Chemical Composition Of Gas Research Articles

Chemical composition of gas and particle–phase products of OH–initiated oxidation of 1,3,5–trimethylbenzene

A laboratory study was performed to investigate the composition of products formed from OH–initiated oxidation of aromatic hydrocarbon 1,3,5–trimethylbenzene. The experiments were conducted by irradiating 1,3,5–trimethylbenzene/CH3ONO/NO/air mixtures in smog chamber. The chemical composition of gas and particle–phase products have been investigated with gas chromatography/mass spectrometry (GC/MS) and the aerosol laser time–of–flight mass spectrometer (ALTOFMS), respectively. Experimental results showed that 3,5–dimethyl benzaldehyde, 2,4,6–trimethylphenol, 2–methyl–4–oxo–2–pentenal and 3,5–dimethyl–2–furanone were the predominant products in both the gas and particle–phases. However, there were some differences between detected gas–phase products and those of particle–phase, for example, oxalic acid, 2–methyl–2–hydroxy–3,4–dioxo–pentanal, and 2,3,5–trimethyl–3–nitro–phenol were only existing in the particle–phase. The possible reaction mechanisms leading to these products are also proposed. Compared to offline methods such as GC–MS measurement, the ALTOFMS detection can analyze real–time the secondary organic aerosol (SOA) successfully and provide more information on the products. Thus, ALTOFMS is a useful tool to reveal the formation and transformation processes of SOA particles in smog chambers.

Fourier-transformed infrared absorption spectroscopy: a tool to characterize the chemical composition of Ar–NH3–SiH4 dielectric barrier discharge

This study brings initial insight into the characterization of the gas chemical composition in a dielectric barrier discharge (DBD) by Fourier-transformed infrared absorption spectroscopy. Capitalizing on a double path of the IR beam, measurements were performed in 5 cm long, 2 mm gap plasma. As the IR beam cross-section in the plasma was 2 × 2 mm2, a translation system was used to scan the plasma along the direction of the gas flow with a 2 mm spatial resolution.In the case of Ar–SiH4(67 ppm)–NH3(133 ppm) glow-mode DBD, all IR spectra peaks from 6000 to 800 cm−1 are related to vibrations of Si–H from SiH4 and N–H from NH3. Here, the N–H vibration is observable but non-quantifiable.At 50 kHz excitation, the absolute concentration of SiH4 was measured at different positions and different power values in continuous and modulated modes. In the absence of powder formation in the plasma and for an initial density of 1.6 × 1015 cm−3, all the measurements are fitted by the same exponential decay leading to an energy of 38 eV per dissociated molecule of SiH4. The presence of powders in the plasma reduces SiH4 dissociation rate by a factor larger than 4.

English

The fixed oils extracted from the fruit (berry) of Withania somnifera were evaluated for their chemical composition. The gas chromatography-mass spectrometry (GC-MS) analysis shows the presence of various saturated and unsaturated fatty acids present in the roots ofWithania somnifera. The total eight fatty acid compounds were identified by GC-MS with the library searches scale with varying percentage such as linoleic acid (11.247%), linoleic acid (4.000%), palmitic acid, (2.842%) and tetracosanoic acid (0.880%), palmitic acid (0.42%), lenoleic acid (0.23%), oleic acid (0.14%), elaidic acid (0.01%). The fixed oil was evaluated for different biological activities such as phytotoxicity, antibacterial, antifungal, cytotoxicity,antibacterial, and antiurease activities. The oil shows moderate percent inhibition against the entire activities. The oil shows dose dependent DPPH radical scavenging activity.   Key words: Withania somnifera, gas chromatography-mass spectrometry (GC-MS), chemical composition, phytotoxicity, cytotoxicity, antimicrobial, diphenylpicrylhydrazyl (DPPH) scavenging, urease assay and inhibition.

