, Tomoe; Che, Dock-Chil; Shirai, Mikiyasu

2013-01-01

Inhaling or ingesting hydrogen (H2) gas improves oxidative stress-induced damage in animal models and humans. We previously reported that H2 was consumed throughout the human body after the ingestion of H2-rich water and that the H2 consumption rate ([Formula: see text]) was 1.0 μmol/min/m(2) body surface area. To confirm this result, we evaluated [Formula: see text]during the inhalation of low levels of H2 gas. After measuring the baseline levels of exhaled H2 during room air breathing via a one-way valve and a mouthpiece, the subject breathed low levels (160 ppm) of H2 gas mixed with purified artificial air. The H2 levels of their inspired and expired breath were measured by gas chromatography using a semiconductor sensor. [Formula: see text] was calculated using a ventilation equation derived from the inspired and expired concentrations of O2/CO2/H2, and the expired minute ventilation volume, which was measured with a respiromonitor. As a result, [Formula: see text] was found to be approximately 0.7 μmol/min/m(2)BSA, which was compatible with the findings we obtained using H2-rich water. [Formula: see text] varied markedly when pretreatment fasting to reduce colonic fermentation was not employed, i.e., when the subject's baseline breath hydrogen level was 10 ppm or greater. Our H2 inhalation method might be useful for the noninvasive monitoring of hydroxyl radical production in the human body.

Incineration of biomass and utilization of product gas as a CO_2 source for crop production in closed systems: gas quality and phytotoxicity

NASA Astrophysics Data System (ADS)

Bubenheim, D. L.; Patterson, M.; Wignarajah, K.; Flynn, M.

1997-01-01

This study addressed the recycle of carbon from inedible biomass to CO_2 for utilization in crop production. Earlier work identified incineration as an attractive approach to resource recovery from solid wastes because the products are well segregated. Given the effective separation of carbon into the gaseous product stream from the incinerator in the form of CO_2 we captured the gaseous stream produced during incineration of wheat inedible biomass and utilized it as the CO_2 source for crop production. Injection rate was based on maintenance of CO_2 concentration in the growing environment. The crop grown in the closed system was lettuce. Carbon was primarily in the form of CO_2 in the incinerator product gas with less than 8% of carbon compounds appearing as CO. Nitrogen oxides and organic compounds such as toluene, xylene, and benzene were present in the product gas at lower concentrations (<4 mumol mol^-1) sulfur containing compounds were below the detection limits. Direct utilization of the gaseous product of the incinerator as the CO_2 source was toxic to lettuce grown in a closed chamber. Net photosynthetic rates of the crop was suppressed more than 50% and visual injury symptoms were visible within 3 days of the introduction of the incinerator gas. Even the removal of the incinerator gas after two days of crop exposure and replacement with pure CO_2 did not eliminate the toxic effects. Both organic and inorganic components of the incinerator gas are candidates for the toxin.

Incineration of biomass and utilization of product gas as a CO2 source for crop production in closed systems: gas quality and phytotoxicity.

PubMed

Bubenheim, D L; Patterson, M; Wignarajah, K; Flynn, M

1997-01-01

This study addressed the recycle of carbon from inedible biomass to CO2 for utilization in crop production. Earlier work identified incineration as an attractive approach to resource recovery from solid wastes because the products are well segregated. Given the effective separation of carbon into the gaseous product stream from the incinerator in the form of CO2 we captured the gaseous stream produced during incineration of wheat inedible biomass and utilized it as the CO2 source for crop production. Injection rate was based on maintenance of CO2 concentration in the growing environment. The crop grown in the closed system was lettuce. Carbon was primarily in the form of CO2 in the incinerator product gas with less than 8% of carbon compounds appearing as CO. Nitrogen oxides and organic compounds such as toluene, xylene, and benzene were present in the product gas at lower concentrations (< 4 micromol mol-1); sulfur containing compounds were below the detection limits. Direct utilization of the gaseous product of the incinerator as the CO2 source was toxic to lettuce grown in a closed chamber. Net photosynthetic rates of the crop was suppressed more than 50% and visual injury symptoms were visible within 3 days of the introduction of the incinerator gas. Even the removal of the incinerator gas alter two days of crop exposure and replacement with pure CO2 did not eliminate the toxic effects. Both organic and inorganic components of the incinerator gas are candidates for the toxin.

Incineration of biomass and utilization of product gas as a CO2 source for crop production in closed systems: gas quality and phytotoxicity

NASA Astrophysics Data System (ADS)

1997-01-01

This study addressed the recycle of carbon from inedible biomass to CO2 for utilization in crop production. Earlier work identified incineration as an attractive approach to resource recovery from solid wastes because the products are well segregated. Given the effective separation of carbon into the gaseous product stream from the incinerator in the form of CO2 we captured the gaseous stream produced during incineration of wheat inedible biomass and utilized it as the CO2 source for crop production. Injection rate was based on maintenance of CO2 concentration in the growing environment. The crop grown in the closed system was lettuce. Carbon was primarily in the form of CO2 in the incinerator product gas with less than 8% of carbon compounds appearing as CO. Nitrogen oxides and organic compounds such as toluene, xylene, and benzene were present in the product gas at lower concentrations (<4 μmol mol-1) sulfur containing compounds were below the detection limits. Direct utilization of the gaseous product of the incinerator as the CO2 source was toxic to lettuce grown in a closed chamber. Net photosynthetic rates of the crop was suppressed more than 50% and visual injury symptoms were visible within 3 days of the introduction of the incinerator gas. Even the removal of the incinerator gas after two days of crop exposure and replacement with pure CO2 did not eliminate the toxic effects. Both organic and inorganic components of the incinerator gas are candidates for the toxin.

Gas production in anaerobic dark-fermentation processes from agriculture solid waste

NASA Astrophysics Data System (ADS)

Sriwuryandari, L.; Priantoro, E. A.; Sintawardani, N.

2017-03-01

Approximately, Bandung produces agricultural solid waste of 1549 ton/day. This wastes consist of wet-organic matter and can be used for bio-gas production. The research aimed to apply the available agricultural solid waste for bio-hydrogen. Biogas production was done by a serial of batches anaerobic fermentation using mix-culture bacteria as the active microorganism. Fermentation was carried out inside a 30 L bioreactor at room temperature. The analyzed parameters were of pH, total gas, temperature, and COD. Result showed that from 3 kg/day of organic wastes, various total gases of O2, CH4, H2, CO2, and CnHn,O2 was produced.

Cyclic Oxidation Behavior and Durability of ODS-FeCrAl Alloys in H2O and CO2 rich environments

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

Dryepondt, Sebastien N; Pint, Bruce A

Cyclic oxidation testing was conducted at 1200 C in O2, dry air and in atmospheres rich in H2O and/or CO2 to simulate combustion environments. The oxidation rates were significantly higher in air + 10%H2O and a mixture of O2-buffered 50%H2O-50%CO2, leading to shorter times to breakaway oxidation. Curve fitting using the COSP cyclic oxidation program confirmed that the presence of H2O results in an increase of the alumina spallation rate. The use of specimen mass gain modeling associated with the characterization of pre-oxidized specimens and in particular the determination of the remaining Al content after exposure, will allow to accuratelymore » estimate the durability of oxide dispersion-strengthened (ODS) FeCrAl alloys in combustion environments.« less

Beneficial synergetic effect on gas production during co-pyrolysis of sewage sludge and biomass in a vacuum reactor.

PubMed

Zhang, Weijiang; Yuan, Chengyong; Xu, Jiao; Yang, Xiao

2015-05-01

A vacuum fixed bed reactor was used to pyrolyze sewage sludge, biomass (rice husk) and their blend under high temperature (900°C). Pyrolytic products were kept in the vacuum reactor during the whole pyrolysis process, guaranteeing a long contact time (more than 2h) for their interactions. Remarkable synergetic effect on gas production was observed. Gas yield of blend fuel was evidently higher than that of both parent fuels. The syngas (CO and H2) content and gas lower heating value (LHV) were obviously improved as well. It was highly possible that sewage sludge provided more CO2 and H2O during co-pyrolysis, promoting intense CO2-char and H2O-char gasification, which benefited the increase of gas yield and lower heating value. The beneficial synergetic effect, as a result, made this method a feasible one for gas production. Copyright © 2015. Published by Elsevier Ltd.

The Effect of N2 Photoabsorption Cross Section Resolution on C2H6 Production in Titan’s Ionosphere

NASA Astrophysics Data System (ADS)

Luspay-Kuti, Adrienn; Mandt, Kathleen E.; Plessis, Sylvain; Greathouse, Thomas K.

2014-11-01

Titan’s rich organic chemistry begins with the photochemistry of only two molecules: N2 and CH4. The details on how higher-order hydrocarbons and nitriles are formed from these molecules have key implications for both the structure and evolution of Titan’s atmosphere, and for its surface-atmosphere interactions. Of high importance is the production of C2H6, which is a sink for CH4, and a main component in the polar lakes. Results of photochemical models, though, may be sensitive to the choice of input parameters, such as the N2 photoabsorption cross section resolution, as previously shown for nitrogen (Liang et al. (2007) ApJL 664, 115-118), and CH4 (Lavvas et al. (2011) Icarus 213, 233-251). Here we investigate the possibility of the same effect on the production rates of C2H6. We modeled production and loss rates, as well as mixing ratio and density profiles between an altitude of 600 and 1600 km for low and high resolution N2 cross sections via a coupled ion-neutral-thermal model (De La Haye et al. (2008) Icarus 197, 110-136; Mandt et al. (2012) JGR 117, E10006). Our results show a clear impact of photoabsorption cross section resolution used on all neutral and ion species contributing to C2H6 production. The magnitude of the influence varies amongst species. Ethane production profiles exhibit a significant increase with better resolution; a factor of 1.2 between 750 and 950 km, and a factor of 1.1 in the total column-integrated production rate. These values are lower limits, as additional reactions involving C2H5 not included in the model may also contribute to the production rates. The clear effect on C2H6 (which is not a parent molecule, nor does it bear nitrogen) may have important implications for other molecules in Titan’s atmosphere as well. The possible non-negligible impact of an isotope of nitrogen may argue for the inclusion of isotopes in photochemical models. For future analysis, development of a more efficient and streamlined model called

CO2 splitting by H2O to CO and O2 under UV light in TiMCM-41silicate sieve

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

Lin, Wenyong; Han, Hongxian; Frei, Heinz

2004-04-06

The 266 nm light-induced reaction of CO{sub 2} and H{sub 2}O gas mixtures (including isotopic modifications {sup 13}CO{sub 2}, C{sup 18}O{sub 2}, and D{sub 2}O) in framework TiMCM-41 silicate sieve was monitored by in-situ FT-IR spectroscopy at room temperature. Carbon monoxide gas was observed as the sole product by infrared, and the growth was found to depend linearly on the photolysis laser power. H{sub 2}O was confirmed as stoichiometric electron donor. The work establishes CO as the single photon, 2-electron transfer product of CO{sub 2} photoreduction by H{sub 2}O at framework Ti centers for the first time. O{sub 2} wasmore » detected as co-product by mass spectrometric analysis of the photolysis gas mixture. These results are explained by single UV photon-induced splitting of CO{sub 2} by H{sub 2}O to CO and surface OH radical.« less

Quick and Selective Dual Mode Detection of H2S Gas by Mobile App Employing Silver Nanorods Array.

PubMed

Gahlaut, Shashank Kumar; Yadav, Kavita; Sharan, Chandrashekhar; Singh, Jitendra Pratap

2017-12-19

Hydrogen sulfide (H 2 S) is a hazardous gas, which not only harms living beings but also poses a significant risk to damage materials placed in culture and art museums, due to its corrosive nature. We demonstrate a novel approach for selective rapid detection of H 2 S gas using silver nanorods (AgNRs) arrays on glass substrates at ambient conditions. The arrays were prepared by glancing angle deposition method. The colorimetric and water wetting properties of as-fabricated arrays were found to be highly sensitive toward the sulfurization, in the presence of H 2 S gas with a minimal concentration in ppm range. The performance of AgNRs as H 2 S gas sensor is investigated by its sensing ability of 5 ppm of gas with an exposure time of only 30 s. We have developed an android-based mobile app to monitor real-time colorimetric detection of H 2 S. The wettability detection has been carried out by a mobile camera. A comparative analysis for different gases reveals the highest sensitivity and selectivity of the array AgNRs toward H 2 S. The rapid detection has also been demonstrated for H 2 S emission from aged wool fabric. Thus, high sensing ability of AgNRs toward H 2 S gas may have potential applications in health monitoring and art conservation.

Rare-gas-rich separates from carbonaceous chondrites

NASA Technical Reports Server (NTRS)

Reynolds, J. H.; Frick, U.; Neil, J. M.; Phinney, D. L.

1978-01-01

This paper describes an analysis of carbon-rich separates prepared by demineralization of colloidal fractions after disaggregation of bulk samples of the type C2 meteorites Murray, Murchison, and Cold Bokkeveld, as well as a methanol colloid extracted from acid-resistant residues of the Allende meteorite (type C3V) obtained by dissolution of most of the minerals in HCl and HF acids. The carbonaceous separates, or lAlates (a coined word designating colloids prepared sometimes before and sometimes after acid treatment), are characterized incompletely and with difficulty. A stepwise heating experiment on a Murray lAlate is discussed which revealed bimodal release of all noble gases, with similar patterns for Ar, Kr, and Xe. Chemical reactions are suggested as the likely mechanism for gas release. The results are shown to support the concept of a carbonaceous gas carrier uniformly present in meteorites of various types.

A feasibility study on the bioconversion of CO2 and H2 to biomethane by gas sparging through polymeric membranes.

PubMed

Díaz, I; Pérez, C; Alfaro, N; Fdz-Polanco, F

2015-06-01

In this study, the potential of a pilot hollow-fiber membrane bioreactor for the conversion of H2 and CO2 to CH4 was evaluated. The system transformed 95% of H2 and CO2 fed at a maximum loading rate of 40.2 [Formula: see text] and produced 0.22m(3) of CH4 per m(3) of H2 fed at thermophilic conditions. H2 mass transfer to the liquid phase was identified as the limiting step for the conversion, and kLa values of 430h(-1) were reached in the bioreactor by sparging gas through the membrane module. A simulation showed that the bioreactor could upgrade biogas at a rate of 25m(3)/mR(3)d, increasing the CH4 concentration from 60 to 95%v. This proof-of-concept study verified that gas sparging through a membrane module can efficiently transfer H2 from gas to liquid phase and that the conversion of H2 and CO2 to biomethane is feasible on a pilot scale at noteworthy load rates. Copyright © 2015 Elsevier Ltd. All rights reserved.

Production of neutron-rich nuclei approaching r-process by gamma-induced fission of 238U at ELI-NP

NASA Astrophysics Data System (ADS)

Mei, Bo; Balabanski, Dimiter; Constantin, Paul; Anh Le, Tuan; Viet Cuong, Phan

2018-05-01

The investigation of neutron-rich exotic nuclei is crucial not only for nuclear physics but also for nuclear astrophysics. Experimentally, only few neutron-rich nuclei near the stability have been studied, however, most neutron-rich nuclei have not been measured due to their small production cross sections as well as short half-lives. At ELI-NP, gamma beams with high intensities will open new opportunities to investigate very neutron-rich fragments produced by photofission of 238U targets in a gas cell. Based on some simulations, a novel gas cell has been designed to produce, stop and extract 238U photofission fragments. The extraction time and efficiency of photofission fragments have been optimized by using SIMION simulations. According to these simulations, a high extraction efficiency and a short extraction time can be achieved for 238U photofission fragments in the gas cell, which will allow one to measure very neutron-rich fragments with short half-lives by using the IGISOL facility proposed at ELI-NP.

The CBM RICH detector

NASA Astrophysics Data System (ADS)

Adamczewski-Musch, J.; Akishin, P.; Becker, K.-H.; Belogurov, S.; Bendarouach, J.; Boldyreva, N.; Chernogorov, A.; Deveaux, C.; Dobyrn, V.; Dürr, M.; Eschke, J.; Förtsch, J.; Heep, J.; Höohne, C.; Kampert, K.-H.; Kochenda, L.; Kopfer, J.; Kravtsov, P.; Kres, I.; Lebedev, S.; Lebedeva, E.; Leonova, E.; Linev, S.; Mahmoud, T.; Michel, J.; Miftakhov, N.; Niebur, W.; Ovcharenko, E.; Pauly, C.; Pfeifer, D.; Querchfeld, S.; Rautenberg, J.; Reinecke, S.; Riabov, Y.; Roshchin, E.; Samsonov, V.; Tarasenkova, O.; Traxler, M.; Ugur, C.; Vznuzdaev, E.; Vznuzdaev, M.

2016-05-01

The CBM RICH detector will use CO2 as radiator gas, focussing glass mirrors with Al+MgF2 reflective and protective coating and Hamamatsu H12700 MAPMTs as photon detectors. The detector will serve for electron to pion separation up to momenta of 8 GeV/c and thus enable in CBM the measurement of electromagnetic radiation from the early and dense fireball in A+A collisions at SIS 100. In this article, the current status of the CBM RICH development will be presented including new measurements of the radiation hardness of the H12700 MAPMT and WLS coatings with p-terphenyl, the new concept for the readout electronics, and optimizations ongoing with respect to the mirror mount structure and overall geometry. Prior to the usage in CBM, part of the already ordered MAPMTs will be used to upgrade the HADES RICH detector for a new measurement campaign at SIS 18 from 2018-2020.

Pt-decorated GaN nanowires with significant improvement in H2 gas-sensing performance at room temperature.

