Oxygen

About: Oxygen is a research topic. Over the lifetime, 48149 publications have been published within this topic receiving 1113788 citations. The topic is also known as: O & Oxygen.

Activated Rate Theory Treatment of Oxygen and Water Transport through Silicon Oxide/Poly(ethylene terephthalate) Composite Barrier Structures

Abstract: Poly(ethylene terephthalate) substrates were coated with thin films of silicon oxide deposited by magnetically enhanced chemical vapor deposition. The rates of oxygen and water vapor transport through the coated and uncoated film systems were obtained as a function of temperature. Activated rate theory treatment of oxygen transmission rates revealed that the silicon oxide coatings were imperfect; the apparent free energies of activation (ΔEp) for transport through film substrates which were coated on a single side were statistically identical to uncoated controls. However, coating both sides of the polymer substrate with identical oxide layers resulted in a 54 kJ/mol increase in the ΔEp value. A simple empirical model for the change in transport mechanism is offered to explain this unanticipated result. Analogous treatment of water vapor transport rates for these same film systems showed no obvious change in transport mechanism. However, ΔEp values obtained for water vapor permeation through silicon oxide...

Reduced oxygen enhancement ratio at low doses of ionizing radiation.

Abstract: A decreased oxygen enhancement ratio (OER) at lower radiation doses has been previously reported (B. Palcic, J. W. Brosing, and L. D. Skarsgard, Br. J. Cancer 46, 980-984 (1984)). The question remained whether or not this effect is due to a possible oxygen contamination at low doses, which was not the case at high doses. To ensure a sufficient degree of hypoxia prior to the start of irradiation, Chinese hamster cells (CHO) were made hypoxic by gas exchange combined with metabolic consumption of oxygen at 37°C. At the same time oxygen levels in cell suspension were measured using a Clark electrode. It was found that under experimental conditions used in this laboratory for hypoxic irradiations, the oxygen levels before the start of irradiation are always below the levels which could give any significant enhancement to radiation inactivation by X rays. Full survival curves were determined in the dose range 0-30 Gy using the conventional survival assay and in the dose range 0-3 Gy using the low dose survival...

Respiration of the Atlantic Cod

Abstract: Measurements of routine and standard rates of oxygen consumption of various sized cod at temperatures between 3 and 15 °C revealed a well-marked size effect; small cod consume oxygen at a greater rate per unit weight than do large ones. Increases in temperature raise oxygen consumption in starved and fed fish. The increase in rate of oxygen consumption of starved fish between 3 and 10° is proportionately greater than that between 10 and 15 °C. Feeding of cod which have previously been starved increases the rate of oxygen consumption by 40–90%. The rate subsides to the starvation level in 4–7 days depending on temperature and amount of food eaten. Handling cod causes them to increase their rate of oxygen consumption; rates return to normal levels in 3–5 hours. Crowding reduces the rate of oxygen consumption apparently by reducing the space for movement and thus restricting activity. Reducing the ambient oxygen from about 10 to 3 mg/l lowers the rate of oxygen consumption slightly, but the respiratory volum...

La-doped BaFeO3−δ perovskite as a cobalt-free oxygen reduction electrode for solid oxide fuel cells with oxygen-ion conducting electrolyte

Abstract: Cobalt-free small La3+-doped BaFeO3−δ is synthesized and systematically characterized towards application as an oxygen reduction electrode material for intermediate temperature solid oxide fuel cells (IT-SOFCs) with oxygen-ion conducting electrolyte. The formation of an oxygen vacancy-disordered perovskite oxide with cubic lattice symmetry is demonstrated by XRD, after the doping of only 5 mol% La3+ into BaFeO3−δ parent oxide with the formation of Ba0.95La0.05FeO3−δ (BLF). The structural, thermal, electrical and electrochemical properties of BLF have been evaluated. High structural stability, high thermal expansion coefficient, high oxygen vacancy concentration, and relatively low electrical conductivity, are demonstrated. BLF shows a superior electrocatalytic activity, which is comparable to those state-of-the-art cobalt-based mixed conducting cathodes, in addition, it demonstrates a favorable long-term operational stability. It thus promises as a new cathode candidate for IT-SOFCs with oxygen-ion conducting electrolyte.

Effect of cerium on the mobility of oxygen on manganese oxides

Abstract: Addition of a small amount of cerium (3 and 5 mol.%) remarkably affected the oxidation state of manganese oxide. Manganese oxide without cerium absorbed oxygen in the temperature region from 600 to 900 K to form Mn2O3, while Mn2O3 was not formed in the presence of cerium. In the low temperature region (< 700 K) the valence of Mn was 3.2 in the presence of cerium while it was 2.85 in the absence of cerium. It was concluded that cerium provided oxygen to manganese oxide at low temperature and, on the contrary, withdrew oxygen at high temperatures. This behavior well explained the catalytic action of manganese-cerium composite oxide in the oxidation of CO and in the decomposition of N2O.