The effects of Si and expanded PTFE substrates on formation and hydrogenation of Mg and Mg–Ti films

In this work, we investigated how DC and pulsed DC Ar gas plasma treatment changes surface topography and chemical composition of silicon and expanded Polytetrafluoroethylene (ePTFE) substrates and how different surface pretreatment techniques can affect the formation and hydrogenation of Mg and Mg–Ti films. It is observed that pre-treating Si and ePTFE substrates with different plasma modes results in significant changes of microstructures of as-deposited Mg and Mg–Ti films. After the hydrogenation of Mg films at 20 bar H2 pressure and 180 °C temperature the formation of crystalline MgH2 phase is observed only for the films deposited on plasma non-treated Si substrates which had the films with smallest dimensions of its columnar structure. It is known that, usually, Ti additives has positive effect on hydrogenation properties of Mg, but in this study independently of the used substrate pre-treatment technique after the hydrogenation of Mg–Ti films their XRD analysis showed no peaks of the crystalline hydride phase. However, depending on the surface properties of the substrate after hydrogenation Mg–Ti films also have several disparities which are discussed and attributed to the potentially related substrate features.

Experimental study of the effect of gas nature on plasma arc cutting of mild steel

This paper is devoted to the experimental investigation of arc cutting of mild steel using plasmas generated in gas and liquid media. Due to different chemical compositions, the examined media have different thermophysical properties, which affect the properties of the generated plasma and cutting performance. The experiments are performed on 15 mm mild steel plates using commercial equipment at 60 A to approach real operation conditions in application areas. The studied gases are chosen according to recommendations of the world's leading manufacturers of arc cutting equipment for mild steel. Specific differences between plasma gases are discussed from the point of view of properties of the gas and the generated plasma, amount of removed material, kerf shape and overall energy balance of the cutting process. The paper describes the role of exothermic reaction of iron oxidation for oxygen cutting and explains its neglect for liquid cutting. This paper explains the potential of facilitating the cutting process by modification of the plasma gas chemical composition and flow rate.

Influence of SO3 in flue gas on electrostatic precipitability of high-alumina coal fly ash from a power plant in China

Abstract In China, particles in flue gasses emitted by coal-fired power plants are mainly cleaned using electrostatic precipitators (ESPs). However, some power plants have experienced decrease in the collection efficiency of ESPs after burning low-sulfur and high-alumina coals. In order to make ESPs collect effectively the PM 2.5 in the flue gas before and after SO 3 -flue gas conditioning (FGC), the resistivity, size distribution, chemical composition, and specific surface of the fly ash sampled from Tuoketuo Power Plant ESPs were analyzed using the portable dust electrical resistivity test instrument, Bahco centrifuge, constant law, and the COULTERTM SA 3100TM specific surface area analyzer. Simultaneously, the SO 2 emission was monitored by a continuous emission monitoring system. The results showed that, when the SO 3 content increased by 34.3 mg/m 3 (12 × 10 − 6 volume fraction), the resistivity of the fly ash in the flue gas decreased by approximately two orders of magnitude. In addition, the surface tension of the fly ash diminished, the adhesive force and size increased, and the specific surface area decreased. The efficiency of the ESPs increased from 96.7% to 99.8%. The SO 2 emissions and the content of SO 3 in the fly ash have not changed appreciably before and after SO 3 -FGC. Therefore, SO 3 -FGC is an effective method of improving the efficiency of ESPs in collecting high-alumina coal fly ash.