PubMed

Abdullah, Q N; Yam, F K; Hassan, Z; Bououdina, M

2015-12-15

Superior sensitivity towards H2 gas was successfully achieved with Pt-decorated GaN nanowires (NWs) gas sensor. GaN NWs were fabricated via chemical vapor deposition (CVD) route. Morphology (field emission scanning electron microscopy and transmission electron microscopy) and crystal structure (high resolution X-ray diffraction) characterizations of the as-synthesized nanostructures demonstrated the formation of GaN NWs having a wurtzite structure, zigzaged shape and an average diameter of 30-166nm. The Pt-decorated GaN NWs sensor shows a high response of 250-2650% upon exposure to H2 gas concentration from 7 to 1000ppm respectively at room temperature (RT), and then increases to about 650-4100% when increasing the operating temperature up to 75°C. The gas-sensing measurements indicated that the Pt-decorated GaN NWs based sensor exhibited efficient detection of H2 at low concentration with excellent sensitivity, repeatability, and free hysteresis phenomena over a period of time of 100min. The large surface-to-volume ratio of GaN NWs and the catalytic activity of Pt metal are the most influential factors leading to the enhancement of H2 gas-sensing performances through the improvement of the interaction between the target molecules (H2) and the sensing NWs surface. The attractive low-cost, low power consumption and high-performance of the resultant decorated GaN NWs gas sensor assure their uppermost potential for H2 gas sensor working at low operating temperature. Copyright © 2015 Elsevier Inc. All rights reserved.

Impact of pH on hydrogen oxidizing redox processes in aquifers due to gas intrusions

NASA Astrophysics Data System (ADS)

Metzgen, Adrian; Berta, Marton; Dethlefsen, Frank; Ebert, Markus; Dahmke, Andreas

2017-04-01

Hydrogen production from excess energy and its storage can help increasing the efficiency of solar and wind in the energy mix. Therefore, hydrogen needs large-scale intermediate storage independent of the intended later use as hydrogen gas or as reactant to produce methane in the Sabatier process. A possible storage solution is using the geological subsurface such as caverns built in salt deposits or aquifers that are not used for drinking water production. However, underground storage of hydrogen gas potentially leads to accidental gas leakages into near-surface potable aquifers triggering subsequent geochemical processes. These leakages pose potential risks that are currently not sufficiently understood. To close this gap in knowledge, a high-pressure laboratory column system was used to simulate a hydrogen gas intrusion into a shallow aquifer. Water and sediment were gained from a sandy Pleistocene aquifer near Neumünster, Germany. In the first stage of the experiment, 100% hydrogen gas was used to simulate dissolved hydrogen concentrations between 800 and 4000 µM by varying pH2 between 2 and 15 bars. pH values rose to between 7.9 and 10.4, partly due to stripping CO2 from the groundwater used during H2 gas addition. In a second stage, the pH was regulated in a range of 6.7 to 7.9 by using a gas mixture of 99% H2 and 1% CO2 at 5 bars of total gas pressure. Observed processes included hydrogen oxidation, sulfate reduction, acetogenesis, formate production, and methanogenesis, which were independent of the hydrogen concentration. Hydrogen oxidation and sulfate reduction showed zeroth order reaction rates and rate constants (106 to 412 µM/h and 12 to 33 µM/h, respectively) in the pH range between 8 and 10. At pH levels between 7 and 8, both reactions started out faster near the column's inflow but then seemed limited towards the columns outflow, suggesting the dependence of sulfate reduction on the pH-value. Acetogenesis dominated the pH range between 8 and 10

Microchannel Reactor System Design & Demonstration For On-Site H2O2 Production by Controlled H2/O2 Reaction

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

Adeniyi Lawal

We successfully demonstrated an innovative hydrogen peroxide (H2O2) production concept which involved the development of flame- and explosion-resistant microchannel reactor system for energy efficient, cost-saving, on-site H2O2 production. We designed, fabricated, evaluated, and optimized a laboratory-scale microchannel reactor system for controlled direct combination of H2 and O2 in all proportions including explosive regime, at a low pressure and a low temperature to produce about 1.5 wt% H2O2 as proposed. In the second phase of the program, as a prelude to full-scale commercialization, we demonstrated our H2O2 production approach by ‘numbering up’ the channels in a multi-channel microreactor-based pilot plant tomore » produce 1 kg/h of H2O2 at 1.5 wt% as demanded by end-users of the developed technology. To our knowledge, we are the first group to accomplish this significant milestone. We identified the reaction pathways that comprise the process, and implemented rigorous mechanistic kinetic studies to obtain the kinetics of the three main dominant reactions. We are not aware of any such comprehensive kinetic studies for the direct combination process, either in a microreactor or any other reactor system. We showed that the mass transfer parameter in our microreactor system is several orders of magnitude higher than what obtains in the macroreactor, attesting to the superior performance of microreactor. A one-dimensional reactor model incorporating the kinetics information enabled us to clarify certain important aspects of the chemistry of the direct combination process as detailed in section 5 of this report. Also, through mathematical modeling and simulation using sophisticated and robust commercial software packages, we were able to elucidate the hydrodynamics of the complex multiphase flows that take place in the microchannel. In conjunction with the kinetics information, we were able to validate the experimental data. If fully implemented across the

Dopant-assisted negative photoionization Ion mobility spectrometry coupled with on-line cooling inlet for real-time monitoring H2S concentration in sewer gas.

PubMed

Peng, Liying; Jiang, Dandan; Wang, Zhenxin; Hua, Lei; Li, Haiyang

2016-06-01

Malodorous hydrogen sulfide (H2S) gas often exists in the sewer system and associates with the problems of releasing the dangerous odor to the atmosphere and causing sewer pipe to be corroded. A simple method is in demand for real-time measuring H2S level in the sewer gas. In this paper, an innovated method based on dopant-assisted negative photoionization ion mobility spectrometry (DANP-IMS) with on-line semiconductor cooling inlet was put forward and successfully applied for the real-time measurement of H2S in sewer gas. The influence of moisture was effectively reduced via an on-line cooling method and a non-equilibrium dilution with drift gas. The limits of quantitation for the H2S in ≥60% relative humidity air could be obtained at ≤79.0ng L(-1) with linear ranges of 129-2064ng L(-1). The H2S concentration in a sewer manhole was successfully determined while its product ions were identified by an ion-mobility time-of-fight mass spectrometry. Finally, the correlation between sewer H2S concentration and the daily routines and habits of residents was investigated through hourly or real-time monitoring the variation of sewer H2S in manholes, indicating the power of this DANP-IMS method in assessing the H2S concentration in sewer system. Copyright © 2016 Elsevier B.V. All rights reserved.

An experimental study of the fluid-melt partitioning of volatiles (H2O, CO2, S) during the degassing of ascending basalt

NASA Astrophysics Data System (ADS)

Le Gall, Nolwenn; Pichavant, Michel; Di Carlo, Ida; Scaillet, Bruno

2017-04-01

We performed decompression experiments to constrain the fluid-melt partitioning of volatiles (H2O, CO2, S) in ascending basalt magmas associated with violent eruptions. Experiments were conducted in an internally heated pressure vessel under oxidizing conditions (fO2: NNO+1.1) so that all sulphur occurs as sulfate (S6+) in the melt. Volatile-bearing (2.72 ± 0.02 wt% H2O, 1291 ± 85 ppm CO2, 1535 ± 369 ppm S) melts, prepared from Stromboli pumice, were synthesized at 1200°C and 200 MPa, decompressed between 150 and 25 MPa at constant rates of 39 and 78 kPa/s (or 1.5 and 3 m/s), and rapidly quenched. Run products were characterized both chemically (by IR spectroscopy and electron microprobe analysis) and texturally (by scanning electron microscopy), and then compared with Stromboli pumice products (glass inclusions, volcanic gases). In H2O-CO2-S-bearing basaltic melts, bubbles start to nucleate heterogeneously on Fe sulfides for supersaturation pressures ΔPHeN ≤ 1 MPa and to nucleate homogeneously for ΔPHoN < 50 MPa (ΔPHeN and ΔPHoN are the difference between the saturation pressure and the pressure at which heterogeneous and homogeneous bubble nucleation are observed, respectively). Bubble growth, coalescence and outgassing occur in addition to continuous bubble nucleation, which is sustained by the preservation of CO2 supersaturated melts during decompression. In addition to model the degassing behaviour of sulphur (and also of CO2 and H2O), our experiments aim to assist in the interpretation of geochemical observables. On the one hand, the volatile degassing trend recorded by Stromboli natural glasses (unsealed glass embayments) was closely experimentally simulated, with a coupled decrease of H2O and S whereas CO2 concentrations remain elevated. On the other hand, the experimental H2O/CO2 and CO2/SO2 fluid molar ratios, calculated by mass balance, both reproduced or closely approached the lower ranges of gas ratios measured at Stromboli for quiescent

A model-based understanding of solid-oxide electrolysis cells (SOECs) for syngas production by H2O/CO2 co-electrolysis

NASA Astrophysics Data System (ADS)

Menon, Vikram; Fu, Qingxi; Janardhanan, Vinod M.; Deutschmann, Olaf

2015-01-01

High temperature co-electrolysis of H2O and CO2 offers a promising route for syngas (H2, CO) production via efficient use of heat and electricity. The performance of a SOEC during co-electrolysis is investigated by focusing on the interactions between transport processes and electrochemical parameters. Electrochemistry at the three-phase boundary is modeled by a modified Butler-Volmer approach that considers H2O electrolysis and CO2 electrolysis, individually, as electrochemically active charge transfer pathways. The model is independent of the geometrical structure. A 42-step elementary heterogeneous reaction mechanism for the thermo-catalytic chemistry in the fuel electrode, the dusty gas model (DGM) to account for multi-component diffusion through porous media, and a plug flow model for flow through the channels are used in the model. Two sets of experimental data are reproduced by the simulations, in order to deduce parameters of the electrochemical model. The influence of micro-structural properties, inlet cathode gas velocity, and temperature are discussed. Reaction flow analysis is performed, at OCV, to study methane production characteristics and kinetics during co-electrolysis. Simulations are carried out for configurations ranging from simple one-dimensional electrochemical button cells to quasi-two-dimensional co-flow planar cells, to demonstrate the effectiveness of the computational tool for performance and design optimization.

Quantification and kinetics of H2 generation during hydrothermal serpentinisation experiments

NASA Astrophysics Data System (ADS)

Castelain, Teddy; Fauguerolles, Colin; Villeneuve, Johan; Pichavant, Michel

2013-04-01

H2-rich hydrothermal fluids generated by serpentinisation of mantle rocks at slow-spreading ridges have been revealed by recent studies [1, 2]. Fluxes and the future of the H2 produced by this process are poorly constrained [1, 3]. In this study, we aim to quantitatively evaluate the H2 production fluxes associated with these hydrothermal systems and to document the kinetics of the hydrogen-producing reaction. For this matter, hydrothermal serpentinisation experiments are being undertaken on mixtures composed of a natural peridotite from the Pindus ophiolite and olivine crystals from San Carlos. The experiments are conducted at a temperature of ~ 300° C and a pressure of 450-500 bars in large-volume Dickson-Seyfried bombs for periods of × 1 month. Starting materials are powders between 1 - 100 μm for the peridotites and individual grains ranging from 1 - 2 mm for the San Carlos olivine. They are reacted with a homemade artificial seawater in such proportion that water-rock ratio = 1.8. The reactants are loaded in a modified Ti cell fitted with a semi-permeable Au-Pd membrane simultaneously allowing direct sampling of the hydrothermal fluid and in situ monitoring of the pH2 during the advancement of the reaction. The gas fraction of the fluid sampled is then analyzed by gas chromatography (GC). The pH2 readings show traces of H2 to be present from the second day of experiment. The increase of the pH2 reaches a maximum after ~ 6 days and the pH2 finally stabilizes after ~ 16 days at ~ 12.5 bars, which corresponds to a local fO2 of about NNO-4. The GC measurements, performed after 30, 43, 51 and 65 days, yield respectively, H2 concentrations of 82.4, 89.7, 90.3 and 101 mmol.kg-1 of water, in reasonable agreement with results from previous studies [4-6]. Further experiments are being undertaken in order to: duplicate observations, especially the pH2 readings, more closely link the GC measurements and the in situ pH2 readings, especially during the first 15 days of

Studies of Hydrogen Production by the Water Gas Shift Reaction and Related Chemistry

DTIC Science & Technology

1983-04-15

HYDROGEN PRODUCTION BY THE WATER GAS SHIFT REACTION AND RELATED CHEMISTRY Institution: The University of Rochester Department of Chemistry -. Rochester...been in siated for the catalysis of the water gas shift reaction, W20 + CO H𔃼 + C02, and for electrocatalytic oxidation of CO, CO + H󈧘 C02 + 2H...particular interest in adopting water gas shift catalysts to act as electrocatalysts for the anode reaction of CO fuel cells. Under these conditions the best

Rich soil carbon and nitrogen but low atmospheric greenhouse gas fluxes from North Sulawesi mangrove swamps in Indonesia.

PubMed

Chen, Guang C; Ulumuddin, Yaya I; Pramudji, Sastro; Chen, Shun Y; Chen, Bin; Ye, Yong; Ou, Dan Y; Ma, Zhi Y; Huang, Hao; Wang, Jing K

2014-07-15

The soil to atmosphere fluxes of greenhouse gases N2O, CH4 and CO2 and their relationships with soil characteristics were investigated in three tropical oceanic mangrove swamps (Teremaal, Likupang and Kema) in North Sulawesi, Indonesia. Mangrove soils in North Sulawesi were rich in organic carbon and nitrogen, but the greenhouse gas fluxes were low in these mangroves. The fluxes ranged -6.05-13.14 μmol m(-2)h(-1), -0.35-0.61 μmol m(-2)h(-1) and -1.34-3.88 mmol m(-2)h(-1) for N2O, CH4 and CO2, respectively. The differences in both N2O and CH4 fluxes among different mangrove swamps and among tidal positions in each mangrove swamp were insignificant. CO2 flux was influenced only by mangrove swamps and the value was higher in Kema mangrove. None of the measured soil parameters could explain the variation of CH4 fluxes among the sampling plots. N2O flux was negatively related to porewater salinity, while CO2 flux was negatively correlated with water content and organic carbon. This study suggested that the low gas emissions due to slow metabolisms would lead to the accumulations of organic matters in North Sulawesi mangrove swamps. Copyright © 2014 Elsevier B.V. All rights reserved.

Sulfur Isotopes in Gas-rich Impact-Melt Glasses in Shergottites

NASA Technical Reports Server (NTRS)

Rao, M. N.; Hoppe, P.; Sutton, S. R.; Nyquist, Laurence E.; Huth, J.

2010-01-01

Large impact melt glasses in some shergottites contain huge amounts of Martian atmospheric gases and they are known as gas-rich impact-melt (GRIM) glasses. By studying the neutron-induced isotopic deficits and excesses in Sm-149 and Sm-150 isotopes resulting from Sm-149 (n,gamma) 150Sm reaction and 80Kr excesses produced by Br-79 (n,gamma) Kr-80 reaction in the GRIM glasses using mass-spectrometric techniques, it was shown that these glasses in shergottites EET79001 and Shergotty contain regolith materials irradiated by a thermal neutron fluence of approx.10(exp 15) n/sq cm near Martian surface. Also, it was shown that these glasses contain varying amounts of sulfates and sulfides based on the release patterns of SO2 (sulfate) and H2S (sulfide) using stepwise-heating mass-spectrometric techniques. Furthermore, EMPA and FE-SEM studies in basaltic-shergottite GRIM glasses EET79001, LithB (,507& ,69), Shergotty (DBS I &II), Zagami (,992 & ,994) showed positive correlation between FeO and "SO3" (sulfide + sulfate), whereas those belonging to olivine-phyric shergottites EET79001, LithA (,506, & ,77) showed positive correlation between CaO/Al2O3 and "SO3".

Synthesis and PGE(2) production inhibition of 1H-furan-2,5-dione and 1H-pyrrole-2,5-dione derivatives.

PubMed

Moon, Jong Taik; Jeon, Ji Young; Park, Hang Ah; Noh, Young-Soo; Lee, Kyung-Tae; Kim, Jungahn; Choo, Dong Joon; Lee, Jae Yeol

2010-01-15

3,4-Diphenyl-substituted 1H-furan-2,5-dione and 1H-pyrrole-2,5-dione derivatives were synthesized and evaluated for the inhibitory activities on LPS-induced PGE(2) production in RAW 264.7 macrophage cells. Both 1H-furan-2,5-dione and 1H-pyrrole-2,5-dione rings as main scaffolds were easily obtained using one of three synthetic methods. Among the compounds investigated, 1H-3-(4-sulfamoylphenyl)-4-phenyl-pyrrole-2,5-dione (6l) showed a strong inhibitory activity (IC(50)=0.61microM) of PGE(2) production. Copyright 2009 Elsevier Ltd. All rights reserved.

