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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.


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Journal ArticleDOI
TL;DR: In this article, the properties of low-index Pt surfaces were investigated using periodic density functional theory and the results of the calculations were discussed in the context of the mechanism of oxygen reduction.
Abstract: Properties of the oxygen molecule, atomic oxygen, and intermediate products of its reduction, OH, OOH, H 2 O 2 on (111), (100), and (110) Pt surfaces have been investigated using periodic density functional theory. The Pt surfaces are modeled as four-layer slabs. Adsorption energies and geometries, as well as the charge-transfer properties are calculated. Computed characteristics of the adsorbed oxygen reduction intermediates supply known tendencies of the low index Pt surface activities under different experimental conditions. Electric field dependencies of the properties of all species adsorbed on a Pt 9 (111) cluster have been also studied. Lowering the field causes an increase of the O-O bond length of O 2ads , attracting the molecule to the Pt surface and increasing the charge transfer from Pt to 2π* orbitals of the oxygen molecule. The weakening of the O-O bond is evidenced by a decrease of the O-O stretching frequency. The charge-transfer from the Pt 9 cluster to the adsorbates is observed for all species. In our calculations hydrogen peroxide was unstable on all three low-index Pt surfaces and dissociated into two hydroxyls or a water molecule and atomic oxygen. The results of the calculations are discussed in the context of the mechanism of oxygen reduction.

172 citations

Journal ArticleDOI
TL;DR: A storage study of orange juice packed in oxygen scavenging (OS) film and oxygen barrier film was conducted to determine the extent of ascorbic acid loss due to oxygen as a function of time and temperature.

172 citations

Journal ArticleDOI
TL;DR: A five-compartment model for the liquid flow and the oxygen transfer into the liquid phase of a large-scale bioreactor is presented to predict the following reactor operating variables: the overall oxygen transfer capacity, the local liquid dissolved oxygen concentrations and the gas-phase exhaustion.
Abstract: A five-compartment model for the liquid flow and the oxygen transfer into the liquid phase of a large-scale bioreactor is presented The aim of the model is to predict the following reactor operating variables: 1) the overall oxygen transfer capacity of the reactor; 2) the local liquid dissolved oxygen concentrations, for estimation of bad aerated zones which can introduce negative effects for the microorganisms and as a base for reliable scaledown experiments to estimate those effects; 3) the gas-phase exhaustion

172 citations

Journal ArticleDOI
TL;DR: This chapter explores the role of minerals in the formation of reactive oxygen species and five different mechanisms by which minerals may promote the formation and transformation of ROS species are explored.
Abstract: The term reactive oxygen species, ROS, is defined by the US National Library of Medicine (NIH 2006) as: “Molecules or ions formed by the incomplete one-electron reduction of oxygen. These reactive oxygen intermediates include singlet oxygen; superoxides; peroxides; hydroxyl radical; and hypochlorous acid. They contribute to the microbicidal activity of phagocytes, regulation of signal transduction and gene expression, and the oxidative damage to nucleic acids; proteins; and lipids.” This chapter explores the role of minerals in the formation of reactive oxygen species. Five different mechanisms by which minerals may promote the formation and transformation of ROS species are explored (Fig. 1⇓). These are: Figure 1. Mineral-induced ROS formation and transformations. Numbers refer to mechanisms listed in text. [Used by permission of Corey Cohn and Martin Schoonen, Stony Brook University, 2006] 1. Mineral release of metal ions: Metals that are released into body fluids via congruent or incongruent mineral dissolution can act as catalysts. In this mechanism minerals are a source of metals, but are not directly involved in any of the reactions. 2. Surface-bound metal-promoted reactions: Insoluble metal-containing minerals can catalyze formation of ROS from molecular oxygen. In this mechanism the conversion of molecular oxygen takes place on the mineral surface, with the mineral surface itself, or adsorbed species, acting as an electron donor. 3. Intrinsic or mechanically-induced surface defects: Defects on the mineral surface, either intrinsic to the mineral structure or generated by crushing, can react to form ROS. In this mechanism, highly reactive defects combine with water, molecular oxygen, or carbon dioxide to form ROS. 4. Inflammatory cell/mineral interactions: Insoluble particles that deposit in the airways and alveoli of the lung may activate airway epithelial cells or macrophages as a result of binding to the cell surface or engulfment mechanisms that bring the particles into the cell interior; these processes can lead to …

172 citations

Patent
Tetsusyo Yamada1, Nobuhiro Hayakawa1
25 Feb 1986
TL;DR: An air/fuel ratio sensor is composed of first and second elements, each having porous electrodes formed on opposite sides of an oxygen-ion-conductive electrolyte plate, arranged to define between them a gas compartment communicating with the atmosphere to be detected via one or more diffusion limiting portions.
Abstract: An air/fuel ratio sensor having an unambiguous output with respect to both the fuel-rich and the fuel-lean regions and which does not require the introduction of atmospheric air. The sensor is composed of first and second elements, each having porous electrodes formed on opposite sides of an oxygen-ion-conductive electrolyte plate. The two elements are arranged to define between them a gas compartment communicating with the atmosphere to be detected via one or more diffusion limiting portions. One of the elements serves as an oxygen concentration differential electrochemical cell and the other one as an oxygen pump. An internal reference oxygen source is formed on the side of one of the elements opposite the gas compartment, and a small current is caused to flow the first element so as to transfer oxygens from the gas compartment to the oxygen source. The second element pumps oxygen into or out of the gas compartment in such a manner that the air/fuel ratio of the gas in the gas compartment is held at a predetermined value.

171 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20233,516
20226,670
20211,229
20201,164
20191,190
20181,153