Sustained Aerobic Oxidation of Vinyl Chloride at Low Oxygen Concentrations

2010 ◽  
Vol 44 (4) ◽  
pp. 1405-1411 ◽  
Author(s):  
James M. Gossett
Keyword(s):  
Vinyl Chloride ◽  
Aerobic Oxidation ◽  
Low Oxygen ◽  
Oxygen Concentrations

scholarly journals The Function of the Gills of Mayfly Nymphs from Different Habitats

1939 ◽  
Vol 16 (3) ◽  
pp. 363-373 ◽  
Author(s):  
C. A. WINGFIELD
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Content ◽  
The Body ◽  
Gaseous Exchange ◽  
Low Oxygen ◽  
Respiratory Mechanism ◽  
Tracheal Gills ◽  
Cloeon Dipterum ◽  
Gill Function ◽  
Oxygen Concentrations

1. The oxygen consumption of normal and gill-less nymphs of the mayflies Baetis sp., Cloeon dipterum and Ephemera vulgata has been measured at various oxygen concentrations. 2. It has been found that over the complete range of oxygen concentrations studied, the tracheal gills do not aid oxygen consumption in Baetis sp. In Cloeon dipterum, at all oxygen concentrations tested, no gaseous exchange takes place through the gills; at low oxygen concentrations, however, the gills function as an accessory respiratory mechanism in ventilating the respiratory surface of the body and so aid oxygen consumption. In Ephemera Vulgata the gills aid oxygen consumption even at high oxygen concentrations. In this species the gills may function both as true respiratory organs and as a ventilating mechanism. 3. It is shown that the differences in gill function can be related to the oxygen content of the habitat of each species.

scholarly journals Isolation of Alcaligenes sp. strain L6 at low oxygen concentrations and degradation of 3-chlorobenzoate via a pathway not involving (chloro)catechols.

1996 ◽  
Vol 62 (7) ◽  
pp. 2427-2434 ◽  
Author(s):  
J Krooneman ◽  
E B Wieringa ◽  
E R Moore ◽  
J Gerritse ◽  
R A Prins ◽  
...  
Keyword(s):  
Low Oxygen ◽  
Oxygen Concentrations

scholarly journals Dead zone or oasis in the open ocean? Zooplankton distribution and migration in low-oxygen modewater eddies

2016 ◽  
Vol 13 (6) ◽  
pp. 1977-1989 ◽  
Author(s):  
Helena Hauss ◽  
Svenja Christiansen ◽  
Florian Schütte ◽  
Rainer Kiko ◽  
Miryam Edvam Lima ◽  
...  
Keyword(s):  
Surface Layer ◽  
Dead Zone ◽  
Trophic Levels ◽  
Zooplankton Abundance ◽  
Depth Range ◽  
Calanoid Copepods ◽  
Long Term Effects ◽  
Low Oxygen ◽  
Oxygen Concentrations ◽  
Ocean Deoxygenation

Abstract. The eastern tropical North Atlantic (ETNA) features a mesopelagic oxygen minimum zone (OMZ) at approximately 300–600 m depth. Here, oxygen concentrations rarely fall below 40 µmol O2 kg−1, but are expected to decline under future projections of global warming. The recent discovery of mesoscale eddies that harbour a shallow suboxic (< 5 µmol O2 kg−1) OMZ just below the mixed layer could serve to identify zooplankton groups that may be negatively or positively affected by ongoing ocean deoxygenation. In spring 2014, a detailed survey of a suboxic anticyclonic modewater eddy (ACME) was carried out near the Cape Verde Ocean Observatory (CVOO), combining acoustic and optical profiling methods with stratified multinet hauls and hydrography. The multinet data revealed that the eddy was characterized by an approximately 1.5-fold increase in total area-integrated zooplankton abundance. At nighttime, when a large proportion of acoustic scatterers is ascending into the upper 150 m, a drastic reduction in mean volume backscattering (Sv) at 75 kHz (shipboard acoustic Doppler current profiler, ADCP) within the shallow OMZ of the eddy was evident compared to the nighttime distribution outside the eddy. Acoustic scatterers avoided the depth range between approximately 85 to 120 m, where oxygen concentrations were lower than approximately 20 µmol O2 kg−1, indicating habitat compression to the oxygenated surface layer. This observation is confirmed by time series observations of a moored ADCP (upward looking, 300 kHz) during an ACME transit at the CVOO mooring in 2010. Nevertheless, part of the diurnal vertical migration (DVM) from the surface layer to the mesopelagic continued through the shallow OMZ. Based upon vertically stratified multinet hauls, Underwater Vision Profiler (UVP5) and ADCP data, four strategies followed by zooplankton in response to in response to the eddy OMZ have been identified: (i) shallow OMZ avoidance and compression at the surface (e.g. most calanoid copepods, euphausiids); (ii) migration to the shallow OMZ core during daytime, but paying O2 debt at the surface at nighttime (e.g. siphonophores, Oncaea spp., eucalanoid copepods); (iii) residing in the shallow OMZ day and night (e.g. ostracods, polychaetes); and (iv) DVM through the shallow OMZ from deeper oxygenated depths to the surface and back. For strategy (i), (ii) and (iv), compression of the habitable volume in the surface may increase prey–predator encounter rates, rendering zooplankton and micronekton more vulnerable to predation and potentially making the eddy surface a foraging hotspot for higher trophic levels. With respect to long-term effects of ocean deoxygenation, we expect avoidance of the mesopelagic OMZ to set in if oxygen levels decline below approximately 20 µmol O2 kg−1. This may result in a positive feedback on the OMZ oxygen consumption rates, since zooplankton and micronekton respiration within the OMZ as well as active flux of dissolved and particulate organic matter into the OMZ will decline.