Influence of Ar/O2/H2O Feed Gas and N2/O2/H2O Environment on the Interaction of Time Modulated MHz Atmospheric Pressure Plasma Jet (APPJ) with Model Polymers

NASA Astrophysics Data System (ADS)

Oehrlein, Gottlieb; Luan, Pingshan; Knoll, Andrew; Kondeti, Santosh; Bruggeman, Peter

2016-09-01

An Ar/O2/H2O fed time modulated MHz atmospheric pressure plasma jet (APPJ) in a sealed chamber was used to study plasma interaction with model polymers (polystyrene, poly-methyl methacrylate, etc.). The amount of H2O in the feed gas and/or present in the N2, O2, or N2/O2 environment was controlled. Short lived species such as O atoms and OH radicals play a crucial role in polymer etching and surface modifications (obtained from X-ray photoelectron spectroscopy of treated polymers without additional atmospheric exposure). Polymer etching depth for Ar/air fed APPJ mirrors the decay of gas phase O atoms with distance from the APPJ nozzle in air and is consistent with the estimated O atom flux at the polymer surface. Furthermore, whereas separate O2 or H2O admixture to Ar enhances polymer etching, simultaneous addition of O2 and H2O to Ar quenches polymer etching. This can be explained by the mutual quenching of O with OH, H and HO2 in the gas phase. Results where O2 and/or H2O in the environment were varied are consistent with these mechanisms. All results will be compared with measured and simulated species densities reported in the literature. We gratefully acknowledge funding from US Department of Energy (DE-SC0001939) and National Science Foundation (PHY-1415353).

Surpassing the current limitations of high purity H2 production in microbial electrolysis cell (MECs): Strategies for inhibiting growth of methanogens.

PubMed

Kadier, Abudukeremu; Kalil, Mohd Sahaid; Chandrasekhar, Kuppam; Mohanakrishna, Gunda; Saratale, Ganesh Dattatraya; Saratale, Rijuta Ganesh; Kumar, Gopalakrishnan; Pugazhendhi, Arivalagan; Sivagurunathan, Periyasamy

2018-02-01

Microbial electrolysis cells (MECs) are perceived as a potential and promising innovative biotechnological tool that can convert carbon-rich waste biomass or wastewater into hydrogen (H 2 ) or other value-added chemicals. Undesired methane (CH 4 ) producing H 2 sinks, including methanogens, is a serious challenge faced by MECs to achieve high-rate H 2 production. Methanogens can consume H 2 to produce CH 4 in MECs, which has led to a drop of H 2 production efficiency, H 2 production rate (HPR) and also a low percentage of H 2 in the produced biogas. Organized inference related to the interactions of microbes and potential processes has assisted in understanding approaches and concepts for inhibiting the growth of methanogens and profitable scale up design. Thus, here in we review the current developments and also the improvements constituted for the reduction of microbial H 2 losses to methanogens. Firstly, the greatest challenge in achieving practical applications of MECs; undesirable microorganisms (methanogens) growth and various studied techniques for eliminating and reducing methanogens activities in MECs were discussed. Additionally, this extensive review also considers prospects for stimulating future research that could help to achieve more information and would provide the focus and path towards MECs as well as their possibilities for simultaneously generating H 2 and waste remediation. Copyright © 2017 Elsevier B.V. All rights reserved.

H2 Gas Improves Functional Outcome After Cardiac Arrest to an Extent Comparable to Therapeutic Hypothermia in a Rat Model

PubMed Central

Hayashida, Kei; Sano, Motoaki; Kamimura, Naomi; Yokota, Takashi; Suzuki, Masaru; Maekawa, Yuichiro; Kawamura, Akio; Abe, Takayuki; Ohta, Shigeo; Fukuda, Keiichi; Hori, Shingo

2012-01-01

Background All clinical and biological manifestations related to postcardiac arrest (CA) syndrome are attributed to ischemia–reperfusion injury in various organs including brain and heart. Molecular hydrogen (H2) has potential as a novel antioxidant. This study tested the hypothesis that inhalation of H2 gas starting at the beginning of cardiopulmonary resuscitation (CPR) could improve the outcome of CA. Methods and Results Ventricular fibrillation was induced by transcutaneous electrical epicardial stimulation in rats. After 5 minutes of the subsequent CA, rats were randomly assigned to 1 of 4 experimental groups at the beginning of CPR: mechanical ventilation (MV) with 2% N2 and 98% O2 under normothermia (37°C), the control group; MV with 2% H2 and 98% O2 under normothermia; MV with 2% N2 and 98% O2 under therapeutic hypothermia (TH), 33°C; and MV with 2% H2 and 98% O2 under TH. Mixed gas inhalation and TH continued until 2 hours after the return of spontaneous circulation (ROSC). H2 gas inhalation yielded better improvement in survival and neurological deficit score (NDS) after ROSC to an extent comparable to TH. H2 gas inhalation, but not TH, prevented a rise in left ventricular end-diastolic pressure and increase in serum IL-6 level after ROSC. The salutary impact of H2 gas was at least partially attributed to the radical-scavenging effects of H2 gas, because both 8-OHdG- and 4-HNE-positive cardiomyocytes were markedly suppressed by H2 gas inhalation after ROSC. Conclusions Inhalation of H2 gas is a favorable strategy to mitigate mortality and functional outcome of post-CA syndrome in a rat model, either alone or in combination with TH. PMID:23316300

Oxygen vacancy rich Cu2O based composite material with nitrogen doped carbon as matrix for photocatalytic H2 production and organic pollutant removal.

PubMed

Lu, Lele; Xu, Xinxin; Yan, Jiaming; Shi, Fa-Nian; Huo, Yuqiu

2018-02-06

A nitrogen doped carbon matrix supported Cu 2 O composite material (Cu/Cu2O@NC) was fabricated successfully with a coordination polymer as precursor through calcination. In this composite material, Cu 2 O particles with a size of about 6-10 nm were dispersed evenly in the nitrogen doped carbon matrix. After calcination, some coordinated nitrogen atoms were doped in the lattice of Cu 2 O and replace oxygen atoms, thus generating a large number of oxygen vacancies. In Cu/Cu2O@NC, the existence of oxygen vacancies has been confirmed by electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS). Under visible light irradiation, Cu/Cu2O@NC exhibits excellent H 2 production with the rate of 379.6 μmol h -1 g -1 . Its photocatalytic activity affects organic dyes, such as Rhodamine B (RhB) and methyl orange (MO). In addition to photocatalysis, Cu/Cu2O@NC also exhibits striking catalytic activity in reductive conversion of 4-nitrophenol to 4-aminophenol with in presence of sodium borohydride (NaBH 4 ). The conversion efficiency reaches almost 100% in 250 s with the quantity of Cu/Cu2O@NC as low as 5 mg. The outstanding H 2 production and organic pollutants removal are attributed to the oxygen vacancy. We expect that Cu/Cu2O@NC will find its way as a new resource for hydrogen energy as well as a promising material in water purification.

Evaluation of gases, condensates, and SO2 emissions from Augustine volcano, Alaska: the degassing of a Cl-rich volcanic system

USGS Publications Warehouse

Symonds, R.B.; Rose, William I.; Gerlach, T.M.; Briggs, P.H.; Harmon, R.S.

1990-01-01

After the March-April 1986 explosive eruption a comprehensive gas study at Augustine was undertaken in the summers of 1986 and 1987. Airborne COSPEC measurements indicate that passive SO2 emission rates declined exponentially during this period from 380??45 metric tons/day (T/D) on 7/24/86 to 27??6 T/D on 8/24/87. These data are consistent with the hypothesis that the Augustine magma reservoir has become more degassed as volcanic activity decreased after the spring 1986 eruption. Gas samples collected in 1987 from an 870??C fumarole on the andesitic lava dome show various degrees of disequilibrium due to oxidation of reduced gas species and condensation (and loss) of H2O in the intake tube of the sampling apparatus. Thermochemical restoration of the data permits removal of these effects to infer an equilibrium composition of the gases. Although not conclusive, this restoration is consistent with the idea that the gases were in equilibrium at 870??C with an oxygen fugacity near the Ni-NiO buffer. These restored gas compositions show that, relative to other convergent plate volcanoes, the Augustine gases are very HCl rich (5.3-6.0 mol% HCl), S rich (7.1 mol% total S), and H2O poor (83.9-84.8 mol% H2O). Values of ??D and ??18O suggest that the H2O in the dome gases is a mixture of primary magmatic water (PMW) and local seawater. Part of the Cl in the Augustine volcanic gases probably comes from this shallow seawater source. Additional Cl may come from subducted oceanic crust because data by Johnston (1978) show that Cl-rich glass inclusions in olivine crystals contain hornblende, which is evidence for a deep source (>25km) for part of the Cl. Gas samples collected in 1986 from 390??-642??C fumaroles on a ramp surrounding the inner summit crater have been oxidized so severely that restoration to an equilibrium composition is not possible. H and O isotope data suggest that these gases are variable mixtures of seawater, FMW, and meteoric steam. These samples are much

Evaluation of gases, condensates, and SO2 emissions from Augustine volcano, Alaska: the degassing of a Cl-rich volcanic system

NASA Astrophysics Data System (ADS)

Symonds, Robert B.; Rose, William I.; Gerlach, Terrence M.; Briggs, Paul H.; Harmon, Russell S.

1990-05-01

After the March April 1986 explosive eruption a comprehensive gas study at Augustine was undertaken in the summers of 1986 and 1987. Airborne COSPEC measurements indicate that passive SO2 emission rates declined exponentially during this period from 380±45 metric tons/day (T/D) on 7/24/86 to 27±6 T/D on 8/24/87. These data are consistent with the hypothesis that the Augustine magma reservoir has become more degassed as volcanic activity decreased after the spring 1986 eruption. Gas samples collected in 1987 from an 870°C fumarole on the andesitic lava dome show various degrees of disequilibrium due to oxidation of reduced gas species and condensation (and loss) of H2O in the intake tube of the sampling apparatus. Thermochemical restoration of the data permits removal of these effects to infer an equilibrium composition of the gases. Although not conclusive, this restoration is consistent with the idea that the gases were in equilibrium at 870°C with an oxygen fugacity near the Ni-NiO buffer. These restored gas compositions show that, relative to other convergent plate volcanoes, the Augustine gases are very HCl rich (5.3 6.0 mol% HCl), S rich (7.1 mol% total S), and H2O poor (83.9 84.8 mol% H2O). Values of δD and δ18O suggest that the H2O in the dome gases is a mixture of primary magmatic water (PMW) and local seawater. Part of the Cl in the Augustine volcanic gases probably comes from this shallow seawater source. Additional Cl may come from subducted oceanic crust because data by Johnston (1978) show that Cl-rich glass inclusions in olivine crystals contain hornblende, which is evidence for a deep source (>25km) for part of the Cl. Gas samples collected in 1986 from 390° 642°C fumaroles on a ramp surrounding the inner summit crater have been oxidized so severely that restoration to an equilibrium composition is not possible. H and O isotope data suggest that these gases are variable mixtures of seawater, FMW, and meteoric steam. These samples are much

Productivity is a poor predictor of plant species richness

USGS Publications Warehouse

Adler, Peter B.; Seabloom, Eric W.; Borer, Elizabeth T.; Hillebrand, Helmut; Hautier, Yann; Hector, Andy; Harpole, W. Stanley; O'Halloran, Lydia R.; Grace, James B.; Anderson, T. Michael; Bakker, Jonathan D.; Biederman, Lori A.; Brown, Cynthia S.; Buckley, Yvonne M.; Calabrese, Laura B.; Chu, Cheng-Jin; Cleland, Elsa E.; Collins, Scott L.; Cottingham, Kathryn L.; Crawley, Michael J.; Damschen, Ellen Ingman; Davies, Kendi F.; DeCrappeo, Nicole M.; Fay, Philip A.; Firn, Jennifer; Frater, Paul; Gasarch, Eve I.; Gruner, Daneil S.; Hagenah, Nicole; Lambers, Janneke Hille Ris; Humphries, Hope; Jin, Virginia L.; Kay, Adam D.; Kirkman, Kevin P.; Klein, Julia A.; Knops, Johannes M.H.; La Pierre, Kimberly J.; Lambrinos, John G.; Li, Wei; MacDougall, Andrew S.; McCulley, Rebecca L.; Melbourne, Brett A.; Mitchell, Charles E.; Moore, Joslin L.; Morgan, John W.; Mortensen, Brent; Orrock, John L.; Prober, Suzanne M.; Pyke, David A.; Risch, Anita C.; Schuetz, Martin; Smith, Melinda D.; Stevens, Carly J.; Sullivan, Lauren L.; Wang, Gang; Wragg, Peter D.; Wright, Justin P.; Yang, Louie H.

2011-01-01

For more than 30 years, the relationship between net primary productivity and species richness has generated intense debate in ecology about the processes regulating local diversity. The original view, which is still widely accepted, holds that the relationship is hump-shaped, with richness first rising and then declining with increasing productivity. Although recent meta-analyses questioned the generality of hump-shaped patterns, these syntheses have been criticized for failing to account for methodological differences among studies. We addressed such concerns by conducting standardized sampling in 48 herbaceous-dominated plant communities on five continents. We found no clear relationship between productivity and fine-scale (meters-2) richness within sites, within regions, or across the globe. Ecologists should focus on fresh, mechanistic approaches to understanding the multivariate links between productivity an

Device for quickly sensing the amount of O2 in a combustion product gas

NASA Technical Reports Server (NTRS)

Singh, Jag J. (Inventor); Davis, William T. (Inventor); Puster, Richard L. (Inventor)

1990-01-01

A sensing device comprising an O2 sensor, a pump, a compressor, and a heater is provided to quickly sense the amount of O2 in a combustion product gas. A sample of the combustion product gas is compressed to a pressure slightly above one atmosphere by the compressor. Next, the heater heats the sample between 800 C and 900 C. Next, the pump causes the sample to be flushed against the electrode located in O2 sensor 6000 to 10,000 times per second. Reference air at approximately one atmosphere is provided to the electrode of O2 sensor. Accordingly, the O2 sensor produces a voltage which is proportional to the amount of oxygen in the combustion product gas. This voltage may be used to control the amount of O2 entering into the combustion chamber which produces the combustion product gas.

BIOSIGNATURE GASES IN H{sub 2}-DOMINATED ATMOSPHERES ON ROCKY EXOPLANETS

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

Seager, S.; Bains, W.; Hu, R.

2013-11-10

Super-Earth exoplanets are being discovered with increasing frequency and some will be able to retain stable H{sub 2}-dominated atmospheres. We study biosignature gases on exoplanets with thin H{sub 2} atmospheres and habitable surface temperatures, using a model atmosphere with photochemistry and a biomass estimate framework for evaluating the plausibility of a range of biosignature gas candidates. We find that photochemically produced H atoms are the most abundant reactive species in H{sub 2} atmospheres. In atmospheres with high CO{sub 2} levels, atomic O is the major destructive species for some molecules. In Sun-Earth-like UV radiation environments, H (and in some casesmore » O) will rapidly destroy nearly all biosignature gases of interest. The lower UV fluxes from UV-quiet M stars would produce a lower concentration of H (or O) for the same scenario, enabling some biosignature gases to accumulate. The favorability of low-UV radiation environments to accumulate detectable biosignature gases in an H{sub 2} atmosphere is closely analogous to the case of oxidized atmospheres, where photochemically produced OH is the major destructive species. Most potential biosignature gases, such as dimethylsulfide and CH{sub 3}Cl, are therefore more favorable in low-UV, as compared with solar-like UV, environments. A few promising biosignature gas candidates, including NH{sub 3} and N{sub 2}O, are favorable even in solar-like UV environments, as these gases are destroyed directly by photolysis and not by H (or O). A more subtle finding is that most gases produced by life that are fully hydrogenated forms of an element, such as CH{sub 4} and H{sub 2}S, are not effective signs of life in an H{sub 2}-rich atmosphere because the dominant atmospheric chemistry will generate such gases abiologically, through photochemistry or geochemistry. Suitable biosignature gases in H{sub 2}-rich atmospheres for super-Earth exoplanets transiting M stars could potentially be detected in

Potential restrictions for CO2 sequestration sites due to shale and tight gas production.

PubMed

Elliot, T R; Celia, M A

2012-04-03

Carbon capture and geological sequestration is the only available technology that both allows continued use of fossil fuels in the power sector and reduces significantly the associated CO(2) emissions. Geological sequestration requires a deep permeable geological formation into which captured CO(2)can be injected, and an overlying impermeable formation, called a caprock, that keeps the buoyant CO(2) within the injection formation. Shale formations typically have very low permeability and are considered to be good caprock formations. Production of natural gas from shale and other tight formations involves fracturing the shale with the explicit objective to greatly increase the permeability of the shale. As such, shale gas production is in direct conflict with the use of shale formations as a caprock barrier to CO(2) migration. We have examined the locations in the United States where deep saline aquifers, suitable for CO(2) sequestration, exist, as well as the locations of gas production from shale and other tight formations. While estimated sequestration capacity for CO(2) sequestration in deep saline aquifers is large, up to 80% of that capacity has areal overlap with potential shale-gas production regions and, therefore, could be adversely affected by shale and tight gas production. Analysis of stationary sources of CO(2) shows a similar effect: about two-thirds of the total emissions from these sources are located within 20 miles of a deep saline aquifer, but shale and tight gas production could affect up to 85% of these sources. These analyses indicate that colocation of deep saline aquifers with shale and tight gas production could significantly affect the sequestration capacity for CCS operations. This suggests that a more comprehensive management strategy for subsurface resource utilization should be developed.

Investigation of the noble gas solubility in H 2O-CO 2 bearing silicate liquids at moderate pressure II: the extended ionic porosity (EIP) model

NASA Astrophysics Data System (ADS)

Nuccio, P. M.; Paonita, A.