Far-ultraviolet and X-ray irradiated protoplanetary disks: a grid of models

Context. Planets are thought to eventually form from the mostly gaseous (~99% of the mass) disks around young stars. The density structure and chemical composition of protoplanetary disks are affected by the incident radiation field at optical, FUV, and X-ray wavelengths, as well as by the dust properties. Aims. The effect of FUV and X-rays on the disk structure and the gas chemical composition are investigated. This work forms the basis of a second paper, which discusses the impact on diagnostic lines of, e.g., C+, O, H2O, and Ne+ observed with facilities such as Spitzer and Herschel. Methods. A grid of 240 models is computed in which the X-ray and FUV luminosity, minimum grain size, dust size distribution, and surface density distribution are varied in a systematic way. The hydrostatic structure and the thermo-chemical structure are calculated using ProDiMo. Results. The abundance structure of neutral oxygen is stable to changes in the X-ray and FUV luminosity, and the emission lines will thus be useful tracers of the disk mass and temperature. The C+ abundance distribution is sensitive to both X-rays and FUV. The radial column density profile shows two peaks, one at the inner rim and a second one at a radius r=5-10 AU. Ne+ and other heavy elements have a very strong response to X-rays, and the column density in the inner disk increases by two orders of magnitude from the lowest (LX = 1e29 erg/s) to the highest considered X-ray flux (LX = 1e32 erg/s). FUV confines the Ne+ ionized region to areas closer to the star at low X-ray luminosities (LX = 1e29 erg/s). H2O abundances are enhanced by X-rays due to higher temperatures in the inner disk and higher ionization fractions in the outer disk. The line fluxes and profiles are affected by the effects on these species, thus providing diagnostic value in the study of FUV and X-ray irradiated disks around T Tauri stars. (abridged)

Physiological and biochemical responses of Theobroma cacao L. genotypes to flooding

Flooding is common in lowlands and areas with high rainfall or excessive irrigation. A major effect of flooding is the deprivation of O2 in the root zone, which affects several biochemical and morphophysiological plant processes. The objective of this study was to elucidate biochemical and physiological characteristics associated with tolerance to O2 deficiency in two clonal cacao genotypes. The experiment was conducted in a greenhouse with two contrasting clones differing in flood tolerance: TSA-792 (tolerant) and TSH-774 (susceptible). Leaf gas exchange, chlorophyll (Chl) fluorescence, chemical composition and oxidative stress were assessed during 40 d for control and flooded plants. Flooding induced a decrease in net photosynthesis, stomatal conductance and transpiration of both genotypes. In flood conditions, the flood-susceptible clone showed changes in chlorophyll fluorescence, reductions in chlorophyll content and increased activity of peroxidase and polyphenol oxidase. Flooding also caused changes in macro- and micronutrients, total soluble sugars and starch concentrations in different plant organs of both genotypes. Response curves for the relationship between photosynthetically active radiation (PAR) and net photosynthetic rate (PN) for flooded plants were similar for both genotypes. In flood conditions, the flood-susceptible clone exhibited (1) nonstomatal limitations to photosynthesis since decreased in maximum potential quantum yield of PSII (Fv/Fm) values indicated possible damage to the PSII light-harvesting complex; (2) oxidative stress; (3) increased leaf chlorosis; and (4) a reduction in root carbohydrate levels. These stresses resulted in death of several plants after 30 d of flooding.

Physiological analyses of Genipa americana L. reveals a tree with ability as phytostabilizer and rhizofilterer of chromium ions for phytoremediation of polluted watersheds

Genipa americana L. is a tree that tolerates soil flooding and high levels of Cr3+, therefore it can be used in recomposition of ciliary forests at chromium-polluted watersheds. In this study, the ability of G. americana to phytoremediate the two major ionic Cr forms was assessed through Cr3+ and Cr6+ speciation, leaf gas exchange, growth and chemical composition of seedlings under Cr3+ and Cr6+ treatments. In greenhouse experiment, 4-month old seedlings were transferred to nutrient solution and, after three months, were submitted to 15 and 30mgL−1 of each ionic Cr form. After 15-days, leaf gas exchanges were measured and seedlings were sampled for evaluation of growth and chemical composition. Results showed that Cr6+ is fully converted into Cr3+ inside the plant; the absorption of Cr3+ and Cr6+ interfered with the absorption kinetics of Zn, Cu, Fe, K, Mg, Ca and P; increments in nutrient solution of Cr6+ decreased root biomass and of both forms decreased shoot biomass; both Cr ions increased leaf area; mainly the exposure to Cr6+ form decreased net photosynthesis per unit leaf area, stomatal conductance to water vapor and leaf transpiration; and Cr highly accumulated in roots only as Cr3+, independently from the ionic form applied to seedlings. Hence, although exposure to Cr3+ and Cr6+ affected growth and development of G. americana seedlings, this woody species demonstrated a relevant capacity for phytoremediation of chromium, by phytostabilizing Cr6+ and rhizofiltering Cr3+.