scholarly journals Thermodynamic modeling of solid fuel gasification in mixtures of oxygen and carbon dioxide

2021 ◽  
Vol 2119 (1) ◽  
pp. 012101
Author(s):  
I G Donskoy
Keyword(s):  
Carbon Dioxide ◽  
Thermodynamic Modeling ◽  
Solid Fuel ◽  
Carbon Capture ◽  
Power Plants ◽  
Thermal Power ◽  
Carbon Capture And Storage ◽  
Low Oxygen ◽  
Fuel Conversion ◽  
Oxygen Concentrations

Abstract One of the main problems in the use of solid fuels is inevitable formation of significant amounts of carbon dioxide. The prospects for reducing CO2 emissions (carbon capture and storage, CCS) are opening up with the use of new coal technologies, such as thermal power plants with integrated gasification (IGCC) and transition to oxygen-enriched combustion (oxyfuel). In order to study the efficiency of solid fuel conversion processes using carbon dioxide, thermodynamic modeling was carried out. Results show that difference between efficiency of fuel conversion in O2/N2 and O2/CO2 mixtures increases with an increase in the volatile content and a decrease in the carbon content. The effect of using CO2 as a gasification agent depends on the oxygen concentration: at low oxygen concentrations, the process temperature turns out to be low due to dilution; at high oxygen concentrations, the CO2 concentration is not high enough for efficient carbon conversion.

Large Eddy Simulation of Multiple-Stage Ignition Process of n-Heptane Spray Flame

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Wanhui Zhao ◽  
Lei Zhou ◽  
Wenjin Qin ◽  
Haiqiao Wei
Keyword(s):  
Oxygen Concentration ◽  
Mixture Fraction ◽  
Ignition Process ◽  
Low Oxygen ◽  
Nonpremixed Combustion ◽  
Eddy Simulation ◽  
Spray Flames ◽  
Large Eddy ◽  
Initial Oxygen ◽  
Oxygen Concentrations

Large eddy simulation of n-heptane spray flames is conducted to investigate the multiple-stage ignition process under extreme (low-temperature, low oxygen, and high-temperature, high-density) conditions. At low oxygen concentrations, the first-stage ignition initiates in the fuel-rich region and then moves to stoichiometric equivalence ratio regions by decreasing the initial temperature. It is also clear that at high temperatures, high oxygen concentrations, or high densities, the reactivity of the mixture is enhanced, where high values of progress variable are observed. Analysis of key intermediate species, including acetylene (C2H2), formaldehyde (CH2O), and hydroxyl (OH) in the mixture fraction and temperature space provides valuable insights into the complex combustion process of the n-heptane spray flames under different initial conditions. The results also suggest that C2H2 appears over a wider range in the mixture fraction space at higher temperature or oxygen concentration condition, implying that it mainly forms at the fuel-rich regions. The initial oxygen concentration of the ambient gas has great influence on the formation and oxidization of C2H2, and the maximum temperature depends on the initial oxygen concentration. OH is mainly formed at the stoichiometric equivalence ratio region, which moves to high-temperature regions very quickly especially at higher oxygen concentrations. Finally, analysis of the premixed and nonpremixed combustion regimes in n-heptane spray flames is also conducted, and both premixed and nonpremixed combustion coexist in spray flames.

Oxygen dependence of redox state of copper in cytochrome oxidase in vitro

1993 ◽  
Vol 74 (4) ◽  
pp. 1622-1627 ◽  
Author(s):  
Y. Hoshi ◽  
O. Hazeki ◽  
M. Tamura
Keyword(s):  
Respiratory Rate ◽  
Cytochrome Oxidase ◽  
Near Infrared ◽  
Energy State ◽  
Oxygen Affinity ◽  
Quantitative Information ◽  
Low Oxygen ◽  
Straight Line ◽  
Oxygen Concentrations

To obtain quantitative information about tissue oxygenation from near-infrared signals, the oxygen dependencies of the redox states of both heme a+a3 and copper in cytochrome oxidase of isolated mitochondria were determined at low oxygen concentrations (10(-6)-10(-9) M) using leghemoglobin as an oxygen indicator. The maximum absorbance changes caused by the aerobic-anaerobic transition measured at 830–760 nm of copper in state 3, state 4, and the uncoupled state were 10, 17, and 5% of those at 605–620 nm of heme a+a3, respectively. Thus the relative absorbance ratio of copper to heme a+a3 could be used as a sensitive indicator for the mitochondrial energy state. The oxygen concentrations required for the half-maximal reduction of heme a+a3 varied with the energy state and the respiratory rate and were 7.8 x 10(-8) and 1.6 x 10(-7) M in state 4 and state 3, respectively. In contrast, that of copper was 7.5 x 10(-8) M and was independent of both the energy state and the respiratory rate. The relationship between the percent oxidation of heme a+a3 and copper in the aerobic-anaerobic transition did not show a straight-line relationship. This was referred to as the difference in oxygen affinity between these two chromophores. The deviation from the straight line was larger in state 3 than in state 4.(ABSTRACT TRUNCATED AT 250 WORDS)

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