2000-12-01

A semi-theoretical model is proposed to predict partitioning of noble gases between any silicate liquid and a H 2O-CO 2 gas phase with noble gas as a minor component, in a large range of pressures (at least up to 300 MPa). The model is based on the relationship between the concentration of dissolved noble gas and ionic porosity of the melt, found by Carroll and Stolper [Geochim. Cosmochim. Acta 57 (1993) 5039-5051] for H 2O-CO 2 free melts. It evaluates the effect of dissolved H 2O and CO 2 on the melt ionic porosity and, consequently on Henry's constants of noble gases. The fugacities of the noble gases in the H 2O-CO 2-noble gas mixtures are also considered in our equilibrium calculations of dissolved gas by using a modified Redlich-Kwong equation of state for the H 2O-CO 2-noble gas system. The formulated model (referred to as the extended ionic porosity model) clearly predicts a positive dependence of noble gas solubility on dissolved H 2O in melt, which becomes negligible when water concentration is higher than 3 wt%. Oppositely, noble gas solubility decreases as a consequence of increasing CO 2 in both basaltic and rhyolitic melts. The increase of noble gas solubility as a consequence of H 2O addition to the melt grows exponentially with the increase of the noble gas atomic size. As a result, although xenon solubility is much lower than the helium solubility in anhydrous melts, they become almost comparable at several percent of dissolved H 2O in the melt. On this basis, an exponential augmentation of the number of large free spaces in silicate liquid can be inferred in relation to increasing dissolved H 2O. Comparison between our predicted values and available experimental data [A. Paonita et al., Earth Planet. Sci. Lett. 181 (2000) 595-604] shows good agreement. At present, the EIP model is the unique tool which predicts how the main volatiles in magmatic systems affect the noble gas solubility in silicate melts, therefore it should be taken into account

A Designed ZnO@ZIF-8 Core-Shell Nanorod Film as a Gas Sensor with Excellent Selectivity for H2 over CO.

PubMed

Wu, Xiaonan; Xiong, Shunshun; Mao, Zhenghao; Hu, Sheng; Long, Xinggui

2017-06-12

The development of H 2 gas sensors is important for H 2 production as a fuel. In this work, a ZnO@ZIF-8 core-shell nanorod film is designed and synthesized as a gas sensor through a facile solution deposition process. This film shows an excellent selective response for H 2 over CO. By fine-tuning the reaction conditions, a ZnO@ZIF-8 core-shell structure with a thin, fine-grain, porous ZIF-8 shell is obtained. Owing to the facile H 2 penetration through the ZIF-8 thin shell (≈110 nm) and the increased oxygen vacancies for the complex film, the ZnO@ZIF-8 nanorod film shows a higher H 2 sensitivity than a raw ZnO nanorod film. More importantly, the ZnO@ZIF-8 nanorod film shows no response for CO at 200 °C. Because of the fine-grain confinement of the porous ZIF-8 shell (<140 nm), the molecular sieving effect is strengthened, which allows the effective separation of H 2 over CO. This work provides a promising strategy for the design of high-performance H 2 sensors. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Origin of methane-rich natural gas at the West Pacific convergent plate boundary.

PubMed

Sano, Yuji; Kinoshita, Naoya; Kagoshima, Takanori; Takahata, Naoto; Sakata, Susumu; Toki, Tomohiro; Kawagucci, Shinsuke; Waseda, Amane; Lan, Tefang; Wen, Hsinyi; Chen, Ai-Ti; Lee, Hsiaofen; Yang, Tsanyao F; Zheng, Guodong; Tomonaga, Yama; Roulleau, Emilie; Pinti, Daniele L

2017-11-15

Methane emission from the geosphere is generally characterized by a radiocarbon-free signature and might preserve information on the deep carbon cycle on Earth. Here we report a clear relationship between the origin of methane-rich natural gases and the geodynamic setting of the West Pacific convergent plate boundary. Natural gases in the frontal arc basin (South Kanto gas fields, Northeast Japan) show a typical microbial signature with light carbon isotopes, high CH 4 /C 2 H 6 and CH 4 / 3 He ratios. In the Akita-Niigata region - which corresponds to the slope stretching from the volcanic-arc to the back-arc -a thermogenic signature characterize the gases, with prevalence of heavy carbon isotopes, low CH 4 /C 2 H 6 and CH 4 / 3 He ratios. Natural gases from mud volcanoes in South Taiwan at the collision zone show heavy carbon isotopes, middle CH 4 /C 2 H 6 ratios and low CH 4 / 3 He ratios. On the other hand, those from the Tokara Islands situated on the volcanic front of Southwest Japan show the heaviest carbon isotopes, middle CH 4 /C 2 H 6 ratios and the lowest CH 4 / 3 He ratios. The observed geochemical signatures of natural gases are clearly explained by a mixing of microbial, thermogenic and abiotic methane. An increasing contribution of abiotic methane towards more tectonically active regions of the plate boundary is suggested.

MSL SAM-Like Evolved Gas Analyses of Si-rich Amorphous Materials

NASA Technical Reports Server (NTRS)

McAdam, Amy; Knudson, Christine; Sutter, Brad; Andrejkovicova, Slavka; Archer, P. Douglas; Franz, Heather; Eigenbrode, Jennifer; Morris, Richard; Ming, Douglas; Sun, Vivian;

Xenobiotic metal-induced autoimmunity: mercury and silver differentially induce antinucleolar autoantibody production in susceptible H-2s, H-2q and H-2f mice

PubMed Central

Hansson, M; Abedi-Valugerdi, M

2003-01-01

Xenobiotic-metals such as mercury (Hg) and silver (Ag) induce an H-2 linked antinucleolar autoantibody (ANolA) production in susceptible mice. The mechanism for induction of ANolA synthesis is not well understood. However, it has been suggested that both metals interact with nucleolar proteins and reveal cryptic self-peptides to nontolerant autoreactive T cells, which in turn stimulate specific autoreactive B cells. In this study, we considered this suggestion and asked if mercury and silver display, if not identical, similar cryptic self-peptides, they would induce comparable ANolA responses in H-2 susceptible mice. We analysed the development of ANolA production in mercury- and/or silver-treated mice of H-2s, H-2q and H-2f genotypes. We found that while mercury stimulated ANolA synthesis in all strains tested, silver induced ANolA responses of lower magnitudes in only H-2s and H-2q mice, but not in H-2f mice. Resistance to silver in H-2f mice was independent of the dosage/time-period of silver-treatment and non-H-2 genes. Further studies showed that F1 hybrid crosses between silver-susceptible A.SW (H-2s) and -resistant A.CA (H-2f) mice were resistant to silver, but not mercury with regard to ANolA production. Additionally, the magnitudes of mercury-induced ANolA responses in the F1 hybrids were lower than those of their parental strains. The above differential ANolA responses to mercury and silver can be explained by various factors, including the different display of nucleolar cryptic peptides by these xenobiotics, determinant capture and coexistence of different MHC molecules. Our findings also suggest that the ability of a xenobiotic metal merely to create cryptic self-peptides may not be sufficient for the induction of an ANolA response. PMID:12605692

The frequency and properties of young tidal dwarf galaxies in nearby gas-rich groups

NASA Astrophysics Data System (ADS)

Lee-Waddell, K.; Spekkens, K.; Chandra, P.; Patra, N.; Cuillandre, J.-C.; Wang, J.; Haynes, M. P.; Cannon, J.; Stierwalt, S.; Sick, J.; Giovanelli, R.

2016-08-01

We present high-resolution Giant Metrewave Radio Telescope (GMRT) H I observations and deep Canada-France-Hawaii Telescope (CFHT) optical imaging of two galaxy groups: NGC 4725/47 and NGC 3166/9. These data are part of a multi-wavelength unbiased survey of the gas-rich dwarf galaxy populations in three nearby interacting galaxy groups. The NGC 4725/47 group hosts two tidal knots and one dwarf irregular galaxy (dIrr). Both tidal knots are located within a prominent H I tidal tail, appear to have sufficient mass (Mgas ≈ 108 M⊙) to evolve into long-lived tidal dwarf galaxies (TDGs) and are fairly young in age. The NGC 3166/9 group contains a TDG candidate, AGC 208457, at least three dIrrs and four H I knots. Deep CFHT imaging confirms that the optical component of AGC 208457 is bluer - with a 0.28 mag g - r colour - and a few Gyr younger than its purported parent galaxies. Combining the results for these groups with those from the NGC 871/6/7 group reported earlier, we find that the H I properties, estimated stellar ages and baryonic content of the gas-rich dwarfs clearly distinguish tidal features from their classical counterparts. We optimistically identify four potentially long-lived tidal objects associated with three separate pairs of interacting galaxies, implying that TDGs are not readily produced during interaction events as suggested by some recent simulations. The tidal objects examined in this survey also appear to have a wider variety of properties than TDGs of similar mass formed in current simulations of interacting galaxies, which could be the result of pre- or post-formation environmental influences.

A Tale of Two Gases: Isotope Effects Associated with the Enzymatic Production of H2 and N2O

NASA Astrophysics Data System (ADS)

Yang, H.; Gandhi, H.; Kreuzer, H. W.; Moran, J.; Hill, E. A.; McQuarters, A.; Lehnert, N.; Ostrom, N. E.; Hegg, E. L.

2014-12-01

Stable isotopes can provide considerable insight into enzymatic mechanisms and fluxes in various biological processes. In our studies, we used stable isotopes to characterize both enzyme-catalyzed H2 and N2O production. H2 is a potential alternative clean energy source and also a key metabolite in many microbial communities. Biological H2 production is generally catalyzed by hydrogenases, enzymes that combine protons and electrons to produce H2 under anaerobic conditions. In our study, H isotopes and fractionation factors (α) were used to characterize two types of hydrogenases: [FeFe]- and [NiFe]-hydrogenases. Due to differences in the active site, the α associated with H2 production for [FeFe]- and [NiFe]-hydrogenases separated into two distinct clusters (αFeFe > αNiFe). The calculated kinetic isotope effects indicate that hydrogenase-catalyzed H2 production has a preference for light isotopes, consistent with the relative bond strengths of O-H and H-H bonds. Interestingly, the isotope effects associated with H2 consumption and H2-H2O exchange reactions were also characterized, but in this case no specific difference was observed between the different enzymes. N2O is a potent greenhouse gas with a global warming potential 300 times that of CO2, and the concentration of N2O is currently increasing at a rate of ~0.25% per year. Thus far, bacterial and fungal denitrification processes have been identified as two of the major sources of biologically generated N2O. In this study, we measured the δ15N, δ18O, δ15Nα (central N atom in N2O), and δ15Nβ (terminal N atom in N2O) of N2O generated by purified fungal P450 nitric oxide reductase (P450nor) from Histoplasma capsulatum. We observed normal isotope effects for δ18O and δ15Nα, and inverse isotope effects for bulk δ15N (the average of Nα and Nβ) and δ15Nβ. The observed isotope effects have been used in conjunction with DFT calculations to provide important insight into the mechanism of P450nor. Similar

Optimization of NO oxidation by H2O2 thermal decomposition at moderate temperatures.

PubMed

Zhao, Hai-Qian; Wang, Zhong-Hua; Gao, Xing-Cun; Liu, Cheng-Hao; Qi, Han-Bing

2018-01-01

H2O2 was adopted to oxidize NO in simulated flue gas at 100-500°C. The effects of the H2O2 evaporation conditions, gas temperature, initial NO concentration, H2O2 concentration, and H2O2:NO molar ratio on the oxidation efficiency of NO were investigated. The reason for the narrow NO oxidation temperature range near 500°C was determined. The NO oxidation products were analyzed. The removal of NOx using NaOH solution at a moderate oxidation ratio was studied. It was proven that rapid evaporation of the H2O2 solution was critical to increase the NO oxidation efficiency and broaden the oxidation temperature range. the NO oxidation efficiency was above 50% at 300-500°C by contacting the outlet of the syringe needle and the stainless-steel gas pipe together to spread H2O2 solution into a thin film on the surface of the stainless-steel gas pipe, which greatly accelerated the evaporation of H2O2. The NO oxidation efficiency and the NO oxidation rate increased with increasing initial NO concentration. This method was more effective for the oxidation of NO at high concentrations. H2O2 solution with a concentration higher than 15% was more efficient in oxidizing NO. High temperatures decreased the influence of the H2O2 concentration on the NO oxidation efficiency. The oxidation efficiency of NO increased with an increase in the H2O2:NO molar ratio, but the ratio of H2O2 to oxidized NO decreased. Over 80% of the NO oxidation product was NO2, which indicated that the oxidation ratio of NO did not need to be very high. An 86.7% NO removal efficiency was obtained at an oxidation ratio of only 53.8% when combined with alkali absorption.

Optimization of NO oxidation by H2O2 thermal decomposition at moderate temperatures

PubMed Central

Wang, Zhong-hua; Gao, Xing-cun; Liu, Cheng-hao; Qi, Han-bing

2018-01-01

H2O2 was adopted to oxidize NO in simulated flue gas at 100–500°C. The effects of the H2O2 evaporation conditions, gas temperature, initial NO concentration, H2O2 concentration, and H2O2:NO molar ratio on the oxidation efficiency of NO were investigated. The reason for the narrow NO oxidation temperature range near 500°C was determined. The NO oxidation products were analyzed. The removal of NOx using NaOH solution at a moderate oxidation ratio was studied. It was proven that rapid evaporation of the H2O2 solution was critical to increase the NO oxidation efficiency and broaden the oxidation temperature range. the NO oxidation efficiency was above 50% at 300–500°C by contacting the outlet of the syringe needle and the stainless-steel gas pipe together to spread H2O2 solution into a thin film on the surface of the stainless-steel gas pipe, which greatly accelerated the evaporation of H2O2. The NO oxidation efficiency and the NO oxidation rate increased with increasing initial NO concentration. This method was more effective for the oxidation of NO at high concentrations. H2O2 solution with a concentration higher than 15% was more efficient in oxidizing NO. High temperatures decreased the influence of the H2O2 concentration on the NO oxidation efficiency. The oxidation efficiency of NO increased with an increase in the H2O2:NO molar ratio, but the ratio of H2O2 to oxidized NO decreased. Over 80% of the NO oxidation product was NO2, which indicated that the oxidation ratio of NO did not need to be very high. An 86.7% NO removal efficiency was obtained at an oxidation ratio of only 53.8% when combined with alkali absorption. PMID:29668672

A combined crossed-beam and theoretical study of the reaction dynamics of O(3P) + C2H3 → C2H2 + OH: Analysis of the nascent OH products with the preferential population of the Π(A') component

NASA Astrophysics Data System (ADS)

Park, Min-Jin; Jang, Su-Chan; Choi, Jong-Ho

2012-11-01

The gas-phase reaction dynamics of ground-state atomic oxygen [O(3P) from the photo-dissociation of NO2] with vinyl radicals [C2H3 from the supersonic flash pyrolysis of vinyl iodide, C2H3I] has been investigated using a combination of high-resolution laser-induced fluorescence spectroscopy in a crossed-beam configuration and ab initio calculations. Unlike the previous gas-phase bulk kinetic experiments by Baulch et al. [J. Phys. Chem. Ref. Data 34, 757 (2005)], 10.1063/1.1748524, a new exothermic channel of O(3P) + C2H3 → C2H2 + OH (X 2Π: υ″ = 0) has been identified for the first time, and the population analysis shows bimodal nascent rotational distributions of OH products with low- and high-N″ components with a ratio of 2.4:1. No spin-orbit propensities were observed, and the averaged ratios of Π(A')/Π(A″) were determined to be 1.66 ± 0.27. On the basis of computations at the CBS-QB3 theory level and comparison with prior theory, the microscopic mechanisms responsible for the nascent populations can be understood in terms of two competing dynamical pathways: a direct abstraction process in the low-N″ regime as the major pathway and an addition-complex forming process in the high-N″ regime as the minor pathway. Particularly, during the bond cleavage process of the weakly bound van der Waals complex C2H2—OH, the characteristic pathway from the low dihedral-angle geometry was consistent with the observed preferential population of the Π(A') component in the nascent OH products. A molecular-level discussion of the reactivity, mechanism, and dynamical features of the title reaction are presented together with a comparison to gas-phase oxidation reactions of a series of prototypical hydrocarbon radicals.

A combined crossed-beam and theoretical study of the reaction dynamics of O(3P) + C2H3 → C2H2 + OH: analysis of the nascent OH products with the preferential population of the Π(A') component.

PubMed

Park, Min-Jin; Jang, Su-Chan; Choi, Jong-Ho

2012-11-28

The gas-phase reaction dynamics of ground-state atomic oxygen [O((3)P) from the photo-dissociation of NO(2)] with vinyl radicals [C(2)H(3) from the supersonic flash pyrolysis of vinyl iodide, C(2)H(3)I] has been investigated using a combination of high-resolution laser-induced fluorescence spectroscopy in a crossed-beam configuration and ab initio calculations. Unlike the previous gas-phase bulk kinetic experiments by Baulch et al. [J. Phys. Chem. Ref. Data 34, 757 (2005)], a new exothermic channel of O((3)P) + C(2)H(3) → C(2)H(2) + OH (X (2)Π: υ" = 0) has been identified for the first time, and the population analysis shows bimodal nascent rotational distributions of OH products with low- and high-N" components with a ratio of 2.4:1. No spin-orbit propensities were observed, and the averaged ratios of Π(A('))∕Π(A") were determined to be 1.66 ± 0.27. On the basis of computations at the CBS-QB3 theory level and comparison with prior theory, the microscopic mechanisms responsible for the nascent populations can be understood in terms of two competing dynamical pathways: a direct abstraction process in the low-N" regime as the major pathway and an addition-complex forming process in the high-N" regime as the minor pathway. Particularly, during the bond cleavage process of the weakly bound van der Waals complex C(2)H(2)-OH, the characteristic pathway from the low dihedral-angle geometry was consistent with the observed preferential population of the Π(A') component in the nascent OH products. A molecular-level discussion of the reactivity, mechanism, and dynamical features of the title reaction are presented together with a comparison to gas-phase oxidation reactions of a series of prototypical hydrocarbon radicals.

