Influence Of Oxygen Concentration Research Articles

Continuous Wave EPR Oximetric Imaging at 300 MHz Using Radiofrequency Power Saturation Effects

A novel continuous wave (CW), radiofrequency (RF), electron paramagnetic resonance (EPR) oximetric imaging technique is proposed, based on the influence of oxygen concentration on the RF power saturation of the EPR resonance. A linear relationship is demonstrated between the partial oxygen pressure (pO(2)) and the normalized signal intensity (I(N)), defined as, I(N) = (I(HP) - I(LP))/I(LP), where I(LP) and I(HP) refer to signal intensities at low (P(L)) and high (P(H)) RF power levels, respectively. A formula for the determination of pO(2), derived on the basis of the experimental results, reliably estimated various oxygen concentrations in a five-tube phantom. This new technique was time-efficient and also avoided the missing angle problem associated with conventional spectral-spatial CW EPR oximetric imaging. In vivo power saturation oximetric imaging in a tumor bearing mouse clearly depicted the hypoxic foci within the tumor.

Ignition of single coal particles in high-temperature oxidizers with various oxygen concentrations

In this investigation, coal pellets were combusted using a high temperature oxidizer with varying oxygen concentration, using a small scale batch reactor able to preheat the oxidizer to 1273 K. In base of the experimental results, the influence of oxygen concentration on the ignition mechanism, the solid temperature inside the particle at the moment of ignition, the mass lost at the moment of the ignition and ignition time is analyzed and discussed. A theoretical basis for the division of the conditions tested into three ignition regimes is developed and a formula for the prediction of the ignition time directly from the material and oxidizer temperature and oxygen concentration is proposed.

Kinetic model of a granular sludge SBR: Influences on nutrient removal

A mathematical model was developed that can be used to describe an aerobic granular sludge reactor, fed with a defined influent, capable of simultaneously removing COD, nitrogen and phosphate in one sequencing batch reactor (SBR). The model described the experimental data from this complex system sufficiently. The effect of process parameters on the nutrient removal rates could therefore be reliably evaluated. The influence of oxygen concentration, temperature, granule diameter, sludge loading rate, and cycle configuration were analyzed. Oxygen penetration depth in combination with the position of the autotrophic biomass played a crucial role in the conversion rates of the different components and thus on overall nutrient removal efficiencies. The ratio between aerobic and anoxic volume in the granule strongly determines the N-removal efficiency as it was shown by model simulations with varying oxygen concentration, temperature, and granule size. The optimum granule diameter for maximum N- and P-removal in the standard case operating conditions (DO 2 mg L(-1), 20 degrees C) was found between 1.2 and 1.4 mm and the optimum COD loading rate was 1.9 kg COD m(-3) day(-1). When all ammonia is oxidized, oxygen diffuses to the core of the granule inhibiting the denitrification process. In order to optimize the process, anoxic phases can be implemented in the SBR-cycle configuration, leading to a more efficient overall N-removal. Phosphate removal efficiency mainly depends on the sludge age; if the SRT exceeds 30 days not enough biomass is removed from the system to keep effluent phosphate concentrations low.

Influence of oxygen concentration on the sooting behavior of ethanol droplet flames in microgravity conditions

The influence of oxygen (O 2) concentration and inert on the sooting and burning behavior of large ethanol droplets under microgravity conditions was investigated through measurements of burning rate, flame temperature, sootshell diameter, and soot volume fraction. The experiments were performed at the NASA Glenn Research Center (GRC) 2.2 s drop tower in Cleveland, OH. Argon (Ar), helium (He), and nitrogen (N 2) were used as the inerts and the O 2 concentration was varied between 21% and 50% mole fraction at 2.4 atm. The unique configuration of spherically symmetric droplet flames enables effective control of sooting over a wide range of residence time of fuel vapor transport, flame temperature, and regimes of sooting to investigate attendant influences on burning behavior of droplets. For all inert cases, soot volume fraction initially increased as a function of the O 2 concentration. The highest soot volume fractions were measured for experiments in Ar environments and the lowest soot volume fractions were measured for the He environments. These differences were attributed to the changes in the residence time for fuel vapor transport and the flame temperature. For the He inert and N 2 inert cases, the soot volume fraction began to decrease after reaching a maximum value. The competition between the influence of residence time, rate of pyrolysis reactions, and soot oxidation can lead to this interesting behavior in which the soot volume fraction varies non-monotonically with increase in O 2 concentration. These experiments have developed new understanding of the burning and sooting behaviors of ethanol droplets under various O 2 concentrations and inert substitutions.