Fungal strain and incubation period affect chemical composition and nutrient availability of wheat straw for rumen fermentation

Eleven white-rot fungi were examined for their potency to degrade lignin and to improve the rumen fermentability of wheat straw. The straw was inoculated with the fungi and incubated under solid state conditions at 24°C for 0–49days to determine changes in in vitro gas production and chemical composition. Results show that some fungi could degrade lignin by as much as 63%, yet the delignification was highly correlated with the degradation of hemicellulose (r=0.96). Reduction in lignin was poorly (r=0.47), but the ratio between lignin and cellulose loss was strongly (r=0.87) correlated with the increase in gas production. Treatment with Ceriporiopsis subvermispora for 49days increased total gas production of the straw from 200 to 309ml/g organic matter (OM). It was concluded that some fungi highly selective for lignin and not for cellulose are able to improve the nutritive value of wheat straw as a ruminant feed.

Large Scale Tritium Recovery from Obsolete Illumination Devices at LLNL

Since 2001, LLNL has supported a program to recover and recycle tritium from exit signs, telephone dials, gun sights and other military and commercial tritium-powered illumination devices. In addition to permitting tritium reuse, this effort also provides an environmentally safe disposal option. Recently, the startup of the Tritium Grinder System (TGS) in the LLNL Tritium Facility has added significantly to the program’s capability and capacity. Actual results, including the collected gas chemical composition and unit processing rate are presented along with a summary of the design features, operating procedures and safety controls.

ROBO: a model and a code for studying the interstellar medium

We present ROBO, a model and its companion code for the study of the interstellar medium (ISM). The aim is to provide an accurate description of the physical evolution of the ISM and to set the ground for an ancillary tool to be inserted in NBody-Tree-SPH (NB-TSPH) simulations of large scale structures in cosmological context or of the formation and evolution of individual galaxies. The ISM model consists of gas and dust. The gas chemical composition is regulated by a network of reactions that includes a large number of species (hydrogen and deuterium based molecules, helium, and metals). New reaction rates for the charge transfer in $\mathrm H^+$ and $\mathrm H_2$ collisions are presented. The dust contains the standard mixture of carbonaceous grains (graphite grains and PAHs) and silicates of which the model follows the formation and destruction by several processes. The model takes into account an accurate treatment of the cooling process, based on several physical mechanisms, and cooling functions recently reported in the literature. The model is applied to a wide range of the input parameters and the results for important quantities describing the physical state of the gas and dust are presented. The results are organized in a database suited to the artificial neural networks (ANNs). Once trained, the ANNs yield the same results obtained by ROBO, with great accuracy. We plan to develop ANNs suitably tailored for applications to NB-TSPH simulations of cosmological structures and/or galaxies.

Chemical Evolution of a Protoplanetary Disk

AbstractIn this paper we review recent progress in our understanding of the chemical evolution of protoplanetary disks. Current observational constraints and theoretical modeling on the chemical composition of gas and dust in these systems are presented. Strong variations of temperature, density, high-energy radiation intensities in these disks, both radially and vertically, result in a peculiar disk chemical structure, where a variety of processes are active. In hot, dilute and heavily irradiated atmosphere only the most photostable simple radicals and atoms and atomic ions exist, formed by gas-phase processes. Beneath the atmosphere a partly UV-shielded, warm molecular layer is located, where high-energy radiation drives rich ion-molecule and radical-radical chemistry, both in the gas phase and on dust surfaces. In a cold, dense, dark disk midplane many molecules are frozen out, forming thick icy mantles where surface chemistry is active and where complex polyatomic (organic) species are synthesized. Dynamical processes affect disk chemical composition by enriching it in abundances of complex species produced via slow surface processes, which will become detectable with ALMA.