[Mechanism and performance of styrene oxidation by O3/H2O2].

PubMed

He, Jue-Cong; Huang, Qian-Ru; Ye, Qi-Hong; Luo, Yu-Wei; Zhang, Zai-Li; Fan, Qing-Juan; Wei, Zai-Shan

2013-10-01

It can produce a large number of free radicals in O3/H2O2, system, ozone and free radical coupling oxidation can improve the styrene removal efficiency. Styrene oxidation by O3/H2O2 was investigated. Ozone dosage, residence time, H2o2 volume fraction, spray density and molar ratio of O3/C8H8 on styrene removal were evaluated. The experimental results showed that styrene removal efficiency achieved 85.7%. The optimal residence time, H2O2, volume fraction, spray density and O3/C8H8 molar ratio were 20. 6 s, 10% , 1.72 m3.(m2.h)-1 and 0.46, respectively. The gas-phase degradation intermediate products were benzaldehyde(C6H5CHO) and benzoic acid (C6H5 COOH) , which were identified by means of gas chromatography-mass spectrometry(GC-MS). The degradation mechanism of styrene is presented.

ALMA Observations of Gas-rich Galaxies in z ˜ 1.6 Galaxy Clusters: Evidence for Higher Gas Fractions in High-density Environments

NASA Astrophysics Data System (ADS)

Noble, A. G.; McDonald, M.; Muzzin, A.; Nantais, J.; Rudnick, G.; van Kampen, E.; Webb, T. M. A.; Wilson, G.; Yee, H. K. C.; Boone, K.; Cooper, M. C.; DeGroot, A.; Delahaye, A.; Demarco, R.; Foltz, R.; Hayden, B.; Lidman, C.; Manilla-Robles, A.; Perlmutter, S.

2017-06-01

We present ALMA CO (2-1) detections in 11 gas-rich cluster galaxies at z ˜ 1.6, constituting the largest sample of molecular gas measurements in z > 1.5 clusters to date. The observations span three galaxy clusters, derived from the Spitzer Adaptation of the Red-sequence Cluster Survey. We augment the >5σ detections of the CO (2-1) fluxes with multi-band photometry, yielding stellar masses and infrared-derived star formation rates, to place some of the first constraints on molecular gas properties in z ˜ 1.6 cluster environments. We measure sizable gas reservoirs of 0.5-2 × 1011 M ⊙ in these objects, with high gas fractions (f gas) and long depletion timescales (τ), averaging 62% and 1.4 Gyr, respectively. We compare our cluster galaxies to the scaling relations of the coeval field, in the context of how gas fractions and depletion timescales vary with respect to the star-forming main sequence. We find that our cluster galaxies lie systematically off the field scaling relations at z = 1.6 toward enhanced gas fractions, at a level of ˜4σ, but have consistent depletion timescales. Exploiting CO detections in lower-redshift clusters from the literature, we investigate the evolution of the gas fraction in cluster galaxies, finding it to mimic the strong rise with redshift in the field. We emphasize the utility of detecting abundant gas-rich galaxies in high-redshift clusters, deeming them as crucial laboratories for future statistical studies.

Study of DC Circuit Breaker of H2-N2 Mixture Gas for High Voltage

NASA Astrophysics Data System (ADS)

Shiba, Yuji; Morishita, Yukinaga; Kaneko, Shuhei; Okabe, Shigemitsu; Mizoguchi, Hitoshi; Yanabu, Satoru

Global warming caused by CO2 etc. is a field where the concern is very high. Especially, automobile emissions are problem for it. Therefore, the hybrid car is widely development and used recently. Hybrid car used electric power and gasoline. So, the car reduces CO2. Hybrid car has engine and motor. To rotate the motor, hybrid car has battery. This battery is large capacity. Therefore, the relay should interrupt high DC current for the switch of the motor and the engine. So, hybrid car used hydrogen gas filling relay We studied interruption test for the research of a basic characteristic of hydrogen gas. DC current has not current zero point. So, it is necessary to make the current zero by high arc voltage and forcible current zero point. The loss coefficient and arc voltage of hydrogen is high. Therefore, we studied interruption test for used high arc voltage. We studied interruption test and dielectric breakdown test of air, pure Hydrogen, and Hydrogen- nitrogen mixture gas. As a result, we realized H2-N2(80%-20%) is the best gas.

Simulations of the Viking Gas Exchange Experiment using palagonite and Fe-rich montmorillonite as terrestrial analogs: implications for the surface composition of Mars.

PubMed

Quinn, R; Orenberg, J

1993-10-01

Simulations of the Gas Exchange Experiment (GEX), one of the Viking Lander Biology Experiments, were run using palagonite and Fe-rich montmorillonite as terrestrial analogs of the Martian soil. These terrestrial analogs were exposed to a nutrient solution of the same composition as that of the Viking Landers under humid (no contact with nutrient) and wet (intimate contact) conditions. The headspace gases in the GEX sample cell were sampled and then analyzed by gas chromatography under both humid and wet conditions. Five gases were monitored: CO2, N2, O2, Ar, and Kr. It was determined that in order to simulate the CO2 gas changes of the Viking GEX experiment, the mixture of soil analog mineral plus nutrient medium must be slightly (pH = 7.4) to moderately basic (pH = 8.7). This conclusion suggests constraints upon the composition of terrestrial analogs to the Mars soil; acidic components may be present, but the overall mixture must be basic in order to simulate the Viking GEX results.

Simulations of the Viking gas exchange experiment using palagonite and Fe-rich montmorillonite as terrestrial analogs - Implications for the surface composition of Mars

NASA Astrophysics Data System (ADS)

Quinn, Richard; Orenberg, James

1993-10-01

Simulations of the Gas Exchange Experiment (GEX), one of the Viking Lander Biology Experiments, were run using palagonite and Fe-rich montmorillonite as terrestrial analogs of the Martian soil. These terrestrial analogs were exposed to a nutrient solution of the same composition as that of the Viking Landers under humid (no contact with nutrient) and wet (intimate contact) conditions. The headspace gases in the GEX sample cell were sampled and then analyzed by gas chromatography under both humid and wet conditions. Five gases were monitored: CO2, N2, O2, Ar, and Kr. It was determined that in order to simulate the CO2 gas changes of the Viking GEX experiment, the mixture of soil analog mineral plus nutrient medium must be slightly (pH = 7.4) to moderately basic (pH = 8.7). This conclusion suggests constraints upon the composition of terrestrial analogs of the Mars soil; acidic components may be present, but the overall mixture must be basic in order to simulate the Viking GEX results.

H2 Detection via Polarography

NASA Technical Reports Server (NTRS)

Dominquez, Jesus; Barile, Ron

2006-01-01

Polarography is the measurement of the current that flows in solution as a function of an applied voltage. The actual form of the observed polarographic current depends upon the manner in which the voltage is applied and on the characteristics of the working electrode. The new gas polarographic H2 sensor shows a current level increment with concentration of the gaseous H2 similar to those relating to metal ions in liquid electrolytes in well-known polarography. This phenomenon is caused by the fact that the diffusion of the gaseous H2 through a gas diffusion hole built in the sensor is a rate-determining step in the gaseous-hydrogen sensing mechanism. The diffusion hole artificially limits the diffusion of the gaseous H2 toward the electrode located at the sensor cavity. This gas polarographic H2 sensor is actually an electrochemical-pumping cell since the gaseous H2 is in fact pumped via the electrochemical driving force generated between the electrodes. Gaseous H2 enters the diffusion hole and reaches the first electrode (anode) located in the sensor cavity to be transformed into an H ions or protons; H ions pass through the electrolyte and reach the second electrode (cathode) to be reformed to gaseous H2. Gas polarographic O2 sensors are commercially available; a gas polarographic O2 sensor was used to prove the feasibility of building a new gas polarographic H2 sensor.

Pre- and Post-Perihelion Observations of C/2009 P1 (Garradd): Evidence for an Oxygen-Rich Heritage?

NASA Astrophysics Data System (ADS)

DiSanti, Michael A.; Villanueva, G. L.; Paganini, L.; Bonev, B. P.; Keane, J. V.; Meech, K. J.; Mumma, M. J.

2013-10-01

We present pre- and post-perihelion observations of Comet C/2009 P1 (Garradd), on UT 2011 October 13 (heliocentric distance Rh = 1.83 AU) and 2012 January 8 (Rh = 1.57 AU), respectively, using the high-resolution infrared spectrometer (NIRSPEC) on the Keck II 10-m telescope on Mauna Kea, HI. On October 13, we obtained production rates for nine primary volatiles (native ices): H2O, CO, CH3OH, CH4, C2H6, HCN, C2H2, H2CO, and NH3. On January 8, we obtained production rates for three of these (H2O, CH4, and HCN) and sensitive upper limits for three others (C2H2, H2CO, and NH3). CO was enriched and C2H2 was depleted, yet C2H6 and CH3OH were close to their current mean values as measured in a dominant group of Oort cloud comets. We compare the composition of Garradd with other CO-rich comets C/1999 T1 (McNaught-Hartley), C/1996 B2 (Hyakutake), and C/1995 O1 (Hale-Bopp), and with other comets in our database. We discuss possible implications regarding the processing history of its pre-cometary ices. Our measurements of C/2009 P1 indicate consistent pre- and post-perihelion abundance ratios for trace species relative to H2O, suggesting we were measuring a homogeneous composition to the depths sampled in the nucleus. The overall gas production was lower post-perihelion despite its smaller heliocentric distance on January 8. This is qualitatively consistent with other studies of C/2009 P1. On October 13, the water profile showed a pronounced excess towards the Sun-facing hemisphere that was not seen in other molecules nor in the dust continuum. Inter-comparison of profiles from October 13 permitted us to estimate the fraction of all H2O released in the coma and contained within our slit. We attribute this excess H2O to release from relatively pure, water-rich icy grains. Similar evidence for extended release was not observed on January 8 and this, together with its overall lower gas production post-perihelion, suggests loss of one or more active regions on the nucleus

Atmospheric reactions of ortho cresol: Gas phase and aerosol products

NASA Astrophysics Data System (ADS)

Grosjean, Daniel

Photo-oxidation of ortho-cresol (0.5-1.1 ppm) and oxides of nitrogen (0.12-0.66 ppm) in air yielded the following gas-phase products: pyruvic acid, acetaldehyde, formaldehyde, peroxyacetylnitrate, nitrocresol and trace levels of nitric acid and methyl nitrate. particulate phase products included 2-hydroxy3-nitro toluene, 2-hydroxy-5-nitro toluene, 2-hydroxy-3,5-dinitrotoluene and, tentatively, several hydroxynitrocresol isomers. Yields of gas-phase products (0.8 % for pyruvic acid, 5-11 % for the sum of the aromatic ring fragmentation products) and of aerosol products (5-19% on a carbon basis, with particulate carbon formation rates of 30-80 μ g m -3 h -1) are discussed in terms of photochemical reaction pathways. From 60 to 89 % of the initial NO x was consumed in these reactions and a significant fraction of the reacted NO x could be accounted for as particulate nitro-aromatic products.

Molecular rotational line profiles from oxygen-rich red giant winds

NASA Technical Reports Server (NTRS)

Justtanont, K.; Skinner, C. J.; Tielens, A. G. G. M.

1994-01-01

We have developed a radiative transfer model of the dust and gas envelopes around late-type stars. The gas kinetic temperature for each star is calculated by solving equations of motion and the energy balance simultaneously. The main processes include viscous heating and adiabatic and radiative cooling. Heating is dominated by viscosity as the grains stream outward through the gas, with some contribution in oxygen-rich stars by near-IR pumping of H2O followed by collisional de-excitation in the inner envelope. For O-rich stars, rotational H2O cooling is a dominant mechanism in the middle part of the envelope, with CO cooling being less significant. We have applied our model to three well-studied oxygen-rich red giant stars. The three stars cover a wide range of mass-loss rates, and hence they have different temperature structures. The derived temperature structures are used in calculating CO line profiles for these objects. Comparison of the dust and gas mass-loss rates suggests that mass-loss rates are not constant during the asymptotic giant branch phase. In particular, the results show that the low CO 1-0 antenna temperatures of OH/IR stars reflect an earlier phase of much lower mass-loss rate.

Enhanced photocatalytic H2-production activity of graphene-modified titania nanosheets

NASA Astrophysics Data System (ADS)

Xiang, Quanjun; Yu, Jiaguo; Jaroniec, Mietek

2011-09-01

Graphene-modified TiO2 nanosheets with exposed (001) facets (graphene/TiO2) were prepared by microwave-hydrothermal treatment of graphene oxide (GO) and hydrothermally synthesized TiO2 nanosheets with exposed (001) facets in an ethanol-water solvent. These nanocomposite samples showed high photocatalytic H2-production activity in aqueous solutions containing methanol, as sacrificial reagent, even without Pt co-catalyst. The optimal graphene content was found to be ~1.0 wt%, giving a H2-production rate of 736 μmol h-1 g-1 with a quantum efficiency (QE) of 3.1%, which exceeded the rate observed on pure TiO2 nanosheets by more than 41 times. This high photocatalytic H2-production activity is due to the deposition of TiO2 nanosheets on graphene sheets, which act as an electron acceptor to efficiently separate the photogenerated charge carriers. The observed enhancement in the photocatalytic activity is due to the lower absolute potential of graphene/graphene z.rad- (-0.08 V vs. SHE, pH = 0) in comparison to the conduction band (-0.24 V) of anatase TiO2, meanwhile the aforementioned absolute value is higher than the reduction potential of H+ (0 V), which favors the electron transfer from the conduction band (CB) of TiO2 to graphene sheets and the reduction of H+, thus enhancing photocatalytic H2-production activity. The proposed mechanism for the observed photocatalytic performance of TiO2 nanosheets, modified with a small amount of graphene, was further confirmed by photoluminescence spectroscopy and transient photocurrent response. This work not only shows a possibility for the utilization of low cost graphene sheets as a substitute for noble metals (such as Pt) in the photocatalytic H2-production but also for the first time shows a significant enhancement in the H2-production activity by using metal-free carbon material as an effective co-catalyst.

Outbursts of H2O in Comet P/Halley

NASA Astrophysics Data System (ADS)

Larson, H. P.; Hu, H.-Y.; Mumma, M. J.; Weaver, H. A.

1990-07-01

Comet Halley gas-production monitoring efforts in March 1986 with the NASA Kuiper Airborne Observatory's Fourier transform spectrometer have indicated rapid temporal variations in H2O emissions; a continuous record of an H2O outburst was thus obtained. The event, in which H2O brightness increased by a factor of 2.2 in less than 10 min, is ascribable to an energetic process in the nucleus whose character may have been that of amorphous H2O ice crystallization, chemical explosion, thermal stress, or a compressed gas pocket. The timing and energy of the event appear to require an internal energy source; amorphous ice crystallization is held to be most consistent with compositional and thermal models of cometary nuclei as well as the observations.

Vertical observation of molecular hydrogen and carbon monoxide: Implication for non-photochemical H2 production at ocean surface and subsurface

NASA Astrophysics Data System (ADS)

Kawagucci, S.; Narita, T.; Obata, H.; Ogawa, H.; Gamo, T.

2009-12-01

Biological nitrogen fixation is a key metabolism controlling marine N-cycling and also known as a main H2 source. Recently, it was proposed that a monitoring of surface H2 concentration could be used quickly to figure out the spatial extent of biological nitrogen fixation activity without onboard incubation required for currently used methods for detecting the activity. However, H2 behavior in ocean water was still unresolved. This study carried out vertical observation of H2 and CO concentrations in south of Japan, western North Pacific. Because carbon monoxide, CO, in seawater has no relation with nitrogen fixation metabolism and is produced dominantly by the photochemical reaction, which is an altanative H2 source, simultaneous observation and comparison of H2 and CO concentration is helpful to investigate H2 behavior in ocean water. Reductive gases in seawater were observed during the R/V Tansei-maru KT-08-14 cruise by using a wired CTD-CMS (CTD-carousel multiple sampling) system to conduct vertical sampling (at most 200 m depth) and by using a plastic bucket for sampling surface seawater. The sample in the Niskin-X bottle was directed to the bottom of a 120 mL brown-colored glass vial allowed to overflow by 2 volumes before the tube was slowly withdrawn. After the addition of 0.5 mL HgCl2-saturated solution for poisoning, the PTFE-lined butyl-gum septum was used to cap the vials. Molecular hydrogen (H2) and carbon monoxide (CO) were analyzed at an onboard laboratory within 6 hours after subsampling. 20 mL of sample water was substituted by 20 mL of H2- and CO-free air using a gas-tight syringe; then the vial was put on an automatic shaker and shaken upside down for 6 minutes to achieve a complete equilibrium between the dissolved and head space gases in the vial. The equilibrated headspace was taken by another gas-tight syringe and then injected into a gas chromatograph equipped with a trace reduced gas detector. Vertical distribution of dissolved H2 and CO

Biomass fast pyrolysis in a fluidized bed reactor under N2, CO2, CO, CH4 and H2 atmospheres.

PubMed

Zhang, Huiyan; Xiao, Rui; Wang, Denghui; He, Guangying; Shao, Shanshan; Zhang, Jubing; Zhong, Zhaoping

2011-03-01

Biomass fast pyrolysis is one of the most promising technologies for biomass utilization. In order to increase its economic potential, pyrolysis gas is usually recycled to serve as carrier gas. In this study, biomass fast pyrolysis was carried out in a fluidized bed reactor using various main pyrolysis gas components, namely N(2), CO(2), CO, CH(4) and H(2), as carrier gases. The atmosphere effects on product yields and oil fraction compositions were investigated. Results show that CO atmosphere gave the lowest liquid yield (49.6%) compared to highest 58.7% obtained with CH(4). CO and H(2) atmospheres converted more oxygen into CO(2) and H(2)O, respectively. GC/MS analysis of the liquid products shows that CO and CO(2) atmospheres produced less methoxy-containing compounds and more monofunctional phenols. The higher heating value of the obtained bio-oil under N(2) atmosphere is only 17.8 MJ/kg, while that under CO and H(2) atmospheres increased to 23.7 and 24.4 MJ/kg, respectively. Copyright © 2010 Elsevier Ltd. All rights reserved.