3-18.木質バイオマスの流動層ガス化反応における酸素濃度の影響((4)ガス化4,Session 3 バイオマス等)

3-18.木質バイオマスの流動層ガス化反応における酸素濃度の影響((4)ガス化4,Session 3 バイオマス等)

EXPERIMENTAL AND NUMERICAL STUDIES OF OPPOSED JET OXYGEN-ENHANCED METHANE DIFFUSION FLAMES

Planar oxygen-enhanced methane counterflow flames are investigated by optical diagnostics and numerical simulation. The major species concentrations and temperature measured from Raman scattering are compared to the detailed simulations of the flame formed between two opposed jets. The effect of stretch and the influence of oxygen concentration in the oxidizer on the flame structure are studied for nitrogen-diluted methane fuel (20% CH4 in N2). The oxygen concentration of reactants changes the flame temperature dramatically. Simulations with the GRI-3.0 and the San Diego chemical kinetic mechanisms show that model-data comparisons for reactants, products such as H2O, and temperature agree very well. The measured CO2 is in agreement at lower oxygen enrichment (≤40% O2) but deviates from prediction at high oxygen enrichment (60%, 100% O2). The effect of the fuel concentration in the nitrogen-diluted fuel is also studied for pure oxygen flames. When pure oxygen is the oxidizer, the measured extinction limit for the minimum amount of fuel in the diluted fuel mixture is very close to the calculated result when using either the GRI-3.0 or the San Diego chemical kinetic mechanisms. At low-level enrichment (i.e., 30% O2) and high-level enrichment (100% O2), the GRI-3.0 and the San Diego mechanisms give almost identical predicted results.

Influence of the Oxygen Concentration of YSZ Gate Dielectric Layer on the Low Voltage Operating Pentacene Thin Film Transistor

We report on the influence of oxygen concentration on structural and electrical properties of the amorphous yttria-stabilized zirconia (YSZ) thin films which are the potential high-k gate dielectric material of organic thin film transistors (OTFTs). The films were prepared by the E-beam evaporation process. To investigate the influence of the oxygen flow rate on the structural and electrical properties of the YSZ films, X-ray diffraction, X-ray photoelectron spectroscopy, current density-electric field, current-voltage were carried out in this work. Oxygen vacancies are expected to be the most predominant type of defect in metal-oxide dielectrics. The leakage current density decreased mainly because of the reduction of oxygen vacancies with increasing oxygen flow rate.

318 金属材料の摩耗に及ぼす酸素濃度の影響(OS3-4,オーガナイズドセッション3:臨床系のバイオメカニクス,学術講演)

318 金属材料の摩耗に及ぼす酸素濃度の影響(OS3-4,オーガナイズドセッション3:臨床系のバイオメカニクス,学術講演)

Influence of Oxygen Concentration on Redox Cycling of Alloxan and Dialuric Acid

Alloxan, a chemical diabetogen, decays in the absence of reductants into alloxanic acid. In the presence of glutathione, it is reduced via the alloxan radical into dialuric acid, which autoxidizes back to alloxan. During this redox cycling process, reactive oxygen species are formed that destroy beta-cells in islets of Langerhans. Previous experiments were conducted with oxygen concentrations about ten times as high as within cells. The aim of our in vitro study was to evaluate the impact of different oxygen concentrations (0, 25, 250 micromol/l) at a given initial ratio of glutathione and alloxan on this redox cycling. Reduction of alloxan, oxidation of glutathione, and the formation of glutathiol (GSSG) were continuously recorded by HPLC for 90 minutes at 25 degrees C in air, calibration gas, or argon. In the absence of reductants, alloxan irreversibly decomposed into alloxanic acid regardless of oxygen presence. When the reaction system contained glutathione, decomposition was significantly retarded and therefore influenced by oxygen. In argon, decay could not be observed due to its reduction and the absence of oxygen. Increasing oxygen concentration enabled a redox cycling and therefore an ongoing decay. The highest decomposition along with the highest consumption of glutathione occurred at 250 micromol/l oxygen. The lower the oxygen, the more dialuric acid could be detected. After calculation, about 33 redox cycles per hour generates an amount of reactive oxygen species sufficient to damage pancreatic beta cells and induce insulin deficiency.