Compact Electron Gun Based on Secondary Emission Through Ionic Bombardment

We present a new compact electron gun based on the secondary emission through ionic bombardment principle. The driving parameters to develop such a gun are to obtain a quite small electron gun for an in-flight instrument performing Electron Beam Fluorescence measurements (EBF) on board of a reentry vehicle in the upper atmosphere. These measurements are useful to characterize the gas flow around the vehicle in terms of gas chemical composition, temperatures and velocity of the flow which usually presents thermo-chemical non-equilibrium. Such an instrument can also be employed to characterize the upper atmosphere if placed on another carrier like a balloon. In ground facilities, it appears as a more practical tool to characterize flows in wind tunnel studies or as an alternative to complex electron guns in industrial processes requiring an electron beam. We describe in this paper the gun which has been developed as well as its different features which have been characterized in the laboratory.

Predicting Chemical Fingerprints of Vadose Zone Soil Gas and Indoor Air from Non-Aqueous Phase Liquid Composition

Complex mixtures of volatile organic chemical (VOC) vapors can exist over subsurface accumulations of non-aqueous phase liquids (NAPLs) and contaminated soils. The ability to predict the relative soil gas chemical composition arising from such NAPLs is relevant to studies of the sources and fate of soil gas, and in assessing the possible intrusion of soil gas chemical constituents to indoor air. However, it is difficult to directly compare the chemical ‘fingerprints’ of NAPL and vapor because the differences are significant in liquid-gas partitioning coefficients among the many volatile hydrocarbons that compose the liquid NAPL. In this article, detailed chemical characterization data from analysis of liquid NAPLs are used to calculate equilibrium vapor phase distributions of 66 diagnostic paraffin, isoparaffin, aromatic, naphthene, and olefin (PIANO) compounds. Measured NAPL and predicted vapor phase chemical composition are presented for a diverse group of 10 hydrocarbon products that include crude oil, solvents, gasoline, distillate fuels, and coal tar. The laboratory investigation and field study described in this article demonstrate that chemical fingerprints of such predicted vapor phase hydrocarbons can be used as compositional benchmarks for reconciling source(s) of soil gas and indoor air-borne hydrocarbons.

New groups of planetary nebulae with peculiar dust chemistry towards the Galactic bulge

We investigate Galactic bulge planetary nebulae without emission-line central stars for which peculiar infrared spectra have been obtained with the Spitzer Space Telescope, including the simultaneous signs of oxygen and carbon based dust. Three separate sub-groups can be defined characterized by the different chemical composition of the dust and the presence of crystalline and amorphous silicates. We find that the classification based on the dust properties is reflected in the more general properties of these planetary nebulae. However, some observed properties are difficult to relate to the common view of planetary nebulae. In particular, it is challenging to interpret the peculiar gas chemical composition of many analyzed objects in the standard picture of the evolution of planetary nebulae progenitors. We confirm that the dual-dust chemistry phenomenon is not limited to planetary nebulae with emission-line central stars.