Mineralization of Basalts in the CO 2-H 2O-H 2S System

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

Schaef, Herbert T.; McGrail, B. Peter; Owen, Antionette T.

2013-05-10

Basalt samples representing five different formations were immersed in water equilibrated with supercritical carbon dioxide containing 1% hydrogen sulfide (H2S) at reservoir conditions (100 bar, 90°C) for up to 3.5 years. Surface coatings in the form of pyrite and metal cation substituted carbonates were identified as reaction products associated with all five basalts. In some cases, high pressure tests contained excess H2S, which produced the most corroded basalts and largest amount of secondary products. In comparison, tests containing limited amounts of H2S appeared least reacted with significantly less concentrations of reaction products. In all cases, pyrite appeared to precede carbonation,more » and in some instances, was observed in the absence of carbonation such as in cracks, fractures, and within the porous glassy mesostasis. Armoring reactions from pyrite surface coatings observed in earlier shorter duration tests were found to be temporary with carbonate mineralization observed with all the basalts tested in these long duration experiments. Geochemical simulations conducted with the geochemical code EQ3/6 accurately predicted early pyrite precipitation followed by formation of carbonates. Reactivity with H2S was correlated with measured Fe(II)/Fe(III) ratios in the basalts with more facile pyrite formation occurring with basalts containing more Fe(III) phases. These experimental and modeling results confirm potential for long term sequestration of acid gas mixtures in continental flood basalt formations.« less

UV Raman spectroscopy of H2-air flames excited with a narrowband KrF laser

NASA Technical Reports Server (NTRS)

Shirley, John A.

1990-01-01

Raman spectra of H2 and H2O in flames excited by a narrowband KrF excimer laser are reported. Observations are made over a porous-plug, flat-flame burner reacting H2 in air, fuel-rich with nitrogen dilution to control the temperature, and with an H2 diffusion flame. Measurements made from UV Raman spectra show good agreement with measurements made by other means, both for gas temperature and relative major species concentrations. Laser-induced fluorescence interferences arising from OH and O2 are observed in emission near the Raman spectra. These interferences do not preclude Raman measurements, however.

Local richness along gradients in the Siskiyou herb flora: R.H. Whittaker revisited

USGS Publications Warehouse

Grace, James B.; Harrison, Susan; Damschen, Ellen Ingman

2011-01-01

In his classic study in the Siskiyou Mountains (Oregon, USA), one of the most botanically rich forested regions in North America, R. H. Whittaker (1960) foreshadowed many modern ideas on the multivariate control of local species richness along environmental gradients related to productivity. Using a structural equation model to analyze his data, which were never previously statistically analyzed, we demonstrate that Whittaker was remarkably accurate in concluding that local herb richness in these late-seral forests is explained to a large extent by three major abiotic gradients (soils, topography, and elevation), and in turn, by the effects of these gradients on tree densities and the numbers of individual herbs. However, while Whittaker also clearly appreciated the significance of large-scale evolutionary and biogeographic influences on community composition, he did not fully articulate the more recent concept that variation in the species richness of local communities could be explained in part by variation in the sizes of regional species pools. Our model of his data is among the first to use estimates of regional species pool size to explain variation in local community richness along productivity-related gradients. We find that regional pool size, combined with a modest number of other interacting abiotic and biotic factors, explains most of the variation in local herb richness in the Siskiyou biodiversity hotspot.

Synthesis of ZnO thin film by sol-gel spin coating technique for H2S gas sensing application

NASA Astrophysics Data System (ADS)

Nimbalkar, Amol R.; Patil, Maruti G.

2017-12-01

In this present work, zinc oxide (ZnO) thin film synthesized by a simple sol-gel spin coating technique. The structural, morphology, compositional, microstructural, optical, electrical and gas sensing properties of the film were studied by using XRD, FESEM, EDS, XPS, HRTEM, Raman, FTIR and UV-vis techniques. The ZnO thin film shows hexagonal wurtzite structure with a porous structured morphology. Gas sensing performance of synthesized ZnO thin film was tested initially for H2S gas at different operating temperatures as well as concentrations. The maximum gas response is achieved towards H2S gas at 300 °C operating temperature, at 100 ppm gas concentration as compared to other gases like CH3OH, Cl2, NH3, LPG, CH3COCH3, and C2H5OH with a good stability.

A massive hydrogen-rich Martian greenhouse recorded in D/H

NASA Astrophysics Data System (ADS)

Pahlevan, K.; Schaefer, L. K.; Desch, S. J.; Elkins-Tanton, L. T.

2017-12-01

The deuterium-to-hydrogen (D/H) ratio in Martian atmospheric water ( 6x standard mean ocean water, SMOW) [1,2] is higher than that of known sources [3,4] alluding to a planetary enrichment process. A recent measurement by the Curiosity rover of Hesperian clays yields a D/H value 3x higher than SMOW [5], demonstrating that most enrichment occurred early in planetary history, buttressing the conclusions of Martian meteorite studies [6,7]. Extant models of the isotopic evolution of the Martian hydrosphere have not incorporated primordial H2, despite its likely abundance on early Mars. Here, we report the first 1D climate calculations with an atmospheric composition determined via degassing from a reducing magma ocean to study Martian climate during an early water ocean stage. A reducing Martian magma ocean is expected based on experimental petrology [8], the degassing of which gives rise to an H2-rich steam atmosphere [9] with strong attendant greenhouse warming [10,11] even after the removal of steam via condensation. At the pressures and temperatures prevailing in such a degassed greenhouse, we find that isotopic exchange in the fluid envelope is rapid, strongly concentrating deuterium in water molecules over molecular hydrogen [12]. The subsequent loss of the isotopically light H2-rich atmosphere results in a 2x D/H enrichment in the oceans via isotopic equilibration alone. These calculations suggest that most of the D/H enrichment observed in the first billion years of Martian history is produced by the evolution of a massive ( 100 bar) H2-rich greenhouse in the aftermath of magma ocean crystallization. The proposed link between early planetary process and modern isotopic observable opens a new window into the earliest history of Mars. [1] Owen, T. et al. Science 240, 1767-1770 (1988). [2] Webster, C. R. et al. Science 341, 260-263 (2013). [3] Lunine, J. I. et al. Icarus 165, 1-8, (2003). [4] Marty, B. et al. EPSL 441, 91-102, (2016). [5] Mahaffy, P. et al

A Novel High-Density Phase and Amorphization of Nitrogen-Rich 1H-Tetrazole (CH2N4) under High Pressure

PubMed Central

Li, Wenbo; Huang, Xiaoli; Bao, Kuo; Zhao, Zhonglong; Huang, Yanping; Wang, Lu; Wu, Gang; Zhou, Bo; Duan, Defang; Li, Fangfei; Zhou, Qiang; Liu, Bingbing; Cui, Tian

2017-01-01

The high-pressure behaviors of nitrogen-rich 1H-tetrazole (CH2N4) have been investigated by in situ synchrotron X-ray diffraction (XRD) and Raman scattering up to 75 GPa. A first crystalline-to-crystalline phase transition is observed and identified above ~3 GPa with a large volume collapse (∼18% at 4.4 GPa) from phase I to phase II. The new phase II forms a dimer-like structure, belonging to P1 space group. Then, a crystalline-to-amorphous phase transition takes place over a large pressure range of 13.8 to 50 GPa, which is accompanied by an interphase region approaching paracrystalline state. When decompression from 75 GPa to ambient conditions, the final product keeps an irreversible amorphous state. Our ultraviolet (UV) absorption spectrum suggests the final product exhibits an increase in molecular conjugation. PMID:28218236

A Novel High-Density Phase and Amorphization of Nitrogen-Rich 1H-Tetrazole (CH2N4) under High Pressure.

PubMed

Li, Wenbo; Huang, Xiaoli; Bao, Kuo; Zhao, Zhonglong; Huang, Yanping; Wang, Lu; Wu, Gang; Zhou, Bo; Duan, Defang; Li, Fangfei; Zhou, Qiang; Liu, Bingbing; Cui, Tian

2017-02-20

The high-pressure behaviors of nitrogen-rich 1H-tetrazole (CH 2 N 4 ) have been investigated by in situ synchrotron X-ray diffraction (XRD) and Raman scattering up to 75 GPa. A first crystalline-to-crystalline phase transition is observed and identified above ~3 GPa with a large volume collapse (∼18% at 4.4 GPa) from phase I to phase II. The new phase II forms a dimer-like structure, belonging to P1 space group. Then, a crystalline-to-amorphous phase transition takes place over a large pressure range of 13.8 to 50 GPa, which is accompanied by an interphase region approaching paracrystalline state. When decompression from 75 GPa to ambient conditions, the final product keeps an irreversible amorphous state. Our ultraviolet (UV) absorption spectrum suggests the final product exhibits an increase in molecular conjugation.

Investigation of the Degradation Mechanisms of Particulate Reinforced Epoxy Coatings and Zinc-Rich Coatings Under an Erosion and Corrosion Environment for Oil and Gas Industry Applications

NASA Astrophysics Data System (ADS)

Wang, Dailin

During oil and gas production and transportation, the presence of an oil-sand slurry, together with the presence of CO2, H2S, oxygen, and seawater, create an erosive/abrasive and corrosive environment for the interior surfaces of undersea pipelines transporting oil and gas from offshore platforms. Erosion/wear and corrosion are often synergic processes leading to a much greater material loss of pipeline cross-section than that caused by each individual process alone. Both organic coatings and metallic sacrificial coatings have been widely employed to provide protection to the pipeline steels against corrosion through barrier protection and cathodic protection, and these protection mechanisms have been well studied. However, coating performance under the synergic processes of erosion/wear and corrosion have been much less researched and coating degradation mechanisms when erosion/wear and corrosion are both going on has not been well elucidated. In the work presented in this dissertation, steel panels coated with filler reinforced epoxy coatings and carbon nanotubes (CNTs) reinforced zinc-rich coatings have been evaluated under erosion/wear followed by an exposure to a corrosive environment. Electrochemical tests and material characterization methods have been applied to study the degradation mechanisms of the coatings during the tests and coating degradation mechanisms have been proposed. While organic coatings with a lower amount of filler particles provided better protection in a corrosive environment alone and in solid particle impingement erosion testing alone, organic coatings with a higher amount of filler particles showed better performance during wear testing alone. A higher amount of filler particles was also beneficial in providing protection against wear and corrosion environment, and erosion and corrosion environment. Coating thickness played a significant role in the barrier properties of the coatings under both erosion and corrosion tests. When the

Synthesis and characterization of nanoscale molybdenum sulfide catalysts by controlled gas phase decomposition of Mo(CO){sub 6} and H{sub 2}S

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

Close, M.R.; Petersen, J.L.; Kugler, E.L.

1999-04-05

Molybdenum sulfide catalysts with surface areas ranging from 16 to 120 m{sup 2}/g were prepared by the thermal decomposition of Mo(CO){sub 6} and H{sub 2}S vapors in a specially designed tubular reactor system. The gas phase decomposition (GPD) reactions performed at 500--1100 C produced only MoS{sub 2} when excess H{sub 2}S was used. The optimum temperature range for the high-yield production of MoS{sub 2} was from 500 to 700 C. By controlling the decomposition temperature, the Mo(CO){sub 6} partial pressure, or the inert gas flow rate, the surface area, oxidation state, chemical composition, and the grain size of the molybdenummore » sulfide product(s) were modified. At reactor temperatures between 300 and 400 C, lower valent molybdenum sulfide materials, which were sulfur deficient relative to MoS{sub 2}, were obtained with formal molybdenum oxidation states intermediate to those found for Chevrel phase compounds, M{prime}Mo{sub 6}S{sub 8} (M{prime} = Fe, Ni, Co) and MoS{sub 2}. By lowering the H{sub 2}S flow rate used for the GPD reaction at 1000 C, mixtures containing variable amounts of MoS{sub 2} and Mo{sub 2}S{sub 3} were produced. Thus, through the modification of critical reactor parameters used for these GPD reactions, fundamental material properties were controlled.« less

Formation of CO2, H2 and condensed carbon from siderite dissolution in the 200-300 °C range and at 50 MPa

NASA Astrophysics Data System (ADS)

Milesi, Vincent; Guyot, François; Brunet, Fabrice; Richard, Laurent; Recham, Nadir; Benedetti, Marc; Dairou, Julien; Prinzhofer, Alain

2015-04-01

Laboratory experiments were conducted to investigate the chemical processes governing the carbon speciation associated to hydrothermal decomposition of siderite. Experiments were carried out in sealed gold capsules using synthetic siderite and deionised water. The samples were reacted at 200 and 300 °C, under a pressure of 50 MPa. Siderite dissolved to reach the 3FeCO3 + H2O = Fe3O4 + 3CO2 + H2 equilibrium and magnetite, Fe3O4, was produced accordingly. The gas phase was dominated by CO2, H2 and CH4, the latter being in strong thermodynamic disequilibrium with CO2. Contrary to the other gas products, H2 concentration was found to decrease with run duration. TEM observations showed the occurrence of condensed carbon phases at the surfaces of magnetite and residual siderite grains. Thermodynamic calculations predict the formation of condensed carbon in the experiments according to the reaction: CO2 + 2H2 ⇒ C + 2H2O, which accounted for the observed H2 concentration decrease up to the point where H2 and CO2 activities were buffered by the graphite-siderite-magnetite assemblage. The well-organized structure of the carbon coating around magnetite emphasizes the high catalytic potential of magnetite surface for carbon reduction and polymerization. The formation of such C-rich phases may represent a potential source of CH4 by hydrogenation. On the other hand, the catalysis of Fischer-Tropsch type reactions may be poisoned by the presence of carbon coating on mineral surfaces. In any case, this study also demonstrates that abiotic H2 generation by water reduction, widely studied in recent years in ultrabasic contexts, can also occur in sedimentary contexts where siderite is present. We show that, in the latter case, natural H2 concentration will be buffered by a condensed carbon phase associated with magnetite.

Downhole monitoring of biogenic gas production at the Maguelone shallow injection experimental site (Languedoc coastline, France).

NASA Astrophysics Data System (ADS)

Abdelghafour, H.; Brondolo, F.; Denchik, N.; Pezard, P. A.

2014-12-01

The controllability of CO2 geological storage can ensure the integrity of storage operations, requiring a precise monitoring of reservoir fluids and properties during injection and over time. In this context, deep saline aquifers offer a large capacity of storing CO2, but the accessibility to long term behavior studies remains limited until now. The Maguelone shallow experimental site located near Montpellier (Languedoc, France) provides such an opportunity for the understanding and accuracy of hydrogeophysical monitoring methods. The geology, petrophysic and hydrology of this site have been studied in details in previous studies, revealing the presence of a thin saline aquifer at 13-16 m depth surrounded by clay-rich materials. The site as a whole provides a natural laboratory to study CO2 injection at field scale, shallow depth, hence reasonable costs. The monitoring setup is composed of a series of hydrogeophysical and geochemical methods offering measurements of fluid pore pressure, electrical resistivity, acoustic velocities as well as pH and fluid properties and chemistry. To assess the response of the reservoir during CO2 injection, all measurements need to be compared to a representative baseline. Long after a series of gas injection experiments at Maguelone, fluctuations overtime of reservoir fluids and properties (such as pore fluid pH) were discovered at steady state, demonstrating the natural variability of the site in terms of biogenic gas (H2S, CH4, CO2) production and transfer. For this, a new resistivity baseline had to be constructed for all observatories. From this, the downhole gas saturation was determined versus depth and time from time-lapse resistivity logs analysed on the basis of other logs and laboratory measurements. The Waxman and Smits model (1968) for electrical properties of sand-clay formations was modified to estimate the gas saturation in 4D, to account for surface conductivity and pore connectivity. High frequency logging and

Characterization of a real time H2O2 monitor for use in studies on H2O2 production by antibodies and cells.

PubMed

Sharma, Harish A; Balcavage, Walter X; Waite, Lee R; Johnson, Mary T; Nindl, Gabi

2003-01-01

It was recently shown that antibodies catalyze a reaction between water and ultraviolet light (UV) creating singlet oxygen and ultimately H2O2. Although the in vivo relevance of these antibody reactions is unclear, it is interesting that among a wide variety of non-antibody proteins tested, the T cell receptor is the only protein with similar capabilities. In clinical settings UV is believed to exert therapeutic effects by eliminating inflammatory epidermal T cells and we hypothesized that UV-triggered H2O2 production is involved in this process. To test the hypothesis we developed tools to study production of H2O2 by T cell receptors with the long-term goal of understanding, and improving, UV phototherapy. Here, we report the development of an inexpensive, real time H2O2 monitoring system having broad applicability. The detector is a Clark oxygen electrode (Pt, Ag/AgCl) modified to detect UV-driven H2O2 production. Modifications include painting the electrode black to minimize UV effects on the Ag/AgCl electrode and the use of hydrophilic, large pore Gelnots electrode membranes. Electrode current was converted to voltage and then amplified and recorded using a digital multimeter coupled to a PC. A reaction vessel with a quartz window was developed to maintain constant temperature while permitting UV irradiation of the samples. The sensitivity and specificity of the system and its use in cell-free and cell-based assays will be presented. In a cellfree system, production of H2O2 by CD3 antibodies was confirmed using our real time H2O2 monitoring method. Additionally we report the finding that splenocytes and Jurkat T cells also produce H2O2 when exposed to UV light.