The effect of oxygen and carbon dioxide concentration on soot formation in nonpremixed flames using time resolved LII technique

The influence of oxygen concentration and CO2 as diluent in oxidizer side on soot characteristics was studied by Laser Induced Incandescence, Time Resolved LII and Transmission Electron Microscopy photography in non-premixed coflowing flames. Through the comparison of TEM photographs and the decay rate of LII signal, suitable two delay times of TIRE-LII method and signal sensitivity (ΔS TIRE - LII /Δ) were determined. The effects of O2 and CO2 as diluent in oxidizer side on soot formation are investigated with these calibrated techniques. The O2+CO2, N2, and [Ar+CO2] mixture in co-flow were used to isolate CO2 effects systematically. The number concentration of primary particle and soot volume fraction abruptly decrease by the addition of CO2 to the co-flow. This suppression is resulted from the short residence time in inception region because of the late nucleation and the decrease of surface growth distance by the low flame temperature due to the higher thermal capacity and the chemical change of CO2 including thermal dissociation. As the oxygen concentration increases, the number concentration of soot particles at the inception region increases and thus this increase of nucleation enhances the growth of soot particle.

The effect of oxygen and carbon dioxide concentration on soot formation in non-premixed flames

The influence of oxygen concentration and carbon dioxide as diluents in the oxidizer side on soot formation was studied by Time Resolved Laser Induced Incandescence (TIRE-LII) and TEM photography in non-premixed co-flowing flames. TIRE-LII method was used to measure the distribution of two-dimensional soot volume fraction and primary particle size. The soot was directly sampled by the thermophoretic method, and its diameter was examined by TEM photography. Two suitable delay times of the TIRE-LII method affecting measurable range and sensitivity were determined by comparing TEM photographs with the TIRE-LII signal. The effects of oxygen concentration and carbon dioxide as diluents in the oxidizer side on soot formation were investigated with these calibrated techniques. An O 2+(CO 2, N 2, and [Ar+CO 2]) mixtures in co-flow were used to isolate carbon dioxide effects systematically. The primary particle number concentration and soot volume fraction were abruptly decreased by the addition of carbon dioxide to co-flow. This suppression was resulted from the short residence time in inception region because of the late nucleation and the decrease of surface growth distance by the low flame temperature due to the higher thermal capacity and the chemical change of carbon dioxide. The increase of oxygen concentration in the co-flow caused an enhancement of soot nucleation and thus the residence time increase, but the specific growth rate showed almost the same value regardless of the co-flow mixture in the growth region. This result suggests that the specific growth rate has a weak dependence on the relative change of co-flow conditions in non-premixed co-flowing flames.

Influence of oxygen concentration and pH on expression of hypoxia induced genes

Background and purpose This study was designed to determine the oxygen dependency for expression of the endogenous hypoxic markers carbonic anhydrase IX (protein: CAIX/gene: CA9), glucose transporter 1 (GLUT1/ GLUT1), osteopontin (OPN/ OPN) and lactate dehydrogenase A (LDH-A/ LDHA), and how this expression was influenced by extracellular pH (pH e). Materials and methods Human cervix squamous cell carcinoma (SiHa) cells were used in all experiments. These cells were gassed in an enclosed environment under either anoxia (95% N 2+5% CO 2) for various times (0–30 h) or under different oxygen concentrations (0–21% O 2) for 24 h at normal pH e (7.4) or low pH e (6.3). Response to radiation (7 Gy) was estimated using a clonogenic assay. Gene expression was determined by real-time PCR (normalized to the housekeeping gene, TFRC) and protein expression by Western blots. Results Under normal pH e conditions, CA9, GLUT1 and LDHA gene expression was upregulated within 1–3 h of anoxia, reaching near maximal values by 6 h. OPN showed a slow increase over 24 h. At 24 h the relative increase was 135, 12, 90 and 5 times for CA9, GLUT1, OPN and LDHA, respectively. No induction was seen with the EGF receptor ( EGFR). Gassing cells with differing oxygen concentrations for 24 h resulted in a maximum level of expression for CA9 at 1% oxygen, whereas with GLUT1 and LDHA maximal expression occurred at 0.01% oxygen, but at 0% oxygen with OPN. The oxygen dependency for radiation response was identical to that seen for GLUT1 and LDHA. Expression of CA9, GLUT1, OPN and LDHA was inhibited under hypoxic conditions when pH e was reduced to 6.3. Expression of CAIX protein mimicked the CA9 gene expression patterns. Conclusion The expression of all the endogenous markers were upregulated by hypoxia, but the timing and oxygen dependencies were different and their expression was influenced by low pH e. This raises concerns about the generalised use of these agents as markers for hypoxia.