Biogas production from maize hybrids

There is an increasing world wide demand for energy crops and animal manures for biogas production. This research project was aimed at optimising anaerobic digestion of maize, using a laboratory digester, and finding out which maturity class of corn and which hybrid of a particular maturity class produces the highest rate of biogas and biomethane. Also the chemical composition of gases was studied. The corn hybrids of FAO 300 – FAO 400, FAO 400 – FAO 500 and FAO 500 – FAO 600 maturity class were tested. Experiments took place in the lab for 35 days within four series of experiments with four repetitions according to the method DIN 38 414. Results show that the highest maturity class of corn (FAO 400, FAO 500) increases the amount of biomethane. The greatest gain of biomethane per hectare according to maturity class is found with hybrids of FAO 400 (7768.4 Nm 3 ha −1 ) and FAO 500 (7050.1 Nm 3 ha −1 ) maturity class. Among the corn hybrids of maturity class FAO 300 – FAO 400, the hybrid PR38F70 gives the greatest production of biomethane per hectare (7646.2 Nm 3 ha −1 ). Among the hybrids of maturity class FAO 400 – FAO 500, the greatest amount of biomethane was achieved by the hybrid PIXXIA (9440.6 Nm 3 ha −1 ). Among the hybrids of maturity class FAO 500 – FAO 600 the hybrid CODISTAR (FAO 500) gives the highest production of biomethane (8562.7 Nm 3 ha −1 ). Production of biomethane varied with corn hybrids from 50 to 60% of produced biogas.

Chemical Composition of Gas- and Aerosol-Phase Products from the Photooxidation of Naphthalene

The current work focuses on the detailed evolution of the chemical composition of both the gas- and aerosol-phase constituents produced from the OH-initiated photooxidation of naphthalene under low- and high-NO(x) conditions. Under high-NO(x) conditions ring-opening products are the primary gas-phase products, suggesting that the mechanism involves dissociation of alkoxy radicals (RO) formed through an RO(2) + NO pathway, or a bicyclic peroxy mechanism. In contrast to the high-NO(x) chemistry, ring-retaining compounds appear to dominate the low-NO(x) gas-phase products owing to the RO(2) + HO(2) pathway. We are able to chemically characterize 53-68% of the secondary organic aerosol (SOA) mass. Atomic oxygen-to-carbon (O/C), hydrogen-to-carbon (H/C), and nitrogen-to-carbon (N/C) ratios measured in bulk samples by high-resolution electrospray ionization time-of-flight mass spectrometry (HR-ESI-TOFMS) are the same as the ratios observed with online high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS), suggesting that the chemical compositions and oxidation levels found in the chemically-characterized fraction of the particle phase are representative of the bulk aerosol. Oligomers, organosulfates (R-OSO(3)), and other high-molecular-weight (MW) products are not observed in either the low- or high-NO(x) SOA; however, in the presence of neutral ammonium sulfate seed aerosol, an organic sulfonic acid (R-SO(3)), characterized as hydroxybenzene sulfonic acid, is observed in naphthalene SOA produced under both high- and low-NO(x) conditions. Acidic compounds and organic peroxides are found to account for a large fraction of the chemically characterized high- and low-NO(x) SOA. We propose that the major gas- and aerosol-phase products observed are generated through the formation and further reaction of 2-formylcinnamaldehyde or a bicyclic peroxy intermediate. The chemical similarity between the laboratory SOA and ambient aerosol collected from Birmingham, Alabama (AL) and Pasadena, California (CA) confirm the importance of PAH oxidation in the formation of aerosol within the urban atmosphere.

Chemical Compositions of Gases Discharged from Fumaroles and Steam Wells in the Takenoyu Geothermal Area, Kyushu, Japan

Chemical Compositions of Gases Discharged from Fumaroles and Steam Wells in the Takenoyu Geothermal Area, Kyushu, Japan

Isotopic-geochemical peculiarities of gases in mud volcanoes of eastern Georgia

Isotopic-geochemical study revealed the presence of mantle He (3He/4He up to 223 × 10−8) in gases from mud volcanoes of eastern Georgia. This fact confirms that the Middle Kura basin fill encloses an intrusive body previously distinguished from geophysical data. Wide variations in the carbon isotopic composition δ13C of CH4 and CO2 and the chemical composition of gas and water at a temporally constant 3He/4He ratio indicate their relation with crustal processes. Unusual direct correlations of the 3He/4He ratio with the contents of He and CH4 and the 40Ar/36Ar ratio can be explained by the generation of gas in the Cenozoic sequence of the Middle Kura basin.