The influence of total solids content and initial pH on batch biohydrogen production by solid substrate fermentation of agroindustrial wastes.

PubMed

Robledo-Narváez, Paula N; Muñoz-Páez, Karla M; Poggi-Varaldo, Hector M; Ríos-Leal, Elvira; Calva-Calva, Graciano; Ortega-Clemente, L Alfredo; Rinderknecht-Seijas, Noemí; Estrada-Vázquez, Carlos; Ponce-Noyola, M Teresa; Salazar-Montoya, J Alfredo

2013-10-15

Hydrogen is a valuable clean energy source, and its production by biological processes is attractive and environmentally sound and friendly. In México 5 million tons/yr of agroindustrial wastes are generated; these residues are rich in fermentable organic matter that can be used for hydrogen production. On the other hand, batch, intermittently vented, solid substrate fermentation of organic waste has attracted interest in the last 10 years. Thus the objective of our work was to determine the effect of initial total solids content and initial pH on H2 production in batch fermentation of a substrate that consisted of a mixture of sugarcane bagasse, pineapple peelings, and waste activated sludge. The experiment was a response surface based on 2(2) factorial with central and axial points with initial TS (15-35%) and initial pH (6.5-7.5) as factors. Fermentation was carried out at 35 °C, with intermittent venting of minireactors and periodic flushing with inert N2 gas. Up to 5 cycles of H2 production were observed; the best treatment in our work showed cumulative H2 productions (ca. 3 mmol H2/gds) with 18% and 6.65 initial TS and pH, respectively. There was a significant effect of TS on production of hydrogen, the latter decreased with initial TS increase from 18% onwards. Cumulative H2 productions achieved in this work were higher than those reported for organic fraction of municipal solid waste (OFMSW) and mixtures of OFMSW and fruit peels waste from fruit juice industry, using the same process. Specific energetic potential due to H2 in our work was attractive and fell in the high side of the range of reported results in the open literature. Batch dark fermentation of agrowastes as practiced in our work could be useful for future biorefineries that generate biohydrogen as a first step and could influence the management of this type of agricultural wastes in México and other countries and regions as well. Copyright © 2013 Elsevier Ltd. All rights reserved.

Accumulative effect of food residues on intestinal gas production.

PubMed

Mego, M; Accarino, A; Malagelada, J-R; Guarner, F; Azpiroz, F

2015-11-01

As mean transit time in the colon is longer than the interval between meals, several consecutive meal loads accumulate, and contribute to colonic biomass. Our aim was to determine the summation effect of fermentable food residues on intestinal gas production. In eight healthy subjects, the volume of endogenous intestinal gas produced in the intestine over a 4-h period was measured by means of a wash-out technique, using an exogenous gas infusion into the jejunum (24 mL/min) and collection of the effluent via a rectal Foley catheter. The exogenous gas infused was labeled (5% SF6 ) to calculate the proportion of endogenous intestinal gas evacuated. In each subject, four experiments were performed ≥1 week apart combining a 1-day high- or low-flatulogenic diet with a test meal or fast. Basal conditions: on the low-flatulogenic diet, intestinal gas production during fasting over the 4-h study period was 609 ± 63 mL. Effect of diet: during fasting, intestinal gas production on the high-flatulogenic diet was 370 ± 146 mL greater than on the low-flatulogenic diet (p = 0.040). Effect of test meal: on the low-flatulogenic diet, intestinal gas production after the test meal was 681 ± 114 mL greater than during fasting (p = 0.001); a similar effect was observed on the high-flatulogenic diet (599 ± 174 mL more intestinal gas production after the test meal than during fasting; p = 0.021). Our data demonstrate temporal summation effects of food residues on intestinal gas production. Hence, intestinal gas production depends on pre-existing and on recent colonic loads of fermentable foodstuffs. © 2015 John Wiley & Sons Ltd.

Enhanced photo-fermentative H2 production using Rhodobacter sphaeroides by ethanol addition and analysis of soluble microbial products

PubMed Central

2014-01-01

Background Biological fermentation routes can provide an environmentally friendly way of producing H2 since they use renewable biomass as feedstock and proceed under ambient temperature and pressure. In particular, photo-fermentation has superior properties in terms of achieving high H2 yield through complete degradation of substrates. However, long-term H2 production data with stable performance is limited, and this data is essential for practical applications. In the present work, continuous photo-fermentative H2 production from lactate was attempted using the purple non-sulfur bacterium, Rhodobacter sphaeroides KD131. As a gradual drop in H2 production was observed, we attempted to add ethanol (0.2% v/v) to the medium. Results As continuous operation went on, H2 production was not sustained and showed a negligible H2 yield (< 0.5 mol H2/mol lactateadded) within two weeks. Electron balance analysis showed that the reason for the gradual drop in H2 production was ascribed to the increase in production of soluble microbial products (SMPs). To see the possible effect of ethanol addition, a batch test was first conducted. The presence of ethanol significantly increased the H2 yield from 1.15 to 2.20 mol H2/mol lactateadded, by suppressing the production of SMPs. The analysis of SMPs by size exclusion chromatography showed that, in the later period of fermentation, more than half of the low molecular weight SMPs (< 1 kDa) were consumed and used for H2 production when ethanol had been added, while the concentration of SMPs continuously increased in the absence of ethanol. It was found that the addition of ethanol facilitated the utilization of reducing power, resulting in an increase in the cellular levels of NAD+ and NADP+. In continuous operation, ethanol addition was effective, such that stable H2 production was attained with an H2 yield of 2.5 mol H2/mol lactateadded. Less than 15% of substrate electrons were used for SMP production, whereas 35% were used in

Gas Transfer Controls Carbon Limitation During Biomass Production by Marine Microalgae.

PubMed

Tamburic, Bojan; Evenhuis, Christian R; Suggett, David J; Larkum, Anthony W D; Raven, John A; Ralph, Peter J

2015-08-24

This study presents the first in-depth analysis of CO2 limitation on the biomass productivity of the biofuel candidate marine microalga Nannochloropsis oculata. Net photosynthesis decreased by 60% from 125 to 50 μmol O2 L(-1)h(-1) over a 12 h light cycle as a direct result of carbon limitation. Continuous dissolved O2 and pH measurements were used to develop a detailed diurnal mechanism for the interaction between photosynthesis, gas exchange and carbonate chemistry in the photo-bioreactor. Gas exchange determined the degree of carbon limitation experienced by the algae. Carbon limitation was confirmed by delivering more CO2 , which increased net photosynthesis back to its steady-state maximum. This study highlights the importance of maintaining replete carbon concentrations in photo-bioreactors and other culturing facilities, either by constant pH operation or preferably by designing a feedback loop based on the dissolved O2 concentration. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fe-doped graphene nanosheet as an adsorption platform of harmful gas molecules (CO, CO2, SO2 and H2S), and the co-adsorption in O2 environments

NASA Astrophysics Data System (ADS)

Cortés-Arriagada, Diego; Villegas-Escobar, Nery; Ortega, Daniela E.

2018-01-01

The adsorption of pollutant gases (CO, CO2, SO2 and H2S) onto Fe-doped graphene nanosheets (FeG) is studied on the basis of density functional theory calculations at the PBE/Def2-SVP level of theory. The most stable adsorption configurations, binding characteristics, electronic properties and stability at room temperature of the FeG-Gas interactions is fully analyzed. The gas molecules are chemisorbed onto FeG with adsorption energies in the range of 0.54-1.8 eV, with an enhanced adsorption strength compared to intrinsic graphene. The stability of the FeG-Gas interactions is dominated by Lewis-acid-base interactions, and its strength is sorted as SO2 > CO > H2S > CO2. The adsorption stability is also retained at room temperature (300 K). Due to the strong interaction of SO2, CO, and H2S, FeG could catalyze or activate these gas molecules, suggesting the possibility of FeG as a catalyst substrate. The electron acceptor/donor character of CO, CO2, SO2 and H2S molecules when adsorbed onto FeG causes charge transfer processes that are responsible for the change in conductance of FeG; thus, the response of the HOMO-LUMO gap of FeG under gas adsorption could be useful for sensing applications. Furthermore, the analysis of the co-adsorption in O2 environments shows that the CO2 interaction turns unstable onto FeG, while the sensing response towards H2S is suppressed. Finally, these results give new insights into the emerging applications of Fe-doped graphene in gas capture/filtration devices, solid-state gas sensors or as a catalyst substrate.

Fundamental Studies of Clay and Clay-rich Mineral Reactions with H2O-CO2 Fluids: Application to Geological Carbon Dioxide Sequestration

NASA Astrophysics Data System (ADS)

Chizmeshya, A. V.

2016-12-01

Geological sequestration is currently being actively developed as a near-term, large-scale carbon sequestration technology in which supercritical carbon dioxide (scCO2) is injected below-ground into saline aquifers, depleted and existing oil and gas reservoir. Implementation strongly depends on the specific geological profile of each candidate injection site. Caprock formations that contain swellable clay minerals are of particular concern, since interaction with injected CO2 may produce complex local structural effects related to shrinkage, desiccation, and plastic response leading to CO2 escape. The current knowledge-base on rock-brine-CO2 interactions often relies on semi-empirical geochemical modeling and autoclave experiments, which necessitate quenching (de-gassing) to ambient conditions for characterization. To avoid these effects we used a moissanite-based microreaction system (Diefenbacher, J et al Rev. Mod. Inst., 76 15103 (2005)) which enables in situ synchrotron characterization of interactions under constant CO2 activity. Synchrotron studies were performed at the GSECARS sector of the Argonne National Lab APS to systematically determine the response of representative Ca- and Na-montmorillonites (STx-1, SWy-1) clays to dry/wet scCO2 (H2O-rich) fluids at T and P encountered in typical aquifers. Our main findings for hydrated STx-1 are that desiccation occurs spontaneously on the scale of minutes-hours over a wide range of conditions in dry scCO2 via release of H2O with volume changes as large as 19% in relation to the initial volume. Desiccation was not observed in wet scCO2, or in corresponding saline solutions containing 1-3 M NaCl, but quenching to ambient conditions from low-pressures leads to re-hydration in STx-1 suggesting a pressure-dependent diffusion barrier for H2O from the clay into bulk scCO2. Similar desiccation transitions with smaller volume changes of 5-9% were also observed in SWy-1 at P 140 atm and T 40 C. At high pressures ( 200 atm

Pressure-induced superconductivity in H2-containing hydride PbH4(H2)2

PubMed Central

Cheng, Ya; Zhang, Chao; Wang, Tingting; Zhong, Guohua; Yang, Chunlei; Chen, Xiao-Jia; Lin, Hai-Qing

2015-01-01

High pressure structure, stability, metallization, and superconductivity of PbH4(H2)2, a H2-containing compound combining one of the heaviest elements with the lightest element, are investigated by the first-principles calculations. The metallic character is found over the whole studied pressure range, although PbH4(H2)2 is metastable and easily decompose at low pressure. The decomposition pressure point of 133 GPa is predicted above which PbH4(H2)2 is stable both thermodynamically and dynamically with the C2/m symmetry. Interestedly, all hydrogen atoms pairwise couple into H2 quasi-molecules and remain this style up to 400 GPa in the C2/m structure. At high-pressure, PbH4(H2)2 tends to form the Pb-H2 alloy. The superconductivity of Tc firstly rising and then falling is observed in the C2/m PbH4(H2)2. The maximum of Tc is about 107 K at 230 GPa. The softening of intermediate-frequency phonon induced by more inserted H2 molecules is the main origin of the high Tc. The results obtained represent a significant step toward the understanding of the high pressure behavior of metallic hydrogen and hydrogen-rich materials, which is helpful for obtaining the higher Tc. PMID:26559369

Contortionist bubbles in andesitic enclaves: implications for gas migration and phase segregation in crystal-rich magmas.

NASA Astrophysics Data System (ADS)

Oppenheimer, J. C.; Cashman, K. V.; Rust, A.; Dobson, K. J.; Bacon, C. R.; Dingwell, D. B.

2016-12-01

In order to constrain gas migration behaviors in crystal-rich magmas, we compare results of analogue experiments to frozen structures in andesitic enclaves. In the analogue experiments air was injected into mixtures of syrup and particles sandwiched between glass plates. We observed a significant increase in bubble deformation and coalescence when particle fractions increased beyond a critical value (the random loose packing). At high particle fractions, bubble growth re-organized (compacted) the particles adjacent to the bubble walls. This caused liquid segregation into patches within the particle suspension and into large void spaces near the outer edge of experiments. We compare these experiments to void morphologies in a 58 x 70 x 73 cm andesitic enclave from silicic-andesite lava flows of Mt Mazama, Oregon (Bacon, 1986). This enclave is zoned, with a vesicle-rich center and a glass-rich rim, suggesting gas-driven melt segregation from the center to the rim. We use both 2D (optical microscopy and SEM) and 3D (X-ray tomography) techniques to image crystal textures and bubble shapes. The center of the enclave bears scattered patches of groundmass in the main phenocryst framework. These patches are similar to those observed in experiments, and thus melt segregation in the enclave may have occurred both toward the rim and toward these patches. Bubble morphologies reveal two main types of bubbles. (1) Lobate and finger-like bubbles, similar to the deformed bubbles in experiments, are found exclusively in the groundmass patches. They are also often associated with compacted crystal structures at the bubble walls. (2) Diktytaxitic textures - angular bubbles flattened against phenocrysts - are abundant in the crystal networks. These voids are entirely connected in 3D and formed the gas-rich center of the enclave. They likely represent a gas migration regime where the expanding gas front cannot deform the crystal structure but instead invades the pore-space between

Doping and defect-induced germanene: A superior media for sensing H2S, SO2, and CO2 gas molecules

NASA Astrophysics Data System (ADS)

Monshi, M. M.; Aghaei, S. M.; Calizo, I.

2017-11-01

First-principles calculations based on density functional theory (DFT) have been employed to investigate the structural, electronic, and gas-sensing properties of pure, defected, and doped germanene nanosheets. Our calculations have revealed that while a pristine germanene nanosheet adsorbs CO2 weakly, H2S moderately, and SO2 strongly, the introduction of vacancy defects increases the sensitivity significantly which is promising for future gas-sensing applications. Mulliken population analysis imparts that an appreciable amount of charge transfer occurs between gas molecules and a germanene nanosheet which supports our results for adsorption energies of the systems. The enhancement of the interactions between gas molecules and the germanene nanosheet has been further investigated by density of states. Projected density of states provides detailed insight of the gas molecule's contribution in the gas-sensing system. Additionally, the influences of substituted dopant atoms such as B, N, and Al in the germanene nanosheet have also been considered to study the impact on its gas sensing ability. There was no significant improvement found in the doped gas sensing capability of germanene over the vacancy defects, except for CO2 upon adsorption on N-doped germanene.

A statistical study of H i gas in nearby narrow-line AGN-hosting galaxies

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

Zhu, Yi-Nan; Wu, Hong, E-mail: zyn@bao.ac.cn, E-mail: hwu@bao.ac.cn

As a quenching mechanism, active galactic nucleus (AGN) feedback could suppress on going star formation in host galaxies. On the basis of a sample of galaxies selected from the Arecibo Legacy Fast ALFA (ALFALFA) H i survey, the dependence of the H i mass (M{sub H} {sub i}), stellar mass (M{sub *}), and H i-to-stellar mass ratio (M{sub H} {sub i}/M{sub *}) on various tracers of AGN activity are presented and analyzed in this paper. Almost all the AGN hostings in this sample are gas-rich galaxies, and there is not any evidence to indicate that the AGN activity could increasemore » or decrease either M{sub H} {sub i} or M{sub H} {sub i}/M{sub *}. The position of the cold neutral gas cannot be fixed accurately based only on available H i data, due to the large beam size of ALFALFA survey. In addition, even though AGN hostings are more easily detected by an H i survey compared with absorption line galaxies, these two types of galaxies show similar star formation history. If an AGN hosting would ultimately evolve into an old red galaxy with low cold gas, then when and how the gas has been exhausted must be solved by future hypotheses and observations.« less

Helium and carbon gas geochemistry of pore fluids from the sediment-rich hydrothermal system in Escanaba Trough

USGS Publications Warehouse

Ishibashi, J.-I.; Sato, M.; Sano, Y.; Wakita, H.; Gamo, T.; Shanks, Wayne C.

2002-01-01

Ocean Drilling Program (ODP) Leg 169, which was conducted in 1996 provided an opportunity to study the gas geochemistry in the deeper part of the sediment-rich hydrothermal system in Escanaba Trough. Gas void samples obtained from the core liner were analyzed and their results were compared with analytical data of vent fluid samples collected by a submersible dive program in 1988. The gas geochemistry of the pore fluids consisted mostly of a hydrothermal component and was basically the same as that of the vent fluids. The He isotope ratios (R/RA = 5.6-6.6) indicated a significant mantle He contribution and the C isotopic compositions of the hydrocarbons [??13C(CH4) = -43???, ??13C(C2H6) = -20???] were characterized as a thermogenic origin caused by hydrothermal activity. On the other hand, the pore fluids in sedimentary layers away from the hydrothermal fields showed profiles which reflected lateral migration of the hydrothermal hydrocarbons and abundant biogenic CH4. Helium and C isotope systematics were shown to represent a hydrothermal component and useful as indicators for their distribution beneath the seafloor. Similarities in He and hydrocarbon signatures to that of the Escanaba Trough hydrothermal system were found in some terrestrial natural gases, which suggested that seafloor hydrothermal activity in sediment-rich environments would be one of the possible petroleum hydrocarbon generation scenarios in unconventional geological settings. ?? 2002 Elsevier Science Ltd. All rights reserved.