413 高湿度雰囲気中での炭化水素-空気混合気の燃焼特性に及ぼす雰囲気酸素濃度の影響について(熱工学II)

413 高湿度雰囲気中での炭化水素-空気混合気の燃焼特性に及ぼす雰囲気酸素濃度の影響について(熱工学II)

Two-step oxygen injection process for growing ZnO nanorods

Uniform hexagonal prismatic zinc oxide rods were grown over the entire alumina substrate at 550°C using a two-step oxygen injection process, whether the substrates were coated with a catalyst or not. X-ray diffraction showed that all of the depositions exhibited a preferred orientation in the (002) plane. The influence of oxygen concentration was investigated by changing the oxygen flow rate. Oxygen concentration affected the size of ZnO nanorods, especially the diameter. The ZnO nanorods were further checked using high-resolution transmission electron microscopy, photoluminescence, Raman spectroscopy, and room-temperature ultraviolet lasing. The results showed that the rods were single crystals and had excellent optical properties. By observing the growth process, we found that the diameter increased slowly, but the longitudinal growth rate was very high. The growth of ZnO nanorods revealed that the uniform hexagonal prismatic ZnO nanorods were synthesized through vapor deposition growth and a self-catalyzed vapor–liquid–solid (VLS) process.

Formation and structure of primary and secondary streamers in positive pulsed corona discharge—effect of oxygen concentration and applied voltage

Primary and secondary streamers of positive pulsed corona discharge are observed in a point-to-plane gap using a short-gated intensified CCD camera in an air-like environment. The influences of oxygen concentration and applied voltage on the properties of both streamers are presented. It is shown that the propagation velocity, the diameter, and the shape of the streamers are strongly influenced by the oxygen concentration. In pure nitrogen, the primary streamer shows branching with a diameter of about 0.2–0.4 mm, while in air, the branching disappears almost completely and the shape of the primary streamer becomes quite smooth with a diameter of more than 1 mm. After the arrival of the primary streamer at the cathode, a secondary streamer develops from the anode toward the cathode as far as the middle of the gap. The propagation length of the secondary streamer increases approximately linearly with the applied voltage. It is shown that the ratio of the energy consumed by the secondary streamer to the whole energy consumed by the discharge increases with the applied voltage.

2,4-D degradation by electron beam irradiation: influence of oxygen concentration.

2,4-D degradation by electron beam irradiation: influence of oxygen concentration.

Oxidation Effect on the Monosized Droplets Generation of the Liquid Metal Jet

The oxide formation on the surface of the molten metal jet was shown to have a drastic effect on the droplet formation process according to the description of some publication. Thus, the main objective of this research is to investigate the influence of oxygen concentration on the breakup and the monosized droplets generation of molten metal jet (Sn63 Pb37 alloy). The breakup phenomena of molten metal jet can be approximately divided into three regimes. They are “breakup regime” for oxygen concentration below C1, “transition regime” for oxgyen concentration between C1 and C2, and “breakup failing regime” for oxygen concentration beyond C2, respectively.

351 炭化水素-空気混合気の燃焼特性に及ぼす酸素濃度及び湿度の影響について

351 炭化水素-空気混合気の燃焼特性に及ぼす酸素濃度及び湿度の影響について

912 高温空気中での固体廃棄物燃料の安定燃焼領域の決定に関する研究 : 燃料表面温度測定による検討

Experiments have been carried out to elucidate the flame stabilization and development on waste fuel combustion in high temperature and low oxygen by concentration using the electric furnace equipped in cylindrical closed bomb. The ambient temperature and oxygen concentration are set up at 400 to 800℃ and 5 to 21% by volume, respectively. Especially, the temperature distribution near the surface of solid waste fuels is measured to conform experimental data including the flame stabilization region. The acquisitions obtained in the study are as follows : (1) the influence of oxygen concentration and ambient temperature on combustion characteristics such as ignition delay, flaming duration and surface combustion period are revealed by temperature measurement in details and (2) the region of flame stabilization on waste fuel combustion has an inverse relationship between ambient temperature and oxygen concentration.

Microstructure and electrophysical properties of SnO 2, ZnO and In 2O 3 nanocrystalline films prepared by reactive magnetron sputtering

The influence of oxygen concentration in the plasma-forming gas on the microstructure, phase composition and electrical conductivity has been investigated for SnO 2, ZnO and In 2O 3 films grown by reactive magnetron sputtering method. The evolution of the oxide microstructure and resistivity under annealing at 400 °C was also studied. The nanocrystallite size remains unaltered for all the investigated films, while the agglomerate size varies significantly depending on the type of oxide and annealing duration. The agglomerate size growth leads to reduction of film resistance and conductivity activation energy.