Exploration of H2O-CO2 Solubility in Alkali Basalt at low-H2O

NASA Astrophysics Data System (ADS)

Roggensack, K.; Allison, C. M.; Clarke, A. B.

2017-12-01

A number of recent experimental studies have found conflicting evidence for and against the influence of H2O on CO2 solubility in basalt and alkali-rich mafic magma (e.g. Behrens et al., 2009; Shishkina et al., 2010;2014; Iacono-Marziano et al., 2012). Some of the uncertainty is due to the error with spectroscopic determination (FTIR) of carbon and the challenge of controlling H2O abundance in experiments. It's been widely observed that even experimental capsules without added H2O may produce hydrous glasses containing several wt.% H2O. We conducted fluid-saturated, mixed-fluid (H2O-CO2) experiments to determine the solubility in alkali basalt with particular emphasis on conditions at low-H2O. To limit possible H2O contamination, materials were dried prior to loading and experimental capsules were sealed under vacuum. Experiments were run using a piston-cylinder, in Pt (pre-soaked in Fe) or AuPd capsules and operating at pressures from 400 to 600 MPa. Post-run the capsules were punctured under vacuum and fluids were condensed, separated, and measured by mercury manometry. A comparison between two experiments run at the same temperature and pressure conditions but with different fluid compositions illustrates the correlation between carbonate and H2O solubility. Uncertainties associated with using concentrations calculated from FTIR data can be reduced by directly comparing analyses on wafers of similar thickness. We observe that the experiment with greater H2O absorbance also has a higher carbonate absorbance than the experiment with lower H2O absorbance. Since the experiments were run at the same pressure, the experiment with more water-rich fluid, and higher dissolved H2O, has lower CO2 fugacity, but surprisingly has higher dissolved CO2 content. Overall, the results show two distinct trends. Experiments conducted at low-H2O (0.5 to 0.8 wt.%) show lower dissolved CO2 than those conducted at moderate-H2O (2 to 3 wt.%) at similar CO2 fugacity. These data show that

H2S: a universal defense against antibiotics in bacteria.

PubMed

Shatalin, Konstantin; Shatalina, Elena; Mironov, Alexander; Nudler, Evgeny

2011-11-18

Many prokaryotic species generate hydrogen sulfide (H(2)S) in their natural environments. However, the biochemistry and physiological role of this gas in nonsulfur bacteria remain largely unknown. Here we demonstrate that inactivation of putative cystathionine β-synthase, cystathionine γ-lyase, or 3-mercaptopyruvate sulfurtransferase in Bacillus anthracis, Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli suppresses H(2)S production, rendering these pathogens highly sensitive to a multitude of antibiotics. Exogenous H(2)S suppresses this effect. Moreover, in bacteria that normally produce H(2)S and nitric oxide, these two gases act synergistically to sustain growth. The mechanism of gas-mediated antibiotic resistance relies on mitigation of oxidative stress imposed by antibiotics.

A Thermodynamic Approach for Modeling H2O-CO2 Solubility in Alkali-rich Mafic Magmas at Mid-crustal Pressures

NASA Astrophysics Data System (ADS)

Allison, C. M.; Roggensack, K.; Clarke, A. B.

2017-12-01

Volatile solubility in magmas is dependent on several factors, including composition and pressure. Mafic (basaltic) magmas with high concentrations of alkali elements (Na and K) are capable of dissolving larger quantities of H2O and CO2 than low-alkali basalt. The exsolution of abundant gases dissolved in alkali-rich mafic magmas can contribute to large explosive eruptions. Existing volatile solubility models for alkali-rich mafic magmas are well calibrated below 200 MPa, but at greater pressures the experimental data is sparse. To allow for accurate interpretation of mafic magmatic systems at higher pressures, we conducted a set of mixed H2O-CO2 volatile solubility experiments between 400 and 600 MPa at 1200 °C in six mafic compositions with variable alkali contents. Compositions include magmas from volcanoes in Italy, Antarctica, and Arizona. Results from our experiments indicate that existing volatile solubility models for alkali-rich mafic magmas, if extrapolated beyond their calibrated range, over-predict CO2 solubility at mid-crustal pressures. Physically, these results suggest that volatile exsolution can occur at deeper levels than what can be resolved from the lower-pressure experimental data. Existing thermodynamic models used to calculate volatile solubility at different pressures require two experimentally derived parameters. These parameters represent the partial molar volume of the condensed volatile species in the melt and its equilibrium constant, both calculated at a standard temperature and pressure. We derived these parameters for each studied composition and the corresponding thermodynamic model shows good agreement with the CO2 solubility data of the experiments. A general alkali basalt solubility model was also constructed by establishing a relationship between magma composition and the thermodynamic parameters. We utilize cation fractions from our six compositions along with four compositions from the experimental literature in a linear

Geraniol (2,6-dimethyl-2,6-octadien-8-ol) reactions with ozone and OH radical: Rate constants and gas-phase products

NASA Astrophysics Data System (ADS)

Forester, Crystal D.; Ham, Jason E.; Wells, J. R.

The bimolecular rate constants, kOH+geraniol, (231±58)×10 -12 cm 3 molecule -1 s -1 and k+geraniol, (9.3±2.3)×10 -16 cm 3 molecule -1 s -1, were measured using the relative rate technique for the reaction of the hydroxyl radical (OH) and ozone (O 3) with 2,6-dimethyl-2,6-octadien-8-ol (geraniol) at (297±3) K and 1 atmosphere total pressure. To more clearly define part of geraniol's indoor environment degradation mechanism, the products of the geraniol+OH and geraniol+O 3 reactions were also investigated. The identified geraniol+OH and geraniol+O 3 reaction products were: acetone, hydroxyacetaldehyde (glycolaldehyde, HC( dbnd O)CH 2OH), ethanedial (glyoxal, HC( dbnd O)C( dbnd O)H), and 2-oxopropanal (methylglyoxal, CH 3C( dbnd O)C( dbnd O)H). The use of derivatizing agents O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) and N,O-bis(trimethylsilyl) trifluoroacetamide (BSTFA) were used to propose 4-oxopentanal as the other major geraniol+OH and geraniol+O 3 reaction product. The elucidation of this other reaction product was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible geraniol+OH and geraniol+O 3 reaction mechanisms based on previously published volatile organic compound+OH and volatile organic compound+O 3 gas-phase reaction mechanisms.

The CBM RICH project

NASA Astrophysics Data System (ADS)

Adamczewski-Musch, J.; Akishin, P.; Becker, K.-H.; Belogurov, S.; Bendarouach, J.; Boldyreva, N.; Chernogorov, A.; Deveaux, C.; Dobyrn, V.; Dürr, M.; Eschke, J.; Förtsch, J.; Heep, J.; Höhne, C.; Kampert, K.-H.; Kochenda, L.; Kopfer, J.; Kravtsov, P.; Kres, I.; Lebedev, S.; Lebedeva, E.; Leonova, E.; Linev, S.; Mahmoud, T.; Michel, J.; Miftakhov, N.; Niebur, W.; Ovcharenko, E.; Patel, V.; Pauly, C.; Pfeifer, D.; Querchfeld, S.; Rautenberg, J.; Reinecke, S.; Riabov, Y.; Roshchin, E.; Samsonov, V.; Tarasenkova, O.; Traxler, M.; Ugur, C.; Vznuzdaev, E.; Vznuzdaev, M.

2017-02-01

The CBM RICH detector is an integral component of the future CBM experiment at FAIR, providing efficient electron identification and pion suppression necessary for the measurement of rare dileptonic probes in heavy ion collisions. The RICH design is based on CO2 gas as radiator, a segmented spherical glass focussing mirror with Al+MgF2 reflective coating, and Multianode Photomultipliers for efficient Cherenkov photon detection. Hamamatsu H12700 MAPMTs have recently been selected as photon sensors, following an extensive sensor evaluation, including irradiation tests to ensure sufficient radiation hardness of the MAPMTs. A brief overview of the detector design and concept is given, results on the radiation hardness of the photon sensors are shown, and the development of a FPGA-TDC based readout chain is discussed.

The HADES-RICH upgrade using Hamamatsu H12700 MAPMTs with DiRICH FEE + Readout

NASA Astrophysics Data System (ADS)

Patel, V.; Traxler, M.

2018-03-01

The High Acceptance Di-Electron Spectrometer (HADES) is operational since the year 2000 and uses a hadron blind RICH detector for electron identification. The RICH photon detector is currently replaced by Hamamatsu H12700 MAPMTs with a readout system based on the DiRICH front-end module. The electronic readout chain is being developed as a joint effort of the HADES-, CBM- and PANDA collaborations and will also be used in the photon detectors for the upcoming Compressed Baryonic Matter (CBM) and PANDA experiments at FAIR . This article gives a brief overview on the photomultipliers and their quality assurance test measurements, as well as first measurements of the new DiRICH front-end module in final configurations.

Characterization of H/V Spectral Ratios for the Assessment of Slope Stability in the Gas Hydrate-rich Area: an Example from Offshore SW Taiwan

NASA Astrophysics Data System (ADS)

Lin, J. Y.; Tsia, C. H.; Cheng, W. B.; Chin, S. J.; Lin, S. S.; Liang, C. W.

2015-12-01

The Nakamura's method, which calculates the ratios between horizontal and vertical component spectra of seismic signals (H/V), is widely used in the inland area. However, few related estimations were performed for the offshore area and little knowledge for the marine sediments were obtained. From 2013 to 2015, three passive ocean bottom seismometer (OBS) experiments were conducted in gas hydrate-rich area offshore SW Taiwan in the aim of acquiring information related to the physical properties of seafloor sediments. The H/V of the seafloor sediments in the three areas were estimated by using the ambient noise and seismic signal recorded by OBSs. The resonance frequency of each site was estimated from the main peak of H/V distribution and a range between 5 and 10 Hz were obtained. Based on the empirical law, this resonance frequency range should correspond to a sediment thickness of approximately several to ten of meters. This estimation is consistent with the thickness of the sedimentary cover imaged by chirp sonar survey, suggesting that the site response of seafloor is dominantly controlled by the unconsolidated sedimentary layer on the top of the sea bed. Remarkably, the H/V ratios obtained in our study area are much larger than that calculated for the inland areas. The magnification can reach as high as 50 to more than 100. This observation infers that the sea water movement might emphasize the horizontal motion of the marine sediments, which is crucial for the slope stability assessment. Moreover, for most stations located in the active margin, no distinct peak is observed for the H/V pattern calculated during earthquakes. However, in the passive margin, the H/V peak calculated from ambient noise and earthquakes is mostly identical. This phenomenon may suggest that relatively unclear sedimentary boundary exist in the active margin environment. Estimating H/V spectral ratios of data recorded by the OBSs deployed in the southwest Taiwan offshore area offers a

Noble gases in CH 4-rich gas fields, Alberta, Canada

NASA Astrophysics Data System (ADS)

Hiyagon, H.; Kennedy, B. M.

1992-04-01

The elemental and isotopic compositions of helium, neon, argon, and xenon in twenty-one CH 4-rich natural gas samples from Cretaceous and Devonian reservoirs in the Alberta, Canada, sedimentary basin were measured. In all but a few cases, radiogenic ( 4He, 40Ar, and 131-136Xe) and nucleogenic ( 21,22Ne) isotopes dominated. Based solely on the noble gas composition, two types of natural gas reservoirs are identified. One (Group B) is highly enriched in radiogenic-nucleogenic noble gases and varies little in composition: 3He /4He = 1.5 ± 0.5 × 10 -8, 40Ar /36Ar = 5000-6500 , 40∗Ar /4He = 0.10 , 136∗Xe /4He ~ 0.7 × 10 -9, and 21∗Ne /22∗Ne = 0.452 ± 0.041 (∗ denotes radiogenic or nucleogenic origin; all 4He is radiogenic). High nitrogen content with 4He /N 2 ~ 0.06 is also characteristic of Group B samples. The remaining samples (Group A) contain a radiogenic-nucleogenic component with a different composition and, relative to Group B samples, the extent of enrichment in this component is less and more variable: 3He /4He = 10-70 × 10 -8, 40Ar /36Ar < 1550 , and 40∗Ar /4He ~ 0.25 . The composition of Group B radiogenic-nucleogenic noble gases is consistent with production in crust of average composition. Enrichment in Group B noble gases and nitrogen increases with proximity to the underlying Precambrian basement, consistent with a present-day mass flux into the overlying sedimentary basin. Inferred 40∗Ar /136∗Xe 4He ratios imply a basement source enriched in thorium relative to uranium and potassium (Th/U > 20). Combined, the overall lower total radiogenic-nucleogenic content of Group A reservoirs, the greater variability in composition, and the appearance of Group A noble gases in reservoirs higher in the sedimentary sequence relative to the underlying basement implies that the Group A radiogenic-nucleogenic noble gases are indigenous to the sediments. The most interesting aspect of the Group A noble gases are the very high 3He /4He ratios; ~ 10

Simultaneous flue gas bioremediation and reduction of microalgal biomass production costs.

PubMed

Douskova, I; Doucha, J; Livansky, K; Machat, J; Novak, P; Umysova, D; Zachleder, V; Vitova, M

2009-02-01

A flue gas originating from a municipal waste incinerator was used as a source of CO(2) for the cultivation of the microalga Chlorella vulgaris, in order to decrease the biomass production costs and to bioremediate CO(2) simultaneously. The utilization of the flue gas containing 10-13% (v/v) CO(2) and 8-10% (v/v) O(2) for the photobioreactor agitation and CO(2) supply was proven to be convenient. The growth rate of algal cultures on the flue gas was even higher when compared with the control culture supplied by a mixture of pure CO(2) and air (11% (v/v) CO(2)). Correspondingly, the CO(2) fixation rate was also higher when using the flue gas (4.4 g CO(2) l(-1) 24 h(-1)) than using the control gas (3.0 g CO(2) l(-1) 24 h(-1)). The toxicological analysis of the biomass produced using untreated flue gas showed only a slight excess of mercury while all the other compounds (other heavy metals, polycyclic aromatic hydrocarbons, polychlorinated dibenzodioxins and dibenzofurans, and polychlorinated biphenyls) were below the limits required by the European Union foodstuff legislation. Fortunately, extending the flue gas treatment prior to the cultivation unit by a simple granulated activated carbon column led to an efficient absorption of gaseous mercury and to the algal biomass composition compliant with all the foodstuff legislation requirements.

Observations of VOC emissions and photochemical products over US oil- and gas-producing regions using high-resolution H3O+ CIMS (PTR-ToF-MS)

NASA Astrophysics Data System (ADS)

Koss, Abigail; Yuan, Bin; Warneke, Carsten; Gilman, Jessica B.; Lerner, Brian M.; Veres, Patrick R.; Peischl, Jeff; Eilerman, Scott; Wild, Rob; Brown, Steven S.; Thompson, Chelsea R.; Ryerson, Thomas; Hanisco, Thomas; Wolfe, Glenn M.; St. Clair, Jason M.; Thayer, Mitchell; Keutsch, Frank N.; Murphy, Shane; de Gouw, Joost

2017-08-01

VOCs related to oil and gas extraction operations in the United States were measured by H3O+ chemical ionization time-of-flight mass spectrometry (H3O+ ToF-CIMS/PTR-ToF-MS) from aircraft during the Shale Oil and Natural Gas Nexus (SONGNEX) campaign in March-April 2015. This work presents an overview of major VOC species measured in nine oil- and gas-producing regions, and a more detailed analysis of H3O+ ToF-CIMS measurements in the Permian Basin within Texas and New Mexico. Mass spectra are dominated by small photochemically produced oxygenates and compounds typically found in crude oil: aromatics, cyclic alkanes, and alkanes. Mixing ratios of aromatics were frequently as high as those measured downwind of large urban areas. In the Permian, the H3O+ ToF-CIMS measured a number of underexplored or previously unreported species, including aromatic and cycloalkane oxidation products, nitrogen heterocycles including pyrrole (C4H5N) and pyrroline (C4H7N), H2S, and a diamondoid (adamantane) or unusual monoterpene. We additionally assess the specificity of a number of ion masses resulting from H3O+ ion chemistry previously reported in the literature, including several new or alternate interpretations.

Amorphous In–Ga–Zn–O Powder with High Gas Selectivity towards Wide Range Concentration of C2H5OH

PubMed Central

Chen, Hongxiang; Jiang, Wei; Zhu, Lianfeng; Yao, Youwei

2017-01-01

Amorphous indium gallium zinc oxide (a-IGZO) powder was prepared by typical solution-based process and post-annealing process. The sample was used as sensor for detecting C2H5OH, H2, and CO. Gas-sensing performance was found to be highly sensitive to C2H5OH gas in a wide range of concentration (0.5–1250 ppm) with the response of 2.0 towards 0.5 ppm and 89.2 towards 1250 ppm. Obvious difference of response towards C2H5OH, H2, and CO was found that the response e.g., was 33.20, 6.64, and 2.84 respectively at the concentration of 200 ppm. The response time and recovery time of was 32 s and 14 s respectively towards 200 ppm concentration of C2H5OH gas under heating voltage of 6.5 V. PMID:28538686

Productivity is a poor predictor of plant species richness

USDA-ARS?s Scientific Manuscript database

For 30 years, the relationship between net primary productivity and species richness has generated intense debate in ecology about the processes regulating fine-scale species richness. The true relationship was thought to be hump-shaped, with richness peaking at intermediate levels of productivity, ...